Control device for an internal combustion engine

Abstract

The present application relates to a control device for an internal combustion engine. In an internal combustion engine having a cylinder in which a mixture of a gaseous fuel and intake air is combusted, an intake passage connected to the cylinder, and a supercharger that supercharges the intake air, when backfire has occurred during a set period before supercharging by the supercharger, the intake air is supercharged at a supercharging pressure that is lower than when backfire has not occurred during the set period.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] Japanese Patent Application Publication No. 2016-118109 discloses an internal combustion engine and its control device. The internal combustion engine has a cylinder, an intake passage connected to the cylinder, and a water injection valve disposed in the intake passage. In an internal combustion engine, during the opening of the intake valve, a phenomenon sometimes occurs where the air-fuel mixture ignites before ignition, causing the flame to flow backward from the cylinder into the intake passage—a phenomenon known as backfire. The control device in Japanese Patent Application Publication No. 2016-118109 injects water from the water injection valve in the event of backfire. This lowers the temperature of the intake passage, thus suppressing backfire. Summary of the Invention

[0003] Internal combustion engines like those described in Japanese Patent Application Publication No. 2016-118109 sometimes have turbochargers. During the turbocharger's pressurization of the intake air, the temperature inside the cylinder tends to rise due to the increased engine load. This makes pre-ignition more likely. Furthermore, the increased pressure in the intake passage and cylinder during turbocharging facilitates flame propagation. Therefore, backfire is prone to occur during engine operation, especially during turbocharging. Even if the technology described in Japanese Patent Application Publication No. 2016-118109 is used in a turbocharged internal combustion engine, injecting water into the intake passage during turbocharging, the high pressure in the intake passage and cylinder during turbocharging remains unchanged. Therefore, it may not be possible to adequately suppress backfire.

[0004] A control device for an internal combustion engine for solving the above-mentioned problems, wherein the internal combustion engine is the controlled object, and the internal combustion engine has:

[0005] A cylinder for burning a mixture of gaseous fuel and intake air;

[0006] An intake passage, wherein the intake passage is connected to the cylinder; and

[0007] A booster, which pressurizes the intake air.

[0008] The control unit of the internal combustion engine performs the following processes:

[0009] The first process, based on the operating state of the internal combustion engine, determines whether backfire has occurred; and

[0010] The second process, in the case that backfire occurs during a predetermined setting period before pressurization by the booster, pressurizes at a lower boost pressure than if no backfire occurs during the setting period.

[0011] In the above configuration, under conditions where backfire is prone to occur in the internal combustion engine, boost pressure is applied at a low level. This makes the internal combustion engine state during boost pressure extremely difficult to achieve. Therefore, backfire during boost pressure can be suppressed.

[0012] A control device for an internal combustion engine for solving the above-mentioned problems, wherein the internal combustion engine is the controlled object, and the internal combustion engine has:

[0013] A cylinder for burning a mixture of gaseous fuel and intake air;

[0014] An intake passage, wherein the intake passage is connected to the cylinder; and

[0015] A booster, which pressurizes the intake air.

[0016] The control unit of the internal combustion engine performs the following processes:

[0017] The first process, based on the operating state of the internal combustion engine, determines whether backfire has occurred; and

[0018] The second process, in the case that backfire occurs during a predetermined setting period before pressurization by the booster, reduces the upper limit of the boost pressure of the booster compared to the case where no backfire occurs during the setting period.

[0019] In the above configuration, the upper limit of the boost pressure is reduced when the internal combustion engine is in a state where backfire is likely to occur. This makes the internal combustion engine state during boost extremely difficult to achieve. Therefore, backfire during boost can be suppressed. Attached Figure Description

[0020] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein:

[0021] Figure 1 It is a schematic diagram of the vehicle's structure;

[0022] Figure 2 It is a schematic diagram of the internal combustion engine;

[0023] Figure 3 This is a diagram representing an example of feature mapping;

[0024] Figure 4 This is a flowchart illustrating the processing steps of the pressurization use case routine in the first embodiment;

[0025] Figure 5 This is a flowchart illustrating the processing steps of the pressurization use case in the second embodiment; and

[0026] Figure 6 This is a diagram representing an example of feature mapping. Detailed Implementation

[0027] Implementation Method 1

[0028] Hereinafter, a first embodiment of the control device for an internal combustion engine will be described with reference to the accompanying drawings.

[0029] Overall composition of the vehicle

[0030] like Figure 1 As shown, vehicle 90 includes: internal combustion engine 10, drive clutch 81, electric generator 82, transmission unit 80, hydraulic mechanism 86, differential 71, multiple drive wheels 72, converter 78, and battery 79. Furthermore, vehicle 90 is a vehicle that mounts the internal combustion engine 10.

[0031] The internal combustion engine 10 is the drive source for the vehicle 90. Details of the internal combustion engine 10 will be described later. The internal combustion engine 10 has a crankshaft 17. The electric generator 82 is the drive source for the vehicle 90. The electric generator 82 functions as both an electric motor and a generator. The electric generator 82 has a stator 82C, a rotor 82B, and a rotating shaft 82A. The rotor 82B is rotatable relative to the stator 82C. The rotating shaft 82A rotates integrally with the rotor 82B. The electric generator 82 is electrically connected to a battery 79 via a converter 78. The battery 79 receives and exchanges power with the electric generator 82. The converter 78 performs DC-AC conversion.

[0032] The drive clutch 81 is located between the internal combustion engine 10 and the electric generator 82. The drive clutch 81 switches between connected and disconnected states based on hydraulic pressure from the hydraulic mechanism 86. When hydraulic pressure is supplied, the drive clutch 81 is in an connected state, connecting the crankshaft 17 to the rotating shaft 82A of the electric generator 82. When the hydraulic pressure supply is stopped, the drive clutch 81 is in a disconnected state, disconnecting the crankshaft 17 from the rotating shaft 82A.

[0033] The transmission unit 80 includes a torque converter 83 and an automatic transmission 85. The torque converter 83 includes a pump impeller 83A, a turbine bushing 83B, and a lock-up clutch 84. The torque converter 83 is a hydraulic coupling with torque amplification function. The pump impeller 83A rotates integrally with the rotating shaft 82A of the electric generator 82. The turbine bushing 83B rotates integrally with the input shaft of the automatic transmission 85. The lock-up clutch 84 receives hydraulic pressure from the hydraulic mechanism 86 and directly connects the pump impeller 83A and the turbine bushing 83B.

[0034] The automatic transmission 85 is a stepped transmission capable of switching gear ratios in multiple stages. The automatic transmission 85 has multiple clutches and brakes as engagement elements, and multiple planetary gear mechanisms. Each engagement element switches between open and closed states based on hydraulic pressure from a hydraulic mechanism 86. Depending on the open / closed state of each engagement element, the automatic transmission 85 can form any one of a pre-set number of gears. Specifically, the automatic transmission 85 can form a forward driving gear, a reverse driving gear, and a non-driving gear. Furthermore, within the forward driving gear, the automatic transmission 85 can form any one of several gears, for example, from "gear 1" to "gear 5". The output shaft of the automatic transmission 85 is connected to the left and right drive wheels 72 via a differential 71. The differential 71 allows for a speed difference between the left and right drive wheels 72. Furthermore, the drive clutch 81, the electric generator 82, and the transmission unit 80 are housed in a single, interconnected housing. In other words, the drive clutch 81, the electric generator 82, and the transmission unit 80 are integrated into a hybrid drive axle.

