Specifications

Vehicle System System Operation 32

Oil Flow

The oil from the control valve flows through inlet

(4). When the steering wheel is stationary

(NEUTRAL), the oil is stopped by spool (1). The oil

can not flow through the steering gear to the

steering cylinder until the steering wheel is turned.

The steering wheel is connected to spool (1) by a

shaft assembly and splines. When the steering

wheel is turned, spool (1) turns a small amount until

springs (7) are compressed. Then, sleeve (2) starts

to turn. As long as the steering wheel is turned, the

spool and sleeve both turn as a unit, but they turn a

few degrees apart.

When the spool and sleeve are a few degrees apart,

oil passages are opened between them. This lets

the pump oil from inlet (4) flow through passages in

body (11) to the metering section.

When the steering wheel is turned, pin (8) turns

with the sleeve and causes drive (12) to turn also.

The drive causes a rotation of gear (5) inside gear

(6). This rotation of the gear sends a controlled

(metered) flow of pilot oil back through body (11).

This oil flows to port (9) or (10) and then to the

steering cylinder. Port (9) or (10), that is not used

for pressure oil to the steering cylinder, is used for

return oil from the other end of the steering cylinder.

Pump Gears In Metering Section

(5) Internal pump gear. (6) External pump gear. (8)

Pin. (12) Drive.

If the steering wheel rotation is stopped, springs(7)

will move sleeve(2) back in alignment with spool(1)

(NEUTRAL position). This will close passages

between the metering section and control section

and the steering gear will be in the NEUTRAL

position.

When the engine is off, the steering gear can be

manually operated. The control section will work as

a pump. The oil that is returned from the steering

cylinder is not returned to the tank. The suction of

the control section will open an internal check valve

and let return oil from the steering cylinder go to the

inlet side of the control section. During power

operation, supply pressure keeps the check valve

closed.

IDCS114S