JPH10244811A - Motorcycle tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a pattern rigidity high and to improve wet road holding by making the direction of external force applied by the road agree with the direction of thread groove. SOLUTION: A first tread groove 10 and a second tread groove 12 crossing the first tread groove 10 at right angles form a block pattern. An acute angle αformed by the first tread groove 10 and the equator of the tire increases gradually toward a tread end (e) and vector components Gx(P), Gy(P) at a point P on the contour of the tread in the direction of the slant of the first tread groove are expressed by the following equations; Gy(P)=Gy(e).tanA(P)/ tanA(e), Bx(P)=√(Gy(e)<2> -Gy(P)<2> ), where Gx(P) is a component in the peripheral direction of the tire, Gy(P) is a component in the axial direction of the tire, A(P) is an angle formed by a tangent at the point P and a line in the axial direction of the tire, A(e) is an angle formed by a tangent at the tread end (e) and a line in the axial direction of the tire, and G(e) is 1 for the sake of convenience.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to improve the drainage performance while maintaining a high pattern rigidity by making the direction of the external force received from the road surface and the direction of the first tread groove substantially improved the wet running performance. The present invention relates to a motorcycle tire.

[0002]

2. Description of the Related Art With the recent increase in output and performance of vehicles, there is a strong demand for high-performance tires that can safely run at high speed even in tires for motorcycles. For this purpose, tread patterns have been improved.

The role of the tread pattern on a wet road surface is to drain water from the ground contact surface by a tread groove, and to maintain the rigidity of the tread land portion (pattern rigidity) to minimize deformation due to an external force to minimize the contact area. Is to ensure. Therefore, it is necessary to direct the inclination direction of the tread groove to the direction of the external force in order to simultaneously improve the drainage property and the maintenance of the pattern rigidity, which are contrary to each other, and to exert more excellent wet running performance. That is, when the external force and the direction of the tread groove are parallel,
The land is most difficult to deform and its rigidity is kept high. In addition, the slip of the land portion generated in the direction of the external force causes relative movement with the water in the groove, so that the water easily flows in the groove and the drainage property is improved.

However, in a motorcycle, the bank angle (posture angle) of the vehicle body changes depending on running conditions such as straight running and turning running, and accordingly, the position of the contact point where the tire contacts the road surface also changes. In addition, the performance required for the tires also shows that in straight running in an upright state where the bank angle is approximately 0,
While the braking performance and the driving performance are important, the importance of the grip performance in the lateral direction increases as the bank angle increases.

[0005] Therefore, in order to maximize the wet running performance, the position of the ground contact point related to the tread contour shape and the bank angle, and the direction and magnitude of the external force that changes for each ground contact point due to the required performance described above. It is necessary to form the tread groove while taking the above into consideration.

Conventionally, as a tread groove, a linear groove extending in the circumferential direction of the tire, an S extending in the circumferential direction of the tire is conventionally used.
Although a U-shaped groove or the like has been proposed, there is no method that takes into consideration the position of such a ground contact point, and the direction and magnitude of external force that changes for each ground contact point, and has insufficiently improved the wet running performance. .

Therefore, according to the first aspect of the present invention, the vector components (Gx (P), Gy (P)) of the vector V (P) in the inclination direction of the first tread groove are represented by a specific mathematical expression. Thereby, the direction of the external force received from the road surface and the direction of the first tread groove can be made to coincide with each other, and the tire for a motorcycle can greatly improve wet running performance while improving pattern drainage while maintaining high pattern rigidity. The purpose is to provide.

Another object of the present invention is to provide a motorcycle tire which can be used as a front wheel tire.

The third object of the present invention is to provide a motorcycle tire that can be used as a rear wheel tire.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, the contour line of the tread surface in the meridional section of the tire is a convex circle from the tire equator to the tread end. A motorcycle tire having a tread portion that curves and extends in an arc shape, wherein the tread surface has a plurality of first tread grooves that extend from the tire equator toward a tread end, and the first tread groove includes a first tread groove.
The angle α on the acute angle side of the tread groove with the tire equatorial plane gradually increases from the tire equator side to the tread end, and the first line on the tire circumferential direction line passing through a point P on the contour line in the contour line. The vector components Gx (P) and Gy (P) of the vector V (P) in the inclination direction of the tread groove are expressed by the following equation (1):
A block is formed on the tread surface by forming a second tread groove which is represented by (2) and is orthogonal to the first tread groove, and a region where the block is formed on the tread surface is the tread surface. The tire for a motorcycle characterized by being in a range of 2/3 or more of the following. Gy (P) = Gy (e) · tanA (P) / tanA (e) --- (1) Gx (P) = √ (G (e) ^2- Gy (P) ² ) --- (2) Here, Gx (P): a component of the vector V (P) in the tire circumferential direction, Gy (P): a component of the vector V (P) in the tire axial direction, A (P): the point P of the contour line A (e): the angle between the tangent at the tread end e of the contour and the tire axial line, and G (e): the first tread groove at the tread end e. When a unit vector is used as a vector V (e) for convenience, G (e) is 1.

