Hybrid vehicle

Abstract

A hybrid vehicle includes an engine and an electric motor as driving power sources, a hydraulic clutch provided between the engine and the electric motor, an electric oil pump that supplies hydraulic pressure to the clutch, a mechanical oil pump that is interlocked with rotation of the electric motor and that supplies hydraulic pressure to the clutch, and a controller that controls the electric motor and the electric oil pump, wherein the controller includes a first control unit that increases a transmission torque capacity of the clutch to a first torque value by driving the electric oil pump when the engine and the electric motor are stopped and there is a request to start the engine, and a second control unit that starts the engine by driving the electric motor after the transmission torque capacity reaches the first torque value and increases the transmission torque capacity to a second torque value that is greater than the first torque value by driving the mechanical oil pump that is interlocked with the rotation of the electric motor.

Description

Technical Field

[0001] This invention relates to hybrid vehicles. Background Technology

[0002] Hybrid vehicles include: an electric hydraulic pump that supplies hydraulic pressure to a hydraulic type clutch located between an engine and an electric motor, which serve as the drive power source; and a mechanical hydraulic pump that is rotary interlocked with the electric motor and supplies hydraulic pressure to the clutch. When the engine starts in such a hybrid vehicle, hydraulic pressure is supplied to the clutch via the electric hydraulic pump, causing the clutch to engage. Subsequently, while the electric motor starts the engine, hydraulic pressure is supplied to the clutch via the mechanical hydraulic pump (see, for example, Japanese Unexamined Patent Application Publication No. 2019-209790).

[0003] An electric motor, as a driving power source, can start an engine. Therefore, an electric motor has a large output torque. A mechanical oil pump, rotary interlocked with this electric motor having a large output torque, can supply high hydraulic pressure to the clutch and can greatly increase the clutch's torque transmission capacity. Here, if the electric oil pump increases the clutch's torque transmission capacity to the same level as the mechanical oil pump before starting the engine, the electric oil pump's power consumption may increase. Summary of the Invention

[0004] Therefore, the object of the present invention is to provide a hybrid vehicle that suppresses the power consumption of the electric oil pump and is able to start the engine properly.

[0005] The aforementioned objective is achieved by a hybrid vehicle comprising: an engine and an electric motor as driving power sources; a hydraulic clutch disposed between the engine and the electric motor; an electric hydraulic pump supplying hydraulic pressure to the clutch; a mechanical hydraulic pump rotaryly interlocked with the electric motor and supplying hydraulic pressure to the clutch; and a controller controlling the electric motor and the electric hydraulic pump, wherein the controller comprises: a first control unit that, when the engine and the electric motor stop and there is a request to start the engine, increases the transmission torque capacity of the clutch to a first torque value by driving the electric hydraulic pump; and a second control unit that, after the transmission torque capacity reaches the first torque value, starts the engine by driving the electric motor and increases the transmission torque capacity to a second torque value greater than the first torque value by driving the mechanical hydraulic pump rotaryly interlocked with the electric motor.

[0006] The second control unit can gradually increase the output torque of the motor while increasing the transmitted torque capacity to a second torque value.

[0007] The magnitude of the first torque value can be 50% or less of the magnitude of the second torque value.

[0008] The first torque value can be less than the reaction torque value of the engine when the electric motor starts the engine, and the second torque value can be greater than the reaction torque value. Effects of the present invention

[0009] According to the present invention, a hybrid vehicle is provided that can suppress the power consumption of the electric oil pump and can properly start the engine. Attached Figure Description

[0010] Figure 1 This is a schematic configuration view of a hybrid vehicle; Figure 2 This is a timing diagram of the engine starting in the comparative example; Figure 3 This is a timing diagram of the engine starting process in this embodiment; and Figure 4 This is a flowchart illustrating an example of engine start control in this embodiment. Detailed Implementation

[0011] [Illustrative configuration of a hybrid vehicle] Figure 1 This is a schematic configuration view of a hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 and an electric motor 15 as the driving power source. The engine 10 is, for example, a gasoline engine, but it can also be a diesel engine. A transmission unit 11 is disposed on the power transmission path from the engine 10 to the wheels 13. The transmission unit 11 and the left and right wheels 13 are driven and connected via differential gears 12.

[0012] The transmission unit 11 is equipped with a K0 clutch 14 and an electric motor 15. In the transmission unit 11, the electric motor 15 is located on the power transmission path from the engine 10 to the wheels 13.

