Hydrostatic positive displacement machine

Abstract

A hydrostatic positive displacement machine has a cylinder drum (4) located in a housing (9) and rotatable around an axis of rotation (2). During rotation of the cylinder drum (4), a piston bore (5) is placed in alternating communication with an inlet side (E) and an outlet side (A). The inlet side (E) and outlet side (A) comprise connections (21; 22) to a control plate (12). A reversing device (30) is located in a reversing area (25; 26) between the connections (21, 22) on the control plate (12). The reversing device (30) damps the pressure adjustment between a displacement chamber (V) and the pressure present in the connection (21; 22). The reversing device (30) includes at least two flow connections which are actuated simultaneously by the displacement chamber (V) as it moves along the reversing area (25; 26).

Claims

1. A hydrostatic positive displacement machine, comprising: a cylinder drum located in a housing and rotatable around an axis of rotation, wherein the cylinder drum is provided with at least one piston bore; a longitudinally displaceable piston located in the piston bore, wherein during rotation of the cylinder drum the piston bore is placed in alternating communication with an inlet side and an outlet side, wherein the inlet side and outlet side comprise connections to a control plate; and a reversing device located in a reversing area between the connections on the control plate and which, by means of a volume flow into or out of a displacement chamber formed by the piston and the piston bore, damps a pressure adjustment between the displacement chamber and a pressure present in the connections of the inlet side and the outlet side, wherein the reversing device comprises at least two flow connections which are actuated simultaneously by the displacement chamber as it moves along the reversing area, wherein all of the at least two flow connections on the control plate are located on a same contour line at a specific instant during movement of the displacement chamber, the contour line corresponding to a leading edge of a connecting opening of the displacement chamber, and wherein the flow connections are located on different reference diameters on the control plate in a radial direction relative to the contour line such that the displacement chamber, as it moves along the control plate, opens all of the flow connections on the contour line simultaneously with a leading edge of a connecting opening of the displacement chamber.

2. The hydrostatic positive displacement machine as recited in claim 1, wherein the flow connections are each in the form of a throttle notch.

3. The hydrostatic positive displacement machine as recited in claim 1, wherein the flow connections are in communication with the inlet side.

4. The hydrostatic positive displacement machine as recited in claim 1, wherein the flow connections are in communication with the outlet side.

5. The hydrostatic positive displacement machine as recited in claim 1, wherein the flow connections are in communication with a hydraulic buffer.

6. The hydrostatic positive displacement machine as recited in claim 1, wherein the positive displacement machine is an axial piston machine.

7. The hydrostatic positive displacement machine as recited in claim 1, wherein the positive displacement machine is selected from a pump or motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages and details of the invention are explained in greater detail below with reference to the exemplary embodiments illustrated in the accompanying schematic figures, in which like reference numbers identify like parts throughout.

(2) FIG. 1 shows an axial piston machine of the invention in longitudinal section;

(3) FIG. 2 is a section along view A in FIG. 1;

(4) FIG. 3 is a section along the view B in FIG. 1 with an embodiment of a reversing device of the known art;

(5) FIGS. 3a, 3b each are a section along line C-C in FIG. 3 with different realizations of the reversing device of the known art;

(6) FIG. 4 is a section along the view B in FIG. 1 with a first embodiment of a reversing device of the invention;

(7) FIGS. 4a, 4b each are a section along the line D-D in FIG. 4 with different realizations of the reversing device of the invention;

(8) FIGS. 4c, 4d show a detail of FIGS. 4a, 4b, respectively, each on an enlarged scale;

(9) FIG. 5 a second embodiment of a reversing device of the invention;

(10) FIG. 6 a third embodiment of a reversing device of the invention; and

(11) FIG. 7 a fourth embodiment of a reversing device claimed by the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) FIG. 1 shows a hydrostatic positive displacement machine, such as an axial piston machine 1 utilizing a swash plate construction, for example, in the form of a pump or motor in a longitudinal section.

