CN113530904A

CN113530904A - Hydraulic control valve and variable displacement hydraulic pump with same

Info

Publication number: CN113530904A
Application number: CN202010298276.8A
Authority: CN
Inventors: 郑鑫; 王立娟; 金晖; 范腾涛
Original assignee: Danfoss Power Solutions Zhejiang Co Ltd
Current assignee: Danfoss Power Solutions Zhejiang Co Ltd
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2021-10-22

Abstract

The embodiment of the invention discloses a hydraulic control valve and a displacement hydraulic pump. The hydraulic control valve includes a valve body and a valve spool. The valve body includes: a first chamber formed in the valve body on one side in the axial direction of the valve chamber and communicating with the valve chamber, and a first output port and a second output port for outputting a control fluid. The spool is movable relative to the valve body in a first position, from the first position to a second position with a first pressure of the first chamber, and from the second position to a third position with a second pressure of the first chamber greater than the first pressure. The input passage is disconnected from the output port when the spool is in the first position, the input passage is connected to the first output port and disconnected from the second output port when the spool is in the second position, and the input passage is connected to the second output port when the spool is in the third position in a state where the input passage is kept connected to the first output port. The hydraulic control valve can realize a low overshoot function.

Description

Hydraulic control valve and variable displacement hydraulic pump with same

Technical Field

Embodiments of the present invention relate to a hydraulic control valve and a variable displacement hydraulic pump having the same.

Background

Generally, the flow rate of a variable displacement hydraulic pump is controlled by a hydraulic control valve of the variable displacement hydraulic pump. However, current hydraulic control valves are slow to respond and the spool tends to produce a large overshoot during regulation.

Disclosure of Invention

An object of an embodiment of the present invention is to provide a hydraulic control valve and a variable displacement hydraulic pump having the same, whereby, for example, the performance of the hydraulic control valve and the variable displacement hydraulic pump can be improved.

An embodiment of the present invention provides a hydraulic control valve including: a valve body, the valve body comprising: a valve cavity extending in an axial direction in the valve body; a first chamber formed in the valve body on one side in an axial direction of the valve chamber and communicating with the valve chamber; an input channel for inputting a fluid; and a plurality of outlets for outputting a control fluid, the plurality of outlets including a first outlet and a second outlet; and a valve core disposed in the valve cavity of the valve body, wherein: the spool is movable in a first position relative to the valve body from the first position to a second position in a direction away from the first chamber by a first pressure of the first chamber and from the second position to a third position in a direction away from the first chamber by a second pressure of the first chamber that is greater than the first pressure, the input passage being disconnected from the plurality of output ports in the case where the spool is in the first position, the input passage being in communication with a first output port of the plurality of output ports and being disconnected from a second output port of the plurality of output ports in the case where the spool is in the second position, and the input passage being in communication with the second output port of the plurality of output ports in a state where the input passage is kept in communication with the first output port of the plurality of output ports in the case where the spool is in the third position.

According to the embodiment of the invention, the stroke of the valve core is between 0.01 mm and 0.5 mm from the time when the input channel starts to communicate with the first output port to the time when the input channel starts to communicate with the second output port.

According to an embodiment of the invention, the valve body further comprises a return port for returning fluid to the tank, a first of the plurality of output ports is in communication with the return port with the spool in the first position, and the first of the plurality of output ports is disconnected from the return port with the spool in the second and third positions.

According to an embodiment of the present invention, the hydraulic control valve further comprises: an input port for inputting a fluid in communication with the input channel, wherein: the input port is disconnected from the plurality of output ports with the spool in the first position, is connected to a first output port of the plurality of output ports and is disconnected from a second output port of the plurality of output ports with the spool in the second position, and is connected to the second output port of the plurality of output ports with the spool in the third position in a state where the input port is kept connected to the first output port of the plurality of output ports.

