JP3360181B2 - Method of manufacturing S-spring spring for seat belt retractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seat belt retractor for reducing the increase in torque accompanying an increase in the amount of pull-out, facilitating the attachment / detachment of the seat belt, and reducing the feeling of pressure when the seat belt is worn. The present invention relates to a method for manufacturing an S-shaped mainspring spring.

[0002]

2. Description of the Related Art An S-spring spring for a seat belt retractor is configured to firstly wind a belt material to cause plastic deformation, and then secondarily wind the belt material in a reverse manner to produce a large residual material. Although the rewind torque is increased by generating stress, in order to achieve ease of attaching / detaching the seat belt and reduce the feeling of pressure when wearing it,
It is desirable to generate a minimum constant torque required for winding up the seat belt, regardless of the amount of pull-out of the seat belt.

[0003] However, in the conventional spring,
Since the stainless steel is mainly used and the tensile force is small, the thickness of the strip cannot be reduced, and the torque constant (the amount of increase in torque per rotation; hereinafter the same) is large, so the seat belt is pulled out. With the increase in the amount, the force required for pulling out is significantly increased, and therefore, a large force is required for attaching and detaching the seat belt, and a large tensile force acts on the seat belt at the time of wearing, which causes a feeling of oppression. There were drawbacks.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks and to produce a S-spring for a seat belt retractor which is easy to attach and detach and has a small feeling of pressure when worn. A hard steel wire is cold-rolled to a reduction of area of 60% to 90% to have a tensile strength of 220 kgf / mm ^{2 to} 280 kgf / mm ^2.
The primary winding of the strip material having a winding index of 50 to 70 is followed by a secondary winding in the opposite direction.

[0005]

The present invention has the above-mentioned structure, and the stainless steel which has been mainly used in the past has a tensile strength of 18%.
Since it was about 0 kgf / mm ^2, it was necessary to increase the thickness because the design stress had to be kept small, and the torque constant had increased. Is reduced to reduce the torque constant, and the ratio of the diameter of the primary winding to the thickness of the band material (this is referred to as a winding index in the present specification) of about 150 is changed to 50 to 70. As a result, the residual stress in the unwinding direction was increased, whereby a desired unwinding torque could be secured.

That is, a torque constant is reduced by reducing the thickness using a strip having a large tensile strength, and a desired torque is obtained by reducing the winding index of the primary winding. In addition, since a change in torque due to a change in the drawer length is small and a desired torque can be obtained, even if the seat belt is pulled out long at the time of attaching and detaching, the force required for this is relatively small, and the attaching and detaching operation is easy, and Also, since the pulling force at the time of wearing is small, the feeling of pressure is small, and the torque required for winding the seat belt can be sufficiently secured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A comparison between the strip of the present invention obtained by cold rolling a piano wire SWRS62 to a reduction of area of 70% and a strip obtained by cold rolling a stainless steel wire SUS301-CSPEH generally used in the past is shown in FIG. The hardness is H
The former is Hv675 and the latter is Hv100.
The tensile strength is 183 kgf / mm ² for the latter, whereas the former is 225 kgf / mm ^{2, which} is 23% higher, and the tensile strength is 1%.
Stress amplitude of 0 ⁶ times time strength latter the former whereas a ± 100 Kgf / mm ² was found to be 10% higher ± 110Kgf / mm ^2.

Further, when comparing the characteristics of the above-mentioned band material according to the present invention with those of the conventional S-shaped mainspring spring using the above-mentioned band material, the S-shaped mainspring spring according to the present invention has a plate thickness of 0.19.
mm whereas the conventional S-spring has a 0.20
mm, the weight is reduced by 5%. As a result, the total number of revolutions is increased from 26 to 28, the pull-out length is increased, and the torque characteristics are as shown in FIG. The torque constant of the portion is 0.21 kgf · mm / time for the conventional product, whereas the S-shaped spring spring according to the present invention is 0.17 kgf · mm / time.
Kgf · mm / time, a decrease of about 20%. As a result, it has been found that the amount of increase in the force required to pull out the seatbelt with the increase in the amount of pullout of the seatbelt is reduced, so that the seatbelt can be easily attached and detached and the feeling of oppression at the time of wearing is reduced.

Furthermore, the durability, 10 to ⁵ times the endurance limit is 2, the fatigue characteristics shall apply in as shown in FIG. 3, both significantly better better S-shaped spiral spring according to the present invention I have.

[Brief description of the drawings]

FIG. 1 shows an S-shaped mainspring according to the present invention and a conventional S-spring.
It is a graph which shows the characteristic of a character spring.

2 is a graph showing the 10 ⁵ times the endurance limit of the S-shaped power spring and a conventional S-shaped spiral spring according to the present invention.

FIG. 3 is a graph showing the set of the S-spring spring according to the present invention and the conventional S-spring spring;

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B21F 35/00 B60R 22/34 F16F 1/02

Claims (1)

(57) [Claims] 1. A piano wire or a hard steel wire with a surface reduction rate of 60% or more.
Cold rolled to 90% to increase the tensile strength to 220 kgf / mm ^{2 to} 28
A seat belt retractor for S-spiral spring manufacturing method, characterized by the secondary winding in the opposite direction after the winding primary in winding Index 50-70 the strip which was 0 kgf / mm ^2.