JP4539622B2 - Engine control device for flex fuel engine - Google Patents

Description

  The present invention relates to an auxiliary fuel in a flex fuel engine using a main fuel stored in a main fuel tank and an auxiliary fuel made of fuel having different properties and stored in an auxiliary fuel tank to assist combustion. The present invention relates to an engine control device for a flex fuel engine that monitors the amount of secondary fuel remaining in a tank.

  In recent years, with increasing awareness of environmental problems, alcohol fuels with low emissions such as carbon monoxide and hydrocarbons have attracted attention as fuels for internal combustion engines such as in-vehicle. In particular, in Brazil, since a tax incentive is provided for manufacturers and users of alcohol-fueled vehicles, vehicles using a mixed fuel of alcohol and gasoline are widely used.

  By the way, alcohol is harder to vaporize in a low temperature environment than gasoline, so in vehicles using a mixed fuel of alcohol and gasoline, poor combustion such as misfire due to poor fuel vaporization at low temperature start and low temperature driving Occurs, and drivability deteriorates easily.

  Therefore, conventionally, as described in Patent Document 1, the concentrations of both the alcohol component in the mixed fuel and the low boiling point component of gasoline are detected, and the fuel injection amount at the time of engine start is determined according to each detected concentration. There has been proposed a technique for improving the startability of an internal combustion engine using the above mixed fuel, that is, a flex fuel engine, by correcting the increase. Specifically, the concentration of the alcohol component in the mixed fuel is detected from the detection value of the alcohol concentration sensor provided in the fuel pipe, and the mixed fuel is detected from the detection values of the vapor pressure sensor and the temperature sensor provided in the fuel tank. Detect the concentration of low boiling point components of gasoline. When the concentration of the alcohol component in the mixed fuel is equal to or higher than a predetermined value, the fuel injection amount at the start of the engine is increased as the concentration of the low boiling point component of gasoline is lower. This makes it possible to accurately determine the amount of fuel that is deficient due to poor vaporization at the time of engine start, regardless of variations in the composition of the mixed fuel used, and to provide fuel for combustion without excess or deficiency at low temperature start. become able to.

On the other hand, when it is assumed that there is no large variation in the composition of the mixed fuel to be used, the cold startability and the low temperature acceleration as a flex fuel engine can be enhanced by using another method. For example, apart from the mixed fuel, which is the main fuel (main fuel), a fuel (for example, gasoline) with better vaporization characteristics at low temperatures is used as an auxiliary fuel (sub fuel), and such auxiliary fuel is used at low temperature start-up or Additional supply at the time of low temperature acceleration can also improve the low temperature startability and low temperature acceleration of a flex fuel engine using a fuel containing a component having poor vaporization characteristics at low temperatures. In such a case, the fuel supply system is provided with a fuel tank dedicated to secondary fuel (sub fuel tank) separately from the fuel tank for the main fuel (main fuel tank), and sub fuel such as gasoline is supplied from this auxiliary fuel tank at low temperatures. It will be configured to supply.
JP-A-5-340286

  By the way, in a flex fuel engine that employs such a fuel supply system, a fuel gauge that measures the remaining amount of fuel in the fuel tank is added to the main fuel tank, and the auxiliary fuel tank that stores infrequently used auxiliary fuel is added. If installed, it would be inefficient in terms of cost, so it is desirable to omit the installation of a fuel gauge for the auxiliary fuel tank. However, if the installation of the fuel gauge is omitted for the auxiliary fuel tank, the remaining fuel management in the auxiliary fuel tank is left to the user's inspection, and the fuel in the auxiliary fuel tank is emptied. However, there is a risk that you will not notice it. If the auxiliary fuel tank becomes empty and it becomes impossible to supply the auxiliary fuel, the low temperature startability of the flex fuel engine deteriorates and the engine itself cannot be started. It can be reached.

  The present invention has been made in view of such circumstances, and an object of the present invention is to determine the fuel remaining amount in the fuel tank of the auxiliary fuel used mainly for assisting combustion at the cold start of the flex fuel engine. It is an object of the present invention to provide an engine control device for a flex fuel engine that can be accurately monitored without being provided.

In order to achieve the above object, according to the first aspect of the present invention, the main fuel stored in each of the different fuel tanks and the main fuel are composed of fuels having different properties, and mainly assist the combustion at the cold start. As an engine control device of a flex fuel engine having a function of monitoring the remaining amount of fuel in the fuel tank of the sub fuel of the flex fuel engine using the sub fuel, the sub fuel in a steady operation state of the flex fuel engine Forcibly executing the fuel supply for a certain period of time, and monitoring the remaining amount of fuel in the fuel tank of the secondary fuel based on the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of the secondary fuel ; did.

As an engine control device for a flex fuel engine, the supply of the auxiliary fuel for monitoring the remaining amount of fuel in the fuel tank of the auxiliary fuel in this way is performed over a certain period of time in a steady operation state of the flex fuel engine. by forcibly performed, along with a change in the air-fuel ratio due to the supply of secondary fuel becomes significant, always because it is possible to measure the variation of the air-fuel ratio in the common conditions, without providing the fuel gauge In both cases, the fuel remaining amount can be monitored easily and with high accuracy .

Note that the air-fuel ratio of the air-fuel mixture subjected to combustion in the combustion chamber of the flex fuel engine is usually detected by a linear air-fuel ratio sensor in which the detection output changes linearly with respect to a change in oxygen concentration in the exhaust system. An oxygen sensor whose detection output changes in a binary manner, such as rich or lean, is used. In any of these sensors, the change amount of the air-fuel ratio can be obtained based on the sensor output. Incidentally, when the linear air-fuel ratio sensor is used, since the air-fuel ratio can be detected linearly, the monitoring accuracy of the fuel remaining amount based on the change in the behavior of the flex fuel engine is improved. In addition, even when an oxygen sensor is used, it is possible to detect rich or lean air-fuel ratios, so that the remaining fuel amount can be easily monitored based on changes in the behavior of the flex fuel engine. .

In order to improve the monitoring accuracy, for example, according to the invention described in claim 2 , (A1) the change amount of the air-fuel ratio is obtained as an integral value, and the auxiliary fuel is calculated based on the obtained integral value. The amount of fuel remaining in the fuel tank is monitored.
Or, according to the invention of claim 3 ,
(A2) A predetermined threshold is set for the amount of change in the air-fuel ratio, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on the duration time exceeding the set threshold.
Alternatively, as in the invention according to claim 4 ,
(A3) One or more threshold values are set for the amount of change in the air-fuel ratio, and an arrival mode for the set threshold value, that is, whether or not the actual air-fuel ratio reaches the set threshold value, or a plurality of threshold values Is set, the remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on which threshold value is reached.
Etc. can be adopted.

That is, according to the configuration of (A1) (claim 2), monitoring the remaining fuel quantity based on the evaluation value of the change amount of the air-fuel ratio is a momentary change was included as well be changes in the air-fuel ratio Therefore, the monitoring accuracy of the fuel remaining amount is further improved. Further, according to the above configuration of (A2) (Claim 3), since the variation of the air-fuel ratio is instantaneous variation is well including the transition of the air-fuel ratio to monitor the fuel remaining amount, the The monitoring accuracy of the remaining amount of fuel is further improved, and this can be easily monitored. Further, according to the configuration of (A3) (Claim 4 ), the fuel remaining amount can be monitored more finely in accordance with the number of threshold values to be set.

By the way, when the auxiliary fuel supply is forcibly executed, the engine output of the flex fuel engine may increase excessively or the air-fuel ratio feedback control may be disturbed. In this regard, for example, according to the invention described in claim 5 , if the steady operation state of the flex fuel engine is set to the idle operation state of the same engine, the engine output is increased even if the engine output is excessively increased. It becomes possible to reduce the influence of the fluctuation of the engine on the operation of the engine. In addition, it becomes possible to collect the disturbance of the air-fuel ratio accompanying the supply of the auxiliary fuel relatively early.

Further, in the engine control device for a flex fuel engine according to any one of claims 1 to 4 , for example, according to the invention according to claim 6 , for example, detection of depression of an accelerator pedal is performed. An engine further comprising: means for detecting a change in operation control condition; and means for canceling monitoring of the remaining amount of fuel in the fuel tank based on detection of the change in operation control condition. This is effective in maintaining the monitoring accuracy of the secondary fuel during operation.

Meanwhile, in the invention described in 請 Motomeko 7, and the secondary fuel is a main fuel and main fuel stored separately to each of the fuel tank to assist the main combustion during cold start becomes different fuels properties As an engine control device of a flex fuel engine having a function of monitoring the remaining amount of fuel in the fuel tank of the sub fuel of the flex fuel engine using the sub fuel, the sub fuel is supplied over a certain time after the ignition switch is turned off. the supply of fuel to force was based on the change in the time the operation of the flex-fuel engine with a supply of the auxiliary fuel is continued and monitoring the amount of fuel remaining in the fuel tank of the auxiliary fuel.

According to such a configuration as the engine control device of the flex fuel engine, the remaining amount of the auxiliary fuel is changed through the change in the duration of the engine operation based on the auxiliary fuel supply control over a certain time after the engine operation stop operation (ignition switch off). The presence / absence of the quantity can be monitored with higher accuracy. That is, in the case of the forcible sub fuel supply control over a certain period of time, if the remaining amount of the sub fuel is sufficient, the sub fuel is actually continuously supplied over the entire period of the supply control over the certain period of time. However, if the remaining amount of the auxiliary fuel is insufficient, even if the supply control over the same fixed time is attempted, the auxiliary fuel is not always supplied over the entire time. The time during which the engine operation is continued naturally changes according to the actual supply time of the auxiliary fuel. Specifically, when the auxiliary fuel is supplied over the entire time of the supply control over the predetermined time, that is, when the remaining amount of the auxiliary fuel is sufficient, a time corresponding to the supply time of the auxiliary fuel. On the other hand, when the supply control for the fixed time is performed, the supply of the auxiliary fuel is interrupted without reaching the same time, that is, the supply of the auxiliary fuel. When the remaining amount is insufficient, the operation of the engine is stopped at a time commensurate with the time until the auxiliary fuel supply is interrupted. For this reason, the presence or absence of the remaining amount of auxiliary fuel is also monitored with higher accuracy according to the relationship between the above-mentioned fixed time required for the supply control of auxiliary fuel and the duration of engine operation after the start of the supply control. It becomes possible. Normally In the these flex-fuel engine, but in synchronization with the ignition switch-off operation the supply of the main fuel is stopped, in achieving execution previous stall prevention of this monitoring, the supply of main fuel and sub It is desirable to provide a period in which the fuel supply overlaps.

In the engine control device for a flex fuel engine according to claim 7 , more specifically, for example, according to the invention according to claim 8 ,
(B1) The time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as the time until the air-fuel ratio of the engine is fixed to the lean side.
Alternatively, as in the invention according to claim 9 ,
(B2) A time during which the engine operation is continued based on the auxiliary fuel supply control is obtained as a time during which the engine rotation is maintained.
Or, according to the invention of claim 10 ,
(B3) The time during which the engine operation is continued based on the sub fuel supply control is obtained as the in-cylinder combustion duration based on the detection of the ion current.
Or, according to the invention of claim 11 ,
(B4) A time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as a time during which the engine vibration detected through a knock sensor or the like is maintained.
Etc. can be adopted.

Incidentally, according to the configuration (Claim 8 ) of the above (B1), the presence or absence of the remaining amount of fuel in the fuel tank of the auxiliary fuel can be monitored in the following manner, for example. That is, while the auxiliary fuel is actually being supplied, the air-fuel ratio repeats lean / rich through the feedback control. However, if the supply of the auxiliary fuel is interrupted, the air-fuel ratio also becomes leaner. It becomes fixed. Therefore, if the time until the air-fuel ratio of the flex-fuel engine is fixed to the lean side when the auxiliary fuel is supplied over the predetermined time is determined empirically as a determination value, for example, the engine By monitoring whether or not the operation continuation time based on the auxiliary fuel supply control over the predetermined time reaches this judgment value every time the stop operation is performed, the amount of fuel remaining in the fuel tank of the auxiliary fuel can be reduced. The presence or absence can be determined.

Further, according to the configuration of (B2) (Claim 9 ), the remaining amount of fuel in the fuel tank of the auxiliary fuel can be monitored in the following manner, for example. That is, while the auxiliary fuel is actually supplied, combustion in the combustion chamber of the flex fuel engine continues and the engine rotation is maintained, but if the supply of the auxiliary fuel is interrupted, the engine rotation is continued. Also stop. Therefore, if the amount of time until the engine rotation of the flex fuel engine stops when it is supplied over the predetermined time empirically, for example, as a judgment value, Each time, it is determined whether or not there is a remaining amount of fuel in the fuel tank of the secondary fuel by monitoring whether or not the operation continuation time based on the secondary fuel supply control over the predetermined time reaches this judgment value. be able to.

