CN111794928A

CN111794928A - Axial piston machine

Info

Publication number: CN111794928A
Application number: CN202010269268.0A
Authority: CN
Inventors: 帕特里克·沃尔豪泽
Original assignee: Liebherr Machines Bulle SA
Current assignee: Liebherr Machines Bulle SA
Priority date: 2019-04-08
Filing date: 2020-04-08
Publication date: 2020-10-20
Also published as: CH716080A1; DE102020109134A1; US20200355171A1

Abstract

The invention relates to an axial piston machine, comprising: a drive shaft; a transmission which is connected in a rotationally fixed manner to the drive shaft and has one or more transmission pistons, the piston stroke of which can be set by means of a swash plate, wherein at least one return spring acts on the swash plate and a servo piston is supported on the swash plate, wherein the axial piston machine has at least one control or regulating valve or at least one control or regulating unit, characterized in that the servo piston is guided in a connecting plate and the servo piston serves as a coupling element between the servo piston and the swash plate, and in that the servo piston axis and the servo rod axis lie in a plane E1, in particular in a half plane E1 from the drive shaft axis M.

Description

Axial piston machine

Technical Field

The invention relates to an axial piston machine of swash plate design, comprising at least one control or regulating valve for setting the angle of inclination of the swash plate.

Background

The term axial piston machine includes neither only axial piston pumps nor axial piston motors. One particular type of axial piston machine is the swash plate machine, which comprises a transmission in the form of a transmission drum in which a plurality of transmission pistons are axially movably supported in respective cylinder bores of the transmission. The gear mechanism is connected in a rotationally fixed manner to a gear shaft of the axial piston machine, which is set into rotation by mechanical work, for example, in the pump operating mode. In pump operation, the plunger performs a lifting movement parallel to the axis of rotation from a specific starting position during a half rotation in order to thereby draw hydraulic liquid, hereinafter referred to for better readability as hydraulic oil, from the low-pressure side, while the plunger performs a lowering movement during the remaining half rotation of the full rotation about the axis of rotation in order to bring the previously drawn hydraulic oil to a high-pressure level and deliver it to the working output, i.e. the high-pressure side. The principle of operation in the motoring mode is reversed by: the rotational movement of the drive shaft is generated by controlled pressure manipulation of the drive mechanism plunger. The stroke of the transmission piston is determined via the pivoting angle of the swash plate, which is also referred to as the pivoting carriage. The transmission piston, which executes a reciprocating motion, is oriented continuously parallel to the transmission shaft when the transmission shaft rotates and performs a movement predetermined by the swash plate and the return plate by means of a sliding shoe, which is mounted in an articulated manner on the piston, pulling or pushing, respectively. The swash plate does not follow the rotational movement of the drive shaft, so that the shoes fixed to the plungers perform a sliding movement on the surface of the swash plate facing the shoes. Thus, the stroke of the transmission plunger used can be set via the pivoting angle of the swash plate. The maximum stroke of the transmission piston results from the maximum possible pivoting angle of the swash plate. The minimum stroke of the transmission piston results from the smallest possible pivoting angle of the swash plate.

There are also axial piston machines in which a so-called continuous pivoting of the swash plate via a neutral position, a so-called parking (moving) operation, is carried out. There are also axial piston machines that can work in a four quadrant operation. At this point it should be noted that the invention can also be applied to such axial piston machines.

The desired/required value determined by the control or regulation of the pivoting angle of the swash plate is achieved by means of mechanical force transmission via a servo unit acting on the swash plate. The force is exerted by the oil pressure, the so-called servo pressure, which acts on a servo plunger belonging to the servo unit. The pressure level of the servo pressure is preset via a control valve hydraulically connected upstream of the servo unit or via a regulating valve hydraulically connected upstream of the servo unit. An oil connection exists between the servo pressure output of the control valve, which is also referred to as the working connection, and the so-called servo chamber. In the servo chamber, the already mentioned loading of the servo piston with hydraulic oil at the servo pressure takes place.

Furthermore, in addition to the control valve, other purely hydraulic or electromechanical components can be provided, which are used to control or regulate the axial piston machine. One example of a purely hydraulic component is a pressure stop device, which can be used, for example, to limit the outlet pressure of an axial piston machine operating in a pump mode. One example of an electromechanical component is an electrically controllable pressure relief unit. The outlet pressure of such a pressure reduction unit can be supplied, for example, to a valve piston of a control valve of a preset servo pressure, which has a control pressure connection and a corresponding control surface provided for this purpose.

