Assist Control Valve
The assist control valve unit consists of the assist control valve, which is controlled by the power steering speed sensor, and the pressure control valve. The pressure control valve and the assist control valve, located between the pump and the speed sensor, control the fluid passage to the rotary valve. The fluid pressure is fed to the assist control valve. The standard pressure is drawn out by the rotation of the speed sensor, producing a pressure gap between the pressure control valve and the assist control valve when the standard pressure fluid passes the sensor orifice. The pressure gap, which changes with the fluid volume drawn (that is, it changes with vehicle speed), is referred to as the power steering speed sensor signal pressure. The assist control valve operates according to this speed sensor signal pressure to change the fluid passage to the high speed rotary valve. See Fig 1 .