CN102006911B - Ball - Google Patents

Abstract

A ball (B) is provided with a ball body (1) having a spherical surface, and also with projections (2) projecting from the surface of the ball body (1). The projections (2) project such that, when the ball body (1) flies while rotating, the projections (2) suppress instability of fluid force acting on the ball body (1), thereby stabilizing the trajectory of the ball body (1) so that the ball body (1) flies along a predetermined trajectory.

Description

ball

technical field

The technology disclosed herein relates to a ball used in various sports, exercises, games, recreational activities, etc., such as a person directly or indirectly throwing, kicking or hitting a ball.

Background technique

The types of balls are roughly divided into solid balls and hollow balls. Among them, as a structure of a hollow ball, the following structure is known. The structure includes a bladder, a reinforcing layer, a covering rubber layer, and a skin layer. Compressed air is enclosed in the bladder. The reinforcing layer is the Nylon filaments etc. are wound around the bladder in all circumferential directions, the covering rubber layer is formed on the reinforcement layer, the skin layer is adhered to the covering rubber layer, and is mainly formed of a plurality of leather plates (for example, refer to Patent Document 1). A ball with this structure is called a stick ball.

Also, as a ball structure different from this, there is known a structure in which, for example, as shown in Patent Document 2, the edge portions of a plurality of leather sheets are sewn together to form a ball to form a skin layer, and the The bladder is housed within this skin layer. Balls with this structure are called seam balls.

Furthermore, as another ball structure, for example, Patent Document 3 discloses a ball having a structure in which a bladder is accommodated in a woven fabric layer formed by sewing a plurality of woven fabric pieces together into a spherical shape. , and stick a plurality of leather plates on the surface of the woven cloth layer to form the surface layer.

-Prior Patent Documents-

-Patent Documents-

Patent Document 1: Specification of US Patent No. 4333648

Patent Document 2: Japanese Laid-Open Patent Publication JP-A-9-19516

Patent Document 3: International Publication No. 2004/56424 Pamphlet

In sports using a ball, it is desirable that the flight trajectory of the ball is always the same when the conditions for directly or indirectly throwing, kicking or hitting (hereinafter also referred to as playing conditions) are the same. That is to say, it is desirable that the trajectory of the flying ball is neither extended nor shortened, and the ball does not deviate from the lateral direction perpendicular to the moving direction of the ball, but arrives at the desired position. In this way, the player can control the ball as intended.

Also, in sports using a ball, the ball is forcibly rotated so that the flight trajectory of the ball becomes a predetermined changing trajectory. For example, if the ball is rotated vertically in the same direction as the moving direction, the trajectory of the ball becomes a falling trajectory in which the ball drops greatly.

When the ball trajectory is changed as described above, it is desirable that the ball trajectory when the same rotation is given to the ball (when the rotation speed is the same) always becomes the same change trajectory, and it is also desired that the amount of change of the ball trajectory is the same as the given ball trajectory. There is a proportional relationship between the amount of rotation (the size of the rotational speed) and the speed of the ball. In this way, the player can realize the desired trajectory of the ball, and the controllability of the ball is improved.

Contents of the invention

The present invention has been researched and developed in view of the above circumstances. Its purpose is to provide a ball with improved controllability.

The inventors of the present application conducted repeated experiments and found that a ball provided with a predetermined convex portion on the surface of the ball suppresses the instability of the fluid force acting on the ball body when the ball body rotates and flies, and stabilizes the orbit of the ball body. so as to become a prescribed track. In addition, it has also been found that, especially when the ball is vertically rotated in the same direction as the moving direction (so-called topspin ball), the drop amount of the ball is relatively large, and the trajectory can be stabilized so as to become a prescribed falling trajectory. . It is presumed that these phenomena are related to the surface roughness (roughness) of the ball.

Disclosed herein is a ball comprising a ball body having a spherical surface and a protrusion raised from the surface of the ball body, the protrusion being raised so as to restrain the ball from acting on the ball when the ball body is in flight in rotation. The instability of the fluid forces on the body, thereby stabilizing the trajectory of the ball body into a defined trajectory.

According to the above-mentioned ball, since the ball includes a predetermined protrusion protruding from the surface of the ball body, when the ball body rotates and flies, the instability of the fluid force acting on the ball body is suppressed, and the trajectory of the ball body is stabilized. thus becoming a prescribed track.

