Plunger pump

Abstract

The present invention relates to the field of hydraulic technology, and more specifically to a plunger pump. The plunger pump includes a swash plate installed inside the pump body, a variable piston that drives the swash plate to oscillate and whose axis is parallel to the axis of the pump body, an output control valve located outside the pump body and on one side of the oscillation path of the swash plate, whose axis is perpendicular to the axis of the pump body, and a feedback member installed parallel and offset from the oscillation axis of the swash plate, with one end connected to the swash plate and the other end acting on the output control valve. The invention further includes a flow control valve installed outside the pump body and whose axis is perpendicular to the axis of the pump body. The invention solves the technical problem that conventional plunger pumps cannot be mounted on mini excavators because they cannot satisfy both the control method requirements and the miniaturization requirements.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic technology, and specifically to a plunger pump.

Background Art

[0002] With the change of the applicable land for construction work, mini excavators have emerged because excavators need to be able to adapt to multi-angle operations in narrow spaces. Both the arms and operating devices of mini excavators are improvements and developments of medium and small excavators, but they are smaller in volume and more compact in structure.

[0003] Excavators generally use a plunger pump as a power element. The plunger pump is an important power element of the hydraulic device and is used to convert mechanical energy into the required hydraulic energy in the system. The plunger pump is driven by a prime mover such as an engine or a motor. By reciprocating the plunger in the cylinder block to output high-pressure oil, the mechanical energy of the prime mover is converted into hydraulic energy. The plunger pump is mainly classified into an axial plunger pump and a radial plunger pump, and the axial plunger pump is further classified into an inclined plate type axial plunger pump and an inclined shaft type axial plunger pump. In the conventional construction machinery market, the axial plunger pump has a very high output-to-weight ratio and flexible flow rate and output control characteristics, so it is widely applied to mobile construction machinery such as excavators, loaders, tractors, and bulldozers. Due to the very compact volume of the mini excavator, the plunger pump installed on it is required to have a smaller volume and a smaller mounting space.

[0004] The document in application number US14719676 discloses an adjustment device for a hydrostatic piston machine and a hydrostatic axial piston machine, the adjustment device comprising an adjustment piston and an adjustment valve, the adjustment piston and adjustment valve being mounted in parallel on the same central axis and inserted into an elongated chamber of a housing body. The adjustment valve has a box-shaped valve housing, the valve housing being screwed into the housing body and having a valve bore, the valve bore extending in the direction of the central axis, and the valve core being movable within the valve bore.

[0005] The adjustment device in the above application includes an adjustment piston and an adjustment valve, and can achieve output adjustment with fewer devices. However, because the adjustment device integrates the adjustment piston and adjustment valve and is installed coaxially, the overall axial length is long, and even if the adjustment device is inclined with respect to the axis of the pump body, the end of the adjustment device exceeds the axial length of the pump body. On the other hand, the axial mounting space of the mini excavator is very limited, so none of the above plunger pumps can meet the installation requirements. [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventional plunger pumps cannot meet both the control system requirements and the miniaturization requirements, and therefore cannot be attached to mini excavators. To solve this technical problem, the present invention provides a plunger pump that solves the above technical problem. The technical solution of the present invention is as follows. [Means for solving the problem]

[0007] It is a plunger pump, A swashplate installed inside the pump body, A variable piston, whose axis is parallel to the axis of the pump body, drives the swash plate to swing, An output control valve located outside the pump body, positioned on one side of the oscillation path of the swash plate, with its axis perpendicular to the axis of the pump body, The system includes a feedback member that is installed parallel to and offset from the oscillation axis of the swash plate, with one end connected to the swash plate and the other end acting on the output control valve.

[0008] In one embodiment of the present invention, a flow control valve is further included, which is installed outside the pump body and whose axis is perpendicular to the axis of the pump body.

[0009] In one embodiment of the present invention, the flow control valve and the output control valve are each located on different outer walls of the pump body, and the flow control valve and the output control valve are installed offset from each other in the axial direction of the pump body.

[0010] In one embodiment of the present invention, the flow control valve and the output control valve are located on two adjacent outer walls of the pump body.

[0011] In one embodiment of the present invention, the control oil of the output control valve enters the variable chamber of the variable piston via the flow control valve.

