METHOD OF CONTROLLING HYBRID VEHICLE AND CONTROL SYSTEM

A method of controlling a hybrid vehicle including an engine, a motor, a starter, a friction engagement element provided between the engine and the motor, and a mechanical oil pump which is driven by the motor and supplies oil to the friction engagement element, is provided. When the friction engagement element is in a disengaged state, a first traveling mode using the motor is performed. When it is in an engaged state, a second traveling mode at least using the engine is performed. The method includes, when the first traveling mode is unperformable, starting the engine by the starter to perform the second traveling mode, activating the motor and performing a hydraulic pressure control for shifting the friction engagement element from the disengaged to engaged state after starting the engine. The hydraulic pressure control uses at least the hydraulic pressure from the mechanical oil pump driven by activating the motor.

TECHNICAL FIELD

The present disclosure relates to a method of controlling a hybrid vehicle provided with an engine and a motor as power sources, and a friction engagement element (clutch) which switches between transmission and interception of torque between the engine and the motor, and also relates to a control system therefor.

BACKGROUND OF THE DISCLOSURE

Conventionally, it is known that hybrid vehicles are provided with an engine (internal combustion engine), a motor (electric motor) provided downstream of the engine in a power transmission path to wheels, and a clutch (friction engagement element) provided between the engine and the motor so as to be connectable and disconnectable. This hybrid vehicle performs a first traveling mode in which the hybrid vehicle travels using torque of the motor without using torque of the engine (electric vehicle (EV) traveling mode) when the clutch is in a released (disengaged) state, and a second traveling mode in which the hybrid vehicle travels at least using the engine torque (engine traveling mode or hybrid traveling mode) when the clutch is in an engaged state.

For example, JP5980436B2 discloses a technique relevant to such a hybrid vehicle. In detail, this technique starts a motor after an engine is cold started, and continues a cold hydraulic pressure control for limiting a transmission to a low line pressure in order to suppress a discharge amount from an oil pump, until a clutch between the engine and the motor is engaged.

Although the hybrid vehicle described above fundamentally performs a first traveling mode using the torque of the motor during a startup of the vehicle without activating the engine in order to improve fuel efficiency, it performs a second traveling mode using the torque of the engine, when a battery which supplies electric power to the motor is low. Normally, when starting the engine in order to perform the second traveling mode, although the engine is started by the torque of the motor (i.e., by cranking with the motor), the motor may be unable to generate the torque required for starting the engine in the case where the battery is low as described above. Here, if the hybrid vehicle is provided with a starter in addition to the motor, the engine can be started appropriately by the starter, without activating the motor.

In this way, when the engine is started by the starter, by engaging the clutch provided between the engine and the motor (i.e., the clutch provided downstream of the engine in a power transmission path to wheels of the vehicle), engine power is transmitted to the wheels via the clutch and the motor. When starting the engine and transmitting the power to the wheels via the motor, in a situation where the motor is not activated because of the reason described above, the motor is also rotated by the rotation of the engine (eventually, when a motor rotational speed coincides with an engine speed, the engine power is transmitted to the wheels via the motor). At this time, the engine startability may be deteriorated by the engine torque being used for raising the motor rotational speed. In other words, the engine startability may be deteriorated by a torque difference between the engine and the motor. In the worst case, the engine may stall.

On the other hand, some hybrid vehicles may operate the clutch provided between the engine and the motor by using a hydraulic pressure from a mechanical oil pump which is driven by the motor. In such a hybrid vehicle, since the motor is not activated when the engine is started by the starter as described above, the controllability for engaging the clutch may be deteriorated because the mechanical oil pump does not operate appropriately.

SUMMARY OF THE DISCLOSURE

The present disclosure is made in view of solving the above-described problems of the conventional technique, and one purpose thereof is to provide a method of controlling a hybrid vehicle having a friction engagement element which is provided between an engine and a motor, and operates using hydraulic pressure from a mechanical oil pump driven by the motor, and to provide a control system therefor. When performing a traveling mode using the engine during a startup, the method suppresses deterioration of the engine startability, while securing the controllability of the friction engagement element.

In order to achieve the above-described purpose, the present disclosure provides a method of controlling a hybrid vehicle including an engine, a motor, a starter which starts the engine, a friction engagement element provided between the engine and the motor so as to be engageable and disengageable, and a mechanical oil pump which is driven by the motor and supplies oil to the friction engagement element. When the friction engagement element is in a disengaged state, a first traveling mode in which the hybrid vehicle travels using torque of the motor without using torque of the engine is performed, and when the friction engagement element is in an engaged state, a second traveling mode in which the hybrid vehicle travels at least using the torque of the engine is performed. The method includes determining whether the first traveling mode is performable during a startup of the hybrid vehicle, starting the engine by the starter to perform the second traveling mode, when the first traveling mode is determined to be unperformable, activating the motor after the starting the engine, and performing a hydraulic pressure control for applying a hydraulic pressure to the friction engagement element so that the friction engagement element shifts from the disengaged state to the engaged state after the starting the engine. The performing the hydraulic pressure control uses at least the hydraulic pressure from the mechanical oil pump driven by the activating the motor.

