Iron golf club head

Abstract

To provide an iron golf club head capable of achieving both of a soft shot feeling at impact and durability while suppressing a manufacturing cost.SOLUTION: An iron golf club head 1 includes a face part 2 and a hosel part 7. The face part 2 and the hosel part 7 are made of soft iron and integrally formed by forging or casting. A striking face 21, in a standard state of the head 1, has a main striking point S, the center position FC in the toe-heel direction of the striking face 21, at a position 12 mm above the lowest end 21e of the striking face 21 along the striking face 21. The face part 2 has a face hardness hf (HV), the Vickers hardness, at a position 4 mm depth from the striking face 21 of the main striking point S. The hosel part 7 has a hosel reference outer periphery 7S extending 30 mm below the upper end of the hosel in the hosel circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an iron-type golf club head. [Background technology]

[0002] There is known an iron-type golf club head having a so-called one-piece structure, which is integrally formed by forging or casting a soft iron material (see Patent Document 1 below). This type of iron-type golf club head has the advantage of providing a soft hitting feel while keeping manufacturing costs down. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-284155 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned iron-type golf club heads have a problem that, while providing a soft hitting feel, they have room for improvement in durability. For example, the above-mentioned heads have a problem that the vicinity of the hosel part is easily deformed by repeated hitting of the ball, which in turn changes the loft angle and lie angle.

[0005] The present invention has been devised in view of the above-mentioned circumstances, and has as its main object to provide an iron-type golf club head that can achieve both a soft hitting feel and durability while keeping manufacturing costs down. [Means for solving the problem]

[0006] The present invention is an iron-type golf club head, comprising a face portion having a hitting surface, and a hosel portion connected to a heel side of the face portion, the face portion and the hosel portion being made of soft iron, the face portion and the hosel portion being integrally formed by forging or casting, the hitting surface having a main hitting point which is a center position of the hitting surface in a toe-heel direction and a position 12 mm above the lowest end of the hitting surface along the hitting surface in a standard state where the head is placed on a horizontal plane with a specified lie angle and loft angle, the face portion having a face hardness hf (HV) which is a Vickers hardness at a position 4 mm deep from the hitting surface of the main hitting point, and the hosel portion having a Vickers hardness hf (HV) which is a Vickers hardness hf (HV) at a position 4 mm deep from the hitting surface of the main hitting point, the hosel portion has a hosel reference outer periphery extending 30 mm downward from an upper end of the hosel along the direction of the hosel axis in the hosel circumferential direction, and when positions of the hosel reference outer periphery around the hosel axis are expressed as angles, with the heel-most position being 0°, the head-most rear side being 90°, the toe-most side being 180°, and the face-most side being 270°, the hosel portion has a hosel hardness hh (HV) which is an average value of Vickers hardnesses at positions 1 mm deep from the outer surface of the hosel reference outer periphery at positions 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, and the hosel hardness hh is greater than the face hardness hf. Effect of the Invention

[0007] By adopting the above-mentioned configuration, the iron-type golf club head of the present invention can achieve both a soft hitting feel and durability while suppressing manufacturing costs. [Brief description of the drawings]

[0008] [Figure 1] 1 is a front view of an iron-type golf club head according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a rear view of the iron-type golf club head of FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an enlarged view of a main part of FIG. [Diagram 5] FIG. 2 is a perspective view illustrating a reference state of an iron type golf club head. [Figure 6] FIG. 11 is a front view of a golf club head showing another embodiment. [Figure 7] 7 is a cross-sectional view taken along line VII-VII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. This specification is not intended to limit the present invention in any manner. Furthermore, each embodiment can be used alone or in various combinations. Furthermore, the same or common elements are designated by the same reference numerals throughout this specification, and duplicate descriptions are omitted.

[0010] 1 to 3 are a front view, a rear view, and a cross-sectional view taken along line III-III in FIG. 1, respectively, of an iron-type golf club head (hereinafter sometimes simply referred to as a "head") 1 of the present embodiment.

