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| Illustration 1 | g01290483 |
This module discusses the features and operation of the implement and steering system. The following motor graders are covered in this module:
- 14L 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 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
- Shutoff valve
- Implement pilot oil filter
- Control manifold
- 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)
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.
The shut-off manifold contains a solenoid that will direct or inhibit pilot oil to the solenoids of the implement system based on the implement lock-out switch position in the cab. The shut-off manifold also contains a shuttle valve to send the appropriate load sense signal from the implement or steering system to the pump control valve.
The pilot oil filter removes debris from the pilot oil for the implement solenoids.
The pilot control manifold directs pilot oil to the solenoids of the implement system. The control manifold contains a main relief valve, a secondary steering relief valve, and a pressure reducing valve. The control manifold also contains a pressure port for the pilot system, a pressure port for the implement and steering system, an SOS port, and a pressure sensor.
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 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
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.
The return filter removes debris from the hydraulic system. The return filter prevents debris from entering the hydraulic tank.
The joystick controls send an electrical signal to the solenoids of the implement system and the steering system.
The steering control valve directs the oil from the pump to the steering circuit and to the implement circuit.
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 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.