JP6243612B2 - Golf club shaft - Google Patents

Description

  The present invention relates to a golf club shaft.

  Golf club shafts have been designed with a flexural rigidity distribution according to the desired function of the shaft. For example, Japanese Patent Application Laid-Open No. 11-347163 discloses a tubular golf club shaft in which a plurality of prepreg sheets are wound and laminated in order to increase the bending rupture strength at the intermediate tip portion and improve durability. It is described that a woven fabric of reinforcing fibers having a high specific strength is stuck between the innermost layer of the shaft and / or the layer of the prepreg sheet over the entire length of the shaft or at least a part in the longitudinal direction.

JP 11-347163 A

  In order to reduce the weight of the shaft, it may be possible to partially reduce the area of any of the prepreg sheets constituting the shaft. There is a problem that the stiffness distribution changes greatly, which adversely affects the head speed and swing stability.

  Therefore, an object of the present invention is to provide a golf club shaft that can reduce the weight of the shaft while maintaining the bending rigidity of the shaft.

In order to achieve the above object, a golf club shaft according to the present invention comprises a bias layer formed from a fiber-reinforced prepreg sheet in a bias direction extending over the entire length of the shaft, and a fiber-reinforced prepreg sheet in a straight direction extending over the entire length of the shaft. A shaft for a golf club comprising a straight layer formed, wherein the bias layer is located on the inner side of the shaft than the straight layer, and the fiber-reinforced prepreg sheet in the bias direction is more than the tip side of the shaft. When the number of turns on the proximal side of the shaft gradually decreases, the number of turns on the tip side is Nt, and the number of turns on the proximal side is Nb, the relationship between Nt and Nb is as follows:
Nt−Nb ≧ 2
And when the area of the fiber-reinforced prepreg sheet in the straight direction is As and the area of the fiber-reinforced prepreg sheet in the bias direction is Aa, the relationship between the area As and Aa is:
Aa / (Aa + As) ≦ 0.55
It is.

  The bias direction refers to a range in which the fiber orientation angle is 15 to 60 ° with respect to the shaft axis. Further, the straight direction refers to a range where the fiber orientation angle is 0 to 10 ° with respect to the shaft axis. The weight of the shaft is preferably 30 to 48 g.

  As described above, according to the present invention, the area of the fiber-reinforced prepreg sheet in the bias direction is made much smaller than before, thereby reducing the weight of the shaft. By adopting a shape in which the number of turns on the proximal side of the shaft gradually decreases from the tip side, at least two turns, the weight of the shaft can be reduced while maintaining the bending rigidity of the shaft.

It is a mimetic diagram showing an example of a shaft for golf clubs concerning the present invention. It is a schematic diagram for demonstrating the method to measure the bending rigidity of the shaft for golf clubs. It is a top view which shows the various prepreg sheets for manufacturing the shaft for golf clubs which concerns on this invention. It is a top view which shows the various prepreg sheets of the comparative example for manufacturing the shaft for golf clubs.

  Hereinafter, an embodiment of a golf club shaft according to the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the golf club shaft 1 has a cylindrical shape whose diameter decreases from the hand 1 </ b> B toward the tip 1 </ b> T. A head 2 is attached to the tip 1T of the shaft 1, and a grip 8 is attached to the hand 1B. Thereby, it becomes a golf club.

  The length of the shaft 1 may be a general length of a wood club shaft, and specifically, 42.5 to 47.0 inches (1080 to 1194 mm) is preferable. The thickness of the shaft 1 may be a general thickness of a shaft for a wood club. Specifically, the outer diameter on the proximal side is preferably 14.0 to 16.0 mm, and the outer diameter on the distal end side is preferably 8.5 to 9.5 mm. The weight of the shaft 1 is preferably in the range of 30 to 48 g in the wood club shaft, more preferably 35 to 46 g, and still more preferably 37 to 44 g.

