Golf club head

Abstract

To improve a ball initial velocity, a high initial velocity area, a launch angle, spinning, hitting touch and durability.SOLUTION: When tensile strength of a first layer 36, a second layer 38 and a third layer 40 constituting a face part 14 are S1, S2, S3, a relation is S3≥S1>S2. When the first layer 36, the second layer 38 and the third layer 40 constituting the face part 14 are deformed by striking a ball on a face surface 1402, the face part 14 is deformed within elastic deformation due to that the soft second layer 38 having the lowest tensile strength is sandwiched between the hard first layer 36 and the third layer 40 having high tensile strength, and with this, the first layer 36 is easily deformed as not a point but a spreading surface, and becomes advantageous for increasing a contact area of the face surface 1402 and the ball and securing a long contact time of the face surface 1402 and the ball.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a golf club head. [Background technology]

[0002] A golf club head has been proposed in which the face portion is constructed of a first metal plate and a second metal plate that supports the first metal plate via a plurality of ribs (see Patent Document 1). In this golf club head, the first metal plate is displaced in a direction along the face surface when impacted, thereby reducing the amount of spin on the ball. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4340177 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the above-mentioned conventional technology, there is a risk that the multiple ribs will become excessively deformed when the ball is hit, and the face portion will not return to its original shape even when the ball leaves the face portion; in other words, there is a risk that the face portion will become excessively deformed, and there is room for improvement in terms of improving the initial ball velocity, high initial velocity area, launch angle, spin, feel, and durability. The present invention has been made in consideration of the above circumstances, and its object is to provide a golf club head that is advantageous in improving ball initial velocity, high initial velocity area, launch angle, spin, hitting feel, and durability. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, one embodiment of the present invention is a golf club head having a hollow structure in which at least a portion of the face portion is composed of a first layer constituting the face surface, a second layer located on the opposite side of the first layer to the face surface, and a third layer located on the opposite side of the second layer to the first layer, and is characterized in that when the tensile strengths of the first layer, the second layer, and the third layer are S1, S2, and S3, respectively, S3≧S1>S2. In one embodiment of the present invention, the first layer has a hardness of durometer hardness D75 or more and Vickers hardness HV520 or less, the second layer has a hardness of durometer hardness A10 or more and durometer hardness D60 or less, and the third layer has a hardness of durometer hardness D85 or more and Vickers hardness HV520 or less. In addition, one embodiment of the present invention is characterized in that the tensile modulus of the first layer is 8 GPa or more and 240 GPa or less, the tensile modulus of the second layer is 0.5 MPa or more and 3000 MPa or less, and the tensile modulus of the third layer is 10 GPa or more and 240 GPa or less. Furthermore, one embodiment of the present invention is characterized in that the thickness of the first layer is 0.1 to 1.5 mm, the thickness of the second layer is 0.1 mm or more and 1.0 mm or less, and the thickness of the third layer is 2.0 mm or more and 5.0 mm or less. Moreover, one embodiment of the present invention is characterized in that the first layer is made of any one of a metal material, a synthetic resin material, or a fiber-reinforced resin material, the second layer is made of any one of a double-sided tape, a synthetic resin material, or an elastic material, and the third layer is made of any one of a metal material, a synthetic resin material, or a fiber-reinforced resin material. Furthermore, one embodiment of the present invention is characterized in that a thin-walled portion that is thinner than other portions is formed in the third layer, the thin-walled portion being composed of an open recess formed in the first layer on the front surface of the third layer facing the first layer, and the second layer is arranged by filling the recess. In one embodiment of the present invention, the front surface of the third layer excluding the recess is superimposed on the first layer. In one embodiment of the present invention, the golf club head comprises a hollow head body including a face outer periphery in which an opening is provided except for the outer periphery of the face part, and a crown part, a sole part, and a side part connected to the face outer periphery, the plate-shaped third face member constituting the third layer is provided on the inner side of the head body inside the face outer periphery, the plate-shaped second face member constituting the second layer is attached to the third face member by overlapping it inside the face outer periphery, the plate-shaped first face member constituting the first layer is attached to the second face member by overlapping it inside the face outer periphery, the outer periphery of the third face member is butted against the inner periphery of a frame-shaped, plate-shaped mounting plate part of the face outer periphery and attached by welding, and a bead generated during the welding is accommodated in a bead accommodating space provided across the outer periphery of the third face member and the inner periphery of the mounting plate part on the side away from the inside of the head body, and the bead accommodating space is covered by the second face member and the first face member. In one embodiment of the present invention, the golf club head includes a hollow head body having an opening formed by removing the face portion, a portion of the crown portion near the face portion, a portion of the sole portion near the face portion, and a portion of the side portion near the face portion, the third face member constituting the third layer includes a third face body corresponding to the face portion, and a third flange protruding from an outer periphery of the third face body toward the head body side, and the second face member constituting the second layer includes a second face body attached by being superimposed on the third face body, and a third flange protruding from an outer periphery of the second face body toward the head body side, the third flange, and the portion of the crown portion near the opening, the portion of the sole portion near the opening, and the portion of the side portion near the face portion. and a second flange, and the first face member constituting the first layer comprises a first face body overlapping and attached to the second face body, and a first flange protruding from the outer periphery of the first face body toward the head body and overlapping and attached to the second flange, the tip end face of the third flange is butted against the tip end face of the crown portion, the tip end face of the sole portion, and the tip end face of the side portion which form the opening, and is attached by welding, a bead generated during the welding is accommodated in a bead accommodating space provided across the outer periphery of the third flange, the outer periphery of the crown portion, the outer periphery of the sole portion, and the outer periphery of the side portion on the side away from the inside of the head body, and the bead accommodating space is covered by the second face member and the first face member. Effect of the Invention

[0006] According to one embodiment of the present invention, the first, second and third layers constituting the face portion are deformed when the ball is hit with the face surface. At this time, since the soft second layer is sandwiched between the hard first and second layers, the face portion deforms within an elastic deformation range, and the first layer is more likely to deform as an expanding surface rather than as a point, thereby increasing the contact area and contact time between the face surface and the ball. Therefore, by ensuring a large contact area and contact time, the recoil effect reduces the amount of backspin on the ball, resulting in a high launch angle and low spin rate for the ball, and an increased flight distance for the ball. Recoil is a phenomenon in which the elastic twist that occurs inside the ball when the ball comes into contact with the face tries to return to its original shape, or in other words, it is an internal spin in the forward direction, which is the opposite direction to backspin. Therefore, the greater the recoil, the less backspin the ball will have. In addition, because the face portion flexes over a wide area, the initial velocity of the ball is high over a wide range of the face surface, which is advantageous in expanding the high initial velocity area. In addition, the soft second layer reduces stress when hitting the ball, which in turn reduces stress generated in the third layer, which is advantageous in ensuring the durability of the face over a wide area of ​​the face. In addition, the soft second layer brings the volume, pitch and reverberation of the impact sound into a comfortable range for golfers, resulting in an appropriately soft feel on impact, which is advantageous in improving the feel on impact over a wide area of ​​the face. [Brief description of the drawings]

