Vehicular parking lock device

The present invention relates to a vehicular parking lock device in which an automatic transmission that includes a starting mechanism and a plurality of hydraulic engagement devices and changes the speed of the driving force from a drive source and outputs the driving force includes a hydraulic actuator that can restrain rotation of a parking gear connected to a wheel and a hydraulic circuit that controls operation of the hydraulic actuator.

An arrangement in which a parking lock device for restraining rotation of an output shaft of an automatic transmission to thus prevent movement of a vehicle is operated by a hydraulic actuator that is operated by a hydraulic circuit is known from Patent Document 1 below.

Patent Documents

Patent Document 1: Japanese Patent Publication No. 2008-503695

Problems to be Solved by the Invention

When the hydraulic circuit of the parking lock device is switched over to a parking lock operation position or a parking lock release position by supplying a hydraulic pressure selectively to one end or the other end of the hydraulic actuator via a plurality of solenoid valves, since a large number of solenoid valves are already used for the hydraulic circuit of the automatic transmission, it is not desirable to further increase the number of solenoid valves as a consequence of the parking lock device.

The present invention has been accomplished in light of the above circumstances, and it is an object thereof to cut the number of solenoid valves used for a hydraulic circuit of an automatic transmission equipped with a parking lock device.

Means for Solving the Problems

In order to attain the above object, according to a first aspect of the present invention, there is provided a vehicular parking lock device in which an automatic transmission that comprises a starting mechanism and a plurality of hydraulic engagement devices and changes a speed of a driving force from a drive source and outputs the driving force includes a hydraulic actuator that can restrain rotation of a parking gear connected to a wheel and a hydraulic circuit that controls operation of the hydraulic actuator, wherein the hydraulic circuit comprises a first solenoid valve that supplies a line pressure to one end of the hydraulic actuator in order to drive the hydraulic actuator to a parking lock release position, an accumulator in which a pressure is stored by the line pressure, a second solenoid valve that supplies the line pressure to the other end of the hydraulic actuator in order to drive the hydraulic actuator to a parking lock operation position, and a third solenoid valve that supplies a hydraulic pressure from the accumulator to the other end of the hydraulic actuator in order to drive the hydraulic actuator to the parking lock operation position, and the first solenoid valve or the second solenoid valve also functions as a solenoid valve that supplies the hydraulic pressure to the starting mechanism or a solenoid valve that supplies the hydraulic pressure to any one of the plurality of hydraulic engagement devices.

Further, according to a second aspect of the present invention, in addition to the first aspect, the drive source is an engine that is subjected to idling stop control at a time of deceleration of the vehicle, and the accumulator also functions as an accumulator that supplies the hydraulic pressure to any one of the plurality of hydraulic engagement devices when recovering from idling stop control.

Furthermore, according to a third aspect of the present invention, in addition to the first or second aspect, the starting mechanism is a torque converter equipped with a lockup clutch, and the second solenoid valve also functions as a solenoid valve that supplies the hydraulic pressure to the lockup clutch.

Moreover, according to a fourth aspect of the present invention, in addition to any one of the first to third aspects, the first solenoid valve comprises two solenoid valves, and a forward travel gear position first range established in the automatic transmission when one thereof supplies the line pressure to one end of the hydraulic actuator and a forward travel gear position second range established in the automatic transmission when the other thereof supplies the line pressure to the one end of the hydraulic actuator at least partially overlap one another.

Further, according to a fifth aspect of the present invention, in addition to the fourth aspect, provided on the other end side of the hydraulic actuator are a first locking oil chamber to which the hydraulic pressure is supplied via the second solenoid valve and a second locking oil chamber to which the hydraulic pressure is supplied via the third solenoid valve, and provided on the one end side of the hydraulic actuator are a first unlocking oil chamber to which the hydraulic pressure is supplied via one of the first solenoid valves and a second unlocking oil chamber to which the hydraulic pressure is supplied via the other one of the first solenoid valves.

Furthermore, according to a sixth aspect of the present invention, in addition to any one of the first to fifth aspects, the first to third solenoid valves are of a normally open type.

