JP4916208B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball having a multilayer structure.

Golf ball flight distances have increased significantly as a result of years of research. Various elements can be cited as factors for increasing the flight distance, one of which is to reduce the spin rate. In order to reduce the amount of spin, it is necessary to increase the moment of inertia of the ball. As a structure for that purpose, it is possible to increase the weight distribution in the radially outward direction of the ball. In order to realize such a structure, for example, in Patent Document 1, by making the core hollow, the weight distribution in the radially inner direction of the ball is reduced, thereby increasing the weight of the radially outer region. Yes.
JP-A-10-174727

  If the core is made hollow as described above, the weight distribution in the radially outward direction can be increased to some extent, but this does not sufficiently satisfy the requirement for the flight distance. On the other hand, it is conceivable to increase the weight distribution in the radial direction by further increasing the hollow area, but if the hollow area is too large, the rigidity of the core decreases and the core The thickness of the intermediate layer between the cover and the cover is reduced. Therefore, there is a problem that the resilience performance is lowered and the flight distance is shortened. Thus, there is a limit to increasing the moment of inertia by simply making the core hollow, and it has been necessary to consider increasing the moment of inertia by a new approach.

  The present invention has been made to solve the above problem, and an object of the present invention is to provide a golf ball capable of reducing the spin rate and increasing the flight distance by increasing the moment of inertia.

The golf ball according to the present invention has been made to solve the above-described problems, and includes a spherical core, a plurality of ribs formed on the surface of the core, and an intermediate filled in a recess surrounded by the ribs. And a cover that covers the rib and the intermediate layer, the core is hollow, the total volume of the intermediate layer is larger than the total volume of the rib, and the specific gravity of the intermediate layer is equal to that of the rib. The intermediate layer has an area along the spherical surface concentric with the core as it goes radially outward, and the specific gravity of the intermediate layer is 1.46 to 1.60. In addition, the specific gravity ratio of the intermediate layer to the rib is configured to be 1.11 to 1.43.

  According to the above configuration, since the weight of the core is 11.60 g or hollow, the weight distribution in the radially outward direction becomes large when the balls are made based on the regulations. Therefore, the moment of inertia of the ball can be increased. In the present invention, the moment of inertia can be further increased by disposing the following ribs and intermediate layer on the surface of the core. In other words, the specific gravity of the intermediate layer is made larger than that of the rib, and the area of the intermediate layer along the spherical surface concentric with the core is configured to increase as it goes radially outward. It is larger than the total volume. Thereby, the weight distribution in the radial direction in the region between the core and the cover can be greatly changed. This will be described in detail below.

  First, it is compared with a golf ball having no conventional rib. In the so-called three-piece golf ball of the conventional example, since the region between the hollow core and the cover is made of one kind of material, the weight of the sphere having a small thickness at a certain position in the radial direction is radially outward. It gradually gets heavier as you go. On the other hand, according to the present invention, in the region close to the core, the ratio of ribs having a small specific gravity is large, whereas in the region close to the cover, the ratio of the intermediate layer having a large specific gravity is large. For this reason, the gradient of change in weight in the radial direction can be increased, and the weight in the vicinity of the cover is increased even if the total weight of the ball is the same as that of the conventional example. Therefore, the moment of inertia can be greatly increased as compared with the conventional ball, and the spin rate can be further suppressed. As a result, the flight distance can be greatly increased.

  As described above, in order to reduce the weight of the core, it can be made hollow. Or a core can be comprised with light materials, such as a foaming material, and the weight of a core can also be 2.00-11.60g. This is because if the weight of the core is lighter than 2.00 g, the rigidity and strength as the core are insufficient, and if it is heavier than 11.60 g, the moment of inertia of the ball cannot be increased.

  At this time, if the diameter of the core is excessively increased, the rigidity of the core is lowered and the thickness of the intermediate layer is reduced, which may reduce the resilience performance. Therefore, the core diameter is preferably 21 to 29 mm.

  Further, as described above, in the golf ball according to the present invention, the specific gravity of the intermediate layer is larger than that of the rib so that the weight increases as it approaches the cover. The greater the ratio (the specific gravity of the intermediate layer / the specific gravity of the rib), the greater the difference in weight between the vicinity of the cover and the vicinity of the core, and the moment of inertia can be increased. In this respect, the specific gravity ratio is preferably 1.03 or more, and more preferably 1.11 or more. On the other hand, it was found that when the specific gravity ratio is too large, for example, when the specific gravity of the intermediate layer is excessively increased, the resilience performance decreases. From such a viewpoint, the specific gravity ratio is preferably 1.50 or less, and more preferably 1.43 or less. In order to increase the specific gravity ratio, for example, a filler having a specific gravity of 8 to 10 may be added to the rubber composition or elastomer to form the intermediate layer.

  Moreover, as a material which comprises an intermediate | middle layer, it is preferable to employ | adopt the material with a favorable resilience characteristic. As an index of the resilience characteristic, for example, a value of tan δ = (E ″) / (E ′) represented by a ratio between a loss elastic modulus and a storage elastic modulus can be given. It is considered that the smaller this value, the richer the elasticity and the higher the resilience characteristics. On the other hand, if it is large, the viscosity becomes high, which causes a problem that the flight distance does not increase.