Description of drawings

FIG. 1 is a perspective view showing a volleyball according to an embodiment;

Figure 2 is an enlarged perspective view showing the surface of the volleyball;

Fig. 3 is a partial sectional view of the volleyball;

Figure 4 is a partial cross-sectional view of a volleyball having a structure different from that of Figure 3;

Fig. 5 is a partial cross-sectional view of a volleyball having a structure different from that of Fig. 3 and Fig. 4;

Fig. 6 is a schematic diagram showing other structures of convex portions;

Fig. 7 is a schematic diagram showing other structures of convex portions;

Fig. 8 is a schematic diagram showing other structures of convex portions;

Fig. 9 is a schematic diagram showing other structures of convex portions;

Fig. 10 is a schematic diagram showing other structures of convex portions;

Fig. 11 is a schematic diagram showing other structures of convex portions;

Fig. 12 is a schematic diagram showing other structures of convex portions;

Fig. 13 is a schematic diagram showing other structures of convex portions;

Fig. 14 is a schematic diagram showing other structures of convex portions;

Fig. 15 is a schematic diagram showing other structures of convex portions;

Fig. 16 is a schematic diagram showing other structures of convex portions;

Fig. 17 is a schematic diagram showing other structures of convex portions;

Fig. 18 is a schematic diagram showing other structures of convex portions;

Fig. 19 is a schematic diagram showing other structures of convex portions;

Fig. 20 is a schematic diagram showing other structures of convex portions;

Fig. 21 is a schematic diagram showing other structures of convex portions;

Fig. 22 is a schematic diagram showing other structures of convex portions;

Fig. 23 is a schematic diagram showing other structures of convex portions;

Fig. 24 is a-a sectional view of Fig. 23;

Fig. 25 is a schematic diagram showing other structures of convex portions;

Fig. 26 is a schematic diagram showing other structures of convex portions;

Fig. 27 is a schematic diagram showing other structures of convex portions;

Fig. 28 is a schematic diagram showing other structures of convex portions;

Fig. 29 is a b-b sectional view of Fig. 28;

Fig. 30 is a schematic diagram showing other structures of convex portions;

Fig. 31 is an explanatory diagram showing the structure of a ball related to a comparative example;

Figure 32A is a graph showing the lift characteristics of the balls involved in the various examples at a rotational speed of 300 rpm;

Figure 32B is a graph showing the lift characteristics of the balls involved in the various examples at a rotational speed of 480 rpm;

Figure 32C is a graph showing the lift characteristics of the balls involved in the various examples at a rotational speed of 600 rpm;

Fig. 33A is a diagram showing lift characteristics of a ball according to a conventional example;

FIG. 33B is a graph showing lift characteristics of a ball related to a comparative example;

Figure 33C is a graph showing the lift characteristics of the ball involved in the embodiment;

Fig. 34A is a graph showing the simulation experiment results of the orbit of the ball involved in each example when the rotational speed is 300 rpm;

Fig. 34B is a graph showing the simulation experiment results of the orbits of the balls involved in each example when the rotational speed is 480rpm;

FIG. 34C is a graph showing the results of simulation experiments of the orbits of the balls involved in each example at a rotational speed of 600 rpm;

Fig. 35 is a graph showing an example of the temporal variation of the lateral force acting on the ball related to the conventional example;

Fig. 36 is a graph showing an example of the temporal variation of the lateral force acting on the ball according to the second embodiment;

Fig. 37 is a diagram showing the arrival position deviation when hitting a ball related to a conventional example with the ball hitting device;

Fig. 38 is a graph showing the deviation of the arrival position when the ball according to the second embodiment is hit by the ball hitting device.

Detailed ways

The ball disclosed herein includes a ball body having a spherical surface and a protrusion raised from the surface of the ball body. The protrusions are raised so as to suppress instability of a fluid force acting on the ball body when the ball body rotates and flies, thereby stabilizing the trajectory of the ball body to become a predetermined trajectory.

The "spin" mentioned here is not limited to the case where a force in the direction of rotation is applied to the ball to forcibly rotate the ball (that is, to rotate at a relatively high speed), and "the main body of the ball rotates and flies" also includes not being conscious of the ball. The case where force is exerted in the direction of rotation. In other words, not to mention the case where the ball rotates at a low speed, "the main body of the ball rotates and flies" can also include the case where the ball rotates at an extremely low speed, so to speak, in a quasi-steady non-rotating state.

