Engine control device

Abstract

The present invention addresses the problem of providing an engine control device capable of performing retreat travel while suppressing excessive temperature rise of a catalyst even when an abnormality occurs in a variable valve mechanism. An engine control device that is mounted in a vehicle and purifies exhaust gas by a catalyst, the engine having a variable valve mechanism capable of changing a valve overlap period during which both an intake valve and an exhaust valve are opened, the engine control device being provided with: a determination unit that determines whether the intake valve and the exhaust valve are open or not; determining whether or not an abnormality has occurred with respect to an operation of the variable valve mechanism for reducing the valve overlap period; and an injection control unit that, when the determination unit determines that the fuel injection amount is positive, increases the fuel injection amount compared to when the determination unit determines that the fuel injection amount is negative.

Description

TECHNICAL FIELD

[0001] The present application relates to a control device of an engine. BACKGROUND

[0002] In a case where the variable valve mechanism generates an abnormality during the change of the overlap period and the overlap period cannot be reduced, excessive warming of the catalyst can occur. In such a case, there is a technology of preventing the excessive warming of the catalyst by stopping fuel injection (for example, refer to Patent Document 1).

[0003] [PRIOR ART DOCUMENTS] [PTENT DOCUMENTS] [Patent Document 1] Japanese Patent Application Laid-Open No. 11-036907

[0004] [PROBLEMS TO BE SOLVED BY THE INVENTION]

[0005] In the above technology, since fuel injection is stopped, in a vehicle in which such an engine is mounted, it can be impossible to perform retreat running. SUMMARY

[0006] Therefore, an object of the present application is to provide a control device of an engine which can perform retreat running while suppressing excessive warming of a catalyst even in a case where a variable valve mechanism generates an abnormality.

[0007] [MEANS FOR SOLVING THE PROBLEMS]

[0008] The above object can be achieved by a control device of an engine which is mounted on a vehicle and purifies exhaust gas by a catalyst, the engine having a variable valve mechanism which can change a valve overlap period in which both an intake valve and an exhaust valve are opened, wherein the control device of the engine comprises: a determination section which determines whether an abnormality occurs with respect to an operation of the variable valve mechanism which reduces the valve overlap period; and an injection control section which, in a case where the determination section determines that an abnormality occurs, increases a fuel injection amount as compared to a case where the determination section determines that an abnormality does not occur.

[0009] [EFFECTS OF THE INVENTION]

[0010] According to the present application, it is possible to provide a control device of an engine which can perform retreat running while suppressing excessive warming of a catalyst even in a case where a variable valve mechanism generates an abnormality. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a schematic configuration view of a vehicle. Figure 2 is an example of a timing chart of fuel injection control.

[0012] Explanation of reference numerals 1 vehicle 10 engine 12 cylinder 17 in-cylinder injection valve 24 intake valve 25 exhaust valve 26 intake variable valve mechanism (variable valve mechanism) 27 exhaust variable valve mechanism (variable valve mechanism) 29 catalyst 50 ECU (control device, determination portion, injection control portion) DETAILED DESCRIPTION

[0013] [Outline structure of vehicle]

[0014] Figure 1 is an outline structure diagram of a vehicle 1. The vehicle 1 is provided with an engine 10, an automatic transmission 41, a differential 43, a wheel 45, and an ECU (Electronic Control Unit) 50. The engine 10 is, for example, a gasoline engine, but can also be a diesel engine. The driving force of the engine 10 is transmitted to the wheel 45 via the automatic transmission 41 and the differential 43.

[0015] A piston 13 is provided inside each cylinder 12 of the engine 10. The piston 13 is linked to a crankshaft 15, which is an output shaft of the engine 10, via a connecting rod 14. The reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 15 by the connecting rod 14.

[0016] A combustion chamber 16 is formed inside each cylinder 12 and above the piston 13, and a spark plug 18, which ignites a mixture of fuel and air, is installed in the combustion chamber 16. The ignition timing of the mixture by the spark plug 18 is adjusted by an igniter 19 provided above the spark plug 18.

[0017] An intake valve 24 and an exhaust valve 25, which open and close the cylinder 12, are provided in the cylinder 12. By opening of the intake valve 24, the combustion chamber 16 is communicated with an intake passage 20, and by closing of the intake valve 24, the communication of the combustion chamber 16 with the intake passage 20 is cut off. By opening of the exhaust valve 25, the combustion chamber 16 is communicated with an exhaust passage 21, and by closing of the exhaust valve 25, the communication of the combustion chamber 16 with the exhaust passage 21 is cut off.

