JP2020054557A - Golf club shaft - Google Patents

Abstract

To provide a golf club shaft that can stabilize torsion behavior of a shaft and enhance directional stability of a hit ball.SOLUTION: A shaft comprises a tip end Tp, a bat end Bt, a bias layer b1, and a straight layer. The bias layer b1 comprises a first angle layer 10 and a second angle layer 20 inclined in directions opposite to each other. The first angle sheet and the second angle sheet each comprise a non-integer ply part in at least a portion in an axial direction. A circumferential position of the first angle layer 10 coincides with a circumferential position of the second angle layer 20. Weight per unit area of the first angle layer 10 is 50 g/mor less. Weight per unit area of the second angle layer 20 is 50 g/mor less.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to golf club shafts.

  A golf club shaft manufactured by winding a prepreg is known. Generally, this shaft has a bias layer. Usually, the bias layer is constituted by a combination of a first angle layer in which fibers are oriented at -45 ° and a second angle layer in which fibers are oriented at + 45 °. As disclosed in Japanese Patent Application Laid-Open No. 2010-207367 and Japanese Patent No. 4116135, the first angle layer and the second angle layer are wound while being shifted in the circumferential direction.

JP 2010-207367 A Japanese Patent No. 4116135

  The present inventor has found that the structure of the conventional bias layer can cause the twisting behavior of the shaft during the swing to be unstable.

  The present disclosure provides a golf club shaft that can stabilize the twisting behavior of the shaft and enhance the directional stability of a hit ball.

In one aspect, a golf club shaft has a tip end, a butt end, a bias layer, and a straight layer. The bias layer has a first angle layer and a second angle layer whose fiber angles are inclined in opposite directions. The first angle layer and the second angle layer have a non-integer ply portion in at least a part in the axial direction. The circumferential position of the first angle layer matches the circumferential position of the second angle layer. The basis weight of the first angle layer is 50 g / m ² or less. The basis weight of the second angle layer is 50 g / m ² or less.

  As one aspect, the directional stability of a hit ball can be improved.

FIG. 1 shows a golf club provided with the shaft of the first embodiment. FIG. 2 shows the shaft of the first embodiment. FIG. 3 is a developed view showing a laminated configuration of the shaft of FIG. FIG. 4 is a process diagram showing a bonding process in the manufacture of the shaft of FIG. FIG. 5 is a process chart showing a bonding process in the manufacture of the shaft according to the reference example. FIGS. 6A, 6B, and 6C are cross-sectional views illustrating an integer ply portion and a non-integer ply portion. FIGS. 7A, 7B, 7C, and 7D are cross-sectional views for explaining the relationship between the relative positions of the non-integer ply portions and the bending torsion. FIG. 8 is a schematic view showing a method for measuring a bending torsion angle. FIG. 9 is a schematic diagram illustrating a method of measuring a shaft torque.

(Knowledge underlying the present disclosure)
As described above, the bias layer is configured by a combination of the first angle layer and the second angle layer inclined in opposite directions. Each of the first angle layer and the second angle layer is formed by winding one prepreg. The prepreg has a thickness. Due to this thickness, the wound prepreg forms a step at a winding start end and a winding end end.

  If the prepreg can be wound exactly an integer ply (for example, exactly one ply), the winding start end and the winding end end abut, and the step does not occur. However, errors inevitably occur when cutting and winding the sheet. Due to this error, a slight gap is formed between the winding start end and the winding end end, depending on the individual, when the prepreg is to be wound exactly in integer plies. In the shaft after the heat curing, the gap becomes a gap or a portion composed of only the resin, and lowers the strength of the shaft.

  In order to prevent the occurrence of the gap, the prepreg is wound with a non-integer ply (for example, a ply slightly more than 1) instead of an integer ply (for example, exactly 1 ply). As a result, the winding start edge and the winding end edge of the prepreg overlap, and a step and a thick portion are formed. This step reduces the strength. In order to suppress the influence of the step, the first angle layer and the second angle layer are wound while being shifted in the circumferential direction. With this configuration, the steps of the first angle layer and the steps of the second angle layer can be dispersed in the circumferential direction.

  The present inventor has obtained a new finding that the above-described structure for suppressing the influence of the step can rather reduce the performance of the shaft.

  In the above structure, a non-integer ply portion occurs in each of the first angle layer and the second angle layer. For example, when the first angle layer has 1.1 plies, a portion of 0.1 plies is a non-integer ply portion. This non-integer ply portion can exhibit bending torsion. The bending torsion is a property of causing the shaft to twist in conjunction with the bending of the shaft. This bending torsion occurs because the fibers are inclined with respect to the bending direction of the shaft. Unintended bending torsion has been found to be potentially present. It has been found that this bending torsion makes the torsion behavior of the shaft during the swing unstable and can reduce the directional stability of the hit ball. The present disclosure is based on this finding.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the present application, the axial direction means the direction of the center line of the shaft. Further, in the present application, the circumferential direction means the circumferential direction of the shaft.

  FIG. 1 shows a golf club 2 including the shaft 6 according to the first embodiment. The club 2 has a head 4, a shaft 6, and a grip 8. The head 4 is attached to the tip end of the shaft 6 on the tip side. The grip 8 is attached to a butt side end of the shaft 6. What is indicated by the double-headed arrow Ls is the length of the shaft 6.

  FIG. 2 shows the shaft 6. The shaft 6 has a tip end Tp and a butt end Bt. The shaft 6 has a tapered portion whose outer diameter decreases from the butt end Bt side to the tip end Tp side. The shaft 6 is a tubular body. The shaft 6 has a center line z1.

  FIG. 3 is a developed view showing a laminated configuration of the shaft 6.

  The shaft 6 is manufactured by a sheet winding manufacturing method. In this production method, a prepreg sheet (also simply referred to as prepreg) is used. In the prepreg sheet, the matrix resin is in a semi-cured state. The shaft 6 is formed by winding and curing a prepreg sheet.

  As the matrix resin of the prepreg sheet, other than the epoxy resin, a thermosetting resin or a thermoplastic resin other than the epoxy resin may be used. From the viewpoint of shaft strength, epoxy resin is preferred.

