JP4489646B2 - Golf shaft - Google Patents

Description

  The present invention relates to a golf shaft with improved timing.

  The timing of the swing of the golf club varies depending on the characteristics, weight, length, center of gravity, hardness, etc. of the player and the golf shaft. In order to facilitate this timing, various improvements have been made to the golf shaft. For example, shaft flex is a golf shaft design item related to timing. It is known that this shaft flex is managed by a bending amount or a natural frequency when a golf shaft is fixed in the vicinity of the grip and a constant load is applied to the tip of the golf shaft.

  The amount of bending of the shaft during the swing is a combination of deformation due to bending in the axial direction of the golf shaft and deformation due to compression in the radial direction perpendicular to the coaxial line (flattening). If the deformation due to compression is large, the deformation due to bending is obstructed, making it difficult for the golfer to feel the shaft's bending feeling, and the restoring force of the golf shaft is also reduced, resulting in a loss of flight distance.

  Therefore, when selecting a flex that is easy for a golfer to take timing, it is necessary to consider the radial rigidity of the golf shaft. In order to satisfy the deformation due to bending and the deformation due to compression at the same time, it is known to employ a multilayer material or a multiaxial woven fabric in which thin prepregs are laminated as a material for the shaft.

For example, Patent Document 1 or Patent Document 2 describes a shaft formed of a woven fabric, particularly a multiaxial woven fabric mainly composed of three axes. According to each of the above documents, since the triaxial fabric has pseudo-isotropic properties, it is possible to reinforce the structure and improve productivity. Non-Patent Document 1 describes that a pseudo-isotropic material (for example, a four-axis woven fabric) exhibits similar characteristics even when a load is applied from any direction. Furthermore, Patent Document 3 describes a golf shaft formed of a four-axis fabric. According to this document, it is possible to obtain a golf shaft that is excellent in bending, twisting, and compression rigidity, can exhibit sufficient strength against force in all directions, has high reactivity, and has a good balance of restoring force. Can do.
JP 58-76559 A Japanese Patent Laid-Open No. 3-151989 JP 2000-245880 A Journal of the Textile Machinery Society of Japan The Textile Society of Japan November 1994, Vol. 47, No. 11 p. 467-472

  A golfer may feel uncomfortable when the golf club swings (for example, when the top of swing or cock is released), because the flatness in the grip portion of the shaft, particularly in the range from the grip end to 200 mm, increases. In this case, in the golf shaft, the flatness tends to increase as the outer diameter increases for the same thickness, and the flatness tends to increase as the thickness decreases for the same outer diameter. In order to cope with this, in order to suppress deformation due to compression, that is, flattening as much as possible and to obtain a sense of stability at the time of swinging, it is necessary to increase the spring constant of the golf shaft, preferably in the range from the grip end to 200 mm. It is requested. However, in the golf shaft of the conventional configuration, the spring constant is naturally determined by the thickness ratio with respect to the outer diameter of the shaft, so that the spring constant cannot be sufficiently increased and deformation due to compression cannot be suppressed. There's a problem.

  An object of the present invention is to provide a golf shaft capable of suppressing deformation due to compression as much as possible by increasing a spring constant.

In order to achieve the above object, the invention described in claim 1 is a golf shaft made of a fiber reinforced resin formed by laminating a plurality of fiber reinforced resin layers, and the fiber reinforced resin layer comprises a four-axis woven fabric. includes a 4-axis fabric layers reinforced with molding resin, and a hoop layer with enhanced reinforcing fibers extending along a direction intersecting the longitudinal direction of the shaft in the molding resin, the hoop layer is inside the four-axis fabric layer The four-axis fabric is a plurality of longitudinal yarns extending in parallel to the longitudinal direction of the shaft, a plurality of transverse shaft yarns extending along a direction orthogonal to the longitudinal direction of the shaft, and left and right with respect to the longitudinal direction of the shaft. Consists of a set of a plurality of oblique shaft yarns that are obliquely crossed,
The gist is that the horizontal axis yarn and the oblique axis yarn are formed of reinforcing fibers having a high tensile elastic modulus.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the fibers contained in the hoop layer intersect with the longitudinal direction of the shaft at an angle of 90 ° ± 3 °.
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the ratio of the thickness to the outer diameter of the grip portion of the shaft is set in a range of 18.0 to 19.0, The gist is that the spring constant is set in the range of 21.0 to 23.0.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the four-axis fabric layer is arranged in the outermost layer of the shaft or the second layer from the outermost layer. The gist.

