Method for estimating the repulsion performance of a golf club head

Abstract

To simply estimate a repulsion performance of a golf club head in a short time.SOLUTION: Provided is a method of estimating a repulsion performance of a golf club head, comprising: a first step S1 of measuring the repulsion performance of each of a plurality of golf club heads, a second step S2 of measuring a feature quantity of each of the plurality of golf club heads; a third step S3 of deriving an estimation formula for directly or indirectly estimating the repulsion performance from the feature quantity; and a fourth step S4 of calculating the repulsion performance of another golf club head, which is different from the plurality of golf club heads, using the estimation formula.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for estimating the repulsion performance of a golf club head. [Background technology]

[0002] The R&A (Royal and Ancient Golf Club of St. Andrews) and the USGA (United States Golf Association) limit the ability of a golf club to transmit power to a golf ball, i.e., its repulsion performance, thereby limiting the possibility of a golfer beating his rival with just his equipment. An index of such repulsion performance is CT (characteristic time). Golf club heads with CT exceeding the rules cannot be used in official competitions.

[0003] Specifically, CT is measured by a pendulum test. In the pendulum test, a golf club is fixed in a pendulum test device in a specific direction, and then an iron ball is struck against the face of the club using a pendulum. The acceleration data of the iron ball is then measured, and the CT is calculated from the contact time between the iron ball and the face. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6604364 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0005] However, golf club heads, which are mass-produced products, contain unavoidable variations and tolerances during manufacturing. Therefore, even golf club heads made with the intention of having the same specifications may have different CTs due to variations during manufacturing. For this reason, it is important for golf club manufacturers to understand the CT of golf club heads prior to sales in order to ensure that the CT of the golf club head falls within the rules. The following Patent Document 1 is an example of related technology.

[0006] However, there is a problem in that performing the pendulum test on all of the golf club heads takes a lot of time.

[0007] The present invention has been devised in view of the above problems, and has as its main object to provide a method for easily estimating the repulsion performance of a golf club head in a short period of time. [Means for solving the problem]

[0008] The present invention is a method for estimating the repulsion performance of a golf club head, comprising: a first step of measuring the repulsion performance of each of a plurality of golf club heads; a second step of measuring characteristic amounts of each of the plurality of golf club heads; a third step of deriving an estimation equation for directly or indirectly estimating the repulsion performance from the characteristic amounts; and a fourth step of calculating the repulsion performance of a golf club head other than the plurality of golf club heads using the estimation equation.

[0009] In another aspect of the present invention, the second step may measure the characteristic amounts without deforming the plurality of golf club heads.

[0010] In another aspect of the present invention, the characteristic amounts can include at least one or more of physical amounts related to the size, angle, weight, volume, thickness, and center of gravity of the golf club head.

[0011] In another aspect of the present invention, the estimation equation may include a regression equation in which the resilience performance is a response variable and the feature amount is an explanatory variable.

[0012] In another aspect of the present invention, the estimation equation can include a regression equation having head stiffness as a dependent variable and the feature amount as an explanatory variable, and the fourth step can include a step of calculating the head stiffness of the other golf club head using the estimation equation, and a step of substituting the calculated head stiffness into an index indicating the stiffness of a numerical calculation model that simulates a pendulum test to calculate the repulsion performance.

[0013] In another aspect of the present invention, the resilience performance may be CT.

[0014] In another embodiment of the present invention, the resilience performance may be a contact time at low speed, medium speed, and high speed in a pendulum test for measuring CT. In this case, the present invention may further include a step of calculating CT using the contact time. Effect of the Invention

[0015] The method of estimating the repulsion performance of a golf club head of the present invention employs the above steps, making it possible to easily estimate the repulsion performance of a golf club head in a short amount of time. [Brief description of the drawings]

