Control device for internal combustion engine

Abstract

To properly calculate a value to be an index of a combustion state of air-fuel mixture.SOLUTION: The control device 100 executes a process of acquiring a shaft torque of the internal combustion engine 10 during combustion of the air-fuel mixture, a process of acquiring a motoring torque that is a shaft torque when the air-fuel mixture is not combusted, and a process of calculating a combustion torque that is a difference between the shaft torque during combustion and the motoring torque. When a crank angle at which a heat generation amount by combustion of fuel supplied to one cylinder in one combustion cycle becomes a predetermined ratio to a total heat generation amount of the fuel is defined as a combustion ratio position, the control device 100 executes processing for calculating the combustion ratio position based on the combustion torque.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] For example, in Patent Document 1, the combustion state of the air-fuel mixture is estimated based on the gas pressure torque within a crank angle range that is set according to the operating state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-164167 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the gas pressure torque varies depending not only on the combustion state but also on the operating state of the internal combustion engine. Therefore, conventional techniques may not be able to properly calculate a value that serves as an index of the combustion state of the air-fuel mixture. [Means for solving the problem]

[0005] A control device for an internal combustion engine that solves the above problem executes a process of acquiring the axial torque of the internal combustion engine when the mixture is being burned, a process of acquiring the motoring torque, which is the axial torque when the mixture is not being burned, a process of calculating the combustion torque, which is the difference between the axial torque and the motoring torque when the mixture is being burned, and a process of calculating the combustion ratio position based on the combustion torque, when the crank angle at which the heat generated by the combustion of fuel supplied to one cylinder in one combustion cycle is a predetermined ratio to the total heat generated by the fuel is defined as the combustion ratio position. [Effects of the Invention]

[0006] According to the present invention, it is possible to appropriately calculate a value that serves as an index of the combustion state of the air-fuel mixture. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a vehicle according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of processing executed by the control device of the embodiment. [Figure 3] FIG. 3 is a diagram showing changes in shaft torque, motoring torque, and combustion torque. [Figure 4] FIG. 4 is a diagram showing the correspondence relationship between the integrated value ratio and the combustion ratio position. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. <Configuration of a vehicle equipped with an internal combustion engine> As shown in FIG. 1, a vehicle 500 is a hybrid vehicle equipped with two prime movers, an internal combustion engine 10 and a motor generator 50.

[0009] The crankshaft 20 of the internal combustion engine 10 is connected to a damper 30. The damper 30 is connected to a rotating shaft of a motor generator 50 via a clutch mechanism 40. Clutch mechanism 40 is a mechanism that adjusts the amount of torque transmitted between crankshaft 20 and the rotating shaft of motor generator 50. When clutch mechanism 40 is in an engaged state, crankshaft 20 is connected to the rotating shaft of motor generator 50, and when clutch mechanism 40 is in a released state, the connection between crankshaft 20 and the rotating shaft of motor generator 50 is released.

[0010] The rotary shaft of the motor generator 50 is connected to an input shaft 60 of the transmission 70. The transmission 70 has a torque converter (not shown) and a speed change mechanism that changes the gear ratio. The output shaft of the transmission 70 is connected to a propeller shaft 80. The propeller shaft 80 is connected to a differential gear 82. The differential gear 82 is connected to driving wheels 90 of the vehicle 500 via a drive shaft 84.

[0011] Various controls such as output control of the internal combustion engine 10, output control of the motor generator 50, and speed change control of the transmission 70 are performed by a control device 100. The control device 100 includes a CPU 110 and a memory 120 that stores control programs and data. The CPU 110 executes the programs stored in the memory 120 to perform various types of control. For example, the control device 100 controls fuel injection of a fuel injection valve provided in the internal combustion engine, and controls the ignition timing of a spark plug provided in the internal combustion engine. The control device 100 also performs EGR control to adjust the amount of EGR introduced into the intake air by an exhaust gas recirculation device provided in the internal combustion engine.

[0012] Although not shown, the control device 100 is made up of a plurality of control units, such as a control unit for the internal combustion engine, a control unit for the motor generator, and a control unit for the transmission.

