JP2000266005A - Hydraulic device and automatic cluth device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of high temperature and high pressure immediately after starting a hydraulic pump in a hydraulic device including the hydraulic pump. SOLUTION: A bypass passage branching from a branch point (d) of a discharge path of a hydraulic pump and reaching an oil tank 15 is provided. A flow control valve 20 is provided in the bypass passage. When speed of rotation of a pump axis is low immediately after starting the hydraulic pump, less flow runs in the discharge path 17 and the flow control valve 20 opens. Therefore, oil is returned from the oil tank 15 to the oil tank through the hydraulic pump, the discharge path 17 and the bypass passage so as to be circulated. When the flow increases with increasing the speed of rotation of the pump axis, the flow control valve 20 closes the bypass passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device including a hydraulic pump, and more specifically, for example, a vehicle automatic clutch device, an ABS (anti-skid brake system).
The present invention relates to a hydraulic device for supplying a hydraulic pressure for driving the like.

[0002]

2. Description of the Related Art A hydraulic device for supplying oil pressure to an automobile device driven by oil pressure sucks oil from an oil tank through a suction passage and supplies the oil through a discharge passage. And has a hydraulic pump that discharges pressure oil and supplies it to each device. By the way, there is a type of hydraulic pump in which oil is not discharged to the outside at the time of starting the pump until the pump pressure becomes equal to or higher than a predetermined pressure. In this type of hydraulic pump, the oil circulates inside the hydraulic pump until the predetermined pressure is reached, so that the oil temperature becomes extremely high. As a result, deterioration of the seal or the like may be accelerated.

When a hydraulic device including a gear pump is applied to an automatic clutch device, for example, the viscosity of brake oil used as hydraulic oil is low and lubricity is poor. Abnormal abrasion may occur in the part. The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic device and an automatic clutch device that can prevent durability deterioration due to high temperature generation and poor lubrication at the time of starting a hydraulic pump. .

[0004]

Means for Solving the Problems As means for solving the problems to achieve the above object, the aspect of the invention described in claim 1 is as follows.
A hydraulic pump that discharges oil sucked from an oil tank through a suction path through a discharge path, a bypass path communicating the discharge path with the oil tank, and valve means disposed in the bypass path; This valve means is characterized by closing the bypass passage with a delay from the start of the hydraulic pump.

In this embodiment, since the bypass is opened immediately after the hydraulic pump is started, the oil returns from the oil tank to the oil tank via the suction path, the hydraulic pump, the discharge path, and the bypass in order. Is circulated. That is, while the rotation speed of the pump shaft of the hydraulic pump is low (the bearing load capacity is small), the oil is circulated through the bypass oil passage, so that the pressure generated by the hydraulic pump can be kept low.
Accordingly, the temperature of the oil does not become high, and an unnecessarily high load is not applied to the bearing of the pump shaft of the hydraulic pump. On the other hand, when the pump rotation speed becomes high (bearing load capacity becomes large), the bypass circuit is closed to increase the generated pressure. Even if the generated pressure increases, metal contact hardly occurs because the lubricating film is formed on the bearing portion.

[0006] In recent years, in recent years, vehicles have been required to save energy.
For example, there is a method of stopping driving of a driving source of a vehicle or other devices while waiting for a traffic light, and starting driving at the same time as starting. In such a case, the frequency at which the hydraulic pump is started and stopped is high, and this embodiment can effectively deal with this. By the way, the gear pump tends to cause abnormal wear due to poor lubrication at the time of starting the pump due to the use of oil having poor lubricity. However, in the present embodiment, when the hydraulic pump is a gear pump, the occurrence of abnormal wear can be particularly prevented. It has a noticeable effect on the point.

The valve means for closing the bypass after a delay from the activation of the hydraulic pump may be a flow control valve which operates according to the flow rate flowing through the bypass, or operates according to the oil pressure in the bypass. It may be a pressure control valve, or may be an electromagnetic valve that operates in response to a timer signal issued after a lapse of a predetermined time from the start of the pump.

According to a second aspect of the present invention, in the first aspect, the valve means comprises a flow control valve that closes the bypass when the flow rate flowing through the bypass exceeds a predetermined flow rate. It is. In this aspect, since the flow control valve is used, the valve structure can be simplified as compared with the case where a pressure-responsive spool valve is used.

