Shaft and golf club

Abstract

To improve the flexural rigidity of a shaft in a golf club and to reduce the weight of the shaft.SOLUTION: A shaft 2 of a golf club 1 has an inner peripheral surface 2a and an outer peripheral surface 5b around an axial line AS. The shaft 2 has a side end portion 21 which is one end portion in an axial direction DA parallel to the axial line AS, and a tip side end portion 22 which is the other end portion. The shaft 2 includes a plurality of carbon fiber layers 50 laminated in the radial direction DR orthogonal to the axial line AS. The weight of the shaft 2 is 39. 0g or less. The plurality of carbon fiber layers 50 include a straight layer 51 in which the orientation angle of the carbon fibers with respect to the axial direction DA is 5° or less. The ratio of the thickness of the straight layer 51 to the thickness of the shaft 2 is 60.0% or more at a position away from the tip-side end part 22 to the 940mm part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a shaft and a golf club. [Background technology]

[0002] For example, a golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis is known, as disclosed in Patent Document 1. The shaft includes a plurality of carbon fiber layers stacked in a direction perpendicular to the axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-022622 Summary of the Invention [Problem to be solved by the invention]

[0004] Increasing the bending rigidity of the shaft can suppress deformation of the shaft during a swing and stabilize the trajectory of the ball. However, in conventional shafts, increasing the bending rigidity also increases the weight of the shaft. The object of the present invention is to improve the bending rigidity of the shaft and reduce its weight. [Means for solving the problem]

[0005] A first shaft according to one embodiment of the present invention comprises: A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers stacked in a direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer having an orientation angle of 5° or less with respect to the axial direction, At a position 940 mm away from the tip-side end, the ratio of the thickness of the straight layer to the thickness of the shaft is 60.0% or more.

[0006] The second shaft according to one embodiment of the present invention comprises: A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, At a position 940 mm away from the tip-side end, the ratio of the cross-sectional area of ​​the straight layer to the cross-sectional area of ​​the shaft is 68% or more.

[0007] A third shaft according to an embodiment of the present invention comprises: A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to an axial direction parallel to the axis is 5° or less, The proportion of the weight of the straight layer to the weight of the shaft is 69.0% or more.

[0008] A fourth shaft according to an embodiment of the present invention comprises: A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, The vibration frequency is 295 [cpm] or higher. [Effects of the Invention]

[0009] According to the present invention, the bending rigidity of the shaft of a golf club can be improved and the shaft can be made lighter. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side view of a golf club for explaining an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a shaft included in the golf club of FIG. [Figure 3] FIG. 3 is a diagram for explaining the measurement method of the three-point bending test. [Figure 4] FIG. 4 is a diagram for explaining a method for determining the orientation angle of the carbon fibers with respect to the axial direction of the shaft. [Figure 5] FIG. 5 is a plan view of a full-length straight sheet. [Figure 6] FIG. 6 is a plan view of a full length bias sheet. [Figure 7] FIG. 7 is a plan view of a full length hoop sheet. [Figure 8] FIG. 8 is a plan view of the first reinforcing straight sheet. [Figure 9] FIG. 9 is a plan view of the first reinforcing bias sheet. [Figure 10] FIG. 10 is a plan view of the first reinforcing hoop sheet. [Figure 11] FIG. 11 is a plan view of the second reinforcing straight sheet. [Figure 12] FIG. 12 is a plan view of the second reinforcing bias sheet. [Figure 13] FIG. 13 is a plan view of the second reinforcing hoop sheet. [Figure 14]FIG. 14 is a diagram for explaining the layer structure and manufacturing method of the shaft of FIG. [Figure 15] FIG. 15 is a diagram for explaining a method for measuring the vibration frequency of the shaft. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention relates to the following [1] to

[11] .

[0012] [1] A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, A shaft, wherein the ratio of the thickness of the straight layer to the thickness of the shaft at a position 940 mm away from the tip side end is 60.0% or more.

[0013] [2] A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt end that is one end in an axial direction parallel to the axis and a tip end that is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, A shaft, wherein the ratio of the cross-sectional area of ​​the straight layer to the cross-sectional area of ​​the shaft at a position 940 mm away from the tip side end is 68% or more.

[0014] [3] A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt end that is one end in an axial direction parallel to the axis and a tip end that is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, A shaft, wherein the weight of the straight layer accounts for 69.0% or more of the total weight of the shaft.

[0015] [4] A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, Weighs 39.0g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, A shaft with a vibration frequency of 295 [cpm] or more.

[0016] [5] The shaft according to any one of [1] to [4], wherein the thickness of the shaft at a position 940 mm away from the tip-side end is 0.85 mm or less.

[0017] [6] The shaft according to any one of [1] to [5], wherein the outer diameter of the shaft at a position 940 mm away from the tip-side end is 1.10 times or less the inner diameter of the shaft.

[0018] [7] The shaft according to any one of [1] to [6], wherein the strength measured by a three-point bending test at a position 90 mm away from the tip-side end is 800 N or more.

[0019] [8] The shaft according to any one of [1] to [7], wherein the strength measured by a three-point bending test at a position 175 mm away from the tip-side end is 400 N or more.

[0020] [9] The shaft according to any one of [1] to [8], wherein the strength measured by a three-point bending test at a position 525 mm away from the tip-side end is 400 N or more.

[0021]

[10] The shaft according to any one of [1] to [8], wherein the strength in a three-point bending test at a position 175 mm away from the butt-side end is 400 N or more.

[0022]

[11] Any of the shafts [1] to

[10] . a grip attached to the butt-side end of the shaft; a head attached to the tip end of the shaft.

[0023] An embodiment will be described below with reference to the drawings. In the drawings, the scale and dimensions are exaggerated for ease of illustration and understanding. Note that components shown in some drawings may be omitted in other drawings.

[0024] Terms such as "orthogonal" and "identical" used to specify shapes and geometric conditions are not limited to their strict meanings, and should be interpreted to include a range within which similar functions can be expected.

[0025] Directions common to the drawings are indicated by arrows with the same symbol in each drawing. In each direction, the tip of the arrow is the first side. In each direction, the side opposite the first side, i.e., the base of the arrow, is the second side. Arrows pointing perpendicular to the paper surface from the front to the back are indicated by a symbol of an X in a circle, as shown in Figure 2, for example.

