JP4296108B2 - Ball bat - Google Patents

Description

  The present invention relates to a ball game bat, and more particularly to a ball game bat with improved coefficient of restitution.

  It has been conventionally known that when a ball collides with a ball game bat having a circular pipe structure, the bat generates bending vibration due to bending deformation and vibration in the circular pipe direction due to deformation of the circular pipe (axial cross section). ing.

  It has also been conventionally known that the rebound characteristics of the bat can be improved by adjusting the natural frequency of the bat in the tube direction.

  For example, in Japanese Patent Application Laid-Open No. 10-248978 (conventional example 1), Japanese Patent Application Laid-Open No. 10-2481979 (conventional example 2), and Japanese Patent Application Laid-Open No. 10-248980 (conventional example 3), the natural vibration of the bat in the tube direction is shown. There has been disclosed a ball game (hard baseball, soft baseball, softball) bat in which the rebound characteristics of the bat are improved by adjusting the number.

  Further, Non-Patent Document 1 (conventional example 4) described later discloses a result obtained by simulation of the change in the coefficient of restitution of the bat when the natural frequency of the bat in the tube direction is changed.

Furthermore, Japanese Patent Laid-Open No. 2001-224725 (conventional example 5) discloses a baseball or softball bat provided with a low-rigidity portion, a high-rigidity portion, and a medium-rigidity portion in a hitting ball portion.
Japanese Patent Laid-Open No. 10-248978 Japanese Patent Laid-Open No. 10-248979 Japanese Patent Laid-Open No. 10-248980 JP 2001-224725 A Takeshi Naruto, Fuminobu Sato, “Study on Repulsive Properties of Bat”, Japan Society of Mechanical Engineers, Proceedings of '97 Sports Engineering Symposium, July 1997, p. 117-121

  However, the ball bat as described above has the following problems.

  As shown in the conventional examples 1 to 3, the range of the natural frequency in the direction of the tube that is optimal for improving the rebound characteristics of the bat is determined for each type of ball game (for example, hard baseball, soft baseball, softball, etc.). Different. Therefore, it is necessary to obtain an optimum range of the natural frequency for each use of the ball game bat.

On the other hand, the present inventor has advanced research focusing on the relationship between the natural frequency (ω _bat ) of the bat in the tube direction and the natural frequency (ω _ball ) of the ball of the ball game in which the bat is used. As a result, it has been found that there is a certain relationship between the value of (ω _bat / ω _ball ) and the coefficient of restitution of the bat. That is, in order to improve the rebound characteristics of the bat, it is necessary to set the value of (ω _bat / ω _ball ) within an optimum range.

  Note that the ball bat disclosed in Conventional Example 5 has a hit ball portion that is easily deformed and uses a restoring force from the deformation to improve the resilience characteristics. The premise and configuration are completely different from those of the present invention in which the resilience characteristics are improved by adjusting.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a ball game bat having excellent resilience characteristics.

The ball game bat according to the present invention is a bat used for a hard baseball or a soft ball as a ball game, and the natural frequency of the hitting ball portion in the tube direction is 1.5 times or more the natural frequency of the ball used for the ball game. It is 5.7 times or less (more preferably 1.6 times or more and 4.7 times or less).

  Thereby, it is possible to provide a ball game bat having excellent resilience characteristics.

The ball game bat includes a hitting ball portion. In one aspect, the hit ball portion preferably includes a first resin layer, a metal layer outside the first resin layer, and a second resin layer outside the metal layer .

  By adopting such a structure, the natural frequency in the direction of the circular tube can be easily set within the above-described range without reducing the strength of the ball game bat. In addition, by providing a metal layer between the first and second resin layers, the impact resistance of the hit ball portion can be increased.

  The first resin layer is a fiber reinforced resin layer having a thickness of 0.8 mm or more and 1.2 mm or less, including a fiber having an elastic modulus of 30 GPa to 50 GPa and a fiber having an elastic modulus of 300 GPa to 500 GPa. The layer is an aluminum alloy layer or a titanium alloy layer having a thickness of 0.7 mm to 1.2 mm, and the second resin layer is a fiber having an elastic modulus of 30 GPa to 50 GPa and a fiber having an elastic modulus of 200 GPa to 400 GPa And a fiber reinforced resin layer having a thickness of 1.0 mm or more and 1.2 mm or less. The metal layer is preferably multi-layered.

