JP4701897B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that calculates a correction value for an injection amount of fuel and injects an amount of fuel according to the calculated correction value.

  Conventionally, in order to maintain the air-fuel ratio of the air-fuel mixture at a desired air-fuel ratio (for example, the stoichiometric air-fuel ratio), there is a technique for detecting the air-fuel ratio in the exhaust gas by an air-fuel ratio sensor or the like and correcting the fuel injection amount by feedback control. Are known.

  Japanese Patent Application Laid-Open No. 58-25540 (Patent Document 1) discloses an air-fuel ratio control method for controlling an air-fuel ratio based on a detection signal of an air-fuel ratio sensor that detects an air-fuel ratio from an exhaust gas component of an engine. In this air-fuel ratio control method, the air-fuel ratio is proportionally integrated based on the detection signal of the air-fuel ratio sensor, and the learning value is made corresponding to the engine operating state based on the proportional-integral correction amount obtained by the proportional-integral processing. The engine state correction amount is calculated and stored, and the stored engine state correction amount as the learned value is set to a predetermined correction amount when the air-fuel ratio sensor is rich or lean or when the proportional integral correction direction is changed. The engine air-fuel ratio is corrected to the target air-fuel ratio according to the engine state correction amount as the corrected learning value.

According to the air-fuel ratio control method described in this publication, the center of the air-fuel ratio can be clarified without being affected by the fluctuation cycle of the air-fuel ratio. Therefore, highly accurate air-fuel ratio control based on accurate correction storage can be performed.
JP 58-25540 A

  By the way, in particular, in an internal combustion engine provided with an in-cylinder injector that directly injects fuel into the cylinder, a large amount of injected fuel may adhere to the cylinder inner circumferential surface (cylinder inner circumferential surface (bore)). . The fuel adhering to the inner circumferential surface of the cylinder is mixed with the lubricating oil adhering to the inner circumferential surface of the cylinder for lubricating the engine piston. As a result, the lubricating oil is diluted with the fuel. Then, the lubricating oil in the cylinder diluted with the fuel is scraped off as the engine piston moves up and down, returned to the oil pan, and then used for lubricating the internal combustion engine. The fuel dissolved in the lubricating oil evaporates in the crankcase or the like, and is returned to the cylinder again via a PCV (Positive Crankcase Ventilation) valve or the like. Therefore, the air-fuel ratio becomes an air-fuel ratio in consideration of the fuel injected from the injector and the fuel for diluting the lubricating oil. Therefore, the learning value of the air-fuel ratio in the air-fuel ratio learning method described in JP-A-58-25540 is affected by the fuel that dilutes the lubricating oil. However, the amount of evaporation of the fuel that dilutes the lubricating oil is not constant and decreases when the temperature is low. Therefore, at the time of cold start of the engine, if the fuel amount is controlled using the learning value obtained during the warm time, the injected fuel amount can be reduced more than necessary. For this reason, the air-fuel ratio becomes leaner than the target air-fuel ratio, which may become inappropriate.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a control device for an internal combustion engine that can appropriately control an air-fuel ratio.

  A control apparatus for an internal combustion engine according to a first aspect controls an internal combustion engine provided with fuel injection means for injecting fuel. The control device includes a detection unit for detecting an air-fuel ratio of the internal combustion engine, a calculation unit for calculating a correction value for the fuel injection amount based on the detected air-fuel ratio, and an amount of fuel corresponding to the correction value. The control means for controlling the fuel injection means, the estimation means for estimating the degree of dilution of the lubricating oil used for lubricating the internal combustion engine with the fuel, and the correction value according to the degree Determining means for determining the storage range.

  According to the first invention, the correction value for the fuel injection amount is calculated based on the air-fuel ratio of the internal combustion engine. The air-fuel ratio of the internal combustion engine is influenced by the fuel that dilutes the lubricating oil of the internal combustion engine in addition to the fuel injected from the fuel injection means. Since the amount of fuel that evaporates from the lubricating oil varies depending on the temperature, if the fuel is injected in the cold state using the correction value obtained when the internal combustion engine is warm, the fuel injection amount is reduced more than necessary, and the air-fuel ratio is reduced. It can be lean with respect to the target air-fuel ratio. This tendency becomes more prominent as the amount of fuel that dilutes the lubricating oil increases and the correction amount of the injection amount increases. In order to suppress such reduction correction of the fuel injection amount, a correction value in a range corresponding to the degree to which the lubricating oil is diluted with fuel is stored. For example, when it is estimated that the degree of dilution of the lubricating oil with the fuel is large, storage of a correction value in a range in which the correction amount of the fuel injection amount is larger than a predetermined amount is prohibited. As a result, when the internal combustion engine is temporarily stopped and then restarted, the amount of fuel corresponding to the correction value obtained in a state where the degree of dilution of the lubricating oil is large and the correction amount of the injection amount is large. Can be suppressed. That is, it is possible not to be caused by abnormality of the fuel injection means, but to suppress the injection of fuel in an amount corresponding to the correction value obtained in a state where the influence of the fuel evaporated from the lubricating oil is strongly received. Therefore, at the time of cold start of the internal combustion engine, it is possible to suppress the fuel injection amount from being reduced more than necessary and to prevent the air-fuel ratio from becoming lean relative to the target air-fuel ratio. As a result, it is possible to provide a control device for an internal combustion engine that can appropriately control the air-fuel ratio.

  In the control apparatus for an internal combustion engine according to the second invention, in addition to the configuration of the first invention, the determining means prohibits the storage of a correction value in a predetermined range when the degree of estimation is estimated to be large. Means for doing so.

