CN217380863U

CN217380863U - Axial plunger pump

Info

Publication number: CN217380863U
Application number: CN202221038374.9U
Authority: CN
Inventors: 李彬; 占彦; 马薇; 王娇
Original assignee: Bosch Rexroth Beijing Hydraulic Co Ltd
Current assignee: Bosch Rexroth Beijing Hydraulic Co Ltd
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2022-09-06
Anticipated expiration: 2032-04-28

Abstract

An axial plunger pump comprising: a pump casing formed by a casing and an end cover; a drive shaft carried by the pump housing; a cylinder block, a flow distribution element, a swash plate and a bearing bush which are arranged in the pump shell, wherein a plurality of plunger cavities are formed in the cylinder block, a plunger is inserted in each plunger cavity, the rear end of each plunger is connected with a corresponding slipper, the rear end surface of each slipper can be slidably pushed against a supporting surface formed by the front surface of the swash plate, the swash plate is supported by the bearing bush in a swinging way, and each plunger cavity sucks and discharges working fluid through the flow distribution element; the axial plunger pump includes a lubrication passage therein, which leads from the flow distributing member through the pump housing to the front surface of the swash plate, and is configured to establish fluid communication between a plunger chamber after moving through an oil discharge groove of the flow distributing member and the front surface of the swash plate. The friction force can be reduced, and the pump efficiency can be improved.

Description

Axial plunger pump

Technical Field

The present application relates to an axial plunger pump.

Background

For axial piston pumps, the pump efficiency is mainly determined by the mechanical and hydraulic efficiency. Mechanical efficiency is mainly affected by friction pairs. The friction pair affecting the mechanical efficiency in the axial plunger pump mainly comprises: a swash plate and shoes; a plunger and a cylinder; cylinder and port plate, etc. The hydraulic efficiency is mainly affected by these friction pairs, the volume of dead space in the plunger cavity, and leakage of working fluid from the plunger cavity.

In order to improve efficiency, in one prior art axial plunger pump, an internal passage is provided in each plunger and the corresponding slipper to communicate a plunger chamber with a bottom surface of the slipper, so that a working fluid in the plunger chamber can be supplied to an interface between the slipper and the swash plate through the internal passage to generate an oil film between the slipper and the swash plate, thereby improving lubrication performance between the swash plate and the slipper, reducing friction between the swash plate and the slipper, and improving pump efficiency.

In this prior art, the hydraulic efficiency is also reduced due to leakage of the working fluid in the plunger cavity, pressure drop, due to internal passages in the plunger and corresponding shoes.

SUMMERY OF THE UTILITY MODEL

An object of the present application is to provide an axial plunger pump capable of improving pump efficiency.

To this end, the present application provides, in one of its aspects, an axial piston pump comprising: a pump casing formed by a casing and an end cover; a drive shaft carried by the pump housing; a cylinder block, a flow distribution element, a swash plate and a bearing bush which are arranged in the pump shell, wherein a plurality of plunger cavities are formed in the cylinder block, a plunger is inserted into each plunger cavity, the rear end of each plunger is connected with a corresponding slipper, the rear end surface of each slipper can be slidably pushed against a supporting surface formed by the front surface of the swash plate, the swash plate is supported by the bearing bush in a swinging way, and each plunger cavity sucks and discharges working fluid through the flow distribution element; the axial plunger pump includes a lubrication passage therein, which leads from the flow distribution member to the front surface of the swash plate through a pump housing, configured to establish fluid communication between a plunger chamber after moving through an oil discharge groove of the flow distribution member and the front surface of the swash plate.

In one embodiment, the starting end of the lubricating channel communicates with a through hole in the flow distribution element, the through hole being located circumferentially between the rear end of the oil discharge groove and the front end of the oil suction groove of the flow distribution element, and the end of the lubricating channel forming a working fluid outlet located on the bearing surface of the swash plate.

In one embodiment, the port member is a port plate disposed between a front end of the cylinder and the end cap;

the lubrication channel comprises the following sections which are connected end to end with each other:

an end cap segment formed in the end cap;

a shell section formed in the shell;

a bearing shell segment formed in the bearing shell;

a swash plate segment formed in the swash plate.