[0013] The K0 clutch 14 is positioned between the engine 10 and the electric motor 15 in the power transmission path. In the K0 clutch 14, the clutch piston moves against the force of the return spring due to the hydraulic pressure supplied from the electric oil pump 23 and the mechanical oil pump 24. The clutch piston presses one of the two rotatable friction plates against the other. As a result, friction is generated between the friction plates, preventing them from rotating relative to each other, thus engaging them. Here, the frictional force acting between the two friction plates changes according to the hydraulic pressure supplied to the K0 clutch 14, which alters the torque capacity that can be transmitted between the two friction plates. That is, the torque capacity of the K0 clutch 14 increases with the increase of the hydraulic pressure supplied to the K0 clutch 14. When the K0 clutch 14 is engaged, the engine 10 and the electric motor 15 are engaged, thereby transmitting power between them. When the hydraulic pressure supply to the K0 clutch 14 is stopped, the K0 clutch 14 is disengaged. As a result, the power transmission between the engine 10 and the electric motor 15 is interrupted.

[0014] Electric motor 15 is connected to main battery 16 via inverter 17. Electric motor 15 serves as an electric motor to generate driving force for the vehicle in response to power supplied from main battery 16. Electric motor 15 also serves as a generator to generate electricity to charge main battery 16 in response to power transmission from engine 10 and wheels 13. The power transmitted and received between electric motor 15 and main battery 16 is regulated by inverter 17.

[0015] An auxiliary battery 16a is connected to the main battery 16 via a DC / DC converter 17a. The DC / DC converter 17a reduces the high-voltage power of the main battery 16 and outputs the low-voltage power to the auxiliary battery 16a. The auxiliary battery 16a is a secondary battery such as a lead-acid battery. The auxiliary battery 16a is charged by the low-voltage power output from the DC / DC converter 17a. The auxiliary battery 16a supplies low-voltage power to the vehicle's auxiliary equipment. Auxiliary equipment includes an electric oil pump 23, an air conditioning compressor, headlights, etc., which will be described later.

[0016] The transmission unit 11 includes a torque converter 18 and an automatic transmission 19. The torque converter 18 is a fluid coupler with torque amplification. The automatic transmission 19 is a stepped automatic transmission that changes gear ratios in a stepped manner by switching gear stages. In the transmission unit 11, the automatic transmission 19 is positioned between the electric motor 15 and the wheels 13 in the power transmission path. The pump impeller 18a of the torque converter 18 is connected to the electric motor 15 and connected to the engine 10 via a K0 clutch 14. The turbine impeller 18b of the torque converter 18 is connected to the automatic transmission 19. The torque converter 18 is equipped with a lock-up clutch 20. The lock-up clutch 20 receives hydraulic pressure, thereby engaging to directly connect the electric motor 15 and the automatic transmission 19.

[0017] Furthermore, the transmission unit 11 is equipped with a hydraulic control mechanism 22, an electric hydraulic pump 23, and a mechanical hydraulic pump 24. Hydraulic pressure generated by the electric hydraulic pump 23 and the mechanical hydraulic pump 24 is supplied via the hydraulic control mechanism 22 to each of the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20. The hydraulic control mechanism 22 is equipped with hydraulic circuits for each of the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20, as well as various hydraulic control valves for controlling the hydraulic pressure supplied to them.

[0018] The electric hydraulic pump 23 is driven by receiving power from the auxiliary battery 16a and supplies hydraulic pressure to the K0 clutch 14, etc. The mechanical hydraulic pump 24 is connected to the pump impeller 18a of the torque converter 18. The pump impeller 18a is connected to the electric motor 15. Therefore, the pump impeller 18a also rotates along with the rotation of the electric motor 15. As a result, the mechanical hydraulic pump 24 is driven, and hydraulic pressure is supplied to the K0 clutch 14, etc. When the engine 10 is started by the electric motor 15, the electric hydraulic pump 23 and the mechanical hydraulic pump 24, described in detail later, supply hydraulic pressure to the K0 clutch 14 to maintain the engagement of the K0 clutch 14.

[0019] The hybrid vehicle 1 is equipped with an Electronic Control Unit (ECU) 30. The ECU 30 is an electronic control unit that includes arithmetic processing circuitry that performs various computational processes related to vehicle driving control and a memory that stores control programs and data. The ECU 30 is an example of a controller and functionally implements the first and second control units as described in detail later.