Also, according to the configuration (B3) (claim 10 ), for example, the remaining amount of fuel in the fuel tank of the auxiliary fuel can be monitored in the following manner. That is, while the auxiliary fuel is actually supplied, combustion in the combustion chamber of the flex fuel engine is continued and the ion current is detected. If the supply of the auxiliary fuel is interrupted, the ion current is detected. Will not be detected. Therefore, if the amount of time until the engine rotation of the flex fuel engine stops when it is supplied over the predetermined time empirically, for example, as a judgment value, Each time, it is determined whether or not there is a remaining amount of fuel in the fuel tank of the secondary fuel by monitoring whether or not the operation continuation time based on the secondary fuel supply control over the predetermined time reaches this judgment value. be able to.

Further, according to the configuration (B4) (claim 11 ), for example, the remaining amount of fuel in the fuel tank of the auxiliary fuel can be monitored in the following manner. That is, while the auxiliary fuel is actually supplied, combustion in the combustion chamber of the flex fuel engine is continued and the engine vibration is detected. However, if the supply of the auxiliary fuel is interrupted, the engine vibration is detected. Will not be detected. Therefore, if the time during which the engine vibration of the flex-fuel engine is maintained when the auxiliary fuel is supplied over the predetermined time is determined empirically, for example, as a judgment value, the stop operation of the engine can be stopped. Each time, it is determined whether or not there is a remaining amount of fuel in the fuel tank of the secondary fuel by monitoring whether or not the operation continuation time based on the secondary fuel supply control over the predetermined time reaches this judgment value. be able to.
On the other hand, in the invention described in claim 12, the main fuel stored in each separate fuel tank and the main fuel are composed of fuels having different properties, and the auxiliary fuel mainly assists the combustion at the cold start. As an engine control device for a flex fuel engine having a function of monitoring the remaining amount of fuel in the fuel tank of the sub fuel of a flex fuel engine using a forcible supply of the sub fuel after the ignition switch is turned off The remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on whether or not the operation of the flex fuel engine is continued with the supply of the auxiliary fuel.
Even with such a configuration as an engine control device of a flex fuel engine, the presence or absence of the remaining amount of auxiliary fuel is monitored by the presence or absence of continued operation based on the forced supply of auxiliary fuel after the engine operation stop operation (ignition switch off). Will be able to. In such a flex-fuel engine, the supply of main fuel is usually stopped in synchronization with the operation of turning off the ignition switch. In this case, however, in order to prevent stall before the execution of this monitoring, the main fuel is also stopped. It is desirable to provide a period in which the supply of fuel and the supply of auxiliary fuel overlap.

Note that, in the auxiliary fuel monitoring device for a flex fuel engine according to any one of claims 1 to 12 , for example, according to the invention described in claim 13 , the supply amount is variable in accordance with the remaining amount of the auxiliary fuel. Specifically, when the remaining amount of fuel in the fuel tank of the auxiliary fuel is large, the supply amount is increased. When the remaining amount of fuel in the fuel tank of the auxiliary fuel is small, the supply amount is decreased. If the variable fuel mechanism is installed in the fuel tank for the secondary fuel, there will be a difference in the degree of change in the parameter indicating whether the engine operation will continue. In addition, the remaining amount can be monitored together.

Furthermore, in the auxiliary fuel monitoring device for a flex fuel engine according to any one of claims 1 to 13 , for example, according to the invention as set forth in claim 14 , the remaining amount of fuel in the fuel tank of the auxiliary fuel is determined. If the notification means for notifying the monitoring result is provided, the remaining fuel amount in the auxiliary fuel tank becomes “0” without leaving the management of the remaining fuel amount in the auxiliary fuel tank to the inspection on the user side. Or a small amount can be suitably notified to the user.

(First embodiment)
A first embodiment of an engine control device for a flex fuel engine according to the present invention will be described below with reference to FIGS.

  In this embodiment, as will be described in detail below, first, the supply of the auxiliary fuel is forcibly executed over a certain period of time when the flex fuel engine is in an idle operation state. Then, the absolute value of the integrated value of the deviation between the detected value of the air-fuel ratio sensor and the theoretical air-fuel ratio after the supply of the auxiliary fuel is executed is obtained, and the auxiliary fuel in the fuel tank is calculated based on the obtained absolute value. Monitor the fuel level. By doing so, the remaining amount of fuel in the fuel tank of the auxiliary fuel can be accurately monitored without providing a fuel gauge.

  FIG. 1 shows an overall configuration of a flex fuel engine to be mounted with an engine control apparatus according to this embodiment and a schematic configuration of the control apparatus. This flex fuel engine is configured as an on-vehicle flex fuel engine mounted on a vehicle. Fuel mainly composed of alcohol is supplied as a main fuel, and fuel composed mainly of gasoline is a subsidiary. Supplied as fuel. In other words, in this embodiment, fuel having a higher vaporization property at a lower temperature than that of the main fuel is supplied as an auxiliary fuel, thereby assisting combustion particularly when the flex fuel engine is started at a low temperature.

  As shown in FIG. 1, a flex fuel engine 10 basically includes an intake passage 11 through which air sucked from the outside flows, and a combustion chamber in which a mixture of air and fuel introduced through the intake passage 11 is burned. 12 and an exhaust passage 13 through which exhaust gas generated by combustion in the combustion chamber 12 flows.

  Among these, the intake passage 11 is branched for each cylinder at an intake manifold 15 downstream of the surge tank 14 and is connected to the combustion chamber 12 of each cylinder via an intake port 16. The intake passage 11 is provided with an intake temperature sensor (not shown) for detecting the temperature of air in the intake passage 11 upstream of the surge tank 14 and a dedicated auxiliary fuel nozzle for supplying auxiliary fuel. 18 is disposed inside the surge tank 14. Further, a main fuel injector 19 for injecting and supplying main fuel is disposed in the intake passage 11 for each intake port 16 of each cylinder. The auxiliary fuel supplied from the auxiliary fuel nozzle 18 is pumped from the auxiliary fuel tank 21 serving as a storage source to the auxiliary fuel passage 20 by the auxiliary fuel supply fuel pump 22. Then, the pumped sub fuel is supplied to the sub fuel nozzle 18 via the sub fuel passage 20. The main fuel injected and supplied from the main fuel injector 19 is pumped from the main fuel tank 24 as a storage source to the main fuel passage 23 by the main fuel supply fuel pump 25. The pumped main fuel is supplied to the main fuel injector 19 through the main fuel passage 23. The remaining amount of main fuel stored in the main fuel tank 24 is measured by a fuel meter (not shown).

  On the other hand, on the upper surface of the combustion chamber 12 formed by the side wall of the cylinder 26 of the flex fuel engine 10 and the upper surface of the piston 27 disposed in the cylinder 26 so as to be able to reciprocate, the introduced air-fuel mixture is sparked. A spark plug 28 for igniting is provided. In addition, a water jacket 29 that is a cooling water flow path for engine cooling is formed on the side wall of the cylinder 26, and a water temperature sensor 30 that detects the temperature of the cooling water flowing through the water jacket 29 is formed in the water jacket 29. It is arranged.

  On the other hand, the exhaust passage 13 connected to the combustion chamber 12 through the exhaust port 31 which is the exhaust discharge port is used for combustion in the combustion chamber 12 based on the oxygen content of the exhaust gas flowing inside. An air-fuel ratio sensor 32 for detecting the air-fuel ratio of the air-fuel mixture is disposed, and a catalyst device 33 for purifying exhaust gas is disposed downstream thereof.

  Here, FIG. 2A shows an example of the relationship between the magnitude of the voltage applied to, for example, the zirconia element constituting the air-fuel ratio sensor 32 and the magnitude of the current flowing by the applied voltage, depending on the air-fuel ratio. Show. In this embodiment, as described above, since the fuel containing alcohol as a main component is supplied as the main fuel, assuming that this is 100% alcohol, the theoretical air-fuel ratio is “9.2”. For example, when the zirconia element is in an atmosphere that is considerably richer than the stoichiometric air-fuel ratio, the relationship between the voltage value and the current value is as indicated by a curve A shown by a broken line in FIG. Further, for example, when the zirconia element is in an atmosphere slightly richer than the stoichiometric air-fuel ratio, the relationship between the voltage value and the current value is as indicated by a curve B indicated by a one-dot chain line in FIG. Further, for example, when the zirconia element is in an atmosphere that is considerably leaner than the stoichiometric air-fuel ratio, the relationship between the voltage value and the current value is as indicated by a curve C shown by a two-dot chain line in FIG. When the zirconia element is in an atmosphere that matches the theoretical air-fuel ratio, no current flows through the zirconia element. The air-fuel ratio sensor 32 is configured such that a constant voltage Va is applied so that a one-to-one correspondence is established between the air-fuel ratio and the current flowing through the zirconia element in the air-fuel ratio atmosphere. The linear relationship between the air-fuel ratio and the current value as shown in FIG. 2B is realized, and the air-fuel ratio of the air-fuel mixture provided for combustion in the combustion chamber 12 can be detected based on the current value at that time. It becomes possible.

  Various controls related to the operation of the flex fuel engine 10 configured as described above are executed by the engine control device 34 shown in FIG. The engine control unit 34 basically includes a central processing unit (CPU) that executes various arithmetic processes related to engine control, and a memory that stores various programs and data used for control of the central processing unit. The main fuel injector 19 and the fuel pumps 22 and 25 are provided with a drive circuit (not shown) for driving the fuel pumps 22 and 25. The engine control unit 34 controls each fuel supply through the main fuel injector 19 and the sub fuel nozzle 18 as a part of the engine control, a sub fuel remaining amount monitoring process for monitoring the fuel remaining amount in the sub fuel tank 21, and the like. Is running. The engine control device 34 cancels the sub fuel remaining amount monitoring process when a change in the operation control condition of the flex fuel engine 10 is detected, for example, when an accelerator pedal (not shown) is depressed. Processes are also executed. The fuel supply control, the sub fuel remaining amount monitoring process, the monitoring stop process, and the like are each actually performed by the central processing unit executing the program stored in the memory. However, here, conceptually, the elements related to the execution of each fuel supply control are the fuel supply control unit 35, and the elements related to the sub fuel remaining amount monitoring process and the monitoring stop process for canceling the process are the sub fuel remaining amount monitoring unit 36. Respectively.

  Among them, the fuel supply control unit 35 includes the water temperature sensor 30 and the air-fuel ratio sensor 32 in addition to the drive circuit for the main fuel injector 19 and the fuel pumps 22 and 25, as shown in FIG. Various sensors for detecting the operating status of the engine 10 are connected. In this embodiment, the fuel supply control unit 35 executes various processes related to the fuel supply based on the detection results. In particular, the engine is in operation after the flex fuel engine 10 has been warmed up. Basically, only main fuel injection from the main fuel injector 19 is supplied. Incidentally, the main fuel injection supply amount at this time is based on the air-fuel ratio feedback control described above. In this air-fuel ratio feedback control, based on the detection result of the air-fuel ratio sensor 32, the air-fuel ratio of the air-fuel mixture of the air introduced through the intake passage 11 and the injected main fuel is a desired value (target air The amount of main fuel injected and supplied from the main fuel injector 19 is feedback-controlled so that the fuel ratio becomes (fuel ratio). Further, the fuel supply control unit 35 is insufficient due to poor vaporization of the alcohol component of the main fuel when the flex fuel engine 10 is at a low temperature, that is, when the engine is started and the engine output is increased when the flex fuel engine 10 is not sufficiently warmed up. In order to supplement the combustion performance, an additional supply of auxiliary fuel through the auxiliary fuel nozzle 18 is executed in addition to the above-described injection supply of the main fuel.

  On the other hand, as shown in FIG. 1, the auxiliary fuel remaining amount monitoring unit 36 also confirms that the fuel in the water temperature sensor 30, the air-fuel ratio sensor 32, and the auxiliary fuel tank 21 has become “0”. A warning lamp (notification means) 39 for notifying the user, a rotation speed sensor 40 for detecting the engine rotation speed of the flex fuel engine 10, and the like are connected. Note that the warning light 39 is disposed at a position where it can be visually recognized by a user seated in a driver's seat of the vehicle, that is, a driver of the vehicle, such as an instrument panel. The sub fuel remaining amount monitoring unit 36 detects the engine cooling water temperature detected by the water temperature sensor 30, the detection result of the air-fuel ratio sensor 32, the rotational speed of the flex fuel engine 10 detected by the rotational speed sensor 40, and the like. Based on this information, a process of monitoring the remaining amount of auxiliary fuel in the auxiliary fuel tank 21 is mainly executed.

  On the other hand, in this embodiment, the sub fuel remaining amount monitoring unit 36 takes in the accelerator operation information by the accelerator opening sensor 41 that detects the opening (depression amount) of the accelerator pedal, and the operation mode of the accelerator pedal changes. In addition, it has a function of stopping the monitoring of the remaining amount of the auxiliary fuel on condition that the operation of the flex fuel engine 10 has changed.

Next, processing related to fuel supply control executed through the fuel supply control unit 35 will be described with reference to FIGS.
FIG. 3 is a flowchart showing a processing procedure for the auxiliary fuel supply request determination process among the processes executed through the fuel supply control unit 35. This process is executed by the fuel supply control unit 35 as a scheduled interruption process, for example, every 16 milliseconds.

