MANIFOLD 4401902 - Caterpillar

Makeup Check Valve
Illustration 8 g00886875
Multifunction Valve Cartridge (24) Makeup Valve (26) Pressure Limiter Valve Spring (27) Charge Check ValveThe makeup valve function of the multifunction valve operates in the low pressure side of the main circuit.The right side of makeup valve (24) and the charge check valve seat is open to the charge oil circuit. As leakage and loop flushing occurs in the closed circuit, the charge oil pressure and the low pressure side of the closed circuit vary. Charge pressure overcomes the force of pressure limiter valve spring (26) and the oil pressure of the low side of the closed circuit. The pressure moves makeup valve (24) to the left. Makeup valve (24) contacts a snap ring on check valve (27). Makeup valve (24) continues to move as charge check valve (27) raises off the seat. When check valve (27) is off the seat, charge oil flows across the seat in order to replenish the closed circuit.High pressure oil from the propel pump flows through the opening. The oil acts on the inlet end of the high pressure valve. The oil acts on the opposite end of the charge check valve. As the circuit pressure increases, the charge oil pressure is overcome. Charge check valve (27) shifts to the right. Charge check valve (27) will also reseat. This stops the flow between the circuit and the charge circuit.High Pressure Relief
Illustration 9 g00887677
Multifunction Valve Cartridge (27) Charge Check ValveThe high pressure relief function of the multifunction valve operates in the high pressure side of the main circuit. This function protects the circuit from high pressure spikes. When the system pressure reaches the high pressure relief setting, charge check valve (27) is forced off the seat. This action dumps high pressure oil instantly to the low pressure side of the circuit, as shown. This condition may occur if the machine encounters a large external force. The high pressure relief is set at a pressure of 3445 kPa (500 psi) above the pressure limiter setting.Electrical Displacement Control (EDC)
Illustration 10 g00886876
Electrical Displacement Control (EDC) (1) Pressure Control Pilot Valve (PCP Valve) (2) Path to the Servo Piston (3) Path to the Servo Piston (4) Metering Spool (5) Control Linkage (6) Swashplate Feedback (7) Path from the Charge PumpThe electrical displacement control (EDC) is a two-stage electro-hydraulic control. The EDC uses swashplate feedback (6) and ported oil from charge pump (7) in order to set up a closed swashplate circuit. The EDC receives electrical input from the ECM that is mounted in the operator's console on PCP valve (1) .Current from the ECM meters charge oil pressure in PCP valve (1) to metering spool (4). This causes metering spool (4) to shift. When the metering spool shifts, passages (2) and (3) open. The valves allow oil to pass from the EDC to the servo piston. The oil flows to the EDC and returns to the hydraulic tank. Oil that is acting upon the servo piston causes the piston to shift. The piston then rotates the