Golf club shafts and golf club shaft fitting method

Abstract

To provide a lineup of shafts for golf club in which a difference of a sense of use such as the feeling of swing and gripping of grip being felt before and after replacement of the shafts for golf club can be reduced, and provide a shaft group for golf club and a fitting method of the shafts for golf club, and also provide the lineup of the shafts for golf club that can reduce a labor of balance adjustment when the club is assembled, the shaft group for golf club and the fitting method of the shafts for golf club.SOLUTION: A lineup of shafts for golf club has multiple weight bands grouped by the weight of the shafts 1, and has multiple shafts 1 different in the flex for each of the weight bands. In at least one weight band, an average value of the weight difference of each shaft 1 is 1.10 g or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention 、 The present invention relates to a group of golf club shafts and a fitting method for golf club shafts. [Background technology]

[0002] Usually, a specific model of golf club shaft is supplied as a lineup of golf club shafts, with multiple golf club shafts having multiple flexes for each weight range according to the type of player. The lineup of golf club shafts is then manufactured and sold to golf club manufacturers and individuals who reshaft golf clubs. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "2020 SPRING / SUMMER MITSUBISHI CHEMICAL GRAPHITE SHAFTS", Mitsubishi Chemical Corporation, April 2020, p.9 Summary of the Invention [Problem to be solved by the invention]

[0004] The ease of movement of the human body changes depending on the season. Specifically, the body tends to become stiff in autumn and winter, and flexible in spring and summer. When playing golf, swing speeds can differ between spring and summer and autumn and winter. For this reason, some golf players use golf club shafts with appropriate flex for their golf clubs depending on the season. For example, of golf club shafts with roughly the same weight, such players use golf club shafts with softer flex in autumn and winter, and golf club shafts with harder flex in spring and summer. However, the current lineup of golf club shafts has the following problems: For example, if there is a large difference in weight between golf club shafts having different flex in the same weight range, even if a golf club shaft in the same weight range is replaced, there will be a difference in swing feel before and after the replacement. Also, when manufacturing multiple golf club shafts with different flexibilities in the same weight range, a method of changing the flex may be adopted by changing the number of prepregs wound around a mandrel during shaft manufacturing. Increasing the number of prepregs increases the natural frequency of the shaft and makes the flex harder. Reducing the number of prepregs decreases the natural frequency of the shaft and makes the flex softer. However, this method results in a large weight difference between golf club shafts with different flexibilities even in the same weight range, resulting in a difference in swing feel before and after replacing the golf club shaft. Also, for example, if there is a large difference in the balance point (balance point will be described later) of golf club shafts in the same weight range, the club balance will change when assembled into a club. In that case, the feeling of the weight of the head will change, causing the swing timing to shift. In such a case, in order to equalize the club balance, it is necessary to adjust the balance for each golf club shaft, for example by attaching lead to the tip of the golf club shaft, which is time-consuming. In addition, there are cases where one golf club shaft in the same lineup is used for a driver and the other for a fairway wood. In such cases, a golf club shaft with a weight range one step heavier than that of a driver and the same flex is cut and used as a fairway wood. On the other hand, generally, golf club shafts with different weight ranges have different thicknesses at the gripping part even if they have the same flex. In such cases, if a golf club shaft is selected from the same lineup of golf club shafts, there is a problem that the gripping feel before and after the replacement will differ.

[0005] The present invention has been made to solve the above problems, and is capable of reducing the difference in the feeling of use, such as the swing feeling and grip feeling, felt before and after replacing the shaft of a golf club. R An object of the present invention is to provide a group of golf club shafts and a fitting method for golf club shafts. In addition, the present invention can reduce the effort required for balance adjustment when assembling a club. R An object of the present invention is to provide a group of golf club shafts and a fitting method for golf club shafts. [Means for solving the problem]

[0017] ( 1 In order to solve the above problems, the golf club shaft group according to the present invention is a golf club shaft group composed of a plurality of golf club shafts, and the difference in first bending rigidity EI value on the tip end side between the golf club shaft having the maximum flex and the golf club shaft having the minimum flex is 0.25×10 6 kgf mm 2 Above 1.00 x 10 6 kgf mm 2 The difference in the second bending stiffness EI value on the butt end side is 1.50 × 10 6 kgf mm 2 Above 3.00 x 10 6 kgf mm 2 the difference in the second bending stiffness EI value is 3.50 to 7.00 times the difference in the first bending stiffness EI value, the weight difference between the golf club shaft having the largest weight and the golf club shaft having the smallest weight is 0.00 g or more and less than 5.50 g, and the difference in natural frequency between the golf club shaft having the largest natural frequency and the golf club shaft having the smallest natural frequency is 30 cpm or more.

[0018] ( 2In order to solve the above problems, the golf club shaft group according to the present invention is a golf club shaft group composed of a plurality of golf club shafts, wherein a difference in a first bending stiffness EI value on a tip end side between the golf club shaft having the maximum flex and the golf club shaft having the minimum flex is 0.25×106 kgf mm 2 Above 1.00 x 10 6 kgf mm 2 The difference in the second bending stiffness EI value on the butt end side is 1.50 × 10 6 kgf mm 2 Above 3.00 x 10 6 kgf mm 2 the difference in the second bending rigidity EI value is 3.50 to 7.00 times the difference in the first bending rigidity EI value, when each of the golf club shafts is compared at a position 150 mm from the butt end of the golf club shaft, the difference between the maximum outer diameter and the minimum outer diameter is 0.00 mm or more and less than 0.20 mm, and the difference in natural frequency between the golf club shaft having the maximum natural frequency and the golf club shaft having the minimum natural frequency is 20 cpm or more.

[0019] ( 3 )the above( 1 )or( 2 In at least four golf club shafts having different flexibilities, the length of the golf club shaft having the smallest flexibilities is L1, the distance from the tip end to the center of gravity is D1, the length of the golf club shaft having the largest flexibilities is L2, and the distance from the tip end to the center of gravity is D2, the lengths L1, L2 and the distances D1, D2 are as follows: |(D1 / L1)×100-(D2 / L2)×100|<1 may be satisfied.

[0020] ( 4 )the above( 1 )from( 3In any one of the above, the golf club shaft may be made of fiber reinforced resin.

[0021] ( 5 In order to solve the above problems, the fitting method for a golf club shaft according to the present invention is 1 )from( 4 The golf club shaft is selected from any one of the golf club shaft groups. Effect of the Invention

[0022] the above of According to the golf club shaft group and the golf club shaft fitting method, the difference in the feeling of use such as swing feeling and grip feeling before and after replacing the golf club shaft can be reduced. Also, the time and effort required for balance adjustment when assembling the club can be reduced. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a schematic diagram of a shaft included in the lineup of shafts according to each embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the positions of the centers of gravity (balance points) of shafts included in the lineup of shafts according to each embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing the shape of a mandrel used in manufacturing a shaft included in the lineup of shafts according to each embodiment. [Figure 4] FIG. 2 is a pattern diagram showing the shape of a prepreg used in the manufacture of a shaft included in the lineup of shafts according to the first embodiment. [Diagram 5] FIG. 11 is a pattern diagram showing the shape of a prepreg used in the manufacture of another shaft included in the lineup of shafts according to the first embodiment. [Figure 6] FIG. 11 is a pattern diagram showing the shape of a prepreg used in the manufacture of another shaft included in the lineup of shafts according to the first embodiment. [Figure 7]FIG. 11 is a schematic diagram of a testing device for measuring the EI value of the shaft according to the second and third embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] [First embodiment] A first embodiment of the present invention will now be described with reference to Figures 1 to 4. A golf club shaft may also be simply called a shaft.

