JP3374123B2 - Golf ball - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball, and more particularly to an improvement in the trajectory of a golf ball. 2. Description of the Related Art A golf ball hit with a golf club flies at an upward launch angle with respect to the horizontal direction. This launch angle results from the golf club head having a loft angle. Also, when jumping out, the golf ball involves a so-called back spin. The back spin is caused by a shear force generated when the golf ball collides with a head having a loft angle. It has been reported that the amount of backspin is approximately proportional to the impulse of the shear force during collision (Dynamicsa).
nd Design Conference '98
in Hokkaido, “Analysis of Spin Expression Mechanism in Golf Impact”). The trajectory of a launched golf ball is greatly affected by the launch angle and the backspin. That is, a golf ball having a large launch angle tends to have a high trajectory, and a golf ball having a small launch angle tends to have a low trajectory. Further, since a lift is generated in the golf ball by the back spin, a golf ball having a large back spin tends to have a high trajectory, and a golf ball having a small back spin tends to have a low trajectory. [0004] The golfer's required performance for the golf ball includes flight distance, shot feeling, control performance, and the like. In particular, when the golfer uses a long iron, middle iron, or wood type golf club (driver, brushy, spoon, buffy, creek, etc.), the flying distance is an important required performance. It is well known that in order to increase the flight distance when hit with a long iron or the like, the golf ball must have a high trajectory to some extent and the flight time must be increased. As described above, a golf ball having a large launch angle or a golf ball having a large back spin has a high trajectory, but a golf ball having a large back spin tends to have a short flight distance. This is presumed to be due to the fact that kinetic energy is consumed by the backspin, and that the lift is applied perpendicular to the flight direction, so that the lift pulls the golf ball backward to the trajectory highest point. It can be said that a golf ball that does not exert much back spin and achieves a high trajectory with a high launch angle is a golf ball that has a large flight distance when hit with a long iron or the like. [0006] Based on these findings, the development of golf balls in which backspin is unlikely to occur at the time of hitting and the launch angle is large has been made from both a compounding aspect and a structural aspect. . However, golfers have a high demand for the flight distance, and no golf ball satisfying this demand has yet been obtained. [0007] The present invention has been made in view of such circumstances, and a golf ball having a larger launch angle than conventional golf balls and a smaller back spin than conventional golf balls when hit under the same conditions. The purpose is to provide a ball. [0008] In order to achieve the above-mentioned object, the invention is directed to a method in which a direction rotated 22 ° counterclockwise with respect to a vertically upward direction is defined as a z direction, and a direction rotated horizontally rightward. The direction rotated by 22 ° counterclockwise is defined as the x direction, and when the golf ball collides with the collision plate whose surface extends in the x direction vertically upward at a speed of 35 m / s, the load cell provided on the back surface of the collision plate The time series data of the force in the z direction is Fn (t), and the time series data of the force in the x direction is Ft.
(T), the time from the start of the collision until the sign of Fn (t) first changes from positive to zero is T1, and Ft (t)
A golf ball in which the value of (T1 / T2) is 1.85 or more and 2.10 or less, where T2 is the time from the start of collision until the sign of (t) first changes from positive to negative. is there. In this golf ball, the value of (T1 / T2) is 1.85 or more and 2.10 or less, which is larger than that of a conventional golf ball. small. Therefore, in this golf ball, the back spin is hardly applied (low spin), and the launch angle is high (high launch). BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Embodiments of the present invention will be described. FIG. 1 is a sectional view showing a golf ball 1 according to one embodiment of the present invention. This golf ball 1 includes a core 3 and a cover 5. The core 3 includes a spherical first layer 7 and a second layer 9 surrounding the first layer 7.
