Hydraulic steering control system

• US 9,878,737 B2
• Filed: 02/20/2015
• Issued: 01/30/2018
• Est. Priority Date: 02/20/2015
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: McIlheran, Carl, Mork, David A., Mather, Daniel T., Johnson, Christopher W., Hudson, Michael D.
• Primary Examiner(s): Rocca, Joseph M
• Assistant Examiner(s): Williams, Maurice L
• Application Number:
  US14/627,887
• Publication Number:
  US 20160244090A1
• Time in Patent Office: 1,075 Days
• 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: B62D 5/075 using priority valves
• CPC Class Codes: B62D 5/093 Telemotor driven by steering wheel movement hydraulic steering gear B62D3/14
• CPC Class Codes: F15B 2211/212 the pressure sources being accumulators

Abstract

A hydraulic fluid supply portion of a hydraulic steering control system may include an accumulator holding a quantity of pressurized steering fluid, and a priority valve. The priority valve may have a priority supply inlet port fluidly connected to the accumulator for receiving pressurized steering fluid from the accumulator, and a priority supply outlet port fluidly connected to a steering flow amplifier circuit. The priority valve may have a normally open position with a minimal pressure drop between the priority supply inlet port and the priority supply outlet port, and a flow restriction position where fluid flow between the ports is restricted. A load signal line from a steering control circuit to the priority valve may bias the priority valve toward the normally open position in response to an operator steering command to provide pressurized steering fluid to the steering flow amplifier circuit.

Claims

1. A hydraulic steering control system comprising:

a steering cylinder;

a steering flow amplifier circuit in fluid communication with the steering cylinder to provide pressurized steering fluid to actuate the steering cylinder;

a steering control circuit in fluid communication with the steering flow amplifier circuit to provide pilot signals to the steering flow amplifier circuit indicative of a direction and speed with which to provide pressurized steering fluid to actuate the steering cylinder; and

a hydraulic fluid supply portion comprising;

an accumulator holding a quantity of pressurized steering fluid and having an accumulator supply conduit, and

a priority valve having a priority supply inlet port fluidly connected to the accumulator supply conduit for receiving pressurized steering fluid from the accumulator, a priority supply outlet port fluidly connected to an amplifier circuit supply inlet port of the steering flow amplifier circuit, wherein the priority valve has a normally open position where pressurized fluid is directed from the priority supply inlet port to the priority supply outlet port with a minimal pressure drop and a flow restriction position where pressurized fluid flow from the priority supply inlet port to the priority supply outlet port is restricted by a maximum restriction amount, wherein a load signal line fluidly connects the steering control circuit to the priority valve to provide a load signal indicative of an amount of pressurized steering fluid to be provided to the steering flow amplifier circuit in response to an operator steering command, and wherein the load signal biases the priority valve toward the normally open position; and

wherein the steering flow amplifier circuit comprises;

a directional control valve having a directional valve supply port fluidly connected to the amplifier circuit supply inlet port, a steering cylinder port fluidly connected to the steering cylinder, a control fluid passage in fluid communication with the steering control circuit, a fluid combiner passage, a directional control spool having a first directional spool end and a second directional spool end and being movable between a neutral position at which the directional valve supply port is blocked from the steering cylinder port and the control fluid passage is blocked from the fluid combiner passage and an infinitely variable operating position at which a first variable flow path is established between the control fluid passage and the fluid combiner passage and a second variable flow path is established between the directional valve supply port and the steering cylinder port;

a check valve combining the fluid in the fluid combiner passage with the fluid in the steering cylinder port when the direction control spool is at an operating position;

a directional valve pilot passage connected to the control fluid passage and the first directional spool end; and

a spring for resisting movement of the directional control spool toward the operating position.

2. The hydraulic steering control system of claim 1, wherein the priority valve comprises a priority spring biasing the priority valve toward the normally open position.

3. The hydraulic steering control system of claim 1, wherein the priority valve comprises a priority signal passage placing the priority supply outlet port in fluid communication with the priority valve to bias the priority valve toward the flow restriction position.

4. The hydraulic steering control system of claim 1, wherein the priority valve comprises:

a priority valve spool having a first end and a second end and being slidable between the normally open position and the flow restriction position;

a priority spring engaging the first end of the priority valve spool and biasing the priority valve spool toward the normally open position; and

a priority signal passage placing the priority supply outlet port in fluid communication with the second end of the priority valve spool to bias the priority valve toward the flow restriction position, wherein the load signal line is in fluid communication with the first end of the priority valve spool so that the load signal biases the priority valve spool toward the normally open position.

5. The hydraulic steering control system of claim 1, wherein the hydraulic fluid supply portion comprises a pump having a pump discharge conduit fluidly connected to the accumulator and discharging pressurized steering fluid into the accumulator.

6. The hydraulic steering control system of claim 5, wherein the hydraulic fluid supply portion comprises a fluid level sensor installed at the accumulator and measuring an amount of pressurized steering fluid in the accumulator, wherein the pump is actuated to replenish the fluid in the accumulator when the fluid level sensor indicates that the amount of fluid in the accumulator is less than a minimum accumulator fluid amount.

7. The hydraulic steering control system of claim 1, wherein the amount of restriction between the priority supply inlet port to the priority supply outlet port is infinitely variable from a minimum restriction amount to the maximum restriction amount as the priority valve moves from the normally open position to the flow restriction position.

8. The hydraulic steering control system of claim 1, wherein the steering control circuit comprises a steering control valve having a steering fluid inlet port, and wherein the load signal line places the steering fluid inlet port in fluid communication with the priority valve when the steering control circuit provides pilot signals to the steering flow amplifier circuit in response to the operator steering command.

9. The hydraulic steering control system of claim 1, wherein the steering flow amplifier circuit comprises a directional valve signal passage for placing the fluid combiner passage in fluid communication with the second directional spool end.