Patent Application
20130109502
The present application claims priority on Patent Application No. 2011-236582 filed in JAPAN on Oct. 28, 2011, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a golf club head. In particular, the present invention relates to a golf club head having a CFRP member.
2. Description of the Related Art
In a golf club head, a coefficient of restitution and a volume of the head are regulated by the rule. In respect of a swing balance, a weight of the head is restricted. Furthermore, in respect of practicality, high strength is required. The regulation and the restriction complicate the design of a head having enhanced performance.
In order to improve the performance of the head, a head using CFRP is known. The CFRP means carbon fiber reinforced plastic. The CFRP can have specific strength higher than that of titanium. An excess weight can be created by using the CFRP. A position of a center of gravity of the head can be changed by redisposing the excess weight. The excess weight can improve a degree of freedom of the design of the head.
Japanese Patent Application Publication No. 4222118 (US2005/0026721) discloses a hollow golf club head having a front face body made of an integral titanium-based metal material, a metal sole plate, and a fiber-reinforced resin body. Paragraph [0036] discloses a sheet having a carbon fiber obliquely oriented by 60 degrees in a clockwise direction to a toe-heel direction, and a sheet having a carbon fiber obliquely oriented by 60 degrees in a counterclockwise direction to the toe-heel direction. In FIG. 6 of Japanese Patent Application Laid-Open No. 2005-253606, a laminate oriented in four directions is disclosed. Japanese Patent Application Laid-Open No. 2005-312646 (US2005/0245328, US2009/0139643, US2009/0176600) discloses a constitution in which fibers are crossed at the angle of 30 to 90 degrees. Japanese Patent Application Laid-Open No. 2005-296626 (US2005/0209022) discloses a resin member including a 0° direction prepreg of which a fiber substantially makes an angle of 0 degree to a front-back direction line of a head, and a 90° direction prepreg of which a fiber substantially makes 90 degrees to the front-back direction line of the head.
The CFRP has a damping ratio (loss factor) greater than that of a metal. For this reason, a hitting sound is apt to be shortened. Furthermore, the primary peak frequency of the hitting sound tends to be low in the head using the CFRP. A short hitting sound having a low frequency is apt to give a poor impression to a golf player. The hitting sound can have an influence on psychology and a swing of the golf player. The hitting sound is preferably improved.
It is an object of the present invention to provide a golf club head having a CFRP member and having an excellent hitting sound.
A golf club head according to the present invention is provided with a head body and a CFRP member. The CFRP member constitutes at least a part of a crown or at least a part of a sole. The CFRP member has a UD lamination part having laminated UD layers. Orientation of a fiber is substantially set to three directions in the UD lamination part.
The three directions are a first direction, a second direction, and a third direction. At this time, preferably, an angle of the second direction to the first direction is substantially +60 degrees, and an angle of the third direction to the first direction is substantially −60 degrees.
Preferably, the UD lamination part has a lamination symmetrical property in an orientation angle of the fiber.
Preferably, the number of layers of the UD lamination part is 5 or greater and 12 or less.
Preferably, the CFRP member constitutes at least a part of the crown.
Preferably, a volume of a head is equal to or greater than 400 cc. Preferably, a weight of the head is equal to or less than 200 g. Preferably, a lateral moment of inertia is equal to or greater than 4600 g·cm2.
A golf club head having a CFRP member and having an excellent hitting sound can be obtained.
Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate references to the accompanying drawings.
In the present application, a base state, a toe-heel direction, and a face-back direction FB are defined.
The base state is a state where a head is placed on a level surface h at a predetermined lie angle and real loft angle. In more detail, the base state is the following state. The head is grounded on the level surface h in a state where a center axis line z of a shaft, hole of the head is provided in an optional perpendicular surface VP1, the center axis line z is inclined to the level surface h at the lie angle, and a face surface is inclined to the perpendicular surface VP1 at the real loft angle. The perpendicular surface VP1 is a plane parallel to a vertical line.
In the head in the base state, a direction parallel to an intersection line of the perpendicular surface VP1 and the level surface h is the toe-heel direction.
In the head in the base state, a direction perpendicular to the toe-heel direction and parallel to the level surface h is the face-back direction.
The head 2 is formed by joining a plurality of members. The head 2 of the embodiment is formed by joining a head body h1 and a crown member c1. The head 2 may be formed by joining the head body h1 and a sole member.