A third layer 11 surrounding the second layer 9, a fourth layer 13 surrounding the third layer 11, a fifth layer 15 surrounding the fourth layer 13, and a sixth layer surrounding the fifth layer 15. Layer 17
Consists of That is, the golf ball 1 has a seven-layer structure including the core 3 and the cover 5 having six layers. The golf ball 1 is usually provided with a coating layer, but this coating layer is not shown in FIG. The first to sixth layers 7 to 17 are formed by crosslinking a rubber composition. As the rubber, polybutadiene having excellent resilience performance is suitably used, and high cis polybutadiene having cis-1,4 bonds of 90% or more is particularly preferable. Also, with polybutadiene,
Other rubbers such as natural rubber, polyisoprene, styrene-butadiene copolymer and ethylene-propylene-diene copolymer may be mixed. Even when other rubbers are mixed, the compounding amount is 5 parts per 100 parts of polybutadiene.
It is preferably 0 parts or less. In addition, in this specification, the numerical value shown by "part" means a ratio based on mass. The rubber composition contains a co-crosslinking agent, an organic peroxide and a filler. Preferred co-crosslinking agents are metal salts of α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms. Specifically, a monovalent or divalent metal salt of acrylic acid or methacrylic acid may be mentioned. Among them, zinc acrylate is preferable because the resilience performance of the core 3 is improved. By adjusting the compounding amount of the co-crosslinking agent, the elastic modulus of each layer is adjusted as described later in detail, whereby the golf ball 1 having a low spin and a high launch is obtained. Suitable organic peroxides include, for example, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane,
5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butyl peroxide and the like,
Dicumyl peroxide is particularly preferred. By adjusting the compounding amount of the organic peroxide, the elastic modulus of each layer is adjusted as will be described later in detail, whereby the golf ball 1 having a low spin and a high launch is obtained. [0015] Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate and calcium carbonate.
Further, a high specific gravity metal filler such as a tungsten powder or a molybdenum powder may be used. Among these fillers, zinc oxide, which also functions as a crosslinking aid, is particularly preferable. By adjusting the blending amount of the filler, the elastic modulus of each layer is adjusted as will be described later in detail, whereby the golf ball 1 having a low spin and a high launch is obtained. Further, the rubber composition may contain additives such as an antioxidant, a peptizer, an organic sulfur compound, and rubber powder in an appropriate amount as required. The core 3 having such a plurality of layers can be formed by a half-crosslinked half-shell method or a rubber injection method, which will be described in detail later. The cover 5 is made of a synthetic resin. Preferred synthetic resins are ionomer resins. The cover 5 may be blended with an appropriate amount of an additive such as a pigment such as titanium dioxide, a dispersant, an antioxidant, an ultraviolet absorber, and a light stabilizer, if necessary. By changing the type and grade of the synthetic resin used for the cover 5, a golf ball 1 having a low spin and a high launch can be obtained as described in detail later. The golf ball 1 has a seven-layer structure.
The number of layers constituting the golf ball 1 is not limited to this. Further, in the golf ball 1, only the outermost layer is made of a synthetic resin, but two outer layers may be formed of a synthetic resin (a so-called two-layer cover). Further, the cover layer may be three or more layers. FIG. 2 shows (T1 / T1) of the golf ball 1 of FIG.
FIG. 4 is a partial cross-sectional view showing an apparatus for measuring the value of T2). This device includes a substrate 19, a load cell 21, a collision plate 23, a main bolt 25, and a small bolt 27. The collision plate 23 includes a main body 29 and a cover plate 31. In this figure, the direction rotated 22 ° (degree) counterclockwise with respect to the vertical upward direction is the z direction.
The direction rotated counterclockwise by 22 ° with respect to the horizontal right direction is the x direction. The symbol α represents 22 ° which is an angle between the horizontal direction and the x direction. The positions of the substrate 19, the load cell 21, and the collision plate 23 are determined so as to extend in the x direction. Substrate 19, main bolt 25 and small bolt 27
Is only required to be excellent in strength and rigidity, and its material is not particularly limited. Usually, steel is used.
