Hydraulic steering system comprising a first and a second steering member and vehicle comprising a hydraulic steering system

• US 8,606,463 B2
• Filed: 11/18/2008
• Issued: 12/10/2013
• Est. Priority Date: 09/30/2008
• Status: Expired due to Fees

• Current Assignee: Volvo Construction Equipment AB (Volvo AB)
• Original Assignee: Volvo Construction Equipment AB (Volvo AB)
• Inventors: Bichler, Olivier, Lastre, Frederic
• Primary Examiner(s): Trammell, James
• Assistant Examiner(s): MELTON, TODD M
• Application Number:
  US13/121,687
• Publication Number:
  US 20120109459A1
• Time in Patent Office: 1,848 Days
• Field of Search: 701/41, 180/441, 180/422, 180/421
• US Class Current: 701/41
• CPC Class Codes: B62D 1/22 Alternative steering-control elements, e.g. for teaching purposes
• CPC Class Codes: B62D 5/09 characterised by means for actuating valves

Abstract

A hydraulic steering system for a vehicle includes a first steering member and a second steering member, wherein the first steering member is operationally connected to a first steering valve unit including a first steering valve, and wherein a priority valve controls a flow of a hydraulic fluid to one or more steering cylinders which provide for steering of the vehicle in a desired steering direction, wherein the priority valve gives priority to steering with the first steering member over the steeling with the second steering member. A second steering valve is provided functionally operable in series with a proportional flow control valve, wherein the second steering valve and/or the proportional flow control valve are controlled at least by the second steering member.

Claims

1. A hydraulic steering system for a vehicle, comprising a first steering member and a second steering member, wherein the first steering member is operationally connected to a first steering valve unit comprising a first steering valve, and wherein a priority valve controls a flow of a hydraulic fluid to one or more steering cylinders which provide for steering of the vehicle in a desired steering direction, wherein the priority valve gives priority to steering with the first steering member over steering with the second steering member, wherein a second steering valve unit is provided comprising a second steering, valve, wherein the priority valve is connected to the second steering valve unit by a hydraulic fluid load line, and the second steering valve is functionally operable in series with a proportional flow control valve with respect to the hydraulic fluid load line, wherein in a first operational mode when the first steering member is not operated the second steering valve and/or the proportional flow control valve are controlled at least by the second steering member and in a second operational mode the second steering valve unit and the first steering valve unit are used simultaneously when the first steering member is operated.

2. The steering system according to claim 1, wherein the second steering valve is controlled by a first control signal and the proportional flow control valve is controlled by a second control signal corresponding to an actuation of the second steering member, and whereby first control signal, second control signal and output signal of the steering member preferably is one of an electric signal or hydraulic pilot signal or electromagnetic signal.

3. The steering system according to claim 2, wherein the first control signal is an ON/OFF signal which can be applied to the second steering valve responsive to the second steering member for selecting the steering direction.

4. The steering system according to claim 2, wherein the second control signal is one of a PWM-signal, PFM-signal or PSM-signal which can be applied to the proportional flow control valve responsive to the second steering member for controlling a steering characteristic.

5. The steering system according to claim 1, wherein the second steering valve and the proportional flow control valve are connected in series with respect of the flow of the hydraulic fluid.

6. The steering system according to claim 1, wherein the second steering valve and the proportional flow control valve form a valve unit which is connected in parallel to the first steering valve unit which in turn is responsive to the first steering member.

7. The steering system according to claim 1, wherein the second steering member is integrated in a joystick.

8. The steering system according to claim 7, wherein the second steering member is one of a thumb slider, thumb wheel, a hat switch being operable with one'"'"'s thumb, preferably arranged on an upper portion of the joystick.

9. The steering system according to claim 1, wherein a pressure sensor is connected to a hydraulic fluid load line between the priority valve and the first steering calve unit, wherein the pressure sensor is coupled to the second steering member so that activation of the second steering unit is controllable depending on an output signal of the pressure sensor.

