JP2002339851A - Capacity control device of hydraulic rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably carry out a switching control of a capacity by preventing air from being mixed into a capacity variable actuator. SOLUTION: When a small capacity position (b) is selected in a capacity control valve 31, a high pressure port 34 is made to communicate with a pressure oil supply port 35, whereby a pressure oil is supplied from an oil passage 30 to an oil chamber 28 of a servo actuator 25. When a large capacity position (a) is selected in the capacity control valve 31, the pressure oil supply port 35 is cut of from the high pressure port 34 to stop supply of the oil pressure to the oil chamber 28. The servo actuator 25 is formed with a restriction passage 29 which makes the oil chamber 28 communicate with a drain passage 42 side, whereby the pressure oil supplied from the oil passage 30 is made to flow to a tank 2 side via the restriction passage 29, and a pressure for carrying out inclined rotation driving of a capacity variable part 3A is generated inside the oil chamber 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement type hydraulic pump provided in a construction machine such as a hydraulic shovel.
The present invention relates to a displacement control device for a hydraulic rotary machine that is preferably used for variably controlling the displacement of a hydraulic motor or the like.

[0002]

2. Description of the Related Art In general, a variable displacement type hydraulic rotary machine is used as a hydraulic pump serving as a hydraulic pressure source and 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.

[0003] Such a capacity control device for a hydraulic motor includes a variable capacity type hydraulic motor having a capacity change section, and a capacity change section of the hydraulic motor driven by supply and discharge of hydraulic oil to thereby control the motor capacity. And a displacement control valve for controlling switching of pressure oil supplied to and discharged from the displacement variable actuator (for example, Japanese Patent Laid-Open No. 7-301205).

Further, the capacity control valve has a spool sliding hole, and a valve housing having a pilot port, a tank port, a high pressure port, and a pressure oil supply / discharge port provided apart from the spool sliding hole in the axial direction. And pressurizing the hydraulic oil supply / discharge port by sliding in the spool sliding hole in the axial direction in accordance with the pilot pressure supplied from the pilot port, which is inserted into the spool sliding hole of the valve housing. And a spool that selectively communicates with and shuts off either the port or the tank port.

In this case, the motor driving pressure (pressure oil) of the hydraulic motor is supplied to the high pressure port of the valve housing via a high pressure selection valve such as a shuttle valve, and the tank port is connected to an external tank or the like. . The pressure oil supply / discharge port is connected to the variable displacement actuator via a pressure oil supply / discharge passage formed in a casing of the hydraulic motor.

When the pressure oil supply / discharge port communicates with the high pressure port due to the sliding displacement of the spool, the pressure oil flows from the high pressure port to the oil chamber of the variable capacity actuator via the pressure oil supply / discharge port and the supply / discharge passage. The variable capacity actuator drives the variable capacity section of the hydraulic motor by the pressure of the pressure oil, and switches the motor capacity of the hydraulic motor to, for example, a small capacity side.

When the pressure oil supply / discharge port communicates with the tank port due to the sliding displacement of the spool, the pressure oil in the variable capacity actuator is supplied to the pressure oil supply / discharge port and the tank port via the supply / discharge passage. The discharged capacity variable actuator allows the capacity variable portion of the hydraulic motor to be driven to the large tilt side due to a decrease in pressure, and for example, the motor capacity is switched to the large capacity side.

In addition, a throttle passage is formed in the spool to narrow a flow passage between the pressure oil supply / discharge port and the tank port when the pressure oil supply / discharge port communicates with the tank port. By restricting the flow rate of pressure oil discharged to the pressure oil supply / discharge port and the tank port via, for example, it is possible to prevent the motor capacity from suddenly switching from small capacity to large capacity, Has the function of reducing

[0009]

By the way, the above-mentioned prior art hydraulic motor displacement control device according to the prior art controls the displacement of the displacement control valve so that the pressure oil composed of, for example, the motor driving pressure or the like is passed through the displacement control valve. The capacity of the hydraulic motor is switched by supplying to the oil chamber of the variable capacity actuator or discharging the pressure oil in the oil chamber to the tank side via the capacity control valve.

However, the pressure oil supplied (discharged) to the oil chamber of the variable displacement actuator at this time flows into and out of the oil chamber with a small amount of oil. In the supply / discharge passage connected to the oil chamber of the variable displacement actuator, the oil liquid (pressure oil) tends to stay with little replacement.

For this reason, if air mixes with the oil in the oil chamber and the supply / discharge passage of the variable displacement actuator, it is difficult to discharge the air to the outside, and the switching control of the motor capacity tends to be unstable. There's a problem.

In particular, when such a displacement control device is applied to a left or right traveling motor of a construction machine, if air is mixed into one of the left and right hydraulic motors, the motor displacement is reduced. There is a problem that a difference occurs in the response speed when switching control is performed, which causes the vehicle to turn while traveling on the road.

The capacity control valve used in the prior art is configured such that when the pressure oil supply / discharge port communicates with the high pressure port due to the sliding displacement of the spool, the pressure oil from the high pressure port is supplied to the pressure oil supply / discharge port. When the pressure oil is supplied to the variable capacity actuator via the discharge passage and the pressure oil supply / discharge port is connected to the tank port, the pressure oil in the variable capacity actuator is supplied to the pressure oil supply / discharge port and the tank port via the supply / discharge passage. It is configured to discharge.

For this reason, the spool of the capacity control valve not only connects and disconnects the pressure oil supply / discharge port to / from the high pressure port, but also lands and oil grooves for connecting / disconnecting the pressure oil supply / discharge port to / from the tank port. And the like, the structure of the capacity control valve becomes complicated, and there is a problem that it is difficult to make the whole compact and to reduce the size.

SUMMARY OF THE INVENTION 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 prevent air from being mixed into a variable displacement actuator, and to stably perform displacement control of a displacement. It is an object of the present invention to provide a capacity control device of a hydraulic rotating machine which is made possible.

Another object of the present invention is to eliminate the tank port of the displacement control valve, to simplify the shape and structure of the spool, and to reduce the size of the spool by making the whole compact. An object of the present invention is to provide a capacity control device for a hydraulic rotating machine.

[0017]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a variable displacement type hydraulic rotary machine having a variable capacity portion, and a hydraulic rotary machine which is supplied and discharged with hydraulic oil. The present invention is applied to a displacement control device for a hydraulic rotary machine comprising a displacement variable actuator for driving a displacement variable section of the machine to change the displacement.

Further, the configuration adopted by the invention of claim 1 is a capacity control valve for controlling switching of pressure oil supplied to the variable capacity actuator, and the capacity control valve for supplying pressure oil to the variable capacity actuator. And a throttle passage provided in the variable displacement actuator, and a throttle passage through which a part of the pressure oil supplied from the oil passage to the variable displacement actuator flows out to the tank side. And that

By employing such a configuration, the throttle passage provided in the variable displacement actuator allows a part of the pressure oil supplied from the displacement control valve to the variable displacement actuator via the oil passage to flow out to the tank side. In addition, since the pressure is generated in the variable capacity actuator, the variable capacity section of the hydraulic rotary machine can be driven by the hydraulic pressure at this time, and the capacity of the hydraulic rotary machine can be variably controlled. And, since the pressure oil supplied from the oil passage to the variable capacity actuator can be constantly circulated to the tank side via the throttle passage, even if air is mixed into the pressure oil, this air is mixed with the pressure oil. It can be discharged to the tank side, and the air can be prevented from staying in the oil chamber of the variable capacity actuator.

