JP2005052272A - Golf club head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf club head where a ball travel distance is improved by the sufficient resilience of a face part by improving the fatigue durability of the face part to repeated hitting. <P>SOLUTION: A face member constituting the face part 2 comprises a member having a structure comprising a thick part 20 thicker than the other part and a thin part 21 thinner than the thick part 20 by forging. An average grain size on the side of a rear surface 2d at the boundary part 22 of the thick part 20 and the thin part 20 of the face part 20 is smaller than an average grain size on the side of a front surface 2c at the boundary part 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a golf club head, and in particular, a metal face portion has a thick portion and a thin portion with respect to the thickness thereof, and in the vicinity of a boundary portion between the thick portion and the thin portion. The golf club head made of metal has an average crystal grain size smaller than the average crystal grain size on the surface side at the boundary between the thick part and the thin part of the face part.

Recently, golf club heads have tended to increase in size. However, if an attempt is made to increase the size without changing the weight of the golf club head, the thickness is reduced by reducing the thickness of the other parts except the face part that requires strength. We have attempted to increase the size by minimizing the increase in
On the other hand, in order to increase the flight distance of the hit ball, it is effective to increase the repulsive force of the face portion. For example, as such means, when a face part of a golf club head and a ball collide with each other, it has been proposed to use a repulsive force when the face part is sufficiently deformed and the deformation returns to the base.
As a device for reducing the weight and improving the resilience of the face part, the thickness of the face part is partially reduced to partially reduce the rigidity of the face part, and the entire face is provided with springiness. Further, a device has been devised to increase the rebound of the ball by utilizing the deformation of the face portion when the golf ball is hit.

  As such, for example, as disclosed in Japanese Patent Laid-Open No. 9-192273, in a metal golf club head, the thickness of the face center portion is set to a thickness having strength to withstand impact with the ball, A golf club head is disclosed in which the thickness of the peripheral portion is made thinner than the center portion so that the entire face has springiness.

  Accordingly, if the thickness of the face portion is made too thin in order to increase the repulsive force, the repulsive force generated when the ball is hit is generated by the elasticity of the thinned face portion. In the metal golf club head disclosed in Japanese Patent Laid-Open No. 9-192273, stress is concentrated on a thin portion of the periphery of the face center or a boundary portion where there is a difference in thickness due to impact force caused by offset hitting. It is easy for damage such as cracks and deformation to occur.

  There is a method of forming the face portion by forging as a face member that has high durability of the face portion and can easily control the direction of the hitting ball and has a long flight distance. In the forging method, for example, a round bar is die-forged to form a face member for forming the face portion, and bonded to a head component other than the face portion to form a golf club head.

  When the face part is produced by the above round bar forging, the crystal grain size (metal structure) of the face part can be made smaller than the crystal grain size of the face member formed by the casting method. In forging, since a block material made of a round bar or square bar is processed into a flat face shape, the amount of plastic deformation at the center of the face is large, and the crystal grain size at the center of the face is smaller than at the periphery of the face. For this reason, the strength of the face portion is highest at the center portion and low at the peripheral portion. In addition, since the portion near the surface of the material is in contact with the mold during forging, the plastic deformation is small, and the crystal grain size becomes finer and the strength becomes higher as it goes inside.

  However, as shown in FIG. 3, when the ball hits the center portion of the face portion 2 when hitting the ball, the face portion 2 bends backward about the impact point S of the ball due to the impact. At this time, compressive stress is applied near the surface of the face portion, and tensile stress is applied near the back surface of the face portion. In fact, repeated hitting of the golf ball will eventually cause fatigue failure of the face portion, but the fracture phenomenon is observed by observing the fracture surface, and initial cracks are generated from the back surface of the face due to repeated tensile stress generated on the back surface of the face. As is well known, it has occurred, developed, and has led to fatigue failure. In particular, in the face portion where the thickness is changed, the tensile stress tends to concentrate on the portion, and the crack progresses from the vicinity, leading to breakage.