The thickness of the substrate 19 is 5.35 mm. Also, JIS
The model number of the main bolt 25 according to the standard is M10, and the model number of the small bolt 27 is M3. As the load cell 21, a three-component force sensor (model 9067) manufactured by Kistler is used. This sensor is capable of measuring force components in the x, y, and z directions. The measurement is performed by connecting a charge amplifier (model 5011B manufactured by Kistler) not shown to the load cell 21. A through hole 33 is provided at the center of the load cell 21, and the main bolt 25 is passed through the through hole 33. The main body 29 of the collision plate 23 is made of stainless steel (SUS-630). The thickness of the main body 29 is
15 mm. The planar shape of the main body 29 is the same as the planar shape of the load cell 21, and is a square having a side of 56 mm. The tip of the main bolt 25 is screwed into the main body 29. Thus, the load cell 21 is sandwiched between the substrate 19 and the main body 29, and the position of the load cell 21 is fixed. The cover plate 31 has two small bolts 27, 27.
Is fixed to the main body 29. The covering plate 31
It consists of a titanium alloy (6-4Ti) containing aluminum by mass and 4% by mass of vanadium. The thickness of the cover plate 31 is 2.5 mm. The planar shape of the covering plate 31 is the same as the planar shape of the load cell 21, and one side is 56 m.
m square. The cover plate 31 is provided to keep the state of the collision surface of the collision plate 23 constant. Cover plate 31
Has a 10-point average roughness Rz of 13.6 μm ± 2.0 μm. When the value of (T1 / T2) is measured by this apparatus, the golf ball 1 is fired vertically upward and collides with the collision plate 23. Golf ball 1 just before collision
Is 35 m / s ± 0.3 m / s. After the collision, the golf ball 1 rebounds in the lower right direction in FIG. F which is time series data of the force in the z direction at the time of this collision
n (t) and Ft which is time-series data of force in the x direction
(T) is measured by the load cell 21. The measurement is performed by sampling data every 500000 Hz. Sampling processing is performed on the sampled data by obtaining a moving average of each of the seven points. The time T1 is obtained from the measured Fn (t). This T1 is the time from the start of the collision until the sign of Fn (t) changes from positive to zero for the first time. Further, the time T2 is obtained from the measured Ft (t). This T2 is the time from the start of the collision until the sign of Ft (t) first changes from positive to negative. FIG. 3 shows Fn measured by the apparatus of FIG.
4 is a graph showing an example of (t) and Ft (t).
The origin P0 of this graph is a position where the load cell 21 starts to sense the force, and substantially corresponds to the time when the collision between the collision plate 23 and the golf ball 1 starts. Fn (t) which is the force in the z direction
Gradually increases from the point P0, reaches the maximum value at the point P1, and gradually decreases from this point to zero at the point P2.
This point P2 is a point where the load cell 21 no longer senses the force, and substantially corresponds to a point in time when the golf ball 1 is separated from the collision plate 23. F which is a force in the x direction (ie, a shear force)
t (t) gradually increases from the point P0, reaches the maximum value at the point P3, gradually decreases from this point, and becomes a negative value after the point P4. After the point P4, the shearing force applied to the golf ball 1 has a curve as shown by a dotted line in FIG. 3, but since the golf ball 1 separates from the load cell 21 at the point P2, Ft (t) sensed by the load cell 21. Goes to point P2, where it becomes zero. Ft (t)
The area Sa of the region filled with oblique lines rising to the right in the region surrounded by the curve and the time axis represents an impulse in which the shearing force is positive. On the other hand, the area Sb of the region surrounded by the oblique line rising to the left in the region surrounded by the curve of Ft (t) and the time axis represents the impulse in which the shear force is negative. The impulse Sa is an impulse of a force acting in the positive direction of the x-axis, and thus acts in a direction to promote backspin. On the other hand, the impulse Sb is an impulse of a force acting in the negative direction of the x-axis, and thus acts in a direction to suppress back spin. As is apparent from FIG. 3, the impulse Sa is much larger than the impulse Sb. The golf ball 1 having a larger value obtained by subtracting the impulse Sb from the impulse Sa is the golf ball 1 in which the backspin is easily applied. T1 shown in FIG. 3 is Fn as described above.
