JPH0531005Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a hydraulic pressure holding valve for locking the brakes in a vehicle, and is specifically designed to maintain the appropriate hydraulic pressure required for locking the brakes without using a solenoid valve. The present invention relates to a hydraulic pressure holding valve for a brake lock, which has a very light operating force, and has a simple and compact structure.

BACKGROUND TECHNOLOGY Conventionally, when working on a stopped vehicle equipped with a hydraulic brake system, in order to increase work safety, the parking brake can be operated manually on the condition that the parking brake is applied. A brake lock device is adopted. In this brake lock device, when the parking brake is operated with an operating force above a certain value while the engine is running, the preparation for brake lock operation is completed, and when the brake lock operation switch is turned on in this state, the electromagnetic valve is activated. The hydraulic pressure required for the brake lock is confined and held within the oil pipe of the brake device, and the brake lock is activated by the hydraulic pressure.

However, in this type of vehicle that uses a solenoid valve to maintain oil pressure, maintaining the oil pressure of the brake lock device depends on the solenoid valve, so if a failure occurs in the vehicle's electrical system, the failure will occur. There was a risk that it would be affected by

In addition, the applicant of the present application proposed a hydraulic pressure holding valve for a manually operated brake lock that does not use a solenoid valve in Utility Application No. 123506/1983 (Patent Application No. 28358/1983), but in this invention, the cylinder A small-diameter cylinder chamber, a medium-diameter cylinder chamber, and a large-diameter cylinder chamber are provided in the cylinder chamber, a plunger and a piston valve are provided in these cylinder chambers, and a valve and a first compression spring are built in the plunger. When locking the brake, the pressing force from the hydraulic pressure acts on the entire cross-sectional area of the plunger, so an extremely large operating force is required when operating the operating member to shift the brake lock to the activated state. Also, since the mechanism is complex and the overall height is considerably high,
The problem was that the device could not be made more compact.

Purpose The present invention was made in order to eliminate the above-mentioned problems of the prior art, and its purpose is to provide a cylinder with a large diameter cylinder chamber and a small diameter cylinder chamber. A push rod that is pressed and operated by an operating member is slidably accommodated in the chamber, and a piston, whose center portion is penetrated by the push rod, is slidably accommodated in the large diameter cylinder chamber. A piston valve is slidably housed in the small-diameter cylinder chamber, and a second compression spring presses the piston valve toward the large-diameter cylinder chamber. Appropriate oil pressure is maintained in the small diameter cylinder chamber, and when operating the operating member that manually operates the push rod, the push rod is pressed when the brake lock is not activated, and the pressure on the push rod is released when the brake lock is activated. The object of the present invention is to reduce the operating force of the operating member. Another object is to simplify the structure by limiting the number of cylinder chambers of the cylinder to two and the number of movable members within the cylinder to two, thereby making the device more compact. Another purpose is to maintain an appropriate hydraulic pressure when the brake lock is activated by balancing the resultant force of the pressing forces of the first compression spring and the second compression spring with the pressing force of the hydraulic pressure acting on the piston and piston valve. Excessive oil pressure is automatically corrected, and it can also flexibly respond to increased pressure on the brake pedal, without relying on electromagnetic valves.
To provide a hydraulic pressure holding valve which can be manually operated and has extremely high reliability so that even if a failure occurs in an electrical system, the hydraulic pressure holding of a brake lock device is not affected.

Configuration In short, the present invention is a hydraulic pressure retention system for brake locking that allows the hydraulic pressure for brake locking to be maintained within the brake device by operating the parking brake with an operating force above a certain value when the vehicle is stopped. In the valve, a large-diameter cylinder chamber that is connected to the master cylinder that is activated by pressing the brake pedal and a small-diameter cylinder chamber that is connected to the booster of the brake device are formed inside and communicate with each other. a cylinder; a push rod slidably housed within the cylinder; one end protruding from the cylinder and the other end facing the small diameter cylinder chamber; a push rod slidably housed within the large diameter cylinder chamber; A piston in which the one end of the push rod slidably passes through the center thereof to form an oil passage around the piston, and a first compression spring that biases the piston toward the small diameter cylinder chamber. The push rod is slidably housed in the small diameter cylinder chamber, and is configured such that the one end of the push rod can come into contact with and press the center portion of the push rod, and the valve seat portion of the piston is arranged around the center portion. a piston valve integrally equipped with a valve that can come into contact with the small diameter cylinder chamber and cut off communication between the small diameter cylinder chamber and the large diameter cylinder chamber; and the piston valve is mounted on the large diameter cylinder chamber side. a second compression spring that presses and biases; and a second compression spring that comes into contact with one end of the push rod to press the push rod when the brake lock is not activated and release the pressure on the push rod when the brake lock is activated. or a locking device having an operating member that manually displaces the push rod when the brake lock is activated, and an electromagnetic solenoid provided with a lock pin that restricts rotation of the operating member; The piston valve is pressed by a push rod to separate the piston valve from the piston, thereby communicating the large diameter cylinder chamber and the small diameter cylinder chamber, and when the brake lock is activated, the push rod presses the piston valve. The invention is characterized in that the piston valve is pressed against the piston by releasing the piston valve, thereby blocking communication between the large-diameter cylinder chamber and the small-diameter cylinder chamber.

