Plunger assembly and plunger pump

Abstract

The utility model discloses a plunger assembly and a plunger pump, and relates to the technical field of power conveying equipment, and the plunger assembly comprises a threaded plug, a supporting seat and a plunger supported on the supporting seat through a spring; wherein a limiting structure is arranged between the seat body of the supporting seat and the end cover of the threaded plug, and the limiting structure is used for limiting the supporting seat at a preset position. Thus, the situation that the position of the spring arranged on the supporting base deviates, and the spring deforms due to the fact that the position of the supporting base deviates can be effectively avoided, the accuracy of force output by the spring is improved, and therefore the pumping performance of the plunger pump can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of power transmission equipment, and in particular to a plunger assembly and a plunger pump. Background Art

[0002] A plunger pump relies on the reciprocating motion of a plunger assembly, causing the volume of the oil chamber within the plunger assembly to change to achieve oil suction and discharge. The plunger assembly typically includes a threaded plug, a support seat, and a plunger supported on the support seat by a spring. Currently, plunger assemblies in related technologies suffer from the problem of spring deflection, resulting in poor pumping performance. Utility Model Content

[0003] In order to solve the above technical problems, the present application provides a plunger assembly and a plunger pump.

[0004] According to the first aspect of the present application, a plunger assembly is provided, which includes a threaded plug, a support seat, and a plunger supported on the support seat by a spring; wherein a limiting structure is provided between the seat body of the support seat and the end cover of the threaded plug, and the limiting structure is used to limit the support seat to a preset position.

[0005] In some embodiments of the present application, the support seat includes a connected head and a rod, the outer end surface of the head is attached to the inner surface of the end cover, the limiting structure includes a first matching portion arranged on the inner surface of the end cover, and the limiting structure also includes a second matching portion arranged on the outer end surface of the head, the first matching portion cooperates with the second matching portion to limit the support seat to the preset position.

[0006] In some embodiments of the present application, the first mating portion includes a limiting groove arranged on the inner surface of the end cover, the outer end surface of the head is inclined in the direction from the center to the edge toward the direction away from the end cover, the limiting groove corresponds to the central area position of the outer end surface of the head, and the outer end surface of the head constitutes the second mating portion.

[0007] In some embodiments of the present application, the outer end surface of the head is a conical surface.

[0008] In some embodiments of the present application, the opening of the limiting groove is circular, and the center of the opening of the limiting groove coincides with the center of the inner surface of the end cover.

[0009] In some embodiments of the present application, the rod portion includes a first rod segment and a second rod segment connected to each other, the diameter of the first rod segment is larger than the diameter of the second rod segment, the first rod segment is connected to the head, the spring is sleeved on the first rod segment and the second rod segment, the spring is adapted to the first rod segment, and the inner diameter of the spring is larger than the diameter of the second rod segment.

[0010] In some embodiments of the present application, the second rod segment is connected to the first rod segment via a transition rod segment, and the outer diameter of the transition rod end gradually decreases from the first rod segment to the second rod segment.

[0011] In some embodiments of the present application, the plunger is a sleeve structure with one end blocked, and an oil inlet hole is provided on the wall of the sleeve structure.

[0012] In some embodiments of the present application, along the circumference of the sleeve structure, a plurality of oil inlet holes are arranged at intervals on the cylinder wall of the sleeve structure.

[0013] According to a second aspect of the present application, a plunger pump is provided, comprising: a body, on which at least one plunger hole is provided; and at least one plunger assembly as described in the first aspect, which is arranged in the plunger hole in a one-to-one correspondence.

[0014] The plunger assembly and plunger pump provided by this application can achieve the following beneficial technical effects:

[0015] The plunger assembly provided in the present application is provided with a limiting structure between the seat body of the support seat and the end cover of the threaded plug. The support seat is limited to a preset position by the limiting structure. In this way, the position of the spring provided on the support seat can be effectively avoided from being offset, and the deformation of the spring caused by the offset of the position of the support seat can be effectively avoided, thereby improving the accuracy of the force output by the spring, thereby effectively improving the pumping performance of the plunger pump.