[0011] As shown in FIGS. 1 to 3, a head 1 includes, for example, a face portion 2 and a hosel portion .

[0012] The face portion 2 is surrounded by a top 3, a sole 4, and a toe 5. The face portion 2 has a hitting surface 21 which is a surface for hitting a ball, and a rear surface 22 on the opposite side to the hitting surface 21.

[0013] A plurality of face lines 8 are formed on the hitting surface 21 for the purpose of increasing friction with the ball. In this embodiment, the face lines 8 are, for example, narrow grooves extending linearly in the toe-heel direction. The face lines 8 are formed in the main hitting area intended for the head 1. Note that in some of the drawings, the face lines 8 are omitted.

[0014] [Reference condition] In Figs. 1 to 3, the head 1 is in a reference state. In this specification, the "reference state" of the head 1 is a state in which the head 1 is placed on a horizontal plane HP so that the face line 8 formed on the striking surface 21 is parallel to the horizontal plane HP, as conceptually shown in Fig. 5. In the reference state, the hosel axis CL (which substantially coincides with the axial center line of the club shaft) that is the central axis of the hosel portion 7 is disposed within the reference vertical plane VP. The reference vertical plane VP is a plane perpendicular to the horizontal plane HP. In the reference state, the face line 8 is parallel to both the horizontal plane HP and the reference vertical plane VP. In Fig. 5, α indicates the lie angle, and β indicates the loft angle. In this specification and the claims, unless otherwise specified, the configuration of each part is described assuming that the head 1 is placed in the reference state.

[0015] [Head directions] With reference to Figure 5, the front side of the head 1 refers to the side of the striking surface 21. The rear side, back side or back surface side of the head refers to the side of the rear surface 22 of the face portion 2. The front-to-rear direction of the head in Figure 5 is the direction of the x-axis perpendicular to the reference vertical plane VP. The toe-heel direction of the head 1 is the direction of the horizontal y-axis perpendicular to the front-to-rear direction of the head. The up-down direction of the head 1 is the direction of the z-axis perpendicular to both the x-axis and y-axis. The "upper side" and "lower side" of the head 1 respectively refer to the "upper side" and "lower side" in the reference state.

[0016] [Head structure] 3, the hitting surface 21 of the face portion 2 is formed as a flat surface. The rear surface 22 of the face portion 2 is formed with, for example, a cavity recessed toward the hitting surface 21. In another embodiment, the rear surface 22 may be, for example, a so-called muscle back in which no cavity is provided.

[0017] As shown in FIG. 3, the top 3 extends, for example, from the upper edge of the striking surface 21 toward the rear of the head, and constitutes the upper surface portion of the head 1.

[0018] The sole 4 extends from the lower edge of the striking surface 21 toward the rear of the head, and constitutes the lower surface of the head 1 .

[0019] 1, the toe 5 means an end portion of the head 1 on the side away from the hosel portion 7 in the toe-heel direction. On this toe side, the top 3 and the sole 4 are smoothly connected.

[0020] The heel 6 is an end portion located on the opposite side to the toe 5 in the toe-heel direction of the head 1, and a hosel portion 7 is connected to the heel 6.

[0021] The hosel portion 7 has a shaft insertion hole 7a for receiving a club shaft (not shown). The central axis of the shaft insertion hole 7a defines the above-mentioned hosel axis CL.

[0022] [Constituent materials, manufacturing method] The face portion 2 and the hosel portion 7 are formed from soft iron. In this specification, soft iron (also called soft steel) refers to a type of carbon steel whose chemical composition has a carbon content of 0.3% by weight or less. The head 1 of this embodiment can provide a soft hitting feel because the face portion 2 is made of soft iron.