10. The steering system according to claim 1, wherein a pressure sensor is connected to a hydraulic fluid load line between the priority valve and the first steering valve unit, wherein the pressure sensor is coupled to the second steering member so that control signals applied to the second steering valve and/or the proportional flow control valve can be modulated according to the actual pressure signal.

11. The steering system according to claim 1, wherein an electronic control unit is provided for controlling the second steering valve and/or the proportional flow control valve.

12. The steering system according to claim 1, wherein a steering sensor is provided for sensing a steering direction and/or a speed of operation of the first steering member.

13. A vehicle comprising a hydraulic steering system according to claim 1.

14. A method for controlling a hydraulic steering, system for a vehicle, comprising

providing a first steering member operationally connected to a first steering valve unit and a second steering member,

controlling, via a priority valve, a flow of a hydraulic fluid to one or more steering cylinders which provide for steering the vehicle in a desired steering direction, wherein the priority valve gives priority to steering with the first steering member over steering with the second steering member,

providing a second steering valve unit comprising a second steering valve, wherein the priority valve is connected to the second steering valve unit by a hydraulic fluid load line, and the second steering valve is functionally operable in series with a proportional flow control valve with respect to the hydraulic fluid load line,

operating the steering system in a first operational mode in which, when the first steering member is not operated the second steering valve and/or the proportional flow control valve are controlled at least by the second steering member, and

operating the steering system in a second operational mode in which the second steering valve unit and the first steering valve unit are used simultaneously when the first steering member is operated.

15. The method according to claim 14, comprising controlling the second steering valve by an ON/OFF signal for steering the vehicle in a desired steering direction.

16. The method according to claim 14, comprising controlling the proportional flow control valve by one of a PWM-signal, PFM-signal or PSM-signal which can be applied to the proportional flow control valve responsive to the sew steering member for controlling a steering characteristic.

17. The method according to claim 14, comprising, if a steering movement of the first steering member is detected, directing, via the priority valve flow of a part of the hydraulic fluid as a function of at least one pressure signal in a hydraulic fluid load line between the proportional valve and the first steering valve unit.

18. The method according to claim 17, comprising switching off the second steering valve unit if pressure in the hydraulic fluid load line is equal to or above a predetermined pressure limit.

19. The method according to claim 14, comprising triggering the proportional flow control valve if a steering action of the second steering member is detected and no steering is performed with the first steering, member, wherein simultaneously the second steering valve is controlled to provide a desired steering direction indicated by a steering action of the second steering member.

20. The method according to claim 14, comprising preventing selection of a steering mode employing the second steering member at a travel speed of the vehicle above a speed threshold value.

21. The method according to claim 14, comprising preventing a travel speed of the vehicle above a speed threshold value upon selecting a steering mode employing the second steering member.

22. The method according to claim 14, comprising preventing selection of a steering mode employing the second steering member upon selecting a gear which is not compatible with the steering mode employing, the second steering member.

23. The method according to claim 14, comprising preventing selection of a near which is not compatible with the steering mode employing the second steering member upon selecting a steering mode employing the second steering member.

24. The method according to claim 14, comprising in a second operational mode, triggering the second steering valve unit if a steering action of the first steering member is detected by measuring the pressure on a load signal line and/or by measuring at least one of detecting steering, steering direction or steering speed, wherein the second steering valve unit and the first steering valve unit are providing simultaneously the flow of hydraulic fluid to the steering cylinder, and thus enhancing the effect of the action of the operator on the first steering member.

25. Computer comprising a computer program code adapted to perform a method or for use in a method according to claim 14.

26. The computer according to claim 25, wherein the computer is adapted to be connected to the internet and download the computer program code to a control unit or one of its components.

27. Computer program product stored on a non-transitory computer readable medium, comprising a program code for use in a method according to claim 14.