CN113446179A - Pump control pressure regulator - Google Patents

Abstract

The present invention relates to a pump control pressure regulator. The regulator (50) is provided with: a housing main body (3a) having a control pressure passage (11), a discharge pressure passage (10), and a signal pressure passage (13); a sleeve (60) that is attached to the attachment hole (67) of the housing main body and that has a first port (60a), a second port (60b), and a third port (60 c); and a control spool (52) which is housed in the sleeve in a slidable manner and is displaced in the axial direction in accordance with the discharge pressure supplied via the second port and the signal pressure supplied via the third port, wherein the sleeve is provided with a drain passage (63) which opens between a second connection section (82) to which the discharge pressure passage and the second port are connected and a third connection section (83) to which the signal pressure passage and the third port are connected.

Description

Pump control pressure regulator

Technical Field

The present invention relates to a pump control pressure regulator.

Background

JP2008-240518A discloses a pump control pressure regulator that supplies a horsepower control pressure to a swash plate type piston pump that controls drive horsepower in accordance with the horsepower control pressure. The horsepower control pressure supplied from the pump control pressure regulator to the swash plate type piston pump is changed in accordance with the signal pressure supplied from the outside.

In the pump control pressure regulator described in japanese patent application laid-open No. JP2008-240518A, a discharge pressure port for guiding a discharge pressure of a swash plate type piston pump and a signal pressure port for guiding a signal pressure from the outside are disposed adjacent to each other. When the discharge pressure port for introducing the relatively high pressure and the signal pressure port for introducing the relatively low pressure are disposed adjacent to each other in this manner, the working oil may leak from the connection portion between the discharge pressure port and the passage formed in the pump housing and flow into the signal pressure port. When the relatively high-pressure hydraulic oil flows into the signal pressure port, even when the signal pressure is not supplied from the outside, the same state as the state in which the signal pressure is supplied is assumed, and therefore, an unexpected magnitude of horsepower control pressure is supplied from the pump control pressure regulator to the swash plate type piston pump.

When the magnitude of the horsepower control pressure supplied from the pump control pressure regulator to the swash plate type piston pump becomes an unexpected magnitude, for example, the discharge amount of the swash plate type piston pump may decrease and a sufficient amount of hydraulic oil may not be supplied to the hydraulic equipment. In addition, when the driving source for driving the swash plate type piston pump is an engine, the driving horsepower of the swash plate type piston pump increases to cause the engine to be in an overload state, and the engine may be stopped.

Disclosure of Invention

The purpose of the present invention is to prevent a situation in which an unexpected level of horsepower control pressure is supplied from a pump control pressure regulator to a pump.

According to one aspect of the present invention, a pump control pressure regulator for supplying a horsepower control pressure to a pump that controls drive horsepower in accordance with the horsepower control pressure, includes: a casing having a first passage for guiding the horsepower control pressure to the pump, a second passage for guiding a discharge pressure of the pump, a third passage for guiding a signal pressure lower than the discharge pressure for changing the horsepower of the pump, and a mounting hole for opening the first passage, the second passage, and the third passage; a sleeve that is attached to the attachment hole and that has a first port that communicates with the first passage, a second port that communicates with the second passage, and a third port that communicates with the third passage; and a pilot spool housed in the sleeve so as to be slidable, and displaced in an axial direction in accordance with the discharge pressure supplied via the second port and the signal pressure supplied via the third port to allow or block communication between the first port and the second port, wherein a drain passage that communicates with a fluid tank that stores a working fluid is provided in either one of the housing and the sleeve, and the drain passage is open between a second connection portion to which the second port and the second port are connected and a third connection portion to which the third port and the third port are connected.

Drawings

Fig. 1 is a sectional view of a swash plate pump including a pump control pressure regulator according to an embodiment of the present invention.

Fig. 2 is a sectional view taken along line II-II in fig. 1.

Fig. 3 is an enlarged sectional view showing an enlarged cross section along the line III-III of fig. 2.

Fig. 4 is a diagram showing a modification of the swash plate pump including the pump control pressure regulator according to the embodiment of the present invention, and is a cross-sectional view showing a cross section corresponding to fig. 2.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to fig. 1, a swash plate type pump 100 (hereinafter, referred to as a "pump 100") including a pump control pressure regulator 50 (hereinafter, referred to as a "regulator 50") according to an embodiment of the present invention will be described. The pump 100 is used as a hydraulic pressure supply source that supplies hydraulic oil as a working fluid to a hydraulic device such as a hydraulic cylinder, and is rotationally driven by a drive source such as an engine.

As shown in fig. 1, the pump 100 is a swash plate type piston pump, and includes: a shaft 1 as a driving shaft, which is rotated by a power source; a cylinder 2 coupled to the shaft 1 and rotating together with the shaft 1; and a housing 3 that houses the cylinder 2.

The housing 3 has: a case body 3a as a case having a bottomed cylindrical shape; and a cover 3b that seals the open end of the housing body 3 a. The inside of the casing 3 is communicated with a not-shown fluid tank for storing the working oil via a not-shown drain pipe. Therefore, the pressure inside the casing 3 is substantially equal to the tank pressure.

An insertion hole 3c through which the shaft 1 is inserted is formed in the cover 3b, and the shaft 1 is rotatably supported by the insertion hole 3c via a bearing 4 a. A power source (not shown) such as an engine is connected to one end 1a of the shaft 1 protruding from the cover 3b to the outside. The end 1b of the other end of the shaft 1 inserted into the housing 3 is accommodated in a shaft accommodating hole 3d provided in the bottom of the housing body 3a, and is rotatably supported in the shaft accommodating hole 3d by a bearing 4 b. A rotary shaft of another hydraulic pump such as a gear pump driven by the power source together with the pump 100 is connected to the other end 1b of the shaft 1.

The cylinder block 2 has a through hole 2a through which the shaft 1 passes, and is spline-coupled to the shaft 1 through the through hole 2 a. Thereby, the cylinder 2 rotates along with the rotation of the shaft 1.

The cylinder 2 is formed with a plurality of cylinders 2b having openings on one end surface thereof in parallel with the shaft 1. The plurality of cylinders 2b are formed with a predetermined interval in the circumferential direction of the cylinder block 2. A cylindrical piston 5 that partitions a volume chamber 6 is inserted into the cylinder 2b so as to be capable of reciprocating. The piston 5 has a distal end side projecting from an opening of the cylinder 2b, and a spherical seat 5a is formed at a distal end portion of the piston 5.

