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| Illustration 1 | g01359249 |
This module discusses the features and operation of the implement and steering system. The following Motor Graders are covered in this module:
- 120M Motor Grader
- 12M Motor Grader
The hydraulic system is a proportional priority pressure compensated system. The PPPC system is a load sensing system. The PPPC system uses a load sensing pump for the implement and steering in order to perform the pressure compensation function. The implement control valves have an internal flow compensator. This flow compensator performs the proportional priority function.
The implement system and the steering system have the following main components:
- Implement control valves
- Control manifold (steering pilot oil backup)
- Implement pilot oil filter
- Control manifold (pilot)
- Main relief valve
- Hydraulic tank
- Piston pump (implement and steering)
- Pump control valve
- Oil filter (hydraulic return)
- Joystick controls
- Steering control valve
- Centershift lock
- Blade accumulators (if equipped)
Implement Control Valves
The implement control valve regulates the operation of each implement. Each implement control valve contains a compensator valve. The compensator valve distributes the oil flow that is available. The implement control valve may contain a relief valve. The relief valve will protect the rod end of the cylinders from thermal cycle.
Control Manifold (Steering Pilot Oil Backup)
The steering pilot valve will direct pilot oil to the steering control valve when the primary steering solenoids have failed.
Implement Pilot Oil Filter
The pilot oil filter removes debris from the pilot oil for the implement solenoids.
Control Manifold
The pilot control manifold directs pilot oil to the solenoids of the implement system. The control manifold contains a main relief valve, a pressure reducing valve, a solenoid for the implement lockout switch, a pressure port and a pressure sensor.
Hydraulic Tank
The hydraulic tank stores oil for the hydraulic system.
Piston Pump (Implement and Steering)
The piston pump for the implement and steering is a variable displacement axial piston pump. When the engine is operating, the pump will produce flow in order to satisfy the following conditions:
- The demand of the steering system
- The margin pressure of the pump
- The demand of the hydraulic implements
- The internal lubrication of the pump components
Pump Control Valve
The pump control valve keeps the pump pressure and the pump flow at the level that is needed to fulfill the requirements of the implement and steering system.
Oil Filter (Hydraulic Return)
The return filter removes debris from the hydraulic system. The return filter prevents debris from entering the hydraulic tank.
Joystick Controls
The joystick controls send an electrical signal to the solenoids of the implement system and the steering system.
Steering Control Valve
The steering control valve directs the oil from the pump to the steering circuit and to the implement circuit.
Centershift Lock
The centershift lock is actuated by oil from the implement pilot system. The centershift lock receives pilot oil from the pilot control manifold. The centershift lock switch sends a signal to the solenoid for the centershift lock in order to actuate the centershift lock.
Blade Accumulators (If Equipped)
The blade cushion accumulators dampen the shock that is made in the blade lift hydraulic circuit when the blade contacts an object that will not move. The blade cushion accumulators have a nitrogen precharge pressure that provides the cushion.