[0025] (shaft) FIG. 1 is a schematic diagram of a shaft 1. As shown in FIG. 1, a golf club shaft 1 according to this embodiment (corresponding to a golf club shaft in the claims) is formed in a cylindrical shape. The shaft 1 is formed so that the outer diameter of a surface perpendicular to the axial direction gradually increases from one end (the right end in FIG. 1) to the other end (the left end in FIG. 1). The shaft 1 may also be formed so that the outer diameter is the same from a diameter change part 1a in the middle of the axial direction to the other end. Hereinafter, the end with the smaller outer diameter of both ends of the shaft 1 is referred to as the tip 2. The end of the shaft 1 on the tip 2 side is referred to as the tip end 2a. The end with the larger outer diameter is referred to as the butt 3. The end of the shaft 1 on the butt 3 side is referred to as the butt end 3a. The butt 3 is a part that is attached to a grip and held, and for example, refers to the part of the shaft 1 from the butt end 3a to the diameter change part 1a.

[0026] (Balance point) FIG. 2 is a schematic diagram showing the position of the center of gravity (balance point) of the shaft 1. As shown in FIG. The shaft 1 is formed so that the balance point is, for example, 40% to 60%. Here, the balance point is the distance L from the tip end 2a of the shaft 1 to the center of gravity of the shaft 1, as shown in FIG. G The total length of the shaft L S It is expressed as a ratio to the Balance point(%)=(L G / L S ) x 100 The balance point is a value that allows the position of the center of gravity to be quantitatively determined.

[0027] The shaft 1 may be made of metal, or may be made of fiber-reinforced resin, which is a cured or solidified prepreg, or both may be used in combination. From the viewpoint of easiness in designing the physical properties of the shaft 1, such as the distribution of stiffness and the distribution of torsional stiffness, it is preferable that the shaft 1 is made of fiber-reinforced resin. A prepreg is a sheet-shaped resin-impregnated reinforced fiber substrate obtained by impregnating a resin composition (matrix resin composition) with a reinforced fiber substrate made of a sheet-shaped fiber material containing a plurality of reinforcing fibers. After cutting the prepreg into a predetermined shape, the prepreg is deformed into a shape close to the shape of a molded product, and is cured or solidified by heating and cooling to obtain a molded fiber-reinforced resin. The thickness of the prepreg is, for example, 30 μm to 250 μm. Carbon fiber and / or glass fiber can be adopted as the reinforcing fiber of the fiber material constituting the prepreg. It is preferable to constitute the fiber material by 40% or more of carbon fiber in terms of manifesting physical properties such as strength and stiffness. The fiber material may be constituted by only carbon fiber or only glass fiber. However, fiber reinforced resins using only carbon fiber as reinforcing fibers are preferable because they have better physical properties such as strength and rigidity than fiber reinforced resins using only glass fiber as reinforcing fibers. From this viewpoint, the proportion of carbon fiber reinforced resin in the fiber reinforced resin is preferably more than 50% with carbon fiber reinforced resin as the main material, more preferably 60% or more, even more preferably 80% or more, and particularly preferably 90% or more. Moreover, the proportion of carbon fiber reinforced resin is usually preferably 100% or less. It is more preferable that it is 100%. In the fiber reinforced resin, the ratio of fibers is preferably 60% or more, more preferably 70% or more, and preferably 75% or more, and is usually 90% or less, and preferably 85% or less. The proportion of carbon fibers in the reinforcing fibers is preferably 80% or more, more preferably 90% or more, and is usually 100% or less. The carbon fibers used in the prepreg have a diameter of, for example, 5 μm to 20 μm, and are preferably 5 μm or more, more preferably 6 μm or more, because they do not have too many defects, have a wide variety of physical properties, and are easily available. Also, they are preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and most preferably 8 μm or less. The most preferred diameter is about 7 μm.

[0028] The matrix resin used in the matrix resin composition used in the prepreg may be a thermosetting resin or a thermoplastic resin. Since the physical properties after molding are high, it is preferable to use a thermosetting resin. The thermosetting resin is not particularly limited, but an epoxy resin is usually used. As the epoxy resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, glycidylamine type epoxy resin, isocyanate-modified epoxy resin, or alicyclic epoxy resin can be used. These epoxy resins can be used from liquid to solid at room temperature. Furthermore, a single type of epoxy resin or a mixture of two or more types of epoxy resins can be used. The shaft 1 may be produced by any method, such as a sheet wrapping method, an internal pressure molding method, a filament winding method, etc. From the viewpoints of the diversity of shaft designs and ease of production, it is preferable to produce the shaft by the sheet wrapping method, in which multiple layers of prepreg are wrapped around a mandrel (core metal) and then heated and shaped.

[0029] (Shaft manufacturing method) The method for manufacturing the shaft 1 will now be described in detail, taking a sheet wrapping method as an example. FIG. 3 is a schematic diagram showing the shape of a mandrel used in manufacturing the shaft 1. As shown in FIG. An iron mandrel 10 having a shape shown in Fig. 3 is prepared. The mandrel 10 is formed in a cylindrical shape. The outer diameter of the mandrel 10 increases linearly from the small diameter end P1 to the switching point P2, and the outer diameter is constant from the switching point P2 to the large diameter end P3.

[0030] Fig. 4 is a pattern diagram showing the shape of the prepreg used in manufacturing shaft 1. The hatched areas in each pattern are shown for convenience of drawing and are areas where there is no prepreg, and the same is true for Figs. 5 and 6. The prepregs (patterns 1 to 8) cut into the shapes shown in FIG. 4 are wound around the mandrel 10 in order, and then a heat-shrinkable tape made of, for example, polypropylene is wound thereon at a predetermined pitch. In the following prepreg pattern drawings, the dimensions of each pattern are shown in mm without the unit of mm. The dashed arrows in each pattern indicate the orientation of the reinforcing fibers in the fiber material. The angle indicated by the dashed arrows indicates the angle of the orientation of the reinforcing fibers in the fiber material with respect to the axial direction of the mandrel 10. If there are no dashed arrows in a pattern, this indicates that the orientation of the reinforcing fibers in the fiber material is along the axial direction of the mandrel.

[0031] Patterns 2, 3, and 7 are made of prepregs that form straight layers (hereinafter simply referred to as "straight layers") in which the reinforcing fibers in the fiber material are oriented at a winding angle of 0° with respect to the axial direction of mandrel 10. Each of patterns 2, 3, and 7 is wound around a portion of mandrel 10 that corresponds to the end of shaft 1 on the tip 2 side. Pattern 1 is formed by overlapping two sheets of prepreg, one for forming a +45° angle layer and the other for forming a -45° angle layer, to form a bias layer (hereinafter simply referred to as "bias layer"). The +45° angle layer is an angle layer in which the reinforcing fibers in the fiber material are oriented at a winding angle of +45° with respect to the axial direction of the mandrel 10. The -45° angle layer is an angle layer in which the reinforcing fibers in the fiber material are oriented at a winding angle of -45° with respect to the axial direction of the mandrel 10. Pattern 1 is wrapped around the entire surface of the mandrel 10. The patterns 4 and 5 are prepregs that form straight layers. Each of the patterns 4 and 5 is a layer that extends over the entire length of the shaft 1. Pattern 6 is formed by stacking two prepregs: one prepreg forming a straight layer and the other prepreg forming a hoop layer (hereinafter simply referred to as the "hoop layer") in which the reinforcing fibers in the fiber material are oriented at a winding angle of 90° with respect to the axial direction of the mandrel 10. Pattern 6 is a layer that extends over the entire length of shaft 1. The pattern 8 is a prepreg that forms a straight layer. The pattern 8 is wound around a portion of the mandrel 8 that corresponds to the end of the shaft 1 on the tip 2 side. The pattern 8 is formed in a triangular shape. The prepregs used in manufacturing the shaft 1 may be only prepregs using a thermoplastic resin as the matrix resin, may be only prepregs using a thermosetting resin as the matrix resin, or may be both prepregs using a thermoplastic resin as the matrix resin and prepregs using a thermosetting resin as the matrix resin. When both prepregs using a thermoplastic resin as the matrix resin and prepregs using a thermosetting resin as the matrix resin are used, the respective prepregs may be arranged as desired. The materials of the prepregs of the patterns 1 to 8 shown in FIG.