  According to the second invention, when it is estimated that the degree of dilution of the lubricating oil with the fuel is large, for example, the correction value in a range in which the correction amount of the fuel injection amount is larger than a predetermined amount. Memory is prohibited. As a result, when the internal combustion engine is temporarily stopped and then restarted, the amount of fuel corresponding to the correction value obtained in a state where the degree of dilution of the lubricating oil is large and the correction amount of the injection amount is large. Can be suppressed. That is, it is possible not to be caused by abnormality of the fuel injection means, but to suppress the injection of fuel in an amount corresponding to the correction value obtained in a state where the influence of the fuel evaporated from the lubricating oil is strongly received. Therefore, at the time of cold start of the internal combustion engine, it is possible to suppress the fuel injection amount from being reduced more than necessary and to prevent the air-fuel ratio from becoming lean relative to the target air-fuel ratio. As a result, the air-fuel ratio can be controlled appropriately.

  In the control device for an internal combustion engine according to the third invention, in addition to the configuration of the second invention, the predetermined range is a range in which the correction amount of the fuel injection amount is larger than the predetermined amount. .

  According to the third invention, when it is estimated that the degree of dilution of the lubricating oil with the fuel is large, the correction value in the range in which the correction amount of the fuel injection amount is larger than a predetermined amount is stored. It is forbidden. As a result, when the internal combustion engine is temporarily stopped and then restarted, the amount of fuel corresponding to the correction value obtained in a state where the degree of dilution of the lubricating oil is large and the correction amount of the injection amount is large. Can be suppressed. That is, it is possible not to be caused by abnormality of the fuel injection means, but to suppress the injection of fuel in an amount corresponding to the correction value obtained in a state where the influence of the fuel evaporated from the lubricating oil is strongly received. Therefore, at the time of cold start of the internal combustion engine, it is possible to suppress the fuel injection amount from being reduced more than necessary and to prevent the air-fuel ratio from becoming lean relative to the target air-fuel ratio. As a result, the air-fuel ratio can be controlled appropriately.

  In the control apparatus for an internal combustion engine according to the fourth invention, in addition to the configuration of any one of the first to third inventions, the fuel injection means is a first fuel injection means for injecting fuel into the cylinder. . The internal combustion engine is provided with a second fuel injection means for injecting fuel into the intake passage in addition to the first fuel injection means.

  According to the fourth aspect of the present invention, in the internal combustion engine in which fuel is injected into the cylinder and the intake passage, the fuel injection amount is reduced more than necessary at the cold start, and the air-fuel ratio becomes leaner than the target air-fuel ratio. Therefore, the air-fuel ratio can be appropriately controlled.

  In the control apparatus for an internal combustion engine according to the fifth invention, in addition to the configuration of the fourth invention, the first fuel injection means is an in-cylinder injector. The second fuel injection means is an intake passage injection injector.

  According to a fifth aspect of the present invention, there is provided an internal combustion engine in which an in-cylinder injector that is a first fuel injection means and an intake passage injection injector that is a second fuel injection means are separately provided to share injected fuel. It is possible to appropriately control the air-fuel ratio by suppressing the fuel ratio from becoming lean with respect to the target air-fuel ratio.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
FIG. 1 shows a schematic configuration diagram of an engine system controlled by an engine ECU (Electronic Control Unit) which is a control device for an internal combustion engine according to a first embodiment of the present invention. Although FIG. 1 shows an in-line four-cylinder gasoline engine as an engine, the present invention is not limited to such an engine, and various types of engines such as a V-type 6-cylinder engine and a V-type 8-cylinder engine can be used. Applicable to engine.

  As shown in FIG. 1, the engine 10 includes four cylinders 112, and each cylinder 112 is connected to a common surge tank 30 via a corresponding intake manifold 20. The surge tank 30 is connected to an air cleaner 50 via an intake duct 40, an air flow meter 42 is disposed in the intake duct 40, and a throttle valve 70 driven by an electric motor 60 is disposed. The opening degree of throttle valve 70 is controlled based on the output signal of engine ECU 300 independently of accelerator pedal 100. On the other hand, each cylinder 112 is connected to a common exhaust manifold 80, and this exhaust manifold 80 is connected to a three-way catalytic converter 90.

  For each cylinder 112, an in-cylinder injector 110 for injecting fuel into the cylinder, and an intake passage injection injector 120 for injecting fuel into the intake port or / and the intake passage. And are provided respectively. These injectors 110 and 120 are controlled based on the output signal of engine ECU 300, respectively. The in-cylinder injectors 110 are connected to a common fuel distribution pipe 130, and this fuel distribution pipe 130 is connected to the fuel distribution pipe 130 through a check valve 140, and is driven by an engine. A high-pressure fuel pump 150 is connected. In the present embodiment, an internal combustion engine in which two injectors are separately provided will be described, but the present invention is not limited to such an internal combustion engine. For example, it may be an internal combustion engine having one injector that has both an in-cylinder injection function and an intake passage injection function. Further, either one of the in-cylinder injector 110 and the intake passage injector 120 may be provided.

  As shown in FIG. 1, the discharge side of the high-pressure fuel pump 150 is connected to the suction side of the high-pressure fuel pump 150 via an electromagnetic spill valve 152. When the amount of fuel supplied from the pump 150 into the fuel distribution pipe 130 is increased and the electromagnetic spill valve 152 is fully opened, the fuel supply from the high pressure fuel pump 150 to the fuel distribution pipe 130 is stopped. ing. Electromagnetic spill valve 152 is controlled based on the output signal of engine ECU 300.

  On the other hand, each intake passage injector 120 is connected to a common low-pressure fuel distribution pipe 160, and the fuel distribution pipe 160 and the high-pressure fuel pump 150 are connected to a common fuel pressure regulator 170 through an electric motor drive type. The low-pressure fuel pump 180 is connected. Further, the low pressure fuel pump 180 is connected to the fuel tank 200 via a fuel filter 190. The fuel pressure regulator 170 returns a part of the fuel discharged from the low-pressure fuel pump 180 to the fuel tank 200 when the fuel pressure of the fuel discharged from the low-pressure fuel pump 180 becomes higher than a predetermined set fuel pressure. Accordingly, the fuel pressure supplied to the intake manifold injector 120 and the fuel pressure supplied to the high-pressure fuel pump 150 are prevented from becoming higher than the set fuel pressure.