In one embodiment, the flow distribution member is a flow distribution ring disposed between an outer periphery of the cylinder block and a peripheral wall of the housing;

a shell section formed in the shell;

a bearing shell segment formed in the bearing shell;

a swash plate segment formed in the swash plate.

In one embodiment, at least one of the segments is formed by a combination of segments extending in different directions and joining each other.

In one embodiment, the bearing shell segment opens at an interface between the swash plate and the bearing shell.

In one embodiment, the front end of the swash plate section forms an opening to the working fluid outlet, and the rear end of the swash plate section forms an arcuate slot extending around the axis of oscillation of the swash plate such that the arcuate slot is always in communication with the housing section throughout the range of oscillation of the swash plate.

In one embodiment, the hydraulic fluid outlet opens on a side of the swash plate corresponding to an oil discharge side of the flow distributing element on a center circle defined by centers of the shoes.

In one embodiment, the working fluid outlets comprise at least two working fluid outlets distributed along a central circle defined by the center of each slipper shoe, each working fluid outlet being connected to the swash plate segment.

In one embodiment, each plunger is a closed hollow structure having an internal hollow that is closed with respect to the exterior of the plunger.

According to the application, a lubricating channel which is communicated with the front surface of the swash plate from the flow distribution element through the pump shell is formed in the axial plunger pump, and the lubricating channel is used for enabling the working fluid which is still at high pressure in the plunger cavity after moving through the oil discharge groove to flow to the front surface of the swash plate, so that the working fluid is provided between the swash plate and the slipper as a lubricating medium, and the friction force between the swash plate and the slipper is reduced. Further, the working fluid is also supplied to the interface between the swash plate and the bearing pads, so that the frictional force between the swash plate and the bearing pads can be reduced. Internal passages do not need to be formed in each plunger and the corresponding sliding shoe, so that working fluid leakage and pressure drop in a plunger cavity can be reduced, and meanwhile, partial pressure of original high-pressure oil directly connected to oil suction is utilized, so that the pump efficiency is improved.

Drawings

The foregoing and other aspects of the present application will be more fully understood and appreciated by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of an axial piston pump according to one possible embodiment of the present application;

FIG. 2 is a schematic cross-sectional view showing the lubrication channels in the axial plunger pump;

FIG. 3 is a schematic elevational view of one form of a port plate that may be employed in an axial piston pump;

FIG. 4 is a schematic front view of a modification of a port plate that may be employed in an axial piston pump;

FIG. 5 is a schematic cross-sectional view of one form of plunger that may be employed in an axial plunger pump;

FIGS. 6 and 7 are schematic views of one possible way of manufacturing the plunger of FIG. 5;

FIG. 8 is a schematic cross-sectional view of an axial piston pump according to another possible embodiment of the present application;

FIG. 9 is an expanded view of a flow distribution ring in the axial piston pump of FIG. 8;

fig. 10 is a schematic cross-sectional view showing a lubrication channel in the axial plunger pump in fig. 8.

Detailed Description

The present application relates generally to an axial piston pump, one embodiment of which is schematically illustrated in fig. 1. It should be noted that the construction of the axial piston pump is shown schematically, not to scale, and that certain elements and details have been omitted from the drawings in order to clearly embody the principles of the present application.

As shown in fig. 1, the axial piston pump comprises a pump housing formed by a housing 1 and an end cap 2. The housing 1 is constituted by a peripheral wall 1a and an end wall 1b, defining an internal space. The end cap 2 closes the inner space.

A drive shaft 3 is carried by the housing 1. The main part of the drive shaft 3 is located in the housing 3, the front end of the drive shaft 3 being supported by bearings in the end cap 2, the rear part by bearings in the end wall 1b, and the rear end projecting from the end wall 1. The drive shaft 3 defines a rotational axis.

In the inner space of the housing 1, the functional elements of the plunger pump are arranged, which are described in turn below.

A cylinder block 4 is fixedly supported on a front portion of the drive shaft 3 such that the cylinder block 4 can be driven to rotate by the drive shaft 3.

The cylinder 4 has formed therein a plurality of plunger chambers 5 arranged parallel to each other around the rotational axis. The front end of each plunger cavity 5 leads to the front end surface of the cylinder body 4, and the rear end thereof is communicated with the rear end surface of the cylinder body 4.