A solenoid valve 32 A of an embodiment corresponds to the second solenoid valve of the present invention, a solenoid valve 32 B of the embodiment corresponds to the third solenoid valve of the present invention, a solenoid valve 32 C and a solenoid valve 32 D of the embodiment correspond to the first solenoid valve of the present invention, a first accumulator 37 and a second accumulator 38 of the embodiment correspond to the accumulator of the present invention, a torque converter 40 of the embodiment corresponds to the starting mechanism of the present invention, and a hydraulic brake 41 of the embodiment corresponds to the hydraulic engagement device of the present invention.

Effects Of The Invention

In accordance with the first aspect of the present invention, the automatic transmission, which includes the starting mechanism and the plurality of hydraulic engagement devices and changes the speed of the driving force from the drive source and outputs it includes the hydraulic actuator, which can restrain the rotation of the parking gear connected to a wheel, and the hydraulic circuit, which controls operation of the hydraulic actuator.

When the line pressure is supplied from the first solenoid valve to one end of the hydraulic actuator, the hydraulic actuator is driven to the parking lock release position to thus release the parking lock, and when the line pressure is supplied from the second solenoid valve to the other end of the hydraulic actuator or the hydraulic pressure of the accumulator in which the line pressure is stored under pressure is supplied from the third solenoid valve to the other end of the hydraulic actuator, the hydraulic actuator is driven to the parking lock operation position to thus operate the parking lock.

Since the first solenoid valve or the second solenoid valve also functions as a solenoid valve that supplies hydraulic pressure to the starting mechanism or a solenoid valve that supplies hydraulic pressure to any one of the plurality of hydraulic engagement devices, it is possible to decrease the total number of solenoid valves, thus cutting the number of components of the hydraulic circuit.

Furthermore, in accordance with the second aspect of the present invention, since the drive source is an engine that is subjected to idling stop control at a time of deceleration of the vehicle, and the accumulator also functions as an accumulator that supplies hydraulic pressure to any one of the plurality of hydraulic engagement devices when recovering from idling stop control, it is possible to decrease the total number of accumulators, thus cutting the number of components of the hydraulic circuit.

Moreover, in accordance with the third aspect of the present invention, since the starting mechanism is the torque converter equipped with the lockup clutch, and the second solenoid valve also functions as a solenoid valve that supplies hydraulic pressure to the lockup clutch, it is possible to decrease the total number of solenoid valves, thus cutting the number of components of the hydraulic circuit.

Furthermore, in accordance with the fourth aspect of the present invention, since the first solenoid valve includes two solenoid valves, and the forward travel gear position first range established in the automatic transmission when one thereof supplies line pressure to one end of the hydraulic actuator and the forward travel gear position second range established in the automatic transmission when the other thereof supplies line pressure to the one end of the hydraulic actuator at least partially overlap one another, the line pressure is supplied from both of the two solenoid valves at the overlapping gear positions to one end of the hydraulic actuator.

Even when one of the two solenoid valves malfunctions and the line pressure cannot be supplied to one end of the hydraulic actuator, the above enables the redundancy for reliably preventing unnecessary operation of the parking lock to be ensured by retaining the hydraulic actuator at the parking lock release position with the line pressure supplied from the remaining one solenoid valve.

Moreover in accordance with the fifth aspect of the present invention, since provided on the other end side of the hydraulic actuator are the first locking oil chamber, to which hydraulic pressure is supplied via the second solenoid valve, and the second locking oil chamber, to which hydraulic pressure is supplied via the third solenoid valve, and provided on the one end side of the hydraulic actuator are the first unlocking oil chamber, to which hydraulic pressure is supplied via one of the two first solenoid valves, and the second unlocking oil chamber, to which hydraulic pressure is supplied via the other one of the two first solenoid valves, even if one of the second solenoid valve and the third solenoid valve malfunctions, the parking lock, can be operated, and even if one of the two first solenoid valves malfunctions, the parking lock can be released, thus enhancing the redundancy for malfunctioning of the solenoid valve.

Furthermore, in, accordance with the sixth aspect of the present invention, since the first to third solenoid valves are of a normally open type, even if the power supply malfunctions, it is possible to supply hydraulic pressure from the accumulator to the other end of the hydraulic actuator via any one of the open first to third solenoid valves, thus making the parking lock operate automatically.

