Golf club head

Abstract

Even when the batting position is inconsistent, it suppresses the decrease in ball distance. [Solution] A golf club head comprising a striking surface 10 for striking a ball. The striking surface 10 includes a sweet spot SS. The striking surface 10 includes a high-friction portion 10H with a large surface roughness, a low-friction portion 10L with a small surface roughness, and an intermediate-friction portion 10M whose surface roughness is smaller than that of the high-friction portion 10H and larger than that of the low-friction portion 10L. When the striking surface 10 is divided into four regions A1 to A4 by a virtual first axis V1 passing through the sweet spot SS and a virtual second axis V2 passing through the sweet spot SS and intersecting the first axis V1, the high-friction portion 10H is located in region A4, which is the closest to the heel and the closest to the sole among the four regions A1 to A4. The low-friction portion 10L is located in region A1, which is the closest to the toe and the closest to the crown among the four regions.

Description

Technical Field

[0001] The present invention relates to a golf club head.

Background Art

[0002] A golf club head has a striking face for hitting a ball, and the striking face has a sweet spot. The sweet spot is the point where a perpendicular line drawn from the head center of gravity to the striking face intersects the striking face. Hitting the ball at the sweet spot is considered effective in terms of flight distance and directionality.

[0003] On the other hand, when the ball is hit at a position shifted vertically or horizontally from the sweet spot, the golf club head rotates slightly around the head center of gravity, and the amount of spin of the ball changes due to the so-called gear effect. Generally, when the ball is hit on the heel side of the sweet spot of the striking face, side spin (hereinafter sometimes simply referred to as "slice spin") in a direction that promotes a slice tends to increase. Also, when the ball is hit on the sole side of the sweet spot of the striking face, backspin tends to increase (see Patent Document 1 regarding the gear effect).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0005] When the above-mentioned side spin and backspin increase, the flight distance of the ball decreases and the directionality deteriorates. Therefore, a golf club head that can suppress a decrease in the flight distance of the ball and the like even when the hitting position varies is desired.

[0006] This invention was devised in view of the above-mentioned problems, and its main objective is to provide a golf club head that can suppress a decrease in ball distance even when the impact position is inconsistent. [Means for solving the problem]

[0007] The present invention relates to a golf club head comprising a striking surface for striking a ball, the striking surface including a sweet spot, the striking surface comprising a high-friction portion with a large surface roughness, a low-friction portion with a small surface roughness, and an intermediate-friction portion whose surface roughness is smaller than that of the high-friction portion and larger than that of the low-friction portion, and when the striking surface is divided into four regions by a virtual first axis passing through the sweet spot and a virtual second axis passing through the sweet spot and intersecting the first axis, the high-friction portion is located in the region furthest towards the heel and furthest towards the sole of the four regions, and the low-friction portion is located in the region furthest towards the toe and furthest towards the crown of the four regions. [Effects of the Invention]

[0008] By adopting the above configuration, the golf club head of the present invention can suppress a decrease in ball distance even when the impact position varies. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view of a golf club head showing one embodiment of the present invention. [Figure 2] Figure 1 is a plan view of a golf club head. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 2. [Figure 4] This is an enlarged view of the striking surface in Figure 1. [Figure 5] This is a front view of the striking surface showing a modified example of a micro-groove. [Figure 6] A partial cross-sectional view of the striking surface oriented perpendicular to the micro-grooves. [Figure 7]This graph shows the distribution of surface roughness in each region of the striking surface. [Figure 8] This is a front view of the striking surface showing a modified example of a micro-groove. [Figure 9] This is a front view of the striking surface showing a modified example of a micro-groove. [Figure 10] This is a front view of a golf club head, incorporating design elements. [Figure 11] This is a front view of the golf club head in the example. [Modes for carrying out the invention]

[0010] One embodiment of the present invention will be described below with reference to the drawings. The drawings may contain exaggerations or representations that differ from the actual structural dimensional ratios in order to aid in understanding the present invention. Furthermore, where there are multiple embodiments, the same or common elements are denoted by the same reference numerals throughout the specification, and redundant descriptions are omitted. Moreover, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the content of the present invention, and the present invention is not limited to the specific configurations shown in the illustrations.

