JPH0727105A - Brake valve - Google Patents

Abstract

PURPOSE:To improve the responsiveness and safety at the time of starting by preventing relief valves from relieving at low pressures when an actuator starts. CONSTITUTION:A pair of check valves 13A, 13B, a counterbalance valve 16, relief valves 24A, 24B, and accumulators 53A, 53B for low pressure relief are provided in the casing 52 of a brake valve 51. Then, the insides of the piston- sliding holes 54A, 54B of the accumulators 53A, 53B are defined by pistons 56A, 56B into oil storage chambers 57A, 57B and pressure chambers 58A, 58B, and the pistons 56A, 56B are constantly energized by weak springs 60A, 60B toward the pressure chambers 58A, 58B sides. Further, the pressure chambers 58A, 58B of the accumulators 53A, 53B are constantly connected to the oil pressure source side oil passages 10A, 10B by communication passages 61A, 61B formed in the casing 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake valve suitable for use in a hydraulic motor drive circuit such as a hydraulic circuit for traveling or a hydraulic circuit for turning of a hydraulic excavator.

[0002]

2. Description of the Related Art Generally, construction machines such as hydraulic excavators and hydraulic cranes are driven (or swung) by supplying and discharging pressure oil from a hydraulic source to and from a hydraulic motor as an actuator. Since an excessive inertial load is received when the brake is stopped, a brake valve is provided in the middle of the hydraulic circuit to convert the inertial load into heat energy of the pressure oil and absorb the heat energy.

Therefore, FIGS. 5 to 11 show an example of a hydraulic motor drive circuit provided with a brake valve according to the prior art.

In the figure, reference numeral 1 denotes a hydraulic motor as an actuator. The hydraulic motor 1 has a pair of pipe lines 2A,
2B and the like, a hydraulic pump 3 as a hydraulic source, a tank 4
The hydraulic pump 3 is connected to the hydraulic pump 3 to supply and discharge the hydraulic oil to drive a vehicle such as a hydraulic excavator. Here, the hydraulic pump 3 is rotationally driven by a prime mover 5 such as a diesel engine, and discharges the hydraulic oil in the tank 4 as high pressure oil toward the hydraulic motor 1 and the like.

Reference numeral 6 denotes a directional control valve provided between the hydraulic motor 1 and the hydraulic pump 3 and provided in the middle of the pipelines 2A and 2B. The directional control valve 6 is operated by the operator from the neutral position (a). Switching operation is performed to the switching positions (b) and (c), and the rotation direction of the hydraulic motor 1 is switched to the directions of arrows F and R in FIG. 5 at the switching positions (b) and (c). Further, when the direction switching valve 6 returns to the neutral position (a), the pressure oil is shut off from the hydraulic pump 3 toward the hydraulic motor 1 and the hydraulic motor 1 is stopped.

Reference numeral 7 denotes a brake valve provided between the hydraulic motor 1 and the direction switching valve 6 and provided in the middle of the pipelines 2A, 2B. The brake valve 7 is a check valve 13A, which will be described later.
13B, counter balance valve 16 and relief valve 24
It is composed of A, 24B and the like, and is integrally provided in the housing of the hydraulic motor 1. And the brake valve 7
Generates a brake pressure in actuator-side oil passages 11A and 11B, which will be described later, when the hydraulic motor 1 inertially rotates when the directional control valve 6 is returned to the neutral position (a). It gives a braking force.

Next, the brake valve 7 will be described with reference to FIGS. 6 and 7.

In the figure, reference numeral 8 denotes a casing of a brake valve 7 attached to the hydraulic motor 1, and a pair of oil passages 9A and 9B are formed in the casing 8 so as to form a part of the pipelines 2A and 2B.
The oil passages 9A, 9B are formed by hydraulic pressure source side oil passages 10A, 10B connected to the hydraulic pump 3 and the tank 4 via the direction switching valve 6, and an actuator side oil passage connected to the hydraulic motor 1. It is generally composed of 11A and 11B. Further, a spool sliding hole 17, which will be described later, is formed between the hydraulic pressure source side oil passages 10A, 10B and the actuator side oil passages 11A, 11B.
Relief passages 12A and 12B are formed between B.

Reference numerals 13A and 13B denote hydraulic pressure source side oil passages 10A and 1B.
0B and a pair of check valves provided between the actuator side oil passages 11A and 11B.
A and 13B are valve seats 14 formed between the hydraulic pressure source side oil passages 10A and 10B and the actuator side oil passages 11A and 11B.
It is slidably arranged in the casing 8 so as to be seated on and off from the valve seats 14A and 14B by the valve springs 15A and 15B.
Always urged toward A and 14B. When the pressure oil from the hydraulic pump 3 flows into the hydraulic pressure source side oil passages 10A and 10B, the check valves 13A and 13B open against the valve springs 15A and 15B by the pressure at this time. ,
The pressure oil from the hydraulic pump 3 is transferred to the actuator side oil passage 11
It is designed to allow distribution to A and 11B. Further, in the opposite direction, the actuator side oil passage 11
When the return oil or the like from the hydraulic motor 1 flows from A, 11B toward the hydraulic source side oil passages 10A, 10B, the valve spring 1
The check valves 13A and 13B are held closed by the valves 5A and 15B to prevent the flow in the opposite direction.

