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| Illustration 1 | g02679259 |
Hydraulic Schematic for Machines that use Command Control Steering (1) Steering pilot valve (2) Steering wheel (3) Steering quad check valve (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) Steering backup relief valve (18) Right neutralizer valve (19) Right turn stop (20) Directional spool (21) Pressure reducing valve (22) Signal line (23) 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 pilot 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 in relation to the non-engine end frame.
The pilot control valve is located on the non-engine end frame and the steering wheel is located on the engine end frame. The NEUTRAL position of the steering wheel is directly related to the angle of the front frame. Whenever the machine is in the STRAIGHT AHEAD position the NEUTRAL position for the steering wheel is also straight ahead. Whenever the front frame of the machine is pointed to the left, the NEUTRAL position for the steering wheel will be pointed to the left. Whenever the front frame of the machine is pointed to the right, the NEUTRAL position for the steering wheel is also pointed to the right.
Turn the steering wheel to the right or to the left 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 the articulation.
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| Illustration 2 | g02679277 |
Left Side View (1) Steering pilot valve (3) Steering quad check valve (4) Left neutralizer valve (10) Left steering cylinder (BB) Pressure tap for checking neutral pilot pressure at the pilot control valve (CC) Pressure tap for checking pilot supply pressure for the steering pilot valve | |
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| Illustration 3 | g02679278 |
Right Side View (5) Manifold (11) Right steering cylinder (12) Steering control valve (18) Right neutralizer valve (23) 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 left 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 under the cab compartment near the upper hitch.
Manifold (5) is located on the right front section of the upper frame. The manifold is just to the right of steering neutralizer valve (18). The manifold contains two orifices and two filter screens.
Steering control valve (12) is located on the right side of the machine under the cab compartment.
Hydraulic oil tank (23) is located behind the cab.
Steering pump (16) is located under the cab 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 (23) .
The primary source of steering pilot oil flows from the hydraulic implement circuit. The oil 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 pressure causes the spool to move. The return path for the oil to be drained from the pilot chambers next to the directional spool are screened orifices. These orifices also perform the correct modulation of the start of steering actuation.
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), steering backup relief valve (17) and hydraulic oil tank (23) .
Oil is drawn from hydraulic oil tank (23) 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 helps control the output of the pump.
A backup relief valve in steering control valve (12) prevents excessive pressure in the high-pressure circuit if the pressure and flow compensator valve malfunctions.
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 process 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 process causes the machine to turn left.
Steering crossover relief valve (9) prevents excessive pressure spikes in the steering cylinders. The pressure spikes could develop if one of the front tires hits an object.