[0016] Other characteristic features and advantages of the present application will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In these drawings, similar reference numerals are used to represent similar elements. The drawings described below are some embodiments of the present application, but not all embodiments. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0018] Figure 1 is a structural schematic diagram of a plunger assembly according to an exemplary embodiment;

[0019] Figure 2 yes Figure 1 Cross-section along the AA direction;

[0020] Figure 3 is a structural schematic diagram of a plunger pump according to an exemplary embodiment;

[0021] Figure 4 is a schematic structural diagram of a plunger pump according to another exemplary embodiment;

[0022] Figure 5 yes Figure 4 Cross-sectional view along the middle BB direction.

[0023] Reference numerals:

[0024] 1. Plunger pump;

[0025] 10. Eccentric shaft; 11. Eccentric portion; 111. Gap;

[0026] 20. Plunger assembly; 21. Threaded plug; 211. End cap; 2111. Limiting groove; 22. Support seat; 221. Head; 2211. Outer end surface; 222. Rod; 2221. First rod segment; 2222. Second rod segment; 2223. Transition rod segment; 23. Spring; 24. Plunger; 241. Oil inlet hole; 242. Working chamber; 25. Limiting structure; 251. First mating portion; 252. Second mating portion;

[0027] 30. Housing; 31. Valve plate; 32. First eccentric shaft seat; 33. Liquid inlet; 34. Liquid outlet; 35. Oil outlet cavity; 36. Oil inlet cavity;

[0028] 40. Front cover; 41. Bottom wall; 42. Side wall; 421. Plunger hole; 43. Second eccentric shaft seat; 43. Oil drain hole;

[0029] 50. Valve body assembly. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other in any way.

[0031] A plunger pump relies on the reciprocating motion of a plunger assembly, causing the volume of the oil chamber within the plunger assembly to change to achieve oil suction and discharge. The plunger assembly typically includes a threaded plug, a support seat, and a plunger supported on the support seat by a spring. Currently, plunger assemblies in related technologies suffer from the problem of spring deflection, resulting in poor pumping performance.

[0032] For example, a threaded plug in the related art includes an end cap with a groove structure on the side facing the support seat. The support seat includes a head and a rod. The outer end surface of the head is attached to the bottom of the groove structure. The spring is sleeved on the support seat rod, and the plunger is sleeved on the spring. The orthographic projection of the outer end surface of the head on the bottom of the groove structure lies within the groove structure, meaning that the head will displace along the groove structure. This will cause the center of the spring to shift, resulting in deformation such as bending of the entire spring. This in turn leads to inaccurate force output by the spring, resulting in reduced pumping performance of the plunger pump.

[0033] In order to solve the above problems, the present application provides a plunger assembly, in which a limiting structure is arranged between the seat body of the support seat and the end cover of the threaded plug. The support seat is limited to a preset position by the limiting structure. In this way, the position of the spring arranged on the support seat can be effectively avoided from being offset, and the deformation of the spring caused by the offset of the position of the support seat can be effectively avoided, thereby improving the accuracy of the force output by the spring, thereby effectively improving the pumping performance of the plunger pump.

[0034] The plunger assembly and plunger pump provided in the present application are described in detail below with reference to the accompanying drawings.

[0035] An exemplary embodiment of the present application provides a plunger assembly, such as Figure 1 and Figure 2 As shown, the plunger assembly 20 includes a threaded plug 21, a support seat 22, and a plunger 24 supported on the support seat 22 by a spring 23. For example, the threaded plug 21 can be used to assemble the plunger assembly 20 to an external device, such as the plunger pump 1. One end of the spring 23 is disposed on the support seat 22, and the other end of the spring 23 is mounted on the plunger 24. Under the action of the spring 23, the plunger 24 can reciprocate along its axial direction, thereby enabling the plunger assembly 20 to complete the oil pumping action.

[0036] A limiting structure 25 is provided between the base of the support base 22 and the end cap 211 of the threaded plug 21. The limiting structure 25 can limit the support base 22 to a predetermined position. For example, the limiting structure 25 can be positioned at a predetermined position, i.e., the position where the limiting structure 25 is located is the predetermined position, thereby limiting the support base 22 to the predetermined position through the limiting structure 25. The predetermined position can be set according to actual needs, for example, it can be the center position of the end cap 211 of the threaded plug 21.