[0023] Also, the face portion 2 and the hosel portion 7 have a structure in which they are integrally formed by forging or casting. In this embodiment, the head 1 has a so-called forged one-piece structure in which the entire head 1 is formed by forging. In another aspect, the head 1 may have a structure in which the head 1 is integrally formed by casting instead of forging. The head 1 having such a one-piece structure can significantly reduce manufacturing costs compared to a head having a two-piece (or three or more pieces) structure in which a face plate and a main body are prepared as separate parts and then the face plate and the main body are fixed together to form the head 1.

[0024] [Relationship between face hardness and hosel hardness] The head 1 of this embodiment is formed with a hosel hardness hh greater than the face hardness hf, assuming a one-piece structure. Such a head 1 can achieve both a soft hitting feel and durability while keeping manufacturing costs down. More specifically, the head 1 of this embodiment can effectively prevent deformation near the hosel portion 7 caused by repeated hitting of the ball, and thus can suppress changes in the lie angle α and loft angle β of the head 1.

[0025] [Face hardness] In this specification, face hardness hf means hardness associated with a main impact point S on the striking surface 21 of the face portion 2. The main impact point S is identified as a representative point of a position where a ball is frequently struck in an iron-type golf club head. More specifically, the main impact point S is located on the center position FC of the striking surface 21 in the toe-heel direction as shown in Fig. 1, and is located 12 mm above the bottom end 21e of the striking surface 21 along the striking surface 21 as shown in Fig. 4 (Fig. 4 is a cross-sectional view taken along line III-III in Fig. 1).

[0026] The center position FC of the striking surface 21 in the toe-heel direction is the center position in the toe-heel direction between the end point 8a of the face line 8 located at the most toe side and the end point 8b of the face line 8 located at the most heel side, as shown in Fig. 1. However, as shown in Fig. 6, there may be a head 1 in which the face line 8 extends beyond the highest position H1 of the top 3 toward the toe 5 side. In the case of such a head 1, the center position FC of the striking surface 21 in the toe-heel direction means the center position in the toe-heel direction between the position 8c located 18 mm away from the end of the striking surface 21 at the most toe side toward the heel 6 side and the end point 8b of the face line 8 located at the most heel side.

[0027] 4, the bottom end 21e of the hitting face 21 means the bottom end of the hitting face 21 which is a plane, and the arc portion connected thereto on the sole 4 side is excluded from the hitting face 21. When the main hitting point S is located on the face line 8, the main hitting point S is considered to be located on a virtual hitting face that fills the face line 8.

[0028] Furthermore, the face hardness hf is the Vickers hardness at a position SP at a depth of 4 mm from the striking surface 21 of the main striking point S. The reason why the hardness at the position SP is adopted as the face hardness hf is as follows. First, the face line 8, which has a very small width and depth, is usually formed by pressing a face line transfer die against the striking surface 21 (press processing). After this press processing, the hardness of the surface layer of the striking surface 21 increases locally. However, as a result of the experiments of the inventors, it was found that the hardness of the surface layer of the striking surface 21 has little effect on the hitting feeling, and it is difficult to control the hitting feeling even if this hardness is evaluated. Then, as a result of further experiments, it was found that the hardness at the position SP at a depth of 4 mm from the striking surface 21 has the greatest effect on the hitting feeling. Therefore, in the present invention, we focus on the face hardness hf at the position SP, which is 4 mm deep from the striking surface 21 of the main striking point S, as the face hardness that has the greatest effect on the golfer's hitting feel, and by making this smaller than the hosel hardness hh, it is possible to maintain a soft hitting feel when hitting the ball.

[0029] The face hardness hf is usually measured by a destructive test. In the destructive test, the head 1 is first cut at the center position FC and perpendicular to the striking surface 21. Next, a position SP at a depth of 4 mm from the striking surface 21 of the main striking point S is identified from the cut surface of the head 1, and a measuring indenter is pressed against this position SP to measure the face hardness hf.

