PIN-CONNECTOR 3497370 - Caterpillar

Illustration 6 g02029141
Operation of the pump and pump control valve
(2) Pressure and flow compensator valve
(25) Margin spring
(26) Passage to the solenoid valve (hydraulic fan)
(27) Internal passage
(28) Flow compensator spool
(30) Actuator spool
(31) Bias spring
(32) Pump outlet
(36) Swashplate
(AA) Supply oil
(DD) Signal oil
(EE) Suction oil
(LL) Sump oil When the hydraulic fan circuit requires flow, the pressure from pump outlet (32) is reduced. Passage (26) connects to the solenoid valve (hydraulic fan) (1). The solenoid valve (hydraulic fan) (1) restricts the flow from the signal line to the tank. Supply oil (AA) flows through internal passage (27) to the left of the spool. Margin spring (25) and signal oil (DD) apply a combined force to the left of flow compensator spool (28). Supply oil (AA) also applies a force to the right of flow compensator spool (28). The force on the left is greater than the force on the right.Flow compensator spool (28) moves to the right which blocks the flow of oil to actuator piston (30). Oil that is in the chamber for the actuator piston (30) is vented to the case drain across flow compensator spool (28). This allows bias spring (31) to move swashplate (36) to a greater angle.The pump now produces more flow. This condition is known as “upstroking”.Reference: For additional information on the solenoid valve (hydraulic fan), refer to Testing and Adjusting, "Hydraulic Fan System".The following conditions can result in upstroking the pump:
When the fan circuit is initially activated, the load sensing signal increases the output flow of hydraulic fan pump (6).
Hydraulic fan pump (6) will upstroke when the solenoid valve (hydraulic fan) (1) closes due to the increase in temperature of the engine coolant.
If the demand on the hydraulic fan system remains constant or the demand increases, hydraulic fan pump (6) will upstroke when the engine speed decreases.Constant Flow
Illustration 7 g02029247
Operation of the pump and pump control valve
(2) Pump control valve
(6) Hydraulic fan pump
(24) Adjustment for the flow compensator spool
(25) Margin spring
(26) Passage to the solenoid valve (hydraulic fan)
(27) Internal passage
(28) Flow compensator spool
(30) Actuator piston
(31) Bias spring
(32) Pump outlet
(36) Swashplate
(AA) Supply oil
(BB) Reduced supply oil
(DD) Signal oil
(EE) Suction oil
(LL) Sump oil When a constant flow of oil is demanded by the fan drive circuit, the supply oil pressure from pump outlet (32) will increase on the right side of flow compensator spool (28). The pressure on left side of flow compensator spool (28) is the sum of the following pressures: load sensing signal (26) and margin spring (25). Flow compensator spool (28) will meter the force on both ends of flow compensator spool (28). Once the forces become equal on each end of flow compensator spool (28) the system will stabilize.Swashplate (36) is held at a relative constant angle in order to maintain the required flow.The difference between the pressure of load sensing signal from passage (26) and the supply oil pressure is called margin pressure. Margin pressure is the value of margin spring (25).Margin pressure is 2000 100 kPa (290