JP6182829B2 - Manufacturing method of shaft for golf club - Google Patents

Description

The present invention relates to a method for manufacturing a shaft for a golf club.

  In order to improve the golf score, it is important to improve the flight distance. In particular, in a hole with a long distance, if the flight distance of the first shot is improved, the distance after the second shot can be shortened and the accuracy can be improved, which can lead to an improvement in score.

  In golf, it is known that the flight distance of a hit ball is determined by the initial velocity, launch angle, and spin amount of the ball. Although the initial velocity, launch angle, and spin amount of the ball depend on the characteristics of the golf head, the movement (deformation) of the shaft at the moment of hitting the ball has a great influence on these three factors. In particular, since the bending stiffness distribution of the shaft greatly affects these factors, shafts having various bending stiffness distributions have been developed. Among them, fiber reinforced plastic golf club shafts using reinforced fibers are easy to adjust the bending stiffness distribution, and in recent years, fiber reinforced plastics are used in many wood golf club shafts.

  It is known that the influence of the bending stiffness distribution on the movement (deformation) of the shaft is due to the hardness (flex) and the inclination of the bending stiffness distribution curve. The effect of hardness (flex) is that the movement (deformation) of the shaft will be smaller if it is hard, and the movement (deformation) of the shaft will be larger if it is soft. Choose a soft shaft. On the other hand, the influence of the inclination of the stiffness distribution curve is such that the greater the inclination, the greater the restoring force to return to the original state, and the smaller the inclination, the smaller the restoring force to return to the original state. Therefore, the higher the slope of the stiffness distribution curve, the faster the return, so it is suitable for people with fast swing tempos and fast head speeds. The smaller the slope of the stiffness distribution curve, the slower the return, so the swing tempo is slow. Suitable for people and people with slow head speeds.

  When considering the relationship between the bending stiffness distribution in the golf club shaft and the movement (deformation) of the shaft, it is considered that the golf club shaft can be divided into three parts as follows.

A) Small diameter end to small diameter end 300mm
B) Narrow end 350mm-Narrow end 800mm
C) The small diameter end 850 mm to the large diameter end A) corresponds to the head mounting portion, and is a portion that affects the launch angle and the spin amount. Hereinafter, this part is referred to as “shaft tip”. Since this part has a small outer diameter displacement of the shaft, the inclination of the bending stiffness distribution curve is small, and the hardness has a great influence on the performance of the shaft.

  About B), it is a central part of the shaft, which is the part where the amount of deformation of the shaft during the swing is the largest and affects the head speed. Hereinafter, this portion is referred to as “shaft central portion”. Since this portion has a large outer diameter displacement of the shaft, the inclination of the bending stiffness distribution curve is large, and the bending stiffness distribution curve has a great influence on the performance of the shaft.

  C) corresponds to a grip mounting portion, and this portion is hereinafter referred to as a “grip portion”. Since this part has a small outer diameter displacement of the shaft, the inclination of the bending stiffness distribution curve is small, and the hardness has a great influence on the performance of the shaft.

  Here, the bending rigidity E · I of the golf club shaft can be calculated from the following equation (1).

Ｅ：ゴルフクラブ用シャフトの長手方向の弾性率
Ｉ：断面二次モーメント
Ｄ：ゴルフクラブ用シャフトの外径
ｄ：ゴルフクラブ用シャフトの内径

以上のことから、ゴルフクラブ用シャフトの曲げ剛性分布曲線は、シャフト外径の４乗に比例することになる。つまり、一般的なゴルフクラブ用シャフトにおいて、外径のテーパーがほぼ均一であることが多いことから、シャフト中央部の曲げ剛性分布曲線の傾きは、シャフト先端部に近いほど小さく、グリップ部に近いほど大きくなっている。 <Formula 1>

E: Elastic modulus in the longitudinal direction of the golf club shaft I: Secondary moment of section D: Outer diameter of the golf club shaft d: Inner diameter of the golf club shaft

From the above, the bending stiffness distribution curve of the golf club shaft is proportional to the fourth power of the shaft outer diameter. That is, in general golf club shafts, the taper of the outer diameter is often substantially uniform, so the inclination of the bending stiffness distribution curve at the center of the shaft is smaller as it is closer to the shaft tip and closer to the grip. It is getting bigger.

  As for the deformation of the golf club shaft, when the swing is started, the grip side becomes large, and the bending of the shaft is transmitted to the tip of the shaft toward the impact, thereby transmitting energy to the head and flying the ball. As described above, in a general golf club shaft, the inclination of the bending stiffness distribution curve at the center of the shaft becomes smaller as it approaches the tip of the shaft. The head speed is difficult to increase.

