JP7573264B2 - Iron Golf Club - Google Patents

Description

The present invention relates to an iron golf club. More specifically, it relates to an iron golf club that can improve the hitting sound without lowering the restitution coefficient of the head.

When trying to achieve greater distance with woods and irons, one method is to increase the coefficient of restitution (COR) from a technical standpoint. One way to increase the coefficient of restitution is to make the face more flexible on impact with the ball. Known methods for making the face more flexible include reducing the thickness of the face.

To achieve this thinning, high strength, high hardness materials are used for the head. In golf clubs with heads made of such high strength, high hardness materials, when hitting the ball, the impact sound is too high and unpleasant. As a method for solving this problem, for example, a golf club head is known that is made up of a metal face and head body that form an internal cavity, and the space of this internal cavity is filled with a vibration absorbing material made of non-metallic synthetic resin, gel, etc. (see, for example, Patent Documents 1 and 2).

Also, for cavity-back irons, a vibration-absorbing material such as rubber or resin has been attached to the back of the face (see, for example, Patent Document 3).

Japanese Patent Application Publication No. 6-39061 JP 2005-143761 A Japanese Patent Application Publication No. 9-322952

The most effective way to improve the impact sound mentioned above is to use vibration damping to reduce the vibration of the impact sound. However, the conventional vibration damping methods mentioned above have the disadvantage of lowering the restitution coefficient of the head.

Therefore, the present invention was developed in consideration of the problems with the conventional technology described above, and its purpose is to provide an iron golf club that can improve the hitting sound without lowering the repulsion coefficient of the head.

The iron golf club according to the present invention, which is intended to achieve the above object, is an iron golf club head that includes a face portion (10) having a face surface (10F) on which the ball is struck, a head body portion (20) having a recess (27) formed on the back surface (10B) of the face, and vibration-isolating material (30, 30A, 30B, 30C) filled into the hollow structure (27), and is characterized in that the vibration-isolating material (30, 30A, 30B, 30C) is filled outside an internal area (A0) of a circle having a predetermined radius (R) and centered on a center of gravity projection point (CGP) projected perpendicularly from the center of gravity (CG) of the head to the wall surface (26a) of the recess.

The second feature of the iron golf club according to the present invention is that the vibration-isolating material (30, 30A, 30B, 30C) is filled in the hollow structure (27) along the toe portion (21) and sole portion (24) of the face portion (10) so as not to overlap the inner area (AO) of the circle.

The third feature of the iron golf club according to the present invention is that the filling height (Y1) of the vibration-isolating material (30, 30A, 30B, 30C) on the toe portion (21) side is higher than the filling height (Y2) on the sole portion (24) side.

The fourth feature of the iron golf club according to the present invention is that the filling height (Y1) of the vibration-isolating material (30, 30A, 30B, 30C) on the toe portion (21) side is higher than the height (YCG) of the center of gravity projection point (CGP).

The fifth feature of the iron golf club according to the present invention is that the filling height (Y2) of the vibration-isolating material (30, 30A, 30B, 30C) on the sole portion (24) side is lower than the height (YCG-R) obtained by subtracting the radius (R) from the height (YCG) of the center of gravity projection point (CGP).

The sixth feature of the iron golf club according to the present invention is that the radius (R) of the inner area (A0) of the circle is a length within a range of 25% to 70% of the height of the center of gravity (YG) when the leading edge of the face surface (10F) is used as the reference point for the center of gravity projection point (CGP).

The seventh feature of the iron golf club according to the present invention is that the Shore hardness of the vibration-isolating material (30, 30A, 30B, 30C) is within the range of A25 to A70.

The eighth feature of the iron golf club according to the present invention is that the material of the vibration-isolating material (30, 30A, 30B, 30C) is a silicone resin, a urethane resin, or a special polymer containing a silyl group.

The iron golf club of the present invention makes it possible to improve the hitting sound without lowering the restitution coefficient of the head.

