PLUG 1177869 - Caterpillar

Forward Travel
Illustration 5 g03650656
Hydraulic schematic for FORWARD TRAVEL
(1) Left travel motor
(2) Swashplate
(3) Motor rotary group
(4) Swashplate control piston
(5) Passage (supply oil)
(6) Brake pilot valve
(7) Passage
(8) Counterbalance valve
(10) Parking brake
(11) Passage (return oil)
(12) Displacement change valve
(13) Passage
(14) Line (pilot system oil pressure)
(15) Right travel motor
(16) Swashplate
(17) Hydraulic tank
(18) Passage (return oil)
(20) Displacement change valve
(21) Passage (supply oil)
(22) Swashplate control piston
(23) Passage
(24) Passage
(25) Passage
(26) Passage
(27) Line (pilot system oil pressure)
(28) Line (return oil)
(29) Line (supply oil)
(30) Swivel
(31) Line (supply oil)
(32) Line (return oil)
(33) Line (supply oil)
(34) Line (return oil)
(35) Passage (supply oil)
(36) Passage (return oil)
(37) Return passage
(38) Left travel control valve
(39) Passage
(41) Right travel control valve
(42) Pilot line (forward left travel)
(43) Pilot line (forward right travel)
(44) Travel pilot control valve
(46) Pressure sensor for drive pump
(47) Pressure sensor for idler pump
(48) Travel speed solenoid valve
(49) Rear pump
(50) Front pump
(51) Pilot pump
(52) Main control valve
Illustration 6 g03650657
Main control valve
(38) Right travel control valve
(41) Left travel control valve When both of the travel levers/pedals are operated, pilot system oil pressure flows from travel pilot control valve (44) through pilot lines (42) and (43) to left travel control valve (41) and right travel control valve (38). The pilot system oil pressure shifts the spools in both of the travel control valves to start the travel function. The travel control valves allow the oil delivery from the front pump and rear pump to flow through the swivel (30). The oil flowing through the swivel transfers the oil delivery from the rotating upper structure to the lines in the lower structure. The oil delivery flows to left travel motor (1) and right travel motor (15).Note: The right and left travel controls function in the same manner. The explanation for the left travel control will be used to explain both the right and left travel controls.When the left travel lever/pedal is moved to the FORWARD TRAVEL position, pilot system oil pressure from travel pilot control valve (44) flows through pilot line (42) to left travel control valve (41). The spool in the left travel control valve shifts to the left. The oil delivery from the front pump flows through passage (39), left travel control valve (41), passage (35), line (33), swivel (30) and line (29) to left travel motor (1).The oil delivery from the front pump enters left travel motor (1) and flows through counterbalance valve (8) and passage (5) to motor rotary group (3). At the same time, a portion of the oil delivery from the front pump flows through passage (7) and brake pilot valve (6) to parking brake (10). The parking brake is released and the oil delivery from the front pump causes the motor to rotate.LOW SPEED
Illustration 7 g03399773
Left travel motor (LOW SPEED)
(1) Left travel motor
(2) Swashplate
(3) Motor rotary group
(4) Swashplate control piston
(5) Passage (supply oil)
(6) Brake pilot valve
(8) Counterbalance valve
(11) Passage (return oil)
(12) Displacement change valve
(13) Passage
(27) Pilot line
(46) Pressure sensor (main control valve)
(48) Travel speed solenoid valve
(50) Front pump
(51) Pilot pump
(52) Main control valve
(56) Travel speed control switch
(58) Left travel lever/pedal
(A) Indicator for HIGH