The ideal seat belt action process is: First, tighten in time, and do not hesitate to "press" the person in the seat at the first moment of the accident. Then, relax moderately, and when the impact peak has passed, or when the person has been protected by the airbag, the seat belt is properly relaxed. Avoid injury to the ribs due to excessive tension. The most advanced seat belts come with pre-tensioning devices and tension limiters. Let's take a look at the functional principles of the two.
1. Seat belt pre-tightening device When the accident occurs, the person moves forward and the seat is backward. At this time, if the seat belt is too loose. The consequence is likely to be: the occupant slips out under the seat belt: or, the person has touched the airbag, and at this time the seat belt is not tightened in time due to the excessive tension, that is, it cannot be eaten as expected. Part of the impulse is lost, but the entire burden is given to the airbag. Both of these conditions can cause serious injury to the occupants. But the problem is that the seat belt is properly installed. Where does the room for relaxation come from? First, because the occupant's clothes have a certain thickness, and some part of the seat belt device hides some loose space, this kind of room can not be eliminated, but in the event of an accident, it should be eliminated as much as possible. How to do? To this end, such a seat belt pre-tensioning device has emerged which is responsible for providing an instant tightened seat belt. The action process is: first, a probe is responsible for collecting the collision information, and then releasing an electric pulse, which is transmitted to the gas generator to detonate the gas. The gas generated by the explosion rapidly expands in the pipe, pressing against the so-called ball chain, causing the ball to squat forward in the pipe, driving the pawl to rotate. The pawl disk is integrated with the uranium and the seat belt is wound around the shaft. Simply put, the gas pressure makes the ball move, the ball drives the pawl to turn, and the pawl disk drives the shaft to turn - the pre-tightening function of the seat belt is realized instantaneously. The entire process from sensing the accident to completing the seat belt pre-tightening lasts only a few thousandths of a second. The end of the pipe is a cavity for holding the ball that rolls over.