CRUISE CONTROL 98-3
CUUM BRAKE
-VARIABLE INDUCTANCE
POSITION SENSOR
-VENT SOLENOID AND VALVE
(NORMALLY OPEN)
6-- STEEL CORE
Fig. 3 Servo Unit
in the servo to increase the throttle opening. The
vent remains closed.
e Vehicle Gaining Speed (due to steep grades
or driver wishes to decrease speed by using the
Coast or 'tap-down' feature)
- The controller
de-energizes the vent solenoid to open the vent
valve to the atmosphere. This reduces vacuum in
the servo and allows the throttle return spring to
decrease the throttle opening. The vacuum valve
remains closed.
When the cruise system is engaged and operating
(without any interference from the driver via the mode
control switches), no speed correction will be made
until the car varies approximately
+ - 1/2 mph from set
speed.
When the controller senses an over or underspeed
condition it will pulse the opening of the vent or
vacuum valve. The pulse will be repeated as required
until the speed correction necessary brings the car to
the set speed. From any set speed, under normal road
load conditions, the vacuum valve will remain in a
completely open position when vehicle speed has The
ignition is turned off.
SPEED SENSORS
VSS
Buffer Amplifier
Figure 4
Fig. 4 VSS (Vehicle Speed Sensor)
This device supplies the vehicle speed input to the
controller on some cars. The optic head portion of the
VSS is located in the speedometer frame. A reflective
blade is attached to the speedometer
cable/head
assembly. The blade spins like a propeller, with its
blades passing through a light beam from a
L.E.D. in
the optic head. As each blade enters the
L.E.D. light
beam, light is reflected back to a photocell in the optic
head, causing a low power speed signal to be sent to the
buffer for amplification and signal conditioning. This
amplified signal is then sent to the cruise controller.
P. M. Generator
Figure 5
dropped 5mph below set speed. Likewise, when vehicle
speed has exceeded
3 mph over the set speed, such as This
device supplies the vehicle speed input to the
down a steep grade, the vent will go into ,-onstant open ~0ntI-011er on some cars. Vehicle speed information is
position. provided
to the controller by a P. M. (permanent
magnet) generator driven by the transmission. The
The servo go into an 'Pen vent position output frequency of the P. M, generator is sent to the under the following conditions:
buffer, which amplifies and conditions the signal to the
@ When the brake (or clutch) pedal is depressed. controller.
a An open variable inductance position sensor coil
in the servo.
a A loss of electrical power to the system.
