JP3321278B2 - Hydraulic pump capacity control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, a variable displacement type hydraulic pump driven by a prime mover and having a variable displacement portion, and a servo piston is slid by supplying and discharging pressure oil, thereby changing the displacement portion of the hydraulic pump. 2. Description of the Related Art There is known a displacement control device for a hydraulic pump including a servo actuator for tilting drive and a displacement control valve for controlling the supply and discharge of pressurized oil to and from the servo actuator by switching the valve arrangement by an external command pressure.

[0003] The configuration and operation of this type of prior art hydraulic pump displacement control device will be described with reference to FIGS.
It will be described based on.

[0004] In the figure, reference numeral 1 denotes a variable displacement type hydraulic pump. The hydraulic pump 1 is a swash plate type or swash plate type hydraulic pump. The capacity (discharge amount) is made variable.
Then, the hydraulic pump 1 discharges the hydraulic oil in the tank 2 as pressure oil into the main pipeline 3 so as to supply the pressure oil to a hydraulic actuator (neither is shown) via a control valve or the like. It has become.

Reference numeral 4 denotes a servo actuator which is attached to the hydraulic pump 1 and drives the variable displacement section 1A. The servo actuator 4 is usually incorporated integrally into a casing (not shown) of the hydraulic pump 1, and is incorporated therein. Servo cylinder 5 having large-diameter chamber 5A and small-diameter chamber 5B formed therein, and large-diameter section 6A and small-diameter section 6B slidably inserted into large-diameter chamber 5A and small-diameter chamber 5B of servo cylinder 5. And large diameter room 5
A and a servo piston 6 defining a small diameter chamber 5B.

The small-diameter portion 6B of the servo piston 6 is connected to the variable-capacity portion 1A of the hydraulic pump 1 through a swing link 7, and the pressure oil for the large-diameter chamber 5A and the small-diameter chamber 5B of the servo cylinder 5 is supplied. When the servo piston 6 slides in the directions indicated by arrows A and B due to supply and discharge, the displacement of the hydraulic pump 1 is increased or decreased by tilting the variable displacement section 1A in the directions indicated by arrows C and D. It has become.

Reference numeral 8 denotes a pilot pump. The pilot pump 8 is connected to a pump port 1 formed in a casing 13 of a displacement control valve 12 to be described later via a pump pressure pipe 9.
It communicates with 7. The pilot pump 8 communicates with the small diameter chamber 5B of the servo cylinder 5 via a branch pipe 10 branched from the pump pressure pipe 9. The large-diameter chamber 5A of the servo cylinder 5 communicates with a servo pressure output port 18 described later formed in the casing 13 through the servo pressure pipe 11.

Reference numeral 12 denotes a displacement control valve for driving the servo piston 6 to change the displacement of the hydraulic pump 1 based on an external command pressure. The displacement control valve 12 includes a casing 13, a sleeve 25 and a spool 30 to be described later. And so on.

Reference numeral 13 denotes a casing of the capacity control valve 12 in which a sleeve sliding hole 13A is formed. Female screws 13B and 13C are formed at both ends of the casing 13. Further, the inner circumferential surface of the sleeve sliding hole 13A at the central portion in the axial direction is provided with circumferential grooves 14, 15,.
16 are formed at predetermined intervals. Further, the casing 13 has a pump port 17 opening in the circumferential groove 14 and a servo pressure output port 1 opening in the circumferential groove 15.
A tank port 19 opening to the groove 8 and the circumferential groove 16 is formed to be spaced apart in the axial direction.

The other tank ports 20, 21 opening on the inner peripheral surface of the casing 13 are separated from the casing 13 by a large distance in the axial direction so as to sandwich the pump port 17, the output port 18, and the tank port 19. And an external command pressure introduction port 22 opening to a hydraulic chamber 43 described later.
Are formed respectively. The tank port 19 and the other tank ports 20 and 21 are connected to the recirculation pipe 2.
The external command pressure introduction port 22 is connected via an external command pressure pipe 24 to a command pressure source (not shown) for changing the capacity of the hydraulic pump 1. .