According to an embodiment of the invention, the spool comprises: a first end facing the first cavity; a second end opposite the first end; an axial bore extending axially from the first end of the spool to between the first end and the second end; a first recess and a second recess formed on an outer periphery of the valve body; and a first communicating hole and a second communicating hole which respectively communicate the axial hole with the first recess portion and the second recess portion, the first recess portion and the second recess portion respectively form a first working chamber and a second working chamber with an inner wall of the valve chamber of the valve body, the input port communicates with the first working chamber, the input port communicates with a first output port of the plurality of output ports through the first working chamber when the spool is in the second position, and the input port communicates with a second output port of the plurality of output ports through the first working chamber, the first communicating hole, the axial hole, the second communicating hole, and the second working chamber when the spool is in the third position in a state where the input port communicates with the first output port of the plurality of output ports through the first working chamber.

According to an embodiment of the invention, the inlet port communicates with the first chamber through a first working chamber, a first communication hole and an axial hole.

According to an embodiment of the present invention, the valve body further includes a second chamber formed in the valve body on the other side in the axial direction of the valve chamber and communicating with the valve chamber, and the hydraulic control valve further includes: a spring disposed in the second chamber of the valve body for urging the valve spool toward the first chamber of the valve body, and the valve spool is movable relative to the valve body to a first position toward the first chamber under urging of the spring.

According to an embodiment of the present invention, the hydraulic control valve further comprises: a plurality of input ports communicating with the input passage and opening into the valve chamber, the plurality of input ports including a first input port and a second input port, the plurality of input ports being disconnected from the plurality of output ports in a case where the spool is in the first position, the first input port of the plurality of input ports being in communication with the first output port of the plurality of output ports and the plurality of input ports being disconnected from the second output port of the plurality of output ports in a case where the spool is in the second position, and the second input port of the plurality of input ports being in communication with the second output port of the plurality of output ports in a state where the first input port of the plurality of input ports is kept in communication with the first output port of the plurality of output ports in a case where the spool is in the third position.

According to an embodiment of the invention, the spool comprises: a first recess and a second recess formed on an outer periphery of the valve body, the first recess and the second recess forming a first working chamber and a second working chamber, respectively, with an inner wall of a valve chamber of the valve body, a first of the plurality of input ports is in communication with the first working chamber and a second of the plurality of input ports is in communication with the second working chamber, with the spool in the second position, a first of the plurality of input ports is in communication with a first of the plurality of output ports through the first working chamber, and with the spool in the third position, in a state where a first input port of the plurality of input ports is kept in communication with a first output port of the plurality of output ports through the first working chamber, a second of the plurality of input ports communicates with the second of the plurality of output ports through a second working chamber.

Embodiments of the present invention also provide a variable displacement hydraulic pump, comprising: the hydraulic control valve described above; a variable displacement hydraulic pump main body, an output port of which is connected to an input passage of the hydraulic control valve; and a pump servo connected to at least one of the plurality of output ports of the hydraulic control valve to control the displacement of the variable displacement hydraulic pump main body.

According to an embodiment of the present invention, the variable displacement hydraulic pump further comprises: a constant power valve connected to the pump servo for controlling power of the variable displacement hydraulic pump body, the constant power valve comprising: a first input port for inputting fluid in communication with an output port of the variable displacement pump body and a second input port in communication with the first of the plurality of output ports of the pressure control valve; and an output port for outputting fluid, which is connected to the pump servo, wherein the second output port of the plurality of output ports of the hydraulic control valve is directly connected to the pump servo.

With the hydraulic control valve and the variable displacement hydraulic pump having the same according to the embodiments of the present invention, for example, the performance of the hydraulic control valve and the variable displacement hydraulic pump can be improved.

Drawings

FIG. 1 is a schematic cross-sectional view of a hydraulic control valve according to one embodiment of the present invention:

FIG. 2 is a schematic cross-sectional view of a hydraulic control valve according to another embodiment of the present invention:

FIG. 3 is a schematic cross-sectional view of a hydraulic control valve according to yet another embodiment of the present invention:

FIG. 4 is a schematic cross-sectional view of the integrated hydraulic control valve and constant power valve shown in FIG. 1, according to one embodiment of the invention:

FIG. 5 is a schematic cross-sectional view of the integrated hydraulic control valve and constant power valve of FIG. 2 according to another embodiment of the invention:

FIG. 6 is a schematic cross-sectional view of the integrated hydraulic control valve and constant power valve of FIG. 3 according to yet another embodiment of the invention:

