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

A plunger pump

[0001] This application claims priority to Chinese Patent Application No. 202311041691.5 filed on August 18, 2023. The contents of the above-mentioned Chinese patent application disclosure are hereby incorporated by reference in their entirety as a part of this application. Technical Field

[0002] The present invention relates to the field of hydraulic technology, in particular to a plunger pump. Background Art

[0003] With the changes in the application sites of construction operations, excavators need to be able to adapt to multi-angle movements in a small space, which has led to the emergence of mini excavators. The boom and working device of mini excavators are improved and developed on the basis of small and medium-sized excavators, but they are smaller in size and more compact in structure.

[0004] Excavators often use plunger pumps as their power element. Plunger pumps are a crucial component in hydraulic systems, converting mechanical energy into the hydraulic energy required by the system. Driven by a prime mover such as an engine or motor, the plunger reciprocates within the cylinder, outputting high-pressure oil to convert the prime mover's mechanical energy into hydraulic energy. Plunger pumps are primarily categorized as axial and radial piston pumps, with axial pumps further divided into swash plate and bevel axis types. In today's construction machinery market, axial piston pumps are widely used in mobile construction machinery such as excavators, loaders, tractors, and bulldozers due to their high power-to-weight ratio and flexible flow and power control characteristics. Micro excavators, due to their compact size, require smaller piston pumps with smaller installation space.

[0005] US Patent Application No. 14719676 discloses a regulating device for a hydrostatic piston engine and a hydrostatic axial piston engine. The regulating device includes a regulating piston and a regulating valve. The regulating piston and regulating valve are arranged side by side on the same central axis and inserted into an elongated cavity of a housing body. The regulating valve has a box-shaped valve housing that is screwed into the housing body and has a valve hole extending along the central axis. A valve core is movable within the valve hole.

[0006] The adjustment device in the above application includes an adjusting piston and a regulating valve, which can achieve power adjustment with fewer devices. However, the adjusting device integrates the adjusting piston and the regulating valve in a coaxial arrangement, and the overall axial length is longer. Even if the adjusting device is tilted compared to the axis of the pump body, the tail end of the adjusting device still exceeds the axial length of the pump body. The axial installation space of the mini excavator is very limited, so the above-mentioned plunger pumps cannot meet the installation requirements.

[0007] Summary of the Invention

[0008] In order to solve the technical problem that the existing plunger pump cannot meet the requirements of control mode and miniaturization and cannot be installed on a mini excavator, the present invention provides a plunger pump that solves the above technical problems. The technical solution of the present invention is as follows:

[0009] A plunger pump comprising:

[0010] A swash plate, disposed within the pump body;

[0011] A variable piston drives the swash plate to deflect, wherein the axis of the variable piston is parallel to the axis of the pump body;

[0012] a power control valve, located outside the pump body and on one side of the slant plate deflection path, wherein the axis of the power control valve is perpendicular to the axis of the pump body;

[0013] A feedback member is provided parallel to and offset from the yaw axis of the swash plate, one end of the feedback member is connected to the swash plate, and the other end of the feedback member acts on the power control valve.

[0014] According to one embodiment of the present invention, the pump further comprises a flow control valve, which is arranged outside the pump body, and an axis of the flow control valve is perpendicular to the axis of the pump body.

[0015] According to one embodiment of the present invention, the flow control valve and the power control valve are respectively located on different outer side walls of the pump body, and the flow control valve and the power control valve are staggered in the axial direction of the pump body.

[0016] According to one embodiment of the present invention, the flow control valve and the power control valve are located on two adjacent outer side walls of the pump body.

[0017] According to one embodiment of the present invention, the control oil of the power control valve enters the variable chamber of the variable piston through the flow control valve.

[0018] According to one embodiment of the present invention, the power control valve comprises:

[0019] A power valve body, wherein a first pressure oil passage and a first variable oil passage are formed in the power valve body, and the first pressure oil passage is connected to the pressure oil pumped out by the pump body;

[0020] A power valve sleeve, the power valve sleeve being slidably assembled in the power valve body, the feedback member acting on the power valve sleeve;

[0021] A power valve spool is slidably assembled in the power valve sleeve. The power valve sleeve and the power valve spool slide to control the connection and disconnection between the first pressure oil passage and the first variable oil passage.