Reference numeral 16 denotes a counter balance valve provided between the oil pressure source side oil passages 10A and 10B and the actuator side oil passages 11A and 11B so as to be in parallel with the check valves 13A and 13B. Valve 16
Oil pressure source side oil passages 10A and 10B and actuator side oil passage 1
1A and 11B, a spool sliding hole 17 formed inside the casing 8 and a spool 18 slidably fitted in the spool sliding hole 17 are provided. 18 is located on the right side in FIG.
A land 19A that communicates and blocks the 0A and 11A, and a land 19B that is located on the left side and that communicates and blocks the oil passages 10B and 11B are provided. And the spool 18
On both end sides of the oil chamber 21A between the lids 20A and 20B,
21B is formed, and springs 22A, 22B for returning the neutral position for constantly biasing the spool 18 toward the neutral position are arranged in the oil chambers 21A, 21B.

Further, throttle passages 23A, 23B are formed at both ends of the spool 18 for communicating the oil pressure source side oil passages 10A, 10B with the oil chambers 21A, 21B at all times. The throttle passages 23A, 23B are connected to the oil pressure source side. Guide the pressure from the oil passages 10A, 10B into the oil chambers 21A, 21B as pilot pressure,
Based on the pilot pressure at this time, the spool 18 is set to the spring 2
Sliding displacement is performed against 2A and 22B. As a result, the counterbalance valve 16 is interlocked with the direction switching valve 6 to switch from the neutral position (a) shown in FIG. 5 to the switching positions (b) and (c), and the switching positions (b) and (c). ) With hydraulic motor 1
It allows the return oil from the tank to be discharged to the tank 4.

24A and 24B are actuator-side oil passages 1
1A and 11B show a pair of relief valves provided in the casing 8 in the middle of the relief valves 24A and 2B.
4B is a valve guide 25 described later, as shown in FIGS.
A, 25B, relief valve elements 28A, 28B, accumulators 32A, 32B, and the like constitute an overload relief valve with a so-called shockless function.

Reference numerals 25A and 25B denote tubular valve guides provided in the casing 8 so that their tip ends face the actuator-side oil passages 11A and 11B, respectively.
Reference numeral B designates a relief valve body 28A, 28B slidably held in the casing 8, and a communication hole 2 for communicating the actuator side oil passages 11A, 11B on the tip side thereof.
6A and 26B are provided in the radial direction.

27A and 27B are valve guides 25A and 25B
Valve seat cylinders 28A and 28B, which are located on the front end side of the valve seats and are fitted into the relief passages 12A and 12B, and serve as valve seats.
5A and 25B show a relief valve body slidably provided in the valve guides 25A and 28B.
Spring chambers 29A and 29B are defined in A and 25B, and setting springs 30A and 30B for urging the relief valve bodies 28A and 28B in the valve closing direction are disposed in the spring chambers 29A and 29B. Further, small-diameter throttle passages 31A and 31B for axially communicating the relief passages 12A and 12B with the spring chambers 29A and 29B are bored in the relief valve bodies 28A and 28B in the axial direction.

Here, the relief valve body 28A (28B)
As shown in FIG. 7, the pressure receiving area A1 on the valve seat cylinder 27A (27B) side is larger than the pressure receiving area A1.
The pressure receiving area A2 on the (29B) side is small (A2
<A1). Also, the spring force f of the setting spring 30A (30B)
Is the relief set pressure P in which the pressure in the actuator-side oil passage 11B (11A) and the spring chamber 29A (29B) is high.
When you go up to h,

[0016]

## EQU1 ## The relationship of A1.times.Ph> A2.times.Ph + f is satisfied. At this time, the relief valve body 28A (28B) is set by the setting spring 30A (30
By opening the valve against B), the actuator-side oil passages 11B and 11A are communicated with each other through the relief passage 12B (12A) and the communication hole 26A (26B), and the inside of the actuator-side oil passage 11B (11A) is opened. Limit the pressure below the relief setting pressure Ph.

32A and 32B are relief valves 24A and 24.
B shows an accumulator for giving a shockless function to the relief valves 24A and 24B. The accumulators 32A and 32B are piston sliding holes 33 described later.
A, 33B, pistons 35A, 35B, oil storage chamber 37A,
37B and pressure chambers 38A, 38B and the like.

33A and 33B are actuator-side oil passages 1
Piston sliding holes formed in the casing 8 so as to be in constant communication with 1A and 11B through oil holes 34A and 34B, 3
5A and 35B are pistons as movable partition walls slidably fitted in the piston sliding holes 33A and 33B,
The pistons 35A and 35B are formed in a cylindrical shape with a bottom, and the bottom side thereof is a lid body 36 screwed to the casing 8 from the outside.
Oil storage chambers 37A and 37B are defined between A and 36B, and pressure chambers 38A and 38B are defined between the oil holes 34A and 34B.

