Golf club head and its manufacturing method

The present invention relates to a golf club head composed of a metal member and a fiber reinforced plastic (FRP) member, and a method for manufacturing the golf club head.

When a golf club hits a golf ball, the golf ball is required to fly well and to have high directional stability. Therefore, a golf club head having a low center of gravity, light weight, and high strength is required, and in recent years, golf club heads formed by combining a metal member and an FRP member have been proposed (for example, Patent Documents 1 to 3). reference). Further, as a design, a golf club head having a small step on the surface (particularly the upper surface) and having a high design is required. Several methods can be considered to reduce the level difference on the surface of the golf club head. For example, as shown in FIG. 5, a face plate 71 having a face 71a and a flange 71c formed extending from the edge of the face 71a to the opposite side of the striking surface 71b, and a metal sole plate 72. The FRP crown 73 and sole 74 and the FRP joint 75 spanning from the flange 71c to the crown 73 or sole 74, and the end face of the flange 71c of the face plate 71 and the crown 73 or sole 74. It is conceivable that the end faces are butted against each other and come into contact with each other. In this case, the joint body 75 comes into contact with the flange 71c via the adhesive 76. In this way, when the end face of the flange 71c and the end face of the crown 73 or the sole 74 are in contact with each other, the outer surface of the flange 71c and the outer surface of the crown 73 or the sole 74 can be made flush with each other. The level difference can be reduced and the design is high.<patcit num="1"><text>Japanese Patent No. 2773009</text></patcit><patcit num="2"><text>JP-A-59-90578</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2002-336389</text></patcit>

<p> However, in the above-mentioned golf club head, the flange of the face plate pushes against the crown or the sole due to the impact force at the time of hitting, so that the vicinity of the flange on the crown or the sole is deformed, and as a result, the crown or the sole is cracked or peeled off. I sometimes cut it. Further, the surface of the golf club head may be painted, and in that case, the paint on the surface may be peeled off at the time of hitting. For this reason, conventionally, it has not been possible to obtain a golf club head in which the end face of the flange and the end face of the crown or sole are abutted and in contact with each other. Therefore, a golf club head having few steps on the surface and a high design quality could not be obtained. The present invention has been made in view of the above circumstances, and even when the flange of the face plate and the crown are abutted at their respective end faces, the deformation of the vicinity of the contact portion between the flange of the face plate and the crown at the time of impact is deformed. It is an object of the present invention to provide a golf club head which is prevented, has few steps on the surface, and has a high design, and a method for manufacturing the golf club head.</p>

<p> The golf club head of the present invention is a head composed of a metal face plate having a flange formed extending from the face and the edge of the face to the opposite side of the striking surface, and a crown and sole made of fiber reinforced plastic. It is a golf club head that has a body, the end face of the flange of the face plate and at least a part of the end face of the head body are in contact, and a joint made of fiber reinforced resin is laid from the flange to the head body and integrated. The head body is characterized in that the magnitude of the rigidity at the contact portion with the flange is in the range of 0.1 to 5 times the magnitude of the rigidity at the flange. In the golf club head of the present invention, it is preferable that a reinforcing body made of a fiber reinforced resin is provided at a contact portion of the head body with a flange. Further, in the golf club head of the present invention, it is preferable that the thickness of the portion of the joint in contact with the head body becomes thinner as the distance from the face increases. Further, the golf club head of the present invention preferably has a metal sole plate. The method for manufacturing a golf club head of the present invention includes a preform forming step of preforming a prepreg into the shape of a head body to form a preform, and the preform and the face and the opposite side of the striking surface from the edge of the face. A joint in which a metal face plate having a flange formed extending to the surface of the preform is brought into contact with the end face of the preform and the end face of the flange of the face plate, and a joining prepreg is bridged from the flange to the preform. It is a manufacturing method of a golf club head having a process and an internal pressure forming process in which these are arranged in a molding die and internally pressure formed. Before the internal pressure forming process, a reinforcing prepreg is attached to a contact portion with a flange in the preform. The feature is that it is attached.</p>

<p> In the present invention, even when the flange of the face plate and the crown are abutted at their respective end faces, it is possible to prevent the crown from cracking, peeling, or cutting at the time of impact, and when the surface is painted, it can be prevented. , The peeling of the paint on the surface can be prevented. Therefore, the end face of the flange and the end face of the crown or the sole can be brought into contact with each other, and as a result, the level difference on the surface can be reduced and the design can be improved.</p>

An embodiment of the golf club head of the present invention and a method for manufacturing the golf club head will be described. FIG. 1 shows a cross-sectional view of a golf club head of the present embodiment. The golf club head 1 includes a face plate 10 including a face 11 and a flange 13 formed extending from the edge of the face 11 to the opposite side of the striking surface 12, a metal sole plate 20, and fiber reinforced. It has a head body 2 composed of a resin crown 30 and a sole 40.

