Plunger, plunger pump and plunger motor

Abstract

The utility model relates to a hydraulic device, in particular to a plunger, a plunger pump and a plunger motor. The peripheral surface of the plunger is the cambered surface, and the vertical distance between the generatrix end of the cambered surface and the axis of the plunger is smaller than the vertical distance between the generatrix middle position of the cambered surface and the axis of the plunger, namely, the structure is thick in the middle and thin at the two ends. In the working process of the plunger, the outer circumferential surface of the cambered surface of the plunger is continuously contacted with the inner wall of the plunger hole, so that the running stability of the plunger is improved, and the mechanical efficiency of a plunger pump or a plunger motor using the plunger is further improved. The arc-surface peripheral surface of the plunger is in linear contact with the inner wall of the plunger hole, so that the contact mode of the plunger and the cylinder body is improved, and the use function of the plunger is improved. Meanwhile, the generatrix of the cambered surface of the plunger is arranged to be the inferior arc section, the gap between the plunger and the plunger hole is reasonably utilized, and the situation that the gap between the plunger and the plunger hole is increased due to the fact that the cambered surface is machined on the plunger is avoided.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to hydraulic devices, in particular to a plunger, a plunger pump and a plunger motor. BACKGROUND

[0002] The hydraulic plunger pump and the plunger motor are mainly composed of a transmission shaft, a shell, a swash plate, a plunger, a cylinder, a spring, a bearing, a distribution plate, a rear cover and the like, wherein the plungers are uniformly distributed in the cylinder along the circumference. In the transmission process, the plungers make reciprocating motion in the plunger holes of the cylinder, and at the same time, the plungers also rotate around the transmission shaft together with the plunger holes of the cylinder.

[0003] In this process, the edge of the plunger end face is in contact with the inner wall of the plunger hole. Since the theoretical contact mode of the two at this time is point contact, the contact state is not ideal, thereby reducing the use function of the plunger. CONTENT OF THE UTILITY MODEL

[0004] In order to solve the problem of the unsatisfactory contact mode between the edge of the plunger end face and the inner wall of the plunger hole in the prior art, thereby causing the use function of the plunger to decline, the present disclosure provides a plunger, a plunger pump and a plunger motor.

[0005] The present disclosure provides a plunger applied to a plunger pump or a plunger motor, wherein the outer peripheral surface of the plunger is provided as an arc surface, the generatrix of the arc surface is a poor arc segment, and the perpendicular distance between the end of the generatrix of the arc surface and the plunger axis is less than the perpendicular distance between the middle position of the generatrix of the arc surface and the plunger axis.

[0006] In an embodiment of the present disclosure, the central angle of the generatrix of the arc surface is 5° to 20°.

[0007] In an embodiment of the present disclosure, the perpendicular distances between the two ends of the generatrix of the arc surface and the plunger axis are equal.

[0008] In an embodiment of the present disclosure, the perpendicular distance between the end of the generatrix of the arc surface close to the one end of the plunger provided with a ball head and the plunger axis is less than the perpendicular distance between the end of the generatrix of the arc surface away from the one end of the plunger provided with a ball head and the plunger axis, and the ratio of the former to the latter is 1:1.1 to 1:1.2.

[0009] In an embodiment of the present disclosure, the ratio of the chord length between the two ends of the generatrix of the arc surface to the overall length of the plunger is 1:2.5 to 1:2.8.

[0010] In an embodiment of the present disclosure, the end of the arc surface away from the one end of the plunger provided with a ball head extends in the axial direction by a preset length to form a first conical surface, the first conical surface is provided with an annular groove in the circumferential direction, and the annular groove is configured to mount a sealing ring.

[0011] In one embodiment of the present disclosure, a second taper surface is arranged between the arc surface and the ball head,

[0012] An angle between a generatrix of the first taper surface and the plunger axis is a first angle, and an angle between a tangent of an end of the generatrix of the arc surface away from the ball head is a second angle, the first angle being smaller than the second angle.

[0013] An angle between a generatrix of the second taper surface and the plunger axis is a third angle, and an angle between a tangent of an end of the generatrix of the arc surface close to the ball head is a fourth angle, the third angle being smaller than the fourth angle.