[0026] When multiple upper limit candidates and multiple lower limit candidates are listed for a certain parameter, the numerical range of the parameter may be formed by combining any one upper limit candidate with any one lower limit candidate. As an example, consider the numerical range of parameter C in the following description: "Parameter C may be A1 or more, A2 or more, or A3 or more. Parameter C may be A4 or less, A5 or less, or A6 or less." The numerical range of parameter C may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0027] 1 to 14 are diagrams illustrating one embodiment. Fig. 1 is a side view of a golf club 1. The golf club 1 includes a shaft 2, a grip 3 attached to the shaft 2, and a head 4.

[0028] The golf club 1 may be a driver (DR), a fairway wood (FW), a utility club (UT), an iron (IRON), or a wedge (WEDGE). The driver, fairway wood, utility club, iron, and wedge are types of the golf club 1.

[0029] The shaft 2 shown in Figures 1 and 2 has a cylindrical shape. The illustrated shaft 2 has an inner circumferential surface 2a and an outer circumferential surface 2b centered on an axis AS. The shaft 2 extends in an axial direction DA that is parallel to the axis AS. The dimensions of the shaft 2 in the axial direction DA may vary depending on the type of golf club 1.

[0030] The weight of the shaft 2 shown in FIG. 1 is 39.0 g or less. The weight of the shaft 2 may be 38.0 g or less, or 37.0 g or less. The weight of the shaft 2 may be 27.0 g or more, 30.0 g or more, or 35.0 g or more. The weight of the shaft 2 is measured using an electronic balance with a minimum unit of 0.1 g. The weight of the shaft 2 may vary depending on the type of golf club 1.

[0031] The shaft 2 shown in FIG. 1 has a butt-side end 21 as one end in the axial direction DA. The shaft 2 has a tip-side end 22 as the other end in the axial direction DA. In the illustrated golf club 1, the butt-side end 21 is housed in the grip 3. The butt-side end 21 is located in a recess formed in the grip 3. In the illustrated golf club 1, the tip-side end 22 is housed in the head 4. The tip-side end 22 is located in a recess formed in the head 4.

[0032] The strength of the shaft 2 shown in Figures 1 and 2 is measured by a three-point bending test, which will be described in detail below. Except for the points described below, the method for measuring the strength of the shaft 2 by the three-point bending test follows the SG-type three-point bending strength test specified by the Consumer Product Safety Association, which is also disclosed in, for example, JP2008-073067A.

[0033] In a three-point bending test, as shown in FIG. 3, a load F is applied from a load point EP to a shaft 2 that is supported from below at two support points FP. The load point EP is located between the two support points FP. The load point EP is located at one of the following positions: 90 mm from the tip end 22, 175 mm from the tip end 22, 525 mm from the tip end 22, and 175 mm from the butt end 21. The load F from the load point EP when the shaft 2 breaks is measured as the strength of the shaft 2 in the three-point bending test.

[0034] The distance DL between the two support points FP shown in Figure 3 is 300 mm when the load point EP is located 525 mm from the tip end 22, 175 mm from the tip end 22, or 175 mm from the butt end 21. When the load point EP is located 90 mm from the tip end 22, the distance DL between the two support points FP is 150 mm.

[0035] 1 and 2, a lower limit value for the strength in a three-point bending test may be set as follows: The upper limit value for the strength in a three-point bending test is not particularly limited.

[0036] 1 and 2, the strength measured by a three-point bending test at a position 90 mm away from the tip end 22 may be 800 N or more, 900 N or more, or 1000 N or more. The strength measured by a three-point bending test at a position 90 mm away from the tip end 22 may be 2000 N or less, 1680 N or less, or 1550 N or less.

[0037] 1 and 2, the strength measured by a three-point bending test at a position 175 mm away from the tip end 22 may be 400 N or more, 500 N or more, or 600 N or more. The strength measured by a three-point bending test at a position 175 mm away from the tip end 22 may be 750 N or less, 680 N or less, or 650 N or less.

[0038] 1 and 2, the strength measured by a three-point bending test at a position 525 mm away from the tip end 22 may be 400 N or more, 450 N or more, 500 N or more, or 550 N or more. The strength measured by a three-point bending test at a position 525 mm away from the tip end 22 may be 1000 N or less, 575 N or less, or 570 N or less.

[0039] 1 and 2, the strength measured by a three-point bending test at a position 175 mm away from the butt end 21 may be 400 N or more, 420 N or more, 450 N or more, 470 N or more, 500 N or more, or 560 N or more. The strength measured by a three-point bending test at a position 175 mm away from the butt end 21 may be 1200 N or less, 600 N or less, or 560 N or less.

[0040] 1, the shaft 2 may become thinner from the butt end 21 toward the tip end 22. The outer diameter of the shaft 2 may become smaller from the butt end 21 toward the tip end 22. The inner diameter of the shaft 2 may become smaller from the butt end 21 toward the tip end 22.

[0041] 2 is a cross-sectional view of the shaft 2 at a position 940 mm away from the tip end 22. The illustrated shaft 2 includes a plurality of carbon fiber layers 50 stacked in a radial direction DR perpendicular to the axis AS. The carbon fiber layers 50 extend in a circumferential direction DC centered on the axis AS.

[0042] The plurality of carbon fiber layers 50 are formed by heating a plurality of prepreg sheets 60 wound around a mandrel 70, as will be described later with reference to FIG. 14. The prepreg sheets 60 contain linear carbon fibers. The plurality of carbon fibers are oriented in the prepreg sheets 60. The prepreg sheets 60 contain a resin composition that restricts the movement of the plurality of carbon fibers. The plurality of carbon fibers are oriented in the carbon fiber layers 50 formed from the prepreg sheets 60. Examples of the prepreg sheets 60 are shown in FIGS. 5 to 13.

[0043] The mandrel 70 shown in Figure 14 is a rod-shaped member extending in an axial direction DB parallel to the axis AX. When the axis AS of the shaft 2 and the axis AX of the mandrel 70 are both written, the axis AS of the shaft 2 may be referred to as the first axis. The axis AX of the mandrel 70 may be referred to as the second axis. When the axial direction DA of the shaft 2 and the axial direction DB of the mandrel 70 are both written, the axial direction DA of the shaft 2 may be referred to as the first axis. The axial direction DB of the mandrel 70 may be referred to as the second axis.

[0044] The "orientation" of the multiple carbon fibers in the prepreg sheet 60 is determined by observing the prepreg sheet 60 using an optical microscope (KEYENCE VHX-950F Digital Microscope) as follows: The prepreg sheet 60, arranged on a flat surface, is observed using the optical microscope described above from the normal direction of the prepreg sheet 60. The prepreg sheet 60 is observed at a magnification such that 50 to 100 linear carbon fibers are included in one field of view. The longitudinal direction of the linear carbon fibers is identified in one field of view. When the longitudinal directions of 10 or more linear carbon fibers in one field of view are located within an angular range of less than 10°, the multiple carbon fibers are oriented. The "orientation direction" of the carbon fibers in the prepreg sheet 60 is the direction in which a line segment passing through the center of the angular range of the multiple carbon fibers identified by the above method extends. For example, when the angle range specified by the above method is 1°, the orientation direction is a direction extending at an angle of 0.5° from both ends of the angle range.