[0016] [Figure 1] 5 is a flowchart showing an example of a processing procedure of a method for estimating the repulsion performance of a golf club head according to the present embodiment. [Diagram 2] FIG. 2 is a front view of the golf club head. [Diagram 3] FIG. 2 is a plan view of the golf club head. [Figure 4] FIG. 2 is a bottom view of the golf club head. [Diagram 5] FIG. 1 is a schematic diagram of a pendulum test machine. [Figure 6]1 is a graph showing the time history of the velocity and acceleration of a hemisphere in a pendulum test. [Figure 7] 1 is a graph showing the relationship between the contact time of a hemisphere and the impact speed in a pendulum test. [Figure 8] FIG. 2 is a vertical cross-sectional view of a golf club head. [Figure 9] FIG. 2 is a horizontal cross-sectional view of a golf club head. [Figure 10] 1 is a schematic diagram of a spring-mass model simulating a collision between a golf club head and a hemisphere. [Figure 11] 11 is a graph showing the relationship between time calculated from a spring-mass model and the displacement of a golf club head and a hemisphere. [Figure 12] 11 is a graph showing the relationship between time calculated from a spring-mass model and the velocity of a golf club head and a hemisphere. [Figure 13] 13 is a graph showing the velocity change of a hemisphere calculated from a spring-mass model. [Figure 14] 13 is a flowchart showing an example of a processing procedure of a third step in the second embodiment. [Figure 15] 13 is a flowchart showing an example of a processing procedure of a fourth step in the second embodiment. [Figure 16] 1 is a graph showing the relationship between actual measured values ​​and estimated values ​​of CT. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the dimensional ratio of the actual structure in order to facilitate understanding of the present invention. In addition, when there are multiple embodiments, the same or common elements are given the same reference numerals throughout the specification, and duplicated explanations are omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0018] 1 is a flowchart of a method (hereinafter, sometimes simply referred to as a "method") for estimating the repulsion performance of a golf club head (hereinafter, simply referred to as a "head") according to one embodiment of the present invention. The method of this embodiment is a method for estimating the repulsion performance of a head, and includes a first step S1 of measuring the repulsion performance of each of a plurality of heads, a second step S2 of measuring characteristic amounts of each of the plurality of heads, a third step S3 of deriving an estimation formula for directly or indirectly estimating the repulsion performance from the characteristic amounts, and a fourth step S4 of calculating the repulsion performance of a head other than the plurality of heads using the estimation formula.

[0019] The first step S1, the second step S2, and the third step S3 obtain the relationship between the repulsion performance and the feature amount based on a plurality of existing heads. In the fourth step S4, the feature amount is measured for a head other than the plurality of heads, and the repulsion performance of the other head is calculated as an estimated value using the feature amount and the relationship. Therefore, in the present invention, the repulsion performance of the other head can be easily estimated in a short time. Each step will be described in detail below, taking the case where the repulsion performance is CT as an example.

[0020] [First step S1] In the first step S1 of this embodiment, the repulsion performance of each of the multiple heads is measured.

[0021] 2 to 4 respectively show a front view, a plan view and a bottom view of the head 1. As shown in Fig. 2 to 4, the head 1 is, for example, a hollow wood-type golf club head, and all of them are in a standard state. The standard state is a state in which the head 1 is placed on a horizontal plane HP (Fig. 2) with a lie angle and a loft angle determined for the head 1.

[0022] The head 1 is entirely or mainly made of a metal material such as titanium alloy, stainless steel, etc. The head 1 includes, for example, a face 2, a crown 3, a sole 4, and a hosel 5 as a typical structure of a wood type.

[0023] The face 2 forms a surface for hitting a ball and has a face center FC which is its geometric center. The crown 3 extends from the upper edge of the face 2 toward the rear of the head so as to form the top surface of the head. A hosel 5 is provided on the heel side of the crown 3. A club shaft (not shown) is fixed to the hosel 5. The sole 4 extends from the lower edge of the face 2 toward the rear of the head so as to form the bottom surface of the head.

[0024] The multiple heads 1 of this embodiment are, for example, all the same mass-produced models, that is, manufactured by industrial techniques with the intention of having the same specifications (weight, volume, loft angle, lie angle, etc.). However, these multiple heads 1 do not have completely the same shape in the sense that they include tolerances and the like that inevitably occur during manufacturing.

[0025] The number of heads 1 used to measure the resilience performance is not particularly limited, but in order to improve the accuracy of the estimation formula obtained in the third step S3, it is preferable to use, for example, 30 or more, preferably 50 or more, and more preferably 100 or more.

[0026] In the first step S1, the CT is measured as the repulsion performance of the head 1. The CT is one of the indicators that correlate with repulsion performance, like the COR. The CT is stipulated in the Pendulum Test Protocol (R&A test internal regulations) and is measured using a pendulum test machine.

