Steering system

Abstract

A steering system (1) is described, which comprises a supply port arrangement with a supply port (P) and a return port (T), a steering command device with a steering sensor (5), a controller (9) connected to the steering sensor (5), an electro-hydraulic steering valve (8) controlled by the controller (9), and a working port device with two working ports (L, R), wherein the working port device is connected to the supply port device via the steering valve (8). Such a steering system should have a good comfort. To this end, the steering command device comprises a steering wheel (4) connected to a hydraulic pumping unit (7), wherein the pumping unit (7) is part of a hydraulic circuit (11) with means for generating a flow resistance.

Description

Technical Field

[0001] The present invention relates to a steering system comprising a supply port arrangement having a supply port and a return port, a steering command device having a steering sensor, a controller connected to the steering sensor, an electro-hydraulic steering valve controlled by the controller, and a working port device having two working ports, wherein the working port device is connected to the supply port device via the steering valve. Background Technology

[0002] Such a steering system is known, for example, from DE 10 2007 053 024 B4. Vehicles equipped with this steering system can be steered under the control of an electro-hydraulic steering valve, or under the control of a conventional steering unit. Summary of the Invention

[0003] The purpose of this invention is to provide a steering system with good comfort.

[0004] This objective is achieved by a steering system as described at the beginning, wherein the steering command device includes a steering wheel connected to a hydraulic pumping unit, wherein the pumping unit is part of a hydraulic circuit having means for generating flow resistance, wherein the hydraulic circuit is connected to a steering valve via a safety valve that establishes or interrupts the hydraulic flow path between the hydraulic circuit and the steering valve.

[0005] In such a system, the electro-hydraulic steering valve is the primary device for controlling the flow rate into and out of the working port device; that is, it determines the amount of hydraulic fluid supplied to the steering motor connected to the working port of the working port device. The hydraulic circuit serves two purposes: When undisturbed, it produces a "steering feel" because the pumping device, driven by the steering wheel, pumps hydraulic fluid through the circuit, and the circuit exhibits a certain flow resistance to the pumped fluid. Therefore, rotating the steering wheel must overcome a certain torque, and the driver experiences a feeling comparable to that produced when the vehicle is steered by a mechanical steering unit. Under normal circumstances, the fluid from the pumping unit is not used for steering purposes, and the fluid is only used for "circulation pumping."

[0006] In embodiments of the invention, the safety valve establishes a hydraulic connection between the hydraulic circuit and the working port device in the event of a lack of pressure at the supply port. Therefore, the safety valve operates automatically, ensuring that steering is always possible in vehicles equipped with steering systems.

[0007] In an embodiment of the invention, the safety valve is connected to the working port device via a diverting valve. Therefore, no additional connection to the working port device is required.

[0008] In embodiments of the invention, the device for generating flow resistance has a variable orifice. The variable orifice is the main element for generating flow resistance. When the orifice is variable, the flow resistance can also vary. Therefore, the steering feel can adapt to different driving conditions. For example, low flow resistance can be achieved when the vehicle speed is low, while high flow resistance can be achieved when the vehicle speed is high.

[0009] In embodiments of the invention, the means for generating flow resistance is at least partially arranged within the safety valve. Therefore, no additional means are required.

[0010] In embodiments of the invention, the flow resistance of the device for generating flow resistance depends on the valve position of the safety valve. For example, the safety valve may have a valve core that is movable within a housing or sleeve. The valve core and a corresponding element define at least one throttling orifice, the size of which is subsequently defined by the position of the valve core.

[0011] In embodiments of the invention, the hydraulic circuit includes a steering feel valve connected to a supply port device. The steering feel valve is capable of providing additional hydraulic flow to the hydraulic circuit. Therefore, such flow can support the rotation of the steering wheel or can generate a larger counter-torque. Furthermore, the steering feel valve can be used for vehicle self-centering, i.e., for aligning the angular position of the steering wheel with the angular position of the steered wheels.

[0012] In embodiments of the invention, the hydraulic circuit includes a pressure relief valve device in a pipeline connecting the two ports of the pumping unit. The pumping unit drives hydraulic fluid from one port to the other, wherein the direction of flow depends on the direction of steering wheel rotation. The pressure relief valve device can be used to limit the maximum torque of the steering wheel. Furthermore, it can simulate the position where the steering wheel stops at an end where it can no longer rotate.

[0013] In an embodiment of the invention, the pressure relief valve device includes two pressure relief valves, each controlled by a pressure differential and bridged by a check valve that opens in a direction away from the other. Therefore, the two pressure relief valves can be arranged in a common pipeline. The pressure upstream of each pressure relief valve corresponds to the pressure generated at the output side of the pumping unit, and the pressure on the opposite side of the pressure relief valve substantially corresponds to the pressure at the input side of the pumping unit. In this case, the pressure drop at the check valve is negligible.