1 is a front view of a head portion of an iron golf club according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA of FIG. 1. FIG. 3 is a view taken along the arrow A in FIG. 2 . FIG. 3 is a view taken along the arrow B in FIG. 2 . FIG. 4 is an explanatory diagram showing the filling position and range of vibration-proof material and the range in which filling is prohibited. FIG. 1 is an explanatory diagram showing the first to third samples of the head body used in a verification test to verify the correlation between the filling position/range of the vibration-damping material and the "rebound coefficient and the vibration damping effect of the hitting sound." FIG. 1 is an explanatory diagram showing the fourth to sixth samples of the head body portion used in a verification test to verify the correlation between the filling position/range of the vibration-damping material and the "rebound coefficient and the vibration damping effect of the hitting sound." FIG. 13 is an explanatory diagram showing the seventh to ninth samples of the head body portion used in a verification test to verify the correlation between the filling position/range of the vibration-damping material and the "rebound coefficient and the vibration damping effect of the hitting sound." FIG. 12 is an explanatory diagram showing the tenth sample of the head body used in a verification test to verify the correlation between the filling position/range of the vibration-damping material and the "rebound coefficient and the vibration damping effect of the hitting sound." FIG. 11 is an explanatory diagram showing the results of measuring the coefficient of restitution (COR) and the vibration damping effect of hitting sounds for the head portions of the iron golf clubs using the first to fifth samples. FIG. 11 is an explanatory diagram showing the results of measuring the coefficient of restitution (COR) and the vibration damping effect of the hitting sound for the head portion of each iron golf club using the sixth sample to the tenth sample.

The following describes an embodiment of the present invention in detail with reference to the attached drawings.

Figures 1 and 2 are explanatory diagrams showing the head portion 100 of an iron golf club according to one embodiment of the present invention. Note that Figure 1 is a front view of the head portion 100 of the iron golf club. Figure 2 is a cross-sectional view taken along line A-A in Figure 1.

As shown in FIG. 1, the head portion 100 of this iron golf club (hereinafter referred to as "head portion 100") is configured with a face portion 10 having a face surface 10F that strikes a golf ball, and a head body portion 20 in which a pocket portion 27 (FIG. 2) is formed on the back side of the face portion 10 when the face portion 10 is welded, and has a toe portion 21 at the front, a top portion 22 at the top, a heel portion 23 at the rear, a sole portion 24 at the bottom that contacts the ground, and a hosel portion 25 that is a shaft connection portion on the shaft 40 side. Each component will be explained below.

On the surface of the face portion 10 (face surface 10F), multiple score lines 18 (for example, 13) are formed to impart spin (rotation) to the golf ball. The score lines 18 have a predetermined width W and a predetermined depth D, and are formed at a predetermined pitch P along the vertical direction (the direction from the top portion 22 to the sole portion 24).

The face portion 10 is made by forging nickel-molybdenum steel such as SAE8655. The thickness of the face portion 10 is, for example, 1.9 mm. On the other hand, the head body portion 20 is made by forging low-carbon steel such as S20C.

As shown in FIG. 2, a pocket portion 27 is formed on the back side of the face portion 10 (face back surface 10B). This pocket portion 27 is formed by cutting out a portion of the cavity bottom wall 26a (dotted portion on the top portion 22 side) that originally covered the entire back side of the head portion 100. As a result, a cavity opening 26b (FIG. 3) is formed on the back side of the face portion 10.

The pocket 27 is filled with anti-vibration material 30 to improve the impact sound. In other words, the iron golf club according to the present invention has the effect of reducing the volume and resonance of the impact sound (hereinafter also referred to as the "impact sound vibration damping effect") while being a distance-oriented iron golf club. The anti-vibration material 30 is selected to have a hardness suitable for improving the impact sound, and is filled in an appropriate position and range within the pocket 27 to improve the impact sound without reducing the restitution coefficient. The filling position and range of the anti-vibration material 30 will be described later with reference to FIG. 5. In this embodiment, the thickness of the anti-vibration material 30 before filling is 2 mm. Therefore, the opening width of the pocket 27 is slightly smaller than 2 mm.

The center of gravity CG, the center of gravity face surface projection point CGF when the center of gravity CG is projected onto the face surface 10F, and the center of gravity pocket projection point CGP when the center of gravity CG is projected onto the cavity bottom wall 26a only differ in Z coordinate, and are the same point (equivalent point) on the XY coordinate plane (two-dimensional plane) ignoring the Z coordinate. Therefore, when the Z coordinate can be ignored, the center of gravity face surface projection point CGF and the center of gravity pocket projection point CGP may also be described as the center of gravity CG.

