JP2000352401A - Variable capacity hydraulic motor displacement control device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To control automatically and stabilize a motor capacity, to reduce an operator's burden at the time of a stop operation, etc., to broaden an applicable range, and to improve versatility. A center bypass port (8A) is provided in a pressure control valve (8) of a counter balance valve (6), and pipeline sections (4A1, 4B) are provided.
From 1 the load pressure of the hydraulic motor 3 is applied to the center bypass port 8
A supplies the gas to the pilot port 15B of the capacity control valve 11 through the pilot line 27. Pipe sections 4A2, 4 located between the hydraulic motor 3 and the counterbalance valve 6.
A shuttle valve 9 is provided between B2 and the high-pressure side hydraulic oil selected by the shuttle valve 9 is supplied to the high-pressure line 28 and the capacity control valve 11.
Is supplied to the servo actuator 10 via the. The pressure receiving area of the capacity control valve 11 with respect to the pilot pressure is changed between the large capacity position (a) and the small capacity position (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement control apparatus for a variable displacement hydraulic motor, which is preferably used for variably controlling the motor displacement of a variable displacement hydraulic motor provided in a construction machine such as a hydraulic shovel. .

[0002]

2. Description of the Related Art Generally, a variable displacement hydraulic motor is used as a traveling or turning hydraulic motor in a construction machine such as a hydraulic shovel. And, for example, when used as a traveling hydraulic motor, by switching the motor capacity between large capacity and small capacity with a variable capacity actuator, the hydraulic motor is rotated at high torque at low speed at large capacity, and at small capacity at large capacity. It rotates at high speed with low torque.

In order to control the motor displacement variably in accordance with the load pressure acting on the hydraulic motor from the outside, the displacement control device for the hydraulic motor supplies the load pressure of the hydraulic motor as a pilot pressure to the displacement control valve. A self-pressure control type capacity control device configured to selectively control the pressure oil supplied to and discharged from the variable capacity actuator by selectively switching the capacity control valve between a large capacity position and a small capacity position in accordance with the pilot pressure. Known (for example, Japanese Patent Application Laid-Open No.
01068 publication).

A conventional self-pressure control type capacity control apparatus of this kind is configured to control a capacity control valve comprising a hydraulic pilot type spool valve to a small capacity position and a large capacity in accordance with a pilot pressure which is a load pressure of a hydraulic motor. The hunting at the time of capacity switching is prevented by controlling the switching to the position and changing the pressure receiving area of the spool with respect to the pilot pressure between the large capacity position and the small capacity position.

That is, when the motor capacity of the hydraulic motor is switched from a small capacity to a large capacity, the load pressure tends to decrease accordingly, so that the motor capacity changes from the large capacity to the small capacity again in accordance with the decrease in the load pressure. May be switched to When the motor capacity is switched to the small capacity, the load pressure increases, so that a so-called hunting phenomenon occurs in which the motor capacity is switched from the small capacity to the large capacity again.

In order to prevent such a hunting phenomenon, in the above-mentioned prior art, the pilot pressure for changing the motor displacement is changed by changing the pressure receiving area of the displacement control valve with respect to the pilot pressure between the large displacement position and the small displacement position. The set value of (load pressure) is given a hysteresis characteristic, for example, as shown in FIG. 5 described later.

[0007]

By the way, in the above-mentioned prior art, a hydraulic pump-side pipe section located between a directional control valve of a hydraulic motor and a hydraulic power source, or a directional control valve and a counterbalance valve are not connected. Pressure oil that is used as a motor drive pressure is taken out from the pipeline between the two, and this pressure oil is used for pilot pressure of the capacity control valve and also used as pressure oil supplied to and discharged from the variable capacity actuator.

For this reason, in the prior art, when the directional control valve is returned from the switching position to the neutral position and the motor drive pressure is reduced to the tank pressure level, regardless of the switching position of the displacement control valve, The pressure oil supplied / discharged to / from the variable actuator also drops to the tank pressure, and the motor capacity may be contrary to the operator's intention during the inertial rotation of the hydraulic motor.

On the other hand, it is also possible to adopt a configuration in which the pressure oil is led out from a pipe section between the counterbalance valve and the hydraulic motor. However, in this case, when stopping a vehicle (inertia body) such as a hydraulic excavator, the motor capacity may be switched by the brake pressure. Therefore, for example, the motor capacity differs between the left and right traveling hydraulic motors. As a result, there arises a problem that it is difficult to stop the vehicle.

That is, when the vehicle stops from a state in which the vehicle is traveling with a small motor capacity, the load pressure (brake pressure) of the left and right traveling hydraulic motors fluctuates due to road surface conditions and the like, and one of the hydraulic motor side When the brake pressure instantaneously increases, only one motor capacity becomes large due to self-pressure control, and the left and right motor capacities become unbalanced. Then, on one hydraulic motor side, a sudden brake is applied due to a sudden increase in the brake pressure, and as a result, a problem such as the vehicle turning or meandering may occur.

As another prior art, for example, Japanese Patent Application Laid-Open No. 57-43002 discloses a main switching valve for selectively supplying pressure oil to a variable displacement actuator, and a main switching valve for sensing a load pressure of a hydraulic motor. A self-pressure control type capacity control device including a pilot valve that performs switching control of a switching valve according to a load pressure is disclosed.

However, in this case as well, pressure oil is taken out from the pipeline between the hydraulic motor and the direction control valve, and this pressure oil is used for the pilot pressure of the displacement control valve and the pressure supplied to and discharged from the displacement-variable actuator. Since it is configured to be used also as oil, the same problem as in the above-described conventional technology occurs.

On the other hand, as another prior art, for example, Japanese Patent Application Laid-Open No. 1-116301 discloses that in order to switch the motor capacity between a large capacity and a small capacity using an external command pressure, an external command pressure is applied to a spool of a capacity control valve. There is disclosed a configuration in which a step portion for receiving pressure is provided, and the pressure receiving area for receiving the external command pressure on the side of the step portion is changed according to the sliding position (switching position) of the spool.

However, in this case, the sleeve is inserted into the step portion of the spool, and the pressure receiving area for the external command pressure is changed according to the relative position between the step portion of the spool and the sleeve. Requires a separate sleeve, which increases the number of parts, complicates the structure of the capacity control valve, and limits its application to a capacity control device using an external command pressure, making it difficult to increase versatility. There is a problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to stabilize a motor capacity and automatically control the same, thereby reducing the burden on an operator at the time of a stop operation and the like. Another object of the present invention is to provide a displacement control device for a variable displacement hydraulic motor that can be applied to a wider range to increase versatility.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a variable displacement hydraulic motor having a variable displacement portion and driven to rotate by hydraulic oil from a hydraulic source, and A directional control valve provided in the middle of a pair of supply / discharge passages connected to a hydraulic source, for switching a direction of pressure oil supplied / discharged from the hydraulic source to the hydraulic motor; and a directional control valve located between the directional control valve and the hydraulic motor. A counterbalance valve provided in the middle of the pair of supply / discharge passages, a variable displacement actuator that drives a variable displacement portion of the hydraulic motor to change a motor displacement, and receives a load pressure of the hydraulic motor as a pilot pressure. Accordingly, the present invention is applied to a displacement control device for a variable displacement hydraulic motor comprising a displacement control valve for switching pressure oil supplied to and discharged from the displacement variable actuator.

A feature of the structure adopted by the first aspect of the present invention is that the variable displacement actuator is driven in a passage portion of the pair of supply / discharge passages located between the counterbalance valve and the hydraulic motor. And a pressure oil deriving means for deriving pressure oil from the passage portion, and a pilot pressure for supplying the displacement control valve between the direction control valve and the counter balance valve. Among them, a pilot pressure deriving means for deriving from the supply / discharge passage on the high pressure side is provided,
When the switching of the displacement control valve is performed in accordance with the pilot pressure from the pilot pressure deriving means, a pressure receiving area for receiving the pilot pressure is changed according to a switching position.

With this configuration, the pressure oil to be supplied to the variable displacement actuator can be derived from the supply / discharge passage between the hydraulic motor and the counterbalance valve by using the pressure oil deriving means. For example, even during the inertial rotation of the hydraulic motor, the supply of the pressure oil to the variable displacement actuator can be continued. In this state, the load pressure of the hydraulic motor is derived as the pilot pressure from the supply / discharge passage between the direction control valve and the counterbalance valve, whereby the displacement of the displacement control valve is affected by the brake pressure during inertial rotation. Can be prevented, and the capacity of the hydraulic motor can be kept in a stable state. When the capacity control valve is controlled to be switched between a large capacity position and a small capacity position according to the pilot pressure, for example, the switching pressure of the capacity control valve (the pilot pressure) is changed by changing the pressure receiving area of the capacity control valve with respect to the pilot pressure. Pressure) can be given a hysteresis characteristic.

Further, according to the invention of claim 2, the pilot pressure deriving means is constituted by a high pressure deriving port provided in the counter balance valve for deriving pressure oil in the supply / discharge passage on the high pressure side among the respective supply / discharge passages. ing.

Thus, a part of the pressure oil (motor driving pressure) flowing through the supply / discharge passage on the high pressure side of the pair of supply / discharge passages located between the direction control valve and the counter balance valve is transferred to the counter balance valve. It can be taken out from the provided high-pressure outlet port and supplied to the displacement control valve as pilot pressure.

According to the third aspect of the present invention, the pilot pressure deriving means is provided between the counter balance valve and the direction control valve and is provided between the pair of supply / discharge passages. And a high-pressure selection valve for selectively extracting pressure oil from the supply / discharge passage. In this case, the motor driving pressure can be taken out as the pilot pressure by using the high pressure selection valve.