  In Patent Document 1, a golf club shaft corresponding to the head speed can be obtained by adjusting the ratio of the inclination of the bending stiffness distribution curve in the vicinity of the grip portion and the inclination of the bending stiffness distribution curve in the center portion of the shaft according to the head speed. It is said.

  However, in Patent Document 1, since the bending stiffness distribution at the center of the shaft is curved like the conventional one, an improvement in feeling according to the head speed can be expected, but an improvement in flight distance can be expected. Absent.

  Further, in Patent Document 2, an intermediate reinforcing layer is provided in the central portion of the shaft, and the bending rigidity distribution curve of the central portion of the shaft is increased closer to the tip of the shaft and closer to the grip portion by increasing the bending rigidity of the central portion of the shaft. It is so small.

  However, in Patent Document 2, since the inclination of the bending stiffness distribution curve at the center of the shaft increases as it approaches the tip of the shaft, the shaft immediately before impact undergoes rapid bending and the acceleration of the head increases. The inner shaft is slow to return, and as a result, the head speed does not increase and the flight distance cannot be improved.

  On the other hand, Patent Document 3 states that a golf shaft having a bending rigidity distribution preferred by everyone can be obtained by making the bending rigidity distribution curve at the central portion of the shaft substantially linear.

  However, as described above, the bending stiffness distribution curve of the golf club shaft is proportional to the fourth power of the outer diameter of the shaft. Therefore, in the example illustrated in Patent Document 3, the bending of the central portion of the shaft is accurately performed. The rigidity distribution cannot be made linear, and a golf shaft having a bending rigidity distribution preferred by everyone cannot be obtained.

JP 2002-177423 A JP 2003-24490 A JP 2002-224256 A

  The present invention has been made in view of the above circumstances, and it is possible to obtain a golf club shaft which improves the head speed and improves the flight distance at the same time as improving the resilience of bending and returning of the golf shaft during a swing. With the goal.

  In order to achieve the above object, the present invention employs the following configuration.

(1) A method for producing a shaft for a golf club formed by winding a prepreg obtained by impregnating a reinforcing fiber with a resin around a mandrel,
Bending the distance of each 50mm from 370mm from the small diameter end of the golf club shaft in the region of 770 mm L (mm), Naru Kara flexural rigidity EI _L and ^{(× 10 6 kgf · mm 2} ) at the position of the distance L When the stiffness group (L, EI _L ) is (x, y) and the (x, y) is linearly regressed to the following formula (A) by the least square method, the square of the correlation coefficient of the following formula (A) R ₁ ² is characterized in that 0.999 or more,
y = -a ₁ x + b ₁ Formula (A)
The taper of the golf club shaft in a region of 370 mm to 770 mm from the narrow diameter end portion of the golf club shaft is gradually reduced in at least three stages from the narrow diameter end side,
The mandrel in which the taper degree gradually decreases over a plurality of stages so that the taper in the region of 370 mm to 770 mm from the narrow end of the golf club shaft to be molded gradually decreases over at least three stages from the narrow end side. A method for producing a shaft for a golf club, which is molded using

( 2 ) The golf club shaft according to (1), wherein the fiber reinforced resin is a carbon fiber reinforced resin.

  According to the golf club shaft of the present invention, it is possible to improve the initial velocity of the ball and obtain the optimum amount of ball spin, which leads to the improvement of the flight distance.

It is explanatory drawing which shows the cutting shape of the prepreg which shows one Embodiment of the shaft for golf clubs of this invention, and winding order. 1 is a schematic explanatory diagram of a mandrel 10. FIG. 2 is a schematic explanatory diagram of a mandrel 11. FIG. It is explanatory drawing which shows the cutting shape of the prepreg used for manufacture of the golf shaft in an Example, and the winding order to the metal core 11. FIG. It is the schematic of the test apparatus in EI value measurement of the shaft for golf clubs. 2 is a schematic explanatory diagram of a mandrel 12. FIG. FIG. 6 is an explanatory diagram showing a cutting shape of a prepreg used for manufacturing a golf shaft in Comparative Example 1 and a winding order around a core metal 12. 2 is a schematic explanatory diagram of a mandrel 13. FIG. 6 is an explanatory diagram showing a cutting shape of a prepreg used for manufacturing a golf shaft in Comparative Example 2 and a winding order around a cored bar 13. FIG. Example, Comparative Example 1, the EI value distribution in Comparative Example 2 is an explanatory diagram showing a result of calculating the square R ² of the correlation coefficient. It is explanatory drawing which shows the outer diameter distribution of the narrow end 350mm-800mm in an Example, the comparative example 1, and the comparative example 2. FIG.