  Therefore, the back surface side of the face portion is repeatedly subjected to excessive tensile stress on the back surface of the face portion due to the deflection caused by the impact at the time of hitting the ball. Stress concentrates on a thin portion of the peripheral portion or a boundary portion where there is a difference in thickness, and breakage such as cracks and deformation occurs from the boundary portion.

As a method for improving the above-described problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-144491, the average crystal grain size of the back surface side portion in the center portion of the face portion is the surface in the center portion of the face portion. A metal golf club head is disclosed that is smaller than the average crystal grain size of the side portions. The golf club head can improve the strength of the back side portion of the face portion, and can improve resistance to tensile stress.
JP-A-9-192273 Japanese Patent Laid-Open No. 2003-144451

  In the golf club head disclosed in Japanese Patent Application Laid-Open No. 2003-144451, the average crystal grain size in the vicinity of the back surface in the center part of the face part is made smaller than the average crystal grain diameter in the surface side part in the center part of the face part. This improves the strength of the back surface side portion of the center portion of the face portion, so that the resistance to tensile stress on the back surface side of the face portion can be improved to some extent, so the thickness of the center portion (near the sweet spot) A face member having a larger thickness and a smaller thickness at other portions than that of the center portion can be formed. As a result, the weight of the golf club head itself can be reduced to some extent.

  However, when the ball is hit at the face portion, the ball does not collide only with the center portion, and there are many collisions around the center portion. In golf club heads in which the thickness of the face portion is partially different, the strength in the vicinity of the boundary portion where there is a thickness difference on the back side of the face portion where stress is concentrated has not been particularly taken into consideration. Therefore, when the collision described above is repeated, stress concentrates on the boundary portion, and breakage such as cracks and deformation occurs.

  Further, the thickness of the face portion, which is a precondition for increasing the repulsive force of the head, is reduced, and an increase in the head weight is suppressed with an increase in the size of the head, thereby expanding the face area. As a result, the deflection of the face portion at the time of impact is likely to be excessive. Therefore, the deflection deformation of the face portion becomes excessive, the tensile stress on the back surface side of the face portion becomes large, and there arises a problem that the durability of the face portion is impaired due to repeated impacts.

  Accordingly, an object of the present invention is to provide a golf club head that solves the above problems, improves the fatigue durability of the face portion against repeated hitting, and improves the flight distance by sufficient repulsive force of the face portion. With the goal.

  The invention according to claim 1 of the present invention is a golf club head having a metal face portion, wherein the face member constituting the face portion is thicker than the other portions by forging. And an average crystal grain size on the back surface side at the boundary between the thick part and the thin part of the face part. A golf club head characterized by being smaller than the average crystal grain size on the surface side at the boundary between the thick part and the thin part of the face part.

  The invention according to claim 2 of the present invention is the golf club head according to claim 1, wherein the thick portion includes a sweet spot portion of the face portion and has a thickness of 1.5 mm to 3.2 mm. A center portion having a substantially constant thickness within a range, wherein the thin portion is formed outside the thick portion and has a thickness of 1.0 mm to 3.0 mm and is smaller than the center portion The golf club head is a peripheral portion, wherein the thin portion is smoothly continuous to the thick portion.

  The invention according to claim 3 of the present invention is the golf club head according to claim 1 or 2, wherein the difference between the thick part and the thin part is at least 0.2 mm to 1.9 mm. And a golf club head.

  According to the golf club of the present invention, the vicinity of the boundary between the thick part and the thin part of the face part having a relatively thick part and a relatively thin part in the face part. Since the average crystal grain size on the back surface side is reduced, the durability of the face portion can be remarkably improved.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
According to the present invention, a face portion of a golf club head is formed of a metal material, and the metal face portion is thickened by forging and thicker than other portions, and is thicker than the thick portion. It has a structure including a thin-walled portion that is small. Further, the strength of the boundary portion is improved by making the average crystal grain size on the back surface side of the boundary portion having different thicknesses smaller than the average grain size on the front surface side of the boundary portion, thereby reducing the fatigue of the face portion. It is intended to improve durability, reduce the thickness of the face portion as much as possible to improve the resilience performance of the head, and increase the size of the head (for example, 350 cm 3 to 500 cm 3).
The golf club head of the present invention can be applied to an iron type or a wood type.