(13) The axial piston machine 1 has a drive assembly 3 which is positioned so that it can rotate around an axis of rotation 2 and comprises a cylinder drum 4 which is provided with a plurality of piston bores 5 which are arranged concentrically with respect to the axis of rotation 2, which are preferably formed by cylinder bores and in each of which a piston 6 is mounted so that it can be displaced longitudinally.

(14) The pistons 6 are each supported in the area in which they project out of the cylinder drum 4 by means of a support element 7, which can be in the form of a sliding shoe, for example, on a track 8 which is formed by a swashplate. The track 8 is inclined with respect to the axis of rotation and can be molded onto a housing 9 or non-rotationally fastened to it, whereby the axial piston machine 1 has a fixed displacement volume. It is also possible, however, to make the swashplate adjustable in its inclination with respect to the axis of rotation 2, as a result of which the axial piston machine 1 has a variable displacement volume. The support elements 7 formed by the sliding shoes are prevented from lifting up from the track 8 by a hold-down plate 10 which is in the shape of an annular disc and rotates together with the cylinder drum 4. The cylinder drum 4 is supported in the axial direction on a control surface 11 which is affixed to the housing. In the illustrated embodiment, the control surface 11 is on a control plate 12 which is non-rotationally fastened to a housing 9 or a corresponding housing cover 9a.

(15) The cylinder drum 4 is penetrated by a central boring, through which a drive shaft 13, which is positioned concentrically in relation to the axis of rotation of the drive assembly 3, is guided through the cylinder drum 4. The drive shaft 13 is rotationally mounted in the housing 9 by means of bearings 15, 16. To provide a seal against the environment, a sealing element 17 such as a shaft gasket, for example, is located in the vicinity of the bearing 15. The cylinder drum 4 is connected so that it is rotationally synchronized but axially movable with respect to the drive shaft 13, for example by means of a drive gearing 18. The drive assembly 3 further comprises a spring 19 which keeps the cylinder drum 4 in contact against the control surface 11.

(16) The axial piston machine 1 has an inlet side E which is formed, for example, by a suction channel in the housing 9, and an outlet side A, which is formed, for example, by a pressure channel in the housing 9. During a rotation of the cylinder drum 4 around the axis of rotation 2, the displacement chambers V formed by the piston bores 4 and the corresponding pistons 6 located in the piston bores 4 come alternately into communication with the inlet side E and the outlet side A.

(17) The piston bores 5 of the cylinder drum 4 are each provided with a connecting opening 20 for the connection with the inlet side E and the outlet side Aas illustrated in further detail in FIG. 2, which is a plan view of the end face of the cylinder drum 4 which is in contact with the control plate 12 and thus the control surface 11. In the illustrated exemplary embodiment, the connecting openings 20 in the end surface of the cylinder drum 4 are each kidney-shaped.

(18) The control plate 12 is provided with kidney-shaped connections 21, 22 for the connection to the inlet side E or to the outlet side A, which connections form control nodules with which the connecting openings 20 in the cylinder drum 4 interact.

(19) FIG. 3 is a plan view of the control surface of the control plate 12 with the kidney-shaped connections 21, 22 and the connecting openings 20 of a known axial piston machine 1.

(20) As shown in FIG. 3, the area of the control surface 11 of the control plate 12 between the kidney-shaped connection 21 which is in communication with the inlet side E and the kidney-shaped connection 22 which is in communication with the outlet side A each form a reversing area 25, 26 in the form of a separation web, in which the connecting openings 20 of the cylinder drum 4 are separated from the connections 21, 22. The reversing areas 25, 26 are located in the area of the dead center positions of the movement of the pistons 6.