  By setting the elastic modulus and thickness of the first and second resin layers and the metal layer within the above ranges, the natural frequency in the circular tube direction of the ball game bat can be easily set within the above range. Further, since the circular pipe rigidity can be lowered by making the metal layer multi-layered, it becomes easy to adjust the natural frequency in the circular pipe direction within the above-described range.

In another aspect, the hit ball portion is made of a fiber reinforced resin including a fiber having an elastic modulus of 30 GPa or more and 50 GPa or less and a fiber having an elastic modulus of 300 GPa or more and 500 GPa or less, and the thickness is 0.8 mm or more and 1.2 mm. It is formed of a fiber reinforced resin including the following first resin layer and a fiber having an elastic modulus of 30 GPa or more and 50 GPa or less and a fiber having an elastic modulus of 200 GPa or more and 400 GPa or less formed on the outside of the first resin layer. A second resin layer having a thickness of 1.0 mm or more and 1.2 mm or less and a fiber having an elastic modulus of 30 GPa or more and 50 GPa or less and a modulus of elasticity of 300 GPa or more and 500 GPa or less formed between the first and second resin layers. It is preferable to have a third resin layer having a thickness of 0.7 mm or more and 1.5 mm or less, which is made of a fiber reinforced resin containing fibers .

  Even with the circular tube structure including the first to third resin layers, the natural frequency in the circular tube direction within the above-described range can be realized.

In yet another aspect, the hitting ball portion has an annular cross section (a deformed cross section) in which a thin portion having a relatively small thickness and a thick portion having a relatively large thickness are alternately provided along the outer circumferential direction. It preferably has a structure .

  In the case where the hitting ball portion has the above-described irregular cross-sectional structure, in one aspect, the hitting ball portion is made of a fiber reinforced resin, the thickness of the thick wall portion is 6.0 mm or more and 7.0 mm or less, and the thickness of the thin wall portion. Is preferably 1.5 mm or more and 3.0 mm or less.

  In the case where the hit ball portion has the above-described irregular cross-sectional structure, in another aspect, the hit ball portion is made of an aluminum alloy, the thickness of the thick portion is 4.0 mm or more and 5.0 mm or less, and the thickness of the thin portion is It is preferable that it is 1.0 mm or more and 2.0 mm or less.

  In the aspect in which the hitting ball portion has the above-described irregular cross-sectional structure, in still another aspect, the hitting ball portion is made of a titanium alloy, the thickness of the thick wall portion is 3.0 mm or more and 4.0 mm or less, and the thickness of the thin wall portion. Is preferably 0.5 mm or more and 1.5 mm or less.

  When the hitting ball portion has the irregular cross-sectional structure, the natural frequency in the direction of the circular tube within the above-described range can be realized in any of the above aspects.

According to the present invention, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) in the circular tube direction of the ball game _{bat to} the natural frequency (ω _ball ) of the _ball used in the ball game is set to an optimum range. By setting, the rebound characteristics of the ball bat can be improved.

  Embodiments of the ball game bat according to the present invention will be described below.

In the ball game bat according to the present embodiment, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the _{bat in the} tube direction to the natural frequency (ω _ball ) of the _ball is within the optimum range. It is a ball game bat with improved rebound characteristics by setting.

  A method for measuring the coefficient of restitution of the ball game bat in the present embodiment will be described below.

  FIG. 6 shows a block diagram of the coefficient of restitution measuring device.

  As shown in FIG. 6, the coefficient of restitution measurement device includes a pitching machine 7, a high-speed video camera 9, and an image analysis device (not shown).

  The bat 1 is placed on the support 10. When the ball 8 launched from the pitching machine 7 in the direction of the broken line arrow in FIG. 6 collides with the hitting portion of the bat 1, translational motion and rotational motion occur in the bat 1, and the gravity center speed of the ball 8 changes. To do. Here, as the collision location of the ball 8, three locations are set, that is, a strike at the hitting ball portion and a position 50 mm away from the strike to the bat tip side and the grip end side. Collide each time. The state at the time of the collision is photographed by the high speed video camera 9. In this case, when the ball is made to collide with the position, the displacement due to the rotational motion of the bat and the displacement due to the translational motion are offset at a location 110 mm away from the grip end to the bat tip side. The position (collision position) where no displacement occurs at that point.

  The coefficient of restitution is obtained from Equation 1.

