| |
| Illustration 1 | g06334503 |
The steering control valve is mounted on the left-hand frame rail above the front axle. The steering control valve receives oil from the steering metering unit and directs the oil to the steering cylinders.
| |
| Illustration 2 | g03733930 |
|
View of steering control valve ports (1) Steering control valve (2) Port to tank (3) Port to steering metering pump (4) Right-hand pilot port (5) Port to left-hand cylinder (6) Port to right-hand cylinder (7) Left-hand pilot port (8) Pump inlet port (9) Load sensing signal port (10) Pilot pressure signal port (11) Load sense relief valve | |
| |
| Illustration 3 | g03733909 |
|
View for the steering control valve in the HOLD position (1) Steering control valve (2) Steering cylinders (3) Cross over relief valves (4) Control valve (5) Amplifier spool (6) Load sense relief valve (7) Tank (8) From steering valve and manifold (9) Load sense gauge (10) Steering metering pump (11) Priority spool | |
When the engine is started, oil for the steering system is drawn from the hydraulic tank by the steering pump. Oil is sent through the steering oil filter to the priority valve that is inside the "Priority Valve and Manifold". The "Priority Valve and Manifold" will give priority to the steering system. The "Priority Valve and Manifold" remains closed until the pressure in the steering system reaches normal operating pressure. Once the steering system requirements are satisfied, the "Priority Valve and Manifold" will OPEN. Oil is directed to the "Final Drive Lube" solenoid and the "Drive Train Cooling Fan" motor. The "Final Drive Lube" solenoid controls the oil flow to the "Final Drive Lube" motor. The "Priority Valve and Manifold" relief valve will OPEN the priority valve and allow oil pressure and flow to the drive train fan circuit and the final drive lube circuit.
Oil from the "Priority Valve and Manifold" flows through an orifice and check valve to the control manifold. Inside the control manifold, oil flows to the relief valve and through a check valve to the brake system. Oil then flows to the accumulator drain solenoid, steering accumulators, and "Steering Control Valve" (1). After the oil pressure increases to a predetermined pressure in the accumulators, the steering pump will de-stroke. When a steering demand occurs, the accumulators supply the necessary oil flow for steering, and pressure in the accumulators decreases. When the oil pressure decreases to a predetermined level, the steering pump will automatically upstroke to maintain the oil pressure in the accumulators.
Oil from the accumulators flows through the priority spool to "Steering Control Valve" (1). If the steering wheel is not turned or in the HOLD position as shown, a small amount of oil flows through control valve (4) to the tank. Allowing oil to circulate through the steering valve while the steering wheel is stationary provides a thermal purge condition, which maintains a temperature differential of less than
| |
| Illustration 4 | g06413965 |
|
View for the steering control valve in the TURN position (1) Steering control valve (2) Steering cylinders (3) Cross over relief valves (4) Control valve (5) Amplifier spool (6) Steering relief valve (7) Tank (8) From steering valve and manifold (9) Pressure gauge (10) Steering metering pump (11) Priority spool | |
When the steering wheel is turned, steering control valve (1) directs oil to one side of "Control Valve Spool" (4). "Control Valve Spool" (4) shifts and directs oil to steering cylinders (2). The direction the steering wheel is turned determines the flow to the steering cylinders. Oil will flow to the head end of one steering cylinder and to the rod end of the other steering cylinder. The action of the oil on the pistons and rods in the steering cylinders causes the wheels to change direction. Displaced oil from the steering cylinders flows through control valve (4) to the tank.