  The shaft 6 is composed of a plurality of sheets. The shaft 6 is composed of eleven sheets from a first sheet s1 to an eleventh sheet s11. This development view shows the sheets constituting the shaft in order from the radially inner side of the shaft. These sheets are wound in order from the sheet located on the upper side in the developed view. In this developed view, the horizontal direction of the drawing coincides with the axial direction of the shaft. In this development, the right side of the drawing is the tip end Tp side of the shaft. In this development, the left side of the drawing is the butt end Bt side of the shaft.

  This development view shows not only the winding order of each sheet but also the arrangement of each sheet in the shaft axis direction. For example, in FIG. 3, the end of the first sheet s1 is located at the tip end Tp.

  In the present application, the term “layer” and the term “sheet” are used. “Layer” is a name after being wound. On the other hand, "sheet" is a name before being wound. The “layer” is formed by winding the “sheet”. That is, the wound “sheet” forms a “layer”. In the present application, the same reference numeral is used for the layer and the sheet. For example, the layer formed by the sheet s1 is the layer s1.

  The shaft 6 has a straight layer, a bias layer, and a hoop layer. In the developed view of the present application, the orientation angle of the fiber is described in each sheet. This orientation angle is an angle with respect to the shaft axis direction.

  The sheet described as “0 °” constitutes the straight layer. The sheet constituting the straight layer is also called a straight sheet. In the straight layer, the absolute angle is 10 ° or less. The absolute angle is an absolute value of the orientation angle. For example, an absolute angle of 10 ° or less means that the orientation angle is −10 ° or more and + 10 ° or less.

  Sheets described as “+ 45 °” and “−45 °” constitute the bias layer b1. The sheet constituting the bias layer b1 is also called a bias sheet. The absolute angle of the bias layer b1 is preferably at least 25 °, more preferably at least 30 °, and more preferably at least 35 °. The absolute angle of the bias layer is preferably 65 ° or less, more preferably 60 ° or less, and more preferably 55 ° or less. In light of the torsional rigidity and the torsional strength of the shaft, the absolute angle of the bias layer b1 is particularly preferably equal to or greater than 40 ° and equal to or less than 50 °.

  The bias layer b1 has a first angle layer 10 and a second angle layer 20. In the present embodiment, the sheet s2 is the first angle layer 10 and the sheet s4 is the second angle layer 20. The positions in the radial direction of the first angle layer 10 and the second angle layer 20 are not limited. The sheet constituting the first angle layer 10 is also referred to as a first angle sheet. The sheet constituting the second angle layer 20 is also referred to as a second angle sheet.

  An intervening layer s3 is provided between the first angle layer 10 and the second angle layer 20. In the present embodiment, the intervening layer s3 is a hoop layer. This intervening layer may be omitted.

  Signs of plus (+) and minus (-) are added to the orientation angle of the bias layer b1. These symbols indicate that the fibers of the bias layer b1 are inclined in opposite directions. In the first angle layer 10 and the second angle layer 20, the fibers are oriented in opposite directions.

  In FIG. 3, the inclination direction of the fibers of the first angle sheet 10 is equal to the inclination direction of the fibers of the second angle sheet 20. However, the sheet 20 is turned over and attached to the sheet 10. As a result, the inclination direction of the seat 10 and the inclination direction of the seat 20 are opposite to each other. In consideration of this point, in the embodiment of FIG. 3, the fiber orientation angle of the sheet 10 is described as −45 °, and the fiber orientation angle of the sheet 20 is described as + 45 °. The absolute angle of the fiber is the same between the first angle layer 10 and the second angle layer 20.

  The sheet described as “90 °” constitutes the hoop layer. In the hoop layer, the absolute angle is from 80 ° to 90 °, more preferably from 85 ° to 90 °.

  The number of plies (number of windings) of one sheet is not limited. For example, when the sheet is one ply, the sheet is wound once. For example, when the sheet has two plies, the sheet is wound twice. For example, if the sheet is 1.5 plies, the sheet will be wound 1.5 turns.

  Although not shown, the prepreg sheet before being used is sandwiched between cover sheets. Usually, this cover sheet is release paper and a resin film. The prepreg sheet before being used is sandwiched between release paper and a resin film. Release paper is affixed to one surface of the prepreg sheet, and a resin film is affixed to the other surface of the prepreg sheet. In the following, the surface to which the release paper is attached is also referred to as a “release-paper-side surface”, and the surface to which the resin film is attached is also referred to as a “film-side surface”.

  The development view in FIG. 3 is a view in which the surface on the film side is the front side. That is, in FIG. 3, the front side of the drawing is the surface on the film side, and the back side of the drawing is the surface on the release paper side.

  To wind the prepreg sheet, first, the resin film is peeled off. By peeling off the resin film, the surface on the film side is exposed. This exposed surface has tackiness (adhesiveness). This tackiness is caused by the matrix resin. That is, since the matrix resin is in a semi-cured state, adhesiveness is exhibited. The edge of the exposed film side surface is attached to the winding target. Due to the adhesiveness of the matrix resin, this edge portion can be smoothly attached. The wound object is a mandrel or a wound object obtained by winding another prepreg sheet around the mandrel. Next, the release paper is peeled off. Next, the object to be wound is rotated, and the prepreg sheet is wound around the object to be wound.

  In the embodiment of FIG. 3, some of the sheets are combined sheets. The united sheet is formed by laminating two or more sheets. The first angle layer 10 and the second angle layer 20 are wound in a state of a united sheet.

  In the present application, a layer arranged substantially over the entirety in the axial direction is referred to as a full length layer. In the present application, a sheet disposed substantially over the entirety in the axial direction is referred to as a full-length sheet. The wound full length sheet forms a full length layer. The first angle layer 10 and the second angle layer 20 are full length layers.

  In the present application, a layer partially arranged in the axial direction of the shaft is referred to as a partial layer. In the present application, a sheet partially arranged in the shaft axis direction is referred to as a partial sheet. The wound partial sheet forms a partial layer. The axial length of the partial sheet is shorter than the axial length of the full length sheet. Preferably, the axial length of the partial sheet is equal to or less than half the total length of the shaft.