FIG. 7 is a diagrammatic, schematic illustration of a variable displacement hydraulic pump according to an embodiment of the present invention;

FIG. 8 is a diagrammatic, schematic illustration of a variable displacement hydraulic pump according to another embodiment of the present invention; and

FIG. 9 is a schematic cross-sectional view of the hydraulic control valve shown in FIG. 1 with the spool in a first position in accordance with an embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view of the hydraulic control valve shown in FIG. 1 with the spool in a second position in accordance with an embodiment of the present invention; and

FIG. 11 is a schematic cross-sectional view of the hydraulic control valve shown in FIG. 1 with the spool in a third position in accordance with an embodiment of the present invention.

Detailed Description

Referring to fig. 1 to 6, and 9 to 11, a hydraulic control valve 100 according to an embodiment of the present invention includes a valve body 10 and a valve spool 20. The valve body 10 includes: a valve chamber 11 extending in the axial direction in the valve body 10; a first chamber 101 formed in the valve body 10 on one side in the axial direction of the valve chamber 11 and communicating with the valve chamber 11; an inlet channel 3 for the inlet of a fluid; and a plurality of

output ports

41, 42 for outputting the control fluid, the plurality of

output ports

41, 42 including a first output port 41 and a second output port 42. The valve spool 20 is disposed in the valve chamber 11 of the valve body 10. Said inlet channel 3 communicates with the first chamber 101, as shown in fig. 1, 3, 4, 6, 9-11, or a separate actuating fluid channel 6 for the inlet of actuating fluid communicates with the first chamber 101, as shown in fig. 2, 5. Referring to fig. 9 to 11, the valve spool 20 is movable relative to the valve body 10 in a first position (see fig. 9), from the first position to a second position (see fig. 10) in a direction away from the first chamber 101 by a first pressure of the first chamber 101, and from the second position to a third position (see fig. 11) in a direction away from the first chamber 101 by a second pressure of the first chamber 101 that is greater than the first pressure. With the spool 20 in the first position (see fig. 9), the input channel 3 is disconnected from the plurality of

output ports

41, 42. In the case where the spool 20 is in the second position (see fig. 10), the input passage 3 is in communication with a first output port 41 of the plurality of

output ports

41, 42 and is disconnected from a second output port 42 of the plurality of

output ports

41, 42, and in the case where the spool 20 is in the third position (see fig. 11), the input passage 3 is in communication with the second output port 42 of the plurality of

output ports

41, 42 while keeping the input passage 3 in communication with the first output port 41 of the plurality of

output ports

41, 42. The valve body 10 further includes a return port 5 for returning the fluid to the tank, a first output port 41 of the plurality of

output ports

41, 42 is in communication with the return port 5 with the valve spool 20 in the first position (see fig. 9), and the first output port 41 of the plurality of

output ports

41, 42 is disconnected from the return port 5, that is, the plurality of

output ports

41, 42 is disconnected from the return port 5 with the valve spool 20 in the second and third positions (see fig. 10, 11). The valve body 10 further includes: an output passage for outputting a control fluid, which communicates with the plurality of output ports 41, 42 (see fig. 7); or a plurality of output channels for outputting the control fluid, which are respectively communicated with the plurality of output ports 41, 42 (see fig. 8).

According to the embodiment of the present invention, referring to fig. 1 to 6 and 9 to 11, from the time when the input passage 3 starts to communicate with the first output port 41 to the time when the input passage 3 starts to communicate with the second output port 42, the stroke of the spool 20 is between 0.01 mm and 0.5 mm.

Referring to fig. 1 to 6, and 9 to 11, according to an embodiment of the present invention, the hydraulic control valve 100 further includes: an inlet 30 to the valve chamber 11 communicating with said inlet channel 3. The input port 30 is disconnected from the plurality of

output ports

41, 42 in the case where the spool 20 is in the first position, the input port 30 is connected to a first output port 41 of the plurality of

output ports

41, 42 and disconnected from a second output port 42 of the plurality of

output ports

41, 42 in the case where the spool 20 is in the second position, and the input port 30 is connected to the second output port 42 of the plurality of

output ports

41, 42 in the state where the input port 30 is kept connected to the first output port 41 of the plurality of