Hereinafter, the best mode of the present invention will be described in detail.

<Shaft>
In the golf club shaft formed by laminating the fiber reinforced resin according to the present invention, the outer diameter of the surface perpendicular to the axial direction increases from one end to the other end in the length direction, and the other end from the diameter switching portion in the middle It is formed so that the outer diameter is the same. Hereinafter, the end portion on the side having a smaller outer diameter is referred to as a small diameter end portion, and the end portion on the side having a large outer diameter is referred to as a large diameter end portion. Further, from the diameter switching portion in the longitudinal direction of the shaft, the small diameter end portion side is referred to as a thin diameter portion, and the large diameter end portion side is referred to as a large diameter portion. The golf club shaft of the present invention is laminated by winding fiber reinforced resins (prepreg) 21 to 27 having a cut shape as shown in patterns 1 to 7 in FIG. 1 around the mandrel 10 in the order of patterns 1 to 7, for example. Then, it is composed of a plurality of fiber-reinforced resin layers that are heat-cured. This golf club shaft has both angle layers in both forward and reverse directions within a range of 20 to 75 ° of the reinforcing fiber winding angle with respect to the main axis of the tubular body, and the winding start position of the two forward and reverse angle layers. Is formed with a plurality of straight layers on the outer side of which the reinforcing fiber has a winding angle within a range of −5 to 5 °.

The golf club shaft of the present invention has a distance L (mm) every 50 mm in a region of 370 mm to 770 mm from the small diameter end portion of the golf club shaft, and a bending rigidity EI _L (× 10 ⁶ kgf) at the position of the distance L. When the bending stiffness group (L, EI _L ) consisting of (mm ² ) is (x, y) and the (x, y) is linearly regressed to the following formula (A) by the least square method, the following formula ( It is satisfied that the square R ₁ ² of the correlation coefficient of A) is 0.999 or more.

y = −a ₁ x + b ₁ (A)
When the square R ₁ ² of the correlation coefficient of the formula (A) is 0.999 or more, the bending stiffness distribution in the region from 370 mm to 770 mm from the narrow diameter end of the shaft is uniform, and there are no spots. Therefore, since the bending rigidity group in this region is a straight line, it is possible to improve the restoring performance of the shaft returning during the swing, and at the same time to improve the head speed and the flight distance.
Here, the expression (A) is a relational expression that affects the speed at which the shaft is bent back. Since the bending stiffness distribution diagrams of shafts are generally curved, it is difficult to compare the bending stiffness distributions of individual shafts. Therefore, the linear characteristics of individual shafts are linearly regressed as in equation (A), thereby making it easy to compare the shaft characteristics. A ₁ linear regression the formula (A) represents the bending speed of the return of the shaft. The larger the a _{1, the} faster the shaft will bend and return, and the shaft will have a strong “feeling of playing”, and the smaller the a ₁ , the slower the shaft will return and the shaft will have a so-called “sticky” strength. B ₁ represents the condition of the shaft. The larger the b _{1, the} higher the bending rigidity on the small diameter end side of the shaft, so that the shaft becomes a so-called “hand-tuned” shaft, and the smaller the b ₁ , the smaller the bending rigidity on the small diameter end side. Become.

  In addition, the golf club shaft of the present invention is characterized in that the taper of the golf club shaft in the region of 370 mm to 770 mm from the narrow end portion gradually decreases in at least three steps from the narrow end portion side. “The taper of the golf club shaft gradually decreases in at least three steps from the side of the small diameter end” means that the golf club shaft has at least three different tapered regions, and the taper of the region is narrow. It means that it becomes smaller as it goes from the diameter end side toward the large diameter part. The taper in each region may be constant or slightly change continuously, but usually the taper in each region is constant for ease of design. Regarding “the taper of the golf club shaft gradually decreases in at least three steps from the side of the small diameter end portion”, in the case of having three different taper areas in the region of 370 mm to 770 mm from the small diameter end portion of the golf club shaft More specifically, by way of example, when each tapered region is defined as the region (1), the region (2), and the region (3) from the thin end side, the taper of the region (1)> the region (2). It is meant that the taper is greater than the taper of region (3). The taper of the golf club shaft in this area is preferred to have a large change in taper in order to approximate the bending stiffness distribution, which is originally a curve, to a straight line with high accuracy, but it becomes difficult to control the mandrel processing accuracy and to wind it. End up. Therefore, in consideration of actual productivity, the change in the taper of the shaft in this region is more preferably three or four.