[0018] An intake variable valve mechanism (hereinafter, referred to as intake VVT) 26 that changes the opening and closing period of the intake valve 24 is provided to the intake valve 24. Likewise, an exhaust variable valve mechanism (hereinafter, referred to as exhaust VVT) 27 that changes the opening and closing period of the exhaust valve 25 is provided to the exhaust valve 25. The intake VVT 26 changes the opening and closing period of the intake valve 24 to the advance side or the retard side by changing the phase of an intake drive cam that opens and closes the intake valve 24 provided to the intake camshaft with respect to the intake camshaft. Likewise, the exhaust VVT 27 changes the opening and closing period of the exhaust valve 25 to the advance side or the retard side by changing the phase of an exhaust drive cam that opens and closes the exhaust valve 25 provided to the exhaust camshaft with respect to the exhaust camshaft. The phase of the drive cam with respect to the camshaft is switched according to the hydraulic pressure adjusted by an oil control valve.

[0019] A throttle valve 23 that adjusts the amount of air introduced to the combustion chamber 16 is provided to the intake passage 20. A catalyst 29 that exhibits the maximum purification capacity when the air-fuel ratio of the mixture gas becomes the stoichiometric air-fuel ratio is provided to the exhaust passage 21. The catalyst 29 is a three-way catalyst that has an oxygen storage capacity of storing oxygen in the exhaust gas leaner than the stoichiometric air-fuel ratio and releasing the stored oxygen in the exhaust gas richer than the stoichiometric air-fuel ratio.

[0020] An intake port injection valve 22 that injects fuel into the intake port 20a is provided to each of the intake ports 20a that constitute a part of the intake passage 20, for each cylinder 12. An in-cylinder injection valve 17 that directly injects fuel into each of the combustion chambers 16 is provided to the engine 10.

[0021] The ECU 50 is an electronic control unit that performs control processing related to the engine 10. The ECU 50 is constituted mainly of a computer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, which are volatile or non-volatile memories. The ECU 50 realizes various control processes related to the engine 10 by executing a program installed in the memory on the CPU. Various sensors are connected to the ECU 50, the details of which will be described later. The ECU 50 is an example of a control device of the engine 10 and functionally realizes a determination section and an injection control section, the details of which will be described later.

[0022] The ECU 50 connects the ignition switch 31, the accelerator pedal opening degree sensor 32, the air flow meter 33, the crank angle sensor 34, the intake cam angle sensor 36, and the exhaust cam angle sensor 37, and inputs output signals from these various sensors. The ignition switch 31 detects the on-off state of ignition. The accelerator pedal opening degree sensor 32 detects the accelerator pedal opening degree. The air flow meter 33 detects the intake air amount. The crank angle sensor 34 detects the rotation angle of the crankshaft 15. The intake cam angle sensor 36 and the exhaust cam angle sensor 37 detect the phases of the intake driving cam and the exhaust driving cam of the engine 10 with respect to the intake camshaft and the exhaust camshaft, respectively.

[0023] The ECU 50 calculates the engine speed based on the detection value of the crank angle sensor 34, and calculates the engine load based on the engine speed and the intake air amount. The ECU 50 calculates the target speed and the target load based on the accelerator pedal opening degree, and controls the fuel injection amount, the intake air amount, and the ignition timing in such a manner that the engine speed and the load become the target speed and the target load, respectively. In addition, the ECU 50 controls the in-cylinder injection rate, which is the ratio of the injection amount from the in-cylinder injection valve 17 with respect to the total fuel injection amount, and the intake port injection rate, which is the ratio of the injection amount from the intake port injection valve 22 with respect to the total fuel injection amount, in accordance with the operating state of the engine 10. In addition, the ECU 50 controls the intake VVT 26 and the exhaust VVT 27 in accordance with the operating state of the engine 10, thereby controlling the opening and closing timing of the intake valve 24 and the exhaust valve 25.

[0024] Figure 2 This control is repeatedly executed in the state where the ignition is on. The ECU 50 determines whether or not an abnormality has occurred with respect to the operation of reducing the valve overlap period in at least one of the intake VVT 26 and the exhaust VVT 27 (step S1).