According to the fourth aspect of the present invention, the displacement control valve has a spool sliding hole, and the high pressure port, the tank port, the pilot port and the variable displacement actuator are spaced apart in the axial direction of the spool sliding hole. A valve housing provided with a pressure oil supply / discharge port, and a pressure oil supply / discharge port which is inserted into a spool sliding hole of the valve housing and is slidably displaced in the spool sliding hole in the axial direction. A spool that selectively communicates with and shuts off the high-pressure port and the tank port; and a biasing means that is provided between one axial side of the spool and the valve housing and constantly biases the spool toward the other side. A first pressure receiving portion provided on the spool, for constantly receiving a pilot pressure guided from the pilot port to slidably displace the spool against the urging means; A bottomed shaft hole which is formed in the pool and extends in the axial direction of the spool and is opened on the other end surface in the axial direction, and is inserted into the shaft hole so as to close the open end of the shaft hole. A piston that is slidably inserted and defines an oil chamber between itself and the bottom of the shaft hole and receives a hydraulic reaction force in the oil chamber; A second pressure receiving portion that changes the pressure receiving area of the spool together with the first pressure receiving portion by receiving the pressure of
An oil passage formed in the spool at a position corresponding to the oil chamber and selectively communicating the oil chamber with a pilot port and a tank port when the spool is displaced in a spool sliding hole. .

With this configuration, when the load pressure (pilot pressure) of the hydraulic motor is small, the spool is slid toward the other end by the urging means, and when the pilot pressure rises, the first pressure is received. When the portion receives the pilot pressure, the spool can be slid and displaced against the urging means. The oil passage selectively connects the oil chamber to a pilot port and a tank port having different pressures according to the sliding displacement of the spool. Then, when the oil chamber communicates with the pilot port, the spool receives the pilot pressure guided into the oil chamber by the second pressure receiving portion,
Since the pilot pressure receiving pressure is released when communicating with the tank port, the total pressure receiving area of the spool by the first and second pressure receiving portions depends on which port the oil chamber communicates with through the oil passage. Therefore, a hysteresis characteristic can be given to the switching pressure of the displacement control valve by utilizing the change in the pressure receiving area.

According to a fifth aspect of the present invention, the capacity control valve has a spool sliding hole, and is separated from the spool sliding hole in the axial direction by a high pressure port, a tank port, a pilot port, an external command pressure. A valve housing provided with a port and a pressure oil supply / discharge port to a variable displacement actuator; and a valve housing which is inserted into a spool sliding hole of the valve housing and is slidably displaced in the spool sliding hole in the axial direction. The oil supply / discharge port is selectively connected to the high pressure port and tank port.
A spool to be shut off, a biasing means provided between the other axial side of the spool and the valve housing, and constantly biasing the spool toward one side; and a biasing means provided at one axial side of the spool. A command pressure receiving portion for receiving the external command pressure guided from the external command pressure port and slidingly displacing the spool against the urging means, and axially facing the command pressure receiving portion. A first pressure receiving portion provided on the spool for constantly receiving a pilot pressure guided from the pilot port for slidingly displacing the spool in the biasing direction of the biasing means; A shaft hole having a bottom and extending in the axial direction of the spool and opening at an end face; and a slidably inserted inside the shaft hole so as to close an open end of the shaft hole. An oil chamber is defined between the bottom of the hole and the oil chamber. A second pressure receiving portion formed by a piston that receives a hydraulic reaction force in the chamber and a bottom portion of the shaft hole, the pressure receiving area of the spool being changed together with the first pressure receiving portion by receiving the pressure in the oil chamber. And an oil passage formed in the spool at a position corresponding to the oil chamber and selectively communicating the oil chamber with a pilot port and a tank port when the spool is displaced in a spool sliding hole. are doing.

With this configuration, the displacement control valve can be switched and controlled using the external command pressure. For example, when the external command pressure is reduced to the tank pressure level, regardless of the pilot pressure from the pilot port, The spool can be held in the one-way sliding position by the biasing means, and the displacement control valve can be fixed at the large displacement position, for example. When the external command pressure is increased and the spool is displaced in the other direction against the urging means, the spool is slidable in one direction or the other according to the load pressure of the hydraulic motor. In addition, the switching control of the capacity having the hysteresis characteristic with respect to the pilot pressure can be performed.

According to the sixth aspect of the present invention, the displacement control valve has a spool sliding hole, and the high pressure port, the tank port, the pilot port, and the variable displacement actuator are spaced apart in the axial direction of the spool sliding hole. A valve housing provided with a pressure oil supply / discharge port, and a pressure oil supply / discharge port which is inserted into a spool sliding hole of the valve housing and is slidably displaced in the spool sliding hole in the axial direction. A spool that selectively communicates with and shuts off the high-pressure port and the tank port; and a biasing means that is provided between one axial side of the spool and the valve housing and constantly biases the spool toward the other side. A first pressure receiving portion provided on the spool to constantly receive a pilot pressure guided from the pilot port to slide and displace the spool against the urging means; A stopper sliding hole which is formed at one end surface of the spool and has a bottom and which is always communicated with the tank port, is inserted into the stopper sliding hole, and the spool slides against the urging means. A stopper that regulates a stroke end when displaced, and is formed between the outer peripheral side of the spool and the spool sliding hole located radially outside the stopper sliding hole, when the spool slides and displaces. An annular oil chamber that is communicated with and interrupted from the pilot port, and is formed on the spool to receive pressure in the oil chamber, and the pressure receiving area of the spool is changed together with the first pressure receiving portion. 2 is formed on the spool between the pressure receiving portion and the oil chamber and the stopper sliding hole, and the oil chamber slides with the stopper while the oil chamber is shut off from the pilot port. In the hole Through so, to the oil chamber Taki communicated with the pilot port constitute from an oil passage communicating with the stopper slide hole is blocked by the stopper.

With this configuration, when the load pressure (pilot pressure) of the hydraulic motor is small, the spool is slid toward the other end by the urging means, and when the pilot pressure rises, the first pressure is received. When the portion receives the pilot pressure, the spool can be slid and displaced against the urging means. The oil chamber communicates with the tank port through a stopper sliding hole by an oil passage until the oil chamber communicates with the pilot port in accordance with the sliding displacement of the spool. When the oil chamber communicates with the pilot port, the oil chamber is shut off from the tank port by the stopper. When the oil chamber communicates with the pilot port, the spool receives the pilot pressure guided into the oil chamber by the second pressure receiving portion, and when the spool communicates with the tank port, the pilot pressure is released.
The total pressure receiving area of the spool by the first and second pressure receiving portions changes depending on which port the oil chamber communicates with. The change in the pressure receiving area is used to change the switching pressure of the capacity control valve. Can be given a hysteresis characteristic.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a displacement control apparatus for a variable displacement hydraulic motor according to an embodiment of the present invention; This will be described in detail.

FIGS. 1 to 5 show a first embodiment of the present invention. In the drawings, reference numeral 1 denotes a hydraulic pump constituting a hydraulic source together with a tank 2, and the hydraulic pump 1 is a prime mover of a hydraulic shovel. (Not shown), the tank 2
The hydraulic oil sucked from the inside is supplied to a hydraulic motor 3 and the like described later as high-pressure hydraulic oil.

Reference numeral 3 denotes a traveling hydraulic motor. The hydraulic motor 3 is constituted by, for example, a swash plate type or swash axis type variable displacement type hydraulic motor, and has a variable capacity portion 3A composed of a swash plate or a valve plate. ing. When the hydraulic motor 3 uses the servo actuator 10 to be described later to tilt and drive the variable capacity section 3A in the direction of arrow A where the tilt angle increases, the motor capacity is increased to the large capacity side, When tilting drive is performed in the direction of arrow B where the angle becomes smaller, the motor capacity is reduced to the smaller capacity side.

4A and 4B denote the hydraulic motor 3 and the hydraulic pump 1
The main pipelines 4A and 4B supply and discharge pressure oil from the hydraulic pump 1 to the hydraulic motor 3 via a directional control valve 5 and the like, which will be described later. ,
As a result, the hydraulic motor 3 rotates forward or reverse to move the hydraulic shovel (vehicle) forward or backward. The main pipelines 4A and 4B are provided with a counter balance valve 6 described later.
Between the counter balance valve 6 and the hydraulic motor 3 between the counterbalance valve 6 and the hydraulic motor 3 is another conduit 4A2 on the actuator side as another passage. , 4B2.

Numeral 5 is a directional control valve for traveling provided in the middle of the main pipelines 4A and 4B. The directional control valve 5 is constituted as a directional control valve having, for example, 4 ports and 3 positions as shown in FIG. When the operator of the shovel switches the operation lever 5A, the switch is switched from the neutral position (a) to the switch positions (b) and (c).

The direction control valve 5 is switched to the switching position (b).
Then, the hydraulic oil from the hydraulic pump 1 is supplied to the hydraulic motor 3 via the main pipeline 4A, and the hydraulic motor 3 is rotated, for example, in the forward direction, and the return oil from the hydraulic motor 3 is supplied to the main pipeline 4B.
Through the tank 2. In addition, the direction control valve 5
Is switched to the switching position (C), the supply direction of the pressure oil is reversed, and the hydraulic motor 3 is rotationally driven in the reverse direction.

Reference numeral 6 denotes a counterbalance valve which constitutes a brake valve attached to the hydraulic motor 3. The counterbalance valve 6 is connected to pipeline sections 4A1 and 4B1 on the hydraulic source side and pipeline sections 4A2 and 4B2 on the actuator side. And a pair of check valves 7A, 7B provided between the hydraulic pressure source side pipe sections 4A1, 4B1 and the actuator side pipe sections 4A2, 4B2 in a parallel relationship with the check valves 7A, 7B. And a pressure control valve 8 disposed at

The pressure control valve 8 of the counter balance valve 6 is switched from the neutral position (a) to the switching positions (b) and (c) almost in conjunction with the direction control valve 5, and the pressure from the hydraulic pump 1 is changed. It compensates for the supply and discharge of oil to and from the hydraulic motor 3. When the pressure control valve 8 returns to the neutral position (a) when the hydraulic motor 3 is rotated by inertia or the like, the counter balance valve 6 is connected between the hydraulic motor 3 and the counter balance valve 6 on the actuator side. The brake pressure is generated within 4A2 or 4B2.

