JP2002065903A - Tennis racket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To damp the vibration of a gut moderately. SOLUTION: A vibration damping material is mounted on a part in contact with gut holes or the gut itself at least at a portion of a head part where the gut is spread. The vibration damping material should be 0.06 or more to less than 0.30 in the loss coefficient tanδ in the measurement of viscoelasticity under the conditions of -5 deg.C and 10 Hz. The vibration dampening member is so arranged as to form grommets to be put through the gut holes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tennis racket, and more particularly to a tennis racket which attenuates the vibration of a gut generated at the time of hitting a ball and prevents the controllability from being deteriorated by the vibration damping action.

[0002]

2. Description of the Related Art In a hard tennis racket, in recent years,
The mainstream is made of fiber reinforced resin. The fiber reinforced resin has a high specific strength and a high degree of freedom in design, can be reduced in weight while maintaining strength, and is suitable for mass production. Tennis rackets are also required to have high vibration damping properties. When a player hits a ball with a tennis racket, vibrations occur in the racket frame and gut. This vibration is transmitted to the player through the grip and causes discomfort.

In a tennis racket, nylon 11, 6-6 nylon and nylon 12 are usually used as guts (strings). These guts have poor vibration damping properties and cause so-called tennis elbows. I have.

Heretofore, as means for attenuating vibration generated at the time of impact, the following have been proposed. An ionomer resin film is interposed in a laminate of a fiber reinforced resin having an epoxy resin as a matrix resin, and the vibration damping of the racket frame is achieved by interposing an ionomer resin. (JP-A-10-337812
No.) The grommet member in contact with the gut is formed of an elastic body such as an elastomer, and the tip end of the grommet through which the gut hole is passed is separated from the gut hole by a gap to attenuate gut vibration and spread the sweet spot. The performance is improved. (Japanese Unexamined Patent Publication No. 11-285549) A gut protective material (grommet) to be inserted into a gut hole is t
It is described that the gut is made of a synthetic resin material or a rubber material having an δ of 0.01 to 1.0 to enhance the vibration absorbing performance of the gut. (Japanese Patent Application Laid-Open No. 62-5369)

[0005]

In the above-mentioned means, the vibration of the racket frame is attenuated, but the vibration generated in the gut is hardly attenuated. In the above-mentioned means, when the grommet member is formed of an elastic body, vibration of the gut is excessively disappeared and the feel at impact is deteriorated, and the force repelling the movement of the gut at the time of hitting by the softness of the elastic body is reduced, and the control is performed. There is a problem that it becomes a racket that is difficult to do.

The above-mentioned tan δ 0.01 to 1.0 of the synthetic resin material or rubber material serving as the vibration absorbing member is measured under the temperature range of 0 to 40 ° C. and the frequency of 10 to 2000 Hz. However, the above condition
Normally, the vibration is measured in a range that is far from the frequency range generated when the tennis racket hits the ball, so that the vibration damping property under normal tennis racket use conditions is not sufficient. That is, the vibration of the frequency of 1000 Hz or more is not the vibration felt by the human body, and the frequency felt by the human body is about 100 to 1000 Hz. Also, the peak of the frequency generated in the gut itself when hitting the ball is also 1000 Hz.
, And a vibration mode generated at the time of impact appears around 500 to 600 Hz. 10 to 2000 including the range largely separated from the frequency generated when the ball is hit as described above.
What is measured under the condition of Hz does not exactly contribute to the vibration damping of the gut under the normal condition.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and effectively attenuates vibrations generated in a gut under normal conditions that occur when a ball is hit, and does not deteriorate controllability due to the vibration damping action. The challenge is to

[0008]

According to the present invention, a vibration damping material is mounted on at least a part of a head portion on which a gut is stretched so as to contact a gut hole or a gut. The above-mentioned vibration damping material provides a tennis racket characterized in that a loss coefficient tan δ at the time of measuring viscoelasticity at a frequency of 10 Hz is 0.06 or more and less than 0.30 at a temperature of -5 ° C. ing.

