JPH07190002A - Hydraulic driving device - Google Patents

Abstract

PURPOSE:To provide a hydraulic driving device for allowing compatibility between reduction of impacts at the time of stop and responsiveness at the time of start by setting the braking pressure of a circuit lower than the maximum set pressure of a relief valve only initially during a hydraulic motor stop and setting the driving pressure thereof to the maximum set pressure of the relief valve at the time of starting. CONSTITUTION:First and second oil chambers 34A (34B) and 35A (35B) sectioned by a piston 33A (33B) are formed on the outer peripheral part of a relief valve 24A (24B) disposed on an actuator side oil path 11A (11B), a spring 55A (55B) for always energizing the piston 33A (33B) in the direction of the second oil chamber 35A (35B) is inserted into the first oil chamber 34A (34B) and a communicating path for linking the oil chamber 34A (34B) with the actuator side oil path 11A (11B) at the neutral time of a counter balance valve 51 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device used in a drive circuit of a hydraulic motor for driving a turning device, a traveling device, etc. of a construction machine such as a hydraulic excavator and a hydraulic crane.

[0002]

2. Description of the Related Art Generally, a construction machine such as a hydraulic excavator or a hydraulic crane has a large inertial mass, and therefore its drive circuit receives a large inertial load when traveling or turning is stopped. Therefore, in order to convert the inertial load into the heat energy of the pressure oil and absorb the heat energy, a hydraulic drive device as described below is provided.

Therefore, a conventional hydraulic drive system will be described with reference to FIGS. 7 to 13 by taking a traveling device of a hydraulic excavator as an example.

In the figure, reference numeral 1 denotes a hydraulic motor as an actuator for driving a traveling body of a hydraulic excavator. The hydraulic motor 1 is paired with a hydraulic pump 3 as a hydraulic source and a tank 4 via conduits 2A and 2B. Connected with the prime mover 5
By supplying and discharging pressure oil discharged from the hydraulic pump 3 driven by the hydraulic pump 3, the hydraulic excavator is driven to travel.

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 a neutral position (a), Equipped with switching positions (b) and (c), these switching positions (b) and (c)
The switching direction of the hydraulic motor 1 is switched to the F or R direction shown by the arrow in FIG. Further, when returning to the neutral position (a), the supply and discharge of pressure oil from the hydraulic pump 3 to the hydraulic motor 1 is blocked, and the hydraulic motor 1 is stopped.

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

Next, the hydraulic drive system 7 will be described with reference to FIGS. 8 and 9. In the drawing, reference numeral 8 denotes a casing of a hydraulic drive system 7 attached to the hydraulic motor 1, and the casing 8 has a first and a second oil passage 9A so as to form a part of a pair of pipelines 2A, 2B. , 9B are formed.

The oil passages 9A and 9B are hydraulic oil source side oil passages 10A and 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 composed of 11A and 11B,
They are connected via check valves 13A and 13B described later. Further, the actuator side oil passage 11A,
Relief passages 12A and 12B are formed between 11B.

The above-mentioned check valves 13A and 13B are provided in the hydraulic pressure source side oil passages 10A and 10B and the actuator side oil passage 11 respectively.
A valve seat 14 formed in the casing 8 between A 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.
It is constantly urged toward A and 14B, and is connected from the hydraulic pressure source side oil passages 10A and 10B to the actuator side oil passages 11A and 11B.
Only the flow toward B is allowed.

Reference numeral 16 denotes a counter balance valve provided between the hydraulic 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. Balance valve 16
Is a spool sliding hole 17 formed between the hydraulic pressure source side oil passages 10A and 10B and the actuator side oil passages 11A and 11B and bored in the casing 8, and the spool sliding hole 17
8 includes a spool 18 slidably inserted therein, and the spool 18 is located on the right side in FIG. 8 to communicate and block between the hydraulic pressure source side oil passage 10A and the actuator side oil passage 11A. A spool land 19A is provided, and a spool land 19B, which is located on the left side, connects and cuts off the hydraulic pressure source side oil passage 10B and the actuator side oil passage 11B. And the spool 1 in the spool sliding hole 17
Both end portions of 8 are closed by lids 20A and 20B to form oil chambers 21A and 21B.
Inside the 1B, springs 22A and 22B that constantly bias the spool 18 toward the neutral position are provided.

At both ends of the spool 18, throttle passages 23A and 23B are formed for communicating the hydraulic pressure source side oil passages 10A and 10B with the oil chambers 21A and 21B at all times.
3A and 23B guide the pressure of the pressure oil in the oil pressure source side oil passages 10A and 10B into the oil chambers 21A and 21B as pilot pressure, and slide the spool 18 against the springs 22A and 22B based on the pilot pressure at this time. Move it dynamically.