Where e is the coefficient of restitution, V _{BALL (IN)} is the center of gravity velocity (m / s) of the ball before the collision, V _{BALL (OUT)} is the center of gravity velocity (m / s) of the ball after the collision, and V _{BAT (PAL )} Is the translation speed (m / s) of the bat's center of gravity after the collision, V _{BAT (ROT)} is the rotational angular velocity (rad / s) around the bat's center of gravity after the collision, and a is the bat's center of gravity to the ball's collision position Distance (m: grip side is positive).

Note that V _{BALL (IN)} , V _{BALL (OUT)} , V _{BAT (PAL)} , and V _{BAT (ROT)} are obtained by analyzing an image photographed by the high-speed video camera 9 with an image analyzer. The coefficient of restitution is an average value of values calculated in each of multiple collisions (for example, 3 locations × 6 times = 18 times as described above).

  When the ball collides with the ball game bat, bending vibration and vibration in the tube direction are generated. The bending vibration of the ball game bat is vibration generated by bending and deforming the bat in the direction of the arrow (vertical direction) in FIG. The vibration in the tube direction of the ball game bat is vibration generated when the axial cross section of the bat is deformed. Details of the vibration in the circular tube direction will be described later.

  A method for measuring the natural frequency of the ball game bat in the circular tube direction in the present embodiment will be described below.

  FIG. 7 shows a block diagram of the natural frequency measuring device in the tube direction.

  As shown in FIG. 7, the natural frequency measuring device includes a butt suspension base 11, a rubber belt 12, an impulse hammer 13, an accelerometer 14, charge amplifiers 15 </ b> A and 15 </ b> B, an FFT (Fast Fourier Transform) analyzer 16, and a computer 17. Prepare.

  The bat 1 is suspended from the bat suspension base 11 by the rubber belt 12, but this restricts mainly the movement in the axial direction (vertical direction in FIG. 7), and the movement / rotation in other directions is almost free. It is held ready for exercise.

  The bat 1 is hit with the impulse hammer 13. A plurality of hitting positions are provided in the axial direction of the bat. The measurement positions may be set at three locations, for example, the bat's striker and the position 50 mm away from the bat tip side and the grip end side, respectively, or 50 mm and 100 mm from the butt tip portion to the grip end side, respectively. , 150 mm, 200 mm, and 250 mm apart.

  At each of the measurement positions described above, a plurality of (for example, twelve) measurement points (striking positions) are provided at approximately equal intervals in the circumferential direction, such as measurement points 18A, 18B, and 18C in FIG.

  The measurement point 18 (18A, 18B, 18C,...) Is hit with the impulse hammer 13, the change over time of the deformation of the outer peripheral surface of the bat 1 is measured with the accelerometer 14, and the measurement result is measured with the FFT analyzer 16. The natural frequency in the tube direction is measured by analysis. Specifically, the natural frequency of the vibration in the circular tube direction shown in FIG. 10 to be described later is calculated from the measurement result obtained by the accelerometer 14. The measurement result is displayed / recorded on the computer 17.

  In the present embodiment, those shown in Table 1 are used as the above-described configurations.

  A method for measuring the natural frequency of the ball 8 in the present embodiment will be described below.

  FIG. 8 shows a schematic diagram of the natural frequency measuring device of the ball 8, and FIG. 9 shows a block diagram thereof. Table 2 shows the measurement apparatus used in this experiment.

  As shown in FIGS. 8 and 9, the ball 8 is placed on the impedance head 20 of the vibration generator 19, and the ball 8 is vibrated by the vibration generator 19. A force pickup signal and an acceleration pickup signal are input from the impedance head 20 to the charge amplifier 21, and a signal from the charge amplifier 21 is input to the noise / vibration analyzer 22.

  Data from the noise / vibration analyzer 22 is input to the computer system 23 to obtain the natural frequency. The noise / vibration analyzer 22 is connected to a power amplifier 24, and predetermined power is given to the vibration generator 19 by the power amplifier 24.

  In the present embodiment, Mizuno Official Victory Baseball 20H-101 is used as a ball for hard baseball, and Mizuno Victory Softball 20S-100 is used as a ball for softball. When measured using the above-mentioned natural frequency measuring device, the natural frequency of the above-mentioned hard baseball was about 269 (Hz), and the natural frequency of the softball ball was about 128 (Hz). .

  The vibration in the tube direction of the ball bat will be described below.

  FIG. 10 is a schematic diagram showing vibration in the circular tube direction of the ball game bat.