[0013] To perform various controls, the control device 100 refers to the intake air amount GA detected by the air flow meter 14. The control device 100 also calculates the angular velocity ωE of the crankshaft 20 and the engine rotation speed NE based on the output signal Scr of the crank angle sensor 12. The control device 100 also calculates the angular velocity ωMG of the rotor of the motor generator 50 based on the output signal Sm of the rotation angle sensor 42. The control device 100 calculates the engine load factor KL and the intake air filling efficiency CE based on the engine rotation speed NE, the intake air amount GA, etc.

[0014] In addition to the various sensors described above, the control device 100 also refers to signals output from various well-known sensors that detect the state of the internal combustion engine 10 and the state of the vehicle. <Calculation of the combustion fraction position> In the crank angle described below, the compression top dead center is defined as "0°", and times before this compression top dead center are represented by negative values, and times after this compression top dead center are represented by positive values.

[0015] The control device 100 executes a process for detecting the combustion state of the air-fuel mixture. In this embodiment, the combustion ratio position is calculated as a value that serves as an index of the combustion state of the air-fuel mixture. The combustion fraction position is the crank angle at which the heat generated by the combustion of fuel supplied to one cylinder in one combustion cycle is a predetermined ratio to the total heat generated by that fuel. In other words, the combustion fraction position is equal to the following value: When the mass combustion ratio, which represents the ratio of the burned mass of the fuel supplied to one cylinder in one combustion cycle, is set to an arbitrary value, the combustion fraction position is equal to the crank angle at which fuel of the set ratio is burned in the expansion stroke.

[0016] For example, the crank angle value when the heat generated by fuel combustion is 10% of the total heat generated is an index value for the ignition delay of the air-fuel mixture. Specifically, the later the combustion fraction position, that is, the larger the value of the combustion fraction position, the longer the ignition delay. In the following, the crank angle when the heat generated by fuel combustion is n% (n is an arbitrary value) of the total heat generated is referred to as the n% combustion fraction position.

[0017] The calculation process for the combustion rate position will be described below. 2 shows the procedure of the process executed by the control device 100 to calculate the combustion ratio position. This process is executed while the internal combustion engine 10 is in operation. In the following, the step number of each process is represented by a number preceded by "S."

[0018] 2 starts, the control device 100 acquires the axial torque Ts of the internal combustion engine 10 when the air-fuel mixture is combusted (S100). The control device 100 calculates the axial torque Ts in the target cylinder for each predetermined crank angle A based on the following equation (1). Then, in the processing of S100, the control device 100 acquires the value of the axial torque Ts calculated for each crank angle A.

[0019] Ts = IE dωE - Tx (1) IE shown in equation (1) is a known value and is the inertial mass of the internal combustion engine 10. dωE shown in equation (1) is the angular acceleration obtained by differentiating the angular velocity ωE of the crankshaft 20.

[0020] Tx shown in equation (1) is a disturbance torque such as a drive system resonance, and the control device 100 calculates the disturbance torque Tx based on the following equation (2). Tx=K·(θMG-θE)…(2) K in equation (2) is the spring constant of damper 30 and is a known value. θMG in equation (2) is the rotation angle of the rotor of motor-generator 50 and is a value calculated based on the output signal Sm of rotation angle sensor 42. θE in equation (2) is the rotation angle of crankshaft 20 and is a value calculated based on the output signal Scr of crank angle sensor 12. The value (θMG - θE) obtained by subtracting the rotation angle θE of crankshaft 20 from the rotation angle θMG of the rotor is a value indicating the torsion angle of damper 30.

[0021] Next, the control device 100 acquires the motoring torque Tm, which is the shaft torque of the internal combustion engine 10 when the air-fuel mixture is not burning (S110). The motoring torque Tm is a value that indicates the magnitude of the compression resistance and friction resistance of the air-fuel mixture that resist the rotation of the crankshaft 20. The control device 100 acquires the engine rotation speed NE, the intake air filling efficiency CE, and the like. Then, the control device 100 calculates the motoring torque Tm for each crank angle A based on these acquired values. Then, in the processing of S110, the control device 100 acquires the value of the motoring torque Tm calculated for each crank angle A.

[0022] Next, the control device 100 calculates the combustion torque T in the target cylinder for each predetermined crank angle A (S120). As shown in Fig. 3, combustion torque T is a difference value obtained by subtracting motoring torque Tm from shaft torque Ts. Therefore, in the process of S120 shown in Fig. 2, control device 100 calculates a value obtained by subtracting motoring torque Tm calculated in the process of S110 from shaft torque Ts calculated in the process of S100. Then, control device 100 substitutes the calculated value for combustion torque T.