In the golf club head 1, the end face of the flange 13 of the face plate 10 and the end faces of the crown 30 and the sole 40 are in contact with each other in an abutting state. Further, the joint 50 is bridged from the flange 13 to the crown 30 and the sole 40 to be integrated. Here, the joint body 50 is in contact with the flange 13 via the film-like adhesives 55a and 55b, and is in contact with the crown 30 or the sole 40 via the reinforcing bodies 31 and 41. Further, in the head body 2, the contact portions of the crown 30 and the sole 40 with the flange 13 have reinforcing bodies 31, 41 made of fiber reinforced resin, and the contact portions with the flange 13 of the crown 30 and the sole 40 are provided. The magnitude of the rigidity of the portion is within the range of 0.1 to 5 times the magnitude of the rigidity of the flange 13. Here, the contact portion with the flange in the crown and the sole (head body) is a portion within 20 mm from the end face in contact with the flange. Further, the sole 40 and the sole plate 20 are joined via a film-like adhesive 55c.

In the golf club head 1, the face plate 10 and the sole plate 20 are manufactured by casting, forging, or cutting metal, and examples thereof include titanium alloys, aluminum high-strength alloys, and stainless steel. , Titanium alloy is preferable in terms of balance between strength and specific gravity. Further, the face plate 10 and the sole plate 20 may be made of the same material or different materials. In particular, since the center of gravity of the golf club head can be easily lowered, the sole plate 20 is more than the face plate 10. It is preferable to use one having a large specific gravity. For example, the sole plate 20 is made of stainless steel, and the face plate 10 is made of titanium. Further, in the face plate 10 and the sole plate 20, since the adhesive strength is high, the surface to be joined to the crown 30 or the sole 40 is roughened in advance by blasting or the like, and the surface roughness Ra becomes 1 μm to 20 μm. It is preferable that For the same reason, it is preferable that the surface to be joined to the crown 30 or the sole 40 is degreased with methyl ethyl ketone, acetone or the like.

The flange 13 of the face plate 10 is a joint portion between the crown 30 and the sole 40, and if the length thereof is long, the joint strength between the flange 13 and the crown 30 and the sole 40 can be increased, but the length of the flange 13 is long. If so, the golf club head 1 becomes heavy. From these points, the preferable length of the flange 13 is 10 mm to 15 mm.

The sole plate 20 is formed with a hole 21 for inserting a pressure bag used in the manufacture of the golf club head 1. The hole 21 is preferably a screw hole (this screw hole is sometimes called a Prader hole). If the hole 21 is a screw hole, it is easy to screw the screw after pulling out the pressure bag from the screw hole to close the hole. If a screw having a large specific gravity such as a tungsten alloy is used as the screw screwed into the screw hole, the center of gravity of the golf club head becomes lower.

The crown 30 and the sole 40 are formed by laminating and integrating a plurality of layers of fiber reinforced plastic. The layers of the fiber reinforced plastics are laminated so that the directions of the reinforcing fibers are oriented in one direction and the orientation directions are orthogonal to each other. Specifically, a layer in which the reinforcing fibers are oriented in the direction orthogonal to the striking surface 12 and a layer in which the reinforcing fibers are oriented in the direction parallel to the striking surface 12 are laminated. Examples of the matrix resin contained in the fiber-reinforced resin forming the crown 30 and the sole 40 include an epoxy resin, a vinyl ester resin, an unsaturated polyester resin, a polyimide resin, a maleimide resin, and a phenol resin. Examples of the reinforcing fiber include carbon fiber, glass fiber, aramid fiber, boron fiber, silicon carbide fiber, high-strength polyethylene, PBO fiber, stainless steel fiber and the like. Among these reinforcing fibers, carbon fiber is preferable from the viewpoint of strength.

