II - 51
WSM Minor Change II Service Engineering Section
i. Proportional control solenoid valve (S/P valve)
1. Outline
This valve is the combination of electro magnetic solenoid valve and hydraulic reducing valve.
Ordinally solenoid valve is controlled ON-OFF by battery 12 V direct current. But this valve is con-
trolled by the PWM (pulse width modulation) current supplied from the micro computer controller
incorporated in the meter panel.
Valve spool function is basically the reducing valve same as the hydraulic pilot control valve, nor-
mally used for the lever control. Difference is as follows.
The hydraulic pilot control valve regulates the pilot pressure, balancing to the operator’s manual
force. This S/P valve is regulated by the PWM current. In either case, this pilot pressure is so-
called the secondary pilot pressure to control the spool stroke of the main control valve.
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