JP2019136281A - Golf club - Google Patents

Abstract

To provide a golf club to which an FRP shaft is attached, which can acquire swing feeling equal to that obtained on a golf club having a steel shaft, and which has good operativity.SOLUTION: A golf club of the invention has a fiber-reinforced resin shaft attached to a head, the shaft has equal to or less than 0.2 of a displacement width of a ratio (Glp/El) of a torsion rigidity and a flexural rigidity in a first range which is a tip side of a region where a grip is attached on a base end side, and in a second range including a region where the grip is attached on the base end side, the ratio (Glp/El) of the torsion rigidity and the flexural rigidity is a numerical value smaller than that in the first range.SELECTED DRAWING: Figure 7

Description

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

  Conventionally, shafts of golf clubs are known to be made of steel and fiber reinforced resin (hereinafter referred to as FRP). Generally, golf clubs equipped with steel shafts have the advantage of stable directionality, and golf clubs equipped with FRP shafts can be reduced in weight, improving swing speed, launch angle and flight distance. The merit of improving is obtained.

The directionality of the hit ball of 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 seems that this 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 ). It is. As shown in this graph, the bending stiffness (EI) and the torsional stiffness (GIp) decrease with the same amount of change (substantially similar) as they move from the proximal side to the distal side. As shown in FIG. 5, the ratio of the torsional rigidity and the bending rigidity (GIp / EI) is uniform over the length direction (a flat linear shape).

  On the other hand, a shaft made of FRP is formed by winding a plurality of prepreg sheets, in which a reinforcing fiber is impregnated with a synthetic resin, around a cored bar, thermosetting the cored sheet, and removing the core. In this case, for example, as disclosed in Patent Document 1, a prepreg sheet for reinforcement (reinforcing reinforced fibers in the axial length direction) is provided on a portion where the head is mounted over a certain length (about 300 mm from the tip). A prepreg sheet oriented to the front is wound. This is because the shaft is formed so that the tip side is reduced in 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, And it is for preventing the intensity | strength of the adhering area | region and its vicinity not falling.

Such an FRP shaft has an anisotropic property in which the longitudinal and lateral elastic coefficients differ depending on the direction in which the reinforcing fibers are oriented. For example, as shown in the graph of FIG. (EI) and torsional rigidity (GIp) are not changed in the same manner as in the steel shaft, and therefore the ratio of torsional rigidity to bending rigidity (GIp / EI) as shown in FIG. 2 (b). Varies over the length (not a flat straight line like the steel shaft shown in FIG. 1).
In this way, the FRP shaft has a torsional rigidity / bending rigidity ratio (GIp / EI) that fluctuates over the length direction. it is conceivable that.

JP 2012-245309 A

  At present, approximately 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 set of wood clubs with FRP shafts and iron clubs with steel shafts. In such cases, both shafts must be used during the round. Become.

As mentioned above, steel shafts have isotropic properties, so it seems that directionality is good, but when using FRP shafts, isotropic properties like steel are used. Because there is no, there will be a deviation from the sense of use of the steel shaft. Also, if the iron club is assembled with a steel shaft, replacing it with an iron club set with an FRP shaft will cause a difference in the sense of use from when using a steel shaft. End up.
Therefore, regarding the FRP shaft, it is possible to realize a good set assembly by giving the same properties as the steel shaft as much as possible.

  By the way, as shown in FIG. 1A, the steel shaft has high bending rigidity on the hand side (grip side), and similarly has high torsional rigidity. For this reason, when starting to swing the shaft (when shifting from the top position to the downswing), the golfer feels the hardness of the shaft and difficulty in twisting. Normally when swinging down from the top position, I want to swing it down while keeping the angle of the wrist and the shaft in the same state, but if the shaft is too hard, it becomes difficult to put in force, and the angle of the wrist and the shaft cannot be maintained, This results in a golf club that is difficult to control (cannot make an ideal swing). In particular, if the torsional rigidity on the hand side is high, it will be difficult to control when the shaft starts to swing, and it will be difficult to control the 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 the ball becomes difficult to catch.