The pump 100 further has: a shoe 7 rotatably connected to the spherical seat 5a of the piston 5 and slidably contacting the spherical seat 5 a; a swash plate 8 that slides in contact with the shoes 7 as the cylinder block 2 rotates; and a valve plate 9 provided between the cylinder block 2 and the bottom surface of the housing main body 3 a.

The shoe 7 includes: a housing portion 7a that houses a spherical seat 5a formed at a tip end of each piston 5; and a circular flat plate portion 7b which is in sliding contact with the sliding contact surface 8a of the swash plate 8. The inner surface of the housing portion 7a is formed into a spherical surface shape and is in sliding contact with the outer surface of the housed spherical seat 5 a. Thereby, the shoe 7 can be angularly displaced in all directions with respect to the spherical seat 5 a.

The swash plate 8 is supported by the cover 3b so as to be tiltable in order to vary the discharge amount of the pump 100.

The valve plate 9 is a circular plate member in which the base end surface of the cylinder block 2 is in sliding contact, and is fixed to the bottom of the casing main body 3 a. The valve plate 9 is formed with an intake port (not shown) for connecting an unillustrated intake passage formed in the cylinder 2 to the volume chamber 6, and a discharge port (not shown) for connecting an unillustrated discharge passage formed in the cylinder 2 to the volume chamber 6.

As shown in fig. 1 and 2, the pump 100 further includes: a first biasing mechanism 20 as a biasing mechanism that biases the swash plate 8 in a direction in which the tilt angle decreases; a second biasing mechanism 30 that biases the swash plate 8 in a direction in which the tilt angle increases; and a regulator 50 that supplies a horsepower control pressure (hereinafter referred to as "control pressure") to the first force application mechanism 20. Fig. 2 is an enlarged cross-sectional view showing a part of a cross section taken along line II-II of fig. 1 in an enlarged manner.

As shown in fig. 1, the first force application mechanism 20 includes: a large diameter piston 22 slidably inserted into a first piston receiving hole 21 formed in the housing body 3a and abutting against the swash plate 8; and a control pressure chamber 23 partitioned by the large diameter piston 22 into the first piston accommodating hole 21.

The control pressure adjusted by the regulator 50 is introduced into the control pressure chamber 23. That is, the large diameter piston 22 of the first biasing mechanism 20 displaces so as to change the tilt angle of the swash plate 8 in accordance with the control pressure supplied from the regulator 50, and biases the swash plate 8 in a direction in which the tilt angle decreases as the control pressure increases.

As shown in fig. 2, the second force application mechanism 30 includes: a small-diameter piston 32 slidably inserted into a second piston receiving hole 31 formed in the housing body 3a and abutting against the swash plate 8; and a pressure chamber 33 partitioned by the small-diameter piston 32 into the second piston accommodating hole 31. Although not shown in fig. 2, of the end portions of the small-diameter pistons 32, the end portion opposite to the end portion facing the pressure chamber 33 is in contact with the swash plate 8.

The discharge pressure of the pump 100 is always led to the pressure chamber 33 through the discharge pressure passage 10 formed in the casing body 3 a. The small-diameter piston 32 of the second biasing mechanism 30 receives the discharge pressure guided to the pressure chamber 33, displaces so as to change the inclination angle of the swash plate 8, and biases the swash plate 8 in a direction in which the inclination angle decreases as the discharge pressure increases.

The large diameter piston 22 has a larger outer diameter than the small diameter piston 32, and the pressure receiving area of the large diameter piston 22 receiving the control pressure led to the control pressure chamber 23 is larger than the pressure receiving area of the small diameter piston 32 receiving the discharge pressure led to the pressure chamber 33.

The regulator 50 is provided to regulate the control pressure introduced into the control pressure chamber 23 mainly in accordance with the discharge pressure of the pump 100, and to control the output of the pump 100, that is, the horsepower required to drive the pump 100.

The regulator 50 has: a feedback pin 40 that is displaced in the axial direction in accordance with the inclination of the swash plate 8; a biasing member 51 that biases the feedback pin 40 toward the swash plate 8; a control spool 52 that moves in accordance with the discharge pressure of the pump 100 and the urging force of the urging member 51 and adjusts the control pressure; a sleeve 60 provided with a spool housing hole 65 for housing the pilot spool 52 and attached to a mounting hole 67 formed in the housing body 3 a; a plug 70 for sealing one end of the spool receiving hole 65 formed in the sleeve 60; one end surface of the cylindrical shaft member 71 is brought into contact with the plug 70, and the other end is inserted into the control spool 52.

The feedback pin 40 is a rod-shaped member, and is slidably inserted into a through-hole 41 formed in the housing main body 3a so as to axially penetrate the through-hole 41. The feedback pin 40 is biased by a biasing member 51 such that one end thereof abuts against the swash plate 8.

The urging member 51 has: the outer spring 51 a; the inner spring 51b has a winding diameter smaller than that of the outer spring 51a, and is disposed inside the outer spring 51 a. The outer spring 51a and the inner spring 51b are coil springs, respectively, and are interposed between a first spring seat 72 and a second spring seat 73, the first spring seat 72 engaging with an end portion of the feedback pin 40 formed in a spherical shape, and the second spring seat 73 engaging with an end portion of the control spool 52.

The natural length (free length) of the outer spring 51a is set to be longer than the natural length of the inner spring 51b, and in a state (state shown in fig. 1) in which the tilt angle of the swash plate 8 is at a maximum, the outer spring 51a is in a state of being compressed between the first spring seat 72 and the second spring seat 73, while the inner spring 51b is in a state of being separated from the spring seat (first spring seat 72 in fig. 1) and floating with either end portion, that is, in a natural length state.

That is, when the tilt angle of the swash plate 8 is decreased from the maximum state, only the outer spring 51a is initially compressed, and when the outer spring 51a is compressed to a state shorter than the natural length of the inner spring 51b, both the outer spring 51a and the inner spring 51b are compressed. Thereby, the elastic forces of the outer spring 51a and the inner spring 51b acting on the swash plate 8 via the feedback pin 40 are gradually increased as the tilt angle of the swash plate 8 becomes smaller.

The mounting hole 67 to which the sleeve 60 is attached is a through-hole formed in the housing main body 3a so that one end thereof opens into the interior of the housing 3 and penetrates in the axial direction, and as shown in fig. 2, a control pressure passage 11 as a first passage for guiding the control pressure to the control pressure chamber 23, a discharge pressure passage 10 as a second passage for guiding the discharge pressure of the pump 100, and a signal pressure passage 13 as a third passage for guiding the signal pressure supplied from the outside are opened in the inner peripheral surface of the mounting hole 67.

