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SYSTEM DESCRIPTION
This air bag system is a supplemental device to protect pas-
sengers in the event of a frontal collision. The driver's seat is
provided with an air bag and a seat belt. The front passenger
seat is provided with a seat belt and optional air bag, whereas
the rear passenger seat is provided with seat belts only.
If the vehicle undergoes a frontal collision and the system de-
tects it and the impact exceeds a specified value, the air
bags deploy to reduce the impact to the passengers.
This air bag system is composed of the following main parts.
·
Air bag ECU (Computer)
·
G sensor (built in the air bag ECU)
·
Safing sensor (built in the air bag ECU)
·
Air bag unit (consists of Inflator and bag)
·
Steering roll connector
·
Warning lamp
Air bag ECU & sensor
The air bag ECU is located under the console panel.
G sensor and a safing sensor are provided as sensors which
sense the deceleration in the event of collision. The crash
sensor is incorporated in the logic circuit of the air bag ECU.
The G sensor calculates the deceleration, based on the mag-
nitude of a potential difference, when the impact waves vi-
brates the sensor during the collision.
The safing sensor is placed on the circuit board inside the
ECU case. If a deceleration exceeding the specified value is
applied to the sensor by the impact, the inertia force of the
pendulum overcomes the reaction force of the spring. As a re-
sult, the pendulum moves to the switch side, thereby closing
the contact points of the switch.
As regards the system operation, the ECU calculates the de-
celeration detected by the G sensor and compares it with the
specified value. If the ECU has judged that a collision is tak-
ing place, it outputs an ignition signal. If the safing sensor is
turned on at this time, an electric current which is necessary
for the ignition is supplied to the air bag inflator.
The air bag ECU has a backup power supply consists of a
backup condenser and voltage set-up circuit.
Air bag warning light
Driver's air bag and inflator
Control unit
Metal diaphragm
+
–
+
–
Piezoelectric ceramics
+
Compression
–
+
Tension
–
Safing sensor
IG 1
Diode
IG 2
circuit
Back-up
condenser
DC-DC
circuit
Ignition
transistor
CPU diagnosis
collision
G sensor
evaluation
Ignition
transistor
BE–53
JBE00167-05004
Front
passenger's air
bag and inflator
JBE00168-05005
0
–
JBE0169-05006
Contact point
JBE00170-05007
Squib
Safing
(Driver's
sensor
seat side)
Squib
(Passenger's
seat side)
JBE00171-05008
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