Control method and control system of hybrid vehicle

Abstract

The present invention is a control method and control system for a hybrid vehicle that can ensure the responsiveness of engine starting and suppress vehicle impact by accurately controlling a first clutch provided between an engine and an electric motor when the engine of the hybrid vehicle is started. When an engine starting request is issued, when a target driving force is less than a specified value, a controller sets the indicated hydraulic pressure for a hydraulic control circuit to a holding hydraulic pressure at which the rising speed of the connection pressure when the first clutch starts to connect is less than a specified value and holds it for a specified time, then sets it to an engine starting hydraulic pressure that causes the first clutch to generate an engine starting connection pressure and holds it until the engine start is completed, then sets it to a maximum hydraulic pressure for setting the first clutch to a connected state, and when the target driving force is greater than a specified value, sets the indicated hydraulic pressure not to a holding hydraulic pressure but to an engine starting hydraulic pressure and holds it until the engine start is completed, then sets it to a maximum hydraulic pressure.

Description

Technical Field

[0001] The present invention relates to a control method and a control system for a hybrid vehicle having an engine as a power source, an electric motor, and a friction coupling unit (clutch) for switching transmission and disconnection of torque between the engine and the electric motor. Background Art

[0002] Conventionally, there is known a hybrid vehicle having an engine (internal combustion engine), an electric motor provided on the downstream side of the engine on a power transmission path to wheels, a first clutch provided between the engine and the electric motor so as to be connectable and disconnectable, and a second clutch provided between the electric motor and wheels (drive shafts) so as to be connectable and disconnectable. The hybrid vehicle is configured to switch between a driving mode (EV driving mode) in which the hybrid vehicle is driven by the torque of the electric motor instead of the torque of the engine and a driving mode (engine driving mode or hybrid driving mode) in which the hybrid vehicle is driven by at least the torque of the engine.

[0003] For example, regarding such a hybrid vehicle, Patent Document 1 discloses the following technology, in which when the engine is started during driving by the electric motor alone, the motor speed is increased while the slip of the second clutch (starting clutch) is controlled, and the first clutch (engine clutch) is connected when the motor speed reaches a specified speed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-255285

[0007] Technical problem to be solved by the invention

[0008] In the hybrid vehicle as described above, when the engine is stopped and started during driving, the first clutch provided between the engine and the electric motor is transferred from the released state to the connected state, so that the torque of the electric motor is transmitted to the engine via the first clutch, thereby starting the engine through the rotation of the electric motor.

[0009] When the connection pressure changes too rapidly when the first clutch is shifted from the released state to the connected state in order to start the engine, the impact on the vehicle (vehicle impact) caused by the decrease in the driving force accompanying the engine start becomes larger. On the other hand, when the connection pressure changes too slowly when the first clutch is shifted from the released state to the connected state, the time until the engine start is completed becomes longer, and the responsiveness of the engine start to the driver's request is deteriorated. Summary of the invention

[0010] The present invention is made to solve the problems of the above-mentioned prior art, and its purpose is to provide a control method and control system for a hybrid vehicle that can ensure the responsiveness of the engine start and suppress the vehicle impact by accurately controlling the first clutch provided between the engine and the electric motor when the engine of the hybrid vehicle is started.

[0011] Technical means for solving technical problems

[0012] In order to achieve the above-mentioned purpose, in the control method of a hybrid vehicle of the present invention, the hybrid vehicle has: an engine, an electric motor, a friction coupling unit arranged between the engine and the electric motor so as to be disconnected and connected by hydraulic pressure, and a hydraulic control circuit for controlling the hydraulic pressure applied to the friction coupling unit. The control method of the hybrid vehicle has the following steps: controlling the hydraulic pressure applied to the friction coupling unit so as to transfer the friction coupling unit from a released state to a specified sliding state or a connected state when a request to start the engine which is stopped is issued during the driving of the hybrid vehicle; and controlling the electric motor and the engine so as to start the engine by starting the electric motor during and / or after the control of the hydraulic pressure applied to the friction coupling unit. The step of controlling the hydraulic pressure applied to the friction coupling unit includes the following steps: Sequence: When a target driving force of a hybrid vehicle is less than a specified value, the indicated hydraulic pressure of the hydraulic control circuit is set to a first hydraulic pressure and maintained for a specified time, the first hydraulic pressure causing the rising speed of the connection pressure when the friction connection unit starts to be connected to be less than a specified value, and then the indicated hydraulic pressure is set to a second hydraulic pressure and maintained until the start of the engine is completed, the second hydraulic pressure causing the friction connection unit to generate an engine starting connection pressure for transmitting the torque required for starting the engine, and then the indicated hydraulic pressure is set to a third hydraulic pressure for setting the friction connection unit to a connected state; and when the target driving force of the hybrid vehicle is greater than a specified value, the indicated hydraulic pressure is not set to the first hydraulic pressure but to the second hydraulic pressure and maintained until the start of the engine is completed, and then the indicated hydraulic pressure is set to the third hydraulic pressure.

[0013] In the present invention thus constituted, when a request to start the engine is issued and the hydraulic pressure applied to the friction coupling unit is controlled, if the target driving force of the hybrid vehicle is less than a specified value, the indicated hydraulic pressure of the hydraulic control circuit is set to a first hydraulic pressure at which the rising speed of the connection pressure at the beginning of the connection of the friction coupling unit becomes less than a specified value and is maintained for a specified time, then the indicated hydraulic pressure is set to a second hydraulic pressure and maintained until the engine is started, and then the indicated hydraulic pressure is set to a third hydraulic pressure and the friction coupling unit is set to a connected state. Thus, when the target driving force is less than a specified value and it is necessary to give priority to suppressing the vehicle shock over the responsiveness of the engine starting, it is possible to suppress the occurrence of the vehicle shock when the friction coupling unit starts to connect in order to start the engine. On the other hand, in the case of a high response mode in which the target driving force is greater than a specified value, the indicated hydraulic pressure is set to the second hydraulic pressure instead of the first hydraulic pressure and is maintained until the engine is started. Thus, when the target driving force is greater than a predetermined value and it is necessary to give priority to improving the responsiveness of engine starting over suppressing the impact of the vehicle, the engine can be quickly cranked and started when the engine start request is issued, thereby ensuring the responsiveness of engine starting. Thus, according to the present invention, the responsiveness of engine starting can be ensured and the impact of the vehicle can be suppressed.

