Method and device for controlling negative-pressure-generation valve of internal combustion engine

Abstract

In the present invention, an internal combustion engine (2) for generating power in a series hybrid vehicle comprises a compressor (15) on the upstream side of a throttle valve (21) of an intake passage (12), and a butterfly-valve-type negative pressure generation valve (27) on the upstream side of the compressor (15). Under EV mode, in which the combustion operation of the internal combustion engine (2) stops, an electric actuator of the negative-pressure-generation valve (27) stops being energized (time t6 to t7). The negative-pressure-generation valve (27) is held fully open by the urging force of a return spring. In order to suppress collision with a fully open stopper, the negative-pressure-generation valve (27) is gradually opened to the fully-open (θmax) position restricted by the fully open stopper after having opened to a predetermined opening degree (θpre) immediately before fully opening (time t2 to t6).

Description

Method and device for controlling a negative pressure generating valve of an internal combustion engine

[0001] The present invention relates to control of a negative pressure generating valve that is provided upstream of a supercharger in an intake passage of an internal combustion engine, separate from a throttle valve.

[0002] Patent Document 1 discloses a configuration in which a turbocharger is provided upstream of a throttle valve in an intake passage, and a butterfly valve-type negative pressure generating valve (also called an admission valve) is provided upstream of the turbocharger. This negative pressure generating valve is used to generate the negative pressure required to introduce recirculated exhaust gas and blow-by gas upstream of the turbocharger.

[0003] The vacuum generating valve is generally configured so that its opening is controlled by an electric actuator such as a motor. For example, when the vacuum generating valve is used for exhaust gas recirculation (EGR), a target opening is set according to the target EGR rate, and feedback control is performed via the electric actuator to follow this target opening.

[0004] In hybrid vehicles, the combustion operation of the internal combustion engine may be stopped while the vehicle is in operation (while the main switch is on). In other words, many types of hybrid vehicles have two driving modes: an EV mode in which the vehicle runs on battery power without the combustion operation of the internal combustion engine, and an HEV mode in which the vehicle runs while generating electricity through the combustion operation of the internal combustion engine.

[0005] In the past, while the vehicle's main switch was on, the vacuum generating valve continued to be controlled and the electric actuator was energized even when the internal combustion engine was not in operation (i.e., in EV mode). Therefore, there was still room for improvement in terms of power consumption and, in turn, the vehicle's fuel consumption rate.

[0006] Japanese Patent Application Laid-Open No. 2018-119406

[0007] This invention relates to a method for controlling a vacuum generation valve of an internal combustion engine used to drive a generator in a hybrid vehicle that is equipped with a turbocharger upstream of a throttle valve in an intake passage and a butterfly valve-type vacuum generation valve upstream of the turbocharger, and that can run on motor output, wherein the vacuum generation valve has a return spring that biases the valve body toward a predetermined position, and when combustion operation of the internal combustion engine is stopped, the supply of electricity to the electric actuator of the vacuum generation valve is stopped.

[0008] While the electric actuator is de-energized, the valve element of the negative pressure generating valve is held in a predetermined position by the biasing force of the return spring.

[0009] In this way, by not energizing the electric actuator while the combustion operation of the internal combustion engine is stopped, power consumption is reduced and the fuel consumption rate of the vehicle is improved.

[0010] The present invention relates to a series hybrid vehicle, an internal combustion engine, and a method for manufacturing the same.

[0011] An embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 schematically illustrates the configuration of a series hybrid vehicle as an example to which the present invention is applied. The series hybrid vehicle includes a power-generating motor / generator 1 that operates primarily as a generator, an internal combustion engine 2 that serves as a power-generating internal combustion engine and drives the power-generating motor / generator 1 in response to a power demand, a traction motor / generator 4 that operates primarily as a motor to drive drive wheels 3, and a battery 5 that stores the generated power. The power obtained by the internal combustion engine 2 driving the power-generating motor / generator 1 is stored in the battery 5 via an inverter device (not shown). The traction motor / generator 4 is driven and controlled using the power from the battery 5. The power generated by the traction motor / generator 4 during regeneration is stored in the battery 5 via an inverter device (not shown).

