COMPONENT OPERATION / Priority Valve OPERATION When steering is in neutral: 1. Pressure oil from the main pump flows to port P and is divided into three directions in the inner passage of the spool. 2. When the steering valve is in neutral (the steering wheel is not operated), pressure oil from port CF to the steering valve is blocked by the steering valve so that pressure in port CF increases. 3. As the pressure in port CF increases, pressure oil from the main pump flows to chamber A and chamber B respectively through orifice A and orifice B.
4. As pressure oil in chamber B flows to the hydraulic oil tank through port LS and the steering valve, pressure in chamber B becomes lower than that in chamber A due to orifice B. 5. When the pressure difference overcomes the spring force, the spool moves to the left. 6. Therefore, pressure oil from the main pump flows to the control valve through port EF.
Steering Valve Port P (From Main Pump) Chamber B
Spring
Spool Priority Valve Chamber A
Port LS (To Steering Valve)
Orifice C
Orifice B
Port EF (To Control Valve) Port CF (To Steering Valve)
Orifice A
T487-03-01-007
Port P (From Main Pump)
Port EF (To Control Valve)
T3-1-3
T487-03-01-003