[0012] In one embodiment of the present invention, the output control valve is An output valve body is formed inside, with a first pressure oil passage and a first variable oil passage, and pressurized oil discharged from the pump body is introduced into the first pressure oil passage. An output valve sleeve slidably assembled within the output valve body, wherein the feedback member acts on the output valve sleeve, The output valve core is slidably assembled within the output valve sleeve, and the output valve core slides against the output valve sleeve to control communication / shutoff between the first pressure oil passage and the first variable oil passage.

[0013] In one embodiment of the present invention, a feedback groove is formed on the outer circumference of the output valve sleeve, the end of the feedback member extends into the feedback groove and pushes the output valve sleeve, the dimensions of the feedback groove are larger than the dimensions of the end of the feedback member, and the end of the feedback member abuts against the groove wall of the feedback groove due to the action of an elastic component.

[0014] In one embodiment of the present invention, an axially parallel discharge oil passage is provided within the output valve sleeve, the discharge oil passage communicates with the feedback groove, the feedback groove communicates with the pump housing chamber, and the oil at both ends of the output valve sleeve flows through the discharge oil passage to the pump housing chamber, thereby enabling oil recirculation.

[0015] In one embodiment of the present invention, the flow control valve includes a flow valve body, a load sensing valve core, and a pressure shut-off valve core. The flow valve body is equipped with a variable oil port and a second variable oil passage, the variable oil port communicates with the first variable oil passage, and the second variable oil passage communicates with the variable chamber. The load sensing valve core and the pressure shut-off valve core are installed inside the flow valve body. In the initial state, the oil in the first variable oil passage enters the flow valve body via the variable oil port, then flows through the load sensing valve core and the pressure shut-off valve core to the second variable oil passage, and enters the variable chamber.

[0016] In one embodiment of the present invention, a first mounting chamber and a second mounting chamber are formed in parallel within the flow valve body, the load sensing valve core is assembled in the first mounting chamber, the pressure shut-off valve core is assembled in the second mounting chamber, the variable oil port communicates with the first mounting chamber, the second variable oil passage communicates with the second mounting chamber, and the first and second mounting chambers communicate with each other via an intermediate oil passage.

[0017] According to the above technical solution, the technical effects that can be achieved by the present invention are as follows.

[0018] 1. In the plunger pump of the present invention, the variable piston and the output control valve are installed separately, thereby shortening the length of the output control valve, the output control valve is located on one side of the oscillation path of the swash plate, the axis of the output control valve is perpendicular to the axis of the pump body, the output control valve does not exceed the axial length of the pump body, and the length of the output control valve itself is shortened so that it does not exceed the width of the pump body, thus achieving both the requirements of output control and miniaturization of the plunger pump, making it easy to assemble into a mini excavator, and when the output control valve is assembled perpendicular to the axis of the pump body, the state of the swash plate is fed back to the output control valve by the feedback member, the feedback member is installed parallel to and offset from the oscillation axis of the swash plate, one end of the feedback member acts on the swash plate, and when the swash plate oscillates, the feedback member oscillates relative to the oscillation axis of the swash plate, feeding back the oscillation motion of the swash plate to the output control valve, thereby realizing dynamic control of the plunger pump.

[0019] 2. In the plunger pump of the present invention, a flow control valve is further installed, which can control the flow rate of the plunger pump, and the axis of the flow control valve is perpendicular to the axis of the pump body, so that the flow control valve does not exceed the axial length of the pump body, and in this way does not lead to an increase in the axial length of the overall structure. Furthermore, the flow control valve and the output control valve are located on different outer walls of the pump body and are installed offset in the axial direction of the pump body, so that interference between the flow control valve and the output control valve can be avoided. Furthermore, the flow control valve and the output control valve are installed so that they are located on two adjacent outer walls of the pump body, which facilitates oil flow between the flow control valve and the output control valve, shortens the length of the oil passage between the flow control valve and the output control valve, and reduces the difficulty of manufacturing.

[0020] 3. In the plunger pump of the present invention, the control oil of the output control valve enters the variable chamber of the variable piston via the flow control valve, thereby reducing the installation of the oil circuit. A feedback groove is formed on the outer periphery of the output valve sleeve, and the dimension of the feedback groove is larger than the dimension of the end portion of the feedback member, so that the feedback member can easily extend into the feedback groove and is easy to assemble. Due to the action of the elastic component, the end portion of the feedback member can abut against the groove wall of the feedback groove, so that the feedback member can accurately feedback the swinging state of the swash plate to the output control valve. By forming a discharge oil circuit in the output valve sleeve, the oil at both ends of the output valve sleeve enters the pump housing chamber via the discharge oil circuit, and oil reflux can be realized.

