Control device for internal combustion engines

Abstract

To provide a control device that can suppress false detection of misfires. [Solution] The control device for the internal combustion engine is mounted on a vehicle and is a control device for an internal combustion engine having an ignition device, a fuel injection device, and a catalytic converter. The control device for the internal combustion engine includes ignition retardation control, which retards the ignition timing of the ignition device; lean control, which controls the fuel injection device to lean the air-fuel ratio; catalytic converter warm-up control, which performs at least one of the ignition retardation control or the lean control to warm up the catalytic converter; and misfire determination control, which determines the misfire state of the internal combustion engine. If the output of the internal combustion engine falls below a predetermined output while the catalytic converter warm-up control is being performed, the misfire determination control is prohibited.

Description

Technical Field

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

Background Art

[0002] Conventionally, a control device for performing misfire determination of an internal combustion engine has been known. The control device for an internal combustion engine of Patent Document 1 determines that the internal combustion engine is misfiring when the rotational fluctuation of the crankshaft becomes large.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The control device for an internal combustion engine of Patent Document 1 determines misfire based on the rotational fluctuation of the crankshaft. In such a control device for an internal combustion engine, there is a possibility of erroneously determining misfire due to the output fluctuation of the internal combustion engine.

[0005] An object of the present disclosure is to provide a control device for an internal combustion engine that can suppress erroneous determination of misfire.

Means for Solving the Problems

[0006] The control device for an internal combustion engine according to this disclosure is mounted on a vehicle and is a control device for an internal combustion engine having an ignition device, a fuel injection device, and a catalytic converter. The control device for the internal combustion engine includes ignition timing retardation control for retarding the ignition timing of the ignition device, lean control for controlling the fuel injection device to lean the air-fuel ratio, catalytic converter warm-up control for warming up the catalytic converter by executing at least one of the ignition timing retardation control or the lean control, and misfire determination control for determining a misfire state of the internal combustion engine, wherein if the output of the internal combustion engine falls below a predetermined output while the catalytic converter warm-up control is being executed, the misfire determination control is prohibited. [Effects of the Invention]

[0007] According to this internal combustion engine control device, if the output of the internal combustion engine falls below a predetermined output during warm-up control, misfire detection control can be prohibited, thereby suppressing false misfire detection. [Brief explanation of the drawing]

[0008] [Figure 1] A system diagram of a hybrid vehicle according to one embodiment of the present disclosure. [Figure 2] A system diagram of an engine according to one embodiment of the present disclosure. [Figure 3] A flowchart illustrating a control procedure performed by a control device according to one embodiment of the present disclosure. [Figure 4] This diagram shows the change in a predetermined output according to the execution state of lean control and ignition retardation control. [Figure 5] A diagram showing the change in a predetermined value according to water temperature. [Figure 6] A diagram showing the changes over a predetermined period in response to water temperature. [Figure 7] A timing chart showing an example of a control procedure performed by a control device according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.

[0010] As shown in Figures 1 and 2, the control system 1 of vehicle (an example of a hybrid vehicle) C comprises an engine (an example of an internal combustion engine) 2, a motor (FrM) 3, a generator (GEN) 4, a drive battery (BT) 6, a transaxle 8, an inverter 12 that controls the motor 3 and generator 4, an accelerator pedal 14 operated by the user of vehicle C, a charger 16 that can be connected to an external power source, an external power supply device 18 that can supply power to external devices such as home appliances, a control device 20, and a fuel tank 22. Vehicle C in this embodiment is a plug-in hybrid electric vehicle (PHEV) equipped with external charging, which allows power from an external power source to be stored in the drive battery 6 by the charger 16, and external power supply, which allows power from the drive battery 6 to be supplied to external devices by the external power supply device 18.

[0011] As shown in Figure 1, the engine 2 is connected to the generator 4 and drives the generator 4. Furthermore, in this embodiment, the engine 2 can drive the wheels (an example of drive wheels) C1 via the transaxle 8. The engine 2 in this embodiment is an inline four-cylinder gasoline engine. The engine 2 receives fuel from the fuel tank 22 and consumes it by burning it.

