JP5244528B2 - Golf club shaft and golf club - Google Patents

Description

  The present invention relates to a golf club shaft and a golf club.

  So-called steel shafts and carbon shafts are known as golf club shafts. The material of the carbon shaft is CFRP (carbon fiber reinforced plastic).

  Many of the carbon shafts are manufactured by a so-called sheet winding method. In the sheet winding method, a prepreg sheet including fibers and a matrix resin is used. In this manufacturing method, a sheet made of a prepreg is wound around a metal mandrel (core body), the matrix resin is then cured by heating, and the mandrel is pulled out after this curing. By this manufacturing method, a shaft formed by winding and curing a prepreg sheet is formed.

  At least a part of the mandrel is provided with a taper that becomes thinner toward the tip (tip) side. This taper enables the mandrel to be pulled out.

  The inner surface of the shaft is formed by the mandrel. The outer diameter of the mandrel is equal to the inner diameter of the shaft. The mandrel determines the inner diameter of the shaft.

  Japanese Patent Application Laid-Open No. 7-213654 discloses a shaft in which a taper is provided on the inner surface of the shaft and the taper angle is changed. The same outer diameter portion is provided on the outer surface of the tip portion of the shaft. Further, the inner surface of the shaft is provided with a first taper portion located closest to the tip side and a second taper portion adjacent thereto. The taper angle of the first taper portion is larger than the taper angle of the second taper portion. Japanese Patent Laid-Open No. 7-213654 discloses a shaft suitable for sharing with all iron counts.

Japanese Patent Laying-Open No. 2005-245736 discloses a shaft in which a grip side end of an outer diameter straight portion located at a tip portion is located between a first taper change point and a second taper change point of the shaft inner diameter.
Japanese Patent Laid-Open No. 7-213654 Japanese Patent Laid-Open No. 2005-245736

  Japanese Patent Application Laid-Open No. 7-213654 aims at shifting a kick point in an iron set without changing a shaft outer diameter. In Japanese Patent Laid-Open No. 7-213654, improvement in strength is not considered. In Japanese Patent Application Laid-Open No. 7-213654, since the taper angle of the first taper portion is larger than the taper angle of the second taper portion, the shaft becomes thin at the boundary between the first taper portion and the second taper portion. Cheap. When the change point of the taper angle is thin, the strength tends to decrease.

  In the shaft of Japanese Patent Application Laid-Open No. 2005-245736, the change in the thickness of the shaft tends to be large between the first taper change point and the second taper change point. Due to this large thickness change, stress concentration tends to occur in a thin portion. Large thickness changes can lead to a reduction in shaft strength.

  An object of the present invention is to provide a golf club shaft having excellent strength at the tip.

  The shaft of the present invention is formed by winding and curing a prepreg sheet including a matrix resin and fibers. The shaft outer surface has a first outer surface portion located closest to the chip side and a second outer surface portion adjacent to the first outer surface portion with the axial position G1 as a boundary. The shaft inner surface has a first inner surface portion located closest to the chip side and a second inner surface portion adjacent to the first inner surface portion with the axial position N1 as a boundary. The diameter of the first outer surface portion is constant. The diameter of the second outer surface portion is made smaller toward the chip side. The diameter of the first inner surface portion is constant or smaller toward the chip side. The diameter of the second inner surface portion is made smaller toward the chip side. The taper rate T1 of the first inner surface portion is smaller than the taper rate T2 of the second inner surface portion. The axial position G1 is located closer to the chip than the axial position N1.

  Preferably, the axial distance between the axial position G1 and the axial position N1 is 5 mm or more. Preferably, the taper ratio T1 is 15/1000 or less.

  A golf club according to the present invention includes the golf club shaft, a head, and a grip.

  When the same outer diameter portion is provided at the shaft tip portion, stress concentration at the shaft tip portion is alleviated. The shaft of the present invention is excellent in strength at the tip.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings. In the present application, the “axial direction” is the direction of the central axis of the shaft and coincides with the longitudinal direction of the shaft.

  FIG. 1 is an overall view of a golf club 2 according to an embodiment of the present invention. The golf club 2 has a head 4, a shaft 6, and a grip 8. The head 4 is attached to the tip portion (tip portion) of the shaft 6. The grip 8 is attached to the butt portion (rear end portion) of the shaft 6.

  The head 4 and the grip 8 attached to the shaft 6 are not limited. Examples of the head 4 include a wood type golf club head, an iron type golf club head, and a putter head.

  The shaft 6 is a tubular body. The shaft 6 has a tip (front end) Tp and a butt (rear end) Bt. The head 4 is attached to the tip including the chip Tp. In the golf club 2, the chip Tp is located inside the shaft hole of the head 4. In the golf club 2, the bat Bt is located inside the shaft insertion hole of the grip 8.

