SLEEVE 6T5747 - Caterpillar

Illustration 1 g01108717
Hydraulic circuit diagram (1) Drain line (2) Passage (load sensing signal pressure) (3) Passage (pump flow) (4) Shuttle valve (5) Signal duplication valve (6) Orifice (7) Passage (pump flow) (8) Passage (pump flow) (9) Solenoid valve (neutral bypass) (10) Neutral flow control valve (11) Differential relief valve (12) Signal relief valve (low pressure) (13) Passage (pump flow) (14) Signal relief valve (high pressure) (15) Passage for true load signal pressure (16) Solenoid valve (high/low relief) for travel and stick (17) Passage (load signal pressure from the stick circuit) (18) Passage (load signal pressure from the left travel circuit) (19) Passage (load signal pressure from the right travel circuit) (20) Differential relief valve (21) Line relief valve (stick cylinder rod end) (22) Passage (return oil flow) (23) Line (return oil) (24) Hydraulic tank (25) Front pump (26) Rear pump (27) True load signal port (28) Passage for duplicate load signal pressure (29) Duplicate load signal portThe following explanation of the limiting of circuit pressure is given for the stick circuit or the travel circuit. The limiting of circuit pressure in the boom circuit and the bucket circuit is performed in the same way.The circuit pressure is limited while the main control valve is in the NEUTRAL position.When the main control valve is in the NEUTRAL position, the machine is at a no-load condition. The machine electronic control module energizes solenoid valve (9) (neutral bypass). When the solenoid valve is energized, a small passage opens. This passage allows the standby oil flow to return to hydraulic tank (24) . The standby oil flow from front pump (25) and rear pump (26) flows through passage (7) , passage (3) , and neutral flow control valve (10) to the hydraulic tank. At this time, the standby pressure of the pumps is maintained at approximately 1960 kPa (285 psi) by the load sensing regulators at the pumps. This is the margin pressure setting of the load sensing adjustment on the pump regulators.Note: Margin pressure is the difference between pump system pressure and the load (working pressure) of the hydraulic system.The maximum circuit pressure is limited when the machine is at a load condition.When the stick control spool is shifted or the travel control spool is shifted, signal relief valve (14) or signal relief valve (12) limits the maximum load sensing signal pressure that is generated by the load sensing system. During a very slow operation of the stick, and during a very slow operation of the travel motors, the maximum pump discharge pressure will be maintained at 3000 kPa (435 psi) above the load sensing signal pressure by differential relief valves (11) and (20) .When the joystick for the stick or the travel levers/pedals are operated, electrical signals are sent to the machine electronic control module. The machine electronic control module de-energizes solenoid valve (9) (neutral bypass). This closes the small passage for return oil to hydraulic tank (24) . Movement of the stick cylinder or the travel motors will not occur