According to the second aspect of the present invention, the displacement control valve has a high pressure port to which pressure oil is supplied from a hydraulic pressure source and a pressure oil supply port opened to an oil passage. A first port for shutting off the pressure oil supply port from a high pressure port;
And a second switching position in which the high pressure port communicates with the pressure oil supply port.

Thus, when the displacement control valve is switched from the first switching position to the second switching position, the high pressure port is communicated with the pressure oil supply port, and the pressure oil from the high pressure port is supplied to the pressure oil supply port and the oil. It can be supplied to the variable capacity actuator via the passage, and the variable capacity section can be driven to, for example, the small capacity side by the hydraulic pressure at this time. Further, when the displacement control valve is returned to the first switching position, the pressure oil supply port is shut off from the high pressure port, so that the pressure oil in the displacement variable actuator is gradually discharged to the tank side through the throttle passage. Accordingly, the variable capacity section can be slowly moved from, for example, the small capacity side to the large capacity side, and the shock at the time of capacity switching can be reduced.

Since the capacity control valve does not need to be provided with a tank port or the like as in the prior art, the spool structure of the capacity control valve can be simplified, and the whole capacity control valve can be made compact. It is possible to achieve miniaturization.

According to the third aspect of the present invention, the hydraulic rotating machine includes a casing, a rotating shaft rotatably provided in the casing, and a rotating shaft provided in the casing so as to rotate integrally with the rotating shaft. A cylinder block having a plurality of cylinders provided in the circumferential direction and separated in the circumferential direction, a plurality of pistons reciprocally inserted into each cylinder of the cylinder block, and a protruding end side of each piston. A swash plate type hydraulic rotating machine comprising a plurality of swingably provided shoes, and a swash plate which has a smooth surface on which each of the shoes slides and which is tiltably provided in the casing and serves as a variable capacity portion. And a tilting cylinder formed in the casing facing the swash plate, and slidably inserted into the tilting cylinder to tilt and drive the swash plate. With tilting piston An oil chamber defined in the tilt cylinder by the tilt piston and supplied with pressurized oil from an oil passage; the inside of the casing becomes a drain chamber communicating with an external tank; and the pressurized oil in the oil chamber is throttled. It is configured to flow into the drain chamber via a passage.

With this configuration, in the variable displacement type swash plate type hydraulic rotary machine, the swash plate is tilted by using a displacement variable actuator including a tilt cylinder, a tilt piston and the like formed in the casing. It can be driven, and the capacity can be changed according to the tilt angle of the swash plate. And
By allowing pressure oil to flow out of the oil chamber defined between the tilt piston and the tilt cylinder through a throttle passage, air can be prevented from staying in the oil chamber, and The movement (sliding displacement) of the tilting piston can be stabilized.

According to the fourth aspect of the present invention, the throttle passage is formed by a gap between the inner peripheral surface of the tilt cylinder and the outer peripheral surface of the tilt piston. In this case, the pressure oil in the oil chamber can be discharged while being throttled by a throttle passage formed by a gap between the inner peripheral surface of the tilt cylinder and the outer peripheral surface of the tilt piston,
At this time, the air can be discharged to the drain chamber in the casing together with the pressure oil.

On the other hand, according to the invention of claim 5, the throttle passage is configured to discharge the pressure oil in the oil chamber toward the vicinity of the bearing that rotatably supports the rotating shaft in the casing.
Thus, the bearing can be maintained in a lubricated state by the oil liquid discharged from the throttle passage.

According to the invention of claim 6, the throttle passage is formed in the tilt piston so as to discharge the pressure oil in the oil chamber toward the contact surface between the swash plate and the tilt piston. Configuration. In this case, the contact surface between the swash plate and the tilt piston can be kept in a lubricated state by the oil liquid discharged from the throttle passage, and the contact surfaces of both can be prevented from being worn and damaged.

Further, according to the invention of claim 7, the throttle passage is configured to also serve as an air vent passage for discharging air mixed in the pressure oil flowing through the oil passage to the tank side. In this case, air can be positively discharged from the oil chamber of the variable capacity actuator through the air release passage, and the air release performance can be improved.

[0029]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a hydraulic rotary machine according to an embodiment of the present invention, which is applied to a traveling hydraulic motor such as a hydraulic shovel. Will be described.

FIGS. 1 to 6 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes a hydraulic pump which constitutes a hydraulic source together with a tank 2. The hydraulic pump 1 is driven to rotate by a motor (not shown) of a hydraulic shovel, and hydraulic oil sucked from the tank 2 is converted into high-pressure hydraulic oil. This is supplied to a hydraulic motor 3 described later.

Reference numeral 3 denotes a traveling hydraulic motor comprising a variable displacement type swash plate type hydraulic rotary machine. The hydraulic motor 3 comprises a casing 11, a drive shaft 15, a cylinder block 18, a swash plate, which will be described later, as shown in FIG. 23 and servo actuator 25
And the like. The hydraulic motor 3 drives the hydraulic excavator (vehicle) to travel by a drive shaft 15 via a traveling speed reducer (not shown) or the like.

The hydraulic motor 3 has a variable capacity portion 3A composed of a swash plate 23 described later.
As shown in the figure, the servo actuator 25 is used to tilt and drive in the directions indicated by arrows A and B. And the hydraulic motor 3
When the displacement variable unit 3A is tilted and driven in the direction of arrow A where the tilt angle increases, the motor capacity is increased from the small capacity to the large capacity side and tilted in the direction of arrow B where the tilt angle decreases. At the time of rolling drive, the motor capacity is reduced to the small capacity side.

4A and 4B denote the hydraulic motor 3 and the hydraulic pump 1
And a pair of main pipelines connected to the tank 2, the main pipelines 4A,
4B supplies and discharges hydraulic oil from the hydraulic pump 1 to the hydraulic motor 3 through a directional control valve 5 and the like described later, whereby the hydraulic motor 3 rotates forward or backward, and moves the hydraulic shovel (vehicle) forward or backward. It is to let.

In the main pipelines 4A and 4B, between the counter balance valve 6 and the direction control valve 5, which will be described later, become pipeline sections 4A1 and 4B1 on the hydraulic power source side, and between the counter balance valve 6 and the hydraulic motor 3. Are the pipe sections 4A2, 4 on the actuator side.
B2.

A traveling direction control valve 5 is provided in the middle of the main pipelines 4A and 4B. The direction control valve 5 is, for example, a directional control valve having four ports and three 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).

Then, the direction control valve 5 is switched to the switching position (b).
The hydraulic oil from the hydraulic pump 1 is supplied to the main pipeline 4A (the pipeline 4A).
1, 4A2) to the hydraulic motor 3 to rotate the hydraulic motor 3 in the forward direction, for example.
The return oil from the tank is discharged to the tank 2 via the main pipeline 4B (the pipelines 4B1, 4B2). When 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 driven to rotate in the reverse direction.

Numeral 6 denotes a counterbalance valve which constitutes a brake valve attached to the hydraulic motor 3. The counterbalance valve 6 includes pipe lines 4A1 and 4B1 on the hydraulic power source side and pipe lines 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.