Here, the pressure control valve 8 of the counter balance valve 6 is, for example, a hydraulic pilot type directional control valve having 6 ports and 3 positions, and has a center bypass port 8A serving as a high pressure outlet port. When the pressure control valve 8 is switched from the neutral position (a) to the switching position (b), the center bypass port 8A is connected to the pipeline portions 4A1, 4A on the hydraulic power source side.
B1 is connected to the pipeline section 4A1 on the high pressure side, and when it is switched to the switching position (c), it is connected to the pipeline section 4B1.

Thus, the center bypass port 8A of the pressure control valve 8 constitutes a pilot pressure deriving means for guiding a motor driving pressure, which is a load pressure of the hydraulic motor 3, into a pilot pipe 27 which will be described later. The switching of the valve 11 is controlled in accordance with the pilot pressure P from the pilot line 27. When the pressure control valve 8 returns to the neutral position (a), the pilot pressure in the pilot line 27 is automatically reduced to the tank pressure level by connecting the center bypass port 8A to a tank line 30 described later. It decreases to.

9 is a hydraulic motor 3 and a counterbalance valve 6
And the pipeline portions 4A2, 4 of the main pipelines 4A, 4B
A shuttle valve provided between B2 and as a high pressure selection valve.
The shuttle valve 9 is connected to the pipe sections 4A2, 4A of the main pipes 4A, 4B.
The pressure oil on the high pressure side is selected from B2, and the selected pressure oil is supplied to the servo actuator 10 via the high pressure pipe 28 and the capacity control valve 11 described later. The shuttle valve 9 and the high-pressure line 28 constitute a pressure oil deriving unit.

Reference numeral 10 denotes a servo actuator serving as a variable displacement actuator attached to the hydraulic motor 3. The servo actuator 10 has a tilt piston 10A for driving a variable displacement portion 3A of the hydraulic motor 3, and always has a spring 10B. This biases the variable capacity section 3A toward the large tilt (large capacity) in the direction of arrow A. When high-pressure oil is supplied into the hydraulic chamber 10C, the servo actuator 10 drives the variable displacement portion 3A in the direction of arrow B against the spring 10B by the tilt piston 10A, thereby increasing the motor displacement. To a small capacity.

Numeral 11 denotes a displacement control valve attached to the hydraulic motor 3 together with the servo actuator 10.
1 includes a valve housing 12 and a spool 19 and a piston 21 which are slidably provided in the valve housing 12 as shown in FIG.
The capacity control valve 11 is composed of a 6-port 2-position hydraulic pilot type switching valve as shown in FIG. 1, and the large capacity position (a) and the small capacity position (b) are controlled by the pilot pressure P from the pilot line 27. And the switching control is performed.

When the displacement control valve 11 is in the small displacement position (b), the pressure oil from the high pressure line 28 is supplied to the hydraulic chamber 10C of the servo actuator 10 to supply and discharge lines 2 to be described later.
The displacement variable unit 3A is driven by the tilt piston 10A in the direction of arrow B where the tilt angle becomes smaller.
When the capacity control valve 11 is switched to the large capacity position (a), the supply / discharge pipe 29 is connected to the tank pipe 26 so that the pressure oil in the hydraulic chamber 10 </ b> C is discharged toward the tank 2. Then, the variable capacity portion 3A is driven by the spring 10B of the servo actuator 10 in the direction of arrow A where the tilt angle becomes large.

Here, the valve housing 1 of the displacement control valve 11
2, a stepped spool sliding hole 13 having one end serving as an open end 13A and the other end serving as a closed end 13B is formed,
On the outer peripheral side of the spool sliding hole 13, an annular oil groove 14A,
14B, 14C, 14D, 14E, and 14F are formed to be spaced apart in the axial direction.

In the valve housing 12, tank ports 15A, 15C, 15F, a pilot port 15B, a high pressure port 15D, and a pressure oil supply / discharge port 15E are formed axially separated from each other.
F communicates with the inside of the spool sliding hole 13 through the oil grooves 14A to 14F.

Reference numeral 16 denotes an opening end 13A of the spool sliding hole 13.
The lid 16 constitutes a part of the valve housing 12, and a spring chamber 17 is formed in the oil groove 14A between the lid 16 and one end surface of a spool 19 described later. ing. A rod-shaped stopper 18 projecting into the spring chamber 17 is provided on the inner surface of the lid 16, and the stopper 18 regulates the stroke end of the spool 19 as shown in FIG.

Numeral 19 denotes a spool inserted into a spool sliding hole 13 of the valve housing 12. The spool 19 has lands 19A, 19B, 1 on its outer peripheral side as shown in FIGS.
9C and 19D are formed to be spaced apart from each other in the axial direction, and between the land 19B and the land 19C, oil grooves 14B and 14D are formed.
An annular groove 19E is formed to communicate with and block C.
Another annular groove 19F is formed between the land 19C and the land 19D of the spool 19 so as to communicate and block between the oil grooves 14D and 14E, and the annular groove 19F and the land 19D are formed.
Thus, the pressure oil supply / discharge port 15E is selectively communicated with and blocked from the high pressure port 15D and the tank port 15F.

Here, the spool 19 is formed as a stepped spool having a maximum diameter on the land 19A side located on one end side, and a step portion (end face side) of the land 19A opposed to the land 19B is connected to the pilot line 27. Is a first pressure receiving portion 19G for receiving the pilot pressure P. The land 19A has an outer diameter Da, and the land 19B has an outer diameter Db.
, And the pressure receiving portion 19G has a pressure receiving area S
Have one.

[0047]

[Number 1] ^{S1 = (Da 2 × π /} 4) - (Db 2 × π / 4) = (Da 2 -Db 2) × π / 4

As a result, the pressure receiving portion 19G has a pressure receiving area S1.
The pilot pressure P is constantly received from the pilot line 27, and when the pilot pressure P is increased, the spool 19 is slid in the direction of arrow C against a return spring 24 described later.

Reference numeral 20 denotes a shaft hole formed in the spool 19 and having a bottomed hole extending in the axial direction. The shaft hole 20 is closed at one end as a bottom, and the other end is open at the end face of the spool 19. . The shaft hole 20 is formed with a relatively small hole diameter Dc (Dc <Db <Da) as shown in FIG. 4, and the bottom of the shaft hole 20 controls the pressure in the oil chamber 22 described later.

[0050]

[Number 2] S2 = Dc ² × the second pressure receiving portion 20A for receiving with [pi / 4 becomes a pressure receiving area S2
It has become.

Reference numeral 21 denotes a piston slidably inserted into the shaft hole 20. The piston 21 always closes the open end of the shaft hole 20, and one end thereof is located between the shaft 21 and the bottom of the shaft hole 20. Oil chamber 2
2 is defined. The other end of the piston 21 projects axially from the end surface of the spool 19 as shown in FIG.
The spool slide hole 13 is in contact with the closed end 13 </ b> B side to receive a hydraulic reaction force due to the pilot pressure P in the oil chamber 22.

Reference numeral 23 denotes a small hole as an oil passage formed in the radial direction of the spool 19 at a position corresponding to the oil chamber 22, and the small hole 23 opens on the outer peripheral surface of the spool 19 at the position of the annular groove 19E. The oil chamber 22 is moved from the tank port 15C (oil groove 14C) to the pilot port 15 according to the sliding position of the spool 19.
B (oil groove 14B).

In this case, the spool 19 is provided with the oil chamber 22 formed by the small hole 23, the tank port 15C, and the pilot port 1.
Since communication with 5B and blocking are performed with zero lap, land 19
An annular groove 19E between B and 19C is formed with an axial length corresponding to a separation dimension between the oil grooves 14B and 14C. The small hole 23 connects the oil chamber 22 to the pilot port 1.
5B, the oil chamber 22 is formed by the annular groove 19E.
Are shut off almost simultaneously with the tank port 15C, and when the oil chamber 22 is communicated with the tank port 15C, it is shut off almost simultaneously with the pilot port 15B.

Reference numeral 24 denotes a return spring which is located between the lid 16 and one side of the spool 19 in the axial direction and constitutes a biasing means disposed in the spring chamber 17. The return spring 24 has a stopper at one end. The other end is attached to one end of the spool 19 by fitting or the like. Then, the return spring 24 constantly urges the spool 19 in the direction of arrow D toward the closed end 13B with an urging force Fa, whereby the displacement control valve 11 is moved to the small displacement position (b) shown in FIG.
Is held in the

Reference numeral 25 denotes a drain pipe for discharging drain (leakage oil) from the hydraulic motor 3 to the tank 2, and reference numeral 26 denotes a tank pipe which constantly connects the tank ports 15 A, 15 C, and 15 F of the capacity control valve 11 to the tank 2. Is shown.

Reference numeral 27 denotes a pilot line connected to the pilot port 15B of the displacement control valve 11. The pilot line 27 is connected to the center bypass port 8A of the counter balance valve 6, and the motor driving pressure of the hydraulic motor 3 is changed. The (load pressure) is led to the pilot port 15B of the capacity control valve 11 as the pilot pressure P.

A high-pressure line 28 connects the shuttle valve 9 to the high-pressure port 15D of the capacity control valve 11.
Is for guiding the high-pressure oil selected by the shuttle valve 9 from the pipe sections 4A2, 4B2 of the main pipes 4A, 4B to the high-pressure port 15D of the capacity control valve 11.

Reference numeral 29 denotes a supply / discharge pipe connecting the hydraulic chamber 10C of the servo actuator 10 to a pressure oil supply / discharge port 15E of the capacity control valve 11. Further, reference numeral 30 denotes another tank line connected to the center bypass port 8A of the counter balance valve 6, and the tank line 30 is provided when the pressure control valve 8 of the counter balance valve 6 returns to the neutral position (a). The center bypass port 8A is connected to the tank 2 to lower the pilot pressure P in the pilot line 27 to the tank pressure level.

The traveling hydraulic circuit of the hydraulic shovel provided with the displacement control valve 11 according to the present embodiment has the above-described configuration. Next, the operation thereof will be described.

