JP6908538B2 - Golf club - Google Patents

Description

The present invention relates to a golf club, and more particularly to a golf club having a shaft formed of fiber reinforced plastic (FRP).

Conventionally, the shaft of a golf club is known to be made of steel or a fiber reinforced resin (hereinafter referred to as FRP). In general, golf clubs equipped with steel shafts have the advantage of stable directionality, and golf clubs equipped with FRP shafts can be made lighter, resulting in improved swing speed, launch angle and flight distance. The merit of improving is obtained.

The direction of hitting a golf club equipped with a steel shaft is good because the metal has an isotropic property, and the ratio of torsional rigidity to bending rigidity (GIp / EI) extends in the length direction. It is considered that the factor is that it is uniform. This will be described with reference to the graph of FIG.
FIG. 1A is a graph showing a change in rigidity of a general steel shaft in which the tip of the shaft on which the head is mounted is 0, the shaft length is the horizontal axis (mm), and the rigidity value is the vertical axis (Kgf · mm ^2). Is. As shown in this graph, the flexural rigidity (EI) and the torsional rigidity (GIp) decrease by the same amount of change (similar shape) as the hand side shifts to the tip side. As shown in, the ratio of torsional rigidity to flexural rigidity (GIp / EI) becomes uniform in the length direction (becomes a flat linear shape).

On the other hand, the shaft made of FRP is formed by winding a plurality of prepreg sheets in which reinforcing fibers are impregnated with a synthetic resin around a core metal, and then thermosetting and decentering the prepreg sheets. In this case, for example, as disclosed in Patent Document 1, a prepreg sheet for reinforcement (reinforcing fiber in the axial length direction) extends over a certain length (about 300 mm from the tip) to the portion where the head is mounted. A prepreg sheet oriented toward the surface) is wound. This is because the shaft is formed so that the tip side has a smaller diameter, and for the portion where the head is mounted, the outer surface of the shaft and the inner surface of the fitting hole of the hosel portion of the head are fixed in a straight shape. Moreover, this is to prevent the strength of the fixed region and its vicinity from being lowered.

Such an FRP shaft has different longitudinal and horizontal elastic moduli depending on the direction of the reinforcing fiber and has anisotropic properties. Therefore, for example, as shown in the graph of FIG. 2A, the flexural rigidity (EI) and torsional rigidity (GIp) are not in the same changed state as steel shafts, and therefore, as shown in FIG. 2 (b), the ratio of torsional rigidity to flexural rigidity (GIp / EI). Fluctuates over the length direction (it does not become a flat linear shape like the steel shaft shown in FIG. 1).
As described above, in the FRP shaft, the ratio of torsional rigidity to bending rigidity (GIp / EI) fluctuates in the length direction, which is a factor that the directional stability cannot be obtained as much as that of the steel shaft. it is conceivable that.

Japanese Unexamined Patent Publication No. 2012-245309

Currently, about 100% of wood type clubs used by general golfers are FRP shafts, and about 40% of iron type clubs are FRP shafts. For this reason, some golfers have a wood club with FRP shaft and an iron club with steel shaft as a set. In such a case, both shafts should be used during the round. Become.

As mentioned above, the steel shaft has isotropic properties, so it seems to have good directionality, but when using an FRP shaft, it has an isotropic property like steel. Because there is no such thing, there will be a deviation from the feeling of using the steel shaft. Also, if an iron club is assembled with a steel shaft and replaced with an iron club set with an FRP shaft, the feeling of use will be different from when using a steel shaft. It ends up.
Therefore, with respect to the shaft made of FRP, it is possible to realize a good set assembly by giving the same properties as the shaft made of steel as much as possible.

By the way, as shown in FIG. 1A, the steel shaft has high flexural rigidity on the hand side (grip side), and also has high torsional rigidity. Therefore, when the golfer starts swinging the shaft (when shifting from the top position to the downswing), the golfer feels the hardness and the difficulty of twisting the shaft. Normally, when swinging down from the top position, you want to swing down while keeping the angle between the wrist and the shaft in the same state, but if the shaft is too hard, it will be difficult to apply force and the angle between the wrist and the shaft cannot be maintained. It becomes a golf club that is difficult to control (ideal swing is not possible). In particular, if the torsional rigidity on the hand side is high, it becomes difficult to control the shaft because it feels difficult to twist when the shaft is started to swing, and it becomes difficult to take the timing of impact. On the other hand, if the bending rigidity on the hand side is too low, the feeling of rigidity on the hand side cannot be obtained and it becomes difficult to catch the ball.

The present invention has been made by paying attention to the above-mentioned problems, and provides a golf club equipped with an FRP shaft, which can provide a swing feeling similar to that of a steel shaft and has good operability. With the goal.

