Patent Application
20250108271
The present disclosure relates to an iron-type golf club head.
Patent Document 1 below discloses an iron-type golf club head of a single piece structure integrally formed by forging or casting soft iron.
Such iron-type golf club head has advantage of providing a soft feel at ball impact while reducing the manufacturing cost.
The iron-type golf club head as described above, however, has a problem in exchange for providing a soft feel at impact, for example, such that, due to repeated ball hits, the head is liable to be permanently deformed near the hosel portion, and as a result, the loft angle and lie angle are altered.
Thus, such iron-type golf club head has room for improvement in durability.
The present disclosure was made in view of the circumstances as described above, and
a primarily object of the present disclosure is to provide an iron-type golf club head in which both the soft feel at impact and durability can be achieved while keeping the manufacturing costs low.
According to one aspect of the present disclosure, an iron-type golf club head comprises:
By adopting the above configuration, the iron-type golf club head of the present disclosure can achieve both the soft feel at impact and durability while suppressing manufacturing costs.
Embodiments of the present disclosure will now be described in detail in conjunction with accompanying drawings.
The following description is not intended to limit the present disclosure in any way.
As shown in
The face portion 2 is surrounded by a top 3, a sole 4 and a toe 5.
The face portion 2 has a front surface including a hitting surface 21 for hitting a ball, and a rear surface 22 on the opposite side of the hitting surface 21.
The hitting surface 21 is provided with face lines 8 for the purpose of increasing friction with the ball.
The face lines 8 in the present embodiment are narrow grooves, for example, extending linearly and parallel with the toe-heel direction of the head.
The face lines 8 are formed in a main hitting area intended for the face portion of the head 1. In
The “reference state” of a head means a state such that, as shown in
The hosel axis CL is the central axis of the hosel portion 7 which substantially coincides with the axial center line of the club shaft when the head is attached thereto.
In the reference state, the face lines 8 are parallel to both the horizontal plane HP and the reference vertical plane VP. Further, the lie angle α and the loft angle β specified for the head are satisfied.
In this application including the description and claims, configurations of portions or parts of the golf club head are described on the basis that the head is placed in the reference state unless otherwise noted.
The front-rear direction of the head is a direction which becomes perpendicular to the reference vertical plane VP (x-axis direction in
The toe-heel direction of the head is a direction which becomes parallel to both the horizontal plane HP and the reference vertical plane VP (y-axis direction in
The up-down direction of the head is a direction which is orthogonal to both the front-rear direction and the toe-heel direction (z-axis direction in
The front side and rear (back) side of the head mean the hitting surface 21 side and the rear surface 22 side, respectively. The upper side and lower side of the head mean those in the up-down direction of the head.
The hitting surface 21 of the front surface of the face portion 2 is a flat surface except for face grooves forming the face lines 8 as shown in
The rear surface 22 of the face portion 2 is provided with a cavity concaved toward the hitting surface 21 in this example. But, the rear surface 22 may be formed without a back cavity to provide a so-called muscle back iron head.
As shown in
The sole 4 extends from the lower edge of the hitting surface 21 toward the rear of the head, forming a lower surface of the head 1.
As shown in
Through the toe 5, the top 3 and the sole 4 are smoothly connected to each other.
The heel 6 is an end portion of the head 1 on the opposite side to the toe 5 in the toe-heel direction, and the hosel portion 7 is connected thereto.
The hosel portion 7 has a shaft insertion hole 7a into which the tip end of a club shaft (not shown) is attached.
The above-mentioned hosel axis CL is defined by the center axis of the shaft insertion hole 7a, and coincides with the axial center line of the attached club shaft.
The face portion 2 and the hosel portion 7 are formed from one kind of soft iron. In the present disclosure, soft iron is a type of carbon steel having a carbon content of not more than 0.3% by weight.
Since the face portion 2 in this embodiment is made of such a soft iron, the head 1 can provide a soft feel at impact.
The face portion 2 and the hosel portion 7 are integrally formed by forging or casting the soft iron.
