Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 114

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S 1
131
S3
S2
B2
S4
Coils
Stato r
Pole pa
tt
ern
of stator
N
MOVEMENT OF VALVE
ISC - ISC Valv e
I
1
OHP 7 1
The valve shaft is screwed into the rotor. The
shaft is prevented from turning by means of a
stopper plate, so it moves in and out as the rotor
rotates . This controls the clearance between the
valve and valve seat, decreasing or increasing it
to regulate the amount of air allowed through
the bypass .
ROTATION OF ROTO R
The direction of rotation of the rotor is reversed
by changing the order in which current is
allowed to pass through the four coils . If the
stator and rotor are the 16-pole type, the rotor is
rotated about 11° (1/32 of a revolution) each
time current passes through the coils .
When the rotor rotates one step, the positional
relationship shown in the figure below develops,
and the stator coils become excited . Since the N
poles tend to be attracted to the S poles in the
stator and rotor, and since like poles in the
stator and rotor tend to repel each other, the
rotor rotates one step .
Stato r
Rotor
V ..(_C.!!!_!'
Stato r
Rotor
102
N
1
I
N
S
s
S
1 1
S
N
N
S
N
N
~- 1/32 revolutio n
s
_L
>
Repulsion
t
*
Attraction
S
S
N S
OHP 71
2 . ROTARY SOLENOID TYP E
The ISC valve is mounted on the throttle body,
and intake air that bypasses the throttle valve
passes through it .
The ISC valve is operated by signals from the
Engine ECU, and controls the amount of intake
air that is allowed to bypass the throttle valve .
Although older models still had an idle speed ad-
justing screw, its use has been discontinued in re-
cent models .
Air
intak e
Thro
tt
le valve chambe r
To cylinde r
OHP 7 2
The ISC valve is a small, lightweight rotary
solenoid type valve .
Since the air flow capacity of the rotary solenoid
type ISC valve is high, it is also used for
controlling fast idle . It is not necessary to use it
in combination with an air valve .