Disclosure of Invention

The most compact design possible is therefore desirable here, so the object of the invention is to disclose a solution which is suitable for arranging and integrating the respective hydraulic components in or at the axial piston machine.

This object is achieved by an axial piston machine. Advantageous embodiments of the axial piston machine are described in the text.

The axial piston machine according to the invention comprises a drive shaft and a transmission connected to the drive shaft in a rotationally fixed manner, which transmission has one or more transmission pistons, the piston stroke of which can be set by means of a swash plate. At least one return spring acts on the swash plate and the servo piston is supported on the swash plate. Furthermore, the axial piston machine has at least one control or regulating valve or at least one control or regulating unit. Now, according to the invention, it is proposed that the servo piston is guided in a connecting plate and that the servo rod serves as a coupling element between the servo piston and the swash plate. It is important here that the servo plunger axis as well as the servo rod axis lie on the plane E1. Preferably, the servo plunger axis and the servo rod axis are located on a half plane E1 from the drive shaft axis M.

The servo piston axis can extend parallel to the drive shaft axis, wherein the servo rod axis lies in a plane E1, in particular in a half plane E1 from the drive shaft axis M. It is envisaged that the servo rod is capable of achieving a functional position approximately parallel to the drive shaft axis and/or a functional position approximately coaxial with the servo plunger axis. Preferably, approximately means that the angular deviation from the respective axis is less than 3 °, particularly preferably less than 2 ° and ideally less than 1 °.

Based on this type of axial piston machine, it can be advantageous for a specific type of control or regulation that a control or regulation valve is located inside the connecting plate of the axial piston machine, which control or regulation valve presets the servo pressure.

It is particularly advantageous if the control valve and/or the regulating valve can be inserted into the connecting plate from the outside, for example can be screwed into a corresponding bore of the connecting plate from the outside. For this purpose, the control or regulating valve concerned is preferably provided with a cartridge-like housing. This allows simple modifications. Depending on the application, different valve or regulator types can be used without problems. Corresponding control or regulating valves have already been integrated in axial piston machines. Nevertheless, the replacement can be carried out without opening the axial piston machine, and the axial piston machine remains the same nevertheless. By means of a correspondingly integrated volume flow control valve, for example, a configuration for the volume flow control of the axial piston machine can be provided, or by means of a correspondingly integrated power regulator, a configuration for the power control of the axial piston machine can be provided.

Furthermore, it is proposed according to the invention that one or more additional hydraulic components, in particular valves or regulators, are stacked on a section of the side surface of the connecting plate, in particular on a section of the connecting plate in the region of the control or regulating valve arranged there, in order to actuate the control or regulating valve and/or the axial piston machine. Thereby, a very short connection path becomes possible when hydraulically connecting the individual hydraulic components. Furthermore, the axial piston machine can be equipped with the desired hydraulic components quickly and without problems. The proposed design also allows the construction of a particularly compact unit which can be integrated into a superordinate machine in a space-saving manner.

A particular advantage of the axial piston machine results if, according to a preferred embodiment of the invention, at least one adjustment axis of the stacked hydraulic components is perpendicular to the transmission axis of the axial piston machine. Ideally, all adjustment axes of the stacked hydraulic components are perpendicular to the transmission axis.

The control or regulating valve is preferably hydraulically acted on a mechanical control unit which mechanically triggers the pivoting of the swash plate as a function of the servo pressure of the control valve. For this purpose, the adjusting device preferably comprises a servo rod which is mechanically connected to the swash plate on the one hand and which is pressurized by the generated servo pressure of the control valve via a servo piston which is fixed on the end face on the other hand. In this case, it is advantageous if the longitudinal axes of the servo rod and/or the servo piston and/or the control piston of the control or regulating valve run parallel. It is particularly advantageous if both the central longitudinal sections of the servo rod, of the servo piston and of the control or regulating valve and the central longitudinal sections of the gear mechanism itself lie in the same plane. Alternatively, the same applies to the return spring of the swash plate and to the other components of the axial piston machine.

According to one possible embodiment of the invention, the control or regulating valve is hydraulically pre-controlled by means of a pressure reduction unit, the pressure output of which is connected to the control input of the control valve, in order to set the desired angle of inclination of the swash plate and thus the volume which can be delivered during operation of the pump or the power during operation of the motor. It is possible that the pressure reduction unit is electromagnetically pre-controlled, so that the control pressure applied at the control valve can be set accordingly. The decompression unit is mounted on a predetermined mounting section on the side surface of the connection plate, where it is stacked with other hydraulic components if necessary.