  FIG. 1 is a perspective view of a wood-type golf club head 10 to which the present invention is applied, FIG. 2 is an explanatory view showing a cross-sectional structure of a face portion 2 along the line AA in FIG. 1, and FIG. FIG. 4 is an explanatory view when the face portion 2 bends backward due to impact at the time of hitting a ball, and FIG. 4 shows a first region 11 having a relatively large average crystal grain size in a cross section of the face portion 2 and a relatively average crystal grain size. It is explanatory drawing which has shown typically the 2nd area | region 12 with small.

As shown in FIG. 1, the golf club head 10 has a hollow outer shell structure, for example, a face portion 2 made of a metal material such as titanium, a titanium alloy or stainless steel, and the same or different kind of the face portion 2. The head body 1 made of a metal material or a non-metal material such as FRP is joined.
The head body 1 includes a crown portion 3 that is continuous with the upper edge of the face portion 2 and forms the upper surface of the head, a sole portion 4 that is continuous with the lower edge of the face portion 2 and forms the bottom surface of the head, and the crown portion 3 and the sole portion 4 A side portion 7 extending from the toe 5 of the face portion 2 through the back face to the heel 6 and a hosel portion 8 to which a shaft (not shown) is attached are provided.

  The head main body 1 is formed by casting, forging, pressing, or the like using a metal material that is the same or different from the face portion 2, or is formed of a non-metallic material such as FRP. In this case, each outer shell member may be formed individually, or any member (for example, toe, heel, back) may be integrally formed, and these separate outer shell members are welded. Alternatively, the head body 1 is formed by integration by bonding or the like.

The shape of the face member 2 attached to the opening of the head main body 1 has a contour that matches the shape of the opening of the head main body 1, and a peripheral portion is applied to the peripheral edge of the opening of the head main body 1 to join the two. As a result, the face member 2 is fixed to the head body 1.
The golf club head 10 of the present embodiment is exemplified by a wood type in which the face member 2 and the head main body 1 are formed of a metal material and the inside is hollow.

  As shown in FIG. 2, the face portion 2 has a thick portion 20 whose thickness is larger than that of the other portion at the center portion 2 a of the face portion 2 by forging, and is thicker than the thick portion 20. It is comprised from the thin part 21 which is small.

  The thick portion is a center portion including a sweet spot portion of the face portion and having a substantially constant thickness within a range of 1.5 mm to 3.2 mm, and the thin portion is the thick wall portion. The peripheral portion is formed on the outer side of the portion and has a thickness of 1.0 mm to 3.0 mm and smaller than the center portion, and the thin portion is smoothly continuous to the thick portion.

  If the thickness of the thick part is less than 1.5 mm, the thickness becomes excessively thin and the durability of the face part is lowered. On the other hand, if the thickness exceeds 3.2 mm, the thickness becomes excessively thick. This tends to cause an increase in weight, which impairs the balance between durability improvement and weight increase. Further, when the thickness of the thin portion is less than 1.0 mm, the thickness is excessively thin and the durability of the face portion is lowered. On the other hand, when the thickness exceeds 3.0 mm, the thickness is excessively thick. As a result, the balance between the improvement in the resilience characteristics and the increase in the weight tends to be lost.

  In FIG. 2, the surface 2c located above the face portion 2 is a ball striking surface, and the surface located below the face portion 2 and facing the internal space of the head portion 1 is a back surface 2d. When a ball hits the face portion 2 by hitting on the surface of the center portion 2a in the face portion 2, the center portion 2a of the face portion 2 bends and deforms backward (downward in FIG. 2). .

  Therefore, as indicated by an arrow in FIG. 3, tensile stress acts on the back surface 2 d of the center portion 2 a of the face portion 2, and compressive stress acts on the surface 2 c of the center portion 2 a of the face portion 2.