[0022] According to one embodiment of the present invention, a feedback groove is formed on the outer periphery of the power valve sleeve, and the end of the feedback member extends into the feedback groove to push the power valve sleeve. The size of the feedback groove is larger than the size of the end of the feedback member. Under the action of the elastic member, the end of the feedback member remains against the groove wall of the feedback groove.

[0023] According to one embodiment of the present invention, an oil drain channel parallel to the axial direction is provided in the power valve sleeve, the oil drain channel is connected to the feedback groove, and the feedback groove is connected to the housing cavity of the pump. The oil at both ends of the power valve sleeve can flow to the housing cavity of the pump through the oil drain channel to realize oil return.

[0024] According to one embodiment of the present invention, the flow control valve comprises:

[0025] a flow valve body, wherein the flow valve body is provided with a variable oil port and a second variable oil passage, the variable oil port is communicated with the first variable oil passage, and the second variable oil passage is communicated with the variable chamber;

[0026] The load-sensitive valve core and the pressure-cut-off valve core are arranged in the flow valve body. In the initial state, the oil in the first variable oil channel enters the flow valve body through the variable oil port, and then flows to the second variable oil channel through the load-sensitive valve core and the pressure-cut-off valve core, and enters the variable chamber.

[0027] According to one embodiment of the present invention, a first installation cavity and a second installation cavity arranged side by side are formed in the valve body of the flow valve, the load-sensitive valve core is installed in the first installation cavity, the pressure-cut-off valve core is installed in the second installation cavity, the variable oil port is connected to the first installation cavity, the second variable oil channel is connected to the second installation cavity, and the first installation cavity and the second installation cavity are connected through an intermediate oil channel.

[0028] Based on the above technical solution, the technical effects that can be achieved by the present invention are:

[0029] 1. The plunger pump of the present invention has a variable piston and a power control valve that are separately provided. This shortens the length of the power control valve, which is located on one side of the sway path of the swash plate. The axis of the power control valve is perpendicular to the axis of the pump body, and the power control valve does not extend beyond the axial length of the pump body. Since the power control valve itself is shortened, it does not extend beyond the width of the pump body. This satisfies both the requirements of power control and miniaturization of the plunger pump, and facilitates assembly on a mini excavator. When the power control valve is assembled perpendicular to the axis of the pump body, the state of the swash plate is fed back to the power control valve via a feedback member. The feedback member is arranged parallel to and offset from the sway axis of the swash plate, and one end of the feedback member acts on the swash plate. When the swash plate deflects, the feedback member swings relative to the sway axis of the swash plate, feeding back the sway motion of the swash plate to the power control valve, thereby achieving dynamic control of the plunger pump.

[0030] 2. The plunger pump of the present invention is further provided with a flow control valve, which can realize flow control of the plunger pump. The axis of the flow control valve is perpendicular to the axis of the pump body, so the flow control valve will not exceed the axial length of the pump body, thereby not increasing the axial length of the overall structure; the flow control valve and the power control valve are further arranged on different outer side walls of the pump body, respectively, and staggered in the axial direction of the pump body, thereby avoiding interference between the flow control valve and the power control valve; the flow control valve and the power control valve are further arranged on two adjacent outer side walls of the pump body, so as to facilitate the flow of oil between the flow control valve and the power control valve, shorten the length of the oil channel between the flow control valve and the power control valve, and reduce the difficulty of processing;

[0031] 3. In the plunger pump of the present invention, the control oil of the power control valve enters the variable cavity of the variable piston through the flow control valve, which can reduce the need for oil passages. A feedback groove is formed on the outer periphery of the power valve sleeve. The size of the feedback groove is larger than the end size of the feedback member, so that the feedback member can easily extend into the feedback groove and is easy to assemble. Under the action of the elastic member, the end of the feedback member can remain against the groove wall of the feedback groove, so that the feedback member can accurately feedback the deflection state of the swash plate to the power control valve. An oil drain channel is formed on the power valve sleeve, so that the oil at both ends of the power valve sleeve can enter the pump housing cavity through the oil drain channel to achieve oil return. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic structural diagram of a plunger pump according to the present embodiment;

