Golf club shaft and golf club

Abstract

To provide a golf club shaft and a golf club capable of attaining a desired trajectory and stabilizing a carry of a ball.SOLUTION: A golf club shaft is obtained by winding a plurality of layers of prepreg having reinforced fibers impregnated with a thermosetting resin, and thermosetting the product. The prepreg includes: 0° prepreg whose fiber direction is in parallel to a shaft longitudinal direction; 90° prepreg whose fiber direction is orthogonal to the shaft longitudinal direction; first bias prepreg whose fiber direction is inclined to the shaft longitudinal direction at an angle from 40°to 50°; and second positive bias prepreg whose fiber direction is inclined to the shaft longitudinal direction at an angle from +10°to +35°, or second negative bias prepreg whose fiber direction is inclined to the shaft longitudinal direction at an angle from -10°to -35°.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a golf club shaft and a golf club using the golf club shaft. [Background technology]

[0002] In place of steel golf club shafts, golf club shafts made of FRP (Fiber Reinforced Plastics) are widely used. These shafts are made by winding multiple layers of prepreg, which is made by impregnating reinforcing fibers such as carbon fibers with thermosetting resin, and then thermosetting the layers.

[0003] Commonly used prepregs include 0° prepregs, in which the fiber direction of the reinforcing fibers is approximately parallel to the longitudinal direction of the shaft; 90° prepregs, in which the fiber direction of the reinforcing fibers is approximately perpendicular to the longitudinal direction of the shaft; and bias prepregs, in which the fiber direction of the reinforcing fibers is inclined at approximately 45° to the longitudinal direction of the shaft.

[0004] By adjusting the combination of prepregs with different fiber directions, the rigidity of the golf club shaft can be adjusted, thereby adjusting the trajectory. For example, a golf club shaft with a relatively low rigidity tends to produce a hook-like ball with a high trajectory, while a golf club shaft with a relatively high rigidity tends to produce a slice-like ball with a low trajectory. On the other hand, differences in the fiber direction between prepregs can affect the rigidity of the golf club shaft, which can lead to variations in the ball's flight distance and directionality. Therefore, there is a need for the development of a golf club shaft that produces a desired trajectory and stabilizes the ball's flight distance and directionality. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-305332 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a golf club shaft and a golf club that can produce a desired trajectory and stabilize the flight distance of the ball. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a golf club shaft formed by winding and heat-curing multiple layers of prepregs in which reinforcing fibers are impregnated with a thermosetting resin, wherein the prepregs include a 0° prepreg in which the fiber direction of the reinforcing fibers is parallel to the longitudinal direction of the shaft, a 90° prepreg in which the fiber direction of the reinforcing fibers is perpendicular to the longitudinal direction of the shaft, a first bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of 40° to 50° with respect to the longitudinal direction of the shaft, and a second positive bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of +10° to +35° with respect to the longitudinal direction of the shaft or a second negative bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of -10° to -35° with respect to the longitudinal direction of the shaft.

[0008] The present invention also provides a golf club comprising the above golf club shaft, a club head, and a grip attached thereto. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a golf club shaft and a golf club that can produce a desired trajectory and stabilize the flight distance of the ball. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1A is an exploded perspective view schematically showing the configuration of a golf club shaft according to one embodiment of the present invention. [Figure 1B]FIG. 1B is a schematic plan view illustrating the fiber direction of the reinforcing fibers of a second positive bias prepreg in one embodiment of the present invention. [Figure 1C] FIG. 1C is a schematic plan view illustrating the fiber direction of reinforcing fibers of a second negative bias prepreg in one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a first embodiment (Example 1) of a laminated structure of prepregs for a golf club shaft according to one embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing a second aspect (Example 2) of the laminated structure of the prepreg of the golf club shaft according to one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing a third aspect (Example 3) of the laminated structure of the prepreg of the golf club shaft according to one embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing a fourth aspect (Example 4) of the laminated structure of the prepreg of the golf club shaft according to one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing a fifth aspect (Example 5) of the laminated structure of the prepreg of the golf club shaft according to one embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing a sixth aspect (Example 6) of the laminated structure of the prepreg of the golf club shaft according to one embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing a seventh aspect (Example 7) of the laminated structure of the prepreg of the golf club shaft according to one embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing the laminated structure of the prepreg of the golf club shaft of Comparative Example 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described. Aspect 1 of this embodiment is a golf club shaft formed by winding and heat-curing multiple layers of prepregs in which reinforcing fibers are impregnated with a thermosetting resin, wherein the prepregs include a 0° prepreg in which the fiber direction of the reinforcing fibers is parallel to the longitudinal direction of the shaft, a 90° prepreg in which the fiber direction of the reinforcing fibers is perpendicular to the longitudinal direction of the shaft, a first bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of 40° to 50° with respect to the longitudinal direction of the shaft, and a second positive bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of +10° to +35° with respect to the longitudinal direction of the shaft or a second negative bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of -10° to -35° with respect to the longitudinal direction of the shaft.