[0032] [Table 1]

[0033] The prepregs of patterns 1 to 8 are sequentially wound around mandrel 10, and then wrapped with heat shrink tape. The resulting structure is placed in a heating furnace and heated, for example at 135°C for 2 hours. As a result, the prepregs of patterns 1 to 8 are hardened or softened to be integrated. Thereafter, the prepregs of patterns 1 to 8 are naturally cooled to room temperature to harden or solidify, thereby forming a fiber reinforced resin layer. Thereafter, the formed fiber reinforced resin layer is removed from mandrel 10, thereby manufacturing shaft 1. Thereafter, the heat shrink tape is peeled off shaft 1, and the surface of shaft 1 is polished so that the natural frequency of shaft 1 becomes a predetermined value.

[0034] Conventionally, when manufacturing shafts with different flexibilities, the same diameter mandrel was used, but the number of layers of prepreg or the thickness of the prepreg was changed. These methods result in large differences in the outer diameter and weight of shafts with different flexibilities.

[0035] In this embodiment, mandrels of different thicknesses are used according to the flex of the shaft 1. Mandrels of the same thickness may be used for shafts 1 of different flexes. The elastic modulus of the prepreg may also be selected according to the flex. In order to adjust the flex of the shaft 1, the use of mandrels of different thicknesses and the selection of the elastic modulus of the prepreg may be combined, or mandrels of different thicknesses may be used alone, or only the selection of the elastic modulus of the prepreg may be performed. When it is desired to increase the flex, a thin mandrel is used to increase the number of prepregs or to make the prepregs thicker. When it is desired to decrease the flex, a relatively thick mandrel is used to decrease the number of prepregs or to make the prepregs thinner. Furthermore, the elastic modulus of the prepreg is adjusted to adjust the flex of each shaft 1 to a specified value. This method makes it possible to reduce the difference in outer diameter of the shaft 1 between different flexes compared to the conventional method. In addition, by adjusting the elastic modulus of the prepreg, the difference in weight of the shaft 1 between different flexes can be reduced compared to the conventional case.

[0036] If mandrels of different thicknesses are used to match the flex of shaft 1, multiple mandrels are required for one series, increasing the manufacturing cost of shaft 1. Furthermore, it is necessary to increase the storage space for the mandrels in the factory. If the storage space increases, the manufacturing space for shaft 1 in the factory decreases. If the manufacturing space for shaft 1 decreases, it becomes difficult to expand the facilities. Furthermore, in order to adjust the elastic modulus of the prepreg, multiple types of prepreg are required for one series, and the inventory of prepreg increases, which further increases the manufacturing cost of the shaft 1. For these reasons, a lineup of golf club shafts or a group of shafts like those in this embodiment have not been manufactured.

[0037] The surface of the shaft 1 may or may not be decorated after polishing. Whether or not the surface of the shaft 1 of this embodiment is decorated can be appropriately selected. When decorating the shaft 1 of this embodiment, the surface of the shaft 1 is painted, for example, by ironing or spray painting, or a transfer foil containing a metal foil is transferred to form a shiny appearance.

[0038] (Golf club shaft lineup) The above-mentioned shaft 1 is manufactured in multiple types with different weights and flexes. Here, flex is an index that indicates the stiffness of the shaft. There are various methods for measuring flex, but for example, the flex is determined based on the vibration frequency of the shaft. The method for measuring the vibration frequency of the shaft will be described in detail later. Hereinafter, a group of shafts with multiple flexes for each weight range will be referred to as a lineup of shafts for golf clubs. "Lineup of shafts for golf clubs" may also be referred to simply as "lineup." A lineup is a collection of shafts that serves as a population from which a user can select a set of shafts that is suitable for him or her. The golf shafts that make up the lineup are preferably a combination of shafts from the same series (product name). In addition, the shafts that make up the lineup are preferably shafts with the same design and preferably have the same appearance.

[0039] The lineup has a plurality of weight bands grouped according to the weight of the shaft, and has a plurality of shafts with different flex for each weight band. The weight difference between the shaft with the smallest weight and the shaft with the largest weight is less than 5.50 g. A weight band is lighter than other weight bands means that the median weight of the shafts in one weight band is smaller than the median weight of the shafts in the other weight bands by 5.0 g or more. Different flex means that the natural frequency of the shafts differs by at least 10 cpm. The weight band may be single, or may have a weight band with a single flex. In this embodiment, the name of each weight band is defined by the tens digit of the median (g). That is, the weight bands in this embodiment are divided, for example, every 10 g. More specifically, the shaft weights are divided into the 40g weight range (40grm), the 50g weight range (50grm), the 60g weight range (60grm), the 70g weight range (70grm), and the 80g weight range (80grm). Preferably there are two or more weight bands, more preferably three or more, even more preferably four or more, and most preferably five or more. Usually there are ten or less, and preferably nine or less. The more weight bands there are, the more options the user has, which is preferable. Cases where the weight difference between the lightest and heaviest shafts exceeds 5.50 g are also included in the present invention, provided that there are four or more shafts within the range where the weight difference from one shaft to another is 5.50 g.

[0040] (Golf club shafts) An assembly made up of a plurality of shafts 1 in the same weight range is referred to as a "group of shafts for golf clubs." Hereinafter, the "group of shafts for golf clubs" may also be referred to simply as a "group of shafts." The shafts constituting the group of golf club shafts are preferably a combination of shafts from the same series (product name).Moreover, the shafts constituting the group of golf club shafts are preferably shafts of the same design, and preferably have the same appearance.

[0041] In at least one weight range in the lineup, the average value of the weight difference of the shaft 1 is 1.10 g or less. Here, the average value of the weight difference of the shaft 1 is the average value of the absolute value of the weight difference between the shafts 1 with adjacent flexes when the shafts 1 are arranged in one weight range in order of softness (smallest) of flex. More specifically, for example, a case where there are five types of shafts 1 with flexes R2, R, SR, S, and X in the 40 g weight range will be described. The average value of the weight difference of the shaft 1 in the 40 g weight range is the average value of the absolute value of the weight difference between the shafts 1 with flexes R2 and R, the absolute value of the weight difference between the shafts 1 with flexes R and SR, the absolute value of the weight difference between the shafts 1 with flexes SR and S, and the absolute value of the weight difference between the shafts 1 with flexes S and X. The average value of the weight difference of the shaft 1 is adjusted to 1.10 g or less by changing the outer diameter of the mandrel 10, the type of reinforcing fiber in the fiber material contained in the prepreg, or the content of the matrix resin composition. The average weight difference of the shaft 1 is preferably 1 g or less, more preferably 0.90 g or less, even more preferably 0.80 g or less, and particularly preferably 0.75 g or less. The average weight difference of the shaft 1 is preferably 0 g or more, and ideally 0 g. Weight is measured in grams to two decimal places using an electronic balance.

[0042] In at least one weight range, the length of the shaft 1 having the softest flex is defined as L1 (mm). The distance from the tip end 2a to the center of gravity is defined as D1 (mm). The length of the shaft 1 having the stiffest (largest) flex is defined as L2 (mm). The distance from the tip end 2a to the center of gravity is defined as D2 (mm). In this case, the lengths L1, L2 and the distances D1, D2 are defined as follows: |(D1 / L1)×100-(D2 / L2)×100|<1…(1) It satisfies. Formula (1) indicates that the absolute value of the difference in balance point between the shaft 1 having the minimum flex and the shaft 1 having the maximum flex is less than 1% point. The left side of formula (1) is 0 or more, and ideally, it is desirable that it is 0. In other words, the absolute value of the difference in balance point between the shaft 1 having the minimum flex and the shaft 1 having the maximum flex is 0% or more, and ideally, it is desirable that it is 0%. The percentage point is the difference between numerical values ​​when the numerical values ​​are expressed as a percentage. The balance point of the shaft 1 is adjusted to satisfy formula (1) by changing the elastic modulus of the fiber material, changing the content of the matrix resin, or adjusting the outer diameter of the mandrel 10. In at least one weight band, the absolute value of the difference between the maximum and minimum balance points of all shafts 1 included in that weight band may be less than 1 percentage point. The balance point is calculated by placing shaft 1 on a fulcrum with a pointed tip and visually determining the position at which the shaft axis becomes parallel. Such a lineup can be produced by changing the outer diameter of the mandrel 10, the type of reinforcing fiber contained in the prepreg, the content of the matrix resin composition, and the like.

