JPS6139133Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hollow coil spring, and particularly to a hollow coil spring having a unique structure in the end portion of the spring.

Generally, it is desirable for a coil spring to be lightweight, and for example, in a relatively large coil spring such as a coil spring for a vehicle suspension, this is particularly necessary due to the demand for reducing the weight of the vehicle. To this end, it is effective to make the coil spring a hollow structure and to make it as thin as possible. The production of thin-walled hollow coil bodies has been fraught with difficulties due to buckling and uneven thickness when bent in the same way as solid materials (thin wall refers to the degree of thickness). Its production was made possible by the technology related to the applicant's earlier application (see Japanese Patent Laid-Open No. 14421/1983). The present invention has been made in order to further popularize such thin-walled hollow coil springs.

When commercializing thin-walled hollow coil springs, processing the end portion of the spring is more difficult than expected because of the thin wall.For example, in the case of a compression spring, it is necessary to press-form (crush) the end portion, or to align the center line of the spring. It is conceivable to create a shape without a lead angle by cutting at right angles, etc., but this tends to cause variations in the terminal shape and spring characteristics, and in the latter case, disadvantages in terms of rust prevention cannot be avoided. In the case of a tension spring, it is not only difficult to process the hook part, but even if the process can be done, there are still concerns about the strength.

The present invention was developed against the background of the above-mentioned circumstances, with the aim of providing a hollow coil spring with high mechanical reliability while achieving the effect of reducing weight due to being hollow. This is achieved by tightly fitting one end of a solid terminal forming member made of a spring material to each end of a hollow coil made of a spring material, and joining them by welding to form an integrated spring body. The point is that

In this way, the shape of the end of the spring can be easily and accurately formed, so that the desired spring constant can be stabilized, and the part that directly receives the load is solid. Furthermore, since the end portion is solid, it is no different from the widely used solid coil springs, so it can be used as is without making any changes to the surrounding parts such as the spring receiver. Can be used in the same way as solid springs.

Moreover, since the parts other than the terminal part are made of hollow coils, not only do they have the advantage of saving on materials such as high-grade materials, but they also have a large spring constant relative to their weight, which reduces the overall weight. The effect is remarkable in large-sized products with large coil diameters and wire diameters.

Furthermore, by increasing the length of the solid portion, the combination of the hollow portion and the solid portion can provide unique spring characteristics compared to the case where the entire portion is solid or hollow.

Hereinafter, embodiments of the present invention will be described based on the drawings.

The hollow coil spring shown in FIG. 1 is an embodiment in which the present invention is applied to a compression coil spring, and the coil spring has terminal forming members 4 connected and integrated at both ends of a hollow coil 2. It consists of

The hollow coil 2 is a thin-walled member with a circular cross section and is made of a suitable spring steel, and cannot be practically manufactured by the same method as a solid coil due to buckling. According to (but not limited to) the apparatus related to the above-mentioned patent application, it can be manufactured without difficulty. That is, a straight C-shaped cross-section material is guided between a core metal having a spiral groove and a forming tool placed close to a part of the spiral groove, and the inner and outer surfaces of the C-shaped cross-section material are formed by both of them. While the metal core is being restrained, the core bar is screwed forward using the same lead as the spiral groove, and as the core metal advances, the material is curved along the spiral groove, and then the opening of the curved material is closed and joined. The hollow coil 2 is then cut to an appropriate length and subjected to heat treatment.

On the other hand, each of the solid terminal forming members 4 is a circular member having the same diameter as the coil diameter (winding diameter) of the hollow coil 2 in this embodiment, and is a spiral portion having the same lead angle as the coil 2. and a seated part without a lead angle continuous thereto, and has a length of about one turn, and has a circular cross section that is approximately equal to the outer diameter of the cross section of the hollow coil 2, gradually moving from one end to the other end. It is made flat and has a planar seating portion that directly receives the load like a normal compression coil spring. This terminal forming member 4 is also made of a suitable spring steel, and since it is solid, its shape is easy to process.

As shown in FIG. 2, one end portion of the circular cross section of each terminal forming member 4 is stepped and formed to have a small diameter, and the small diameter portion is a tapered portion 6. The tapered portion 6 is formed with a small taper angle α so that the outer diameter gradually decreases toward the tip.
Excluding the chamfered tip, the outer diameter of the whole or at least the part near the base is slightly larger than the inner diameter of the hollow coil 2, and each terminal forming member 4 has a tapered portion 6 on the inner side of both ends of the hollow coil 2, respectively. They are tightly fitted by press-fitting or the like. Shrink fitting or cold fitting can also be used for interference fitting.