In order to achieve the above object, the golf club according to the present invention has a shaft made of fiber reinforced resin attached to the head, and the shaft is the front side of the region where the grip on the proximal end side is attached. Within the first range, the displacement width of the ratio of torsional rigidity to flexural rigidity (GIp / EI) is 0.2 or less, and within the second range including the area where the grip on the proximal end side is mounted. The characteristic is that the ratio of torsional rigidity to flexural rigidity (GIp / EI) is formed to be a value lower than that within the first range.

Usually, the torsional rigidity and the bending rigidity of the shaft have a great influence on the swing feeling and the shot feeling of a golf club for a golfer. That is, the torsional rigidity is the resistance to twisting, and the bending rigidity indicates the difficulty of deformation with respect to bending. If the rigidity is low, the shaft can be hit by using the deformation of the shaft itself. In this case, if the ratio of torsional rigidity to bending rigidity is uniform (flat linear shape) over the entire length, the shaft will be isotropic, and the overall rigidity will be uniform and the ball will be hit. The direction is also stable. Therefore, if the ratio changes greatly (large variation) depending on the position of the shaft in the axial length direction, a sense of discomfort tends to occur in the swing feeling and the shot feeling, which is not preferable for stabilizing the hit ball. In particular, if there are golf clubs having such a large variation in one golf club set, the difference in sensation (difference in atmosphere) between the golf clubs becomes large. For example, when a golf club with a steel shaft having an isotropic property and a golf club with an FRP shaft having a large ratio are used together in one round, the difference in sensation between the golf clubs becomes large. It may lead to missed shots. Further, if the iron club set of the steel shaft is replaced with the iron club of the FRP shaft, a deviation from the previous feeling will occur.

In the FRP shaft of the present invention, the displacement width of the ratio of torsional rigidity to bending rigidity (GIp / EI) is 0.2 or less in the region (first range) on the front side of the portion where the grip is mounted. Since the fluctuation range is minimized by forming the golf club, it is possible to obtain a golf club that approaches the isotropic property of a steel shaft and does not cause a sense of discomfort with the steel shaft (steel). A golf club that can stabilize the direction of the hit ball, such as a steel shaft, can be obtained). Further, in the region where the grip is mounted (second range), the ratio of the torsional rigidity to the bending rigidity (GIp / EI) is formed to be a value lower than that in the first range. This is because in the grip region, the GIp of the grip region is set relatively low (the difference between the torsional rigidity and the bending rigidity is set high) with respect to the isotropic property in the first range, and the grip side is set. Is to make the characteristic easy to twist, which makes it easy to control without feeling the difficulty of twisting when the shaft starts to swing, and makes it easy to take the timing of impact. That is, in the grip region, by increasing the rigidity difference to some extent (lowering the torsional rigidity and increasing the rigidity difference), the hand side does not bend during the downswing, and the bending from the middle to the tip is created, resulting in this. At the same time, it becomes easier to catch the hit ball, and at the same time, it becomes easier to control because it does not feel difficult to twist. Moreover, since the shaft is made of FRP, it is lightweight and easy to swing.

According to the present invention, in a golf club equipped with an FRP shaft, it is possible to obtain a swing feeling similar to that of a steel shaft and to obtain a golf club with good operability.

(A) is a graph showing the flexural rigidity distribution of a steel shaft, and (b) is a graph showing the ratio of torsional rigidity to flexural rigidity (GIp / EI) in the rigidity distribution shown in FIG. (A). (A) is a graph showing the flexural rigidity distribution of a general FRP shaft, and (b) is a graph showing the ratio of torsional rigidity to flexural rigidity (GIp / EI) in the rigidity distribution shown in FIG. (A). The front view which shows an example of the golf club which concerns on this invention. The figure which shows each characteristic of the example of the shaft made of FRP. FIG. 6 is a list showing the characteristics of each of the comparative examples compared with the shaft shown in FIG. The graph which showed the characteristic of each Example of FIG. 4 and FIG. 5, and each comparative example. It is a graph which shows the rigidity distribution of the shaft made of FRP which concerns on one Embodiment of this invention, (a) is a graph which shows the rigidity distribution of a shaft, (b) is the torsion in the rigidity distribution shown in FIG. The graph which shows the ratio (GIp / EI) of rigidity and bending rigidity. FIG. 5 is a pattern diagram showing an arrangement and a configuration example of a prepreg seat and a reinforcing prepreg seat constituting a shaft of a golf club according to the present invention.

Hereinafter, embodiments of the golf club according to the present invention will be described with reference to the drawings. The golf club according to the present invention corresponds to a wood-type golf club equipped with an FRP shaft and an iron-type golf club, and further, such golf clubs are set with different counts (wood). Club set, iron club set) is included.