It is also possible that the convex portion is raised to reduce the variation in the arrival position of the ball body when flying under the same conditions. The "arrival position" mentioned here includes the flight distance of the ball body (arrival position in the flight direction) and the arrival position in the lateral direction perpendicular to the flight direction. That is, the convex portion suppresses the lengthening or shortening of the flight path of the ball main body and suppresses the lateral deviation of the ball, thereby reducing the deviation of the arrival position.

It is also possible that the convex portion is raised so that when the ball body is vertically rotated and flies in the same direction as the ball body moves, the orbit of the ball body is stabilized to become a predetermined drop. track. The "vertical spin" as used herein refers to forcibly turning the ball so that the ball spins vertically at a relatively high speed.

That is to say, the inventors of the present application found that when the ball rotates and flies, the trajectory of the ball body is stabilized and the deviation of the arrival position is reduced; when the ball is forcibly rotated vertically, the trajectory of the ball is stabilized. And become the prescribed falling track.

Alternatively, the protrusions may be arranged in a predetermined pattern on the entire surface of the ball body.

It may also be such that the protrusions are uniformly arranged on the entire surface of the ball body.

It is also possible that the surface of the ball body is mainly formed by a plurality of plates.

Next, embodiments of the ball will be described with reference to the drawings. As an aside, the following description of the preferred embodiments is merely an example in nature.

Fig. 1 shows a ball according to this embodiment. Here, a volleyball is used as an example to describe a ball. Just to add, the ball is not limited to volleyball. For example, it may be a ball used in other sports such as soccer, handball, and basketball.

As shown enlarged in FIG. 2 , the volleyball B includes a ball body 1 and a protrusion 2 protruding from the surface of the ball body 1 .

As shown in FIG. 3 , FIG. 4 or FIG. 5 , the ball main body 1 in this embodiment has a so-called ball-sticking structure. That is to say, the ball body 1 is composed of a bladder 11, a reinforcing layer 12, a covering rubber layer 13 and a skin layer 15. The bladder 11 is spherical and hollow, the reinforcing layer 12 covers the surface of the bladder 11, and the covering rubber A layer 13 covers a reinforcing layer 12, for example formed of natural rubber, and the skin layer 15 consists of a plurality (eighteen in this volleyball B) of leather panels 14 adhered via an adhesive on the surface of the covering rubber layer 13, forming The spherical surface of the ball body 1.

The bladder 11 is formed of a non-breathable elastomer such as butyl rubber. Compressed air is sealed into the bladder 11 through a valve not shown.

The reinforcing layer 12 is composed of a winding layer formed by winding nylon filaments with a length of several thousand m around the bladder 11 in all circumferential directions, or a cloth layer in which a plurality of woven cloth pieces are sewn into a spherical shape. This reinforcing layer 12 stabilizes the quality of the ball. That is, due to the reinforcing layer 12, the ball body 1 has improved spherical properties, durability, spherical shape maintenance, and strength against changes over time.

The leather sheet 14 is made of natural leather, artificial leather, or synthetic leather, and each has a predetermined elongated shape. The leather plate 14 is arranged in the following state, that is, when the surface of the ball body 1 extends upward, downward, left and right, and front and rear, that is, through the center of the ball body and vertically intersecting six axes (hereinafter, also referred to as the central axis) When the respective directions are divided into six areas, three leather plates 14 are provided in each of the approximately rectangular areas, and the peripheral edge portions of the respective leather plates 14 are in contact with each other. The leather plate 14 covers the surface of the ball body 1, thereby forming the skin layer 15. As an additional note, the shape and number of individual leather plates are not limited, and appropriate shapes and numbers may be employed.

In addition, although illustration is omitted, the back peripheral edge part of each leather board 14 is chipped off in the direction inclined with respect to the thickness direction. As a result, a recess having a substantially V-shaped transverse cross-section is formed at the portion where the peripheral edge portions of the leather plates 14 on the surface of the ball body 1 are joined to each other. That is, predetermined irregularities are formed on the surface of the volleyball B in advance.

As a supplementary note, the cross section of the ball body 1 is schematically depicted in FIGS. 3 to 5 for easy understanding. Although the respective layers are depicted with approximately equal thicknesses in the drawings, the thicknesses of the respective layers are actually not equal to each other.

As shown in FIG. 2 , the convex portion 2 has a linear shape in the volleyball B according to the present embodiment. On each of the leather panels 14 , a large number of the linear protrusions 2 are arranged at equal intervals along two perpendicularly intersecting directions. As a result, a square lattice formed by the protrusions 2 is formed on the surface of the ball body 1 . In other words, many rectangular patterns are uniformly arranged on the entire surface of the ball body 1 .