Furthermore, the head body h1 may be formed by joining a plurality of members. For example, the head body h1 may be formed by a first member having an opened face portion and a second member forming the face.
As shown in
The crown member c1 forms a part of the crown 6. The crown member c1 forms the most of the crown 6. The crown member c1 occupies 50% or greater of the area of the crown 6.
A method for joining the crown member c1 and the head body h1 is adhesion. An adhesive is used for the adhesion. A region between the crown opening cp1 and the level difference part cp2 is an overlapped part a1. In the overlapped part a1, the crown member c1 and the head body h1 are overlapped. In the overlapped part a1, the crown member c1 and the head body h1 are joined. The overlapped part a1 is provided over the whole circumference of the crown opening cp1.
The crown member c1 is not backed up by the head body h1 in a portion other than the overlapped part a1. In the portion other than the overlapped part a1, the crown member c1 independently forms the crown 6.
The crown member c1 is formed by CFRP. The CFRP means carbon fiber reinforced plastic. In the embodiment, the crown member c1 is a CFRP member 16.
In the present application, a portion including only the CFRP member is referred to as a CFRP single part. In the crown member c1, a portion except the overlapped part a1 is the CFRP single part. In other words, the CFRP single part is a portion inside the crown opening cp1. The CFRP single part is not backed up by the head body h1. The CFRP single part occupies 50% or greater of the area of the crown 6.
The CFRP member 16 may be disposed on a portion other than the crown 6. The CFRP member 16 may be provided in the crown 6 and the side 14. The CFRP member 16 may be provided in the crown 6, the side 14, and the sole 8. The CFRP member 16 may be provided in the sole 8. The CFRP member 16 may be provided in the sole 8 and the side 14.
The CFRP member 16 is a laminate. The CFRP member 16 is formed by a plurality of layers. All the layers are formed by the CFRP.
A prepreg is used to produce the CFRP member 16. The prepreg has a matrix resin and a carbon fiber. One layer is formed by one prepreg. The laminate is formed by superposing a plurality of prepregs.
A metal mold for molding the CFRP member 16 is prepared to produce the CFRP member 16. As shown in
The CFRP member 16 has a UD lamination part 18 and a cloth layer 20. The UD lamination part 18 is a portion having laminated UD layers. The term “UD” stands for uni-direction. In the UD layer, orientation of a fiber is to one direction. The UD layer is formed by a UD prepreg. In the cloth layer 20, orientation of a carbon fiber is generally set to two directions. The typical cloth layer 20 has a carbon fiber fabric. The typical cloth layer 20 is formed by a fabric prepreg.
In the embodiment, the first layer s1 to the sixth layer s6 are included in the UD lamination part 18. The seventh layer s7 is the cloth layer 20. The cloth layer 20 is located outside the UD lamination part 18. The UD lamination part 18 and the cloth layer 20 are brought into contact with each other.
The term “lamination symmetrical property” is used in the present application. The term is independently defined in the present application. The lamination symmetrical property is defined in the UD lamination part 18. The lamination symmetrical property can be defined for every specification. Examples of the specification include an orientation angle of a fiber, a layer thickness, a carbon fiber kind, a fiber content, and a prepreg kind.
The lamination symmetrical property means that a specification in an outer nth layer counted from a neutral plane is substantially the same as a specification in an inner nth layer counted from the neutral plane, in all n. n is an integer equal to or greater than 1.
When the number N of layers of the UD lamination part is even, the neutral plane means a boundary between a [N/2]-th layer and a [(N/2)+1]-th layer. For example, as shown in
(a1) The orientation angle of the fiber in the third layer s3 is substantially the same as that in the fourth layer s4.
(a2) The orientation angle of the fiber in the second layer s2 is substantially the same as that in the fifth layer s5.
(a3) The orientation angle of the fiber in the first layer s1 is substantially the same as that in the sixth layer s6.
On the other hand, when the number N of layers of the UD lamination part is odd, the neutral plane means a [(N/2)+1]-th layer itself. For example, as shown in
(b1) The orientation angle of the fiber in the second layer s2 is substantially the same as that in the fourth layer s4.
(b2) The orientation angle of the fiber in the first layer s1 is substantially the same as that in the fifth layer s5.
In the orientation angle of the fiber, the term “substantially” has a purpose of allowing an error of ±10 degrees (preferably ±5 degrees). Usually, the outer surface of the head 2 is formed by a free curved surface, and is not a plane. For this reason, an error is inevitably generated in some extent in the orientation angle of the fiber.