  In the golf ball, the concave portion surrounded by the rib is preferably formed in a cone shape by the side surface of the rib, and by doing so, the area of the intermediate layer in the spherical direction is gradually increased outward in the radial direction. Can be increased. Therefore, since the weight distribution in the ball also increases with increasing radial direction, the weight increases with increasing proximity to the cover as described above. As a result, the moment of inertia of the ball can be further improved, leading to a reduction in spin and an increase in flight distance.

  The “conical shape” as used in the present invention means that the concave portion is surrounded by the side surface of the rib to form a conical region, and the area of the surface cut by the spherical surface concentric with the core is the cover. It means a shape that becomes smaller as it goes from the core to the core. In this case, the shape of the surface is not particularly limited, and may be a polygonal shape or a circular shape. In addition, the concave portion may be formed in a cone shape surrounded only by the ribs, or may be formed in a cone shape by exposing the core from the back end portion and the side surface of the rib and the core. Even when the core is not exposed to the outside, the rib is designed to be arranged based on the core in the present invention. Even when the core is exposed, there are few exposed portions, and the whole is formed in a cone shape.

  In the above golf ball, the rib can take various forms. For example, the rib can be formed along three great circles orthogonal to each other on the surface of the core. In this case, since the ribs are uniformly arranged on the surface of the core, even when hitting any position on the surface of the ball, substantially uniform performance, that is, flight distance and spin performance are exhibited.

  Moreover, it is preferable that the rib is provided with at least one notch part which connects between the said adjacent recessed parts. Thus, when the notch is formed in the rib, the following advantages can be obtained during manufacturing. For example, when the intermediate layer is filled in the recess surrounded by the ribs by press molding, in the golf ball according to the present invention, since the adjacent recess communicates with the notch portion, The material spreads to each recess through the notch. Therefore, it is not necessary to directly fill the material for the intermediate layer in each of the recesses, and the manufacturing equipment can be simplified and the manufacturing time can be shortened. Also, when forming the intermediate layer by injection molding, the intermediate layer can be formed with one or a small number of gates, and the manufacturing cost can be reduced.

  By the way, in the present invention, the hardness of the intermediate layer and the rib is not particularly limited, but different types of golf balls can be provided by changing these hardnesses. For example, when the hardness of the rib is larger than the hardness of the intermediate layer, the following ball can be obtained. That is, when the intermediate layer with low hardness is filled in the recess surrounded by the high hardness rib, the deformation of the intermediate layer in the spherical direction at the time of hitting is limited by the rib. Therefore, it is possible to prevent the hitting force applied to the ball from being dispersed in the spherical direction, and to transmit the hitting force toward the center of the ball with high efficiency. As a result, although a soft shot feeling can be obtained by the intermediate layer having low hardness, a large flight distance can be obtained.

  On the other hand, when the hardness of the intermediate layer is larger than the hardness of the rib, the following advantages are obtained. That is, since the total volume of the intermediate layer is larger than the total volume of the ribs, high resilience performance can be obtained by increasing the hardness of the intermediate layer as described above. Therefore, the flight distance can be extended even when the club head speed is low. Furthermore, the following effects can also be obtained. Generally, when a golf ball and a golf club come into contact with each other, the ball is twisted in the circumferential direction due to friction with the club face surface. The twisted ball is restored to its original state by elastic resistance, and a force opposite to the backspin is applied to the ball. At this time, the greater the deformation of the twisted ball, the more backspin is suppressed and the flight distance can be extended.

  At this time, since the elastic resistance for returning the ball to the original state is promoted by the rib, backspin can be effectively suppressed. More specifically, in this golf ball, since the hardness of the rib is lower than the hardness of the intermediate layer, the rib is deformed more greatly than the intermediate layer by hitting. Since the rib is configured not as a simple protrusion but as a wall surrounding the periphery of the intermediate layer, the force of the entire wall acts greatly from the periphery of the intermediate layer when the rib is restored. Force opposite to the pin is encouraged. As a result, the flight distance can be greatly increased. Such an effect is particularly apparent when hitting with a club aiming at a flight distance such as a driver.

  According to the golf ball of the present invention, since the moment of inertia can be increased, the spin rate can be reduced and the flight distance can be increased.

  Hereinafter, an embodiment of a golf ball according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a golf ball according to the present embodiment, FIG. 2A is a perspective view of a semi-finished product comprising a core and a rib, and FIG. 2B is a perspective view of a semi-finished product further covering an intermediate layer. 1 is a cross-sectional view taken along the line A in FIG. 2, and the lines A in FIGS. 2A and 2B are lines along the same cross section.

  As shown in FIG. 1, a golf ball 1 according to this embodiment is a so-called four-piece golf ball in which a rib 3 is formed on the surface of a core 1 and covered with an intermediate layer 5 and a cover 7. The diameter of the golf ball needs to be 42.67 mm or more according to the rules (see R & A and USGA). However, in consideration of aerodynamic characteristics and the like, it is preferable to make the ball diameter as small as possible, for example, 42.7 to 43.7 mm.

  The core 1 is formed in a spherical shape, and the inside thereof is hollow. The diameter of the core 1 is preferably 21 to 29 mm, and the wall thickness is preferably 2 to 3 mm, for example, from the viewpoint of maintaining rigidity, although it varies depending on the material forming the core 1. This is because if the diameter of the core 1 is too small, the weight distribution of the radially inward balls cannot be moved radially outward, so an increase in the moment of inertia cannot be expected. This is because the area between them becomes smaller and the resilience performance decreases.

