CN116044698A

CN116044698A - Piston pump with double freedom of movement

Info

Publication number: CN116044698A
Application number: CN202211718762.6A
Authority: CN
Inventors: 王灵锋; 潘成剑; 黄叶青; 孙健博; 郭明; 关成启
Original assignee: Beijing Aerospace Technology Institute
Current assignee: Beijing Aerospace Technology Institute
Priority date: 2022-12-29
Filing date: 2022-12-29
Publication date: 2023-05-02

Abstract

The invention provides a piston pump with double degrees of freedom of movement, which aims to solve the technical problems of the existing piston pump. The piston pump includes: a drive shaft assembly; the pump core is arranged in the pump shell structure and is rotatably arranged on the transmission shaft assembly, the pump core adopts an upper/lower two-way pump core integrated serial structure, the serial structure comprises a first piston structure and a second piston structure, the first piston structure and the second piston structure are rotatably arranged on the transmission shaft assembly at intervals along the axial direction of the transmission shaft assembly, the first piston structure and the second piston structure respectively adopt a piston and cam guide rail integrated structure, the cam guide rail is positioned in the middle of the piston, two sleeve structures symmetrically grow out from two sides of the cam guide rail, any sleeve structure respectively comprises an outer cylinder and an inner cylinder, a plurality of oil suction ports are circumferentially arranged on the outer cylinder, a plurality of oil discharge ports are circumferentially arranged on the inner cylinder, and any oil suction ports and any oil discharge ports are alternately arranged; the outer cylinder and the inner cylinder form an annular cavity, the annular cavities of the two sleeve structures are not communicated, and the inner cylinders on two sides are communicated and form an inner cavity of the piston structure.

Description

Piston pump with double freedom of movement

Technical Field

The invention belongs to the technical field of fluid machinery, and relates to a piston pump with double degrees of freedom of movement.

Background

A pump is an energy conversion device that converts mechanical energy into fluid pressure energy, and is typically used to output high pressure fluid. In the conventional pumps such as a common piston type pump, a vane type pump, a gear type pump and a screw type pump, the kinematic pair of the mechanical structure of the pump is mainly in a sliding friction mode in the working process, so that a large amount of friction energy loss is generated, the shape of parts is complex, and the processing cost is high.

The piston pump with double degrees of freedom of motion integrally designs a shaft and a piston, realizes continuous oil suction and discharge by utilizing the principle of motion with double degrees of freedom of circumferential rotation and axial reciprocation of the piston, and omits a valve plate structure of the traditional piston pump. Meanwhile, a symmetrical cam guide rail roller structure is adopted to replace a sliding shoe swash plate structure, the original sliding friction pair is changed into rolling friction, and a symmetrical stress structure enables the piston to have no lateral force, so that two friction pairs of the piston, a cylinder body and a valve plate are omitted, the pump efficiency is higher, and the restriction of the sliding friction pair on the pump performance and the like is broken through.

In the existing dual freedom of movement piston pump structure, there are mainly the following problems: 1. the piston of the piston pump with double freedom degrees is of a single-side extending structure, parts such as cam guide rails, rollers and the like are concentrated on the extending side, and the axial length of the piston pump is larger along with the increase of the power of the piston pump. 2. The piston is a groove type piston, and when the piston works, the piston drives oil to rotate to cause oil stirring loss, and particularly in a high-flow state, the oil stirring power loss of the piston is large, and the energy conversion rate is low. 3. The oil inlet flow passage is complex, the along-path pressure loss is large, and the self-priming capability is not strong; 4. the piston is a groove type piston, the circumferential rotation speed of the piston cavity is extremely high in a high-speed state, oil cannot fill the piston cavity in time, so that suction is caused, and the cavitation resistance of the pump is weak; 5. the piston is uniformly distributed with 4 distribution grooves on the cylindrical surface, and the distribution grooves are uniformly distributed with a single side (outwards or inwards) during working, the interval between the distribution grooves is small, namely the circumferential sealing length is short, and the leakage quantity is large. For example, patent 202111544343.0 discloses a piston structure and a dual freedom of movement piston pump, which utilizes a locating pin to connect a guide rail and a piston into a whole, and rollers and guide rails are distributed on the extending side of the piston, which increases the length of the pump in the axial direction, and simultaneously the fluid in the piston cavity rotates along with the rotation of the piston, which increases the oil stirring loss. The distributing grooves of the piston are uniformly distributed on the cylindrical surface, and are unilaterally distributed when in operation, the interval between the distributing grooves is small, the sealing distance is short, and the leakage quantity is large. The patent 202011354623.0 discloses a shaft flow distribution double-acting piston and a piston pump with the piston, the functions of sucking, discharging oil and distributing oil are realized by adopting a rotary reciprocating piston with a large middle part and two small ends, when the pump works, the piston can drive fluid in a piston cavity to rotate, so that the oil stirring loss is increased, meanwhile, the rotary reciprocating functional component is complex, the structural inertia force of the rotary reciprocating functional component is increased under the condition of high speed and heavy load, the mechanical efficiency is reduced, and a distributing groove also has the defects in the patent 202111544343.0 and has low volume efficiency. The two-dimensional piston pump disclosed in the patent has the problems of complex structure, low mechanical efficiency, large axial dimension, poor reliability of the pump structure and the like.

In addition, in order to realize the double-freedom-degree motion of the piston of circumferential rotation and axial reciprocation, the transmission torsion structure of the piston pump is important, and in the existing double-freedom-degree piston pump transmission torsion structure, the following problems mainly exist: 1. the volume and weight of the shifting fork roller transmission structure are larger, meanwhile, the axial space of the piston pump is occupied, and as the power of the piston pump is increased, the volume and weight of the piston pump are increased, and the axial length of the pump is changed greatly; 2. the weight of the shifting fork roller transmission structure is larger, the rotational inertia of the pump core is larger, the start-stop performance of the piston pump is poorer, and the control performance of the piston pump is poorer; 3. the shifting fork roller torque transmission structure can drive oil to rotate to cause oil stirring loss, and especially under the working condition of high rotating speed, the oil stirring loss of the torque transmission structure is huge; 4. the torque transmission structure with the through shaft and the balls has extremely high requirement on the coaxiality of the through shaft and the upper/lower pump core, and the manufacturability and the processing time cost of processing and assembly are increased.

The patent 202010894767.9 discloses a shift fork roller torque transmission structure and a double-motion degree of freedom piston pump with the structure, the structure utilizes a pair of shift forks to be linked with the roller into a whole, the shift forks and the roller are distributed on the overhanging side of the piston, the length of the pump in the axial direction is increased, and meanwhile, the shift fork roller torque transmission structure rotates along with the rotation of the piston, and the oil stirring loss is increased. The volume and the weight of the shifting fork roller transmission structure are large, the rotational inertia of the pump core is increased, and the start-stop performance and the control performance of the pump are reduced. Patent 202111544343.0 discloses a piston structure and a piston pump with double degrees of freedom of movement, in which a transmission through shaft is axially provided with two groups of linear ball channels parallel to an axis, balls are arranged in the linear ball channels, and input torque is transmitted through the transmission through shaft, the linear ball channels, the balls and the piston, however, the torque transmission structure cannot well ensure coaxiality of the through shaft and an up/down pump core, and if the coaxiality of the transmission through shaft and the up/down pump core is insufficient in the processing and assembling processes, the pump is difficult to stably operate at a high speed. The torque transmission structure and the double-motion degree-of-freedom piston pump comprising the structure disclosed by the patent have the problems of large volume and weight, large axial size, low mechanical efficiency, high processing precision requirement and the like, and are not beneficial to stable operation of the pump under a high-speed working condition.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art.

To this end, the present invention provides a dual freedom of motion piston pump.

The technical scheme of the invention is as follows: there is provided a dual freedom of movement piston pump comprising:

the front end cover, the pump shell and the rear end cover are sequentially fixedly connected to form a pump shell structure;

a drive shaft assembly;

the pump core is arranged in the pump housing structure and is rotatably arranged on the transmission shaft assembly, the pump core adopts an upper/lower two-way pump core integrated serial structure, the serial structure comprises a first piston structure and a second piston structure, the first piston structure and the second piston structure are rotatably arranged on the transmission shaft assembly at intervals along the axial direction of the transmission shaft assembly, the first piston structure and the second piston structure both adopt a piston and cam guide rail integrated structure, the cam guide rail is positioned in the middle of the piston, two sleeve structures are symmetrically grown on two sides of the cam guide rail, for any sleeve structure, the pump core comprises an outer cylinder and an inner cylinder positioned in the outer cylinder, a plurality of oil suction ports are circumferentially arranged on the outer cylinder, a plurality of oil discharge ports are circumferentially arranged on the inner cylinder, and the random oil suction ports and random oil discharge ports are alternately arranged; the outer cylinder and the inner cylinder form an annular cavity, the annular cavities of the two sleeve structures are not communicated, and the inner cylinders on two sides are communicated and form an inner cavity of the piston structure.