Brief Description of the Drawings

[0021] [Figure 1] Figure 1 is a schematic structural diagram of the plunger pump of the present embodiment. [Figure 2] Figure 2 is a cross-sectional view of the plunger pump. [Figure 3] Figure 3 is a cross-sectional view of the plunger pump viewed from a direction perpendicular to Figure 2. [Figure 4] Figure 4 is a schematic structural diagram of the plunger pump with a part of the housing removed. [Figure 5] Figure 5 is a cross-sectional view of the output control valve of the plunger pump. [Figure 6] Figure 6 is a schematic structural diagram of the output control valve. [Figure 7] Figure 7 is a cross-sectional view of the output control valve. [Figure 8] Figure 8 is a cross-sectional view of the output valve sleeve. [Figure 9] Figure 9 is a left end view of the output valve sleeve shown in Figure 8. [Figure 10] Figure 10 is a right end view of the output valve sleeve shown in Figure 8. [Figure 11] Figure 11 is a cross-sectional view taken along the line B-B of Figure 8. [Figure 12] Figure 12 is a cross-sectional view taken along the line C-C of Figure 8. [Figure 13] Figure 13 is a schematic diagram of the structure of a flow control valve. [Figure 14] Figure 14 is a cross-sectional view of a flow control valve. [Figure 15] Figure 15 is a plan view of the flow control valve. [Figure 16] Figure 16 is a cross-sectional view of Figure 15. [Modes for carrying out the invention]

[0022] The following description will clearly and completely explain the technical solutions of embodiments of the present invention with reference to the drawings of embodiments of the present invention, and it will be obvious that the embodiments described are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is for illustrative purposes only and should not be considered as any limitation on the present invention or its application or use. All other embodiments that a person skilled in the art can obtain without creative work based on embodiments of the present invention are within the scope of the protection of the present invention.

[0023] The terms used herein are for the sole purpose of describing specific embodiments and are not intended to limit the exemplary embodiments relating to this application. Where used herein, the singular form is intended to include the plural form unless otherwise explicitly stated in the context, and further, where the terms “include” and / or “contain” are used herein, it is understood that features, steps, operations, devices, assemblies and / or combinations thereof exist.

[0024] Unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions, and numerical values ​​described in these embodiments do not limit the scope of the present invention. Furthermore, for the sake of clarity, it should be understood that the dimensions of the parts shown in the drawings are not drawn to actual scale. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered as part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as illustrative only, and not restrictive. Therefore, other examples of exemplary embodiments may have different values. However, it should be noted that similar reference numerals and letters indicate similar items in subsequent drawings, and therefore, once an item is defined in one drawing, it does not need to be discussed further in subsequent drawings.

[0025] In describing this invention, it is important to understand that the directions or positional relationships indicated by directional terms such as "front, back, up, down, left, right," "horizontal, vertical, vertical, horizontal," and "top, bottom" are usually directions or positional relationships based on the illustrations and are merely there to make the invention easier to explain concisely. Unless otherwise stated, these directional terms do not indicate or imply that the device or element in question necessarily has a specific direction or is configured or operated in a specific direction, and therefore do not limit the scope of protection of this invention. The directional terms "inside" and "outside" refer to the inside and outside of the contour of each component itself.

[0026] For the sake of clarity, spatial relative terms such as "on top of," "above," "on the top surface," and "on top" may be used here to describe the spatial relationship between one device or feature shown in the diagram and another device or feature. It is important to understand that spatial relative terms are intended to include different orientations during use or operation other than the orientation described in the diagram of the device. For example, if the device in the drawing is upside down, a device described as "above another device or structure" or "on top of another device or structure" would subsequently be positioned as "below the other device or structure" or "below the other device or structure." Thus, the exemplary term "above" may include two orientations: "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein should be interpreted accordingly.

[0027] Furthermore, it should be understood that using terms such as "first," "second," etc., to specify parts is merely for the purpose of distinguishing corresponding parts, and unless otherwise stated, these terms have no special meaning and do not limit the scope of protection of the present invention.

