JP7779128B2 - Shaft and manufacturing method thereof - Google Patents

Description

This disclosure relates to a shaft and a method for manufacturing the same.

In recent years, shafts made of fiber-reinforced resin have been used in fishing rods, golf clubs, rackets, and various other sports equipment. To improve the operability of these tools, there is a demand for lighter shafts.

Japanese Unexamined Patent Publication No. 7-163691

A fiber-reinforced resin shaft is a composite of reinforcing fibers and resin. One way to make the shaft lighter is to try to reduce the resin content. However, when considering the moldability of the shaft, there is a natural limit to how much the resin content can be reduced.

This disclosure was devised in light of the above-mentioned circumstances, and its main objective is to provide a shaft that can be made lighter.

The present disclosure relates to a shaft made of fiber-reinforced resin, which includes at least a lightweight layer made of fiber-reinforced resin, the lightweight layer including a plurality of hollow portions extending in the axial direction of the shaft, the plurality of hollow portions being spaced apart from one another and arranged circumferentially around the shaft.

The shaft disclosed herein is lightweight due to the adoption of the above-mentioned configuration.

FIG. 2 is a cross-sectional view of the shaft of the present embodiment. FIG. 2 is a partial perspective view of a lightweight layer made of sheet material before molding. FIG. 2 is a partial cross-sectional view of a lightweight layer. FIG. 10 is a partial cross-sectional view of a lightweight layer according to another embodiment. FIG. 10 is a cross-sectional view of a shaft according to another embodiment. FIG. 2 is a development view showing the arrangement of sheet materials that constitute the shaft of the present embodiment. FIG. 10 is a development view showing the arrangement of sheet materials constituting a shaft of a comparative example.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.
The specific configurations shown in the embodiments and drawings are for the purpose of understanding the contents of the present disclosure, and the present disclosure is not limited to the specific configurations shown. Furthermore, in multiple embodiments, the same or common elements are designated by the same reference numerals throughout the specification, and redundant explanations will be omitted.

Figure 1 is a cross-sectional view of a fiber-reinforced resin shaft 1 according to this embodiment. The shaft 1 according to this embodiment is configured as a golf club shaft. In other embodiments, the shaft 1 may be configured as a fishing rod, various sports equipment, or the like. The shaft 1 according to this embodiment is configured, for example, in the shape of a pipe having a circular outer circumferential surface 1A and a circular inner circumferential surface 1B.

As shown in FIG. 1, the shaft 1 includes at least one lightweight layer 2 made of fiber-reinforced resin.

The lightweight layer 2 of this embodiment includes multiple hollow portions 3 extending in the shaft axial direction. The shaft axial direction refers to the longitudinal direction of the shaft 1. Therefore, the hollow portions 3 extending in the shaft axial direction refer to elongated cavities in the shaft axial direction. The hollow portions 3 may be formed over the entire range of the shaft 1 in the shaft axial direction, or may be formed only partially. Furthermore, the multiple hollow portions 3 are spaced apart from one another and arranged circumferentially around the shaft. Such hollow portions 3 reduce the weight of the lightweight layer 2, thereby enabling the weight of the shaft 1 to be reduced.

It is desirable for the lightweight layer 2 to extend continuously around the shaft for at least one revolution. This further reduces the weight of the shaft 1. In this embodiment, the lightweight layer 2 is composed of a single layer that extends continuously around the shaft. In another embodiment, as shown in Figure 5, multiple lightweight layers 2 may be stacked in the radial direction of the shaft.

In this embodiment, the lightweight layer 2 is a sheet material that defines an outer surface 2A in the shaft radial direction and an inner surface 2B in the shaft radial direction, and extends annularly along the shaft circumferential direction. Both the outer surface 2A and the inner surface 2B of this lightweight layer 2 are formed annularly along the shaft circumferential direction.

Figure 2 shows a partial cross-sectional view of the sheet material 20 before the lightweight layer 2 is molded into the shaft 1. In Figure 2, the symbol A is linear, but indicates the direction that will become the circumferential direction of the shaft when this sheet material 20 is molded into the shaft 1. Also, in Figure 2, the symbol B indicates the direction that will become the axial direction of the shaft when this sheet is molded into the shaft 1.

