Hydraulic Schematic
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| Illustration 1 | g00297139 |
(1) Steering accumulators (2) Steering cylinders (3) Steering solenoid and relief valve (4) Steering check valve (5) Steering filter (6) Steering hydraulic tank (7) Steering piston pump (8) Steering pump pressure switch (9) Breaker relief valve (10) Orifice fitting (11) Pressure compensator valve (12) Steering metering pump (13) Cylinder crossover relief valve (14) Steering relief valve (15) Steering solenoid valve | |
Location of Components
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| Illustration 2 | g00297271 |
Top view of the steering oil lines. (1) Steering accumulators (2) Steering cylinders (3) Steering solenoid and relief valve (4) Steering check valve (5) Steering filter (6) Steering hydraulic tank (7) Steering piston pump (8) Steering pump pressure switch (9) Breaker relief valve (10) Orifice fitting (11) Pressure compensator valve (12) Steering metering pump (13) Cylinder crossover relief valve (15) Steering solenoid valve (16) Case drain line | |
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| Illustration 3 | g00297273 |
Side view of steering oil lines. (1) Steering accumulators (2) Steering cylinders (3) Steering solenoid and relief valve (4) Steering check valve (5) Steering filter (6) Steering hydraulic tank (7) Steering piston pump (8) Steering pump pressure switch (9) Breaker relief valve (10) Orifice fitting (11) Pressure compensator valve (12) Steering metering pump (13) Cylinder crossover relief valve (14) Steering relief valve (16) Case drain line | |
Operation
The steering system is hydraulic. There is no mechanical connection between the steering wheel and steering cylinders (2) that move the front wheels. The steering system is a closed center system. The steering system is independent of all other hydraulic systems. Oil for the steering system is stored in steering hydraulic oil tank (6).
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| Illustration 4 | g00301281 |
(7) Steering piston pump (11) Pressure compensator valve (17) Pump drive | |
Steering piston pump (7) is a pressure compensated piston type pump. On the tractor, the pump drive (17) drives the steering piston pump (7), the transmission gear pump and the hoist and rear brake cooling gear pump. On the truck, the pump drive (17) drives the steering piston pump (7), the transmission gear pump and the hoist and rear brake cooling gear pump. The pump drive (17) is on the right hand frame rail near the rear of the torque converter. The pump drive (17) is driven by a drive shaft. The drive shaft is connected between the pump drive and the engine. Steering piston pump (7) operates only when the engine is running. The pressure of the steering piston pump (7) is controlled by a pressure compensator valve (11). Pressure compensator valve (11) is fastened to steering piston pump (7) .
Internal leakage from steering piston pump (7) is returned to steering hydraulic tank (6) through case drain line (16). Steering filter (5) is bolted to steering hydraulic tank (6). Return oil from the steering system flows through the steering filter and clean oil is returned to steering hydraulic tank (6). Any debris in the oil is stopped by steering filter (5) .
If the filter element becomes full of debris, the restriction to flow causes a pressure increase. A pressure above the setting of the bypass valve causes the bypass valve to open. Oil now bypasses steering filter (5). The oil goes directly to steering hydraulic tank (6). When the oil bypasses the filter element, debris in the oil will cause damage to other system components. Proper maintenance must be used to ensure that the filter element does not stop the flow of clean oil to the hydraulic system.
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| Illustration 5 | g00301282 |
(3) Steering solenoid and relief valve (4) Steering check valve (14) Steering relief valve (15) Steering solenoid valve | |
Steering hydraulic tank (6) supplies oil to steering piston pump (7). Steering piston pump (7) pumps oil through steering check valve (4) to steering solenoid and relief valve (3). Steering check valve (4) prevents oil from flowing back through steering piston pump (7) if the engine stops. Blocking the oil in the lines keeps all of the oil stored in the steering accumulators at the time of engine shutdown. If the key is not in the OFF position, the oil will be available to steer the moving machine while you try to stop. Steering check valve (4) is mounted to steering solenoid and relief valve (3) .
Steering solenoid and relief valve (3) acts as a manifold for inlet oil and return oil. Full pressure oil is supplied to steering accumulators (1) until the pressure setting of pressure compensator valve (11) is reached. When steering accumulators (1) are charged, the pressure compensator valve (11) will cause steering piston pump (7) to destroke. The steering piston pump (7) will operate at a volume in order to maintain the pressure setting of the pressure compensator valve.
When the steering wheel is turned, oil from steering accumulators (1) is used. This causes the pressure in steering accumulators (1) to drop. This causes steering piston pump (7) to stroke up to full flow in order to refill the steering accumulators (1). The pressure will increase to the pressure setting of the pressure compensator valve (11) .
Steering relief valve (14) is mounted in the lower half of the body of steering solenoid and relief valve (3). Steering relief valve (14) protects steering piston pump (7) and all other system components if the steering piston pump (7) fails to destroke after reaching the maximum steering accumulator pressure.
Steering solenoid valve (15) is mounted on the side of the body of steering solenoid and relief valve (3). When the engine is shut off with the ignition key, the electronic control for the steering accumulator activates the steering solenoid valve (15). When the steering solenoid valve is activated, the steering solenoid valve releases pressure oil in steering accumulators (1). This also prevents the machine from being turned when the machine is not in operation.
Note: The battery disconnect switch and the engine shutdown control do not activate steering solenoid valve (15) .
Steering metering pump (12) pumps a fixed amount of oil to the steering cylinders (2) in order to turn the machine. The speed of the turn is determined by the rate of the steering wheel rotation. The steering linkage is designed in order to use the head end of each cylinder as a mechanical stop.
The cylinder crossover relief valve (13) protects the steering system from sudden pressure increases. When the cylinder crossover relief valve (13) opens, oil can go between the head and rod ends of the steering cylinders (2) .