Golf club head

Abstract

The present invention achieves weight reduction, high strength, high rebound performance, an increase in a high initial velocity area, and a good feel when striking, while ensuring durability.　Provided is a golf club head 10A which has a hollow structure and in which a face part 14 is constituted by a face part body 30 and a fiber-reinforced resin layer 32 that has a structure with thickness variations, wherein the fiber-reinforced resin layer 32 is constituted by laminating a plurality of first fiber-reinforced resin unit layers 36 which are circular, elliptical, or polygonal in a manner such that the centroids thereof match with the center of the face part 14, and is formed such that the thickness of the fiber-reinforced resin layer 32 changes gradually with increasing distance from the center of the face part 14. The shape of fiber non-continuous parts changes smoothly, and the fiber non-continuous parts are distributed so as not to be concentrated. Thus, it is possible to ensure a long distribution distance of the fiber non-continuous parts, which is advantageous in preventing interlayer separation as compared to prior art.

Description

Golf club head

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

[0002] As shown in FIGS. 27(A) and (B), by laminating a plurality of elongated prepreg cut patterns (fiber reinforced resin layers) 2 in the shape of a strip in a plan view while shifting them in the circumferential direction over several tens of layers, a golf club head is proposed that includes a face portion having an uneven wall thickness structure where the center point of the face surface has the thickest wall thickness and the wall thickness becomes thinner as it moves away from the center point (see Patent Document 1). In FIG. 27(A), the fiber direction of the prepreg cut pattern 2 extends in the long direction of the prepreg cut pattern 2.

[0003] Japanese Patent No. 5363090

[0004] However, the above prior art has the following problems. The portion indicated by the broken line in FIG. 27(A) is a portion where the number of layers of the laminated prepreg cut patterns 2 changes. Specifically, it is a portion where the number of layers changes from 1 layer to 2 layers, from 2 layers to 3 layers, from 3 layers to 4 layers, and from 4 layers to 5 layers. As shown in FIG. 28, the portion where the number of layers of the prepreg cut pattern laminated in this way changes is a fiber discontinuity portion X. In the figure, reference numeral Y indicates a resin-rich portion formed by resin flowing into the voids generated between the layers in the vicinity of the fiber discontinuity portion X. When bending stress occurs, the fiber discontinuity portion X is likely to cause delamination Z between the laminated prepreg cut patterns. Further, in the above prior art, since it has a structure in which the elongated prepreg cut patterns 2 in the shape of a strip in a plan view are overlapped, the shape of the fiber discontinuity portion X in a plan view呈 a V shape that intersects at an acute angle, so that when bending stress occurs in the fiber discontinuity portion X, delamination Z is more likely to occur. Therefore, since delamination is likely to occur due to the bending stress generated in the face portion during hitting, it is disadvantageous in ensuring the durability of the face portion. The present invention has been made in view of the above circumstances, and its object is to provide a golf club head that is advantageous in obtaining weight reduction, high strength, high repulsion performance, expansion of the high initial velocity area, and good hitting feeling while ensuring durability.

[0005] To achieve the above objective, one embodiment of the present invention provides a hollow golf club head in which the face portion is composed of a face portion body and a fiber-reinforced resin layer having a variable thickness structure, wherein the fiber-reinforced resin layer is configured such that a plurality of circular, elliptical, or polygonal first fiber-reinforced resin unit layers are laminated with their centroids aligned with the center of the face portion, and the variable thickness structure is formed by arranging the plurality of first fiber-reinforced resin unit layers such that the thickness of the fiber-reinforced resin layer gradually changes as it moves away from the center of the face portion. Furthermore, one embodiment of the present invention is characterized in that a body opening is provided at the location of the face portion body located at the center of the face portion, the fiber-reinforced resin layer is provided at the body opening, the first fiber-reinforced resin unit layer forming the face surface of the face portion is formed as a fiber-reinforced resin unit layer for the face surface, the surface of the fiber-reinforced resin unit layer for the face surface is formed as a continuous surface with the surface of the face portion body surrounding the opening, the outer contour of the plurality of first fiber-reinforced resin unit layers is formed to become progressively smaller in size as it moves away from the fiber-reinforced resin unit layer for the face surface, the thickness of the fiber-reinforced resin layer is greatest at the center of the face portion, and the thickness of the fiber-reinforced resin layer is formed to become progressively smaller as it moves away from the center of the face portion. Furthermore, in one embodiment of the present invention, a fiber-reinforced resin layer receiving recess is provided at the center of the face portion body, the size of which matches the contour of the outer circumference of the fiber-reinforced resin layer, the center of the face portion is the deepest, and the depth gradually decreases as it moves away from the center of the face portion, the fiber-reinforced resin layer is arranged in the fiber-reinforced resin layer receiving recess, the surface of the first fiber-reinforced resin unit layer forming the face surface of the face portion is formed as a continuous surface with the face surface of the face portion body surrounding the fiber-reinforced resin layer receiving recess, the thickness of the fiber-reinforced resin layer is greatest at the center of the face portion, and the thickness of the fiber-reinforced resin layer gradually decreases as it moves away from the center of the face portion.Furthermore, in one embodiment of the present invention, a body opening is provided at the location of the face portion body located at the center of the face portion, the fiber-reinforced resin layer is provided at the body opening, and among the plurality of laminated first fiber-reinforced resin unit layers, the first fiber-reinforced resin unit layer constituting the face surface of the face portion is designated as the fiber-reinforced resin unit layer for the face surface, the surface of the fiber-reinforced resin unit layer for the face surface is formed as a surface continuous with the surface of the face portion body around the body opening, the remaining first fiber-reinforced resin unit layer laminated on the fiber-reinforced resin unit layer for the face surface has the same outer contour as the fiber-reinforced resin unit layer for the face surface, and a unit layer opening is provided around the centroid of the first fiber-reinforced resin unit layer, the unit layer opening is formed such that it gradually increases as the remaining first fiber-reinforced resin unit layer moves away from the fiber-reinforced resin unit layer for the face surface, the thickness of the fiber-reinforced resin layer is smallest at the center of the face portion, and the thickness of the fiber-reinforced resin layer gradually increases as it moves away from the center of the face portion.Furthermore, in one embodiment of the present invention, a fiber-reinforced resin layer receiving recess is provided at the center of the face portion body, the size of which matches the contour of the outer circumference of the fiber-reinforced resin layer, the shallowest at the center of the face portion, and the depth gradually increases as it moves away from the center of the face portion, the fiber-reinforced resin layer is arranged in the fiber-reinforced resin layer receiving recess, and if the first fiber-reinforced resin unit layer constituting the face surface of the face portion is designated as the fiber-reinforced resin unit layer for the face surface, the surface of the fiber-reinforced resin unit layer for the face surface is the area around the opening of the main body The remaining first fiber-reinforced resin unit layer, which is formed on a surface continuous with the face surface of the face portion body and laminated on the fiber-reinforced resin unit layer for the face surface, has the same outer contour as the fiber-reinforced resin unit layer for the face surface, and a unit layer opening is provided at the centroid of the first fiber-reinforced resin unit layer, and the unit layer opening is formed to gradually increase in size as it moves away from the fiber-reinforced resin unit layer for the face surface, and the thickness of the fiber-reinforced resin layer is formed to be smallest at the center of the face portion, and the thickness of the fiber-reinforced resin layer is formed to gradually increase as it moves away from the center of the face portion. Furthermore, in one embodiment of the present invention, the fiber-reinforced resin layer is composed of a plurality of second fiber-reinforced resin unit layers of the same shape, such as circular, elliptical, or polygonal, and the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately. Furthermore, in one embodiment of the present invention, the fiber-reinforced resin layer is composed of a plurality of second fiber-reinforced resin unit layers of the same shape, such as circular, elliptical, or polygonal, the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately, and when a virtual axis passing through the center of the thickness of the fiber-reinforced resin layer and extending in a direction perpendicular to the thickness is defined as the neutral axis, the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately in the thickness direction with respect to the neutral axis, so that the fiber-reinforced resin layer is formed on both sides of the thickness direction of the neutral axis, and the first fiber-reinforced resin unit layer arranged in symmetrical positions with respect to the neutral axis is formed in the same shape.Furthermore, in one embodiment of the present invention, the fiber-reinforced resin layer is composed of a plurality of second fiber-reinforced resin unit layers of the same shape, such as circular, elliptical, or polygonal, the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately, and when a virtual axis passing through the center of the thickness of the fiber-reinforced resin layer and extending in a direction perpendicular to the thickness is defined as the neutral axis, the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately in the thickness direction with respect to the neutral axis, forming the fiber-reinforced resin layer on both sides of the thickness direction of the neutral axis, and the first fiber-reinforced resin unit layer, which is arranged in a symmetrical position across the neutral axis, is formed in a different shape. Furthermore, in one embodiment of the present invention, the fiber-reinforced resin layer constitutes a pseudo-isotropic lamination. Furthermore, in one embodiment of the present invention, an outermost layer made of metal, synthetic resin, or paint is provided extending from the surface of the face portion body to the surface of the fiber-reinforced resin layer, wherein the thickness of the outermost layer is 0.2 mm to 1.0 mm in the case of metal, and 50 μm to 500 μm in the case of synthetic resin or paint. Furthermore, in one embodiment of the present invention, the plurality of first fiber-reinforced resin unit layers constituting the fiber-reinforced resin layer are characterized in that their contour dimensions gradually differ as the lamination direction progresses. Furthermore, in one embodiment of the present invention, the plurality of first fiber-reinforced resin unit layers constituting the fiber-reinforced resin layer have contour shapes of the same dimensions, and among the plurality of first fiber-reinforced resin unit layers, the first fiber-reinforced resin unit layers other than the first fiber-reinforced resin unit layers constituting the face surface of the face portion are provided with openings around the centroid that gradually differ in size as the lamination direction progresses.