The pressure control valve 8 of the counter balance valve 6 is provided on a rear casing 13 described later, as shown in FIG. Further, a shuttle valve 9 and a capacity control valve 31, which will be described later, are also provided on the rear casing 13 side.

Reference numeral 9 denotes a shuttle valve as a high-pressure selection valve. The shuttle valve 9 is located between the hydraulic motor 3 and the counterbalance valve 6 as shown in FIG. 1 and is a pipe section 4A2 of the main pipes 4A and 4B. , 4B2. The shuttle valve 9 is connected to the pipe sections 4A2, 4B2 of the main pipes 4A, 4B.
Of the high pressure side, and supplies the selected pressure oil to the servo actuator 25 via the high pressure passage 36 and the capacity control valve 31 described later.

Next, reference numeral 11 denotes a casing of the hydraulic motor 3 composed of a swash plate type hydraulic rotating machine.
As shown in the figure, one side (front side) in the axial direction has a small diameter portion 12A.
The casing body 12 includes a stepped cylindrical casing body 12 having a large-diameter portion 12B on the other side (rear side), and a rear casing 13 covering the large-diameter portion 12B side of the casing main body 12.

Here, the small diameter portion 12 of the casing body 12
On the A side, a swash plate support portion 12C that supports a swash plate 23 described later is provided.
And a shaft insertion hole 12D through which a drive shaft 15 described later is inserted. A tilt cylinder 26 of a servo actuator 25 described later is formed at a position radially outside the shaft insertion hole 12D.

On the other hand, a supply / discharge passage (not shown) for pressurized oil which forms a part of the main pipelines 4A and 4B is formed in the rear casing 13, and these supply / discharge passages are provided via a valve plate 20 described later. The pressure oil is supplied to and discharged from the cylinder 19.

In the casing 11 of the hydraulic motor 3, a space defined by the casing body 12 and the rear casing 13 is a drain chamber 14, and the inside of the drain chamber 14 is connected to a tank via a drain pipe 42 described later. 2 is always in communication. Also, the drain chamber 14 of the casing 11
A drive shaft 15, a cylinder block 18, and the like, which will be described later, are housed therein.

Reference numeral 15 denotes a drive shaft as a rotation shaft provided in the casing 11. The drive shaft 15 is rotatably supported on the rear side by a rear casing 13 via a bearing 16, and the front side is formed by a casing body 12 on the front side. Shaft insertion hole 12D
It is rotatably supported through a bearing 17 inside.

Reference numeral 18 denotes a cylinder block which rotates integrally with the drive shaft 15 in a casing 11.
Numeral 8 is located in the drain chamber 14 of the casing 11 and spline-coupled to the outer peripheral side of the drive shaft 15. The cylinder block 18 is provided with a plurality of cylinders 19, 19,...

Reference numeral 20 denotes a valve plate located between the rear casing 13 and the cylinder block 18 and fixed to the rear casing 13. The valve plate 20 is a pair of intermittently communicating with each cylinder 19 of the cylinder block 18. For supplying and discharging the pressure oil from the main pipelines 4A and 4B into each cylinder 19 of the cylinder block 18.

Are a plurality of pistons inserted into the respective cylinders 19 of the cylinder block 18. Each of the pistons 21 is driven by pressure oil supplied and discharged into and from the cylinders 19. It reciprocates in the cylinder 19 so as to extend and contract.

Reference numerals 22, 22,... Denote a plurality of shoes that are swingably provided at the protruding ends of the respective pistons 21. Each of the shoes 22 slides on a smooth surface 23A of a swash plate 23, which will be described later.
In accordance with the rotation of the cylinder block 18, the cylinder block 18 moves on the smooth surface 23A so as to draw an arc-shaped trajectory.

Reference numeral 23 denotes a small diameter portion 12A of the casing body 12.
The swash plate 23 constitutes a variable displacement section 3A of the hydraulic motor 3 shown in FIG. 2 and 3, the swash plate 23 is tiltably supported by a swash plate support portion 12C of the casing body 12 via a support member 24 described later, and each shoe 22 slides on the surface side thereof. 23A.

On the back side of the swash plate 23, a portion opposed to the tilt piston 27 described later becomes a contact surface 23B which comes into contact with the tilt piston 27 as shown in FIGS. Is formed as an inclined surface extending in a direction substantially perpendicular to the axis of the tilt piston 27.

Reference numeral 24 denotes the swash plate support 1 of the casing body 12.
2C, the support member 24 is formed as a spherical member as shown by a dotted line in FIGS. 2 and 3, and is, for example, left and right with the shaft insertion hole 12D of the casing body 12 interposed therebetween. (Only one is shown).

The swash plate 23 is tilted by the tilting piston 27 in the directions indicated by arrows A and B in FIG. 3 with the left and right support members 24 as fulcrums, whereby the motor capacity of the hydraulic motor 3 is increased. Is variably controlled.

Numeral 25 denotes a servo actuator as a variable capacity actuator for tilting and driving the swash plate 23 to change the motor capacity of the hydraulic motor 3. The servo actuator 25 has a shaft insertion hole 12D as shown in FIGS. The tilting cylinder 26 is formed on the casing main body 12 at the radially outer side (lower side) and includes a tilting piston 27 and an oil chamber 28 described later.

The tilt cylinder 26 has a bottomed hole formed in the casing body 12 at an angle.
The swash plate 23 has an opening facing the contact surface 23B, and extends in a direction substantially orthogonal to the contact surface 23B of the swash plate 23.

A tilt piston 27 is slidably inserted into the tilt cylinder 26. The tilt piston 27 defines an oil chamber 28 between itself and the bottom of the tilt cylinder 26. The oil chamber 28 is always in communication with an oil passage 30 described later. The tilt piston 27 slides and displaces in the tilt cylinder 26 by the pressure of the pressure oil supplied from the oil passage 30 into the oil chamber 28 in the direction of arrow C in FIG. 27
A pushes the contact surface 23B of the swash plate 23 in the directions of arrows A and B.

29 is a tilt cylinder 26 and tilt piston 2
7, a throttle passage formed of an annular gap formed between
As shown in FIG. 4, the throttle passage 29
A part of the (pressure oil) is caused to flow toward the swash plate 23 in the direction of arrow D, and a pressure for driving the swash plate 23 in the direction of arrow B by the tilting piston 27 is generated in the oil chamber 28. Things. Then, the throttle passage 29 is connected to the oil liquid F in the oil chamber 28.
It also serves as an air vent passage for discharging the air G mixed into the (pressure oil) to the outside.

For this reason, the throttle passage 29 is designed such that the fitting length (length in the axial direction) between the inner peripheral surface of the tilt cylinder 26 and the outer peripheral surface of the tilt piston 27 and the radial clearance are designed at the design stage. It is formed by managing the pressure, and adjusts the pressure (the pressing force of the tilt piston 27) generated in the oil chamber 28 according to the effective flow path area.

In this case, the servo actuator 25
When the supply of pressurized oil from the oil passage 30 is interrupted by the capacity control valve 31 described later, the oil liquid F (including the air G) in the oil chamber 28 flows through the throttle passage 29 in the direction of arrow D in FIG. And the swash plate 23 is pressed by the hydraulic reaction force from each piston 21 shown in FIG.