The coordinate system according to this embodiment is a three-dimensional coordinate system in which the axis LS of the shaft is perpendicular to the ground at a given lie angle θ (FIG. 1), the axis on the face surface 10F parallel to the ground is the X-axis, the axis on the face surface 10F perpendicular to the X-axis is the Y-axis, and the axis perpendicular to both the X-axis and the Y-axis is the Z-axis. The center of gravity height YG is defined as the distance in the Y-axis direction from the leading edge of the face surface 10F to the center of gravity face projection point CGF.

FIG. 3 is a view of the head main body 20 in FIG. 2 as seen from an arrow A. As shown in FIG.
3, a portion (on the top portion 22 side) of the cavity bottom wall 26a is cut to form a cavity opening 26b. A step is formed between the sole portion 24 and the cavity bottom wall 26a. The sole portion 24 protrudes toward the front side of the paper (in the +Z direction).

FIG. 4 is a view of the head main body 20 in FIG. 2 as seen from the arrow B. As shown in FIG.
4, steps are formed between the cavity bottom wall 26a and each of the toe portion 21, sole portion 24, and heel portion 23. As a result, when the face portion 10 is welded to the head body portion 20, a pocket portion 27 is formed.

Figure 5 is an explanatory diagram showing the filling position and range of the vibration-isolating material 30 and the non-filled range. The "non-filled range" is the area in the pocket portion 27 that is not filled with the vibration-isolating material 30 in order to minimize the decrease in the restitution coefficient. Quantitatively, it is defined by the inner area of a circle (hereinafter referred to as the "non-filled circle A0") that has its center at the center of gravity pocket projection point CGP and a specified radius R. Therefore, the vibration-isolating material 30 is filled in the pocket portion 27, avoiding the non-filled circle A0 so as not to overlap with this non-filled circle A0.

The radius R, which represents the size of the non-filled circle A0, is determined, for example, by the percentage of the center of gravity height YG. The percentage of the center of gravity height YG is appropriately selected from within a range of 25% to 70% depending on the plate thickness of the face portion 10 and the opening width of the pocket portion 27. In this embodiment, the radius R of the non-filled circle A0 is set to 51.5% of the center of gravity height YG. The center of gravity height YG is the height along the Y-axis direction when the leading edge of the face surface 10F is used as the reference.

The "filling position" of the vibration isolating material 30 is an area that does not overlap with the non-filling circle A0 along the toe portion 21 and sole portion 24 in the pocket portion 27. The "filling range" of the vibration isolating material 30 is determined by the toe side filling height Y1 and the sole side filling height Y2 along the Y-axis direction when the lowest point of the pocket portion 27 is used as the reference. The toe side filling height Y1 is set to be higher than the sole side filling height Y2. Therefore, the toe side filling range A1 of the vibration isolating material 30 is wider than the sole side filling range A2.

When the upper part of the toe side filling area A1 is not flat, the toe side filling height Y1 can be, for example, the average value of the height of the upper part. The same applies when the upper part of the sole side filling area A2 is not flat.

The toe side filling height Y1 is set to be higher than the center of gravity height YCG along the Y-axis direction when the lowest point of the pocket portion 27 at the center of gravity pocket projection point CGP is used as a reference. On the other hand, the sole side filling height Y2 is set to be lower than the height obtained by subtracting the radius R of the non-filled circle A0 from the center of gravity height YCG. This indicates that more vibration-proofing material 30 is filled on the toe side 21 than in the sole portion 24. Filling more vibration-proofing material 30 on the toe side 21 minimizes the decrease in the resilience coefficient and increases the vibration damping effect of the hitting sound. This will be described later with reference to Figures 10 and 11.

Figure 6 is an explanatory diagram showing the first to third samples of the head body used in a verification test to verify the correlation between the filling position and range of the vibration-proofing material 30 and the "restitution coefficient and impact sound vibration damping effect." The first sample is a conventional head body that is the target for the restitution coefficient, and the second sample is a conventional head body that is the target for the impact sound vibration damping effect.