This is the time from the start of the collision until the sign of (t) first changes from plus to zero, and is the time from point P0 to point P2. Further, T2 is the time from the start of the collision until the sign of Ft (t) first changes from positive to negative as described above, and is the time from point P0 to point P4. From T1 and T2 thus obtained,
The value of (T1 / T2) is calculated. In the golf ball 1 shown in FIG. 1, the value of (T1 / T2) is from 1.85 to 2.10. This value is the value of the conventional golf ball 1
(T1 / T2) is larger than 1.72 to 1.83. That is, the golf ball 1 shown in FIG.
Then, T2 is relatively smaller than T1. For this reason,
The impulse Sa is smaller and the impulse Sb is larger than the conventional golf ball 1. Therefore, the golf ball 1 has a small value obtained by subtracting the impulse Sb from the impulse Sa, and is unlikely to cause back spin. FIG. 4 is a schematic diagram for explaining the relationship between the back spin and the launch angle. In this figure, a state where the golf ball 1 is hit with the head 35 of the golf club is shown. The golf ball 1 shown in FIG. 4A is easy to apply back spin, and the golf ball 1 shown in FIG. 4B is hard to apply back spin. An arrow E is a vector of kinetic energy given to the golf ball 1 by hitting, and an arrow B is a vector of backspin energy. Arrow B in FIG.
Arrow B in FIG. 4B is shorter than. Therefore, the arrow E
The angle formed by the arrow L, which is a vector obtained by combining the arrow B and the arrow B, with the horizontal direction is larger in FIG. This means that the launch angle of FIG. 4B is larger than that of FIG. 4A. As described above, the golf ball 1 having a smaller back spin tends to have a larger launch angle. Since the golf ball 1 of FIG. 1 has a value of (T1 / T2) of 1.85 or more and 2.10 or less and does not easily cause back spin, the golf ball 1 also has a high launch. When the value of (T1 / T2) is less than 1.85, the value obtained by subtracting the impulse Sb from the impulse Sa becomes large, and the golf ball does not have low spin and high launch. When (T1 / T2) exceeds 2.10, the curve of Ft (t) turns more positive by the point P2, and the impulse for promoting the backspin increases. It is no longer a launch golf ball. From these viewpoints, the value of (T1 / T2) is 1.95
It is preferably from 2.10 to 2.10, and particularly preferably from 2.00 to 2.09. The individual values of T1 and T2 are 1.8
Any combination that achieves (T1 / T2) of 5 or more and 2.10 or less suffices, but usually T1 is 0.6 ms to 0.8 ms, and T2 is 0.3 ms to 0.4 ms. The value of (T1 / T2) is 1.85 or more and 2.1
The golf ball 1 having a value of 0 or less can be obtained by making the elastic modulus of the inner layer smaller and increasing the elastic modulus of the outer layer as compared with the conventional golf ball. For example, the outer diameter of the first layer 7 is 5 mm or more and 10 mm or less, the thickness of the second layer 9 to the sixth layer 17 is 1.0 mm or more and 3.0 mm or less, and the thickness of the cover 5 is 1.5 mm or less.
In the golf ball 1 from 3.0 mm to 3.0 mm, the elastic modulus of each layer is appropriately combined within the range shown in Table 1 below to obtain the (T1 / T) of 1.95 to 2.10.
2) is achieved. Examples of combinations are described in detail in the examples section below. Table 1 Range of elastic modulus of each layer First layer 20 to 60 MPa Second layer 30 to 70 MPa Third layer 35 to 100 MPa Fourth layer 40 to 140 MPa Fifth layer 70 to 150 MPa Sixth layer 100 to 160 MPa Cover 200 to Of course, a three-layer structure other than the seven-layer structure,
Even in a golf ball having a five-layer structure, a five-layer structure, a six-layer structure, etc., the elastic modulus of the layer closer to the inside and the elastic modulus of the layer closer to the outside are increased as compared with a conventional golf ball. , (T1 / T2) is 1.85 or more.2.