  When the ball collides with the bat 1, the cross-sectional shape in the axial direction of the bat changes from a perfect circle shape shown in FIG. 10 (a) to a vertical ellipse shape shown in FIG. 10 (b), and a square shape shown in FIG. 10 (c). Through the shape, the horizontal ellipse shape shown in FIG. 10 (d) is obtained, and further, from the square shape shown in FIG. 10 (c) to the vertical ellipse shape shown in FIG. 10 (b) reversibly. It returns to the perfect circle shape shown in. This periodic change in the axial cross section is referred to as vibration in the tube direction of the ball game bat, and its natural frequency (Hz) is referred to as the natural frequency in the tube direction of the ball game bat.

  FIG. 11 is a dynamic model diagram for explaining the primary bending vibration and the vibration in the tube direction of the ball game bat with which the ball collides.

In the dynamic model shown in FIG. 11, the ball is composed of a one-degree-of-freedom forked model, that is, one spring, one mass point, and one damper. The directional vibrations are each connected as a forked model with one degree of freedom. For example, each parameter shown in FIG. 11 can be set as shown in Table 3, the natural frequency of the ball can be set to ω _ball = 269 (Hz), and the loss coefficient can be set to ζ = 0.082. The equation of motion is as shown in Equation 2.

In the present embodiment, the analysis is performed while changing the parameter k _{2 in the range} of 0 (N / m) or more and 2.0 × 10 ⁸ (N / m) or less. The relationship with the coefficient of restitution of the bat was obtained. The Newmark β method (direct integration method) was used as the analysis method, and the parameters β = 0.25 and time increment Δt = 10 ⁻⁵ (s) were used as the analysis conditions. The initial values (coordinate X (m), external force F (N), speed (m / s)) are as shown in Equation 3, and when the external force acting on the ball from the bat disappears, And the convergence of the calculation.

12 and 13 show the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) in the tube direction of the ball game bat to the natural frequency (ω _ball ) of the _ball , and the coefficient of restitution ( It is the figure shown about the relationship with e / _emax ).

The solid lines in FIGS. 12 and 13 show the results obtained by the numerical analysis (FIG. 11) described above, and the plots (types a to f) in FIGS. The result obtained by 9) is shown. FIG. 12 shows the results obtained with a hard baseball bat and ball (ω _ball = 269 (Hz)), and FIG. 13 shows a softball bat and ball (ω _ball = 128 (Hz)). Shows the results obtained. Further, e _max in FIGS. 12 and 13 means the maximum value of the coefficient of restitution obtained by the above numerical analysis.

  Referring to FIG. 12 and FIG. 13, the analysis results and the experimental results are in good agreement, the type b and e bats are more than the type c and f bats, and the type b and e bats are the type. The a and d bats have better resilience characteristics.

12 and 13, if the value of ω _bat / ω _ball is about α1 to α2 or less, e / e _max is 0.975 or more, and if the value of ω _bat / _ωball is about β1 to β2 or less. e / e _max is 0.980 or more. The values of α (α1, α2) and β (β1, β2) in FIGS. 12 and 13 are as shown in Table 4.

As shown in Table 4, regardless of the difference between the hard baseball bat (FIG. 12) and the softball bat (FIG. 13), the value of e / e _max is set to a certain value or more (that is, a certain rebound characteristic is set). Value of ω _bat / ω _ball for securing) is almost equal. In other words, the natural frequency of the hitting ball portion in the tube direction is about 1.5 times to 5.7 times the natural frequency of the ball used in the ball game (more preferably about 1.6 times to 4.7 times). And more preferably about 2.0 or more and 4.0 or less), the rebound characteristics of the bat can be improved regardless of differences in ball games.

  The structure of the hit ball portion capable of realizing the above-described natural frequency will be described below.

  In one aspect, a laminated structure having a first resin layer, a metal layer outside the first resin layer, and a second resin layer outside the metal layer is conceivable.

  In another aspect, a laminated structure having first to third resin layers having a predetermined thickness, which is made of a fiber reinforced resin containing fibers having a predetermined elastic modulus, is conceivable. Here, the elastic modulus of the fibers and the thicknesses of the first to third resin layers can be arbitrarily changed.

  In still another aspect, an annular cross-section (deformed cross-section) structure in which a thin portion having a relatively small thickness and a thick portion having a relatively large thickness are alternately and periodically provided along the outer peripheral direction can be considered. . Here, the material constituting the irregular cross section and the thickness of the thin portion and the thick portion can be arbitrarily changed.

  The structure of the hitting ball portion is not limited to that described above. For example, the metal layer between the first and second resin layers may be multilayered, or the number of resin layers may be increased. In any structure, the outer diameter, length, weight, and the like of the bat are set to those normally used.