Further, the series structure further comprises a first bushing, a second bushing and a pump core supporting frame, the first bushing, the first piston structure, the pump core supporting frame, the second piston structure and the second bushing are coaxially arranged along the axis of the transmission shaft assembly in sequence, the first bushing and the second bushing both comprise a baffle and a bushing sleeve arranged on the baffle, the bushing sleeve consists of a bushing outer cylinder and a bushing inner cylinder positioned in the bushing outer cylinder, an annular cavity is formed between the bushing inner cylinder and the bushing outer cylinder, a plurality of oil distribution ports are uniformly distributed in the circumferential direction of the bushing sleeve, any oil distribution port penetrates through the bushing outer cylinder and the bushing inner cylinder at the same time, the baffle is provided with an inner hole penetrating through the baffle, and the inner hole is communicated with the bushing inner cylinder to form an inner cavity of the bushing; the pump core support frame adopts an integrated cylinder body structure and comprises a pump core support frame body, the pump core support frame body is fixedly connected with a pump shell, an oil drainage channel is formed in the pump core support frame body, a first support arm bushing assembly and a second support arm bushing assembly are respectively grown at two ends of the pump core support frame body, the two assemblies are arranged in a staggered preset angle, the first support arm bushing assembly consists of a first support arm assembly and a first support arm sleeve, the second support arm bushing assembly consists of a second support arm assembly and a second support arm sleeve, the first support arm sleeve and the second support arm sleeve are identical in structure with the bushing sleeve, and an inner side barrel of the first support arm sleeve and an inner side barrel of the second support arm sleeve are communicated with the oil drainage channel to form an inner cavity of the pump core support frame;

The first bushing, the first piston structure and the first support arm bushing assembly are matched, the second bushing, the second piston structure and the second support arm bushing assembly are matched, the piston structure is arranged between the corresponding bushing and the support arm bushing assembly, and the inner cavities of the first bushing, the first piston structure, the pump core support frame and the second bushing are sequentially communicated; the support arm assembly is fixedly connected with the baffle corresponding to the bushing, the bushing sleeve is embedded in the annular cavity corresponding to the sleeve on one side of the cam guide rail to form a closed oil cavity, the corresponding support sleeve is embedded in the annular cavity corresponding to the sleeve on the other side of the cam guide rail to form another closed oil cavity, and the four closed oil cavities in the series structure regularly perform oil sucking and discharging work.

Further, the series structure further comprises a first end cover and a second end cover, the first end cover is fixedly connected with the baffle of the first bushing, the first end cover is provided with an inner hole penetrating through the first end cover and is communicated with the inner hole on the baffle, bushing sleeves on the first end cover and the baffle are respectively arranged on two sides of the baffle, and the second end cover is fixedly connected with the baffle of the second bushing and is respectively arranged on two sides of the baffle with the bushing sleeves on the baffle.

Further, the piston pump further comprises a first thrust bearing and a second thrust bearing which are respectively arranged at the first end cover and the second end cover, one end of the transmission shaft assembly is matched with the first thrust bearing and arranged in an inner hole of the first end cover, the end is a power input end, and the other end of the transmission shaft assembly is matched with the second thrust bearing.

Further, in the first piston structure and the second piston structure, for any sleeve structure, a pair of oil suction ports are symmetrically formed on the outer cylinder, a pair of oil discharge ports are symmetrically formed on the inner cylinder, and the pair of oil suction ports and the pair of oil discharge ports are orthogonally arranged; for any bushing sleeve, the bushing sleeve is provided with symmetrically arranged oil distribution ports along the circumferential direction of the bushing sleeve, and any oil distribution port is formed by an oil distribution port on the bushing outer side cylinder and an oil distribution port on the bushing inner side cylinder, and the oil distribution port on the bushing outer side cylinder and the oil distribution port on the bushing inner side cylinder are mutually parallel.

Further, any oil distributing port also extends to the free end of the corresponding sleeve.

Further, the end face of the oil suction port adopts a chamfer design, wherein the area of an outer opening of the oil suction port is larger than that of an inner opening; and/or the end face of the oil drain port adopts a chamfer design, wherein the area of an opening at the outer side of the oil drain port is larger than that of an opening at the inner side of the oil drain port.

Further, the cross-sectional area of the oil suction port is larger than the cross-sectional area of the oil discharge port.

Further, a plurality of shifting forks are symmetrically grown on the inner cavity of the piston structure along the radial direction, and a linear ball channel is formed on each shifting fork and used for ball torque transmission.

Further, a high-pressure runner is processed on the inner cavity wall except the shifting fork and is communicated with the oil drain port and the oil drain runner.

Further, the pump core support frame body is the round platform shape, be equipped with the annular groove on the round platform circumference lateral wall, set up the body oil drain port on the annular groove to communicate with the internal oil extraction runner of this body, constitute high-pressure chamber between annular groove and the pump case.

Further, a plurality of oil through grooves are formed in the pump core support frame body along the circumferential direction, any oil through grooves are formed in the axial direction of the pump core support frame body and are not communicated with the oil discharging flow passage, and the oil through grooves are used for realizing oil through in the whole pump shell.

Further, the first support arm assembly and the second support arm assembly are each composed of two symmetrically arranged support arms; the cam guide rail is a double-sided cam guide rail; the double-side flow distribution structure further comprises a first roller frame component and a second roller frame component, the first roller frame component is matched with the first support arm component and the first piston structure, the second roller frame component is matched with the second support arm component and the second piston structure, the first roller frame component and the second roller frame component respectively comprise two groups of roller components, the two groups of roller components are arranged at intervals along the length direction of the corresponding support arm component, any roller components respectively comprise a roller frame and a plurality of rollers, the roller frame is fixedly connected with the corresponding two support arms, the rollers are arranged on the inner wall of the roller frame at intervals along the circumferential direction of the roller frame, the corresponding double-sided cam guide rail is clamped between the rollers of the two groups of roller components, and the rollers of the two groups of roller components can respectively move along the two circumferential directions of the double-sided cam guide rail when the piston structure rotates.

Further, the transmission shaft assembly comprises an input transmission shaft, a first transmission block, a first transmission shaft and a second transmission shaft of a second transmission block which are sequentially connected; the two end surfaces of the first transmission block are provided with a chute a and a chute b which are orthogonally distributed; the two end surfaces of the second transmission block are provided with a chute c and a chute d which are orthogonally distributed; one end of the input transmission shaft is a power input end and is matched with the first thrust bearing, and the other end of the input transmission shaft is of a flat square structure c and is matched with the chute a; the first transmission shaft is arranged in the inner cavity of the first piston structure, and a plurality of linear ball channels parallel to the axis are uniformly distributed in the circumferential direction of the first transmission shaft and are used for placing balls and matched with the linear ball channels of the first piston structure; the two ends of the first transmission shaft are respectively provided with a flat square structure a and a flat square structure b which are respectively matched with the chute b and the chute c; the second transmission shaft is arranged in the inner cavity of the second piston structure, and a plurality of linear ball channels parallel to the axis are uniformly distributed in the circumferential direction of the second transmission shaft and are used for placing balls and matched with the linear ball channels of the second piston structure; one end of the second transmission shaft is also provided with a flat square structure d which is matched with the chute d; the other end of the second transmission shaft is matched with a second thrust bearing;

The transmission faces of the sliding grooves on the two end faces of the same transmission block are mutually perpendicular, the transmission faces matched with the corresponding sliding grooves and the non-transmission faces are arranged on the flat square structure a, the flat square structure b, the flat square structure c and the flat square structure d, the transmission faces of the arbitrary flat square structure are tightly attached to the transmission faces of the corresponding sliding grooves, gaps are reserved between the non-transmission faces of the arbitrary flat square structure and the non-transmission faces of the corresponding sliding grooves, and when the transmission device is in operation, an input transmission shaft and a first transmission shaft can slide along the normal direction of the non-transmission faces while transmitting torque through the transmission faces, and the first transmission shaft and a second transmission shaft can slide along the normal direction of the non-transmission faces while transmitting torque through the transmission faces.

Further, any sliding groove is a rectangular groove, two inner wall surfaces of one group of rectangular grooves, which are arranged in parallel, are arranged as transmission surfaces, and the other two surfaces are non-transmission surfaces.

Further, the length of the driving surface is greater than the length of the non-driving surface.

Further, any of the linear ball grooves is not fully covered with balls, and the length of the linear ball grooves, in which balls are not placed, is Δl, Δl=h/pi, wherein h is the guide rail travel of the piston pump.

Further, the length of any linear ball channel is L:

L＝nD+h/π

wherein L is the length of the linear ball channel, D is the diameter of the balls, n is the number of the balls, and h is the guide rail travel.

Further, the propeller shaft assembly includes:

the two transmission blocks are respectively arranged in one-to-one correspondence with the first piston structure and the second piston structure, each transmission block is of a hollow columnar structure with two open ends, and a pair of inner side transmission channels are uniformly formed in the circumferential direction of the inner cavity wall of each transmission block; a pair of external transmission channels are uniformly formed on the outer wall surface in the circumferential direction, any internal transmission channel and any external transmission channel are arranged along the length direction of the transmission block, the pair of internal transmission channels and the pair of external transmission channels are orthogonally arranged, any transmission block is arranged in an inner cavity corresponding to the piston structure, and the transmission channel on the external side of the transmission block is matched with a ball in the ball channel corresponding to the piston structure;

the transmission through shaft is circumferentially and symmetrically provided with a pair of shifting forks which are also arranged along the length direction of the transmission through shaft; the transmission through shafts are arranged in the two transmission blocks at the same time, and the two transmission blocks are arranged at intervals along the axial direction of the transmission through shafts; the inner side transmission channel of any transmission block is matched with a shifting fork of a transmission through shaft, and two ends of the transmission through shaft are respectively matched with a first thrust bearing and a second thrust bearing;

The two ends of any transmission block are provided with the limiting parts in a distributed mode, the limiting parts are fixedly sleeved on the transmission through shaft, and the limiting parts are used for limiting the two transmission blocks to move along the axial direction of the transmission through shaft;

when the device works, the transmission through shaft drives the two transmission blocks to rotate, torque is transmitted to the first piston structure and the second piston structure through the balls by the two transmission blocks, and the first piston structure and the second piston structure are enabled to rotate circumferentially.