FIG. 1 is a diagram showing the structure of a parking lock device. (first embodiment)

FIG. 2 is a hydraulic circuit diagram of the parking lock device, (first embodiment)

FIG. 3 is a diagram for explaining the operation when running in a D range or an R range (parking lock release). (first embodiment)

FIG. 4 is a diagram for explaining the operation when parking in a P range (engine ON) (parking lock operation). (first embodiment)

FIG. 5 is a diagram for explaining the operation when an engine is OFF (parking lock operation). (first embodiment)

FIG. 6 is a diagram for explaining the operation at a time of idling stop control. (first embodiment)

FIG. 7 is a diagram for explaining the operation when recovering from idling stop control. (first embodiment)

12 Parking gear

25 Hydraulic actuator

31 Hydraulic circuit

29 A First locking oil chamber

29 B Second locking oil chamber

30 A First unlocking oil chamber

30 B Second unlocking oil chamber

32 A Solenoid valve (second solenoid valve)

32 B Solenoid valve (third solenoid valve)

32 C Solenoid valve (first solenoid valve)

32 D Solenoid valve (first solenoid valve)

37 First accumulator (accumulator)

38 Second accumulator (accumulator)

40 Torque converter (starting mechanism)

40 a Lockup clutch

41 Hydraulic brake (hydraulic engagement device)

An embodiment of the present invention is explained below by reference to FIG. 1 to FIG. 7 .

First Embodiment

The structure of a parking lock device is now explained by reference to FIG. 1 .

A parking gear 12 is fixed to a gear shaft 11 of an automatic transmission, and a latching claw 14 a provided at one end of a parking pawl 14 pivotably supported on a support shaft 13 is urged by a spring 15 in a direction in which it disengages from tooth grooves 12 a of the parking gear 12 . One end of a parking rod 18 is pivotably supported, via a pin 19 , on a detent plate 17 pivotably supported on a support shaft 16 , and a cone-shaped cam 20 provided at the other end of the parking rod 18 abuts against a cam follower 14 b provided at the other end of the parking pawl 14 . A detent roller 22 provided at one end of a swingable arm 21 is urged by a spring 23 in a direction in which it engages with either one of two recess portions 17 a and 17 b of the detent plate 17 . A link 24 pivotably supported on the support shaft 16 and swinging integrally with the detent plate 17 is connected to a hydraulic actuator 25 .

The hydraulic actuator 25 includes a piston 27 slidably fitted into a cylinder 26 , and the link 24 is connected to the piston 27 via a pin 28 . Formed on the left end side of the cylinder 26 are a first locking oil chamber 29 A and a second locking oil chamber 29 B for driving the piston 27 in a direction (rightward) in which parking lock is operated, and formed on the right end side of the cylinder 26 are a first unlocking oil chamber 30 A and a second unlocking oil chamber 30 B for driving the piston 27 in a direction (leftward) in which parking lock is released.

When a hydraulic pressure is supplied to the first locking oil chamber 29 A and the second locking oil chamber 29 B, the piston 27 moves rightward, the movement of the piston 27 pushes up the cam follower 14 b of the parking pawl 14 via the link 24 , the detent plate 17 , the parking rod 18 , and the cam 20 , the parking pawl 14 swings against the resilient force of the spring 15 to make the latching claw 14 a engage with one of the tooth grooves 12 a of the parking gear 12 , and parking lock is operated to thus suppress movement of the vehicle. In the operated state of parking lock, the detent roller 22 engages with the recess portion 17 b of the detent plate 17 , thus maintaining the state in a stable manner.

On the other hand, when the hydraulic pressure is supplied to the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B, the piston 27 moves leftward, the latching claw 14 a of the parking pawl 14 disengages from the tooth groove 12 a of the parking gear 12 , and parking lock is released to thus enable the vehicle to move. In the released state of parking lock, the detent roller 22 engages with the recess portion 17 a of the detent plate 17 , thus maintaining the state in a stable manner.

A hydraulic circuit 31 for controlling the operation of the hydraulic actuator 25 is now explained by reference to FIG. 2 .