  The lubrication system of the engine 10 includes an oil pan formed as a part of a crankcase and a lubricating oil supply device. This lubricating oil supply device includes an oil pump, a filter, an oil jet mechanism, and the like. The lubricating oil in the oil pan is sucked by the oil pump through the filter and supplied to the oil jet mechanism. In lubricating between the piston and the cylinder inner peripheral surface (bore), the lubricating oil supplied to the oil jet mechanism is supplied from this mechanism to the cylinder inner peripheral surface. Thereafter, as the piston reciprocates, the lubricating oil is scraped downward from the inner circumferential surface of the cylinder and finally returned to the oil pan. Then, the scraped lubricating oil is mixed with the lubricating oil in the oil pan and then used for lubricating the engine 10 again. The lubricating oil supplied to the cylinder inner peripheral surface and used for lubricating the piston rises in temperature due to the combustion heat of the engine 10 and is then returned to the oil pan.

  The engine ECU 300 is composed of a digital computer, and is connected to each other via a bidirectional bus 310, a ROM (Read Only Memory) 320, a RAM (Random Access Memory) 330, a CPU (Central Processing Unit) 340, and an input port 350. And an output port 360.

  The air flow meter 42 generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 42 is input to the input port 350 via the A / D converter 370. A water temperature sensor 380 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine 10, and the output voltage of the water temperature sensor 380 is input to the input port 350 via the A / D converter 390.

  A fuel pressure sensor 400 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 130 is attached to the fuel distribution pipe 130, and the output voltage of the fuel pressure sensor 400 is input via the A / D converter 410. Input to port 350. The exhaust manifold 80 upstream of the three-way catalytic converter 90 is provided with an air-fuel ratio sensor 420 that generates an output voltage proportional to the oxygen concentration in the exhaust gas. The output voltage of the air-fuel ratio sensor 420 is converted into an A / D converter. It is input to the input port 350 via 430.

The air-fuel ratio sensor 420 in the engine system according to the present embodiment is a global air-fuel ratio sensor (linear air-fuel ratio sensor) that generates an output voltage proportional to the air-fuel ratio of the air-fuel mixture burned by the engine 10. The air-fuel ratio sensor 420 may be an O ₂ sensor that detects whether the air-fuel ratio of the air-fuel mixture burned in the engine 10 is rich or lean with respect to the stoichiometric air-fuel ratio. Good.

  In the present embodiment, engine ECU 300 calculates a feedback correction amount for the total fuel injection amount based on the output voltage of air-fuel ratio sensor 420. Further, when a predetermined learning condition is satisfied, a learning value of the feedback correction amount (a value representing a constant deviation amount of the fuel injection amount) is calculated. The calculation of the feedback correction amount and its learning value is performed within a predetermined learning region with the intake air amount as a parameter. The learning area will be described in detail later.

  In the present embodiment, when the air-fuel ratio is lean (when leaner than the stoichiometric air-fuel ratio), the feedback correction amount is calculated to increase. When the air-fuel ratio is rich (when it is richer than the theoretical air-fuel ratio), the feedback correction amount is calculated to decrease. In addition, since it is sufficient to use a known general technique for the calculation method of the feedback correction amount, further detailed description will not be repeated here.

  The learning value is calculated by adding the update amount determined based on the map to the previously calculated learning value or subtracting from the previously calculated learning value when a predetermined learning condition is satisfied. The The predetermined learning condition is, for example, a condition that the average value (control center value) of the feedback correction amount is smaller than the threshold value (1) or the threshold value (2) (threshold value (2)> threshold value. It is a condition that it is larger than (1)).

The learning value is calculated as a smaller value as the fuel injection amount is excessive (as the actual fuel injection amount is larger than the target fuel injection amount). On the other hand, the smaller the fuel injection amount (the smaller the actual fuel injection amount than the target fuel injection amount), the larger the learning value is calculated.
In addition, about the calculation method of a learning value, what is necessary is just to use a well-known general technique, Therefore Here, detailed description is not repeated.

  The fuel injection amount is corrected based on the feedback correction amount and the learned value. That is, the larger the feedback correction amount and the learning value, the more the fuel injection amount is corrected. The smaller the feedback correction amount and the learned value, the smaller the fuel injection amount is corrected. In the present embodiment, the fuel injection amount correction amount (hereinafter also referred to as fuel correction amount) is calculated as the sum of the feedback correction amount and the learning value.

  The accelerator pedal 100 is connected to an accelerator opening sensor 440 that generates an output voltage proportional to the depression amount of the accelerator pedal 100, and the output voltage of the accelerator opening sensor 440 is input to the input port 350 via the A / D converter 450. Is input. The input port 350 is connected to a rotational speed sensor 460 that generates an output pulse representing the engine rotational speed. The fuel injection set in the ROM 320 of the engine ECU 300 is set in accordance with the operating state (intake air amount, etc.) based on the engine load factor and the engine speed obtained by the accelerator opening sensor 440 and the engine speed sensor 460 described above. A quantity value, a correction value based on the engine coolant temperature, and the like are previously mapped and stored.

Referring to FIGS. 2 and 3, the injection ratio of in-cylinder injector 110 and intake manifold injector 120 (hereinafter referred to as DI ratio (r)), which is information corresponding to the operating state of engine 10, is also referred to. Will be described). These maps are
It is stored in ROM 320 of engine ECU 300. FIG. 2 is a map for the warm of the engine 10, and FIG. 3 is a map for the cold of the engine 10.

  As shown in FIG. 2 and FIG. 3, these maps are expressed in percentages where the engine 10 rotational speed is on the horizontal axis, the load factor is on the vertical axis, and the share ratio of the in-cylinder injector 110 is the DI ratio r. It is shown.