[0014] In the present invention, preferably, the step of controlling the hydraulic pressure applied to the friction coupling unit further includes the step of first setting the indicated hydraulic pressure to a fourth hydraulic pressure capable of causing the friction coupling unit to generate a connection pressure higher than the engine starting connection pressure and maintaining the pressure for a predetermined time when an engine starting request is issued.

[0015] According to the present invention configured as described above, hydraulic oil can be quickly supplied to the friction coupling unit immediately after a request to start the engine is issued, thereby improving the responsiveness of the friction coupling unit in subsequent control.

[0016] In the present invention, preferably, when the target driving force is equal to or greater than a predetermined value, the time during which the command hydraulic pressure is maintained at the fourth hydraulic pressure is longer than when the target driving force is less than the predetermined value.

[0017] According to the present invention configured as above, the responsiveness of the friction coupling unit can be further improved.

[0018] In the present invention, it is preferred that, in a process of controlling the hydraulic pressure applied to the friction coupling unit, when the target driving force of the hybrid vehicle is less than a specified value, after setting the indicated hydraulic pressure to the first hydraulic pressure and maintaining it for a specified time, before setting the indicated hydraulic pressure to the second hydraulic pressure, the indicated hydraulic pressure is set to a fifth hydraulic pressure for making the friction coupling unit standby in a state to be connected, and maintained until the specified conditions are met.

[0019] In the present invention thus constituted, when the engine startup needs to be put on standby until, for example, other equipment is ready, the friction coupling unit can be quickly connected to start the engine startup while the torque transmission between the motor and the engine is cut off after the other equipment is ready.

[0020] In the present invention, the friction coupling unit is a normally open clutch, and the command hydraulic pressure increases in the order of the third hydraulic pressure, the second hydraulic pressure, and the first hydraulic pressure.

[0021] Alternatively, in the present invention, the friction coupling unit is a normally closed clutch, and the command hydraulic pressure is sequentially reduced in the order of the third hydraulic pressure, the second hydraulic pressure, and the first hydraulic pressure.

[0022] In other viewpoints, in order to achieve the above-mentioned purpose, the control system of the hybrid vehicle of the present invention comprises: an engine and an electric motor; a friction coupling unit, which is arranged between the engine and the electric motor so as to be disconnected and connected by hydraulic pressure; a hydraulic control circuit, which controls the hydraulic pressure applied to the friction coupling unit; and a control device, which is configured to control the engine, the electric motor, the friction coupling unit and the hydraulic control circuit. The control device is configured so that when a request to start the stopped engine is issued during the driving of the hybrid vehicle, the control device controls the hydraulic pressure applied to the friction coupling unit so that the friction coupling unit is transferred from a released state to a specified sliding state or a connected state. During and / or after the control of the hydraulic pressure applied to the friction coupling unit, the control device controls the electric motor and the engine so as to start the engine by starting the electric motor. The control device The arrangement is such that, when controlling the hydraulic pressure applied to the friction coupling unit, if the target driving force of the hybrid vehicle is less than a specified value, the control device sets the indicated hydraulic pressure of the hydraulic control circuit to a first hydraulic pressure and maintains it for a specified time, the first hydraulic pressure causing the rising speed of the connection pressure when the friction coupling unit starts to be connected to be less than a specified value, and then sets the indicated hydraulic pressure to a second hydraulic pressure and maintains it until the start of the engine is completed, the second hydraulic pressure causing the friction coupling unit to generate an engine starting connection pressure for transmitting the torque required for starting the engine, and then sets the indicated hydraulic pressure to a third hydraulic pressure for setting the friction coupling unit to a connected state, and if the target driving force of the hybrid vehicle is greater than a specified value, the control device sets the indicated hydraulic pressure to the second hydraulic pressure instead of the first hydraulic pressure, and maintains it until the start of the engine is completed, and then sets the indicated hydraulic pressure to the third hydraulic pressure.

[0023] According to the present invention thus constituted, it is also possible to ensure the responsiveness of the engine start and suppress the vehicle shock.

[0024] Effects of the Invention

[0025] According to the control method and control system of the hybrid vehicle of the present invention, when the engine of the hybrid vehicle is started, the responsiveness of the engine start can be ensured and the vehicle shock can be suppressed by accurately controlling the first clutch provided between the engine and the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the configuration of a hybrid vehicle according to an embodiment of the present invention.

[0027] Figure 2 This is a block diagram showing the electrical configuration of a hybrid vehicle according to an embodiment of the present invention.

[0028] Figure 3 1 is a timing chart showing control of the first clutch according to the embodiment of the present invention.

[0029] Figure 4 1 is a timing chart showing control of the first clutch according to the embodiment of the present invention.

[0030] Figure 5 This is a flowchart showing the start-up control according to the embodiment of the present invention.

[0031] Explanation of symbols

[0032] 1 Hybrid vehicles

[0033] 2 Engine

[0034] 4 Electric motor

[0035] 5. Batteries

[0036] 6 Speed ​​changer

[0037] 8 Powertrain

[0038] 12 Wheels

[0039] 14 Hydraulic control circuit

[0040] 20 Controller (control device)

[0041] CL1 First Clutch (Friction Link Unit)

[0042] CL2 Second Clutch DETAILED DESCRIPTION

[0043] Hereinafter, a control method and a control system for a hybrid vehicle according to an embodiment of the present invention will be described with reference to the drawings.

[0044] [Device structure]

[0045] Figure 1 This is a schematic configuration diagram of a hybrid vehicle to which a control method and a control system for a hybrid vehicle according to an embodiment of the present invention are applied.