  When the region of the golf shaft is divided into three, it can be divided into a “head mounting portion” on the side where the head is attached, a “grip portion” on the side where the grip is attached, and the other “shaft central portion”. The bending rigidity in the region from the shaft small diameter end corresponding to the “head mounting portion” to the small diameter end 300 mm greatly affects the ball launch angle, and the shaft small diameter end corresponding to the “grip portion” from 800 mm to the large diameter end. The flexural rigidity of the region has a great influence on the “tick” at the start of the swing. The so-called “shaft central portion” other than these is an important region for transmitting the energy generated by the bending of the shaft created by “Tame” to the head at the time of starting the swing. Focusing on the bending stiffness distribution in the region of 370 mm to 770 mm from the small-diameter end of the shaft, and finding the shaft that leads to the improvement of the flight distance by making the bending stiffness distribution in this region optimal.

<Fiber reinforced resin>
A thermoplastic resin or a thermosetting resin can be used as the resin component (matrix resin constituting the golf club shaft of the present invention) used for the fiber reinforced resin, but a thermosetting resin is preferably used. .

  As the thermoplastic resin, polyamide resins, polyacrylate resins, polystyrene resins, polyethylene resins, and mixed resins thereof can be used. On the other hand, as thermosetting resins, epoxy resins, unsaturated polyester resins, phenol resins, urea resins, melamine resins, diallyl phthalate resins, urethane resins, polyimide resins, and mixed resins thereof are used. Can be used. Among these, epoxy resins are most preferably used because they have a low cure shrinkage and high rigidity and toughness.

  Further, the fibers used for the fiber reinforced resin (fibers constituting the golf club shaft of the present invention) include inorganic fibers such as metal fibers, boron fibers, carbon fibers, glass fibers, ceramic fibers, aramid fibers, and the like. High-strength synthetic fibers can be used. Inorganic fibers are preferably used because of their light weight and high strength. Among these, carbon fiber is optimal because it is excellent in specific strength and specific rigidity.

  These fibers can be used alone or in combination. Further, any length of fibers such as long fibers, short fibers, and mixed fibers thereof may be used.

<Manufacturing method of shaft>
In order to manufacture the golf shaft of the present invention, the degree of taper is increased in a plurality of stages so that the taper in the region of 370 mm to 770 mm gradually decreases over at least three stages from the small diameter end of the golf club shaft to be molded. The shaft for a golf club of the present invention can be obtained by appropriately selecting mandrels that gradually decrease over time. The gist of the present invention is that the bending stiffness distribution in the above region is very close to a straight line. However, since the bending rigidity of the shaft is proportional to the fourth power of the outer diameter, the bending rigidity distribution becomes a concave curve in a mandrel having a uniform taper degree. In order to prevent this, it is sufficient to use a mandrel having a convex curve shape. However, since it is very difficult to actually manufacture such a mandrel with high accuracy, the taper degree is increased from the small diameter end to the large diameter. It is practical to use a mandrel that gradually decreases towards the edge. In addition, the taper of the golf club shaft in the above region preferably has a large change in taper in order to approximate the bending rigidity distribution, which is originally a curve, to a straight line with high accuracy, but it is necessary to control the mandrel processing accuracy and to wind it. It will be difficult. Therefore, in consideration of actual productivity, the change in the taper of the shaft in this region is more preferably three or four.

  In addition, although there is no particular limitation on the method for producing the shaft of the present invention, in the case of a fiber reinforced resin, a sheet-like prepreg in which a reinforced fiber is impregnated with an uncured matrix resin is prepared, and this prepreg is formed into a rod shape. There is a so-called sheet wrap method in which a core metal (mandrel) is wound and then cured to extract the core metal.

  In the sea trap method, it is common to prepare a plurality of types of prepregs having different areas and orientations of the reinforcing fibers contained therein, and sequentially winding them one by one on a core bar to produce a multi-layered shaft. However, at this time, by adjusting the area of each prepreg, the direction of the reinforcing fiber contained in each prepreg, the position where each prepreg is wound, or by changing the number of layers of the prepreg, A shaft can be manufactured. At this time, adjusting the degree of taper of the shaft and the outer diameter of the shaft as appropriate is also effective in manufacturing the shaft of the present invention.

The conditions for producing the golf club shaft of the present invention will be specifically described below. For example, a prepreg 21 having a cutting shape as shown in patterns 1 to 7 in FIG. 1 using a mandrel 10 having a shape in which the taper gradually decreases from the small diameter end toward the large diameter end as shown in FIG. -27 can be obtained by heating and curing after winding around the mandrel 10 in the order of patterns 1-7. Further, the points P 1 2 and P 1 3 at which the taper degree of the mandrel in FIG. 2 changes are adjusted to be in the region of 370 mm to 770 mm of the shaft obtained after heat forming, and the patterns 1 to 7 are wound around A shaft can be obtained.