In this embodiment, the entire head 1 is formed by forging so as to have a so-called forged one-piece structure. But, it is also possible to integrally form the head 1 by casting instead of forging.
The heads having such one-piece structures can significantly reduce the manufacturing costs as compared to two-piece (or three or more piece) structure heads, where at least a face plate and a main body are prepared as separate parts and then connected together.
In the head 1 in this embodiment, based on the premise that the head 1 is of a one-piece structure, a hosel hardness hh is made higher than a face hardness hf. Such head 1 can achieve both a soft feel at impact and durability while keeping manufacturing costs low.
More specifically, the head 1 in this embodiment effectively prevents permanent deformation occurring in the vicinity of the hosel portion 7 due to repeated ball hits, and as a result, it is possible to suppress alterations in the lie angle α and loft angle β of the head 1.
In the present disclosure, the face hardness hf means a hardness relating to a main impact point S on the hitting surface 21 of the face portion 2.
The main impact point S means a representative point for typical impact points where, in an iron-type golf club head, the hitting surface 21 is most frequently hit by the balls.
Specifically, the main impact point S is located
The center position FC of the hitting surface 21 means the center position in the head toe-heel direction between
However, as shown in
In this case, the center position FC of the hitting surface 21 in the toe-heel direction means the center position in the toe-heel direction between
The lowest end 21e of the hitting surface 21 means the lowest end at the center position FC, of the hitting surface 21 which is flat in
Incidentally, if the above-mentioned main impact point S is located just on the face line 8 (namely, within the width of the face groove), it can be defined by assuming that the main impact point S is located on the virtual hitting surface where the face lines 8 are filled up into a flat surface of the hitting surface 21.
The face hardness hf means Vickers hardness at a measuring position SP located at a depth of 4 mm from the hitting surface 21 at the main impact point S.
The reason why the hardness at such measuring position SP was adopted as the face hardness hf is as follows.
First, the face lines 8 having a very small width and depth, are usually formed by pressing a face-line transfer mold onto the hitting surface 21.
Through such press working, a surface layer of the hitting surface 21 becomes hardened, and the hardness is increased.
However, the increase in the hardness of such surface layer of the hitting surface 21 has little effect on the feel at impact, and thus, it is difficult to control the feel at impact by changing the hardness of the surface layer. This was found as a result of experiments conducted by the inventor.
Further, it was also found that the hardness measured at a depth of 4 mm from the hitting surface 21 most affects the feel at impact.
Therefore, the face hardness hf at the position SP at a depth of 4 mm from the hitting surface 21 of the main impact point S was adopted as the face hardness hf which has the most influence on the golfer's feel at impact, in the present disclosure, and the face hardness hf is made lower than the hosel hardness hh so that the soft feel at impact can be maintained.
The face hardness hf can be measured by a destructive testing, for example.
In the destructive testing, first, the head 1 is cut perpendicularly to the hitting surface 21 at the center position FC.
Then, the face hardness hf is measured by pressing the indenter of the measuring device onto the cut surface of the head 1 at the measuring position SP at a depth of 4 mm from the hitting surface 21 at the main impact point S.
In the present disclosure, the hosel hardness hh means a hardness relating to a reference hosel outer peripheral portion 7S.
The reference hosel outer peripheral portion 7S is defined as extending in the circumferential direction of the hosel around the hosel axis CL at a position which is downward from the upper end of the hosel by 30 mm along the direction of the hosel axis CL as shown in
In
The hosel hardness hh (HV) is defined by the average of the Vickers hardness values at the respective positions P1 to P8 measured at a depth of 1 mm from the outer surface of the hosel in the reference hosel outer peripheral portion 7S.
Incidentally, as shown in
As a result of experiments conducted by the inventor, it was found that, in the heads having a one-piece soft iron structure, permanent deformation of the hosel portion 7 due to repeated ball hits mainly occurs at the reference hosel outer peripheral portion 7S. Further, it was also found that, for increasing the hardness of the reference hosel outer peripheral portion 7S, it is not sufficient to locally increase the hardness of only the outer surface layer of the hosel, and it is necessary to increase the hardness at the depth of 1 mm from the outer surface of the hosel as with the face hardness hf.
