Plunger pump

Abstract

The present invention relates to the hydraulic technical field, and in particular to a plunger pump. The plunger pump comprises: a swash plate, which is arranged in a pump body; a variable piston, which drives the swash plate to be deflected, the axis of the variable piston being parallel to the axis of the pump body; a power control valve, which is located outside the pump body and on one side of a deflection trajectory of the swash plate, the axis of the power control valve being perpendicular to the axis of the pump body; and a feedback member, which is configured to be parallel to and offset from a deflection axis of the swash plate, one end of the feedback member being connected to the swash plate, and the other end of the feedback member acting on the power control valve. The plunger pump further comprises a flow control valve, wherein the flow control valve is arranged outside the pump body, with the axis of the flow control valve being perpendicular to the axis of the pump body. The technical problem of an existing plunger pump being unable to meet the requirements for both a control method and miniaturization, thus being unable to be mounted on a mini excavator is solved.

Description

[0001] This application claims the priority and benefits of the Chinese Patent Application No. 202311041691.5, which was filed on August 18, 2023, the disclosure of which is incorporated herein by reference in its entirety as part of the present application.TECHNICAL FIELD

[0002] The present invention relates to a field of hydraulic technology, and specifically to a plunger pump.BACKGROUND

[0003] With the changing application environments of construction operations, excavators are required to adapt to perform multi-angle movements in confined spaces, giving rise to mini-excavators. The boom and the working device of the mini-excavator are improved and developed on the basis of a small and medium-sized excavator, but with a smaller volume and a compact structure.

[0004] Excavators often use plunger pumps as power components. Plunger pumps are essential power elements in hydraulic systems, and are used for converting mechanical energy into the hydraulic energy required by the system. A plunger pump is driven by a prime mover such as an engine or a motor, and through the reciprocating motion of the plunger in the cylinder body, it outputs high-pressure oil to convert the mechanical energy of the prime mover into hydraulic energy. Plunger pumps are mainly categorized into axial plunger pumps and radial plunger pumps, among which the axial plunger pumps are further divided into swash-plate type axial plunger pumps and bent-axis type axial plunger pumps. In the current construction machinery market, the axial plunger pumps are widely used in mobile engineering machinery such as excavators, loaders, tractors, and bulldozers due to their high power-to-weight ratio and flexible flow and power control characteristics. Among these, the mini-excavators, owing to their highly compact size, impose requirements for smaller volume and reduced installation space on the installed plunger pumps.

[0005] The document with application number US14719676 discloses an adjustment device for a hydrostatic piston machine and a hydrostatic axial piston machine. The adjustment device includes an adjustment piston and an adjustment valve, which are arranged side by side on a same central axis and inserted into an elongated cavity in the housing body. The adjustment valve has a box-shaped valve housing which is screwed into the housing body, and has a valve hole that extends in a direction of a central axis and allows the valve spool to move in the valve hole.

[0006] The adjustment device in the aforementioned application includes an adjustment piston and an adjustment valve, achieving power regulation with fewer components. However, the adjustment device integrates and coaxially arranges the adjustment piston and the adjustment valve, resulting in an overall long axial length. Even if the adjustment device is inclined relative to the axis of the pump body, the tail end of the adjustment device still extends beyond the axial length of the pump body. However, the axial installation space of a mini excavator is extremely limited, so none of the aforementioned plunger pumps can meet the installation requirements.SUMMARY

[0007] To solve the technical problem that the existing plunger pumps fail to simultaneously meet the requirements for control modes and miniaturization and thus cannot be installed on mini excavators, the present disclosure provides a plunger pump which solves the above mentioned technical problem. The technical solution of the present disclosure is set forth as follows: a plunger pump, including: a swash plate, arranged inside a pump body; a variable displacement piston, driving the swash plate to tilt, an axis of the variable displacement piston is parallel to an axis of the pump body; a power control valve, located outside the pump body and on a side of an tilting path of the swash plate, an axis of the power control valve is perpendicular to the axis of the pump body; a feedback member, the feedback member is arranged parallel to and offset from an tilting axis of the swash plate, one end of the feedback member is connected with the swash plate, and another end of the feedback member acts on the power control valve.

[0008] According to one embodiment of the present disclosure, the plunger pump further includes a flow control valve, the flow control valve is arranged outside the pump body, and an axis of the flow control valve is perpendicular to the axis of the pump body.

[0009] According to one embodiment of the present disclosure, the flow control valve and the power control valve are respectively located on different outer sidewalls of the pump body, and the flow control valve and the power control valve are staggered in an axial direction of the pump body.