That is, a gut stretched on the head of a tennis racket under normal tension (about 50 pounds) has a frequency of 50 out of plane primary vibration of the gut at room temperature (25 ° C.).
It is about 0 to 600 Hz. On the other hand, the loss coefficient tan of the viscoelastic member having a frequency of 10 Hz and a temperature of −5 ° C.
According to the temperature-frequency conversion law, the measurement condition of δ corresponds to a condition at a normal temperature (25 ° C.) of 500 to 600 Hz, and this frequency substantially matches the frequency of the out-of-plane primary vibration of the gut. Therefore, the fact that the vibration damping material has a good tan δ vibration damping property measured under the conditions of a temperature of −5 ° C. and a frequency of 10 Hz exactly corresponds to the good vibration damping performance of a gut under normal use conditions.

According to the intense experimental results by the present inventors,
When the tan δ of the vibration damping material measured under the condition of a temperature of −5 ° C. and a frequency of 10 Hz is 0.06 or more and less than 0.3,
It has been found that the vibration of the gut generated upon hitting the ball can be attenuated to such an extent that the player does not feel uncomfortable, and that the vibration is not excessively attenuated and the controllability is not deteriorated. The reason that the tan δ of the vibration damping material is specified to be 0.06 or more and less than 0.30 is that if it is less than 0.06, the vibration damping property of the gut cannot be sufficiently ensured, and the hit feeling is deteriorated. You. On the other hand, when tan δ is 0.30 or more, the vibration damping material excessively follows the bending of the gut, and the controllability deteriorates due to the gap between the shot feeling and the hit ball. Also, in the hit ball feeling test, a result was obtained in which the shot feeling was dull, unresponsive and lacked in exhilaration. Furthermore, when tan δ 0.30 or more, the vibration damping material becomes too soft, causing contact resistance with the gut when the gut is stretched, and there is a disadvantage that the gut stretching operation cannot be performed smoothly. The tan δ of the vibration damping material
Is preferably 0.07 or more and less than 0.24, and most preferably 0.10 or more and less than 0.20.

The vibration damping material has a frequency of 10H.
It is preferable that the complex elastic modulus in viscoelasticity measurement under the conditions of z and the temperature of −5 ° C. is 1.0 × 10 ^{9 to} 25 × 10 ⁹ dyn / cm ² . In order to attenuate the vibration of the racket frame generated at the time of hitting, it is preferable that the gut acts as a dynamic vibration absorber of the racket frame, and the vibration damping material functions as a kind of spring, and the gut reduces the vibration of the racket frame. It is necessary to resonate. In that case, if the complex elastic modulus of the vibration damping material is in the above range,
In the experiment of the present inventor, it was confirmed that the in-plane secondary vibration damping performance of the frame at the time of hitting the ball was high, and if it was smaller than the above range, the in-plane secondary vibration was insufficiently damped, and sufficient controllability was obtained. On the other hand, when it was larger than the above range, it was recognized that the vibration damping performance was lowered and the flight performance was also lowered. The complex elastic modulus of the vibration damping material under the above measurement conditions is preferably 14 × 10 ^{9 to} 25.
× 10 ⁹ dyn / cm ² , most preferably 16 × 10 ⁹
２３23 × 10 ⁹ dyn / cm ² .

The loss coefficient tan δ and the complex elastic modulus of the vibration damping material are measured by a viscoelasticity measuring device (a viscoelastic spectrometer “DVA200 improved type” manufactured by Shimadzu Corporation). The measurement conditions are as follows, and the temperature dispersion method is used. Specimen: width 4 mm x length 30 mm x thickness 1.66 mm Length of deformed part in sample: 20 mm (length 30 mm)
5 mm at both ends) Initial strain: 2 mm Amplitude: ± 12.5 μm Frequency: 10 Hz Heating rate: 2 ° C./min

[0013] The vibration damping member is formed as a grommet made of a cylindrical member that fits inside the gut hole, and the grommet is attached to a gut hole through which both ends of one gut passing at least through a sweet spot of the hitting surface are inserted. And the thickness of at least a part of the gut contact portion is set to be 0.2 mm or more and 5.0 mm or less.

The reason for setting the thickness of the vibration damping material in contact with the gut in the above range is that if the thickness is less than 0.2 mm,
Vibration absorption performance is insufficient, and it cannot withstand gut tension, and is easily damaged. On the other hand, if the thickness is more than 5.0 mm, the gut is bent by the impact at the time of hitting and the vibration damping material is also compressed, and the gut is bent more than necessary, and the controllability is reduced. In addition, the said thickness is preferably 0.1.
8 mm or more and 2.1 mm or less, most preferably 0.9 mm
It is not less than 1.5 mm. Further, it is preferable that the gut contact portion of the vibration damping material has a uniform thickness in the above range.