[0035] Vehicle 90 has a vehicle speed sensor 58, an accelerometer sensor 59, a battery sensor 60, and an odometer 35. The vehicle speed sensor 58 detects the vehicle 90's speed as the vehicle speed SP. The accelerometer sensor 59 detects the amount of time the accelerometer pedal is depressed as the accelerometer operation (opening) ACC. The battery sensor 60 detects battery information B, such as current, voltage, and temperature of the battery 79. The odometer 35 measures the distance traveled by vehicle 90 in meters.

[0036] General Components of an Internal Combustion Engine

[0037] like Figure 2 As shown, the internal combustion engine 10 has multiple cylinders 11, multiple pistons 51, and the aforementioned crankshaft 17. Furthermore, in Figure 2 Only one of the multiple cylinders 11 is shown in the diagram. The same applies to the piston 51. Additionally, although omitted from the diagram, the internal combustion engine 10 has multiple connecting rods. A piston 51 and a connecting rod are provided for each cylinder 11. The number of cylinders 11 is four.

[0038] Cylinder 11 is the space for combustion of the mixture of fuel and intake air. Piston 51 is located inside cylinder 11. Piston 51 reciprocates within cylinder 11. Piston 51 is connected to crankshaft 17 via connecting rod. Crankshaft 17 rotates according to the reciprocating motion of piston 51.

[0039] The internal combustion engine 10 has multiple spark plugs 15. Furthermore, in Figure 2Only one of the multiple spark plugs 15 is shown in the diagram. A spark plug 15 is provided for each cylinder 11. The front end of the spark plug 15 is located inside the cylinder 11. The spark plug 15 ignites the air-fuel mixture inside the cylinder 11.

[0040] The internal combustion engine 10 has an intake passage 12, an intercooler 52, a throttle valve 16, multiple fuel injection valves 14, and an exhaust passage 13. The intake passage 12 is a passage for introducing intake air into the cylinders 11. The intake passage 12 is connected to each cylinder 11. The intercooler 52 is located along the intake passage 12. The intercooler 52 cools the intake air. The throttle valve 16 is located in the intake passage 12, downstream of the intercooler 52. The throttle valve 16 is adjustable in opening. The intake air volume GA changes according to the opening of the throttle valve 16. A fuel injection valve 14 is provided for each cylinder 11. The fuel injection valve 14 is located in the intake passage 12, downstream of the throttle valve 16. The fuel injection valve 14 supplies fuel to the cylinders 11 via the intake passage 12. The fuel injection valve 14 injects hydrogen as fuel. The exhaust passage 13 is a passage for discharging exhaust gas from each cylinder 11. The exhaust passage 13 is connected to each cylinder 11.

[0041] The internal combustion engine 10 has multiple intake valves 18 and multiple exhaust valves 19. Furthermore, in Figure 2 Only one of the multiple intake valves 18 is shown in the diagram. The same applies to the exhaust valve 19. An intake valve 18 is provided for each cylinder 11. The intake valve 18 is located in the intake passage 12, at the connection port with the cylinder 11. The intake valve 18 opens and closes the aforementioned connection port of the intake passage 12. An exhaust valve 19 is provided for each cylinder 11. The exhaust valve 19 is located in the exhaust passage 13, at the connection port with the cylinder 11. The exhaust valve 19 opens and closes the aforementioned connection port of the exhaust passage 13.

[0042] The internal combustion engine 10 includes a turbocharger 20. The turbocharger 20 is positioned across the intake passage 12 and the exhaust passage 13. The turbocharger 20 includes a compressor impeller 21, a turbine impeller 22, a bypass passage 24, and a waste gas bypass valve (hereinafter referred to as WGV) 25. The compressor impeller 21 is located in the intake passage 12, upstream of the intercooler 52. The turbine impeller 22 is located in the exhaust passage 13. The turbine impeller 22 rotates according to the exhaust flow. The compressor impeller 21 and the turbine impeller 22 rotate together. At this time, the compressor impeller 21 compresses the intake air and delivers it. That is, the compressor impeller 21 pressurizes the intake air.

[0043] The bypass passage 24 connects the upstream and downstream portions of the exhaust passage 13 relative to the turbine impeller 22. That is, the bypass passage 24 is a passage that bypasses the turbine impeller 22. WGV 25 is located at the downstream end of the bypass passage 24. The opening of WGV 25 can be adjusted by an actuator. The larger the opening of WGV 25, the more exhaust gas flows through the bypass passage 24, bypassing the turbine impeller 22. Simultaneously, the rotational speeds of the turbine impeller 22 and the compressor impeller 21 decrease. At the same time, the pressure of the intake air, i.e., the boost pressure QP, between the compressor impeller 21 and the throttle valve 16 in the intake passage 12 decreases.

[0044] The internal combustion engine 10 includes an air flow meter 33, a boost pressure sensor 37, and an intake air temperature sensor 34. The air flow meter 33 is located in the intake passage 12, upstream of the compressor impeller 21. The air flow meter 33 detects the intake air volume GA. The boost pressure sensor 37 is located in the intake passage 12, between the intercooler 52 and the throttle valve 16. The boost pressure sensor 37 detects the boost pressure QP. The intake air temperature sensor 34 is located in the intake passage 12, downstream of the throttle valve 16. The intake air temperature sensor 34 detects the temperature (hereinafter referred to as the downstream intake temperature) T of the intake air in the intake passage 12, downstream of the throttle valve 16.

[0045] The internal combustion engine 10 has a sensor plate (sensing plate) 53 and a crankshaft position sensor 36. The sensor plate 53 has a disc-shaped body and multiple teeth protruding from the outer periphery of the body. The body rotates integrally with the crankshaft 17. The multiple teeth are arranged at substantially equal intervals. However, there is a gap between adjacent teeth that is larger than the gap between adjacent teeth. The crankshaft position sensor 36 is located opposite the outer periphery of the sensor plate 53. When the sensor plate 53 rotates along with the crankshaft 17, the crankshaft position sensor 36 alternately faces the teeth of the sensor plate 53 and the gap between adjacent teeth. The crankshaft position sensor 36 outputs an L signal when facing the teeth of the sensor plate 53 and an H signal when facing the gap. Corresponding to the arrangement of the teeth, the crankshaft position sensor 36 alternately outputs the L signal and the H signal at substantially constant normal intervals. The crankshaft position sensor 36 outputs a missing tooth signal as an H signal with an interval longer than the normal interval only when the missing tooth passes in front of the crankshaft position sensor 36. Hereinafter, all signals output by the crankshaft position sensor 36 will be collectively referred to as crankshaft signals CR. Furthermore, in this embodiment, the position of the missing tooth is determined by the tooth located next to the missing tooth portion being opposite the crankshaft position sensor 36 when the piston 51 of one specific cylinder out of the four cylinders 11 is at top dead center. During the rotation of the sensor plate 53, this tooth is opposite the crankshaft position sensor 36 after passing the missing tooth portion. Under this setting, the crankshaft signal CR switches from a missing tooth signal to an L signal before and after the piston 51 of the specific cylinder reaches top dead center.