[0010] According to one embodiment of the present disclosure, the flow control valve and the power control valve are located on two adjacent outer sidewalls of the pump body.

[0011] According to one embodiment of the present disclosure, control oil of the power control valve enters a variable displacement chamber of the variable displacement piston through the flow control valve.

[0012] According to one embodiment of the present disclosure, the power control valve includes: a power valve body, a first pressure oil passage and a first variable displacement oil passage are formed inside the power valve body, and the first pressure oil passage is connected to pressure oil discharged from the pump body; a power valve sleeve, the power valve sleeve is slidably assembled in the power valve body, the feedback member acts on the power valve sleeve; a power valve spool, power valve spool is slidably assembled in the power valve sleeve, the power valve sleeve and the power valve spool slidably control connection and disconnection between the first pressure oil passage and the first variable displacement oil passage.

[0013] According to an embodiment of the present disclosure, a feedback groove is formed on outer circumference of the power valve sleeve, an end part of the feedback member extends into the feedback groove to push the power valve sleeve, a size of the feedback groove is larger than a size of the end part of the feedback member, and under an action of an elastic member, the end part of the feedback member remains pressed against a wall of the feedback groove.

[0014] According to an embodiment of the present disclosure, an oil drain passage parallel to an axial direction is arranged inside the power valve sleeve, the oil drain passage is in communication with the feedback groove, the feedback groove is in communication with a housing cavity of the plunger pump, and oil at two ends of the power valve sleeve flows through the oil drain passage to the housing cavity of the plunger pump to achieve oil return.

[0015] According to an embodiment of the present disclosure, the flow control valve includes: a flow valve body, a variable displacement oil port and a second variable displacement oil passage are arranged on the flow valve body, the variable displacement oil port is in communication with the first variable displacement oil passage, and the second variable displacement oil passage is in communication with the variable displacement chamber; a load sensing spool and a pressure cut-off spool, the load sensing spool and the pressure cut-off spool are arranged inside the flow valve body, and in an initial state, oil in the first variable displacement oil passage enters the flow valve body through the variable displacement oil port, and then flows through the load sensing spool and the pressure cut-off spool to the second variable displacement oil passage and into the variable displacement chamber.

[0016] According to an embodiment of the present disclosure, a first installation cavity and a second installation cavity arranged side by side are formed within the flow valve body, the load sensing spool is assembled in the first installation cavity, the pressure cut-off spool is assembled in the second installation cavity, the variable displacement oil port is in communication with the first installation cavity, the second variable displacement oil passage is in communication with the second installation cavity, and the first installation cavity is in communication with the second installation cavity through an intermediate passage.

[0017] Based on the above technical solution, the technical effects achieved by the present disclosure are as follows: 1. In the plunger pump of the present disclosure, the variable displacement piston and the power control valve are arranged separately, resulting in a shorter length of the power control valve. The power control valve is located at a side of the tilting path of the swash plate, and the axis of the power control valve is perpendicular to the axis of the pump body, ensuring that the power control valve does not exceed the axial length of the pump body. Due to its reduced length, it also does not exceed the width of the pump body, thereby balancing the requirements of power control and miniaturization of the plunger pump, facilitating installation on the mini-excavators. With the power control valve installed perpendicular to the axis of the pump body, the state of the swash plate is fed back to the power control valve via the feedback member. The feedback member is arranged parallel to and offset from the tilting axis of the swash plate, with one end acting on the swash plate. In the case that the swash plate tilts, the feedback member swings relative to the tilting axis of the swash plate, transmitting the tilting motion of the swash plate to the power control valve, thereby achieving dynamic control of the plunger pump. 2. The plunger pump of the present disclosure further includes a flow control valve, which enables flow control of the plunger pump. The axis of the flow control valve is perpendicular to the axis of the pump body, ensuring that the flow control valve does not exceed the axial length of the pump body, thereby preventing an increase in the overall axial length of the structure. Additionally, the flow control valve and the power control valve are positioned on different outer sidewalls of the pump body and staggered in the axial direction of the pump body, avoiding interference between them. Furthermore, placing the flow control valve and the power control valve on two adjacent outer sidewalls of the pump body facilitates oil flow between them, shortens the length of the oil passages between the flow control valve and the power control valve, and reduces machining difficulty. 3. In the plunger pump of the present disclosure, the control oil from the power control valve enters the variable displacement chamber of the variable displacement piston through the flow control valve, minimizing the need for additional oil passages. A feedback groove is formed on the outer circumference of the power valve sleeve, with a size of the feedback groove is larger than a size of the end part of the feedback member, making it easier for the feedback member to extend into the feedback groove and simplifying assembly. Under the action of the elastic member, the end part of the feedback member remains pressed against the wall of the feedback groove, ensuring accurate transmission of the swash plate's tilting state to the power control valve. Additionally, an oil drain passage is formed in the power valve sleeve, allowing oil from two ends of the power valve sleeve to enter the housing cavity of the plunger pump via the oil drain passage to achieve oil return. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a structural schematic diagram of a plunger pump according to the present embodiment; Fig. 2 is a cross-sectional schematic diagram of a plunger pump; Fig. 3 is a cross-sectional schematic diagram of the plunger pump from a vertical perspective relative to Fig. 2; Fig. 4 is a structural schematic diagram of a plunger pump with a part of the housing removed; Fig. 5 is a cross-sectional schematic diagram of a power control valve on the plunger pump; Fig. 6 is a structural schematic diagram of the power control valve; Fig. 7 is a cross-sectional schematic diagram of the power control valve; Fig. 8 is a cross-sectional schematic diagram of the power valve sleeve; Fig. 9 is a schematic diagram of a left end of the power valve sleeve shown in Fig. 8; Fig. 10 is a schematic diagram of a right end of the power valve sleeve shown in Fig. 8; Fig. 11 is a cross-sectional schematic diagram taken along a line B-B in Fig. 8; Fig. 12 is a cross-sectional schematic diagram taken along a line C-C in Fig. 8; Fig. 13 is a structural schematic diagram of a flow control valve; Fig. 14 is a cross-sectional schematic diagram of a flow control valve; Fig. 15 is a top schematic diagram of a flow control valve; Fig. 16 is a cross-sectional schematic diagram taken along a line D-D in Fig. 15.