According to a third aspect of the present invention, in the second aspect, the flow control valve includes a ball capable of closing a valve hole and an elastic member for pushing the ball in an opening direction via an intermediate member. In addition, the intermediate member receives a pressure difference between the front and rear of the intermediate member, and is displaced in a direction allowing the ball to close the valve hole against the elastic member.

In this aspect, the valve hole is opened and closed by the ball using the intermediate member which receives the differential pressure, so that the opening and closing is reliable. Further, by setting the urging force of the elastic member, the flow rate for operating the ball can be easily adjusted. Claim 4
According to a preferred embodiment of the present invention, in claim 1, further comprising a throttle provided in series with the valve means in the bypass passage, wherein the valve means shuts off the bypass passage using a pressure generated upstream of the throttle as a pilot pressure. It is characterized by comprising a control valve. In this aspect, since the pilot-type pressure control valve is used, it is possible to reliably suppress an increase in the internal pressure immediately after the start of the hydraulic pump.

According to a fifth aspect of the present invention, in the automatic clutch device, a friction clutch for connecting and disconnecting the power transmitted from the power source to the transmission by moving the release member is provided.
A hydraulic device according to any one of claims 1 to 4, which supplies a hydraulic pressure for driving the release member in a direction in which the friction clutch is disengaged. According to this aspect, the operation and effect according to any one of claims 1 to 4 can be obtained in the automatic clutch device.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a vehicular auto clutch device including a hydraulic device according to an embodiment of the present invention. Referring to FIG. 1, an automatic clutch device 1 responds to a signal for connecting / disconnecting a friction clutch 2, a slave cylinder 5 for driving a release bearing 3 of the friction clutch 2 via a release fork 4, and a friction clutch 2. And a pump unit 7 serving as a hydraulic device for supplying hydraulic pressure to the slave cylinder 5 via the electromagnetic valve 6.

The friction clutch 2 has a clutch cover 9 attached to a flywheel 8 which rotates integrally with an output shaft of a drive source of a vehicle such as an engine or an electric motor to form an outer shell. And a pressure plate 11. When the slave cylinder 5 pushes one end (the upper end in FIG. 1) of the release fork 4, the release fork 4 swings around the fulcrum 12,
The other end (the lower end in FIG. 1) of the release fork 4 pushes the inner periphery of the diaphragm spring 13 via the release bearing 3. As a result, the diaphragm spring 13 assumes a posture that warps in the opposite direction, and the diaphragm spring 13
The pressure plate 11 is pulled back by the outer periphery of the clutch disk 10 and separates from the clutch disk 10, so that the clutch is disengaged.

The pump unit 7 as a hydraulic device includes a hydraulic pump 14 composed of, for example, a gear pump, a motor M for driving the hydraulic pump 14, an oil tank 15, a check valve 18, and a flow control valve as valve means. 20 as a main part. The hydraulic pump 14 sucks oil from the oil tank 15 through the suction passage 16 and discharges the pressure oil to the solenoid valve 6 through the discharge passage 17. The check valve 18 is disposed in the discharge path 17 and prevents the oil from flowing back to the hydraulic pump 14 side.

A bypass passage 19 connecting a branch point d provided at an intermediate portion of the discharge passage 17 (an intermediate portion between the hydraulic pump 14 and the check valve 18 in the discharge passage 7) to the oil tank 15 is provided. The bypass 19 is provided with the flow control valve 20. Pump unit 7
Is connected to an external oil passage 21, and this oil passage 2
1 is connected to the slave cylinder 5 via the above-mentioned solenoid valve 6. Reference numeral 22 denotes an accumulator provided in the oil passage 21 upstream of the solenoid valve 6. Reference numeral 70 denotes a pressure switch that controls on / off of a motor M for driving the hydraulic pump 14 according to the pressure of the oil passage 21.

The flow control valve 20 as the above valve means is
When the flow rate flowing through the bypass 19 becomes equal to or more than a predetermined flow rate, the bypass 19 is closed. 2 (a) and 2 (b), the flow control valve 20 is composed of a ball 24 capable of closing a valve hole 23 and a compression coil spring pressing the ball 24 in an opening direction via an intermediate member 25. Elastic member 26.