  As shown in FIG. 3, when the sub fuel supply request determination process is started, the fuel supply control unit 35 first determines that the engine cooling water temperature read from the water temperature sensor 30 is the flex fuel as the process of step S100. It is determined whether or not the engine 10 is lower than a low determination value (for example, 20 degrees) indicating that the engine 10 is not sufficiently warmed up. That is, it is determined whether the engine 10 is in a state before completion of warm-up or after completion of warm-up. Here, when it is determined that the engine coolant temperature is high (NO), the engine 10 is already in a state after the completion of warm-up, so that a shortage of combustion performance due to poor vaporization of the alcohol component of the main fuel is unlikely to occur. The need to supply is low. Therefore, the fuel supply control unit 35 temporarily ends the current process without requesting the supply of the auxiliary fuel.

  On the other hand, when it is determined in the determination process of step S100 that the engine coolant temperature is low (YES), that is, when the engine 10 is in a state before completion of warm-up, combustion due to poor vaporization of the alcohol component of the main fuel. Since the shortage of performance tends to occur, the fuel supply control unit 35 basically requests the supply of auxiliary fuel. However, even when the engine 10 is in a low temperature state, it is not necessary to supply auxiliary fuel unless the engine is started or the output is increased after the engine is started. Therefore, the fuel supply control unit 35 determines whether the engine 10 is at the time of starting the engine or when the output is increased after the engine is started, through the determination process at step S101 and the determination process at step S102. When this is determined (YES in the process of step S101, or NO in the process of step S101 and YES in the process of step S102), the fuel supply control unit 35 supplies sub fuel as the subsequent process of step S103. After setting the sub fuel supply request flag indicating the necessity to perform this process, the current process is temporarily terminated.

  FIG. 4 shows a processing procedure of the fuel supply execution process executed by the fuel supply control unit 35 based on the result of the sub fuel supply request determination process. This process is executed as a crank angle interruption process synchronized with the engine rotation.

  As shown in FIG. 4, when the fuel supply execution process is started, the fuel supply control unit 35 first determines whether or not it is the fuel supply timing as the determination process of step S110. The fuel supply timing is set to an appropriate crank angle in advance. Here, when it is determined that the supply timing is reached (YES), the fuel supply control unit 35 determines whether or not the sub fuel supply request flag (basically, the process of step S103 in FIG. 3) is set. The process proceeds to the determination process of determination step S111. On the other hand, when it is determined that the supply timing is not reached (NO), the fuel supply control unit 35 is not suitable for supplying fuel in the first place, so the current process is not performed without shifting to the process of step S111. Exit once.

  When it is determined in the determination process of step S111 that there is a sub fuel supply request (YES), the fuel supply control unit 35 performs the processes of the main fuel pump 25 and the sub fuel pump 22 as the subsequent process of step S112. Supplying the main fuel and the sub fuel through the driving is performed. Specifically, the fuel supply control unit 35 drives the main fuel pump 25 so that the main fuel in an amount based on the air-fuel ratio feedback control is supplied through the driving of the main fuel injector 19, and also the alcohol component in the main fuel. The auxiliary fuel pump 22 is driven so that the auxiliary fuel is supplied through the auxiliary fuel nozzle 18 in an amount sufficient to compensate for the insufficient combustion performance due to insufficient vaporization.

  On the other hand, when it is determined that there is no sub fuel supply request (NO), the fuel supply control unit 35 proceeds through the drive of the main fuel injector 19 as the processing of the subsequent step S113 through the driving of the main fuel injector 19 based on the air / fuel ratio feedback control. Only the main fuel pump 25 is driven to be supplied.

  FIGS. 5A and 5B are timing charts showing examples of fuel supply modes executed through the fuel supply control unit 35 when the flex fuel engine 10 is started at a low temperature. In this example, the flex fuel engine 10 is in a state in which a sufficient amount of time has passed since the previous engine stop and the engine cooling water temperature also shows a low value, for example, less than a normal temperature value (for example, 20 degrees). It is said. In this case, as shown in FIGS. 5 (a) and 5 (b), when the flex fuel engine 10 is operated by turning on the ignition switch at time t101, the fuel supply control unit 35 causes the main fuel pump 25 to operate. In addition, both the auxiliary fuel pump 22 and the main fuel injector 19 are driven to supply main fuel and auxiliary fuel. Then, as shown in FIG. 5B, the supply of the auxiliary fuel is stopped at time t102 after the supply time (a fixed time) has elapsed from time t101. Thus, when the flex fuel engine 10 is at a low temperature, the combustion performance that is insufficient due to poor vaporization of the alcohol component of the main fuel is compensated.

  FIGS. 6A and 6B are timing charts showing examples of fuel supply modes executed through the fuel supply control unit 35 when the flex fuel engine 10 is warmed up. In this example, it is assumed that the flex fuel engine 10 is in a state in which the engine coolant temperature is higher than the above-described determination value without much time from the previous engine stop. In this case, as shown in FIGS. 6A and 6B, when the flex fuel engine 10 is operated through the ignition switch ON operation at time t111, the fuel supply control unit 35 causes the main fuel pump 25 to operate. And the main fuel injection supply from the main fuel injector 19 are performed based on the air-fuel ratio feedback control. In FIG. 6, the fuel supply mode is shown only during the warm-up start. However, the fuel supply mode in which only the main fuel injection supply is performed is not limited to the warm-up start, but the flex fuel engine. The same applies when the engine is warmed up after 10 warm-ups or when the engine is started in a specific season (summer season in Japan).

  FIG. 7 is a flowchart showing a processing procedure of the sub fuel remaining amount monitoring process executed by the sub fuel remaining amount monitoring unit 36. FIGS. 8 and 9 show the monitoring executed in the sub fuel remaining amount monitoring process. It is a flowchart which shows the process sequence of a request determination process and a monitoring execution process, respectively. Next, the sub fuel remaining amount monitoring process executed through the sub fuel remaining amount monitoring unit 36 will be described with reference to FIGS. The process shown in FIG. 7 (including the processes shown in FIGS. 8 and 9) is executed by the auxiliary fuel remaining amount monitoring unit 36 as a scheduled interruption process every 16 milliseconds, for example.

  As shown in FIG. 7, when the sub fuel remaining amount monitoring process is started, the sub fuel remaining amount monitoring unit 36 first executes a series of monitoring request determination processes shown in FIG. 8 as the process of step S200. . Then, as a process of subsequent step S300, a series of monitoring execution processes shown in FIG. 9 is executed. After executing the processing of step S200 and step S300, the current processing is temporarily terminated.

  Here, when the monitoring request determination process in step 200 is started, the auxiliary fuel remaining amount monitoring unit 36 is first read from the rotation speed sensor 40 as the determination process in step S201 as shown in FIG. Based on the rotational speed of the flex fuel engine 10 or the like, it is determined whether or not the flex fuel engine 10 is in an idle operation state. Specifically, the sub fuel remaining amount monitoring unit 36 determines whether or not the read rotational speed is within a predetermined range that is set in advance as a range indicating that the flex fuel engine 10 is in an idle operation state. judge. At this time, the accelerator opening detected through the accelerator opening sensor 41 (FIG. 1) may be “0”, that is, the fact that the accelerator operation is not performed may be added to the criterion.

  In the idle operation state, monitoring of the remaining amount of auxiliary fuel, which will be described later, can be executed with high monitoring accuracy. Therefore, when it is determined that the flex fuel engine 10 is in the idle operation state (YES in the determination process of step S201), the sub fuel remaining amount monitoring unit 36 performs the process of step S202 as the flex fuel engine 10 Is set to a monitoring feasible flag, which is a flag indicating that the sub fuel remaining amount can be monitored. On the other hand, when it is determined that the flex fuel engine 10 is not in the idling operation state (NO in the determination process of step S201), the sub fuel remaining amount monitoring unit 36 performs monitoring of the sub fuel remaining amount described later. However, since the monitoring accuracy is low, the monitoring executable flag is reset as the processing of the subsequent step S203. The determination process in step S201 corresponds to “means for detecting a change in the operation control condition of the flex fuel engine”, and the determination process in step S201 and the process in step S203 are performed as “a change in the operation control condition is detected. It corresponds to “means for canceling monitoring of the remaining amount of fuel in the fuel tank of the auxiliary fuel”.

  After completing the monitoring request determination process, the sub fuel remaining amount monitoring unit 36 continues to start the monitoring execution process in step S300. In this monitoring execution process, as shown in FIG. 9, the sub fuel remaining amount monitoring unit 36 first determines whether or not the monitoring executable flag (the process of step S202) is set as the determination process of step S301. to decide. Here, when it is determined that the monitoring executable flag is set (YES), the flex fuel engine 10 is in an idle operation state, and the fuel remaining amount can be monitored with high monitoring accuracy. Therefore, the sub fuel remaining amount monitoring unit 36 sets a sub fuel supply request flag as the processing of the subsequent step S302. When the auxiliary fuel supply request flag is set in this way, the fuel supply control unit 35 (FIG. 1) performs main fuel and auxiliary fuel through the determination process of step S111 and the process of step S112 shown in FIG. Supply is performed.

  Then, as the subsequent process of step S303, the sub fuel remaining amount monitoring unit 36 executes the sub fuel supply by the fuel supply control unit 35 and the detected value (sensor output) of the air / fuel ratio sensor 32 and the stoichiometric air / fuel ratio (the stoichiometric air / fuel ratio). Here, the absolute value of the integral value of the deviation from “9.2”) is calculated. That is, since the monitoring executable flag is set, the flex fuel engine 10 is in an idle operation state, and main fuel injection through the main fuel injector 19 is executed based on air-fuel ratio feedback control. For this reason, the detected value of the air-fuel ratio sensor 32 stably changes so as to cross the stoichiometric air-fuel ratio alternately between the rich side and the lean side.

  In this state, when the amount of remaining fuel in the auxiliary fuel tank 21 is sufficient, if the auxiliary fuel supply is executed over a certain period of time by the fuel supply control unit 35, the detection value of the air-fuel ratio sensor 32 is rich. Then, the air-fuel ratio gradually approaches the stoichiometric air-fuel ratio, and again stably transitions so that the stoichiometric air-fuel ratio crosses alternately the rich side and the lean side. At this time, since the detection value of the air-fuel ratio sensor 32 deviates greatly from the theoretical air-fuel ratio, the absolute value is a large value.

  On the other hand, in the above state, when the remaining fuel amount in the auxiliary fuel tank 21 is not sufficient, the detected value of the air-fuel ratio sensor 32 is stabilized so as to cross the stoichiometric air-fuel ratio alternately between the rich side and the lean side without changing. Therefore, the absolute value takes a small value. Thus, the remaining fuel amount in the auxiliary fuel tank 21 has a deep correlation with the absolute value. Therefore, by setting a predetermined threshold value for the absolute value and determining whether or not the set threshold value is exceeded, it is possible to monitor the fuel remaining amount of the auxiliary fuel in the fuel tank 21. Become.

  Specifically, the sub fuel remaining amount monitoring unit 36 determines whether or not the absolute value acquired in the processing of the previous step S303 exceeds the threshold as the determination processing of the subsequent step S304. Here, when it is determined that the same absolute value exceeds the same threshold value (YES), it means that the detected value of the air-fuel ratio sensor 32 has greatly deviated from the theoretical air-fuel ratio. In the subsequent step S305, it is determined that the sub fuel remaining amount is “present”. In this case, the warning light 39 (FIG. 1) is kept off as the processing of the subsequent step S306. On the other hand, when it is determined in the determination process of step S304 that the absolute value is less than the threshold value (NO), it means that the detection value of the air-fuel ratio sensor 32 has not changed, so that the sub fuel remaining amount The monitoring unit 36 determines that the remaining amount of auxiliary fuel is “None” as the process of subsequent Step S307. Further, the auxiliary fuel remaining amount monitoring unit 36 turns on the warning lamp 39 as a process of subsequent step S308 to notify the user of that fact.

  FIGS. 10A to 10C show examples of monitoring modes of the remaining amount of fuel according to this embodiment. Next, with reference to FIGS. 10A to 10C, the remaining fuel remaining amount monitoring mode will be described.

  For example, it is assumed that the flex fuel engine 10 is in an idling state and the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. In this state, as described above and as shown in FIG. 10A, the main fuel injection supply through the driving of the main fuel pump 25 is executed based on the air-fuel ratio feedback control. Therefore, the detection value of the air-fuel ratio sensor 32 stably changes so as to cross the theoretical air-fuel ratio alternately between the rich side and the lean side, as indicated by the solid line in FIG.

  Then, as shown in FIG. 10B, when the auxiliary fuel supply control is executed over a certain period of time from, for example, time t11 to time t12 through the fuel supply control unit 35, the auxiliary fuel is actually supplied. Therefore, the detection value of the air-fuel ratio sensor 32 greatly fluctuates toward the rich side as shown by the solid line in FIG. After that, the detected value gradually approaches the stoichiometric air-fuel ratio, and again changes stably so that the stoichiometric air-fuel ratio straddles the rich side and the lean side again.

  At this time, the auxiliary fuel remaining amount monitoring unit 36 executes the integration of the deviation between the detected value of the air-fuel ratio sensor 32 and the theoretical air-fuel ratio after the supply of auxiliary fuel is executed at time t11 (FIG. 10C). The absolute value of the hatched area is determined, and it is determined whether or not a predetermined threshold set for the absolute value is exceeded. In this monitoring mode example, since the detected value of the air-fuel ratio sensor 32 deviates greatly from the theoretical air-fuel ratio, the sub fuel remaining amount monitoring unit 36 determines that the absolute value acquired by the monitoring unit 36 has the threshold value. It is determined that the amount of fuel is exceeded, and it is determined that the sub fuel remaining amount is “present”.

