Abstract:
Provided is a hollow golf club head capable of improving repulsion and degree of design freedom compared to the case where a golf club head is formed using only a single metallic material, by combining different kinds of materials as component materials of a face section. The face section of the hollow golf club head is made of a composite material in which metal and fiber-reinforced plastic are combined. For example, in the hollow golf club head comprising a plate member disposed on the face section, the plate member is partially made of fiber-reinforced plastic in a plane direction and the remainder of said plate member is made of metal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a golf club head having a hollow structure and, more specifically, to a hollow golf club head in which repulsion and degree of design freedom are improved compared to the case where the golf club head is formed using only a single metallic material, by combining different kinds of materials as component materials of the face section.  
         [0003]     2. Description of the Related Art  
         [0004]     In a metallic hollow golf club head, in general, a large weight proportion is placed in the sole section in order to keep the center of gravity low. However, recently, it has been required to increase the head volume as much as possible within a limited mass of the head. Thus, the margin of the weight for keeping the center of gravity low becomes small and the varsity of the possible form features becomes limited. Therefore, the center of gravity of the head cannot be maintained sufficiently low or deep. Further, in the conventional hollow golf club head, the repulsion of the face surface cannot be utilized to maximum.  
         [0005]     Japanese Patent No. 2764883, Japanese Patent Laid-Open No. 2000-229135, and Japanese Patent No. 2773009 disclose a golf club head formed by using a composite material in which different kinds of materials are combined. However, in the golf club head formed by using the material in which properties of the different kinds of materials are combined, the varsity of the possible form features and the repulsion are still insufficient.  
         [0006]     Also, Japanese Patent No. 3007840 discloses a hollow golf club head in which several plate members are laminated to be disposed on the face section and only peripheral portions of the plate members are bonded to a head body. In the hollow golf club head, plate members can mutually slide to allow displacement. Thus, by reducing the thickness of each plate member, it is possible to increase the deflection amount and improve repulsion while maintaining the strength based on the overall thickness of a plurality of plate members. However, in the golf club head in which pluralities of the plate members are laminated to be disposed on the face section, the weight is increased, so that the weight margin is decreased and the varsity of the possible form features becomes limited. Thus, it is difficult to keep the center of gravity low or deep. The repulsion of the head is also insufficient.  
       SUMMARY OF THE INVENTION  
       [0007]     An object of the present invention is to provide a hollow golf club head capable of improving repulsion and degree of design freedom compared to the case where the golf club head is formed using only a single metallic material, by combining different kinds of materials as component materials of the face section.  
         [0008]     In order to achieve the foregoing object, the hollow golf club head of the present invention in which a plate member is disposed on the face section is characterized in that the plate member is partially made of fiber-reinforced plastic in a plane direction and the remainder of the plate member is made of metal. More specifically, at least either the peripheral portion or the center portion is made of fiber-reinforced plastic over the entire thickness and the remainder of the plate member is made of metal.  
         [0009]     Further, in order to achieve the foregoing object, the hollow golf club head of the present invention in which a plate member is disposed on the face section is characterized in that the plate member is made of metal and a reinforcing member made of fiber-reinforced plastic is laminated to the back face of the plate member.  
         [0010]     As described, metal and fiber-reinforced plastic are combined as the component material of the face section so that weight of the face section can be reduced and a larger weight margin can be obtained. Accordingly, compared to the case where the face section is formed using only a single kind of metal, the degree of design freedom can be improved. As a result, the center of gravity of the head can be lowered and deepened. Also, by specifying the area to which the metal and the fiber-reinforced plastic are applied as described above, it enables to improve the repulsion of the head.  
         [0011]     Further, in order to achieve the foregoing object, the hollow golf club head of the present invention in which several laminated plate members are disposed on the face section and only the peripheral portions of the plate members are bonded to a head body is characterized in that at least one of the plate members is made of metal and the other members are made of fiber-reinforced plastic.  