According to this configuration, during the startup of the hybrid vehicle, when it is determined that the first traveling mode using the torque of the motor is unperformable, the motor is activated after starting the engine by the starter in order to perform the second traveling mode, and the hydraulic pressure control for applying hydraulic pressure to the friction engagement element is performed so that it shifts from the disengaged state to the engaged state. Particularly, according to the present disclosure, the hydraulic pressure control is performed by at least using the hydraulic pressure from the mechanical oil pump driven by the activation of the motor.

By thus activating the motor before performing the hydraulic pressure control of the friction engagement element, the mechanical oil pump can be operated appropriately, and the controllability of the friction engagement element can be secured. Further, when controlling the friction engagement element in this way to shift it from the disengaged state to the engaged state (i.e., when transmitting the torque of the engine to the motor via the friction engagement element), since the motor is operated, the startability deterioration of the engine which is caused by the torque of the engine being used for raising the motor rotational speed (in other words, caused by a torque difference between the engine and the motor) can be suppressed, as compared with the case where the motor is not operated. Therefore, according to the present disclosure, when performing the second traveling mode using the engine during the startup of the vehicle, it can suppress the startability deterioration of the engine, and it can secure the controllability of the friction engagement element.

Further, according to the present disclosure, by activating the motor after the startup of the engine, it can shorten the operating time of the motor so that the power consumption of the battery is reduced.

The performing the hydraulic pressure control may be started substantially at the same time as the activation start of the motor.

According to this configuration, the friction engagement element can be promptly shifted from the disengaged state to the engaged state, as compared with the case where the hydraulic pressure control is started after the activation of the motor.

The hybrid vehicle may further include an electric oil pump which supplies oil to the friction engagement element, separately from the mechanical oil pump. The electric oil pump may be activated before the mechanical oil pump is activated, and the hydraulic pressure control may be performed using the hydraulic pressure from the electric oil pump.

According to this configuration, the electric oil pump is activated before the mechanical oil pump is activated, and the hydraulic pressure control is performed using the hydraulic pressure from the electric oil pump. Therefore, the friction engagement element can be promptly shifted from the disengaged state to the engaged state, as compared with the case where only the mechanical oil pump is used.

The electric oil pump may be smaller than the mechanical oil pump.

According to this configuration, by using the small electric oil pump, an improvement in mountability, a simplification of the configuration, and power saving can be realized.

Meanwhile, in the above-described configuration, in other words, the electric oil pump discharges a smaller amount of oil than the mechanical oil pump. Thus, it is difficult to perform a precise hydraulic pressure control using the oil supplied from the electric oil pump. However, since the precise control is not required at the beginning of the hydraulic pressure control using the electric oil pump, the electric oil pump can still fully satisfy the control demand. In a subsequent stage which requires the precise control, the mechanical oil pump which can perform the precise control can certainly satisfy the control demand.

The friction engagement element may have a hydraulic chamber into which oil is introduced, and become in one of the engaged state and the disengaged state according to the oil introduced into the hydraulic chamber. When the performing the hydraulic pressure control is started, the hydraulic chamber of the friction engagement element may be filled up with the oil at least using the hydraulic pressure from the electric oil pump.

According to this configuration, the hydraulic chamber of the friction engagement element is filled up (precharged) with oil by using at least the hydraulic pressure from the electric oil pump, during the start of the hydraulic pressure control. Therefore, the precharge can be performed appropriately by the electric oil pump during the start of hydraulic pressure control at which the mechanical oil pump is not fully activated.

The method may further include temporarily activating the electric oil pump before the starting the engine so that at least a hydraulic system which supplies oil to the friction engagement element is filled up with oil.

According to this configuration, by temporarily activating the electric oil pump before the startup of the engine (i.e., immediately after the start of the hybrid vehicle), the oil can be filled up in advance inside the hydraulic system which supplies the oil to the friction engagement element, etc. Therefore, the subsequent hydraulic pressure control of the friction engagement element can be started promptly.

The electric oil pump may suspend the supply of oil to the friction engagement element after the activation of the mechanical oil pump.

According to this configuration, the power consumption by the electric oil pump can be reduced.