[0033] Figure 2 is a cross-sectional view of the plunger pump;

[0034] FIG3 is a cross-sectional view of the plunger pump taken at a vertical angle compared to FIG2 ;

[0035] FIG4 is a schematic diagram of the structure of the plunger pump after removing part of the housing;

[0036] FIG5 is a cross-sectional view of a power control valve on a plunger pump;

[0037] Figure 6 is a schematic structural diagram of a power control valve;

[0038] FIG7 is a cross-sectional view of the power control valve;

[0039] FIG8 is a cross-sectional view of a power valve sleeve;

[0040] FIG9 is a left end view of the power valve sleeve shown in FIG8;

[0041] FIG10 is a right end view of the power valve sleeve shown in FIG8;

[0042] FIG11 is a sectional view taken along line BB of FIG8 ;

[0043] FIG12 is a cross-sectional view taken along line CC of FIG8 ;

[0044] FIG13 is a schematic structural diagram of a flow control valve;

[0045] FIG14 is a cross-sectional view of the flow control valve;

[0046] FIG15 is a top view of the flow control valve;

[0047] FIG16 is a DD cross-sectional view of FIG15;

[0048] In the figure: 1-swash plate; 2-variable piston; 21-variable chamber; 3-power control valve; 31-power valve body; 32-power valve sleeve; 321-feedback groove; 322-first annular groove; 323-first radial hole; 324-second annular groove; 325-second radial hole; 326-oil drain passage; 33-power valve core; 34-elastic member; 35-power elastic component; 351-large elastic member; 352-small elastic member; 36-power adjustment screw; 37-pilot valve core; 38-proportional pressure reducing valve; 39-power adjustment screw sleeve; 4-feedback member; 5-flow control valve; 51-flow valve Body; 511-variable oil port; 512-second variable oil channel; 513-second pressure oil channel; 514-return oil channel; 515-intermediate oil channel; 52-load-sensing valve core; 521-first annular groove; 53-pressure cut-off valve core; 531-second annular groove; 54-first elastic component; 55-second elastic component; 56-first adjusting screw; 57-second adjusting screw; 6-connecting seat; 7-return piston; 71-return spring; 10-pump body; 101-housing; 102-end cover; 1021-inlet; 1022-outlet; 103-rotating cylinder; 104-spindle. DETAILED DESCRIPTION

[0049] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when 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.

[0051] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0052] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0053] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0054] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0055] As shown in Figure 1-16, this embodiment provides a plunger pump, which includes a pump body 10. A swash plate 1 is provided in the pump body 10 to adjust the displacement of the plunger pump. A variable piston 2 is also provided in the pump body 10, and the variable piston 2 pushes the swash plate 1 to swing; a power control valve 3 and a flow control valve 5 are also provided on the outer wall of the pump body 10. The power control valve 3 can control the power of the plunger pump; the flow control valve 5 can control the flow of the plunger pump.

[0056] The pump body 10 includes a housing 101, with an end cap 102 disposed at the opening of the housing 101. The housing 101 and the end cap 102 form a relatively sealed internal space, within which a rotating cylinder 103 is accommodated. A main shaft 104 is mounted on the centerline of the rotating cylinder 103, with one end of the main shaft 104 extending beyond the end of the housing 101 away from the end cap 102.

[0057] A swash plate 1 is further provided in the pump body 10 , and the swash plate 1 controls the displacement of the plunger pump by its deflection. A variable piston 2 is also provided in the pump body 10 , and the variable piston 2 drives the swash plate 1 to deflect.

[0058] As a preferred technical solution of this embodiment, the variable piston 2 is arranged parallel to the axis of the pump body 10. When the control oil enters the variable chamber 21, it can push the variable piston 2 to extend, driving the swash plate 1 to swing.

[0059] As a preferred technical solution of this embodiment, a return piston 7 is further provided. The return piston 7 is arranged opposite to the variable piston 2. The return piston 7 acts on the other end of the swash plate 1. A return spring 71 is sleeved on the outside of the return piston 7. Under the action of the return spring 71, the return piston 7 resets the swash plate 1.