output ports

41, 42 in the case where the spool 20 is in the third position. Referring to fig. 1, the valve cartridge 20 includes: towards the first end 21 of the first chamber 101; a second end 22 opposite the first end 21; an axial bore 23 extending axially from the first end 21 of the spool 20 to between the first and

second ends

21, 22; a first recess 24 and a second recess 25 formed on the outer periphery of the valve spool 20; and a first communication hole 26 and a second communication hole 27 that communicate the axial hole 23 with the first recess 24 and the second recess 25, respectively. The first recessed portion 24 and the second recessed portion 25 form a first working chamber 51 and a second working chamber 52 with the inner wall of the valve chamber 11 of the valve body 10, respectively, and the input port 30 communicates with the first working chamber 51. In the case where the valve spool 20 is in the second position, the input port 30 is communicated with the first output port 41 of the plurality of

output ports

41, 42 through the first working chamber 51, and in the case where the valve spool 20 is in the third position, the input port 30 is communicated with the second output port 42 of the plurality of

output ports

41, 42 through the first working chamber 51, the first communication hole 26, the axial hole 23, the second communication hole 27, and the second working chamber 52, while keeping the input port 30 communicated with the first output port 41 of the plurality of

output ports

41, 42 through the first working chamber 51. Referring to fig. 1 to 3 and 9 to 11, the valve body 20 further includes a third recess 28 formed on an outer periphery of the valve body 20, the third recess 28 and an inner wall of the valve chamber 11 of the valve body 10 form a third working chamber 53, and the third working chamber 53 communicates with the return port 5, and referring to fig. 9, in a case where the valve body 20 is in the first position, the first output port 41 communicates with the third working chamber 53, so that the first output port 41 communicates with the return port 5.

According to some embodiments of the present invention, referring to fig. 1, 4, 9-11, the input port 30 is in communication with the first chamber 101. For example, the inlet port 30 communicates with the first chamber 101 through the first working chamber 51, the first communication hole 26 and the axial hole 23.

According to further embodiments of the invention, referring to fig. 3, a communication channel 35 communicates the inlet channel 3 with said first chamber 101.

According to an embodiment of the present invention, referring to fig. 1 to 6, 9 to 11, the valve body 10 further includes a second chamber 102 formed in the valve body 10 on the other side in the axial direction of the valve chamber 11 and communicating with the valve chamber 11, and the hydraulic control valve 100 further includes: a spring 7, said spring 7 being arranged in the second chamber 102 of the valve body 10 for urging said valve spool 20 towards the first chamber 101 of the valve body 10, and said valve spool 20 being movable relative to the valve body 10 under the urging of said spring 7 towards said first chamber 101 to a first position.

According to some further embodiments of the present invention, referring to fig. 2, 3, 5, 6, the hydraulic control valve 100 further comprises: a plurality of

input ports

31, 32 for inputting fluid, the plurality of

input ports

31, 32 including a first input port 31 and a second input port 32, communicating with the input channel 3. In the case where the spool 20 is in the first position, the plurality of

input ports

31, 32 are disconnected from the plurality of

output ports

41, 42, in the case where the spool 20 is in the second position, the first input port 31 of the plurality of

input ports

31, 32 is connected to the first output port 41 of the plurality of

output ports

41, 42 and the plurality of

input ports

31, 32 is disconnected from the second output port 42 of the plurality of

output ports

41, 42, and in the case where the spool 20 is in the third position, the second input port 32 of the plurality of

input ports

31, 32 is connected to the second output port 42 of the plurality of

output ports

41, 42 in a state where the first input port 31 of the plurality of

input ports

31, 32 is kept connected to the first output port 41 of the plurality of

output ports

41, 42. According to an example of the present invention, the spool 20 includes: a first recessed portion 24 and a second recessed portion 25 formed on an outer periphery of the valve body 20, the first recessed portion 24 and the second recessed portion 25 and an inner wall of the valve chamber 11 of the valve body 10 forming a first working chamber 51 and a second working chamber 52, respectively, a first input port 31 of the plurality of

input ports

31, 32 communicating with the first working chamber 51, and a second input port 32 of the plurality of

input ports

31, 32 communicating with the second working chamber 52. With the spool 20 in the second position, a first input port 31 of the plurality of

input ports

31, 32 is in communication with a first output port 41 of the plurality of

output ports

41, 42 through a first working chamber 51, and with the spool 20 in the third position, a second input port 32 of the plurality of

input ports

31, 32 is in communication with a first output port 41 of the plurality of

output ports

41, 42 through a second working chamber 52, while maintaining the first input port 31 of the plurality of

input ports

31, 32 in communication with the first output port 41 of the plurality of

output ports

41, 42 through the first working chamber 51.