The sleeve 60 is a cylindrical member having a spool valve accommodating hole 65 into which the pilot spool 52 is inserted, formed so as to penetrate in the axial direction. As shown in fig. 2, the spool accommodation hole 65 includes: a first hole portion 65a that slidably supports the control spool 52; the second hole portion 65b has a larger inner diameter than the first hole portion 65 a. The spool valve accommodating hole 65 is sealed by screwing the plug 70 to the second hole portion 65 b.

A recovery chamber 66 for recovering the hydraulic oil leaking from the clearance between the sleeve 60 and the pilot spool 52 and the clearance between the pilot spool 52 and the shaft member 71 is provided inside the second hole portion 65b whose open end is sealed by the plug 70. Further, a recovery passage 62 is formed in the sleeve 60 so as to return the working oil recovered in the recovery chamber 66 to the tank. The recovery passage 62 is a plurality of through holes formed so as to penetrate along the axial direction of the sleeve 60 with one end thereof opened in the recovery chamber 66, and the other end of the recovery passage 62 is opened to the inside of the housing 3.

A first port 60a, a second port 60b, and a third port 60c are formed as annular grooves in the outer periphery of the sleeve 60 in this order from the end facing the inside of the housing 3. Further, the sleeve 60 is formed with a first communication hole 61a, a second communication hole 61b, and a third communication hole 61c, which communicate with the first port 60a, the second port 60b, and the third port 60c, respectively, as through holes penetrating in the radial direction. The first communication hole 61a, the second communication hole 61b, and the third communication hole 61c are open on the inner circumferential surface of the first hole 65 a.

In a state where the sleeve 60 is attached to the attachment hole 67, the first port 60a communicates with the control pressure passage 11 that leads the control pressure to the control pressure chamber 23, the second port 60b communicates with the discharge pressure passage 10 that always leads the discharge pressure of the pump 100, and the third port 60c communicates with the signal pressure passage 13. The signal pressure led to the signal pressure passage 13 is, for example, a hydraulic pressure discharged from another pump driven by the power source together with the pump 100, and when the signal pressure is changed, as described later, the inclination angle of the swash plate 8 is changed, and the driving horsepower characteristic of the pump 100 can be changed by changing the amount of the pump 100.

As shown in fig. 2, the pilot spool 52 has: a main body portion 53 slidably supported by the first hole portion 65a of the spool housing hole 65; a flange portion 54 provided at one end of the body portion 53 and having a larger outer diameter than the body portion 53; and a protrusion 55 provided at an end opposite to the flange portion 54 and inserted into the second spring seat 73. The outer diameter of the protruding portion 55 is formed smaller than the main body portion 53, and a stepped surface 55a generated by the difference in outer diameters between the main body portion 53 and the protruding portion 55 abuts against the second spring seat 73.

A first control port 56a, a second control port 56b, and a third control port 56c are formed as annular grooves in the outer periphery of the body portion 53 in this order from the protrusion 55 side. Further, the pilot spool 52 is formed with a first control passage 57a, a second control passage 57b, and a third control passage 57c, which communicate with the first control port 56a, the second control port 56b, and the third control port 56c, respectively, as through holes that penetrate in the radial direction.

Further, an axial passage 58a having one end opened to the distal end surface of the projection 55 and the other end connected to the first control passage 57a is formed in the pilot spool 52 along the axial direction. The axial passage 58a is provided to communicate the first control passage 57a with the inside of the housing 3 together with the connection passage 73a formed in the second spring seat 73. In other words, the first control passage 57a communicates with the inside of the housing 3 via the axial passage 58a and the connection passage 73a, and the pressure in the first control passage 57a is equal to the tank pressure.

In the pilot spool 52, a first insertion hole 58b that opens at an end portion on the plug 70 side and a second insertion hole 58c that is provided continuously with the first insertion hole 58b are formed coaxially along the axial direction. The first insertion hole 58b has a length reaching the third control passage 57c in the axial direction, and the second insertion hole 58c has a length reaching the second control passage 57b in the axial direction. The first insertion hole 58b is formed to have an inner diameter larger than that of the second insertion hole 58c, a large diameter portion 71a formed on the base end side of the shaft member 71 in contact with the plug 70 is slidably inserted into the first insertion hole 58b, and a small diameter portion 71b formed on the tip end side of the shaft member 71 and having a smaller diameter than the large diameter portion 71a is slidably inserted into the second insertion hole 58 c. The shaft member 71 inserted into the control spool 52 is formed of a member different from the plug 70, but may be formed integrally with the plug 70.

As shown in fig. 2, in a state where the flange portion 54 of the control spool 52 is in contact with the plug 70, the second control passage 57b opens in the discharge pressure liquid chamber 59a defined by the second insertion hole 58c and the end surface of the small diameter portion 71b inserted into the second insertion hole 58 c.

Since the second control passage 57b is always communicated with the discharge pressure passage 10 via the second control port 56b, the second communication hole 61b, and the second port 60b, the discharge pressure of the pump 100 is always led to the discharge pressure liquid chamber 59 a. The discharge pressure led into the discharge pressure liquid chamber 59a via the second control passage 57b acts to expand the discharge pressure liquid chamber 59a, that is, to press out the small diameter portion 71b from the second insertion hole 58 c. In other words, the pilot spool 52 is pressed in a direction axially away from the plug 70, that is, in a direction to compress the outer spring 51a and the inner spring 51b, by the pressure of the hydraulic oil guided to the discharge pressure liquid chamber 59 a.

As shown in fig. 2, in a state where the flange portion 54 of the control spool 52 is in contact with the plug 70, the first control passage 57c is opened in the signal pressure liquid chamber 59b defined by the step surface 71c formed by the difference in outer diameters of the large diameter portion 71a and the small diameter portion 71b, the first insertion hole 58b, and the outer peripheral surface of the small diameter portion 71 b.

Since the third control passage 57c is always communicated with the signal pressure passage 13 via the third control port 56c, the third communication hole 61c, and the third port 60c, the signal pressure supplied from the outside is always led to the signal pressure liquid chamber 59 b. The signal pressure led into the signal pressure liquid chamber 59b via the third control passage 57c acts to expand the signal pressure liquid chamber 59b, that is, to press out the large diameter portion 71a from the first insertion hole 58 b. In other words, the pilot spool 52 is pressed in a direction axially away from the plug 70, that is, in a direction to compress the outer spring 51a and the inner spring 51b, by the pressure of the hydraulic oil led to the signal pressure liquid chamber 59 b.