The present invention will be explained below based on embodiments shown in the drawings. In FIG. 1, a hydraulic pressure holding valve 1 for brake lock according to the present invention is connected to a master cylinder 4 and an oil reservoir tank 5 operated by a brake pedal 3 of a brake lock device 2, a front brake FB, and a rear brake RB. The circuits connected to the booster 6, drawn with thick solid lines in the figure, are hydraulic circuits, and those drawn with thin solid lines are electrical circuits.

The hydraulic pressure holding valve 1 includes a lock device 9 equipped with an electromagnetic solenoid 8, a brake lock position switch 11 that detects the position of the operating member 10,
A pressure switch 12 for detecting the hydraulic pressure for the brake lock held is attached to each of them.

Further, in the electric circuit shown in FIG. 1, a parking brake lever 14, a parking lamp switch 15, a parking brake main body 16 and its interlocking mechanism 18, a parking brake operating force sensor switch 19, a brake lock operation preparation lamp 20, and a movable piece 21 and a relay switch 23 consisting of a relay coil 22, a brake lock pressure holding lamp 24, a movable piece 25, and a relay coil 26.
a relay switch 28 consisting of and an alarm buzzer 2
9, diode 30, parking lamp 31, vacuum warning switch 32, and brake warning light 3
3 is connected to a power source 34 as shown in the figure, and since these are well known, their explanation will be omitted.

The hydraulic pressure holding valve 1 for locking the brake according to the present invention can hold the hydraulic pressure for locking the brake in the brake device 45 by operating the parking brake with an operating force of a certain value or more when the vehicle is stopped. The second
As shown in the figure, a cylinder 40, a push rod 41, a piston 42, and a first compression spring 51
, a piston valve 43, and a second compression spring 52.
, an operating member 10 , and a locking device 9 .

The cylinder 40 includes a large-diameter cylinder chamber 40a that is communicatively connected to a master cylinder 4 that is activated by pressing the brake pedal 3, and a brake device 45.
A small-diameter cylinder chamber 40b, which is connected to the booster 6, is formed inside the cylinder chamber 40b, which is in communication with each other, and an oil port 40c is formed in the large-diameter cylinder chamber 40a. Oil ports 40d are formed in the cylinder chambers 40b to communicate with each other. The oil port 40c is connected to the master cylinder 4 via an oil pipe 46, and the oil port 40d is connected to an oil pipe 55.
It is communicatively connected to the booster 6 via. The lower end 40e of the cylinder 40 is closed,
The upper end 40f is open. Opened upper end 40f
The bearing member 4 is sealed by a seal member 47.
8 is installed. Further above the bearing member 48, a bracket 49 is fixed, and the brake lock position switch 11 and the operating member 10 are attached to the bracket 49.

The push rod 41 is slidably housed in the cylinder 40, and one end 41a is attached to the cylinder 40.
0, and the other end 41b is arranged so as to face the small diameter cylinder chamber 40b.
The upper end 41a of the push rod 41 is formed to have the largest diameter, and is slidably accommodated in a bracket 49. The shaft portion 41c passes through the bracket 49 and the bearing member 48, and a seal member 50 is interposed between the shaft portion and the bearing member 48. Also, between the shaft portion 41c and the one end 41b, there is a medium diameter portion 41d.
is formed. The medium diameter portion serves as a stopper that limits the upward movement stroke of the piston 42. One end 41b is formed to have the smallest diameter, passes through the piston 42, and engages with the piston valve 43.

The piston 42 is slidably housed in a large-diameter cylinder chamber 40a, and is connected to the push rod 41.
One end 41b slidably passes through the center thereof, and an oil passage 42a is formed around the end 41b. Further, a seal member 53 is installed between the piston 42 and the cylinder 40.