FIG. 3 is a diagram showing an example of a golf club according to the present invention.
The golf club 1 shown in FIG. 3 illustrates an iron-type golf club, in which a head (iron head) 5 is attached to the tip end side of the shaft 10 and formed of rubber or the like on the base end side of the shaft 10. The grip 12 is attached.
The head 5 has a hosel 5a into which the shaft 10 is inserted to fix the tip region, and a plate-shaped face portion 5b on which a ball is hit, and the outer surface of the shaft 10 and the fitting hole of the hosel 5a. The range of adhesion to the inner surface depends on the type of golf club, but is generally about 25 mm to 40 mm.

The total length L of the shaft 10 differs depending on the type of golf club (wood type, iron type) and the count (loft angle differs for each count). As will be described later, in the shaft of the present invention, the ratio of torsional rigidity to flexural rigidity (GIp / The ratio of torsional rigidity to flexural rigidity is within the second range in which the displacement width of EI) is 0.2 or less and includes the region L1 in which the grip 12 on the proximal end side is mounted. (GIp / EI) is formed so as to have a value lower than that in the first range.

The second range may include a region held by the golfer at the time of hitting a ball. Specifically, when the total length of the shaft 10 is L, the second range is from the base end position to 0.4 L. It suffices if it exists in. That is, if it is from the base end position to 0.4 L, the area where the grip 12 is mounted is included, and as will be described later, the torsional rigidity within this second range is lowered (with flexural rigidity). By forming the ratio of torsional rigidity to flexural rigidity (GIp / EI) to be lower than the first range, a swing feeling similar to that of a steel shaft can be obtained, and a swing feeling similar to that of a steel shaft can be obtained. A golf club with good operability can be obtained.

As is known, the shaft 10 is made of FRP formed by winding a plurality of prepreg sheets in which reinforcing fibers are impregnated with a synthetic resin around a core metal, and then thermosetting and decentering the prepreg sheets. .. In this case, the tip region of the shaft 10 is reduced in diameter by a taper, a heavy object is attached by attaching a head, an impact is received at the time of hitting a ball, and so on, so that a prepreg sheet for reinforcement (reinforcement) Sheet) is wound. The reinforcing sheet of the present embodiment exhibits a function of maintaining a constant ratio of torsional rigidity to bending rigidity (GIp / EI) within the first range while improving bending rigidity and torsional rigidity of the tip region. Further, it forms a straight fixing region between the inner surface of the fitting hole of the hosel 5a and the outer surface of the shaft, and plays a role of improving the fixing strength of the head. The configuration of the prepreg sheet and the reinforcing sheet wound around the core metal, and an example of their arrangement will be described later.

In the present invention, the FRP shaft mounted on the head is configured to have the following characteristics. Here, before explaining the structure of the shaft according to the present embodiment, the characteristics of the shaft which is the basic principle of the present invention will be described.

The rigidity of the shaft has a great influence on the feeling when the golfer swings, and when the golfer swings and hits the ball, the golfer intuitively grasps the bending rigidity and the torsional rigidity (a feeling of rigidity of the shaft). Can be grasped).

As for the flexural rigidity of the shaft, the higher it is, the more difficult it is to bend (so-called tension becomes stronger). Therefore, a shaft with high rigidity is a characteristic suitable for golfers with a high swing speed, and a shaft with low rigidity is a shaft. Since it is possible to hit the ball using the flexibility, it is a characteristic suitable for golfers with slow swing speeds. It should be noted that such bending can be sensuously grasped by the golfer when swinging. Further, the torsional rigidity of the shaft affects the feeling of operation in the rotational direction, and the golfer can intuitively grasp the resistance and reactivity in the torsional direction at the grip portion. That is, for a shaft with high torsional rigidity, the feeling of twisting at the grip is directly transmitted to the head, and for a shaft with low torsional rigidity, the feeling of twisting at the grip is transmitted to the head with some margin (playability). It will be transmitted.

The steel shaft has an isotropic property, and as shown in FIG. 1, the flexural rigidity and the torsional rigidity characteristics are substantially the same over the entire length, and the shaft diameter is about the base end side. Because of its thickness, the golfer can feel its hardness, especially on the base end side. In this case, when the shaft is made of FRP, if it is not necessary to cause a sense of discomfort with the steel shaft, the characteristics of the bending rigidity and the torsional rigidity may be substantially matched over the entire length. Since the golfer directly grasps and controls the hardness of the grip side, it is preferable to configure the grip side so that the operability can be improved in this area.