[0037] By limiting the support seat 22 through the limiting structure 25, the position of the spring 23 set on the support seat 22 can be effectively avoided from being offset, and the deformation of the spring 23 caused by the offset of the position of the support seat 22 can be avoided, thereby improving the accuracy of the force output by the spring 23, thereby effectively improving the pumping performance of the plunger pump 1.

[0038] like Figure 2 As shown, in one embodiment, the support seat 22 includes a connected head portion 221 and a rod portion 222. The outer end surface 2211 of the head portion 221 is attached to the inner surface of the end cap 211, that is, the end cap 211 can act as a stop and limiter for the head portion 221, thereby helping the plunger assembly 20 to complete actions such as pumping oil. The limiting structure 25 includes a first matching portion 251 provided on the inner surface of the end cap 211, and a second matching portion 252 provided on the outer end surface 2211 of the head portion 221. The first matching portion 251 and the second matching portion 252 cooperate to limit the support seat 22 to a predetermined position. For example, the first matching portion 251 can be, for example, a groove provided on the inner surface of the end cap 211, the groove being located at the predetermined position, and the second matching portion 252 can be, for example, a protrusion provided on the outer end surface 2211 of the head portion 221. By engaging the protrusion with the groove, the support seat 22 is limited to the predetermined position. The first matching portion 251 and the second matching portion 252 can also be other matching forms, such as magnetic positioning, etc. The matching form of the first matching portion 251 and the second matching portion 252 can be set according to actual needs and is not specifically limited here.

[0039] Such a configuration makes the limiting structure 25 simple in structure and easy to process, while also improving the convenience and accuracy of limiting the support seat 22 , thereby helping to improve the pumping performance of the plunger pump 1 .

[0040] Continue to refer Figure 2 In one embodiment, the first mating portion 251 includes a limiting groove 2111 provided on the inner surface of the end cap 211. The position of the limiting groove 2111 can be, for example, a preset position. The outer end surface 2211 of the head 221 is inclined from the center to the edge in a direction away from the end cap 211. For example, the center of the outer end surface 2211 of the head 221 can be a point, that is, the outer end surface 2211 of the head 221 is inclined from the center point to the edge in a direction away from the end cap 211, thereby making the outer end surface 2211 of the head 221 a conical surface. The center of the outer end surface 2211 of the head 221 can also be an area, which can be, for example, circular, square, triangular, etc., that is, the outer end surface 2211 of the head 221 is inclined from the center area to the edge in a direction away from the end cap 211, thereby making the outer end surface 2211 of the head 221 a frustum or a prism.

[0041] The outer end surface 2211 of the head 221 constitutes the second matching portion 252, and the limiting groove 2111 corresponds to the central area of the outer end surface 2211 of the head 221, so that the outer end surface 2211 of the head 221 can be snapped into the limiting groove 2111 to limit the support seat 22 at a preset position.

[0042] By adopting such a setting form, on the one hand, the structure of the limiting structure 25 is simplified and easy to process. On the other hand, after the second matching portion 252 is inserted into the limiting groove 2111, a gap 111 is generated between the outer end surface 2211 of the head 221 and the inner surface of the end cover 211, thereby providing a movable space for the support seat 22. When the support seat 22 is subjected to an external force, for example, during the process of the plunger assembly 20 pumping oil, the spring 23 provides a thrust to the support seat 22, and the support seat 22 can make a circular motion around the central area of the outer end surface 2211 of the head 221. During this process, the axial position of the support seat 22 remains unchanged, thereby effectively avoiding the position of the spring 23 set on the support seat 22 from being offset, and the deformation of the spring 23 caused by the offset of the position of the support seat 22, thereby improving the accuracy of the force output by the spring 23, thereby effectively improving the pumping performance of the plunger pump 1.

[0043] In one embodiment, the outer end surface 2211 of the head 221 is conical, that is, the outer end surface 2211 of the head 221 is inclined from the center point to the edge, away from the end cap 211. This arrangement, on the one hand, facilitates machining of the outer end surface 2211 of the head 221, thereby improving the machining efficiency of the plunger assembly 20. On the other hand, it effectively improves the smoothness of the second engaging portion 252 when it is engaged with the retaining groove 2111, thereby enhancing the retaining effect of the support seat 22.