[0011] Figure 1 is a front view of the golf club head (hereinafter sometimes simply referred to as "head") 1 of this embodiment, Figure 2 is a plan view of the head 1 of Figure 1, and Figure 3 is a cross-sectional view taken along line III-III in Figure 1. The head 1 of this embodiment shown in Figures 1 to 3 is, for example, a wood-type head with a hollow section i inside. The head 1 includes, for example, a face section 2, a crown section 3, a sole section 4, a hosel section 5, a toe section 6, and a heel section 7. The head 1 includes, for example, a driver, a fairway wood, a hybrid, etc., and the head 1 of this embodiment is configured as a driver.

[0012] In FIGS. 1 to 3, the head 1 is in a reference state. The reference state means that the head 1 is held at the loft angle α and the lie angle β defined for the head 1 and placed on the horizontal plane HP. Also, in the reference state, the shaft axis center line CL of the head 1 is arranged within the reference vertical plane VP. The shaft axis center line CL is defined by the axis center line of the shaft insertion hole 5a formed in the hosel portion 5 of the head 1. In this specification, unless otherwise specified, the head 1 is assumed to be in this reference state.

[0013] In this specification, an x - y - z coordinate system is associated with the head 1. The x - axis is an axis orthogonal to the reference vertical plane VP and parallel to the horizontal plane HP. The y - axis is an axis parallel to both the reference vertical plane VP and the horizontal plane HP. The z - axis is an axis orthogonal to both the x - axis and the y - axis. And with respect to the head 1, the direction along the x - axis is defined as the head front - rear direction, the direction along the y - axis is defined as the toe - heel direction, and the direction along the z - axis is defined as the crown - sole direction. Note that with respect to the head front - rear direction, the side of the face portion 2 is the front side, and the opposite side is the rear side.

[0014] The head 1 of the present embodiment is essentially formed of a metallic material. The metallic material constituting the head 1 is not particularly limited, but for example, stainless steel, maraging steel, titanium, titanium alloy, magnesium alloy, aluminum alloy, etc. are suitable. A non - metallic material, for example, resin or fiber - reinforced resin may be used for a part of the head 1.

[0015] The face portion 2 includes a striking surface 10 which is a surface for striking a ball. The striking surface 10 includes, for example, a loft angle β of 40° or less and a sweet spot SS.

[0016] The sweet spot SS is the point where the perpendicular line drawn from the head center of gravity (not shown) to the striking surface 10 intersects the striking surface 10. FIG. 3 is a cross - sectional view in a vertical plane perpendicular to the reference vertical plane VP and passing through this sweet spot SS.

[0017] The loft angle β means the angle of the hitting face 10 with respect to the shaft axis center line CL (reference vertical plane VP), that is, the real loft angle. Specifically, the loft angle β is the angle formed by the tangent passing through the sweet spot SS of the hitting face 10 and the reference vertical plane VP in the longitudinal section that passes through the sweet spot SS of the hitting face 10 and is perpendicular to the reference vertical plane VP.

[0018] When hitting a ball with the hitting face 10 having a loft angle β on the head 1, various spins are generated on the hit ball based on the frictional force with the hitting face 10. As clarified in "Analysis of Spin Generation Mechanism in Golf Impact" etc. in the Transactions of the Japan Society of Mechanical Engineers [No. 98 - 9 I] Proceedings of the Mechanical Mechanics and Measurement Control Performance Conference (Vol. B), it has been confirmed that when the loft angle β of the hitting face 10 is small, the larger the surface roughness (friction coefficient), the smaller the amount of backspin. Also, when the loft angle β of the hitting face 10 is large, it has been confirmed that the larger the surface roughness (friction coefficient), the larger the amount of backspin. Such a phenomenon is considered to be affected by the recoil phenomenon occurring in the ball.