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

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

  Usually, the golf club swing feeling and hitting feeling of a golf club are greatly influenced by the torsional rigidity and bending rigidity of the shaft. That is, torsional rigidity is resistance to torsion, and bending rigidity indicates the difficulty of deformation with respect to bending. Therefore, the higher the torsional rigidity, the more easily the movement of the hand is transmitted to the head (good reactivity), and the bending If the rigidity is lowered, the shaft can be hit using the deformation of the shaft itself. In this case, if the ratio of torsional rigidity and bending rigidity is uniform over the entire length (flat linear shape), an isotropic shaft is obtained, and the overall rigidity is made uniform, and Directionality is also stable. Therefore, if the ratio changes greatly depending on the position of the shaft in the axial length direction (the variation is large), a sense of incongruity is likely to occur in the swing feeling and the hit feeling, which is not preferable for stabilizing the hit ball. In particular, if there is a golf club having such a large variation in one set of golf clubs, a difference in feeling (difference in atmosphere) between the golf clubs becomes large. For example, in one round, when a golf club made of steel shaft having isotropic properties and a golf club made of FRP shaft having a large ratio are combined, the difference in feeling between the golf clubs becomes large. It may lead to a miss shot. Moreover, if the steel club iron club set is replaced with an FRP shaft iron club set, a deviation from the previous sensation 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 area on the front side (first range) where the grip is attached. Since the variation range is made as small as possible, a golf club that approaches the isotropic property of a steel shaft and does not cause a sense of incongruity with the steel shaft can be obtained (steel) A golf club capable of stabilizing the directionality of the hit ball, such as a shaft made of a shaft, is obtained. In the region where the grip is attached (second range), the ratio of torsional rigidity and bending rigidity (GIp / EI) is set to a value lower than that in the first range. In the grip area, the GIp of the grip area is set relatively low (the rigidity difference between the torsional rigidity and the bending rigidity is set high) with respect to the isotropic property in the first range. Is to make the characteristics easy to twist. This makes it easy to control without feeling the difficulty of twisting when the shaft is started to swing, and to make the timing of impact easy. In other words, in the grip area, by increasing the rigidity difference to a certain extent (lowering the torsional rigidity and increasing the rigidity difference), the hand side does not move during the downswing, resulting in a middle-to-end bending, resulting in The ball can be easily caught at the same time, and at the same time, the difficulty of twisting is not felt, so that it is easy to control. Further, since the shaft is made of FRP, it is lightweight and easy to swing.

  According to the present invention, a golf club equipped with an FRP shaft can provide a swing feeling similar to that of a steel shaft and a golf club with good operability.

(A) is a graph which shows the bending rigidity distribution of a steel shaft, (b) is a graph which shows the ratio (GIp / EI) of torsional rigidity and bending rigidity in the rigidity distribution shown in FIG. (A) is a graph which shows the bending rigidity distribution of the shaft made from a general FRP, (b) is a graph which shows the ratio (GIp / EI) of torsional rigidity and bending rigidity in the rigidity distribution shown to Fig. (A). 1 is a front view showing an example of a golf club according to the present invention. FIG. 5 is a list showing characteristics of each of the examples of the shaft made of FRP. The list figure which shows each characteristic of the comparative example 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 from FRP which concerns on one Embodiment of this invention, (a) is a graph which shows the rigidity distribution of a shaft, (b) is a torsion in the rigidity distribution shown to Fig. (A). The graph which shows the ratio (GIp / EI) of rigidity and bending rigidity. The pattern figure which shows arrangement | positioning of the prepreg sheet | seat which comprises the shaft of the golf club which concerns on this invention, and the prepreg sheet for a reinforcement, and a structural example.

  Hereinafter, embodiments of a 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 and an iron type golf club having a shaft made of FRP, and further, such a golf club is set with different counts (wood Club set, iron club set).

FIG. 3 is a view 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. A head (iron head) 5 is mounted on the distal end side of the shaft 10 and is formed on the proximal end side of the shaft 10 with rubber or the like. A grip 12 is attached.
The head 5 has a hosel 5a for inserting the shaft 10 and fixing the tip region thereof, and a plate-like face portion 5b on which a hit ball is formed, and a fitting hole between the outer surface of the shaft 10 and the hosel 5a. The fixing range with the inner surface is approximately 25 mm to 40 mm, although it depends on the type of golf club.

