Golf club shaft

Abstract

To provide a golf club shaft having a novel laminated structure capable of increasing shaft strength.SOLUTION: A shaft 6 is formed of a plurality of fiber reinforced resin layers. The shaft 6 includes a straight layer, a bias layer, and a hoop layer. The straight layer includes at least one full-length straight layer having a length of 0.7 L or more with respect to the full length L of the shaft. The hoop layer includes a full-length hoop layer having a length of 0.7 L or more with respect to the full length L of the shaft. The full-length hoop layer is composed of only one inner full-length hoop layer f1 and one outer full-length hoop layer f2. At least one full-length straight layer is disposed inside the outer full-length hoop layer f2. When the thickness of the inner full-length hoop layer is T1 and the thickness of the outer full-length hoop layer is T2, T2 / T1 is greater than 1 and less than 2. The resin content of the outer full-length hoop layer is smaller than the resin content of the inner full-length hoop layer.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A shaft formed of a plurality of fiber-reinforced resin layers is known. In this shaft, various shafts can be designed by stacking the plurality of fiber-reinforced resin layers. JP 2023-36259 A discloses a shaft including a full-length hoop layer and a partial hoop layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-36259 A Summary of the Invention [Problem to be solved by the invention]

[0004] The laminated structure capable of increasing the strength of the shaft contributes to making the shaft lighter and increasing the design freedom of the shaft.

[0005] One example of the present invention provides a golf club shaft with a new layered structure that can increase the strength of the shaft. [Means for solving the problem]

[0006] In one embodiment, the golf club shaft is formed of a plurality of fiber-reinforced resin layers and has a tip end and a butt end. The golf club shaft includes a straight layer, a bias layer, and a hoop layer. The straight layer includes at least one full-length straight layer having a length of 0.7L or more with respect to the total length L of the shaft. The hoop layer includes a full-length hoop layer having a length of 0.7L or more with respect to the total length L of the shaft. The full-length hoop layer is composed of only one inner full-length hoop layer and one outer full-length hoop layer located outside the inner full-length hoop layer. At least one of the full-length straight layers is disposed inside the outer full-length hoop layer. When the thickness of the inner full-length hoop layer is T1 (mm) and the thickness of the outer full-length hoop layer is T2 (mm), T2 / T1 is greater than 1 and less than 2. The resin content of the outer full-length hoop layer is less than the resin content of the inner full-length hoop layer. Effect of the Invention

[0007] As one aspect, a new layer structure that can increase the strength of a shaft formed of a plurality of fiber-reinforced resin layers can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an overall view of a golf club equipped with a golf club shaft of an embodiment. [Diagram 2] FIG. 2 is a development view of the golf club shaft shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram showing a method for measuring the three-point bending strength. [Figure 4] FIG. 4 is a schematic diagram showing a method for measuring the crushing strength. [Diagram 5] FIG. 5 is an explanatory diagram showing a cross section of the shaft when it is pressed radially inward from above. [Figure 6] FIG. 6 is an explanatory diagram showing a longitudinal section of the shaft when it is bent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate.

[0010] In this application, the terms "layer" and "sheet" are used. A "layer" is the name after it has been rolled, whereas a "sheet" is the name before it has been rolled. A "layer" is formed by rolling a "sheet." In other words, the rolled "sheet" forms a "layer."

[0011] In this application, the same reference numerals are used for layers and sheets, for example, the layer formed by sheet s1 is referred to as layer s1.

[0012] In this application, the axial direction means the axial direction of the shaft. In this application, the circumferential direction means the circumferential direction of the shaft. Unless otherwise specified, the length in this application means the length in the axial direction. Unless otherwise specified, the position in this application means the position in the axial direction. Unless otherwise specified, the "inner" in this application means the inner side in the radial direction of the shaft, and is also referred to as the inner layer side. Unless otherwise specified, the "outer" in this application means the outer side in the radial direction of the shaft, and is also referred to as the outer layer side.

[0013] FIG. 1 shows a golf club 2 equipped with a golf club shaft 6 according to the present invention. The golf club 2 includes a head 4, a shaft 6, and a grip 8. The head 4 is provided at the tip portion of the shaft 6. The grip 8 is provided at the butt portion of the shaft 6. The shaft 6 is a shaft for a wooden club. The golf club 2 is a driver (No. 1 wood). The head 4 is a driver head. The shaft 6 is a shaft for a driver.

[0014] The head 4 and the grip 8 are not limited. Examples of the head 4 include a wood type head, a utility type head, an iron type head, and a putter head. In this embodiment, the head 4 is a wood type head.

[0015] The shaft 6 is formed of a plurality of fiber-reinforced resin layers. The type of fiber is not limited. Examples of the fiber-reinforced resin layer include a carbon fiber-reinforced resin layer and a glass fiber-reinforced resin layer. The shaft 6 is a tubular body. Although not shown in FIG. 1, the shaft 6 has a hollow structure. The shaft 6 has a tip end Tp and a butt end Bt. The head 4 is attached to the tip portion including the tip end Tp. The grip 8 is attached to the rear end portion including the butt end Bt. In the golf club 2, the tip end Tp is located inside the head 4. In the golf club 2, the butt end Bt is located inside the grip 8.

[0016] The shaft 6 has a tapered portion in which the outer diameter continuously increases toward the butt end Bt. At least an area of ​​the shaft 6 that is 200 mm or more and 900 mm or less away from the tip end Tp is the tapered portion.

[0017] In Fig. 1, the double-headed arrow L indicates the overall length of the shaft 6. This overall length L of the shaft is measured along the axial direction. The overall length L of the shaft is the distance between the tip end Tp and the butt end Bt. In this application, the letter L is used as a symbol in the drawings and also as a symbol representing the overall length of the shaft.

[0018] The shaft 6 is formed by winding a plurality of prepreg sheets. In these prepreg sheets, the fibers are substantially oriented in one direction. A prepreg in which the fibers are substantially oriented in one direction is also called a UD prepreg. "UD" is an abbreviation for unidirectional. Note that a prepreg other than a UD prepreg may be used. For example, the fibers may be woven in the prepreg sheet. In the present application, the prepreg sheet is also simply called a sheet.

[0019] The prepreg sheet includes fibers and a resin. The resin is also called a matrix resin. Examples of the fibers include carbon fibers and glass fibers. Typically, the matrix resin is a thermosetting resin.