[0060] As a preferred technical solution of this embodiment, an inlet 1021 and an outlet 1022 are provided on the end cover 102 , and the rotating cylinder 103 rotates to alternately connect the inlet 1021 and the outlet 1022 .

[0061] The power control valve 3 is arranged outside the pump body 10 . Specifically, the power control valve 3 is arranged on the outer wall of the housing 101 . The axis of the power control valve 3 is perpendicular to the axis of the pump body 10 , and the power control valve 3 does not exceed the axial range of the pump body 10 .

[0062] The power control valve 3 includes a power valve body 31, a power valve sleeve 32 and a power valve core 33. The power valve body 31 is formed with a mounting cavity. The power valve sleeve 32 is slidably assembled in the mounting cavity of the power valve body 31. The power valve core 33 is slidably assembled in the power valve sleeve 32. A power regulating assembly is provided at one end of the power valve spool 33, and a pilot assembly is provided at the other end of the power valve spool 33. A first pressure oil passage and a first variable oil passage are formed in the power valve body 31. A feedback groove 321, a first annular groove 322, and a second annular groove 324 are formed on the power valve sleeve 32. The first annular groove 322 is connected to the center hole of the power valve sleeve 32 through a plurality of first radial holes 323, and the second annular groove 324 is connected to the center hole of the power valve sleeve 32 through a plurality of second radial holes 325. The first pressure oil passage is connected to the pressure oil pumped out of the pump body 10. The first annular groove 322 is connected to the first pressure oil passage, the second annular groove 324 is connected to the first variable oil passage, and the feedback groove 321 is connected to the housing cavity of the pump to facilitate oil return.

[0063] As a preferred technical solution of this embodiment, 2-4 first radial holes 323 and 2-4 second radial holes 325 can be provided respectively, all first radial holes 323 are evenly arranged circumferentially, and all second radial holes 324 are evenly arranged circumferentially.

[0064] As a preferred technical solution of this embodiment, the feedback groove 321 is located between the first annular groove 322 and the second annular groove 324. The power valve sleeve 32 is formed with an oil drain passage 326 parallel to the axis. The oil drain passage 326 extends to both end surfaces of the power valve sleeve 32 and communicates with the feedback groove 321. Preferably, drainage grooves are formed on both end surfaces of the power valve sleeve 32, allowing oil to flow through the drainage grooves into the oil drain passage 326 and then return through the feedback groove 321.

[0065] As the preferred technical solution of this embodiment, the power adjustment component includes a power elastic component 35, a power adjustment screw 36 and a power adjustment screw sleeve 39. The power elastic component 35 includes a large elastic part 351 and a small elastic part 352. One end of the large elastic part 351 and the small elastic part 352 act on the power valve sleeve 32 and the power valve spool 33 through the spring seat. The power adjustment screw sleeve 39 is threadedly assembled on the power valve body 31, and the power adjustment screw sleeve 39 resists the other end of the large elastic part 351. The power adjustment screw 36 is threadedly assembled on the power adjustment screw sleeve 39, and the power adjustment screw 36 resists the other end of the small elastic part 352. The pre-compression amount of the large elastic part 351 can be adjusted by adjusting the position of the power adjustment screw sleeve 39 on the power valve body 31; the pre-compression amount of the small elastic part 352 can be adjusted by adjusting the position of the power adjustment screw 36 on the power adjustment screw sleeve 39.

[0066] As a preferred technical solution of this embodiment, the pilot assembly includes a pilot valve core 37 and a proportional pressure reducing valve 38 . The pilot valve core 37 acts on the power valve core 33 under the action of the proportional pressure reducing valve 38 .

[0067] The power control valve 3 is located on one side of the yaw path of the swash plate 1. A feedback member 4 feeds back the yaw of the swash plate 1 to the power control valve 3. Specifically, the feedback member 4 is arranged parallel to and offset from the yaw 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 power valve sleeve 32. During operation, the first pressure oil passage is connected to the outlet port 1022 on the end cover 102. The pressure oil pumped out by the pump body 10 enters through the first pressure oil passage, and then flows through the first annular groove 322 and the first radial hole 323 on the power valve sleeve 32 to the space between the power valve spool 33 and the power valve sleeve 32. The aperture of the central hole of the power valve sleeve 32 changes, and the pressure oil can act on the power valve spool 33, causing the power valve spool 33 to slide against the force of the power elastic component 35. The power valve spool 33 controls the communication between the first radial hole 323 and the second radial hole 325. The pressure oil can enter the variable chamber 21 of the variable piston 2 through the first variable oil passage, driving the swash plate 1 to deflect. The deflection of the swash plate 1 is then fed back to the power valve sleeve 32 through the feedback member 4. The power valve sleeve 32 then slides along the sliding direction of the power valve spool 33, disconnecting the first radial hole 323 and the second radial hole 325. This process is repeated to achieve dynamic balance.