As a result, the tilting piston 27 is pushed in the direction of the arrow A in FIGS. 3 and 4 so as to contract into the tilting cylinder 26, so that the tilting angle of the swash plate 23 is increased. , And the hydraulic motor 3 is switched to the large capacity side where the motor capacity is maximized.

When pressure oil is supplied from the oil passage 30 by the capacity control valve 31 described later, the servo actuator 25 moves the oil chamber 2 in the direction of arrow C in FIGS.
8, the tilting piston 27
B is extended so as to extend (project) from the tilt cylinder 26.
And the swash plate 23 is driven in the direction with a small tilt angle.

As a result, the hydraulic motor 3 is switched to the small capacity side where the motor capacity is minimized. Further, while the supply of the pressure oil from the oil passage 30 into the oil chamber 28 is continued, a part of the oil liquid F (pressure oil) in the oil chamber 28 as shown in FIG. Is discharged in the direction of arrow D through
The throttle passage 29 functions as an air vent passage, and generates an oil pressure in the oil chamber 28 that presses the tilt piston 27 in the direction of arrow B by a differential pressure generated before and after the throttle passage 29.

Reference numeral 30 denotes an oil passage formed in the casing 11 of the hydraulic motor 3 and serving as a pressure oil supply passage.
Reference numeral 0 designates a rear-side oil passage portion 30A provided on the rear casing 13 side as shown in FIG. 2 and a main-body-side oil passage portion provided on the casing main body 12 and constantly communicating with the oil chamber 28 of the servo actuator 25. 30B.

The rear-side oil passage 30A is formed as shown in FIG.
As shown in FIG. 6, one end communicates with a pressure oil supply port 35 of the displacement control valve 31 which will be described later, and the other end as shown in FIG. It communicates with the oil passage 30B. The oil passage 30 supplies pressure oil from the pressure oil supply port 35 of the capacity control valve 31 to the oil chamber 28 of the servo actuator 25.

Reference numeral 31 denotes a displacement control valve provided in the rear casing 13. The displacement control valve 31 is constituted by a valve housing composed of the rear casing 13, a spool 40 and a return spring 41, which will be described later. A spool sliding hole 32 extending in a direction substantially perpendicular to the axis of the drive shaft 15 is formed in the rear casing 13 also serving as a valve housing of the capacity control valve 31, as shown in FIG. A spool 40 is inserted into the spool sliding hole 32.

A pilot port 33 having an oil passage smaller in diameter than the spool sliding hole 32 is formed on one axial side of the spool sliding hole 32. The pilot port 33 constitutes an external command pressure port. It is connected to a later-described command pressure line 44 shown in FIG. And the capacity control valve 31
As shown in FIGS. 5 and 6, the spool sliding hole 32 has a high-pressure port 34 and a pressure oil supply port 35 which are spaced apart in the axial direction.
The pressure oil supply port 35 is always in communication with the oil chamber 28 of the servo actuator 25 via the oil passage 30 shown in FIG.

On the other hand, the high pressure port 34 of the capacity control valve 31
Is connected to the outflow side of the shuttle valve 9 via a high-pressure passage 36 formed in the rear casing 13, and pressurized oil (motor drive pressure) from the shuttle valve 9 is introduced into the spool sliding hole 32. Is what you do. In addition, spool sliding hole 3
An annular oil groove 34A in which the high-pressure port 34 opens and another annular oil groove 35A in which the pressure oil supply port 35 opens are formed on the outer peripheral side of 2.

A plug 37 closes the other side of the spool slide hole 32 in the axial direction.
0, a spring chamber 38 is defined, and a rod-shaped stopper 39 is disposed in the spring chamber 38 together with a return spring 41 described later. The stopper 39 contacts the spool 40 as shown in FIG. 5, and regulates the stroke end of the spool 40. The spring chamber 38 is connected to the tank 2 via a low-pressure passage (not shown) or the like, and is always kept at a low pressure.

Reference numeral 40 denotes a spool inserted into the spool sliding hole 32. The spool 40 has lands 40A and 40B formed on the outer peripheral side thereof so as to be axially separated from each other as shown in FIGS. An annular groove 40 is provided between the land 40A and the land 40B for communicating and blocking between the oil grooves 34A and 35A.
C. Then, the spool 40 is displaced in the axial direction in the spool sliding hole 32 according to an external command pressure described later introduced from the pilot port 33.

That is, when the displacement control valve 31 is at the large displacement position (a) as the first switching position as shown in FIG. 1, the spool 40 is connected to the high pressure port 34 by the land 40B as shown in FIG. The connection with the pressure oil supply port 35 is shut off. Then, at this time, since the pressure oil supply port 35 is cut off from the high pressure port 34, the supply of the pressure oil to the servo actuator 25 shown in FIGS. 2 and 3 is stopped.

When the displacement control valve 31 is switched from the large displacement position (a) shown in FIG. 1 to the small displacement position (b) as the second switching position, the spool 40 is moved as shown in FIG. An annular groove 40C between the lands 40A and 40B connects the high pressure port 34 and the pressure oil supply port 35 via oil grooves 34A and 35A. Then, at this time, the pressure oil from the high pressure port 34 is
The oil is supplied to the oil chamber 28 of the servo actuator 25 shown in FIGS.

Here, the capacity control valve 31 is composed of, for example, a 2-port 2-position hydraulic pilot type switching valve as shown in FIG.
Is selectively switched to one of a large capacity position (a) and a small capacity position (b) by an external command pressure supplied as a pilot pressure supplied through the switch.

Reference numeral 41 denotes a return spring as biasing means constituting a part of the capacity control valve 31. The return spring 41 is provided in FIG.
As shown in FIG. 6, a coil spring is inserted through the outer peripheral side of the stopper 39, and is disposed between the plug 37 and the spool 40. Then, the return spring 41 constantly urges the spool 40 toward the pilot port 33 side, and the urging force of the return spring 41 causes the displacement of the displacement control valve 31.
Is pushed back to the large capacity position (a) shown in FIG.

Reference numeral 42 denotes a drain pipe provided in the hydraulic motor 3. One end of the drain pipe 42 is connected to the drain chamber 14 in the hydraulic motor 3 and the other end is connected to the tank 2 as shown in FIG. Have been. The drain pipe 42 is connected to the cylinder block 18 in the casing 11 of the hydraulic motor 3.
The oil liquid (drain) leaked from between each cylinder 19 and the piston 21 is discharged from the drain chamber 14 in the casing 11 to the tank 2.

The oil chamber 2 of the servo actuator 25
The oil flowing out from inside the drain chamber 8 into the drain chamber 14 through the throttle passage 29 is also drained by the drain pipe 42 into the tank 2.
Discharged to the side. For this reason, the drain chamber 14 in the casing 11 is maintained at a low pressure state like the tank 2.

Reference numeral 43 denotes a shaft insertion hole 12 of the casing body 12.
D and the drive shaft 15, and the seal member 43 is, as shown in FIGS.
The first drain chamber 14 is sealed around the drive shaft 15, and the leakage of the oil liquid in the drain chamber 14 to the outside of the casing 11 is sealed.

Reference numeral 44 denotes a command pressure supply line connected to the pilot port 33 of the capacity control valve 31, and reference numeral 45 denotes a command pressure supply device serving as command pressure generation means.
As shown in FIG.
8, a pressure reducing valve 49, a tank 2 and the like, for supplying an external command pressure as a pilot pressure to a pilot port 33 of the capacity control valve 31 via a command pressure line 44.

