Control device for internal combustion engine

Abstract

To ensure both the responsiveness and accuracy of fuel injection correction.SOLUTION: A control device 70 performs fuel injection correction to suppress variation in output torque between cylinders. The control device 70 executes: processing of calculating individual cylinder torque, which is the output torque of an individual cylinder; processing of calculating, for each cylinder, short-period individual cylinder average torque, which is the average value of the individual cylinder torque calculated within a first cycle period; processing of calculating, for each cylinder, long-period individual cylinder average torque, which is the average value of the individual cylinder torque calculated within a second cycle period longer than the first cycle period; and processing of calculating an injection correction amount for performing fuel injection correction based on the short-period individual cylinder average torque until the number of cycles since starting of an internal combustion engine 10 reaches a predetermined value, while calculating an injection correction amount for performing fuel injection correction based on the long-period individual cylinder average torque after the number of cycles since starting of the internal combustion engine 10 reaches the predetermined value.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] The control device described in Patent Document 1 estimates the output torque of an internal combustion engine based on various values.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an internal combustion engine having a plurality of cylinders, fuel injection correction may be performed to suppress fluctuations in output torque between cylinders. In this fuel injection correction, the torque per cylinder, which is the output torque per cylinder in one cycle, is calculated, and the average torque per cylinder, which is the average value of the torque per cylinder, is calculated. Then, it is conceivable to calculate an injection correction amount for performing fuel injection correction based on the average torque per cylinder.

[0005] Here, if the number of samples when calculating the average torque per cylinder is increased, although the accuracy of the fuel injection correction improves because the calculation accuracy of the average torque per cylinder improves, the responsiveness of the fuel injection correction deteriorates. On the other hand, if the number of such samples is decreased, although the responsiveness of the fuel injection correction improves, the calculation accuracy of the average torque per cylinder decreases, so the accuracy of the fuel injection correction deteriorates. Therefore, it is difficult to ensure both the responsiveness and accuracy of the fuel injection correction unless the number of samples when calculating the average torque per cylinder is set appropriately.

Means for Solving the Problems

[0006] The control device for an internal combustion engine that solves the above problems is a control device applied to an internal combustion engine having a plurality of cylinders, and performs fuel injection correction for suppressing fluctuations in output torque between cylinders. This control device executes a process of calculating the cylinder-specific torque, which is the output torque for each cylinder, a process of calculating, for each cylinder, a short-term cylinder-specific average torque that is an average value of the cylinder-specific torque calculated within a first cycle period, a process of calculating, for each cylinder, a long-term cylinder-specific average torque that is an average value of the cylinder-specific torque calculated within a second cycle period longer than the first cycle period, and a process of calculating an injection correction amount for performing the fuel injection correction based on the short-term cylinder-specific average torque until the number of cycles after starting the internal combustion engine reaches a predetermined value, and calculating an injection correction amount for performing the fuel injection correction based on the long-term cylinder-specific average torque after the number of cycles after starting the internal combustion engine reaches the predetermined value.

Advantages of the Invention

[0007] This control device for an internal combustion engine can ensure both the responsiveness and accuracy of fuel injection correction.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, an embodiment will be described with reference to the drawings. <Configuration of the Drive System and Control Device of the Internal Combustion Engine> As shown in FIG. 1, the internal combustion engine 10 mounted on the vehicle 500 includes four cylinders #1 to #4. A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10. A port injection valve 16 for injecting fuel into the intake port 12a, which is the downstream portion of the intake passage 12, is provided in the intake port 12a. The air inhaled into the intake passage 12 and the fuel injected from the port injection valve 16 flow into the combustion chamber 20 as the intake valve 18 opens. Fuel is injected into the combustion chamber 20 from the in-cylinder injection valve 22. Further, the air-fuel mixture in the combustion chamber 20 is used for combustion with the spark discharge of the spark plug 24. The combustion energy generated at that time is converted into the rotational energy of the output shaft 26.

[0010] The air-fuel mixture used for combustion in the combustion chamber 20 is discharged into the exhaust passage 30 as exhaust with the opening of the exhaust valve 28. A three-way catalyst 32 having an oxygen storage capacity and a gasoline particulate filter (GPF 34) are provided in the exhaust passage 30. In this embodiment, it is assumed that the GPF 34 is a filter that collects PM and has a three-way catalyst supported thereon.