Each plunger chamber 5 has a corresponding plunger 6 inserted therein from the rear end, each plunger 6 being axially slidable in the plunger chamber 5, and each plunger 6 rotating with the cylinder 5.

A ball head 7 is formed or attached to a rear end of each plunger 6 that emerges from the plunger cavity 5, the ball head 7 being inserted into a respective slipper 8 such that each slipper 8 is able to rotate relative to the respective ball head 7.

A swash plate (also referred to as a variable head) 9 is disposed on the rear side of each shoe 8, and the rear end surface (bottom surface) of each shoe 8 slidably abuts against a support surface 9a constituted by the front surface of the swash plate 9. The return disc 10 keeps the shoes 8 simultaneously pushed against the swash plate 9.

The swash plate 9 does not rotate with the drive shaft 3, but is swingable about a swing axis. For this purpose, the rear portion of the swash plate 9 is formed with protruding circular arc-shaped support portions 11 on both lateral sides of the drive shaft 3, the two support portions 11 being integral parts of the swash plate 9 and being supported by the bearing shoes 12. The front portion of the bearing shell 12 is formed with a pair of concave circular arc surfaces, respectively supporting the support portions 11 such that the support portions 11 can swing with respect to the bearing shell 12. The axis of oscillation intersects perpendicularly the axis of rotation of the drive shaft 3.

The bearing shell 12 is fixed in the housing 1. In the illustrated example, the bush 12 is fixed to the front side of the end wall 1b, but it is needless to say that the bush 12 may be fixed to the inside of the peripheral wall 1 a. Alternatively, the bearing shell 12 is formed as an integral part of the housing 1, for example integrally with the front side of the end wall 1b and/or the inside of the peripheral wall 1 a.

The drive shaft 3 passes through the bearing shell 12, the swash plate 9, the return plate 10 and the cylinder block 4.

A port plate 13 is fixed to the rear end surface of the head cover 2 facing the front end surface of the cylinder 4. Port plate 13 has an oil discharge side and an oil suction side. An oil discharge groove 14 is formed in the oil discharge side of the port plate 13, and the oil discharge groove 14 is connected to an oil outlet port 16 of the plunger pump through an oil outlet passage 15 in the end cover 2. An oil suction groove 17 is formed in the oil suction side of the port plate 13, which oil suction groove 17 is connected to an oil inlet port (not shown) of the plunger pump via an oil inlet channel 18 in the end cover 2.

When the cylinder block 4 is rotated by the drive shaft 3, the respective plungers 6 and shoes 8 rotate with the cylinder block 4, and the respective shoes 8 slide on the bearing surfaces 9a of the swash plate 9. Due to the swing angle of the swash plate 9, each plunger 6 on the oil suction side retreats relative to the cylinder block 4 to suck the working fluid from the oil suction groove 17 into the corresponding plunger chamber 5, and each plunger 6 on the oil discharge side extends forward relative to the cylinder block 4 to pressurize the working fluid in the corresponding plunger chamber 5 and discharge it through the oil discharge groove 14.

The displacement of the plunger pump depends on the angle of oscillation of the swash plate 9. In order to adjust the swing angle of the swash plate 9, a variable displacement mechanism is provided in the plunger pump for driving the swash plate 9 to swing. Various forms of variable mechanisms known in the art may be used herein and are not shown or described herein.

When each shoe 8 rotates with the cylinder block 4, the rear end surface of the shoe 8 slides on the support surface 9a of the swash plate 9. In order to reduce the friction between the shoes 8 and the swash plate 9, it is desirable to provide sufficient lubrication therebetween.

For this purpose, the present application proposes that a lubrication channel 20 leading from the port plate 13 to the bearing surface 9a of the swash plate 9 is formed in the pump housing, the lubrication channel 20 passing through the interface between the swash plate 9 and the bearing shell 12. The lubrication passage 20 is configured such that the working fluid in the plunger chamber after moving through the oil discharge groove 14, which is still at a high pressure, flows to the interface between the swash plate 9 and the shoe 12 and to the bearing surface 9a of the swash plate 9 through the lubrication passage 20, thereby supplying the working fluid as a lubrication medium between the swash plate 9 and the shoe 12 and between the swash plate 9 and the shoe 8.