The shaft 1 is manufactured by a sheet winding method. In the embodiment shown in FIG. 3, first, the prepreg sheets 31 to 34 of fiber reinforced resin (FRP) are wound around a mandrel (not shown) in order. And after adding heat to this and making it harden | cure, the shaft 1 can be manufactured by extracting a mandrel. As the reinforcing fiber of the fiber reinforced resin, a carbon fiber alone, a composite fiber made of carbon fiber and a fiber of another material, a metal fiber, or the like can be used. Further, as the matrix resin of the fiber reinforced resin, a thermosetting resin such as an epoxy resin can be used. In order to obtain a shaft having a predetermined bending rigidity, the prepreg sheet preferably has a basis weight of 130 g / m ² or more, more preferably 150 g / m ² or more. In addition, although the upper limit of the fabric weight of a prepreg sheet is not specifically limited, 250 g / m < ² > or less is preferable. However, the prepreg sheet used for the hoop layer disposed in the 90 ° direction with respect to the shaft axis is not in this range, and a fabric having a basis weight of 25 to 40 g / m ² may be used.

  As the prepreg sheet, a fiber in which fibers are generally oriented in one direction is used. A fiber in which the fiber direction is arranged obliquely is referred to as a biased prepreg sheet 31. Those in which the direction of the fibers is arranged in parallel to the axis of the shaft are referred to as prepreg sheets 32 to 34 in the straight direction. For example, the prepreg sheet 31 in the bias direction has a fiber orientation angle in the range of 30 to 60 ° with respect to the shaft axis, and a 45 ° orientation angle is more preferable. The prepreg sheet 31 in the bias direction is usually wound by shifting the prepreg sheets 31a and 31b of two layers whose fiber orientation angles are opposite to each other (for example, the orientation angles are + 45 ° and −45 °) by a half turn. In the prepreg sheets 32 to 34 in the straight direction, the fiber orientation angle with respect to the shaft axis is usually 0 °, but is not limited thereto, and may be in the range of 0 ± 10 °. In the prepreg sheet in the hoop direction, the fiber orientation angle with respect to the shaft axis is usually 90 °, but is not limited to this and may be in the range of 90 ± 10 °.

  In addition to the main sheets 31 to 34 having the same length as the entire length of the shaft 1, reinforcing sheets 35 and 36 shorter than the entire shaft length are also used as the prepreg sheet. The main sheet usually has a tapered shape in which the mandrel (not shown) becomes thicker from the tip toward the hand, so that the hand side has a long trapezoidal side so that a predetermined circumference is uniformly wound around the mandrel. It has a shape. As shown in FIG. 3, the reinforcing sheet 35 has a rectangular shape obtained by obliquely cutting the trapezoidal length direction in the middle. The reinforcing sheet 36 has a triangular shape. In the rectangular reinforcing sheet 35, the fiber direction may be any of a straight direction, a bias direction, and a hoop direction, and can be arbitrarily selected according to the purpose. For example, when the straight reinforcing sheet 35 is employed, rigidity can be efficiently given. By adopting the reinforcing sheet 35 in the bias direction, the outer diameter of the shaft can be adjusted without increasing the rigidity of the shaft more than necessary. By adopting the hoop-direction reinforcing sheet 35, rigidity in the crushing direction of the shaft (referring to a direction in which a shaft having a circular cross section is flattened) can be given. The reinforcing sheet 36 having a triangular shape is a prepreg sheet in a straight direction.

In the present invention, the prepreg sheets 32 to 34 in the straight direction are designed with the length of the side on the tip side and the hand side so that the number of windings on the tip side and the hand side is the same. The length of the side on the front end side and the hand side is designed so that the sheet 31 has a winding number Nb on the hand side smaller than the winding number Nt on the front end side. Specifically, the relationship between the number of turns Nt on the front end side and the number of turns Nb on the proximal side can be expressed by the following equation.
Nt−Nb ≧ 2

A more preferable relationship between the number of turns Nt on the front end side and the number of turns Nb on the proximal side is as follows.
Nt−Nb ≧ 2.5

  The upper limit of Nt−Nb, which is the relationship between the number of turns Nt on the tip side and the number of turns Nb on the proximal side, is not particularly limited, but is preferably 4 or less. Further, the number of turns Nt on the front end side of the prepreg sheet 31 in the bias direction is not particularly limited, but is usually preferably 3 to 6. The number of windings of the prepreg sheets 32 to 34 in the straight direction is preferably the number of windings on the tip side, and is usually 0.3 to 1 winding with respect to one winding of the prepreg sheet 31 in the bias direction. More preferably, the winding is set to 5 to 0.8.

