Steering device for wheel loader

Patent metadata

Field	Value
Publication number	US-9309647-B2
Application number	US-201514726670-A
Country	US
Kind code	B2
Filing date	Jun 1, 2015
Priority date	Mar 29, 2012
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

A steering device for a wheel loader includes a handle for steering, a lever for steering, a steering cylinder, a steering valve that controls a direction of operating fluid to the steering cylinder, and a pump that supplies operating fluid to the steering cylinder via the steering valve. The steering device further includes a handle control valve that controls the supply direction of the operating fluid according the handle, a lever electromagnetic control valve that controls the supply direction of operating fluid according to the lever, and a handle prioritization valve that shuts off a pilot hydraulic pressure supplied from the lever electromagnetic control valve to the steering valve according to a pressure produced by operating fluid flowing through the handle control valve when the handle is operated. Communication between the lever electromagnetic control valve and the steering valve is allowed when only the lever electromagnetic control valve is operated.

First claim

What is claimed is:

1. A steering device for a wheel loader in which a front frame and a rear frame are pivotably coupled in a horizontal direction, the steering device comprising:
a handle operated by rotation for steering;
a lever operated by tilting for steering;
a steering cylinder configured to pivot the front frame in relation to the rear frame by expansion and contraction;
a steering valve configured to control a supply direction of operating fluid to the steering cylinder with pilot hydraulic pressure;
a pump configured to supply operating fluid to the steering cylinder via the steering valve;
a handle control valve configured to supply pilot hydraulic pressure in order to control the supply direction to the steering valve according to a rotation operation of the handle;
a lever electromagnetic control valve configured to supply pilot hydraulic pressure in order to control the supply direction to the steering valve according to a tilting operation of the lever;
a handle prioritization valve configured to shut off the pilot hydraulic pressure supplied from the lever electromagnetic control valve to the steering valve according to a differential pressure or an absolute pressure in a hydraulic circuit produced due to operating fluid flowing through the handle control valve when the handle is operated;

a left pilot oil passage provided between the handle control valve and the steering valve; and
a right pilot oil passage provided between the handle control valve and the steering valve;
the handle prioritization valve including:
a priority control valve disposed between the handle control valve and the lever electromagnetic control valve and the steering valve, the priority control valve including
a handle stage that allows communication between the handle control valve and the steering valve and that shuts off communication between the lever electromagnetic control valve and the steering valve, and
a lever stage that shuts off communication between the handle control valve and the steering valve and that allows communication between the lever electromagnetic control valve and the steering valve; and

a switching valve that switches the priority control valve to the handle stage when operating fluid flows to the handle control valve, and that switches the priority control valve to the lever stage when operating fluid flows only to the lever electromagnetic control valve.

2. The steering device according to claim 1 , wherein:
an output port of the switching valve is connected to a pilot port of the priority control valve.

3. The steering device according to claim 2 , wherein
the left and right pilot oil passages are connected to a pilot port of the switching valve via a first shuttle valve.

4. The steering device according to claim 1 , wherein
the left and right pilot oil passages are connected to a pilot port of the switching valve via a first shuttle valve.

5. The steering device according to claim 1 , further comprising
left and right lever pilot oil passages connected between input ports of the priority control valve and output ports of the lever electromagnetic control valve.

6. The steering device according to claim 5 , wherein
the left and right lever pilot oil passages are connected to an input port of the switching valve via a first shuttle valve.

7. The steering device according to claim 6 , wherein
the left and right pilot oil passages are connected to a pilot port of the switching valve via a second shuttle valve.

8. The steering device according to claim 6 , wherein
an output port of the switching valve is connected to a pilot port of the priority control valve.

9. The steering device according to claim 8 , wherein
the left and right pilot oil passages are connected to a pilot port of the switching valve via a second shuttle valve.

Assignees

• Komatsu Mfg Co Ltd

Inventors

• Imanishi Kota
• Chikugo Hiroyuki
• Hori Shuuji
• Akashi Mitsumasa
• Hasebe Akira
• Akushichi Shuki
• Takamatsu Nobumasa

Classifications

• E02F9/2285

  Pilot-operated systems · CPC title

• B62D5/28

  for pivoted bogies · CPC title

• B62D5/20

  specially adapted for particular type of steering gear or particular application (steering gears per se B62D3/00; steering linkages not characterised by being power-assisted or power-driven B62D7/00) · CPC title

• B62D1/22

  Alternative steering-control elements, e.g. for teaching purposes · CPC title

• B62D12/00

  Steering specially adapted for vehicles operating in tandem or having pivotally connected frames (steering endless tracks or the like B62D11/00; steering specially adapted for trailers B62D13/00) · CPC title