The invention according to claim 2 is characterized in that the first tread groove is inclined from the tire equator side to the tread end in the tire rotation direction.
The described invention is characterized by tilting in the anti-rotation direction.

Here, the equations (1) and (2) will be described. The contour line 2S of the tread surface of the motorcycle tire is
Since it is close to an arc, as shown in FIG.
Is substantially zero, that is, in straight running, the vehicle touches the ground at a point P on the tire equator C, and only the driving force (or braking force) Fx acting in the tire circumferential direction acts on the ground point P.

In turning, as shown in FIG. 8 (B), as the bank angle θ increases, the contact point P shifts to the tread end e, and the contact point P Lateral force Fy in axial direction and driving force F in tire circumferential direction
The resultant force F with x acts. In order to prevent the motorcycle from falling over when turning, the line of action of the resultant force F0 of the load reaction force Fz (constant) received from the road surface and the lateral force Fy needs to pass through the center of gravity g of the motorcycle. At this time, Fy = Fz · tan θ ---- (3) holds.

Further, as shown in FIG. 9, the camber angle θ coincides with an angle A (P) formed between a tangent L of the contour 2S at the ground contact point P and a line N in the tire axial direction. This means that the position of the contact point P is uniquely determined by the camber angle θ, that is, the angle A (P) is determined, and the lateral force Fy at each contact point P is also determined by the equation (3). Means that.

In addition to the lateral force Fy, each contact point P
As described above, the driving force Fx acting in the tire circumferential direction acts,
This driving force Fx changes variously depending on the running conditions. Therefore, in the present application, it is assumed that the tire is in an extreme state in which a slip starts to occur, and by specifying the magnitude of the external force F acting in the extreme state, the wet running performance in the limit running is improved. Is to ensure driving safety.

In other words, the concept of the maximum frictional force Fm, which is the limit value of the grip determined by the product of the road surface maximum friction coefficient and the tire load, is introduced, as shown in FIG.
By setting a friction circle having a radius equal to the maximum friction force Fm, the maximum driving force Fx in the limit traveling can be obtained from the lateral force Fy determined by the above equation (3) and the friction circle. The lateral force Fy and the driving force Fx are a vector component Fy (P) in the tire axial direction and a vector component Fx (P) in the tire circumferential direction of the external force F, which is the resultant force, and are expressed by the following equations, respectively.
(4), given by (5). Fy = Fy (P) = Fz · tan A (P) ---- (4) Fx = Fx (P) = √ (Fm ² -Fy (P) ² ) ---- (5)

That is, an arbitrary ground point P on the contour line 2S
In the formula, the maximum external force F acting on each contact point P is calculated by the above equation.
It can be determined by (4) and (5). Accordingly, the vector components (Gx (P), Gx) of the vector V (P) in the inclination direction of the tread groove.
y (P)) to the vector components of this external force F (Fx (P), Fy (P))
The above equations (1) and (2), in which the vector of the groove V (P) and the vector of the external force F are in the same direction, are derived. Gy (P) = Gy (e) · tanA (P) / tanA (e) --- (1) Gx (P) = √ (G (e) ^2- Gy (P) ² ) --- (2) This is due to the shape of the contour 2S of the tread and the tread edge e.
Means that the groove vector V (P) at each position P is determined by defining the groove vector V (e) as the initial value. In other words, the streamline K formed by the vector V (P) is specified. By forming the tread groove along the streamline K, the direction of the tread groove can be made to coincide with the direction of the external force F in the limit state, and the wet running performance in the limit running can be improved. Note that the vector V (e) determines the direction of the groove at the tread end e, and a unit vector can be used for convenience. Therefore, G (e) is 1.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section when the motorcycle tire 1 (hereinafter referred to as tire 1) is a rear wheel tire for a large vehicle.