Here, the oil storage chambers 37A, 37B are connected to the casing 8 by small-diameter communication passages 39A, 39B and the valve guides 25A, 25B.
The relief valves 24A and 24B are provided with a shockless function by communicating with the spring chambers 29A and 29B via A and 40B and temporarily storing a part of the pressure oil flowing into the spring chambers 29A and 29B. Relief valve 24A, as described below,
24B low pressure relief. Also, the piston 35A,
35B has a weak spring 41 between the oil holes 34A and 34B.
A and 41B are provided, and the weak springs 41A and 41B constantly urge the pistons 35A and 35B toward the lids 36A and 36B.

The actuator side oil passages 11A, 1
1B causes a pressure difference, and for example, the actuator side oil passage 1
The pressure oil in 1B (11A) is the relief valve body 28A (28
B) through the throttle passage 31A (31B) of the valve guide 25
When it flows into the spring chamber 29A (29B) of A (25B), the piston 35A (35B) transfers the pressure oil at this time to the throttle passage 40A (40B) and the communication passage 39A (39B) of the valve guide 25A (25B). ) Via the oil storage chamber 37A (3
7B) so that oil is stored in the piston sliding hole 33A
The inside of (33B) is slidably displaced to a position where it abuts on the oil hole 34A (34B) side, and during this time, the relief valve 24A (24B)
Low pressure relief.

That is, as shown in FIGS. 10 and 11, even if the pressure oil in the actuator side oil passage 11B (11A) is a pressure P1 lower than the high relief set pressure Ph by the relief valve 24A (24B), the piston 35A (35
B) is slidably displaced and a part of the pressure oil is stored in the oil storage chamber 37A (37B).
When the oil is stored inside, the pressure P2 in the spring chamber 29A (29B) is relatively lower than the pressure P1 (P1> P2).
Therefore, the relief valve body 28A (28B) of the relief valve 24A (24B) is

[0022]

[Equation 2] Under the relationship of A1 x P1> A2 x P2 + f, the relief valve body 28A (28B) temporarily opens against the setting spring 30A (30B) to exhibit a so-called shockless function. Low pressure relief should be done.

The brake valve 7 according to the prior art has the above-mentioned structure, and its operation will be described below.

First, when the operator switches the direction switching valve 6 from the neutral position (a) to the switching position (b), the pressure oil from the hydraulic pump 3 flows into the hydraulic pressure source side oil passage 10A via the pipe 2A. To do. When the check valve 13A opens as shown in FIG. 8 against the valve spring 15A due to the pressure difference between the hydraulic pressure source side oil passage 10A and the actuator side oil passage 11A, the hydraulic pressure source side oil passage 10A is opened. Since the hydraulic fluid is communicated with the passage 11A and the pressure oil from the hydraulic pump 3 is supplied to the hydraulic motor 1 as a motor drive pressure, the vehicle, which is an inertial body, is driven to travel by the hydraulic motor 1.

When the pressure oil flows into the oil pressure source side oil passage 10A, the counterbalance valve 16 causes a part of the pressure oil to flow into the oil chamber 21A through the throttle passage 23A of the spool 18, Since the spool 18 is pushed leftward in FIG. 8 against the spring 22B, the land 19B of the spool 18
Moves to the left to communicate between the hydraulic pressure source side oil passage 10B and the actuator side oil passage 11B, whereby the counterbalance valve 16 is switched from the neutral position (a) shown in FIG. 5 to the switching position (b). Replace As a result, the return oil from the hydraulic motor 1 passes from the actuator-side oil passage 11B to the hydraulic-source-side oil passage 1
It is discharged to the outside of the brake valve 7 via 0B through the direction switching valve 6 and the conduit 2B and the like to the tank 4.

When the hydraulic motor 1 is started, as shown in FIG. 8, the high pressure (motor driving pressure) in the actuator-side oil passage 11A passes through the relief passage 12A and the relief valve 2
4B acts on the relief valve body 28B, part of which flows into the spring chamber 29B through the throttle passage 31B of the relief valve body 28B, while the accumulator 32B accumulates from the spring chamber 29A through the communication passage 39B. Since it is supplied into the oil chamber 37B, the accumulator 32B is slidably displaced to a position where the piston 35B abuts against the weak spring 41B and contacts the oil hole 34B side, and accumulates pressure oil in the oil storage chamber 37B. As a result, the pressure P2 in the spring chamber 29B becomes lower than the pressure P1 in the actuator-side oil passage 11A, the relief valve body 28B opens based on the equation (2), and the relief valve 24B is shown in FIG. The low pressure relief is performed at the pressure P1 as indicated by the characteristic line 42.