The reinforcing bodies 31 and 41 are made of the same type of fiber reinforced resin as the crown 30 and the sole 40, and are layers in which the reinforcing fibers are oriented in the direction orthogonal to the striking surface 12. The rigidity of the crown 30 and the sole 40 can be increased by orienting the reinforcing fibers in the reinforcing bodies 31 and 41 in the direction orthogonal to the striking surface 12.

The joint body 50 is made of a fiber reinforced plastic of the same type as the crown 30 and the sole 40, and is a layer in which the reinforcing fibers are oriented in the direction orthogonal to the striking surface 12, and the thickness of the portion in contact with the crown 30 or the sole 40 is increased. It becomes thinner as it is separated from the face 11. In order to change the thickness in this way, the number of layers of the fiber reinforced resin may be changed. If the flange 13 and the reinforcing bodies 31, 41 are joined by the joint body 50, these can be surely joined and the durability at the time of impact can be further improved. Since the face plate 10 and the crown 30 or the sole 40 can be firmly integrated with the joint body 50, it is preferable that the flange 13 and the crown 30 or the sole 40 are joined to each other with a length of 10 mm or more.

The film-like adhesives 55a, 55b and 55c are adhesives having a uniform thickness. When such an adhesive is used , spots are unlikely to occur, so that stable adhesive strength can be obtained. Here, examples of the resin constituting the film-shaped adhesives 55a, 55b, 55c include epoxy resin, polyester resin, acrylic resin, and the like, and epoxy resin is preferable in terms of adhesive strength. It is more preferable that the epoxy resin composition contains an elastomer component in addition to the epoxy resin component and the curing agent component. Examples of the elastomer component include Carboxy-Terminated Butadiene Acrylonitrile Copolymer (CTBN). Further, when the film-shaped adhesives 55a, 55b, 55c contain a base material made of a non-woven fabric or a woven fabric, the handleability and adhesive retention of the film-shaped adhesives 55a, 55b, 55c are improved. Further, when stress is applied to the adhesive layer after curing, even if minute cracks are generated, the growth of the cracks can be suppressed, so that the breaking strength of the adhesive layer can be improved. Examples of the materials for the non-woven fabric and the woven fabric used in the film-like adhesives 55a, 55b, 55c include, but are not limited to, polyester fiber, nylon fiber, aramid fiber, acrylic fiber, and glass fiber.

The flange 13 and the crown 30 and the sole 40, and the sole plate 20 and the sole 40 may be joined with a liquid adhesive, but in a three-dimensional shape such as the golf club head 1, the liquid adhesive has a uniform thickness. Great care should be taken when applying in width. Since the coating unevenness and the thickness unevenness of the adhesive cause a decrease in the adhesive strength, it is difficult to obtain a golf club head having stable strength.

Next, the method for manufacturing the golf club head 1 described above will be described. First, by casting, forging or cutting, a metal face plate and a sole plate having a face and a flange are separately obtained. Further, in the preform forming step, the prepreg is preformed into the shape of the sole to prepare the first preform, and the prepreg is preformed into the shape of the crown to prepare the second preform. At the time of producing the first preform, an opening is formed so as not to block the screw hole formed in the sole plate. Here, the preliminary shaping is to stack a plurality of prepregs and integrate them by the adhesive force to shape them into a rough shape close to the final crown or sole.

In the production of the preform, it is preferable to form a cut in the prepreg in advance before the preliminary shaping. If a cut is made in the prepreg in advance, when the laminated prepreg is preformed, the ends of the cut are bonded to each other, so that a curved sole or crown shape can be easily formed.

Next, in the joining step, as shown in FIG. 2, the bottom surface of the first preform 61 and the upper surface of the sole plate 20 are joined via the film-like adhesive 55c, and then in the first preform 61. A reinforcing prepreg 62a is attached to the contact portion with the flange so that the reinforcing fibers are oriented in one direction orthogonal to the striking surface 12. At the same time, a film-like adhesive 55a is attached to the lower inner surface of the flange 13, and the bonding prepreg 63a is provided on the film-like adhesive 55a so that the reinforcing fibers are oriented in one direction perpendicular to the striking surface 12. Paste a part. When the thickness of the joining prepreg 63a is changed, it is preferable that the thickest portion is on the face 11 side. Then, while bringing the end face of the first preform 61 into contact with the lower end face of the flange 13 of the face plate 10, the joining prepreg 63a is attached to the reinforcing prepreg 62a attached to the first preform 61, and the flange is attached. The joining prepreg is hung from 13 to the first preform 61. At this time, it is preferable that the bonding prepreg 63a is attached to each of the film-like adhesive 55a and the reinforcing prepreg 62a with a length of 10 mm or more. Further, it is preferable that the thickest portion is located on the striking surface 12 side. Next, as shown in FIG. 3, the pressure bag 70 is inserted through the hole 21 of the sole plate 20. Examples of the material of the pressure bag 70 include silicone rubber, nylon, and polyester.