Reference numeral 46 denotes a pilot pump serving as a hydraulic pressure source for external command pressure. Reference numeral 47 denotes a relief valve for determining the maximum discharge pressure of the pilot pump 46. The relief valve 47 opens when excessive pressure is generated on the discharge side of the pilot pump 46. A valve is provided to relieve the excess pressure to the tank 2 side.

Reference numeral 48 denotes a pressure selection valve as an external selection means for selectively connecting the command pressure line 44 to the tank 2 and the pilot pump 46. The pressure selection valve 48 is operated by a hydraulic shovel operator or the like by operating an operation lever 48A. By manual operation, it can be switched between the low-speed position (c) and the high-speed position (d).

While the pressure selection valve 48 is switched to the low speed position (c) as shown in FIG.
Is connected to the tank 2 so that the external command pressure is in a low pressure state of about the tank pressure. And the capacity control valve 3
In 1, the pressure of the pilot port 33 becomes the tank pressure level and is returned to the large capacity position (a) shown in FIG.

When the pressure selection valve 48 is switched from the low-speed position (c) to the high-speed position (d) shown in FIG. 1, the external command pressure set by the pressure reducing valve 49 to be described later is applied to the pilot port of the capacity control valve 31. 33. Then, the spool 40 of the capacity control valve 31 is pushed in the direction of arrow E against the return spring 41 by an external command pressure supplied from the pilot port 33 in the direction of arrow E as shown in FIG. As a result, the capacity control valve 31 switches from the large capacity position (a) shown in FIG. 1 to the small capacity position (b).

Reference numeral 49 denotes a pressure reducing valve provided between the pilot pump 46 and the pressure selection valve 48. The pressure reducing valve 49 prevents the external command pressure supplied into the command pressure line 44 from increasing to a set pressure or more. When the discharge pressure from the pilot pump 46 rises above the set pressure, the valve is closed and the supply of the discharge pressure is stopped.

The displacement control device for the hydraulic motor 3 according to the present embodiment has the above-described configuration. Next, the operation of the displacement control device will be described.

First, when the operator of the excavator switches the direction 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.

Here, when the directional control valve 5 is switched from the neutral position (a) to the switching position (b) or (c) during running of the vehicle, the pipeline sections 4A2, 4B2 on the actuator side.
The shuttle valve 9 selects the high-pressure side oil (motor drive pressure) on the side, and the high-pressure oil composed of the motor drive pressure is supplied to the high-pressure passage 36.
From the pressure control valve 31 to the high pressure port 34 of the capacity control valve 31.

The operator operates the pressure selection valve 48 in FIG.
1 is switched from the low-speed position (c) to the high-speed position (d), the external command pressure is supplied to the pilot port 33 of the capacity control valve 31, so that the capacity control valve 31
Is switched from the large capacity position (a) to the small capacity position (b).

Therefore, the pressure oil supply port 35 of the capacity control valve 31 communicates with the high pressure port 34, and the pressure oil from the high pressure port 34 is supplied to the servo actuator 25 via the pressure oil supply port 35 and the oil passage 30. 3 is supplied to the chamber 28 in the direction of arrow C in FIG. 3, and the tilting piston 27 of the servo actuator 25 is pushed in the direction of arrow B by the pressure in the oil chamber 28 as shown in FIGS. .

At this time, part of the pressure oil in the oil chamber 28 flows out in the direction indicated by the arrow D in FIG. 4 through the throttle passage 29 between the tilt cylinder 26 and the tilt piston 27. However, since a pressure difference occurs before and after the throttle passage 29,
In the oil chamber 28, a pressure sufficient to drive the swash plate 23 by the tilting piston 27 in the direction of arrow B is secured.

As a result, the tilting piston 27 is pushed by the pressure in the oil chamber 28 in the direction in which it extends (projects) from the tilting cylinder 26 (the direction indicated by the arrow B in FIGS. 3 and 4), and the swash plate 23 is moved.
Can be driven in a direction in which the tilt angle becomes smaller,
By switching the motor capacity to the small capacity side, the hydraulic motor 3 can be rotated at high speed with low torque.

Further, as shown in FIG. 4, the oil fluid F supplied from the oil passage 30 into the oil chamber 28 of the servo actuator 25
Even when air G is mixed in (pressure oil), the throttle passage 29 between the tilt cylinder 26 and the tilt piston 27
This air G can be discharged in the direction of arrow D together with the oil liquid F, and functions as an air vent passage.

On the other hand, when the operator switches the pressure selection valve 48 from the high-speed position (d) to the low-speed position (c) shown in FIG. 1, the external command pressure supplied to the pilot port 33 of the capacity control valve 31 becomes equal to the tank pressure. By lowering to
The capacity control valve 31 returns from the small capacity position (b) to the large capacity position (a) shown in FIG.

Therefore, the pressure oil supply port 35 of the capacity control valve 31 is shut off from the high pressure port 34, and the supply of the pressure oil from the oil passage 30 to the oil chamber 28 of the servo actuator 25 is stopped. Then, in this case, when the supply of the pressure oil from the oil passage 30 is cut off,
The oil liquid F (including the air G) in the oil chamber 28 is discharged through the throttle passage 29 in the direction indicated by the arrow D in FIG.
3 is pressed by the hydraulic reaction force from each piston 21 shown in FIG.

As a result, the tilting piston 27 of the servo actuator 25 is pushed in the direction of arrow A in FIGS. 3 and 4 so as to contract into the tilting cylinder 26, whereby the swash plate 23 tilts. The direction in which the turning angle increases (arrow A in FIG. 3)
Direction), and by switching the motor capacity to a large capacity side, the hydraulic motor 3 can be rotated at a high torque at a low speed.

Further, while the tilting piston 27 is displaced in the direction of arrow A, the servo actuator 25 draws the oil liquid F (pressure oil) in the oil chamber 28 through the throttle passage 29 as shown in FIG. Since it is gradually discharged in the D direction, the tilting piston 27
Can be reduced, and the impact (shock) when the swash plate 23 is tilted from the small capacity side to the large capacity side can be reduced.

Also during this time, the throttle passage 29 functions as an air vent passage, and the oil fluid F (pressure oil) in the oil chamber 28 is supplied to the air G
4 can be discharged in the direction indicated by the arrow D in FIG. 4, and the air G can be prevented from staying in the oil liquid F in the oil chamber 28.

Thus, according to the present embodiment, when the displacement control valve 31 is provided with the high pressure port 34 and the pressure oil supply port 35 and the displacement control valve 31 is switched to the small displacement position (b), The pressure oil 34 is communicated with the pressure oil supply port 35 to supply the pressure oil from the oil passage 30 to the oil chamber 28 of the servo actuator 25. When the displacement control valve 31 is switched to the large displacement position (a), the pressure oil supply port 35 is shut off from the high pressure port 34 and the supply of pressure oil to the oil chamber 28 of the servo actuator 25 is stopped.

A throttle passage 29 formed of an annular gap is formed between the tilt cylinder 26 and the tilt piston 27 of the servo actuator 25.
A part of the pressure oil supplied from the oil passage 30 is
To the drain chamber 14 (tank 2) side of the
The pressure for tilting and driving the swash plate 23 by the tilting piston 27 is generated in the oil chamber 28.