In order to clearly show the lubrication channel 20, fig. 2 shows the plunger pump with the drive shaft 3, cylinder 4, plunger 6, slipper 8, and return disc 10 removed.

As shown in fig. 2, the starting end of the lubrication channel 20 communicates with the through hole 21 in the port plate 13, and includes the following sections in succession: an end cover section 22 formed in the end cover 2, a housing section 23 formed in the housing 1, a bearing shell section 24 formed in the bearing shell 12, and a swash plate section 25 formed in the swash plate 9. These segments are joined end to form a continuous lubrication channel 20. It is noted that one or more of the segments may be a combination of a plurality of segments extending in different directions and joining each other in the respective part.

The ends of the bearing shell segments 24 form branches which open into the two circular arc surfaces of the bearing shell 12. In this way, the interface between the swash plate 9 and the bearing shell 12 can be lubricated by the working fluid.

The rear end of the swash plate section 25 forms an arcuate slot 26. The curved groove 26 extends over an arc about the pivot axis, so that the curved groove 26 is always in communication with one limb of the housing section 23 over the entire pivoting range of the swash plate 9. The front end of the swash plate section 25 is connected to a working fluid outlet 27 opening on the front surface of the swash plate, i.e., the support surface 9 a. The working fluid outlet 27 constitutes the end of the lubrication channel 20.

The radial position of the working fluid outlet 27 is located on a central circle defined by the centre of each slipper 8. The circumferential position of the working fluid outlet 27 is located on the swash plate 9 on the side corresponding to the drain side of the port plate, for example, near the axially rearward position. Since the thrust force of each slipper 8 on the swash plate 9 from the axially rearward position to the axially forward position is gradually increased, the working fluid outlet 27 is opened on the swash plate 9 on the side corresponding to the oil discharge side of the port plate, which is advantageous for providing better lubrication to the slipper 8 on the side of the swash plate 9 that is subjected to a large force.

Alternatively, at least two working fluid outlets 27 may be provided along a central circle defined by the center of each slipper 8, each working fluid outlet 27 being connected to a swash plate segment 25.

It is noted that for each section of the lubrication channel 20, some sections are composed of segments extending in different directions. One possible way of working in order to form the segments in the respective part is to drill holes in different directions at different locations on the surface of the part, which holes are joined end to form the segments. If a hole is not open on the surface of the component, it may be plugged or otherwise blocked from opening on the surface. Such ways of forming the plurality of segments in the component are well known in the art and will not be described in detail.

Referring to fig. 3, the oil discharge groove 14 on the oil discharge side in the port plate 13 is a continuous arc groove having a front end 14a and a rear end 14b in the rotational direction of the drive shaft 3 as indicated by the arrows; the oil suction groove 17 on the oil suction side is a continuous arc groove and has an oil suction groove front end 17a and an oil suction groove rear end 17b in the rotational direction of the drive shaft 3 as indicated by the arrow. The through hole 21 is located circumferentially between the oil drain groove rear end 14b and the oil suction groove front end 17 a.

Fig. 4 shows a modification of the port plate 13, in which the oil drainage groove 14 is formed by a series of oil drainage holes distributed in the circumferential direction. The most upstream oil drain hole in the rotation direction of the drive shaft 3 may be regarded as the oil drain groove front end, and the most downstream oil drain hole in the rotation direction of the drive shaft 3 may be regarded as the oil drain groove rear end. The through hole 21 is located between the most downstream oil discharge hole in the rotation direction of the drive shaft 3 and the oil suction groove leading end 17a in the circumferential direction.

It will be appreciated that as a certain plunger chamber 5 rotates past the oil drain groove 14, its corresponding shoe 8 slides on one side of the swash plate 9, so that the corresponding plunger 6 undergoes a process of being pushed forward by the swash plate 9 via the shoe 8, whereby the working fluid in the plunger chamber 5 is pushed into the oil drain groove 14 by the plunger 6, and an oil drain cycle is achieved. On the other hand, when a certain plunger chamber 5 rotates through the oil suction groove 17, its corresponding shoe 8 slides on the other side of the swash plate 9, so that the corresponding plunger 6 undergoes a process of being pulled backward with the shoe 8, whereby the working fluid in the oil suction side 17 is sucked into the plunger chamber 5, achieving an oil suction cycle. On the oil discharge side the pressure in the plunger chamber 5 is higher than the pressure in the oil suction side. After the plunger chamber 5 has rotated past the rear end 14b of the oil drain groove, the pressure in the plunger chamber 5 is still at a certain high pressure. When the plunger chamber 5 rotates past the through hole 21, the working fluid in the plunger chamber 5 enters the lubrication passage 20 through the through hole 21 to be supplied to the working fluid outlet 27 of the swash plate 9 and flows toward the support surface 9 a.

