Control device for internal combustion engines

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 such the number of 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 if the number of samples when calculating the average torque per cylinder is not set appropriately.

Means for Solving the Problems

[0006] The control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine having multiple cylinders and is a control device that performs fuel injection correction to suppress fluctuations in output torque between cylinders. This control device performs the following processes: calculating cylinder-specific torque, which is the output torque for each cylinder; calculating short-term cylinder-specific average torque for each cylinder, which is the average value of the cylinder-specific torques calculated during the first cycle period; calculating long-term cylinder-specific average torque for each cylinder, which is the average value of the cylinder-specific torques calculated during the second cycle period, which is longer than the first cycle period; and calculating the injection correction amount for performing the fuel injection correction based on the short-term cylinder-specific average torque until the number of cycles since the start of the internal combustion engine reaches a predetermined value, and then calculating the injection correction amount for performing the fuel injection correction based on the long-term cylinder-specific average torque after the number of cycles since the start of the internal combustion engine reaches the predetermined value. [Effects of the Invention]

[0007] This internal combustion engine control system can ensure both the responsiveness and accuracy of fuel injection correction. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing the configuration of the drive system and control device of an internal combustion engine according to one embodiment. [Figure 2] A flowchart showing the procedure of processing performed by the control device according to the said embodiment. [Modes for carrying out the invention]

[0009] The following describes one embodiment with reference to the drawings. <Configuration of the drive system and control system of an internal combustion engine> As shown in Figure 1, the internal combustion engine 10 mounted on the vehicle 500 has 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 is provided in the intake port 12a, which is the downstream part of the intake passage 12, for injecting fuel into the intake port 12a. The air drawn into the intake passage 12 and the fuel injected from the port injection valve 16 flow into the combustion chamber 20 when the intake valve 18 opens. Fuel is injected into the combustion chamber 20 from the in-cylinder injection valve 22. The mixture of air and fuel in the combustion chamber 20 is subjected to combustion by the spark discharge of the spark plug 24. The combustion energy generated at that time is converted into rotational energy of the output shaft 26.

[0010] The fuel-air mixture used for combustion in the combustion chamber 20 is discharged as exhaust into the exhaust passage 30 when the exhaust valve 28 opens. The exhaust passage 30 is equipped with a three-way catalyst 32 having oxygen storage capacity and a gasoline particulate filter (GPF 34). In this embodiment, the GPF 34 is assumed to be a filter for collecting PM on which the three-way catalyst is supported.

[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 sun gear S of the planetary gear mechanism 50 is mechanically connected to the rotating shaft 52a of the first motor generator 52. The ring gear R of the planetary gear mechanism 50 is mechanically connected to the rotating shaft 54a of the second motor generator 54 and the drive wheel 60. An AC voltage is applied to the terminals of the first motor generator 52 by an inverter 56. An AC voltage is also applied to the terminals of the second motor generator 54 by an inverter 58. In a vehicle 500 with this configuration, torque from the internal combustion engine 10 and the first motor generator 52 acts on the output shaft 26.

[0012] The control device 70 controls the internal combustion engine 10 and operates the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, and spark plug 24 of the internal combustion engine 10 in order to control the torque, exhaust component ratio, and other control quantities of the engine. The control device 70 also controls the first motor generator 52 and operates the inverter 56 to control its rotational speed, which is a control quantity of the first motor generator 52. The control device 70 also controls the second motor generator 54 and operates the inverter 58 to control its torque, which is a control quantity of the second motor generator 54. Figure 1 shows the operation signals MS1 to MS6 for the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, spark plug 24, and inverters 56 and 58, respectively.

[0013] The control device 70 refers to the intake air volume Ga detected by the airflow meter 80, the output signal Scr from the crank angle sensor 82, and the water temperature THW detected by the water temperature sensor 86 in order to control the amount of control of the internal combustion engine 10. The control device 70 also refers to the output signal Sm1 from the first rotation angle sensor 90, which detects the rotation angle of the first motor generator 52, in order to control the amount of control of the first motor generator 52. The control device 70 also refers to the output signal Sm2 from the second rotation angle sensor 92, which detects the rotation angle of the second motor generator 54, in order to control the amount of control of the second motor generator 54. The control device 70 also refers to the output signal Sm3 from the third rotation angle sensor 96, which detects the rotation angle of the input shaft 51. The control device 70 also refers to the accelerator operation amount ACCP, which is the amount of depression 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 rotation speed NE based on the output signal Scr of the crank angle sensor 82. The control device 70 also 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. The control device 70 also calculates the angular velocity ωinp of the input shaft 51 based on the output signal Sm3 of the third rotation angle sensor 96. The control device 70 also calculates the engine load ratio KL based on the engine rotation speed NE and the intake air volume Ga. Here, the engine load ratio KL represents the ratio of the current cylinder inflow air volume to the cylinder inflow air volume when the internal combustion engine 10 is operated steadily with the throttle valve 14 fully open at the current engine rotation speed NE. The cylinder inflow air volume is the amount of intake air flowing into each cylinder during the intake stroke.