Reference numerals 24A and 24B denote relief valves provided in the casing 8 located in the middle of the actuator-side oil passages 11A and 11B. The relief valves 24A and 24B are provided.
As shown in FIG. Sleeves 25A and 25 described later
B, poppets 28A and 28B, lids 29A and 29B, and the like.

The sleeves 25A and 25B are formed in a cylindrical shape and slidably hold the poppets 28A and 28B in the casing 8. One end of the sleeves 25A and 25B is for communicating between the actuator side oil passages 11A and 11B. Communication hole 26A,
26B is provided in the radial direction, one end side of which is provided in the casing 8 so as to face the actuator-side oil passages 11A and 11B, and the other end side of which is a lid 29A, respectively.
It is blocked by 29B.

27A and 27B are sleeves 25A and 25
A cylindrical valve seat located at one end of B and fitted into the relief passages 12A and 12B.
A and 28B are slidably provided in the sleeves 25A and 25B so as to be separated from and seated on the valve seats 27A and 27B, and the poppets 28A and 28B and the sleeves 25A and 25B.
Spring chambers 30A, 30B are formed in the sleeves 25A, 25B by the lids 29A, 29B closing the 25B,
Poppets 28A and 28B are provided in the spring chambers 30A and 30B.
Spring 3 for constantly urging the valve toward the valve seats 27A and 27B
1A and 31B are arranged. Also, poppet 28
A and 28B have a small diameter throttle passage 32 that allows the relief passages 12A and 12B to communicate with the spring chambers 30A and 30B at all times.
A and 32B are bored in the axial direction.

Further, pistons 33A and 33B are provided on the outer peripheral portions of the sleeves 25A and 25B of the relief valves 24A and 24B, the outer peripheral surfaces of which are slidable in the axial direction, and an oil chamber for accommodating the pistons is formed. The oil chamber on one side divided by the pistons 33A and 33B is
Oil chambers 34A, 34B, and the other side of the second oil chambers 35A, 3B
5B.

The second oil chambers 35A and 35B communicate with the actuator-side oil passages 11A and 11B via orifices 36A and 36B, respectively, and the first oil chamber 34
A and 34B are spring chambers 30A and 30A via diaphragms 37A and 37B provided in the radial directions of the sleeves 25A and 25B.
It communicates with B.

Here, the above-mentioned relief valves 24A, 24A
B poppet 28A (28B) has a valve seat 27A (27
The pressure receiving area A1 is on the B) side, and the pressure receiving area A2 on the spring chamber 30A (30B) side is smaller than the pressure receiving area A1 (A1> A2). Also, the setting spring 31A (31B)
Spring force f of the actuator side oil passage 11B (11A)
And, when the pressure in the spring chamber 30A (30B) rises to a preset maximum set pressure Ph, it is set to satisfy the relationship of A1 × Ph> A2 × Ph + f (1). Therefore, at this time, the poppet 28A (28B) is set by the setting spring 31A.
By opening the valve against (31B), the relief passage 12B (12B) is provided between the actuator-side oil passages 11B and 11A.
A) and the communication holes 26A (26B),
The pressure in the actuator side oil passage 11B (11A) is limited to the maximum set pressure Ph or less.

Next, the operation of the hydraulic drive system 7 according to the prior art constructed as described above will be examined.

First, in order to drive the hydraulic motor 1, when the operator switches the direction switching valve 6 from the neutral position (a) shown in FIG. 7 to the switching position (b), the pressure oil from the hydraulic pump 3 flows through the pipeline. It flows into the hydraulic pressure source side oil passage 10A via 2A. Then, the check valve 13A causes the hydraulic pressure source side oil passage 10
Due to the pressure difference between A and the actuator side oil passage 11A,
When opened as shown in FIG. 10 against the valve spring 15A, the oil pressure source side oil passage 10A communicates with the actuator side oil passage 11A, and the pressure oil from the hydraulic pump 3 is supplied to the hydraulic motor 1 as the driving pressure of the motor. A part of the pressure oil that has flowed into the hydraulic pressure source side oil passage 10A flows into the oil chamber 21A through the throttle passage 23A of the spool 18 of the counterbalance valve 16, and the spool 18 resists the valve spring 22B. Then, by moving to the left in the figure, the spool land 19B of the spool 18 moves to the left to connect the hydraulic pressure source side oil passage 10B and the actuator side oil passage 11B. As a result, the return oil from the hydraulic motor 1 is discharged from the actuator side oil passage 11B to the tank 4 via the hydraulic pressure source side oil passage 10B, the direction switching valve 6 and the pipe 2B. As a result, the hydraulic motor 1 drives the hydraulic excavator, which is an inertial body, to travel.