Also, the prepregs are laminated to obtain a second preform preformed in the shape of the crown of the golf club head. Next, the reinforcing prepreg 62b is attached to the contact portion of the second preform 64 with the flange so that the reinforcing fibers are oriented in one direction orthogonal to the striking surface 12. At the same time, a film-like adhesive 55b is attached to the upper inner surface of the flange 13, and the bonding prepreg 63b is formed on the film-like adhesive 55b so that the reinforcing fibers are oriented in one direction perpendicular to the striking surface 12. Paste a part. Then, while bringing the end face of the second preform 64 into contact with the upper end face of the flange 13 of the face plate 10, the joining prepreg 63b is attached to the reinforcing prepreg 62b attached to the second preform 64, and the flange is attached. Bridge the joining prepreg from 13 to the second preform 64. At this time, it is preferable that the bonding prepreg 63b is attached to each of the film-like adhesive 55b and the reinforcing prepreg 62b with a length of 10 mm or more. Further, it is preferable that the thickest portion is located on the striking surface 12 side. In this way, the molded product precursor 3 is obtained.

Next, in the internal pressure molding step, the molded product precursor 3 is internally pressure molded. Specifically, as shown in FIG. 4, the molded product precursor 3 is placed in the mold 71 composed of the upper mold 71a and the lower mold 71b, the mold is closed, and then air is placed in the pressure bag 70. To inflate the pressurizing bag 70. Then, while pressing the first preform 61 and the second preform 64 against the mold 71 by the inflated pressure bag 70, the mold 71 is heated to a temperature corresponding to the curing temperature of the matrix resin, and each pump is heated. The reform matrix resin is thermoset and molded. By this molding, the first preform 61 becomes the sole, the second preform 64 becomes the crown, the reinforcing prepreg 62a becomes the sole reinforcement, the reinforcing prepreg 62b becomes the crown reinforcement, and so on. The joining prepreg 63a is the joint between the sole and the face plate, and the joining prepreg 63b is the joint between the crown and the face plate.

Next, the mold is opened, the obtained molded product is taken out, and the pressure bag is pulled out from the hole. Finally, an alloy screw is screwed into the hole of the sole plate to close the screw hole to obtain a golf club head. Here, the screw screwed into the screw hole of the sole plate is preferably one having a large specific gravity because the golf club head can have a lower center of gravity, and examples thereof include those made of copper alloy and tungsten alloy.

In the embodiment described above, the reinforcing body is provided at the contact portion of the crown and the sole with the flange, and the rigidity of the contact portion of the crown and the sole with the flange is high. As a result, the magnitude of the rigidity of the contact portion of the crown and the sole with the flange is within the range of 0.1 to 5 times the magnitude of the rigidity of the flange. Therefore, since the magnitude of the rigidity of the contact portion of the crown and the sole with the flange is substantially the same as the magnitude of the rigidity of the flange, deformation at the time of impact can be suppressed and damage to the crown can be prevented. Further, when the surface of the golf club head is painted, it is possible to prevent the paint from peeling off at the time of hitting. As described above, in the golf club head of the present embodiment, even when the end surface of the flange of the metal member and the end surface of the crown are abutted against each other, deformation at the time of impact is suppressed, so that the outer surface of the flange and the outer surface of the crown can be separated from each other. Can be on the same side. Therefore, this golf club head has few steps and has a high design. Further, since the thickness of the portion of the joint body in contact with the crown or sole becomes thinner as the distance from the face increases, the flange and the crown or sole can be joined while increasing the durability of the joint body at the time of impact. In addition, there is little waste and the golf club head can be made lighter.