The hydraulic circuit 31 includes an ON/OFF type solenoid valve 32 A that supplies to the first locking oil chamber 29 A of the hydraulic actuator 25 a line pressure supplied to an oil passage L 1 from a hydraulic pump, which is not illustrated, forming the hydraulic pressure supply source of the present invention, and an ON/OFF type solenoid valve 32 B that supplies to the second locking oil chamber 29 B of the hydraulic actuator 25 a line pressure of an oil passage L 2 connected to the downstream side of the oil passage L 1 via a check valve 36 . By being open the solenoid valve 32 A supplies the line pressure directly to the first locking oil chamber 29 A, but by being open the solenoid valve 32 B opens a first ball valve 33 A. The solenoid valve 32 A and the solenoid valve 32 B are both of a normally open type.

Furthermore, the hydraulic circuit 31 includes an ON/OFF type solenoid valve 32 C that supplies a line pressure of an oil passage L 3 to the first unlocking oil chamber 30 A of the hydraulic actuator 25 , and an ON/OFF type solenoid valve 32 D that supplies a line pressure of an oil passage L 4 on the downstream of the check valve 36 to the second unlocking oil chamber 30 B of the hydraulic actuator 25 . By being open the solenoid valve 32 D supplies the line pressure directly to the second unlocking oil chamber 30 B, but by being open the solenoid valve 32 C moves a spool of a parking inhibit valve 35 leftward to thus supply the line pressure to the first unlocking oil chamber 30 A and by being closed it moves the spool rightward to thus drain the line pressure of the first unlocking oil chamber 30 A. The solenoid valve 32 C and the solenoid valve 32 D are both of a normally open type.

Connected to the oil passage L 2 between the check valve 36 and the solenoid valve 32 B are a pressure storage chamber 37 a of a first accumulator 37 and a pressure storage chamber 38 a of a second accumulator 38 , a back chamber 37 b of the first accumulator 37 communicating with the first unlocking oil chamber 30 A, and a back chamber 38 b of the second accumulator 38 communicating with the second unlocking oil chamber 30 B. Disposed between the check valve 36 and the first accumulator 37 and second accumulator 38 is a second ball valve 33 B that is opened and closed by an ON/OFF type solenoid valve 32 E. By being open the solenoid valve 32 E increases the flow rate of oil by opening the second ball valve 33 B. The solenoid valve 32 E is of a normally closed type.

A lockup clutch shift valve 39 is connected to the oil passage L 1 on the downstream of the solenoid valve 32 A, and the lockup clutch pressure of an oil passage L 5 is supplied to a lockup clutch 40 a of a torque converter 40 , which is a starting mechanism, via the lockup clutch shift valve 39 .

Furthermore, a hydraulic brake 41 , which is a hydraulic engagement device for shift change, is connected to an oil passage L 6 on the downstream side of the check valve 36 , and a linear solenoid valve 42 and a brake cut valve 43 are disposed in the oil passage L 6 . The brake cut valve 43 is driven to open and close by the solenoid valve 32 D. The linear solenoid valve 42 includes an in port 42 a, an out port 42 b, and a drain port 42 c, and it is thereby possible to regulate the hydraulic pressure inputted via the in port 42 a and output it via the out port 42 b or to drain via the drain port 42 c the hydraulic pressure inputted via the in port 42 a.

The operation of the embodiment of the present invention having the above arrangement is now explained.

As shown in FIG. 3 , when the shift lever is operated to a D range or an R range and the vehicle is traveling in a predetermined gear position, the line pressure generated by the hydraulic pump driven by the engine is transmitted to the oil passage L 1 and the oil passage L 3 , and the hydraulic pressure of the oil passage L 1 passes through the check valve 36 and is transmitted to the oil passage L 2 , the oil passage L 4 , and the oil passage L 6 . When the normally closed solenoid valve 32 E is energized and opened, the second ball valve 33 B is opened in response thereto, the line pressure is supplied to the oil passage L 2 , and the hydraulic pressure is stored under pressure in the pressure storage chambers 37 a and 38 a of the first accumulator 37 and the second accumulator 38 .

The normally open solenoid valve 32 C and solenoid valve 32 D are de-energized and open, the spool of the parking inhibit valve 35 moves leftward due to the solenoid valve 32 C being opened, the line pressure of the oil passage L 3 is thus transmitted to the first unlocking oil chamber 30 A of the hydraulic actuator 25 via the parking inhibit valve 35 , and due to the solenoid valve 32 D being open the line pressure of the oil passage L 4 is transmitted to the second unlocking oil chamber 30 B of the hydraulic actuator 25 .