  The shaft 10 has a total length L that differs depending on the type of golf club (wood type, iron type) and the number (the loft angle differs for each number). As will be described later, the shaft of the present invention has a torsional rigidity / bending rigidity ratio (GIp / G) in a first range that is the front side of the region where the proximal end grip 12 is attached (the region indicated by L1). In the second range including the region L1 where the proximal end side grip 12 is mounted, the displacement width of EI) is 0.2 or less, and the ratio of torsional rigidity to bending rigidity (GIp / EI) is formed to be a numerical value lower than that in the first range.

  The second range only needs to include a region where the golfer grips at the time of hitting the ball. Specifically, when the total length of the shaft 10 is L, the second range is from the base end position to 0.4L. As long as it exists. That is, if it is from 0.4 L to the base end position, the region where the grip 12 is attached is included, and as described later, the torsional rigidity in this second range is lowered (bending rigidity and By increasing the torsional rigidity and bending rigidity ratio (GIp / EI) to a value lower than the first range, a swing feeling similar to that of a steel shaft can be obtained. A golf club with good operability can be obtained.

  As is well known, the shaft 10 is made of FRP, which is formed by winding a plurality of prepreg sheets in which a reinforcing fiber is impregnated with a synthetic resin around a cored bar, thermosetting the core sheet, and removing the core. . In this case, the tip region of the shaft 10 is reduced in diameter by a taper, a head is attached and a heavy object is added, a shock is applied when a ball is hit, etc. 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 the bending rigidity and torsional rigidity of the tip region. In addition, a straight fixing region is formed between the inner surface of the fitting hole of the hosel 5a and the outer surface of the shaft, thereby improving the fixing strength of the head. In addition, the structure of the prepreg sheet | seat wound around a metal core, the reinforcement sheet | seat, and the example of arrangement | positioning are mentioned later.

  In the present invention, the FRP shaft mounted on the head is configured to have the following characteristics. Here, before describing the configuration 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. When the golfer swings and hits the ball, the golfer grasps the bending rigidity and the torsional rigidity sensibly (shaft rigidity feeling). Can grasp).

  The higher the bending rigidity of the shaft, the more difficult it becomes to bend (so-called tension becomes stronger), so the shaft with high rigidity is suitable for golfers with high swing speed, and the shaft with low rigidity is the shaft. Since it is possible to hit the ball using the bend, the characteristic is suitable for a golfer with a slow swing speed. Such a bend can be perceived sensuously by the golfer when swinging. Further, the torsional rigidity of the shaft affects the operational feeling in the rotational direction, and the golfer can sensuously grasp the resistance and reactivity in the torsional direction at the grip portion. In other words, a shaft with high torsional rigidity can directly transmit the sense of torsion at the grip to the head, and a shaft with low torsional rigidity has a sense of torsion at the grip with a slight margin (play). It comes to be transmitted.

  The steel shaft has an isotropic property, and as shown in FIG. 1, the characteristics of the bending rigidity and the torsional rigidity are substantially the same over the entire length, and the shaft diameter is about the proximal end side. Since the golf ball is thick, the golfer can feel its hardness especially on the base end side. In this case, when the shaft is made of FRP, the bending rigidity and the torsional rigidity may be substantially matched over the entire length so long as it does not cause an uncomfortable feeling with the steel shaft. On the grip side, since the golfer directly senses and controls the hardness directly, it is preferable to configure this area so that the operability can be improved.

Specifically, in order to make a good swing, it is preferable to swing down with the wrist and shaft at the same angle when swinging down from the top position (such control is easy). When there is little play in the twisting direction (hard to twist), such control becomes difficult, and as a result, it becomes a characteristic that the timing of impact is difficult to take.
In this case, if the grip portion is easily twisted and the bending rigidity is lowered, the sense of rigidity on the hand side is lost, and the ball is difficult to catch at the time of impact. Therefore, in order to make the shaft easy to take the timing and catch the ball, the hand side (grip side) has a certain degree of play with respect to torsion (play), and can be sensed of rigidity. It is preferable. However, if the bending rigidity is too high, it becomes difficult to bend and control is difficult, so it is better not to make the bending rigidity too high.