Further, as described above, the vibration damping material is formed as a grommet consisting of a cylindrical member which fits inside the gut hole,
The grommet is attached to a gut hole through which both ends of one gut passing at least through a sweet spot of the ball striking face are brought into contact with the gut. Therefore, at least two or more pairs of vibration damping materials are required to be formed as grommets, and the number is 30 or less. Preferably, if the top face is assumed to be 12:00 when the face face surrounded by the head portion is regarded as a clock face, the gut holes near 12:00 and 6 o'clock and near 3 o'clock and 9 o'clock passing through the sweet spot at the hitting position are provided. Preferably, it is mounted and the number of grommets is preferably 4 to 18, most preferably 8 to 18.

The grommet has a cylindrical shape having the same diameter in the length direction. The grommet comes into contact with the inner peripheral surface of the grommet, and the outer peripheral surface comes into contact with the inner peripheral surface of the gut hole. The vibration is damped. Note that a minute gap may be provided between the outer peripheral surface of the grommet and the inner peripheral surface of the gut hole near the inner peripheral surface side of the head portion. Also, the grommet passing through each gut hole has a configuration in which one end of a plurality of grommets is connected by a support band made of the same material, but it is not always necessary to connect a plurality of cylindrical members by a support band, and one grommet is used. The grommet may be attached to one gut hole. These grommets may be attached alone to the head portion, or may be attached to the inner surface of the bumper in advance and attached to the head portion together with the bumper.

The vibration damping rate of the gut is set to 0.25 or more and less than 0.45 in a state where the vibration damping material is attached to the head portion and the vibration damping material is in contact with the gut stretched on the head portion. Is set to The reason why the vibration damping rate is defined in the above range is that if it is less than 0.25, the vibration will remain excessively at the time of hitting, resulting in a racket lacking a mild feeling. This results in a gap between the feeling of hitting and the feeling of hitting, resulting in an unpleasant hitting feel.

The weight of the vibration damping material is based on the total weight of the racket frame when no gut is stretched.
It is preferable that the content be 0.3% or more and 12% or less. It is specified in the above range that if it is less than 0.3%, the damping effect of gut and the damping effect of the out-of-plane secondary vibration of the frame are poor,
This is due to poor hit feeling. Also, 12%
Beyond that, the weight concentrates on the head, which makes the racket difficult to swing. The above range is preferably 0.5% or more and 11% or less, and most preferably 1% or less.
Not less than 8%.

The vibration damping material may be a triblock copolymer having a polystyrene block having a relatively high vibration damping property and a vinyl polyisoprene block (for example, "HIBLER" manufactured by Kuraray Co., Ltd.) and a polypropylene having a relatively low vibration damping property. It is formed from a mixed material. In other words, a material with relatively high vibration damping and a material with relatively low vibration damping are mixed to attenuate the vibration of the gut and frame, and to avoid damping the vibration and damaging the shot feeling and controllability. Used.

