GB1598027A

GB1598027A - Hydrostatic radial piston machine

Info

Publication number: GB1598027A
Application number: GB19041/78A
Authority: GB
Original assignee: G Duesterloh GmbH
Current assignee: G Duesterloh GmbH
Priority date: 1976-12-02
Filing date: 1978-05-11
Publication date: 1981-09-16
Also published as: NL7804073A; FR2426149A1; NL172357C; NL172357B; FR2426149B1; DE2654526C3; DE2654526A1; DE2654526B2

Description

(54) HYDROSTATIC RADIAL PISTON MACHINE (71) We, G. DÜSTERLOH GMBH, of 4322 Sprockhövel, Federal Republic of Germany, a Limited Liability Company organised under the Laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement::- This invention relates to a hydrostatic radial piston machine wherein the piston shoes of the work pistons engage the external periphery of a cam ring radially displaceable by a positioning piston provided in the crank shaft (that is to say, the power input or power output shaft), the crank shaft engaging in the machine housing by means of a spigot and the positioning piston being pressurizable by a hydraulic positioning fluid via connecting passages in the crank shaft spigot and a rotary passage between the machine housing and the crank shaft spigot.

In a conventional structure, two positioning pistons independent of one another are arranged radially movable in the crank shaft and displaceable in a countersense by a hydraulic positioning fluid. Each positioning piston guided in its own cylinder space internally engages the cam ring with its external face. One of the positioning pistons is continuously pressurized by the positioning fluid at its internal face. The positioning fluid passes to the cylinder spaces via connecting passages provided in the crank shaft spigot, said connecting passages being connected to a supply and return conduit for the positioning fluid via a rotary passage with sealing rings between the crank shaft spigot and the machine housing.

A disadvantage of the conventional structure is that the positioning pistons are able to be moved only into the two extremes positions.

A stable intermediate position is not possible as a result of the continuous pressurizing one of the cylinder spaces by the positioning fluid.

Use of the conventional structure is thus limited to specific applications and not variable at will. It is furthermore of a disadvantage that one of the positioning pistons always is subject to the full pressure of the positioning fluid. A result thereof is that the rotary passage be tween the machine housing and the crank shaft spigot is also always pressurized. Leakage losses in the region of the rotary passage thus are high. Also, the sealing rings in the region of the rotary passage are strained by the continuous pressure load of the positioning fluid, and this results in continuous frictional forces which then will be noted by an increased wear of the respective countersurface of the rotary passage as well as the sealing rings themselves.

Consequently, by friction on the one hand and by leakage on the other hand both the mechani and the volumetric efficiencies of the conventional hydrostatic radial piston machine structures are reduced.

It is, therefore, the object of the present invention to avoid these disadvantages and to provide a hydrostatic radial piston machine of the species set forth initially wherein it is possible with low leakage losses to shift the cam ring in any of a plurality of well-defined positions between the two extreme positions without the positioning fluid being permanentlz effective.

According to the present invention, there is provided a hydrostatic radial piston machine comprising a housing; a plurality of radially extending cylinders in a star arrangement in the housing, each cylinder having a reciprocable work piston therein and each piston having a piston shoe at one end; a rotary power output, or power input shaft having a radial bore and a spigot, which spigot is provided with connecting passages for a hydraulic fluid and is encircled by an annular gap between itself and the housing; a double-acting positioning piston located in the bore and having two end faces and being sealingly guided in the bore by an annular collar in the central longitudinal region of the positioning piston, the collar being slidable in the radial bore of the shaft by a hydraulic positioning fluid which enters and leave the bore via the connecting passages in the shaf spigot and the annular gap between the spigot of the shaft and the housing, the annular collar separating two sealed spaces in the bore from each other; a cam ring mounted in the housing and radially displaceable by means of the positioning piston relative to the longitudinal axis of the shaft, the external periphery of the cam ring being engaged by the piston shoes of the work pistons and the internal periphery of the cam ring being engaged by the two end faces of the positioning piston; and two check valves, only one of which is open at any given moment, incorporated in respective ones of the said connecting passages to control the supply of the hydraulic positioning fluid to the said sealed spaces so that fluid is supplied only when the cam ring is being displaced.