[0012] The operation of the motor generators 1 and 4, the charging and discharging of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is composed of multiple controllers connected to each other so that they can communicate with each other, such as a motor controller 7 that controls the motor generators 1 and 4, an engine controller 8 that controls the internal combustion engine 2, and a battery controller 9 that manages the battery 5. Information such as the accelerator pedal position and vehicle speed (not shown) is input to the controller 6. The battery controller 9 also calculates the SOC of the battery 5 based on the voltage and current of the battery 5. When the SOC drops to a predetermined lower limit, the internal combustion engine 2 is started via the engine controller 8 to generate electricity. Such a series hybrid vehicle has two driving modes: an EV mode in which the vehicle runs on power from the battery 5 without combustion operation of the internal combustion engine 2, and an HEV mode in which the vehicle runs while generating electricity through combustion operation of the internal combustion engine 2. Even if the SOC is above the lower limit, the internal combustion engine 2 is driven and the vehicle runs in the HEV mode when the required driving force of the vehicle is relatively large. Therefore, the internal combustion engine 2 repeatedly performs combustion operation and stops of combustion operation while the main switch of the vehicle is on.

[0013] 2 shows the configuration of the intake system and exhaust system of an internal combustion engine 2. The internal combustion engine 2 of this embodiment is a four-stroke, spark-ignition gasoline engine equipped with a turbocharger 13 as a supercharger, and an exhaust turbine 14 of the turbocharger 13 is disposed in the exhaust passage 11, with an upstream catalytic converter 17 and a downstream catalytic converter 18, each using, for example, a three-way catalyst, disposed downstream of the exhaust turbine 14. An exhaust silencer 19 is provided in the exhaust passage 11 further downstream of the downstream catalytic converter 18, and the exhaust passage 11 is opened to the outside via the exhaust silencer 19.

[0014] A compressor 15 of the turbocharger 13 is disposed in the intake passage 12 of the internal combustion engine 2, and an electronically controlled throttle valve 21 for controlling the amount of intake air is disposed downstream of the compressor 15. A water-cooled intercooler 22, for example, for cooling the supercharged intake air is provided between the compressor 15 and the throttle valve 21. The throttle valve 21 is a typical butterfly type with a circular valve body, and includes a return spring that constantly biases the valve body in a fully closed direction, an electric actuator that drives the valve body to open and close against the biasing force of the return spring, and an opening sensor that detects the opening (angular position) of the valve body. The opening of the throttle valve 21 is feedback-controlled to conform to a target opening set by the engine controller 8.

[0015] An exhaust gas recirculation passage 24 for recirculating a portion of the exhaust gas to the intake system is provided between the exhaust passage 11 and the intake passage 12. A base end 24a of the exhaust gas recirculation passage 24 branches off from the exhaust passage 11 downstream of the exhaust turbine 14, specifically between the upstream catalytic converter 17 and the downstream catalytic converter 18. A tip end 24b of the exhaust gas recirculation passage 24 is connected to the intake passage 12 at a position upstream of the compressor 15.

[0016] That is, the illustrated exhaust gas recirculation system is a so-called low-pressure exhaust gas recirculation system in which exhaust gas that has passed through the exhaust turbine 14 and has become low-pressure is recirculated to the intake system.

[0017] An EGR valve 25, the opening of which is variably controlled by the engine controller 8, is disposed in the exhaust gas recirculation passage 24. Furthermore, an EGR gas cooler 26, for example a water-cooled type, that cools the recirculated exhaust gas is provided at a position closer to the exhaust passage 11 than the EGR valve 25 (i.e., upstream in terms of the exhaust flow).

[0018] A negative pressure generating valve 27 for generating a pressure difference required for exhaust gas recirculation is disposed upstream of the compressor 15 in the intake passage 12, more specifically, upstream of the connection with the exhaust gas recirculation passage 24. An air cleaner 28 is disposed upstream of the negative pressure generating valve 27.

[0019] The vacuum generating valve 27 is a butterfly-type valve with a circular valve element, similar to the throttle valve 21, and includes a return spring that constantly biases the valve element in the fully open direction, an electric actuator (e.g., a motor) that drives the valve element to open and close against the biasing force of the return spring, and an opening sensor that detects the opening degree (angular position) of the valve element. The opening degree of the vacuum generating valve 27 is feedback-controlled so as to follow a target opening degree set by the engine controller 8. The target opening degree of the vacuum generating valve 27 is set according to a target EGR rate (in other words, the operating conditions of the internal combustion engine 2).

[0020] Here, while the vehicle's main switch is on and the combustion operation of the internal combustion engine 2 is stopped (i.e., during EV mode), as will be described later, the supply of electricity to the electric actuator of the vacuum generation valve 27 is stopped. While the supply of electricity to the electric actuator is stopped, the valve element of the vacuum generation valve 27 is maintained in a fully open state by the biasing force of a return spring. The vacuum generation valve 27 is equipped with a full-open stopper that determines the full-open position of the valve element. For example, a part of a gear inside the electric actuator that rotates integrally with the valve element physically abuts against a stopper portion inside the case, thereby functioning as the full-open stopper.