[0019] In the figures: 1 - swash plate; 2 - variable displacement piston; 21 - variable displacement chamber; 3 - power control valve; 31 - power valve body; 32 - power valve sleeve; 321 - feedback groove; 322 - first ring groove; 323 - first radial hole; 324 - second ring groove; 325 - second radial hole; 326 - oil drain passage; 33 - power valve spool; 34 - elastic member; 35 - power elastic assembly; 351 - large elastic member; 352 - small elastic member; 36 - power adjustment screw; 37 - pilot valve spool; 38 - proportional pressure reducing valve; 39 - power adjustment nut; 4 - feedback member; 5 - flow control valve; 51 - flow valve body; 511 - variable displacement oil port; 512 - second variable displacement oil passage; 513 - second pressure oil passage; 514 - return oil passage; 515 - intermediate passage; 52 - load sensing spool; 521 - first annular groove; 53 - pressure cut-off spool; 531 - second annular groove; 54 - first elastic assembly; 55 - second elastic assembly; 56 - first adjustment screw; 57 - second adjustment screw; 6 - connection seat; 7 - return piston; 71 - return spring; 10 - pump body; 101 - housing; 102 - end cover; 1021 - inlet port; 1022 - outlet port; 103 - rotating cylinder block; 104 - main shaft.DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. It is apparent that the described embodiments are only a part of the embodiments of the present disclosure, rather than all of them. The following description of at least one exemplary embodiment is merely illustrative and shall not be construed as any limitation on the present disclosure or its application or use. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present disclosure without making creative efforts shall fall within the scope of protection of the present disclosure.

[0021] It should be noted that the terminology used herein is only for describing specific embodiments and is not intended to limit the exemplary embodiments of the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are intended to include the plural forms as well. Furthermore, it should be understood that in a case that the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present disclosure. At the same time, it should be understood that for ease of description, the sizes of various parts shown in the drawings are not drawn according to actual proportional relationships. Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail but should be considered a part of the specification where appropriate. In all examples shown and discussed herein, any specific value should be interpreted as merely illustrative and not restrictive. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further discussion in subsequent drawings.

[0023] In the description of the present disclosure, it should be understood that directional terms such as "front, rear, up, down, left, right," "horizontal, vertical, perpendicular, horizontal," and "top, bottom," etc., generally refer to the orientations or positional relationships shown in the accompanying drawings. These terms are used only for convenience in describing the present disclosure and simplifying the description. Unless otherwise specified, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed or operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the present disclosure. The directional terms "inner, outer" refer to the inside and outside relative to the contour of the respective components.