The invention described in 請 Motomeko 5 is the invention according to any one of claims 1-4, wherein the fiber reinforced resin layer is a reinforcing fiber obliquely intersect the longitudinal direction of the shaft in the molding resin The gist is to further include an enhanced bias layer.

A sixth aspect of the invention is characterized in that, in the fifth aspect of the invention, the bias layer is arranged inside the hoop layer.

  ADVANTAGE OF THE INVENTION According to this invention, the golf shaft which can raise the spring constant and can suppress the deformation | transformation by compression as much as possible can be provided.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, in a golf shaft 1 (hereinafter simply referred to as a shaft), a head 2 is attached to the tip of the small diameter side, and a grip 3 is attached to the rear end of the large diameter side. The shaft 1 is formed in a tapered shape, and its outer diameter gradually increases from the front end toward the rear end. The shaft 1 is formed by laminating a plurality of fiber reinforced resin layers, and its total length is 1143 mm.

  As shown in FIG. 2, the shaft 1 is composed of first to fifth fiber reinforced resin prepregs 11 to 15 cut out so that the orientation angle of the reinforcing fibers becomes a predetermined angle, and a four-axis woven reinforced prepreg 10. These are laminated to form a substantially tubular shape. The shaft 1 is formed by winding and stacking the prepregs 10 to 15 around the mandrel 7 in the order of the first to fourth fiber reinforced resin prepregs 11 to 14, the four-axis fabric reinforced prepreg 10, and the fifth fiber reinforced resin prepreg 15. ing. In addition, a fiber reinforced resin prepreg (not shown) is usually partially wound around the front end portion and the rear end portion of the shaft 1 separately from the prepregs 10 to 15 for the purpose of reinforcing the shaft 1. .

  In each of the first to fifth fiber reinforced resin prepregs 11 to 15 and the four-axis fabric reinforced prepreg 10, carbon fibers are used as reinforcing fibers, and epoxy resin is used as a matrix resin. The reinforcing fibers are not limited to carbon fibers, and glass fibers, aramid fibers, boron fibers, aromatic polyamide fibers, aromatic polyester fibers, ultrahigh molecular weight polyethylene fibers, and the like can also be used. The matrix resin is preferably a thermosetting resin typified by an epoxy resin, such as an unsaturated polyester resin, a phenol resin, a melamine resin, a urea resin, a diallyl phthalate resin, a polyurethane resin, Examples thereof include polyimide resins and silicon resins.

  As shown in FIG. 3, the four-axis fabric reinforced prepreg 10 is formed by the four-axis fabric layer 4. The four-axis fabric layer 4 includes a plurality of vertical axis threads 41 and a plurality of horizontal axis threads 42 woven so as to be orthogonal to each other, and further to the left and right (+ direction) with respect to the vertical axis threads 41 and the horizontal axis threads 42. And a pair of oblique shaft yarns 43 woven so as to intersect with each other in the − and − directions). The vertical axis thread 41 of the four-axis fabric layer 4 is arranged in parallel to the longitudinal direction of the shaft 1, the horizontal axis thread 42 is arranged perpendicular to the longitudinal direction of the shaft 1, and the oblique axis thread 43 is arranged in the shaft 1. It arrange | positions so that it may cross diagonally with respect to the longitudinal direction.

  The longitudinal thread 41 needs to be strong in the bending direction along the axis of the shaft 1. For this reason, a reinforcing fiber having a high tensile strength is used for the vertical thread 41. In this case, for example, carbon fibers having a tensile strength of 4000 MPa to 7000 MPa are preferably used as the reinforcing fibers.

  The horizontal axis thread 42 requires a material having a higher spring constant as the golfer's strength increases. Here, the golfer's ability can be expressed by the head speed and the maximum deflection of the shaft 1 during the swing. As the head speed increases and the maximum deflection of the shaft 1 increases, the heavier and harder shaft 1 is required. Therefore, the higher the shaft 1 becomes heavier and the harder, the higher the tensile elastic modulus of the reinforcing fiber employed in the horizontal shaft thread 42 is better. For this reason, a reinforcing fiber having a high tensile elastic modulus is used for the horizontal axis thread 42.

