Komatsu WA250-3 Wheel Loader Service Manual

Table of Content (Shop Manual)

• General
• Structure and Functions
• Testing and Adjusting
• Disassembly and Assembly
• Maintenance Standard
• Others

Manual Extract When parking brake lever is pulled (OFF to ON):

Outline

The steering valve is connected directly to the shaft of the steering wheel. It switches the flow of oil from the steering pump to the left and right steering cylinders to determine the direction of travel of the machine.

The steering valve, broadly speaking, consists of the following components: rotary type spool (3) and sleeve (5), which have the function of selecting the direction, and the Gyrator set (a combination of rotor (8) and stator (9)), which acts as a hydraulic motor during normal steering operations, and as a hand pump (in fact, the operating force of the steering wheel is too high, so it cannot be operated) when the steering pump or engine have failed and the supply of oil has stopped.
Structure

Spool (3) is directly connected to the drive shaft of the steering wheel, and is connected to sleeve (5) by center pin (4) (it does not contact the spool when the steering wheel is at neutral) and centering spring (12).

The top of drive shaft (6) is meshed with center pin (4), and forms one unit with sleeve (5), while the bottom of the drive shaft is meshed with the spline of rotor (8) of the Gyrator.

There are four ports in valve body (2), and they are connected to the pump circuit, tank circuit, and the circuits at the head end and bottom end of the steering cylinders. The pump port and tank port are connected by the check valve inside the body. If the pump or engine fail, the oil can be sucked in directly from the tank by this check valve.