US20140178226A1

US20140178226A1 - Hydraulic pump for excavator and excavator comprising the same

Info

Publication number: US20140178226A1
Application number: US14/134,157
Authority: US
Inventors: Ralf Scharffenberg; Sheng Lin
Original assignee: Bosch Rexroth Beijing Hydraulic Co Ltd
Current assignee: Bosch Rexroth Beijing Hydraulic Co Ltd
Priority date: 2012-10-20
Filing date: 2013-12-19
Publication date: 2014-06-26
Also published as: CN103882905A; DE102013225922A1

Abstract

A hydraulic pump for an excavator, which comprises a housing having a supporting wall extending therein; a pair of rotary hydraulic cylinders provided in the housing, each of the rotary hydraulic cylinders being provided with a piston which is movable reciprocatingly in the rotary hydraulic cylinder; and a pair of spindles disposed parallel to the rotary hydraulic cylinders, the spindles being connected with each other via a coupler and driving the rotary hydraulic cylinders to rotate about their respective central axes, each of the rotary hydraulic cylinders comprising a swash plate for receiving and guiding the piston, and the swash plate being stationary relative to the respective spindle, wherein the supporting wall comprises a mounting hole, and the coupler is supported in the mounting hole by means of a sliding bearing.

Description

TECHNICAL FIELD

The present invention relates to a hydraulic pump, in particular to a hydraulic pump for an excavator, and to an excavator comprising the hydraulic pump.

BACKGROUND ART

A hydraulic pump used in an excavator generally comprises a housing and a pair of rotary hydraulic cylinders accommodated in the housing. The rotary hydraulic cylinders are disposed coaxially opposite to each other. A driving shaft is supported in the housing parallel to longitudinal axes of the rotary hydraulic cylinders. Two swath plates are mounted in the housing fixedly relative to the driving shaft. In the rotary hydraulic cylinder there is provided with a reciprocating piston. Each of the swash plates comprises a mating surface for receiving and guiding the piston. Each of the rotary hydraulic cylinders is driven to rotate about a central axis of the driving shaft, and thus the piston is driven to move reciprocatingly in the respective rotary hydraulic cylinder as the driving shaft rotates.
In the prior art, in order to reduce manufacturing and assembly cost, the driving shaft mentioned above is configured as two separate spindles which are disposed coaxially with each other and have substantially the same length, the two spindles being connected with each other via a coupler. A needle bearing for supporting purpose is provided substantially in the middle of the driving shaft and therefore at the coupler because the driving shaft formed by connecting via the coupler is long, which provides sufficient support to the driving shaft and prevents the driving shaft from bending and deforming caused by the long driving shaft consisting of the coupler.
On one hand, the needle bearing has a relative precise structure, and on the other hand, the excavator generally works under bad conditions. This causes a loud noise to be generated during the running of the needle bearing in the hydraulic pump and causes a high failure possibility. The hydraulic pump works at a low work efficiency and may even be damaged, and then the service life of the excavator is affected and its maintenance period is shortened.
It is thus desired to improve the bearing of the hydraulic pump in term of its service life and to reduce the failure possibility of the bearing, in order to improve the work efficiency of the hydraulic pump and to prolong the service life of the excavator or the maintenance period.
In addition, the swash plates may be disposed at an angle relative to the driving shaft depending on the work conditions, and a certain bending moment or a centrifugal force can then be generated (the reasons will be described in the following description) at the coupler when the driving shaft is driven to rotate. Excessive bending moment or centrifugal force may cause an excessive vibration on the driving shaft, and then the efficiency of the hydraulic pump will be affected.
It is thus desired to decrease the bending moment as possible as it can by improving the hydraulic pump, to reduce the vibration of the driving shaft and thus improve the efficiency of the hydraulic pump.