In any of the above aspects, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the ball _{bat in the} tube direction to the natural frequency (ω _ball ) of the _ball is set within the above range. It becomes easy. As a result, the rebound characteristics of the ball game bat are improved.

  Below, the Example of the ball game bat based on this invention is described.

  FIG. 1 is a side view showing a bat 1 according to Example 1 and Examples 2 to 8 described later. The bat 1 includes a hitting ball portion 1A, a grip end 1B, and a bat tip portion 1C.

  FIG. 2 is an axial cross-sectional view (A-A cross-sectional view in FIG. 1) of the hit ball portion 1 </ b> A of the bat 1.

  With reference to FIG. 2, the hitting portion 1 </ b> A of the ball game bat has a first resin layer 2, a metal layer 3 outside the first resin layer 2, and a second resin layer 4 outside the metal layer 3. .

  The first resin layer 2 includes a prepreg containing carbon fiber having an elastic modulus of about 30 GPa to 50 GPa (more preferably about 35 GPa to 45 GPa), and about 300 GPa to 500 GPa (more preferably about 350 GPa to 450 GPa). It is a fiber reinforced resin layer formed by combining with other prepregs containing carbon fibers having an elastic modulus. The prepreg and other prepregs are formed by combining a plurality of prepreg sheets so that the orientation angles of the carbon fibers are 45 ° and 60 ° with respect to the axial direction of the bat 1, respectively. The thickness of the first resin layer 2 is about 0.8 mm to 1.2 mm (more preferably about 0.9 mm to 1.1 mm).

  On the other hand, the second resin layer 4 includes a prepreg containing carbon fibers having an elastic modulus of about 30 GPa to 50 GPa (more preferably about 35 GPa to 45 GPa), and about 200 GPa to 400 GPa (more preferably about 250 GPa to 350 GPa). ) Is a fiber reinforced resin layer formed by combining with other prepregs containing carbon fibers having an elastic modulus. The prepreg and other prepregs are formed by combining a plurality of prepreg sheets so that the orientation angles of the carbon fibers are 45 ° and 60 ° with respect to the axial direction of the bat 1, respectively. The thickness of the second resin layer 4 is about 1.0 mm to 1.2 mm (more preferably about 1.1 mm to 1.2 mm).

  In the present specification, the prepreg means a sheet in which fibers are aligned in one direction and impregnated with various resins.

  In addition, the metal layer 3 formed between the first and second resin layers 2 and 4 has a thickness of about 7000 to 1.2 mm (more preferably about 0.9 to 1.1 mm). It is a system duralumin layer (aluminum alloy layer).

The bat 1 according to this embodiment is a hard baseball bat, and the natural frequency (ω _bat ) in the circular tube direction is about 1426 (Hz). On the other hand, the natural frequency of the ball used for the hard baseball is, for example, about 269 (Hz). Therefore, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the bat 1 in the tube direction to the natural frequency (ω _ball ) of the _ball is about 5.3.

  The ball bat according to the second embodiment is a modification of the ball bat according to the first embodiment, and is different from the first embodiment in that the metal layer 3 is made of Ti-6Al-4V (titanium alloy).

  In this case, the elastic modulus of the metal layer 3 is about 40 GPa or more and 70 GPa or less. The thickness of the titanium alloy layer (metal layer 3) is about the same as the thickness of the aluminum alloy layer of Example 1.

The bat 1 according to this embodiment is a hard baseball bat, and the natural frequency (ω _bat ) in the circular tube direction is about 1076 (Hz). Therefore, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the bat 1 in the tube direction to the natural frequency (ω _ball ) of the _ball is about 4.0.

  Since other matters are the same as in the first embodiment, detailed description will not be repeated.

  FIG. 3 is an axial cross-sectional view (AA cross-sectional view in FIG. 1) of the hitting portion 1A of the bat 1 according to the third embodiment.

  The ball game bat according to the third embodiment is a modification of the ball game bat according to the first and second embodiments, and is implemented in that the metal layer 3 is multilayered (3A, 3B) as shown in FIG. Different from the first and second embodiments.

  The first and second metal layers 3A and 3B each have a thickness of about 0.5 mm to 0.7 mm and are stacked without being bonded to each other.

Thus, by making the metal layer 3 multi-layered, the rigidity of the circular pipe can be lowered, so that the natural frequency in the direction of the circular pipe can be easily reduced. As a result, a desired range (ω _bat / ω _ball ) is easily obtained.

