WO2005061897A1

WO2005061897A1 - Hydraulic motor

Info

Publication number: WO2005061897A1
Application number: PCT/DK2004/000879
Authority: WO
Inventors: Henning Lund Larsen; Kim René HANSEN
Original assignee: Sauer Danfoss ApS
Current assignee: Danfoss Power Solutions ApS
Priority date: 2003-12-20
Filing date: 2004-12-17
Publication date: 2005-07-07
Anticipated expiration: 2006-06-20
Also published as: DE10360172C5; DE10360172B4; DE10360172A1

Abstract

The invention concerns a hydraulic motor with a displacement section having a rotating and orbiting displacement element, a valve section having a valve slide supported to be rotatable in a housing bore, and a coupling device, which transmits the rotating movement of the displacement element to the valve slide. It is endeavoured to improve the operational behavior of such a motor. For this purpose, it is ensured that the coupling device has at least one coupling element (19), which is connected with the displacement element (7) via an annular engagement path (21), covering, in each position of the displacement element (7), a predetermined radial area of the valve slide (12).

Description

Hydraulic motor

The invention concerns a hydraulic motor with a displacement section having a rotating and orbiting displacement element, a valve section having a valve slide supported to be rotatable in a housing bore, and a coupling device, which transmits the rotating movement of the displacement element to the valve slide.

Such a hydraulic motor is, for example, known from US

5,788,471. The displacement section has a gear wheel with outer teeth, which orbits in a gear ring with inwardly directed teeth, and at the same time rotates. In this connection, pressure chambers occur between the teeth of the gear wheel and the teeth of the gear ring, which pressure chambers are supplied with pressurised hydraulic fluid or discharge hydraulic fluid to the tank under the control of the valve slide in accordance with the individual, relative positions of the gear wheel in relation to the gear ring. The connection between the gear wheel and the valve slide occurs via a cardan shaft, also called "dog bone", which engages with the gear wheel via a toothing. This toothing permits an inclination of the cardan shaft in relation to the rotation axis of the gear wheel . The valve slide is connected with the cardan shaft via a further toothing. An output shaft is connected to form one piece with the valve slide, so that the cardan shaft also drives the output shaft. With such an embodiment, a first problem occurs in that certain leakages occur around the valve slide. A second problem occurs in that the control of the individual pressure chambers by the valve slide is load dependent . Due to the two toothings at the ends of the cardan shaft a play occurs, which complicates the control of the displacement section by the valve section.

A similar motor is known from US 4,992,034. Here, the valve section is decoupled from the output shaft. Accordingly, two cardan shafts are provided, one cardan shaft driving the valve slide, the other cardan shaft driving the output shaft. The cardan shaft driving the valve slide is substantially shorter so that the risk of distortion during a heavy load remains small. Still, two toothings are provided, whose plays are added, causing that the valve slide runs somewhat behind the gear wheel .

The invention is based on the task of improving the opera- tion behaviour of the motor.

With a hydraulic motor as mentioned in the introduction, this task is solved in that the coupling device has at least one coupling element, which is connected with the displacement element via an annular engagement path, covering, in each position of the displacement element, a predetermined radial area of the valve slide.

With this embodiment, the valve slide can be arranged con- centrically to the axis of a circle, which determines the orbiting movement of the displacement element. With such a displacement element, there is, along the engagement path, a point for each position of the displacement element, which points lie on a circle. During a movement of the displacement element, this point moves along the engagement path. At the same time, this point is guided by the displacement element in a circular movement around the rotation axis of the valve slide. When, now, the valve slide is brought to engage this point, a direct driving of the valve slide by means of the displacement element can be achieved in a relatively simple manner, without requiring an inclined or at least inclinable cardan shaft. The rota- tion speeds of displacement element and valve slide are in accordance, so that a synchronous control of the pressure chambers, which are formed in the displacement element, with the valve slide can be achieved in a simple manner.

The fact that the valve slide is driven directly by the displacement element makes fewer connections between mutually moving parts required, so that a play caused by such connections can be substantially reduced. Thus, it is possible to control the individual pressure chambers substantially more accurately than before.

It is also advantageous that the coupling element is connected in a play- free manner with the valve slide. This is most simply realised by means of a rigid connection. In this case, a play can only occur in the connection between the coupling element and the displacement element, which can, however, be kept relatively small, as here a toothing is not required.

Preferably, the coupling element exists in the form of a projection, which is located in a frontside of the valve side facing the displacement section. This projection can on the one hand be made in one piece with the valve slide. On the other hand, however, it can also be a separate part, which is connected with the valve slide. For exam- pie, a cylinder pin can be inserted in the frontside of the valve slide. Of course, also another geometry can be used instead of a cylinder pin, for example, a half ball, a cone or the like. Preferably, the engagement path is made to be circular. Thus, it can be ensured that the movements of valve slide and displacement element occur exactly synchronously with each other.