For this reason, the servo actuator 25
Even when air is mixed into the pressure oil supplied from the oil passage 30, the air is circulated from the oil chamber 28 to the drain chamber 14 side of the casing 11 through the throttle passage 29 through the throttle passage 29. It can be discharged to the tank 2 side together with the pressurized oil, preventing air from remaining in the oil chamber 28 of the servo actuator 25 and improving the air bleeding performance of the servo actuator 25.

The throttle passage 29 generates pressure in the oil chamber 28 of the servo actuator 25, and the tilting piston 27 can be pushed in the direction of arrow B in FIG. The tilting piston 27 drives the swash plate 23 in the direction of arrow B to the small tilting side, so that the capacity of the hydraulic motor 3 can be reliably switched to the minimum capacity side.

On the other hand, the displacement control valve 31 is moved to the small displacement position (b).
1, the pressure oil supply port 35 is shut off from the high pressure port 34 and the supply of the pressure oil from the oil passage 30 to the oil chamber 28 of the servo actuator 25 is stopped. The servo actuator 25 can discharge the oil liquid F in the oil chamber 28 through the throttle passage 29 in the direction indicated by the arrow D in FIG. 4 when the supply of the pressure oil from the oil passage 30 is cut off.

At this time, since the swash plate 23 is pressed by the hydraulic reaction force from each piston 21 shown in FIG. 2, the tilt piston 27 of the servo actuator 25 is retracted into the tilt cylinder 26. 3, the swash plate 23 can be driven in a direction in which the tilt angle increases, and the displacement of the hydraulic motor 3 can be switched to the large displacement side.

Also, the servo actuator 2
Also when the tilting piston 27 of FIG. 5 is retracted into the tilting cylinder 26, the throttle passage 29 functions as an air venting passage, so that the oil liquid F in the oil chamber 28 is discharged as illustrated in FIG. G can be discharged in the direction of arrow D together with the oil G, and the air G can be prevented from staying in the oil liquid F in the oil chamber 28.

Further, the capacity control valve 31 may be formed with a high pressure port 34 and a pressure oil supply port 35 as shown in FIGS. 1, 5 and 6, and a tank port and the like as in the prior art described above. Since it is not necessary to provide the capacity control valve 3,
One spool 40 only needs to form a single annular groove 40C between the lands 40A and 40B, so that the shape and structure of the spool 40 can be simplified, and the entire capacity control valve 31 can be made compact. Thus, downsizing can be achieved.

Therefore, according to the present embodiment, by providing the throttle passage 29 in the servo actuator 25 of the hydraulic motor 3, air can be reliably discharged from the oil chamber 28 of the servo actuator 25, It is possible to prevent the air from remaining in the inside 28 and to stably perform the switching control of the motor capacity using the servo actuator 25.

In the left and right traveling motors (left and right hydraulic motors 3) of a hydraulic shovel equipped with such a capacity control device, air is mixed into the oil chamber 28 of the servo actuator 25. The response speed when switching the motor capacity is changed, so that the left and right hydraulic motors 3
There is no difference between them, and problems such as the vehicle turning while traveling on the road can be solved.

Further, since it is not necessary to provide a tank port or the like specially in the capacity control valve 31 as in the prior art, the shape and structure of the spool 40 can be simplified, and the capacity control valve 3
1 can be made compact to reduce the size, and stable capacity control can be performed.

Next, FIG. 7 shows a second embodiment of the present invention. The feature of this embodiment is that a plurality of annular projections are provided on the outer peripheral side of the tilting piston, and the tilting is performed by each of the annular projections. The throttle passage is formed between the cylinder and the tilt piston. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 51 denotes a servo actuator as a variable capacity actuator adopted in this embodiment.
The servo actuator 51 includes a tilt cylinder 52, a tilt piston 53, and an oil chamber 54, similarly to the servo actuator 25 described in the first embodiment. The projecting-side end surface 53A of the tilt piston 53 is in contact with the contact surface 23B of the swash plate 23.

However, on the outer peripheral side of the tilt piston 53, two annular projections 53B and 53C are formed axially separated from each other, and the tilt piston 53 is formed with the annular projections 53B and 53C.
The sliding displacement is performed in the tilting cylinder 52 in the axial direction via. And these annular projections 53B, 53C
Are formed with an outer diameter slightly smaller than the inner diameter of the tilt cylinder 52, and constitute a part of a throttle passage 55 described later.

Reference numeral 55 denotes the tilt cylinder 52 and the tilt piston 5
3, a throttle passage formed of an annular gap formed between
The throttle passage 55 includes the tilt cylinder 52 and the tilt piston 5.
The swash plate 23 is tilted by the tilt piston 53 while the pressure oil in the oil chamber 54 flows toward the swash plate 23 by narrowing the flow passage area between the swash plate 23 and the annular projections 53B and 53C. A pressure for rolling is generated in the oil chamber 54.

The throttle passage 55 functions as an air vent passage similarly to the throttle passage 29 described in the first embodiment, and prevents air from remaining in the pressurized oil in the oil chamber 54. It is.

Thus, in the present embodiment configured as described above, substantially the same operation and effect as those of the first embodiment can be obtained. By providing the annular projections 53B and 53C on the side, a throttle passage 55 composed of an annular gap is formed between the tilt cylinder 52 and the tilt piston 53.

For this reason, the annular projections 53B and 53C act like thin blade orifices, for example, to reduce the flow passage area between the tilt cylinder 52 and the tilt piston 53, thereby reducing the influence of the temperature change of the oil liquid. . Thus, the pressure generated in the oil chamber 54 can be suppressed from fluctuating due to the oil temperature, and the tilt control of the swash plate 23 can be stabilized.

In the second embodiment, the annular projections 53B, 53C are provided on the outer peripheral side of the tilt piston 53. However, these annular projections 53B, 53C are provided.
May be constituted by a member such as a piston ring formed of a member different from the tilting piston 53, and the number of annular projections is 1
It may be an individual or three or more.

Further, a notch or the like is formed on the outer peripheral side of the annular projections 53B and 53C, and this notch is vented (throttle action).
May be used for In this case, the outer diameters of the annular projections 53B and 53C can be formed to have dimensions substantially equal to the inner diameter of the tilt cylinder 52.

Next, FIG. 8 shows a third embodiment of the present invention. The feature of this embodiment is that a throttle passage is provided on the oil chamber side of the variable displacement actuator, and the throttle passage is provided with a pressure in the oil chamber. It is configured to discharge oil toward a bearing that supports a drive shaft of a hydraulic motor. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 61 denotes a servo actuator as a variable capacity actuator employed in this embodiment.
The servo actuator 61 includes a tilt cylinder 62, a tilt piston 63, and an oil chamber 64, similarly to the servo actuator 25 described in the first embodiment. The tilting piston 63 has its protruding end surface 63A in contact with the contact surface 23B of the swash plate 23.

However, an O-ring 65 as a sealing member is mounted on the outer peripheral side of the tilt piston 63, and the O-ring 65 is connected to the inner peripheral surface of the tilt cylinder 62 and the tilt piston 63.
Is sealed in a liquid-tight manner with respect to the outer peripheral side. Therefore, the pressurized oil in the oil chamber 64 does not flow out (leak) from between the tilt cylinder 62 and the tilt piston 63 to the swash plate 23 side as in the above-described embodiment, and a throttle described later is used. The pressure oil is discharged through the passage 66.

