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

Abstract

An electric power generation engine (2) of a series hybrid vehicle has a compressor (15) on an upstream side of a throttle valve (21) of an intake passage (12), and has a negative pressure generation valve (27) of a butterfly valve type on an upstream side of the compressor (15). In an EV mode in which a combustion operation of the engine (2) is stopped, energization to an electric actuator of the negative pressure generation valve (27) is stopped (time t6-t7). The negative pressure generation valve (27) is kept in a fully open state by a pressing force of a return spring. In order to suppress a collision against a fully open limiter, after a prescribed opening degree (θpre) before opening to a full opening, the negative pressure generation valve (27) is gently opened to a position of a full opening (θmax) limited by the fully open limiter (time t2-t6).

Description

Technical Field

[0001] This invention relates to the control of a negative pressure generating valve located upstream of the turbocharger in the intake passage of an internal combustion engine, separate from the throttle valve. Background Technology

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

[0003] Negative pressure generating valves are typically structures whose opening is controlled by an electric actuator such as a motor. For example, when a negative pressure generating valve is used for exhaust gas recirculation (EGR), a target opening corresponding to the target EGR rate is set, and feedback control via an electric actuator is performed to follow that target opening.

[0004] In hybrid vehicles, the internal combustion engine is sometimes stopped while the vehicle is running (during the period when the main switch is on). That is, for various types of hybrid vehicles, as operating modes, there are EV mode and HEV mode. In EV mode, the internal combustion engine does not run and the vehicle is driven by the power of the battery. In HEV mode, the vehicle is driven while generating electricity through the combustion of the internal combustion engine.

[0005] Previously, even when the internal combustion engine was not running (i.e., during EV mode), the negative pressure generation valve continued to control and supply power to the electric actuators while the vehicle's main switch was on. Therefore, there was room for improvement in terms of power consumption and vehicle fuel efficiency.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-119406 Summary of the Invention

[0007] This invention relates to a negative pressure generating valve control method for an internal combustion engine. The internal combustion engine has a turbocharger upstream of the throttle valve in the intake passage, and a butterfly-type negative pressure generating valve upstream of the turbocharger. This internal combustion engine is used to drive a generator in a hybrid vehicle capable of operating via an electric motor. In the negative pressure generating valve control method of this internal combustion engine, The aforementioned negative pressure generating valve has a return spring that applies pressure to the valve body toward a specified position. When the combustion operation of the internal combustion engine stops, the power supply to the electric actuator of the negative pressure generating valve is stopped.

[0008] During the period when the power supply to the electric actuator is stopped, the valve body of the negative pressure generating valve is held in the specified position by the pressure applied by the return spring.

[0009] In this way, when the internal combustion engine stops running, no electricity is supplied to the electric actuator, thereby reducing power consumption and improving the vehicle's fuel efficiency. Attached Figure Description

[0010] Figure 1 This is a structural diagram illustrating a series hybrid electric vehicle.

[0011] Figure 2 This is a structural illustration of the intake and exhaust systems of an internal combustion engine according to one embodiment.

[0012] Figure 3 It is a timing diagram showing the operation of various parts in an embodiment. Detailed Implementation

[0013] Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings. Figure 1 The structure of a series hybrid vehicle is schematically shown as an example of applying the present invention. The series hybrid vehicle is configured to include: a generator 1, which primarily functions as a generator; an internal combustion engine 2, which serves as a generator-generating internal combustion engine to drive the generator 1 upon power request; a driving generator 4, which primarily functions as a motor to drive drive wheels 3; and a battery 5, which stores the generated electricity. The electricity obtained by driving the generator 1 through the internal combustion engine 2 is stored in the battery 5 via an inverter device (not shown). The power from the battery 5 is used to drive the driving generator 4. The electricity generated by the driving generator 4 during regeneration is also stored in the battery 5 via an inverter device (not shown).