When the hydraulic motor 1 is started,
As shown in FIG. 10, the pressure in the actuator-side oil passage 11A (driving pressure of the hydraulic motor 1) acts on the second oil chamber 35A of the relief valve 24A via the orifice 36A to move the piston 33A to the right in the drawing. It slides to a position where it abuts against the body 29A and acts on the poppet 28B of the relief valve 24B via the relief passage 12A, and a part of it acts on the poppet 28B via the throttle passage 32B of the poppet 28B.
While flowing into B, it is supplied from the spring chamber 30B to the first oil chamber 34B via the throttle 37B.
B slides to the position in the right direction in the drawing where it abuts against the casing 8 and accumulates pressure oil in the first oil chamber 34B. Accordingly, even if the pressure of the pressure oil in the actuator-side oil passage 11A is the pressure P1 lower than the maximum set pressure Ph by the relief valve 24B, the piston 33B slides and a part of the pressure oil becomes the first pressure. When the oil is stored in the oil chamber 34B, the pressure P2 in the spring chamber 30B is relatively lower than P1 (P
1> P2), so the poppet 28 of the relief valve 24B
B is placed under the relationship of A1 × P1> A2 × P2 + f (2), and the poppet 28B is the setting spring 31B.
Against this, the relief valve 24B operates at the pressure P1 as indicated by the characteristic line 40 shown in FIG.

As a result, the activation of the hydraulic motor 1 is delayed by a constant time t1 of, for example, about 0.1 to 0.5 seconds, the piston 33B comes into contact with the casing 8 after the constant time t1, and the first oil chamber 34B is reached. When the pressure oil cannot be stored any more, the pressure in the spring chamber 30B rises and becomes equal to the pressure in the actuator-side oil passage 11A, so the poppet 28B is closed again by the setting spring 31B.
As a result, the pressure in the actuator-side oil passage 11A (driving pressure of the motor) rises to a pressure required to rotationally drive the hydraulic motor 1 in the arrow F direction, and the hydraulic motor 1 operates as an inertial hydraulic pressure. The shovel will drive (start).

On the other hand, when the directional control valve 6 is returned from the switching position (b) shown in FIG. 7 to the neutral position (a) in order to stop the hydraulic excavator as an inertial body, the hydraulic pump 3 discharges. Since the supply of pressure oil is cut off,
As described above, the check valve 13A is seated on the valve seat 14A by the valve spring 15A, and the communication state between the hydraulic pressure source side oil passage 10A and the actuator side oil passage 11A is cut off. Further, since the supply of the pressure oil is cut off, the pressure of the pressure oil in the oil chamber 21A of the counterbalance valve 16 is reduced, and the spool 18 moves to the spring 2
It is urged by 2B to return to the neutral position, whereby the communication between the hydraulic pressure source side oil passage 10B and the actuator side oil passage 11B is also cut off.

However, even after the directional control valve 6 is returned to the neutral position (a) and the counter balance valve 16 is returned to the neutral position as described above, the hydraulic motor 1 is still driven by the inertial force of the hydraulic excavator. May continue to rotate due to inertia, and when the hydraulic motor 1 rotates due to inertia,
Sucks pressure oil from the actuator side oil passage 11A,
This pressure oil is discharged into the actuator-side oil passage 11B.
It performs a so-called pumping action. As a result, the pressure oil is confined in the actuator-side oil passage 11B, the pressure of the pressure oil increases, 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 poppet 28A of the relief valve 24A via the relief passage 12B, and a part of it acts via the throttle passage 32A of the poppet 28A. Spring chamber 3
While flowing into 0A, from the spring chamber 30A, the throttle 37A
Is supplied to the first oil chamber 34A via. As a result, the piston 33A slides to the position where it abuts the casing 8 on the left side in the drawing, and the pressure oil is accumulated in the first oil chamber 34A. Therefore, the pressure P in the spring chamber 30A is reduced.
2 is lower than the pressure P1 in the actuator-side passage 11B, and the poppet 28A is opened based on the equation (2),
The relief valve 24A comes to operate at the pressure P1 as indicated by the characteristic line 41 shown in FIG. And, for example, 0.1
Piston 33A after a fixed time t2 of about 0.5 seconds has elapsed
Comes into contact with the casing 8 and pressure oil can no longer be stored in the first oil chamber 34A, the pressure in the spring chamber 30A rises, and the throttle passage 3 communicating with the poppet 28A.
2A equalizes the pressure in the actuator-side oil passage 11B, so the poppet 28A is closed again by the setting spring 31A, whereby the actuator-side oil passage 1A is closed.
The pressure of the pressure oil (brake pressure) in 1B rises in accordance with the inertial rotation of the hydraulic motor 1. Then, when the pressure (brake pressure) in the actuator-side oil passage 11B rises to the maximum set pressure Ph, the poppet 28A based on the above equation (1).
When the valve is opened against the set spring 31A, the pressure at this time is converted into thermal energy when passing through the relief valve 24A, 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), the operation is almost the same as the above case.

