JPH1016709A - Pretensioner for seat belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sealing of a piston to a cylinder without obstructing slide motion of the piston by filling grease between an inner wall of the cylinder and the piston. SOLUTION: A gas generator operates to generate high pressure expansion gas at emergency such as vehicle collision and the like. At this time, grease 30 is filled in a space between an outer periphery surface of a large size pillar part 30 of a piston 10 and an inner wall of a cylinder 20 and when the piston moves in the cylinder 20, the space is filled with the grease 30. As the grease 30 can be expanded in the space by pressure P of the expansion gas, the cylinder 20 is deformed to expansion direction by the pressure P of the expansion gas and sealing with the piston 10 and the cylinder 20 can be improved even if the space is expanded. Thus, the expansion gas generated by a gas generator will not leak outside the cylinder 20 from this space and the pressure P of the expansion gas is effectively acted on the piston 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seat belt pretensioner for retracting and tightening a seat belt in an emergency, and more particularly to a seat belt pretensioner which is slidably guided in a cylinder and driven by a high-pressure inflation gas. To improve the piston which displaces the webbing and retracts the webbing.

[0002]

2. Description of the Related Art Conventionally, a seatbelt device for holding an occupant of a vehicle or the like safely in a seat tends to reduce a retracting force of a webbing by a retractor in order to reduce an occupant's feeling of wearing a webbing. If a large force is applied during a collision, the play of the webbing is inevitably increased, and the restraint is delayed due to the play of the webbing, so that the occupant cannot be effectively and safely restrained.

[0003] In order to eliminate the play of the seat belt by pulling the webbing in tension in an emergency,
The seat belt device incorporates a seat belt pre-tensioner (tightening device) that instantaneously rotates the retractor winding shaft in the winding direction and a seat belt pre-tensioner that instantaneously pulls the buckle itself in the webbing tension direction. is there.

The seat belt pretensioner includes:
For example, a piston is connected to one end of a cord that is hung on a pulley that is attached to a winding shaft of a retractor,
Tension is exerted on the cable by a thrust generated by the pressure of the inflation gas acting on the piston slidably received in the cylinder, and the cable draws and drives the shaft of the retractor in the webbing winding direction. In this way, the webbing in a state of being extended to the occupant is drawn in in an emergency.

[0005] The piston guided into the hollow cylindrical cylinder and driven by the pressure of the inflation gas is a caulking region for connecting and fixing the wire 6 like a piston 10 shown in Fig. 4, for example. , A large-diameter cylinder 13 having a diameter sufficient to effectively convert the pressure of the inflation gas into thrust, and a cone connecting the small-diameter cylinder 11 and the large-diameter cylinder 13 continuously. It is formed in a stepped cylindrical shape having a portion 12. On the other hand, the cylinder 20 has a hollow cylindrical shape,
The distal end opening 21 has a conical inner peripheral wall 22 narrowed in a substantially conical shape toward the distal end of the cylinder to brake the piston 10, and prevents the piston 10 from jumping out of the cylinder 20.

[0006]

In a conventional pretensioner for a seat belt, FIGS.
As shown in the figure, the outer diameter of the large-diameter cylindrical portion 13 of the piston 10 is made slightly smaller than the inner diameter of the cylinder 20 so as to be slidable in the cylinder. A gap 16 is provided between the outer peripheral surface of the portion 13 and the inner wall 24 of the cylinder 20.

Therefore, a part of the inflation gas generated by a gas generator (not shown) leaks from the gap 16 to the outside of the cylinder, so that the pressure of the inflation gas cannot be used effectively, and the propellant of the gas generator is not used. There is a possibility that a flame or a spark generated when the gas is burned out of the cylinder 20 from the upper end opening 23 of the cylinder 20 through the gap 16.
In addition, when the pretensioner is activated, the pressure in the cylinder rises sharply due to the high-pressure inflation gas, and the cylinder 20 is deformed in the radially expanding direction.
The gap with zero expands, and the possibility that the above-mentioned phenomenon occurs further increases.

In order to prevent the leakage of the inflation gas as described above, it is conceivable to attach a sealing member such as a resin washer to the piston. In this case, a method of fixing the sealing member to the piston is considered. And a problem such as an increase in cost due to an increase in parts occurs. Therefore, an object of the present invention is to solve the above-mentioned problems, and to effectively utilize an inflation gas with a simple structure and to prevent a flame or a spark from being ejected to the outside of a cylinder. The present invention provides a pretensioner.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pretensioner for a seat belt which draws in and drives a webbing in an emergency with a thrust by an expansion gas acting on a piston slidably guided in a cylinder. , Wherein grease is filled between the inner wall of the cylinder and the piston.

[0010] According to the above configuration, the degree of sealing of the piston with respect to the cylinder can be increased without hindering the sliding of the piston by the grease filled between the inner wall of the cylinder and the piston. No flames or sparks are emitted from the cylinder when the medicine or the like burns.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. The seat belt pretensioner shown in FIG. 1 includes a wire housing (not shown) provided on a base side wall 2 of a retractor 1 which is a device for automatically retracting the webbing 9 when the seat belt is not used, and a wire housing (not shown) inside the wire housing. Tractor 1
A wire 6 which is a cable body wound around a pulley (not shown) attached to the shaft with a slight clearance;
A piston 10 connected to one end of the wire 6, a cylinder 20 in which the piston 10 is slidably received,
The cylinder 20 has a gas generator (not shown) for supplying a high-pressure gas.