Reference numeral 66 denotes a throttle passage formed of a small-diameter oil passage formed on the bottom side of the tilt cylinder 62.
6 has one end opening to the oil chamber 64 and the other end
Between the bearing 17 for use and the seal member 43 and open to the shaft insertion hole 12D side of the casing body 12.

The throttle passage 66 allows the pressure oil in the oil chamber 64 to flow toward the vicinity of the bearing 17 in the direction of arrow D1 in FIG. The pressure for tilting the swash plate 23 by the tilt piston 63 is generated in the oil chamber 64. Also, the throttle passage 6
Numeral 6 functions as an air vent passage similarly to the throttle passage 29 described in the first embodiment, and prevents air from remaining in the pressurized oil in the oil chamber 64.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained. The structure is such that the pressure oil in the chamber 64 flows out in the direction of arrow D1 in FIG. 8 toward the vicinity of the bearing 17, so that the oil liquid can be circulated to the bearing 17 and supplied.
7 can be kept in a lubricated state.

As illustrated in FIG. 8, while the swash plate 23 is driven to the minimum tilt side, the drive shaft 15 of the hydraulic motor 3 is rotated at high speed with low torque, so that the bearing 17 is lubricated. It is in a state where oil shortage tends to occur. However, at this time, the pressure oil from the oil passage 30 is supplied into the oil chamber 64 of the servo actuator 71 in the direction of arrow C, and a part of this pressure oil flows out through the throttle passage 66 in the direction of arrow D1. .

For this reason, when the drive shaft 15 of the hydraulic motor 3 is rotated at a high speed and the bearing 17 is likely to run out of lubricating oil,
The oil liquid can be positively supplied from the throttle passage 66 toward the bearing 17, and the lubricity of the bearing 17 can be reliably improved.

Next, FIG. 9 shows a fourth embodiment of the present invention. The feature of this embodiment is that a throttle passage is formed in the tilting piston of the variable displacement actuator, and the oil chamber is formed by the throttle passage. Is discharged to the contact surface between the swash plate and the tilting piston. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 71 denotes a servo actuator as a variable capacity actuator adopted in this embodiment.
The servo actuator 71 includes a tilt cylinder 72, a tilt piston 73, and an oil chamber 74, similarly to the servo actuator 25 described in the first embodiment. The tilting piston 73 has its protruding end surface 73A in contact with the contact surface 23B of the swash plate 23.

However, an O-ring 75 as a sealing member is mounted on the outer peripheral side of the tilt piston 73, and the O-ring 75 is connected to the inner peripheral surface of the tilt cylinder 72 and the tilt piston 73.
Is sealed in a liquid-tight manner with respect to the outer peripheral side.

Reference numeral 76 denotes a throttle passage formed of a small-diameter oil passage bored in the axial direction of the tilt piston 73.
6 has one end opening to the oil chamber 74 and the other end opening to the protruding end face 73A side of the tilt piston 73.

[0129] Then, the pressure oil in the oil chamber 74 is directed toward the contact surface 23B of the swash plate 23 by an arrow D2 in FIG.
The swash plate 23 is tilted by the tilt piston 73 to generate pressure in the oil chamber 74 by allowing the swash plate 23 to flow out in the direction and giving throttle resistance to the spilled oil. Also, the throttle passage 76 is provided with the throttle passage 29 described in the first embodiment.
In the same manner as described above, it functions as an air vent passage to prevent air from remaining in the pressure oil in the oil chamber 74.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained. In this embodiment, however, the oil chamber is formed by the throttle passage 76. The configuration is such that the pressure oil in 74 flows out toward the contact surface 23B of the swash plate 23 in the direction of arrow D2 in FIG.

Therefore, the oil liquid from the throttle passage 76 is supplied to the contact surface 23B of the swash plate 23 and the projecting end surface 7 of the tilt piston 73.
3A can be positively supplied, and the space between the contact surfaces can be kept in a lubricated state. Thereby, the tilting piston 7
3 can smoothly perform the tilting operation of the swash plate 23, and the contact surface between the swash plate 23 and the tilt piston 73 can be prevented from being worn or damaged for a long time.

In the first embodiment, the throttle passage 29 having an annular gap is formed between the tilt cylinder 26 and the tilt piston 27. However, the present invention is not limited to this. Instead, for example, one or a plurality of grooves extending in the axial direction may be formed on the outer peripheral surface of the tilt piston 27, and the groove may form a throttle passage.

In the first embodiment, the pilot port 33 of the capacity control valve 31 is connected to the command pressure line 44, and the capacity control valve 31 is moved to the large capacity position by the external command pressure from the command pressure supply device 45. (A) and the configuration for switching to the small capacity position (b) have been described by way of example. However, the present invention is not limited to this. For example, the motor drive pressure of the hydraulic motor 3 is used as the pilot pressure for the capacity. The present invention can also be applied to a self-pressure control type capacity control device configured to lead to a control valve.

Furthermore, in each of the above embodiments, the case where the displacement control device of the hydraulic rotary machine is applied to the traveling hydraulic motor 3 has been described as an example. However, the present invention is not limited to this, and for example, The present invention can also be applied to a hydraulic motor for rope winches or a hydraulic motor for rope winches. Further, the present invention can be widely applied to a displacement control device for a hydraulic pump serving as a hydraulic pressure source for a hydraulic shovel, a hydraulic crane, and the like.

[0135]

As described above in detail, according to the first aspect of the present invention, an oil passage for supplying pressure oil to the variable displacement actuator is provided between the displacement control valve and the variable displacement actuator. Since the variable displacement actuator is provided with a throttle passage for allowing a part of the pressure oil supplied from the oil passage to flow out to the tank side, the pressure oil supplied to the variable displacement actuator from the oil passage side passes through the throttle passage. Even when the fluid flows out to the tank side, pressure can be generated in the capacity variable actuator by the throttle passage, and by driving the capacity variable section of the hydraulic rotary machine with the hydraulic pressure at this time, the capacity of the hydraulic rotary machine is reduced. Can be variably controlled. Since the pressure oil supplied from the oil passage to the variable displacement actuator can be circulated to the tank via the throttle passage, it is possible to prevent air from being mixed into the pressure oil, and to stabilize the capacity switching control. Can be done.

Further, according to the second aspect of the present invention, the displacement control valve is provided with a high pressure port and a pressure oil supply port, and the first switching position for shutting off the pressure oil supply port from the high pressure port; The pressure control valve is switched between a second switching position that communicates with the pressure oil supply port, so that it is not necessary to provide a tank port used in the prior art in the capacity control valve, and In addition to simplifying the spool structure and the like, the structure of the entire valve can also be simplified, and the capacity control valve can be made compact to achieve downsizing. Further, when the displacement control valve is returned to the first switching position, the pressure oil supply port is shut off from the high pressure port, so that the pressure oil in the displacement variable actuator is gradually discharged to the tank side through the throttle passage. Accordingly, the variable capacity section can be slowly moved from, for example, the small capacity side to the large capacity side, and the shock at the time of capacity switching can be reduced.

