JP2008200116A - Shaft for iron type golf club and iron type golf club - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft for an iron type golf club which has low rigidity while being made heavy thereby enables even a golfer who has physical strength but can not fully bend the shaft for instance to increase distance, and the iron type golf club. <P>SOLUTION: The shaft for the iron type golf club is composed of a fiber reinforced resin, and has 39 inches converted shaft weight W of 55-95 g and an average flexural rigidity value EIa of ≥1.5 (kgf m<SP>2</SP>), wherein the shaft weight W and the average flexural rigidity value EIa satisfy formulation (1): EIa≤0.05W-1.25. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an iron-type golf club shaft and an iron-type golf club that are useful for increasing the flight distance of a hit ball, and more specifically, by reducing the rigidity while increasing the weight of the shaft, for example, although the arm force is sufficient, the shaft can be made sufficient. The present invention relates to a technique capable of increasing a flight distance even for a golfer who cannot be made.

  The optimum golf club shaft during the swing is to accelerate the speed of the golf club head (hereinafter referred to as “head speed”) immediately before hitting the ball and increase its dynamic loft angle to achieve the optimum hit ball. Provides a launch angle. Therefore, in order to increase the flying distance of the hit ball by accelerating the head speed, it is necessary to optimize the bending of the golf club shaft during the swing. Since the swing form and the head speed differ greatly from golfer to golfer, the weight, bending rigidity, and the like of the golf club shaft have conventionally been set in consideration of the golfer's ability and swing form.

  For example, many professional and advanced golfers tend to have sufficient swing strength and high head speed because they have a strong swinging force and a correct swing form. For this reason, it is common for iron type golf clubs intended for them to be equipped with a shaft (weight and high rigidity) having a large weight and a high bending rigidity. On the other hand, beginners and senior golfers cannot swing using the bending of the shaft sufficiently, and the head speed tends to be relatively low. For this reason, a golf club targeted at them is generally mounted with a shaft having a small weight and low bending rigidity (light weight and low rigidity). Thus, conventional shafts for iron-type golf clubs are roughly divided into the above two types of shafts.

  In recent years, adjustment of shaft weight, bending rigidity, etc. is relatively easy as compared with metal shafts, and therefore fiber reinforced resin shafts are frequently used. As a related technique, for example, the following Patent Document 1 has been proposed.

JP 2002-253714 A

  However, there are golfers who do not have a sufficient shaft at the time of swing because the swing form is not appropriate although they have arm strength. When such an iron type golf club having a large weight and high rigidity shaft mounted thereon is used, the head speed cannot be accelerated because the shaft is not sufficient. In addition, there is a problem that the face of the club head does not return during the swing, and consequently the direction of the hit ball varies and the flight distance decreases. Conversely, using an iron-type golf club equipped with a lightweight and low-rigidity shaft makes the shaft easy to bend, but the shaft is lightweight, so the timing and tempo of the swing is incorrect, and the club head when the ball is hit The orientation of the face is often not stable, and the directionality of the hit ball is likely to vary.

  The present invention has been devised in view of the above problems, and is based on the fact that the shaft weight and the average bending rigidity are limited to each other while being related to each other, for example, a beginner golfer having an arm strength, etc. In addition, an iron type golf club shaft and an iron type golf club that can transmit the power of the swing to the head to the maximum without changing the swing timing so far and can stabilize the direction of the hit ball. It is intended to provide.

The invention according to claim 1 of the present invention is a shaft for an iron type golf club made of fiber reinforced resin, the shaft weight W converted to 39 inches is 55 to 95 g, and the average bending rigidity value EIa is 1. 0.5 (kgf · m ² ) or more, and the shaft weight W and the average bending stiffness value EIa satisfy the following formula (1).
EIa ≦ 0.05W−1.25 (1)

The invention according to claim 2 is the shaft for an iron type golf club according to claim 1, wherein the following expression (2) is satisfied.
EIa ≦ 0.05W−1.75 (2)

According to a third aspect of the present invention, there is provided the iron type golf club shaft according to the first aspect of the present invention, wherein the following formula (3) is satisfied.
EIa ≧ 0.1W−6.5 (3)

  According to a fourth aspect of the present invention, there is provided an iron type golf club in which an iron type golf club head is mounted on the iron type golf club shaft according to any one of the first to third aspects.