[0012] As shown in Figure 2, the engine 2 includes a fuel injector 40, an ignition device 42, a water temperature sensor (an example of a detection device) 44, a catalytic converter 46, and a crank angle sensor 48. The fuel injector 40 of this embodiment includes an intake port injector 40a that injects fuel into the intake port 41 and an in-cylinder injector 40b that injects fuel into the cylinder N. The ignition device 42 ignites the air-fuel mixture supplied to the cylinder N. The water temperature sensor 44 detects the temperature of the coolant that cools the engine 2 (hereinafter referred to as water temperature WT in this specification). The catalytic converter 46 purifies the exhaust gas discharged from the engine 2. The crank angle sensor 48 detects the rotation of the crankshaft 50.

[0013] As shown in Figure 1, the motor 3 is connected to the wheel C1 via the transaxle 8 and axle 10, and drives the wheel C1. The motor 3 is driven by at least one of the first power generated by the generator 4 (described later) and the second power output from the drive battery 6. The motor 3 in this embodiment is a three-phase AC motor having multiple coils and multiple permanent magnets. The motor 3 is also driven by the rotation of the wheel C1 to generate electricity (regenerative braking). Therefore, the motor 3 is a motor-generator capable of both powering and generating electricity.

[0014] The generator 4 is connected to the engine 2 and is capable of driving the engine 2. While the vehicle is powered by the drive battery 6, the generator 4 performs motoring, driving the engine 2. Conversely, while the engine 2 is running, the generator 4 is driven by the engine 2 to generate electricity. Therefore, the generator 4 is a motor-generator capable of both powering and generating electricity.

[0015] The drive battery 6 outputs power to the motor 3 and generator 4, and also receives the first power generated by the motor 3 and generator 4. Furthermore, the drive battery 6 receives external power via the charger 16. In this embodiment, the drive battery 6 is composed of multiple lithium-ion batteries.

[0016] The transaxle 8 has multiple gears and a clutch 8a. The engine 2 is connected to the generator 4 and the axle 10 via the transaxle 8. When the clutch 8a is open, power transmission between the engine 2 and the axle 10 is interrupted, and when the clutch 8a is engaged, power from the engine 2 is transmitted to the axle 10.

[0017] The inverter 12 controls the motor torque of the motor 3 by converting the DC power supplied from the drive battery 6 into AC power and adjusting the power supplied to the motor 3. Furthermore, when the motor 3 is regenerating, the inverter 12 controls the regenerative torque of the motor 3 by converting the AC power supplied from the motor 3 into DC power and adjusting the power supplied to the drive battery 6.

[0018] The control device 20 is electrically connected to the motor 3 via the engine 2 and the inverter 12, and is a device that controls the engine 2 and the motor 3. The control device 20 is actually an ECU (Electronic Control Unit) constituted by a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The control device 20 controls the vehicle C based on the maps and programs stored in the memory.

[0019] The control device 20 executes ignition retard control, lean control, and catalyst warm-up control. The ignition retard control is control for retarding the ignition timing of the ignition device 42. The control device 20 increases the temperature of the exhaust gas by executing the ignition retard control. The lean control is control for making the air-fuel ratio, which is the ratio of air to the air-fuel mixture supplied to the engine 2, lean. In the present embodiment, the control device 20 executes lean control for making the air-fuel ratio lean by reducing the injection amount of the fuel injection device 40. The control device 20 increases the temperature of the exhaust gas by executing the lean control. The catalyst warm-up control is control for heating the catalyst 46 until the catalyst 46 becomes an activated state. The control device 20 executes at least one of the ignition retard control or the lean control in the catalyst warm-up control, and warms up the catalyst 46 faster by increasing the exhaust gas temperature than in the state where the catalyst warm-up control is not being executed.

[0020] The control device 20 executes misfire determination control for determining the misfire state of the engine 2. In the present embodiment, in the misfire determination control, the control device 20 detects the rotational fluctuation of the crankshaft 50 by the crank angle sensor 48, and determines that the engine 2 misfires when the rotational fluctuation is large. Note that the misfire state may include a partial misfire state. The partial misfire state is a state that has not reached a complete misfire but is close to the misfire state. In the misfire determination control, the control device 20 may not only determine a complete misfire of the engine 2 but also detect a partial misfire state.