[0028] As shown in Figure 1-16, this embodiment provides a plunger pump, which includes a pump body 10, a swash plate 1 for adjusting the discharge amount of the plunger pump installed inside the pump body 10, a variable piston 2 for pushing and oscillating the swash plate 1 installed inside the pump body 10, and an output control valve 3 and a flow control valve 5 installed on the outer wall of the pump body 10, the output control valve 3 for output control of the plunger pump and the flow control valve 5 for flow control of the plunger pump.

[0029] The pump body 10 includes a housing 101, with an end cover 102 installed at the opening of the housing 101. The housing 101 and the end cover 102 form a relatively sealed internal space, and the rotating cylinder block 103 is housed within the internal space formed by the housing 101 and the end cover 102. The main shaft 104 is assembled on the centerline of the rotating cylinder block 103, with one end of the main shaft 104 extending from the end of the housing 101 away from the end cover 102.

[0030] A swash plate 1 is further installed inside the pump body 10, and the swash plate 1 oscillates to control the discharge amount of the plunger pump. A variable piston 2 is further installed inside the pump body 10, and the variable piston 2 drives the swash plate 1 to oscillate.

[0031] A preferred technical solution in this embodiment is that the variable piston 2 is installed parallel to the axis of the pump body 10, and when control oil enters the variable chamber 21, the variable piston 2 extends and drives the swash plate 1 to oscillate.

[0032] A preferred technical solution in this embodiment is to further install a return piston 7, which is installed opposite the variable piston 2, which acts on the other end of the swash plate 1, which is fitted with an expansion / contraction spring 71, which is fitted outside the return piston 7, which plays the role of returning the swash plate 1 by the action of the expansion / contraction spring 71.

[0033] A preferred technical solution in this embodiment is to install an inlet 1021 and an outlet 1022 in the end cover 102, and rotate the rotating cylinder block 103 to alternately connect the inlet 1021 and the outlet 1022.

[0034] The output control valve 3 is installed outside the pump body 10. Specifically, the output control valve 3 is installed on the outer wall of the housing 101, the axis of the output control valve 3 is perpendicular to the axis of the pump body 10, and the output control valve 3 does not extend beyond the axial range of the pump body 10.

[0035] The output control valve 3 includes an output valve body 31, an output valve sleeve 32, and an output valve core 33. A mounting chamber is formed inside the output valve body 31, the output valve sleeve 32 is slidably assembled within the mounting chamber of the output valve body 31, the output valve core 33 is slidably assembled within the output valve sleeve 32, an output adjustment assembly is installed at one end of the output valve core 33, a pilot assembly is installed at the other end of the output valve core 33, a first pressure oil passage and a first variable oil passage are formed inside the output valve body 31, and a feedback groove 321 is provided in the output valve sleeve 32. A first circumferential groove 322 and a second circumferential groove 324 are formed, the first circumferential groove 322 communicates with the central hole of the output valve sleeve 32 via a plurality of first radial holes 323, the second circumferential groove 324 communicates with the central hole of the output valve sleeve 32 via a plurality of second radial holes 325, pressurized oil discharged from the pump body is introduced into the first pressure oil passage 10, the first circumferential groove 322 communicates with the first pressure oil passage, the second circumferential groove 324 communicates with the first variable oil passage, and the feedback groove 321 communicates with the housing chamber of the pump, thereby facilitating oil recirculation.

[0036] A preferred technical solution in this embodiment is to provide 2 to 4 first radial holes 323 and 2 radial holes 325, with all first radial holes 323 and all second radial holes 324 uniformly arranged in the circumferential direction.

[0037] A preferred technical solution in this embodiment is that the feedback groove 321 is located between the first circumferential groove 322 and the second circumferential groove 324, and an oil discharge passage 326 parallel to the axis is formed in the output valve sleeve 32, the oil discharge passage 326 extends to the end faces of both ends of the output valve sleeve 32 and communicates with the feedback groove 321. Preferably, guide grooves are formed on the end faces of both ends of the output valve sleeve 32, and oil enters the oil discharge passage 326 via the guide grooves and then recirculates via the feedback groove 321.