The shaft for an iron type golf club made of the fiber reinforced resin of the present invention has a shaft weight W converted to 39 inches and is set as large as 55 to 95 g. Therefore, a golfer who has strength can swing without losing timing and tempo. On the other hand, the average bending stiffness value EIa of the shaft is set to 1.5 kgf · m ² or more, and the average bending stiffness value is set to be small according to the shaft weight. Such a shaft has a bending rigidity sufficiently smaller than the shaft weight W, so that even a golfer who has an arm strength but is not good at constraining the shaft, the shaft tends to bend during the swing, and as a result, the head Speed can be accelerated to increase the flight distance of the hit ball. Further, the directionality of the hit ball can be stabilized by appropriately returning the club head face to the addressed state.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an iron type golf club 1 (hereinafter sometimes simply referred to as “golf club”) equipped with a shaft for an iron type golf club (hereinafter also simply referred to as “shaft”) of the present embodiment. A front view is shown.

  The golf club 1 includes a shaft 2, an iron type golf club head (hereinafter simply referred to as a “head”) 3 attached to a tip 2 a side (TIP side) thereof, and a rear end 2 b of the shaft 2. And a grip 4 mounted on the side (BUTT side). The iron-type golf club may include not only the so-called 1 to 9 irons but also wedges such as a sand wedge, a pitching wedge, and an approach wedge.

The main part of the head 3 is made of a metal material such as aluminum alloy, titanium, titanium alloy or stainless steel. The head 1 may be hollow or solid. For example, the head 1 preferably has a volume of 25 to 40 cm ³ and a weight of about 220 to 300 g. Needless to say, a part of the head 3 may be made of a non-metallic material such as a fiber reinforced resin. Further, as the grip 4, various types such as a rubber grip, a resin grip, or a leather grip are used according to the custom.

  The shaft 2 is made of a fiber reinforced resin, and is formed as a pipe body having a tapered shape and a circular cross section with an outer diameter decreasing from the rear end 2b toward the tip 2a. The shaft 2 made of fiber reinforced resin is particularly preferable in that it is lighter than a steel shaft and can easily adjust the bending rigidity. The shaft 2 made of such a fiber reinforced resin is easily formed by various manufacturing methods according to a customary method such as a sheet winding manufacturing method, a filament winding manufacturing method, or an internal pressure molding method.

The reinforcing fiber used in the fiber reinforced resin is not particularly limited, and examples thereof include inorganic fibers such as carbon fiber, glass fiber, boron fiber, silicon carbide fiber or alumina fiber, organic fibers such as polyethylene or polyamide, and metal fibers. 1 type or multiple types of these can be used. In particular, reinforcing fibers having a tensile elastic modulus of 3 to 50 ton / mm ² are particularly preferable from the viewpoint of weight reduction and strength improvement of the shaft.

  Moreover, as a matrix resin used for a fiber reinforced resin, a thermosetting resin or a thermoplastic resin is mentioned. Examples of the thermosetting resin include epoxy resins, unsaturated polyester resins, phenol resins, melamine resins, urea resins, diallyl phthalate resins, polyurethane resins, polyimide resins, and silicon resins. Examples of the thermoplastic resin include polyamide resin, saturated polyester resin, polycarbonate resin, polystyrene resin, polyethylene resin, polyvinyl acetate resin, AS resin, methacrylic resin, polypropylene resin, and fluorine resin.

The shaft 2 has a shaft weight W converted to 39 inches (990.6 mm) set to 55 to 95 g. Here, the shaft weight W (g) converted to 39 inches is calculated by the following formula, where SL is the actual shaft length (inch) and Wr is the actual shaft weight (g) at that time. .
W = Wr × 39 / SL

  In the iron-type golf club 1, the shaft length is changed according to, for example, the loft angle or other specifications. For this reason, there is little technical significance which prescribes | regulates a shaft weight, without fixing the shaft length. In the present invention, in view of the average shaft length of the iron golf club being 39 inches, the weight of the shaft when converted to 39 inches instead of the actual weight of the shaft 2 is defined as the shaft weight. .

