JPH04253537A - Production of s-shaped spring for seat belt winder - Google Patents

Abstract

PURPOSE:To lessen the increase in torque arising from an increase in a pulling quantity and to facilitate the attachment and detachment of a seat belt as well as to decrease the compressive feel when the belt is put on. CONSTITUTION:A strip material formed to have 220 to 280kgf/mm<2> tensile strength by cold rolling a piano wire or hard steel at 60 to 90% reduction of area is subjected to primary coiling at 50 to 70 coiling index and is then subjected to secondary coiling in an opposite direction.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a seatbelt retractor that reduces the increase in torque that accompanies an increase in the amount of pullout, makes it easier to attach and detach the seatbelt, and reduces the feeling of pressure when wearing the seatbelt. This invention relates to a method of manufacturing an S-shaped mainspring spring for use.

0002

[Prior Art and Problems to be Solved by the Invention] In an S-shaped mainspring spring for a seat belt retractor, a band material is first wound to cause plastic deformation, and then a large amount of residual material is left by second winding in the reverse direction. The unwinding torque is increased by creating stress, but in order to make it easier to put on and take off the seat belt and reduce the feeling of pressure when wearing it,
It is desirable to generate a minimum constant torque necessary for winding up the seat belt, regardless of the amount of pull-out of the seat belt.

However, the conventional mainspring spring has
Since stainless steel is mainly used and the tensile force is small, it is not possible to reduce the thickness of the belt material, and the torque constant (increase in torque per rotation, the same applies hereinafter) is large, so it is difficult to pull out the seat belt. As the amount of seat belts increases, the force required to pull them out increases significantly, and therefore a large amount of force is required to attach and detach the seat belt, and the tensile force that acts on the seat belt when it is attached is large, causing a feeling of pressure. There were flaws.

0004

[Means for Solving the Problems] The present invention aims to eliminate these drawbacks and to manufacture an S-shaped mainspring spring for a seatbelt retractor that is easy to attach and detach and provides less pressure when attached. Hard steel wire is cold rolled to an area reduction rate of 60% to 90% and has a tensile strength of 220Kgf/mm2 to 280Kg.
The belt material having a f/mm2 was first wound with a winding index of 50 to 70, and then secondly wound in the opposite direction.

[0005]

Effects and Effects of the Invention The present invention has the above-described structure, and stainless steel, which has been mainly used in the past, has a tensile strength of 18.
Since it was about 0Kgf/mm2, it was necessary to increase the thickness to keep the design stress small, and the torque constant was increased, but by using a strip material with high tensile strength, the thickness was increased. Conventionally, the ratio between the diameter of the primary winding and the thickness of the strip material (herein referred to as the winding index) is 15.
The residual stress in the unwinding direction was increased from about 0 to 50 to 70, thereby making it possible to secure the desired unwinding torque.

[0006] That is, by using a strip material with high tensile strength and reducing the thickness, the torque constant is made small, and the desired torque is obtained by making the winding index of the primary winding small. Since the change in torque due to changes in the pull-out length is small and the desired torque can be obtained, even if the seat belt is pulled out for a long time when attaching and detaching the seat belt, the force required to do so is relatively small and the attaching and detaching operations are easy. , the tensile force when worn is small, so there is less pressure.
Furthermore, there is an effect that sufficient torque required for retracting the seat belt can be ensured.

[0007]

[Example] Comparing a strip according to the present invention made by cold rolling piano wire SWRS62 to an area reduction rate of 70% and a strip made by cold rolling stainless steel wire SUS301-CSPEH, which has been commonly used in the past, it is found that The hardness of the latter is H
V560, while the former is Hv675 and Hv100
The tensile strength of the latter is 183Kgf/mm2, while the former is 225Kgf/mm2, which is 23% higher, and the stress amplitude of the 106 times time strength is ±1 for the latter.
00Kgf/mm2, while the former is ±110Kg
It was found that f/mm2 was 10% higher.

[0008] Furthermore, when comparing the characteristics of the above-mentioned band material according to the present invention and the conventional S-shaped mainspring spring using the above-mentioned band material, it is found that the S-shaped mainspring spring according to the present invention has a plate thickness of 0.19 m.
m, whereas the conventional S-shaped mainspring spring is 0.20
As a result, the total number of revolutions increased from 26 to 28 times, the pull-out length increased, and the torque characteristics became as shown in Figure 1, resulting in a linear The torque constant of the conventional product is 0.21Kgf・mm/
times, whereas the S-shaped mainspring spring according to the present invention has 0 times.
．． It was 17Kgf·mm/times, which was a decrease of about 20%. As a result, it was found that the amount of increase in the force required to pull out the seat belt due to the increase in the amount of pull out of the seat belt was reduced, making it easier to attach and detach the seat belt, and reducing the feeling of pressure when wearing the seat belt.

Furthermore, regarding durability, the 105-cycle durability limit is shown in FIG. 2, and the fatigue characteristics are shown in FIG. 3, and the S-shaped mainspring spring according to the present invention is significantly superior in both cases. .

[Brief explanation of the drawing]

[Fig. 1] S-shaped mainspring spring according to the present invention and conventional S-shaped mainspring spring
It is a graph showing the characteristics of a mainspring spring.

FIG. 2 is a graph showing the 105 cycle durability limit of the S-shaped mainspring spring according to the present invention and the conventional S-shaped mainspring spring.

FIG. 3 is a graph showing the fatigue of the S-shaped mainspring spring according to the present invention and the conventional S-shaped mainspring spring.

Claims (1)

[Claims] [Claim 1] Piano wire or hard steel wire with area reduction rate of 60%
~90% cold rolled to tensile strength of 220Kgf/mm
Wrap a strip material with a rate of 2 to 280 Kgf/mm2 with an index of 50 to
A method for manufacturing an S-shaped mainspring spring for a seat belt retractor, which comprises first winding the spring at a speed of 70, and then second winding in the opposite direction.