The principle is identical, whether inertia reels or pretensioners are used: the change in the state of the inertia switch generates the order to trigger by a supply to the trigger wires
If the battery +ve supply is cut in a collision, this command is given by a capacitor incorporated in the ECU up and lasts up to 50 milliseconds for the pretensioners
The main components of the ECU are
- 1 impact detector
- 1 резерв энергии
- 1 triggering device
- 1 diagnostic unit
(1): инерционный переключатель
(2): Питание
(3): силовой транзистор
(4): правый воспламенитель
(5): левый воспламенитель
(6): diagnostic unit
(C): конденсатор (/)
(M): inertia switch weight
(R): сопротивление
Principle of the impact detector
(7): возвратная пружина
(8): Reed bulb
(9): weight with power supply
The impact detector is the heart of the device; in the event of a collision, the magnetic sliding ring is moved close to the contacts inside a Reed bulb
The contacts close and release a transistor to provide a negative signal to the triggers
A few figures
- Triggering threshold greater than 15 km/h (frontal impact against fixed obstacle)
- Moment of triggering: 20 milliseconds after start of the impact
- Pre-tensioning period: 5 мс
- Maximum travel: 80 mm
ПримечаниеThe belts only and belts + airbag(s) triggering thresholds are different