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| Illustration 1 | g01102091 |
This module discusses the features and operation of the brake system and the hydraulic fan system. The following motor graders are covered in this module:
- 12M
- 120M
The brake system and the hydraulic fan system have the following main components:
- Monitoring system
- Piston pump (brake and hydraulic fan)
- Pump Control Valve
- Control manifold
- Brake accumulator
- Service brake control
- Wheel group
- Parking brake
- Parking brake solenoid
- Gear motor (hydraulic fan)
- Oil cooler (brake and hydraulic fan)
Monitoring System
The Caterpillar Monitoring System consists of an action alarm, action light and a monitoring panel. The monitoring panel contains individual alert indicators for each machine system and two LCD display screens. The Caterpillar Monitoring System provides three warning categories. The first warning category requires only operator awareness. The second warning category needs operator response. The third warning category requires immediate shutdown of the machine systems.
ReferenceRefer to the Monitoring System Systems Operations for your machine for additional information.
Piston Pump Brake and Hydraulic Fan
The brake and the hydraulic fan pump is a variable displacement axial piston pump. When the engine is operating, the pump will produce flow in order to satisfy the following demands:
- The demand of the brake system
- The demand of the hydraulic fan systems
The pump will produce flow until the following conditions are met:
- The pressure setting of the pressure compensator is reached.
- The brakes and the hydraulic fan are not being operated.
Pump Control Valve
The pump control valve is mounted on the piston pump (brake and hydraulic fan). The pump control valve has two functions. The pump control valve controls system pressure. The pump control valve is load sensing. The piston pump (brake and hydraulic fan) will only produce enough oil flow in order to satisfy the demand of the brake and the hydraulic fan system.
Control Manifold
The control manifold directs the oil from the brake and the hydraulic fan pump to the brake circuit and to the fan circuit.
Brake Accumulator
There are two brake accumulators in the brake system. The brake accumulators maintain brake system pressure when the brake and the hydraulic fan pump is not supplying oil.
Service Brake Control
The service brake control valve for the service brakes provides the proper flow in order to engage the service brakes. The service brake control for the service brakes also balances the oil pressure between the left side brakes and the right side brakes.
Wheel Group
Service Brakes
The service brakes are located in the wheel groups. The service brakes are actuated by oil pressure from the service brake control valve for the service brakes. The service brakes are activated when the brake pedal is depressed.
Parking Brake
Refer to the Power Train Systems Operation/Testing and Adjusting for information regarding the parking brake and parking brake components for your machine.
Parking Brake Solenoid
The parking brake solenoid controls the operation of the parking brake. The parking brake is applied when the parking brake solenoid is the de-energized state. When the parking brake solenoid is energized oil flows to the parking brake. The oil disengages the parking brake. Refer to the Power Train Systems Operation/Testing and Adjusting for information regarding the parking brake and parking brake components for your machine.
Gear Motor (Hydraulic Fan)
The gear motor (hydraulic fan) is located in the cooling group of the motor grader. The fan is attached to the gear motor. The gear motor converts hydraulic energy into mechanical energy in order to rotate the fan.
Oil Cooler (Brake and Hydraulic Fan)
The oil cooler (brake and hydraulic fan) is located in front of the radiator group. Oil flows from the gear motor (hydraulic fan) through the cooler. The oil flows through the return filter and into the hydraulic tank.