Furthermore, since the hosel portion 7 receives forces from various directions when hitting a ball, it is not sufficient to increase the hardness at only one location around the hosel axis, and it is necessary to increase the hardness at plural locations around the hosel axis.
Thus, it is important to pay attention to the hardness at the different circumferential positions P1 to P8.
Therefore, in the present disclosure, the hosel hardness hh is defined as the average of the Vickers hardness values measured at at least eight equiangular positions P1 to P8.
The hosel hardness hh can be measured by a destructive testing, for example. In the destructive testing, first, the hosel portion 7 is cut perpendicularly to the hosel axis CL at the position of the reference hosel outer peripheral portion 7S.
Then, the Vickers hardness values at the positions P1 to P8 are measured by pressing the indenter of the measuring device onto the cut surface of the hosel portion 7 at the depth of 1 mm, and their average is calculated as the hosel hardness hh.
In the present disclosure, the Vickers hardness is measured according to Japanese Industrial Standard (JIS) Z2244, by applying a force of 9.807 N. Incidentally, in order to measure the Vickers hardness, “Akashi Vickers Hardness Meter AVK-C20” was used as the measuring device.
As described above, the head 1 according to the present disclosure has the one-piece structure made of one kind of soft iron, and can achieve both a soft feel at impact and durability while keeping manufacturing costs low.
Hereinafter, further features of the head 1 in this embodiment will be described. These features are preferable, but optional.
The soft iron has a carbon content of not more than 0.30%, preferably not more than 0.20%, more preferably not more than 0.15%.
Limiting the carbon content of the soft iron in this way helps to provide a softer feel at impact.
Examples of such soft iron include carbon steels for machine structural use such as S20C, S17C, S15C, and S12C.
The face hardness hf is not particularly limited as long as it is lower than the hosel hardness hh. But, the value of the face hardness hf is preferably less than 180 (HV), more preferably less than 160 (HV), still more preferably less than 145 (HV). Thereby, the head 1 can more reliably provide a soft feel at impact.
On the other hand, from the viewpoint of durability, the value of the face hardness hf is not less than 100 (HV), more preferably not less than 105 (HV), still more preferably not less than 110 (HV).
The hosel hardness hh is not particularly limited as long as it is higher than the face hardness hf. But, the value of the hosel hardness hh is preferably not less than 120 (HV), more preferably not less than 130 (HV), still more preferably not less than 140 (HV). Thereby, the permanent deformation of the hosel portion 7 due to repeated ball hits can be reliably suppressed.
On the other hand, higher hosel hardness hh values are advantageous for the durability, but disadvantageous in the angle tuning process for fine tuning the lie angle α and loft angle β of the head 1 after manufactured.
When considering ease of tuning in such angle tuning process, the value of the hosel hardness hh is preferably not more than 190 (HV), more preferably not more than 180 (HV), still more preferably not more than 170 (HV).
In order to achieve both a soft feel at impact and durability at a higher level, the ratio hh/hf of the hosel hardness hh to the face hardness hf is preferably not less than 1.10, more preferably not less than 1.15, still more preferably not less than 1.20.
Further, in order to achieve both a soft feel at impact and durability at a higher level, the ratio hh/hf is preferably not more than 1.90, more preferably not more than 1.60, still more preferably not more than 1.40.
Next, a technique for increasing the hardness of the reference hosel outer peripheral portion 7S will be described.
In the case of the head 1 in which the face portion 2 and the hosel portion 7 are integrally formed by forging, the hosel portion 7 is forged so as to have a metal structure such that crystal grains of at least a part of the soft iron in the reference hosel outer peripheral portion 7S are finer than crystal grains of the soft iron at the main impact point S.
Usually, in the hot forging process, the final shape of the forged product is achieved through multiple steps such as preforming, rough forming and final forming.
According to an example of the technique for increasing the hardness of the hosel portion, one or more protrusions are formed on the outer surface of the hosel portion at reference hosel outer peripheral portion 7S through the rough molding step, and then these protrusions are compressed and smoothed through the final forming step.