When the face 2 has a portion with a different thickness, when the ball is hit, the ball is hit at approximately the center 2a of the face 2 and the vicinity thereof (off-center hit). Tensile stress is repeatedly applied to the nearby back surface 2d side,
Stress concentrates on the boundary portion 22 between the thin portion 21 and the thick portion 20 having the thickness difference on the back surface 2d side, and the face portion 2 is damaged such as cracks and deformation.

  Therefore, the damage at the face portion 2 greatly depends on whether or not it has resistance to the tensile stress on the back surface 2d side of the face portion 2, and therefore, the boundary between the thick portion and the thin portion on the back surface side of the face portion 2 It is necessary to increase the strength.

  In a metal member, since the yield strength and tensile strength can be increased by reducing the average crystal grain size, and the progress of fatigue cracks can be suppressed, the thick portion 20 and the thin portion on the back surface 2d side of the face portion 2 In order to increase the strength of the boundary portion 22, the average crystal grain size in the vicinity of the boundary portion 22 between the thick portion 20 and the thin portion 21 on the back surface 2d side in the face portion 2 may be reduced. At this time, the average crystal grain size may be uniformly reduced over the entire face portion 2, but in the present embodiment, in the vicinity of the boundary portion 22 between the thick portion 20 on the back surface side and the thin portion 21 in the face portion 2. The average crystal grain size is selectively reduced.

  More specifically, as shown in FIG. 4, a second region 12 having a relatively small average crystal grain size is provided in the cross section of the face portion 2 while leaving the first region 11 having a relatively large average crystal grain size, The second region 12 is disposed in the vicinity of the back surface 2 d side at the boundary portion 22 between the thick portion 20 and the thin portion 21 of the face portion 2.

  As a result, the resistance to tensile stress at the boundary between the thick and thin parts on the back side of the face part where the tensile stress is concentrated especially when off-center hitting can be improved, and damage to the face part can be suppressed. Can do.

  In the example shown in FIG. 4, the second region 12 is a band-like region, and is mainly on the surface 2 c side in the center portion 2 a of the face portion 2, and is a boundary portion between the peripheral thick portion 20 and the thin portion 21. 22 is mainly on the back surface 2d side, and both extend smoothly and continuously.

  In the specification of the present application, the “average crystal grain size” refers to an expression obtained by using a two-dimensional number of crystal grains included in a square region having a side of 25 mm in an enlarged photograph of 100 times.

  The difference between the thick portion 20 and the thin portion 21 of the face portion 2 is preferably at least 0.2 mm to 1.9 mm. When the difference between the thick portion 20 and the thin portion 21 is 0.2 mm or less, the rebound characteristics of the face portion cannot be obtained. On the other hand, when the difference exceeds 1.9 mm, the difference is too large and stress is applied to the boundary portion. Concentration will cause damage such as cracks and deformation from the boundary.

Next, the average crystal grain size of the face portion 2 according to the present invention will be described in more detail.
The average crystal grain size at the boundary between the thick part and the thin part on the back surface side of the face part is not less than 2 to 3 times the average crystal grain size on the surface side at the boundary part between the thick part and the thin part of the face part. The average crystal grain size on the surface side at the boundary between the thick part and the thin part of the face part is preferably 10-20 times or more and 100 times or less, more preferably the face part. The average crystal grain size on the surface side at the boundary between the thick part and the thin part is 30 to 50 times to 100 times.

  The average crystal grain size at the boundary between the thick part and the thin part on the back side of the face part and the average crystal grain size on the surface side at the boundary part between the thick part and the thin part of the face part so as to satisfy the above relationship By setting this, the strength on the back surface side at the boundary between the thick part and the thin part of the face part can be increased.

  The average crystal grain size on the back surface side at the boundary between the thick part and the thin part of the face part is 0.1 μm or more and less than 50 μm, preferably 0.1 μm or more and 20 μm or less, and more preferably 0 .1 μm or more and 10 μm or less. Thus, by reducing the average crystal grain size on the back surface side at the boundary between the thick part and the thin part of the face part, the strength of the boundary part can be effectively increased.