[0019] Recoil is a kind of restoring force that tries to return the elastic torsion generated inside the ball due to contact with the hitting face 10. When this recoil is strongly manifested, the amount of spin decreases (recoil phenomenon). That is, in a golf club head with a small loft angle β, the larger the surface roughness of the hitting face 10, the relatively higher the effect of recoil, and the lower the spin amount of the ball. Also, in a golf club head with a small loft angle β, the smaller the surface roughness of the hitting face 10, the more the effect of recoil is suppressed, and the higher the spin amount of the ball. In the present invention, it is premised on a golf club head 1 having a hitting face 10 with a loft angle β of 40° or less, preferably 5 - 40°, more preferably 5 - 32°, in which such a recoil phenomenon is effectively manifested.

[0020] Figure 4 is an enlarged view of the striking surface 10 in Figure 1. As shown in Figure 4, the striking surface 10 of this embodiment includes a high-friction portion 10H with a large surface roughness, a low-friction portion 10L with a small surface roughness, and an intermediate-friction portion 10M whose surface roughness is less than that of the high-friction portion 10H and greater than that of the low-friction portion 10L. In this embodiment, the high-friction portion 10H has the largest surface roughness among the striking surface 10, and the low-friction portion 10L has the smallest surface roughness among the striking surface 10.

[0021] Furthermore, when the striking surface 10 is divided into four regions by a virtual first axis V1 passing through the sweet spot SS and a virtual second axis V2 passing through the sweet spot SS and intersecting the first axis V1, the high-friction portion 10H is located in the region furthest towards the heel 7 and furthest towards the sole portion 4. The low-friction portion 10L is located in the region furthest towards the toe 6 and furthest towards the crown portion 3.

[0022] As described above, hitting the ball at a position closer to the heel 7 than the sweet spot SS on the hitting surface 10 increases slice spin. Also, hitting the ball at a position closer to the sole 4 than the sweet spot SS on the hitting surface 10 increases the amount of backspin. Since these increases in spin reduce the distance the ball travels, hitting the ball at a position closer to both the heel 7 and the sole 4 than the sweet spot SS on the hitting surface 10 results in a significant decrease in distance. In the head 1 of this embodiment, the high-friction area 10H is located furthest towards the heel 7 and furthest towards the sole 4 out of the four areas, so the recoil phenomenon suppresses the increase in spin of the launched ball and prevents a decrease in distance. In addition, the variation in left and right direction is also reduced.

[0023] In the head 1 of this embodiment, the low-friction area 10L is located in the area furthest towards the toe 6 and furthest towards the crown 3 among the four areas. When the ball is struck in this area, the increase in backspin due to the gear effect is less compared to when the ball is struck on the heel 7 side and sole 4 side of the sweet spot SS. Rather, if the surface roughness is made rough in this area, the variation in flight distance when the striking position varies will increase. From this viewpoint, the head 1 of this embodiment reduces the variation in flight distance even when the striking position varies by positioning the low-friction area 10L in the area furthest towards the toe 6 and furthest towards the crown 3 among the four areas.

[0024] As described above, the head 1 of this embodiment can control the spin of the ball by utilizing the recoil phenomenon by setting an appropriate surface roughness distribution in each area of ​​the striking surface 10, thereby suppressing a decrease in flight distance and variations in left-right direction.

[0025] In a preferred embodiment, the first axis V1 extends in the crown-sole direction, and the second axis V2 extends in the toe-heel direction. More specifically, the first axis V1 is parallel to the crown-sole direction, and the second axis V2 is parallel to the toe-heel direction. Thus, the first axis V1 and the second axis V2 are orthogonal to each other. In other embodiments, the first axis V1 may be inclined at an angle θ1 with respect to the crown-sole direction, and the second axis V2 may be inclined at an angle θ2 with respect to the toe-heel direction. The angles θ1 and θ2 may be, for example, 15° or less. The intersection angle of the first axis V1 and the second axis V2 is preferably substantially 90°.

