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| Illustration 1 | g06601714 |
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Travel motor (partial cross section) (1) Piston (2) Swashplate (4) Passage (5) Passage (6) Pilot port (automatic speed change) (7) Displacement change valve (8) Port (9) Port (11) Spring (12) Piston | |
Small Displacement Change Operation
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| Illustration 2 | g06256403 |
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Small displacement change operation (1) Piston (2) Swashplate (4) Passage (6) Pilot port (automatic speed change) (7) Displacement change valve (13) Plug (14) Spring (15) Spool (16) Plug (17) Line (19) Passage (20) Passage (21) Piston chamber | |
When the travel speed control is placed in the HIGH SPEED MODE position, the travel speed solenoid is energized. When travel resistance is light and the pump delivery pressure is below a certain value, pilot oil flows to pilot port (6) of displacement change valve (7).
The pilot oil pressure moves spool (15) to the right against the force of spring (14) until the spring contacts plug (13). Then, the oil flows from passage (4) through passage (19) to piston chamber (21). The oil pushes piston (1) to the left to pivot swashplate (2) to the minimum angle position. The motor holds the swashplate at the minimum angle position for the small displacement.
Large Displacement Change Operation
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| Illustration 3 | g06256406 |
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Large displacement change operation (1) Piston (2) Swashplate (4) Passage (6) Pilot port (automatic speed change) (7) Displacement change valve (13) Plug (14) Spring (15) Spool (16) Plug (17) Line (19) Passage (20) Passage (21) Piston chamber | |
When the travel speed control is placed in the LOW SPEED MODE position, the travel speed solenoid is not energized. Pilot oil is not supplied to pilot port (6) of displacement change valve (7). Spool (15) is forced to the left by the force of spring (14) until the spool contacts plug (16). The oil in piston chamber (21) of piston (1) flows to the case drain of the motor through passages (19) and (20). Since the pressurized oil is not being sent to piston (1), the swashplate (2) turns to the maximum angle position.