 | |
| Illustration 1 | g00859119 |
(1) Brake disc. (2) Sun gear. | |
The front axle group contains the service brake. Brake disc (1) is splined to the sun gear shaft. Brake disc (1) rotates at the same speed as sun gear (2). When the service brake is applied, pressurized oil moves the brake piston in order to clamp brake disc (1) between the piston and the brake reaction plate.
 | |
| Illustration 2 | g00911235 |
(3) Service brake. (4) Foot brake control (service). (5) Combination valve. (6) Low brake pressure switch. (7) Brake accumulator. (8) Service brake charging switch. (9) Load sensing valve. (10) Ball resolver valve. (11) Brake accumulator charging valve. (12) Pressure reducing valve. (13) Implement pump. (14) Hydraulic tank. | |
When the operator pushes on the service brake pedal, the spool inside foot brake control (4) will move. This allows oil from brake accumulator (7) to flow to service brake (3). Service brake (3) engages the brake disc pack inside the axle. The heat from the brakes is removed by the oil inside the axle housing.
When the operator releases the brake pedal, the spool inside foot brake control (4) returns to the center position. Oil flow from brake accumulator (7) is now blocked. Oil then flows from solenoid valve (11) to the hydraulic tank.
Accumulator Charging System
Electrical current will energize brake accumulator charging valve (11) when the operator turns the engine start switch. Brake accumulator charging valve (11) blocks signal pressure oil from brake accumulator (7). This assists the starting of the engine by decreasing the load on the engine.
When the operator releases the key, current is cutoff to brake accumulator charging valve (11) and signal pressure oil flows from brake accumulator (7) to load sensing valve (9) and implement pump (13) .
A signal pressure that is equal to the accumulator pressure will travel through brake accumulator charging valve (11) and ball resolver valve (10) to the pump controls. The signal pressure will upstroke pump (13). This will increase the flow in order to charge accumulator (7) .
Brake accumulator charging valve (11) is energized when the brake accumulator pressure drops below 10350 kPa (1500 psi). Brake accumulator charging valve (11) is de-energized when the brake accumulator pressure reaches 13800 kPa (2000 psi). When the brake accumulator pressure drops below 8960 kPa (1300 psi), service brake charging switch (8) and low brake pressure switch (6) are activated. Service brake charging switch (8) will activate brake accumulator charging valve (11). Low brake pressure switch (6) will activate a low brake pressure indicator in the cab. If the service brake pressure continues to decrease, the brake will be spring applied. Once brake accumulator (7) is charged to 10350 kPa (1500 psi), service brake charging switch (8) and low brake pressure switch (6) will deactivate. This will cause brake accumulator charging valve (11) to deactivate.
Reference: For additional information, refer to Operation and Maintenance Manual, "Caterpillar Monitoring System" for the machine that is being serviced.