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| Illustration 1 | g00901529 |
Hydraulic Schematic for Machines that use Command Control Steering (1) Steering pilot valve (2) Steering wheel (3) Check valves (4) Left neutralizer valve (5) Manifold (orifice and screen) (6) Orifice (7) Screen (8) Left turn stop (9) Steering crossover relief valve (10) Left steering cylinder (11) Right steering cylinder (12) Steering control valve (13) Shuttle valve (14) Hydraulic line from the hydraulic implement pilot circuit (15) Hydraulic line from the hydraulic implement pump (16) Steering pump (17) Relief valve for the case drain for the steering pump (18) Right neutralizer valve (19) Right turn stop (20) Directional spool (21) Pressure reducing valve (22) Signal line (23) Backup relief valve (24) Hydraulic line from the pilot/brake pump (25) Pump group (26) Breaker relief valve (27) Steering return line (28) Hydraulic oil tank (AA) Pressure tap for checking pilot pressure for left turns at the steering control valve (BB) Pressure tap for checking neutral pilot pressure at the pilot control valve (CC) Pressure tap for checking supply pressure for the steering pilot valve (DD) Pressure tap for checking steering pump pressure (EE) Pressure tap for checking pilot pressure for right turns at the steering control valve (FF) Pressure tap for checking signal pressure | |
This machine uses Command Control steering. With this type of steering system, the turning speed of the machine does not depend on the turning speed of the steering wheel. Instead, the turning speed of the machine depends on the rotational position of the steering wheel.
Turn the steering wheel to the left and to the right and hold the steering wheel in that position. The machine will articulate until the angle of the non-engine end frame and the angle of the steering wheel are identical. As the angle of the non-engine end frame nears the held position (NEUTRAL position) of the steering wheel, the speed of articulation will slow down. The machine will then stop articulating when the NEUTRAL position is reached. The steering wheel will remain in the NEUTRAL position and the machine will remain at the current angle of articulation.
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| Illustration 2 | g00457327 |
Left Side View (1) Steering pilot valve. (4) Left neutralizer valve. (10) Left steering cylinder. (12) Steering control valve. (BB) Pressure tap for checking neutral pilot pressure at the pilot control valve. (CC) Pressure tap for checking supply pressure for the steering pilot valve. | |
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| Illustration 3 | g00457347 |
Right Side View (3) Steering quad check valve. (5) Manifold. (11) Right steering cylinder. (18) Right neutralizer valve. (25) Pump group. (26) Breaker relief valve. (28) Hydraulic oil tank. (AA) Pressure tap for checking pilot pressure for left turns at the steering control valve. (DD) Pressure tap for checking steering pump pressure. (EE) Pressure tap for checking pilot pressure for right turns at the steering control valve. (FF) Pressure tap for checking signal pressure. | |
The primary steering system is made up of two basic circuits. The two basic circuits are the pilot circuit and the high pressure circuit. When a machine is equipped with secondary steering attachment, the steering system includes one additional circuit.
Steering pilot valve (1) is located between the articulated hitch and the front axle. Steering quad check valve (3) is located on the right side of the front frame next to steering pilot valve (1) .
Neutralizer valves (4) and (18) are located on the front center section of the upper frame. The neutralizer valves are also located under the operator's compartment and near the upper hitch.
Manifold (5) is located on the right rear section of the upper frame. The manifold is just to the right of steering control valve (12). The manifold contains two orifices and two screens.
Steering control valve (12) is located on the left side of the machine under the operator's compartment. Steering control valve (12) is also located between the operator's compartment and the engine.
Hydraulic oil tank (28) is located on the right side of the machine. Breaker relief valve (26) is located at the top of the front side of hydraulic oil tank (28) .
Steering pump (16) is part of pump group (25). Pump group (25) consists of steering pump (16), an implement pump, and a pilot/brake pump. The pump group is located under the operator's compartment on the right side of the machine. A pressure and flow compensator valve is attached to steering pump (16) .
Pilot Circuit
The pilot system controls the movement of directional spool (20) in steering control valve (12) .
The pilot system consists of the following components: steering pilot control valve (1), steering quad check valve (3), left neutralizer valve (4), shuttle valve (13), steering pump (16), right neutralizer valve (18), pressure reducing valve (21) and hydraulic oil tank (28) .
The primary source of steering pilot oil flows from the pilot/brake pump to the hydraulic implement circuit (14). The oil then flows through a pressure reducing valve, and then to shuttle valve (13) .
If the pilot oil from the implement circuit is inadequate, there is a secondary source of pilot oil that is available. The secondary source of pilot oil flows from steering pump (16) and through pressure reducing valve (21). Pressure reducing valve (21) is located in steering control valve (12). The oil then flows to shuttle valve (13) .
When you turn the steering wheel, steering pilot control valve (1) supplies oil to steering quad check valve (3). The oil then flows to steering quad check valve (3), and then to neutralizer valves (4) and (18) .
From neutralizer valves (4) and (18), the oil flows to steering control valve (12). The pilot oil then pressurizes the respective end of directional spool (20). This causes the spool to move.
High Pressure Circuit
The high pressure circuit provides the high pressure oil for the steering cylinders.
The high pressure circuit consists of the following components. Steering crossover relief valve (9), left steering cylinder (10), right steering cylinder (11), steering control valve (12), steering pump (16), directional spool (20), backup relief valve (23) and hydraulic oil tank (28) .
Oil is drawn from hydraulic oil tank (28) by steering pump (16). Steering pump (16) is a variable piston pump. A pressure and flow compensator valve is attached to steering pump (16). The pressure and flow compensator valve controls the output of the pump.
Backup relief valve (23) in steering control valve (12) prevents excessive pressure in the high pressure circuit if there is a malfunction with the pressure and flow compensator valve.
When the pilot oil moves directional spool (20), the pressure oil is directed to the steering cylinders. When a right turn is made, the pressure oil flows to the head end of steering cylinder (10). The pressure oil also flows to the rod end of steering cylinder (11). This causes the machine to turn right.
When a left turn is made, the pressure oil flows to the head end of steering cylinder (11). The high pressure oil also flows to the rod end of steering cylinder (10). This causes the machine to turn left.
Steering crossover relief valve (9) prevents excessive pressure spikes in the steering cylinders if one of the tires hit an object.