  The gist of the present invention is that the bending stiffness distribution in the above-mentioned region is very close to a straight line. However, in a conventional mandrel having a uniform taper degree, the bending stiffness distribution becomes a concave curve. In order to prevent this, it is sufficient to use a mandrel having a convex curve shape. However, since it is very difficult to actually manufacture such a mandrel with high accuracy, the taper degree is increased from the small diameter end to the large diameter. It is desirable to use a mandrel that gradually decreases towards the edge. In the above region, in order to make the bending stiffness distribution linear, it is preferable to use a mandrel that gradually decreases from at least three steps from the end of the narrow diameter. I can't make it. In addition, in the mandrel where the taper degree of the shaft gradually decreases as described above, if the change in the taper degree is too large, the bending stiffness distribution curve in this region will become a convex curve shape this time. Since it is different from what is intended by the invention, it is important to accurately control the shape of the mandrel.

<Usage pattern>
When the golf club shaft of the present invention is applied to a so-called wood golf club shaft having a golf club length of 1041 mm to 1219 mm and a mass of the shaft of 40 g to 85 g, the effect is more fully exhibited.

The golf club shaft of the present invention is also suitable for combination with a large head. Examples of the large head include a large head having a volume of 380 cm ^{3 to} 460 cm ³ and an inertia moment of 3500 g · cm ^{2 to} 5900 g · cm ² . The shaft for a golf club of the present invention can improve the head speed and the flight distance at the same time as improving the resilience of the golf shaft during swinging even when such a large head is mounted. .

  Next, the present invention will be described more specifically based on examples.

  The materials for the golf club shafts produced in the examples and comparative examples are shown below.

Prepreg A: Carbon fiber prepreg MRX350E100R (thickness 0.093 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
Prepreg B: Carbon fiber prepreg HSX350C100S (thickness 0.076 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
Prepreg C: Carbon fiber prepreg MR350J050S (thickness 0.050 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
Prepreg D: Carbon fiber prepreg MRX350C100R (thickness 0.084 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
Prepreg E: Carbon fiber prepreg MRX350C150S (thickness 0.127 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
Prepreg F: Carbon fiber prepreg TR350E125S (thickness 0.113 mm, manufactured by Mitsubishi Rayon Co., Ltd.)
Example 1
<Mandrel>
A mandrel 11 (made of iron) having the shape shown in FIG. 3 was prepared. The mandrel 11 has an overall length L27, and its outer diameter gradually increases linearly from its small diameter end P21 to the position (switching point) P22 of the length L21. Similarly, from P22 to the length L22. The outer diameter increases linearly gradually from position P23, from P23 to position P24 of length L23, from P24 to position P25 of length L24, and from P25 to position P26 of length L25. And from the switching point P26 to the large diameter end P27 of length L26, the outer diameter consists of an iron cylinder which is constant. Specific outer diameters, lengths, and taper degrees at the respective portions of the mandrel 11 according to the present embodiment are as follows.

  The outer diameter of the small diameter end P21 is 4.20 mm, the outer diameter of the switching point P22 is 5.80 mm, the outer diameter of the switching point P23 is 7.30 mm, the outer diameter of the switching point P24 is 10.50 mm, outside the switching point P25. The diameter is 12.10 mm, the outer diameter of the switching point P26 is 13.50 mm, the same outer diameter from the switching point P26 to the large diameter end P27, and the outer diameter is 13.50 mm. The length L21 from the small diameter end P21 to the switching point P22 is 200 mm, the length L22 from the switching point P22 to the switching point P23 is 100 mm, the length L23 from the switching point P23 to the switching point P24 is 330 mm, and from the switching point P24 The length L24 from the switching point P25 to the switching point P26 is 200 mm, the length L25 from the switching point P25 to the switching point P26 is 200 mm, and the length L26 from the switching point P26 to the large diameter end P27 is 470 mm. The overall length L27 of the mandrel 11 is 1500 mm.

  Further, the taper degree from the small diameter end P21 to the switching point P22 is 8.00 / 1000, the taper degree from the switching point P22 to the switching point P23 is 15.00 / 1000, and the taper degree from the switching point P23 to the switching point P24. Is 9.70 / 1000, the degree of taper from the switching point P24 to the switching point P25 is 8.00 / 1000, and the degree of taper from the switching point P25 to the switching point P26 is 7.00 / 1000.