[0026]

In the hydraulic drive system 7 according to the above-mentioned conventional technique, the relief valve 24 is provided.
A and 24B have first and second oil chambers 34A, 34B and 35, respectively.
A, 35B and pistons 33A, 33B are provided so that the relief valves 24A, 24B can be temporarily operated at a pressure lower than a preset maximum pressure in the actuator-side oil passages 11A, 11B. . Therefore, for example, the direction switching valve 6 is switched from the neutral position (a) to the switching position (b) or (c) to start the vehicle, or the direction switching valve 6 is switched from the switching position (b) or (c) to the neutral position (b). When the vehicle is stopped by returning to (a), the first and second oil chambers 34A, 34B, 35
The pistons 33A and 33B are connected to the second oil chamber 3 in A and 35B.
The relief valves 24A, 2 are slidably moved until they come into contact with the casing 8 on the 5A, 35B side, and only for a certain time t1 (t2) until the pressure oil is stored in the first oil chambers 34A, 34B.
4B can be operated, and the impact can be prevented from occurring when the vehicle starts or stops. However, in the prior art, the operator moves the directional control valve 6 from the neutral position (a) to the switching position (b) to activate the hydraulic motor 1.
Or when switching to (C) and starting the vehicle,
As shown in FIG. 13, the relief valve 24 is operated for a certain time t2.
Since A and 24B are activated, the operator delays the activation of the hydraulic motor 1 for a certain period of time t2 after switching the directional control valve 6, and not only the responsiveness at the time of activation is deteriorated, but also the constant response. There is a problem that the operator feels that the vehicle suddenly starts to move after a lapse of time, and the safety and operability at the time of starting cannot be improved.

Further, the time t1 (t2) until the pressure oil is stored in the first oil chambers 34A and 34B is the sleeve 25.
Since it is determined by the flow rate of the pressure oil passing through the throttles 37A, 37B formed in A, 25B, especially when the viscosity of the pressure oil becomes large due to a decrease in ambient temperature in a cold region or the like, the throttle 37
The time t1 (t2) until the pressure oil cannot smoothly flow through A and 37B and the pressure oil is stored in the first oil chambers 34A and 34B becomes longer than the normal state,
There is a problem that the responsiveness of the start-up time is significantly reduced.

The present invention has been made in view of the above problems, and an object thereof is to set the brake pressure of the circuit to a pressure lower than the maximum set pressure of the relief valve only in the initial stage when the hydraulic motor is stopped, and to start it. An object of the present invention is to provide a hydraulic drive system that can make the impact at the time of stop and the improvement of the response at the time of starting compatible by making the drive pressure always the maximum set pressure of the relief valve.

[0029]

The features adopted by the present invention in order to solve the above-mentioned problems are that first and second oil passages connecting a hydraulic source and a hydraulic motor, and the first oil passage. A check valve provided in the first oil passage for allowing only the flow of pressure oil from the hydraulic source to the hydraulic motor; a counter balance valve arranged in the first oil passage in parallel with the check valve; A relief valve having a discharge side connected to a first oil passage between the valve and a second oil passage and an inflow side connected to a second oil passage; and a relief valve for accumulating pressure oil in the spring chamber. An oil chamber is attached, and a piston is movably housed in the oil chamber.
In a hydraulic drive device that forms a second oil chamber, connects the first oil chamber and the spring chamber, and connects the second oil chamber to the first oil passage, in the first oil chamber. A spring for constantly pressing the piston in the direction of the second oil chamber is inserted so that the first oil passage communicates with the first oil chamber when the counterbalance valve is in a neutral position, and is disconnected when the switching is performed. There is a passage.