[0045] The carbon fiber layer 50 may include a cured resin. The cured resin is a cured product of a curable resin composition. The cured resin in the carbon fiber layer 50 may be formed by curing the resin composition contained in the prepreg sheet 60.

[0046] The resin composition contained in the prepreg sheet 60 may include a thermosetting resin. A thermosetting resin is typically a resin that hardens when heated. The resin composition contained in the prepreg sheet 60 may include a curing agent. The thermosetting resin contained in the prepreg sheet 60 may harden by reaction with the curing agent. The thermosetting resin may include one or more of a phenolic resin, a urea resin, a diallyl phthalate resin, a melamine resin, a guanamine resin, an unsaturated polyester resin, a polyurethane resin, an epoxy resin, an aminoalkyd resin, a melamine-urea co-condensation resin, and a silicone resin.

[0047] In the carbon fiber layer 50, the linear carbon fibers have anisotropy with respect to Young's modulus. The linear carbon fibers are less likely to deform when subjected to tensile stress in the longitudinal direction. In other words, the Young's modulus of the linear carbon fibers in the longitudinal direction is greater than the Young's modulus in a direction non-parallel to the longitudinal direction of the linear carbon fibers. In the carbon fiber layer 50, the Young's modulus decreases as the angle between the longitudinal direction of the linear carbon fibers and the direction in which the carbon fibers are pulled increases.

[0048] The multiple carbon fiber layers 50 shown in Fig. 2 include a straight layer 51 made of linear carbon fibers extending in the axial direction DA. In the straight layer 51, the orientation angle of the carbon fibers with respect to the axial direction DA is equal to or greater than 0° and equal to or less than 5°. The straight layer 51 is formed of a prepreg sheet 60 (straight sheet 61) in which the orientation angle of the carbon fibers with respect to the axial direction DB of the mandrel 70 is equal to or greater than 0° and equal to or less than 5°. In the cross section of the illustrated shaft 2, the straight layer 51 extending circumferentially is shown.

[0049] When the shaft 2 undergoes bending deformation, the carbon fiber layers 50 are subjected to tensile stress in the axial direction DA. As will be shown in the examples described later, when the longitudinal direction of the linear carbon fibers is substantially parallel to the axial direction DA of the shaft 2, that is, when the multiple carbon fiber layers 50 include straight layers 51, the bending rigidity of the shaft 2 can be improved.

[0050] The straight layer 51 shown in FIG. 2 has a certain thickness, i.e., a length in the radial direction DR. At a position 940 mm away from the tip-side end 22 of the illustrated shaft 2, the ratio of the thickness of the straight layer 51 to the thickness of the shaft 2 is 60.0% or more. The ratio of the thickness of the straight layer 51 to the thickness of the shaft 2 may be 65.0% or more, 67.0% or more, 72.0% or more, 73.0% or more, 80.0% or more, or 86.0% or more. The ratio of the thickness of the straight layer 51 to the thickness of the shaft 2 may be 90.0% or less, or 87.0% or less.

[0051] The thickness of the straight layer 51 is determined by observing the cross section of the shaft 2 using the optical microscope described above. The thickness of the shaft 2 is determined as half the difference between the outer diameter and inner diameter of the shaft 2 at a position 940 mm away from the tip end 22. The inner diameter of the shaft 2 is determined as the outer diameter of the mandrel 70 at a position corresponding to a position 940 mm away from the tip end 22. The outer diameters of the shaft 2 and the mandrel 70 are measured using a micrometer with a minimum reading of 0.01 mm. Note that the inner diameter of the shaft 2 may be measured using a vernier caliper with a minimum reading of 0.01 mm instead of the outer diameter of the mandrel 70 described above. The vernier caliper is used to measure the inner diameter of the shaft 2 while in contact with the cross section at a position 940 mm away from the tip end 22.

[0052] The orientation angle of the carbon fibers with respect to the axial direction DA in the carbon fiber layer 50 of the shaft 2 is calculated by the following method. The shaft 2 is cut by a plane that passes through the axis AS and extends in the axial direction DA and the radial direction DR. The cross section of the shaft 2 is observed using the optical microscope described above. At least the first surface 50a of the carbon fiber layer 50 is observed in the field of view of the optical microscope, as shown in FIG. 4. The second surface 50b of the carbon fiber layer 50 may also be observed in the field of view of the optical microscope, as shown in FIG. 4. The illustrated first surface 50a and second surface 50b extend in the axial direction DA. The first surface 50a and second surface 50b are spaced apart from each other in the radial direction DR. In the illustrated carbon fiber layer 50, the second surface 50b is farther from the axis AS in the radial direction DR than the first surface 50a.

[0053] As shown in FIG. 4, when the carbon fibers 80 have a certain orientation angle θ with respect to the axial direction DA, the carbon fibers 80 observed in the cross section of the shaft 2 extend between the first surface 50a and the second surface 50b in a direction inclined with respect to the axial direction DA. The orientation angle θ between the carbon fibers 80 and the inner circumferential surface 2a is calculated as an arctangent function from the ratio of the length LA of the carbon fibers 80 in the axial direction DA to the length LR of the carbon fibers 80 in the radial direction DR. Using this method, the angles θ between 50 different carbon fibers 80 and the inner circumferential surface 2a are calculated. The orientation angle of the carbon fibers with respect to the axial direction DA in the carbon fiber layer 50 is calculated as the average value of the calculated angles between the 50 carbon fibers and the inner circumferential surface 2a. Unlike in FIG. 4, the length LR of the carbon fibers 80 in the radial direction DR may be shorter than the distance between the first surface 50a and the second surface 50b. The length LR of the carbon fiber 80 in the radial direction DR may be the maximum value of the distance in the radial direction DR between the first surface 50a and the carbon fiber 80 in the field of view when the cross section of the shaft 2 is observed.

[0054] 1 and 2, the weight of the straight layer 51 accounts for a certain proportion of the overall weight of the shaft 2. The weight of the straight layer 51 may be 69.0% or more, 71.0% or more, 73.0% or more, or 75.0% or more of the weight of the shaft 2. The weight of the straight layer 51 may be 90.0% or less, 80.0% or less, or 77.0% or less of the weight of the shaft 2.