The lamination symmetrical property in the orientation angle of the fiber is described above. The lamination symmetrical property in the other specification is also similarly defined. For example, when the number N of layers of the UD lamination part is 6, the UD lamination part satisfying the following items (a4), (a5), and (a6) has the lamination symmetrical property in the layer thickness.
(a4) The layer thickness in the third layer s3 is substantially the same as that in the fourth layer s4.
(a5) The layer thickness in the second layer s2 is substantially the same as that in the fifth layer s5.
(a6) The layer thickness in the first layer s1 is substantially the same as that in the sixth layer s6.
In the layer thickness, the term “substantially” has a purpose of allowing an error of ±10% (preferably ±5%). Usually, the matrix resin partially flows in the molding process of the UD lamination part 18. For this reason, an error is inevitably generated in some extent in the layer thickness.
Similarly, when the number N of layers of the UD lamination part is, for example, 6, the UD lamination part satisfying the following items (a7), (a8), and (a9) has the lamination symmetrical property in the prepreg kind.
(a7) The kind of the prepreg used in the third layer s3 is the same as that used in the fourth layer s4.
(a8) The kind of the prepreg used in the second layer s2 is the same as that used in the fifth layer s5.
(a9) The kind of the prepreg used in the first layer s1 is the same as that used in the sixth layer s6.
The kind of the prepreg can be distinguished by the part number of the prepreg.
The orientation angle of the fiber is notated by the numerical value in the present application. In order to facilitate the understanding, the following rules are defined to notate the orientation angle θ in the present application (see
[Rule 1]: The orientation angle of the fiber is determined in a plan view from the crown side.
[Rule 2]: The inclination angle of 45 degrees to the face-back direction FB is defined as a reference direction X1. The reference direction X1 is defined as 0 degree.
[Rule 3]: A clockwise rotation direction viewed from the crown side is defined as plus, and a counterclockwise rotation direction viewed from the crown side is defined as minus.
The orientation angle θ has an allowable range of ±10 degree (preferably ±5 degrees).
As shown in
Therefore, the UD lamination part 18 has the lamination symmetrical property in the orientation angle of the fiber.
In the UD lamination part 18, the kind of the prepreg used in the third layer s3 is the same as that used in the fourth layer s4. The kind of the prepreg used in the second layer s2 is the same as that used in the fifth layer s5. The kind of the prepreg used in the first layer s1 is the same as that used in the sixth layer s6. Therefore, the UD lamination part 18 has the lamination symmetrical property in the prepreg kind. When the kind of the prepreg is the same, the layer thickness is the same; the carbon fiber kind is also the same; and the fiber content (% by mass) is also the same. Therefore, the UD lamination part 18 has the lamination symmetrical property in the layer thickness. The UD lamination part 18 has the lamination symmetrical property in the carbon fiber kind. The UD lamination part 18 has the lamination symmetrical property in the fiber content.
As described above, in the UD lamination part 18, the orientation of the fiber is −60 degrees (±10 degrees), 0 degree (±10 degrees), and 60 degrees (±10 degrees). That is, in the UD lamination part 18, the orientation of the fiber is substantially set to three directions.
The three directions are defined as a first direction, a second direction, and a third direction. In the UD lamination part 18, the angle of the second direction to the first direction is +60 degrees (±10 degrees). Furthermore, the angle of the third direction to the first direction is −60 degree (±10 degrees). In the UD lamination part 18, a fiber oriented in a direction other than the three directions does not exist.
It was found that the UD lamination part 18 having the fiber substantially oriented in the three directions can exhibit an advantageous effect as compared with the cases of the two direction and the four directions. It was found that the orientation in the three directions is advantageous for improvement in a hitting sound. The effect is shown in examples to be described later.
One of the objects of the use of the CFRP member 16 is to create an excess weight. Therefore, the lighter CFRP member 16 is desired. In order to achieve a reduction in a weight, the number of layers is limited. The improvement in the hitting sound is desired in the limited number of layers. The disposal of the fiber in the three directions can effectively improve the hitting sound under a condition where the number of layers is limited.
Furthermore, it was found that the lamination symmetrical property is advantageous to increase the natural frequency of the head. The lamination symmetrical property is advantageous to improve the hitting sound. The detailed reason is unknown.
The effect of the lamination symmetrical property is shown in examples to be described later.