As a result, the activation of the hydraulic motor 1 is delayed by a fixed time t1 of, for example, about 0.1 to 0.5 seconds, and after the fixed time t1, the piston 35B abuts on the oil hole 34B side and the oil storage chamber 37B. When the pressure oil cannot be stored any more, the pressure in the spring chamber 29B rises and becomes equal to the pressure in the actuator-side oil passage 11A, so the relief valve body 28B is closed again by the setting spring 30B. ,
As a result, the pressure in the actuator-side oil passage 11A (motor drive pressure) rises to the pressure required to drive the hydraulic motor 1 to rotate in the direction of the arrow F, and the hydraulic motor 1 drives the vehicle, which is an inertial body, to travel. (Start) will be started.

On the other hand, when the operator returns the directional control valve 6 from the switching position (b) to the neutral position (a) in order to stop the vehicle as an inertial body, the pressure oil is supplied from the hydraulic pump 3. Check valve 1 as shown in FIG.
3A is seated on the valve seat 14A by the valve spring 15A, and the hydraulic pressure source side oil passage 10A and the actuator side oil passage 11A are shut off. Further, the counter balance valve 16 has an oil chamber 21.
The pressure in A decreases, the spool 18 is urged by the spring 22B, and returns to the neutral position (a) as shown in FIG. 6, whereby the oil pressure source side oil passage 10B and the actuator side oil passage 11B are separated from each other. It will also be cut off.

However, even after the direction switching valve 6 is returned to the neutral position (a) and the counterbalance valve 16 is returned to the neutral position, the hydraulic motor 1 continues to rotate in the F direction indicated by the arrow due to the inertial force of the vehicle. Therefore, when the hydraulic motor 1 rotates due to inertia, the hydraulic motor 1 moves to the actuator side oil passage 11
While sucking the pressure oil from A, the pressure oil is discharged into the actuator side oil passage 11B to perform a so-called pumping action. As a result, the pressure oil is confined in the actuator-side oil passage 11B, and the brake pressure is generated by the inertial rotation of the hydraulic motor 1.

The pressure oil (brake pressure) in the actuator-side oil passage 11B acts on the relief valve body 28A of the relief valve 24A via the relief passage 12B, and a part of it acts in the throttle passage 31A of the relief valve body 28A. While flowing into the spring chamber 29A via the throttle chamber 4A from the spring chamber 29A.
Accumulator 32A through 0A and communication passage 39A
It is supplied into the oil storage chamber 37A. As a result, the accumulator 32A is slidably displaced to the position where the piston 35A resists the weak spring 41A and comes into contact with the oil hole 34A side, and the oil storage chamber 3
Since the pressure oil is stored in 7A, the spring chamber 29
The pressure P2 in A becomes lower than the pressure P1 in the actuator-side oil passage 11B, the relief valve body 28A opens as shown in FIG. 9, and the relief valve 24A shows in FIG. As shown by the characteristic line 43, the low pressure relief is performed at the pressure P1.

Next, when a fixed time t2 of, for example, about 0.1 to 0.5 seconds elapses, the piston 35A comes into contact with the oil hole 34A side, and pressure oil can no longer be stored in the oil storage chamber 37A. At this time, the pressure in the spring chamber 29A rises and becomes equal to the pressure in the actuator-side oil passage 11B, so the relief valve body 28A is closed again by the setting spring 30A, whereby the pressure in the actuator-side oil passage 11B is reduced. The (brake pressure) increases according to the inertial rotation of the hydraulic motor 1.

When the pressure (brake pressure) in the actuator-side oil passage 11B rises to the high relief set pressure Ph, the relief valve body 28A opens against the set spring 30A based on the equation (1). The pressure at this time due to the so-called high pressure relief is applied to the relief valve 24A.
Is converted into heat energy while passing through, and the inertial rotation of the hydraulic motor 1 is gradually stopped.

When the direction switching valve 6 is switched from the neutral position (A) to the switching position (C) and returned to the neutral position (A) again, the operation is almost the same as in the above case.

[0034]

By the way, in the above-mentioned conventional brake valve 7, the relief valves 24A, 2A are provided.
4B is provided with accumulators 32A and 32B, and the accumulators 32A and 32B provide relief valves 24A,
Since a shockless function is provided to 24B, for example, the direction switching valve 6 is switched from the neutral position (a) to the switching positions (b) and (c) to start the vehicle, or the direction switching valve 6 is moved to the neutral position. When returning to (a) and stopping the vehicle, the pistons 35A and 35B are slidably displaced in the piston sliding holes 33A and 33B of the accumulators 32A and 32B to the positions where they abut against the oil holes 34A and 34B, respectively. The relief valves 24A and 24B can be relieved at a low pressure for a fixed time t1 (t2) until the pressure oil is stored in the oil storage chambers 37A and 37B, and the impact is prevented when the vehicle starts or stops. it can.

However, in the prior art, when the operator starts the vehicle by switching the direction switching valve 6 from the neutral position (a) to the switching positions (b) and (c) to start the hydraulic motor 1. As shown in FIG. 10, since the relief valves 24A and 24B perform low-pressure relief for a certain time t1, the operator delays the activation of the hydraulic motor 1 for a certain time t1 after the directional control valve 6 is switched. Not only the responsiveness of the vehicle deteriorates, but after a certain period of time, the operator suddenly feels that the vehicle has started to start,
There is a problem that the safety at the time of starting cannot be improved.