Reference numeral 25 denotes a sleeve which is slidably inserted into the sleeve sliding hole 13A and has a spool sliding hole 25A formed on the inner peripheral side thereof. 26, 27 and 28 are formed at predetermined intervals in the axial direction. Further, one end of a feedback link 29 as a connecting member is connected to the sleeve 25, and the other end of the feedback link 29 is connected to the small diameter portion 6 </ b> B of the servo piston 6. Then, the sleeve 25 follows the movement of the servo piston 6 and slides and displaces in the casing 13 in the axial direction.

Reference numeral 30 denotes a spool sliding hole 2 of the sleeve 25.
5A shows a spool that is slidably inserted into the spool 5A. The spool 30 has two lands 30A, 3 that are spaced apart in the axial direction.
0B is formed, and a spool annular chamber 31 is defined between the lands 30A and 30B in the sleeve 25.

Reference numeral 32 denotes a lid provided at one end of the casing 13. The lid 32 is screwed into the female screw 13 </ b> C of the casing 13, and a large-diameter male screw 32 </ b> A fixed to the casing 13 by screwing a lock nut 33 into a fitting inserted into the casing 13. Insert 32
B and the land 30B of the spool 30 from the fitting portion 32B.
And a small-diameter cylindrical stopper portion 32C protruding toward the side with a protrusion size of L1.
The space between B and the casing 13 is sealed by an O-ring 34. In the casing 13, the spring chamber 3 is surrounded by the inner peripheral surface of the casing 13, the insertion portion 32 </ b> B of the lid 32, the sleeve 25, and the land 30 </ b> B of the spool 30, and in which a compression coil spring 36 described later is disposed.
5 are formed.

Reference numeral 36 denotes a compression coil spring disposed in a spring chamber 35. The compression coil spring 36 has its inner peripheral side loosely inserted into a stopper portion 32C of the lid 32, and a fitting portion of the lid 32. It is arranged with an initial load between 32B and the land 30B of the spool 30. When the urging force of the compression coil spring 36 is larger than an external command pressure described later,
The spool 30 takes an initial position where the land 30A as shown in FIG. 4 comes into contact with a stopper portion 38C of the lid 38 described later, and in this state, the land 30B of the spool 30 and the lid 32
Is the maximum stroke of the spool 30. Therefore, the spool 30
Is at the initial position, the dimension L, which is the sum of the dimensions L1 and L2, is the set height of the compression coil spring 36,
The spring force of the compression coil spring 36 at the set height L is the set load.

Reference numeral 38 denotes another lid provided at the other end of the casing 13. The lid 38 is provided on the casing 1.
3, a large-diameter male screw portion 38A fixed to the casing 13 by being screwed with the lock nut 39, a fitting portion 38B inserted into the casing 13, and the fitting portion 38B. Land 3 of spool 30 from insertion portion 38B
Small-diameter cylindrical stopper portion 38C protruding toward 0A side
And the insertion portion 38B of the lid 38 and the casing 1
3 is sealed by an O-ring 40.

Reference numeral 41 denotes a piston sliding hole extending in the axial direction of the lid 38 and opened at an end face of the stopper portion 38C. Reference numeral 42 denotes a piston slidably inserted into the piston sliding hole 41. Reference numeral 42 defines a hydraulic chamber 43 in the piston sliding hole 41 of the lid 38, and pushes the spool 30 in the axial direction according to an external command pressure supplied into the hydraulic chamber 43.

Reference numeral 44 denotes a circumferential groove formed over the entire outer peripheral surface of the fitting portion 38B of the cover 38, and reference numeral 45 denotes an external command drilled in the radial direction of the cover 38 at the position of the circumferential groove 44. The external command pressure passage 45 has one end opened to the peripheral groove 44 and the other end opened to the hydraulic chamber 43 so that the hydraulic chamber 43 communicates with the peripheral groove 44. Here, the lid 38 is screwed into the female screw portion 13 </ b> B of the casing 13 to a position where the external command pressure introduction port 22 formed in the casing 13 and the peripheral groove 44 face each other, and fixed by the lock nut 39.

In the displacement control device for a hydraulic pump configured as described above, the cover 38 is connected to the external command pressure introduction port 22 through the cover 38.
When the external command pressure Pi supplied into the hydraulic chamber 43 through the peripheral groove 44 and the external command pressure passage 45 is equal to or lower than the pressure P1 as indicated by a characteristic line 46 shown in FIG. The pressure is lower than the urging force of the spool 30 by the compression coil spring 36, and the spool 30
As shown in FIG. 4, the A side takes a position (hereinafter, referred to as an initial position) in which it comes into contact with the end surface of the stopper 38C of the lid 38.

