Hydraulic steering device

Abstract

A hydraulic steering device (1) includes a supply port (2), a return port (4), a working port device having two working ports (5, 6), a main flow path (7) between the supply port (2) and one of the working ports (5), and a return path (8) between the other working port (6) and the return port. The main flow path (7) includes a main orifice (A1), a flowmeter (9), a first flowmeter orifice (A2) upstream of the flowmeter, a second flowmeter orifice (A3) downstream of the flowmeter, and a first working port orifice (A4). The return path includes a second working port orifice (A5), a load sensing point (17) is arranged between the main orifice (A1) and the first flowmeter orifice (A2), and a drain orifice (A d ) is arranged between the load sensing point (17) and the return port (4), and a priority valve device (10) is arranged between the supply port (2) and the main orifice (A1).

Description

Technical Field

[0001] The present invention relates to a hydraulic steering device, which includes a supply port, a return port, a working port device having two working ports, a main flow path between one of the supply port and the working ports, and a return path between the other working port and the return port. Wherein, the main flow path includes a main orifice, a flowmeter, a first flowmeter orifice upstream of the flowmeter, a second flowmeter orifice downstream of the flowmeter, and a first working port orifice; the return path includes a second working port orifice; a load sensing point is arranged between the main orifice and the first flowmeter orifice; a discharge orifice is arranged between the load sensing point and the return port; and a priority valve device is arranged between the supply port and the main orifice, wherein the load sensing port of the priority valve device is connected to the load sensing point. Background Art

[0002] Such a hydraulic steering device is used to steer a vehicle, especially a heavy vehicle. Such a heavy vehicle has a relatively large steering motor connected to the working port device. This large steering motor requires a certain flow rate of hydraulic oil. This flow rate determines the speed at which the steering wheel can move, or when the vehicle is an articulated steering vehicle, the speed at which the components of the vehicle can tilt relative to each other through this flow rate.

[0003] When the steered wheel hits an obstacle during the movement in the steering direction, the driver of the vehicle experiences a sudden movement of the steering wheel. This behavior is usually referred to as "kickback". Kickback also occurs when the driver starts steering in the same steering direction as he did just before reaching neutral. In other words, when steering, for example, to the right, the chamber of the cylinder that pushes the piston to the right is loaded with high pressure. When the operator stops steering, this high pressure will be trapped in the cylinder chamber and the hose connected to the right port of the steering unit because all the orifices in the spool sleeve assembly are closed, while the pressure at the load sensing point drops to the tank pressure and the pressure at the supply port drops to the margin pressure. If the operator starts steering in the same direction (to the right) again, there will be a flow from the high-pressure side of the cylinder through the main flow path to the load sensing chamber and the supply port of the steering unit, which will cause the gear and thus the steering wheel to suddenly turn in the opposite direction.

[0004] To avoid this kickback, a check valve is arranged between the main orifice and the priority valve device. If the steering device is a dynamic steering device, another check valve is arranged between the load sensing port of the check valve device and the load sensing point in the main flow path.

[0005] The pressure drop that can be observed across the check valve reduces the pressure difference across the main orifice. The pressure difference across the main orifice, i.e., the so-called margin, determines the flow rate through the main orifice, and thus determines the flow rate that can be supplied to the steering motor through the working port orifice. Summary of the Invention

[0006] The object of the present invention is to achieve a high steering speed without loss of comfort.

[0007] This object is solved by the externally described hydraulic steering device, wherein the priority outlet of the priority valve is directly connected to the main orifice, the load sensing port of the priority valve device is directly connected to the load sensing point, and the main flow path includes a check valve located between the load sensing point and the working port of the main flow path, and the check valve opens in the direction towards the working port.

