Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine, which can inhibit determination of a misfire from becoming unable to do, by correcting an amount of fuel to be injected into each cylinder to equalize the combustion torque of each cylinder.SOLUTION: A control device for an internal combustion engine can execute ignition retard control to retard the ignition timing for igniting a mixture in a combustion chamber as compared with that at the time of normal operation. The control device comprises: an individual cylinder torque calculation unit that calculates the amount of variation in the combustion torque of each cylinder while the ignition retard control is executed; an injection amount correction unit that corrects the amount of fuel injection to each cylinder so as to reduce the amount of variation in the combustion torque of each cylinder calculated by the individual cylinder torque calculation unit; and a misfire determination unit that determines a misfire in a specified cylinder based on the combustion torque of a specified one of the cylinders. If the combustion torque of any of the cylinders is equal to or less than a specified torque (Yes in Step S11), the injection amount correction unit does not correct the amount of fuel injection to each cylinder (Step S12).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine that can change the timing of ignition of an air-fuel mixture. [Background technology]

[0002] Patent Document 1 describes a control device configured to retard the ignition timing of the engine from the normal timing when warming up a catalytic device that purifies exhaust gas output from the engine. This control device is configured to calculate the crankshaft rotation speed in order to suppress differences in torque generated by each cylinder caused by retarding the ignition timing to warm up the catalytic device as described above, and to control the fuel injection amount for each cylinder so as to suppress the amount of variation in the calculated crankshaft rotation speed.

[0003] Patent Document 2 describes a control device that heats a gasoline particulate filter (GPF) that captures particulate matter (PM) in engine exhaust gas to burn and remove PM accumulated in the GPF. This control device is configured to determine whether to execute GPF regeneration control to burn and remove PM when the differential pressure across the GPF becomes equal to or greater than a predetermined pressure, and to retard the ignition timing of the engine when it is determined that it is necessary to execute GPF regeneration control, compared to when GPF regeneration control is not executed. In addition, the control device is configured to suppress a decrease in engine output caused by executing GPF regeneration control by decreasing the opening of the wastegate valve and increasing the supercharging pressure.

[0004] Furthermore, Patent Document 3 describes a control device for appropriately determining misfire even when engine combustion becomes unstable by retarding the ignition timing to warm up the catalyst. This control device is configured to determine the presence or absence of misfire based on the amount of change in the measured time required for the crank angle to rotate 30° CA due to combustion in the cylinder to be determined. Specifically, when retard control for warming up the catalyst is not being executed, the control device subtracts the measured time one cycle ago from the latest measured time, and if the value is equal to or greater than a predetermined time, it determines that a misfire has occurred. When retard control is being executed, the control device extracts the five shortest measured times from the measured times ten cycles ago, calculates the average value, subtracts the latest measured time from the average value, and determines that a misfire has occurred if the value is equal to or greater than a predetermined time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-297933 A [Patent Document 2] JP 2017-141791 A [Patent Document 3] Patent Publication No. 2022-062848 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the control devices described in Patent Document 1 and Patent Document 2, the ignition timing of the engine is retarded when the catalytic converter is warmed up or the GPF is regenerated. Retarding the ignition timing of the engine in this way makes the combustion in the engine unstable, and in order to suppress the variation in the crankshaft rotation speed, the control device described in Patent Document 1 is configured to control the amount of fuel injected into each cylinder based on the variation in the crankshaft rotation speed. In other words, the control device described in Patent Document 1 suppresses the variation in the crankshaft rotation speed.

[0007] On the other hand, the control device described in Patent Document 3 determines whether or not a misfire has occurred based on the amount of change in the time required to rotate a given crank angle. Therefore, if the fuel injection amount is controlled to suppress variations in the crankshaft rotation speed, as in the control device described in Patent Document 1, the fuel injection amount for the cylinder in which the crankshaft rotation speed has changed due to the occurrence of a misfire is changed, and the crankshaft rotation speed is made uniform, so that the time required to rotate a given crank angle is also made uniform, which may make it impossible to determine whether or not a misfire has occurred.

[0008] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide a control device for an internal combustion engine that can suppress the inability to determine misfire by correcting the amount of fuel injected into each cylinder and equalizing the combustion torque of each cylinder. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides a control device for an internal combustion engine capable of executing ignition retard control in which the ignition timing for igniting a mixture in a combustion chamber is retarded from a predetermined timing during normal operation, the control device including a controller for controlling the internal combustion engine, the controller including: a cylinder-specific torque calculation unit that calculates the amount of variation in the combustion torque of each cylinder during execution of the ignition retard control; an injection amount correction unit that corrects the amount of fuel injection into each cylinder so as to reduce the amount of variation in the combustion torque of each cylinder calculated by the cylinder-specific torque calculation unit; and a misfire judgment unit that judges misfire of a specified cylinder based on the combustion torque of a specified cylinder among the cylinders or the rotational speed of the internal combustion engine, and when the combustion torque of any of the cylinders is equal to or lower than a predetermined torque, the injection amount correction unit does not correct the amount of fuel injection into each cylinder.

[0010] The present invention also provides a control device for an internal combustion engine capable of executing ignition retard control to retard the ignition timing for igniting a mixture in a combustion chamber from a predetermined timing during normal operation, the control device including a controller for controlling the internal combustion engine, the controller including: a cylinder torque calculation unit that calculates an amount of variation in the combustion torque of each cylinder during execution of the ignition retard control; an injection amount correction unit that corrects the amount of fuel injection into each cylinder so as to reduce the amount of variation in the combustion torque of each cylinder calculated by the cylinder torque calculation unit; and a misfire judgment unit that judges misfire of the specified cylinder based on the combustion torque associated with combustion in a specified cylinder among the cylinders or the rotational speed of the internal combustion engine and a specified judgment threshold value, and the misfire judgment unit corrects the judgment threshold value by an amount of torque or rotational speed corresponding to the correction amount of the fuel injection amount into the specified cylinder when the injection amount correction unit corrects the amount of fuel injection into each cylinder.