[0068] As a preferred technical solution of this embodiment, the feedback member 4 and the connecting seat 6 can be separately provided and then fixedly connected, or they can be an integrated structure. As long as the feedback member 4 is parallel to and deviates from the yaw axis of the swash plate 1, it can perform yaw motion driven by the swash plate 1, thereby driving the power valve sleeve 32 to slide.

[0069] As a preferred technical solution of this embodiment, the end of the feedback member 4 extends into the feedback groove 321. When the swash plate 1 deflects, the feedback member 4 deflects accordingly, driving the power valve sleeve 32 to move axially along its own axis.

[0070] As a preferred technical solution of this embodiment, the dimensions of feedback groove 321 are larger than the end of feedback member 4, allowing the end of feedback member 4 to easily extend into feedback groove 321, simplifying assembly. To prevent the end of feedback member 4 from dangling within feedback groove 321, an elastic member 34 is provided. This elastic member 34 acts on the power valve housing 32, ensuring that the end of feedback member 4 always abuts against the wall of feedback groove 321, maintaining a fixed relative position between the two. Preferably, elastic member 34 is located on the side of pilot valve core 37, fitting over pilot valve core 37. One end of elastic member 34 abuts against power valve housing 32, while the other end abuts against proportional pressure reducing valve 38.

[0071] A flow control valve 5 is also provided, which can control the flow of the pump body 10. The flow control valve 5 is mounted outside the pump body 10 and includes a flow valve body 51. The flow valve body 51 has a first mounting cavity and a second mounting cavity arranged side by side. The first mounting cavity houses a load-sensing valve core 52, and the second mounting cavity houses a pressure-cut-off valve core 53. The first mounting cavity also houses a first elastic component 54, which acts on the load-sensing valve core 52. Pressurized oil pushes the load-sensing valve core 52 to slide, overcoming the force of the first elastic component 54. The second mounting cavity also houses a second elastic component 55, which acts on the pressure-cut-off valve core 53. Pressurized oil pushes the pressure-cut-off valve core 53 to slide, overcoming the force of the second elastic component 55.

[0072] A variable oil port 511, a second variable oil channel 512, a second pressure oil channel 513 and an oil return channel 514 are also formed on the flow valve body 51. The variable oil port 511 is connected to the first installation chamber. The variable oil port 511 can be used to access the variable oil flowing into the first variable oil channel. The variable oil flows to the first installation chamber through the variable oil port 511. One end of the second variable oil channel 512 is connected to the second installation chamber, and the other end of the second variable oil channel 512 is connected to the variable chamber 21. The first installation chamber and the second installation chamber are connected through the intermediate oil channel 515. The second pressure oil channel 513 is connected to the outlet 1022 of the pump body 10 to lead out the pressure oil pumped out by the plunger pump. The second pressure oil channel 513 is connected to both the first installation chamber and the second installation chamber, and the oil return channel 514 is connected to the second installation chamber. In the initial state, the variable oil in the first variable oil passage enters the first installation cavity through the variable oil port 511 , flows to the second installation cavity through the intermediate oil passage 515 , and then flows into the variable cavity 21 through the second variable oil passage 512 , pushing the swash plate 1 to swing.

[0073] As a preferred technical solution of this embodiment, the first elastic component 54 and the second elastic component 55 each comprise two spring members disposed inside and outside of each other. The flow valve body 51 is also equipped with a first adjusting screw 56 and a second adjusting screw 57. The first adjusting screw 56 adjusts the pre-compression of the first elastic component 54, while the second adjusting screw 57 adjusts the pre-compression of the second elastic component 55. Specifically, the two mounting cavities of the flow valve body 51 are provided through-hole. An end seat is fixed to one end of the flow valve body 51. The first adjusting screw 56 and the second adjusting screw 57 are mounted on the end seat to adjust the pre-compression of the first and second elastic components 54, 55. A plug is provided at the other end of the flow valve body 51, corresponding to each mounting cavity.