[0023] Next, the control device 100 sets the first section based on the currently set ignition timing of the air-fuel mixture (S130). As shown in FIG. 3, the first section is the crank angle section for calculating the combustion torque T, and more specifically, it is a period that includes the combustion torque rise section. The combustion torque rise section is the section from when the combustion torque starts to be generated until it reaches its maximum value. Here, it has been found that the adiabatic expansion section after the combustion of the air-fuel mixture is completed generates combustion torque, but this section does not correlate with the combustion ratio position. Therefore, it would be ideal to set the first section from when the combustion torque starts to be generated by ignition of the air-fuel mixture to just before the adiabatic expansion section begins. However, in this embodiment, for simplicity, the start of the first section is set to top dead center of compression stroke.

[0024] Furthermore, if the ignition timing is retarded, the ignition timing will be delayed. Therefore, if the first interval is not set appropriately, it may not be possible to include the entire rise interval of the combustion torque within the first interval. Therefore, in the processing of S130, the control device 100 sets the first interval based on the ignition timing of the currently set air-fuel mixture. More specifically, the first interval is set so that the end timing of the first interval becomes later as the retard amount of the ignition timing from the compression top dead center increases.

[0025] Next, the control device 100 calculates a first integrated value Ti1 and a second integrated value Ti2 (S140). The first integrated value Ti1 is a value obtained by integrating the combustion torque T calculated for each predetermined crank angle A within the first section.

[0026] The second integrated value Ti2 is a value obtained by integrating the combustion torque T calculated for each predetermined crank angle A within the second interval. As shown in FIG. 3, the second interval includes the first interval and is wider than the first interval. Ideally, the second interval should include the entire period during which combustion torque is generated. However, in this embodiment, the compression top dead center is simply set as the start timing of the second interval. Also, in this embodiment, 180° after the compression top dead center is simply set as the end timing of the second interval.

[0027] Next, the control device 100 calculates the integrated value ratio RT (S150). The integrated value ratio RT is the value obtained by dividing the first integrated value Ti1 by the second integrated value Ti2 (RT=Ti1 / Ti2). Next, the control device 100 calculates the combustion rate position based on the calculated integrated value rate RT (S160).

[0028] 4, in the process of S160, the control device 100 calculates the combustion ratio position by referring to preset map data or the like so that the greater the value of the integrated value ratio RT, the smaller the value of the combustion ratio position. The integrated value ratio RT and the combustion ratio position are calculated after the second interval in the target cylinder ends, that is, after the combustion cycle in the target cylinder ends. Based on the calculated combustion ratio position, the control device 100 sets various combustion control parameters, such as the ignition timing, fuel injection amount, and EGR amount, to optimal values ​​for the next and subsequent combustion cycles in the target cylinder.

[0029] For example, when the ignition timing is significantly retarded to warm up the catalyst during a cold start, the first integrated value Ti1 for a cylinder in which ignition delay occurs will be smaller than the first integrated value Ti1 for a cylinder in which ignition delay does not occur. Therefore, the integrated value ratio RT for a cylinder in which ignition delay occurs will be smaller than the integrated value ratio RT for a cylinder in which ignition delay does not occur. Therefore, the 10% combustion fraction position calculated based on the integrated value ratio RT for a cylinder in which ignition delay occurs will be larger than the 10% combustion fraction position calculated based on the integrated value ratio RT for a cylinder in which ignition delay does not occur. In other words, the 10% combustion fraction position calculated based on the integrated value ratio RT for a cylinder in which ignition delay occurs will be at a crank angle that is more retarded from the compression top dead center than the 10% combustion fraction position calculated based on the integrated value ratio RT for a cylinder in which ignition delay does not occur. Therefore, the degree of ignition delay in the target cylinder can be determined based on the value of this 10% combustion fraction position. Therefore, for example, when the ignition timing is significantly retarded to warm up the catalyst during a cold start, in cylinders where ignition delay occurs, the occurrence of unpleasant vibrations can be suppressed by implementing control such as advancing the ignition timing according to the value of the 10% combustion fraction position.

[0030] When the process of S160 is completed, the control device 100 ends this process. <Actions and Effects of This Embodiment> (1) The difference between the shaft torque Ts during combustion and the motoring torque Tm during non-combustion is the torque generated by the combustion of fuel, and is correlated with the calorific value of the fuel. On the other hand, the crank angle at which the calorific value of the fuel is a predetermined ratio to the total has traditionally been used as an indicator of the combustion state of the mixture.