  In the present application, the full length layer that is a straight layer is referred to as a full length straight layer. In the embodiment of FIG. 3, the full length straight layers are the layer s6, the layer s8, and the layer s10.

  In the present application, the full length layer that is the angle layer is referred to as a full length angle layer. In the embodiment of FIG. 3, the first angle layer 10 (layer s2) and the second angle layer 20 (layer s4) are full-length angle layers.

  In the present application, the full length hoop layer is referred to as a full length hoop layer. In the embodiment of FIG. 3, the full length hoop layers are a layer s3, a layer s7, and a layer s9. The full length hoop layer s3 is the intervening layer. The full length hoop layer s3 is arranged between the first angle layer 10 and the second angle layer 20.

  In the present application, a partial layer that is a straight layer is referred to as a partial straight layer. In the embodiment of FIG. 3, the partial straight layers are a layer s1 and a layer s11.

  In the present application, a partial layer located on the chip end Tp side is referred to as a chip partial layer. The axial distance between the chip partial layer (chip partial sheet) and the chip end Tp is preferably 40 mm or less, more preferably 30 mm or less, more preferably 20 mm or less, and more preferably 0 mm. In this embodiment, this distance is 0 mm in all the chip partial layers.

  The chip partial layer includes a chip partial straight layer. In the embodiment of FIG. 3, the chip partial straight layers are the layer s1 and the layer s11.

  In the present application, the partial layer located on the butt end Bt side is referred to as a butt partial layer. The axial distance between the butt partial layer (butt partial sheet) and the butt end Bt is preferably 40 mm or less, more preferably 30 mm or less, more preferably 20 mm or less, and more preferably 0 mm. In the butt partial layer s5, this distance is 0 mm.

  The butt partial layer includes a butt partial hoop layer. In the embodiment of FIG. 3, the butt partial hoop layer is the layer s5.

  The outline of the manufacturing process of the shaft 6 will be described below.

[Outline of shaft manufacturing process]

(1) Cutting Step In the cutting step, the prepreg sheet is cut into a desired shape. Through this process, each sheet shown in FIG. 3 is cut out.

  The cutting may be performed by a cutting machine. The cutting may be done manually. In the case of manual work, for example, a cutter knife is used.

(2) Laminating Step In the laminating step, a united sheet is produced. In the bonding step, the first angle layer 10 and the second angle layer 20 are bonded. In this embodiment, the sheet s3 is also bonded to the first angle layer 10 and the second angle layer 20. The sheet s5 is bonded to the sheet s6.

(3) Winding Step In the winding step, a mandrel is prepared. Typical mandrels are made of metal. A release agent is applied to the mandrel. Further, an adhesive resin is applied to the mandrel. This resin is also called a tacking resin. The cut sheet is wound around this mandrel. With this tacking resin, the end of the sheet is easily attached to the mandrel.

  The sheets are wound in the order described in the development. The upper sheet in the developed view is wound first. The sheet to be bonded is wound in a state of a united sheet.

  Each sheet is firstly terminated to the object to be wound at a predetermined termination position. Next, the object to be wound is rolled. This winding may be performed manually or may be performed by a machine. This machine is called a rolling machine. All the sheets are wound to obtain a wound body.

(4) Tape Wrapping Step In the tape wrapping step, a tape is wound around the outer peripheral surface of the wound body. This tape is also called a wrapping tape. The tape is wound while being tensioned. The tape applies pressure to the wound body. This pressure reduces voids.

(5) Curing Step In the curing step, the wound body after tape wrapping is heated. This heating cures the matrix resin. During this curing process, the matrix resin is temporarily fluidized. By fluidizing the matrix resin, air between the sheets or in the sheets can be discharged. The discharge of the air is promoted by the pressure (clamping force) of the wrapping tape. By this curing, a cured laminate is obtained.

(6) Step of pulling out mandrel and step of removing wrapping tape After the curing step, a step of pulling out the mandrel and a step of removing the wrapping tape are performed. From the viewpoint of improving the efficiency of the wrapping tape removing step, it is preferable that the wrapping tape removing step is performed after the mandrel drawing step.

(7) Both ends cutting step In this step, both ends of the cured laminate are cut. By this cutting, the end face of the tip end Tp and the end face of the butt end Bt are made flat.

(8) Polishing Step In this step, the surface of the cured laminate is polished. Spiral irregularities exist on the surface of the cured laminate. These irregularities are traces of the wrapping tape. By polishing, the irregularities disappear, and the surface is made smooth. Preferably, in the polishing step, whole polishing and tip portion polishing are performed.

(9) Painting Step The cured laminate after the polishing step is painted.

  As described above, in the bonding step, the two sheets 10 and 20 forming the bias layer b1 are bonded.

  FIG. 4 shows a process in which the first angle sheet 10 and the second angle sheet 20 are bonded. As described above, the sheet s3 is actually bonded in addition to the first angle sheet 10 and the second angle sheet 20, but the illustration of the sheet s3 is omitted in FIG.

  The first angle sheet 10 (first angle layer 10) has a winding start edge 12 and a winding end edge 14.

  The second angle sheet 20 (the second angle layer 20) has a winding start edge 22 and a winding end edge 24.

  The second angle sheet 20 is bonded to the first angle sheet 10 to form the united sheet 30. As described above, the second angle sheet 20 is attached to the first angle sheet 10 while being turned upside down. As a result, in the united sheet 30, the fibers are inclined in the opposite directions between the first angle sheet 10 and the second angle sheet 20. In the present embodiment, the inclination angle θ (absolute angle) is 45 °.

  In the united sheet 30, the first angle sheet 10 and the second angle sheet 20 are bonded to each other without displacement. The winding start edge 12 of the first angle sheet 10 and the winding start edge 22 of the second angle sheet 20 are overlapped without displacement. As a result, in the shaft 6, the circumferential position of the winding start edge 12 is the same as the circumferential position of the winding start edge 22.