  In other words, the grip area has high bending rigidity and suppresses torsional rigidity (suppresses the ratio of torsional rigidity to bending rigidity (GIp / EI)), making it difficult to feel the torsion when starting to swing the shaft. The shaft can be easily controlled, the impact timing 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 fiber of the prepreg sheet to be wound, and has anisotropy characteristics, and therefore, as shown in FIG. However, in the present invention, the ratio of bending stiffness to torsional stiffness (GIp / EI) is not uniform over the entire length of the shaft. However, in the present invention, the prepreg sheet is arranged in the tip region on the head side, for example. By devising the configuration of the reinforcing sheet provided, the ratio of the bending rigidity and the torsional rigidity is made uniform (the displacement width is reduced).

  For example, in the shaft made of FRP having the characteristics shown in FIG. 2A, the torsional rigidity is lowered toward the tip or the bending rigidity is directed toward the tip with respect to the reinforcing sheet wound around the tip. By raising it, it is possible to bring the ratio of bending rigidity and torsional rigidity (GIp / EI) closer to the characteristics of a steel shaft as shown in FIG. 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 fiber is inclined with respect to the axial direction of the shaft is reduced, or it is wound on the inner layer side, This can be achieved, for example, by winding a cross sheet having a small oblique angle of the reinforcing fiber. On the contrary, as a technique for increasing the bending 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 winding it on the outer layer side. .

Next, when equalizing the ratio of bending rigidity and torsional rigidity (GIp / EI) over the entire length of the shaft, what is the displacement width, the feeling is good (feeling close to a steel shaft) Whether it is obtained will be specifically described with reference to FIGS.
Here, a plurality of golf club shafts equipped with the same head are prepared, and the characteristics of the shaft according to the present invention are shown as Example A, Example I, 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 a comparative example, a comparative example, and a comparative example (see FIG. 5).

The numerical values shown in FIGS. 4 and 5 are such that the tip of the shaft is 0, the shaft positions are specified at intervals of 50 mm, the values of the bending rigidity (ΣEI) and torsional rigidity (ΣGIp) at that position are calculated, and the ratio (GIp / EI) is derived (the unit of each stiffness is Kgf · mm ² ). In each shaft, the maximum value (MAX) and the minimum value (MIN) of (GIp / EI) are shown, and the difference between them is shown (MAX−MIN). Therefore, the larger the difference, the larger the displacement width.
In the tables of FIGS. 4 and 5, the values of bending rigidity (ΣEI) and torsional rigidity (ΣGIp) and the ratio (GIp / EI) are shown up to three digits after the decimal point, with the shaft being 50 mm apart. There are examples and comparative examples in which the maximum value and the minimum value 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 the comparative example F is calculated at the position of 280 mm, the minimum value (0.539) of the ratio in the comparative example is calculated at the position of 910 mm, and the ratio value in the comparative example The maximum value (0.492) is calculated at a position of 170 mm.

In this case, bending rigidity (EI) and torsional rigidity (GIp) are derived by the following calculation method.
Regarding the bending rigidity, the Young's modulus (longitudinal elastic modulus) E can be specified by calculation from the specifications of the configuration (material) of the prepreg sheet constituting the shaft and the arrangement mode (laminated structure), and I (cross section) For the second moment)
I = π (D ₂ ⁴ −D ₁ ⁴ ) / 64 (Equation 1).
As for the torsional rigidity (GIp), the shear elastic modulus (lateral elastic modulus) G is calculated from the specifications of the configuration (material) of the prepreg sheet constituting the shaft and the arrangement mode (laminated structure), as described above. For Ip (cross-sectional torsional moment)
Ip = π (D ₂ ⁴ −D ₁ ⁴ ) / 32 (Equation 2).
In the above (Expression 1) and (Expression 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 formed 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 bending rigidity (EI) of the FRP shaft that is actually molded, the shaft is leveled and two points away from the measurement point (L / 2) are supported, and the force from above is applied 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 following formula.
The maximum load P is 20 kgf, and the distance L between supports is 200 mm.
With the above method, it is possible to obtain the EI of the center position measurement point between the two points of support, and it is possible to continuously calculate numerical values by shifting the support position.

As for the torsional rigidity (GIp) of the FRP shaft that is actually molded, the end of one side is fixed with the shaft horizontal, the position separated by Lmm from the fixed part, and the torque Tr is applied to the holding part. It can be derived by measuring the twist angle A (radian) of the shaft when given. In particular,
GIp = L × Tr / A
It is possible to derive from the following formula.
The torque Tr is 139 (kgf · mm), and the distance L between fixing and holding of the shaft is 200 mm.
With the above method, the GIp at the central position between the shaft fixing and holding can be obtained, and the numerical value can be continuously calculated by shifting the position.