[0046] Furthermore, the internal combustion engine 10 is a 4-stroke, 1-cycle internal combustion engine in which the intake stroke, compression stroke, expansion stroke, and exhaust stroke of each cylinder 11 are cyclically completed by rotating the crankshaft 17 by 720 degrees. Hereinafter, the series of periods in which one cylinder 11 sequentially experiences the intake stroke, compression stroke, expansion stroke, and exhaust stroke is referred to as one combustion cycle.

[0047] General structure of the control device

[0048] like Figure 1As shown, the vehicle 90 has a control device 100. The control device 100 can be configured as one or more processors that perform various processes according to a computer program (software). Furthermore, the control device 100 can also be configured as one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), or circuits including combinations thereof, that perform at least a portion of the various processes. The processor includes a CPU 111 and memories such as RAM and ROM 112. The memories store program code or instructions configured to cause the CPU 111 to perform processes. Memory, i.e., computer-readable media, includes all available media that can be accessed by a general-purpose or special-purpose computer. The control device 100 includes a real-time clock as a circuit for generating date and time information. The control device 100 includes a storage device 113 as an electrically rewritable non-volatile memory.

[0049] The control device 100 repeatedly receives various information from the vehicle 90 to obtain equipment detection or measurement information. Specifically, the control device 100 receives the following information.

[0050] The intake air volume GA detected by air flow meter 33

[0051] The boost pressure QP detected by boost pressure sensor 37

[0052] The downstream intake air temperature T detected by the intake air temperature sensor 34

[0053] Vehicle speed SP detected by vehicle speed sensor 58

[0054] Accelerator operation quantity ACC detected by accelerator sensor 59

[0055] Battery information B detected by battery sensor 60

[0056] The odometer reads 35 and the vehicle travels 90 meters.

[0057] In addition to the information mentioned above, the control device 100 repeatedly receives the crankshaft signal CR output by the crankshaft position sensor 36. Based on the shift of the crankshaft signal CR, the control device 100 continuously calculates the rotational position (hereinafter referred to as crankshaft position) CRA of the crankshaft 17. Specifically, the control device 100 sets the crankshaft position CRA to zero degrees when the crankshaft signal CR switches from a missing tooth signal to an L signal. Furthermore, using this crankshaft position CRA as a reference, the control device 100 calculates the crankshaft position CRA within the range of zero degrees to 360 degrees based on the shift of the crankshaft signal CR. In addition, based on the consistency with the position of the missing tooth portion mentioned above, the control device 100 sets the crankshaft position CRA to zero degrees when the piston 51 of a specific cylinder is at top dead center.

[0058] In addition to the crankshaft position CRA, the control device 100 also calculates the following parameters in real time. Based on the shift of the crankshaft signal CR received from the crankshaft position sensor 36, the control device 100 calculates the rotational speed of the crankshaft 17, i.e., the internal combustion engine speed NE. Furthermore, the control device 100 calculates the internal combustion engine load rate KL based on the internal combustion engine speed NE and the intake air volume GA. The internal combustion engine load rate KL is a parameter that determines the amount of air filling the cylinder 11. Specifically, the internal combustion engine load rate KL is the ratio of the amount of air flowing into one cylinder 11 per combustion cycle to a reference air volume. The reference air volume changes according to the internal combustion engine speed NE. Additionally, the control device 100 calculates the state of charge (SOC) of the battery 79 based on battery information B. The state of charge (SOC) of the battery 79 is the ratio of the remaining charge amount to the full charge capacity of the battery 79.

[0059] The control device 100 designates various parts of the vehicle 90 as control objects. For example, the control device 100 designates the internal combustion engine 10 and the electric generator 82 as control objects. When controlling the internal combustion engine 10 and the electric generator 82, the control device 100 calculates the required driving force, i.e., the required driving force, based on the accelerator control input (ACC) and the vehicle speed (SP). Then, the control device 100 determines the torque distribution between the internal combustion engine 10 and the electric generator 82 based on the required driving force and the state of charge (SOC) of the battery 79. The control device 100 then calculates the torque required from the internal combustion engine 10 to achieve the required driving force, i.e., the internal combustion engine required torque, and the torque required from the electric generator 82, i.e., the motor required torque. The control device 100 then controls the internal combustion engine 10 and the electric generator 82 based on these required torques. During the operation of the vehicle 90, the control device 100 repeatedly calculates each required torque and controls the internal combustion engine 10 and the electric generator 82 based on the required torques.

[0060] When controlling the internal combustion engine 10, the control device 100 controls various control quantities in the internal combustion engine 10 by operating various operating devices such as the throttle valve 16, fuel injection valve 14, spark plug 15, and WGV 25. These control quantities include, for example, the intake air quantity GA, the injected fuel quantity, and the boost pressure QP. By controlling these control quantities, the control device 100 ensures that the actual torque of the internal combustion engine 10 matches the required torque. Furthermore, in the case of performing the second process described later, the actual torque of the internal combustion engine 10 is less than the required torque. In this case, the control device 100 compensates for this torque decrease using the electric generator 82.

[0061] Depending on the situation, the control device 100 sometimes stops the internal combustion engine 10 and only drives the electric generator 82, and sometimes drives the electric generator 82 while running the internal combustion engine 10. In the former case, the control device 100 disengages the drive clutch 81, and in the latter case, engages the drive clutch 81. For example, when the state of charge (SOC) of the battery 79 has a margin, the control device 100 stops the operation of the internal combustion engine 10 when a lower driving force is required, and runs the internal combustion engine 10 when a higher driving force is required. Examples of situations requiring a lower driving force include when starting the vehicle 90, or when driving under light load with low forward acceleration. Furthermore, running the internal combustion engine 10 means that the air-fuel mixture is burned in each cylinder 11 through fuel injection and ignition. In this case, the internal combustion engine speed NE is greater than zero.

[0062] In addition, the control device 100 controls the automatic transmission 85. Based on the accelerator operation amount ACC and the vehicle speed SP, the control device 100 calculates the target value of the transmission level of the automatic transmission 85, i.e., the target transmission level. Furthermore, the control device 100 controls the automatic transmission 85 in a manner that ensures the actual transmission level matches the target transmission level. The control device 100 repeatedly calculates the target transmission level and controls the automatic transmission 85 during the operation of the vehicle 90.

[0063] Detailed information on the handling of internal combustion engines

[0064] The control device 100 is capable of performing a first process for monitoring the state of the internal combustion engine 10 during operation. This first process determines whether backfire has occurred. Backfire is a phenomenon where, during the opening of the intake valve 18, the air-fuel mixture ignites before ignition, causing a flame to flow backward from the cylinder 11 into the intake passage 12. In other words, backfire occurs during the intake stroke of each cylinder 11. Here, hydrogen is used as fuel in the internal combustion engine 10. Hydrogen is more flammable than, for example, gasoline, so ignition is easily caused when the hydrogen is injected into the cylinder 11 by the fuel injection valve 14 during the intake stroke. Under these conditions, during the turbocharger 20's pressurization of the intake air, the temperature inside the cylinder 11 easily increases with the increase in the internal combustion engine load rate KL. When the temperature inside the cylinder 11 is high, pre-ignition ignition is more likely to occur. Furthermore, during pressurization, the high pressure of the gas in the intake passage 12 and the cylinder 11 facilitates flame propagation. Given this situation, backfire is likely to occur during the operation of the internal combustion engine 10, especially during turbocharging.