In this state, since the communication hole 26 of the sleeve 25 is blocked by the land 30A of the spool 30, pressure oil from the pilot pump 8 guided from the pump pressure pipe 9 to the pump port 17 is supplied to the spool annular chamber 3.
1, the spool 30, the sleeve 25 and the servo piston 6 are held at the positions shown in FIG. 4, and the variable capacity section 1A of the hydraulic pump 1 has the capacity Q of the hydraulic pump 1 shown in FIG. The position where the minimum value Q1 is obtained is held.

Next, when the external command pressure Pi is increased from the pressure P1 to the pressure Pa (Pa> P1), the pressing force of the piston 42 on the spool 30 is reduced by the compression coil spring 3
6 exceeds the urging force on the spool 30, and the spool 30
Moves in the direction of arrow A. As a result, the communication hole 28 of the sleeve 25 blocked by the land 30 </ b> B is opened, and the output port 18 through the communication holes 27 and 28, the spool annular chamber 31 and the circumferential grooves 15 and 16 of the casing 13.
And the tank port 19 communicate with each other.

As a result, the large-diameter chamber 5A of the servo cylinder 5
The internal pressure oil flows back to the tank 2 through the servo pressure pipe 11, the output port 18, the tank port 19, and the return pipe 23, so that the servo piston 6 moves in the direction of arrow A. As a result, the variable displacement portion 1A of the hydraulic pump 1 connected to the servo piston 6 via the swing link 7 is
, The capacity Q of the hydraulic pump 1 increases to the value Qa.

At this time, the sleeve 25 connected to the servo piston 6 via the feedback link 29 follows the movement of the servo piston 6 and moves in the direction of arrow A. Spool 3
The sliding displacement is performed to a position where the lands are interrupted by the zero land 30A. As a result, the movement of the servo piston 6 and the sleeve 25 in the direction of arrow A is stopped,
The displacement variable portion 1A of the hydraulic pump 1 stops moving in the direction of arrow C, and the displacement Q of the hydraulic pump 1 is maintained at a value Qa corresponding to the pressure Pa of the external command pressure Pi.

Next, the external command pressure Pi becomes the pressure P2 (P2>
In the state where Pa) has been reached, as shown in FIG. 5, the spool 30 moving in the direction of arrow A is positioned such that the end surface on the land 30B side abuts against the stopper portion 32C of the lid 32 (hereinafter, referred to as “the position”).
Further movement is restricted by taking the maximum stroke position). Also in this state, the servo actuator 4 is operated and controlled by the displacement control valve 12 in the same manner as described above, so that the displacement Q of the hydraulic pump 1 is reduced.
Is maintained at the maximum value Q2 shown in FIG. 6, and the capacity Q of the hydraulic pump 1 does not exceed the maximum value Q2 even if the external command pressure Pi exceeds the pressure P2.

On the other hand, when the external command pressure Pi is reduced from the pressure P2 to the pressure Pa (P2> Pa), the urging force of the compression coil spring 36 on the spool 30
The pressing force of the piston 42 with respect to
Moves in the direction of arrow B from the position shown in FIG. As a result, the sleeve 25 blocked by the land 30A
The communication port 26 is opened, and the pump port 17 and the output port 18 communicate with each other via the communication holes 26 and 27, the spool annular chamber 31, and the circumferential grooves 14 and 15 of the casing 13.

As a result, the pressure oil from the pilot pump 8 flows into the large-diameter chamber 5A of the servo cylinder 5 through the pump pressure pipe 9, the spool annular chamber 31, and the servo pressure pipe 11, so that the servo piston 6 Diameter 6A and small diameter 6
Due to the area difference from B, the servo piston 6 moves in the direction of arrow B. As a result, the displacement variable portion 1A of the hydraulic pump 1 connected to the servo piston 6 via the swing link 7 moves in the direction of arrow D, and the displacement Q of the hydraulic pump 1 decreases to the value Qa.