[0020] Examples of the matrix resin of the prepreg sheet include thermosetting resins and thermoplastic resins. From the viewpoint of shaft strength, the matrix resin is preferably a thermosetting resin, and more preferably an epoxy resin.

[0021] The shaft 6 is manufactured by a sheet winding method. In the prepreg, the matrix resin is in a semi-cured state. In the shaft 6, a prepreg sheet is wound and cured. This curing means that the matrix resin in the semi-cured state is cured. This curing is achieved by heating. The manufacturing process of the shaft 6 includes a heating step. This heating cures the matrix resin of the prepreg sheet.

[0022] FIG. 2 is a development of a prepreg sheet constituting the shaft 6. FIG. 2 shows the sheets constituting the shaft 6. The shaft 6 is composed of a plurality of sheets. As shown in FIG. 2, the shaft 6 is composed of 12 sheets. The shaft 6 has a first sheet s1 to a twelfth sheet s12. This development shows the sheets constituting the shaft in order from the inside of the shaft 6. The sheets are wound in order from the sheet located at the top in FIG. 2. In FIG. 2, the left-right direction of the drawing coincides with the axial direction. In FIG. 2, the right side of the drawing is the tip side of the shaft. In FIG. 2, the left side of the drawing is the butt side of the shaft.

[0023] Fig. 2 shows not only the winding order but also the arrangement in the axial direction. For example, in Fig. 2, one end of the sheet s1 is located at the tip end Tp.

[0024] The shaft 6 has a straight layer, a bias layer, and a hoop layer. The shaft 6 does not have a resin layer that does not contain fibers. The shaft 6 may have a resin layer that does not contain fibers. Each layer of the shaft 6 is a carbon fiber reinforced layer or a glass fiber reinforced layer. All layers of the shaft 6 may be carbon fiber reinforced layers.

[0025] The orientation angle of the fibers of each sheet is shown in Figure 2. The sheet marked with "0°" is a straight sheet. The straight sheet constitutes a straight layer.

[0026] The straight layer is a layer in which the fiber orientation is substantially 0° with respect to the axial direction. Due to errors during winding, etc., the fiber orientation may not usually be completely parallel to the shaft axis direction. In the straight layer, the absolute angle of the fibers with respect to the shaft axis is 10° or less. The absolute angle is the absolute value of the angle (fiber angle) between the shaft axis and the fiber direction. In other words, an absolute angle of 10° or less means that the fiber angle is between -10 degrees or more and +10 degrees or less.

[0027] In the embodiment of FIG. 2, the straight layers are layer s1, layer s7, layer s9, layer s11 and layer s12.

[0028] The bias layer is a layer in which the fiber orientation is substantially inclined with respect to the axial direction. In FIG. 2, the layer indicated as "-45°" or "+45°" is the bias layer. Preferably, the bias layer is formed by a combination of two sheets in which the fiber orientation is inclined in the opposite directions. This combination of sheets is also called a sheet pair. Preferably, this sheet pair includes a sheet having a fiber angle of -60° or more and -30° or less, and a sheet having a fiber angle of 30° or more and 60° or less. That is, preferably, the bias layer includes a layer having a fiber angle of -60° or more and -30° or less, and a layer having a fiber angle of 30° or more and 60° or less. Thus, in the bias layer, it is preferable that the absolute angle is 30° or more and 60° or less. More preferably, the absolute angle of the bias layer is 45°±5°.

[0029] In the shaft 6, the bias layers are layer s2, layer s4, layer s5, and layer s6. The layers s2 and s4 are formed of a first sheet pair. The layers s5 and s6 are formed of a second sheet pair.

[0030] In the bias layer, the plus (+) and minus (-) in the fiber angle indicate the inclination direction of the fibers. In a sheet pair, a sheet with a positive fiber angle is combined with a sheet with a negative fiber angle. In each sheet pair, the fibers are inclined in opposite directions. Note that in FIG. 2, the fiber orientation direction is the same in layers s2 and s4, but since sheet s4 is turned over and attached to sheet s2, the fiber directions are opposite to each other. The relationship between layers s5 and s6 is similar.

[0031] The hoop layer is a layer in which the fibers are arranged substantially along the circumferential direction of the shaft. In FIG. 2, the layer marked "90°" is the hoop layer. Preferably, in the hoop layer, the absolute angle of the fibers is substantially 90° with respect to the shaft axis. However, due to errors during winding, the orientation of the fibers may not be completely 90° with respect to the shaft axis direction. Usually, in this hoop layer, the absolute angle of the fibers is 80° or more and 90° or less.

[0032] In the embodiment of FIG. 2, the hoop layers are layer s3, layer s8 and layer s10.

[0033] As described above, in this application, sheets and layers are classified according to the orientation angle of the fibers. In addition, in this application, sheets and layers are classified according to the length in the axial direction.

[0034] A layer having an axial length of 70% (0.7L) or more of the total shaft length L is referred to as a full length layer. The axial length of the full length layer may be 0.7L or more, even 0.8L or more, and even 0.9L or more. The axial length of the full length layer may be the same as the total shaft length L. In the embodiment of FIG. 2, the axial lengths of all the full length layers are equal to the total shaft length L. In the embodiment of FIG. 2, the full length layers are layer s2, layer s3, layer s4, layer s7, layer s9, layer s10, and layer s11.

[0035] A layer having an axial length less than 70% (0.7L) of the total shaft length L is referred to as a partial layer. In the embodiment of Fig. 2, the partial layers are layer s1, layer s5, layer s6, layer s8, and layer s12.

[0036] A full length layer that is a bias layer is called a full length bias layer. A full length layer that is a straight layer is called a full length straight layer. A full length layer that is a hoop layer is called a full length hoop layer.

[0037] The shaft 6 has a plurality of full length straight layers. In the embodiment of FIG. 2, the full length straight layers are layer s7, layer s9, and layer s11. The shaft 6 has a plurality of full length bias layers. The full length bias layers are layer s2 and layer s4. The shaft 6 has a plurality (two) full length hoop layers. The full length hoop layers are layer s3 and layer s10. The full length hoop layers are only layer s3 and layer s10. The layer s3 is located on the inner side of the layer s10. Therefore, the layer s3 is the inner full length hoop layer f1. The number of plies of the inner full length hoop layer f1 is 1. The layer s10 is located on the outer side of the layer s3. Therefore, the layer s10 is the outer full length hoop layer f2. The number of plies of the outer full length hoop layer f2 is 1. The layer s3 (the inner full length hoop layer f1) is located between the full length bias layer s2 and the full length bias layer s4. The layer s10 (outer full length hoop layer f2) is a layer adjacent to the inside of the full length straight layer s11 which is the full length layer located outermost.