  Moreover, as shown in FIG.1 and FIG.2, on the surface of the core 1, the three ribs (projection) 3 formed with the rubber composition are provided. Each rib 3 is drawn on the surface of the core 1 and extends along a great circle orthogonal to each other. The rib 3 forms eight concave portions 4 on the surface of the core 1. The height of the rib is preferably 2.85 to 9.65 mm, for example. As shown in FIG. 1, each rib 3 is formed in a trapezoidal cross section so that its width increases as it goes to the core 1 side. The width a of the radially upper end of the rib 3 is preferably 1.5 to 3.0 mm, and the width b of the radially inner lower end of the rib 3 is 3.0 to 12.0 mm. It is preferable to do. Although it can be outside this range, by setting the lower limit of each end of the rib 3 in this way, when filling an intermediate layer, which will be described later at the time of manufacture, filling of the intermediate layer resulting from the pressure of mold clamping The rib 3 can be prevented from being deformed by pressure. As a result, the core 1 can be accurately held at the center of the mold. The widths a and b of the respective end portions are preferably increased as the height of the rib 3 is increased. For example, when the height of the rib 3 is 4.6 mm, the width b of the lower end portion is set. Can be set to 6.0 mm. Due to the shape of the rib 3, each recess 4 is formed in a triangular pyramid shape surrounded by the three ribs 3 and the slightly exposed surface of the core 1.

  The intermediate layer 5 is made of a rubber composition or an elastomer, covers the surface of the core 1, and has an outer shape that is substantially spherical. As shown in FIG. 1, the intermediate layer 5 has a layer thickness substantially the same as the height of the rib 3 and is filled in eight concave portions 4 surrounded by the rib 3, and the tip of the rib 3 is exposed from the surface of the intermediate layer 5. is doing. As described above, the rib 3 is configured to increase in width as it goes from the cover 7 side to the core 1 side. Therefore, the intermediate layer 5 is concentric with the core 1 as it goes radially outward. The area in the spherical direction is large. That is, as shown in FIG. 1, with respect to the area in the spherical direction concentric with the core 1, the ratio R <b> 1 of the rib 3 decreases while the ratio R <b> 2 of the intermediate layer 5 increases as it goes radially outward.

  The total volume of the intermediate layer 5 filled in the eight recesses 4 is larger than the total volume of the ribs 3, and the specific gravity of the intermediate layer 5 is larger than the specific gravity of the ribs 3. Thereby, the total weight of the intermediate layer 5 is larger than the total weight of the ribs 3. More specifically, the specific gravity ratio of the intermediate layer to the rib (specific gravity of the intermediate layer / specific gravity of the rib) is preferably 1.03 or more, and more preferably 1.11 or more. On the other hand, the specific gravity ratio is preferably 1.50 or less, and more preferably 1.43 or less. This point will be described later.

  The cover 7 is made of an elastomer, covers the tip portion of the rib 3 and the intermediate layer 5, and predetermined dimples (not shown) are formed on the surface thereof. The layer thickness of the cover 7 is preferably 1.2 to 2.0 mm. Outside this range is possible, but the reason is that if the layer thickness of the cover 7 is smaller than 1.2 mm, the durability of the cover 7 is remarkably lowered and molding becomes difficult. This is because the feeling becomes too hard. Further, the hardness is preferably a Shore D hardness of 56 to 68. The layer thickness of the cover 7 is a value obtained by measuring a distance from an arbitrary point on the outermost side in the radial direction where no dimples are formed to an arbitrary point in contact with the intermediate layer 5 along the normal line.

  Next, materials constituting each member of the golf ball will be described in detail. The core can be formed of a light and relatively rigid resin material such as ionomer resin, ABS resin, polyamide resin, polycarbonate resin, PBT resin, PSF resin, FRP, FRTP, and the like.

  The rib 3 can be manufactured with the well-known rubber composition which mix | blended base rubber, the crosslinking material, the metal salt of unsaturated carboxylic acid, a filler, etc. As the base rubber, natural rubber, polyisobrene rubber, styrene butadiene rubber, EPDM and the like can be used, but high cis polybutadiene having at least 40% or more, preferably 80% or more of cis 1,4 bonds should be used. Is particularly preferred.

  As the crosslinking agent, for example, organic peroxides such as dicumyl peroxide and t-butyl peroxide can be used, but it is particularly preferable to use dicumyl peroxide. A compounding quantity is 0.3-5 weight part with respect to 100 weight part of base rubbers, Preferably it is 0.5-2 weight part.

  As the metal salt of the unsaturated carboxylic acid, it is preferable to use a metal salt of a monovalent or divalent unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid, but zinc acrylate is used. Then, the resilience performance of the ball can be improved, which is particularly preferable. The blending amount is preferably 15 to 45 parts by weight with respect to 100 parts by weight of the base rubber. When the blending amount is less than 15 parts by weight, the resilience performance is lowered and the flight distance is shortened. On the other hand, when the blending amount is more than 45 parts by weight, it becomes too hard and the soft feeling may be lowered.

  What is normally mix | blended with a core can be used for a filler, for example, a zinc oxide, barium sulfate, a calcium carbonate etc. can be used. The blending amount is preferably 2 to 50 parts by weight with respect to 100 parts by weight of the base rubber. Moreover, you may mix | blend an anti-aging agent or a peptizer as needed.