         [0012]     Furthermore, in order to achieve the foregoing object, the hollow golf club head of the present invention in which several laminated plate members are disposed on the face section and only the peripheral portions of the plate members are bonded to the head body is characterized in that at least one of the plate members is partially made of fiber-reinforced plastic in a plane direction and the remainder of the plate members is made of metal. More specifically, at least either the peripheral portions or the center portions of the plate members are made of fiber-reinforced plastic over the entire thickness and the remainder of said plate members is made of metal.  
         [0013]     Further, in order to achieve the foregoing object, the hollow golf club head of the present invention in which a plurality of laminated plate members are disposed on the face section and only the peripheral portions of the plate members are bonded to a head body is characterized in that the plurality of the plate members are made of metal and a reinforcing member made of fiber-reinforced plastic is laminated to an opposing face of the plate members.  
         [0014]     Furthermore, in order to achieve the foregoing object, the hollow golf club head of the present invention in which a plurality of laminated plate members are disposed on the face section and only the peripheral portions of the plate members are bonded to a head body is characterized in that the plurality of the plate members are made of metal and a spacer made of fiber-reinforced plastic is interposed between the peripheral portions of the plate members.  
         [0015]     In the hollow golf club head in which a plurality of laminated plate members are disposed on the face section, metal and fiber-reinforced plastic are combined as the component material of the face section, so that weight of the face section can be reduced and a larger weight margin can be obtained. Accordingly, compared to the case where the face section is formed using only a single kind of metal, the degree of design freedom can be improved. As a result, the center of gravity of the head can be lowered and deepened. Also, the plurality of the plate members can be slid to be displaced from each other. Thus, by reducing the thickness of each plate member, it is possible to increase the deflection amount of the face section and improve the repulsion while maintaining the strength based on the overall thickness of a plurality of plate members.  
         [0016]     As for the metal to be used, two or more kinds of metals can be combined. As for the fiber-reinforced plastic to be used, two or more kinds of fiber-reinforced plastics can be combined. As the fiber-reinforced plastic, the one with the fiber having an elastic modulus of less than 27 ton/mm 2  or the one with the fiber having an elastic modulus of 27 ton/mm 2  or more can be appropriately selected according to the position of the face section so as to increase the rigidity in the peripheral portion of the face section than that of the center portion of the face section. Thereby, the face section can be easily deflected, so that the repulsion can be further improved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     FIGS.  1 ( a ) to  1 ( c ) show a golf club head according to the first embodiment of the present invention, in which  FIG. 1 ( a ) is a plan view,  FIG. 1 ( b ) is a front view, and  FIG. 1 ( c ) is a cross section taken along the line I-I;  
         [0018]     FIGS.  2 ( a ) to  2 ( c ) show a golf club head according to a second embodiment of the present invention, in which  FIG. 2 ( a ) is a plan view,  FIG. 2 ( b ) is a front view, and  FIG. 2 ( c ) is a cross section taken along the line II-II;  
         [0019]     FIGS.  3 ( a ) to  3 ( c ) show a golf club head according to a third embodiment of the present invention, in which  FIG. 3 ( a ) is a plan view,  FIG. 3 ( b ) is a front view, and  FIG. 3 ( c ) is a cross section taken along the line III-III;  
         [0020]     FIGS.  4 ( a ) to  4 ( c ) show a golf club head according to a fourth embodiment of the present invention, in which  FIG. 4 ( a ) is a plan view, FIG. 4( b ) is a front view, and  FIG. 4 ( c ) is a cross section taken along the line IV-IV;  
         [0021]     FIGS.  5 ( a ) to  5 ( c ) show a golf club head according to a fifth embodiment of the present invention, in which  FIG. 5 ( a ) is a plan view,  FIG. 5 ( b ) is a front view, and  FIG. 5 ( c ) is a cross section taken along the line V-V;  
         [0022]     FIGS.  6 ( a ) to  6 ( c ) show a golf club head according to a sixth embodiment of the present invention, in which  FIG. 6 ( a ) is a plan view,  FIG. 6 ( b ) is a front view, and  FIG. 6 ( c ) is a cross section taken along the line VI-VI;  