  As shown in FIG. 1, the outer surface of the shaft 6 has a tapered surface. The outer diameter of the tapered surface decreases as it approaches the shaft tip Tp.

  The shaft 6 is a so-called carbon shaft. The shaft 6 is formed by curing a prepreg sheet. In this prepreg sheet, the fibers are substantially oriented in one direction. Thus, the prepreg in which the fibers are substantially oriented in one direction is also referred to as a UD prepreg. “UD” is an abbreviation for unidirection. This UD prepreg is preferably used for the shaft according to the present invention. This prepreg sheet has fibers and a matrix resin. Typically, this fiber is carbon fiber. Typically, this matrix resin is a thermosetting resin.

  The shaft 6 is formed by winding and curing a prepreg sheet including a matrix resin and fibers. The shaft 6 is manufactured by a so-called sheet winding manufacturing method. In the prepreg state, the matrix resin is in a semi-cured state. The shaft 6 is formed by winding and curing a prepreg sheet. This curing is to cure the semi-cured matrix resin. This curing is achieved by heating. The manufacturing process of the shaft 6 includes a heating process. By this heating step, the matrix resin of the prepreg sheet is cured.

  A shaft is configured by combining a plurality of sheets. The type, arrangement, combination, etc. of the sheet are not limited. A plurality of sheets are wound around a mandrel (core metal), the wound body is cured by heating, and then the mandrel is pulled out to manufacture a shaft.

  In the manufacture of the shaft 6, sheets cut into predetermined dimensions are sequentially wound around a mandrel. By adjusting the sheet type, fiber orientation, sheet size, axial sheet arrangement, radial sheet arrangement (winding order), etc., a shaft having desired characteristics can be obtained.

  The sheet is cured after being wound into a layer. The shaft 6 has a straight layer and a bias layer. The straight layer is a layer in which the fiber orientation direction is substantially parallel to the shaft axis direction. Due to errors in winding, etc., the fiber orientation direction is usually not completely parallel to the shaft axis direction. In the present application, the straight layer has an angle Af formed by the fiber orientation direction and the shaft axis direction of more than −10 degrees and less than +10 degrees. That is, in the present application, the absolute value of the angle Af of the straight layer is 0 degree or more and less than 10 degrees. The straight layer has a high correlation with the bending rigidity and bending strength of the shaft.

  The bias layer is provided for the purpose of increasing the torsional rigidity and torsional strength of the shaft. The bias layer is composed of a sheet set in which fiber orientation directions are inclined in opposite directions. The bias layer includes a layer having the angle Af of −80 degrees to −10 degrees and a layer having the angle Af of 10 degrees to 80 degrees. That is, the absolute value α of the angle Af of the bias layer is 10 degrees or more and 80 degrees or less. From the viewpoint of torsional rigidity and torsional strength, the absolute value α should be close to 45 degrees. Therefore, the lower limit value of the absolute value α is preferably 25 degrees or more, and more preferably 35 degrees or more. The upper limit value of the absolute value α is preferably 65 degrees or less, and more preferably 55 degrees or less.

  Layers other than the straight layer and the bias layer may be provided. For example, a hoop layer may be provided. In the hoop layer, the fiber orientation direction is substantially perpendicular to the shaft axis. The hoop layer is provided to increase the crushing rigidity and crushing strength of the shaft. The crushing rigidity is the rigidity against a force that crushes the shaft inward in the radial direction. The crushing strength is strength against a force that crushes the shaft toward the inside in the radial direction. The crushing strength can also be related to the bending strength. Crushing deformation can occur in conjunction with bending deformation. In particular, this linkage is large in a light-weight shaft with a thin wall thickness. The bending strength can be improved by improving the crushing strength. The absolute value α of the angle Af in the hoop layer is more than 80 degrees and not more than 90 degrees.

  The shaft 6 may include a partial sheet provided in a part in the shaft axial direction in addition to a full length sheet provided over the entire length in the shaft axial direction. The partial sheet can partially reinforce the shaft. The partial sheet can partially increase the bending rigidity or torsional rigidity of the shaft. The partial sheet can change the rigidity distribution of the shaft. The design flexibility is increased by the partial sheet.

  FIG. 2 is an enlarged cross-sectional view of the tip portion of the shaft 6. FIG. 3 is a view showing a mandrel md used for manufacturing the shaft 6. In FIG. 3, a part (including the tip) of the mandrel md is shown.

  As shown in FIG. 2, the shaft 6 has an outer surface 6a and an inner surface 6b. The cross-sectional shape of the shaft outer surface 6a is circular. The cross-sectional shape of the shaft inner surface 6b is circular. The diameter of the shaft inner surface 6b (shaft inner diameter) is determined by the outer diameter of the mandrel md. The diameter of the shaft outer surface 6a (shaft outer diameter) is determined by the outer diameter of the mandrel md and the thickness of the shaft.

