CRANKSHAFT AS 7C7976 - Caterpillar

High Pressure Cutoff
Illustration 1 g00487376
(1) Adjustment screw (2) Spring (3) Spool (4) Valve chamber (5) Outlet port (AA) Pressure oil (BB) Reduced pressure oil (EE) Charge oilThe multifunction valve is in the high pressure side of the closed loop circuit. The valve sends oil to the steering pump's servo cylinder in order to destroke the steering pump. This protects the system from damage due to high pressure.The oil pressure in the high pressure side of the closed loop circuit is 36510 1000 kPa (5300 145 psi) above charge pressure. This pressure is present in chamber (4). The oil pressure in chamber (4) depresses spool (3) against spring (2). Pressure oil flows around spool (3). This oil flows through port (5) to the steering pump's servo cylinder. Then, the servo cylinder destrokes the steering pump.The steering pump destrokes in order to maintain the high load on the pump. The force that is required to unseat spool (3) can be adjusted. This is done with adjustment screw (1) and spring (2). Pressure Relief
Illustration 2 g00487378
(1) Adjustment screw (2) Spring (3) Spool (4) Valve chamber (5) Outlet port (6) Spring (7) Spool (AA) Pressure oil (BB) Reduced pressure oil (EE) Charge oilThe multifunction valve is in the high pressure side of the closed loop circuit. The valve sends oil to the steering pump's servo cylinder in order to destroke the steering pump. The valve also sends oil through the hydraulic displacement control valve to the drain. This protects the system from damage due to pressure spikes. Pressure spikes may occur when the machine encounters a large external force.The oil pressure in the high pressure side of the closed loop circuit is 36510 1000 kPa (5300 145 psi) above charge pressure. This pressure is present in chamber (4). The oil pressure in chamber (4) depresses spool (3) against spring (2). Pressure oil flows around spool (3). This oil flows through port (5) to the steering pump's servo cylinder. Then, the servo cylinder destrokes the steering pump.Spool (3) cannot relieve enough pressure. The pressure in the circuit unseats spool (7). Spool (7) compresses spring (6). Oil flows around spool (7) to the charge circuit. Oil in the charge circuit flows through the hydraulic displacement control valve to the drain. The pressure is relieved in the high pressure side of the closed loop circuit when the pressure is 3450 kPa (500 psi) above the high pressure cutoff.Makeup Operation
Illustration 3 g00487379
(4) Valve chamber (6) Spring (7) Spool (8) Spool (EE) Charge oil (JJ) Return oil (LL) Sump oilDuring makeup operation, the multifunction valve transfers oil from the charge circuit to the return side of the closed loop circuit. This prevents cavitation of oil in the steering pump. Pressure oil in the charge circuit is provided by the charge pump.The multifunction valve is in the return side of the closed loop circuit. Oil from the charge pump applies pressure on the outside of spool (8). This pressure pushes spool (8) to the left. The pressure