[0038] A preferred technical solution in this embodiment is that the output adjustment assembly includes an output elastic assembly 35, an output adjustment screw 36, and an output adjustment nut 39, wherein the output elastic assembly 35 includes a nested large elastic component 351 and a small elastic component 352, one end of the large elastic component 351 and the small elastic component 352 acting on the output valve sleeve 32 and the output valve core 33 via a spring seat, the output adjustment nut 39 is assembled by screwing it onto the output valve body 31 and abuts against the other end of the large elastic component 351, the output adjustment screw 36 is assembled by screwing it onto the output adjustment nut 39 and abuts against the other end of the small elastic component 352, the amount of pre-compression of the large elastic component 351 can be adjusted by adjusting the position of the output adjustment nut 39 on the output valve body 31, and the amount of pre-compression of the small elastic component 352 can be adjusted by adjusting the position of the output adjustment screw 36 on the output adjustment nut 39.

[0039] A preferred technical solution in this embodiment is that the pilot assembly includes a pilot valve core 37 and a proportional pressure reducing valve 38, wherein the pilot valve core 37 acts on the output valve core 33 through the action of the proportional pressure reducing valve 38.

[0040] The output control valve 3 is located on one side of the oscillation path of the swash plate 1, and the feedback member 4 feeds back the oscillation of the swash plate 1 to the output control valve 3. Specifically, the feedback member 4 is installed parallel to and offset from the oscillation axis of the swash plate 1, one end of the feedback member 4 is connected to the swash plate 1 via a connecting seat 6, and the other end of the feedback member 4 acts on the output valve sleeve 32. During operation, the first pressure oil passage communicates with the outlet 1022 of the end cover 102, and the pressure oil discharged from the pump body 10 enters through the first pressure oil passage and further flows through the first circumferential groove 322 and the first radial hole 323 of the output valve sleeve 32 to the space between the output valve core 33 and the output valve sleeve 32. The diameter of the central hole of the output valve sleeve 32 changes, and the pressure oil can act on the output valve core 33, causing the output valve core 33 to slide against the force acting on the output elastic assembly 35, and the output valve core The 33 controls the first radial hole 323 and the second radial hole 325 to communicate, and the pressurized oil enters the variable chamber 21 of the variable piston 2 via the first variable oil passage, driving the swash plate 1 to oscillate. The oscillation of the swash plate 1 is further fed back to the output valve sleeve 32 via the feedback member 4, and the output valve sleeve 32 slides along the sliding direction of the output valve core 33, blocking communication between the first radial hole 323 and the second radial hole 325. This process is repeated to achieve dynamic balance.

[0041] A preferred technical solution in this embodiment is that the feedback member 4 and the connecting seat 6 may be installed separately and then fixed and connected, or they may be an integrated structure. It is sufficient to ensure that the feedback member 4 is offset parallel to the oscillation axis of the swash plate 1, is driven by the swash plate 1 to perform an oscillation motion, and can slide the output valve sleeve 32.

[0042] A preferred technical solution in this embodiment is that the end of the feedback member 4 extends into the feedback groove 321, and when the swash plate 1 swings, the feedback member 4 swings along with it, causing the output valve sleeve 32 to move axially along its axis.

[0043] A preferred technical solution in this embodiment is that the dimensions of the feedback groove 321 are larger than the dimensions of the end of the feedback member 4, so that the end of the feedback member 4 can extend very easily into the feedback groove 321, and the difficulty of assembly is low. To prevent the end of the feedback member 4 from swinging in the feedback groove 321, an elastic component 34 is further installed, and the elastic component 34 acts on the output valve sleeve 32 to keep the end of the feedback member 4 in constant contact with the groove wall of the feedback groove 321, fixing the relative position of the two. Preferably, the elastic component 34 is located on the side where the pilot valve core 37 is located, the elastic component 34 is fitted outside the pilot valve core 37, one end of the elastic component 34 is in contact with the output valve sleeve 32 and the other end is in contact with the proportional pressure reducing valve 38.

[0044] A flow control valve 5 is further installed, and the flow control valve 5 can control the flow rate of the pump body 10. The flow control valve 5 is assembled outside the pump body 10, and the flow control valve 5 includes a flow valve body 51, within which a first mounting chamber and a second mounting chamber are formed in parallel. A load sensing valve core 52 is assembled in the first mounting chamber, and a pressure shut-off valve core 53 is assembled in the second mounting chamber. A first elastic assembly 54 is assembled in the first mounting chamber, and the first elastic assembly 54 acts on the load sensing valve core 52, and the pressurized oil pushes the load sensing valve core 52 to slide against the force acting on the first elastic assembly 54. A second elastic assembly 55 is further assembled in the second mounting chamber, and the second elastic assembly 55 acts on the pressure shut-off valve core 53, and the pressurized oil pushes the pressure shut-off valve core 53 to slide against the force acting on the second elastic assembly 55.