The first compression spring 51 connects the spring receiver 54 and the piston 4 that are in contact with the bearing member 48 so as to press and bias the piston 42 toward the small-diameter cylinder chamber 40a.
It is installed between 2. The spring constant is set to such a value that the piston 42 will not be pushed up by the appropriate oil pressure when the small diameter cylinder chamber 40b maintains an appropriate oil pressure.

The piston valve 43 has a small diameter cylinder chamber 40.
One end 41b of the push rod 41 is configured to abut against and press the center of the push rod 41, and a valve seat 42b of the piston 42 is fitted around the center of the push rod 41. A small diameter cylinder chamber 40b and a large diameter cylinder chamber 40a are in contact with each other.
A valve 43c that can cut off communication with is integrally installed. This valve 43c is
For example, it is made of oil-resistant rubber. In addition, a metal bush 4 is located in the center of this valve 43c.
3d is attached, and one end 41b of a push rod 41 is engaged with the bush.

The second compression spring 52 presses the piston valve 43 toward the large-diameter cylinder chamber 40a, and pushes the valve 43c toward the valve seat portion 4 of the piston 42.
2b so that an appropriate hydraulic pressure can be maintained in the small diameter cylinder chamber 40b.

Referring also to FIG. 6, the operating member 10 is configured to come into contact with one end 41a of the push rod 41 to press the push rod when the brake lock is not activated, and to release the pressure on the push rod 41 when the brake lock is activated. The push rod is manually moved to a brake lock non-operating state or a brake lock operating state. Fixed shaft 57 of operating member 10
is fixed to the bracket 49 by a set screw 56, a pair of cams 58, 59 are rotatably fitted to the fixed shaft 57, a lever 60 is screwed onto the cam 58, and is tightened and fixed by a lock nut 61. There is. Inside the lever 60 is a lock bar 62.
is slidably accommodated, and its large diameter portion 62a
is pressed toward the fixed shaft 57 by the compression spring 63, the tip 62b is always in contact with the fixed shaft 57, and only one lever is provided on the outer peripheral surface of the fixed shaft 57 in order to keep the lever 60 in the brake lock operation state. It is designed so that it can be engaged with a lock hole 57a formed therein. The cams 58 and 59 are connected by a connecting pin 65 and restrained in the axial direction by a retaining ring 66. The cam 58 is formed with a minimum lift portion 58a, a maximum lift portion 58b, and a switch lift portion 58c, and the cam 59 is formed with a minimum lift portion 58a, a maximum lift portion 58b, and a switch lift portion 58c.
A minimum lift portion 59a for keeping the brake in the non-operating state is formed at only one location.

A knob 68 is fixed to the upper end 62b of the lock lever 62 for pulling up the lock lever against the compression spring 63.

Although not shown in FIGS. 2 to 5, the pressure switch 12 shown in FIG. 1 is attached to the small-diameter cylinder chamber 40b of the cylinder 40 so that the pressure in the small-diameter cylinder chamber 40b can be measured. ing.

The brake lock position switch 11 has a threaded portion 11a screwed onto a bracket 49, and a slidable actuator 11b is pressed by a switch lift portion 58c of a cam 58 of the operating member 10.

Function The present invention is constructed as described above, and its function will be explained below. In FIGS. 1 and 2, when the brake lock device 2 is in the non-operating state, the operating member 10 of the hydraulic pressure holding valve 1 is set to be inclined to the left in the figure, as shown in the figures. In this case, the tip 62b of the lock lever 62 of the operating member 10 is in contact with the outer peripheral surface of the fixed shaft 57, so that the operating member 10 can be freely rotated. However, since the electromagnetic solenoid 8 is not energized, the lock pin 70 of the electromagnetic solenoid 8 is pressed by the compression spring 74 and the cam 59
The brake is kept in a stable non-operating state by contacting the minimum lift portion 59a of the brake.

Further, since the maximum lift portion 58b of the cam 58 is in contact with one end 41a of the push rod 41, the push rod is pressed downward. A gap is created between the valve 43c and the valve seat portion 42b of the piston 42, and the large diameter cylinder chamber 40a and the small diameter cylinder chamber 40b communicate with each other. Further, in this case, since the piston 42 is in contact with the stepped portion 40g of the cylinder 40, it cannot move downward from the illustrated position even if it is pressed by the first compression spring 51.