[0030] [Hosel hardness] In this specification, the hosel hardness is a hardness associated with a hosel reference outer periphery 7S extending 30 mm downward from the upper end of the hosel along the hosel axis CL in the hosel circumferential direction, as shown in Fig. 1. Fig. 7 shows a cross-sectional view taken along line VII-VII in Fig. 1. As shown in Fig. 7, when the positions of the hosel reference outer periphery 7S around the hosel axis CL are expressed as angles in the circumferential direction, with the heelmost side being 0°, the headmost rear side being 90°, the toemost side being 180°, and the facemost side being 270°, the hosel hardness hh (HV) is specified as an average value of Vickers hardness at positions P1 to P8 at a depth of 1 mm from the outer surface of each of the positions (total of eight positions) of the hosel reference outer periphery 7S at 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

[0031] As a result of the experiments by the inventors, it was found that in the head 1 having a soft iron one-piece structure, the deformation of the hosel part 7 due to repeated impacts mainly occurs at the hosel reference outer periphery part 7S. It was also found that, similar to the face hardness hf, when hardening the hosel reference outer periphery part 7S, it is not sufficient to simply harden the outer surface locally, but it is necessary to harden the hosel part 7 at a depth of 1 mm from the outer surface. Furthermore, since the hosel part 7 receives forces from various directions when hitting a ball, it is not sufficient to focus on the hardness at one location for the hosel hardness hh, and it is important to focus on the average value of the hardness at eight circumferential positions P1 to P8 of the hosel part 7. Based on the above findings, in the present invention, the hosel hardness hh is specified as the average value of the Vickers hardness at the positions P1 to P8 as described above.

[0032] The measurement of the hosel hardness hh is also usually performed by a destructive test. In the destructive test, the hosel portion 7 is first cut perpendicularly to the hosel axis CL at the hosel reference outer periphery 7S. Next, a measuring indenter is pressed against positions P1 to P8 on the cut surface of the hosel portion 7, and the Vickers hardness at each position is measured. Finally, the average value of each Vickers hardness is calculated, and this is defined as the hosel hardness hh.

[0033] In this specification, the Vickers hardness is measured in accordance with JIS Z 2244, and the measurement load is 9.807 N. In this specification, the Vickers hardness is measured using an "Akashi Vickers hardness tester AVK-C20."

[0034] As described above, the head 1 of this embodiment, which is made of soft iron and has a one-piece structure, can achieve both a soft hitting feel and durability while keeping manufacturing costs down. Further preferable features of the head 1 of this embodiment will be described below. However, these features do not limit the present invention.

[0035] [Mild steel] The carbon content of the soft iron is preferably 0.30% or less, more preferably 0.20% or less, and even more preferably 0.15% or less. When the carbon content of the material is limited in this way, it helps to provide an even softer hitting feel. Such soft iron materials include carbon steels for machine construction, such as S20C, S17C, S15C, and S12C.

[0036] [Face hardness value] The value of the face hardness hf is not particularly limited as long as it is smaller than the hosel hardness hh, but is preferably less than 180 (HV), more preferably 160 (HV) or less, and even more preferably 145 (HV) or less. This allows the head 1 to more reliably provide a soft hitting feeling. On the other hand, from the viewpoint of durability, the value of hf may be, for example, 100 (HV) or more, more preferably 105 (HV) or more, and even more preferably 110 (HV) or more.

[0037] [Hosel hardness value] The value of the hosel hardness hh is not particularly limited as long as it is greater than the face hardness hf, but is preferably 120 (HV) or more, more preferably 130 (HV) or more, and even more preferably 140 (HV) or more. This allows the head 1 to reliably suppress deformation of the hosel portion 7 caused by repeated hitting of the ball. On the other hand, a high hosel hardness hh is advantageous for durability, but is disadvantageous in the so-called angle adjustment process in which the lie angle α and the loft angle β are intentionally fine-tuned after the head 1 is manufactured. When convenience in such an angle adjustment process is further taken into consideration, the hosel hardness hh may be, for example, 190 (HV) or less, more preferably 180 (HV) or less, and even more preferably 170 (HV) or less.