[0011] An input shaft 51 is connected to the carrier C of the planetary gear mechanism 50 that constitutes the power split device. The input shaft 51 is connected to the output shaft 26 via a damper 150. The rotating shaft 52a of the first motor generator 52 is mechanically connected to the sun gear S of the planetary gear mechanism 50. Further, the rotating shaft 54a of the second motor generator 54 and the drive wheel 60 are mechanically connected to the ring gear R of the planetary gear mechanism 50. An AC voltage is applied to the terminals of the first motor generator 52 by an inverter 56. Also, an AC voltage is applied to the terminals of the second motor generator 54 by an inverter 58. In the vehicle 500 having such a configuration, the torques from the internal combustion engine 10 and the first motor generator 52 act on the output shaft 26.

[0012] The control device 70 controls the internal combustion engine 10, and operates the operating parts of the internal combustion engine 10 such as the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, and the ignition plug 24 in order to control the torque, the exhaust component ratio, etc. as the control amounts thereof. Further, the control device 70 controls the first motor generator 52, and operates the inverter 56 in order to control the rotational speed which is the control amount thereof. Further, the control device 70 controls the second motor generator 54, and operates the inverter 58 in order to control the torque which is the control amount thereof. FIG. 1 shows the respective operation signals MS1 to MS6 of the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, the ignition plug 24, and the inverters 56 and 58.

[0013] The control device 70 refers to the intake air amount Ga detected by the air flow meter 80, the output signal Scr of the crank angle sensor 82, and the water temperature THW detected by the water temperature sensor 86 in order to control the control amounts of the internal combustion engine 10. Further, the control device 70 refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor generator 52 in order to control the control amount of the first motor generator 52. Further, the control device 70 refers to the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54 in order to control the control amount of the second motor generator 54. Further, the control device 70 refers to the output signal Sm3 of the third rotation angle sensor 96 that detects the rotation angle of the input shaft 51. Further, the control device 70 refers to the accelerator operation amount ACCP which is the depression amount of the accelerator pedal detected by the accelerator sensor 94, and the vehicle speed SP which is the vehicle speed of the vehicle 500 detected by the vehicle speed sensor 95.

[0014] The control device 70 calculates the angular velocity ωE of the output shaft 26 and the engine rotational speed NE based on the output signal Scr of the crank angle sensor 82. Further, the control device 70 calculates the angular velocity ωG of the rotor of the first motor generator 52 based on the output signal Sm1 of the first rotation angle sensor 90. Further, the control device 70 calculates the angular velocity ωinp of the input shaft 51 based on the output signal Sm3 of the third rotation angle sensor 96. Further, the control device 70 calculates the engine load factor KL based on the engine rotational speed NE and the intake air amount Ga. Here, the engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 10 is in steady operation with the throttle valve 14 fully open at the current engine rotational speed NE. The cylinder inflow air amount is the amount of intake air flowing into each cylinder during the intake stroke.

[0015] The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and a peripheral circuit 76, and they are communicable via a communication line 78. Here, the peripheral circuit 76 includes a circuit that generates a clock signal for defining internal operations, a power supply circuit, a reset circuit, and the like. The control device 70 controls the control amount by the CPU 72 executing the program stored in the ROM 74.

[0016] The control device 70 performs fuel injection control of the port injection valve 16 and the in-cylinder injection valve 22. Further, the control device 70 performs ignition timing control of the ignition plug 24. The control device 70 calculates the required torque necessary for the vehicle to travel based on the accelerator operation amount ACCP and the vehicle speed SP. Further, the control device 70 controls the required output Pe of the internal combustion engine 10 and the output torques of the first motor generator 52 and the second motor generator 54 so as to satisfy the required torque of the vehicle. The control device 70 calculates the required injection amount Qd so as to obtain the required output Pe. The required injection amount Qd is the target value of the fuel supplied from the port injection valve 16 and the in-cylinder injection valve 22 to the combustion chamber 20. Then, the control device 70 controls the port injection valve 16 and the in-cylinder injection valve 22 so as to obtain the required injection amount Qd. In the idle operation state immediately after engine start, the required injection amount Qd is calculated based on the water temperature THW, the elapsed time after engine start, and the like.

[0017] The control device 70 executes rapid warm-up control in accordance with engine startup. The rapid warm-up control is a control for increasing the temperature of the exhaust gas by significantly retarding the ignition timing. By executing this rapid warm-up control, the temperature of the three-way catalyst 32 is increased early after engine startup.