[0006] According to one embodiment of the present invention, the fiber-reinforced resin layer is constructed by laminating a plurality of circular, elliptical, or polygonal first fiber-reinforced resin unit layers with their centroids aligned with the center of the face portion, and the thickness of the fiber-reinforced resin layer is formed to gradually change as it moves away from the center of the face portion. Therefore, although discontinuous fiber portions are formed between adjacent laminated first fiber-reinforced resin unit layers, the shape of the fiber discontinuities changes smoothly and the fiber discontinuities are dispersed without concentrating, so a longer dispersion distance of the fiber discontinuities can be secured, which is advantageous in preventing delamination compared to conventional methods. As a result, it is possible to reduce the weight while ensuring the durability of the golf club head, and the variable thickness structure of the face portion is advantageous in ensuring the performance required of a golf club head, such as high strength, high rebound performance, expanded high initial velocity area, and good feel. Furthermore, if a fiber-reinforced resin layer is provided in the opening of the main body, and the outer contour of the first fiber-reinforced resin unit layer is formed to gradually decrease in size as it moves away from the fiber-reinforced resin unit layer for the face, and the thickness of the fiber-reinforced resin layer is formed to be greatest at the center of the face, and gradually decreases as it moves away from the center of the face, then the strength and bending rigidity near the center of the face are secured, which is advantageous in obtaining high rebound performance, and the strength and bending rigidity of the outer periphery of the face are suppressed, which is advantageous in expanding the high initial velocity area.Furthermore, a fiber-reinforced resin layer is provided at the opening of the main body, and the remaining first fiber-reinforced resin unit layer laminated on the fiber-reinforced resin unit layer for the face surface has the same outer contour as the fiber-reinforced resin unit layer for the face surface, and a unit layer opening is provided at the centroid of the first fiber-reinforced resin unit layer, and the unit layer opening is formed to gradually increase in size as it moves away from the fiber-reinforced resin unit layer for the face surface, and the thickness of the fiber-reinforced resin layer is smallest at the center of the face portion, which is advantageous in obtaining high rebound performance because the strength and bending rigidity at the center of the face portion are suppressed. Furthermore, if the fiber-reinforced resin layer is placed in the fiber-reinforced resin layer receiving recess, and the remaining first fiber-reinforced resin unit layer laminated on the fiber-reinforced resin unit layer for the face surface has the same outer contour as the fiber-reinforced resin unit layer for the face surface, and a unit layer opening is provided at the centroid of the first fiber-reinforced resin unit layer, and the unit layer opening is formed to gradually increase in size as it moves away from the fiber-reinforced resin unit layer for the face surface, and the thickness of the fiber-reinforced resin layer is smallest at the center of the face portion, the strength and bending rigidity at the center of the face portion are suppressed, which is advantageous in obtaining high rebound performance. In addition, if the fiber-reinforced resin layer is composed of a plurality of second fiber-reinforced resin unit layers of the same shape, such as circular, elliptical, or polygonal, and the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately, the fiber discontinuities formed between adjacent laminated first fiber-reinforced resin unit layers and second fiber-reinforced resin unit layers can be further dispersed, and a longer dispersion distance for the fiber discontinuities can be secured, which is advantageous in preventing delamination between layers. Furthermore, if the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are alternately arranged in the thickness direction with respect to the neutral axis, and fiber-reinforced resin layers are formed on both sides of the thickness direction of the neutral axis, and the first fiber-reinforced resin unit layers arranged symmetrically across the neutral axis are formed in the same shape, then the fiber discontinuities formed between adjacent laminated first fiber-reinforced resin unit layers and second fiber-reinforced resin unit layers can be more dispersed, and a longer dispersion distance for the fiber discontinuities can be secured, which is advantageous in preventing delamination.Furthermore, if the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are alternately arranged in the thickness direction with respect to the neutral axis, forming fiber-reinforced resin layers on both sides of the thickness direction of the neutral axis, and the first fiber-reinforced resin unit layers, which are positioned symmetrically across the neutral axis, are formed in different shapes, a longer dispersion distance for the fiber discontinuities can be secured, which is advantageous in preventing delamination. In addition, if the fiber-reinforced resin layer constitutes a pseudo-isotropic lamination, the fiber-reinforced resin layer constituting the face portion will have roughly the same strength in all directions, which is advantageous not only in improving the durability of the golf club head but also in ensuring the performance required for the golf club head. Furthermore, if an outermost layer made of metal, synthetic resin, or paint is provided across the surface of the face portion and the surface of the fiber-reinforced resin layer, and the thickness of the outermost layer is 0.2 mm to 1.0 mm in the case of metal, and 50 μm to 500 μm in the case of synthetic resin or paint, it is advantageous in ensuring the aesthetic design of the face portion and face surface of the golf club head while also improving durability.

[0007] This is a front view of the golf club head according to the first embodiment, seen from the front of the face. This is a cross-sectional view taken along line A-A in Figure 1. (A) is a view taken along arrow A in Figure 2, and (B) is a plan view showing a plurality of first fiber-reinforced resin unit layers constituting the fiber-reinforced resin layer. This is a cross-sectional view of the golf club head according to the second embodiment. This is a cross-sectional view of the golf club head according to the third embodiment. This is a plan view showing a plurality of first fiber-reinforced resin unit layers constituting the fiber-reinforced resin layer in the third embodiment. This is a cross-sectional view of the golf club head according to the fourth embodiment. This is an explanatory diagram showing the configuration of a fiber-reinforced resin layer in which a plurality of first fiber-reinforced resin unit layers and a second fiber-reinforced resin unit layer are laminated in the fifth embodiment. This is a plan view showing a plurality of first fiber-reinforced resin unit layers and a second fiber-reinforced resin unit layer in the fifth embodiment. This is an explanatory diagram showing the configuration of a fiber-reinforced resin layer in which a plurality of first fiber-reinforced resin unit layers and a second fiber-reinforced resin unit layer are laminated in the sixth embodiment. This is an explanatory diagram showing the configuration of a fiber-reinforced resin layer in which a plurality of first fiber-reinforced resin unit layers and a second fiber-reinforced resin unit layer are laminated in the seventh embodiment. This is a plan view showing a plurality of first fiber-reinforced resin unit layers and second fiber-reinforced resin unit layers in the seventh embodiment. This is a first explanatory diagram showing a method for defining the center point Pc of the face. This is a second explanatory diagram showing a method for defining the center point Pc of the face. This is a third explanatory diagram showing a method for defining the center point Pc of the face. This is a fourth explanatory diagram showing a method for defining the center point Pc of the face. This is a cross-sectional view of a golf club head showing the relationship between the center of gravity G0 of the golf club head and the center of gravity FG on the face. This is a front view of a golf club head explaining the definition of the contour line I of the face. This is a cross-sectional view of a golf club head explaining the definition of the contour line I of the face. This is a front view of a golf club head explaining the definition of the center point Pc of the face. This is a diagram showing the evaluation results of an experimental example under condition 1. This is an explanatory diagram of the fiber direction of the fiber-reinforced resin unit layer under condition 1. This is a diagram showing the evaluation results of an experimental example under condition 2. This is an explanatory diagram of the fiber direction of the fiber-reinforced resin unit layer under condition 2. This is a diagram showing the evaluation results of an experimental example under condition 3. This is an explanatory diagram of the fiber direction of the fiber-reinforced resin unit layer under condition 3.(A) is a schematic diagram showing the face portion of a conventional technology, which is composed of multiple elongated prepreg cut patterns arranged in a plan view, and (B) is a cross-sectional view of (A) along line B-B. This is an explanatory diagram of delamination that occurs at the fiber discontinuity.

[0008] (First Embodiment) First, the first embodiment will be described. As shown in Figures 1 and 2, in this embodiment, the golf club head 10A is a hollow-structured wood-type golf club head (driver). The golf club head 10A comprises a head body 12 and a hosel 28. The golf club head 10A is made of a metal material or a fiber-reinforced resin material (FRP), or a combination of a metal material and a fiber-reinforced resin material. As the metal material, one or more types such as stainless steel, maraging steel, pure titanium, titanium alloy, or aluminum alloy can be used. Examples of such titanium alloys include 6-4Ti and 8-1-1Ti, which are titanium alloys. As the fiber-reinforced resin material, carbon fiber reinforced resin material (CFRP) can be used. The head body 12 comprises a face 14, a crown 16, a sole 18, and a side 20. The head body 12 has a hollow structure in which the interior, surrounded by the face portion 14, crown portion 16, sole portion 18, and side portion 20, is a hollow portion 22 (see Figure 2). The face portion 14 has vertical height and extends horizontally.

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

[0010] (Definition of the center point Pc of the face surface 1402) Here, we will explain how to define the center of the face, or in other words, the center point Pc of the face surface 1402. The center point Pc of the face surface 1402 is the geometric center of the face surface 1402, and various conventionally known methods can be used to define the center point Pc, including the first definition method and the second definition method illustrated below.

[0011] [A] First method for defining the center point Pc of the face surface 1402: This is a method for defining the center point Pc when the boundary between the face surface 1402 and the other part of the golf club head 10A is clear, in other words, when the periphery of the face surface 1402 is defined by a ridge. In this case, the face surface 1402 is clearly defined. Figures 13 to 16 are explanatory diagrams showing the method for defining the center point Pc of the face surface 1402.

[0012] (1) First, as shown in Figure 13, the golf club head 10A is placed on the horizontal plane HP so that the lie angle and face angle are set to the specified values. The state of the golf club head 10A at this time is considered the reference state. The set values ​​for the lie angle and face angle are, for example, the values ​​listed in the product catalog.

[0013] (2) Next, we determine the provisional center point c0 in the direction connecting the crown portion 16 and the sole portion 18. That is, as shown in Figure 13, draw a perpendicular line f0 that intersects with the approximate center point of the line parallel to the horizontal plane HP connecting the toe 24 and the heel 26 (hereinafter referred to as the horizontal line). The provisional center point c0 is defined as the midpoint between point a0, where this perpendicular line f0 intersects with the upper edge of the face surface 1402, and point b0, where the perpendicular line f0 intersects with the lower edge of the face surface 1402.

[0014] (3) Next, draw a horizontal line g0 passing through the temporary center point c0 as shown in Figure 14. (4) Next, as shown in Figure 15, set the midpoint of point d0 where the horizontal line g0 intersects with the toe 24 side edge of the face surface 1402 and point e0 where the horizontal line g0 intersects with the heel 26 side edge of the face surface 1402 as the temporary center point c1.

[0015] (5) Next, as shown in Figure 16, draw a perpendicular line f1 passing through the provisional center point c1, and define the provisional center point c2 as the midpoint between point a1 where the perpendicular line f1 intersects with the upper edge of the face surface 1402 and point b1 where the perpendicular line f1 intersects with the lower edge of the face surface 1402. If the provisional center points c1 and c2 coincide, that point is defined as the center point Pc of the face surface 1402. If the provisional center points c1 and c2 do not coincide, repeat the procedure in (2) to (5). Since the face surface 1402 is a curved surface, when determining the midpoint of the horizontal line g0 and the midpoints of the perpendicular lines f0 and f1, the lengths of the horizontal line g0 and the perpendicular lines f0 and f1 shall be the lengths along the curved surface of the face surface 1402. The face center line CL is defined as a straight line that passes through the center point Pc and extends in a direction perpendicular to the toe-heel direction.

[0016] [B] Second method for defining the center point Pc of the face surface 1402: Next, we will explain the definition of the center point Pc when the periphery of the face surface 1402 is connected to another part of the golf club head 10A by a curved surface and the face surface 1402 cannot be clearly defined.

[0017] As shown in Figure 17, the golf club head 10A is hollow, the symbol G0 indicates the center of gravity of the golf club head 10A, and the symbol Lp is the straight line connecting the center of gravity G0 and the center of gravity FG on the face. In other words, the straight line Lp is the perpendicular to the face 1402 passing through the center of gravity G0. That is, the center of gravity FG on the face is the point obtained by projecting the center of gravity G0 of the golf club head 10A onto the face 1402. Now, as shown in Figure 18, consider a number of planes H1, H2, H3, ..., Hn that include the straight line Lp connecting the center of gravity G0 and the center of gravity FG on the face.

