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| Illustration 1 | g00495357 |
Differential steer unit () Transmission pinion | |
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| Illustration 2 | g00643209 |
Differential steer unit (2) Center axle shaft (3) Bevel gear (4) Planetary gear set (5) Carrier (6) Sun gear (7) Right outer axle shaft (8) Carrier (9) Ring gear (10) Bevel gear shaft (11) Support (12) Sun gear (13) Sun gear (14) Left outer axle shaft (15) Carrier (16) Planetary gears (steering) (17) Carrier (18) Planetary gears (drive) (19) Ring gear (20) Ring gear | |
This machine uses a differential steering system. The basic system consists of the following items: differential steer unit, steering pump, steering motor and steering controls.
The differential steer unit receives power input from the following two sources: input from the transmission for speed and direction (forward or reverse) and input from the steering motor for steering (right or left).
The differential steer unit uses the power input from the steering motor in order to increase the speed of one belt. Also, the power input is used to equally decrease the speed of the other belt. The resulting difference in the speed of the belts turns the machine.
The rotational direction of the steering motor determines the direction of the turn. The speed of the steering motor determines the speed difference between the belts.
The main function of the differential steering system is a controlled steering response under varying operating conditions.
This machine is equipped with a mechanical differential steer unit. The power input is received from the hydrostatic steering system that is closed loop. Also, the power input is received from the transmission.
The power input that is from the hydrostatic steering system determines if the machine turns toward the left or if the machine turns toward the right. Also, the speed of the turn is controlled by the input from the hydrostatic steering system.
The power input from the transmission controls the direction (forward or reverse) of the turn. Also, the power or torque of the turn is controlled by the input from the transmission.
Through a combination of three planetary gear sets, the differential steer unit supplies power to both belts.
When straight line operation is required, the differential steer unit distributes the power between the belts.
When a turn is required, the differential steering divides the power between the two belts. This causes one belt to turn faster than the other belt. Power to both belts is maintained throughout the turn.
The hydrostatic steering system provides the power input to the differential steer unit through the steering motor. The steering motor is controlled by the output flow of the steering pump.
When a turn is required, the closed loop hydrostatic circuit that is between the steering pump and the steering motor maintains a consistent power input to the differential steer unit .
The differential steering system consists of the following components:
- Steering wheel
- Steering control
- Steering filter
- Steering pump
- Diverter valve
- Steering motor
- Differential steer unit
The steering pump output is controlled by the direction and the amount of steering wheel rotation. The signal pressure increases as the steering wheel is turned. This causes the turning radius of the machine to decrease.
The steering pump contains both a charge pump and a charge relief valve. The internal charge pump is charged by part of the flow from the large section of the tandem charge pump.
The steering pump contains two multifunction valves. The multifunction valves limit the system operating pressure. Also, the multifunction valves protect the steering system from high impact loads.
The power input from the transmission and the steering motor flows through the differential steer unit to the final drives.
The differential steer unit consists of the following items: three planetary gear sets, bevel gear and pinion and cluster gear. The planetary gear sets and the bevel gear are connected together by the following components: bevel gear shaft, center axle shaft, three sun gears and two outer axle shafts.
Transmission pinion (1) and bevel gear (3) are connected to carrier (17) by bevel gear shaft (10). Power from carrier (17) is divided in two directions.
Half of the power is sent through planetary gears (18) to ring gear (20). This power is a lower speed and higher torque. Ring gear (20) sends power through carrier (15) to left outer axle shaft (14) .
The other half of the power which is a higher speed and lower torque is sent through planetary gears (18) to sun gear (12). This power is a higher speed and lower torque. Sun gear (12) sends power through center axle (2) to sun gear (6).
The input from sun gear (6) is a higher speed and lower torque. This input is converted by planetary gears (4) to a lower speed and a higher torque. This output is sent through carrier (8) to right outer axle shaft (7) .
Power flows through the differential steering system in the following three ways: transmission power flow, steering power flow and a combination of transmission power flow and steering power flow. See Systems Operation/Testing and Adjusting, "Differential Steering System Power Flow" for more information.