As shown in FIG. 6(a), the first sample is a conventional head body portion in which no vibration-isolating material 30 is filled in the pocket portion 27. Since the vibration-isolating material 30 is not present in the pocket portion 27, there is no effect of damping the vibration of the hitting sound, but the restitution coefficient is the largest among the samples. Therefore, in the samples other than the first and second samples, the vibration-isolating material 30 is filled in the pocket portion 27 so as to be as close as possible to the restitution coefficient of the first sample.

As shown in FIG. 6(b), the second sample is a conventional head body in which the entire pocket portion 27 is filled with anti-vibration material 30. Because the entire pocket portion 27 is filled with anti-vibration material 30, the vibration damping effect on the impact sound is the greatest among the samples, but the restitution coefficient is the smallest among the samples. Therefore, in the samples other than the first sample, the anti-vibration material 30 is filled in the pocket portion 27 so as to be as similar as possible to the vibration damping effect on the impact sound of the second sample.

In this embodiment, vibration-isolating materials with Shore hardnesses of A25, A50, and A70 are used to verify the effect of the hardness of the vibration-isolating material on the resilience coefficient and the vibration damping effect of the hitting sound. The vibration-isolating material 30 used in the second to seventh samples is a resin with a Shore hardness of A70. This vibration-isolating material 30 can be, for example, a silicone resin made of a silicone potting agent (product number TB1230 made by ThreeBond Co., Ltd.).

As shown in Figure 6 (c), in the third sample, the vibration-proofing material 30 is filled along the toe portion 21 and sole portion 24 in the pocket portion 27 so as not to overlap the non-filled circle A0. In this case, the toe side filling height Y1 is at a position higher than the center of gravity pocket projection point CGP (Y1>YCG), and the sole side filling height Y2 is at a height (Y2<YCG-R) that does not interfere with the non-filled circle A0. For convenience, in this embodiment, the filling height (<YCG-R) of the vibration-proofing material 30 located below the non-filled circle A0 (sole portion 24 side) is referred to as the "sole side filling height". In addition, the filling height of the vibration isolation material 30 located to the left (toe portion 21 side) of the non-filled circle A0 that is higher than the lowest point height of the non-filled circle A0 (= YCG-R) is referred to as the "toe portion side filling height," and the filling height of the vibration isolation material 30 located to the right (heel portion 23 side) of the non-filled circle A0 that is higher than the lowest point height of the non-filled circle A0 (= YCG-R) is referred to as the "heel portion filling height."

Figure 7 is an explanatory diagram showing the fourth to sixth samples of the head body used in a verification test to verify the correlation between the filling position and range of the vibration-proof material 30 and the "rebound coefficient and the vibration damping effect of the hitting sound."

As shown in FIG. 7(a), the fourth sample is a head body portion 20 in which vibration-isolating material 30 is filled on both sides of the unfilled circle A0 of the pocket portion 27.

As shown in FIG. 7(b), the head body 20 is filled with vibration-isolating material 30 to a height where the toe-side filling height Y1 is zero and the sole-side filling height Y2 does not interfere with the non-filled circle A0 (Y2<YCG-R).

As shown in FIG. 7(c), the sixth sample is a head body 20 in which the toe side filling height Y1 is higher than the sole side filling height Y2, is located below the center of gravity pocket projection point CGP (Y2<Y1<YCG), and the sole side filling height Y2 is filled with vibration-isolating material 30 to a height (Y2<YCG-R) that does not interfere with the non-filled circle A0.

Figure 8 is an explanatory diagram showing the seventh to ninth samples of the head body used in a verification test to verify the correlation between the filling position and range of the vibration-proofing materials 30, 30A, and 30B and the "rebound coefficient and the vibration damping effect of the hitting sound."

As shown in FIG. 8(a), the seventh sample is a head body 20 in which the toe side filling height Y1 is located above the center of gravity pocket projection point CGP (Y1>YCG) and the sole side filling height Y2 is zero.