  As described above, the mandrel md is pulled out during shaft manufacture. From the viewpoint of enabling the mandrel md to be pulled out, the taper rate of the shaft inner surface 6b is zero or plus in the entire region of the shaft inner surface 6b. The definition of the taper rate will be described later.

  The shaft outer surface 6a has a first outer surface portion a1 located closest to the tip Tp and a second outer surface portion a2 adjacent to the first outer surface portion a1. The boundary position between the first outer surface portion a1 and the second outer surface portion a2 is the axial position G1. The axial position G1 is the position of the end point on the butt Bt side of the first outer surface portion a1. The first outer surface portion a1 is a portion from the tip Tp to the axial position G1. The taper rate of the first outer surface part a1 is constant. The taper rate of the second outer surface portion a2 is constant.

  The shaft inner surface 6b has a first inner surface portion b1 positioned closest to the tip Tp and a second inner surface portion b2 adjacent to the first inner surface portion b1. The boundary position between the first inner surface portion b1 and the second inner surface portion b2 is the axial position N1. The first inner surface portion b1 is a portion from the tip Tp to the axial position N1. The taper rate of the first inner surface portion b1 is constant. The taper rate of the second inner surface part b2 is constant.

  Furthermore, the shaft inner surface 6b has a third inner surface portion b3 adjacent to the second inner surface portion b2. The boundary position between the second inner surface portion b2 and the third inner surface portion b3 is the axial position N2. The second inner surface portion b2 is a portion from the axial position N1 to the axial position N2. The taper rate of the third inner surface portion b3 is constant. Note that the third inner surface portion b3 may not exist. That is, the second inner surface portion b2 may reach the butt Bt of the shaft 6. The shape of the shaft inner surface 6b on the butt Bt side with respect to the second inner surface portion b2 is not limited as long as it has zero or a positive taper rate.

  The diameter s1 of the first outer surface portion a1 is constant. The first outer surface part a1 is the outer surface of the part 10 having the same outer diameter. The taper ratio R1 of the first outer surface portion a1 is zero.

  A portion of the shaft 6 having a constant outer diameter is referred to as a portion having the same outer diameter. In the present embodiment, the same outer diameter portion 10 is provided at the tip of the shaft 6. Usually, the inner diameter of the shaft hole of the head 4 is constant. The portion 10 having the same outer diameter at the tip is easily bonded to the shaft hole of the head 4.

  In addition, the outer diameter identical part 10 may be provided in positions other than a front-end | tip part. For example, the same outer diameter portion 10 may be provided at the rear end portion of the shaft 6. It is preferable that the same outer diameter portion other than the front end portion is provided only at the rear end portion. A grip is attached to the rear end of the shaft. Due to the same outer diameter at the rear end of the shaft, the compatibility between the shaft and the grip can be improved. From the viewpoint of compatibility, the axial length Lbt of the rear end portion having the same outer diameter is preferably 100 mm or more, more preferably 150 mm or more, and more preferably 200 mm or more. In light of the bending characteristics of the shaft, the axial length Lbt is preferably equal to or less than 400 mm, more preferably equal to or less than 300 mm, and even more preferably equal to or less than 250 mm. From the viewpoint of bending characteristics and strength of the shaft, it is preferable that the same outer diameter portion is not provided except for the front end portion and the rear end portion.

  The second outer surface part a2 has a taper. The diameter s2 of the second outer surface portion a2 is made smaller toward the chip Tp side. That is, the taper rate of the second outer surface portion a2 is positive.

  In addition, the 3rd outer surface part which has a taper rate different from the 2nd outer surface part a2 may be provided in the butt Bt side rather than the 2nd outer surface part a2. The taper ratio of the third outer surface portion may be zero, a positive value, or a negative value. Furthermore, another outer surface portion having a taper rate different from that of the third outer surface portion may be provided on the butt Bt side with respect to the third outer surface portion. The shape of the shaft outer surface 6a on the butt Bt side with respect to the second outer surface portion a2 is not limited.

  The diameter n1 of the first inner surface portion b1 is made smaller toward the chip Tp side. That is, the taper rate T1 of the first inner surface portion b1 is positive.

  The diameter n1 of the first inner surface part b1 may be constant. That is, the taper rate T1 of the first inner surface portion b1 may be zero. In other words, the first inner surface portion b1 may be a portion having the same inner diameter.

  From the viewpoint of pulling out the mandrel md in the shaft manufacturing process, it is preferable that the diameter of the first inner surface portion b1 is made smaller toward the tip Tp side.

  The diameter n2 of the second inner surface portion b2 is made smaller toward the chip Tp side. That is, the taper rate T2 of the second inner surface portion b2 is positive.