  With the above configuration, the face portion 2 has the center portion 2a of the face portion 2 as a thick portion 20 that can withstand the collision of the ball, and a thin portion 21 is formed outside the thick portion 20. In addition, the durability of the face portion 2 can be improved while reducing the weight, and the rebound characteristics of the face portion 2 can also be improved.

  Next, a method for manufacturing a golf club head according to the present invention will be described with reference to FIGS. 5 to 7 are sectional views showing characteristic manufacturing steps in the method of manufacturing a golf club head according to the present invention.

  First, a beta titanium (15V-6Cr-4AL) round bar (metal material) having a diameter of 21 mm and a length of 140 mm is prepared, and the round bar and the mold are heated to a predetermined temperature. Then, a round bar is installed in a metal mold and roughly forged into a plate shape by a 1600 t press. Thereby, the round bar is plastically deformed into a plate shape, and the metal material 9 having the shape shown in FIG. 5 is obtained.

  At this time, the metal material 9 is plastically deformed so that the thick portion 20 and the thin portion 21 are formed on the back surface side of the center portion 9a of the metal material 9. Thereby, the plastic flow of the metal material 9 on the surface 9b side of the center portion 9a can be made larger than the plastic flow of the metal material 9 on the back surface 9c side of the center portion 9a.

  This is because the plastic flow of the metal material 9 is suppressed by the mold on the back surface 9c side of the center portion 9a of the metal material 9, but the plastic flow of the metal material 9 is substantially suppressed on the surface 9c side of the metal material 9. This is because the metal material 9 flows freely because there are no elements. In addition, in the peripheral part of the metal material 9, the metal material 9 flows like the surface 9b side of the metal material 9.

  As described above, by making the plastic flow on the surface 9b side of the center portion 9a of the metal material 9 larger than the plastic flow on the back surface 9c side of the center portion 9a, the strain at the forging on the surface 9b side increases, and the metal material 9 can reduce the average crystal grain size of the boundary portion 22 between the thick portion 20 and the thin portion 21 on the back surface 9c side, and the average crystal grain size in the surface 9b side portion of the center portion 9a of the metal material 9 is It can be made smaller than the average crystal grain size in the back 9c side portion of the portion 9a.

  In addition, the forged product shown in FIG. 5 can be subjected to mechanical processing such as cutting, or plastic processing such as forging, sheet metal, bending, or pressing. Thereby, as shown in FIG. 2, the metal material 9 can be formed into the shape of the face portion 2 in the head portion 1 of the golf club.

  In addition, as shown in FIG. 6, a structure in which the average crystal grain size in the back surface 9c side portion of the center portion 9a of the metal material 9 is made smaller than the average crystal grain size in the surface 9c side portion of the center portion 9a of the metal material 9 5, the forged product shown in FIG. 5 is turned upside down as shown in FIG. 7, and a concave portion corresponding to the thick portion 20 is provided in a die for forming the back side of the metal material 9. What is necessary is just to forge further the metal raw material 9 of the form shown in FIG.

  As described above, it is possible to refine the crystal at the boundary between the thick part and the thin part on the back side of the metal material and the surface side of the center part or the surface side of the center part on the back side by one forging as described above. Therefore, the crystal on the surface side can be further refined by performing a heat treatment such as a solution treatment or an aging treatment.

  The inventor of the present application actually manufactured the face portion 2 by the method of the present invention and confirmed the metal structure of the cross section, and the result will be described.

8A, 8B and 8C show the metal structures of the respective portions in the thickness direction of the cross section of the face portion 2. FIG.
8a shows a cross-sectional metal structure located on the surface side of the boundary between the thick part and the thin part of the face part 2, and FIG. 8b shows the central part of the boundary part between the thick part and the thin part of the face part 2. FIG. 8 c shows the metal structure of the cross section located on the back side of the boundary between the thick part and the thin part of the face part 2.

