Power steering system for a working machine

Patent metadata

Field	Value
Publication number	US-12509144-B2
Application number	US-202017927946-A
Country	US
Kind code	B2
Filing date	Jun 8, 2020
Priority date	Jun 8, 2020
Publication date	Dec 30, 2025
Grant date	Dec 30, 2025

Abstract

The invention relates to a power steering system for a working machine, said power steering system comprising at least one steering cylinder comprising two compartments separated by a piston, a tank, a steering unit comprising a steering valve and a metering device, for supplying one compartment of the steering cylinder with a metered liquid flow, a hydraulic pump for pumping liquid from the tank to the steering unit through a supply line (SL), a return line (RL) through which the liquid flows back to the tank, a recirculation line connecting the RL to the SL, a check valve being arranged on said recirculation line to prevent liquid from flowing from the SL to the RL, two control lines, respectively connecting the steering unit to the two compartments and a liquid accumulator connected through a branch to the RL. A relief valve is arranged on the RL between the tank and an accumulator connection point.

First claim

The invention claimed is:

1 . A power steering system for a working machine, said power steering system comprising:
at least one steering cylinder, comprising two compartments separated by a piston, a liquid tank, a steering unit comprising a steering valve and a metering device, for supplying one compartment of the steering cylinder with a metered flow of liquid, a hydraulic pump, for pumping liquid from the liquid tank to the steering unit through a supply line, a return line through which the liquid can flow from the steering unit back to the liquid tank, a recirculation line connecting the return line to the supply line, a check valve being arranged on said recirculation line to prevent liquid from flowing from the supply line to the return line, two control lines, respectively connecting the steering unit to the two compartments of the at least one steering cylinder, a liquid accumulator connected through a branch to the return line; and a relief valve arranged on the return line between the liquid tank and a connection point of the liquid accumulator, wherein the relief valve enables the liquid to flow from the steering unit to the liquid tank only when a pressure threshold has been reached.

2 . The power steering system according to claim 1 , wherein the relief valve is a spring-loaded check valve.

3 . The power steering system according to claim 1 , wherein a liquid filter is arranged on the return line between the liquid tank and the connection point of the accumulator between the liquid tank and the relief valve.

4 . The power steering system according to claim 1 , wherein the hydraulic pump is driven by an electric motor.

5 . The power steering system according to claim 1 , wherein the steering cylinder is a double acting cylinder.

6 . The power steering system according to claim 1 , wherein an additional check valve is arranged on the supply line for preventing liquid from flowing from the steering unit back to the pump.

7 . The power steering system according to claim 1 , wherein the volume of the accumulator is superior or equal to the volume of the steering cylinder.

8 . The power steering system according to claim 1 , wherein the steering valve is a rotary valve comprising an input shaft connected to a steering wheel.

9 . The power steering system according to claim 8 , wherein the metering device is a gerotor consisting of an inner rotor and an outer rotor and the inner rotor is mechanically linked to the input shaft.

10 . The power steering system according to claim 1 , wherein the system further includes a priority valve designed so that the hydraulic pump supplies the power steering system as a priority.

11 . A working machine, wherein the working machine comprises a power steering system according to claim 1 .

12 . The working machine according to claim 11 , wherein the working machine includes only one hydraulic pump.

13 . The working machine according to claim 11 , wherein the working machine includes a full electric powertrain.

14 . The working machine according to claim 11 , wherein the working machine is a wheel loader.

15 . The working machine according to claim 11 , wherein the working machine is an articulated wheel loader.

16 . The working machine according to claim 11 , wherein a liquid filter is arranged on the return line between the liquid tank and the connection point of the accumulator between the liquid tank and the relief valve.

17 . The working machine according to claim 11 , wherein the hydraulic pump is driven by an electric motor.

18 . The working machine according to claim 11 , wherein an additional check valve is arranged on the supply line for preventing liquid from flowing from the steering unit back to the pump.

19 . The working machine according to claim 11 , wherein the system further includes a priority valve designed so that the hydraulic pump supplies the power steering system as a priority.

Assignees

• Volvo Constr Equip Ab

Inventors

• Hahn Christian

Classifications

• B62D5/097

  gerotor type · CPC title

• B62D5/07

  Supply of pressurised fluid for steering also supplying other consumers {; control thereof} · CPC title

• B62D5/32 Primary

  for telemotor systems · CPC title