The number of layers of the UD lamination part 18 is not limited. In respect of setting the fiber to the three directions, the number of layers of the UD lamination part 18 is set to be equal to or greater than 3. In respect of increasing the frequency of the hitting sound, the number of layers of the UD lamination part 18 is preferably equal to or greater than 5, and more preferably equal to or greater than 6. In respect of the reduction in the weight, the number of layers of the UD lamination part 18 is preferably equal to or less than 12, more preferably equal to or less than 9, and still more preferably equal to or less than 7.
In respect of increasing the frequency of the hitting sound, the thickness of the UD lamination part 18 is preferably equal to or greater than 0.5 mm, and more preferably equal to or greater than 0.6 mm. In respect of the reduction in the weight, the thickness of the UD lamination part 18 is preferably equal to or less than 0.9 mm, and more preferably equal to or less than 0.8 mm.
In respect of the increasing the frequency of the hitting sound, the thickness (total thickness) of the CFRP member is preferably equal to or greater than 0.5 mm, and more preferably equal to or greater than 0.6 mm. In respect of the reduction in the weight, the thickness of the CFRP member is preferably equal to or less than 0.9 mm, and more preferably equal to or less than 0.8 mm.
The excess weight is caused by use of the CFRP member. The excess weight improves a degree of freedom in design of the head. More preferably, the CFRP member is used in order to lower a position of a center of gravity of the head. A high launch angle and a low backspin rate can be achieved by lowering the position of the center of gravity of the head. The low position of the center of gravity can contribute to an increase in a flight distance. In this respect, the position of a center of gravity of the CFRP member is preferably above the position of the center of gravity of the whole head. Preferred examples of the disposal of the CFRP member include the following disposals A to D.
[Disposal A]: The CFRP member constitutes a part of the crown.
[Disposal B]: The CFRP member constitutes the whole crown.
[Disposal C]: The CFRP member constitutes a part of the crown and a part of the side.
[Disposal D]: The CFRP member constitutes the whole crown and a part of the side.
The CFRP single part described above greatly contributes to the creation of the excess weight. In other words, the CFRP single part greatly contributes to the movement of the position of the center of gravity. In this respect, the following disposals E to H are more preferable.
[Disposal E]: The CFRP single part constitutes a part of the crown.
[Disposal F]: The CFRP single part constitutes the whole crown.
[Disposal G]: The CFRP single part constitutes a part of the crown and a part of the side.
[Disposal H]: The CFRP single part constitutes the whole crown and a part of the side.
In respect of lowering the center of gravity of the head, it is preferable that the CFRP member does not constitute the sole.
The CFRP member is used, and thereby the improvement in the hitting sound is achieved. Furthermore, the CFRP member is used, and thereby a weight of the head can be suppressed while a volume of the head and a moment of inertia of the head are increased. In this respect, the volume of the head is preferably equal to or greater than 400 cc. In respects of a reduction in air resistance and ease to address, the volume of the head is preferably equal to or less than 500 cc, more preferably equal to or less than 470 cc, and still more preferably equal to or less than 460 cc. The weight of the head can be suppressed to be equal to or less than 200 g by the CFRP member having the constitution described above. In respect of durability, the weight of the head is preferably equal to or greater than 100 g, and more preferably equal to or greater than 150 g.
In respect of the directional stability of a hitting ball, the lateral moment of inertia (lateral MI) of the head is preferably equal to or greater than 4600 g·cm2, more preferably equal to or greater than 5000 g·cm2, and still more preferably equal to or greater than 5500 g·cm2. There is no need for limiting the lateral MI on performance. However, the lateral MI may be limited to be equal to or less than 8000 g·cm2 in consideration of a material and a structure which are used, and may be further limited to be equal to or less than 7000 g·cm2.
A Z axis is considered in measurement (calculation) of the lateral MI. The Z axis is an axis line perpendicular to the level surface h in the head in the base state. The lateral MI is a moment of inertia around an axis passing through the center of gravity of the head and being parallel to the Z axis.
The cloth layer 20 may be used and may not be used. The cloth layer 20 can improve formability. During the forming of the CFRP member, wrinkles may be generated in each layer. The cloth layer 20 can suppress the generation of the wrinkles. In respect of obtaining the effect, the cloth layer 20 is preferably provided in the outermost layer and/or the innermost layer, and more preferably provided in the outermost layer.
