JP2020081419A - Golf club shaft - Google Patents

Abstract

To provide a golf club shaft having an excellent quality.SOLUTION: A golf club shaft 6 has a tip end Tp and a butt end Bt. The shaft 6 is formed from a plurality of fiber-reinforced layers including two or more bias layers and one or more straight layers. At least the one fiber-reinforced layer is a winding-start spiral layer in which the winding-start edge forms spirals. A winding-end edge of the winding-start spiral layer may form spirals. At least the one straight layer may be the winding-start spiral layer. At least the one bias layer may be the winding-start spiral layer. The winding-start spiral layer may be a full length layer disposed from the tip end Tp to the butt end Bt.SELECTED DRAWING: Figure 9

Description

The present disclosure relates to golf club shafts.

A golf club shaft formed by winding and laminating a prepreg sheet is known. With this shaft, since the position and material can be selected for each seat, a high degree of design freedom can be obtained.

Attempts to improve the quality of shafts are known. In JP 2011-245139 A, the winding start position and the winding end position of each prepreg sheet are defined. In JP2012-95856A, the winding start position is defined for each of the first bias layer, the second bias layer, and the first straight layer.

JP, 2011-245139, A JP2012-95856A

The present inventor has found that a novel structure different from the conventional one can improve the quality of the shaft.

The present disclosure provides a golf club shaft with excellent quality.

In one aspect, the golf club shaft has a tip end and a butt end. The shaft is formed by a plurality of fiber reinforced layers including two or more bias layers and one or more straight layers. At least one said fiber-reinforced layer is a winding-start spiral layer whose winding edges form a spiral.

As one aspect, it is possible to provide a golf club shaft with little bending (warping) or excellent circumferential uniformity.

FIG. 1 illustrates a golf club including a shaft according to an embodiment. FIG. 2 shows a shaft of one embodiment. FIG. 3 is a development view showing an example of a laminated structure of the shaft. FIG. 4 is an explanatory diagram showing a laminating step for producing a united sheet. FIG. 5: is explanatory drawing which shows the conventional end attachment. FIG. 6 is an explanatory diagram showing an example of end attachment in which the winding start edge is inclined with respect to the shaft center line. FIG. 7: is explanatory drawing which shows the other example of the end attachment which made the winding start edge incline with respect to the shaft centerline. FIG. 8 is an explanatory view showing still another example of end attachment in which the winding start edge is inclined with respect to the shaft center line. In FIG. 8, the united sheet is end-attached. FIG. 9 is a perspective view showing an example of a spiral formed by the winding start edge. FIG. 10 is a perspective view showing a method of measuring straightness. FIG. 11: is a side view which shows the measuring method of straightness. FIG. 12 is a schematic diagram showing a method of measuring a forward flex.

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

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

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

FIG. 3 is a development view showing an example of a laminated structure of the shaft 6.

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

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

The shaft 6 is composed of a plurality of sheets. The shaft 6 is composed of six sheets from the first sheet s1 to the sixth sheet s6. In this developed view, the seats forming the shaft are shown in order from the radial inner side of the shaft. These sheets are wound in order from the sheet located on the upper side in the development view. In this development view, the horizontal direction of the drawing corresponds to the axial direction of the shaft. In this developed view, the right side of the drawing is the tip end Tp side of the shaft. In this developed view, the left side of the drawing is the butt end Bt side of the shaft.

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

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

The shaft 6 has a straight layer and a bias layer. In the developed view of the present application, the fiber angle is described on each sheet. The fiber angle described in the drawing is the angle with respect to the winding start edge of the sheet.

The sheet described as “0°” constitutes the straight layer. The sheet forming the straight layer is also referred to as a straight sheet. In the straight layer, the absolute value (absolute angle) of the fiber angle with respect to the shaft center line z1 is preferably 10° or less, more preferably 7° or less, and further preferably 5° or less. For example, an absolute angle of 10° or less means that the fiber angle is −10° or more and +10° or less.

As described below, in the straight sheet, the winding start edge can be inclined with respect to the axial direction. In this case, the fiber angle of the straight layer is different from the angle with respect to the axial direction. On the other hand, when the winding start edge is parallel to the axial direction, the fiber angle matches the angle with respect to the axial direction.

The sheets described as “+45°” and “−45°” form the bias layer. In the bias layer, the absolute value (absolute angle) of the fiber angle with respect to the shaft center line z1 is preferably 15° or more, more preferably 20° or more, and more preferably 25° or more. In the bias layer, the absolute value (absolute angle) of the fiber angle with respect to the shaft center line z1 is preferably 75° or less, more preferably 70° or less, and more preferably 65° or less. From the viewpoint of increasing the torsional rigidity of the shaft 6, in the bias layer, the absolute value (absolute angle) of the fiber angle with respect to the shaft center line z1 is particularly preferably 35° or more and 55° or less.

Plus (+) and minus (-) in the fiber angle indicate that the fibers of the bias sheet are inclined in the opposite directions. In the sheets s2 and s3, the fibers are oriented in opposite directions.

In FIG. 3, the inclination direction of the fibers of the sheet s3 is equal to the inclination direction of the fibers of the sheet s2. However, the sheet s3 is turned over and attached to the sheet s2. As a result, the inclination direction of the sheet s2 and the inclination direction of the sheet s3 are opposite to each other.

In the present application, the bias layer in which the fibers are inclined in opposite directions is also referred to as a first bias layer and a second bias layer. For example, the layer s2 is also called the first bias layer and the layer s3 is also called the second bias layer. The shaft 6 has a first bias layer s2 and a second bias layer s3.

The number of plies (number of windings) of one sheet is not limited. For example, when the number of plies of a sheet is 1, this sheet is wound once. For example, when the number of plies of a sheet is 2, this sheet is wound twice. For example, when the number of plies of a sheet is 1.5, this sheet is wound 1.5 times. When the ply number of the sheet is 1.5, the sheet forms one layer at a circumferential position of 0 to 180° and two layers at a circumferential position of 180° to 360°.

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

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

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

In the embodiment of FIG. 3, the bias sheet s2 and the bias sheet s3 are bonded together to form a united sheet. The bias sheets s2 and s3 are wound in the state of this united sheet.

In the present application, a layer arranged substantially in the entire axial direction is referred to as a full length layer. In the present application, a sheet arranged substantially in the entire axial direction is referred to as a full length sheet. The wound full length sheet forms a full length layer. As described later, the winding start spiral layer according to the present disclosure is preferably a full length layer.

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

In the present application, the full length layer which is a straight layer is referred to as a full length straight layer. In the embodiment of FIG. 3, the full length straight layers are layers s4 and s5.

In the present application, the full length layer that is the bias layer is referred to as a full length bias layer. In the embodiment of FIG. 3, the full length bias layers are layers s2 and s3.

In the present application, a partial layer that is a straight layer is referred to as a partial straight layer. In the embodiment of FIG. 3, the partial straight layers are layers s1 and s6.

In this application, the word chip partial layer is used. The axial distance between the tip portion layer (tip portion sheet) and the tip end Tp is preferably 40 mm or less, more preferably 30 mm or less, more preferably 20 mm or less, and more preferably 0 mm. In this embodiment, this distance is 0 mm in all the chip partial layers.

An example of the tip partial layer is a tip partial straight layer. In the embodiment of FIG. 3, the chip portion straight layers are layers s1 and s6.

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

[Outline of shaft manufacturing process]

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

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

(2) Bonding Step In the bonding step, the above-mentioned united sheet is produced.

(3) Winding Step In the winding step, a mandrel is prepared. A typical mandrel is made of metal. A release agent is applied to this mandrel. Further, a resin having an adhesive property is applied to this mandrel. This resin is also called a tacking resin. The cut sheet is wound around this mandrel. This tacking resin facilitates the attachment of the sheet end portion to the mandrel.

The sheets are wound in the order shown in the development view. The sheet on the upper side in the development view is wound earlier. The sheets related to the above-mentioned lamination are wound in a state of a united sheet.

First, each sheet is end-attached to the wound object at a predetermined end-attachment position. Next, this wound object is rolled. This winding may be done manually or by machine. This machine is called a rolling machine. All sheets are wound to obtain a wound body.

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

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

(6) Mandrel Extracting Step and Lapping Tape Removing Step After the curing step, the mandrel extracting step and the wrapping tape removing step are performed. From the viewpoint of improving the efficiency of the wrapping tape removing step, it is preferable that the wrapping tape removing step is performed after the mandrel drawing step.

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

(8) Polishing Step In this step, the surface of the cured laminate is polished. Spiral irregularities are present on the surface of the cured laminate. The irregularities are marks of the wrapping tape. By polishing, this unevenness disappears and the surface becomes smooth. Preferably, in the polishing step, overall polishing and tip partial polishing are performed.

(9) Coating process The cured laminate after the polishing process is coated.

In the bonding step, the sheets that are inclined in opposite directions are bonded to each other. On the shaft 6, the sheet s2 and the sheet s3 are attached. A pair of bias layers that are inclined in opposite directions, such as the layers s2 and s3, is also referred to as a bias layer pair.

FIG. 4 shows a process in which the sheet s2 (first bias sheet s2) and the sheet s3 (second bias sheet s3) are bonded together.

The width of the sheet s2 is X ply at the tip end Tp and Y ply at the butt end Bt. X may be the same as Y or may be different. The sheet s2 has a winding start edge 21 and a winding end edge 22. The fiber angle is +θ° with respect to the winding start edge 21. In this embodiment, θ is 45.

The width of the sheet s3 is X ply at the tip end Tp and Y ply at the butt end Bt. X and Y may be the same or different. The sheet s3 has a winding start edge 31 and a winding end edge 32. The fiber angle is +θ° with respect to the winding start edge 31.

The sheet s3 is attached to the sheet s2 to form a united sheet s23. The sheet s3 is turned over and attached to the sheet s2. As a result, the fibers are inclined in opposite directions between the sheets s2 and s3.

In the united sheet s23, the sheet s3 is offset and attached to the sheet s2. This deviation width is X1 ply at the tip end Tp and Y1 ply at the butt end Bt. That is, at the tip end Tp, the winding start edge 21 of the sheet s2 and the winding start edge 31 of the sheet s3 differ by X1 plies in the circumferential direction. Further, at the butt end Bt, the winding start edge 21 of the sheet s2 and the winding start edge 31 of the sheet s3 differ in Y1 ply in the circumferential direction.

X1 may be the same as Y1 or may be different. In this embodiment, X1 and Y1 are equal. In this embodiment, X1 is 0.5 and Y1 is 0.5. In this embodiment, the deviation width between the winding start edge 21 and the winding start edge 31 is 0.5 ply at any position in the axial direction. 0.5 ply is a half circumference, that is, 180°.

The bias sheets s2 and s3 are subjected to the winding step in the state of the united sheet s23. That is, in the winding step, the united sheet s23 is wound around the winding target object.

[Starting spiral layer]
The shaft 6 may have a winding start spiral layer. The winding start spiral layer is a layer whose winding start edge is inclined with respect to the center line of the shaft 6. In the winding start spiral layer, the winding start edge forms a spiral. The spiral extends spirally around the center line of the shaft 6.

All layers constituting the shaft 6 can be a spiral layer that starts winding. In the winding step, the winding start spiral layer may be formed by inclining the winding start edge with respect to the axial direction to end the winding start edge.

5, 6 and 7 are diagrams for explaining the winding start spiral layer. 5, 6 and 7 show the end-attached state in the winding step.

Here, as an example, consider a case where the sheet s4 of the shaft 6 is wound. This sheet s4 is a full length straight sheet. The width of the sheet s4 is 1 ply at all positions in the axial direction. The sheet s4 has a winding start edge 41 and a winding end edge 42. The winding start edge 41 is a straight line. The winding end edge 42 is a straight line.

In the embodiment of FIG. 5, the end is made in a state where the winding start edge 41 is parallel to the center line of the winding object 70. That is, in the embodiment of FIG. 5, the winding start edge 41 is parallel to the shaft center line z1. The winding start edge 41 is not inclined with respect to the shaft center line z1. When the layer s4 obtained by winding the sheet s4 from this state is the layer 4a, the winding start edge 41 does not form a spiral in the layer 4a. The layer 4a is not the winding start spiral layer. The circumferential position of the winding start edge 41 is the same at all positions in the axial direction.

In FIG. 5, the circumferential position on the layer 4a is indicated by a chain double-dashed line. In the layer 4a, the circumferential position of the winding start edge 41 is 0° over the entire length. The winding start edge 41 does not form a spiral. In the layer 4a, the circumferential position of the winding end edge 42 is 360° over its entire length. The winding end edge 42 does not form a spiral. At the tip side edge 43, the winding start edge 41 is located at 0° and the winding end edge 42 is located at 360°. Also on the butt side edge 44, the winding start edge 41 is located at 0° and the winding end edge 42 is located at 360°.

In the embodiment shown in FIG. 6, the winding start edge 41 is inclined with respect to the center line of the winding object 70, and the end is attached. That is, in the embodiment of FIG. 6, the winding start edge 41 is inclined with respect to the shaft center line z1. When the layer s4 obtained by winding the sheet s4 from this state is referred to as the layer 4b, the winding start edge 41 forms a spiral in the layer 4b. The layer 4b is a winding start spiral layer. In the embodiment of FIG. 6, the circumferential position of the winding start edge 41 gradually moves as the axial position changes.

In FIG. 6, the circumferential position on the layer 4b is indicated by a chain double-dashed line. In the layer 4b, the circumferential position of the winding start edge 41 is 0° at the tip side end and 360° at the butt side end. Therefore, the winding start edge 41 forms a spiral. In the layer 4b, the circumferential position of the winding end edge 42 is 360° at the tip side end and 720° at the butt side end. Therefore, the winding end edge 42 forms a spiral.

In the embodiment of FIG. 7, the winding start edge 41 is inclined with respect to the center line of the winding object 70, and the end is attached. That is, in the embodiment of FIG. 7, the winding start edge 41 is inclined with respect to the shaft center line z1. However, the direction of inclination is opposite to that in the embodiment of FIG. When the layer s4 obtained by winding the sheet s4 from this state is referred to as the layer 4c, the winding start edge 41 forms a spiral in the layer 4c. The layer 4c is a winding start spiral layer. In the embodiment of FIG. 7, the circumferential position of the winding start edge 41 gradually moves as the axial position changes.

In FIG. 7, the circumferential position on the layer 4c is indicated by a chain double-dashed line. In the layer 4c, the circumferential position of the winding start edge 41 is 360° at the tip side end and 0° at the butt side end. Therefore, the winding start edge 41 forms a spiral. In the layer 4c, the circumferential position of the winding end edge 42 is 720° at the tip side end and 360° at the butt side end. Therefore, the winding end edge 42 also forms a spiral.

In this way, the winding start edge 41 can be formed into a spiral by tilting the winding start edge 41 with respect to the center line of the shaft and attaching the winding start edge 41. As a result, a winding start spiral layer is formed.

FIG. 8 shows an example of end attachment in the case of forming a spiral layer by starting winding with a bias layer. In FIG. 8, the united sheet s23 is used.

The bias sheet is preferably wound as a united sheet. In the embodiment of FIG. 8, the winding start edge 21 is inclined with respect to the shaft center line z1 to end the united sheet s23. By winding the united sheet s23 from this state, the winding start edge 21 of the sheet s2 forms a spiral. Further, the winding start edge 31 of the sheet s3 also forms a spiral. In addition, the winding end edge 22 also forms a helix and the winding end edge 32 also forms a helix.

When the winding start spiral layer is formed using the united sheet s23, the positional relationship between the first spiral formed by the winding start edge 21 and the second spiral formed by the winding start edge 31 is different from that described above. It depends on the width. When the deviation width X1 on the tip side and the deviation width Y1 on the butt side are 0.5 plies (180°), the circumferential positions of the first spiral and the second spiral also differ by 180°.

[Effect of the spiral layer at the beginning of winding]
It has been found that the winding start spiral layer can enhance the quality of the shaft.

[Effects when the straight layer is a spiral layer that starts winding]
By using the straight layer as the winding start spiral layer, the circumferential position of the winding start end is dispersed according to the difference in the axial position. Due to this dispersion, the uniformity of the flex (flexural rigidity) in the circumferential direction is enhanced (the circumferential uniformity effect).

When the winding start spiral layer is a full length layer, the circumferential uniform effect is further enhanced.

If the straight layer is substantially an integral number of plies, the winding edge becomes spiral and the winding end edge becomes spiral. Therefore, in addition to the circumferential position of the winding start edge, the circumferential position of the winding end edge is dispersed. As a result, the circumferential uniformity effect is further enhanced. From this viewpoint, the number of plies in the straight layer forming the spiral layer at the beginning of winding is preferably close to an integer. Specifically, the number of plies in the straight layer forming the spiral layer at the beginning of winding is preferably [N-0.1] or more and [N+0.1] or less, and is [N-0.05] or more and [N+0.05] or less is more preferable. However, N is an integer of 1 or more. If the width of the straight sheet is too wide, wrinkles are likely to occur during winding. From this viewpoint, N is preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less. From the viewpoint of the circumferential uniformity effect, in a certain straight layer, the number of plies in the straight layer is preferably constant regardless of the axial position.

If there is a gap between the winding start edge and the winding end edge of the straight layer, the shaft strength may decrease. This is because the gap can be filled with the resin due to the flow of the matrix resin in the curing step, but the reinforcing fiber does not exist or the density of the reinforcing fiber can be a small portion. From this viewpoint, it is preferable that the spine portion in which the winding start edge and the winding end edge of the straight layer overlap is formed. On the other hand, the spine portion may reduce the circumferential uniformity of the flex. From this viewpoint, it is preferable that the range of the spine portion in the circumferential direction is small. Taking the above into consideration comprehensively, the number of plies in the straight layer is preferably [N+0.01] or more and [N+0.10] or less, and more preferably [N+0.01] or more and [N+0.05] or less. For example, when N is 1, the number of plies in the straight layer is preferably 1.01 or more and 1.10 or less, and more preferably 1.01 or more and 1.05 or less. For example, when N is 2, the number of plies in the straight layer is preferably 2.01 or more and 2.10 or less, and more preferably 2.01 or more and 2.05 or less. For example, when N is 3, the number of plies in the straight layer is preferably 3.01 or more and 3.10 or less, and more preferably 3.01 or more and 3.05 or less.

The angle between the winding start edge 41 of the straight layer and the shaft center line z1 is shown by a double-headed arrow θs in FIGS. 6 and 7. From the viewpoint of approaching the fiber angle of the straight layer to 0°, the angle θs is preferably 6.0° or less, more preferably 4.5° or less, and further preferably 3.0° or less. From the viewpoint of the circumferential uniformity effect, the angle θs is preferably 0.5° or more, more preferably 1.0° or more, and even more preferably 1.5° or more. The angle θs is an absolute value that does not depend on the direction of inclination.

What is indicated by a double-headed arrow D1 in FIGS. 6 and 7 is a deviation width between the tip side end and the butt side end in the winding start edge 41 of the straight layer. The end attachment deviation width D1 is an amount of deviation in the circumferential direction and is expressed by a ply or an angle. 6 and 7 show the case where the end attachment deviation width D1 is 1 ply (360°).

From the viewpoint of the circumferential uniformity effect, the end attachment deviation width D1 is preferably 0.25 ply (90°) or more, more preferably 0.5 ply (180°) or more, and 0.75 ply (270°) or more. More preferable. From the viewpoint of approaching the fiber angle of the straight layer to 0°, the edge attachment deviation width D1 is preferably 2 ply (720°) or less, more preferably 1.5 ply (540°) or less, and 1.25 ply (450°). ) The following is more preferable. The end attachment deviation width D1 may be 1 ply (360°) or less.

In forming the straight layer, the number of straight sheets can be increased and the winding start positions thereof can be dispersed in the circumferential direction. In this case, the spine parts are dispersed in the circumferential direction, and the uniformity in the circumferential direction can be improved. However, as the number of straight sheets increases, the work in the winding process increases and the productivity decreases. By wrapping the straight layer into a spiral layer, a circumferential uniform effect can be obtained without increasing the number of straight sheets. From this viewpoint, the number of full length straight sheets is preferably 3 or less (1 or more and 3 or less), and preferably 2 or less (1 or more and 2 or less). Even when the number of full length straight sheets is one, the circumferential direction uniform effect can be obtained.

From the viewpoint of thinning the spine portion, it is preferable to thin the straight sheet. By making the spine portion thin, circumferential uniformity can be improved. When the straight layer is wound to form a spiral layer, the circumferential uniform effect can be obtained even if the spine portion is thick. From this viewpoint, the straight sheet may be thickened. For example, the thickness of the straight sheet forming the winding start spiral layer can be 0.12 mm or more, and further 0.14 mm or more. The upper limit of this thickness is preferably 0.20 mm or less.

Even when the spine portion is provided, the spine portion can be spiraled by forming the straight layer into the spiral layer to start winding. Therefore, the circumferential direction uniform effect can be obtained.

[Effect when the bias layer is a spiral layer that starts winding]
It was found that the bending error of the shaft was suppressed by starting the winding of the bias layer and forming the spiral layer. (Bending error suppression effect). By making the winding end edge of the winding start spiral layer a spiral, the bending error suppressing effect is further enhanced. When the winding start spiral layer is the full length layer, the effect of suppressing the bending error is further enhanced.

The present inventor has found a bending deformation phenomenon in which the bending error increases due to the bias layer. Further, the present inventor has found a bending error suppressing effect due to the spiral layer at the beginning of winding. The cause of this bending deformation phenomenon and bending error suppressing effect is unknown, but it is presumed as follows. The bias layer causes non-uniform flow of resin and air during the curing process due to the tilt in the fiber direction. It is believed that this non-uniformity causes it to harden under stress and bend when the mandrel is pulled out. It is considered that by making the winding start edge of the bias layer a spiral, the nonuniformity is suppressed and the bending error is suppressed.

It has been found that the bending deformation phenomenon is likely to occur when the numbers of plies of the first bias layer and the second bias layer are the same on the chip side and the butt side. Therefore, in this case, the effect of suppressing the bending error is enhanced. From this viewpoint, the following (a) and (b) are preferably satisfied, and the following (a), (b) and (c) are more preferably satisfied.
(A) In the first bias layer, the number of plies on the tip side and the number of plies on the butt side are the same.
(B) In the second bias layer, the number of plies on the tip side and the number of plies on the butt side are the same.
(C) The number of plies in the first bias layer and the number of plies in the second bias layer are the same at all axial positions.

What is indicated by a double-headed arrow θb in FIG. 8 is an angle formed by the winding start edge 21 of the bias layer and the shaft center line. From the viewpoint of the bending error suppressing effect, the angle θb is preferably 0.5° or more, more preferably 1.0° or more, and further preferably 1.5° or more. From the viewpoint of approaching the fiber angle of the bias layer to a predetermined angle (for example, 45°), the angle θb is preferably 6.0° or less, more preferably 4.5° or less, and further preferably 3.0° or less. The angle θb is an absolute value that does not depend on the direction of inclination.

What is indicated by a double-headed arrow D2 in FIG. 8 is a deviation width between the tip side and the butt side edge in the winding start edge 21 of the bias layer. This end attachment deviation width D2 is a deviation amount in the circumferential direction and is expressed by a ply or an angle. In addition, in the embodiment of FIG. 8, the end deviation width D2 of the winding start edge 21 matches the end deviation width D2 of the winding start edge 31.

From the viewpoint of the bending error suppressing effect, the end attachment deviation width D2 is preferably 0.25 ply (90°) or more, more preferably 0.5 ply (180°) or more, and 0.75 ply (270°) or more. More preferable. From the viewpoint of approaching the fiber angle of the bias layer to a predetermined angle (for example, 45°), the edge attachment deviation width D2 is preferably 2 plies (720°) or less, more preferably 1.5 plies (540°) or less, and 1 More preferably, it is 0.25 ply (450°) or less. The end attachment deviation width D2 may be 1 ply (360°) or less.

What is indicated by double-headed arrows X1 and Y1 in FIG. 4 is a deviation width between the first bias sheet s2 and the second bias sheet s3 in the united sheet s23. X1 is the deviation width at the tip side end, and Y1 is the deviation width at the butt side end.

From the viewpoint of dispersing the winding start edge 21 and the winding start edge 31 in the circumferential direction, X1 is preferably 0.25 ply (90°) or more, most preferably 0.5 ply (180°), and 0.75 ply. It is preferably (270°) or less. From the viewpoint of suppressing the asymmetry of the torque in the twisting direction, X1 is preferably 1 ply (360°) or less.

From the viewpoint of dispersing the winding start edge 21 and the winding start edge 31 in the circumferential direction, Y1 is preferably 0.25 ply (90°) or more, most preferably 0.5 ply (180°) or more, and 0.75. Ply (270°) or less is preferable. From the viewpoint of suppressing the asymmetry of the torque in the twisting direction, Y1 is preferably 1 ply (360°) or less.

X1 and Y1 may be the same or different. By bending the spiral formed by the winding start edge 21 and the spiral formed by the winding start edge 31 in the circumferential direction, the bending error can be suppressed. From this viewpoint, X1 is preferably the same as Y1.

In FIG. 4, what is indicated by a double-headed arrow W1 is the overlapping width of the sheet s2 and the sheet s3 in the united sheet s23. From the viewpoint of suppressing the deviation between the sheets s2 and s3 in the winding process, the overlapping width W1 is preferably 1 ply or more in the shaft tip region. Considering the number of plies of each bias layer, the overlapping width W1 is preferably 2 plies or less in the shaft tip region. The shaft tip region means the region closest to the tip end Tp among the three regions obtained by dividing the entire shaft length Ls into three equal parts. From the viewpoint of suppressing the deviation between the sheets s2 and s3 in the winding step, it is preferable that the overlapping width W1 is 1 ply or more over the entire shaft. Considering the number of plies in each bias layer, the overlapping width W1 is preferably 2 plies or less over the entire shaft.

[Spiral (winding edge, winding edge)]
FIG. 9 is a conceptual diagram showing a winding start edge E1 forming a spiral. In FIG. 3, the winding start edge 21, the winding start edge 31, the winding start edge 41, and the winding start edge 51 are shown. These are the winding start edges of the full length layer. Further, in FIG. 3, the winding start edge 11 and the winding start edge 61 are shown. These are the winding start edges of the partial layers. These winding start edges can be configured like this winding start edge E1. In FIG. 9, the winding start edge E1 of the full length layer is shown. The spiral of the winding start edge E1 extends over the entire length of the shaft 6.

The winding start edge E1 forms a spiral around the shaft center line z1. The center of the helix coincides with the shaft center line z1. As can be understood from FIGS. 6 and 7, the rotation direction of the spiral is not limited. In the embodiment of FIG. 9, the spiral of the winding start edge E1 rotates clockwise as it moves from the bat side to the tip side when viewed from the bat side. On the contrary, the spiral of the winding start edge E1 may rotate counterclockwise as it moves from the bat side to the tip side as viewed from the bat side. The same applies to the spiral formed by the winding end edge.

In the embodiment of FIG. 9, the circumferential position of the winding start edge E1 is 0° at the butt-side end and 360° at the tip-side end. At the winding start edge E1, the deviation width between the tip side end and the butt side end (the above-mentioned end attachment deviation widths D1 and D2) is one ply. This deviation width is not limited.

The spiral formed by the winding start edge E1 is a three-dimensional curve. Needless to say, this spiral need not be a regular spiral as represented by a single equation. For example, the rotation angle per inch in the axial direction may change depending on the axial position. The winding start edge may be a straight line or a curved line. For example, the helix can be irregular if the winding start edge is free-form. The helix can also be irregular if the taper angle of the shaft changes. The spiral in the present application is a concept including such an irregular spiral. The same applies to the spiral formed by the winding end edge.

[Amount of change in circumferential direction per inch 1 inch θ1]
In FIG. 9, what is indicated by a double-headed arrow L1 is the axial length (inch) of the spiral. When the layer having the winding start edge E1 is a full length layer, the length L1 (inch) corresponds to the shaft length Ls. At the winding start edge E1, the change amount (circumferential change amount) θ1 (°) of the circumferential position per inch of the axial direction is 360/L1.

At the winding start edge and the winding end edge, which are spirals, the circumferential change amount θ1 per inch of the axial direction is defined. When the rotation angle of the spiral from the end on the tip side to the end on the bat side is θw (°) and the axial length of the spiral is L1 (inch), the circumferential change amount θ1 is calculated by the following formula. It
θ1=θw/L1

It should be noted that the angle θw correlates with the edge deviation width D2. When the end attachment deviation width D2 is 0.25 ply, the angle θw is 90°. When the end attachment deviation width D2 is 0.5 ply, the angle θw is 180°. When the end attachment deviation width D2 is 0.75 ply, the angle θw is 270°. When the end attachment deviation width D2 is 1 ply, the angle θw is 360°.

From the viewpoint of the circumferential direction uniform effect, the circumferential direction change amount θ1 at the winding start edge of the straight layer is preferably 0.98° or more, more preferably 1.96° or more, and more preferably 2.61° or more. It is more preferably 0.91° or more, and more preferably 7.83° or more. In consideration of the above-mentioned edge attachment deviation width D1, it is preferable that the circumferential direction change amount θ1 at the winding start edge of the straight layer is 15.7° or less. These preferred ranges also apply to the end of winding of the straight layer.

From the viewpoint of the circumferential direction uniform effect, the circumferential direction change amount θ1 at the winding start edge of the bias layer is preferably 0.98° or more, more preferably 1.96° or more, and more preferably 2.61° or more. It is more preferably 0.91° or more, and more preferably 7.83° or more. In consideration of the above-mentioned marginal deviation width D2, the circumferential direction change amount θ1 at the winding start edge of the bias layer is preferably 15.7° or less. These preferred ranges also apply to the end of winding of the bias layer.

[Bias sheet shape]
In the embodiment of FIG. 3, the first bias sheet s2 is trapezoidal. In the sheet s2, the winding start edge 21 is perpendicular to the tip-side edge 23 and the butt-side edge 24, and the winding end edge 22 is inclined with respect to the winding start edge 21. This shape is also applied to the second bias sheet s3. In the sheet s3, the winding start edge 31 is perpendicular to the tip side edge 33 and the butt side edge 34, and the winding end edge 32 is inclined with respect to the winding start edge 31. The shape of the bias sheet serving as the winding start spiral layer is not limited to such a shape. For example, the bias sheet may be substantially fan-shaped with no 90° angle. The bias sheet may have a triangular shape like the sheet s6 or a pentagonal shape like the sheet s1. Further, as described above, the winding start edges 21 and 31 may be curved.

[Straight sheet shape]
In the embodiment of FIG. 3, the straight sheet s4 is trapezoidal. In the sheet s4, the winding start edge 41 is perpendicular to the tip side edge 43 and the butt side edge 44, and the winding end edge 42 is inclined with respect to the winding start edge 41. This shape is also applied to the straight sheet s5. In the sheet s5, the winding start edge 51 is perpendicular to the tip side edge 53 and the bat side edge 54, and the winding end edge 52 is inclined with respect to the winding start edge 51. The shape of the straight sheet which becomes the spiral layer at the beginning of winding is not limited to such a shape. For example, the straight sheet may have a substantially fan shape with no 90° angle. The straight sheet may have a triangular shape like the sheet s6 or a pentagonal shape like the sheet s1. Further, as described above, the winding start edges 41 and 51 may be curved.

[Direction of inclination of winding start edge]
As shown in FIGS. 6 and 7, the direction of inclination of the winding start edge is not limited. This point is the same for the straight sheet and the bias sheet. In the form of FIG. 6, the tip side of the winding start edge is wound before the butt side. This form is called pattern A. In the form of FIG. 7, the butt side of the winding start edge is wound prior to the tip side. This form is called pattern B. The fiber angles of the pattern A and the pattern B with respect to the shaft center line z1 were compared. The setting conditions in this comparison are as follows.
-The sheet is a straight sheet, and the fiber direction is parallel to the winding start edge.
-The sheet shape is a trapezoid having 90° corners as shown in FIG.
・The width of the sheet is 1 ply (1 ply on both the tip side and the butt side).
-The edge displacement width D1 is 1 ply.

The results were as follows. In pattern A, the maximum absolute value of the fiber angle with respect to the shaft center line z1 was 2.9°, whereas in pattern B the maximum absolute value of the fiber angle with respect to the shaft center line z1 was 5. It was 0°. In other words, the pattern B had a larger effect on the fiber angle due to the tilting of the winding start edge, although the end attachment deviation width D1 was the same as that of one ply. From this viewpoint, the pattern A is preferable.

The number and type of the spiral layers at the beginning of winding are not limited. Only one or two or more straight layers may be the winding start spiral layers. Only one or more bias layers may be winding-start spiral layers. As in the embodiment of FIG. 8, the bias layer pair s2, s3 may be a winding start spiral layer. When there are two or more bias layer pairs, the two or more bias layer pairs may be winding start spiral layers. The one or more straight layers and the one or more bias layers may be winding-start spiral layers. When there are two or more winding start spiral layers, the circumferential positions of the winding start edges are preferably different at all axial positions.

When the number of straight layers is two or more, the shaft may include a first straight layer that constitutes the outermost layer of the shaft and a second straight layer that is arranged inside the first straight layer. In the embodiment of FIG. 3, layer s5 may be the first straight layer and layer s4 may be the second straight layer.

In this case, it is preferable that the second straight layer s4 is a winding start spiral layer. The second straight layer s4 is not the outermost layer. The second straight layer s4 is covered with another layer s5 over the entire axial direction. The second straight layer s4 is not polished. The spine portion of the second straight layer s4 is not polished. Therefore, by setting the second straight layer s4 as the winding start spiral layer, the effect resulting from the winding start edge 41 and the winding end edge 42 forming a spiral is maximized.

On the other hand, the first straight layer s5 is the outermost layer and is polished. By this polishing, the winding end edge 52 of the first straight layer s5 is polished, and the step due to the winding end edge 52 is reduced. Therefore, the effect of turning the first straight layer s5 into a spiral layer to start winding is smaller than the effect of turning the second straight layer s4 into a spiral layer to start winding.

Assuming that the direction of the fibers is parallel to the winding start edge, when the straight layer is started to be the spiral layer, the direction of the fibers is slightly inclined with respect to the axial direction. Since the angle of this inclination is very small, the influence of this inclination is limited, but it is not completely ineffective. It is possible to cut the straight sheet so that the fibers become parallel to the axial direction in the state of the winding start spiral layer, but this increases the waste of the sheet and the time and effort involved in the cutting.

The configuration in which the second straight layer s4 is the winding start spiral layer and the first straight layer s5 is not the winding start spiral layer can alleviate the problem of the minute inclination of the fiber. By making the winding start edge of the first straight layer s5 parallel to the axial direction, the fibers of the first straight layer s5 can be parallel to the axial direction. Further, by polishing the first straight layer s5, the spine portion of the first straight layer s5 is thinned, and its adverse effect is suppressed. The above effect can be enjoyed by setting the second straight layer s4 to be a spiral layer at the beginning of winding.

The first straight layer s5 may be a winding start spiral layer, and the second straight layer s4 may be a winding start spiral layer. In this case, the rotation direction of the spiral of the winding start edge 51 of the first straight layer s5 may be opposite to the rotation direction of the spiral of the winding start edge 41 of the second straight layer s4. In this configuration, the spiral of the winding start edge 41 and the spiral of the winding start edge 51 intersect, and the dispersibility of the winding start edges 41, 51 can be enhanced. Similarly, the end edges 42 and 52 have higher dispersibility. Further, between the first straight layer s5 and the second straight layer s4, the directions of the minute inclination of the straight fibers can be made opposite to each other. In this case, it is possible to prevent a decrease in straightness due to the minute inclination. Further, it is possible to prevent the torsional rigidity of the shaft from being non-uniform due to the minute inclination. In order to realize this structure, the second straight sheet s4 may be wound on one of the pattern A or the pattern B and the first straight sheet s5 may be wound on the other of the pattern A or the pattern B.

[Evaluation methods]
The evaluation method is as follows.

[Straightness]
FIG. 10 is a perspective view showing a method of measuring straightness. FIG. 11: is a side view which shows the measuring method of straightness.

The straightness measuring device 100 has a butt end contact surface 102, a first support portion 104, and a second support portion 106. The butt end contact surface 102 is a flat surface along the vertical direction. As shown in FIG. 10, the first support portion 104 has a support surface 104a. The second support portion 106 has a support surface 106a. The support surface 104a and the support surface 106a are V-shaped. The support surface 104a is the same as the support surface 106a. The support surface 104a and the support surface 106a are arranged such that the axis of the round bar is horizontal when a completely straight round bar having a constant outer diameter is placed. The first support portion 104 is provided at a position 198 mm from the butt end contact surface 102. The second support portion 106 is provided at a position 698 mm from the butt end contact surface 102. The axial width of the first support portion 104 is 10 mm, and the axial width of the second support portion 106 is also 10 mm.

The shaft 6 is placed on the support surface 104a and the support surface 106a with the butt end Bt being in contact with the butt end contact surface 102. The shaft 6 is rotated one or more times while being placed on the support surface 104a and the support surface 106a, and the displacement amount (maximum swing width) of the tip position P1 is measured. This displacement amount (mm) is straightness. The displacement amount is measured along a direction perpendicular to the axis. The smaller the straightness value, the less the bending of the shaft 6.

[Progressive flex]
FIG. 12 shows a method of measuring a forward flex. As shown in FIG. 12, the first support point S1 is set at a position of 1093 mm from the tip end Tp. Further, the second support point S2 is set at a position 953 mm from the tip end Tp. A support B1 that supports the shaft 6 from above is provided at the first support point S1. A support B2 that supports the shaft 6 from below is provided at the second support point S2. When there is no load, the shaft axis of the shaft 6 is horizontal. A load of 2.7 kgf is applied vertically downward to the load point m1 separated from the tip end Tp by 129 mm. The distance (mm) at the load point m1 between a state without a load and a stable state with a load applied is the forward flex. This distance is measured along the vertical direction. In the present invention, the total shaft length Ls is not limited. The measuring method shown in FIG. 12 can be applied when the shaft length Ls is relatively long. In a relatively short shaft such as an iron shaft, the forward flex can be measured by setting the positions of the instruction points S1 and S2 and the load point m1 that match the shaft length Ls. Regardless of the positions of the designated points S1, S2 and the load point m1, the flex difference is found and the circumferential uniformity can be evaluated by measuring the forward flex in a plurality of circumferential directions under the same condition.

<Evaluation of bias layer>
[Example 1a]
A shaft having the laminated structure of FIG. 3 was manufactured by the manufacturing process described above. The number of plies of the first bias layer s2 was 2.5 plies at the tip side end and the butt side end. The number of plies of the second bias layer s3 was also 2.5 plies at the tip side end and the butt side end.
In the united sheet s23, the deviation width X1 on the chip side was 0.5 ply, and the deviation width Y1 on the butt side was 0.5 ply (see FIG. 4). The united sheet s23, which was end-attached so that the winding start edge 21 was inclined with respect to the shaft center line z1, was wound. An end attachment deviation width D2 (see FIG. 8) of the winding start edge 21 was set to 0.25 ply. The other sheet was wound with the winding start edge being parallel to the shaft center line z1. As a result, a shaft was obtained in which only the bias layers s2 and s3 started to be wound and were spiral layers. The total shaft length Ls was 1168 mm.

The product names of the prepreg sheets used in Example 1a were as follows.
-Sheet s1: "TR350C-125S" (manufactured by Mitsubishi Chemical Corporation)
-Seat s2: "HRX350C-110S" (manufactured by Mitsubishi Chemical Corporation)
-Sheet s3: "HRX350C-110S" (manufactured by Mitsubishi Chemical Corporation)
-Sheet s4: "MRX350C-150S" (manufactured by Mitsubishi Chemical Corporation)
-Sheet s5: "MR350C-125S" (manufactured by Mitsubishi Chemical Corporation)
-Seat s6: "TR350C-100S" (manufactured by Mitsubishi Chemical Corporation)

Further, in each sheet, the circumferential position of the butt end of the winding start edge was as follows.
・Seat s1:0°
・United sheet s23: 180°
・Seat s4: 0°
・Seat s5: 90°
・Seat s6: 180°

[Example 2a]
A shaft of Example 2a was obtained in the same manner as in Example 1a, except that the end attachment deviation width D2 of the winding start edge 21 was 0.5 ply.

[Example 3a]
A shaft of Example 3a was obtained in the same manner as in Example 1a, except that the end attachment deviation width D2 of the winding start edge 21 was 0.75 ply.

[Example 4a]
A shaft of Example 4a was obtained in the same manner as in Example 1a, except that the end attachment deviation width D2 of the winding start edge 21 was 1.0 ply.

[Comparative Example 1a]
A shaft of Comparative Example 1a was obtained in the same manner as in Example 1a, except that the end attachment deviation width D2 of the winding start edge 21 was set to 0 ply. In other words, the shaft of Comparative Example 1a is obtained in the same manner as in Example 1a except that the united sheet s23 whose end is wound such that the winding start edge 21 is parallel to the shaft center line z1 is wound. It was Comparative Example 1a did not have a winding start spiral layer.

The straightness of Examples 1a to 4a and Comparative Example 1a was as follows. The smaller the value, the less the bending error.
<Result of straightness evaluation>
(1) Comparative Example 1a (edge mounting deviation width D2=0 ply): 3.4 mm
(2) Example 1a (edge mounting deviation width D2=0.25 ply): 2.6 mm
(3) Example 2a (edge mounting deviation width D2=0.5 ply): 1.7 mm
(4) Example 3a (edge mounting deviation width D2=0.75 plies): 0.9 mm
(5) Example 4a (edge mounting deviation width D2=1.0 ply): 0.0 mm

As described above, in Examples 1a to 4a in which the bias layer was the winding start spiral layer, the bending error was smaller than that in Comparative Example 1a in which the bias layer was not the winding start spiral layer. Further, the larger the end attachment deviation width D2, the smaller the bending error.

<Evaluation of straight layer>
[Example 1b]
A shaft having the laminated structure of FIG. 3 was manufactured by the manufacturing process described above. The number of plies of the straight layer s4 was 1.03 plies at the tip side end and the butt side end. Therefore, in the straight layer s4, a spine portion in which the winding start end and the winding end end overlap each other was formed. The number of plies of the straight layer s5 was 2.03 plies at the tip side end and the butt side end. Therefore, also in the straight layer s5, a spine portion in which the winding start end and the winding end end overlap each other was formed. The number of plies of the bias layer s2 and the bias layer s3 was 2.03 plies at the tip end and the butt side end.

The straight sheet s4 and the straight sheet s5 were wound while being inclined and attached to the shaft center line z1. In the sheet s4, the end deviation width D1 (see FIG. 7) of the winding start edge 41 was 0.25 ply. As a result, the end attachment deviation width D1 of the winding end edge 42 was also 0.25 ply. In the sheet s5, the end attachment deviation width D1 of the winding start edge 51 was set to 0.25 ply. As a result, the end deviation width D1 of the winding end edge 52 was also 0.25 ply. The sheets other than the sheets s4 and s5 were wound with the winding start edge end parallel to the shaft center line z1. As a result, a shaft was obtained in which only the straight layers s4 and s5 started to wind and were spiral layers. The total shaft length Ls was 1168 mm.

The product names of the prepreg sheets used in Example 1b were as follows.
-Sheet s1: "TR350C-125S" (manufactured by Mitsubishi Chemical Corporation)
-Seat s2: "HRX350C-110S" (manufactured by Mitsubishi Chemical Corporation)
-Sheet s3: "HRX350C-110S" (manufactured by Mitsubishi Chemical Corporation)
-Sheet s4: "MR350C-175S" (manufactured by Mitsubishi Chemical Corporation)
-Sheet s5: "TR350C-125S" (manufactured by Mitsubishi Chemical Corporation)
-Seat s6: "TR350C-100S" (manufactured by Mitsubishi Chemical Corporation)

The fiber areal weight of "MR350C-175S" is 175 g/m ² , and the fiber areal weight of "TR350C-125S" is 125 g/m ² . The fiber modulus of "MR350C-175S" is 30t / mm ^2, the fiber elastic modulus of the "TR350C-125S" is 24t / mm ^2.

In each sheet, the circumferential position of the butt end of the winding start edge was as follows.
・Seat s1:0°
・United sheet s23: 180°
・Seat s4: 90°
・Seat s5: 0°
・Seat s6: 180°

[Example 2b]
A shaft of Example 2b was obtained in the same manner as in Example 1b, except that the end attachment deviation width D1 of the winding start edge 41 and the winding start edge 51 was 0.5 ply.

[Example 3b]
A shaft of Example 3b was obtained in the same manner as in Example 1b, except that the deviation width D1 of the winding start edge 41 and the winding start edge 51 was 0.75 ply.

[Example 4b]
A shaft of Example 4b was obtained in the same manner as in Example 1b, except that the end deviation width D1 of the winding start edge 41 and the winding start edge 51 was 1.0 ply.

[Comparative Example 1b]
A shaft of Comparative Example 1b was obtained in the same manner as in Example 1b, except that the deviation width D1 of the winding start edge 41 and the winding start edge 51 was 0 ply. In other words, a shaft of Comparative Example 1b was obtained in the same manner as in Example 1b except that the winding start edge 41 and the winding start edge 51 were end-mounted so as to be parallel to the shaft center line z1. Comparative Example 1b had no spiral layer at the beginning of winding.

In Examples 1b to 4b and Comparative Example 1b, the forward flex in the 0° direction and the forward flex in the 90° direction were measured. The forward flex in the 0° direction is a forward flex measured with 0° in the circumferential direction of the shaft being set to the upper side in the vertical direction. The 90° direction forward flex is a forward flex measured at 90° in the shaft circumferential direction with the vertical direction being set to the upper side in the vertical direction. The evaluation results were as follows. The absolute value of the difference between the 0° direction forward flex and the 90° direction forward flex is also referred to as the flex difference. The smaller the flex difference, the higher the circumferential uniformity.

<Evaluation result of flex difference>
(1) Comparative Example 1b (edge mounting deviation width D1=0 ply)
・Forward flex in 0° direction: 119.0 mm
・Forward flex in 90° direction: 113.0 mm
・Flex difference: 6.0 mm
(2) Example 1b (edge mounting deviation width D1=0.25 ply)
・Forward flex in 0° direction: 118.3mm
・Forward flex in 90° direction: 113.7 mm
・Flex difference: 4.6 mm
(3) Example 2b (edge mounting deviation width D1=0.5 ply)
・Forward flex in 0° direction: 117.5 mm
・Forward flex in 90° direction: 114.5 mm
・Flex difference: 3.0 mm
(4) Example 3b (edge mounting deviation width D1=0.75 plies)
-Forward flex in 0° direction: 116.8 mm
・Forward flex in 90° direction: 115.2 mm
・Flex difference: 1.6 mm
(5) Example 4b (edge mounting deviation width D1=1.0 ply)
・Forward flex in 0° direction: 116.0 mm
・Forward flex in 90° direction: 116.0 mm
・Flex difference: 0.0 mm

As described above, Examples 1b to 4b in which the straight layer is the winding-start spiral layer were evaluated higher than Comparative Example 1b in which the straight layer was not the winding-start spiral layer. Further, the larger the end attachment deviation width D1, the smaller the flex difference and the better the circumferential uniformity.

The embodiment of FIG. 3 has a first straight layer s4 which is not the outermost layer and a second straight layer s5 which constitutes the outermost layer. The straight layer s5 constitutes the outermost layer except for the region where the layer s6 is provided. The first straight layer s4 and the second straight layer s5 are full length layers.

As can be seen from the number of plies of the sheets s4 and s5 described above, in Examples 1b to 4b and Comparative Example 1b, the first straight layer s4 and the second straight layer s5 have spine portions. Of these, the spine portion of the second straight layer s5 is shaved by the entire polishing in the polishing step. As a result, the spine portion of the second straight layer s5 becomes thin, and the influence of the spine portion of the first straight layer s4 is relatively increased.

By dispersing the spine portion of the first straight layer s4 and the spine portion of the second straight layer s5 in the circumferential direction, a dispersing effect that alleviates the non-uniformity in the circumferential direction may occur. However, when the spine portion of the second straight layer s5 is thinned by polishing, this dispersion effect is diminished. Therefore, in Comparative Example 1b, the flex difference was large. By setting the first straight layer s4 as a spiral layer to start winding, the flex difference can be effectively suppressed even when the second straight layer s5 is present in the outermost layer.

In Examples 1b to 4b and Comparative Example 1b, the fiber elastic modulus of the first straight layer s4 is higher than the fiber elastic modulus of the second straight layer s5. Due to this difference in fiber elastic modulus, the influence of the first straight layer s4 is relatively large. Therefore, the dispersion effect is easily diminished. By setting the first straight layer s4 as a spiral layer to start winding, the flex difference can be effectively suppressed even when the fiber elastic modulus of the first straight layer s4 is high.

In Examples 1b to 4b and Comparative Example 1b, the fiber areal weight of the first straight layer s4 is larger than that of the second straight layer s5. Due to this difference in fiber areal weight, the influence of the first straight layer s4 is relatively large. Therefore, the dispersion effect is easily diminished. By setting the first straight layer s4 as a spiral layer to start winding, the flex difference can be effectively suppressed even when the fiber weight of the first straight layer s4 is large. The fiber areal weight is the fiber weight of the prepreg sheet per unit area.

Regarding the above-described embodiment, the following supplementary notes are disclosed.
[Appendix 1]
It has a tip end and a butt end,
Formed of a plurality of fiber reinforced layers including two or more bias layers and one or more straight layers,
A golf club shaft, wherein at least one of said fiber-reinforced layers is a winding start spiral layer whose winding start edge forms a spiral.
[Appendix 2]
2. The golf club shaft according to appendix 1, wherein the winding end edge of the winding start spiral layer forms a spiral.
[Appendix 3]
3. The golf club shaft according to appendix 1 or 2, wherein at least one of the straight layers is the winding start spiral layer.
[Appendix 4]
The straight layer includes a first straight layer forming an outermost layer of the shaft, and a second straight layer arranged inside the first straight layer,
4. The golf club shaft according to Appendix 3, wherein the second straight layer is the winding start spiral layer.
[Appendix 5]
5. The golf club shaft according to attachment 4, wherein the winding start edge of the first straight layer is along the axial direction.
[Appendix 6]
The straight layer includes a first straight layer forming an outermost layer of the shaft, and a second straight layer arranged inside the first straight layer,
The first straight layer is the winding start spiral layer,
The second straight layer is the winding start spiral layer,
4. The golf club shaft according to Appendix 3, wherein the rotation direction of the spiral of the winding start edge of the first straight layer is opposite to the rotation direction of the spiral of the winding start edge of the second straight layer.
[Appendix 7]
7. The golf club shaft according to any one of appendices 1 to 6, wherein at least one of the bias layers is the winding start spiral layer.
[Appendix 8]
The bias layer includes a first bias layer and a second bias layer in which the orientation angles of the fibers are inclined in opposite directions,
8. The golf club shaft according to Appendix 7, wherein the first bias layer and the second bias layer are the winding start spiral layers.
[Appendix 9]
9. The golf club shaft according to any one of appendices 1 to 8, wherein at least one of the winding start spiral layers is a full length layer arranged from the tip end to the butt end.
[Appendix 10]
10. The golf club shaft according to any one of appendices 1 to 9, wherein, in at least one of the winding start spiral layers, a circumferential change amount of the winding start edge per inch in an axial direction is 0.98° or more. .

2... Golf club 4... Head 6... Shaft 21, 31, 41, 51... Winding start edge 22, 32, 42, 52... Winding end edge E1... Form a chain line Starting winding edge s1 to s6... Prepreg sheet s2, s3... Full length bias sheet s4, s5... Full length straight sheet s23... Combined sheet

Claims (10)

It has a tip end and a butt end,
Formed of a plurality of fiber reinforced layers including two or more bias layers and one or more straight layers,
A golf club shaft, wherein at least one of said fiber-reinforced layers is a winding start spiral layer whose winding start edge forms a spiral. The golf club shaft according to claim 1, wherein the winding start edge of the winding start spiral layer forms a spiral. The golf club shaft according to claim 1 or 2, wherein at least one of the straight layers is the winding start spiral layer. The straight layer includes a first straight layer forming an outermost layer of the shaft, and a second straight layer arranged inside the first straight layer,
The golf club shaft according to claim 3, wherein the second straight layer is the winding start spiral layer. The golf club shaft according to claim 4, wherein the winding start edge of the first straight layer is along the axial direction. The straight layer includes a first straight layer forming an outermost layer of the shaft, and a second straight layer arranged inside the first straight layer,
The first straight layer is the winding start spiral layer,
The second straight layer is the winding start spiral layer,
The golf club shaft according to claim 3, wherein a rotation direction of a spiral of a winding start edge of the first straight layer is opposite to a rotation direction of a spiral of a winding start edge of the second straight layer. 7. The golf club shaft according to claim 1, wherein at least one of the bias layers is the winding start spiral layer. The bias layer includes a first bias layer and a second bias layer in which the orientation angles of the fibers are inclined in opposite directions,
The golf club shaft according to claim 7, wherein the first bias layer and the second bias layer are the winding start spiral layers. 9. The golf club shaft according to claim 1, wherein at least one of the winding start spiral layers is a full-length layer arranged from the tip end to the butt end. The golf club according to any one of claims 1 to 9, wherein in at least one of the winding start spiral layers, a circumferential change amount of the winding start edge per inch in the axial direction is 0.98° or more. shaft.

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