[0024] For ease of description, spatially relative terms such as "on", "above", "on an upper surface of", "upper" and the like may be used herein to describe the spatial positional relationship between one element or feature and other elements or features as illustrated in the drawings. It should be understood that the spatially relative terms are intended to encompass different orientations of the element in use or operation in addition to the orientation depicted in the drawings. For example, if an element in the drawings is inverted, elements described as "above" or "on top of" other elements or structures would then be oriented "below" or "under" the other elements or structures. Thus, the exemplary term "above" may encompass both an orientation of "above" and "below". The element may also be positioned in other different ways (rotated 90 degrees or at other orientations), and the spatially relative descriptions used herein shall be interpreted accordingly.

[0025] Furthermore, it should be noted that terms such as "first" and "second" are used to define components merely for the purpose of distinguishing between them. Unless otherwise stated, these terms do not carry any special meaning and should not be construed as limiting the scope of protection of the present disclosure.

[0026] As shown in Fig. 1 to Fig. 16, the present embodiment provides a plunger pump, which includes a pump body 10. A swash plate 1 is arranged inside the pump body 10 to adjust the displacement of the plunger pump. A variable displacement piston 2 is also provided inside the pump body 10 to drive the swash plate 1 to tilt. Additionally, a power control valve 3 and a flow control valve 5 are installed on the outer wall of the pump body 10. The power control valve 3 enables power control of the plunger pump, while the flow control valve 5 enables flow control of the plunger pump.

[0027] The pump body 10 includes a housing 101, and an end cover 102 is provided at the opening of the housing 101. The housing 101 and the end cover 102 form a relatively sealed internal space, and a rotating cylinder block 103 is accommodated in the internal space. A main shaft 104 is assembled along the central axis of the rotating cylinder block 103, one end of the main shaft 104 extends out of the end of the housing 101 away from the end cover 102.

[0028] A swash plate 1 is also arranged inside the pump body 10. The tilt of the swash plate 1 controls the displacement of the plunger pump. Additionally, a variable displacement piston 2 is provided inside the pump body 10 to drive the swash plate 1 to tilt.

[0029] As a preferred technical solution of the present embodiment, the variable displacement piston 2 is arranged parallel to an axis of the pump body 10. In the case that control oil enters the variable displacement chamber 21, the control oil can push the variable displacement piston 2 to extend, thereby driving the swash plate 1 to tilt.

[0030] As a preferred technical solution of the present embodiment, a return piston 7 is also provided. The return piston 7 is positioned opposite the variable displacement piston 2, and the return piston 7 acts on the other end of the swash plate 1. A return spring 71 is sleeved outside the return piston 7. Under the action of the return spring 71, the return piston 7 provides a resetting function for the swash plate 1.

[0031] As a preferred technical solution of the present embodiment, an inlet port 1021 and an outlet port 1022 are provided on the end cover 102. The rotating cylinder block 103 rotates to alternately connect the inlet port 1021 and the outlet port 1022.

[0032] The power control valve 3 is arranged outside the pump body 10. Specifically, the power control valve 3 is installed on the outer wall of the housing 101, an axis of the power control valve 3 is perpendicular to an axis of the pump body 10. The power control valve 3 does not extend beyond an axial range of the pump body 10.

[0033] The power control valve 3 includes a power valve body 31, a power valve sleeve 32, and a power valve spool 33. An installation cavity is formed in the power valve body 31. The power valve sleeve 32 is slidably assembled in the installation cavity of the power valve body 31, and the power valve spool 33 is slidably assembled in the power valve sleeve 32. A power adjustment assembly is provided at an end of the power valve spool 33, and a pilot assembly is provided at another end of the power valve spool 33. A first pressure oil passage and a first variable displacement oil passage are formed in the power valve body 31. A feedback groove 321, a first ring groove 322, and a second ring groove 324 are formed on the power valve sleeve 32. The first ring groove 322 is in communication with a central hole of the power valve sleeve 32 through a plurality of first radial holes 323, and the second ring groove 324 is in communication with the central hole of the power valve sleeve 32 via a plurality of second radial holes 325. The first pressure oil passage is connected to pressure oil discharged from the pump body 10. The first ring groove 322 remains in communication with the first pressure oil passage, and the second ring groove 324 remains in communication with the first variable displacement oil passage. The feedback groove 321 remains in communication with a housing cavity of the plunger pump to achieve oil return.

[0034] As a preferred technical solution of the present embodiment, the first radial holes 323 and the second radial holes 325 may be provided in numbers of 2 to 4 respectively. All the first radial holes 323 are uniformly arranged circumferentially, and all the second radial holes 325 are uniformly arranged circumferentially.

