JP4196897B2 - Control device for hydrogenated internal combustion engine - Google Patents

Description

  The present invention relates to a control device for a hydrogenated internal combustion engine that can be operated using gasoline and hydrogen as fuel, and more particularly to a technique for suppressing combustion noise by increasing or decreasing the hydrogen addition rate.

Conventionally, as disclosed in, for example, Patent Document 1, a technique of using hydrogen as a fuel for an internal combustion engine together with gasoline is known. Since hydrogen is excellent in combustibility, adding hydrogen to gasoline can suppress knocking and improve output and fuel consumption.
JP 2004-116398 A JP-A-6-200805

  By the way, in an internal combustion engine, noise is generated when fuel burns in the combustion chamber. This combustion noise tends to increase as the increase in in-cylinder pressure accompanying combustion increases more rapidly. In the case of an internal combustion engine in which hydrogen is added to gasoline as in the above-described prior art, the in-cylinder pressure is likely to increase as compared with the case where only gasoline is used, because hydrogen with good combustibility is added. For this reason, depending on the degree of addition of hydrogen, combustion noise may become excessive due to a rapid rise in the in-cylinder pressure. Although it is conceivable to reduce the amount of hydrogen added as a method for suppressing combustion noise, simply reducing the amount of hydrogen added makes it impossible to obtain the required torque due to a decrease in the total calorific value.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for a hydrogenated internal combustion engine that can suppress combustion noise without reducing torque.

In order to achieve the above object, a first invention provides a control device for a hydrogenated internal combustion engine operable with gasoline and hydrogen as fuels.
Fuel injection amount control means for performing injection amount control of gasoline and hydrogen at a ratio determined according to the operating state of the internal combustion engine;
Noise level detection means for detecting an index value related to the magnitude of combustion noise of the internal combustion engine;
A hydrogen addition ratio correction means for correcting the hydrogen addition ratio to a decreasing side when an index value related to the magnitude of combustion noise detected by the noise level detection means exceeds a predetermined value;
It is characterized by having.

  In a second aspect based on the first aspect, the noise level detecting means is an in-cylinder pressure sensor for detecting an in-cylinder pressure of the internal combustion engine, and an increase in the in-cylinder pressure detected by the in-cylinder pressure sensor. The rate is used as an index value related to the magnitude of combustion noise.

  According to a third invention, in the first invention, the noise level detecting means is a sound sensor for detecting a sound generated from the internal combustion engine, and a loudness detected by the sound sensor is a magnitude of a combustion noise. It is characterized by being used as an index value related to the above.

  According to a fourth invention, in any one of the first to third inventions, the fuel injection amount control means determines a target value of a load factor of the internal combustion engine from an operating state of the internal combustion engine. Setting means and a hydrogen addition ratio setting means for determining a hydrogen addition ratio from the operating state of the internal combustion engine, calculating a load factor shared by gasoline and hydrogen from the target load factor and the hydrogen addition ratio, The fuel injection amount is determined from the load factor shared by the fuel, and the hydrogen injection amount is determined from the load factor shared by the hydrogen.

  According to the first aspect of the invention, when the index value related to the magnitude of the combustion noise exceeds a predetermined value, the hydrogen addition ratio is corrected to the decrease side, so that the combustion rate is suppressed and the increase rate of the in-cylinder pressure is decreased. . This prevents the combustion noise from becoming excessive. Further, since the gasoline injection amount is increased by the amount by which the hydrogen injection amount is reduced, a decrease in torque output from the internal combustion engine is suppressed.

  According to the second aspect of the present invention, the in-cylinder pressure sensor used for other control of the internal combustion engine can be used, so that combustion noise can be controlled without incurring costs.

  According to the third aspect of the invention, combustion noise can be directly detected and fed back to the hydrogen addition rate, so that combustion noise control that matches the audibility of the occupant can be realized.

