PLATE AS 3114370 - Caterpillar

Illustration 6 g02173267
Main control valve compartmentTypical example (36) Right travel control valve (38) Straight travel control valve (39) Left travel control valveWhen the travel pedals are operated, pilot oil from pilot control valve (27) shifts the stem in travel control valves (36) and (39). Travel control valves (36) and (39) allow oil flow from idler pump (46) and drive pump (45) to flow to swivel (13). The swivel transfers oil from the rotating upper structure to the lines in the lower structure. The oil flows to left travel motor (14) and right travel motor (18) .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.Pilot oil from control valve (27) flows through line (29) and into left travel control valve (39). The pilot oil shifts the stem of left travel control valve (39). Idler pump oil in passage (35) flows through passage (34), line (31), swivel (13), line (10), and counterbalance valve (8). Pump oil enters motor rotary group (2) through passage (15) from the counterbalance valve.Part of the idler pump oil flows through passage (11), brake pilot valve (12), and passage (17) to parking brake assembly (1). Parking brake assembly (1) releases. The left travel motor rotates in the forward direction.For more information concerning the travel parking brake, refer to Systems Operation, "Travel Parking Brake".Low Speed
Illustration 7 g03582205
Left travel motor (LOW SPEED) (2) Motor rotary group (3) Swashplate (4) Swashplate control piston (5) Displacement change valve (6) Passage (return oil) (8) Counterbalance valve (14) Left travel motor (15) Passage (supply oil) (26) Pilot line (37) Main control valve (40) Pressure sensor (idler pump) (43) Travel speed solenoid valve (44) Pilot pump (46) Idler pump (50) Travel speed control switch (51) Left travel lever/pedal (A) Indicator for HIGH SPEED (B) Indicator for LOW SPEED (C) Machine ECMWhen travel speed control switch (50) is set at the LOW SPEED position, an electrical signal is sent to machine ECM (C). The machine ECM does not energize travel speed solenoid valve (43) and pilot system oil pressure does not flow through pilot line (26) to displacement change valve (5). The spool in the displacement change valve does not shift. Oil flows from the idler pump in passage (15) to the motor rotary group (2). Since displacement change valve (5) is not shifted, oil is restricted from swashplate control piston (4). The swashplate remains in the maximum displacement position. One rotation of motor rotary group (2) displaces a larger amount of oil flow. The rotational speed of the left travel motor decreases. The left track moves slowly and increases the drawbar pull.The return oil from motor rotary group (2) flows through passage (6), counterbalance valve (8), line (9) and swivel (13). The return oil then flows through line (32), left travel control valve (39) and return passage (33) to the hydraulic tank.Right travel motor (18) receives the oil delivery from the drive pump.