[0055] The weight ratio of the straight layer 51 is calculated as the ratio of the weight of the prepreg sheet 60 (straight sheet 61) constituting the straight layer 51 to the total weight of the plurality of prepreg sheets 60 constituting the plurality of carbon fiber layers 50. The weight of a certain prepreg sheet 60 is calculated as the product of the area of ​​the prepreg sheet 60 and the weight per unit area of ​​the prepreg sheet 60.

[0056] The plurality of carbon fiber layers 50 may include layers other than the straight layer 51. The plurality of carbon fiber layers 50 may include a bias layer composed of linear carbon fibers extending in a direction inclined with respect to the axial direction DA. In the bias layer, the orientation angle of the carbon fibers with respect to the axial direction DA is 40° or more and 50° or less. The bias layer is formed of a prepreg sheet 60 (bias sheet 62) with an orientation angle with respect to the axial direction of the mandrel of 40° or more and 50° or less. The bias layer improves the torsional rigidity of the shaft 2.

[0057] The multiple carbon fiber layers 50 may include a hoop layer made of linear carbon fibers extending in a circumferential direction DC centered on the axis AS of the shaft 2. As shown in Figures 7, 10, and 13, the hoop layer is formed from a prepreg sheet 60 (hoop sheet 63) having an orientation angle of 85° or more and 90° or less with respect to the axial direction DA. The hoop layer improves the rigidity of the shaft 2 against forces in the radial direction DR.

[0058] The carbon fiber layer 50 may include a full-length layer that extends over the entire length of the shaft 2. The full-length layer is formed by a full-length sheet 64. Examples of the full-length sheet 64 are shown in FIGS. 5 to 7. The illustrated full-length sheet 64 is a prepreg sheet 60 having a length equal to or greater than the entire length of the shaft 2.

[0059] 5 is a full-length straight sheet 641. The full-length straight sheet 641 is wound around the mandrel 70 so that the orientation angle of the carbon fibers with respect to the axial direction is between 0° and 5°. In the shaft 2, a full-length straight layer is formed from the full-length straight sheet 641.

[0060] 6 is a full length bias sheet 642. The full length bias sheet 642 is wound around the mandrel 70 so that the orientation angle of the carbon fibers with respect to the axial direction is 40° or more and 50° or less. In the shaft 2, a full length bias layer is formed from the full length bias sheet 642.

[0061] 7 is a full-length hoop sheet 643. The full-length hoop sheet 643 is wound around the mandrel 70 so that the orientation angle of the carbon fibers relative to the axial direction is 85° or more and 90° or less. In the shaft 2, the full-length hoop layer is formed from the full-length hoop sheet 643.

[0062] The carbon fiber layer 50 may include a first reinforcing layer. The first reinforcing layer reinforces a first reinforcing portion located on the butt-side end 21 side of the shaft 2. The first reinforcing layer is formed by a first reinforcing sheet 65. Examples of the first reinforcing sheet 65 are shown in FIGS. 8 to 10. The illustrated first reinforcing sheet 65 is a prepreg sheet 60 that is shorter than the overall length of the shaft 2. The first reinforcing sheet 65 is wrapped around the shaft 2 at a position that will form the first reinforcing portion.

[0063] 8 is a first reinforcing straight sheet 651. The first reinforcing straight sheet 651 is wound around the mandrel 70 so that the orientation angle of the carbon fibers with respect to the axial direction is between 0° and 5°. In the shaft 2, the first reinforcing straight sheet 651 forms a first reinforcing straight layer.

[0064] 9 is a first reinforcing bias sheet 652. The first reinforcing bias sheet 652 is wound around the mandrel 70 so that the orientation angle of the carbon fibers with respect to the axial direction is 40° or more and 50° or less. In the shaft 2, the first reinforcing bias sheet 652 forms a first reinforcing bias layer.

[0065] 10 is a first reinforcing hoop sheet 653. The first reinforcing hoop sheet 653 is wound around the mandrel 70 so that the orientation angle of the carbon fibers relative to the axial direction is 85° or more and 90° or less. In the shaft 2, the first reinforcing hoop sheet 653 forms a first reinforcing hoop layer.

[0066] The carbon fiber layer 50 may include a second reinforcing layer. The second reinforcing layer reinforces a second reinforcing portion located on the tip-side end 22 side of the shaft 2. The second reinforcing layer is formed by a second reinforcing sheet 66. An example of the second reinforcing sheet 66 is shown in FIGS. 11 to 13. The illustrated second reinforcing sheet 66 is a prepreg sheet 60 that is shorter than the overall length of the shaft 2. The second reinforcing sheet 66 is wrapped around the shaft 2 at a position where the second reinforcing portion will be formed.

[0067] 11 is a second reinforcing straight sheet 661. The second reinforcing straight sheet 661 is wound around the mandrel 70 so that the orientation angle of the carbon fibers with respect to the axial direction is between 0° and 5°. In the shaft 2, the second reinforcing straight sheet 661 forms a second reinforcing straight layer.

[0068] 12 is a second reinforcing bias sheet 662. The second reinforcing bias sheet 662 is wound around the mandrel 70 so that the orientation angle of the carbon fibers with respect to the axial direction is 40° or more and 50° or less. In the shaft 2, the second reinforcing bias sheet 662 forms a second reinforcing bias layer.

[0069] 13 is a second reinforcing hoop sheet 663. The second reinforcing hoop sheet 663 is wound around the mandrel 70 so that the orientation angle of the carbon fibers relative to the axial direction is 85° or more and 90° or less. In the shaft 2, the second reinforcing hoop sheet 663 forms a second reinforcing hoop layer.

[0070] An example of a method for manufacturing the shaft 2 shown in FIG. 2 will be described with reference to FIG.

[0071] A plurality of prepreg sheets 60 are wound around a mandrel 70. In the example shown in FIG. 14 , two full-length bias sheets 642, one second reinforcing straight sheet 661, two full-length straight sheets 641, one full-length hoop sheet 631, two full-length straight sheets 641, and one second reinforcing straight sheet 661 are wound around the mandrel 70 in this order. The prepreg sheet 60 wound around the mandrel 70 first forms the carbon fiber layer 50 located on the inner side in the radial direction DR. In the example shown in FIG. 14 , the two full-length bias sheets 642 form the carbon fiber layer 50 located on the inner side in the radial direction DR compared to the one second reinforcing straight sheet 661.

[0072] The prepreg sheet 60 wrapped around the mandrel 70 is heated. Heating the prepreg sheet 60 cures the thermosetting resin contained in the prepreg sheet 60. Heating the prepreg sheet 60 forms a laminate including a plurality of carbon fiber layers 50. The laminate has an axial direction DA that is parallel to the axial direction of the mandrel 70.