[0020] The ECU 30 controls the drive of the engine 10 and the electric motor 15. For example, the ECU 30 controls the torque of the engine 10 by controlling the throttle opening degree, ignition timing, and fuel injection quantity of the engine 10. Furthermore, the ECU 30 controls the inverter 17 to regulate the amount of power sent and received between the electric motor 15 and the main battery 16, thereby controlling the torque of the electric motor 15. Additionally, the ECU 30 controls the drive of the K0 clutch 14, the lock-up clutch 20, and the automatic transmission 19 by controlling the hydraulic control mechanism 22. The ECU 30 is input with signals from the ignition switch 31, an engine speed sensor 32 that detects the engine speed of the engine 10, and a throttle opening signal as determined by the driver's input to the accelerator pedal.

[0021] The ECU 30 can supply hydraulic pressure to the K0 clutch 14 by controlling the drive of the electric oil pump 23. In addition, the ECU 30 can control the hydraulic pressure supplied to the K0 clutch 14 via the mechanical oil pump 24 by controlling the output torque of the electric motor 15.

[0022] [Starting the engine in the comparison example] The starting of engine 10 in the comparative example will then be described. Figure 2 This is a timing diagram of starting engine 10 in the comparative example. Figure 2 This illustrates the changes in the supplied hydraulic pressure P [Pa], the transmitted torque capacity Tc [N·m], the electric motor output torque Tm [N·m], and the engine reaction torque Te [N·m]. Figure 2 In the diagram, the vertical axis represents torque and oil pressure, and the horizontal axis represents time. Here, the supply hydraulic pressure P is the pressure of the hydraulic oil supplied to the K0 clutch 14. The transmitted torque capacity Tc is the magnitude of the torque that can be transmitted between the engine 10 and the electric motor 15 via the K0 clutch 14. The electric motor output torque Tm is the torque output from the electric motor 15. The engine reaction torque Te will be described later. Furthermore, in... Figure 2 In the diagram, the hydraulic supply P is represented by a long dashed line, the transmitted torque capacity Tc is represented by a solid line, the motor output torque Tm is represented by a dotted dashed line, and the engine reaction torque Te is represented by alternating long and short dashed lines.

[0023] The engine reaction torque Te is a negative torque that acts to reduce the engine speed of the engine 10 when the electric motor 15 starts and stops the engine 10. The engine reaction torque Te mainly consists of the reaction force generated when air is compressed by the piston of the engine 10, the inertial torque generated when accelerating a rotating object, and the drag torque of each rotating component. When the electric motor 15 starts the engine 10, the engine reaction torque Te increases with the engine speed of the engine 10. The engine reaction torque Te reaches its maximum value Tem immediately before combustion in the engine 10 begins at a predetermined speed or higher. Afterward, the engine 10 begins to drive itself in a self-sustaining manner, and the engine reaction torque Te gradually decreases to zero. Therefore, in order to start the engine 10 by the electric motor 15, the output torque Tm of the electric motor needs to be greater than the maximum value Tem of the engine reaction torque Te.

[0024] like Figure 2 As shown, when the ignition switch 31 is turned on, the electric oil pump 23 is driven while the engine 10 and electric motor 15 are stopped, and the hydraulic pressure P supplied to the K0 clutch 14 begins to increase (time t1). Afterwards, the clutch piston overcomes the force of the return spring of the K0 clutch 14 and begins to drive (time t2), then the supplied hydraulic pressure P becomes substantially constant. Then, the clutch piston of the K0 clutch 14 presses one of the two friction plates against the other (time t3), the friction plates of the K0 clutch 14 come into contact with each other, which puts the K0 clutch 14 into the engaged state, and then the supplied hydraulic pressure P increases to its maximum value Pm (time t4). As a result, the transmitted torque capacity Tc also increases to its maximum value Tcm. Here, as... Figure 2 As shown, the maximum value Tcm is greater than the maximum value Ten of the engine reaction torque Te. In other words, when the supplied hydraulic pressure P increases to its maximum value Pm, the maximum value Tcm of the transmitted torque capacity Tc becomes greater than the maximum value Ten of the engine reaction torque Te.

[0025] Subsequently, the electric motor 15 starts, and its output torque Tm increases to the target torque Tmt for starting the engine 10. Then, the engine 10 begins to start via the K0 clutch 14 (time t5). As a result, the hydraulic pressure P supplied is maintained at its maximum value Pm through the electric oil pump 23 and the mechanical oil pump 24, which is rotary interlocked with the electric motor 15. Furthermore, the target torque Tmt of the electric motor output torque Tm is set to a value greater than the maximum value Tem of the engine reaction torque Te. Therefore, when the electric motor 15 starts the engine 10 and its speed reaches the speed at which the engine 10 can be driven in a self-sustaining manner, fuel injection and ignition begin (time t6), and then the engine 10 starts, gradually reducing the engine reaction torque Te.