Therefore, when performing normal brake operation,
When the brake pedal 3 is depressed, oil is sent from the master cylinder 4 to the oil port 40c through the oil pipe 46, flows from the oil port 40c into the large diameter cylinder chamber 40a of the cylinder 40 as shown by arrow A, and the oil Hydraulic pressure flows from the gap between the piston 42 and the piston valve 43 to the small-diameter cylinder chamber 40b through the passage 42a, flows from there to the oil port 40d, and is supplied to the booster 6 through the oil pipe 55. As a result, hydraulic pressure as a service brake is supplied to the front brake FB and rear brake RB of the brake device 45, so that brake operations can be performed without any trouble while the vehicle is running.

Further, in this case, the actuator 11b of the brake lock position switch 11 is operated by the cam 58.
Since the brake lock position switch is pressed by the switch lift part 58c, the brake lock position switch is
It is set to OFF.

That is, in FIG. 1, since the parking brake lever 14 is not pulled upward as shown by the imaginary line, the parking lamp switch 15 is not pulled upward.
OFF, and therefore no current flows from the power supply 34 to the relay coil 22 and parking lamp 31, the relay coil is deenergized, and the parking lamp 31 does not light up. As a result, the movable piece 21 maintains the relay switch 23 in the OFF state, the electromagnetic solenoid 8 is not energized, the lock pin 73 contacts the minimum lift portion 59a of the cam 59, and the brake lock operation preparation lamp is turned on. 20
The light is not even lit. Since the operating member 10 is not operated, the brake lock position switch 11 is OFF, so the brake lock pressure holding lamp 24 is not lit either.

Next, referring to FIG. 3, a case will be described in which the hydraulic pressure holding valve 1 maintains an appropriate hydraulic pressure for brake locking in the small diameter cylinder chamber 40b.
To activate the brake lock, pull the parking brake lever 14 upward as shown by the solid line in FIG. As a result, the parking lamp switch 15 is turned ON, current flows from the power supply 34 to the relay coil 22 of the relay switch 23 and the parking lamp 31, the parking lamp lights up, and the movable piece 21 turns on the relay switch 23.
Turn it on. As a result, the brake lock operation preparation lamp 20 becomes ready to light up.
Furthermore, when the parking brake lever 14 is pulled sufficiently and the parking brake body can apply a sufficient parking brake via the interlocking mechanism 18, the operating force sensor switch 19 is also turned on.
As a result, the brake lock operation preparation lamp 20 lights up for the first time.

On the other hand, when the relay switch 23 is turned on, current flows from the power supply 34 to the electromagnetic solenoid 8, and as a result, the lock pin 7 of the lock device 9 is turned on.
3 changes from the state shown in FIG. 2 to the state shown in FIG. 3, that is, the lock pin 73 is pulled to the right and the cam 5
9 from the minimum lift portion 59a. As a result, the operating member 10 can be rotated to the brake lock operating state, and after the brake pedal 3 is depressed and an appropriate hydraulic pressure is generated in the small diameter cylinder chamber 40b, the operating member 10 is rotated as shown in FIG. Rotate clockwise as shown. This causes the cam 58 to rotate so that its minimum lift portion 58a faces the one end 41a of the push rod 41.
The push rod is raised by the second compression spring 52, and the piston valve 43 is raised and its valve 43c is pressed against the valve seat 42b of the piston 42, thereby establishing communication between the large diameter cylinder chamber 40a and the small diameter cylinder chamber 40b. is blocked.

At this time, the tip 62b of the lock lever 62 of the operating member 10 engages with the lock hole 57a of the fixed shaft 57, and is pressed by the compression spring 63 to become unable to rotate, and the operating member 10 is reliably held in the brake lock operating state. It turns out.

As a result, in FIG. 3, even if the trapped oil were to flow backwards as indicated by arrow B, this backflow is prevented by the piston 42 and the piston valve 43. That is, the pressing force of the first compression spring 51 exceeds the appropriate hydraulic pressure to push it up, so the piston 42 does not rise and the valve 43 comes into close contact with the valve seat 42b of the piston 42, causing the large diameter This is because communication between the cylinder chamber 40a and the small-diameter cylinder chamber 40b is completely cut off.

When the proper oil pressure is maintained in this way, the pressure switch 12 is in the OFF state, so
Even if the brake lock position switch 11 is turned on by operating the operating member 10 to the brake lock state, the alarm buzzer 29 will not be energized, and therefore the alarm buzzer will not sound. . Also, since no current flows to the relay coil 26, the relay switch 28 is turned on and the brake lock pressure holding lamp 24 lights up to inform the driver that the proper oil pressure is being maintained. This proper hydraulic pressure for brake locking is supplied to the booster 6 via the oil pipe 55, and is supplied to the front brake FB and rear brake RB by the brake device 45, thereby operating the normal brake lock.