Further, the time t1 (t2) until the pressure oil is stored in the oil storage chambers 37A, 37B of the accumulators 32A, 32B is equal to the pressure in the throttle passages 40A, 40B etc. formed in the valve guides 25A, 25B. Since it is determined by the time when the oil circulates, especially in cold regions and the like, when the ambient temperature becomes low and the viscosity of the pressure oil increases, the throttle passages 40A, 40A
Time t1 until the pressure oil cannot smoothly flow through 0B etc. and the pressure oil is accumulated in the oil storage chambers 37A, 37B.
(T2) becomes longer than that at room temperature, and there is a problem in that the responsiveness at the time of startup is greatly reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and the present invention can reliably prevent a low pressure relief of the relief valve when the actuator is started,
It is intended to provide a brake valve capable of improving responsiveness and safety at the time of starting.

[0038]

In order to solve the above-mentioned problems, the present invention relates to a casing, a hydraulic pressure source side oil passage connected to the hydraulic pressure source side and connected to an actuator side provided in the casing. A pair of oil passages made up of actuator-side oil passages, and pressure oil is provided between the oil-pressure-source-side oil passages and the actuator-side oil passages of the respective oil passages. Allowed to circulate,
A pair of check valves for preventing reverse flow, a counter balance valve provided between the hydraulic pressure source side oil passage and the actuator side oil passage in parallel with each check valve, A pair of relief valves that are provided between the actuator-side oil passages and limit the pressure in each actuator-side oil passage to a high relief setting pressure or less, and are attached to each of the relief valves and are lower than the relief setting pressure. In a brake valve consisting of a pair of accumulators that temporarily relieves each of the relief valves by pressure, in each accumulator, an oil storage chamber that relieves each of the relief valves by low pressure by storing pressure oil, A pressure chamber defined by a movable partition wall with respect to the oil storage chamber, and a communication passage for always communicating the pressure chamber with the hydraulic pressure source side oil passage are provided. It adopts a configuration that.

In this case, each of the relief valves is provided in the casing such that a valve seat is provided between the actuator-side oil passages and one end of the relief valve is seated on the valve seat, and the other end of the casing is the casing. A relief valve body having a spring chamber defined therein, and a small-diameter throttle passage formed in the relief valve body for communicating the spring chamber with a counterpart actuator-side oil passage,
Disposed in the spring chamber to urge the relief valve body toward the valve seat member, and normally closes the relief valve body,
And a setting spring that allows the relief valve element to open when the pressure in the actuator-side oil passage reaches the relief setting pressure, and the spring chamber is always in communication with the oil storage chamber of the accumulator. Preferably.

Each of the accumulators is fitted in a piston sliding hole formed in the casing and slidably fitted in the piston sliding hole, and the accumulator and the pressure chamber are formed in the piston sliding hole. It may be constituted by a piston as a movable partition wall which is defined, and a spring which constantly urges the piston toward the pressure chamber side.

[0041]

With the above structure, when pressure oil is being supplied to one of the pair of oil passages for driving the actuator, a part of this pressure oil is connected to the oil passage on one hydraulic pressure source side. Since it is introduced into the pressure chamber of one accumulator through the passage, the pressure chamber becomes higher in pressure than the oil storage chamber, the movable partition moves to the oil storage chamber side, and the oil liquid is discharged to the oil storage chamber. Will be in a state of When the pressure oil supply to one hydraulic pressure source side oil passage is stopped to stop the actuator, the pressure chamber in one accumulator becomes low pressure, and the high pressure oil (from the other actuator side oil passage is stored in the oil storage chamber). Brake pressure)
Therefore, the movable partition of the accumulator moves to the pressure chamber side to store the pressure oil in the oil storage chamber, and the low pressure relief of the relief valve can be reliably performed when the actuator is stopped.

In the other oil passage on the pressure oil discharge side when the actuator is driven, the check valve continues to be closed.
Since the other hydraulic pressure source side oil passage remains in the low pressure state, the pressure chamber of the other accumulator communicating with the other hydraulic pressure source side oil passage also becomes low pressure, and the accumulator keeps the movable partition wall moving to the pressure chamber side. Therefore, the pressure oil is held in the oil storage chamber. As a result, when pressure oil is supplied to one of the oil passages to start the actuator, the other accumulator is kept in a state where the pressure oil has already been accumulated in the oil storage chamber, and the relief valve causes the low pressure relief valve when the actuator is started. You can prevent it.