The "magnitude of rigidity" in the present invention is a value obtained by the following formula. Rigidity (N m) = Young's modulus of material (N / m)²) × (Plate thickness (m))³ For example, Young's modulus 1.1 × 10¹¹N / m²1.5mm thick (= 1.5 × 10) using the titanium alloy of^-3When the flange of m) is formed on the face plate, the rigidity of this flange is 3.7 × 10.²It becomes N m. An anisotropic material having a Young's modulus different depending on the orientation direction of the fibers at the time of measurement, such as a fiber reinforced resin, may be used for the golf club head. Therefore, in the present invention, "the magnitude of the rigidity of the contact portion with the flange" is such that when the golf club head is used, a load is applied to the fiber reinforced resin in the direction along a straight line parallel to the longitudinal direction of the flange end face. The Young's modulus when measured is used as the magnitude of the rigidity. Further, the magnitude of rigidity in the case of a laminated body composed of a plurality of layers can be obtained as the sum of the magnitudes of rigidity of each layer. For example, as described above, in the case of a contact portion composed of a crown and a joint, the sum of the magnitude of the rigidity of the crown and the magnitude of the rigidity of the joint is the magnitude of the rigidity of the contact portion.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the crown and the sole are provided with a reinforcing body only at the contact portion with the flange to increase the rigidity, but may be provided at a portion other than the contact portion, specifically. , The reinforcement may be provided over the entire crown or sole. Further, the thickness of the portion of the joint in contact with the crown or sole became thinner as the distance from the face increased, but the joint may have the same thickness. Further, in the joint, the reinforcing fibers are oriented in the direction orthogonal to the striking surface, but may be oriented in another direction or in two directions. However, from the viewpoint of increasing the rigidity, it is preferable that the reinforcing fibers are oriented in one direction orthogonal to the striking surface. Further, a decorative layer may be provided on the surface of the golf club head (excluding the striking surface). If a decorative layer is provided, the design of the golf club head is further improved. As the decorative layer, it is preferable to use a layer made of a woven fabric made of reinforcing fibers from the viewpoint of improving the design and the strength of the golf club head.

Further, in the above-described embodiment, the fiber reinforced resin portion is divided into two parts, a crown and a sole, but it may be divided into three or more parts. An example of dividing the preform into three or more is to divide the head body into three parts: sole, crown, and side.

First, by casting, a titanium alloy (Young's modulus: 1.1 x 10) having a face (thickness 2.8 mm) and a flange (thickness 1.5 mm).¹¹N / m²) And a stainless steel sole plate were manufactured separately, and the surface to be joined to the sole plate and the preform of the face plate was roughened by blasting and degreased with acetone. Next, in the preform forming step, a prepreg (Pyrofil (registered trademark) TR350 manufactured by Mitsubishi Rayon Co., Ltd.) impregnated with an epoxy resin was applied to the carbon fibers aligned in one direction, and the orientation direction of the carbon fibers in each layer was 0 °. Four layers were laminated so as to be / 90 ° / 0 ° / 90 ° and preformed into the shape of the sole of the golf club head to obtain the first preform (thickness 1.0 mm). In the first preform, an opening was formed so as not to block the screw hole of the sole plate. Next, in the joining step, as shown in FIG. 2, the bottom surface of the first preform 61 and the top surface of the sole plate 20 were joined via a film-like adhesive 55c. At this time, the carbon fibers are formed in the longitudinal direction of the carbon fibers of the prepreg laminated so that the orientation direction of the carbon fibers is 0 ° in the prepreg, and then in the contact portion with the flange in the first preform 61. A reinforcing prepreg 62a (thickness 1.0 mm) was attached so as to be oriented in two directions orthogonal to the striking surface 12. At the same time, a film-like adhesive 55a is attached to the inner surface of the lower portion of the flange 13, and a 30 mm-long joint is formed on the film-like adhesive 55a so that the carbon fibers are oriented in one direction perpendicular to the striking surface 12. A part of the prepreg 63a (thickness 0.75 mm) for use was pasted. The prepreg 63a for joining has three levels of thickness, and the thickest part is on the face 11 side. Then, while bringing the end face of the first preform 61 into contact with the lower end face of the flange 13 of the face plate 10, the joining prepreg 63a is attached to the reinforcing prepreg 62a attached to the first preform 61, and the flange is attached. A joining prepreg was hung from 13 to the first preform 61. At this time, the length of the bonding prepreg 63a on the film-like adhesive 55a was set to 10 mm, and the length of the reinforcing prepreg 62a on the reinforcing prepreg 62a was set to 20 mm.