  It is preferable to use carbon fibers having a tensile modulus of 240 GPa to 800 GPa as the reinforcing fibers forming the horizontal axis yarns 42. In order to obtain the same effect, a method of increasing the fineness of the carbon fiber or increasing the number of converged fibers (the number of filaments) for constituting one horizontal axis thread 42 can be employed. In that case, since the unevenness | corrugation which arises on the surface of the shaft 1 becomes large, it is necessary to increase the grinding | polishing allowance of the outermost layer which forms the shaft 1. FIG. From such a viewpoint, it is preferable that the fineness of the reinforcing fiber of the 4-axis fabric layer 4 is 50 tex to 200 tex. The fineness unit tex is a value equal to the number of grams per 1000 m of fibers (1 tex = 1 g / 1000 m).

  The reinforcing fiber forming the horizontal axis yarn 42 preferably has a higher tensile elastic modulus as the golfer's ability increases, but the fiber having a higher tensile elastic modulus tends to have a lower tensile strength. Therefore, in the process of weaving fibers in the horizontal axis direction, the influence of the yield due to fiber breakage may become large. Therefore, regarding the tensile elastic modulus of the horizontal axis thread 42, it is more preferable to use a carbon fiber of 240 GPa to 500 GPa.

  Since the oblique shaft yarn 43 affects the spring constant of the shaft 1, a reinforcing fiber having a high tensile elastic modulus is used for the oblique shaft yarn 43 in order to increase the spring constant. In this case, it is preferable to use a carbon fiber having a tensile modulus of 400 GPa to 800 GPa as the reinforcing fiber forming the oblique shaft yarn 43. The higher the tensile modulus, the better. However, in the process of weaving the fibers along the oblique axis, the tensile strength of the fibers tends to decrease as the tensile modulus increases. Therefore, regarding the tensile elastic modulus of the oblique shaft yarn 43, it is more preferable to use a carbon fiber of 400 GPa to 500 GPa.

  In the reinforcing fiber used for the oblique axis yarn 43, it is preferable that the characteristics in the + direction oblique axis and the − direction oblique axis are the same. Further, the reinforcing fibers of the oblique shaft yarn 43 are more preferably arranged so that the orientation angle with respect to the axis of the shaft 1 is ± 45 °. This is because if the characteristics are different between the + direction and the − direction, the twist characteristics of the shaft 1 are anisotropic.

  In such a 4-axis woven fabric prepreg 10, it is preferable to reduce the amount of resin contained in the prepreg 10 in order to obtain a desired spring constant for the shaft 1. This is because as the resin content of the prepreg 10 increases, the thickness of the shaft 1 increases correspondingly, and accordingly, the spring constant with respect to the outer diameter / thickness of the shaft 1 decreases.

  Moreover, the ratio of the resin amount contained in the 4-axis fabric reinforced prepreg 10 and the first to fifth fiber reinforced resin prepregs 11 to 15 is the weight of each prepreg 10 to 15 from the viewpoint of the spring constant of the shaft 1 and ease of making. It is preferable to set in the range of 20 wt% to 50 wt%. Moreover, it is preferable that the ratio which occupies for the whole shaft 1 of the amount of resin used for all the prepregs 10-15 is set to the range of 20 wt%-30 wt%.

  In order to efficiently achieve the object of the present invention, it is more effective to dispose the four-axis fabric reinforced prepreg 10 including the four-axis fabric layer 4 in the outermost layer of the shaft 1. Depending on the above requirements, it is not limited to the outermost layer, and it is preferable to arrange it at a position closer to the outermost layer, specifically, from the outermost layer to the second layer.

  When the fiber reinforced resin shaft 1 is formed by a so-called sheet wrapping method, the first to fourth fiber reinforced resin prepregs 11 to 14, the four-axis fabric reinforced prepreg 10, and the fifth fiber reinforced resin prepreg 15 are arranged in this order. After winding 10 to 15 on the mandrel 7, a wrapping tape is wound and fixed. Then, after curing this, the wrapping tape is removed, the surface is polished, and further painted to obtain the shaft 1 as a finished product. When this manufacturing method is adopted, a fifth fiber reinforced resin prepreg 15 is provided outside the four-axis woven fabric reinforced prepreg 10 in order to secure a polishing allowance. In this case, the thickness of the fifth fiber reinforced resin prepreg 15 is preferably 0.02 mm to 0.15 mm.