Further, the two transmission blocks, the first piston structure, the second piston structure and the transmission through shaft are coaxially arranged; and/or the hollow columnar structure with two open ends is a hollow columnar structure with two open ends.

Compared with the prior art, the invention has the beneficial effects that:

(1) According to the invention, the piston sleeve and the double-sided guide rail are integrated, the rollers can be distributed on the outer side of the piston sleeve, so that the axial distance of the piston can be fully utilized, the axial length of the pump is effectively shortened, the volume and weight of the pump are reduced, and the power-weight ratio of the pump is improved;

(2) The piston and the bushing are both in baffle structures, the bushing is utilized to replace a cylinder body part in the traditional sense, meanwhile, the middle of the piston and the bushing is hollowed out, and the circumferential grooves are formed, so that the weight of the pump is greatly reduced;

(3) According to the invention, the piston and the bushing are both in baffle structures, so that the resistance of the integrated guide rail piston during rotary reciprocating motion is reduced, the oil stirring power loss is reduced, and the mechanical efficiency of the pump is improved;

(4) According to the double-side flow distribution type piston, the oil suction ports and the oil discharge ports are distributed on different cylinders, so that the distance between the oil ports is indirectly increased, the sealing length is increased, the leakage quantity is effectively reduced, and the volumetric efficiency of the pump is improved;

(5) The oil suction port of the piston cavity is arranged on the outer sleeve of the guide rail piston and is directly communicated with the oil, and the oil can enter the piston cavity without passing through any flow channel, so that the self-priming capacity of the pump is effectively improved.

(6) The piston is of a baffle structure, oil entering the piston cavity hardly has circumferential rotation movement, meanwhile, the axial speed of the oil is small due to the fact that the stroke of the piston is small, the kinetic energy loss of the oil is small, and the energy conversion rate of the pump is high.

(7) The piston is of a baffle structure, and oil can rapidly follow the axial movement of the piston and timely fill the piston cavity when the pump is at high speed, so that the cavitation resistance of the pump is greatly enhanced.

(8) When the piston cavity is in the pressure oil stroke, the bushing is slightly deformed under the action of high pressure oil, so that the gap between the bushing and the piston is reduced, the leakage amount is reduced, the volumetric efficiency is improved, and the gap compensation structure is also applicable to high temperature.

(9) Compared with a shifting fork roller torque transmission structure, the orthogonal/cross torque transmission structure is small in size, and the torque transmission structure is arranged inside the piston and does not influence the axial length of the pump; the orthogonal/cross transmission and torsion structure has the advantages of light weight, short radius gyration, small moment of inertia, good start-stop performance and good control performance of the pump; compared with an external shifting fork roller torque transmission structure, the orthogonal/cross torque transmission structure is distributed in the piston, has extremely low oil stirring loss and is suitable for high-speed working conditions; the orthogonal/cross transmission and twisting structure of the invention realizes decoupling of the upper and lower pump cores in rotation, reduces the coaxiality requirement of the upper and lower pump cores, reduces the machining precision requirement, reduces the machining cost and improves the economic benefit.

Drawings

The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.

FIG. 1 is a schematic diagram of a dual freedom of motion piston pump of the present invention;

FIG. 2 is a schematic view (perspective view) of a pump core assembly according to the present invention;

FIG. 3 is a schematic view (exploded view) of a pump core assembly according to the present invention;

FIG. 4 is a schematic view of an integrated baffle type guide rail piston structure according to the present invention;

FIG. 5 is a cross-sectional view of FIG. 4;

FIG. 6 is a top view of FIG. 4;

FIG. 7 is a schematic view of the locations of peaks and troughs in the profile of a rail piston rail;

FIG. 8 is a schematic diagram of the current distribution principle of the present invention;

FIG. 9 is a block diagram of a pump core support frame;

FIG. 10 is a schematic view of a roller frame;

FIG. 11 is a schematic view of an integrated rail piston structure with balanced support in accordance with the present invention;

FIG. 12 is a schematic view (front view and cross-sectional view) of a cross-shaped torsion transmission structure of the present invention;

FIG. 13 is an exploded view of FIG. 12;

FIG. 14 is a schematic view of a driving face of a driving block according to the present invention;

FIG. 15 is a schematic view (front view and cross-sectional view) of an orthogonal transmission structure according to the present invention;

FIG. 16 is an isometric view of FIG. 15 (with the second piston structure hidden);

FIG. 17 is a schematic diagram (top view) of an orthogonal transmission structure of the present invention;

FIG. 18 is a schematic view (perspective) of a transmission through shaft according to the present invention;

fig. 19 is a schematic view (perspective view) of the structure of the transmission block of the present invention.

Detailed Description

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

As shown in fig. 1-19, in one embodiment of the present invention, a dual degree of freedom of motion piston pump is provided, the piston pump comprising: the novel oil pump comprises a front end cover 1, a pump shell 6, a rear end cover 9, a pump core and a transmission shaft assembly, wherein the front end cover 1, the pump shell 6 and the rear end cover 9 are sequentially and fixedly connected to form a pump shell structure, the pump core is arranged in the pump shell structure, the pump core adopts an upper-lower two-unit pump core integrated serial structure, the serial structure comprises a first piston structure 4 and a second piston structure 18, the first piston structure 4 and the second piston structure 18 are rotatably arranged on the transmission shaft assembly at intervals along the axial direction of the transmission shaft assembly, the first piston structure 4 and the second piston structure 18 both adopt a piston and cam guide rail integrated structure, the cam guide rail is positioned in the middle of a piston, two sleeve structures are symmetrically grown on two sides of the cam guide rail, the cam guide rail comprises an outer sleeve and an inner sleeve positioned in the outer sleeve, a plurality of oil suction ports are circumferentially arranged on the outer sleeve, and a plurality of oil discharge ports are circumferentially arranged on the inner sleeve, and the oil suction ports and the oil discharge ports are alternately arranged; the annular cavity is formed between the outer cylinder and the inner cylinder, the annular cavities of the two sleeve structures are not communicated, and the inner cylinders on two sides are communicated and form an inner cavity of the piston structure.

That is, as shown in FIG. 5, the failure to communicate between the annular chambers of the two sleeve structures means that the annular chambers are separated by an annular baffle 48.

Specifically, as shown in fig. 3 to 8, the first piston structure 4 includes a first cam guide 43 and sleeve structures on both sides thereof, each including a first outer cylinder 41 and a first inner cylinder 42, and an oil suction port and an oil discharge port are provided on the first outer cylinder 41 and the first inner cylinder 42, respectively. Similarly, the second piston structure 18 includes a second cam guide 181 and sleeve structures on both sides thereof, each including a second outer cylinder 182 and a second inner cylinder 183, and an oil suction port and an oil discharge port are provided on the second outer cylinder 182 and the second inner cylinder 183, respectively.

In the embodiment of the invention, the outer cylinder and the inner cylinder of the piston structure are both of an opening structure, the inner cylinders at the two ends are communicated, and the end surfaces of the outer cylinder and the inner cylinder of the sleeve are preferably flush.

Preferably, the outer cylinder and the inner cylinder of the piston structure are both cylindrical cylinders.

Furthermore, it will be appreciated by those skilled in the art that the rotary shaft assembly of the present embodiment is similar to the drive shaft of a conventional piston pump, which is disposed within the pump core, and through rotation of which rotates the piston structure, which reciprocates axially under the guidance of the cam track.

Therefore, the first piston structure and the second piston structure (sleeve structure) are both baffle structures, the middle is hollowed, the circumferential grooves are formed, the weight of the pump is greatly reduced, and the power-weight ratio of the pump is improved; meanwhile, the stirring effect on the oil liquid is small during rotation, the stirring loss is reduced, the mechanical efficiency is high, the oil liquid can rapidly follow the axial movement of the piston and timely fill the piston cavity when the pump is at high speed, and the cavitation resistance of the pump is greatly enhanced; the piston is provided with two sides for flow distribution, the oil suction port and the oil discharge port are distributed on different cylinders, the distance between the oil ports is indirectly increased, the sealing length is increased, the leakage amount is effectively reduced, and the volumetric efficiency of the pump is improved. According to the embodiment of the invention, the oil suction port of the piston cavity is arranged on the outer sleeve of the piston structure, and by adopting the piston structure, the oil suction port can be directly communicated with oil, and the oil can enter the piston cavity without passing through any flow channel, so that the self-priming capacity of the pump is effectively improved. In addition, the cam guide rails are all arranged in the middle of the piston, and compared with the conventional guide rail and roller structures which are intensively distributed on one side, the roller can be distributed on the outer side of the piston sleeve, so that the axial distance of the piston can be fully utilized, the axial length of the pump is effectively shortened, and the volume of the pump is reduced.

