The function of car seat belts
The car seat belt is a vehicle safety device designed to secure the occupant of a vehicle against harmful movement that may result during a collision or a sudden stop. And it can control the driver and passengers’ chest acceleration and compression at the lowest value. In the overall occupant restraint system, including seat belt, airbag, seat, steering wheel and steering mechanism with endergonic device etc. The most essential component is the seat belt. With the growing improvement of the requirement for the performance about car collision safety and comfort, the technology for seat belt has promoted a leap.
The type and working principles of seat belts
1.The common seat belt:
The sensor induct the car body acceleration or webbing acceleration. When the webbing acceleration is more than 2g or a car body acceleration is more than 0.45g, the retractor has a locking mechanism that stops the spool from rotating. Then the lock will absorb the collision energy from man body through the seat belt flexing so that it will reduce the chest acceleration and compression. But due to the protect effective is limited, it is used only in some low price cars.
2.Load-limited seat belts
It is based on the common seat belt, adding a force limited shaft in the center of retractor. It will restrict force growing of webbing through the twisted of the limited shaft. Controlling the webbing strength into a constant range, it will reduce the chest acceleration and displacement. At present, it is only used in the low price cars.
3. Pretensioner seat belts
It is based on the common seat belt, adding the pretensioner. The pretensioner mechanism uses an explosive charge to drive a concealed piston when Airbag ECU sensors detect the signature abrupt deceleration of an accident. This extra seatbelt “pre-“ tension, moments prior to the full force of impact, pulls the bodies of the driver and front-seat passenger firmly into their seats. This positions them so as to receive the maximum protection benefit of the front airbags. At present, the pretensioner seat belt is widely used in the mid-to high end cars.
4. Seat belts with pre-retractor
It is based on the pretensioner seat belt, adding the pre-retractor motor system. The working principle is with radar device to induce the car space between the front car. If the space is smaller than the setting value, the ECU will give a signal to control the motor moving, which will eliminate the gap between the webbing and man body. What’s more, it will remind the driver to take a emergency brake or emergency brake. This type of seat belt involves many new devices, such as detection radar and computer program. So the whole price is a little expensive and it is used in high-end cars.