Golf club heads and golf club sets

Abstract

The aim is to improve initial ball speed and distance, as well as enhance the feel of the shot. [Solution] In the standard state of the golf club head 10, the thickness t of the face portion 12 is formed to gradually decrease from the bottom to the top of the face portion 12, and on the face center line FL, the thickness t of the top of the face portion 12 is 65% to 85% of the thickness t of the bottom, and multiple back surface grooves 32 extending in the toe-heel direction are formed in a direction intersecting the toe-heel direction in the area of ​​the back surface 12B of the face opposite the band-shaped region 24, and at least a part of the back surface grooves 32 extends to the area of ​​the back surface 12B of the face that corresponds to the impact area 34 of the face surface 12A.

Description

Technical Field

[0001] The present invention relates to an iron-type golf club head and a golf club set.

Background Art

[0002] The sweet spot of an iron-type golf club head coincides with the center of gravity point on the face surface (that is, the point where the normal line to the face surface passing through the center of gravity point of the face portion intersects the face surface), but according to investigations by the present inventors, it has been found that the average hitting point position of general golfers is biased to a location below the sweet spot. Accordingly, the present inventors have proposed forming a back groove portion extending in the toe-heel direction in the lower portion of the back face of the face located on the face back side of the face surface to increase the amount of deflection at the time of ball impact in the vicinity of the average hitting point position, thereby improving the initial velocity and the flight distance (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the above-described conventional technique has room for improvement in bringing the sweet spot (the center of gravity point on the face surface) close to the average hitting point position. Further, in the above-described conventional technique, no particular consideration is given to the hit feeling, and there is room for improvement in achieving a better hit feeling. The present invention has been made in view of such circumstances, and an object thereof is to provide an iron-type golf club head and a golf club set that are advantageous in improving the initial velocity and the flight distance as well as achieving a better hit feeling.

Means for Solving the Problems

[0005] To achieve the above objective, one embodiment of the present invention provides an iron-type golf club head comprising a face portion having a face surface, a blade portion connected to the upper part of the face portion, and a sole portion connected to the lower part of the face portion, wherein in a reference state in which the golf club head is set up with respect to a horizontal plane according to predetermined lie angles and loft angles, the thickness of the face portion is formed to gradually decrease from the bottom to the top of the face portion, and when the face center line is defined as the line where the face surface intersects with a reference plane which is a plane perpendicular to the horizontal plane and includes the normal passing through the center point of the face portion in the reference state, the front of the face portion on the face center line The thickness of the uppermost part is 65% to 85% of the thickness of the lowermost part, and the face surface is formed in a portion of the face surface sandwiched by a plurality of scorelines that are spaced apart and parallel to each other in a direction intersecting the toe-heel direction, and a plurality of elongated strip-shaped regions extending in the toe-heel direction are formed in a direction intersecting the toe-heel direction, and a plurality of back surface grooves extending in the toe-heel direction are formed on the back surface of the face surface located on the face-back side of the face surface, opposite to the strip-shaped regions, and at least a portion of the back surface grooves extends to a portion of the back surface of the face surface corresponding to the impact area of ​​the face surface. Furthermore, in one embodiment of the present invention, when the distance from the lower end to the upper end of the face center line is defined as the face height, the groove on the back surface is formed at a position less than 50% of the face height. Further, in one embodiment of the present invention, a plane parallel to the reference plane and spaced 20 mm in the toe direction in the reference state is defined as a first reference plane, a plane parallel to the reference plane and spaced 20 mm in the heel direction is defined as a second reference plane, a plane parallel to the horizontal plane and spaced 30 mm in the blade portion direction along the back face of the face from the center point of the back face of the face where the back face of the face intersects the normal line is defined as a third reference plane, and a plane parallel to the horizontal plane and spaced 3 mm in the sole portion direction along the back face of the face from the center point of the back face of the face is defined as a fourth reference plane, wherein a region of the back face of the face surrounded by the first reference plane, the second reference plane, the third reference plane, and the fourth reference plane is formed as a groove exclusion region where the back face groove portion is not formed. Further, in one embodiment of the present invention, the back face groove portions are provided one by one for each of the band-shaped regions, at least one ends in the extending direction of the plurality of back face groove portions are connected by a connection groove portion extending in a direction intersecting the extending direction of the back face groove portions, and the contour of the connection groove portion as viewed from the face surface does not overlap with the contour of the score line. Further, one embodiment of the present invention is a golf club set including n (n is a natural number of 2 or more) golf clubs each having the golf club head according to claim 3 with mutually different loft angles, wherein when the shortest distance between the center point of the back face of the face and the intersection line where the back face of the face intersects the fourth reference plane is defined as L, and the shortest distances L from the smaller loft angle value to the larger loft angle value of the golf club head are respectively defined as L(1), L(2), ···L(n), L(1)≦L(2)≦···≦L(n) or L(1)<L(n) is satisfied. Further, one embodiment of the present invention is a golf club set including n (n is a natural number of 2 or more) golf clubs each having the golf club head according to any one of claims 1 to 4 with mutually different loft angles, wherein when the number of the back face groove portions is defined as N (N is a natural number of 1 or more), and the numbers N of the back face groove portions from the smaller loft angle value to the larger loft angle value of the golf club head are respectively defined as N(1), N(2), ···N(n), N(1)≧N(2)≧···≧N(n) and N(1) > N(n) are satisfied. [Effects of the Invention]