[0014] In one embodiment of the present disclosure, a length ratio of the first taper surface to the second taper surface is 3:1 to 3.5:1.

[0015] In a second aspect, the present disclosure further provides a plunger pump, which at least comprises:

[0016] a pump body having an oil inlet passage and an oil outlet passage;

[0017] a cylinder body provided with a plunger hole and configured to rotate relative to the pump body under the action of a drive shaft;

[0018] a plunger movably arranged in the plunger hole and configured to reciprocate in the plunger hole under an external force to suck a medium from the oil inlet passage into the plunger hole, compress the medium, and then discharge the medium from the oil outlet passage, the plunger being any one of the plunger 1 described above.

[0019] In a third aspect, the present disclosure further provides a plunger motor, which at least comprises:

[0020] a pump body having an oil inlet passage and an oil outlet passage;

[0021] a cylinder body provided with a plunger hole;

[0022] a plunger configured to reciprocate axially along the plunger hole under the medium pushing of the oil inlet passage, and drive the cylinder body to rotate together with a drive shaft, the plunger being any one of the plunger described above.

[0023] One beneficial effect of the present disclosure is that the plunger outer peripheral surface is provided as an arc surface, and the perpendicular distance between an end of the generatrix of the arc surface and the plunger axis is smaller than the perpendicular distance between a middle position of the generatrix of the arc surface and the plunger axis, i.e., a structure of thick in the middle and thin at both ends.

[0024] During the working process of the plunger, the curved outer circumferential surface of the plunger continuously contacts the inner wall of the plunger hole, thereby improving the stability of the plunger operation, and further improving the mechanical efficiency of the plunger pump or plunger motor using the plunger. At the same time, the curved outer circumferential surface of the plunger and the inner wall of the plunger hole form a line contact, which improves the contact mode and improves the use function of the plunger.

[0025] At the same time, the curved generatrix of the plunger is arranged as a minor arc segment, which reasonably utilizes the gap between the plunger and the plunger hole, and avoids the increase of the gap between the plunger and the plunger hole due to the processing of the curved surface of the plunger.

[0026] Other features of the present disclosure and its advantages will become apparent from the following detailed description of exemplary embodiments thereof, with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0028] Figure 1 is a schematic view of the overall structure of a plunger pump motor provided by an embodiment of the present disclosure;

[0029] Figure 2 is an axial sectional view of a plunger provided by an embodiment of the present disclosure;

[0030] Figure 3 is a schematic view of the central angle of the curved generatrix of a plunger provided by an embodiment of the present disclosure;

[0031] Figure 4 is Figure 2 is an enlarged schematic view of the structure at A;

[0032] Figure 5 is Figure 2 is an enlarged schematic view of the structure at B.

[0033] Figures 1 to 5 The one-to-one correspondence between the names of various components and the reference numerals in the drawings is as follows:

[0034] 1, plunger; 11, curved surface; 12, first conical surface; 121, annular groove; 13, second conical surface; 14, ball head;

[0035] 2, swash plate; 3, drive shaft; 4, plunger hole; 5, pump body. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present disclosure unless otherwise specifically stated.

[0037] The following description of at least one example embodiment is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses.

[0038] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification.

[0039] It should be noted that like reference numerals and letters refer to like items throughout the attached drawings, and as a result, further discussion of such items is unnecessary in subsequent drawings.

[0040] The specific embodiments of the present disclosure will be described below with reference to the drawings.

[0041] In this document, "upper", "lower", "front", "rear", "left", "right", and the like are used to describe relative positions between relevant parts, and do not limit the absolute positions of the relevant parts.

[0042] In this document, "first", "second", and the like are used only to distinguish between each other, and do not represent importance and order, and are not a prerequisite for each other.

[0043] In this document, "equal", "same", and the like are not strictly limited in the mathematical and / or geometric sense, but also include errors that can be understood by those skilled in the art and allowed in manufacturing or use.

[0044] As shown in Figure 1 To solve the problem that the edge of the end face of the plunger 1 is not in an ideal contact with the inner wall of the plunger hole 4 in the prior art, thereby causing the use function of the plunger 1 to decline, the present disclosure provides a plunger 1.