[0065] During the operation of the internal combustion engine 10, the control device 100 continuously performs the first process. Here, when backfire occurs in a cylinder 11, the downstream intake temperature T instantaneously increases during the intake stroke of that cylinder 11. Therefore, during the first process, the control device 100 continuously monitors the downstream intake temperature T detected by the intake temperature sensor 34. Furthermore, using zero degrees at crankshaft position CRA as a reference, the control device 100 determines whether a specific condition is met at every 180-degree interval at that crankshaft position CRA. The specific condition is that the downstream intake temperature T exceeds the determination temperature for the duration of the determination period. The control device 100 determines that backfire has occurred if the specific condition is met, and determines that backfire has not occurred if the specific condition is not met. When determining whether backfire has occurred, the control device 100 stores an index value indicating its determination result in the storage device 113. For example, if the control device 100 determines that backfire has occurred, it stores "1" in the storage device 113; if it determines that backfire has not occurred, it stores "2" in the storage device 113. The control device 100 repeatedly performs this determination and records the determination result at every 180-degree interval of crankshaft position CRA. That is, the control device 100 determines whether backfire has occurred each time during the intake stroke of each cylinder 11. Furthermore, the control device 100 obtains four determination results in one combustion cycle. In addition, while rewriting old data with new data, the control device 100 stores a predetermined number of data points in the storage device 113 over time. The control device 100 processes this data set over time as a backfire occurrence data set. The predetermined number is twice the number of times the set number of times described later. This predetermined number is equivalent to the number of times the intake stroke is executed when the crankshaft 17 rotates a set number of times.

[0066] The control device 100 pre-stores the aforementioned determination temperature and determination period. The determination temperature is a relatively high temperature that can be detected when tempering occurs, and is preset, for example, through experimentation or simulation. In addition, the determination period is the minimum length of time that the downstream intake air temperature T remains above the determination temperature when tempering occurs, and is preset, for example, through experimentation or simulation.

[0067] Regarding the treatment used for boosting

[0068] When the required torque of the internal combustion engine exceeds a specified torque, the control device 100 pressurizes the intake air in the internal combustion engine 10. The control device 100 performs a basic process as a prerequisite for pressurization. This basic process calculates the basic value of the target boost pressure QPt, i.e., the basic boost pressure QPn. The target boost pressure QPt is the target value of the boost pressure QP. The control device 100 continuously performs this basic process during the operation of the internal combustion engine 10. During this basic process, the control device 100 repeatedly calculates the basic boost pressure QPn. The basic boost pressure QPn is the boost pressure QP required to achieve the current required torque of the internal combustion engine at the current internal combustion engine speed NE and internal combustion engine load rate KL. The control device 100 calculates the basic boost pressure QPn based on the latest required torque of the internal combustion engine, the latest internal combustion engine speed NE, and the latest internal combustion engine load rate KL. When this basic boost pressure QPn is greater than zero, a boost requirement is generated.

[0069] The control device 100 is capable of performing a pressurization process to actually increase pressure when a pressurization requirement is generated. The pressurization process involves repeatedly calculating the target pressurization pressure QPt and controlling the WGV25 based on the target pressurization pressure QPt. Controlling the WGV25 based on the target pressurization pressure QPt means providing feedback control to the opening degree of the WGV25 so that the actual pressurization pressure QP detected by the pressurization pressure sensor 37 matches the target pressurization pressure QPt. Based on this feedback control of the WGV25's opening degree, the control device 100 outputs a command signal to the actuator to activate the WGV25.

[0070] The pressurization process includes a normal process and a second process. The target pressurization pressure QPt is set differently in the normal process and the second process. If no backfire occurs during the setting period before pressurization using the pressurizer 20, the control device 100 performs the normal process. In this normal process, the control device 100 sets the aforementioned basic pressurization pressure QPn as the target pressurization pressure QPt.

[0071] On the other hand, if backfire occurs during the pre-boost setting period, the control device 100 performs a second process. In this second process, the control device 100 boosts at a lower boost pressure QP than if no backfire occurred during the pre-boost setting period. Specifically, in this process, the control device 100 calculates an adjustment boost pressure ΔQP as an adjustment value to reduce the boost pressure QP. Furthermore, as shown in Equation 1 below, the control device 100 sets the value obtained by subtracting the adjustment boost pressure ΔQP from the basic boost pressure QPn as the target boost pressure QPt. This target boost pressure QPt is lower than the target boost pressure QPt under normal processing conditions where the internal combustion engine required torque, internal combustion engine speed NE, and internal combustion engine load rate KL are the same, by the amount of reduction in the adjustment boost pressure ΔQP.

[0072] (Equation 1) QPt=QPn-ΔQP

[0073] Furthermore, when the boost pressure ΔQP is adjusted to exceed the basic boost pressure QPn, the control device 100 sets the target boost pressure QPt to zero.

[0074] The control device 100 pre-stores a specific mapping as information for calculating the adjustment of the boost pressure ΔQP. For example... Figure 3 As shown, the specific mapping represents the relationship between the frequency K of tempering occurrence and the adjusted boost pressure ΔQP within a set period. In this embodiment, the frequency K of tempering occurrence is the number of tempering occurrences within the set period itself. The specific mapping is based on experiments or simulations, assuming that tempering is detected by the method of the first process.

[0075] In a specific mapping, the frequency of tempering (K) and the adjusted boost pressure (ΔQP) are related as follows: When the frequency of tempering (K) is below the execution threshold (K1), the adjusted boost pressure (ΔQP) becomes zero. On the other hand, when the frequency of tempering (K) is above the execution threshold (K1), the higher the frequency of tempering (K), the larger the adjusted boost pressure (ΔQP). Furthermore, the adjusted boost pressure (ΔQP) corresponds to the decrease in the target boost pressure (QPn) from the basic boost pressure (QPn) when setting the target boost pressure (QPt). In other words, a large adjusted boost pressure (ΔQP) means a greater reduction in the target boost pressure (QPt) compared to the case where no tempering occurs. Moreover, if the basic boost pressure (QPn) is the same, the higher the frequency of tempering (K), the smaller the target boost pressure (QPt).

[0076] The execution threshold K1 is explained below. Here, the frequency of backfire occurrence K is an indicator of the susceptibility of backfire in an internal combustion engine. It can be said that the higher the frequency of backfire occurrence K, the more likely the engine is to experience backfire. The execution threshold K1 is set as the minimum boost pressure QP required to ensure that the internal combustion engine 10 is in a state prone to backfire and that measures are needed to suppress backfire.

[0077] The setting period will be explained. The setting period is preset to determine whether the internal combustion engine 10 is in a state prone to backfire under current conditions. In this embodiment, the setting period is preset, for example, as the period during which the crankshaft 17 rotates 2000 times. In other words, the setting period is set as the period during which the internal combustion engine 10 performs a preset number of combustion cycles. Thus, the setting period in this embodiment is not constant on a time scale and can change according to the internal combustion engine speed NE.

[0078] Specific processing routines for boosting pressure

[0079] like Figure 4 As shown, when a pressurization request is generated, the control device 100 starts a processing routine for pressurizing the intake air (hereinafter referred to as the pressurization use routine). That is, the control device 100 starts the pressurization use routine when the basic pressurization pressure QPn calculated by the basic processing switches from a state where it is zero to a value greater than zero. When the control device 100 starts the pressurization use routine, it first executes the processing of S10.