  As shown in FIGS. 2 and 3, the DI ratio r is set for each operation region determined by the rotation speed and load factor of the engine 10. “DI ratio r = 100%” means a region where fuel injection is performed only from in-cylinder injector 110, and “DI ratio r = 0%” means from intake manifold injector 120. This means that only the region where fuel injection is performed. “DI ratio r ≠ 0%”, “DI ratio r ≠ 100%” and “0% <DI ratio r <100%” indicate that in-cylinder injector 110 and intake passage injector 120 perform fuel injection. It means that the area is shared. In general, the in-cylinder injector 110 contributes to an increase in output performance, and the intake manifold injector 120 contributes to the uniformity of the air-fuel mixture. By using two types of injectors having different characteristics depending on the rotation speed and load factor of the engine 10, the engine 10 is in a normal operation state (for example, when the catalyst is warmed up at idle when the engine 10 is in an abnormal state other than the normal operation state). In this case, only homogeneous combustion is performed.

  Further, as shown in FIG. 2 and FIG. 3, the DI share ratio r of the in-cylinder injector 110 and the intake manifold injector 120 is defined by dividing it into a warm map and a cold map. did. If the temperature of the engine 10 is different, the temperature of the engine 10 is detected by detecting the temperature of the engine 10 using a map set so that the control areas of the in-cylinder injector 110 and the intake manifold injector 120 are different. If it is equal to or higher than a predetermined temperature threshold value, the warm time map shown in FIG. 2 is selected. Otherwise, the cold time map shown in FIG. 3 is selected. Based on the selected maps, the in-cylinder injector 110 and / or the intake manifold injector 120 are controlled based on the rotation speed and load factor of the engine 10.

  In the present embodiment, the fuel injection amount from in-cylinder injector 110 and the fuel from intake manifold injector 120 are based on DI ratio r so that the total fuel injection amount becomes a desired injection amount. The injection amount is determined.

  The engine speed and load factor of engine 10 set in FIGS. 2 and 3 will be described. In FIG. 2, NE (1) is set to 2500 to 2700 rpm, KL (1) is set to 30 to 50%, and KL (2) is set to 60 to 90%. Further, NE (3) in FIG. 3 is set to 2900-3100 rpm. That is, NE (1) <NE (3). In addition, NE (2) in FIG. 2 and KL (3) and KL (4) in FIG. 3 are also set as appropriate.

  When FIG. 2 and FIG. 3 are compared, NE (3) of the map for cold shown in FIG. 3 is higher than NE (1) of the map for warm shown in FIG. This indicates that as the temperature of the engine 10 is lower, the control range of the intake manifold injector 120 is expanded to a higher engine speed range. That is, since the engine 10 is in a cold state, deposits are unlikely to accumulate at the injection port of the in-cylinder injector 110 (even if fuel is not injected from the in-cylinder injector 110). For this reason, it sets so that the area | region which injects a fuel using the intake manifold injector 120 may be expanded, and a homogeneity can be improved.

  Comparing FIG. 2 and FIG. 3, in the region where the engine 10 has a rotational speed of NE (1) or higher in the warm map and in the region of NE (3) or higher in the cold map, “DI ratio r = 100% ". Further, the load factor is “DI ratio r = 100%” in the region of KL (2) or higher in the warm map and in the region of KL (4) or higher in the cold map. This indicates that only the in-cylinder injector 110 is used in a predetermined high engine speed region, and only the in-cylinder injector 110 is used in a predetermined high engine load region. . That is, in the high speed region and the high load region, even if the fuel is injected only by the in-cylinder injector 110, the engine 10 has a high rotational speed and load, and the intake amount is large. It is because it is easy to homogenize. Thus, the fuel injected from the in-cylinder injector 110 is vaporized with latent heat of vaporization (sucking heat from the combustion chamber) in the combustion chamber. Thereby, the temperature of the air-fuel mixture at the compression end is lowered. As a result, the knocking performance is improved. Further, since the temperature of the combustion chamber is lowered, the suction efficiency is improved and high output can be expected.

  In the warm map shown in FIG. 2, only the in-cylinder injector 110 is used below the load factor KL (1). This indicates that when the temperature of the engine 10 is high, only the in-cylinder injector 110 is used in a predetermined low load region. This is because when the engine 10 is warm, the engine 10 is in a warm state, and deposits are likely to accumulate at the injection port of the in-cylinder injector 110. However, since the injection port temperature can be lowered by injecting fuel using the in-cylinder injector 110, it is conceivable to avoid deposit accumulation, and the minimum fuel injection amount of the in-cylinder injector Therefore, it is conceivable that the in-cylinder injector 110 is not blocked, and for this reason, the in-cylinder injector 110 is used as an area.

  Comparing FIG. 2 and FIG. 3, the region of “DI ratio r = 0%” exists only in the cold map of FIG. 3. This indicates that when the temperature of the engine 10 is low, only the intake manifold injector 120 is used in a predetermined low load region (KL (3) or less). This is because the engine 10 is cold and the load on the engine 10 is low and the intake air amount is low, so that the fuel is difficult to atomize. In such a region, it is difficult to perform good combustion with the fuel injection by the in-cylinder injector 110. In particular, a high output using the in-cylinder injector 110 is required in the region of low load and low rotation speed. Therefore, only the intake passage injector 120 is used without using the in-cylinder injector 110.

  In addition, in the case other than the normal operation, the in-cylinder injector 110 is controlled so as to perform stratified combustion when the engine 10 is at the time of catalyst warm-up when idling (in a non-normal operation state). By performing stratified charge combustion only during such catalyst warm-up operation, catalyst warm-up is promoted and exhaust emission is improved.

  With reference to FIG. 4 and FIG. 5, the learning region in which the feedback correction amount and its learning value are calculated will be described. FIG. 4 shows a learning region in the warm map, and FIG. 5 shows a learning region in the cold map.

  In FIG. 4 and FIG. 5, a region sandwiched by curves indicated by alternate long and short dashed lines is a learning region. The learning area is divided according to the intake air amount. The reason why the learning area is set according to the intake air amount is that the error in the output of the air flow meter 42 differs depending on the intake air amount.

  In the present embodiment, four learning areas from learning areas (1) to (4) are provided. The intake air amount increases in the order of the learning area (1), the learning area (2), the learning area (3), and the learning area (4). Note that the number of learning regions is not limited to four.