Further, if the movable partition of each accumulator is constituted by a piston and the piston is biased toward the pressure chamber by a spring, the movable partition of each accumulator is compressed by the spring before the actuator is activated. Since it can be moved to the side in advance, it is possible to reliably hold the pressure oil stored in the oil storage chamber and more reliably prevent the relief valve from performing low pressure relief when the actuator is activated.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same components as those of the prior art shown in FIGS. 5 to 9 described above are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, 51 is a hydraulic motor 1 and a direction switching valve 6.
And a brake valve provided between the brake valve 5 and
1 includes a pair of check valves 13A and 13B, a counterbalance valve 16 and relief valves 24A and 24B, like the brake valve 7 described in the related art, but the brake valve 51 includes a casing 52 and an accumulator 53A described later. , 53B is different from the prior art.

Reference numeral 52 indicates a casing of the brake valve 51 attached to the hydraulic motor 1, and the casing 52 is similar to the casing 8 described in the prior art, and the hydraulic source side oil passage 10 is provided.
A, 10B and actuator side oil passages 11A, 11B
Composed of a pair of oil passages 9A, 9B and a relief passage 12A located between the actuator side oil passages 11A, 11B,
12B, etc., the casing 52 has piston sliding holes 54A, 54B and a communication passage 61 which will be described later.
A, 61B, etc. are formed.

53A and 53B are a pair of relief valves 24
A pair of accumulators provided in the casing 52 so as to be respectively attached to A and 24B are shown. The accumulators 53A and 53B are piston slide holes 54A and 5B described later.
4B, pistons 56A and 56B, oil storage chambers 57A and 57B
And pressure chambers 58A, 58B and the like.

Reference numerals 54A and 54B denote piston sliding holes formed as bottomed holes on the left and right sides of the casing 52. The piston sliding holes 54A and 54B are closed at their open ends by lids 55A and 55B. On the bottom side, communication passages 61A, 6 to be described later, which communicate with the oil pressure source side oil passages 10A, 10B.
1B is formed.

56A and 56B are piston sliding holes 54A,
54B shows a piston as a movable partition wall slidably inserted in 54B, the pistons 56A and 56B are formed in a cylindrical shape with a bottom, and the oil storage chambers 57A and 5B are formed between the pistons 56A and 56B and the lids 55A and 55B.
7B, and pressure chambers 58A and 58B are defined between the piston sliding holes 54A and 54B and the bottoms thereof.

Here, the oil storage chambers 57A, 57B communicate with the spring chambers 29A, 29B through the small diameter communication passages 59A, 59B formed in the casing 52 and the throttle passages 40A, 40B of the valve guides 25A, 25B. The spring chamber 29A,
By temporarily storing a part of the pressure oil flowing into 29B, the relief valves 24A and 24B have a shockless function. Also, the pistons 56A, 5
6B has a weak spring 60A between the lids 55A and 55B,
60B is provided, and the weak springs 60A and 60B constantly urge the pistons 56A and 56B toward the bottom side of the piston sliding holes 54A and 54B.

Further, reference numerals 61A and 61B denote other communication passages formed on the bottom side of the piston sliding holes 54A and 54B. One end side of the communication passages 61A and 61B is connected to the pressure chambers 58A and 58B of the accumulators 53A and 53B. The other end communicates with the hydraulic pressure source side oil passages 10A and 10B. The communication passages 61A, 61B are connected to the hydraulic pressure source side oil passages 10A, 1B.
By introducing pressure oil from 0B into the pressure chambers 58A, 58B of the accumulators 53A, 53B, the piston 5
6A and 56B are slidably displaced against the weak springs 60A and 60B to allow the oil liquid in the oil storage chambers 57A and 57B to communicate with the communication passages 59A and 59A.
59B is discharged to the spring chambers 29A and 29B.

The brake valve 51 according to the present embodiment has the above-mentioned structure, and its basic operation is not different from that of the prior art.

Therefore, in this embodiment, the accumulator 5
The piston sliding holes 54A, 54B of 3A, 53B are defined by the pistons 56A, 56B into oil storage chambers 57A, 57B and pressure chambers 58A, 58B, and weak springs 60A, 60B.
The pistons 56A and 56B to the pressure chambers 58A and 58
The accumulator 53 is always urged toward the B side.
The pressure chambers 58A and 58B of A and 53B are connected to the casing 52.
Since the hydraulic pressure source side oil passages 10A and 10B are always communicated with each other through the communication passages 61A and 61B formed in the above, the following operational effects can be obtained.

That is, when the operator switches the direction switching valve 6 from the neutral position (a) to the switching position (b) in order to start the hydraulic motor 1, the pressure oil from the hydraulic pump 3 passes through the conduit 2A. Flow into the hydraulic pressure source side oil passage 10A,
The check valve 13A is opened to supply pressure oil as the motor driving pressure into the actuator-side oil passage 11A as shown in (4), and this motor driving pressure acts on the relief valve 24B via the relief passage 12A. However, at this time, in the accumulator 53B of the relief valve 24B, as shown in FIG. 3, the piston 56B is already pushed to the pressure chamber 58B side by the weak spring 60B, and the oil storage chamber 57B is filled with the oil liquid. Therefore, the relief valve 24B does not relieve low pressure, the motor drive pressure rises quickly as shown by a characteristic line 62 shown by a dotted line in FIG. 10, and the hydraulic motor 1 can be started early. The vehicle can be started with good responsiveness.