By virtue of these features, it is possible in an advantageous way not only to determine with good definition the two extreme positions of the cam ring, but also to move the cam ring to any desired, well-defined stabilizable intermediate position between the maximum and minimum eccentricity, even during operation of the machine. In this regard, it is essential that a supply of the hydraulic positioning fluid to one side or the other of the annular collar, into the cylinder space provided there, is effected only for the period of time of displacement from one position to the other. Thus no leakage occurs when no positioning is being performed.The check valves are releasable by the hydraulic positioning fluid in alternation with one another via accordingly arranged control lines and positively prevent a return flow of the positioning fluid so that any intermediate position of the positioning piston is also maintained with good definition for the subsequent operation of the machine.

The single positioning piston may comprise a cylindrical pin to which an annular collar is applied and sealingly secured. The positioning piston and the annular collar may on the other hand also be integral. The annular collar is sealed relative to the preferably cylindrical recess in the crank shaft so that a passage of the positioning fluid from the one cylinder space to the other is not possible. The cylinder spaces disposed at both sides of the annular collar are also sealed in direction of the external faces of the positioning piston. For this purpose, to advantage cylinder ring seals may be used. The positioning piston is arranged with small axial clearance within the cam ring, but does have a relatively free motion clearance both in direction of rotation and in axial direction of the crank shaft.The cylinder space for the annular collar may comprise a radial bore in the crank shaft in which at the end an annular insert for limiting the path of movement of the annular collar is arrested by means of adapter rings.

Both the annular insert and the base of the radial bore are provided with passages and cylinder ring seals for the two longitudinal sections of the piston.

In order to permit a slow and precise positioning of the cam ring it is advantageous to provide restrictions in the connecting passages.

These restrictions prevent a sudden displacement of the cam ring and contribute to preservation of the other drive parts.

Furthermore, it is advantageous to arrange the check valves radially in the crank shaft spigot. This for instance permits a simple drill pattern which is readily producible. In this context, it is convenient to generally arrange the check valves in the transverse plane of a crank shaft bearing at the spigot side.

Thereby, not only an advantageous structural design of the crank shaft and the crank shaft spigot, but also an advantageous configuration of the machine housing and the mutual assocation is achieved. Specifically, in a relatively simple fashion dual fits which are difficult to dominate in manufacturing aspects are able to be avoided.

Preferably, the check valves are releasable by means of control pins which are associated with a control piston arranged centrally in the crank shaft spigot and pressurizable at both sides by the hydraulic positioning fluid. The control pins may integrally or loosely be associated with the control piston. At any rate, it is ensured that double fits are avoided with the insufficiencies associated therewith. The control piston is pressurizable at both sides by the positioning fluid. The check valves are conveniently formed as seat valves with respectively ball-shaped valve bodies and a coiled compression spring and thereby ensure nonleakage along with simple configuration. The control piston requires no special peripheral sealing relative to the piston space.Its configuration and its position do permit, however that a peripheral leak-free cylinder ring seal may be provided, if required.

The check valves may be incorporated directly into stepped radial bores of the crank shaft spigot. A preferred embodiment of the invention is, however, that the check valves are provided in insert bodies which are sealingly fixed in a bore extending transversely through the crank shaft spigot. The bore may be drilled in one operation as a non-stepped through bore to the benefit of manufacture, and the insert bodies may be arrested in this bore along with the check valves as completely prefabricated assemblies by means of adapter rings. Also, maintenance of the check valves is thereby greatly facilitated, because they are relatively simple to assemble and disassemble.

Furthermore, they may be of a completely symmetrical structure thereby simplifying their production and facilitating spare part storing. Leak-proofness is.ensured by cylinder ring seals arranged peripherally of the insert bodies.

Although the restrictions may be arranged anywhere in the course of the connecting passages, a particularly advantageous arrangement of the invention is that the restrictions constitute components of the check valves.