[0043] Here, when the weight ranges are arranged in order from light to heavy, the difference in outer diameter between two shafts 1 having the same flex and provided for two adjacent weight ranges at a position 150 mm from the butt end 3a is 0.30 mm or less. 0.28 mm or less is more preferable, and 0.25 mm or less is even more preferable in terms of being less likely to cause discomfort. Moreover, it is desirable that the difference in outer diameter between a position 150 mm from the butt end 3a be 0 mm or more, and ideally 0 mm. The outer diameter is measured by a laser type length measuring sensor. Such a lineup can be produced by changing the outer diameter of the mandrel 10, the type of reinforcing fiber contained in the prepreg, the content of the matrix resin composition, and the like.

[0044] Shaft 1 in one lineup is for woods. Each weight range has at least three flexes.

[0045] Within one lineup, the outer diameter of shaft 1 at a position 150 mm from butt end 3a tends to become gradually thinner as the weight range becomes heavier, when compared at the same flex. Here, "the outer diameter becomes gradually thinner as the weight range becomes heavier" means that when the weight ranges are lined up in order from light to heavy, the outer diameter of the heavier weight range shaft at the same flex between adjacent weight ranges is thinner. Advanced players tend to have faster head speeds, so they often choose a heavier weight range. Usually, as the weight increases, the outer diameter of the shaft 1 becomes thicker. It is easier to use the wrist to hit the ball with a thinner outer diameter at a position 150 mm from the butt end 3a of the shaft 1. Therefore, a lineup in which the outer diameter gradually becomes thinner as the weight range increases makes it easy for beginners and advanced players to choose a shaft that is suitable for them.

[0046] As the weight range becomes heavier, the mandrel 10 is made thinner overall, and furthermore, the taper from the switching point P2 of the mandrel 10 toward the vicinity of the small diameter end P1 (corresponding to the tip end 2a of the shaft 1) becomes steeper. By using such a mandrel 10, it is possible to increase the weight of the shaft 1 by winding more prepreg on the tip 2 side without significantly changing the number of windings of the prepreg on the butt 3 side. Furthermore, because the outer diameter itself on the large diameter end P3 side of the mandrel 10 also becomes thinner, the outer diameter of the shaft 1 at a position 150 mm from the butt end 3a can be reduced as the weight range becomes heavier.

[0047] (Action and effect) Incidentally, until the end of the 19th century, wood was the mainstream material for golf club shafts, but in the early 20th century, steel shafts were developed. With wooden or steel shafts, there were often no shaft variations. In most cases, only one shaft1 was prepared for one type of head. Even if there were shaft variations, the shaft itself was heavy, and no consideration was given to standardizing the weight and stiffness indexes between shafts. In the second half of the 20th century, carbon shafts were developed, which are lighter than wood or steel shafts. This led to an increase in shaft variations and a demand for uniform weight and stiffness indexes across shafts. In recent years, as golf club heads and grips have become lighter, there has been interest in standardizing the weight of the shafts to make the swing feel of golf clubs uniform, and in standardizing the outer diameter of the shaft located inside the grip to make the feel of the golf club in hand uniform.

[0048] In the lineup of this embodiment, in at least one weight range, the average weight difference of the shafts 1 is 1.10 g or less. According to this configuration, in a weight range where the average weight difference of the shaft 1 is 1.10 g or less, it is possible to reduce the weight difference felt by the user when replacing the shaft 1. As a result, even if the shaft 1 is replaced, the difference in swing feel felt by the user before and after replacement can be reduced so long as the average weight difference of the shaft 1 is in a weight range of 1.10 g or less. In particular, when replacing the shaft 1 with a shaft 1 of adjacent flex in the same weight range, the difference in swing feel felt by the user before and after replacement can be reduced. Furthermore, clubs using shaft 1 in the lineup of this embodiment can be assembled with the same balance with less balance adjustment.

[0049] In this embodiment, among the shafts constituting the shaft group, the length of the shaft 1 with the minimum flex is L1 (mm). The distance from the tip end 2a of the shaft 1 to the center of gravity is D1 (mm). The length of the shaft 1 with the maximum flex is L2 (mm). The distance from the tip end 2a of the shaft 1 to the center of gravity is D2 (mm). In this case, the lengths L1 and L2 and the distances D1 and D2 satisfy the above formula (1). According to this configuration, when a golf club manufacturer or an individual user puts together a golf club and replaces the shaft 1 within the same weight range, it is possible to prevent the balance point from changing so greatly that the user feels uncomfortable. Furthermore, when using a lineup of shafts for normal golf clubs, it is necessary to adjust the balance of the golf club when assembling the golf club, for example by attaching lead to the tip of shaft 1, so that the club balance does not change significantly. However, if the shaft group satisfies formula (1), this becomes unnecessary. Therefore, the effort required for balance adjustment can be reduced.

[0050] In the lineup of this embodiment, when the weight ranges are arranged in order from light to heavy, the following conditions are met: Two shafts 1 having the same flex, each of which is provided for two adjacent weight ranges, have an outer diameter difference of 0.30 mm or less at a position 150 mm from the butt end 3a of each shaft 1. The same flex usually means that the difference in frequency is less than 10 cpm, preferably less than 9 cpm, and more preferably less than 8 cpm. The position 150 mm from the butt end 3a is a position that is generally held in the axial direction of the shaft 1 by both hands gripping the shaft 1. According to the above configuration, when replacing two shafts 1 having the same flex prepared for two adjacent weight bands, the difference in outer diameter felt by the user before and after the replacement can be suppressed. As a result, even if the shaft 1 is replaced between two shafts 1 having the same flex prepared for two adjacent weight bands, the difference in grip feeling felt by the user before and after the replacement can be reduced.

[0051] In the lineup of this embodiment, the following first to third requirements are satisfied in at least one weight band. The first requirement is that the weight difference of the shaft 1 is 1.10 g or less. The second requirement is that the above formula (1) is satisfied. The third requirement is that the difference in the outer diameter of the two shafts 1 having the same flex, which are prepared for two adjacent weight bands, at a position 150 mm from the butt end 3a of each shaft 1 is 0.25 mm or less. However, this is not limited to this, and it is sufficient to satisfy any one of the combination of the first and second requirements, the combination of the first and third requirements, the combination of the second and third requirements, and the combination of the first, second and third requirements. This configuration allows for an increased variety of lineups. In addition, since a combination of the first to third requirements that can be implemented can be selected depending on costs and facilities, it becomes possible to produce the lineup under a wider variety of conditions.

[0052] The shaft 1 in the lineup of this embodiment is made of fiber reinforced resin. According to this configuration, it is easier to design the physical properties of the shaft 1, such as the stiffness distribution and the torsional stiffness distribution, as compared to a case in which the shaft 1 is made of, for example, a metal material.

[0053] The shaft 1 in the lineup of this embodiment is for a wood. Since woods have longer shafts than other types of golf clubs, they are more susceptible to differences in shaft weight and flex than other types of golf clubs, which means that the weight and flex of the shaft of woods must be adjusted more precisely than other types of golf clubs. When the lineup is for wood, the effect of the present invention can be maximized.

[0054] Each weight range in the lineup of this embodiment has at least three flexes. When there is little variation in flex within the same weight range, the weight difference between the shafts with the smallest flex and the largest flex within the same weight range is small. In other words, the average value of the weight difference between the shafts tends to be small. However, as the variation in flex is small, the options available to players are limited. On the other hand, this configuration has a large variation in flex within the same weight range, making it possible to accommodate a variety of players. Furthermore, this configuration ensures options for flex when exchanging shafts 1 within the same weight range. This makes it possible to manufacture golf clubs by adjusting the flex of shaft 1 to suit the player's preferences.

