RING-RETAINING 9D6538 - Caterpillar

Illustration 1 g03566230
Implement pump (parts removed for clarity)
(1) Implement pump
(2) Case drain port
(3) Pump inlet port
(4) Load sensing port
(5) Pump outlet port
(6) Pump control
Illustration 2 g03566443
Implement pump (section view)
(7) Barrel
(8) Swashplate
(9) Control valve
Illustration 3 g03566670
Pump control valve
(10) Load sensing spool
(11) Margin spring
(12) Adjustment screw The pump is a variable displacement piston pump with sensing for load limit control. The flow and pressure are dependent on the system demands that are sensed by the implement valve.The pump draws oil from the hydraulic tank. Oil flows from the implement pump to the main control valve. When the engine is off, the bias spring holds swashplate (8) at a maximum angle. The maximum angle allows the pump to produce flow when the engine is started.When the engine is started, the shaft starts to rotate. Oil flows into the piston bore from pump inlet port (3). Oil is forced out of pump outlet (5) and into the system as cylinder barrel (7) rotates.When the pump produces flow, the system pressure begins to increase because the oil flow is blocked at the main control valve. The increased pressure is felt at the top side of the load sensing spool (10). Pressure is also felt at the small end of actuator piston within the control valve. The load sensing spool (10) moves against margin spring (11). When no load sensing pressure exists at load sensing port (4), the spool will drain oil from the actuator piston to the case drain (2). This draining will occur until there is a pressure balance on load sensing spool. The pump will maintain this margin pressure by increasing or decreasing the volume of the pump as needed.When the pressure on the small side of actuator piston increases, the force of margin spring (11) is overcome. Swashplate (8) is moved to a minimum angle.The pump produces enough flow in order to compensate for normal system leakage when swashplate (8) is moved to a minimum angle. Also, the pump has sufficient pressure in order to provide instantaneous response when an implement command is activated.If there is no flow demand from an implement circuit, no load sensing signal is generated at load sensing port (4).