[0030]

With the above structure, when pressure oil is being supplied from the oil pressure source to the first oil passage in order to drive the hydraulic motor, this pressure oil flows from the first oil passage to the outer peripheral portion of the relief valve. Since it is injected into the second oil chamber provided, the piston provided in the oil chamber moves in the direction of the first oil chamber against the spring provided therein. Then, when the supply of the pressure oil from the hydraulic source to the first oil passage is stopped to stop the hydraulic motor,
Since the counterbalance valve returns to the neutral position and the pressure oil returned from the hydraulic motor is shut off, the pressure of the pressure oil in the second oil passage rises to a high pressure. The pressure oil is stored in the first oil chamber via the spring chamber of the relief valve, and the piston is moved toward the second oil chamber. As a result, the volume of the spring chamber is substantially expanded, the pressure in the spring chamber becomes lower than the pressure in the second oil passage, and when the hydraulic motor is stopped, the relief valve is reliably set at a pressure higher than the preset maximum pressure. It can be operated at low pressure. When the counterbalance valve is in the neutral position and the piston is on the side of the first oil chamber, the communication passage is in communication with the movement of the piston in the direction of the second oil chamber. The pressure of the pressure oil in the chamber and the pressure oil in the second oil chamber communicating with the first oil passage become the same, and the piston rapidly moves toward the second oil chamber due to the spring force arranged in the first oil chamber. Moving.

As a result, when the hydraulic motor is stopped, the piston rapidly moves in the direction of the second oil chamber, so that the first oil chamber is in a state where oil is stored, and the first from the spring chamber of the relief valve to the first oil chamber. Even if the oil is not supplied to the oil chamber, the relief valve is prevented from operating even if it is restarted immediately after the stop, and the drive pressure of the hydraulic motor is always set to the maximum set pressure of the relief valve. be able to.

[0032]

Embodiments of the present invention will be described below with reference to FIGS. In addition, in the embodiment, the same components as those of the above-described conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, 50 is a directional control valve 6 and a hydraulic motor 1.
Reference numeral 52 denotes a hydraulic drive device provided between the hydraulic motor 1 and the hydraulic motor 1, and a casing integrally configured with the hydraulic drive device 50. The casing 52 includes the casing 8 described in the related art. Similarly to the hydraulic pressure source side oil passage 10A,
10B and a pair of oil passages 9A and 9B composed of actuator side oil passages 11A and 11B, and relief passages 12A and 12 located between the actuator side oil passages 11A and 11B.
In addition to having B etc., the connecting paths 53A, 53B described later
Third oil passages 64A and 64B forming a part of the above are provided.

In the first oil chambers 34A, 34B provided on the outer peripheral portions of the relief valves 24A, 24B, as shown in FIG. 3, springs 55A for constantly biasing the pistons 33A, 33B toward the second oil chambers, 55B is provided.

Further, the counter balance valve 51 includes oil pressure source side oil passages 10A, 10B and actuator side oil passages 11A,
11B, the spool slide hole 17 is provided in the casing 52, and the spool 56 slidably fitted in the spool slide hole 17 is provided.
6, the hydraulic pressure source side oil passages 10A, 10B
And the first spool lands 57A and 57B for connecting and disconnecting with the actuator-side oil passages 11A and 11B, and the first spool lands 57A and 57B.
A second spool land 58 that is formed between the spool lands 57A and 57B and blocks the communication between the actuator-side oil passages 11A and 11B. Similarly to the prior art, the oil chambers 21A and 21B are formed by being closed by the lids 20A and 20B, and the oil chambers 21A and 21B are formed.
Inside, springs 22A and 22B for urging the spool toward the neutral position are disposed. Also, the spool 56
Throttle passages 54A and 54B are formed on both end sides of the oil pressure source side oil passages 10A and 10B so as to always communicate with the oil chambers 21A and 21B.

The above-mentioned communication passages 53A and 53B are formed in the casing 52, and one ends of the communication passages 53A and 53B are located in the first oil chambers 34A and 34B.
3 and the third oil passages 64A and 64B connected to the second spool land 58 of the spool 56 as shown in FIG. 4, one end of which is formed on the actuator side oil passages 11A and 11B.
And the first oil passages 59A and 59B connected to the second spool land 58 and the third oil passages 64A and 64B.
And second oil passages 60A, 60B connecting the first oil passages 59A, 59B. In addition, between the first oil passages 59A and 59B and the second oil passages 60A and 60B, check valves 61A and 61B which allow only the flow from the first oil passage to the second oil passage. And the check valves 61A and 61B are connected to the first oil passages 59A and 59B.
And the second oil passages 60A and 60B, the valve seats 62A and 62B are slidably attached to the spool 56 so as to be separated from and seated in the valve seats 62A and 62B. Always urged towards.