Other hydraulic components for controlling/regulating the axial piston machine can also be placed on the side surface of the connecting plate, for example in a sandwich-like manner on the pressure relief unit described above. In this case, it is expedient for at least one adjustment axis, ideally all adjustment axes, of the stacked hydraulic components to run parallel to one another and to be oriented perpendicularly to the longitudinal axis of the drive shaft.

One or more valves of the type used to carry out the regulation are understood as further hydraulic components. In particular for pressure regulation, volume regulation, power regulation or a combination thereof. Mechanical hydraulic actuators are conceivable, but also electrohydraulic actuators are conceivable.

One specific example of such further hydraulic components is, for example, a pressure shutoff, in particular in combination with a load sensing stage. The load sensing stage with the pressure shut-off device can be compactly arranged in a double housing on the housing of the pressure relief unit.

In a preferred embodiment, the pressure relief unit is provided with a pressure stop device, which is arranged in the longitudinal direction of the pressure relief unit and which is connected to the load sensing device. In particular, the central longitudinal axis of the pressure reduction unit is offset from the common central longitudinal section of the load sensing stage and the pressure stop device.

In a further advantageous embodiment of the invention, the axial piston is designed mechanically as a modular kit with at least two connecting plates. At least two available connection plates allow the axial plunger to be mechanically simple and quickly matched to the type of application desired. In particular, the connection board can also be replaced on the client side without special knowledge.

A decisive advantage of such a kit is that, for example, at least one connecting plate is prepared for each direction of rotation of the drive shaft. By modifying the connecting plate, the axial piston machine can be quickly and flexibly switched to a desired rotational direction during operation of the pump and/or the motor. In the ideal case, the at least two connection plates differ only in the position of the hydraulic connection, i.e. the positioning of the high-pressure or low-pressure connection (suction connection during pump operation), which is provided only in the manner of a transposition for the respective direction of rotation. The low-pressure and high-pressure connections in axial piston machines are usually distinguished by the diameter size.

The advantageous modular design allows additional variants of the connecting plates, so that the high-pressure and low-pressure connections in one connecting plate can be located at the axially rear end of the axial piston machine, while the other connecting plate has a laterally positioned pressure connection. Likewise, the available connection plates can be equipped or not with a shaft continuous transmission for connecting downstream machines, in particular axial piston machines. The detachable arrangement of the flange adapter is expedient if the connection plate comprises a corresponding continuous drive, in order to be able to achieve a flexible connection of different flange types.

Drawings

Further advantages and characteristics of the invention will be elucidated in the following on the basis of an embodiment shown in the drawing. The figures show:

figure 1 shows a longitudinal section through an axial piston machine according to the invention along a drive shaft,

figure 2 shows a schematic view of an axial piston machine corresponding to the longitudinal section of figure 1,

figure 3 shows another schematic view of an axial piston machine in a top view,

fig. 4 shows the diagram of fig. 3 with the axis of adjustment plotted.

Detailed Description

Fig. 1 shows an axial longitudinal section through an axial piston machine according to the invention. The invention is described below with the aid of an axial piston pump, but it is explicitly pointed out that the inventive features according to the invention can also be used without limitation in axial piston motors. It should also be noted that the features according to the invention can equally be used for axial piston machines working in a multi-quadrant operation.

A gear mechanism drum 2, in which a plurality of gear mechanism plungers 3 are inserted in a drum-like manner into cylinder bores 4, is arranged on the gear shaft 1 in a rotationally fixed manner. The transmission plungers 3 are supported on a swash plate 6 via shoes 5. The swash plate is supported on a main housing 8 via a compression spring 7. When the drive shaft 1 rotates, the transmission piston 3 slides on the sliding surface of the swash plate 6 by means of its shoe 5, and the transmission piston 3 reciprocates depending on the pivot angle of the swash plate 6. Depending on the operating mode of the axial piston machine, i.e. pump operation or motor operation, hydraulic energy or mechanical work is thereby generated.

The retaining device ensures that the running surface of the shoe 5 of the transmission plunger 3 does not lose contact with the sliding surface of the swash plate 6 even during its suction phase. The retaining device is constituted in particular by a return disc 10 and a return ball 9 coaxially located on the drive shaft 1. The latter is pressed via the spring 12 to the left in the drawing plane (plane E1) and in the illustrated embodiment in the half plane E1 from the drive shaft axis against the swash plate 6 and is supported here on the return plate 10. The return disk 10 is thereby in constant contact with the slipper 5 and presses its running surface against the swash plate 6. The gear drum 2 is pressed against the control disk 13 by a central spring 12.