[0018] When the golf club head 10A is fractured along each of the planes H1, H2, H3, ..., Hn, the radius of curvature r0 of the outer surface of the golf club head 10A is measured in the cross-section, as shown in Figure 19. When measuring the radius of curvature r0, it is assumed that there are no face lines, punch marks, etc. on the face surface 1402. The radius of curvature r0 is measured continuously from the center point Pc of the face surface 1402 outward (upward and downward in Figure 19). The portion where the radius of curvature r0 first falls below a predetermined value is defined as the contour line I representing the periphery of the face surface 1402. The predetermined value is, for example, 200 mm. The region enclosed by the contour line I determined based on the numerous planes H1, H2, H3, ..., Hn is defined as the face surface 1402, as shown in Figures 18 and 19.

[0019] Next, as shown in Figure 20, the golf club head 10A is placed on a horizontal surface (horizontal plane HP) such that the lie angle and face angle are set to the specified values. The straight line LT extends vertically, passing through the toe-side point PT of the face surface 1402. The straight line LH extends vertically, passing through the heel-side point PH of the face surface 1402. The straight line LC is parallel to the straight lines LT and LH. The distance between the straight line LC and the straight line LT is equal to the distance between the straight line LC and the straight line LH. The symbol Pu indicates the upper point of the face surface 1402, and the symbol Pd indicates the lower point of the face surface 1402. Both the upper point Pu and the lower point Pd are intersections of the straight line LC and the contour line I. The center point Pc is defined as the midpoint of the line segment connecting the upper point Pu and the lower point Pd.

[0020] As shown in Figures 1 and 2, the face portion 14 of the golf club head 10A is composed of a face portion body 30, which is the part of the head body 12 that constitutes the face portion 14, and a fiber-reinforced resin layer 32. In this embodiment, we will describe the case in which the fiber-reinforced resin constituting the fiber-reinforced resin layer 32 is made of carbon fiber reinforced resin (CFRP) using carbon fibers. As shown in Figure 2, a body opening 34 is provided at the location of the face portion body 30, which is located at the center of the face portion 14. The center of the face portion 14 is the same as the center point Pc of the face surface 1402 described above. The body opening 34 includes an inner circumferential surface 3402 formed along the contour of the fiber-reinforced resin layer 32, and an annular surface 3404 that is connected to the end of the inner circumferential surface 3402 on the hollow side and extends toward the center of the body opening 34 while extending along the end of the inner circumferential surface 3402.

[0021] As shown in Figures 3(A) and 3(B), the fiber-reinforced resin layer 32 is constructed by laminating multiple first fiber-reinforced resin unit layers 36, each having an elliptical shape with its longitudinal direction substantially aligned with the toe-heel direction and different dimensions of its outer contour, with their centroids (geometric centers) aligned with the center of the face portion 14. In this embodiment, in order to clarify the invention, the case in which there are eight first fiber-reinforced resin unit layers 36 will be described, but of course, the number of first fiber-reinforced resin unit layers 36 may be, for example, 30 or more or 50 or more. The shape of the multiple first fiber-reinforced resin unit layers 36 may be circular, polygonal, or a combination of different shapes.

[0022] The fiber-reinforced resin layer 32 can be broadly classified into UD (Uni-directional) material, i.e., unidirectional continuous fiber-reinforced material, in which the fibers are aligned in one direction, and cloth material, which is woven with warp and weft threads. In the first to fourth embodiments, the direction of the fibers is not particularly considered, and any material may be used as the first fiber-reinforced resin unit layer 36. Of course, a laminated structure (laminated configuration) that takes into account the "pseudo-isotropic lamination" described later is also acceptable.

[0023] Furthermore, the fiber-reinforced resin layer 32 may be molded by laminating a plurality of first fiber-reinforced resin unit layers 36, in other words, by laminating prepregs and heating and curing them in a mold, or by vacuum forming using a mold and a sheet, and various conventionally known molding methods can be used. As shown in Figures 3(A) and (B), the fiber-reinforced resin layer 32 is composed of a plurality of elliptical first fiber-reinforced resin unit layers 36 with different dimensions of their outer contours, which are laminated so that their centroids coincide with the center of the face portion 14. The first fiber-reinforced resin unit layer 36 with the largest outer contour becomes the face surface fiber-reinforced resin unit layer 36A that forms the face surface 1402 of the face portion 14, and thereafter, as you move away from the face surface fiber-reinforced resin unit layer 36A, the outer contours of the first fiber-reinforced resin unit layers 36 gradually become smaller. In this way, eight layers of first fiber-reinforced resin unit layers 36 are laminated to obtain the fiber-reinforced resin layer 32. Therefore, the thickness of the fiber-reinforced resin layer 32 is greatest at the center of the face portion 14 (center point Pc of the face surface 1402), and the thickness of the fiber-reinforced resin layer 32 gradually decreases as it moves away from the center of the face portion 14.

[0024] The surface constituting the face surface 1402 of the fiber-reinforced resin unit layer 36A for the face surface is defined as the surface 3202 of the fiber-reinforced resin layer 32, the surface of the first fiber-reinforced resin unit layer 36 furthest from the fiber-reinforced resin unit layer 36 for the face surface facing in the opposite direction from the surface 3202 is defined as the back surface 3204 of the fiber-reinforced resin layer 32, and the surface connecting the surface 3202 and the back surface 3204 is defined as the outer peripheral surface 3206 of the fiber-reinforced resin layer 32. The fiber-reinforced resin layer 32 is inserted into the main body opening 34, and the outer peripheral surface 3206 and the outer peripheral portion of the back surface 3204 are bonded to the inner peripheral surface 3402 and the annular surface 3404 of the main body opening 34 by an adhesive described later, thereby attaching it to the face part body 30.

[0025] With the fiber-reinforced resin layer 32 attached to the main body opening 34, the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface is continuous with the surface 3002 of the face portion body 30 surrounding the main body opening 34, and the face surface 1402 is formed by the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface and the surface 3002 of the face portion body 30. Therefore, the surface 3202 of the fiber-reinforced resin layer 32 is a slightly convex curved surface in front of the face surface 1402 that is continuous with the surface 3002 of the face portion body 30 surrounding the main body opening 34, and the back surface 3204 of the fiber-reinforced resin layer 32 is a convex curved surface in the face-back direction. In addition, most of the face portion 14, including the central part, is composed only of the fiber-reinforced resin layer 32, and the remaining part of the face portion 14 is composed of the face portion body 30 (metal material in this embodiment). Therefore, in the first embodiment, the fiber-reinforced resin layer 32 constitutes the uneven thickness structure of the face portion 14. Of course, a variable thickness structure can also be achieved by combining fiber-reinforced resin layers other than the eight layers mentioned above, and the variable thickness structure of the face portion 14 may be constructed by a laminated structure (lamination configuration) that takes into account the "pseudo-isotropic lamination" described later.

[0026] Next, the adhesive will be described. In this embodiment, the adhesive is a thermosetting adhesive that is liquid and hardens when heated. Other types of adhesives, such as thermoplastic hot melts, may also be used. The hardness of the hardened adhesive at 25°C is Shore A 40 to 95. The tanδ of the hardened adhesive from 25°C to 80°C is 0.05 to 0.4. If the hardness and tanδ of the hardened adhesive are within the above range, it is advantageous in suppressing variations in the high initial velocity area, flight distance, and durability, which will be described later. If the hardness and tanδ of the hardened adhesive are outside the above range, the above effects will decrease. For example, the following can be used as the adhesive. For heat-curing adhesives: - Bond MOS8 (product name), an elastic epoxy resin adhesive from Konishi Corporation - Cemedyne EP001K (product name), an epoxy-modified silicone elastic adhesive from Cemedyne Corporation - ThreeBond 3953 (product name), a two-component, room-temperature curing strong adhesive from ThreeBond Corporation - Sekisui Bond #55 (product name), from Sekisui Fuller Co., Ltd. For thermoplastic adhesives, which are hot melt adhesives: - FIXELON (product name), from Icello Co., Ltd. - Metaseal (product name), from Fujimori Kogyo Co., Ltd.

[0027] In the case of thermosetting, the adhesive may contain a silyl group-terminated polymer and an organometallic catalyst necessary for the silyl groups to form a crosslinked structure through a condensation reaction. Furthermore, the silyl group-terminated polymer may have terminal groups represented by structural formula 1, and may contain an average of 1.5 to 3 such terminal groups per polymer molecule.

[0028]

[0029] (However, n=2 or 3, n+m=3, R:CH) ３ -, C ２ H ５ -, C ３ H ９ (Includes at least one of the above.) The adhesive may also contain an amine catalyst necessary for the epoxy resin and epoxy resin to crosslink together through an addition reaction, along with the silyl group-terminated polymer.

[0030] According to this embodiment, in a hollow golf club head 10A in which the face portion 14 is composed of a face portion body 30 and a fiber-reinforced resin layer 32 having a variable thickness structure, the fiber-reinforced resin layer 32 is constructed by laminating a plurality of circular, elliptical, or polygonal first fiber-reinforced resin unit layers 36 with their centroids aligned with the center of the face portion 14, and the thickness of the fiber-reinforced resin layer 32 is formed to gradually change as it moves away from the center of the face portion 14. Therefore, as shown in Figure 3(A), although discontinuous fiber portions are formed between adjacent laminated first fiber-reinforced resin unit layers 36, compared to the conventional structure in which elongated strip-shaped prepreg cut patterns are stacked, the shape of the fiber discontinuities changes smoothly and the fiber discontinuities are dispersed without concentrating, so that a longer dispersion distance of the fiber discontinuities can be secured, which is advantageous in preventing delamination compared to the conventional method. Therefore, while ensuring the durability of the golf club head 10A, it is possible to reduce its weight, and the variable thickness structure of the face portion 14 is advantageous in ensuring the performance required of the golf club head 10A, such as high strength, high rebound performance, expanded high initial velocity area, and good feel.

[0031] Furthermore, in this embodiment, the fiber-reinforced resin layer 32 is provided at the opening 34 of the face body 30, and the outer contour of the first fiber-reinforced resin unit layer 36 is formed to gradually decrease in size as it moves away from the fiber-reinforced resin unit layer 36A for the face surface, with the fiber-reinforced resin layer 32 being thickest at the center of the face 14, and the thickness of the fiber-reinforced resin layer 32 gradually decreasing as it moves away from the center of the face 14. Therefore, durability and bending rigidity are ensured near the center of the face 14, while the bending rigidity of the outer periphery of the face 14 is suppressed, which is advantageous in obtaining an expanded high-speed area. In addition, since most of the face 14 is composed of the fiber-reinforced resin layer 32, it is advantageous in achieving weight reduction compared to when the face 14 is composed only of metal material.

[0032] (Second Embodiment) Next, the golf club head 10B of the second embodiment will be described with reference to Figure 4. In the following embodiments, parts and components that are the same as in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted, while the differences will be described in detail. The second embodiment differs from the first embodiment in that the fiber-reinforced resin layer 32 is arranged in the fiber-reinforced resin layer receiving recess 38 rather than in the opening 34 provided in the face body 30, and is otherwise the same as the first embodiment.

