JPH10138366A - Manufacturing method of resin spring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain always specific spring characteristics while yielding of the spring is little by a method wherein a resin spring is manufactured by releasing preliminary compression after applying the preliminary compression to crystalline thermoplastic resin, a recessed part is preliminarily formed before preliminary compression, to a part which is especially largely deformed in compression. SOLUTION: A cylindrical resin material 1 composed of polyester elastomer being crystallin thermoplastic resin is annealed after molding in a mold, a peripheral wall 3 is formed with a through hole 3 passing vertically through an inside, and an almost cylindrical shape is formed. Though an outer shape of the cylindrical resin material 1 is uniform over in an axial direction, an inner diameter of the throughhole 2 is gradually increased from upper and lower opening ends toward a center, and a recessed part 4 of an axial central part wherein a central part expands is formed. When preliminary compression is carried out by applying specific compression force axially, stress is concentrated to an axial central part, the cylindrical resin material 1 is deformed flatly, the axial central part is largely bent, and then though released by unfastening press, the resin spring which is deformed in almost such the shape is obtained as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin spring from a crystalline thermoplastic resin.

[0002]

2. Description of the Related Art A crystalline thermoplastic resin is generally considered to be plastically deformed when compressed by 10% or more and is not particularly suitable as a compression spring. Thereby, a spring characteristic can be provided. It is already known to obtain a resin spring in this manner, as disclosed in Japanese Patent Publication No. 61-12779 and Japanese Patent Publication No. 2-2.
No. 9485, etc.

FIGS. 11 and 12 show an example described in Japanese Patent Publication No. 2-29485. FIG. 11 is a cross-sectional view of a cylindrical elastic body 01 made of a copolymerized polyester elastomer material, in which a central opening 02 is formed so as to penetrate vertically and is symmetric with respect to a central axis, and a peripheral wall has a uniform thickness.

[0004] The cylindrical elastic body 01 is annealed for a predetermined time, and is compressed at least 30% in the axial direction as shown in FIG.
The peripheral wall of the cylindrical elastic body 01 expands outward to form a toroidal hollow elastic body, which is then opened.

[0005] Due to this compression, crystallization proceeds and the physical properties of the polymer material are changed, so that compression spring properties can be obtained.

[0006]

However, in the resin spring thus manufactured, the distortion is not sufficiently released by the return after being compressed, and the relationship between the compression force and the amount of deformation is determined by the compression side and the release side (return side). ) Is different.

[0007] This is considered to be due to insufficient crystallization in a portion where the resin spring is largely displaced by compression. If sag occurs in the resin spring, the required spring characteristics cannot always be expected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing a resin spring which has a small set of the resin spring and can always maintain required spring characteristics.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method in which a crystalline thermoplastic resin is pre-compressed in a deformation direction with a predetermined compressive force, and is then opened to release a resin spring. In the method of manufacturing a resin spring, a concave portion is formed in advance in a portion where the resin spring is particularly largely deformed when compressed, before the preliminary compression.

[0010] By forming a concave portion in advance in a portion which is particularly greatly deformed by the compression of the resin spring, stress is concentrated in the concave portion by pre-compression, and crystallization proceeds locally.
The manufactured resin spring minimizes the set to compression and release and can always maintain the required spring characteristics.

In the method of manufacturing a resin spring, annealing is performed on the crystalline thermoplastic resin before pre-compression, whereby crystallization can be further promoted, and further generation of set can be suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIGS. 1 and 2 show a cylindrical resin material 1 made of a polyester-based elastomer which is a crystalline thermoplastic resin.

The cylindrical resin material 1 is annealed after being molded and formed into a substantially cylindrical shape by forming a peripheral wall 3 with a through hole 2 penetrating vertically through the inside as shown in FIGS. ing.

The outer diameter of the cylindrical resin material 1 is uniform in the axial direction, but the inner diameter of the through hole 2 gradually increases from the upper and lower open ends toward the center, and the central portion expands. A concave portion 4 is formed at the center. That is, the concave portion 4 is formed on the peripheral wall 3 at the central portion in the axial direction, which is particularly greatly deformed by compression.
Are formed.

As shown in FIG. 3, a predetermined compressive force is applied in the axial direction so as to sandwich the cylindrical resin material 1 between the press plates 11 and 12, thereby performing a preliminary compression. The compression amount is about 50%,
Although the cylindrical resin material 1 is deformed flatly, stress concentrates on the central portion in the axial direction where the concave portion 4 of the cylindrical resin material 1 is formed as shown in FIG. The crystallization of the site is further advanced locally.

When the cylindrical resin material 1 is released by releasing the press, it expands and returns somewhat, but does not return to the original state, and a resin spring 5 as shown in FIG. 4 is formed. Resin spring 5
FIG. 5 shows the results obtained by measuring the spring characteristics of.

As shown by the solid line in FIG. 5, when the displacement is large, the load increases more than when the displacement is small, and the characteristic curve shown in the compression process is generally traced in the opening (returning) process. Tracing and hardly any sag.

FIG. 5 shows, for comparison, the result of measurement on the resin spring of the example described in the above-mentioned prior art by a broken line. Is causing a slip.