  In FIG. 10C, an example of a monitoring mode in which the flex fuel engine 10 is in an idle operation state and the sub fuel remaining in the fuel tank 21 is not sufficient is shown with a broken line. Show. In this monitoring mode example, as shown in FIG. 10B, even if the auxiliary fuel is supplied through the fuel supply control unit 35 over a certain period of time from time t11 to time t12, for example, The secondary fuel is not supplied sufficiently. Therefore, the detection value of the air-fuel ratio sensor 32 stably changes so as to straddle the theoretical air-fuel ratio over the rich side and the lean side, as indicated by a broken line in FIG. At this time, the sub fuel remaining amount monitoring unit 36 determines that the absolute value acquired by the sub fuel remaining amount monitoring unit 36 is less than the threshold value, and determines that the sub fuel remaining amount is “none”. .

As described above, according to the first embodiment, the following excellent effects can be obtained.
(1) The absolute value of the integrated value of the deviation between the detected value of the air-fuel ratio sensor 32 and the theoretical air-fuel ratio after the sub-fuel supply is executed by the fuel supply control unit 35 is obtained. Based on the determination as to whether or not the set threshold value is exceeded, the remaining amount of fuel in the fuel tank 21 of the auxiliary fuel is monitored. This makes it possible to accurately monitor the auxiliary fuel tank 21 with high accuracy without providing a fuel gauge.

  (2) When the flex fuel engine 10 is in an idle operation state, the supply of the auxiliary fuel is forcibly executed over a certain period of time. Thus, as a result of forcibly executing the supply of the auxiliary fuel, even if the engine output of the flex fuel engine 10 is excessively increased or the air-fuel ratio feedback control is disturbed, the fluctuation of the engine output affects the operation of the engine. The influence can be reduced. In addition, it becomes possible to collect the disturbance of the air-fuel ratio accompanying the supply of auxiliary fuel relatively early.

  (3) In the auxiliary fuel request determination process (FIG. 8) for monitoring the remaining amount of the auxiliary fuel in the auxiliary fuel tank 21, the operation of the flex fuel engine 10 is detected, for example, by detecting that the accelerator pedal is depressed. Based on the detection of the change in the control condition, the monitoring stop process (the determination process in step S201 and the process in step S203) for canceling the monitoring of the remaining amount of fuel in the auxiliary fuel tank 21 is performed. Thereby, the monitoring accuracy of the auxiliary fuel during the engine operation of the flex fuel engine 10 can be effectively maintained.

  (4) Notifying the user that the remaining amount of fuel in the auxiliary fuel tank 21 has become “0” as notification means for notifying the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21. The warning light 39 is installed at a position that is visible to the user seated in the driver's seat of the vehicle. As a result, when the fuel in the auxiliary fuel tank 21 becomes empty without leaving the management of the remaining amount of fuel in the auxiliary fuel tank 21 to the inspection on the user side, this is immediately notified to the user. Will be able to.

Note that the first embodiment described above can be implemented with appropriate modifications in the following forms, for example.
In the above embodiment, the auxiliary fuel remaining amount monitoring unit 36 determines whether or not the flex fuel engine 10 is in the idling operation state as shown in the determination process (step S201 in FIG. 8). Based on the above, the flag processing of the monitoring executable flag related to the forced execution of the auxiliary fuel supply is executed, but this processing mode is not limited to this. In addition, for example, the sub fuel remaining amount monitoring unit 36 determines whether or not the monitoring executable flag is based on a determination process of whether or not the flex fuel engine 10 is in a steady operation state associated with a constant speed traveling of the mounted vehicle. Flag processing may be executed. This also makes it possible to properly monitor the remaining amount of fuel in the auxiliary fuel tank 21 because the change in the air-fuel ratio accompanying the forced execution of the supply becomes significant when the auxiliary fuel remains. .

  In the above embodiment (including the modified example), as shown in the determination process of step S304 in FIG. 9, the auxiliary fuel remaining amount monitoring unit 36 performs the empty operation after the supply of the auxiliary fuel is executed. Based on whether or not the absolute value of the integral value of the deviation between the detected value of the fuel ratio sensor 32 and the stoichiometric air-fuel ratio exceeds the threshold value, the remaining amount of fuel in the fuel tank 21 of the auxiliary fuel is monitored. The monitoring execution process is not limited to this mode. For example, the output value of the air-fuel ratio sensor 32 after the sub fuel supply is executed is obtained as an integral value, and a threshold value set for the obtained integral value is obtained. The remaining amount of fuel in the auxiliary fuel tank 21 may be monitored based on the determination process for determining whether or not the fuel amount exceeds. In short, if the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of secondary fuel is obtained as an integral value, and the remaining amount of fuel in the fuel tank of the secondary fuel is monitored based on this obtained integral value, high accuracy It is possible to monitor the remaining amount of fuel.

  Further, for example, as a process that replaces the process of step S302 and step S304 of FIG. 9, the process shown as step S313 and step S314 in FIG. 11 may be executed. That is, the duration in which the transition value that is richer than the predetermined air-fuel ratio in the rich region occurs in the detected value of the air-fuel ratio sensor 32 after the sub fuel supply is executed is measured (processing in step S313), The remaining fuel amount in the sub fuel tank 21 may be monitored by determining whether or not the duration period exceeds the threshold (determination process in step S314). As described above, since the monitoring executable flag is set (YES in the determination process in step S301), the detected value of the air-fuel ratio sensor 32 causes the stoichiometric air-fuel ratio to alternately cross the rich side and the lean side. To be stable. In such a state, when the amount of sub fuel in the sub fuel tank 21 is sufficient, if the sub fuel is supplied over a certain time by the fuel supply control unit 35, the detected value of the air-fuel ratio sensor 32 is detected. After being greatly swung to the rich side, it gradually approaches the stoichiometric air-fuel ratio, and again stably shifts so that the stoichiometric air-fuel ratio crosses the rich side and the lean side alternately. On the other hand, in the above state, when the remaining amount of the auxiliary fuel in the auxiliary fuel tank 21 is not sufficient, the detected value of the air-fuel ratio sensor 32 does not change as described above. It will transition stably so as to cross the lean side alternately. Therefore, the auxiliary fuel remaining amount monitoring unit 36 measures the duration during which the detected value of the air-fuel ratio sensor 32 is richer than the predetermined air-fuel ratio in the rich region as the process of step S313, and continues. As a determination process in step S314, it is possible to monitor the remaining amount of fuel in the auxiliary fuel tank 21 by determining whether or not this duration exceeds a threshold value. In short, a predetermined threshold is set for the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of secondary fuel, and the fuel in the fuel tank of the secondary fuel is based on the duration that exceeds the set threshold. By monitoring the remaining amount, it is possible to easily monitor the remaining amount of fuel.

Still further, for example, as shown in FIG. 12 as the determination process in step S324, the sub fuel supply is executed, and the detected value of the air-fuel ratio sensor 32 thereafter becomes richer than the predetermined air-fuel ratio in the rich region. The remaining amount of fuel in the auxiliary fuel tank 21 may be monitored based on the determination process of whether or not there is a transition. In short, a predetermined threshold value is set for the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of auxiliary fuel, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is determined based on the mode of reaching the set threshold value. It can also be monitored.
(Second Embodiment)
Next, a second embodiment of the engine control apparatus for a flex fuel engine according to the present invention will be described with reference to FIGS. 13 to 15 focusing on differences from the first embodiment. . FIG. 13 is a flowchart corresponding to FIG. 4 described above, and is a flowchart showing a processing procedure of a fuel supply execution process executed by the fuel supply control unit 35. FIG. 14 is a flowchart showing the processing procedure of the pre-monitoring execution process similarly executed by the fuel supply control unit 35 and the sub fuel remaining amount monitoring unit 36, and FIG. 15 is a diagram corresponding to FIG. It is a flowchart showing the processing procedure of the monitoring execution process executed in the pre-monitoring execution process.

  In the engine control apparatus of the flex fuel engine of this embodiment, as described in detail below, first, the supply of the auxiliary fuel is forcibly executed for a certain time after the stop operation of the flex fuel engine. Then, the time until the air-fuel ratio of the engine is fixed to the lean side is obtained, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on the obtained time. By doing so, the remaining amount of fuel in the fuel tank of the auxiliary fuel can be accurately monitored without providing a fuel gauge.

  That is, as shown in FIG. 13, when the fuel supply execution process is started, the fuel supply control unit 35 (FIG. 1) first determines the ignition of the flex fuel engine 10 (FIG. 1) as the determination process in step S121. It is determined whether or not the switch is turned off (engine stop operation). Here, when it is determined that the engine stop operation has not been performed (NO), the flex fuel engine 10 is basically in a normal operation state, so that the fuel supply control unit 35 performs the subsequent step S122. The normal supply (injection) of the main fuel is maintained so that the amount of the main fuel based on the air-fuel ratio feedback control is supplied through the drive of the main fuel injector 19.

  On the other hand, when it is determined that the engine stop operation is performed in the determination process of step S121 (YES), the fuel supply control unit 35 performs the main fuel injector as a process of step S123 in order to execute a monitoring execution process described later. The supply of main fuel is stopped through the drive stop at 19. In conjunction with the stop of the supply of the main fuel, the fuel supply control unit 35 controls the supply of the auxiliary fuel for a predetermined time by driving the auxiliary fuel pump 22 to temporarily overlap the supply of the main fuel. That is, in such a flex fuel engine 10, supply of all fuel is normally stopped in synchronism with the engine stop operation. In this embodiment, after the engine stop operation, the auxiliary fuel is supplied for a certain period of time. Execute. However, in order to prevent the engine from stalling due to the switching of the fuel accompanying the stop operation, the main fuel is also supplied and the engine operation is assisted for a short period at the beginning of the auxiliary fuel supply.

  Then, the fuel supply control unit 35 executes the pre-monitoring execution process shown in FIG. As shown in FIG. 14, when the pre-monitoring execution process is started, the fuel supply control unit 35 first performs an off operation (engine stop operation) of the ignition switch of the flex fuel engine 10 as a determination process in step S500. ) To determine whether or not the main fuel supply has been stopped. That is, the timing at which the engine operation is performed only by supplying the auxiliary fuel is monitored. In the determination process of step S500, when it is determined by the fuel supply control unit 35 that the supply of the main fuel due to the ignition switch OFF operation has been stopped, the sub fuel remaining amount monitoring unit 36 performs the subsequent process of step S600. As shown in FIG. That is, the sub fuel remaining amount monitoring unit 36 continues to start the monitoring execution process shown in FIG.

  In this monitoring execution process, as shown in FIG. 15, the auxiliary fuel remaining amount monitoring unit 36 first performs the supply of the auxiliary fuel by the fuel supply control unit 35 as the process of step S601, and thereafter the air-fuel ratio sensor. The time until 32 detection values (sensor output) are fixed to the lean side is acquired. That is, when a sufficient amount of auxiliary fuel remains in the auxiliary fuel tank 21 during the supply control of the auxiliary fuel over a certain period of time, the auxiliary fuel is not supplied over the entire time of the auxiliary fuel supply control over this certain period of time. Actually, the engine 10 continues to be supplied, and the operation of the engine 10 is continued for a time commensurate with the supply time of the auxiliary fuel. On the other hand, if a sufficient amount of secondary fuel does not remain in the secondary fuel tank 21, even if the secondary fuel supply control over the predetermined time is attempted, the supply of the secondary fuel is interrupted without reaching the predetermined time, The operation of the engine 10 is stopped at a time commensurate with the time until the supply of the auxiliary fuel stops. In this case, the detected value of the air-fuel ratio sensor 32 is fixed to the lean side when the supply of the auxiliary fuel is interrupted.

  Then, the sub fuel remaining amount monitoring unit 36 determines whether or not the time acquired in the process of step S601 exceeds a predetermined time as the determination process of step S602. The predetermined time is a time determined as a time commensurate with the supply time when the auxiliary fuel is continuously supplied over the entire time of the supply control of the auxiliary fuel over the predetermined time. The That is, when it is determined in the determination process of step S602 that the acquired time exceeds the predetermined time (YES), the auxiliary fuel remaining amount monitoring unit 36 supplies the auxiliary fuel for a time corresponding to the supply time. As a result, in the subsequent step S603, it is determined that the sub fuel remaining amount is “present”. In this case, as a process in step S604, the warning light 39 (FIG. 1) is kept off. On the other hand, when it is determined in the determination process of step S602 that the acquired time is less than the predetermined time (NO), it is determined that the auxiliary fuel has not been supplied for a time corresponding to the supply time, and subsequent step S605 is performed. In this process, it is determined that the sub fuel remaining amount is “none”. In this case, in step S606, the warning light 39 is turned on to notify the user that the remaining amount of sub fuel is “0” and to warn the user. Thus, the sub fuel remaining amount monitoring unit 36 ends the current process.