Further, the above-mentioned third oil passages 64A and 64B are
The spool 56 of the counter balance valve 51 is connected to the second oil passages 60A and 60B at the neutral position and is disconnected from the second oil passages 60A and 60B at the switching position.

The hydraulic drive system 50 according to this embodiment is constructed as described above, and its basic operation is not so different from that of the prior art.

Therefore, in this embodiment, the relief valve 24
The pistons 33A and 33B on the outer peripheral portions of A and 24B are connected to the spring 5
The third oil passages 64A, 64B, which constantly urge the second oil chambers 35A, 35B toward the second oil chambers 35A, 35B and form the first oil chambers 34A, 34B in the casing 52,
Second oil passages 60A, 60B, check valves 61A, 61
Since it is configured to communicate with the actuator-side oil passages 11A and 11B via the B and first oil passages 59A and 59B, the following operational effects can be obtained.

That is, when the operator switches the direction switching valve 6 from the neutral position (a) shown in FIG. 1 to the switching position (b) in order to start the hydraulic motor 1, the hydraulic pump 3
The pressure oil discharged from the hydraulic pressure source side oil passage 1 passes through the pipe 2A.
0A, the check valve 13A opens as shown in FIG. 5, the pressure oil as the motor driving pressure is supplied to the actuator-side oil passage 11A, and this motor driving pressure is applied to the spool 56 of the counter balance valve 51. Through the throttle passage 54A into the oil chamber 21A so that the spool 56 can move the valve spring 22B.
By moving to the left in the figure against the above, the first spool land 57B connects the hydraulic pressure source side oil passage 10B and the actuator side oil passage 11B. Further, the pressure oil as the motor driving pressure is supplied to the relief valve 2 via the relief passage 12A.
Acts on 4B. However, the piston 33B on the outer peripheral portion of the relief valve 24B has been previously pushed by the spring 55B to a position where it comes into contact with the casing 52 on the right side in the drawing,
Since the pressure oil is stored in the first oil chamber 34B in a full state, the relief valve 24B is moved by the movement of the piston 33B.
Will not operate below the maximum set pressure,
The motor drive pressure rapidly rises as indicated by the characteristic line 42 shown by the dotted line in FIG. 12, the hydraulic motor 1 can be started early, and the vehicle can be started with good responsiveness.

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 of the pressure oil in the actuator-side oil passage 11A is reduced by the relief valve. Orifice 36A at the outer periphery of 24A
Flow into the second oil chamber 35A through the piston and continue to act on the piston 33A.
The sliding state is maintained at the position where it comes into contact with.

Next, when the operator returns the directional control valve 6 from the switching position (b) to the neutral position (a) in order to stop the rotation of the hydraulic motor 1, the pressure oil is supplied to the hydraulic pressure source side oil passage 10A. Therefore, the check valve 13A cuts off the communication between the hydraulic pressure source side oil passage 10A and the actuator side oil passage 11A, and the counter balance valve 51 returns to the neutral position, so that the actuator side oil passage 11B and the hydraulic pressure. The communication with the source side oil passage 10B is cut off. Then, at this time, the hydraulic motor 1 inertially rotates, and the pressure oil discharged from the hydraulic motor 1 increases the pressure of the pressure oil in the actuator side oil passage 11B, and when the brake pressure is generated, the inside of the actuator side oil passage 11B is increased. The pressure oil (brake pressure) is applied to the orifice 3
6B, acting on the piston 33B, the piston 33B
Slides to a position where it comes into contact with the lid 29B on the left side in the figure, and also the relief valve 24 is passed through the relief passage 12B.
Acts on A's poppet 28A, part of which is poppet 2
While flowing into the spring chamber 30A through the throttle passage 32A of 8A, it flows into the first oil chamber 34A from the spring chamber 30A through the throttle 37A, and the piston 33A moves into the second oil chamber 35A.
Energize in the A direction. Then, the piston 33A slides until it comes into contact with the casing 52 on the left side in the figure, and pressure oil is stored in the first oil chamber 34A. Therefore, the pressure P2 in the spring chamber 30A is Actuator side oil passage 11B
The pressure is lower than the internal pressure P1, and the poppet 28A is opened as shown in FIG. 6 based on the equation (2), and the relief valve 24A is opened.
Operates at pressure P1 as in the prior art, as indicated by the characteristic line 41 shown in FIG. Then, after a lapse of a certain time t2, the piston 33A comes into contact with the casing 52,
When the pressure oil cannot be stored any more in the first oil chamber 34A, the pressure of the pressure oil in the spring chamber 30A rises, and the throttle passage 32A provided in the poppet 28A causes the pressure passage in the actuator side oil passage 11B. Since the pressure becomes equal to the pressure, the poppet 28A is closed again, so that the pressure of the pressure oil in the actuator-side oil passage 11B rises in accordance with the inertial rotation of the hydraulic motor 1. And actuator side oil passage 1
When the pressure in 1B rises to the maximum set pressure Ph, the relief valve 24A is opened again, and this pressure oil is released from the relief valve 24.
It is converted into heat energy by passing through the communication hole 26A of A, and the inertial rotation of the hydraulic motor 1 is gradually stopped.