As a result, the reference hosel outer peripheral portion 7S is compressed more than other portions, therefore, the reference hosel outer peripheral portion 7S can be forged to have a metal structure in which some of the metal crystal grains are finer than the crystal grains at the main impact point S. (Hereinafter, this method is referred to as the condensation method.)
Another example of the technique for increasing the hardness is heat treatment. By locally heat-treating (quenching) the reference hosel outer peripheral portion 7S of the hosel portion 7, it is possible to increase the hardness of the reference hosel outer peripheral portion 7S.
Thereby, the hosel portion 7 has a heat-treated metal structure in the reference hosel outer peripheral portion 7S.
As such heat treatment, induction hardening and laser hardening can be employed.
While detailed description has been made of preferable embodiments of the present disclosure, the present disclosure can be embodied in various forms without being limited to the illustrated embodiments.
Iron-type forged soft iron heads having the one-piece structure shown in
In Examples 1 and 2, the hardness of the hosel portion of each head was increased by the condensation method described above.
In Comparative Examples 1 and 2, the hardness of the hosel portion of each head was not increased although the head had the same finished shape as Examples 1 and 2.
Using these golf clubs, there were conducted tests for evaluating the feel at impact and the durability.
The evaluation methods are as follows.
Each golf club was attached to a swing robot, and hit golf balls a number of times at the same head speed. And the loft angle and lie angle were measured every 1000 hits. In the result of measuring the angles, when either the loft angle or the lie angle was first changed by 1 degrees or more as compared with the initial angle value, the number of hits was recorded as the durability evaluation value.
The obtained durability evaluation values of the golf clubs are indicated by an index based on Comparative Example 1 being 7, wherein the larger the index number, the higher the resistance to deformation caused by repeated impact.
With each golf club, an advanced golfer hit golf balls five times, and evaluated, by the golfer's senses, the softness of the feel at impact into ten ranks, wherein the higher the rank number, the softer the feel at impact.
The test results are shown in Table 1.
From the test results, it was confirmed that, as compared to Comparative examples, Examples according to the present disclosure were able to achieve both the soft feel at impact and the higher durability.
The present disclosure is as follows.
An iron-type golf club head comprises:
The iron-type golf club head according to Present Disclosure 1, wherein
The iron-type golf club head according to Present Disclosure 1, wherein
The iron-type golf club head according to Present Disclosure 1, 2 or 3, wherein
The iron-type golf club head according to any one of Present Disclosures 1 to 4, wherein
The iron-type golf club head according to any one of Present Disclosures 1 to 5, wherein
The iron-type golf club head according to any one of Present Disclosures 1 to 5, wherein
A method for manufacturing an iron-type golf club head comprising a face portion having a hitting surface, and a hosel portion continuous to the face portion on a heel-side thereof, the hitting surface having a main impact point defined as being positioned at the center in a toe-heel direction of the hitting surface and 12 mm above the lowermost end of the hitting surface along the hitting surface in a reference state in which the golf club head is set on a horizontal plane at its lie angle and loft angle,
A method for manufacturing an iron-type golf club head comprising a face portion having a hitting surface, and a hosel portion continuous to the face portion on a heel-side thereof, the hitting surface having a main impact point defined as being positioned at the center in a toe-heel direction of the hitting surface and 12 mm above the lowermost end of the hitting surface along the hitting surface in a reference state in which the golf club head is set on a horizontal plane at its lie angle and loft angle,
The method according to Present Disclosure 9, wherein
The method according to Present Disclosure 8, 9 or 10, wherein the soft iron has a carbon content of not more than 0.20% by weight.
The method according to Present Disclosure 8, 9 or 10, wherein the face hardness hf is less than 130 (HV) and the hosel hardness hh is 130 to 190 (HV).
The method according to Present Disclosure 8, 9 or 10, wherein the ratio hh/hf of the hosel hardness hh to the face hardness hf is not less than 1.10.
An iron-type golf club head comprises:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-171580 | Oct 2023 | JP | national |
