JPH08309780A - Bicycle wheel and manufacturing method thereof - Google Patents

Abstract

PURPOSE: To further increase characteristics such as wt. reduction or the expansion of the degree of freedom of a design by subjecting a thermoplastic resin to hollow integral injection molding by a method performing the multi-point injection of gas from the places corresponding to the root parts of spoke parts in the outer peripheral part of a wheel. CONSTITUTION: Pressure gas injection ports 11 are provided in a mold in the same number as the number of spokes at the places corresponding to the root parts of the spoke parts 2 in the outer peripheral part 3 of a wheel and gas is injected from the injection ports to form hollow parts 4 in the spoke parts 2. In order to easily adjust the balance of the hollow ratios of the respective spoke parts 2, resin injection ports, that is, gates at a time of injection molding are provided in the places 12 corresponding to the intermediate parts of the outer peripheral part 3 between the spoke parts 2. By this constitution, a wheel excellent in wt. balance in its circumferential direction, flatness and the roundness of the circumference of a circle is obtained by a hollow integral injection molding method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bicycle wheel made of a thermoplastic resin, and more specifically, it is obtained by hollow-injection molding a thermoplastic resin and has a high rigidity, an excellent impact resistance, and a lightweight design. The present invention relates to a bicycle wheel having a high degree of freedom.

[0002]

2. Description of the Related Art In recent years, the use of synthetic resin for metal parts has been actively carried out. However, by changing from metal to synthetic resin, there are advantages such as weight reduction and durability improvement by rust prevention. Is obtained. Above all, bicycle wheel
In addition to the above-mentioned advantages, synthetic resin has been attracting attention because it has a wider degree of freedom in design, allows various coloring, and improves fashionability.

[0003]

On the other hand, an injection molding machine is used to inject a molten synthetic resin into a mold cavity and then pressurize a pressurized gas to produce an injection molded article having a hollow structure. A molding method, that is, a hollow integral injection molding method is known, and it is considered that when the present molding method is applied to a synthetic resin bicycle wheel, the features such as weight reduction and expansion of design freedom are further increased.

However, since the bicycle wheel satisfies the requirements for the running performance of the bicycle, it is required that the weight balance in the circumferential direction, the flatness, the roundness of the circumference, etc. be extremely precise. It was difficult to obtain such a bicycle wheel by the hollow integral injection molding method. In view of the above background, the present invention has a first object to provide a bicycle wheel that solves the problems of the prior art, and a second object is to provide a method for manufacturing such a bicycle wheel. It is intended.

[0005]

Means for Solving the Problems As a result of intensive studies by the present inventors, the above problems can be solved by adopting a specific method for gas injection when obtaining a bicycle wheel by hollow integral injection molding. And completed the present invention. That is, according to the present invention, the first object is composed of a shaft portion, a radial spoke portion, and an outer peripheral portion, and multipoint gas injection is performed from a portion corresponding to a root portion of each spoke portion in the outer peripheral portion. It is achieved by a bicycle wheel obtained by hollow-injection molding a thermoplastic resin by the method described above. Further, according to the present invention, the second object is composed of a shaft portion, a radial spoke portion and an outer peripheral portion, and multipoint gas is supplied from a portion of the outer peripheral portion which is a root portion of each spoke portion. This is achieved by a method for manufacturing a bicycle wheel, which comprises injecting and molding a thermoplastic resin into a hollow body.

The bicycle wheel of the present invention comprises a material thermoplastic resin (hereinafter sometimes simply referred to as resin),
It is obtained by a sympress molding method (gas assist injection molding method) in which a pressurized gas for forming a hollow portion is injected.
That is, the mold is closed and the molten resin and the pressurized gas are injected and injected into the mold cavity. While maintaining the pressure of the pressurized gas, the molten resin is cooled and solidified, and then the pressurized gas is removed. Obtained by This will be described with reference to the accompanying drawings. FIG. 1 shows a bicycle wheel according to the present invention.
FIG. 2 is an explanatory diagram in which reference numerals are added to the front schematic view of an example of the wheel to show the molding method of the wheel, and FIG. 2 is a schematic cross-sectional view of a spoke portion at a portion indicated by an arrow A in FIG. is there.

In the figure, 1 is a shaft portion of the wheel, and 2 is a spoke portion thereof.
A hollow portion 3 is formed in the spoke portion 2, and a hollow portion 4 is formed inside the spoke portion 2. An outline of the hollow portion 4 is shown by a dotted line. Reference numeral 11 indicates a position in the mold where the pressurized gas is injected. That is, the outer peripheral portion 3 is provided at each of the locations corresponding to the root portions of the spoke portions 2. Reference numeral 12 denotes a position where the molten resin is injected in the mold, and in the figure, it is provided at a position corresponding to the middle of the outer peripheral portion 3 sandwiched by the spoke portions 2.

As described above, in the mold, a plurality of pressurizing gases, that is, the same number as the number of spokes, are injected into the outer peripheral portion of the wheel at a portion corresponding to the root of the spoke portion 2. There is an inlet, from which gas is injected and each
It is possible to obtain a bicycle wheel having a well-balanced hollow ratio. Further, since the pressurized gas is injected at multiple points as described above, the gas pipe has a branched structure, but a gas injection device arranged so that the pipe path length to each gas injection port is even It is preferable to use it because it is easy to balance the hollow of each part of the molded product.

In order to make it easier to adjust the balance of the hollow ratios of the spokes 2, the resin injection port, that is, the gate at the time of injection molding, is more likely than that at the position where it contacts the shaft 1. It is preferable to provide it at a position corresponding to the outer peripheral portion 3 as shown in Fig. 3, and it is more preferable to make the number of gates plural, and it is more preferable to make it the same as the number of spoke portions if possible. It is preferable to arrange them in a well-balanced manner so that the filling speed into the spoke portion becomes uniform.