[0027] Fig. 5 is a schematic diagram of a pendulum test machine 100. As shown in Fig. 5, the pendulum test machine 100 includes a pendulum 101. A hemispherical hemisphere 102 is provided at the tip of the pendulum 101 as a metallic impactor. An acceleration pickup 103 for measuring the acceleration of the hemisphere 102 is attached to the pendulum 101. The pendulum test machine 100 also includes a jig (not shown) for holding the shaft 11 of the golf club 10 to be measured.

[0028] CT is measured as follows. First, the hemisphere 202 of the pendulum 101 is collided with the face 2. The collision speed is set to three conditions, low speed, medium speed, and high speed, by changing the height of the pendulum 101. Under each condition, the acceleration signal of the hemisphere 102 is measured by the acceleration pickup 103.

[0029] Fig. 6 is a graph showing the change in acceleration of the hemisphere 102 before and after it collides with the face 2, and the velocity obtained by integrating the acceleration with time. In Fig. 6, the horizontal axis shows time, the left side of the vertical axis shows acceleration, and the right side of the vertical axis shows velocity. The velocity is adjusted so that it is zero the moment the hemisphere 102 collides with the face 2, and shows the velocity in the direction away from the face 2. In Fig. 6, the time period from 5% to 95% of the maximum value of the velocity of the hemisphere 102 (approximately 0.6 m / s in Fig. 6) is called the contact time.

[0030] 7 shows the relationship between the contact time obtained under three conditions of impact speed of the hemisphere 102, namely, low, medium, and high speed, and the impact speed raised to the power of -1 / 3. The CT is specified as the intercept (contact time) of the linear approximation line F obtained from the results of the three conditions (low speed / medium speed / high speed). The Rules of Golf stipulate that the CT must not exceed 239 μsec + 18 μsec (tolerance), i.e., 257 μsec.

[0031] In the first step S1, the CT of each of the multiple heads 1 is measured in the above manner.

[0032] [Second step S2] In the second step S2 of this embodiment, the characteristic quantities of each of the multiple heads 1 whose CT has been measured as the repulsion performance are measured. The characteristic quantities may include at least one, preferably two or more, and more preferably three or more of the physical quantities related to the dimensions, angle, weight, volume, thickness, and center of gravity of the head 1.

[0033] The dimensions of the head 1 are mainly characteristic quantities determined from the outer shape of the head 1, and can include, for example, as shown in FIG. 2 or FIG. 3, head height H1, face height H2, face length L1, length L2 of the face center FC in the front-to-back direction of the head, length L3 in the toe-heel direction of the head, hosel outer diameter r, face roll R1 which is the radius of curvature of the face 2 in the vertical cross section of the head as shown in FIG. 8, and face bulge R2 which is the radius of curvature of the face 2 in the horizontal cross section of the head as shown in FIG. 9.

[0034] The weight and volume of the head 1 may include, for example, the entire weight and volume of the head 1.

[0035] The angle of the head 1 is a characteristic amount relating to the angle at any position of the head 1, and can include, for example, the lie angle, the hook angle, the real loft angle, the face progression, and the like.

[0036] The thickness of the head 1 is a feature amount relating to the thickness at any position of the head 1, and can include, for example, the thickness of each portion of the face 2, the thickness of the crown 3, the thickness of the sole 4, and the like.

[0037] Physical quantities related to the center of gravity of head 1 can include, for example, the center of gravity height, the sweet spot height, the center of gravity depth, the moment of inertia about a vertical axis passing through the center of gravity, the moment of inertia about a horizontal axis extending in the toe-heel direction through the center of gravity, the moment of inertia about the shaft axis, etc.

[0038] Moreover, all of the above-mentioned characteristic amounts can be measured statically, that is, without deforming the head 1.

[0039] For example, the shape of the head 1 can be easily measured without contacting the head 1 by using a three-dimensional measuring device or the like. Similarly, the thickness of the head 1 can be easily measured without deforming the head 1 by using, for example, an ultrasonic thickness gauge. In this way, when the feature amounts are measured in the second step S2 without deforming the multiple heads 1, this is desirable in that it solves the problem of the head 1 being scratched during measurement (the above-mentioned Patent Document 1 does not solve the problem of the head being scratched because an impact body is collided with the head).