[0011] Furthermore, the present invention is a control device for an internal combustion engine capable of executing ignition retard control to retard the ignition timing for igniting a mixture in a combustion chamber from a predetermined timing during normal operation, the control device including a controller for controlling the internal combustion engine, the controller including: a cylinder torque calculation unit that calculates an amount of variation in the combustion torque of each cylinder during execution of the ignition retard control; an injection amount correction unit that corrects the amount of fuel injection into each cylinder so as to reduce the amount of variation in the combustion torque of each cylinder calculated by the cylinder torque calculation unit; and a misfire judgment unit that judges misfire of the specified cylinder based on the combustion torque associated with combustion in a specified cylinder among the cylinders or the rotational speed of the internal combustion engine and a specified judgment threshold value, and the misfire judgment unit corrects the combustion torque or the rotational speed by an amount of torque or rotational speed corresponding to the correction amount of the fuel injection amount into the specified cylinder when the injection amount correction unit corrects the amount of fuel injection into each cylinder.

[0012] In the present invention, the engine may further include a filter that collects particulate matter contained in the exhaust gas discharged from each of the cylinders, and the controller may include an overtemperature determination unit that determines abnormal heating of the filter when the occurrence rate of misfire determined by the misfire determination unit is equal to or higher than a predetermined rate.

[0013] In the present invention, the over-temperature judgment unit may set the specified rate when the fuel injection amount to each cylinder is corrected to a value smaller than the specified rate when the fuel injection amount to each cylinder is not corrected.

[0014] In the present invention, when the fuel injection amount to each cylinder is corrected, the over-temperature judgment unit may judge that the filter has been abnormally heated if the occurrence rate of misfire judged by the misfire judgment unit is equal to or greater than a value obtained by multiplying the predetermined rate by a coefficient that is smaller than 1.

[0015] In the present invention, the over-temperature determination section may include a three-dimensional map that determines the predetermined rate using the rotation speed of the internal combustion engine, the load on the internal combustion engine, and the amount of retardation of the ignition timing as parameters. Effect of the Invention

[0016] According to the present invention, the engine includes an injection amount correction unit that corrects the fuel injection amount to each cylinder so as to reduce the variation in the combustion torque of each cylinder during the execution of the ignition retard control in which the ignition timing is retarded from that during normal operation. By correcting the fuel injection amount to each cylinder in this manner, the variation in the combustion torque during the execution of the ignition retard control can be suppressed, so that the vibration can be suppressed. Furthermore, when the combustion torque of any of the cylinders is equal to or less than a predetermined torque, the fuel injection amount is not corrected by the injection amount correction unit. That is, when there is a possibility that a misfire has occurred in any of the cylinders, the fuel injection amount is not corrected. In other words, the fuel injection amount is corrected only when there is a possibility that a misfire has not occurred in all of the cylinders. Therefore, it is possible to suppress a situation in which it becomes impossible to determine whether a cylinder has misfire based on the combustion torque of the cylinder or the rotation speed of the internal combustion engine due to the correction of the fuel injection amount.

[0017] Furthermore, according to the present invention, when the fuel injection amount for each cylinder is corrected, the judgment threshold for judging misfire is corrected by the amount of correction of the fuel injection amount for a specific cylinder, or the combustion torque or rotation speed for judging misfire is corrected by the amount of fuel injection for the specific cylinder. That is, the detection value or threshold for judging misfire is corrected taking into account the correction of the fuel injection amount. Therefore, it is possible to suppress the variation in combustion torque caused by executing ignition retard control and to judge misfire at the same time. That is, it is possible to suppress the occurrence of vibration caused by the variation in combustion torque while judging misfire. As a result, it is possible to promote ignition retard control. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating an example of a hybrid vehicle equipped with an internal combustion engine according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram for explaining the configuration of an ECU. [Diagram 3] 4 is a flowchart for explaining an example of fuel injection correction control. [Figure 4] 4 is a flowchart illustrating an example of a control that enables misfire determination. [Diagram 5] 4 is a flowchart for explaining an example of control for determining the presence or absence of a misfire by correcting a misfire determination threshold value. [Figure 6] 4 is a flowchart illustrating an example of a control for determining the presence or absence of a misfire by correcting an actual combustion torque. [Figure 7] 5 is a flowchart for explaining a control example in which an OT determination threshold value is changed depending on whether or not a fuel injection correction control is being performed. [Figure 8] FIG. 4 is a diagram illustrating an example of a misfire rate map. [Figure 9] 10 is a flowchart for explaining a control example in which an OT determination threshold is set based on a three-dimensional map having engine speed, engine load, and ignition retard amount as parameters. [Figure 10]10 is a flowchart for explaining a control example in which an OT determination threshold is set according to an ignition retard amount. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will be described based on the embodiment shown in the drawings. Note that the embodiment described below is merely one example of a specific embodiment of the present invention, and is not intended to limit the present invention.

[0020] An example of a hybrid vehicle equipped with an internal combustion engine (hereinafter referred to as an engine) according to an embodiment of the present invention is shown in Fig. 1. The hybrid vehicle (hereinafter referred to simply as a vehicle) Ve shown in Fig. 1 includes an engine 1, a first motor 2, and a second motor 3 as driving force sources.

[0021] The engine 1 shown in Fig. 1 is a four-cylinder engine 1 having four cylinders #1, #2, #3, and #4. A piston is provided in each of the cylinders #1, #2, #3, and #4 so as to be capable of reciprocating motion via a connecting rod (not shown) on a crankshaft 4, which is the output shaft of the engine 1, and fuel and air are supplied to a combustion chamber 5, which is the space above the piston. The crankshaft 4 is rotated by the load that pushes down the piston by burning the mixture of fuel and air.

[0022] An intake passage 7 is connected to each combustion chamber 5 via an intake manifold 6. This intake passage 7 is configured so that outside air flows through an air cleaner (not shown), and a throttle valve 8 for controlling the flow rate (air volume) of that air is disposed upstream. Therefore, as the opening of the throttle valve 8 increases, the volume of air flowing through the intake passage 7 increases.

[0023] The intake manifold 6, which is connected to the downstream side of the intake passage 7, branches the air flowing through the intake passage 7 and supplies it to each of the cylinders #1, #2, #3, and #4. Each of the branched flow paths of the intake manifold 6 is provided with a port injection valve 9 that injects fuel toward the intake ports provided in each of the cylinders #1, #2, #3, and #4.