As shown in fig. 7, the variable displacement hydraulic pump 200 according to the embodiment of the present invention includes: the hydraulic control valve 100, the variable displacement hydraulic pump main body 201, and the pump servo 8 described above. An output port of the variable displacement hydraulic pump main body 201 is connected to an input passage 3 of the hydraulic control valve 100. The pump servo 8 is connected to at least one of the plurality of

output ports

41, 42 of the hydraulic control valve 100 to control the displacement of the variable displacement hydraulic pump main body 201.

Referring to fig. 4 and 7, the pressure fluid at the output port of the variable displacement pump main body 201 (e.g., variable displacement plunger pump) is communicated to the input passage 3 through the flow passage in the valve body 10, and enters the first chamber 101 from the input passage 3 through the input port 30, the first working chamber 51, the first communication hole 26 and the axial hole 23. When the left end of the valve core 20 is acted on by the fluid in the first cavity 101, the right end of the valve core 20 is acted on by the spring 7, and when the pressure of the fluid in the first cavity 101 can push the valve core 20 to enable the valve core 20 to be located at the second position, the input port 30 is communicated with the first output port 41 of the

output ports

41 and 42, the hydraulic control valve 100 is acted on, the pressure fluid goes to the control cylinder of the variable displacement pump main body 201, and the displacement of the variable displacement pump main body 201 is reduced. There are some conditions, such as when the external load suddenly rises, that require the displacement of the variable displacement pump body 201 to be rapidly reduced to reduce load shock. If the displacement of the variable displacement pump main body 201 cannot be rapidly reduced and the pressure at the output port of the variable displacement pump main body 201 continues to rise, for example, if it is necessary to rapidly reduce the travel speed of a tool of a machine connected to a hydraulic cylinder by rapidly reducing the displacement of the variable displacement pump main body 201 of the machine, the pressure of the fluid in the first chamber 101 pushes the spool 20 to continue to move to the right, the spool 20 is in the third position, and the input port 30 is communicated with the second output port 42 of the plurality of

output ports

41, 42 while keeping the input port 30 communicated with the first output port 41 of the plurality of

output ports

41, 42. The second output port 42 delivers high pressure fluid to the control cylinder of the variable displacement pump body 201. The control cylinder of the variable displacement pump main body 201 is made to have a more sufficient flow rate, and the variable displacement pump main body 201 is made to have a small displacement more quickly, and the pressure increase amount is reduced.

According to the present embodiment, the first output port 41 can satisfy the demand at the time of steady operation (when the flow rate is stable and small). However, when the system is in dynamic operation, sometimes the required flow rate change is very large, so that the valve core needs to provide a very large flow rate, and at the moment, the valve core stroke has a large overshoot which is to be avoided in the hydraulic system. By providing the second output port 42, when the spool overshoots, the flow rate can be simultaneously output through the first output port 41 and the second output port 42, and thereafter the spool does not rush in a direction away from the first position, whereby the overshoot of the spool stroke can be controlled to a small extent. And when the valve core returns to the steady-state operation, the valve core returns to the state of only being output by the first output port 41.

Referring to fig. 8, it is similar to fig. 7, but the variable displacement hydraulic pump 200 also includes a constant power valve 9. The constant power valve 9 is connected to the pump servo 8, and is configured to control the power of the variable displacement hydraulic pump body 201, for example, to make the power of the variable displacement hydraulic pump body 201 substantially constant. The constant power valve 9 includes: a first input port 91 and a second input port 92 for inputting fluid, and an output port 93 for outputting fluid connected to the pump servo 8, the first input port 91 communicating with an output port of the variable displacement pump main body 201, the second input port 92 communicating with the first output port 41 of the plurality of

output ports

41, 42 of the hydraulic pressure control valve 100. The second output port 42 of the plurality of

output ports

41, 42 of the hydraulic control valve 100 is directly connected to the pump servo 8 without passing through the constant power valve 9.

