BEARING-SLEEVE 8D9749 - Caterpillar

Illustration 1 g03446117
Implement pump (1) Pump inlet port (2) Pump outlet port (3) Shaft (4) Load sensing port (5) Pump
Illustration 2 g03447493
Pump control valve (section view) (5) Pump (6) Cylinder barrel (7) Swashplate (8) Flow compensator screw (9) Pressure compensator screw (10) Actuator piston (11) Bias spring (12) Bias piston (13) Piston (14) Margin spring (15) Load sensing sleeve (16) Load sensing spool (17) Pump intake (18) Pump outputThe 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 (11) holds swashplate (7) at a maximum angle. The maximum angle allows the pump to produce flow when the engine is started.When the engine is started, shaft (3) starts to rotate. Oil flows into the piston bore from pump inlet port (1). Oil is forced out of pump outlet (2) and into the system as cylinder barrel (6) 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 (16) and at the small end of actuator piston (10). Load sensing spool (16) moves against margin spring (14). When no load sensing pressure exists at load sensing port (4), the spool will drain oil from the actuator piston to the case drain. This draining will occur until there is a pressure balance on load sensing spool (16). 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 (10) increases, the force of bias spring (11) is overcome. Swashplate (7) is moved to a minimum angle.The pump produces enough flow in order to compensate for normal system leakage when swashplate (7) 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).