[0038] The number of layers interposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2 is not limited. Preferably, at least one full-length layer is interposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. In the embodiment of FIG. 2, multiple full-length layers are interposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. Multiple (two) full-length straight layers are interposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2.

[0039] Of the full length straight layers, the innermost layer s7 is located between the inner full length hoop layer f1 and the outer full length hoop layer f2. Of the full length straight layers, the second innermost layer s9 is located between the inner full length hoop layer f1 and the outer full length hoop layer f2. Of the full length straight layers, the outermost layer s11 is located outside the outer full length hoop layer f2.

[0040] A partial layer that is a bias layer is referred to as a partial bias layer. A partial layer that is a straight layer is referred to as a partial straight layer. A partial layer that is a hoop layer is referred to as a partial hoop layer.

[0041] The shaft 6 has a partial bias layer. In the embodiment of Fig. 2, the partial bias layer is a layer s5 and a layer s6. The partial bias layers s5 and s6 are located between the inner full length hoop layer f1 and the outer full length hoop layer f2.

[0042] The shaft 6 has partial straight layers. In the embodiment of Fig. 2, the partial straight layers are a layer s1 and a layer s12. Of the partial straight layers, the innermost layer s1 is located on the inner side of the inner full-length hoop layer f1. Of the partial straight layers, the outermost layer s12 is located on the outer side of the outer full-length hoop layer f2.

[0043] The shaft 6 has a partial hoop layer. In the embodiment of FIG. 2, the partial hoop layer is layer s8. The partial hoop layer s8 is located between the inner full length hoop layer f1 and the outer full length hoop layer f2. When one or more partial hoop layers are provided, all of the partial hoop layers may be located between the inner full length hoop layer f1 and the outer full length hoop layer f2.

[0044] The shaft 6 has a tip partial straight layer. The layer s1 and the layer s12 are the tip partial straight layer. The tip partial straight layer is a partial straight layer disposed at the tip portion of the shaft 6. One end of the tip partial straight layer is located at the tip end Tp.

[0045] The shaft 6 does not have a butt partial straight layer. The butt partial straight layer is a partial straight layer arranged at the butt end of the shaft 6. One end of the butt partial straight layer is located at the butt end Bt. The shaft 6 may have a butt partial straight layer.

[0046] The shaft 6 has a butt partial hoop layer. The layer s8 is a butt partial hoop layer. The butt partial hoop layer s8 is disposed at the rear end of the shaft 6. One end of the butt partial hoop layer s8 is located at the butt end Bt. The butt partial hoop layer s8 is provided between the inner full length hoop layer f1 and the outer full length hoop layer f2. When one or more butt partial hoop layers are provided, all of the butt partial hoop layers may be located between the inner full length hoop layer f1 and the outer full length hoop layer f2.

[0047] The shaft 6 has a range Rf in which both the inner full length hoop layer f1 and the outer full length hoop layer f2 are arranged. The range Rf is an axial range. In the shaft 6, the inner full length hoop layer f1 and the outer full length hoop layer f2 are both arranged from the tip end Tp to the butt end Bt, so the range Rf is a range from the tip end Tp to the butt end Bt. The range Rf may be a part of the shaft 6.

[0048] The shaft 6 has full length layers other than the full length hoop layers f1 and f2. In the embodiment of Fig. 2, the full length layers other than the full length hoop layers f1 and f2 are full length bias layers s2 and s4 and full length straight layers s7, s9, and s11. Except for the outermost full length straight layer s11, the full length layers other than the full length hoop layers f1 and f2 are disposed inside the outer full length hoop layer f2.

[0049] As described below, in the finishing process, the surface of the shaft 6 is polished. Of the multiple fiber-reinforced resin layers that make up the shaft 6, the outermost layer is polished. In the present application, the layer to be polished is referred to as a protective layer. In the embodiment of FIG. 2, the protective layer p1 is a layer s11 and a layer s12. The protective layer p1 includes a full-length straight layer s11. The protective layer p1 includes a partial straight layer s12. In the completed shaft 6, the protective layer p1 has been polished. That is, in the completed shaft 6, at least a portion of the thickness of the protective layer p1 has been removed by polishing.

[0050] In this application, the layers located inside the protective layers s11 and s12 are referred to as body layers. In the embodiment of FIG. 2, layers s1 to s10 are the body layer m1. The body layer m1 includes an inner full-length hoop layer f1 and an outer full-length hoop layer f2. The body layer m1 includes two full-length straight layers s7 and layer s9. The body layer m1 includes two full-length bias layers s2 and s4. The body layer m1 includes multiple full-length layers s2, s3, s4, s7, s9, and s10.

[0051] In this way, the multiple fiber-reinforced resin layers constituting the shaft 6 are composed of a polished protective layer p1 and a main layer m1 located inside the protective layer p1. In the embodiment of FIG. 2, the protective layer p1 is straight layers s11 and s12. The protective layer p1 includes a full-length straight layer s11. The protective layer p1 may be a resin layer that does not include fibers. An example of this resin layer is an epoxy resin layer.

[0052] The main body layer m1 includes full length layers s2, s3, s4, s7, s9, s10, and s11 each having a length of 0.7L or more relative to the total shaft length L. Of the full length layers belonging to the main body layer m1, the layer s11 (outer full length hoop layer f2) is located at the outermost position. Of the full length layers belonging to the main body layer m1, the layer s2 is located at the innermost position. This layer s2 is a full length bias layer. The inner full length hoop layer f1 (layer s3) is disposed in a position in contact with this layer s2. Of the full length layers belonging to the main body layer m1, the inner full length hoop layer f1 may be located at the innermost position.

[0053] The manufacturing process of this shaft 6 will be outlined below.

[0054] [Outline of shaft manufacturing process]

[0055] (1) Cutting process In the cutting process, the prepreg sheet is cut into a desired shape. Through this process, each sheet shown in FIG. 2 is cut out.

[0056] The cutting may be performed by a cutting machine or manually, for example, by using a utility knife.

[0057] (2) Bonding process In this process, a plurality of sheets are laminated together to produce a combined sheet. The sheet pair of the bias layer described above is preferably made into a combined sheet. In addition, since the hoop layer is difficult to wind by itself, it is preferably made into a combined sheet between another layer. In the lamination process, heating and / or pressing may be used.