In this way, the pilot spool 52 is biased in a direction away from the swash plate 8 (left direction in fig. 2) by the biasing forces generated by the outer spring 51a and the inner spring 51b, and biased in a direction toward the swash plate 8 (right direction in fig. 2) by the discharge pressure and the signal pressure. That is, the control spool 52 moves relative to the sleeve 60 toward a position where the biasing force of the biasing member 51 configured by the outer spring 51a and the inner spring 51b, the biasing force generated by the discharge pressure of the pump 100 guided to the discharge pressure liquid chamber 59a, and the biasing force generated by the signal pressure guided to the signal pressure liquid chamber 59b are balanced.

Specifically, the control spool 52 moves between two positions, a first position where the flange 54 abuts against a step portion 65c formed between the first hole portion 65a and the second hole portion 65b, and a second position where the flange 54 abuts against the plug 70. Fig. 1 and 2 show a state in which the pilot spool 52 is in the second position. The position of the pilot spool 52 is switched to the first position by the pilot spool 52 moving in the rightward direction in the drawing from the second position shown in fig. 1 and 2.

In the first position, the first communication hole 61a and the second communication hole 61b of the sleeve 60 communicate via the second control port 56b of the pilot spool 52, and the communication of the first control passage 57a and the first communication hole 61a of the pilot spool 52 is cut off. Therefore, at the second position, the discharge pressure of the pump 100 is guided to the control pressure chamber 23 of the first biasing mechanism 20 via the control pressure passage 11 communicating with the first communication hole 61a, and as a result, the inclination angle of the swash plate 8 decreases, and the discharge capacity of the pump 100 decreases.

On the other hand, at the second position, the first communication hole 61a and the first control passage 57a communicate via the first control port 56a, and the communication of the second communication hole 61a and the second communication hole 61b is cut off. Since the first control passage 57a communicates with the inside of the housing 3 via the axial passage 58a and the connection passage 73a as described above, the tank pressure is led to the control pressure chamber 23 via the control pressure passage 11 at the second position, and as a result, the tilt angle of the swash plate 8 increases, and the discharge capacity of the pump 100 increases.

When the position of the pilot spool 52 is switched between the first position and the second position, the first communication hole 61a of the sleeve 60 communicates with both the second communication hole 61b of the sleeve 60 and the first pilot passage 57a of the pilot spool 52. In other words, when the position of the pilot spool 52 is switched between the first position and the second position, the regulator 50 is configured such that the first communication hole 61a is not communicated with any passage, and the pressure is not blocked in the first communication hole 61a and the pilot pressure chamber 23.

Next, the operation of the pump 100 including the regulator 50 configured as described above will be described.

The pump 100 is controlled by the regulator 50 to produce the following characteristics: the relationship between the discharge pressure and the discharge flow rate of the pump 100 is a rated horsepower characteristic having a substantially inverse proportion, that is, a characteristic in which the product of the discharge pressure and the discharge flow rate is substantially constant.

The discharge pressure of the pump 100 increases as, for example, the load of the hydraulic cylinder driven by the discharge pressure of the pump 100 increases. When the discharge pressure of the pump 100 increases from the state where the swash plate 8 is held at the maximum inclination angle, the biasing force of the discharge pressure of the pump 100 acting on the pilot spool 52 becomes higher than the biasing force of the outer spring 51a, and the pilot spool 52 moves from the second position toward the first position.

When the pilot spool 52 moves to the first position, the discharge pressure is led to the pilot pressure chamber 23 via the pilot pressure passage 11 as described above, and therefore the pressure in the pilot pressure chamber 23 rises. Since the pressure in the control pressure chamber 23 rises, the large diameter piston 22 is pushed out from the first piston housing hole 21, and the swash plate 8 is tilted in a direction in which the tilt angle decreases.

When the swash plate 8 tilts in a direction in which the tilt angle decreases, the feedback pin 40 follows the swash plate 8 to move leftward in fig. 1 so as to compress the outer spring 51a and the inner spring 51 b. In other words, when the swash plate 8 tilts in the direction in which the tilt angle decreases, the feedback pin 40 moves so as to increase the biasing force of the outer spring 51a and the inner spring 51b that bias the pilot spool 52 toward the second position.

When the biasing force of the outer spring 51a and the inner spring 51b increases due to compression and the pilot spool 52 is pushed back by the biasing force of the outer spring 51a and the inner spring 51b and moves to the second position, the pilot pressure chamber 23 communicates with the inside of the housing 3 through the pilot pressure passage 11. Therefore, the pressure in the control pressure chamber 23 gradually decreases.

When the pressure in the control pressure chamber 23 decreases, the large diameter piston 22 is pushed back into the first piston receiving hole 21 by the biasing forces of the outer spring 51a and the inner spring 51b acting through the swash plate 8. That is, when the pressure in the control pressure chamber 23 decreases, the swash plate 8 tilts in the direction in which the tilt angle increases, and the biasing forces of the outer spring 51a and the inner spring 51b that bias the control spool 52 decrease. Since the biasing forces of the outer spring 51a and the inner spring 51b are reduced, the pilot spool 52 is moved again to the first position by the discharge pressure of the pump 100, and the swash plate 8 is tilted again in the direction in which the tilt angle is reduced.

The pilot spool 52 repeats such an operation, and stops at a position where the biasing force of the discharge pressure of the pump 100 acting on the pilot spool 52 and the biasing forces of the outer spring 51a and the inner spring 51b are balanced. The swash plate 8 is stopped at a tilt angle at which the biasing force of the large diameter piston 22 and the biasing forces of the outer spring 51a and the inner spring 51b are balanced.

Since the higher the discharge pressure of the pump 100, the higher the pressure in the control pressure chamber 23, the higher the discharge pressure of the pump 100, the smaller the inclination angle of the swash plate 8. Thereby, the discharge capacity of the pump 100 decreases as the discharge pressure of the pump 100 increases.

On the other hand, when the load of the hydraulic cylinder driven by the discharge pressure of the pump 100 is reduced, the discharge pressure of the pump 100 is reduced accordingly. When the discharge pressure of the pump 100 decreases, the biasing force of the discharge pressure of the pump 100 acting on the pilot spool 52 is lower than the biasing forces of the outer spring 51a and the inner spring 51b, and the pilot spool 52 moves from the first position to the second position.

When the pilot spool 52 moves to the second position, as described above, the tank pressure is led to the pilot pressure chamber 23 via the pilot pressure passage 11, and therefore the pressure in the pilot pressure chamber 23 decreases. When the pressure in the control pressure chamber 23 decreases, the large diameter piston 22 is pushed back into the first piston receiving hole 21 by the biasing forces of the outer spring 51a and the inner spring 51b acting through the swash plate 8. As a result, the swash plate 8 tilts in a direction in which the tilt angle increases.