         [0023]     FIGS.  7 ( a ) to  7 ( c ) show a golf club head according to a seventh embodiment of the present invention, in which  FIG. 7 ( a ) is a plan view,  FIG. 7 ( b ) is a front view, and  FIG. 7 ( c ) is a cross section taken along the line VII-VII;  
         [0024]     FIGS.  8 ( a ) to  8 ( c ) show a golf club head according to en eighth embodiment of the present invention, in which  FIG. 8 ( a ) is a plan view,  FIG. 8 ( b ) is a front view, and  FIG. 8 ( c ) is a cross section taken along the line VIII-VIII;  
         [0025]     FIGS.  9 ( a ) to  9 ( c ) show a golf club head according to a ninth embodiment of the present invention, in which  FIG. 9 ( a ) is a plan view,  FIG. 9 ( b ) is a front view, and  FIG. 9 ( c ) is a cross section taken along the line IX-IX;  
         [0026]     FIGS.  10 ( a ) to  10 ( c ) show a golf club head according to a tenth embodiment of the present invention, in which  FIG. 10 ( a ) is a plan view,  FIG. 10 ( b ) is a front view, and  FIG. 10 ( c ) is a cross section taken along the line X-X; and  
         [0027]     FIGS.  11 ( a ) to  11 ( c ) show a golf club head according to an eleventh embodiment of the present invention, in which  FIG. 11 ( a ) is a plan view,  FIG. 11 ( b ) is a front view, and  FIG. 11 ( c ) is a cross section taken along the line XI-XI; 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Referring to the appended drawings, the configuration of the present invention will be described in detail below.  
         [0029]     FIGS.  1 ( a ) to  1 ( c ) show the golf club head according to the first embodiment of the present invention. As shown in FIGS.  1 ( a ) to  1 ( c ), the golf club head according to the present embodiment has a hollow structure, and a plate member  2  is disposed on the face section of a head body  1  thereof. A peripheral portion  2   a  of the plate member  2  is made of fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of less than 27 ton/mm 2  is used for the peripheral portion  2   a  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0030]     FIGS.  2 ( a ) to  2 ( c ) show the golf club head according to the second embodiment of the present invention. As shown in FIGS.  2 ( a ) to  2 ( c ), the golf clu b head according to the present embodiment has a hollow structure, and a plate member  2  is disposed on the face section of a head body  1  thereof. A center portion  2   b  of the plate member  2  is made of fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of 27 ton/mm 2  or more is used for the center portion  2   b  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0031]     FIGS.  3 ( a ) to  3 ( c ) show the golf club head according to the third embodiment of the present invention. As shown in FIGS.  3 ( a ) to  3 ( c ), the golf club head according to the present embodiment has a hollow structure, and a plate member  2  is disposed on the face section of a head body  1  thereof A peripheral portion  2   a  and a center portion  2   b  of the plate member  2  are made of fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of less than 27 ton/mm 2  is used for the peripheral portion  2   a  of the plate member  2 , while the fiber-reinforced plastic with the elastic modulus of fiber of 27 ton/mm 2  or more is used for the center portion  2   b  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0032]     FIGS.  4 ( a ) to  4 ( c ) show the golf club head according to the fourth embodiment of the present invention. As shown in FIGS.  4 ( a ) to  4 ( c ), the golf club head according to the present embodiment has a hollow structure, and a plate member  2  is disposed on the face section of a head body  1  thereof. The plate member  2  is made of metal as the other section of the head body  1  than the face section, and a reinforcing member  3 , which is made of fiber-reinforced plastic, is laminated to the back face thereof. Furthermore, the thickness of the plate member  2  is reduced compared to the conventional case with the addition of the reinforcing member  3 . In this case, the thickness of the reinforcing member  3  is increased gradually from the peripheral portion side of the face section towards the center thereof. As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0033]     In the first to fourth embodiments described above, the face section of the head body  1  is made of composite material of metal and fiber-reinforced plastic. Thus, the mass of the face section can be lightened and a larger weight margin can be obtained. Accordingly, compared to the case where the face section is formed using only a single kind of metal, the degree of design freedom can be improved. As a result, the center of gravity of the head can be lowered and deepened. Furthermore, by appropriately selecting the properties of the fiber-reinforced plastic, the center and the peripheral portion of the face section are provided with high rigidity and low rigidity respectively. Thereby, the face section can be easily deflected and the repulsion can be further improved.  