[0026] In the comparative example above, before the electric motor 15 starts the engine 10, the electric oil pump 23 increases the transmitted torque capacity Tc to its maximum value Tcm. Therefore, the electric oil pump 23 consumes a large amount of electricity.

[0027] [In this embodiment, the engine is started] Figure 3 This is a timing diagram of starting engine 10 in this embodiment. Figure 3 Corresponding to Figure 2 In this embodiment, the electric hydraulic pump 23 increases the supplied hydraulic pressure P to a value Pn, which is less than the aforementioned maximum value Pm. Therefore, the transmitted torque capacity Tc increases to a value Tcn, which is less than the maximum value Tcm illustrated in the comparative example. Furthermore, although the transmitted torque capacity Tc of value Tcn causes the K0 clutch 14 to engage when the engine 10 and electric motor 15 are stopped, this value Tcn is less than the maximum value Tem of the engine reaction torque Te. Assuming that the engine starts without driving the mechanical hydraulic pump 24 when the transmitted torque capacity Tc is maintained at value Tcn, the K0 clutch 14 may slip when the engine reaction torque Te becomes value Tcn or greater. Therefore, it is difficult to increase the engine speed of 10 to a speed at which the engine 10 can be driven in a self-sustaining manner. The value Tcn is an example of the first torque value.

[0028] Similar to the comparative example, in this embodiment, the electric hydraulic pump 23 drives and increases the supply hydraulic pressure P (time t1), the piston of the K0 clutch 14 begins to drive (time t2), and then the piston presses one of the two friction plates against the other (time t3). Afterwards, the friction plates of the K0 clutch 14 come into contact with each other, which engages the K0 clutch 14 (time t4). Here, in this embodiment, as described above, the electric hydraulic pump 23 increases the supply hydraulic pressure P to a value Pn, and the transmitted torque capacity Tc also increases to a value Tcn.

[0029] Subsequently, when the electric motor 15 starts the engine 10 (time t5), in this embodiment, compared to the comparative example, the electric motor output torque Tm increases at a gradually increasing rate to the target torque Tmt. Specifically, although the electric motor output torque Tm and the transmitted torque capacity Tc remain greater than the engine reaction torque Te, the electric motor output torque Tm gradually increases to the target torque Tmt. The transmitted torque capacity Tc remains greater than the engine reaction torque Te, which prevents slippage of the K0 clutch 14. Furthermore, the electric motor output torque Tm remains greater than the engine reaction torque Te, which allows the engine 10 to start properly. As a result, while the engine 10 is starting, the electric oil pump 23 and the mechanical oil pump 24 increase the supplied hydraulic pressure P to its maximum value Pm, and the transmitted torque capacity Tc also increases to its maximum value Tcm.

[0030] When the speed of engine 10 increases to a speed at which engine 10 can drive itself in a self-sustaining manner, fuel injection and ignition are performed to start combustion in engine 10 (time t6), and then the engine reaction torque Te gradually decreases.

[0031] In this embodiment as described above, the electric motor 15 starts and starts the engine 10 even when the electric oil pump 23 increases the transmitted torque capacity Tc only to the value Tcn. Therefore, the power consumption of the electric oil pump 23 can be suppressed. For example, instead of the electric oil pump 23, a low-output electric oil pump or a small electric oil pump that can increase the transmitted torque capacity Tc only to the value Tcn can be used. By using a low-power electric oil pump, its manufacturing cost can be suppressed. Furthermore, by using a small electric oil pump, the space occupied by it in the hybrid vehicle 1 can be reduced.

[0032] Additionally, the value Tcn of the transmission torque capacity Tc is preferably 50% or less of the maximum value Tcm of the transmission torque capacity Tc. This effectively suppresses the power consumption of the electric oil pump 23.

[0033] Furthermore, in this embodiment as described above, compared to the comparative example, the output torque Tm of the electric motor gradually increases, causing the rotational speed of the already started engine 10 to gradually increase as well. This allows the maximum value Tem of the engine reaction torque Te to be suppressed to a lower level. In particular, this allows the inertial torque of the engine 10 to be suppressed to a lower level. Therefore, it is possible to prevent the K0 clutch 14 from slipping during startup and to suppress the power consumption of the electric motor 15 consumed by startup.

[0034] Furthermore, after the electric motor 15 starts, both the transmitted torque capacity Tc and the motor output torque Tm can be maintained at a value greater than the engine reaction torque Te, and the target torque Tmt of the motor output torque Tm can be set to a smaller value. Therefore, the power consumption of the electric motor 15 due to starting can be further suppressed.