[0014] In embodiments of the invention, the steering command device includes a steering command mechanism in addition to the steering wheel, wherein the steering wheel is connected to the pumping unit via a releasable coupling. The steering command mechanism may be, for example, a lever. When the vehicle is steered via the lever, the steering wheel does not necessarily rotate during vehicle steering. This rotation can be prevented by using a releasable coupling.

[0015] In embodiments of the invention, the steering valve includes a safety valve port connected to a safety valve. The steering valve includes a main fluid path arranged for each steering direction and a check valve assembly that allows hydraulic fluid to flow from the safety valve to one of the working ports and out of the other working port to the safety valve, depending on the valve position of the steering valve. Therefore, if desired, the flow rate of hydraulic fluid generated by the rotation of the steering wheel can be used to increase the flow rate delivered to the working port assembly and increase the steering speed.

[0016] In an embodiment of the invention, in the neutral position of the steering valve, the check valve device disconnects the connection between the safety valve port and the return port. This is an additional safety measure. Hydraulic fluid cannot leak to the return port. In an emergency, all hydraulic fluid flow generated by the rotation of the steering wheel and the pumping unit is supplied to the working port device.

[0017] In embodiments of the invention, the safety valve includes an actuation device that allows for remote actuation of the safety valve. For example, the safety valve can be electrically operated via a solenoid device or hydraulically operated by a corresponding pressure.

[0018] In an embodiment of the invention, the pumping unit is a measuring motor. In this case, the steering system can be equipped with a conventional mechanical steering unit.

[0019] In an alternative embodiment, the pumping unit is a hydraulic pump, particularly a hydraulic pump in the form of a steering gear. Therefore, only a portion of a conventional steering unit is used in this type of steering unit. Attached Figure Description

[0020] Now, embodiments of the present invention will be described in more detail with reference to the accompanying drawings, in which:

[0021] Figure 1 The steering system is shown schematically;

[0022] Figure 2 The components of the steering system are schematically shown; and

[0023] Figure 3 A second embodiment of a portion of a hydraulic steering system is shown. Utilizing... Figure 1 and Figure 2 The same reference numerals in the figures indicate the same elements. Detailed Implementation

[0024] Figure 1 A steering system 1 is schematically shown, comprising a supply port device having a supply port P and a return port T. The supply port P is connected to a pump 2, which can be operated by, for example, the combustion engine of a vehicle to be steered by the steering system. The return port T is connected to a housing 3.

[0025] The steering system 1 includes a steering wheel 4, which forms at least part of the steering command device. The steering wheel 4 is connected to a steering sensor 5 and a column 6, and the steering wheel 4 is connected to a pumping unit 7 via the column 6. The pumping unit 7 may be in the form of a measuring motor of a conventional hydraulic steering unit, or it may be a simple hydraulic pump, such as in the form of an orbitrol.

[0026] The steering system also includes an electro-hydraulic steering valve 8 controlled by a controller 9, wherein the controller 9 receives sensor signals from the steering sensor 5. The steering valve 8 includes a working port device with two working ports L and R, which are connected to the steering motor 10.

[0027] Steering valve 8 establishes a connection between supply port P and one of the working ports L and R, and simultaneously establishes a connection between the other of the working ports R and L and return port T. The direction of fluid flow from pump 2 to steering motor 10 depends on the direction of rotation of steering wheel 4 detected by steering sensor 5. Steering sensor 5 can detect not only the angle of rotation of steering wheel 4, but also the rotation speed.

[0028] The pumping unit 7 is connected to the hydraulic circuit 11, which has a device for generating flow resistance, particularly a throttling orifice, such as... Figure 2 As shown. Furthermore, hydraulic circuit 11 is connected to steering valve 8 via safety valve 12. Safety valve 12 establishes or interrupts the hydraulic flow path between hydraulic circuit 11 and steering valve 8.

[0029] Therefore, under "normal" conditions, it is equipped with a basis Figure 1 The vehicle is steered only under the control of steering valve 8, which is actuated by the rotation of steering wheel 4. Only in emergency situations, such as when the pressure of pump 2 is insufficient to actuate steering motor 10, a connection is established between pumping unit 7 and steering motor 10 via safety valve 12 and hydraulic circuit 11, so that the rotation of steering wheel 4 drives hydraulic fluid to steering motor 10 in a controlled manner.

[0030] More details about steering system 1 are as follows: Figure 2 As shown. Identical components are indicated by the same reference numerals. Figure 2 Steering sensor 5 is not shown.