  Within this range, the thickness of the fifth fiber-reinforced resin prepreg 15 is adjusted according to the thickness of the reinforcing fibers of the four-axis fabric layer 4. If the thickness of the fifth fiber reinforced resin prepreg 15 is 0.02 mm or less, the reinforcing fibers of the four-axis woven fabric layer 4 are scraped off by surface polishing, which may adversely affect the performance of the shaft 1. On the other hand, when the thickness of the fifth fiber reinforced resin prepreg 15 is 0.15 mm or more, the distance from the surface to the four-axis fabric layer 4 increases, and therefore, the four-axis fabric layer 4 is arranged outside the shaft 1. The effect is reduced.

  However, in the following cases, it is necessary to increase the thickness of the fifth fiber reinforced resin prepreg 15. That is, each axial yarn 41, 42, 43 of the four-axis fabric layer 4 is usually formed by converging 1000 to 6000 carbon fibers, but converging carbon fiber filaments having a high fineness to each axial yarn 41, When 42 and 43 are formed, the thickness of the 4-axis fabric layer 4 becomes large at the intersections of the shaft yarns 41, 42 and 43. Therefore, when the surface of the shaft 1 is made smooth, it is necessary to take a lot of polishing allowance. In order to secure the polishing allowance, it is necessary to increase the thickness of the fifth fiber reinforced resin prepreg 15.

  Manufacturing methods that do not require polishing after curing, such as a method of covering and forming prepregs 10 to 15 with a stretchable tube instead of a wrapping tape, an internal pressure forming method, or a sheet wrapping method. In the case where polishing is not required, the 4-axis woven fabric prepreg 10 can be used as the outermost layer of the shaft 1.

  The first and second fiber reinforced resin prepregs 11 and 12 are disposed by being wound 2 to 4 times over the entire length of the shaft 1, and the reinforcing fibers are ± 30 ° to ± 65 ° with respect to the longitudinal direction of the shaft 1. It is arranged to make. The layer made of the first and second fiber reinforced resin prepregs 11 and 12 is called a bias layer, and is arranged to determine the twist angle of the shaft 1 at the time of swing. In general, in the case of a golfer with a large head moment of inertia or a fast head speed, a reinforcing fiber having a high tensile elastic modulus is used for the bias layer in order to keep the twist angle small when the golf club swings. On the other hand, when the inertia moment of the head is small or the head speed is slow, a reinforcing fiber having high tensile strength is used for the bias layer.

  The third fiber reinforced resin prepreg 13 is disposed by being wound once over the entire length of the shaft 1, and the reinforcing fiber is approximately 90 ° with respect to the longitudinal direction of the shaft 1, specifically, on the axis of the shaft 1. It arrange | positions so that 90 degrees +/- 3 degrees may be made | formed with respect to it. The layer made of the third fiber reinforced resin prepreg 13 is called a hoop layer, and the spring constant of the shaft 1 can be remarkably increased by forming the shaft 1 in combination with the four-axis fabric layer 4. Thus, deformation due to compression occurring in the shaft 1, that is, flattening of the shaft 1 can be effectively suppressed. In addition, this hoop layer can also increase the spring constant of the shaft 1 by combining the bias layer and the four-axis fabric layer described above, and more effectively suppress the flattening of the shaft 1. it can.

  The 4th and 5th fiber reinforced resin prepregs 14 and 15 are arranged so as to be wound 1-2 times over the entire length of the shaft 1, and are arranged so that the reinforcing fibers are substantially parallel to the longitudinal direction of the shaft 1. Has been. In addition, about the 5th fiber reinforced resin prepreg 11, as mentioned above, it may not be used depending on a manufacturing method.