<Cutting and winding prepreg>
Various prepregs (prepregs A to F) were cut into shapes shown in patterns 1 to 7 in FIG. All these patterns are wound with the position 90 mm from the narrow end of the mandrel 11 as a reference point of the winding position, and the narrow end of the pattern is aligned with this reference point. As a result, in the region from 370 mm to 770 mm from the narrow end portion of the obtained golf club shaft, the taper degree gradually decreases in three stages.

  In the pattern 1, the size of the prepreg A is such that the fibers are oriented in the longitudinal axis direction of the shaft, and la and lb in FIG. 4 are la = 110 mm and lb = 100 mm, respectively. The number of windings was adjusted to gradually decrease in the range of lb.

  In the pattern 2, the prepreg B cut by + 45 ° with respect to the longitudinal axis direction of the shaft, and the prepreg B cut similarly by −45 ° were attached to each other so as to shift substantially half a circumference. Then, the size of the prepreg B obtained by bonding the two sheets was adjusted so that the total length was 1190 mm and the number of windings was three.

    In Pattern 3, the size of the prepreg C was adjusted so that the fibers were oriented at 90 ° with respect to the longitudinal axis direction of the shaft, the total length was 1190 mm, and the number of windings was one.

  In patterns 4 to 6, the sizes of the prepregs D and E were adjusted so that the fibers were oriented in the longitudinal axis direction of the shaft, the total length was 1190 mm, and the number of windings was one.

  In the pattern 7, the size of the prepreg D is such that the fibers are oriented in the longitudinal axis direction of the shaft, and lc and ld in FIG. 4 are lc = 170 mm and ld = 140 mm, respectively, and the number of windings is 2 in the range of lc. The number of windings was adjusted to gradually decrease in the range of ld.

  In Pattern 8, the size of the prepreg F was adjusted so that the fibers were oriented in the longitudinal axis direction of the shaft and the outer diameter of the narrow end portion was about 8.70 mm.

Next, the cut prepregs were wound around the mandrel 11 in the order of patterns 1-7. For winding, 90 mm from the narrow end of the mandrel was used as the winding end.
Next, a heat-shrinkable polypropylene tape (not shown) having a thickness of 20 μm and a width of 30 mm was wound and fixed at a winding pitch of 2 mm to obtain a shaft blank formed on the mandrel 11.

<Hardening of resin and polishing of shaft surface>
The shaft base tube was put in a curing furnace and heated at 145 ° C. for 2 hours to cure the resin of the prepreg, and then the polypropylene tape and the mandrel 11 were removed. Both ends of the obtained golf club shaft base tube were cut by 11 mm to a total length of 1168 mm. The cantilever flex of the shaft before polishing (the amount of deflection of the shaft small diameter end when the position of 920 mm from the small diameter end is fixed and a weight of 3 kg is hung on the position of 10 mm from the small diameter end of the shaft) was 136 mm. It was. Further, the outer diameter of the small diameter end of the golf club shaft blank before polishing was 8.71 mm, and the outer diameter of the large diameter end was 15.27 mm.

  The surface of this golf club shaft tube was polished with a cylindrical grinder so that the outer diameter of the narrow end was 8.50 mm and the cantilever flex was 152 mm, and the golf club shaft of the example was obtained. . Further, as a result of measuring the outer diameter of the obtained golf club shaft, as shown in FIG. 11, in the region from 370 mm to 770 mm from the narrow end, a shape in which the taper degree gradually decreased in three stages was obtained. .

  The weight of the golf club shaft of the example is 59.1 g, and the twist angle of the shaft (fixed at a position of 1035 mm from the shaft small diameter end, 138.5 kgf · The angle at which the shaft was twisted when a torque of mm was applied) was 3.8 degrees.

<Measurement of EI value of shaft>
The bending rigidity EI value of the shaft employed in the present invention was determined by the method described in JP-A-2001-120696. That is, as shown in FIG. 5, the shaft is supported at a fulcrum distance of 300 mm, a load of 20 kg is applied to the position of the distance L (mm) from the small diameter end of the shaft, and the bending deflection (mm) at the distance L (mm). ) Then, the distance between the fulcrums is a (mm), the load is b (kg), the amount of bending deflection is c (mm), and from these values, the EI value [kgf · mm ² ] at the distance L (mm) is calculated by the following formula. Asked.

