Control system for hybrid vehicles

Abstract

To provide a control device for hybrid vehicles that can suppress clutch burnout. [Solution] A hybrid vehicle comprises an engine, a motor generator, a clutch interposed between the engine and the motor generator, and a starter motor for starting the engine. In an extremely low-temperature environment, the clutch is disengaged, and the engine is started by the starter motor. After the engine is started by the starter motor, the control device of the hybrid vehicle starts engaging the clutch. After starting to engage the clutch, if the amount of heat absorbed by the clutch exceeds a predetermined amount, the control device of the hybrid vehicle interrupts the engagement of the clutch.

Description

Technical Field

[0005]

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

Background Art

[0002] A hybrid vehicle includes an engine, a motor generator, a clutch, a starter motor, and a battery. The clutch is interposed between the engine and the motor generator. The starter motor starts the engine. The battery exchanges electric power with the motor generator. It is described in Patent Document 1 that in an extremely low temperature environment, the clutch is in a disengaged state and the engine is started by the starter motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an extremely low temperature environment, it is difficult to rotationally drive the motor generator by the electric power from the battery, so it is necessary to increase the rotational speed of the motor generator by the engine and the clutch. However, in an extremely low temperature environment, since the friction of the motor generator is large, when trying to engage the clutch while suppressing the occurrence of engine stall, the time during which the clutch is in a slip state becomes long. When the time during which the clutch is in a slip state becomes long, the heat absorption amount of the clutch becomes large, so there is a risk that the clutch will burn out.

Means for Solving the Problems

[0005] A control device for a hybrid vehicle that solves the above problems comprises an engine, a motor generator, a clutch interposed between the engine and the motor generator, and a starter motor for starting the engine, wherein in an extremely low temperature environment, the clutch is disengaged and the engine is started by the starter motor, and after the engine is started by the starter motor, the clutch is engaged, and after the clutch is engaged, if the amount of heat absorbed by the clutch exceeds a predetermined amount of heat absorbed, the engagement of the clutch is interrupted. [Effects of the Invention]

[0006] According to the present invention, clutch burnout can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a block diagram showing the vehicle configuration. [Figure 2] Figure 2 is a flowchart showing the startup control of the hybrid system performed by the power supply ECU. [Modes for carrying out the invention]

[0008] Hereinafter, one embodiment of a control device for a hybrid vehicle will be described with reference to the drawings. <Hybrid Vehicle 10> As shown in Figure 1, the hybrid vehicle 10 is equipped with a hybrid system 11. The hybrid system 11 comprises an engine 12, a starter motor 13, a motor generator 14, a battery 15, a clutch 16, a transmission 17, a torque converter 18, and a hybrid ECU 19.

[0009] The engine 12 in this embodiment is a gasoline engine. The engine 12 may also be a diesel engine or a hydrogen engine. The starter motor 13 starts the engine 12. The battery 15 exchanges power with the motor generator 14.

[0010] The clutch 16 is interposed between the engine 12 and the motor generator 14. The clutch 16 can be in one of three states: engaged, slipped, or disengaged. The engaged state is when the engine 12 and the motor generator 14 are mechanically connected. The disengaged state is when there is virtually no torque transmission between the engine 12 and the motor generator 14 via the clutch 16. The slipped state is when the engine 12 and the motor generator 14 can rotate relative to each other while torque is transmitted between them via the clutch 16.

[0011] The transmission 17 is hydraulic. The transmission 17 is connected to a differential (not shown). A torque converter 18 is interposed between the motor generator 14 and the transmission 17.

[0012] The hybrid ECU 19 has a CPU 19a and a memory 19b for storing programs. The hybrid ECU 19 performs various processes by having the CPU 19a execute the programs stored in the memory 19b. The hybrid ECU 19 controls the entire hybrid system 11. The hybrid ECU 19 controls the state of the clutch 16.

[0013] The hybrid vehicle 10 is equipped with a first rotational speed sensor 21, a second rotational speed sensor 22, and a temperature sensor 23. The first rotational speed sensor 21 detects the rotational speed of the engine 12. The second rotational speed sensor 22 detects the rotational speed of the motor generator 14. The temperature sensor 23 detects the oil temperature of the transmission 17.