[0073] The mandrel 70 is pulled out from the laminate wound around the mandrel 70. Both ends of the laminate in the axial direction DA may be cut. In this manner, the shaft 2 is produced. The shaft 2 produced from the plurality of prepreg sheets 60 shown in FIG. 14 includes, in this order from the inner circumferential surface 2a to the outer circumferential surface 2b, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, and a second reinforcing straight layer.

[0074] The operation of the shaft 2 shown in Figures 1 and 2 will be described. Specifically, a method for evaluating the bending rigidity of the illustrated shaft 2 will be described. More specifically, a method for measuring the vibration frequency of the illustrated shaft 2 will be described.

[0075] The weight 7 is attached to the tip end 22 of the shaft 2. The weight 7 and the shaft 2 form a test specimen 8. FIG. 15 shows a side view of the test specimen 8. The test specimen 8 has a first end 81 formed by the weight 7 and a second end 82 opposite the first end 81. The first end 81 of the test specimen 8 shown in FIG. 15 is formed by the butt end 21 of the shaft 2.

[0076] The weight 7 shown in FIG. 15 has a cylindrical shape. When attaching the weight 7 to the shaft 2, the shaft 2 is inserted into the inner diameter portion 7r of the weight 7 from the tip end 22. The weight 7 has an inner diameter large enough to allow the tip end 22 of the shaft 2 to be inserted therein. The axial length LW of the weight 7 is 50 mm. When the shaft 2 is used with a driver or fairway wood, the weight of the weight 7 is 200 g. When the shaft 2 is used with a utility, iron, or wedge, the weight of the weight 7 is 250 g. The "weight of the weight" includes the weight of a fixing means (not shown) for fixing the weight 7 to the shaft 2. The fixing means is a screw. The weight 7 has a hole for attaching the fixing means. The hole is located 25 mm away from the axial end of the weight 7, i.e., in the axial center of the weight 7.

[0077] The test specimen 8 is attached to a frequency measuring device 100. The frequency measuring device 100 is fixed on a flat surface. In the test specimen 8, a portion of the shaft 2 near the butt-side end 21 is clamped by a clamp 101 of the frequency measuring device 100. The portion clamped by the clamp 101 of the frequency measuring device 100 is restricted from moving relative to the frequency measuring device 100.

[0078] Dimension B of the test specimen 8 attached to the frequency measuring device 100, i.e., the shortest distance between the second end 82 and the clamp 101, is 965 mm when the shaft 2 is used for a driver. Dimension B is 914 mm when the shaft 2 is used for a fairway wood. Dimension B is 838 mm when the shaft 2 is used for a utility club. Dimension B is 762 mm when the shaft 2 is used for an iron. Dimension B is 711 mm when the shaft 2 is used for a wedge.

[0079] With the test piece 8 attached to the frequency measuring instrument 100, the weight 7 is pressed towards the flat surface on which the frequency measuring instrument 100 is fixed. From this state, the weight 7 is released, causing the test piece 8 to vibrate.

[0080] The vibration frequency [cpm] of the shaft 2 is measured with the test specimen 8 in a vibrating state. The vibration frequency [cpm] of the shaft 2 is measured as the number of reciprocating movements per minute of the vibrating test specimen 8 between the position farthest from the flat surface and the position closest to the flat surface. The number of reciprocating movements of the vibrating test specimen 8 is measured by the receiver of the frequency measuring instrument 100. The receiver is placed at a position 575 mm away from the clamp end of the frequency measuring instrument.

[0081] The vibration frequency of the shaft 2 shown in Figures 1 and 2 measured under the above measurement conditions is 295 [cpm] or higher. Note that other measurement conditions related to the vibration frequency measurement method are in accordance with "IX. Guidelines for 'Shaft Stiffness Measurement Standards'" in the "Guidelines for Golf Club 'Specification Measurement' (Revised 3rd Edition: January 1, 2023)" issued by the Japan Golf Goods Association. There are no particular limitations on the upper limit of the vibration frequency of the shaft 2 measured under the above measurement conditions. The vibration frequency of the shaft 2 may be 360 ​​[cpm] or lower, or 330 [cpm] or lower.

[0082] Incidentally, the vibration frequency of a shaft increases by increasing the bending rigidity of the shaft. The bending rigidity of a shaft is the product of the Young's modulus E of the shaft material and the moment of inertia I of the shaft. The moment of inertia I of a cylindrical shaft having inner and outer surfaces is expressed by the following formula. In the following formula, d represents the inner diameter of the shaft, and D represents the outer diameter of the shaft.

number

[0083] In a conventional shaft having a cylindrical shape and including multiple carbon fiber layers stacked radially perpendicular to the axis, increasing the outer diameter of the shaft increases its bending stiffness. Specifically, increasing the outer diameter of the shaft, i.e., D in the above formula, increases the second moment of area I of the shaft. In a shaft, increasing the second moment of area I results in an increase in bending stiffness. However, increasing the outer diameter of the shaft also increases the weight of the shaft. This creates a problem in conventional shafts, making it difficult to improve bending stiffness while reducing weight.

[0084] To address the above-mentioned problem, the present inventors discovered that a lower limit can be set for the ratio of the thickness of the straight layer to the thickness of the shaft. In the shaft 2 shown in Figures 1 and 2, the ratio of the thickness of the straight layer 51 to the thickness of the shaft 2 at a position 940 mm away from the tip end 22 is 60.0% or more.

[0085] In response to the above-mentioned problem, the inventors of the present invention have found that a lower limit can be set for the ratio of the cross-sectional area of ​​the straight layer to the cross-sectional area of ​​the shaft. In the shaft 2 shown in Figures 1 and 2, the ratio of the cross-sectional area of ​​the straight layer 51 to the cross-sectional area of ​​the shaft 2 at a position 940 mm away from the tip end 22 is 68% or more.

[0086] At a position 940 mm away from the tip-side end 22, the ratio of the cross-sectional area of ​​the straight layer 51 to the cross-sectional area of ​​the shaft 2 is measured by the following method.

[0087] The cross-sectional area of ​​the shaft 2 is calculated at a position 940 mm away from the tip-side end 22. The cross-sectional area of ​​the shaft 2 is calculated by subtracting the area of ​​a circle whose diameter is the inner diameter of the shaft 2 from the area of ​​a circle whose diameter is the outer diameter of the shaft 2. The outer diameter and inner diameter of the shaft 2 are measured by the method described above.