In the manufacturing process of the head, the surface of the CFRP member is usually polished. The cloth layer 20 provided in the outermost layer prevents the outer layer in the UD lamination part 18 from being polished. When the outer layer of the UD lamination part 18 is polished, the lamination symmetrical property of the UD lamination part 18 is lost. Even when the surface is polished, the lamination symmetrical property of the UD lamination part 18 is maintained by the existence of the cloth layer 20. The cloth layer 20 provided in the outermost layer is useful to smooth the surface after being polished. The smoothness can improve the aesthetic appearance of the head. In these respects, the cloth layer 20 is preferably provided in the outermost layer.
In respect of enhancing these effects, and in respect of a cost reduction, the cloth layer 20 preferably has two-directional fibers oriented to be different by 90 degrees from each other.
As shown in examples to be described later, it was found that the influence of the orientation of the fiber in the cloth layer 20 is small. The orientation of the fiber in the UD lamination part 18 is important. In this respect, the orientation of the fiber in the cloth layer 20 is not limited.
In respect of suppressing the weight, the number of layers of the cloth layer 20 is preferably equal to or less than 2, and more preferably 1.
The tensile elastic modulus of the carbon fiber used for the CFRP member is not limited. In respect of a balance between strength and rigidity, the tensile elastic modulus is preferably 23.5 (tonf/mm2) or greater and 40 (tonf/mm2) or less.
Examples of the prepreg usable as a material of the CFRP member are shown in Table 1.
As described above, the three directions are set to the first direction, the second direction, and the third direction. Herein, the number of the layers in which the direction of the fiber is the first direction is defined as N1. The number of the layers in which the direction of the fiber is the second direction is defined as N2. The number of the layers in which the direction of the fiber is the third direction is defined as N3. N1 is an integer equal to or greater than 1. N2 is an integer equal to or greater than 1. N3 is an integer equal to or greater than 1.
In respect of the reduction in the weight, N1 is preferably equal to or less than 4, and more preferably equal to or less than 3. Similarly, N2 is preferably equal to or less than 4, and more preferably equal to or less than 3. Similarly, N3 is preferably equal to or less than 4, and more preferably equal to or less than 3.
The maximum value of N1, N2, and N3 is defined as Nmax, and the minimum value of N1, N2, and N3 is defined as Nmin. In respect of the lamination symmetrical property, a difference (Nmax−Nmin) is preferably equal to or less than 1, and particularly preferably 0.
Preferably, the natural mode and the natural frequency of the head are considered. The hitting sound of the head using the CFRP member can be effectively improved by considering the natural mode and the natural frequency of the head.
The following terms are used in the present application.
All objects have a natural form when the objects vibrate. The natural form is a natural mode. The natural mode of the head (whole head) is considered in the present application. The natural mode of the head is associated with the hitting sound.
“The natural mode” of the present application is a natural mode of the head. When “the natural mode” is merely described in the present application, “the natural mode” means the natural mode of the whole head. When “the natural mode of the head” is described in the present application, “the natural mode of the head” means the natural mode of the whole head.
A method for obtaining the natural mode is not limited. A mode test (also referred to as experiment mode analysis) or mode analysis can be used. In the mode test, an excitation experiment is conducted and the natural mode is obtained based on the result of the experiment. In the mode analysis, the natural mode is obtained by simulation. In the simulation, for example, a finite element method may be used. The methods of the mode test and the mode analysis are known.
The mode test or the mode analysis is conducted under a free support condition. That is, a constraint condition is made free. In the mode analysis, for example, commercially available natural value analyzing software is used. Examples of the software include “ABAQUS” (trade name) (manufactured by SIMULIA), “MARC” (trade name) (manufactured by MSC Software Corporation) and “NX” (manufactured by Siemens PLM Solutions).
In examples to be described later, the mode analysis using the natural value analyzing software is conducted. On the other hand, the mode test by actual measurement, for example, is executed as follows. A thread is fixed to a region of the head (for example, an end face of a neck). Each of parts of the head is struck by an impact hammer in a state where the head is hung with the thread. The mode is obtained by measuring a transfer function with acceleration response of a center of a face.
“The natural frequency” of the present application is a natural frequency of the head. When “the natural frequency” is merely described in the present application, “the natural frequency” means the natural frequency of the whole head.