[0012] Aspect 2 of this embodiment is a golf club shaft characterized in that, in the above-mentioned aspect 1, the second positive bias prepreg or the second negative bias prepreg is positioned between the first bias prepreg and the 90° prepreg.

[0013] Aspect 3 of this embodiment is a golf club shaft characterized in that, in Aspect 1 or Aspect 2 above, the second positive bias prepreg or the second negative bias prepreg is located closer to the inner layer of the golf club shaft than the first bias prepreg.

[0014] Aspect 4 of this embodiment is a golf club shaft characterized in that, in any of Aspects 1 to 3 above, the second positive bias prepreg or the second negative bias prepreg is located between the 90° prepreg and the 0° prepreg.

[0015] Aspect 5 of this embodiment is a golf club shaft characterized in that, in any of Aspects 1 to 4 above, the first bias prepreg includes a first positive bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of +40° to +50° relative to the longitudinal direction of the shaft, and a first negative bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of -40° to -50° relative to the longitudinal direction of the shaft.

[0016] Aspect 6 of this embodiment is a golf club shaft characterized in that, in any of Aspects 1 to 5 above, the first bias prepreg, the 90° prepreg, and the 0° prepreg are wound in that order from the innermost layer side to the outermost layer side of the golf club shaft.

[0017] A seventh aspect of this embodiment is a golf club characterized by having a club head and a grip attached to the golf club shaft of any one of the first to sixth aspects.

[0018] FIG. 1 is an exploded perspective view showing a schematic configuration of a golf club shaft 1 according to this embodiment, FIGS. 2 to 8 are views showing first to seventh modes of the prepreg laminate structure of the golf club shaft 1 according to this embodiment, and FIG. 9 is a view showing the prepreg laminate structure of a golf club shaft of Comparative Example 1.

[0019] 2 to 9, "angle (°)" indicates the angle of the reinforcing fibers in each prepreg with respect to the longitudinal direction of the shaft (in this embodiment, 0°, +15°, +45°, -45°, or 90°). In the shape of each prepreg shown in Figures 2 to 9, the left side of the drawing is the small diameter end (head side end, tip side) of the golf club shaft, and the right side is the large diameter end (grip side end, base side) of the golf club shaft.

[0020] The golf club shaft 1 according to this embodiment is formed by winding multiple layers of prepreg, which is made by impregnating reinforcing fibers with a thermosetting resin, and then thermally curing the prepreg. Various materials can be used as reinforcing fibers, such as carbon fiber, alumina fiber, aramid fiber, glass fiber, Tyranno fiber, carbon silicate fiber, and amorphous fiber. Various materials can be used as thermosetting resins, such as epoxy resin, unsaturated polyester resin, phenolic resin, vinyl ester resin, and PEEK resin.

[0021] The golf club shaft 1 has a tapered shape in which the diameter gradually increases from the small diameter side at the tip to the large diameter side at the grip. A club head (not shown) is attached to the small diameter end 11 of the golf club shaft 1, and a grip (not shown) is attached to the large diameter end 12 of the golf club shaft 1. A golf club is constructed by attaching the club head to the small diameter end 11 and the grip to the large diameter end 12.

[0022] The prepregs include a 0° prepreg 21 in which the fiber direction of the reinforcing fibers is parallel to the longitudinal direction of the shaft, a 90° prepreg 22 in which the fiber direction of the reinforcing fibers is perpendicular to the longitudinal direction of the shaft, a first bias prepreg 23 in which the fiber direction of the reinforcing fibers is inclined at a predetermined angle (40° to 50°, preferably approximately 45°) with respect to the longitudinal direction of the shaft, and a second bias prepreg 24 in which the fiber direction of the reinforcing fibers is inclined at a predetermined angle (10° to 35°, preferably 15° to 25°, particularly preferably approximately 15°) with respect to the longitudinal direction of the shaft (see Figure 1).