First, when the operator of the hydraulic excavator switches the directional control valve 5 shown in FIG. 1 from the neutral position (a) to the switching position (b) in order to drive the vehicle, the hydraulic oil from the hydraulic pump 1 It is supplied to the hydraulic motor 3 from the main pipeline 4A side as a motor drive pressure. At this time, the pressure control valve 8 of the counter balance valve 6 is connected to the pipe sections 4A1, 4B1.
The pressure is switched from the neutral position (a) to the switching position (b) by the pressure difference, and the return oil from the hydraulic motor 3 is transferred to the tank 2 from the main pipeline 4B (the pipeline 4B1) via the pressure control valve 8. And the vehicle is driven to travel in the forward direction.

On the other hand, when the traveling direction control valve 5 is switched from the neutral position (a) to the switching position (c), the motor driving pressure is supplied to the main pipeline 4B side, and the hydraulic motor 3 is different from the above case. It is driven to rotate in the opposite direction. In this case, the pressure control valve 8 is switched from the neutral position (a) to the switching position (c).
And the return oil from the hydraulic motor 3 is supplied to the pressure control valve 8.
Through the main pipeline 4A (the pipeline section 4A1) to the tank 2, whereby the vehicle is driven to travel in the reverse direction.

When the pressure control valve 8 is switched from the neutral position (a) to the switching position (b) or (c) during running of the vehicle, the center bypass port 8 of the pressure control valve 8
A is connected to the pipeline 4A1 or 4B1 on the hydraulic pressure side,
The motor drive pressure becomes the pilot pressure P and is supplied from the pilot line 27 to the pilot port 15B of the capacity control valve 11.

Further, the pipeline section 4A2 on the actuator side,
On the 4B2 side, the motor drive pressure is selected by the shuttle valve 9 and the selected pressure oil is supplied from the high pressure line 28 to the capacity control valve 1.
It is led to one high pressure port 15D.

The pilot pressure P supplied to the pilot port 15B of the capacity control valve 11 acts on the pressure receiving portion 19G of the spool 19 shown in FIG. 2 and pushes the spool 19 with the pressure receiving area S1 according to the equation (1). The pressure F1 is pressed in the direction of arrow C against the urging force Fa of the return spring 24.

[0065]

F1 = S1 × P Further, the urging force Fa of the return spring 24 is

[0066]

## EQU3 ## The pilot pressure P is set in advance so as to satisfy the relationship of Fa = S1.times.P1 = (S1 + S2) .times.P2, and the pilot pressures P1 and P2 (P1>) as shown by a characteristic line 31 in FIG.
P2), a hysteresis characteristic is given to the switching control pressure of the motor displacement.

That is, for example, when the vehicle is traveling uphill on a slope, the load pressure of the hydraulic motor 3 increases, and the pilot pressure P increases to the pressure P1 or more. At this time, the spool 19 applies a pressing force F1 (F1 = S1 × P1) in the direction of arrow C.
), The return spring 24 is bent and deformed as shown in FIG.

Thus, the displacement control valve 11 is connected to the return spring 2
4 is switched from the small capacity position (b) shown in FIG. 1 to the large capacity position (a) against the urging force Fa, and the high pressure port 15D of the capacity control valve 11 is supplied and discharged by the land 19D of the spool 19. The port 15E is shut off and the pressure oil supply / discharge port 15E is connected to the tank port 15F (tank line 2).
It is communicated to 6).

For this reason, the hydraulic chamber 10C of the servo actuator 10 is connected to the tank 2 via the supply / discharge line 29, the pressure oil supply / discharge port 15E of the capacity control valve 11, the tank line 26, and the like. The variable displacement section 3A of the motor 3 is driven in the direction of arrow A to the large tilt side. Thus, the hydraulic motor 3 is controlled to have a large motor capacity so that the hydraulic motor 3 can rotate at a high torque and a low speed in preparation for traveling uphill.

At this time, the capacity control valve 11 allows the oil chamber 22 in the spool 19 to move the pilot port 15 through the small hole 23, the annular groove 19E and the oil groove 14B as shown in FIG.
By being connected to B, a pilot pressure P equal to or higher than the pressure P1, for example, is supplied into the oil chamber 22.

The spool 19 receives the pilot pressure P with the pressure receiving area S1 at the pressure receiving portion 19G.
On the pressure receiving portion 20A side in the oil chamber 22, the pilot pressure P is received with the pressure receiving area S2 according to the above equation (2).
At this time, the spool 19 has a pressure receiving portion 19G and a pressure receiving portion 20A.
With the total pressure receiving area (S1 + S2), the pilot pressure P is continuously received.

As a result, even when the capacity of the hydraulic motor 3 changes from a small capacity to a large capacity, and the motor driving pressure (load pressure) slightly decreases, the spool 19 remains at a pressure equal to or higher than the pressure P2. But,

[0073]

F2 = (S1 + S2) .times.P

[0074]

## EQU6 ## With a pressing force F2 satisfying F2≥Fa (where P≥P2), as shown in FIG.
4 is deformed in the direction indicated by the arrow C to maintain the displacement control valve 11 at the large displacement position (a).

On the other hand, when the vehicle has finished traveling uphill, for example, moving straight on flat ground, the pilot pressure P becomes
The pressure drops below the pressure P2 shown in FIG. by this,
The pressing force F2 of the spool 19 is equal to the urging force F of the return spring 24.
a, so that the spool 19 is
, Is slid back to the initial position shown in FIG. 2, and the capacity control valve 11 returns to the small capacity position (b) again.

At this time, since the high pressure port 15D of the capacity control valve 11 is communicated with the pressure oil supply / discharge port 15E, the servo actuator 10 is inserted into the hydraulic chamber 10C from the high pressure pipe 28 selected by the shuttle valve 9. Pressurized oil is supplied through the supply / discharge pipe line 29 and the like, and the displacement piston 3A drives the variable displacement portion 3A of the hydraulic motor 3 in the direction of arrow B to the small displacement side. As a result, the capacity of the hydraulic motor 3 can be controlled to a small capacity suitable for traveling on level ground, and the vehicle can run at high speed with low torque.

At this time, in the capacity control valve 11, the oil chamber 22 in the spool 19 is connected to the tank port 15C through the small hole 23 and the oil groove 14C as shown in FIG. The pressure drops to the tank pressure level. Therefore, the spool 19 does not receive the pilot pressure P on the pressure receiving portion 20A side in the oil chamber 22, but receives the pilot pressure P with the pressure receiving area S1 only on the pressure receiving portion 19G side. It is reduced to S1.

As a result, even when the capacity of the hydraulic motor 3 changes from a large capacity to a small capacity and the motor driving pressure (load pressure) slightly increases, the spool pressure is maintained until the pilot pressure P reaches the pressure P1. 19 is the pressing force F1 according to the equation (7).
And only presses the return spring 24 in the direction of arrow C in FIG.

[0079]

F1 <Fa (where P <P1) The spool 19 is urged to the initial position by the return spring 24 to hold the capacity control valve 11 at the small capacity position (b).

Thus, according to the present embodiment, the center bypass port 8A is provided in the pressure control valve 8 of the counter balance valve 6, and the pipe sections 4A1, 4B1 of the main pipes 4A, 4A are provided.
, A motor drive pressure, which is a load pressure of the hydraulic motor 3, is guided into the pilot pipeline 27 through the center bypass port 8 </ b> A, and is supplied as a pilot pressure P to the pilot port 15 </ b> B of the displacement control valve 11.

The main pipelines 4A, 4B located between the hydraulic motor 3 and the counterbalance valve 6 have the pipeline sections 4A2, 4A2,
A shuttle valve 9 is provided between the shuttle valves 4B2, and the high-pressure side oil of the pipelines 4A2 and 4B2 selected by the shuttle valve 9 is supplied to the servo actuator 10 via the high-pressure pipeline 28 and the capacity control valve 11. It has a configuration.

Thus, when the directional control valve 5 is returned from the switching position (b) or (c) to the neutral position (a) during the running of the vehicle to stop the vehicle, or when the vehicle is going downhill, the directional control valve 5 is controlled. 5, when the pressure control valve 8 of the counter balance valve 6 returns to the neutral position (a) and the hydraulic motor 3 continues the inertial rotation,
The brake pressure generated at A2 and 4B2 is taken out as pressure oil by the shuttle valve 9, and the pressure oil can be continuously supplied from the high pressure line 28 to the servo actuator 10.

At this time, the counter balance valve 6
The pressure control valve 8 returns to the neutral position (a), and connects the center bypass port 8A to the tank 2 through the tank line 30.
Can be automatically reduced to the tank pressure level to prevent the capacity control valve 11 from switching due to the influence of the brake pressure during the inertial rotation, and the capacity control valve 11 can be held at the small capacity position (b) shown in FIG. At the same time, the hydraulic motor 3 can be kept in a stable state with a small capacity.

For this reason, as described in the related art, it is possible to prevent the motor capacity from becoming a capacity contrary to the intention of the operator during the inertial rotation of the hydraulic motor 3, and for example, the load pressure of the left and right hydraulic motors 3 ( It is possible to solve the problem that the left and right motor capacities are unbalanced due to the fluctuation of the brake pressure) due to the road surface condition or the like. Then, the brake pressure suddenly increases due to the influence of the load during the inertial rotation, and the problems such as sudden braking of the hydraulic motor 3 are eliminated, and the problem of the vehicle turning and meandering can be solved.

The spool 19 of the capacity control valve 11 is provided with a land 19A having a maximum diameter at one end side so that the annular pressure receiving portion 1 is provided.
9G, a pilot pressure P from the pilot port 15B is received by the pressure receiving portion 19G with a pressure receiving area S1 and a piston 21 is inserted into a bottomed shaft hole 20 extending in the axial direction from the other end of the spool 19. Is slidably inserted to define an oil chamber 22, and the oil chamber 22 is inserted into the tank port 15 </ b> C by a small hole 23 according to the sliding position of the spool 19.
And the pilot port 15B.

While the spool 19 is at the initial position shown in FIG. 2, that is, while the capacity control valve 11 is at the small capacity position (b), the oil chamber 22 is communicated with the tank port 15C to thereby control the pilot pressure of the spool 19. The pressure receiving area for P is reduced to only the pressure receiving area S1 on the pressure receiving portion 19G side, and the spool 19 can be held at the initial position by the return spring 24 until the motor drive pressure (pilot pressure P) rises to the pressure P1 or more. 11 can be kept at the small capacity position (b).