[0006] According to one embodiment of the present invention, the face portion has a gradually changing structure in which the wall thickness of the face portion gradually decreases from the lowermost portion to the uppermost portion of the face portion, and a back surface groove portion is formed on the back surface of the face, whereby the deflection amount of the face portion can be secured to improve the repulsion performance, which is advantageous for improving the initial velocity and flight distance as well as improving the hitting feel. In particular, by adopting a gradually changing structure in which the wall thickness t of the face portion gradually decreases from the lowermost portion to the uppermost portion of the face portion, the center of gravity point of the face portion is lowered so that the center of gravity point on the face surface approaches the average hitting point position, which is of course advantageous for improving the initial velocity and flight distance, and it is advantageous for suppressing the tendency that the frequency of the hitting sound generated at the time of ball hitting becomes higher due to the formation of the back surface groove portion by increasing the wall thickness t of the face portion at the average hitting point position. In addition, when the back surface groove portion is formed at a position less than 50% of the face height, it is advantageous for securing the effect of reducing the rigidity of the face portion in the vicinity of the average hitting point position to secure the deflection amount, and improving the initial velocity and flight distance of the hit ball. In addition, forming a groove exclusion range in which no back surface groove portion is formed on the back surface of the face is advantageous for moderately suppressing the repulsion performance of a golf club head with a large club number and improving the hitting feel. Further, in the golf club set, when the shortest distance L from the small value to the large value of the loft angle of the golf club head is defined as L(1), L(2), ··· L(n) respectively, satisfying L(1)≦L(2)≦···≦L(n) or L(1)<L(n) is advantageous for suppressing the influence of the back surface groove portion in the vicinity of the average hitting point position as the club number of the golf club head increases, the deflection amount of the face portion does not become excessively large, which is advantageous for moderately suppressing the repulsion performance of the golf club head with a large club number and improving the hitting feel. Furthermore, in a golf club set, if the number of grooves on the back surface of the golf club head from small to large loft angles are N(1), N(2), ...N(n), then satisfying N(1)≧N(2)≧...≧N(n) and N(1) > N(n) is advantageous in suppressing the influence of the grooves on the back surface near the average impact point for golf club heads with higher loft numbers. This prevents the amount of face deflection from becoming excessively large, moderately suppresses the rebound performance of golf club heads with higher loft numbers, and is advantageous in improving the feel of the shot. [Brief explanation of the drawing]

[0007] [Figure 1] This is a front view of an iron-type golf club head in an embodiment. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a front view showing the face of the faceplate. [Figure 4] This is a rear view showing the back of the face. [Figure 5] This is a cross-sectional view of the face. [Figure 6] (A) is an explanatory diagram showing the case where the end of the groove on the back surface is not connected to the connecting groove, and (B) is an explanatory diagram showing the case where the end of the groove on the back surface is connected to the connecting groove. [Figure 7] This is an explanatory diagram showing the exclusion area for the grooves on the back of the clubface. [Figure 8] This is a rear view showing examples of the back of the clubface, with (A) showing the case for clubs #5 to #7, (B) showing the case for clubs #8 to pitching wedge, and (C) showing the case for approach wedge and gap wedge. [Figure 9] This is an explanatory diagram showing examples of the structure of golf club heads for each club number. [Figure 10] Figure 1 shows the evaluation results of the experimental example. [Figure 11] This is the first explanatory diagram showing the configuration of the groove on the back surface corresponding to each experimental example. [Figure 12] Figure 2 shows the evaluation results of the experimental examples. [Figure 13] This is a second explanatory diagram showing the configuration of the back surface groove portion corresponding to each experimental example. [Modes for Carrying Out the Invention]