In another aspect, in order to achieve the above-described purpose, the present disclosure provides a control system for a hybrid vehicle including an engine, a motor, a starter which starts the engine, a friction engagement element provided between the engine and the motor so as to be engageable and disengageable, a mechanical oil pump which is driven by the motor and supplies oil to the friction engagement element, and a control device which controls the engine, the starter, the motor, and the friction engagement element. When the friction engagement element is in a disengaged state, the control device performs a first traveling mode in which the hybrid vehicle travels using torque of the motor without using torque of the engine. When the friction engagement element is in an engaged state, the control device performs a second traveling mode in which the hybrid vehicle travels at least using the torque of the engine. The control device further determines whether the first traveling mode is performable during a startup of the hybrid vehicle, starts the engine by the starter to perform the second traveling mode, when the first traveling mode is determined to be unperformable, activates the motor after the startup of the engine, and performs a hydraulic pressure control for applying a hydraulic pressure to the friction engagement element so that the friction engagement element shifts from the disengaged state to the engaged state after the startup of the engine. The control device further performs the hydraulic pressure control at least using the hydraulic pressure from the mechanical oil pump driven by the activation of the motor.

Also according to this configuration, when performing the second traveling mode using the engine during the startup of the vehicle, the startability deterioration of the engine can be suppressed, and the controllability of the friction engagement element can be secured.

DETAILED DESCRIPTION OF THE DISCLOSURE

Hereinafter, a method of controlling a hybrid vehicle according to one embodiment of the present disclosure, and a control system therefor, will be described with reference to the accompanying drawings.

Device Configuration

FIG.1is an outline block diagram of the hybrid vehicle to which the method of controlling the hybrid vehicle according to this embodiment of the present disclosure is applied, and the control system therefor.

As illustrated inFIG.1, a hybrid vehicle1mainly includes an engine2(for example, a gasoline engine) which generates a torque for driving or propelling the hybrid vehicle1, a starter3which is a motor for starting the engine2, a motor4which is provided downstream of the engine2in a power transmission path of the hybrid vehicle1, and generates the torque for driving the hybrid vehicle1, a battery5which delivers and receives electric power to and from the motor4via an inverter (not illustrated), a transmission6which is provided downstream of the motor4in the power transmission path of the hybrid vehicle1, and changes an engine speed of the engine2and/or a rotational speed of the motor4, a power transmission system8which transmits a torque from the transmission6to a downstream side thereof, a drive shaft10which drives wheels12by the torque from the power transmission system8, and the wheels (driving wheels)12.

An output shaft of the engine2and a rotational shaft of the motor4are coaxially coupled to each other by an axis AX1via a first clutch CL1which is connectable and disconnectable (engageable and disengageable). This first clutch CL1switches between transmission and interception of the torque between the engine2and the motor4. For example, the first clutch CL1is comprised of a dry multiplate clutch or a wet multiplate clutch which controls continuously or stepwisely a clutch operating fluid flow rate and/or a clutch operating fluid pressure by a motor or a solenoid (not illustrated) and is able to change a transmitting torque capacity.

Here, referring toFIG.2, a concrete structure of the first clutch CL1is described.FIG.2is an outline block diagram illustrating one example of the first clutch CL1. As illustrated inFIG.2, the first clutch CL1includes a hydraulic chamber15ainto which oil is introduced, an oil passage15b(see an arrow A1) which supplies oil to the hydraulic chamber15a, a clutch piston15c(see an arrow A2) which operates according to the oil supplied to the hydraulic chamber15a(i.e., hydraulic pressure), a first clutch plate15dwith which the clutch piston15ccontacts, a second clutch plate15ewhich becomes transmittable of a torque with the first clutch plate15dwhen the clutch piston15ccontacts the first clutch plate15d, and a solenoid15fwhich is provided to the oil passage15band is adjustable of the hydraulic pressure supplied to the hydraulic chamber15a.

The first clutch CL1is able to change, by controlling the hydraulic pressure applied, between a released or disengaged state where the clutch piston15cseparates from the first clutch plate15d, and an engaged state where the clutch piston15ccontacts the first clutch plate15d. In the disengaged state of the first clutch CL1, the torque transmission between the engine2and the motor4is intercepted, and in the engaged state of the first clutch CL1, the torque is transmitted between the engine2and the motor4. Although this engaged state is the state where the clutch piston15cis in contact with the first clutch plate15das described above, this state includes a slip state where the first clutch plate15dand the second clutch plate15eslip (typically, a state where the first clutch plate15dand the second clutch plate15eseparate from each other, and the torque is transmitted via oil therebetween), and a fully engaged state where the torque is fully transmitted between the first clutch plate15dand the second clutch plate15e(fundamentally, a state where the first clutch plate15dand the second clutch plate15econtact each other firmly). Note that such a first clutch CL1is one example of a “friction engagement element” in the present disclosure.

