RING 0888395 - Caterpillar

Illustration 2 g06050374
Hydraulic System FORWARD, LOW-SPEED, Parking Brake OFF
(1) Parking brake (right)
(2) Right propel motor
(3) Shift spool
(4) Flushing spool
(5) Flushing relief valve
(6) Shift solenoid
(7) Manual brake release
(8) Needle valve
(9) Flushing relief valve
(10) Flushing spool
(11) Shift spool
(12) Left propel motor
(13) Parking brake (left)
(14) Propel pump
(15) Charge filter
(16) From fan pump
(17) Reverse combination valve
(18) Right rotating group
(19) Forward combination valve
(20) Hydraulic tank
(21) Tank breather
(23) From fan motor
(24) From fan and steering pump
(24) Oil cooler
(25) Charge relief valve
(26) From steering unit
(27) Return manifold
(28) Forward combination valve
(29) Left rotating group
(30) Reverse combination valve
(31) Brake interlock valveThe above illustration shows the propel hydraulic system under the following conditions:
The parking brake switch is in the OFF position.
The propel gear setting is set to LOW gear.
The machine is traveling forward.Charge oil is directed to charge relief valve (25), to combination valves (17), (19), (28) and (30), and to brake interlock valve (31). With the parking brake switch in the OFF position, the brake interlock valve directs charge oil to directional control solenoids on propel pump (14). Charge oil is also directed to the piston cavity of parking brakes (1) and (13). The charge pressure in the parking brake piston cavities overcomes the spring force, and the parking brakes release.When the propel gear setting is set to LOW gear, shift solenoid (6) is not energized. In this case, propel motors (2) and (12) operate at low speed.When the machine ECM determines that the machine should be moving forward, the ECM energizes forward solenoid "C2" on rotating group (18). At the same time the ECM energizes forward solenoid "C2" on rotating group (29). In this case, the solenoids direct charge oil into the forward side of the servo pistons. 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 the rotating groups. The stronger the signal to the solenoids, the greater the swashplate angle, and therefore, the greater the oil flow from propel pump (14).As the swashplates move, the feedback linkages tend to move the direction control spools back to neutral through internal feedback springs. This action prevents the servo pistons from tilting the swashplates too far.Supply oil from right rotating group (18) flows to the following locations:
Port "B" of right propel motor (2)
Forward combination valve (19)The pressure differential between the forward and reverse sides of right propel motor (2) causes the motor to turn. After turning the motor, oil at a reduced pressure flows to the following locations:
The reverse side of right propel motor (2)
Flushing spool (4)
Flushing relief valve (5)
Port "C" of right rotating group (18)Supply oil from