  The intermediate layer 5 is composed of the rubber composition or elastomer as described above. When the intermediate layer 5 is composed of the rubber composition, it can be composed of the same components as the rib 3 described above.

  When the intermediate layer 5 is composed of an elastomer, for example, styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene- Styrenic thermoplastic elastomers such as ethylene-propylene-styrene block copolymer (SEPS); Olefin thermoplastic elastomers with polyethylene or polypropylene as hard segments and butadiene rubber, acrylonitrile butadiene rubber, or ethylene / propylene rubber as soft segments; Crystalline polyvinyl chloride as a hard segment and amorphous polyvinyl chloride or acrylonitrile butadiene rubber as a soft segment Thermoplastic elastomer; Urethane thermoplastic elastomer with polyurethane as hard segment and polyether or polyester as soft segment; Polyester thermoplastic elastomer with polyester as hard segment and polyether or polyester as soft segment; Polyamide as hard segment And a polyamide-based thermoplastic elastomer having a polyether or polyester as a soft segment; an ionomer resin, or the like can be used.

  Further, as described above, the intermediate layer 5 needs to have a higher specific gravity than the rib 3. For that purpose, it is preferable to add a high specific gravity filler having a specific gravity of 8 to 20 as the filler. Such a high specific gravity filler is, for example, a filler selected from the group consisting of metal powders, metal oxides, metal nitrides and the like or mixtures thereof. Specifically, the specific gravity can be increased by adding tungsten, tungsten carbide, molybdenum, lead, lead oxide, nickel, cobalt, copper, or a mixture thereof. The cover 7 is made of a known elastomer, and barium sulfate, titanium dioxide, and zinc oxide, which are inorganic fillers used for rubber fillers, can be used.

  As described above, according to the present embodiment, since the core 1 is formed hollow, the weight distribution of the region between the core 1 and the cover 7 is increased. Therefore, the moment of inertia of the ball can be increased. Furthermore, in the present embodiment, the area of the intermediate layer 5 along the spherical surface concentric with the core 1 is configured to increase as it goes radially outward, and the specific gravity of the intermediate layer 5 is larger than that of the rib 3. It has become. Further, the total volume of the intermediate layer 5 is larger than the total volume of the ribs 3. Therefore, in addition to the fact that the weight distribution of the region between the core 1 and the cover 7 is increased by the hollow structure, there are the following advantages.

First, it is compared with a golf ball having no conventional rib. FIG. 3 is a cross-sectional view of a conventional three-piece golf ball having a hollow core. As shown in the figure, in the conventional golf ball, since the region from the hollow portion to the cover is made of one kind of material, a sphere with a minute thickness (Δr) at a certain position in the radial direction (radius r) The weight of X (a shell-only sphere) becomes heavier as it goes radially outward. More specifically, when the specific gravity of the spheres X and [rho _1, the weight can be approximated as 4πr ² × ρ ₁ × Δr. A graph of this is X in FIG. Here, a ₁ in the graph is the radius of the core 1, a ₂ is the length of the radial direction to the cover inner wall surface.

On the other hand, if the golf ball according to this embodiment has the same weight as the golf ball of the conventional example, the weight of the region between the surface of the core 1 and the cover 7 is the same. When the specific gravity of the intermediate layer 5 is ρ ₂ and the specific gravity of the rib 3 is ρ ₃ , the relationship between the three specific gravity is ρ ₂ > ρ ₁ > ρ ₃ . Here, in the golf ball according to the present embodiment, the ratio of the rib 3 having a small specific gravity is large in the vicinity of the core 1, and the ratio of the intermediate layer 5 having a high specific gravity is increased toward the cover 7. Therefore, when the sphere Y having a very small thickness in the ball according to the present embodiment is considered with the same calculation formula as that of the sphere X, the weight can be approximated to a graph like Y in FIG.

  As apparent from the graph of FIG. 4, the golf ball according to the present embodiment has the same weight as a conventional ball, but the weight in the vicinity of the cover increases. Therefore, the moment of inertia can be greatly increased as compared with the conventional ball, and the spin rate can be further suppressed. Moreover, in this embodiment, since the shape of the recessed part 4 is made into the shape of a triangular pyramid, the ratio R2 (refer FIG. 1) of the intermediate | middle layer 5 becomes large gradually as it goes to radial direction outward. Therefore, the weight distribution of the balls surely increases as it goes outward in the radial direction, and the weight surely increases as it approaches the cover as described above.

From the above viewpoint, if the specific gravity ratio of the intermediate layer 5 to the rib 3 is increased, the weight at a ₁ is reduced, while the weight at a ₂ is increased, and the weight difference between the vicinity of the core and the vicinity of the cover is increased. . Therefore, the weight in the vicinity of the cover can be further increased, and the moment of inertia can be increased accordingly. On the other hand, when the specific gravity ratio decreases, the graph drawn by the sphere X approaches. Therefore, to increase the moment of inertia, the specific gravity ratio of the intermediate layer to the rib needs to be large to some extent. Therefore, how much the specific gravity ratio should be increased will be examined.

  First, in order to extend the flight distance of the ball, it is necessary to extend both the so-called Carry and Run. In order to extend the run, it is effective to reduce the amount of backspin, and this reduces the drop angle, so the run is extended. In the golf ball according to the present embodiment, since the amount of backspin can be reduced by increasing the moment of inertia as described above, the run can be increased. On the other hand, to extend the carry, it is necessary not only to reduce the backspin amount but also to improve the initial velocity of the ball. For this purpose, the rebound characteristics of the ball must be improved. Hereinafter, the result of examining the resilience performance will be described.