  According to the fourth aspect of the invention, since the hydrogen injection amount and the gasoline injection amount are determined on the assumption of the target load factor, a decrease in torque output from the internal combustion engine is more reliably suppressed.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which a control device according to an embodiment of the present invention is applied. The internal combustion engine 2 includes a cylinder block 6 in which a piston 8 is disposed, and a cylinder head 4 assembled to the cylinder block 6. A space from the upper surface of the piston 8 to the cylinder head 4 forms a combustion chamber 10, and an intake port 18 and an exhaust port 20 are formed in the cylinder head 4 so as to communicate with the combustion chamber 10. An intake valve 12 for controlling the communication state between the intake port 18 and the combustion chamber 10 is provided at a connection portion between the intake port 18 and the combustion chamber 10, and an exhaust gas is provided at a connection portion between the exhaust port 20 and the combustion chamber 10. An exhaust valve 14 for controlling the communication state between the port 20 and the combustion chamber 10 is provided. In addition, an in-cylinder pressure sensor 76 that detects a pressure in the combustion chamber 10 (in-cylinder pressure) is attached to the top of the combustion chamber 10 together with a spark plug (not shown). In the present embodiment, it is assumed that the in-cylinder pressure sensor 76 is attached only to a specific representative cylinder, not to all the cylinders.

  The intake port 18 is provided with two injectors 50 and 60 for injecting fuel for each cylinder. One injector 60 is a gasoline injector, and is an electromagnetic valve that is driven to open and close by energization control and injects gasoline. The gasoline injector 60 is connected to a gasoline tank 62 via a gasoline passage 64. A gasoline pump 66 is disposed in the gasoline passage 64, and the gasoline in the gasoline tank 62 is compressed by the gasoline pump 66 and supplied to the gasoline injector 60. The other injector 50 is a hydrogen injector, which is an electromagnetic valve that is driven to open and close by energization control and injects hydrogen. The hydrogen injector 50 is connected to the hydrogen tank 52 via the hydrogen passage 54. A hydrogen pump 56 is disposed in the hydrogen passage 54, and hydrogen in the hydrogen tank 52 is compressed by the hydrogen pump 56 and supplied to the hydrogen injector 50.

  Further, the internal combustion engine 2 is provided with an ECU (Electronic Control Unit) 70 as its control device. Various devices such as the gasoline injector 60 and the hydrogen injector 50 described above are connected to the output side of the ECU 70. In addition to the in-cylinder pressure sensor 76 described above, various sensors such as an accelerator position sensor 72, a crank angle sensor 74, and a vehicle speed sensor 78 are connected to the input side of the ECU 70. The accelerator position sensor 72 is a sensor that outputs a signal corresponding to the opening degree of the accelerator pedal, and the crank angle sensor 74 is a sensor that outputs a signal corresponding to the crank angle. The vehicle speed sensor 78 is a sensor that outputs a signal corresponding to the vehicle speed of the vehicle on which the internal combustion engine 2 is mounted. The ECU 70 drives each device according to a predetermined control program based on the output of each sensor.

  As one of the controls of the internal combustion engine 2 performed by the ECU 70, there is fuel injection amount control for determining the gasoline injection amount from the gasoline injector 60 and the hydrogen injection amount from the hydrogen injector 50. FIG. 2 is a flowchart showing a fuel injection amount control routine executed by the ECU 70. This routine is periodically executed at every constant crank angle.

  In the first step 100 of the fuel injection amount control routine, the accelerator opening is read from the signal of the accelerator position sensor 72, and the rotation speed (the rotation speed of the crankshaft) is read from the signal of the crank angle sensor 74. In the next step 102, a target value (target load factor) of the load factor of the internal combustion engine 2 corresponding to the accelerator opening and the rotational speed read in step 100 is calculated from a map stored in advance. The load factor is a numerical value representing the load state of the internal combustion engine 2, and is 0% when there is no load and 100% when there is a full load. In step 104, a hydrogen addition ratio corresponding to the accelerator opening and the rotational speed read in step 100 is calculated from a map stored in advance. In the present embodiment, the hydrogen addition ratio is defined as the ratio of the calorific value of hydrogen to the total calorific value of the entire fuel including gasoline and hydrogen.