When the motor drive pressure rises above the pressure P 1, the spool 19 slides to the stroke end against the return spring 24, so that the oil chamber 22 is displaced.
The pilot pressure P from the pilot port 15B is introduced through the small hole 23, the pressure receiving area of the spool 19 is increased by the pressure receiving area S2 by the pressure receiving portion 20A in the oil chamber 22, and the total pressure receiving area (S1 + S2) is obtained. The pilot pressure P can be continuously received.

For this reason, even when the capacity of the hydraulic motor 3 increases from a small capacity to a large capacity and the motor driving pressure slightly decreases, the spool 19 having a large pressure receiving area (S1 + S2) is used to move the spool 19 shown in FIG. The displacement of the hydraulic motor 3 is maintained at a large value by switching the displacement control valve 11 to the large displacement position (a) until the motor drive pressure falls to or below the pressure P2 during traveling on level ground. be able to.

Therefore, according to the present embodiment, the motor capacity of the hydraulic motor 3 can be automatically controlled with stabilization, the burden on the operator at the time of a stop operation or the like can be reduced, and the vehicle can turn or meander. Can be prevented. In addition, the motor capacity can be self-pressure controlled without requiring external command pressure, etc.
The versatility can be enhanced by expanding the applicable range of the capacity control device including the capacity control valve 11 and the like.

The switching control pressure of the displacement control valve 11 can be provided with a hysteresis characteristic in the range of the pressures P1 and P2, thereby preventing the hunting phenomenon accompanying the switching of the displacement and stabilizing the displacement control automatically. It can be carried out. Further, since the capacity control valve 11 can be constituted by the valve housing 12, the spool 19, the piston 21, and the return spring 24, the number of parts can be reduced and the workability at the time of assembling can be improved. Can be achieved.

Further, since the spool 19 is formed as a stepped spool having a large diameter at one end and a pressure receiving portion 19G for the pilot pressure P is provided on the outer peripheral side of the spool 19, the axial length of the spool 19 is increased. Can be shortened, and the entire volume control valve 11 can be reduced in size.

Further, the oil chamber 2 defined in the spool 19
2 communicates with the pilot port 15B and the tank port 15C with almost zero lap during the switching control of the capacity control valve 11,
Because of the shut-off configuration, the pressure receiving area of the spool 19 with respect to the pilot pressure P can be instantaneously increased or decreased when the capacity is switched, and the spool 19 can be smoothly slid and displaced between the initial position and the stroke end. In addition, the occurrence of the hunting phenomenon due to the switching of the motor capacity can be suppressed well, and stable capacity control can be realized.

Next, FIGS. 6 to 8 show a second embodiment of the present invention. The feature of this embodiment is that an external command pressure port is additionally provided to the capacity control valve to control the external command pressure. The configuration is such that the control for fixing the motor capacity to a large capacity and the automatic capacity switching control are selectively performed in accordance with the operating conditions by selecting the motor capacity by the external selection means. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 41 denotes a displacement control valve employed in the present embodiment. The displacement control valve 41 comprises a valve housing 42, a spool 49 and a piston 5 which will be described later, as shown in FIG.
1 and the like. And the capacity control valve 4
1 is substantially the same as the capacity control valve 11 described in the above embodiment, but the capacity control valve 41 is connected to an external command pressure from a command pressure
The switching between the large capacity position (a) and the small capacity position (b) is performed by the pilot pressure P from the controller.

Here, the valve housing 4 of the capacity control valve 41
2, a stepped spool sliding hole 43 having an open end 43A at one end and a closed end 43B at the other end is formed.
On the outer peripheral side of the spool sliding hole 43, an annular oil groove 44A,
44B, 44C, 44D and 44E are formed to be spaced apart in the axial direction.

The valve housing 42 is axially separated from the external command pressure port 45A, the pilot port 45B, the tank ports 45C and 45F, and the high pressure port 45.
D and a pressure oil supply / discharge port 45E are formed, and these ports 45A to 45E communicate with the inside of the spool sliding hole 43 via oil grooves 44A to 44E.

Reference numeral 46 denotes an open end 43A of the spool sliding hole 43.
The lid 46 constitutes a part of the valve housing 42, and the external command pressure chamber 47 is located in the oil groove 44 </ b> A between the lid 46 and one end surface of a spool 49 described later. Has formed.

Reference numeral 48 denotes a closed end 43A of the spool sliding hole 43.
And a spring chamber formed between the other end surface of the spool 49 and a return spring 55, a stopper 54, and the like, which will be described later, are disposed in the spring chamber 48. The spring chamber 48 is always connected to the tank 2 via the tank port 45F and the tank line 26.

Reference numeral 49 denotes a spool inserted into the spool sliding hole 43 of the valve housing 42. The spool 49 has lands 49A, 49B, 4 on its outer peripheral side as shown in FIGS.
9C and 49D are formed apart from each other in the axial direction, and oil grooves 44B and 44D are provided between the land 49B and the land 49C.
An annular groove 49E is formed to communicate and block C.
Further, between the land 49C and the land 49D of the spool 49, there is formed an annular groove 49F for communicating and blocking between the oil grooves 44D and 44E, and the pressure oil supply / discharge port 45E is formed by the annular groove 49F and the land 49D. Is selectively connected to and blocked from the high-pressure port 45D and the tank port 45F.

Here, the spool 49 is formed as a stepped spool having the largest diameter on the land 49A side located at one end side, and the stepped portion (end face side) of the land 49A facing the land 49B is connected to the pilot line 27. An annular first pressure receiving portion 49G for receiving the pilot pressure from the first pressure receiving portion. The pressure receiving portion 49G has a pressure receiving area S1 according to the equation (1), similarly to the pressure receiving portion 19G of the spool 19 according to the first embodiment described above.

The end surface of one end of the spool 49 located on the land 49A side is a command pressure receiving portion 49H for receiving an external command pressure in a direction opposite to the pressure receiving portion 49G, and the pressure receiving portion 49H is provided with an external command pressure. The chamber 47 has a pressure receiving area S3 according to the following equation (8).

Reference numeral 50 denotes a shaft hole formed in the spool 49 and having a bottomed hole extending in the axial direction. The shaft hole 50 is closed at one end as a bottom, and the other end is open at the end face of the spool 49. . The shaft hole 50 has a second pressure receiving portion 50A having a pressure receiving area S2 on the bottom side, similarly to the shaft hole 20 described in the first embodiment.

Reference numeral 51 denotes a piston slidably inserted into the shaft hole 50. The piston 51 always closes the open end of the shaft hole 50, and one end of the piston 51 is connected to the bottom of the shaft hole 50. Oil chamber 5
2 is defined. The other end of the piston 51 projects axially from the end surface of the spool 49 as shown in FIG.
It is in contact with the end face of the stopper 54 to receive a hydraulic reaction force due to the pilot pressure P in the oil chamber 52.

Reference numeral 53 denotes a small hole serving as an oil passage formed in the radial direction of the spool 49 at a position corresponding to the oil chamber 52. The small hole 53 is different from the small hole 23 described in the first embodiment. In substantially the same manner, the oil chamber 52 is connected to the tank port 45C (oil groove 44C) and the pilot port 45B in accordance with the sliding position of the spool 49.
(The oil groove 44B).

The small hole 53 is provided with an annular groove 49E which is always in communication with the small hole 53 so that the oil chamber 52 communicates with the pilot port 45B and the tank port 45C at zero lap when the spool 49 is slid and displaced. But the oil grooves 44B, 44
It is formed with a groove width corresponding to the separation dimension of C.

Reference numeral 54 denotes a closed end 43B of the spool sliding hole 43.
The stopper 54 is formed of a columnar rod or the like, and protrudes into the spring chamber 48 from the closed end 43B side of the spool sliding hole 43. One end of the stopper 54 contacts the other end of the piston 51, and when the spool 49 is slid and displaced as shown in FIG. 8, the stopper 54 contacts the end surface of the spool 49 to restrict the stroke end of the spool 49. It is.

A return spring 55 is provided between the valve housing 42 and the spool 49 and constitutes a biasing means disposed in the spring chamber 48. One end of the return spring 55 is connected to the end of the spool 49. The other end is inserted through the outer peripheral side of the stopper 54 so that the spool sliding hole 4 is inserted.
3 is in contact with the closed end 43B. And the return spring 5
5 always biases the spool 49 in the direction of arrow C with the biasing force Fb, whereby the displacement control valve 41 is held at the large displacement position (a) shown in FIG.

Reference numeral 56 denotes a pilot pump serving as a hydraulic pressure source for external command pressure. Reference numeral 57 denotes a relief valve for determining the maximum discharge pressure of the pilot pump 56. The relief valve 57 opens when excessive pressure is generated on the discharge side of the pilot pump 56. A valve is provided to relieve the excess pressure to the tank 2 side.

Reference numeral 58 denotes a command pressure line connected to the external command pressure port 45A of the capacity control valve 41, and 59 denotes a command pressure line 5
8 is a pressure selection valve as an external selection means for selectively connecting the tank 8 and the pilot pump 56 to each other.
Is manually switched to either the fixed capacity position (c) or the automatic switching position (d).

While the pressure selection valve 59 is switched to the fixed capacity position (c), the command pressure line 58 is connected to the tank 2.
7, the pressure in the external command pressure chamber 47 of the capacity control valve 41 becomes the tank pressure level, and the spool 49 returns to the initial position and is urged by the spring 55 or the like as shown in FIG. The capacity control valve 41 is held at the large capacity position (a) shown in FIG.

While the pressure selection valve 59 is being switched to the automatic switching position (d), the command pressure line 58 is connected to the pilot pump 56 side, and the pressure value Pg is set outside the pressure value Pg set by the pressure reducing valve 60 described later. The command pressure is supplied to the external command pressure chamber 47 of the capacity control valve 41. And the capacity control valve 41
When the pressure receiving portion 49H in the external command pressure 47 receives the external command pressure of the pressure value Pg, the spool 49 is pressed in the direction of arrow D against the return spring 55.