[0031] The pumping unit 7 includes two ports, L1 and R1; these two ports serve as the input and output ports of the pumping unit 7, depending on the rotation direction of the steering wheel 4. The two ports L1 and R1 are connected to the hydraulic circuit 11. The hydraulic circuit 11 includes a variable throttle orifice 13 arranged in the safety valve 12. Figure 2 The location of safety valve 12 is shown, where the hydraulic connection between hydraulic circuit 11 and steering valve 8 is interrupted. In this case, a loop is formed between the two ports L1, R1 of pumping unit 7, which includes the flow resistance generated by throttle orifice 13, so the hydraulic fluid is only "circulated pumped" and generates a counter-torque related to the torque used to rotate steering wheel 4.

[0032] It should be noted that the orifice 13 can be a variable orifice. The flow resistance of the orifice 13 can be changed by altering the position of the safety valve 12. For this purpose, the safety valve 12 can, for example, be equipped with a valve core that can be displaced within the housing. The orifice 13 can be formed by corresponding openings in the valve core and the housing, such that the displacement of the valve core within the housing alters the flow resistance of the orifice 13.

[0033] Safety valve 12 can be electrically actuated. For this purpose, it includes one or more solenoids 14, 15, which can be used, for example, to displace the valve spool within the housing. In an alternative embodiment, safety valve 12 can be hydraulically actuated.

[0034] The actuation of safety valve 12 can, for example, be automatic when the pressure of pump 2 drops below a predetermined level.

[0035] The hydraulic circuit 11 also includes a steering feel valve 16, which is connected to the supply port P and the return port T. The steering feel valve 16 can be used, for example, for vehicle self-centering, i.e., for electrical following of the steering wheel position. Furthermore, it can be used to change the pressure conditions in the hydraulic circuit 11. For example, when the supply port P is connected to the left-hand port L1 of the pumping unit 7 and the steering wheel 4 is rotated to the left, the driver must generate greater torque to rotate the steering wheel 4. On the other hand, when the driver rotates the circular steering wheel 4 to the right-hand side under the same conditions, he requires less torque than before. Therefore, the steering feel valve 16 can alter the vehicle feedback experienced by the driver at the steering wheel 4.

[0036] Furthermore, the hydraulic circuit 11 includes a pressure relief valve assembly in the pipeline 17 connecting the two ports L1 and R1 of the pumping unit 7. The pressure relief valve assembly includes two pressure relief valves 18 and 19. Each pressure relief valve 18 and 19 is pressure-loaded in the opening direction by the pressure at the port L1 or R1 of the pumping unit 7 connected to the corresponding pressure relief valve. In the closing direction, the pressure relief valves 18 and 19 are pressure-loaded by the pressure at their respective outlets. Additionally, each pressure relief valve 18 and 19 is bridged by check valves 20 and 21, which open in a direction away from the other pressure relief valve 19 or 18.

[0037] Therefore, a pressure relief valve assembly with two pressure relief valves 18 and 19 can be used to limit the maximum torque that must be overcome by the steering wheel 5. When this torque is exceeded, for example when the pressure at the left port L1 of the pumping unit 7 is too high, the pressure relief valve 18 opens, and fluid is allowed to escape through the check valve 21 of the other pressure relief valve 19 to the right port R1 of the pumping unit 7.

[0038] In addition, it can be used to limit the pressure that can simulate the position of the end stop steering wheel.

[0039] exist Figure 1 The diagram shows a releasable connector 22 that connects the column 6 of the steering wheel 4 to the pumping unit 7. Thus, for example, the pumping unit 7 can be actuated by the flow rate through the hydraulic circuit 11 without rotating the steering wheel 4.

[0040] Hydraulic circuit 11 can also be used to supply additional hydraulic flow to the working ports L and R of the working port device, for example, to increase steering speed. For this purpose, safety valve 12... Figure 2 The closed position shown is moved to the open position, in which a connection is established between the hydraulic circuit 11 and the steering valve 8.

[0041] The steering valve 8 includes safety valve ports L2 and R2 that are connected to the safety valve 12.

[0042] The steering valve 8 includes a check valve assembly with check valves 23-29. The steering valve 8 includes a main fluid path assembly represented by two flow paths 32 (30), 33 (31) for each direction of steering (one flow path leads to the left working port L and returns from the right working port R, while the other flow path leads to the right working port R and returns from the left working port L). The check valves 23-29 of the check valve assembly allow hydraulic fluid to flow from safety valve 12 to one of the working ports and back to safety valve 2 from the other working port, depending on the valve position of the steering valve 8.