“The N-th order natural frequency” of the present application is “an N-th natural frequency counted from the smallest natural frequency among the natural frequencies in the whole head”. N is an integer equal to or greater than 1. A rigidity mode in which the head is not deformed is not counted as the order. For example, “a first-order natural frequency” is “a first-order natural frequency in the whole head”. For example, “a second-order natural frequency” is “a second-order natural frequency in the whole head”. When “the N-th order natural frequency” is merely described in the present application, “the N-th order natural frequency” means the N-th order natural frequency in the whole head.
“The N-th order mode” of the present application is “an N-th order natural mode in the whole head”. N is an integer equal to or greater than 1. For example, “a first-order mode” is “a first-order natural mode in the whole head”. For example, “a second-order mode” is “a second-order natural mode in the whole head”. When “the N-th order mode” is merely described in the present application, “the N-th order mode” means the N-th order natural mode in the whole head.
“The first-order natural frequency” is the smallest natural frequency among the natural frequencies of the head. “The second-order natural frequency” is a second natural frequency from the smallest natural frequency. “The third-order natural frequency” is a third natural frequency from the smallest natural frequency. “The N-th order natural frequency” is an N-th natural frequency from the smallest natural frequency. The increase of “the first-order natural frequency” is considered to be most effective in making the higher-pitch hitting sound. The lower order tends to greatly affect the hitting sound.
The order of the head means the order of the natural mode in the whole head.
In the N-th order natural mode, a point having the greatest amplitude is a maximum amplitude point. The maximum amplitude point is ordinarily set at one place per each order natural mode. For example, a maximum amplitude point Pm1 in the first-order mode is ordinarily set at one place. Similarly, a maximum amplitude point Pm2 in the second-order mode is ordinarily set at one place. The maximum amplitude point Pm1 is a point having the greatest amplitude in the first-order mode. The maximum amplitude point Pm2 is a point having the greatest amplitude in the second-order mode.
It is considered that the hitting sound is one of the important performances of a golf club. In order to improve the hitting sound, in examples to be described later, vibration in a region in which the CFRP member is provided is analyzed. The CFRP member has a damping ratio greater than that of a metal such as a titanium alloy. The greater damping ratio shortens the sound of the hitting ball. The CFRP member tends to reduce the frequency of the hitting sound as compared with the metal such as a titanium alloy. A longer and higher-pitch hitting sound is desired.
The provision of the CFRP member tends to reduce the frequency of the hitting sound, and shorten the hitting sound. In order to improve the hitting sound, the vibration in the region in which the CFRP member is provided is preferably analyzed. The analysis is shown in examples to be described later.
The present invention can improve the hitting sound. Therefore, the present invention is preferably applied to a head having a loud hitting sound. In this respect, a hollow head is preferable, and the thickness of the head is preferably reduced. In respect of the volume of the hitting sound, the average thickness Ts of the sole is preferably equal to or less than 1.5 mm, more preferably equal to or less than 1.2 mm, still more preferably equal to or less than 1.0 mm, and yet still more preferably equal to or less than 0.8 mm. In respect of the strength of the head, the average thickness Ts of the sole is preferably equal to or greater than 0.5 mm. In respect of the volume of the hitting sound, the average thickness Tc of the crown is preferably equal to or less than 1.2 mm, more preferably equal to or less than 1.0 mm, still more preferably equal to or less than 0.8 mm, and yet still more preferably equal to or less than 0.7 mm. In respect of the strength of the head, the average thickness Tc of the crown is preferably equal to or greater than 0.4 mm.
In respect of the pitch of the hitting sound, the material of the head body h1 is preferably a metal. Examples of the metal include one or more kinds of metals selected from pure titanium, a titanium alloy, stainless steel, maraging steel, an aluminium alloy, a magnesium alloy, and a tungsten-nickel alloy. Examples of the stainless steel include SUS630 and SUS304. Specific examples of the stainless steel include CUSTOM450 (manufactured by Carpenter Technology Corporation). Specific examples of the titanium alloy include 6-4 titanium (Ti-6Al-4V), and Ti-15V-3Cr-3Sn-3Al. When the volume of the head is great, the hitting sound tends to be loud. The present invention is particularly effective in the head having a loud hitting sound. In this respect, the material of the head body h1 is particularly preferably the titanium alloy. In this respect, the materials of the sole and side are preferably the titanium alloy.
Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be interpreted in a limited way based on the description of the examples.