[0007] [Figure 1] 1 is a front view of a golf club head according to a first embodiment, as viewed from the front of the face surface. [Diagram 2] 1, and FIG. 3B is a partial cross-sectional view showing a modified example. [Diagram 3] 4(A)-(F) are cross-sectional views showing a schematic configuration of the face portion. [Figure 4] FIG. 13(A) is a cross-sectional view that shows a schematic view of a face portion of a second embodiment, and FIG. 13(B) is a cross-sectional view that shows a schematic view of a face portion of a third embodiment. [Diagram 5] FIG. 13(A) is a cross-sectional view of a golf club head according to a fourth embodiment, and (B) is a partial cross-sectional view showing a modified example. [Figure 6] FIG. 13 is a cross-sectional view of a golf club head according to a fifth embodiment. [Figure 7]13(A)-(E) are cross-sectional views showing a manufacturing process for a golf club head according to a sixth embodiment. [Figure 8] 5A and 5B are cross-sectional views showing a first modified example of the golf club head of the first embodiment, in which (A) shows the state before assembly and (B) shows the state after assembly. [Figure 9] 5A and 5B are cross-sectional views showing a second modified example of the golf club head of the first embodiment, in which (A) shows the state before assembly and (B) shows the state after assembly. [Figure 10] 13A and 13B are cross-sectional views showing a first modified example of a golf club head according to the fourth embodiment, in which (A) shows the state before assembly and (B) shows the state after assembly. [Figure 11] 13A and 13B are cross-sectional views showing a second modified example of the golf club head according to the fourth embodiment, in which (A) shows the state before assembly and (B) shows the state after assembly. [Figure 12] FIG. 11 is a diagram showing evaluation results of an experimental example under condition 1 in the embodiment. [Figure 13] FIG. 13 is a diagram showing an evaluation result of an experimental example under condition 2 in the embodiment. [Figure 14] FIG. 13 is a diagram showing an evaluation result of an experimental example under condition 3 in the embodiment. [Figure 15] FIG. 13 is a diagram showing an evaluation result of an experimental example under condition 4 in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (First embodiment) First, the first embodiment will be described. As shown in FIGS. 1 and 2(A), in this embodiment, a golf club head 10A is a hollow wood-type golf club head (driver). Of the golf club head 10A, the head body 12A excluding the face portion 14 described below is made of a metal material or a fiber reinforced plastic material (FRP), or is made of a combination of a metal material and a fiber reinforced plastic material. As the metallic material, for example, one or more of stainless steel, maraging steel, pure titanium, titanium alloy, aluminum alloy, and the like are used. Examples of such titanium alloys include 6-4Ti and 8-1-1Ti. As the fiber reinforced plastic material, a carbon fiber reinforced plastic material (CFRP) or the like is used. The golf club head 10A includes a face portion 14, a crown portion 16, a sole portion 18, and a side portion 20. The golf club head 10A has a hollow structure in which the inside surrounded by the face portion 14, the crown portion 16, the sole portion 18, and the side portion 20 is a hollow portion 22 (see FIG. 2(A)). The face portion 14 has a vertical height and extends laterally.

[0009] The crown portion 16 has a thickness smaller than that of the face portion 14 and extends rearward from an upper portion of the face portion 14 . The surface of the face portion 14 exposed to the outside is a face surface 1402 that strikes the ball. A hosel 28 connected to the shaft S is provided on the crown portion 16 at a position on the face surface 1402 side and close to the heel 24, and the golf club 100 is formed by connecting the shaft S to the hosel 28. The sole portion 18 extends rearward from the lower portion of the face portion 14 . The side portion 20 extends between a toe 24 side edge and a heel 26 side edge of the face portion 14 between the crown portion 16 and the sole portion 18 through the back of the face.

[0010] As shown in FIG. 2(A), the golf club head 10A is composed of a hollow head body 12A, a plate-shaped first face member 30, and a plate-shaped second face member 32, and the face portion 14 of the golf club head 10A is composed of the first and second face members 30, 32 and a face portion plate portion 34 of the head body 12A. In other words, the face portion 14 of the golf club head 10A is composed of a first layer 36 constituting the face surface 1402, a second layer 38 located on the opposite side of the face surface 1402 of the first layer 36, and a third layer 40 located on the opposite side of the second layer 38 to the first layer 36. The first layer 36 is composed of the first face member 30 . The second layer 38 is constituted by the second face member 32 and is attached to and overlaps the surface of the first face member 30 opposite the face surface 1402 . The third layer 40 is constituted by the face plate portion 34 of the head body 12A, and the second face member 32 is attached to and overlapped on the outer surface of this face plate portion 34. In this embodiment, the head body 12A and the face portion forming plate portion 34 are made of the same material, for example, 8-1-1Ti (cast material). When the tensile strengths of the first layer 36, the second layer 38 and the third layer 40 are material strengths S1, S2 and S3, respectively, S3≧S1>S2.

[0011] (hardness) The hardness of the first layer 36 is set to a durometer hardness of D75 or more and a Vickers hardness of HV520 or less. The hardness of the second layer 38 is set to a durometer hardness of A10 or more and durometer hardness D60 or less. The hardness of the third layer 40 is set to a durometer hardness of D85 or more and a Vickers hardness of HV520 or less. Having the hardness of the first layer 36, the second layer 38, and the third layer 40 each fall within the above range is advantageous in improving the ball's initial velocity, high initial velocity area, launch angle, spin, feel, and durability, as described below. If the hardness of the first layer 36, the second layer 38, and the third layer 40 is less than the above-mentioned range, the face portion 14 will deform excessively when hitting the ball (it will no longer be within the elastic deformation range described below), resulting in energy loss when hitting the ball and reducing the effects of improving the ball's initial velocity, high initial velocity area, launch angle, spin, feel, and durability. If the hardness of the first layer 36, the second layer 38, and the third layer 40 exceeds the respective ranges described above, the deformation (amount of deflection) of the face portion 14 when hitting the ball will be insufficient, and the effects of improving the ball's initial velocity, high initial velocity area, launch angle, spin, hitting feel, and durability will be reduced.

[0012] (tensile modulus) The tensile modulus of the first layer 36 is set to be equal to or greater than 8 GPa and equal to or less than 240 GPa. The tensile modulus of elasticity of the second layer 38 is set to be equal to or greater than 0.5 MPa and equal to or less than 3000 MPa. The tensile modulus of the third layer 40 is set to be equal to or greater than 10 GPa and equal to or less than 240 GPa. Having the tensile modulus of elasticity of the first layer 36, the second layer 38, and the third layer 40 each fall within the above ranges is advantageous in improving the ball initial velocity, high initial velocity area, launch angle, spin, feel, and durability, which will be described later. If the tensile modulus of elasticity of the first layer 36, the second layer 38, and the third layer 40 are each less than the above range, the deformation of the face portion 14 when hitting the ball will be excessive (it will no longer be within the range of elastic deformation described below), resulting in energy loss when hitting the ball and reducing the effects of improving the ball's initial velocity, high initial velocity area, launch angle, spin, feel, and durability. If the tensile modulus of elasticity of the first layer 36, the second layer 38, and the third layer 40 exceeds the above range, respectively, the deformation (amount of deflection) of the face portion 14 when hitting the ball will be insufficient, and the effects of improving the ball's initial velocity, high initial velocity area, launch angle, spin, hitting feel, and durability will be reduced.

[0013] (Thickness) The thickness of the first layer 36 was set to 0.1 to 1.5 mm. The thickness of the second layer 38 is set to be not less than 0.1 mm and not more than 1.0 mm. The thickness of the third layer 40 is set to be not less than 2.0 mm and not more than 5.0 mm. Having the thicknesses of the first layer 36, second layer 38, and third layer 40 each fall within the above ranges is advantageous in improving the ball's initial velocity, high initial velocity area, launch angle, spin, feel, and durability, as described below. If the thicknesses of the first layer 36, the second layer 38, and the third layer 40 are each less than the above ranges, the face portion 14 will undergo excessive deformation when hitting the ball (it will no longer be within the elastic deformation range described below), resulting in energy loss when hitting the ball and reducing the effects of improving the ball's initial velocity, high initial velocity area, launch angle, spin, feel, and durability. If the thickness of the first layer 36, the second layer 38, and the third layer 40 exceed the above-mentioned ranges, respectively, the deformation (amount of deflection) of the face portion 14 when hitting the ball will be insufficient, and the effects of improving the ball's initial velocity, high initial velocity area, launch angle, spin, hitting feel, and durability will be reduced.

[0014] (material) The first layer 36 is made of any one of a metal material, a synthetic resin material, and a fiber-reinforced resin material. The second layer 38 is made of either a double-sided tape, a synthetic resin material, or an elastic material. The third layer 40 is made of any one of a metal material, a synthetic resin material, and a fiber-reinforced resin material. The elastic material used for the second layer 38 may be a material made of rubber, resin, or the like. Examples of rubber include natural rubber, polybutadiene rubber, styrene butadiene rubber, isoprene rubber, etc. Examples of resin include ionomer resin, urethane resin, polyester resin, polyamide resin, etc. As the elastic material, an elastic adhesive 42 (FIG. 3(A)) or a hot melt adhesive (sheet adhesive: thermoplastic sheet adhesive) can be used. The hardness is Shore A40 to 90. Adhesives with soft hardness are often used. An example of the metal material used for the third layer 40 is a rolled plate of 6-4Ti, which is a titanium alloy.

[0015] The head volume is, for example, 150 cc or more and 460 cc or less, and the golf club head 10A is applicable to drivers, fairway woods, utilities, and the like.

