JPH07117772A - Front fork for bicycle and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a front fork for a bicycle and a manufacturing method thereof by which rigidity to force in the cross-sectional diameter direction can be balanced and the productivity can be enhanced. CONSTITUTION:A skin layer 17 is integrally molded on the periphery of a bar-shaped core material 16 formed of a material such as urethane foam, and plural reinforcing projections 18 in the lengthwise direction are integrally formed toward the center of the core material 16 inside of this skin layer 17. The reinforcing projections 18 are arranged at regular intervals in the circumferential direction inside of the skin layer 17, or are arranged in symmetric positions inside of the skin layer 17 as shown in the drawing 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front fork for a bicycle and a method for manufacturing the same, and more specifically, it balances the rigidity of a circular cross section against the force from the radial direction without affecting the appearance. Furthermore, RTM (Resin T
ransfer Molding) The present invention relates to a bicycle front fork that can improve productivity by a molding method and a manufacturing method thereof.

[0002]

2. Description of the Related Art Generally, a front fork supporting a front wheel of a bicycle is required to have higher rigidity than other fork portions because a load is applied during a sudden braking. By the way, as a conventional bicycle fork and its manufacturing method, for example, as shown in Japanese Patent Laid-Open No. 63-2786 and FIG. 7, core materials 1a and 1b which are radially divided into two by polyurethane foam resin or the like are used. When the core material 1a, 1b is molded in advance and placed in the molding mold, the core material 1
A carbon fiber 2 is sandwiched between a and 1b, a carbon fiber 3 is disposed around the carbon fiber 2, and this preform is placed in a molding mold (not shown), and then epoxy is placed in the molding mold. A resin material such as a resin is injected to impregnate the carbon fiber with the resin material, and the skin layer 4 is integrally molded by heating and curing, so-called RTM (Resin T
A molding method of the front fork 5 by a ransfer molding method is known.

[0003]

However, in the front fork 5 formed as described above, the reinforcing rib 6 is connected to the skin layer 4 through the centers of the core members 1a and 1b as shown in FIG. It has a different structure. Therefore, the front fork 5 has a large rigidity with respect to the load in the X direction, but has a low rigidity with respect to the load in the Y direction, and there is a problem as a balance of the rigidity in the radial direction of the cross section. Further, in the case of the conventional manufacturing direction as described above, since the two core materials 1a and 1b have to be molded in advance, the processing is expensive, and a lot of them are set in the molding mold. There is a problem that productivity is extremely poor because it takes time and labor.

The present invention has been devised in view of the above-mentioned conventional problems, and has a bicycle front fork and a bicycle front fork which can balance the rigidity against the force in the radial direction of the section and can improve the productivity. It is intended to provide a manufacturing method thereof.

[0005]

In order to achieve the above object, the present invention provides a plurality of reinforcing projections inside a skin layer forming a front fork, toward the center of a core material, and along the longitudinal direction. The gist is that they are integrally formed. Further, the reinforcing protrusions are arranged at equal intervals in the circumferential direction inside the skin layer or at symmetrical positions inside the skin layer.

[0006]

The present invention is configured as described above, in which concave grooves are formed at equal intervals along the longitudinal direction around a rod-shaped core material, and bundled carbon fibers are embedded along the concave grooves. And the carbon fiber around the rod-shaped core material,
After disposing this preformed product in the molding mold, a resin material such as an epoxy resin in the molding mold is injected to impregnate the carbon fiber with the resin material, and the carbon fiber is integrally molded by heating and curing. Therefore, the rigidity against the force from the radial direction of the cross section is balanced, and the productivity can be improved.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a perspective view of a bicycle frame body 10 embodying the present invention, in which 11 is a front fork, and 1 is a front fork.
2, 2 is a top tube, 13 is a back fork, 14 is a seat stay tube, and 15 is a down tube. The front fork 11 according to the present invention has a rod-like shape made of a material such as urethane foam as shown in FIG. A skin layer 17 is integrally formed around the core material 16, and a plurality of reinforcing protrusions 18 are integrally formed inside the skin layer 17 along the longitudinal direction toward the center of the core material 16. There is.