  In the present embodiment, the dimensions of the first angle sheet 10 are the same as the dimensions of the second angle sheet 20. When the winding start edge 12 and the winding start edge 22 overlap, the winding end edge 14 and the winding end edge 24 also overlap. That is, in the united sheet 30, the winding end edge 14 of the first angle sheet 10 and the winding end edge 24 of the second angle sheet 20 are overlapped without displacement. In the shaft 6, the circumferential position of the winding end edge 14 is the same as the circumferential position of the winding end edge 24.

  The first angle sheet 10 is rectangular. The winding start edge 12 forms a first side. The winding end edge 14 forms a second side. The chip side edge 16 forms a third side. The butt side edge 18 forms a fourth side. The chip side edge 16 is located at the chip end Tp. The butt side edge 18 is located at the butt end Bt. Although it is difficult to understand in FIG. 4, the length of the chip side edge 16 is different from the length of the butt side edge 18. The tip side edge 16 is longer than the butt side edge 18. The tip side edge 16 may be longer than the butt side edge 18, may be shorter than the butt side edge 18, or may have the same length as the bat side edge 18.

  The second angle sheet 20 is square. The winding start edge 22 constitutes the first side. The winding end edge 24 constitutes the second side. The chip side edge 26 forms a third side. The butt side edge 28 forms a fourth side. The chip side edge 26 is located at the chip end Tp. The butt side edge 28 is located at the butt end Bt. Although not apparent in FIG. 4, the length of the chip side edge 26 is different from the length of the butt side edge 28. The tip side edge 26 is longer than the butt side edge 28. The tip side edge 26 may be longer than the butt side edge 28, may be shorter than the butt side edge 28, or may be the same length as the bat side edge 28.

  As described above, the dimensions of the first angle sheet 10 are the same as the dimensions of the second angle sheet 20. The first angle sheet 10 and the second angle sheet 20 are congruent with each other. In the united sheet 30, the first angle sheet 10 and the second angle sheet 20 exactly overlap. The winding start edge 12 overlaps the winding start edge 22. The winding end edge 14 overlaps the winding end edge 24. The chip side edge 16 overlaps the chip side edge 26. The butt side edge 18 overlaps the bat side edge 28.

  The length of the chip side edge 16 corresponds to the X ply. That is, the number of plies of the first angle layer 10 at the chip end Tp is X. The length of the chip side edge 26 also corresponds to the X ply. That is, the number of plies of the second angle layer 20 at the chip end Tp is X. X may be an integer or a non-integer.

  The length of the butt side edge 18 corresponds to the Y ply. That is, the number of plies of the first angle layer 10 at the butt end Bt is Y. The length of the butt side edge 28 also corresponds to the Y ply. That is, the number of plies of the second angle layer 20 at the butt end Bt is Y. Y may be an integer or a non-integer.

  X may be different from Y or the same as Y. X may be larger than Y or smaller than Y. In the present embodiment, X is different from Y. In the present embodiment, X is larger than Y.

  In the shaft 6 obtained by winding the united sheet 30, the circumferential position of the first angle layer 10 matches the circumferential position of the second angle layer 20.

  The first angle layer 10 has a non-integer ply portion. The second angle layer 20 has a non-integer ply portion. Details of the non-integer ply portion will be described later.

  FIG. 5 shows a bonding step in the reference example. The laminated configuration of the shaft according to this reference example is the same as that of the shaft 6 (FIG. 3) described above.

  Also in this reference example, the first angle sheet 10 and the second angle sheet 20 are bonded. However, the second angle sheet 20 is staggered and bonded to the first angle sheet 10. As a result, the united sheet 40 is obtained. In the united sheet 40, the winding start edge 12 of the first angle sheet 10 and the winding start edge 22 of the second angle sheet 20 are shifted by a width of 0.5 ply. As a result, in the shaft of the reference example, the circumferential position of the winding start edge 12 and the circumferential position of the winding start edge 22 differ by 180 °. Similarly, the circumferential position of the winding end edge 14 and the circumferential position of the winding end edge 24 differ by 180 °.

  In the conventional shaft, the circumferential position of the first angle layer does not match the circumferential position of the second angle layer as in this reference example. In this configuration, the steps are dispersed in the circumferential direction. This configuration has been regarded as preferred from the point of view of strength and uniformity.

  However, the inventor has found a new problem with such a configuration. It has been found that when the first angle layer and the second angle layer do not have the same circumferential position, bending torsion occurs. The bending torsion property is a property that a torsion is generated by bending a shaft. That is, the bending torsion property is a property that the shaft is twisted by itself just by bending the shaft.

  Hereinafter, the non-integer ply portion and the bending torsion will be described with reference to the drawings.

  FIG. 6A is a cross-sectional view of the first angle layer 50. The first angle layer 50 is 1.25 plies. FIG. 6B is a cross-sectional view of the first angle layer 60. The first angle layer 60 is 1.5 plies. FIG. 6C is a cross-sectional view of the first angle layer 70. The first angle layer 70 has 1.75 plies. In the cross-sectional views of FIGS. 6A, 6B, and 6C, the cross sections are schematically indicated by lines. Here, 1.25 plies, 1.5 plies, and 1.75 plies are selected as easy-to-understand examples.

  In the first angle layer 50 of FIG. 6A, a portion of the first angle layer 50 other than the integer ply portion 52 is a non-integer ply portion 54. In FIG. 6A, the integer ply unit 52 is indicated by a solid line, and the non-integer ply unit 54 is indicated by a broken line. In the first angle layer 50, the integer ply part 52 is one ply, and the non-integer ply part 54 is 0.25 ply.

  Hereinafter, the bending torsion caused by the two angle layers will be described. First, the bending torsion caused by a single angle layer will be described, and then the bending torsion based on the mutual relationship between the two angle layers will be described.

  First, the bending torsion caused by a single angle layer (first angle layer) will be described. In the first angle layer 50, the integer ply portion 52 does not exhibit bending torsion. When the fiber angle θ and the inclination direction are the same, the portions having the circumferential position different by 180 ° cancel each other out of the bending torsion. For this reason, in the integer ply part 52, the bending and torsion cancel each other in all parts in the circumferential direction. As a result, the integer ply portion 52 does not exhibit bending torsion.