Returning toFIG.1, the rotational shaft of the motor4and the rotational shaft of the transmission6are coaxially coupled to each other via an axis AX2. Typically, the transmission6includes therein one or more planetary gear sets having a sun gear S1, a ring wheel R1, a pinion gear P1(planet gear), and a carrier C1, and a friction engagement element, such as a clutch and a brake, and is an automatic transmission having a function for automatically switching a gear stage (gear ratio) according to a vehicle traveling speed, an engine speed, etc. The ring wheel R1is disposed coaxially with the sun gear S1, and the pinion gear P1is disposed between the sun gear S1and the ring wheel R1so that it meshes with the sun gear S1and the ring wheel R1. The carrier C1holds the pinion gear P1so as to be rotatable, and so as to be able to revolve around the sun gear S1.

Further, the transmission6includes therein a second clutch CL2which is connectable and disconnectable (engageable and disengageable), and the second clutch CL2switches between transmission and interception of a torque between the upstream side of the transmission6(the engine2and the motor4) and the downstream side of the transmission6(the wheel12, etc.). For example, the second clutch CL2is comprised of a dry multiplate clutch or a wet multiplate clutch which controls continuously or stepwisely the clutch operating fluid flow rate and/or the clutch operating fluid pressure by the motor and the solenoid (not illustrated) and is changeable of the transmitting torque capacity. Further, the second clutch CL2is also able to switch a state between a released or disengaged state and an engaged state (a slip state or a fully engaged state) by controlling the hydraulic pressure applied.

Note that, in fact, the second clutch CL2is comprised of a large number of clutches which are used to variously switch the gear stage of the transmission6. Further, although inFIG.1only one planetary gear set is illustrated for simplification, the transmission6is actually provided with a plurality of planetary gear sets. For example, by selectively engaging the friction engagement elements, such as a plurality of clutches which are represented by the second clutch CL2, and a plurality of brakes (not illustrated), and switching the power transmission path passing through the planetary gear sets, a plurality of forward gear stages and one reverse gear stage can be realized.

A torque is inputted into the power transmission system8via an output axis AX3of the transmission6. The power transmission system8is comprised of a differential gear which distributes a driving force to a pair of left and right wheels12, and a final gear.

Further, the hybrid vehicle1includes a mechanical oil pump17which supplies oil to the first clutch CL1and the second clutch CL2by being driven by the motor4(in detail, it is coupled to an axis AX2immediately downstream of the motor4to be driven by the motor4), an electric oil pump18which supplies oil to the first clutch CL1and the second clutch CL2by being driven by electric power from the battery5, a hydraulic system19which is provided with a hydraulic circuit, a solenoid valve, etc., and supplies oil from the mechanical oil pump17and the electric oil pump18to the first clutch CL1and the second clutch CL2. The electric oil pump18is configured smaller than the mechanical oil pump17. In other words, the electric oil pump18is smaller in the discharge amount of oil than the mechanical oil pump17.

The hydraulic system19has a shift valve19awhich is able to switch its state so that oil is supplied from either one of the mechanical oil pump17and the electric oil pump18. When oil at a sufficient hydraulic pressure is supplied from the mechanical oil pump17, this shift valve19aintercepts an oil passage for supplying oil from the electric oil pump18. In more detail, in a case where both the mechanical oil pump17and the electric oil pump18operate, when the mechanical oil pump17does not generate the sufficient hydraulic pressure (for example, when the operation of the motor4which drives the mechanical oil pump17is started), the shift valve19amakes oil from both the mechanical oil pump17and the electric oil pump18flow downstream, and when the mechanical oil pump17generates the sufficient hydraulic pressure, it intercepts the oil passage from the electric oil pump18and makes only the oil from the mechanical oil pump17flow downstream. Note that, actually, the hydraulic system19supplies oil also from other than the mechanical oil pump17and the electric oil pump18, and supplies oil to other than the first clutch CL1and the second clutch CL2.

Here, a traveling mode of the hybrid vehicle1is changeable by switching engagement and release of the first clutch CL1. That is, the hybrid vehicle1has a first traveling mode in which the first clutch CL1is set to the disengaged state and the travel hybrid vehicle1travels using the torque of the motor4, without using the torque of the engine2, and a second traveling mode in which the first clutch CL1is set to the engaged state, and the hybrid vehicle1travels at least using the torque of the engine2. The first traveling mode is a so-called electric vehicle (EV) traveling mode, and the second traveling mode includes an engine traveling mode in which the hybrid vehicle1travels only using the torque of the engine2, and a hybrid traveling mode in which the hybrid vehicle1travels using the torques of both the engine2and the motor4.

