SRS System Description
The SRS system consists of the driver's and front passenger's airbag, driver and front passenger's knee airbag, side airbag, side curtain airbag, the seat belt tensioner and seat belt outer lap tensioner.
Trouble Diagnosis Function
Refer to the General Troubleshooting Information for detailed functions .
Driver's and Front Passenger's Airbag
In case of a frontal collision, the vehicle has a function to mitigate the impact forces acting on the head and chest of the front seat occupant that is used in combination with a seat belt tensioner as a body restraint device in addition to the impact-absorbing construction of the body shell.
Seat Belt Tensioner and Seat Belt Outer Lap Tensioner
The seat belt tensioner and the seat belt outer lap tensioner instantaneously retracts the seat belt at the time of a collision, and the effect of the seat belt is increased further by securely restraining the occupant in the seat. In the case of a low-speed collision, since the seat belt can adequately secure the occupant, only the seat belt tensioner and the seat belt outer lap tensioner are activated to retract the seat belt without deploying the airbags. In the case of a medium to high speed collision, the airbags, seat belt tensioners and the seat belt outer lap tensioner are activated to improve the restraining effect of the occupant and safety performance.
Knee Airbag
The knee airbags inflate in a moderate to severe frontal collision to help keep the occupant in the proper position and to help maximize the benefit provided by the vehicle's other safety features.
Operating process of the driver's/front passenger's airbag/tensioner deployment:
1. The impact force generated by a frontal collision is transmitted through the vehicle's structural components and input to each of the front impact sensors, front impact G sensors and the safing drive circuit inside the SRS unit.
2. The front impact sensor converts the collision force into electrical signals which are sent to the microprocessor and the safing drive circuit inside the SRS unit. At the same time, the front impact G sensors inside the SRS unit converts the collision force input into waveform electrical signals and sends them to the microprocessor and the safing drive circuit.
3. The microprocessor outputs actuation signals if the outputs from the front impact sensors and front impact G sensor exceed the preset threshold value. At this time, if the output from the safing drive circuit inside the SRS unit exceeds the preset threshold value, current flows through a trigger circuit, which deploys the SRS airbag and/or operates the seat belt tensioners and the seat belt outer lap tensioners.
SRS airbags do not deploy in the following cases:
The SRS airbags deploy when a strong impact comes from the left-front or right-front direction, within 30 degrees from the front face when the vehicle is in the ON mode. Therefore, in the following cases, the SRS airbags do not deploy because there is no effect on occupant protection but it may deploy depending on the state of the collision.
SRS airbags may not deploy in the following cases:
The deployment of the SRS airbags are designed based on the scale of the impact felt by the occupant(s). Therefore, the deployment of the SRS airbags are not always related to the amount of damage to the vehicle.
Side Airbag System, Rear Side Airbag System and Side Curtain Airbag System
In case of a side impact, the side airbag, the rear side airbag, the side curtain airbag, and the seat belt tensioner on the side impacted operate in addition to the impact-absorbing body shell of the vehicle, which mitigates the impact forces acting on the head and chest of the occupant. Moreover, the side impact sensors detect the various states of collision so that the airbag deploys accordingly. The side airbag and the rear side airbag use a variable volume type which it's construction and deployment process of the airbag pressure chamber have been improved and enable a safe deployment regardless of the position of the occupant. Due to this design, conventional parts related to OPDS* are not equipped.*OPDS: Occupant Position Detection System
Side airbag, rear side airbag and side curtain airbag deployment process:
1. The collision force generated from the side impact is inputted to each of the side impact sensors and the side impact G sensor inside the SRS unit.
2. If the microprocessor inside the SRS unit determines that the side impact sensor(s) output exceeds a preset threshold value, and if the output from the side impact G sensor inside the SRS unit exceeds a preset threshold value, the circuit creates an actuation signal.
3. The actuation signal is sent from the microprocessor to the trigger circuit, which deploys the side airbag, the rear side airbag, the side curtain airbag, the seat belt tensioner and the seat belt outer lap tensioner.
NOTE:
In cases of a strong frontal collision, the threshold value for a side impact is exceeded in the SRS unit, the side curtain airbag may deploy.
Side airbag, rear side airbag and side curtain airbag deployment conditions:
When the vehicle is subject to a strong side impact and the side impact G sensor detects an impact that exceeds the preset threshold value, the side airbags, the rear side airbag and side curtain airbags on the side receiving the impact will deploy.
NOTE: The side curtain airbags may deploy along with the front airbags during a front-end collision in order to protect the heads of occupants if the collision force to the side of the vehicle exceeds a certain value.
Conditions in which side airbag, rear side airbag and side curtain airbag may not deploy:
Since the side airbags and the side curtain airbags are designed to deploy when an impact force to the vehicle side exceeds a preset value, they may not deploy when impact forces are reduced by the vehicle's crush zone, or when a side impact is applied in the front or behind the passenger compartment. Also, these airbags may deploy in the case of side slip collision or when the vehicle roll overs, but in such cases, will not provide full occupant protection.