         [0034]     The fiber-reinforced plastic mentioned above includes those obtained by impregnating matrix resin such as epoxy resin, unsaturated polyester resin, vinyl ester resin or the like with reinforcing fiber such as carbon fiber, glass fiber, aramid fiber or the like. The fiber-reinforced plastic that uses carbon fiber as the reinforcing fiber is especially preferable. Further, titanium alloy, aluminum alloy, stainless steel or the like can be used alone or in combination for the metal mentioned above.  
         [0035]     FIGS.  5 ( a ) to  5 ( c ) show the golf club head according to the fifth embodiment of the present invention. As shown in FIGS.  5 ( a ) to  5 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . The outer plate member  2  is made of metal as the other section of the head body  1  than the face section, and the inner plate member  2  is made of fiber-reinforced plastic. In this case, the thickness of the plate member  2 , which is made of fiber-reinforced plastic, is increased gradually from the peripheral portion side of the face section towards the center thereof. As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0036]     FIGS.  6 ( a ) to  6 ( c ) show the golf club head according to the sixth embodiment of the present invention. As shown in FIGS.  6 ( a ) to  6 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . The peripheral portion  2   a  of each plate member  2  is made of the fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of less than 27 ton/mm 2  is used for the peripheral portion  2   a  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0037]     FIGS.  7 ( a ) to  7 ( c ) show the golf club head according to the seventh embodiment of the present invention. As shown in FIGS.  7 ( a ) to  7 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . The center portion  2   b  of each plate member  2  is made of the fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of 27 ton/mm 2  or more is used for the center portion  2   b  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0038]     FIGS.  8 ( a ) to  8 ( c ) show the golf club head according to the eighth embodiment of the present invention. As shown in FIGS.  8 ( a ) to  8 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . A peripheral portion  2   a  and a center portion  2   b  of the plate member  2  are made of fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of less than 27 ton/mm 2  is used for the peripheral portion  2   a  of the plate member  2 , and the fiber-reinforced plastic with the elastic modulus of fiber of 27 ton/mm 2  or more is used for the center portion  2   b  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively.  
         [0039]     FIGS.  9 ( a ) to  9 ( c ) show the golf club head according to the ninth embodiment of the present invention. As shown in FIGS.  9 ( a ) to  9 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . The plate members  2 ,  2  are made of metal as the other section of the head body  1  than the face section, and a reinforcing member  3 , which is made of fiber-reinforced plastic, is laminated to the opposing back thereof. In this case, the thickness of the reinforcing member  3  is increased gradually from the peripheral portion side of the face section towards the center. As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively. Furthermore, the thickness of the plate member  2  is reduced compared to the conventional case with the addition of the reinforcing member  3 .  
         [0040]     FIGS.  10 ( a ) to  10 ( c ) show the golf club head according to the tenth embodiment of the present invention. As shown in FIGS.  10 ( a ) to  10 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . The plate members  2 ,  2  are made of metal as the other section of the head body  1  than the face portion, and a spacer  4 , which is made of fiber-reinforced plastic, is inserted between the peripheral portions of the plate members. In other words, the metal spacer that is conventionally inserted between the peripheral portions of several plate members is replaced with the fiber-reinforced plastic spacer in the present embodiment.  