(21) To achieve an adaptation of the pressure in a displacement chamber V, which as the cylinder drum 4 rotates in the direction indicated by the arrow N and thus as it moves along the reversing area 26 from the inlet side E formed by the suction channel to the outlet side A formed by the pressure channel, to the pressure in the outlet side A, in the reversing area 26 between the connections 21, 22 there is a reversing device 30 on the control surface 11 of the control plate 12. Accordingly, in the reversing area 25 between the connections 21, 22 there is a reversing device 30 on the control surface 11 of the control plate 12, by means of which an adjustment of the pressure in a displacement chamber V to the pressure in the inlet side E can be achieved as the displacement chamber V moves along the reversing area from the outlet side A that forms the pressure channel to the inlet side E that forms the suction channel.

(22) In FIGS. 3a, 3b, the reversing device 30 of the known art is illustrated in further detail, whereby a development along section line C-C in FIG. 3 in the vicinity of the reversing area 26 is presented in greater detail on a larger scale.

(23) The reversing device 30 has two connecting borings 31, 32 in the form of throttling or nozzle bores whichas is apparent by comparison with FIG. 3are located on the same reference diameter one behind the other in the peripheral direction and are therefore actuated and opened sequentially one after the other by the connection opening 20 of the displacement chamber V as it moves along the reversing area 26 in the direction of the arrow N. In the embodiment illustrated in FIG. 3a, the connecting borings 31, 32 are directly in connection with the outlet side A and thus with the pressure channel in the housing 9. In the embodiment illustrated in FIG. 3b, the connecting borings 31, 32 are in communication with a hydraulic buffer 33 which serves as the damping volume.

(24) By means of the connecting borings 31, 32 in the reversing area 26, which form the corresponding circular nozzle cross sections, there is a volume flow out of the outlet side A or out of the hydraulic buffer 33 into the displacement chamber V, to achieve a damped pressure increase in the displacement chamber V. The volume flow via the connecting borings 31, 32 into the displacement chamber V is identified in FIGS. 3a, 3b by corresponding arrows. As a result of the pressure increase by means of the reversing device 30 in the reversing area 26, high pressure peaks can be prevented during the subsequent connection of the displacement chamber V with the outlet side A, if the connecting opening 20 of the cylinder drum 4, as it continues to move in the direction indicated by the arrow N, comes into communication with the kidney-shaped connection 22 and thus with the pressure channel.

(25) The reversing device 30, in the vicinity of the reversing area 25, has corresponding connecting borings 31, 32 in the form of throttling or nozzle bores, whichas illustrated in FIG. 3 are located on the same reference diameter and one behind the other in the peripheral direction and are therefore actuated and opened one after the other by the connecting opening 20 of the displacement chamber V as it moves along the reversing area 25 in the direction indicated by the arrow N. Analogous to FIG. 3a, the connecting borings 31, 32 can be in direct communication with the inlet side E or, analogous to FIG. 3b, with a hydraulic buffer 33 which acts as the damping volume.

(26) By means of the connecting borings 31, 32 in the reversing area 25, which form corresponding throttle cross sections, there is a volume flow from the displacement chamber V into the inlet side E or into the hydraulic buffer 33, to achieve a damped pressure decrease in the displacement chamber V. As a result of the pressure decrease by means of the reversing device 30 in the reversing area 25, high pressure peaks as the displacement chamber V subsequently comes into communication with the inlet side E can be prevented, when the connecting opening 20 of the cylinder drum 4, as it continues to move in the direction indicated by the arrow N, comes into communication with the kidney-shaped connection 21 and thus with the suction channel.

(27) A defined cross sectional area of the connecting borings 31, 32 is necessary for the desired pressure control, i.e., the decrease or increase of the pressure in the displacement chamber V, by means of the damped volume flow via the connecting borings 31, 32. Because in the known art as illustrated in FIGS. 3, 3a, 3b, the connecting borings 31, 32 are actuated and opened one after the other in the direction of movement of the cylinder drum 4 and thus with some delay between their individual openings, the defined cross sectional area is necessary on each connecting boring 30, 31, which means that each of the connecting borings 30, 31 requires a defined diameter.

