Subaru 1600 Service Manual page 744

3) Cruise Control Unit
The cruise control unit compares the
actual car speed detected by feedback
signals from the speedometer with the
speed set in the memory memorized
when the set switch was turned on.
Detection of car speed
{
Slow car speed
j
Car speed pulse :
Fast car speed
ELECTRICAL SYSTEM
A signal is then transmitted according
to the difference between the two
speeds.
This signal is transmitted to the sole-
noid valve of the vacuum actuator
I
located in the engine compartment.
The movement of the actuator oper-
ates the carburetor throttle valve,
thereby keeping the car speed con-
stant.
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I
T' m ' " , p.'e
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,r-------
\
~14---------------------~~1~·~~·1
I Measurement of car speed
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Operates solenoid valve Comparison-of-car-speeds pulses
(Signal is transmitted according to The number of pulses are trans-
the comparison made while timing mitted while timing pulses appear,
pulses disappeared previously) and the car speeds are compared
when timing pulses disappear.
4) Actuator
Vacuum
Vacuum
valve
Valve movement
Vacuum
movement
Diaphragm
movement
pressure
L
Safety valve and
bent valve
Filter
Fig. 15-259
To link assembly A25-625
and carburetor
Vacuum valve
Operation of
valves
Vent and safety
valves
When the cruise control is out of
operation, the safety valve and vent
valve are opened and the vacuum valve
is closed. Therefore, the inside of the
actuator is at atmospheriC pressure,
Vacuum
Electrified
Not electrified
Electrified
Not electrified
and the diaphragm does not operate.
During constant-speed driving with the
main switch on, the safety valve closes,
and the vacuum valve and vent valve
open and close to introduce a vacuum
15-81
The actuator has a vacuum valve, vent
valve, and safety valve. The opening
and closing of each valve introduces a
vacuum from the engine or air at
atmospheric pressure into the actuator
to operate the diaphragm, which in
turn operates the carburetor throttle
valve.
Inside actuator Atmosphere
Valve closes
Valve closes
0
~ .....,
or air at atmospheric pressure into the
vacuum actuator. This moves the
diaphragm, which operates the carbu-
retor throttle valve to provide control
over the car speed.
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