Preferably, the restrictions are defined by the control pins and the bores receiving them. By selected heat clearances of the control pins on the one hand and their receiving bores on the other hand, the annular gaps thereby defined are insensitive relative to contamination and plugging even in the event of low flow and small clearance.

The maximum and minimum extreme pos itions of the cam ring may be determined in that in the cylinder spaces abutment means are provided. These abutment means are preferably provided releasable and according to a preferred embodiment of the invention may be defined by abutment discs insertable into the cylinder spaces.

Preferably, the cam ring is radially guided between a radial flange of the crank shaft and axially adjustable engagement discs as well as at two planar surfaces of the crank shaft extending parallel to one another, the planar surfaces at the same time ensuring rotary security.

The cam ring is thus freely shiftable in positioning direction, but movable in axial and rotary direction of the crank shaft only within the limits of the necessary clearance. Possible wear may be compensated for by a readjustment or by an exchanging of the engagement discs.

The pressurizing surfaces of the annular collar may be of the same size. It is, however, also feasible that the pressurizing surfaces of the annular collar are of different sizes. In this instance, it is convenient that the larger pressurizing surface is subjected to the effect of the positioning fluid when the eccentricity is to be reduced.

The risk of jamming in the area of the rotary passage and the possibility of a camming and blocking is reduced in that the crank shaft spigot is preferably supported in the machine housing with substantial clearance. Conveniently, the connecting passages in the crank shaft spigot are separated from the supply conduits in the machine housing by gas-proof metal sealing rings. The large clearance is now permitted because the rotary passage is subject to the effect of the hydraulic positioning fluid only for the period of time of displacement of the cam ring. Since this period of time generally is very short, in this case a short-period higher leakage rate can readily be accepted.After termination of the positioning process, the rotary passage will immediately become pressureless again, however, so that consequently this feature provides for that a machining of oil-conducting annular grooves in the crank shaft spigot is not necessary any more. In addition thereto, double fits are avoided.

The supply of the hydraulic positioning fluid to the positioning piston may be effected via a shut-off element incorporated into the supply conduits for the positioning fluid.

This shut-off element may be provided within the machine housing or outside of the machine housing. Conveniently, this shut-off element is defined by a 4/3-way valve. It is ensured by this shut-off element that after termination of the positioning process the rotary passage always becomes pressureless and thus free of leakage and friction. The respective position of the positioning piston is maintained by the check valves as long, however, as by operation of the shut-off element a new position has been reached.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a semi-diagrammatic illustration of the positioning area of the drive cam ring of a radial piston machine in accordance with the invention along with the supply and discharge of the positioning fluid; Figure 2 is a vertical longitudinal sectional view of an embodiment of a positioning means for the cam ring of Figure 1; Figure 3 is a vertical cross-sectional view, on an enlarged scale, of the positioning means taken on the line III-III of Figure 2, and Figure 4 is a vertical longitudinal sectional view of part of a further embodiment of the positioning means.

Figure 1 shows a housing section 1 of a hydro static radial piston machine, for instance of a radial piston motor. In the motor housing, in a star arrangement, a plurality of work pistons 2 are guided radially displaceable in cylinders 3.

The work pistons 2 rest on the external periphery of a cam ring 5 by means of piston shoes 4, said cam ring 5 being radially displaceable by means of a positioning piston 6, relative to the longitudinal axis of a rotary power-output shaft, or so-called crank shaft 7, thereby determining the stroke of the work pistons 2.

The positioning piston 6 has an annular collar 8 in the central longitudinal region. The cylinder spaces 9 and 10, respectively, adjacent to the annular collar at both sides are connected via connecting passages 11 and 12 to supply and return lines 13 and 14, respectively, for the hydraulic positioning fluid which may for instance be pressure oil. The connecting passages 11 and 12 pass through the crank shaft 7 and have restrictions 15 and 16 as well as check valves 17 and 18 which valves are respectively releasable alternatingly from the other connecting passage. The corresponding control lines are designated by the reference numerals 19 and 20.