[0040] Moreover, the measurement of the above-mentioned characteristic quantities can be performed in a shorter time than performing a pendulum test.

[0041] As described above, various values ​​can be adopted for the feature amount of the head 1, but it is preferable to select a value that has a large variation during manufacturing and contributes greatly to the repulsion performance of the head 1. This makes it possible to estimate the repulsion performance of the head with higher accuracy. As such feature amount, for example, one or more, preferably two or more, of the thickness of each part of the face 2, the face roll R1, the face bulge R2, etc. are desirable. The face 2 is a part that directly contacts the ball and contributes greatly to the repulsion performance of the head 1. In addition, in general, the face 2 is often formed by pressing or forging, and the mold is worn with use, so it is presumed that the feature amount is likely to have variation during manufacturing.

[0042] In the second step S2 of this embodiment, the thickness and face roll R1 of the head 1 are measured as the feature amounts.

[0043] The thickness of the head 1 is measured at multiple locations, and in this embodiment, at least one location is measured from each of the face 2, the crown 3, and the sole 4. For example, the thickness of the face 2 is preferably measured at multiple locations, and in this embodiment, thicknesses t1, t2, and t3 are measured at the face center FC, the toe side of the face center FC, and the sole side of the face center FC. Furthermore, for the crown 3 and the sole 4, thicknesses t4 and t5 are measured near the face side (for example, within 10 mm from the face 2) and at approximately the middle position in the toe-heel direction. Furthermore, the face roll R1 is measured as the radius of curvature of the face 2 in the head vertical section passing through the face center FC.

[0044] As described above, in the second step S2 of this embodiment, a plurality of feature amounts can be measured without deforming the head 1. However, the second step S2 is not limited to such a specific example.

[0045] [Third step S3] In a third step S3, an estimation formula for directly or indirectly estimating the repulsion performance from the characteristic amount obtained in the second step S2 is derived.

[0046] First, a description will be given of an embodiment (first embodiment) in which an estimation formula for directly estimating repulsion performance is derived from the feature quantities obtained in the second step S2. Here, the term "directly" refers to a case in which the objective variable of the estimation formula is the repulsion performance itself.

[0047] In the first embodiment, a regression equation is obtained as an estimation equation, in which the CT as the resilience performance measured in the first step S1 is used as the objective variable, and the feature quantities measured in the second step S2 are used as explanatory variables. In this embodiment, the following multiple regression equation (1) is created, in which the CT as the resilience coefficient is explained using the six feature quantities t1 to t5 and R1. This multiple regression equation (1) is input to a computer, for example. In equation (1), a1, b1, c1, d1, e1, and f1 are all constants.

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[0048] [Fourth step S4] In the fourth step S4 of this embodiment, the estimation equation obtained in the third step S3 is used to calculate the repulsion performance of a head (hereinafter simply referred to as "head 1a") other than the multiple heads 1 (whose repulsion performance has already been measured).

[0049] Specifically, first, the feature amount of the head 1a is measured by the same procedure as in the second step S2. Therefore, the feature amount of the head 1a is measured without, for example, deformation, so that the head 1a is prevented from being scratched, and the commercial value of the head 1a is not reduced.

[0050] Next, the characteristic quantities of the head 1a are substituted into the multiple regression equation (1) derived in the third step S3, and CT is calculated as the repulsion performance of the head 1a. This calculation is performed, for example, by inputting the characteristic quantities into the computer that stores the multiple regression equation (1). That is, the third step S3 and the fourth step S4 can be processed using a computer.

[0051] As described above, according to the method for estimating the repulsion performance of a head in this embodiment, by measuring predetermined characteristic parameters for another head 1a and substituting them into the estimation formula, the repulsion performance of the head 1a can be easily estimated by calculation.

[0052] Furthermore, since the time required for measuring the feature amounts in the second step S2 is shorter than the time required for the pendulum test, the estimation method of this embodiment can estimate the repulsion performance of the head 1a in a short time.

[0053] Furthermore, by including as feature quantities the thickness of the face 2, which has a large contribution to the repulsion performance, and the thicknesses of the crown 3 and the sole 4, the repulsion performance can be estimated with high accuracy.