[0058] (3) Winding process In the winding process, a mandrel is prepared. Typically, the mandrel is made of metal. A release agent is applied to the mandrel. Furthermore, a tacky resin is applied to the mandrel. This resin is also called a tacking resin. The cut sheets are wound around the mandrel. The combined sheet is wound in the combined sheet state. The tacking resin makes it easy to attach the ends of the sheets to the mandrel.

[0059] This winding step results in a wound body. In this wound body, the prepreg sheet is wound around the outside of the mandrel. This winding is performed, for example, by rolling the object to be wound on a flat surface. This winding may be performed manually or by a machine. This machine is called a rolling machine.

[0060] (4) Tape wrapping process In the tape wrapping process, a tape is wrapped around the outer circumferential surface of the wound body. This tape is also called wrapping tape. This wrapping tape is wound in a spiral shape without gaps while being tensioned. This wrapping tape applies pressure to the wound body. This pressure contributes to reducing voids.

[0061] (5) Curing process In the curing process, the wound body after the tape wrapping is heated. This heating causes the matrix resin to harden. During this curing process, the matrix resin temporarily becomes fluid. This fluidization of the matrix resin can cause air to be expelled between or within the sheets. The clamping force of the wrapping tape promotes the expulsion of this air. As a result of this curing, a hardened laminate is obtained.

[0062] (6) Mandrel removal process and wrapping tape removal process After the curing step, the steps of pulling out the mandrel and removing the wrapping tape are performed. Preferably, the step of pulling out the mandrel is followed by the step of removing the wrapping tape.

[0063] (7) Both ends cutting process In this step, both ends of the cured laminate are cut to make the end faces of the tip end Tp and the butt end Bt flat.

[0064] (8) Polishing process In this process, the surface of the cured laminate is polished. The wrapping tape leaves spiral-shaped irregularities on the surface of the cured laminate. Polishing removes these irregularities and makes the surface smooth.

[0065] (9) Painting process After the sanding step, the cured laminate is painted.

[0066] The strength of the shaft 6 is evaluated by three-point bending strength and crushing strength.

[0067] The three-point bending strength can be measured by the SG-type three-point bending strength test. This test is a test for golf club shafts established by the Japan Product Safety Association (CPSA number 0098). Usually, in this test, the strength is measured at points T, A, B, and C. Point T is located 90 mm from the tip end Tp. Point A is located 175 mm from the tip end Tp. Point B is located 525 mm from the tip end Tp. Point C is located 175 mm from the butt end Bt. Also, in this test, the strength can be measured at point AB. Point AB is located midway between points A and B, and 350 mm from the tip end Tp.

[0068] FIG. 3 shows a method for measuring three-point bending strength. In this measurement method, the shaft 6 is supported from below at two support points e1 and e2, while the indenter R applies a load F from above to below at the load point e3. The speed of the descent of the indenter R is 20 mm / min. Silicone rubber St is attached to the tip of the indenter R. The position of the load point e3 is a position that bisects the distance between the support points e1 and e2. This load point e3 is the measurement point. The distance between the two support points e1 and e2 is the span S. When points A, B, and C are measured, the span S is 300 mm. When point T is measured, the span S is 150 mm. The load F (peak value) at which the shaft 6 breaks is the measured value.

[0069] The crushing strength is a test in which the shaft 6 is crushed in the vertical direction (up and down direction) of the cross section. FIG. 4 shows a method for measuring the crushing strength. A universal testing machine (220X type) manufactured by INTESCO is used for the measurement. A sliced ​​sample 20 having an axial width of 10 mm is cut out from the shaft 6 with the measurement position as the center. The sample is placed on a receiving jig 22 whose upper surface 22a is a horizontal plane, and the sample 20 is compressed by an indenter jig 24. The lower surface 24a of the indenter jig 24, which is the surface that presses the sample 20, is a plane parallel to the upper surface 22a of the receiving jig 22. The indenter jig 24 is lowered vertically downward to compress the sample 20. The lowering speed of the indenter jig 24 is 5 mm / min. As the indenter jig 24 descends, the lower surface 24a approaches the upper surface 22a. As the lower surface 24a approaches the upper surface 22a, the sample 20 deforms so that the shaft cross section becomes flat (see the lower drawing in FIG. 4). When the indenter jig 24 is further lowered, the shaft 6 breaks. The load (peak value) at which the shaft 6 breaks is the measured value.

[0070] Figure 5 shows a cross section of a shaft 6 deformed by the application of an external force radially inward. To facilitate understanding, the degree of deformation is exaggerated in Figure 5 compared to the actual degree. The deformation in Figure 5 is the deformation when compressed from above, and corresponds to the deformation during measurement of three-point bending strength.

[0071] The inventors have found that the strength of the shaft can be increased by suppressing the decrease in bending rigidity caused by the flattening deformation of the shaft cross section. In the deformation shown in FIG. 5, a region A is generated in which tensile stress is applied to the inner layer side of the shaft 6 and compressive stress is applied to the outer layer side of the shaft 6, and a region B is generated in which compressive stress is applied to the inner layer side of the shaft 6 and tensile stress is applied to the outer layer side of the shaft 6. When tensile stress is applied to the inner layer side of the shaft 6, the flattening deformation can be suppressed by arranging the hoop layer on the inner layer side. When tensile stress is applied to the outer layer side of the shaft 6, the flattening deformation can be suppressed by arranging the hoop layer on the outer layer side. By providing the inner full-length hoop layer f1 and the outer full-length hoop layer f2, the flattening deformation is suppressed in both the region A where the tensile stress is applied to the inner layer side and the region B where the tensile stress is applied to the outer layer side. As a result, the decrease in bending rigidity caused by the flattening deformation of the shaft is suppressed, and the strength of the shaft 6 is improved.

[0072] As shown in FIG. 4(a), in the measurement of crushing strength, the shaft 6 before being flattened has a longitudinal position V and a transverse position H. The longitudinal position V and the transverse position H are positions in the circumferential direction of the shaft 6. The longitudinal position V is a position having a circumferential width of ±45° from the direction in which the receiving jig 22 and the indenter jig 24 are in contact (the longitudinal direction of the cross section). The longitudinal position V is indicated by a solid double-headed arrow. The transverse position H is a position having a circumferential width of ±45° from the direction perpendicular to the longitudinal direction of the cross section (the transverse direction of the cross section). The transverse position H is indicated by a dashed double-headed arrow. All positions other than the longitudinal position V are transverse positions H.