[0016] Next, specific configuration examples of the face portion 14 will be described with reference to Figures 3(A) to 3(F). Note that the dimensions, hardness, and material names in the following configuration examples are merely examples and do not limit the present invention. In addition, the configuration of the third layer 40 is common in the examples shown in FIGS. In the face portion 14 shown in FIG. 3(A), the first layer 36 is made of CFRP (carbon fiber reinforced plastic) with a thickness of 0.75 mm. The second layer 38 is made of an elastic adhesive 42 having a thickness of 0.2±0.1 mm (durometer A 87 degrees), and the second layer 38 is bonded to the first layer 36 and the third layer 40 by the adhesive force of this elastic adhesive 42. The third layer 40 is made of a titanium alloy having a thickness of 2.0 mm or more and 5.0 mm or less. In the face portion 14 shown in FIG. 3(A), the first layer 36 is made of CFRP (carbon fiber reinforced plastic) with a thickness of 0.75 mm. The second layer 38 is made of an elastic adhesive 42 having a thickness of 0.2±0.1 mm (durometer A 87 degrees), and the second layer 38 is bonded to the first layer 36 and the third layer 40 by the adhesive force of this elastic adhesive 42. The third layer 40 is made of a titanium alloy having a thickness of 2.0 mm or more and 5.0 mm or less.

[0017] In the face portion 14 shown in FIG. 3(B), the first layer 36 is configured to include CFRP having a thickness of 0.75 mm. The second layer 38 is made of a urethane sheet having a thickness of 0.1 mm (durometer A 90 degrees). The third layer 40 is made of a titanium alloy and has a thickness of 2.0 mm or more and 5.0 mm or less. The second layer 38 is bonded to the CFRP of the first layer 36 by a 0.25 mm thick epoxy adhesive 44A, and is bonded to the titanium alloy of the third layer 40 by a 0.25 mm thick epoxy adhesive 44B. Here, the hardness of the epoxy adhesives 44A and 44B is, for example, about 75 to 90 degrees in terms of durometer D. The hardness of the epoxy resins 44A and 44B used in the second embodiment and the third embodiment described later all satisfy the above-mentioned hardness regulation. Thus, the first layer 36 is comprised of an epoxy adhesive 44A, and the third layer 40 is comprised of an epoxy adhesive 44B.

[0018] In the face portion 14 shown in FIG. 3(C), the first layer 36 is configured to include CFRP having a thickness of 0.75 mm. The second layer 38 is composed of a 0.25 mm thick double-sided tape (foaming agent) 46. As the double-sided tape 46, various types of double-sided tape known in the art can be used, such as double-sided tape using an acrylic foam base material, a urethane foam base material, a polypropylene base material, or a polyester base material. The double-sided tape 46 of the second layer 38 is adhered to the first layer 36 by a 0.25 mm thick epoxy adhesive 44A and to the third layer 40 by a 0.25 mm thick epoxy adhesive 44B. The third layer 40 is made of a titanium alloy and has a thickness of 2.0 mm or more and 5.0 mm or less. Thus, the first layer 36 is comprised of an epoxy adhesive 44A, and the third layer 40 is comprised of an epoxy adhesive 44B. In this example, epoxy adhesives 44A and 44B are used to reinforce the adhesive strength of the double-sided tape 46, but if there is no need to reinforce the adhesive strength of the double-sided tape 46, the epoxy adhesives 44A and 44B can be omitted. Also, the second layer 38 may be made of only an acrylic foam base material, a urethane foam base material, a polypropylene base material, or a polyester base material, excluding the adhesive component used in the double-sided tape 46.

[0019] In the face portion 14 shown in FIG. 3(D), the first layer 36 is made of SUS (stainless steel sheet) having a thickness of 0.2 mm. The second layer 38 is made of an elastic adhesive 42 having a thickness of 0.2±0.1 mm (durometer A 87 degrees), and the second layer 38 is bonded to the first layer 36 and the third layer 40 by the adhesive force of this elastic adhesive 42. The third layer 40 is made of a titanium alloy having a thickness of 2.0 mm or more and 5.0 mm or less.

[0020] In the face portion 14 shown in Fig. 3(E), the first layer 36 is configured to include a 0.2 mm thick SUS (stainless steel sheet). As an alternative to the SUS (stainless steel sheet), for example, a 0.4 mm thick titanium sheet or a 0.6 mm thick aluminum sheet can be used. The second layer 38 is made of a urethane sheet having a thickness of 0.1 mm (durometer A 90 degrees). The third layer 40 is made of a titanium alloy and has a thickness of 2.0 mm or more and 5.0 mm or less. The second layer 38 is adhered to the SUS (stainless steel sheet) of the first layer 36 by an epoxy adhesive 44A having a thickness of 0.25 mm, and is adhered to the titanium alloy of the third layer 40 by an epoxy resin 44B having a thickness of 0.25 mm. Thus, the first layer 36 is comprised of an epoxy adhesive 44A, and the third layer 40 is comprised of an epoxy adhesive 44B.

[0021] In the face portion 14 shown in FIG. 3(F), the first layer 36 is configured to include SUS (stainless steel sheet) having a thickness of 0.2 mm. The second layer 38 is made of double-sided tape (foaming agent) 46 having a thickness of 0.25 mm. The double-sided tape 46 of the second layer 38 is adhered to the first layer 36 by an epoxy adhesive 44A having a thickness of 0.25 mm, and is adhered to the second layer 38 by an epoxy adhesive 44B having a thickness of 0.25 mm. The third layer 40 is made of a titanium alloy and has a thickness of 2.0 mm or more and 5.0 mm or less. Thus, the first layer 36 is comprised of an epoxy adhesive 44A, and the third layer 40 is comprised of an epoxy adhesive 44B. Also, the second layer 38 may be made of only an acrylic foam base material, a urethane foam base material, a polypropylene base material, or a polyester base material, excluding the adhesive component used in the double-sided tape 46. In this example, epoxy adhesives 44A and 44B are used to reinforce the adhesive strength of the double-sided tape 46, but if there is no need to reinforce the adhesive strength of the double-sided tape 46, the epoxy adhesives 44A and 44B can be omitted.

[0022] Next, a manufacturing method of the golf club head 10A of the present embodiment will be described. First, as shown in FIG. 2(A) and FIG. 3(A) to (F), the golf club head 10A excluding the first layer 36 and the second layer 38 of the face portion 14 is manufactured. Next, the second layer 38 is superimposed and attached to the third layer 40 of the face portion 14, and then the first layer 36 is superimposed and attached to the second layer 38. As described above, the second layer 38 and the first layer 36 can be attached using the double-sided tape 46 and the epoxy adhesives 44A and 44B. For example, when a thermosetting adhesive is used as the epoxy adhesives 44A and 44B, the second layer 38 and the first layer 36 are superimposed on the third layer 40 and then heated and pressed to cure the epoxy adhesives 44A and 44B. In addition, when the outermost layer is CFRP, the CFRP may be cured first (150°C, 60 minutes) and then the cured CFRP may be bonded with an adhesive. The cured CFRP may be heated at 120°C for 60 minutes to conform to the shape of the bottom layer.

[0023] As shown in FIG. 2(A), the outer surface (face surface 1402) of the first layer 36 is higher than the outer surface of the third layer 40 by the thickness of the first layer 36 and the second layer 38, and an annular step is formed with respect to the outer surface of the third layer 40 by the outer peripheral surfaces of the first layer 36 and the second layer 38. Therefore, in order to eliminate this step, a ring-shaped synthetic resin 48 of the same thickness as the step is bonded between the outer peripheral surfaces of the first layer 36 and the second layer 38 and the outer surface of the third layer 40, and then the outer peripheral portion of the first layer 36 and the synthetic resin 48 are polished to connect the outer surface of the third layer 40 and the outer surface of the first layer 36 (face surface 1402) with a smooth curved surface. Then, a coating (not shown) is applied in an annular shape over the outer periphery of the outer surface (face surface 1402) of the first layer 36, the curved surface of the synthetic resin 48, and the outer surface of the third layer 40. By applying such a coating, the steps are concealed, and the appearance of the golf club head 10A is improved. In this manner, the golf club head 10A having the face portion 14 including the first layer 36, the second layer 38, and the third layer 40 is manufactured. In addition, instead of providing such synthetic resin 48, as shown in FIG. 2(B), in order to eliminate the annular step portion between the first layer 36 and the second layer 38 formed on the outer surface of the third layer 40, the first layer 36 and the second layer 38 may be processed into a tapered surface and paint 49 may be applied to the surface of the tapered surface to hide the step and improve the appearance of the golf club head 10A.