For example, it is preferable to form each convex portion 2 on the surface of the ball body 1 as follows. That is, for example, as shown in FIG. 3 , the covering rubber layer 13 is integrally formed with a protruding line portion 13 a protruding radially outward. The leather sheet 14 adhered to the covering rubber layer 13 bulges outward in the radial direction of the ball body 1 due to the protruding portion 13a, thereby forming the convex portion 2 that protrudes from the surface of the ball body 1.

It should be added that the protrusions 13a may be formed integrally with the covering rubber layer 13, but the method of forming the protrusions 13a is not limited to integral molding. For example, although not shown, the protruding part 13a may be formed by attaching a protruding member having a predetermined height to the surface of the covering rubber layer 13 by means of adhesion or the like.

Alternatively, unlike the above, the leather plate 14 may be integrally formed with the protrusion 14a protruding from the surface of the leather plate 14, thereby forming the convex portion 2 protruding from the surface of the ball body 1, for example Figure 4 shows.

In addition, it is also possible to form the protruding part 14a not integrally with the leather plate 14, but to install the protruding part 14b on the surface of the leather plate 14 by, for example, sticking. The protrusion 2 protruding from the surface of the ball body 1 is shown in FIG. 5, for example.

To be described in detail below, each protrusion 2 protruding from the surface of the ball main body 1 has a function of suppressing inappropriate fluid force acting on the ball main body when the ball main body 1 rotates (including very low-speed rotation) and flies. Stability, the orbit of the ball body is stabilized to become a prescribed orbit. That is, variation in the ball body 1 arrival position (the flight distance and the position in the lateral direction perpendicular to the flight direction) of the ball body 1 is suppressed when the playing conditions of the ball body 1 are the same. In addition, each convex portion 2 has a function of stabilizing the trajectory of the ball body 1 so as to become a predetermined falling trajectory when the ball body 1 is vertically rotating and flying in the same direction as the movement direction of the ball body 1. . That is, when the same rotation is given to the ball main body 1, the trajectory of the ball always becomes the same falling trajectory. Also, the amount of drop varies substantially in proportion to the rotational speed and the ball speed.

Here, the height of each convex portion 2 is preferably about 0.05 mm to 0.4 mm, more preferably about 0.1 mm to 0.2 mm. In this way, it is possible to stabilize the trajectory of the ball without impairing the operability of the ball body 1 .

Also, the ratio of the surface area of the convex portion 2 (for example, see FIG. 3 ) to the total surface area of the ball body 1 is preferably about 10% to 40%, more preferably about 20% to 30%. In this way, it is possible to stabilize the trajectory of the ball while ensuring the operability of the ball main body 1 . Incidentally, this ratio gives an index of how many convex portions 2 should be provided on the ball body 1 .

The configuration and shape of the protrusions 2 are not limited to those shown in FIG. 2 . Next, modifications of the arrangement and shape of the convex portion 2 will be described with reference to the drawings.

In FIG. 6 , hexagonal patterns are formed by linear protrusions 2 , and the hexagonal patterns are arranged in contact with each other. That is, the honeycomb lattice is formed by the protrusions 2 .

In FIG. 7 , the protrusions 2 forming a hexagonal pattern are arranged so as to be spaced apart from each other. The arrangement of adjacent hexagonal patterns is set to be a staggered arrangement.

In FIG. 8 , the short-segment-shaped protrusions 2 are arranged at equal intervals along two oblique directions perpendicularly intersecting in FIG. 8 . In this way, a square lattice inclined obliquely is formed by the protrusions 2 .

In FIG. 9 , three short-segment-shaped protrusions 2 are arranged to form a triangle to form a triangular pattern, and the triangular pattern is arranged at equal intervals along the up, down, left, and right directions in FIG. 9 .

In FIG. 10 , short-segment-shaped protrusions 2 are also arranged in each grid of the square grid pattern shown in FIG. 8 . In adjacent grids, the orientations of the protrusions 2 are different from each other.

In FIG. 11 , three short-segment-shaped protrusions 2 are arranged to form a Y shape to form a Y-shaped pattern, and the Y-shaped pattern is arranged at equal intervals along the up, down, left, and right directions in FIG. 11 . The arrangement of adjacent Y-shaped patterns is set to be a staggered arrangement. Also, the orientation of the Y-shaped pattern in the vertical direction is switched according to a predetermined regularity. Thereby, a hexagonal grid is formed by six Y-shaped patterns, and a Y-shaped pattern is arranged in each of these grids.