  FIGS. 16A to 16D show examples of monitoring modes of the remaining fuel amount in this embodiment. Next, this remaining amount monitoring mode example will be described with reference to FIGS. 16 (a) to 16 (d).

  For example, it is assumed that the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. In such a state, even if the ignition switch is turned off (engine stop operation) at the timing shown in FIG. 16A, and the main fuel supply is stopped at the timing shown in FIG. By supplying the auxiliary fuel shown in 16 (c), the engine operation is maintained over the supply period. Therefore, as shown by the solid line in FIG. 16D, the detection value of the air-fuel ratio sensor 32 once swings to the rich side, and then the time t24 at which the supply of the auxiliary fuel is stopped for the predetermined time. Thereafter, the vibration moves to the lean side, and is fixed to the lean side at time t26, for example. In FIG. 16, the time t21 is the time (timing) when the ignition switch is turned off and the supply of auxiliary fuel is started, and the time t22 is the stop of the supply of main fuel thereafter. Time (timing). The supply of the main fuel and the supply of the auxiliary fuel are overlapped over the period (time) from the time t21 to the time t22, thereby preventing the engine from stalling due to the switching of these fuels.

  On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is “0” or not sufficient, all of the fuel is supplied at the timing (time t22) at which the main fuel supply shown in FIG. Since the fuel supply is stopped, for example, as indicated by a broken line in FIG. 16D, the detection value of the air-fuel ratio sensor 32 is fixed to the lean side immediately or immediately after time t22.

  For this reason, as described above, the auxiliary fuel remaining amount monitoring unit 36 determines that the detected value of the air-fuel ratio sensor 32 is on the lean side after the supply of the auxiliary fuel is forcibly executed for a certain time after the stop operation of the flex fuel engine 10. It is possible to monitor the remaining amount of fuel in the auxiliary fuel tank 21 by acquiring the time until the fuel is fixed to and determining whether the acquired time exceeds a predetermined time.

According to the second embodiment described above, the following excellent effects can be obtained.
(1) After the stop operation of the flex fuel engine 10, the supply of the auxiliary fuel is forcibly executed for a certain period of time, and the inside of the auxiliary fuel tank 21 is based on the time until the air-fuel ratio of the engine 10 is fixed to the lean side. It was decided to monitor the fuel level at This makes it possible to accurately monitor the remaining amount of fuel in the fuel tank 21 of the auxiliary fuel without providing a fuel gauge.

  (2) When the fuel is switched from the main fuel to the sub fuel accompanying the stop operation of the flex fuel engine 10, the main fuel supply period and the sub fuel supply period are temporarily overlapped. As a result, it is possible to prevent a stall before executing the monitoring execution process (FIG. 15).

  (3) A warning light 39 for notifying the user that the remaining amount of fuel in the auxiliary fuel tank 21 has become “0” as notification means for notifying the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21. In addition, it is arranged at a position that can be visually recognized by a user seated in the driver's seat of the vehicle. Thus, when the fuel in the auxiliary fuel tank 21 becomes empty without leaving the management of the remaining amount of fuel in the auxiliary fuel tank 21 to the inspection on the user side, it is immediately suitable for the user. Can be notified.

In addition, this 2nd Embodiment demonstrated above can be suitably changed and implemented, for example with the following forms.
In the embodiment described above, the auxiliary fuel remaining amount monitoring unit 36 first forcibly supplies the auxiliary fuel for a certain time after the stop operation of the flex fuel engine 10. Then, the time until the detected value of the air-fuel ratio sensor 32 after the supply of the auxiliary fuel is fixed to the lean side is acquired, and based on the determination whether or not the acquired time exceeds a predetermined period, The remaining amount of fuel in the auxiliary fuel tank 21 is monitored. That is, the time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as the time until the air-fuel ratio of the engine 10 is fixed to the lean side, and the fuel in the auxiliary fuel tank 21 is calculated based on the obtained time. The remaining amount was monitored. However, the present invention is not limited to this monitoring mode, and the time during which the engine operation is continued based on the sub fuel supply control is obtained as the time during which the engine rotation is maintained, and the remaining fuel in the sub fuel tank 21 is determined based on the obtained time. The amount may be monitored. As described above, if the remaining amount of fuel in the auxiliary fuel tank 21 is insufficient, even if the auxiliary fuel supply control is executed through the driving of the auxiliary fuel pump 22, it can actually be used for engine operation. No auxiliary fuel is supplied. Therefore, in this case, as shown in FIG. 16 (b), if the main fuel supply is stopped at time t22, the rotational speed sensor 40 ( The detection signal according to FIG. 1 also ceases at, for example, time t23 immediately after that (engine rotation is not maintained). On the other hand, if the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient, the auxiliary fuel is actually supplied along with the auxiliary fuel supply control through the driving of the auxiliary fuel pump 22. Therefore, in this case, as shown in FIG. 16 (b), even if the main fuel supply is stopped at time t22, as shown by the solid line in FIG. The detection signal is maintained until, for example, time t25 after a sufficient time thereafter (engine rotation is maintained). FIG. 17 illustrates the execution procedure for such a monitoring mode as a diagram corresponding to FIG. That is, as shown in step S611 of FIG. 17, in this case, first, the time during which the engine rotation is maintained based on the detection output of the rotation speed sensor 40 (FIG. 1) after the ignition switch is turned off. To get. Then, as the determination process in subsequent step S612, the remaining fuel amount in the auxiliary fuel tank 21 is monitored by determining whether or not the acquired time exceeds a predetermined time.

  In addition, the time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as the in-cylinder combustion duration based on the detection of the ion current, and the fuel in the fuel tank of the auxiliary fuel is calculated based on the obtained time. The remaining amount can be monitored. That is, as described above, if the remaining amount of fuel in the auxiliary fuel tank 21 is insufficient, even if the auxiliary fuel supply control is executed through the driving of the auxiliary fuel pump 22, the engine is actually operated. No auxiliary fuel is provided. Therefore, in this case, as shown in FIG. 16 (b), if the main fuel supply is stopped at time t22, the combustion chamber 12 (see FIG. The ion current in 1) is also not detected immediately after, for example, time t23 immediately after that (combustion is not continued). On the other hand, if the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient, the auxiliary fuel is actually supplied along with the auxiliary fuel supply control through the driving of the auxiliary fuel pump 22. Therefore, in this case, as shown in FIG. 16B, even if the main fuel supply is stopped at time t22, as shown by the solid line in FIG. The ion current continues to be detected (combustion continues) until a sufficient time thereafter, for example, until time t25. Incidentally, FIG. 18 illustrates an execution procedure of such a monitoring mode as a diagram corresponding to FIG. 15 described above. That is, as shown in step S621 in FIG. 18, in this case, first, the ignition switch is turned off, and the in-cylinder combustion duration time is acquired based on the subsequent detection of the ion current in the combustion chamber 12. Then, as a determination process in subsequent step S622, the remaining fuel amount in the auxiliary fuel tank 21 is monitored by determining whether or not the acquired time exceeds a predetermined time.

  ・ In addition, the time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as the time during which the engine vibration is maintained, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is calculated based on the obtained time. Can also be monitored. As described above, if the amount of fuel remaining in the auxiliary fuel tank 21 is insufficient, even if the auxiliary fuel supply control is executed through the driving of the auxiliary fuel pump 22, the engine is actually operated. No auxiliary fuel is provided. Therefore, in this case, as shown in FIG. 16 (b), if the main fuel supply is stopped at time t22, it is detected through, for example, a knock sensor or the like, as shown by a dashed line in FIG. 16 (g). The engine vibration to be performed is not immediately detected, for example, at time t23 immediately after that (engine vibration is not maintained). On the other hand, if the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient, the auxiliary fuel is actually supplied along with the auxiliary fuel supply control through the driving of the auxiliary fuel pump 22. Therefore, in this case, as shown in FIG. 16B, even if the main fuel supply is stopped at time t22, as shown by the solid line in FIG. The detected engine vibration continues to be detected until a sufficient time thereafter, for example, until time t25 (the engine vibration is maintained). FIG. 19 exemplifies the execution procedure for such a monitoring mode as a diagram corresponding to FIG. That is, as shown as the processing of step S631 in FIG. 19, first, in this case, the time during which the ignition switch is turned off and the subsequent engine vibration is maintained is obtained through, for example, a knock sensor. Then, as the determination process in subsequent step S632, the remaining fuel amount in the auxiliary fuel tank 21 is monitored by determining whether or not the acquired time exceeds a predetermined time.

  In the above-described embodiment (including the above-described modifications), the supply of the auxiliary fuel is forcibly executed via the auxiliary fuel nozzle 18, but an injector, for example, is provided instead of the auxiliary fuel nozzle 18 and the injector is driven. The supplementary fuel supply may be forcibly executed. As a result, the time required until the auxiliary fuel is actually supplied can be shortened, and the time when the supply of the main fuel and the supply of the auxiliary fuel overlap can be reduced or omitted. .

In the above-described embodiment (also including the above-described modifications), the remaining fuel amount in the auxiliary fuel tank 21 is monitored every time the ignition switch of the flex fuel engine 10 is turned off (engine stop operation) However, it is not limited to this monitoring mode. That is, it is possible to determine whether or not the number of startups of the engine 10 is greater than or equal to a predetermined number, and when it is determined that the number is greater than or equal to the predetermined number, the remaining amount of fuel in the auxiliary fuel tank 21 may be monitored. Alternatively, it may be determined whether or not the integrated value of the driving time of the auxiliary fuel pump 22 is equal to or longer than a predetermined time, and when the cumulative value is equal to or longer than the predetermined time, the remaining amount of fuel in the auxiliary fuel tank 21 may be monitored. As a result, the consumption of the auxiliary fuel stored in the auxiliary fuel tank 21 can be suppressed. The predetermined number of times set for the number of times the engine 10 is started and the predetermined time set for the integrated value of the driving time of the auxiliary fuel pump 22 are used for the capacity of the auxiliary fuel tank 21 or for one trip. It can be set in consideration of the average amount of auxiliary fuel to be used, the average driving time of the auxiliary fuel pump 22, and the like.
(Third embodiment)
Next, a third embodiment of an engine control apparatus for a flex fuel engine according to the present invention will be described with reference to FIGS. 20 to 23, focusing on differences from the first embodiment. . 20 (a) and 20 (b) show a structural example of the auxiliary fuel tank of this embodiment from the side direction, and FIG. 21 shows the remaining fuel amount and auxiliary fuel in the auxiliary fuel tank. It shows the relationship with the supply rate of secondary fuel supplied from the supply system.

  The fuel remaining amount monitoring apparatus of this embodiment is basically configured in accordance with the first embodiment shown in FIGS. However, in this embodiment, as described in detail below, the auxiliary fuel tank of the flex fuel engine is provided with a supply amount variable mechanism that makes the supply amount variable according to the remaining amount of the auxiliary fuel, so that the auxiliary fuel is changed. It is possible to monitor not only the presence / absence of fuel remaining in the tank but also the amount of fuel remaining in the auxiliary fuel tank.

That is, as shown in FIGS. 20A and 20B, the auxiliary fuel tank 21 provided with this variable supply amount mechanism is basically configured as follows.
A large-diameter passage 20 a having a large diameter that opens to the bottom surface of the auxiliary fuel tank 21.

A small-diameter passage 20 b having a small diameter that opens to the bottom surface of the auxiliary fuel tank 21.
A float 211 whose height is changed according to the amount of fuel remaining in the tank 21 (the height of the liquid level) by floating on the liquid level of the auxiliary fuel stored in the auxiliary fuel tank 21.

It is arranged between the movable point m of the float 211 and the fulcrum f of the float 211 provided on the inner bottom surface of the auxiliary fuel tank 21 to close or open the opening of the large diameter passage 20a. A float valve 212 for prohibiting or permitting the outflow of the auxiliary fuel from the radial passage 20a.
And so on.

  Accordingly, when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient, the liquid level of the fuel is high, so that the float valve 212 opens the opening of the large-diameter passage 20a as shown in FIG. Thus, the outflow of fuel into both the large diameter passage 20a and the small diameter passage 20b is permitted. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is insufficient, the liquid level of the fuel is low, so that the float valve 212 closes the opening of the large-diameter passage 20a as shown in FIG. However, although fuel outflow into the small diameter passage 20b is permitted, fuel outflow into the large diameter passage 20a is prohibited.

  FIG. 21 shows the relationship between the height of the liquid level in the sub fuel tank 21 configured as described above (the amount of remaining fuel) and the amount of sub fuel supplied from the sub fuel tank 21. As shown in FIG. 21, if the remaining amount of fuel is sufficient and the liquid level is high, the amount of secondary fuel flowing out to the engine 10 increases and the supply amount increases. On the contrary, if the remaining amount of fuel is small and the liquid level is low, the amount of secondary fuel flowing out to the engine 10 decreases, and the supply amount decreases.

  FIG. 22 shows a processing procedure of the monitoring execution process executed through the auxiliary fuel remaining amount monitoring unit 36 when the auxiliary fuel tank 21 configured as described above is adopted. The process shown in FIG. 22 is also executed as a scheduled interrupt process every 16 milliseconds, for example.