[0018] <Regarding fuel injection correction> Immediately after engine startup, since the combustion of the air-fuel mixture is unstable, the variation in the output torque for each cylinder is large, and the variation in the output torque between cylinders is likely to occur. In particular, when the above rapid warm-up control is executed, since the ignition timing is significantly retarded and the combustion of the air-fuel mixture becomes weak, such variation in the output torque between cylinders is likely to become prominent. When the output torque varies, rattling noises and the like are likely to occur from the drive system. Therefore, the control device 70 performs fuel injection correction to correct the required injection amount Qd in order to suppress such variation in the output torque.

[0019] FIG. 2 shows the procedure of the process executed by the control device 70 to perform the above fuel injection correction. The process shown in FIG. 2 is realized by the CPU 72 executing the program stored in the ROM 74 at a predetermined cycle. Hereinafter, the step numbers of each process are represented by numbers with "S" added at the beginning.

[0020] When starting this process, the control device 70 determines whether or not the number of cycles NCS after startup is equal to or greater than the threshold value A (S100). The number of cycles NCS after startup is the number of cycles (combustion cycles) of the internal combustion engine 10 that have been performed from the start of engine startup to the present. The threshold value A is a default value and is, for example, a value on the order of several cycles.

[0021] When it is determined that the number of cycles NCS after startup is equal to or greater than the threshold value A (S110: YES), the control device 70 determines whether or not the number of cycles NCS after startup is equal to or greater than the threshold value B (S110). The threshold value B is a default value larger than the threshold value A and is, for example, a value on the order of several tens of cycles.

[0022] When it is determined that the number of cycles NCS after startup is less than the threshold value B (S110: NO), the control device 70 determines whether or not the absolute value of the short-term torque deviation ΔTS is greater than or equal to the threshold value α (S120).

[0023] The short-term torque deviation ΔTS is a value obtained by subtracting the short-term average torque TAVS from the short-term average torque per cylinder TAVSC, and is calculated by the control device 70. The short-term average torque per cylinder TAVSC is a value calculated by the control device 70 for each cylinder, and is a moving average value of the torque per cylinder TE calculated within the first cycle period. The first cycle period is a period defined by a predetermined number of cycles, for example, the number of cycles less than or equal to the above threshold value A.

[0024] The torque per cylinder TE is the output torque per cylinder of the internal combustion engine 10, and is calculated by the control device 70. The control device 70 calculates, for example, every 1°CA, the instantaneous torque per cylinder TEins, which is the instantaneous value of the torque per cylinder TE, based on the following formula (1) during the expansion stroke. Then, the sum of the calculated plurality of instantaneous torques per cylinder TEins is substituted into the torque per cylinder TE of the cylinder that was symmetric to the calculation of the instantaneous torque per cylinder TEins.

[0025] TEins = IE * dωE + Iinp * dωinp + (1 + ρ) / ρ * (IG * dωG - TG) ··· (1) Here, IE is the moment of inertia of the internal combustion engine 10, and dωE is the angular acceleration obtained by differentiating the angular velocity ωE of the output shaft 26. Also, Iinp is the moment of inertia of the input shaft 51, and dωinp is the angular acceleration obtained by differentiating the angular velocity ωinp of the input shaft 51. Also, ρ is the gear ratio of the planetary gear mechanism 50, IG is the moment of inertia of the first motor generator 52, and dωG is the angular acceleration obtained by differentiating the angular velocity ωG of the rotor of the first motor generator 52. Also, TG is the torque reaction force of the first motor generator 52. Note that TG is equal to the output torque of the first motor generator 52.

[0026] In the formula (1) above, the moment of inertia IE of the internal combustion engine 10, the moment of inertia Iinp of the input shaft 51, the moment of inertia IG of the first motor generator 52, and the ratio ρ of the planetary gear mechanism 50 are constants that are respectively input in advance to the ROM 74. Further, the torque reaction force TG of the first motor generator 52 is a value managed by the CPU 72 as a control parameter and is always input to the CPU 72.

[0027] The short-term average torque TAVS is the average value of the short-term cylinder-by-cylinder average torques TAVSC calculated for each cylinder. That is, the short-term average torque TAVS is the average value of the output torque of the internal combustion engine 10 within the first cycle period.