[0045] The flow valve body 51 is formed with a variable oil port 511, a second variable oil passage 512, a second pressure oil passage 513, and a return oil passage 514. The variable oil port 511 communicates with the first mounting chamber and can be used to introduce variable oil flowing in from the first variable oil passage. The variable oil flows through the variable oil port 511 to the first mounting chamber. One end of the second variable oil passage 512 communicates with the second mounting chamber, and the other end of the second variable oil passage 512 communicates with the variable chamber 21. The first and second mounting chambers are connected via an intermediate oil passage 515. The second pressure oil passage 513 communicates with the outlet 1022 of the pump body 10 and leads out the pressure oil discharged from the plunger pump. The second pressure oil passage 513 communicates with both the first and second mounting chambers, and the return oil passage 514 communicates with the second mounting chamber. In the initial state, the variable oil in the first variable oil passage enters the first mounting chamber via the variable oil port 511, then flows through the intermediate oil passage 515 to the second mounting chamber, and then flows through the second variable oil passage 512 into the variable chamber 21, pushing and oscillating the swash plate 1.

[0046] A preferred technical solution in this embodiment is that the first elastic assembly 54 and the second elastic assembly 55 each include two spring members nested internally and externally, and the flow valve body 51 is further fitted with a first adjustment screw 56 and a second adjustment screw 57, the first adjustment screw 56 can adjust the pre-compression amount of the first elastic assembly 54, and the second adjustment screw 57 can adjust the pre-compression amount of the second elastic assembly 55. Specifically, the two mounting chambers of the flow valve body 51 are installed through each other, an end support is fixed to one end of the flow valve body 51, the first adjustment screw 56 and the second adjustment screw 57 are assembled to the end support to adjust the pre-compression amounts of the first elastic assembly 54 and the second elastic assembly 55. Plugs are installed at the other end of the flow valve body 51 corresponding to each mounting chamber.

[0047] A preferred technical solution in this embodiment is to form a first annular groove 521 on the outer surface of the load-sensing valve core 52 and a second annular groove 531 on the outer surface of the pressure-shut-off valve core 53. In the initial state, the load-sensing valve core 52 contacts the plug due to the action of the first elastic assembly 54, and the pressure-shut-off valve core 53 contacts the plug due to the action of the second elastic assembly 55. At this time, the first annular groove 521 and the second annular groove 531 are in communication via an intermediate oil passage 515, and the variable oil of the output control valve 3 enters the first annular groove 521 via the variable oil port 511, then flows through the intermediate oil passage 515 to the second annular groove 531, and finally flows through the second variable oil passage 512 to the variable chamber 21.

[0048] A preferred technical solution in this embodiment is that the pressure set by the first elastic assembly 54 is smallest, the pressure set by the output elastic assembly 35 is moderate, and the pressure set by the second elastic assembly 55 is largest. For example, when the pressure of the pressurized oil is 0-14 megapascals, the load-sensing valve core 52 can only be pushed to slide against the action of the first elastic assembly 54, and the output valve core 33 and the pressure shut-off valve core 53 cannot be operated. In this case, the load-sensing valve core 52 operates and determines the oscillation angle of the swash plate 1. When the pressure of the pressurized oil is 14-28 megapascals (less than 28 megapascals), the pressurized oil can push the output valve core 33 to slide against the action of the output elastic assembly 35. In this case, the output control valve 3 operates and determines the oscillation angle of the swash plate 1, maintaining the product of the flow rate and pressure of the plunger pump, i.e., maintaining a constant output. When the pressure of the pressurized oil reaches 28 megapascals, the pressurized oil pushes the pressure shut-off valve core 53 to slide against the action of the second elastic assembly 55, and at this point the pressure shut-off valve core 53 operates.