  On the other hand, the non-integer ply portion 54 exhibits bending torsion. In the non-integer ply portion 54, there is no partner whose circumferential position is different by 180 °, so that there is no cancellation of bending torsion. As a result, the non-integer ply portion 54 exhibits bending torsion.

  In the first angle layer 60 of FIG. 6B, the integer ply part 62 is one ply, and the non-integer ply part 64 is 0.5 ply.

  As described above, in the first angle layer 60, the integer ply portion 62 does not exhibit bending torsion. On the other hand, the non-integer ply portion 64 exhibits bending torsion. In the non-integer ply portion 64, there is no partner whose circumferential position is different by 180 °, so that there is no cancellation of bending torsion. As a result, the non-integer ply portion 64 exhibits bending and torsion.

  In the first angle layer 70 of FIG. 6C, the integer ply part 72 is one ply, and the non-integer ply part 74 is 0.75 ply.

  As described above, in the first angle layer 70, the integer ply portion 72 does not exhibit bending torsion. On the other hand, the non-integer ply portion 74 exhibits bending torsion. In the non-integer ply portion 74, there is a portion whose circumferential position is different by 180 °. As shown in FIG. 6 (c), in the non-integer ply portion 74, the bending torsion cancels out between a portion from 0 ° to 90 ° and a portion from 180 ° to 270 °. On the other hand, the portion from 270 ° to 360 ° does not have a counterpart, and thus exhibits bending torsion.

  As described above, in the single angle layer (first angle layer), the non-integer ply portion can exhibit bending torsion.

  Next, the influence of the mutual relationship between the two angle layers (the first angle layer and the second angle layer) on the bending torsion will be described. In the following, as an easy-to-understand example, a case will be described in which the positional deviation between the first angle layer and the second angle layer in the circumferential direction is 0 °, 45 °, 90 °, and 180 °.

  FIGS. 7A, 7B, 7C, and 7D show a non-integer ply portion 54 of the first angle layer and a non-integer ply portion 84 of the second angle layer. It is sectional drawing. Here, a case where the non-integer ply portion is 0.25 ply as shown in FIG. 6A will be described as an example. 7 (a), 7 (b), 7 (c) and 7 (d) show only the non-integer ply portions of the first and second angle layers, and show the first and second angle layers. The description of the integer ply part of the layer is omitted.

  FIG. 7A is a cross-sectional view when the circumferential position of the first angle layer matches the circumferential position of the second angle layer. In this case, the circumferential position of the non-integer ply portion 54 matches the circumferential position of the non-integer ply portion 84. The fiber angles of the non-integer ply portion 54 and the non-integer ply portion 84 are inclined in opposite directions. Therefore, between the non-integer ply portion 54 and the non-integer ply portion 84, the bending and twisting properties cancel each other. Therefore, in this case, bending torsion does not occur despite the presence of the non-integer ply portions 54 and 84.

  FIG. 7B is a cross-sectional view when the circumferential position of the first angle layer is different from the circumferential position of the second angle layer by 45 °. In this case, in a portion where the non-integer ply portion 54 and the non-integer ply portion 84 have the same circumferential position, the bending and twisting properties cancel each other. That is, in the range from 225 ° to 270 °, the bending and torsion cancel each other between the non-integer ply portion 54 and the non-integer ply portion 84. However, in other portions, the cancellation does not occur. That is, a portion from 180 ° to 225 ° in the non-integer ply portion 54 exhibits bending torsion. Further, a portion from 270 ° to 315 ° in the non-integer ply portion 84 exhibits bending torsion.

  FIG. 7C is a cross-sectional view when the circumferential position of the first angle layer is different from the circumferential position of the second angle layer by 90 °. In this case, there is no portion where the non-integer ply portion 54 and the non-integer ply portion 84 have the same circumferential position. Therefore, the non-integer ply portion 54 and the non-integer ply portion 84 do not cancel each other out of the bending torsion. The whole non-integer ply portion 54 and the whole non-integer ply portion 84 exhibit bending torsion.

  FIG. 7D is a cross-sectional view when the circumferential position of the first angle layer is different from the circumferential position of the second angle layer by 180 °. Also in this case, there is no portion where the non-integer ply portion 54 and the non-integer ply portion 84 have the same circumferential position. As described above, in the case where the positions in the circumferential direction are different by 180 ° between the portions where the fiber angles are inclined in the same direction, the bending and twisting properties cancel each other. However, when the positions in the circumferential direction differ by 180 ° between the portions where the fiber angles are inclined in opposite directions, the bending and torsional properties do not cancel each other, but the bending and torsional properties are added. Also in this case, the entire non-integer ply portion 54 and the entire non-integer ply portion 84 exhibit bending torsion.

  Bending torsion depends on the direction of bending. In the present application, the term “bending position in the circumferential direction” is defined for this bending direction. The circumferential bending position is a circumferential position outside the bend. For example, in a case where a shaft is fixed at a butt end to be horizontal and a shaft is bent by suspending a weight at a tip end, a circumferential position directly above in a vertical direction is a circumferential bending position. The circumferential bending position is anywhere from 0 ° to 360 °.

  For example, in the embodiment of FIG. 7D, when the circumferential bending position is 45 ° or 225 °, the absolute value of the bending torsion angle becomes maximum. In the embodiment of FIG. 7D, when the circumferential bending position is 135 ° or 315 °, the absolute value of the bending torsion angle is minimum (zero). The bending torsion angle changes depending on the circumferential bending position.

  In the embodiment of FIG. 7D, the direction of twisting is opposite between the case where the circumferential bending position is 45 ° and the case where the circumferential bending position is 225 °. For example, when the shaft is twisted in the direction in which the face opens when the circumferential bending position is 45 °, the shaft is twisted in the direction in which the face closes when the circumferential bending position is 225 °. The reason why this phenomenon occurs is that when the circumferential bending position changes by 180 °, the inclination direction of the shaft with respect to the bending direction is reversed.