When a certain sliding shoe 8 slides through the working fluid outlet 27 of the swash plate 9, the working fluid with certain pressure in the working fluid outlet 27 establishes an oil film with certain thickness between the sliding shoe 8 and the swash plate 9, and the oil film reduces the friction force between the sliding shoe 8 and the swash plate 9, thereby improving the mechanical efficiency of the plunger pump.

After the sliding shoe 8 slides away from the working fluid outlet 27, the working fluid with a certain pressure in the working fluid outlet 27 flows toward the supporting surface 9a of the swash plate 9, so that the pressure in the plunger cavity 5 is relieved, thereby avoiding the hydraulic efficiency loss caused by the fact that the working fluid in the plunger cavity 5 enters the oil suction groove 17 in a high-pressure state.

Further, the hydraulic efficiency of the plunger pump is also affected by the volume of dead space in the plunger cavity 5. The dead zone of the plunger chamber 5 is the region of the operating fluid remaining in the plunger chamber 5 at the front of the plunger 6 after the end of the drain cycle. The working fluid in this region is not pushed into the oil drain groove 14, but enters the oil suction cycle with the plunger chamber 5. It is clear that the hydraulic fluid in the dead space is not useful for hydraulic efficiency, is a waste, but certainly not avoidable. In one prior art axial plunger pump, the plungers have open cavities that open into the plunger cavity, and internal channels are provided in each plunger and the respective shoes that communicate the cavities with the bottom surface of the shoes. The open cavity in the plunger increases the dead volume and the internal passage results in leakage of the working fluid and pressure loss in the plunger cavity.

According to a further aspect of the present application, each plunger 6 is configured as a closed hollow structure, as shown in fig. 5. On the one hand, the plunger 6 has an internal hollow to reduce the weight of the plunger 6 and therefore its moment of inertia, increasing mechanical efficiency. On the other hand, the inner hollow is closed with respect to the outside of the plunger 6, and no working fluid can enter the inner hollow. In this way, the dead volume of the plunger cavity 5 can be reduced relative to a plunger having an open cavity, so that hydraulic efficiency can be improved. In addition, an internal channel is not formed in the plunger 6, so that the working fluid in the plunger cavity 6 is prevented from leaking, and the hydraulic efficiency is further improved.

The hollow structure of the plunger 6 may be formed by any suitable machining method. For example, a small hole 6a with a smaller diameter may be first drilled in the plunger 6 from the front end face of the plunger 6 as shown in fig. 6, and this small hole 6a may be drilled into the ball head 7. Then, as shown in fig. 7, a large hole 6b with a larger diameter is punched from the front end face of the plunger 6, and most of the material in the body of the plunger 6 is removed from the large hole 6 b; then, the opening of the large hole 6b on the front end face of the plunger 6 is closed by welding with an end plate 6 c. It is understood that the small holes 6a may not be formed, but only the large holes 6b may be formed.

Other methods of forming the hollow structure of the plunger 6 that will be apparent to those skilled in the art may be employed.

Another embodiment of the present application is schematically illustrated in fig. 8. The same points of the axial plunger pump as those in the previously described embodiment will not be described repeatedly. Only the differences of the axial piston pump in fig. 8 will be described below.

As shown in fig. 8, the port plate at the front end surface of the cylinder block 4 described in the previous embodiment is eliminated, and a port ring 30 provided around the outer periphery of the cylinder block 4 is employed.

Specifically, the flow distribution ring 30 is cylindrical. The distribution ring 30 has an oil discharge side and an oil suction side. The oil discharge groove 14 is formed in the oil discharge side of the flow distribution ring 30, and the oil suction groove 17 is formed in the oil suction side.