[0046] like Figure 1 As shown, the hybrid vehicle 1 mainly includes: an engine 2 (for example, a gasoline engine) that generates torque for driving the hybrid vehicle 1, an electric motor 4 that is arranged on the downstream side compared to the engine 2 on the power transmission path of the hybrid vehicle 1 and generates torque for driving the hybrid vehicle 1, a battery 5 that gives and receives electric power to and from the electric motor 4 via an inverter not shown, a transmission 6 that is arranged on the downstream side compared to the electric motor 4 on the power transmission path of the hybrid vehicle 1 and changes the rotation speed based on the engine 2 and / or the electric motor 4, a power transmission system 8 that transmits the torque from the transmission 6 to the downstream side, a drive shaft 10 that drives the wheel 12 by the torque from the power transmission system 8, and the wheel (drive wheel) 12.

[0047] The output shaft of the engine 2 and the rotating shaft of the motor 4 are connected to each other coaxially through the shaft AX1 via the first clutch CL1, and the first clutch CL1 can be disconnected and connected (disconnected and connected) by hydraulic pressure. Through the first clutch CL1 (friction connection unit), the transmission and disconnection of the torque between the engine 2 and the motor 4 can be switched. The first clutch CL1 is composed of a dry multi-plate clutch, a wet multi-plate clutch, etc., which can change the transmission torque capacity by continuously or step-by-step controlling the clutch working oil flow and / or the clutch working hydraulic pressure through the hydraulic control circuit 14. The first clutch CL1 is configured as a normally open clutch in a released state when no hydraulic pressure is applied or a normally closed clutch in a connected state when no hydraulic pressure is applied. In addition, the hydraulic control circuit 14 includes: a hydraulic pump driven by the engine 2 and an electric motor not shown, a solenoid valve for regulating the hydraulic pressure supplied to the first clutch CL1 and the second clutch CL2, and an oil circuit connecting each valve to the first clutch CL1 and the second clutch CL2.

[0048] The rotating shaft of the motor 4 and the rotating shaft of the transmission 6 are connected coaxially by the shaft AX2. The transmission 6 is typically an automatic transmission, which has one or more planetary gear sets including a sun gear S1, a ring gear R1, a pinion gear P1 (planetary gear) and a carrier C1, as well as a friction coupling unit such as a clutch and a brake, and has a function of automatically switching the gear stage (speed ratio) according to the vehicle speed, engine speed, etc. The ring gear R1 is arranged on a circle concentric with the sun gear S1, and the pinion gear P1 is arranged between the sun gear S1 and the ring gear R1 in a manner that meshes with the sun gear S1 and the ring gear R1. The carrier C1 keeps the pinion gear P1 so that it can rotate and revolve around the sun gear S1.

[0049] In addition, the transmission 6 is internally provided with a second clutch CL2 capable of disconnecting and connecting (cutting off and connecting), and through the second clutch CL2, the transmission and disconnection of the torque between the upstream side (engine 2 and motor 4) of the transmission 6 and the downstream side (wheels 12, etc.) of the transmission 6 can be switched. For example, the second clutch CL2 is also composed of a dry multi-plate clutch, a wet multi-plate clutch, etc., which can change the transmission torque capacity by continuously or step-by-step controlling the clutch working oil flow rate and / or the clutch working hydraulic pressure through the hydraulic control circuit 14.

[0050] In addition, the second clutch CL2 is actually composed of a plurality of clutches used to switch various gear stages in the transmission 6. Figure 1 In the figure, for simplicity, only one planetary gear set is shown, but in fact, the transmission 6 has a plurality of planetary gear sets. By selectively connecting a plurality of clutches represented by the second clutch CL2, a plurality of brakes not shown, and other friction coupling units, and switching the power transmission path through each planetary gear set, for example, a plurality of forward speed stages and a single reverse speed stage can be realized.

[0051] The power transmission system 8 receives torque via the output shaft AX3 of the transmission 6. The power transmission system 8 includes a differential gear that distributes driving force to a pair of left and right wheels 12, a final reduction gear, and the like.

[0052] The hybrid vehicle 1 can switch the driving mode by switching the connection and release of the first clutch CL1. That is, the hybrid vehicle 1 has a first driving mode, in which the first clutch CL1 is set to a released state, so that the hybrid vehicle 1 is driven by the torque of the motor 4 instead of the torque of the engine 2, and a second driving mode, in which the first clutch CL1 is set to a connected state, so that the hybrid vehicle 1 is driven by at least the torque of the engine 2. The first driving mode is a so-called EV driving mode, and the second driving mode includes an engine driving mode in which the hybrid vehicle 1 is driven by only the torque of the engine 2 and a hybrid driving mode in which the hybrid vehicle 1 is driven by the torque of both the engine 2 and the motor 4.

[0053] then, Figure 2 It is a block diagram showing the electrical configuration of a hybrid vehicle 1 according to the embodiment of the present invention.

[0054] like Figure 2As shown, a signal from an engine speed sensor SN1 for detecting the rotation speed of the engine 2, a signal from a motor speed sensor SN2 for detecting the rotation speed of the motor 4, a signal from a throttle opening sensor SN3 for detecting the throttle opening corresponding to the amount of depression of the accelerator pedal by the driver, a signal from a vehicle speed sensor SN4 for detecting the vehicle speed of the hybrid vehicle 1, a signal from an acceleration sensor SN5 for detecting the acceleration in the front and rear directions of the hybrid vehicle 1, and a signal from an SOC sensor SN6 for detecting the SOC (State of Charge) indicating the charging state of the battery 5 are input to the controller 20.

[0055] The controller 20 is composed of a computer having one or more processors 20a (typically a CPU), and a memory 20b such as a ROM and a RAM storing various programs interpreted and executed on the processor (including basic control programs such as an OS, and application programs that realize specific functions started on the OS), and various data. The controller 20 is equivalent to the "control device" in the present invention, and executes the "hybrid vehicle control method" in the present invention.

[0056] Specifically, the controller 20 outputs control signals mainly to the engine 2, the motor 4, and the hydraulic control circuit 14 based on the detection signals from the above-mentioned sensors SN1 to SN6, thereby controlling them. For example, the controller 20 controls the ignition timing, fuel injection timing, and fuel injection amount of the engine 2, the rotation speed and torque of the motor 4, and the hydraulic pressure applied to the first clutch CL1 and the second clutch CL2 from the hydraulic control circuit 14. In fact, the controller 20 controls the spark plug, fuel injection valve, throttle valve, etc. of the engine 2, controls the motor 4 via the inverter, and controls the motor, solenoid, etc. of the hydraulic control circuit 14.