[0024] Next, the effects will be described. In the golf club head 10A of the present embodiment, when the tensile strengths of the first layer 36, second layer 38, and third layer 40 constituting the face portion 14 are material strengths S1, S2, and S3, respectively, S3≧S1>S2. Therefore, when the ball is hit with the face surface 1402, the first layer 36, the second layer 38, and the third layer 40 that make up the face portion 14 are deformed. At this time, since the second layer 38, which has the lowest tensile strength and is soft, is sandwiched between the first layer 36 and the second layer 38, which have high tensile strength and are hard, the face portion 14 deforms within an elastic deformation range, and the first layer 36 is more likely to deform as a spreading surface rather than as a point, which is advantageous for increasing the contact area between the face surface 1402 and the ball and ensuring a long contact time between the face surface 1402 and the ball.

[0025] Here, deformation within the elastic deformation of the second layer 38 does not mean deformation within a range in which the face portion 14 does not undergo plastic deformation, but means deformation in which the shape of the face portion 14 nearly restores to the shape before deformation at the time when the ball struck against the face surface 1402 leaves the face surface 1402. In other words, when the ball hit by face surface 1402 leaves face surface 1402, the shape of face portion 14 is still significantly deformed and face portion 14 is in a state that is significantly different from the shape before deformation, and the face portion 14 has not returned to the shape before deformation, the deformation is not within the range of elastic deformation. In this way, when the face portion 14 undergoes deformation that is not within the range of elastic deformation, there is a disadvantage that a large energy loss occurs, leading to a decrease in the initial velocity.

[0026] In this way, when the contact area and contact time between the ball and face surface 1402 are increased at the time of hitting the ball, the recoil effect reduces the amount of backspin of the ball, resulting in a high launch angle and low spin, and increasing the flight distance of the ball. In addition, since the face portion 14 deforms within an elastic range, the face portion 14 bends over a wide area, so that the initial velocity of the ball becomes high over a wide range of the face surface 1402, which is advantageous in expanding the high initial velocity area. In addition, since the soft second layer 38 reduces the stress generated when hitting the ball, the stress generated in the third layer 40 can be reduced, which is advantageous in ensuring the durability of the face portion 14 over a wide area of ​​the face surface 1402. In addition, the soft second layer 38 ensures that the volume, pitch, and reverberation of the impact sound are within a comfortable range for the golfer, resulting in an appropriately soft impact feel, which is advantageous in improving the impact feel over a wide area of ​​the face 1402.

[0027] Here, the tensile strength, hardness, tensile modulus, and thickness of the first layer 36, the second layer 38, and the third layer 40 will be described. In the present invention, it is important that the soft layer (second layer 38) deforms moderately on the surface during elastic deformation while ensuring the durability of the golf club head. As a result, the high initial velocity area can be expanded without decreasing the initial velocity, and the flight distance can be increased with a high launch angle and moderately low backspin, and a soft hitting feel can also be achieved. In order to ensure durability, it is necessary to increase the tensile strength. Since the outermost layer (first layer 36) and the innermost layer (third layer 40) are subject to greater deformation (tensile or compressive stress) when hitting the ball than the intermediate layer (second layer 38), it is necessary to use a high-strength material for them. On the other hand, the soft layer (second layer 38) that deforms in a plane within the elastic deformation must be moderately soft. For example, if it is too soft, energy loss occurs and the initial velocity decreases. In order for the soft layer (second layer 38) to deform in a plane appropriately within the elastic deformation, hardness is an important factor. In addition, bending rigidity (Bending rigidity (EI) = Longitudinal Young's modulus (E) x Second moment of area (I)), and Longitudinal Young's modulus (E) is the tensile modulus of elasticity in this specification. is also important, and the tensile modulus and wall thickness of each material are interrelated. In other words, the four factors of tensile strength, hardness, tensile modulus, and wall thickness are intricately intertwined, and an important point in the golf club head according to the present invention is to appropriately and appropriately arrange them.

[0028] Next, first and second modified examples of the first embodiment will be described with reference to FIGS. In the first and second modified examples, the thickness of the second layer 38 is ensured to be a constant dimension. As shown in Figures 8(B) and 9(B), similar to Figure 2(B), a coating 49 is applied to eliminate the annular step portion between the first layer 36 and the second layer 38 formed on the outer surface of the third layer 40. As shown in Figures 8(A) and (B), in the first modified example, the first layer 36 (first face member 30) constituting the face surface 1402 is made of CFRP with a thickness of 0.75 mm, the second layer 38 (second face member 32) is made of an elastic adhesive 42 (or a hot melt adhesive), and the third layer 40 (face plate portion 34) is made of a 6-4Ti rolled plate. On the front surface of the third layer 40 (6-4Ti rolled plate), i.e., the front surface where the face plate portion 34 faces the second layer 38, a plurality of cylindrical protrusions 3402, each 0.25 mm high and 2 mm in diameter, protruding toward the second layer 38 are provided at intervals of 15 mm in the toe-heel and cransole directions. Then, as the tips of the multiple protrusions 3402 abut against the rear surface of the first layer 36 (CFRP), the protrusions 3402 create a gap of 0.25 mm between the front surface of the third layer 40 (6-4Ti rolled plate) and the rear surface of the first layer 36 (CFRP), and by filling this gap with elastic adhesive 42, a second layer 38 with a thickness of 0.25 mm is formed.

[0029] In the second modified example shown in FIG. 9, the first layer 36, the second layer 38, and the third layer 40 have the same configurations as in the first modified example. As shown in Figures 9(A) and (B), in the second modified example, on the rear surface of the first layer 36 (CFRP) having a thickness of 0.75 mm, i.e., the rear surface where the first face member 30 faces the second layer 38, a plurality of cylindrical protrusions 3002 having a height of 0.25 mm and a diameter of 1 mm that protrude toward the second layer 38 are provided at intervals of 15 mm in the toe-heel direction and the crest-sole direction. Then, as the tips of the multiple protrusions 3002 abut against the front surface of the third layer 40 (6-4Ti rolled plate), the protrusions 3002 create a gap of 0.25 mm between the front surface of the third layer 40 (6-4Ti rolled plate) and the rear surface of the first layer 36 (CFRP), and by filling this gap with elastic adhesive 42, a second layer 38 with a thickness of 0.25 mm is formed. In both the first and second modified examples, the shape of the protrusions 3402, 3002 is not limited to cylindrical as long as a gap can be secured between the front surface of the third layer 40 (6-4Ti rolled plate) and the rear surface of the first layer 36 (CFRP). According to the first and second modified examples, the simple structure of providing a plurality of protrusions 3402, 3002 is advantageous in ensuring that the thickness of the elastic adhesive 42 constituting the second layer 38 is constant.

[0030] (Second embodiment) Next, a second embodiment will be described with reference to FIG. In the following embodiment, the same parts and members as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and the description will focus on the differences. As shown in FIG. 4(A), the third layer 40 has a thin portion 4002 that is thinner than other portions. The thin portion 4002 is configured as a recess 4004 formed in an open manner in the first layer 36 on the front surface of the third layer 40 facing the first layer 36 . The first layer 36 is configured to include a SUS (stainless steel sheet) having a thickness of 0.2 mm or a CFRP (prepreg sheet) having a thickness of 0.75 mm. The second layer 38 is disposed by filling the recesses 4004 . The third layer 40 is made of a titanium alloy and has a thickness of 2.0 mm or more and 5.0 mm or less. In detail, the second layer 38 is constructed by stacking a urethane sheet 50A having a thickness of 0.3 mm (durometer A 90 degrees) that is formed with a shape and thickness corresponding to the recess 4004 and fills the recess 4004, and a urethane sheet 50B having a thickness of 0.1 mm (durometer A 90 degrees) that is provided on the front surface of the third layer 40 including the recess 4004. The second layer 38 is adhered to the SUS (stainless steel sheet) of the first layer 36 by an epoxy adhesive 44A having a thickness of 0.25 mm, and is adhered to the titanium alloy of the third layer 40 by an epoxy adhesive 44B having a thickness of 0.13 mm. Thus, the first layer 36 and the third layer 40 are comprised of epoxy adhesives 44A, 44B.

[0031] According to the second embodiment, not only can the same effects as those of the first embodiment be achieved, but also, by providing a recess 4004 on the front surface of the third layer 40, a thin-walled portion 4002 in which the thickness of the third layer 40 is partially thinned can be formed, and an uneven thickness structure can be formed in the face portion 14. Therefore, for example, forming an annular thin portion 4002 surrounding the center of face surface 1402 increases the amount of deflection of face portion 14, which is advantageous in increasing the initial velocity of the ball and increasing the flight distance. Furthermore, a recess 4004 may be provided on the rear surface of the third layer 40 to form an uneven thickness structure in the face portion 14; however, when a recess 4004 is provided on the front surface of the third layer 40 as in the embodiment to form an uneven thickness structure in the face portion 14, it is possible to increase the surface deformation in the portion closer to the striking surface than by providing a recess on the rear surface of the third layer 40, which is advantageous in expanding the high initial velocity area, ensuring the recoil effect, and improving durability. The shape and number of the thin-walled portion 4002 constituting the uneven thickness structure are not limited.