[0021] Vehicle C in this embodiment has driving modes such as EV mode, series mode, and parallel mode. In EV mode, with the engine 2 stopped, the motor 3 is driven by second power from the drive battery 6. In series mode, the clutch 8a is disengaged, the engine 2 drives the generator 4, and the first power generated by the generator 4 is used to drive the motor 3 and drive the wheels C1. In parallel mode, the clutch 8a is engaged, and the power from the engine 2 is used to drive the wheels C1 via the axle 10. In vehicle C, the control device 20 switches between each driving mode according to the depression state of the accelerator pedal 14, and controls the motor 3 and generator 4 via the inverter 12, as well as the engine 2.

[0022] Next, the control procedure executed by the control device 20 will be described. In this embodiment, the control device 20 starts the control procedure when an ignition switch (not shown) is turned on.

[0023] In step S1, the control device 20 determines whether or not the catalyst is warming up. If the control device 20 is performing catalyst warm-up control, it determines that the catalyst is warming up. If the control device 20 determines that the catalyst is warming up (step S1 YES), it proceeds to step S2. If the control device 20 determines that the catalyst is not warming up (step S1 NO), it returns.

[0024] In step S2, the control device 20 determines whether it is performing either ignition retardation control or lean control. If the control device 20 determines that it is performing either ignition retardation control or lean control (step S2 YES), it proceeds to step S3. If the control device 20 determines that it is not performing either ignition retardation control or lean control (step S2 NO), it returns.

[0025] In step S3, the control device 20 determines whether the output Q of the engine 2 is less than or equal to a predetermined output Qt. The predetermined output Qt is an output that may cause a misjudgment in the misfire detection control. The predetermined output Qt is a larger value the greater the amount of retardation in the ignition timing retardation control. Also, the predetermined output Qt is a larger value the leaner the air-fuel ratio in the lean control. As shown in Figure 4, in this embodiment, the larger the value P obtained by multiplying the retard coefficient and the leaning coefficient, the larger the predetermined output Qt. The retard coefficient is a larger value the more retarded the ignition timing is. The leaning coefficient is a larger value the leaner the air-fuel ratio. In other words, the greater the amount of retardation in the ignition timing retardation control, the more unstable the combustion tends to be, and the higher the output Q at the combustion limit. In lean control as well, the leaner the air-fuel ratio, the more unstable the combustion tends to be, and the higher the output Q at the combustion limit. For this reason, the greater the amount of retardation and the leaner the air-fuel ratio, the more likely the control device 20 is to make a misjudgment in the misfire detection control. Therefore, the control device 20 can suppress misjudgments more easily by increasing the predetermined output Qt as the value P increases. In this embodiment, for example, the control device 20 increases the predetermined output Qt from value P 0.3 to value P 1.0. The predetermined output Qt at value P 0.3 is, for example, 10 Nm. The control device 20 keeps the predetermined output Qt constant when value P is 1.0 or greater. In this embodiment, output Q is defined by torque. The predetermined output Qt is defined by predetermined torque. As shown in Figure 3, if the control device 20 determines that output Q is less than or equal to the predetermined output Qt (step S3 YES), it proceeds to step S4. If the control device 20 determines that output Q is greater than the predetermined output Qt (step S3 NO), it returns.

[0026] In step S4, the control device 20 prohibits misfire detection control. Once the control device 20 prohibits misfire detection control, it proceeds to step S5.

[0027] In step S5, the control device 20 determines whether the output Q of the engine 2 is greater than a predetermined output Qt. If the control device 20 determines that the output Q is greater than the predetermined output Qt (step S5 YES), it proceeds to step S6. If the control device 20 determines that the output Q is less than the predetermined output Qt (step S5 NO), it returns.