Specifically, in order to make a good swing, when swinging down from the top position, it is preferable to swing down with the wrist and shaft at the same angle (such control is easy), but the grip part If there is little play in the twisting direction (difficult to twist), such control becomes difficult, and as a result, the impact timing becomes difficult to take.
In this case, if the grip portion is easily twisted and the bending rigidity is also lowered, the feeling of rigidity on the hand side is lost, and it becomes difficult to catch the ball at the time of impact. Therefore, in order to make the shaft easy to take timing and catch the ball, the hand side (grip side) has a certain amount of play (play) against twisting, and the structure is such that a sense of rigidity can be grasped. Is preferable. However, if the bending rigidity is made too high, it becomes difficult to bend and control the bending rigidity. Therefore, it is better not to make the bending rigidity too high.

That is, in the grip region, the bending rigidity is high and the torsional rigidity is suppressed (the ratio of the torsional rigidity to the bending rigidity (GIp / EI) is suppressed), so that the torsional difficulty when the shaft is started to be swung is not felt. The shaft can be easily controlled, the timing of impact can be easily taken, and the ball can be easily caught.

As described above, a general FRP shaft is affected by the direction of the reinforcing fibers of the prepreg sheet to be wound and has a characteristic of anisotropy, as shown in FIG. 2 (a). The ratio of flexural rigidity to torsional rigidity (GIp / EI) is not uniform over the entire length of the shaft, but in the present invention, the prepreg sheet is arranged, for example, in the tip region on the head side. By devising the structure of the reinforcing sheet to be installed, the ratio of flexural rigidity to torsional rigidity is made uniform (the displacement width is reduced).

For example, in the FRP shaft having the characteristics shown in FIG. 2A, the torsional rigidity of the reinforcing sheet wound toward the tip side is lowered toward the tip, or the flexural rigidity is directed toward the tip. By raising the ratio, the ratio of flexural rigidity to torsional rigidity (GIp / EI) can be brought close to the characteristics of the steel shaft as shown in FIG. 1 (b). In this case, as a method of reducing the torsional rigidity, the number of windings of the reinforcing sheet (cross sheet) in which the reinforcing fibers are obliquely oriented in the axial length direction of the shaft is reduced, or the reinforcing sheet is wound toward the inner layer side. This can be achieved by winding a cross sheet having a small oblique angle of the reinforcing fibers. On the contrary, as a method of increasing the flexural rigidity, it can be achieved by increasing the number of windings of the reinforcing sheet (straight sheet) in which the reinforcing fibers are oriented in the axial length direction, or by winding it toward the outer layer side. ..

Next, when equalizing the ratio of flexural rigidity to torsional rigidity (GIp / EI) over the entire length of the shaft, the displacement width should give a good feeling (a feeling close to that of a steel shaft). Whether or not it can be obtained will be specifically described with reference to FIGS. 4 to 6.
Here, a plurality of shafts of a golf club equipped with the same head are prepared, and the characteristics of the shaft according to the present invention are shown as Example A, Example B, Example C, and Example D. (See FIG. 4), the characteristics of the shaft to be compared with the configuration of the present invention are shown as Comparative Example F, Comparative Example G, and Comparative Example C (see FIG. 5).

In the numerical values shown in FIGS. 4 and 5, the tip of the shaft is set to 0, the shaft position is specified at intervals of 50 mm, the values of flexural rigidity (ΣEI) and torsional rigidity (ΣGIp) at that position are calculated, and the ratio thereof is calculated. (GIp / EI) is derived (the unit of each rigidity is Kgf · mm ² ). Further, in each shaft, the maximum value (MAX) and the minimum value (MIN) of (GIp / EI) are shown, and the difference is shown (MAX-MIN). Therefore, the larger this difference, the larger the displacement width.
In the tables of FIGS. 4 and 5, the values of flexural rigidity (ΣEI) and torsional rigidity (ΣGIp) and the ratio (GIp / EI) are shown up to three decimal places with the shafts at intervals of 50 mm. There are also examples and comparative examples in which the maximum and minimum values of the ratio (GIp / EI) occur at positions that do not exist in the table. That is, the minimum value (0.303) of the ratio in Example A is calculated at the position of 1110 mm, and the maximum value (0.963) of the ratio in Example C is calculated at the position of 1110 mm. Further, the maximum value (0.563) of the ratio in Comparative Example F is calculated at the position of 280 mm, and the minimum value (0.539) of the ratio in Comparative Example G is calculated at the position of 910 mm. The maximum value (0.492) is calculated at the 170 mm position.