  In the present embodiment, in addition to the learning area, the injection area ("DI ratio r = 100%" area, "0% <DI ratio r <100%" area, and "DI ratio r = 0%" area) ), The feedback correction amount and its learning value are calculated. That is, for each injection region, a feedback correction amount is calculated for each learning region, and a learning value is calculated corresponding to the injection region and the learning region as shown in FIG. FIG. 6 shows a state in which one learning value is calculated for each learning region in each injection region. Square points in FIG. 6 indicate learning values in the region of “DI ratio r = 100%”. Circle points indicate learning values in the region of “0% <DI ratio r <100%”. Triangular points indicate learning values in the region of “DI ratio r = 0%”. The calculated learning value is stored in the RAM 330. For example, an SRAM (Static Random Access Memory) is used as the RAM 330 in which the learning value is stored.

  With reference to FIG. 7, a control structure of a program executed by engine ECU 300 which is the control apparatus according to the present embodiment will be described. The program shown in the flowchart of FIG. 7 is performed every predetermined time period T.

  In step (hereinafter, step is abbreviated as S) 100, engine ECU 300 executes an oil dilution degree calculation process. The processing in S100 is provided as a separate subroutine and will be described in detail with reference to FIG.

  In S200, engine ECU 300 determines whether or not the oil dilution is large. This determination is made based on whether or not a fuel dilution occurrence flag XS, which will be described later, is in an ON state. If fuel dilution occurrence flag XS indicating that the oil dilution is large is ON (YES in S200), the process proceeds to S300. If not (NO in S200), this process ends.

  In S300, engine ECU 300 prohibits storage of a learned value in a range smaller than the threshold value. That is, engine ECU 300 prohibits storage of a learned value in a range where the fuel injection amount reduction correction amount is larger than a predetermined amount. Thereby, when the oil dilution degree is large, engine ECU 300 has only a learning value in a range larger than the threshold value (learning value in a range where the fuel injection amount reduction correction amount is smaller than a predetermined amount). Is stored in the RAM 330. Thereafter, this process ends.

  With reference to FIG. 8, the control structure of the subroutine program of the oil dilution degree calculation process in S100 of FIG. 7 will be described.

  In the present embodiment, the increase rate and decrease rate of the fuel dilution degree of the entire lubricating oil are periodically calculated, and the currently estimated value of the fuel dilution degree is calculated as the increase rate and decrease rate. And the updated value is learned as a new value of the degree of fuel dilution.

  Since engine ECU 300 executes the program shown in the flowchart of FIG. 7 every predetermined time period T, the subroutine program shown in the flowchart of FIG. 8 is also repeatedly executed every predetermined time period T.

  In S110, engine ECU 300 calculates fuel dilution amount ΔFD per unit time based on equation (1), that is, the amount of fuel newly mixed into the lubricating oil through fuel injection performed during time period T. The Further, this fuel dilution amount ΔFD corresponds to an increase rate of the degree of fuel dilution when fuel evaporation from the entire lubricating oil is not taken into consideration.

ΔFD ← Σf (QINJi, AINJi, THWi) (1)
Here, i = 1, 2, 3,..., N, f () is a function for obtaining a fuel dilution amount generated by one fuel injection, and when the fuel injection is executed, The fuel injection amount QINJ, fuel injection timing AINJ, and engine coolant temperature THW are used as parameters. “I” indicates how many times the fuel injection corresponds to the previous control cycle. For example, when fuel injection is performed three times between the previous control cycle and the current control cycle, Equation (1) can be expressed as Equation (2).

ΔFD ← f (QINJ1, AINJ2, THW1) + f (QINJ2, AINJ2, THW2) + f (QINJ3, AINJ2, THW3) (2)
This function f () is obtained in advance by experiments or the like, and is stored as a function map in the ROM 320 of the engine ECU 300. Further, the basic characteristics are: 1) the value of the function f () increases as the fuel injection amount QINJ increases. 2) the value of the function f () increases as the fuel injection timing AINJ is on the retard side. 3) The value of the function f () increases as the engine coolant temperature THW decreases.

  The reason why the fuel injection amount QINJ, the fuel injection timing AINJ, and the engine coolant temperature THW are selected as the parameters of the function f () is as follows. Fuel dilution caused by fuel injection occurs when the fuel adhering to the cylinder inner peripheral surface remains without being combusted. Therefore, as the amount of fuel adhering to the cylinder inner peripheral surface increases, the fuel of the entire lubricating oil increases. It is thought that the degree of dilution also increases greatly. It is usually difficult to directly detect the amount of fuel adhering to the cylinder inner surface, but if a parameter having a correlation with the amount of fuel adhering to the cylinder inner surface is appropriately selected, this can be estimated accurately. Can be requested.

The fuel injection amount QINJ, the fuel injection timing AINJ, and the engine cooling water temperature THW are all representative examples of parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface. For example, if the fuel injection amount QINJ increases, the amount of fuel attached to the cylinder inner peripheral surface naturally increases. Further, when fuel adheres to the cylinder inner peripheral surface, there is an upper limit for the amount of fuel that can adhere per unit area, in other words, the thickness of the fuel layer formed on the cylinder inner peripheral surface. Therefore, if the fuel adhesion area increases, the thickness of the fuel layer does not reach the upper limit value, and more fuel can adhere to the cylinder inner peripheral surface. This fuel adhesion area, that is, the area of the cylinder inner peripheral surface exposed to the combustion chamber without being covered by the piston at the time of fuel injection, is determined by the fuel injection timing AINJ. The time becomes larger as the time AINJ is set to the retarded time. Therefore, the fuel deposition amount on the cylinder inner peripheral surface increases as the fuel injection timing AINJ is set to a more retarded timing.

