REGULATOR AS-VR4 7C7557 - Caterpillar

Note: Refer to Illustration 26 for information on the color codes that are used in the following graphics.Travel Speed And Direction Function
Illustration 27 g00953824
Travel speed and direction functionFull FORWARDPosition sensor (5) for the speed/direction control lever converts the position of the lever into an electrical signal that is sent to the power train ECM. Power train ECM (11) sends current to the steering solenoid valves that corresponds to the direction that is selected by the operator. The solenoid valves open proportionally to the current that is sent by the speed that is selected by the operator. When the speed mode switch is placed in the Work Mode position, speed is reduced to 70 percent of the normal speed. Normal speed is the speed that results when the speed mode switch is placed in the Travel Mode position.Steering Function
Illustration 28 g00975052
Right steering function (Right spot turn)Right pedal that is fully depressedPower train ECM (11) monitors the position of both of the steering pedals with the left and right steering pedal position sensors. The synchronizing valve is energized and open when the steering pedals are not pressed. This valve connects both of the right and left FORWARD drive loops and the two REVERSE drive loops together. The equal flow ensures that the machine will track straight. As a pedal is pressed, the power train ECM reduces the speed of the appropriate track by reducing the electrical signal to the appropriate steering valves. This causes the machine to turn in the selected direction. When a steering pedal is pressed, the power train ECM de-energizes synchronizing valve (19). The valve closes in order to allow the left track and the right track to operate independently. When a pedal is pressed all the way, the track will slow down and the track will reverse direction. This will cause the machine to turn sharply.Braking And Anti-Rollback Function
Illustration 29 g00953830
Braking and anti-rollback functionPower train ECM (11) monitors the position of the center brake pedal (35) with position sensor (3). When the pedal is pressed, the ECM reduces the speed of the machine in proportion to the position of the pedal by reducing the current to the steering solenoid valves. At the bottom of the pedal travel, the mechanical brake is actuated when the ECM sends a signal to parking brake solenoid valve (26). An anti-rollback function gives the operator the ability to preload the transmission against the brake. The anti-rollback function keeps the machine from rolling downhill when the machine is performing stopping operations on a slope and restarting operations on a slope. Engine Underspeed Function
Illustration 30 g00953832
Engine underspeed functionFull FORWARDPower train ECM (11) monitors the engine speed by reading the signal from engine speed sensor (1). The engine speed decreases as power demands increase. This will occur if power is demanded by the implements or if power is demanded by the hydrostatic transmission.If the engine speed decreases below a specific value the power train ECM will reduce the machine speed by reducing the signal to the steering solenoid