Preferably, a recess on the frontside of the displacement element facing the valve section forms the engagement path. The projection on the valve slide then projects into this recess. When the displacement element moves, that is, rotates or orbits, the coupling element, that is, for example the projection, always rests on the outside of the recess .

In a preferred embodiment it is ensured that the engagement path is formed by a bore in the displacement element, the diameter of said bore corresponding to the diameter of a circle, on which the displacement element orbits. The fact that actually merely a flank is required for the en- gagement path, via which flank a pressure force can be exerted on the coupling element, means that the engagement path can also be made as a bore. In this case, the inner wall of the bore only controls the coupling element. This is sufficient to ensure a reliable connection between the displacement element and the valve slide in both rotation directions. The fact that the bore is made with a diameter, which has a close relation to the orbit circle of the displacement element, ensures in a simple manner that the connection between the coupling element and the engagement path is practically free of play. The coupling element slides along a sliding surface of the engagement path. Preferably, the valve slide rests with its frontside on the displacement element. This is a simple way of sealing the pressure pockets, which are formed in the displacement section. The side of the valve slide opposite the dis- placement section is finished by a front plate anyway.

Preferably, the frontside of the valve slide covers the engagement path in any position of the displacement element. In this case it is avoided that the engagement path generates a short-circuit between neighbouring pressure pockets .

It is also advantageous that the displacement element is made as a gear wheel and that several engagement paths are distributed evenly on the teeth in the circumferential direction. In this case, a load, which is required for driving the valve slide, is distributed evenly on the displacement element in the circumferential direction. This keeps the wear small and prevents that an irregular con- trol of the pressure chambers in the displacement section occurs over the time.

Preferably, each tooth has an engagement path. In this case, the load of one single coupling element is minimised and the life of the machine is increased.

It is also advantageous, when at least three coupling elements are provided in the circumferential direction. With three coupling elements a satisfactory engagement between the displacement element and the valve slide is achieved.

In a preferred embodiment, it is ensured that in the radial direction the engagement path is located radially in- side an area, in which pressure chambers of the displacement section are located. Also in this case it is prevented that short-circuits between pressure chambers can occur via the engagement path(s) . From the pressure cham- bers no hydraulic fluid can flow into the engagement paths .

In the following, the invention is described on the basis of preferred embodiments in connection with the drawings, showing:

Fig. 1 a schematic longitudinal section through a hydraulic machine

Fig. 2 a section II-II according to Fig. 1

Fig. 3 a corresponding view of a modified embodiment

Fig. 4 different positions of a displacement element for explaining the mode of operation of the hydraulic motor

A hydraulic motor 1 has a displacement section 2 and a valve section 3, which are connected through a valve plate 4. On the side opposite the valve section 3, a cover 5 closes the displacement section 2. On the side opposite the displacement section 2, a cover 6 also closes the valve section 3.

In the displacement section 2 is located a gear wheel 7 with outer teeth 8 inside a gear ring 9, whose inner teeth 10 are formed by rolls. Together with the gear ring 9, the gear wheel 7 borders pressure chambers 11, which expand and reduce, when the gear wheel 7 rotates and orbits in the gear ring 9. During this process, the expanding pressure chambers 11 are supplied with pressurised hydraulic fluid. Hydraulic fluid can flow off from the reducing pressure chambers 11. In order to control this fluid supply and discharge, the valve section 3 has a valve slide 12, which is supported to be rotatable in a bore 13 of a housing 14. The valve slide 12 is located concentrically to the gear ring 9.

The valve slide 12 has several, merely schematically shown, grooves 15, 16, which can extend in the circumferential direction or axially, and are meant for guiding fluid via housing channels 17 from a pressure connection, which is not shown in detail, to pressure chambers 11, or from pressure chambers 11 via a housing channel 18 to a tank connection, which is not shown in detail.

On the frontside opposite the displacement section 2, the valve slide 12 is provided with several pin-like projections 19. The gear wheel 7 has a corresponding number of circular recesses 20. When, now, the gear wheel 7 moves in the gear ring 9, that is, rotates and orbits, the projections 19 are carried along in the recesses 20 in such a manner that merely the rotating movement is transferred to the projections 19. The orbiting movement is adopted in that the projections 19 can move in the recess 20. The projections 19 thus slide along a sliding surface 21, which is formed by the inner wall of the recesses 20. The sliding surface 21 thus forms an engagement path, with which the projections 19 engage. In this connection, the recesses 20 overlap an annulus, in which the projections 19 are located. Theoretically, it is a circle line. As, however, the projections 19 have a final extension, they are located on an annulus. The recesses 20 are located so, and have such a dimension that in each position of the gear wheel 7, each recess 20 releases this annulus.

As can be seen from Fig. 1, the recesses 20 are formed in the frontside of the gear wheel 7, which lies opposite the valve section 3. Therefore, they have a limited depth. They are located so far radially inside that they do not get to overlap the end of a housing channel 17, 18 or otherwise short-circuit neighbouring pressure chambers 11. The recesses 20 merely serve the purpose of guiding the projections 19.