[0088] As shown in FIG. 2, a straight layer 51 is identified in the cross-sectional view of the shaft 2. In the cross-sectional view of the shaft 2, the straight layer 51 can be identified as a layer having at least 100 carbon fibers with circular cross sections. When the carbon fibers have a circular cross section, the ratio of the length of the minor axis to the length of the major axis in the cross section of the carbon fiber is 0.996 or more and 1.00 or less. The major axis is the portion of the cross section of the carbon fiber that has the longest dimension. The minor axis is the portion of the cross section of the carbon fiber that is perpendicular to the major axis.

[0089] The outer diameter and inner diameter of the straight layer 51 are determined. The inner diameter of the straight layer 51 is calculated as the sum of the shortest distances in the radial direction DR between the straight layer 51 and the inner circumferential surface 2a. The outer diameter of the straight layer 51 is calculated as the sum of the longest distances in the radial direction DR between the straight layer 51 and the inner circumferential surface 2a.

[0090] The cross-sectional area of ​​the straight layer 51 is determined from the outer diameter and inner diameter of the straight layer 51. The cross-sectional area of ​​the straight layer 51 is calculated by subtracting the area of ​​a circle whose diameter is the inner diameter of the straight layer 51 from the area of ​​a circle whose diameter is the outer diameter of the straight layer 51.

[0091] The ratio of the cross-sectional area of ​​the straight layer 51 to the cross-sectional area of ​​the shaft 2 is determined by dividing the cross-sectional area of ​​the straight layer 51 determined as described above by the cross-sectional area of ​​the shaft 2. When the shaft 2 has multiple straight layers 51, the "cross-sectional area of ​​the straight layers 51" is the sum of the areas determined by the above-described method for each of the multiple straight layers 51.

[0092] Furthermore, to address the above-mentioned problem, the present inventors have found that a lower limit can be set for the ratio of the weight of the straight layer 51 to the weight of the shaft 2. In the shaft 2 shown in Figures 1 and 2, the ratio of the weight of the straight layer 51 to the weight of the shaft 2 is 69.0% or more.

[0093] As described above, the straight layers 51 included in the multiple carbon fiber layers 50 of the shaft 2 shown in FIGS. 1 and 2 can improve the bending rigidity of the shaft 2. Furthermore, in the illustrated shaft 2, the bending rigidity is increased while suppressing increases in the outer diameter and thickness. The outer diameter of the shaft 2 may be 1.10 times or less, 1.08 times or less, or 1.07 times or less of the inner diameter. The thickness of the shaft 2 may be 0.85 mm or less, 0.60 mm or less, or 0.50 mm or less. The outer diameter of the shaft 2 may be 1.03 times or more, or 1.06 times or more of the inner diameter. The thickness of the shaft 2 may be 0.45 mm or more.

[0094] 1 and 2, an increase in the outer diameter and thickness is suppressed, and as a result, an increase in weight is suppressed. The weight of the shaft 2 may be 39.0 g or less, 38.0 g or less, or 37.0 g or less.

[0095] Therefore, with the illustrated shaft 2, as will be shown in the examples described below, it is possible to improve the bending rigidity of the shaft, which is evaluated as frequency [cpm], and also achieve weight reduction, compared to conventional shafts.

[0096] Furthermore, the shaft 2 shown in FIG. 3 has a certain degree of strength in a three-point bending test. As will be shown in the examples described later, the strength of the illustrated shaft 2 in a three-point bending test at a position 90 mm away from the tip end 22 is 800 N or more. The strength of the illustrated shaft 2 in a three-point bending test at a position 175 mm away from the tip end 22 is 400 N or more. The strength of the illustrated shaft 2 in a three-point bending test at a position 525 mm away from the tip end 22 is 400 N or more. The strength of the illustrated shaft 2 in a three-point bending test at a position 175 mm away from the butt end 21 is 400 N or more. Ensuring the strength of the shaft 2 can improve the durability of the shaft 2 described above.

[0097] In the embodiment described above, the shaft 2 is the shaft 2 of the golf club 1, having an inner circumferential surface 2a and an outer circumferential surface 2b centered on the axis AS. The shaft 2 has a butt end 21, which is one end in the axial direction DA parallel to the axis AS, and a tip end 22, which is the other end. The shaft 2 includes a plurality of carbon fiber layers 50 laminated in a radial direction DR perpendicular to the axis AS. The weight of the shaft 2 is 39.0 g or less. The plurality of carbon fiber layers 50 includes a straight layer 51 in which the orientation angle of the carbon fibers with respect to the axial direction DA is 5° or less. At a position 940 mm away from the tip end 22, the ratio of the thickness of the straight layer 51 to the thickness of the shaft 2 is 60.0% or less.

[0098] In the embodiment described above, the shaft 2 is the shaft 2 of the golf club 1, having an inner circumferential surface 2a and an outer circumferential surface 2b centered on the axis AS. The shaft 2 has a butt-side end 21, which is one end in the axial direction DA parallel to the axis AS, and a tip-side end 22, which is the other end. The shaft 2 includes a plurality of carbon fiber layers 50 laminated in a radial direction DR perpendicular to the axis AS. The weight of the shaft 2 is 39.0 g or less. The plurality of carbon fiber layers 50 includes a straight layer 51 in which the orientation angle of the carbon fibers with respect to the axial direction DA is 5° or less. At a position 940 mm away from the tip-side end 22, the proportion of the cross-sectional area of ​​the straight layer 51 to the cross-sectional area of ​​the shaft 2 is 68% or more.

[0099] Furthermore, in the embodiment described above, the shaft 2 is the shaft 2 of the golf club 1, having an inner circumferential surface 2a and an outer circumferential surface 2b centered on the axis AS. The shaft 2 has a butt-side end 21, which is one end in the axial direction DA parallel to the axis AS, and a tip-side end 22, which is the other end. The shaft 2 includes a plurality of carbon fiber layers 50 laminated in a radial direction DR perpendicular to the axis AS. The weight of the shaft 2 is 39.0 g or less. The plurality of carbon fiber layers 50 includes straight layers 51 in which the orientation angle of the carbon fibers with respect to the axial direction DA is 5° or less. The weight of the straight layers 51 accounts for 69.0% or more of the weight of the shaft 2.

[0100] Furthermore, in the embodiment described above, the shaft 2 is the shaft 2 of the golf club 1, having an inner circumferential surface 2a and an outer circumferential surface 2b centered on the axis AS. The shaft 2 has a butt end 21, which is one end in the axial direction DA parallel to the axis AS, and a tip end 22, which is the other end. The shaft 2 includes a plurality of carbon fiber layers 50 laminated in a radial direction DR perpendicular to the axis AS. The weight of the shaft 2 is 39.0 g or less. The vibration frequency of the shaft 2 measured with the head 4 attached to the tip end 22 is 295 [cpm] or more.