The vibration damping material is not limited to the above, and the loss coefficient tan δ in the above-mentioned viscoelasticity measurement at a temperature of -5 ° C. and a frequency of 10 Hz is 0.06 to 0.3.
As long as the condition satisfying the condition of less than 0 is satisfied, the materials listed below are used alone or in combination. (A) Thermoplastic polyurethane (b) Styrene-based elastomer (c) 6-nylon obtained by polymerization reactivity with / without rubber molecular chain (d) Compounded rubber based on natural rubber, butyl rubber, acrylonitrile butadiene, etc. For example, a block copolymer in which polystyrene and vinyl polyisoprene are bonded to 100 parts of a rubber material is added in a range of 5 to 80 parts. The block copolymer in which polystyrene and vinyl polyisoprene are bonded includes Kuraray's "HIBLER"
There is. Not only the block copolymer in which polystyrene and vinyl polyisoprene are bonded, but also various other thermoplastic resins, for example, PR-1 of Sumilite resin
There are 2686. In addition, as an additive, norbornene is synthesized from ethylene and cyclopentadiene, and a polymer structure having a five-membered ring and a double bond in the main chain obtained by ring-opening polymerization of this norbornene is added with a large amount of extender oil. A rubbery oil-extended polymer to which is added. (E) A styrene-based thermoplastic elastomer in which the hard segment is polystyrene and the unsaturated double bond part contained in the diene component of the soft segment is epoxidized (Daicel Chemical Industries "Epofriend"). (F) Polybutylene terephthalate-poly Ether glycol (Hytrel, DuPont) (g) Cashew-modified phenolic resin (Sumilite Resin PR-12687, Sumitomo Durez) (h) Various polymers consisting of ester polymers, halogen polymers and other polymers Polymer alloy type material with function (Tosoh “Elastage”) (i) A material composed of thermoplastic resin, rubber, or a modified product of them. For example, polyvinyl chloride, polyethylene,
Polypropylene, ethylene-vinyl acetate copolymer, polymethyl methacrylate, polyvinylidene fluoride, polyisoprene,
Polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, N
Polymer materials such as BR, SBR, butadiene rubber, natural rubber, isoprene rubber, and blends thereof are used as the main components, and mica, glass fragments, class fiber, carbon fiber, calcium carbonate, barlite, precipitated sulfuric acid are used as main components. A substance to which substances such as barium, a corrosion inhibitor, a dye, an antioxidant, a stabilizer, a wetting agent, and the like are added as needed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a tennis racket frame 1 according to an embodiment of the present invention. A frame body 2 of the racket frame 1 is formed of a hollow pipe made of fiber reinforced resin and surrounds a face S on which a gut 3 is stretched. The head part 4, the throat part 5, the shaft part 6, and the grip part 7 are continuously formed. Therefore, the shaft portion 6 and the grip portion 7 have a structure in which two pipes are overlapped. The head portion 4 has a yoke 8 formed of a separate member in an annular shape surrounding the face surface S continuously with the frame body 2 on the throat side.

Gut holes 10 are provided at intervals in the head section 4 and the yoke 8. In addition, a recess 15 for mounting a grommet and a bumper that is continuous in the length direction is provided at a central portion in the thickness direction where the gut hole 10 is formed in the outer peripheral surface of the frame.

The cylindrical grommet 11 mounted in the gut hole 10 is formed of a vibration damping material. In the present embodiment, one end of each of the plurality of grommets 11 is connected by a support band 12, and the support band 12 is also connected to the grommet 11. It is formed of the same vibration damping material and is integrally formed. The support band 12 is fitted into the recess 15 of the head 4 and the yoke 8. The protective member 13 integrated with the grommet 11 and the support band 12 is mounted on the top side of the head portion 4, near the maximum width position at 3 o'clock and 9 o'clock, and at the yoke position facing the top. .

At the top side and at the 3 o'clock and 9 o'clock positions, a bumper 14 made of hard resin is attached to the outer surface of the support band 12 of the protective member 13, and the outer surface in the thickness direction of the frame is protected by the bumper 14. are doing. In addition,
The bumper 14 is not necessarily required to be mounted, but is preferably mounted on the head side from the viewpoint of frame protection. The bumper 14 is integrally provided with a cylindrical portion 14a that is inserted into a gut hole where the grommet 11 made of the vibration damping material is not attached.

The vibration damping material constituting the grommet 11 has a loss coefficient tan δ of 0.06 or more and less than 0.30 in viscoelasticity measurement at a temperature of -5 ° C. and a frequency of 10 Hz, and a complex elastic modulus E ^* Is 1.0 × 10 ^{9 to} 25 ×
A resin, rubber or elastomer of 10 ⁹ dyn / cm ² is used. In this embodiment, a mixture of a triblock copolymer having a polystyrene block and a vinyl polyisoprene block having relatively high vibration damping properties and a polypropylene having relatively low vibration damping properties is used.

The grommet 11 which comes into contact with the gut 3
Has a thickness of 0.2 mm or more and 5.0 mm or less.
The total weight of the protection member 13 including the grommet 11 and the support band 12 attached to the head portion 4 and the yoke 8 (the total weight of the four protection members 13 in the present embodiment) is:
It is 0.3% or more and 12% or less with respect to the total weight of the racket frame 1 in a state where no gut is stretched.