In the figure, a tire 1 has a tread portion 2 and
It has sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and bead portions 4 located at radially inner ends of the respective sidewall portions 3 in the tire radial direction. The tire strength and rigidity are increased by the carcass 6 to be bridged and the belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2.

The carcass 6 has, at a main body portion extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, a folded portion for turning around the bead core 5 from the inside in the tire axial direction to the outside. The bead apex rubber 8 having a triangular cross section extending from the bead core 5 to the tire radially outer side is filled between the main body portion and the folded portion. In the present embodiment, the carcass 6 is composed of one radial ply in which nylon cords are arranged at an angle of 90 ° with respect to the tire equator C. The cord includes polyester, rayon and other various kinds of ply. Organic fiber cord can be appropriately adopted.

In the present embodiment, the inner and outer belts are formed by arranging an aromatic polyamide cord at a small angle of 30 ° or less with respect to the tire equator C, in this example, at an angle of 20 °. The belt layer 7 is formed from plies 7A and 7B.
Are arranged with the orientations of the plies 7A and 7B changed so that the cords cross each other.

In the tread portion 2, in the tire meridional section, the contour 2S of the tread surface smoothly extends in a convex arc shape from the tire equator C toward the tread end e, and the tread end e, The tread width TW, which is the distance in the tire axial direction between e and t, is formed so as to be the maximum width of the tire. In this example, the contour 2S is a single arc having a radius of curvature R centered on the tire equatorial plane C0,
The radius of curvature R is 0.50 to 0.50 of the tread width TW.
It is set to about 0.66 times, and in this example, about 0.58.
The contour 2S may be formed by various curves other than a single arc.

The camber angle A at the tread end e
(e) has a range of 50 to 65 degrees, in this example, 60 degrees in order to obtain high turning characteristics.

As shown in FIG. 2B, a plurality of first tread grooves 10 extending from the tire equator side toward the tread end e (upward to the right in FIG. 2) are provided on the tread surface. In this example, in addition to the first tread groove 10, a vertical groove 11 extending linearly in the tire circumferential direction, and a direction intersecting the first tread groove 10 and the vertical groove 11 (right in FIG. Downwardly extending second tread grooves 12 for forming blocks are arranged.

The vector V (P) in the inclination direction of the first tread groove 10 on the tire circumferential direction line M passing through the point P on the contour line 2S has vector components Gx (P) and Gy ( P)
Are represented by the above formulas (1) and (2).

FIG. 3A shows that the contour line 2S is a single arc having a radius of curvature R = 110 mm, and the groove vector V (e) at the tread end e is (Gx (e) = 0). , Gy (e) =
The streamline K in the case of 1) is illustrated by developing the tread surface into a plane. The streamline K is curved and extends from the tire equator side to the tread end e, and the angle α of the streamline K between the tire equatorial plane CO and the acute angle gradually increases from the tire equator side to the tread end e. By satisfying the above-mentioned expressions (1) and (2), the direction of the external force F in the extreme state matches.

FIG. 3B shows the streamline K of FIG.
And a stream line J orthogonal to the stream line K. When a tread pattern is formed, as shown in FIG. 3B, the stream line K and the stream line J orthogonal to the stream line K are formed. And to use. The vector components of this orthogonal streamline J (Gx (P),
Gy (P)) is given by: Gy (P) = √ (G (e) ² −Gy (P) ² )-(6) Gx (P) = − Gy (e) · tanA (P) / tanA (e) --- (7), and by forming the second tread groove 12 along the streamline J, a block pattern based on FIG. 3B can be obtained. At this time, the second tread groove 1
Since the edge of (2) is perpendicular to the direction in which the block moves, a wiping effect such as wiping water is exhibited, and drainage is further improved. Moreover, since it is orthogonal to the direction of the external force F,
Uneven wear is less likely to occur, which is advantageous for wear resistance.

The tread pattern of the present embodiment shown in FIG. 2B corresponds to the stream lines K1 and K2 which are part of the stream lines K among the stream lines K and J shown in FIG. The block pattern is a combination of first tread grooves 10A and 10B formed along the first tread groove and second tread grooves 12A formed along a stream line portion J1 which is a part of the stream line J. In the example, the vertical groove 11 is formed on the tire equator C and in the vicinity thereof.