[0101] According to these embodiments, the straight layer 51 included in the plurality of carbon fiber layers 50 can improve the bending rigidity of the shaft 2. By improving the bending rigidity of the shaft 2 using the straight layer 51, an increase in the weight of the shaft 2 can be suppressed. Therefore, the bending rigidity of the shaft 2 can be improved and the weight can be reduced. As a result, deformation during a swing can be suppressed in the lightweight shaft 2, and the trajectory of the hit ball can be stabilized.

[0102] Although one embodiment has been described with reference to specific examples, the above-described specific examples do not limit the present invention. The above-described embodiment can be implemented with various other specific examples, and various omissions, substitutions, changes, additions, etc. can be made without departing from the spirit of the present invention. [Example]

[0103] Hereinafter, an embodiment of the present invention will be described in more detail using examples, but the present invention is not limited to the following examples.

[0104] Shafts according to Examples 1 to 7 and shafts according to Comparative Examples 1 and 2 were fabricated. The fabricated shafts had an inner peripheral surface and an outer peripheral surface centered on the axis. The fabricated shafts had a butt end, which was one end in the axial direction parallel to the axis, and a tip end, which was the other end. The fabricated shafts included multiple carbon fiber layers laminated in a radial direction perpendicular to the axis. The shafts according to Examples 1 to 7 and the shafts according to Comparative Examples 1 and 2 had the above configuration in common.

[0105] Example 1 A plurality of prepreg sheets were wound around a mandrel. In producing the shaft according to Example 1, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a full-length hoop sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around the mandrel in this order. The prepreg sheets wound around the mandrel were heated to form a laminate including a plurality of carbon fiber layers. The mandrel was pulled out from the laminate, and both ends of the laminate were cut. In the shaft according to Example 1, the plurality of carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0106] <Example 2> The shaft according to Example 2 differed from the shaft according to Example 1 in the layer configuration of the multiple carbon fiber layers 50. In producing the shaft according to Example 2, a second reinforcing bias sheet, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a full-length hoop sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft according to Example 2, the multiple carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a second reinforcing bias layer, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0107] Example 3 The shaft of Example 3 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers 50. In producing the shaft of Example 3, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a full-length bias sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. No hoop sheet was used in producing the shaft of Example 3. In the shaft of Example 3, the multiple carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length bias layer, a full-length straight layer, and a second reinforcing straight layer in this order. In the shaft of Example 3, the multiple carbon fiber layers did not include a hoop layer.

[0108] Example 4 The shaft of Example 4 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers. In producing the shaft of Example 4, a second reinforcing bias sheet, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a first reinforcing hoop sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft of Example 4, the multiple carbon fiber layers included, from the inner circumferential surface toward the outer circumferential surface, a second reinforcing bias layer, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a first reinforcing hoop layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0109] <Example 5> The shaft of Example 5 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers. In producing the shaft of Example 5, a second reinforcing bias sheet, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a full-length hoop sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft of Example 5, the multiple carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a second reinforcing bias layer, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0110] Example 6 The shaft of Example 6 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers. In producing the shaft of Example 6, a second reinforcing bias sheet, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a full-length hoop sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft of Example 6, the multiple carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a second reinforcing bias layer, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0111] Example 7 The shaft of Example 7 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers. In producing the shaft of Example 7, a second reinforcing hoop sheet, a full-length bias sheet, a second reinforcing bias sheet, a second reinforcing straight sheet, a full-length straight sheet, a full-length hoop sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft of Example 7, the multiple carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a second reinforcing hoop layer, a full-length bias layer, a second reinforcing bias layer, a second reinforcing straight layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0112] <Comparative Example 1> The shaft of Comparative Example 1 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers. In producing the shaft of Comparative Example 1, a full-length bias sheet, a full-length straight sheet, a full-length hoop sheet, a full-length straight sheet, a second reinforcing straight sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft of Comparative Example 1, the multiple carbon fiber layers included, from the inner circumferential surface to the outer circumferential surface, a full-length bias layer, a full-length straight layer, a full-length hoop layer, a full-length straight layer, a second reinforcing straight layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0113] <Comparative Example 2> The shaft of Comparative Example 2 differed from the shaft of Example 1 in the layer configuration of the multiple carbon fiber layers. In producing the shaft of Comparative Example 2, a full-length bias sheet, a second reinforcing straight sheet, a full-length straight sheet, and a second reinforcing straight sheet were wound around a mandrel in this order. In the shaft of Comparative Example 2, the multiple carbon fiber layers included, from the inner circumferential surface toward the outer circumferential surface, a full-length bias layer, a second reinforcing straight layer, a full-length straight layer, and a second reinforcing straight layer in this order.

[0114] <Shaft weight [g]> The weight [g] of the shafts according to each example and each comparative example was measured using an electronic balance (A&D Corporation's "Personal Electronic Balance (EK-1200i)"). The minimum unit of the electronic balance was 0.1 g. The measurement results for the shafts according to each example are shown in the "Shaft Weight [g]" column of Table 1 below. The measurement results for the shafts according to each comparative example are shown in the "Shaft Weight [g]" column of Table 2 below.

[0115] <Straight layer weight ratio [%]> The weight of the straight layer in the shafts according to each example and each comparative example was measured using the method described above. From the measurement results, the weight ratio of the straight layer to the weight of the shaft was calculated. The calculation results for the shafts according to each example are shown in the "weight ratio of straight layer [%]" column in Table 1 below. The calculation results for the shafts according to each comparative example are shown in the "weight ratio of straight layer [%]" column in Table 2 below.

[0116] <Straight layer cross-sectional area ratio [%]> For the shafts according to Examples 1, 3, and 4, the cross-sectional area of ​​the shaft at a position 940 mm away from the tip end and the cross-sectional area of ​​the straight layer were measured using the method described above. From the measurement results, the ratio of the cross-sectional area of ​​the straight layer to the cross-sectional area of ​​the shaft was calculated. The calculation results for the shafts according to Examples 1, 3, and 4 are shown in the "Straight Layer Cross-sectional Area Ratio [%]" column in Table 1 below. Note that in Table 1, a "-" next to the "Straight Layer Cross-sectional Area Ratio [%]" for the shafts according to Examples 2, 5, 6, and 7 indicates that the above-mentioned ratio was not calculated for those examples. In Table 2, a "-" next to the "Straight Layer Cross-sectional Area Ratio [%]" for the shafts according to Comparative Examples 1 and 2 indicates that the above-mentioned ratio was not calculated for those comparative examples.

