Hybrid vehicle control device

Abstract

To provide a hybrid vehicle control device that provides ensured engine startability.SOLUTION: A hybrid vehicle control device is applied to a hybrid vehicle including a clutch and a motor disposed in order on a power transmission path from an engine to wheels, and a battery for supplying power to the motor, and restricts output torque of the motor when a voltage of the battery is a voltage threshold or lower. The hybrid vehicle control device comprises: a calculation unit for calculating a cranking torque request value required to the motor when cranking is performed on the engine via the clutch; and a threshold changing unit for changing the voltage threshold to a value small compared to a case where the cranking torque request value is less than a predetermined value when the cranking torque request value is the predetermined value or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] 2. Description of the Related Art A hybrid vehicle is known that includes a clutch and a motor provided in this order on a power transmission path from an engine to wheels, and a battery that supplies power to the motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-054165 Summary of the Invention [Problem to be solved by the invention]

[0004] When the motor output torque is large, a large amount of power is supplied from the battery to the motor, causing a temporary drop in the battery voltage. If the battery voltage drops excessively, it will affect the battery's performance, so it is possible to limit the motor output torque in order to prevent further voltage drops. If the motor output torque is also limited when cranking the engine by the motor via the clutch, the motor output torque may be insufficient, which may affect the startability of the engine.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS The present invention has an object to provide a control device for a hybrid vehicle that ensures engine startability. [Means for solving the problem]

[0006] The above object can be achieved by a hybrid vehicle control device that is applied to a hybrid vehicle including a clutch and a motor arranged in sequence on a power transmission path from an engine to wheels, and a battery that supplies power to the motor, and that limits the output torque of the motor when the voltage of the battery is below a voltage threshold, the hybrid vehicle control device including: a calculation unit that calculates a cranking torque requirement value that is required of the motor when cranking the engine via the clutch; and a threshold change unit that, when the cranking torque requirement value is equal to or greater than a predetermined value, changes the voltage threshold to a smaller value than when the cranking torque requirement value is less than the predetermined value. Effect of the Invention

[0007] According to the present invention, it is possible to provide a control device for a hybrid vehicle that ensures engine startability. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Diagram 2] FIG. 2 is a flowchart showing an example of the voltage threshold change control executed by the ECU. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [General configuration of hybrid vehicle] FIG. 1 is a schematic 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 provided in this order in a power transmission path from an engine 10 to wheels 13. The engine 10 and the motor 15 are mounted as a driving source for running the hybrid vehicle 1. The engine 10 is, for example, a V6 gasoline engine, but the number of cylinders is not limited thereto, and may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, the torque converter 18, and the automatic transmission 19 are provided in a 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 power transmission path. The K0 clutch 14 is switched to any one of an open state, a slip state, and an engaged state according to the supply of hydraulic pressure. In detail, when the K0 clutch 14 is in the open state, the K0 clutch 14 is switched to the slip state or the engaged state by the supply of hydraulic pressure, and the power transmission between the engine 10 and the motor 15 is connected. In addition, the K0 clutch 14 is switched to the open state according to the stop of the hydraulic pressure supply, and the power transmission between the engine 10 and the motor 15 is interrupted. The slip state is a state in which the engagement element of the K0 clutch 14 on the engine 10 side and the engagement element on the motor 15 side are in sliding contact with each other with a predetermined difference in rotation speed. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotation speed. The released state is a state in which both engagement 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 supplied from the battery 16, and also functions as a generator that generates electric power to charge the battery 16 in response to power transmission from the engine 10 and 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 the ECU 100 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 powering 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 regenerative operation in which the motor 15 generates power, 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 amplifying function. The automatic transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by changing 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 is supplied with hydraulic pressure and enters an engaged state to directly connect the motor 15 and the automatic transmission 19. The torque converter 18 is not necessarily provided.

[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 automatic transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for each of 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 the operating hydraulic pressures thereof.

[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 a calculation processing circuit that performs various calculation processes related to vehicle driving control, and a memory that stores control programs and data. The ECU 100 is an example of a control device for a hybrid vehicle, and functionally realizes a calculation unit and a threshold value changing unit, which will be described later.

[0016] The ECU 100 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the rotation speed and torque of the motor 15 by controlling the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16. The ECU 100 also controls the operation 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 100 receives signals from an ignition switch 71, a crank angle sensor 72, and a motor revolution speed sensor 73. The crank angle sensor 72 detects the rotation speed of a crankshaft of the engine 10. The motor revolution speed sensor 73 detects the rotation speed of an output shaft of the motor 15. The voltage sensor 74 detects the voltage of the battery 16.

[0018] The ECU 100 runs 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 the vehicle using the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. The hybrid mode includes a mode in which the vehicle runs using only the power of the engine 10, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 10 and the motor 15 as power sources.

[0019] The driving mode is switched based on the vehicle's required driving force calculated from the vehicle speed and accelerator opening, and the state of charge of the battery 16. For example, when the required driving force is relatively small and the SOC (State Of Charge) indicating the charge amount of the battery 16 is relatively high, the motor mode in which the engine 10 is 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 in which at least the engine 10 is driven is selected.

[0020] When there is a request to switch from the motor mode to the hybrid mode, when an automatic restart condition is satisfied during intermittent operation, etc., a request is made to start the engine 10. When there is a request to start the engine 10, the ECU 100 controls the K0 clutch 14 to a slip state to start cranking the engine 10 by the motor 15 and starts combustion in the engine 10.