  In the present embodiment, the shaft 1 is formed by using a sheet winding method. In this sheet winding method, first, the first to fourth fiber reinforced resin prepregs 11 to 14, the four-axis fabric reinforced prepreg 10, and the fifth fiber reinforced resin prepreg 15 are wound around the mandrel 7 in this order and laminated. A cylindrical laminate is obtained by winding the outer periphery with a wrapping tape. And after heating and pressurizing and hardening the laminated body formed in this way, the shaft 1 can be obtained by pulling out the mandrel 7 from the laminated body.

  For the shaft 1 thus formed, at least the ratio of the outer diameter to the wall thickness (outer diameter / wall thickness) in the grip portion is set in the range of 18.0 to 19.0, and the spring constant of the grip portion is 21. It is preferably set in the range of 0.0 to 23.0. This is because if the spring constant of the shaft 1 is smaller than 21.0, deformation due to compression, that is, flattening of the shaft 1 is not suppressed, and an excellent sense of stability during swing cannot be obtained. Further, if the spring constant of the shaft 1 is larger than 23.0, the bending strength of the shaft 1 is lowered.

  When the sum of the volume ratio of the hoop layer occupying the entire shaft 1 and the volume ratio of the 4-axis fabric layer 4 is set in the range of 24.0% to 26.0%, the mass of the shaft 1 is 45 inches ( 1143 mm) It is preferably set in the range of 50.0 g to 60.0 g in terms of length. This is because if the mass of the shaft 1 is smaller than 50.0 g, the spring constant of the shaft 1 is not sufficiently increased and deformation due to compression is not suppressed, and if the mass is larger than 60.0 g, This is because the bending strength of the shaft 1 is lowered and the reliability is lowered. If the volume ratio is less than 24.0%, deformation due to compression may not be suppressed, and if the volume ratio is greater than 26.0%, the strength of the shaft 1 may be reduced.

  Next, the present embodiment will be described more specifically with reference to Examples 1 to 4 and Comparative Examples 1 to 11. Tables 1 to 3 show the manufacturing conditions of the shaft 1 of each example and each comparative example. In each example and each comparative example, the mass and bending rigidity of the shaft 1 are set to be substantially the same by adjusting the thickness of each layer.

（実施例１）
本実施形態で示された製造方法を用いて、４軸織物強化プリプレグ１０、及び第１〜第５繊維強化樹脂プリプレグ１１〜１５を積層して実施例１における１１４３ｍｍの長さのシャフト１を形成した。この場合、４軸織物層４の斜交軸糸４３及び横軸糸４２に引張弾性率が３８５ＧＰａの炭素繊維を３０００本収束したものをそれぞれ用い、縦軸糸４１に引張弾性率が２４０ＧＰａの炭素繊維を１０００本収束したものを用いた。ここで、表１〜３に示される１Ｋとは炭素繊維を１０００本収束した束、即ち１０００本束の単位を意味し、１ｐｌｙとはマンドレル７に巻回されたプリプレグの枚数を意味している。

Example 1
Using the manufacturing method shown in the present embodiment, the 4-axis woven fabric reinforced prepreg 10 and the first to fifth fiber reinforced resin prepregs 11 to 15 are laminated to form the shaft 1 having a length of 1143 mm in Example 1. did. In this case, carbon fibers having a tensile elastic modulus of 240 GPa are used for the vertical yarn 41, respectively, using the converging axial yarns 43 and the horizontal shaft yarns 42 of the four-axis woven fabric layer 4 having 3000 pieces of carbon fibers having a tensile elastic modulus of 385 GPa. What converged 1000 fibers was used. Here, 1K shown in Tables 1 to 3 means a bundle of 1000 carbon fibers, that is, a unit of 1000 bundles, and 1ply means the number of prepregs wound around the mandrel 7. .

  A prepreg obtained by impregnating a synthetic resin with carbon fiber having a tensile elastic modulus of 445 GPa was used for the third fiber reinforced resin prepreg 13 forming the hoop layer. The third fiber reinforced resin prepreg 13 having a molding thickness of 0.047 mm was used.

  A prepreg containing carbon fibers having a tensile elastic modulus of 540 GPa was used for the first and second fiber reinforced resin prepregs 11 and 12 forming the bias layer. Further, the first and second fiber reinforced resin prepregs 11 and 12 having a molding thickness of 0.081 mm were used.

