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| Illustration 1 | g00274368 |
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Top View of Steering Component Locations (1) Hydraulic and steering pump (2) Combination valve (3) Steering accumulator (4) Steering metering pump (AA) Outlet port to the combination valve (BB) Inlet port from the combination valve (CC) Outlet port to the right steering cylinder (DD) Load sensing signal port (EE) Outlet port to the left steering cylinder | |
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| Illustration 2 | g00274369 |
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Right Side View of Steering Component Locations (1) Hydraulic and steering pump (2) Combination valve (4) Steering metering pump (5) Steering cylinder crossover relief valve (6) Right steering cylinder (AA) Outlet port to the combination valve (BB) Inlet port from the combination valve (CC) Outlet port to the right steering cylinder (DD) Load sensing signal port (EE) Outlet port to the left steering cylinder | |
The steering circuit is composed of three main components:
- Steering priority valve
- Steering metering pump (4).
- Left and right steering cylinders.
Hydraulic oil for the steering circuit is supplied by the hydraulic and steering pump (1). The steering priority valve gives priority to the steering function over the available hydraulic pump flow. The priority valve senses pressure in the steering circuit. Then, the priority valve directs flow to steering accumulator (3) until the demand is satisfied.
Typically, the requirements of the oil flow for the steering circuit are significantly less than the available hydraulic pump flow. This means that oil flow to other implement circuits will not be interrupted when the steering is operated. Steering metering pump (4) provides oil flow to the steering cylinders. This depends on the direction and the rotation of the steering wheel. The steering cylinders that are mounted on the front axle turn the front wheels to the right or to the left.
Oil Flow of the Steering Hydraulic System
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| Illustration 3 | g00274371 |
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Steering System in the HOLD Position (1) Hydraulic and steering pump and pressure and flow compensator valve (2) Combination valve (3) Steering accumulator (4) Steering metering pump (5) Steering cylinder crossover relief valve (6) Steering cylinders (7) Gerotor (8) Rotary sleeve (9) Signal resolver (10) Steering priority valve (11) Hydraulic tank (BB) First pressure reduction oil (CC) Second pressure reduction oil (FF) Reduced pilot oil (JJ) Trapped oil (LL) Tank oil | |
Second pressure reduction oil (CC) is approximately
The pilot reduced oil (FF) from steering priority valve (10) then flows to the signal port on steering metering pump (4). Signal oil then flows through an orifice in rotary sleeve (8) back to hydraulic tank (11).
When there is no steering demand, the oil pressure in the signal line is approximately
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| Illustration 4 | g00274372 |
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Hydraulic and Steering Pump and Combination Valve in the HOLD Position (1) Hydraulic and steering pump and pressure and flow compensator valve (2) Combination valve (3) Steering accumulator (9) Signal resolver (10) Steering priority valve (11) Hydraulic tank (12) Steering relief valve (13) Implement relief valve (14) Signal relief valve (15) Signal purge valve (16) Flow compensator (17) Pressure compensator (BB) First pressure reduction (CC) Second pressure reduction (FF) First reduced pilot oil (HH) Trapped oil (LL) Tank oil | |
When the steering wheel is turned, oil flow from steering priority valve (10) and steering accumulator (3) is directed to the steering cylinders through rotary sleeve (8) and metering action of gerotor (7). The load sensing line on steering metering pump (4) is internally connected to the pressurized cylinder ports. This action limits the signal pressure that originates from the steering priority valve to the actual steering cylinder pressure. Signal pressure upstrokes the hydraulic and steering pump in order to meet the highest pressure and the flow demands.
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| Illustration 5 | g00274373 |
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Steering Metering Pump in the HOLD Position (4) Steering metering pump (5) Steering cylinder crossover relief valve (6) Steering cylinders (7) Gerotor (8) Rotary sleeve (18) Check valve for the supply oil (19) Anticavitation check valve (CC) Second pressure reduction oil (FF) First reduced pilot oil (HH) Trapped oil (LL) Tank oil | |
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| Illustration 6 | g00274374 |
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Steering System During a Right Turn (1) Hydraulic and steering pump and pressure and flow compensator valve (2) Combination valve (3) Steering accumulator (4) Steering metering pump (5) Steering cylinder crossover relief valve (6) Steering cylinders (7) Gerotor (8) Rotary sleeve (11) Hydraulic tank (AA) High pressure oil (CC) Second pressure reduction oil (EE) Pilot oil (LL) Tank oil | |
In order to make a right turn, gerotor (7) pumps oil through rotary sleeve (8) to the crossover relief valve (5). Oil then flows to steering cylinders (6). Oil flows to the head end of the left steering cylinder. This forces the cylinder rod outward. Also, oil flows to the rod end of the right steering cylinder. This forces the cylinder rod inward. The steering cylinders pivot the wheels so that the machine turns right.
Oil that is forced out of the opposite ends of the steering cylinders flows back to rotary sleeve (8). The oil continues to combination valve (2) and flows back to hydraulic tank (11).
Crossover relief valve (5) prevents damage from high pressure oil in the steering circuit. When the oil pressure increases to