BODY AS-LH 5T7547 - Caterpillar

Illustration 2 g06130892
Hydraulic Schematic "FORWARD, LOW SPEED, PARKING BRAKE OFF"
(1) Propulsion pump
(2) Axle reverse combination valve
(3) Axle forward solenoid "C1"
(4) Axle reverse solenoid "C2"
(5) Servo piston
(6) Sequence valve solenoid
(7) Port"E" (charge inlet)
(8) Servo piston
(9) Drum reverse solenoid "C2"
(10) Drum forward solenoid "C1"
(11) Drum forward combination valve
(12) Test manifold
(13) Axle brakes (optional)
(14) Servo piston
(15) Axle forward combination valve
(16) Shift spool
(17) Flushing relief valve
(18) Flushing spool
(19) Axle rotating group
(20) Charge relief valve
(21) Shift solenoid
(22) Port"P" (charge inlet)
(23) Return manifold
(24) Drum rotating group
(25) Drum reverse combination valve
(26) Flushing spool
(27) Flushing relief valve
(28) Servo piston
(29) Shift spool
(30) Drum motor
(31) Drum speed sensor
(32) Parking brake
(33) Axle speed sensor
(34) Axle motor
(35) Shuttle valve
(36) Oil cooler
(37) Relief valve
(38) Thermal bypass valve
(39) Passage from vibratory motor case
(40) Temperature sensor
(41) Shuttle valveThe above illustration shows the propulsion hydraulic system under the following conditions:
The parking brake switch in the OFF position
The propulsion mode is set to low
The machine traveling forwardCharge oil to charge relief valve (20), to the combination valves, and to sequence valve solenoid (6). With the parking brake switch in the OFF position, the sequence valve solenoid directs charge oil into the piston cavities of parking brakes (32) and axle brakes (13), if equipped. The charge pressure in the parking brake piston cavities overcomes the spring force, and the parking brakes release.When the propulsion mode is set to low, solenoid in shift valve (21) is not energized. In this case, propulsion motors (30) and (34) operate with the swashplates at the maximum displacement angle.When the machine ECM determines that the machine should be moving forward, the ECM energizes axle forward solenoid"C1" (3) and drum forward solenoid"C1" (10). In this case, the solenoids direct charge oil into the forward side of servo pistons (5) and (8). The pressure in the forward side of the servo pistons causes the pump servos to move. This movement changes the angle of the swashplate in each rotating group (19) and (24). The stronger the signal to the solenoids, the greater the swashplate angle, and therefore, the greater the oil flow from the propulsion pump.As a swashplate moves, the feedback linkage tends to move the pump solenoid spool back to neutral through an internal feedback spring. This action prevents the servo piston from tilting the swashplate too far.Supply oil from axle rotating group (19) flows to the following locations:
Port"A" on the forward side of axle motor (34)
Forward combination valve (15)
Port"AF" of test manifold (12)The pressure differential between the forward and reverse sides of axle motor (34) causes the motor to turn. After turning the axle motor, oil at a reduced pressure flows to the following locations:
Flushing spool (18) in the axle motor
The reverse side of axle rotating group (19)
Port"AR" of test manifold (12)Supply oil from drum rotating group (24) flows to the following locations:
Port"A" on the forward side of drum motor (30)
Forward combination valve (11)
Port"DF" of test manifold (12)Drum motor (30) turns. Reduced pressure oil flows to drum motor flushing spool (26), back to the reverse side of drum rotating group (24), and