At this time, the sleeve 25 connected to the servo piston 6 via the feedback link 29 moves in the direction of arrow B following the movement of the servo piston 6 at this time. Spool 3
The sliding displacement is performed to a position where the lands are interrupted by the zero land 30A. As a result, the movement of the servo piston 6 and the sleeve 25 in the direction of arrow B is stopped.
The displacement variable portion 1A of the hydraulic pump 1 stops moving in the direction of arrow D, and the displacement Q of the hydraulic pump 1 is held at a value Qa corresponding to the pressure Pa of the external command pressure Pi.

As described above, the follow-up operation of the servo actuator 4 causes the variable displacement section 1A of the hydraulic pump 1 to move in the direction indicated by the arrow A or B in response to the change in the external command pressure Pi. By moving in the direction C or D, the capacity Q of the hydraulic pump 1 corresponding to the external command pressure Pi is obtained, and the sleeve 25 moves in the direction A or B in the casing 13 in synchronization with this. As a result, the spool annular chamber 31 is
6 and 28 are shut off again, and the capacity Q of the hydraulic pump 1 is variably controlled according to the external command pressure Pi.

[0028]

In the above-mentioned prior art, the external command pressure Pi is reduced to the pressure P1,
When the spool 30 assumes the initial position, the capacity Q of the hydraulic pump 1 becomes the minimum value Q1, and the external command pressure Pi is reduced to the pressure P2.
The control characteristic of the capacity control valve 12 is set so that the capacity Q becomes the maximum value Q2 when the spool 30 takes the maximum stroke position. The pressure P1 of the external command pressure Pi corresponding to the minimum value Q1 of the capacity Q and the pressure P2 of the external command pressure Pi corresponding to the maximum value Q2
It is determined by the set load of the compression coil spring 36 disposed between the second insertion portion 32B and the land 30B of the spool 30.

However, the set load of the compression coil springs 36 may vary from one compression coil spring 36 to another, and the variation in the set load causes the following problems.

That is, when the set load of the compression coil spring 36 is an appropriate value, the relationship between the capacity Q of the hydraulic pump 1 and the external command pressure Pi is set to an appropriate characteristic as shown by a characteristic line 46 shown by a solid line in FIG. can do. However, when the set load of the compression coil spring 36 is smaller than the appropriate value, the capacity Q of the hydraulic pump 1 increases from the minimum value Q1 when the external command pressure Pi becomes equal to or higher than the pressure P1 'smaller than the pressure P1. First, the external command pressure Pi is smaller than the pressure P2.
2 ′, the capacity Q of the hydraulic pump 1 becomes the maximum value Q
You reach 2. As a result, the capacity Q and the external command pressure Pi
The relationship changes as shown by a characteristic line 47 shown by a one-dot chain line in FIG.

When the set load of the compression coil spring 36 is larger than an appropriate value, the external command pressure Pi becomes equal to the pressure P1.
When the pressure becomes greater than the larger pressure P1 ″, the capacity Q of the hydraulic pump 1 starts to increase from the minimum value Q1, and the external command pressure P
When i becomes a pressure P2 ″ greater than the pressure P2, the capacity Q of the hydraulic pump 1 reaches the maximum value Q2. As a result, the relationship between the capacity Q and the external command pressure Pi is two points in FIG. It changes like the characteristic line 48 shown by the chain line.

For this reason, in the prior art, if the set load of the compression coil spring 36 varies, the hydraulic pump 1
Therefore, an error occurs between the capacity Q of the hydraulic pump 1 and the external command pressure Pi corresponding to the capacity Q, so that the capacity control of the hydraulic pump 1 cannot be performed with high accuracy.

On the other hand, for example, by adjusting the set height L of the compression coil spring 36 by changing the screwing position of the lid 32 to the casing 13, the compression coil spring 3
It is possible to adjust the set load of No. 6. But,
In this case, since the dimension L2 shown in FIG. 4 changes, the maximum stroke position of the spool 30 changes, and the maximum value of the capacity Q of the hydraulic pump 1 changes from the maximum value Q2 shown in FIG. There is a problem that it changes.