  Since other matters are the same as those in the first and second embodiments, detailed description will not be repeated.

  FIG. 4 is an axial cross-sectional view (AA cross-sectional view in FIG. 1) of the hitting portion 1 </ b> A of the bat 1 according to the fourth embodiment.

  The ball game bat according to the fourth embodiment is a modification of the ball game bat according to each of the above-described embodiments. As illustrated in FIG. 4, a third resin is interposed between the first and second resin layers 2 and 4. It differs from Examples 1-3 by the point provided with the layer 4A.

  In the present embodiment, the first resin layer 2 includes a prepreg containing carbon fiber having an elastic modulus of about 30 GPa to 50 GPa (more preferably about 35 GPa to 45 GPa), and about 300 GPa to 500 GPa (more preferably 350 GPa or more). It is a fiber reinforced resin layer formed by combining with other prepregs containing carbon fibers having an elastic modulus of about 450 GPa or less. The prepreg and other prepregs are formed by combining a plurality of prepreg sheets so that the orientation angles of the carbon fibers are 45 ° and 60 ° with respect to the axial direction of the bat 1, respectively. The thickness of the first resin layer 2 is about 0.8 mm to 1.2 mm (more preferably about 0.9 mm to 1.1 mm).

  On the other hand, the second resin layer 4 includes a prepreg containing carbon fibers having an elastic modulus of about 30 GPa to 50 GPa (more preferably about 35 GPa to 45 GPa), and about 200 GPa to 400 GPa (more preferably about 250 GPa to 350 GPa). ) Is a fiber reinforced resin layer formed by combining with other prepregs containing carbon fibers having an elastic modulus. The prepreg and other prepregs are formed by combining a plurality of prepreg sheets so that the orientation angles of the carbon fibers are 45 ° and 60 ° with respect to the axial direction of the bat 1, respectively. The thickness of the second resin layer 4 is about 1.0 mm to 1.2 mm (more preferably about 1.1 mm to 1.2 mm).

  The third resin layer 4A formed between the first and second resin layers includes a prepreg containing carbon fibers having an elastic modulus of about 30 GPa to 50 GPa (more preferably about 35 GPa to 45 GPa), and 300 GPa. It is a fiber reinforced resin layer formed by combining with other prepreg containing carbon fiber having an elastic modulus of about 500 GPa or less (more preferably about 350 GPa or more and 450 GPa or less). The prepreg and other prepregs are formed by combining a plurality of prepreg sheets so that the orientation angles of the carbon fibers are 45 ° and 60 ° with respect to the axial direction of the bat 1, respectively. The thickness of the third resin layer 4A is about 0.7 mm to 1.5 mm (more preferably about 0.9 mm to 1.3 mm).

The bat 1 according to the present embodiment is a hard baseball bat, and the natural frequency (ω _bat ) in the circular tube direction is about 1184 (Hz). Therefore, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) in the circular tube direction of the bat 1 to the natural frequency (ω _ball ) of the _ball is about 4.4.

  Since other matters are the same as those in the above-described embodiments, detailed description will not be repeated.

  The ball game bat according to the fifth embodiment is a modified example of the ball game bat according to the first to fourth embodiments described above, and a VGCF (Vapor Growth Carbon Fiber) is formed on the resin layer of the ball game bat according to each of the above-described embodiments. Or it differs from each Example mentioned above by the point which contained CNT (Carbon Nano Tube).

  The content of VGCF or CNT is about 0.5 wt% or more and 40 wt% or less. The diameters of VGCF and CNT are about 0.1 nm or more and 150 nm or less.

  All the resin layers (first resin layer 2, second resin layer 4, third resin layer 4A) may contain VGCF or CNT at the above ratio, or only in some resin layers. You may let them.

  By including VGCF or CNT as described above in the matrix resin of the prepreg, the strength of the bat 1 can be improved without increasing the tube rigidity (that is, without changing the natural frequency in the tube direction). Can be planned.

  Since other matters are the same as those in the above-described embodiments, detailed description will not be repeated.

  FIG. 5 is an axial cross-sectional view (AA cross-sectional view in FIG. 1) of the hitting portion 1 </ b> A of the bat 1 according to the sixth embodiment.

  Referring to FIG. 5, the hitting ball portion 1 </ b> A of the bat 1 is periodically provided with a relatively thin portion 5 and a relatively thick portion 6 along the outer circumferential direction. It has an annular profile 1D.