[0080] In S10, the control device 100 determines whether a flashback has occurred during the period from the current time point to the set period. Specifically, the control device 100 refers to the occurrence data set created in the first process. In relation to the aforementioned method of creating the occurrence data set, the occurrence data set represents, over time, whether a flashback has occurred during the period from the set timing point to the current time point. The set timing point is the time point from the current time point back to the set number of crankshaft 17 rotations, that is, the time point from the current time point back to the set period. The control device 100 determines whether there is at least one identification value in the occurrence data set indicating the occurrence of flashback. If there is no identification value indicating the occurrence of flashback (S10: No), the control device 100 proceeds to S80.

[0081] In S80, the control device 100 selects the normal process as the boost process. Then, the control device 100 begins boosting the intake air based on the normal process. That is, thereafter, the control device 100 directly uses the latest basic boost pressure QPn calculated through the basic process as the target boost pressure QPt to control the WGV25. The control device 100 repeatedly calculates the target boost pressure QPt and controls the WGV25 based on the target boost pressure QPt. Here, the basic boost pressure QPn calculated by the control device 100 changes over time according to the shift in the internal combustion engine's required torque, etc. Before ending the normal process in S50 (described later), the control device 100 performs feedback control on the opening of the WGV25 based on the basic boost pressure QPn in a way that allows the time-varying basic boost pressure QPn to be realized. When the normal process begins, the control device 100 causes the process to proceed to S40.

[0082] On the other hand, in S10, if the control device 100 has at least one identification value indicating the occurrence of tempering in the data set (S10: Yes), the process proceeds to S20.

[0083] In S20, the control device 100 selects the second process as the pressurization process. Then, the control device 100 calculates the adjusted pressurization pressure ΔQP as a preparation stage process in the second process. Specifically, the control device 100 refers to the occurrence data set. Furthermore, the control device 100 counts the number of tempering occurrences. The control device 100 processes the counted number of tempering occurrences as the tempering occurrence frequency K, i.e., the pre-pressurization frequency, during the period from the current time point to the set period. Next, the control device 100 refers to a specific mapping. Based on the specific mapping, the control device 100 calculates the adjusted pressurization pressure ΔQP corresponding to the pre-pressurization frequency. Afterward, the control device 100 proceeds to S30.

[0084] In S30, the control device 100 begins the main processing of the second process. That is, thereafter, the control device 100 repeatedly calculates the target boost pressure QPt using Equation 1 and controls WGV25 based on the target boost pressure QPt. When calculating the target boost pressure QPt, the control device 100 applies the latest basic boost pressure QPn calculated at any time through the basic process and the adjustment boost pressure ΔQP calculated in S20 to Equation 1. As explained in S80, the basic boost pressure QPn calculated by the control device 100 in the basic process changes over time. Correspondingly, the target boost pressure QPt calculated by the control device 100 using Equation 1 at each timing also changes over time. Before ending the second process in S50 (described later), the control device 100 performs feedback control on the opening of WGV25 in a manner that enables the target boost pressure QPt to change over time. When the main processing of the second process begins, the control device 100 causes the process to enter S40. Furthermore, during the execution of the second process, the control device 100 ensures that the torque of the electric generator 82 is greater than the required torque of the motor, determined according to the required driving force. Specifically, the control device 100 calculates an estimated value of the torque of the current internal combustion engine 10 based on the latest internal combustion engine speed NE, the latest internal combustion engine load rate KL, and the latest target boost pressure QPt. Then, the control device 100 increases the torque of the electric generator 82 by the absolute value of the difference between this estimated value and the required torque of the internal combustion engine.

[0085] In S40, the control device 100 determines whether there is no longer a pressurization requirement. Specifically, the control device 100 determines whether the basic pressurization pressure QPn calculated through the basic process has switched from a value greater than zero to zero. If the basic pressurization pressure QPn remains greater than zero (S40: No), the control device 100 executes the process of S40 again. The control device 100 repeats the process of S40 until the basic pressurization pressure QPn switches to zero. When the basic pressurization pressure QPn switches to zero (S40: Yes), the control device 100 causes the process to proceed to S50.

[0086] In S50, the control device 100 terminates the pressurization process executed under the current conditions. Afterwards, the control device 100 terminates a series of processes within the pressurization use routine.

[0087] The function of the first implementation method

[0088] Assume that flashback is currently frequent. Assume that there is a pressure boosting requirement under this condition. Therefore, the control device 100 calculates the adjusted boosting pressure ΔQP corresponding to the frequency K of flashback occurrence during the period from the current time point to the set period (S20). Then, the control device 100 sets the value obtained by subtracting the adjusted boosting pressure ΔQP from the basic boosting pressure QPn as the target boosting pressure QPt to control WGV25 (S30).

[0089] Effects of the first embodiment

[0090] (1-1) If backfire occurs during the set period before the boost demand is generated, the engine state at the time the boost demand is generated is often in a state prone to backfire. Furthermore, in this case, boosting may be performed in an engine state prone to backfire. Therefore, in this embodiment, if backfire occurs before the boost demand is generated, boosting is performed at a lower boost pressure QP than if no backfire occurs. Therefore, the engine state during boosting can be made to be an engine state where backfire is extremely difficult to occur. Thus, backfire during boosting can be suppressed.

[0091] (1-2) As described above, the frequency K of backfire occurrence within the set period is an indicator of the internal combustion engine condition regarding the susceptibility of backfire. Furthermore, the higher the frequency K of backfire occurrence, the more likely the internal combustion engine condition is to experience backfire. Therefore, in this embodiment, the higher the frequency K of backfire occurrence, that is, the more likely the backfire is to occur, the greater the decrease in the target boost pressure QPt, i.e., the adjustment of the boost pressure ΔQP. In this way, by determining the decrease in the target boost pressure QPt based on the susceptibility of backfire, backfire can be more appropriately suppressed.

[0092] (1-3) If the number of combustion cycles, i.e., the number of intake strokes, is high, the frequency of backfire occurrence, K, will also increase accordingly. In this embodiment, the setting period is determined based on the number of combustion cycles. Therefore, the decrease in target boost pressure QPt, i.e., the adjustment of boost pressure ΔQP, can be determined based on the frequency K of backfire occurrence under the same number of combustion cycles. Therefore, a more appropriate target boost pressure QPt can be set to suppress backfire.

[0093] Implementation Method 2

[0094] A second embodiment of the control device for an internal combustion engine will be described. In this second embodiment, only the turbocharging process differs from the first embodiment. Hereinafter, the description will focus on the parts that differ from the first embodiment, and the description of content that is repeated in the first embodiment will be simplified or omitted.

[0095] Similar to the first embodiment, the control device 100 repeatedly calculates the target boost pressure QPt and controls the WGV25 based on the target boost pressure QPt during the boosting process. However, in this embodiment, the control device 100 calculates the target boost pressure QPt in a different manner than in the first embodiment. Specifically, the control device 100 calculates the target boost pressure QPt by taking into account the upper limit of the boost pressure QP of the turbocharger 20. As prerequisite information for this purpose, the control device 100 stores a substantially limited value Vs in advance. The substantially limited value Vs is the upper limit of the boost pressure QP that is permissible when backfire suppression is not required, for example, by experiment or simulation. The substantially limited value Vs is a value determined by taking into account, for example, the volume of the cylinder 11, the boosting capacity of the turbocharger 20, and other limits determined according to various specifications of the internal combustion engine 10. Before calculating the target boost pressure QPt, the control device 100 calculates the upper limit value of the boost pressure QP that should be set under the current condition, i.e., the upper limit boost pressure Vm, based on the basic limit value Vs. Then, the control device 100 calculates the target boost pressure QPt using this upper limit boost pressure Vm as the upper limit.