The thermoplastic resin used in the present invention is not particularly limited, and may be a thermoplastic resin capable of injection molding, a thermoplastic elastomer and alloys thereof, and these and known stabilizers. Blends with additives, fillers, etc. can also be applied, but especially engineering plastics,
For example, it is preferable to apply a crystalline resin such as polyacetal resin, polyamide resin, polybutylene terephthalate resin or the like, or a non-crystalline resin such as polycarbonate resin, modified polyphenylene ether resin or the like. A reinforced polyamide resin to which an agent is added is preferable because it has an excellent balance between rigidity and impact strength.

The polyamide resin is selected from nylon 6, nylon 66, and nylon 6/66 copolymer 1
Type or two or more types of resin are used, and glass fiber,
Inorganic fillers such as glass flakes, carbon fibers, talc, wollastonite, mica and potassium titanate whiskers are blended. These inorganic fillers are preferably surface-treated with a silane coupling agent or the like in order to improve the adhesive strength with polyamide. Further, in order to improve the impact resistance of the resin, an impact modifier such as an olefin elastomer may be added. In addition, known additives such as heat stabilizers, light stabilizers, release agents and colorants may be added. The compounding is carried out at any stage from the polymerization of the resin to the molding. The pressurized gas used at the time of molding includes nitrogen, air and the like.

[0012]

EXAMPLE An example of the present invention will be described below, but the present invention is not limited to this example. Example 1 70% by weight of nylon 6 resin having a relative viscosity of 3.0 measured at a temperature of 25 ° C and a concentration of 1% in 98% concentrated sulfuric acid, and 30% by weight of glass fiber (ECSO3T283 manufactured by Nippon Electric Glass) having a diameter of 13 microns. Using the pellets obtained by melt-kneading with a twin-screw extruder,
The bicycle wheel shown in FIG. 1 was injection-molded as follows. 650MM manufactured by Mitsubishi Heavy Industries, Ltd. as a molding machine
II was used.

After the mold is clamped using the above molding machine,
After injecting a molten resin (temperature of about 280 ° C) into the mold cavity (mold temperature of 80 ° C) (injected from the resin gate at the position indicated by reference numeral 12 in Fig. 1) and injecting a predetermined amount of resin , The injection operation is stopped, compressed nitrogen gas is immediately pressed in from a position indicated by reference numeral 11 in FIG. 1, and after a predetermined cooling time, the compressed nitrogen gas is discharged from the inside of the molded product, and the mold is opened, The bicycle wheel having the shape shown in FIG. 1 was taken out. Each of the spokes of the obtained molded product was cut at the location indicated by the arrow A in FIG. 1, and the dimension of the major axis of the elliptical hollow portion in the cross section shown in FIG. 2 was measured to find a range of 15 to 16 mm. And the hollow balance was good. The size of the outer periphery (the size of the major axis of the ellipse) was 28 mm.

[0014]

EFFECT OF THE INVENTION The bicycle wheel of the present invention is excellent in rust prevention, has a wide degree of design freedom, is light in weight, and is excellent in the hollow balance of the spoke portion.

[Brief description of drawings]

FIG. 1 is an explanatory view in which a reference numeral is added to a front schematic view of an example of a bicycle wheel of the present invention to show a method for forming the wheel.

FIG. 2 is a schematic cross-sectional view of a spoke portion at a portion indicated by an arrow A in FIG.

[Explanation of symbols]

 1 Shaft part of wheel 2 Spoke part of wheel 3 Outer part of wheel 4 Hollow part formed inside spoke part 11 Injection point of pressurized gas in mold 12 In mold Injection point of molten resin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29K 105: 16 B29L 22:00 31:32 (72) Inventor Masami Suzuki 370 Enzo, Chigasaki City, Kanagawa Prefecture Mitsubishi Engineering Plastics Co., Ltd. Technical Center-Chigasaki

Claims (8)

[Claims] 1. A thermoplastic resin is hollow by a method of injecting gas from a plurality of points from a portion corresponding to a root portion of each spoke portion in the outer peripheral portion, which comprises a shaft portion, a radial spoke portion and an outer peripheral portion. A bicycle wheel obtained by integral injection molding. 2. A multi-point gage provided at a portion contacting an outer peripheral portion.
The bicycle wheel according to claim 1, wherein a thermoplastic resin is injected into the hollow wheel by injection molding. 3. The bicycle wheel according to claim 1, wherein the thermoplastic resin is a reinforced polyamide resin composed of polyamide and an inorganic filler. 4. The thermoplastic resin is hollow integrated by using a gas injection device arranged so that the gas pipe path lengths to the gas injection ports at locations corresponding to the roots of the spokes are equalized. The bicycle wheel according to claim 1, which is injection-molded. 5. A thermoplastic resin is hollow-integrated by injecting gas from a plurality of points from a portion corresponding to a root portion of each spoke portion in the outer peripheral portion, which comprises a shaft portion, a radial spoke portion and an outer peripheral portion. Bicycle wheel characterized by injection molding
Manufacturing method of le. 6. A multi-point gage provided at a portion contacting an outer peripheral portion.
The method for manufacturing a bicycle wheel according to claim 5, wherein a thermoplastic resin is injected from the outer shell. 7. The method for manufacturing a bicycle wheel according to claim 5, wherein the thermoplastic resin is a reinforced polyamide resin composed of polyamide and an inorganic filler. 8. A thermoplastic resin is hollowed by using a gas injection device arranged so that the gas pipe path lengths to the gas injection ports at locations corresponding to the roots of the spokes are equalized. The method for manufacturing a bicycle wheel according to claim 5, wherein the method is carried out by integral injection molding.