THEORY OF OPERATION - CONTINUED
STEERING SYSTEM - CONTINUED
Steering column is connected to spool by a spline coupling. Pump oil flows into control section through inlet port.
When steering wheel is not being turned, most flow is blocked by spool and sleeve. A small amount of oil flows
through a restriction on its way to hydraulic oil tank. This ensures a supply of oil at operating temperature is
always available to metering pump.
When steering wheel is turned, spool turns a small amount until centering springs are compressed. When pin con-
tacts ends of slots, sleeve also turns.
While steering wheel is turning, spool and sleeve turn as one unit. Centering springs are compressed.
This initial movement of spool opens passages between control section and metering section, allowing oil to flow
from inlet port to metering section.
Steering wheel rotation causes rotor to rotate inside rotor ring. As rotor turns, a controlled flow of oil flows
through housing. This oil flows to right-turn port or left-turn port, then to steering control valve.
When steering wheel rotation is stopped, centering springs move both spool and sleeve into alignment. This closes
passages between metering section and control section.