SUMMARY OF THE INVENTION

An object of the invention is to provide a hydraulic pump and an excavator comprising the hydraulic pump, which have prolonged service life and reduced manufacturing cost, to reduce vibration of a driving shaft in the hydraulic pump and to improve efficient of the hydraulic pump.
According to one aspect of the invention, a hydraulic pump for an excavator is provided, which comprises a housing having a supporting wall extending therein; a pair of rotary hydraulic cylinders provided in the housing, each of the rotary hydraulic cylinders being provided with a piston which is movable reciprocatingly in the rotary hydraulic cylinder; and a pair of spindles disposed parallel to the rotary hydraulic cylinders, the spindles being connected with each other via a coupler and driving the rotary hydraulic cylinders to rotate about their respective central axes, each of the rotary hydraulic cylinders comprising a swash plate for receiving and guiding the piston, and the swash plate being stationary relative to the respective spindle, wherein the supporting wall comprises a mounting hole, and the coupler is supported in the mounting hole by means of a sliding bearing. According to the above technical solution of the invention, the sliding bearing has a relative simple structure, a more impact resistant property, a significantly prolonged service life, and a reduced manufacturing cost, and the noise generated during its running is low. Optionally, the swash plate has an adjustable angle relative to the spindle to adjust an amount of a stroke of the piston in the rotary hydraulic cylinder.
Preferably, the hydraulic pump is provided with an adapting bushing therein, and the sliding bearing is mounted in the mounting hole via the adapting bushing so that the adapting bushing is located between an outer circumferential surface of the sliding bearing and an inner surface of the mounting hole. The adapting bushing is made of a material different from that of the sliding bearing. For example, the adapting bushing is made of a steel material, in particular an alloy steel material, while the sliding bearing is made of a powder metallurgy material. Accordingly, the sliding bearing is not directly mounted in the mounting hole of the supporting wall, but via the adapting bushing, which results in the wear to the housing itself being reduced and the service life of the hydraulic pump being prolonged.
Preferably, a circumferential flange extends out radially from an outer circumferential surface of the adapting bushing near an end of the adapting bushing which is adjacent to a surface of the supporting wall, and the circumferential flange is configured for contacting with the supporting wall. The circumferential flange is configured for fixing the adapting bushing into position, preventing the adapting bushing from being displaced during mounting or after mounting and thus ensuring the normal work of the sliding bearing.
Preferably, the sliding bearing is configured as a pair of sliding bearings axially spaced from each other; and/or the adapting bushing is configured as a pair of adapting bushings axially spaced from each other. In this way, heat generated during the running of the hydraulic pump and in particular during the rotating of the coupler can be dissipated more rapidly, and the temperature of the sliding bearings is reduced. In addition, the manufacturing cost is reduced accordingly because the material from which the sliding bearings and/or the adapting bushings are manufactured is expensive. This also results in a smaller bending moment generated at the bearing during the running of the hydraulic pump (details will be described in the following), and thus the vibration generated on the spindle is reduced or even eliminated. The work efficiency of the hydraulic pump is therefore improved.
Preferably, the supporting wall is formed with an oil guiding hole, and the oil guiding hole is aligned with and communicated with an axial gap between the adapting bushings. Lubricant oil can be injected into the axial gap via the oil guiding hole to lubricate the bearing and cool the sliding bearing when the spindle rotates. It is conceivable that the oil guiding hole can be configured for receiving oil leaked in the running of the rotary hydraulic cylinders, so that the leaked oil can pass by the sliding bearing and flow out via the oil guiding hole after cooling the bearings.
Preferably, the sliding bearing is provided with chamfers at opposite ends, so that the sliding bearing can be easily inserted into the mounting hole or into the adapting bushing when assembling, and lubricant oil can reach the sliding bearing more easily to achieve a good lubricant effect.
Preferably, the adapting bushing is provided with chamfers at opposite ends and preferably out-chamfers, so that the adapting bushing can be inserted into the mounting hole easily.
Preferably, a pair of spherical splines are amounted between the coupler and the spindles. According to another aspect of the invention, an excavator comprising the hydraulic pump described above is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the invention will be better understood from the following description in conjunction with the drawings, in which:

FIG. 1 shows an axial cross-sectional view of a hydraulic pump according to one illustrative embodiment of the invention;

FIG. 2 shows an enlarged view of a portion of the hydraulic pump shown in FIG. 1;

FIG. 3 shows an axial cross-sectional view of a hydraulic pump according to another illustrative embodiment of the invention;

FIG. 4 shows an enlarged view of a portion of the hydraulic pump shown in FIG. 3; and