  Here, when the shaft weight W converted to 39 inches is less than 55 g, it is too light for a golfer having an arm strength, and it becomes easy to cause a sense of incongruity when addressed, and the swing is not stable and easily varies. This deteriorates the directionality of the hit ball. Further, the rigidity and strength of the shaft 2 may be insufficient. From such a viewpoint, the weight W is more preferably 60 g or more. On the other hand, when the shaft weight W exceeds 95 g, it is difficult to swing out even if there is an arm force, and the swing speed may be reduced and the flight distance may be reduced. From such a viewpoint, the shaft weight is more preferably 80 g or less.

  Further, the actual shaft weight Wr when the shaft 2 is used as the golf club 1 is preferably 40 g or more, more preferably 45 g or more, still more preferably 50 g or more, for the same reason as described above. The upper limit is preferably 105 g or less, more preferably 100 g or less, and still more preferably 95 g or less.

  Also, the actual shaft length SL is not particularly limited, but if it is too small, it will not be possible to sufficiently improve the head speed by taking advantage of the shaft length. May decrease. From such a viewpoint, the actual shaft length SL is preferably 500 mm or more, more preferably 525 mm or more, further preferably 550 mm or more, and the upper limit is preferably 1100 mm or less, more preferably 1075 mm or less. More preferably, it is 1050 mm or less.

Further, the shaft 2 of the present invention has an average bending rigidity value EIa of 1.5 kgf · m ² or more. Here, as shown in FIG. 2, the average bending stiffness value EIa was measured from the position 2 mm from the tip 2a of the shaft 2 to the measurement start point and from there to the rear end at 100 mm intervals in the axial direction. The average value of the bending rigidity values EI of the shaft 2 is used.

Each bending stiffness value EI of the shaft 2 is measured by bending the shaft 2 by three-point bending using a universal material testing machine. Specifically, first, the shaft 2 is supported by the jigs J1 and J2 whose distance between the fulcrums is set to 200 mm so that the axis center line CL is horizontal. At this time, the intermediate point of the support spans of the jigs J1 and J2 is positioned so as to be the measurement position 2P. Next, the indenter P is lowered to the measurement position 2P from above. At this time, the descending speed of the indenter P is set to 5 mm / min. When the applied load reaches 20 kgf, the descending of the indenter P is stopped, and the deflection amount of the shaft 2 at the pressing position 2P at this time is measured. Then, the bending rigidity value EI at the measurement position 2P is obtained from the following equation.
Flexural rigidity value EI = (Load load × Distance between fulcrums ³ ) / (48 × Deflection)
Note that the curvature of the tips of the jigs J1 and J2 is 12.5R, the tip of the indenter is 6.0R, the unit of distance and deflection is meter, and the unit of force is kgf. When the axial distance between the measurement position 2P and the rear end 2b of the shaft 2 is less than 130 mm, the measurement position is set as the measurement end point on the rear end 2b side of the shaft 2.

  In general, the shaft 2 is made to have different peak positions and distributions of bending rigidity, such as a point tone and a hand tone, but in order to evaluate the overall bending of the shaft 2, the bending stiffness at a specific position is determined. Instead of focusing on the value EI, the inventors have found that the average bending stiffness value EI is most optimal. In the present invention, in view of such a situation, the average bending rigidity value EIa is used as an index indicating the bending rigidity of the shaft 2.

Here, when the average bending stiffness value EIa is less than 1.5 kgf · m ² , the shaft becomes excessively large during the swing, making it difficult to swing, and the orientation of the face of the club head 3 is not stable. Directionality is likely to deteriorate. Also, you cannot hit a strong ball with impact. From such a viewpoint, the average bending rigidity value EI of the shaft 2 is preferably 1.7 kgf · m ² or more. On the other hand, if the average bending stiffness value EIa of the shaft 2 becomes large, the shaft 2 cannot be sufficiently made during the swing, and as a result, the head speed and the dynamic loft angle at the time of impact cannot be increased. As a result, the flight distance cannot be sufficiently improved.