[0028] In step S6, the control device 20 determines whether the change in the output Q of the engine 2, ΔQ, is less than or equal to a predetermined change value ΔQt. In this embodiment, the control device 20 detects the rotational speed V (angular velocity) of the crankshaft 50 using the crank angle sensor 48, and considers the change in the rotational speed V of the crankshaft 50 per unit time, ΔV, as the change in output Q, ΔQ. In other words, the control device 20 considers the change in output Q, ΔQ, to be larger the larger the change in the rotational speed V of the crankshaft 50, ΔV.

[0029] The predetermined change value ΔQt indicates that combustion is stable. As shown in Figure 5, the predetermined change value ΔQt increases as the water temperature WT increases. When the water temperature WT is low (for example, when the water temperature WT is 40°C or lower), the friction of the engine 2 is high. Therefore, the change in rotational speed V of the crankshaft 50, ΔV, becomes small. As a result, combustion may be stable even if the change in output Q, ΔQ, is small. On the other hand, when the water temperature WT is high (for example, when the water temperature WT is 80°C or higher), the friction of the engine 2 is lower than when the water temperature WT is low. Therefore, the change in rotational speed V of the crankshaft 50, ΔV, becomes large. As a result, combustion may be unstable even if the change in output Q, ΔQ, is large. The control device 20 takes into account the effect of the change in output Q, ΔQ, due to such friction, and varies the predetermined change value ΔQt according to the water temperature WT, as shown in Figure 5.

[0030] Furthermore, friction decreases inversely proportional to the water temperature WT. That is, the amount of friction reduction decreases as the water temperature WT increases. For this reason, the control device 20 reduces the amount of increase in the predetermined change value ΔQt as the water temperature WT increases.

[0031] As shown in Figure 3, if the control device 20 determines that the change in output Q ΔQ is less than or equal to a predetermined change value ΔQt (step S6 YES), it proceeds to step S7. If the control device 20 determines that the change in output Q ΔQ is greater than the predetermined change value ΔQt (step S6 NO), it returns.

[0032] In step S7, the control device 20 determines whether the state in which the change in output Q ΔQ has reached a predetermined change value ΔQt has continued for a predetermined period T. If the state in which the change in output Q ΔQ has reached a predetermined change value ΔQt has continued for a predetermined period T, it means that the combustion has remained stable for a predetermined period T. As a result, even if the misfire detection control is restarted, the possibility of the control device making a false determination is reduced. As shown in Figure 6, the predetermined period T is shorter the higher the water temperature WT. The higher the water temperature WT, the more stable the combustion is, and the more easily the change in output Q ΔQ converges. Furthermore, above a predetermined temperature WTt, the predetermined period T is constant. The predetermined temperature WTt is, for example, 40°C, and the engine 2 switches from a cold state to a warm state at the predetermined temperature WTt. In the warm state, the change in output Q ΔQ converges easily. Therefore, as shown in Figure 3, if the control device 20 determines that the predetermined period has continued (step S7 YES), it proceeds to step S8 and restarts the misfire detection control. The control device 20 returns when it restarts the misfire detection control. The control device 20 also returns if it determines that the misfire detection control has not continued for a predetermined period of time (step S7 NO).

[0033] A hybrid vehicle C having such a motor 3 can perform catalytic converter warm-up control of the engine 2 while driving using the motor 3. In this embodiment, the control device 20 performs catalytic converter warm-up control in series mode. However, as shown in Figure 7, even during catalytic converter warm-up control, the control device 20 may temporarily lower the output Q of the engine 2 from the catalytic converter warm-up output Qw, which is an output suitable for catalytic converter warm-up control, due to requirements such as ensuring negative pressure in the master back (not shown) used when operating the mechanical brakes (not shown) of the vehicle C, for example, when the vehicle C is decelerating. When the requirement to ensure negative pressure is no longer needed, the control device 20 raises the output Q of the engine 2 back to the catalytic converter warm-up output Qw. In this way, the rotation of the engine 2 fluctuates as the control device 20 raises and lowers the output Q of the engine 2.

[0034] As shown at time t1 in Figure 7, if the output Q falls below a predetermined output Qt (step S2 YES, step S3 YES in Figure 3) while at least one of the ignition retardation control and lean control is being performed during catalyst warm-up control, the control device 20 turns on the misfire determination control prohibition flag to prohibit misfire determination control.