In FIG. 12 , the linear protrusions 2 are arranged at equal intervals in the vertical direction and the oblique direction, thereby forming a triangular lattice. In other words, many equilateral triangular patterns are arranged in contact with each other.

In FIG. 13 , a rhombus pattern is formed by linear protrusions 2 , and the rhombus patterns are arranged so as to be in contact with each other.

In FIG. 14 , circular patterns are formed by the linear protrusions 2 , and the circular patterns are arranged so as to be in contact with each other in the up, down, left, and right directions in FIG. 14 .

In FIG. 15 , circular patterns are formed by short-segment-shaped protrusions 2 , and the circular patterns are arranged at intervals along the up, down, left, and right directions in FIG. 15 .

In FIG. 16 , the circular patterns in FIG. 15 are arranged in a zigzag shape.

In FIG. 17 , the circular patterns in FIG. 14 are arranged so as to be arranged in the up, down, left, and right directions in FIG. 17 so as to partially overlap each other.

In FIG. 18 , the short-segment-shaped protrusions 2 are arranged in a well-shaped pattern, and the well-shaped pattern is arranged in a zigzag shape along two perpendicularly intersecting directions. It should be added that the configuration is not limited to the interleaved configuration.

In FIG. 19 , the short-segment-shaped protrusions 2 are arranged so as to be arranged in two perpendicularly intersecting directions. As a result, a square lattice is formed in which no convex portion 2 exists at a lattice point.

In FIG. 20 , the short-segment-shaped protrusions 2 are arranged in an X shape, and the X-shaped patterns are arranged in two directions perpendicularly intersecting each other.

In FIG. 21 , the relatively long segment-shaped protrusions 2 are arranged so as to line up in one direction. Here, as shown in the figure, the intervals between the protrusions 2 may be periodically changed, and the intervals may be equal intervals.

In FIG. 22 , the short-segment-shaped protrusions 2 are arranged in a V shape, and the V-shaped patterns are arranged in two directions perpendicularly intersecting each other.

In FIGS. 23 and 24 , the protrusions 2 raised from the surface in a spike shape are arranged to form a hexagonal pattern, and the hexagonal pattern is arranged to be aligned in the up, down, left, and right directions in FIG. 23 .

In FIG. 25, the hexagonal pattern in FIG. 23 is arranged in a zigzag shape.

In FIG. 26 , the protrusions 2 protruding from the surface in a pin shape are arranged to form a square pattern, and the square patterns are arranged at intervals along the up, down, left, and right directions in FIG. 26 .

In FIG. 27 , the protrusions 2 protruding from the surface into a pin shape are arranged to form a triangular pattern and an inverted triangular pattern, and the triangular pattern and the inverted triangular pattern are arranged so as to overlap with each other along the upper and lower sides in FIG. 27 . Arranged left and right.

In FIGS. 28 and 29 , the convex portions 2 protruding from the surface in dot shapes are arranged so as to be arranged at equal intervals along the up, down, left, and right directions in FIG. 28 . Also, an annular groove 21 is formed around each protrusion 2 . It should be added that the groove 21 can be omitted.

In FIG. 30 , the dot-shaped protrusions 2 in FIG. 28 are arranged in a zigzag shape.

As a supplementary note, two or more of the arrangements and shapes of the protrusions 2 shown in FIG. 2 and FIGS. 6 to 30 may be used in combination.

-First embodiment-

Next, specific implementation examples will be described. First, a commercially available volleyball (diameter: 209 mm) in which eighteen leather plates 14 are attached to the surface is prepared as a conventional example.

On the other hand, as shown in FIG. 2 , a volleyball in which a square lattice-shaped convex portion 2 was formed was prepared as an example.

Also, as shown in FIG. 31, the following volleyball was produced as a comparative example. The volleyball was made by attaching a circular line member 3 with a diameter of 0.45 mm in section to the surface of volleyball B sold on the market. Apparently, the line member 3 is formed into a circle centered on the central axis of the volleyball B and having a predetermined diameter (see D in FIG. 31 ). Specifically, the volleyball involved in the comparative example is formed by sticking six linear parts 3 on the surface of the volleyball. The centers respectively form a circle with a diameter of 187 mm. As a supplementary note, five line members 3 are shown in FIG. 31 , and one line member arranged on the back side of the ball body 1 is not shown in this figure.