[0057] [Control of hybrid vehicles]

[0058] Next, the control content performed by the controller 20 in this embodiment is described. In this embodiment, when a request to start the engine 2 is issued during driving in a state where the engine 2 is stopped, the controller 20 controls the hydraulic pressure applied to the first clutch CL1 through the hydraulic control circuit 14 so that the first clutch CL1 provided between the engine 2 and the motor 4 is transferred from a released state to a predetermined slip state or a connected state. As a result, the torque of the motor 4 is transmitted to the engine 2 via the first clutch CL1, so that the engine 2 is started by the motor 4, thereby starting the engine 2. In addition, when starting the engine 2 like this, the controller 20 transfers the second clutch CL2 provided between the motor 4 and the wheel 12 from a connected state to a predetermined slip state. As a result, the torque transmission via the second clutch CL2 between the power source (especially the engine 2) and the wheel 12 can be reduced as much as possible, thereby suppressing the impact (vehicle impact) generated in the hybrid vehicle 1 due to the torque transmission. For example, the vehicle impact includes the deceleration of the vehicle caused by the kinetic energy of the hybrid vehicle 1 being transmitted to the engine 2 side during driving for the engine to start.

[0059] In particular, in the present embodiment, when the controller 20 transfers the first clutch CL1 from the release state to the slip state or the connection state, the controller 20 changes the indicated hydraulic pressure for the hydraulic control circuit 14 according to whether the target driving force of the hybrid vehicle 1 set based on the driver's accelerator pedal operation and the driving conditions of the hybrid vehicle 1 (including vehicle speed, acceleration, gear stage, driving mode, etc.) is less than a specified value. Specifically, when the target driving force is less than the specified value (hereinafter referred to as "normal mode"), the controller 20 sets the indicated hydraulic pressure for the hydraulic control circuit 14 so that the first clutch CL1 is transferred from the release state to the specified slip state slowly, giving priority to suppressing the vehicle shock over the responsiveness of starting the engine 2. On the other hand, when the target driving force is greater than the specified value (hereinafter referred to as "high response mode"), the controller 20 sets the indicated hydraulic pressure for the hydraulic control circuit 14 so that the first clutch CL1 is transferred from the release state to the specified slip state more quickly than in the normal mode, giving priority to improving the responsiveness of starting the engine 2 over suppressing the vehicle shock. This makes it possible to achieve both ensuring the responsiveness of the engine start and suppressing the vehicle shock as required.

[0060] Next, refer to Figure 3 and Figure 4 Next, control of the first clutch CL1 according to the present embodiment will be described in detail. Figure 3 1 is a timing chart showing control of the normally open first clutch CL1 .

[0061] exist Figure 3In the figure, curve G1a represents the indicated hydraulic pressure when the hydraulic pressure applied to the first clutch CL1 is indicated to the hydraulic control circuit 14 in the normal mode, and curve G1b represents the actual hydraulic pressure applied to the first clutch CL1 in the normal mode. In addition, curve G1c represents the indicated hydraulic pressure when the hydraulic pressure applied to the first clutch CL1 is indicated to the hydraulic control circuit 14 in the high response mode, and curve G1d represents the actual hydraulic pressure applied to the first clutch CL1 in the high response mode.

[0062] In the normal mode, when the start request of the engine 2 is issued at time t11, the controller 20 temporarily raises the command hydraulic pressure for the hydraulic control circuit 14 to the pre-filling hydraulic pressure in a step-like manner from time t11 to t12. The pre-filling hydraulic pressure is the command hydraulic pressure (fourth hydraulic pressure) that enables the first clutch CL1 to generate a connection pressure higher than the engine start connection pressure for transmitting the torque required for starting the engine 2 when the actual hydraulic pressure of the first clutch CL1 reaches the pre-filling hydraulic pressure. In the case where the first clutch CL1 is a normally open clutch, the pre-filling hydraulic pressure is set according to the necessary flow rate when filling the hydraulic chamber of the first clutch CL1 with hydraulic oil. In addition, the time (time from time t11 to t12) for setting the command hydraulic pressure for the hydraulic control circuit 14 to the pre-filling hydraulic pressure is set based on the capacity of the hydraulic chamber of the first clutch CL1. In this way, by temporarily setting a relatively high command hydraulic pressure immediately after the start request of the engine 2 is issued, the hydraulic chamber of the first clutch CL1 can be quickly filled with hydraulic oil, and the responsiveness of the first clutch CL1 in the subsequent control can be improved.

[0063] After that, during the period from time t12 to t13, the controller 20 temporarily steps down the indicated hydraulic pressure for the hydraulic control circuit 14 to the holding hydraulic pressure. The holding hydraulic pressure is the indicated hydraulic pressure (first hydraulic pressure) at which the rising speed of the connection pressure becomes less than a predetermined value when the first clutch CL1 starts to connect in a state where the indicated hydraulic pressure for the hydraulic control circuit 14 is set to the holding hydraulic pressure. By setting the indicated hydraulic pressure in this way, the occurrence of vehicle shock when the first clutch CL1 starts to connect can be suppressed.

[0064] After that, during the period from time t13 to t14, the controller 20 temporarily steps down the indicated hydraulic pressure for the hydraulic control circuit 14 to the standby hydraulic pressure. The standby hydraulic pressure is the indicated hydraulic pressure (fifth hydraulic pressure) for making the first clutch CL1 standby in a state to be connected. By setting the indicated hydraulic pressure in this way, when it is necessary to wait for the start of the engine 2 until the preparation of other equipment is completed (for example, until the second clutch CL2 is transferred from the connected state to the specified slip state), the torque transmission between the motor 4 and the engine 2 can be cut off, and the first clutch CL1 can be quickly connected after the preparation of other equipment is completed to start the start of the engine 2.