         [0041]     FIGS.  11 ( a ) to  11 ( c ) show the golf club head according to the eleventh embodiment of the present invention. As shown in FIGS.  11 ( a ) to  11 ( c ), the golf club head according to the present embodiment has a hollow structure, and several plate members  2 ,  2  are laminated and disposed on the face section of a head body  1  thereof. Only the peripheral portions of the plate members  2 ,  2  are unified with the head body  1 . The center portion  2   b  of each plate member  2  is made of fiber-reinforced plastic, and the remainder is made of metal as the other section of the head body  1  than the face section. In this case, the fiber-reinforced plastic with the elastic modulus of fiber of 27 ton/mm 2  or more is used for the center portion  2   b  of the plate member  2 . As a result, the center and the peripheral portion of the face section have high rigidity and low rigidity respectively. Furthermore, a spacer  4 , which is made of fiber-reinforced plastic, is inserted between the peripheral portions of the plate members  2 ,  2 .  
         [0042]     In the fifth to eleventh embodiments described above, the face section of the head body  1  is made of composite material of metal and fiber-reinforced plastic. Thus, the mass of the face section can be lightened and a larger weight margin can be obtained. Accordingly, compared to the case where the face section is formed using only a single kind of metal, the degree of design freedom can be improved. As a result, the center of gravity of the head can be lowered and deepened. Furthermore, by appropriately selecting the properties of the fiber-reinforced plastic, the center and the peripheral portion of the face section are provided with high rigidity and low rigidity respectively. Thereby, the face section can be easily deflected and the repulsion can be further improved.  
         [0043]     Furthermore, in the fifth to eleventh embodiments described above, a plurality of the plate members  2 ,  2  can be slid and displaced from each other by collision of the face section of the head body  1  and a ball, causing the deflection of these plate members  2 ,  2 . In such a case, the break strength of the face section is proportional to the overall thickness (including the reinforcing member  3 ) of a plurality of the plate members  2 ,  2 , realizing the setup of a sufficient strength based on the overall thickness thereof. Meanwhile, the deflection amount of the face section increases as each of the plate members  2 ,  2  becomes thinner. Thus, when the face section comprises the lamination of several plate members  2 ,  2  as described above, the repulsion can be improved while maintaining the sufficient strength. Therefore, it is possible to achieve a notable improvement in the repulsion due to multiplier effect together with the effect of improving the repulsion by using the composite material.  
         [0044]     The fiber-reinforced plastic mentioned above includes those obtained by impregnating matrix resin such as epoxy resin, unsaturated polyester resin, vinyl ester resin or the like with reinforcing fiber such as carbon fiber, glass fiber, aramid fiber or the like. The fiber-reinforced plastic that uses carbon fiber as the reinforcing fiber is especially preferable. Further, titanium alloy, aluminum alloy, stainless steel or the like can be used alone or in combination for the metal mentioned above.  
         [0045]     The preferred embodiments of the present invention are described above in detail; however, it should be understood that various modifications, replacements, and displacements may be made therein, as long as such modifications, replacements, and displacements fall within the true spirit and the scope of the present invention covered by the appended claims.  
       EXAMPLES  
       [0046]     First, an experiment regarding the first to fourth embodiments was carried out. The hollow golf club heads of comparative examples 1, 2 (conventional ones) in which the face sections were made of a single metallic material and that of examples 1 to 4 in which the face sections were made of a composite material of metal and fiber-reinforced plastic were fabricated, respectively. In table 1, “FRP” means the fiber-reinforced plastic, “below 27t” means that the fiber elasticity modulus is less than 27 ton/mm 2 , and “above 27t” means that the fiber elasticity modulus is 27 ton/mm 2  or more.  
         [0047]     The restitution coefficient and the degree of design freedom of the golf club heads were evaluated. The results are shown in table 1. The results of the evaluation are shown with the comparative example 1 being the index as 100. A larger index value of the restitution coefficient means the increased initial ball speed and the increased carry. The degree of design freedom is the weight margin when the overall mass of the head is constant and a larger index value of the varsity means a larger weight margin.  