[0014] The first rotational speed sensor 21, the second rotational speed sensor 22, and the temperature sensor 23 are each connected to the hybrid ECU 19. The hybrid ECU 19 obtains the rotational speed of the engine 12 from the first rotational speed sensor 21. The hybrid ECU 19 obtains the rotational speed of the motor generator 14 from the second rotational speed sensor 22. The hybrid ECU 19 obtains the oil temperature of the transmission 17 from the temperature sensor 23.

[0015] The hybrid vehicle 10 is equipped with a power supply ECU 31. The power supply ECU 31 is the control device for the hybrid vehicle 10. The power supply ECU 31 has a CPU 31a and a memory 31b for storing programs. The power supply ECU 31 performs various processes by having the CPU 31a execute the programs stored in the memory 31b. The memory 31b includes non-volatile memory. The power supply ECU 31 is connected to the hybrid ECU 19. The power supply ECU 31 can obtain the rotational speed of the engine 12, the rotational speed of the motor generator 14, and the oil temperature of the transmission 17 via the hybrid ECU 19.

[0016] The hybrid vehicle 10 is equipped with a start switch 32. The start switch 32 is operated by the user of the hybrid vehicle 10. The start switch 32 is connected to the power supply ECU 31.

[0017] <Startup control of hybrid system 11> This section describes the startup control of the hybrid system 11 performed by the power supply ECU 31. While there are multiple types of startup control for the hybrid system 11 depending on the ambient temperature, this section will focus only on the startup control of the hybrid system 11 under cryogenic conditions. A cryogenic environment is, for example, an environment with temperatures of several tens of degrees below zero.

[0018] The power supply ECU 31 initiates the startup control of the hybrid system 11 when the start switch 32 is pressed. Specifically, the power supply ECU 31 outputs a command to the hybrid ECU 19 to start the engine 12. In the case of an extremely low temperature environment, the hybrid ECU 19 starts the engine 12 using the starter motor 13. The hybrid ECU 19 can determine whether or not an extremely low temperature environment exists, for example, by the oil temperature of the transmission 17 or the output voltage of the battery 15. At the start of the startup control of the hybrid system 11, the clutch 16 is in an unengaged state.

[0019] As shown in FIG. 2, in step S11, the power supply ECU 31 determines whether or not the engine 12 has started based on the rotational speed of the engine 12. If the engine 12 has started (step S11: YES), the power supply ECU 31 executes the process of step S12. If the engine 12 has not started (step S11: NO), the power supply ECU 31 executes the process of step S11 again. Therefore, step S11 is repeatedly executed until the engine 12 starts.

[0020] In step S12, the power supply ECU 31 determines whether or not the number of start / stop times of the hybrid system 11 is equal to or greater than a predetermined number of times. Although details will be described later, in the present embodiment, when an engine stall occurs or when the heat absorption amount of the clutch 16 is equal to or greater than a predetermined heat absorption amount, the start of the hybrid system 11 is aborted. Specifically, the engagement of the clutch 16 is interrupted and the power supply of the hybrid ECU 19 is turned off. The number of start / stop times of the hybrid system 11 is stored in the non-volatile memory of the memory 31b.

[0021] When the number of start / stop times of the hybrid system 11 is equal to or greater than a predetermined number of times (step S12: YES), the motor generator 14 and the torque converter 18 are warmed up by the heat of the engine 12. In step S13, the power supply ECU 31 determines whether or not the warm-up of the motor generator 14 and the torque converter 18 has been completed. The power supply ECU 31 determines whether or not the warm-up of the motor generator 14 and the torque converter 18 has been completed based on, for example, the oil temperature of the transmission 17. When the oil temperature of the transmission 17 is equal to or higher than a predetermined temperature, the power supply ECU 31 determines that the warm-up of the motor generator 14 and the torque converter 18 has been completed. When the oil temperature of the transmission 17 is lower than the predetermined temperature, the power supply ECU 31 determines that the warm-up of the motor generator 14 and the torque converter 18 has not been completed.