[0026] In this embodiment, the striking surface 10 is divided into four areas by the first axis V1 and the second axis V2: the upper toe region A1, the upper heel region A2, the lower toe region A3, and the lower heel region A4. The high-friction portion 10H is provided in the lower heel region A4, the low-friction portion 10L is provided in the upper toe region A1, and the intermediate-friction portion 10M is provided in the upper heel region A2 and the lower toe region A3, respectively.

[0027] In a preferred embodiment, substantially the entire area of ​​the lower heel region A4 is formed of a high-friction portion 10H, substantially the entire area of ​​the upper toe region A1 is formed of a low-friction portion 10L, and substantially the entire areas of the upper heel region A2 and the lower toe region A3 are formed of an intermediate-friction portion 10M. However, considering the precision of the machining to adjust the actual surface roughness, a similar effect can be expected if most of each region A1 to A4 is formed of the friction portion described above. For example, more than 60% of the lower heel region A4 may be formed of a high-friction portion 10H, more than 60% of the upper toe region A1 may be formed of a low-friction portion 10L, and more than 60% of each of the upper heel region A2 and the lower toe region A3 may be formed of an intermediate-friction portion 10M.

[0028] As shown in Figure 4, in this embodiment, the high-friction portion 10H and the intermediate-friction portion 10M are provided with a plurality of micro-grooves 20 in order to give the striking surface 10 different surface roughness. Thus, in this embodiment, by providing micro-grooves 20 with varying widths, lengths, groove depths, and / or spacings on the striking surface 10 which has a smooth surface, the striking surface 10 is adjusted to have a high-friction portion 10H, an intermediate-friction portion 10M, and a low-friction portion 10L.

[0029] In this specification, the micro-grooves 20 are defined as elongated grooves having a groove depth smaller than the "grooves" provided in the impact area markings of the Rules of Golf. More specifically, the micro-grooves 20 have a groove depth of less than 0.025 mm. Although not shown in the drawings, the striking surface 10 may also have grooves provided in the impact area markings of the Rules of Golf (hereinafter referred to as "face lines"). If face lines are provided on the striking surface 10, the surface roughness of the striking surface 10 shall be measured in areas excluding the face lines.

[0030] In this embodiment, the micro-grooves 20 extend in the toe-heel direction and / or the crown-sole direction.

[0031] In this embodiment, a plurality of micro-grooves 21 (hereinafter referred to as "first micro-grooves 21") extending in the toe-heel direction are provided in the region on the sole portion 4 side of the sweet spot SS (i.e., the toe lower region A3 and the heel lower region A4). The first micro-grooves 21 extend continuously, for example, from the toe side to the heel side of regions A3 and A4. The first micro-grooves 21 are also arranged at predetermined intervals in the crown-sole direction. In this example, the first micro-grooves 21 are formed at substantially constant intervals.

[0032] In this embodiment, a plurality of micro-grooves 22 (hereinafter referred to as "second micro-grooves 22") extending in the crown-sole direction are provided in the region on the heel 7 side of the sweet spot SS (i.e., the upper heel region A2 and the lower heel region A4). The second micro-grooves 22 extend continuously, for example, from the crown side to the sole side of regions A2 and A4. The second micro-grooves 22 are also arranged at predetermined intervals in the toe-heel direction. In this example, the second micro-grooves 22 are formed at substantially constant intervals.

[0033] In this embodiment, both the first micro-grooves 21 and the second micro-grooves 22 are formed in the lower heel region A4. In this embodiment, the first micro-grooves 21 and the second micro-grooves 22 intersect with each other. Therefore, the lower heel region A4 has the highest density of micro-grooves 20 (total length of micro-grooves 20 per unit surface area) compared to the other regions A1 to A3, and the lower heel region A4 is adjusted to be a high-friction area 10H.

[0034] In this embodiment, only the first micro-grooves 21 are formed in the lower toe region A3. Also, only the second micro-grooves 22 are formed in the upper heel region A2. Furthermore, the upper toe region A1 does not have micro-grooves 20 (or if it does, it has fewer than any of the other regions). As a result, with respect to surface roughness, the lower toe region A3 and the upper heel region A2 are adjusted to be intermediate friction regions 10M, and the upper toe region A1 is adjusted to be a low friction region 10L.