[0008] Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1 and FIG. 2, an iron-type golf club head (hereinafter simply referred to as golf club head) 10 according to the present embodiment includes a face portion 12, a sole portion 14, a blade portion 16, a cavity portion 18, and a hosel 20. The face portion 12 has a face surface 12A that has a vertical height and extends left and right for striking a ball, and a face back surface 12B located on the rear side of the face surface 12A, that is, on the face back side of the face surface 12A. A plurality of score lines 22 and a plurality of strip-shaped regions 24 are formed on the face surface 12A. The plurality of score lines 22 are formed by groove portions extending in the toe-heel direction and formed parallel to each other at intervals in the direction intersecting the toe-heel direction. The dimensions and shape of the score lines 22 conform to the provisions in "c. Marking of the Impact Area" under "5. Club Face" of "Part 2 Club Conformity" edited by R&A / USGA. The plurality of strip-shaped regions 24 are formed by the portion of the face surface 12A sandwiched between the plurality of score lines 22, and extend in an elongated shape in the plurality of toe-heel directions arranged in the direction intersecting the toe-heel direction. Further, a peripheral edge portion 26 bulging along the periphery of the face back surface 12B is provided, and the face back surface 12B is constituted by a portion excluding the peripheral edge portion 26.

[0009] The sole portion 14 is formed by the lower part of the peripheral edge portion 26 connected to the lower part of the face portion 12, and the lower surface of the sole portion 14 serves as a sole surface 14A. The blade portion 16 is formed by the portion of the peripheral edge portion 26 extending in the toe-heel direction along the upper part of the face back surface 12B. The cavity portion 18 is formed by the face back surface 12B and the peripheral edge portion 26, and is formed to be open rearward. In the drawing, reference numeral 28 denotes a toe, and reference numeral 30 denotes a heel.

[0010] The hosel 20 stands up from a position on the heel 30 side of the face portion 12, and one end of a shaft (not shown) is inserted into and attached to the hosel 20, whereby the shaft is connected to the golf club head 10. The portion of the golf club head 10 excluding the face portion 12 is integrally formed of a metal material such as titanium alloy, stainless steel, or carbon steel. The face portion 12 is formed of a metal material such as titanium alloy, stainless steel, carbon steel, or maraging steel. In the present embodiment, the case where the golf club head 10 is of a cavity back type will be described, but the present invention is of course also applicable to the case where the golf club head 10 has a hollow structure. The wall thickness, structure, and material of the golf club head conform to the provisions in "c. Spring Effect and Dynamic Properties" under "4. Club Head" in "Part 2. Conformity of Clubs" edited by The R&A / USGA in the Equipment Rules.

[0011] Next, the provisions for each part of the golf club head 10 will be described in detail. As shown in FIG. 2, in a reference state where the golf club head 10 is installed on a horizontal plane HP according to a predetermined lie angle and loft angle, a plane that includes the normal line Lc of the face surface 12A passing through the center point Pc of the face surface 12A and is orthogonal to the horizontal plane is defined as a reference plane PL0 as shown in FIG. 1 and FIG. 3. The center point Pc of the face surface 12A refers to the geometric center of the face surface 12A. The line where this reference plane PL0 intersects the face surface 12A is defined as a face center line FL. As shown in Figure 1, in the above reference state, the distance between the toe-side end of the scoreline 22, which is located furthest to the toe, and the heel-side end, which is located furthest to the heel, may be divided into two equal parts, and a straight line extending perpendicular to the scoreline 22 along the face surface 12A may be defined as the face center line FL, with the midpoint of the face center line FL being defined as the center point Pc of the face surface 12A. In Figure 1, the symbol Lt represents a straight line extending along the face surface 12A, connecting the toe-side ends of the scorelines 22 that are located furthest to the toe, and the symbol Lh represents a straight line extending along the face surface 12A, connecting the heel-side ends of the scorelines 22 that are located furthest to the heel. The portion of the face surface 12A between the straight lines Lt and Lh is defined as the impact area 34.

[0012] (Average hitting position) In the diagram, the symbol Pa indicates the average dot position and is defined as follows. In a standard state where the golf club head 10 is positioned relative to the horizontal plane HP according to predetermined lie angles and loft angles, the average impact point Pa is the position on the face surface 12A where the height from the horizontal plane HP is 17 mm on the reference plane PL0.

[0013] (Thickness of the face) As shown in Figure 2, in a standard state where the golf club head 10 is positioned relative to the horizontal plane HP according to predetermined lie and loft angles, the thickness t of the face portion 12 is formed to gradually decrease from the bottom to the top of the face portion 12. Note that the face portion 12 is the part excluding the peripheral edge portion 26. Furthermore, on the face center line FL, the thickness t of the uppermost part of the face 12 is between 65% and 85% of the thickness t of the lowermost part. If the thickness t of the uppermost part of the face 12 is within the range of 65% to 85% of the thickness t of the lowermost part, it is advantageous in reducing the rigidity of the face 12 and ensuring sufficient deflection, thereby improving the initial velocity and distance of the ball. Furthermore, if the thickness t of the uppermost part of the face portion 12 falls below the above range, the rigidity of the face portion 12 will become excessively low, which will not only reduce the effectiveness of ensuring durability but also impair the feel characteristic of an iron head. Furthermore, if the thickness t of the uppermost part of the face portion 12 exceeds the above range, the rigidity of the face portion 12 increases, which reduces the effect of ensuring the amount of deflection of the face portion 12.