[0045] The plunger 1 is applied to a plunger pump or a plunger motor, and specifically, referring to Figure 2 The outer peripheral surface of the plunger 1 is provided as an arc surface 11, the generatrix of the arc surface 11 is a poor arc segment, and the vertical distance between the end of the generatrix of the arc surface 11 and the axis of the plunger 1 is less than the vertical distance between the middle position of the generatrix of the arc surface 11 and the axis of the plunger 1.

[0046] It should be noted that the arc surface 11 is formed by rotating a continuous curve around the axis for one revolution, and the continuous curve becomes the generatrix of the arc surface 11.

[0047] In use, the plunger 1 is installed in the plunger hole 4 of the plunger pump or the plunger motor. After the plunger pump or the plunger motor is started, the plunger 1 reciprocates along the plunger hole 4, and at the same time, the plunger 1 rotates with the plunger hole 4 relative to the drive shaft 3.

[0048] Due to the force generated by the medium on the plunger 1, the axis of the plunger 1 is offset relative to the axis of the plunger hole 4, which in turn causes the end of the plunger 1 away from the ball head 14 to be more easily in contact with the inner wall of the plunger hole 4. The plunger 1 provided by the present disclosure, because the outer circumferential surface of the plunger 1 is the arc surface 11, and the perpendicular distance between the generatrix end of the arc surface 11 and the axis of the plunger 1 is less than the perpendicular distance between the middle position of the generatrix of the arc surface 11 and the axis of the plunger 1, that is, the plunger 1 is thick in the middle and thin at both ends.

[0049] When the plunger 1 is tilted by the force of the medium towards the inner wall of the plunger hole 4, the arc surface 11 provided by the plunger 1 will be in contact with the inside of the plunger hole 4, thereby avoiding the end edge of the plunger 1 from being in contact with the inner wall of the plunger hole 4.

[0050] Specifically, in actual application, the contact mode between the end edge of the plunger 1 and the inner wall of the plunger hole 4 is point contact or no contact, and the no contact means that there is an oil film between the plunger 1 and the plunger hole 4 to separate them, but once the plunger 1 is subjected to too much force from the medium, the oil film may be damaged, and the end edge of the plunger 1 will be in point contact with the inner wall of the plunger hole 4, which is not ideal for the relative state of the plunger 1 and the plunger hole 4. The plunger 1 of the present disclosure replaces the end edge of the plunger 1 with the arc surface 11 to make the arc surface 11 form a line contact with the plunger hole 4, so that the motion state is more stable.

[0051] At the same time, because the contact mode between the arc surface 11 of the plunger 1 and the inner wall of the plunger hole 4 is line contact, the pressure in the contact area between the plunger 1 and the inner wall of the plunger hole 4 is small, so it also avoids the damage of the oil film between the plunger 1 and the plunger hole 4 due to excessive pressure, thereby affecting the lubrication between the plunger 1 and the plunger hole 4.

[0052] Furthermore, because the arc surface 11 of the plunger 1 is in contact with the inner wall of the plunger hole 4, it supports the plunger 1, so that the offset of the axis of the plunger 1 relative to the axis of the plunger hole 4 is reduced, thereby enhancing the stability of the plunger 1 in operation, and further improving the mechanical efficiency of the plunger pump or plunger motor.

[0053] In an embodiment of the present disclosure, the central angle of the generatrix of the arc surface 11 is 5° to 20°.

[0054] As shown in FIG. 3, in actual application, because the generatrix of the arc surface 11 is a minor arc, and the central angle a of the generatrix of the arc surface 11 is set in the interval of 5° to 20°. Therefore, the plunger 1 is appropriately thickened in the middle position, which ensures the stable contact between the arc surface 11 of the plunger 1 and the plunger hole 4, and reasonably utilizes the gap between the plunger 1 and the plunger hole 4, that is, by setting the central angle a of the generatrix of the arc surface 11 in the interval of 5° to 20°, the gap between the end of the plunger 1 and the plunger hole 4 will not be enlarged due to the processing of the arc surface 11 of the plunger 1.

[0055] In one embodiment of the present disclosure, the chord length between the two ends of the generatrix of the arc surface 11 is in the proportion of 1:2.5 to 1:2.8 to the overall length of the plunger 1.

