System Description
System Diagram (Part 1):
System Diagram (Part 2):
SYSTEM DESCRIPTION
1. GENERAL
a. In conjunction with an impact absorbing structure for front collisions, the Supplemental Restraint System (SRS) airbags are designed to supplement seat belts by helping to reduce injuries to the head and chest in the event of a front collision. This system has a 3 sensor type airbag system that detects the collision impact, and deploys the airbag system and seat belt pretensioner.
b. In order to detect the extent of the collision in detail during the initial stages of the collision, the deceleration sensors are located in the 2 front airbag sensors in the engine compartment. Accordingly, the deployment output of the airbag for the driver and front passenger can be controlled in 2 stages in accordance with the extent of the collision.
c. Side collisions are detected by the door side and side airbag sensors, which deploy the side airbags.
d. The occupant detection sensor and seat belt buckle switch detect whether or not the front passenger seat is occupied.
HINT: w/o Occupant classification system
e. The center airbag sensor memorizes the driver and front passenger's seat belt wearing condition while inflating the airbag.
2. CONSTRUCTION AND OPERATION
a. FRONT AIRBAG SENSOR
1. The front airbag sensors are installed on the right and left front side radiator support side.
2. The deceleration sensor is built into the front airbag sensor. The 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 bottom of the right and left center pillars. They receive signals from the deceleration sensor and determine whether the front seat airbag should be activated, and diagnose system malfunctions simultaneously.
2. The side airbag sensor consists of the deceleration sensor, ignition control circuit, and diagnostic circuit.
c. DOOR SIDE AIRBAG SENSOR
1. The door side airbag sensors are installed in the right and left doors. They receive signals from the deceleration sensor and determine whether the front seat airbag should be activated, and diagnose system malfunctions simultaneously.
2. Each door side airbag sensor consists of the deceleration sensor, safing sensor, ignition control circuit, and diagnostic circuit.
d. OCCUPANT DETECTION SENSOR (w/o Occupant classification system)
1. The occupant detection sensor, installed in the seat cushion of the front passenger seat, detects whether or not the front passenger seat is occupied.
e. CENTER AIRBAG SENSOR
1. General
- The center airbag sensor transmits airbag deployment signals to the ECUs (theft warning ECU and ECM) via the BEAN line in order to effect the respective controls (collision door lock release control and fuel control).
- The center airbag sensor memorizes the driver and front passenger seat belt conditions while inflating the airbag.
2. Backup power source
- The backup power source consists of a power supply capacitor and a DC-DC converter. When the backup power source does not function during a collision, the power supply capacitor 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.
3. Diagnostic circuit
- This circuit constantly diagnoses system malfunctions. When a malfunction is detected, it illuminates the SRS warning light on the combination meter to inform the driver.
4. Memory circuit
- Then a malfunction is detected in the diagnostic circuit, it is coded and stored in the memory circuit.
f. SRS WARNING LIGHT
1. The SRS warning light is located on the combination meter. It illuminates to inform the driver when a malfunction is detected in the self-diagnosis of the center airbag sensor and side airbag sensor. Under normal operating conditions when the ignition switch is turned ON, it illuminates for approximately 6 seconds.
3. IGNITION JUDGMENT AND CONDITIONS
a. FRONT COLLISION
1. When the vehicle collides in the hatched area (Fig.1) and the shock is greater than the specified value, the airbags (driver ad front passenger) are activated automatically. The deceleration sensor of the center airbag sensor determines whether or not ignition is necessary based on signals from the deceleration sensor of the front airbag sensor.
2. The safing sensor of the center airbag sensor was designed to be turned on at a smaller deceleration rate than the deceleration sensor. If the safing sensor and the deceleration sensor turn on simultaneously, current flows to the squib and deploys the driver and front passenger airbags.
b. SIDE COLLISION
1. The safing sensor of the "side" airbag sensor was designed to be turned on at a smaller deceleration rate than the deceleration sensor of the side airbag sensor. As illustrated below, when both the safing sensor and the deceleration sensor operate simultaneously, current flows to the initiator and deployment occurs.
4. AIRBAG DEPLOYMENT PROHIBITION FUNCTION (w/ o Occupant classification system)
a. The occupant detection sensor and front passenger seat belt buckle switch detect whether or not the front passenger seat is occupied. If the center airbag sensor receives a front passenger seat unoccupied signal, it prohibits the deployment of the front passenger airbags (front and side) and front passenger seat belt pretensioner.
5. AIRBAG DEPLOYMENT PROHIBITION FUNCTION (w/ Occupant classification system)
a. The occupant classification ECU detects whether or not the front passenger seat is occupied. If the center airbag sensor receives a front passenger seat unoccupied signal, it prohibits the deployment of the front passenger airbags (front and side) and front passenger seat belt pretensioner.