The stroke of the transmission piston 3 is preset by the pivot angle of the swash plate 6, which can be changed during operation via the adjusting device.

The servo rod 21 has spherical end regions on both sides, wherein the servo rod 21 forms a ball-and-socket joint on one side with the swash plate 6 and on the other side with the servo piston 22. The servo rod 21 can be designed rotationally symmetrical about its longitudinal axis and/or mirror-symmetrical with respect to a vertical axis. The servo rod 21 extends in the axial direction from the swashplate 6 beyond the control disk 13 into a blind bore 11a, which is located in the connecting plate 11 and in which a servo piston 22 is guided.

A control or regulating valve 30 can be arranged inside the connection plate 11.

The spherical servo rod end facing the swash plate 6 forms a ball-and-socket joint connection with a spherical recess in the servo plunger 22. The servo plunger 22 is axially movably supported in the blind hole 11a of the connecting plate 11. The servo piston 22 shown in the exemplary embodiment has a small cylindrical projection 23 on its end face opposite the spherical recess, on which a compression spring of the control or regulating valve 30 can be supported. In this configuration, the position of the servo plunger 22 exerts a force on this compression spring, which is then also referred to as a feedback spring. The control or regulation with which the valve is involved is thus controlled or regulated by the influence of the position of the servo piston 22, which is desirable, for example, for volume flow regulation.

In the region of the blind hole 11a, two stops for the servo piston 22 serve to limit the adjusting movement of the swash plate 6. A first stop for limiting the maximum pivoting angle is formed by the bottom of the blind hole 11a, so that here the maximum insertion path of the servo rod 21 into the blind hole 11a is limited. The second stop for the servo piston 22, which limits the minimum pivoting angle, is formed by a flat projection of the machine housing 8 in the region of the blind hole 11 a.

The arrangement described makes it possible to utilize the overall length of the connecting plate 11 for the arrangement of the control or regulating valve 30. The control or regulating valve can be inserted or screwed into the connecting plate 11 from the outside, so that a simple replacement of the valve 30 is possible.

Fig. 2 shows a schematic representation of an axial piston machine which now has a plurality of attached

hydraulic components

50, 51, 52, which are stacked in a sandwich-like manner and are fastened to the connecting plate 11 on the housing side. Such a hydraulic component is also a control valve or a regulating valve. In order to better distinguish from the control or regulating valve 30 mounted in the connecting plate, such a hydraulic component fixed on the outer side surface of the connecting plate 11 is referred to as a control or regulating unit. A plurality of adjustment units can also be fixed on the outer side surface of the connection plate 11. Likewise, a control unit or a plurality of control units can be fastened to the connecting plate 11 by means of an adjusting unit or a plurality of adjusting units, such as

units

50, 51, 52, in a corresponding position.

These mentioned

units

50, 51, 52 mounted on the connection plate are located immediately adjacent to: in the case of the position in question, in the presence of the control or regulating valve 30, it can be screwed into the connecting plate 11. This compact arrangement offers the advantage of a short oil connection which also runs in the solid valve housing or regulator housing and the connecting plate. This results in a robust construction, which is clearly advantageous in applications for mobile work machines, in which particularly high and frequently occurring shock and vibration loads are present.

One specific application example of the illustrated exemplary embodiment can be the following arrangement: the unit 50 directly fixed to the connection plate can be an electrically actuatable pressure relief unit. Via electrical actuation, a desired control pressure is generated at the pressure output of this point, which acts on the valve piston of the control valve 30. The control valve 30 can be a volumetric flow control valve. The units fixed above the decompression unit 50 can be a pressure cutoff device 51 and a load sensing unit 52.

The sandwich-like stack of

units

50, 51, 52 can likewise be seen in the top view of fig. 3. Fig. 4 shows the top view of fig. 3 again, but with the control or regulating

axes

50a, 51a, 52a of the control or regulating

units

50, 51, 52 drawn in dashed lines and the central longitudinal axis of the drive shaft 1, likewise drawn in dashed lines. It can be clearly seen that all the mentioned

axes

50a, 51a, 52a of the

units

50, 51, 52 are perpendicular to the longitudinal axis of the propeller shaft 2. It is also clear that in the embodiment described, the respective longitudinal axes of the drive shaft 1, of the servo rod 21, of the servo plunger 22 and of the regulating or servo valve are all located on a common half-plane E1. The half plane E1 is limited by the longitudinal axis of the drive shaft. Regardless of the position of the servo plunger, the same half-plane E1 is always involved.