When the swash plate 8 tilts in a direction in which the tilt angle increases, the feedback pin 40 is urged by the outer spring 51a and the inner spring 51b, particularly the outer spring 51a, and moves rightward in fig. 1 following the swash plate 8. In other words, when the swash plate 8 tilts in the direction in which the tilt angle increases, the feedback pin 40 moves so as to decrease the urging forces of the outer spring 51a and the inner spring 51b that urge the pilot spool 52 toward the second position.

The outer spring 51a and the inner spring 51b decrease in biasing force due to the expansion, and when the biasing force of the outer spring 51a and the inner spring 51b acting on the pilot spool 52 is lower than the biasing force generated by the discharge pressure of the pump 100, the pilot spool 52 moves from the second position toward the first position. When the pilot spool 52 moves to the first position by compressing the outer spring 51a and the inner spring 51b, the discharge pressure of the pump 100 is led to the pilot pressure chamber 23 through the pilot pressure passage 11, and therefore the pressure in the pilot pressure chamber 23 gradually increases. However, since the discharge pressure of the pump 100 is reduced, the degree of pressure rise in the control pressure chamber 23 is small as compared with the case where the discharge pressure of the pump 100 is high.

When the pressure in the control pressure chamber 23 increases, the large diameter piston 22 is pushed out from the first piston accommodating hole 21, and the swash plate 8 is tilted in a direction in which the tilt angle decreases. When the swash plate 8 tilts in the direction in which the tilt angle decreases in this way, the biasing forces of the outer spring 51a and the inner spring 51 that bias the pilot spool 52 increase. Since the biasing forces of the outer spring 51a and the inner spring 51b are increased, the pilot spool 52 moves to the second position again, and the swash plate 8 tilts again in the direction in which the tilt angle increases.

The pilot spool 52 repeats such an operation, and stops at a position where the biasing force of the discharge pressure of the pump 100 acting on the pilot spool 52 and the biasing forces of the outer spring 51a and the inner spring 51b are balanced. The swash plate 8 is stopped at a tilt angle at which the biasing force of the large diameter piston 22 and the biasing forces of the outer spring 51a and the inner spring 51b are balanced.

Since the lower the discharge pressure of the pump 100, the lower the pressure in the control pressure chamber 23, the lower the discharge pressure of the pump 100, the larger the inclination angle of the swash plate 8. Thereby, the discharge capacity of the pump 100 increases as the discharge pressure of the pump 100 becomes lower.

As described above, the pump 100 is controlled by the regulator 50 such that the discharge capacity of the pump 100 decreases as the discharge pressure of the pump 100 increases and the discharge capacity of the pump 100 increases as the discharge pressure of the pump 100 decreases, that is, such that the relationship between the discharge pressure and the discharge capacity of the pump 100 is substantially inversely proportional.

In addition to the rated horsepower control described above, a horsepower reduction control is performed to reduce the driving horsepower of the pump 100 in order to avoid a stop of the generator due to overload when an auxiliary machine such as an air conditioner or a generator is driven by an engine (driving source) that drives the pump 100.

Next, the horsepower reduction control performed by the regulator 50 will be described.

When the auxiliary machine is driven by the generator, the signal pressure is supplied to the signal pressure passage 13 from the outside. Specifically, the discharge pressure of a signal pressure generation pump, not shown, serving as a signal pressure supply source is led to the signal pressure passage 13 as a signal pressure via a signal pressure control valve, not shown. The pressure in the signal pressure passage 13 is controlled by the signal pressure control valve in accordance with the driving state of the auxiliary machine, and is controlled to have a signal pressure of a predetermined magnitude while the auxiliary machine is driven by the engine and to be equal to the tank pressure while the auxiliary machine is stopped.

When the auxiliary machine is driven and the signal pressure of the predetermined pressure is supplied to the signal pressure passage 13 via the signal pressure control valve, the supplied signal pressure is guided to the signal pressure liquid chamber 59b via the third communication hole 61c, the third control port 56c, and the third control passage 57c as described above. The pressure led to the signal pressure liquid chamber 59b is the same as the discharge pressure of the pump 100 led to the discharge pressure liquid chamber 59a, and acts to press the control spool 52 in the direction axially away from the plug 70, that is, in the direction compressing the outer spring 51a and the inner spring 51 b.

That is, during the assist engine driving, the control spool 52 is acted upon by the urging force generated by the discharge pressure of the pump 100 led to the discharge pressure liquid chamber 59a, and the urging force generated by the signal pressure led to the signal pressure liquid chamber 59b acts in the direction of moving the control spool 52 to the first position. Therefore, the pilot spool 52 operates in the same manner as in the case where the discharge pressure of the pump 100 increases by a predetermined amount.

Therefore, during the driving of the auxiliary machine, the discharge capacity of the pump 100 is reduced as compared with when the auxiliary machine is stopped, that is, when the pressure in the signal pressure liquid chamber 59b is equal to the tank pressure. Since the drive horsepower of the pump 100 is reduced by reducing the discharge capacity of the pump 100 when the auxiliary machine is driven in this way, the engine can be provided with the horsepower for driving the auxiliary machine.

Here, if the third port 60c for introducing the signal pressure is provided so as to be adjacent to the second port 60b for always introducing the discharge pressure of the pump 100 and the first port 60a for appropriately introducing the discharge pressure of the pump 100, the relatively high-pressure hydraulic oil leaking from the first connection portion 81 as the connection portion between the first port 60a and the control pressure passage 11 and the second connection portion 82 as the connection portion between the second port 60b and the discharge pressure passage 10 may reach the third connection portion 83 as the connection portion between the third port 60c and the signal pressure passage 13 and flow into the third port 60 c.

When relatively high-pressure hydraulic oil is caused to flow into the third port 60c in this way, the pressure in the signal pressure liquid chamber 59b is in a relatively high state, and therefore, even when the signal pressure is not supplied to the third port 60c, that is, even when the auxiliary machine is not driven, the state is the same as the state in which the signal pressure is supplied to the third port 60c, that is, the state in which the auxiliary machine is driven. Therefore, an unexpected control pressure that decreases the discharge capacity is continuously or intermittently supplied from the regulator 50 to the pump 100 via the control pressure passage 11. As a result, the discharge capacity of the pump 100 is unexpectedly reduced or varied, and the operation of the hydraulic equipment to which the hydraulic oil is supplied may be unstable.