At this time, in order to achieve the effect of improving the wet running performance, it is necessary that the area Q in which the block formed by the tread grooves 10 and 12 is formed is set to be at least 2/3 of the tread surface. is there. That is, the width W of the region Q in which the tread grooves 10A, 10B, and 12A are arranged is set to 2/3 or more of the width SW along the contour line 2S of the tread surface. Preferably, the region Q is provided on the tread end side. The groove depth and groove width of the tread grooves 10 and 12 can be set in the same manner as in a conventional tire.

Further, the total area S0 of the tread surface and each groove 10,
Groove area ratio S1 which is the ratio of the total area S1 of the areas 11 and 12
/ S0 is preferably 0.2 to 0.5. If the groove area ratio S1 / S0 is less than 0.2, no drainage effect can be expected, and if it exceeds 0.5, the actual contact area is too small. As a result, the grip properties in both wet and dry conditions are significantly reduced.

FIGS. 4A and 4B show another example of the tread pattern. FIG. 4B shows a stream line portion K which is a part of the stream line K among the stream lines K and J shown in FIG.
3, first tread groove 1 formed along K4, K5
OC, 10D, 10E, and a second tread groove 12 formed along stream line portions J2, J3 which are part of stream line J.
B and 12C are respectively combined, and are tread grooves 10C, 10D, 10E, 12B,
The width W of the region Q where the 12C is arranged is set to be about 70% of the width SW of the tread surface.

Since the rear tire is on the driving side,
As the vector component Fx in the tire circumferential direction of the external force F, the driving force in the direction opposite to the tire rotation direction T acts exclusively. Therefore, in the case of the tire on the rear wheel side, FIG.
As shown in FIG. 4B, the first tread groove 10 extends from the tire equator side to the tread end in the anti-rotation direction of the tire.

FIG. 5 shows a meridional section in the case of a tire for a front wheel. As a carcass 6, two carcass plies having nylon cords arranged at an angle of 88 ° with respect to the tire equator C are used, and a belt is used. As the layer 7, an aromatic polyamide cord is formed from two belt plies 7A and 7B arranged at an angle of 16 ° with respect to the tire equator C.

On the tread surface, an example of a block pattern is disclosed as shown in FIGS. 6 (A) and 6 (B). FIG.
(A), the contour 2S is a single arc with a radius of curvature R = 65 mm, and the groove vector V (e) at the tread end e is (Gx (e) = 0, Gy (e) = 1). In FIG. 6, a streamline K and a streamline J orthogonal thereto are shown.
(B) shows the first tread grooves 10A and 10B formed along the stream line portions K1 and K2 which are a part of the stream line K among the stream lines K and J, and a part of the stream line J. Streamline part J
The second tread groove 12A formed along 1 is combined.

At this time, since the front wheel tire is on the driven side, a braking force always acts as a vector component Fx of the external force F in the tire circumferential direction. The tire extends from the equator side of the tire toward the tread end in the direction T.

FIGS. 7A and 7B show another example of the tread pattern. FIG. 7B shows a stream line portion K3 which is a part of the stream line K among the stream lines K and J shown in FIG.
First tread groove 10 formed along K4, K5
C, 10D, and 10E, and a block pattern in which second tread grooves 12B formed along a stream line portion J2 that is a part of the stream line J are combined.

As described above, the tires for the front and rear wheels can form a tread pattern having tread grooves of various shapes by combining some or all of the streamlines K and J.
Further, each of the tread patterns can be changed into various modes such as symmetrical and asymmetrical with respect to the tire equator C.

[0038]

EXAMPLE A Tire size 19 having the basic structure of FIG.
A 0 / 55R17 rear wheel tire was prototyped based on the specifications in Table 1 (Example products 1A to 2A, Comparative product 1
A), rim (MT 6.25 x 17), internal pressure (210 kP
Based on a), the motorcycle was mounted on the rear wheel of a 750 cc motorcycle and traveled on a real vehicle, and the wet grip performance and uneven wear resistance of each test tire were measured. As the front wheel tire, the tire of Comparative Example 1B used in the test of Example B was used.

(1) Wet grip property: The level of the grip force at the time of turning was determined by the driver's sensuality while traveling on a dry pavement course sprinkled with water at the limit speed, and the product of Comparative Example 1A was set to 100. The index was evaluated. The higher the number, the better. (2) Uneven wear: 3000 km on dry pavement under the above conditions
After running, it was determined whether or not visible uneven wear occurred.