(28) Since, however, on account of the high volume flows through the connecting borings 31, 32 of the reversing device 30, high volume flows occur which lead to cavitation and cavitation erosion, with the connecting borings 30, 31 of a reversing device 30 of the known art high amounts of material erosion occur on account of the large diameter and cross sectional areas of the connecting borings 30, 31, which are proportional to the square of the cross sectional area of the connecting borings 30, 31 and thus to the fourth power of the diameter of the connecting borings 30, 31, which are in the form of nozzle bores.

(29) FIGS. 4 and 4a to 4d illustrate a reversing device 30 of the invention. Elements which are identical to those illustrated in FIGS. 3, 3a and 3b are identified by the same reference numbers.

(30) FIG. 4, which is analogous to FIG. 3, shows a plan view of the control surface 11 of the control plate 12 with the kidney-shaped connections 21, 22 and the connecting openings 20 in the cylinder drum 4 of a positive displacement machine of the invention. FIGS. 4a, 4b, which are analogous to FIGS. 3a, 3b, illustrate the reversing device 30 in the vicinity of the reversing area 26 in greater detail. A development along section D-D in FIG. 4 is shown on a larger scale and in greater detail. FIG. 4c shows a detail of FIG. 4a on a larger scale and FIG. 4d shows a detail of FIG. 4b on a larger scale.

(31) The reversing device 30 of the invention has a plurality of relatively small flow connections 40 which are located on different reference diameters and each of which forms an opening cross section for the damped volume flow into the displacement chamber V or out of the displacement chamber V. In addition, the flow connections 40 are also located one behind another in the peripheral direction.

(32) On account of the arrangement of the flow connections 40 on different reference diameters, at least two flow connections 40 lie on a contour line L which corresponds to the leading edge K of the connecting opening 20 of the cylinder drum 4 in the direction of movement indicated by the arrow N, so that during the movement of the connecting opening 20 along the reversing area 25 or 26, at least two flow connections 40 are actuated and opened simultaneously, i.e., in the same angular position of the cylinder drum, by the leading edge K of the connecting opening 20.

(33) In the invention, therefore the cross sectional area of the reversing device 30 necessary for a damped volume flow via the reversing device 30 and therefore for a desired pressure control, i.e. pressure increase or pressure decrease, in the displacement chamber V is divided into a plurality of flow connections 40, each of which has a relatively small opening cross section and, as a function of the number of the plurality of flow connections, presents a total cross sectional area which equals the required cross sectional area for the desired pressure control.

(34) On account of the increase in the number of flow connections 40 actuated simultaneously, the cross sectional area of the individual flow connections 40 can therefore be reduced. Because the material erosion caused by cavitation is inversely proportional to the number of flow connections 40, the reversing device 30 of the invention achieves a reduction of cavitation erosion and a reduction of cavitation noise.

(35) FIGS. 4, 4a to 4d show the individual flow connections 40 of the reversing device 30, each in the form of nozzle bores 41, which are realized in the control plate 12 and empty into the control surface 11.

(36) As shown in the exemplary embodiment illustrated in FIGS. 4a and 4c, the individual flow connections 40 are in communication with the outlet side A. In the exemplary embodiment illustrated in FIGS. 4b and 4d, the individual flow connections 40 are in communication with a hydraulic buffer 33 which acts as a damping volume.

(37) In the exemplary embodiment illustrated in FIG. 4, there are eight flow connections. It goes without saying, however, that the reversing device 30 of the invention can have a variable number of flow connections with a higher or lower number of flow connections. For example, four flow connections can be provided, two of which are located on different reference diameters on a contour line L, and are therefore actuated and opened simultaneously by the leading edge K of the connecting opening 20, and the two additional flow openings in the direction of rotation indicated by the arrow N are actuated and opened before or after the two flow connections. These two additional flow connections can also be located on different reference diameters on a contour line L and are therefore actuated and opened simultaneously by the leading edge K of the connecting opening 20.