[0043] Which check valves are active depends on the position of the diverting valve 8. Safety valve port L2 connects to check valve 23, which is open away from safety valve port L2, or to check valve 25, which is open in the direction towards safety valve port L2. The same applies to the other safety valve port R2, which is connected to check valves 24 and 26, depending on the position of the diverting valve 8. In the neutral position of the diverting valve 8, the left safety valve port L2 connects to check valve 27, and the right safety valve port R2 connects to check valve 28. Both check valves 27 and 28 are closed by the pressure at their respective safety valve ports L2 and R2. Furthermore, the connection between the two check valves 27 and 28 connects to another check valve 29, which is closed in the direction towards the return port T.

[0044] Figure 3 A second embodiment of a portion of the hydraulic steering system 1 is shown. Utilizing... Figure 1 and Figure 2 The same reference numerals in the figures indicate the same elements.

[0045] The pumping unit 7' is in the form of a hydraulic steering unit, including a measuring motor 35 and a steering valve 34. The steering valve 34 includes a valve core and a sleeve in a manner known in the art, arranged within a housing and rotatable relative to each other. The valve core is connected to the column 6 of the steering wheel. When the steering wheel rotates, the valve core rotates relative to the sleeve, opening some orifices and closing others. Furthermore, the column 6 is connected to the measuring motor 35, which in this embodiment functions as a hydraulic pump. This pumping unit 7' is also referred to as a "steering gear".

[0046] Safety valve 12 is positioned between measuring motor 35 and directional valve 34. Therefore, when the safety valve is not "activated," i.e., in the position shown in the figure where measuring motor 35 is short-circuited, safety valve 12 is only used to generate flow resistance in the hydraulic circuit.

Claims

1. A steering system (1), comprising: The device comprises a supply port device with a supply port (P) and a return port (T), a steering command device with a steering sensor (5), a controller (9) connected to the steering sensor (5), an electro-hydraulic steering valve (8) controlled by the controller (9), and a working port device with two working ports (L, R), wherein the working port device is connected to the supply port device via the steering valve (8), and the steering command device includes a steering wheel (4) connected to a hydraulic pumping unit (7, 7'), the pumping unit (7, 7') being part of a hydraulic circuit (11) having a device for generating flow resistance, the hydraulic circuit (11) being connected to the steering valve (8) via a safety valve (12), the safety valve (12) establishing or interrupting the hydraulic flow path between the hydraulic circuit (11) and the steering valve (8). The safety valve (12) is connected to the working port device via the steering valve (8).

2. The steering system according to claim 1, characterized in that, The device for generating the flow resistance has a variable throttling orifice (13).

3. The steering system according to claim 1, characterized in that, The safety valve (12) establishes a hydraulic connection between the hydraulic circuit (11) and the working port device in the event of a lack of pressure at the supply port (P).

4. The steering system according to any one of claims 1 to 3, characterized in that, The device for generating the flow resistance is arranged at least partially in the safety valve (12).

5. The steering system according to claim 4, characterized in that, The flow resistance of the device used to generate the flow resistance depends on the valve position of the safety valve (12).

6. The steering system according to any one of claims 1 to 3, characterized in that, The hydraulic circuit (11) includes a steering feel valve (16) connected to the supply port device.

7. The steering system according to any one of claims 1 to 3, characterized in that, The hydraulic circuit (11) includes a pressure relief valve device in the pipeline (17) connecting the two ports (L1, R1) of the pumping unit (7, 7').

8. The steering system according to claim 7, characterized in that, The pressure relief valve assembly includes two pressure relief valves (18, 19), each of which is controlled by a pressure differential and is bridged by a check valve (20, 21) that opens in a direction away from the other pressure relief valve.

9. The steering system according to any one of claims 1 to 3, characterized in that, The steering command device includes a steering command device in addition to the steering wheel, wherein the steering wheel (4) is connected to the pumping unit (7, 7') via a releasable coupling (22).

10. The steering system according to any one of claims 1 to 3, characterized in that, The steering valve (8) includes safety valve ports (L2, R2) connected to the safety valve (12), wherein the steering valve (8) includes a main fluid path (30, 31; 32, 33) device for each steering direction and a check valve device (23-29), the check valve device (23-29) allowing hydraulic fluid to flow from the safety valve (12) to one of the two working ports (L, R) and back to the safety valve (12) from the other working port, depending on the valve position of the steering valve (8).

11. The steering system according to claim 10, characterized in that, In the neutral position of the steering valve (8), the check valve device (23-29) disconnects the connection between the safety valve port (L2, R2) and the return port (T).

12. The steering system according to any one of claims 1 to 3, characterized in that, The safety valve (12) includes actuation devices (14, 15) that allow remote actuation of the safety valve (12).

13. The steering system according to any one of claims 1 to 3, characterized in that, The pumping unit (7) is a measuring motor.

14. The steering system according to any one of claims 1 to 3, characterized in that, The pumping unit (7') is a hydraulic pump.

15. The steering system according to claim 14, characterized in that, The hydraulic pump is in the form of a steering gear.

Images