[0054] In the first embodiment, the resilience performance is expressed as CT, but instead, it may be expressed as the contact times at low, medium and high speeds in a pendulum test for measuring CT. In this case, the estimation method of the first embodiment may further include a step of calculating CT using the contact times at the three speed conditions, as shown in FIG.

[0055] [Second embodiment] Next, a second embodiment of the present invention will be described. In the third step S3 of the first embodiment, an estimation formula for directly estimating the repulsion performance from the measured feature amount is derived, but in the second embodiment, an estimation formula for indirectly estimating the repulsion performance is derived. Here, the term "indirectly" means that the objective variable of the estimation formula is not the repulsion performance itself. Since the CT as the repulsion performance is a so-called natural frequency fixed at one end, if it is estimated by a simple regression formula, there is a risk that it will deviate from its physical meaning. Therefore, in this embodiment, as a physical meaning, only the rigidity is linked to the characteristics (structure) of the head 1a, and the weight is treated separately. As a result, in the second embodiment, it is possible to estimate the repulsion performance with higher accuracy than in the first embodiment.

[0056] The estimation equation derived in the second embodiment is a regression equation that uses the head stiffness as a response variable and the feature amount as an explanatory variable.

[0057] In order to verify the measurement principle of the pendulum test, R&A adopts a numerical calculation model that uses Herlz's contact theory as a spring mass model. Since this numerical calculation model incorporates a head stiffness parameter, in the second embodiment, first, an estimation formula for estimating the head stiffness from the characteristic amount of the head 1 is derived, and this estimated head stiffness is substituted into the numerical calculation model to calculate (estimate) the repulsion performance.

[0058] First, the measurement principle of the pendulum test will be described with reference to Fig. 10. Fig. 10 shows a spring mass model that simplifies the pendulum test as a numerical calculation model. This spring mass model includes a first model M1 that simplifies the hemisphere 102 of the pendulum 101, and a second model M2 that simplifies the golf club 10.

[0059] The first model M1 is modeled with a mass 6 of the hemisphere 102 with a mass mb, and a spring 7 with a nonlinear spring constant kH corresponding to the rigidity of the hemisphere 102. The second model M2 is modeled with a mass 8 of the head 1 with a mass mc, and a spring 9 with a linear spring constant kc (sometimes referred to as head rigidity kc) corresponding to the head rigidity. The first model M1 and second model M2 come into contact at point P. Furthermore, at a certain time, the displacement of the mass 6 of the first model M1 is represented by xb, the displacement of the mass 8 of the second model M2 by xc, and the displacement of the point P by xf.

[0060] The reason why the first model M1 is a nonlinear spring is that the spring constant changes depending on the displacement of the point P where the hemisphere 102 contacts the face 2. This nonlinear spring constant kH can be calculated by the following formula (2).

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[0061] In addition, in formula (2), R * and E * can be calculated based on the Herlz contact theory using equations (3) and (4), respectively.

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[0062] Furthermore, the equations of motion of the above spring-mass model can be expressed by equations (5) and (6).

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[0063] Next, by numerically integrating the above equations of motion (5) and (6) and evolving them over time, the positions and velocities of the first model M1 and the second model M2 at a certain time can be successively obtained after a short time from their positions and velocities. As the numerical integration method, for example, the Euler method or the second or fourth order Runge-Kutta method can be used.

[0064] Figures 11 to 13 show examples of the results of the above numerical calculations. Figure 11 shows the time history of the displacements xb and xc of masses 6 and 8, respectively. Figure 12 shows the time history of the velocities Vb and Vc of masses 6 and 8, respectively. Figure 13 shows the time history of the velocity (integral value of acceleration) of mass 6 (i.e., the hemisphere). It can be seen that the graph in Figure 13 shows the same tendency as the graph of the velocity time history of the hemisphere measured in the pendulum test shown in Figure 6.

[0065] Therefore, when estimating the repulsion performance, first, the head stiffness (i.e., the linear spring constant kc of the second model M2) is estimated from the feature amount, and the estimated head stiffness is used to numerically integrate the equation of motion of the above numerical calculation model, thereby obtaining the relationship shown in Fig. 13. From this relationship, the time in the section from 5% to 95% of the maximum value of the speed of the hemisphere 102 (approximately 1.62 m / s in Fig. 13) can be obtained as the "contact time".