As shown in FIG. 8(b), in the eighth sample, like the third sample, the vibration isolating material 30A is filled in the pocket 27 so that the toe side filling height Y1 is higher than the center of gravity pocket projection point CGP (Y1>YCG) and the sole side filling height Y2 is at a height that does not interfere with the non-filled circle A0 (Y2<YCG-R). The vibration isolating material 30A used in the eighth sample is a resin with a Shore hardness of A25. For example, a resin made of a silyl group-containing special polymer with product number TB1530P manufactured by ThreeBond Co., Ltd. can be used as the vibration isolating material 30A.

As shown in FIG. 8(c), in the ninth sample, like the third sample, the vibration-isolating material 30B is filled in the pocket portion 27 so that it does not interfere with the non-filled circle A0, the toe side filling height Y1 is higher than the center of gravity pocket projection point CGP (Y1>YCG), and the sole side filling height Y2 is at a height (Y2<YCG-R) that does not interfere with the non-filled circle A0. The vibration-isolating material 30B used in the ninth sample is a resin with a Shore hardness of A50. For example, a urethane resin can be used as the vibration-isolating material 30B.

Figure 9 is an explanatory diagram showing the tenth sample of the head body used in a verification test to verify the correlation between the filling position and range of the vibration-proof material 30C and the "rebound coefficient and the vibration damping effect of the hitting sound."

As with the third sample, the tenth sample has a toe-side filling height Y1 that is higher than the center of gravity CG (Y1>YCG) and a sole-side filling height Y2 that does not interfere with the non-filled circle A0 (Y2<YCG-R). The vibration-isolating material 30C used in the tenth sample is a resin with a Shore hardness of A50. Silicone resin manufactured by Togawa Rubber Co., Ltd. can be used as this vibration-isolating material 30C.

Figures 10 and 11 are explanatory diagrams showing the results of measuring the coefficient of restitution (COR) and the vibration damping effect of the impact sound for the head of each iron golf club using the first to tenth samples. The vibration curve of the impact sound was obtained by impacting a metal ball with the head of each iron golf club, collecting the impact sound generated at that time with a microphone, and inputting the electrical signal related to the sound pressure output from the microphone into a signal processing device in a chronological order. Therefore, the horizontal axis of the vibration curve of the impact sound is the time axis. The vertical axis is the sound pressure.

Measurement result 1 shows the restitution coefficient and the vibration damping effect of the hitting sound of the head part of the conventional iron golf club according to the first sample in which the "pocket portion 27 is empty". The restitution coefficient was 0.815, which was the best result among all the samples. Therefore, the head part 100 of the iron golf club of the present invention has the restitution coefficient (0.815) of the first sample as the target value. On the other hand, regarding the vibration damping effect of the hitting sound, the loudness and convergence time (resonance time) of the hitting sound were the worst results among all the samples. Note that the "loudness of the hitting sound" here means the amplitude when the time series signal (vibration curve) of the sound pressure at the time of hitting the ball is Fourier transformed. Also, the "convergence time (resonance time) of the hitting sound" means the time required for the sound pressure in the time series signal of the sound pressure at the time of hitting the ball to converge to near zero after reaching the maximum peak value.

Measurement result 2 shows the resilience coefficient and impact sound vibration damping effect of the conventional iron golf club head part of the second sample in which "the entire pocket part 27 is filled with vibration-proofing material 30". Therefore, the convergence time (resonance time) of the impact sound of the second sample is shorter than the convergence time (resonance time) of the impact sound of the first sample. Also, the volume of the impact sound of the second sample is smaller than the volume of the impact sound of the first sample. Therefore, the head part 100 of the iron golf club of the present invention aims for the impact sound vibration damping effect of the second sample. On the other hand, the resilience coefficient of the second sample was the worst among all the samples.

Measurement result 3 shows the resilience coefficient and impact sound vibration damping effect of the head portion 100 of the iron golf club of the present invention relating to the third sample, in which "the vibration-proofing material 30 does not interfere with the non-filled circle A0, the toe-side filling height Y1 is at a position higher than the center of gravity pocket projection point CGP (Y1>YCG), and the sole-side filling height Y2 is at a height (Y2<YCG-R) that does not interfere with the non-filled circle A0." The resilience coefficient of the third sample was the same as that of the first sample. This shows that the filling position and range of the vibration-proofing material 30 in the pocket portion 27 of the third sample does not reduce the resilience coefficient.

