1990 MITSUBISHI ECLIPSE power steering fluid

19-2 POWER STEERING
Rlh
integral rack and pinion type. This power steering
oear and the oil reservoir for effective cooling of
Fhe power steering fluid.The steering gear box is of a compact, light-weight

Steering
SYJo& assembly
oil pump
\Pressure hose
A

19-6POWER STEERING- Pinion and Valve Assembly Construction
PINION AND VALVE ASSEMBLY
CONSTRUCTION
RISKAMThe pinion and valve assembly is composed of the
input shaft, torsion bar, pinion gear and rotary valve.torsion bar, the pinion gear is provided with a
stopper. Note that this stopper also functions to
The input shaft is hollow and incorporates the
fa&tate the transmission 6i the turning effort of
torsion bar within it; the upper end is secured bythe steering wheel directly to the pinion gear by
a pin to the torsion bar, and the lower end is heldthe input shaft in the event of a malfunction of
by the bushing within the pinion gear.the hydraulic system (such as breakage of the oil
The torsion bar is coupled to the pinion gear bypump’s V-belt, fluid leakage, etc.).
the serrated part at the lower end.
lThe rotary valve is attached to the pinion gear by
In order to prevent excessive torsion of thea dowel pin.
Torsion barPm13AOO76Dowel
Section A-A
Input shaft\Torsion barpin’Stopper
/Rotary valvePinion gear1310202

:POWER STEERING
- Pinion and Valve Assembly Construction19-7 ’fOPERATION OF THE PINION AND VALVE
fi %EMBLYdulation of the hydraulic pressure applied to the
power cylinder is performed by the input shaft and
the rotary valve.
The concave and convex parts at the input shaft
surface and the rotary valve inner surface, due to
the rotational difference, function to either constrict
or expand the fluid passageway (by varying the
aperture surface area of the fluid passageway), and,
as a result, thereby regulating the hydraulic pressure
of the hydraulic circuit from the oil pump to the
cylinder tube left chamber or right chamber and
from the cylinder tube right chamber or left chamber
to the oil reservoir.
WHEN THE STEERING WHEEL IS TURNED TOTHE
RIGHTWhen the steering wheel is turned to the right, the
Port b\
Port a\Pond’
Ltorsion bar is. as shown in the illustration, caused to
torque in the direction of turning to the right, with
the result that the input shaft rotates by the
corresponding amount to the right, and a rotational
difference between the input shaft and rotary valve
develops. The concave and convex parts of the
input shaft and rotary valve cause oil passageways
R’ and L to become constricted, with the result that,
for the fluid sent from the oil pump, the flow of fluid
is stopped from port “a” to port “d” and port “c”.
When this happens, the fluid flows from the oil
pump to sleeve “a”,port “a”, port “b” and sleeve
‘lb”, and is sent to the cylinder tube right chamber,
thus causing the generation of a force to move the
rack in the leftward direction, thereby assisting the
steering effort of the steering wheel. At the same
time, the cylinder tube left chamber fluid flows
through sleeve “c”, port “c”, port “d” and chamber
“A”, and is returned to the oil reservoir.
Port c
Oil pumpOil ryetvoir
From the leftcylinder tubeChamber “A”
Torsion bar Port
b
//II YPO< aPond
4Cylinder tube
left chamberCylinder tube
right chamber

19-8POWER STEERING -Pinion and Valve Assembly Construction
WHEN THE STEERING IS AT THE CENTER POSI-
TIONBecause the input shaft does not rotate, the
and chamber “A”,returning to the oil reservoir.
position is the center (neutral) position relative to
Note that the power assist is not activated, because
the rotary valve, and the fluid supplied from the oil
no pressure difference develops in the left and right
pump flows through sleeve “a”, port “a”, port “d”
cylinder tube chambers.
Fromoil pumpVTo the left
cylinder tubeOil pump
Oil reservoir
/
13L0072Chamber “A”
JI& chamberright chamber