[0096] As described in the first embodiment, the pressurization process includes a normal process and a second process. The normal process is the process in which no tempering occurs before pressurization. The second process is the process in which tempering occurs before pressurization. In this embodiment, the upper limit pressurization pressure Vm is set differently in the normal process and the second process. In the normal process, the control device 100 sets the aforementioned basic upper limit value Vs as the upper limit pressurization pressure Vm.

[0097] On the other hand, in the second process, the control device 100 reduces the upper limit boost pressure Vm compared to the case where no backfire occurred during the pre-pressurization setting period. As a specific process for this, in the second process, the control device 100 calculates an adjustment boost pressure ΔQP as an adjustment value for reducing the upper limit boost pressure Vm. Furthermore, as shown in Equation 2 below, the control device 100 sets the value obtained by subtracting the adjustment boost pressure ΔQP from the essentially limit value Vs as the upper limit boost pressure Vm. This upper limit boost pressure Vm reduces the adjustment boost pressure ΔQP compared to the upper limit boost pressure Vm under normal processing conditions.

[0098] (Equation 2) Vm=Vs-ΔQP

[0099] The control device 100 pre-stores a specific mapping, similar to that in the first embodiment, as information for calculating the adjusted boost pressure ΔQP. That is, the specific mapping represents the relationship between the frequency K of tempering occurrence and the adjusted boost pressure ΔQP within a set period. However, the adjusted boost pressure ΔQP specified by the specific mapping in this embodiment is a value specifically for adjusting the upper limit boost pressure Vm. Furthermore, the maximum value of the adjusted boost pressure ΔQP specified by the specific mapping is smaller than the essentially lower limit Vs. As explained in the first embodiment, the relationship between the tempering frequency K and the adjusted boost pressure ΔQP is as follows: When the tempering frequency K is lower than the execution threshold K1, the adjusted boost pressure ΔQP is zero. On the other hand, when the tempering frequency K is higher than or equal to the execution threshold K1, the higher the tempering frequency K, the greater the adjusted boost pressure ΔQP. Furthermore, similar to the first embodiment, the tempering frequency K is the number of tempering occurrences within the set period itself.

[0100] The role of the second implementation method

[0101] As to the purpose of this embodiment, a brief explanation is provided. Figure 5 The pressurization process shown is as follows. Furthermore, the processing content of S10, S40, and S50 is the same as in the first embodiment, so descriptions are omitted. If the control device 100 determines in S10 that no backfire has occurred (S10: No), the process proceeds to S180. In this case, the control device 100 begins pressurizing the intake air based on the normal processing. As described above, in normal processing, the control device 100 directly sets the essentially limit value Vs as the upper limit pressurization pressure Vm. Furthermore, the control device 100 calculates the smaller of the upper limit pressurization pressure Vm and the latest basic pressurization pressure QPn as the target pressurization pressure QPt. The control device 100 controls WGV25 based on the target pressurization pressure QPt. The control device 100 repeatedly calculates the target pressurization pressure QPt and controls WGV25 based on the target pressurization pressure QPt.

[0102] On the other hand, if the control device 100 determines in S10 that a backfire has occurred (S10: Yes), the process proceeds to S20. Then, in S20, the control device 100 calculates the adjusted boost pressure ΔQP in the same manner as in S20 of the first embodiment. Then, in S130, the control device 100 begins the main process of the second process. As described above, in the second process, the control device 100 calculates the upper limit boost pressure Vm by applying the essentially limit value Vs and the adjusted boost pressure ΔQP calculated in S20 to Equation 2. Then, the control device 100 calculates the smaller of the upper limit boost pressure Vm and the latest basic boost pressure QPn as the target boost pressure QPt. Then, the control device 100 controls WGV25 based on the target boost pressure QPt. The control device 100 repeatedly calculates the target boost pressure QPt and controls WGV25 based on the target boost pressure QPt.

[0103] Effects of the second implementation method

[0104] (2-1) As explained in the first embodiment, if backfire occurs during the set period before the boost demand is generated, the internal combustion engine state at the time the boost demand is generated tends to be in a state prone to backfire. Therefore, in this embodiment, if backfire occurs before the boost demand is generated, the upper limit boost pressure Vm is reduced compared to the case where backfire does not occur. In this way, boosting can be performed at an extremely low boost pressure QP. Furthermore, this makes the internal combustion engine state during boosting extremely difficult to cause backfire. Therefore, the occurrence of backfire during boosting can be suppressed.

[0105] (2-2) In this embodiment, the higher the frequency K of tempering, that is, the more likely tempering is to occur, the greater the decrease in the upper limit boost pressure Vm, i.e., the greater the adjustment of the boost pressure ΔQP. In this way, by determining the decrease in the upper limit boost pressure Vm based on the likelihood of tempering, tempering can be suppressed more appropriately.

[0106] (2-3) Similar to the first embodiment, in this embodiment, the setting period is determined based on the number of combustion cycles. Therefore, the decrease in the upper limit boost pressure Vm, i.e., the boost pressure ΔQP, can be determined based on the frequency K of backfire occurring under the same number of combustion cycles. Therefore, a more appropriate upper limit boost pressure Vm can be set to suppress backfire.

[0107] Change Example

[0108] Furthermore, the above embodiments can be implemented by modification as follows. The embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0109] The method for determining whether backfire occurs in the first process is not limited to the examples of the above embodiments. For example, parameters other than the downstream intake air temperature T can be used to determine whether backfire occurs. Here, when backfire occurs, the pressure of the intake air in the intake passage 12 downstream of the throttle valve 16 increases instantaneously. With this in mind, the occurrence of backfire can also be determined based on the shift in the pressure of the intake air in the intake passage 12 downstream of the throttle valve 16. In the case of adopting such a technical solution, an intake air pressure sensor that detects the pressure of the intake air can be installed in the intake passage 12 downstream of the throttle valve 16. In addition, the shift in the pressure of the gas in the cylinder 11, the shift in the internal combustion engine speed NE, etc., can also be used to determine whether backfire occurs. As long as the method for determining whether backfire occurs is based on the operating state of the internal combustion engine 10 and can appropriately capture the occurrence of backfire, the determination method is not limited.

[0110] The method of recording the determination result in the first process is not limited to the examples of the above embodiments. The method of recording the determination result is sufficient to understand the occurrence of tempering in the preceding stage when a pressurization requirement is generated. As in the following modified examples, the number of data sets required to understand the tempering frequency K varies depending on the method for determining the setting period. Therefore, the method of recording the determination result can also be changed according to the method for determining the setting period.

[0111] In S10, determining whether tempering occurred before pressurization can be based on whether multiple tempering events occurred, rather than just whether a single tempering event occurred. That is, it can also be determined whether a predetermined number of tempering events occurred before pressurization. In S10, it is sufficient to determine whether tempering occurred before pressurization.

[0112] In S20, the adjusted boost pressure ΔQP is calculated based on the correspondence with the tempering frequency K. The definition of the tempering frequency K used here is not limited to the number of tempering events. The tempering frequency K can be any parameter that allows for the assessment of the degree of tempering. For example, the tempering frequency K may not be the number of tempering events, but rather a proportion (ratio). If the definition of the tempering frequency K is changed, the specific mapping content can be changed accordingly.