  The irregular cross section 1D is constituted by a fiber reinforced resin layer containing carbon fibers. By winding and stacking a plurality of prepregs on a mandrel having an axial cross section including a concave portion and a convex portion, an irregular cross section 1D having irregularities on the inner peripheral surface and a circumferential shape on the outer periphery is formed. The

  As the prepreg, a prepreg containing carbon fibers having an elastic modulus of about 300 GPa or more and 500 GPa or less can be used. The prepreg is formed by combining a plurality of prepreg sheets such that the orientation angles of the carbon fibers are 45 ° and 60 ° with respect to the axial direction of the bat 1, respectively. In addition, you may use the other prepreg containing the carbon fiber which has an elasticity modulus about 30 GPa or more and 50 GPa or less in combination with the said prepreg.

  In the present embodiment, the thickness of the thin portion 5 (t1 in FIG. 5) is about 1.5 mm to 3 mm (more preferably about 1.8 mm to 2.6 mm or less), and the thickness of the thick portion 6 ( T2) in FIG. 5 is about 6 mm to 7 mm (more preferably about 6.3 mm to 6.8 mm).

The bat 1 according to the present embodiment is a hard baseball (ω _ball = 269 (Hz)) bat, and the natural frequency (ω _bat ) in the circular tube direction is about 1291 (Hz). Therefore, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the bat 1 in the tube direction to the natural frequency (ω _ball ) of the _ball is about 4.8.

  The bat 1 according to the seventh embodiment is a modification of the bat 1 according to the sixth embodiment, and is different from the sixth embodiment in that the deformed cross section 1D is made of an aluminum alloy.

  In this embodiment, the thickness of the thin portion 5 (t1 in FIG. 5) is about 1 mm to 2 mm (more preferably about 1.3 mm to 1.8 mm), and the thickness of the thick portion 6 (FIG. 5). T2) is about 4 mm to 5 mm (more preferably about 4.3 mm to 4.8 mm).

The bat 1 according to this embodiment is a hard baseball bat, and the natural frequency (ω _bat ) in the circular tube direction is about 1157 (Hz). Therefore, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the bat 1 in the tube direction to the natural frequency (ω _ball ) of the _ball is about 4.3.

  Since other matters are the same as in the sixth embodiment, detailed description will not be repeated.

  The bat 1 according to the seventh embodiment is a modification of the bat 1 according to the sixth embodiment, and differs from the sixth embodiment in that the deformed cross section 1D is made of a titanium alloy.

  In the present embodiment, the thickness of the thin portion 5 (t1 in FIG. 5) is about 0.5 mm to 1.5 mm (more preferably about 0.8 mm to 1.3 mm). The thickness (t2 in FIG. 5) is about 3 mm to 4 mm (more preferably about 3.3 mm to 3.8 mm).

The bat 1 according to this embodiment is a hard baseball bat, and the natural frequency (ω _bat ) in the circular tube direction is about 1022 (Hz). Therefore, the ratio (ω _bat / ω _ball ) of the natural frequency (ω _bat ) of the bat 1 in the tube direction to the natural frequency (ω _ball ) of the _ball is about 3.8.

  Since other matters are the same as in the sixth embodiment, detailed description will not be repeated.

  Although the embodiments and examples of the present invention have been described above, it is planned from the beginning to appropriately combine the features of the above-described embodiments and examples. Further, it should be considered that the embodiments and examples disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is the side view which showed the bat for ball games concerning Examples 1-8 of the present invention. It is the figure which showed the axial direction cross section (AA cross section in FIG. 1) which showed the ball game bat which concerns on Example 1, 2, 5 of this invention. It is the figure which showed the axial direction cross section (AA cross section in FIG. 1) which showed the ball game bat which concerns on Example 3, 5 of this invention. It is the figure which showed the axial direction cross section (AA cross section in FIG. 1) which showed the ball game bat which concerns on Example 4, 5 of this invention. It is the figure which showed the axial direction cross section (AA cross section in FIG. 1) which showed the ball game bat which concerns on Examples 6-8 of this invention. It is the figure which showed the structure of the restitution coefficient measuring apparatus of a ball game bat. It is a block diagram of the natural frequency measurement apparatus of the circular tube direction of a ball game bat. 1 is a schematic diagram showing an apparatus for measuring the natural frequency of a ball. It is a block diagram of the natural frequency measuring device of a ball. It is a schematic diagram which shows the vibration of the circular tube direction of a ball game bat. It is a dynamic model figure for demonstrating the primary bending vibration of the ball game bat which a ball collides, and the vibration of a circular pipe direction. It is a figure which shows the result of having measured the restitution coefficient of the bat by experiment and simulation using the hard baseball bat and the hard baseball. It is a figure which shows the result of having measured the restitution coefficient of the bat by experiment and simulation using the softball bat and the softball ball.

