COMPONENT OPERATION / Priority Valve

from TCM 820-3 Wheel Loader Technical Manual SEW-62M-MAE - PDF DOWNLOAD

COMPONENT OPERATION / Others

When steering cylinder is at stroke end:

1. Pressure oil to port P in the steering valve is divided inside the spool. One flows to the gerotor. The other flows to port LS in the priority valve and acts on chamber B through orifice C.

2. As pressure in port P increases when the steering cylinder reaches the stroke end, pressure in chamber B in the priority valve also increases through port LS.

3. When pressure in chamber B increases more than the set pressure, the relief valve in the priority valve is operated and pressure oil acting on chamber B flows to the hydraulic oil tank through the relief valve.

4. As pressure oil in chamber B flows to the hydraulic oil tank when the relief valve is operated, the pressure difference between chamber A and chamber B occurs due to orifice B.

5. When the pressure difference overcomes the spring force, the spool in the priority valve moves to the left.

6. Pressure oil from the main pump flows to the control valve through port EF and the spool in the priority valve.

7. Therefore, when the steering cylinder is at the stroke end, pressure oil flows to the control valve. At this time, pressure acting on the steering cylinder is as much as the set pressure of the relief valve.