[0031] Therefore, in this embodiment, the crank angle at which the heat generation amount due to the combustion of fuel supplied to one cylinder in one combustion cycle is a predetermined ratio to the total heat generation amount of the fuel is defined as the combustion ratio position. The control device 100 calculates the combustion ratio position based on the combustion torque T, which is the difference. Therefore, it is possible to appropriately calculate a value that serves as an index of the combustion state of the air-fuel mixture.

[0032] (2) The control device 100 calculates the combustion torque T for each predetermined crank angle A. The control device 100 executes the following process to calculate the combustion proportion position based on the combustion torque T. The control device 100 executes a process to calculate a first integrated value Ti1, which is the integrated value of the combustion torque T in a predetermined first section that includes the rise section of the combustion torque T. The control device 100 executes a process to calculate a second integrated value Ti2, which is the integrated value of the combustion torque T in a second section that includes the first section but is wider than the first section. The control device 100 executes a process to calculate an integrated value ratio RT, which is the value obtained by dividing the first integrated value Ti1 by the second integrated value Ti2. The control device 100 executes a process to calculate the combustion proportion position based on the integrated value ratio RT.

[0033] In any section including the rising section of combustion torque T, the earlier the ignition and the faster the combustion rate of the air-fuel mixture, the larger the integrated value of combustion torque T within that section. Therefore, such integrated value can be correlated with the combustion proportion position. However, regardless of the combustion proportion position, if the combustion torque itself is large due to high-load operation, the integrated value also becomes large. Therefore, in this embodiment, a first integrated value Ti1, which is the integrated value of combustion torque T in the first section, is calculated, and a second integrated value Ti2, which is the integrated value of combustion torque T in a second section that includes the first section but is wider than the first section, is calculated. The integrated value of combustion torque T is then normalized by calculating the integrated value ratio RT, which is the value obtained by dividing the first integrated value Ti1 by the second integrated value Ti2. The combustion proportion position is then calculated based on this normalized integrated value ratio RT. This reduces the impact of the magnitude of the combustion torque itself, which varies depending on the operating state of the internal combustion engine 10, on the combustion proportion position.

[0034] (3) The control device 100 executes a process for setting the first section based on the ignition timing of the air-fuel mixture. Although the adiabatic expansion section after combustion is complete generates combustion torque T, there is no correlation with the combustion rate position. Therefore, if the adiabatic expansion section is included in the first section, the calculation accuracy of the combustion rate position will deteriorate. On the other hand, if the first section is optimized under conditions of a fast combustion speed, if the ignition timing is delayed by retarding the ignition timing, the entire rise section of combustion torque T may not be included in the first section. In this regard, in this embodiment, the first section is set based on the ignition timing of the air-fuel mixture, and therefore the first section is set to an appropriate section depending on the ignition timing. Therefore, it is possible to prevent the accuracy of the combustion rate position from deteriorating due to the setting of an inappropriate first section.

[0035] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0036] The rise interval of combustion torque T correlates with the combustion interval in which the air-fuel mixture burns. Therefore, the crank angle at which combustion torque T is at its maximum and the crank angle position at which combustion is completed also correlate. Therefore, the crank angle at which combustion torque T is a predetermined ratio of the maximum value of combustion torque T correlates with the combustion ratio position, which is the crank angle at which the heat generated by fuel combustion is a predetermined ratio of the total heat generated by that fuel.

[0037] Therefore, the combustion proportion position may be calculated based on the crank angle at which the combustion torque T is a predetermined ratio of the maximum value of the combustion torque T. For example, the control device 100 acquires the crank angle Aind at which the combustion torque T is a predetermined ratio (e.g., 10% or 50%) of the maximum value Tmax of the combustion torque T. Then, based on the acquired crank angle Aind, the control device 100 executes a process to calculate the combustion proportion position. When calculating this combustion proportion position, the control device 100 may calculate the combustion proportion position by referring to preset map data or the like so that the larger the value of the crank angle Aind, the larger the value of the combustion proportion position.