[0014] The operation of electric generators 1 and 4, the charging and discharging of battery 5, and the operation of internal combustion engine 2 are controlled by controller 6. Controller 6 consists of multiple controllers connected to each other in a communicable manner, including motor controller 7 which controls electric generators 1 and 4, engine controller 8 which controls internal combustion engine 2, and battery controller 9 which manages battery 5. Information such as accelerator pedal opening (not shown) or vehicle speed is input to controller 6. Additionally, battery controller 9 calculates the state of charge (SOC) of battery 5 based on its voltage and current. When the SOC drops to a predetermined lower limit, internal combustion engine 2 is started via engine controller 8 to generate electricity. As operating modes of this series hybrid vehicle, there are EV mode and HEV mode. In EV mode, the internal combustion engine 2 does not operate, but the vehicle is driven using electricity from battery 5. In HEV mode, the vehicle drives while generating electricity through the combustion of internal combustion engine 2. Furthermore, even if the SOC is greater than or equal to the lower limit, internal combustion engine 2 is driven when the vehicle's required driving force is high, thus operating in HEV mode. Therefore, the internal combustion engine 2 repeatedly performs combustion operation and combustion operation stoppage during the period when the vehicle's main switch is turned on.

[0015] Figure 2 The structure of the intake and exhaust systems of the internal combustion engine 2 is shown. One embodiment of the internal combustion engine 2 is a four-stroke spark-ignition gasoline internal combustion engine with a turbocharger 13 as the supercharger. An exhaust turbine 14 of the turbocharger 13 is arranged in its exhaust passage 11. Downstream of the exhaust turbine 14 are an upstream catalytic converter 17 and a downstream catalytic converter 18, using, for example, a three-way catalytic converter. Further downstream of the downstream catalytic converter 18 in the exhaust passage 11, an exhaust muffler 19 is provided, through which the exhaust passage 11 opens to the outside.

[0016] A compressor 15, containing the aforementioned turbocharger 13, is arranged in the intake passage 12 of the internal combustion engine 2. Further downstream of the compressor 15, an electronically controlled throttle valve 21 is arranged to control the amount of intake air. Between the compressor 15 and the throttle valve 21, an intercooler 22, such as a water-cooled intercooler, is provided to cool the boosted intake air. The throttle valve 21 is a typical butterfly valve type with a circular valve body, and includes: a return spring that always presses the valve body in the fully closed direction; an electric actuator that drives the valve body to open and close against the pressure of the return spring; and an opening sensor that detects the opening degree (angular position) of the valve body. The opening degree of the throttle valve 21 is controlled by feedback in a manner that follows a target opening degree set by the engine controller 8.

[0017] Between the aforementioned exhaust passage 11 and the aforementioned intake passage 12, an exhaust return passage 24 is provided for returning a portion of the exhaust gas to the intake system. Regarding this exhaust return passage 24, the base end 24a branches off from the downstream side of the exhaust turbine 14 of the exhaust passage 11, specifically between the upstream catalytic converter 17 and the downstream catalytic converter 18. Furthermore, the front end 24b connects to the intake passage 12 at a position further upstream than the compressor 15.

[0018] That is, the exhaust recirculation device in the figure is a so-called low-pressure exhaust recirculation device that recirculates low-pressure exhaust gas back to the intake system through the exhaust turbine 14.

[0019] An EGR valve 25, whose opening is variably controlled by the engine controller 8, is disposed midway through the aforementioned exhaust return passage 24. Furthermore, an EGR gas cooler 26, for example a water-cooled type, is disposed at a position that is closer to the exhaust passage 11 than the EGR valve 25 (i.e., upstream of the exhaust flow).

[0020] More upstream of the compressor 15 in the intake passage 12, specifically upstream of the connection with the exhaust return passage 24, a negative pressure generating valve 27 is provided to generate the pressure difference required for exhaust return. Additionally, an air filter 28 is provided upstream of the negative pressure generating valve 27.

[0021] Like the throttle valve 21, the aforementioned negative pressure generating valve 27 is a butterfly valve type with a circular valve body. It includes: a return spring that always applies pressure to the valve body in the fully open direction; an electric actuator (e.g., a motor) that drives the valve body to open and close against the pressure of the return spring; and an opening sensor that detects the opening degree (angular position) of the valve body. The opening degree of the negative pressure generating valve 27 is feedback-controlled in a manner that follows a target opening degree set by the engine controller 8. The target opening degree of the negative pressure generating valve 27 is set in accordance with the target EGR rate (in other words, the operating conditions of the internal combustion engine 2).

[0022] Here, during the period when 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 described later, the energization to the electric actuator of the negative pressure generating valve 27 is stopped. During the period when the energization to the electric actuator is stopped, the valve body of the negative pressure generating valve 27 is maintained in a fully open state by the pressure applied by the return spring. The negative pressure generating valve 27 has a fully open limiter that defines the fully open position of the valve body. For example, it functions as a fully open limiter by physically abutting a portion of the gear inside the electric actuator, which rotates integrally with the valve body, against the limiter portion inside the housing.

