What Is an Air Bag?
An air bag is a piece of automotive safety equipment, designed to cushion occupants’ impact in the event of a collision.
Typically, air bags deploy at impacts of 20 kilometers per hour or more, equivalent to a head-on collision against a fixed wall. Driver and passenger air bags are primarily effective in frontal impacts and may not activate in diagonal or side impacts.
Increasingly, vehicles are equipped with side air bags and side curtain air bags to protect occupants in side impacts.
Uses of Air Bags
1. Automobiles
Air bags protect passengers from impacts with the steering wheel, instrument panel, dashboard, windshield, etc., during a collision.
Without a seat belt, the air bag may not provide adequate protection, even if deployed. Additionally, since the air bag deflates after inflation, it does not protect against subsequent impacts in multi-collision accidents.
2. Non-Automotive Applications
Air bags also find applications beyond automobiles, such as:
- Motorcycle air bags
- Bicycle air bags
- Avalanche protection air bags
- Planetary probe air bags
Principles of Air Bags
An air bag system includes a sensor to detect accidents, an inflator (gas generator), a bag, a control unit, and for the driver’s seat, a rotating connector.
1. Inflation Upon Impact
The sensor detects a specific impact and signals the control unit. Upon receiving this signal, the inflator ignites, generating gas and inflating the bag in about 0.03 seconds.
2. Shock Absorption
The air bag features a gas vent for pressure release when compressed by an occupant, converting the impact into kinetic energy and mitigating force. Without this vent, the impact could cause serious injury or death.
Types of Air Bags
1. Deployment Method Classification
Three types of air bags vary by deployment method:
Mechanical Air Bag
Uses a mechanical sensor and mechanism, such as a spring, to ignite the gas generator. Often found in older vehicles.
Electronic Air Bag
Employs an acceleration sensor to detect deceleration, triggering the air bag when deceleration exceeds a set threshold. Common in newer vehicles.
Electromechanical Air Bag
Combines a mechanical impact sensor with electronic signal transmission to the gas generator.
2. Storage Location Classification
Common air bag types include driver and passenger air bags, with side air bags and side curtain air bags for side impacts. In some regions, these are standard equipment.
Additional types for occupant protection include:
-
- Knee airbags
- Seat cushion air bags
- Rear window curtain air bags
- Rear airbag
- Rear center airbag
- Seat belt airbag
- Door-mounted curtain airbag
- ITS head airbag
- Pervis airbag
Other Information on Air Bags
Gas Generator Types
Three main types of gas generators are used in air bags:
Pyro System
Generates gas through the combustion of gunpowder, notable for its compactness and light weight.
Stored Gas Method
Utilizes high-pressure gas stored in a container, enabling rapid deployment.
Hybrid Method
Combines the pyro and stored gas systems, characterized by compact size, light weight, and quick deployment.