[0028] Also, as the above threshold value α, based on the fact that the absolute value of the short-term torque deviation ΔTS is greater than or equal to this threshold value α, the magnitude of the value is set so that it is possible to accurately determine that the current torque fluctuation has become large enough to require fuel injection correction.

[0029] In the process of S120 above, when it is determined that the absolute value of the short-term torque deviation ΔTS is greater than or equal to the threshold value α (S120: YES), the control device 70 acquires the short-term correction amount QS from the first map (S130). The short-term correction amount QS is the injection correction amount for each cylinder for performing the fuel injection correction described above based on the short-term cylinder-by-cylinder average torque TAVSC. The first map is a map for obtaining the short-term correction amount QS based on the short-term torque deviation ΔTS and the water temperature THW and is stored in the ROM 74. When the short-term cylinder-by-cylinder average torque TAVSC is greater than the short-term average torque TAVS and the short-term torque deviation ΔTS is a positive value, the short-term correction amount QS is set to a negative value, that is, a value on the reduction correction side. On the other hand, when the short-term cylinder-by-cylinder average torque TAVSC is less than the short-term average torque TAVS and the short-term torque deviation ΔTS is a negative value, the short-term correction amount QS is set to a positive value, that is, a value on the increase correction side. Also, the greater the absolute value of the short-term torque deviation ΔTS, the greater the absolute value of the short-term correction amount QS.

[0030] When the short-term correction amount QS is obtained in the process of S130, next, the control device 70 substitutes the short-term correction amount QS for the injection correction amount QH (S140). When the injection correction amount QH is set in this way, the control device 70 corrects the fuel injection amount (S180). In the process of S180, the control device 70 calculates a new required injection amount Qd by adding the injection correction amount QH to the current required injection amount Qd. Then, the fuel injection amounts of the port injection valve 16 and the in-cylinder injection valve 22 are controlled so that the required injection amount Qd is obtained.

[0031] On the other hand, in the process of S110, when it is determined that the number of cycles NCS after starting is equal to or greater than the threshold value B (S110: YES), the control device 70 determines whether the absolute value of the long-term torque deviation ΔTL is equal to or greater than the threshold value β (S150).

[0032] The long-term torque deviation ΔTL is a value obtained by subtracting the long-term average torque TAVL from the long-term cylinder-by-cylinder average torque TAVLC, and is calculated by the control device 70. The long-term cylinder-by-cylinder average torque TAVLC is a value calculated by the control device 70 for each cylinder, and is a moving average value of the cylinder-by-cylinder torque TE calculated within the second cycle period. The second cycle period is a period defined by a predetermined number of cycles, for example, a number of cycles greater than the threshold value A and less than or equal to the threshold value B.

[0033] The long-term average torque TAVL is an average value of the long-term cylinder-by-cylinder average torques TAVLC calculated for each cylinder. That is, the long-term average torque TAVL is an average value of the output torque of the internal combustion engine 10 within the second cycle period.

[0034] Also, as the threshold value β, based on the fact that the absolute value of the long-term torque deviation ΔTL is large enough to be equal to or greater than this threshold value β, the magnitude of its value is set so that it can accurately determine that the current torque fluctuation has become large enough to require fuel injection correction.

[0035] In the process of S150, when it is determined that the absolute value of the long-term torque deviation ΔTL is equal to or greater than the threshold value β (S150: YES), the control device 70 acquires the long-term correction amount QL from the second map (S160). The long-term correction amount QL is the injection correction amount for each cylinder for performing the fuel injection correction described above based on the long-term average torque TAVLC for each cylinder. The second map is a map for obtaining the long-term correction amount QL based on the long-term torque deviation ΔTL and the coolant temperature THW, and is stored in the ROM 74. When the long-term average torque TAVLC for each cylinder is greater than the long-term average torque TAVL and the long-term torque deviation ΔTL is a positive value, the long-term correction amount QL is set to a negative value. On the other hand, when the long-term average torque TAVLC for each cylinder is less than the long-term average torque TAVL and the long-term torque deviation ΔTL is a negative value, the long-term correction amount QL is set to a positive value. Also, the larger the absolute value of the long-term torque deviation ΔTL, the larger the absolute value of the long-term correction amount QL.

[0036] Note that when the fuel correction amount is calculated using the second map, since the fuel correction amount has already been calculated using the first map, the variation in the output torque is somewhat reduced and is often stable. Therefore, even if the values of the torque deviation and the coolant temperature are the same, it is preferable that the absolute value of the long-term correction amount QL is smaller than the absolute value of the short-term correction amount QS.