[0065] Furthermore, when the preparation of other devices is completed at time t14, the controller 20 raises the indicated hydraulic pressure to the hydraulic control circuit 14 to the engine starting hydraulic pressure, and maintains the engine starting hydraulic pressure from time t15 to time t16 until the start of the engine 2 is completed. The engine starting hydraulic pressure is the indicated hydraulic pressure (second hydraulic pressure) for causing the first clutch CL1 to generate the engine starting connection pressure for transmitting the torque required for starting the engine 2. By setting the indicated hydraulic pressure in this way, the torque required for starting the engine 2 can be transmitted from the motor 4 to the engine 2 via the first clutch CL1, so that the engine 2 is started and started.

[0066] Afterwards, when the start of the engine 2 is completed at time t16, the controller 20 raises the indicated hydraulic pressure to the hydraulic control circuit 14 to the rotation synchronization hydraulic pressure, and maintains the rotation synchronization hydraulic pressure from time t17 to time t18 until the rotation speed of the engine 2 increases and the rotation speed difference between the motor 4 and the engine 2 becomes sufficiently small. The rotation synchronization hydraulic pressure is an indicated hydraulic pressure for applying a hydraulic pressure higher than the engine starting hydraulic pressure and lower than the maximum hydraulic pressure that can be applied to the first clutch CL1 to the first clutch CL1. By setting the indicated hydraulic pressure in this way, the first clutch CL1 is kept in a slipping state even after the start of the engine 2 is completed until the rotation speed difference between the engine 2 and the motor 4 becomes sufficiently small, thereby suppressing the occurrence of vehicle shock even when the rotation speed of the engine 2 increases excessively.

[0067] Afterwards, when the speed of the engine 2 increases at time t18 and the speed difference between the motor 4 and the engine 2 becomes sufficiently small, the controller 20 increases the indicated hydraulic pressure for the hydraulic control circuit 14 and sets the indicated hydraulic pressure to the maximum hydraulic pressure at time t19. The maximum hydraulic pressure is the indicated hydraulic pressure (third hydraulic pressure) for setting the first clutch CL1 to the connected state. By setting the indicated hydraulic pressure in this way, the output torque of the engine 2 is transmitted to the motor 4 side via the first clutch CL1.

[0068] On the other hand, in the case of the high response mode, when the start request of the engine 2 is issued at time t21, the controller 20 temporarily increases the command hydraulic pressure to the hydraulic control circuit 14 to the pre-charge hydraulic pressure in a step-like manner during the period from time t21 to t22, as in the case of the normal mode. Figure 3 The time for which the indicated hydraulic pressure is maintained as the pre-filling hydraulic pressure in the normal mode is substantially the same as the time for which the indicated hydraulic pressure is maintained as the pre-filling hydraulic pressure in the high response mode, but the time for which the indicated hydraulic pressure is maintained as the pre-filling hydraulic pressure in the high response mode may be longer than that in the normal mode. Thus, the responsiveness of the first clutch CL1 can be further improved.

[0069] After that, the controller 20 does not set the command hydraulic pressure for the hydraulic control circuit 14 to the holding hydraulic pressure or the standby hydraulic pressure, but lowers it stepwise to the engine starting hydraulic pressure, and maintains the engine starting hydraulic pressure from time t22 to time t23 until the start of the engine 2 is completed. By setting the command hydraulic pressure in this way, it is possible to give priority to improving the responsiveness of the start of the engine 2 over suppressing the vehicle impact, so that the engine 2 can be quickly cranked and started when the start request of the engine 2 is issued.

[0070] Afterwards, when the start of the engine 2 is completed at time t23, the controller 20 increases the command hydraulic pressure to the hydraulic control circuit 14 to the rotation synchronization hydraulic pressure as in the normal mode, and maintains the rotation synchronization hydraulic pressure from time t24 to time t25 until the rotation speed of the engine 2 increases and the rotation speed difference between the motor 4 and the engine 2 becomes sufficiently small. Afterwards, when the rotation speed of the engine 2 increases at time t25 and the rotation speed difference between the motor 4 and the engine 2 becomes sufficiently small, the controller 20 increases the command hydraulic pressure to the hydraulic control circuit 14 and sets the command hydraulic pressure to the maximum hydraulic pressure at time t26.

[0071] Figure 4 : is a timing chart showing the control of the normally closed first clutch CL1. Figure 4 In the figure, curve G1e represents the indicated hydraulic pressure when the hydraulic control circuit 14 is instructed to apply the hydraulic pressure to the first clutch CL1 in the normal mode, and curve G1f represents the actual hydraulic pressure applied to the first clutch CL1 in the normal mode. In addition, curve G1g represents the indicated hydraulic pressure when the hydraulic control circuit 14 is instructed to apply the hydraulic pressure to the first clutch CL1 in the high response mode, and curve G1h represents the actual hydraulic pressure applied to the first clutch CL1 in the high response mode.

[0072] In the normal mode, when a start request for the engine 2 is issued at time t31, the controller 20 temporarily drops the indicated hydraulic pressure for the hydraulic control circuit 14 to the pre-filling hydraulic pressure in a step-like manner during the period from time t31 to t32. In the case where the first clutch CL1 is a normally closed clutch, the pre-filling hydraulic pressure is set according to the necessary flow rate when the working oil is discharged from the hydraulic chamber of the first clutch CL1. In addition, the time (the time from time t31 to t32) for setting the indicated hydraulic pressure for the hydraulic control circuit 14 to the pre-filling hydraulic pressure is set based on the capacity of the hydraulic chamber of the first clutch CL1. In this way, immediately after the start request for the engine 2 is issued, by temporarily setting a relatively low indicated hydraulic pressure, the working oil can be quickly discharged from the hydraulic chamber of the first clutch CL1, thereby improving the responsiveness of the first clutch CL1.

[0073] Thereafter, during the period from time t32 to t33, the controller 20 temporarily increases the indicated hydraulic pressure to the hydraulic control circuit 14 in a step-like manner to the holding hydraulic pressure. By setting the indicated hydraulic pressure in this way, the occurrence of vehicle shock when the first clutch CL1 starts to be connected can be suppressed, similar to the case where the first clutch CL1 is a normally open clutch.