Next,FIG.3is a block diagram illustrating an electric configuration of the hybrid vehicle according to this embodiment of the present disclosure.

As illustrated inFIG.3, a signal from an engine speed sensor SN1which detects an engine speed of the engine2, a signal from a motor rotational speed sensor SN2which detects a rotational speed of the motor4, a signal from an accelerator opening sensor SN3which detects an accelerator opening corresponding to a depressing amount of an accelerator pedal by a vehicle driver, a signal from a start switch SN4for starting the hybrid vehicle1, and a signal from an SOC sensor SN5which detects an SOC (State of Charge) indicative of a charged amount of the battery5, are inputted into a controller20.

The controller20is comprised of a computer provided with one or more processors20a(typically, central processing units (CPUs)), and memory20b, such as ROM and RAM, which stores various kinds of programs interpreted and executed by the processors (including a basic control program, such as an operating system (OS), and an application program which is booted on the OS and realizes a specific function), and various kinds of data. The controller20is one example of a “control device” in the present disclosure, and performs a “method of controlling a hybrid vehicle” in the present disclosure.

In detail, the controller20outputs a control signal mainly to the engine2, the starter3, the motor4, the first clutch CL1, the second clutch CL2, and the electric oil pump18to control them based on the signals from the sensors (including the switch) SN1-SN5described above. For example, the controller20performs a control for adjusting an ignition timing, a fuel injection timing, a fuel injection amount of the engine2, a control for adjusting a rotational speed and a torque of the motor4, a hydraulic pressure control for switching states of the first and second clutches CL1and CL2(a disengaged state, a slip state, and a fully engaged state), a control for switching ON/OFF of the electric oil pump18, etc. Actually, the controller20controls a spark plug, a fuel injection valve, and a throttle of the engine2, controls the motor4via an inverter, and controls the first and second clutches CL1and CL2via a hydraulic control circuit (the motor, the solenoid15f, etc.).

Content of Control

Next, the controls performed by the controller20in this embodiment are described. In this embodiment, during a startup of the hybrid vehicle1by the driver operating the start switch SN4, when the first traveling mode using the torque of the motor4is unperformable (typically, when the SOC of the battery5is below a given value), the controller20activates the motor4, after starting the engine2by the starter3, in order to perform the second traveling mode, and performs a hydraulic pressure control for applying a hydraulic pressure to the first clutch CL1so that it shifts from the disengaged state to the engaged state. Below, such a control performed during the startup of the hybrid vehicle1is referred to as “vehicle startup control.” Particularly, in this embodiment, the controller20performs the hydraulic pressure control for shifting the first clutch CL1from the disengaged state to the engaged state, by at least using the hydraulic pressure from the mechanical oil pump17driven by the activation of the motor4, when performing the vehicle startup control.

According to this embodiment, by activating the motor4before performing the hydraulic pressure control of the first clutch CL1, the mechanical oil pump17can be operated appropriately, and the controllability of the first clutch CL1can be secured. Further, when controlling the first clutch CL1in this way to shift it from the disengaged state to the engaged state (i.e., when transmitting the torque of the engine2to the motor4via the first clutch CL1), since the motor4is operated, the startability deterioration of the engine2which is caused by the torque of the engine2being used for raising the motor rotational speed can be suppressed, as compared with the case where the motor4is not operated.

Further, in this embodiment, the controller20activates the electric oil pump18before the mechanical oil pump17is activated, and performs the above-described hydraulic pressure control using the hydraulic pressure from the electric oil pump18. Therefore, the first clutch CL1can be promptly shifted from the disengaged state to the engaged state, as compared with the case where only the mechanical oil pump17is used. Since the supply of oil from the electric oil pump18activated in this way to the first clutch CL1is suspended by the above-described shift valve19aof the hydraulic system19after the mechanical oil pump17is fully activated, the power consumption thereafter by the electric oil pump18can be reduced.

Further, in this embodiment, the controller20mainly uses the oil supplied to the first clutch CL1from the electric oil pump18activated as described above for the oil filling (precharge) to the hydraulic chamber15aof the first clutch CL1which is made when the hydraulic pressure control is started. Since the electric oil pump18is less in the oil discharging amount than the mechanical oil pump17, it is difficult to perform a precise hydraulic pressure control using the oil supplied from the electric oil pump18. However, since the precise control is not required during the start of the hydraulic pressure control at which the precharge is carried out, the electric oil pump18can also fully satisfy the control demand. Further, in a stage after the precharge where the precise control is required in the hydraulic pressure control (for example, a stage where the clutch piston15cis moved inside the first clutch CL1to bring it into contact with the first clutch plate15d), since the mechanical oil pump17which can perform the precise control is fully activated, the mechanical oil pump17can certainly satisfy the control demand.

