HOUSING 1S5472 - Caterpillar

Main Pump Control
Part of the oil delivery from pilot pump (21) flows directly to the pump control manifold block. The pump control manifold block controls the negative flow control pressure and the power shift pressure to the main pump regulators.The machine ECM continually monitors all of the input signals. The input signals are processed by the machine ECM and an output signal is sent to negative flow control PRV's (23) and (24) at pump control manifold (17). The NFC proportional reducing valves use pilot oil to control the output flow of the front pump and rear pump.Note: For more information concerning the operation of the negative flow control system, refer to Systems Operation, "Negative Flow Control System".Power Shift Pressure System
During machine operation, the machine ECM receives input signals from the following components:
Hydraulic torque output (engine speed dial)
Actual engine speed
Desired engine speed
Front pump delivery pressure
Rear pump delivery pressureThe machine ECM continually monitors all of the input signals. The input signals are processed by the machine ECM and an output signal is sent to power shift pressure PRV (25) at pump control manifold (17). The power shift pressure PRV assists in controlling the output flow of front pump and rear pump.The electrical signal from the machine ECM controls power shift pressure PRV (25). Power shift pressure PRV (25) regulates the pilot pressure that is supplied to the main pump regulators. This regulated pressure is called power shift pressure (PS). The proportional reducing valve sends the regulated pilot oil pressure through lines to the pump regulators on the main hydraulic pumps. The output flow of the front pump and the rear pump is controlled in accordance with the power shift pressure. The power shift pressure is used to regulate the maximum allowable hydraulic pump output.The output signal from the machine ECM to power shift pressure PRV (25) will vary as inputs change. The regulated power shift pressure that is sent to the pump regulators varies in pressure. The powers shift pressure changes in order to regulate the maximum allowable hydraulic pump output at the given engine speed. The desired engine speed is maintained.An increase in engine speed decreases the power shift pressure. A decrease in power shift pressure causes an upstroke condition of the front pump and the rear pump. The maximum allowable hydraulic power output is increased.A decrease in engine speed increases the power shift pressure. An increase in power shift pressure causes a destroke condition of the front pump and the rear pump. The maximum allowable hydraulic power output is decreased.Note: For more information concerning the operation of the pump regulators, refer to Systems Operation, "Pump Control (Main Hydraulic)".Pilot Control Valve Circuits
Oil from pilot pump (21) flows through pilot line (20), pilot filter (19), and pilot line (16) to pilot manifold (11). When the hydraulic activation control lever is shifted to the UNLOCKED position, the machine ECM energizes the hydraulic activation solenoid valve (14). The pilot oil then shifts valve (13), allowing oil to flow through valve (13). The