When the counterbalance valve 51 is returned to the neutral position of the spool 56, the third oil passage 64B and the second oil passage 60B are connected to each other, so that the actuator-side oil passage 11B and the relief valve 24B are connected to each other. No. 1 oil chamber 34B communicates with each other via a check valve 61B, and the piston 33B of the relief valve 24B moved to the left side in the figure by the pressure of the hydraulic oil in the actuator-side oil passage 11B when the hydraulic motor 1 is stopped.
Is pushed toward the actuator-side oil passage 11B by a spring 55B provided in the first oil chamber 34B, and the check valve 61 is moved as the piston 33B moves.
B is opened, and the pressure oil in the actuator-side oil passage 11B is supplied to the first oil chamber 34B through the communication passage 53B, so that the first oil chamber 34B and the second oil chamber 35B are the same. Pressure is applied, and the piston 54B rapidly slides until it comes into contact with the casing 52 on the second oil chamber 35B side. As a result, when the relief valve 24A performs relief at the preset maximum set pressure and the hydraulic motor 1 stops, the operator again switches the direction switching valve 6 from the neutral position (a) to the switching position (b). Also, since the pressure oil is stored in the first oil chamber 34B at the outer peripheral portion of the relief valve 24B in a full state, when the hydraulic motor 1 is started in the arrow F direction, the piston 33B is already , The relief valve 24B does not operate at a pressure lower than the maximum set pressure because it is in contact with the casing 52 on the second oil chamber 35B side and is at the stroke end position. Can always start with high responsiveness.

When the direction switching valve 6 is switched between the neutral position (a) and the switching position (c), the operation is similar to that described above.

Therefore, according to this embodiment, the hydraulic motor 1
Even when the starting and stopping of the piston 33 are repeated, the piston 33 provided on the outer peripheral portions of the relief valves 24A and 24B
By holding A and 33B in advance at positions where they come into contact with the casing 52 on the second oil chamber 35A and 35B side, the relief valves 24A and 24B temporarily operate at a pressure lower than the maximum set pressure Ph at the time of startup. Surely prevent it from happening,
It is possible to improve the responsiveness at the time of starting and greatly improve the safety and operability 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 is used.
4A, 24B can be operated at a pressure lower than the maximum set pressure, the impact at the time of stop can be mitigated, and when this brake pressure rises to the maximum set pressure Ph,
The relief valves 24A and 24B can be operated at the maximum set pressure, and the vehicle can be stopped reliably.

[0047]

Since the hydraulic drive system of the present invention is constructed as described above, it is possible to prevent the relief valve from temporarily operating at a pressure lower than the maximum set pressure when the hydraulic motor is started. By always setting the drive pressure of the hydraulic motor to the maximum set pressure of the relief valve, it is possible to improve the responsiveness at the time of starting. Then, when the hydraulic motor is stopped, the pressure oil in the spring chamber of the relief valve is injected into the first oil chamber so that the brake pressure in the circuit is lower than the maximum set pressure of the relief valve only in the initial stage. Thus, the impact at the time of stopping can be reliably reduced.

Further, the pistons respectively accommodated in the oil chambers provided on the outer peripheral portion of the relief valve are constantly urged in the direction of the second oil chamber by the springs. By providing the communication passage communicating with the first oil passage, the piston can be moved to the second oil chamber side in advance, and the moving speed thereof can be increased, so that the hydraulic motor is stopped. Responsiveness can be improved even if it is immediately restarted.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a hydraulic drive system according to an embodiment of the present invention.

FIG. 3 is an enlarged view of part A (relief valve) shown in FIG.

FIG. 4 is an enlarged view of part B (counter balance valve) shown in FIG.