[0023] The engine controller 8, although not shown, receives input signals directly or via other controllers from a large group of sensors, including an air flow meter for detecting intake air volume, an air-fuel ratio sensor for detecting exhaust air-fuel ratio, a crank angle sensor for detecting engine speed, a coolant temperature sensor for detecting coolant temperature, a boost pressure sensor for detecting boost pressure, an accelerator pedal depressor sensor for detecting accelerator pedal depressor position, an atmospheric pressure sensor for detecting atmospheric pressure, and an ambient temperature sensor for detecting ambient temperature. Based on these detection signals or requests from other controllers, the engine controller 8 optimizes the fuel injection quantity and timing, ignition timing, throttle valve 21 opening, boost pressure, EGR rate, and negative pressure generation valve 27 opening.

[0024] Figure 3 This is a timing diagram showing the actions of various parts when the vehicle is driving in HEV mode, the power generation request disappears and the vehicle switches to EV mode, and then returns to HEV mode. From top to bottom, the diagram shows (a) the rotational speed Ne of the internal combustion engine 2, (b) the command to stop combustion, i.e., the combustion prohibition flag fFCSTP, (c) the rotation flag fEGST indicating that the crankshaft of the internal combustion engine 2 is rotating, (d) the full-open permission flag fADMVMAX indicating that the negative pressure generating valve 27 is fully open, (e) the opening degree ADMPOS of the negative pressure generating valve 27 (dashed line is the target opening degree tADMPOS, solid line is the actual opening degree rADMPOS), (f) the current ADMCOM to the electric actuator of the negative pressure generating valve 27, and (g) the control permission flag fADMVCNT indicating that the opening degree control of the negative pressure generating valve 27 is in progress.

[0025] Prior to time t1 in the timing diagram, during driving in HEV mode, the internal combustion engine 2 is running. At this time, the opening of the negative pressure generating valve 27, ADMPOS, is controlled to a small opening corresponding to the target EGR rate (approximately 20° in the example). 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 cease. Simultaneously, the speed Ne of the internal combustion engine 2 slowly decreases, reaching 0 at time t2. During the period from time t1 to t2, the opening of the negative pressure generating valve 27 remains unchanged from its position before time t1.

[0026] At time t2, the rotation flag fEGST becomes 0 (OFF), thereby making the full-open enable flag fADMVMAX become 1 (ON). The process of setting the negative pressure generating valve 27 to full open begins. Initially, to avoid strong impact on the full-open limit switch of the negative pressure generating valve 27, the target opening tADMPOS is set to a predetermined opening θpre (in a preferred example, for example, 80°) that is smaller than full open but close to full open. Through feedback control at a normal rate (i.e., gain), 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 value of full open θmax. The rate of change of the target opening tADMPOS at this time is set to be smaller than the rate of change of opening achieved by the feedback control during the period from time t2 to t3. The actual opening rADMPOS gradually increases following the target opening tADMPOS, and at time t5, it comes into contact with the fully open limit switch, thus being physically limited to the fully open position θmax. By making the rate of change of the target opening tADMPOS relatively small, the negative pressure generating valve 27 makes gentle contact with the fully open limit switch.

[0027] At time t5 and thereafter, the target opening degree tADMPOS is also assigned a value exceeding the full opening degree θmax, thus the valve body of the negative pressure generating valve 27 is pressed against the full opening limit switch. Based on the latching current, this state of being pressed against the full opening limit switch is determined, and after this state has lasted for a predetermined time (time t6), the control enable flag fADMVCNT becomes 0 (OFF), thereby stopping the energization of the electric actuator.

[0028] Therefore, the negative pressure generating valve 27 is then kept fully open by applying pressure from the return spring. That is, during the EV mode when the combustion of the internal combustion engine 2 is stopped, no power is supplied to the electric actuator, thus suppressing battery power consumption.

[0029] Time t7 indicates the timing of the power generation request during driving in EV mode. That is, at time t7, a request is made to switch from EV mode to HEV mode. Accompanying this power generation request, the control enable flag fADMVCNT becomes 1, and the fully open enable flag fADMVMAX becomes 0, restarting the opening control via the negative pressure generation valve 27 of the electric actuator. During the period from time t7 to t8, motor drive, implemented by the electric generator 1, is performed to start the internal combustion engine 2. At time t8, when the predetermined speed is reached, the combustion disable flag fFCSTP becomes 0, and combustion operation of the internal combustion engine 2 begins.