In this case, the flexural rigidity (EI) and the torsional rigidity (GIp) are derived by the following calculation method.
Regarding flexural rigidity, Young's modulus (longitudinal elastic modulus) E can be specified by calculation from the specifications of the configuration (material) and arrangement mode (laminated structure) of the prepreg sheet constituting the shaft, and I (cross section). Secondary moment)
It can be derived by I = π (D ₂ ^4- D ₁ ⁴ ) / 64 (Equation 1).
Regarding the torsional rigidity (GIp), the shear elastic modulus (transverse elastic modulus) G is calculated from the specifications of the configuration (material) and the arrangement mode (laminated structure) of the prepreg sheets constituting the shaft, as described above. It can be specified, and for Ip (cross-section torsional moment),
^{_{Ip = π (D 2 4 -D}} 1 4) / 32 can be derived by (Equation 2).
In the above (Equation 1) and (Equation 2), D ₂ is the outer diameter of the shaft, and D ₁ is the inner diameter of the shaft.
Further, since the FRP shaft is constructed by winding a plurality of materials, the numerical value of the entire shaft is calculated by adding the calculated values of each layer.

Regarding the flexural rigidity (EI) of the actually molded FRP shaft, the shaft is leveled to support two points separated from the measurement point by a distance (L / 2), and a force is applied from above to the position of the central measurement point. It can be derived by measuring the amount of deflection (δ) when (P) is added. In particular,
^{EI = (L 3/48)} × (P / δ)
It is possible to derive from the formula of.
The maximum load P is 20 kgf, and the distance between supports L is 200 mm.
With the above method, it is possible to obtain the EI of the central position measurement point between two points of support, and by shifting the support position, it is possible to continuously calculate the numerical value.

Regarding the torsional rigidity (GIp) of the actually molded FRP shaft, the shaft is horizontal, one end is fixed, the position is held at a distance of L mm from the fixed part, and the torque Tr is applied to the holding part. It can be derived by measuring the torsion angle A (radian) of the shaft when given. In particular,
GIp = L × Tr / A
It is possible to derive from the formula of.
The torque Tr is 139 (kgf · mm), and the fixed holding distance L of the shaft is 200 mm.
By the above method, it is possible to obtain the GIp at the center position between the fixed and held shafts, and by shifting the position, it is possible to continuously calculate the numerical value.

Since the steel shaft has isotropic properties as described above, the GIp / EI ratio is made uniform over the entire length of the shaft, but the value is the Poisson's ratio (ν) of the constituent material. ) Depends on the situation. Considering that iron is the main component of the shaft, its Poisson's ratio is about 0.3, so it is considered to be about 0.87 from the relationship of E = 2 (1 + ν). Therefore, in an actual steel shaft, it is considered that the shaft is within the range of 0.85 ± 0.1 (0.85 in FIG. 6 below), although it depends on the constituent materials.

FIG. 6 is a graph showing the ratio (GIp / EI) of the shafts shown in FIGS. 4 and 5 to the longitudinal direction (horizontal axis) of the shafts.
In Examples A, B, C, and D, the arrangement and configuration of the prepregs to be wound (main body prepreg sheet and reinforced prepreg sheet, which will be described later) are set so that the displacement width of the ratio is 0.2 or less. It is a thing. The displacement width is set so that the displacement width is the lowest in Example C and the ratio is close to 1 (displacement is in the range of 0.8 to 1.0), and the characteristics are closest to those of a steel shaft. It is configured to be.

On the other hand, Comparative Example F is a shaft having a ratio displacement width of 0.368, and Comparative Example G is a shaft having a ratio displacement width of 0.784 (a shaft having the characteristics shown in FIG. 2). , The displacement width of the ratio is set to 0.230, which is close to 0.2. As for the displacement width of the ratio, as described above, the feeling is lowered as the displacement width is increased, and the feeling is improved as it approaches 0. Here, as a result of examining in advance as a simulation, if the displacement width of the ratio is within 0.2, it can be predicted that the feeling will be improved to some extent. Therefore, in the actual sensory test, the displacement width is 0. We prepared the ones around 2 (0.194 in Example D and 0.2030 in Comparative Example C) and actually verified them.

The contents of the sensory test and the results thereof will be described below.
In the sensory test, seven golf clubs shown in FIGS. 4 and 5 were prepared, and 10 ordinary average golfers were asked to try out each golf club. In this case, each person was randomly provided with seven golf clubs, hit at least 10 balls, and had each club evaluated relative to each other. In the relative evaluation, golf clubs that are evaluated as having a good feeling at the time of hitting and having good direction are marked with a circle (one or more golf clubs may be selected), and the golf clubs that are evaluated as good are evaluated relative to each other. Although it is a little inferior, it is better to have the golf clubs evaluated as acceptable by adding a triangle (one or more golf clubs may be selected), and to improve by comparing with the golf clubs evaluated as good. Those who evaluated it as good were marked with a cross (one or more may be selected).
The results are shown in the table below.

