HYDRAULIC STEERING ARRANGEMENT

Abstract

A hydraulic steering arrangement (1) including a supply port arrangement having a supply port (2) and a return port (3), a working port arrangement having two working ports (4, 5), a supply flow path (7) between the supply port (2) and one of the working ports (4, 5), a return flow path (9) between the other of the working ports (5, 4) and the return port (3) and a valve arrangement having a spool/sleeve set, wherein the supply flow path (7) includes a supply orifice (A.sub.4) and the return flow path (9) comprises a return orifice (A.sub.5). Such a hydraulic steering arrangement should give a comfortable feeling when used in connection with an articulated vehicle. To this end a variable damping orifice (A.sub.dp) is arranged downstream the supply orifice (A.sub.4) and upstream the return orifice (A.sub.5).

Claims

1. A hydraulic steering arrangement comprising a supply port arrangement having a supply port and a return port, a working port arrangement having two working ports, a supply flow path between the supply port and one of the working ports, a return flow path between the other of the working ports and the return port, and a valve arrangement having a spool/sleeve set, wherein the supply flow path comprises a supply orifice and the return flow path comprises a return orifice, wherein a variable damping orifice is arranged downstream the supply orifice and upstream the return orifice.

2. The hydraulic steering arrangement according to claim 1, wherein the variable damping orifice is closed in neutral position of the spool/sleeve set.

3. The hydraulic steering arrangement according to claim 1, wherein the variable damping orifice is closed at a maximum deflection of the spool/sleeve set.

4. The hydraulic steering arrangement according to claim 1, wherein the variable damping orifice opens at a deflection of the spool/sleeve set which is larger than a deflection of the spool/sleeve set at which the supply orifice and/or the return orifice open.

5. The hydraulic steering arrangement according to claim 1, wherein the variable damping orifice is formed by the spool/sleeve set.

6. The hydraulic steering arrangement according to claim 1, wherein an amplification flow path is arranged in parallel to the main flow path, wherein the amplification flow path opens into the main flow path upstream the damping orifice.

7. The hydraulic steering arrangement according to claim 6, wherein the amplification flow path opens into the main flow path upstream the supply orifice.

8. The hydraulic steering arrangement according to claim 2, wherein the variable damping orifice is closed at a maximum deflection of the spool/sleeve set.

9. The hydraulic steering arrangement according to claim 2, wherein the variable damping orifice opens at a deflection of the spool/sleeve set which is larger than a deflection of the spool/sleeve set at which the supply orifice and/or the return orifice open.

10. The hydraulic steering arrangement according to claim 3, wherein the variable damping orifice opens at a deflection of the spool/sleeve set which is larger than a deflection of the spool/sleeve set at which the supply orifice and/or the return orifice open.

11. The hydraulic steering arrangement according to claim 2, wherein the variable damping orifice is formed by the spool/sleeve set.

12. The hydraulic steering arrangement according to claim 3, wherein the variable damping orifice is formed by the spool/sleeve set.

13. The hydraulic steering arrangement according to claim 4, wherein the variable damping orifice is formed by the spool/sleeve set.

14. The hydraulic steering arrangement according to claim 2, wherein an amplification flow path is arranged in parallel to the main flow path, wherein the amplification flow path opens into the main flow path upstream the damping orifice.

15. The hydraulic steering arrangement according to claim 3, wherein an amplification flow path is arranged in parallel to the main flow path, wherein the amplification flow path opens into the main flow path upstream the damping orifice.

16. The hydraulic steering arrangement according to claim 4, wherein an amplification flow path is arranged in parallel to the main flow path, wherein the amplification flow path opens into the main flow path upstream the damping orifice.

17. The hydraulic steering arrangement according to claim 5, wherein an amplification flow path is arranged in parallel to the main flow path, wherein the amplification flow path opens into the main flow path upstream the damping orifice.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] An embodiment of the invention will now be described with reference to the drawing, in which:

[0017] FIG. 1 schematically shows a hydraulic steering arrangement and

[0018] FIG. 2 schematically shows opening degrees of several orifices shown in FIG. 1.

DETAILED DESCRIPTION

[0019] FIG. 1 schematically shows a hydraulic steering arrangement 1 having a supply port arrangement, known for example from DE102018125053. The supply port arrangement comprises a supply port 2 and a return port 3. Furthermore, two working ports 4, 5 are provided, wherein the working ports 4, 5 form a working port arrangement. A steering motor 6 is connected to the working ports 4, 5.