[0015] The control device 70 comprises a CPU 72, a ROM 74, a storage device 75, and peripheral circuits 76, which are able to communicate with each other via a communication line 78. Here, the peripheral circuits 76 include a circuit that generates a clock signal that defines the internal operation, a power supply circuit, a reset circuit, etc. The control device 70 controls the control quantity by having the CPU 72 execute a program stored in the ROM 74.

[0016] The control device 70 controls the fuel injection of the port injection valves 16 and the in-cylinder injection valves 22. The control device 70 also controls the ignition timing of the spark plugs 24. The control device 70 calculates the required torque necessary for the vehicle to run based on the accelerator pedal operation amount ACCP and the vehicle speed SP. The control device 70 also 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 to meet the required torque of the vehicle. The control device 70 calculates the required injection amount Qd so that the required output Pe is obtained. The required injection amount Qd is the target value of the fuel supplied to the combustion chamber 20 from the port injection valves 16 and the in-cylinder injection valves 22. The control device 70 then controls the port injection valves 16 and the in-cylinder injection valves 22 so that the required injection amount Qd is obtained. In the idle operation state immediately after engine start, the required injection amount Qd is calculated based on the water temperature THW and the elapsed time since engine start.

[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 output torque for each cylinder is large, and fluctuations in output torque are likely to occur between cylinders. In particular, when the above-described rapid warm-up control is executed, since the ignition timing is significantly retarded and the combustion of the air-fuel mixture becomes weak, such fluctuations in output torque between cylinders are likely to become prominent. When the output torque fluctuates, it is likely that rattling noises or the like will 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 fluctuations in output torque.

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

[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 predetermined value, 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 predetermined value greater than the threshold value A, 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 equation (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 is 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 equation (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 all constants pre-programmed into the ROM 74. In addition, 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] Short-term average torque TAVS is the average of the short-term cylinder-specific average torque TAVSC calculated for each cylinder. In other words, short-term average torque TAVS is the average output torque of the internal combustion engine 10 during the first cycle period.

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

[0029] In the process of S120 described above, if it is determined that the absolute value of the short-term torque deviation ΔTS is greater than or equal to the threshold α (S120: YES), the control device 70 obtains 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 to perform the fuel injection correction described above based on the short-term average torque TAVSC. The first map is a map for determining 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. Note that if the short-term 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, to the value on the reduction correction side. On the other hand, if the short-term 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, to the value on the increase correction side. Also, the larger the absolute value of the short-term torque deviation ΔTS, the larger the absolute value of the short-term correction amount QS will be.

[0030] In the process of S130, the short-term correction amount QS is obtained, and then the control device 70 substitutes the short-term correction amount QS into the injection correction amount QH (S140). Once the injection correction amount QH is set, 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, it controls the fuel injection amount of the port injection valve 16 and the in-cylinder injection valve 22 so that the required injection amount Qd is obtained.

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

[0032] The long-term torque deviation ΔTL is calculated by the control device 70 by subtracting the long-term average torque TAVL from the long-term average torque TAVLC. The long-term average cylinder torque TAVLC is a value calculated by the control device 70 for each cylinder, and is a moving average value of the 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 that is greater than threshold A and less than or equal to threshold B.

[0033] The long-term average torque TAVL is the average of the long-term cylinder-specific average torques TAVLC, which are calculated for each cylinder. In other words, the long-term average torque TAVL is the average output torque of the internal combustion engine 10 during the second cycle period.