[0035] The micro-grooves 20 may extend in a straight line when viewed from the front of the striking surface 10, for example, but the micro-grooves 20 in this embodiment are non-linear. Non-linear micro-grooves 20 have a larger groove area per effective groove length compared to linear ones, and thus can effectively adjust the high-friction section 10H, etc. The non-linear micro-grooves 20 in this embodiment are zigzag in shape, but they may also extend in a wave-like shape, as shown in Figure 5. Furthermore, the micro-grooves 20 may also be dotted lines with some sections interrupted.

[0036] The micro-grooves 20 can be processed by various methods, such as machining, laser milling, and etching. In this embodiment, the micro-grooves 20 are formed by laser milling. In one example of laser milling, the striking surface 10 is moved in a predetermined direction while being irradiated with a computer-controlled laser, thereby forming the micro-grooves 20 along the laser's trajectory. The groove width and groove depth of the micro-grooves 20 can be controlled by adjusting the laser output and movement speed. The groove width of the micro-grooves 20 is preferably 0.05 to 2.0 mm, more preferably 0.05 to 0.4 mm.

[0037] Figure 6 shows a cross-section of the striking surface 10 perpendicular to the micro-grooves 20. In the cross-section shown in Figure 6, the micro-grooves 20 processed by laser milling are machined to have a roughly triangular cross-section such that the groove width continuously decreases as the depth increases. However, the cross-sectional shape of the micro-grooves may also be arc-shaped. Furthermore, micro-grooves formed by machining rather than laser milling may have a pair of substantially parallel groove walls.

[0038] In laser milling, the area irradiated by the laser is locally melted and removed to form a micro-groove 20. However, some of the removed material rises up near the groove edge 20e of the micro-groove 20, forming a protrusion 30. This protrusion 30 rises locally from the flat surface 10P of the striking surface 10 before laser processing. Such a protrusion 30 forms a peak on the striking surface 10, which can more effectively increase the surface roughness there. The height of the protrusion 30 can be adjusted by adjusting the laser output. In a preferred embodiment, the height of the protrusion 30 from the flat surface 10P may be, for example, 1 to 3 μm. In this specification, the groove depth of the micro-groove 20 refers to the groove depth (depth from the flat surface 10P) that does not include the height of the protrusion 30.

[0039] Furthermore, the micro-grooves 20 shown in Figure 6 are formed such that the groove centerline GCL is substantially parallel to the normal to the flat surface 10P of the striking surface 10. In other embodiments, the micro-grooves 20 may be formed such that the groove centerline GCL is inclined with respect to the normal.

[0040] Figure 7 shows preferred ranges of surface roughness for the high-friction section 10H, the intermediate-friction section 10M, and the low-friction section 10L. In Figure 7, the horizontal axis represents the maximum height roughness Rz (μm), and the vertical axis represents the arithmetic mean roughness Ra (μm). In this embodiment, the surface roughness of the striking surface 10 can be specified by the maximum height roughness Rz and / or the arithmetic mean roughness Ra. The maximum height roughness Rz allows evaluation or specification of the state of maximum irregularities in each region of the striking surface 10. The arithmetic mean roughness Ra allows evaluation or specification of the average roughness state in each region of the striking surface 10. The maximum height roughness Rz and the arithmetic mean roughness Ra are measured in accordance with JIS B 0601-2013.

[0041] As shown in Figure 7, the high-friction section 10H preferably has a maximum height roughness Rz in the range of 18 to 30 μm and an arithmetic mean roughness Ra in the range of 2.5 to 5.0 μm. The low-friction section 10L preferably has a maximum height roughness Rz of 10 μm or less and an arithmetic mean roughness Ra of 1.8 μm or less. Furthermore, the intermediate-friction section 10M preferably has a maximum height roughness Rz in the range of 8 to 20 μm and an arithmetic mean roughness Ra in the range of 1.0 to 3.3 μm.