In view of such a situation, the shaft 2 of the present invention is made so that the shaft weight W and the average bending rigidity value EIa satisfy the following formula (1).
EIa ≦ 0.05W−1.25 (1)

  FIG. 3 is a graph showing the relationship between the average bending stiffness value EIa of the shaft 2 and the shaft weight W converted to 39 inches.

  As a result of various experiments, the inventors presuppose a design philosophy that a shaft having a large shaft weight W is set to a large average bending stiffness value EI for the conventional shafts represented by black diamonds. I found out. However, as mentioned above, the swing form is not suitable, although it has arm strength, so if a golfer who cannot fully swing the shaft during the swing uses a high weight and high rigidity shaft, The shaft cannot be effectively compliant. Accordingly, it is not possible to expect an increase in the flight distance of the hit ball and an improvement in directionality.

  In the shaft 2 of the present invention, by limiting the shaft weight W converted to 39 inches to a certain range, an optimum weight that is easy to address and can take a swing timing is secured, and the upper limit of the average bending stiffness value EIa of the shaft is secured. By limiting the range to a certain range, it is possible to ensure appropriateness when swinging. Moreover, the shaft 2 of the present invention can reduce the average bending stiffness value EIa with respect to the shaft weight as compared with the conventional case by satisfying the above-described formula (1). As a result, for golfers who have the above-mentioned arm strength but are unable to improve the shaft well, it is possible to obtain the optimum result for the shaft 2 during the swing while ensuring the same swing timing as before, and thus hitting the ball. The directionality and the flight distance are greatly improved.

Further, in order to further improve the bending of the shaft 2, the shaft 2 preferably satisfies the following formula (2).
EIa ≦ 0.05W−1.75 (2)
Here, since Formula (2) further rounds down the upper limit value of the average bending stiffness value EIa of the shaft 2, it can have a smaller average bending stiffness value EIa.

The average bending stiffness value EIa of the shaft 2 may be 1.5 kgf · m ² or more, but it is particularly preferable that the lower limit value is rounded up by the following formula (3). Thereby, the average bending rigidity value EIa of the shaft 2 is set more optimally.
EIa ≧ 0.1W−6.5 (3)

  As shown in FIG. 4, the shaft 2 as described above can be manufactured using, for example, a plurality of types of prepregs S <b> 1 to S <b> 2 (referred to simply as “prepreg S” when collectively referred to). A long shaft (intermediate member) may be formed in advance, and the front end side and / or the rear end side may be cut to manufacture a shaft having a predetermined length.

  The prepreg S is a sheet-like composite material obtained by impregnating an uncured resin with reinforcing fibers f aligned in parallel. These prepregs S are wound around a mandrel (core material) (not shown) and first formed into a cylindrical laminate. Next, an expandable bladder or the like is inserted into the hollow portion of the laminate while being extracted from the mandrel from the laminate. Then, these are put into a mold and cured into a predetermined shape while applying pressure and heat, whereby the resin and the reinforcing fiber f are integrated, and the shaft 2 made of fiber-reinforced resin is formed. In FIG. 4, the upper layer is wound around the mandrel sequentially to form the inner layer side of the shaft 2.

  The prepreg S includes, for example, small piece-like tip side prepregs S1 stacked on a portion of the shaft 2 on the tip 2a side, and a full length prepreg S2 constituting the full length of the shaft.

  The tip side prepreg S1 is useful for adjusting the rigidity in the vicinity of the tip 2a of the shaft 2 and increasing the strength. For this reason, it is desirable that the front end side prepreg S1 is composed of, for example, about 1 to 20 layers. When the tip side prepreg S1 is less than one layer, the durability of the tip 2a portion of the shaft 2 may be lowered. On the other hand, when the tip side prepreg S1 exceeds 20 layers, the portion becomes thick and a step may be formed on the shaft 2. Since stress concentrates on such a level difference, it is not preferable. From the above viewpoints, the tip side prepreg S1 is preferably two or more layers, and the upper limit is preferably 19 layers or less, more preferably 18 layers or less.