[0024] Each of the cylinders #1, #2, #3, and #4 shown in Fig. 1 is formed with two intake ports and two exhaust ports, and is provided with an intake valve 10 for opening and closing the intake port, and an exhaust valve 11 for opening and closing the exhaust port. These intake valves 10 and exhaust valves 11 are configured to be opened and closed by a camshaft 12 that rotates in synchronization with the crankshaft 4 via a timing belt or the like (not shown).

[0025] Each of the cylinders #1, #2, #3, and #4 is provided with an in-cylinder injection valve 15 that injects fuel into the combustion chamber 5, and a spark plug 16 that ignites the mixture in the combustion chamber 5. Therefore, the intake valve 10 opens, and air and fuel injected from the port injection valve 9 are supplied into the combustion chamber 5. Furthermore, by injecting fuel from the in-cylinder injection valve 15, an air-fuel mixture is formed in the combustion chamber 5, and the mixture is ignited by the spark plug 16 and burns, generating a load that pushes the piston down.

[0026] An exhaust passage 17 for discharging exhaust gas generated by burning the air-fuel mixture as described above is connected to each of the cylinders #1, #2, #3, and #4 via an exhaust manifold 18. In this exhaust passage 17, a three-way catalyst (hereinafter referred to as a catalyst device) 19 for purifying the hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas through oxidation and reduction, and a gasoline particulate filter (hereinafter referred to as a GPF) 20 for collecting particulate matter (hereinafter referred to as PM) contained in the exhaust gas are provided in sequence from the upstream side.

[0027] A power split mechanism 21 is connected to the crankshaft 4. This power split mechanism 21 can be configured by a single-pinion type planetary gear mechanism, in which the crankshaft 4 is connected to its carrier C, the first motor 2 is connected to its sun gear S, and the ring gear R is connected to driving wheels 22 via a gear train section (not shown). In addition, the second motor 3 is connected to the gear train section between the ring gear R and the driving wheels 22.

[0028] Therefore, the output torque of the engine 1 is divided and transmitted to the first motor 2 and the drive wheels 22 according to the gear ratio of the power split mechanism 21, and by outputting torque from the second motor 3, the output torque of the second motor 3 can be added to the torque transmitted to the drive wheels 22.

[0029] The motors 2 and 3 can be configured in the same manner as motors provided as driving power sources for conventional electric vehicles and hybrid vehicles. That is, in addition to functioning as a motor that outputs driving torque when power is supplied, the motors also function as generators that convert part of the motive power into electric power when the output shaft is rotated. For example, permanent magnet synchronous motors and induction motors can be used as such motors 2 and 3.

[0030] Therefore, there are provided a power storage device 23 which serves as the power source for the motors 2 and 3, and a first inverter 24 and a second inverter 25 which convert the DC power output from the power storage device 23 into AC power and output it to the motors 2 and 3, and also convert the AC power generated by the motors 2 and 3 into DC power and output it to the power storage device 23.

[0031] 1 is provided with an electronic control unit (hereinafter, referred to as ECU) 26 for controlling the throttle valve 8, the spark plug 16, the port injection valve 9, the in-cylinder injection valve 15, and the inverters 24 and 25. This ECU 26 is mainly composed of a microcomputer, similar to the ECUs provided in conventional vehicles, and is configured to determine the amount of fuel injection to the engine 1, the ignition timing for igniting the mixture, the output torque and rotation speed of the first motor 2 and the second motor 3, etc., based on input signals and pre-stored maps and arithmetic expressions, and output the signals to the throttle valve 8, the spark plug 16, the port injection valve 9, the in-cylinder injection valve 15, and the inverters 24 and 25. The ECU 26 corresponds to the "controller" in the embodiment of the present invention, and is not limited to a single one. It may be configured to include an engine ECU for controlling the engine 1 and a motor ECU for controlling the motors 2 and 3, and to determine the output signals by communicating between these ECUs.

[0032] The sensors that input signals to the ECU 26 include, for example, an air flow meter 27 that detects the amount of air flowing through the intake passage 7, a water temperature sensor 28 that detects the engine water temperature, a crank angle sensor 29 that detects the rotation angle (crank angle) of the crankshaft 4, a first resolver 30 that detects the rotation speed of the first motor 2, and a second resolver 31 that detects the rotation speed of the second motor 3.

[0033] FIG. 2 shows a block diagram for explaining the configuration of the ECU 26. The ECU 26 shown in FIG. 2 includes a cylinder torque calculation unit 32, an injection amount correction unit 33, a misfire determination unit 34, and an over-temperature determination unit 35. The cylinder torque calculation unit 32 calculates the variation of the output torque (combustion torque) of each cylinder #1, #2, #3, #4. For example, the combustion torque generated by the first cylinder #1 combusting the mixture is calculated from the torque acting on the first motor 2 at that time. Specifically, the combustion torque of the first cylinder #1 is calculated based on the reaction torque based on the command value to the first motor 2, the inertia torque obtained by multiplying the rate of change of the rotation speed of the first motor 2 by the moment of inertia of the first motor 2, the gear ratio of the power split mechanism 21, and the inertia torque of the engine 1. Similarly, the combustion torque of the second cylinder #2, the third cylinder #3, and the fourth cylinder #4 is calculated. Then, the difference between the average value (average torque) of the combustion torque of each cylinder #1, #2, #3, #4 and the combustion torque of each cylinder #1, #2, #3, #4 is calculated as the amount of variation.

[0034] The injection amount correction unit 33 corrects the amount of fuel injected into each of the cylinders #1, #2, #3, #4 so as to reduce the amount of variation in the combustion torque calculated by the cylinder-by-cylinder torque calculation unit 32. For example, when the combustion torque of the first cylinder #1 is higher than the average torque, the amount of fuel injected into the first cylinder #1 is reduced according to the torque difference, and when the combustion torque of the first cylinder #1 is lower than the average torque, the amount of fuel injected into the first cylinder #1 is increased according to the torque difference.

