oil pressure MITSUBISHI ECLIPSE 1990 Owner's Manual

FUEL SYSTEM -Idle Speed Control14-49
Servo ControlServo control includes feedback control and position
ontrol. In feedback control, the engine control uniti;onstantly calculates the actual idle speed, and if
the
value differs from the target idle speed, the unit
drives the stepper motor to adjust actual speed to
Feedback ControlWhile the engine runs at idle speed, the stepper
motor is activated to keep the engine speed at the
preset target idle speed by controlling the bypass air
volume.
The target idle speed that is optimum for each
operating condition (including air conditioner switch
ON/OFF) has been preset. This engine speed
feedback control is provided under stabilized idling
conditions and not when any of the following
conditions occur.
l When the vehicle is moving at 2.5 km/h (1.6
mph) or more.the target value. In position control, the idle speed
control
is adjusted to the target position to cope
with air conditioner and other load changes. Position
control is also performed when cranking the engine
and decelerating.
lWhen the idle switch is turned from OFF to ON,
and while the idle switch is in the OFF position.
lWhen the air conditioner switch is turned from
ON to OFF, or vice versa.
l When power steering oil pressure switch is
turned from ON to OFF, or vice versa.
l When the ignition switch is turned from ST to
IG, or vice versa.
l While the dash pot control is in operation.
lWhen the inhibitor switch is switched from “N”
range to “D” range or vice versa.
If-1Air conditioner switch
Idle speed
control servo
r------ -- -‘,
(N range)4* I-I
BI
8
IL -L
- !5ysr motor 1I
zIdle upIStepper motor 7Engine
PII2. I.1Coolant temperature
tL.---m--v--JJ
Engine speed
I6Fuo6oo
Servo Drive Steps
(1) If there is a difference between the target and actual idle
speeds, the servo is activated the number of angular steps
corresponding to the difference, thereby extending or
.retracting the pintle to control the amount of bypass air, and
adjusts the actual idle speed to the target value.
Difference between the target
and actual idle speed fpm6FUO699I
Time sec.
c
6FUO76!The sewo drive steps during idle speed feedback Control
van/ as shown at the left.

14-50FUEL SYSTEM- Idle Speed Control
SDeed adiustina screwI -Throttle valve
Lw-3O(-22) 0132) 30(86! 601140) 9ofl94)Coolant temperature
“C (OF)6FUO641
E94
72--2--I
Q--.-.-z
3201.000 --4-\-\
5P9.o%IIIaI L-2O(-41 Of3214Of104)801176)Coolant temperature
“C VF)6FU028E
-201-4) Of3214OI104180(176(2) When the engine coolant temperature is low, the fast idle
air valve together with the idle speed control
servoperated to supply an adequate volume of bypass
,.raccording to the engine coolant temperature.
Feedback Control at
Idle(1) Basic target idle speed
The basic target idle’ speed is preset as a map value
optimized according to the engine coolant temperature.
This speed is maintained to ensure stabilized idle speed.
(2) Idle speed while the air conditioner is being operated
When the engine coolant temperature is high with the air
conditioner switch in the ON position, the idle speed is set
higher than the basic idle speed.
,
ICoolant temperature “C VF)6FUO28:Position Control
When the steering wheel is turned or the air
conditioner switch is operated while idling, theachieve the target position, thus controlling the
engine load changes and consequently the idlebypass air volume and suppressing engine speed
changes. The engine control unit also activates the
speed changes sharply. Therefore, immediately
after detection of such a load signal, the engine
control unit activates the idle speed control servo toidle speed control servo to achieve the optimum
target position while cranking, driving and decelerat-
ing, according to the operating conditions.
Power steering oil
pressure switchIInhibitor
switch
IDash pot
concjition“D”
xl
rangeposition-
UP W-U
IAlPower
steeringposition-
UP.4~i~hnditioner
IIdle speed
control servor”--““IiiI
I
c
IEngine
I
I
1wuosu
-

