BUSHING AS-YM 3940192 - Caterpillar

Illustration 1 g00499226
Steering Control Valve (steer left position) (1) Lever (2) Spring (3) Passage (4) Load check valve (5) Chamber (6) Primary outlet holes (7) Priority flow control valve (8) Inlet holes (9) Inlet passage for pump oil (10) Outlet passage to next control valve (11) Chamber (12) Spring (13) Passage (14) Orifice (15) Chamber (signal oil) (16) Steering valve spool (17) Signal oil passage to inlet manifold (18) Shuttle valve (19) Signal oil passage from bulldozer lift control valve (20) Outlet passage to tank (21) Steer right passage to steering motor (22) Makeup valve (23) Outlet passage to tank (24) Makeup valve (25) Steer left passage to steering motor (26) Outlet passage to tank (27) Signal oil passage (AA) High pressure oil (BB) Pressure oil with the first pressure reduction (EE) Signal oil (LL) Tank oilNote: Shuttle valve (18) may be called a resolver valve.The steering control valve is the first control valve in the valve stack. The steering control valve controls the speed of the steering motor and the direction of rotation for the steering motor. Pump oil flows to the steering control valve from the inlet manifold. The control valve has steering valve spool (16), shuttle valve (18), priority flow control valve (7), load check valve (4) and makeup valves (22) and (24) .The steering valve is a spring centered valve. Steering valve spool (16) is a closed center spool and a manually operated spool with three positions: STEER RIGHT, HOLD and STEER LEFT.Spring (2) keeps the spool in the HOLD position when the steering circuit is not active. Movement of the spool is controlled manually by the operator. The steering control lever is connected to lever (1) by a linkage. Lever (1) is connected to steering valve spool (16) .Shuttle valve (18) is a double check valve. Shuttle valve (18) sends the signal oil with the highest pressure to the inlet manifold. The inlet manifold sends the signal oil to the compensator valve on the pump. Priority flow control valve (7) gives flow priority to the steering control valve over all of the implement control valves. There are more descriptions of the shuttle valve and of the priority flow control valve in this section. These descriptions are given with the steering valve spool in different positions. Descriptions for makeup valves (22) and (24) and for load check valve (4) are in separate sections.Hold Position
When the steering valve spool and all implement valve spools are in the HOLD position, pump oil from the inlet manifold flows to inlet passage (9). Then, oil flows through inlet holes (8). The oil moves priority flow control valve (7) against spring (12). Then, pump oil flows out of outlet passage (10) to the next control valve. Because all implement control valves are in the HOLD position, pump oil fills the parallel oil passages at approximately 3000 kPa (435 psi). Passage (27), chamber (15), shuttle valve (18), passage (17), and passage (19) are drained. The oil that is in steer passages