CYLINDER GP-STEERING 2505465 - Caterpillar

Illustration 1 g00591298
Hydraulic circuit diagram (1) Drain line (2) Passage (load sensing signal pressure) (3) Passage (pump flow) (4) Shuttle valve (5) Signal duplication valve (stick side) (6) Orifice (7) Passage (pump flow) (8) Passage (pump flow) (9) Signal relief valve (travel) (10) Load sensing differential pressure relief valve (rear pump) (11) Load sensing differential pressure relief valve (front pump) (12) Solenoid valve (neutral bypass) (13) Solenoid valve (high/low relief) for travel and stick (14) Passage (pump flow) (15) Signal relief valve (stick) (16) Passage (true load signal pressure from the stick circuit) (17) Passage (true load signal pressure from the left travel circuit) (18) Passage (true load signal pressure from the right travel circuit) (19) Passage (load sensing signal pressure) (20) Passage (return oil flow) (21) Line relief valve (stick cylinder rod end) (22) Line (return oil) (23) Hydraulic tank (24) Front pump (25) Rear pump (47) Passage (return oil flow) (48) Orifice (49) Signal duplication valve (boom side) (50) Signal relief valve (boom and/or bucket) (51) Signal relief valve (heavy lift) (52) Solenoid valve (high/low relief) for boom, bucket and heavy lift (53) Passage (rear pump output) (70) Load signal control valveThe following explanation of limiting circuit pressure is given for the stick circuit or the travel circuit. Limiting circuit pressure in the boom circuit and the bucket circuit is accomplished in the same manner.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 the solenoid valve (neutral bypass) (12). When the solenoid valve (neutral bypass) is energized, a small passage opens. This passage allows the standby oil flow to return to hydraulic tank (23). The standby oil flow from front pump (24) and rear pump (25) flows through passages (14), passage (53), passage (7), passage (3), valve (12) and passage (47) to the hydraulic tank. At this time, the standby pressure of the pumps will be 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.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, the signal relief valve (travel) (9) or the signal relief valve (stick) (15) limits the maximum load sensing signal pressure that is sent to the main pump regulators. During a very slow operation of the stick, during a very slow operation of the travel motors or during a stall condition, the maximum pump discharge pressure will be maintained at 1960 kPa (285 psi) above the load sensing signal pressure by the load sensing regulators at the main pumps. This is also the margin pressure setting of the load sensing adjustment on the pump regulators. When the stick operation or the travel operation becomes faster, the 1960 kPa