[0035] The misfire determination unit 34 determines whether or not a misfire has occurred in each cylinder #1, #2, #3, #4. For example, the combustion torque generated by the mixture being burned by the predetermined cylinder #1 (#2, #3, #4) to be determined at all times is obtained from the torque acting on the first motor 2 at that time. Then, if the difference between the combustion torque at the time of determination and the past combustion torque in the predetermined cylinder #1 (#2, #3, #4) is equal to or greater than a predetermined difference, it is determined that a misfire has occurred in the predetermined cylinder #1 (#2, #3, #4). Alternatively, if the difference between the combustion torque at the time of determination and the average value of the past combustion torque of a predetermined number of times in the predetermined cylinder #1 (#2, #3, #4) is equal to or greater than a predetermined difference, it is determined that a misfire has occurred in the predetermined cylinder #1 (#2, #3, #4). Alternatively, to determine whether a specified cylinder #1 (#2, #3, #4) is completely misfiring, such as being unable to fire, if the difference between the combustion torque of the specified cylinder #1 (#2, #3, #4) and the combustion torque of the other cylinder #2 (#1, #3, #4) is greater than a specified difference, it is determined that a misfire has occurred in the specified cylinder #1 (#2, #3, #4).

[0036] That is, the misfire judgment unit 34 judges misfire in a specified cylinder #1 (#2, #3, #4) based on the combustion torque at the time of judgment in the specified cylinder #1 (#2, #3, #4) and the specified judgment threshold value, using past combustion torque, the average value of past combustion torque, or the combustion torque of another cylinder #2 (#1, #3, #4) as a specified judgment threshold value.

[0037] As in the control device described in Patent Document 3, the misfire determination unit 34 may determine that a misfire has occurred by comparing the amount of rotational fluctuation of the crankshaft 4 (i.e., the rotation speed of the engine 1) at the time of misfire determination with the amount of rotational fluctuation before the rotation angle (crank angle) of the crankshaft 4 was 720° CA. In this case, the amount of rotational fluctuation before 720° CA becomes the "predetermined determination threshold" in the embodiment of the present invention.

[0038] The over-temperature determination unit 35 determines whether the temperature of the GPF 20 is equal to or higher than the allowable upper limit temperature. Specifically, when the rate of occurrence (number of occurrences) of misfires in the engine 1 is equal to or higher than a predetermined rate (predetermined number of times) that is determined in advance according to the operating state of the engine 1, the over-temperature determination unit 35 determines that the temperature of the GPF 20 is equal to or higher than the allowable upper limit temperature.

[0039] The engine 1 configured as described above can perform catalyst warm-up control to heat the catalyst device 19 to an activation temperature. This catalyst warm-up control is executed when the bed temperature of the catalyst device 19 is equal to or lower than a predetermined temperature (activation temperature), and includes HV catalyst warm-up control that retards the ignition timing from that during normal operation when the catalyst device 19 has been heated to the activation temperature, and rapid catalyst warm-up control that retards the ignition timing by a greater amount than that of HV catalyst warm-up control and injects fuel from the in-cylinder injection valve 15 into the combustion chamber 5 at the later stage of the compression stroke to perform stratified injection combustion to bring the vicinity of the spark plug 16 into a rich state at the ignition timing. The rapid catalyst warm-up control can increase the temperature of the catalyst device 19 faster than the HV catalyst warm-up control.

[0040] Furthermore, when the amount of PM accumulated in the GPF 20 exceeds a predetermined amount, for example, GPF regeneration control can be performed to restore the collection function of the GPF 20. This GPF regeneration control is a control that burns and removes the PM accumulated in the GPF 20 by supplying air containing oxygen to the GPF 20. Specifically, the GPF regeneration control retards the ignition timing more than when the GPF regeneration control is not executed.

[0041] In the above-mentioned warm-up control and GPF regeneration control, the combustion in each cylinder #1, #2, #3, #4 becomes unstable as the ignition timing is retarded. That is, the combustion torque generated in each cylinder #1, #2, #3, #4 varies, and the engine 1 may vibrate excessively. Therefore, the control device in the embodiment of the present invention is configured to correct the amount of fuel injected into each cylinder #1, #2, #3, #4 in order to suppress the variation in the combustion torque generated in each cylinder #1, #2, #3, #4 when ignition retard control that retards the ignition timing is executed.

[0042] Fig. 3 shows a flowchart for explaining a control example for suppressing variations in combustion torque due to the execution of ignition retard control. In the control example shown in Fig. 3, first, it is determined whether or not the conditions for executing ignition retard control are met (step S1). Specifically, it is determined whether or not there is a request to execute HV catalyst warm-up control or rapid catalyst warm-up control, or whether or not there is a request to execute GPF regeneration control. In other words, it is determined whether or not the catalyst bed temperature is lower than a predetermined activation temperature, and whether or not the pressure on the upstream side of the GPF 20 is higher than the pressure on the downstream side by a predetermined pressure or more.

[0043] If the condition for executing the ignition retard control is not satisfied and the result of the determination in step S1 is negative, the routine is terminated. On the other hand, if the condition for executing the ignition retard control is satisfied and the result of the determination in step S1 is positive, the ignition retard control is executed (step S2).

[0044] Next, it is determined whether or not the preconditions for the fuel injection amount correction control are satisfied (step S3). This step S3 is a step for determining whether or not the combustion torque can be detected in order to obtain the amount of variation in the combustion torque, and in the control example shown here, the first motor 2 is configured to detect the combustion torque of each of the cylinders #1, #2, #3, and #4. Therefore, step S3 determines whether or not the system is functioning normally, for example, whether or not the first motor 2 and the resolver 30 that detects the rotation speed thereof are functioning normally.

[0045] If the preconditions for the fuel injection amount correction control are not satisfied and therefore the result of the negative determination in step S3 is negative, this routine is terminated. On the other hand, if the preconditions for the fuel injection amount correction control are satisfied and therefore the result of the positive determination in step S3 is positive, then the correction amount of the fuel injection amount for each cylinder #1, #2, #3, #4 is calculated (step S4). Specifically, first, the cylinder torque calculation unit 32 sequentially calculates the combustion torque of each cylinder #1, #2, #3, #4 based on the torque acting on the first motor 2, and calculates the average torque of the calculated combustion torque. Next, the difference between the combustion torque and the average torque of each cylinder #1, #2, #3, #4 is calculated to calculate the variation amount. In other words, the correction torque required to reduce the variation amount is calculated for each cylinder #1, #2, #3, #4. Then, the correction amount of the fuel injection amount is calculated by multiplying the correction torque by a predetermined coefficient that associates the fuel amount with the torque. In addition, when the difference between the combustion torque and the average torque is equal to or smaller than a predetermined difference, such as a small difference that does not affect the vibration of the vehicle, the correction torque may be set to "0".