  Moreover, the angle with respect to the shaft axial direction of the reinforcing fiber f of the tip side prepreg S1 can be widely adopted, for example, from 0 degree to 90 degrees. For example, when it is desired to increase the bending rigidity value EI on the distal end side of the shaft 2, the angle of the reinforcing fiber f is preferably 10 degrees or less (most preferably 0 degrees). On the other hand, when it is desired to increase the torsional rigidity of the shaft 2, the angle of the reinforcing fiber f is preferably 40 to 50 degrees (most preferably 45 degrees). The unfolded shape of the tip side prepreg S1 before molding may be either a quadrangular sheet S1a or a triangular sheet S1b. However, in order to reduce the level difference from the layer of the full length prepreg S2, the triangular shape The sheet S1b is desirable.

  The full length prepreg S2 determines the basic bending rigidity value and strength of the shaft 2. For this reason, it is desirable that the full length prepreg S2 is composed of 5 to 20 layers. If the number of layers is less than 5, the rigidity and strength of the shaft 2 may decrease. Conversely, if the number of layers exceeds 20, the productivity may deteriorate due to an increase in the number of windings and voids may be generated between the layers. is there. From such a viewpoint, the number of layers of the full length prepreg S2 is preferably 6 layers or more, more preferably 7 layers or more, and the upper limit is preferably 19 layers or less, more preferably 18 layers or less.

  In the present embodiment, the full length prepreg S2 includes the inclined layer S2a inclined at an angle of 10 to 80 degrees, more preferably 20 to 70 degrees with respect to the shaft axis direction of the reinforcing fibers f, and the shaft axis direction of the reinforcing fibers f. And a parallel layer S2b having an angle of substantially 0 degrees (parallel to the shaft axial direction).

  The inclined layer S2a mainly serves to increase the torsional rigidity of the shaft 2. Therefore, the graded layer S2a is preferably 1 layer or more, more preferably 2 layers or more, more preferably 3 layers or more, and the upper limit is preferably 12 layers or less, more preferably 11 layers or less, and further It is desirable to be composed of 10 layers or less. The inclined layer S2a particularly preferably includes at least two layers inclined in directions opposite to each other, particularly at least two layers having reinforcing fibers f inclined at ± 45 degrees with respect to the shaft axial direction.

  The parallel layer S2b mainly serves to increase the bending rigidity of the shaft 2. For this reason, the parallel layer S2b is preferably 2 layers or more, more preferably 3 layers or more, and the upper limit is preferably 10 layers or less, more preferably 9 layers or less, and even more preferably 8 layers or less. It is desirable to be done.

  Although not shown, an orthogonal layer in which the angle of the reinforcing fiber f with respect to the shaft axial direction is substantially 90 degrees (perpendicular to the shaft axial direction) may be included. Such an orthogonal layer mainly serves to increase the crushing strength (crushing strength) of the shaft 2 by intersecting with the inclined layer S2a and the parallel layer S2b. Further, when sufficient shaft strength and crushing strength are obtained in the inclined layer S2a and the parallel layer S2b, the orthogonal layer can be omitted as in this embodiment. In order to suppress an increase in the shaft weight W, it is desirable that the orthogonal layers be stopped at 4 layers or less, more preferably 3 layers or less, and even more preferably 2 layers or less.

  Similarly, although not shown, for example, a rear end prepreg disposed only on the rear end 2b side of the shaft 2 may be provided.

  In the present invention, the average bending stiffness value EIa of the shaft 2 is not particularly limited as long as it meets the above-mentioned rules, but it is desirable that the bending stiffness value EI at each measurement position has a constant value. . For example, in the case of a preferable shaft length of 500 to 1100 mm, the bending rigidity value EI is measured at 3 to 9 positions depending on the shaft length, and the number of measurement of the bending rigidity value EI per one shaft is determined. m ″ (when the shaft length is 1100 mm, m = 9). A variable that can take an integer value of 4 or more and (m−3) or less is set to “n” (when m = 9, n = 4, 5, and 6). Then, each bending stiffness value EI (x) actually measured from the shaft 2 can be expressed as follows. However, “x” is an axial distance (millimeter) from the tip 2a of the shaft 2 to the measurement position.