In the above embodiment, as shown in fig. 2-3, in order to realize bidirectional flow distribution, the serial structure further includes a first bushing 13, a second bushing 20, and a pump core support frame 16, where the first bushing 13, the first piston structure 4, the pump core support frame 16, the second piston structure 18, and the second bushing 20 are coaxially disposed along the axis of the transmission shaft assembly in sequence, where each of the first bushing 13 and the second bushing 20 includes a baffle plate and a bushing sleeve disposed on the baffle plate, where the bushing sleeve is composed of a bushing outer cylinder and a bushing inner cylinder located in the bushing outer cylinder, an annular cavity is formed between the bushing inner and outer cylinders, multiple oil distribution ports are uniformly distributed along a circumferential direction of the bushing sleeve, and any oil distribution port simultaneously penetrates through the bushing outer cylinder and the bushing inner cylinder, and the baffle plate has an inner hole penetrating through the baffle plate, and the inner hole is communicated with the bushing inner cylinder to form an inner cavity of the bushing; the pump core support frame 16 adopts an integrated cylinder body structure, and comprises a pump core support frame body 161, the pump core support frame body 161 is fixedly connected with a pump shell 6, an oil drainage channel is formed in the pump core support frame body 161, a first support arm bushing assembly and a second support arm bushing assembly are respectively grown at two ends of the pump core support frame body 161, the two assemblies are arranged at a preset angle in a staggered mode, the first support arm bushing assembly consists of a first support arm assembly and a first support sleeve, the second support arm bushing assembly consists of a second support arm assembly and a second support sleeve, the first support sleeve and the second support sleeve are identical in structure with the bushing sleeve, and an inner side barrel of the first support sleeve and an inner side barrel of the second support sleeve are communicated with the oil drainage channel to form an inner cavity of the pump core support frame 16; wherein, the first bushing 13, the first piston structure 4 and the first supporting arm bushing assembly are matched, the second bushing 20, the second piston structure 18 and the second supporting arm bushing assembly are matched, the piston structure is arranged between the corresponding bushing and the supporting arm bushing assembly, and the inner cavities of the first bushing 13, the first piston structure 4, the pump core supporting frame 16 and the second bushing 20 are sequentially communicated; the support arm assembly is fixedly connected with the baffle corresponding to the bushing, the bushing sleeve is embedded in the annular cavity corresponding to the sleeve on one side of the cam guide rail to form a closed oil cavity, the corresponding support sleeve is embedded in the annular cavity corresponding to the sleeve on the other side of the cam guide rail to form another closed oil cavity, and the four closed oil cavities in the series structure regularly perform oil sucking and discharging work.

That is, the first bushing 13, the first piston structure 4, the pump core supporting frame 16, the second piston structure 18, and the second bushing 20 are coaxially disposed along the axis in sequence, the first piston structure 4 is disposed between the first bushing 13 and the first supporting arm bushing assembly, the first bushing 13 is fixedly connected with the first supporting arm assembly, the bushing sleeve of the first bushing 13 is embedded in the annular cavity of the cam rail side sleeve of the first piston structure 4, and the first bracket sleeve is embedded in the annular cavity of the other side sleeve, thereby forming two closed oil cavities. Likewise, the second piston structure 18, the second bushing 20 and the second support arm bushing assembly also use the same mating pattern, thereby enabling the formation of four closed oil chambers in a tandem configuration.

Preferably, the first support arm bushing assembly and the second support arm bushing assembly are arranged at an offset 45 degrees, i.e., it will be understood by those skilled in the art that the first support arm assembly and the second support arm assembly are arranged at an offset 45 degrees, and the first bracket sleeve and the second bracket sleeve are also arranged at an offset 45 degrees, and this arrangement enables pump output flow to be pulsation-free.

Preferably, the bushing sleeve and the bracket sleeve are both cylindrical sleeves.

Preferably, in the first piston structure 4 and the second piston structure 18, for any sleeve structure, a pair of oil suction ports are symmetrically arranged on the outer cylinder, a pair of oil discharge ports are symmetrically arranged on the inner cylinder, and the pair of oil suction ports and the pair of oil discharge ports are orthogonally arranged; for any bushing sleeve, the bushing sleeve is provided with symmetrically arranged oil distribution ports along the circumferential direction of the bushing sleeve, and any oil distribution port is formed by an oil distribution port on the bushing outer side cylinder and an oil distribution port on the bushing inner side cylinder, and the oil distribution port on the bushing outer side cylinder and the oil distribution port on the bushing inner side cylinder are mutually parallel.

Specifically, the piston structure of the embodiment of the invention integrates oil suction, flow distribution and transmission functions. As shown in fig. 3 to 8, the first piston structure 4 includes a first cam guide 43 and sleeve structures on both sides thereof, each including a first outer cylinder 41 and a first inner cylinder 42, and a pair of oil suction ports 44 and oil discharge ports 45 are respectively provided orthogonally to the first outer cylinder 41 and the first inner cylinder 42. Similarly, the second piston structure 18 includes a second cam guide 181 and sleeve structures on both sides thereof, each including a second outer cylinder 182 and a second inner cylinder 183, and a pair of oil suction ports and oil discharge ports are orthogonally provided on the second outer cylinder 182 and the second inner cylinder 183, respectively.

In addition, the first bracket sleeve and the second bracket sleeve in the embodiment of the present invention are the same as the bushing sleeve in structure, and are not described in detail herein.

In the above embodiment, in order to achieve better oil drainage, as shown in fig. 3 and 9, any of the oil distribution ports also extends to the free end of the corresponding sleeve.

That is, the serial structure of the embodiment of the invention is a double-sided flow distribution structure, a novel baffle type piston structure (a first piston structure and a second piston structure) is provided, the baffle type piston is an integrated structure of a cam guide rail and a piston, the cam guide rail is positioned in the middle of the piston, two inner and outer cylindrical sleeves symmetrically grow out of two sides of the cam guide rail, meanwhile, the structure also designs a traditional lining structure matched with the piston structure into a baffle type lining structure (a first lining, a second lining, a first support sleeve and a second support sleeve in the embodiment of the invention), the baffle type lining is nested and installed in the baffle type piston to form a closed volume, and the piston pump can complete expansion and compression of fluid along with the enlargement and the reduction of the closed volume. Wherein. A pair of oil distribution ports are respectively arranged on the inner sleeve and the outer sleeve of the piston structure, and the two pairs of oil distribution ports are positioned in orthogonal positions. The oil distributing port on the outer sleeve is an oil absorbing port, and the oil distributing port on the inner sleeve is an oil draining port. One side of the baffle type bushing is provided with an inner baffle plate and an outer baffle plate (an inner sleeve and an outer sleeve), and two pairs of oil grooves (oil distributing ports) which are symmetrical in center are formed in parallel on the baffle type bushing. When the piston pump operates, the transmission shaft assembly drives the piston structure to rotate through the torque transmission balls, and the piston structure can complete axial reciprocating motion under the guidance of the curved surface of the cam guide rail. When the oil suction port is communicated with the oil through groove of the outer baffle plate, the piston is in an oil suction stroke, and oil enters the piston cavity from the pump cavity through the oil suction port; when the oil outlet is communicated with the oil through groove of the inner baffle, the piston is in a pressure oil stroke, and fluid flows out from the piston cavity through the oil drain port.

Therefore, in the embodiment of the invention, the piston and the double-sided guide rail are integrated to form the integrated guide rail piston, the cam guide rail is positioned in the middle of the piston, and compared with the traditional guide rail and roller structure which is intensively distributed on one side, the roller can be distributed outside the piston sleeve, so that the axial distance of the piston can be fully utilized, the axial length of the pump is effectively shortened, and the volume of the pump is reduced. In addition, the two sides of the piston are provided with the flow distribution, the oil suction port and the oil discharge port are distributed on different cylinders, so that the distance between the oil ports is indirectly increased, the sealing length is increased, the leakage quantity is effectively reduced, and the volumetric efficiency of the pump is improved. By adopting the piston structure, oil can directly enter the piston cavity without passing through a complex flow passage, so that the self-priming capacity of the pump is improved; the oil enters the piston cavity and almost does not have circumferential rotation movement, meanwhile, the axial speed of the oil is small due to the fact that the stroke of the piston is not large, the kinetic energy loss of the oil is extremely small, and the energy conversion rate of the pump is high; at high speed, the oil can quickly follow the axial movement of the piston and timely fill the piston cavity, so that the cavitation resistance of the pump is greatly enhanced.

In the above embodiment, in order to realize rotation, a plurality of shifting forks are symmetrically and radially extended from the inner cavities of the first piston structure 4 and the second piston structure 18, and linear ball grooves are formed on the shifting forks for ball torque transmission.

For the cross torque transmission, any shifting fork is provided with a linear ball channel, and for the orthogonal torque transmission, any shifting fork is provided with two linear ball channels which are arranged side by side.

Preferably, the number of the shifting forks is 2, and the two shifting forks are symmetrically arranged.

In the above embodiment, in order to better realize oil discharge, a high-pressure flow passage 49 is formed on the inner cavity wall except for the shifting fork, and the high-pressure flow passage communicates with the oil discharge port and the oil discharge flow passage.

Specifically, because the first piston structure 4 and the second piston structure 18 are identical in structure, taking the first piston structure 4 as an example, as shown in fig. 4-8, a through hole is machined in the center of the first piston structure 4, a high-pressure flow passage 49 is machined on the wall surface of the through hole, a first torque transmission fork 46 is machined at the orthogonal position of the high-pressure flow passage 49, and a linear ball channel a47 is formed on the first torque transmission fork 46 for transmitting torque of the balls 15.

In the above embodiment, the end surface of the oil suction port adopts a chamfer design, wherein the area of the outer opening of the oil suction port is larger than that of the inner opening; the end face of the oil drain port adopts a chamfer design, wherein the area of an opening at the outer side of the oil drain port is larger than that of an opening at the inner side of the oil drain port. The end face of the oil suction and discharge port is designed with an inclined surface, so that the self-absorption capacity can be effectively increased when the piston rotates, and the hydraulic loss caused by the end face of the outer diameter can be reduced. Under the high-pressure working condition, the bushing is slightly deformed under the action of high-pressure oil, so that the gap between the bushing and the piston is reduced, the leakage quantity is reduced, and the volumetric efficiency is improved.

In the above embodiment, the cross-sectional area of the oil suction port is larger than the cross-sectional area of the oil discharge port.