The fitting portion of the end forming member 4 to the hollow coil 2 may be a parallel surface without a taper, but it is preferable to form the tapered portion 6 as described above in order to facilitate press-fitting, etc. Fitting length l
Although it cannot be said unconditionally due to differences in the use of the spring, etc., it is recommended to select a value larger than 1.5d, where d is the inner diameter of the hollow coil 2, from the viewpoint of stability of the connection.

The stepped portion forming the base end of the tapered portion 8 is rounded to alleviate stress concentration, and the rounded portion 8 is arranged close to the end surface of the hollow coil 2. In the vicinity of the rounded portion 8, the end of the hollow coil 2 and the terminal forming member 4 are joined by appropriate welding means such as partial (discontinuous) electron beam welding or laser beam welding. Furthermore, in a dot-like recess (a drilled hole, a plastically worked recess, etc.) 10 provided on the outer circumferential surface of the hollow coil 2 corresponding to the distal end portion of the tapered portion 6 of the end forming member 4, the hollow coil 2 is dot-welded to the outer circumferential surface of the tapered portion 8 by beam welding as described above, thereby increasing the joint strength of the hollow coil 2 and the end forming member 4 against relative torsional loads around the center line of the tapered portion 8. is enhanced. It is also possible to set a plurality of dotted welding locations.

As described above, each of the terminal forming members 4 is connected to both ends of the hollow coil 2 by tight fitting and welding to form an integrated spring body, so reliability in terms of accuracy and strength is high. It provides stable spring characteristics and exhibits sufficient durability even under large loads. In addition, while the hollow coil 2 has a lightweight effect, the terminal part has the same structure as a normal solid coil spring, so it can be used as an alternative to a solid coil spring without worrying about the current location. For example, if it is used as a coil spring for a vehicle suspension, it will have a remarkable effect on reducing the weight of the vehicle.

Note that the form of welding the terminal forming member 4 and the hollow coil 4 is not limited to the above-mentioned form; for example, if sufficient joint strength can be obtained only by welding in the vicinity of the rounded portion 8, welding may be performed in a dot-shaped recess. Welding in step 10 may be omitted, and various other welding forms may be employed.

Further, the winding length of the terminal forming member 4 is not limited to about one winding length as in the above embodiment,
By varying the length ratio of the end forming member 4 to the hollow coil 2 within a certain range, it is possible to obtain a spring with unique spring characteristics without changing the spring wire diameter or coil diameter.

Further, in the above embodiments, an example of a compression coil spring is shown, but the present invention can also be applied to a tension coil spring as shown in FIG. In this embodiment, each of the terminal forming members 12 having a spiral portion forming a part of the spiral and a hook-like portion continuous thereto is connected to both ends of the hollow coil 2 at one end thereof in the same manner as described above. An integral spring body is constructed, and substantially the same effect as the compression spring example is obtained. The same applies to torsion coil springs.

Further, in the above description, the hollow coil 2 has a circular cross section, but it may have a rectangular cross section, for example, and in that case, the hollow coil 2 may have a rectangular cross section. The shape of the fitting portion of the terminal forming member is determined.

In addition, it goes without saying that the present invention can be implemented with various changes and improvements without departing from the scope of the claims for utility model registration.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a hollow coil spring that is an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the main part thereof, and also shows a welding form. There is also. FIG. 3 is a partially cutaway front view of a hollow coil spring according to another embodiment of the present invention, and corresponds to FIG. 1. 2: Hollow coil, 4, 12: Terminal forming member,
6: Tapered portion, 8: Rounded portion, 10: Point-like recess.

Claims (1)

[Claims for Utility Model Registration] (1) One end of a solid terminal forming member made of a spring material is tightly fitted to each end of a hollow coil made of a spring material, and the coils are joined by welding. A hollow coil spring characterized by having an integral spring body. (2) The hollow coil spring according to claim 1, wherein each end portion of the terminal forming member is provided with a tapered portion having a smaller diameter toward the distal end, and the welding is partial beam welding.