Then, while the hydraulic motor 1 continues to be driven with the direction switching valve 6 switched from the neutral position (a) to the switching position (b), the pressure in the hydraulic pressure source side oil passage 10A is kept constant.
Since it continues to act on the pressure chamber 58A of the accumulator 53A via 1A, the piston 56A is in the state of sliding displacement to the oil storage chamber 57A side as shown in FIG.
The oil liquid inside is discharged from the communication passage 59A to the spring chamber 29A side, and the piston 56A remains held at the stroke end shown in FIG.

Next, in order to stop the rotation of the hydraulic motor 1,
When the operator returns the directional control valve 6 from the switching position (b) to the neutral position (a), the supply of the pressure oil to the oil pressure source side oil passage 10A is cut off, so that the pressure chamber 58A of the accumulator 53A also has the oil pressure source 58A. As with the side oil passage 10A, the pressure becomes low, and the piston 56A of the accumulator 53A can be slidably displaced to the pressure chamber 58A side.

At this time, when the hydraulic motor 1 inertially rotates and a brake pressure is generated in the actuator side oil passage 11B, the pressure oil (brake pressure) in the actuator side oil passage 11B is released through the relief passage 12B. 24A
Of the relief valve body 28A, and a part of the relief valve body 28A flows into the spring chamber 29A through the throttle passage 31A of the relief valve body 28A, and from the spring chamber 29A through the throttle passage 40A and the communication passage 59A. Oil storage room 57
Supplied into A.

As a result, the accumulator 53A is shown in FIG.
Since the piston 56A is slidably displaced to the stroke end position where it abuts on the bottom side of the piston sliding hole 54A as shown in, the pressure oil (oil liquid) is stored in the oil storage chamber 57A. The pressure P2 in the spring chamber 29A becomes lower than the pressure P1 in the actuator-side oil passage 11B, and the relief valve body 28A opens based on the equation (2), and the relief valve 2
4A performs low pressure relief at pressure P1 as in the prior art, as indicated by the characteristic line 43 shown in FIG. Then, when the brake pressure in the actuator-side oil passage 11B rises to the relief set pressure Ph after the elapse of the fixed time t2, the relief valve 24A comes to perform high pressure relief.

Further, even if the operator again switches the direction switching valve 6 from the neutral position (a) to the switching position (b) when the relief valve 24A performs high pressure relief and the rotation of the hydraulic motor 1 is stopped, The accumulator 53B of the relief valve 24B is already in the piston 5 as illustrated in FIG.
6B is pushed to the pressure chamber 58B side by the weak spring 60B, and the oil storage chamber 57B is filled with the oil liquid. Therefore, when the hydraulic motor 1 is started in the arrow F direction, Since the piston 56B of the accumulator 53B is at the stroke end and the relief valve 24B does not perform low pressure relief, the hydraulic motor 1 can always start the vehicle with high responsiveness.

On the other hand, when the direction switching valve 6 is switched between the neutral position (a) and the switching position (c), the operation is almost the same as the above case.

Therefore, according to this embodiment, the hydraulic motor 1
Even when the starting and stopping of the relief valve 24 are repeated, the piston (56B) of the accumulator (53B) is always held at the stroke end at the time of starting.
It is possible to surely prevent the low pressure relief of the 4B, improve the responsiveness at the time of starting, and significantly improve the safety and reliability when the vehicle is started.

Also, when the direction switching valve 6 is switched between the neutral position (a) and the switching position (c), the operation is almost the same as the above case.

Therefore, according to this embodiment, the hydraulic motor 1
It is possible to reliably prevent the relief valves 24A and 24B from performing low-pressure relief at the time of starting, and to improve the responsiveness at the time of starting to improve the safety when starting the vehicle.

When the hydraulic motor 1 inertially rotates and brake pressure is generated when the vehicle is stopped, the relief valve 2
4A and 24B can be relieved at a low pressure, the impact at the time of stop can be mitigated, and when this brake pressure rises to the relief set pressure Ph, the relief valve 24A,
24B can be relieved under high pressure, and the vehicle can be reliably stopped.

In the above embodiment, the accumulator 5
3A and 53B have been described as being provided separately from the relief valves 24A and 24B, but in place of this, in fact,
An accumulator may be provided integrally with the relief valve, like the relief valve described in Japanese Patent Publication No. 2-31681.

Further, in the above embodiment, the accumulator 5
3A, 53B piston 56A, 56B is a weak spring 60
Although it has been described that the pressure chambers 58A and 58B are constantly urged by the A and 60B, the present embodiment is not limited to this, and for example, the piston 56A is caused by the pressure difference between the oil storage chambers 57A and 57B and the pressure chambers 58A and 58B. , 56B may be slidably displaced. In this case, the weak springs 60A, 6B
0B can be omitted.