[0023] The laminate structure of the prepregs in the golf club shaft 1 according to this embodiment preferably has a wound laminate structure of the first bias prepreg 23, the 90° prepreg 22, and the 0° prepreg 21 in order from the inner layer side (lower layer side) to the outer layer side (upper layer side) of the golf club shaft 1 (see FIGS. 2 to 8). Note that in this embodiment, the lamination order of the 0° prepreg 21, the 90° prepreg 22, and the first bias prepreg 23 is not limited to the form shown in FIGS. 2 to 8.

[0024] The second bias prepreg 24 may be located on the inner layer side (lower layer side) of the first bias prepreg 23, or may be located between the first bias prepreg 23 and the 90° prepreg 22, or may be located between the 90° prepreg 22 and the 0° prepreg 21, or may be located on the outer layer side (upper layer side) of the 0° prepreg 21. When the golf club shaft 1 according to the present embodiment includes a plurality of second bias prepregs 24, the plurality of second bias prepregs 24 may be laminated at a plurality of positions arbitrarily selected from the above positions (inner layer side (lower layer side) of the first bias prepreg 23, between the first bias prepreg 23 and the 90° prepreg 22, between the 90° prepreg 22 and the 0° prepreg 21, and outer layer side (upper layer side) of the 0° prepreg 21).

[0025] In this embodiment, the first bias prepreg 23 includes a first positive bias prepreg and a first negative bias prepreg. In this embodiment, the first positive bias prepreg is inclined at a predetermined angle with respect to the longitudinal direction LS of the shaft so that the fiber direction FD of the reinforcing fibers slopes upward to the right in a plan view in which the small diameter side end 11 of the golf club shaft 1 is located on the left and the large diameter side end 12 is located on the right, and the first negative bias prepreg is inclined at a predetermined angle with respect to the longitudinal direction LS of the shaft so that the fiber direction FD of the reinforcing fibers slopes upward to the left.

[0026] In this embodiment, the second bias prepreg 24 may include a second positive bias prepreg 241 or a second negative bias prepreg 242. In this embodiment, the second positive bias prepreg 241 is inclined at a predetermined angle θ with respect to the longitudinal direction LS of the shaft so that the fiber direction FD of the reinforcing fibers slopes upward to the right in a plan view in which the small diameter side end 11 of the golf club shaft 1 is located on the left side and the large diameter side end 12 is located on the right side, and the second negative bias prepreg 242 is inclined at a predetermined angle θ with respect to the longitudinal direction LS of the shaft so that the fiber direction FD of the reinforcing fibers slopes upward to the left (see FIGS. 1B and 1C ).

[0027] A first aspect of the laminated structure may be, for example, a wound laminate of, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a tip reinforcing 0° prepreg P10, a pair of first bias prepregs P11, P12 (a first positive bias prepreg (+45° prepreg) P11 and a first negative bias prepreg (-45° prepreg) P12), a 90° prepreg P13, a second positive bias prepreg P14 (+15° prepreg P14), a tip reinforcing 0° prepreg P15, a 0° prepreg P16, a 0° prepreg P17, a 0° prepreg P18, and a triangular 0° prepreg (reinforcing prepreg) P19 (see Figure 2).

[0028] A second aspect of the laminated structure may be, for example, a wound laminate of, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a tip reinforcing 0° prepreg P20, a pair of first bias prepregs P21, P22 (a first positive bias prepreg (+45° prepreg) P21 and a first negative bias prepreg (-45° prepreg) P22), a second positive bias prepreg P23 (+15° prepreg P23), a 90° prepreg P24, a tip reinforcing 0° prepreg P25, a 0° prepreg P26, a 0° prepreg P27, a 0° prepreg P28, and a triangular 0° prepreg (reinforcing prepreg) P29 (see Figure 3).

[0029] A third aspect of the laminated structure may be, for example, a wound laminate of, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a tip reinforcing 0° prepreg P30, a pair of first bias prepregs P31, P32 (a first positive bias prepreg (+45° prepreg) P31 and a first negative bias prepreg (-45° prepreg) P32), a second positive bias prepreg P33 (+15° prepreg P33), a 90° prepreg P34, a second positive bias prepreg P35 (+15° prepreg P35), a 0° prepreg P36, a tip reinforcing 0° prepreg P37, a 0° prepreg P38, and a triangular 0° prepreg (reinforcing prepreg) P39 (see FIG. 4).