[0037] When the long-term correction amount QL is acquired in the process of S160, next, the control device 70 substitutes the long-term correction amount QL into the injection correction amount QH (S170). When the injection correction amount QH is set in this way, the control device 70 corrects the fuel injection amount by performing the process of S180 described above.

[0038] When the process of S180 is completed, or when a negative determination is made in any of the processes of S100, S120, and S150 described above, the control device 70 ends this process in the current execution cycle.

[0039] <Actions and Effects of this Embodiment> (1) Immediately after starting the internal combustion engine 10 with a large variation in output torque between cylinders, the short-term correction amount QS is calculated based on the short-term average torque TAVSC for each cylinder. Since the first cycle period for calculating the short-term average torque TAVSC for each cylinder is shorter than the second cycle period for calculating the long-term average torque TAVLC for each cylinder, the calculation of the short-term average torque TAVSC for each cylinder is performed earlier. Therefore, the calculation of the injection correction amount based on the short-term average torque TAVSC for each cylinder is also performed earlier. As a result, compared with the case where the calculation of the injection correction amount is not performed earlier, the responsiveness of the fuel injection correction for suppressing the variation in output torque between cylinders is improved.

[0040] On the other hand, when a certain period has elapsed after starting the internal combustion engine, the long-term correction amount QL is calculated based on the long-term average torque TAVLC for each cylinder. Since the second cycle period for calculating the long-term average torque TAVLC for each cylinder is longer than the first cycle period for calculating the short-term average torque TAVSC for each cylinder, the number of samples for calculating the long-term average torque TAVLC for each cylinder increases. Therefore, compared with when the number of samples is small, the influence of the variation in torque TE for each cylinder on the long-term average torque TAVLC for each cylinder becomes smaller, and the accuracy of the long-term average torque TAVLC for each cylinder is improved. As a result, compared with the case where the accuracy of the long-term average torque TAVLC for each cylinder is low, the accuracy of the injection correction amount is improved. Therefore, both the responsiveness and accuracy of the fuel injection correction for suppressing the variation in output torque between cylinders can be ensured.

[0041] (2) Since both the responsiveness and accuracy of the fuel injection correction described above can be ensured, the variation in output torque between cylinders can be appropriately suppressed. Therefore, rattling noises in the drive system caused by such variations in output torque can be suppressed.

[0042] <Modification Example> Note that the above embodiment can be modified and implemented as follows. The above embodiment and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0043] ·When there is no significant difference between the set value of the first map and the set value of the second map, the short-term correction amount QS and the long-term correction amount QL may be obtained using either one of the maps. ·The short-term cylinder-by-cylinder average torque TAVSC and the long-term cylinder-by-cylinder average torque TAVLC were moving average values, but other average values may also be used.

[0044] ·In the above embodiment, the formula (1) was used to calculate the cylinder-by-cylinder torque TE, but the cylinder-by-cylinder torque TE may be calculated by another formula or method. ·In the above embodiment, the configuration of the vehicle 500 is not limited to the example of the above embodiment. For example, a vehicle that does not have the first motor generator 52 or the second motor generator 54 and is equipped with only the internal combustion engine 10 as a prime mover may also be used. Even in such a vehicle, if the cylinder-by-cylinder torque TE described above can be calculated, the same operations and effects as those of the above embodiment can be obtained.

Description of Reference Numerals

[0045] 10…Internal combustion engine, 70…Control device

Claims

[Claim 1] A control device that is applied to an internal combustion engine having a plurality of cylinders and performs fuel injection correction to suppress variation in output torque between the cylinders, A process of calculating a torque for each cylinder, which is an output torque for each cylinder; A process of calculating a short-term cylinder average torque for each cylinder, which is an average value of the cylinder torques calculated within a first cycle period; calculating a long-term average torque for each cylinder, which is an average value of the torque for each cylinder calculated within a second cycle period that is longer than the first cycle period; a process of calculating an injection correction amount for performing the fuel injection correction based on the short-term average torque for each cylinder until the number of cycles since the start of the internal combustion engine reaches a preset value, and a process of calculating an injection correction amount for performing the fuel injection correction based on the long-term average torque for each cylinder after the number of cycles since the start of the internal combustion engine reaches the preset value; A control device for an internal combustion engine.

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