Passing of the pressure oil from the connecting passages 11 and 12 in the crank shaft 7 to supply channels 21 and 22 in the machine housing 1 and vice versa is effected by a rotary passage 23. The commutation of the hydraulic work fluid has merely been illustrated by connectors 24 and 25 with connecting lines 26 and 27. A shut-off element in the form of a 4/3-way valve 28 is incorporated into the supply channels 21 and 22 between the supply and return lines 13 and 14 and the rotary passage 23, said 4/3way valve being operable manually or by remote control, if desired.

Upon displacement of the 4/3-way valve 28 into the left-hand extreme position in Figure 1, pressure oil will flow via the channel 21, the rotary passage 23, the check valve 17 and the restriction 15 into the cylinder space 9 as long as the 4/3-way valve stays displaced. Thereby, the positioning piston 6 is moved relative to the crank shaft 7, and as a result of the engagement of the two faces 29 and 30 of the positioning piston 6 internally of the cam ring 5, it is also displaced accordingly eccentrically relative to the longitudinal axis of the crank shaft 7.

The pressure oil from the cylinder space 10 at the same time flows through the connecting passage 12, the check valve 18 opened via the control line 20, the rotary passage 23, the supply channel 22 and the 4/3-way valve to the return line 14.

When the 4/3-way valve 28 after the positioning process is transferred into the illustrated lock position again, the supply channels 21 and 22 as well as the connecting passages 11 and 12 between the 4/3-way valve 28 and the cylinder spaces 9 and 10 become pressureless, and by virtue of the check valves 17 and 18, the pressure oil present in the cylinder spaces and in the channel sections adjacent thereto is prevented from flowing off. The positioning piston 6 maintains its set well-defined position.

Upon displacement of the 4/3-way valve 28 into the right-hand extreme position in Figure 1, the pressure oil flows from the supply line 13 via the channel 22, the rotary passage 23, the check valve 18 and the restriction 16 to the cylinder space 10 and displaces the positioning piston 6 into the other direction as long as the 4/3-way valve 28 is maintained open.

The pressure oil from the cylinder space 9 flows via the channel 11, the check valve 17 opened via the control line 19, the rotary passage 23, the channel 21 and the 4/3-way valve 28 to the return line 14.

When the 4/3-way valve 28 is transferred from the right-hand extreme position back into the illustrated lock position, the channels between the 4/3-way valve and the check valves 17 and 18 likewise again become pressureless, and the positioning piston 6 remains in the position now attained, since the check valves 17 and 18 prevent a flowing-off of the pressure oil from the cylinder spaces 9 and 10 and the channel sections between the cylinder spaces and the check valves.

According to the embodiment shown in Figures 2 and 3, the crank shaft 7 is supported by means of an anti-friction bearing 31 in the machine housing and is provided with a cylindrical radial bore 32 of a large diameter and a further radial bore 33 which is smaller relative thereto. These radial bores 32 and 33 have coextending therethrough a cylindrical positioning piston 6 in longitudinal direction. The end faces 29, 30 of the positioning piston engage the internal faces 34 and 35 of a cam ring 5 with a small clearance. The diameter of the positioning piston 6 corresponds to the diameter of the radial bore 33. The seal between the positioning piston section 36 extending through the smaller bore 33 and the crank shaft 7 is provided by means of a cylinder ring seal 37 in the crank shaft 7.

In the central longitudinal region of the positioning piston 6, there is provided an annular collar 8 which is peripherally sealed by means of a cylinder ring seal 38 relative to the larger radial bore 32. A longitudinal section 39 of the positioning piston is sealingly guided in an annular insert 40. Sealing is effected via a cylinder ring seal 41 in the annular insert. The annular insert is fixed in the bore 32 by means of adapter rings 42 and sealed relative to the bore by means of a cylinder ring seal 43.

As shown in outline in Figure 3, the extreme positions of the positioning piston 6 may be varied by the provision of exchangeable abutment discs 44 and 45 of different thicknesses.