[0021] [Voltage feedback control] When the output torque of the motor 15 increases, the power supplied from the battery 16 to the motor 15 increases, and this causes a temporary drop in the voltage of the battery 16. If the voltage of the battery 16 drops excessively, this may affect the performance of the battery 16. For this reason, when the voltage of the battery 16 detected by the voltage sensor 74 falls below a predetermined voltage threshold, the ECU 100 starts voltage feedback control to limit the output torque of the motor 15. The voltage feedback control is a control that limits the output torque of the motor 15 based on the deviation between the voltage of the battery 16 and a target voltage higher than the voltage threshold, so that the voltage of the battery 16 increases to the target voltage. Specifically, the output torque of the motor 15 is limited to a smaller value as the deviation increases. When the voltage of the battery 16 returns to the target voltage, the ECU 100 stops the voltage feedback control. This makes it possible to prevent the voltage of the battery 16 from dropping excessively to the extent that it affects the performance degradation of the battery 16. In addition, the ECU 100 changes the voltage threshold as follows.

[0022] [Voltage threshold change control performed by ECU] 2 is a flowchart showing an example of voltage threshold change control executed by the ECU 100. This control is repeatedly executed at predetermined intervals while the ignition is on. The ECU 100 determines whether or not there is a request to start the engine 10 (step S1). If the result in step S1 is No, this control is terminated.

[0023] If the answer is Yes in step S1, the ECU 100 calculates a cranking torque requirement value (step S2). The cranking torque requirement value is a torque required of the motor 15 to increase the rotation speed of the engine 10 to a target rotation speed. The target rotation speed is a rotation speed that is set when a start request is made for the engine 10, and is set to a higher value, for example, as the accelerator opening degree increases. If the rotation speed of the engine 10 when a start request is made is lower than the target rotation speed, the cranking torque requirement value is calculated to be a larger value as the difference between the two rotation speeds increases.

[0024] If the rotation speed at the time of a start request of the engine 10 is higher than the target rotation speed, the cranking torque request value is calculated as 0, and combustion in the engine 10 is started without cranking by the motor 15. For example, if the accelerator opening is reduced during operation of the engine 10 and combustion stops during coasting, and then the accelerator opening is increased again and a start request is made, the rotation speed at the time of the start request may be higher than the target rotation speed.

[0025] The cranking torque requirement value may be calculated by a theoretical formula or by referring to a map that specifies experimental values. The cranking torque requirement value may be calculated to be a larger value as the temperature of the coolant of the engine 10 is lower. This is because the lower the temperature of the coolant, the lower the temperature of the lubricating oil of the engine 10 and the larger the friction torque of the engine 10. Step S2 is an example of a process executed by the calculation unit.

[0026] Next, the ECU 100 determines whether or not the cranking torque requirement value is equal to or greater than a predetermined value T (step S3). The predetermined value T is calculated in advance by experiment, and is the minimum cranking torque value at which the voltage of the battery 16 may reach a value Va (described later) and voltage feedback control may be started when the engine 10 is cranked by the motor 15.

[0027] If the answer is No in step S3, the ECU 100 selects a value Va as the voltage threshold at which voltage feedback control starts (step S4). The value Va is a value that is higher than the lower voltage limit at which performance degradation of the battery 16 may occur by a predetermined margin. If the answer is Yes in step S3, the ECU 100 selects a value Vb as the voltage threshold at which voltage feedback control starts (step S5). The value Vb is a value smaller than the value Va, but a value higher than the above-mentioned lower voltage limit. Steps S4 and S5 are an example of processing executed by the threshold change unit.

[0028] In this way, by changing the voltage threshold to a small value when the cranking torque requirement value is equal to or greater than the predetermined value T, it is possible to prevent the voltage feedback control from being started. This makes it possible to prevent the output torque of the motor 15 from being limited by the voltage feedback control, resulting in a shortage of cranking torque. In this way, it is possible to ensure the startability of the engine 10.

[0029] Furthermore, the voltage threshold value at which the voltage feedback control starts is changed from value Va to value Vb only when there is a request to start the engine 10 and the cranking torque request value is large, equal to or greater than a predetermined value T. In other words, when the above conditions are not satisfied, the voltage threshold value Va is selected, and the battery 16 can be sufficiently protected.

[0030] In the above embodiment, the voltage feedback control has been described as an example of the control for limiting the output torque of the motor 15, but the invention is not limited to this. For example, the output torque of the motor 15 may be limited by a control for lowering the upper limit value of the output torque of the motor 15. In this case, when the cranking torque request value becomes equal to or greater than the upper limit value lowered by the above control, the voltage threshold value is changed from value Va to value Vb.

[0031] In the above embodiment, a hybrid vehicle is controlled by a single ECU 100, but this is not limited to the above. The above-mentioned control may be performed by multiple 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.

[0032] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0033] 10 Engine 13 wheels 14 K0 clutch 15 Motor 40 ECU (calculation section, threshold change section)

Claims

[Claim 1] A control device for a hybrid vehicle that is applied to a hybrid vehicle including a clutch and a motor that are provided in this order on a power transmission path from an engine to wheels, and a battery that supplies power to the motor, and that limits an output torque of the motor when a voltage of the battery is equal to or lower than a voltage threshold value, a calculation unit that calculates a cranking torque requirement value that is required of the motor when cranking the engine via the clutch; A control device for a hybrid vehicle comprising: a threshold changing unit that changes the voltage threshold to a smaller value when the cranking torque request value is equal to or greater than a predetermined value than when the cranking torque request value is less than the predetermined value.

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