  The diameter n3 of the third inner surface portion b3 is made smaller toward the chip Tp side. That is, the taper rate T3 of the third inner surface portion b3 is positive. The taper rate T3 may be zero. The third inner surface part b3 may be omitted.

 Another inner surface portion having a taper rate different from that of the third inner surface portion b3 may be provided on the butt Bt side with respect to the third inner surface portion b3.

  The taper rate T1 of the first inner surface part b1 is smaller than the taper rate T2 of the second inner surface part b2. That is, T1 <T2.

  The taper rate T3 of the third inner surface part b3 is smaller than the taper rate T2 of the second inner surface part b2. That is, T3 <T2.

  As described above, the first inner surface portion b1 may be a portion having the same inner diameter. The part with the same inner diameter may be provided at a position other than the tip part. For example, the same inner diameter portion may be provided at the rear end portion of the shaft 6. It is preferable that the same inner diameter portion other than the front end portion is provided only at the rear end portion. When the same outer diameter portion is provided at the rear end of the shaft, the same inner diameter portion is provided inside the same outer diameter portion, so that the thickness is constant and the durability of the shaft can be improved. In addition, when the same outer diameter portion is provided at the rear end portion of the shaft, the shaft can be reduced in weight by the same inner diameter portion at the rear end portion of the shaft. From this viewpoint, the axial length Lbn of the same inner diameter portion of the rear end portion is preferably 100 mm or more, more preferably 150 mm or more, and more preferably 200 mm or more. From the viewpoint of facilitating extraction of the mandrel md in the shaft manufacturing process, the axial length Lbn is preferably 400 mm or less, more preferably 300 mm or less, and more preferably 250 mm or less. From the viewpoint of facilitating the extraction of the mandrel and improving productivity, it is preferable that the same inner diameter portion does not exist on the butt Bt side with respect to the axial position N1. In other words, in all the sections on the butt Bt side with respect to the axial position N1, it is preferable that the inner diameter is made smaller toward the tip Tp.

[Taper rate]
The taper rate in the present application is defined as follows. The diameter at the point A is Da (mm), the diameter at the point B located on the butt Bt side from the point A is Db (mm), and the axial distance between the point A and the point B is Ls ( mm), the taper rate Ts between the point A and the point B is as follows.
Ts = (Db−Da) / Ls

  When the diameter decreases toward the tip Tp, the taper rate is positive. When the diameter increases toward the tip Tp side, the taper rate is negative.

  The shape of the shaft inner surface 6b is equal to the outer surface shape of the mandrel md. In FIG. 3, the position of the tip Tp on the shaft 6 is indicated by the symbol Tp1. FIG. 3 also shows an axial position N1 and an axial position N2. On the outer surface of the mandrel md, the taper ratio of the section from the position Tp1 to the axial position N1 is T1. On the outer surface of the mandrel md, the taper ratio of the section from the axial position N1 to the axial position N2 is T2. On the outer surface of the mandrel md, the taper ratio of the section on the butt Bt side with respect to the axial position N2 is T3.

  As shown in FIG. 2, the axial position G1 is located closer to the chip Tp than the axial position N1. In this case, the thickness change near the axial position G1 and the axial position N1 tends to be small. When the thickness change is small, the stress concentration is relaxed.

  In FIG. 2, what is indicated by a double-headed arrow P1 is the axial distance between the axial position G1 and the axial position N1. From the viewpoint of suppressing the thickness change, the axial distance P1 is preferably 5 mm or more, more preferably 10 mm or more, more preferably 15 mm or more, and more preferably 20 mm or more. If the axial distance P1 is too long, the length of the same outer diameter portion 10 may be restricted. Further, when the axial distance P1 is too long, a thick portion increases at the tip end of the shaft, and the shaft weight may be excessive. If the axial distance P1 is too long, the shaft tip may become excessively hard. From these viewpoints, the axial distance P1 is preferably 40 mm or less, more preferably 30 mm or less, and more preferably 25 mm or less.

  As long as it is zero or plus, the taper rate T1 of the first inner surface portion b1 is not limited. When the taper ratio T1 is excessive, the thickness of the same outer diameter portion 10 in the vicinity of the axial position G1 tends to be small. From this viewpoint, the taper ratio T1 is preferably 15/1000 or less, more preferably 13/1000 or less, more preferably 10/1000 or less, and more preferably 8/1000 or less. From the viewpoint of facilitating the extraction of the mandrel md at the time of manufacturing the shaft, the taper ratio T1 is preferably 1/1000 or more, more preferably 3/1000 or more, and more preferably 5/1000 or more.

  As long as the relationship of T1 <T2 is satisfied, the taper rate T2 of the second inner surface portion b2 is not limited. From the viewpoint of alleviating stress concentration at the axial position N1, the taper rate T2 is preferably 30/1000 or less, more preferably 28/1000 or less, and more preferably 25/1000 or less.