[0074] As a preferred technical solution of this embodiment, a first annular groove 521 is formed on the outer surface of the load-sensing valve core 52, and a second annular groove 531 is formed on the outer surface of the pressure-cutoff valve core 53. In the initial state, the load-sensing valve core 52 abuts against the plug under the action of the first elastic component 54, and the pressure-cutoff valve core 53 abuts against the plug under the action of the second elastic component 55. At this time, the first annular groove 521 and the second annular groove 531 are connected through the intermediate oil passage 515. The variable oil of the power control valve 3 enters the first annular groove 521 through 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.

[0075] As a preferred technical solution of this embodiment, the first elastic component 54 is set to the minimum pressure, the power elastic component 35 is set to the middle pressure, and the second elastic component 55 is set to the maximum pressure. For example, when the pressure oil pressure is between 0 and 14 MPa, it can only push the load sensing valve core 52 to slide against the action of the first elastic component 54, but cannot drive the power valve core 33 and the pressure cut-off valve core 53 to operate. In this case, the load sensing valve core 52 is in operation, and the load sensing valve core 52 determines the swing angle of the swash plate 1. When the pressure oil pressure is between 14 and 28 MPa (before reaching 28 MPa), the pressure oil can push the power valve core 33 to slide against the action of the power elastic component 35. At this time, the power control valve 3 is in operation, and the power control valve 3 determines the swing angle of the swash plate 1, maintaining the product of the flow rate and pressure of the plunger pump constant, that is, constant power. When the pressure oil pressure reaches 28 MPa, the pressure oil pushes the pressure cut-off valve core 53 to slide against the action of the second elastic component 55, and the pressure cut-off valve core 53 is in operation.

[0076] As a preferred technical solution of this embodiment, in order to ensure that the load-sensitive valve core 52 is in the initial position during the operation of the power control valve 3, a control oil port is further provided on the flow valve body 51. The control oil port is connected to the installation cavity where the first elastic component 54 is located. The control oil enters through the control oil port and can act on the load-sensitive valve core 52, so that the load-sensitive valve core 52 remains against the plug. The variable oil of the power control valve 3 can flow into the variable cavity 21 through the flow control valve 5.

[0077] As a preferred technical solution of this embodiment, the flow control valve 5 is mounted on 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 power control valve 3 are located on different side walls of the pump body 10. More preferably, the flow control valve 5 and the power control valve 3 can be located on two adjacent side walls of the pump body 10 near the outlet 1022. The outlet 1022 facilitates communication with the flow control valve 5 and the power control valve 3, shortening the oil passage length.

[0078] Based on the above technical solution, the working principle of the plunger pump of this embodiment is as follows: when the oil pressure at the outlet 1022 of the pump body 10 reaches the pressure set by the first elastic component 54, it can only push the load-sensing valve core 52 to overcome the action of the first elastic component 54 and slide, the power valve core 33 and the pressure cut-off valve core 53 do not move, and the pressure oil pushes the load-sensing valve core 52 to slide. Under the control of the load-sensing valve core 52, the second pressure oil channel 513 is connected to the intermediate oil channel 515, and the pressure oil enters the variable chamber 21 through the intermediate oil channel 515, the second annular groove 531 of the pressure cut-off valve core 53, and the second variable oil channel 512, pushing the variable piston 2 to extend and pushing the swash plate 1 to swing to a smaller swing angle position, thereby reducing the displacement of the plunger pump, thereby realizing displacement control of the plunger pump.