[0040]

Embodiment B Tire size 12 having the basic structure of FIG.
A 0 / 70R17 front wheel tire was prototyped based on the specifications in Table 2 (Example products 1B to 2B, Comparative product 1
B), rim (MT 3.50x17), internal pressure (200 kP
Under a), the motorcycle was mounted on the front wheel of a 750 cc motorcycle and traveled on a real vehicle. The wet grip performance and uneven wear resistance of each test tire were measured by the same method as in Example A. As the rear tire, the tire of Comparative Example 1A used in the test of Example A was used.

[0041]

[Table 1]

[0042]

[Table 2]

As shown in Tables 1 and 2, it can be confirmed that the tires of the examples have significantly improved wet grip performance in addition to uneven wear resistance.

[0044]

Since the present invention is configured as described above,
The direction of the external force received from the road surface can be made to coincide with the direction of the tread groove, and the drainage performance can be improved while keeping the pattern rigidity high, so that the wet running performance in critical running can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view when an embodiment of the present invention is a rear wheel tire.

FIGS. 2A and 2B are a development view showing an example of a tread pattern of the tire, and a diagram showing streamlines of grooves used for the tread pattern.

FIGS. 3A and 3B are streamlines K of a tread groove, respectively.
It is a diagram showing an example of.

FIGS. 4A and 4B are a development view showing another example of a tread pattern of a rear wheel tire, and a diagram showing streamlines of grooves used for the tread pattern.

FIG. 5 is a cross-sectional view in the case where one embodiment of the present invention is a front wheel tire.

FIGS. 6A and 6B are a developed view showing an example of a tread pattern of the tire, and a diagram showing streamlines of grooves used for the tread pattern.

FIGS. 7A and 7B are a development view showing another example of a tread pattern of a front wheel tire, and a diagram showing streamlines of grooves used therein.

FIGS. 8A and 8B are diagrams illustrating external forces acting on a ground contact point during straight running and turning running. FIG.

FIG. 9 is a diagram illustrating a relationship between a camber angle θ and an angle A (P).

FIG. 10 is a diagram showing an external force acting at each ground contact point for explaining equations (1) and (2) of the present application.

FIGS. 11A and 11B are developed views showing tread patterns of comparative tires used in tables.

[Explanation of symbols]

2 Tread 2S Contour 10, 10A, 10B, 10C, 10D, 10E First
Tread groove 12, 12A, 12B, 12C Second tread groove C Tire equator e Tread edge L Tangent line of contour line M Tire circumferential line N Tire axial line T Tire rotation direction

Claims (3)

[Claims] 1. A tire for a motorcycle having a tread portion in which a contour line of a tread surface in a meridional section of a tire curves and extends in a convex arc shape from a tire equator toward a tread end, wherein the tread surface is a tire equator. A plurality of first tread grooves extending in a curved manner from the side toward the tread edge, and the angle α of the acute angle side of the first tread groove and the tire equatorial plane gradually increases from the tire equatorial side toward the tread edge. And the vector components Gx (P) and Gy (P) of the vector V (P) in the inclination direction of the first tread groove on the tire circumferential direction line passing through the point P on the contour line , The following equation
(1) and (2), and a block is formed on the tread surface by forming a second tread groove orthogonal to the first tread groove, and an area on the tread surface where the block is formed The tire for a motorcycle according to claim 1, wherein the area is at least 2/3 of the tread surface. Gy (P) = Gy (e) · tanA (P) / tanA (e) --- (1) Gx (P) = √ (G (e) ^2- Gy (P) ² ) --- (2) Here, Gx (P): a component of the vector V (P) in the tire circumferential direction, Gy (P): a component of the vector V (P) in the tire axial direction, A (P): the point P of the contour line A (e): the angle between the tangent at the tread end e of the contour and the tire axial line, and G (e): the first tread groove at the tread end e. When a unit vector is used as a vector V (e) for convenience, G (e) is 1. 2. The motorcycle tire according to claim 1, wherein the first tread groove extends from the tire equator side toward the tread end in a tire rotation direction. 3. The motorcycle tire according to claim 1, wherein the first tread groove extends from the tire equator side to the tread end in a direction opposite to the rotation of the tire.