[0033] Similar to the first embodiment, the fiber-reinforced resin layer 32 is formed such that the thickness of the fiber-reinforced resin layer 32 is greatest at the center of the face portion 14, and the thickness of the fiber-reinforced resin layer 32 gradually decreases as it moves away from the center of the face portion 14. Furthermore, similar to the first embodiment, the multiple first fiber-reinforced resin unit layers 36 have an elliptical shape with their longitudinal direction substantially aligned with the toe-heel direction, and are laminated with their centroids aligned with the center of the face portion 14.

[0034] The fiber-reinforced resin layer receiving recess 38 is located at the center of the face portion body 30, and is sized to match the outer contour of the fiber-reinforced resin layer 32. The recess is deepest at the center of the face portion 14 and gradually becomes shallower as it moves away from the center of the face portion 14. The fiber-reinforced resin layer receiving recess 38 has a bottom surface 3802 that faces the back surface 3204 of the fiber-reinforced resin layer 32, and an inner circumferential surface 3804 that rises from the outer circumference of the bottom surface 3802 and faces the outer circumferential surface 3206 of the fiber-reinforced resin layer 32. The fiber-reinforced resin layer 32 is placed in the fiber-reinforced resin layer receiving recess 38, and the back surface 3204 and outer circumferential surface 3206 of the fiber-reinforced resin layer 32 are bonded and attached to the bottom surface 3802 and inner circumferential surface 3804 of the fiber-reinforced resin layer receiving recess 38 using an adhesive similar to that of the first embodiment.

[0035] With the fiber-reinforced resin layer 32 attached to the fiber-reinforced resin layer receiving recess 38, the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface is continuous with the surface 3002 of the face body 30 surrounding the fiber-reinforced resin layer receiving recess 38, and the face surface 1402 is formed by the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface and the surface 3002 of the face body 30. Therefore, the surface 3202 of the fiber-reinforced resin layer 32 is a slightly convex curved surface in front of the face surface 1402 which is continuous with the surface 3002 of the face body 30 surrounding the fiber-reinforced resin layer receiving recess 38, and the back surface 3204 of the fiber-reinforced resin layer 32 is a convex curved surface in the face-back direction that matches the bottom surface 3802 of the fiber-reinforced resin layer receiving recess 38. Furthermore, the majority of the face portion 14, including the central portion, is composed of the fiber-reinforced resin layer 32 and the fiber-reinforced resin layer receiving recess 38 of the face portion body 30 (metal material in this embodiment), while the remaining portion of the face portion 14 is composed of the face portion body 30. Therefore, in the second embodiment, the uneven thickness structure of the face portion 14 is formed by the fiber-reinforced resin layer 32 and the fiber-reinforced resin layer receiving recess 38.

[0036] In this second embodiment, as in the first embodiment, the shape of the fiber discontinuities changes smoothly, and the fiber discontinuities are dispersed without concentrating. This allows for a longer dispersion distance of the fiber discontinuities, which is advantageous in preventing delamination compared to conventional designs, and thus advantageous in ensuring the durability of the golf club head 10B. Furthermore, as you move from the outer periphery of the face portion 14 towards the center, the proportion of the fiber-reinforced resin layer 32 in the thickness direction of the face portion 14 gradually increases. In other words, as you move from the outer periphery of the face portion 14 towards the center, the proportion of the face portion body 30 (metal material) in the thickness direction of the face portion 14 gradually decreases. This suppresses the strength and bending rigidity in the center of the face portion 14, which is advantageous in expanding the high initial velocity area. Of course, as in the first embodiment, a variable thickness structure is possible even if fiber-reinforced resin layers other than the eight layers are combined, and a laminated structure (laminated configuration) that considers the "pseudo-isotropic lamination" described later is also acceptable. Furthermore, in the second embodiment, since most of the face portion 14 is composed of the first fiber-reinforced resin unit layer 36 and the metal material of the face portion body 30, it is advantageous in terms of weight reduction compared to the case where the face portion 14 is composed only of metal material.

[0037] (Third Embodiment) Next, the golf club head 10C of the third embodiment will be described with reference to Figures 5 and 6. The third embodiment is a modification of the first embodiment, and the shape of the fiber-reinforced resin layer 32 is different from that of the first embodiment, but all other aspects are the same as the first embodiment. That is, as shown in Figure 6, the fiber-reinforced resin layer 32 is composed of a fiber-reinforced resin unit layer 36A for the face surface and a plurality of remaining first fiber-reinforced resin unit layers 36 laminated on the fiber-reinforced resin unit layer 36A for the face surface. In this embodiment, in order to clarify the invention, we will describe the case in which the fiber-reinforced resin layer 32 is composed of a total of 5 layers, consisting of one fiber-reinforced resin unit layer 36A for the face surface and four first fiber-reinforced resin unit layers 36, but of course the total number of layers may be, for example, 30 layers or more or 50 layers or more.

[0038] The remaining first fiber-reinforced resin unit layers 36, which are laminated onto the fiber-reinforced resin unit layer 36A for the face surface, have the same outer contour as the fiber-reinforced resin unit layer 36A for the face surface, and a unit layer opening 40 is provided at the centroid of the first fiber-reinforced resin unit layer 36. The unit layer opening 40 is formed to gradually increase in size as it moves away from the fiber-reinforced resin unit layer 36A for the face surface. In this way, the fiber-reinforced resin unit layer 32 is obtained by laminating the fiber-reinforced resin unit layer 36A for the face surface and the remaining multiple first fiber-reinforced resin unit layers 36 with their centroids aligned with the center of the face portion 14. The outer contours of the fiber-reinforced resin unit layer 36A for the face surface and the remaining multiple first fiber-reinforced resin unit layers 36 are elliptical, with their longitudinal direction substantially aligned with the toe-heel direction, and the contours of the unit layer openings 40 of the first fiber-reinforced resin unit layers 36 are also elliptical, with their longitudinal direction substantially aligned with the toe-heel direction. A shape other than an ellipse, such as one that matches the contour of the face surface 1402, is also acceptable. Therefore, as shown in Figure 5, the fiber-reinforced resin layer 32 is formed to be thinnest at the center of the face portion 14 (center point Pc of the face surface 1402), and the thickness of the fiber-reinforced resin layer 32 gradually increases as it moves away from the center of the face portion 14. The fiber-reinforced resin layer 32 is inserted into the main body opening 34, and its outer peripheral surface 3206 and the outer peripheral portion of the back surface 3204 are bonded to the inner peripheral surface 3402 and the annular surface 3404 of the main body opening 34 with an adhesive similar to that of the first embodiment, thereby attaching it to the face portion body 30.

[0039] Furthermore, with the fiber-reinforced resin layer 32 attached to the main body opening 34, the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface is continuous with the surface 3002 of the face part body 30 surrounding the main body opening 34, and the face surface 1402 is formed by the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface and the surface 3002 of the face part body 30. Therefore, the surface 3202 of the fiber-reinforced resin layer 32 is a slightly convex curved surface in front of the face surface 1402 which is continuous with the surface 3002 of the face part body 30 surrounding the main body opening 34, and the back surface 3204 of the fiber-reinforced resin layer 32 is a concave curved surface in the face-back direction. Also, most of the face part 14, including the central part, is made up of only the fiber-reinforced resin layer 32, and the remaining part of the face part 14 is made up of the face part body 30 (metal material in this embodiment). Therefore, in the third embodiment, the fiber-reinforced resin layer 32 constitutes the uneven thickness structure of the face portion 14.

[0040] In this third embodiment, as in the first embodiment, the shape of the fiber discontinuity changes smoothly, and the fiber discontinuity is dispersed without concentration. This allows for a longer dispersion distance of the fiber discontinuity, which is advantageous in preventing delamination compared to the conventional design. This ensures the durability of the golf club head 10C while reducing weight. Furthermore, the variable thickness structure of the face portion 14 is advantageous in ensuring the performance required of the golf club head 10C, such as high strength, high rebound performance, expanded high initial velocity area, and good feel. In addition, in the third embodiment, the thickness of the fiber-reinforced resin layer 32 is smallest at the center of the face portion 14, and the thickness of the fiber-reinforced resin layer 32 gradually increases as it moves away from the center of the face portion 14. Therefore, as the thickness of the fiber-reinforced resin layer 32 gradually decreases from the outer circumference of the face portion 14 towards the center, the strength of the center of the face portion 14 is ensured while bending rigidity is suppressed, which is advantageous in improving rebound performance. Furthermore, in the third embodiment, since the majority of the face portion 14 is composed of the first fiber-reinforced resin unit layer 36 and the metal material of the face portion body 30, it is advantageous in terms of weight reduction compared to the case where the face portion 14 is composed only of metal material.

[0041] (Fourth Embodiment) Next, the golf club head 10D of the fourth embodiment will be described with reference to FIG. 7. The fourth embodiment is different from the third embodiment in that the fiber reinforced resin layer 32 is disposed in the fiber reinforced resin layer housing recess 38 instead of the opening 34 provided in the face portion main body 30, and other points are the same as those of the third embodiment. Similar to the third embodiment shown in FIG. 6, the fiber reinforced resin layer 32 is formed such that the thickness of the fiber reinforced resin layer 32 at the center of the face portion 14 is the smallest, and the thickness of the fiber reinforced resin layer 32 gradually increases as the distance from the center of the face portion 14 increases. It is the same as in the third embodiment that the fiber reinforced resin layer 32 is obtained by laminating the face surface fiber reinforced resin unit layer 36A and the remaining plurality of first fiber reinforced resin unit layers 36 with their centroids aligned with the center of the face portion 14. Also, it is the same as in the third embodiment that the outer peripheral contour of the face surface fiber reinforced resin unit layer 36A and the remaining plurality of first fiber reinforced resin unit layers 36 and the contour of the unit layer opening 40 of the first fiber reinforced resin unit layer 36 are elliptical with the longitudinal direction substantially aligned with the toe-heel direction. Of course, a shape other than an ellipse that matches the contour of the face surface 1402 may also be used.

[0042] The fiber reinforced resin layer housing recess 38 is provided at a location of the face portion main body 30 located at the center of the face portion 14 with a size that matches the outer peripheral contour of the fiber reinforced resin layer 32, and the center of the face portion 14 is the shallowest, and the depth gradually increases as the distance from the center of the face portion 14 increases. The fiber reinforced resin layer 32 is disposed in the fiber reinforced resin layer housing recess 38, and the back surface 3204 and the outer peripheral surface 3206 of the fiber reinforced resin layer 32 are adhered and attached to the bottom surface 3802 and the inner peripheral surface 3804 of the fiber reinforced resin layer housing recess 38 by an adhesive similar to that in the first embodiment.