The resin spring 5 has a central portion in the axial direction that is bent and bulged outward, and the portion is greatly deformed when subjected to compression. Since the concave portion 4 is provided in advance in the central portion in the axial direction and pre-compression is performed, it is possible to obtain a spring characteristic without settling as shown by a solid line in FIG. 5, and use a resin spring without settling as described above. By doing so, required spring characteristics can be constantly maintained.

Next, another embodiment will be described with reference to FIGS. The resin spring 20 of the embodiment is
It is used for a front wheel suspension device of a motorcycle.

A resin spring 20 which is made of a polyester type elastomer, formed into an original shape by a mold, annealed, and preliminarily compressed is finally manufactured, which is a resin spring having a shape shown in FIGS.

The resin spring 20 has a fan-like shape in a side view and a cross section, has an appropriate thickness in the width direction, and has a large projection 21 protruding from the rear surface. The projection 21 has a long hole 22 penetrating along the rear surface.
Are formed.

Inside the resin spring 20, a large deformed rectangular hole 23 penetrating in the width direction is formed in a rear half portion, and an oblong elongated hole 25 is formed along the front surface in the front half portion. An arc-shaped long hole 24 is formed in front of the deformed rectangular hole 23.

As shown in FIGS. 8 and 9, concave portions 26 and 27 are formed on the left and right side surfaces. The resin spring 20 is swung around a pivot of a fan shaped like a side view and compressed so as to sandwich the front and rear surfaces. The compression forms recesses 26 and 27 on the rear side surface where deformation is particularly large. I have.

In the process of manufacturing the resin spring 20, a concave portion is previously formed on a corresponding side surface portion of the resin material before the pre-compression, and the concave portion is particularly crystallized by the pre-compression, and the spring characteristic is reduced. No sag occurs as in the previous embodiment.

The resin spring 20 is used for a front wheel suspension system. Referring to FIG. 10, a swing arm 31 is pivotally supported at the lower end of a front fork 30 by a pivot arm bolt 33, and the free end of the swing arm 31 is connected to a front wheel (not shown) via a front axle 34. Is supported.

From the base pivot portion of the swing arm 31, a plate-like lever 32 extends in the centrifugal direction at an angle of about 60 degrees with respect to the swing arm 31, and is integrally formed. A fan-shaped case 35 is fixed to the front fork 30 adjacent above the base pivot portion of the swing arm 31 pivotally supported at the lower end of the front fork 30, and the resin spring 20 is housed in the case 35. The front long hole 25 is penetrated by the locking member 36 and is fixed to the case 35.

An opening is formed in the lower wall of the case 35, and the lever 32 enters the case 35 through the opening and fits into the elongated hole 22 formed in the rear end projection 21 of the resin spring 20. Accordingly, the resin spring 20 has a front end fixed to the front fork 30 by the locking member 36 and a rear end formed by the lever 32 integrated with the swing arm 31.
It is stuck to.

With the front wheel suspension structure as described above, when the front wheel receives the unevenness of the ground and the swing arm 31 swings, as shown in FIG. 10, the swing arm 31 and a lever integrated therewith. 32 swings from the state shown by the solid line and changes as shown by the two-dot chain line. Therefore, the lever 32 compresses the resin spring 20 toward the front fork 30 and elastically deforms it, thereby generating a damping force.

Since the resin spring 20 does not set, as described above, the required spring characteristics are secured from the beginning of the attachment, and it is possible to prevent the function from being deteriorated due to the set.

In the above embodiment, a polyester elastomer is used as the material of the resin spring.
The invention is not limited to this, and other crystalline thermoplastic resins can be used.

[Brief description of the drawings]

FIG. 1 is a perspective view of a cylindrical resin material before pre-compression according to an embodiment of the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is a cross-sectional view showing a state where pre-compression is applied to the cylindrical resin material.

FIG. 4 is a cross-sectional view of the manufactured resin spring.

FIG. 5 is a graph showing spring characteristics of the resin spring.

FIG. 6 is a side view of a resin spring according to another embodiment.

FIG. 7 is a view taken in the direction of the arrow VII in FIG. 6;

FIG. 8 is a view taken in the direction of the arrow VIII in FIG. 6;

FIG. 9 is a view taken in the direction of the arrow IX in FIG. 6;

FIG. 10 is a side view partially in section showing a use state of the resin spring.

FIG. 11 is a cross-sectional view of a conventional cylindrical elastic body.

FIG. 12 is a cross-sectional view showing a state where the cylindrical elastic body is pre-compressed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylindrical resin material, 2 ... Through-hole, 3 ... Peripheral wall, 4 ... Depression, 5
... resin springs, 11,12 ... press plate, 20 ... resin spring, 21 ... projection, 22 ... long hole, 23 ... deformed rectangular hole, 24,25 ... long hole, 26,27
... recess, 30 ... front fork, 31 ... swing arm, 32 ...
Lever, 33 ... pivot arm bolt, 34 ... front axle, 35 ...
Case, 36 ... locking member.

Claims (2)

[Claims] 1. A method of manufacturing a resin spring by preliminarily compressing a crystalline thermoplastic resin in a deformation direction with a predetermined compressive force, and then releasing the preliminarily compressed resin, wherein the resin spring is particularly largely deformed when compressed. A method of manufacturing a resin spring, wherein a concave portion is formed in a portion before the preliminary compression. 2. The method according to claim 1, wherein annealing is performed on the crystalline thermoplastic resin before the preliminary compression.