On the other hand, the impact sound vibration damping effect of the third sample is very good and close to the target impact sound vibration damping effect of the second sample. This shows that the filling position and range of the filling prevention material 30 of the third sample is effective in improving the impact sound.

Measurement result 4 shows the resilience coefficient and impact sound vibration damping effect of the head portion 100 of the iron golf club of the present invention relating to the fourth sample in which "both sides of the unfilled circle A0 are filled with vibration-proofing material 30." The resilience coefficient of the fourth sample is slightly lower than that of the first sample, but at the same level. From this, it can be seen that the filling position and range of the vibration-proofing material 30 in the pocket portion 27 of the fourth sample hardly reduces the resilience coefficient.

On the other hand, regarding the vibration damping effect of the impact sound of the fourth sample, the convergence time (resonance time) of the impact sound shows similar characteristics to the first sample, but the volume of the impact sound is smaller than the first sample, and is generally good. From this, it can be seen that the filling position and range of the filling prevention material 30 of the fourth sample is effective in improving the impact sound.

Measurement result 5 shows the restitution coefficient and impact sound vibration damping effect for the head of the iron golf club of the fifth sample, in which the toe side filling height Y1 is zero and the sole side filling height Y2 is a height that does not interfere with the non-filled circle A0 (Y2<YCG-R). The restitution coefficient of the fifth sample is slightly lower than that of the fourth sample, but at the same level. From this, it can be seen that the filling position and range within the pocket portion 27 of the fifth sample does not reduce the restitution coefficient much.

On the other hand, regarding the vibration damping effect of the impact sound of the fifth sample, the convergence time (resonance time) of the impact sound shows similar characteristics to the third sample, but the volume of the impact sound is louder than the fourth sample, and is not very good overall. From this, it can be seen that the filling position and range of the filling prevention material 30 of the fifth sample is not very effective in improving the impact sound.

Measurement result 6 shows the restitution coefficient and the impact sound vibration damping effect for the head of the iron golf club according to the sixth sample, in which "the toe side filling height Y1 is located below the center of gravity pocket projection point CGP (Y2<Y1<YCG) and the sole side filling height Y2 is filled with vibration-proof material 30 at a height (Y2<YCG-R) that does not interfere with the unfilled circle A0." The restitution coefficient for the sixth sample was the same as that of the first sample. This shows that the filling position and range of the vibration-proof material 30 in the pocket portion 27 of the sixth sample does not reduce the restitution coefficient.

On the other hand, the impact sound vibration damping effect of the sixth sample shows the same tendency as the first sample in terms of both the volume and convergence time (resonance time), and is generally not very good. This shows that the filling position and range of the filling prevention material 30 of the sixth sample does not have much effect on improving the impact sound.

Measurement result 7 shows the restitution coefficient and impact sound vibration damping effect for the head of the iron golf club of the seventh sample, in which the toe side filling height Y1 is located above the center of gravity pocket projection point CGP (Y1>YCG) and the sole side filling height Y2 is zero. The restitution coefficient of the seventh sample was the same as that of the first sample. This shows that the filling position and range of the vibration-proofing material 30 of the seventh sample within the pocket portion 27 does not reduce the restitution coefficient.

On the other hand, the impact sound vibration damping effect of the seventh sample shows the same tendency as the first sample in terms of both the volume and convergence time (resonance time), and is generally not very good. This shows that the filling position and range of the vibration-proofing material 30 of the seventh sample does not have much effect on improving the impact sound.

Summarizing the measurement results so far, from Measurement Result 2 and Measurement Result 4, it can be seen that providing the non-filled circle A0 of the vibration-isolating material 30 in the pocket portion 27 has the effect of minimizing the decrease in the restitution coefficient caused by the vibration-isolating material 30 and improving the volume and convergence time (resonance time) of the hitting sound.

In addition, from Measurement Results 3 and 4, it can be seen that when the vibration-proofing material 30 is filled on the toe portion 21 side, the vibration damping effect of the impact sound is higher (improving the volume and convergence time (resonance time) of the impact sound) when the vibration-proofing material 30 is filled on the sole portion 24 side rather than the heel portion 23 side.