[0113] Tracing back from the point when pressurization was required, the tempering that occurs at the most recent point in time is called final tempering. Alternatively, the period from the timing of final tempering to the point when pressurization was required can be used as the tempering frequency K. Furthermore, it can be considered that the shorter this period, the higher the tempering frequency K.

[0114] The method for determining the setting period is not limited to the examples of the above embodiments. For example, the setting period may be set to a constant fixed value (hereinafter referred to as the fixed setting period). The fixed setting period may also be set to approximately several minutes. Such a time scale is suitable for determining whether the internal combustion engine 10 is in a state prone to backfire under the current conditions.

[0115] In the case of using a fixed set period, unlike the above-described embodiment where the set period is determined based on the number of rotations of crankshaft 17 and thus the number of combustion cycles, the set period is set as an absolute time. In this case, when calculating the frequency K of backfire occurrence within the set period in S20, if there is a backfire history along the time progression rather than a backfire history along the combustion cycle progression, the frequency K of backfire occurrence can be easily determined. Based on this, in the case of using a fixed set period, a first technical solution can also be used in the first process to record the occurrence of backfire. Here, in the above embodiment, not only when backfire occurs, but also when backfire does not occur, the determination results are recorded sequentially to create an occurrence data set. In the first technical solution, information on cases where backfire does not occur is not recorded; only information on cases where backfire occurs is stored in the storage device 113. That is, only when the above-described specific conditions are met is the first specific information stored in the storage device 113. The first specific information is expressed in units of seconds or less as the time when the specific conditions are met. If the timing information is recorded, when a pressurization request is made, by comparing the time when the pressurization request is made with the time when tempering occurs, it can be determined whether tempering occurred within a set period prior to the pressurization request. In the first technical solution, a certain number of such timing information are accumulated to form an occurrence data group while rewriting old data with new data, thus forming an occurrence data group. In such an occurrence data group, by omitting information indicating that tempering did not occur, the amount of data required to determine the occurrence status of tempering can be minimized. Therefore, the number of data constituting the occurrence data group can be reduced. Furthermore, the data capacity of the occurrence data group can be reduced.

[0116] The setting period can also be set to the period during which the vehicle 90 travels a pre-set travel distance (hereinafter referred to as the specified distance). The specified distance is, for example, about 1 km, and the distance for the setting period can be determined from the same perspective as the above-described embodiment. Hereinafter, the setting period determined by corresponding to the travel distance of the vehicle 90 will be referred to as the travel setting period.

[0117] When using the driving setting period, a second technical solution can also be adopted in the first process to record the occurrence of backfire. That is, in the second technical solution, similar to the first technical solution, the second specific information is stored in the storage device 113 only when the specific conditions mentioned above indicating the occurrence of backfire are met. The second specific information represents the value of the odometer 35 at the time when the specific conditions are met, in meters. That is, the occurrence data set in this case is obtained by accumulating a certain number of odometer 35 values ​​while rewriting old data with new data. Furthermore, in this case, the value of the odometer 35 is used to determine whether backfire occurs during the driving setting period before boosting, and thus to determine the number of times backfire occurs. Specifically, the occurrence of backfire can be determined by the following method. Now, suppose there is a boosting requirement. The value of the odometer 35 at the time when the boosting requirement is met is called the instrument value at the time of requirement. Furthermore, the value that is a certain distance smaller than the instrument value at the time of requirement is called the inverse operation value. If the value of the odometer 35 stored in the storage device 113 is a value between the required instrument value and the inverse operation value, then it can be known that backfire occurred after the specified timing. The specified timing is the timing of the driving period traversing a specified distance from the time point when the boost requirement was made, that is, the timing of the driving setting period traversing from the time point when the boost requirement was made. In this way, by judging whether the value of the odometer 35 included in the occurrence data group is a value between the required instrument value and the inverse operation value, it is possible to know the occurrence status of backfire during the driving setting period before boosting.

[0118] When using the aforementioned driving setting period, the backfire occurrence frequency K, calculated for adjusting the boost pressure ΔQP, is preferably the backfire occurrence ratio. The reason is as follows. Here, consider the situation where the vehicle 90 maintains a constant gear ratio while traveling the specified distance. Since the gear ratio is constant, the number of crankshaft 17 rotations required to travel this specified distance, and consequently the number of combustion cycles, is determined to be a unique value corresponding to the wheel diameter and gear ratio. Furthermore, this unique value differs for each gear ratio. In other words, when maintaining a constant gear ratio during the driving setting period, the number of combustion cycles during this driving setting period is determined to be an inherent value for each gear ratio. Therefore, when using the driving setting period, although the condition of a constant gear ratio during the driving setting period exists, the number of backfire occurrences can be counted by adjusting the number of combustion cycles for each gear ratio. With this in mind, the following technical solution is also effective when using the driving setting period. That is, in the technical solution, the number of combustion cycles during the driving setting period is pre-stored in the storage device 113 for each gear ratio. Furthermore, when an acceleration requirement is requested, the number of backfire occurrences during the driving setting period prior to the acceleration requirement is divided by the number of combustion cycles corresponding to the gear shift during that driving setting period. The backfire occurrence ratio is then calculated as the backfire frequency K. The calculated backfire occurrence ratio is then applied to a specific mapping to calculate the adjusted boost pressure ΔQP. If the gear shift during the driving setting period is constant, the above-described technical solution is also effective. In this technical solution, a mapping representing the relationship between the backfire occurrence ratio and the adjusted boost pressure ΔQP is pre-created as the specific mapping. In this specific mapping, the following relationship holds: the higher the backfire occurrence ratio, the higher the adjusted boost pressure ΔQP. Additionally, when using this technical solution, the history of the target gear shift set at any time during the vehicle 90's driving period can be pre-stored in the storage device 113. This allows the gear shift during the driving setting period prior to boosting to be known.

[0119] When the above-described technical solution is adopted, the following advantages are available. First, as described above, by utilizing the driving setting period, the number of backfire occurrences can be counted by adjusting the number of combustion cycles for each gear level. Based on this, by using the backfire occurrence ratio, the influence of the different number of combustion cycles for each gear level can be eliminated, and the backfire occurrence frequency K can be calculated. By calculating the adjusted boost pressure ΔQP based on this occurrence frequency K, the ease of backfire occurrence can be calculated under the same reference. Here, when utilizing the driving setting period, the second technical solution described above can be used to record the backfire occurrence status. In this case, in the second technical solution, similar to the first technical solution, the data capacity of the occurrence data set can be suppressed. Therefore, by combining the second technical solution and the specified technical solution, an appropriate adjusted boost pressure ΔQP can be set while suppressing the data capacity.