Reference numeral 60 denotes a pressure reducing valve provided between the pilot pump 56 and the pressure selection valve 59. The pressure reducing valve 60 controls the external command pressure supplied to the command pressure line 58 by the following formulas 9 to 12. In order to prevent the pressure from rising above the pressure value Pg that satisfies the equation, the valve is normally opened, and when the discharge pressure from the pilot pump 56 rises above the pressure value Pg, the valve is closed and the supply of the discharge pressure is stopped. is there.

Thus, in the present embodiment configured as described above, substantially the same operation and effects as those of the first embodiment can be obtained. Command pressure port 45A, external command pressure chamber 47
And the like, and the configuration is such that the external command pressure is selected and supplied by the pressure selection valve 59, so that the following operational effects can be obtained.

That is, while the pressure selection valve 59 is switched to the fixed capacity position (c), the command pressure line 58 is connected to the tank 2.
, And the pressure in the external command pressure chamber 47 of the capacity control valve 41 becomes the tank pressure level.
The pressing force in the direction is not generated, and the spool 49 is continuously urged by the return spring 55 or the like to the initial position shown in FIG. 7, so that the capacity control valve 41 is held at the large capacity position (a) shown in FIG. Thus, the hydraulic motor 3 is fixed at a large capacity.

On the other hand, when the pressure selection valve 59 is switched from the fixed capacity position (c) to the automatic switching position (d), the external command pressure chamber 47 of the capacity control valve 41 is passed through the command pressure line 58 and the external command pressure port 45A. An external command pressure of the pressure value Pg is supplied.

In this case, the land 49A of the spool 49
Is the land 1 of the spool 19 described in the first embodiment.
9A, the pressure receiving portion 49H of the spool 49 receives the external command pressure in the external command pressure chamber 47 with a pressure receiving area S3 according to the following equation (8). Things.

[0117]

Equation 8] ^{S3 = (Da 2 × π /} 4) Then, when setting the external command pressure in the pressure value Pg is

[0118]

The spool 49 is pressed in the direction of arrow D with a pressing force F3 of F3 = S3.times.Pg.

In the initial position shown in FIG. 7, the spool 49 receives the pilot pressure P guided from the pilot port 45B at the pressure receiving portion 49G with the pressure receiving area S1 and also receives the pilot pressure P at the pressure receiving portion 50A inside the oil chamber 52. S
2, the pressing force F2 according to the above equation (5) acts on the spool 49 in the direction of arrow C in FIG.

The return spring 55 urges the spool 49 in the direction of arrow C with the urging force Fb.
9, a pressing force F2 and an urging force Fb act in the direction of arrow C, and a pressing force F3 by an external command pressure acts in the direction of arrow D.

[0121]

When the relationship of F3> F2 + Fb is satisfied, the spool 49 is slid to the stroke end shown in FIG. 8 by the external command pressure of the pressure value Pg.

As a result, when the external command pressure of the pressure value Pg is supplied to the external command pressure chamber 47 in a state where the pilot pressure P of the spool 49 is reduced to the pressure P2 or less as indicated by the characteristic line 31 shown in FIG. Then, the displacement is slid to the stroke end position shown in FIG. 8, and the capacity control valve 41 is switched from the large capacity position (a) to the small capacity position (b) shown in FIG.

In the stroke end state shown in FIG. 8, the oil chamber 52 in the spool 49 has the small holes 53 and the oil grooves 4.
4C is connected to the tank port 45C via the oil chamber 52C.
The internal pressure drops to the tank pressure level. Therefore, the spool 49 receives the pilot pressure P with the pressure receiving area S1 only on the pressure receiving portion 49G side without receiving the pilot pressure P on the pressure receiving portion 50A side in the oil chamber 52.
The spool 49 is reduced to the pressure receiving area S1.

As a result, the spool 49 receives the pressing force F1 and the urging force Fb in the direction of arrow C in FIG. 8 and receives the pressing force F3 by the external command pressure in the direction of arrow D in FIG. By

[0125]

While satisfying the relationship of F3> F1 + Fb, the displacement control valve 41 is held at the small displacement position (b) at the stroke end.

Even when the capacity of the hydraulic motor 3 changes from a large capacity to a small capacity and the motor driving pressure (load pressure) slightly increases, the spool 49 remains in the spool 49 until the pilot pressure P reaches the pressure P1. FIG.
At the stroke end shown in FIG.

Next, in this state, if the pilot pressure P rises to the pressure P1 shown in FIG. 5 or more, the pressing force F1 generated in the pressure receiving portion 49G of the spool 49 in the direction of arrow C becomes large.

[0128]

F3 <F1 + Fb where P ≧ P1, and the spool 49 slides and displaces in the direction of arrow C against the pressure in the external command pressure chamber 47, and returns to the initial position shown in FIG. The capacity control valve 41 returns to the large capacity position (a) shown in FIG.

In this state, since the pressure receiving area of the spool 49 increases to the area (S1 + S2), even when the motor driving pressure slightly decreases as the motor capacity changes from the small capacity to the large capacity. The displacement control valve 41 can be held at the large displacement position (a), and the motor displacement can be kept large until the motor drive pressure (pilot pressure P) decreases again to the pressure P2 or less.

Therefore, in this embodiment, while the pressure selection valve 59 for external command pressure is switched to the fixed displacement position (c), the motor displacement can be fixed to a large displacement, for example, to facilitate the steering operation of the vehicle. And the burden on the operator can be reduced. Further, when the pressure selection valve 59 is switched to the automatic switching position (d), the displacement control valve 41 can be automatically switched according to the increase or decrease of the motor driving pressure,
The self-pressure control of the motor capacity can be appropriately performed.

Then, when the directional control valve 5 is returned from the switching position (b) or (c) to the neutral position (a) during the running of the vehicle to perform the stop operation of the vehicle, or when the vehicle is going downhill, the directional control valve 5 is turned on. When the fine control is being performed, the pressure control valve 8 of the counter balance valve 6 returns to the neutral position (A), and while the hydraulic motor 3 continues the inertial rotation, the pipeline sections 4A2, 4B
2 is taken out as hydraulic oil by the shuttle valve 9 and supplied to the servo actuator 10 from the high-pressure line 28.

At this time, the pressure control valve 8 of the counter balance valve 6 returns to the neutral position (A), and the center bypass port 8A communicates with the tank 2 through the tank line 30. The pilot pressure P can be automatically reduced to the tank pressure level, and the displacement of the displacement control valve 11 affected by the brake pressure during inertial rotation can be prevented.

Accordingly, the pressure selection valve 5 for external command pressure
As long as 9 is switched to the fixed capacity position (c), the motor capacity can be kept fixed at a large capacity, and the motor capacity can be prevented from fluctuating during the inertial rotation of the hydraulic motor 3. Further, when the pressure selection valve 59 is switched to the automatic switching position (d), the motor drive pressure drops to the tank pressure level due to the inertial rotation of the hydraulic motor 3, and accordingly, the displacement control valve 41 is moved to the small displacement position. The state switched to (b) can be maintained, and the hydraulic motor 3 can be maintained in a stable state with a small capacity.

Next, FIG. 9 shows a third embodiment of the present invention. In this embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof will be omitted. It shall be. However, the feature of this embodiment is that the main pipelines 4A,
A shuttle valve 71 as a high-pressure selection valve is provided between the pipeline sections 4A1 and 4B1 of the 4B, and the motor drive pressure is used as the pilot pressure P from the pipeline section 4A1 or the pipeline section 4B1 on the high pressure side selected by the shuttle valve 71. The configuration is such that it is guided into the pilot pipeline 27.

Here, the shuttle valve 71 is connected to the direction control valve 5.
4A located between the valve and the counter balance valve 72
Pilot pressure deriving means is disposed between 1, 4B1 and derives a pilot pressure P to the pilot port 45B of the capacity control valve 41 via the pilot line 27.

The counterbalance valve 72 employed in this embodiment is substantially the same as the counterbalance valve 6 described in the first embodiment.
, 4B1 and the conduits 4A2, 4B2 on the actuator side.
And a pair of check valves 7A and 7B provided between the first and second check valves 7A and 7B, and the pipeline sections 4A1 and 4B1 on the hydraulic power source side and the pipeline section 4A2 on the actuator side in a parallel relationship with the check valves 7A and 7B.
, 4B2. However, the pressure control valve 73 of the counterbalance valve 72 is, for example, a hydraulic pilot type directional control valve having four ports and three positions, and does not have a center bypass port or the like.

Thus, also in the present embodiment configured as described above, substantially the same operation and effect as in the second embodiment can be obtained.

Next, FIGS. 10 to 13 show a fourth embodiment of the present invention.
The embodiment is characterized in that an annular oil chamber is formed between the valve housing of the displacement control valve and the spool, and the oil chamber is connected to the tank port in accordance with the sliding displacement of the spool. The present invention is configured to change the pressure receiving area of the spool with respect to the pilot pressure by selectively communicating with the pilot port. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 81 denotes a capacity control valve employed in the present embodiment. The capacity control valve 81 includes a valve housing 82 as shown in FIGS. It is constituted by. The capacity control valve 81 is configured in substantially the same manner as the capacity control valve 11 described in the first embodiment, and the large capacity position (a) and the small capacity position (b) are controlled by the pilot pressure P from the pilot line 27. ).

When the displacement control valve 81 is in the small displacement position (b), the pressure oil from the high pressure line 28 is supplied to the hydraulic chamber 10C of the servo actuator 10 via the supply / discharge line 29 to be tilted. Variable capacity part 3A by rolling piston 10A
Is driven in the direction of arrow B where the tilt angle becomes smaller. Also,
When the capacity control valve 81 is switched to the large capacity position (a), the supply / discharge pipe 29 is connected to the tank pipe 26, and the hydraulic chamber 10C
By discharging the internal pressure oil toward the tank 2, the variable capacity portion 3 </ b> A is driven by the spring 10 </ b> B of the servo actuator 10 in the direction of arrow A where the tilt angle increases.