上記の評価結果に見られるように、変位幅が０．１０４の実施例ウ、変位幅が０．１３２の実施例イ、変位幅が０．１６８の実施例アについては、良いと評価、もしくは許容できる範囲と評価されていることから、フィーリングが良いゴルフククラブであると評価することができる。

As seen in the above evaluation results, Example c with a displacement width of 0.104, Example a with a displacement width of 0.132, and Example A with a displacement width of 0.168 are evaluated as good or evaluated as good. Since it is evaluated as an acceptable range, it can be evaluated as a golf club with a good feeling.

On the other hand, there were many evaluations that improvement was better for Comparative Example F with a displacement width of 0.368 and Comparative Example G with a displacement width of 0.784. Further, the evaluations of Example D having a displacement width of 0.194 and Comparative Example C having a displacement width of 0.230 are slightly different, but the evaluations of Examples A, B, and C, and Comparative Example F, As a result of considering the evaluation of the key, in the present invention, it is determined that the displacement width 0.2 is the limit value at which a good feeling can be obtained in practical use (for example, 〇 is 2 points, Δ is 1 point, ×. When the score is converted to 0 points, Example D has 12 points and Comparative Example C has 10 points. Therefore, in the present invention, the limit value of the displacement width is specified as 0.2).

From the above, when constructing a shaft made of FRP, by forming the displacement width of the ratio of torsional rigidity to bending rigidity (GIp / EI) to 0.2 or less, it is possible to approach the feeling of a steel shaft. It will be possible.

In the shaft configuration described above, in the present invention, the torsional rigidity is further lowered (the difference in rigidity from the bending rigidity is increased) within the second range including the region where the grip 12 on the proximal end side is mounted. , The ratio of torsional rigidity to bending rigidity (GIp / EI) is formed so as to be lower than the first range in order to improve operability.

FIG. 7 is a graph showing the rigidity distribution of the FRP shaft according to the embodiment of the present invention, (a) is a graph showing the rigidity distribution of the shaft, and (b) is the rigidity distribution shown in FIG. Is a graph showing the ratio of torsional rigidity to bending rigidity (GIp / EI).
In this embodiment, a golf club having a shaft length of 1081 mm (a shaft for FW No. 3) is illustrated, and the range is approximately 800 mm to 1100 mm (the second range on the grip side, which is 0.4 L with respect to the shaft length L). The torsional rigidity of the included range) is formed to be lower than the characteristics of the steel shaft described above.

As shown in FIG. 7B, a shaft having such a rigidity distribution characteristic has a ratio of torsional rigidity to flexural rigidity (GIp / EI) within the first range, which is the front side of the region where the grip is mounted. ) Is 0.2 or less (within the range of approximately 0.42 to 0.62), and within the second range including the area where the grip is mounted, the torsional rigidity and the flexural rigidity are included. The ratio (GIp / EI) of is lower than that within the first range.

In this case, regarding the ratio of torsional rigidity to flexural rigidity (GIp / EI) in the second range, it is better not to make the displacement width too large, and the displacement width is 0. It is preferably formed so as to be within the range of 2 (in the present embodiment, it is within the range of approximately 0.35 to 0.42 and is set within the range of 0.2). This is because if the displacement width exceeds 0.2 and becomes too large, the feeling of the steel shaft deviates greatly. Specifically, if the flexural rigidity is made too high, the cock will be easily unraveled at the turning back from the top position to the downswing, and the hardness of the shaft will also make it difficult, and conversely, the torsional rigidity will be too low. This is because the balance between hardness and torsion becomes poor, and it becomes difficult to control the torsion. That is, the golfer unconsciously tries to adjust the bending and torsion from the top position to the downswing to the impact, but if the bending rigidity is too high or the torsional rigidity is too low, this adjustment cannot be performed well. As a result, the direction of the hit ball varies. Therefore, it is preferable to set the displacement width within the second range so as not to exceed 0.2.

Here, the operation is performed between the FRP shaft having the rigidity distribution characteristic shown in FIG. 7 and the steel shaft (the ratio of torsional rigidity to bending rigidity (GIp / EI) is substantially uniform over the entire length of the shaft). The sensory test and its result will be described.
Ease of hitting (operability when shifting from the top position to the downswing) by having 10 ordinary average golfers who conducted the trial hitting test in Table 1 try hitting with two golf rubs equipped with the above shafts. , And the ease of catching the ball) were evaluated on a 5-point scale, and the following results were obtained.