[0043] With the fiber-reinforced resin layer 32 attached to the fiber-reinforced resin layer receiving recess 38, the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface is continuous with the surface 3002 of the face body 30 surrounding the fiber-reinforced resin layer receiving recess 38, and the face surface 1402 is formed by the surface 3202 of the fiber-reinforced resin unit layer 36A for the face surface and the surface 3002 of the face body 30. Therefore, the surface 3202 of the fiber-reinforced resin layer 32 is a slightly convex curved surface in front of the face surface 1402 which is continuous with the surface 3002 of the face body 30 surrounding the fiber-reinforced resin layer receiving recess 38, and the back surface 3204 of the fiber-reinforced resin layer 32 is a concave curved surface in the face-back direction which matches the bottom surface 3802 of the fiber-reinforced resin layer receiving recess 38. Furthermore, the majority of the face portion 14, including the central portion, is composed of the fiber-reinforced resin layer 32 and the fiber-reinforced resin layer receiving recess 38 of the face portion body 30, while the remaining portion of the face portion 14 is composed of the face portion body 30 (a metal material in this embodiment). Therefore, in the fourth embodiment, the uneven thickness structure of the face portion 14 is formed by the fiber-reinforced resin layer 32 and the fiber-reinforced resin layer receiving recess 38.

[0044] In this fourth embodiment, as in the first embodiment, the shape of the fiber discontinuities changes smoothly, and the fiber discontinuities are dispersed without concentration. This allows for a longer dispersion distance of the fiber discontinuities, which is advantageous in preventing delamination compared to the conventional method, and thus advantageous in ensuring the durability of the golf club head 10D. Furthermore, as you move from the outer periphery of the face portion 14 towards the center, the proportion of the fiber-reinforced resin layer 32 in the thickness direction of the face portion 14 gradually decreases. In other words, as you move from the outer periphery of the face portion 14 towards the center, the proportion of the face portion body 30 (metal material) in the thickness direction of the face portion 14 gradually increases. This ensures strength near the outer periphery of the face portion 14 while suppressing bending rigidity, which is advantageous in expanding the high-speed area. In addition, in the fourth embodiment, since most of the face portion 14 is composed of the first fiber-reinforced resin unit layer 36 and the metal material of the face portion body 30, it is advantageous in reducing weight compared to the case where the face portion 14 is composed only of metal material.

[0045] (Fifth Embodiment) Next, the golf club head 10E of the fifth embodiment will be described with reference to FIGS. 8 and 9. Before that, the method of laminating the fiber reinforced resin will be described. When forming the fiber reinforced resin layer 32 by laminating the unidirectional continuous fiber reinforced material (UD material) in which the fibers described above are arranged in one direction, it is preferable that the fiber reinforced resin layer 32 becomes a pseudo-isotropic laminate. That is, the unidirectional continuous fiber reinforced material is an anisotropic material in which the strength in the fiber direction becomes strong and the strength in the direction orthogonal to the fiber direction becomes weak. Therefore, the strength depends on the fiber direction. On the other hand, when it is required that the face portion 14 has the same strength in any direction like a metal material, that is, an isotropic material, a pseudo-isotropic laminate in which unidirectional continuous fiber reinforced materials having different fiber directions are laminated can be adopted to pseudo-reproduce an isotropic material. Specifically, the pseudo-isotropic laminate means laminating the unidirectional continuous fiber reinforced material with different fiber directions, for example, 0 degrees, 90 degrees, 45 degrees, -45 degrees, 0 degrees, 90 degrees, 45 degrees, -45 degrees, 0 degrees... Note that the angles of the fiber direction are not limited to 0 degrees, 90 degrees, 45 degrees, and -45 degrees described above. In the fifth embodiment, by configuring the fiber reinforced resin layer 32 as a pseudo-isotropic laminate, the fiber reinforced resin layer 32 constituting the face portion 14 has the same strength in any direction.

[0046] In this invention, "the fiber-reinforced resin layer is composed of a pseudo-isotropic lamination" includes both cases: "the entire fiber-reinforced resin layer is composed of a pseudo-isotropic lamination," and "most of the fiber-reinforced resin layer is composed of a pseudo-isotropic lamination, and the remaining part of the fiber-reinforced resin layer is composed of a lamination structure that is not a pseudo-isotropic lamination" (in other words, "the fiber-reinforced resin layer is composed of a lamination structure similar to a pseudo-isotropic lamination"). In this invention, the case where "the entire fiber-reinforced resin layer is composed of a pseudo-isotropic lamination" is treated as preferable. The reason is that there is no deformation of the FRP (fiber-reinforced plastic) after heat curing. Without deformation, the thickness of the adhesive layer (adhesive layer) between the CFRP face (fiber-reinforced resin layer 32) and the body (face part main body 30) can be made uniform, and the occurrence of unevenness and steps at the boundary between the body and the face can be reduced.

[0047] In the fifth embodiment, the fiber-reinforced resin layer 32 is composed of a plurality of first fiber-reinforced resin unit layers 36, plus a plurality of second fiber-reinforced resin unit layers 42 that are circular, elliptical, or polygonal and have the same shape (in other words, the same dimensions of the outer contour). Figure 8 is a schematic cross-sectional view showing the stacked state of the plurality of first fiber-reinforced resin unit layers 36 and the plurality of second fiber-reinforced resin unit layers 42 that constitute the fiber-reinforced resin layer 32, and Figure 9 is a plan view showing the fiber direction of the plurality of first fiber-reinforced resin unit layers 36 and the plurality of second fiber-reinforced resin unit layers 42 that constitute the fiber-reinforced resin layer 32, indicated by arrows.

[0048] As shown in Figure 8, first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 are arranged alternately. A virtual axis passing through the center of the thickness of the fiber-reinforced resin layer 32 and extending in a direction perpendicular to the thickness is defined as the neutral axis NA. The neutral axis NA is the position where the stress generated inside the fiber-reinforced resin layer 32 is zero when a bending moment is applied to the fiber-reinforced resin layer 32. As shown in Figure 8, the first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 are arranged alternately in the thickness direction with the neutral axis NA as the center, so that fiber-reinforced resin layers 32 are formed on both sides of the thickness direction of the neutral axis NA. The first fiber-reinforced resin unit layers 36 arranged in symmetrical positions across the neutral axis NA are formed in the same shape. Furthermore, multiple first fiber-reinforced resin unit layers 36 and multiple second fiber-reinforced resin unit layers 42 are laminated with their centroids aligned with the center of the face portion 14.

[0049] Figure 9 shows the multiple first fiber-reinforced resin unit layers 36 and multiple second fiber-reinforced resin unit layers 42 that constitute one half of the fiber-reinforced resin layer 32 when it is divided into two halves around the neutral axis NA, arranged in order from those closest to the neutral axis NA to those furthest away. In Figure 9, the leftmost second fiber-reinforced resin unit layer 42 in the upper row is closest to the neutral axis NA in the lamination direction, and the first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 move further away from the neutral axis NA as you move to the right. Similarly, in the lower row, they are arranged sequentially from left to right. Note that in Figure 9, the rightmost second fiber-reinforced resin unit layer 42 in the lower row forms the face surface 1402 of the face portion 14, and is therefore formed as the fiber-reinforced resin unit layer 42A for the face surface. Although not shown in Figure 9, the multiple first fiber-reinforced resin unit layers 36 and multiple second fiber-reinforced resin unit layers 42 that constitute the other half of the fiber-reinforced resin layer 32 when it is divided into two halves along the neutral axis NA are arranged symmetrically with respect to the neutral axis NA as shown in Figure 9.

[0050] In the fifth embodiment, the dimensions of the outer contour of the first fiber-reinforced resin unit layer 36 are formed to gradually increase as it moves away from the neutral axis NA, while the second fiber-reinforced resin unit layer 42 has the same shape. Therefore, similar to the first embodiment, the thickness of the fiber-reinforced resin layer 32 is greatest at the center of the face portion 14, and the thickness of the fiber-reinforced resin layer 32 gradually decreases as it moves away from the center of the face portion 14.

[0051] Furthermore, the arrows drawn inside the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 in Figure 9 indicate the fiber direction of the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42. As shown in the upper left of Figure 9, there are four types of fiber directions: 0 degrees, 45 degrees, 90 degrees, and -45 degrees. The left side of Figure 8 shows the numerical values ​​indicating the angle of the fiber direction. As shown in Figure 8, the fiber direction of the second fiber-reinforced resin unit layer 42 on the side closer to the neutral axis NA is the same as the fiber direction of the first fiber-reinforced resin unit layer 36 laminated on this second fiber-reinforced resin unit layer 42 on the side further from the neutral axis NA. Then, as you move away from the neutral axis NA, the fiber directions of the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 change in the order of 0 degrees, 90 degrees, 45 degrees, -45 degrees, 0 degrees, 90 degrees, 45 degrees, -45 degrees, and 0 degrees. Furthermore, the fiber directions of the two first fiber-reinforced resin unit layers 36, which are positioned symmetrically across the neutral axis NA, are the same, and the fiber directions of the two second fiber-reinforced resin unit layers 42, which are positioned symmetrically across the neutral axis NA, are also the same. Note that the two second fiber-reinforced resin unit layers 42 adjacent to the neutral axis NA are directly laminated together without the first fiber-reinforced resin unit layer 36 acting as an intermediary.

[0052] In the fifth embodiment, the fiber-reinforced resin layer 32 can be provided in the main body opening 34 as in the first embodiment. In this case, the fiber-reinforced resin layer 32 constitutes the uneven thickness structure of the face portion 14, and the same effects as in the first embodiment are achieved. Furthermore, in the fifth embodiment, the fiber-reinforced resin layer 32 can be placed in the fiber-reinforced resin layer receiving recess 38 of the face portion body 30 as in the second embodiment. In this case, the fiber-reinforced resin layer 32 and the fiber-reinforced resin layer receiving recess 38 constitute the uneven thickness structure of the face portion 14, and the same effects as in the second embodiment are achieved.

[0053] Furthermore, in the fifth embodiment, the fiber-reinforced resin layer 32 is constructed by laminating a plurality of first fiber-reinforced resin unit layers 36, the dimensions of which gradually increase as they move away from the neutral axis NA, with a second fiber-reinforced resin unit layer 42 of the same shape. Therefore, the fiber discontinuities formed between adjacent laminated first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 can be dispersed more smoothly, and a longer dispersion distance for the fiber discontinuities can be secured, which is advantageous in preventing delamination. As a result, the durability of the golf club head 10E can be ensured while reducing weight, and the variable thickness structure of the face portion 14 is advantageous in ensuring the expansion of the high initial velocity area, which is one of the performances required for the golf club head 10E, such as high strength, high rebound performance, expanded high initial velocity area, and good feel. Furthermore, by laminating the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 with different fiber directions of 0 degrees, 90 degrees, 45 degrees, and -45 degrees, the fiber-reinforced resin layer 32 is constructed in a pseudo-isotropic lamination. As a result, the fiber-reinforced resin layer 32 constituting the face portion 14 has roughly the same strength in all directions, which is advantageous not only in increasing the durability of the golf club head 10E but also in ensuring the performance required for the golf club head 10E.