The casing K of the flow control valve 20 has a valve hole 2
Before and after 3, a ball accommodation chamber 27 having a larger diameter than the valve hole 23 and an intermediate member accommodation chamber 28 are defined. The peripheral edge of the valve hole 23 on the ball storage chamber 27 side serves as a valve seat. Reference numeral 38 denotes an oil groove for allowing oil to flow before and after the ball 24 in the ball storage chamber 27. The ball 24 is accommodated in the ball accommodating chamber 27 so as to be able to advance and retreat by a predetermined distance.
The intermediate member 25 is slidably received in the intermediate member storage chamber 28.

The intermediate member 25 slides on the inner wall surface of the intermediate member accommodating chamber 28 and has a plurality of oil holes 32 penetrating in the axial direction.
And a small-diameter push rod 3 extending in the axial direction from the center of one end of the disk portion 29 and pushing the ball 24.
0, a guide rod 31 extending in the axial direction from the other end of the disk portion 29 and internally fitted into a compression coil spring as the elastic member 26.
And

The elastic member 26 composed of a compression coil spring
A part of the intermediate member 25 is interposed between the retainer 33 that is inserted into the intermediate member storage chamber 28 and screwed to the other end of the intermediate member 25. The retainer 33 is a joint of a pipe (not shown) for connecting to the oil tank 15 side. 34 is the discharge path 1
7 is a joint of a pipe (not shown) for connection to the 7 side. A part of the joint 34 enters the ball accommodating chamber 27 and serves to prevent the ball 24 from coming off.

When the intermediate member 25 moves toward the valve hole 23, the intermediate member storage chamber 28 is formed with a receiving portion 35 formed of an annular step which comes into contact with the outer edge of the disk portion 29 and receives it. ing. A predetermined distance is provided between an end surface of the disk portion 29 of the intermediate member 25 on the valve hole 23 side and an end surface 36 of the intermediate member storage chamber 28 on the valve hole 23 side, and an oil chamber 37 is formed therebetween. The receiving portion 35 is connected to the end surface 3 of the intermediate member storage chamber 28 so that the capacity of the oil chamber 37 is ensured even when the intermediate member 25 urged by the elastic member 26 is in contact with the receiving portion 35.
6 are arranged at a position separated from the reference numeral 6. FIG.
As shown in (a), with the intermediate member 25 urged by the elastic member 26 in contact with the receiving portion 35, the valve stem 30 pushes up the ball 24 through the valve hole 23, and the ball 24
From the periphery of the valve hole 23 to open the valve. As a result, oil is discharged from the discharge passage 17 side to the ball housing chamber 27 and the valve
3, the intermediate member accommodating chamber 28 and the oil tank 15 through the oil chamber 37 and the oil hole 32.

In this embodiment, the rotation speed of the pump shaft is low and the flow rate is small until a predetermined time t elapses from the start of the hydraulic pump 14. Therefore, since the differential pressure across the intermediate member 25 is small, as shown in FIG. 2A, the intermediate member 25 is pushed up by the elastic member 26 and
4, the valve hole 23 is opened. For this reason, as shown by the solid line arrow in FIG.
6. The oil is returned to and circulated through the oil tank 15 via the hydraulic pump 14, the discharge path 17 and the bypass path 19.

As a result, the pressure generated by the hydraulic pump 14 can be reduced as compared with the conventional case in which oil is circulated in the hydraulic pump. Unnecessarily high load is not applied to the bearing portion of the motor. That is, while the rotation speed of the pump shaft is low and the bearing load capacity is small, the generated pressure is suppressed and the bearing load is reduced, so that metal contact and the like hardly occur and the durability of the bearing portion can be improved. . In particular, the hydraulic pump 1
When the gear pump 4 is a gear pump, a remarkable effect can be obtained with respect to the durability of the bearing portion.

Even if the solenoid valve 6 is opened while oil is circulated through the bypass 19, the hydraulic pump 14
The oil is supplied from the accumulator 22 arranged in parallel to the slave cylinder 5 side as indicated by a dashed line arrow in FIG. 1, so that there is no delay in the rise of the supply hydraulic pressure. When a predetermined time t elapses from the start and the rotational speed of the pump shaft increases and the flow rate increases to a predetermined flow rate or more, the pressure drop when passing through the oil hole 32 increases. As a result, the pressure difference before and after the intermediate member 25 increases, and the intermediate member 25 that has received the pressure difference, as shown in FIG.
Displaced in the direction buried in the valve hole 23. As a result, the ball 24 closes the valve hole 23 and the bypass 1
9 is closed. As a result, the pressure oil discharged from the hydraulic pump 14 to the discharge path 17 is sent to the solenoid valve 6 via the check valve 18 as shown by a broken arrow in FIG. Thus, the friction clutch 2 can be driven by the hydraulic pump 14.