POWER STEERING -Pinion and Valve Assembly Construction
WHEN THE STEERING WHEEL IS TURNED TO
THE LEFT
IS-9
JVhen the steering wheel is turned to the left, the
torsion bar is, as shown in the illustration, caused to
torque in the direction of turning to the left, with the
result that the input shaft rotates by the correspond-
ing amount to the left, and a rotational
diff.erencebetween the input shaft and rotary valve develops.
The concave and convex parts of the input shaft androtary valve cause oil passageways L’ and
R to
become constricted, with the result that, for the
fluid sent from the oil pump, the flow of fluid is
stopped from port “a” to port “d” and port “b”.
IPort dnber “A”
SleeveWhen this happens, the fluid flows from the oil
pump to sleeve “a”. port “a”, port “c” and sleeve
“c” and is sent to the cylinder tube left chamber,
thus causing the generation of a force to move the
rack in the rightward direction, thereby assisting the
steering effort of the steering wheel.
At the same time, the cylinder tube right chamber
fluid flows through sleeve “b”, port
“b”, port “d”
and chamber “A”, and is returned to the oil
reservoir.Oil pump
Oil reservoir
Cylinder tube
left chamberCylinder tube
right chamber
\
Port a
Port cSleeve
coil pump
VTo the left
cylinder tube
13L0073

POWER STEERING - Oil Pump13A0067
Insi
OIL PUMPRlUAM
The oil pump has a separate oil reservoir; it is a vane-type pumpthat generates hydraulic pressure by the rotor, vanes and cam
y”ht oil pump incorporates a flow-control valve (in order to
reduce the power-assist effect during high-speed driving and
thereby improve steering stability) and a relief valve (in order to
maintain the hydraulic pressure and steering linkage rela-
tionship).
NOTEThe relief valve is incorporated within the flow-control valve.
OPERATION OF THE OIL PUMP
The rotation of the rotor causes the ten vanes to move radially
by centrifugal force, and when there is rotation along the cam
curved surface of the circular cam ring, there is action in the
radial direction along the cam curved surface.
The fluid chamber is formed by the cam ring, rotor and vanes;
when the rotor rotates the inner surface of the cam ring
(circular), the fluid chamber pressure changes to negative
pressure, with the result that the fluid within the oil reservoir,
which is at atmospheric pressure, is drawn in (suction step),
after which the rotor rotates further, discharging the fluid
(discharge step).
The action of this pump is two intake strokes and
two
discharge strokes for each vane during one rotation of the rotor.

POWER STEERING- Pinion and Valve Assembly Construction19-9
WHEN THE STEERING WHEEL IS TURNED TO
THE LEFT
JVhen the steering wheel is turned to the left, the
torsion bar is, as shown in the illustration, caused to
torque in the direction of turning to the left, with the
result that the input shaft rotates by the correspond-
ing amount to the left, and a rotational difference
between the input shaft and rotary valve develops.
The concave and convex parts of the input shaft androtary valve cause oil passageways L’ and
R to
become constricted, with the result that, for the
fluid sent from the oil pump, the flow of fluid is
stopped from port “a” to port “d” and port
“b”.
IPort dnber
*oil pump
VTo the left
cylinder tube13LOO73
SleeveWhen this happens, the fluid flows from the oil
pump to sleeve “a”,port “a”, port “c” and sleeve
“c” and is sent to the cylinder tube left chamber,
thus causing the generation of a force to move the
rack in the rightward direction, thereby assisting the
steering effort of the steering wheel.
At the same time, the cylinder tube right chamber
fluid flows through sleeve “b”, port “b”, port “d”
and chamber “A”,
and is returned to the oil
reservoir.Oil pump
Oil reservoir
Sleeve
cCylinder tube
left chamberCylinder tube
right chamber
‘Y R

POWER STEERING - Oil Pump
OIL PUMP13A0067
Insi
m-
The oil pump has a separate oil reservoir; it is a vane-type pumpthat generates hydraulic pressure by the rotor, vanes and cam
;Inhz oil pump incorporates a flow-control valve (in order to
reduce the power-assist effect during high-speed driving and
thereby improve steering stability) and a relief valve (in order to
maintain the hydraulic pressure and steering linkage rela-
tionship).
NOTEThe relief valve is incorporated within the flow-control valve.
.OPERATION OF THE OIL PUMP
The rotation of the rotor causes the ten vanes to move radially
by centrifugal force, and when there is rotation along the cam
curved surface of the circular cam ring, there is action in the
radial direction along the cam curved surface.
The fluid chamber is formed by the cam ring, rotor and vanes;
when the rotor rotates the inner surface of the cam ring
(circular), the fluid chamber pressure changes to negative
pressure, with the result that the fluid within the oil reservoir,
which is at atmospheric pressure, is drawn in (suction step),
after which the rotor rotates further, discharging the fluid
(discharge step).
The action of this pump is two intake strokes and two
discharge strokes for each vane during one rotation of the rotor.