In addition, from measurement results 3 and 5, it can be seen that if the vibration-proofing material 30 is filled only in the sole portion 24 and not in the toe portion 21, the vibration-damping effect on the impact sound is weakened. From this, it is necessary for the vibration-proofing material 30 to be filled at least in the toe portion 21.

In addition, from measurement results 3 and 6, it can be seen that the vibration damping effect on the impact sound is greater when the toe side filling height Y1 of the vibration-proof material 30 is higher than the height YCG of the center of gravity pocket projection point.

In addition, from the above measurement results 4 and 7, it can be seen that when the filling height Y2 of the vibration-proofing material 30 on the sole side is zero, the vibration damping effect on the impact sound is weakened. From this, when the vibration-proofing material 30 is filled on the toe part 21 side and the sole part 24 side, the vibration damping effect on the impact sound is enhanced.

Next, we will explain the effect that the Shore hardness of the vibration-isolating material has on the coefficient of restitution (COR) and the vibration damping effect of the hitting sound.

Measurement result 8 in Figure 11 shows the restitution coefficient and impact sound vibration damping effect of the head portion 100 of the iron golf club of the present invention relating to the above-mentioned eighth sample, which is "wherein the vibration-isolating material 30 in the above-mentioned third sample has been changed to vibration-isolating material 30A." The vibration-isolating material 30A is a resin made of a silyl group-containing special polymer with a Shore hardness of A25 (product number TB1530P made by ThreeBond Co., Ltd.). Incidentally, the vibration-isolating material 30 is a resin made of a silicone potting agent with a Shore hardness of A70 (product number TB1230 made by ThreeBond Co., Ltd.).

Although the resilience coefficient of the eighth sample is slightly lower than that of the third sample, from 0.815 to 0.814, it still has the same level of resilience coefficient as the fourth sample. This shows that even when the Shore hardness of the vibration isolating material is changed from A70 (silicone resin) to A25 (silyl group-containing special polymer), the filling position and range of the vibration isolating material 30A of the eighth sample does not reduce the resilience coefficient very much.

On the other hand, the impact sound vibration damping effect of the eighth sample is slightly increased in volume and convergence time (resonance time) compared to the third sample, but has the same level of impact sound vibration damping effect as the fourth sample. This shows that even when the Shore hardness of the vibration-proofing material is changed from A70 (silicone resin) to A25 (silyl group-containing special polymer), the filling position and range of the vibration-proofing material 30A of the eighth sample is effective in improving the impact sound.

Measurement result 9 shows the restitution coefficient and the vibration damping effect of the impact sound for the head portion 100 of the iron golf club of the present invention relating to the above-mentioned ninth sample, which is "the third sample in which the vibration-proof material 30 has been changed to vibration-proof material 30B." The vibration-proof material 30B is a resin made of urethane with a Shore hardness of A50.

The restitution coefficient for the ninth sample remains at 0.815, and is not reduced compared to the third sample. This shows that even if the Shore hardness of the vibration isolating material is changed from A70 (silicone resin) to A50 (urethane resin), the filling position and range of the vibration isolating material 30B for the ninth sample does not reduce the restitution coefficient.

On the other hand, the impact sound vibration damping effect of the ninth sample is also at the same level as the third sample in terms of the volume and convergence time (resonance time), and the impact sound vibration damping effect is not weaker than that of the third sample. This shows that even when the Shore hardness of the vibration-proofing material is changed from A70 (silicone resin) to A50 (urethane resin), the filling position and range of the vibration-proofing material 30A of the eighth sample is effective in improving the impact sound.

Measurement result 10 shows the restitution coefficient and the vibration damping effect of the impact sound for the head portion 100 of the iron golf club of the present invention relating to the above-mentioned ninth sample, which is "the third sample in which the vibration-proof material 30 has been changed to vibration-proof material 30C." The vibration-proof material 30C is a resin made of silicone with a Shore hardness of A50 (manufactured by Togawa Rubber Co., Ltd.).

The restitution coefficient for the 10th sample remains at 0.815, and is not reduced compared to the 3rd sample. This shows that even if the Shore hardness of the vibration isolating material is changed from A70 (silicone resin) to A50 (silicone resin), the filling position and range of the vibration isolating material 30C for the 9th sample does not reduce the restitution coefficient.