As described above, when the rotation speed of the pump shaft increases, the bypass circuit 19 is closed to increase the generated pressure. However, since the bearing load capacity is also large, metal contact occurs at the bearing portion. Never. If the bypass passage 19 and the flow control valve 20 are incorporated in the casing of the hydraulic pump 14, the entire pump unit 7 can be made compact. Further, the present pump unit 7 can be easily applied to other devices.

FIG. 3 is a graph showing changes over time in the rotation speed of the pump shaft of the hydraulic pump 14 and changes in the oil pressure in the discharge path 17 over time in the present embodiment. In FIG. 3, the two-dot chain line indicates the rotation speed of the pump shaft, the solid line indicates the discharge hydraulic pressure in the present embodiment, and the one-dot chain line indicates the discharge in the conventional case in which the bypass passage 19 is removed from the present embodiment. Shows hydraulic pressure. In the conventional case, the discharge oil pressure of the hydraulic pump 14 rises immediately after the start, whereas in the present embodiment, the discharge oil pressure rises with a delay of time t from the start, and the pressure increase until the time t elapses is ensured. Can be prevented.

Next, another embodiment of the present invention will be described with reference to FIGS. Referring to FIG. 4, the present embodiment is different from the embodiment of FIG. 1 in that pump control unit 7 as a hydraulic device of the embodiment of FIG. However, in the pump unit 7A as the hydraulic device of the present embodiment,
The point is that the pressure control valve 40 and the throttle 41 are arranged in series in the bypass passage 19.

The throttle 41 is arranged closer to the oil tank 15 than the pressure control valve 40, and the pressure control valve 40 has a pilot oil passage 42. The pilot oil passage 42 is connected to a connection point e between the pressure control valve 40 and the throttle 41 in the bypass passage 19 in order to pilot the secondary pressure of the pressure control valve 40. Immediately after the start of the hydraulic pump 14, when the rotation speed of the pump shaft is low and the pressure in the discharge passage 17 is low, the pressure control valve 40 opens the bypass passage 19 through the internal oil passage 44 as shown in FIG. In state. Therefore, the oil is supplied to the oil tank 1 through the bypass 19.
Circulated to 5.

On the other hand, when the rotation speed of the pump shaft increases and the pressure in the discharge passage 17 increases, the pressure in the portion of the bypass passage 19 closer to the discharge passage 17 than the throttle 41 in the bypass passage 19 increases. Using this pressure as the pilot pressure, the pressure control valve 40 enters the second state in which the bypass passage 19 is shut off as shown in FIG. 5 and is sent from the discharge passage 17 to the solenoid valve 6 side. 4 and FIG.
Therefore, the same reference numerals are given to the drawings and description thereof will be omitted.

FIG. 6 is a graph showing the change over time in the number of revolutions of the pump shaft of the hydraulic pump 14 and the oil pressure in the discharge passage 17 over time in this embodiment. In FIG. 6, the two-dot chain line indicates the rotation speed of the pump shaft, the solid line indicates the discharge hydraulic pressure in the present embodiment, and the one-dot chain line indicates the discharge in the conventional case where the bypass passage 19 is removed from the present embodiment. Shows hydraulic pressure. In the conventional case, the discharge hydraulic pressure of the hydraulic pump 14 rises immediately after the start, whereas in the present embodiment, the discharge hydraulic pressure is reduced until the time t elapses from the start.
It rises slowly. That is, high pressure can be prevented from being generated during this time.

Next, the specific structure of the pressure control valve 40 and the throttle 41 will be described with reference to FIG. Pressure control valve 4
Numeral 0 denotes an elastic member 47 comprising a spool 45, a circular hole 46 for slidably housing the spool 45, and a compression coil spring for urging the cylindrical comb-shaped spool 45 in the opening direction.
And The spool 45 has a circumferential groove 49 for partitioning an annular oil passage 48 between the spool 45 and the inner circumferential surface of the circular hole 46. 50 and a second large diameter portion 51.