[0073] In this crushing strength measurement, the shaft 6 is pressed radially inward, so the above-mentioned regions A and B can occur. In Fig. 5, the external force is applied only from above, but in the crushing strength measurement in Fig. 4, the external force is applied from above and below, so region A can also occur on the above and below.

[0074] In the crush strength test, the starting point of the fracture occurs at either the longitudinal position V or the transverse position H. At the longitudinal position V, compressive stress acts on the outer layer side and tensile stress acts on the inner layer side. At the transverse position H, tensile stress acts on the outer layer side and compressive stress acts on the inner layer side. When the starting point of the fracture is at the longitudinal position V, it is considered that the fracture starts in the region A where tensile stress acts on the inner layer side. In this case, the inner full-length hoop layer f1 can effectively act to increase the fracture strength. When the starting point of the fracture is at the transverse position H, it is considered that the fracture starts in the region B where tensile stress acts on the outer layer side. In this case, the outer full-length hoop layer f2 can effectively act to increase the fracture strength.

[0075] The shaft 6 may have a longitudinal destruction portion V1, the destruction origin of which is a longitudinal position V in a crushing strength test, and a transverse destruction portion H1, the destruction origin of which is a transverse position H in the crushing strength test (see FIG. 1). In this case, the inner full-length hoop layer f1 can act effectively at one of the longitudinal position V and the transverse position H, and the outer full-length hoop layer f2 can act effectively at the other of the longitudinal position V and the transverse position H. Thus, the strength of the shaft 6 can be effectively increased by the inner full-length hoop layer f1 and the outer full-length hoop layer f2. From this viewpoint, it is preferable that the longitudinal destruction portion V1 and the transverse destruction portion H1 are present in the range Rf where both the inner full-length hoop layer f1 and the outer full-length hoop layer f2 are arranged.

[0076] The lamination radius is large on the outer layer side of the shaft 6. The lamination radius is small on the inner layer side of the shaft 6. Just as a large-diameter cylinder is easily crushed, a large lamination radius tends to reduce the effect of suppressing flattening deformation. When comparing hoop layers of the same thickness, a hoop layer with a large radius has a smaller effect of suppressing flattening deformation than a hoop layer with a small radius. By making the thickness T2 of the outer full-length hoop layer f2 thicker than the thickness T1 of the inner full-length hoop layer f1, flattening deformation is suppressed on both the outer layer side and the inner layer side. In addition, by not making the inner full-length hoop layer f1 thicker than necessary, the shaft can be made lighter. The thickness T1 is calculated by multiplying the thickness of the prepreg sheet constituting the inner full-length hoop layer f1 by the number of plies (number of turns). When the number of plies is 1, the thickness of the prepreg sheet of the inner full-length hoop layer f1 is the thickness T1. Similarly, the thickness T2 is calculated by multiplying the thickness of the prepreg sheet constituting the outer full-length hoop layer f2 by the number of plies. When the number of ply is 1, the thickness of the prepreg sheet of the outer full-length hoop layer f2 is thickness T2.

[0077] As described above, by making the outer full-length hoop layer f2 thicker, it is possible to suppress flattening deformation. However, as the outer full-length hoop layer f2 becomes thicker, the full-length straight layer arranged inside the outer full-length hoop layer f2 is stacked relatively closer to the inner layer side. When the full-length straight layer is arranged on the inner layer side, the bending rigidity of the shaft 6 decreases, and more straight layers are required to increase the bending rigidity. By making the resin content of the outer full-length hoop layer f2 smaller than the resin content of the inner full-length hoop layer f1, it is possible to maintain the fiber amount of the outer full-length hoop layer f2 while suppressing the thickness of the outer full-length hoop layer f2. Therefore, it is possible to increase the strength of the shaft 6 while maintaining the bending rigidity.

[0078] Fig. 6 is a longitudinal cross-sectional view of a shaft 6 undergoing bending deformation. Fig. 6 corresponds to the deformation of the shaft 6 during measurement of the three-point bending strength. To facilitate understanding, the degree of deformation is exaggerated in Fig. 6 compared to the actual degree.

[0079] As shown in FIG. 6, the bending deformation of the shaft 6 produces an outer side C with a large radius of curvature of the bend and an inner side D with a small radius of curvature of the bend. When the outer full-length hoop layer f2 becomes thick and the full-length straight layer is laminated relatively to the inner layer side, the tensile strength of the outer side C of the bend decreases. Therefore, tensile failure is likely to occur in the outer side C of the bend, not in the inner side D of the bend. By making the resin content of the outer full-length hoop layer f2 lower than that of the inner full-length hoop layer f1, the fiber amount of the outer full-length hoop layer f2 can be maintained while suppressing the thickness T2 of the outer full-length hoop layer f2. Therefore, tensile failure in the outer side C of the bend during bending deformation is suppressed. In addition, even if tensile failure occurs in the outer side C of the bend, the strength until failure can be increased. As a result, the strength of the shaft 6 can be increased.

[0080] The shaft 6 may have an inner bending fracture portion D1 in which the fracture initiation point in a three-point bending strength test occurs on the inner bending side D rather than the outer bending side C (see FIG. 1). In this case, tensile fracture on the outer bending side C is avoided, and the strength of the shaft 6 can be effectively increased. From this viewpoint, it is preferable that the inner bending portion D1 is present in the range Rf where both the inner full length hoop layer f1 and the outer full length hoop layer f2 are arranged.

[0081] The outer full-length hoop layer f2 is located outside the inner full-length hoop layer f1 and has a large lamination radius, so the prepreg area is large. By reducing the resin content of this outer full-length hoop layer f2, the prepreg weight can be effectively reduced. This allows the shaft 6 to be made lighter while maintaining its strength.

[0082] The effect of the inner full-length hoop layer f1 is enhanced by being disposed closer to the inner layer side. The effect of the outer full-length hoop layer f2 is enhanced by being disposed closer to the outer layer side. From these viewpoints, it is preferable that at least one full-length straight layer is disposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. In the embodiment of FIG. 2, two full-length straight layers s7 and s9 are disposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. In the embodiment of FIG. 2, all full-length straight layers s7 and s9 except for the outermost full-length straight layer s11 are disposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. In the embodiment of FIG. 2, the full-length straight layer s7 is one ply, and the full-length straight layer s9 is one ply. From the same viewpoint, it is preferable that at least one full-length bias layer is disposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. In the embodiment of FIG. 2, one full-length bias layer s4 is disposed between the inner full-length hoop layer f1 and the outer full-length hoop layer f2. Two full length bias layers s2, s4 may be disposed between the inner full length hoop layer f1 and the outer full length hoop layer f2. All full length bias layers s2, s4 may be disposed between the inner full length hoop layer f1 and the outer full length hoop layer f2. In the embodiment of Fig. 2, the innermost layer of the main body layer m1 is the full length bias layer s2, and the inner full length hoop layer f1 is disposed adjacent to the outer side of the full length bias layer s2.