[0049] A preferred technical solution in this embodiment is that, in order to ensure that the load sensing valve core 52 is in its initial position during the operation of the output control valve 3, a control oil port is further provided on the flow valve body 51, the control oil port is in communication with the mounting chamber where the first elastic assembly 54 is located, and the control oil enters from the control oil port and acts on the load sensing valve core 52, causing the load sensing valve core 52 to contact the plug, and the variable oil of the output control valve 3 can flow into the variable chamber 21 via the flow control valve 5.

[0050] A preferred technical solution in this embodiment is that the flow control valve 5 is assembled to the side wall 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, and 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 output control valve 3 are located on different side walls of the pump body 10, and more preferably, the flow control valve 5 and the output control valve 3 are located on two adjacent side walls close to the outlet 1022 of the pump body 10, which facilitates communication between the outlet 1022 and the flow control valve 5 and the output control valve 3, and shortens the length of the oil passage.

[0051] Based on the above technical solution, the operating principle of the plunger pump of this embodiment is as follows: When the hydraulic pressure at the outlet 1022 of the pump body 10 reaches the pressure set by the first elastic assembly 54, the load sensing valve core 52 can only be pushed to slide against the action of the first elastic assembly 54, the output valve core 33 and the pressure shut-off valve core 53 do not operate, the pressurized oil slides the load sensing valve core 52, and under the control of the load sensing valve core 52, the second pressurized oil passage 513 and the intermediate oil passage 515 are connected, the pressurized oil enters the variable chamber 21 via the intermediate oil passage 515, the second annular groove 531 and the second variable oil passage 512 of the pressure shut-off valve core 53, extends the variable piston 2, swings the swash plate 1 to a position with a small swing angle, further reduces the discharge amount of the plunger pump, and achieves discharge amount control of the plunger pump.

[0052] When the hydraulic pressure at the outlet 1022 of the pump body 10 reaches the pressure set by the output elastic assembly 35, the control oil port of the flow control valve 5 introduces control oil, setting the load sensing valve core 52 to its initial position. The pressure oil pushes the output valve core 33 so that it slides against the output elastic assembly 35, the first radial hole 323 and the second radial hole 325 communicate, and the pressure oil enters the first variable oil passage via the first pressure oil passage, and further enters the variable chamber 21 via the flow control valve 5, extending the variable piston 2. The swash plate 1 is pushed by the variable piston 2 and begins to swing to a position with a small swing angle. Furthermore, the discharge amount of the plunger pump decreases, and the output P*Q is maintained as is, during the process in which the swash plate swings in the direction of the small swing angle. As the feedback member 4 attached to the swash plate 1 swings accordingly, the output valve sleeve 32 slides in the sliding direction of the output valve core 33 until the second radial hole 325 communicates with the end face of the output valve sleeve 32 via the output valve core 33 (i.e., communicates with the pump housing chamber via the discharge oil passage 326 and the feedback groove 321). At this time, the variable chamber 21 of the plunger pump is maintained at a constant pressure, the variable mechanisms such as the variable piston 2, swash plate 1, output valve core 33, and output valve sleeve 32 maintain dynamic balance, the plunger pump operates at a specific stable discharge rate, and the plunger pump always maintains an output of P*Q.

[0053] When the hydraulic pressure at the outlet 1022 of the pump body 10 reaches the pressure set by the second elastic assembly 55, the pressurized oil slides the pressure shut-off valve core 53, the second pressurized oil passage 513 communicates with the second variable oil passage 512 via the pressure shut-off valve core 53, the pressurized oil enters the variable chamber 21 of the variable piston 2, extending the variable piston 2, the swash plate 1 is pushed by the variable piston 2 and begins to swing to a position with a small swing angle, and further the discharge volume of the plunger pump decreases.

[0054] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention within the scope of the knowledge of those skilled in the art. [Explanation of Symbols]

[0055] 1-Swash plate; 2-Variable piston; 21-Variable chamber; 3-Output control valve; 31-Output valve body; 32-Output valve sleeve; 321-Feedback groove; 322-First circumferential groove; 323-First radial hole; 324-Second circumferential groove; 325-Second radial hole; 326-Oil discharge passage; 33-Output valve core; 34-Elastic component; 35-Output elastic assembly; 351-Large elastic component; 352-Small elastic component; 36-Output adjustment screw; 37-Pilot valve core; 38-Proportional pressure reducing valve; 39-Output adjustment nut; 4-Feedback member; 5-Flow control valve; 51-Flow valve body 511-Variable oil port; 512-Second variable oil passage; 513-Second pressure oil passage; 514-Recirculation oil passage; 515-Intermediate oil passage; 52-Load sensing valve core; 521-First annular groove; 53-Pressure shutoff valve core; 531-Second annular groove; 54-First elastic assembly; 55-Second elastic assembly; 56-First adjustment screw; 57-Second adjustment screw; 6-Connecting seat; 7-Return piston; 71-Expansion spring; 10-Pump body; 101-Housing; 102-End cover; 1021-Inlet; 1022-Outlet; 103-Rotating cylinder block; 104-Main shaft.