FIG. 5 is a cross-sectional view of the hydraulic drive system showing the starting time of the hydraulic motor of the present invention.

FIG. 6 is a sectional view of the hydraulic drive system when the hydraulic motor of the present invention is stopped.

FIG. 7 is a drive circuit diagram of a hydraulic motor provided with a hydraulic drive device according to a conventional technique.

FIG. 8 is a vertical cross-sectional view showing a hydraulic drive system according to the prior art.

9 is an enlarged view of a portion C (relief valve) shown in FIG.

FIG. 10 is a cross-sectional view of the hydraulic drive system showing the start-up of the hydraulic motor according to the related art.

FIG. 11 is a cross-sectional view of the hydraulic drive system when the hydraulic motor according to the related art is stopped.

FIG. 12 is a characteristic diagram showing a characteristic of a motor drive pressure according to a conventional technique.

FIG. 13 is a characteristic diagram showing a characteristic of brake pressure according to a conventional technique.

[Explanation of symbols]

 1 Hydraulic Motor 3 Hydraulic Pump 9A, 9B 1st, 2nd Oil Passage 13A, 13B Check Valve 24A, 24B Relief Valve 30A, 30B Spring Chamber 34A, 34B 1st Oil Chamber 35A, 35B 2nd Oil Chamber 50 Hydraulic Pressure Drive device 51 Counter balance valve 53A, 53B Communication passage 55A, 55B Spring 59A, 59B First oil passage 60A, 60B Second oil passage 61A, 61B Check valve 64A, 64B Third oil passage

Claims (4)

[Claims] 1. A first connecting a hydraulic power source and a hydraulic motor
A second oil passage, a check valve provided in the first oil passage for allowing only the flow of pressure oil from a hydraulic source to a hydraulic motor, and a check valve provided in the first oil passage in parallel with the check valve. A counterbalance valve arranged, a relief valve having its discharge side connected to a first oil passage between the hydraulic motor and the counterbalance valve, and its inflow side connected to a second oil passage, and the relief valve. An oil chamber for storing pressure oil in the spring chamber is attached to the piston, and a piston is movably housed in the oil chamber, and the piston forms first and second oil chambers in the oil chamber. In a hydraulic drive system in which a first oil chamber and the spring chamber are communicated with each other, and a second oil chamber is communicated with the first oil passage, the piston is always provided in the first oil chamber and the second oil chamber is provided. Insert a spring that presses in the chamber direction, and when the counterbalance valve is in the neutral position, Communicating oil passage and the first oil chamber, the hydraulic drive apparatus is characterized in that a communication passage is blocked to the switching. 2. A check valve for allowing only the flow of pressure oil from a hydraulic pressure source to a hydraulic motor and a counter balance valve arranged in parallel to the check valve are provided in the second oil passage. Further, a relief valve having its discharge side connected to a second oil passage between the hydraulic motor and the counterbalance valve, and its inflow side connected to the first oil passage, and the relief valve having its spring chamber An oil chamber for accumulating the pressure oil of the first oil chamber is attached, a piston is movably housed in the oil chamber, and the piston forms first and second oil chambers in the oil chamber. And a spring chamber, and a second oil chamber communicates with the second oil passage.
A spring for constantly pressing the piston in the direction of the second oil chamber is inserted into the oil chamber, and the second oil passage and the first oil chamber are communicated with each other when the counterbalance valve is in the neutral position, and when the switching is performed. The hydraulic drive system according to claim 1, further comprising a communication passage that is cut off. 3. A first oil passage that connects the communication passage to the spool of the counterbalance valve, one side of which is connected to the first oil passage, and a third oil passage that is connected to the first oil chamber on one side. Oil passage and a second oil passage provided on the spool of the counterbalance valve, which connects the first oil passage and the third oil passage when the valve is neutral and cuts off the connection when switching. The first oil passage to the first oil passage between the first oil passage and the third oil passage.
2. The hydraulic drive system according to claim 1, further comprising a check valve which allows only the flow of the oil into the oil chamber. 4. A first oil passage that connects the communication passage to the spool of the counterbalance valve and has one side connected to the second oil passage, and a third oil passage that is connected to the first oil chamber on one side. Oil passage and a second oil passage provided on the spool of the counterbalance valve, which connects the first oil passage and the third oil passage when the valve is neutral and cuts off the connection when switching. A first oil passage between the first oil passage and the second oil passage,
3. The hydraulic drive system according to claim 2, further comprising a check valve that permits only the flow of the oil into the oil chamber.