  As shown in FIG. 22, when the monitoring execution process is started, the sub fuel remaining amount monitoring unit 36 first sets the monitoring executable flag (step S202 in FIG. 8) as the determination process in step S701. Judge whether or not. Here, when it is determined that the monitoring executable flag is set (YES), the flex fuel engine 10 is in an idle operation state, and the fuel remaining amount can be monitored with high monitoring accuracy. As a result, the sub fuel remaining amount monitoring unit 36 sets a sub fuel supply request flag as the processing of the subsequent step S702. When the auxiliary fuel supply request flag is set in this way, the fuel supply control unit 35 supplies the main fuel and the auxiliary fuel through the determination process of step S111 and the process of step S112 shown in FIG. The

  Then, as the subsequent process of step S703, the sub fuel remaining amount monitoring unit 36 executes the sub fuel supply by the fuel supply control unit 35 and the detected value (sensor output) of the air / fuel ratio sensor 32 and the stoichiometric air / fuel ratio (following). Here, the absolute value of the integral value of the deviation from “9.2”) is acquired. That is, since the monitoring executable flag is set, the flex fuel engine 10 is in an idle operation state, and main fuel injection through the main fuel injector 19 is executed based on air-fuel ratio feedback control. For this reason, the detected value of the air-fuel ratio sensor 32 stably changes so as to cross the stoichiometric air-fuel ratio alternately between the rich side and the lean side.

  In such a state, when the amount of remaining fuel in the auxiliary fuel tank 21 is sufficient, the fuel supply control unit 35 supplies a large amount of auxiliary fuel over a certain period of time, and the detected value of the air-fuel ratio sensor 32 is rich. Then, the air-fuel ratio gradually approaches the stoichiometric air-fuel ratio, and again stably transitions so that the stoichiometric air-fuel ratio crosses alternately the rich side and the lean side. At this time, since the detection value of the air-fuel ratio sensor 32 deviates greatly from the theoretical air-fuel ratio, the absolute value is a large value.

  On the other hand, in the above state, when the remaining amount of fuel in the auxiliary fuel tank 21 is not sufficient, the fuel supply control unit 35 supplies a small amount of auxiliary fuel over a fixed time, and the detected value of the air-fuel ratio sensor 32 is: After a slight fluctuation toward the rich side, the air-fuel ratio approaches the stoichiometric air-fuel ratio, and again, the stoichiometric air-fuel ratio changes stably so as to alternately cross the rich side and the lean side. At this time, since the detected value of the air-fuel ratio sensor 32 slightly deviates from the theoretical air-fuel ratio, the absolute value takes a smaller value than when the remaining fuel amount in the sub fuel tank 21 is sufficient. Become.

  On the other hand, in the above state, when the remaining amount of fuel in the auxiliary fuel tank 21 is “0”, the detected value of the air-fuel ratio sensor 32 does not change, and the stoichiometric air-fuel ratio alternately spans the rich side and the lean side. Therefore, the absolute value takes a smaller value.

  Thus, the remaining fuel amount in the auxiliary fuel tank 21 has a deep correlation with the absolute value. Therefore, by setting a plurality of threshold values for the absolute value and based on the reaching mode for the set threshold values, not only the presence / absence of the remaining amount of fuel in the auxiliary fuel tank 21, but also the amount of remaining fuel is combined. Can be monitored.

  Specifically, the sub fuel remaining amount monitoring unit 36 determines whether or not the absolute value acquired in the process of step S703 exceeds the first threshold as the determination process of subsequent step S704. Here, when it is determined that the absolute value exceeds the first threshold value (YES), it means that the detected value of the air-fuel ratio sensor 32 has greatly deviated from the theoretical air-fuel ratio. In the subsequent step S705, it is determined that the sub fuel remaining amount is “large”. In this case, the warning lamp 39 (FIG. 1) is kept off as the process of subsequent step S706.

  On the other hand, when it is determined in the determination process of step S704 that the absolute value is less than the first threshold (NO), the auxiliary fuel remaining amount monitoring unit 36 performs the absolute process as the determination process of the subsequent step S707. It is determined whether or not the value exceeds a second threshold value that is smaller than the first threshold value. Here, when it is determined that the absolute value exceeds the second threshold value (YES), it means that the detected value of the air-fuel ratio sensor 32 is slightly deviated from the stoichiometric air-fuel ratio. In the subsequent step S708, it is determined that the sub fuel remaining amount is “low”. In this case, the sub fuel remaining amount monitoring unit 36 blinks the warning lamp 39 as the processing of the subsequent step S709 in order to notify the user of that fact.

  On the other hand, when it is determined in the determination process in step S707 that the absolute value is less than the second threshold (NO), it means that the detection value of the air-fuel ratio sensor 32 has not changed. The remaining fuel amount monitoring unit 36 determines that the remaining amount of auxiliary fuel is “None” as the subsequent processing in step S710. Also in this case, the sub fuel remaining amount monitoring unit 36 turns on the warning lamp 39 as the processing of the subsequent step S711 in order to notify the user to that effect.

  FIGS. 23A to 23C show examples of monitoring modes for monitoring the remaining amount of auxiliary fuel according to this embodiment. Next, this monitoring mode will be described with reference to FIGS. 23 (a) to 23 (c).

  For example, it is assumed that the flex fuel engine 10 is in an idling state and the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. In this state, as described above and as shown in FIG. 23A, the main fuel injection supply through the driving of the main fuel pump 25 is performed based on the air-fuel ratio feedback control. Therefore, the detection value of the air-fuel ratio sensor 32 stably changes so as to straddle the theoretical air-fuel ratio over the rich side and the lean side, as indicated by a solid line in FIG.

  Then, as shown in FIG. 23 (b), when the auxiliary fuel supply control is executed through the fuel supply control unit 35 over a certain period of time from time t31 to time t32, for example, the auxiliary fuel is actually supplied. Therefore, the detection value of the air-fuel ratio sensor 32 greatly fluctuates to the rich side as shown by the solid line in FIG. After that, the detected value gradually approaches the stoichiometric air-fuel ratio, and again changes stably so that the stoichiometric air-fuel ratio straddles the rich side and the lean side again.

  At this time, the auxiliary fuel remaining amount monitoring unit 36 executes the integral control of the deviation between the detected value of the air-fuel ratio sensor 32 and the theoretical air-fuel ratio after the supply control of the auxiliary fuel is executed at time t31 (FIG. 23 (c ) The absolute value of the area of the hatched portion surrounded by the solid line is determined, and the arrival mode for a plurality of threshold values set for the absolute value is determined. In the monitoring mode example indicated by the solid line in FIG. 23 (c), the detected value of the air-fuel ratio sensor 32 deviates greatly from the stoichiometric air-fuel ratio. It is determined that the absolute value acquired by 36 exceeds the first threshold value, and it is determined that the remaining amount of auxiliary fuel is “large”.

  Further, in FIG. 23C, when the flex fuel engine 10 is in an idle operation state and the remaining amount of fuel in the auxiliary fuel tank 21 is small, that is, in the mode shown in FIG. An example of a monitoring mode when fuel is supplied is also shown by a one-dot chain line. In this monitoring example, as shown in FIG. 23C, when the sub fuel supply control is executed through the fuel supply control unit 35 over a certain period of time from time t31 to time t32, for example, The detected value of the fuel ratio sensor 32 slightly deviates from the theoretical air fuel ratio. Therefore, the sub fuel remaining amount monitoring unit 36 has the absolute value (the area of the hatched portion surrounded by the one-dot chain line in FIG. 23C) acquired by the sub fuel remaining amount monitoring unit 36 as the first value. It is determined that the size is between the threshold value and the second threshold value, and it is determined that the sub fuel remaining amount is “low”.

  Further, in FIG. 23C, an example of a monitoring mode in which the flex fuel engine 10 is in an idle operation state and the remaining fuel amount in the auxiliary fuel tank 21 is “0” is shown together with a broken line. Yes. In this monitoring mode example, as shown in FIG. 23C, even if the auxiliary fuel supply control is executed through the fuel supply control unit 35 over a certain period of time from time t31 to time t32, for example, Actually, no auxiliary fuel is supplied. Therefore, no significant change occurs in the detected value of the air-fuel ratio sensor 32, and the detected value changes stably so as to straddle the theoretical air-fuel ratio over the rich side and the lean side. At this time, the sub fuel remaining amount monitoring unit 36 determines that the absolute value acquired by the monitoring unit 36 is less than the second threshold value, and determines that the sub fuel remaining amount is “none”. .

According to the third embodiment described above, the following excellent effects can be obtained.
(1) The auxiliary fuel tank 21 of the flex fuel engine 10 is provided with a supply amount variable mechanism that makes the supply amount variable according to the remaining amount of fuel. As a result, not only the presence or absence of the remaining amount of fuel in the auxiliary fuel tank 21 but also the amount of remaining fuel in the auxiliary fuel tank 21 can be monitored.

  (2) The absolute value of the integrated value of the deviation between the detected value of the air-fuel ratio sensor 32 and the theoretical air-fuel ratio after the sub-fuel supply is executed by the fuel supply control unit 35 is obtained, and the obtained absolute value is A plurality of threshold values are set, and the amount of remaining fuel in the auxiliary fuel tank 21 is monitored based on the arrival mode with respect to the set threshold values. As a result, it is possible to more accurately monitor the auxiliary fuel tank 21 with high accuracy without providing a fuel gauge.

  (3) When the flex fuel engine 10 is in the idle operation state, the supply of the auxiliary fuel is forcibly executed over a certain period of time. Thus, as a result of forcibly executing the supply of the auxiliary fuel, even if the engine output of the flex fuel engine 10 is excessively increased or the air-fuel ratio feedback control is disturbed, the fluctuation of the engine output affects the operation of the engine. The influence can be reduced. In addition, it becomes possible to collect the disturbance of the air-fuel ratio accompanying the supply of auxiliary fuel relatively early. In the auxiliary fuel request determination process (FIG. 8) for monitoring the remaining amount of fuel in the auxiliary fuel tank 21, there is a change in the operation control condition of the flex fuel engine 10 such as, for example, detecting that the accelerator pedal is depressed. Canceling the monitoring of the remaining amount of fuel in the auxiliary fuel tank 21 based on the detection is the same as in the first embodiment. Thereby, the monitoring accuracy of the auxiliary fuel during the engine operation of the flex fuel engine 10 can be effectively maintained.

  (4) A warning lamp 39 for notifying the user of the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21 is provided as a notification means for notifying the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21. It was decided to install it at a position visible to the user seated on the seat. This makes it possible to notify the user of the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21 without entrusting the management of the remaining amount of fuel in the auxiliary fuel tank 21 to the inspection on the user side.

Note that the third embodiment described above can be implemented with appropriate modifications, for example, in the following forms.
In the above embodiment, as shown in the processing of step S703 in FIG. 22, the sub fuel remaining amount monitoring unit 36 performs the air fuel ratio after the sub fuel is supplied by the fuel supply control unit 35. Although the absolute value of the integrated value of the deviation between the detected value of the sensor 32 and the theoretical air-fuel ratio is obtained, the value to be monitored does not have to be the absolute value of the integrated value of such deviation. In addition, for example, the output value of the air-fuel ratio sensor 32 after the sub fuel supply is executed by the fuel supply control unit 35 is obtained as an integral value, and a plurality of threshold values are set for the obtained integral value. The amount of remaining fuel in the auxiliary fuel tank 21 may be monitored based on the reaching mode with respect to the threshold value. Further, even if one threshold value is set without setting a plurality of threshold values for the obtained absolute value or integral value, the amount of remaining fuel in the auxiliary fuel tank 21 can be monitored in the same manner. In short, the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of auxiliary fuel is obtained as an integral value, and one or more threshold values are set for the obtained integral value, and based on how the threshold value is reached. If the amount of remaining fuel in the auxiliary fuel tank is monitored, the amount of remaining fuel can be monitored with high accuracy.

  In place of the process shown in FIG. 22, for example, a monitoring execution process as exemplified in FIG. 24 can be adopted. That is, in the process shown in FIG. 24, the sub fuel remaining amount monitoring unit 36 first causes the detected value of the air / fuel ratio sensor 32 to be richer than the predetermined air / fuel ratio in the rich region as the process of step S713. To get a duration. Then, as the subsequent determination processing in step S714 and step S717, the remaining amount of fuel in the auxiliary fuel tank 21 is monitored based on the manner of reaching the plurality of threshold values set for the acquired duration. In short, one or a plurality of threshold values are set for a duration in which the change amount of the air-fuel ratio of the flex fuel engine 10 accompanying the supply of the auxiliary fuel exceeds a predetermined threshold value, and the auxiliary fuel is determined based on the arrival mode with respect to this threshold value. The remaining amount of fuel can be easily monitored by monitoring the remaining amount of fuel in the fuel tank. Incidentally, in this case, the first threshold value used in the determination process of step S714 is the supply time when the auxiliary fuel is supplied over a certain period of time when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. It is a duration set as a reasonable time. Similarly, the second threshold value used in the determination process of step S717 corresponds to the supply time when the auxiliary fuel is supplied over a certain period of time when there is not enough fuel remaining in the auxiliary fuel tank 21. It is a duration defined as a specific time. Of course, also here, the first threshold value is set as a larger (longer) value than the second threshold value.

