Vehicle control device

Abstract

To provide a vehicle control device in which a deterioration in accuracy of a stop position of an internal combustion engine is suppressed.SOLUTION: A control device for a hybrid vehicle includes: a control section which, during inertial rotation with combustion stopped when an internal combustion engine is automatically stopped, switches a throttle opening from a first opening to a larger second opening and then switches it to a third opening smaller than the second opening, thereby executing stop position control of the internal combustion engine; an acquisition section which acquires an intake manifold pressure at a timing at which an intake valve of any cylinder is closed after the throttle opening is switched to the third opening during execution of the stop position control; and an adjustment section which maintains the second opening when the intake manifold pressure is included in an allowable range with respect to a target value, which decreases the second opening as compared to when the intake manifold pressure is included in the allowable range, when the intake manifold pressure is higher than the allowable range, and which increases the second opening as compared to when the intake manifold pressure is included in the allowable range, when the intake manifold pressure is lower than the allowable range.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle.

Background Art

[0002] There is known a technique for controlling the stop position of an internal combustion engine by temporarily increasing the throttle opening during inertia rotation when combustion stops at the automatic stop of the internal combustion engine (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above stop position control, due to variations in the control accuracy of the throttle opening and the secular change of the throttle valve, it may not be possible to fill a desired cylinder with only a desired intake air amount, and the accuracy of the stop position of the internal combustion engine may decrease.

[0005] Therefore, an object of the present invention is to provide a control device for a vehicle in which a decrease in the accuracy of the stop position of an internal combustion engine is suppressed.

Means for Solving the Problems

[0006] In a control device for a vehicle equipped with an internal combustion engine as a driving power source, when the internal combustion engine automatically stops, during the inertia rotation in which combustion has stopped, the throttle opening is switched from a first opening to a second opening larger than the first opening and then switched from the second opening to a third opening smaller than the second opening, thereby executing a control unit for controlling the stop position of the internal combustion engine; an acquisition unit that acquires an intake manifold pressure, which is the pressure in the intake passage on the downstream side of the throttle valve, at the timing when the intake valve of any cylinder closes after the throttle opening is switched to the third opening during the execution of the stop position control; and an adjustment unit that maintains the second opening when the intake manifold pressure is within an allowable range with respect to a target value, decreases the second opening as compared with the case where the intake manifold pressure is within the allowable range when the intake manifold pressure is higher than the allowable range, and increases the second opening as compared with the case where the intake manifold pressure is within the allowable range when the intake manifold pressure is lower than the allowable range. The object can be achieved by a control device for a hybrid vehicle provided with the above components.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a control device for a vehicle in which a decrease in the accuracy of the stop position of an internal combustion engine is suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] [Schematic Configuration of Hybrid Vehicle] FIG. 1 is a schematic configuration diagram of a hybrid vehicle 1. In the power transmission path from the engine 10 to the drive wheels 13 of the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and a transmission 19 are provided in this order. The engine 10 and the motor 15 are mounted as the driving power sources of the hybrid vehicle 1. The engine 10 is, for example, a V-type 6-cylinder gasoline engine, but the number of cylinders is not limited to this, and it may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, the torque converter 18, and the transmission 19 are provided in the transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential 12.

[0010] The K0 clutch 14 is provided between the engine 10 and the motor 15 on the same power transmission path. The K0 clutch 14 receives hydraulic pressure supply from the released state and becomes engaged to connect the power transmission between the engine 10 and the motor 15. The K0 clutch 14 becomes released in response to the stop of the hydraulic pressure supply to cut off the power transmission between the engine 10 and the motor 15. The engaged state means a state in which both engaging elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotational speed. The released state means a state in which both engaging elements of the K0 clutch 14 are separated.

[0011] The motor 15 is connected to the battery 16 via an inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supply from the battery 16, and further functions as a generator that generates electric power for charging the battery 16 in response to power transmission from the engine 10 or the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0012] The inverter 17 is controlled by an ECU 100, which will be described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor 15 into a DC voltage. In the case of a power running operation where the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor 15. In the case of a regenerative operation where the motor 15 generates electricity, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0013] The torque converter 18 is a fluid coupling having a torque amplification function. The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple steps by switching the gear stage, but is not limited thereto and may be a continuously variable transmission. The transmission 19 is provided between the motor 15 and the drive wheels 13 on the power transmission path. The motor 15 and the transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that receives the supply of hydraulic pressure and engages to directly connect the motor 15 and the transmission 19.

[0014] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22, respectively. The hydraulic control mechanism 22 is provided with respective hydraulic circuits for the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures. Note that a wet clutch may be provided instead of the torque converter 18.

[0015] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 as a control device for the vehicle. The ECU 100 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to the running control of the vehicle, and a memory in which control programs and data are stored. The ECU 100 is an example of a control device for the vehicle, and specifically, functionally realizes a control unit, an acquisition unit, and an adjustment unit, which will be described in detail later.