上記の表に見られるように、図７で示すような剛性分布を有するＦＲＰ製のシャフト（グリップ側のねじり剛性を低くして（ＧＩｐ／ＥＩ）を低く設定したシャフト）の方が、スチール製のシャフトと比較して総合点が高くなっており、打ち易いゴルフクラブであるとの評価が得られた。

As can be seen in the above table, the FRP shaft having the rigidity distribution as shown in FIG. 7 (the shaft in which the torsional rigidity on the grip side is set low (GIp / EI) is set low) is made of steel. The overall score is higher than that of the shaft, and it was evaluated as an easy-to-hit golf club.

As described above, by making the shaft of the golf club made of FRP, it is possible to reduce the weight, which makes it easier to swing, and the torsional rigidity and bending of the front side (first range) of the area where the grip is mounted. By forming the displacement width of the rigidity ratio (GIp / EI) to 0.2 or less, it is possible to approach a straightforward feeling like a steel shaft, stabilize the shot, and stabilize the directionality. Will be. Therefore, even if a wood-type golf club equipped with such a shaft is set and used in a round together with an iron club set equipped with a steel shaft, there is no great discomfort between the two. It is possible to make a stable shot between both clubs. Alternatively, even if the iron club set equipped with a steel shaft is switched to an iron club set equipped with such an FRP shaft, it can be used without discomfort.

Further, in the area where the grip is mounted (second range), the torsional rigidity is lowered to keep the ratio of the torsional rigidity to the bending rigidity (GIp / EI) low, so that the operability is good and it is easy to hit. It can be a golf club.

Next, a specific configuration example of the shaft having the above characteristics will be described with reference to FIG.
FIG. 8 is a pattern diagram showing an example of the arrangement and configuration of the prepreg sheet and the reinforcing prepreg sheet forming the shaft having the rigidity distribution as shown in FIG. 7.

In the shaft of the present embodiment, the main body prepreg sheet (hereinafter referred to as the main body sheet) is sequentially wound around the core metal 20 having a smaller diameter at the tip side, and the reinforcing prepreg sheet is formed on the tip side, and the base is formed from the intermediate region. It is formed by winding a reinforcing prepreg sheet (hereinafter referred to as a reinforcing sheet) over an end region, heating and firing in this state, decentering, and surface treating. In this case, the 1114 mm portion of the core metal 20 constitutes the total length of the shaft.

The main body sheet is wound in a plurality of sheets to form the entire length of the shaft (forms the main body layer), and the main body sheet 31, which is the innermost layer, has reinforcing fibers aligned in the axial length direction and is 1 on the tip side. It is cut so that it is wound with 1 ply and 1.1 plies on the base end side. In the main body sheet 32 wound on the main body sheet 31, the first oblique sheet in which the reinforcing fibers are oriented in the + 45 ° direction with respect to the axial length direction and the reinforcing fibers are oriented in the −45 ° direction with respect to the axial length direction. It is cut so that it is overlapped with a second oblique sheet oriented toward the surface and wound so that 3.0 plies are wound on the tip side and 1.5 plies are wound on the base end side.

The main body sheet 33 wound on the main body sheet 32 is cut so that the reinforcing fibers are aligned in the axial length direction and wound with 1.00 plies on the tip side and 1.00 plies on the base end side. Has been done. Further, on the main body sheet 33, a reinforcing sheet 41 in which reinforcing fibers are aligned in the axial length direction is wound from a position of 364 mm from the rear end to a base end position. The reinforcing sheet 41 is cut so as to be wound with 1.00 plies at a position 60 mm rearward from a position 364 mm from the rear end and 1.00 plies at the base end side.

The main body sheets 35 and 36 wound on the reinforcing sheet 41 are cut so that the reinforcing fibers are aligned in the axial length direction and wound with 1.00 plies on the tip side and 1.00 plies on the base end side, respectively. Has been done.

Among the above-mentioned multiple wound main body sheets, the main body sheets 33, 34, 35 in which the reinforcing fibers are aligned in the axial length direction contribute to the improvement of the bending rigidity, and the main body in which the reinforcing fibers are oriented in the cross direction. The sheet 32 contributes to the improvement of the torsional rigidity. In this case, it is the reinforcing fibers oriented at ± 45 ° that most effectively contribute to the improvement of the torsional rigidity, but the angle is not limited. Further, the main body sheet 31 in which the reinforcing fibers are aligned in the circumferential direction contributes to the improvement of the crushing strength.
As described above, in the present embodiment, since the torsional rigidity is lowered and the difference between the torsional rigidity and the bending rigidity is increased on the grip side, the main body sheet 32 in which the reinforcing fibers are oriented in the cross direction is wound on the inner layer side. Such a configuration can be realized by turning, reducing the number of windings on the proximal end side from that on the distal end side, and winding the reinforcing sheet 41 for adjustment from the intermediate region to the proximal region. I have to.

