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| Illustration 1 | g01088242 |
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PS-150C | |
The steering hydraulic system shares a common hydraulic tank with the propel hydraulic system. The steering system is equipped with a separate pump.
The steering system section of this presentation is divided into segments. The first segment shows the location of all hydraulic components on the machine which are part of the steering system. This segment provides a general overview of the steering system.
The last segment explains the operation of the steering hydraulic system. Hydraulic schematics are used in this segment to trace hydraulic oil through the hydraulic system.
Location of Steering Components
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| Illustration 2 | g01088253 |
The following components are part of the steering system:
- Metering pump (1)
- Hydraulic tank (2)
- Steering pump (3)
- Steering cylinder (4)
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| Illustration 3 | g01088254 |
Hydraulic tank (2) is located at the front of the engine compartment. The engine compartment cover provides access to this component.
All of the hydraulic systems on the machine share a common hydraulic tank. The capacity of the hydraulic tank is
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| Illustration 4 | g01088425 |
The machine is equipped with a single steering cylinder (4) which is located under the front of the machine. The head end of the steering cylinder is connected to the machine frame. The rod end of the steering cylinder is connected to the front bolster. The action of the steering cylinder causes the front bolster to pivot around a center pin. The front wheels are mounted to the front bolster.
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| Illustration 5 | g01088454 |
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Steering Hydraulic System in Hold | |
When the engine is operating, the steering pump sends flow to the P port of the metering pump. The steering control unit consists of a spool and a metering pump. The control spool is a rotary valve which is spring centered. The metering pump is a gerotor pump. The control spool governs the direction of the turn while the metering pump controls the rate of turn.
If the machine is traveling and the engine stops, the operator can manually operate the metering pump. When the operator turns the steering wheel, the metering section of the control unit acts as a pump. The suction from the metering section opens the check valve in the control unit. Under these conditions, oil flows from one end of the steering cylinder to the other end.
When the machine is traveling in a straight line, the center envelope of the metering pump is active. This prevents oil from flowing to the metering pump and to the steering cylinder. Pump supply oil flows across the center of the control spool and returns to the hydraulic tank.
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| Illustration 6 | g01088458 |
When the operator turns the steering wheel to the left, pump supply oil flows across the control spool to the metering section. The metering pump rotates with the rotation of the steering wheel. The metering pump directs flow through the control spool and into the head end of the steering cylinder. Oil that flows into the head end of the steering cylinder causes the rod to extend. Rod extension causes the machine to turn left. Oil in the rod end of the steering cylinder returns to the hydraulic tank through the control spool.
As the operator turns the steering wheel faster, the metering pump increases the flow to the head end of the steering cylinder. Therefore, the machine turns faster. The metering pump continues to direct flow to the head end until the operator stops turning the steering wheel. When rotation of the steering wheel is stopped, the centering springs in the control spool return the spool to the center position. Oil is blocked at the steering cylinder. The machine continues to turn at the same radius until the operator moves the steering wheel again.
If the steering cylinder reaches the end of the cylinder's stroke but the operator continues to turn the steering wheel, pressure in the system increases. When pressure in the system reaches
Note: Operation of the steering system follows a similar logic when the machine is turned to the right. During a right turn, oil is directed into the rod end of the steering cylinder.