Engine control device

Abstract

To provide a control device of an engine capable of performing retreat traveling while suppressing excessive temperature rise of a catalyst even when abnormality occurs in a variable valve train.SOLUTION: A control device for an engine, which is mounted on a vehicle and has a variable valve mechanism capable of changing a valve overlap period in which exhaust gas is purified by a catalyst and both of an intake valve and an exhaust valve are opened, the control device being further provided with a determination section for determining whether or not an abnormality occurs in an operation for reducing the valve overlap period of the variable valve mechanism, and an injection control section for increasing a fuel injection amount more when the determination section makes an affirmative determination than when the determination section makes a negative determination.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] If an abnormality occurs in the variable valve mechanism that changes the overlap period and the overlap period cannot be reduced, the catalyst may overheat. In such a case, there is a technology to prevent the catalyst from overheating by stopping fuel injection (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-036907 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above technology, fuel injection is stopped, so there is a risk that a vehicle equipped with such an engine will not be able to make an evacuation run.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine control device that is capable of performing evacuation driving while suppressing excessive temperature rise of the catalyst even when an abnormality occurs in the variable valve mechanism. [Means for solving the problem]

[0006] The above object can be achieved by an engine control device that is mounted on a vehicle, has exhaust purified by a catalyst, and has a variable valve mechanism that can change the valve overlap period when both the intake valve and the exhaust valve are open, and that includes: a judgment unit that judges whether an abnormality has occurred in the operation of the variable valve mechanism to reduce the valve overlap period; and an injection control unit that increases the amount of fuel injected when the judgment unit judges yes compared to when the judgment unit judges no. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an engine control device that is capable of performing evacuation running while suppressing excessive temperature rise of the catalyst even when an abnormality occurs in the variable valve mechanism. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle. [Figure 2] 4 is an example of a timing chart of fuel injection control. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Vehicle outline] 1 is a schematic diagram of a vehicle 1. The vehicle 1 includes an engine 10, an automatic transmission 41, a differential 43, wheels 45, and an ECU (Electronic Control Unit) 50. The engine 10 is, for example, a gasoline engine, but may also be a diesel engine. The driving force of the engine 10 is transmitted to the wheels 45 via the automatic transmission 41 and the differential 43.

[0010] Each cylinder 12 of the engine 10 is provided with a piston 13. The piston 13 is connected to a crankshaft 15, which is the 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.

[0011] A combustion chamber 16 is formed above the piston 13 in each cylinder 12, and a spark plug 18 that ignites the mixture of fuel and air is attached to this combustion chamber 16. The timing at which this spark plug 18 ignites the mixture is adjusted by an igniter 19 provided above the spark plug 18.

[0012] Each cylinder 12 is provided with an intake valve 24 and an exhaust valve 25 that open and close the cylinder 12. When the intake valve 24 opens, the combustion chamber 16 and the intake passage 20 communicate with each other, and when the intake valve 24 closes, the communication between the combustion chamber 16 and the intake passage 20 is blocked. When the exhaust valve 25 opens, the combustion chamber 16 and the exhaust passage 21 communicate with each other, and when the exhaust valve 25 closes, the communication between the combustion chamber 16 and the exhaust passage 21 is blocked.

[0013] The intake valve 24 is provided with an intake variable valve timing mechanism (hereinafter referred to as intake VVT) 26 that changes the opening and closing timing of the intake valve 24. Similarly, the exhaust valve 25 is provided with an exhaust variable valve timing mechanism (hereinafter referred to as exhaust VVT) 27 that changes the opening and closing timing of the exhaust valve 25. The intake VVT ​​26 changes the phase of an intake drive cam that opens and closes the intake valve 24, relative to the intake camshaft, thereby changing the opening and closing timing of the intake valve 24 to the advance or retard side. Similarly, the exhaust VVT 27 changes the phase of an exhaust drive cam that opens and closes the exhaust valve 25, relative to the exhaust camshaft, thereby changing the opening and closing timing of the exhaust valve 25 to the advance or retard side. The phase of the drive cam relative to the camshaft is switched depending on the oil pressure adjusted by the oil control valve.

[0014] The intake passage 20 is provided with a throttle valve 23 that adjusts the amount of air introduced into the combustion chamber 16. The exhaust passage 21 is provided with a catalyst 29 that exhibits maximum purification capacity when the air-fuel ratio of the mixture is stoichiometric. The catalyst 29 is a three-way catalyst that has the oxygen storage capacity to store oxygen in exhaust gas that is leaner than the stoichiometric air-fuel ratio and release the stored oxygen into exhaust gas that is richer than the stoichiometric air-fuel ratio.

[0015] Each intake port 20a constituting a part of the intake passage 20 is provided with a port injection valve 22 for injecting fuel into the intake port 20a for each cylinder 12. The engine 10 is also provided with an in-cylinder injection valve 17 for directly injecting fuel into each combustion chamber 16.

[0016] The ECU 50 is an electronic control unit that performs control processing related to the engine 10. The ECU 50 is mainly composed of a computer including a CPU (Central Processing Unit) and volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 50 executes programs installed in the memory on the CPU to perform various control processing related to the engine 10. Various sensors are connected to the ECU 50, which will be described in detail later. The ECU 50 is an example of a control device for the engine 10, and functionally realizes a determination unit and an injection control unit, which will be described in detail later.