The piston 10 is, as shown in FIG.
A small-diameter cylindrical portion 11 which is a caulking region for connecting and fixing the wire 6; a large-diameter cylindrical portion 13 having a diameter sufficient to effectively convert the pressure of the inflation gas into thrust; It is formed in a stepped column shape having a conical portion 12 that continuously connects the radial column portion 13. The outer diameter of the large-diameter cylindrical portion 13 is slightly smaller than the inner diameter of the cylinder 20 so as to be slidable in the cylinder, and between the outer peripheral surface of the large-diameter cylindrical portion 13 and the inner wall 24 of the cylinder 20. The provided gap is filled with grease 30 as shown in FIGS. 2 and 3.

The grease 30 is preliminarily provided with the large-diameter cylindrical portion 13.
After applying to the outer peripheral surface of the or the inner wall 24 of the cylinder 20,
The clearance can be easily filled by assembling the piston 10 with the cylinder 20. At this time, the grease 30 may be applied over the entire circumference of the large-diameter cylindrical portion 13 or the cylinder 20, or may be applied to a part thereof. In other words, even when the grease 30 is partially applied, the grease 30 can spread over the entire gap due to the pressure of the inflation gas during the operation of the pretensioner.

Next, the operation of the piston 10 of this embodiment will be described. When an unillustrated gas generator operates to generate high-pressure inflation gas in an emergency such as a vehicle collision,
The piston 10 in the cylinder 20 is driven upward by the pressure P of the expansion gas generated from the gas generator, and is displaced toward the tip of the cylinder 20 while pulling the wire 6. Then, the portion of the wire 6 wound around the pulley is tightened on the outer peripheral surface of the pulley. For this reason, frictional engagement occurs between the wire 6 wound around the pulley and the outer peripheral surface of the pulley, and when the piston 10 is further driven upward as shown by a dashed line in FIG. Is driven in the webbing take-up direction, the webbing in a state of being wrapped around the occupant is pulled in, and play of the webbing is eliminated.

At this time, the gap between the outer peripheral surface of the large-diameter cylindrical portion 13 of the piston 10 and the inner wall 24 of the cylinder 20 is filled with grease 30, and the piston 10
When it moves within 0, the gap is filled with grease 30. Since the grease 30 can spread into the gap due to the pressure P of the inflation gas, even if the cylinder 20 is deformed in the radially expanding direction by the pressure P of the inflation gas, the gap between the piston 10 and the cylinder 20 is increased. Can be increased.

Accordingly, the inflation gas generated by the gas generator does not leak out of the cylinder 20 from this gap, and the pressure P of the inflation gas generated by the gas generator can be applied to the piston 10 effectively. Also, grease 3
0 has lubricity, so the inner wall 2 of the cylinder 20
The frictional resistance of the large-diameter cylindrical portion 13 to the cylinder 4 decreases, and the movement of the piston 10 sliding in the cylinder 20 becomes smooth.

Further, since the gap between the piston 10 and the cylinder 20 is closed by the grease 30, flames and sparks when the propellant or the like of the gas generator burns do not blow out of the cylinder from the gap. That is, the seat belt pretensioner according to the present embodiment can effectively apply the pressure of the inflation gas to the piston 10 without waste, and can smoothly move the piston 10. Can also be used.

Further, since the grease 30 can absorb the dimensional tolerance of the gap between the piston 10 and the cylinder 20, the processing accuracy of the piston 10 and the cylinder 20 can be reduced and the manufacturing cost can be reduced. Further, since the gap between the piston 10 and the cylinder 20 can be closed only by applying the grease 30 in advance, leakage of the inflation gas can be prevented very easily as compared with a case where a sealing member such as a resin washer is attached to the piston. be able to.

It should be noted that the present invention is not limited to the above-described embodiment, but can take various forms based on the gist of the present invention. For example, in the above embodiment, the case where the seat belt pretensioner based on the present invention is attached to the retractor has been described, but the seat belt pretensioner of the present invention is not limited to this.
The buckle itself can be applied to a pretensioner for a seat belt that instantaneously pulls in the webbing tension direction. Further, the configuration of the retractor with a pretensioner in the above embodiment is not limited to the above-described type, and various types can be used. Furthermore,
The shape of the piston is not limited to the stepped cylindrical shape as described above,
Various shapes of pistons, such as a cylindrical shape, can be used.

[0020]

According to the seat belt pretensioner of the present invention, the degree of sealing of the piston with respect to the cylinder can be increased without hindering the sliding of the piston by the grease filled between the inner wall of the cylinder and the piston. it can. Therefore, the inflation gas generated by the gas generator does not leak out of the cylinder from the gap, and the pressure of the inflation gas generated by the gas generator can be effectively applied to the piston. Further, since the grease has lubricity, the movement of the piston sliding in the cylinder becomes smooth.

Furthermore, since the gap between the piston and the cylinder is closed by grease, no flame or spark when the propellant or the like of the gas generator is burned is ejected from the gap to the outside of the cylinder. Therefore, it is possible to provide a good seat belt pretensioner that can effectively use the inflation gas with a simple structure and can prevent a flame or a spark from being ejected to the outside of the cylinder.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view of a seat belt pretensioner according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the pretensioner shown in FIG.

FIG. 3 shows a piston and a cylinder III- shown in FIG. 2;
It is a III sectional view.

FIG. 4 is an enlarged sectional view of a main part of a conventional seat belt pretensioner.

FIG. 5 is a cross-sectional view of the piston and the cylinder shown in FIG. 4 taken along line VV.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Retractor 2 Base side wall 6 Wire 9 Webbing 10 Piston 11 Small diameter cylindrical part 12 Conical part 13 Large diameter cylindrical part 20 Cylinder 24 Inner wall 30 Grease

Claims (1)

[Claims] 1. A pretensioner for a seat belt which draws in and drives a webbing in an emergency with a thrust by the pressure of an inflation gas acting on a piston slidably guided in a cylinder, wherein the inner wall of the cylinder and the piston are A pretensioner for a seat belt, characterized by being filled with grease therebetween.