In the next step 106, the load factor shared by gasoline and hydrogen is calculated from the target load factor and the hydrogen addition ratio using the following equations (1) and (2).
Hydrogen load factor = target load factor x hydrogen addition ratio (1)
Gasoline load factor = target load factor-hydrogen load factor (2)
In the above formulas (1) and (2), the value calculated in step 102 is used as the target load factor. On the other hand, as the hydrogen addition ratio, a value obtained by correcting the basic value by a hydrogen addition ratio control routine described later, using the hydrogen addition ratio calculated in step 104 as a basic value, is used.

In the next step 108, the valve opening time of the hydrogen injector 50 is calculated from the hydrogen load factor using the following equation (3), and the gasoline injector 60 is calculated from the gasoline load factor using the following equation (4). The valve opening time is calculated.
Hydrogen injector valve opening time = Hydrogen load factor x Factor 1 (3)
Gasoline injector valve opening time = gasoline load factor x factor 2 (4)
In the above equations (3) and (4), each coefficient is determined from the fuel injection amount per unit valve opening time of each injector, the heat generation amount per unit amount of each fuel, and the like. These coefficients may be fixed values or variables. However, the coefficient 1 is preferably a variable determined by the temperature and pressure of hydrogen flowing through the hydrogen passage 54 in consideration of the volume change of hydrogen due to temperature and pressure.

  The hydrogen injector valve opening time calculated in step 108 is set in a driver in the ECU 70 that drives the hydrogen injector 50. The gasoline injector valve opening time is set in a driver in the ECU 70 that drives the gasoline injector 60. The process of step 108 is executed before the fuel injection timing, and each driver drives each injector 50, 60 based on each valve opening time set in step 108.

  The ECU 70 also executes the following hydrogen addition ratio control routine as a routine related to the fuel injection amount control together with the fuel injection amount control routine. FIG. 3 is a flowchart showing a hydrogen addition ratio control routine executed by the ECU 70. This routine is executed for the purpose of suppressing combustion noise, and is periodically executed at every constant crank angle (for example, every cycle of a representative cylinder provided with the in-cylinder pressure sensor 76).

  In the hydrogen addition ratio control routine, the hydrogen addition ratio is controlled based on the cylinder pressure increase rate per crank angle. The in-cylinder pressure increase rate is related to the combustion noise, and the magnitude of the combustion noise is determined by the maximum value of the in-cylinder pressure increase rate. Therefore, if the target level of the cylinder pressure rise rate corresponding to the allowable level of combustion noise is determined and the hydrogen addition ratio can be controlled so that the maximum value of the cylinder pressure rise rate does not exceed this target level, the combustion noise Can be suppressed within an allowable level.

  In the first step 200 of the hydrogen addition ratio control routine, the target level is read from a prepared map. In the map, as shown in FIG. 4, the target level is set with the load and rotation speed of the internal combustion engine 2 as parameters, and the target level is set lower as the rotation speed is lower and the load is lower. . This is because the combustion noise becomes more worrisome for the occupant when the engine speed is low and the load is low. The ECU 70 acquires the current rotational speed and load, and reads a target level corresponding to the rotational speed and load from the map. The load can be calculated from the rotational speed and the accelerator opening, but when an air flow meter for measuring the intake air amount is provided, the load may be calculated from the intake air amount.

  In the next step 202, the cylinder pressure increase rate dP / dθ is calculated from the change per cylinder angle of the cylinder pressure detected by the cylinder pressure sensor 76, and the maximum value (dP / dθ) max is held. . The maximum value (dP / dθ) max of the in-cylinder pressure increase rate is the maximum value from the previous execution of step 202 to the current execution of step 202, and is updated each time this routine is executed. It is like that.