[0016] The ECU 100 controls the driving of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotational speed of the engine 10 by controlling the throttle opening degree, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the rotational speed and torque of the motor 15 by controlling the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16. Further, the ECU 100 performs drive control of the K0 clutch 14, the lock-up clutch 20, and the transmission 19 through the control of the hydraulic control mechanism 22.

[0017] Signals from an ignition switch 71, a crank angle sensor 72, a motor rotational speed sensor 73, an accelerator opening sensor 74, an air flow meter 75, a pressure sensor 76, and a water temperature sensor 77 are input to the ECU 100. The crank angle sensor 72 detects the rotational speed of the crankshaft of the engine 10. The motor rotational speed sensor 73 detects the rotational speed of the output shaft of the motor 15. The accelerator opening sensor 74 detects the accelerator pedal opening, which is the amount of depression of the driver's accelerator pedal. The air flow meter 75 detects the intake air amount of the engine 10. The pressure sensor 76 detects the pressure (hereinafter referred to as intake manifold pressure) in the intake passage 37 on the downstream side of the throttle valve 40, which will be described later. The water temperature sensor 77 detects the temperature of the cooling water of the engine 10.

[0018] The ECU 100 drives the hybrid vehicle in either a motor mode or a hybrid mode. In the motor mode, the ECU 100 disengages the K0 clutch 14 and runs on the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to the engaged state and runs at least on the power of the engine 10. Note that the hybrid mode includes a mode of running only on the power of the engine 10 and a mode of running with both the engine 10 and the motor 15 as power sources by powering the motor 15 in a power running operation.

[0019] The switching of the driving mode is performed based on the required driving force of the vehicle obtained from the vehicle speed and the accelerator opening degree, the state of charge of the battery 16, etc. For example, when the required driving force is relatively small and the SOC (State Of Charge) indicating the power storage amount of the battery 16 is relatively high, the motor mode with the engine 10 stopped is selected to improve fuel efficiency. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the hybrid mode with the engine 10 driven is selected.

[0020] The ECU 100 executes intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is satisfied and restart the automatically stopped engine 10 when a predetermined restart condition is satisfied. For example, when the accelerator opening degree becomes zero in the hybrid mode, the ECU 100 automatically stops the engine 10 assuming that the automatic stop condition is satisfied. Also, when the accelerator opening degree becomes larger than zero, for example, the ECU 100 automatically restarts the engine 10 assuming that the restart condition is satisfied. At the time of automatic stop, the ECU 100 disengages the K0 clutch 14 to stop combustion. At the time of automatic restart, the ECU 100 cranks the engine 10 by the motor 15 via the K0 clutch 14 to start combustion, and then engages the K0 clutch 14. Also, when the accelerator opening degree increases again and the restart condition is satisfied while the combustion has stopped and the engine 10 is coasting during automatic stop, the combustion is started and the K0 clutch 14 is engaged.

[0021] [Schematic Configuration of Engine] Figure 2 is a schematic configuration diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, intake valves 36, an exhaust passage 37, and exhaust valves 38. Only one of the plurality of cylinders 30 that the engine 10 has is shown in Figure 2. Combustion of the air-fuel mixture takes place in the cylinder 30. The piston 31 is reciprocally accommodated in each cylinder 30 and is connected to the crankshaft 33, which is the output shaft of the engine 10, via the connecting rod 32. The connecting rod 32 converts the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0022] The intake passage 35 is connected to the intake port of each cylinder 30 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port of each cylinder 30 via the exhaust valve 38. The intake passage 35 is provided with an air flow meter 75, a pressure sensor 76, and a throttle valve 40 for adjusting the intake air amount. The exhaust passage 37 is provided with a catalyst 43 for exhaust purification.

[0023] The cylinder 30 is provided with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into the cylinder 30. Incidentally, instead of or in addition to the in-cylinder injection valve 41, a port injection valve that injects fuel toward the intake port may be provided. Each cylinder 30 is provided with an ignition device 42 that ignites the air-fuel mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41 by spark discharge.

[0024] [Engine Stop Position Control] When the engine 10 automatically stops, stop position control is executed to control the stop position of the engine 10 by temporarily increasing the throttle opening. By setting the stop position of the engine 10 to a desired stop position, the cranking torque of the engine 10 required for the motor 15 when the engine 10 restarts can be reduced. Therefore, for example, when restarting the engine 10 during traveling in motor mode, the portion of the output torque of the motor 15 consumed by the cranking torque is suppressed. As a result, the torque consumed for traveling the hybrid vehicle 1 can be ensured from the output torque of the motor 15, and the driving range in which traveling in motor mode is possible can be ensured to improve fuel efficiency.