The aerodynamic characteristics of the balls of the respective examples were investigated by conducting wind tunnel experiments on the respective examples. In FIGS. 32 and 33 , the results of this wind tunnel experiment are shown as a change in the lift coefficient CL with respect to the Reynolds number Re. Furthermore, the movement of the ball was also studied for these values (see FIG. 34 ). Here, FIG. 32A shows a comparison of the lift coefficients of each ball when the ball is vertically rotated in the same direction as the moving direction at 300 rpm; Comparison of the lift coefficients of each ball in the case; FIG. 32C shows a comparison of the lift coefficients of each ball when the ball is vertically rotated at 600 rpm in the same direction as the moving direction. Also, FIG. 33A shows a comparison of the lift coefficients when the balls in the conventional example are changed in rotation speed; FIG. 33B shows a comparison of the lift coefficients in the case of changing the rotation speed of the balls in the comparative example; The comparison of the lift coefficients when the rotation speed of the balls related to the examples is changed. Here, the vertical line in FIG. 32 and FIG. 33 represents the Reynolds number Re corresponding to a ball speed of 50 km/h, and the area where the Reynolds number Re is higher than the Reynolds number Re on the vertical line is, for example, a practical speed area of a volleyball. Therefore, the following attention is paid to the area on the right side of the vertical line.

First, look at Figure 32A. Compared with the ball in the prior art, the lift coefficient of the ball in the comparative example and the ball in the embodiment all is the bigger negative value of absolute value (absolute value is bigger), compared with the ball in the prior art The downward force experienced by the ball in the example and the ball in the embodiment is all greater. Therefore, the balls in the comparative examples and the balls in the examples drop more than the balls in the conventional example.

Also, refer to FIG. 32B and FIG. 32C. The ball in the comparative example has a larger lift coefficient than the ball in the conventional example, and the lift coefficient of the ball in the embodiment is a negative value that is larger in absolute value than the ball in the conventional example. Therefore, even when the rotational speed is relatively high, the drop amount of the ball in the embodiment is larger than the drop amount of the ball in the conventional example.

Also, see Figure 33A. The lift coefficient CL of the ball in the conventional example when the rotation speed is 480rpm and 600rpm has a large change compared with the lift coefficient CL when the rotation speed is 300rpm, and the lift coefficient CL changes sharply according to the change of the rotation speed. Also, in some cases, the lift coefficient CL of the ball in the conventional example does not change monotonously according to the change of the Reynolds number Re. For example, although the lift coefficient CL decreases monotonously with an increase in the Reynolds number Re at a rotational speed of 300 rpm, the lift coefficient CL hardly changes (or slightly increases) at a rotational speed of 600 rpm in accordance with an increase in the Reynolds number Re. Larger), the characteristics of the lift coefficient CL are completely different. Note that, for example, when the rotational speed is 480 rpm, there is a Reynolds number Re at which the lift coefficient CL decreases, and the lift coefficient CL does not change monotonously with an increase in the Reynolds number Re.

Also, with the ball in the comparative example, the difference between the lift coefficient CL at the rotational speed of 300 rpm and the lift coefficient CL at the rotational speed of 480 rpm, and the difference between the lift coefficient CL at the rotational speed of 480 rpm and the lift coefficient CL at the rotational speed of 600 rpm Differently, the change of the lift coefficient CL relative to the change of the rotational speed is not constant. Also, in some cases, the lift coefficient CL of the ball in the comparative example does not change monotonously according to the change of the Reynolds number Re when the rotational speed is constant. For example, although the lift coefficient CL hardly changes with the increase of the Reynolds number Re when the rotation speed is 300 rpm, but at the rotation speeds of 480 rpm and 600 rpm, the lift coefficient CL increases monotonously with the increase of the Reynolds number Re, and the lift The characteristics of the coefficient CL are different.

On the contrary, the lift coefficient CL of the ball in the embodiment does not change sharply according to the change of the rotational speed, and the lift coefficient CL is roughly proportional to the change of the rotational speed. Also, when the rotation speed is constant, the lift coefficient CL increases relatively monotonously with the increase of the Reynolds number Re. It can be seen that the drop amount of the ball in the example is larger than that of the ball in the conventional example and the ball in the comparative example, and the drop amount of the ball in the example is proportional to the rotation speed and the change amount of the ball speed. Therefore, according to the ball in the embodiment, it is possible to obtain a stable falling trajectory upon vertical rotation.