[0046] Next, fuel injection correction control for each cylinder #1, #2, #3, #4 is executed (step S5). That is, the fuel injection amount is increased for a cylinder whose combustion torque is smaller than the average torque, and the fuel injection amount is decreased for a cylinder whose combustion torque is larger than the average torque. In this control example, the retard amount of the ignition timing is further increased (step S6), and this routine is temporarily terminated. This step S6 is for further increasing the temperature rise rate of the catalyst device 19 or for quickly performing the regeneration process of the GPF 20, since the variation in the combustion torque can be reduced by correcting the fuel injection amount as described above, and the additional retard amount is determined so that the variation in the fuel torque is within an allowable range. Note that the step of further retarding the ignition timing in step S6 does not have to be executed.

[0047] By executing the fuel injection correction control when executing the ignition retard control in this way, even if the combustion becomes unstable due to the ignition retard control, the fuel injection amount to each cylinder #1, #2, #3, #4 is corrected, so that the variation in the combustion torque can be reduced. In other words, the vibration of the vehicle caused by the variation in the combustion torque can be suppressed. In addition, since the amount of retard of the ignition timing can be increased compared to the case where the fuel injection amount to each cylinder #1, #2, #3, #4 is not corrected, the temperature of the catalyst device 19 can be raised quickly, or the regeneration process of the GPF 20 can be performed quickly.

[0048] On the other hand, as described above, the misfire judgment unit 34 judges misfire in a specified cylinder #1 (#2, #3, #4) based on the combustion torque at the time of judgment in the specified cylinder #1 (#2, #3, #4) and the amount of rotational fluctuation corresponding to the combustion torque, and a specified judgment threshold value, so there is a possibility that it will not be possible to judge misfire by correcting the fuel injection amount.

[0049] Therefore, the control device in the embodiment of the present invention is configured not to correct the fuel injection amount when there is a possibility of misfire occurring. A flow chart for explaining an example of such control is shown in Fig. 4. Note that the same steps as those in the control example shown in Fig. 3 are given the same reference numerals and their explanations are omitted.

[0050] 4, following step S4, it is determined whether the combustion torque of any cylinder is equal to or less than a predetermined torque (step S11). This step S11 is a step for determining whether there is a possibility that a misfire is occurring in any cylinder, and therefore the predetermined torque can be set to the magnitude of the torque generated when a misfire occurs, or to a torque slightly larger than the magnitude of that torque.

[0051] If the combustion torque of any cylinder is equal to or less than a predetermined torque and the result of the affirmative determination in step S11 is negative, the fuel injection amount is corrected to reduce the variation in the combustion torque of each cylinder #1, #2, #3, #4, and misfire cannot be determined. Also, for example, if a misfire occurs because firing cannot be performed, the combustion torque of that cylinder is almost zero, so if the variation in the combustion torque of each cylinder #1, #2, #3, #4 is reduced, the fuel injection amount to that cylinder is increased, and in such a case, there is a possibility that the combustion chamber 5 becomes excessively fueled and a fuel hammer occurs. Therefore, if the result of the affirmative determination in step S11 is negative, the fuel injection correction control is not executed (step S12), and this routine is temporarily terminated.

[0052] On the other hand, if the combustion torque of all cylinders is higher than the predetermined torque and the result of step S11 is negative, fuel injection correction control is executed for each cylinder #1, #2, #3, #4 (step S5). That is, the fuel injection amount is increased for cylinders whose combustion torque is smaller than the average torque, and the fuel injection amount is decreased for cylinders whose combustion torque is larger than the average torque, and this routine is temporarily terminated.

[0053] As described above, when the combustion torque of any cylinder is equal to or less than a predetermined torque and thus there is a possibility that a misfire is occurring in that cylinder, the fuel injection correction control is prohibited. In other words, the fuel injection correction control is executed only when there is no possibility that a misfire is occurring. In other words, the determination of the presence or absence of a misfire is prioritized over suppressing the variation in the combustion torque. As a result, it is possible to suppress the situation where the fuel injection correction control is executed and it becomes impossible to determine the presence or absence of a misfire.

[0054] Figures 5 and 6 show flow charts for explaining a control example that can simultaneously correct the fuel injection amount to suppress variations in combustion torque and determine misfire. The control example shown in Figure 5 is configured to correct a determination threshold for determining the presence or absence of misfire, and to compare the combustion torque and the rotation fluctuation amount of the crankshaft 4 after the fuel injection amount has been corrected with the corrected determination threshold to determine the presence or absence of misfire. Note that the same steps as those in the control examples shown in Figures 3 and 4 are given the same reference numerals and their description will be omitted.

[0055] In the control example shown in FIG. 5, after the fuel injection correction control is executed in step S5, the misfire determination unit 34 corrects the determination threshold value for determining the presence or absence of misfire (step S21). That is, when the misfire determination unit 34 determines the presence or absence of misfire by comparing the combustion torque at the time of executing this routine with the past combustion torque, the past combustion torque is corrected. Specifically, when the fuel injection amount of a specific cylinder #1 (#2, #3, #4) is increased, the torque increased by increasing the fuel injection amount is added to the past combustion torque before the fuel injection amount is corrected. Conversely, when the fuel injection amount of a specific cylinder #1 (#2, #3, #4) is decreased, the torque decreased by decreasing the fuel injection amount is subtracted from the past combustion torque before the fuel injection amount is corrected. Note that the increase or decrease in the combustion torque due to the correction of the fuel injection amount can be obtained by multiplying the correction amount of the fuel injection amount by a predetermined coefficient.

[0056] Similarly, when the misfire judgment unit 34 judges whether or not a misfire has occurred by comparing the combustion torque at the time this routine is executed with the average value of the past combustion torque before the fuel injection amount is corrected, the average value of the past combustion torque before the fuel injection amount is corrected. When the misfire judgment unit 34 judges whether or not a misfire has occurred by comparing the combustion torque at the time this routine is executed with the combustion torque of another cylinder, the combustion torque of the other cylinder is corrected.