[0055] The outer diameter at a position 150 mm from the butt end 3a of the shaft 1 in the lineup of this embodiment becomes gradually thinner as the weight range becomes heavier, when compared at the same flex. By the way, the more advanced a player is, the more they use their dominant hand to control their swing. If the thickness of the part of the shaft that is held by the dominant hand becomes thinner, such control becomes easier. In addition, since the heavier the shaft is, the more prepreg is wound in the shaft, the heavier the weight range becomes, and the thicker the shaft becomes, so this effect is often not achieved. According to the above configuration, as the weight range of the shaft 1 becomes heavier, the shaft 1 can be manufactured into a slimmer shape that is preferred by advanced players.

[0056] [Second embodiment] A second embodiment of the present invention will be described below. The same components as those in the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0057] (Golf club shaft lineup) The total length L of shaft 1 that makes up the lineup s For example, the length L of the longest shaft 1 in one lineup is 1168 mm. s and the total length L of the shortest shaft 1 s The difference between the total length L of shaft 1 and the total length L of shaft 2 is 26 mm or less. s It is preferable that the difference is 0 mm.

[0058] In each weight range, the multiple shafts 1 all have the same bending stiffness distribution. Specifically, the following points have been confirmed between the shaft 1 with the maximum flex and the shaft 1 with the minimum flex in each weight range. The difference in the first bending stiffness EI value on the tip end 2a side is usually 0.25×10 6 kgf mm 2 Above 0.30 x 10 6 kgf mm 2 More than 1.00×10 is preferable. 6 kgf mm 2 is less than or equal to 0.80 x 10 6 kgf mm 2 Less than 0.50×10 is preferable. 6 kgf mm 2 The first bending stiffness EI value is, for example, the bending stiffness EI value in the range of 170 mm to 270 mm from the tip end 2a. The difference in the second bending stiffness EI value on the butt end 3a side is usually 1.00×10 6 kgf mm 2 That's it, 1.25 x 10 6 kgf mm 2 More than 1.50×10 is preferable. 6 kgf mm 2 More preferably, 1.75×10 6 kgf mm2 More preferably, 2.00×10 6 kgf mm 2 More preferably, it is 4.00×10 6 kgf mm 2 Below, 3.50 x 10 6 kgf mm 2 Less than or equal to 3.00 x 10 is preferred 6 kgf mm 2 Less than or equal to 2.75×10 is preferable. 6 kgf mm 2 Less than 2.50×10 is more preferable. 6 kgf mm 2 More preferably, the second bending stiffness EI value is, for example, a bending stiffness EI value in a range of 870 mm or more and 970 mm or less from the tip end 2a. In each weight range, the difference in the second bending stiffness EI value is usually 2.50 times or more of the difference in the first bending stiffness EI value, preferably 3.00 times or more, more preferably 3.50 times or more, and even more preferably 4.00 times or more. Also, it is usually 9.00 times or less, preferably 8.00 times or less, more preferably 7.00 times or less, and more preferably 6.50 times or less.

[0059] Furthermore, when the bending stiffness distribution of shaft 1 of this embodiment is compared with that of a conventional shaft having the same overall length and classified into the same weight range and flex, it was confirmed that the bending stiffness EI value is smaller in the range of 300 mm to 500 mm from the tip end 2a and in the range of 800 mm to 900 mm from the tip end 2a.

[0060] In addition, in at least one weight range of the lineup, the weight difference between the shaft 1 having the maximum weight and the shaft 1 having the minimum weight is equal to or greater than 0.00 g and less than 5.50 g.

[0061] (Measurement of the EI value of the shaft) FIG. 7 is a schematic diagram of a test device used to measure the EI value of the shaft 1. The bending stiffness EI value of the shaft 1 was calculated by the method described in JP 2001-120696 A. First, a three-point bending test was performed on the shaft 1 to measure the amount of bending deflection at each point of the shaft 1, and the bending stiffness EI value was calculated. Specifically, as shown in FIG. 7, the shaft 1 was supported with a support distance of 300 mm, and the distance L from the tip end 2a of the shaft 1 was EI A load of 20 kg is applied at the position (mm) and the distance L EI The deflection (mm) at (mm) was calculated. The distance between the supports was a (mm), the load was b (kg), and the deflection was c (mm). From these values, the distance L was calculated using the following formula: EI EI value in (mm) [kgf mm 2 ] was requested. EI value = (1 / 48) × (b a 3 / c)

[0062] (Method of fitting golf club shafts) In the golf club shaft fitting method of the present embodiment, a shaft 1 suitable for a user is selected from the above-mentioned lineup. Hereinafter, the "golf club shaft fitting method" may also be simply referred to as the "fitting method".

[0063] (Action and effect) The lineup of the second embodiment described above includes each of the configurations of the first embodiment described above, and therefore provides the following operational effects while exhibiting the effects of the first embodiment described above.

[0064] In the lineup of this embodiment, the following conditions are satisfied in each weight range. The difference in the first bending rigidity EI value on the tip end 2a side between the shaft 1 having the maximum flex and the shaft 1 having the minimum flex is 0.25×10 6 kgf mm 2 Above 1.00 x 10 6 kgf mm 2 The difference in the second bending rigidity EI value on the butt end 3a side is 1.50×10 6 kgf mm 2 Above 3.00 x 10 6kgf mm 2 The difference in the second bending stiffness EI value is 3.50 times or more and 7.00 times or less than the difference in the first bending stiffness EI value. This configuration makes it possible to make the relationship between the bending stiffness EI value and the distance from the tip end similar for shafts 1 of the same weight range but different flex, thereby reducing the difference in swing feel felt by the user before and after replacement when replacing with a shaft of the same weight range but different flex.

[0065] In the lineup of this embodiment, at least one weight range satisfies the following condition: The weight difference between the shaft 1 having the largest weight and the shaft 1 having the smallest weight among the multiple shafts 1 is 0.00 g or more and less than 5.50 g. It is preferably 5.00 g or less, more preferably 4.50 g or less, and most preferably 4.00 g or less. According to this configuration, the weights of shafts 1 with different flexibilities can be made uniform within the same weight range. This reduces the difference in swing feel felt by the user before and after changing the flex within the same weight range.

[0066] In the lineup of this embodiment, the longest shaft 1 has a total length L s and the total length L of the shortest shaft 1 s The difference is less than 26 mm. According to this configuration, in one lineup, the total length L of the shaft 1 having different flex s As a result, even when the shaft 1 is cut before use, it is possible to prevent the balance point of the shaft 1 from changing significantly before and after cutting the shaft 1. The lineup of this embodiment may not include shafts 1 with a length of 26 mm or more. s and the total length L of the shortest shaft 1 s The difference is more preferably 20 mm or less, and most preferably 13 mm or less.

[0067] In the fitting method of this embodiment, the user selects the shaft 1 from the lineup described above. This allows the user to easily select from a number of shafts 1 with little difference in feel when using them, such as swing feel, by simply selecting a shaft 1 from a lineup without actually performing a swing or the like. Furthermore, when the shaft 1 satisfies the above formula (1) detailed in the first embodiment, it is easy to select a plurality of shafts 1 that require less effort to adjust the balance of the golf club.

[0068] [Third embodiment] Hereinafter, a third embodiment of the present invention will be described. The same components as those in the above-described embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0069] (Golf club shafts) The shaft group is made up of at least four or more shafts 1 having different flexibilities. The shafts 1 constituting the shaft group are made of fiber reinforced resin. The shafts 1 constituting the shaft group are for woods.

