Closed circuit steering circuit for mobile vehicle

• US 6,923,290 B1
• Filed: 05/27/2004
• Issued: 08/02/2005
• Est. Priority Date: 09/11/2003
• Status: Expired due to Fees

• Current Assignee: Sauer-Danfoss Incorporated (Danfoss A/S)
• Original Assignee: Sauer-Danfoss Incorporated (Danfoss A/S)
• Inventors: MacLeod, Ian J. C., Sporrer, Rick J.
• Primary Examiner(s): Hurley, Kevin
• Application Number:
  US10/855,303
• Time in Patent Office: 432 Days
• Field of Search: 180/403, 180/417, 180/421, 180/422, 180/423
• US Class Current: 180/403
• CPC Class Codes: B62D 3/14 hydraulic
• CPC Class Codes: B62D 5/065 characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
• CPC Class Codes: F15B 11/0445 with counterbalance valves, e.g. to prevent overrunning or for braking
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/27 Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/30505 Non-return valves, i.e. check valves
• CPC Class Codes: F15B 2211/50545 using braking valves to maintain a back pressure
• CPC Class Codes: F15B 2211/5059 using double counterbalance valves
• CPC Class Codes: F15B 2211/5153 being connected to an output member and a directional control valve
• CPC Class Codes: F15B 2211/613 Feeding circuits
• CPC Class Codes: F15B 2211/615 Filtering means
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6355 having valve means
• CPC Class Codes: F15B 2211/7054 Having equal piston areas
• CPC Class Codes: F15B 2211/76 Control of force or torque of the output member

Abstract

A closed-circuit pump is provided that receives input from a steering unit in order to drive a steering cylinder. The closed-circuit pump is preferably a proportional bi-directional pump. The steering unit includes a steering wheel or similar device controlled by an operator. In one embodiment, the steering unit is a conventional hydraulic system that includes a servo pump. In another embodiment, the steering unit is an electronic displacement control system. The steering cylinder engages with a steering assembly to perform the steering function by physically turning the wheels of the vehicle. The inlet of the steering cylinder includes a counterbalance valve, which prevents flow into the steering cylinder when there is no steering input from the operator.

Claims

1. A hydraulic steering system for vehicles comprising:

an electronic displacement control unit including a steering element;

a closed-circuit pump in communication with the electronic displacement control unit wherein the electronic displacement control unit actuates the closed-circuit pump and the pump is a proportional bi-directional pump; and

at least one steering cylinder in communication with the closed-circuit pump wherein the closed-circuit pump actuates the steering cylinder to control the steering of the vehicle.

2. The hydraulic steering system of claim 1 wherein the steering cylinder includes at least one counterbalance valve along the inlet to the steering cylinder to prevent actuation of the steering cylinder when there is no steering input from the operator.

3. The hydraulic steering system of claim 1 wherein the steering element comprises a steering wheel with electronic encoding devices that relays an electronic signal to the electronic displacement control unit.

4. The hydraulic steering system of claim 1 wherein the steering element comprises a joystick that relays an electronic signal to the electronic displacement control unit.