[0117] <Inner diameter / outer diameter ratio> The outer diameter of each example shaft and each comparative example shaft was measured at a position 940 mm away from the tip end. For each example shaft and each comparative example shaft, the outer diameter of the mandrel was measured at a position 940 mm away from the tip end as the inner diameter of the shaft. A micrometer (count outside micrometer (193-101) manufactured by Mitutoyo Corporation) was used to measure the outer diameter of the shaft and the outer diameter of the mandrel. The minimum display of the micrometer was 0.01 mm. From the measurement results, the ratio of the outer diameter to the inner diameter was calculated for each example shaft and each comparative example shaft. The calculated ratios for each example shaft are shown in the "Outer diameter to inner diameter ratio" column in Table 1 below. The calculated ratios for each comparative example shaft are shown in the "Inner diameter to outer diameter ratio" column in Table 2 below.

[0118] <Shaft thickness [mm]> The thickness of the shafts according to each example and each comparative example was calculated at a position 940 mm away from the tip end. The thickness of the shaft was calculated as half the difference between the outer diameter and inner diameter of the shaft measured by the method described above. The measurement results for the shafts according to each example are shown in the "Shaft Thickness (mm)" column of Table 1 below. The measurement results for the shafts according to each comparative example are shown in the "Shaft Thickness (mm)" column of Table 2 below.

[0119] <Straight layer thickness ratio [%]> For each example shaft and each comparative example shaft, the thickness of the shaft and the thickness of the straight layer were measured at a position 940 mm away from the tip end. From the measurement results, the ratio of the thickness of the straight layer to the thickness of the shaft was calculated. The calculation results for each example shaft are shown in the "Straight layer thickness ratio [%]" column in Table 1 below. The calculation results for each comparative example shaft are shown in the "Straight layer thickness ratio [%]" column in Table 2 below.

[0120] <Vibration frequency [cpm]> The vibration frequency [cpm] of test specimens including the shafts according to each example and each comparative example was measured by the method described above. A "Golf Club Timing Harmonizer" manufactured by Fujikura Composites Co., Ltd. was used as the vibration frequency measuring device. The weight had a weight of 200 g. The measurement results for the shafts according to each example are shown in the "Vibration Frequency [cpm]" column of Table 1 below. The measurement results for the shafts according to each comparative example are shown in the "Vibration Frequency [cpm]" column of Table 2 below.

[0121] <3-point bending strength [N]> The above-described three-point bending test was performed on the shafts according to each example and each comparative example to measure the strength of the shafts. The measurement results for the shafts according to each example when the load point was 90 mm from the tip end are shown in the "3-point bending strength T-90 [N]" column of Table 1 below. The measurement results for the shafts according to each comparative example when the load point was 90 mm from the tip end are shown in the "3-point bending strength T-90 [N]" column of Table 2 below. The measurement results for the shafts according to each example when the load point was 175 mm from the tip end are shown in the "3-point bending strength T-175 [N]" column of Table 1 below. The measurement results for the shafts according to each comparative example when the load point was 175 mm from the tip end are shown in the "3-point bending strength T-175 [N]" column of Table 2 below. The measurement results for the shafts according to each example when the load point was 525 mm from the tip end are shown in the "3-point bending strength T-525 [N]" column of Table 1 below. The measurement results of the shafts according to each comparative example when the load point was located 525 mm from the tip end are shown in the "3-point bending strength T-525 [N]" column in Table 2 below. The measurement results of the shafts according to each example when the load point was located 175 mm from the butt end are shown in the "3-point bending strength B-175 [N]" column in Table 1 below. The measurement results of the shafts according to each example when the load point was located 175 mm from the butt end are shown in the "3-point bending strength B-175 [N]" column in Table 2 below.

[0122] [Table 1]

[0123] [Table 2] [Explanation of symbols]

[0124] 1: golf club, 2: shaft, 2a: inner peripheral surface, 2b: outer peripheral surface, 21: butt-side end, 22: tip-side end, 3: grip, 4: head, 50: carbon fiber layer, 51: straight layer, 60: prepreg sheet, 61: straight sheet, 62: bias sheet, 63: hoop sheet, 64: full-length sheet, 65: first reinforcing sheet, 66: second reinforcing sheet, 70: mandrel, DA: axial direction, DR: radial direction, DC: circumferential direction

Claims

1. A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, The weight is 39.0 g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, A shaft, wherein the ratio of the thickness of the straight layer to the thickness of the shaft at a position 940 mm away from the tip side end is 60.0% or more.

2. A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, The weight is 39.0 g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to the axial direction is 5° or less, A shaft, wherein at a position 940 mm away from the tip side end, the ratio of the cross-sectional area of ​​the straight layer to the cross-sectional area of ​​the shaft is 68% or more.

3. A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, The weight is 39.0 g or less, the plurality of carbon fiber layers include a straight layer in which the orientation angle of the carbon fibers with respect to an axial direction parallel to the axis is 5° or less, A shaft, wherein the ratio of the weight of the straight layer to the weight of the shaft is 69.0% or more.

4. A golf club shaft having an inner circumferential surface and an outer circumferential surface centered on an axis, a butt-side end portion which is one end in an axial direction parallel to the axis line, and a tip-side end portion which is the other end, a plurality of carbon fiber layers laminated in a radial direction perpendicular to the axis, The weight is 39.0 g or less, A shaft with a vibration frequency of 295 [cpm] or more.

5. The shaft according to any one of claims 1 to 4, wherein the thickness of the shaft at a position 940 mm away from the tip side end is 0.85 mm or less.

6. The shaft according to any one of claims 1 to 4, wherein the outer diameter of the shaft at a position 940 mm away from the tip side end is 1.10 times or less the inner diameter of the shaft.

7. The shaft according to any one of claims 1 to 4, wherein a strength measured by a three-point bending test at a position 90 mm away from the tip side end is 800 N or more.

8. The shaft according to any one of claims 1 to 4, wherein a strength measured by a three-point bending test at a position 175 mm away from the tip side end is 400 N or more.

9. The shaft according to any one of claims 1 to 4, wherein a strength measured by a three-point bending test at a position 525 mm away from the tip side end is 400 N or more.

10. The shaft according to any one of claims 1 to 4, wherein a strength measured by a three-point bending test at a position 175 mm away from the butt-side end is 400 N or more.

11. A shaft according to any one of claims 1 to 4, a grip attached to the butt-side end of the shaft; a head attached to the tip end of the shaft.

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