[0042] Figure 8 shows a modified example of the microgroove 20. As shown in Figure 8, the microgroove 20 may include a third microgroove 23 extending in an arc shape. It is desirable that the multiple third microgrooves 23 be arranged concentrically around the sweet spot SS of the striking surface 10. In this example, the multiple third microgrooves 23 are circular grooves centered on the sweet spot SS.

[0043] In the specific example shown in Figure 8, the third micro-grooves 23 are provided in the lower heel region A4, the upper heel region A2, and the lower toe region A3, respectively, but not in the upper toe region A1. Furthermore, the spacing of the third micro-grooves 23 in the lower heel region A4 is set smaller than the spacing of the third micro-grooves 23 in the upper heel region A2 and the lower toe region A3. As a result, the density of micro-grooves 20 is highest in the lower heel region A4, and consequently, the lower heel region A4 is adjusted to be a high-friction area 10H. On the other hand, the upper toe region A1 does not have micro-grooves 20 (third micro-grooves 23), resulting in a smooth surface and thus being adjusted to be a low-friction area 10L. In addition, the upper heel region A2 and the lower toe region A3 have a lower density of micro-grooves 20 than the lower heel region A4, and are therefore considered to be intermediate-friction areas 10M.

[0044] In other aspects of the present invention, the surface roughness may be varied within each region A1 to A4 of the striking surface 10 by changing the spacing of the micro-grooves 20 and / or the groove depth. For example, the gear effect tends to be more pronounced when the ball is struck at a position further away from the sweet spot SS on the striking surface 10. On the other hand, the recoil phenomenon also tends to be more pronounced the greater the surface roughness of the striking surface 10. Therefore, it is desirable that the surface roughness of the lower heel region A4 increases continuously or stepwise as it moves away from the sweet spot SS towards the heel 7 side or the sole 4 side.

[0045] To obtain the heel lower region A4 with the surface roughness described above, it is desirable that the high-friction portion 10H of the heel lower region A4 has a continuous or stepwise decreasing spacing between the multiple micro-grooves 20 as it moves away from the sweet spot SS, for example, as shown in Figure 9. For example, the spacing of the first micro-grooves 21 decreases as it moves away from the sweet spot SS towards the sole portion 4, such as Pz1>Pz2>Pz3… Similarly, the spacing of the second micro-grooves 22 decreases as it moves away from the sweet spot SS towards the heel 7, such as Py1>Py2>Py3… In addition to, or alternatively to, such variation in the spacing of the micro-grooves 20, the high-friction portion 10H may also have a continuous or stepwise increasing groove depth of the micro-grooves 20 as it moves away from the sweet spot SS.

[0046] In such high-friction areas 10H, the surface roughness increases continuously or gradually as it moves away from the sweet spot SS. Therefore, when the ball is struck at a position further away from the sweet spot SS on the striking surface 10, a greater recoil phenomenon can be produced, and the occurrence of a greater gear effect can be suppressed.

[0047] Figure 10 is a front view of head 1 of another embodiment of the present invention. In this embodiment, the striking surface 10 is decorated with micro-grooves 20 of various designs. Distinguishing in this embodiment by a common design feature of micro-grooves 20 machined on the striking surface 10, the striking surface 10 includes a toe-side region B1, a heel-side region B2, a crown-side region B3, a sole-side region B4, and a central region B5 surrounded by these.

[0048] However, in the embodiment shown in Figure 10, the groove depth of the micro-grooves 20 is changed so that the lower heel region A4 becomes a high-friction region 10H, the upper toe region A1 becomes a low-friction region 10L, and the upper heel region A2 and lower toe region A3 become intermediate-friction regions 10M. Specifically, in all micro-grooves 20, regardless of the design features of the micro-grooves, the groove depth d1 of the micro-grooves 20 extending within the lower heel region A4 is formed to be the deepest, the groove depth d3 of the micro-grooves 20 extending within the upper toe region A1 is formed to be the shallowest, and the groove depth d2 of the micro-grooves 20 extending within the upper heel region A2 and lower toe region A3 is formed to satisfy the relationship d1>d2>d3. Therefore, in this embodiment, the striking surface 10 does not have an area divided by the common design features of the micro-grooves 20 and an area divided by the actual surface roughness. The head 1 in this embodiment can solve a new problem: it can suppress the reduction in ball distance even when the hitting position is inconsistent, without sacrificing the design elements provided to the hitting surface 10.