  As long as it is zero or plus, the taper rate T3 of the third inner surface portion b3 is not limited. From the viewpoint of facilitating extraction of the mandrel md, the taper ratio T3 is set to 0 or more, preferably exceeds 0, and more preferably 1/1000 or more.

Preferably, the axial distance P1 (mm) satisfies the following relational expression. However, s1 (mm) is the diameter of the 1st outer surface part a1, and T1 and T2 are as above-mentioned.
P1> s1 × {T2 / (T1 + T2)}
That is, the axial distance P1 is preferably larger than “s1 × {T2 / (T1 + T2)}”. In this case, the thickness change is suppressed and the stress concentration is easily relaxed. Therefore, in this case, the strength of the tip can be improved.

  In the golf club according to the present invention, the head is attached to the tip of the shaft. The head has a shaft hole and a hosel end surface. The tip of the shaft is inserted into the shaft hole and bonded. Stress tends to concentrate on the end face of the hosel. From the viewpoint of alleviating the stress concentration at the axial position N1 and the axial position G1, a golf club in which the hosel end surface is located closer to the chip Tp than the axial position G1 is preferable.

  The axial length L1 of the first outer surface portion a1 (the same outer diameter portion 10) is not limited. By inserting the same outer diameter portion 10 into the shaft hole having a constant inner diameter, the adhesive force between the shaft hole and the same outer diameter portion 10 can be improved. From this viewpoint, the length L1 is preferably equal to or longer than the length of the shaft hole. From the viewpoint of the adhesion area, the length L1 is preferably 40 mm or more, and more preferably 50 mm or more. When the length L1 is too long, the same outer diameter portion 10 tends to be thin in the vicinity of the axial position G1. In this respect, the length L1 is preferably equal to or less than 200 mm, more preferably equal to or less than 175 mm, and still more preferably equal to or less than 150 mm.

  The taper ratio of the shaft outer surface 6a in the region closer to the butt Bt than the first outer surface portion a1 is R2. The taper rate R2 is not limited. Considering the taper ratio of the shaft inner surface 6b, the rigidity distribution of the shaft, etc., the taper ratio R2 is preferably 1/1000 or more and 30/1000 or less. The taper ratio R2 may not be constant. That is, the taper rate R2 may be changed.

  The shaft length L2 (see FIG. 1) is not limited. From the viewpoint of adapting to the length of the shortest club (for example, short iron or putter), the shaft length L2 is preferably 762 mm or more, more preferably 787 mm or more, and more preferably 813 mm or more. From the viewpoint of adapting to the length of the longest club (for example, a driver), the shaft length L2 is preferably 1219 mm or less, more preferably 1194 mm or less, and more preferably 1168 mm or less.

  When the grip outer diameter is too thin, the grip is easy to loosen and the hitting direction can be lowered. From this viewpoint, the shaft outer diameter Dt of the butt Bt is preferably 14.5 mm or more, more preferably 14.6 mm or more, and more preferably 14.7 mm or more.

  If the grip outer diameter is too thick, it is difficult to perform a wrist turn, and the head speed tends to decrease. In this respect, the shaft outer diameter Dt is preferably 16.3 mm or less, more preferably 16.1 mm or less, and even more preferably 16.0 mm or less.

  The axial length L3 from the tip Tp to the axial position N1 is not limited. From the viewpoint of setting the length L1 of the first outer surface portion a1 within a preferable range, the length L3 is preferably 55 mm or more, more preferably 60 mm or more, and more preferably 65 mm or more. If the length L3 is excessive, the thick part increases, the shaft tip becomes excessively hard, and the rigidity distribution of the shaft is restricted. From this viewpoint, the length L3 is preferably 240 mm or less, more preferably 230 mm or less, and more preferably 220 mm or less.

  The axial length L4 from the axial position N1 to the axial position N2 is not limited. When the axial position N1 and the axial position N2 are close, the taper change points are close to each other, and stress concentration is likely to occur. From the viewpoint of relaxing the stress concentration, the length L4 is preferably 50 mm or more, more preferably 60 mm or more, and more preferably 70 mm or more. When the length L4 is excessively long, the shaft 6 tends to be thin at the axial position N1 or the axial position N2. In this respect, the length L4 is preferably equal to or less than 150 mm, more preferably equal to or less than 140 mm, and still more preferably equal to or less than 130 mm.