When the variable displacement hydraulic pump 200 includes the hydraulic control valve 100 and the constant power valve 9, the operation principle of the hydraulic control valve 100 is the same as that of the hydraulic control valve 100 shown in fig. 7. When the pressure of the fluid in the first chamber 101 of the hydraulic control valve 100 is able to push the valve spool 20 to place the valve spool 20 in the second position, the input port 30 is connected to the first output port 41 of the plurality of

output ports

41, 42, and the pressure fluid needs to be input to the control cylinder of the variable displacement pump main body 201 through the constant power valve 9. If the spool of the constant power valve 9 is in the left position in fig. 8, which would block the input of pressure fluid to the control cylinder of the variable displacement pump main body 201, the variable displacement pump main body 201 cannot rapidly decrease the displacement. In the case where the displacement of the variable displacement pump main body 201 cannot be rapidly reduced and the pressure of the output port of the variable displacement pump main body 201 continues to rise, the pressure of the fluid in the first chamber 101 of the hydraulic control valve 100 pushes the spool 20 to continue to move rightward, the spool 20 is in the third position, and the input port 30 is in communication with the second output port 42 of the plurality of

output ports

41, 42 while keeping the input port 30 in communication with the first output port 41 of the plurality of

output ports

41, 42. The second output port 42 delivers high pressure fluid directly (without passing through the constant power valve 9) to the control cylinder of the variable displacement pump body 201. Thereby more quickly bringing the variable displacement pump main body 201 to a small displacement and reducing the pressure increase amount. In addition, the effect of reducing overshoot described in connection with the above embodiment can also be achieved.

The hydraulic control valve 100 and the variable displacement hydraulic variable displacement pump main body 201 according to the embodiment of the invention can realize the low overshoot function. The first output port is a normal output port, and the second output port is an overshoot output port. The starting position of the overshoot output port can be adjusted according to the actual flow demand.

According to the hydraulic control valve 100 and the variable displacement hydraulic variable displacement pump main body 201 provided by the embodiment of the invention, because the plurality of output ports are arranged, the flow gain is improved, and the overshoot of the valve core is reduced. In addition, in normal operation, the first output port 41 operates, and leakage does not increase. When integrated with other valves, the second output port 42 may be directly connected to the control cylinder of the variable displacement pump servo system without interfering with the other valves. This reduces interference with other valves.

Although the

output ports

41, 42 of the hydraulic control valve 100 are described in the above embodiment, the hydraulic control valve 100 may include more output ports, for example, three, four, or more output ports.

Claims

1. A hydraulic control valve comprising:

a valve body, the valve body comprising: a valve cavity extending in an axial direction in the valve body; a first chamber formed in the valve body on one side in an axial direction of the valve chamber and communicating with the valve chamber; an input channel for inputting a fluid; and a plurality of outlets for outputting a control fluid, the plurality of outlets including a first outlet and a second outlet; and

a valve spool disposed in a valve cavity of the valve body, wherein:

the valve spool is movable relative to the valve body in a first position from the first position in a direction away from the first chamber to a second position with a first pressure of the first chamber and from the second position in a direction away from the first chamber to a third position with a second pressure of the first chamber greater than the first pressure,

with the spool in the first position, the input passage is disconnected from the plurality of output ports,

with the spool in the second position, the input passage is open to a first of the plurality of output ports and is open to a second of the plurality of output ports, and

when the spool is in the third position, the input channel is in communication with the second of the plurality of output ports while maintaining the input channel in communication with the first of the plurality of output ports.

2. The hydraulic control valve of claim 1, wherein:

the stroke of the valve core is between 0.01 mm and 0.5 mm from the time when the input channel is communicated with the first output port to the time when the input channel is communicated with the second output port.

3. The hydraulic control valve of claim 1, wherein:

the valve body further includes a return port for returning fluid to the tank, a first of the plurality of output ports being in communication with the return port when the spool is in the first position, and being out of communication with the return port when the spool is in the second and third positions.