The inner periphery of the flow distribution ring 30 supports the outer periphery of the cylinder 4 so that the cylinder 4 can slidably rotate within the flow distribution ring 30. The outer periphery of the distribution ring 30 is tightly fixed to the inner peripheral surface of the corresponding portion of the peripheral wall 1 a.

At the front of the cylinder 4, an oil port 31 is formed extending radially outward from the front end of each plunger chamber 5 to the outer periphery of the cylinder 4. The oil discharge groove 14 and the oil suction groove 17 are provided at axial positions communicating with the respective oil ports 31 so as to establish communication with the respective oil ports 31.

Further, in the peripheral wall 1a, oil outlet ports 16 and oil inlet ports 32 extending radially are formed. The oil outlet port 16 is communicated with the oil discharge groove 14, and the oil inlet port 32 is communicated with the oil suction groove 17.

Fig. 9 shows an expanded view of the distribution ring 30. The distribution ring 30 may be viewed as a cylinder formed by longitudinally joining end-to-end elongated sheets of material. The oil discharge groove 14 and the oil suction groove 17 are long holes formed in the flow distribution ring 30, i.e., each extend in a circumferential direction by a certain arc. In the present embodiment, the oil drain groove 14 may be formed by a set of oil drain holes distributed in the circumferential direction.

Returning to fig. 8, the rear end of the cylinder block 4 is fixed around the front of the drive shaft 3. The front end face of the cylinder 4 faces a pressure ring 44 provided in the rear end face of the head cover 2. The pressure ring 44 is made of a wear-resistant material, such as copper, in the form of a flat circular ring and is fixed to the rear end face of the end cap 2, for example, embedded in an annular groove in the rear end face of the end cap 2. When the drive shaft 3 rotates, it rotates the cylinder block 4, and the front end of the cylinder block 4 slides and rotates along the pressure receiving ring 44.

The front end of the cylinder 4 may be configured in the form of a circular ring-shaped protrusion protruding forward from the body portion of the cylinder 4. The wall thickness of the annular protrusion is less than the radial width of the pressure ring 44.

The cylinder block 4 is formed with a central cavity facing forward, into which the front end of the drive shaft 3 is inserted a short distance. In the central cavity, a spring support 41 is arranged, which spring support 41 is fixed to the front end of the drive shaft 3. The rear end of the spring 42 is axially urged against the spring support 41, and the front end is axially urged against a snap ring 43 fixed in the front portion of the cylinder 4. Thus, the spring 42 applies a forward urging force to the cylinder 4 via the snap ring 43 to urge the front end of the cylinder 4 against the pressure ring 44.

When the cylinder block 4 is rotated by the drive shaft 3, the respective plungers 6 and shoes 8 rotate with the cylinder block 4, the respective shoes 8 slide on the front surface of the swash plate 9, and a return plate, not shown, holds the respective shoes 8 while being pushed against the swash plate 9. Due to the swing angle of the swash plate 9, each plunger 6 on the oil suction side is retreated relative to the cylinder block 4 to suck the working fluid into the corresponding plunger chamber 5 through the corresponding oil port 31 and oil suction groove 17 from the oil inlet port 32, and each plunger 6 on the oil discharge side is advanced relative to the cylinder block 4 to pressurize the working fluid in the corresponding plunger chamber 5 and discharge the same through the corresponding oil port 31 and oil discharge groove 14 via the oil outlet port 16.

The distribution ring 30 constitutes a sliding bearing of the cylinder 4 during rotation of the cylinder 4 to support the cylinder 4. Since the support of the flow distribution ring 30 is obtained, the centrifugal force of the cylinder 4 is offset by the flow distribution ring 30, which can prevent the cylinder 4 from tilting.

In order to be able to be used as a sliding bearing, the distribution ring 30 is made of a wear-resistant material, for example copper.

In addition, a small amount of the working fluid inevitably leaks out of the oil drain groove 14, and enters a minute gap between the outer periphery of the cylinder 4 and the inner periphery of the flow distribution ring 30 to form an oil film. This oil film contributes to the sliding support action of the distribution ring 30.

Due to the supporting function of the flow distribution ring 30 on the cylinder block 4, the structural rigidity of the cylinder block 4 and the driving shaft 3 is improved. Therefore, the drive shaft 3 can be supported only by the bearing in the end wall 1b as shown in fig. 8, and it is not necessary to provide the bearing in the end cover 2 to support the front end of the drive shaft 3. Meanwhile, the front end of the drive shaft 3 may protrude into only the rear portion of the cylinder block 4. Thus, the length of the drive shaft 3 is shortened, and the centrifugal force generated by the drive shaft 3 can be reduced.