[0054] (Sixth Embodiment) Next, the sixth embodiment of the golf club head 10F will be described with reference to Figure 10. The sixth embodiment is a modification of the fifth embodiment. In the sixth embodiment, as in the fifth embodiment, the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 are arranged alternately, and the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 are arranged alternately in the thickness direction with respect to the neutral axis NA, so that fiber-reinforced resin layers 32 are formed on both sides of the thickness direction of the neutral axis NA. On the other hand, in the sixth embodiment, unlike the fifth embodiment, the two first fiber-reinforced resin unit layers 36 arranged in symmetrical positions with respect to the neutral axis NA are not the same shape but are formed in different shapes. In other words, the dimensions of the outer contours of the two first fiber-reinforced resin unit layers 36 arranged in symmetrical positions with respect to the neutral axis NA are different. Therefore, similar to the fifth embodiment, the fiber-reinforced resin layer 32 is formed such that the thickness of the fiber-reinforced resin layer 32 is greatest at the center of the face portion 14, and the thickness of the fiber-reinforced resin layer 32 gradually decreases as it moves away from the center of the face portion 14. In addition, the fiber directions of the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 are different, so that the fiber-reinforced resin layer 32 forms a pseudo-isotropic laminate.

[0055] In the sixth embodiment, the fiber-reinforced resin layer 32 may be provided in the main body opening 34 as in the first embodiment, or it may be placed in the fiber-reinforced resin layer receiving recess 38 of the face portion main body 30 as in the second embodiment, and the same effects as in the first and second embodiments will be achieved in each case. Furthermore, in the sixth embodiment, the fiber-reinforced resin layer 32 is constructed by laminating a plurality of first fiber-reinforced resin unit layers 36, the dimensions of which of the outer circumference contour gradually increase as they move away from the neutral axis NA, with a second fiber-reinforced resin unit layer 42 of the same shape, and the first fiber-reinforced resin unit layers 36, which are arranged in symmetrical positions across the neutral axis NA, are formed with different shapes. Therefore, the fiber discontinuities formed between adjacent laminated first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 can be dispersed more smoothly compared to the fifth embodiment, and a longer dispersion distance for the fiber discontinuities can be secured, which is more advantageous in preventing delamination. Therefore, while ensuring the durability of the golf club head 10F, weight reduction can be achieved, and the variable thickness structure of the face portion 14 is particularly advantageous in ensuring the expansion of the high initial velocity area, which is one of the performance requirements for the golf club head 10F, such as high strength, high rebound performance, expanded high initial velocity area, and good feel. Furthermore, since the fiber-reinforced resin unit layers are laminated in a pseudo-isotropic manner, the fiber-reinforced resin layer 32 constituting the face portion 14 has roughly the same strength in all directions, which is advantageous not only in increasing the durability of the golf club head 10F, but also in ensuring the performance requirements for the golf club head 10F.

[0056] (Seventh Embodiment) Next, the golf club head 10G of the seventh embodiment will be described with reference to Figures 11 and 12. The seventh embodiment is a modified version of the fifth embodiment, and the configuration of the first fiber-reinforced resin unit layer 36 differs from that of the fifth embodiment, among the plurality of first fiber-reinforced resin unit layers 36 and plurality of second fiber-reinforced resin unit layers 42. Figure 11 is a schematic cross-sectional view showing the laminated state of the plurality of first fiber-reinforced resin unit layers 36 and plurality of second fiber-reinforced resin unit layers 42 that constitute the fiber-reinforced resin layer 32, and Figure 12 is a plan view showing the fiber direction of the plurality of first fiber-reinforced resin unit layers 36 and plurality of second fiber-reinforced resin unit layers 42 that constitute the fiber-reinforced resin layer 32 with arrows.

[0057] Figure 12 shows the multiple first fiber-reinforced resin unit layers 36 and multiple second fiber-reinforced resin unit layers 42 that constitute one half of the fiber-reinforced resin layer 32 when it is divided into two halves along the neutral axis NA, arranged in order from those closest to the neutral axis NA to those furthest away. In the upper row of Figure 12, the leftmost second fiber-reinforced resin unit layer 42 is closest to the neutral axis NA in the lamination direction, and the first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 move further away from the neutral axis NA as you move to the right. Similarly, the middle and lower rows are arranged sequentially from left to right, and the rightmost second fiber-reinforced resin unit layer 42 in the lower row constitutes the fiber-reinforced resin unit layer 42A for the face surface. In other words, in the seventh embodiment, similar to the sixth embodiment, the fiber-reinforced resin layer 32 is composed of a plurality of second fiber-reinforced resin unit layers 42 of the same shape, which can be circular, elliptical, or polygonal, and the first fiber-reinforced resin unit layers 36 and the second fiber-reinforced resin unit layers 42 are arranged alternately. Although not shown in Figure 12, the plurality of first fiber-reinforced resin unit layers 36 and the plurality of second fiber-reinforced resin unit layers 42 that constitute the other half of the fiber-reinforced resin layer 32 when the fiber-reinforced resin layer 32 is divided into two halves along the neutral axis NA are arranged symmetrically with respect to Figure 12, with respect to the neutral axis NA.

[0058] As shown in Figures 11 and 12, the multiple second fiber-reinforced resin unit layers 42 are formed in the same shape (with the same dimensions of the outer contour) as in the sixth embodiment. Unlike the sixth embodiment, the multiple first fiber-reinforced resin unit layers 36 have the same dimensions of the outer contour as the second fiber-reinforced resin unit layers 42, and are provided with unit layer openings 40 similar to those in the third and fourth embodiments. That is, the first fiber-reinforced resin unit layers 36 have the same outer contour as the second fiber-reinforced resin unit layers 42, and the unit layer openings 40 are provided at the centroid of the first fiber-reinforced resin unit layers 36. The first fiber-reinforced resin unit layers 36 and the second fiber-reinforced resin unit layers 42 are stacked alternately, and the first fiber-reinforced resin unit layers 36 are arranged such that the dimensions of the unit layer openings 40 gradually increase as they move away from the neutral axis NA in the stacking direction. Furthermore, the two first fiber-reinforced resin unit layers 36, positioned symmetrically across the neutral axis NA, have the same shape; in other words, the dimensions of the unit layer openings 40 are identical.

[0059] Furthermore, the arrows drawn inside the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 in Figure 12 indicate the fiber direction of the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42, and there are four types of fiber directions: 0 degrees, 45 degrees, 90 degrees, and -45 degrees. As shown in the figure, the fiber direction of the second fiber-reinforced resin layer 32 on the side closer to the neutral axis NA is the same as the fiber direction of the first fiber-reinforced resin unit layer 36 laminated on the second fiber-reinforced resin layer 32 on the side further from the neutral axis NA. Then, as you move away from the neutral axis NA, the fiber directions of the first fiber-reinforced resin layer 32 and the second fiber-reinforced resin unit layer 42 change in the order of 0 degrees, 90 degrees, 45 degrees, -45 degrees, 0 degrees, 90 degrees, 45 degrees, -45 degrees, and 0 degrees. Furthermore, the fiber directions of the two first fiber-reinforced resin layers 32, which are positioned symmetrically across the neutral axis NA, are the same, and the fiber directions of the two second fiber-reinforced resin unit layers 42, which are positioned symmetrically across the neutral axis NA, are also the same. Note that the two second fiber-reinforced resin unit layers 42 closest to the neutral axis NA are directly laminated together without the interposition of the first fiber-reinforced resin unit layer 36.

[0060] A fiber-reinforced resin layer 32 is obtained by laminating multiple first fiber-reinforced resin unit layers 36 and multiple second fiber-reinforced resin unit layers 42 with their centroids aligned with the center of the face portion 14, and the fiber-reinforced resin layer 32 constitutes a pseudo-isotropic lamination. In this case, the second fiber-reinforced resin unit layer 42 that forms the face surface 1402 of the face portion 14 is formed as the fiber-reinforced resin unit layer 42A for the face surface. The fiber-reinforced resin layer 32 configured in this way is formed so that the thickness of the fiber-reinforced resin layer 32 is smallest at the center of the face portion 14, and the thickness of the fiber-reinforced resin layer 32 gradually increases as it moves away from the center of the face portion 14, similar to the third and fourth embodiments.

[0061] The fiber-reinforced resin layer 32 shown in the seventh embodiment can be provided in the main body opening 34 as in the third embodiment, in which case the fiber-reinforced resin layer 32 constitutes the uneven thickness structure of the face portion 14, and the same effects as in the third embodiment are achieved. Furthermore, the fiber-reinforced resin layer 32 shown in the seventh embodiment can be placed in the fiber-reinforced resin layer receiving recess 38 of the face portion body 30 as in the fourth embodiment, in which case the uneven thickness structure of the face portion 14 is constituted by the fiber-reinforced resin layer 32 and the fiber-reinforced resin layer receiving recess 38, and the same effects as in the fourth embodiment are achieved.

[0062] Furthermore, in the seventh embodiment, the fiber-reinforced resin layer 32 is constructed by laminating a second fiber-reinforced resin unit layer 42 of the same shape with a first fiber-reinforced resin unit layer 36 having the same outer contour dimensions as the second fiber-reinforced resin unit layer 42 but different unit layer opening dimensions 40. Therefore, the fiber discontinuities formed between the laminated adjacent first fiber-reinforced resin unit layers 36 and the second fiber-reinforced resin unit layer 42 can be dispersed more smoothly, and a longer dispersion distance for the fiber discontinuities can be secured, which is advantageous in preventing delamination. As a result, the durability of the golf club head 10G can be ensured while reducing weight, and the variable thickness structure of the face portion 14 is advantageous in ensuring the performance required of the golf club head 10G, such as high strength, high rebound performance, expanded high initial velocity area, and good feel. Furthermore, by laminating the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 with different fiber directions of 0 degrees, 90 degrees, 45 degrees, and -45 degrees, the fiber-reinforced resin layer 32 is laminated in a pseudo-isotropic manner. As a result, the fiber-reinforced resin layer 32 constituting the face portion 14 has roughly the same strength in all directions, which is advantageous not only in improving the durability of the golf club head 10G, but also in ensuring the performance required for the golf club head 10G.

[0063] In the seventh embodiment, the case was described in which the shapes of the two first fiber-reinforced resin unit layers 36, which are arranged symmetrically across the neutral axis NA, are identical (the dimensions of the unit layer openings 40 are identical). However, the shapes of the two first fiber-reinforced resin unit layers 36, which are arranged symmetrically across the neutral axis NA, may be made different (the dimensions of the unit layer openings 40 may be made different). In this case, the fiber discontinuities formed between the laminated adjacent first fiber-reinforced resin unit layers 36 and the second fiber-reinforced resin unit layer 42 can be dispersed more smoothly compared to the seventh embodiment, and a longer dispersion distance for the fiber discontinuities can be secured, which is advantageous in preventing delamination. Therefore, it is possible to reduce the weight while ensuring the durability of the golf club head, and the variable thickness structure of the face portion 14 is particularly advantageous in terms of improving rebound performance among the performances required of a golf club head, such as high strength, high rebound performance, expanded high initial velocity area, and good feel. Furthermore, since the fiber-reinforced resin layer 32 is laminated in a pseudo-isotropic manner, the fiber-reinforced resin layer 32 constituting the face portion 14 has roughly the same strength in all directions, which is advantageous not only in improving the durability of the golf club head, but also in ensuring the performance required for the golf club head 10G.

