Control device for a hybrid vehicle

Abstract

To provide a hybrid-vehicular control apparatus with a shock suppressed when starting an engine.SOLUTION: A hybrid-vehicular control apparatus is applied to a hybrid vehicle that includes an engine, a motor disposed in a power transmission path between the engine and a wheel, and a clutch disposed in the power transmission path between the engine and motor. In a case where the engine is required to start, the apparatus causes the motor to crank the engine by allowing the clutch to slip, followed by engaging the clutch. The apparatus includes: a first start control unit for starting combustion of the engine with the clutch slipping if a rotation speed of the motor is equal to or higher than a threshold in a case where the engine is required to start; and a second start control unit for starting combustion of the engine with the clutch engaged when the rotation speed of the motor is less than the threshold in a case where the engine is required to start.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Some hybrid vehicles are equipped with an engine, a motor provided in the power transmission path between the engine and the wheels, and a clutch provided between the engine and the motor in the power transmission path. When starting the engine, the clutch is slipped and the motor is used to crank the engine, and then the clutch is engaged to start the 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] As described above, when starting the engine, if the clutch slips and the combustion of the engine starts, the engine can be started early. However, in this case, the engine speed may rise above the motor speed, and the rotation of the motor may increase due to the rotation of the engine, which may cause a shock to the hybrid vehicle.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle in which shock during engine start is suppressed.

Means for Solving the Problems

[0006] The above object is applied to a hybrid vehicle including an engine, a motor provided in a power transmission path between the engine and wheels, and a clutch provided between the engine and the motor in the power transmission path. In a control device for the hybrid vehicle, when there is a start request for the engine, the clutch is slipped and the motor is used to crank the engine, and then the clutch is engaged. When there is a start request for the engine at the first startup and the rotational speed of the motor is First equal to or higher than a threshold value, a first start control unit that starts combustion of the engine with the clutch in a slip state; when there is a startup request for the engine and it is the first startup when the rotational speed of the motor is less than the First threshold value, a second start control unit that starts combustion of the engine with the clutch in an engaged state, is provided , when the rotational speed of the motor is equal to or greater than a second threshold value greater than the first threshold value in the case of a restart after the startup request for the engine and the startup of the engine has failed, the first startup control unit starts the combustion of the engine with the clutch in a slip state, and when the rotational speed of the motor is less than the second threshold value in the case of a restart after the startup request for the engine and the startup of the engine has failed, the second startup control unit starts the combustion of the engine with the clutch in an engaged state. The clutch being in a slip state means that the absolute value of the difference between the rotational speed of the engine and the rotational speed of the motor is equal to or greater than a predetermined value, and the clutch being in an engaged state means that the absolute value is less than the predetermined value that can be regarded as approximately 0 and can be achieved by a control device for a hybrid vehicle.

Advantages of the Invention

[0007] According to the present invention, a control device for a hybrid vehicle in which shock at engine start is suppressed can be provided.

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] Figure 1 is a schematic configuration diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and an automatic transmission 19 are sequentially provided in the power transmission path from the engine 10 to the wheels 13. The engine 10 and the motor 15 are mounted on the hybrid vehicle 1 as drive sources. 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 also be an in-line engine or a diesel engine. The K0 clutch 14, the motor 15, the torque converter 18, and the automatic transmission 19 are provided in the transmission unit 11. The transmission unit 11 and the left and right 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 the supply of hydraulic pressure and enters an engaged state to connect the power transmission between the engine 10 and the motor 15. The K0 clutch 14 enters an open state in response to the stop of the hydraulic pressure supply to cut off the power transmission between the engine 10 and the motor 15.

[0011] The motor 15 is connected to the battery 16 via an inverter 17. The motor 15 functions as a motor that generates the driving force of the vehicle in response to the power supply from the battery 16, while also functioning as a generator that generates electric power for charging the battery 16 in response to the power transmission from the engine 10 or the 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 40 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 in which 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 in which 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 automatic transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple steps by switching the gear stage. The automatic transmission 19 is provided between the motor 15 and the wheels 13 on the power transmission path. The motor 15 and the automatic 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 automatic transmission 19.

[0014] The shift 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 automatic 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 automatic transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures.

[0015] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 40 as a control device for the vehicle. The ECU 40 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 40 is an example of a control device for a hybrid vehicle, and specifically functionally realizes a first starting control unit and a second starting control unit, which will be described later.

[0016] The ECU 40 controls the driving of the engine 10 and the motor 15. For example, the ECU 40 controls the torque and rotational speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 40 also performs drive control of the K0 clutch 14, the lock-up clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22.

[0017] The ECU 40 controls the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16, thereby controlling the rotational speed and torque of the motor 15. More specifically, although it will be described later in detail, the ECU 40 controls the power supplied from the motor 15 to the battery 16 by the inverter 17 so that the motor braking torque during regenerative operation reaches the target value.

[0018] Signals from the ignition switch 31, the crank angle sensor 32, the motor rotational speed sensor 33, and the accelerator opening sensor 34 are input to the ECU 40. The crank angle sensor 32 detects the rotational speed of the crankshaft of the engine 10. The motor rotational speed sensor 33 detects the rotational speed of the output shaft of the motor 15. The accelerator opening sensor 34 detects the accelerator pedal opening, which is the amount of depression of the driver's accelerator pedal.