On the other hand, the normally open solenoid valve 32 A and solenoid valve 32 B are energized and close; due to the solenoid valve 32 A being closed the oil of the first locking oil chamber 29 A of the hydraulic actuator 25 is drained from the solenoid valve 32 A via the arrowed path, due to the solenoid valve 32 B being closed the first ball valve 33 A closes, and the oil of the second locking oil chamber 29 B of the hydraulic actuator 25 is thereby drained from the first ball valve 33 A via the arrowed path. As a result, the piston 27 of the hydraulic actuator 25 moves leftward and releases the parking lock.

Although the flow rate of oil that can pass through the solenoid valve 32 B is relatively small, since the flow rate of oil that can pass through the first ball valve 33 A opened and closed by the solenoid valve 32 B is relatively large, due to the first ball valve 33 A being present therebetween the operating responsiveness of the hydraulic actuator 25 can be enhanced.

As described above, when the vehicle is traveling, due to the solenoid valve 32 A and the solenoid valve 32 B being closed and the solenoid valve 32 C and the solenoid valve 32 D being open, the hydraulic actuator 25 is operated to an unlock position, thus enabling the parking lock to be released. In this arrangement, since the hydraulic actuator 25 includes two locking oil chambers, that is, the first locking oil chamber 29 A and the second locking oil chamber 29 B, and two unlocking oil chambers, that is, the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B, even if one of the solenoid valve 32 C and the solenoid valve 32 D seizes to a valve-closed state and the hydraulic pressure is not supplied to the first unlocking oil chamber 30 A or the second unlocking oil chamber 30 B, or even if one of the solenoid valve 32 A and the solenoid valve 32 B seizes to a valve-open state and the hydraulic pressure is supplied to the first locking oil chamber 29 A or the second locking oil chamber 29 B, the hydraulic actuator 25 can be operated to an unlock position without problems, thus ensuring that there is redundancy.

The solenoid valve 32 C opens at a first predetermined gear position, the solenoid valve 32 D opens at a second predetermined gear position, and the first predetermined gear position and the second predetermined gear position partially overlap each other. Therefore, there is a case in which the line pressure is supplied only to the first unlocking oil chamber 30 A according to a gear position that is established at that time, a case in which the line pressure is supplied only to the second unlocking oil chamber 30 B, and a case in which the line pressure is supplied to both the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B; in any of these cases the piston 27 of the hydraulic actuator 25 moves leftward to thus release the parking lock, and there are no problems. Since the line pressure is supplied to both the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B at the overlapping gear position, even if the solenoid valve 32 C or the solenoid valve 32 D malfunctions and the supply of line pressure is discontinued, the parking lock is retained in an operation released state, thus enhancing the redundancy.

As shown in FIG. 4 , when the vehicle stops with the shift lever operated to a P range while the engine is running, the solenoid valve 32 A and the solenoid valve 32 B are de-energized and open, and the solenoid valve 32 C and the solenoid valve 32 D are energized and close. Due to the solenoid valve 32 A being open the line pressure of the oil passage L 1 is transmitted to the first locking oil chamber 29 A of the hydraulic actuator 25 , and due to the solenoid valve 32 B being open the first ball valve 33 A opens and the line pressure of the oil passage L 2 is transmitted to the second locking oil chamber 29 B of the hydraulic actuator 25 .

On the other hand, due to the solenoid valve 32 C being closed, the oil of the first unlocking oil chamber 30 A of the hydraulic actuator 25 is drained via the arrowed path from the parking inhibit valve 35 , and due to the solenoid valve 32 D being closed the oil of the second unlocking oil chamber 30 B of the hydraulic actuator 25 is drained from the solenoid valve 32 D via the arrowed path. As a result, the piston 27 of the hydraulic actuator 25 moves rightward to thus operate the parking lock.