  The maximum value t1 of the shaft thickness is not limited. Due to the taper rate of the mandrel md and the presence of the same outer diameter portion 10, the thickness at the tip Tp is often the maximum value t1. Therefore, when the maximum value t1 is small, the strength of the shaft tip tends to decrease. In this respect, the maximum value t1 is preferably 1.5 mm or more, more preferably 1.8 mm or more, and more preferably 2.0 mm or more. When the maximum value t1 is excessively large, the tip portion of the mandrel md may be excessively thinned. When the tip of the mandrel md is too thin, workability when the prepreg sheet is wound around the mandrel md is deteriorated. When the maximum value t1 is excessively large, the mass of the shaft on the tip Tp side becomes excessively large, and the degree of freedom in designing the club tends to be reduced. In this respect, the maximum value t1 is preferably 4.0 mm or less, more preferably 3.8 mm or less, and more preferably 3.5 mm or less.

  The minimum value t2 of the shaft thickness is not limited. From the viewpoint of shaft strength, the maximum value t1 is preferably 0.5 mm or more, more preferably 0.6 mm or more, and more preferably 0.7 mm or more. From the viewpoint of suppressing an excessive shaft weight, the minimum value t2 is preferably 1.5 mm or less, more preferably 1.4 mm or less, and more preferably 1.3 mm or less.

  The shaft thickness t3 at the axial position N1 is not limited. In light of shaft strength, the thickness t3 is preferably equal to or greater than 1.2 mm, more preferably equal to or greater than 1.3 mm, and still more preferably equal to or greater than 1.5 mm. In light of suppressing the shaft weight, the thickness t3 is preferably equal to or less than 3.0 mm, more preferably equal to or less than 2.8 mm, and even more preferably equal to or less than 2.5 mm.

  From the viewpoint of shaft rigidity and shaft strength, the shaft weight (g) is preferably 35 g or more, more preferably 38 g or more, and more preferably 40 g or more. From the viewpoint of increasing the head speed, the shaft weight (g) is preferably 70 g or less, more preferably 67 g or less, and more preferably 65 g or less.

  The diameter s1 of the first outer surface portion a1 (the same outer diameter portion 10) is not limited. When the bending rigidity is excessively small, the strength is likely to decrease. From the viewpoint of increasing the bending moment by increasing the cross-sectional second moment, the diameter s1 is preferably 8.5 mm or more, more preferably 8.7 mm or more, and more preferably 9.0 mm or more. In light of shaft weight and club balance, the diameter s1 is preferably 11.0 mm or less, more preferably 10.7 mm or less, and even more preferably 10.5 mm or less.

  The material of the prepreg sheet is not limited. Examples of the matrix resin include thermosetting resins and thermoplastic resins. Examples of the thermosetting resin include epoxy resins, unsaturated polyester resins, phenol resins, melamine resins, urea resins, diallyl phthalate resins, polyurethane resins, polyimide resins, silicon resins, and the like. As thermoplastic resins, polyamide resins, saturated polyester resins, polycarbonate resins, ABS resins, polyvinyl chloride resins, polyacetal resins, polystyrene resins, polyethylene resins, polyvinyl acetate resins, AS resins (acrylonitrile styrene) Resin), methacrylic resin, polypropylene resin, fluororesin and the like. From the viewpoint of strength and rigidity, a thermosetting resin is preferable, and an epoxy resin is more preferable.

  The fiber used for the fiber reinforced resin is preferably a carbon fiber from the viewpoint of low specific gravity and high elastic modulus and strength. In addition to carbon fibers, fibers that are generally used as high-performance reinforcing fibers are used. For example, graphite fiber, aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, glass fiber and the like can be used.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
In producing the shaft of Example 1, first, a prepreg sheet before cutting and a mandrel md shown in FIG. 5 were prepared.

  The dimensions are described in the mandrel md shown in FIG. The unit of this dimension is mm. The position 150 mm from the mandrel tip corresponds to the axial position N1 of the shaft. The position 250 mm from the mandrel tip corresponds to the axial position N2 of the shaft. The position 1100 mm from the mandrel tip corresponds to the axial position N3 of the shaft. The tip diameter of the mandrel md was 4.8 mm. The outer diameter of the mandrel md at the axial position N1 was 6.0 mm. The outer diameter of the mandrel md at the axial position N2 was 7.5 mm. The outer diameter of the mandrel md at the axial position N3 was 14.0 mm. In the section from the mandrel tip to the axial position N1, the taper rate was 8/1000. In the section from the axial position N1 to the axial position N2, the taper rate was 15/1000.

  Using this mandrel md, a shaft was produced according to the following steps.

(1) Cutting process In the cutting process, the prepreg sheet was cut into a predetermined shape. Cutting was done by a cutting machine or manually. By this cutting process, the cut prepreg sheet shown in FIG. 4 was obtained. FIG. 4 shows the dimensions of the cut sheet. The unit of this dimension is mm.