                                                                                                       TABLE 1                                           Material of           Material of plate member of face section   reinforcing                    Center   Peripheral   Remainder   member of   Thickness of face   Repulsion   Degree of           Figure   portion   portion   portion   face section   section   coefficient   design freedom                        Comparative   —   Titanium   Titanium   Titanium   —   Uniform   100   100       example 1       alloy   alloy   alloy       Comparative   —   Titanium   Titanium   Titanium   —   Center -thick   105   106       example 2       alloy   alloy   alloy       Peripheral -thin       Example 1       FRP   Titanium   Titanium   —   Uniform   107   110               (above 27t)   alloy   alloy       Example 2       Titanium   Titanium   Titanium   FRP   Center-thick   109   115               alloy   alloy   alloy   (above 27t)   Peripheral-thin       Example 3       FRP   FRP   Titanium   —   Uniform   111   119               (above 27t)   (below 27t)   alloy       Example 4       FRP   FRP   Titanium   —   Center-thick   115   122               (above 27t)   (below 27t)   alloy       Peripheral-thin                  
 
         [0048]     As can be seen from table 1, all of the golf club heads of examples 1 to 4 exhibited a larger degree of design freedom and the restitution coefficient compared to comparative examples 1, 2.  
         [0049]     Next, an experiment regarding the fifth to eleventh embodiments was carried out. The hollow golf club head of comparative examples 11 (conventional one) in which the face section was made of a single metallic material and that of examples 11 to 17 in which the face sections were made of a composite material of metal and fiber-reinforced plastic were fabricated, respectively. In table 2, “SUS alloy” means stainless steel, “FRP” means the fiber-reinforced plastic, “below 27t” means that the fiber elasticity modulus is less than 27 ton/mm 2 , and “above 27t” means that the fiber elasticity modulus is 27 ton/mm 2  or more.  
         [0050]     The restitution coefficient and the degree of design freedom of the golf club heads were evaluated. The results are shown in table 2. The results of the evaluation are shown with the comparative example 11 being the index as 100. A larger index value of the restitution coefficient means the increased initial ball speed and the increased carry. The degree of design freedom is the weight margin when the overall mass of the head is constant and a larger index value of the varsity means a larger weight margin.  
                                                                                                                                               TABLE 2                                                   Materi-       Degree           Material of outer plate member of face   Material of inner plate member of face   Material of   al of   Repul-   of           section   section   reinforcing   spacer   sion   design                    Center   Peripheral   Remainder   Center   Peripheral   Remainder   member of   of face   coeffi-   free-           Figure   portion   portion   portion   portion   portion   portion   face section   section   cient   dom                        Comparative   —   Titanium   Titanium   Titanium   Titanium   Titanium   Titanium   —   Titanium   100   100       example 11       alloy   alloy   alloy   alloy   alloy   alloy       alloy       Example 11       Titanium   Titanium   Titanium   FRP   FRP   FRP   —   —   103   118               alloy   alloy   alloy   (above27t)   (below27t)   (below27)       Example 12       Titanium   Titanium   Titanium   Titanium   Titanium   Titanium   FRP   —   104   102               alloy   alloy   alloy   alloy   alloy   alloy   (above27t)       Example 13       FRP   Titanium   Titanium   FRP   Titanium   Titanium   —   —   106   105               (above27t)   alloy   alloy   (above27t)   alloy   alloy       Example 14       Titanium   FRP   Titanium   Titanium   FRP   Titanium   —   —   105   103               alloy   (below27t)   alloy   alloy   (below27t)   alloy       Example 15       FRP   FRP   Titanium   FRP   FRP   Titanium   —   —   108   106               (above27t)   (below27t)   alloy   (above27t)   (below27t)   alloy       Example 16       Titanium   Titanium   Titanium   Titanium   Titanium   Titanium   —   FRP (be-   109   103               alloy   alloy   alloy   alloy   alloy   alloy       low27t)       Example 17       FRP   Titanium   Titanium   FRP   SUS alloy   SUS alloy   —   FRP (be-   110   106               (above27t)   alloy   alloy   (above27t)               low27t)                  
 
         [0051]     As can be seen from table 2, all of the golf club head of examples 11 to 17 exhibited a larger degree of design freedom and the restitution coefficient compared to the comparative example 11.