[0020] The steering arrangement 1 comprises a main flow path 7 which comprises a main orifice A.sub.1 and a measuring motor 8. A first measuring motor orifice A.sub.2 is arranged upstream the measuring motor 8 and a second measuring motor orifice A.sub.3 is arranged downstream the measuring motor 8. The terms upstream and downstream relate to the direction of the flow through the main flow path 7 and the measuring motor 8. The main flow path 7 is connected to one of the working ports 4 via a supply orifice A.sub.4. The other working port 5 is connected to a return flow path 9 via a return orifice A.sub.5.

[0021] The orifices A.sub.1, A.sub.2, A.sub.3, A.sub.4, and A.sub.5 are part of a valve arrangement which is formed by a spool/sleeve set as it is known in the art. The valve arrangement determines which of the two working ports 4, 5 is connected to the main flow path 7 and which of the working ports 5, 4 is connected to the return flow path 9.

[0022] The hydraulic steering arrangement 1 can also comprise an amplification flow path 10 which is connected to the supply port 2 and opens into the main flow path 7 between the supply orifice A.sub.4 and the second measuring motor orifice A.sub.3. The amplification flow path 10 comprises an amplification orifice AU which is also formed in the spool/sleeve set of the valve arrangement and controlled in a way similar, but not necessarily identically to the control of the main orifice A.sub.1.

[0023] In the present steering arrangement 1 a drain orifice A.sub.dr is arranged between the main flow path 7 and the return flow path 9, more precisely between a point between the main orifice A.sub.1 and the first measuring motor orifice A.sub.2 and the return flow path 9.

[0024] A check valve 11 is arranged upstream the main orifice A.sub.1 and opens in direction towards the main orifice A.sub.1.

[0025] The main flow path 7 is connected to a relief valve 12 which branches of a line 13 connecting the main flow path 7 downstream the main orifice A.sub.1 to a load sensing port 14 of a priority valve 15. The priority valve 15 controls a supply of hydraulic fluid from a tank 16 to the supply port 2. The hydraulic fluid is pumped by means of a pump 17.

[0026] Since the arrangement and construction of the priority valve 15 is known in the art, it is not further described. The same applies for the valve 12 and the over pressure valves which normally would be placed/in connection with the working ports 4,5.

[0027] A variable damping orifice A.sub.dp is arranged downstream the supply orifice A4 and upstream the return orifice A.sub.5. The terms downstream and upstream relate to the flow of hydraulic fluid towards and from the steering motor 6. In the present case, the damping orifice A.sub.dp connects the main fluid path 7 and the return fluid path 9 between the supply orifice A.sub.4 and one of the working ports 4 on the one hand and between the other working port 5 and the return orifice A.sub.5 on the other side.

[0028] The damping orifice A.sub.dp is a variable orifice which is closed in neutral position of the spool/sleeve set. Furthermore, the variable damping orifice A.sub.dp is closed at a maximum deflection of the spool/sleeve set. This is schematically shown in FIG. 2.

[0029] The spool/sleeve set comprises a spool and a sleeve, wherein the sleeve surrounds the spool and is arranged in a bore of a housing. The spool and the sleeve are rotatably with respect to each other. One of spool and sleeve is connected to a steering command device, for example, a steering wheel. The other of spool and sleeve is connected to a part of the measuring motor. When the steering wheel (or any other steering command device) is rotated, the deflection between the spool and the sleeve is changed. This change opens some orifices, as shown in FIG. 2, and closes others.

[0030] In FIG. 2 the deflection is shown on the horizontal axis and the opening degree of the orifices is shown on the vertical axis. In the present embodiment, the drain orifice A.sub.dr is closed at the beginning of the deflection, wherein the main orifice A.sub.1, the amplification orifice AU, the supply orifice A.sub.4, the return orifice A.sub.5 and the two measuring motor orifices A.sub.2, A.sub.3 are opened. Hydraulic fluid flowing to a working port through the supply orifice A.sub.4 flows through the measuring motor 8 and drives it. The measuring motor 8 restores the angular position or deflection between the spool and the sleeve to neutral, so that the drain orifice A.sub.dr is opened, and the other orifices are closed.

[0031] As it is shown in FIG. 2, the damping orifice A.sub.dp opens at a deflection which is larger than a deflection at which the main orifice A.sub.1 and the amplification orifice AU opens. Furthermore, the opening degree of the damping orifice A.sub.dp is nearly constant over a large range of the deflection angle. The damping orifice A.sub.dp still forms a throttle resistance, i.e. the opening area of the damping orifice A.sub.dp is always smaller than the opening area of the main orifice A.sub.1 and of the amplification orifice AU.

[0032] While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.