Here, the valve housing 8 of the displacement control valve 81
2, a stepped spool sliding hole 83 having an open end 83A on one end and a closed end 83B on the other end is formed.
On the outer peripheral side of the spool sliding hole 83, an annular oil groove 84A,
84B, 84C, 84D, 84E are formed to be spaced apart in the axial direction. The oil groove 84A is provided in the valve housing 82.
Is formed as a stepped oil groove which is located at one end side and has a two-step diameter.

In the valve housing 82, the tank ports 85A and 85E, the pilot port 85B, the high pressure port 85C, and the pressure oil supply / discharge port 8 are separated from each other in the axial direction.
5D is formed, and these ports 85A to 85E communicate with the inside of the spool sliding hole 83 via the oil grooves 84A to 84E.

Reference numeral 86 denotes an open end 83A of the spool sliding hole 83.
The lid 86 forms a part of the valve housing 82, and forms a spring chamber 87 at a position between an end surface of one end of a spool 88 described later and the stopper 92.

Reference numeral 88 denotes a spool inserted into a spool sliding hole 83 of the valve housing 82.
1, the lands 88A, 88B,
88C and 88D are formed separately from each other in the axial direction. The spool 88 has a land 88C and a land 88C.
An annular groove 88E for communicating and blocking between the oil grooves 84C and 84D is formed between the oil groove 84C and the oil groove 84D, and the hydraulic oil supply / discharge port 85D is selected from the high pressure port 85C and the tank port 85E by the annular groove 88E and the land 88D. Communication and interruption.

Here, the spool 88 is formed as a stepped spool whose one end is enlarged in two stages, and the land 88B,
The annular step between 88C is a first pressure receiving portion 88F. Further, an annular step portion located between the lands 88A and 88B of the spool 88 is a second pressure receiving portion 88G for receiving a pressure in the oil chamber 90 described later. The pressure receiving portion 88F of the spool 88 receives the pilot pressure P guided from the pilot port 85B with a pressure receiving area S4.
The pressure receiving portion 88G receives the pilot pressure P in the oil chamber 90 with a pressure receiving area S5 when the oil chamber 90 communicates with the pilot port 85B as shown in FIG.

[0146] 89 is formed at one end of the spool 88,
The stopper slide hole 89 is a stopper slide hole having a bottomed hole extending in the axial direction. One end of the stopper slide hole 89 is opened on the end surface of the spool 88, and the other end is closed as a bottom. The stopper slide hole 89 is located radially inward of the lands 88A and 88B, and has a hole diameter substantially corresponding to the outer diameter of the land 88C.

Reference numeral 90 denotes an annular oil chamber located radially outside the stopper sliding hole 89 and formed between the outer peripheral side of the spool 88 and the spool sliding hole 83. The land 88B communicates with and is blocked from the oil groove 84B (pilot port 85B). The oil chamber 90 is connected to the pilot port 8 as shown in FIG.
5B, the pilot pressure P is received by the pressure receiving portion 88G of the pressure receiving area S5 to generate a pressing force (S5.times.P) in the direction of arrow C on the spool 88.

Reference numeral 91 denotes a small hole as an oil passage formed in the radial direction of the spool 88 at a position corresponding to the oil chamber 90. The small hole 91 connects the oil chamber 90 to the stopper sliding hole 89 (spring chamber) inside. 8
7), and while the spool 88 is at the initial position shown in FIG. 11, the oil chamber 90 communicates with the tank port 85A via an oil hole 92A described later.

Reference numeral 92 denotes a stopper slidably inserted into the stopper sliding hole 89. The stopper 92 is formed as a bottomed cylindrical body, and the bottom at one end is covered by a return spring 93 to be described later. Is in contact with The open end of the stopper 92 is located in the stopper sliding hole 89, and when the spool 88 is displaced in the direction of arrow C as shown in FIG. , Spool 8
8 restricts the stroke end.

As a result, at the stroke end of the spool 88 shown in FIG. 12, the oil chamber 90 is shut off from the spring chamber 87 and communicates with the pilot port 85B so that the pressure receiving portion 88G is directed in the direction of arrow C. Pilot pressure P
Generates a pressing force. The stopper 92 has a radial oil hole 92A formed therein.
It is always in communication with the tank port 85A via 2A.

Reference numeral 93 denotes a stopper sliding hole 89 of the spool 88.
The return spring 93 is disposed between the spring 92 and the stopper 92 and constitutes a biasing means disposed in the spring chamber 87. One end of the return spring 93 is in contact with the bottom of the stopper 92, and the other end is connected to the bottom of the stopper 92. The stopper slide hole 89 is in contact with one end of the spool 88. Then, the return spring 93 moves the spool 88 to an arrow D.
The displacement control valve 81 is constantly biased in the direction toward the closed end 83B, whereby the displacement control valve 81 is held at the small displacement position (b) shown in FIG.

Thus, also in the present embodiment configured as described above, while the capacity control valve 81 is at the small capacity position (b) shown in FIG. 10, the oil chamber 90 communicates with the tank port 85A side. The pressure receiving area of the spool 88 is limited to the pressure receiving area S4 by the pressure receiving portion 88F. When the capacity control valve 81 is switched to the large capacity position (a), the oil chamber 90 is communicated with the pilot port 85B as shown in FIG. Thus, the pressure receiving area of the spool 88 is reduced to the pressure receiving portions 88F, 8F.
8G total pressure receiving area (S4 + S5) can be increased,
The third embodiment has substantially the same functions and effects as those of the first embodiment.

In the above embodiments, the hydraulic oil selected by the shuttle valve 9 is supplied to the hydraulic chamber 10C side of the servo actuator 10 via the high-pressure pipe 28 or the like. The invention is not limited to this.
As described in JP-A-116301, a configuration may be adopted in which pressure oil is respectively taken out from a pair of supply / discharge passages for supplying / discharging pressure oil to / from a hydraulic motor.

Further, in each of the above embodiments, the case where the traveling hydraulic motor 3 is used as the variable displacement type hydraulic motor has been described as an example. However, the present invention is not limited to this. Alternatively, the present invention can be applied to a hydraulic motor for a rope winch or the like.

[0155]

As described above, according to the first aspect of the present invention, the pressure oil for driving the variable displacement actuator is supplied from the supply / discharge passage between the hydraulic motor and the counterbalance valve. The pilot pressure is derived from the supply / discharge passage between the directional control valve and the counter balance valve as pilot pressure by the pilot pressure deriving means, and the displacement control valve is driven in accordance with the pilot pressure. When the switching control is performed, the pressure receiving area of the displacement control valve with respect to the pilot pressure is changed, so that, for example, the hydraulic oil can be continuously supplied to the displacement variable actuator even during the inertial rotation of the hydraulic motor. By deriving the pilot pressure from the supply / discharge passage between the valve and the counterbalance valve, the displacement control valve is affected by the brake pressure during inertial rotation. Prevents switching switched of, it is possible to maintain the capacity of the hydraulic motor in a stable state. By changing the pressure receiving area of the displacement control valve with respect to the pilot pressure, a hysteresis characteristic can be given to the switching pressure (pilot pressure) of the displacement control valve. The burden on the operator at the time of operation or the like can be reduced, and the range of application of the capacity control device can be expanded to increase versatility.

According to the second aspect of the present invention, the pilot pressure deriving means is constituted by a high pressure deriving port provided in the counter balance valve for deriving pressure oil from the high pressure side supply / discharge passage among the respective supply / discharge passages. Of the pair of supply / discharge passages located between the direction control valve and the counterbalance valve, a part of the pressure oil flowing through the supply / discharge passage on the high pressure side is supplied from a high pressure outlet port provided on the counterbalance valve. The pilot pressure can be led out to the capacity control valve, and the number of parts can be reduced to improve the workability during assembly.

According to the third aspect of the present invention, the pilot pressure deriving means is provided between the counter balance valve and the direction control valve and is provided between the pair of supply and discharge passages. High pressure selector valve that selectively derives pressure oil from the supply / discharge passage on the high pressure side allows the motor drive pressure to be derived as pilot pressure using the high pressure selector valve. Can be controlled with the motor capacity stabilized.

According to a fourth aspect of the present invention, an oil chamber is provided between a capacity control valve, a valve housing, a spool, a biasing means, a first pressure receiving portion, a bottomed shaft hole, and a bottom of the shaft hole. And a second pressure receiving portion formed by a bottom portion of the shaft hole and an oil passage for selectively communicating the oil chamber with the pilot port and the tank port.
The total pressure receiving area of the spool by the first and second pressure receiving portions may be changed depending on which port the oil chamber communicates with through the oil passage to give a hysteresis characteristic to the switching pressure of the capacity control valve. it can. Therefore, the hunting phenomenon accompanying the switching of the capacity can be prevented, the capacity control can be stably performed automatically, and the number of parts can be reduced to improve the workability at the time of assembling. The size can be reduced by forming.

On the other hand, according to the fifth aspect of the present invention, the displacement control valve can be switched using the external command pressure. For example, when the external command pressure is reduced to the tank pressure level, the pilot pressure from the pilot port is reduced. Regardless, the biasing means keeps the spool in a one-way sliding position and fixes the displacement control valve at, for example, a large displacement position. When the external command pressure is increased and the spool is displaced in the other direction against the urging means, the spool is slidable in one direction or the other according to the load pressure of the hydraulic motor. In addition, the switching control of the capacity having the hysteresis characteristic with respect to the pilot pressure can be performed.

Therefore, while the external command pressure is being reduced, the motor capacity can be kept fixed, for example, at a large capacity, and the motor capacity can be prevented from fluctuating during the inertial rotation of the hydraulic motor. When the external command pressure is increased,
As the motor drive pressure drops to the tank pressure level due to the inertial rotation of the hydraulic motor, the displacement control valve can be held in a state where it is switched to, for example, a small displacement position, and the hydraulic motor can be kept in a stable state with a small displacement. .

