JPS5813766B2 - coil spring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coil spring that equalizes the shear stress generated in the strands and reduces the weight.

Generally, a coil spring is formed by winding a solid wire into a coil shape.

When this coil spring deforms in the axial direction of the coil, the strands are twisted and deformed to absorb and store energy.

By the way, the shear stress caused by the twisting of the wire is different between the inner and outer parts of the coil due to the fact that the wire is formed into a coil shape, and the shear stress is non-uniform and the shear stress per unit volume of the material, that is, per weight. The stored energy decreases, and the efficiency of the spring decreases.

For this reason, attempts have been made to equalize the shear stress by using wires with irregular cross sections to increase the stored energy per unit weight and thereby reduce the weight of the spring.

However, when using a wire with such an irregular cross section,
It is difficult to wind this into a coil, requiring a special winding device, and because existing winding devices cannot be used, manufacturing costs increase significantly.

Additionally, from a different perspective than the above, some springs have been made lighter by using hollow strands, but even in these types of springs, the shear stress between the inner and outer parts of the coil is unequal. This did not solve the problem, and there were limits to how much weight could be reduced.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to reduce the weight of the spring by equalizing the stress on the inner and outer parts of the coil of strands, and to reduce the weight of the spring compared to the conventional coil. The object of the present invention is to obtain a coil spring which can be wound using an existing winding device and which can reduce manufacturing costs.

An embodiment of the present invention will be described below according to an embodiment shown in the drawings.

1 to 3 show a first embodiment of the present invention, in which numeral 1 represents a wire.

The strand 1 has an eccentric hollow shape having a circular cross-sectional outer shape and a hollow portion 2 with a circular cross-section formed parallel to the central axis and eccentric by a predetermined amount to one of the central axes.

The wire 1 is wound into a coil so that the eccentric side of the hollow part 2 is located inside the coil, and the coil springs 3.
is formed.

Incidentally, the eccentricity ε of the hollow part 2 is appropriately set depending on the shape of the coil spring 3 and other factors. In this case, it is desirable that the eccentricity ε is set to .

Such a coil spring 3 is made by first preparing a hollow tubular material that is not eccentric, and then making the outer surface of this material eccentric by a predetermined amount with respect to the hollow part by hot rolling, cold drawing, cutting, etc. It is formed into a circular shape to form a strand 1 as shown in FIG.

Then, the coil spring 3 is formed by winding the wire 1 in a manner similar to the conventional method so that the eccentric side thereof is located inside the coil.

Next, the operation of the first embodiment of the present invention constructed as above will be explained.

First, when a solid wire 1' having a circular cross section as shown in FIG. 4 is straight, when twist is applied to the wire 1', the central axis 0 of the wire 1' becomes the center of the twist.

By the way, when this strand 1' is wound into a coil and compression or tension is applied to it, twist acts on this strand 1', but in this case, when the strand 1' is wound into a coil, Due to the effect of

The amount of movement δ of the torsion center at this time is normally as follows, where d is the wire diameter and R is the coil radius.

As a result, the shear stress distribution at each part of the strand 1' along the line XX in the radial direction of the coil becomes as shown in FIG.

The ratio of the shear stress τa2 at point a2 on the outer surface of the coil of this strand 1' to the shear stress τa2 at point a1 on the inner surface of the coil is given by Wahl's equation when the spring index is C=2R/d. .

This value can actually be quite large, for example 2R=8
Calculating with 0 birds, d=10 fight C=2R/d=8, τa1/τa2=1.4.

Therefore, the shear 1 stress at point a1 inside the coil is 4
0% is also a big deal.

Next, when the eccentric hollow wire 1 as in the first embodiment shown in FIG. Occurs on the opposite side.

Then, as in the first embodiment, this strand 1 is inserted into the hollow part 2.
When the coil is wound so that the eccentric side thereof is located inside the coil, the torsion center moves to the inside of the coil, that is, to the eccentric side of the hollow portion 2, from the torsion center in the case of the linear case.

Therefore, if the dimensions of each part are set so that the displacement of the torsional center due to the eccentricity of the hollow part 2 is equal to the amount of movement of the torsional center due to winding the coil, the coiled shape will be formed as shown in Figure 5. The center of twist when wound can be made to coincide with the central axis 0 of the outer shape of the strand 1.