  In the next step 204, it is determined whether or not the maximum value (dP / dθ) max of the in-cylinder pressure increase rate calculated in step 202 exceeds the target level set in step 200. As a result of the determination, when it is determined that the maximum value (dP / dθ) max of the in-cylinder pressure increase rate exceeds the target level, the hydrogen addition ratio is corrected to the decreasing side (step 206). Specifically, a predetermined ratio (for example, several%) is subtracted as a correction value from the current hydrogen addition ratio. As described above, the hydrogen addition ratio calculated in step 104 is a basic value, and the correction value is subtracted from the basic value every time the process of step 206 is executed. Since the hydrogen injector valve opening time calculated in step 108 is set based on the corrected hydrogen addition rate, the hydrogen injection rate from the hydrogen injector 50 is reduced as a result of correcting the hydrogen addition rate to the decreasing side. . Conversely, the gasoline injection amount from the gasoline injector 60 is increased by the increase in the gasoline addition rate accompanying the decrease in the hydrogen addition rate.

  As described above, the hydrogen addition ratio is corrected to the decrease side, and the hydrogen injection amount excellent in combustibility is reduced. As a result, the combustion speed in the combustion chamber 10 decreases and the increase rate of the in-cylinder pressure decreases. As a result, excessive combustion noise is prevented and kept within an allowable level. At this time, the hydrogen injection amount and the gasoline injection amount are determined based on the target load factor in the fuel injection amount control routine, although there is a slight decrease in torque due to the decrease in the hydrogen injection amount with excellent combustibility. Therefore, it is possible to prevent the torque from greatly decreasing.

  As a result of the determination in step 204, if it is determined that the maximum value (dP / dθ) max of the in-cylinder pressure increase rate is equal to or lower than the target level, the processing from step 208 is executed. The processing after Step 208 is processing for returning the hydrogen addition ratio corrected in Step 206 to the hydrogen addition ratio (map value) determined from the accelerator opening and the rotational speed. First, in step 208, a map value corresponding to the accelerator opening and the rotational speed is read from the aforementioned map. In the next step 210, the current hydrogen addition rate and the map value are compared. Normally, as described in the fuel injection control routine, the hydrogen addition ratio is set to a map value determined from the accelerator opening and the rotational speed. However, when the hydrogen addition rate is corrected to decrease in step 206, the hydrogen addition rate is smaller than the map value. If the result of determination in step 210 is that the hydrogen addition rate is equal to the map value, the hydrogen addition rate is maintained at the current value. On the other hand, when it is determined that the hydrogen addition ratio is smaller than the map value, the hydrogen addition ratio is corrected to increase so that the hydrogen addition ratio matches the map value (step 212). By performing the series of processing in steps 208 to 212, for example, when the increase in the in-cylinder pressure increase rate is a temporary phenomenon, the maximum value (dP / dθ) max of the in-cylinder pressure increase rate. After the value falls below the target level, the hydrogen addition ratio is quickly returned to the original value according to the accelerator opening and the rotational speed.

  In the above embodiment, the ECU 70 executes the fuel injection amount control routine of FIG. 2 so that the “fuel injection amount control means” of the first invention and the “target load factor setting means” of the fourth invention, "Hydrogen addition ratio setting means" and "fuel injection amount control means" are realized. Further, the “hydrogen addition ratio correcting means” of the first invention is realized by the ECU 70 executing the hydrogen addition ratio control routine of FIG.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, the cylinder pressure sensor 76 is provided only in a specific representative cylinder, but the cylinder pressure sensor 76 is provided in all cylinders, and the hydrogen addition ratio control shown in FIG. 3 is performed for each cylinder. May be. According to this, combustion noise is aligned between the cylinders, and sound quality is improved.