As described above, when the shift lever is put into the P range while the engine is running, the solenoid valve 32 A and the solenoid valve 32 B are opened, the solenoid valve 32 C and the solenoid valve 32 D are closed, and the hydraulic actuator 25 can be operated to a lock position. In this arrangement, since the hydraulic actuator 25 includes two locking oil chambers, that is, the first locking oil chamber 29 A and the second locking oil chamber 29 B, and two unlocking oil chambers, that is, the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B, even if one of the solenoid valve 32 C and the solenoid valve 32 D seizes to a valve-open state and the hydraulic pressure is supplied to the first unlocking oil chamber 30 A or the second unlocking oil chamber 30 B, or even if one of the solenoid valve 32 A and the solenoid valve 32 B seizes to a valve-closed state and no hydraulic pressure is supplied to the first locking oil chamber 29 A and the second locking oil chamber 29 B, the hydraulic actuator 25 is operated to a lock position without problems, thus ensuring that there is redundancy.

As shown in FIG. 5 , when the shift lever is operated to the P range and the ignition is turned OFF, the engine stops and the line pressure thereby disappears, but in accordance with the present embodiment the parking lock device can be operated without problems by the hydraulic pressure stored under pressure in the first accumulator 37 and the second accumulator 38 .

That is, due to the ignition being turned OFF the normally open solenoid valve 32 A, solenoid valve 32 B, solenoid valve 32 C, and solenoid valve 32 D are all de-energized and open, and the normally closed solenoid valve 32 E is de-energized and closed. Even if the line pressure disappears, due to the solenoid valve 32 E being closed the second ball valve 33 B closes, and the hydraulic pressure stored under pressure in the first accumulator 37 and the second accumulator 38 is retained without leakage.

Due to the solenoid valve 32 B being open the hydraulic pressure of the first accumulator 37 and of the second accumulator 38 is transmitted to the second locking oil chamber 29 B of the hydraulic actuator 25 via the opened first ball valve 33 A, whereas due to the solenoid valve 32 C being open the oil of the first unlocking oil chamber 30 A of the hydraulic actuator 25 is drained from the parking inhibit valve 35 via the arrowed path, and due to the solenoid valve 32 D being open the oil of the second unlocking oil chamber 30 B of the hydraulic actuator 25 is drained from the solenoid valve 32 D via the arrowed path. As a result, the piston 27 of the hydraulic actuator 25 moves rightward to thus operate the parking lock.

As described above, even if the line pressure disappears due to the shift lever being operated to the P range and the ignition being turned OFF, the parking lock device can be operated without problems by the hydraulic pressure stored under pressure in the first accumulator 37 and the second accumulator 38 .

The vehicle of the present embodiment can be subjected to idling stop control, and the line pressure disappears due to the engine E stopping at a time of a temporary stop such as when waiting for a traffic light. During this idling stop control, as shown in FIG. 6 , the normally closed solenoid valve 32 E is de-energized and closes, in response thereto the second ball valve 33 B closes, and the hydraulic pressure stored under pressure in the first accumulator 37 and the second accumulator 38 is thereby retained without leakage. Furthermore, due to the line pressure disappearing, the hydraulic pressure of the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B of the hydraulic actuator 25 also disappears, and due to engagement between the detent plate 17 and the detent roller 22 the parking lock is maintained in the operation released state.

Since the line pressure does not immediately rise even when the engine starts when recovering from idling stop control, the hydraulic pressure cannot be supplied to the hydraulic brake 41 , which is a hydraulic engagement device necessary for starting, and there is a possibility that smooth starting will be inhibited. However, in accordance with the present embodiment, the hydraulic brake 41 can be operated without delay by the hydraulic pressure of the first accumulator 37 and the second accumulator 38 retained during idling stop control.

That is, as shown in FIG. 7 , when the second ball valve 33 B is opened by energizing and opening the solenoid valve 32 E at the same time as recovering from idling stop control, the hydraulic pressure stored under pressure in the first accumulator 37 and the second accumulator 38 is transmitted from the oil passage L 2 to the oil passage L 4 and the oil passage L 6 via the second ball valve 33 B. In this arrangement, since the solenoid valve 32 D disposed in the oil passage L 4 is de-energized and open, the spool of the brake cut valve 43 moves rightward. Therefore, opening the linear solenoid valve 42 disposed in the oil passage L 6 at a predetermined degree of opening enables the hydraulic pressure stored under pressure in the first accumulator 37 and the second accumulator 38 to be supplied to the hydraulic brake 41 and the vehicle to be started promptly.