Further, a reinforcing sheet is wound around the tip region of the shaft (the tip side on which the head is mounted). The reinforcing sheet is wound up to a range of 201 mm from the tip, and the first reinforcing sheet 42 in which the reinforcing fibers are oriented in the axial length direction and the reinforcing fibers are oriented in the + 45 ° direction with respect to the axial length direction. It has a second reinforcing sheet 43 in which a first oblique sheet to be oriented and a second oblique sheet to which the reinforcing fibers are oriented in the −45 ° direction with respect to the axial length direction are overlapped.

The first reinforcing sheet 42 is cut so as to have 3.28 plies at the tip position and 0 plies at the proximal end position (position 201 mm from the tip). Further, the second reinforcing sheet 43 is a sheet cut so as to have 3 plies at the tip position and 0 plies at the proximal end position (position 201 mm from the tip) at a fiber angle of + 45 °, and −45 °. It is composed of laminated sheets cut to the same size at the fiber angle. By winding such a reinforcing sheet, the change states of the flexural rigidity and the torsional rigidity on the tip side of the shaft can be substantially matched, and the ratio of the bending rigidity to the torsional rigidity (GIp / EI) is 0.2 or less. Can be easily set to. Further, in this way, the first reinforcing sheet 42 and the second reinforcing sheet 43 are wound so that the ends on the grip side coincide with each other, whereby the positions of the inflection points match and the bending rigidity And the ratio of torsional rigidity (GIp / EI) is prevented from being significantly displaced.

The first reinforcing sheet 42 and the second reinforcing sheet 43 may be wound discontinuously in the circumferential direction (the main body sheet may be interposed between them), as shown in FIG. In addition, it is preferable that the reinforcing sheets are continuously wound, and further, these reinforcing sheets are preferably arranged in the outermost layer of the shaft in a continuous state. By winding continuously in this way, it is possible to wind without creating a gap in the radial direction, and further, by winding on the outer layer side (outermost layer), the ratio of flexural rigidity to torsional rigidity. It becomes easy to set (GIp / EI) to 0.2 or less.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be variously modified. The present invention is formed so that the displacement width of the ratio (GIp / EI) of the torsional rigidity to the bending rigidity (GIp / EI) in the first range of the shaft is 0.2 or less, and the ratio is the second in the second range. It suffices if it is formed so as to be lower than the range of 1, and the structure of the main body sheet and the reinforcing sheet constituting the shaft can be appropriately deformed if such a condition is satisfied. The above-mentioned arrangement example of each sheet and the number and length of plies of each sheet are shown only as an example. For example, in the pattern diagram shown in FIG. 8, another main body sheet may be wound. However, the prepreg sheet for adjustment may be wound around.

Further, the numerical value of the ratio of torsional rigidity to bending rigidity (GIp / EI) can be appropriately deformed. In the graph shown in FIG. 4, the ratio of torsional rigidity to flexural rigidity (GIp / EI) in the first range is in the range of 0.42 to 0.62, but in the present invention, it is larger than 1.0, for example. The displacement width may be configured to be 0.2 or less (for example, in the range of 1.1 to 1.3) by the value.

1 Golf club 5 Head 10 FRP shaft 20 Core metal 31-35 Main body prepreg sheet 41-43 Reinforcing prepreg sheet

Claims (4)

In a golf club with a fiber reinforced plastic shaft attached to the head,
When the total length from the tip position to the proximal end position of the shaft is L, the shaft has a second range including a region where the grip on the proximal end side is mounted and a front side of the second range. It has the first range and
The second range exists from the base end position of the shaft to the position of 0.4 L.
The first range exists on the tip side of the area where the grip is mounted, including the tip position of the shaft.
The shaft, in the front side der Ru said first range of areas grip base end side is mounted, 0.2 displacement range of the ratio of flexural rigidity torsional rigidity (GIP / EI) is over all , and the and the within a second range, the ratio of flexural rigidity torsional rigidity (GIP / EI) is to be a lower value than the value of the said first range over all (GIP / EI) A golf club characterized by being formed in. The golf club according to claim 1, wherein the displacement width of the ratio of torsional rigidity to bending rigidity (GIp / EI) within the second range of the shaft is 0.2 or less. A prepreg sheet for reinforcement is wound around the shaft on the tip side on which the head is mounted.
The prepreg sheet for reinforcement has a first reinforcing sheet in which reinforcing fibers are oriented in the axial length direction and a second reinforcing sheet in which reinforcing fibers are cross-oriented, according to claim 1 or 2. Golf clubs listed in. A golf club set including a plurality of golf clubs, wherein the shaft of each golf club includes the shaft according to any one of claims 1 to 3.

Images