[0083] The ratio (T2 / T1) is the ratio of the thickness T2 of the outer full length hoop layer f2 to the thickness T1 of the inner full length hoop layer f1. From the viewpoint of suppressing flattening deformation to increase strength and making the shaft lighter, T2 / T1 is preferably greater than 1, more preferably 1.2 or more, and even more preferably 1.4 or more. By suppressing the thickness T2 of the outer full length hoop layer f2, the full length straight layer can be disposed relatively on the outer layer side, and the bending rigidity of the shaft 6 can be maintained. In addition, if the thickness T1 is too small compared to the thickness T2, the effect of the inner full length hoop layer f1 on the effect of the outer full length hoop layer f2 is reduced, and the strength against tensile stress on the inner layer side of the shaft 6 is reduced. From these viewpoints, T2 / T1 is preferably less than 2, more preferably 1.9 or less, and even more preferably 1.8 or less.

[0084] From the viewpoint of making the thickness T2 larger than the thickness T1, the thickness T2 of the outer full length hoop layer f2 is preferably 0.020 mm or more, more preferably 0.030 mm or more, and still more preferably 0.040 mm or more. From the viewpoint of making T2 / T1 less than 2, the thickness T2 is preferably 0.085 mm or less, more preferably 0.075 mm or less, and still more preferably 0.065 mm or less.

[0085] The fiber weight of the inner full-length hoop layer f1 is F1 (g / m 2 The fiber weight of the outer full-length hoop layer f2 is F2 (g / m 2 This basis weight is the weight of carbon fiber per unit area of ​​the prepreg.

[0086] (F1+F2) is the sum of the fiber weight of the inner full-length hoop layer f1 and the fiber weight of the outer full-length hoop layer f2. From the viewpoint of suppressing flattening deformation, (F1+F2) is 60 (g / m 2 ) or more is preferable, and 75 (g / m 2 ) or more is more preferable, and 90 (g / m 2 From the viewpoint of reducing the weight of the shaft 6, (F1+F2) is preferably 150 (g / m 2 ) or less is preferable, and 140 (g / m 2 ) or less is more preferable, and 130 (g / m 2 ) or less is more preferable.

[0087] The number of plies in the inner full length hoop layer f1 is not limited. From the viewpoint of uniformity in the circumferential direction of the shaft 6, the number of plies in the inner full length hoop layer f1 is preferably an integer. From the viewpoint of reducing the weight of the shaft, the inner full length hoop layer f1 is preferably 1 to 3 plies, more preferably 1 to 2 plies, and more preferably 1 ply.

[0088] The number of plies in the outer full length hoop layer f2 is not limited. From the viewpoint of uniformity in the circumferential direction of the shaft 6, the number of plies in the outer full length hoop layer f2 is preferably an integer. From the viewpoint of reducing the weight of the shaft, the outer full length hoop layer f2 is preferably 1 to 3 plies, more preferably 1 to 2 plies, and more preferably 1 ply.

[0089] The number of plies means the number of turns, and for example, a number of plies of 1 means that the number of turns is 1, meaning that the layer goes around once (360°). In consideration of errors in cutting and winding the prepreg, the integer in the number of plies may allow an error of ±0.1 plies or ±0.05. For example, 1 ply (the number of plies is 1) may mean 0.9 plies or more and 1.1 plies or less, or may mean 0.95 plies or more and 1.05 plies or less.

[0090] The above structure including the inner full length hoop layer f1 and the outer full length hoop layer f2 can realize a shaft that is lightweight yet has high strength. The above structure is highly effective in lightweight shafts. From this viewpoint, the weight of the shaft 6 is preferably 60 g or less, more preferably 50 g or less, more preferably 40 g or less, and more preferably 30 g or less. From the viewpoint of bending rigidity (flexibility), the weight of the shaft 6 is preferably 15 g or more, more preferably 20 g or more, and more preferably 25 g or more.

[0091] As described above, by suppressing the thickness T2 of the outer full length hoop layer f2 while maintaining the fiber amount of the outer full length hoop layer f2, the strength of the shaft 6 can be increased while maintaining the bending rigidity. From this viewpoint, the resin content of the outer full length hoop layer f2 is preferably less than 30%, more preferably less than 25%, and more preferably less than 20%. If the resin content is low, the tackiness of the prepreg may decrease, and the workability during winding of the prepreg may decrease. From this viewpoint, the resin content of the outer full length hoop layer f2 is preferably 10% or more, more preferably 12% or more, and more preferably 14% or more. In the present application, the unit of the resin content is % by weight. The value obtained by subtracting the resin content from 100 is the fiber content (% by weight).

[0092] Considering the difference with the resin content of the outer full length hoop layer f2, the resin content of the inner full length hoop layer f1 is preferably 18% or more, more preferably 24% or more, and even more preferably 30% or more. From the viewpoint of reducing the weight of the shaft, the resin content of the inner full length hoop layer f1 is preferably 60% or less, more preferably 50% or less, and even more preferably 40% or less.

[0093] In order to enhance the effect of suppressing flattening deformation, the fiber elastic modulus (tensile elastic modulus) of at least one of the two full-length hoop layers f1 and f2 is set to 30 (t / mm 2 ) or more is preferable, and 33 (t / mm 2 ) or more is more preferable, and 40 (t / mm 2 ) or more is more preferable. Fibers with a high tensile modulus tend to have a low tensile strength. From this viewpoint, the fiber modulus (tensile modulus) of at least one of the two full-length hoop layers f1 and f2 is preferably 60 (t / mm 2 ) or less is preferable, and 55 (t / mm 2 ) or less is more preferable, and 50 (t / mm 2 ) or less. It is more preferable that both the inner full length hoop layer f1 and the outer full length hoop layer f2 satisfy these numerical ranges of fiber elastic modulus. From the viewpoint of flattening deformation, it is preferable that the fiber elastic modulus of at least the outer full length hoop layer f2 is 30 (t / mm 2 ) or more, and even 33 (t / mm 2 ) or more, and even 40 (t / mm 2 ) or more.

[0094] As described above, the shaft 6 has a full length layer other than the full length hoop layers f1 and f2. The above structure can increase the strength of a lightweight shaft, and is effective for a lightweight shaft. From this viewpoint, at least one of the full length layers other than the full length hoop layers f1 and f2 preferably has a resin content of less than 25%, more preferably less than 20%, and more preferably less than 18%. If the resin content is low, the tackiness of the prepreg may decrease, and the workability during winding of the prepreg may decrease. From this viewpoint, at least one of the full length layers other than the full length hoop layers f1 and f2 preferably has a resin content of 10% or more, more preferably 12% or more, and more preferably 14% or more. The full length layer other than the full length hoop layers f1 and f2 may be, for example, a full length straight layer. That is, at least one of the full length straight layers may have a resin content of less than 25%, further less than 20%, and further less than 18%. The full length layer other than the full length hoop layers f1 and f2 may be, for example, a full length bias layer. That is, at least one of the full length bias layers may have a resin content of less than 25%, further less than 20%, or even less than 18%.

[0095] The total shaft length L is not limited. When the total shaft length L is long, it is necessary to reduce the weight per unit length in order to reduce the weight of the shaft. Therefore, in this case, a structure that is strong and lightweight is more effective. From this viewpoint, the total shaft length L is preferably 1016 mm or more, more preferably 1054 mm or more, and even more preferably 1092 mm or more. From the viewpoint of ease of hitting and weight reduction, the total shaft length L is preferably 1270 mm or less, more preferably 1245 mm or less, and even more preferably 1219 mm or less.

[0096] The shaft 6 may be for a driver (No. 1 wood), a fairway wood, a hybrid club, or an iron club. As described above, when the total shaft length L is long, a structure that is strong and lightweight is effective. From this viewpoint, the shaft 6 is preferably for a driver, a fairway wood, or a hybrid club, and more preferably for a driver or a fairway wood. EXAMPLES

[0097] [Example 1] According to the manufacturing process described above, a shaft similar to shaft 6 was produced. The laminated structure of the shaft was as shown in FIG. 2. The layer s1 was a glass fiber reinforced layer, and the other layers s2 to s12 were carbon fiber reinforced layers. The total length L of the shaft was 1168 mm. The weight of the shaft was 38.0 g. The inner full length hoop layer f1 was made of a material manufactured by Toray Industries, Inc. under the product name "8253S-4". This inner full length hoop layer f1 had a thickness T1 of 0.037 mm, a resin content of 30 wt %, and a fiber elastic modulus of 30 t / mm 2 The outer full-length hoop layer f2 was made of a material manufactured by Toray Industries, Inc. under the trade name "2255S-7". This outer full-length hoop layer f2 had a thickness T2 of 0.061 mm, a resin content of 24% by weight, and a fiber elastic modulus of 30 t / mm 2 It was.

[0098] [Comparative Example 1] The outer full-length hoop layer f2 was made of a material manufactured by Toray Industries, Inc., with a product name of "8253S-4," and was wound in two plies. This outer full-length hoop layer f2 had a thickness T2 of 0.074 mm, a resin content of 30% by weight, and a fiber elastic modulus of 30 t / mm 2 The rest of the conditions were the same as in Example 1, and a shaft of Comparative Example 1 was obtained.

[0099] [Comparative Example 2] Comparative Example 2 was prepared by exchanging the material of the inner full-length hoop layer f1 and the material of the outer full-length hoop layer f2 in Example 1. That is, the inner full-length hoop layer f1 was a product name "2255S-7" manufactured by Toray Industries, Inc., had a thickness T1 of 0.061 mm, a resin content of 24 wt %, and a fiber elastic modulus of 30 t / mm 2 The outer full-length hoop layer f2 was manufactured by Toray Industries, Inc. under the trade name "8253S-4", had a thickness T2 of 0.037 mm, a resin content of 30% by weight, and a fiber elastic modulus of 30 t / mm 2 The rest of the conditions were the same as in Example 1, and a shaft of Comparative Example 2 was obtained.

[0100] [Comparative Example 3] The inner full-length hoop layer f1 is manufactured by Toray Industries, Inc. under the trade name "8253S-4", has a thickness T1 of 0.037 mm, a resin content of 30% by weight, and a fiber elastic modulus of 30 t / mm 2 The outer full-length hoop layer f2 was manufactured by Mitsubishi Chemical Corporation under the trade name "MRX350C-100S", had a thickness T2 of 0.083 mm, a resin content of 25% by weight, and a fiber elastic modulus of 30 t / mm 2 The T2 / T1 ratio was 2.2. The rest of the process was the same as in Example 1 to obtain a shaft of Comparative Example 3.

[0101] [Comparative Example 4] The inner full-length hoop layer f1 is manufactured by Toray Industries, Inc. under the trade name "8053S-3", has a thickness T1 of 0.024 mm, a resin content of 30% by weight, and a fiber elastic modulus of 30 t / mm 2 The outer full-length hoop layer f2 was manufactured by Mitsubishi Chemical Corporation under the trade name "MRX350C-100S", had a thickness T2 of 0.083 mm, a resin content of 25% by weight, and a fiber elastic modulus of 30 t / mm 2 The T2 / T1 ratio was 3.5. The rest of the process was the same as in Example 1 to obtain a shaft of Comparative Example 4.

[0102] The specifications and evaluation results of the examples and comparative examples are shown in Table 1 below.

[0103] [Table 1]

[0104] [evaluation] The three-point bending strength and crushing strength were evaluated. The methods for measuring these strengths are as described above. The three-point bending strength was measured at point T, which is close to the head and where strong stress acts, and points AB and B, where the curvature of the flexure is likely to become large. The crushing strength was measured at points in the middle of the shaft, where the curvature of the flexure is likely to become large (points 550 mm and 650 mm from the tip end Tp). In measuring the three-point bending strength, five samples were measured, and the average value was calculated. This average value is shown in Table 1. In measuring the crushing strength, two samples were measured, and the average value was calculated. This average value is shown in Table 1.

[0105] For Example 1, crushing strength was measured at multiple locations, and it was found that there were vertically fractured areas where the fracture originated at vertical position V (see FIG. 4) and horizontally fractured areas where the fracture originated at horizontal position H. The vertically fractured area was located 550 mm from the tip end Tp. The horizontally fractured area was located 650 mm from the tip end Tp.