[0025] The abnormality with respect to the operation of reducing the valve overlap period refers to, for example, an advance-side abnormality in which the opening and closing timing of the intake valve 24 based on the intake VVT 26 is fixed on the advance side than the desired timing, or a delay-side abnormality in which the opening and closing timing of the exhaust valve 25 based on the exhaust VVT 27 is fixed on the delay side than the desired timing. In the case where the advance-side abnormality has occurred in the intake VVT 26, it is not possible to change the opening and closing timing of the intake valve 24 to the delay side, and thus it is not possible to reduce the valve overlap period by the intake VVT 26. In addition, in the case where the delay-side abnormality has occurred in the exhaust VVT 27, it is not possible to change the opening and closing timing of the exhaust valve 25 to the advance side, and thus it is not possible to reduce the valve overlap period by the exhaust VTT 27. In the case where at least one of the advance-side abnormality of the intake VTT 26 and the delay-side abnormality of the exhaust VTT 27 has occurred, the determination in step S1 is "Yes".

[0026] Specifically, in a case where the actual timing of the opening and closing of the intake valve 24 deviates from the target timing by a prescribed value or more to the advance side, it is determined that an advance-side abnormality has occurred in the intake VVT 26. In a case where the actual timing of the opening and closing of the exhaust valve 25 deviates from the target timing by a prescribed value or more to the retard side, it is determined that a retard-side abnormality has occurred in the exhaust VVT 27. The actual timing of the opening and closing of the intake valve 24 and the actual timing of the opening and closing of the exhaust valve 25 are respectively calculated on the basis of the detection values of the intake cam angle sensor 36 and the exhaust cam angle sensor 37. In a case where the determination in step S1 is NO, the control ends. Step S1 is an example of the processing performed by the determination section.

[0027] In a case where the determination in step S1 is YES, the ECU 50 performs correction to increase the fuel injection amount (step S2). The ECU 50 performs fuel injection with an injection amount obtained by adding the total fuel injection amount calculated on the basis of the operating state of the engine 10 to the increase amount based on the correction. The increase amount based on the correction is set to an amount by which the temperature of the exhaust gas is lowered by the latent heat of vaporization of the fuel at the injection amount after the increase, thereby suppressing excessive warming of the catalyst 29. Thus, even in a case where the above-described abnormality has occurred, excessive warming of the catalyst 29 is suppressed.

[0028] In addition, since fuel injection is continued, the operation of the engine 10 is continued. Thus, for example, the driver is notified that the above-described abnormality has occurred by the MIL (Malfunction Indicator Light) or the like, and the driver can perform evasive driving of the vehicle 1. Step S2 is an example of the processing performed by the injection control section.

[0029] In the above-described embodiment, the engine 10 provided with both the intake VVT 26 and the exhaust VVT 27 is described as an example, but the present application is not limited thereto. For example, for an engine provided with only the intake VVT 26, step S2 is performed in a case where an advance-side abnormality has occurred in the intake VVT 26. In addition, for an engine provided with only the exhaust VVT 27, step S2 is performed in a case where a retard-side abnormality has occurred in the exhaust VVT 27.

[0030] The above describes an embodiment of the present application, but the present application is not limited to this particular embodiment, and various modifications / changes can be made within the scope of the gist of the present application recited in the claims.

Claims

1. A control device of an engine mounted on a vehicle and purifying exhaust gas by a catalyst, the engine having a variable valve mechanism capable of changing a valve overlap period in which both an intake valve and an exhaust valve are open, wherein the control device of the engine comprises: a determination section that determines whether an abnormality occurs with respect to an operation of the variable valve mechanism that reduces the valve overlap period; and an injection control section that increases a fuel injection amount in a case where the determination section determines positively as compared with a case where the determination section determines negatively.

2. The control device according to claim 1, wherein the variable valve mechanism includes a first valve mechanism that changes the valve overlap period by changing an opening / closing timing of the intake valve and a second valve mechanism that changes the valve overlap period by changing an opening / closing timing of the exhaust valve, and the determination section determines whether an abnormality occurs with respect to an operation of the first valve mechanism and an operation of the second valve mechanism.

3. The control device according to claim 1 or 2, wherein the variable valve mechanism includes a third valve mechanism that changes the valve overlap period by changing a lift amount of the intake valve, and the determination section determines whether an abnormality occurs with respect to an operation of the third valve mechanism.

4. The control device according to any one of claims 1 to 3, wherein the variable valve mechanism includes a fourth valve mechanism that changes the valve overlap period by changing a lift amount of the exhaust valve, and the determination section determines whether an abnormality occurs with respect ​

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