[0074] After that, during the period from time t33 to t34, the controller 20 temporarily raises the indicated hydraulic pressure to the hydraulic control circuit 14 in a step-like manner to the standby hydraulic pressure. By setting the indicated hydraulic pressure in this way, as in the case where the first clutch CL1 is a normally open clutch, when it is necessary to wait for the start of the engine 2 until the preparation of other equipment is completed (for example, until the second clutch CL2 is transferred from the connected state to a predetermined slip state), the torque transmission between the motor 4 and the engine 2 can be cut off, and the first clutch CL1 can be quickly connected after the preparation of other equipment is completed to start the start of the engine 2.

[0075] Then, when the preparation of other devices is completed at time t34, the controller 20 reduces the indicated hydraulic pressure to the hydraulic control circuit 14 to the engine starting hydraulic pressure, and maintains the engine starting hydraulic pressure from time t35 to time t36 until the starting of the engine 2 is completed. By setting the indicated hydraulic pressure in this way, the torque required for starting the engine 2 can be transmitted from the motor 4 to the engine 2 via the first clutch CL1, similarly to the case where the first clutch CL1 is a normally open clutch, so that the engine 2 is turned and started.

[0076] After that, when the start of the engine 2 is completed at time t36, the controller 20 reduces the command hydraulic pressure to the hydraulic control circuit 14, and sets the command hydraulic pressure to the minimum hydraulic pressure (at time t37). Figure 4 The minimum hydraulic pressure is an instruction hydraulic pressure (third hydraulic pressure) for setting the first clutch CL1 to the connected state. By setting the instruction hydraulic pressure in this way, the output torque of the engine 2 is transmitted to the motor 4 side via the first clutch CL1.

[0077] On the other hand, in the high response mode, when a request to start the engine 2 is issued at time t41, the controller 20 temporarily drops the command hydraulic pressure to the hydraulic control circuit 14 to the pre-charge hydraulic pressure in a step-like manner during the period from time t41 to t42, as in the normal mode.

[0078] After that, the controller 20 does not set the command hydraulic pressure for the hydraulic control circuit 14 to the holding hydraulic pressure or the standby hydraulic pressure, but increases it stepwise to the engine starting hydraulic pressure, and maintains the engine starting hydraulic pressure from time t42 to time t43 until the starting of the engine 2 is completed. By setting the command hydraulic pressure in this way, as in the case where the first clutch CL1 is a normally open clutch, it is possible to give priority to improving the responsiveness of the starting of the engine 2 over suppressing the vehicle shock, and to quickly start the engine 2 when the starting request of the engine 2 is issued.

[0079] Thereafter, when the start of the engine 2 is completed at time t43, the controller 20 reduces the command hydraulic pressure to the hydraulic control circuit 14 as in the normal mode, and sets the command hydraulic pressure to the minimum hydraulic pressure at time t44.

[0080] Next, refer to Figure 5 , the overall flow of the start control of the engine 2 according to the present embodiment will be described. Figure 5 2 is a flowchart showing the start-up control according to the present embodiment. This flow is repeatedly executed by the controller 20 in a predetermined cycle.

[0081] First, in step S100, the controller 20 acquires various information. Specifically, the controller 20 acquires detection signals from at least the sensors SN1 to SN6.

[0082] Next, in step S101, the controller 20 determines whether a start request for the currently stopped engine 2 has been issued. For example, the start request is issued when the driver requests a larger acceleration in EV mode (i.e., when the driver requests an acceleration that requires switching the driving mode from EV mode to HV mode). In addition to such a driver request, the start request is also issued from a control system including a power transmission system, etc. (hereinafter, the start request is appropriately referred to as a "system request"). The system request is issued when the driving mode of the hybrid vehicle 1 needs to be switched from EV mode to HV mode based on the vehicle speed, load, battery status, engine temperature, etc. The system request is issued, for example, when the driving force of the motor 4 alone is insufficient to achieve the target driving force, when the battery 5 needs to be charged (when the SOC of the battery 5 is less than a specified value), when the engine brake based on the engine 2 needs to be applied during deceleration, etc.

[0083] In step S101, if it is determined that a start request has not been issued (step S101: No), the controller 20 ends the processing related to the present start control. On the other hand, if it is determined that a start request has been issued (step S101: Yes), the controller 20 starts the transition of the second clutch CL2 from the connected state to the predetermined slip state, and proceeds to step S102. In step S102, the controller 20 sets the command hydraulic pressure for the hydraulic control circuit 14 to the pre-charge hydraulic pressure, and maintains it for a predetermined time.

[0084] Next, in step S103, the controller 20 determines whether a predetermined time has passed since the command hydraulic pressure for the hydraulic control circuit 14 was set as the pre-charging hydraulic pressure, and thus the pre-charging is completed. As a result, if the controller 20 determines that the predetermined time has passed and thus the pre-charging is completed (step S103: Yes), the controller 20 proceeds to step S104. On the other hand, if the controller 20 determines that the predetermined time has not passed and thus the pre-charging is not completed (step S104: No), the controller 20 returns to step S102. The controller 20 repeats the processing of steps S102 and S103 until the pre-charging is completed.

[0085] Next, in step S104, the controller 20 determines whether the target driving force of the hybrid vehicle 1 is less than a predetermined value, that is, whether it is in the normal mode. If the controller 20 determines that it is in the normal mode (step S104: Yes), the process proceeds to step S105.

[0086] In step S105, the controller 20 sets the command hydraulic pressure for the hydraulic control circuit 14 to the holding hydraulic pressure and keeps it for a predetermined time. Next, in step S106, the controller 20 determines whether a predetermined time has passed since the command hydraulic pressure for the hydraulic control circuit 14 was set to the holding hydraulic pressure. As a result, if the controller 20 determines that the predetermined time has passed (step S106: Yes), it proceeds to step S107. On the other hand, if the controller 20 does not determine that the predetermined time has passed (step S106: No), it returns to step S105. In this case, the controller 20 repeats the processing of steps S105 and S106 until the predetermined time has passed.

