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| Illustration 1 | g03668994 |
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(1) Hydraulic tank
(2) Steering control valve (3) Secondary steering pump (4) Implement electronic control module (ECM) (5) Oil filter (pilot) (6) Shutoff valve (7) Steering cylinders (8) Joystick control (9) Oil filter (hydraulic Return) (10) Implement and steering pump and pump control valve (11) Pilot control manifold | |
This module discusses the features and operation of the steering system. The following motor graders are covered in this module:
- 16M Series 3 Motor Grader
- 18M Series 3 Motor Grader
The machines are equipped with an electro-hydraulically controlled steering system.
The following components make up the electro-hydraulic steering system:
- Implement Pilot Oil Filter
- Control manifold
- Shut-off manifold
- Hydraulic tank
- Piston Pump (Implement and Steering)
- Pump Control Valve
- Oil Filter (hydraulic return)
- Joystick controls
- Steering control valve
- Secondary steering pump
- Implement #2 electronic control module (ECM)
- Transmission/Chassis electronic control module (ECM)
- Steering cylinders
The implement #2 ECM controls the primary steering system. The implement #2 ECM uses a closed loop system with cylinder position feedback in order to control the steering angle. The ECM determines the desired steering angle based on the position of the steering axis on the left-hand joystick. The ECM sends control signals to the primary steering valve solenoids to change the position of the steering cylinders to achieve the desired steering angle. As the steering cylinders reach the commanded position, the ECM will decrease the control signals to the solenoids until movement of the cylinders are stopped. The cycle repeats as the position of the steering axis on the left-hand joystick changes.
The implement #2 ECM outputs to the steering valve control the primary steering solenoid valves and the primary steering pilot supply ON/OFF solenoid. The implement #2 ECM receives inputs from the steering valve spool position sensor based on the position of the valve spool.
When the key start switch is in the ON position, the implement #2 ECM will turn ON the primary steering pilot supply ON/OFF solenoid. This action will result in available pilot pressure being passed through to the primary steering solenoid valves.
The pilot oil filter removes debris from the pilot oil for the implement and steering 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 two pressure ports, an oil sampling port, and a pressure sensor.
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 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
The pump control valve keeps the pump pressure and the pump flow at a level 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 via the ECM's.
The steering control valve directs the oil from the pump to the steering circuit and to the implement circuit.