FUEL SYSTEM -Idle Speed Control14-51
_ 0 (32)80 (175)Coolant temperature “C (“F)6FUO2653
ATarget position during operation
of the power steering systemIDLE CONTROL SERVO POSITION CONTROL WHEN THE
ENGINE IS IDLING
(1) Basic position
The basic position is preset as a map value Optimized
according to the engine coolant temperature. The idle
speed control servo is activated to conform to this position,
thereby maintaining the optimum idle speed.
This basic position of the idle control servo
diiectlycorresponds to the basic idle speed described earlier.
1II
0(32)
80(176)Coolant temperature
“C VW6FUO291Servo position
during operation of
the air conditioner
0(32)
80(176)Coolant temperature “C (“F)6FUO757
1L)760 (30)Barometric pressure mmHg
(in.Hg)BFUlOlC(2) Servo position during shift to “D” range
For models equipped with the automatic
transaxle.when
the position of the shift lever is anywhere other than the
“P” or “N” range, the servo position is increased in
proportion to the load of the torque-converter.
(3) Idle control servo position during operation of the power
steering system
When the power steering oil pressure switch is turned on
because the steering wheel is being turned while
thevehicle is stationary, the servo position is changed to
correspond to the increased power steering pump load.
(4) Servo position while the air conditioner is being operated
When the air conditioner switch is turned on, the servo
position is changed to correspond to the increased air
conditioner load.
(5) High altitude compensation
A correction is performed by increasing the opening of the
idle speed control servo to allow increasing bypass air flow
in order to compensate for the loss of intake air volume
(asmeasured by weight) caused by a reduction in intake air
density due to a drop in barometric pressure at increased
altitude.
(6) “Training” function
A “training” function that enters a value based upon the
engine rpm and the target rpm into the memon/,
andcorrects the servo position according to this value, is
provided in order to obtain an even higher degree of
precision of position control.

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

: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 - 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 - 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.

POWER STEERING - Oil Pump
PERFORMANCE OF THE OIL PUMP
(1)
19-11 i
P-Qf characteristic (pump pressure vs. discharge quantity)
At pump rotation of 600 rpm and fluid temperature of
50-6O”C (122-l 40°F):4.4
litmin. (268.5 cu.in./min.), or more at pump pressure of
4,000
kPa (569 psi)
N-Qf Characteristic (pump rpm vs. discharge quantity)
At pump pressureof 2,000
kPa (285 psi) and fluid
temperature of
50-60X (122-140°F):
6.58
lit./min. (396.7-488.2 cu.in./min.) at pump rotation of
1,500 rpm.
3.8-6 lit./min. (231.9-366.1 cu.in./min.) at pump rotation of
3,000 rpm.
2.5-3.5 Mnin. (152.6-213.6 cu.in./min.) at pump rotation
of 4,500 rpm.
OPERATION OF THE FLUID
FLOW-
r7NTROL SYSTEM
I t 13 plunger and flow-control valve are activated bythe oil pump, thus regulating the amount of fluid
the hydraulic pressure of the fluid discharged fromflow to the gear box.
Pl;lgRelief ipring\
Relief valve13POO37

19-12POWER STEERING - Oil Pump
WHEN OIL PUMP OPERATES AT LOW SPEED
(70&l ,000 RPM)
A part of the fluid discharged from the oil pumpvariable orifices. As a result of this action the fluid
passes through the pilot port and hydraulic pressurepasses through the variable and fixed orifices, and is
is applied to the rear surface of the plunger, but,sent, by way of the plunger, to the gear box. The
because this hydraulic pressure is weak, the plungeramount of discharge to the gear box at this time is
is pushed toward the left as a result of the forcealmost maximum, with the result that an extremely
applied by the plunger’s spring, thus opening thelow steering effort is required.
PlungerVariable orificeFixed,orificeFioycontrol valve
/ I
From oil pump
To oil pumpVariable orifice
13POO38-.
Pilot portFixed orifice
.WHEN OIL PUMP OPERATES AT MEDIUM
SPEED
(1 ,OOm,OOO RPM)
When the engine speed increases and the pump’ssame time, the flow-control valve also is pressed
speed also increases, the hydraulic pressure of thetoward the
right, the bypass port opens more, and
fluid discharged from the pump becomes higher,the surplus fluid is returned back to the oil pump. In
overcoming the plunger spring’s force, and causingthis way, the amount of discharge flow to the gear
the plunger to move toward the right. As a result ofbox is reduced, thus resulting in a somewhat
this action, one of the variable orifices closes. At the“heavier” steering effort.
Variable orifice
PlungerFlow-control valve
\\Fixed yrifice/
Variable &iflceBypass ‘LrllJPOO59