Returning to Figure 1, each cavity 3 is located between the outer surface 2A and the inner surface 2B of the lightweight layer 2. In this embodiment, the multiple cavities 3 are arranged substantially evenly around the shaft.

In Figure 1, the maximum diameter d of each hollow portion 3 is not particularly limited, but from the perspective of reducing the weight of the shaft 1, it is set to, for example, 0.01 mm or more, preferably 0.02 mm or more, and more preferably 0.1 mm or more. Furthermore, to maintain the durability of the shaft 1, the maximum diameter d is set to, for example, 2.0 mm or less, preferably 1.5 mm or less, and more preferably 1.0 mm or less.

In Figure 1, the arrangement pitch p of each hollow portion 3 in the circumferential direction of the shaft is not particularly limited, but from the perspective of reducing the weight of the shaft 1, it may be, for example, 5 times or less, and preferably 2 times or less, the maximum diameter d of the hollow portion 3. Furthermore, to maintain the durability of the shaft 1, the arrangement pitch p of each hollow portion 3 may be, for example, 20 times or more, preferably 30 times or more, and more preferably 50 times or more, the maximum diameter d of the hollow portion 3.

In Figure 1, the cross-sectional shape of the hollow portion 3 is not particularly limited, and a circular or polygonal shape is preferred. To avoid stress concentration in the hollow portion 3 when the shaft 1 is in use, it is desirable that the cross-sectional shape of the hollow portion 3 be curved.

The lightweight layer 2 is constructed as a composite of reinforcing fibers and resin (matrix resin).

Carbon fiber is particularly preferred as a reinforcing fiber because it is lightweight and has high strength. In addition to carbon fiber, other reinforcing fibers may also be used, such as glass fiber, graphite fiber, aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, aromatic polyamide fiber, aromatic polyester fiber, and ultra-high molecular weight polyethylene fiber.

The resin may be, for example, a thermosetting resin or a thermoplastic resin. For example, epoxy resins are preferred as thermosetting resins, due to their strength and rigidity. Other than epoxy resins, for example, unsaturated polyester resins (vinyl ester resins), phenolic resins, melamine resins, urea resins, diallyl phthalate resins, polyurethane resins, polyimide resins, and silicone resins can be used alone or in combination. Furthermore, for example, polyamide resins such as nylon 6 and nylon 12 are preferred as thermoplastic resins, due to their excellent moldability. Other than these, saturated polyester resins, polycarbonate resins, ABS resins, polyvinyl chloride resins, polyacetal resins, polystyrene resins, polyethylene resins, polyvinyl acetate resins, AS resins, methacrylic resins, polypropylene resins, and fluororesins can be used alone or in combination.

As shown in Figure 3, in one example of a composite, the reinforcing fibers may be short fibers f1. The short fibers f1 may be randomly arranged in the matrix resin R, or may be oriented in a specific direction. In a preferred embodiment, the short fibers f1 are oriented along the axial direction of the shaft.

The diameter of the short fibers f1 is not particularly limited, but is preferably in the range of 1 to 50 μm. The length of the short fibers f1 is also not particularly limited, but is preferably in the range of 100 to 3000 μm. The aspect ratio, which is the length/diameter ratio of the short fibers f1, is preferably in the range of 10 to 500.

Figure 4 shows another embodiment of the composite. As shown in Figure 4, the reinforcing fibers may include long fibers f2 formed into a hollow pipe shape surrounding the cavity 3, in addition to or instead of the short fibers f1. In the example shown in Figure 4, the long fibers f2 are woven into a pipe shape. Such long fibers f2 not only maintain the shape of the cavity 3, but also help to increase the bending rigidity, torsional rigidity, etc. of the shaft 1.

Referring to FIG. 1, in the shaft 1 of this embodiment, the lightweight layer 2 forms, for example, an intermediate layer in the radial direction of the shaft. In other words, layers other than the lightweight layer are arranged inside and outside the lightweight layer 2. This embodiment helps to maintain the strength of the shaft 1.

In the shaft 1 of this embodiment, a bias layer 6 is disposed radially inward of the lightweight layer 2. The bias layer 6 of this embodiment is composed of at least one prepreg in which reinforcing fibers (long fibers f2) are oriented at an angle of 45°±15° relative to the axial direction of the shaft. In a preferred embodiment, the bias layer 6 is formed, for example, by laminating multiple prepregs. The prepregs are laminated so that the reinforcing fibers intersect with each other. Such a bias layer 6 can improve the torque (torsional rigidity) of the shaft 1, and ultimately helps to stabilize the direction of the ball when constructed as a golf club.