Further, according to the invention, when the load pressure of the hydraulic motor is small, the spool is slid to the other end by the urging means, and when the pilot pressure rises, the first pressure receiving portion is displaced. By receiving the pilot pressure, the spool can be slid and displaced against the urging means. When the oil chamber communicates with the pilot port, the pilot pressure guided into the oil chamber can be received by the second pressure receiving portion, and when the oil chamber communicates with the tank port, the pilot pressure can be released. The total pressure receiving area of the spool by the pressure receiving portion can be changed depending on which port the oil chamber communicates with, and hysteresis characteristics can be given to the switching pressure of the displacement control valve.

[Brief description of the drawings]

FIG. 1 is a traveling hydraulic circuit diagram of a hydraulic shovel to which a displacement control device according to a first embodiment of the present invention is applied.

FIG. 2 is an enlarged longitudinal sectional view showing a capacity control valve in FIG. 1;

FIG. 3 is a longitudinal sectional view of the displacement control valve showing a state in which the spool has been slid to the stroke end.

FIG. 4 is a longitudinal sectional view showing the spool in FIG. 2;

FIG. 5 is a characteristic diagram showing a hysteresis characteristic of a switching control pressure by a capacity control valve.

FIG. 6 is a traveling hydraulic circuit diagram of a hydraulic shovel to which the displacement control device according to the second embodiment of the present invention is applied.

FIG. 7 is an enlarged longitudinal sectional view of the capacity control valve in FIG. 6;

FIG. 8 is a longitudinal sectional view of the displacement control valve showing a state in which the spool is slid to the stroke end.

FIG. 9 is a traveling hydraulic circuit diagram of a hydraulic shovel to which a displacement control device according to a third embodiment of the present invention is applied.

FIG. 10 is a traveling hydraulic circuit diagram of a hydraulic shovel to which a displacement control device according to a fourth embodiment of the present invention is applied.

FIG. 11 is an enlarged longitudinal sectional view showing the capacity control valve in FIG. 10;

FIG. 12 is a longitudinal sectional view of the displacement control valve showing a state where the spool is slid to the stroke end.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Hydraulic pump (hydraulic source) 2 Tank 3 Hydraulic motor 4A, 4B Main pipeline (supply / drain passage) 4A1, 4B1 Hydraulic source side pipeline (passage) 4A2, 4B2 Actuator side pipeline (passage) 5 Directional control valve 6,72 Counter balance valve 8,73 Pressure control valve 8A Center bypass port (pilot pressure deriving means) 9 Shuttle valve (pressure oil deriving means) 10 Servo actuator (variable capacity actuator) 11,41,81 Capacity control valve 12, 42, 82 Valve housing 13, 43, 83 Spool sliding hole 15B, 45B, 85B Pilot port 15C, 15F, 45C, 45F, 85A, 85E Tank port 15D, 45D, 85C High pressure port 15E, 45E, 85D Pressure oil Supply / discharge port 19,49,88 Spool 19G, 49G, 88F Part 20, 50 Shaft hole 20A, 50A, 88G Second pressure receiving part 21, 51 Piston 22, 52, 90 Oil chamber 23, 53, 91 Small hole (oil passage) 24, 55, 93 Return spring (biasing means) 45A External command pressure port 49H Command pressure receiving part 71 Shuttle valve (pilot pressure deriving means) 89 Stopper sliding hole 92 Stopper

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsuyoshi Kobayashi F-term in Tsuchiura Works, Hitachi Construction Machinery Co., Ltd. DB37 DB46 DB49 EE15 GG02 JJ02

Claims (6)

[Claims] 1. A variable displacement hydraulic motor having a variable capacity portion and driven to rotate by hydraulic oil from a hydraulic source, and a hydraulic motor provided in the middle of a pair of supply / discharge passages connecting the hydraulic motor to a hydraulic source. A directional control valve for switching the direction of pressure oil supplied and discharged from the source to the hydraulic motor, a counterbalance valve provided between the directional control valve and the hydraulic motor and provided in the middle of the pair of supply and discharge passages, A capacity variable actuator that drives the capacity variable section of the hydraulic motor to change the motor capacity; and a capacity control valve that switches pressure oil supplied to and discharged from the capacity variable actuator by receiving a load pressure of the hydraulic motor as a pilot pressure. A displacement control device for a variable displacement hydraulic motor, comprising: a passage portion of the pair of supply / discharge passages located between the counterbalance valve and the hydraulic motor; A pressure oil deriving unit for deriving pressure oil for driving the actuator from the passage portion is provided. Between the directional control valve and the counterbalance valve, a pilot pressure for supplying the capacity control valve to the pair of pilot pressures is provided. Pilot pressure deriving means for deriving from the high pressure side supply / discharge passage of the supply / discharge passage, wherein the displacement control valve receives the pilot pressure when the switching is controlled in accordance with the pilot pressure from the pilot pressure derivation means. A capacity control device for a variable displacement hydraulic motor, wherein a pressure receiving area to be changed is changed according to a switching position. 2. The pilot pressure deriving means comprises a high pressure deriving port provided in the counter balance valve for deriving pressure oil in a supply / discharge passage on a high pressure side among the respective supply / discharge passages. 3. The displacement control device for a variable displacement hydraulic motor according to claim 1. And a pilot pressure deriving means provided between the counter balance valve and the directional control valve and provided between the pair of supply / discharge passages. 2. The displacement control device for a variable displacement hydraulic motor according to claim 1, wherein the displacement control device is constituted by a high pressure selection valve for selectively discharging pressure oil from a passage. 4. The displacement control valve has a spool sliding hole, and supplies and discharges pressure oil to and from a high pressure port, a tank port, a pilot port, and the variable displacement actuator while being spaced apart in the axial direction of the spool sliding hole. A valve housing provided with a port; and a pressure oil supply / discharge port inserted into a spool sliding hole of the valve housing, and slidably displaced in the axial direction in the spool sliding hole, thereby connecting the pressure oil supply / discharge port to a high pressure port and a tank port. A spool for selectively communicating and blocking, a biasing means provided between one axial side of the spool and the valve housing, and constantly biasing the spool toward the other side; and a spool provided on the spool. A first pressure receiving portion that constantly receives a pilot pressure guided from the pilot port to slidably displace the spool against the urging means; and a first pressure receiving portion formed on the spool. A bottomed shaft hole extending in the axial direction of the spool and opening to the other end surface in the axial direction, and slidably inserted into the shaft hole so as to close the open end of the shaft hole. A piston fitted to define an oil chamber between the bottom of the shaft hole and receiving a hydraulic reaction force in the oil chamber, and a piston formed by the bottom of the shaft hole to receive pressure in the oil chamber. A second pressure receiving portion that changes the pressure receiving area of the spool together with the first pressure receiving portion, and is formed on the spool at a position corresponding to the oil chamber, and when the spool is displaced in the spool sliding hole. 4. The displacement control device for a variable displacement hydraulic motor according to claim 1, wherein the oil chamber comprises an oil passage for selectively communicating with a pilot port and a tank port. 5. The capacity control valve has a spool sliding hole, and a high pressure port, a tank port, a pilot port,
A valve housing provided with an external command pressure port and a pressure oil supply / discharge port to the variable capacity actuator; a valve housing that is inserted into a spool sliding hole and slides in the spool sliding hole in the axial direction. A spool for selectively communicating and blocking the pressure oil supply / discharge port with the high pressure port and the tank port; and a spool provided between the other axial side of the spool and the valve housing, with the spool facing one side. Biasing means for constantly biasing the spool; and receiving the external command pressure guided from the external command pressure port provided on one side of the spool in the axial direction to slide the spool against the biasing means. A command pressure receiving portion to be dynamically displaced; and a pilot port for slidingly displacing the spool in a biasing direction of the biasing means. A first pressure-receiving portion that constantly receives a pilot pressure guided from the first pressure-receiving portion, and a bottomed shaft hole that includes a bottomed hole formed in the spool, extends in the axial direction of the spool, and is opened on the other end surface. It is slidably inserted into the shaft hole so as to close the open end of the shaft hole, and defines an oil chamber between itself and the bottom of the shaft hole and receives a hydraulic reaction force in the oil chamber. A piston, a second pressure receiving portion formed by a bottom portion of the shaft hole, and receiving a pressure in the oil chamber to change a pressure receiving area of the spool together with the first pressure receiving portion; An oil passage formed in said spool at a position and selectively communicating said oil chamber with a pilot port and a tank port when said spool is displaced in a spool sliding hole. 3. Capacity control of the variable displacement hydraulic motor described in 3. Control device. 6. The capacity control valve has a spool sliding hole, and supplies and discharges hydraulic oil to a high-pressure port, a tank port, a pilot port, and the variable displacement actuator while being spaced apart in the axial direction of the spool sliding hole. A valve housing provided with a port; and a pressure oil supply / discharge port inserted into a spool sliding hole of the valve housing, and slidably displaced in the axial direction in the spool sliding hole, thereby connecting the pressure oil supply / discharge port to a high pressure port and a tank port. A spool for selectively communicating and blocking, a biasing means provided between one axial side of the spool and the valve housing, and constantly biasing the spool toward the other side; and a spool provided on the spool. A first pressure receiving portion that constantly receives a pilot pressure guided from the pilot port to slidably displace the spool against the urging means; and a first end surface of the spool. A stopper sliding hole formed of an open bottomed hole and always communicating with the tank port; and a stroke end when the spool is displaced by sliding in the stopper sliding hole against a biasing means. A stopper which is formed radially outside of the stopper sliding hole and formed between the outer peripheral side of the spool and the spool sliding hole, and which is positioned relative to the pilot port when the spool slides. An annular oil chamber that is communicated with and interrupted by a second pressure receiving section formed on the spool to receive pressure in the oil chamber, and that changes a pressure receiving area of the spool together with the first pressure receiving section; The oil chamber is formed between the oil chamber and the stopper sliding hole and is formed on the spool.The oil chamber communicates with the stopper sliding hole while the oil chamber is shut off from the pilot port, and the oil is Room Variable displacement hydraulic motor of the displacement control device according to claim 1, 2 or 3 formed by composed of an oil passage communicating is interrupted between the stopper slide hole by the stopper in Taki communicated with the pilot port.