  Thus, the bending torsion varies depending on the circumferential bending position. During the swing, the bending direction (bending direction) of the shaft changes. The swing includes aspects such as take-back, top-of-swing, early stage of downswing, middle stage of downswing, late stage of downswing, impact, and the like, and the bending direction may change depending on each aspect. In addition, the swing has individuality, and the bending direction and the bending amount in each phase differ for each golfer. If bending torsion exists, different torsion occurs for each phase of the swing. Due to this different twist, the twisting behavior of the shaft during the swing becomes unstable. In addition, particularly advanced users perceive this complicated twisting behavior as a twisting feeling, which can deteriorate the feeling of use (feeling) of the shaft. As a result, the directional stability of the hit ball may decrease. In addition, a smooth swing can be hindered by the deterioration of the feeling.

  In the shaft 6 of the present embodiment, the circumferential position of the first angle layer matches the circumferential position of the second angle layer. In this case, as described with reference to FIG. 7A, the bending torsion does not appear theoretically. However, in practice, slight bending torsion may occur due to errors in the fiber angle, misalignment during winding, and the like. By suppressing the difference between the maximum value and the minimum value of the bending torsion angle to 0.3 ° or less, adverse effects due to the bending torsion can be prevented.

  FIG. 8 shows a method for measuring the bending torsion angle.

  As shown in FIG. 8, in the measurement of the bending torsion angle, a portion from 60 mm from the butt end Bt to the bat end Bt is fixed by the fixing jig 100. The gyro sensor GS is attached to the tip end Tp. The gyro sensor GS is attached at a position where the rotation angle at the tip end Tp can be measured. Before the weight 102 is suspended, the shaft axis of the shaft 6 is horizontal. The weight 102 is suspended at a position 100 mm from the tip end Tp. The weight of the weight 102 is 1.05 kg. The shaft 6 is bent by the gravity of the weight 102. By comparing the angles before and after suspending the weight 102, the torsion angle due to bending is calculated. This torsion angle is a bending torsion angle. The direction in which the shaft bends (the circumferential bending position) is changed by rotating the shaft, and the maximum value and the minimum value are measured.

  In the measurement of the bending torsion angle, a circumferential bending position is selected. The circumferential bending position is the upper side in the vertical direction. For example, when the circumferential bending position is 90 °, the shaft 6 is fixed such that the 90 ° is the uppermost position in the vertical direction.

  As described above, the bending torsion angle changes depending on the circumferential bending position. Therefore, a certain shaft has a maximum value and a minimum value in the bending torsion angle. Assuming that the twist angle twisted in the first direction (for example, clockwise) is plus and the twist angle twisted in the second direction (for example, counterclockwise) is minus, the maximum value is a plus value and the minimum value is a minus value. Value. For example, when the maximum value is + θ ° and the minimum value is −θ °, the difference between the maximum value and the minimum value of the bending torsion is [+ θ − (− θ)] = 2θ.

  From the viewpoint of suppressing the bending torsion, stabilizing the torsional behavior of the shaft during the swing, and improving the directional stability of the hit ball, the difference between the maximum value and the minimum value of the bending torsion is preferably 0.3 ° or less, 0.2 ° or less is more preferable, and 0.2 ° or less is more preferable. Most preferably, this difference is 0.0 °. It is difficult to reduce the bending and twisting property to 0.0 ° due to manufacturing errors (e.g., errors in bonding, errors in the orientation of the ends). As described above, the difference between the maximum value and the minimum value of the bending torsion is about 0.5 ° even in a shaft designed to have a bending torsion of 0.3 ° or less due to the above error. sell.

  As shown in FIG. 4, the number of plies of the first angle layer 10 and the second angle layer 20 at the chip end Tp is X. The number of plies of the first angle layer 10 and the second angle layer 20 at the butt end Bt is Y.

  When X and Y are different, a non-integer ply portion is indispensably formed in at least a part of the axial direction. Even if X and Y are integers, if X and Y are different, a non-integer ply is formed. For example, when X is 3 and Y is 2, the number of plies gradually decreases from 3 to 2 as going from the chip end Tp to the butt end Bt. Therefore, non-integer ply portions are formed at all axial positions except the tip end Tp and the butt end Bt. Needless to say, if X or Y is a non-integer, a non-integer ply portion is formed even if X and Y are the same. When X and Y are non-integers, and X and Y are the same, a non-integer ply portion is formed entirely in the axial direction.

  As described above, a shaft having a non-integer ply portion in at least a part of the axial direction can exhibit bending torsion, so that the effect of suppressing the bending torsion is exerted. In this respect, X and Y are preferably different. X is preferably larger than Y from the viewpoint of reducing the weight of the bias layer while suppressing the torsional rigidity of the entire shaft.

  In a shaft having a large difference (X-Y), a non-integer ply portion is generated, and the necessity of suppressing bending torsion increases. In addition, by increasing the difference (XY), the pitch of the spiral formed by the winding end of the angle layer is reduced, and the uniformity of the shaft in the circumferential direction is increased. Further, by increasing the difference (X-Y), the torsional rigidity on the tip end Tp side having a small diameter is selectively increased, and both suppression of shaft torque and weight reduction of the shaft can be achieved. In these respects, the difference (XY) is preferably equal to or greater than 1, preferably equal to or greater than 1.5, and more preferably equal to or greater than 2. Considering the restrictions on the tip diameter and the shaft weight, the difference (X-Y) is preferably 5 or less, more preferably 4 or less, and even more preferably 3.5 or less.

The basis weight of the first angle layer is preferably 50 g / m ² or less. By reducing the basis weight, the first angle layer is thinned, and the step at the winding start edge and the winding end edge is reduced. Similarly, the basis weight of the second angle layer is preferably 50 g / m ² or less. By making the first angle layer and the second angle layer thin, even if the winding start edges overlap, a step is suppressed. From this point of view, the basis weight of the first angle layer is preferably 50 g / ^{m 2} or less, 45 g / ^{m 2} or less is more preferable. In light of cost, the basis weight of the first angle layer is preferably equal to or greater than 20 g / m ^{2, and} more preferably equal to or greater than 25 g / m ² . Similarly, the basis weight of the second angle layer is preferably 50 g / m ² or less, more preferably 45 g / m ² or less. In light of cost, the basis weight of the second angle layer is preferably equal to or greater than 20 g / m ^{2, and} more preferably equal to or greater than 25 g / m ² . The basis weight is the weight per unit area (1 m ² ) in the prepreg sheet.