[0057] Furthermore, when the misfire determination unit 34 determines that a misfire has occurred by comparing the amount of rotational fluctuation of the crankshaft 4 at the time of misfire determination with the amount of rotational fluctuation at a crank angle a predetermined angle ago, the amount of rotational fluctuation at the predetermined angle ago is corrected. Specifically, first, the amount of increase or decrease in the combustion torque resulting from the correction of the fuel injection amount is calculated by multiplying the correction amount of the fuel injection amount by a predetermined coefficient. Since the amount of rotational fluctuation of the crankshaft 4 increases or decreases according to the combustion torque, the amount of change in the amount of rotational fluctuation resulting from the correction of the fuel injection amount is calculated by multiplying the amount of increase or decrease in the combustion torque resulting from the correction of the fuel injection amount by a predetermined coefficient. Then, the calculated amount of change in the amount of rotational fluctuation is added to or subtracted from the amount of rotational fluctuation at the predetermined angle ago.

[0058] On the other hand, if the precondition is not satisfied and the result of the determination in step S3 is negative, the fuel injection correction control is not executed (step S12). Therefore, the determination threshold for determining the presence or absence of misfire by the misfire determination unit 34 is not corrected either (step S22). In other words, when misfire is determined based on the past combustion torque before the fuel injection amount is corrected, its average value, the combustion torque of another cylinder, or the rotation fluctuation amount of the crankshaft 4, the rotation fluctuation amount a predetermined angle ago is used as the determination threshold.

[0059] Following steps S21 and S22, it is determined whether or not the preconditions for misfire determination are met (step S23). This step S23 determines, for example, whether the rotation speed of the crankshaft 4 is equal to or higher than a predetermined rotation speed after the engine is started, that is, whether the number of past combustion torque samples is equal to or higher than a predetermined number, or whether the change in the fuel injection amount by the correction amount by the fuel injection control is completed.

[0060] If the preconditions for misfire determination are not met and therefore the answer is negative in step S23, the routine is terminated. On the other hand, if the preconditions for misfire determination are met and therefore the answer is positive in step S23, then the misfire determination process is executed (step S24).

[0061] In this control example, the misfire determination unit 34 compares the combustion torque at the time of executing this routine with the past combustion torque to determine whether or not a misfire has occurred. Therefore, when the misfire determination process is executed, the combustion torque generated by injecting the fuel injection amount corrected in step S4 is detected, and it is determined whether or not the detected actual combustion torque is equal to or less than the determination threshold (step S25). That is, when the determination threshold is corrected in step S21, it is determined whether or not the actual combustion torque is equal to or less than the corrected determination threshold, and when step S22 is executed and the determination threshold is not corrected, it is determined whether or not the actual combustion torque is equal to or less than the past combustion torque before the fuel injection amount was corrected.

[0062] If the actual combustion torque is equal to or less than the judgment threshold and thus the answer is affirmative in step S25, it is determined that a misfire abnormality has occurred (step S26). Conversely, if the actual combustion torque is higher than the judgment threshold and thus the answer is negative in step S25, it is determined that a misfire abnormality has not occurred, i.e., the engine is normal (step S27), and this routine is temporarily terminated.

[0063] In the above-described control example, the fuel injection amount is corrected to suppress the variation in the combustion torque, and the actual combustion torque (actual rotation fluctuation amount) resulting from the injection of the corrected fuel injection amount is compared with the corrected judgment threshold value by the combustion torque (or the rotation fluctuation amount) that changes due to the correction of the fuel injection amount to judge the presence or absence of misfire. Therefore, it is possible to suppress the variation in the combustion torque caused by executing the ignition retard control and to judge the misfire at the same time. That is, it is possible to suppress the occurrence of vibration caused by the variation in the combustion torque while judging the misfire. As a result, it is possible to promote the ignition retard control, and it is possible to quickly activate the catalytic device 19 and quickly regenerate the GPF 20.

[0064] The control example shown in Fig. 6 is configured to obtain a virtual combustion torque obtained by increasing or decreasing the amount of change in the combustion torque caused by correcting the fuel injection amount from the actual combustion torque after correcting the fuel injection amount, and to determine the presence or absence of a misfire by comparing the virtual combustion torque with a determination threshold value for determining the presence or absence of a misfire. Note that the same steps as those in the control examples shown in Fig. 3 to Fig. 5 are denoted by the same reference numerals and their description will be omitted.

[0065] In the control example shown in FIG. 6, after step S5, a virtual combustion torque is calculated (step S31). In this step S31, the combustion torque generated when the fuel injection amount is not corrected is calculated as the virtual combustion torque. Therefore, in step S31, the combustion torque after the fuel injection amount is corrected is detected, and the increase or decrease in the combustion torque due to the correction of the fuel injection amount is added or subtracted from the detected actual combustion torque. Specifically, when the fuel injection amount is increased in step S5, the torque increased by increasing the fuel injection amount is subtracted from the actual combustion torque. Conversely, when the fuel injection amount is decreased in step S5, the torque decreased by decreasing the fuel injection amount is added to the actual combustion torque.

[0066] When the misfire determination unit 34 determines a misfire based on the rotation fluctuation amount of the crankshaft 4, it detects the actual rotation fluctuation amount of the crankshaft 4 after the fuel injection amount is corrected, and adds or subtracts the increase or decrease in the rotation fluctuation amount caused by correcting the fuel injection amount from the detected actual rotation fluctuation amount. The increase or decrease in the rotation fluctuation amount caused by correcting the fuel injection amount can be found based on the increase or decrease in the combustion torque caused by correcting the fuel injection amount as described above.

[0067] Then, in the control example shown in FIG. 6, when the misfire determination process is executed in step S24, the misfire determination unit 34 determines whether or not the virtual combustion torque calculated in step S31 is equal to or less than a determination threshold value such as the past combustion torque before the fuel injection amount was corrected, its average value, or the combustion torque of another cylinder (step S32).

[0068] If the virtual combustion torque is equal to or less than the judgment threshold and thus the answer is affirmative in step S32, it is determined that a misfire abnormality has occurred (step S26). Conversely, if the virtual combustion torque is higher than the judgment threshold and thus the answer is negative in step S32, it is determined that a misfire abnormality has not occurred, i.e., the engine is normal (step S27), and this routine is temporarily terminated.