[0019] The ECU 40 drives the hybrid vehicle in either the motor mode or the hybrid mode. In the motor mode, the ECU 40 releases the K0 clutch 14 and drives by the power of the motor 15. In the hybrid mode, the ECU 40 engages the K0 clutch 14 and drives at least by the power of the engine 10. Note that in the hybrid mode, it includes a mode of driving only by the power of the engine 10 and a mode of driving with both the engine 10 and the motor 15 as power sources by powering the motor 15.

[0020] 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, and 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 remaining charge 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 at least the engine 10 driven is selected.

[0021] For example, when the accelerator opening becomes equal to or greater than a predetermined value during traveling in the motor mode, starting of the engine 10 is requested. When there is a request to start the engine 10, the ECU 40 controls the hydraulic control mechanism 22 to shift the K0 clutch 14 from the released state to the slip state. Thereby, cranking of the engine 10 is started by the motor 15. Further, although details will be described later, the ECU 40 starts combustion of the engine 10 with the K0 clutch 14 in the slip state according to the motor speed at the time when there is a request to start the engine 10, or starts combustion of the engine 10 with the K0 clutch 14 in the engaged state. The engine 10 is started in this way, and the traveling mode is switched from the motor mode to the hybrid mode. Note that starting combustion of the engine 10 means that fuel injection is started from the fuel injection valve and ignition of the air-fuel mixture is started.

[0022] [Engine start control] Next, before describing the engine start control of the present embodiment, the engine start control in the comparative example will be described. FIG. 2 is a timing chart showing the engine start control in the comparative example. FIG. 2 shows the engine speed [rpm], the motor speed [rpm], the state of the K0 clutch 14, and the combustion state of the engine 10. Note that the engine speed is indicated by a one-dot chain line, and the others are indicated by solid lines.

[0023] At time t0, the K0 clutch 14 is in the released state, the engine speed is 0, and combustion of the engine 10 has stopped. After that, when there is a request to start the engine 10, at time t1, the K0 clutch 14 becomes the slip state, and the output torque of the motor 15 increases by the torque for cranking the engine 10. Thereby, cranking of the engine 10 is started by the motor 15 while maintaining the motor speed at the current speed, and the engine speed increases.

[0024] When the combustion of the engine 10 starts at time t2 when the K0 clutch 14 is in a slip state and the engine speed is lower than the motor speed, the rate of increase in the engine speed further increases. As a result, the engine speed exceeds the motor speed at time t3. Since the K0 clutch 14 is in a slip state, the motor speed also temporarily increases due to the rotation of the engine 10, which may cause the hybrid vehicle 1 to accelerate and generate a shock. After that, the engine speed stabilizes and matches the motor speed at time t4, and the K0 clutch 14 enters an engaged state. Thus, the phenomenon that the engine speed exceeds the motor speed at engine startup is likely to occur when the motor speed is relatively low, for example, when the motor speed is equal to or lower than a threshold value α described later.

[0025] FIG. 3 is a timing chart showing an example of the engine startup control of this embodiment. In FIG. 3, similar to FIG. 2, the engine speed [rpm], the motor speed [rpm], the state of the K0 clutch 14, and the combustion state of the engine 10 are shown. Similar to the comparative example, from time t0 when the K0 clutch 14 is in an open state and the engine 10 is in a stopped state, the K0 clutch 14 enters a slip state at time t1 due to an engine startup request, and the cranking of the engine 10 starts. When the engine speed rises to the motor speed at time t2, the K0 clutch 14 enters an engaged state, and the combustion of the engine 10 starts from time t3 thereafter. Thus, in this embodiment, since the combustion of the engine 10 starts with the K0 clutch 14 in an engaged state, the shock that occurs in the comparative example where the combustion of the engine 10 starts with the K0 clutch 14 in a slip state can be suppressed.

[0026] When starting the combustion of the engine 10 in the engaged state of the K0 clutch 14 as in this embodiment, it is preferable to start the combustion of the engine 10 immediately after the engagement of the K0 clutch 14. This is to suppress the starting delay of the engine 10. Also, when starting the combustion of the engine 10 in the engaged state of the K0 clutch 14 as in this embodiment, vibration may occur in the hybrid vehicle 1 due to the increase in the torque of the engine 10. Therefore, in accordance with the timing of starting the combustion of the engine 10, the torque of the motor 15 may be reduced so as to cancel out the increase in the torque of the engine 10.

[0027] As described above, the shock at the time of engine start is likely to occur when the motor speed is relatively low. For this reason, in this embodiment, when the motor speed is less than the threshold value α, the combustion of the engine 10 is started with the K0 clutch 14 in the engaged state, and when the motor speed is equal to or higher than the threshold value, the combustion of the engine 10 is started with the K0 clutch 14 in the slip state. Here, the threshold value α is set to the upper limit value at which the engine speed may exceed the motor speed when the combustion of the engine 10 is started with the K0 clutch 14 in the slip state. Therefore, by starting the combustion of the engine 10 with the K0 clutch 14 in the slip state when the motor speed is equal to or higher than the threshold value at which the motor speed is less likely to be exceeded by the engine speed, the engine 10 can be started earlier.