The casing K1 of the pressure control valve 40 has a first internal oil passage 52, a second internal oil passage 53, and a third internal oil passage 54 orthogonal to the above-mentioned circular hole 46, respectively. The first and second internal flow paths 52 and 53 are arranged to face each other with the circular hole 46 interposed therebetween in the radial direction. The annular oil passage 48 is connected to the oil chamber 57 via the pilot oil passage 42 including the second internal oil passage 53, the oil passage 55, and the oil passage 56.
Is in communication with One end of the spool 45 enters the oil chamber 57, and the pressure guided into the oil chamber 57 as pilot pressure via the pilot oil passage 42 urges the spool 45 in the closing direction. I have. Reference numeral 58 denotes a stopper for sealing the oil chamber 57, and abuts on one end of the spool 45 to position the spool 45 at the open position.

The first and second internal oil passages 52 and 53 are disposed so as to be able to communicate with one end of the annular oil passage 48, while the third internal oil passage 54 is connected to the other end of the annular oil passage 48. It is arranged to be able to communicate with the end side. An orifice forming body 59 that forms a fixed orifice as the throttle 41 is fitted in the third internal oil passage 54. The first internal oil passage 52 communicates with the branch point d of the discharge passage 17 and the third internal passage 5
4 leads to the oil tank 15 side. Immediately after the start of the hydraulic pump 14, the oil discharged to the discharge path 17 passes through the first internal oil path 52, the annular oil path 48, and the third internal oil path 54 in which the throttle 41 is arranged in order, and Refluxed to 15.

Reference numeral 61 denotes a retainer 6 at the other end of the spool 45.
An accommodation hole for accommodating the elastic member 47 with which one end is engaged through the accommodation hole 2, and the accommodation hole 62 communicates with the drain hole 60. The accommodation hole 62 is closed in a liquid-tight manner by a bottomed cylindrical cover 63, and a guide member 64 engaged with the other end of the elastic member 47 is provided on the inner peripheral surface of the cover 63.
Are slidably and liquid-tightly accommodated. The guide member 64 is integrally provided with a screw rod 66 which is screw-coupled to a state penetrating a screw hole 65 formed in the cover 63. 67
Is a lock nut which is fastened to the end face of the cover 63 in a state of being connected to the screw rod 66 and locks a position where the screw rod 66 is connected to the screw hole 65. The preload of the elastic member 47 is adjusted by adjusting the coupling position of the threaded rod 66, and the pressure when the valve closes can be adjusted through this.

When the discharge oil pressure is low immediately after the start of the pump, the spool 45 opens the circular hole 46 as shown in FIG. 7.
When the pilot pressure guided to the oil chamber 57 via the
And the first large-diameter portion 50 is displaced toward the first internal oil passage 5.
The circular hole 46 is closed between the second and third internal oil passages 54, whereby the bypass passage 19 is shut off.

In the present embodiment, similarly to the embodiment of FIG. 1, it is possible to suppress the generation of high temperature and high pressure immediately after the start of the hydraulic pump 14 and to improve the durability of the seal and the bearing. In particular, since a valve that operates according to the internal pressure is used, it is possible to reliably prevent high pressure from being generated. Further, since the throttle 41 is built in the casing K1 of the pressure control valve 40, the structure can be simplified.

The present invention is not limited to the above embodiments. For example, instead of the flow control valve 20 and the pressure control valve 40, an electromagnetic valve operated by a timer signal may be used to bypass the passage 19. May be opened and closed. Further, the accumulator 22, the pressure switch 70, and the solenoid valve 6 may be included in the pump units 7, 7A as hydraulic devices. In addition, various changes can be made within the scope of the present invention, such as applying the pump unit of each of the above embodiments to ABS.

[0037]

According to the first aspect of the present invention, since the hydraulic pump is circulated through the bypass circuit immediately after the start and while the rotation speed of the pump shaft of the hydraulic pump is low (bearing load capacity is small), the hydraulic pump is generated. As a result of keeping the pressure low, the oil does not become hot, and an unnecessarily high load is not applied to the bearing of the pump shaft. On the other hand, when the pump rotation speed becomes high (bearing load capacity becomes large), the bypass circuit closes and the generated pressure becomes high. However, since the bearing load capacity becomes large, metal contact hardly occurs. Particularly when the hydraulic pump is a gear pump, there is a remarkable effect in improving the durability of the bearing.