[0044] In one embodiment, the notch of the limiting groove 2111 is circular to match the shape of the outer end surface 2211 of the head 221, thereby facilitating the second matching portion 252 to be inserted into the limiting groove 2111 while further improving the smoothness of the second matching portion 252 when being inserted into the limiting groove 2111, thereby effectively improving the limiting effect of the support seat 22.

[0045] The center of the limiting groove 2111 coincides with the center of the inner surface of the end cap 211, i.e., the preset position is the center of the inner surface of the end cap 211. This design improves the uniformity of the distance between the outer edge of the head 221 and the outer edge of the inner surface of the end cap 211, thereby effectively preventing interference between the support base 22 and the end cap 211 during the circular motion, thereby ensuring the normal operation of the plunger assembly 20 and further improving the pumping performance of the plunger pump 1.

[0046] like Figure 2As shown, in one embodiment, the rod portion 222 includes a first rod segment 2221 and a second rod segment 2222. The first rod segment 2221 is connected to the head portion 221, and the diameter of the first rod segment 2221 is larger than the diameter of the second rod segment 2222. The spring 23 is sleeved between the first rod segment 2221 and the second rod segment 2222, and the spring 23 is adapted to the first rod segment 2221. With this arrangement, the first rod end can support and limit the spring 23, facilitating the securement of the spring 23 while also improving the stability of the spring 23 fixed to the support base 22.

[0047] The inner diameter of spring 23 is greater than the diameter of second rod segment 2222, resulting in a gap 111 between spring 23 and second rod segment 2222. This design, on the one hand, prevents the second rod segment 2222 from causing resistance to the expansion and contraction of spring 23, thereby facilitating the contraction and extension of spring 23 along the axial direction of rod 222, effectively improving the deformation efficiency of spring 23 and thereby facilitating enhanced pumping performance of plunger pump 1. Furthermore, it prevents friction between spring 23 and second rod segment 2222 that could cause wear on rod 222, thereby effectively extending the service life of rod 222 and enhancing the reliability of plunger assembly 20.

[0048] Continue to refer Figure 2 In one embodiment, the second rod segment 2222 is connected to the first rod segment 2221 via a transition rod segment 2223. The outer diameter of the transition rod end gradually decreases from the first rod segment 2221 to the second rod segment 2222. This design, on the one hand, effectively improves the structural strength of the connection between the first rod segment 2221 and the second rod segment 2222, thereby effectively preventing fracture of the rod portion 222 and further improving the reliability of the plunger assembly 20. On the other hand, the provision of the transition rod segment 2223 also provides a guide for the assembly of the spring 23, facilitating the sleeve installation of the spring 23 from the second rod segment 2222 onto the first rod end, thereby effectively improving the assembly efficiency of the plunger assembly 20.

[0049] Continue to refer Figure 2 In one embodiment, the plunger 24 is a sleeve structure with one end blocked. The sleeve structure is sleeved onto the spring 23 through the open end of the sleeve structure. An oil inlet hole 241 is provided on the wall of the sleeve structure. For example, only one oil inlet hole 241 may be provided on the wall of the sleeve structure, or multiple oil inlet holes 241 may be provided on the wall of the sleeve structure. This arrangement facilitates the plunger assembly 20 to achieve the oil pumping action while simplifying the structure of the plunger assembly 20 and facilitating processing and assembly.

[0050] In one embodiment, when multiple oil inlet holes 241 are provided on the sleeve wall, the multiple oil inlet holes 241 are spaced apart along the circumference of the sleeve. This design, on the one hand, increases the amount of oil entering the sleeve, thereby effectively improving the pumping efficiency of the plunger assembly 20. Furthermore, the placement of the multiple oil inlet holes 241 along the circumference of the sleeve ensures consistent positioning of the multiple oil inlet holes 241, thereby facilitating the setting of the oil inlet and outlet positions of the plunger 24.

[0051] like Figure 3 As shown, an exemplary embodiment of the present application provides a plunger pump 1, which includes a body and at least one plunger assembly 20 as described above. At least one plunger hole 421 is provided on the body, and at least one plunger assembly 20 is provided in the plunger hole 421 in a one-to-one correspondence. Exemplarily, the plunger pump 1 may be provided with only one plunger assembly 20, and accordingly, only one plunger hole 421 is provided on the body, and the plunger assembly 20 is provided in the plunger hole 421. The plunger pump 1 may also be provided with multiple plunger assemblies 20, for example, 8 plunger assemblies 20 are provided, and accordingly, multiple plunger holes 421 are also provided on the body, for example, 8 plunger holes 421, and multiple plunger assemblies 20 are provided in the plunger hole 421 in a one-to-one correspondence.