[0035] exist Figure 3 In the example, the value of the transmitted torque capacity Tc, Tcn, is less than the maximum value of the engine reaction torque Te, Ten, but it is not limited to this. For example, as long as the value of the transmitted torque capacity Tc, Tcn, is less than the maximum value Tcm, the value of the transmitted torque capacity Tc, Tcn, can be greater than the maximum value of the engine reaction torque Te, Ten. In this case, compared with the comparative example where the electric oil pump 23 increases the transmitted torque capacity Tc to the maximum value Tcm, the power consumption of the electric oil pump 23 can also be suppressed.

[0036] exist Figure 3 In the example, the rate of increase from the motor output torque Tm to the target torque Tmt is constant, but it is not limited to this. The rate of increase can be changed as the motor output torque Tm increases.

[0037] Figure 4 This is a flowchart illustrating an example of engine starting control in this embodiment. With the ignition switch 31 on, this control is repeated. The ECU 30 determines whether the engine 10 and the electric motor 15 are stopped (step S1). If a negative determination is made in step S1, the control ends. If an affirmative determination is made in step S1, the ECU 30 determines whether there is a request to start the engine 10 (step S2). If a negative determination is made in step S2, the control ends.

[0038] When a positive determination is made in step S2, the ECU 30 drives the electric oil pump 23 (step S3) and determines whether a predetermined time has elapsed since the moment the electric oil pump 23 is driven (step S4). Here, the predetermined time is the time required from the moment the electric oil pump 23 begins to drive until the K0 clutch 14 engages and the transmitted torque capacity Tc reaches the value Tcn. This predetermined time is pre-calculated based on experimental results and stored in the memory of the ECU 30. When a negative determination is made in step S4, the process of step S3 continues. Steps S3 and S4 are examples of processes performed by the first control unit.

[0039] When a positive determination is made in step S4, the ECU 30 starts the engine 10 using the electric motor 15 (step S5). Specifically, as... Figure 3 As shown, the motor output torque Tm gradually increases to the target torque Tmt, so as to keep the motor output torque Tm and the transmitted torque capacity Tc greater than the engine reaction torque Te. The rate of increase of the motor output torque Tm is set to a value pre-calculated based on experimental results. Step S5 is an example of a process executed by the second control unit.

[0040] ECU 30 determines whether the engine speed of 10 exceeds a threshold (step S6). The threshold is set to the engine speed at which 10 can be driven in a self-sustaining manner. If a negative determination is made in step S6, the process in step S5 continues. If a positive determination is made in step S6, ECU 30 executes fuel injection and ignition in engine 10 to start combustion (step S7). Therefore, engine 10 starts in a self-sustaining manner. In this way, the power consumption of electric fuel pump 23 can be suppressed, and engine 10 can be started appropriately.

[0041] In this embodiment, the case where engine start control is performed by a single ECU 30 is illustrated, but it is not limited to this. For example, engine start control can be performed by an engine ECU that controls the engine 10, an electric motor ECU that controls the electric motor 15, a clutch ECU that controls the K0 clutch 14, and a hybrid power ECU that controls these ECUs.

[0042] While some embodiments of the invention have been described in detail, the invention is not limited to the specific embodiments, but can be modified or varied within the scope of the invention as claimed.

Claims

1. Hybrid vehicles, including: Engines and electric motors serve as driving power sources; A hydraulic clutch is disposed between the engine and the electric motor; An electric hydraulic pump supplies hydraulic pressure to the clutch; A mechanical oil pump is rotaryly interlocked with the electric motor and supplies hydraulic pressure to the clutch; as well as The controller controls the electric motor and the electric oil pump. in, The controller includes: The first control unit, when the engine and the electric motor stop and there is a request to start the engine, increases the transmission torque capacity of the clutch to a first torque value by driving the electric oil pump; and The second control unit, after the transmitted torque capacity reaches the first torque value, starts the engine by driving the electric motor, and increases the transmitted torque capacity to a second torque value greater than the first torque value by driving the mechanical oil pump, which is rotary interlocked with the electric motor. When the motor starts the engine, the second control unit gradually increases the output torque of the motor while increasing the transmission torque capacity to the second torque value, keeping the output torque of the motor and the transmission torque capacity greater than the reaction torque value of the engine.

2. The hybrid vehicle according to claim 1, wherein, The magnitude of the first torque value is 50% or less of the magnitude of the second torque value.

3. The hybrid vehicle according to claim 1 or 2, wherein, The first torque value is less than the reaction torque value of the engine when the electric motor starts the engine, and The second torque value is greater than the reaction torque value.

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