  Similarly, instead of the process shown in FIG. 22, a monitoring execution process as exemplified in FIG. 25 may be employed. That is, in the process shown in FIG. 25, as the determination process of step S724, the auxiliary fuel remaining amount monitoring unit 36 is the first air-fuel ratio in the rich region in the detection value of the air-fuel ratio sensor 32 after the auxiliary fuel is supplied. It is determined whether there is a transition that becomes richer. Further, as the determination processing in step S727, there is a transition in which the sub fuel is supplied and the detected value of the air-fuel ratio sensor 32 thereafter becomes richer than the second air-fuel ratio leaner than the first air-fuel ratio. It is determined whether or not to do. Based on these determination results, the amount of remaining fuel in the auxiliary fuel tank 21 is monitored. In short, a plurality of threshold values are set for the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of auxiliary fuel (the vertical axis in FIG. 23 (c)), and the auxiliary fuel is determined based on the arrival mode with respect to the set threshold values. The remaining amount of fuel can be easily monitored by monitoring the remaining amount of fuel in the fuel tank.

In the above embodiment, the passages 20a and 20b opened on the bottom surface of the auxiliary fuel tank 21 have different diameters. However, a sufficient flow rate difference is ensured according to the opening and closing of the passage 20a by the float valve 212. If it is possible, the passages having the same diameter may be adopted as the passages 20a and 20b.
(Fourth embodiment)
Next, a fourth embodiment of an engine control apparatus for a flex fuel engine according to the present invention will be described with reference to FIG. 26, focusing on differences from the second and third embodiments. . FIG. 26 is a flowchart showing the procedure of the monitoring execution process executed through the sub fuel remaining amount monitoring unit 36. This embodiment is also basically the same as the second embodiment shown in FIGS. 13 to 15 and the third embodiment shown in FIGS. It has a conforming configuration. That is, in this embodiment, the auxiliary fuel tank of the flex fuel engine is provided with a variable supply amount mechanism that makes the supply amount variable according to the remaining amount of the auxiliary fuel, and after a stop operation of the engine for a certain period of time. Force supply of secondary fuel. Then, a time until the air-fuel ratio of the engine is fixed to the lean side is obtained, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on the obtained time. By doing so, the amount of remaining fuel in the auxiliary fuel tank can be accurately monitored without providing a fuel gauge.

  Specifically, the sub fuel remaining amount monitoring unit 36 starts the monitoring execution process based on the determination that the main fuel supply is stopped in accordance with the ignition switch OFF operation in step S500 of FIG. When the monitoring execution process is started, the sub fuel remaining amount monitoring unit 36 first performs the sub fuel supply by the fuel supply control unit 35 as a process of step S801 as shown in FIG. Time until the detection value (sensor output) of the air-fuel ratio sensor 32 is fixed to the lean side is acquired.

  Here, when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient, when the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the supply control of the auxiliary fuel for the certain time is performed. Over the entire time, a relatively large amount of secondary fuel corresponding to the state of FIG. As a result, the operation of the flex fuel engine 10 is continued for a time commensurate with the supply time and supply amount of the auxiliary fuel. That is, in this case, a relatively long time is required until the detection value of the air-fuel ratio sensor 32 is fixed to the lean side.

  On the other hand, when the amount of fuel remaining in the auxiliary fuel tank 21 is small, the amount of fuel corresponding to the state shown in FIG. That is, although it is a relatively small amount, the auxiliary fuel is actually supplied over the entire time of the supply control of the auxiliary fuel over a certain period of time. As a result, the operation of the engine 10 is continued for a time commensurate with the supply time and supply amount of the auxiliary fuel. That is, in this case, it does not take as much time as when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient until the detection value of the air-fuel ratio sensor 32 is fixed to the lean side.

  On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is “0”, even if the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the auxiliary fuel is not supplied in the first place. The operation of the engine 10 is immediately stopped.

  As described above, since the time during which the engine 10 continues to be operated changes depending on the actual supply amount of the auxiliary fuel, the predetermined time required for the supply control of the auxiliary fuel and the engine operation after the start of the supply control are changed. Depending on the relationship with the duration, it is possible to monitor the presence or absence of the remaining amount of auxiliary fuel.

  Therefore, the sub fuel remaining amount monitoring unit 36 determines whether or not the time acquired in the process of step S801 exceeds the first predetermined time as the determination process of step S802. Here, when it is determined that the time exceeds the first predetermined time (YES), the auxiliary fuel remaining amount monitoring unit 36 determines that the remaining amount of auxiliary fuel is “large” as the processing of the subsequent step S803, As a process of step S804, the warning lamp 39 is kept off. As the first predetermined time, the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient (the fuel supply rate is large), and over the entire period of the auxiliary fuel supply control over the predetermined time. When the auxiliary fuel continues to be actually supplied, a time determined as a time commensurate with the supply time is adopted.

  On the other hand, when it is determined in the determination process of step S802 that the time is less than the first predetermined time (NO), the auxiliary fuel remaining amount monitoring unit 36 further performs the above time as the determination process of step S805. Whether or not exceeds a second predetermined time shorter than the first predetermined time. Here, when it is determined that the time exceeds the second predetermined time (YES), the sub fuel remaining amount monitoring unit 36 determines that the sub fuel remaining amount is “low” as the processing of the subsequent step S806, As a process of step S807, the warning lamp 39 is blinked. As the second predetermined time, the remaining amount of fuel in the auxiliary fuel tank 21 is insufficient (the fuel supply rate is small), and the entire amount of the auxiliary fuel supply control over the predetermined time is over. When the auxiliary fuel is continuously supplied, the time determined as the time corresponding to the supply time is adopted.

  On the other hand, in the determination process of S805, when it is determined that the time is less than the second predetermined time (NO), the sub fuel remaining amount monitoring unit 36 determines that the sub fuel remaining amount is in the subsequent step S808. While determining “None”, the warning lamp 39 is turned on as the processing of step S809.

According to the fourth embodiment described above, the following excellent effects can be obtained.
(1) The auxiliary fuel tank 21 of the flex fuel engine 10 is provided with a supply amount variable mechanism that makes the supply amount variable according to the remaining amount of fuel. As a result, not only the presence or absence of the remaining amount of fuel in the auxiliary fuel tank 21 but also the amount of remaining fuel in the auxiliary fuel tank 21 can be monitored.

  (2) After the engine stop operation of the flex fuel engine 10, the supply of the auxiliary fuel was forcibly executed for a fixed time, and the time until the air-fuel ratio of the engine 10 was fixed to the lean side was obtained. Then, a plurality of threshold values are set for the obtained time, and the amount of remaining fuel in the auxiliary fuel tank 21 is monitored based on the manner of reaching the set threshold values. This makes it possible to more accurately monitor the remaining amount of fuel in the fuel tank of the auxiliary fuel without providing a fuel gauge. Note that when the fuel is switched from the main fuel to the sub fuel accompanying the stop operation of the flex fuel engine 10, the main fuel supply period and the sub fuel supply period are temporarily overlapped. This is the same as in the embodiment, and it is possible to prevent a stall before executing the monitoring execution process (FIG. 15).

  (3) A warning lamp 39 for notifying the user of the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21 is provided as a notification means for notifying the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21. It was decided to install it at a position visible to the user seated on the seat. Thereby, the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21 can be suitably notified to the user without leaving the management of the remaining amount of fuel in the auxiliary fuel tank 21 to inspection on the user side. Become.

Note that the fourth embodiment described above can be implemented with appropriate modifications, for example, in the following forms.
In the above embodiment, the auxiliary fuel remaining amount monitoring unit 36 first starts until the air-fuel ratio when the auxiliary fuel supply is forcibly executed for a certain time after the operation of stopping the flex fuel engine 10 is fixed to the lean side. And a plurality of threshold values are set for the obtained times, and the remaining amount of the auxiliary fuel is monitored based on the arrival mode with respect to the set threshold values. However, the present invention is not limited to this monitoring mode, and the time during which the engine operation is continued based on the auxiliary fuel supply control is obtained as the time during which the engine rotation is maintained, and the remaining fuel in the auxiliary fuel tank 21 is determined based on the obtained time. The amount may be monitored. As described above, if the amount of fuel remaining in the auxiliary fuel tank 21 is sufficient, when the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the amount of the auxiliary fuel for the certain time is increased. The relatively large amount of the auxiliary fuel described above continues to be actually supplied over the entire supply control time. That is, the operation of the engine 10 is continued for a time corresponding to the supply time and supply amount of the auxiliary fuel, and the detection of the engine rotation through the rotation speed sensor 40 (FIG. 1) is also performed for a relatively long time. Will be maintained. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is small, the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35. The auxiliary fuel is continuously supplied over the entire supply control time, and the operation of the engine 10 is continued for a time corresponding to the supply time and supply amount of the auxiliary fuel. In other words, in this case, the detection of the engine rotation through the rotation speed sensor 40 is not continued as much as the time maintained when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is “0”, even if the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the auxiliary fuel is not supplied in the first place. The operation of the engine 10 stops immediately. That is, in this case, the detection of the engine rotation through the rotation speed sensor 40 is hardly maintained. Thus, since the time during which the operation (rotation) of the engine 10 is continued to change according to the actual supply amount of the auxiliary fuel, the above-mentioned fixed time required for the supply control of the auxiliary fuel is the same as that after the start of the supply control. Depending on the relationship with the duration of engine rotation, it is possible to monitor the presence or absence of the remaining amount of auxiliary fuel. FIG. 27 exemplifies the execution procedure of such a monitoring mode as a diagram corresponding to FIG. That is, as shown in FIG. 27, in this case, the sub fuel remaining amount monitoring unit 36 first acquires the time during which the engine rotation is maintained after the ignition switch is turned off as the processing of step S811. Then, as subsequent determination processes in steps S812 and S815, determination is made as to whether the time exceeds a first predetermined time and whether the time exceeds a second predetermined time shorter than the first predetermined time. Execute the process. By such a process, it is possible to obtain an effect according to the effect of the fourth embodiment.

  In addition, the time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as the in-cylinder combustion duration based on the detection of the ion current, and the fuel in the fuel tank of the auxiliary fuel is calculated based on the obtained time. The remaining amount can be monitored. That is, if the amount of fuel remaining in the auxiliary fuel tank 21 is sufficient, when the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the supply control of the auxiliary fuel for the certain time is performed. The relatively large amount of the auxiliary fuel described above will continue to be supplied over the entire time. Since the operation of the engine 10 is continued for a time corresponding to the supply time and supply amount of the auxiliary fuel, the in-cylinder combustion continuation time based on the detection of the ionic current is also maintained for a relatively long time. Become so. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is small, the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35. The auxiliary fuel is continuously supplied over the entire supply control time, and the operation of the engine 10 is continued for a time corresponding to the supply time and supply amount of the auxiliary fuel. That is, in this case, the in-cylinder combustion continuation time based on the detection of the ionic current is not continued as much as the time maintained when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is “0”, even if the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the auxiliary fuel is not supplied in the first place. The operation of the engine 10 stops immediately. That is, in this case, there is almost no combustion duration in the cylinder based on the detection of the ion current. As described above, since the time during which the operation (combustion) of the engine 10 is continued naturally changes in accordance with the actual supply amount of the auxiliary fuel, the fixed time required for the supply control of the auxiliary fuel is equal to or longer than the start of the supply control. Depending on the relationship with the duration of engine combustion, the remaining amount of secondary fuel can be monitored. FIG. 28 exemplifies the execution procedure for such a monitoring mode as a diagram corresponding to FIG. That is, as shown in FIG. 28, in this case, the auxiliary fuel remaining amount monitoring unit 36 first obtains the in-cylinder combustion duration based on the detection of the ion current after the ignition switch is turned off as the processing of step S821. To do. Then, in the subsequent determination processing in steps S822 and S825, whether or not the combustion duration time exceeds a first predetermined time and whether or not the combustion duration time exceeds a second predetermined time shorter than the first predetermined time A determination process of whether or not is executed. Also by such processing, it is possible to obtain an effect according to the effect of the fourth embodiment.

  ・ In addition, the time during which the engine operation is continued based on the supply control of the auxiliary fuel is obtained as the time during which the engine vibration is maintained, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is calculated based on the obtained time. Can also be monitored. That is, if the amount of fuel remaining in the auxiliary fuel tank 21 is sufficient, when the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the supply control of the auxiliary fuel for the certain time is performed. The relatively large amount of the auxiliary fuel described above will continue to be supplied over the entire time. Then, the operation of the engine 10 is continued for a time commensurate with the supply time and supply amount of the auxiliary fuel, and the engine vibration detected by, for example, a knock sensor or the like is maintained for a relatively long time. It will be. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is small, the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35. The auxiliary fuel is continuously supplied over the entire supply control time, and the operation of the engine 10 is continued for a time corresponding to the supply time and supply amount of the auxiliary fuel. That is, in this case, the engine vibration detected by the knock sensor or the like is not continued for a time that is maintained when the remaining amount of fuel in the auxiliary fuel tank 21 is sufficient. On the other hand, when the remaining amount of fuel in the auxiliary fuel tank 21 is “0”, even if the supply control of the auxiliary fuel is executed for a certain time by the fuel supply control unit 35, the auxiliary fuel is not supplied in the first place. The operation of the engine 10 stops immediately. That is, in this case, the engine vibration is hardly detected by a knock sensor or the like. As described above, the time during which the operation (vibration) of the engine 10 is continued to change depending on the actual supply amount of the auxiliary fuel, so that the fixed time required for the supply control of the auxiliary fuel is the same as that after the start of the supply control. Depending on the relationship with the duration of engine vibration, it is possible to monitor the presence or absence of the remaining amount of secondary fuel. FIG. 29 exemplifies the execution procedure for such a monitoring mode as a diagram corresponding to FIG. That is, as shown in FIG. 29, in this case, the sub fuel remaining amount monitoring unit 36 first acquires the duration of the engine vibration detected by the knock sensor or the like after the ignition switch is turned off as the process of step S831. To do. Then, as subsequent determination processing in steps S832 and S835, whether or not the time during which engine vibration is maintained exceeds a first predetermined time, and a second predetermined time that is shorter than the first predetermined time. A process for determining whether or not the maximum value is exceeded is executed. Also by such processing, it is possible to obtain an effect according to the effect of the fourth embodiment.