[0030] A fourth aspect of the laminated structure may be, for example, a wound laminate of, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a 0° prepreg P40 for tip reinforcement, a second positive bias prepreg P41 (+15° prepreg P41), a pair of first bias prepregs P42, P43 (a first positive bias prepreg (+45° prepreg) P42 and a first negative bias prepreg (-45° prepreg) P43), a 90° prepreg P44, a 0° prepreg P45, a 0° prepreg P46 for tip reinforcement, a 0° prepreg P47, a 0° prepreg P48, and a triangular 0° prepreg (reinforcing prepreg) P49 (see FIG. 5).

[0031] A fifth aspect of the laminated structure may be one in which, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a tip reinforcing 0° prepreg P50, a second positive bias prepreg P51 (+15° prepreg P51), a pair of first bias prepregs P52, P53 (a first positive bias prepreg (+45° prepreg) P52 and a first negative bias prepreg (-45° prepreg) P53), a 90° prepreg P54, a second positive bias prepreg P55 (+15° prepreg P55), a tip reinforcing 0° prepreg P56, a 0° prepreg P57, a 0° prepreg P58, and a triangular 0° prepreg (reinforcing prepreg) P59 are wound and laminated (see FIG. 6).

[0032] A sixth aspect of the laminated structure may be, for example, a wound laminate of, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a tip reinforcing 0° prepreg P60, a second positive bias prepreg P61 (+15° prepreg P61), a pair of first bias prepregs P62, P63 (a first positive bias prepreg (+45° prepreg) P62 and a first negative bias prepreg (-45° prepreg) P63), a second positive bias prepreg P64 (+15° prepreg P64), a 90° prepreg P65, a tip reinforcing 0° prepreg P66, a 0° prepreg P67, a 0° prepreg P68, and a triangular 0° prepreg (reinforcing prepreg) P69 (see FIG. 7).

[0033] A seventh aspect of the laminated structure may be, for example, a wound laminate of, in order from the inner layer side (lower layer side) to the outer layer side (upper layer side), a 0° prepreg P70 for tip reinforcement, a second positive bias prepreg P71 (+15° prepreg P71), a pair of first bias prepregs P72, P73 (a first positive bias prepreg (+45° prepreg) P72 and a first negative bias prepreg (-45° prepreg) P73), a second positive bias prepreg P74 (+15° prepreg P74), a 90° prepreg P75, a second positive bias prepreg P76 (+15° prepreg P76), a 0° prepreg P77, a 0° prepreg P78 for tip reinforcement, and a triangular 0° prepreg (reinforcing prepreg) P79 (see FIG. 8).

[0034] In the golf club shaft 1 according to this embodiment, the number of turns (number of plies) of each prepreg in the laminate structure is not particularly limited and may be set appropriately depending on the total weight of the golf club shaft 1. For example, the number of turns (number of plies) of each prepreg may be at least one turn (one ply), and the number of turns (number of plies) of all prepregs in the laminate structure may be the same, or the number of turns (number of plies) of at least one prepreg may be different.

[0035] The total weight of the golf club shaft 1 according to this embodiment may be, for example, about 30 to 120 g. Note that the total weight of the golf club shaft 1 in this embodiment refers to the weight of the golf club shaft 1 having the above-mentioned laminated structure in which a plurality of prepregs are wound and laminated, and does not refer to the weight of the golf club shaft 1 having the above-mentioned laminated structure that has been subjected to a paint treatment.

[0036] In the golf club shaft 1 according to this embodiment, the mass ratio of the second bias prepreg 24 to the total weight of the golf club shaft 1 may be 10 to 35%. Although FIG. 1A shows the 0° prepreg 21, the 90° prepreg 22, the first bias prepreg 23, and the second bias prepreg 24 as if they were each composed of one layer, FIG. 1A is a schematic diagram for facilitating understanding of the layered structure of the golf club shaft 1, and the golf club shaft 1 is not limited to this form. The golf club shaft 1 according to this embodiment may include a plurality of second bias prepregs 24. Therefore, in this embodiment, the mass of the second bias prepreg 24 means the total mass of the plurality of second bias prepregs 24, and the above-mentioned mass ratio may be calculated using this total mass.

[0037] The golf club shaft 1 according to this embodiment can be manufactured by winding each prepreg around a tapered rod-shaped mandrel (rod-shaped core) in order from the inner layer side (lower layer side) to the outer layer side (upper layer side) according to the above-described laminated structure, thermally curing them, and then pulling out the rod-shaped mandrel. The golf club shaft 1 manufactured in this manner may be subjected to a painting treatment.