A golf ball of 10 or less can be obtained. The elastic modulus in the present specification means a complex elastic modulus E ^* measured in a compression mode by a rheology viscoelastic spectrometer. Measurements were as follows: initial strain 0.4 mm, displacement amplitude ± 1.5 μm, frequency 10H
z, the starting temperature is −70 ° C., the ending temperature is 110 ° C., the heating rate is 4 ° C./min, and the elastic modulus is determined from the ratio of the amplitude and the phase difference between the drive unit and the response unit at 20 ° C. Can be The measurement is 4 mm long and 4 mm wide,
A test piece having a thickness of 2 mm is used. This test piece is cut out from the golf ball 1. When the thickness of the layer is too small to cut out the test piece, a slab having a thickness of 2 mm is formed from a polymer composition having the same composition as this layer, and the test piece is punched from the slab. When the layer from which a test piece cannot be cut is made of a crosslinked rubber, a rubber composition having the same composition as this layer is charged into a mold having a cavity having a thickness of 2 mm, and is crosslinked at a crosslinking temperature of 160 ° C and a crosslinking time of 30 minutes. By doing so, a slab is obtained. When a layer from which a test piece cannot be cut is made of a synthetic resin composition, a synthetic resin composition having the same composition as this layer is injected into a mold having a cavity having a thickness of 2 mm to form a slab. The value of (T1 / T2) is 1.85 or more and 2.1
The golf ball 1 of 0 or less can be obtained by relatively increasing the elastic modulus of the outer layer and relatively decreasing the elastic modulus of the inner layer as described above. As means for obtaining the golf ball 1 having the distribution, the following means are exemplified. (1) The synthetic resin used for the cover 5 has high rigidity. (2) In the core 3, the amount of the co-crosslinking agent in the inner layer is reduced, and the amount of the co-crosslinking agent in the outer layer is increased. (3) In the core 3, the amount of the organic peroxide in the inner layer is reduced, and the amount of the organic peroxide in the outer layer is increased. (4) In the core 3, the amount of the filler in the inner layer is reduced, and the amount of the filler in the outer layer is increased. (5) A filler having a high specific gravity is added to the cover 5. (6) A filler having a high specific gravity is added to the outer layer of the core 3. (7) The crosslinking temperature of the core 3 is adjusted so that the layer closer to the outside increases the crosslinking density. (8) Increase the thickness of the cover 5. (9) Two or more layers of the cover 5 are provided. (10) The inner layer of the core 3 is made of a foam. EXAMPLES Hereinafter, the effects of the present invention will be clarified by examples, but it is needless to say that the present invention should not be limitedly interpreted based on the description of the examples. [Example 1] 100 parts of high cis polybutadiene (trade name "BR01" of Nippon Synthetic Rubber Co., Ltd.), 18 parts of zinc acrylate, dicumyl peroxide (trade name "Park Mill D" of Nippon Yushi Co., Ltd.) 0 parts and zinc oxide 2
3.9 parts were kneaded with an internal kneader to obtain a rubber composition (combination indicated by symbol J in Table 3 below). The rubber composition was charged into a mold having upper and lower mold halves each having a hemispherical cavity, and crosslinked at 160 ° C. for 20 minutes to obtain a first layer having a diameter of 6.4 mm. The elastic modulus of the first layer was 44.9 MPa. Next, a rubber composition represented by the symbol H in Table 3 below is charged into a mold having a large inner diameter of a hemispherical cavity, and a core having the same outer diameter as the first layer is charged into the mold. Closed. And it heated at 160 degreeC for 20 minutes, and formed the half shell of the half bridge | crosslinking state. The mold was opened, the core was taken out, and the first layer was put into the cavity of the half shell. Close the mold and crosslink at 160 ° C for 20 minutes.