[0070] The following points have been confirmed regarding the shaft group: The weight difference between the shaft 1 having the largest weight and the shaft 1 having the smallest weight is 0.00 g or more and less than 5.50 g (first shaft group requirement). Ideally, this weight difference is desired to be 0.00 g. It is preferable that the shaft group does not include any shaft whose weight deviates by 5.50 g or more from the weight of the other shafts. More preferably, it does not include any shaft whose weight deviates by 5.00 g or more, even more preferably, it does not include any shaft whose weight deviates by 4.50 g or more, and most preferably, it does not include any shaft whose weight deviates by 4.00 g or more. In addition, the difference in natural frequency between the shaft 1 having the maximum natural frequency and the shaft 1 having the minimum natural frequency is 30 cpm or more (requirement for the second shaft group). This difference in natural frequency is 60 cpm or less, and ideally, it is desirable that it is 45 cpm or less.

[0071] The shaft group may include at least four shafts 1 that satisfy at least one of the first shaft group requirements and the second shaft group requirements described above.

[0072] In addition, in the shaft group, each shaft 1 is, like the shaft 1 of the same weight range in the lineup of the first embodiment described above, |(D1 / L1)×100-(D2 / L2)×100|<1…(1) It meets the following criteria.

[0073] (Method of fitting golf club shafts) In the fitting method of the present embodiment, a shaft 1 suitable for a user is selected from the group of shafts described above.

[0074] (Action and effect) The shaft group of this embodiment satisfies the following condition, as in the second embodiment described above. Between the shaft 1 having the maximum flex and the shaft 1 having the minimum flex, the difference in the first bending rigidity EI value on the tip end 2a side is 0.25×10 6 kgf mm 2 Above 1.00 x 10 6 kgf mm 2 The difference in the second bending rigidity EI value on the butt end 3a side is 1.50×10 6 kgf mm 2 Above 3.00 x 10 6 kgf mm 2 The difference in the second bending stiffness EI value is 3.50 times or more and 7.00 times or less than the difference in the first bending stiffness EI value. This configuration makes it possible to make the bending stiffness of shafts 1 with different flexural strengths uniform, thereby reducing the difference in swing feel felt by the user before and after changing the flex.

[0075] The shaft group of this embodiment satisfies the following conditions: The weight difference between the shaft 1 having the largest weight and the shaft 1 having the smallest weight is 0.00 g or more and less than 5.50 g. The difference in natural frequency between the shaft 1 having the largest natural frequency and the shaft 1 having the smallest natural frequency is 30 cpm or more. According to this configuration, it is possible to make the weight of the shaft 1 uniform within the shaft group while widening the range of flex. This allows the flex to be changed significantly without increasing the difference in swing feel felt by the user before and after replacing the shaft 1. Furthermore, a club using the shaft 1 of the shaft group of this embodiment can be assembled with the same balance with less balance adjustment.

[0076] In the shaft group of this embodiment, each shaft 1 is, like the shaft 1 of the same weight range in the lineup of the first embodiment described above, |(D1 / L1)×100-(D2 / L2)×100|<1…(1) It meets the following criteria. According to this configuration, when a golf club manufacturer or an individual user puts together a golf club and replaces shaft 1 from the shaft group, it is possible to prevent the balance point from changing so greatly that the user feels uncomfortable. Furthermore, when using a lineup of shafts for normal golf clubs, it is necessary to adjust the balance of the golf club when assembling the golf club, for example by attaching lead to the tip of shaft 1, so that the club balance does not change significantly. However, by satisfying formula (1), this becomes unnecessary. Therefore, the effort required for balance adjustment can be reduced.

[0077] The shaft 1 of the shaft group of this embodiment is made of fiber reinforced resin. According to this configuration, it is easier to design the physical properties of the shaft 1, such as the stiffness distribution and the torsional stiffness distribution, as compared to a case in which the shaft 1 is made of, for example, a metal material.

[0078] The shaft 1 of the shaft group of this embodiment is for a wood. Since woods have longer shafts than other types of golf clubs, they are more susceptible to differences in shaft weight and flex than other types of golf clubs, which means that the weight and flex of the shaft of woods must be adjusted more precisely than other types of golf clubs. The effect of the present invention can be maximized when shaft 1 of the shaft group is for a wood. In the present embodiment, the shaft 1 of the shaft group is for a wood, but the present invention is not limited to this. The shaft 1 may be for an iron, for example.

[0079] In the fitting method of this embodiment, the user selects the shaft 1 from the group of shafts described above. This allows the user to easily select from a number of shafts 1 with little difference in feel when using them, such as swing comfort, by simply selecting a shaft 1 from the shaft set without actually swinging, etc. Also, the time and effort required for balance adjustment when assembling a club can be reduced. Furthermore, when the shaft 1 satisfies the above formula (1) detailed in the first embodiment, it is easy to select a plurality of shafts 1 that require less effort to adjust the balance of the golf club.

[0080] In addition, a lineup can be created by combining multiple shaft sets described above.

[0081] [Fourth embodiment] Hereinafter, a fourth embodiment of the present invention will be described. The same components as those in the above-described embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0082] The following points have been confirmed for the shaft group. When comparing each shaft 1 at a position 150 mm from the butt end 3a, the difference between the maximum outer diameter and the minimum outer diameter is 0.00 mm or more and less than 0.20 mm (requirement for the third shaft group). Ideally, it is desirable for the difference between the maximum outer diameter and the minimum outer diameter to be 0.00 mm. In addition, the difference in natural frequency between the shaft 1 having the maximum natural frequency and the shaft 1 having the minimum natural frequency is 20 cpm or more (fourth shaft group requirement). This difference in natural frequency is 60 cpm or less, and ideally, it is desirable that it is 45 cpm or less.

[0083] The shaft group may include at least four shafts 1 that satisfy at least one of the above-mentioned third shaft group requirements and fourth shaft group requirements.

[0084] (Action and effect) In the shaft group of this embodiment, when comparing each shaft 1 at a position 150 mm from the butt end 3a, the difference between the maximum outer diameter and the minimum outer diameter is 0.00 mm or more and less than 0.20 mm. The difference in natural frequency between the shaft 1 having the maximum natural frequency and the shaft 1 having the minimum natural frequency is 20 cpm or more.

[0085] The position 150 mm from the butt end 3a is a position that is generally held in the axial direction of the shaft 1 by both hands gripping the shaft 1. This configuration allows the range of flex to be increased while keeping the thickness of the shafts held by the user consistent within the shaft group, thereby allowing a large change in flex without increasing the difference in grip feel felt by the user before and after replacing shaft 1.

[0086] In the fitting method of the present embodiment, shaft 1 is selected from the group of shafts described above. According to this configuration, multiple shafts 1 with little difference in feel when gripping the grip, etc. can be easily selected by the simple procedure of selecting a shaft 1 from a group of shafts without actually swinging the club, etc. Also, the effort of adjusting the balance when assembling the club can be reduced.

[0087] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible without departing from the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the attached claims.

[0088] In the above embodiment, the case where carbon fiber having excellent mechanical properties is used as the fiber material constituting the prepreg has been described, but the present invention is not limited to this. For example, the fiber material constituting the prepreg may be glass fiber, aramid fiber, silicon carbide fiber, alumina fiber, steel fiber, or the like.

[0089] In the above embodiment, the case where three straight layers (pattern 2 to 4) are formed on the bias layer (pattern 1) has been described, but the present invention is not limited to this. As long as the bias layer is formed on the innermost side in the radial direction, the number of hoop layers and straight layers, and the order of layers formed on the radial outer side of the bias layer can be changed as appropriate.

[0090] In the above embodiment, the shaft 1 in the lineup is for a wood, but the present invention is not limited to this. The shaft 1 may be for an iron, for example.

[0091] In addition, within the scope of the invention, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and it is also possible to combine the components and variations in each of the above-described embodiments as appropriate.