[0017] An ignition switch 31, an accelerator pedal position sensor 32, an air flow meter 33, a crank angle sensor 34, an intake cam angle sensor 36, and an exhaust cam angle sensor 37 are connected to the ECU 50, and output signals from these various sensors are input. The ignition switch 31 detects the on / off state of the ignition. The accelerator pedal position sensor 32 detects the accelerator pedal position. 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 drive cam and exhaust drive cam of the engine 10 relative to the intake camshaft and exhaust camshaft, respectively.

[0018] 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 a target engine speed and a target load based on the accelerator opening, and controls the fuel injection amount, intake air amount, and ignition timing so that the engine speed and load become the target engine speed and target load, respectively. The ECU 50 also controls the in-cylinder injection rate, which is the ratio of the injection amount from the in-cylinder injection valve 17 to the total fuel injection amount, and the port injection rate, which is the ratio of the injection amount from the port injection valve 22 to the total fuel injection amount, according to the operating state of the engine 10. The ECU 50 also controls the intake VVT ​​26 and the exhaust VVT 27 according to the operating state of the engine 10, thereby controlling the opening and closing timing of the intake valve 24 and the exhaust valve 25.

[0019] 2 is an example of a flowchart showing the control executed by the ECU 50. This control is repeatedly executed while the ignition is on. The ECU 50 determines whether or not an abnormality has occurred in at least one of the intake VVT ​​26 and the exhaust VVT 27 in the operation of reducing the valve overlap period (step S1).

[0020] An abnormality related to the operation of reducing the valve overlap period is, for example, an advance side abnormality in which the opening / closing timing of the intake valve 24 by the intake VVT ​​26 is stuck on the advance side of the desired timing, or a retard side abnormality in which the opening / closing timing of the exhaust valve 25 by the exhaust VVT 27 is stuck on the retard side of the desired timing. If an advance side abnormality has occurred in the intake VVT ​​26, the opening / closing timing of the intake valve 24 cannot be changed to the retard side, and therefore the valve overlap period cannot be reduced by the intake VVT ​​26. Furthermore, if a retard side abnormality has occurred in the exhaust VVT 27, the opening / closing timing of the exhaust valve 25 cannot be changed to the advance side, and therefore the valve overlap period cannot be reduced by the exhaust VVT 27. If at least one of an advance side abnormality in the intake VVT ​​26 or a retard side abnormality in the exhaust VVT 27 has occurred, the determination in step S1 is Yes.

[0021] Specifically, if the actual opening and closing timing of the intake valve 24 deviates from the target timing by a predetermined value or more on the advance side, it is determined that an advance side abnormality has occurred in the intake VVT ​​26. If the actual opening and closing timing of the exhaust valve 25 deviates from the target timing by a predetermined value or more on the retard side, it is determined that a retard side abnormality has occurred in the exhaust VVT 27. The actual opening and closing timing of the intake valve 24 and the actual opening and closing timing of the exhaust valve 25 are calculated based on the detection values ​​of the intake cam angle sensor 36 and the exhaust cam angle sensor 37, respectively. If the answer is No in step S1, this control ends. Step S1 is an example of processing executed by the determination unit.

[0022] If step S1 is Yes, the ECU 50 performs a correction to increase the fuel injection amount (step S2). The ECU 50 performs fuel injection with an injection amount obtained by adding the increase due to the correction to the total fuel injection amount calculated according to the operating state of the engine 10. The increase due to the correction is set to an amount that reduces the temperature of the exhaust gas due to the latent heat of vaporization of the fuel at the increased injection amount, thereby suppressing excessive temperature rise of the catalyst 29. This prevents excessive temperature rise of the catalyst 29 even if the abnormality described above occurs.

[0023] Furthermore, since fuel injection continues, operation of the engine 10 continues. As a result, the driver is notified of the occurrence of the above-mentioned abnormality, for example, through a Malfunction Indicator Light (MIL) or the like, and the driver can evacuate the vehicle 1. Step S2 is an example of processing executed by the injection control unit.

[0024] In the above embodiment, the engine 10 is equipped with both the intake VVT ​​26 and the exhaust VVT 27, but is not limited to this. For example, for an engine equipped with only the intake VVT ​​26, step S2 is executed when an advance side abnormality occurs in the intake VVT ​​26. Also, for an engine equipped with only the exhaust VVT 27, step S2 is executed when a retard side abnormality occurs in the exhaust VVT 27.

[0025] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0026] 1 vehicle 10 Engine 12 cylinders 17 In-cylinder injection valve 24 Intake valve 25 Exhaust valve 26 Variable intake valve mechanism (variable valve mechanism) 27 Exhaust variable valve mechanism (variable valve mechanism) 29 Catalyst 50 ECU (control unit, judgment unit, injection control unit)

Claims

[Claim 1] A control device for an engine that is mounted on a vehicle, has exhaust gas purified by a catalyst, and has a variable valve mechanism that can change a valve overlap period during which both an intake valve and an exhaust valve are open, a determination unit that determines whether an abnormality has occurred in the operation of the variable valve mechanism to reduce the valve overlap period; an injection control unit that increases the fuel injection amount when the determination unit makes a positive determination compared to when the determination unit makes a negative determination.

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