  Furthermore, fuel adhesion on the cylinder inner peripheral surface or the like basically becomes noticeable when the atomization of the injected fuel is not promoted and its particle size is large. In addition, the degree of atomization greatly depends on the temperature of the combustion chamber and the fuel when the fuel injection pressure is constant. Furthermore, the temperature of these combustion chambers and fuel has a correlation with the engine coolant temperature THW. Therefore, as the engine coolant temperature THW is lower, the atomization of the fuel is not promoted, so that the amount of fuel adhering to the inner circumferential surface of the cylinder increases.

  In the present embodiment, in consideration of these points, the fuel injection amount QINJ, the fuel injection timing AINJ, and the engine cooling water temperature THW are selected as parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface. .

  In S120, engine ECU 300 calculates fuel evaporation amount ΔFV per unit time, that is, the amount of fuel evaporated from the entire lubricating oil during time period T, based on equation (3). Further, this fuel evaporation amount ΔFV corresponds to the rate of decrease in the degree of fuel dilution when fuel dilution due to fuel injection is not taken into consideration.

ΔFV ← g (THWST, QINJSUM, GASUM) (3)
Here, g () is a function for obtaining the fuel evaporation amount ΔFV per time period T, the engine starting water temperature THWST, the fuel injection amount integrated value QINJSUM after the engine start, and the intake air amount integration after the engine start. The value GASUM is used as a parameter. Incidentally, the engine starting water temperature THWST is for estimating the initial temperature of the lubricating oil at the time of engine starting, and the fuel injection amount integrated value QINJSUM and the intake air amount integrated value GASUM after the engine start are the subsequent lubricating oil. It is for estimating the temperature rise amount. That is, the function g () is basically for estimating the lubricating oil temperature and converting the estimation result into the amount of fuel evaporation. This function g () is obtained in advance through experiments or the like, and is stored as a function map in the ROM 320 of the engine ECU 300. The basic characteristics are as follows. 1) The value of g () increases as the engine coolant temperature THWST increases. 2) The value of g () increases as the fuel injection amount integrated value QINJSUM after the engine starts increases. 3) Suction after the engine starts. As the air amount integrated value GSUM increases, the value of g () increases. In this way, the fuel dilution amount ΔFD and the fuel evaporation amount ΔFV per unit time are calculated.

  In S130, engine ECU 300 calculates a fuel dilution degree FDSUM based on equation (4).

FDSUM ← FDSUM + ΔFD−ΔFV (4)
As shown in Expression (4), here, the current fuel dilution degree FDSUM is updated based on the increase rate ΔFD and the decrease rate ΔFV of the fuel dilution degree FDSUM. Then, the updated value is learned as a new fuel dilution degree FDSUM and stored in a non-volatile RAM constituting engine ECU 300. By storing the fuel dilution degree FDSUM in the non-volatile RAM, it is possible to prevent erroneous detection of OBD (On Board Diagnosis) when the auxiliary battery is replaced.

  In S140, engine ECU 300 compares fuel dilution degree FDSUM with determination value FDSUMH. If the fuel dilution degree FDSUM is equal to or greater than the determination value FDSUMH (YES in S140), the fuel dilution degree of the entire lubricating oil is increased. If the fuel dilution further proceeds, the adverse effects such as deterioration of the lubricating performance are no longer ignored. It is determined that the size becomes too large to be performed, and the process proceeds to S150. If not (NO in S140), the process proceeds to S160.

  In S150, engine ECU 300 sets fuel dilution occurrence flag XS to “ON”.

  In S160, engine ECU 300 compares fuel dilution degree FDSUM with determination value FDSUML (<FDSUMH). If fuel dilution degree FDSUM is equal to or smaller than determination value FDSUML (YES in S160), the fuel dilution degree of the entire lubricating oil is small, so that fuel dilution is temporarily generated by fuel injection, and the fuel dilution degree of the entire lubricating oil is reduced. Even if it proceeds, it is determined that the adverse effect on the engine 10 due to this is almost negligible, and the process proceeds to S170. Otherwise (NO in S160), this process ends.

  In S170, engine ECU 300 sets fuel dilution occurrence flag XS to “OFF”.

  It should be noted that the determination values FDSUML, FDSUMH are set so as to be different from each other by setting a magnitude relationship of (FDSUML <FDSUMH), so that a so-called hysteresis is given to the execution condition when the fuel dilution occurrence flag XS is turned on / off. With this setting, for example, the fuel dilution occurrence flag XS is excessively turned on / off even though the operating state of the engine 10 has not changed, and the fuel pressure is frequently changed in a short time. Instability of fuel injection control, which is a concern when such hysteresis is not set, can be avoided.

  The operation of engine ECU 300 that is the control device for the internal combustion engine according to the present embodiment based on the above-described structure and flowchart will be described. In the following description, it is assumed that the fuel dilution occurrence flag XS shown in FIG. 8 is set to the ON state.

  In this state, it is determined that the degree of dilution of the oil is large due to the fuel injected from the injector (YES in S200). In this case, the fuel that evaporates from the oil and returns to the cylinder from the PCV valve or the like has a great influence on the air-fuel ratio of the air-fuel mixture. Therefore, the air-fuel ratio detected by the air-fuel ratio sensor 420 becomes richer than the target air-fuel ratio (for example, the theoretical air-fuel ratio). Therefore, the learning value of the feedback correction amount is calculated so as to reduce the fuel injection amount from the injector.

  If this learning value is stored in the RAM 330 as it is, an amount of fuel based on the stored learning value is injected when the engine 10 is once stopped and then restarted. At this time, when the engine 10 is cold, that is, at the time of cold start, the amount of fuel evaporated from the oil is smaller than that at the warm time. When the learned value obtained is used, the amount of fuel to be injected is insufficient with respect to the target air-fuel ratio. That is, the actual air-fuel ratio becomes leaner than the target air-fuel ratio.

  In order to suppress this, when it is determined that the degree of oil dilution with fuel is large (YES in S200), storage of learned values in a range smaller than the threshold is prohibited (S300). As a result, storage of a learned value in a range where the fuel injection amount reduction correction amount is larger than a predetermined amount is prohibited, and a learning value in a range larger than the threshold value (the fuel injection amount reduction correction amount is predetermined). Only learned values in a range smaller than the determined amount) are stored in the RAM 330. Therefore, when the engine 10 is once stopped and the engine 10 is cooled and started, the amount of fuel to be injected is reduced more than necessary, and the air / fuel ratio is prevented from becoming leaner than the target air / fuel ratio. it can.