[0028] [Engine Start Control Executed by ECU] FIG. 4 is a flowchart showing an example of the engine start control executed by the ECU 40. This control is repeatedly executed at a predetermined cycle with the ignition on. The ECU 40 determines whether there is a start request for the engine 10 (step S1). If the answer is No in step S1, this control is terminated.

[0029] If the answer is Yes in step S1, the ECU 40 determines whether it is a restart after a starting failure of the engine 10 (step S2). Here, for example, in the ECU 40 of this embodiment, when the engine speed cannot be increased to a self-sustaining rotation speed by cranking the motor 15, it is determined as a starting failure and the failure history flag is turned on. The ECU 40 makes the determination in step S2 by referring to this flag. When a starting failure occurs, the ECU 40 immediately restarts by cranking the engine 10 again. At this time, the ECU 40 increases the cranking torque of the motor 15 by a predetermined value more than the cranking torque before the failure.

[0030] If the answer is No in step S2, that is, if the start of the engine 10 is the first start after a start request, the ECU 40 determines whether the motor speed is equal to or higher than the threshold value α (step S3).

[0031] If the answer is Yes in step S3, assuming that the above-mentioned shock is less likely to occur, the ECU 40 starts the engine 10 by starting the combustion of the engine 10 with the K0 clutch 14 in a slip state (step S4). Thereby, the engine 10 can be started earlier. Note that the state of the K0 clutch can be determined based on the absolute value of the difference between the engine speed and the motor speed. When this absolute value is less than a predetermined value that can be regarded as approximately 0, the K0 clutch 14 is in an engaged state, and when this absolute value is equal to or greater than the predetermined value, the K0 clutch 14 can be regarded as being in a slip state. The process of step S4 is an example of the process executed by the first start control unit.

[0032] If the answer is No in step S3, that is, if the motor speed is less than the threshold value α, the ECU 40 starts the engine 10 by starting the combustion of the engine 10 with the K0 clutch 14 in an engaged state (step S5). Thereby, the occurrence of the above-mentioned shock can be suppressed. The process of step S5 is an example of the process executed by the second start control unit.

[0033] If the answer in step S2 is Yes, that is, if the start of the engine 10 is a restart after a failure after a start request, the ECU 40 determines whether the motor speed is equal to or higher than the threshold value β (step S6). Here, the threshold value β is a value larger than the threshold value α. As described above, at the time of restart after a start failure, the cranking torque increases more than at the time of the first start, so at the time of restart, the engine speed is more likely to exceed the motor speed than at the time of the first start. For this reason, at the time of restart after a start failure, it is determined whether the motor speed is equal to or higher than the threshold value β, which is larger than the threshold value α.

[0034] If the answer in step S6 is Yes, the ECU 40 starts the combustion of the engine 10 with the K0 clutch 14 in a slip state to start the engine 10 (step S4). Also in this case, the engine 10 can be started earlier. If the answer in step S6 is No, the ECU 40 starts the combustion of the engine 10 with the K0 clutch 14 engaged to start the engine 10 (step S5). Also in this case, the occurrence of the shock described above can be suppressed.

[0035] In the above embodiment, the case where a hybrid vehicle is controlled by a single ECU 40 is illustrated, but the present invention is not limited to this. 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.

[0036] As described above, the embodiments of the present invention have been described in detail, but 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.

Description of Reference Numerals

[0037] 10 Engine 14 K0 Clutch 15 Motor 40 ECU (First Start Control Unit, Second Start Control Unit)

Claims

【Claim 1】 Applied to a hybrid vehicle comprising an engine, a motor provided in a power transmission path between the engine and wheels, and a clutch provided between the engine and the motor in the power transmission path, in a control device for a hybrid vehicle that slips the clutch and cranks the engine with the motor and then engages the clutch when there is a start request for the engine, a first start control unit that starts combustion of the engine with the clutch in a slip state when there is a start request for the engine and it is the first start and the rotational speed of the motor is equal to or higher than a first threshold value; a second start control unit that starts combustion of the engine with the clutch in an engaged state when there is a start request for the engine and it is the first start and the rotational speed of the motor is less than the first threshold value, the control device for a hybrid vehicle comprising: the first start control unit starts combustion of the engine with the clutch in a slip state when there is a start request for the engine and it is a restart after a start of the engine has failed and the rotational speed of the motor is equal to or higher than a second threshold value that is greater than the first threshold value; the second start control unit starts combustion of the engine with the clutch in an engaged state when there is a start request for the engine and it is a restart after a start of the engine has failed and the rotational speed of the motor is less than the second threshold value; the state where the clutch is in a slip state is a case where the absolute value of the difference between the rotational speed of the engine and the rotational speed of the motor is equal to or greater than a predetermined value; the state where the clutch is in an engaged state is a case where the absolute value is less than the predetermined value that can be regarded as substantially zero, a control device for a hybrid vehicle.

Images