[0087] Next, in step S107, the controller 20 sets the command hydraulic pressure for the hydraulic control circuit 14 to the standby hydraulic pressure, and maintains it until the condition for completion of the standby is satisfied (for example, until the second clutch CL2 is transferred from the connected state to the prescribed slip state). Next, in step S108, the controller 20 determines whether the condition for completion of the standby is satisfied. As a result, when the condition for completion of the standby is satisfied (step S108: Yes), for example, when the second clutch CL2 is transferred from the connected state to the prescribed slip state, the controller 20 proceeds to steps S109 and S110. In contrast, when the controller 20 does not determine that the condition for completion of the standby is satisfied (step S108: No), it returns to step S107. In this case, the controller 20 repeats the processing of steps S107 and S108 until the condition for completion of the standby is satisfied.

[0088] In addition, when the controller 20 does not determine in the above step S104 that the target driving force of the hybrid vehicle 1 is less than the specified value in the normal mode (step S104: No), that is, when the target driving force of the hybrid vehicle 1 is in the high response mode above the specified value, the above-mentioned processing from steps S105 to S108 is omitted and the process proceeds to steps S109 and S110.

[0089] In step S109, the controller 20 controls the motor 4 to start the engine 2 by the rotation of the motor 4. Then, when the engine 2 is started, the controller 20 proceeds to step S112.

[0090] In addition, in parallel with the processing of the above-mentioned step S109, in step S110, the controller 20 sets the command hydraulic pressure for the hydraulic control circuit 14 to the hydraulic pressure for engine starting, and maintains it until the starting of the engine 2 is completed. Next, in step S111, the controller 20 determines whether the starting of the engine 2 is completed. As a result, if the starting of the engine 2 is completed (step S111: Yes), the controller 20 proceeds to step S112. On the other hand, if the controller 20 does not determine that the starting of the engine 2 is completed (step S111: No), it returns to step S110. In this case, the controller 20 repeats the processing of steps S110 and S111 until the starting of the engine 2 is completed.

[0091] Next, in step S112, the controller 20 sets the indicated hydraulic pressure for the hydraulic control circuit 14 to the hydraulic pressure for rotation synchronization, and maintains it until the rotation synchronization is completed (that is, the rotation speed of the engine 2 increases so that the rotation speed difference between the motor 4 and the engine 2 becomes sufficiently small). Next, in step S113, the controller 20 determines whether the rotation synchronization is completed. As a result, if the rotation synchronization is completed (step S113: Yes), the controller 20 proceeds to step S114. In contrast, if the controller 20 does not determine that the rotation synchronization is completed (step S113: No), it returns to step S112. In this case, the controller 20 repeats the processing of steps S112 and S113 until the rotation synchronization is completed.

[0092] Next, in step S114, the controller 20 sets the command hydraulic pressure to the hydraulic control circuit 14 to the maximum hydraulic pressure, thereby connecting the first clutch CL1. At the same time, the controller 20 also connects the second clutch CL2. Thereafter, the controller 20 ends the processing related to the present start control.

[0093] [Function and Effect]

[0094] Next, the operation and effects of the hybrid vehicle control method and control system according to the embodiment of the present invention will be described.

[0095] According to the present embodiment, when the start request of the engine 2 is issued and the hydraulic pressure applied to the first clutch CL1 is controlled, in the case of the normal mode in which the target driving force of the hybrid vehicle 1 is less than a predetermined value, the controller 20 sets the command hydraulic pressure for the hydraulic control circuit 14 to a holding hydraulic pressure at which the increase rate of the connection pressure at the start of the connection of the first clutch CL1 becomes less than a predetermined value and holds it for a predetermined time, then sets the command hydraulic pressure to an engine starting hydraulic pressure at which the first clutch CL1 generates an engine starting connection pressure for transmitting the torque required for starting the engine 2, and holds it until the start of the engine 2 is completed, and then sets the command hydraulic pressure to a maximum hydraulic pressure for setting the first clutch CL1 to the connected state. Thus, when the target driving force is less than a predetermined value and the responsiveness of suppressing the vehicle shock is required to be prioritized over the start of the engine 2, the generation of the vehicle shock when the first clutch CL1 starts to be connected in order to start the engine 2 can be suppressed. On the other hand, in the case of the high response mode in which the target driving force is greater than the specified value, the controller 20 does not set the indicated hydraulic pressure for the hydraulic control circuit 14 to the holding hydraulic pressure, but sets the indicated hydraulic pressure for the hydraulic control circuit 14 to the hydraulic pressure for engine starting, and maintains it until the start of the engine 2 is completed, and then sets the indicated hydraulic pressure to the maximum hydraulic pressure. Thus, when the target driving force is greater than the specified value and it is necessary to give priority to improving the responsiveness of the start of the engine 2 over suppressing the impact of the vehicle, the engine 2 can be quickly started and started when the start request of the engine 2 is issued, and the responsiveness of the engine start can be ensured. In this way, according to the present embodiment, the responsiveness of the engine start can be ensured, and the impact of the vehicle can be suppressed.

[0096] In addition, according to the present embodiment, when a request to start the engine 2 is issued, the controller 20 first sets the command hydraulic pressure to a pre-filling hydraulic pressure that can cause the first clutch CL1 to generate a connection pressure higher than the engine starting connection pressure, and maintains the pre-filling hydraulic pressure for a predetermined time. Thus, immediately after the request to start the engine 2 is issued, the hydraulic chamber of the first clutch CL1 can be quickly filled with hydraulic oil, thereby improving the responsiveness of the first clutch CL1 in subsequent control.

[0097] In the case of the high response mode, the responsiveness of the first clutch CL1 can be further improved by maintaining the command hydraulic pressure at the pre-fill hydraulic pressure for a longer period of time than the time of maintaining the command hydraulic pressure at the pre-fill hydraulic pressure in the normal mode.

[0098] In addition, according to the present embodiment, in the normal mode, after the controller 20 sets the indicated hydraulic pressure to the holding hydraulic pressure for a predetermined time, before setting the indicated hydraulic pressure to the engine starting hydraulic pressure, the controller sets the indicated hydraulic pressure to the standby hydraulic pressure for making the first clutch CL1 standby in a state to be connected, and maintains the state until the predetermined condition is satisfied. Thus, when it is necessary to make the start of the engine 2 standby until the preparation of other equipment is completed, the torque transmission between the motor 4 and the engine 2 can be cut off, and the first clutch CL1 can be quickly connected after the preparation of other equipment is completed to start the start of the engine 2.