  On the other hand, if the learned value is larger than the threshold value (NO in S300), that is, if the fuel injection amount reduction correction amount is smaller than a predetermined amount, the amount of fuel based on the learned value at this time Even when the engine is injected at a cold start after the engine is stopped, the degree of fuel shortage is small. Therefore, storage of learning values is not prohibited. Thereby, the fuel quantity appropriately controlled by the learning value can be obtained. Therefore, the air-fuel ratio can be brought close to the target air-fuel ratio.

  As described above, according to the engine ECU that is the control device according to the present embodiment, when it is determined that the degree of oil dilution by fuel is large, the learning value (fuel injection range) smaller than the threshold value is determined. Storage of a learning value in a range where the amount of reduction correction amount is large. Therefore, when the engine is warm and the degree of dilution of the oil by the fuel is large, the learning value obtained so as to greatly reduce the fuel injection amount is used. It is possible to suppress the amount of fuel injected at, and the air-fuel ratio from becoming lean relative to the target air-fuel ratio.

  In the present embodiment, the fuel dilution degree FDSUM is calculated from the fuel dilution amount ΔFD and the fuel evaporation amount ΔFV per unit time. However, the method for calculating the fuel dilution degree FDSUM is not limited to this. The fuel dilution degree FDSUM may be calculated without calculating the fuel dilution amount ΔFD and the fuel evaporation amount ΔFV. That is, at least one of fuel injection amount QINJ, fuel injection timing AINJ, engine cooling water temperature THW, engine starting water temperature THWST, fuel injection amount integrated value QINJSUM after engine start, and intake air amount integrated value GASUM after engine start As a parameter, the fuel dilution degree FDSUM may be calculated.

  In addition, when it is determined that the degree of oil dilution by fuel is large, instead of prohibiting storage of learned values in a range smaller than the threshold value, only the feedback correction amount is calculated and the range smaller than the threshold value is calculated. The learning value calculation itself may be prohibited.

<Second Embodiment>
With reference to FIG. 9 and FIG. 10, a second embodiment of the present invention will be described. In the present embodiment, the DI ratio r is calculated using a map different from that of the first embodiment.

  Other structures and processing flow are the same as those in the first embodiment. The function about them is the same. Therefore, detailed description thereof will not be repeated here.

  With reference to FIG. 9 and FIG. 10, a map representing an injection ratio between in-cylinder injector 110 and intake passage injector 120 that is information corresponding to the operating state of engine 10 will be described. These maps are stored in the ROM 320 of the engine ECU 300. FIG. 9 is a map for the warm of the engine 10, and FIG. 10 is a map for the cold of the engine 10.

  9 and 10 differ from FIGS. 2 and 3 in the following points. The rotational speed of the engine 10 is “DI ratio r = 100%” in the region of NE (1) or more in the warm map and in the region of NE (3) or more in the cold map. In the region where the load factor is KL (2) or higher excluding the low rotational speed region in the warm map, and in the region where KL (4) is higher than the low rotational speed region in the cold map, “DI” Ratio r = 100% ”. This is because only the in-cylinder injector 110 is used in a predetermined high engine speed region, and only the in-cylinder injector 110 is used in a predetermined high engine load region. Indicates. However, in the high load region of the low engine speed region, mixing of the air-fuel mixture formed by the fuel injected from the in-cylinder injector 110 is not good, and the air-fuel mixture in the combustion chamber is inhomogeneous and combustion is unstable. Tend to be. For this reason, the injection ratio of the in-cylinder injector is increased with the shift to the high rotation speed region where such a problem does not occur. In addition, the injection ratio of the in-cylinder injector 110 is decreased as the engine shifts to a high load region where such a problem occurs. These changes in the DI ratio r are shown by cross arrows in FIGS. If it does in this way, the fluctuation | variation of the output torque of an engine resulting from combustion being unstable can be suppressed. It should be noted that these things can be achieved by reducing the injection ratio of the in-cylinder injector 110 as the engine shifts to the predetermined low rotational speed region, or by the in-cylinder injection as the vehicle shifts to the predetermined low load region. The fact that it is substantially equivalent to increasing the injection ratio of the injector 110 for operation will be described. Further, areas other than such areas (areas where the cross arrows are shown in FIGS. 9 and 10) and areas where fuel is injected only by the in-cylinder injector 110 (high rotation side, low load) On the other hand, it is easy to homogenize the air-fuel mixture with the in-cylinder injector 110 alone. Thus, the fuel injected from the in-cylinder injector 110 is vaporized with latent heat of vaporization (sucking heat from the combustion chamber) in the combustion chamber. Thereby, the temperature of the air-fuel mixture at the compression end is lowered. As a result, the knocking performance is improved. Further, since the temperature of the combustion chamber is lowered, the suction efficiency is improved and high output can be expected.

  In the engine 10 described in the first and second embodiments, the homogeneous combustion is performed by setting the fuel injection timing of the in-cylinder injector 110 as the intake stroke, and the stratified combustion is performed by the in-cylinder injector 110. This can be realized by setting the fuel injection timing in the compression stroke. That is, by setting the fuel injection timing of the in-cylinder injector 110 as the compression stroke, stratified combustion is realized in which the rich air-fuel mixture is unevenly distributed around the spark plug and the entire combustion chamber ignites a lean air-fuel mixture. Can do. Further, even when the fuel injection timing of the in-cylinder injector 110 is set to the intake stroke, if rich air-fuel mixture can be unevenly distributed around the spark plug, stratified combustion can be realized even with the intake stroke injection.