[0021] The engine controller 8 receives detection signals directly or via other controllers from a number of sensors (not shown), including an air flow meter that detects the intake air amount, an air-fuel ratio sensor that detects the exhaust air-fuel ratio, a crank angle sensor that detects the engine speed, a water temperature sensor that detects the coolant temperature, a boost pressure sensor that detects the boost pressure, an accelerator opening sensor that detects the amount of depression of the accelerator pedal, an atmospheric pressure sensor that detects the atmospheric pressure, and an outside air temperature sensor. Based on these detection signals and requests from the other controllers, the engine controller 8 optimally controls the fuel injection amount and injection timing, ignition timing, the opening of the throttle valve 21, the boost pressure, the EGR rate, the opening of the vacuum generating valve 27, and the like.

[0022] 3 is a time chart showing the operation of each part when the vehicle transitions to EV mode due to the absence of a power generation request while traveling in HEV mode, and then returns from EV mode to HEV mode. From top to bottom, the chart shows (a) the rotation speed Ne of the internal combustion engine 2, (b) a combustion prohibition flag fFCSTP that is a command to stop combustion operation, (c) a rotation flag fEGST that indicates that the crankshaft of the internal combustion engine 2 is rotating, (d) a full-open permission flag fADMVMAX that indicates that full opening of the vacuum generation valve 27 is permitted, (e) the opening degree ADMPOS of the vacuum generation valve 27 (the dashed line indicates the target opening degree tADMPOS, and the solid line indicates the actual opening degree rADMPOS), (f) the current ADMCOM to the electric actuator of the vacuum generation valve 27, and (g) a control permission flag fADMVCNT that indicates that the opening degree of the vacuum generation valve 27 is being controlled.

[0023] Before time t1 in the time chart, the vehicle is running in HEV mode, and the internal combustion engine 2 is operating in combustion mode. At this time, the opening degree ADMPOS of the vacuum generation valve 27 is controlled to a relatively small opening degree (approximately 20° in the illustrated example) corresponding to the target EGR rate. Therefore, current flows through the electric actuator. At time t1, the combustion prohibition flag fFCSTP becomes 1, and fuel injection and ignition of the internal combustion engine 2 are stopped. Accordingly, the rotation speed Ne of the internal combustion engine 2 gradually decreases and becomes 0 at time t2. Between times t1 and t2, the opening degree of the vacuum generation valve 27 is maintained at the opening degree before time t1.

[0024] At time t2, the rotation flag fEGST becomes 0 (OFF), which causes the full-open permission flag fADMVMAX to become 1 (ON), starting the process of fully opening the vacuum generating valve 27. First, to prevent the vacuum generating valve 27 from strongly colliding with the full-open stopper, the target opening tADMPOS is set to a predetermined opening θpre (e.g., 80° in a preferred example) that is smaller than but close to full-open. Feedback control is performed at a normal speed (i.e., gain), so that the actual opening rADMPOS quickly reaches the predetermined opening θpre (time t3). After the actual opening rADMPOS remains at the predetermined opening θpre for a predetermined time (time t4), the target opening tADMPOS is gradually increased until it exceeds the full-open θmax. The rate of change of the target opening tADMPOS at this time is set to be slower than the rate of change of the opening due to feedback control between times t2 and t3. The actual opening rADMPOS gradually increases in line with the target opening tADMPOS, and at time t5, it abuts against the full-open stopper, thereby being physically restricted to the full-open position θmax. By making the rate of change of the target opening tADMPOS relatively slow, the negative pressure generating valve 27 gradually comes into contact with the full-open stopper.

[0025] Since the target opening tADMPOS is given at a value exceeding the full-open opening θmax even after time t5, the valve element of the negative pressure generating valve 27 remains pressed against the full-open stopper. This state of being pressed against the full-open stopper is determined based on the lock current, and if this state continues for a predetermined time (time t6), the control permission flag fADMVCNT becomes 0 (OFF), and accordingly, power to the electric actuator is stopped.

[0026] Therefore, thereafter, the negative pressure generating valve 27 is maintained in the fully open state by the biasing force of the return spring. In other words, during the EV mode in which the combustion operation of the internal combustion engine 2 is stopped, no current is applied to the electric actuator, and power consumption of the battery is reduced.

[0027] Time t7 indicates the timing when a request for power generation is made while the vehicle is traveling in EV mode. That is, at time t7, a request is made to switch from EV mode to HEV mode. In response to this request for power generation, the control permission flag fADMVCNT becomes 1, and the full-open permission flag fADMVMAX becomes 0, and control of the opening degree of the negative pressure generating valve 27 via the electric actuator is resumed. Between times t7 and t8, motoring is performed by the motor generator 1 to start the internal combustion engine 2. At time t8, when a predetermined rotation speed is reached, the combustion prohibition flag fFCSTP becomes 0, and the internal combustion engine 2 begins combustion operation.