4. The hydraulic control valve of claim 1, further comprising:

an input port for inputting a fluid in communication with the input channel, wherein:

with the spool in the first position, the input port is disconnected from the plurality of output ports,

with the spool in the second position, the input port is open to a first of the plurality of output ports and is closed to a second of the plurality of output ports, and

when the spool is in the third position, the input port is communicated with the second one of the plurality of output ports while maintaining the input port in communication with the first one of the plurality of output ports.

5. The hydraulic control valve of claim 4, wherein:

the valve core includes:

a first end facing the first cavity;

a second end opposite the first end;

an axial bore extending axially from the first end of the spool to between the first end and the second end;

a first recess and a second recess formed on an outer periphery of the valve body; and

a first communicating hole and a second communicating hole which respectively communicate the axial hole with the first recess portion and the second recess portion, the first recess portion and the second recess portion and an inner wall of the valve chamber of the valve body respectively forming a first working chamber and a second working chamber, the input port communicating with the first working chamber,

with the spool in the second position, the input port is in communication with a first output port of the plurality of output ports through the first working chamber, and

when the spool is in the third position, the input port is communicated with a first output port of the plurality of output ports through the first working chamber, the first communication hole, the axial hole, the second communication hole, and the second working chamber while maintaining the state in which the input port is communicated with the first output port of the plurality of output ports through the first working chamber.

6. The hydraulic control valve of claim 5, wherein:

the input port is communicated with the first cavity through the first working cavity, the first communication hole and the axial hole.

7. The hydraulic control valve of claim 1 or 3, wherein:

the valve body further includes a second chamber formed in the valve body on the other side in the axial direction of the valve chamber and communicating with the valve chamber, and

the hydraulic control valve further includes: a spring disposed in the second chamber of the valve body for urging the valve spool toward the first chamber of the valve body, and the valve spool is movable relative to the valve body to a first position toward the first chamber under urging of the spring.

8. The hydraulic control valve of claim 1, further comprising:

a plurality of input ports communicating with the input passage and opening into the valve chamber, the plurality of input ports including a first input port and a second input port,

with the spool in the first position, the plurality of input ports are disconnected from the plurality of output ports,

with the spool in the second position, a first of the plurality of input ports is in communication with a first of the plurality of output ports and the plurality of input ports is disconnected from a second of the plurality of output ports, and

with the spool in the third position, a second one of the plurality of input ports is communicated with a second one of the plurality of output ports while maintaining the first one of the plurality of input ports in communication with the first one of the plurality of output ports.

9. The hydraulic control valve of claim 8, wherein:

the valve core includes:

a first recessed portion and a second recessed portion formed on an outer periphery of the spool, the first and second recessed portions and an inner wall of the valve chamber of the valve body forming a first working chamber and a second working chamber, respectively, a first input port of the plurality of input ports communicating with the first working chamber, and a second input port of the plurality of input ports communicating with the second working chamber,

with the spool in the second position, a first of the plurality of input ports is in communication with a first of the plurality of output ports through a first working chamber, and

with the spool in the third position, a second one of the plurality of input ports is communicated with a first one of the plurality of output ports through a second working chamber while maintaining the first one of the plurality of input ports in communication with the first one of the plurality of output ports through the first working chamber.

10. A variable displacement hydraulic pump comprising:

the hydraulic control valve of claims 1 to 9;

a variable displacement hydraulic pump main body, an output port of which is connected to an input passage of the hydraulic control valve; and

a pump servo connected to at least one of the plurality of output ports of the hydraulic control valve to control a displacement of the variable displacement hydraulic pump main body.

11. The variable displacement hydraulic pump of claim 10, further comprising:

a constant power valve connected to the pump servo for controlling power of the variable displacement hydraulic pump body, the constant power valve comprising:

a first input port for inputting fluid, the first input port in communication with an output port of the variable displacement pump body, and a second input port in communication with the first of the plurality of output ports of the hydraulic control valve; and

an output port connected to the pump servo for outputting fluid,

wherein the second output port of the plurality of output ports of the hydraulic control valve is directly connected to the pump servo system.