  The trade name “TR350C-125S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the first sheet (sheet St1). The product name “HRX350C-075S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the second and third sheets (bias sheets St2, St3). The trade name “MR350C-100S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the fourth sheet (sheet St4). The trade name “TR350C-150S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the fifth sheet (sheet St5). The trade name “MR350C-150S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the sixth sheet (sheet St6). The trade name “MR350C-150S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the seventh sheet (sheet St7). The trade name “TR350C-100S” manufactured by Mitsubishi Rayon Co., Ltd. was used for the eighth and ninth sheets (tip sheets St8, St9).

  FIG. 4 shows the fiber orientation angle. The sheet described as “0 °” constitutes the straight layer. Sheets described as “−45 °” and “+ 45 °” constitute the bias layer. These orientation angles are angles with respect to the shaft axis direction. In the layer made of the sheet St2 and the layer made of the sheet St3, the fiber orientation directions are inclined in opposite directions.

(2) Bonding process In the bonding process, the bias layer sheets were bonded to each other. That is, the sheet St2 and the sheet St3 were bonded together to produce a bonded body.

(3) Winding Step In the winding step, a plurality of cut sheets were sequentially wound around the mandrel md to produce a wound body. As shown in FIG. 5, the winding was performed such that the position Tp1 of the tip Tp of the shaft was 70 mm from the tip of the mandrel md. Regarding the bias layer, the bonded body was wound.

  FIG. 4 also shows the winding order in the winding step. In the winding process, winding was performed in order from the upper sheet in FIG. FIG. 4 also shows the arrangement of the sheets in the axial direction. For example, the sheet St1 was wound around the tip of the shaft. For example, the sheet St4 is wound around the rear end portion of the shaft.

(4) Tape wrapping step In the tape wrapping step, a wrapping tape was wound around the outer peripheral surface of the wound body. The wrapping tape was wound with tension applied. As the wrapping tape, a tape made of polyethylene or polyethylene terephthalate was used.

(5) Curing process In the curing process, the wound body after tape wrapping was heated. This heating cured the matrix resin.

(6) Mandrel md extraction step and wrapping tape removal step For the wound body after curing, a mandrel extraction step and a wrapping tape removal step were performed, and a cured laminate was obtained.

(7) Both-ends cut process In this process, the both ends of the hardening laminated body were cut. By this cutting, the end surfaces at both ends of the shaft were made flat. In FIG. 5, the description of the portions corresponding to the cut ends is omitted. The actually used prepreg sheet was made longer than the length L2.

(8) Polishing process In this process, the surface of the cured laminate was polished. By polishing, the irregularities as traces of the wrapping tape disappeared, and the surface was smoothed. In the polishing step, tip end polishing and overall polishing were performed. After the tip portion was polished, the entire surface was polished. A first outer surface portion a1 (the same outer diameter portion) was formed by the tip portion polishing. The diameter (tip diameter) of the first outer surface part a1 was set to 9.0 mm by the tip polishing. The length L1 of the portion having the same outer diameter was adjusted by the tip polishing. Through this polishing step, the shaft according to Example 1 was obtained.

  In the completed shaft, the shaft length is 1168 mm, the shaft weight is 52 g, the distance L3 from the tip Tp to the axial position N1 is 80 mm, and the distance L4 from the axial position N1 to the axial position N2 Was 100 mm, the taper rate T1 of the first inner surface part b1 was 8/1000, and the taper rate T2 of the second inner surface part b2 was 15/1000.

  The obtained shaft was subjected to a three-point bending fracture test, a cantilever bending test, and an endurance test. The specifications and evaluation results of Example 1 are shown in Table 1 below.

[Example 2 and Comparative Examples 1 to 4]
The shafts of Example 2 and Comparative Examples 1 to 4 were obtained in the same manner as Example 1 except that the length L1 of the first outer surface part a1 was changed by the tip part polishing. The specifications and evaluation results for each example are shown in Table 1 below.

  Table 1 shows the aforementioned distance P1. When the axial position G1 is closer to the chip Tp than the axial position N1, the distance P1 is a positive value. When the axial position G1 is closer to the butt Bt than the axial position N1, the distance P1 is a negative value.

  The evaluation method was as follows.

[Three-point bending fracture strength]
SG type three point bending test was adopted. This is a test established by the Product Safety Association. FIG. 6 shows a measuring method of the SG type three-point bending test. As shown in FIG. 6, while the shaft 6 is supported from below at the two support points e1 and e2, a load F is applied from above to below at the load point e3. The position of the load point e3 is a position that bisects the support point e1 and the support point e2. The load point e3 is a measurement point.

  The measurement points were T point and A point. T point is a point of chip Tp90mm. A point is a point of 175 mm from the chip Tp. The value (peak value) of the load F when the shaft 6 was broken was measured. When the T point was measured, the span S was set to 150 mm. When the point A was measured, the span S was set to 300 mm. The measurement results are shown in Table 1 below.