  As described above, the steel shaft is isotropic, so that the ratio of GIp / EI is uniform over the entire length of the shaft, but the Poisson's ratio (ν ) Will vary slightly. Considering that iron is the main component of the shaft, since the Poisson's ratio is about 0.3, it is considered to be about 0.87 from the relationship of E = 2 (1 + ν). For this reason, an actual steel shaft is considered to fall within the range of 0.85 ± 0.1 depending on the constituent materials (in FIG. 6 below, it is 0.85).

FIG. 6 is a graph of the ratio (GIp / EI) to the longitudinal direction (horizontal axis) of each shaft shown in FIGS. 4 and 5.
In Examples A, A, U, and D, the arrangement and configuration of the prepreg to be wound (main body prepreg sheet and reinforcing prepreg sheet described later) were set so that the displacement width of the ratio was 0.2 or less. Is. The displacement width is set so that Example C is the lowest and the ratio is close to 1 (displacement is in the range of 0.8 to 1.0). It is comprised so that it may become.

  On the other hand, the comparative example F is a shaft (shaft having the characteristics shown in FIG. 2) in which the ratio displacement width is 0.368, and the comparative example key is 0.784. The displacement width of the ratio is 0.230 and is close to 0.2. As the displacement width of the ratio increases, the feeling decreases as described above, and the closer to 0, the better the feeling. Here, as a result of examination in advance as a simulation, if the displacement width of the ratio is within 0.2, it can be predicted to some degree that the feeling can be improved. A sample having a value close to 2 was prepared (0.194 in Example D, 0.2030 in Comparative Example), and actually verified.

The contents of the sensory test and the results will be described below.
In the sensory test, the seven golf clubs shown in FIGS. 4 and 5 were prepared, and 10 normal average golfers gave each golf club a test shot. In this case, each person provided 7 golf clubs at random and hit at least 10 balls to have each club evaluated relative. In the relative evaluation, a golf club evaluated as having a good feeling at the time of hitting and having good directionality is marked with a circle (you may select one or more golf clubs), and relative evaluation with a golf club evaluated as good Although it is somewhat inferior, it is better to have a △ attached to those evaluated as an acceptable range (more than one may be selected), and to improve relative to a golf club evaluated as good Those who evaluated it as good were given a cross (you could choose more than one).
The results are shown in the table below.

As can be seen from 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 were evaluated as good, or Since it is evaluated as an acceptable range, it can be evaluated that the golf club has a good feeling.

  On the other hand, many of the evaluations that it was better to improve the comparative example with a displacement width of 0.368 and the comparative example with a displacement width of 0.784 were seen. In addition, the evaluation of Example D with a displacement width of 0.194 and the Comparative Example K with a displacement width of 0.230 is somewhat different, but the evaluation of Examples A, A and C, and Comparative Example C, As a result of considering the evaluation of the key, in the present invention, it was determined that a displacement width of 0.2 is a limit value for obtaining a good feeling in practice (for example, ◯ is 2 points, Δ is 1 point, × In the present invention, the limit value of the displacement width is specified as 0.2 because the example D is 12 points and the comparative example is 10 points.

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

  In the shaft configuration described above, the present invention further reduces torsional rigidity (increases the rigidity difference from bending rigidity) within a second range including the region where the proximal end side grip 12 is attached. The ratio of torsional rigidity to bending rigidity (GIp / EI) is formed to be a numerical value lower than that in the first range so as to improve operability.

FIG. 7 is a graph showing the stiffness distribution of an FRP shaft according to an embodiment of the present invention, where (a) is a graph showing the stiffness distribution of the shaft, and (b) is a stiffness distribution shown in FIG. Is a graph showing the ratio (GIp / EI) of torsional rigidity and bending rigidity.
In the present embodiment, a golf club (shaft for FW No. 3) having a shaft length of 1081 mm is exemplified, and is in a range of approximately 800 mm to 1100 mm (second range on the grip side, 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, the shaft having such rigidity distribution characteristics has a ratio of torsional rigidity to bending rigidity (GIp / EI) within a first range that is the front side of the region where the grip is attached. ) Is less than or equal to 0.2 (within a range of approximately 0.42 to 0.62), and within the second range including the region where the grip is attached, torsional rigidity and bending rigidity The ratio (GIp / EI) is lower than that in the first range.