EI (130)
EI (230)
EI (330)
EI (n * 100 + 30)
EI {(m-2) * 100 + 30)}
EI {(m-1) * 100 + 30)}
EI (m * 100 + 30)

Then, EI (130) is a flexural rigidity of the distal end 2a of the shaft 2, EI (230) and EI (330) is preferably 0.5 kgf · m ² or more, more preferably 0.6 kgf · m ² or more Further, 0.7 kgf · m ² or more is desirable, and the upper limit is preferably 3.0 kgf · m ² or less, more preferably 2.8 kgf · m ² or less, and further preferably 2.5 kgf · m ² or less. Is desirable. When the bending stiffness values EI (130), EI (230), and EI (330) are less than 0.5 kgf · m ² , the bending on the tip 2a side of the shaft 2 at the time of hitting ball is remarkably increased and the durability is deteriorated. In addition, the orientation of the head during the swing is not stable, and the directionality of the hit ball may be deteriorated. On the contrary, when the bending rigidity values EI (130), EI (230) and EI (330) exceed 3.0 kgf · m ² , the bending on the tip 2a side of the shaft 2 becomes small, and the head speed is increased immediately before hitting the ball. In addition to the difficulty of accelerating, vibrations at the time of hitting the ball are transmitted to the player's hand, which may deteriorate the hit feeling.

Further, the bending stiffness value EI (n * 100 + 30) of the intermediate portion of the shaft 2 is preferably 0.8 kgf · m ² or more, more preferably 0.9 kgf · m ² or more, and further preferably 1.0 kgf · m. ² or more, most preferably 1.1 kgf · m ² or more is desirable, and the upper limit is preferably 6.5 kgf · m ² or less, more preferably 6.0 kgf · m ² or less, and even more preferably 5.5 kgf · m ^{2. 2} or less, most preferably 5.0 kgf · m ² or less is desirable. When the bending rigidity value EI (n * 100 + 30) of the intermediate part of the shaft 2 is less than 0.8 kgf · m ² , the deflection at the intermediate part becomes large during swinging, making it difficult to control the timing. May worsen. On the other hand, if the bending rigidity value EI (n * 100 + 30) of the intermediate part of the shaft 2 exceeds 6.5 kgf · m ² , the deflection of the shaft 2 becomes small, and there is a possibility that the head speed cannot be sufficiently improved. In addition, there is a possibility that the player's force cannot be effectively transmitted to the club head.

  In particular, the bending rigidity value EI (n * 100 + 30) of the intermediate portion is larger than EI (130), EI (230) and EI (330) which are bending rigidity values on the tip 2a side of the shaft 2. Desirably, more preferably, it gradually increases toward the rear end 2b of the shaft 2.

Furthermore, EI {(m−2) * 100 + 30}}, EI {(m−1) * 100 + 30}} and EI (m * 100 + 30) which are bending rigidity values on the rear end 2b side of the shaft Is preferably 1.5 to 8.5 kgf · m ² . If these bending stiffness values are less than 1.5 kgf · m ² , the deflection at the time of swing becomes large and the timing becomes difficult to take, and the swing rhythm may be deteriorated. On the other hand, when these bending stiffness values exceed 8.5 kgf · m ² , it is difficult to feel the bending of the shaft 2 during a swing, which may make it difficult to swing.

It is particularly preferable that the bending rigidity value EI on the rear end 2b side of the shaft 2 is desirable such that the bending rigidity value EI increases toward the rear end 2b, that is, the following expression. This increases the bending on the head 3 side and helps to further accelerate the head speed.
EI {(m-2) * 100 + 30)} <EI {(m-1) * 100 + 30)} <EI (m * 100 + 30)
In particular, EI {(m-2) * 100 + 30)} is 1.5 to 7.0 kgf · m ² , and EI {(m-1) * 100 + 30)} is 1.8 to 8.0 kgf · m ² . m ² and EI (m * 100 + 30) are preferably 2.0 to 8.5 kgf · m ² .