[0092] Example 1 The shaft 1 constituting the lineup of Example 1 was manufactured by the shaft manufacturing method described above. The lineup of Example 1 includes a total of 21 shafts 1 shown in Table 1. In Example 1, both unpainted shafts 1 and painted shafts 1 were manufactured, and a lineup was produced for each. Among the shafts 1 included in the lineup of Example 1, 40R was manufactured from a prepreg having a pattern shown in FIG. 4. 40S was manufactured from a prepreg of the type shown in Table 2 and a prepreg of the pattern shown in FIG. 5, and was manufactured in the same manner as 40R. 50R was manufactured from a prepreg of the type shown in Table 3 and a prepreg of the pattern shown in FIG. 6, and was manufactured in the same manner as 40R. Among the shafts 1 included in the lineup of Example 1, those other than 40R, 40S, and 50R were manufactured in the same manner as 40R, 40S, and 50R, except that the type and shape of the prepreg were changed.

[0093] [Table 2]

[0094] [Table 3]

[0095] Overall axial length of shaft 1 L S The outer diameter of the tip 2 was 1168 mm. The outer diameter of the tip 2 was 8.60 mm when the surface of the shaft 1 was painted. In the lineup of Example 1, the weight range of the shaft 1 is divided in 10g increments, ranging from the 40g range (40grm) to the 80g range (80grm). The multiple shafts 1 constituting the lineup are further classified by flex within each weight range. The flexes in the 40g range are R2, R, SR, S, and X. The flexes in the 50g range are R, SR, S, X, and TX. The flexes in the 60g range are R, SR, S, X, and TX. The flexes in the 70g range are S, X, and TX. The flexes in the 80g range are S, X, and TX. The flex, weight (g), frequency (cpm), outer diameter (mm) at a position 150 mm from the butt end 3a, torque, and balance point of each shaft 1 were evaluated, and the results are shown in Table 4. In addition, the bending rigidity EI value at each point of the shaft 1 was also evaluated.

[0096] Here, we will describe the methods for measuring the weight, outer diameter, total length, vibration frequency, torque, and balance point of shaft 1. Each parameter (total length, vibration frequency, torque, and balance point) was measured before painting. Each parameter (weight, outer diameter) was measured after painting. We will also describe the method for calculating the bending rigidity EI value of shaft 1. (1) Weight Weight was measured to two decimal places using a commercially available electronic balance (EK-300i, manufactured by A&D Co., Ltd.). (2) Outer diameter The outer diameter at a position 150 mm from the butt end 3a was measured by a laser type CCD length measuring sensor ZX-TG manufactured by Omron Corporation. (3) Total length The overall length was measured using a commercially available stainless steel ruler. (4) Frequency The vibration frequency was measured by the method described in JP-A-10-225541. That is, the vibration frequency was measured using a golf club timing harmonizer manufactured by Fujikura Rubber Co., Ltd. A weight with a mass of 196 g simulating a head was attached to the thin-diameter end of shaft 1, and fixed 180 mm from the thick-diameter end of shaft 1, to obtain the natural frequency of shaft 1. (5) Torque: The twist angle of the entire shaft 1 The torque was measured according to the method of measuring torque (the torsion angle of the entire shaft 1) described in Japanese Patent Application Laid-Open No. 5-337223. That is, the tip 2 and the butt 3 were each clamped in a chuck, and a torsional torque (1.36 N·m) was applied to the shaft 1 via each chuck to measure the torsion angle. (6) Balance point The balance point was measured by placing the shaft 1 on a fulcrum with a pointed tip and visually confirming that the shaft was balanced (the shaft axis was horizontal).

[0097] (7) EI value The bending deflection amount was measured at each point from 170 mm to 970 mm from the tip end 2a by the three-point bending test described in detail in the second embodiment, and the bending rigidity EI value at each point of the shaft 1 was calculated. A change point where the bending rigidity distribution changed was confirmed in all weight bands and all flexes. The change point was confirmed in the range of 300 mm to 400 mm from the tip end 2a. The bending rigidity EI value of the shaft 1 was approximately constant from a point 170 mm away from the tip end 2a toward the butt end 3a to the change point, and gradually increased linearly from the change point to a point 970 mm away from the tip end 2a toward the butt end 3a. The measurement results of the first bending rigidity EI value in the range of 170 mm to 270 mm from the tip end 2a and the second bending rigidity EI value in the range of 870 mm to 970 mm from the tip end 2a in each weight band will be described in detail below.

[0098] At 40g, the first bending stiffness EI value is 2.11×10 6 kgf mm 2 More than 2.74 x 10 6 kgf mm 2 The second bending stiffness EI value is 5.04 x 10 6 kgf mm 2 More than 7.53 x 10 6 kgf mm 2 The results were as follows. For example, at flex S, the first bending stiffness EI value is 2.39 x 10 6 kgf mm 2 More than 2.49 x 10 6 kgf mm 2 The second bending stiffness EI value is 6.20 x 10 6 kgf mm 2 More than 6.94 x 10 6 kgf mm 2 The results were as follows. Moreover, the difference in the second bending rigidity EI value was 3.90 times or more and 4.00 times or less the difference in the first bending rigidity EI value.

[0099] At the 50g level, the first bending stiffness EI value is 2.21 x 10 6 kgf mm 2 More than 3.17 x 10 6 kgf mm 2 The second bending stiffness EI value is 5.91 x 10 6 kgf mm 2 More than 9.13×10 6 kgf mm 2 The results were as follows. For example, at flex S, the first bending stiffness EI value is 2.63 x 10 6 kgf mm 2 More than 2.73 x 10 6 kgf mm 2 The second bending stiffness EI value is 6.65 x 10 6 kgf mm 2 More than 7.32 x 10 6 kgf mm 2 The results were as follows. Moreover, the difference in the second bending rigidity EI value was 3.30 times or more and 3.40 times or less the difference in the first bending rigidity EI value.

[0100] In the 60g range, the first bending stiffness EI value is 2.30 x 10 6 kgf mm 2 More than 3.09 x 10 6 kgf mm 2 The second bending stiffness EI value is 6.20 x 10 6 kgf mm 2 More than 9.57 x 10 6 kgf mm 2 The results were as follows. For example, at flex S, the first bending stiffness EI value is 2.58 x 10 6 kgf mm 2 More than 2.76 x 10 6 kgf mm 2 The second bending stiffness EI value is 7.08 x 10 6 kgf mm 2More than 8.03 x 10 6 kgf mm 2 The results were as follows. Moreover, the difference in the second bending rigidity EI value was 4.20 times or more and 4.30 times or less the difference in the first bending rigidity EI value.

[0101] In the 70g range, the first bending stiffness EI value is 2.60 x 10 6 kgf mm 2 More than 3.21 x 10 6 kgf mm 2 The second bending stiffness EI value is 7.68 x 10 6 kgf mm 2 More than 10.33 x 10 6 kgf mm 2 The results were as follows. For example, at flex S, the first bending stiffness EI value is 2.60 x 10 6 kgf mm 2 More than 2.80 x 10 6 kgf mm 2 The second bending stiffness EI value is 7.68 x 10 6 kgf mm 2 More than 8.54 x 10 6 kgf mm 2 The results were as follows. Moreover, the difference in the second bending rigidity EI value was 4.30 times or more and 4.40 times or less the difference in the first bending rigidity EI value.

[0102] In the 80g range, the first bending stiffness EI value is 2.62 x 10 6 kgf mm 2 More than 3.06 x 10 6 kgf mm 2 The second bending stiffness EI value is 7.93 x 10 6 kgf mm 2 More than 10.88 x 10 6 kgf mm 2 The results were as follows. For example, at flex S, the first bending stiffness EI value is 2.62 x 10 6 kgf mm 2 More than 2.73 x 10 6 kgf mm 2The second bending stiffness EI value is 7.93 x 10 6 kgf mm 2 More than 9.40 x 10 6 kgf mm 2 The results were as follows. Moreover, the difference in the second bending rigidity EI value was 6.65 times or more and 6.75 times or less the difference in the first bending rigidity EI value.

