SOFTWARE GP-MACHINE 4305252 - Caterpillar

Proportional Reducing Solenoid Valve (PRV)
Illustration 1 g02703776
"Power shift presure PRV"
"Negative flow control PRV (flow limit valve)"
Power Shift Pressure PRV
The Power Shift Pressure PRV is used to control engine speed and pump pressure of the machine. The main functions of the PRV, in conjunction with the monitoring system, are listed below:
The PRV transfers engine power to hydraulic power as needed.
The system controls the output of the pump according to the workload, improving fuel efficiency.
The monitoring system decelerates the speed of the engine when the machine is in the no load condition.The PRV valve is an output of the Machine ECM. The solenoid is the proportional type. The ECM uses a pulse width modulated signal (PWM) to vary the current to the solenoid. The distance that is traveled by the solenoid valve is proportional to the electrical current. The position of the valve opens or blocks the flow of oil to the drive pump regulator and the idler pump regulator. The "Power Shift Pressure" PRV is used to maintain the maximum allowable output from the hydraulic pump. A decrease in the speed of the engine increases the power shift pressure. An increase in power shift pressure causes a destroke condition of the drive pump and the idler pump.Negative Flow Control PRV
The negative flow control PRV's are used in order to control the main pump output flow. The machine ECM receives inputs from various pressure sensors and pressure switches. The machine ECM also receives inputs from the throttle dial position and the engine speed.The machine ECM uses a PWM signal to vary the current that is sent to the negative flow control PRV. An increase in current causes an increase in hydraulic pressure which is then sent to the pump regulators. This increase in pressure to the pump regulators causes the main hydraulic pumps to destroke, decreasing the flow. The amount of pump destroke is determined by the machine ECM.A decrease in current to the negative flow control PRV causes a decrease in hydraulic pressure to the pump regulators. This decrease of pressure to the pump regulators causes the main hydraulic pumps to upstroke, increasing the flow.Boom Regeneration PRV
Illustration 2 g02703637
"Boom regeneration PRV"
The boom regeneration PRV is used in order to control the amount of regeneration oil in the boom circuit. The machine ECM receives an input signal from pressure sensor for the boom down control and the boom cylinder head end pressure sensor. When the boom cylinder head end pressure is high and the pressure sensor for boom down control detects pilot pressure, the boom regeneration PRV remains de-activated. Pilot oil is then directed through the boom regeneration PRV and to the boom regeneration valve allowing regeneration.When the boom cylinder head end pressure is low and the pressure sensor for boom down control detects pilot pressure, the boom regeneration PRV begins to receive a PMW signal from the machine ECM. The machine ECM begins to increase current flow which decreases the amount of pilot oil supplied to the boom regeneration valve. The