[0032] (Third embodiment) Next, a third embodiment will be described with reference to FIG. The third embodiment is a modified version of the second embodiment, and differs from the second embodiment in that the front surface of the third layer 40, excluding the recess 4004, is directly superimposed on the first layer 36 without the second layer 38 interposed therebetween. In detail, the first layer 36 is configured to include a SUS (stainless steel sheet) having a thickness of 0.2 mm or a CFRP (prepreg sheet) having a thickness of 0.75 mm. The second layer 38 is constituted by a urethane sheet 50C having a thickness of 0.2 mm (durometer A 90 degrees) and a shape corresponding to the recess 4004, and the recess 4004 is filled with the urethane sheet 50C. The third layer 40 is made of a titanium alloy and has a thickness of 2.0 mm or more and 5.0 mm or less. In detail, the front surface of the second layer 38 and the front surface of the third layer 40 excluding the recess 4004 are bonded to the SUS (stainless steel sheet) of the first layer 36 with a 0.25 mm thick epoxy adhesive 44A, and the portion of the second layer 38 filled in the recess 4004 is bonded to the recess 4004 (titanium alloy) of the third layer 40 with a 0.13 mm thick epoxy adhesive 44B. That is, the first layer 36 is configured to include an epoxy adhesive 44A, and the third layer 40 is configured to include an epoxy resin 44B. Therefore, the front surface of the third layer 40 excluding the recessed portion 4004 and the first layer 36 are directly overlapped. In the third embodiment as described above, substantially the same effects as in the second embodiment are achieved.

[0033] (Fourth embodiment) Next, a fourth embodiment will be described with reference to FIG. In the fourth embodiment, the mutual attachment structure of the first layer 36, the second layer 38, and the third layer 40, i.e., the mutual attachment structure of the first face member 52, the second face member 54, and the third face member 56 described below, is similar to that of the first embodiment, and therefore will not be described again. The golf club head 10B of the fourth embodiment is configured to include a hollow head body 12B, a plate-shaped first face member 52, a plate-shaped second face member 54, and a plate-shaped third face member 56. The head body 12B includes a face outer periphery 60 in which an opening 58 is provided, leaving only the outer periphery of the face portion 14, and a crown portion 16, a sole portion 18, and a side portion 20 connected to the face outer periphery 60. The head body 12B, like the head body 12B of the first embodiment, is made of a metal material or a fiber reinforced plastic material (FRP), or is made of a combination of a metal material and a fiber reinforced plastic material. When a titanium alloy is used as the metal material constituting the head main body 12B, for example, the titanium alloy is 8-1-1Ti. The face outer periphery 60 is composed of a frame-shaped outer periphery plate portion 62 that forms the outer periphery of the face surface 1402, a frame-shaped protruding plate portion 64 that protrudes from the inner periphery of the frame-shaped outer periphery plate portion 62 into the inside of the head body 12B, and a frame-shaped inner periphery plate portion 66 that protrudes inward from the tip of the frame-shaped protruding plate portion 64. The face portion 14 of the golf club head 10B is composed of a first layer 36 constituting a face surface 1402, a second layer 38 located on the opposite side of the face surface 1402 of the first layer 36, and a third layer 40 located on the opposite side of the second layer 38 to the first layer 36.

[0034] The third layer 40 is composed of a third face member 56, and the third face member 56 is provided inside the head body 12B inside the face outer periphery 60. In detail, the outer periphery end face of the third face member 56 is butted against the tip end face of an inner periphery plate portion 66 of the face outer periphery 60 and welded. The third face member 56 is made of, for example, a rolled plate or a forged metal material. An example of such a metal material is a rolled plate of 6-4Ti, which is a titanium alloy. The material is set so that the strength (tensile strength) of the third face member 56 made of a rolled plate of 6-4Ti is greater than that of the head body 12B made of 8-1-1Ti (cast material). This is to maintain the durability of the face portion 14 so that it will not be destroyed when hitting the ball. A bead accommodating space 68 is provided across the outer surface of the protruding plate portion 64 located on the side away from the inside of the head body 12B and the outer surface of the outer periphery of the third face member 56, and a bead B generated when the outer periphery end face of the third face member 56 is butted against the tip end face of the inner periphery plate portion 66 of the face outer periphery 60 and welded is accommodated in the bead accommodating space 68. The second layer 38 is constituted by a second face member 54 , and the second face member 54 is attached to and overlapped with a third face member 56 inside an outer peripheral plate portion 62 of a face outer periphery 60 . The first layer 36 is composed of the first face member 52, which is attached by overlapping it on the surface of the second face member 54 inside the outer peripheral plate portion 62 of the face peripheral portion 60, and the face surface 1402 is composed of the surface of the outer peripheral plate portion 62 of the face peripheral portion 60 and the surface of the first face member 52. The bead accommodating space 68 is covered by the second face member 54 and the first face member 52 . Before covering the bead accommodating space 68 with the second face member 54, the bead accommodating space 68 may be optionally filled with a resin, an adhesive, or the like. Alternatively, a convex portion having a shape corresponding to the bead receiving space 68 may be formed in advance on the second face member 54, and the bead receiving space 68 may be filled with the convex portion. In addition, the annular gap 70 generated between the outer peripheral end faces of the first face member 52 and the second face member 54 and the outer peripheral plate portion 62 may be filled with resin or the like, or the gap 70 may be covered with paint, thereby concealing the gap 70 and improving the appearance of the golf club head 12B. Furthermore, as shown in FIG. 5(B), when the outer peripheral end faces of the first face member 52 and the second face member 54 abut against the outer peripheral plate portion 62 without any gaps, forming a boundary line between them, the boundary line may be concealed by covering it with paint 71, thereby improving the appearance of the golf club head 12B.

[0035] According to the fourth embodiment, not only can the same effects as those of the first embodiment be achieved, but also, since the bead accommodating space 68 that accommodates the bead B formed by welding the third face member 56 to the head body 12B is covered by the second face member 54 and the first face member 52, the polishing work of the welded bead B that was conventionally required can be omitted, which is advantageous in reducing the manufacturing cost of the golf club head 10B. It is also possible to weld third face member 56 and head body 12B without providing a recess recessed into hollow portion 22 at the welded portion between them. However, if weld bead B protrudes outward, grinding (machining) of weld bead B is required, which increases manufacturing costs. Therefore, in the fourth embodiment, weld bead B is completely contained in bead containing space 68, eliminating the need to grind weld bead B. Moreover, the fourth embodiment may be arbitrarily combined with the uneven thickness structure of the second and third embodiments.

[0036] In the fourth embodiment, the third face member 56 and the main body are made of different metal materials, and the third face member 56 can be made of a metal material having higher strength than the main body. For example, the third face member 56 can be made of a rolled 6-4Ti plate, and the head body 12B can be made of 8-1-1Ti. In the fourth embodiment, the third face member 56 and the main body are made of different materials, and the third face member 56 can be made of a material having higher strength than the main body. For example, the third face member 56 can be made of a 6-4Ti rolled plate, and the head body 12B can be made of CFRP.

[0037] In the fourth embodiment, it is also possible to not provide the bead accommodating space 68, and instead grind the bead B formed by welding the third face member 56 and the head body 12B together as in the conventional method, and cover the welded portion between the third face member 56 and the head body 12B with the second face member 54 and the first face member 52; however, using the fourth embodiment is advantageous in terms of reducing manufacturing costs.