The above description is based on the lift coefficient CL, and to study the actual drop amount, it is necessary to also consider the influence of the speed reduction related to the drag coefficient CD. Fig. 34A ~ Fig. 34C show the result of simulation experiment, in this simulation experiment, according to described experiment result and the influence that also considers the speed reduction to calculate to each volleyball in the prior art example, comparative example and embodiment. The trajectory of the serve. In Fig. 34A, the rotational speed of the ball is set at 300 rpm; in Fig. 34B, the rotational speed of the ball is set at 480 rpm; in Fig. 34C, the rotational speed of the ball is set at 600 rpm.

Here, in the simulation experiment, the trajectory of the ball when the ball is played at a position set back 2 m from the end line and at a height of 2.2 m at a speed of 50 km/h is simulated and calculated. In addition, the hitting angles in the conventional example, the comparative example, and the working example are set to be the same as each other. That is, under various rotational speeds, the hitting angle in the conventional example and the comparative example is set to be an angle equal to the hitting angle of the ball passing over the net in the center of the court in the embodiment.

According to the results of the simulation experiment, when the rotational speed is 300rpm (refer to FIG. 34A ), the trajectories of the balls in the conventional example and the comparative example are approximately the same, while the trajectories of the balls in the embodiment after the highest point are higher than those of the conventional ones. example and comparative examples are lower. That is, the track of the ball in the example varies more than the conventional example, and thus the flight distance of the ball in the example is slightly shorter than the conventional example and the comparative example.

Also, when the rotational speed was 480 rpm (refer to FIG. 34B ), the flying distance of the ball in the comparative example was longer than that of the ball in the conventional example, and the flying distance of the ball in the embodiment was longer than that of the ball in the conventional example. The flight distance is short. This tendency also exists similarly when the rotational speed is 600 rpm. Also, as the rotational speed increases, the difference between the ball trajectory in the embodiment and the ball trajectory in the conventional example becomes more remarkable.

-Second embodiment-

Next, prepare a commercially available volleyball, that is, a ball in a conventional example (the ball in this conventional example is the same as the ball in the above-mentioned conventional example) and a ball with a honeycomb lattice-like convex portion 2 formed therein as shown in FIG. 6 . With regard to the volleyball of another embodiment (the second embodiment), the stability of the trajectory of the ball was compared with the conventional example and the second embodiment.

Fig. 35 is a diagram showing the change over time of the force in the direction perpendicular to the flight direction of the ball (hereinafter, the force acting on the ball is also referred to as lateral force). obtained from wind tunnel experiments. Fig. 36 is a graph showing the variation with time of the lateral force L obtained by conducting a wind tunnel experiment on the second embodiment. Here, each ball is made to stand still without rotating. The wind speed is 14m/s. Referring to FIG. 35 , the amplitude of the lateral force L in the conventional example is about ±0.5N, while the amplitude of the lateral force L in the second embodiment is smaller, about ±0.25N. That is to say, the variation of the lateral force in the second embodiment is smaller than that of the conventional example, so when the ball related to the second embodiment is actually flown, the flight trajectory of the ball is prevented from being perpendicular to the moving direction. The lateral deviation of the intersection.

Next, the variation in the arrival position when each ball in the conventional example and the second embodiment were actually hit by the ball hitting device was evaluated. The illustration of the ball-playing device is omitted here, and the ball-playing device is composed of a rotary arm and a flat plate, the base end side of the rotary arm is supported by a pivot, the rotary arm rotates around the pivot, and the flat plate is mounted on On the top of the slewing arm, the ball playing device is configured so that the ball can be installed near the lowest position within the rotation range of the slewing arm, so as to simulate people playing volleyball with their arms. The hitting plate hits the approximate center of the ball due to the rotation of the swivel arm, and the ball hitting device hits the ball thereby. Due to this structure, the ball hitting device does not impart force in the direction of rotation to the ball when hitting the ball, so the balls in each example fly while rotating at low or extremely low speeds. The ball hitting device is configured such that the initial speed of the ball can be changed by adjusting the rotational speed of the slewing arm, and the angle of the hitting plate when hitting the ball can be changed by adjusting the mounting position of the ball, thereby changing the hitting angle. In this embodiment, the playing conditions of the playing device are set as follows: the initial speed is 14 m/s, and the playing angle is about 20°. FIG. 37 is a diagram showing the arrival position deviation of the ball according to the conventional example; FIG. 38 is a diagram showing the arrival position deviation of the ball according to the second embodiment. Figure 37 and Figure 38 are drawn based on the orientation of the ball flying from left to right, the horizontal axis (X axis) in each figure represents the flight distance of the ball, and the vertical axis (Y axis) in each figure represents the distance of the ball in the lateral direction. Offset. Therefore, these two diagrams of Fig. 37 and Fig. 38 show the arrival position of the ball on the floor surface by plotting on the XY plane. As an additional note, 90 trials are performed for each example here.