In order to avoid this, in the present embodiment, the drain passage 63 communicating with the tank is opened between the first port 60a and the first connection portion 81 and the second port 60b of the control pressure passage 11 and the second connection portion 82 of the discharge pressure passage 10, and between the third port 60c and the third connection portion 83 of the signal pressure passage 13, thereby preventing the relatively high-pressure hydraulic oil leaking from the first connection portion 81 and the second connection portion 82 from reaching the third connection portion 83.

The drain passage 63 will be described below with reference to fig. 2 and 3. Fig. 3 is a cross-sectional view showing a part of a cross section taken along the line III-III in fig. 2 in an enlarged manner.

The drain passage 63 is configured by a fourth port 60d formed as an annular groove on the outer periphery of the sleeve 60, a fourth communication hole 61d as a through hole, and a fourth control port 56 d; the fourth communication hole 61d is formed to penetrate the sleeve 60 in the radial direction, and communicates with the fourth port 60 d; the fourth control port 56d is formed as an annular groove on the outer periphery of the body portion 53 of the pilot spool 52, and is always communicated with the communication hole 61 d.

As shown in fig. 2, the fourth port 60d is disposed between the second port 60b and the third port 60c, and the fourth control port 56d is disposed between the second control port 56b and the third control port 56 c. Thus, one end of the drain passage 63 opens to the outer peripheral surface of the sleeve 60, and the other end opens to a sliding surface between the sleeve 60 and the pilot spool 52.

As shown in fig. 3, a fourth communication hole 61d that communicates the fourth port 60d and the fourth control port 56d is connected to a recovery passage 62 formed so as to penetrate the sleeve 60 in the axial direction. As shown in fig. 3, the recovery passage 62 is provided so as to be spaced apart from the communication holes 61a, 61b, and 61c by a certain distance in the circumferential direction in order to avoid the first communication hole 61a, the second communication hole 61b, and the third communication hole 61c formed to penetrate the sleeve 60 in the radial direction.

The direction in which the fourth communication hole 61d is formed is not limited to the radial direction of the sleeve 60, and may be formed arbitrarily as long as the fourth port 60d and the fourth control port 56d communicate with each other and are connected to the recovery passage 62. Although the fourth communication hole 61d and the recovery passage 62 are not formed in the same cross section of the communication holes 61a, 61b, and 61c and the sleeve 60, the fourth communication hole 61d and the recovery passage 62 are illustrated in a broken line in fig. 2 so that the positional relationship between the fourth communication hole 61d and the recovery passage 62 and the communication holes 61a, 61b, and 61c can be easily understood.

Since the recovery passage 62 is open to the interior of the housing 3 as described above, the drain passage 63 communicates with the interior of the housing 3 communicating with the tank via the recovery passage 62, and the pressure of the drain passage 63 is equal to the tank pressure.

Therefore, by opening the drain passage 63 connected to the recovery passage 62 between the first port 60a and the first connection portion 81 and the second port 60b of the control pressure passage 11 and the second connection portion 82 of the discharge pressure passage 10, and between the third port 60c and the third connection portion 83 of the signal pressure passage 13, the relatively high-pressure working oil leaking from the first connection portion 81 and the second connection portion 82 is guided to the tank through the drain passage 63 and the recovery passage 62 so as not to reach the third connection portion 83.

By thus preventing the relatively high-pressure hydraulic oil leaking from the first connection portion 81 and the second connection portion 82 from flowing into the third port 60c, when the signal pressure is not supplied to the regulator 50 from the outside, it is possible to avoid the situation where the regulator 50 is operated as if the signal pressure is supplied, and as a result, it is possible to prevent an unexpected control pressure from being continuously or intermittently supplied from the regulator 50 to the pump 100. Further, since the control pressure supplied from the regulator 50 to the pump 100 is stable, the discharge capacity and the drive horsepower of the pump 100 are stable, and the operation of the hydraulic equipment to which the hydraulic oil is supplied from the pump 100 and the operation of the drive source such as the engine that drives the pump 100 are also stable.

The drain passage 63 is formed to penetrate the sleeve 60 in the radial direction, and also opens at a sliding surface between the sleeve 60 and the pilot spool 52. Therefore, even if relatively high-pressure hydraulic oil leaks from the portion where the sliding surfaces of the control spool 52 are connected via the sleeve 60, such as the connection portion between the second control port 56b and the first communication hole 61a and the connection portion between the second control port 56b and the second communication hole 61b, the leaked hydraulic oil is guided to the tank via the drain passage 63 (the fourth control port 56d, the fourth communication hole 61d) and the recovery passage 62 so as not to reach the connection portion between the third control port 56c and the third communication hole 61 c.

By thus opening the drain passage 63 also in the inner peripheral surface of the first hole portion 65a of the sleeve 60, the relatively high-pressure working oil is suppressed from flowing into the signal pressure liquid chamber 59 and the third communication hole 61c, the third control port 56c not only through the clearance between the sleeve 60 and the housing main body 3a but also through the clearance between the sleeve 60 and the control spool 52. As a result, it is possible to further reliably prevent the unexpected control pressure from being continuously or intermittently supplied from the regulator 50 to the pump 100.

The drain passage 63 communicates with the tank through a recovery passage 62, and the recovery passage 62 is provided in the sleeve 60 to communicate the recovery chamber 66 with the inside of the housing 3. In this way, by using a passage formed in advance in the sleeve 60, such as the recovery passage 62, and communicating the drain passage 63 with the fluid tank, it is not necessary to separately provide a communication passage for communicating the drain passage 63 with the fluid tank. Therefore, an increase in manufacturing cost due to the addition of the drain passage 63 can be suppressed.

According to the above embodiment, the following effects are obtained.

In the regulator 50 configured as described above, the drain passage 63 communicating with the tank is opened between the first port 60a and the first connection portion 81 of the control pressure passage 11, the second port 60b and the second connection portion 82 of the discharge pressure passage 10, and between the third port 60c and the third connection portion 83 of the signal pressure passage 13. Therefore, even if relatively high-pressure hydraulic oil leaks from the first connection portion 81 or the second connection portion 82, the leaked hydraulic oil flows into the drain passage 63 so as not to reach the third connection portion 83.

With this, when the signal pressure is not supplied to the regulator 50 from the outside, the regulator 50 is prevented from being operated as if the signal pressure was supplied. As a result, it is possible to prevent an unexpected control pressure from being continuously or intermittently supplied from the regulator 50 to the pump 100. Further, since the control pressure supplied from the regulator 50 to the pump 100 is stable, the discharge capacity and the drive horsepower of the pump 100 are stable, and as a result, the operation of the hydraulic equipment to which the hydraulic oil is supplied and the operation of the drive source such as the engine that drives the pump 100 can be stabilized.

