TUBE 8B0009 - Caterpillar

Illustration 6 shows the regulator for the idler pump in the STANDBY position. All of the joysticks and the travel levers/pedals are in the NEUTRAL position. The main pump regulators are controlled by the negative flow control pressure (PN) in piston chamber (65) .The engine and pump controller controls the power shift pressure (PS) to a level that is dependent on engine speed. When the main pump regulator is in the STANDBY position, decreased power shift pressure flows through passage (38). The decreased power shift pressure acts on the end of pilot piston (42) .The cross sensing control delivers the average delivery pressure of the drive pump and the idler pump (PM) through passage (33). The average delivery pressure of the drive pump and the idler pump (PM) acts on shoulder (52) in the center of pilot piston (42). Since the main pump regulators are in the STANDBY position, pressure (PM) in passage (33) is low pressure standby pressure.When all of the joysticks and the travel levers/pedals are in the NEUTRAL position, all of the control valves for the implements, swing and travel are in the NEUTRAL position. The oil flow rate through the center bypass passage in the main control valve is maximum. The oil flow through the center bypass passage is restricted at the negative flow control orifice. High negative flow control pressure (PN) flows from the main control valve through line (44) and port (17) to piston chamber (65) of the regulator for the idler pump. When the negative flow control pressure is maximum, the output flow of the pump is maintained at a minimum (STANDBY).Negative flow control pressure (PN) enters the regulator for the idler pump at port (17). The negative flow control pressure (PN) flows to piston chamber (65). When the negative flow control pressure (PN) increases, control piston (43) is pushed to the left against the force of spring (64). As the negative flow control pressure increases further, control piston (43) pushes pilot piston (42) and spool (41) to the left. The movement of the control piston, the pilot piston and the spool will stop when the force of the negative flow control pressure becomes equal to the force of springs (39), (40) and (64). Delivery pressure for the idler pump (P2) is now blocked at passage (49) .The negative flow control pressure in piston chamber (48) flows through passage (31), passage (50), past spool (41) and through passage (55) to the case drain of the pump.The delivery pressure for the idler pump (P2) in piston chamber (53) pushes piston (47) to the right. Piston (47) moves to the right until the piston contacts stopper (57). Control linkage (36) causes swashplate (20) to rotate toward the minimum angle position. As a result, the output flow of the pump decreases.UPSTROKE Position
Illustration 7 g00747108
Main pump regulator in the UPSTROKE position (20) Swashplate (31) Passage (32) Passage (33) Passage (average delivery pressure of the drive pump and the idler pump) (34) Guide (36) Control linkage (38)