Claims

1. A control method for a hybrid vehicle, the hybrid vehicle comprising: an engine, an electric motor, a friction coupling unit provided between the engine and the electric motor so as to be disconnectable and connectable by hydraulic pressure, and a hydraulic control circuit for controlling the hydraulic pressure applied to the friction coupling unit, characterized in that: The process is as follows: controlling the hydraulic pressure applied to the friction coupling unit so as to shift the friction coupling unit from a released state to a predetermined slip state or a coupled state when a request to start the engine which is stopped is issued while the hybrid vehicle is traveling; and The electric motor and the engine are controlled so that the engine is started by starting the electric motor during and / or after the control of the hydraulic pressure applied to the friction coupling unit. The step of controlling the hydraulic pressure applied to the friction coupling unit includes the following steps: In a case where the target driving force of the hybrid vehicle is less than a prescribed value, the indicated hydraulic pressure for the hydraulic control circuit is set to a first hydraulic pressure and maintained for a prescribed time, the first hydraulic pressure causing the increase speed of the connection pressure when the friction connection unit starts to be connected to be less than a prescribed value, and then the indicated hydraulic pressure is set to a second hydraulic pressure and maintained until the start of the engine is completed, the second hydraulic pressure causing the friction connection unit to generate an engine start connection pressure for transmitting a torque required for starting the engine, and then the indicated hydraulic pressure is set to a third hydraulic pressure for setting the friction connection unit to a connected state; and When the target driving force of the hybrid vehicle is equal to or greater than a predetermined value, the indicated hydraulic pressure is set to the second hydraulic pressure instead of the first hydraulic pressure and maintained until the engine is started, and then the indicated hydraulic pressure is set to the third hydraulic pressure.

2. The control method of a hybrid vehicle according to claim 1, characterized in that: The step of controlling the hydraulic pressure applied to the friction coupling unit further includes the step of first setting the command hydraulic pressure to a fourth hydraulic pressure capable of causing the friction coupling unit to generate a connection pressure higher than the engine starting connection pressure, and maintaining the pressure for a predetermined time when a request to start the engine is issued.

3. The control method of a hybrid vehicle according to claim 2, characterized in that: When the target driving force is equal to or greater than a predetermined value, the time during which the command hydraulic pressure is maintained at the fourth hydraulic pressure is longer than the time during which the command hydraulic pressure is maintained at the fourth hydraulic pressure when the target driving force is less than a predetermined value.

4. The control method for a hybrid vehicle according to any one of claims 1 to 3, characterized in that: In the process of controlling the hydraulic pressure applied to the friction coupling unit, when the target driving force of the hybrid vehicle is less than a specified value, after setting the indicated hydraulic pressure to the first hydraulic pressure and maintaining it for a specified time, before setting the indicated hydraulic pressure to the second hydraulic pressure, the indicated hydraulic pressure is set to a fifth hydraulic pressure that allows the friction coupling unit to stand by in a state to be connected, and maintained until a specified condition is met.

5. The control method for a hybrid vehicle according to any one of claims 1 to 3, characterized in that: The friction coupling unit is a normally open clutch, and the instruction hydraulic pressure increases in the order of the third hydraulic pressure, the second hydraulic pressure, and the first hydraulic pressure.

6. The control method of a hybrid vehicle according to claim 4, characterized in that: The friction coupling unit is a normally open clutch, and the instruction hydraulic pressure increases in the order of the third hydraulic pressure, the second hydraulic pressure, and the first hydraulic pressure.

7. The control method for a hybrid vehicle according to any one of claims 1 to 3, characterized in that: The friction coupling unit is a normally closed clutch, and the instruction hydraulic pressure decreases in the order of the third hydraulic pressure, the second hydraulic pressure, and the first hydraulic pressure.

8. The control method of a hybrid vehicle according to claim 4, characterized in that: The friction coupling unit is a normally closed clutch, and the instruction hydraulic pressure decreases in the order of the third hydraulic pressure, the second hydraulic pressure, and the first hydraulic pressure.

9. A control system for a hybrid vehicle, characterized in that: have: Engines and electric motors; a friction coupling unit provided between the engine and the electric motor so as to be disconnectable and connectable by hydraulic pressure; a hydraulic control circuit that controls hydraulic pressure applied to the friction coupling unit; and a control device configured to control the engine, the electric motor, the friction coupling unit, and the hydraulic control circuit; The control device is configured as follows: When a request to start the engine that is stopped is issued while the hybrid vehicle is traveling, the control device controls the hydraulic pressure applied to the friction coupling unit so that the friction coupling unit is transferred from a released state to a predetermined sliding state or a connected state. During and / or after the control of the hydraulic pressure applied to the friction coupling unit, the control device controls the electric motor and the engine so that the engine is started by the rotation of the electric motor. The control device is configured to, when controlling the hydraulic pressure applied to the friction coupling unit, When the target driving force of the hybrid vehicle is less than a prescribed value, the control device sets the indicated hydraulic pressure for the hydraulic control circuit to a first hydraulic pressure and maintains it for a prescribed time, wherein the first hydraulic pressure makes the rising speed of the connection pressure when the friction connection unit starts to be connected become less than a prescribed value, and then sets the indicated hydraulic pressure to a second hydraulic pressure and maintains it until the start of the engine is completed, wherein the second hydraulic pressure makes the friction connection unit generate an engine starting connection pressure for transmitting the torque required for starting the engine, and then sets the indicated hydraulic pressure to a third hydraulic pressure for setting the friction connection unit to a connected state, When the target driving force of the hybrid vehicle is equal to or greater than a predetermined value, the control device sets the indicated hydraulic pressure to the second hydraulic pressure instead of the first hydraulic pressure, maintains the setting until the engine is started, and then sets the indicated hydraulic pressure to the third hydraulic pressure.

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