FIG. 5 is similar to FIG. 4, showing an enlarged view of a portion of a hydraulic pump according to a further illustrative embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Illustrative embodiments of the invention will be described with reference to the drawings. It should be noted that same reference numbers throughout the drawings denote functionally and/or structurally identical elements or devices.
FIG. 1 shows an axial cross-sectional view of a hydraulic pump 1 according to one embodiment of the invention. The hydraulic pump according to the invention can be used in a mechanical device working in bad conditions, for example in an excavator.
As shown in FIG. 1, the hydraulic pump 1 comprises a housing 2 and end caps 3 and 4 mounted on opposite ends of the housing 2. Two spindles 5 and 6, two rotary hydraulic cylinders 9 and 10, and two swash plates 7 and 8 for driving the rotary hydraulic cylinders are provided in the housing 2. The swash plates 7 and 8 are configured for adjusting working strokes of the rotary hydraulic cylinders 9 and 10 respectively.
The two spindles 5 and 6 are disposed coaxially and are connected with each other at their opposite ends via a coupler 13 in a known way. In the illustrated embodiment, the spindle 5 comprises an end which extends out of the end cap 3 to be connected with a driving device, for example, a diesel engine (not shown), so that the two spindles 5 and 6 can be driven by the driving device to rotate.
For example, the swash plate 7 is mounted on the end cap 3 fixedly relative to the housing 2, and for example, the swash plate 8 is mounted on the end cap 4 fixedly relative to the housing 2. The swash plates 7 and 8 comprise central openings respectively, and the central openings are sized such that the spindles 5 and 6 can pass through the central openings respectively without contacting with them.
The rotary hydraulic cylinders 9 and 10 are arranged substantially parallel to the spindles 5 and 6, and are connected with the spindles 5 and 6 via spline structures 26 and 27 respectively. A piston 11 is provided to be slidable in the rotary hydraulic cylinder 9, and a piston 12 is provided to be slidable in the rotary hydraulic cylinder 10. The pistons 11 and 12 are provided with piston heads 11 a and 12 a at their ends respectively to be mated with sliding shoes 24 and 25 respectively.
The swash plates 7 and 8 comprise guiding and mating surfaces for guiding sliding shoes 24 and 25 respectively. The rotary hydraulic cylinders 9 and 10 are driven by the spindles 5 and 6 to rotate about central axes of the spindles respectively together with their pistons 11 and 12 during the running of the hydraulic pump. Because the sliding shoes 24 and 25 remains always contact with the corresponding guiding and mating surfaces of the swash plates 7 and 8, the pistons 11 and 12 can be slided axially and reciprocatingly in the rotary hydraulic cylinders 9 and 10. The rotary hydraulic cylinders 9 and 10 comprise their own separate outlets respectively, so that the moving pistons 11 and 12 supply hydraulic oil for hydraulic operating components of the excavator one independent of another.
Angles of inclination of the swash plates 7 and 8 relative to the spindles 5 and 6 are adjustable, so that reciprocating strokes of the pistons 11 and 12 in the rotary hydraulic cylinders 9 and 10 can be adjusted accordingly. For example, the swash plate 7 is shown, in the left of FIG. 1, to be at a larger angle of inclination relative to an axis perpendicular to the spindle 5 to set the maximum reciprocating stroke of the piston 11 in the rotary hydraulic cylinder 9; and the swash plate 8 is shown, in the right of FIG. 1, to be at a smaller angle of inclination relative to an axis perpendicular to the spindle 6 to set the minimum reciprocating stroke of the piston 12 in the rotary hydraulic cylinder 10.
With reference to FIG. 2, a sliding bearing 14 is provided in the housing 2 which is configured for providing sufficient support for the spindles 5 and 6. The sliding bearing can be configured as an integral or split bearing bush made of any suitable wear resistant metal material, such as a bearing alloy or powder metallurgy material. The sliding bearing 14 is disposed over the coupler 13 with an inner circumferential surface of the sliding bearing 14 in contact with an outer circumferential surface of the coupler 13.
The housing 2 comprises a supporting wall 2 a, and the supporting wall 2 a is provided with a mounting hole for mounting the bearing 14 therein.
As shown in FIG. 2, preferably, the sliding bearing 14 is mounted in the mounting hole via an adapting bushing 15 in order to protect the supporting wall 2 a and improve service life of the sliding bearing 14. Preferably, the sliding bearing 14 and the adapting bushing 15 have substantially the same longitudinal length, and their longitudinal lengths are greater than the thickness of the supporting wall 2 a in a direction of the central axes of the spindles 5 and 6.
As can be seen from FIG. 1, a majority of the spindle 5, the swash plate 7 and the rotary hydraulic cylinder 9 are at the left side of the supporting wall 2 a, while a majority of the spindle 6, the swash plate 8 and the rotary hydraulic cylinder 10 are at the right side of the supporting wall 2 a. Preferably, the two rotary hydraulic cylinders 9 and 10 are disposed coaxially.