In addition, the following modifications are also within the scope of the present invention, and the configurations described in the modifications and the configurations described in the above embodiments may be combined, or the configurations described in the following different modifications may be combined with each other.

In the above embodiment, the pump 100 to which the control pressure is supplied from the regulator 50 is a swash plate type piston pump. The form of the pump 100 is not limited to this, and any form may be used as long as the pump is a pump that changes the capacity by supplying the control pressure from the regulator 50 to the mechanism that changes the capacity, and for example, a variable capacity type vane pump may be used.

In the above embodiment, the drain passage 63 is provided in the sleeve 60. Instead, the drain passage may be provided in the housing main body 3 a. In this case, the drain passage is formed between the discharge pressure passage 10 and the signal pressure passage 13 so as to be open to the inner peripheral surface of the mounting hole 67. In this case, as in the above-described embodiment, even if the relatively high-pressure hydraulic oil leaks from the first connection portion 81 or the second connection portion 82, the leaked hydraulic oil flows into the drain passage provided in the housing main body 3a so as not to reach the third connection portion 83. In order to guide the leaked hydraulic oil to the drain passage, it is preferable that an annular groove communicating with the drain passage is provided on the outer peripheral surface of the sleeve 60 or the inner peripheral surface of the mounting hole 67.

In the above embodiment, the drain passage 63 is connected to the recovery passage 62 formed in the sleeve 60. Instead, a communication passage for communicating the drain passage 63 with the fluid tank or the interior of the housing 3 may be separately provided in the housing main body 3a, for example. In this case, the communication path is formed so as to open to the inner peripheral surface of the mounting hole 67 formed in the housing main body 3a and communicate with the fourth port 60 d.

In the above embodiment, the signal pressure supplied to the signal pressure passage 13 is either one of a signal pressure and a tank pressure, which are predetermined pressures. Alternatively, the signal pressure may be a pressure whose magnitude changes stepwise or steplessly between the signal pressure of the predetermined pressure and the tank pressure. In this case, the discharge capacity of the pump 100 can be changed to an arbitrary size, and the drive horsepower of the pump 100 can be changed to an arbitrary size. Since the driving load of the pump 100 can be appropriately changed in this way, for example, the engine that drives the pump 100 can be operated at a rotation and a load with high efficiency.

In the above embodiment, the regulator 50 performs the power-reducing control, and the signal pressure is supplied only when the auxiliary machine is driven by the engine. Alternatively, for example, in a normal state, a signal pressure of a predetermined pressure is supplied to the signal pressure passage 13 to reduce the driving power of the pump 100, and when there is a margin in the output of the engine or when the flow rate of the hydraulic oil required for the hydraulic equipment is increased, the signal pressure passage 13 may be communicated with the tank, so that when predetermined conditions are met, the discharge capacity of the pump 100 is increased and the driving power of the pump 100 is increased as compared with the normal state. In this way, the regulator 50 may be used not for the purpose of performing the horsepower reducing control but for the purpose of performing the horsepower increasing control.

In the above embodiment, the signal pressure led to the regulator 50 is a biasing force that presses the pilot spool 52 in a direction axially away from the plug 70, that is, in a direction to compress the outer spring 51a and the inner spring 51b, similarly to the discharge pressure of the pump 100. Instead, as in the modification shown in fig. 4, the signal pressure supplied to the regulator 150 may be an urging force that presses the pilot spool 52 in a direction opposite to the discharge pressure of the pump 100.

In the modification shown in fig. 4, the sleeve 60 has a third hole portion 65d, the third hole portion 65d is provided between the first hole portion 65a and the second hole portion 65b, has a larger inner diameter than the first hole portion 65a and a smaller inner diameter than the second hole portion 65b, and the control spool 52 has a second body portion 53a provided between the body portion 53 and the flange portion 54 and slidably supported by the third hole portion 65 d.

In this modification, the signal pressure liquid chamber 59c to which the signal pressure is led is defined by the first hole portion 65a, the third hole portion 65d, a connection surface connecting the first hole portion 65a and the third hole portion 65d, the third control port 56c, the first step surface 53b formed by the difference in outer diameters between the third control port 56c and the second main body portion 53a, and the second step surface 53c formed by the difference in outer diameters between the third control port 56c and the main body portion 53.

The signal pressure led into the thus-defined signal pressure liquid chamber 59c via the signal pressure passage 13 and the third communication hole 61c acts on the first step surface 53b and the second step surface 53c which are opposed to each other in the axial direction. Here, since the outer diameter of the second body portion 53a is larger than the outer diameter of the body portion 53, the area of the first stepped surface 53b formed by the difference in the outer diameters of the third control port 56c and the second body portion 53a is naturally larger than the area of the second stepped surface 53c formed by the difference in the outer diameters of the third control port 56c and the body portion 53.

Since there is a difference between the area of the first step surface 53b and the area of the second step surface 53c in this way, the signal pressure led into the signal pressure liquid chamber 59c acts so as to press the first step surface 53b having a large area, that is, so as to press the second body portion 53a out of the third hole portion 65 d. In other words, the pilot spool 52 is pressed in a direction to approach the plug 70 in the axial direction, that is, in a direction to extend the outer spring 51a and the inner spring 51b, by the pressure of the hydraulic oil guided to the signal pressure liquid chamber 59 c.

As described above, in the modification shown in fig. 4, the signal pressure led to the signal pressure liquid chamber 59c is different from that in the above-described embodiment, and is a biasing force that presses the pilot spool 52 in a direction opposite to the discharge pressure of the pump 100. Therefore, when the signal pressure of the predetermined pressure is led to the signal pressure liquid chamber 59c, the pilot spool 52 operates in the same manner as in the case where the discharge pressure of the pump 100 is reduced by the predetermined magnitude. That is, when a predetermined signal pressure is introduced into the signal pressure liquid chamber 59c, the discharge capacity of the pump 100 increases, and the drive horsepower of the pump 100 increases.

Therefore, in this modification, as in the above-described embodiment, when the horsepower reduction control is performed by the regulator 150, the pressure in the signal pressure passage 13 is controlled by the signal pressure control valve so as to be equal to the tank pressure while the auxiliary machine is driven by the engine, and so as to be equal to the signal pressure of a predetermined magnitude while the auxiliary machine is stopped.