[0066] Next, a more specific procedure of the third step S3 and the fourth step S4 of the second embodiment will be described.

[0067] [Third step (second embodiment)] 14 is a more detailed flowchart of the third step S3 of the second embodiment. In the third step S3 of the second embodiment, first, for three impact speed conditions of low speed, medium speed, and high speed in the pendulum test for measuring CT, the head stiffness kc is calculated by a parameter study using the spring mass model (FIG. 10) and the contact time measured in the first step S1 (step S31).

[0068] Next, for three impact speed conditions, low speed, medium speed, and high speed, a regression equation such as the following equation (7) is derived, in which the head stiffness kc is the objective variable and the feature amount measured in the second step S2 is the explanatory variable (step S32). This multiple regression equation is input to, for example, a computer. In addition, in equation (7), a2, b2, c2, d2, e2, and f2 are all constants.

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[0069] [Fourth step (second embodiment)] 15 is a more detailed flowchart of the fourth step S4 of the second embodiment. In the fourth step S4 of the second embodiment, first, the characteristic amount of the other head 1a is measured (step S41).

[0070] Next, for three impact speed conditions of low speed, medium speed, and high speed, the head stiffness kc of another head 1a is calculated as an estimated value using the above regression equation (7) (step S42).

[0071] Next, for three impact speed conditions, low speed, medium speed, and high speed, the head stiffness kc of another head 1a is substituted into an index indicating stiffness of a numerical calculation model that simulates a pendulum test. In this embodiment, the head stiffness is substituted into a spring mass model (FIG. 10) as a numerical calculation model, and the equation of motion is numerically integrated to calculate the contact time (step S43). This contact time may be adopted as the repulsion performance.

[0072] In a preferred embodiment, next, CT is calculated from the contact times under three collision speed conditions, low speed, medium speed and high speed (step S44).

[0073] Fig. 16 is a graph showing the relationship between the measured CT value and the estimated CT value calculated by the second embodiment (n=85). As is clear from Fig. 16, a good correlation is obtained between the measured CT value and the estimated CT value. In this example, the correlation coefficient is about 0.933.

[0074] Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific disclosure, and can be modified and implemented within the scope of the technical idea described in the claims. For example, the repulsion performance is not limited to CT, and in other aspects, it may be, for example, COR. In addition, the present invention includes a method equivalent to the above disclosure. [Explanation of symbols]

[0075] 1, 1a Golf club head 2 Face 10. Golf Clubs

Claims

1. A method for estimating the repulsion performance of a golf club head, comprising: A first step of measuring the repulsion performance of each of a plurality of golf club heads; a second step of measuring a characteristic amount of each of the plurality of golf club heads; a third step of deriving an estimation formula for directly or indirectly estimating the repulsion performance from the feature amount; and a fourth step of calculating the repulsion performance of a golf club head other than the plurality of golf club heads by using the estimation formula, the estimation formula includes a regression formula having head stiffness as a response variable and having the feature amount as an explanatory variable, the fourth step is a step of calculating the head stiffness of the other golf club head using the estimation equation; and calculating the repulsion performance by substituting the calculated head rigidity into an index indicating the rigidity of a numerical calculation model that simulates a pendulum test. A method for estimating the repulsion performance of a golf club head.

2. 2. The method for estimating the repulsion performance of a golf club head according to claim 1, wherein the second step measures the feature amounts without deforming the plurality of golf club heads.

3. The method for estimating the repulsion performance of a golf club head according to claim 1 , wherein the feature amount includes at least one of physical amounts related to a dimension, an angle, a weight, a volume, a thickness, and a center of gravity of the golf club head.

4. The method for estimating the repulsion performance of a golf club head according to claim 1 or 2, wherein the feature amount includes two or more of physical amounts related to the size, angle, weight, volume, thickness, and center of gravity of the golf club head.

5. A method for estimating the repulsion performance of a golf club head described in any one of claims 1 to 4, wherein the repulsion performance is CT.

6. A method for estimating the repulsion performance of a golf club head described in any one of claims 1 to 4, wherein the repulsion performance is the contact time at low speed, medium speed and high speed in a pendulum test for measuring CT.

7. A method for estimating the rebound performance of a golf club head as described in claim 6, further comprising a step of calculating CT using the contact time.

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