Further, in the above-mentioned embodiment, the movable partition walls of the accumulators 53A, 53B are described as being constituted by the pistons 56A, 56B, but instead of this, the movable partition walls of the accumulator may be constituted by a diaphragm or the like. .

[0068]

As described in detail above, according to the present invention, the oil storage chamber of each accumulator is defined by a movable partition wall as a pressure chamber, and each pressure chamber is provided with a hydraulic pressure source of a pair of oil passages. Since it is configured to always communicate with the side oil passage, it is possible to reliably prevent the relief valve from performing low pressure relief when the actuator is activated, and it is possible to improve responsiveness at the time of activation and improve safety. When the actuator is stopped, the pressure oil can be stored in the oil storage chamber of the accumulator to relieve the low pressure of the relief valve, and the impact at the time of stop can be reliably reduced.

If the movable partition of each accumulator is constituted by a piston and the piston is biased toward the pressure chamber by a spring, the movable partition of each accumulator is compressed by the spring before the actuator is activated. It can be moved to the side in advance, and it is possible to more reliably prevent the relief valve from performing low pressure relief when the actuator is started.

[Brief description of drawings]

FIG. 1 is a hydraulic motor drive circuit diagram provided with a brake valve according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a brake valve according to an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a brake valve when the hydraulic motor is started.

FIG. 4 is a vertical cross-sectional view of the brake valve when the hydraulic motor is stopped.

FIG. 5 is a hydraulic motor drive circuit diagram provided with a brake valve according to the prior art.

FIG. 6 is a vertical sectional view showing a brake valve according to the prior art.

7 is an enlarged sectional view of the relief valve shown in FIG.

FIG. 8 is a vertical cross-sectional view of the brake valve when the hydraulic motor is started.

FIG. 9 is a vertical cross-sectional view of the brake valve when the hydraulic motor is stopped.

FIG. 10 is a characteristic diagram showing a characteristic of a motor drive pressure according to a conventional technique.

FIG. 11 is a characteristic diagram showing a characteristic of brake pressure according to a conventional technique.

[Explanation of symbols]

 1 hydraulic motor (actuator) 3 hydraulic pump (hydraulic power source) 4 tank 5 prime mover 6 directional switching valve 9A, 9B oil passage 10A, 10B hydraulic oil source side oil passage 11A, 11B actuator side oil passage 12A, 12B relief passage 13A, 13B check Valve 16 Counterbalance valve 24A, 24B Relief valve 25A, 25B Valve guide 27A, 27B Valve seat cylinder (valve seat) 28A, 28B Relief valve body 29A, 29B Spring chamber 30A, 30B Setting spring 31A, 31B Throttle passage 51 Brake valve 52 Casing 53A, 53B Accumulator 54A, 54B Piston sliding hole 56A, 56B Piston (movable partition wall) 57A, 57B Oil storage chamber 58A, 58B Pressure chamber 59A, 59B, 61A, 61B Communication passage 60A, 60B Weak spring

Claims (3)

[Claims] 1. A pair of oil passages, each of which includes a casing, a hydraulic pressure source side oil passage connected to the hydraulic pressure source side and an actuator side oil passage connected to the actuator side, and each oil passage. Is provided between the hydraulic pressure source side oil passage and the actuator side oil passage, and allows the pressure oil to flow from the hydraulic pressure source side oil passage to the actuator side oil passage, and prevents a reverse flow. A check valve, a counter balance valve provided between the hydraulic pressure source side oil passage and the actuator side oil passage so as to be parallel to each check valve, and provided between the actuator side oil passages, A pair of relief valves that limit the pressure in the actuator-side oil passage to a high relief setting pressure or less, and the relief valves that are respectively attached to the respective relief valves and operate at a pressure lower than the relief setting pressure. In a brake valve consisting of a pair of accumulators for temporarily low-pressure relief, in each of the accumulators, an oil storage chamber for low-pressure relief of each relief valve by storing pressure oil, and to the oil storage chamber A brake valve, comprising: a pressure chamber defined by a movable partition wall; and a communication passage for always communicating the pressure chamber with the hydraulic pressure source side oil passage. 2. Each of the relief valves is provided in the casing such that a valve seat is provided between the actuator-side oil passages, and one end of the relief valve is seated on the valve seat, and the other end of the relief valve is inside the casing. A relief valve body defining a spring chamber, a small-diameter throttle passage formed in the relief valve body for communicating the spring chamber with an actuator-side oil passage on the other side, and a relief valve body facing the valve seat member. The relief valve body is disposed in the spring chamber for biasing, normally closes the relief valve body, and opens the relief valve body when the pressure in the actuator side oil passage reaches the relief set pressure. The brake valve according to claim 1, further comprising a setting spring that allows the spring chamber to communicate with the oil storage chamber of the accumulator at all times. 3. Each of the accumulators has a piston sliding hole formed in the casing, and is slidably fitted into the piston sliding hole, and the accumulator and the pressure chamber are provided in the piston sliding hole. A piston as a movable partition to define,
The brake valve according to claim 1 or 2, comprising a spring that constantly biases the piston toward the pressure chamber.