[0069] In the above-described control example, the fuel injection amount is corrected to suppress the variation in the combustion torque, and the virtual combustion torque is calculated by adding or subtracting the combustion torque (or the rotational fluctuation amount) that changes due to the correction of the fuel injection amount from the actual combustion torque (actual rotational fluctuation amount) resulting from the injection of the corrected fuel injection amount, and the virtual combustion torque is compared with the judgment threshold value to judge the presence or absence of misfire. Therefore, it is possible to suppress the variation in the combustion torque caused by executing the ignition retard control and to judge the misfire at the same time. That is, it is possible to suppress the occurrence of vibration caused by the variation in the combustion torque while judging the misfire. As a result, it is possible to promote the ignition retard control, and it is possible to quickly activate the catalytic device 19 and quickly regenerate the GPF 20.

[0070] As described above, by executing the fuel injection correction control, the amount of retardation of the ignition timing can be increased, so that the GPF 20 can be quickly regenerated. However, the temperature rise of the GPF 20 due to the occurrence of a misfire occurs more quickly than in the case of executing normal ignition retard control without executing the fuel injection control. In other words, the frequency (number of occurrences) of misfires reaching the upper limit temperature set to protect the GPF 20 decreases. Therefore, the control device in the embodiment of the present invention is configured to change the threshold value for determining abnormal heating of the GPF 20 depending on whether or not the fuel injection correction control is executed.

[0071] 7, 9, and 10 show flowcharts for explaining the control example, which can be executed following the control examples of FIGS. 4 to 6. The control example shown in FIG. 7 is configured to change a threshold value for determining abnormal heating of the GPF 20 depending on whether or not the fuel injection correction control has been executed. Therefore, first, it is determined whether or not the fuel injection correction control has been executed (step S41). This step S41 determines whether or not the ignition retard amount has been increased compared to the ignition retard amount in the case where the fuel injection correction control is not executed, by determining that the fuel injection correction control is executed. Note that the determination can be made based on whether or not the above step S5 has been executed.

[0072] If the fuel injection correction control is not executed and therefore the result of the negative determination in step S41 is negative, a predetermined normal determination value is set as a threshold value for determining abnormal heating (OT determination threshold value) (step S42). Since the temperature of the GPF 20 increases according to the degree of occurrence of misfire as described above, the misfire rate (OT misfire rate) can be adopted as a threshold value for determining abnormal heating. An example of the OT misfire rate is shown as a map in FIG. 8. The OT misfire rate map shown in FIG. 8 is a rate of occurrence of misfires that cause abnormal heating of the GPF 20, which is determined in advance by experiments or the like using the engine speed and the engine load as parameters, and is stored in the ECU 26 (overtemperature determination unit 35). As shown in FIG. 8, the OT misfire rate map is configured so that the lower the engine speed is, the higher the OT misfire rate (i.e., normal determination value) is set, and the smaller the engine load is, the higher the OT misfire rate (i.e., normal determination value) is set. The misfire occurrence rate is the ratio (number of misfire occurrences / predetermined number of combustions) of the number of misfire occurrences to a predetermined number of combustions (i.e., equivalent to the engine speed) in the engine 1. In other words, the misfire occurrence rate can be calculated by accumulating the number of misfire occurrences in each of cylinders #1, #2, #3, and #4 and calculating the number of misfire occurrences.

[0073] Therefore, in step S42, the engine speed and the engine load are detected, and the OT determination threshold is determined by referring to the OT misfire rate map. Note that the misfire rate is the number of misfires among a predetermined number of combustions, so the misfire rate and the number of misfires are essentially synonymous.

[0074] On the other hand, if the fuel injection correction control is executed and the result of the determination in step S41 is affirmative, a correction determination value that is set to a lower misfire occurrence rate than the normal determination value is set as the OT determination threshold (step S43). Similarly, in this step S43, the misfire occurrence rate at which the GPF 20 becomes abnormally heated when the engine 1 is operated with an ignition retard amount that can be set when the fuel injection correction control is executed is determined by experiment or the like, and the misfire occurrence rate is mapped and stored in the ECU 26, whereby the correction determination value can be determined. In this case, even if the engine speed and engine load are the same as those in the normal state, the GPF 20 becomes abnormally heated at a low misfire occurrence rate.

[0075] Following steps S42 and S43, it is determined whether the misfire occurrence rate is equal to or greater than the OT determination threshold (step S44). That is, the ECU 26 stores the history of each misfire abnormality determination performed by executing the control examples shown in Figs. 4 to 6, and calculates the misfire occurrence rate for a predetermined number of combustions. Then, in step S44, the misfire occurrence rate is compared with the OT determination threshold.

[0076] If the misfire occurrence rate is equal to or greater than the OT determination threshold and thus the result of step S44 is affirmative, an OT abnormality determination is made (step S45), whereas if the misfire occurrence rate is less than the OT determination threshold and thus the result of step S44 is negative, then a normality determination is made (step S46) and this routine is temporarily terminated. If an OT abnormality is determined in step S45, for example, a warning may be given to the driver by displaying a message on the instrument panel indicating that the GPF 20 has overheated abnormally, or control may be executed to limit the output of the engine 1 and suppress further temperature rise of the GPF 20.

[0077] When the fuel injection correction control is executed as described above to increase the amount of ignition retard, the OT determination threshold is changed to a misfire occurrence rate that is lower than when the ignition retard amount is used in normal ignition retard control, thereby making it possible to suppress the occurrence of abnormal heating of the GPF 20 or to accurately determine abnormal heating of the GPF 20.

[0078] The control example shown in Fig. 9 differs from the control example shown in Fig. 7 only in the means for setting the OT determination threshold. Specifically, in the control example shown in Fig. 9, the OT determination threshold is set (step S51) by referring to an OT misfire rate map (three-dimensional map) in which the ignition retard amount is used as a parameter in addition to the engine speed and engine load, and then the above-mentioned step S44 and subsequent steps are executed. This OT misfire rate map can be determined so that the OT determination threshold (misfire occurrence rate) becomes smaller as the ignition retard amount becomes larger.

[0079] As described above, by determining the OT determination threshold based on the OT misfire rate map with the ignition retard amount as a parameter, even if the ignition retard amount is arbitrarily changed, the OT determination threshold corresponding to the ignition retard amount can be set. As a result, it is possible to suppress the occurrence of abnormal heating of the GPF 20, or to accurately determine abnormal heating of the GPF 20.