  Although not shown in the table, prepregs containing carbon fibers having a tensile modulus of 300 GPa were used for the fourth and fifth fiber reinforced resin prepregs 14 and 15. The 1st-5th fiber reinforced resin prepregs 11-15 used the ratio (resin content rate) of resin contained in each prepreg of 25 wt%.

In Tables 1 to 3, the 4-axis layer ratio (%) and the hoop layer ratio (%) indicate the volume ratios of the 4-axis fabric layer 4 and the hoop layer in the entire shaft 1, respectively. The mass (g) indicates the total mass of the shaft 1.
(Example 2)
A prepreg containing carbon fibers having a tensile modulus of 240 GPa was used for the hoop layer. Other manufacturing conditions were the same as in Example 1.
(Example 3)
A prepreg containing carbon fibers having a tensile modulus of 240 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.
Example 4
A prepreg containing carbon fibers having a tensile modulus of 240 GPa was used for the hoop layer, and a prepreg containing carbon fibers having a tensile modulus of 240 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 1)
A set of 1000 carbon fibers having a tensile elastic modulus of 240 GPa was used for the horizontal axis yarn 42 and the oblique axis yarn 43 of the four-axis fabric layer 4, respectively. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 2)
A prepreg containing carbon fibers having a tensile elastic modulus of 240 GPa in the hoop layer is used for each of the horizontal axis yarns 42 and the oblique axis yarns 43 of the four-axis woven fabric layer 4 having converged 1000 carbon fibers having a tensile elastic modulus of 240 GPa. Using. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 3)
The hoop layer was omitted and the other production conditions were the same as in Example 1.
(Comparative Example 4)
The horizontal axis yarn 42 and the oblique axis yarn 43 of the four-axis fabric layer 4 were each made by converging 1000 carbon fibers having a tensile modulus of 240 GPa, and the hoop layer was omitted. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 5)
A prepreg containing carbon fibers having a tensile modulus of 240 GPa in the bias layer is used for each of the horizontal axis yarns 42 and the oblique shaft yarns 43 of the four-axis woven fabric layer 4 having converged 1000 carbon fibers having a tensile modulus of 240 GPa. Using. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 6)
A prepreg containing carbon fibers having a tensile elastic modulus of 240 GPa in the hoop layer is used for each of the horizontal axis yarns 42 and the oblique axis yarns 43 of the four-axis woven fabric layer 4 that have converged 1000 carbon fibers having a tensile elastic modulus of 240 GPa. A prepreg containing carbon fibers having a tensile elastic modulus of 240 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 7)
The hoop layer was omitted, and a prepreg containing carbon fibers having a tensile elastic modulus of 240 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 8)
A set of 1000 carbon fibers having a tensile elastic modulus of 240 GPa was used for the horizontal axis yarn 42 and the oblique axis yarn 43 of the four-axis fabric layer 4, respectively. Further, the hoop layer was omitted, and a prepreg containing carbon fibers having a tensile elastic modulus of 240 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 9)
The 4-axis fabric layer 4 and the hoop layer were omitted, and other production conditions were the same as those in Example 1. In this case, the rigidity of the shaft 1 is increased by increasing the thicknesses of the fourth and fifth fiber reinforced resin prepregs 14 and 15 as much as the four-axis fabric layer 4 and the hoop layer are omitted. Adjustments were made to be the same as the example.
(Comparative Example 10)
The biaxial woven fabric layer 4 was omitted, a prepreg containing carbon fibers having a tensile elastic modulus of 300 GPa was used for the hoop layer, and a prepreg containing carbon fibers having a tensile elastic modulus of 240 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.
(Comparative Example 11)
The biaxial woven fabric layer 4 was omitted, a prepreg containing carbon fibers having a tensile modulus of 300 GPa was used for the hoop layer, and a prepreg containing carbon fibers having a tensile modulus of 540 GPa was used for the bias layer. Other manufacturing conditions were the same as in Example 1.