[0030] Thus, in the above embodiment, during the period when combustion of the internal combustion engine 2 is stopped in EV mode, the power supply to the electric actuator of the negative pressure generating valve 27 is stopped, and it remains fully open due to the pressure applied by the return spring. Therefore, power consumption is reduced, and the vehicle's fuel efficiency is improved.

[0031] Furthermore, before combustion operation is about to stop, the opening degree of the negative pressure generating valve 27 is usually reduced. However, when the negative pressure generating valve 27 is set to fully open, it temporarily stops at a predetermined opening degree θpre just before it is fully open, and then smoothly opens to the fully open θmax. Therefore, the negative pressure generating valve 27 does not violently impact the fully open limiter. In addition, the energization to the electric actuator is stopped when the negative pressure generating valve 27 reliably abuts against the fully open limiter, so the valve body does not move when the energization stops.

[0032] Furthermore, in the above embodiment, the negative pressure generating valve 27 is pressurized to the fully open direction by a return spring. Therefore, in the event of a failure in the drive system such as the electric actuator, the negative pressure generating valve 27 remains open. This prevents excessive negative pressure from being generated by the negative pressure generating valve 27 becoming fully closed in the event of a failure, and suppresses leakage of lubricating oil from the turbocharger 13 caused by negative pressure.

[0033] The present invention has been described above as an embodiment, but it is not limited to this embodiment and various modifications are possible. For example, the present invention can also be applied to the internal combustion engine of hybrid vehicles other than series hybrid vehicles. Furthermore, the return spring can be a structure that applies pressure to the valve body toward the fully closed position, and it can also be a structure that maintains the valve at an intermediate opening by its elastic force when the power to the electric actuator is stopped. Additionally, the negative pressure generating valve can also be a structure that generates negative pressure for purposes other than exhaust recirculation, such as the introduction of blow-by gas.

Claims

1. A method for controlling a negative pressure generating valve in an internal combustion engine, the internal combustion engine having a turbocharger upstream of a throttle valve in the intake passage, and a butterfly valve-type negative pressure generating valve upstream of the turbocharger, the internal combustion engine being used to drive a generator in a hybrid vehicle capable of operation via an electric motor output. In the negative pressure generating valve control method of this internal combustion engine, The aforementioned negative pressure generating valve has a return spring that applies pressure to the valve body toward a specified position. When the combustion operation of the internal combustion engine stops, the power supply to the electric actuator of the negative pressure generating valve is stopped.

2. The negative pressure generating valve control method for an internal combustion engine according to claim 1, wherein, The aforementioned return spring applies pressure to the valve body toward the fully open position. With the negative pressure generating valve in the fully open position, stop energizing.

3. The negative pressure generating valve control method for an internal combustion engine according to claim 2, wherein, After the combustion operation of the internal combustion engine stops, when the rotation of the internal combustion engine stops, the negative pressure generating valve is controlled to the fully open position by the electric actuator, and the power supply is stopped when it is in the fully open position.

4. The negative pressure generating valve control method for an internal combustion engine according to claim 3, wherein, The aforementioned negative pressure generating valve has a fully open limiter that specifies the fully open position of the valve body. When the aforementioned negative pressure generating valve is in contact with the fully open limiter, the power supply is stopped.

5. The negative pressure generating valve control method for an internal combustion engine according to claim 4, wherein, After the negative pressure generating valve has been pressed against the fully open limit switch for a specified time under the control of the electric actuator, the power supply is stopped.

6. The negative pressure generating valve control method for an internal combustion engine according to claim 4, wherein, Controlled by the aforementioned electric actuator, after the valve body is moved at a first speed to the opening degree just before it abuts against the fully open limit switch, the valve body is moved at a relatively low second speed to the fully open position where it abuts against the fully open limit switch.

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

8. A negative pressure generation valve control device for an internal combustion engine, the internal combustion engine having a turbocharger upstream of a throttle valve in the intake passage, the internal combustion engine being used to drive a generator in a hybrid vehicle capable of operation via an electric motor output. This internal combustion engine has the following features: A butterfly-type negative pressure generating valve is installed on the upstream side of the aforementioned booster in the aforementioned intake passage; An electric actuator drives the valve body of the negative pressure generating valve to open and close. A return spring that applies pressure to the valve body of the negative pressure generating valve, orienting it to a predetermined position; and The controller controls the aforementioned electric actuator. When the internal combustion engine stops running, the controller stops supplying power to the electric actuator.

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