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| Illustration 1 | g06130926 |
Steering control valve (1) is mounted under the hydraulic tank.
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| Illustration 2 | g06195304 |
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(1) Steering control valve
(2) Remote steering pilot supply solenoid (3) Steering solenoids (4) Steering relief and make-up valves (5) Pump back-up relief valve (6) Spool position sensor | |
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| Illustration 3 | g06238624 |
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(3) Steering solenoids
(4) Steering relief and make-up valves (5) Pump back-up relief valve (7) Passages to steering cylinder ports (8) Pilot chamber (9) Inlet from the steering pump (10) Steering spool (11) Drain passage to the hydraulic oil tank (12) Check valve (13) Pilot chamber | |
Oil is drawn from the hydraulic oil tank by the steering pump. The steering pump provides flow to the steering control valve through the inlet passage (9). This flow is controlled by the pressure and flow compensator valve attached to the steering pump. Pump supply oil is also sent to the brake accumulator charging valve for supplemental pilot pressure. This oil provides a secondary source of pilot oil in the event of brake, pilot, fan pump failure.
When pilot oil shifts steering spool (10), high-pressure oil is directed to the steering cylinders through passages to steering cylinder ports (7). When turning right, oil flows to the rod end of the right steering cylinder and to the head end of the left steering cylinder. This action causes the machine to turn right. When turning left, the oil flows to the rod end of the left steering cylinder and to the head end of the right steering cylinder. This action causes the machine to turn left. Steering relief and make-up valves (4) prevent excessive pressure spikes and voiding in the steering cylinders.
Steering control valve (1) contains pump back-up relief valve (5) and check valve (12). Pump back-up relief valve (5) limits the maximum pressure in steering control valve (1). Pump back-up relief valve limits this pressure in case the pressure cutoff spool in the pump controller fails. Check valve (12) restricts the return oil flow to the hydraulic tank through passage (11). Check valve (12) maintains enough pressurized oil in an internal passage to prevent cylinder voiding when articulating the machine on a slope.
Steering relief and make-up valves (4) protect the steering cylinders from sudden pressure spikes. Steering relief and make-up valves (4) will dump oil in drain passage (11) when pressure raises above the relief setting. Steering relief and make-up valve (4) eliminates cylinder voiding.
Pilot supply solenoid (2) is only energized when the remote control switch is pressed. Energizing the solenoid allows pilot oil to be sent to steering solenoids (3).
The steering solenoids (3) regulate the pilot oil sent through pilot chambers (8) and (13) to steering spool (10). Pilot oil sent to steering valve (1) is regulated by the amount of current sent to the steering solenoids (3) from the Implement ECM. Steering spool (10) directs supply oil to the steering cylinders. The Implement ECM receives input from the spool position sensor (6) of steering valve (1) to indicate the position of steering spool (10). The Implement ECM will monitor the position of the steering cylinders and spool position sensor (6). The Implement ECM will decrease the current to steering solenoids (3) as the steering cylinders approach the desired position.