And about the shaft 1 of each Example and each comparative example, the spring constant was measured with the following method. The measurement results of the spring constant are shown in Tables 1-3.
<Measurement of spring constant>
The method for measuring the spring constant is in accordance with the flat test of the S-type shaft of the golf club certification standard and the standard confirmation method (product safety association). In this flat test method, first, the shaft 1 of each example and each comparative example is cut at a position of 50 mm from the grip end to prepare a test piece having a length of 50 mm. When a constant load P is applied to the test piece at a load speed of 5 mm / min, the spring constant K is calculated from the load P and the displacement amount Δ of the test piece by using the following equation (1). In this test, Δ is the amount of displacement when a load of 200 N to 300 N is applied to the test piece.

K = P / Δ (1)

Here, the outer diameter and thickness of each test piece used for measuring the spring constant are also measured. In this case, three outer diameters were measured near the center of each test piece, specifically, at a position 25 mm from the end of the test piece, and the average of these measured values was determined as the outer diameter of each test piece. Further, the thickness was measured in the same manner to obtain an average value. Tables 1 to 3 show the outer diameter (mm) and the wall thickness (mm) of the test pieces used for the measurement of the spring constant for each example and each comparative example, together with the measurement results of the spring constant. Further, the value of the spring constant corresponding to the outer diameter / wall thickness is plotted in the graph of FIG. 4 as the actual measurement value of the example and the comparative example. The circle mark and square mark in FIG. 4 show the measured values of the spring constants in the example and the comparative example, respectively. Moreover, the spring constant K of the test piece calculated | required by Formula (1) is described below as spring constant K '.
<Calculation method of approximate curve ratio>
First, twelve commercially available golf clubs are randomly extracted, and the shaft 1 of each golf club is cut at a position of 50 mm from the grip end to produce a 50 mm test piece. The outer diameter (mm), the wall thickness (mm), and the spring constant K ′ of these test pieces are obtained by the same method as in the above-described examples and comparative examples. Then, using a commercially available spreadsheet software, the relationship between the measured value y of the spring constant of each test piece and the measured value x of the outer diameter / thickness was determined. The result is shown by the third-order approximation formula (2) and the degree of correlation r ² (3). The rhombus marks in FIG. 4 indicate measured values of the spring constant in the conventional product, and the curve in FIG. 4 indicates the obtained approximate expression (2). According to Equation (3), a very high correlation is recognized between the actual measurement values x and y of the conventional product.

y = −0.1x ³ + 6.1x ² -125.4x + 876.9 (2)

r ² = 0.830 (3)

Next, the approximate value y of the spring constant is calculated by substituting the actually measured value of the outer diameter / thickness obtained in each example and each comparative example into x in the above equation (2). A ratio between the approximate value y of the obtained spring constant and the actual value y of the spring constant obtained by the flattening test is obtained as an approximate curve ratio. The obtained approximate curve ratio values are shown in Tables 1-3. Here, the approximate curve ratio is an index for determining the presence or absence of a significant difference with respect to the approximate value, and the larger the value, the greater the significant difference with respect to the conventional product.

  As shown in Tables 1 to 3, in Examples 1 to 4, it was possible to obtain a value of 1.52 or more for the approximate curve ratio, but in Comparative Examples 1 to 11, only a value of 1.32 or less was used for the approximate curve ratio. It was not obtained. That is, in the example, if the same outer diameter / thickness was obtained, a spring constant having a value that was clearly higher (50% or more) than the approximate value could be obtained. Only a spring constant with no significant difference was obtained. This is because, in Comparative Examples 1, 2, 5, and 6, carbon fibers having a high tensile elastic modulus are not used for the oblique shaft yarns 43 and the transverse shaft yarns 42 constituting the four-axis woven fabric layer 4, and thus the shaft It is estimated that the spring constant of 1 was not sufficiently increased. Further, in Comparative Examples 3, 4, 7, and 8, the hoop layer is omitted, and in Comparative Examples 9, 10, and 11, the 4-axis fabric layer 4 is omitted. Therefore, the spring constant of the shaft 1 cannot be sufficiently increased. Estimated.

  “Pro golfers can distinguish between two shafts if the difference between the spring constants of the two shafts is 5%. Generally, a golfer must have a difference of 30% or more to distinguish between the two shafts. With respect to the shafts 1 of Examples 1 to 4, the general golfer feels a difference with respect to any of Comparative Examples 1 to 11. In each example, as a result of sufficiently increasing the spring constant of the shaft 1, it was confirmed that deformation due to compression, that is, flattening of the shaft 1, was suppressed as much as possible and excellent stability was obtained during a swing.