[0022] When the warm-up of the motor generator 14 and the torque converter 18 is completed (step S13: YES), the power supply ECU 31 executes the process of step S14. When the warm-up of the motor generator 14 and the torque converter 18 is not completed (step S13: NO), the power supply ECU 31 executes the process of step S13 again. Therefore, step S13 is repeatedly executed until the warm-up of the motor generator 14 and the torque converter 18 is completed.

[0023] When the number of start-stop times of the hybrid system 11 is less than a predetermined number of times, that is, when it is less than the predetermined number of times (step S12: NO), in step S15, the power supply ECU 31 determines whether the cooling of the clutch 16 is completed.

[0024] Specifically, the power supply ECU 31 calculates the temperature of the clutch 16. In the present embodiment, the power supply ECU 31 estimates the temperature of the clutch 16 from the oil temperature of the transmission 17. The power supply ECU 31 estimates the cooling required time, which is the time required for the temperature of the clutch 16 to drop to a predetermined engagement possible temperature, from the estimated temperature of the clutch 16. The engagement possible temperature is set to a temperature at which the clutch 16 does not burn out when the clutch 16 is engaged. Further, the power supply ECU 31 measures the power-off time, which is the time during which the power of the hybrid ECU 19 is off. While the power of the hybrid ECU 19 is off, the clutch 16 is cooled. Therefore, the power-off time is the cooling time of the clutch 16. When the cooling time of the clutch 16 is equal to or longer than the cooling required time, the power supply ECU 31 determines that the cooling of the clutch 16 is completed. When the cooling time of the clutch 16 is less than the cooling required time, the power supply ECU 31 determines that the cooling of the clutch 16 is not completed.

[0025] If the clutch 16 has finished cooling (step S15: YES), the power ECU 31 executes the process in step S14. If the clutch 16 has not finished cooling (step S15: NO), the power ECU 31 executes the process in step S15 again. Therefore, step S15 is repeatedly executed until the clutch 16 has finished cooling.

[0026] Step S14 is performed when the motor generator 14 and torque converter 18 have finished warming up, or when the clutch 16 has finished cooling down. In step S14, the power supply ECU 31 outputs a command to the hybrid ECU 19 to start engaging the clutch 16. When the hybrid ECU 19 receives a command from the power supply ECU 31 to start engaging the clutch 16, it transitions the state of the clutch 16 from the disengaged state to the engaged state via the slipped state.

[0027] In step S16, the power supply ECU 31 determines whether or not an engine stall has occurred based on the rotational speed of the engine 12. If an engine stall occurs (step S16: YES), in step S17, the power supply ECU 31 outputs a command to the hybrid ECU 19 to interrupt the engagement of the clutch 16. When the hybrid ECU 19 receives a command from the power supply ECU 31 to interrupt the engagement of the clutch 16, it changes the state of the clutch 16 from the slip state to the disengaged state. In step S18, the power supply ECU 31 counts up the number of times the hybrid system 11 has been aborted. The counted number of times the hybrid system 11 has been aborted is stored in the non-volatile memory of memory 31b.

[0028] If no engine stall occurs (step S16: NO), in step S19, the power supply ECU 31 calculates the amount of heat absorbed by the clutch 16. The amount of heat absorbed by the clutch 16 is proportional to the product of the clutch difference rotation and the clutch torque. The clutch difference rotation is the difference between the rotation speed of the engine 12 and the rotation speed of the motor generator 14. The power supply ECU 31 calculates the amount of heat absorbed by the clutch by calculating the clutch difference rotation from the rotation speed of the engine 12 and the rotation speed of the motor generator 14.

[0029] In step S20, the power supply ECU 31 determines whether the clutch 16 has engaged or not based on the rotational speed of the engine 12 and the rotational speed of the motor generator 14. When the clutch 16 is engaged, that is, when the clutch 16 is engaged, the rotational speed of the motor generator 14 is the same as the rotational speed of the engine 12. Therefore, if the rotational speed of the motor generator 14 is the same as the rotational speed of the engine 12, the power supply ECU 31 determines that the clutch 16 has engaged. If the rotational speed of the motor generator 14 is less than the rotational speed of the engine 12, the power supply ECU 31 determines that the clutch 16 has not engaged.

