Chevrolet 10 Series 1970, Руководство по обслуживанию

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ACCESSORIES 15-3
H O U S IN G C O V E R
R E G U L A T O R
Fig . 3 —R e g u la to r U n it
balance o f a ir and vacuum is blended at the " T e e " fittin g
and is im posed upon the S ervo unit to maintain an “ on
s p e e d " cru ise condition. See F ig . 3 & 8.
An additional function o f the R egu lator is to d riv e
the sp eed om eter. Since the c a r speed is sensed by a
sp e e d o m e te r-lik e
m echanism w i t h i n the unit, the
sp eed om eter cable fro m the tran sm ission d riv e s the
R egu lator which d r iv e s a second cable (at a one to one
ra tio ) to the speedom eter.
The R egu lator is e le c tr ic a lly engaged and disengaged
through operation o f the Engagem ent Switch and the
E le c t r ic B rake R e le a s e Switch. It has two subassem blies
which make up the unit: one being the m agnetic speed
sensing assem b ly and the other being the solenoid a c ­
tuated vacuum sw itch, a ir b leed and filt e r , and low lim it
speed switch assem bly. See F ig. 8.
M ag n etic Speed Sensing A ssem bly
The speed sensing assem b ly op erates in the sam e man­
n er as a speedom eter unit except that instead o f rotating
a needle through an angle p rop ortion a l to the veh icle
speed, it rotates a rubber drum which is clutched to the
a ir b leed v a lv e when the system is in operation. The
assem b ly is driven by the sp eed om eter cable fro m the
tra n sm issio n which turns a disk shaped fe r r it e magnet.
Facin g the m agnetic disk is the d riven copper disk
mounted on a shaft with the rubber drum mounted on the
sam e shaft. A s p ira l h a irsp rin g connects the shaft to the
housing and allow s it to rotate through an angle which is
p ro p o rtio n a l to car speed. If the ca r doubled its speed,
the shaft would rotate to tw ice its p reviou s angle as may
be seen by noting the operation of a speedom eter. The
d riv e n disk is sandwiched between the m agnetic disk and
a fie ld plate. The fie ld plate fo rm s a returning path fo r
the m agnetic fie ld fro m the m agnetic disk.
The input shaft d riv e s both the m agnetic disk and the
sp eed om eter d riv e cable.
Vacuum Switch, A ir Bleed and Filter, and Low
Limit Speed Switch
The end o f the shaft fro m the speed sensing a ssem b ly
with the rubber drum extends into the a ir b leed m eterin g
assem bly. T h is rubber drum has a tang extending fro m
its su rface which allow s a set o f points to clo se at a
sp e c ific c a r speed. When the c a r reach es about 35 mph,
the rubber drum has rotated fa r enough (m oved by the
b ra s s d riven disk in the m agnetic fie ld ) so that its tang
has allow ed a spring loaded e le c tr ic a l point to contact
another point. T h ese points a re in s e r ie s with the s o le ­
noid c o il so that under 30 mph, no R egu lator operation
is p ossib le.
Surrounding the rubber drum is a " U ” shaped spring
c lip which is held spread away fro m the drum by the
nose o r cam o f the solenoid when the solen oid is in the
re la x e d position. The rubber drum and this clip com ­
p r is e the speed clutch o f the regu la tor. When the s o le ­
noid is e n e rg ized , the solenoid nose m oves tow ard the
drum and re le a s e s the ends o f the clip. The clip springs
inw ard and attaches its e lf by fric tio n to the drum. Now,
any change in ca r speed w ill rotate the drum and m ove
the “ U ” clip just as a sp eed om eter m oves its needle.
Th e top o f the “ U ” clip is attached to the a ir b leed va lve.
T h e clip m oves a s le e v e which s lid es on the o r ific e
tube therby c o v e rin g and u ncovering a ir ports in the
w a ll o f the tube (the tube inner end is plugged) w henever
ca r speed changes fro m the speed at which the solenoid
w as en ergized . The d irectio n o f drum rotation is such
that resu ltin g b leed v a lv e operation w ill cause the S ervo
to d ecrea se engine p ow er if the ca r exceeds the p re s e t
speed and in crea se engine p ow er i f ca r speed d ec re a s e s .
Th e a ir which passes out the o r ific e tube en ters the
R egulator through the openings in the solenoid housing,
p asses through the o il wetted polyurethane filt e r , and then
en ters the o r ific e tube p orts.
Fig. 4 —Servo U n it
CHEVROLET TRUCK SERVICE MANUAL