[0103] Comparative Example 1 The shafts constituting the lineup of Comparative Example 1 were manufactured in the same manner as in Example 1. In Comparative Example 1, only unpainted shafts were manufactured. The total axial length of the shafts was 1168 mm. The outer diameter of the tip was 8.55 mm. The shafts in the lineup are further classified by flex in each weight range. The flex, weight (g), outer diameter (mm) at a position 150 mm from the butt end, and torque of each shaft were evaluated in the same manner as in Example 1, and the results are shown in Table 5. Table 5 shows the results for the 40g and 50g weight ranges.

[0104] A comparison between Example 1 and Comparative Example 1 will be described. For example, focusing on the 40g weight range, the average weight difference from the minimum flex R2 to the maximum flex X was 1.88g in Comparative Example 1. In contrast, the average weight difference from the minimum flex R2 to the maximum flex X in Example 1 was 0.5g. In Example 1, the weight difference felt by the user when replacing the shaft 1 in the same weight range is smaller than in Comparative Example 1. Therefore, it can be said that in Example 1, when replacing the shaft 1 in the same weight range, the difference in the feeling of use felt by the user before and after replacement is smaller than in Comparative Example 1.

[0105] In Example 1, the difference in outer diameter at a position 150 mm from the butt end 3a in the flex S in the 40 g weight range and the flex S in the 50 g weight range was 0.10 mm. In Example 1, the difference in outer diameter at a position 150 mm from the butt end 3a for adjacent weight ranges (for example, 40g and 50g) with the same flex is small. Therefore, in Example 1, when shafts 1 having adjacent weight ranges and the same flex are replaced with each other, it is considered that the difference in the feeling of use felt by the user before and after the replacement is small.

[0106] Comparative Example 2 The shafts constituting the lineup of Comparative Example 2 were manufactured in the same manner as in Example 1. The total axial length of the shaft of Comparative Example 2 was 1168 mm. The shafts in the lineup are further classified by flex in each weight range. The flex S shafts in the 40g, 50g, and 60g ranges were evaluated for bending stiffness EI at each point in the same manner as in Example 1.

[0107] The change points where the bending stiffness distribution changed were confirmed in all weight ranges. The change points were confirmed in the range of 250 mm to 300 mm from the tip end 2a.

[0108] At 40g flex S, the first bending stiffness EI value is 2.18 x 10 6 kgf mm 2 More than 2.33 x 10 6 kgf mm 2 The second bending stiffness EI value is 5.43 x 10 6 kgf mm 2 More than 6.55 x 10 6 kgf mm 2 The results were as follows.

[0109] At 50g flex S, the first bending stiffness EI value is 2.46 x 10 6 kgf mm 2 More than 2.52 x 10 6 kgf mm 2 The second bending stiffness EI value is 6.42 x 10 6 kgf mm 2 More than 7.71 x 10 6 kgf mm 2 The results were as follows.

[0110] At 60g flex S, the first bending stiffness EI value is 2.43 x 10 6 kgf mm 2 More than 2.52 x 10 6 kgf mm 2 The second bending stiffness EI value is 7.25 x 10 6 kgf mm 2 More than 8.46 x 10 6 kgf mm 2 The results were as follows.

[0111] A comparison between Example 1 and Comparative Example 2 will be described. It was confirmed that in the flex S weight range of 40g to 60g, the first bending rigidity EI value was larger in Example 1 than in Example 2, and the maximum value of the second bending rigidity EI value was larger in Example 1 than in Example 2. Also, in Example 1, the change point where the bending rigidity distribution changed was confirmed in the range of 300mm or more and 400mm or less, whereas in Comparative Example 2, the change point was confirmed in the range of 250mm or more and 300mm or less.

[0112] [Table 4]

[0113] [Table 5] [Industrial Applicability]

[0114] The lineup of golf shafts according to the embodiment of the present invention has a plurality of weight bands grouped according to the weight of the shaft 1, and has a plurality of shafts 1 with different flex for each weight band. In at least one weight band, the average weight difference of each shaft 1 is 1.10g or less. This makes it possible to reduce the weight difference felt by the user when replacing the shaft 1 in a weight band where the weight difference of the shaft 1 is 1.10g or less. Therefore, if the weight difference of the shaft 1 is in a weight band where the weight difference is 1.10g or less, the difference in swing feel felt by the user before and after replacement can be reduced even when the shaft 1 is replaced. In particular, when replacing the shaft 1 with a shaft 1 of the same weight band and adjacent flex, the difference in swing feel felt by the user before and after replacement can be reduced. In the group of golf shafts according to the embodiment of the present invention, the weight difference between the shaft 1 having the largest weight and the shaft 1 having the smallest weight is 0.00 g or more and less than 5.50 g among at least four or more shafts 1 having different flexibilities. In addition, the difference in natural frequency between the shaft 1 having the largest natural frequency and the shaft 1 having the smallest natural frequency is 30 cpm or more. This makes it possible to make the bending rigidity of the shafts 1 having different flexibilities uniform. Therefore, when a user changes the flex, the difference in swing feel felt by the user before and after the change can be reduced. In the fitting method according to the embodiment of the present invention, the user selects the shaft 1 from the group of shafts described above. This makes it easy to select multiple shafts 1 that have little difference in feel when used, such as swing feel and grip feel. [Explanation of symbols]

[0115] 1. Shaft (golf club shaft) 2a Tip end 3a Butt end

Claims

1. A group of golf club shafts including a plurality of golf club shafts, wherein between the golf club shaft having a maximum flex and the golf club shaft having a minimum flex, The difference in the first bending stiffness EI value on the chip end side is 0.25×10 ６ kgf / mm ２ Above 1.00 x 10 ６ kgf / mm ２ is as follows: The difference in the second bending rigidity EI value on the butt end side is 1.50×10 ６ kgf / mm ２ Above 3.00 x 10 ６ kgf / mm ２ is as follows: The difference in the second bending stiffness EI value is 3.50 times or more and 7.00 times or less than the difference in the first bending stiffness EI value, A group of golf club shafts, comprising four or more golf club shafts having different flexes, the weight difference between the golf club shaft having the largest weight and the golf club shaft having the smallest weight being 0.00 g or more and less than 5.50 g, and the difference in natural frequency between the golf club shaft having the largest natural frequency and the golf club shaft having the smallest natural frequency being 30 cpm or more.

2. A group of golf club shafts including a plurality of golf club shafts, wherein between the golf club shaft having a maximum flex and the golf club shaft having a minimum flex, The difference in the first bending stiffness EI value on the chip end side is 0.25×10 ６ kgf / mm ２ Above 1.00 x 10 ６ kgf / mm ２ is as follows: The difference in the second bending rigidity EI value on the butt end side is 1.50×10 ６ kgf / mm ２ Above 3.00 x 10 ６ kgf / mm ２ is as follows: The difference in the second bending stiffness EI value is 3.50 times or more and 7.00 times or less than the difference in the first bending stiffness EI value, A group of golf club shafts, comprising four or more golf club shafts having different flexes, the difference between the maximum outer diameter and the minimum outer diameter being 0.00 mm or more and less than 0.20 mm, when each golf club shaft is compared at a position 150 mm from the butt end of the golf club shaft, and the difference in natural frequency between the golf club shaft having the maximum natural frequency and the golf club shaft having the minimum natural frequency being 20 cpm or more.

3. In at least four golf club shafts having different flexibilities, the length of the golf club shaft having the smallest flexibilities is L1, the distance from the tip end to the center of gravity is D1, and the length of the golf club shaft having the largest flexibilities is L2, the distance from the tip end to the center of gravity is D2. The lengths L1, L2 and the distances D1, D2 are as follows: |(D1 / L1)×100-(D2 / L2)×100|<1 3. The shaft group for golf clubs according to claim 1, wherein the above-mentioned condition is satisfied.

4. 4. The group of golf club shafts according to claim 1, wherein the golf club shafts are made of fiber reinforced resin.

5. A golf club shaft fitting method, comprising the steps of: selecting the golf club shaft from the group of golf club shafts according to any one of claims 1 to 4.

Images