  In this case, the torsional rigidity / bending rigidity ratio (GIp / EI) in the second range should not be excessively large. As in the first range, the displacement width is 0. It is preferable to form it within a range of 2 (in the present embodiment, it is within a range of about 0.35 to 0.42, and is set within a range of 0.2). This is because if the displacement width exceeds 0.2 and becomes too large, it will deviate greatly from the sensation of a steel shaft. Specifically, if the bending stiffness is made too high, the cock will be easily unraveled by turning over from the top position to the downswing, and the hardness of the shaft will also be difficult, and conversely, the torsional stiffness will be made too low. This is because the balance between hardness and torsion becomes worse and it becomes difficult to control torsion. In other words, the golfer tries to adjust the bending and torsion unconsciously from the top position down to the impact, but if the bending rigidity is too high or the torsional rigidity is too low, this adjustment cannot be performed successfully. As a result, the directionality of the hit ball varies. For this reason, it is preferable to set the displacement width within the second range so as not to exceed 0.2.

Here, it is performed between the shaft made of FRP having the stiffness distribution characteristic shown in FIG. 7 and the shaft made of steel (the ratio of torsional rigidity to bending rigidity (GIp / EI) is substantially uniform over the entire length of the shaft). The sensory test and the results will be described.
Ease of hitting (operability when shifting from top position to downswing) with 10 normal average golfers who performed the test hit test in Table 1 to make a test hit with two golf rubs equipped with the above shaft And 5), the following results were obtained.

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

  As described above, since the golf club shaft is made of FRP, the weight can be reduced, so that the swing can be easily performed, and the torsional rigidity and bending on the front side (first range) of the region where the grip is attached By forming the displacement ratio of the stiffness ratio (GIp / EI) to be 0.2 or less, the shot can be stabilized and the directionality can be stabilized by approaching an honest feeling like a steel shaft. It becomes like this. For this reason, a wood type golf club equipped with such a shaft is set, and even if this is 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. Or even if it switches from the iron club set equipped with the steel shaft to the iron club set equipped with such a shaft made of FRP, it can be used without a sense of incongruity.

  Furthermore, in the region where the grip is attached (second range), the torsional rigidity is lowered and the ratio of the torsional rigidity to the bending rigidity (GIp / EI) is kept low, so that the operability is good and easy to hit. 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 a prepreg sheet and a reinforcing prepreg sheet that form a shaft capable of obtaining a rigidity distribution as shown in FIG.

  The shaft of the present embodiment sequentially winds a main body prepreg sheet (hereinafter referred to as a main body sheet) around a cored bar 20 having a reduced diameter on the front end side, and a reinforcing prepreg sheet on the front end side. A reinforcing prepreg sheet (hereinafter referred to as “reinforcing sheet”) is wound over the end region, heated and fired in this state, and then decentered and surface-treated. In this case, the 1114 mm portion of the cored bar 20 constitutes the entire length of the shaft.

  A plurality of the main body sheets are wound to form the entire length of the shaft (form a main body layer). The main body sheet 31 which is the innermost layer is formed by aligning reinforcing fibers in the axial length direction, and 1 on the front end side. .1 ply, it is cut so that 1.1 ply is wound on the base end side. The main body sheet 32 wound on the main body sheet 31 includes a 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 in the −45 ° direction with respect to the axial length direction. And a second oblique sheet oriented in the direction of 3.0, and is cut so that 3.0 ply is wound on the front end side and 1.5 ply is wound on the base end side.

  The main body sheet 33 wound on the main body sheet 32 is cut so that reinforcing fibers are aligned in the axial direction and wound at 1.00 ply at the distal end side and 1.00 ply at the proximal end side. Has been. Further, a reinforcing sheet 41 in which reinforcing fibers are aligned in the axial length direction is wound on the main body sheet 33 from the position of 364 mm from the rear end to the base end position. The reinforcing sheet 41 is cut so that 1.00 ply is wound at a position 364 mm from the rear end and 60 mm behind, and 1.00 ply is wound on the base end side.