According to the second aspect of the present invention, since the flow control valve is used, the valve structure can be simplified as compared with the case where a pressure-sensitive spool valve is used. According to the third aspect of the present invention, since the valve hole is opened and closed by the ball using the intermediate member that receives the differential pressure, the opening and closing are reliable. Further, by setting the urging force of the elastic member, the flow rate for operating the ball can be easily adjusted.

According to the fourth aspect of the present invention, since the pilot-type pressure control valve is used, an increase in the internal pressure immediately after the start of the hydraulic pump can be reliably suppressed. According to a fifth aspect of the present invention, in the automatic clutch device, the first to fourth aspects are provided.
The operation and effect obtained in the above can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram schematically showing an automatic clutch device to which a pump unit as a hydraulic device according to an embodiment of the present invention is applied.

2 (a) and 2 (b) are cross-sectional views respectively showing a flow control valve included in the pump unit of FIG. 1 when it is opened and when it is closed.

FIG. 3 is a graph showing how the rotational speed of the pump shaft and the oil pressure in the pump unit change over time after the hydraulic pump of the pump unit of FIG. 1 is started.

FIG. 4 is a schematic configuration diagram schematically showing an automatic clutch device to which a pump unit as a hydraulic device according to another embodiment of the present invention is applied, and shows a state immediately after the start of the pump.

FIG. 5 shows a state after a predetermined time has elapsed from the start of the pump in the automatic clutch device of FIG. 4;

6 is a graph showing, over time, how the rotational speed of the pump shaft and the oil pressure in the pump unit change after starting the hydraulic pump of the pump unit of FIG. 4;

FIG. 7 is a cross-sectional view of a pressure control valve included in the pump unit of FIG. 4, illustrating a state where the pressure control valve is opened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Auto-clutch device 2 Friction clutch 3 Release bearing 4 Release fork 5 Slave cylinder 6 Solenoid valve 7, 7A Pump unit (hydraulic device) 8 Flywheel 10 Clutch disk 11 Pressure plate 13 Diaphragm spring 14 Hydraulic pump 15 Oil tank 16 Suction path 17 Discharge path 18 Check valve 19 Bypass path 20 Flow control valve 22 Accumulator 23 Valve hole 24 Ball 25 Intermediate member 26 Elastic member 40 Pressure control valve 41 Throttle 42 Pilot oil passage 45 Spool 46 Circular hole 47 Elastic member 48 Annular oil passage 59 Orifice Formed body

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 3H044 AA02 BB01 CC00 CC08 CC12 CC16 CC18 CC21 CC26 DD10 DD11 DD24 DD42 DD43 DD45 3H045 AA02 AA09 AA12 AA24 AA34 BA43 BA44 CA03 CA06 DA19 EA43 3H089 AA90 BB30 CB30 DB01 3J057 AA06 BB03 CB12 GA02 GD04 GD25 HH02 JJ01

Claims (5)

[Claims] 1. A hydraulic pump for discharging oil sucked from an oil tank through a suction path through a discharge path, a bypass path communicating the discharge path with the oil tank, and a valve disposed in the bypass path. Means, wherein the valve means closes the bypass passage with a delay from activation of the hydraulic pump. 2. The hydraulic device according to claim 1, wherein said valve means comprises a flow control valve which closes the bypass passage when a flow rate flowing through the bypass passage becomes equal to or higher than a predetermined flow rate. 3. The flow control valve includes a ball capable of closing a valve hole, and an elastic member that pushes the ball in an opening direction through an intermediate member. 3. The hydraulic device according to claim 2, wherein the hydraulic device is displaced in a direction allowing the ball to close the valve hole against the elastic member in response to the differential pressure. 4. The apparatus according to claim 1, further comprising a throttle provided in series with the valve means in the bypass passage, wherein the valve means comprises a pressure control valve for shutting off the bypass passage using a pressure generated upstream of the throttle as a pilot pressure. The hydraulic device according to claim 1, wherein 5. A friction clutch for connecting and disconnecting power transmitted from a power source to a transmission by movement of a release member, and a hydraulic pressure for driving the release member in a direction in which the friction clutch is disengaged. An automatic clutch device including the hydraulic device according to any one of the above.