Next, with reference to FIG. 4, a case will be described in which the oil pressure to be maintained is excessive beyond an appropriate value. In this case, as shown by arrow C, hydraulic pressure exceeding the appropriate value acts on the piston 42 and overcomes the pressing force of the first compression spring 51, so that the piston 42 resists the first compression spring 51. push up,
On the other hand, the piston valve 43 is pushed up by the second compression spring 52, but one end 41b of the push rod 41 prevents it from rising above a certain value, so there is a gap between the valve seat 42b of the piston 42 and the piston valve 43. occurs, and the oil flows from the oil port 40d through the oil passage 42a into the large-diameter cylinder chamber 40a as shown by arrow C, and flows from the oil port 40c to the oil pulp 46, and in this way, the oil flows into the oil pressure holding valve 1. As a result of the reverse flow inside, the maintained hydraulic pressure gradually decreases and reaches the appropriate hydraulic pressure. Then, the pressing force of the first compression spring 51 again overcomes the maintained hydraulic pressure, and the third compression spring 51
As shown in the figure, the valve 43c is in close contact with the valve seat portion 42b of the piston 42, and hydraulic pressure is confined within the small diameter cylinder chamber 40b.

Next, a case will be described in which, for example, when the operating member 10 is rotated to the brake lock operating state with the brake pedal 3 insufficiently depressed, the held oil pressure falls below the appropriate value. In this case, since the pressure inside the small diameter cylinder chamber 40b is below a certain value, the pressure switch 12 is turned on.
As a result, the brake lock position switch 11
is already turned on, and power supply 3
4 flows to the alarm buzzer 29, the alarm buzzer sounds, and the driver is notified that the brake lock is abnormal. Also, the pressure switch 12
When it is turned on, current flows through the relay coil 26, energizing it, and the relay switch 28
is turned OFF and the brake lock pressure holding lamp 24 is turned off.

Next, a case will be described with reference to FIG. 5 in which the brake pedal 3 is further depressed to increase the maintained hydraulic pressure when the brake locking hydraulic pressure is insufficient. In this case, the operating member 10
has already rotated to the brake lock operating position, and if the brake pedal 3 is further depressed in this state, more oil will flow from the oil reservoir tank 5 to the oil port 4 via the oil pipe 46.
0c, flows into the large-diameter cylinder chamber 40a as shown by arrow E, flows through the oil passage 42a, and flows into the small-diameter cylinder chamber 40b.
The oil pressure supplied to and held in the oil pipe 55 from 0d gradually increases. In this case, when the additional depression of the brake pedal 3 is completed with sufficient hydraulic pressure being supplied to the oil port 40d and the small diameter cylinder chamber 40b, the pressure switch 12 is turned off again.
OFF, the alarm buzzer 29 stops sounding, and the brake lock pressure holding lamp 24 lights up, confirming that the brake lock has operated normally.

Also, from the brake lock operation state shown in Figure 3, the second
To return the operating member 10 to the brake lock non-operating state shown in the figure, pull the knob 68 upward against the compression spring 63 to lock the tip 6 of the lock lever 62.
2b from the lock hole 57a of the fixed shaft 57, and rotate it counterclockwise. As a result, the maximum lift portion 58b of the cam 58 presses the push rod 41, and the push rod descends to reach its one end 41b.
pushes down the piston valve 43 against the second compression spring 52. This releases the brake lock and stops energizing the electromagnetic solenoid 8 again, so that the lock pin 73 is pressed by the compression spring 74 and comes into contact with the minimum lift portion 59a of the cam 59. As a result, when the brake pedal 3 is depressed, a normal service brake operating state is achieved.

In the present invention, when the operating member 10 is to be moved from the brake lock non-operating state to the operating state, the pressure on the push rod 41 is relaxed, so that the operating force can be very small.

Furthermore, since the cylinder 40 consists of only two cylinder chambers 40a with a large diameter and cylinder chambers with a small diameter 40b, the total height of the hydraulic pressure holding valve 1 can be reduced, which not only makes the whole compact. , the structure is also simple.