[0049] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the specific disclosures described above, and can be implemented with various modifications within the scope of the technical idea described in the claims. [Examples]

[0050] More specific and non-limiting embodiments of the present invention are described below. As shown in Figure 11, a golf club head 1 (loft angle 10.5°) was prototyped in which the surface roughness of the striking surface 10 was adjusted by forming linear micro-grooves 20 (Example). For comparison, a golf club head with the same shape as the Example but without micro-grooves formed on the striking surface 10 was also prepared (Comparative Example). The two golf club heads were then mounted on a swing robot, and a striking test was conducted by hitting a ball. In the striking test, the backspin and sidespin of the launched ball were measured. The conditions of the striking test were as follows.

[0051] <Hitting test> The hitting test was adjusted so that the head speed was set to 42 m / s and the center of the ball made contact with the next hitting position. Hitting position 1: Sweet spot Hitting position 2: This position is 5mm towards the crown and 15mm towards the toe from the sweet spot, and corresponds to hitting in the upper toe area. Hitting position 3: This position is 10mm towards the sole and 15mm towards the toe from the sweet spot, and corresponds to hitting in the lower toe area. Hitting position 4: This is 15mm from the sweet spot towards the heel. Hitting position 5: This position is 10mm towards the sole and 15mm towards the heel from the sweet spot, and corresponds to hitting in the lower heel area.

[0052] In the examples and comparative examples, the surface roughness of each area (striking position) of the striking surface is as shown in Table 1. Here, the surface roughness was set independently of the rules of golf. For measurement, a measurement length of 4 mm was set with the target area as the center, and the surface roughness was measured at a reference length of 0.8 mm. In addition, measurements were taken in multiple directions, and the direction that showed the greatest surface roughness was adopted.

[0053] [Table 1]

[0054] The test results are shown in Table 2.

[0055] [Table 2]

[0056] The test results confirmed that the head of the embodiment suppressed changes in backspin and sidespin even when the impact position varied, compared to the head of the comparative example. This indicates that it suppresses the decrease in ball distance and deterioration of direction.

[0057] [Note] The present invention includes the following embodiments.

[0058] [Invention 1] It is a golf club head, Equipped with a hitting surface for striking the ball, The striking surface includes a sweet spot, The striking surface includes a high-friction portion with a large surface roughness, a low-friction portion with a small surface roughness, and an intermediate-friction portion whose surface roughness is smaller than that of the high-friction portion and larger than that of the low-friction portion. When the striking surface is divided into four regions by a virtual first axis passing through the sweet spot and a virtual second axis passing through the sweet spot and intersecting the first axis, the high-friction portion is located in the region that is furthest towards the heel and furthest towards the sole among the four regions. The low-friction portion is located in the region that is closest to the toe and closest to the crown among the four regions. Golf club head. [2nd Invention] The golf club head according to Invention 1, wherein the first axis extends in the crown-sole direction and the second axis extends in the toe-heel direction. [Invention 3] The golf club head according to invention 1 or 2, wherein the surface roughness of the high-friction portion increases as it moves away from the sweet spot. [4th Invention] The golf club head according to any one of inventions 1 to 3, wherein the high-friction portion and the intermediate-friction portion are provided with a plurality of fine grooves having a groove depth of less than 0.025 mm. [5th ​​Invention] The golf club head according to claim 4 of the present invention, wherein the plurality of micro-grooves extend in the toe-heel direction and / or in the crown-sole direction. [Invention 6] The golf club head according to the present invention, wherein the plurality of micro-grooves extend in an arc shape and are arranged concentrically around the sweet spot. [7th Invention] The golf club head according to any one of claims 4 to 6, wherein the high-friction portion has a continuous or stepwise decreasing spacing between the plurality of micro-grooves as it moves away from the sweet spot. [8th Invention] The golf club head according to any one of claims 4 to 7, wherein the groove depth of the fine grooves in the high-friction portion increases continuously or in stages as it moves away from the sweet spot. [Invention 9] A golf club head according to any one of 4 to 8 of the present invention, wherein in a cross-section of the striking surface oriented perpendicular to the micro-grooves, protrusions are formed on the groove edges of the micro-grooves, which rise locally from the striking surface. [Invention 10] The golf club head according to any one of inventions 1 to 9, wherein the high-friction portion has a maximum height roughness Rz in the range of 18 to 30 μm and an arithmetic mean roughness Ra in the range of 2.5 to 5.0 μm. [Invention 11] The low-friction portion has a maximum height roughness Rz of 10 μm or less and an arithmetic mean roughness Ra of 1.8 μm or less, as described in any one of invention 1 to 10. [Invention 12] The intermediate friction portion has a maximum height roughness Rz in the range of 8 to 20 μm and an arithmetic mean roughness Ra in the range of 1.0 to 3.3 μm, as described in any one of invention 1 to 11. [Explanation of Symbols]

