SHEET AS 1177672 - Caterpillar

Small Displacement Change Operation
Illustration 1 g03358463
Travel motor (partial view) (1) Swashplate (2) Piston (3) Chamber (4) Passage (5) Displacement change valve (6) Pilot port (automatic speed change) (7) Shuttle valve (8) Passage (9) Port (10) Port (11) Spring (12) Piston (13) Spring
Illustration 2 g02929803
Small displacement change operation (1) Swashplate (2) Piston (4) Passage (5) Displacement change valve (6) Pilot port (automatic speed change) (7) Shuttle valve (10) Port (14) Plug (15) Line (16) Spring (17) Cover (18) Spool (19) Passage (20) Spool Chamber (21) Passage (22) Passage (23) Passage (24) Piston chamber (25) Passage (26) PassageWhen the travel speed control switch is placed in the HIGH position, the travel speed solenoid valve is energized. If the pump delivery pressure is below a certain level, pilot oil flows from line (15) to pilot port (6) of displacement change valve (5). The oil then flows into spool chamber (20). Spool (18) shifts to the right against the force of spring (16) and the pressure at passage (26). Spool (18) shifts against cover (17). Pump oil enters motor port (10) and flows through passage (8), shuttle valve (7), passage (22), passage (19), passage (4), and flows into piston chamber (24). The force of piston (2) overcomes force (F) which is produced by motor piston (12) and spring (13). Swashplate (1) rotates in order to decrease the angle. Swashplate (1) is held at the minimum angle position. Decreasing the angle decreases the displacement.Large Displacement Change Operation
Illustration 3 g02929818
Large displacement change operation (1) Swashplate (2) Piston (4) Passage (5) Displacement change valve (6) Pilot port (7) Shuttle valve (10) Port (14) Plug (15) Line (16) Spring (17) Cover (18) Spool (21) Passage (22) Passage (23) Passage (24) Piston chamber (25) Passage (26) Passage (27) Passage (28) PassageWhen the travel speed control switch is placed in the LOW position, the travel speed solenoid valve is not energized. Pilot oil does not flow to port (6) of displacement change valve (5). Spool (18) is shifted to the left by spring (16) and the pressure at passage (26). Spool (18) shifts to the left against plug (14). Passage (23) closes and passage (29) opens. Force (F), which is produced by piston (12) and spring (13), rotates swashplate (1) .Swashplate (1) rotates in order to increase the angle. The oil in piston chamber (24) goes through passage (4), passage (28), and passage (27). The oil then flows back to the hydraulic tank. Swashplate (1) is held at the maximum angle position. Increasing the angle increases the displacement.Automatic Change From Small Displacement To Large Displacement
Illustration 4 g02929820
Large displacement change operation (1) Swashplate (2) Piston (4) Passage (5) Displacement change valve (6) Pilot port (7) Shuttle valve (10) Port (14) Plug (15) Line (16) Spring (17) Cover (18) Spool (21) Passage (22) Passage (23) Passage (24) Piston chamber (25) Passage (26) Passage (27) Passage (28) PassageWhen the load pressure in passage (27) increases to a specified pressure setting, the combined forces of this pressure and spring (16) overcomes the pilot pressure from port