[0035] As a preferred technical solution of the present embodiment, the feedback groove 321 is located between the first ring groove 322 and the second ring groove 324. An oil drain passage 326 parallel to the axis is formed in the power valve sleeve 32, the oil drain passage 326 extends to two end faces of the power valve sleeve 32 and communicates with the feedback groove 321. Preferably, drainage grooves are formed on two end faces of the power valve sleeve 32, allowing oil to enter the oil drain passage 326 via the drainage grooves and then return through the feedback groove 321.

[0036] As a preferred technical solution of the present embodiment, the power adjustment assembly includes a power elastic assembly 35, a power adjustment screw 36, and a power adjustment nut 39. The power elastic assembly 35 includes a large elastic member 351 and a small elastic member 352 which are sleeved one on the other. One end of the large elastic member 351 and one end of the small elastic member 352 act on the power valve sleeve 32 and the power valve spool 33 via a spring seat. The power adjustment nut 39 is threadedly assembled onto the power valve body 31 and abuts against the other end of the large elastic member 351. The power adjustment screw 36 is threadedly assembled into the power adjustment nut 39 and abuts against the other end of the small elastic member 352. The pre-compression of the large elastic member 351 can be adjusted by adjusting the position of the power adjustment nut 39 on the power valve body 31, and the pre-compression of the small elastic member 352 can be adjusted by adjusting the position of the power adjustment screw 36 in the power adjustment nut 39.

[0037] As a preferred technical solution of the present embodiment, the pilot assembly includes a pilot valve spool 37 and a proportional pressure reducing valve 38. The pilot valve spool 37 acts on the power valve spool 33 under the action of the proportional pressure reducing valve 38.

[0038] The power control valve 3 is located at a side of the tilting path of the swash plate 1, and the feedback member 4 transmits the tilt of the swash plate 1 to the power control valve 3. Specifically, the feedback member 4 is arranged parallel to and offset from the tilting axis of the swash plate 1. One end of the feedback member 4 is connected to the swash plate 1 via a connection seat 6, while the other end of the feedback member 4 acts on the power valve sleeve 32. During operation, the first pressure oil passage is in communication with the outlet port 1022 on the end cover 102. Pressure oil discharged from the pump body 10 enters the first pressure oil passage, flows to the region between the power valve spool 33 and the power valve sleeve 32 via the first ring groove 322 and the first radial holes 323 on the power valve sleeve 32. As the diameter of the central hole of the power valve sleeve 32 changes, the pressure oil acts on the power valve spool 33, causing the power valve spool 33 to slide against the force of the power elastic assembly 35. The power valve spool 33 controls the communication between the first radial holes 323 and the second radial holes 325, allowing pressure oil to enter the variable displacement chamber 21 of the variable displacement piston 2 through the first variable displacement oil passage, thereby driving the swash plate 1 to tilt. The tilt of the swash plate 1 is then fed back to the power valve sleeve 32 via the feedback member 4, causing the power valve sleeve 32 to slide along the sliding direction of the power valve spool 33, thereby disconnecting the communication between the first radial holes 323 and the second radial holes 325. This process repeats to achieve dynamic balance.

[0039] As a preferred technical solution of the present embodiment, the feedback member 4 and the connection seat 6 may be separate components fixed together or integrated as a single structure. The key requirement is to ensure that the feedback member 4 is parallel to and offset from the tilting axis of the swash plate 1, allowing it to tilt under the drive of the swash plate 1 and thereby driving the power valve sleeve 32 to slide.

[0040] As a preferred technical solution of the present embodiment, an end part of the feedback member 4 extends into a feedback groove 321. In a case that the swash plate 1 tilts, the feedback member 4 tilts accordingly, driving the power valve sleeve 32 to move axially along its own axis.

[0041] As a preferred technical solution of the present embodiment, a size of the feedback groove 321 is larger than a size of the end part of the feedback member 4, allowing the end part of the feedback member 4 to easily extend into the feedback groove 321 and reducing assembly difficulty. To prevent the end part of the feedback member 4 from shaking in the feedback groove 321, an elastic member 34 is also provided. The elastic member 34 acts on the power valve sleeve 32, ensuring that the end part of the feedback member 4 remains pressed against the wall of the feedback groove 321, thereby fixing their relative positions. Preferably, the elastic member 34 is located at a side where the pilot valve spool 37 is located, and the elastic member 34 is sleeved over the pilot valve spool 37. One end of the elastic member 34 abuts against the power valve sleeve 32, while the other end of the elastic member 34 abuts against the proportional pressure reducing valve 38.