In the present invention, the area Aa of the prepreg sheet 31 in the bias direction is designed to be substantially the same as or narrower than the area As of the prepreg sheets 32 to 34 in the straight direction. Specifically, the relationship between the area Aa of the prepreg sheet in the bias direction and the area As of the prepreg sheet in the straight direction can be expressed by the following expression.
Aa / (Aa + As) ≦ 0.55

A more preferable relationship between the area Aa of the prepreg sheet in the bias direction and the area As of the prepreg sheet in the straight direction is as follows.
Aa / (Aa + As) ≦ 0.53

  The lower limit of Aa / (Aa + As), which is the relationship between the area Aa of the prepreg sheet in the bias direction and the area As of the prepreg sheet in the straight direction, is not particularly limited, but is preferably 0.4 or more.

  Thus, the biased prepreg sheet 31 has a trapezoidal shape in which the side on the hand side is shorter than the normal trapezoidal shape of the prepreg sheets 32 to 34 in the straight direction. The area of the seat is reduced, and the weight of the shaft 1 can be reduced. And if the shaft 1 is manufactured using each of the prepreg sheets 31 to 36 having such a shape, the bias layer formed by the prepreg sheet 31 in the bias direction gradually becomes thinner toward the proximal side, so that the shaft 1 is reduced in weight. However, the bending stiffness distribution similar to the conventional one can be maintained. In addition, as shown in FIG. 3, about the prepregs 32-34 of the straight direction, you may make it the shape which cut off a part of edge | side so that a sheet | seat width might become short on the hand side. The reason for cutting out a part of the side in this way is to make the number of windings in the straight direction an integer and avoid hardness anisotropy in the circumferential direction in the part where the mandrel shape becomes a parallel shape. Therefore, it is preferable that the cut-out portion is parallel to the side facing it.

In the present invention, the bending rigidity of the shaft 1 is represented by EI which is the product of the Young's modulus E and the cross-sectional secondary moment I. The value of EI can be calculated by the following formula 1 after a three-point bending test. In the three-point bending test of the shaft, as shown in FIG. 2, first, the shaft 1 is horizontally supported by a pair of support tools 20 separated by a constant interval D. Then, a load P is applied perpendicularly to the shaft 1 at the middle position between the pair of supports 20, that is, at the EI measurement point. The amount of strain σ of the shaft 1 at this measurement point is measured, and the value of EI (unit: kgf · m ² ) is obtained. Usually, the distance D between the supports 20 is 0.3 m, and the load P is 20 kg. The measurement point of EI is represented by the length L from the tip T of the shaft.

^{EI = (D 3/48)} · (P / σ) ··· ( Equation 1)
D: Distance between a pair of supports [m]
P: Load applied to the shaft [kg]
σ: Shaft distortion when a load is applied [m]

  In this way, the bending stiffness distribution of the shaft 1 can be obtained by changing the measurement point (that is, the length L from the shaft tip) over the entire shaft 1 and measuring.

In the bending rigidity distribution, it is preferable that the bending rigidity EI increases monotonously in a section where the length L from the shaft tip is 400 mm to 700 mm. Further, it is preferable that the bending rigidity EI increases monotonously even in a section where the length L from the shaft tip is 800 mm to 950 mm. In flexural rigidity distribution, bending stiffness in the length L is the position of 900mm from the tip of the shaft is preferably 4.5 kgf · ^{m 2} or more, 5.0 kgf · ^{m 2} or more is more preferable. The upper limit of the bending rigidity at the position where the length L from the shaft tip is 900 mm is not particularly limited, but is preferably 6.0 kgf · m ² or less. Moreover, bending stiffness in the length L is the position of 300mm from the tip of the shaft is preferably 2.5 kgf · ^{m 2} or less, more preferably 2.2 kgf · ^{m 2.} The lower limit of the bending rigidity at the position where the length L from the shaft tip is 300 mm is not particularly limited, but is preferably 1.5 kgf · m ² or more.