In the embodiment of the invention, the sectional area of the oil suction port is larger than that of the oil discharge port, and the inner diameter of the outer cylinder is larger than that of the inner cylinder, so that the sectional area of the oil suction port is larger than that of the oil pressing port, and oil in the pump shell can directly enter the piston cavity through the oil suction port of the outer cylinder without passing through a complex flow passage, thereby being more beneficial to oil suction of the pump. Meanwhile, due to the adoption of the baffle type piston structure and the bushing structure, the oil entering the piston cavity does not generate rotary motion, the oil can quickly follow the axial motion of the guide rail piston to timely fill the piston cavity, and cavitation resistance of the pump is enhanced while oil stirring loss is reduced.

Specifically, the invention adopts an upper/lower two-way pump core integrated serial structure, as shown in fig. 2 and 3, and comprises a first bushing 13, a first piston structure 4, an integrated pump core supporting frame 16, a second piston structure 18 and a second bushing 20. The bushing sleeve (formed by the first bushing outer cylinder 131 and the first bushing inner cylinder 132) of the first bushing 13, the first piston structure 4, and the first bracket sleeve (formed by the first bracket outer cylinder 1610 and the first bracket inner cylinder 1611) are nested and assembled to form two closed oil chambers; meanwhile, the bushing sleeve (composed of the second bushing outer cylinder 201 and the second bushing inner cylinder 202) of the second bushing 20, the second piston structure 18 and the second bracket sleeve (composed of the second bracket outer cylinder 167 and the second bracket inner cylinder 168) are nested and assembled to form two other closed oil cavities, and the four closed oil cavities perform oil sucking and discharging operations according to rules. In order to realize no pulsation of pump output flow, the upper and lower pump cores are arranged 45 degrees different. The two bushings are fastened to the pump core support frame 16 by nuts and serve to both support and lubricate the first piston structure 4 and the second piston structure 18. Because the piston structure and the bushing are both baffle structures, the bushing is utilized to replace the cylinder body part in the traditional sense, the middle of the piston structure and the bushing is hollowed out, and the circumferential grooves are formed, so that the weight of the pump is greatly reduced. Meanwhile, the oil liquid is not influenced by the rotary motion of the guide rail piston when entering the closed oil cavity, the oil liquid does not generate rotary motion, the oil stirring power loss is reduced, and the mechanical efficiency of the pump is improved.

Since the first piston structure 4 and the second piston structure 18 have the same oil extraction, flow distribution and transmission principle, the oil extraction, flow distribution and transmission principle of the first piston structure 4 will be described as an example. When the transmission shaft assembly drives the first piston structure 4 to rotate, the first piston structure 4 axially reciprocates under the guidance of the curved surface of the guide rail, and a closed oil cavity can be formed by the first piston structure 4 and the first bushing 13. In the process that the first piston structure 4 moves from the highest point to the lowest point, the first piston structure 4 is in an oil discharge stroke, the volume of a piston cavity is reduced, oil is compressed, and the oil in the piston cavity flows into a high-pressure flow channel 49 through an inner oil through groove on the first bushing 13 and an oil discharge port 45 of the first piston structure 4, so that oil discharge is completed; in the process that the first piston structure 4 moves from the lowest point to the highest point, the first piston structure 4 is in an oil suction stroke, the volume of a piston cavity is enlarged, vacuum is formed, oil in a shell can be sucked into the piston cavity through an oil suction port 44 of the first piston structure 4 and an oil through groove on the outer side of the first bushing 13 without a complex flow passage, oil suction is completed, and oil suction and discharge work of the left piston cavity and the right piston cavity of the first piston structure 4 is alternately performed.

In the above embodiment, as shown in fig. 9, in order to better realize oil discharge, the pump core support frame body 161 is in a shape of a truncated cone, an annular groove 166 is provided on a circumferential side wall of the truncated cone, an oil discharge port 1612 of the body is provided on the annular groove 166 and communicates with an oil discharge channel in the body, and a high-pressure cavity is formed between the annular groove 166 and the pump casing 6.

In the above embodiment, as shown in fig. 9, in order to realize oil passing between the upper/second pump cores in the pump, a plurality of oil passing grooves 169 are formed in the pump core supporting frame body 161 along the circumferential direction, any oil passing groove 169 is disposed along the axial direction of the pump core supporting frame body 161 and is not communicated with the oil discharging flow channel, and the oil passing grooves 169 are used for realizing oil passing in the whole pump housing structure.

That is, when the pump core support frame 16 of the present invention is assembled with the pump casing 6, the annular groove 166 on the pump core support frame body 161 is sealed with the pump casing 6 circumferentially (as shown in fig. 9, two annular seal grooves 163 are provided on the pump core support frame body 161 and distributed on both sides of the annular groove 166, and seal rings can be placed in the seal grooves to realize the seal with the pump casing 6), so as to form a high-pressure cavity, thereby dividing the pump casing structure into two chambers, namely, a front chamber and a rear chamber, and in order to realize the oil passage in the whole pump, a plurality of oil passage grooves 169 can be provided on the body so as to realize the circulation in the pump casing structure.

According to one embodiment of the present invention, as shown in fig. 3 and 9, the first support arm assembly and the second support arm assembly are each comprised of two symmetrically arranged support arms 164. The support arms on both sides are arranged at 45 deg. different, and two mounting holes 162 are formed in the support arm 164 for mounting the roller frame 8.

In addition, the end face of the pump core support frame body 161 is provided with two pump core support frame 16 lugs 165, preferably uniformly distributed, for positioning the axial direction and the angular direction of the pump core, and the two lugs are arranged in lug grooves of the pump shell 6.

The through hole in the middle of the integrated cylinder structure ensures the coaxiality of the upper and lower two-way pump cores through one-step processing and forming, solves the problems of eccentric wear and adhesion of pistons caused by different shafts of the upper and lower two-way pump cores, and improves the working reliability of the pump.

According to an embodiment of the present invention, as shown in fig. 2, 10 and 11, the cam rail is a double-sided cam rail, the serial structure further includes a first roller frame component and a second roller frame component, the first roller frame component is matched with the first support arm component and the first piston structure 4, the second roller frame component is matched with the second support arm component and the second piston structure 18, the first roller frame component and the second roller frame component each include two groups of roller components, the two groups of roller components are arranged at intervals along the length direction of the corresponding support arm component, any roller component includes a roller frame and a plurality of rollers, the roller frame is fixedly connected with the corresponding two support arms, the plurality of rollers are arranged on the inner wall of the roller frame at intervals along the circumferential direction of the roller frame, the corresponding double-sided cam rail is clamped between the plurality of rollers of the two groups of roller components, and the rollers of the two groups of roller components can respectively move along the circumferential directions of the double-sided cam rail while the piston structure rotates.

In the embodiment of the invention, the curved surface of the cam guide rail is provided with the wave crest and the wave trough, and more preferably, the wave crest and the wave trough are respectively two.

In the embodiment of the invention, preferably, the roller frame is connected with the two corresponding supporting arms through pins and can rotate around the pins. And the two rollers at one side are in contact with the cam guide rail at the moment, and the axial force born by the piston structure is shared evenly.

In particular, the four roller assemblies of the present invention are identical in structure, namely, first, second, third and fourth roller assemblies, each comprising a roller and a roller frame. The first, second, third and fourth roller assembly structures will be described below using the first roller assembly as an example.

As shown in fig. 10 and 11, the first roller assembly includes a first roller frame 8 and first rollers 5, preferably 2 first rollers 5, further preferably, the rollers are roller needle bearings of bolts, and are uniformly distributed circumferentially and fixed on positioning holes 81 of the roller frame 8 by bolts. The first roller assemblies are fixedly installed on the installation holes 162 of the supporting arms 164 of the pump core supporting frame 16 in pairs through the pins a19 (the corresponding first roller frames 8 are provided with pin holes 83 which are matched and connected with the supporting arms 164), the rollers 5 are tightly attached to the first cam guide rails 43 through a zero-clearance assembly method, the roller assemblies can rotate around the pins a19, the contact of the two rollers on one side with the cam guide rails is ensured at any time, and the axial force borne by the guide rail piston is shared evenly.

Further, as shown in fig. 3, the tandem structure further includes a first end cover 12 and a second end cover 10, where the first end cover 12 is fixedly connected with the baffle of the first bushing 13, the first end cover 12 has an inner hole penetrating through the first end cover 12 and is communicated with the inner hole on the baffle, the first end cover 12 and the bushing sleeves on the baffle are respectively disposed on two sides of the baffle, and the second end cover 10 is fixedly connected with the baffle of the second bushing 20 and is respectively disposed on two sides of the baffle with the bushing sleeves on the baffle.

Further, as shown in fig. 1, the piston pump further includes a first thrust bearing 22 and a second thrust bearing 27 disposed at the first end cap 12 and the second end cap 10, respectively, and one end of the transmission shaft assembly is matched with the first thrust bearing 22 and disposed in the inner hole of the first end cap 12, the end is a power input end, and the other end of the transmission shaft assembly is matched with the second thrust bearing 27. Two thrust bearings are provided at the first end cap 12 and the second end cap 10 for balancing the hydraulic pressure of the drive shaft assembly.