The axial piston pump shown in fig. 8 is preferably used as a closed piston pump, i.e. the working fluid discharged through the outlet port 16 drives the hydraulic actuators and returns to the inlet port 32, thereby forming a closed circulation path for the working fluid. In the present embodiment, each plunger 6 may also be configured in the closed hollow structure described above.

The distribution ring in the axial piston pump shown in fig. 8 simultaneously acts as a slide bearing supporting the cylinder. In this way, the rotating cylinder can be supported by the distribution ring, resisting the radial centrifugal force generated by the rotation of the cylinder, thus allowing to increase the maximum allowable rotation speed of the pump.

Further, in the axial piston pump shown in fig. 8, a lubrication passage 20 leading from the distribution ring 30 to the support surface 9a of the swash plate 9 is also formed in the pump housing, and the lubrication passage 20 passes through the interface between the swash plate 9 and the bearing pads 12. The lubrication passage 20 is configured such that the working fluid in the plunger chamber after moving through the oil discharge groove 14, which is still at a high pressure, flows to the interface between the swash plate 9 and the shoe 12 and to the bearing surface 9a of the swash plate 9 through the lubrication passage 20, thereby supplying the working fluid as a lubrication medium between the swash plate 9 and the shoe 12 and between the swash plate 9 and the shoe 8.

In order to clearly show the lubrication channel 20, the axial piston pump of fig. 8 is shown in fig. 10 with the drive shaft 3, cylinder 4, piston 6 and piston shoe 8 removed.

As shown in fig. 10, the starting end of the lubrication passage 20 communicates with the through hole 21 in the distribution ring 30, and includes the following successive segments: a housing section 23 formed in the housing 1, a bearing section 24 formed in the bearing shell 12, and a swash plate section 25 formed in the swash plate 9. These segments are joined end to form a continuous lubrication channel 20. It is noted that one or more of the segments may be a combination of a plurality of segments in the respective part extending in different directions and joining each other.

The ends of the bearing shell segments 24 form branches which open out into the two circular arc surfaces of the bearing shell 12. In this way, the interface between the swash plate 9 and the bearing shell 12 can be lubricated by the working fluid.

The rear end of the swash plate section 25 forms an arcuate slot 26. The curved groove 26 extends over an arc about the pivot axis, so that the curved groove 26 is always in communication with one branch of the housing section 23 over the entire pivoting range of the swash plate 9. The front end of the swash plate section 25 is connected to a working fluid outlet 27 opening on the front surface of the swash plate, i.e., the support surface 9 a.

The radial position of the working fluid outlet 27 is located on a central circle defined by the centre of each slipper 8. The circumferential position of the working fluid outlet 27 is located on the swash plate 9 on the side corresponding to the drain side of the port plate, for example, near the axially rearward position. Because the thrust of each slipper 8 on the swash plate 9 from the axially backward position to the axially forward position is gradually increased on the swash plate 9, the working fluid outlet 27 is opened on the side of the swash plate 9 corresponding to the oil discharge side of the port plate, which is beneficial to providing better lubrication for the slipper 8 on the side of the swash plate 9 which is greatly stressed.

For each section of the lubrication channel 20, some sections are composed of segments extending in different directions.

Referring to fig. 9, the oil discharge groove 14 on the oil discharge side and the oil suction groove 17 on the oil suction side in the flow distribution ring 30 are continuous arc grooves, and the through hole 21 is provided between the rear end of the oil discharge groove 14 and the front end of the oil suction groove 17 in the circumferential direction (corresponding to the rotational direction of the cylinder block 4).

The axial piston pump of fig. 8-10, provided with the lubrication channel 20, achieves the same technical effects as the embodiment described above with reference to fig. 1-7, and will not be described again.

The port plate and the port ring for introducing and discharging the operating fluid in the present application may be collectively referred to as a port member.