In addition, a second preform obtained by preforming the above prepreg into the shape of the crown of a golf club head (thickness 0.7 mm) was obtained. Next, a reinforcing prepreg 62b (thickness 1.0 mm) was attached to the contact portion of the second preform 64 with the flange so that the carbon fibers were oriented in two directions orthogonal to each other with respect to the striking surface 12. At the same time, a film-like adhesive 55b is attached to the inner surface of the upper part of the flange 13, and a 30 mm long joint is formed on the film-like adhesive 55b so that the carbon fibers are oriented in one direction perpendicular to the striking surface 12. A part of the prepreg 63b (thickness 0.75 mm) for use was pasted. The prepreg 63b for joining has three levels of thickness, and the thickest part is on the face 11 side. Then, while bringing the end face of the second preform 64 into contact with the upper end face of the flange 13 of the face plate 10, the joining prepreg 63b is attached to the reinforcing prepreg 62b attached to the second preform 64, and the flange is attached. A joining prepreg was laid from 13 to the second preform 64. At this time, the length of the bonding prepreg 63b on the film-like adhesive 55b was set to 10 mm, and the length of the reinforcing prepreg 62b on the reinforcing prepreg 62b was set to 20 mm. In this way, the molded product precursor 3 was obtained.

Next, in the internal pressure molding step, the molded product precursor 3 was internally pressure molded. Specifically, as shown in FIG. 4, the molded product precursor 3 is placed in the mold 71 composed of the upper mold 71a and the lower mold 71b, the mold is closed by a hydraulic press, and then the pressure bag is used. Air was sent to 70 to inflate the pressurizing bag 70. Then, the first preform 61 and the second preform 64 are pressed against the mold 71 with a pressure of 2 atm by the inflated pressure bag 70, and the mold 71 is brought to a temperature corresponding to the curing temperature of the matrix resin. The matrix resin of each preform was heat-cured by heating and molded. By this molding, the first preform 61 becomes the sole, the second preform 64 becomes the crown, the reinforcing prepreg 62a becomes the sole reinforcing body, and the reinforcing prepreg 62b becomes the crown reinforcing body. The joining prepreg 63a became the joint between the sole and the face plate, and the joining prepreg 63b became the joint between the crown and the face plate.

Next, the mold is opened, the obtained molded product is taken out, and the pressure bag is pulled out from the hole. Finally, a tungsten alloy screw was screwed into the hole of the sole plate, and the screw hole was closed to obtain a golf club head. The rigidity of the flange of the obtained golf club head is 3.7 × 10.²It was Nm. On the other hand, when the magnitude of the rigidity of the contact part with the flange was measured, the contact part with the flange of the face plate of the crown was 3.4 × 10.²N m, the contact part with the flange of the face plate of the sole is 5.6 × 10²It was Nm, which was 0.91 times and 1.5 times the rigidity of the flange, respectively.

In this golf club head, the flange of the face plate and the crown are butted at their respective end faces, but a reinforcing body is provided at the contact portion between the flange and the sole of the crown and the sole, and the crown cracks or peels off when hit. It was possible to prevent it from being cut or cut. Specifically, even if a striking test of 3000 shots was performed at a head speed of 50 m / sec, it had durability to withstand the striking test.

<figref num="1">It is sectional drawing which shows one Embodiment of the golf club head of this invention.</figref><figref num="2">It is sectional drawing which shows one process of the manufacturing method of the golf club head shown in FIG.</figref><figref num="3">It is sectional drawing which shows one process of the manufacturing method of the golf club head shown in FIG.</figref><figref num="4">It is sectional drawing which shows one process of the manufacturing method of the golf club head shown in FIG.</figref><figref num="5">It is sectional drawing which shows the golf club head of the conventional example.</figref>

Code description

1 Golf club head 2 Head body 10 Face plate 11 Face 12 Strike surface 13 Flange 20 Sole plate 30 Crown 40 Sole 31,41 Reinforcement body 50 Joint body 61 First preform (preform) 62a, 62b Reinforcement prepreg 63a, 63b Joining prepreg 64 Second preform (preform)