Although the flow rate of oil that can pass through the solenoid valve 32 E is relatively small, since the flow rate of oil that can pass through the second ball valve 33 B, which is opened and closed by the solenoid valve 32 E, is relatively large, it is possible by disposing the second ball valve 33 B therebetween to enhance the responsiveness of supply of the hydraulic pressure from the first accumulator 37 and the second accumulator 38 , thereby enabling the hydraulic brake 41 to be promptly engaged.

In the explanation above, the operation of the hydraulic brake 41 when recovering from idling stop control is explained, but the hydraulic brake 41 can also be controlled during normal traveling of the vehicle by operating the brake cut valve 43 with the solenoid valve 32 D. When the solenoid valve 32 D is closed in order to move the spool of the brake cut valve 43 leftward to thus cut off communication between the linear solenoid valve 42 and the hydraulic brake 41 , the supply of hydraulic pressure to the second unlocking oil chamber 30 B of the hydraulic actuator 25 is cut off, but since the hydraulic actuator 25 is retained at an unlock position with the hydraulic pressure supplied to the first unlocking oil chamber 30 A, there is no possibility that parking lock will be operated.

Furthermore, in accordance with the present embodiment, the solenoid valve 32 A for operation of the hydraulic actuator 25 is also used for operation of the lockup clutch 40 a of the torque converter 40 . That is, since the solenoid valve 32 A is closed when the vehicle is traveling as shown in FIG. 3 , the spool of the lockup clutch shift valve 39 moves rightward, and the lockup clutch pressure is supplied to the lockup clutch 40 a of the torque converter 40 . When in this state the solenoid valve 32 A is de-energized and opened, the spool of the lockup clutch shift valve 39 operates to drain the hydraulic pressure of the lockup clutch 40 a, and the lockup clutch 40 a can thereby be disengaged.

When the solenoid valve 32 A is opened, the line pressure is supplied to the first locking oil chamber 29 A of the hydraulic actuator 25 , but since the line pressure is being supplied to both the first unlocking oil chamber 30 A and the second unlocking oil chamber 30 B at this point, even if the line pressure is supplied to the first locking oil chamber 29 A, the piston 27 of the hydraulic actuator 25 does not move to the lock position, and there is no possibility that the parking lock will be operated.

As described above, in accordance with the present embodiment, since the solenoid valve 32 A and the solenoid valve 32 D, which control the operation of the hydraulic actuator 25 , are also used for control of the lockup clutch 40 a of the torque converter 40 and control of the hydraulic brake 41 respectively, it is possible to reduce the number of solenoid valves to thus simplify the structure of the hydraulic circuit 31 and, moreover, since the first accumulator 37 and the second accumulator 38 are used not only for operation of the parking lock but also for operation of the hydraulic brake 41 , which is a hydraulic engagement device when recovering from idling stop control, it is possible to reduce the number of accumulators to thus further simplify the structure of the hydraulic circuit 31 .

An embodiment of the present invention is explained above, but the present invention may be modified in a variety of ways as long as the modifications do not depart from the spirit and scope thereof.

For example, the number of solenoid valves for locking (the second solenoid valve and the third solenoid valve) of the present invention is not limited to the two of the embodiment, that is, the solenoid valve 32 A and the solenoid valve 32 B, and may be one or three or more.

Furthermore, the number of solenoid valves for unlocking (the first solenoid valve) of the present invention is not limited to the two of the embodiment, that is, the solenoid valve 32 C and the solenoid valve 32 D, and may be one or three or more.

Moreover, in the embodiment the solenoid valve 32 A is also used as a solenoid valve for supplying the hydraulic pressure to the lockup clutch 40 a of the torque converter 40 , but the solenoid valve 32 B may also be used therefor, or the solenoid valve 32 A (or the solenoid valve 32 B) may also be used as a solenoid valve for supplying the hydraulic pressure to the hydraulic engagement device. That is, the solenoid valve 32 A or the solenoid valve 32 B may also be used as a solenoid valve for supplying the hydraulic pressure to a starting mechanism or as a solenoid valve for supplying the hydraulic pressure to any one of a plurality of hydraulic engagement devices.

Furthermore, the hydraulic engagement device of the present invention is not limited to the hydraulic brake 41 of the embodiment and may be another hydraulic engagement device such as a hydraulic clutch.

Moreover, the starting mechanism of the present invention is not limited to the torque converter 40 of the embodiment and may be another starting mechanism such as a starting clutch.