  As shown in FIGS. 8a, b, and c, the crystal grains on the back side of the boundary between the thick part and the thin part of the face part 2 are crystals on the surface side of the boundary part between the thick part and the thin part of the face part 2. It can be seen that it is much finer than grains.

  While the face part 2 of the golf club head 10 is produced as described above, the head body 1 such as the crown part 3 and the sole part 4 other than the face part 2 is formed by casting or the like. Then, the golf club head 10 can be manufactured by joining the head body 1 and the face portion 2 by welding or the like.

  As described above, the wood type golf club head has been described as an example in the embodiment and the drawings of the present invention. However, the present invention includes not only a wood type golf club head but also an iron type golf club head.

As shown in FIG. 1, the golf club head 10 of the present embodiment joins a face portion 2 obtained by the present invention and a head body 1 such as a crown portion 3 and a sole portion 4 formed by casting by welding. A wood-type golf club head 10 was formed.
In addition, in the face part 2 shown in FIG. 2, the thickness was 2.8 mm, the thin part was 2.1 mm, and the material was 15V-6Cr-4AL titanium material.
A wood-type golf club was manufactured by attaching a shaft to the golf club head 10.

  Then, the golf club is attached to an endurance tester that continuously hits the ball, the head speed is set to 50 m / s, the hitting position is set to the face center, and the hitting is continued continuously. A test was conducted to confirm the durability until the golf club head breaks by confirming the occurrence of cracks and fractures around the face contour ridgeline.

  For comparison, a golf club head having the same thickness and material as the golf club head of the above embodiment is used, and the crystal grains at the boundary between the thick part and the thin part on the back side of the face part are fine. A golf club head (conventional product) that does not change was formed, and a hit durability test was similarly conducted. Table 1 shows the test results.

○：問題なし。×：破損発生。

○: No problem. X: Damage occurred.

  As shown in Table 1, the face part 2 was damaged after 4000 hits in the comparative example, whereas the face part 2 was damaged after 5000 hits in the product of the present invention. Therefore, the durability of the face portion 2 can be remarkably improved by the present invention.

1 is a perspective view of a wood-type golf club head to which the present invention is applied. Explanatory drawing which shows the cross-section of the face part in alignment with the AA in FIG. Explanatory drawing when a face part bends back by the impact at the time of a hit ball. Explanatory drawing which has shown typically the 1st area | region with a large average crystal grain diameter, and the 2nd area | region with a relatively small average crystal grain diameter. Explanatory drawing which shows the manufacturing method of the golf club head which concerns on this invention. Explanatory drawing which shows the manufacturing method of the golf club head which concerns on this invention. Explanatory drawing which shows the manufacturing method of the golf club head which concerns on this invention. Explanatory drawing which confirms the metal structure of the cross section of a face part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head main body 2 Face part 2a Center part 2b Peripheral part 2c Front surface 2d Back surface 3 Crown part 4 Sole part 5 Toe 6 Heel 7 Side part 8 Hosel part 9 Metal material 9a Center part 9b Front surface 9c Back surface 10 Golf club head 11 1st area | region 12 Second region 20 Thick part 21 Thin part 22 Boundary part

Claims (3)

  A golf club head having a metal face portion, wherein a face member constituting the face portion is thickened by forging and has a thickness larger than that of other portions and smaller than the thick portion. And the average crystal grain size on the back surface side at the boundary between the thick part and the thin part of the face part is the boundary between the thick part and the thin part of the face part. A golf club head characterized by being smaller than the average grain size on the surface side in the portion.   The thick portion is a center portion including a sweet spot portion of the face portion and having a substantially constant thickness within a range of 1.5 mm to 3.2 mm, and the thin portion is a portion of the thick portion. A peripheral portion formed on the outside and having a thickness of 1.0 mm to 3.0 mm and smaller than the center portion, wherein the thin portion is smoothly continuous to the thick portion. The golf club head according to claim 1. 3. The golf club head according to claim 1, wherein a difference between the thick part and the thin part is at least 0.2 mm to 1.9 mm.

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