As shown in FIG. 8, the hydraulic pump 1
In order to set the capacity Q of the battery to a value Q3 smaller than the maximum value Q2,
When the cover 32 is tightened to reduce the dimension L2, the set height L of the compression coil spring 36 is reduced and the set load is increased. Therefore, the capacity control characteristic is shown by a solid line in FIG. It changes from the characteristic line 46 to a characteristic line 49 shown by a dashed line, and for example, there arises a problem that the capacity Q when the external command pressure Pi is the pressure Pa changes from the value Qa to the value Qa '.

The present invention has been made in view of the above-mentioned problems of the prior art, and can easily adjust the variation in spring force.
It is an object of the present invention to provide a hydraulic pump displacement control device capable of performing displacement control of a hydraulic pump in accordance with an external command pressure with high accuracy.

[0036]

In order to solve the above-mentioned problems, a displacement control device for a hydraulic pump according to the present invention has a sleeve sliding hole, and the pump is spaced apart in the axial direction of the sleeve sliding hole. A casing in which a port, an output port, and a tank port are formed, a sleeve slidably provided in a sleeve sliding hole of the casing, and an inner peripheral side serving as a spool sliding hole; Slidably provided, communicating the output port of the casing to a pump port or a tank port via the sleeve,
A cover provided at one end of the casing and having a spring chamber formed between the spool and one end of the spool; and a spring chamber positioned between the lid and one end of the spool. And a spring that constantly biases the spool toward the initial position, and is provided in the casing at the other end of the spool, and is provided with a command pressure from the outside, so that the spool is A hydraulic chamber that slides and displaces against the spring; a servo actuator that is connected to an output port of the casing and that drives a variable displacement section of the hydraulic pump by supplying and discharging pressure oil from the output port; And a connecting member provided between the servo actuator and the sleeve and slidingly displacing the sleeve following the variable capacity portion.

The features of the structure adopted by the present invention are as follows.
The lid is provided at one end of the casing so as to be movable in the axial direction, and a first cylindrical stopper that adjusts a spring force of the spring between the one end of the spool and a base end of the first stopper. 1 movably disposed axially in the stopper, and configured from the leading end side protrudes into the spring chamber, a second stopper for restricting the maximum stroke position of the spool, the spring
Is located at the outer periphery of the tip end side of the second stopper.
A structure arranged between the other end of the topper and one end of the spool
It was to be successful.

[0038]

According to the above arrangement, if the spring force varies, the spring force can be easily adjusted by moving the first stopper in the axial direction of the casing. And
At this time, if the second stopper is moved in the axial direction with respect to the first stopper, the maximum stroke position of the spool can be easily adjusted, and the dimension L2 illustrated in FIG.
Can always be set to a fixed size.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same components as those in the prior art shown in FIGS. 4 and 5 are denoted by the same reference numerals, and description thereof will be omitted.

In the drawing, reference numeral 51 denotes a displacement control valve according to the present embodiment. The displacement control valve 51 is constituted by a casing 13, a sleeve 25, a spool 30, and the like in substantially the same manner as the displacement control valve 12 described in the prior art. However, the capacity control valve 51 is different in that a lid 52 described later is provided.

Reference numeral 52 denotes a lid closing one end of the casing 13. The lid 52 forms a spring chamber 35 between the spool 30 and the lid 32 as in the case of the lid 32 described in the related art. The lid 52 is provided with a first stopper 53 and a second stopper
And a stopper 55.

Here, the first stopper 53 is screwed into the female screw portion 13C of the casing 13 and a large-diameter male screw portion 53A fixed to the casing 13 by screwing a lock nut 54 therein. The insertion portion 53B is formed on the inner peripheral side of the insertion portion 53B.
A small-diameter hole 53C into which the stopper 55 is inserted,
The screw hole 53D is formed to have a diameter larger than 3C, and extends in the axial direction on the inner peripheral side of the male screw portion 53A. The first stopper 53 is movable in the axial direction of the casing 13 by changing the screwing position of the male screw portion 53A. Further, the insertion portion 5 of the first stopper 53
3B and the casing 13 are provided with an O-ring 34, and the end face of the fitting portion 53B and the land 30B of the spool 30 are provided.
A compression coil spring 36 having a set height L is disposed between the compression coil spring 36 and the side end surface.