[0038] Next, first and second modified examples of the fourth embodiment will be described with reference to FIGS. In the first and second modified examples, the thickness of the second layer 38 is ensured to be a constant dimension. 10 and 11, in order to simplify the illustration, the weld bead B formed by welding the plate-like third face member 56 to the opening 58 of the head body 12B, the bead accommodating space 68, and the like are omitted. As shown in Fig. 10(B) and Fig. 11(B), a coating 71 is applied to cover the boundary between the outer peripheral end faces of the first face member 52 and the second face member 54 and the outer peripheral plate portion 62, as in Fig. 5(B). As shown in Figures 10(A) and (B), in the first modified example, the first layer 36 (first face member 52) constituting the face surface 1402 is made of CFRP with a thickness of 0.75 mm, the second layer 38 (second face member 54) is made of an elastic adhesive 42 (or a hot melt adhesive), and the third layer 40 (third face member 56) is made of a 6-4Ti rolled plate. On the front surface of the third layer 40 (6-4Ti rolled plate), i.e., the front surface where the third face member 56 faces the second layer 38, a plurality of cylindrical protrusions 5602 each having a height of 0.25 mm and a diameter of 2 mm are provided at intervals of 15 mm in the toe-heel and cransole directions protruding toward the second layer 38. Then, as the tips of the multiple protrusions 5602 abut against the rear surface of the first layer 36 (CFRP), the protrusions 5602 create a gap of 0.25 mm between the front surface of the third layer 40 (6-4Ti rolled plate) and the rear surface of the first layer 36 (CFRP), and by filling this gap with elastic adhesive 42, a second layer 38 with a thickness of 0.25 mm is formed.

[0039] In the second modified example shown in FIGS. 11(A) and (B), the configurations of the first layer 36, the second layer 38, and the third layer 40 are similar to those in the first modified example. As shown in Figures 11(A) and (B), in the second modified example, on the rear surface of the first layer 36 (CFRP) having a thickness of 0.75 mm, i.e., the rear surface where the first face member 52 faces the second layer 38, a plurality of cylindrical protrusions 5202 having a height of 0.25 mm and a diameter of 1 mm that protrude toward the second layer 38 are provided at intervals of 15 mm in the toe-heel direction and the crest-sole direction. The tips of the multiple protrusions 5202 abut against the front surface of the third layer 40 (6-4Ti rolled plate), thereby creating a gap of 0.25 mm between the front surface of the third layer 40 (6-4Ti rolled plate) and the rear surface of the first layer 36 (CFRP) by the protrusions 5202, and by filling this gap with elastic adhesive 42, a second layer 38 with a thickness of 0.25 mm is formed. In both the first and second modified examples, the shape of the protrusions 5602, 5202 is not limited to cylindrical as long as a gap can be secured between the front surface of the third layer 40 (6-4Ti rolled plate) and the rear surface of the first layer 36 (CFRP). According to the first and second modified examples, the simple structure of providing a plurality of protrusions 5602, 5202 is advantageous in ensuring that the thickness of the elastic adhesive 42 constituting the second layer 38 is a constant dimension. Of course, the same structures as the first and second modified examples can be employed in the fifth embodiment described later.

[0040] (Fifth embodiment) Next, a fifth embodiment will be described with reference to FIG. In the fifth embodiment, the mutual attachment structure of the first layer 36, the second layer 38, and the third layer 40, i.e., the mutual attachment structure of the first face member 72, the second face member 74, and the third face member 76 described below, is similar to that of the first embodiment, and therefore will not be described again. The golf club head 10C includes a hollow head body 12C, a plate-shaped first face member 72, a plate-shaped second face member 74, and a plate-shaped third face member . The head body 12C has a crown portion 16, a sole portion 18, and a side portion 20, and further has an opening 78 formed by cutting out the face portion 14, the portion of the crown portion 16 closer to the face portion 14, the portion of the sole portion 18 closer to the face portion 14, and the portion of the side portion 20 closer to the face portion 14. The head main body 12C is made of a metal material or a fiber reinforced plastic material (FRP), or is made of a combination of a metal material and a fiber reinforced plastic material. When a titanium alloy is used as the metal material constituting the head main body 12C, for example, 8-1-1Ti, which is a titanium alloy, is exemplified. The face portion 14 of the golf club head 10C is composed of a first layer 36 constituting a face surface 1402, a second layer 38 located on the opposite side of the face surface 1402 of the first layer 36, and a third layer 40 located on the opposite side of the second layer 38 to the first layer 36.

[0041] The third layer 40 is composed of a third face member 76, and the third face member 76 has a third face body 7602 corresponding to the face portion 14, and a third flange 7604 protruding from the outer periphery of the third face body 7602 toward the head body 12C. The third face member 76 is made of, for example, a rolled plate or a forged metal material. An example of such a metal material is a rolled plate of 6-4Ti, which is a titanium alloy. The material is set so that the strength (tensile strength) of the third face member 76 is greater than that of the head main body 12C. The tip end surface of the third flange 7604 is butted against the tip end surfaces of the crown portion 16 and the sole portion 18 which define the opening 78 , and the tip end surface of the side portion 20 , and is welded to these. A bead accommodating space 80 is provided on the side away from the inside of the head body 12C, spanning the outer periphery of the tip of the third flange 7604, the outer periphery of the crown portion 16, the outer periphery of the sole portion 18, and the outer periphery of the side portion 20, and a bead B generated during welding is accommodated in the bead accommodating space 80.

[0042] The second layer 38 is composed of the second face member 74, and the second face member 74 includes a second face body 7402 that is overlapped and attached to the third face body 7602, and a second flange 7404 that protrudes from the outer periphery of the second face body 7402 toward the head body 12C to cover the bead accommodating space 80, and is overlapped and attached to the third flange 7604 and the portion of the crown portion 16 near the opening 78, the portion of the sole portion 18 near the opening 78, and the portion of the side portion 20 near the face portion 14.

[0043] The first layer 36 is composed of a first face member 72, which includes a first face body 7202 that is attached by overlapping it on the second face body 7402, and a first flange 7204 that protrudes from the outer periphery of the first face body 7202 toward the head body 12C and is attached by overlapping it on the second flange 7404. Therefore, the bead accommodating space 80 is covered by the second face member 74 and the first face member 72 . The first flange 7204, the second flange 7404, and the third flange 7604 correspond to the portion of the crown portion 16 near the face portion 14, the portion of the sole portion 18 near the face portion 14, and the portion of the side portion 20 near the face portion 14 that are cut away by the opening 78. Furthermore, before covering the bead accommodating space 80 with the second face member 74, the bead accommodating space 80 may be filled with a resin or the like. Alternatively, a convex portion having a shape corresponding to the bead receiving space 80 may be formed in advance on the second face member 74, and the bead receiving space 80 may be filled with the convex portion.

[0044] As shown in FIG. 6, the first flange 7204 (first layer 36) and the second flange 7404 (second layer 38) are higher than the outer surface of the head body 12C by the thickness of the first layer 36 and the second layer 38, and a ring-shaped step is formed by the tip end faces of the first flange 7204 and the second flange 7404 with respect to the outer surface of the head body 12C. Therefore, in order to eliminate this step, synthetic resin 82 of the same thickness as the step is bonded between the tip end faces of the first flange 7204 and the second flange 7404, the outer surface of the third layer 40, and the outer surface of the head body 12C, and then the first flange 7204 and synthetic resin 82 are polished to connect with a smooth curved surface that connects the outer surface of the head body 12C and the outer surface of the first flange 7204. Then, the outer surface of the first flange 7204, the curved surface of the synthetic resin, and the outer surface of the head main body 12C are painted. By painting in this manner, the steps are hidden and the appearance of the golf club head 10C is improved.

[0045] According to the fifth embodiment, not only can the same effects as those of the first embodiment be achieved, but the bead accommodating space 80 containing the bead B formed by welding the third face member 76 to the head body 12C is covered by the second face member 74 and the first face member 72, so that the polishing work of the welded bead B that was conventionally required can be omitted, which is advantageous in reducing the manufacturing cost of the golf club head 10C. Moreover, the fifth embodiment may be arbitrarily combined with the uneven thickness structure of the second or third embodiment.

[0046] In the fifth embodiment, the third face member 76 and the main body are made of different metal materials, and the third face member 76 can be made of a metal material having higher strength than the main body. For example, the third face member 76 can be made of a rolled 6-4Ti plate, and the head body 12C can be made of 8-1-1Ti. In the fifth embodiment, the third face member 76 and the main body are made of different materials, and the third face member 76 can be made of a material having higher strength than the main body. For example, the third face member 76 can be made of a 6-4Ti rolled plate, and the head body 12C can be made of CFRP.