Shown is that the projections 19 have the shape of cylinder pins. However, this is not a requirement. The projections 19 can also have the shape of half balls, balls, cones or similar elements. Favourable is, however, that the projections 19 have a circular cross-sectional shape.

An output shaft 22 is connected with the gear wheel 7 via a tooth pairing 23. The output shaft 22 is led through the valve slide 12, however, without transferring forces to the valve slide 12.

In the embodiment according to Fig. 2, the gear wheel has six teeth 8. A recess 20 is allocated to every second tooth 8, so that in total three recesses 20 and accordingly three projections 19 occur.

Fig. 3 shows a modified embodiment, in which merely a view according to a line II-II according to Fig. 1 can be seen, this view being directed from the gear wheel 7 to the valve slide 12. Same parts have the same reference numbers as in the Figs. 1 and 2.

This time, the recesses 20 are located radially further outwards, that is, in the teeth. The valve slide 12 now covers a part of the recesses. Radially inside the valve slide 12 is located a cover 24, which also covers, and thus seals, the frontside of the gear wheel 7.

The recesses 20 are made as through-bores. The recesses 20 have a diameter, which corresponds to a circle 25, which the orbiting movement of the gear wheel 7 describes in the gear ring 9. However, the recesses 20 are somewhat larger than this circle 25, to be able to adopt the final dimen- sion of the projections 19.

It can be seen that all projections 19 always rest on the sliding surface 21 of their recess 20. This will be explained on the basis of Fig. 4.

Fig. 4a shows a situation, in which a tooth 8 is moved from a position, in which the corresponding pressure chamber 11 has assumed its smallest volume. Thus, here, pressurised hydraulic fluid is supplied into the pressure chamber 11. During the further movement in the direction of an arrow 26, the projection 19 moves somewhat downwards in the recess 20, however, still resting on the sliding surface 21. This resting remains, also when, as shown in Fig. 4c, the tooth 8 continues turning in the direction of the arrow 26. When, as shown in Fig. 4d, the peak of the outer tooth 8 lies opposite the peak of the inner tooth 10, the projection 19 has travelled approximately to the largest radial extension of the recess 20. Here, it must be considered that not only the shown projection 19 is driven by the gear wheel 7, but also the other three projections 19. Thus, it can be assumed that at least one projection 19 is always pushed in the circumferential di- rection.

With the embodiment shown, it is possible to drive the valve slide 12 directly through the gear wheel 7, merely the rotating movement of the gear wheel 7 being trans- ferred to the valve slide 12, not, however, the orbiting movement .

As merely one movable connection is available, namely the connection between the projections 19 and the sliding sur- faces 21, also merely a correspondingly small play exists. The position of the valve slide 12 can thus follow the position of the gear wheel 7 in a substantially better manner.

Here, the engagement path is shown as sliding surface 21. This is also the simplest embodiment, as during the movement of the gear wheel 7, the projections are always held to rest on the sliding surface 21. However, it is of course also possible to make an engagement path by means of a circular groove.

Claims

Patent Claims

1. Hydraulic motor with a displacement section having a rotating and orbiting displacement element, a valve section having a valve slide supported to be ro- tatable in a housing bore, and a coupling device, which transmits the rotating movement of the displacement element to the valve slide, characterised in that the coupling device has at least one coupling element (19) , which is connected with the displacement element (7) via an annular engagement path (21) , covering, in each position of the displacement element (7) , a predetermined radial area of the valve slide (12) .

2. Motor according to claim 1, characterised in that the coupling element (19) is connected in a play-free manner with the valve slide (12) .

Motor according to claim 1 or 2 , characterised in that the coupling element (19) exists in the form of a projection, which is located in a frontside of the valve slide (12) facing the displacement section (2) ,

Motor according to one of the claims 1 to 3 , characterised in that the engagement path (21) is made to be circular.

5. Motor according to one of the claims 1 to 4 , characterised in that a recess (20) on the frontside of the displacement element (7) facing the valve section (3) forms the engagement path (21) .

6. Motor according to one of the claims 1 to 5, characterised in that the engagement path (21) is formed by a bore in the displacement element (7) , the diameter of said bore corresponding to the diameter of a circle (25) , on which the displacement element (7) orbits .

7. Motor according to one of the claims 1 to 6 , characterised in that the valve slide (12) rests with its frontside on the displacement element (7) .

8. Motor according to claim 7, characterised in that the frontside of the valve slide (12) covers the engagement path (21) in any position of the displacement element (7) .

9. Motor according to one of the claims 1 to 8 , charac- terised in that the displacement element is made as a gear wheel and that several engagement paths (21) are distributed evenly on the teeth (8) in the circumferential direction.

10. Motor according to claim 9, characterised in that each tooth (8) has an engagement path (21) .

11. Motor according to one of the claims 1 to 10, characterised in that at least three coupling elements (19) are provided in the circumferential direction.

12. Motor according to one of the claims 1 to 11, characterised in that in the radial direction the engage- ment path is located radially inside an area, in which pressure chambers (11) of the displacement section (2) are located.