EI value = (1/48) × (b · a ³ / c)
Then, a measuring step for measuring the bending rigidity EI _L (mm) at a predetermined position on the shaft, and the position where the shaft is in contact with the lower support jig is moved by a predetermined length to the large diameter side to increase the distance L, Obtain the bending displacement group (L, EI _L ) obtained by the repetition process of repeating the measurement process and the measurement process and the repetition process. Next, a bending stiffness group consisting of a distance L (mm) for each 50 mm in a region from 370 mm to 770 mm from the narrow-diameter end portion and a bending stiffness EI _L (× 10 ⁶ kgf · mm ² ) at the position of the distance L ( L, EI _L ) is (x, y), and (x, y) is linearly regressed to the following formula (A) by the least square method, and then the square of the correlation coefficient of the following formula (A) R ₁ ² Was 0.9994 (see FIG. 10).
y = −a ₁ x + b ₁ (A)
<Measurement of outer diameter>
The outer diameter at a shaft distance L = 350 to 800 mm was measured at intervals of 25 mm using a micrometer (see FIG. 11).

<Attaching the golf club head and grip>
A commercially available titanium golf club head for driver (volume: 440 cm ³ , mass: 203 g, loft angle: 9.5 °) was attached to the small diameter end portion with an epoxy resin adhesive on the golf club shaft of the example. Further, the end of the shaft with a large diameter was cut by 70 mm, and a commercially available rubber grip was attached to the shaft using a double-sided tape to produce a golf club of the example.

<Evaluation of hit ball>
The golf club of the example was hit with a golf ball five times using a golf trial hitting robot “SHOTROBO-IV” manufactured by Miyamae Co., Ltd., and measurement such as flight distance measurement was performed using “TRACKMAN” manufactured by ISG. The measured results are shown in Table 1. In Table 1, the average value of the rotation axis is defined as 0 ° for the flying ball direction, positive (+) for the right direction (slice) of the rotation axis, and negative (-) for the left direction (hook) of the rotation axis. The total value was calculated by adding the values measured in 10 hits, and the total was calculated by dividing the total by the number of hits (5 times).

A mandrel 12 (made of iron) having the shape shown in FIG. 6 was prepared. This mandrel 12 has an overall length L35, and its outer diameter gradually increases linearly from its small diameter end P31 to the position (switching point) P32 of the length L31. Similarly, the mandrel 12 has a length L32 from P32. From the position P33 to the position P34 having the length L33, the outer diameter is gradually increased linearly. And from the switching point P34 to the large diameter end P35 of length L34, the outer diameter consists of an iron cylinder which is constant. Specific outer diameters, lengths, and taper degrees at the respective portions of the mandrel 12 according to this comparative example are as follows.

  The outer diameter of the narrow end P31 is 4.15 m, the outer diameter of the switching point P32 is 5.90 mm, the outer diameter of the switching point P33 is 7.35 mm, the outer diameter of the switching point P34 is 13.50 mm, and from this switching point P34 The outer diameter up to the large diameter end P35 is the same, and the outer diameter is 13.50 mm. The length L31 from the small diameter end P31 to the switching point P32 is 200 mm, the length L32 from the switching point P32 to the switching point P33 is 100 mm, the length L33 from the switching point P33 to the switching point P34 is 700 mm, and from the switching point P34 The length L34 to the large diameter end P35 is 500 mm. The overall length L35 of the mandrel 12 is 1500 mm.

  Further, the taper degree from the small diameter end P31 to the switching point P32 is 8.75 / 1000, the taper degree from the switching point P32 to the switching point P33 is 14.50 / 1000, and the taper degree from the switching point P33 to the switching point P34. Is 8.79 / 1000.

  Except that this mandrel 12 was used, a shaft was produced in the same manner as in the example, and each evaluation was performed. The evaluation results are shown in FIGS.

  When the mandrel 12 is used, the taper degree gradually decreases gradually as shown in FIG. 11 in the region from 370 mm to 770 mm from the narrow diameter end of the obtained golf club shaft. In Patent Document 1 and Patent Document 3, the same tapered mandrel as in Comparative Example 1 is used, and it is estimated that the same result is obtained.

  The weight of the golf club shaft of Comparative Example 1 is 59.4 g, and the twist angle of the shaft (fixed at a position of 1035 mm from the narrow shaft end and 138.5 kgf from the small shaft end to 50 mm from the small shaft end). The angle at which the shaft was twisted when a torque of mm was applied) was 3.8 degrees. Using the golf club shaft of Comparative Example 1, a golf club was produced and evaluated in the same manner as in the Example. The evaluation results are shown in Table 1.

A mandrel 13 (made of iron) having the shape shown in FIG. 8 was prepared. The mandrel 13 has an overall length L47, and its outer diameter gradually increases linearly from the small diameter end P41 to the position (switching point) P42 of the length L41. Similarly, the mandrel 13 has a length L42 of P42. The outer diameter increases linearly gradually from position P43, from P43 to position P44 of length L43, from P44 to position P45 of length L44, and from P45 to position P46 of length L45. And from the switching point P46 to the large diameter end P47 of length L46, the outer diameter consists of an iron cylinder which is constant. Specific outer diameters, lengths, and taper degrees at the respective portions of the mandrel 13 according to this comparative example are as follows.