Claims

1. It is a plunger pump, A slanted plate (1) is installed inside the pump body (10), The swash plate (1) is driven to swing, and a variable piston (2) whose axis is parallel to the axis of the pump body (10) is provided, An output control valve (3) is located outside the pump body (10), on one side of the oscillation path of the swash plate (1), and its axis is perpendicular to the axis of the pump body (10), A plunger pump characterized by including a feedback member (4) which is installed parallel to and offset from the oscillation axis of the swash plate (1), with one end connected to the swash plate (1) and the other end acting on the output control valve (3).

2. The plunger pump according to claim 1, further comprising a flow control valve (5) installed outside the pump body (10) and whose axis is perpendicular to the axis of the pump body (10).

3. The plunger pump according to claim 2, characterized in that the flow control valve (5) and the output control valve (3) are each located on different outer walls of the pump body (10), and the flow control valve (5) and the output control valve (3) are installed offset from each other in the axial direction of the pump body (10).

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

5. The plunger pump according to any one of claims 2 to 4, characterized in that the control oil of the output control valve (3) enters the variable chamber (21) of the variable piston (2) via the flow control valve (5).

6. The output control valve (3) is An output valve body (31) has a first pressure oil passage and a first variable oil passage formed inside, and pressurized oil discharged from the pump body (10) is introduced into the first pressure oil passage. An output valve sleeve (32) is slidably assembled within the output valve body (31), wherein the feedback member (4) acts on the output valve sleeve (32), The plunger pump according to claim 5, further comprising an output valve core (33) slidably assembled within the output valve sleeve (32), wherein the output valve core (33) slides with the output valve sleeve (32) to control communication / shutoff between the first pressure oil passage and the first variable oil passage.

7. The plunger pump according to claim 6, characterized in that a feedback groove (321) is formed on the outer circumference of the output valve sleeve (32), the end of the feedback member (4) extends into the feedback groove (321) and pushes the output valve sleeve (32), the dimensions of the feedback groove (321) are larger than the dimensions of the end of the feedback member (4), and the end of the feedback member (4) contacts the groove wall of the feedback groove (321) due to the action of the elastic component (34).

8. The plunger pump according to claim 6, characterized in that an axially parallel discharge oil passage (326) is installed inside the output valve sleeve (32), the discharge oil passage (326) communicates with the feedback groove (321), the feedback groove (321) communicates with the pump housing chamber, and the oil at both ends of the output valve sleeve (32) flows through the discharge oil passage (326) to the pump housing chamber, thereby enabling oil recirculation.

9. The flow control valve (5) includes a flow valve body (51), a load sensing valve core (52), and a pressure shut-off valve core (53). The flow valve body (51) is equipped with a variable oil port (511) and a second variable oil passage (512), the variable oil port (511) is in communication with the first variable oil passage, and the second variable oil passage (512) is in communication with the variable chamber (21), The plunger pump according to claim 5, characterized in that the load sensing valve core (52) and the pressure shut-off valve core (53) are installed within the flow valve body (51), and in the initial state, the oil in the first variable oil passage enters the flow valve body (51) via the variable oil port (511), and further flows through the load sensing valve core (52) and the pressure shut-off valve core (53) to the second variable oil passage (512), and enters the variable chamber (21).

10. The plunger pump according to claim 9, characterized in that a first mounting chamber and a second mounting chamber are formed in parallel within the flow valve body (51), the load sensing valve core (52) is assembled in the first mounting chamber, the pressure shut-off valve core (53) is assembled in the second mounting chamber, the variable oil port (511) communicates with the first mounting chamber, the second variable oil passage (512) communicates with the second mounting chamber, and the first and second mounting chambers communicate via an intermediate oil passage (515).

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