The shaft 1 of this embodiment also has a straight layer 5 disposed radially outward of the lightweight layer 2. The straight layer 5 of this embodiment is made of at least one prepreg in which reinforcing fibers are oriented at an angle of 0°±5° relative to the axial direction of the shaft. In a preferred embodiment, the straight layer 5 is formed, for example, from a single prepreg. Such a straight layer 5 improves the bending rigidity of the shaft 1 and helps to improve the durability of the shaft 1 when constructed as a golf club.

Next, a method for manufacturing the shaft 1 of this embodiment will be described. The manufacturing method of this embodiment includes a first step, a second step, and a third step.

The first step is to prepare a sheet material 20 for the lightweight layer 2. As shown in Figure 2, when molded, this sheet material 20 includes an outer surface 2A in the shaft radial direction, an inner surface 2B in the shaft radial direction, and multiple cavities 3 disposed between them.

Figure 6 shows an exploded view of the prepared sheet materials. In this example, shaft 1 is formed from sheet materials s1 to s8. In Figure 6, the symbol Ls corresponds to the axial length of shaft 1, with the right side corresponding to the tip end and the left side corresponding to the butt end. In this example, the total shaft length Ls is 1,168 mm.

The developed view also shows the sheet materials that make up the shaft 1, starting from the radially inner side of the shaft 1. Therefore, the sheets are wound around the mandrel in order, starting with the sheet located at the top of the developed view. Furthermore, this developed view not only shows the winding order of each sheet, but also the arrangement of each sheet in the axial direction of the shaft. For example, the end of the first sheet material s1 is located at the tip end. The angle indications written to the left of each sheet material s1 to s8 or on the sheet itself indicate the orientation angle of the reinforcing fibers contained in that sheet material with respect to the axial direction of the shaft. All reinforcing fibers are carbon fibers.

In this embodiment, sheet materials s1 and s5 to s8 are straight prepregs. In straight prepregs, the reinforcing fibers are oriented at an angle of 0°±5° relative to the shaft axial direction, forming the above-mentioned straight layer 5. In this embodiment, sheet materials s2 and s3 are bias prepregs. In bias prepregs, the reinforcing fibers are oriented at an angle of 45°±15° relative to the shaft axial direction, forming the above-mentioned bias layer 6.

Furthermore, in this embodiment, sheet material s4 is used as sheet material 20 that constitutes lightweight layer 2. As shown in Figure 4, this sheet material s4 contains short fibers f1 made of carbon fiber and long fibers f2 formed into a pipe shape. Before molding, the maximum diameter d of the hollow portion 3 was 0.2 mm, and the arrangement pitch p was 1 mm (p/d = 5). The thickness of sheet material 20 was approximately 0.5 mm. The long fibers f2 were woven into a tubular shape using a twill weave oriented in two directions: the axial direction and the circumferential direction of the shaft.

The matrix resin for each sheet material is epoxy resin.

The second step is to wind sheet materials s1 to s8 in an annular shape around the shaft. Typically, the second step is performed by sequentially winding sheet materials s1 to s8 around a mandrel (core metal). If necessary, it is then desirable to fasten the sheet materials with wrapping tape or the like.

In the third step, the sheet material wound around the mandrel is heated in a mold. This hardens the matrix resin, producing a pipe-shaped shaft 1 (example).

For comparison, a shaft was manufactured using the sheet materials shown in Figure 7 (Comparative Example). In this example, shaft 1 is formed from first through ninth sheet materials s1 to s9. The example in Figure 7 differs from the example in Figure 6 in that the fourth sheet is a straight prepreg rather than a lightweight layer, and three straight prepregs are used along the entire length of the shaft; otherwise, it is the same as the developed view in Figure 6.

The Example achieved a weight reduction of approximately 1.3 g compared to the Comparative Example. Furthermore, when the three-point bending strength of the Example shaft and the Comparative Example shaft were compared, they showed essentially the same performance. Furthermore, the same metal wood-type golf club head was attached to each shaft, and golf balls were struck approximately 3,000 times at a head speed of 45 m/s, but no damage was observed in either shaft, demonstrating good durability.

Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the specific disclosure above and can be implemented in various modifications within the scope of the technical concept described in the claims.

[Note]
The present disclosure includes the following aspects.

[Disclosure 1]
A shaft made of fiber reinforced resin,
At least a lightweight layer made of fiber reinforced resin,
the lightweight layer includes a plurality of cavities extending in the shaft axial direction,
The plurality of cavities are spaced apart from one another in the circumferential direction of the shaft.
shaft.
[Disclosure 2]
The shaft described in Disclosure 1, wherein the lightweight layer is continuous around the shaft for at least one revolution.
[Disclosure 3]
The shaft according to Disclosure 1 or 2, wherein the lightweight layer is a sheet-like body that defines an outer surface in the shaft radial direction and an inner surface in the shaft radial direction and extends annularly along the shaft circumferential direction.
[Disclosure 4]
The shaft according to any one of Disclosures 1 to 3, wherein the lightweight layer is a composite of reinforcing fibers and resin.
[Disclosure 5]
The shaft of Disclosure 4, wherein the reinforcing fibers include short fibers.
[Disclosure 6]
The shaft according to Disclosure 4 or 5, wherein the reinforcing fibers include pipe-shaped fibers surrounding the hollow portion.
[Disclosure 7]
The shaft according to any one of Disclosures 1 to 6, which is a golf club shaft.
[Disclosure 8]
The shaft described in Disclosure 7, further comprising a bias layer on the radially inner side of the lightweight layer in which reinforcing fibers are oriented at an angle of 45°±15° relative to the axial direction of the shaft.
[Disclosure 9]
A shaft as described in Disclosure 7 or 8, comprising a straight layer on the radial outside of the lightweight layer in which reinforcing fibers are oriented at an angle of 0°±5° relative to the axial direction of the shaft.
[Disclosure 10]
A method for manufacturing a shaft according to any one of Disclosures 1 to 9, comprising:
a first step of preparing the lightweight layer in the form of a sheet material, the lightweight layer including an outer surface in the shaft radial direction, an inner surface in the shaft radial direction, and the plurality of cavities disposed therebetween;
a second step of winding the sheet material annularly around the shaft;
A method for manufacturing a shaft.

1 shaft 2 lightweight layer 2A outer surface 2B inner surface 3 hollow portion 5 straight layer 6 bias layer f1 short fiber f2 long fiber

Claims (9)

A method for manufacturing a shaft made of fiber reinforced resin,
The shaft includes at least a lightweight layer made of fiber reinforced resin,
the lightweight layer includes a plurality of cavities extending in the shaft axial direction,
The plurality of cavities are spaced apart from one another in the circumferential direction of the shaft,
The method for manufacturing the shaft includes:
a first step of preparing the lightweight layer in the form of a sheet material, the lightweight layer including an outer surface in the shaft radial direction, an inner surface in the shaft radial direction, and the plurality of cavities disposed therebetween;
a second step of winding the sheet material annularly around the shaft;
A method for manufacturing a shaft. The method for manufacturing a shaft according to claim 1 , wherein the lightweight layer is continuous around the shaft circumferentially for at least one revolution. 3. The method for manufacturing a shaft according to claim 1, wherein the lightweight layer is a sheet-like body that defines an outer surface in the shaft radial direction and an inner surface in the shaft radial direction and extends annularly along the shaft circumferential direction. The method for manufacturing a shaft according to claim 1 , wherein the lightweight layer is a composite of reinforcing fibers and a resin. The method for manufacturing a shaft according to claim 4 , wherein the reinforcing fibers include short fibers. The method for manufacturing a shaft according to claim 4 or 5 , wherein the reinforcing fibers include pipe-shaped fibers surrounding the hollow portion. The method for manufacturing a shaft according to claim 1 , wherein the shaft is a golf club shaft. The method for manufacturing a shaft according to claim 7 , wherein the shaft includes a bias layer on the radially inner side of the lightweight layer, the bias layer having reinforcing fibers oriented at an angle of 45°±15° relative to the axial direction of the shaft. 9. The method for manufacturing a shaft according to claim 7 , wherein the shaft comprises a straight layer radially outward of the lightweight layer, the straight layer having reinforcing fibers oriented at an angle of 0°±5° relative to the axial direction of the shaft.