Next, referring toFIG.4, the vehicle startup control according to this embodiment is described concretely.FIG.4is a time chart illustrating the vehicle startup control according to this embodiment.

InFIG.4, a graph G11illustrates an engine speed, a graph G12illustrates a motor rotational speed, a graph G21illustrates a command value (indicated hydraulic pressure) of the hydraulic pressure given to the first clutch CL1in the hydraulic pressure control (hereinafter, referred to as “CL1hydraulic pressure”), a graph G22illustrates an actual hydraulic pressure of the CL1hydraulic pressure when applying the indicated hydraulic pressure, a graph G31illustrates an operating state (ON/OFF) of the electric oil pump18, a graph G32illustrates an operating state (ON/OFF) of the mechanical oil pump17, and a graph G4illustrates an output torque of the motor4(motor torque).

Note that ON/OFF of the electric oil pump18means existence/non-existence of the supply of oil from the electric oil pump18to the first clutch CL1, and does not necessarily correspond to activation/inactivation of the electric oil pump18. Even if the electric oil pump18does not supply oil to the first clutch CL1, the electric oil pump18may operate, and, in this case, the electric oil pump18may supply oil to components other than the first clutch CL1(for example, it may supply oil for lubricating those components).

First, at time t0, the driver operates the start switch SN4to start the hybrid vehicle1. At time t1immediately thereafter, the controller20temporarily activates the electric oil pump18so that the hydraulic system19which supplies oil to various components, such as the first clutch CL1and the second clutch CL2, is filled up with oil (graph G31). Then, at time t2, since the SOC of the battery5is below the given value, the controller20determines that the first traveling mode is unperformable, and starts the engine2by the starter3to perform the second traveling mode (graph G11).

Then, when the engine2is started (in detail, the engine speed reaches a given idling speed), the controller20starts the activation of the motor4at time t3. Therefore, the motor rotational speed and the motor torque rise gradually (graphs G12and G4). Note that in the state where the SOC of the battery5is below the given value as described above, the motor4cannot be activated to perform the first traveling mode, but the motor4can be activated to raise the motor rotational speed.

Further, substantially at the same time as such an activation of the motor4, the controller20starts activating the electric oil pump18(graph G31), and in order to start the hydraulic pressure control for shifting the first clutch CL1from the disengaged state to the engaged state, it sets the solenoid15fas “open” so that oil is supplied to the first clutch CL1(not illustrated inFIG.4). Although the motor4starts operating promptly after an activation command is issued, since the solenoid15fof the first clutch CL1takes more time than the motor4until it starts operating after the command is issued, the hydraulic pressure control of the first clutch CL1starts (in detail, the indicated hydraulic pressure of the CL1hydraulic pressure for the hydraulic pressure control rises) slightly after the time t3at which the motor4starts the operation (graph G21).

When the hydraulic pressure control is started, the controller20first sets the indicated hydraulic pressure to a comparatively large hydraulic pressure for filling up (precharge) the hydraulic chamber15aof the first clutch CL1with oil (graph G21). The indicated hydraulic pressure during the precharge can be realized initially by the oil supplied from the electric oil pump18. Then, at time t4, the mechanical oil pump17begins to operate by being driven by the motor4(graph G32). Thereafter, the indicated hydraulic pressure during the precharge can be realized by the oil supplied from both the mechanical oil pump17and the electric oil pump18.

Then, at time t5, the controller20ends the above-described precharge, and greatly reduces the indicated hydraulic pressure from the hydraulic pressure during the precharge and maintains it substantially constant (graph G21), to move the clutch piston15cwhich is separated from the first clutch plate15din the first clutch CL1so that the clutch piston15cis brought into contact with the first clutch plate15d. That is, the first clutch CL1is engaged. In more detail, the first clutch CL1is changed from the disengaged state into the slip state, and maintains the slip state thereafter.

In the middle of performing the hydraulic pressure control from the time t5, the mechanical oil pump17is fully activated at time t6, and the shift valve19aof the hydraulic system19is thus operated to suspend the supply of oil from the electric oil pump18to the first clutch CL1(graph G31). Then, at time t7, since the motor rotational speed coincides with the engine speed, the controller20suspends the operation of the motor4(graph G4). Further, the controller20raises the indicated hydraulic pressure in order to set the first clutch CL1to the fully engaged state, and then maintains the indicated hydraulic pressure constant from time t8to maintain the first clutch CL1at the fully engaged state (graph G21). Then, the controller20ends the hydraulic pressure control, and ends the vehicle startup control.