Here, in order to easily evaluate the resilience performance, a resilience coefficient e ₀ when the ball collides with the iron plate at 40 m / s is obtained, and this is converted into a COR value e defined by R & A. Since it is known from experiments that the ratio of e ₀ to e, that is, e / e ₀ is about 1.107, e is derived from e ₀ and used as a restitution coefficient based on this equation. FIG. 5 is a graph showing the relationship between the specific gravity ratio and the coefficient of restitution e, and the specific gravity ratio and the moment of inertia. This graph was created by keeping the ball diameter, the ball weight, the cover material, and the specific gravity of the rib constant, and appropriately changing the height of the rib (the thickness of the intermediate layer), the material of the intermediate layer, and the specific gravity.

  As described above, when the specific gravity ratio is improved, the moment of inertia I increases accordingly. On the other hand, with respect to the relationship between the specific gravity ratio and the coefficient of restitution e, it was found that, as shown in FIG. 5, a curve having a maximum specific gravity ratio of about 1.21 was drawn. As described above, the moment of inertia I and the coefficient of restitution e are important parameters that affect the flight distance, and the higher the both, the longer the flight distance. According to the two graphs in FIG. 5, the flight distance is expected to be the longest in the vicinity of the specific gravity ratio of 1.28. Therefore, the relationship between the specific gravity ratio and the total flight distance (the total of carry and run) is calculated by ballistic trajectory, and this is shown in the graph as shown in FIG. The conditions in this calculation are as follows. That is, the calculation was performed with a head speed of 40 m / s assuming a No. 1 wood having a loft angle of 9 °, a length of 44.75 inches (113.66 cm), and a shaft hardness S).

  From the results shown in FIGS. 5 and 6, in order to obtain a high total, the specific gravity ratio of the intermediate layer to the rib is preferably 1.03 or more, and more preferably 1.11 or more. In this way, the value of the moment of inertia increases, and a decrease in backspin can be expected. And this specific gravity ratio is preferably 1.50 or less, and more preferably 1.43 or less. As can be seen from the graph of FIG. 5, when the specific gravity ratio is too large, the coefficient of restitution decreases. Therefore, when the upper limit of the specific gravity ratio is set as described above, a high coefficient of restitution can be obtained and a long carry can be expected.

  By the way, in the said golf ball, the ball according to the objective can be comprised by changing the hardness of the rib 3 and the intermediate | middle layer 5. FIG. First, the case where the hardness of the rib 3 is made lower than the hardness of the intermediate layer 5 will be described. In this case, since the intermediate layer 5 is filled in the concave portion 4 surrounded by the rib 3, the portion of the cover 7 that contacts the inner wall surface is larger in the proportion of the intermediate layer 5 than the rib 3. Therefore, when the ball is hit, most of the hitting force acts on the intermediate layer 5 having high hardness. Thereby, even if the club head speed is low, high resilience performance can be obtained and the flight distance can be extended. There are also the following advantages. Generally, when a golf ball and a golf club come into contact with each other, the ball is twisted in the circumferential direction due to friction with the club face surface. The twisted ball is restored to its original state by elastic resistance, and a force opposite to the backspin is applied to the ball. At this time, the greater the deformation of the twisted ball, the more backspin is suppressed and the flight distance can be extended.

  Here, in the golf ball as described above, the elastic resistance that the ball tries to return to the original state is promoted by the rib 3, and therefore, backspin can be effectively suppressed. More specifically, as shown in FIG. 7A, in this golf ball, since the hardness of the rib 3 is lower than the hardness of the intermediate layer 5, the rib 3 is larger than the intermediate layer 5 by hitting with the club C. Deform. Due to this impact, a stress that generates back spin B acts on the ball itself. When the ball leaves the club C, as shown in FIG. 7B, the deformation of the rib 3 having a low hardness is restored, so that the force F acts in a direction to cancel back spin B by this restoration. To do. As a result, the spin is reduced and the jump angle is increased, so that the flight distance can be further extended. In particular, in the golf ball described above, the rib 3 is not a mere protrusion but is configured as a wall surrounding the periphery of the intermediate layer 5, so that the force when the rib 3 is restored depends on the entire wall 5. Acts greatly from the surroundings, and this promotes a force F opposite to the backspin B. Accordingly, the backspin amount is reduced, and the flight distance can be greatly increased. Such an effect becomes prominent particularly when a club aiming at a flight distance such as a driver is used. In FIG. 7, the current state is represented by a solid line, and the state immediately before is represented by a broken line. In order to obtain the effects as described above, it is preferable that the hardness of the rib 3 is 35 to 58, the hardness of the mid layer 5 is 48 to 68, and the difference between the two is 2 to 17 in Shore D hardness. However, the reason is that, for example, if the hardness difference between the rib 3 and the intermediate layer 5 is too large and the hardness of the intermediate layer 5 is increased, the hardness of the intermediate layer 5 is significantly increased, and the hit feeling Because it becomes hard. On the other hand, if the hardness difference is too small, the degree of deformation of the rib 3 with respect to the intermediate layer 5 becomes small, and the force opposite to the backspin becomes difficult to act.