[0056] Specifically, in one embodiment, the chord length between the two ends of the generatrix of the arc surface 11 is 34 mm, and the overall length of the plunger 1 is 85 mm. In another embodiment, the chord length between the two ends of the generatrix of the arc surface 11 is 25 mm, and the overall length of the plunger 1 is 70 mm.

[0057] The plunger 1 provided by the present disclosure controls the proportion of the arc surface 11 to the overall plunger 1 to ensure that the arc surface 11 of the plunger 1 achieves smooth contact with the plunger hole 4 while ensuring that it does not affect the normal operation of other components of the plunger 1, such as the ball head 14. At the same time, the reasonable length of the arc surface 11 provided on the outer circumferential surface of the plunger 1 also helps to enhance the overall strength of the plunger 1.

[0058] The specific structure of the plunger 1 is described below through two embodiments.

[0059] Embodiment one:

[0060] In this embodiment, the vertical distance between the two ends of the generatrix of the arc surface 11 and the axis of the plunger 1 is equal, and the radial cross-sectional size of the two ends of the arc surface 11 is equal from the radial cross-sectional view of the plunger 1. This kind of setting method is convenient for processing, and can also meet the smooth contact of the arc surface 11 of the plunger 1 with the inner wall of the plunger hole 4, and improve the smoothness of the plunger 1 operation.

[0061] Embodiment two:

[0062] In this embodiment, the vertical distance between the end of the generatrix of the arc surface 11 close to the ball head 14 and the axis of the plunger 1 is less than the vertical distance between the end of the generatrix of the arc surface 11 away from the ball head 14 and the axis of the plunger 1, and the proportion of the former to the latter is 1:1.1 to 1:1.2.

[0063] That is, the radial cross-sectional size of the end of the arc surface 11 of the plunger 1 close to the ball head 14 is less than the radial cross-sectional size of the end of the arc surface 11 of the plunger 1 away from the ball head 14. In one embodiment, the vertical distance between the end of the generatrix of the arc surface 11 close to the ball head 14 and the axis of the plunger 1 is 9 mm, and the vertical distance between the end of the generatrix of the arc surface 11 away from the ball head 14 and the axis of the plunger 1 is 9.9 mm. In another embodiment, the vertical distance between the end of the generatrix of the arc surface 11 close to the ball head 14 and the axis of the plunger 1 is 8.5 mm, and the vertical distance between the end of the generatrix of the arc surface 11 away from the ball head 14 and the axis of the plunger 1 is 10.2 mm.

[0064] In this arrangement, the arc surface 11 of the plunger 1 is thinner at the end close to the ball head 14 to transition the part where the plunger 1 is connected to the ball head 14, and is thicker at the end away from the ball head 14 to compensate for the weakened strength at this end due to the annular groove 121.

[0065] In addition, in the plunger 1 provided by the present disclosure, the end of the arc surface 11 away from the ball head 14 extends axially for a predetermined length to form a first taper surface 12, and the first taper surface 12 is circumferentially provided with an annular groove 121 configured to mount a sealing ring.

[0066] Meanwhile, a second taper surface 13 is provided between the arc surface 11 and the ball head 14, the angle between the generatrix of the first taper surface 12 and the plunger axis is a first angle, the tangent line at the end of the generatrix of the arc surface 11 away from the ball head 14 is a second angle, and the first angle is smaller than the second angle.

[0067] The angle between the generatrix of the second taper surface 13 and the plunger axis is a third angle, and the tangent line at the end of the generatrix of the arc surface 11 close to the ball head 14 is a fourth angle, and the third angle is smaller than the fourth angle.

[0068] If the entire outer circumferential surface of the plunger 1 is arranged as an arc surface 11, the middle position of the plunger 1 will be too thick, and the two ends will be too thin, which will result in the plunger 1 not meeting the strength requirements. Therefore, the plunger 1 provided by the present disclosure further connects the first taper surface 12 and the second taper surface 13 at both ends of the arc surface 11 to strengthen the strength of both ends of the arc surface 11.