Reference numeral 55 denotes a second stopper. The second stopper 55 is screwed into a screw hole 53D of the first stopper 53,
A male screw portion 55A fixed to the first stopper 53 by screwing the lock nut 56, and the male screw portion 55A
And a small-diameter cylindrical stopper portion 55B protruding from the leading end side of the spool 30 toward the land 30B of the spool 30 and inserted into the small-diameter hole 53C of the first stopper 53.
The second stopper 55 moves in the first stopper 53 in the axial direction by changing the screwing position of the male screw portion 55A in the screw hole 53D of the first stopper 53, thereby reducing the protrusion dimension L1 of the stopper portion 55B. It can be adjusted variably. Further, the stopper portion 55B of the second stopper 55
An O-ring 57 is mounted between the first stopper 53 and the first stopper 53. The O-ring 57 prevents oil in the spring chamber 35 from leaking from between the first stopper 53 and the second stopper 55. I have.

The displacement control device for the hydraulic pump 1 according to the present embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.

In this embodiment, however, the lid 52 for closing one end of the casing 13 is connected to the first cylindrical stopper 53 screwed to the female screw portion 13C of the casing 13 and the first stopper 53, Since the second stopper 55 is screwed into the screw hole 53D of the stopper 53 and is movable in the axial direction with respect to the first stopper 53, the following operation and effect can be obtained.

In other words, when the set load of the compression coil spring 36 varies from product to product when assembling the capacity control valve 51, the first stopper 5
By changing the screwing position of No.3, the spool 30
By changing the set height L of the compression coil spring 36 when it is at the initial position shown in (1), the set load can be easily adjusted.

After the set load is adjusted, the screw position of the second stopper 55 with respect to the first stopper 53 is changed, and the protrusion dimension L1 of the stopper portion 55B is changed. Spool 3
The dimension L2 between the zero and the end face of the land 30B can be appropriately adjusted, and the dimension L2 can be kept constant even when the set height L of the compression coil spring 36 is changed.

Therefore, in this embodiment, the compression coil spring 3
Even if the set load varies, the set load of the compression coil spring 36 can be easily adjusted without changing the maximum stroke position of the spool 30.
The capacity control characteristic of the capacity control valve 51 can be maintained at an appropriate characteristic as shown by a characteristic line 46 shown by a solid line in FIG. 3, and when the external command pressure Pi is changed from the pressure P1 to the pressure P2, the hydraulic pump 1 From the minimum value Q1 to the maximum value Q2
Can be variably controlled with appropriate characteristics in the range of.

The maximum value of the capacity Q of the hydraulic pump 1 is represented by Q
In the case where the capacity Q of the hydraulic pump 1 is controlled in the range from the minimum value Q1 to the maximum value Q3, the screw position of the first stopper 53 with respect to the casing 13 is changed without changing the screw position. By changing the screwing position of the second stopper 55, while maintaining the set height L of the compression coil spring 36 constant, the gap between the end surface of the stopper portion 55B of the second stopper 55 and the end surface of the land 30B of the spool 30 is maintained. Only the dimension L2 can be reduced. Thus, the maximum stroke position of the spool 30 can be easily adjusted without changing the set load of the compression coil spring 36, and the capacity Q of the hydraulic pump 1 is reduced as indicated by a characteristic line 58 shown by a dashed line in FIG. Appropriate capacity control characteristics in which the maximum value is reduced to the value Q3 can be obtained.

In this case, for example, when the external command pressure Pi is pressure Pa (P1 <Pa <P2), the capacity Q of the hydraulic pump 1 is set to a value Qa (Q1 <Qa <Q3) and the capacity Q In the range from the minimum value Q1 to the maximum value Q3, the capacity control characteristic similar to the characteristic line 46 shown by the solid line is obtained.
Even when the capacitance control characteristic is changed from the characteristic line 46 to the characteristic line 58, high-precision capacitance control can always be performed.