[0030] If the clutch 16 is fully engaged (step S20: YES), in step S21, the power supply ECU 31 determines that the hybrid system 11 has finished starting up. Once the hybrid system 11 has finished starting up, the hybrid vehicle 10 is ready to drive. In step S22, the power supply ECU 31 resets the number of times the hybrid system 11 has been stopped from starting up to 0.

[0031] If the clutch 16 is not fully engaged (step S20: NO), in step S23, the power supply ECU 31 determines whether the amount of heat absorbed by the clutch 16 is greater than or equal to a predetermined amount. If the amount of heat absorbed by the clutch 16 is greater than or equal to a predetermined amount (step S23: YES), the power supply ECU 31 executes the processes of steps S17 and S18 described above. That is, the power supply ECU 31 outputs a command to the hybrid ECU 19 to interrupt the engagement of the clutch 16, and then counts up the number of times the hybrid system 11 has been stopped from starting.

[0032] If the amount of heat absorbed by the clutch 16 is not equal to or less than a predetermined amount, i.e., less than a predetermined amount (step S23: NO), the power supply ECU 31 repeats the process in step S16. In other words, the power supply ECU 31 returns to determining whether or not an engine stall has occurred.

[0033] When the power supply ECU 31 counts up or resets the number of times the hybrid system 11 has been aborted, the series of processes ends. [Operation and Effects of This Embodiment] The operation and effects of this embodiment will now be explained.

[0034] (1) The hybrid vehicle 10 includes an engine 12, a motor generator 14, a clutch 16 interposed between the engine 12 and the motor generator 14, and a starter motor 13 for starting the engine 12. In an extremely low temperature environment, the clutch 16 is disengaged and the engine 12 is started by the starter motor 13. The power supply ECU 31 of the hybrid vehicle 10 starts engaging the clutch 16 after the engine 12 is started by the starter motor 13. After starting to engage the clutch 16, the power supply ECU 31 interrupts the engagement of the clutch 16 if the amount of heat absorbed by the clutch 16 exceeds a predetermined amount of heat absorbed.

[0035] With this configuration, if the amount of heat absorbed by the clutch 16 exceeds a predetermined amount, the engagement of the clutch 16 is interrupted, thereby suppressing burnout of the clutch 16. (2) The power supply ECU 31 does not output a command to the hybrid ECU 19 to start engaging the clutch 16 until the clutch 16 has finished cooling down. This configuration prevents the clutch 16 from being engaged when it is hot, i.e., when it is prone to burning out. Therefore, burnout of the clutch 16 can be further suppressed.

[0036] (3) If the number of times the hybrid system 11 has been started or stopped exceeds a predetermined number, the motor generator 14 and torque converter 18 are warmed up by the heat of the engine 12. After the motor generator 14 and torque converter 18 have finished warming up, the power supply ECU 31 outputs a command to the hybrid ECU 19 to start engaging the clutch 16. With this configuration, the engagement of the clutch 16 is started with reduced friction in the motor generator 14 and torque converter 18, so the amount of heat absorbed by the clutch 16 can be reduced. Therefore, the starting of the hybrid system 11 is more likely to succeed. [Explanation of Symbols]

[0037] 10...Hybrid vehicle, 12...Engine, 13...Starter motor, 14...Motor generator, 16...Clutch, 31...Power ECU (control unit)

Claims

[Claim 1] A control device for a hybrid vehicle comprising an engine, a motor generator, a clutch interposed between the engine and the motor generator, and a starter motor for starting the engine, wherein in an extremely low temperature environment, the clutch is disengaged and the engine is started by the starter motor, After the engine is started by the starter motor, the clutch is engaged. A control device for a hybrid vehicle that interrupts the engagement of the clutch if, after the clutch has started to engage, the amount of heat absorbed by the clutch exceeds a predetermined amount of heat absorbed.

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