The adapting bushing 15 can be made of a metal material which is more wear resistant than the housing 2. For example, the adapting bushing 15 is made of a steel material. Still for example, the adapting bushing 15 can be made of a material same as or different from that of the sliding bearing 14. A circumferential flange 15 a extends out radially from an outer circumferential surface of the adapting bushing 15 near an end (for example, the left end in FIG. 2) of the adapting bushing 15 for the purpose of positioning. The circumferential flange 15 a is configured for abutting against an end surface of the supporting wall 2 a so that the adapting bushing 15 can be fixed into position.
Upon mounting into position, an inner circumferential surface of the adapting bushing 15 is in contact with an outer circumferential surface of the sliding bearing 14, while the outer circumferential surface of the adapting bushing 15 is in contact with a surface of the mounting hole in the supporting wall 2 a. For a mechanical device working in bad conditions, such as an excavator, a hydraulic pump according to the invention incorporates the sliding bearing so that the structure becomes simpler and the enduring ability for heavy loads is improved. The service life of hydraulic pump is significantly prolonged and the manufacturing cost is reduced. In addition, according to the technical solutions of the invention, the sliding bearing 14 can be mounted in the housing of hydraulic pump via the adapting bushing 15, and the wear to the housing 2 itself is therefore reduced and the service life of the hydraulic pump is improved accordingly.
FIG. 3 and FIG. 4 show a hydraulic pump according to another illustrative embodiment of the invention. This hydraulic pump differs from the previous embodiment in that the coupler 13 comprises a pair of sliding bearings 18 and 19 which are spaced from each other axially and mounted on the coupler 13. The sliding bearings 18 and 19 can be made of the same material as the sliding bearing 14 shown in FIG. 1.
Due to the sliding bearings 18 and 19 spaced axially, heat generated during the running of the hydraulic pump and in particular during the rotating of the coupler 13 can be dissipated more rapidly, and the temperature of the sliding bearings is reduced significantly. The sliding bearings 18 and 19 have substantially the same axial length and are disposed over the coupler 13, so that inner circumferential surfaces of the sliding bearings 18 and 19 are in contact with the outer circumferential surface of the coupler 13. As can be seen from FIG. 4, the sliding bearings 18 and 19 are spaced from each other sysmetrically with reference to a mid plane L of the coupler 13 which is perpendicular to the coupler 13.
Similar to the previous embodiment, the sliding bearings 18 and 19 are provided with adapting bushings 16 and 17 respectively via which the sliding bearings 18 and 19 are mounted in the mounting hole in the supporting wall 2 a of the housing 2. As shown in FIG. 4, the two adapting bushings 16 and 17 may have same axial lengths as the sliding bearings 18 and 19 and extend over the sliding bearings 18 and 19. Upon mounting into position, inner circumferential surfaces of the adapting bushings 16 and 17 are in contact with outer circumferential surfaces of the sliding bearings 18 and 19.
The adapting bushings 16 and 17 and the adapting bushings 15 may be manufactured from the same material. Circumferential flanges 16 a and 17 a extend out radially from outer circumferential surfaces of the adapting bushings 16 and 17 near ends of the adapting bushings 16 and 17 approximate to the corresponding end surfaces of the supporting wall 2 a, also for the purpose of the positioning. The circumferential flanges 16 a and 17 a are configured for abutting against the corresponding end surfaces of the supporting wall 2 a so that the adapting bushings 16 and 17 can be fixed into position.
It can be found when comparing FIG. 2 with FIG. 4, for the couplers 13 with the same axial length, through manufacturing the sliding bearing of the invention as two sliding bearings 18 and 19 axially spaced from each other and/or manufacturing the adapting bushing of the invention as two sliding bushings 16 and 17 axially spaced from each other, the material from which they are manufactured can be saved. This reduces the manufacturing cost accordingly because the material from which the sliding bearings and/or the adapting bushings are manufactured is expensive.
As shown in FIG. 3, by way of the left swash plate 7 as an example, the swash plate 7 is stationary relative to the spindle 5 during the running of the hydraulic pump, the rotary hydraulic cylinder 9 is driven by the spindle 5 to rotate about its central axis, and at the same time the piston 11 moves reciprocatingly in the rotary hydraulic cylinder 9. It can be known from theoretically technical analysis known in the prior art, an action point O of a resultant force the rotary hydraulic cylinder 9 applies upon the spindle 5 is situated on the central axis of the spindle 5.
The sliding bearing 18 has a center of gravity G, and the axial length from the center of gravity G to the action point O of the resultant force is A. A bending moment will be generated at the area in which the bearing is contacted with the mounting hole during the running of the hydraulic pump. Excessive bending moment may cause the spindle to vibrate or even destabilize, and so affect the work efficiency of the hydraulic pump. It can known from the theoretical calculation that the amount of the bending moment depends on the distance between the center of gravity of the sliding bearing and the action point O of the resultant force. The smaller the distance is, the smaller the bending moment generated during the running of the hydraulic pump is, and then the smaller the vibration is.