The above-mentioned protection member 13 is attached to the racket frame 1 and, with the gut 3 stretched, the vibration damping rate of the gut 3 is set to be 0.25 or more and less than 0.45.

FIGS. 3A and 3B show a modification.
In (A), one grommet 11 'is attached to the gut hole 10 at the opposing position at 3 o'clock and 9 o'clock. In this case, both ends of one gut come into contact with the grommet 11 ', so that vibration is damped. FIG. 3 (B) shows a case where the grommet is brought into contact with a gut which is stretched between the uppermost portion of the head portion and the lowermost portion of the yoke at 3: 00-9 o'clock in FIG. The grommet 11 'is attached to the lowermost gut hole, and thus four grommet 11' are attached to the racket frame. In this way, when attaching the grommets 11 'one by one to the gut hole,
As shown in FIG. 3 (C), a short supporting band 12 ′ fitted to the bumper 14 is provided on both ends of one end of the grommet 11 ′.
The projection of the bumper 14 is fitted into the hole formed in the support band 12 'and assembled.

In order to evaluate the physical properties and the like of the tennis racket frame of the present invention, a protective member provided with the grommet of the following Examples 1 to 6 and a protective member provided with the grommet of the comparative example were prepared and mounted on the racket frame. Then, an evaluation test was performed.

The racket frame to be mounted is the same,
A tennis racket frame made of a fiber-reinforced resin formed by laminating and molding a carbon prepreg using carbon fiber as a reinforcing fiber and an epoxy resin as a matrix resin. The tennis racket frame includes the following Examples 1 to 6 and a comparison. The protective members of Examples 1 and 2 were prepared and mounted.
The total length of the racket frame is 28 inches, the face area is 115 square inches, and the total weight of the racket frame is 230 g.

(Example 1) Hybler (manufactured by Kuraray Co., Ltd.) and polypropylene were adjusted to a weight ratio of 7: 3, and were melt-mixed with an extruder to prepare pellet-like tablets. The tablet was injected into a mold by an injection machine using an injection machine to form a protective member to be mounted at the 3 o'clock and 9 o'clock positions shown in FIG. The protective member is an integrally molded product of a grommet composed of nine cylindrical members and a support band for connecting these grommets. The tan δ of the protective member including the grommet mounted in the gut hole is 0.23. The two protective members were mounted around the 3 o'clock and 9 o'clock positions of the head portion of the racket frame. The thickness of the grommet is 0.8 mm, and the weight of the protective member with respect to the weight of the racket frame is 1.0%.

(Embodiment 2) One protection member having the same structure as that of Embodiment 1 and having four grommets connected by a support band was provided, and attached to the yoke of the racket frame. The tan δ of the protection member is 0.23, and the weight of the protection member is 0.5% based on the weight of the racket frame.

(Embodiment 3) One protection member is provided by connecting eight grommet having the same configuration as that of Embodiment 1 with a support band, and the top of the head portion of the racket frame (12:00)
Attached to. The tan δ of the protection member is 0.23,
The weight of the protective member relative to the weight of the racket frame is 0.
5%.

(Example 4) The same as the grommet of Example 1 except that the weight ratio of Hibler (manufactured by Kuraray Co., Ltd.) and polypropylene was adjusted to 3: 7, and the thickness of the grommet was changed to 2.0 mm. As in the case of Example 1, two protection members were provided with nine grommets continuous with a support band, and attached at the 3 o'clock and 9 o'clock positions. The tan δ of the protection member is 0.07, and the weight of the protection member with respect to the weight of the racket frame is 5.0%.

(Example 5) The same as the grommet of Example 1 except that the weight ratio of Hibler (manufactured by Kuraray Co., Ltd.) and polypropylene was adjusted to 5: 5 and the thickness of the grommet was changed to 1.0 mm. As in the case of Example 1, two protection members were provided with nine grommets continuous with a support band, and attached at the 3 o'clock and 9 o'clock positions. The tan δ of the protection member is 0.13, and the weight of the protection member with respect to the weight of the racket frame is 3.0%.

(Example 6) The thickness of the grommet was 8.0 m.
Except for the point of m, the grommet was the same as the grommet of Example 1, and two grommets were provided in the same manner as in Example 1 by providing two protection members continuous with a support band at 3 o'clock and 9 o'clock. The tan δ of the protection member is 0.23, and the weight of the protection member is 10% of the weight of the racket frame.

