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| Illustration 1 | g01175001 |
(1) Drain port T1, T2 (2) Pressure port P1 (3) Pilot port Ps (4) Pressure port P2 (5) Two-speed changeover valve (6) Control piston for the swashplate | |
The travel motors consist of a stationary section and a rotary section. The stationary section consists of the travel motor and the hydraulic valve. The rotary section (final drive) of the travel motor consists of a two-stage simple planetary gear train. The final drive reduces the output speed of the motor. This is done in order to produce high torque.
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| Illustration 2 | g01175122 |
Travel motor (7) Rear flange (8) Barrel (9) Piston (10) Timing plate (11) Swashplate (12) Motor shaft | |
The travel motors convert hydraulic force into mechanical rotation. Pressure oil from the main pump enters the travel motor through rear flange (7), and the oil passes through the brake mechanism. The oil is then routed through port plate (10) into cylinder barrel (8) .
The port plate has ports that align with pistons (9). The oil enters the port in the cylinders that are aligned with the inlet port. The oil pushes the pistons (9), and the pushing force is converted into rotation by the swashplate (11). The shaft is splined to the barrel (8), and the rotation of the barrel turns the motor shaft (12). The oil flows out of the motor through the outlet port in the port plate (10). For reverse rotation, the oil enters through opposite ports in the timing plate.
The swashplate (11) can be positioned at the maximum or minimum angles against the body of the travel motor. When the swashplate is seated against the body of the travel motor, the motor displacement is large. This is the LOW SPEED position. When the two-speed switch is moved to the HIGH SPEED position, the swashplate is then positioned so that the displacement is small. This results in higher speed and lower torque. The swashplate is moved by control piston (6). When the two-speed switch on the blade control lever is moved to the HIGH position, hydraulic oil flows through a passage and hydraulic oil pressure begins to build up. The hydraulic pressure forces the control piston to decrease the angle of the swashplate.
Two-Stage Changeover
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| Illustration 3 | g01175206 |
Operation at low speed (3) Pilot port Ps (5) Two-speed changeover valve (6) Control piston for the swashplate (11) Swashplate (13) Spring (14) Spindle (15) Maximum swashplate angle (16) Motor case (17) Port | |
When pilot pressure is not supplied to pilot port Ps (3), two-speed changeover valve (5) is pushed to the left by the force of spring (13) and pressure oil at supply port (17) is shut off. Oil in the control piston for the swashplate (6) is released to the inside of motor case (16) through the valve.
At this point, swashplate (11) is at the maximum angle (15). The volume of the cylinder is at the maximum displacement, and the motor operates at low speed and high torque.
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| Illustration 4 | g01175413 |
Operation at high speed (3) Pilot port Ps (5) Two-speed changeover valve (6) Control piston for the swashplate (11) Swashplate (13) Spring (14) Spindle (16) Motor case (17) Port (18) Minimum displacement angle | |
When pilot pressure is supplied to pilot port Ps (3), two-speed changeover valve (5) is pressed to the right against the force of spring (13). Pressure oil at supply port (17) is directed to the control piston for the swashplate (6) through the two-speed changeover valve. The oil will act on the control piston for the swashplate (6) which will push up swashplate (11). The swashplate will touch the face of the spindle (14). The swashplate is held at the minimum displacement angle. The volume of the cylinder is at the minimum displacement, and the motor operates at high speed and low torque.