[0069] Specifically, the first taper surface 12 is arranged at the end of the arc surface 11 away from the ball head 14 of the plunger 1, and the annular groove 121 is provided on the first taper surface 12 to mount a sealing ring. The second taper surface 13 is arranged at the end of the arc surface 11 close to the ball head 14 of the plunger 1 to connect the ball head 14 of the plunger 1.

[0070] As shown in Figure 4 , Figure 5 The first angle is specifically β1, the second angle is γ1, the third angle is β2, and the fourth angle is γ2. Since γ1>β1, γ2>β2, the strength of the plunger 1 is avoided from not meeting the use requirements due to the too thin ends of the arc surface 11.

[0071] In one embodiment, the length of the first taper surface 12 is 18 mm, and the length of the second taper surface 13 is 6 mm. In another embodiment, the length of the first taper surface 12 is 14 mm, and the length of the second taper surface 13 is 4 mm. The plunger 1 provided by the present disclosure sets the length ratio of the first taper surface 12 and the second taper surface 13 to be between 3:1 and 3.5:1, which provides sufficient processing space for the annular groove 121 on the first taper surface 12, and also provides sufficient transition space between the arc surface 11 and the ball head 14.

[0072] In a second aspect, the present disclosure provides a plunger pump, comprising a pump body 5, a cylinder body, and the above-mentioned plunger 1, wherein the pump body 5 has an oil inlet oil path and an oil outlet oil path, the cylinder body is provided with a plunger hole 4 and is configured to rotate relative to the pump body 5 under the action of a drive shaft 3; the plunger 1 is configured to suck the medium from the oil inlet oil path into the plunger hole 4, and after compressing the medium, the medium is discharged from the oil outlet oil path.

[0073] Specifically, the plunger pump is provided with a drive shaft 3, which rotates and drives the cylinder body to rotate around the drive shaft 3, so that the plunger 1 in the plunger hole 4 of the cylinder body also rotates.

[0074] At the same time, under the action of the swash plate 2 of the plunger pump, the plunger 1 is forced to perform axial reciprocating motion along the plunger hole 4. In this process, the plunger 1 in the plunger hole 4 communicating with the oil inlet oil path, the chamber space between the plunger 1 and the plunger hole 4 gradually increases during the relative motion between the plunger 1 and the plunger hole 4, so that the medium is sucked into the plunger hole 4 from the oil inlet oil path of the plunger pump.

[0075] Subsequently, the plunger 1 and the cylinder body rotate with the drive, and when the plunger hole 4 of the cylinder body communicates with the oil outlet oil path of the plunger pump, the plunger 1 moves relative to the plunger hole 4 under the action of the swash plate 2. At this time, the chamber space between the plunger 1 and the plunger hole 4 decreases, the medium is extruded, and the medium is discharged from the plunger hole 4, and finally discharged from the oil outlet oil path of the plunger pump.

[0076] In this process, under the action of the medium, the axis of the plunger 1 deviates from the axis of the plunger hole 4, and the curved surface 11 of the plunger 1 stably contacts the inner wall of the plunger hole 4, avoiding the contact between the end surface edge of the plunger 1 and the inner wall of the plunger hole 4, which causes the contact state to be not ideal, thereby improving the service life of the plunger 1.

[0077] In a third aspect, the present disclosure provides a plunger motor, comprising a pump body 5, a cylinder body, and the above-mentioned plunger 1, wherein the pump body 5 has an oil inlet oil path and an oil outlet oil path; the cylinder body is provided with a plunger hole 4; the plunger 1 is configured to reciprocate axially along the plunger hole 4 under the push of the medium in the oil inlet oil path, and drive the cylinder body to rotate together with the drive shaft 3.

[0078] Specifically, after the plunger motor is started, the medium enters the plunger hole 4 from the oil inlet oil path of the plunger motor, and pushes the plunger 1 to move relative to the plunger hole 4. At the same time, under the action of the swash plate 2, the medium also pushes the plunger 1 to rotate together with the plunger hole 4 and the drive shaft 3 relative to the axis of the drive shaft 3. When the plunger 1 rotates together with the plunger hole 4 to a position where the plunger hole 4 communicates with the oil outlet oil path, the medium in the plunger hole 4 is discharged from the oil outlet oil path.