First, referring to Fig. 37 (conventional example), it can be seen that although the ball reaches the position within the range of 1200 cm to 1700 cm (X axis) and -250 cm to 250 cm (Y axis), there are cases where the flight distance is extended or shortened and the amount of lateral deviation A larger case is shown by a dot-and-dash encircled line in the figure. In order to evaluate the deviation of the arrival position, the average value on the X direction and the average value on the Y direction are calculated respectively according to the data, and the calculated average value is defined as the average arrival position, and then the average arrival position and each The standard deviation of the distances between arrival locations across trials. The standard deviation calculated from the data in this Figure 37 is 54.66.

On the other hand, referring to FIG. 38 (second embodiment), the ball arrival position is in the range of 1200 cm to 1700 cm (X axis) and -250 cm to 250 cm (Y axis) same as the conventional example, but different from the conventional example. , in the second embodiment, there are almost no cases where the flight distance is extended or shortened and the lateral deviation is large. The standard deviation of the distance calculated from the data in FIG. 38 is 41.29, which shows that the deviation is smaller than that in the conventional example. From this, regarding the flight distance of the ball, it can be known that in the second embodiment, the extension or shortening of the trajectory of the ball can be suppressed, and the lateral deviation of the trajectory perpendicular to the moving direction of the ball can be suppressed. This means that it is beneficial when the player wants to get the ball where he wants it to be, which means controlling the ball as intended.

In addition, as mentioned above, the ball to which the technology disclosed here can be applied is not limited to the volleyball B. The technology can also be applied to various other balls used for sports, exercise, games or recreational activities and the like. As a supplementary note, specific examples of sports balls include soccer balls, handballs, and the like.

Also, the structure of the ball is not limited to the stick ball. This technique can be applied to balls of various structures. For example, the structure is not limited to hollow spheres, and this technique can be applied to solid spheres.

As a specific example of the structure of a hollow ball other than a pasted ball, there are, for example: a skin layer that is formed into a spherical shape by sewing the edge portions of a plurality of leather plates together, and a ball housed in the skin layer. The ball of the structure of the gall, the so-called seamed ball. When this technique is applied to the seam ball, the protruding part can be integrally formed on the leather plate to provide the convex part, or the protruding part can be attached to the surface of the leather plate by adhesion or the like to provide the protruding part.

In addition, as another specific example of the structure of the hollow ball, for example, a structure in which the bladder is accommodated in a woven fabric layer formed by sewing a plurality of woven fabric sheets into a spherical shape, and the multiple woven fabric pieces are A leather plate is adhered to the surface of the woven cloth layer. Like the seamed ball, when this technique is applied to a ball having this structure, it is only necessary to integrally form the protruding part on the leather plate, or to attach the protruding part to the leather plate by means of adhesion or the like. In addition, it is also possible to provide protrusions protruding from the ball surface by, for example, affixing the protruding member to the woven fabric layer and adhering a leather sheet thereon.

-Industrial Applicability-

As mentioned above, according to the technology disclosed here, it is possible to stabilize the trajectory of the ball during rotation and improve the controllability of the ball, so this technology is useful for various balls.

Claims (3)

1. A ball, the ball being a volleyball, soccer ball, handball or basketball, the ball comprising a ball body with a spherical surface and a protrusion protruding from the surface of the ball body, characterized in that: The convex portion is raised so that the instability of the fluid force acting on the ball body is suppressed when the ball body rotates and flies, thereby stabilizing the orbit of the ball body to become a prescribed orbit, The convex portion is raised so that the ratio of the surface area of the convex portion to the total surface area of the ball body is set at 10% to 40%, so that when the ball body moves in the same direction as the ball body When flying in a vertically rotating direction, the trajectory of the main body of the ball is stabilized to become a predetermined falling trajectory, The protrusions form a honeycomb lattice, or the protrusions form adjacent hexagonal patterns arranged in a staggered shape. 2. The ball according to claim 1, characterized in that: The protrusion is raised to reduce the variation in the arrival position of the ball body when flying under the same conditions. 3. The ball according to claim 1 or 2, characterized in that: The surface of the ball body is mainly formed by a plurality of plates.