[0038] The crank angle at which the differential value of the combustion torque T is maximum is the crank angle at which the rise speed of the combustion torque T is maximum, and is correlated with the combustion ratio position described above. Therefore, the combustion percentage position may be calculated based on the crank angle at which the derivative of the combustion torque T is maximized. For example, the control device 100 acquires the crank angle Ad at which the time derivative Td of the combustion torque T is maximized. Then, based on the acquired crank angle Ad, the control device 100 executes a process to calculate the combustion percentage position. When calculating this combustion percentage position, the control device 100 may calculate the combustion percentage position by referring to preset map data or the like so that the larger the value of the crank angle Ad, the larger the value of the combustion percentage position.

[0039] Although the first interval is set based on the ignition timing, it may be set to a fixed value. Even in this case, functions and effects other than those described in (3) above can be obtained. The disturbance torque Tx may be calculated using a formula other than the above formula (2).

[0040] The shaft torque Ts calculated when a fuel cut is being executed in the internal combustion engine 10 may be substituted for the motoring torque Tm. The shaft torque Ts and motoring torque Tm may be detected by a sensor or the like.

[0041] Although the above embodiment describes the 10% burn rate position, the burn rate can be set arbitrarily. For example, the 50% or 90% burn rate position may be calculated.

[0042] The hybrid system of the vehicle 500 is not limited to the one shown in Fig. 1, but may be any other hybrid system. The vehicle 500 is not limited to a hybrid vehicle, but may be a vehicle that has only an internal combustion engine 10 as a prime mover.

[0043] The control device 100 is not limited to a device equipped with a CPU and memory and executing software processing. For example, the control device 100 may be equipped with a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of the software processing performed in the above embodiments. That is, the control device 100 may include a processing circuit having any of the following configurations (a) to (c): (a) a processing circuit equipped with one or more processing devices that execute all of the above processing according to a program and one or more program storage devices, such as ROM, that store the program; (b) a processing circuit equipped with one or more processing devices and one or more program storage devices that execute part of the above processing according to a program, and one or more dedicated hardware circuits that execute the remaining processing; (c) a processing circuit equipped with one or more dedicated hardware circuits that execute all of the above processing. Program storage devices, i.e., computer-readable media, include any available media that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0044] 10...Internal combustion engine 12...Crank angle sensor 14...Air flow meter 20...Crankshaft 30...Damper 40...Clutch mechanism 42...Rotation angle sensor 50...Motor generator 60...Input shaft 70...Gearbox 80...Propeller shaft 82...Differential gear 84...Drive shaft 90...Drive wheels 100...Control device 110...CPU 120...Memory 500...vehicle

Claims

1. A process of acquiring a shaft torque of the internal combustion engine when the air-fuel mixture is combusted; A process of acquiring a motoring torque, which is the shaft torque when the air-fuel mixture is not combusted; A process of calculating a combustion torque that is a difference between the shaft torque and the motoring torque during combustion; and executing a process of calculating a combustion ratio position based on the combustion torque when the crank angle at which the heat generation amount due to the combustion of fuel supplied to one cylinder in one combustion cycle is a predetermined ratio to the total heat generation amount of the fuel is defined as the combustion ratio position. Control device for internal combustion engines.

2. Calculating the combustion torque for each predetermined crank angle; The process of calculating the combustion ratio position based on the combustion torque includes: a process of calculating a first integrated value that is an integrated value of the combustion torque in a predetermined first section that includes a rise section of the combustion torque; a process of calculating a second integrated value that is an integrated value of the combustion torque in a second section that includes the first section and is wider than the first section; A process of calculating an integrated value ratio, which is a value obtained by dividing the first integrated value by the second integrated value; and calculating the combustion ratio position based on the integrated value ratio. The control device for an internal combustion engine according to claim 1.

3. A process for setting the first interval is executed based on the ignition timing of the air-fuel mixture. The control device for an internal combustion engine according to claim 2.

4. Calculating the combustion torque for each predetermined crank angle; The process of calculating the combustion ratio position based on the combustion torque includes: and a process of calculating the combustion ratio position based on the crank angle at which the combustion torque is a predetermined ratio to the maximum value of the combustion torque. The control device for an internal combustion engine according to claim 1.

5. Calculating the combustion torque for each predetermined crank angle; The process of calculating the combustion ratio position based on the combustion torque includes: and a process of calculating the combustion ratio position based on the crank angle at which the differential value of the combustion torque is maximized. The control device for an internal combustion engine according to claim 1.

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