According to a preferred embodiment of the present invention, as shown in fig. 12 to 14, the transmission shaft assembly adopts a cross torque transmission structure, and the transmission shaft assembly includes an input transmission shaft 11, a first transmission block 2, a first transmission shaft 3, a second transmission block 7 and a second transmission shaft 17 which are sequentially connected; the two end surfaces of the first transmission block 2 are provided with a chute a and a chute b which are orthogonally distributed; the two end surfaces of the second transmission block 7 are provided with a chute c and a chute d which are orthogonally distributed; one end of the input transmission shaft is a power input end and is matched with the first thrust bearing 22, and the other end of the input transmission shaft is of a flat square structure c and is matched with the chute a; the first transmission shaft 3 is arranged in the inner cavity of the first piston structure 4, and a plurality of linear ball channels b34 parallel to the axis are uniformly distributed in the circumferential direction of the first transmission shaft 3 and are used for placing the balls 15 and matched with the linear ball channels a47 of the first piston structure 4; the two ends of the first transmission shaft 3 are respectively provided with a flat square structure a and a flat square structure b which are respectively matched with the chute b and the chute c; the second transmission shaft 17 is arranged in the inner cavity of the second piston structure, and a plurality of linear ball channels c174 parallel to the axis are uniformly distributed in the circumferential direction of the second transmission shaft 17 and are used for placing balls and matched with the linear ball channels of the second piston structure 18; one end of the second transmission shaft 17 is also provided with a flat square structure d which is matched with the chute d; the other end of the second transmission shaft 17 is matched with a second thrust bearing 27; the transmission faces of the sliding grooves on the two end faces of the same transmission block are mutually perpendicular, the transmission faces matched with the corresponding sliding grooves and the non-transmission faces are arranged on the flat square structure a, the flat square structure b, the flat square structure c and the flat square structure d, the transmission faces of the arbitrary flat square structure are tightly attached to the transmission faces of the corresponding sliding grooves, gaps are reserved between the non-transmission faces of the arbitrary flat square structure and the non-transmission faces of the corresponding sliding grooves, and in operation, the input transmission shaft 11 and the first transmission shaft 3 can slide along the normal direction of the non-transmission faces while transmitting torque through the transmission faces, and the first transmission shaft 3 and the second transmission shaft 17 can slide along the normal direction of the non-transmission faces while transmitting torque through the transmission faces.

For example, as shown in fig. 13, the flat square structure c has a flat square structure c driving surface 111 and a flat square structure c non-driving surface 112, the flat square structure a has a flat square structure a driving surface 31 and a flat square structure a non-driving surface 32, and the chute b matched with the flat square structure a has a chute b driving surface 210 and a chute b non-driving surface 211, wherein the flat square structure c driving surface 111 of the input transmission shaft 11 and the flat square structure a driving surface 31 of the first transmission shaft 3 are respectively closely adhered to and mutually perpendicular to the driving surfaces at two ends of the first transmission block 2. Similarly, the flat square structure b is provided with a flat square structure b driving surface 33, the flat square structure d is provided with a flat square structure d driving surface 172 and a flat square structure d non-driving surface 171, and the chute d of the second driving block 7 is provided with a chute d driving surface 72 and a chute d non-driving surface 71. The other end of the second drive shaft 17 is provided as a smooth shaft 173 which cooperates with a second thrust bearing 27.

That is, in operation, the input transmission shaft 11 and the first transmission shaft 3 can slide along the normal direction of the non-transmission surface while transmitting torque through the transmission surface, the input transmission shaft 11 and the first transmission shaft 3 are adjusted to transmit torque while adjusting the coaxiality of the input transmission shaft 11 and the first transmission shaft 3, the different coaxiality between the input transmission shaft 11 and the first transmission shaft 3 is compensated, and the first transmission shaft 3 and the second transmission shaft 17 can also compensate the different coaxiality in the process of processing, assembly and operation through the cross transmission torsion structure. Therefore, the two sets of cross torque transmission structures can reduce the coaxiality requirement of the transmission shaft and the upper/lower pump core, reduce the matching processing quantity of parts, improve the manufacturability of processing and assembly and greatly save money and time cost.

Therefore, the invention adopts the transmission shaft, the transmission block and the ball torque transmission in the straight groove to replace the traditional through shaft transmission structure, realizes the decoupling of the rotary motion of the upper and lower two-way transmission shafts, can compensate the relative displacement of the input transmission shaft, the first transmission shaft and the second transmission shaft during processing, assembly and operation, and allows larger radial and axial deviation. Meanwhile, the cross torque transmission structure formed by the transmission shaft and the transmission block has the advantages of simple structure, convenience in installation, zero rotation clearance, high torque, high rigidity, high sensitivity and the like, and the processing cost of the conventional torque transmission shaft is greatly reduced.

In the above embodiment, as shown in fig. 13, any of the sliding grooves is a rectangular groove for better coaxiality adjustment.

Preferably, two inner wall surfaces of one group of rectangular grooves, which are arranged in parallel with each other, are arranged as transmission surfaces, and the other two surfaces are non-transmission surfaces.

In the above embodiments, the length of the driving surface is greater than the length of the non-driving surface for better torque transmission and better coaxiality adjustment.

In the above embodiment, in order to prevent the balls from falling out of the ball grooves, the cross-shaped torsion structure includes a plurality of limiting assemblies, and any linear ball groove on the first transmission shaft and the second transmission shaft corresponds to a limiting assembly, and the limiting assemblies are disposed in the corresponding linear ball grooves and are used for limiting the balls to slide out of the linear ball grooves.

According to one embodiment of the invention, the limiting assembly is composed of a first limiting piece and a second limiting piece, the first limiting piece and the second limiting piece are respectively arranged in the corresponding linear ball channels at intervals, and the plurality of balls are further arranged between the first limiting piece and the second limiting piece.

According to one embodiment of the invention, the first and second stop members are each pins b14.

It can be seen that, in the embodiment of the invention, two groups of ball channels on the first transmission shaft and the second transmission shaft correspond to the ball channels of the first piston structure and the inner hole of the first piston structure respectively, balls are placed in the ball channels of the transmission shafts, and the ball limiting pin is used for limiting the balls. The first transmission shaft and the second transmission shaft drive the first piston structure and the second piston structure to rotate around the first bushing, the pump core support frame and the second bushing through balls, and meanwhile, the piston structure axially reciprocates under the guidance of the curved surface of the guide rail.

Further, each group of linear ball channels are uniformly distributed in the circumferential direction of the corresponding transmission shaft, and the lengths and the depths of all the linear ball channels are the same.

Preferably, any of the linear ball grooves is not fully covered with balls, the length of the linear ball groove where no balls are placed is Δl=h/pi, where h is a guide track stroke, further preferably, the lengths of the linear ball groove b34 and the linear ball groove c174 are l=nd+h/pi, where D is a ball diameter, n is a number of balls, and the number of balls is determined together according to the bearing capacity of the balls and the torque to be transmitted, which is specifically set as a technology known in the art.

Because the balls in the linear ball channels are not fully distributed in the channels, when the initial positions of the balls on the channels are inconsistent, the balls can generate a tilting moment on the transmission shaft and the guide rail piston, and the moment can be balanced through the first bushing, the pump core support frame and the second bushing of the piston pump.

Further, the first transmission shaft 3, the second transmission shaft 17, the linear ball channel, the ball channel in the first piston structure 4 and the ball channel in the second piston structure 18, the distribution groove and the molded surface are all finished by one-time clamping processing. The linear ball channel in the piston structure of the linear ball channel through the transmission shaft is in clearance-free fit, so that the instantaneous flow of the up/down pump core can be kept constant all the time, and the flow pulsation and the pressure pulsation of the pump can be well eliminated.

According to another preferred embodiment of the present invention, as shown in fig. 15 to 19, the transmission shaft assembly may further be designed to include two transmission blocks 25, a plurality of limiting portions 23 and a transmission through shaft 21, where the two transmission blocks 25 are respectively arranged in one-to-one correspondence with the first piston structure 4 and the second piston structure 18, and the transmission blocks 25 are hollow columnar structures with two open ends, and have an inner cavity 252, and a pair of inner transmission grooves 253 are uniformly formed on the inner cavity wall in the circumferential direction; a pair of external transmission channels 251 are uniformly formed on the outer wall surface of the transmission block 25 in the circumferential direction, any of the internal transmission channels 253 and the external transmission channels 251 are arranged along the length direction of the transmission block 25, the pair of internal transmission channels 253 are orthogonally arranged with the pair of external transmission channels 251, the two transmission blocks 25 are also respectively arranged in the first piston structure 4 and the inner cavity of the second piston structure 18, and the transmission channels 251 on the external side of the transmission block 25 are matched with balls in ball channels of the corresponding piston structures; a pair of shifting forks 211a are symmetrically arranged on the transmission through shaft 21 in the circumferential direction, and the shifting forks 211a are also arranged along the length direction of the transmission through shaft 21; the transmission through shaft 21 is simultaneously arranged in the two transmission blocks 15, the two transmission blocks 25 are arranged at intervals along the axial direction of the transmission through shaft 21, the inner transmission channel 253 of any transmission block 25 is matched with the shifting fork 211a of the transmission through shaft, and two ends of the transmission through shaft 21 are respectively matched with the first thrust bearing 22 and the second thrust bearing 27; the two ends of any transmission block 25 are provided with the limiting parts 23 in a distributed manner, the limiting parts 23 are fixedly sleeved on the transmission through shaft 21 (namely, the limiting parts 23 can not move along the axial direction of the transmission through shaft 21 and can rotate along with the transmission through shaft 21), and the limiting parts 23 are used for limiting the movement of the two transmission blocks 25 along the axial direction of the transmission through shaft 21; when the piston assembly works, the transmission through shaft 21 drives the two transmission blocks 25 to rotate, and the two transmission blocks 25 transmit torque to the first piston structure 4 and the second piston structure 18 through the balls, so that the first piston structure 4 and the second piston structure 18 rotate circumferentially.

That is, the propeller shaft assembly of the present invention may also employ an orthogonal torque transmission structure.