[0035] As shown in Figure 7 at time t2, the requirement for negative pressure maintenance disappears, and the output Q of engine 2 attempts to return to its original value. As shown from time t2 to time t3 in Figure 7, the change in output Q ΔQ becomes large at this time. If misfire detection control is not prohibited between time t2 and time t3, the control device 20 may make a false determination that there is a misfire, even though there is no actual misfire, due to this change in output Q ΔQ.

[0036] As shown in Figure 7 from time t3 to time t4, if the control device 20 maintains a state where the change in output Q ΔQ is a predetermined change value ΔQt for a predetermined period T (the period from time t3 to time t4), it turns off the misfire detection control prohibition flag and restarts the misfire detection control.

[0037] As explained above, this disclosure provides a control device 20 for an internal combustion engine that can suppress misjudgments of misfires.

[0038] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0039] In the above embodiment, an example was described in which the control device 20 reduces the output Q of the engine 2 in response to a request to ensure negative pressure in the mechanical brakes during deceleration of the vehicle C, but the disclosure is not limited thereto. The control device 20 may also perform control to reduce the output Q of the engine 2 in response to a request from other equipment mounted on the vehicle C, such as a request to reduce the amount of power generated by the generator 4 during catalyst warm-up control, and may prohibit misfire detection control.

[0040] In the above embodiment, vehicle C was described as a plug-in hybrid vehicle, but this disclosure is not limited thereto. Vehicle C may be a vehicle that is powered solely by an internal combustion engine. [Explanation of Symbols]

[0041] 1: Control system, 2: Engine, 3: Motor, 4: Generator 6: Drive battery, 20: Control device, 40: Fuel injection device, 42: Ignition device 44: Water temperature sensor, 46: Catalytic converter C: Vehicle, Q: Output, Qt: Specified output, T: Specified period WT:Water temperature ΔQ: change, ΔQt: predetermined change value, ΔV: velocity change

Claims

1. A control device for an internal combustion engine mounted on a vehicle, having an ignition system, a fuel injection system, and a catalytic converter, Ignition timing retardation control that retards the ignition timing of the ignition device, Lean control, which controls the fuel injection device to lean the air-fuel ratio, A catalyst warm-up control is performed to warm up the catalyst by executing at least one of the ignition retardation control or the lean control, A misfire detection control that determines the misfire state of the internal combustion engine, Equipped with, If the output of the internal combustion engine falls below a predetermined output while the catalyst warm-up control is being performed, the misfire detection control is prohibited. Control device for internal combustion engines.

2. The predetermined output is a larger value the greater the amount of ignition retardation in the ignition retardation control, and a larger value the leaner the air-fuel ratio in the lean control. The control device for an internal combustion engine according to claim 1.

3. If the output becomes greater than the predetermined output, and the change in the output falls within a predetermined change value, the misfire detection control is restarted. A control device for an internal combustion engine according to claim 1.

4. The internal combustion engine has a detection device for detecting the temperature of the internal combustion engine, The higher the temperature, the higher the predetermined change value. The control device for an internal combustion engine according to claim 3.

5. The higher the temperature, the smaller the increase in the predetermined change value. The control device for an internal combustion engine according to claim 4.

6. If the change in the output remains within a predetermined change value for a predetermined period of time, the misfire detection control is restarted. A control device for an internal combustion engine according to any one of claims 3 to 5.

7. The internal combustion engine has a detection device for detecting the temperature of the internal combustion engine, The higher the temperature, the shorter the predetermined period. The control device for an internal combustion engine according to claim 6.

8. If the temperature is above a predetermined temperature, the predetermined period is constant. The control device for an internal combustion engine according to claim 7.

9. The vehicle comprises an internal combustion engine, a generator driven by the internal combustion engine, a drive battery to which first power generated by the generator is input, and a motor driven by at least one of the first power and a second power output from the drive battery. The vehicle executes the prohibition of the misfire detection control while decelerating. The control device for an internal combustion engine according to claim 1.

Images