(Comparative Example 1) The same as the grommet of Example 1 except that the weight ratio of Hibler (manufactured by Kuraray Co., Ltd.) and polypropylene was adjusted to 5:95, and the thickness of the grommet was changed to 1.0 mm. As in the case of Example 1, two protection members were provided with nine grommets continuous with a support band, and attached at the 3 o'clock and 9 o'clock positions. The tan δ of the protection member is 0.04, and the weight of the protection member with respect to the weight of the racket frame is 1.0%.

(Comparative Example 2) Nylon material was injection-molded. Nine grommets were provided with two protective members continuous with a support band in the same manner as in Example 1, and attached at the 3 o'clock and 9 o'clock positions. The tan δ of the protection member is 0.05,
The weight of the protective member relative to the weight of the racket frame is 1.
0%.

The complex elastic moduli E * of Examples 1 to 6 and Comparative Examples 1 and 2 are as shown in the following table. Examples 1 to 6 fall within the scope of claim 2 of the present invention, while Comparative Examples 1 and 2 fall outside the range. The thickness of the grommet in Example 6 is too large and is outside the scope of Claim 3 of the present invention.

The gut was stretched on the racket frames of Examples 1 to 6 and Comparative Examples 1 and 2 with a tension of 60 pounds in length and 55 pounds in width, and the vibration damping rate of the gut and the out-of-plane secondary vibration damping of the racket frame. The rate, coefficient of restitution, and control performance were evaluated. The results of these evaluations are also shown in the table below.

[0041]

[Table 1]

(Measurement of Vibration Damping Rate of Gut) The racket frames of the examples and comparative examples were set upright as shown in FIG. 4 and the lower grip was fixed with a vice. A reflecting plate 40 was attached as a pickup meter to the center of the gut stretched on the face surface, irradiated with a laser 41, and the yoke was vibrated with an impact hammer 41, and a waveform was obtained with the laser 41. The damping rate of the primary vibration mode of gut was measured using the half width method from the frequency response function.

(Measurement of Out-of-Plane Secondary Vibration Damping Factor) As shown in FIG. 5A, the racket frame of each of the examples and the comparative example was suspended at the upper end of the head part 4 by a string 51, and the throat part 5 and the shaft An accelerometer 53 was fixed perpendicular to the frame surface at a continuous point with the part 6. In this state, FIG.
As shown in the figure, the frame on the back side of the accelerometer 53 was vibrated by the impact hammer 55. Input vibration (F) measured by force pickup meter attached to impact hammer 55 and acceleration pickup meter 53
Of the response vibration (α) measured by the amplifier 56A and 56B via a frequency analyzer 57 (Dynamic Single Analyzer HP3562 manufactured by Hewlett-Packard Company)
A) was input and analyzed. The transfer function in the frequency domain obtained by the analysis was obtained, and the frequency of the racket frame was obtained. The vibration damping ratio (ζ) was obtained from the following equation and was defined as an out-of-plane secondary vibration damping ratio. Table 1 shows the average values measured for the 14 racket frames of each example and comparative example.

Ζ = (1/2) × (Δω / ωn) To = Tn / √2

(Measurement of the coefficient of restitution) As shown in FIG. 6, the coefficient of restitution was determined by fixing the rack portion softly so that the racket frame was free in the vertical state, and fixed to the striking surface F from the ball launcher at a constant speed V1. (30 m / s), the tennis ball collides with the ball striking surface, and the speed V2 of the rebounded ball
Was measured. The restitution coefficient is a ratio (V2 / V1) between the firing speed V1 and the repulsion speed V2, and indicates that the larger the restitution coefficient, the better the flight of the ball.

(Evaluation method of controllability)
6. Using the tennis rackets of Comparative Examples 1 and 2, the controllability was evaluated by a feeling test by 20 players of both sexes (amateur players playing tennis about once a week). Evaluation was made out of 5 points, and the average value was taken. ◎ indicates 3 or more points, and X indicates less than 3 points.