[0008] In such a hydraulic steering device, there is no check valve between the priority valve device and the main orifice, so that the pressure difference across the main orifice is not reduced due to the pressure drop across the check valve between the priority valve device and the main orifice. However, backflow can be avoided by providing a check valve downstream of the load sensing point. This has the additional advantage that a second check valve between the load sensing point and the load sensing port of the priority valve device can be avoided. High steering speeds can be achieved in the LS steering unit without loss of comfort, and backflow can even be avoided in the LS static steering unit.

[0009] In an embodiment of the present invention, the check valve is arranged between the load sensing point and the first flowmeter orifice. The first flowmeter orifice is commonly referred to as the "A2" orifice.

[0010] In an alternative embodiment, the check valve is arranged downstream of the second flowmeter orifice. The second flowmeter orifice is commonly referred to as the "A3" orifice.

[0011] In an embodiment of the present invention, the check valve is arranged between the second flowmeter orifice and the working port orifice of the main flow path. The working port orifice of the main flow path is commonly referred to as the "A4" orifice. Therefore, it is advantageous when the check valve is arranged directly in front of the A2 orifice or directly behind the A3 orifice. In all cases, the check valve at these positions is sufficient to avoid backflow. The pressure drop across the check valve does not have an adverse effect on the steering speed of the steering motor.

[0012] In an embodiment, the hydraulic steering unit includes a housing and a set of spools and sleeves in the holes of the housing, wherein the check valve is arranged in the housing. This allows the check valve to be arranged as close as possible to the A2 orifice or the A3 orifice.

[0013] In an embodiment of the present invention, the check valve includes a valve element, for example in the form of a ball, which seals a part of the housing in one position and is held in place by a component mounted in the housing from the outside of the housing in another position. This forms a very simple construction.

[0014] In an embodiment of the present invention, the component is mounted in the housing from the front side of the housing. This means that the valve element moves in the axial direction relative to the rotational axis of the sleeve and the spool. Therefore, the check valve does not require much additional space.

[0015] In an embodiment of the present invention, the component is screwed into the housing. This is a simple way to install the component.

[0016] In an embodiment of the present invention, the priority valve device includes a load sensing flow path from the priority outlet to the load sensing port. Although there is no check valve in this path, this is possible. The negative impact of backflow can be avoided by arranging a check valve in the main flow path. Description of the Drawings

[0017] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0018] Figure 1 A hydraulic steering device according to the prior art is shown,

[0019] Figure 2 A first hydraulic steering device according to the present invention is shown

[0020] Figure 3 A second hydraulic steering device according to the present invention is shown, and

[0021] Figure 4 A schematic diagram of multiple parts of the steering device is shown. Detailed Description

[0022] Figure 1 A hydraulic steering device 1 including a supply port 2 is shown. The supply port 2 is connected to a pressure source 3, such as a pump. The steering device 1 further includes a reservoir port 4 and two working ports 5, 6 forming a working port device.

[0023] A main flow path 7 is arranged between one of the working ports 5, 6 and the supply port 2. The other working port 6, 5 is connected to the return port 4 through a return path 8. The selection of the working ports 5, 6 depends on the direction in which the vehicle equipped with the hydraulic steering device 1 should turn.

[0024] The main flow path 7 includes a main orifice A1, a flow meter 9, a first flow meter orifice A2 upstream of the flow meter 9, a second flow meter orifice A3 downstream of the flow meter 9, and a first working port orifice A4 between the second flow meter orifice A3 and the working port 5.

[0025] The return path 8 includes a second working port orifice A5.

[0026] The main flow path is connected to the supply port 2 through the priority valve device 10. The priority valve device 10 includes a priority valve 11 and a load sensing orifice A. LS . The priority outlet CF of the priority valve 11 is connected to the main flow path 7. The priority outlet CF is connected to the first pressure chamber 12 via the orifice A pp and is connected to the second pressure chamber 13 via a second orifice A dyn . A spring 14 is arranged in the second pressure chamber 13.

[0027] Dynamic orifice A dyn defines a load sensing flow path from the priority outlet CF of the priority valve device 10 to the load sensing port 16.