  Subsequently, the case where the hardness of the intermediate layer 5 is lower than the hardness of the rib 3 will be described. With such a configuration, since the recess 4 surrounded by the high-hardness rib 3 is filled with the intermediate layer 5 having a low hardness, deformation of the intermediate layer 5 in the spherical direction at the time of impact is limited by the rib 3. The Therefore, it is possible to prevent the hitting force applied to the ball from being dispersed in the spherical direction, and to transmit the hitting force toward the center of the ball with high efficiency. As a result, although a soft feel at impact can be obtained, a large flight distance can be obtained.

  In particular, in the above embodiment, since the recess 4 is formed in a cone shape and filled with the intermediate layer 5, the following effects can be obtained. That is, in the region between the core 1 and the cover 7, the proportion R <b> 1 of the rib 3 in the spherical surface concentric with the core 1 increases as the distance from the cover 7 to the core 1 increases. That is, as shown in FIG. 1, the ratio R <b> 2 of the intermediate layer 5 is large in the vicinity of the cover 7, while the rib ratio R <b> 1 increases as the core 1 is approached. At this time, since the hardness of the rib 3 is larger than the hardness of the intermediate layer 5, the properties of the intermediate layer 5 are strongly reflected in the vicinity of the cover 7, and the properties of the ribs 5 are gradually reflected strongly toward the core 1. It becomes hard. For this reason, since the hardness of the intermediate layer 5 is low in the vicinity of the cover 7, a soft feeling can be obtained at the initial stage of hitting, and the hardness increases as the hitting progresses and high resilience performance can be obtained. Thus, since the region between the cover 7 and the core 1 has an inclination function in which the hardness changes smoothly, it is possible to have a good soft feeling and high resilience performance in a well-balanced manner. In order to obtain the above effects, it is preferable that the hardness of the rib 3 is 48 to 65, the hardness of the intermediate layer 5 is 35 to 50, and the difference between the two is 2 to 17 in Shore D hardness.

  By the way, although the rib mentioned above can be made into various shapes, it is preferable to form the following notch in the rib from the viewpoint of efficiently forming the intermediate layer at the time of manufacture. FIG. 8 is a perspective view of a semi-finished product comprising a core and a rib, and FIG. 9 is a front view thereof.

As shown in FIGS. 8 and 9, the notch 31 is formed to have a bottom surface 31 a extending along a tangential plane H passing through the intersection point P of the great circle. That is, the notch 31 is formed by cutting the rib 3 by the tangential plane H. By forming the notches 31 in this way, the four recesses 4 arranged around the intersection point P of the great circle communicate with each other, and as will be described later, the intermediate layer material is passed through the notches 31 to each recess. 4 can be easily distributed. In this case, as shown in FIG. 10, the plane H ₁ inclined by 1 to 3 ° from the tangential plane H to the center side of the rib 3, that is, the normal n of the core 1 passing through the intersection point P and 91 to 93 ° in plan view. You may make it form the bottom face 31a of the notch part 31 along the plane which makes an angle. In this way, the inclination becomes a draft, and for example, when the mold is composed of two molds, an upper mold and a lower mold, the semi-finished product including the core 1 and the rib 3 can be easily taken out from the mold. it can.

  Further, when the notch 31 is formed as described above, as shown in FIG. 9, the arc direction of the upper end where the notch 31 is not formed in each arc section S delimited by each intersection P in the rib 3. It is preferable that the length L is 10 mm or more.

  Further, a notch can be provided in the middle of each arc section S of the rib 3. That is, as shown in FIG. 11, the notch 32 is formed to have two bottom surfaces 32a extending from one point on the normal m of the semi-finished product passing through the center point Q in the arc direction of the arc section S to the intersection P side of both ends. You can also In this case, it is preferable that the bottom surface 32a and the normal line m form 45 to 48 degrees in front view. If it does in this way, as above-mentioned, the semi-finished product 1 can be easily extracted from a shaping | molding die. However, if the angle is larger than 48 degrees, the length L of the rib in the arc direction is not preferable. In this case, the depth D of the notch 32 is preferably 1.2 mm or more. Although it is possible outside this range, the material for the intermediate layer can be smoothly circulated between the recesses 4 within the above range. The depth D of the notch 32 refers to the distance from the upper end of the virtual rib 3 to the deepest part of the notch 32 when there is no notch 32. Further, in the middle portion of the arc section S, two or more cutout portions can be provided as long as the shape can be easily removed.

  Moreover, you may make it the circular arc section S have both the notch part 31 shown in FIG.8, FIG.9 or FIG.10 and the notch part 32 shown in FIG.

  Next, an example of a method for manufacturing the golf ball configured as described above will be described with reference to the drawings. Below, the manufacturing method in the case of forming an intermediate | middle layer with a rubber composition is demonstrated. 12 and 13 are views showing a method for manufacturing the golf ball having the rib shown in FIG.

  First, the hollow core 1 is formed. A known method can be used as a method for manufacturing the core. For example, a half hemispherical shell is prepared, and the opening edge is bonded and joined by an ultrasonic welder to manufacture a hollow core. To do. The core 1 thus molded is placed in a first mold 2 shown in FIG. The first mold 2 is composed of an upper mold 2a and a lower mold 2b, and a hemispherical core receiving portion 21 corresponding to the surface of the core 1 is formed in each. A cavity 22 for forming the rib 3 described above is formed on the wall surface of the core receiving portion 21. The cavity 22 is composed of a plurality of grooves formed along the great circle of the core receiving portion 21, but the grooves at the intersections of the three great circles are shallower than the other portions. Thereby, the above-mentioned notch part 31 is formed. Further, the surface of the cavity 22 is roughly finished by rough polishing, whereby fine irregularities can be formed on the surface of the rib 31 formed thereby, and the adhesion to the intermediate layer 5 can be improved.