In this case, the distance Oa2 between the point a2 on the outer surface of the coil of the strand 1 and the torsion center, and the distance Oa2 on the inner surface of the coil
The distance Oa1 between the point and the center of twist becomes equal, and the shear stresses τa1 and τa2 at these points become equal as shown in FIG. 5, so that the shear stress is equalized, the efficiency of the spring is improved, and the weight can be reduced.

In this case, since the hollow part 2 is formed near the central axis 0 where the shear stress is small, this is due to the fact that the wire is made hollow, similar to the conventional coil spring using a wire with a hollow center. It also has the effect of reducing weight.

The diameter d1 of the hollow portion 2 and its eccentricity ε are set appropriately under various conditions.
In a general case, in order to fully exhibit the weight reduction effect due to the eccentricity of the hollow part 2, the outer diameter of the wire should be set to d2.
Also, let the diameter of the hollow part 2 be d1 and the coil radius R
In this case, it is preferable to set ε to .

Next, an experiment conducted to confirm the effect of eccentricity of the hollow portion 2 will be explained.

First, find the weight WH when coil springs with the same specifications are manufactured using concentric hollow wires and eccentric hollow wires with a spring index C = 8, and calculate the weight WH of coil springs with the same specifications using solid wires. FIG. 6 shows the results of comparison with the weight Ws of the spring produced.

From this result, when a concentric hollow strand is used (indicated by the broken line in Fig. 6), the ratio n of the outer diameter d2 and the diameter d1 of the hollow part is
= When dl/d is around 0.5 to 0.6, the weight ratio WH/Ws with respect to the solid wire is about 0.9, and the weight is reduced by only about 10%, whereas the weight is reduced by only about 10%. In the invention (shown by the solid line in Figure 6), WH/Ws is approximately 0.82, which is 18
The weight is also reduced by about %.

Note that the present invention is not limited to the first embodiment described above, and various modifications are possible.

For example, FIGS. 7-8 show a second embodiment of the present invention.

In this second embodiment, a coil spring 3' is formed using an eccentric hollow strand 1 of unequal diameter with reduced outer diameters at both ends, and the configuration of the hollow part 2' and The operation is similar to that of the first embodiment.

Furthermore, the present invention is not limited to the first and second embodiments described above, and the cross-sectional shape of the wire is not limited to a circular shape but may be any other shape. Something like that would be fine.

Further, the shape of the spring is not limited to a cylindrical shape, but can be applied to any shape such as a conical drum shape, a barrel shape, and can also be applied to compression, tension, torsion, and other coil springs.

As described above, in the present invention, an eccentric hollow wire having a hollow portion formed eccentrically with respect to the central axis is wound such that the eccentric side of the hollow portion is located inside the coil.

Therefore, the stress in each part of the wire inside and outside the coil is equalized, the stored energy per unit volume, that is, weight is increased, and the weight of the spring can be reduced.

In addition, the cross-sectional shape of the outer shape of the strands may be circular, etc., as in the past, and there is no need to make it into an irregular cross-section that makes it difficult to form a coil.
Its industrial utility value is significant, such as being able to use a conventional coil winding device and thus reducing costs.

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention.
The figure is a longitudinal cross-sectional view, FIG. 2 is a cross-sectional view showing a part of it enlarged, FIG. 3 a is a side view of the wire before coil forming, and FIG. 3 b is a-- It is a sectional view along the a line. 4 to 6 are explanatory diagrams of the functions and effects of the first embodiment, in which FIG. 4 is a stress distribution diagram of the solid wire, and FIG.
The figure is a stress distribution diagram of the eccentric hollow strand, and FIG. 6 is a graph showing the weight reduction effect. Further, FIGS. 7 and 8 show a second embodiment of the present invention,
Fig. 7 is a longitudinal sectional view, Fig. 8a is a side view of the wire before coil forming, and Figs. 8b and C are respectively shown in Fig. 8a.
It is a sectional view taken along line b and line ■C-■C. 1,1"...strand (eccentric hollow wire), 2.2'...hollow part, 3.3'...coil spring.

Claims (1)

[Claims] 1. A coil made by winding an eccentric hollow wire having a hollow part formed eccentrically with respect to the central axis so that the eccentric side of the hollow part is located inside the coil.