In the embodiment of the present invention, the two sides of the transmission shaft 21 are provided with

bearing mounting posts

210 and 212, and the middle optical axis is longer than a pair of shifting forks 211a along the radial direction.

According to the embodiment of the invention, the transmission block is added between the transmission through shaft and the piston, the pair of shifting forks are arranged in the inner hole of the piston, the ball grooves are formed in the shifting forks, the pair of shifting forks are arranged on the transmission through shaft, the transmission grooves are formed in the transmission block in a radial orthogonal mode, the grooves on the outer side are matched with balls in the ball grooves of the shifting fork rollaway nest of the piston, and the grooves on the inner side are matched with the shifting forks of the transmission through shaft. When the piston is in operation, the transmission block is driven to rotate by the through shaft (no relative axial movement exists between the transmission block and the piston), and torque is transmitted to the piston by the transmission block through the balls, so that the piston is enabled to rotate circumferentially. By adopting the orthogonal torque transmission structure, the transmission through shaft and the piston are stressed in the orthogonal direction, and no radial component force exists, so that the piston can not extrude the copper bush. Even if the transmission through shaft and the first/second piston are different in small dimension, the transmission through shaft and the first/second piston can be adaptively adjusted through the transmission block, so that the coaxiality requirement of the transmission through shaft and the upper/lower pump core can be reduced, the pairing processing number of parts is reduced, the manufacturability of processing and assembly is improved, and money and time cost can be greatly saved.

Preferably, in order to prevent the balls 26 from falling out, ball blocking blocks 24 are added at two ends of any transmission block 25 for blocking.

Preferably, the two transmission blocks 25, the piston structure and the transmission through shaft 21 are coaxially arranged; and/or, the transmission block 25 is a hollow cylinder structure with two open ends.

Therefore, the double-freedom-degree piston pump of the embodiment of the invention provides a novel baffle type piston structure, a novel double-side flow distribution structure and a novel transmission shaft assembly structure (a cross torque transmission structure and an orthogonal torque transmission structure).

Specific:

the embodiment of the invention provides a novel baffle type piston structure, wherein the whole piston is in a design form of large outer diameter, small inner diameter and no inner wall surface, the middle cylindrical surface is a drainage surface, and two symmetrical pairs of inlets and outlets are respectively distributed on two sides. The oil directly enters the piston cavity without a complex flow passage, so that the self-priming capability of the pump is improved; the end surfaces of the inlet and the outlet of the piston are designed with bevel surfaces, so that hydraulic loss caused by the end surfaces of the outer diameter can be effectively reduced when the piston rotates; the oil enters the piston cavity and almost does not have circumferential rotation movement, meanwhile, the axial speed of the oil is small due to the fact that the stroke of the piston is not large, the kinetic energy loss of the oil is extremely small, and the energy conversion rate of the pump is high; at high speed, the oil can quickly follow the axial movement of the piston and timely fill the piston cavity, so that the cavitation resistance of the pump is greatly enhanced. The piston is internally provided with a through hole, a pair of shifting forks are radially arranged on the through hole, and four ball grooves are uniformly distributed on the shifting forks and are used for torque transmission.

The embodiment of the invention provides a bidirectional flow distribution structure, which mainly comprises a bidirectional flow distribution integrated baffle type piston, a baffle type bushing, an integrated cylinder body and the like. The two-way flow distribution integrated baffle type piston is of an integrated structure of a cam and a piston, the cam is positioned in the middle of the piston, two sides of the cam symmetrically grow an inner cylindrical sleeve and an outer cylindrical sleeve, and the baffle type sleeve is nested and arranged in the baffle type piston to form a closed volume. The sleeve and the boss are respectively provided with a pair of oil distribution ports, and the two pairs of oil distribution ports are positioned in orthogonal positions. The oil distribution port on the outer sleeve is an oil suction port, the oil distribution port on the inner sleeve is an oil discharge port, a through hole is formed in the center of the inner sleeve, a ball channel and a high-pressure groove are orthogonally arranged in the through hole, and the cross torque transmission/orthogonal torque transmission structure penetrates through the through hole and drives the piston to rotate through the balls. The piston and the double-sided guide rail are integrated to form an integrated guide rail piston, the cam is positioned in the middle of the piston, and compared with the prior guide rail and roller structures which are intensively distributed on one side, the roller can be distributed on the outer side of the piston sleeve, so that the axial distance of the piston can be fully utilized, the axial length of the pump is effectively shortened, and the volume of the pump is reduced; the piston and the bushing are of baffle structures, the bushing is utilized to replace a cylinder body part in the traditional sense, meanwhile, the middle of the piston and the bushing is hollowed out, and the circumferential grooves are formed, so that the weight of the pump is greatly reduced, and the power-weight ratio of the pump is improved; meanwhile, the piston and the bushing are both in baffle structures, the stirring effect on oil is small when the piston and the bushing rotate, the stirring loss is reduced, and the mechanical efficiency is high; the piston is provided with two sides for flow distribution, the oil suction port and the oil discharge port are distributed on different cylinders, the distance between the oil ports is indirectly increased, the sealing length is increased, the leakage amount is effectively reduced, and the volumetric efficiency of the pump is improved.

The embodiment of the invention provides a cross torque transmission structure, a transmission through shaft is replaced by an upper transmission shaft and a lower transmission shaft, a transmission block is added between an input transmission shaft and a first transmission shaft as well as between the first transmission shaft and a second transmission shaft, and ball grooves are respectively formed in the upper transmission shaft and the lower transmission shaft. A pair of shifting forks are radially arranged in the inner hole of the piston, and ball grooves are formed in the shifting forks. The channel of the transmission shaft is matched with the balls in the piston shifting fork rollaway nest, and two limiting pins are respectively arranged on the upper/lower two-way transmission shaft to plug the balls in order to prevent the balls in the piston rollaway nest from falling off. When the pump works, the input transmission shaft drives the transmission block to rotate, the transmission block drives the first transmission shaft to rotate, the first transmission shaft transmits torque to the first piston structure through the balls, the pistons are enabled to circumferentially rotate, meanwhile, the pistons axially reciprocate under the action of the guide rail, and the lower pump core transmits torque in the same mode. With this kind of structural style transmission is turned round, and upper/lower allies oneself with pump core and transmission through-axle exist certain different axiality can be through the self-adaptation adjustment of transmission piece, reduce the processing spare part precision requirement.

The embodiment of the invention provides an orthogonal torque transmission structure, a transmission block is added between a transmission through shaft and a piston, a pair of shifting forks are radially arranged in an inner hole of the piston, and ball grooves are formed in the shifting forks. Bearing mounting columns are arranged on two sides of the transmission through shaft, and a pair of shifting forks are radially extended from the middle optical axis. The transmission block is provided with transmission channels in a radial orthogonal mode, the outer channels are matched with balls in the piston shifting fork rollaway nest, and the inner channels are matched with shifting forks of the transmission through shaft. In order to prevent the balls in the piston rollaway nest from falling out, a blocking block is added to the transmission block for blocking. When the device works, the transmission block is driven to rotate by the through shaft (no relative axial movement exists between the transmission block and the piston), torque is transmitted to the piston by the transmission block through the balls, so that the piston circumferentially rotates, and meanwhile, the transmission block axially reciprocates under the action of the guide rail. By adopting the orthogonal torque transmission structure, the transmission through shaft and the piston are stressed in the orthogonal direction, and no radial component force exists, so that the piston can not extrude the copper bush. Even if the transmission through shaft and the first/second piston structure are different in small dimension, the transmission through shaft and the first/second piston structure can be adaptively adjusted through the transmission block, so that the coaxiality requirement of the transmission through shaft and the up/down pump core can be reduced, the pairing processing number of parts is reduced, the manufacturability of processing and assembly is improved, and money and time cost can be greatly saved.

In summary, the piston sleeve and the double-sided guide rail of the double-freedom-degree piston pump are integrated, the rollers can be distributed on the outer side of the piston sleeve, the axial distance of the piston can be fully utilized, the axial length of the pump is effectively shortened, the volume and the weight of the pump are reduced, and the power-weight ratio of the pump is improved; the piston and the bushing are both in baffle structures, the bushing is utilized to replace a cylinder body part in the traditional sense, meanwhile, the middle of the piston and the bushing is hollowed out, and the circumferential grooves are formed, so that the weight of the pump is greatly reduced; according to the invention, the piston and the bushing are both in baffle structures, so that the resistance of the integrated guide rail piston during rotary reciprocating motion is reduced, the oil stirring power loss is reduced, and the mechanical efficiency of the pump is improved; according to the double-side flow distribution type piston, the oil suction ports and the oil discharge ports are distributed on different cylinders, so that the distance between the oil ports is indirectly increased, the sealing length is increased, the leakage quantity is effectively reduced, and the volumetric efficiency of the pump is improved; the oil suction port of the piston cavity is arranged on the outer sleeve of the guide rail piston and is directly communicated with the oil, and the oil can enter the piston cavity without passing through any flow channel, so that the self-priming capacity of the pump is effectively improved. The piston is of a baffle structure, oil entering the piston cavity hardly has circumferential rotation movement, meanwhile, the axial speed of the oil is small due to the fact that the stroke of the piston is small, the kinetic energy loss of the oil is small, and the energy conversion rate of the pump is high. The piston is of a baffle structure, and oil can rapidly follow the axial movement of the piston and timely fill the piston cavity when the pump is at high speed, so that the cavitation resistance of the pump is greatly enhanced. When the piston cavity is in the pressure oil stroke, the bushing is slightly deformed under the action of high pressure oil, so that the gap between the bushing and the piston is reduced, the leakage amount is reduced, the volumetric efficiency is improved, and the gap compensation structure is also applicable to high temperature.

