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| Illustration 1 | g02645376 |
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Service Brake Circuit (1) Pilot/differential manifold (2) Accumulator (3) Pressure reducing valve (4) Rear differential lock (5) Auxiliary pump arming valve (6) Proportional solenoid valve (Rear differential lock) (7) Auxiliary pump (8) Attachment pump arming valve (9) Charging valve (10) Hydraulic tank (11) Service brake (12) Front brake/differential manifold (13) Proportional solenoid valve (Service brakes) (14) Accumulator pressure switch | |
When the operator pushes the arming button on the keypad with the machine running, a signal is sent to the machine electronic control module (ECM). The machine ECM activates auxiliary pump arming valve (5) and attachment pump arming valve (8)
The auxiliary pump (7) draws oil from hydraulic tank (10). The oil from auxiliary pump (7) flows to pilot/differential manifold (1). The oil flows through an orifice, a check valve to accumulator (2) and pressure reducing valve (3). The oil then flows to proportional solenoid valve (6) for rear differential lock (4). The oil also flows through a second orifice to charging valve (9). Charging valve (9) charges accumulator (2).
The oil from pressure reducing valve (3) also flows out of pilot/differential manifold (1) into front brake/differential manifold (12) to proportional solenoid valve (13) for service brakes (11). Accumulator pressure switch (14) will alert the operator if the pressure is low to the front brake/differential manifold (12).
When the operator pushes the service brake pedal, a signal is sent from the machine ECM to proportional solenoid valve (13) for service brakes (11). The oil pressure is regulated by proportional solenoid valve (13). The oil flows through proportional solenoid valve (13) to service brakes (11). The service brakes (11) are applied.
This action allows oil from accumulator (2) via auxiliary pump (7) to flow to service brake (11). Service brakes (11) engages the brake disc 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 machine ECM turns off oil proportional solenoid valve (13). Proportional solenoid valve (13) shift blocking the flow from accumulator (2) via auxiliary pump (7). Oil then flows from service brakes (11) through proportional solenoid valve (13) then out of front brake/differential manifold (12) to hydraulic tank (10).
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| Illustration 2 | g02644556 |
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(15) Brake disc
(16) Sun gear | |
The front axle group contains two service brakes. Brake disc (15) is splined to the sun gear shaft. Brake disc (15) rotates at the same speed as sun gear (16). When the service brake is applied, pressurized oil moves the brake piston to clamp brake disc (15) between the piston and the brake reaction plate. This action applies the service brake.
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| Illustration 3 | g02646625 |
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Service Brakes for the Axle (1) Service brake oil passage (2) Plate (3) Disc (4) Plate (5) Piston (6) Axle (7) Carrier (8) Sun gear (9) Pins (three) (10) Springs (three) (11) Ring gear | |
Each service brake contains the following components: disc (3), plate (4), piston (5), pins (9), and springs (10).
Note: The following section will describe the operation of the service brakes.
Plates (2) and (4) and piston (5) are held stationary by three pins (9). The pins are fastened in the differential housing and in the housing for the axle shaft. The piston and the plates are able to slide on the three pins, but the pistons and the plates do not rotate. Springs (10) keep piston (5) in the RETRACTED position when the piston is not being used.
Disc (3) has splines on the inside diameter that fit on the splines of sun gear (8). This causes disc (3) to rotate at the speed of the sun gear. Grooves are cut into the faces of disc (3). The grooves permit the passage of cooling oil between disc (3) and plates (2) and (4).
This action will occur even when the service brakes are applied. If the groove depths are within specifications, cooling oil will constantly flow between disc (3) and plates (2) and (4) as disc (3) rotates.
Carrier (7) is fastened with splines to axle (6). The axle turns with the carrier. The gears in carrier (7) rotate between sun gear (8) and stationary ring gear (11).
When the brake pedal is pushed, pressurized oil from the service brake control valve flows through oil passage (1) in the differential housing. The force of the oil behind piston (5) moves plate (2) against the force of springs (10).
The force of the oil also pushes disc (3) against plate (4). This causes friction between disc (3) and plates (2) and (4). The friction causes the rotation of sun gear (8), axle (6), carrier (7) and the wheels to slow down. When the friction is great enough, the rotation will come to a stop.
The heat that is created from the friction of the service brakes is removed by the oil that is in the axle housings.
When the brake pedal is released, the oil behind piston (5) flows through oil passage (1). This oil flows to the service brake control valve. The oil then returns to the hydraulic oil tank. With no oil pressure behind piston (5), springs (10) move the piston to the RETRACTED position and the service brakes are released.
If the machine loses power, or if the hydraulic pump fails, the service brakes can still be applied. The pressure in the nitrogen charged accumulators for the service brakes allows several applications of the brake pedals.