On the other hand, the impact sound vibration damping effect of the 10th sample is the same as that of the third sample in terms of the volume and convergence time (resonance time), and the impact sound vibration damping effect is not weaker than that of the third sample. This shows that even when the Shore hardness of the vibration-proofing material is changed from A70 (silicone resin) to A50 (silicone resin), the filling position and range of the vibration-proofing material 30C of the 10th sample is effective in improving the impact sound.

From the above, measurement results 3 and measurement results 8 to 10, it can be seen that if the hardness of the vibration prevention material is in the range of Shore hardness A25 or more, preferably in the range of Shore hardness A50 to A70, it is possible to improve the hitting sound without reducing the resilience coefficient.

The head portion 100 of an iron golf club according to one embodiment of the present invention has been described above with reference to the drawings, but the present invention is not limited to the above embodiment. In other words, various changes and modifications can be made without departing from the technical scope of the present invention. For example, the present invention can also be applied to a cavity-back iron golf club that does not have a pocket portion 27 and has a sealed hollow structure.

In addition, for the radius R of the non-filled circle A0, instead of the center of gravity height YG based on the leading edge of the face surface 10F, it is also possible to use another reference value, for example the center of gravity height YCG based on the lowest point of the pocket portion 27.

10 Face portion 20 Head body portion 21 Toe portion 22 Top portion 23 Heel portion 24 Sole portion 25 Hosel portion 26 Cavity portion 26a Cavity bottom wall 27 Pocket portion 30 Vibration prevention material 100 Head portion of iron golf club A0 Non-filled circle CG Center of gravity CGF Center of gravity face surface projection point CGP Center of gravity pocket projection point R Radius of no-fill circle Y1 Toe portion side filling height Y2 Heel portion side filling height YG Center of gravity height YCG when the leading edge is used as the reference Center of gravity height when the lowest point of the pocket is used as the reference

Claims (7)

A face portion (10) having a face surface (10F) on which a ball is struck;
a head body portion (20) having a recess (27) formed on a face back surface (10B) side;
In the iron golf club head, a vibration-proof material (30, 30A, 30B, 30C) is filled in the recess (27),
The vibration-isolating material (30, 30A, 30B, 30C) is filled outside an inner area (A0) of a circle having a predetermined radius (R) and centered on a center of gravity projection point (CGP) vertically projected from the center of gravity (CG) of the head to a wall surface (26a) of the recess ,
The filling height (Y1) of the vibration isolating material (30, 30A, 30B, 30C) on the toe portion (21) side of the face portion (10) is higher than the height (YCG) of the center of gravity projection point (CGP).
The iron golf club is characterized by: 2. The iron golf club according to claim 1,
the vibration-proof material (30, 30A, 30B, 30C) is filled in the recess (27) along the toe portion (21) and the sole portion (24) of the face portion (10) so as not to overlap with the inner area (AO) of the circle. 3. The iron golf club according to claim 2,
an infill height (Y1) of the vibration-isolating material (30, 30A, 30B, 30C) on the toe portion (21) side is higher than an infill height (Y2) on the sole portion (24) side. 4. The iron golf club according to claim 3 ,
The iron golf club is characterized in that a filling height (Y2) of the vibration-isolating material (30, 30A, 30B, 30C) on the sole portion (24) side is lower than a height (YCG-R) obtained by subtracting the radius (R) from the height (YCG) of the center of gravity projection point (CGP). The iron golf club according to any one of claims 1 to 4 ,
said radius (R) of said inner area (A0) of said circle has a length within a range of 25% to 70% of a center of gravity height (YG) when the leading edge of said face surface (10F) for said center of gravity projection point (CGP) is used as a reference. 2. The iron golf club according to claim 1 ,
The iron golf club, wherein the Shore hardness of the vibration-isolating material (30, 30A, 30B, 30C) is within a range of A25 to A70. 2. The iron golf club according to claim 1 ,
The iron golf club, wherein the material of the vibration isolating material (30, 30A, 30B, 30C) is a silicone resin, a urethane resin, or a special polymer containing a silyl group.