[Cantilever bending strength]
The shaft was inserted and bonded into the shaft hole of the head. A portion from the tip Tp to 40 mm was inserted into the shaft hole. The product name “Srixon ZR-700” manufactured by SRI Sports was used as the head.

  In this cantilever bending strength test, first, the head was fixed with a jig while the shaft was substantially horizontal. Next, an indenter was applied to a point separated from the hosel end face by 150 mm, and a load was applied downward in the vertical direction by this indenter. The load was gradually increased and the load at the moment when the shaft broke was measured. The measurement results are shown in Table 1 below.

[An endurance test]
A golf club was produced by attaching a head and a grip to the shaft. As the head, a trade name “Srixon ZR-700” (loft 9.5 degrees) manufactured by SRI Sports was used. This golf club was mounted on a swing robot manufactured by Miyamae, and a golf ball was repeatedly hit at a head speed of 52 m / s. The upper limit of the number of hits was 10,000. As a golf ball, the trade name “DDH Tour Special” manufactured by SRI Sports Co., Ltd. was used. The hitting point was a position 20 mm away from the face center toward the heel side. The presence or absence of destruction was confirmed after every 500 hits. The number of hits when the shaft breakage is confirmed is shown in Table 1 below. If no destruction occurs even after 10000 hits, “10000” is displayed in Table 1 below.

  As shown in the table, the examples have higher evaluation than the comparative examples. From these evaluation results, the superiority of the present invention is clear.

  The present invention can be applied to any golf club shaft such as a wood-type golf club shaft, an iron-type golf club shaft, and a putter shaft.

FIG. 1 is an overall view of a golf club equipped with a shaft according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a tip portion of the shaft of FIG. FIG. 3 is a view showing a mandrel used for manufacturing the shaft of FIG. 1. FIG. 4 is a development view showing the prepreg configurations of Examples 1 and 2 and Comparative Examples 1 to 4. FIG. 5 is a diagram showing the mandrels used in the production of Examples 1 to 2 and Comparative Examples 1 to 4. FIG. 6 is a diagram for explaining a test method of a three-point bending fracture strength.

Explanation of symbols

2 ... Golf club 4 ... Golf club head 6 ... Shaft for golf club 8 ... Grip Tp ... Tip (shaft tip)
Bt ... Bat (shaft rear end)
md: Mandrel St1, St2, St3, St4, St5, St6, St7, St8 and St9 ... Cut prepreg sheets

Claims (3)

A prepreg sheet comprising a matrix resin and fibers is wound and cured,
The shaft outer surface has a first outer surface portion located closest to the chip side, and a second outer surface portion adjacent to the first outer surface portion with the axial position G1 as a boundary,
The shaft inner surface has a first inner surface portion located closest to the chip side, and a second inner surface portion adjacent to the first inner surface portion with the axial position N1 as a boundary,
A diameter of the first outer surface portion is constant;
The diameter of the second outer surface portion is made smaller toward the chip side,
The diameter of the first inner surface portion is constant or is made smaller toward the chip side,
The diameter of the second inner surface portion is made smaller toward the chip side,
The taper rate T1 of the first inner surface portion is smaller than the taper rate T2 of the second inner surface portion,
The axial position G1 is located closer to the chip than the axial position N1 ,
The first outer surface portion having a constant diameter is formed by tip portion polishing,
A golf club shaft in which the length L1 of the first outer surface portion is adjusted by tip end polishing . Ri der axial distance 5mm or 30mm or less between the axial position G1 and the axial position N1,
The tapered rate T1 is Ri der 15/1000 below,
The diameter s1 of the first outer diameter portion is 8.7 mm or more and 11.0 mm or less,
The length L1 of the first outer surface portion, a golf club shaft of claim 1 Ru der least 70mm below 55 mm. With head, shaft and grip,
The shaft is formed by winding and curing a prepreg sheet including a matrix resin and fibers,
The shaft outer surface has a first outer surface portion located closest to the chip side, and a second outer surface portion adjacent to the first outer surface portion with the axial position G1 as a boundary,
The shaft inner surface has a first inner surface portion located closest to the chip side, and a second inner surface portion adjacent to the first inner surface portion with the axial position N1 as a boundary,
A diameter of the first outer surface portion is constant;
The diameter of the second outer surface portion is made smaller toward the chip side,
The diameter of the first inner surface portion is constant or is made smaller toward the chip side,
The diameter of the second inner surface portion is made smaller toward the chip side,
The taper rate T1 of the first inner surface portion is smaller than the taper rate T2 of the second inner surface portion,
The axial position G1 is located closer to the chip than the axial position N1 ,
The first outer surface portion having a constant diameter is formed by tip portion polishing,
A golf club in which the length L1 of the first outer surface portion is adjusted by tip end polishing .

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