  The main body sheets 35 and 36 wound on the reinforcing sheet 41 are arranged so that the reinforcing fibers are aligned in the axial direction, and are wound so that 1.00 ply is wound on the distal end side and 1.00 ply is wound on the proximal end side, respectively. Has been.

The main body sheets 33, 34 and 35 in which the reinforcing fibers are aligned in the axial length direction among the plurality of main body sheets wound as described above contribute to the improvement of the bending rigidity, and the main body has the reinforcing fibers oriented in the cross direction. The sheet 32 contributes to improvement of torsional rigidity. In this case, the most effective contribution to the improvement in torsional rigidity is that the reinforcing fibers are oriented at ± 45 °, but the angle is not limited. Moreover, the main body sheet | seat 31 which aligned the reinforcement fiber in the circumferential direction contributes to the improvement of crushing strength.
As described above, in this embodiment, on the grip side, the torsional rigidity is lowered, and the difference between the torsional rigidity and the bending rigidity is increased. Therefore, the main body sheet 32 in which the reinforcing fibers are oriented in the cross direction is wound on the inner layer side. And rotating the reinforcing sheet 41 for adjustment from the intermediate region to the proximal region so as to realize such a configuration. I have to.

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

  The first reinforcing sheet 42 is cut so as to be 3.28 ply at the distal end position and 0 ply at the proximal end position (position of 201 mm from the distal end). The second reinforcing sheet 43 includes a sheet cut to have a fiber angle of + 45 °, 3 plies at the distal end position, and 0 ply at the proximal end position (position of 201 mm from the distal end), and −45 °. It is configured by bonding sheets cut to the same dimensions at the fiber angle. By winding such a reinforcing sheet, the bending rigidity and torsional rigidity on the front side of the shaft can be substantially matched, and the ratio of bending rigidity to torsional rigidity (GIp / EI) is 0.2 or less. Can be easily set. Further, in this way, the first reinforcing sheet 42 and the second reinforcing sheet 43 are wound so that the end portions on the grip side coincide with each other. The torsional rigidity ratio (GIp / EI) is not displaced greatly.

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

  As mentioned above, although embodiment of this invention was described, this invention is not limited to above-described embodiment, It can change variously. The present invention is formed so that the displacement width of the ratio of torsional rigidity and bending rigidity (GIp / EI) in the first range of the shaft is 0.2 or less, and in the second range, the ratio is As long as it is formed so as to be lower than the range of 1, the structure of the main body sheet and the reinforcing sheet constituting the shaft can be appropriately modified as long as such a condition is satisfied. The above-described arrangement example of each sheet and the number of plies and the length of each sheet are merely examples. For example, in the pattern diagram shown in FIG. 8, another main body sheet may be wound. Then, a prepreg sheet for adjustment may be wound.

  Further, the numerical value of the ratio of the torsional rigidity and the bending rigidity (GIp / EI) can be appropriately changed. In the graph shown in FIG. 4, the torsional rigidity / bending rigidity ratio (GIp / EI) in the first range is in the range of 0.42 to 0.62, but in the present invention, for example, it is larger than 1.0. You may comprise so that a displacement width may be 0.2 or less (for example, the range of 1.1-1.3 etc.) by a value.

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

Claims (5)

In the golf club with a fiber reinforced resin shaft attached to the head,
The shaft has a torsional rigidity-bending rigidity ratio (GIp / EI) displacement width of 0.2 or less within a first range that is the front side of the region where the proximal grip is attached, and In the second range that includes the region where the grip on the proximal end side is attached, the ratio of torsional rigidity and bending rigidity (GIp / EI) is formed to be a lower numerical value than in the first range. A golf club characterized by being made.   2. The golf club according to claim 1, wherein a displacement width of a ratio of torsional rigidity to bending rigidity (GIp / EI) within the second range of the shaft is 0.2 or less.   3. The golf club according to claim 1, wherein when the total length of the shaft is L, the second range exists from a base end position to 0.4 L. 4. The shaft has a reinforcing prepreg sheet wound around the tip side where the head is mounted,
4. The reinforcing prepreg sheet 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 crossed and oriented. The golf club according to any one of the above.   A golf club set comprising a plurality of golf clubs, wherein the shaft of each golf club comprises the shaft according to any one of claims 1 to 4.