CITROEN DS series Technical Manual page 39

U
The Citroën Guide
into the reservoir via the rotor of the control
valve. This pressure difference moves the pis-
ton 7 to the left inside the cylinder, helping
the car to make a right turn. If the steering
wheel stays at the right lock, the pressure
limiting valve 3 inside the flow distributor
m a i n t a i n s a m a x i m u m p r e s s u r e o f
140 bar—when the pressure rises above this
value, the fluid pushes the ball of the valve
backwards, sending the excess fluid back to
the reservoir..
When the steering wheel is turned to the
left, the rotor 5 rotates in the opposite direc-
tion. It starts by cutting of the return of fluid
to the main reservoir. The pressure will rise
again in the circuit between the flow distrib-
utor and the control valve. The rotor allows the LHM to en-
ter both chambers of the steering ram, however, the
pressed area of the left chamber is twice as large as that of
the right chamber, thus the piston will move to the right,
helping the car turn to the left.
The hydraulic assistance is only needed while the driver is
actually turning the steering wheel. When the rotating
force on the steering wheel ceases—the driver has finished
turning the wheel—, the angle difference between the dis-
tributor 4 and the rotor 5, made possible by the flexibility
Steering: Power Assisted Steering
TO LEFT
reservoir flow distributor
control
valve
5
6
4
left chamber right chamber
piston
of the torsion bar 6 disappears, reverting the system to the
neutral position, stopping the power assistance. When the
driver releases the steering wheel back to the straight-
ahead position, an opposite operation will start.
Later XMs and Xantiae omit this distributor and use a
two-section high pressure pump with two independent out-
puts instead: six pistons provide LHM for the power steer-
ing, two pistons for the rest of the hydraulics.
TO RIGHT
reservoir flow distributor
control
valve
6
5
4
left chamber right chamber
piston
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