The three-dimensional data of a head shown in
The crown opening cp1 (see
Natural value analysis was conducted using the head to calculate a natural frequency and a mode shape. Natural value analyzing software was used for the natural value analysis. “NASTRAN” manufactured by MSC Software was used as the software. A boundary condition was set to free support (no restraint).
The laminated constitution of the CFRP member was variously changed using the head data thus prepared, to conduct simulation (natural value analysis). The thickness of each layer was equalized in all the following calculation models. That is, the thickness of each layer was set to a value obtained by dividing the thickness of the CFRP member by the number of layers.
The following physical values were used in the simulation. In a layer having a fiber elastic modulus of 24 (tonf/mm2), an elastic modulus in a lengthwise direction was set to 142 GPa; a poisson ratio was set to 0.32; an elastic modulus in a crosswise direction was set to 8.8 GPa; and an in-plane shearing elastic modulus was set to 4.2 GPa. In a layer having a fiber elastic modulus of 30 (tonf/mm2), an elastic modulus in a lengthwise direction was set to 168 GPa; a poisson ratio was set to 0.31; an elastic modulus in a crosswise direction was set to 7.9 GPa; and an in-plane shearing elastic modulus was set to 4.1 GPa. In a layer having a fiber elastic modulus of 40 (tonf/mm2), an elastic modulus in a lengthwise direction was set to 228 GPa; a poisson ratio was set to 0.26; an elastic modulus in a crosswise direction was set to 7.2 GPa; and an in-plane shearing elastic modulus was set to 4.1 GPa. The lengthwise direction means a direction parallel to fiber orientation. The crosswise direction means a direction perpendicular to the fiber orientation.
Three kinds of simulations were executed in order to confirm the effects of the present invention in detail. Simulation A, simulation B, and simulation C will be described in this order.
Heads (calculation models) A1 to A16 were obtained by changing the specification of the CFRP member. The first-order natural frequencies of the heads were calculated. As the first-order natural frequency is higher, a hitting sound tends to have higher-pitch. As first-order natural frequency is higher, it can be said that the result is good.
The specification of the CFRP member in the head A1 was as follows. The specification of the head A1 is shown also in the following Table 2.
The number of layers of the UD lamination part was set to 6 in the heads A2 to A10. The number was set to 8 in the head A11. The number was set to 10 in the head A12. The number was set to 5 in the heads A13 to A16. The specifications of the heads are shown in the following Table 2.
The calculation results of the first-order natural frequencies in the heads are as follows.
In
As shown in
In the heads A1 to A8, the specification of the CFRP member is common except for the orientation of the fiber. When the first-order natural frequencies of the heads A1 to A8 are compared with each other, the head A8 has the lowest first-order natural frequency, and the head A1 has the next lower the first-order natural frequency. The heads A2 to A7 have a comparatively high first-order natural frequency. The orientation of the fiber of the head A8 is set two directions. The orientation of the fiber of the head A1 is set to four directions. On the other hand, the orientation of the fiber of the heads A2 to A7 is set to three directions. From the result, the advantage of the orientation of the fiber set to three directions is shown.
The head A2 and the head A3 are the same except the order of the lamination. The head A2 has a lamination symmetrical property in the orientation angle of the fiber. However, the head A3 does not have the lamination symmetrical property. When both the heads A2 and A3 are compared with each other, the head A2 has a higher first-order natural frequency. This shows the advantage of the lamination symmetrical property. Similarly, the advantage of the lamination symmetrical property is shown in comparison of the head A4 with the head A5. Similarly, the advantage of the lamination symmetrical property is shown in comparison of the head A6 with the head A7.
In the heads A8 to A10, only the tensile elastic modulus of the fiber is different. As the tensile elastic modulus is greater, the first-order natural frequency is higher.
The number of layers is increased in the heads A11 and A12, and the thickness of the CFRP member is also great. Nevertheless, the first-order natural frequencies of the heads A11 and A12 are lower than those of the heads A2 to A7. The result also shows the advantage of the orientation of the fiber set to three directions.
In the heads A13 to A16, the number of layers is 5. The head A13 and the head A15 are the same except for the order of the lamination. The head A15 has a lamination symmetrical property in the orientation angle of the fiber. However, the head A13 does not have the lamination symmetrical property. When both the heads A13 and A15 are compared with each other, the head A15 has a higher first-order natural frequency. This shows the advantage of the lamination symmetrical property. Similarly, the advantage of the lamination symmetrical property is shown in comparison of the head A14 with the head A16.
