SYSTEM / Hydraulic System

Steering Circuit (When Steering is Operated)

• When the steering wheel is operated, the oil passage (orifice 4) between the spool and the sleeve of the steering valve is opened in proportion to the steering wheel rotation speed. Port P is connected to the gerotor in the steering valve.

• When the steering wheel is operated quickly, the orifice 4 opening becomes large and pressure oil flow rate to the steering valve increases. When the steering wheel is operated slowly, the orifice 4 opening becomes small and pressure oil flow rate to the steering valve decreases.

• Orifice 4 is opened at the moment when the steering wheel is operated, pressure oil between LS1 and port CF in the priority valve and orifice 4 in the steering valve flows to the gerotor.

• As pressure oil flows to the gerotor, the oil pressure between LS1 and port CF in the priority valve and orifice 4 in the steering valve decreases, the spool in the priority valve moves rightward.

• The spool in the priority valve becomes balanced at the position where pressure oil corresponding to orifice 4 open area the priority valve flows to the steering valve.

• At this time, pressure oil from the main pump flows to both the steering valve and the control valve.

• Pressure oil from the main pump flows to the gerotor through the spool and sleeve in the steering valve. The gerotor delivers pressure oil while rotating as a hydraulic motor. Pressure oil from gerotor flows to the steering cylinder and the machine turns.

• When the rotation of the steering wheel is stopped, the oil passage between the spool and the sleeve in the steering valve is closed. The spool and the sleeve are returned to the neutral position by the spring force completely. Pressure oil from the pump does not flow to the gerotor and the steering cylinder is stopped. (Refer to COMPONENT OPERATION/Steering Valve.)

NOTE: Load sensing control is performed by using the combinations of orifice 4 and the spool in priority valve. The spool in the priority valve corresponds to the flow rate control valve.

NOTE: As the gerotor is connected to the middle shaft of the steering valve, powered steering effect is generated. (Refer to COMPONENT OPERATION/Steering Valve.)

T2-2-8