A second layer was formed. The thickness of this second layer is 3.2 mm. The molding of each layer by the half-crosslinked half-shell method was sequentially repeated to form a third layer to a sixth layer having a thickness of 3.2 mm to obtain a core. However, each of the third to sixth layers is a rubber composition represented by the symbol H, a rubber composition represented by the symbol C, a rubber composition represented by the symbol C, and a symbol A in Table 3 below. Rubber composition was used. The type of rubber composition used for each layer and the elastic modulus of each layer are shown in Table 2 below. On the other hand, 50 parts of an ionomer resin neutralized with sodium ions (trade name “Himilan 1605” of Mitsui DuPont Polychemicals Co., Ltd.) and an ionomer resin neutralized with zinc ions (Mitsui DuPont Polychemicals Co., Ltd.) (Trade name “Himilan 1706”) and 50 parts of titanium dioxide were prepared. And
A core was put into a mold including upper and lower molds each having a hemispherical cavity, and a resin composition was injected around the core to form a cover having a thickness of 2.2 mm. The elastic modulus of the cover was 343.1 MPa. The cover was pre-treated by a conventional method and further coated to obtain a golf ball of Example 1. Examples 2 and 3 and Comparative Examples 1 and 2
Golf balls of Examples 2 and 3 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that the rubber composition used for each layer of the core was as shown in Table 2 below. The composition of each rubber composition is as shown in Table 3 below. The type of rubber composition used for each layer of these golf balls and the elastic modulus of each layer are shown in Table 2 below. [Striking Test] Ten golf balls were prepared for each of the examples and comparative examples. On the other hand, No. 4 iron (trade name of HI-BRID AUTOFOCUS by Sumitomo Rubber Industries, Ltd.)
And the machine conditions were adjusted so that the head speed was 38.8 m / s. Then, each golf ball is hit, and the backspin rotation speed, launch angle, and flight distance immediately after the hit (distance from the launch point to the ball rest point)
Was measured. Table 2 below shows the results of calculating the average value of the ten pieces of data for each example and each comparative example. [Table 1] [Table 2] In Table 2, the golf ball of each example has a lower spin than the golf ball of each comparative example.
High launch and excellent flight distance. From the evaluation results, the superiority of the present invention is confirmed. Although the present invention has been described in detail by taking a solid golf ball having a multilayer structure as an example, even a golf ball having a thread wound core has a value of (T1 / T2) of 1.85 or more and 2 or more. .10 or less, the effect of increasing the flight distance can be obtained. As described above, in the golf ball of the present invention, the launch angle when hit under the same conditions is larger than that of the conventional golf ball, and the back spin is higher than that of the conventional golf ball. Is also small. This golf ball has an excellent flight distance particularly when hit with a long iron, a middle iron and a wood type golf club.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a golf ball according to one embodiment of the present invention. FIG. 2 is a view (T1 / T2) of the golf ball of FIG. 1;
FIG. 4 is a partial cross-sectional view showing an apparatus for measuring the value of the. FIG. 3 is a graph showing an example of Fn (t) and Ft (t) measured by the apparatus of FIG. FIG. 4 is a schematic diagram for explaining a relationship between a back spin and a launch angle. [Description of Signs] 1 golf ball 3 core 5 cover 7 first layer 9 second layer 11 third layer 13 fourth layer 15 ... Fifth layer 17 ... Sixth layer 19 ... Substrate 21 ... Load cell 23 ... Collision plate 29 ... Main body 31 ... Coating plate

Continuation of the front page (56) References JP-A-10-127818 (JP, A) JP-A-9-266959 (JP, A) JP-A-6-154357 (JP, A) JP-A-6-98949 (JP) , A) JP-A-7-194735 (JP, A) JP-A-11-417 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A63B 37/00 A63B 37/04

Claims (1)

(57) [Claims] [Claim 1] 22 ° counterclockwise with respect to vertical upward
The rotated direction is the z direction, the direction rotated 22 ° counterclockwise with respect to the horizontal right is the x direction, and the surface is x
The time series data of the force in the z direction applied to the load cell provided on the back surface of the collision plate when the golf ball collides vertically upward with the collision plate extending at a speed of 35 m / s is Fn.
(T), and the time series data of the force in the x direction is Ft (t)
The time from the start of the collision until the sign of Fn (t) first changes from positive to zero is T1, and the time from the start of the collision until the sign of Ft (t) first changes from positive to negative. Is T2, the value of (T1 / T2) is 1.8
A golf ball having a size of 5 to 2.10.