[0014] (Grove on the back) As shown in Figures 4 and 5, multiple back surface grooves 32 extending in the toe-heel direction are formed on the back surface 12B of the face opposite the band-shaped region 24, arranged in a direction intersecting the toe-heel direction. The groove portion 32 on the back surface extends to a part of the back surface 12B of the face that corresponds to the impact area 34 of the face surface 12A. As shown in Figures 5, 6(A), and (B), one groove 32 is provided on the back surface for each strip-shaped region 24. As shown in Figure 6(B), the back grooves 32 are connected by connecting grooves 36 that extend in a direction intersecting the extending direction of the back grooves 32, with at least one end of each back groove 32 in the extending direction (toe-heel direction). When viewed from the face surface 12A, the contour of the connecting grooves 36 does not overlap with the contour of the scorelines 22. As shown in Figure 6(B), when the connecting groove 36 is provided, compared to the case where only the back groove 32 is formed on the back surface 12B of the face as shown in Figure 6(A), the area of ​​the groove on the back surface 12B of the face increases by the amount of the connecting groove 36 in addition to the back groove 32. This further enhances the effect of lowering the rigidity of the face portion 12 and securing the amount of deflection, which is more advantageous in improving the initial velocity and distance of the ball. Furthermore, the width of the groove 32 on the back surface being 0.5 mm or more and less than 3.0 mm, and the depth being 0.3 mm or more and less than 1.0 mm, has the effect of lowering the rigidity of the face portion 12 and ensuring the amount of deflection. This is preferable in ensuring the initial velocity and distance of the batted ball. Furthermore, if the width and depth of the groove 32 on the back surface fall below the above range, the rigidity of the face portion 12 tends to decrease, reducing the effect of ensuring sufficient deflection. Furthermore, if the width and depth of the groove 32 on the back surface exceed the above range, the rigidity of the face portion 12 becomes excessively low, which reduces the effectiveness of ensuring the durability of the golf club head 10. Furthermore, it is more preferable for the width of the groove 32 on the back surface to be 0.7 mm or more and less than 2.5 mm, and the depth to be 0.3 mm or more and less than 0.7 mm, in order to obtain the above effect, and it is even more preferable for the width of the groove 32 on the back surface to be 1.0 mm or more and less than 2.0 mm, and the depth to be 0.3 mm or more and less than 0.5 mm, in order to obtain the above effect.

[0015] As shown in Figure 4, when the distance from the lower end to the upper end of the face center line FL is defined as the face height HF, the back groove 32 is formed at a position less than 50% of the face height HF. If the groove 32 on the back surface is formed at a position less than 50% of the face height HF, it is advantageous in improving the initial velocity and distance of the ball by lowering the rigidity of the face portion 12 near the average impact point Pa and ensuring sufficient deflection. If the groove 32 on the back surface is formed at a position exceeding 50% of the face height HF, the rigidity of the face 12 becomes excessively low, reducing its effectiveness in ensuring durability. Furthermore, there is a concern that it does not comply with the regulations in "c. Marking of the Impact Area" of "5. Club Face" in the R&A / USGA's "Part 2 Club Conformity."

[0016] (Exclusion range of grooves) As shown in Figure 7, the first reference plane PL1 is defined as a plane that is parallel to the reference plane and 20 mm away in the tow direction in the reference state. The second reference plane PL2 is defined as a plane parallel to the reference plane and 20 mm away in the heel direction. The third reference plane PL3 is defined as a plane 30 mm away in the direction of the blade portion 16, along the face surface 12B, from the center point Pc' of the face surface where the face surface 12B and the normal Lc (Figure 2) intersect, parallel to the horizontal plane HP. The fourth reference plane PL4 is defined as a plane parallel to the horizontal plane HP, 3 mm away from the center point Pc' on the back of the face, along the back of the face surface 12A, in the direction of the sole portion 14. The area enclosed by the first reference plane PL1, the second reference plane PL2, the third reference plane PL3, and the fourth reference plane PL4 on the back surface 12B of the face is formed as a groove exclusion area 38 in which the back surface groove 32 is not formed. Forming such a groove exclusion area 38 is advantageous in suppressing the excessive influence of the back groove 32 near the average impact point Pa, preventing the amount of deflection of the face 12 from becoming excessively large, and is advantageous in moderately suppressing the rebound performance of the golf club head 10 with a larger club number.