  Then, as shown in FIG. 12 (b), the core 1 is disposed in the core receiving portion 21 of the first mold 2, and an unvulcanized rubber composition that is a rib material is disposed in the cavity 22. For example, all the vulcanization is performed at 140 to 165 ° C. for 10 to 30 minutes and press molding is performed to form a plurality of ribs 3 on the surface of the core.

  Subsequently, the semi-finished product including the core 1 and the rib 3 is taken out from the first mold 2 and placed in the second mold 6. As shown in FIG. 13A, the second mold 6 includes an upper mold 6 a and a lower mold 6 b, and each has a spherical cavity 61 corresponding to the outermost diameter of the rib 3. That is, the upper end surface of the rib 3 is in contact with the wall surface of the cavity 61. The cavities 61 of the upper mold 6a and the lower mold 6b are finished with a rough surface like the first mold 2 and a plurality of concave burrs 62 are formed around the cavities 61. Yes.

  And as shown to Fig.13 (a), while inserting the unvulcanized rubber composition N2 in the cavity 61 of the lower mold | type 6b, arrange | positioning the rubber composition N2 on the upper part of the semi-finished product formed as mentioned above, This semi-finished product is disposed between the upper mold 6a and the lower mold 6b. Subsequently, as shown in FIG. 13 (b), the upper die 6a and the lower die 6b are brought into contact with each other, and the rubber composition N2 is fully vulcanized at 140 to 165 ° C. for 10 to 30 minutes to perform press molding. Layer 5 is formed.

  At this time, the rubber composition N2 disposed in the upper and lower cavities 61 of the semi-finished product is filled in the recess 4 while being pressed onto the surface of the semi-finished product. As described above, the adjacent concave portions 4 communicate with each other through the notch portions 31, so that the rubber composition N2 reaches all the concave portions 4 and is uniformly filled. In addition, the intermediate | middle layer 5 can also be shape | molded by injection molding using the shaping | molding die 8 as shown, for example in FIG. In this case, the rubber composition N2 is not uniformly filled unless gates are provided for all the recesses 4 if the notches 31 are not provided. , 8b, after inserting the semi-finished product, even if the rubber composition is injected from one gate 81, the rubber composition is uniformly filled into the concave portions 4 through the notches 31 as described above.

  Thus, since the notch 31 is formed in the rib 3 and the adjacent recessed part 4 is connected via the notch 31, even if the rubber composition N2 is pressed from any position on the surface of the semi-finished product, It fills in the recesses 4 of the. Therefore, the intermediate layer 5 can be coated on the semi-finished product by one-step press molding, and as a result, the manufacturing time can be greatly shortened. Here, the intermediate layer 5 is made of a rubber composition, but an elastomer can also be used. If it does in this way, the intermediate | middle layer 5 can be formed by injection molding.

  When the molding of the intermediate layer 5 is completed in this way, the semi-finished product including the core 1, the rib 3 and the intermediate layer 5 is taken out from the second mold 6. Subsequently, when the cover 7 is covered on the surface of the semi-finished product by press molding or injection molding so as to have a predetermined dimple, a four-piece golf ball can be obtained.

  In the above description, a method for manufacturing a golf ball having a rib having a notch is described. However, a golf ball having no notch can be manufactured by a substantially similar method. However, when there is no notch, it is necessary to arrange and press-mold the material so that each recess is filled with the intermediate layer. In the case of injection molding, it is necessary to provide a plurality of gates corresponding to each recess. .

  The embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the ribs are provided along the three great circles on the surface of the core. However, the present invention is not limited to this, and ribs having other shapes or numbers may be provided. That is, if the above-mentioned recess is formed on the surface of the core, the shape of the rib can be changed as appropriate.

  In the above embodiment, the layer thickness of the intermediate layer 5 and the height of the rib 3 are the same, but it is not necessarily the same. For example, the layer thickness of the intermediate layer 5 is made larger than the height of the rib 3. May be. However, it is desirable that the height is slightly higher than the height of the rib 3, for example, within 1.5 mm.

  Moreover, in the said embodiment, although the core 1 is made hollow, as long as the weight of the core 1 is low, for example, 2.0-11.6g, it may be solid. For example, when a foam is added and the core is formed by casting, injection molding, RIM molding, or the like, the core can be reduced in weight.

Hereinafter, an embodiment of the present invention, comparative examples to be compared with this, and the reference example shown. Here, three types of golf balls according to examples of the present invention and four types of golf balls according to comparative examples are compared. Examples 1 to 3, Reference Example and Comparative Examples 1 and 2 are golf balls having substantially the same cores and ribs as shown in FIG. Comparative Example 3 is a golf ball having substantially the same core and rib as shown in FIG. In this golf ball, since the core 1 has a large diameter, the rib 3 is low, and the core 1 is exposed from between the ribs 3. Comparative Example 4 is a conventional three-piece golf ball. The materials constituting the golf balls of the examples , reference examples, and comparative examples are shown in Table 2 below.