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

[0035] In the process of S150 described above, if it is determined that the absolute value of the long-term torque deviation ΔTL is greater than or equal to the threshold β (S150: YES), the control device 70 obtains the long-term correction amount QL from the second map (S160). The long-term correction amount QL is the cylinder-specific injection correction amount for performing the fuel injection correction described above based on the long-term cylinder-specific average torque TAVLC. The second map is a map for determining the long-term correction amount QL based on the long-term torque deviation ΔTL and the water temperature THW, and is stored in the ROM 74. Note that if the long-term cylinder-specific average torque TAVLC 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, if the long-term cylinder-specific average torque TAVLC 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 will be.

[0036] Furthermore, when the fuel correction amount is calculated using the second map, the fuel correction amount has already been calculated using the first map, so the fluctuations in output torque are usually contained to some extent and stable. Therefore, even if the torque deviation value and water temperature are the same, it is preferable that the absolute value of the long-term correction amount QL be smaller than the absolute value of the short-term correction amount QS.

[0037] In the process of S160, the long-term correction amount QL is obtained, and then the control device 70 substitutes the long-term correction amount QL for the injection correction amount QH (S170). Once the injection correction amount QH is set, the control device 70 corrects the fuel injection amount by performing the process described in S180 above.

[0038] Then, if the process in S180 is completed, or if a negative result is obtained in any of the processes in S100, S120, or S150, the control device 70 terminates this process for the current execution cycle.

[0039] <Operation and Effects of This Embodiment> (1) Immediately after starting the internal combustion engine 10, which has large fluctuations in output torque between cylinders, the short-term correction amount QS is calculated based on the short-term average torque TAVSC. The first cycle period for calculating the short-term average torque TAVSC is shorter than the second cycle period for calculating the long-term average torque TAVLC, so the calculation of the short-term average torque TAVSC is performed early. Consequently, the calculation of the injection correction amount based on the short-term average torque TAVSC is also performed early. As a result, the responsiveness of the fuel injection correction to suppress fluctuations in output torque between cylinders is improved compared to the case where the injection correction amount is not calculated early.

[0040] On the other hand, after a certain period of time has elapsed since the internal combustion engine was started, the long-term correction amount QL is calculated based on the long-term average cylinder torque TAVLC. The second cycle period for calculating the long-term average cylinder torque TAVLC is longer than the first cycle period for calculating the short-term average cylinder torque TAVSC, so the number of samples used when calculating the long-term average cylinder torque TAVLC is increased. Therefore, the influence of variations in cylinder torque TE on the long-term average cylinder torque TAVLC is reduced compared to when the number of samples is small, and the accuracy of the long-term average cylinder torque TAVLC improves. As a result, the accuracy of the injection correction amount improves compared to when the accuracy of the long-term average cylinder torque TAVLC is low. Consequently, both the responsiveness and accuracy of fuel injection correction, which suppresses fluctuations in output torque between cylinders, can be ensured.

[0041] (2) As both the responsiveness and accuracy of the fuel injection correction described above can be ensured, fluctuations in output torque between cylinders can be appropriately suppressed. Therefore, it is possible to suppress drivetrain noises such as gear noise caused by such fluctuations in output torque.

[0042] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0043] If there is no significant difference between the settings of the first map and the second map, the short-term correction amount QS and the long-term correction amount QL may be determined using either map. • While the short-term cylinder-by-cylinder average torque TAVSC and long-term cylinder-by-cylinder average torque TAVLC were moving averages, other average values ​​are also good.

[0044] In the above embodiment, the formula (1) above was used to calculate the torque TE for each cylinder, but the torque TE for each cylinder may be calculated using a different 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, the vehicle may not be equipped with the first motor generator 52 or the second motor generator 54, and may be equipped only with the internal combustion engine 10 as the prime mover. Even with such a vehicle, if the cylinder-specific torque TE described above can be calculated, the same operation and effects as in the above embodiment can be obtained. [Explanation of symbols]

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

Claims

[Claim 1] A control device applied to an internal combustion engine having multiple cylinders, which performs fuel injection correction to suppress fluctuations in output torque between cylinders, The process of calculating the torque for each cylinder, which is the output torque for each cylinder, A process to calculate the short-term average torque for each cylinder, which is the average value of the torque for each cylinder calculated during the first cycle period, A process for calculating the long-term average torque for each cylinder, which is the average value of the torque for each cylinder calculated during a second cycle period that is longer than the first cycle period, The process involves calculating the injection correction amount for implementing 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 predetermined value, and then, after the number of cycles since the start of the internal combustion engine reaches the predetermined value, calculating the injection correction amount for implementing the fuel injection correction based on the long-term average torque for each cylinder. Control device for internal combustion engines.

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