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| Illustration 1 | g00684967 |
(1) Travel motor. | |
Travel motor (1) is used on the 550 Wheel Harvester and the 570 Wheel Harvester. Travel motor (1) is also used on the rear wheels of 580 Wheel Harvesters. Travel motor (1) has two speeds.
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| Illustration 2 | g00685026 |
(2) Travel motor ( 580 Wheel Harvester). | |
Travel motor (2) is used on front wheels of the 580 Wheel Harvester only. The front travel motor (2) turns a bogie drive chain. Two tires are mounted on each bogie assembly. Travel motor (2) has three speeds.
Travel motors are hydraulic radial piston motors. In low speed, the travel motor generates high torque and high displacement. In high speed, the travel motor generates low torque and low displacement.
A charge pressure is required to change the displacement of the travel motor. This charge pressure is provided by the speed control valve.
The speed selection of the machine determines when the IQAN changes the displacement of the travel motor.
Each travel motor has an internal brake. The brake is spring applied and pressure released. The brake is used to hold the machine in position when the drive system is not activated. The brakes are automatically applied when the accelerator is released.
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| Illustration 3 | g00685003 |
Pistons and Cam of the Travel Motors (3) Cylinder block. (4) Piston. (5) Cam ring. (6) Distribution valve. (7) Roller. (CC) Return oil. (DD) Supply oil. | |
The travel motor uses six pistons (4) with rollers (7). These components work against cam ring (5). This causes cam ring (5) to turn. The wheel is connected to the cam ring.
The displacement of the travel motor is controlled by the charge pump oil that is acting against the spring loaded displacement spool.
In each travel motor, pistons (4) are radially positioned in the cylinder block (3). Cylinder block (3) is fixed.
Cam ring (5) has eight lobes. The cam is shaped similarly to a sine wave that is wrapped in a circle. High pressure oil from the power train pump works against the pistons, when the pistons are on the downward slope. Cam ring (5) and distribution valve (6) are connected together.
Torque is generated when the pistons push the rollers down the slope of the cam ring.
When the roller is at the bottom of the slope, the piston and the cylinder are blocked from the supply and return passages. When the roller moves beyond the bottom of the slope, the piston is connected to the return side of the loop and the oil is forced out of the cylinder as the roller moves up a slope on the cam.
When the roller is at the top of the slope, the piston and the cylinder are blocked from the supply passages and the return passages. The piston and the cylinder will be blocked from the supply passages and from the return passages until the roller passes over the center and the cycle begins again.
Neutralization of the Front Travel Motor (Freewheeling)
Note: Only the front travel motors of the 580 Wheel Harvesters can be neutralized.
The front travel motors are neutralized when the following conditions exist.
- The machine is in second speed or third speed.
Oil from the front power train is also blocked from flowing to the front travel motors.
Freewheeling is accomplished by introducing pressure into the casing of the front travel motors. The case pressure pushes the pistons into the bores in the cylinder blocks. The rollers are held off of the cam.
The pressure that is needed to neutralize the travel motors is 150 kPa (22 psi) at normal operating temperature or 300 kPa (44 psi) at cold start temperature.