  Further, the stratified combustion here includes both stratified combustion and weakly stratified combustion described below. In the weak stratified combustion, the intake passage injector 120 is injected with fuel in the intake stroke to produce a lean and homogeneous mixture in the entire combustion chamber, and the in-cylinder injector 110 is injected with fuel in the compression stroke. A rich air-fuel mixture is generated around the spark plug to improve the combustion state. Such weak stratified combustion is preferable when the catalyst is warmed up. This is due to the following reason. That is, it is necessary to significantly retard the ignition timing and maintain a good combustion state (idle state) in order to allow high-temperature combustion gas to reach the catalyst during catalyst warm-up. Moreover, it is necessary to supply a certain amount of fuel. Even if this is done by stratified combustion, there is a problem that the amount of fuel is small, and even if this is done by homogeneous combustion, there is a problem that the retard amount is small compared to stratified combustion in order to maintain good combustion. is there. From such a viewpoint, it is preferable to use the above-described weak stratified combustion at the time of warming up the catalyst, but either stratified combustion or weak stratified combustion may be used.

  In the engine described in the first and second embodiments, the timing of fuel injection by the in-cylinder injector 110 is preferably performed in the compression stroke for the following reason. However, in the engine 10 described above, in a basic most region (a weak operation that is performed only when the catalyst is warmed up, the intake passage injection injector 120 is injected in the intake stroke and the in-cylinder injector 110 is compressed in the compression stroke. The timing of fuel injection by the in-cylinder injector 110 other than the stratified combustion region is a basic region) is the intake stroke. However, for the following reasons, the fuel injection timing of the in-cylinder injector 110 may be temporarily set to the compression stroke injection for the purpose of stabilizing the combustion.

  By setting the fuel injection timing from the in-cylinder injector 110 during the compression stroke, the air-fuel mixture is cooled by fuel injection at a time when the in-cylinder temperature is higher. Since the cooling effect is enhanced, knock resistance can be improved. Furthermore, if the fuel injection timing from the in-cylinder injector 110 is in the compression stroke, the time from the fuel injection to the ignition timing is short, so that the air flow can be strengthened by spraying and the combustion speed can be increased. From these improvement in knocking property and increase in combustion speed, combustion fluctuation can be avoided and combustion stability can be improved.

  Furthermore, regardless of the temperature of the engine 10 (that is, whether the engine is warm or cold), it is off-idle (when the idle switch is off or the accelerator pedal is depressed). 2 or 9 may be used (the in-cylinder injector 110 is used in the low load region regardless of the cold temperature).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of the engine system controlled by the control apparatus which concerns on the 1st Embodiment of this invention. It is a figure showing DI ratio map at the time of warm memorized by engine ECU which is a control device concerning a 1st embodiment of the present invention. It is a figure showing the DI ratio map at the time of cold memorized by engine ECU which is a control device concerning a 1st embodiment of the present invention. It is FIG. (1) which shows the learning area | region of the fuel injection quantity memorize | stored in engine ECU which is a control apparatus which concerns on the 1st Embodiment of this invention. FIG. 8 is a diagram (No. 2) illustrating a fuel injection amount learning region stored in the engine ECU that is the control device according to the first embodiment of the present invention. It is a figure which shows the state by which the learning value was calculated for every learning area | region about each injection area | region. It is a flowchart (the 1) which shows the control structure of the program which engine ECU which is a control apparatus which concerns on the 1st Embodiment of this invention performs. It is a flowchart (the 2) which shows the control structure of the program which engine ECU which is a control apparatus which concerns on the 1st Embodiment of this invention performs. It is a figure showing the DI ratio map at the time of warm memorize | stored in engine ECU which is a control apparatus which concerns on the 2nd Embodiment of this invention. It is a figure showing DI ratio map at the time of cold memorized by engine ECU which is a control device concerning a 2nd embodiment of the present invention.

Explanation of symbols

10 engine, 20 intake manifold, 30 surge tank, 40 air intake duct, 42 air flow meter, 50 air cleaner, 60 electric motor, 70 throttle valve, 80 exhaust manifold, 90 three-way catalytic converter, 100 accelerator pedal, 110 in-cylinder injector , 112 cylinder, 120 Injector injector, 130 Fuel distribution pipe, 140 Check valve, 150 High pressure fuel pump, 152 Electromagnetic spill valve, 160 Fuel distribution pipe (low pressure side), 170 Fuel pressure regulator, 180 Low pressure fuel pump, 190 fuel filter, 200 fuel tank, 300 engine ECU, 310 bidirectional bus, 320 ROM, 330 RAM, 340 CPU, 350 input port, 360 output port, 370, 390, 410, 430, 50 A / D converter, 380 a water temperature sensor, 400 a fuel pressure sensor, 420 an air-fuel ratio sensor, 440
Accelerator opening sensor, 460 rpm sensor.

Claims (4)

A control device for an internal combustion engine comprising a fuel injection means for injecting fuel,
Detecting means for detecting an air-fuel ratio of the internal combustion engine;
Calculation means for calculating a correction value of the fuel injection amount based on the detected air-fuel ratio;
Means for storing the correction value;
Control means for controlling the fuel injection means such that an amount of fuel corresponding to the stored correction value is injected;
Estimating means for estimating the degree of dilution of the lubricating oil used for lubricating the internal combustion engine with fuel;
Determining means for determining a storage range of correction values according to the degree,
It said determining means, when the degree is estimated to be greater includes means for inhibiting the storage of the correction values in the range of the correction amount of fuel injection amount is larger than a predetermined amount, the internal combustion Engine control device. Said determining means, when the degree is estimated to be greater includes means for inhibiting the storage of the correction values in the range of the decrease correction amount of fuel injection amount is greater than the amount it said predetermined The control device for an internal combustion engine according to claim 1. The fuel injection means is a first fuel injection means for injecting fuel into a cylinder,
The control device for an internal combustion engine according to claim 1 or 2, wherein the internal combustion engine is provided with second fuel injection means for injecting fuel into the intake passage in addition to the first fuel injection means. . The first fuel injection means is an in-cylinder injector,
The control apparatus for an internal combustion engine according to claim 3, wherein the second fuel injection means is an intake passage injection injector.

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