[0028] In this manner, in the above embodiment, during the period when the combustion operation of the internal combustion engine 2 is stopped in the EV mode, the power supply to the electric actuator of the vacuum generating valve 27 is stopped and the valve is kept fully open by the biasing force of the return spring, thereby reducing power consumption and improving the fuel consumption rate of the vehicle.

[0029] Furthermore, the opening of the negative pressure generation valve 27 is normally small immediately before the combustion operation is stopped, but when the negative pressure generation valve 27 is fully opened, it temporarily stops at a predetermined opening θpre just before full opening and then gradually opens to the full opening θmax, so the negative pressure generation valve 27 does not strongly collide with the full opening stopper. Furthermore, since the power supply to the electric actuator is stopped with the negative pressure generation valve 27 securely abutting the full opening stopper, the valve element does not move when the power supply is stopped.

[0030] Furthermore, in the above embodiment, the negative pressure generating valve 27 is biased in the fully open direction by the return spring, so that in the unlikely event of a failure in the drive system such as the electric actuator, the negative pressure generating valve 27 is opened. Therefore, in the unlikely event of a failure, the generation of excessive negative pressure caused by the negative pressure generating valve 27 being fully closed is avoided, and leakage of lubricating oil from the turbocharger 13 due to negative pressure is suppressed.

[0031] While one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, the present invention can be applied to internal combustion engines of hybrid vehicles other than series hybrid vehicles. The return spring may bias the valve body toward the fully closed position, or may be configured to maintain an intermediate opening by spring force when the electric actuator is de-energized. The vacuum generating valve may also be configured to generate vacuum for purposes other than exhaust gas recirculation, such as introducing blow-by gas.

Claims

1. A method for controlling a negative pressure generating valve of an internal combustion engine used for driving a generator in a hybrid vehicle equipped with a supercharger upstream of a throttle valve in an intake passage and a butterfly valve type negative pressure generating valve upstream of the supercharger and capable of traveling by motor output, wherein the negative pressure generating valve has a return spring for biasing a valve body toward a predetermined position, and in a state where the combustion operation of the internal combustion engine is stopped, power supply to the electric actuator of the negative pressure generating valve is stopped. A method for controlling a negative pressure generating valve of an internal combustion engine.

2. The method for controlling a negative pressure generating valve of an internal combustion engine according to claim 1, wherein the return spring biases the valve body toward the fully open position, and power supply is stopped in a state where the negative pressure generating valve is in the fully open position.

3. The method for controlling a negative pressure generating valve of an internal combustion engine according to claim 2, wherein when the rotation of the internal combustion engine stops after the combustion operation of the internal combustion engine stops, the negative pressure generating valve is controlled to the fully open position via the electric actuator, and power supply is stopped in a state where the fully open position is reached.

4. The method for controlling a negative pressure generating valve of an internal combustion engine according to claim 3, wherein the negative pressure generating valve includes a fully open stopper that defines the fully open position of the valve body, and power supply is stopped in a state where the negative pressure generating valve abuts against the fully open stopper.

5. The method for controlling a negative pressure generating valve of an internal combustion engine according to claim 4, wherein power supply is stopped after maintaining the state in which the negative pressure generating valve is pressed against the fully open stopper by control of the electric actuator for a predetermined time.

6. The method for controlling a negative pressure generating valve of an internal combustion engine according to claim 4, wherein the valve body is moved at a first speed to an opening immediately before abutting against the fully open stopper by control of the electric actuator, and then the valve body is moved at a relatively low second speed to the fully open position where it abuts against the fully open stopper.

7. The method for controlling a negative pressure generating valve of an internal combustion engine according to claim 1, wherein when there is a power generation request from the vehicle side in a state where the combustion operation of the internal combustion engine is stopped, control to a target opening via the electric actuator is restarted.

8. In an internal combustion engine used for driving a generator in a hybrid vehicle equipped with a supercharger upstream of a throttle valve in an intake passage and capable of running by motor output, a butterfly valve type negative pressure generating valve provided upstream of the supercharger in the intake passage, an electric actuator for opening and closing the valve body of the negative pressure generating valve, a return spring for biasing the valve body of the negative pressure generating valve toward a predetermined position, and a controller for controlling the electric actuator, wherein the controller stops energization to the electric actuator when the combustion operation of the internal combustion engine is stopped, a negative pressure generating valve control device for an internal combustion engine.

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