FIG. 3 shows a center of gravity G′ of the coupler 13. For the sliding bearing 14 shown in FIG. 1, the center of gravity of the sliding bearing 14 is consistent with the center of gravity G′ of the coupler 13. That is to say, the distance between the center of gravity of the sliding bearing 14 shown in FIG. 1 and the action point O of the resultant force is A′. It can be clearly seen from FIG. 3 that the distance A is smaller than the distance A′ because the sliding bearings 18 and 19 are disposed over the coupler 13 with one spaced from each another. Consequently, compared with the embodiment shown in FIG. 1, the hydraulic pump according to the embodiment shown in FIG. 3 has a smaller bending moment generated at the bearing during running, and thus the vibration generated on the spindle is smaller or even eliminated. The work efficiency of the hydraulic pump is improved.
The same also applies to the right swash plate 8, the spindle 6, the rotary hydraulic cylinder 10 and the piston 12 shown in FIG. 3.
FIG. 5 shows a hydraulic pump according to a further embodiment of the invention. The supporting wall 2 a is formed with a through hole 20 therein which extends in a direction perpendicular to the central axes of the spindles 5 and 6. The through hole 20 is aligned with and communicated with a gap between the sliding bearings 18 and 19 so that lubricant oil can be injected into the gap to lubricate the bearings and at the same time to lower the temperature of the sliding bearings 18 and 19 when the spindles 5 and 6 rotate. It is conceivable that the through hole 20 can be further configured for receiving the oil leaked from the rotary hydraulic cylinders 9 and 10 during their running. In this way, the received oil can pass by the sliding bearings 18 and 19, cause the temperature of the bearings to be lowered, and then flows out of the through hole.
In another embodiment, a pair of spherical splines are mounted between the coupler 13 and the spindles 5, 6.
Optionally, in order to further improve lubricating and temperature decreasing effect, a plurality of through holes 20 can be provided in the supporting wall 2 a, which extend perpendicularly to the central axes of the spindles 5 and 6, and all the through holes 20 are aligned and communicated with the gap between the sliding bearings 18 and 19. In addition, optionally, the through hole 20 may be arranged at another angle with reference to the central axes of the spindles 5 and 6.
To facilitate assembling, as shown in FIGS. 2, 4 and 5, the sliding bearings 14, 18 and 19 are manufactured preferably with chamfers at outer surfaces of opposite ends respectively, so that the sliding bearings can be inserted into the adapting bushings 15 and 17 smoothly when assembling, and the lubricant oil can enter the areas between the sliding bearings and the mating components around more easily.
Although in the above embodiments the sliding bearing 14 or the sliding bearings 18 and 19 according to the invention is/are shown to support the coupler 13 between the two spindles 5 and 6, it is conceivable that, in a case that the swash plates 7 and 8 in the hydraulic pump are only driven by a single spindle, the sliding bearing 14 or the sliding bearings 18 and 19 according to the invention may be supported in the mounting hole of the supporting wall 2 a at a substantially central location of the single the spindle in its longitudinal direction via the adapting bushing 15 or the adapting bushings 16 and 17.
It is conceivable that, in the embodiment shown in FIG. 4, the adapting bushings 16 and 17 can be replaced with the adapting bushing 15; or the sliding bearings 18 and 19 can be replaced with the sliding bearing 14. It is conceivable that, in the embodiment shown in FIG. 5, the sliding bearings 18 and 19 can be replaced with the sliding bearing 14. In addition, it is conceivable that the axial separation between the adapting bushings 16 and 17 may also be different from the axial separation between the sliding bearings 18 and 19.
Although the sliding bearing 14 or the sliding bearings 18 and 19 is/are configured for supporting the coupler 13 in the supporting wall 2 a inside the housing 2 in the embodiments of the invention, it is conceivable that the sliding bearing 14 or the sliding bearings 18 and 19 may also be configured as bearings in the end cap 3 and/or the end cap 4 for supporting the spindle 5 and/or the spindle 6.
It is conceivable that, in a case that N (in which N is an integer larger than 2) spindles are provided coaxially in a hydraulic pump and are connected via N−1 couplers, the sliding bearing 14 or the sliding bearings 18 and 19 may be provided at locations of the N−1 couplers respectively for supporting the respective spindles.
According to the invention, a sliding bearing with a relative simple structure is incorporated into a hydraulic pump, which results in an improved stress distribution, a prolonged service life of the hydraulic pump, and at the same time reduced manufacturing and assembly cost. In addition, through providing the sliding bearings spaced from each other axially, heat generated during the running of a spindle can be dissipated efficiently, the working temperature of the bearing can be reduced, and thus the failure risk is avoided. Through providing an oil guiding hole in a housing of the hydraulic pump which is aligned and communicated with a gap between the sliding bearings, the bearing can be lubricated efficiently and the heat generated during the rotation can be taken away efficiently. This may further reduce the working temperature of the bearing.
Although special embodiments of the invention have been described above, they are presented only for illustration purpose and not intended to limit the scope of the invention. Rather, various substitutions, variants and changes can be conceived without departing from the spirit and scope of the invention.