[0038] [Hardness ratio] In order to achieve a higher level of both soft hitting feel and durability, the ratio hh / hf of the hosel hardness hh and the face hardness hf is preferably 1.10 or more, more preferably 1.15 or more, and even more preferably 1.20 or more. In order to achieve a higher level of both soft hitting feel and durability, the ratio hh / hf may be preferably 1.90 or less, more preferably 1.60 or less, and even more preferably 1.40.

[0039] [Methods for increasing hardness] Next, a method for increasing the hardness of the hosel reference outer periphery 7S will be described. For example, in the head 1, when the face portion 2 and the hosel portion 7 are formed integrally by forging, the hosel portion 7 is forged so that at least some of the crystal grains of the soft iron at the hosel reference outer periphery 7S have a metal structure that is finer than the crystal grains at the main impact point S.

[0040] In hot forging, the final shape is usually finished through a number of steps, such as preforming, rough forming, and finish forming. In order to harden the hosel portion, for example, one or more protrusions are formed on the outer surface of the hosel reference outer periphery 7S by rough forming, and these protrusions are compressed and smoothed by finish forming to form the hosel reference outer periphery 7S. As a result, the hosel reference outer periphery 7S is compressed more than other parts. Therefore, the hosel reference outer periphery 7S can be forged so that some metal grains have a metal structure that is finer than the grains at the main impact point S (hereinafter, this may be referred to as the condensation method).

[0041] Another method is heat treatment. For example, the hosel reference outer periphery 7S of the hosel part 7 can be locally heat-treated (hardened) to increase hardness. As a result, the hosel part 7 has a heat-treated metal structure at the hosel reference outer periphery 7S. As such heat treatment, induction hardening or laser hardening can be adopted.

[0042] Although the embodiment of the present invention has been described in detail above, it goes without saying that the present invention is not limited to the above embodiment and may be modified and implemented in various forms. EXAMPLES

[0043] Golf clubs having soft iron forged one-piece heads shown in Figs. 1 to 3 were prototyped based on the specifications in Table 1. The hosel parts of the heads of Examples 1 and 2 were hardened by the above-mentioned condensation method. On the other hand, the heads of Comparative Examples 1 and 2 have the same finished shapes as Examples 1 and 2, respectively, but the hosel parts are not hardened. Then, using these golf clubs, the shot feeling and durability were evaluated. In addition, the angle adjustment process was evaluated as an optional evaluation item. The evaluation method is as follows.

[0044] [Durability] Each golf club was attached to a swing robot, and a golf ball was hit multiple times with the same head speed. For evaluation, the loft angle and lie angle were measured before and after the hit, and the number of hits when either angle changed by 1° or more was counted in units of 1000 shots. The evaluation is expressed as an index with Comparative Example 1 being "7", and the higher the number, the higher the resistance to deformation due to repeated hits.

[0045] [Ball feel] An advanced golfer hit a ball five times with each golf club. The golfer then evaluated the softness of the hitting feel on a five-point scale. The higher the score, the softer the hitting feel.

[0046] The test results are shown in Table 1.

[0047] [Table 1]

[0048] As a result of the test, it was confirmed that the embodiment can achieve both a soft hitting feel and high durability compared to the comparative example.

[0049] [Note] The present invention includes the following aspects.