The radial guiding of the cam ring 5 on the one hand is determined by a radial flange 46 of the crank shaft 7 as well as engagement discs 47 and 48 and on the other hand by planar surfaces 49 and 50 of the crank shaft and 51 and 52 of the cam ring 5, respectively, which planar surfaces extend parallel to one another.

The engagement discs 47 and 48 are supported on a crank shaft bearing 53 located adjacent to, and radially outwardly from, a spigot incorporated in the crank shaft, by means of which bearing the spigot 54 is supported in the machine housing 1.

The connecting passages 11 and 12 in which the check valves 17 and 18 are incorporated open into the cylinder spaces 9 and 10 disposed at respective sides of the annular collar 8 of the positioning piston 6. The un-used end sections of the connecting passages are sealingly closed by plugs 55 as shown in Figures 2 and 4.

Each of the check valves 17 and 18 comprises a ball-shaped valve body 56 and a coiled compression spring 57 which rests against a threaded closure 58 and is positioned in a stepped radial bore of the crank shaft 7. The check valve 18 is arranged in an insert body 59 while the other check valve 17 is directly provided in the stepped bore of the crank shaft. Each of the check valves 17 and 18 is releasable by one of two control pins 61 and 60 with which a contro piston 62 arranged centrally in the crank shaft 7 is associated. In the embodiment referred to here, the control pin 60 is firmly associated with the control piston 62, while the other control pin 61 only loosely engages the control piston 62. The control pins are inserted with large clearance in the bores of the crank shaft spigot 54 or of the insert body 59 receiving them, so that restrictions 15 and 16 for the pressure oil are defined between the external periphery of the control pins and the bore walls.

Connecting channels 11' and 12', extend through the crank shaft spigot 54 and open into cylinder spaces 63 and 64, respectively, located on respective sides of the control piston 62. The connecting channel 11' is connected to the supply channel 21 in the area of the rotary passage 23 and the connecting channel 12' is connected to the supply channel 22. The channel connections 11' to 21 and 12' to 22 are sealed relative to one another by gas proof metal seal rings 65. It will furthermore be noted that the crank shaft spigot 54 engages in the machine housing 1 with large clearance.

In the embodiment of Figure 4, the check valves 17 and 18 are incorporated into respective insert bodies 59 which are arrestable in a continuous unstepped transverse bore 66 of the crank shaft spigot 54. Each insert body 59 is leak-free sealed relative to the bore 66 by means of cylinder ring seals 67. The two insert bodies 59 are supported relative to one another by means of an insert ring 68 which guides the control piston 62 internally. Externally, the insert bodies 59 are fixed in the bore 66 by means of adapter rings 69. The remaining configuration of the crank shaft spigot 54 and the cam ring positioning piston cross-sectional portion is identical to that of Figures 2 and 3.

WHAT WE CLAIM IS: 1. A hydrostatic radial piston machine comprising a housing; a plurality of radially extending cylinders in a star arrangement in the housing, each cylinder having a reciprocable work piston therein and each piston having a piston shoe at one end; a rotary power output or power input shaft having a radial bore and a spigot, which spigot is provided with connecting passages for a hydraulic fluid and is encircled by an annular gap between itself and the housing; a double-acting positioning piston located in the bore and having two end faces and being sealingly guided in the bore by an annular collar in the central longitudinal region of the positioning piston, the collar being slidable in the radial bore of the shaft by a hydraulic positioning fluid which enters and leaves the bore via the connecting passages in the shaft spigot and the annular gap between the spigot of the shaft and the housing, the annular collar separating two sealed spaces in the bore from each other; a cam ring mounted in the housing and radially displaceable by means of the positioning piston relative to the longitudinal axis of the shaft, the external periphery of the cam ring being engaged by the piston shoes of the work pistons and the internal periphery of the cam ring being engaged by the two end faces of the positioning piston; and two check valves, only one of which is open at any given moment, incorporated in respective ones of the said connecting passages to control the supply of the hydraulic positioning fluid to the said sealed spaces so that fluid is supplied only when the cam ring is being displaced.