[0028] The priority valve 11 includes a spool 15, and the position of the spool 15 is determined by the pressure difference between the two pressure chambers 12 and 13 and the force of the spring 14.

[0029] The priority valve device 10 includes a load sensing port 16, which is connected to a load sensing point 17 in the main flow path between the main orifice A1 and the first flowmeter orifice A2.

[0030] The main flow path 7 includes a check valve 18 that opens in a direction away from the priority valve device 10. Another check valve 19 is arranged in the load sensing pipeline 20 between the load sensing port 16 of the priority valve device 10 and the load sensing port 17 in the main flow path.

[0031] The main flow path 7 is connected to the return path 8 through another check valve 21, and this check valve 21 is connected to the main flow path 7 at a point between the main orifice A1 and the check valve 18. In addition, the load sensing point 17 of the main flow path 7 is connected to the return path 8 via a drain orifice A d .

[0032] Such a steering device includes ( Figure 4 ) a housing 25 and a set of spools 26 and sleeves 27 arranged in the hole 28 of the housing 25. The steering device is usually operated by the driver of the vehicle through a steering wheel (not shown). When the steering wheel rotates, the spools 26 and sleeves 27 rotate relative to each other. This rotation opens some orifices (main orifice A1, first flowmeter orifice A2, second flowmeter orifice A3, first working port orifice A4, second working port orifice A5) and closes the drain orifice A d . The hydraulic fluid flows from the priority valve device 10 through the main flow path 7 to the working port device and then to the steering motor 22 connected to the working ports 5 and 6. This flow drives the flowmeter 9, and the flowmeter 9 in turn restores the neutral position of the spool and the sleeve relative to each other.

[0033] The flow rate through the main flow path 7 is basically determined by the pressure difference across the main orifice A1. This pressure difference is the difference between the pressure at the priority outlet CF of the priority valve 11 and the load sensing pressure at the load sensing point 17. However, this difference is reduced by the pressure drop across the check valve 18. Therefore, the maximum flow rate achievable through the main orifice A1 is reduced by the pressure difference across the check valve 18. This in turn results in the flow rate to the steering motor 22 not being able to increase to the maximum flow rate, such that the steering speed of the steering motor 22 is not in an optimal state.

[0034] To allow for a greater steering speed, the Figure 1 shown prior art steering unit has been modified as Figure 2 and Figure 3 shown.

[0035] In all the figures, the same reference numerals denote the same elements.

[0036] Figure 2 and Figure 3 principally show the same steering unit, since the A2 orifice and the A3 orifice depend on the steering direction "change position".

[0037] As can be seen in Figure 2 and Figure 3 the main orifice A1 is directly connected to the priority outlet CF of the priority valve means 10. In other words, there is no check valve or other element in the pipeline between the priority outlet CF and the main orifice A1 which could cause a pressure drop, such that the full pressure difference between the pressure at the load sensing point 17 in the main flow path 7 and the priority outlet CF of the priority valve means 10 is used to drive the hydraulic fluid flow through the main orifice A1.

[0038] Similarly, there is no check valve between the load sensing point 17 in the main flow path 7 and the load sensing port 16 of the priority valve means 10. The priority valve means 10 may still have a load sensing orifice A LS but it is not shown in Figure 2 and Figure 3 here.

[0039] A pressure relief valve 23 is arranged between the load sensing point 17 and the return port. This valve ensures that the load sensing pressure does not increase beyond an allowed or specified value.

[0040] Downstream of the load sensing point 17, more precisely downstream of the second flowmeter orifice A3, and more precisely between the second flowmeter orifice A3 and the first working port orifice A4, a check valve 24 is arranged which opens in the direction of the working port 5 towards the main flow path 7.

[0041] Alternatively, the check valve 24 may be arranged upstream of the first flowmeter orifice A2, i.e., between the load sensing point 17 and the first flowmeter orifice A2.