[0017] As described above, according to the golf club head 10 of this embodiment, in the standard state of the golf club head 10, the thickness t of the face portion 12 is formed to gradually decrease from the bottom to the top of the face portion 12, and on the face center line FL, the thickness t of the top of the face portion 12 is 65% to 85% of the thickness t of the bottom, and multiple back surface grooves 32 extending in the toe-heel direction are formed in a direction intersecting the toe-heel direction at the location of the band-shaped region 24 on the back surface 12B of the face, and at least a part of the back surface grooves 32 extends to the location of the face surface 12A corresponding to the impact area 34 on the face surface 12A on the back surface 12B. In other words, by creating a gradually changing structure in which the thickness t of the face portion 12 gradually decreases from the bottom to the top of the face portion 12, and by forming a groove portion 32 on the back surface 12B of the face, the amount of deflection of the face portion 12 can be secured, improving rebound performance and providing an advantage in improving initial velocity and distance. In particular, by creating a gradually changing structure in which the thickness t of the face portion 12 gradually decreases from the bottom to the top of the face portion 12, the center of gravity of the face portion 12 is lowered (to achieve a lower center of gravity), and as a result the center of gravity on the face surface (i.e., the point where the normal of the face surface 12A passing through the center of gravity of the face portion 12 intersects with the face surface 12A) and the average impact point position Pa are brought closer together, which is advantageous in improving initial velocity and distance. Furthermore, the formation of the grooves on the back surface 32 tends to increase the frequency of the impact sound generated when the ball is hit. This can be suppressed by increasing the thickness t of the face portion 12 at the average impact point Pa, which is advantageous in improving the feel of the ball when it is hit. It is known that with drivers, a high frequency metallic sound at impact is associated with a higher feel rating, while with irons, a high frequency metallic sound at impact is associated with a lower feel rating. This embodiment is advantageous in suppressing the high frequency of the impact sound, taking into account the characteristics of the feel required for irons.

[0018] (Golf club set) Next, we will describe a golf club set equipped with the golf club head 10 mentioned above. An iron-type golf club set consists of clubs numbered #1-#9, PW (pitching wedge), AW (approach wedge), GW (gap wedge), SW (sand wedge), etc., with the club numbers increasing in the order mentioned above. Figure 9 shows an example of the configuration of a golf club set to which the present invention is applied. In this example, the set includes eight golf clubs: #5-#9, PW (pitching wedge), AW (approach wedge), and GW (gap wedge). In the figure, the symbol CB indicates that a carbon shaft is used. As shown in Figure 9, in a golf club set, the higher the club number (the higher the club number), the greater the loft angle and the shorter the club length. In other words, the launch angle is higher and the required distance is shorter. In other words, the higher the club number, the shorter the distance needed; to put it another way, excessive distance is unnecessary. Therefore, it is preferable for a golf club set to moderately suppress the rebound performance of the larger club heads (10). Furthermore, regarding the presence or absence of changes in the thickness t of the face portion 12, those described as "gradual face variation" in Figure 9 are those in which the thickness t of the face portion 12 is changed, similar to the embodiments described above. PW (pitching wedge), AW (approach wedge), and GW (gap wedge), which are not described as "gradual face variation," have a uniform thickness.

[0019] Furthermore, the configuration of the groove portion 32 on the back surface is of the type shown in Figures 9 and 8(A)-(C). In other words, as shown in Figure 8(A), for #5-#9, there are a total of eight grooves 32 on the back surface: four that extend long in the toe-heel direction, and two that extend short on both the toe side and the heel side. In other words, the groove portion exclusion area 38 mentioned above does not have a groove portion 32 on the back surface; in other words, the groove portion exclusion area 38 is not covered by the groove portion 32 on the back surface. By creating a larger number of grooves 32 on the back surface in this way, the sweet spot of the golf club head 10 is enlarged, making mis-shots less likely. Furthermore, as shown in Figure 8(B), for #8-PW, the back groove portion 32 consists of three grooves that extend long in the toe-heel direction, and similar to Figure 8(A), the back groove portion 32 does not extend to the groove exclusion area 38. By forming a slightly larger number of grooves 32 on the back surface in this way, the initial velocity when striking at the average impact point Pa is improved. Furthermore, as shown in Figure 8(C), the groove 32 on the back surface is not formed on AW and GW. By not forming the groove 32 on the back surface in this way, the flight distance is prevented from becoming too long. In other words, with iron-type golf club heads, the higher the club number, the greater the height dimension from the sole portion 14 to the blade portion 16 of the face portion 12. Therefore, the higher the club number, the greater the coefficient of restitution, and consequently, the higher the frequency of the impact sound tends to be. Accordingly, as shown in Figures 8(A), (B), and (C), the larger the club number, the smaller the number of back surface groove portions 32 (or no back surface groove portions 32 are formed), and by forming the groove portion exclusion range 38, the repulsion performance of the golf club head 10 with a larger club number is suppressed, the frequency of the impact sound does not increase, and the feel at impact is improved. Note that in the present embodiment, the case where the back surface groove portions 32 are formed for #5 to #9 and PW has been described, but it goes without saying that the back surface groove portions 32 may be formed for #1 to #4.

