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| Illustration 1 | g00484423 |
Steering clutches and brakes (1) Clutch piston (2) Brake housing (3) Belleville spring (4) Brake piston (5) Passage (brake pressure oil) (6) Input hub (7) Passage (clutch pressure oil) (8) Output hub (9) Passage (lubrication and cooling oil) (10) Brake plates and discs (11) Clutch plates and discs | |
The steering clutch and brake is a modular unit. There is one unit per side. These units are multiple disc, and oil cooled units that transfer power from the bevel gear to the final drives. The functioning of the clutch and brake is hydraulically controlled by a control valve which is mounted on the bevel gear case.
See this manual, "Steering and Brake Control Valve" section.
The clutch is engaged hydraulically while the brake is spring applied. This arrangement provides an automatic application of the brakes if hydraulic pressure is lost.
Power from the bevel gear is sent through an inner axle shaft to input hub (6). Input hub (6) is connected to output hub (8) by clutch plates and discs (11). Stationary brake housing (2) is connected to output hub (8) by brake discs and plates (10) .
When the machine is moving straight ahead, pressure oil from the steering and brake control valve is sent through two passages in brake housing (2). Pressure oil from one passage is sent to passage (5). This oil pushes brake piston (4) against belleville spring (3) in order to hold the brakes in the released position.
Pressure oil from the other passage is sent to passage (7) and pushes against clutch piston (1) in order to engage the steering clutches. This connects input hub (6) to output hub (8). The splines inside the output hub turn the outer axle shaft which sends power to the final drives.
Move one of the steering control levers until a resistance is felt. This will cause the flow of pressure oil to the respective clutches (right or left) to proportionally decrease. The decrease in pressure causes the clutch to slip. Also, the decrease will release the clutch.
The inner axle shaft still turns input hub (6) and clutch discs (11), but reduced power or no power is sent through the clutch to output hub (8). Pressure oil is still flowing to the respective brake which keeps the brake released. The result is a gradual turn.
As previously described, when the steering control lever is pulled past the detent, the steering clutch is released. Then, the pressure of oil to the brake immediately decreases. This pressure decreases to approximately 2000 kPa (285 psi) so that a gradual application of the brake can begin.
Further movement of the control lever decreases the oil pressure proportionally to approximately 200 kPa (28 psi) at full travel. This allows belleville spring (3) to push brake piston (4). The movement of the brake piston engages the brake. At the same time, this connects output hub (8) with stationary brake housing (2). This stops the rotation of the outer axle shaft and movement of the tracks. The result is a faster turn (sharper turn).
When the service brake pedal is pushed, the flow of pressure oil to the brakes is reduced or stopped. The rate of oil flow is determined by the position of the brake pedal. This allows belleville spring (3) to engage the brake. The flow of pressure oil to the steering clutches is not stopped, so the steering clutches remain engaged. When the brake is fully engaged, the components cannot turn. All components are stopped.
Note: It may be possible to drive through the brakes in first gear.
If hydraulic pressure is lost, the oil flow to the steering clutches and brakes is stopped and the brakes are applied by the action of the belleville spring.
Steering Clutch and Brake Lubrication
Oil for lubrication and cooling of the steering clutches and brakes comes from the oil cooler and flows through a passage in brake housing (2). The oil then goes through internal passages (9) to the discs and plates.