Operation
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| Illustration 1 | g02245215 |
Travel Motor (1) Displacement change valve (2) Pilot port (automatic speed change) (3) Shuttle valve (4) Drain port (5) Port (supply oil or return oil) (6) Port (supply oil or return oil) (7) Housing (8) Piston (9) Swashplate (10) Retainer plate (11) Shoe (12) Piston (13) Barrel (14) Friction disk (15) Separator plate (16) Brake piston (17) Brake spring (18) Head (19) Motor shaft (20) Hold down ball (21) Spacer (22) Spring (23) Port plate | |
The travel motor can be divided into the following three groups:
- The rotary group consists of the following components: retainer (10) , shoes (11) , pistons (12) , barrel (13) , shaft (19) , hold down ball (20) , spacer (21) and springs (22) .
- The parking brake group consists of the following components: friction disks (14) , separator plates (15) , brake piston (16) and springs (17) .
- The displacement change group consists of the following components: displacement change valve (1) , shuttle valve (3) and piston (8) .
The flow of the pump oil depends on the direction of travel. Pump oil flows into the travel motor through port (5) or port (6) . Pump oil is forced out of the travel motor through port (6) or (5) .
The case drain oil returns to the hydraulic tank through drain port (4) of housing (7) .
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| Illustration 2 | g02245216 |
Motor passages (top view from head) (A) Bottom center (B) Inlet side (high pressure) (C) Top center (D) Outlet side (low pressure) (24) Passage (barrel) (25) Passage (port plate) (26) Passage (port plate) | |
During forward travel, supply oil flows into the left travel motor through port (6) . The oil from port (6) flows through head (18) to passage (25) in port plate (23) . The oil then flows into barrel (13) and forces pistons (12) to move to the left.
Shoes (11) are coupled to pistons (12) . Shoes (11) slide on the surface of swashplate (9) . Shoes (11) and pistons (12) rotate with barrel (13) . Shoes (11) rotate around swashplate (9) from top center (C) to bottom center (A) .
During forward travel, oil flows through passage (25) of port plate (23) into passages (24) of barrel (13) . Oil is discharged through passages (24) of barrel (13) to passage (26) of port plate (23) . The oil then flows through port (5) to the return system. The barrel rotates counterclockwise as viewed from the head end of the motor.
Motor shaft (19) is splined to barrel (13) . The shaft and barrel of the left travel motor rotate counterclockwise for forward travel.
In reverse travel, port (6) functions as an oil return port. Port (5) functions as a supply port. The left travel motor rotates clockwise as viewed from the head end of the motor.
Note: The right travel motor functions in the same manner as the left travel motor.
Parking Brake
Pump oil is supplied to the travel motor during a travel operation. Pump oil is used to release the parking brake so that the motor shaft will rotate. When no pump oil is supplied to the motor, the motor stops and the parking brake engages.
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| Illustration 3 | g02245218 |
Parking brake (partial view) (5) Port (supply oil or return oil) (6) Port (supply oil or return oil) (7) Housing (13) Barrel (14) Friction disks (15) Separator plates (16) Brake piston (17) Brake spring (27) Piston chamber (28) Passage (29) Passage (30) Orifice (31) Passage (32) Orifice (33) Counterbalance valve (34) Valve (35) Spring (36) Passage | |
In the parking brake section of the travel motor, separator plates (15) are splined to housing (7) . Friction disks (14) are splined to barrel (13) . Brake springs (17) force brake piston (16) to the left. Brake piston (16) presses separator plates (15) and friction disks (14) together. Pressing the plates and discs together locks barrel (14) to housing (7) . The motor shaft is splined to barrel (13) . Because the plates and disks lock the barrel to the housing, the motor shaft is locked to the housing. The parking brake prevents rotation of the motor shaft.
When no pump oil is supplied to the travel motor, brake piston (16) is pushed to the left by the force of brake springs (17) . The oil in piston chamber (27) flows through passage (28) , passage (29) to orifice (30) . The oil flows through orifice (30) and passage (31) into valve (34) . The oil then flows through valve (34) and orifice (32) to the drain line. Brake piston (16) moves to the left. Friction disks (14) and separator plates (15) are held together by brake springs (17) . The rotation of the travel motor stops.
Orifice (30) and orifice (32) restrict return oil flow from piston chamber (27) to the return line. The restriction of the oil flow delays the application of the parking brake. The parking brake is delayed in order to give the machine time to stop. Earlier wear and/or damage to the machine could result if the machine stayed in motion when the parking brake is engaged.
Prior to the operation of the travel motor, oil flows through port (6) and into counterbalance valve (33) . The oil then flows through passage (36) to valve (34) . Valve (34) shifts against the force of spring (35) . Oil flows to passage (31) and to orifice (30) . The oil then flows through passage (29) and passage (28) to piston chamber (27) . Brake piston (16) moves to the right against the force of brake springs (17) . The spring load which compresses friction disks (14) and separator plates (15) together is released.
Oil flows from port (6) into counterbalance valve (33) to barrel (13) . Since the parking brake is disengaged, barrel (13) and the motor shaft now rotate. Return oil from barrel (13) flows through counterbalance valve (33) to port (5) and to the return system.
When pump oil is supplied to port (5) , return oil from counterbalance valve (33) flows through passage (6) . Barrel (13) and the motor shaft rotate in the opposite direction.