[0042] Additionally, a flow control valve 5 is provided, the flow control valve 5 enables flow control of the pump body 10. The flow control valve 5 is assembled outside the pump body 10 and includes a flow valve body 51. A first installation cavity and a second installation cavity, arranged side by side, are formed in the flow valve body 51. A load sensing spool 52 is assembled in the first installation cavity, and a pressure cut-off spool 53 is assembled in the second installation cavity. A first elastic assembly 54 is also installed in the first installation cavity, and the first elastic assembly 54 acts on the load sensing spool 52. Pressure oil pushes the load sensing spool 52 to slide against the force of the first elastic assembly 54. A second elastic assembly 55 is installed in the second installation cavity, and the second elastic assembly 55 acts on the pressure cut-off spool 53. Pressure oil pushes the pressure cut-off spool 53 to slide against the force of the second elastic assembly 55.

[0043] The flow valve body 51 is further formed with a variable displacement oil port 511, a second variable displacement oil passage 512, a second pressure oil passage 513, and a return oil passage 514. The variable displacement oil port 511 is in communication with the first installation cavity and is used to receive variable oil flowing in from the first variable displacement oil passage. The variable oil flows through the variable displacement oil port 511 to the first installation cavity. One end of the second variable displacement oil passage 512 is in communication with the second installation cavity, and the other end of the second variable displacement oil passage 512 is in communication with the variable displacement chamber 21. The first installation cavity and the second installation cavity are in communication with each other through an intermediate passage 515. The second pressure oil passage 513 is in communication with the outlet port 1022 of the pump body 10 to draw off the pressure oil discharged by the plunger pump, and the second pressure oil passage 513 is also in communication with both the first installation cavity and the second installation cavity. The return oil passage 514 is in communication with the second installation cavity. In the initial state, the variable oil from the first variable displacement oil passage enters the first installation cavity through the variable displacement oil port 511, then flows to the second installation cavity via the intermediate passage 515, and finally flows into the variable displacement chamber 21 through the second variable displacement oil passage 512, thereby pushing the swash plate 1 to tilt.

[0044] As a preferred technical solution of the present embodiment, both the first elastic assembly 54 and the second elastic assembly 55 include two spring members sleeved one inside the other. A first adjustment screw 56 and a second adjustment screw 57 are also assembled on the flow valve body 51. The first adjustment screw 56 can adjust the pre-compression of the first elastic assembly 54, and the second adjustment screw 57 can adjust the pre-compression of the second elastic assembly 55. Specifically, the two installation cavities in the flow valve body 51 are through-holes. One end of the flow valve body 51 is fixed with an end seat, on which the first adjustment screw 56 and the second adjustment screw 57 are assembled to adjust the pre-compression of the first elastic assembly and the second elastic assembly. The other end of the flow valve body 51 is provided with a plug corresponding to each of the installation cavities.

[0045] As a preferred technical solution of the present embodiment, a first annular groove 521 is formed on the outer surface of the load sensing spool 52, and a second annular groove 531 is formed on the outer surface of the pressure cut-off spool 53. In the initial state, the load sensing spool 52 is pressed against the plug under the action of the first elastic assembly 54, and the pressure cut-off spool 53 is pressed against the plug under the action of the second elastic assembly 55. At this time, the first annular groove 521 is in communication with the second annular groove 531 via the intermediate passage 515. The variable oil from the power control valve 3 enters the first annular groove 521 through the variable displacement oil port 511, then flows to the second annular groove 531 via the intermediate passage 515, and finally flows into the variable displacement chamber 21 through the second variable displacement oil passage 512.

[0046] As a preferred technical solution of the present embodiment, the pressure set by the first elastic assembly 54 is the lowest, the pressure set by the power elastic assembly 35 is intermediate, and the pressure set by the second elastic assembly 55 is the highest. For example, in the case that the pressure of the pressure oil is between 0 MPa to14 MPa, it can only push the load sensing spool 52 to slide against the force of the first elastic assembly 54 and cannot actuate the power valve spool 33 or the pressure cut-off spool 53. At this time, the load sensing spool 52 is operational and determines the tilting angle of the swash plate 1. In the case that the pressure of the pressure oil is between 14 MPa to 28 MPa (without reaching 28 MPa), the pressure oil can push the power valve spool 33 to slide against the force of the power elastic assembly 35. In this case, the power control valve 3 is operational and determines the tilting angle of the swash plate 1, which maintains a constant product of the plunger pump's flow rate and pressure, that is the power is unchanged. In the case that the pressure of the pressure oil reaches 28 MPa, the pressure oil pushes the pressure cut-off spool 53 to slide against the force of the second elastic assembly 55, and the pressure cut-off spool 53 becomes operational at this time.