[0120] The parameter (hereinafter referred to as the specified parameter) that specifies the magnitude of the adjusted boost pressure ΔQP when calculating the boost pressure ΔQP in S20 is not limited to the frequency of backfire occurrence K. The specified parameter can be any parameter representing the engine state regarding the susceptibility to backfire. The downstream intake temperature T can also be used as the specified parameter. In this case, for example, the following can also be used: Figure 6The adjusted boost pressure ΔQP is calculated using a specific mapping of the temperatures shown. This specific mapping represents the relationship between the downstream intake temperature T before boosting, i.e., the pre-intake temperature TB, and the adjusted boost pressure ΔQP. The pre-intake temperature TB is, for example, the average value of the downstream intake temperature T over a certain period prior to the point when boosting is required. This certain period is, for example, 1 minute, and is preset to be the length of time for which the average downstream intake temperature T at the start of boosting can be obtained. The set period used in S10 can also be used as the certain period. In the specific mapping, the relationship between the pre-intake temperature TB and the adjusted boost pressure ΔQP is as follows: When the pre-intake temperature TB is below the first threshold T1, the adjusted boost pressure ΔQP is zero. On the other hand, when the pre-intake temperature TB is above the first threshold T1, the higher the pre-intake temperature TB, the greater the adjusted boost pressure ΔQP. Moreover, even during periods when the pre-intake temperature TB is above the first threshold T1, the rate of increase of the adjusted boost pressure ΔQP relative to the pre-intake temperature TB varies depending on the magnitude of the pre-intake temperature TB. Specifically, compared to the case where the pre-intake temperature TB is above the first threshold T1 and below the second threshold T2, the increase rate is greater when the pre-intake temperature TB is above the second threshold T2. Under this setting, when the pre-intake temperature TB is above the second threshold T2, the adjustment of the boost pressure ΔQP is quite large. The first threshold T1 is explained below. It can be said that the higher the pre-intake temperature TB, the more likely the internal combustion engine will be in a state where backfire is likely to occur. The first threshold T1 is set as the minimum pre-intake temperature TB required to ensure that the internal combustion engine 10 is in a state where backfire is likely to occur and that measures are needed to suppress backfire. The second threshold T2 is explained below. The second threshold T2 is set as the pre-intake temperature TB that requires extensive measures to suppress backfire. The specific mappings of the first threshold T1 and the second threshold T2 described above are based on experiments or simulations.

[0121] In Figure 6When the specific mapping shown is applied to the configuration of the first embodiment, the following can be stated. As explained in the first embodiment, adjusting the boost pressure ΔQP corresponds to the decrease in the basic boost pressure QPn when the target boost pressure QPt is set. In other words, a larger adjustment of the boost pressure ΔQP means a greater decrease in the target boost pressure QPt compared to the case where backfire does not occur. Therefore, when setting the adjustment of the boost pressure ΔQP using the specific mapping described above, the higher the pre-inlet temperature TB, the greater the decrease in the boost pressure QP compared to the case where backfire does not occur. If the basic boost pressure QPn is the same, the higher the pre-inlet temperature TB, the smaller the target boost pressure QPt. Furthermore, by determining the decrease in the target boost pressure QPt based on the susceptibility of backfire in this way, backfire can be suppressed more appropriately.

[0122] Similarly, in the case of Figure 6 When the specific mapping shown is applied to the configuration of the second embodiment, the following can be stated. As explained in the second embodiment, adjusting the boost pressure ΔQP corresponds to the decrease in the basic limit value Vs when the upper limit boost pressure Vm is set. In other words, a larger adjustment of the boost pressure ΔQP means that the decrease in the upper limit boost pressure Vm is increased compared to the case where backfire does not occur. Therefore, when setting the adjustment of the boost pressure ΔQP using the specific mapping described above, the higher the pre-inlet temperature TB, the greater the decrease in the upper limit boost pressure Vm compared to the case where backfire does not occur. Furthermore, by determining the decrease in the upper limit boost pressure Vm based on the susceptibility of backfire in this way, backfire can be suppressed more appropriately.

[0123] In addition, in utilizing Figure 6 When calculating the adjusted boost pressure ΔQP using the specific mapping shown, the historical downstream intake temperature T can be stored in the storage device 113. In this way, when there is a boost requirement, the aforementioned pre-intake temperature TB can be calculated for the period from that point in time to a certain point in time.

[0124] As described in the various modification examples above, the content of the specific mapping is not limited to the examples of the above embodiments. The content of the specific mapping can also be appropriately changed according to the setting method during the setting period, the specified parameters, etc. The specific mapping is only required to be able to appropriately calculate the content of the adjusted boost pressure ΔQP. The specific mapping is not limited to tables or graphs, but can also be a mathematical formula.

[0125] There is no need to increase or decrease the boost pressure ΔQP based on the frequency K of tempering. That is, the boost pressure ΔQP can be set to a predetermined fixed value.

[0126] The overall configuration of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the number of cylinders 11 can be changed. The fuel injection valve 14 can also be changed to a type that directly injects fuel into the cylinders 11. The fuel injected by the fuel injection valve 14 is not limited to hydrogen, as long as it is a gaseous fuel. If the downstream intake air temperature T is not used in either the first or second process, the intake air temperature sensor 34 can be discarded. The internal combustion engine 10 can have cylinders 11, intake passages 12, and a turbocharger 20.

[0127] The configuration of the booster 20 can also be modified. For example, a variable-capacity booster with nozzle blades can be used. In this case, to make the actual boost pressure QP match the target boost pressure QPt during the boosting process, the opening of the nozzle blades can be changed. Alternatively, an electric booster that rotates the compressor impeller via an electric motor can also be used. In this case, to make the actual boost pressure QP match the target boost pressure QPt during the boosting process, the speed of the electric motor can be changed.

[0128] The overall configuration of the vehicle 90 is not limited to the examples of the embodiments described above. For example, a continuously variable transmission (CVT) can also be used as the automatic transmission 85. The vehicle may also have only an internal combustion engine 10 as the drive source. In this case, for example, the decrease in torque of the internal combustion engine 10 accompanying the second process can be compensated by adjusting the ignition timing, air-fuel ratio, etc.

Claims

1. A control device for an internal combustion engine, wherein the control device takes the internal combustion engine as the controlled object, and the internal combustion engine has: A cylinder for burning a mixture of gaseous fuel and intake air; An intake passage, wherein the intake passage is connected to the cylinder; A booster, which pressurizes the intake air; and Crankshaft The vehicle equipped with the internal combustion engine is designated as the vehicle, and the vehicle equipped with the internal combustion engine has an odometer for measuring the vehicle's travel distance and a stepped automatic transmission. When the period of rotating the crankshaft 720 degrees is defined as one combustion cycle, The number of combustion cycles required for the vehicle to travel 1 km is pre-stored for each gear of the automatic transmission. During the operation of the vehicle, the target value of the transmission level, i.e., the history of the target transmission level, is stored. During the operation of the internal combustion engine, the control device of the internal combustion engine performs the following processes: The first process, based on the operating state of the internal combustion engine, determines whether the conditions indicating backfire are met, and is limited to the case where the conditions are met, and stores the odometer value at the time when the conditions are met as specific information; and The second process involves setting the odometer value at the point when a boost requirement is requested as the required instrument value, setting a value 1 km less than the required instrument value as the inverse operation value, and setting the driving period of the vehicle from the inverse operation value to the required instrument value as the set period. In the set period prior to the boost requirement, if the target transmission is constant, the process calculates the number of backfire occurrences between the inverse operation value and the required instrument value based on the specific information stored in the first process. The backfire occurrence ratio is calculated by dividing the calculated number of occurrences by the number of combustion cycles corresponding to the transmission during the set period, which is historically known from the target transmission. A higher occurrence ratio allows for a lower boost pressure than if no backfire occurred during the set period prior to the boost requirement.

Images