[0047] (Sixth embodiment) Next, a sixth embodiment will be described with reference to FIG. The sixth embodiment of the golf club head 10D is a modified example of the fifth embodiment, in which no bead accommodating space 80 is provided, and the weld bead B formed on the outside of the third face member 76 and the head body 12D by welding the third face member 76 to the head body 12D as in the conventional case is polished, and the welded area between the third face member 76 and the head body 12C is covered with the second face member 74 and the first face member 72. In the sixth embodiment, as in the fifth embodiment, the mutual attachment structure of the first layer 36, the second layer 38, and the third layer 40, i.e., the mutual attachment structure of the first face member 72, the second face member 74, and the third face member 76, is the same as in the first embodiment, and therefore a description thereof will be omitted. That is, as shown in Figures 7(A) and (B), by welding the third face member 76 and the head body 12D together, a weld bead B is formed on the inside (the hollow portion 22 side) of the third face member 76 and the head body 12D and on the outside (the opposite side to the hollow portion 22) of the third face member 76 and the head body 12D. Next, as shown in FIG. 7(C), the weld bead B formed on the outside of the third face member 76 and the head body 12D (the side opposite the hollow portion 22) is polished so that the outside of the third face member 76 and the outside of the head body 12D are connected by a smooth curved surface. Next, as shown in FIG. 7(D), the second layer 38 (second face member 74) is overlapped and attached to the third layer 40 (third face member 76), and then the first layer 36 (first face member 72) is overlapped and attached to the second layer 38 (second face member 74) of the second face member 74. In this case, as in the fifth embodiment, an annular step is formed on the outer surface of the head body 12D by the tip end faces of the first flange 7204 and the second flange 7404. In order to eliminate this step, synthetic resin 82 of the same thickness as the step is bonded between the tip end faces of the first flange 7204 and the second flange 7404, the outer surface of the third layer 40, and the outer surface of the head body 12D, and then the first flange 7204 and the synthetic resin 82 are polished to connect the outer surface of the head body 12D and the outer surface of the first flange 7204 with a smooth curved surface. Then, the outer surface of the first flange 7204, the curved surface of the synthetic resin, and the outer surface of the head main body 12D are painted. By painting in this manner, the steps are hidden and the appearance of the golf club head 10D is improved. In addition, instead of providing synthetic resin 82, as shown in FIG. 7(E), in order to eliminate the annular step portion of the tip end faces of the first flange 7204 and the second flange 7404 formed on the outer surface of the head body 12D, the tip portions of the first flange 7204 and the second flange 7404 may be processed into tapered surfaces and paint 83 may be applied to the surfaces of the tapered surfaces to hide the step and improve the appearance of the golf club head 10D. Even in this case, the same effects as those of the fifth embodiment can be achieved.

[0048] Next, experimental examples of the present invention will be described. 12 to 15 are diagrams showing experimental results of the golf club head according to the present invention. A sample golf club head was prepared for each experimental example, and the following five evaluation items were measured to determine an index (evaluation score), and the total score of the five indexes was calculated.

[0049] (1) High initial velocity area (sweet area) With the center point Pc of the face surface 1402 as the center, 45 points spaced equally in the toe-heel direction and the crown-sole direction were set as impact points Pi. A special swing robot was used to swing a golf club at a hitting point Pi of 45, and the initial velocity of the golf ball was measured with a measuring device. The head speed was set to 40 m / s. The initial velocity data of 45 impact points was interpolated, and the area of ​​the high initial velocity area of ​​the face surface 1402 where the maximum initial velocity of the golf ball is 98% or more was indexed. Note that the data of the upper impact point (crown part 16 side) and the data of the lower impact point (sole part 18 side) from the center point Pc were weighted more heavily in accordance with the actual impact point position of the golfer. The data for the high initial velocity area is expressed as an index, with the measurement result of the golf club head of Experimental Example 1 being set at 100. The higher the index, the better the evaluation.

[0050] (2) Launch angle The launch angle obtained in an actual hitting test at the above-mentioned impact position was measured. The index for Experimental Example A is set to 100, and the larger the index, the larger the launch angle and the better the evaluation.

[0051] (3) Spin rate Based on the spin amount (backspin amount) obtained in the actual hitting test at the above-mentioned impact point Pi, the index of Experimental Example 1 was set to 100, with a larger index indicating a smaller spin amount and a better evaluation.

[0052] (4) Feel The feel of a hit is dominated by the sound of the ball being struck with a golf club head, and generally, a hit sound with a moderately short reverberation and low pitch is considered to have a soft feel and is highly rated by golfers. The evaluation method for the hitting feeling is as follows. Using a dedicated swing robot, a golf club is swung at a head speed of 40 m / s with the center point Pc as the impact point, and the impact sound of the golf ball is measured using a sound level meter. The vibration waveform data of the impact sound is sampled and recorded at a predetermined sampling period. Next, the reverberation parameter T is calculated. The reverberation parameter T is a parameter that represents the degree of attenuation of the hitting sound. In calculating the reverberation parameter T, first, the first sample data (start point data) on the time axis of the recorded vibration waveform data is set as a reference number, and a block group α is created in which the sound pressure vibration waveform is sequentially divided from this number by a predetermined number of samples, for example, 100 samples. Then, the sum of squares of the level of the vibration waveform is calculated for each block Ak of ​​the block group α, and the logarithmic value of this sum of squares (hereinafter, referred to as the block value) is calculated for each block. Then, from each block of the block group α, the maximum sound pressure block with the maximum block value is extracted as the starting block. A value lower than the block value of this maximum sound pressure block by a predetermined value (30 dB in this embodiment) is set as the end block value, and the end block whose block value is the first to be equal to or lower than the end block value is extracted from among the blocks following the starting block. The time span between the earliest sample data on the time axis of each of the start and end blocks is defined as a reverberation parameter T. Therefore, the reverberation parameter T corresponds to the reverberation time of the hitting sound, and the shorter the reverberation parameter T, the shorter the reverberation, the softer the hitting feel, and the higher the evaluation of the hitting feel. In this case, the data on the hitting feeling is expressed as an index with the reciprocal 1 / T of the reverberation parameter T of the golf club head of Experimental Example 1, which corresponds to the comparative example, being set to 100. The larger the index, the better the evaluation of the hitting feeling. The reverberation parameter T can be calculated using the method described in Japanese Patent No. 4840106, for example. However, there is no limitation on the method for evaluating the reverberation time of the hitting sound, and it is possible to obtain the reverberation time of the hitting sound and evaluate the hitting feeling using various conventionally known methods. In addition to evaluating the feel of the impact by calculating the reverberation parameters and the reverberation time, the feel of the impact may be evaluated by having a golfer actually swing a golf club to hit a ball and listening to the impact sound.

[0053] (5)Durability A golf ball was repeatedly hit by an air cannon against the face surface 1402 of a golf club head fixed to a shaft, and the number of hits required until deformation or damage occurred in the face part 1424 was measured and the number of hits was indexed. The ball speed was 50 m / s. The impact point was the center point Pc of the face surface 1402. In this case, the measurement results of the golf club heads of the experimental examples corresponding to the comparative examples are expressed as an index, with the index being set at 100. The higher the index, the better the evaluation.

[0054] (6) Total score The total score was calculated by adding up the five indexes mentioned above: high initial velocity area, launch angle, backspin, feel, and durability. The experimental examples corresponding to the comparative examples were assigned a total score of 500, with a higher total score indicating a better evaluation.

[0055] The experimental conditions will now be described. Experimental Example 1 is a comparative example and corresponds to Patent Document 1 (Patent No. 4340177) listed in the prior art, and is a golf club head whose face portion is constructed of a first metal plate and a second metal plate that supports the first metal plate via multiple ribs. Experimental Example 1 does not satisfy the provisions of claim 1 and is outside the scope of the present invention. The specifications of each part in Experimental Example 1 are as follows: Head body material: Titanium alloy Ti-8Al-1Mo-1V Face material: Titanium alloy Ti-6Al-4V Loft angle 10.5° Lie angle 59° Head weight 200g Head volume 460cc

[0056] The golf club heads used in Experimental Examples 2-25 correspond to the present invention and are hollow type drivers, and have the following common specifications except for the parameters specified in each experimental example. Loft angle 10.5° Lie angle 59° Head weight 200g Head volume 460cc Moreover, the golf club head used in Experimental Example 2-25 was constructed with the structure of the fourth embodiment (FIG. 5(A)). In addition, the materials constituting the first layer 36, the second layer 38, and the third layer 40 in Experimental Example 2-25 are shown in FIGS. Examples of typical tensile strengths of materials include titanium alloy (6-4Ti) about 1047 MPa, CFRP (long fiber) about 1250 to 2500 MPa, polyurethane about 200 to 450 MPa, polycarbonate about 65 MPa, and vinyl chloride about 50 MPa.