[0025] FIG. 3 is a timing chart showing an example of the stop position control of the engine 10. FIG. 3 shows the transitions of the engine speed [rpm], the throttle opening [deg], and the intake manifold pressure [kPa]. Combustion of the engine 10 stops and the throttle opening is controlled to the first opening A1 (hereinafter referred to as the opening A1), and the engine speed decreases (time t1). The opening A1 is a value close to 0 and may be 0. Next, at a predetermined timing, the throttle opening is switched from the opening A1 to the second opening A2 (hereinafter referred to as the opening A2), and the throttle opening is maintained at the opening A2 for a predetermined time. The opening A2 is a value closer to the maximum opening than 0. Next, the throttle opening is switched from the opening A2 to the third opening A3 (hereinafter referred to as the opening A3) (time t3). The opening A3 is a value close to 0 and may be 0. Due to such a temporary increase in the throttle opening, intake air is introduced into the intake passage 35 on the downstream side of the throttle valve 40, and the intake manifold pressure increases to the target intake manifold pressure (time t4). The target intake manifold pressure is the target value of the intake manifold pressure suitable for stopping the engine 10.

[0026] Next, when the intake valve 36 of the cylinder 30 in the intake stroke closes, a part of the intake air introduced downstream of the throttle valve 40 is filled into the cylinder 30 (time t5). Next, when the intake valve 36 of the cylinder 30 that will enter the intake stroke closes, a part of the intake air is filled into the cylinder 30 (time t6). Thereafter, the piston 31 of the cylinder 30 first filled with intake air is in the expansion stroke, and the piston 31 of the cylinder 30 next filled with intake air is in the compression stroke, and the rotation of the engine 10 stops (time t7). Thereafter, the intake manifold pressure returns to the atmospheric pressure (time t8).

[0027] In this way, the engine 10 stops at a position where the compression reaction forces of the intake air filled in the two cylinders 30 are balanced. Thereby, when the engine 10 is restarted, combustion can be started from the cylinder 30 where the piston 31 stopped in the compression stroke, and the restartability can be ensured. The stop position control is an example of the processing executed by the control unit.

[0028] [Throttle Opening Control] FIG. 4 is a flowchart showing an example of the throttle opening adjustment control executed by the ECU 100. In this control, it is repeatedly executed at a predetermined cycle with the ignition on. The ECU 100 determines whether the engine 10 is in the execution of the stop position control (step S1). If the result in step S1 is No, this control ends.

[0029] If the result in step S1 is Yes, the ECU 100 acquires the intake manifold pressure for each cylinder 30 at the timing when each cylinder 30 closes the intake valve 36 (step S2). The higher the intake manifold pressure at the timing when the intake valve 36 closes, the greater the filling amount of the intake air in the cylinder 30 provided with the intake valve 36. Therefore, by grasping the intake manifold pressure at the timing when the intake valve 36 of each cylinder 30 closes, the filling amount of the intake air in each cylinder 30 during the execution of the stop position control can be grasped.

[0030] Next, the ECU 100 determines whether or not the stop position control has ended, that is, whether or not the rotation of the engine 10 has stopped (step S3). If the answer in step S3 is No, step S2 is continued. That is, since the engine 10 of this embodiment is a six-cylinder engine, the ECU 100 always acquires and updates the intake manifold pressure for six cylinders during the execution of the stop position control. Step S2 is an example of the process executed by the acquisition unit.

[0031] If the answer in step S3 is Yes, the ECU 100 determines whether the maximum value among the acquired intake manifold pressures for six cylinders is higher than the target intake manifold pressure and whether the maximum value is higher than a predetermined value when compared with the target intake manifold pressure (step S4). The maximum value of the intake manifold pressure means the maximum value of the intake charge amount in each cylinder 30. Also, the predetermined value in step S4 is the upper limit value of the allowable range that does not affect the accuracy of the stop position of the engine 10 when the maximum value is higher than the intake manifold pressure. If the answer in step S4 is Yes, regarding the above-described maximum value as being too high with respect to the target intake manifold pressure, the ECU 100 adds "1" to the HI counter value and subtracts "1" from the LO counter value (step S5).

[0032] If the answer in step S4 is No, it is determined whether the above-described maximum value is lower than the target intake manifold pressure and whether the maximum value is lower than a predetermined value when compared with the target intake manifold pressure (step S6). The predetermined value in step S6 is the upper limit value of the allowable range that does not affect the accuracy of the stop position of the engine 10 when the maximum value is lower than the intake manifold pressure. If the answer in step S6 is Yes, regarding the maximum value as being too low with respect to the target intake manifold pressure, the ECU 100 subtracts "1" from the HI counter value and adds "1" to the LO counter value (step S7). If the answer in step S6 is No, this control is ended. That is, in steps S4 and S6, it is determined whether the maximum value is outside the allowable range with respect to the target intake manifold pressure.

