Chevrolet 10 Series 1970 Service Manual page 633

R E G U L A T O R
Fig. 3 —R eg 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
sp ee d o m e te r-lik e m echanism
speedom eter cable fro m
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
E le c tr ic Brake R e lea 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 switch, a ir b leed and filte r , and low lim it
speed switch assem bly. See F ig. 8.
M agnetic Speed Sensing Assem bly
The speed sensing assem bly op erates in the same man­
n er as a speedom eter unit except that instead o f rotating
a needle through an angle prop ortion al 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
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
prop ortion 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
speedom eter d riv e cable.
H O U S IN G C O V E R
sensed by a
w i t h i n the unit,
the tran sm ission d riv e s the
Engagem ent Switch and the
is in operation. The
Vacuum Switch, A ir Bleed and Filter, and Low
Limit Speed Switch
The end o f the shaft fro m the speed sensing assem bly
with the rubber drum extends into the a ir bleed 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 ecific ca r speed. When the c a r reaches about 35 mph,
the rubber drum has rotated fa r enough (m oved by the
b ra s s driven disk in the m agnetic fie ld )
has allow ed a spring loaded e le c tr ic a l point to contact
another point. Th ese points a re in s e r ie s with the s o le ­
noid co il so that under 30 mph, no R egu lator operation
is p ossible.
Surrounding the rubber drum is a " U "
c lip which is held spread away fro m
nose o r cam o f the solenoid when the solen oid is in the
rela x ed position.
p ris e the speed clutch o f the regu la tor. When the s o le ­
noid is en erg ized , the solenoid nose m oves tow ard the
drum and re le a s e s the ends of the clip. The clip springs
inward 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 speedom eter m oves its needle.
The top o f the " U " clip is attached to the a ir b leed valve.
Th e clip m oves a sle e v e which slid es on the o r ific e
tube therby co verin g and u ncovering a ir ports in the
w a ll o f the tube (the tube inner end is plugged) w henever
car speed changes fro m the speed at which the solenoid
w as en ergized . The d irection of drum rotation is such
that resu lting bleed va lve operation w ill cause the S ervo
to d ecrea se engine pow er if the car exceeds the p reset
speed and in crea se engine pow er if ca r speed d ecrea ses.
The a ir which passes out the o r ific e tube en ters the
the
Regulator through the openings in the solenoid housing,
passes through the o il wetted polyurethane filt e r , and then
en ters the o r ific e tube ports.
ACCESSORIES 15-3
so that its tang
shaped spring
the drum by the
The rubber drum and this clip com ­
Fig. 4 —Servo U n it
CHEVROLET TRUCK SERVICE MANUAL