2. A machine according to claim 1, wherein restrictions are provided in the connecting passages.

3. A machine according to claim 2, wherein the restrictions are components of the check valves.

4. A machine according to any one of claims 1 to 3 wherein the check valves are arranged radially in the shaft spigot.

5. A machine according to any one of the preceding claims, wherein the check valves are generally arranged in the transverse plane of a shaft bearing at the spigot side.

6. A machine according to any one of the preceding claims, wherein the check valves are releasable by means of control pins which are associated with a control piston arranged centrally in the shaft spigot and pressurizable at both sides by the hydraulic positioning fluid.

7. A machine according to claim 6 when dependent upon claim 2, wherein the restrictions are defined by the control pins and the bores receiving the control pins.

8. A machine according to any one of the preceding claims wherein the check valves are provided in insert bodies which are sealingly fixed in a bore transversely extending through the shaft spigot.

9. A machine according to any one of the preceding claims, wherein abutment means are provided in the cylinder spaces.

10. A machine according to claim 9, wherein the abutment means are defined by abutment discs insertable in the cylinder spaces.

11. A machine according to any one of the preceding claims, wherein the cam ring is radial) guided between a radial flange of the power input or power output shaft and axially adjustable engagement discs as well as at two planar surfaces of the shaft extending parallel to one another.

12. A machine according to any one of the preceding claims, wherein the faces of the annular collar which are adapted to be acted upon by the hydraulic positioning fluid are of the same size.

13. A machine according to any one of claims 1 to 11, wherein the faces of the annular collar which are adapted to be acted upon by the hydraulic positioning fluid are of a different size.

14. A machine according to any one of the preceding claims wherein the shaft spigot is supported in the machine housing with substantial clearance.

15. A machine according to any one of the preceding claims, wherein a shut-off element is incorporated into the supply lines for the hydraulic positioning fluid.

16. A machine according to claim 15, wherein the shut-off element is defined by a 4/3-way valve.

17. A hydrostatic radial piston machine, substantially as herein described with reference to, and as shown in, the accompanying drawings

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 22. The channel connections 11' to 21 and 12' to 22 are sealed relative to one another by gas proof metal seal rings 65. It will furthermore be noted that the crank shaft spigot 54 engages in the machine housing 1 with large clearance. In the embodiment of Figure 4, the check valves 17 and 18 are incorporated into respective insert bodies 59 which are arrestable in a continuous unstepped transverse bore 66 of the crank shaft spigot 54. Each insert body 59 is leak-free sealed relative to the bore 66 by means of cylinder ring seals 67. The two insert bodies 59 are supported relative to one another by means of an insert ring 68 which guides the control piston 62 internally. Externally, the insert bodies 59 are fixed in the bore 66 by means of adapter rings 69. The remaining configuration of the crank shaft spigot 54 and the cam ring positioning piston cross-sectional portion is identical to that of Figures 2 and 3. WHAT WE CLAIM IS:

1. A hydrostatic radial piston machine comprising a housing; a plurality of radially extending cylinders in a star arrangement in the housing, each cylinder having a reciprocable work piston therein and each piston having a piston shoe at one end; a rotary power output or power input shaft having a radial bore and a spigot, which spigot is provided with connecting passages for a hydraulic fluid and is encircled by an annular gap between itself and the housing; a double-acting positioning piston located in the bore and having two end faces and being sealingly guided in the bore by an annular collar in the central longitudinal region of the positioning piston, the collar being slidable in the radial bore of the shaft by a hydraulic positioning fluid which enters and leaves the bore via the connecting passages in the shaft spigot and the annular gap between the spigot of the shaft and the housing, the annular collar separating two sealed spaces in the bore from each other; a cam ring mounted in the housing and radially displaceable by means of the positioning piston relative to the longitudinal axis of the shaft, the external periphery of the cam ring being engaged by the piston shoes of the work pistons and the internal periphery of the cam ring being engaged by the two end faces of the positioning piston; and two check valves, only one of which is open at any given moment, incorporated in respective ones of the said connecting passages to control the supply of the hydraulic positioning fluid to the said sealed spaces so that fluid is supplied only when the cam ring is being displaced.