  In the above embodiment, the target level is determined from a map (FIG. 4) using the rotation speed and the load as parameters. However, the map shown in FIG. 4 is prepared for each vehicle speed, and the rotation speed, load, and vehicle speed are prepared. The target level may be determined according to the above. In this case, the combustion noise becomes more noticeable to the occupant at lower speeds, so the target level is set lower as the vehicle speed is lower.

  Further, in the above embodiment, the in-cylinder pressure sensor 76 is used as a noise level detection means, and the maximum value of the in-cylinder pressure increase rate detected by the in-cylinder pressure sensor 76 is used as an index value related to the magnitude of combustion noise. However, the combustion noise may be directly detected by a sound sensor. For example, if a sound sensor is installed in the passenger compartment and the hydrogen addition ratio is controlled in accordance with the magnitude of the combustion noise detected by the sound sensor, the combustion noise can be controlled in accordance with the passenger's audibility. Since the sound detected by the sound sensor includes noise other than combustion noise, it is necessary to remove the noise by filter processing or the like.

  In the configuration of FIG. 1, the hydrogen injector 50 is arranged in the intake passage 30, but the arrangement is not limited to this. That is, the hydrogen injector 50 may be incorporated in the cylinder head 4 so that hydrogen can be injected directly into the combustion chamber 10. The same applies to the gasoline injector 60, and the gasoline injector 60 may be incorporated in the cylinder head 4 so that gasoline can be injected directly into the combustion chamber 10.

1 is a diagram showing a schematic configuration of an internal combustion engine to which a control device as an embodiment of the present invention is applied. It is a flowchart shown about the fuel injection amount control routine performed in embodiment of this invention. It is a flowchart shown about the hydrogenation ratio control routine performed in embodiment of this invention. It is a map for setting the target level of the in-cylinder pressure increase rate based on the rotation speed and the load.

Explanation of symbols

2 Internal combustion engine 10 Combustion chamber 12 Intake valve 14 Exhaust valve 18 Intake port 20 Exhaust port 50 Hydrogen injector 52 Hydrogen tank 60 Gasoline injector 62 Gasoline tank 70 ECU (Electronic Control Unit)
72 Acceleration position sensor 74 Crank angle sensor 76 In-cylinder pressure sensor 78 Vehicle speed sensor

Claims (4)

In a control device for a hydrogenated internal combustion engine that can be operated using gasoline and hydrogen as fuel,
Fuel injection amount control means for performing injection amount control of gasoline and hydrogen at a ratio determined according to the operating state of the internal combustion engine;
Noise level detection means for detecting an index value related to the magnitude of combustion noise of the internal combustion engine;
A hydrogen addition ratio correction means for correcting the hydrogen addition ratio to a decreasing side when an index value related to the magnitude of combustion noise detected by the noise level detection means exceeds a predetermined value;
A control apparatus for a hydrogenated internal combustion engine, comprising:   The noise level detecting means is an in-cylinder pressure sensor for detecting an in-cylinder pressure of the internal combustion engine, and an increase rate of the in-cylinder pressure detected by the in-cylinder pressure sensor is used as an index value related to the magnitude of combustion noise. The control apparatus for a hydrogenated internal combustion engine according to claim 1, wherein   The noise level detection means is a sound sensor for detecting sound generated from the internal combustion engine, and the loudness detected by the sound sensor is used as an index value related to the loudness of combustion noise. The control device for a hydrogenated internal combustion engine according to claim 1.   The fuel injection amount control means includes target load factor setting means for determining a target value of a load factor of the internal combustion engine from the operating state of the internal combustion engine, and hydrogen addition for determining a hydrogen addition ratio from the operating state of the internal combustion engine. Load ratio that is shared by gasoline and hydrogen from the target load ratio and hydrogen addition ratio, and determines the gasoline injection amount from the load ratio that gasoline shares, and the load ratio that hydrogen shares The control apparatus for a hydrogenated internal combustion engine according to any one of claims 1 to 3, wherein the hydrogen injection amount is determined from the fuel injection amount.

Images