[0064] Furthermore, in each of the embodiments described above, an outermost layer may be provided that covers the surface 3002 of the face body 30 and the surface 3202 of the fiber-reinforced resin layer 32. Metal, synthetic resin, or paint can be used as the outermost layer. Providing such an outermost layer is advantageous in ensuring the aesthetic appeal of the face 14 and face surface 1402 of the golf club head, as well as improving durability. The thickness of the outermost layer is preferably 0.2 mm to 1.0 mm in the case of metal. The thickness of the outermost layer is preferably 50 μm to 500 μm in the case of synthetic resin or paint. In the case of metal materials, if the thickness of the outermost layer falls below the above range, the effect of ensuring the durability of the outermost layer and the indentation strength decrease; if it exceeds the above range, the effect of reducing the weight of the golf club head decreases. In the case of synthetic resin materials or paint, if the thickness of the outermost layer falls below the above range, the effect of ensuring the durability of the outermost layer decreases; if it exceeds the above range, the coating becomes too thick, reducing the effect of ensuring workability during painting.

[0065] Next, experimental examples of the present invention will be described. Figures 21 to 26 show the experimental results of the golf club heads 10A-10G (hereinafter simply referred to as golf club head 10) according to the present invention. A sample of golf club head 10 was prepared for each experimental example, and the following four evaluation items were measured to determine the index (evaluation score), and the total score of the four indices was also calculated.

[0066] (1) The number of hits required to cause deformation or damage to the face 1402 of a golf club head 10 fixed to a durable shaft was measured using an air cannon. The ball speed was set to 50 m / s. The point of impact was set to the center point Pc of the face 1402. The number of hits was then determined for each of the 20 samples and expressed as an index with the number of hits of the golf club head 10 in Experimental Example 1 set to 100. A higher index indicates higher durability and a better evaluation.

[0067] (2) Rebound performance (initial velocity) Rebound performance was evaluated by initial velocity. A golf club equipped with a hollow golf club head 10 was mounted on a swing robot, and a real-world test was conducted under the following conditions, and the average value of the initial velocity at 9 impact points was evaluated as an index. The index of Experimental Example 1, which corresponds to the comparative example, is set to 100, and a larger index indicates a faster initial velocity and a better evaluation. Head speed: 40 m / s There were a total of 9 impact points as follows, and the ball was struck 5 times at each impact point. The center point Pc of the face surface 1402, and 3 impact points on a straight line passing through the center point Pc and perpendicular to the face center line CL, 7 mm away from the center point Pc in the toe direction and 7 mm away in the heel direction. Three impact points: one point on the face center line CL 5 mm away from the center point Pc in the direction of the crown 16; and two points on a line passing through this point and perpendicular to the face center line CL, 5 mm above, 7 mm away from the above point in the toe direction and 7 mm away in the heel direction. Three impact points: one point on the face center line CL 5 mm away from the center point Pc in the direction of the sole 18; and two points on a line passing through this point and perpendicular to the face center line CL, 5 mm below, 7 mm away from the above point in the toe direction and 7 mm away in the heel direction.

[0068] (3) High initial velocity area 45 impact points Pi were set at equal intervals in the toe-heel direction and crown-sole direction, centered on the center point Pc of the face surface 1402. The golf club was swung at the 45 impact points Pi using a dedicated swing robot, and the initial velocity of the golf ball was measured using a measuring instrument. The head speed was set to 40 m / s. The initial velocity data from the 45 impact points was interpolated to determine the area of ​​the high initial velocity area on the face surface 1402 where the golf ball's maximum initial velocity is 98% or more. The data from impact points above the center point Pc (crown 16 side) and the data from impact points below the center point Pc (sole 18 side) were weighted more heavily to match the actual impact points used by golfers. The area of ​​the high initial velocity area was then determined for each of the 20 samples, and the results were shown as an index with the area of ​​the high initial velocity area of ​​the golf club head 10 in Experimental Example 1 set to 100. A larger index indicates a wider high initial velocity area and a better evaluation.

[0069] (4) Feel The feel of the club was evaluated by 50 golfers on a 10-point scale for the same sample. The average of the 50 evaluation scores was then calculated as the average feel score. The feel is expressed as an index with the average feel score of the 10 golf club heads in Experimental Example 1 set to 100. A higher index indicates a better feel and a higher evaluation.

[0070] (5) Total Score The total score was calculated by summing the four indices mentioned above: durability, high initial velocity area, rebound performance, and feel. The total score for Experimental Example 1, which corresponds to the comparative example, was set at 400, and a higher total score indicates a better evaluation.

[0071] The experimental conditions will now be described. Experimental Example 1 is a comparative example and corresponds to Japanese Patent Publication No. 5363090 mentioned in the background art. It is a hollow-type driver equipped with a face portion 14 having an uneven thickness structure in which multiple elongated prepreg cut patterns, which are strip-shaped in plan view, are stacked over several dozen layers while shifting in the circumferential direction, and the center of the face portion 14 is formed to be the thickest. Experimental Example 1 does not satisfy any of the provisions of claims 1-10 and is outside the scope of the present invention. The specifications of each part of Experimental Example 1 are as follows. The material of the head body 12 is a titanium alloy Ti-8Al-1Mo-1V. The material of the face portion 14 is a laminate of CFRP. Loft angle: 10.5° Lie angle: 59° Head mass: 200g Head volume: 460cc The elongated prepreg cut patterns consist of eight identical layers of the same shape and size, laminated at 45-degree intervals in the circumferential direction, with each layer having a thickness of 0.15mm. Therefore, the thickness of the CFRP constituting the face portion 14 is 1.2mm.

[0072] The golf club head 10 used in Experimental Example 2-17 is a hollow driver corresponding to the present invention, and shares the following specifications except for the parameters specified in each experimental example: Material of the head body 12: Titanium alloy Ti-8Al-1Mo-1V Loft angle: 10.5° Lie angle: 59° Head mass: 200g Head volume: 460cc

[0073] (Condition 1: Figures 21, 22 / Experimental Examples 2-5) As shown in Figure 21, under Condition 1, as defined in Claim 2 (First Embodiment, Figure 2), a fiber-reinforced resin layer 32, with a thicker center at the face portion 14, is arranged in the main body opening 34 of the face portion body 30. In Experimental Example 2, the outer contour shape of the fiber-reinforced resin layer 32 (first fiber-reinforced resin unit layer 36) is triangular, in Experimental Example 3, the contour shape is pentagonal, in Experimental Example 4, the contour shape is elliptical, and in Experimental Example 5, the contour shape of the first fiber-reinforced resin unit layer 36 is a combination of multiple shapes such as circles, hexagons, squares, and triangles. Furthermore, under Condition 1, in all of Experimental Examples 2-5, as shown in Figure 22, a total of 24 layers of first fiber-reinforced resin unit layers 36 are laminated with different fiber directions symmetrically with respect to the neutral axis NA, and the fiber-reinforced resin layer 32 is laminated in a pseudo-isotropic manner. In Figure 22, the numbers indicated as "Layer No." are assigned to multiple first fiber-reinforced resin unit layers 36 for convenience. Also, as shown in Figure 21, under condition 1, the dimensions of the contour of the first fiber-reinforced resin unit layer 36 increase as it moves away from the neutral axis NA, and the shapes (contour dimensions) of the two first fiber-reinforced resin unit layers 36 symmetrical with respect to the neutral axis NA are made different. As shown in Figure 21, experimental example 2-5, which satisfies the provisions of the present invention, is superior to experimental example 1, which does not satisfy the provisions of the present invention, in terms of durability, rebound performance, high initial velocity area, feel, and total score.

[0074] (Condition 2: Figures 23, 24 / Experimental Example 6-11) As shown in Figure 23, under Condition 2, a fiber-reinforced resin layer 32, formed with a thicker center at the face portion 14 as defined in Claim 3 (Second Embodiment: Figure 4), is arranged in the fiber-reinforced resin layer receiving recess 38 of the face portion body 30, and the fiber-reinforced resin layer 32 is constructed by alternately arranging a first fiber-reinforced resin unit layer 36 and a second fiber-reinforced resin unit layer 42 as defined in Claim 6. In Experimental Example 6-11, the outer contour shapes of the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42 are all elliptical, with the longitudinal direction substantially coinciding with the toe-heel direction. As shown in Figure 24, except for Experimental Examples 9 and 10, a total of 14 first fiber-reinforced resin unit layers 36 are laminated with different fiber directions symmetrically with respect to the neutral axis NA, and the fiber-reinforced resin layer 32 is laminated in a pseudo-isotropic manner. Note that in Figure 24, layer No. The numbers indicated are assigned for convenience to multiple first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42. In Experimental Example 7, the dimensions of the contour of the first fiber-reinforced resin unit layer 36 are made smaller as they move away from the neutral axis NA, while in Experimental Examples 6, 8-11, the dimensions of the contour of the first fiber-reinforced resin unit layer 36 are made larger as they move away from the neutral axis NA. In Experimental Example 9, one layer of the second fiber-reinforced resin unit layer 42 with a fiber direction of 90 degrees is omitted, and in Experimental Example 10, one layer of the second fiber-reinforced resin unit layer 42 with a fiber direction of 0 degrees is omitted. Therefore, in Experimental Examples 9 and 10, the majority of the fiber-reinforced resin layer 32 is composed of a pseudo-isotropic lamination, satisfying the provisions of claim 9 of the present invention, but differing from the other Experimental Examples 6-8 and 11 in that the fiber-reinforced resin layer 32 includes a laminated structure that is not a pseudo-isotropic lamination in part. Furthermore, in Experimental Example 8, the shapes of the two first fiber-reinforced resin unit layers 36 located symmetrically across the neutral axis NA are identical, while in the remaining Experimental Examples, the shapes of the two first fiber-reinforced resin unit layers 36 are different. As shown in Figure 23, although the effect of ensuring durability strength is slightly reduced in Experimental Examples 9 and 10 compared to the other Experimental Examples 6-8 and 11, Experimental Examples 6-11 are superior in durability strength, rebound performance, high initial velocity area, feel, and overall score compared to Experimental Example 1, which does not satisfy the provisions of the present invention.

