Chevrolet 10 Series 1968, Руководство по обслуживанию

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ACCESSORIES 15-4
orifice. If no air was allowed to bleed into the chamber,
the diaphragm would move until it contacted the housing,
however, the Regulator meters bleed air into the chamber
and the diaphragm reaches a point at which the air is
bled out of the chamber through the vacuum port orifice
as fast as it enters the air bleed port. If the Regulator
begins to supply less bleed air, (vehicle speed decreas­
ing) the vacuum in the chamber increases and the dia­
phragm moves toward the vacuum port. In so doing, the
tapered needle closes the vacuum port orifice even more
F ig . 6 —Servo, Regulator and Hose
and the air bled into the chamber again equals the air
bled out. A balance occurs again with the diaphragm in
a new position. If the Regulator begins to supply more
bleed air, (vehicle speed increasing) the vacuum in the
chamber drops and the diaphragm moves away from the
vacuum port, withdrawing the tapered needle from the
orifice and enlarging it. Since the vacuum orifice is
now larger, the greater quantity of air being bled into
the chamber may be bled out by vacuum and a balance
again occurs with the diaphragm in a new position.
REGULATOR
The Regulator is a device which has two primary
functions: First, it is a vacuum switch which, when en­
gaged by the driver, supplies engine manifold vacuum to
the Servo. Second, it meters a small variable quantity
of air to the Servo unit in order to change the carburetor
throttle opening to effect speed control. A secondary
function of the Regulator is to drive the speedometer.
Since the car speed is sensed by a speedometer-like
mechanism within the unit, the speedometer cable from
the transmission drives the Regulator which drives a
second cable (at a one to one ratio) to the speedometer.
The Regulator is electrically engaged and disengaged
through operation of the Engagement Switch and the
Electric Brake, or Clutch Release Switch. It has two
sub-assemblies which make up the unit: one being the
magnetic speed sensing assembly and the other being
the solenoid actuated vacuum switch, air bleed and filter,
and low limit speed switch assembly (fig. 8 and 9).
Magnetic Speed Sensing Assembly
The speed sensing assembly operates in the same man­
ner as a speedometer unit except that instead of rotating
a needle through an angle proportional to the vehicle
SERVO
POWER UNIT
AIR BLEED HOSE
TO SERVO
MANIFOLD
VACUUM HOSE VACUUM
REGULATOR
VACUUM
PORT
VACUUM HOSE
TO SERVO
POWER UNIT
AIR BLEED HOSE
FROM REGULATOR
MANIFOLD
VACUUM HOSE
FROM ENGINE
CHEVROLET TRUCK SERVICE MANUAL