(38) During the movement of the connecting opening 20 over the reversing area 25, 26, the opening cross sections formed by the individual flow connections 40 are therefore opened simultaneously as the connecting opening 20 moves over the reversing area 25, 26, and sequentially and therefore with a delay in the direction of movement of the cylinder drum 4.

(39) FIG. 5 illustrates a second exemplary embodiment of the invention in which the reversing device 30 comprises a high-porosity material 50 with a plurality of pores, whereby each of the individual pores forms a flow connection 40. The volume flow for the pressure equalization of the displacement chamber V is guided through the high-porosity material 50 into the displacement chamber V or out of the displacement chamber V. The high-porosity material 50 is advantageously in the form of an open-pore metal foam such as a sinter material. The pores of such a high-porosity material 50 are formed by the spaces in the material, each of which acts like an individual small opening cross section and thus flow connections 40.

(40) The high-porosity material 50 is in the form of an insert, such as a cylindrical insert, which is located and fastened in a boring 52 in the control plate 12.

(41) FIG. 6 illustrates an additional embodiment of the invention in which the reversing device 30 comprises a screen-like or grid-like structure 60 with a plurality of pores, whereby the individual pores each form a flow connection 40.

(42) The screen-like or grid-like structure 60 can be formed by a fabric, such as a mesh fabric for example. The screen-like or grid-like structure 60 can also be formed by a flat plate provided with perforations. The perforations can be introduced into the plate by means of a laser process.

(43) The screen-like or grid-like structure 60, analogous to FIG. 5, is advantageously in the form of a cylindrical insert, which is located and fastened in a boring 52 in the control plate 12.

(44) With the high-porosity material 50 in FIG. 5 or the screen-like or grid-like structure 60 in FIG. 6 with the plurality of pores, as the cylinder drum 4 moves across the reversing area 25, 26, a plurality of flow connections 40, each formed by an individual pore, lies on a contour line L which corresponds to the leading edge K of the connecting opening 20 so that a plurality of pores are simultaneously actuated and opened by the leading edge K. In addition, other pores and thus additional flow connections are actuated and opened sequentially during the movement of the connecting opening 20. With the high-porosity material 50 in FIG. 5 or the screen-like or grid-like structure 60 in FIG. 6, it is therefore easily possible for a plurality of flow connections 40 and opening cross sections formed by the pores to be opened simultaneously as the connecting opening 20 moves over the reversing area 25, 26, and to be opened sequentially and therefore with some delay as the connecting opening 20 moves over the reversing area 25, 26 in the direction of movement of the cylinder drum 4.

(45) In the embodiments illustrated in FIG. 5 or 6, the reversing device 30 can be in direct communication with the outlet side A or the inlet side E or a hydraulic buffer of 33 which acts as the damping volume.

(46) FIG. 7 illustrates an additional embodiment of the invention, in which the individual flow connections 40 are in the form of throttle notches 70 in the control surface 11 of the control plate 12 and extend from the reversing area 25 or 26 to the connection 22 or 21 and thus to the outlet side A or the inlet side E. The throttle notches 70 are located on different reference diameters in the radial direction. The tips of the throttle notches 70 lie on the contour line L which corresponds to the leading edge K of the connecting opening 20 of the cylinder drum 4, so that the throttle notches 70 are actuated and opened simultaneously by the leading edge K of the connecting opening 20 as it moves in the direction indicated by the arrow N along the reversing area 25 or 26 toward the connection 21 or 22.

(47) The reversing device 30 of the invention with a plurality of flow connections 40 as illustrated in FIGS. 4 to 7 can be located in the reversing area 25 and/or in the reversing area 26.

(48) The positive displacement machine can be in the form of a pump in which the inlet connection E is in the form of a suction channel and the outlet connection A is in the form of a pressure channel. The displacement machine can also be in the form of a motor, in which the inlet connection E is in the form of a pressure channel and the outlet connection A is in the form of a suction channel.

(49) It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.