[0042] In both cases, backflow can be avoided because the pressure peak generated by the steering motor 22 and transmitted via the respective working ports 5, 6 to the main flow path 7 does not create a reverse flow through the main flow path 7 so as not to have a negative impact on the vehicle driver's steering wheel.

[0043] The corresponding check valve 24 is arranged downstream of the second flowmeter orifice A3 ( Figure 2 ) or upstream of the first flowmeter orifice A2 ( Figure 3 ).

[0044] In both cases, the check valve 24 can be arranged in the housing accommodating the set of spools and sleeves, so that the check valve 24 can be arranged as close as possible to the set of spools and sleeves defining the respective orifices.

[0045] The check valve 24 includes a valve element 29, for example in the form of a ball made of steel or another material, which seals a part 30 of the housing 25 in one position and is held in place in another position by a part 31 mounted on the housing 25 from the outside of the housing. This part 30 of the housing forms a valve seat. The part 31 is mounted from the front face 32 of the housing 25 and is preferably screwed into the housing. The part 31 forms a stop 33 for the valve element 29. Thus, the valve element 29 can move between a first position, in which the check valve 24 is closed and the valve element 29 seals a part 30 of the housing 25, and a second position, in which the valve element 29 is moved away from this part 30 of the housing 25, i.e., away from the valve seat, so that the check valve 24 is open. The stop 33 limits the movement of the valve element 29.

Claims

1. A hydraulic steering device (1) comprising a supply port (2), a return port (4), a working port device having two working ports (5, 6), a main flow path (7) between the supply port (2) and one of the working ports (5), and a return path (8) between the other working port (6) and the return port (4), wherein, The main flow path (7) includes a main orifice (A1), a flow meter (9), a first flow meter orifice (A2) upstream of the flow meter (9), a second flow meter orifice (A3) downstream of the flow meter (9), and a first working port orifice (A4). The return path (8) includes a second working port orifice (A5). A load sensing point (17) is arranged between the main orifice (A1) and the first flow meter orifice (A2), and a discharge orifice (A d ) is arranged between the load sensing point (17) and the return port (4), and a priority valve device (10) is arranged between the supply port (2) and the main orifice (A1). A load sensing port (16) of the priority valve device (10) is connected to the load sensing point (17), Characterized in that the priority outlet (CF) of the priority valve device (10) is directly connected to the main orifice (A1), the load sensing port (16) of the priority valve device (10) is directly connected to the load sensing point (17), and the main flow path (7) includes a check valve (24) between the load sensing point (17) and the working port (5) of the main flow path (7), the check valve (24) opening in the direction towards the working port (5).

2. The hydraulic steering device according to claim 1, characterized in that, The check valve (24) is arranged between the load sensing point (17) and the first flowmeter orifice (A2).

3. The hydraulic steering device according to claim 1, characterized in that, The check valve (24) is arranged downstream of the second flowmeter orifice (A3).

4. The hydraulic steering device according to claim 3, characterized in that, The check valve (24) is arranged between the second flowmeter orifice (A3) and the working port orifice (A4) of the main flow path (7).

5. The hydraulic steering device according to any one of claims 1 to 4, characterized in that, The hydraulic steering device includes a housing and a set of spools and sleeves located in the bores of the housing, wherein the check valve (24) is arranged in the housing.

6. The hydraulic steering device according to claim 5, characterized in that, The check valve (24) includes a valve element (29), the valve element (29) sealing a part (30) of the housing (25) in one position and being held in place in the housing (25) by a component (31) mounted from the outside of the housing (25) in the housing (25).

7. The hydraulic steering device according to claim 6, characterized in that, The component (31) is mounted in the housing (25) from the front face (32) of the housing (25).

8. The hydraulic steering device according to claim 7, characterized in that, The component (31) is screwed into the housing (25).

9. The hydraulic steering device according to any one of claims 1 to 8, characterized in that, The priority valve device (10) includes a load sensing flow path from the priority outlet (CF) to the load sensing port (16).

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