[0047] As a preferred technical solution of the present embodiment, in order to ensure that the load sensing spool 52 remains in its initial position during the operation of the power control valve 3, a control oil port is also provided on the flow valve body 51. The control oil port is in communication with the installation cavity where the first elastic assembly 54 is located. By introducing control oil through the control oil port to act on the load sensing spool 52, it can be kept pressed against the plug, which allows the variable oil from the power control valve 3 to flow to the variable displacement chamber 21 via the flow control valve 5.

[0048] As a preferred technical solution of the present embodiment, the flow control valve 5 is assembled on the sidewall of the end cover 102 of the pump body 10. The axis of the flow control valve 5 is perpendicular to the axis of the pump body 10, which ensures that the flow control valve 5 does not extend beyond the axial range of the pump body 10. Preferably, the flow control valve 5 and the power control valve 3 are located on different sidewalls of the pump body 10. More preferably, the flow control valve 5 and the power control valve 3 can be located on two adjacent sidewalls of the pump body 10 close to the outlet port 1022, which facilitates the connection of the outlet port 1022 to both the flow control valve 5 and the power control valve 3, thereby shortening the length of the oil passage.

[0049] Based on the above technical solution, the working principle of the plunger pump in the present embodiment is as follows: in the case that the oil pressure at the outlet port 1022 of the pump body 10 reaches the pressure set by the first elastic assembly 54, it can only push the load sensing spool 52 to slide against the force of the first elastic assembly 54. The power valve spool 33 and the pressure cut-off spool 53 remain inactive. The pressure oil pushes the load sensing spool 52 to slide. Under the control of the load sensing spool 52, the second pressure oil passage 513 is in communication with the intermediate passage 515. The pressure oil then flows through the intermediate passage 515, the second annular groove 531 of the pressure cut-off spool 53, and the second variable displacement oil passage 512 into the variable displacement chamber 21, pushing the variable displacement piston 2 to extend and drive the swash plate 1 to tilt to a smaller tilting angle. As a result, the displacement of the plunger pump decreases, achieving displacement control of the plunger pump.

[0050] In the case that the oil pressure at the outlet port 1022 of the pump body 10 reaches the pressure set by the power elastic assembly 35, control oil is introduced through the control oil port of the flow control valve 5 to keep the load sensing spool 52 in its initial position. The pressure oil pushes the power valve spool 33 to slide against the force of the power elastic assembly 35, establishing communication between the first radial holes 323 and the second radial holes 325. The pressure oil enters the first variable displacement oil passage via the first pressure oil passage and then flows into the variable displacement chamber 21 through the flow control valve 5, pushing the variable displacement piston 2 to extend. Under the action of the variable displacement piston 2, the swash plate 1 begins to tilt to a smaller tilting angle, thereby reducing the displacement of the plunger pump and maintaining a constant P*Q, that is the power is unchanged. During the process of the swash plate oscillating toward the smaller angle, the feedback member 4 installed on the swash plate 1 tilts accordingly. As the feedback member 4 tilts, the power valve sleeve 32 slides along the sliding direction of the power valve spool 33 until the second radial holes 325 is in communication with the end face between the power valve spool 33 and the power valve sleeve 32 (i.e., communicating with the housing cavity of the plunger pump via the oil drain passage 326 and the feedback groove 321). At this point, the variable displacement chamber 21 of the plunger pump maintains a certain pressure, and the variable mechanism including the variable displacement piston 2, the swash plate 1, the power valve spool 33, and the power valve sleeve 32 remains in dynamic equilibrium. The plunger pump operates at a stable displacement while consistently maintaining a constant P*Q, that is the power is unchanged.

[0051] In the case that the oil pressure at the outlet port 1022 of the pump body 10 reaches the pressure set by the second elastic assembly 55, the pressure oil pushes the pressure cut-off spool 53 to slide. The second pressure oil passage 513 is in communication with the second variable passage 512 via the pressure cut-off spool 53, allowing pressure oil to enter the variable displacement chamber 21 of the variable displacement piston 2, which pushes the variable displacement piston 2 to extend, causing the swash plate 1 to tilt to a smaller tilting angle under the action of the variable displacement piston 2, thereby reducing the displacement of the plunger pump.