[0052] like Figure 2 As shown, in the above-mentioned plunger assembly 20, the plunger assembly 20 includes a threaded plug 21, a support seat 22, and a plunger 24 supported on the support seat 22 by a spring 23. For example, the plunger assembly 20 can be assembled on the plunger pump 1 through the threaded plug 21. One end of the spring 23 is set on the support seat 22, and the other end of the spring 23 is installed on the plunger 24. Under the action of the spring 23, the plunger 24 can make a reciprocating motion along its axial direction, so that the plunger assembly 20 can complete the oil pumping action.

[0053] A limiting structure 25 is provided between the base of the support seat 22 and the end cap 211 of the threaded plug 21. The limiting structure 25 can limit the support seat 22 to a preset position. By limiting the support seat 22 by the limiting structure 25, the position of the spring 23 provided on the support seat 22 can be effectively prevented from being offset, and deformation of the spring 23 caused by the offset of the support seat 22 can be effectively avoided. This improves the accuracy of the force output by the spring 23, thereby effectively improving the pumping performance of the plunger pump 1.

[0054] like Figure 4 and Figure 5As shown, in one embodiment, the body includes an eccentric shaft 10 and a housing 30 and a front cover 40 connected thereto. The housing 30 is provided with a liquid inlet 33 and a liquid outlet 34. A valve plate 31 is provided at one end of the housing 30 facing the front cover 40. The valve plate 31 and the housing 30 together form an oil outlet cavity 35, which is in communication with the liquid outlet 34. A first eccentric shaft seat 32 is provided on the side of the valve plate 31 facing the front cover 40. The first eccentric shaft seat 32 and the valve plate 31 together form an oil inlet cavity 36, which is in communication with the liquid outlet 34.

[0055] The front cover 40 includes a connected bottom wall 41 and side walls 42. The side walls 42 are provided with at least one plunger hole 421, each extending radially along the front cover 40. The outer circumference of the first eccentric shaft seat 32 abuts the side surface. A second eccentric shaft seat 43 is provided on the bottom wall 41. The ends of the eccentric shaft 10 are mounted on the first eccentric shaft seat 32 and the second eccentric shaft seat 43, respectively. The eccentric shaft 10 includes an eccentric portion 11. A first end surface of the eccentric portion 11 faces the first eccentric shaft seat 32, and a second end surface of the eccentric portion 11 faces the second eccentric shaft seat 43. A gap 111 is formed between the outer circumference of the eccentric portion 11 and the side walls 42 of the front cover 40. This gap 111 constitutes an oil suction chamber or an oil discharge chamber. A through hole is provided in the first eccentric shaft seat 32 to connect the oil inlet chamber 36 with the gap 111.

[0056] The plunger hole 421 includes a first end and a second end facing each other. The first end of the plunger hole 421 communicates with the gap 111, and the second end of the plunger hole 421 communicates with the outer surface of the front cover 40. Each plunger assembly 20 is disposed in a one-to-one correspondence within the plunger hole 421. The threaded plug 21 of the plunger assembly 20 is threadedly engaged with the second end of the plunger hole 421. The blocking end of the plunger 24 of the plunger assembly 20 abuts against the outer circumferential surface of the eccentric portion 11. The support seat 22, threaded plug 21, and plunger 24 of the plunger assembly 20 collectively enclose a working chamber 242 that communicates with the oil inlet hole 241 on the plunger 24.

[0057] The eccentric shaft 10 may be drivably connected to a driving device, which may be, for example, a motor. For example, the driving device may drive the eccentric shaft 10 to rotate forward or reverse according to actual working conditions.