[0051]

According to the above in detail it was as the present invention, cable
The lid provided at one end of the shing is connected to one end of the spool.
A first cylindrical stopper for adjusting the spring force of the spring between
An end is provided on the first stopper so as to be movable in the axial direction.
The end side projects into the spring chamber and the maximum stroke of the spool
A second stopper for regulating the position of the spring;
Is located at the outer periphery of the tip end side of the second stopper.
A structure arranged between the other end of the topper and one end of the spool
Since was formed, can in regulating the spring force of the spring integer for squirrel pool by the first stopper provided to be movable in one end of the casing in the axial direction, movable in the axial direction on the first inside stopper the second stopper was set only can be appropriately adjust the maximum stroke position of the spool. This result
As a result, even when the spring force of the spring varies for each component, the first stopper and the second
By relatively moving the stopper, the spring force on the spool can be easily adjusted, and the relationship between the capacity of the hydraulic pump and the external command pressure can always be properly maintained, and the capacity control of the hydraulic pump can be improved. Accuracy can be improved, and reliability can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a displacement control device of a hydraulic pump according to an embodiment of the present invention with a spool in an initial position.

FIG. 2 is a longitudinal sectional view similar to FIG. 1, showing a state in which a spool has reached a maximum stroke position.

FIG. 3 is a characteristic diagram showing a relationship between an external command pressure and a capacity of a hydraulic pump according to the embodiment of the present invention.

FIG. 4 is a sectional view showing a displacement control device for a hydraulic pump according to the related art in a state where a spool is at an initial position.

FIG. 5 is a longitudinal sectional view similar to FIG. 4, showing a state where the spool has reached a maximum stroke position.

FIG. 6 is a characteristic diagram showing a relationship between an external command pressure and a capacity of a hydraulic pump according to a conventional technique.

FIG. 7 is a characteristic diagram showing a relationship between an external command pressure and a capacity of a hydraulic pump when a set load of a compression coil spring changes.

FIG. 8 is a characteristic diagram showing a relationship between the maximum displacement of the hydraulic pump and an external command pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 1A Variable capacity part 4 Servo actuator 6 Servo piston 7 Oscillating link 8 Pilot pump 13 Casing 17 Pump port 18 Output port 19, 20, 21 Tank port 25 Sleeve 29 Feedback link (connection member) 30 Spool 36 Compression coil spring (Spring) 38 Lid 42 Piston 43 Hydraulic chamber 51 Capacity control valve 52 Lid 53 First stopper 55 Second stopper

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shigetaka Nakamura 650, Kandate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Within the Tsuchiura Plant (72) Inventor Tetsuya Sakairi 650, Kandate-cho, Tsuchiura-shi, Ibaraki Prefecture Within the Tsuchiura Plant, Hitachi Construction Machinery Co., Ltd. 56) References JP-A-62-199977 (JP, A) JP-A-2-173368 (JP, A) JP-A-63-117183 (JP, A) JP-A-62-169285 (JP, U) (58) ) Field surveyed (Int.Cl. ⁷ , DB name) F04B 49/00 F16K 3/24

Claims (1)

(57) [Claims] 1. A casing having a sleeve sliding hole, in which a pump port, an output port and a tank port are formed apart from each other in the axial direction of the sleeve sliding hole, and sliding in the sleeve sliding hole of the casing. And a sleeve whose inner peripheral side is a spool sliding hole, and a sleeve that is slidably provided in the spool sliding hole of the sleeve, and the output port of the casing is connected to a pump port or a tank port via the sleeve. A lid that is provided at one end of the casing and that forms a spring chamber between the spool and the one end of the spool; and a lid that is located between the lid and one end of the spool. A spring disposed in the spring chamber and constantly biasing the spool toward the initial position; and a spring provided at the other end of the spool and provided with the command pressure from the outside. Thus, the hydraulic chamber that slides and displaces the spool against the spring and the output port of the casing, and drives the variable capacity portion of the hydraulic pump by supplying and discharging pressure oil from the output port a servo actuator which, in the capacity control device of the hydraulic pump is provided, comprising a connecting member for sliding displacement of the sleeve to follow the variable volume portion between said sleeve and said servo actuator, before Kifutatai is provided movably in the axial direction on one end side of the casing, a tubular first stopper for adjusting the spring force of the spring between the one end of the spool, the base end side to the first stop movably provided in the axial direction, and configured from the leading end side protrudes into the spring chamber, a second stopper for restricting the maximum stroke position of the spool, the spring, the second scan Tsu before and positioned at the front end side outer periphery of the path
Between the other end of the first stopper and one end of the spool.
Capacity control device for a hydraulic pump, characterized in that a configuration in which settings.