In addition to this, it can be seen from fig. 4 that all control or

adjustment axes

52a, 51a, 50a of the

units

50, 51, 52 run parallel to one another in pairs.

The control or regulating

units

50, 51, 52 can be used independently of the direction of rotation of the drive shaft or of the drive mechanism. When the direction of rotation is changed, the units only have to be rotated 180 ° with respect to their longitudinal direction.

Further advantages relating to the constructive arrangement of the axial piston machine according to the invention are: by means of the small angular change of the servo rod 21 relative to the center axis of the servo piston 22, a force transmission with virtually no transverse forces is achieved in the region of the servo piston 22. This is also facilitated by the spherical region of the servo plunger 21 sinking into the inner region of the servo plunger 22.

It is particularly advantageous if the swash plate support 40 is loaded uniformly due to forces from the adjustment direction which are introduced centrally with respect to the bearing point.

The arrangement of the control or regulating valve and the control or regulating unit ensures that the installation space required for the series operation of a plurality of axial piston machines is not blocked by the arrangement.

List of reference numerals

Drive shaft 1

Drive mechanism cylinder 2

Transmission plunger 3

Cylinder bore 4

Sliding shoes 5

Swash plate 6

Compression spring 7

Main casing 8

Retraction ball 9

Return disk 10

Connecting plate 11

Blind hole 11a

Spring 12

Control panel 13

Servo rod 21

Servo plunger 22

Cylindrical protrusion 23

Control or regulating valve 30

Swash plate supporting device 40

Decompression unit 50

Control or regulating axis 50a

Pressure stop device 51

Control or regulating axis 51a

Load sensing unit 52

Control or regulating axis 52a

Plane E1

Semi-plane E1

Claims

1. An axial piston machine comprising a drive shaft (1) and a transmission (20) connected to the drive shaft in a rotationally fixed manner, the transmission having one or more transmission pistons (3), the piston stroke of which can be set by means of a swash plate (6), wherein at least one return spring (7) acts on the swash plate (6) and a servo piston (22) is supported on the swash plate (6), wherein the axial piston machine has at least one control or regulating valve (30) or at least one control or regulating unit,

characterized in that the servo piston (22) is guided in the connecting plate (11) and the servo rod (21) acts as a coupling element between the servo piston (22) and the swash plate (6), and in that the servo piston axis and the servo rod axis are located in a plane E1, in particular in a half plane E1 from the drive shaft axis M.

2. Machine as claimed in claim 1, characterized in that said servo plunger axis extends parallel to said drive shaft axis M and in that said servo rod axis lies in said plane E1 and in particular in a half plane E1 from said drive shaft axis M.

3. Machine according to claim 1 or 2, characterized in that said servo rod (21) is capable of achieving a functional position approximately parallel to said drive shaft axis M and/or a functional position approximately coaxial to said servo plunger axis, wherein preferably the angular deviation from the respective axis is less than 3 °, preferably less than 2 ° and particularly preferably less than 1 °.

4. Machine according to claim 2 or 3, characterized in that the median axis stretch of said at least one return spring (7) lies in said plane E1 and in particular in a half plane E1 from said drive shaft axis M.

5. Machine according to claim 4, wherein said plane E1 and in particular a half plane E1 starting from said drive shaft axis M runs centrally or almost centrally with respect to the swash plate support (40).

6. Machine according to any one of the preceding claims, characterized in that in said connection plate (11) is a control or regulating valve (30), wherein the axis of said control or regulating valve (30) lies on said half-plane E1 and wherein preferably the axis of said control or regulating valve (30) is arranged parallel to said transmission shaft (1).

7. Machine according to any one of claims 1 to 5 or 6, characterised in that at least one control or regulating unit (50, 51, 52) is provided on said connecting plate (11), wherein the axis (50a, 51a, 52a) of said control or regulating unit (50, 51, 52) extends approximately at right angles and preferably at right angles to said half plane E1.

8. Machine according to claim 7, characterized in that a plurality of units (50, 51, 52) for control and/or regulation are provided on said connecting plate (11), wherein each axis (50a, 51a, 52a) of such a control or regulation unit (50, 51, 52) extends approximately at right angles and preferably at right angles to said half-plane E1 or approximately parallel and preferably at right angles to said half-plane E1.

9. Machine according to claim 6, characterised in that each axis of a control or regulating valve (30) mounted in said connecting plate (11) is oriented approximately at right angles and preferably at right angles to at least one axis (50a, 51a, 52a) of a control or regulating unit (50, 51, 52) provided on said connecting plate (11).