Effects The present invention provides a cylinder with a large-diameter cylinder chamber and a small-diameter cylinder chamber as described above, and slidably accommodates a push rod that is pressed and operated by an operating member in the large-diameter cylinder chamber. The push rod slidably accommodates the piston passing through its center in the large diameter cylinder chamber, and presses the piston toward the small diameter cylinder chamber by the first compression spring. A valve piston is slidably accommodated, and a second compression spring presses the valve piston toward the large-diameter cylinder chamber to maintain an appropriate hydraulic pressure in the small-diameter cylinder chamber, and the push rod is manually operated. When operating the operating member, the push rod is pressed when the brake lock is not activated, and the pressure on the push rod is released when the brake lock is activated, which has the effect of reducing the operating force of the operating member. . Furthermore, since the cylinder has two cylinder chambers and the number of movable members within the cylinder is limited to two, the structure can be simplified and the apparatus can be made more compact. In addition, due to the force balance between the resultant force of the pressing force by the first compression spring and the second compression spring and the pressing force by the hydraulic pressure acting on the piston and piston valve, an appropriate hydraulic pressure can be maintained when the brake lock is activated, and excessive hydraulic pressure can be prevented. is automatically corrected, can flexibly respond to increased pressure on the brake pedal, can be operated manually without relying on electromagnetic valves, and has an extremely reliable hydraulic pressure holding valve integrated into the electrical system. This has the effect that even if a failure occurs, the oil pressure retention of the brake locking device will not be affected.

[Brief explanation of the drawing]

The drawings relate to an embodiment of the present invention, and FIG. 1 is a schematic diagram of the brake lock device when the brake lock is not activated, FIG. 2 is a longitudinal cross-sectional view of the oil pressure holding valve when the brake lock is not activated, and FIG. Vertical sectional view of the oil pressure holding valve showing a state in which proper oil pressure is maintained in the lock operating state, No. 4
The figure is a vertical sectional view of the oil pressure holding valve showing the state when the held oil pressure exceeds the appropriate value, and Figure 5 is a longitudinal sectional view of the oil pressure holding valve showing the state when the brake pedal is further depressed in the brake lock activated state. FIG. 6 is a cross-sectional view of the main parts of the operating member and the locking device. 1 is a hydraulic pressure holding valve for locking the brake, 2 is a brake lock device, 3 is a brake pedal, 4 is a master cylinder, 6 is a booster, 8 is an electromagnetic solenoid, 9 is a lock device, 10 is an operating member, 40 is a cylinder , 40a is a large diameter cylinder chamber, 40b is a small diameter cylinder chamber, 41 is a push rod, 41
a is one end, 41b is the other end, 42 is a piston,
42a is an oil passage, 43 is a piston valve, 4
3c is a valve, 51 is a first compression spring, 52 is a second compression spring, and 73 is a lock pin.

Claims (1)

[Scope of utility model registration request] The hydraulic pressure holding valve for brake locking is designed to hold the hydraulic pressure for locking the brake in the brake device by operating the parking brake with an operating force above a certain value when the vehicle is stopped. A cylinder formed inside of which a large-diameter cylinder chamber is communicated with a master cylinder that is operated by operation and a small-diameter cylinder chamber that is communicated with a booster of a brake device; a push rod that is slidably housed in the cylinder, with one end protruding from the cylinder and the other end facing the small diameter cylinder chamber; and a push rod that is slidably housed in the large diameter cylinder chamber, with the one end of the push rod at its center. a first compression spring that presses the piston toward the small diameter cylinder chamber, and a first compression spring that presses the piston toward the small diameter cylinder chamber; The one end of the push rod is configured to abut against and press the center portion of the push rod, and the small-diameter portion of the push rod abuts against the valve seat portion of the piston around the center portion. a piston valve integrally equipped with a valve capable of blocking communication between a cylinder chamber and the large-diameter cylinder chamber;
a second compression spring that presses and urges the piston valve toward the large diameter cylinder chamber; A lock device having an electromagnetic solenoid provided with an operating member that manually displaces the push rod to a brake lock non-operating state or a brake lock operating state by releasing the pressure, and a lock pin that restricts rotation of the operating member. and when the brake lock is not activated, the push rod presses the piston valve to separate the piston valve from the piston, thereby communicating the large diameter cylinder chamber and the small diameter cylinder chamber,
When the brake lock is activated, the pressure on the piston valve by the push rod is released, the piston valve is pressed against the piston, and communication between the large diameter cylinder chamber and the small diameter cylinder chamber is cut off. A hydraulic pressure holding valve for brake locking, which is characterized by: