JP2008029810A - Golf club shaft and golf club - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf club shaft which exhibits good carrying performance and a ball directivity and a golf club. <P>SOLUTION: Points acquired by plotting flexural rigidity EI measured at ten points of the shaft are represented by T(1)... T(10) sequentially from the head side, and the formula of a straight line K passing T(1) and T(10) is [Y=aX+b1]. The values of Y fragments in a straight line parallel with the straight line K and passing the points T(2)... T(9) are represented by b2... b9, and the smallest of the values b2 to b9 of the Y fragments is represented by bmin. The shaft shows the inclination a of the straight line K of 0.04 or larger and 0.06 or smaller, and b3, b4, b5, b6, b7 and b8 smaller than b1. The bmin is one from among b4 to b7, (b1-bmin) is 24(N m<SP>2</SP>) or larger and 35(N m<SP>2</SP>) or smaller, and (b9-b1) is 0 or larger and 10(N m<SP>2</SP>) or smaller. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a golf club shaft and a golf club.

  In recent years, so-called carbon shafts are frequently used as shafts for golf clubs. Carbon fibers having high specific strength and specific rigidity are used for the carbon shaft. As the specific strength and specific rigidity of the carbon fiber increase, it is possible to manufacture a golf club shaft that is reduced in weight.

During the swing, the shaft bends and twists. The behavior of the shaft during the swing can vary depending on the stiffness distribution of the shaft. Japanese Patent Application Laid-Open Nos. 2003-169871 and 2005-34550 disclose shafts in which rigidity distribution is considered. The invention described in Japanese Patent Application Laid-Open No. 2003-169871 defines the rigidity at the tip of the shaft. Japanese Patent Laying-Open No. 2005-34550 defines a position where the bending rigidity is minimized.
Japanese Patent Laid-Open No. 2003-168771 JP 2005-34550 A

  Even according to the above prior art inventions, the flight distance, hitting ball directivity and the like were insufficient. The present inventor has discovered a new technical problem that the prior art has potentially. The present invention solves this new technical problem by a technical idea that is completely different from the above-described prior art. According to the present invention, a shaft capable of improving the flight distance and the hitting ball directivity can be provided. Unlike the prior art described above, the present invention has been made in consideration of the shaft behavior during a swing in detail. According to the present invention, new functions and effects that have not been conceived in the past can occur.

  An object of the present invention is to provide a golf club shaft and a golf club excellent in flight distance performance and hitting directionality.

In the golf club shaft according to the present invention, the position 130 mm from the head side end of the shaft is the first position, the position 130 mm from the grip side end of the shaft is the tenth position, the first position and the tenth position. The positions that divide the position into nine equal parts are the second position, the third position,..., The eighth position, and the ninth position in order from the head side, and there are 10 positions from the first position to the tenth position. The measured bending rigidity EI is set to EI (1), EI (2),..., EI (9) and EI (10) in order from the head side, and the distance from the head end side of the measurement position ( mm) is the X-axis and the bending stiffness EI value (N · m ² ) is the Y-axis, and each of the points obtained by plotting the measured values at the 10 positions is T (1), T (2),..., T in order from the head side 9) and T (10), and the equation of the straight line K passing through the T (1) and the T (10) on the XY coordinate plane is [Y = aX + b1], which is parallel to the straight line K. And the values (N · m ² ) of Y-intercepts on straight lines passing through the points T (2), T (3),..., T (8) and T (9) are b2, b3, .., B8 and b9, and when the minimum value of the Y-intercept values b2 to b9 is bmin, it is defined as follows.

The slope a of the straight line K is 0.04 or more and 0.06 or less. B3, b4, b5, b6, b7 and b8 are all smaller than b1. The bmin is any one of b4, b5, b6 or b7. (B1-bmin) is 24 (N · m ² ) or more and 35 (N · m ² ) or less. (B9-b1) is 0 or more and 10 (N · m ² ) or less.

Preferably, when the minimum value from EI (1) to EI (10) is E1, and the maximum value from EI (1) to EI (7) is E2, it is defined as follows: Is done. E1 is EI (2), EI (3), EI (4) or EI (5). E1 is 16 (N · m ² ) or more and 25 (N · m ² ) or less. (E2-E1) is 20 (N · m ² ) or less. The EI (10) is 60 (N · m ² ) or more and 90 (N · m ² ) or less.

  Preferably, the total shaft length is 43 inches or more. Preferably, the forward flex of the shaft is 95 mm or more and 120 mm or less.

  The behavior of the shaft during the swing is improved, and the golf club shaft is excellent in hitting directionality and flight distance performance.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is an overall view of a golf club shaft 1 according to an embodiment of the present invention. The golf club shaft 1 is tubular. The shaft 1 is generally tapered as a whole. The shaft 1 has a head side end T and a grip side end B. The head side end T is an end on the small diameter side. The grip side end B is an end on the large diameter side. Although not shown, a golf club head is mounted near the head side end T, and a grip is mounted near the grip side end B. The material of the shaft 1 is not particularly limited. A typical shaft 1 is a carbon shaft or a steel shaft. The carbon shaft is made of CFRP (carbon fiber reinforced plastic). The steel shaft is made of steel.

  In the present invention, the bending stiffness EI at 10 positions is defined. The position in the present invention is a position in the shaft axial direction. The shaft defined as follows is excellent in flight distance performance and hitting directionality. This will be described later.

  Ten positions from the first position to the tenth position are defined as measurement positions of the bending rigidity EI. As shown in FIG. 1, the position 130 mm from the head side end T of the shaft 1 is the first position p1. A position 130 mm from the grip side end B of the shaft 1 is a tenth position p10. Positions that divide the first position p1 and the tenth position p10 into nine equal parts are, in order from the head side, the second position p2, the third position p3, the fourth position p4, the fifth position p5, the sixth position p6, The seventh position p7, the eighth position p8, and the ninth position p9.

The first position p1 to the tenth position p10 are arranged at equal intervals in the shaft axis direction. In FIG. 1, what is indicated by L1 is an interval between adjacent positions. When the total length of the shaft is L (mm), the interval L1 (mm) between adjacent positions is expressed by the following formula.
L1 = (L-260) / 9

  The bending stiffness EI measured at 10 positions from the first position p1 to the tenth position p10 is EI (1), EI (2),..., EI (9) and EI (10 ). That is, it is as follows.

The bending rigidity EI measured at the first position p1 is EI (1).
The bending stiffness EI measured at the second position p2 is EI (2).
The bending rigidity EI measured at the third position p3 is EI (3).
The bending rigidity EI measured at the fourth position p4 is EI (4).
The bending rigidity EI measured at the fifth position p5 is EI (5).
-The bending stiffness EI measured at the sixth position p6 is EI (6).
-The bending stiffness EI measured at the seventh position p7 is EI (7).
-The bending stiffness EI measured at the eighth position p8 is EI (8).
The bending rigidity EI measured at the ninth position p9 is EI (9).
The bending stiffness EI measured at the tenth position p10 is EI (10).

Based on these measured values, a graph is created on the XY coordinate plane. An example of this graph is shown in FIG. In this XY coordinate plane, the distance (mm) from the head side end T of the measurement position is taken as the X axis. The value (N · m ² ) of the bending stiffness EI is taken as the Y axis. Each of the points obtained by plotting the measured values at the 10 positions on the XY coordinate plane is T (1), T (2),..., T (9) and T (10). That is, it is as follows.

The X coordinate of T (1) is 130, and the Y coordinate of T (1) is EI (1).
The X coordinate of T (2) is (L1 × 1 + 130), and the Y coordinate of T (2) is EI (2).
The X coordinate of T (3) is (L1 × 2 + 130), and the Y coordinate of T (3) is EI (3).
The X coordinate of T (4) is (L1 × 3 + 130), and the Y coordinate of T (4) is EI (4).
The X coordinate of T (5) is (L1 × 4 + 130), and the Y coordinate of T (5) is EI (5).
The X coordinate of T (6) is (L1 × 5 + 130), and the Y coordinate of T (6) is EI (6).
The X coordinate of T (7) is (L1 × 6 + 130), and the Y coordinate of T (7) is EI (7).
The X coordinate of T (8) is (L1 × 7 + 130), and the Y coordinate of T (8) is EI (8).
The X coordinate of T (9) is (L1 × 8 + 130), and the Y coordinate of T (9) is EI (9).
The X coordinate of T (10) is (L1 × 9 + 130), and the Y coordinate of T (10) is EI (10).

On the XY coordinate plane, the equation of the straight line K passing through T (1) and T (10) is [Y = aX + b1]. That is, the slope of the straight line K is a, and the Y intercept (N · m ² ) of the straight line K is b1.

  The values of the Y intercepts on the straight lines parallel to the straight line K and passing through the points T (2), T (3),..., T (8) and T (9) are b2, b3,. .., b8 and b9. That is, it is as follows.

T2 is a point on the straight line [Y = aX + b2].
T3 is a point on the straight line [Y = aX + b3].
T4 is a point on the straight line [Y = aX + b4].
T5 is a point on the straight line [Y = aX + b5].
T6 is a point on the straight line [Y = aX + b6].
T7 is a point on the straight line [Y = aX + b7].
T8 is a point on the straight line [Y = aX + b8].
T9 is a point on the straight line [Y = aX + b9].

  FIG. 2 is an example of a graph in which measured values at 10 locations are plotted. The solid line in FIG. 2 indicates the straight line K. A broken line indicates a straight line [Y = aX + b8] passing through T8 as an example of a straight line passing through each of T2 to T9. FIG. 2 is a graph of Example 1 described later.

  The minimum value of the Y intercept values b2 to b9 is defined as bmin. That is, the minimum value among b2, b3, b4, b5, b6, b7, b8 and b9 is bmin.

In the shaft 1 defined as described above, the inclination a of the straight line K is preferably 0.04 or more, and more preferably 0.05 or more. The inclination a of the straight line K is preferably 0.06 or less. All of b3, b4, b5, b6, b7 and b8 are preferably smaller than b1. The bmin is preferably any of b4, b5, b6 or b7. (B1-bmin) is preferably 24 (N · m ² ) or more and 35 (N · m ² ) or less. (B9-b1) is preferably 0 or more and 10 (N · m ² ) or less.

  Next, the operational effects of the shaft 1 and the shaft behavior that is the premise thereof will be described.

  In a golf club, a head is mounted on the head side end T of the shaft. This head has a relatively large mass. Due to the inertia of the head and the like, the shaft behavior during the swing is as follows.

  When the swing starts, that is, when the swing-up (takeback) starts, the shaft is delayed in the head side. As a result of this reaction, at the end of the swing-up, the head side of the shaft precedes the swing-up direction. This bend is further increased at the start of the downswing. That is, at the start of the downswing, the head side of the shaft is delayed with respect to the downswing direction. Due to this natural reaction, the shaft tends to lead the head side in the swing direction from the start of the downswing to the impact. The behavior of the shaft affects the head speed during impact. The shaft flexure returns from a state where the head side is delayed to a state where the head side is not delayed, so that the head speed at the time of impact can be accelerated.

  Thus, the head speed Si at the time of impact is the sum of the swing speed S1 of the entire shaft and the head speed S2 resulting from the bending. That is, the relationship [Si = S1 + S2] is established. The swing speed S1 is a head speed resulting from movement of the entire shaft.

  The head speed S2 can change depending on the state of the shaft at the time of impact. The head speed S2 can vary depending on the timing of the bending behavior of the shaft and the impact. When the timing between the shaft behavior and the impact is bad, the head speed S2 may be negative. The head can be accelerated or decelerated by the return. If an impact is reached in a state where the head side is delayed, the acceleration due to the bending is not sufficient, and the head speed S2 becomes small. The head speed S2 can be maximized when the impact is reached at the moment when the bending in the direction in which the head side is delayed returns. In other words, the head speed S2 can be maximized by the fact that the bend in the direction of delaying the head side is almost coincident with the moment when the return shaft becomes almost straight and the moment of impact. By maximizing the head speed S2, the head speed Si at the time of impact can be maximized.

  In order to increase the head speed S2 due to the bending of the shaft, it is necessary to increase the bending of the shaft during the swing. In order to increase the bending of the shaft during the swing, it is preferable to decrease the bending rigidity EI of the intermediate portion of the shaft. However, simply reducing the bending rigidity EI of the shaft intermediate portion tends to have an impact with the shaft being delayed toward the head side. This tendency is particularly noticeable for beginner golfers. In order to improve this tendency, it is effective to increase the bending rigidity EI on the grip side of the shaft. That is, by reducing the bending rigidity EI at the intermediate portion and increasing the bending rigidity EI on the grip side, the bending in the direction in which the head is delayed increases, and the moment when this bending almost disappears can be an impact. .

  The bending of the shaft at the time of impact also affects the directionality of the hit ball. This is because the orientation of the face at the time of impact can change due to the bending of the shaft at the time of impact. For example, when the head is bent in the delayed direction, the face is easily opened. Due to the open face, the hit ball is likely to be sliced. On the contrary, the bending in the direction in which the head side precedes makes the face easy to close. The closed face makes it easier for the hit ball to become a hook. The impact in a state where the bending of the shaft is almost eliminated can improve the directionality of the hit ball.

  The bending of the shaft during impact also affects the launch angle. The bending in the direction in which the head side is delayed can reduce the loft angle at the time of impact. If the loft angle at the time of impact is small, the launch angle becomes small and a low hitting ball is produced. The impact when the shaft bending is almost eliminated can increase the loft angle at the time of impact compared to the impact when the head side is delayed. Increasing the loft angle at impact increases the launch angle. Increasing the launch angle can contribute to an increase in flight distance.

  From the viewpoint of increasing the head speed S2 by increasing the bending of the shaft at the start of the downswing, as described above, it is preferable that all of b3, b4, b5, b6, b7, and b8 are smaller than b1. . From the viewpoint of increasing the head speed S2 by increasing the bending of the shaft at the start of the downswing, the bmin is preferably any of b4, b5, b6 or b7, and the bmin is b5 or b6. More preferably.

From the viewpoint of increasing the head bending at the start of the downswing to increase the head speed S2, (b1-bmin) is preferably 24 (N · m ² ) or more, and more preferably 25 (N · m ² ) or more. Preferably, 26 (N · m ² ) is particularly preferable. From the viewpoint of suppressing the impact of the shaft without returning completely, (b1-bmin) is preferably 35 (N · m ² ) or less, more preferably 34 (N · m ² ) or less, 33 ( N · m ² ) or less is particularly preferable.

The value of (b9-b1) is related to the ease of return of the bent shaft. As the value of (b9-b1) is larger, the bending tends to return. From the standpoint of proper return and suppressing the impact when the head is delayed, (b9-b1) is preferably 0 (N · m ² ) or more, and more preferably 1 (N · m ² ) or more. It is preferably 2 (N · m ² ) or more. If the flexure returns too much, an impact is likely to occur in the state where the head precedes. (B9-b1) is preferably equal to or less than 10 (N · m ² ), more preferably equal to or less than 9 (N · m ² ), from the viewpoint of suppressing impact in the state in which the head precedes and suppressing hook balls. It is preferably 8 (N · m ² ) or less.

  From the viewpoint of improving the hit feeling and hitting timing while softening the central portion of the shaft, it is necessary to make the rear end portion of the shaft harder than the front end portion of the shaft. From the viewpoint of improving the hit feeling and hitting timing, the inclination a of the straight line K is preferably 0.04 or more, and more preferably 0.05 or more. From the viewpoint of suppressing the feeling of hitting ball from becoming excessively hard, the slope a of the straight line K is preferably 0.06 or less.

  In the present application, the minimum value from EI (1) to EI (10) is E1, and the maximum value from EI (1) to EI (7) is E2. From the viewpoint of increasing the head speed S2 by softening the intermediate portion of the shaft, E1 is preferably EI (2), EI (3), EI (4) or EI (5).

E1 is preferably 16 (N · m ² ) or more, and 17 (N · m ² ), from the viewpoint of suppressing excessive bending at the start of the downswing and suppressing the impact when the bending does not return completely. The above is more preferable, and 18 (N · m ² ) or more is particularly preferable. From the viewpoint of increasing the head speed S2 by increasing the bending of the shaft at the start of the downswing, E1 is preferably 25 (N · m ² ) or less, more preferably 24 (N · m ² ) or less, and 23 (N -M ² ) or less is particularly preferred.

From the viewpoint of optimizing the timing of the bending behavior and impact of the shaft and optimizing the amount of bending of the shaft, the lower limit of (E2-E1) is preferably 12 (N · m ² ) or more, and 15 (N M ² ) or more is more preferable, and the upper limit of (E2-E1) is preferably 23 (N · m ² ) or less, more preferably 20 (N · m ² ) or less, and particularly preferably 19 (N · m ² ) or less. preferable.

From the standpoint of proper return and suppressing the impact when the head is delayed, EI (10) is preferably 60 (N · m ² ) or more. EI (10) is preferably 90 (N · m ² ) or less from the viewpoint of suppressing the impact in the state where the head precedes and suppressing the hook ball.

  As the weight of the shaft is reduced, the amount of carbon fiber used tends to be reduced. For example, in the case of a shaft manufactured by a sheet winding method, weight reduction can be achieved by reducing the prepreg weight per unit area. By reducing the amount of carbon fiber, the shaft flex becomes softer and the torque becomes larger.

In addition to the shaft, the weight of the golf club tends to be reduced by reducing the weight of the head. The golf club reduced in weight tends to increase the head speed. If the soft shaft is swung at a high head speed, the shaft may become excessive at the start of the downswing. The impact in a state where the bend does not return is not preferable as described above. Therefore, the present invention is particularly effective for a relatively lightweight shaft. If the shaft is too heavy, the operability as a golf club is deteriorated. From these viewpoints, the shaft weight is preferably 70 g or less, more preferably 68 g or less, and particularly preferably 66 g or less in terms of 1169 mm. From the viewpoint of increasing the strength of the shaft and making the forward flex suitable, the shaft weight is preferably 40 g or more, more preferably 50 g or more, still more preferably 52 g or more, and particularly preferably 54 g or more, in terms of 1169 mm. A 1169 mm equivalent value W1 (g) of a shaft having a total length of L (mm) and a weight of W (g) is calculated by the following equation.
W1 = W × 1169 / L

  The present invention relates to shaft flexing and flexing return. The longer the overall length L of the shaft, the greater the influence of bending. The longer the overall length L of the shaft, the more easily the effect of the present invention becomes apparent. From this viewpoint, the total shaft length L is preferably 41 inches (1041 mm) or more, more preferably 43 inches (1092 mm) or more, and more preferably 44 inches (1117 mm) or more. It is particularly preferable that the thickness be 45 inches (1143 mm) or more. From the viewpoint of securing the strength of the shaft, the total shaft length L is preferably 52 inches (1321 mm) or less, more preferably 50 inches (1270 mm) or less, and particularly preferably 48 inches (1219 mm) or less.

  From the viewpoint of suppressing the feeling that is too soft and suppressing the impact when the head side is delayed, the forward flex f of the shaft is preferably 95 mm or more, more preferably 96 mm or more, and particularly preferably 97 mm or more. From the viewpoint of suppressing the feeling that is too hard and increasing the head speed S2 due to the bending of the shaft, the forward flex f is preferably 120 mm or less, more preferably 119 mm or less, and particularly preferably 118 mm or less.

  The manufacturing method of a shaft is not specifically limited. As described above, the shaft may be a so-called steel shaft or a carbon shaft. From the viewpoint of the degree of freedom in designing the bending rigidity EI, a carbon shaft is preferable. As a method for manufacturing the carbon shaft, a sheet winding method, a filament winding method, or the like can be used. The sheet winding method is preferable from the viewpoints of design flexibility and weight reduction of the bending rigidity EI. CFRP (carbon fiber reinforced plastic) that can be used for a carbon shaft is formed by impregnating a reinforcing fiber made of carbon fiber with an epoxy resin. As the matrix resin, an epoxy resin, a thermosetting resin other than the epoxy resin, a thermoplastic resin, or the like can be used.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

  The measuring method is as follows.

[Measurement method of bending stiffness EI]
FIG. 3 is a diagram for explaining a method of measuring the bending rigidity EI. The bending stiffness EI was measured using an Intesco 2020 model (maximum load 500 kg). As shown in FIG. 3, while the shaft 1 is supported from below at two support points 3 and 5, the deflection amount α when a load F is applied to the measurement point P from above is measured. The measurement point P is any one of p1 to p10 described above. The distance (span) between the support point 3 and the support point 5 was 200 mm. The measurement point P was a position that divides the support point 3 and the support point 5 into two equal parts. The tip of the indenter 7 to which the load F is applied from above is rounded. The cross-sectional shape of the tip of the indenter 7 has a curvature radius of 10 mm in a cross section parallel to the shaft axial direction. In the cross section perpendicular to the shaft axis direction, the cross-sectional shape of the tip of the indenter 7 is a straight line, and the length of this straight line is 45 mm.

  The support 9 supports the shaft 1 from below at the support point 3. The tip of the support 9 has a convex roundness. The cross-sectional shape of the tip of the support 9 has a radius of curvature of 15 mm in a cross section parallel to the shaft axial direction. In the cross section perpendicular to the shaft axis direction, the cross-sectional shape of the tip of the support 9 is a straight line, and the length of this straight line is 50 mm. The shape of the support 11 is the same as that of the support 9. The support 11 supports the shaft 1 from below at the support point 5. The tip of the support 11 has a convex roundness. The cross-sectional shape of the tip of the support 11 has a radius of curvature of 15 mm in a cross section parallel to the shaft axial direction. In the cross section perpendicular to the shaft axis direction, the cross-sectional shape of the tip of the support 11 is a straight line, and the length of this straight line is 50 mm.

The indenter 7 was moved downward at a speed of 5 mm / min while fixing the support 9 and the support 11. The movement of the indenter 7 was completed when the load F reached 20 kg. The deflection amount α (mm) of the shaft 1 at the moment when the movement of the indenter 7 was completed was measured. The bending stiffness EI (N · m ² ) was calculated by the following formula.
EI (N · m ² ) = 32.7 / α

[Measurement of forward flex f]
FIG. 4A is a diagram for explaining a method of measuring the forward flex f. As shown in FIG. 4, the first support point 13 was set at a position 75 mm from the grip side end B. Further, a second support point 15 was set at a position 215 mm from the grip side end B. The first support point 13 is provided with a support 17 that supports the shaft 1 from above. The second support point 15 is provided with a support 19 that supports the shaft 1 from below. In a state where there was no load, the shaft axis of the shaft 1 was substantially horizontal. A load of 2.7 kg was applied to the load point m, which is 1039 mm from the grip side end B, vertically downward. The moving distance (mm) of the load point m from the state without load to the state with load applied was defined as the forward flex f. This movement distance is a movement distance along the vertical direction.

  In addition, the cross-sectional shape of the part (henceforth a contact part) contact | abutted with the shaft of the support body 17 is as follows. In the cross section parallel to the shaft axis direction, the cross-sectional shape of the contact portion of the support 17 has a convex roundness. The radius of curvature of this roundness is 15 mm. In the cross section perpendicular to the shaft axis direction, the cross-sectional shape of the contact portion of the support 17 has a concave roundness. The radius of curvature of the concave roundness is 40 mm. In the cross section perpendicular to the shaft axis direction, the horizontal length (length in the depth direction in FIG. 4) of the contact portion of the support 17 is 15 mm. The cross-sectional shape of the contact portion of the support 19 is the same as that of the support 17. The cross-sectional shape of the contact portion of a load indenter (not shown) that applies a load of 2.7 kg at the point m has a convex roundness in a cross section parallel to the shaft axial direction. The radius of curvature of this roundness is 10 mm. The cross-sectional shape of the contact portion of a load indenter (not shown) that applies a load of 2.7 kg at the point m is a straight line in a cross section perpendicular to the shaft axial direction. The length of this straight line is 18 mm. In this way, the forward flex f was measured.

[Example 1]
A shaft was produced by a sheet winding method. A plurality of prepregs were wound around a metal mandrel and laminated. A developed view of the laminated prepreg is shown in FIG. Eight prepregs were wound around a mandrel (not shown) in the order of prepreg s1, prepreg s2, ... prepreg s8. In FIG. 5, the prepreg shown on the upper side is laminated on the inner side.

  The prepreg s1 is a layer that reinforces the tip. In the prepreg s1, the fiber orientation angle is substantially 0 degree with respect to the shaft axis. That is, the prepreg s1 constitutes a straight layer. The prepreg s2 is provided over the entire length of the shaft. The prepreg s2 is a so-called bias layer. In the prepreg s2, the fiber orientation angle is substantially −45 degrees with respect to the shaft axis. The prepreg s3 is also provided over the entire length of the shaft. The prepreg s3 is a so-called bias layer. In the prepreg s3, the fiber orientation angle is substantially +45 degrees with respect to the shaft axis. The prepreg s3 and the prepreg s4 are overlapped with each other and wound in this state. When the prepreg s3 and the prepreg s4 are overlapped, the prepreg s3 is reversed from the state of FIG. By this turning over, the fiber orientation angle of the prepreg s2 and that of the prepreg s3 are opposite to each other. The prepreg s4 is a reinforcing layer that reinforces the tip. In the prepreg s4, the fiber orientation angle is substantially 0 degree with respect to the shaft axis. That is, the prepreg s4 constitutes a straight layer. The prepreg s5 is a layer that reinforces the rear end. In the prepreg s5, the fiber orientation angle is substantially 0 degree with respect to the shaft axis. That is, the prepreg s5 constitutes a straight layer. The prepreg s6 is provided over the entire length of the shaft. In the prepreg s6, the fiber orientation angle is substantially 0 degree with respect to the shaft axis. That is, the prepreg s6 constitutes a straight layer. The prepreg s7 is provided over the entire length of the shaft. In the prepreg s7, the fiber orientation angle is substantially 0 degree with respect to the shaft axis. That is, the prepreg s7 constitutes a straight layer. The prepreg s8 is a reinforcing layer that reinforces the tip. In the prepreg s8, the fiber orientation angle is substantially 0 degree with respect to the shaft axis. That is, the prepreg s8 constitutes a straight layer. The dimensions of the prepregs s1 to s8 are as shown in FIG. The unit of this dimension is mm.

The prepreg varieties (product names) used from prepreg s1 to prepreg s8 and the elastic modulus of the carbon fiber are shown in Table 1 below. All of the varieties shown in Table 1 are prepregs manufactured by Toray. “-7” or the like given to the end of the prepreg product name indicates the thickness of the prepreg. Specifically, “−7” indicates that the thickness is 0.0570 mm. “−10” indicates that the thickness is 0.0840 mm. “−11” indicates that the thickness is 0.0820 mm. “−12” indicates that the thickness is 0.1030 mm. “−15” indicates that the thickness is 0.1450 mm. For example, “3255G-12” has a tensile modulus of carbon fiber used of 24 t / mm ² and a thickness of 0.1030 mm. In all varieties shown in Table 1, the matrix resin is an epoxy resin.

  A polypropylene tape was wound around the prepregs s1 to s8 laminated in this manner. This was molded while being cured by heating and pressing in an oven. The mandrel was extracted from the molded body taken out from the oven. Both ends were cut in order to align the length, surface polishing was performed, and the shaft according to Example 1 was obtained. A head and a grip were attached to this shaft, and a golf club according to the shaft 1 was obtained. As the head, “SRIXON W-505 Loft 10.5 degrees” manufactured by SRI Sports Co., Ltd. was used.

[Example 2]
A shaft and a golf club according to Example 2 were obtained in the same manner as in Example 1 except that the types and configurations of the prepregs s1 to s8 were as shown in Table 1.

[Comparative Examples 1 to 3]
The shafts and golf clubs according to Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 except that the varieties and configurations of the prepregs s1 to s8 were as shown in Table 1. In Comparative Example 2, the prepreg s4, the prepreg s5, and the prepreg s8 were not used.

  The specifications and evaluation results of Examples and Comparative Examples are shown in Tables 2 to 4 below. The method for measuring the bending stiffness EI is as described above. The method for measuring the forward flex f is as described above. In the reverse flex measurement method, the first support point 13 is positioned at 12 mm from the head side end T, the second support point 15 is positioned at 152 mm from the head side end T, and the load point m is at the head side end T. 932 mm and measured in the same manner as the forward flex f except that the load was 1.3 kg. This inverse flex measurement method is shown in FIG.

  FIG. 6 is a line graph in which T1 to T10 are plotted and connected with a straight line in each of Examples 1 and 2 and Comparative Examples 1 to 3.

  The evaluation result by actual hitting will be described. As Table 2 shows, there are four items for evaluation by actual hits: [Head speed], [Launch angle], [Flight distance] and [Feeling].

Twenty testers hit 10 golf balls at each golf club, and by averaging all these data, [Head speed], [Launch angle], [Flight distance] and [Feeling] data were obtained. Obtained. The handicap of 20 testers is 20 or more and 35 or less. These data are shown in Table 2 below. As the golf ball, “HI-BRID Everio” (registered trademark) manufactured by SRI Sports, which is a commercially available three-piece ball, was used. [Flying distance] is a distance in a direction connecting the hit ball position and the target position. Each tester gave an evaluation score according to the following criteria, and an average value of evaluation scores of 10 golfers was set as an evaluation value of [feeling]. The closer the evaluation value is to 3, the better the result.
・ The shaft feels very hard ・ ・ ・ 1 point ・ The shaft feels a little hard.・ ・ ・ Two points ・ The shaft hardness is just right.・ ・ ・ 3 points ・ The shaft feels a little soft.・ ・ ・ 4 points ・ The shaft feels very soft. ... 5 points

  As shown in the table, the example has a higher evaluation than the comparative example. In Examples 1 and 2, since the central portion of the shaft is soft, the head speed is improved. In Comparative Example 1, since the central portion of the shaft is excessively soft, the head speed is smaller than that of the embodiment and the launch angle is also low. In Comparative Examples 2 and 3, the central portion is hard and the head speed is small. From this evaluation result, the superiority of the present invention is clear.

  The present invention can be applied to all types of golf clubs, such as wood type golf clubs and iron type golf clubs, and their shafts.

FIG. 1 is a diagram for explaining a position where a bending rigidity EI is measured in a shaft according to the present invention. FIG. 2 is an example of a graph in which measured values of bending stiffness EI at 10 locations are plotted on an XY coordinate plane. FIG. 3 is a diagram for explaining a method of measuring the bending rigidity EI. FIG. 4A is a diagram for explaining a method of measuring the forward flex f. FIG. 4B is a diagram illustrating a method for measuring the inverse flex. FIG. 5 is a development view of the prepreg on the shaft of the embodiment or the like. FIG. 6 is a graph of Examples 1 and 2 and Comparative Examples 1 to 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Shaft T ... Head side end B ... Grip side end p1 ... 1st position p2 ... 2nd position p3 ... 3rd position p4 ... 4th position p5 ... 5th position p6 ... 6th position p7 ... 7th position p8 ... 8th position p9 ... 9th position p10 ... 10th position L ... Total shaft length

Claims (5)

The position 130 mm from the head side end of the shaft is the first position, the position 130 mm from the grip side end of the shaft is the tenth position, and the position that divides the first position and the tenth position into nine equal parts Are the second position, the third position, ..., the eighth position and the ninth position in order from the head side,
The bending stiffness EI measured at 10 positions from the first position to the tenth position is EI (1), EI (2),..., EI (9) and EI (10) in order from the head side. And
The measured values at the above 10 positions are plotted on the XY coordinate plane in which the distance (mm) from the head end side of the measurement position is the X axis and the bending rigidity EI value (N · m ² ) is the Y axis. , T (1), T (2),..., T (9) and T (10) in order from the head side.
On the XY coordinate plane, the equation of the straight line K passing through T (1) and T (10) is [Y = aX + b1],
A value (N · m ² ) of a Y-intercept in a straight line parallel to the straight line K and passing through each of the points T (2), T (3), ..., T (8) and T (9) is B2, b3,..., B8 and b9, respectively.
When the minimum value of the Y intercept values b2 to b9 is bmin,
The slope a of the straight line K is 0.04 or more and 0.06 or less,
B3, b4, b5, b6, b7 and b8 are all smaller than b1,
The bmin is any one of b4, b5, b6 or b7,
(B1-bmin) is 24 (N · m ² ) or more and 35 (N · m ² ) or less,
A golf club shaft in which (b9-b1) is 0 or more and 10 (N · m ² ) or less. The minimum value from EI (1) to EI (10) is E1,
When the maximum value from EI (1) to EI (7) is E2,
E1 is EI (2), EI (3), EI (4) or EI (5);
E1 is 16 (N · m ² ) or more and 25 (N · m ² ) or less,
(E2-E1) is 20 (N · m ² ) or less,
^2. The golf club shaft according to claim 1, wherein the EI (10) is 60 (N · m ² ) or more and 90 (N · m ² ) or less.   The golf club shaft according to claim 1, wherein the overall length of the shaft is 43 inches or more.   2. The golf club shaft according to claim 1, wherein the forward flex is 95 mm or more and 120 mm or less. It has a head, a shaft, and a grip.
This shaft
The position 130 mm from the head side end of the shaft is the first position, the position 130 mm from the grip side end of the shaft is the tenth position, and the position that divides the first position and the tenth position into nine equal parts Are the second position, the third position, ..., the eighth position and the ninth position in order from the head side,
The bending rigidity EI measured at 10 positions from the first position to the tenth position is EI (1), EI (2),..., EI (9) and EI (10) in order from the head side. And
The measured values at the above 10 positions are plotted on the XY coordinate plane in which the distance (mm) from the head end side of the measurement position is the X axis and the bending rigidity EI value (N · m ² ) is the Y axis. , T (1), T (2),..., T (9) and T (10) in order from the head side.
On the XY coordinate plane, the equation of the straight line K passing through T (1) and T (10) is [Y = aX + b1],
A value (N · m ² ) of a Y-intercept in a straight line parallel to the straight line K and passing through each of the points T (2), T (3),..., T (8) and T (9) B2, b3,..., B8 and b9, respectively.
When the minimum value of the Y intercept values b2 to b9 is bmin,
The slope a of the straight line K is 0.04 or more and 0.06 or less,
B3, b4, b5, b6, b7 and b8 are all smaller than b1,
The bmin is any one of b4, b5, b6 or b7,
(B1-bmin) is 24 (N · m ² ) or more and 35 (N · m ² ) or less,
A golf club in which (b9-b1) is 0 or more and 10 (N · m ² ) or less.

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