The fiber elastic modulus of the bias layer b1 (the first angle layer 10 and the second angle layer 20) is not limited. When the fiber elastic modulus of the bias layer b1 is high, the bending and twisting property due to the non-integer ply portion tends to increase. Therefore, in this case, it is effective to suppress the bending torsion. In this respect, the fiber elastic modulus of the bias layer b1 is preferably equal to or greater than 30 t / mm ^2, more preferably equal to or greater than 35 t / mm ^{2, and} still more preferably equal to or greater than 40 t / mm ² . In view of the strength, fiber elastic modulus of the bias layer b1 is preferably 90t / mm ² or less, more preferably 80t / mm ² or less, more preferably 70 t / mm ^2.

  The resin content of the bias layer b1 (the first angle layer 10 and the second angle layer 20) is not limited. When the winding start edge 12 of the first angle layer 10 and the winding start edge 22 of the second angle layer 20 overlap, the step is likely to increase. This step may form a void. This gap can reduce the strength of the shaft. By increasing the resin content of the bias layer b1, the matrix resin that has flowed during heating and curing can be easily filled in the voids. In this respect, the resin content of the bias layer b1 is preferably equal to or greater than 30% by weight. In respect of reducing the weight of the shaft, the resin content of the bias layer b1 is preferably equal to or less than 50% by mass, and more preferably equal to or less than 40% by mass. This resin content is the resin content of the prepreg.

  As described above, when the difference (X−Y) is 1 or more, both suppression of the shaft torque and reduction in the weight of the shaft can be achieved. That is, it is preferable that the difference (X−Y) is 1 or more in the lightweight shaft. Therefore, in the lightweight shaft, the non-integer ply portion is easily increased, and the bending and twisting property is easily developed. The configuration capable of suppressing the bending torsion is effective for a lightweight shaft. In this respect, the shaft weight is preferably equal to or less than 50 g, more preferably equal to or less than 49 g, and still more preferably equal to or less than 48 g. In light of shaft strength, the shaft weight is preferably equal to or greater than 30 g, and more preferably equal to or greater than 32 g.

  The shaft torque is a twist angle of the shaft when a predetermined torque is applied, and indicates a torsional rigidity of the entire shaft. The larger the value of the shaft torque, the lower the torsional rigidity.

  When the shaft torque is large, the torsional rigidity of the shaft is small, so that the bending torsion is easily developed. Therefore, in this case, it is effective to suppress the bending torsion. In this respect, the shaft torque is preferably equal to or greater than 5 °, more preferably equal to or greater than 5.5 °, and more preferably equal to or greater than 6 °. In light of directional stability of the hit ball, the shaft torque is preferably equal to or less than 10 °, and more preferably equal to or less than 9 °.

FIG. 9 shows a method for measuring the shaft torque. The part from the point 40 mm from the tip end Tp to the tip end Tp is fixed by the jig M1. This fixing is achieved by an air chuck, and the air pressure of the air chuck is 2.0 kgf / cm ² . A jig M2 is fixed to a portion having a width of 50 mm from a position separated by 825 mm from the jig M1. This fixation is achieved by an air chuck, and the air pressure of the air chuck is 1.5 kgf / cm ² . By rotating the jig M2 with the jig M1 fixed, a torque of 13.9 kg · cm is applied to the shaft 6. The twist angle due to this torque is the shaft torque.

  The shaft length Ls is not limited. The shaft may be for an iron club, a hybrid club, or a wood club. The adverse effect of torsion due to bending torsion increases as the shaft length Ls increases. In this respect, the shaft length Ls is preferably equal to or greater than 40 inches, more preferably equal to or greater than 42 inches, and more preferably equal to or greater than 44 inches. Considering the golf rules regarding the club length, the shaft length Ls is preferably equal to or less than 47 inches.

[Example 1]
A shaft of Example 1 which is the same as the shaft 6 described above was produced. The shaft length Ls was 1187 mm. The lamination structure was as shown in FIG. As shown in FIG. 4, a united sheet 30 in which the winding start edge 12 of the first angle sheet 10 and the winding start edge 22 of the second angle sheet 20 overlap was produced, and the united sheet 30 was wound. As the first angle sheet 10 and the second angle sheet 20, prepreg (product name "9053S-4") manufactured by Toray Industries, Inc. was used. The specifications of 9053S-4 are that the basis weight is 40 g / m ² , the fiber elastic modulus is 40 t / mm ² , and the resin content is 30% by weight.

  The golf club of Example 1 was obtained by attaching the driver head and the grip to the shaft of Example 1.

[Comparative Example 1]
A shaft and a club of Comparative Example 1 were obtained in the same manner as in Example 1 except that a prepreg (product name: 9255S-7A) manufactured by Toray was used as the first angle sheet and the second angle sheet. The specifications of 9255S-7A are that the basis weight is 70 g / m ² , the fiber elastic modulus is 40 t / mm ² , and the resin content is 24% by weight.

[Comparative Example 2]
As shown in FIG. 5, the winding start edge 22 of the second angle sheet 20 is displaced from the winding start edge 12 of the first angle sheet 10 by a width of 0.5 ply and bonded to form a united sheet 40. Then, the united sheet 40 was wound. Except for this point, a shaft and a club of Comparative Example 2 were obtained in the same manner as in Example 1.

[Comparative Example 3]
As shown in FIG. 5, the winding start edge 22 of the second angle sheet 20 is displaced from the winding start edge 12 of the first angle sheet 10 by a width of 0.5 ply and bonded to form a united sheet 40. Then, the united sheet 40 was wound. Except for this point, the shaft and the club of Comparative Example 3 were obtained in the same manner as Comparative Example 1.

  The evaluation results of Examples and Comparative Examples are shown in Table 1 below.

  The evaluation method is as follows.

[Bending strength]
The bending strength was measured based on the SG-type three-point bending strength test set by the Japan Society for Product Safety. As measurement points, T point, A point, AB point, B point, BC point and C point were adopted. The point AB is a point that divides the point A and the point B into two equal parts. The BC point is a point that divides the point B and the point C into two equal parts. The positions of point T, point A, point B and point C are determined in the above test. The index (%) when the result of Comparative Example 2 is set to 100 is shown in Table 1 above.