Next, referring toFIG.5, the overall flow of the vehicle startup control according to this embodiment is described.FIG.5is a flowchart illustrating the vehicle startup control performed by the controller20in this embodiment.

This vehicle startup control is started when the driver operates the start switch SN4of the hybrid vehicle1. First, at Step S101, the controller20acquires a variety of information. In detail, the controller20acquires the signals at least from the sensors (including the switch) SN1-SN5described above. Then, at Step S102, the controller20temporarily activates the electric oil pump18for a given period of time set beforehand to fill up the hydraulic system19, which supplies oil to the various components, such as the first clutch CL1and the second clutch CL2, with oil.

Next, at Step S103, the controller20determines whether the SOC of the battery5detected by the SOC sensor SN5is below the given value. Here, it determines whether the SOC of the battery5is so low that the first traveling mode (EV traveling mode) using the torque of the motor4cannot be performed. From such a viewpoint, the SOC of the battery5below which the first traveling mode becomes impossible to be performed is set as the given value used for the determination of Step S103.

As a result of the determination of Step S103, if the SOC is below the given value (Step S103: Yes), the controller20proceeds to Step S104, where it sets the traveling mode which is applied to the hybrid vehicle1to the second traveling mode. On the other hand, if the SOC is above the given value (Step S103: No), the controller20proceeds to Step S105, where it sets the traveling mode which is applied to the hybrid vehicle1to the first traveling mode. Then, the controller20ends the vehicle startup control according to this embodiment which is the control related to the startup of the hybrid vehicle1in the second traveling mode, in order to start the hybrid vehicle1in the normal first traveling mode.

After Step S104, the controller20proceeds to Step S106, where it controls the starter3to start the engine2. Then, at Step S107, the controller20determines whether the engine2is started. In detail, the controller20determines the startup of the engine2by determining whether the engine speed detected by the engine speed sensor SN1reaches a given idling speed. As a result, if the engine2is started (Step S107: Yes), the controller20proceeds to Steps S108and S109, and if the engine2is not started (Step S107: No), it returns to Step S107. In the latter case, the controller20repeats the determination of Step S107until the engine2is started.

When the engine2is started, the controller20starts the activation of the motor4(Step S108), and substantially at the same time, it starts the operation of the electric oil pump18(Step S109), and sets the solenoid15fof the first clutch CL1as “open” in order to start the hydraulic pressure control for shifting the first clutch CL1from the disengaged state to the engaged state (Step S110).

Next, the controller20proceeds to Step S111, where it performs the hydraulic pressure control. In detail, the controller20first sets the indicated hydraulic pressure to a comparatively large hydraulic pressure to fill up (precharge) the hydraulic chamber15aof the first clutch CL1with oil. This indicated hydraulic pressure during the precharge is initially realized only by the oil supplied from the electric oil pump18because the mechanical oil pump17is not activated, but when the mechanical oil pump17is activated by being driven by the motor4thereafter, it is realized by the oil supplied from both the mechanical oil pump17and the electric oil pump18. Then, after the above-described precharge is completed, the controller20greatly reduces the indicated hydraulic pressure from the hydraulic pressure during the precharge and maintains it substantially constant, to move the clutch piston15cwhich is separated from the first clutch plate15din the first clutch CL1so that the clutch piston15cis brought into contact with the first clutch plate15d. In this case, the controller20changes the first clutch CL1from the disengaged state to the slip state, and maintains the slip state thereafter. In the middle of performing such a hydraulic pressure control, by the mechanical oil pump17being fully activated, the shift valve19aof the hydraulic system19is operated to suspend the supply of oil from the electric oil pump18to the first clutch CL1.

Next, at Step S112, the controller20determines whether the motor rotational speed which is raised by the above-described activation of the motor4reaches the engine speed. In this case, the controller20performs the determination of Step S112based on the motor rotational speed detected by the motor rotational speed sensor SN2and the engine speed detected by the engine speed sensor SN1. As a result, if the motor rotational speed reaches the engine speed (Step S112: Yes), the controller20proceeds to Step S113, and if the motor rotational speed does not reach the engine speed (Step S112: No), it returns to S112. In the latter case, the controller20repeats the determination of Step S112until the motor rotational speed reaches the engine speed.

Next, at Step S113, since the motor rotational speed reaches the engine speed, the controller20suspends the operation of the motor4. Then, at Step S114, the controller20raises the indicated hydraulic pressure in order to set the first clutch CL1to the fully engaged state, then maintains the indicated hydraulic pressure constant in order to maintain the first clutch CL1at the fully engaged state, and ends the hydraulic pressure control. Then, the controller20ends the vehicle startup control.

Operation and Effects

Next, operation and effects of the method of controlling the hybrid vehicle and the control system according to this embodiment of the present disclosure are described.