また、各実施例、参考例及び比較例に係るゴルフボールのコア径等の寸法、比重、慣性モーメント、反発係数等を表２に示す。

In addition, Table 2 shows dimensions such as the core diameter, specific gravity, moment of inertia, coefficient of restitution, etc. of the golf balls according to the examples , reference examples, and comparative examples.

以上のように構成された実施例、参考例及び比較例を用い、打撃ロボット（ミヤマエ株式会社製ＳＨＯＴＲＯＢＯ ｖ）による１番ウッド（１Ｗ：ミズノ株式会社製ミズノ３００Ｓ−II３８０、ロフト角９°、長さ４４．７５インチ（１１３．６６ｃｍ）、シャフト硬さＳ）を使用した打撃テストを行い飛距離を測定した。ここで、１番ウッドのヘッドスピードは４０ｍ／ｓとした。結果は、表３の通りである。

No. 1 Wood (1W: Mizuno 300S-II380 manufactured by Mizuno Co., Ltd., loft angle 9 °, long by striking robot (SHOTROB v manufactured by Miyamae Co., Ltd.) using the Examples , Reference Examples and Comparative Examples configured as described above. A striking test using a length of 44.75 inches (113.66 cm) and a shaft hardness S) was performed to measure the flight distance. Here, the head speed of No. 1 wood was 40 m / s. The results are shown in Table 3.

打撃テストでは、比較例１で示されるように、リブに対する中間層の比重比が低すぎると、慣性モーメントが低くなるため、バックスピンが大きくなり、飛距離が伸びていない。反対に、比較例２では、比重比が大きすぎるため、慣性モーメントは大きいものの、反発係数が小さくなっている。その結果、ボールの初速が小さくなり、キャリーが伸びていない。比較例３では、コアの径が大きすぎるため、中間層の領域が小さく反発性能が小さくなっている。また、コアの径が大きく、中空の部分が大きいため、慣性モーメントは大きくなっている。その結果、落下角度が小さくなり、ランは伸びている。しかし、反発係数が小さいため、キャリーが伸びておらず、トータルの飛距離は、小さくなっている。比較例４は従来の３ピースのゴルフボールであり、リブがないため、バックスピンも大きく、飛距離も伸びていない。

In the impact test, as shown in Comparative Example 1, when the specific gravity ratio of the intermediate layer to the rib is too low, the moment of inertia is reduced, so that the backspin is increased and the flight distance is not increased. On the contrary, in Comparative Example 2, the specific gravity ratio is too large, so the moment of inertia is large but the coefficient of restitution is small. As a result, the initial velocity of the ball is reduced and the carry is not extended. In Comparative Example 3, since the core diameter is too large, the region of the intermediate layer is small and the resilience performance is small. Moreover, since the core diameter is large and the hollow portion is large, the moment of inertia is large. As a result, the drop angle is reduced and the run is extended. However, since the coefficient of restitution is small, the carry does not extend and the total flight distance is small. Comparative Example 4 is a conventional three-piece golf ball, which has no ribs, and therefore has a large back spin and a long flight distance.

On the other hand, in Examples 1 to 3 , the height of the rib, the specific gravity of each member, and the repulsion parameter were set appropriately, so that a longer flight distance was obtained than in the comparative example.

1 is a cross-sectional view showing an embodiment of a golf ball according to the present invention. It is a perspective view which shows the semi-finished product (a) which consists of the core and rib of the golf ball of FIG. 1, and the semi-finished product (b) which provided the intermediate | middle layer in it. It is sectional drawing of the conventional golf ball. It is a graph which shows the weight of the radial direction in a ball | bowl. It is a graph which shows the relationship between specific gravity ratio, a coefficient of restitution, and a moment of inertia. It is a graph which shows the relationship between specific gravity ratio and total flight distance. FIG. 2 is a partial cross-sectional view illustrating a state when the golf ball of FIG. 1 is hit. It is a perspective view which shows the other example of the rib of FIG. It is a front view which shows the other example of the core of FIG. It is a partial front view which shows the other example of the core of FIG. It is a front view which shows the other example of the core of FIG. It is a figure which shows an example of the manufacturing method of the golf ball shown in FIG. It is a figure which shows an example of the manufacturing method of the golf ball shown in FIG. It is a figure which shows the other example of the manufacturing method of the golf ball shown in FIG. 10 is a cross-sectional view of a golf ball according to Comparative Example 3. FIG.

Explanation of symbols

1 Core 3 Ribs 31 and 32 Notch 5 Mid layer 7 Cover

Claims (5)

A spherical core,
A plurality of ribs formed on the surface of the core;
An intermediate layer filled in a recess surrounded by the rib;
A cover covering the rib and the intermediate layer,
The core is hollow;
The total volume of the intermediate layer is larger than the total volume of the ribs, and the specific gravity of the intermediate layer is larger than the specific gravity of the ribs,
As the intermediate layer goes radially outward, the area along the spherical surface concentric with the core increases,
The intermediate layer has a specific gravity of 1.46 to 1.60,
The golf ball having a specific gravity ratio of the intermediate layer to the rib of 1.11 to 1.43. The diameter of the core is 21～29Mm, golf ball according to claim 1. The recess is formed in cone shape by the side surface of the rib, golf ball according to claim 1 or 2. The golf ball according to claim 1, wherein the rib is formed along three great circles orthogonal to each other on the surface of the core. 5. The golf ball according to claim 1, wherein the rib includes at least one notch communicating between the adjacent recesses. 6.

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