The invention can realize decoupling of the rotary motion of the two-way pump core through the cross torque transmission/orthogonal torque transmission structure, greatly reduces the coaxiality requirement of the two-way pump core, has simpler transmission structure, and can solve the problem of eccentric wear of pistons at high speed and high pressure caused by different shafts of the pump cores connected in series. Specifically, compared with a shifting fork roller torque transmission structure, the orthogonal/cross torque transmission structure is small in size, and the torque transmission structure is arranged inside the piston and does not influence the axial length of the pump; the orthogonal/cross transmission and torsion structure has the advantages of light weight, short radius gyration, small moment of inertia, good start-stop performance and good control performance of the pump; compared with an external shifting fork roller torque transmission structure, the orthogonal/cross torque transmission structure is distributed in the piston, has extremely low oil stirring loss and is suitable for high-speed working conditions; the orthogonal/cross transmission and twisting structure of the invention realizes decoupling of the upper and lower pump cores in rotation, reduces the coaxiality requirement of the upper and lower pump cores, reduces the machining precision requirement, reduces the machining cost and improves the economic benefit.

In the description of the present invention, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be constructed and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present invention; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual freedom of motion piston pump, the piston pump comprising: front end housing, pump housing and rear end cap, front end housing, pump housing and rear end cap link firmly in proper order form pump housing structure, its characterized in that, the piston pump still includes:

a drive shaft assembly;

2. The piston pump with double degrees of freedom of movement according to claim 1, wherein the series structure further comprises a first bushing, a second bushing and a pump core supporting frame, the first bushing, the first piston structure, the pump core supporting frame, the second piston structure and the second bushing are coaxially arranged along the axis of the transmission shaft assembly in sequence, the first bushing and the second bushing comprise a baffle plate and a bushing sleeve arranged on the baffle plate, the bushing sleeve consists of a bushing outer cylinder and a bushing inner cylinder positioned in the bushing outer cylinder, an annular cavity is formed between the bushing inner cylinder and the bushing outer cylinder, a plurality of oil distribution ports are uniformly distributed in the circumferential direction of the bushing sleeve, any oil distribution port penetrates through the bushing outer cylinder and the bushing inner cylinder at the same time, the baffle plate is provided with an inner hole penetrating through the baffle plate, and the inner hole is communicated with the bushing inner cylinder to form an inner cavity of the bushing; the pump core support frame adopts an integrated cylinder body structure and comprises a pump core support frame body, the pump core support frame body is fixedly connected with a pump shell, an oil drainage channel is formed in the pump core support frame body, a first support arm bushing assembly and a second support arm bushing assembly are respectively grown at two ends of the pump core support frame body, the two assemblies are arranged in a staggered preset angle, the first support arm bushing assembly consists of a first support arm assembly and a first support arm sleeve, the second support arm bushing assembly consists of a second support arm assembly and a second support arm sleeve, the first support arm sleeve and the second support arm sleeve are identical in structure with the bushing sleeve, and an inner side barrel of the first support arm sleeve and an inner side barrel of the second support arm sleeve are communicated with the oil drainage channel to form an inner cavity of the pump core support frame;

3. The dual freedom of piston pump of claim 2 wherein the tandem structure further includes a first end cap and a second end cap, the first end cap being fixedly connected to the baffle of the first liner, the first end cap having an inner bore therethrough and extending through the inner bore in the baffle, the first end cap and the liner sleeve in the baffle being disposed on each side of the baffle, the second end cap being fixedly connected to the baffle of the second liner and being disposed on each side of the baffle with the liner sleeve in the baffle.

4. A dual freedom of movement piston pump of claim 3 further comprising a first thrust bearing and a second thrust bearing disposed at the first end cap and the second end cap, respectively, wherein one end of the drive shaft assembly is coupled to the first thrust bearing and disposed within the bore of the first end cap, the end being a power input end, and the other end of the drive shaft assembly is coupled to the second thrust bearing.

5. The piston pump of claim 1, wherein, in the first piston structure and the second piston structure, for any sleeve structure, a pair of oil suction ports are symmetrically arranged on the outer cylinder, a pair of oil discharge ports are symmetrically arranged on the inner cylinder, and the pair of oil suction ports and the pair of oil discharge ports are orthogonally arranged; for any bushing sleeve, the bushing sleeve is provided with symmetrically arranged oil distribution ports along the circumferential direction of the bushing sleeve, and any oil distribution port is formed by an oil distribution port on the bushing outer side cylinder and an oil distribution port on the bushing inner side cylinder, and the oil distribution port on the bushing outer side cylinder and the oil distribution port on the bushing inner side cylinder are mutually parallel.

6. The dual freedom of motion piston pump of claim 5 wherein any of the ports further extends to the free end of the corresponding sleeve.

7. The dual freedom of motion piston pump of claim 5 or 6 wherein the oil suction port end face is of a chamfer design wherein the oil suction port has an outer open area greater than an inner open area; and/or the end face of the oil drain port adopts a chamfer design, wherein the area of an opening at the outer side of the oil drain port is larger than that of an opening at the inner side of the oil drain port.

8. The dual freedom of motion piston pump of claim 7 wherein the cross-sectional area of the oil suction port is greater than the cross-sectional area of the oil discharge port.

9. The piston pump of claim 1, wherein a plurality of shift forks are symmetrically elongated in a radial direction on the inner cavity of the piston structure, and linear ball grooves are formed on the shift forks for ball torque transmission.

10. The dual freedom of piston pump of claim 9 wherein the inner chamber wall except for the fork is formed with a high pressure flow passage communicating with the oil drain port and the oil drain flow passage.

11. The piston pump with double degrees of freedom of movement according to claim 2, wherein the pump core supporting frame body is in a shape of a circular truncated cone, an annular groove is arranged on the circumferential side wall of the circular truncated cone, an oil drain port of the body is arranged on the annular groove and is communicated with an oil drain flow passage in the body, and a high-pressure cavity is formed between the annular groove and the pump shell.

12. The dual freedom piston pump of claim 11 wherein a plurality of oil grooves are formed in the pump core support body along the circumferential direction, any of the oil grooves being formed in the axial direction of the pump core support body and not in communication with the oil discharge flow passage, the oil grooves being configured to allow oil to pass through the pump housing.

13. The dual freedom of motion piston pump of claim 2 wherein the first support arm assembly and the second support arm assembly are each comprised of two symmetrically disposed support arms; the cam guide rail is a double-sided cam guide rail; the double-side flow distribution structure further comprises a first roller frame component and a second roller frame component, the first roller frame component is matched with the first support arm component and the first piston structure, the second roller frame component is matched with the second support arm component and the second piston structure, the first roller frame component and the second roller frame component respectively comprise two groups of roller components, the two groups of roller components are arranged at intervals along the length direction of the corresponding support arm component, any roller components respectively comprise a roller frame and a plurality of rollers, the roller frame is fixedly connected with the corresponding two support arms, the rollers are arranged on the inner wall of the roller frame at intervals along the circumferential direction of the roller frame, the corresponding double-sided cam guide rail is clamped between the rollers of the two groups of roller components, and the rollers of the two groups of roller components can respectively move along the two circumferential directions of the double-sided cam guide rail when the piston structure rotates.

14. The dual freedom of motion piston pump of claim 9 wherein the drive shaft assembly includes an input drive shaft, a first drive block, a first drive shaft, a second drive block, and a second drive shaft connected in series; the two end surfaces of the first transmission block are provided with a chute a and a chute b which are orthogonally distributed; the two end surfaces of the second transmission block are provided with a chute c and a chute d which are orthogonally distributed; one end of the input transmission shaft is a power input end and is matched with the first thrust bearing, and the other end of the input transmission shaft is of a flat square structure c and is matched with the chute a; the first transmission shaft is arranged in the inner cavity of the first piston structure, and a plurality of linear ball channels parallel to the axis are uniformly distributed in the circumferential direction of the first transmission shaft and are used for placing balls and matched with the linear ball channels of the first piston structure; the two ends of the first transmission shaft are respectively provided with a flat square structure a and a flat square structure b which are respectively matched with the chute b and the chute c; the second transmission shaft is arranged in the inner cavity of the second piston structure, and a plurality of linear ball channels parallel to the axis are uniformly distributed in the circumferential direction of the second transmission shaft and are used for placing balls and matched with the linear ball channels of the second piston structure; one end of the second transmission shaft is also provided with a flat square structure d which is matched with the chute d; the other end of the second transmission shaft is matched with a second thrust bearing;

15. The dual freedom of motion piston pump of claim 14 wherein any of the slide grooves is a rectangular groove, wherein two of the inner wall surfaces of one set of rectangular grooves disposed parallel to each other are defined as driving surfaces, and the remaining two surfaces are non-driving surfaces.

16. A dual freedom of movement piston pump according to claim 14 or 15 wherein the length of the drive face is greater than the length of the non-drive face.

17. The dual freedom of motion piston pump of claim 14 wherein none of the linear ball channels are full of balls, the linear ball channels being of length Δl, Δl = h/pi, where h is the rail travel of the piston pump.

18. The dual freedom of motion piston pump of claim 17 wherein the length of any linear ball channel is L:

L＝nD+h/π

19. The dual freedom of motion piston pump of claim 9 wherein the drive shaft assembly includes:

20. The dual freedom of motion piston pump of claim 19 wherein the piston pump is

The two transmission blocks, the first piston structure, the second piston structure and the transmission through shaft are coaxially arranged; and/or the number of the groups of groups,

The hollow columnar structure with two open ends is a hollow columnar structure with two open ends.