[0080] The control example shown in Fig. 10 differs from the control examples shown in Fig. 7 and Fig. 9 only in the means for setting the OT judgment threshold. Specifically, in the control example shown in Fig. 10, the OT judgment threshold is set by multiplying a predetermined coefficient determined according to the amount of ignition retard by the normal judgment threshold (step S61), and then steps S44 and after are executed. This predetermined coefficient is a coefficient smaller than "1" and is set to a smaller value as the amount of ignition retard increases.

[0081] As described above, by multiplying the normal judgment threshold by a predetermined coefficient according to the ignition retard amount to determine the OT judgment threshold, even if the ignition retard amount is arbitrarily changed, the OT judgment threshold corresponding to the ignition retard amount can be set. As a result, it is possible to suppress the occurrence of abnormal heating of the GPF 20, or to accurately determine abnormal heating of the GPF 20.

[0082] In the above-described control example, the first motor 2 has a high detection speed and good detection accuracy, so that the combustion torque of each cylinder #1, #2, #3, #4 is calculated from the torque acting on the first motor 2 by the first motor 2. However, the cylinder-by-cylinder torque calculation unit in the embodiment of the present invention may be configured to detect the combustion torque of each cylinder #1, #2, #3, #4 by other sensors. In addition, the internal combustion engine in the embodiment of the present invention is not limited to the one mounted on a so-called series-parallel hybrid vehicle configured as shown in FIG. 1, but may be mounted on a series hybrid vehicle or a parallel hybrid vehicle, or may be mounted on a so-called conventional vehicle equipped with only an engine as a driving force source. [Explanation of symbols]

[0083] 1 Engine 2 Motors 4 Crankshaft 5. Combustion chamber 15 In-cylinder injection valve 16 Spark plug 19 Catalytic device 20 Gasoline Particulate Filter (GPF) 26 Electronic Control Unit (ECU) 29 Crank angle sensor 30,31 Resolver 32 Cylinder-specific torque calculation section 33 Injection amount correction section 34 Misfire determination section 35 Overtemperature judgment section Ve Hybrid Vehicle

Claims

1. A control device for an internal combustion engine capable of executing ignition retard control for retarding an ignition timing for igniting an air-fuel mixture in a combustion chamber from a predetermined timing during normal operation, A controller for controlling the internal combustion engine, The controller: a cylinder torque calculation unit that calculates a variation in combustion torque of each cylinder during execution of the ignition retard control; an injection amount correction unit that corrects a fuel injection amount for each of the cylinders so as to reduce an amount of variation in the combustion torque of each of the cylinders calculated by the cylinder torque calculation unit; a misfire determination unit that determines a misfire in a specific cylinder among the cylinders based on a combustion torque of the specific cylinder or a rotation speed of the internal combustion engine, When the combustion torque of any one of the cylinders is equal to or less than a predetermined torque, the fuel injection amount correction unit does not correct the fuel injection amount to the cylinder. A control device for an internal combustion engine.

2. A control device for an internal combustion engine capable of executing ignition retard control for retarding an ignition timing for igniting an air-fuel mixture in a combustion chamber from a predetermined timing during normal operation, A controller for controlling the internal combustion engine, The controller: a cylinder torque calculation unit that calculates a variation in combustion torque of each cylinder during execution of the ignition retard control; an injection amount correction unit that corrects a fuel injection amount for each of the cylinders so as to reduce an amount of variation in the combustion torque of each of the cylinders calculated by the cylinder torque calculation unit; a misfire determination unit that determines a misfire in a specific cylinder among the cylinders based on a combustion torque associated with combustion in the specific cylinder or a rotation speed of the internal combustion engine and a specific determination threshold value, The misfire determination unit corrects the determination threshold by an amount of torque or rotation speed corresponding to a correction amount of the fuel injection amount for the specific cylinder when the fuel injection amount for each cylinder is corrected by the injection amount correction unit. A control device for an internal combustion engine.

3. A control device for an internal combustion engine capable of executing ignition retard control for retarding an ignition timing for igniting an air-fuel mixture in a combustion chamber from a predetermined timing during normal operation, A controller for controlling the internal combustion engine, The controller: a cylinder torque calculation unit that calculates a variation in combustion torque of each cylinder during execution of the ignition retard control; an injection amount correction unit that corrects a fuel injection amount for each of the cylinders so as to reduce an amount of variation in the combustion torque of each of the cylinders calculated by the cylinder torque calculation unit; a misfire determination unit that determines a misfire in a specific cylinder among the cylinders based on a combustion torque associated with combustion in the specific cylinder or a rotation speed of the internal combustion engine and a specific determination threshold value, The misfire determination unit corrects the combustion torque or the rotation speed by an amount of torque or rotation speed corresponding to a correction amount of the fuel injection amount for the specific cylinder when the fuel injection amount for each cylinder is corrected by the injection amount correction unit. A control device for an internal combustion engine.

4. The control device for an internal combustion engine according to claim 2 or 3, The engine further includes a filter for collecting particulate matter contained in the exhaust gas discharged from each of the cylinders. The controller: The misfire occurrence rate determined by the misfire determination unit is equal to or higher than a predetermined rate, the misfire occurrence rate being determined by an overtemperature determination unit. A control device for an internal combustion engine.

5. The control device for an internal combustion engine according to claim 4, The over-temperature determination unit sets the predetermined rate when the fuel injection amount to each of the cylinders is corrected to a value smaller than the predetermined rate when the fuel injection amount to each of the cylinders is not corrected. A control device for an internal combustion engine.

6. The control device for an internal combustion engine according to claim 4, The over-temperature determination unit determines that the filter is abnormally heated if the occurrence rate of misfire determined by the misfire determination unit is equal to or greater than a value obtained by multiplying the predetermined rate by a coefficient smaller than 1 when the fuel injection amount to each cylinder is corrected. A control device for an internal combustion engine.

7. The control device for an internal combustion engine according to claim 4, The over-temperature determination unit has a three-dimensional map that determines the predetermined rate using the rotation speed of the internal combustion engine, the load of the internal combustion engine, and the amount of retardation of the ignition timing as parameters. A control device for an internal combustion engine.

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