S -2
S -2
Priority Valve 2.2 Right steering
flowrate corresponding to the opening area is
1. Turning the steering wheel right changes the oil
ensured.
passages in the orbitrol as shown in the figure. In this case, the oil used for steering assistance
4. In other words, with the steering wheel turned in
flows through the following two separate
either direction, the oil is allowed to flow to the
passages.
orbitrol at an appropriate flowrate preferentially
• Port CF → Port P of orbitrol → Orifice Ci →
selected for the particular steering, and all the
Hydraulic motor
excess oil is available for use by the other
• Port CF → Orifice Cdy → Pressure chamber B
actuator circuits.
→ Orifice Cls → Port LS of orbitrol → Hydraulic
5. The variable orifice Ci stays closed when the
motor
steering wheel is in the neutral position, but
2. The pressure oil from the hydraulic motor is
begins to open as the steering wheel is turned.
routed through port R to the steering cylinder for
The quicker the steering wheel is turned, the
assisting the rightward steering motion.
wider the orifice opens. When orifice Ci is wide open, the pressure difference between before and
3. In the priority valve, the difference in pressure between chambers A and B causes spool to move
after the orifice is small, that is, the pressure
leftward from the neutral position until the leftward
difference between pressure chambers A and B is
pressure on the spool balances with the force of
small. As a result, spring forces the spool toward
spring. The opening area of the variable orifice Ci
the left, allowing more oil to flow to the orbitrol.
changes so that the flowrate required for a particular steering will be obtained, and the spool is made balance at a stroke position where the
5
W126-0021E