[0075] (Condition 3: Figures 25, 26 / Experimental Examples 12-17) As shown in Figure 25, in Condition 3, a fiber-reinforced resin layer 32, formed with a thin center at the face portion 14 as defined in Claim 5 (Fourth Embodiment: Figures 6, 7), is placed in the fiber-reinforced resin layer receiving recess 38 of the face portion body 30, and the fiber-reinforced resin layer 32 is constructed by alternately arranging a first fiber-reinforced resin unit layer 36 and a second fiber-reinforced resin unit layer 42 as defined in Claims 7 and 8. As shown in Figure 26, except for experimental examples 15 and 16, a total of eight first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 are laminated with different fiber directions symmetrically with respect to the neutral axis NA, and the fiber-reinforced resin layer 32 is laminated in a pseudo-isotropic manner. Furthermore, in experimental examples 12-17, the contour shapes of the outer periphery of the first fiber-reinforced resin unit layer 36 and the second fiber-reinforced resin unit layer 42, and the contour shape of the unit layer opening 40 of the first fiber-reinforced resin unit layer 36, are all elliptical in shape, with the longitudinal direction substantially aligned with the toe-heel direction. Note that the numbers indicated by layer No. in Figure 26 are assigned to multiple first fiber-reinforced resin unit layers 36 and second fiber-reinforced resin unit layers 42 for convenience. In experimental example 13, the dimensions of the unit layer opening 40 of the first fiber-reinforced resin unit layer 36 are made smaller as they move away from the neutral axis NA, while in experimental examples 12, 14-17, the dimensions of the unit layer opening 40 of the first fiber-reinforced resin unit layer 36 are made larger as they move away from the neutral axis NA. Furthermore, in Experimental Example 14, the shapes (dimensions of the unit layer openings 40) of the two first fiber-reinforced resin unit layers 36 located symmetrically across the neutral axis NA are identical, while in the remaining Experimental Examples, the shapes (dimensions of the unit layer openings 40) of the two first fiber-reinforced resin unit layers 36 are different. In Experimental Example 15, one layer of the second fiber-reinforced resin unit layer 42 with a fiber direction of 90 degrees is omitted, and in Experimental Example 16, one layer of the second fiber-reinforced resin unit layer 42 with a fiber direction of 0 degrees is omitted. Therefore, in Experimental Examples 15 and 16, the majority of the fiber-reinforced resin layer 32 is composed of a pseudo-isotropic lamination, satisfying the provisions of the present invention, but they differ from the other Experimental Examples 12-14 and 17 in that the fiber-reinforced resin layer 32 includes a laminated structure that is not a pseudo-isotropic lamination in part.As shown in Figure 25, in experimental examples 15 and 16, the effect of ensuring durability strength is slightly reduced compared to the other experimental examples 12-14 and 17. However, experimental examples 12 and 17 are superior to experimental example 1, which does not satisfy the provisions of the present invention, in terms of durability strength, rebound performance, high initial velocity area, feel, and overall score.

[0076] As mentioned above, in condition 2 (experimental example 6-11), the proportion of the face portion body 30 (metal material) in the thickness direction of the face portion 14 gradually decreases as you move from the outer periphery of the face portion 14 towards the center. Therefore, compared to condition 3 (experimental example 12-17), the strength and bending rigidity in the center of the face portion 14 are suppressed, which is advantageous for obtaining high rebound performance. On the other hand, in condition 3 (experimental example 12-17), the proportion of the face portion body 30 (metal material) in the thickness direction of the face portion 14 gradually increases as you move from the outer periphery of the face portion 14 towards the center. Therefore, compared to condition 2 (experimental example 6-11), the strength and bending rigidity near the outer periphery of the face portion 14 are suppressed, which is advantageous for expanding the high initial velocity area.

[0077] In this embodiment, the case where the golf club head is a hollow wood-type golf club head (driver) has been described, but the present invention is of course also applicable to hollow utility clubs and fairway woods.

[0078] 100 Golf Club S Shaft 10A-10G Golf Club Head 12 Head Body 14 Face 1402 Face Surface 16 Crown 18 Sole 20 Side 22 Hollow 24 Toe 26 Heel 28 Hosel 30 Face Body 3002 Surface 32 Fiber-reinforced resin layer 3202 Surface 3204 Back 3206 Outer surface 34 Body opening 3402 Inner surface 4404 Annular surface 36 First fiber-reinforced resin layer 36A Fiber-reinforced resin unit layer for face 38 Fiber-reinforced resin layer housing recess 3802 Bottom surface 3804 Inner surface 40 Unit layer opening 42 Second fiber-reinforced resin unit layer 42A Fiber-reinforced resin unit layer for face NA Neutral axis 2 Prepreg cut pattern 4 Face area X Fiber discontinuity Y Resin-rich area Z Delamination

Claims

1. A hollow golf club head whose face is composed of a face body and a fiber-reinforced resin layer having a variable thickness structure, wherein the fiber-reinforced resin layer is configured such that a plurality of circular, elliptical, or polygonal first fiber-reinforced resin unit layers are stacked with their centroids aligned with the center of the face, and the variable thickness structure is formed by arranging the plurality of first fiber-reinforced resin unit layers such that the thickness of the fiber-reinforced resin layer gradually changes as it moves away from the center of the face.

2. A hollow golf club head according to claim 1, characterized in that a body opening is provided at the center of the face portion body, the fiber-reinforced resin layer is provided at the body opening, the first fiber-reinforced resin unit layer forming the face surface of the face portion is formed as a fiber-reinforced resin unit layer for the face surface, the surface of the fiber-reinforced resin unit layer for the face surface is formed as a continuous surface with the surface of the face portion body around the opening, the outer contours of the plurality of first fiber-reinforced resin unit layers are formed to become progressively smaller in dimension as they move away from the fiber-reinforced resin unit layer for the face surface, the thickness of the fiber-reinforced resin layer is greatest at the center of the face portion, and the thickness of the fiber-reinforced resin layer is formed to become progressively smaller as it moves away from the center of the face portion.

3. A hollow golf club head according to claim 1, characterized in that a fiber-reinforced resin layer receiving recess is provided at the center of the face portion body, the size of which matches the outer contour of the fiber-reinforced resin layer, the center of the face portion is the deepest, and the depth gradually decreases as it moves away from the center of the face portion, the fiber-reinforced resin layer is arranged in the fiber-reinforced resin layer receiving recess, the surface of the first fiber-reinforced resin unit layer forming the face surface of the face portion is formed as a continuous surface with the face surface of the face portion body surrounding the fiber-reinforced resin layer receiving recess, the thickness of the fiber-reinforced resin layer is greatest at the center of the face portion, and the thickness of the fiber-reinforced resin layer gradually decreases as it moves away from the center of the face portion.

4. A body opening is provided at the location of the face portion body located at the center of the face portion, the fiber-reinforced resin layer is provided at the body opening, and of the plurality of laminated first fiber-reinforced resin unit layers, the first fiber-reinforced resin unit layer constituting the face surface of the face portion is designated as the face surface fiber-reinforced resin unit layer, the surface of the face surface fiber-reinforced resin unit layer is formed as a continuous surface with the surface of the face portion body surrounding the body opening, the remaining first fiber-reinforced resin unit layers laminated on the face surface fiber-reinforced resin unit layer have the same outer contour as the face surface fiber-reinforced resin unit layer, and a unit layer opening is provided around the centroid of the first fiber-reinforced resin unit layer, the unit layer opening is formed such that it gradually increases as the remaining first fiber-reinforced resin unit layer moves away from the face surface fiber-reinforced resin unit layer, the thickness of the fiber-reinforced resin layer is smallest at the center of the face portion, and the thickness of the fiber-reinforced resin layer gradually increases as it moves away from the center of the face portion. A hollow golf club head as described in feature 1.

5. A fiber-reinforced resin layer receiving recess is provided at the center of the face portion body, the size of which matches the outer contour of the fiber-reinforced resin layer, the shallowest at the center of the face portion, and the depth gradually increases as it moves away from the center of the face portion, the fiber-reinforced resin layer is arranged in the fiber-reinforced resin layer receiving recess, and of the plurality of laminated first fiber-reinforced resin unit layers, the first fiber-reinforced resin unit layer constituting the face surface of the face portion is designated as the fiber-reinforced resin unit layer for the face surface, the surface of the fiber-reinforced resin unit layer for the face surface is formed as a surface continuous with the face surface of the face portion body around the opening of the body, the remaining first fiber-reinforced resin unit layers laminated on the fiber-reinforced resin unit layer for the face surface have the same outer contour as the fiber-reinforced resin unit layer for the face surface, and a unit layer opening is provided at the centroid of the first fiber-reinforced resin unit layer, the unit layer opening is formed to gradually increase in size as it moves away from the fiber-reinforced resin unit layer for the face surface, The hollow structure of the golf club head according to claim 1, characterized in that the thickness of the fiber-reinforced resin layer is smallest at the center of the face portion, and the thickness of the fiber-reinforced resin layer gradually increases as it moves away from the center of the face portion.

6. The hollow structure of a golf club head according to any one of claims 1 to 5, characterized in that the fiber-reinforced resin layer comprises a plurality of second fiber-reinforced resin unit layers of the same shape, which are circular, elliptical, or polygonal, and the first fiber-reinforced resin unit layer and the second fiber-reinforced resin unit layer are arranged alternately.

7. The hollow structure of a golf club head according to any one of claims 1 to 5, characterized in that the fiber-reinforced resin layer comprises a plurality of second fiber-reinforced resin unit layers of the same shape, which are circular, elliptical, or polygonal, the first fiber-reinforced resin unit layers and the second fiber-reinforced resin unit layers are arranged alternately, and when a virtual axis passing through the center of the thickness of the fiber-reinforced resin layer and extending in a direction perpendicular to the thickness is defined as the neutral axis, the first fiber-reinforced resin unit layers and the second fiber-reinforced resin unit layers are arranged alternately in the thickness direction with respect to the neutral axis, so that the fiber-reinforced resin layer is formed on both sides of the thickness direction of the neutral axis, and the first fiber-reinforced resin unit layers arranged in symmetrical positions across the neutral axis are formed in the same shape.

8. The hollow structure of a golf club head according to any one of claims 1 to 5, characterized in that the fiber-reinforced resin layer comprises a plurality of second fiber-reinforced resin unit layers of the same shape, which are circular, elliptical, or polygonal, the first fiber-reinforced resin unit layers and the second fiber-reinforced resin unit layers are arranged alternately, and when a virtual axis passing through the center of the thickness of the fiber-reinforced resin layer and extending in a direction perpendicular to the thickness is defined as the neutral axis, the first fiber-reinforced resin unit layers and the second fiber-reinforced resin unit layers are arranged alternately in the thickness direction with respect to the neutral axis, forming the fiber-reinforced resin layer on both sides of the thickness direction of the neutral axis, and the first fiber-reinforced resin unit layers arranged in symmetrical positions across the neutral axis are formed in different shapes.

9. The hollow structure of the golf club head according to claim 1, characterized in that the fiber-reinforced resin layer constitutes a pseudo-isotropic laminate.

10. A hollow golf club head according to claim 1, characterized in that an outermost layer made of metal, synthetic resin, or paint is provided extending over the surface of the face body and the surface of the fiber-reinforced resin layer, the thickness of the outermost layer being 0.2 mm or more and 1.0 mm or less in the case of metal, and 50 μm or more and 500 μm or less in the case of synthetic resin or paint.

11. The hollow structure of the golf club head according to claim 1, characterized in that the plurality of first fiber-reinforced resin unit layers constituting the fiber-reinforced resin layer have contour dimensions that gradually differ with respect to the lamination direction.

12. The hollow structure of a golf club head according to claim 1, characterized in that the plurality of first fiber-reinforced resin unit layers constituting the fiber-reinforced resin layer have the same contour shape, and among the plurality of first fiber-reinforced resin unit layers, the first fiber-reinforced resin unit layers other than the first fiber-reinforced resin unit layer constituting the face surface of the face portion have openings around the center of gravity that gradually change in size as the lamination direction progresses.

Images