  In addition to the above, according to the comparison between Example 1 and Example 2, Comparative Example 1 and Comparative Example 2, and Comparative Example 5 and Comparative Example 6, the tensile elastic modulus of the reinforcing fiber of the hoop layer becomes the spring constant of the shaft 1. It was confirmed that the effect was small. Moreover, according to the comparison between Example 1 and Example 3 and Comparative Example 10 and Comparative Example 11, it was confirmed that the influence of the tensile elastic modulus of the reinforcing fiber of the bias layer on the spring constant of the shaft 1 was small. Further, according to the comparison between Example 1 and Comparative Example 1, the spring constant of the shaft 1 can be obtained by simply adopting a high tensile elastic modulus carbon fiber for the oblique shaft yarn 43 and the transverse shaft yarn 42 of the four-axis fabric layer 4. It was confirmed that it could be higher. Further, according to the comparison between Example 1 and Comparative Example 1, Example 2 and Comparative Example 3, Example 3 and Comparative Example 7, the influence of the presence or absence of the hoop layer on the spring constant of the shaft 1 and the four-axis fabric layer 4 It was confirmed that the effects of the tensile elastic modulus of the horizontal axis yarn 42 and the oblique axis yarn 43 constituting the same are approximately the same.

The front view which shows the whole golf shaft structure in this embodiment. Explanatory drawing for demonstrating each fiber reinforced resin prepreg which comprises a golf shaft similarly. The partial enlarged front view which shows the structure of a 4-axis fabric layer. The graph which shows the relationship between the thickness ratio with respect to the outer diameter of a golf shaft, and a spring constant.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Golf shaft, 2 ... Head, 3 ... Grip, 4 ... 4-axis textile layer, 7 ... Mandrel, 10 ... 4-axis textile reinforced prepreg, 11 ... 1st fiber reinforced resin prepreg, 12 ... 2nd fiber reinforced resin prepreg, DESCRIPTION OF SYMBOLS 13 ... 3rd fiber reinforced resin prepreg, 14 ... 4th fiber reinforced resin prepreg, 15 ... 5th fiber reinforced resin prepreg, 41 ... Vertical axis thread, 42 ... Horizontal axis thread, 43 ... Oblique axis thread

Claims (6)

A golf shaft made of fiber reinforced resin formed by laminating a plurality of fiber reinforced resin layers,
The fiber-reinforced resin layer includes a 4-axis fabric layer obtained by reinforcing a 4-axis fabric with a molding resin, and a hoop layer in which reinforcing fibers extending along a direction intersecting the longitudinal direction of the shaft are reinforced with a molding resin.
The hoop layer is disposed inside the four-axis fabric layer,
The four-axis fabric has a plurality of longitudinal yarns extending in parallel to the longitudinal direction of the shaft, a plurality of transverse shaft yarns extending along a direction orthogonal to the longitudinal direction of the shaft, and a slanting left and right with respect to the longitudinal direction of the shaft. A golf shaft comprising a plurality of oblique shaft yarns, wherein the horizontal shaft yarns and oblique shaft yarns are formed of reinforcing fibers having a high tensile elastic modulus. The golf shaft according to claim 1,
2. The golf shaft according to claim 1, wherein the fibers contained in the hoop layer intersect with the longitudinal direction of the shaft at an angle of 90 ° ± 3 °. The golf shaft according to claim 1 or 2,
The ratio between the wall thickness and the outer diameter of the grip portion of the shaft is set in the range of 18.0 to 19.0,
A golf shaft, wherein a spring constant of the grip portion is set in a range of 21.0 to 23.0. In the golf shaft according to any one of claims 1 to 3,
4. The golf shaft according to claim 1, wherein the four-axis fabric layer is disposed on the outermost layer of the shaft or on the second layer from the outermost layer. In the golf shaft according to any one of claims 1 to 4 ,
2. The golf shaft according to claim 1, wherein the fiber reinforced resin layer further includes a bias layer in which reinforcing fibers that are oblique to the longitudinal direction of the shaft are reinforced with a molding resin. The golf shaft according to claim 5 ,
The golf shaft according to claim 1, wherein the bias layer is disposed inside the hoop layer.

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