Explanation of symbols

  1 butt, 1A hitting portion, 1B grip end, 1C butt tip, 1D irregular cross section, 2 first resin layer, 3 metal layer, 3A first metal layer, 3B second metal layer, 4 second resin layer, 4A first 3 resin layer, 5 thin part, 6 thick part, 7 pitching machine, 8 ball, 9 high speed video camera, 10 strut, 11 butt suspension base, 12 rubber belt, 13 impulse hammer, 14 accelerometer, 15A, 15B charge Amplifier, 16 FFT analyzer, 17 computer, 18A, 18B, 18C measurement point, 19 vibration generator, 20 impedance head, 21 charge amplifier, 22 noise / vibration analyzer, 23 computer system, 24 power amplifier.

Claims (10)

A ball bat for use in hard baseball or softball as a ball game,
A ball game bat in which a natural frequency in a tube direction of a hitting portion of the ball game bat is 1.5 times or more and 5.7 times or less of a natural frequency of a ball used in the ball game. A ball bat for use in hard baseball or softball as a ball game,
A ball game bat in which a natural frequency in a tube direction of a hitting portion of the ball game bat is 1.6 times or more and 4.7 times or less than a natural frequency of a ball used in the ball game. A ball bat used for ball games,
It has a hitting part,
The hitting portion is
A first resin layer;
A metal layer outside the first resin layer;
The ball game bat according to claim 1, further comprising a second resin layer outside the metal layer. The first resin layer is a fiber reinforced resin layer having a thickness of 0.8 mm or more and 1.2 mm or less, including a fiber having an elastic modulus of 30 GPa or more and 50 GPa or less and a fiber having an elastic modulus of 300 GPa or more and 500 GPa or less,
The metal layer is an aluminum alloy layer or a titanium alloy layer having a thickness of 0.7 mm to 1.2 mm,
The second resin layer is a fiber reinforced resin layer having a thickness of 1.0 mm or more and 1.2 mm or less, including fibers having an elastic modulus of 30 GPa or more and 50 GPa or less and fibers having an elastic modulus of 200 GPa or more and 400 GPa or less. The ball game bat according to claim 3.   The ball game bat according to claim 3 or 4, wherein the metal layer is multilayered. A ball bat used for ball games,
It has a hitting part,
The hitting portion is
A first resin layer having a thickness of 0.8 mm or more and 1.2 mm or less, comprising a fiber reinforced resin including a fiber having an elastic modulus of 30 GPa or more and 50 GPa or less and a fiber having an elastic modulus of 300 GPa or more and 500 GPa or less;
A thickness of 1.0 mm or more and 1 is formed of a fiber reinforced resin formed on the outside of the first resin layer and including a fiber having an elastic modulus of 30 GPa or more and 50 GPa or less and a fiber having an elastic modulus of 200 GPa or more and 400 GPa or less. A second resin layer of 2 mm or less;
A thickness of 0. 1 is formed between the first and second resin layers and includes a fiber reinforced resin including a fiber having an elastic modulus of 30 GPa to 50 GPa and a fiber having an elastic modulus of 300 GPa to 500 GPa. The ball game bat according to claim 1, further comprising a third resin layer of 7 mm or more and 1.5 mm or less. A ball bat used for ball games,
It has a hitting part,
The said hitting ball portion has an annular cross-sectional structure in which a thin portion having a relatively small thickness and a thick portion having a relatively large thickness are alternately and periodically provided along the outer peripheral direction. Item 3. The ball game bat according to item 2. The hitting portion is made of a fiber reinforced resin,
The thickness of the thick part is 6.0 mm or more and 7.0 mm or less,
The ball game bat according to claim 7, wherein the thin portion has a thickness of 1.5 mm to 3.0 mm. The hitting portion is made of an aluminum alloy,
The thickness of the thick part is 4.0 mm or more and 5.0 mm or less,
The ball bat according to claim 7, wherein the thin portion has a thickness of 1.0 mm to 2.0 mm. The hitting portion is made of a titanium alloy,
The thickness of the thick part is 3.0 mm or more and 4.0 mm or less,
The ball game bat according to claim 7, wherein a thickness of the thin portion is not less than 0.5 mm and not more than 1.5 mm.

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