In this embodiment, when the first traveling mode using the torque of the motor4is unperformable during the startup of the hybrid vehicle1, the controller20activates the motor4after the engine2is started by the starter3in order to perform the second traveling mode, and performs the hydraulic pressure control for applying hydraulic pressure to the first clutch CL1so that the first clutch CL1shifts from the disengaged state to the engaged state. Particularly, the controller20performs this hydraulic pressure control, at least using the hydraulic pressure from the mechanical oil pump17driven by the operation of the motor4.

Thus, by activating the motor4before performing the hydraulic pressure control of the first clutch CL1, the mechanical oil pump17can be operated appropriately so that the controllability of the first clutch CL1is secured. Further, when controlling the first clutch CL1in this way to shift the state from the disengaged state to the engaged state (i.e., when transmitting the torque of the engine2to the motor4side via the first clutch CL1), since the motor4is activated, it can suppress the startability deterioration of the engine2which is caused by the torque of the engine2being used for raising the motor rotational speed (in other words, caused by a torque difference between the engine2and the motor4), as compared with the case where the motor4is not operated. Thus, according to this embodiment, when performing the second traveling mode using the engine2during the startup, it can suppress the startability deterioration of the engine2, and it can secure the controllability of the first clutch CL1.

Further, according to this embodiment, by activating the motor4after the startup of the engine2, it can shorten the operating time of the motor4so that the power consumption of the battery5is reduced.

Moreover, in this embodiment, since the controller20starts the hydraulic pressure control substantially at the same time as the activation of the motor4, it can shift the first clutch CL1from the disengaged state to the engaged state promptly, as compared with the case where the hydraulic pressure control is started after the activation of the motor4.

Further, in this embodiment, since the controller20activates the electric oil pump18before the mechanical oil pump17is activated to perform the hydraulic pressure control using the hydraulic pressure from the electric oil pump18, it can shift the first clutch CL1from the disengaged state to the engaged state promptly, as compared with the case where only the mechanical oil pump17is used.

Further, in this embodiment, the electric oil pump18is configured to be smaller than the mechanical oil pump17. In this case, since the electric oil pump18is less in the discharge amount of oil than the mechanical oil pump17, it is difficult to perform the precise hydraulic pressure control using the oil supplied from the electric oil pump18, but since the precise control is not required at the beginning of the hydraulic pressure control using the electric oil pump18, the electric oil pump18can still fully satisfy the control demand. In the subsequent stage which requires the precise control, the mechanical oil pump17which can perform the precise control can certainly satisfy the control demand. Further, by configuring the electric oil pump18to be small, an improvement in mountability, a simplification of the configuration, and power saving can be realized.

Further, in this embodiment, the controller20fills up (precharges) the hydraulic chamber15aof the first clutch CL1with oil by using at least the hydraulic pressure from the electric oil pump18, during the start of the hydraulic pressure control. Therefore, the precharge can be performed appropriately by the electric oil pump18during the start of hydraulic pressure control at which the mechanical oil pump17is not fully activated.

Further, in this embodiment, since the controller20temporarily activates the electric oil pump18immediately after the startup of the hybrid vehicle1, the oil can be filled up in advance inside the hydraulic system19which supplies the oil to the first clutch CL1, etc.

Further, in this embodiment, since the electric oil pump18suspends the supply of oil to the first clutch CL1after the activation of the mechanical oil pump17, the power consumption by the electric oil pump18can be reduced.

Modifications

In the above embodiment, when the SOC of the battery5is below the given value, it is determined that the first traveling mode by the motor4is unperformable, but, in another example, also when the temperature of the battery5is outside a given temperature range, and when there is an abnormality in a component related to the execution of the first traveling mode, it may be determined that the first traveling mode by the motor4is unperformable.

Further, in the above embodiment, after the engine2is fully started, the operation of the motor4is started, but, in another example, while the engine2is being started (in detail, before the engine speed reaches the given idling speed), the operation of the motor4may be started. That is, the operation of the motor4may be started after the startup of the engine2is started. Similarly, while the engine2is started, the operation of the electric oil pump18may be started, and the solenoid15fof the first clutch CL1may be set as “open.”

Further, although in the above embodiment the supply of oil from the electric oil pump18to the first clutch CL1is stopped after the precharge (seeFIG.4), in another example, the supply of oil from the electric oil pump18to the first clutch CL1may be stopped by the mechanical oil pump17being fully activated and the shift valve19abeing operated during the precharge. Further, although in the above embodiment the mechanical oil pump17starts to operate during the precharge (seeFIG.4), in another example, the mechanical oil pump17may start to operate after the precharge.

DESCRIPTION OF REFERENCE CHARACTERS