[0020] In a golf club set including n (n is a natural number of 2 or more) golf clubs having golf club heads 10 with different loft angles from each other as described above, as shown in Figure 7, when the shortest distance between the face back surface center point Pc' and the intersection line where the face back surface 12B intersects the fourth reference plane PL4 is defined as L, and the shortest distances L of the golf club head 10 from the smaller loft angle value to the larger loft angle value are respectively defined as L(1), L(2), ... L(n), L(1)≦L(2)≦···≦L(n) or L(1)<L(n) is satisfied. In other words, the groove portion exclusion range 38 expands in the vertical direction connecting the blade portion 16 and the sole portion 14 as the club number of the golf club head increases. This arrangement is advantageous for suppressing the influence of the back surface groove portions 32 in the vicinity of the average hitting point position Pa as the club number of the golf club head 10 increases, the deflection amount of the face portion 12 does not become excessively large, the repulsion performance of the golf club head 10 with a larger club number is moderately suppressed, and this is advantageous for improving the feel at impact.

[0021] Further, when the number of the back surface groove portions 32 is N (N is a natural number of 1 or more), and the numbers N of the back surface groove portions 32 of the golf club head 10 from the smaller loft angle value to the larger loft angle value are respectively defined as N(1), N(2), ... N(n), N(1)≧N(2)≧···≧N(n) and N(1) > N(n) are satisfied. In other words, the number of grooves 32 on the back surface decreases as the grit number increases. This arrangement is advantageous in suppressing the influence of the grooves 32 on the back surface near the average impact point Pa in the golf club head 10 with a larger club number, preventing the amount of deflection of the face 12 from becoming excessively large, and moderately suppressing the rebound performance of the golf club head 10 with a larger club number, which is advantageous in improving the feel of the shot.

[0022] (Example of experiment) The following describes experimental examples of the present invention. Figures 10 and 12 show the experimental results of the golf club head 10 according to the present invention. Ten golf club heads were prepared as samples for each experimental example, and the following three evaluation items were measured to determine the index (evaluation score), and the total score of the three indices was also calculated. The golf club head 10 is a 7-iron, with a loft angle of 28 degrees and a lie angle of 62 degrees.

[0023] (1) Initial velocity (average hitting position Pa) A golf club equipped with a golf club head 10 was mounted on a swing robot, and actual swing tests were conducted under the following conditions. The average initial velocity was evaluated using an index. The index of the experimental example corresponding to the comparative example was set to 100, and a higher index indicates a faster initial velocity and a better evaluation. Head speed: 40 m / s Ball: Progear TR Spin (product name) manufactured by Progear Co., Ltd. The hitting point was set to the average hitting point Pa (17 mm above the horizontal plane HP) as shown in Figure 2, and the ball was hit five times.

[0024] (2) Feel The feel of the ball was evaluated by 50 golfers using the same sample, who rated the feel on a 10-point scale. Then, the average of the evaluation scores from 50 people was calculated as the average evaluation score for the feel of the ball. The feel of the clubface was expressed as an index, with the average feel rating of the 10 golf club heads in Experimental Example 1 set to 100. A higher index indicates a better feel and a higher rating.

[0025] (3)Durability A golf ball was repeatedly struck against the face 12A of a golf club head 10 fixed to a shaft using an air cannon. The number of hits required before deformation or damage to the face 12 was measured and indexed. The ball speed was set to 40 m / s. The impact point was defined as the average impact point Pa. In this case, the measurement results of the golf club head 10, which corresponds to the comparative example, are shown as an index with a value of 100. A higher index indicates a better evaluation.

[0026] (4) Total score The total score was calculated by summing the three indices mentioned above: initial velocity, feel, and durability. The total score for the experimental examples corresponding to the comparative examples is set at 300, and a higher total score indicates a better evaluation.

[0027] Furthermore, the experiment was conducted under the following conditions. (Condition 1: Figure 10) The conditions defined in claims 1, 2, 3, and 4 are modified for the golf club head 10. (Condition 2: Figure 12) The conditions specified in claims 5 and 6 are modified to apply to golf club sets.