  In the above-described embodiment (including the above-described modifications), the supply of the auxiliary fuel is forcibly executed via the auxiliary fuel nozzle 18, but an injector, for example, is provided instead of the auxiliary fuel nozzle 18, and this injector The auxiliary fuel supply may be forcibly executed through the driving of. As a result, the time required until the auxiliary fuel is actually supplied can be shortened, and the time when the supply of the main fuel and the supply of the auxiliary fuel overlap can be reduced or omitted. .

In the above-described embodiment (also including the above-described modifications), the remaining fuel amount in the auxiliary fuel tank 21 is monitored every time the ignition switch of the flex fuel engine 10 is turned off (engine stop operation) However, it is not limited to this monitoring mode. That is, it is possible to determine whether or not the number of startups of the engine 10 is greater than or equal to a predetermined number, and when it is determined that the number is greater than or equal to the predetermined number, the remaining fuel amount in the auxiliary fuel tank 21 may be monitored. Alternatively, it may be determined whether or not the integrated value of the driving time of the auxiliary fuel pump 22 is equal to or longer than a predetermined time, and the remaining fuel amount in the auxiliary fuel tank 21 may be monitored when it is equal to or longer than the predetermined time. As a result, the consumption of the auxiliary fuel stored in the auxiliary fuel tank 21 can be suppressed. The predetermined number of times set for the number of times the engine 10 is started and the predetermined time set for the integrated value of the driving time of the auxiliary fuel pump 22 are used for the capacity of the auxiliary fuel tank 21 or for one trip. It can be set in consideration of the average amount of auxiliary fuel to be used, the average driving time of the auxiliary fuel pump 22, and the like.
(Other embodiments)
In addition, each said embodiment can also be implemented with the following forms, for example.

  In each of the above-described embodiments, the air-fuel ratio sensor 32 whose detection output changes linearly with respect to the change in the oxygen concentration of the exhaust of the flex fuel engine 10 is adopted. Instead, the air-fuel ratio is rich or lean. Alternatively, an oxygen sensor whose detection output changes in a binary manner may be employed.

  In each of the above-described embodiments (including the corresponding modifications), the warning lamp 39 is used as a notification unit that notifies the monitoring result of the remaining amount of fuel in the auxiliary fuel tank 21. However, an equivalent notification is possible. For example, any notification means such as a buzzer or a display device can be employed.

  In each of the above-described embodiments (including the corresponding modifications), the monitoring mode in which the supply of the auxiliary fuel is forcibly executed over a certain period of time when the flex fuel engine 10 is in an idle operation state (steady operation state). Alternatively, any monitoring mode in which the supply of the auxiliary fuel is forcibly executed over a certain time after the stop operation of the flex fuel engine 10 is adopted. Not limited to this, the remaining fuel amount in the auxiliary fuel tank 21 may be monitored in both monitoring modes.

  In each of the above-described embodiments (including corresponding variations), the remaining amount of fuel in the auxiliary fuel tank 21 is monitored using an air-fuel ratio sensor, an oxygen sensor, a rotation speed sensor, an ion current sensor, a knock sensor, etc. Although sensors are used, available sensors are not limited to these. In short, any sensor that can detect a change in the engine behavior of the flex fuel engine 10 when the supply of the auxiliary fuel is forcibly executed may be used.

  In each of the above embodiments (including corresponding variations), the present invention is applied to a flex fuel engine that supplies alcohol as a main fuel and gasoline as a secondary fuel. The present invention can be similarly applied to any flex-fuel engine that uses an auxiliary fuel having different properties from the main fuel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an overall configuration of a flex fuel engine to be mounted and a schematic configuration of a control device of an engine control device according to a first embodiment of the present invention. About the air fuel ratio sensor employ | adopted by the said 1st Embodiment, (a) is the graph which showed the relationship between the applied voltage and electric current according to the air fuel ratio. (B) is a graph showing the relationship between the air-fuel ratio and current when a predetermined constant voltage is applied as the drive voltage. The flowchart which shows the process sequence about the auxiliary | assistant fuel supply request | requirement determination process among the processes performed through the fuel supply control part of the said 1st Embodiment. The flowchart which shows the process sequence of the fuel supply execution process performed by the fuel supply control part based on the result of the sub fuel supply request | requirement determination process shown in FIG. (A) And (b) is a timing chart which shows an example of the supply mode of each fuel performed through a fuel supply control part at the time of the low temperature start of the said flex fuel engine. (A) And (b) is a timing chart which shows an example of the supply mode of each fuel performed through a fuel supply control part at the time of warming-up start of the said flex fuel engine. The flowchart which shows the process sequence about the sub fuel remaining amount monitoring process performed through the sub fuel remaining amount monitoring part of the said 1st Embodiment. The flowchart which shows the process sequence about the monitoring request | requirement determination process performed in the said auxiliary fuel remaining amount monitoring process. The flowchart which shows the process sequence about the monitoring execution process performed in the said auxiliary fuel residual amount monitoring process. (A)-(c) is a timing chart which shows the example about the monitoring aspect of the sub fuel remaining amount monitoring performed in the said 1st Embodiment. The flowchart which shows the other process sequence of the sub fuel residual amount monitoring process performed through the sub fuel residual amount monitoring part of the said 1st Embodiment. The flowchart which shows the further another process sequence of the sub fuel remaining amount monitoring process performed through the sub fuel remaining amount monitoring part of the said 1st Embodiment. The flowchart which shows the process sequence of the fuel supply execution process performed through the fuel supply control part of 2nd Embodiment of this invention. The flowchart which shows the process sequence of the monitoring pre-execution process performed through the fuel supply control part of the said 2nd Embodiment. The flowchart which shows the process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of the said 2nd Embodiment. (A)-(g) is a timing chart which shows the example of a monitoring aspect of the sub fuel remaining amount monitoring performed in the said 2nd Embodiment (a modification is also included). The flowchart which shows the other process sequence of the sub fuel remaining amount monitoring process performed through the sub fuel remaining amount monitoring part of the said 2nd Embodiment. The flowchart which shows the further another process sequence of the sub fuel remaining amount monitoring process performed through the sub fuel remaining amount monitoring part of the said 2nd Embodiment. The flowchart which shows the further another process sequence of the sub fuel remaining amount monitoring process performed through the sub fuel remaining amount monitoring part of the said 2nd Embodiment. (A) And (b) is a figure which shows the example of a side surface structure of the supply amount variable mechanism employ | adopted by 3rd Embodiment of this invention. The figure which shows the relationship between the fuel residual amount in a sub fuel tank, and the supply amount of sub fuel about the supply amount variable mechanism employ | adopted by the said 3rd Embodiment. The flowchart which shows the process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of the said 3rd Embodiment. (A)-(c) is a timing chart which shows the example of a monitoring aspect of the sub fuel remaining amount monitoring performed in the 3rd Embodiment. The flowchart which shows the other process sequence of the monitoring execution process performed through the sub fuel remaining amount monitoring part of the said 3rd Embodiment. The flowchart which shows the further another process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of the said 3rd Embodiment. The flowchart which shows the process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of 4th Embodiment of this invention. The flowchart which shows the other process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of the same 4th Embodiment. The flowchart which shows the further another process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of the same 4th Embodiment. The flowchart which shows the further another process sequence of the monitoring execution process performed through the sub fuel residual amount monitoring part of the same 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Flex fuel engine, 11 ... Intake passage, 12 ... Combustion chamber, 13 ... Exhaust passage, 14 ... Surge tank, 15 ... Intake manifold, 16 ... Intake port, 17 ... Rotation speed sensor, 18 ... Sub fuel nozzle, 19 ... Main fuel injector, 20 ... sub fuel passage, 20a ... large diameter passage, 20b ... small diameter passage, 21 ... sub fuel tank, 22 ... sub fuel pump (for sub fuel), 23 ... main fuel passage, 24 ... main fuel tank, 25 ... main fuel pump (for main fuel), 26 ... cylinder, 27 ... piston, 28 ... spark plug, 29 ... water jacket, 30 ... water temperature sensor, 31 ... intake port, 32 ... air-fuel ratio sensor, 33 ... catalyst device, 34 ... Engine control device, 35 ... Fuel supply control unit, 36 ... Sub fuel remaining amount monitoring unit, 39 ... Warning light, 40 ... Rotational speed sensor, 41 ... Throttle sensor, 42 ... Float 211 ... float, 212 ... float valve.

Claims (14)

The auxiliary fuel of the flex fuel engine using the main fuel stored in each separate fuel tank and the auxiliary fuel composed of fuel having different properties and mainly assisting combustion at the cold start An engine control device for a flex fuel engine having a function of monitoring the remaining amount of fuel in a tank,
The supply of the auxiliary fuel is forcibly executed over a predetermined time in a steady operation state of the flex fuel engine, and the fuel of the auxiliary fuel is based on the amount of change in the air-fuel ratio of the flex fuel engine accompanying the supply of the auxiliary fuel. An engine control device for a flex fuel engine characterized by monitoring the remaining amount of fuel in the tank. The engine control apparatus for a flex fuel engine according to claim 1, wherein the change amount of the air-fuel ratio is obtained as an integral value, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on the obtained integral value. 2. The fuel remaining amount in the fuel tank of the sub fuel is monitored based on a duration over which the predetermined threshold is set for the amount of change in the air-fuel ratio. Engine control system for flex fuel engines. 2. The flex according to claim 1, wherein one or more threshold values are set for the amount of change in the air-fuel ratio, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is monitored based on a mode of reaching the set threshold value. Engine control device for fuel engines. The engine control apparatus for a flex fuel engine according to any one of claims 1 to 4, wherein a steady operation state of the flex fuel engine is an idling operation state of the engine. In the engine control device of the flex fuel engine according to any one of claims 1 to 4,
Means for detecting a change in operation control condition of the flex fuel engine, and means for canceling monitoring of the remaining amount of fuel in the fuel tank based on detection of the change in operation control condition. An engine control device for a flexure fuel engine. The auxiliary fuel of the flex fuel engine using the main fuel stored in each separate fuel tank and the auxiliary fuel composed of fuel having different properties and mainly assisting combustion at the cold start An engine control device for a flex fuel engine having a function of monitoring the remaining amount of fuel in a tank,
The auxiliary fuel is forcibly executed for a certain period of time after the ignition switch is turned off, and the auxiliary fuel is changed based on a change in time during which the operation of the flex fuel engine is continued as the auxiliary fuel is supplied. An engine control device for a flex fuel engine characterized by monitoring the remaining amount of fuel in the fuel tank. The engine control device for a flex fuel engine according to claim 7, wherein a time for which the operation of the flex fuel engine is continued is obtained as a time until the air-fuel ratio of the engine is fixed to the lean side. The engine control device for a flex fuel engine according to claim 7, wherein a time during which the operation of the flex fuel engine is continued is obtained as a time during which the engine rotation is maintained. The engine control device for a flex fuel engine according to claim 7, wherein a time during which the operation of the flex fuel engine is continued is obtained as a combustion duration in a cylinder based on detection of an ion current. The engine control device for a flex fuel engine according to claim 7, wherein a time during which the operation of the flex fuel engine is continued is obtained as a time during which engine vibration is maintained. The auxiliary fuel of the flex fuel engine using the main fuel stored in each separate fuel tank and the auxiliary fuel composed of fuel having different properties and mainly assisting combustion at the cold start An engine control device for a flex fuel engine having a function of monitoring the remaining amount of fuel in a tank,
After the ignition switch is turned off, the supply of the auxiliary fuel is forcibly executed, and the remaining amount of fuel in the fuel tank of the auxiliary fuel is determined based on whether the operation of the flex fuel engine is continued due to the supply of the auxiliary fuel. An engine control device for a flex fuel engine characterized by monitoring the engine. The flex fuel engine according to any one of claims 1 to 12, wherein the fuel tank for the auxiliary fuel is provided with a supply amount variable mechanism for changing a supply amount in accordance with a remaining fuel amount of the auxiliary fuel. Engine control device. The engine control apparatus for a flex fuel engine according to any one of claims 1 to 13,
An engine control apparatus for a flex fuel engine, further comprising an informing means for informing a monitoring result of a remaining amount of fuel in the fuel tank of the auxiliary fuel .

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