[0050] [Invention 1] An iron-type golf club head, A face portion having a striking surface; a hosel portion connected to a heel side of the face portion, the face portion and the hosel portion are made of soft iron, the face portion and the hosel portion have a structure integrally formed by forging or casting, In a standard state in which the head is placed on a horizontal plane with a specified lie angle and loft angle, the striking surface has a main striking point which is at a center position of the striking surface in a toe-heel direction and which is located 12 mm above the lowermost end of the striking surface along the striking surface; The face portion has a face hardness hf (HV) which is a Vickers hardness at a position 4 mm deep from the striking surface of the main striking point, the hosel portion has a hosel reference outer periphery portion extending 30 mm downward from a hosel upper end along a hosel axis direction in a hosel circumferential direction, When positions of the hosel reference outer periphery around the hosel axis are expressed as angles, with 0° at the heel side, 90° at the head rear side, 180° at the toe side, and 270° at the face side, the hosel portion has a hosel hardness hh (HV) which is an average value of Vickers hardness at positions 1 mm deep from the outer surface of the hosel reference outer periphery at each of the positions 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, The hosel hardness hh is greater than the face hardness hf. Iron type golf club head. [Invention 2] 2. The iron-type golf club head according to claim 1, wherein the soft iron has a carbon content of 0.20% by weight or less. [Invention 3] 2. The iron-type golf club head according to claim 1, wherein the soft iron has a carbon content of 0.15% by weight or less. [Invention 4] 4. The iron-type golf club head according to any one of claims 1 to 3, wherein the face hardness hf is less than 130 (HV), and the hosel hardness hh is 130 to 190 (HV). [Invention 5] 5. The iron-type golf club head according to any one of claims 1 to 4, wherein a ratio hh / hf of the hosel hardness hh to the face hardness hf is 1.10 or more. [Invention 6] the face portion and the hosel portion are integrally formed by forging, An iron-type golf club head as described in any one of claims 1 to 5, wherein the hosel portion has a metal structure in which at least some of the crystal grains of the soft iron at the hosel reference outer periphery are finer than the crystal grains at the main impact point. [Invention 7] 6. The iron-type golf club head according to any one of claims 1 to 5, wherein the hosel portion has a heat-treated metal structure at a reference outer periphery of the hosel. [Explanation of symbols]

[0051] 1. Iron type golf club head 2 Face section 5 Tou 6 Heel 7 Hosel 7S hosel reference outer circumference 21 Striking surface 21e Bottom of the striking surface CL hosel axis S Main hitting point

Claims

1. An iron-type golf club head, A face portion having a striking surface; a hosel portion connected to a heel side of the face portion, the face portion and the hosel portion are made of soft iron, the face portion and the hosel portion have a structure integrally formed by forging or casting, In a standard state in which the head is placed on a horizontal plane with a specified lie angle and loft angle, the striking surface has a main striking point that is a center position of the striking surface in a toe-heel direction and is located 12 mm above the lowermost end of the striking surface along the striking surface; The face portion has a face hardness hf (HV) which is a Vickers hardness at a position at a depth of 4 mm from the striking surface of the main striking point, the hosel portion has a hosel reference outer periphery portion extending 30 mm downward from a hosel upper end along a hosel axis direction in a hosel circumferential direction, When positions of the hosel reference outer periphery around the hosel axis are expressed as angles, with the heel side being 0°, the head rear side being 90°, the toe side being 180°, and the face side being 270°, the hosel portion has a hosel hardness hh (HV) which is an average value of Vickers hardnesses at positions 1 mm deep from an outer surface of the hosel reference outer periphery at each of the positions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, The hosel hardness hh is greater than the face hardness hf. Iron type golf club head.

2. 2. The iron-type golf club head according to claim 1, wherein the soft iron has a carbon content of 0.20% by weight or less.

3. 2. The iron-type golf club head according to claim 1, wherein the soft iron has a carbon content of 0.15% by weight or less.

4. 2. The iron-type golf club head according to claim 1, wherein the face hardness hf is less than 130 (HV), and the hosel hardness hh is 130 to 190 (HV).

5. 2. The iron-type golf club head according to claim 1, wherein a ratio hh / hf of the hosel hardness hh to the face hardness hf is 1.10 or more.

6. the face portion and the hosel portion are integrally formed by forging, 6. The iron-type golf club head according to claim 1, wherein the hosel portion has a metal structure in which at least a portion of the crystal grains of the soft iron at the hosel reference outer periphery are finer than the crystal grains at the main impact point.

7. 6. The iron-type golf club head according to claim 1, wherein the hosel portion has a heat-treated metal structure at a reference outer periphery of the hosel.

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