[0028] (Condition 1) Next, we will explain an example of an experiment under condition 1 with reference to Figure 10. Experimental Example 1 involves forming a groove 32 on the lower part of the back surface 12B of the face, and is configured in the same way as the prior art (Japanese Patent Publication No. 6347305). It is equivalent to a comparative example and does not satisfy the provisions of claim 1 of the present invention, and is therefore outside the scope of the present invention.

[0029] Experimental examples 2 and 3 satisfy all the requirements of claims 1-3. Experimental Example 4 shows that the thickness t at the top of the face portion 12 is 90% of that at the bottom, which does not satisfy the provision of Claim 1 that it is 85% or less, and is therefore outside the scope of the present invention. Experimental Example 5 does not satisfy the provision of Claim 1 that the back groove 32 extends to the impact area 34, and is therefore outside the scope of the present invention. Experimental Example 6 is outside the scope of the present invention because the thickness t at the top of the face portion 12 of Claim 1 is 90% of that at the bottom, failing to meet the requirement of 85% or less, and the back groove portion 32 of Claim 1 does not extend to the impact area 34. Experimental example 7 satisfies the requirements of claim 1, but the groove 32 on the back surface is located at 55% of the face height HF, and does not satisfy the requirement of less than 50% of claim 2. Experimental examples 8 and 9 satisfy the requirements of claims 1 and 2, but the groove portion 32 on the back surface extends into the groove exclusion area 38, and therefore do not satisfy the requirements of claim 3. Experimental example 10 satisfies all the requirements of claims 1-4.

[0030] Figure 11 is a schematic diagram illustrating the arrangement of the grooves 32 on the back surface in the experimental example. Figure 11(A) shows an example where the groove 32 on the back surface extends to the impact area 34. Figure 11(B) shows an example where the groove 32 on the back surface does not extend to the impact area. Figures 11(C), (D), and (E) show examples where the back groove 32 is located at 30%, 40%, and 25% of the face height HF, respectively. Figure 11(F) shows an example where the groove 32 on the back surface does not extend to the groove exclusion area 38. Figure 11(G) shows an example where the groove 32 on the back surface slightly extends into the groove exclusion area 38. Figure 11(H) shows an example where the groove 32 on the back surface extends far into the groove exclusion area 38. Figure 11(I) shows an example in which the connecting groove 36 is formed. Figure 11(J) shows an example where the connecting groove 36 is not formed.

[0031] As shown in Figure 10, experimental examples 2, 3, 7, 8, 9, and 10, which fall within the scope of the present invention, clearly show superior initial velocity, feel, durability, and overall evaluation compared to experimental examples 1, 4, 5, and 6, which fall outside the scope of the present invention.

[0032] Next, we will explain an example of an experiment under condition 2 with reference to Figure 12. Under Condition 2, the test subject is a golf club set that includes clubs with loft angles and shaft lengths corresponding to the five golf clubs from #5 to #9 out of the eight golf clubs from #5 to GW shown in Figure 9. Experimental Example 1 is configured similarly to the prior art (Japanese Patent Publication No. 6347305) as Condition 1, and is equivalent to a comparative example. It does not satisfy the provisions of claims 4 and 5 of the present invention and is therefore outside the scope of the present invention. In other words, the groove exclusion area 38 does not widen as the club number increases, and the number of grooves on the back surface 32 is the same for all club numbers (the number of grooves on the back surface 32 does not decrease as the club number increases).

[0033] Experimental example 11 satisfies the provisions of claims 4 and 5 and is within the scope of the present invention, in which the groove exclusion range 38 widens as the grit number increases, and the number of grooves 32 on the back surface decreases as the grit number increases. Experimental Example 12 satisfies the provisions of Claim 4 and is within the scope of the present invention, with the groove exclusion range 38 widening as the grit number increases, while it does not satisfy the provisions of Claim 5, with the number of grooves on the back surface 32 being the same for all grit numbers (the number of grooves on the back surface 32 does not decrease as the grit number increases). Experimental example 13 does not satisfy the provisions of claims 4 and 5 and is outside the scope of the present invention. The groove exclusion range 38 actually narrows as the grit number increases, and the number of grooves on the back surface 32 actually increases as the grit number increases.

[0034] Figure 13 is an explanatory diagram illustrating the number of grooves 32 on the back surface and the width of the groove exclusion area 38. Figures 13(A)-(C) show an example in which the number of grooves 32 on the back surface is the same regardless of the grade, and the width of the groove exclusion area 38 is the same. Figures 13(D)-(F) show an example in which the number of grooves 32 on the back surface decreases as the grit number increases, and the groove exclusion area 38 widens as the grit number increases. Figure 13(G)-(I) shows an example where the number of grooves 32 on the back surface is the same regardless of the club number, and the groove exclusion area 38 widens as the club number increases. Figures 13(J)-(L) show an example where the number of grooves 32 on the back surface increases as the club number increases, and the groove exclusion area 38 narrows as the club number increases.