[0058] Oil enters the oil inlet chamber 36 from the liquid inlet 33. The oil in the oil inlet chamber 36 enters the gap 111 through the through hole. As the eccentric shaft 10 rotates, the eccentric portion 11 presses each plunger assembly 20 to reciprocate between the liquid inlet position and the liquid outlet position along the radial direction of the front cover 40. In the liquid inlet position, the oil inlet hole 241 of the plunger 24 extends into the gap 111, connecting the working chamber 242 with the gap 111. The oil flows into the working chamber 242 of the plunger assembly 20 through the oil inlet hole 241. The front cover 40 is provided with oil drain holes 43 that correspond to and communicate with each plunger hole 421. The oil drain holes 43 are also connected to the working chamber 242 of the plunger assembly 20. The oil drain holes 43 extend along the axial direction of the front cover 40 to the housing 30 and then communicate with the oil outlet chamber 35.

[0059] The plunger pump 1 further includes a valve assembly 50 disposed within each oil discharge hole 43. When the eccentric shaft 10 rotates to press the plunger 24 back into the plunger hole 421, placing the plunger 24 in the liquid discharge position, the oil inlet hole 241 on the plunger 24 is located within the plunger hole 421. The valve assembly 50 acts to allow the oil in the working chamber 242 to be discharged into the oil discharge chamber 35 and then discharged from the liquid outlet 34. This completes the pumping of the oil.

[0060] It should be noted that the eccentric portion 11 presses each plunger assembly 20 to reciprocate between the liquid inlet position and the liquid outlet position along the radial direction of the front cover 40, and the gap range where the plunger 24 moving from the liquid inlet position to the liquid outlet position is located constitutes an oil discharge chamber, and the gap range where the plunger 24 moving from the liquid outlet position to the liquid inlet position is located constitutes an oil suction chamber.

[0061] The contents described above can be implemented individually or in combination in various ways, and these variations are all within the scope of protection of this application.

[0062] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the statement "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0063] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of this application and are not intended to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they may modify the technical solutions described in the above embodiments or replace some of the technical features therein with equivalents; and such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A plunger assembly, characterized in that: The plunger assembly includes a threaded plug, a support seat, and a plunger supported on the support seat by a spring; Wherein, a limiting structure is provided between the seat body of the support seat and the end cover of the threaded plug, and the limiting structure is used to limit the support seat to a preset position.

2. The plunger assembly according to claim 1, wherein: The support seat includes a connected head and a rod, the outer end surface of the head is attached to the inner surface of the end cover, the limiting structure includes a first matching portion arranged on the inner surface of the end cover, and the limiting structure also includes a second matching portion arranged on the outer end surface of the head, the first matching portion cooperates with the second matching portion to limit the support seat to the preset position.

3. The plunger assembly according to claim 2, wherein: The first fitting portion includes a limiting groove arranged on the inner surface of the end cover, the outer end surface of the head is inclined in the direction from the center to the edge in the direction away from the end cover, the limiting groove corresponds to the central area position of the outer end surface of the head, and the outer end surface of the head constitutes the second fitting portion.

4. The plunger assembly according to claim 3, wherein: The outer end surface of the head is a conical surface.

5. The plunger assembly according to claim 3, wherein: The notch of the limiting groove is circular, and the center of the notch of the limiting groove coincides with the center of the inner surface of the end cover.

6. The plunger assembly according to any one of claims 2 to 5, characterized in that The rod portion includes a first rod segment and a second rod segment connected to each other, the diameter of the first rod segment is larger than the diameter of the second rod segment, the first rod segment is connected to the head, the spring is sleeved on the first rod segment and the second rod segment, the spring is adapted to the first rod segment, and the inner diameter of the spring is larger than the diameter of the second rod segment.

7. The plunger assembly according to claim 6, wherein: The second rod segment is connected to the first rod segment via a transition rod segment, and the outer diameter of the transition rod end gradually decreases from the first rod segment to the second rod segment.

8. The plunger assembly according to any one of claims 1 to 5, characterized in that The plunger is a sleeve structure with one end blocked, and an oil inlet hole is provided on the wall of the sleeve structure.

9. The plunger assembly according to claim 8, wherein: Along the circumference of the sleeve structure, a plurality of oil inlet holes are arranged at intervals on the cylinder wall of the sleeve structure.

10. A plunger pump, characterized in that: The plunger pump comprises: a body, wherein the body is provided with at least one plunger hole; At least one plunger assembly according to any one of claims 1 to 9 is disposed in the plunger hole in a one-to-one correspondence.

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