[0033] Next, the ECU 100 determines whether the HI counter value is equal to or greater than a predetermined value (step S8). If Yes in step S8, the ECU 100 learns the opening degree obtained by subtracting a predetermined minute opening degree ΔA2 from the opening degree A2 as the new opening degree A2 (step S9). If No in step S8, the ECU 100 determines whether the LO counter value is equal to or greater than a predetermined value (step S10). If Yes in step S10, the ECU 100 learns the opening degree obtained by adding the minute opening degree ΔA2 to the opening degree A2 as the new opening degree A2 (step S11). Steps S9 and S11 are examples of the processes executed by the adjustment unit. Note that the minute opening degree ΔA2 when decreasing the opening degree A2 and the minute opening degree ΔA2 when increasing the opening degree A2 may be the same or different. If No in step S10, this control ends. That is, if No in step S10, it is considered that the opening degree A2 is currently set to an appropriate opening degree, and the opening degree A2 is maintained at the current opening degree without adjustment. Also, similarly, if No in step S6, the opening degree A2 is not adjusted assuming that it is an appropriate opening degree.

[0034] As described above, when the maximum value of the intake manifold pressure at the timing when the intake valve 36 closes is within the allowable range with respect to the target intake manifold pressure, the opening degree A2 is maintained at the current opening degree. When the maximum value is too high with respect to the target intake manifold pressure, the opening degree A2 is adjusted to the decreasing side. When it is too low, the opening degree A2 is adjusted to the increasing side. Thereby, it is possible to adjust the opening degree A2 in response to variations in the control accuracy of the throttle opening degree and secular changes in the throttle valve 40, and to fill a desired cylinder with a desired intake air amount. As a result, it is possible to suppress a decrease in the accuracy of the stop position of the engine 10.

[0035] In the above-described embodiment, during the execution of the stop position control, the intake manifold pressure at the timing when the intake valve 36 is closed for each cylinder 30 was acquired, and the maximum value among them was compared with the target intake manifold pressure. Here, the intake manifold pressure increases with a delay after the throttle opening is switched from the opening A2 to the opening A3. For this reason, the maximum value among the acquired intake manifold pressures is the intake manifold pressure after the throttle opening is switched to the opening A3. Therefore, instead of the above-described maximum value, for example, the intake manifold pressure at the timing when the intake valve 36 is first closed after the throttle opening is switched to the opening A3 may be compared with the target intake manifold pressure. Further, the intake manifold pressure at the timing when the intake valve 36 is closed second after the throttle opening is switched to the opening A3 may be compared with the target intake manifold pressure. Further, after the throttle opening is switched to the opening A3, the intake manifold pressure at the timing when the intake valve 36 is closed may be acquired for each cylinder, and the maximum value among them may be compared with the target intake manifold pressure.

[0036] The respective predetermined values in steps S4 and S6 may be the same or different. The addition values and subtraction values for each counter value in steps S5 and S7 are all the same value, but are not limited thereto, and some or all of them may be different. The respective predetermined values in steps S8 and S10 may be the same or different.

[0037] In the above-described embodiment, the case where a hybrid vehicle is controlled by a single ECU 100 is illustrated, but the present invention is not limited thereto. For example, the above-described control may be executed by a plurality of ECUs such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

[0038] In the above-described embodiment, the hybrid vehicle 1 has been described as an example, but the present invention is not limited thereto. For example, the stop position control of the present embodiment can also be applied to an engine vehicle in which only an engine is provided as a driving power source and the engine is automatically stopped and restarted by an idling stop function.

[0039] As described above in detail with reference to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Signs

[0040] 1 Hybrid vehicle (vehicle) 10 Engine (internal combustion engine) 15 Motor 40 Throttle valve 100 ECU (control unit, acquisition unit, adjustment unit)

Claims

【Claim 1】 In a control device for a vehicle equipped with an internal combustion engine as a driving power source, a control unit that executes stop position control of the internal combustion engine by switching a throttle opening from a first opening to a second opening larger than the first opening and then switching from the second opening to a third opening smaller than the second opening during inertial rotation with combustion stopped when the internal combustion engine automatically stops; an acquisition unit that acquires an intake manifold pressure, which is the pressure in the intake passage on the downstream side of the throttle valve, at the timing when the intake valve of any cylinder closes after the throttle opening is switched to the third opening during the execution of the stop position control; a adjustment unit that maintains the second opening when the intake manifold pressure is within an allowable range with respect to a target value, decreases the second opening as compared with the case where the intake manifold pressure is within the allowable range when the intake manifold pressure is higher than the allowable range, and increases the second opening as compared with the case where the intake manifold pressure is within the allowable range when the intake manifold pressure is lower than the allowable range. A control device for a hybrid vehicle comprising the above.

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