As shown in Table 1 above, in Examples 1 to 6, the vibration damping rate of the gut was 0.29 or more, whereas in Comparative Examples 1 and 2, 0.20 and 0.21 were obtained. It was low, and it was confirmed that the vibration damping rate of the gut can be increased by attaching the protective member of the example. Further, regarding the out-of-plane secondary vibration damping rate of the frame, Examples 1 to 5 were confirmed to have a good vibration damping rate of 0.70 or more. On the other hand, in Example 6, since the thickness of the grommet is large,
The vibration damping rate of the frame was getting worse. Also, the vibration damping rates of the frames of Comparative Examples 1 and 2 were as low as 0.40 and 0.50, and it was confirmed that the vibration damping rates of the frames were also low.

The resilience performance was almost the same in both the examples and comparative examples, and it was confirmed that the resilience performance was not deteriorated even when the vibration damping member of the present invention was used for the grommet. Regarding the controllability, all the examples were ◎, but the comparative example was ×, and when the protective member made of the vibration damping material of the present invention was attached, the vibration damping property was appropriately maintained. Therefore, it was confirmed that the controllability was good.

[0049]

As is clear from the above description, the vibration damping member attached to the tennis racket according to the present invention is:
In addition to damping the vibration of the gut when hitting the ball when in contact with the gut and improving the feel of the ball shot by the player, there is no gap between the ball and the feeling of hitting due to excessive attenuation of the vibration, and also in controllability No inhibition. As described above, the vibration damping material such as the grommet according to the present invention has an advantage that both the vibration damping property and the controllability can be satisfied.

[Brief description of the drawings]

FIG. 1 shows a tennis racket according to a first embodiment of the present invention;
It is a drawing showing a protection member attached to the tennis racket.

2A is a perspective view of a protective member provided with a grommet, FIG. 2B is an exploded perspective view of a grommet and a bumper,
(C) is a sectional view in a state where the protection member is attached to the racket frame.

FIGS. 3A and 3B are schematic diagrams showing modified examples, and FIGS.
FIG. 4 is a front view of the protection member.

FIG. 4 is a view showing a method for measuring a vibration damping rate of gut.

FIG. 5 is a view showing a method of measuring a vibration damping rate of a frame.

FIG. 6 is a drawing showing a method of measuring a coefficient of restitution of a tennis racket.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Racket frame 2 Frame main body 3 Gut 4 Head part 10 Gut hole 11 Grommet 12 Support band 13 Protective member 14 Bumper

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Takeuchi 3-6-9, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Within Sumitomo Rubber Industries, Ltd. (72) Inventor Takeshi Ashino 3, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture 6-9, Sumitomo Rubber Industries, Ltd.

Claims (6)

[Claims] 1. A vibration damping material is attached to at least a part of a gut hole or a portion that comes into contact with a gut of a head portion on which a gut is stretched, wherein the vibration damping material has a temperature of −5 ° C. and a frequency of 10 Hz. The loss coefficient tan δ in the viscoelasticity measurement under the condition is 0.06
A tennis racket characterized by being at least less than 0.30. 2. The vibration damping material has a complex elastic modulus of 1.0 × 10 ^{9 to} 25 × 10 ⁹ dyn / cm ² in viscoelasticity measurement at a temperature of -5 ° C. and a frequency of 10 Hz. The tennis racket according to 1. 3. The vibration damping member is formed as a grommet made of a cylindrical member fitted in the gut hole, and the grommet is attached to a gut hole through which both ends of one gut passing at least through a sweet spot of the hitting surface are inserted. The tennis racket according to claim 1 or 2, wherein the tennis racket is in contact with the gut, and a thickness of at least a part of the gut contact portion is 0.2 mm or more and 5.0 mm or less. 4. The vibration damping material is formed from a mixture of a triblock copolymer having a polystyrene block and a vinyl polyisoprene block having a relatively high vibration damping property and a polypropylene having a relatively low vibration damping property. The tennis racket according to any one of claims 1 to 3. 5. The vibration damping material is attached to a head portion,
The vibration damping rate of the gut in a state where the gut stretched on the head portion and the vibration damping material are in contact with each other is 0.25 or more and 0.4 or more.
The tennis racket according to any one of claims 1 to 4, wherein the tennis racket is less than 5. 6. The weight of the vibration damping material is 0.3% or more and 12% or less with respect to the total weight of the racket frame in a state where no gut is stretched. A tennis racket according to any one of the preceding claims.