Air Bag: Description and Operation
General InformationThe SIPS bag is activated by certain side impact collisions and is designed to help increase protection to front seat passengers.
The SIPS bag is being introduced as standard equipment in some markets and as an option in others, beginning with model year 1995.
SIPS bag installed in front seat
The SIPS.bag system consists of three main components:
1. Sensor unit
2. Firing circuit
3. Cushion module
NOTE: Illustrations in the information show left front seat. SIPS-bag components for right front seat are identical, except that the pressure plate (at the front of the sensor unit) is specific to left or right side.
Sensor unit
The sensor unit is located in a sensor mount at the outer end of the forward SIPS tube. The mount is the part of the chair that protrudes the most toward the inside of the door.
A pressure plate is mounted forward of the sensor unit. In the event of a collision, the pressure plate transfers the force from the inside door panel to the sensor unit.
Firing circuit
The pyrotechnic firing circuit runs through the seat back and under the seat cushion.
The firing circuit consists of two tubes coated on the inside with a pyrotechnic material. When triggered, the signal is transmitted as a shock wave.
The tubes are covered with a black protective sleeve to protect them from mechanical damage.
SIPS-bag cushion module
The cushion module is located on the seatback frame to help provide protection to the driver/passenger where the rib cage is closest to the inside door panel.
Cushion
The cushion, made of silicone-coated polyamid fabric, is folded under a cover. When inflated, the cushion has a volume of about 12 liters (0.4 cubic feet).
Gas generators
Two gas generators inflate the cushion. When activated, the gas generators produce a harmless gas which inflates the cushion very quickly.
Functional description, general
The SIPS bag is a separate system in each front seat. There is no connection between the two SIPS bags. In the event of a certain side impact collision, the SIPS bag will be activated only on the side of the collision. The sensor unit is a pyrotechnic impact sensor, which will be activated only if it is struck with an impact that causes the deformed door to hit the sensor with a speed of about 2 m/s (6.6 ft/sec). The system is calibrated to avoid unnecessary activation such as by a blow to the door or a light impact with a stationary object.
The pressure plate will deform the aluminum cover, pushing a firing pin and releasing the ignition charge. The ignition charge creates an impulse which is transmitted through the firing circuit as a shock wave. When the shock wave reaches the cushion module, it ignites the powder charge in the gas generator.
When released, the gas blows through a firing chamber tube and into the cushion. Activation of the first gas generator occurs immediately and the second is activated after a delay of about 3 milliseconds. The delay is designed to maintain the pressure and volume of the inflated cushion for an adequate time.
During inflation, the cushion breaks open the cushion module cover, rips open the chair upholstery seam and pushes out to inflate to its full volume. The cushion inflates toward the door panel to help protect the passenger's rib cage during the collision. There is a vent though a hole in the cushion, so it will collapse slowly enough to act as a brake on the driver/passenger.
There is no diagnostic system or warning lamp connected to the SIPS bag.
The SIPS bag is available only in cars equipped with the SRS system, and it is always installed in both front seats.
SIPS-bag Components
Sensor-unit components
4. Sensor housing
5. Aluminum cover
6. Spring washer
7. Firing pin
8. Compression washer
9. Ignition charge
10. Transport safety device
Cushion module components
11. Cushion
12. Gas generators
13. Firing chamber
14. Mount