[0059] 1 Golf club head 6 Tou 7 heels 10 Hitting surface 10H High friction part 10L low friction part 10M intermediate friction section 20 micro grooves 20e groove edge 21 First micro-groove 22 Second Microgroove 23 Third micro-groove 30 Convex part A1 Upper toe region A2 Upper heel area A3 Lower heel area A4 Lower heel area SS Sweet Spot V1 1st axis V2 2nd axis

Claims

1. It is a golf club head, Equipped with a hitting surface for striking the ball, The striking surface includes a sweet spot, The striking surface includes a high-friction portion with a large surface roughness, a low-friction portion with a small surface roughness, and an intermediate-friction portion whose surface roughness is smaller than that of the high-friction portion and larger than that of the low-friction portion. When the striking surface is divided into four regions by a virtual first axis passing through the sweet spot and a virtual second axis passing through the sweet spot and intersecting the first axis, the high-friction portion is located in the region that is furthest towards the heel and furthest towards the sole among the four regions. The low-friction portion is located in the region that is closest to the toe and closest to the crown among the four regions. Golf club head.

2. The golf club head according to claim 1, wherein the first axis extends in the crown-sole direction and the second axis extends in the toe-heel direction.

3. The golf club head according to claim 1, wherein the surface roughness of the high-friction portion increases as it moves away from the sweet spot.

4. The golf club head according to claim 1, wherein the high-friction portion and the intermediate-friction portion are provided with a plurality of fine grooves having a groove depth of less than 0.025 mm.

5. The golf club head according to claim 4, wherein the plurality of micro-grooves extend in the toe-heel direction and / or in the crown-sole direction.

6. The golf club head according to claim 4, wherein the plurality of micro-grooves extend in an arc shape and are arranged concentrically around the sweet spot.

7. The golf club head according to claim 4, wherein the high-friction portion has a continuous or gradual decrease in the spacing between the plurality of micro-grooves as it moves away from the sweet spot.

8. The golf club head according to claim 4, wherein the groove depth of the fine grooves in the high-friction portion increases continuously or in stages as it moves away from the sweet spot.

9. The golf club head according to claim 4, wherein in a cross-section of the striking surface oriented perpendicular to the micro-grooves, protrusions are formed on the groove edges of the micro-grooves, which rise locally from the striking surface.

10. The golf club head according to any one of claims 1 to 9, wherein the high-friction portion has a maximum height roughness Rz in the range of 18 to 30 μm and an arithmetic mean roughness Ra in the range of 2.5 to 5.0 μm.

11. The low-friction portion has a maximum height roughness Rz of 10 μm or less and an arithmetic mean roughness Ra of 1.8 μm or less, as described in any one of claims 1 to 9, for the golf club head.

12. The golf club head according to any one of claims 1 to 9, wherein the intermediate friction portion has a maximum height roughness Rz in the range of 8 to 20 μm and an arithmetic mean roughness Ra in the range of 1.0 to 3.3 μm.

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