[0038] The fiber direction of the 0° prepreg, tip reinforcing 0° prepreg, and triangular 0° prepreg in the first to seventh aspects of the laminate structure is parallel to the longitudinal direction of the golf club shaft 1. The fiber direction of the 90° prepreg is perpendicular to the longitudinal direction of the golf club shaft 1. The fiber direction of the first bias prepreg is inclined at an angle of ±40 to 50°, preferably ±45°, relative to the longitudinal direction of the golf club shaft 1. The fiber direction of the second positive bias prepreg is inclined at an angle of +10 to +35°, preferably +15 to +25°, particularly preferably +15°, relative to the longitudinal direction of the golf club shaft 1.

[0039] The 0° prepreg, 90° prepreg, first bias prepreg and second positive bias prepreg are made up of full length layers extending over the entire length of the golf club shaft 1, and are formed in a trapezoidal shape that narrows from the large diameter end (grip side end, base end) to the small diameter end (head side end, tip end) so that when wound around the rod-shaped mandrel M, the number of turns is the same over the entire length of the golf club shaft 1.

[0040] The tip reinforcing 0° prepreg is wound only around the vicinity (part of the longitudinal direction) of the small diameter end (tip) of the golf club shaft 1 to reinforce the vicinity (part of the longitudinal direction) of the small diameter end (tip) of the golf club shaft 1. The triangular 0° prepreg is used to make the small diameter end (tip) of the golf club shaft 1 a straight section that corresponds to the hosel diameter of the club head (not shown).

[0041] The golf club shaft 1 of this embodiment includes a second bias prepreg 24 in which the fiber direction of the reinforcing fibers is inclined at a predetermined angle (10° to 35°) relative to the longitudinal direction of the shaft, thereby allowing the ball to be hit with a golf club using the golf club shaft 1 to have a desired trajectory and stabilize the ball's flight distance.

[0042] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0043] In the first to seventh aspects of the above-described embodiment (see FIGS. 2 to 8), the second bias prepreg 24 includes a second positive bias prepreg 241 whose fiber direction is inclined at an angle of +10° to +35°, preferably +15°, relative to the longitudinal direction of the shaft, but is not limited to this aspect. For example, the second bias prepreg 24 may include a second negative bias prepreg 242 whose fiber direction is inclined at an angle of -10° to -35°, preferably -15°, relative to the longitudinal direction of the shaft.

[0044] In the first to seventh aspects of the above-described embodiment (see FIGS. 2 to 8), a pair of first bias prepregs 23 is illustrated in which a first positive bias prepreg (+45° prepreg) whose fiber direction is inclined at an angle of +40° to +50° (+45°) relative to the longitudinal direction of the shaft and a first negative bias prepreg (-45° prepreg) whose fiber direction is inclined at an angle of -40° to -50° (-45°) relative to the longitudinal direction of the shaft are laminated together, but this is not limiting. For example, the pair of first bias prepregs may include at least one prepreg selected from a 0° prepreg, a 90° prepreg, and a second bias prepreg positioned between the first positive bias prepreg (+45° prepreg) and the first negative bias prepreg (-45° prepreg). [Example]

[0045] The present invention will be explained in more detail below by way of test examples, but the present invention is not limited to the following examples and test examples.

[0046] [Test Example 1] Golf clubs were prepared by attaching a club head to the small-diameter end of the golf club shaft 1 of the first to seventh embodiments (see Examples 1 to 7 and Figures 2 to 8) and the golf club shaft of Comparative Example 1 (see Figure 9) and attaching a grip to the large-diameter end. A test-hitting robot (product name: Golf Shot Robo ROBO-10, manufactured by Miyamae Co., Ltd.) was used to hit golf balls with the golf clubs, and the characteristics of the golf club shaft were measured using a trajectory and swing measuring device (product name: Trackman 4, manufactured by TRACKMAN Co., Ltd.) (robot test). Four male subjects also hit golf balls five times each with the golf clubs, and the characteristics of the golf club shaft were measured using the trajectory and swing measuring device (human test). The results are shown in Table 1. Table 1 also shows the mass ratio (%) of the second bias prepreg 24 to the total weight of the golf club shaft 1.

[0047] [Table 1]

[0048] In Table 1, "Attack" represents the golf club's angle of incidence (deg), "Face" represents the orientation of the club head's face relative to the ball's launch direction (deg), "Launch" represents the ball's launch angle (deg), "HS" represents the head speed (m / sec), "Carry" represents the distance the ball travels to its landing point (yd), and "Total" represents the distance the ball travels including the run (yd). Additionally, "Ave." represents the arithmetic mean of five measurements taken by each of four subjects (a total of 20 measurements), and "±" represents the difference between the maximum and minimum values ​​of five measurements taken by each of four subjects (a total of 20 measurements).