In the simulation B, the relative relation of the fiber angle between lamination layers was fixed, and the influence of the absolute value of the orientation angle was considered. First, the following two kinds of lamination patterns Bx and By were determined. In the lamination pattern Bx, the orientation of the fiber was set to two directions. In the lamination pattern By, the orientation of the fiber was set to three directions. The number of layers of each pattern was 6.
In each of the lamination patterns Bx and By, the thicknesses of the layers were set to 0.1 mm/0.1 mm/0.15 mm/0.15 mm/0.1 mm/0.1 mm in order from the inner side.
Heads Bx1 to Bx7 in which a relative relation of a fiber angle was the same as that of the pattern Bx were prepared.
That is, these heads Bx1 to Bx7 can be obtained by rotating the lamination pattern Bx.
Similarly, heads By1 to By7 in which a relative relation of a fiber angle was the same as that of the pattern By were prepared.
That is, these heads By1 to By7 can be obtained by rotating the lamination pattern By.
In the simulation B, lowest order Dc when the maximum amplitude point was located in the crown was determined. A natural frequency fm in the lowest order Dc was calculated. For example, when a maximum amplitude point Pmt in the first-order mode is located in a sole; a maximum amplitude point Pm2 in a second-order mode is also located in the sole; a maximum amplitude point Pm3 in a third-order mode is also located in the sole; and a maximum amplitude point Pm4 in a fourth-order mode is located in a crown, the lowest order Dc is fourth-order. The natural frequency fm in the lowest order Dc is a fourth-order natural frequency. In the present application, the lowest order Dc is referred to as crown first-order. The natural frequency fm is referred to as a crown first-order natural frequency.
The natural frequency fm in the lowest order Dc reflects vibration in a region (crown) in which the CFRP member exists. The natural frequency fm shows the relationship between the hitting sound and the CFRP member.
The natural frequencies fm in the heads were as follows.
Furthermore, as shown in
As shown in
The metal single part of the embodiment is a titanium single part. The titanium single part is a portion made of only a titanium alloy.
In the simulation C, the influence of the cloth layer was considered. The natural frequency fm of a head in which an outermost layer is the cloth layer was calculated.
The specification of the CFRP member in the head C1 was as follows. The specification of the head C1 is shown also in the following Table 3.
For the sake of simplicity, the cloth layer was constituted by superposing two layers having a thickness which was half of that of a UD layer. The orientation angles of the fibers were made different by 90 degrees from each other in the two layers.
The heads C2 to C8 were prepared in the same manner as in the head C1 except that the orientations of the UD layer and the cloth layer were changed as shown in the following Table 3. The specifications of these heads are shown in the following Table 3.
As the calculation result of the head C1, the first-order natural frequency was 3395 Hz; the second-order natural frequency was 3809 Hz; the third-order natural frequency was 3837 Hz; and the fourth-order natural frequency was 4277 Hz. In the head C1, a head fourth-order mode was the crown first-order mode.
The natural frequencies fm in the heads were as follows.
As the order (the order in the whole head) of the head in the crown first-order mode, the orders of the heads C1 to C5 were fourth-order, and the orders of the heads C6 to C8 were second-order.
The order of the head in the crown first-order mode is associated with the frequency of sound caused by the vibration of the crown. The higher-pitch hitting sound caused by the vibration of the crown can be obtained by increasing the order of the head in the crown first-order mode. Therefore, even if the CFRP member is provided in the crown, the frequency of the hitting sound is hardly reduced. In this respect, the order of the head in the crown first-order mode is preferably equal to or greater than third-order, and more preferably equal to or greater than fourth-order.
As shown in Table 3, in the heads C1 to C5, the orientation of the fiber in the UD lamination part is set to three directions. On the other hand, the orientation of the fiber in the UD lamination part is set to two directions in the heads C6 to C8. As shown in
As shown in
In respect of increasing the frequency of the hitting sound, the natural frequency fm is preferably equal to or greater than 3900 Hz, more preferably equal to or greater than 4000 Hz, and still more preferably equal to or greater than 4100 Hz.
As described above, the high effect is obtained by orienting the fiber in the three directions. Advantages of the present invention are apparent from these simulation results.
The method described above can be applied to all golf club heads.
The description hereinabove is merely for an illustrative example, and various modifications can be made in the scope not to depart from the principles of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-236582 | Oct 2011 | JP | national |