The reinforcing projections 18 are arranged at equal intervals in the circumferential direction inside the skin layer 17 as shown in FIG. 2, or are arranged at symmetrical positions inside as shown in FIG. It is a thing. By configuring the front fork 11 as described above, it is possible to obtain substantially uniform rigidity with respect to the force from any direction in the radial direction of the cross section, and thus to make the front fork 11 in which the rigidity is balanced. Can be done. Table 1 shows an experimental example comparing the rigidity of the front fork 11 according to the present invention and the conventional front fork.

[0009]

[Table 1] As a rigidity test, the position of 30 mm away from the crown portion 11b of the stem portion 11a of the front fork 11 as shown in FIG. A load W of 30 kg was applied in the horizontal and horizontal directions, and the amount of movement from the original position was measured as the amount of deflection. The smaller the bending amount, the higher the rigidity.

As is apparent from Table 1, the front fork 1 according to the present invention is different from the front fork having a circular cross section in Comparative Example 1 and the rib in the central portion of Comparative Example 2.
It was found that No. 1 had high rigidity in both the front-rear direction and the left-right direction. Also, when the production time of the core material and the production time of the preformed product are compared, the production time of the core material and the preformed product according to the present invention is shortened, and the productivity can be improved. .

Next, a method for manufacturing the front fork 11 will be described. First, rod-shaped core members 16a and 16b having a cross shape and a substantially Y shape as shown in FIG. 3 or FIG.
Is formed of a material such as urethane foam. Then
The bundle-like carbon fibers 18a forming the reinforcing projections 18 are embedded along the concave groove portions 20 in the concave groove portions 20 of the core materials 16a and 16b, respectively, and the rod-shaped core material 16 is formed.
A carbon fiber forming the skin layer 17 is arranged around a and 16b and temporarily fixed to produce a preform.

Then, after placing this preform (not shown) in the molding mold, a resin material such as an epoxy resin is injected into the molding mold to impregnate the carbon fibers 17 and 18a with the resin material and heat it. By curing, the front fork 11 is integrally molded. This molding method is the RTM (Resin Transfer Molding) molding method.

By molding by such a method, the front fork 11 having sufficient rigidity can be manufactured without manufacturing a plurality of core materials as in the conventional case. That is, the rigidity is balanced against the force from the radial direction of the cross section (force from the X and Y directions), and the productivity can be improved. As described above, according to the present invention, the manufacturing time of the core material and the preform is shortened, the productivity can be improved, and the rigidity of the front fork 11 against the force from the front-rear direction and the left-right direction is improved. Also has sufficient rigidity.

[0014]

As described above, according to the present invention, since a plurality of reinforcing projections are integrally formed inside the skin layer toward the center of the core material and along the longitudinal direction as described above, The rigidity is balanced against the force of
Since it is manufactured with one core material by the esin transfer molding (molding) method, the manufacturing time of the core material and the pre-molded product is shortened, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a frame body of a bicycle embodying the present invention.

FIG. 2 is a sectional view of a front fork.

FIG. 3 is a perspective view of a core material forming the front fork of FIG.

FIG. 4 is a sectional view showing another embodiment of the front fork.

5 is a perspective view showing another embodiment of the front fork of FIG. 4. FIG.

FIG. 6 is an explanatory diagram of a rigidity test device.

FIG. 7 is a perspective view of a conventional core material.

FIG. 8 is a cross-sectional view of a front front made of a conventional core material.

[Explanation of symbols]

10 Frame Body 11 Front Fork 16 Core Material 17 Skin Layer 18 Reinforcing Protrusion 20 Recessed Groove

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29L 31:30

Claims (4)

[Claims] 1. A bicycle front fork comprising a rod-shaped core member, a fiber reinforced resin disposed in the longitudinal direction, and a skin layer integrally molded by an RTM molding method.
A bicycle front fork, characterized in that a plurality of reinforcing protrusions are integrally formed inside the skin layer along the longitudinal direction toward the center of the core material. 2. The bicycle front fork according to claim 1, wherein the reinforcing protrusions are arranged at equal intervals in a circumferential direction inside the skin layer. 3. The bicycle front fork according to claim 1, wherein the reinforcing protrusions are arranged at symmetrical positions inside the skin layer. 4. Grooves are formed around the rod-shaped core material at equal intervals along the longitudinal direction, and bundle-shaped carbon fibers are embedded along the groove to be arranged. After arranging carbon fiber around it and arranging this preform in the molding mold, resin material is injected into the molding mold to impregnate the carbon fiber with the resin material, and heat and cure to make it integral. For manufacturing a front fork for a bicycle that is molded in a mechanical manner.