[0049] As shown in Table 1, the golf club shafts of Examples 1 to 7 were evaluated to be equivalent to Comparative Example 1 in terms of the attack angle, face direction, and launch angle in the robot test.

[0050] Furthermore, the golf club shafts of Examples 1 to 7 were evaluated as having excellent stability in distance, with head speed (HS), carry distance to ball landing point (Carry) and total ball distance in human tests being equivalent to those of Comparative Example 1, but with smaller variations in these characteristics than Comparative Example 1.

[0051] [Test Example 2] Three-point bending strength test A three-point bending strength test was conducted on the golf club shafts 1 of the first to seventh embodiments (see Examples 1 to 7 and Figures 2 to 8) and the golf club shaft of Comparative Example 1 (see Figure 9). The three-point bending strength test was conducted by applying loads to positions 90 mm (T-90), 175 mm (T-175), and 525 mm (T-525) from the tip of the shaft and a position 175 mm (B-175) from the butt end of the shaft, and measuring the load (N) when the shaft broke. The results are shown in Table 2.

[0052] [Test Example 3] Torque measurement test and torsional breaking strength test Torque measurement tests and torsional breaking strength tests were conducted on the golf club shafts 1 of the first to seventh embodiments (see Examples 1 to 7 and FIGS. 2 to 8) and the golf club shaft of Comparative Example 1 (see FIG. 9). In the torque measurement test, the shaft was fixed at a position 40 mm from the tip, and the torsional angle when a torsional moment of 13.83 kgf·cm was applied to the tip was measured as torque (deg). In the torsional breaking strength test, the force at which the golf club shaft was twisted and broken along its entire length was measured as breaking force A (N·m), and the angle at which it twisted and broke (torsion angle) was measured as breaking angle B (deg). The product of breaking force A and breaking angle B (A×B) was calculated as the torsional breaking strength. The results are also shown in Table 2.

[0053] [Table 2]

[0054] As is clear from the results shown in Table 2 above, it was confirmed that the golf club shafts 1 of Examples 1 to 7 have sufficient bending strength, equivalent to that of the golf club shaft of Comparative Example 1. The golf club shafts 1 of Examples 1 to 7 were also evaluated to have torque equivalent to that of the golf club shaft of Comparative Example 1. Furthermore, the golf club shafts 1 of Examples 1 to 7 have higher torsional fracture strength than the golf club shaft of Comparative Example 1, and are therefore less susceptible to torsional fracture. [Explanation of symbols]

[0055] 1...Golf club shaft 21...0° prepreg 22...90° prepreg 23...First bias prepreg 24...Second bias prepreg

Claims

1. A golf club shaft made by winding and heat-curing multiple layers of prepreg, in which reinforcing fibers are impregnated with a thermosetting resin, The golf club shaft is characterized in that the prepregs include a 0° prepreg in which the fiber direction of the reinforcing fibers is parallel to the longitudinal direction of the shaft, a 90° prepreg in which the fiber direction of the reinforcing fibers is perpendicular to the longitudinal direction of the shaft, a first bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of 40° to 50° with respect to the longitudinal direction of the shaft, and a second positive bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of +10° to +35° with respect to the longitudinal direction of the shaft or a second negative bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of -10° to -35° with respect to the longitudinal direction of the shaft.

2. 2. The golf club shaft according to claim 1, wherein the second positive bias prepreg or the second negative bias prepreg is located between the first bias prepreg and the 90° prepreg.

3. 2. The golf club shaft according to claim 1, wherein the second positive bias prepreg or the second negative bias prepreg is located on an inner layer side of the golf club shaft than the first bias prepreg.

4. 2. The golf club shaft according to claim 1, wherein the second positive bias prepreg or the second negative bias prepreg is located between the 90° prepreg and the 0° prepreg.

5. 2. The golf club shaft of claim 1, wherein the first bias prepreg includes a first positive bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of +40° to +50° relative to the longitudinal direction of the shaft, and a first negative bias prepreg in which the fiber direction of the reinforcing fibers is inclined at an angle of -40° to -50° relative to the longitudinal direction of the shaft.

6. 6. The golf club shaft according to claim 1, wherein the first bias prepreg, the 90° prepreg, and the 0° prepreg are wound in that order from the innermost layer side to the outermost layer side of the golf club shaft.

7. A golf club comprising the golf club shaft according to any one of claims 1 to 5, a club head and a grip attached thereto.

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