[0057] (Condition 1: Figure 12 / Experimental Example 2-8) In addition, in the following Figures 12 to 15, the symbol ◯ in the column describing tensile strength S3 ≧ S1 > S2 indicates that the above tensile strength condition is satisfied, and the symbol × indicates that the above tensile strength condition is not satisfied. As shown in FIG. 12, Experimental Example 1 is a comparative example and is outside the scope of the present invention. In all of Experimental Examples 2 to 8, the tensile strengths satisfy the condition S3≧S1>S2 as specified in claim 1. Experimental Examples 2-8 all meet the provisions of claims 1, 2, 3, 4, and 5. Moreover, the experimental example 8 satisfies the provisions of claim 6 (uneven thickness structure) in addition to 1, 2, 3, 4, and 5. The uneven thickness structure of the experimental example 8 is the same as that of the third embodiment (FIG. 4(A)). Therefore, compared to Experimental Example 1, which is outside the scope of the present invention, Experimental Examples 2-8, which are within the scope of the present invention, are superior in high initial velocity area, launch angle, backspin, durability, hitting feel, and total score.

[0058] (Condition 2: Figure 13 / Experimental Example 9-17) Among Experimental Examples 9-17, Experimental Examples 9, 10, 13, 16, and 17 do not satisfy the requirements of claim 1 and at least claim 2 (hardness of first layer 36, second layer 38, and third layer 40) and are outside the scope of the present invention. The remaining experimental examples 11, 12, 14, and 15 satisfy the provisions of claim 1 and at least the provisions of claim 2. In FIG. 13, the hardness M70 of the second layer 38 in Experimental Example 10 indicates Rockwell hardness. Therefore, compared to at least Experimental Examples 9, 10, 13, 16, and 17 which do not satisfy the provisions of claim 2, Experimental Examples 11, 12, 14, and 15 which satisfy the provisions of claim 2 are superior in high initial velocity area, launch angle, backspin, durability, hitting feel, and total score.

[0059] (Condition 3: Figure 14 / Experimental Examples 18-21) Among experimental examples 18-21, experimental examples 18 and 19 satisfy the provisions of claim 1, but do not satisfy the provision regarding the thickness of the second layer 38 among the provisions of claim 4 (thicknesses of the first layer 36, the second layer 38, and the third layer 40), and are therefore outside the scope of the present invention. The remaining experimental examples 20 and 21 satisfy the provisions of claim 1 and at least the provisions of claim 4. Therefore, compared to Experimental Examples 18 and 19 which do not satisfy the provisions of claim 4, Experimental Examples 20 and 21 which satisfy the provisions of claim 4 are superior in high initial velocity area, launch angle, backspin, durability, hitting feel, and total score.

[0060] (Condition 4: Figure 15 / Experimental Examples 22-24) Experimental Examples 22-24 differ in head volume, and all of them satisfy the provisions of claims 1-4. Therefore, compared to Experimental Example 1, which is outside the scope of the present invention, Experimental Examples 22-24, which are within the scope of the present invention, are superior in high initial velocity area, launch angle, backspin, durability, hitting feel, and total score.

[0061] In the present embodiment, the golf club head is a hollow wood type golf club head (driver), but the present invention is of course also applicable to hollow utilities and fairway woods. [Explanation of symbols]

[0062] 100 Golf Club 10A, 10B, 10C, 10D Golf Club Heads 12A, 12B, 12C, 12D Head body 14 Face section 1402 Face surface 16 Crown section 18 Sole 20 Side section 22 Hollow part 24 Tou 26 Heels 28 Hosel 30 First face member 3002 Protrusion 32 Second face member 34 Face plate 3402 Protrusion 36 1st layer 38 2nd layer 40 3rd layer 4002 Thin section 4004 Recess 42 Elastic Adhesive 44A, 44B Epoxy Adhesive 46 Double-sided tape 48 Synthetic resin ring plate 49 Painting 50A, 50B, 50C Urethane sheet 52 First face member 5202 Protrusion 54 Second face member 56 Third face member 5602 Protrusion 58 Opening 60 Face Outer Part 62 Outer periphery plate 64 Projecting plate part 66 Inner plate 68 Bead receiving space B Bead 70 Gap 71 Painting 72 First face member 7202 1st face body 7204 First flange 74 Second face member 7402 2nd face body 7404 Second flange 76 Third face member 7602 3rd face body 7604 3rd flange 78 Opening 80 Bead storage space 82 Synthetic Resins 83 Painting

Claims

1. A golf club head having a hollow structure, at least a part of a face portion of which is composed of a first layer constituting a face surface, a second layer located on the opposite side of the first layer to the face surface, and a third layer located on the opposite side of the second layer to the first layer, When the tensile strengths of the first layer, the second layer, and the third layer are S1, S2, and S3, respectively, S3≧S1>S2. A golf club head comprising:

2. The hardness of the first layer is a durometer hardness of D75 or more and a Vickers hardness of HV520 or less, The hardness of the second layer is a durometer hardness of A10 or more and a durometer hardness of D60 or less, The hardness of the third layer is a durometer hardness of D85 or more and a Vickers hardness of HV520 or less.

2. The golf club head according to claim 1.

3. The first layer has a tensile modulus of elasticity of 8 GPa or more and 240 GPa or less, The second layer has a tensile modulus of elasticity of 0.5 MPa or more and 3000 MPa or less, The third layer has a tensile modulus of 10 GPa or more and 240 GPa or less.

2. The golf club head according to claim 1.

4. The thickness of the first layer is 0.1 to 1.5 mm or less, The thickness of the second layer is 0.1 mm or more and 1.0 mm or less, The thickness of the third layer is 2.0 mm or more and 5.0 mm or less.

2. The golf club head according to claim 1.

5. The first layer is made of any one of a metal material, a synthetic resin material, and a fiber-reinforced resin material, the second layer is made of any one of a double-sided tape, a synthetic resin material, and an elastic material; The third layer is made of any one of a metal material, a synthetic resin material, and a fiber-reinforced resin material.

2. The golf club head according to claim 1.

6. A thin portion that is thinner than other portions is formed in the third layer, the thin-walled portion is a recess formed in the first layer in an open manner on a front surface of the third layer facing the first layer, The second layer is disposed by filling the recess.

2. The golf club head according to claim 1.

7. the front surface of the third layer excluding the recess is superimposed on the first layer; 7. The golf club head according to claim 6.

8. The golf club head comprises a hollow head body including a face outer periphery having an opening except for the outer periphery of the face, and a crown portion, a sole portion, and a side portion connected to the outer periphery of the face, a plate-like third face member constituting the third layer is provided inside the outer periphery of the face and on the inner side of the head body, a plate-like second face member constituting the second layer is attached to the third face member on the inside of the face outer periphery; a plate-like first face member constituting the first layer is attached to the surface of the second face member on the inside of a face outer periphery; the third face member has an outer peripheral surface that is butted against an inner peripheral surface of a frame-shaped, plate-shaped mounting plate portion of the face outer peripheral portion and is attached by welding; a bead formed during the welding is accommodated in a bead accommodating space provided across an outer periphery of the third face member and an inner periphery of the mounting plate portion on a side away from the inside of the head body; the bead accommodating space is covered by the second face member and the first face member; 2. The golf club head according to claim 1.

9. the golf club head comprises a hollow head body having openings formed by removing the face portion, a portion of a crown portion near the face portion, a portion of a sole portion near the face portion, and a portion of a side portion near the face portion, a third face member constituting the third layer includes a third face body corresponding to the face portion, and a third flange protruding from an outer periphery of the third face body toward the head body, the second face member constituting the second layer includes a second face body that is attached by overlapping with the third face body, and a second flange that protrudes from an outer periphery of the second face body toward the head body and is attached by overlapping with the third flange, a portion of the crown portion near the opening, a portion of the sole portion near the opening, and a portion of the side portion near the face portion, the first face member constituting the first layer includes a first face body that is attached to the second face body by overlapping it, and a first flange that protrudes from an outer periphery of the first face body toward the head body and is attached to the second flange by overlapping it, a tip end surface of the third flange is butted against a tip end surface of the crown portion, a tip end surface of the sole portion, and a tip end surface of the side portion, which form the opening, and is attached by welding; a bead formed during the welding is accommodated in a bead accommodating space provided on a side away from the inside of the head body, the bead accommodating space being provided across an outer periphery of the third flange, an outer periphery of the crown portion, an outer periphery of the sole portion, and an outer periphery of the side portion; the bead accommodating space is covered by the second face member and the first face member; 2. The golf club head according to claim 1.

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