[0106] For Example 1, when the starting point of fracture in the three-point bending strength test was investigated, it was found that there was a fractured part on the inside of the bend, with the fracture starting point being on the inside of the bend D. Point B was the fractured part on the inside of the bend.

[0107] As shown in Table 1, the examples were rated higher than the comparative examples.

[0108] The following supplementary notes are part of the invention included in this invention. [Appendix 1] A golf club shaft formed of a plurality of fiber reinforced resin layers and having a tip end and a butt end, The fabric includes a straight layer, a bias layer, and a hoop layer, The straight layer includes at least one full-length straight layer having a length of 0.7L or more with respect to the full length L of the shaft, The hoop layer includes a full-length hoop layer having a length of 0.7L or more with respect to the full length L of the shaft, The full-length hoop layer is composed of only one inner full-length hoop layer and one outer full-length hoop layer located outside the inner full-length hoop layer, At least one full-length straight layer is disposed on the inner side of the outer full-length hoop layer, When the thickness of the inner full length hoop layer is T1 (mm) and the thickness of the outer full length hoop layer is T2 (mm), T2 / T1 is greater than 1 and less than 2; The golf club shaft has a resin content of the outer full length hoop layer that is less than a resin content of the inner full length hoop layer. [Appendix 2] 2. The golf club shaft of claim 1, wherein the outer full length hoop layer has a resin content of less than 30%. [Appendix 3] At least one of the inner full-length hoop layer and the outer full-length hoop layer has a fiber elastic modulus of 30t / mm 2 The golf club shaft according to claim 1 or 2. [Appendix 4] 4. The golf club shaft according to any one of claims 1 to 3, wherein the shaft weight is 15 g or more and 60 g or less. [Appendix 5] The plurality of fiber-reinforced resin layers are composed of a polished protective layer and a main body layer located inside the protective layer, 5. The golf club shaft according to claim 1, wherein the protective layer is the straight layer or a resin layer that does not contain fibers. [Appendix 6] The main body layer includes a plurality of full-length layers each having a length of 0.7L or more relative to the total shaft length L, 6. The golf club shaft according to claim 5, wherein the outermost full length hoop layer is the outer full length layer belonging to the main body layer. [Appendix 7] 7. The golf club shaft according to any one of claims 1 to 6, wherein at least one full-length straight layer is disposed between the inner full-length hoop layer and the outer full-length hoop layer. [Appendix 8] The bias layer includes at least one full-length bias layer having a length of 0.7L or more with respect to the full length L of the shaft, 8. The golf club shaft of claim 1, wherein at least one full-length bias layer is disposed between the inner full-length hoop layer and the outer full-length hoop layer. [Appendix 9] The shaft has a longitudinal rupture portion in which the origin of rupture is located in the longitudinal direction in a crushing strength test in which the shaft is crushed in the longitudinal direction of the cross section, and a lateral rupture portion in which the origin of rupture is located in the lateral direction in the crushing strength test, 9. A golf club shaft as described in any one of appendix 1 to 8, wherein the longitudinal destruction portion and the transverse destruction portion are present in the area where both the outer full length hoop layer and the inner full length hoop layer are arranged. [Appendix 10] The fracture origin in the three-point bending strength test occurs on the inside of the bend. 10. The golf club shaft according to any one of claims 1 to 9, wherein the bending inner destruction portion exists in an area where both the outer full length hoop layer and the inner full length hoop layer are arranged. [Explanation of symbols]

[0109] 2. Golf clubs 4 Head 6. Shaft 8. Grip s1~s12: Prepreg sheets (layers) f1: Full inner hoop layer f2...Outer full length hoop layer m1: Main layer p1...Protective layer Bt: Butt end Tp: Chip end

Claims

1. A golf club shaft formed of a plurality of fiber reinforced resin layers and having a tip end and a butt end, The fabric includes a straight layer, a bias layer, and a hoop layer, The straight layer includes at least one full-length straight layer having a length of 0.7L or more with respect to the full length L of the shaft, The hoop layer includes a full-length hoop layer having a length of 0.7L or more with respect to the full length L of the shaft, The full-length hoop layer is composed of only one inner full-length hoop layer and one outer full-length hoop layer located outside the inner full-length hoop layer, At least one full-length straight layer is disposed on the inner side of the outer full-length hoop layer, When the thickness of the inner full length hoop layer is T1 (mm) and the thickness of the outer full length hoop layer is T2 (mm), T2 / T1 is greater than 1 and less than 2; The golf club shaft has a resin content of the outer full length hoop layer that is less than a resin content of the inner full length hoop layer.

2. 2. The golf club shaft of claim 1, wherein the outer full length hoop layer has a resin content of less than 30%.

3. At least one of the inner full-length hoop layer and the outer full-length hoop layer has a fiber elastic modulus of 30 t / mm ２ 3. The golf club shaft according to claim 1 or 2.

4. 3. The golf club shaft according to claim 1, wherein the shaft weight is 15 g or more and 60 g or less.

5. The plurality of fiber reinforced resin layers are composed of a polished protective layer and a main body layer located inside the protective layer, 3. The golf club shaft according to claim 1, wherein the protective layer is the straight layer or a resin layer that does not contain fibers.

6. The main body layer includes a plurality of full length layers each having a length of 0.7L or more relative to the total length L of the shaft, 6. The golf club shaft according to claim 5, wherein the outermost full length hoop layer is one of the full length layers belonging to the main body layer.

7. 3. The golf club shaft according to claim 1, wherein at least one of the full length straight layers is disposed between the inner full length hoop layer and the outer full length hoop layer.

8. The bias layer includes at least one full-length bias layer having a length of 0.7L or more with respect to a total length L of the shaft, 8. The golf club shaft of claim 7, wherein at least one of said full length bias layers is disposed between said inner full length hoop layer and said outer full length hoop layer.

9. The shaft has a longitudinal rupture portion in which the origin of rupture is located in the longitudinal direction in a crushing strength test in which the shaft is crushed in the longitudinal direction of the cross section, and a lateral rupture portion in which the origin of rupture is located in the lateral direction in the crushing strength test, 3. The golf club shaft according to claim 1, wherein the longitudinal destruction portion and the lateral destruction portion are present in an area where both the outer full length hoop layer and the inner full length hoop layer are arranged.

10. The specimen has an inner bending fracture part in which the fracture origin occurs on the inner side of the bend in a three-point bending strength test, 3. The golf club shaft according to claim 1, wherein the bending inner destruction portion exists in an area where both the outer full length hoop layer and the inner full length hoop layer are arranged.

Images