  The outer diameter of the narrow end P41 is 4.20 m, the outer diameter of the switching point P42 is 5.80 mm, the outer diameter of the switching point P43 is 7.30 mm, the outer diameter of the switching point P44 is 10.75 mm, and the outside of the switching point P45. The diameter is 12.50 mm, the outer diameter of the switching point P46 is 13.50 mm, the same outer diameter from the switching point P46 to the large diameter end P47, and the outer diameter is 13.50 mm. The length L41 from the small diameter end P41 to the switching point P42 is 200 mm, the length L42 from the switching point P42 to the switching point P43 is 100 mm, the length L43 from the switching point P43 to the switching point P44 is 330 mm, from the switching point P44. The length L44 from the switching point P45 to the switching point P46 is 220 mm, the length L45 from the switching point P45 to the switching point P46 is 230 mm, and the length L46 from the switching point P46 to the large diameter end P47 is 420 mm. The overall length L47 of the mandrel 13 is 1500 mm.

  Further, the taper degree from the narrow end P41 to the switching point P42 is 8.00 / 1000, the taper degree from the switching point P42 to the switching point P43 is 15.00 / 1000, and the taper degree from the switching point P43 to the switching point P44. Is 10.45 / 1000, the degree of taper from the switching point P44 to the switching point P45 is 7.95 / 1000, and the degree of taper from the switching point P45 to the switching point P46 is 4.35 / 1000.

  Except that this mandrel 13 was used, a shaft was produced in the same manner as in the example, and each evaluation was performed. The evaluation results are shown in FIGS.

When the mandrel 13 is used, the taper degree gradually decreases in three stages as shown in FIG. 11 in the region from 370 mm to 770 mm from the narrow diameter end of the obtained golf club shaft. After linear regression of the bending stiffness distribution in this region, the square R ₁ ² of the correlation coefficient of the linear approximation formula was calculated to be 0.9975.

  The weight of the golf club shaft of Comparative Example 2 is 59.1 g, and the twist angle of the shaft (fixed at a position of 1035 mm from the shaft small diameter end and 138.5 kgf at a position from the shaft small diameter end to the shaft small diameter end to 50 mm) The angle at which the shaft was twisted when a torque of mm was applied) was 3.7 degrees. Using the golf club shaft of Comparative Example 2, a golf club was produced and evaluated in the same manner as in the Example. The evaluation results are shown in Table 1.

表１の通り、実施例におけるゴルフクラブ用シャフトを用いたゴルフクラブでは、比較例に対してヘッドスピードが速くなると同時にバックスピン量も抑えることが出来、平均した飛距離も大きい結果となった。比較例においては、ヘッドスピードが実施例に対して遅く、バックスピン量も多いことから、平均飛距離を損失する結果となった。

As shown in Table 1, in the golf clubs using the golf club shafts in the examples, the head speed was increased and the backspin amount was simultaneously suppressed as compared with the comparative example, and the average flight distance was large. In the comparative example, the head speed was slower than in the example and the backspin amount was large, resulting in a loss of the average flight distance.

  As described above, in the golf club shaft according to the embodiment, the head spin rate can be increased and the backspin amount can be decreased at the same time, so that an increase in the average flight distance can be expected.

Claims (2)

A method for producing a golf club shaft comprising a prepreg formed by impregnating a reinforcing fiber with a resin and wound around a mandrel,
Bending the distance of each 50mm from 370mm from the small diameter end of the golf club shaft in the region of 770 mm L (mm), Naru Kara flexural rigidity EI _L and ^{(× 10 6 kgf · mm 2} ) at the position of the distance L When the stiffness group (L, EI _L ) is (x, y) and the (x, y) is linearly regressed to the following formula (A) by the least square method, the square of the correlation coefficient of the following formula (A) R ₁ ² is 0.999 or more,
y = -a ₁ x + b ₁ Formula (A)
The taper of the golf club shaft in a region of 370 mm to 770 mm from the narrow end portion of the golf club shaft gradually decreases from at least three steps from the narrow end portion side,
The mandrel in which the taper degree gradually decreases over a plurality of stages so that the taper in the region of 370 mm to 770 mm from the narrow end of the golf club shaft to be molded gradually decreases over at least three stages from the narrow end side. Mold using
A method for producing a shaft for a golf club .   The golf club shaft manufacturing method according to claim 1, wherein the fiber reinforced resin is a carbon fiber reinforced resin.

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