  Although the embodiment of the present invention has been described above, the shaft 2 of the present invention is not limited to the illustrated embodiment, and can be implemented in various forms.

  A shaft was prototyped based on the specifications in Table 1 and its performance was tested. The shaft was first set to a length of 1000 mm by forming a shaft intermediate member having a length of 1200 mm and cutting the front end side and the rear end side thereof. A basic development view of the prepreg is as shown in FIG. 5, and this figure shows a development view of the prepreg of the shaft after being cut. The average bending stiffness value EIa was adjusted by changing the number of plies (number of windings) of each prepreg and the tensile elastic modulus of the reinforcing fiber as shown in Table 1. Each prepreg was wound around a core material in order from the A layer and molded. Then, an iron type golf club head having a loft angle of 32 degrees and a soft iron made of rubber and a rubber grip were mounted on each test shaft, thereby producing an iron type golf club. The specifications of each prepreg are as follows.

8255S-12: Tensile modulus of fiber: 30 ton / mm ² (Toray Industries, Inc.)
3255G-12: Tensile modulus of fiber: 24 ton / mm ² (manufactured by Toray Industries, Inc.)
E1026A-09N: Tensile modulus of fiber: 10 ton / mm ² (Nippon Graphite Fiber Co., Ltd.)
E052AA-10N: Tensile modulus of fiber: 5 ton / mm ² (Nippon Graphite Fiber Co., Ltd.)
The test method is as follows.

<Head speed>
Ten right-handed golfers (handicap 0-20, age 20-40) hit the ball (SRI Sports' golf ball “XXIO”) 10 balls at each golf club. It was. Then, the head speed immediately before hitting was measured using a laser sensor, and an average value (10 players × 10 balls) was calculated for each club. A result is an index | exponent which makes Example 1 100, and shows that the head speed is accelerated by the bending of a shaft, so that a numerical value is large.

<Launch angle>
The angle immediately after launching the hit ball in the actual hit test was measured by a laser sensor, and the average launch angle (10 players × 10 balls) of each club was calculated. The result is an index in which Example 1 is set to 100, and the larger the numerical value, the greater the launch angle is obtained by the optimum shaft.

<Direction of hit ball>
In the actual hit test, the deviation amount with respect to the target flying ball direction was measured for 10 hit balls, and the standard deviation was evaluated. The result is an index with the standard deviation of Example 1 as 100, and the smaller the value, the better.

<Easy to swing>
Evaluation based on the following criteria was performed based on the sensuality of the ten golfers. The average score is shown.
5: Very good 4: Good 3: Normal 2: Not very good 1: Not good Table 1 shows the test results.

  As a result of the test, it was confirmed that the golf club equipped with the shaft according to the present invention had a high head speed and excellent flight distance and directionality.

1 is a front view of an iron type golf club showing an embodiment of the present invention. It is a diagram explaining the measuring method of the bending rigidity value of a shaft. It is a graph which shows the relationship between a shaft weight and a bending rigidity value. It is an expanded view of the prepreg which comprises the shaft of this embodiment. It is an expanded view of the prepreg which comprises the shaft of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Iron type golf club 2 Iron type golf club shaft 3 Iron type golf club head W Shaft weight EIa converted into 39 inches Average bending rigidity value of shaft

Claims (4)

An iron type golf club shaft made of fiber reinforced resin,
The shaft weight W converted to 39 inches is 55 to 95 g, the average bending stiffness value EIa is 1.5 (kgf · m ² ) or more, and the shaft weight W and the average bending stiffness value EIa are as follows: An iron type golf club shaft characterized by satisfying the formula (1).
EIa ≦ 0.05W−1.25 (1) The iron type golf club shaft according to claim 1, wherein the following formula (2) is satisfied.
EIa ≦ 0.05W−1.75 (2) The iron type golf club shaft according to claim 1, wherein the following formula (3) is satisfied.
EIa ≧ 0.1W−6.5 (3)   An iron-type golf club having an iron-type golf club head mounted on the iron-type golf club shaft according to any one of claims 1 to 3.

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