According to the third aspect of the present invention, a hydraulic rotating machine includes a casing, a rotating shaft, a cylinder block having a plurality of cylinders, a plurality of pistons, a plurality of shoes, and a swash plate, and has a variable capacity. The actuator includes a tilt cylinder, a tilt piston, and an oil chamber, and is configured to flow the pressure oil in the oil chamber to a drain chamber in a casing through a throttle passage. Pressure oil flows out from the oil chamber defined in the oil chamber through the throttle passage, and it is possible to prevent air from staying in the oil chamber,
The movement (sliding displacement) of the tilting piston in the tilting cylinder can be stabilized, and the switching control of the capacity can be stably performed.

According to the fourth aspect of the present invention, the throttle passage is formed between the inner peripheral surface of the tilt cylinder and the outer peripheral surface of the tilt piston. The pressure oil in the oil chamber can be discharged while being throttled from a gap formed between the surface and the outer peripheral surface of the tilt piston, and at this time, air can also be discharged to the drain chamber in the casing together with the pressure oil.

On the other hand, the invention according to claim 5 has the throttle passage for discharging the pressure oil in the oil chamber toward the vicinity of the bearing that rotatably supports the rotating shaft in the casing. The bearing can be kept in a lubricated state by the oil liquid discharged from the bearing, and for example, even when the rotating shaft rotates at high speed, it is possible to prevent the bearing from running out of lubricating oil or the like.

According to the sixth aspect of the present invention, the throttle passage is formed in the tilt piston so as to discharge the pressure oil in the oil chamber toward the contact surface between the swash plate and the tilt piston. The contact surface between the swash plate and the tilt piston can be kept in a lubricated state by the oil liquid discharged from the throttle passage, and wear and damage of the contact surfaces of both can be prevented for a long time. Can be prevented.

Further, according to the invention of claim 7,
The throttle passage also serves as an air vent passage for discharging air mixed in the pressure oil flowing through the oil passage to the tank side, so that air can be discharged from the oil chamber of the variable capacity actuator to the tank side, and the air vent performance Can be improved, and the switching control of the capacity can be prevented from becoming unstable due to the mixing of air.

[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 a longitudinal sectional view showing the traveling hydraulic motor in FIG.

FIG. 3 is an enlarged longitudinal sectional view showing a swash plate, a servo actuator, and the like in FIG. 2;

FIG. 4 is an enlarged sectional view for explaining an air bleeding operation by the servo actuator in FIG. 3;

FIG. 5 is an enlarged longitudinal sectional view showing a capacity control valve in FIG. 2 at a small capacity position.

6 is a longitudinal sectional view of the displacement control valve, showing a state in which the spool in FIG. 5 has been slid to the large displacement position.

FIG. 7 is a longitudinal sectional view substantially similar to FIG. 3, showing a servo actuator of a capacity control device according to a second embodiment.

FIG. 8 is a longitudinal sectional view substantially similar to FIG. 3, showing a servo actuator of a capacity control device according to a third embodiment.

FIG. 9 is a longitudinal sectional view substantially similar to FIG. 3, showing a servo actuator of a capacity control device according to a fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Tank 3 Hydraulic motor (hydraulic rotating machine) 3A Variable capacity part 4A, 4B Main pipeline 5 Direction control valve 9 Shuttle valve 11 Casing 14 Drain chamber 15 Drive shaft (rotary shaft) 17 Bearing 18 Cylinder block 19 Cylinder 20 Valve plate 21 Piston 22 Shoe 23 Swash plate 23A Smooth surface 25, 51, 61, 71 Servo actuator (variable capacity actuator) 26, 52, 62, 72 Tilting cylinder 27, 53, 63, 73 Tilting piston 28, 54, 64, 74 Oil chamber 29, 55, 66, 76 Throttle passage 30 Oil passage 31 Capacity control valve 32 Spool sliding hole 33 Pilot port 34 High pressure port 35 Pressure oil supply port 36 High pressure passage 40 Spool 42 Drain line 44 Command pressure line 45 Command pressure supply device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F15B 11/02 F15B 11/02 E 21/04 F04B 21/00 G (72) Inventor Takeshi Kobayashi Kandatecho, Tsuchiura City, Ibaraki Prefecture No. 650 Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant F-term (reference) JJ02

Claims (7)

[Claims] 1. A variable displacement type hydraulic rotary machine having a variable capacity section, and a variable capacity actuator for driving a variable capacity section of the hydraulic rotary machine by supplying and discharging pressure oil to change a capacity. A capacity control device for a hydraulic rotary machine, comprising: a capacity control valve for controlling switching of pressure oil supplied to the variable capacity actuator; and a capacity control valve and a variable capacity actuator for supplying pressure oil to the variable capacity actuator. And a throttle passage provided in the variable displacement actuator and a part of the pressure oil supplied from the oil passage to the variable displacement actuator flows out to the tank side. Control device for hydraulic rotating machine. 2. The pressure control valve has a high-pressure port to which the pressure oil is supplied from a hydraulic pressure source, and a pressure oil supply port that opens to the oil passage. 2. The hydraulic rotary machine according to claim 1, wherein the hydraulic rotary machine is configured to switch between a first switching position in which the port is disconnected from the high pressure port and a second switching position in which the high pressure port communicates with the pressure oil supply port. 3. Capacity control device. 3. The hydraulic rotating machine includes a casing, a rotating shaft rotatably provided in the casing, and a rotating shaft provided in the casing so as to rotate integrally with the rotating shaft. A cylinder block having a plurality of cylinders extending in the axial direction, a plurality of pistons reciprocally inserted into each cylinder of the cylinder block, and a swingably provided at a protruding end side of each piston. A plurality of shoes, and a swash plate as a swash plate type hydraulic rotating machine having a smooth surface on which each of the shoes slides, and a swash plate serving as the variable capacity portion provided to be tiltable in the casing; A variable actuator, a tilt cylinder formed in the casing facing the swash plate, and a tilt piston slidably inserted into the tilt cylinder to tilt the swash plate; The tilt piston Therefore, an oil chamber defined in the tilt cylinder and supplied with pressure oil from the oil passage is provided.The inside of the casing is a drain chamber communicating with an external tank, and the pressure oil in the oil chamber passes through the throttle passage. The capacity control device for a hydraulic rotary machine according to claim 1 or 2, wherein the capacity control device is configured to flow into the drain chamber through the drain chamber. 4. The displacement control device for a hydraulic rotary machine according to claim 3, wherein the throttle passage is formed by a gap between an inner peripheral surface of the tilt cylinder and an outer peripheral surface of the tilt piston. . 5. The hydraulic rotary machine according to claim 3, wherein the throttle passage is configured to discharge pressure oil in the oil chamber toward a vicinity of a bearing that rotatably supports a rotary shaft in the casing. Capacity control device. 6. The tilting piston according to claim 3, wherein the throttle passage is formed in the tilting piston so as to discharge the pressure oil in the oil chamber toward a contact surface between the swash plate and the tilting piston. A capacity control device for a hydraulic rotary machine as described in the above. 7. The throttle passage according to claim 1, wherein the throttle passage also serves as an air vent passage for discharging air mixed in the pressure oil flowing through the oil passage to the tank side.
7. The capacity control device for a hydraulic rotary machine according to 4, 5, or 6.