According to the application, a lubricating channel which is communicated with the front surface of the swash plate from the flow distribution element through the pump shell is formed in the axial plunger pump, and the lubricating channel is used for enabling the working fluid which is still at high pressure in the plunger cavity after moving through the oil discharge groove to flow to the front surface of the swash plate, so that the working fluid is provided between the swash plate and the slipper as a lubricating medium, and the friction force between the swash plate and the slipper is reduced. Thus, there is no need to form an internal passage in each plunger and the corresponding shoe as in the prior art, and thus leakage of the working fluid and pressure drop in the plunger chamber can be reduced, thereby improving pump efficiency. In addition, the lubrication passage passes through an interface between the swash plate and the bearing bush, so that the working fluid can also be supplied to the interface between the swash plate and the bearing bush, thereby enabling the friction force between the swash plate and the bearing bush to be reduced.

In addition, due to the pressure relief effect of the lubricating channel, the plunger cavity can be prevented from being communicated with the oil suction groove in a high-pressure state, and the pump efficiency can be further improved.

In addition, in the case of the plungers configured in the closed hollow structure, on the one hand, the weight of each plunger can be reduced, and on the other hand, the volume of the working fluid dead space in the plunger cavity can be reduced, which can further improve the pump efficiency.

Although the present application has been described herein with reference to particular embodiments, the scope of the present application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims

1. An axial plunger pump comprising:

a pump housing formed by a housing (1) and an end cover (2);

a drive shaft (3) carried by the pump housing;

a cylinder block (4), a flow distribution element, a swash plate (9) and a bearing bush (12) which are arranged in the pump shell, wherein a plurality of plunger cavities (5) are formed in the cylinder block, a plunger (6) is inserted in each plunger cavity, the rear end of each plunger is connected with a corresponding slipper (8), the rear end surface of each slipper can be slidably pushed against a supporting surface (9a) formed by the front surface of the swash plate (9), the swash plate is swingably supported by the bearing bush, and each plunger cavity sucks and discharges working fluid through the flow distribution element;

characterized in that it comprises a lubrication channel (20) leading from said distributing element through the pump housing to the front surface of said swash plate, arranged to establish fluid communication between the plunger cavity after moving through the oil discharge groove of said distributing element and the front surface of said swash plate.

2. The axial plunger pump as recited in claim 1, characterized in that the starting end of the lubrication channel communicates with a through hole (21) in the distribution element, the through hole being located circumferentially between the rear end of the oil discharge groove (14) of the distribution element and the front end of the oil suction groove (17), the end of the lubrication channel forming a working fluid outlet (27) located on the bearing surface of the swash plate.

3. The axial piston pump as recited in claim 2, characterized in that said port member is a port plate (13) disposed between the front end of said cylinder and said end cap;

an end cap segment (22) formed in the end cap;

a housing section (23) formed in the housing;

a bearing shell segment (24) formed in the bearing shell;

a swash plate section (25) formed in the swash plate.

4. The axial plunger pump according to claim 2, characterized in that the flow distribution member is a flow distribution ring (30) provided between the outer periphery of the cylinder block and the peripheral wall (1a) of the housing;

a housing section (23) formed in the housing;

a bearing shell segment (24) formed in the bearing shell;

a swash plate section (25) formed in the swash plate.

5. The axial piston pump as claimed in claim 3 or 4, characterized in that at least one of the segments is composed of a combination of segments which extend in different directions and which engage one another.

6. The axial piston pump as recited in claim 3 or 4, characterized in that the bearing shell segment opens at an interface between the swash plate and the bearing shell.

7. The axial piston pump as claimed in claim 3 or 4, characterized in that the front end of the swash plate section forms an opening to the working fluid outlet and the rear end of the swash plate section forms an arcuate groove (26) which extends about the axis of oscillation of the swash plate so that the arcuate groove always remains in communication with the housing section throughout the entire range of oscillation of the swash plate.

8. The axial piston pump as recited in claim 7, wherein said working fluid outlet port opens on a side of said swash plate corresponding to an oil discharge side of the port member on a center circle defined by centers of the shoes.

9. The axial piston pump of claim 8 wherein said working fluid outlets include at least two working fluid outlets distributed along a central circle defined by the center of each slipper shoe, each working fluid outlet being connected to said swash plate segment.

10. The axial plunger pump of any of claims 1-4, wherein each plunger is of closed hollow construction having an internal hollow closed to the exterior of the plunger.