[Torsion strength]
The torsional strength was measured according to the SG-type torsional test defined by the Japan Society for Product Safety. In this test, first, a fixing jig was bonded to both ends of the shaft. Next, torque was applied to the shaft by rotating the jig on the tip end Tp side while the jig on the butt end Bt side was fixed. The value obtained by multiplying the torque value when the shaft is broken by the torsion angle is the torsional strength. The index (%) when the result of Comparative Example 2 is set to 100 is shown in Table 1 above.

[Difference between maximum and minimum bending torsion angles]
The bending torsion angle was measured by the method described above. The measurement was performed while changing the bending position in the circumferential direction, and the maximum value and the minimum value were obtained. These differences are shown in Table 1 above.

[Direction]
Five testers with a handicap of 0 or more and 10 or less hit five balls at a time, and the distance between the target point and the stationary point of the hit ball in the left-right direction was measured. This distance was a positive value whether it shifted to the right or to the left. The standard deviation of this distance is shown in Table 1 above as the directionality.

  The winding workability is workability in a winding process. In Example 1, Comparative Example 2 and Comparative Example 3, the winding workability was good. In Comparative Example 1, the united sheet 40 was difficult to wind because two thick sheets were bonded together without displacement.

  In Comparative Example 1 and Comparative Example 3, the two angle sheets were thick and the step caused by the sheets was large, so that the strength was low. In particular, in Comparative Example 1 in which thick angle sheets were arranged without displacement, the step was particularly large and the strength was lower.

  In Example 1 and Comparative Example 1, the circumferential position of the first angle layer coincided with the circumferential position of the second angle layer. For this reason, the bending torsion was suppressed, and the difference between the maximum value and the minimum value of the bending torsion angle was small. As a result, the twisting behavior of the shaft was stabilized, and the directional stability of the hit ball was good.

  About the feeling of the shaft at the time of swing, the five golfers described above performed a sensory evaluation. Evaluation results of this feeling (combination of evaluations by five golfers) are shown in three stages of A, B, and C. In Example 1 and Comparative Example 1, since the bending torsion was suppressed, the feeling of twist did not occur, and the feeling during the swing was good. In Comparative Example 2, a feeling of twist was generated due to the bending torsion, and the feeling was not good. In Comparative Example 3, the feeling of twist was larger and the feeling was worse.

Regarding the above-described embodiment, the following supplementary notes are disclosed.
[Appendix 1]
The tip end,
Butt end,
A bias layer,
With a straight layer,
Has,
The bias layer has a first angle layer and a second angle layer in which fiber angles are inclined in directions opposite to each other,
The first angle layer and the second angle layer have a non-integer ply portion in at least a part of the axial direction,
A circumferential position of the first angle layer coincides with a circumferential position of the second angle layer;
The basis weight of the first angle layer is 50 g / m ² or less;
A golf club shaft having a basis weight of the second angle layer of 50 g / m ² or less.
[Appendix 2]
When the number of plies of the first angle layer and the second angle layer at the tip end is X, and the number of plies of the first angle layer and the second angle layer at the butt end is Y,
The golf club shaft according to claim 1, wherein the difference (XY) is 1 or more and 5 or less.
[Appendix 3]
When the number of plies of the first angle layer and the second angle layer at the tip end is X, and the number of plies of the first angle layer and the second angle layer at the butt end is Y,
The golf club shaft according to claim 1, wherein the difference (XY) is 1 or more and 3.5 or less.
[Appendix 4]
The golf club shaft according to any one of supplementary notes 1 to 3, wherein a fiber elastic modulus of the bias layer is 30 t / mm ² or more.
[Appendix 5]
5. The golf club shaft according to claim 1, wherein the bias layer has a resin content of 30% by weight or more.
[Appendix 6]
The golf club shaft according to any one of supplementary notes 1 to 5, wherein the shaft weight is 50 g or less and the shaft torque is 5 ° or more.
[Appendix 7]
7. The golf club shaft according to any one of appendices 1 to 6, wherein a difference between a maximum value and a minimum value of the bending torsion angle is 0.3 ° or less.

2 golf club 4 head 6 shaft 10 first angle layer (first angle sheet)
20 ... second angle layer (second angle sheet)
12, 22 ... winding start edge 14, 24 ... winding end edge 30, 40 ... united sheet 54 ... non-integer ply portion of first bias layer 84 ... non-integer of second bias layer Ply section s1 to s11 prepreg sheet b1 bias layer (bias sheet)
Tp: Tip end Bt: Bat end

Claims (7)

The tip end,
Butt end,
A bias layer,
With a straight layer,
The bias layer has a first angle layer and a second angle layer in which fiber angles are inclined in directions opposite to each other,
The first angle layer and the second angle layer have a non-integer ply portion in at least a part of the axial direction,
A circumferential position of the first angle layer coincides with a circumferential position of the second angle layer;
The basis weight of the first angle layer is 50 g / m ² or less;
A golf club shaft having a basis weight of the second angle layer of 50 g / m ² or less. , When the number of plies of the first angle layer and the second angle layer at the tip end is X, and the number of plies of the first angle layer and the second angle layer at the butt end is Y,
The golf club shaft according to claim 1, wherein the difference (X-Y) is 1 or more and 5 or less. When the number of plies of the first angle layer and the second angle layer at the tip end is X, and the number of plies of the first angle layer and the second angle layer at the butt end is Y,
The golf club shaft according to claim 1, wherein the difference (X-Y) is 1 or more and 3.5 or less. 4. The golf club shaft according to claim 1, wherein the fiber elastic modulus of the bias layer is 30 t / mm ² or more. 5.   The golf club shaft according to any one of claims 1 to 4, wherein the resin content of the bias layer is 30% by weight or more.   The golf club shaft according to any one of claims 1 to 5, wherein the shaft weight is 50 g or less, and the shaft torque is 5 ° or more.   The golf club shaft according to any one of claims 1 to 6, wherein a difference between a maximum value and a minimum value of the bending torsion angle is 0.3 ° or less.

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