Air Bag Systems: Description and Operation

SUPPLEMENTAL RESTRAINT SYSTEM: AIRBAG SYSTEM:

SYSTEM DIAGRAM






SYSTEM DESCRIPTION

1. SRS AIRBAG SYSTEM OUTLINE
(a) FRONTAL COLLISION
(1) The driver and front passenger airbag are designed to supplement seat belts in the event of a front collision in order to help reduce shock to the head and chest of the driver and front passenger.
(2) Frontal collisions are detected by the center airbag sensor and two front airbag sensors. The driver and front passenger airbag and the seat belt pretensioner then operate simultaneously.
(3) Electrical deceleration sensors are built into the two front airbag sensors in the engine compartment in order to detect the severity of the impact during the initial stage of the collision. The deployment of the driver and front passenger airbags are controlled in two stages according to the severity of the impact.
(b) SIDE COLLISION
(1) The front seat airbag and curtain shield airbag are designed to help reduce shock to the driver, front passenger and rear outer passenger. The curtain shield airbag was designed to help reduce shock to the front and rear passengers in the event of a side collision.
(2) Side collisions are detected by the side airbag sensor installed in the bottom of the center pillar and the rear airbag sensor installed in the bottom of the rear pillar. Front side collisions are detected by the side airbag sensor, causing the front seat side airbag and curtain shield airbag to deploy simultaneously. Rear side collisions are detected by the rear airbag sensor to deploy only the curtain shield airbag.
2. CONSTRUCTION AND OPERATION
(a) FRONT AIRBAG SENSOR
(1) The front airbag sensors are installed on the right and left side members.
(2) The deceleration sensor and safing sensor are built into the airbag sensor front and distortion that is created in the sensor is converted into an electric signal based on the vehicle deceleration rate during a frontal collision. Accordingly, the extent of the initial collision can be detected in detail.
(b) SIDE AIRBAG SENSOR
(1) The side airbag sensors are installed on the right and left center pillars.
(2) The side airbag sensor consists of the deceleration sensor, safing sensor, ignition control circuit, and diagnostic circuit. The side airbag sensor receives signals from the deceleration sensor and determines whether the front seat side airbag and curtain shield airbag should be activated, and diagnoses system malfunctions simultaneously.
(c) REAR AIRBAG SENSOR
(1) The rear airbag sensor is installed on the bottom of the right and left rear pillars respectively.
(2) The deceleration sensor and safing sensor are built into the rear airbag sensor and the distortion that is created in the sensor is converted into an electric signal based on the vehicle deceleration rate during a rear side collision.
(d) CENTER AIRBAG SENSOR
(1) General

- The center airbag sensor is installed on the center floor under the instrument panel.
- The center airbag sensor consists of the deceleration sensor, safing sensor, electrical safing sensor, ignition control circuit and diagnostic circuit.
- The center airbag sensor receives signals from the deceleration sensors and safing sensors built into the center airbag sensor and front airbag sensor.
- The center airbag sensor causes the front seat side airbag and the curtain shield airbag to deploy when receiving signals from the deceleration sensor and the safing sensor built into the side airbag sensor.
- The center airbag sensor receives signals from the deceleration sensors and the electrical safing sensors built into the center airbag sensor and the rear airbag sensor, and determines whether or not the curtain shield airbag should be activated, and then diagnoses system malfunctions.
- The center airbag sensor can be check using check mode, which can detect and output DTCs. If the malfunction does not recur during troubleshooting, joggling each connector or driving on various type of roads with the center airbag sensor in check mode as a simulation method makes it possible to obtain more accurate information.
(2) Deceleration sensor and ignition control circuit

- The deceleration sensor is built into the center airbag sensor, and the distortion created based on the deceleration of the vehicle during a frontal or rear side collision is converted into an electric signal.
- The ignition control circuit performs calculations based on the signal output from the deceleration sensors of the center airbag sensor and front airbag sensor. If the calculated values are greater than the specified values, the airbag deploy.
(3) Safing sensor

- The safing sensor is built into the center airbag sensor. During a frontal collision, the sensor turns on and outputs an ON signal to the center airbag sensor if a deceleration rate greater than the specified value is applied to the safing sensor.
(4) Electronic safing sensor

- The electronic safing sensor is built into the center airbag sensor. During a rear side collision, the sensor turns on and outputs an ON signal to the center airbag sensor if a deceleration rate greater than the specified value is applied to the electronic safing sensor.
(5) Back-up power source

- The back-up power source consists of a condenser and a DC-DC converter. When the power system does not function during a collision, the condenser discharges and supplies electric power to the system. The DC-DC converter operates as a boosting transformer when the battery voltage falls below a predetermined level.
(6) Diagnostic circuit

- This circuit constantly diagnoses the system malfunctions. When a malfunction is detected, it lights up the SRS warning light on the combination meter to inform the driver.
(7) Memory circuit

- When a malfunction is detected in the diagnostic circuit, it is coded and stored in the memory circuit.

(e) SRS WARNING LIGHT
(1) The SRS warning light is located on the combination meter. The SRS warning light informs the driver of detected malfunctions in the diagnostic circuit of the center airbag sensor or the SRS airbag system. Under normal operating conditions when the power switch is turned on, the SRS warning light comes on for approximately 6 seconds and then goes off.
3. DEPLOYMENT CONDITION
When the vehicle collides and the shock is greater than the specified value, the SRS is activated automatically. The center airbag sensor includes the safing sensor and deceleration sensor. The safing sensor was designed to the turned on at a smaller deceleration rate than the deceleration sensor.
(a) The center airbag sensor determines whether or not ignition is necessary based on signals from the deceleration sensor and the front airbag sensor*. If the deceleration sensor, front airbag sensor* and safing sensor turn on simultaneously, current flows to the squibs to deploy the SRS as shown in the illustration below.




HINT: *: In case of front collision, the ignition signal could be output with the deceleration sensor ON signal even without a signal from the front airbag sensor.

(b) The center airbag sensor determines whether or not ignition is necessary based on signals from the side airbag sensor. If the side airbag sensor and safing sensor turn on simultaneously, current flows to the squib to deploy the SRS as shown in the illustration below.





(c) The center airbag sensor determines whether or not ignition is necessary based on signals from the rear airbag sensor. If the rear airbag sensor and safing sensor turn on simultaneously, current flows to the squib to deploy the SRS as shown in the illustration below.




HINT: *: If the front seat side airbag deploys, the curtain shield airbag will also deploy, regardless of whether the signal is output from the rear airbag sensor.