[0035] As shown in Figure 12, it is clear that experimental examples 11 and 12, which fall within the scope of the present invention (satisfying the provisions of claims 4 and 5), are superior in initial velocity, feel, durability, and overall evaluation compared to experimental examples 1 and 13, which fall outside the scope of the present invention. [Explanation of symbols]

[0036] 10 Golf Club Heads 12 Face section 14. Sole 14A Sole surface 14B Face back 16 Blade section 18 Cavity section 20 Hosel 22 scorelines 24. Band-shaped region 26 Peripheral area 28 Tou 30 heel 32. Groove on the back surface 34 Impact Area 36 Connection groove 38. Exclusion range of grooves t Thickness PC center point Pc' Center point on the back of the face Lc normal PL0 Reference plane Lt Straight line connecting the toe ends Lh is a straight line connecting the heel ends. HF Face Height HP horizontal plane FL Face Center Line PL1 1st reference plane PL2 2nd reference plane PL3 3rd reference plane PL4 4th reference plane Pa Average hitting position

Claims

1. An iron-type golf club head comprising a face portion having a face surface, a blade portion connected to the upper part of the face portion, and a sole portion connected to the lower part of the face portion, In a standard state in which the golf club head is positioned relative to a horizontal plane according to predetermined lie and loft angles, the thickness of the face portion is formed such that it gradually thins from the bottom to the top of the face portion. In the aforementioned reference state, when the line at which the reference plane, which is a plane perpendicular to the horizontal plane and includes the normal passing through the center point of the face surface, intersects with the face surface is defined as the face center line, on the face center line, the thickness of the uppermost part of the face portion is 65% or more and 85% or less of the thickness of the lowermost part. On the face surface, a plurality of elongated, band-shaped regions extending in the toe-heel direction are formed in the portion of the face surface sandwiched between a plurality of scorelines that extend in the toe-heel direction and are spaced apart and parallel to each other in a direction intersecting the toe-heel direction, and are arranged in a direction intersecting the toe-heel direction. Multiple grooves extending in the toe-heel direction are formed on the back surface of the face, on the face-back side of the face surface, in a direction that intersects with the toe-heel direction, in a manner that is opposite to the band-shaped region. The groove on the back surface extends, at least a portion thereof, to the portion of the back surface of the face that corresponds to the impact area of ​​the face surface. A golf club head characterized by the following features.

2. When the distance from the lower end to the upper end of the aforementioned face center line is defined as the face height, The groove on the back surface is formed at a position less than 50% of the face height. The golf club head as described in feature 1.

3. When, in the aforementioned reference state, a plane parallel to the reference plane and 20 mm away in the toe direction is defined as the first reference plane, a plane parallel to the reference plane and 20 mm away in the heel direction is defined as the second reference plane, a plane parallel to the horizontal plane and 30 mm away from the center point of the back surface of the face where the back surface of the face intersects with the normal is defined as the third reference plane along the back surface of the face in the direction of the blade, and a plane parallel to the horizontal plane and 3 mm away from the center point of the back surface of the face and 3 mm away from the back surface of the face in the direction of the sole, The area of ​​the face surface enclosed by the first reference surface, the second reference surface, the third reference surface, and the fourth reference surface is formed as a groove exclusion area where the surface groove is not formed. The golf club head as described in feature 2.

4. The aforementioned grooves on the back surface are provided one for each of the strip-shaped regions. Multiple back surface grooves are connected by connecting grooves that extend in a direction intersecting the direction of extension of the back surface grooves, When viewed from the face surface, the contour of the connecting groove portion does not overlap with the contour of the scoreline. A golf club head according to any one of claims 1 to 3.

5. A golf club set comprising n (n is a natural number of 2 or more) golf clubs, each having a golf club head according to claim 3 with a different loft angle from the others, When L is the shortest distance between the center point of the back surface of the face and the intersection line where the back surface of the face and the fourth reference plane intersect, When the shortest distance L from the smallest to the largest loft angle of the golf club head is denoted as L(1), L(2), ..., L(n), L(1) ≤ L(2) ≤ ... ≤ L(n) or L(1) < L(n) A golf club set characterized by the following features.

6. A golf club set comprising n (n is a natural number of 2 or more) golf clubs, each having a golf club head according to any one of claims 1 to 4, with a different loft angle from each other. When the number of grooves on the back surface is N (where N is a natural number of 1 or more), When the number of grooves on the back surface of the golf club head for loft angles ranging from small to large is denoted as N(1), N(2), ..., N(n), N(1) ≥ N(2) ≥ ... ≥ N(n) and N(1) > N(n) A golf club set characterized by the following features.

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