[0052] The implementation methods of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the aforementioned implementation methods. Within the scope of knowledge possessed by those skilled in the art, various modifications may be made without departing from the essence of the present disclosure.

Claims

1. A plunger pump, which is characterized in that, the plunger pump comprises: a swash plate (1), arranged inside a pump body (10); a variable displacement piston (2), driving the swash plate (1) to tilt, wherein an axis of the variable displacement piston (2) is parallel to an axis of the pump body (10); a power control valve (3), located outside the pump body (10) and on a side of an tilting path of the swash plate (1), wherein an axis of the power control valve (3) is perpendicular to the axis of the pump body (10); a feedback member (4), wherein the feedback member (4) is arranged parallel to and offset from a tilting axis of the swash plate (1), one end of the feedback member (4) is connected with the swash plate (1), and another end of the feedback member (4) acts on the power control valve (3).

2. The plunger pump according to claim 1, which is characterized in that, the plunger pump further comprises a flow control valve (5), wherein the flow control valve (5) is arranged outside the pump body (10), and an axis of the flow control valve (5) is perpendicular to the axis of the pump body (10).

3. The plunger pump according to claim 2, which is characterized in that, the flow control valve (5) and the power control valve (3) are respectively located on different outer sidewalls of the pump body (10), and the flow control valve (5) and the power control valve (3) are staggered in an axial direction of the pump body (10).

4. The plunger pump according to claim 3, which is characterized in that, the flow control valve (5) and the power control valve (3) are located on two adjacent outer sidewalls of the pump body (10).

5. The plunger pump according to any one of claims 2 to 4, which is characterized in that, control oil of the power control valve (3) enters a variable displacement chamber (21) of the variable displacement piston (2) through the flow control valve (5).

6. The plunger pump according to claim 5, which is characterized in that, the power control valve (3) comprises: a power valve body (31), wherein a first pressure oil passage and a first variable displacement oil passage are formed inside the power valve body (31), and the first pressure oil passage is connected to pressure oil discharged from the pump body (10); a power valve sleeve (32), wherein the power valve sleeve (32) is slidably assembled in the power valve body (31), and the feedback member (4) acts on the power valve sleeve (32); a power valve spool (33), wherein the power valve spool (33) is slidably assembled in the power valve sleeve (32), the power valve sleeve (32) and the power valve spool (33) slidably control connection and disconnection between the first pressure oil passage and the first variable displacement oil passage.

7. The plunger pump according to claim 6, which is characterized in that, a feedback groove (321) is formed on outer circumference of the power valve sleeve (32), an end part of the feedback member (4) extends into the feedback groove (321) to push the power valve sleeve (32), a size of the feedback groove (321) is larger than a size of the end part of the feedback member (4), and under an action of an elastic member (34), the end part of the feedback member (4) remains pressed against a wall of the feedback groove (321).

8. The plunger pump according to claim 6, which is characterized in that, an oil drain passage (326) parallel to an axial direction is arranged inside the power valve sleeve (32), the oil drain passage (326) is in communication with the feedback groove (321), the feedback groove (321) is in communication with a housing cavity of the plunger pump, and oil at two ends of the power valve sleeve (32) flows through the oil drain passage (326) to the housing cavity of the plunger pump to achieve oil return.

9. The plunger pump according to claim 5, which is characterized in that, the flow control valve (5) comprises: a flow valve body (51), wherein a variable displacement oil port (511) and a second variable displacement oil passage (512) are arranged on the flow valve body (51), the variable displacement oil port (511) is in communication with the first variable displacement oil passage, and the second variable displacement oil passage (512) is in communication with the variable displacement chamber (21); a load sensing spool (52) and a pressure cut-off spool (53), wherein the load sensing spool (52) and the pressure cut-off spool (53) are arranged inside the flow valve body (51), and in an initial state, oil in the first variable displacement oil passage enters the flow valve body (51) through the variable displacement oil port (511), and then flows through the load sensing spool (52) and the pressure cut-off spool (53) to the second variable displacement oil passage (512) and into the variable displacement chamber (21).

10. The plunger pump according to claim 9, which is characterized in that, a first installation cavity and a second installation cavity arranged side by side are formed within the flow valve body (51), the load sensing spool (52) is assembled in the first installation cavity, the pressure cut-off spool (53) is assembled in the second installation cavity, the variable displacement oil port (511) is in communication with the first installation cavity, the second variable displacement oil passage (512) is in communication with the second installation cavity, and the first installation cavity is in communication with the second installation cavity through an intermediate passage (515).

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