[0079] When the oil pressure at the outlet 1022 of the pump body 10 reaches the pressure set by the power elastic component 35, the control oil is introduced into the control oil port of the flow control valve 5, so that the load-sensitive valve core 52 is in the initial position; the pressure oil pushes the power valve core 33 to overcome the sliding of the power elastic component 35, and the first radial hole 323 and the second radial hole 325 are connected. The pressure oil enters the first variable oil channel through the first pressure oil channel, and then enters the variable chamber 21 through the flow control valve 5, pushing the variable piston 2 to extend. Under the push of the variable piston 2, the swash plate 1 begins to swing to a smaller swing angle position, and then the displacement of the plunger pump is reduced, maintaining P*Q unchanged, that is, the power remains unchanged; the above-mentioned swash plate 1 As the swash plate swings toward the small swing angle, the feedback member 4 mounted on the swash plate 1 swings accordingly. As the feedback member 4 swings, the power valve sleeve 32 slides along the sliding direction of the power valve core 33 until the second radial hole 325 is connected to the end face of the power valve sleeve 32 via the power valve core 33 (i.e., connected to the pump housing cavity via the oil drain passage 326 and the feedback groove 321). At this time, the variable cavity 21 of the plunger pump maintains a certain pressure, and the variable mechanisms, including the variable piston 2, swash plate 1, power valve core 33, and power valve sleeve 32, maintain dynamic balance. The plunger pump operates at a certain stable displacement, and the plunger pump always maintains a constant P*Q, that is, a constant power.

[0080] When the oil pressure at the outlet 1022 of the pump body 10 reaches the pressure set by the second elastic component 55, the pressure oil pushes the pressure cut-off valve core 53 to slide, and the second pressure oil channel 513 is connected to the second variable oil channel 512 through the pressure cut-off valve core 53. The pressure oil enters the variable chamber 21 of the variable piston 2, pushing the variable piston 2 to extend. Under the push of the variable piston 2, the swash plate 1 begins to swing to a smaller swing angle position, and then the displacement of the plunger pump is reduced.

[0081] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A plunger pump, characterized in that: include: A swash plate (1) is disposed in a pump body (10); A variable piston (2) drives the swash plate (1) to oscillate, and the axis of the variable piston (2) is parallel to the axis of the pump body (10); A power control valve (3) is located outside the pump body (10) and on one side of the sway path of the swash plate (1), and the 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 the yaw axis of the swash plate (1), one end of the feedback member (4) is connected to the swash plate (1), and the other end of the feedback member (4) acts on the power control valve (3).

2. A plunger pump according to claim 1, characterized in that: It also comprises a flow control valve (5), wherein the flow control valve (5) is arranged outside the pump body (10), and the axis of the flow control valve (5) is perpendicular to the axis of the pump body (10).

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

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

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

6. A plunger pump according to claim 5, characterized in that: The power control valve (3) comprises: A power valve body (31), wherein a first pressure oil passage and a first variable oil passage are formed in the power valve body (31), and the first pressure oil passage is connected to the pressure oil pumped out by 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 core (33) is slidably assembled in the power valve sleeve (32), and the power valve sleeve (32) and the power valve core (33) slide to control the connection and disconnection between the first pressure oil passage and the first variable oil passage.

7. A plunger pump according to claim 6, characterized in that: A feedback groove (321) is formed on the outer periphery of the power valve sleeve (32), and the end of the feedback member (4) extends into the feedback groove (321) to push the power valve sleeve (32), and the size of the feedback groove (321) is larger than the size of the end of the feedback member (4). Under the action of the elastic member (34), the end of the feedback member (4) is kept against the groove wall of the feedback groove (321).

8. A plunger pump according to claim 6, characterized in that: An oil drain passage (326) parallel to the axial direction is arranged in the power valve sleeve (32); the oil drain passage (326) is communicated with the feedback groove (321); the feedback groove (321) is communicated with the housing cavity of the pump; the oil at both ends of the power valve sleeve (32) can flow to the housing cavity of the pump through the oil drain passage (326) to realize oil return.

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

10. A plunger pump according to claim 9, characterized in that: The flow valve body (51) is formed with a first installation cavity and a second installation cavity which are arranged side by side. The load-sensitive valve core (52) is mounted in the first installation cavity, and the pressure cut-off valve core (53) is mounted in the second installation cavity. The variable oil port (511) is connected to the first installation cavity, and the second variable oil passage (512) is connected to the second installation cavity. The first installation cavity and the second installation cavity are connected via an intermediate oil passage (515).

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