[0079] In the process, under the action of the medium, the axis of the plunger 1 is offset relative to the axis of the plunger hole 4, and the arc surface 11 of the plunger 1 is in stable contact with the inner wall of the plunger hole 4, which avoids the contact state being not ideal due to the contact between the end face edge of the plunger 1 and the inner wall of the plunger hole 4, thereby improving the service life of the plunger 1. Meanwhile, due to the action of the arc surface 11 of the plunger 1, the offset of the plunger 1 relative to the plunger hole 4 is reduced, thereby improving the stability of the operation of the plunger motor.

[0080] Embodiments of the present disclosure have been described above, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles, practical application or technical improvement in the market of the embodiments, or to enable other ordinary skilled in the art to understand the embodiments disclosed herein. The scope of the present disclosure is defined by the appended claims.

Claims

1. A plunger, said plunger (1) being used in a plunger pump or plunger motor, characterized in that, The outer peripheral surface of the plunger (1) is set as an arc surface (11), the generatrix of the arc surface (11) is a minor arc segment, and the vertical distance between the end of the generatrix of the arc surface (11) and the axis of the plunger (1) is less than the vertical distance between the middle position of the generatrix of the arc surface (11) and the axis of the plunger (1).

2. The plunger according to claim 1, characterized in that, The central angle of the generatrix of the arc surface (11) is 5° to 20°.

3. The plunger according to claim 1, characterized in that, The two ends of the generatrix of the arc surface (11) are equidistant from the vertical distance of the piston axis.

4. The plunger according to claim 2, characterized in that, The vertical distance between the generatrix of the arc surface (11) near the end of the plunger (1) where the ball head (14) is located and the axis of the plunger is less than the vertical distance between the generatrix of the arc surface (11) away from the ball head (14) and the axis of the plunger, and the ratio of the former to the latter is 1:1.1 to 1:1.

2.

5. The plunger according to claim 1, characterized in that, The ratio of the chord length between the two ends of the generatrix of the arc surface (11) to the overall length of the plunger (1) is 1:2.5 to 1:2.

8.

6. The plunger according to claim 4, characterized in that, The arc surface (11) is provided with a ball head (14) at one end away from the plunger (1) and extends axially for a predetermined length to form a first conical surface (12). The first conical surface (12) is provided with an annular groove (121) in the circumferential direction. The annular groove (121) is configured to install a sealing ring.

7. The plunger according to claim 6, characterized in that, A second conical surface (13) is provided between the arc surface (11) and the ball head (14). The angle between the generatrix of the first conical surface (12) and the axis of the plunger is the first included angle, and the tangent of the generatrix of the arc surface (11) at the end away from the ball head (14) is the second included angle. The first included angle is smaller than the second included angle. The angle between the generatrix of the second conical surface (13) and the axis of the plunger is the third angle, and the tangent of the generatrix of the arc surface (11) near the end of the ball head (14) is the fourth angle. The third angle is smaller than the fourth angle.

8. The plunger according to claim 7, characterized in that, The length ratio of the first conical surface (12) to the second conical surface (13) is 3:1 to 3.5:

1.

9. A plunger pump, characterized in that, The plunger pump includes at least: Pump body (5), the pump body (5) has an oil inlet passage and an oil outlet passage; The cylinder body is provided with a plunger bore (4) and is configured to rotate relative to the pump body (5) under the action of the drive shaft (3); A plunger (1) is movably disposed in the plunger hole (4) and configured to reciprocate in the plunger hole (4) under external force to draw the medium from the oil inlet passage into the plunger hole (4), and after compressing the medium, discharge the medium from the oil outlet passage. The plunger (1) is the plunger (1) according to any one of claims 1 to 8.

10. A piston motor, characterized in that, The plunger motor includes at least: Pump body (5), the pump body (5) has an oil inlet passage and an oil outlet passage; Cylinder body, wherein the cylinder body is provided with a plunger hole (4); A plunger (1) is configured to reciprocate along the plunger hole (4) under the push of the medium in the oil inlet passage, and drive the cylinder block together with the drive shaft (3) to rotate. The plunger (1) is the plunger (1) according to any one of claims 1 to 8.

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