Claims

1. A hydraulic pump for an excavator comprising:

a housing having a supporting wall extending therein;

a pair of rotary hydraulic cylinders provided in the housing, each of the rotary hydraulic cylinders being provided with a respective piston which is movable reciprocatingly in the rotary hydraulic cylinder; and

a pair of spindles disposed parallel to the rotary hydraulic cylinders, the spindles being connected with each other via a coupler and driving the rotary hydraulic cylinders to rotate about respective central axes, each of the rotary hydraulic cylinders comprising a swash plate for receiving and guiding the respective piston, and the swash plate being stationary relative to the respective spindle,

wherein the supporting wall comprises a mounting hole, and the coupler is supported in the mounting hole by means of a sliding bearing.

2. The hydraulic pump according to claim 1, further comprising an adapting bushing, wherein the sliding bearing is mounted in the mounting hole via the adapting bushing so that the adapting bushing is located between an outer circumferential surface of the sliding bearing and an inner surface of the mounting hole.

3. The hydraulic pump according to claim 2, wherein a circumferential flange extends out radially from an outer circumferential surface of the adapting bushing near an end of the adapting bushing which is adjacent to a surface of the supporting wall, and the circumferential flange is configured for contacting with the supporting wall.

4. The hydraulic pump according to claim 3, wherein the sliding bearing is configured as a pair of sliding bearings axially spaced from each other.

5. The hydraulic pump according to claim 4, wherein the adapting bushing is configured as a pair of adapting bushings axially spaced from each other.

6. The hydraulic pump according to claim 5, wherein the supporting wall is formed with an oil guiding hole, and the oil guiding hole is aligned with and communicated with an axial gap between the adapting bushings.

7. The hydraulic pump according to claim 6, wherein the oil guiding hole is configured for receiving oil leaked in running of the rotary hydraulic cylinders, so that the leaked oil can pass by the sliding bearing and flow out via the oil guiding hole after cooling the bearings.

8. The hydraulic pump according to claim 2, wherein at least one of the sliding bearing and the adapting bushing is provided with chamfers at opposite ends.

9. The hydraulic pump according to claim 2, wherein the adapting bushing is made of an alloy steel material, and the sliding bearing is made of a powder metallurgy material.

10. The hydraulic pump according to claim 1, wherein a pair of spherical splines are mounted between the coupler and the spindles.

11. The hydraulic pump according to claim 7, wherein at least one of the sliding bearing and the adapting bushing is provided with chamfers at opposite ends.

12. The hydraulic pump according to any claim 11, wherein the adapting bushing is made of an alloy steel material, and the sliding bearing is made of a powder metallurgy material.

13. The hydraulic pump according to claim 12, wherein a pair of spherical splines are mounted between the coupler and the spindles.

14. An excavator comprising a hydraulic pump according to claim 1.