A shaft (Example 1) was produced using each prepreg sheet shown in FIG. 3, and the weight and bending stiffness distribution of the shaft were measured. Table 1 shows the size, area, and basis weight of each prepreg sheet. As shown in FIG. 3, the dimensions of the prepreg sheet are represented by L ₁ for the entire length, Wt for the width on the leading end side, and Wb on the proximal side. Straight direction of the prepreg sheet 32 to 34, part of the sides so that the width becomes shorter in proximal side is cut away so as to be parallel to the side facing, the truncated length by L ₂ Show. The dimensions of the rectangular reinforcing sheet 35 are indicated by L _{1 for} the longer length and L ₂ for the shorter length because the proximal side is cut obliquely. Moreover, the width | variety of the hand side at the time of not cutting diagonally is shown by Wb. The reinforcing sheet 35 used was a fiber having a straight direction.

  Further, as shown in Table 2, a shaft (Example 2) was produced with the same configuration as the prepreg sheet shown in FIG. 3 except that the dimensions were partially changed, and the weight and bending stiffness distribution were measured.

  On the other hand, for comparison, shafts (Comparative Example 1 and Comparative Example 2) were prepared using the prepreg sheets shown in FIG. 4, and the weight and bending stiffness distribution were measured. Tables 3 and 4 show the dimensions, area, and basis weight of each prepreg sheet. The reinforcing sheet 55 used was a fiber having a straight direction as in the example.

In Examples 1 and 2 and Comparative Examples 1 and 2, the number of turns Nt on the tip side and the number of turns Nb on the proximal side of the prepreg sheet in the bias direction, the area Aa of the prepreg sheet in the bias direction, and the prepreg sheet in the straight direction Table 5 shows the area As and the relationship thereof, and the weight of the manufactured shaft and the bending rigidity EI _{300 and} EI ₉₀₀ at positions where the length L from the shaft tip is 300 mm and 900 mm.

  As shown in Table 5, the number of turns Nb on the hand side is reduced by 2 turns from the number of turns Nt on the leading end side of the prepreg sheet in the bias direction, and the area As of the prepreg sheet in the straight direction and the area As of the prepreg sheet in the straight direction In Example 1 in which the total area is 54%, the number of windings Nt and Nb on the front end side and the proximal side is equal or the number of windings Nb on the proximal side is large, compared with Comparative Example 1 and Comparative Example 2. The weight of the shaft could be reduced by about 10 to 15 g while substantially maintaining the bending rigidity. Further, the number of turns Nb on the hand side is reduced by 2.5 turns from the number of turns Nt on the leading end side of the prepreg sheet in the bias direction, and the area Aa of the prepreg sheet in the bias direction is the total area of the area As of the prepreg sheet in the straight direction. In Example 2, which was 52%, the weight of the shaft could be further reduced than that of Example 1 while substantially maintaining the bending rigidity of the shaft.

DESCRIPTION OF SYMBOLS 1 Shaft 2 Head 3 Face 5 Hosel 8 Grip 10 Shaft 20 Support tool 31-36 Prepreg sheet 51-56 Prepreg sheet

Claims (5)

A golf club shaft comprising a bias layer formed from a fiber-reinforced prepreg sheet in the bias direction extending over the entire length of the shaft, and a straight layer formed from a fiber-reinforced prepreg sheet in the straight direction extending over the entire length of the shaft,
The bias layer is located inside the shaft from the straight layer,
The fiber-reinforced prepreg sheet in the bias direction has a shape such that the number of turns on the proximal side of the shaft gradually decreases from the tip side of the shaft,
When the number of turns on the tip side is Nt and the number of turns on the hand side is Nb, the relationship between Nt and Nb is
Nt−Nb ≧ 2
And when the area of the fiber-reinforced prepreg sheet in the straight direction is As and the area of the fiber-reinforced prepreg sheet in the bias direction is Aa, the relationship between the area As and Aa is:
Aa / (Aa + As) ≦ 0.55
A golf club shaft.   The golf club shaft according to claim 1, wherein the weight of the shaft is 30 to 48 g. The golf club shaft according to claim 2, wherein the weight of the shaft is 35 to 46 g. The relationship between Nt and Nb is
Nt−Nb ≧ 2.5
The golf club shaft according to any one of claims 1 to 3. The relationship between the area As and Aa is
Aa / (Aa + As) ≦ 0.53
The shaft for golf clubs according to any one of claims 1 to 4.

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