Thereby, the discharge capacity of the pump 100 is reduced during the driving of the auxiliary machine as compared with when the auxiliary machine is stopped. Since the drive horsepower of the pump 100 is reduced by reducing the discharge capacity of the pump 100 when the auxiliary machine is driven in this way, the engine can be provided with the horsepower for driving the auxiliary machine.

In addition, in this modification, the drain passage 63 is also opened between the first connection portion 81 and the second connection portion 82 and the third connection portion 83, and the relatively high-pressure hydraulic oil leaking from the first connection portion 81 and the second connection portion 82 is prevented from flowing into the third port 60c, so that it is possible to prevent an unexpected control pressure, which increases the discharge capacity from the regulator 150 to the pump 100, from being continuously or intermittently supplied. As a result, the discharge capacity of the pump 100 is stabilized, and the operation of the hydraulic equipment to which the hydraulic oil is supplied is also stabilized, as in the above-described embodiment.

In this modification, since the signal pressure of a predetermined magnitude is not supplied to the signal pressure passage 13 due to a failure of the signal pressure control valve or the like, and the drive horsepower of the pump 100 is reduced even if the pressure of the signal pressure passage 13 is equal to the tank pressure, it is possible to avoid a situation where the load of the engine becomes an overload even if the signal pressure is not supplied due to a failure or the like.

Hereinafter, the structure, operation, and effects of the embodiments of the present invention will be summarized.

The regulators 50 and 51 for supplying the control pressure to the pump 100 include: a casing body 3a having a control pressure passage 11 for guiding a control pressure to the pump 100, a discharge pressure passage 10 for guiding a discharge pressure of the pump 100, a signal pressure passage 13 for guiding a signal pressure lower than the discharge pressure for changing a horsepower of the pump 100, and a mounting hole 67 for opening the control pressure passage 11, the discharge pressure passage 10, and the signal pressure passage 13; a sleeve 60 attached to the attachment hole 67 and having a first port 60a communicating with the control pressure passage 11, a second port 60b communicating with the discharge pressure passage 10, and a third port 60c communicating with the signal pressure passage 13; and a pilot spool 52 housed in the sleeve 60 so as to be slidable, and axially displaced in accordance with a discharge pressure supplied through the second port 60b and a signal pressure supplied through the third port 60c so as to allow or block communication between the first port 60a and the second port 60b, wherein a drain passage 63 communicating with a tank storing working oil is provided in either the housing body 3a or the sleeve 60, and the drain passage 63 opens between a second connection portion 82, to which the discharge pressure passage 10 and the second port 60b are connected, and a third connection portion 83, to which the signal pressure passage 13 and the third port 60c are connected.

In this configuration, the drain passage 63 communicating with the tank is opened between the second connection portion 82 of the discharge pressure passage 10 and the second port 60b and the third connection portion 83 of the signal pressure passage 13 and the third port 60 c. Therefore, even if relatively high-pressure hydraulic oil leaks from the second connection portion 82, the leaked hydraulic oil flows into the drain passage 63 so as not to reach the third connection portion 83. With this, when the signal pressure is not supplied to the regulators 50 and 150 from the outside, the regulators 50 and 150 are prevented from operating as if the signal pressure was supplied. As a result, it is possible to prevent an unexpected control pressure from being continuously or intermittently supplied from the regulator 50, 150 to the pump 100. Further, since the control pressure supplied from the regulators 50 and 150 to the pump 100 is stable, the discharge capacity and the drive horsepower of the pump 100 are stable, and as a result, the operation of the hydraulic equipment to which the hydraulic oil is supplied and the operation of the drive source such as the engine that drives the pump 100 can be stabilized.

One end of the drain passage 63 opens to the outer peripheral surface of the sleeve 60, and the other end opens to a sliding surface between the sleeve 60 and the pilot spool 52.

In this configuration, the drain passage 63 opens not only in the outer peripheral surface of the sleeve 60 but also in the sliding surface between the sleeve 60 and the pilot spool 52. This suppresses the relatively high-pressure hydraulic oil from flowing into the third port 60c not only through the clearance between the sleeve 60 and the housing body 3a but also through the clearance between the sleeve 60 and the pilot spool 52. As a result, it is possible to further reliably prevent the unexpected control pressure from being continuously or intermittently supplied from the regulator 50, 150 to the pump 100.

The sleeve 60 is provided with a recovery chamber 66 for recovering the hydraulic oil that leaks through the gap between the pilot spool 52 and the sleeve 60, and a recovery passage for recovering the hydraulic oil recovered in the recovery chamber 66 to the tank, and the drain passage 63 is connected to the recovery passage 62.

In this configuration, the drain passage 63 is connected to the recovery passage 62, and the recovery passage 62 recovers the hydraulic oil that leaks through the gap between the pilot spool 52 and the sleeve 60. In this way, by using a passage formed in advance in the sleeve 60, such as the recovery passage 62, and communicating the drain passage 63 with the fluid tank, it is not necessary to separately provide a communication passage for communicating the drain passage 63 with the fluid tank. Therefore, an increase in manufacturing cost due to the provision of the drain passage 63 can be suppressed.

Although the embodiments of the present invention have been described above, the above embodiments are merely some of application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments.

Claims (3)

1. A pump control pressure regulator for supplying a horsepower control pressure to a pump that controls drive horsepower in accordance with the horsepower control pressure, the pump control pressure regulator comprising:

a casing having a first passage for guiding the horsepower control pressure to the pump, a second passage for guiding a discharge pressure of the pump, a third passage for guiding a signal pressure lower than the discharge pressure for changing the horsepower of the pump, and a mounting hole for opening the first passage, the second passage, and the third passage;

a sleeve that is attached to the attachment hole and that has a first port that communicates with the first passage, a second port that communicates with the second passage, and a third port that communicates with the third passage;

a pilot spool housed in the sleeve so as to be slidable, and displaced in an axial direction in accordance with the discharge pressure supplied via the second port and the signal pressure supplied via the third port, so as to allow or block communication between the first port and the second port,

a drain passage communicating with a fluid tank storing a working fluid is provided in any one of the housing and the sleeve,

the drain passage opens between a second connection portion at which the second passage and the second port are connected and a third connection portion at which the third passage and the third port are connected.

2. The pump control pressure regulator of claim 1,

one end of the drain passage is open to the outer peripheral surface of the sleeve, and the other end is open to a sliding surface between the sleeve and the pilot spool.

3. The pump controlled pressure regulator of claim 1 or 2,

the sleeve is provided with a recovery chamber for recovering the working fluid that leaks through a gap between the control spool and the sleeve, and a recovery passage for recovering the working fluid recovered in the recovery chamber to the fluid tank,

the drain passage is connected to the recovery passage.

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