JPH02225102A - Tire for motorcycle - Google Patents

Abstract

PURPOSE:To obtain a tire for a motorcycle excellent in its riding property, road surface trailing property, and attraction property, and particularly suitable for running on a bad road as motocross use, by specifying respectively a carcass compression, a tire compression, and a tire height ratio. CONSTITUTION:In a tire 1, an area ratio which is a ratio between the ground area of a block part 13 and the non-ground area consisting of a groove area 11 on a tread part 2, is set to less than 0.3. On the other hand, a carcass compression H2/W2 which is a ratio between a carcass height H2 from the bottom part of a bread part 4 to the maximum height of a carcass 6, and a carcass maximum wide W2, is set to less than 0.75. And also, a tire compression H1/W1 which is a ratio between a tire height H1 from the bottom part of the bead part 4 to the maximum height of the tire 1, and the maximum wide W1 of the tire is set to less than 0.9. And the height ratio H2/H1 between the carcass height H2 and the tire height H2, is set to less than 0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a motorcycle tire that has excellent riding comfort, road surface following performance, and traction performance, and can be particularly suited for use in motocross running on rough roads.

[Conventional technology]

For motocross tires that run under harsh conditions on rough roads with uneven surfaces such as gaps and ruts, tires with a bias structure that have an envelope effect, that is, excellent road surface contact and have high running stability during cornering, are generally used. It's coming. However, tires with such a bias structure,
Because it is usually used in a stress-free natural equilibrium state,
Due to the bump from the road surface when driving through a gap, the tire tends to jump up like a rubber ball, especially when driving at high speeds, impairing road tracking ability and causing trough silane loss.

On the other hand, as the performance and output of vehicles increases, the road tracking ability
There has been a strong desire to improve traction, and in recent years,
This problem has been improved by flattening the bias tire to have an aspect ratio of about 0.9, for example. The purpose of this is to reduce the flex area in the sidewall portion by flattening the tire, thereby suppressing the above-mentioned bounce, and it also has many advantages, such as being useful for reducing the tire weight by reducing the cross-sectional volume of the tire.

[Problem to be solved by the invention]

However, in this case, the sidewall rigidity of the bias structure itself is increased by the triangular carcass cord, so by reducing the flex area, the longitudinal rigidity of the tire increases excessively, and as a result, ride comfort is greatly reduced. A new problem arises: the width decreases.

An object of the present invention is to provide a tire for a motorcycle that has improved riding comfort, road surface following performance, and traction performance by employing a flattened radial structure.

[Means to solve the problem]

In order to achieve the above object, the motorcycle tire of the present invention has a pair of left and right bead portions that are locked around the bead core with both ends folded back, pass through the sidewall portion and the tread portion, and have an angle of 70 to 70 mm with respect to the tire equator. a carcass comprising a folded carcass ply having carcass cords arranged at an angle of 90 degrees; and a carcass arranged inwardly of the tread portion and radially outwardly of the carcass and at an angle of 10 to 25@ with respect to the tire equator. a belt layer consisting of a belt ply having an array of belt cords, and a groove portion is provided in the tread portion, and a ratio of the ground contact area of the tread surface of the tread portion to the non-ground contact area S formed by the groove portion. The area ratio L/S is 0.3 or less, and the carcass flattening ratio H2/W2 is the ratio of the carcass height N2 from the bead bottom of the bead portion to the maximum carcass width W2. is 0.75 or less, and the tire aspect ratio H1/W is the ratio of the tire height Hl from the bead to the maximum tire height and the tire maximum width W1.
1 is set to 0.9, and the height ratio H2/H1, which is the ratio between the carcass height H2 and the tire height Hl, is set to 0.8 or less.

The carcass may include the folded carcass ply, which has both ends folded back around the bead core and is locked therein, and the non-folded carcass ply, which has both ends cut off above the bead core.

The belt layer may be formed from at least two belt plies, and the width of the narrowest belt ply is preferably 0.35 times or more and 0.85 times or less the tread width, and the belt edge and The distance C between the groove and the groove bottom is 3
It is preferable that the number is greater than or equal to n and less than or equal to 611.

Further, it is preferable that the carcass and belt layer have a strength balance coefficient T determined by the following formula (Tl) of 0.55 or more and 1.00 or less.

[Effect]

By adopting a radial structure with lower sidewall rigidity than a bias structure, motorcycle tires constructed in this way can prevent an excessive increase in longitudinal rigidity due to flattening, and improve riding comfort. It is possible to measure the improvement in

In addition, since this tire has a dayless shape in which the tread portion is restrained by a belt layer, it has poor bounce performance, and improves road tracking performance and trough stability.

Since this belt layer has belt cords arranged at a relatively deep angle of 10 to 25 degrees, it maintains the impact-reducing effect while increasing tread rigidity to an appropriate degree, and also reduces carcass height H.
Since it has a high tread gauge thickness with a height ratio H2/H1 of 2 and the tire height Hl of 0.8 or less, the area ratio L/H1 is 0.8 or less.
It is possible to form a tread pattern in which S is 0.3 or less, that is, a large non-contact area ratio and a large groove depth, and the traction properties can be further improved. By setting the above-mentioned high tread gauge thickness, separation of rubber #I of the belt layer can be suppressed and durability can be improved, making it possible to adopt a radial structure in motocross tires used under severe conditions. To improve this durability, distance C should be 3tm.
It is more effective to regulate

Furthermore, when the strength balance coefficient T is set to 0.55 or more and 1.00 or less, the tire load can be supported in a well-balanced manner between the tread and the sidewall, and the rise of rubber marks can be greatly suppressed, and especially when starting from zero. This can improve the feeling of stiffness that tends to occur when driving and cornering.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a plan view showing a part of the tread pattern.

In the figure, motorcycle tires (hereinafter referred to as tires) 1
The tire 1 has a tread part 2, a sidewall part 3 extending radially inward from both ends of the tread part 2, and a bead part 4 located at the radially inner end of the sidewall part 3. The frame is reinforced by a structure 8 consisting of a toroidal carcass 6 extending between bead cores 5.5 provided in the bead portion 4, and a belt layer 7 disposed on the radially outer side of the toroidal carcass 6 and inside the tread portion 2.

The tread portion 2 maintains camber thrust during cornering by having a straight line that exceeds the tire maximum width W1 of the sidewall portion 3.

The carcass 6 includes at least one folded carcass ply 16 in which both ends of the main body passing through the sidewall portion 3 and tread portion 2 are folded back around the bead core 5 and locked. In this example, the carcass 6 includes two It is composed of two folded carcass plies 16A and 16B, and both ends thereof are folded back from the inside to the outside around the bead core 5, for example, and terminate within the sidewall portion 3.

In this example, the folded part 16a of the folded carcass ply 16A located on the outside of the tire extends to a higher position than the folded part 16b of the folded carcass ply 16B on the inner side, and completely covers the inner folded part 16b. This alleviates stress concentration at the carcass ends.

The carcass plies 16A and 16B each include carcass cords arranged parallel to each other at an angle of 70 to 90 degrees with respect to the tire equator, and the carcass cords have an initial tensile modulus of 200 to 1500 ksr/cd. Low modulus organic fiber cords such as nylon, rayon, polyester cords, etc. are used. Note that if the cord angle is less than 70'', the longitudinal rigidity will increase excessively due to tire flattening, which will be described later, and ride comfort will be impaired. In order to compensate for the low lateral rigidity of the carcass ply 16B and maintain cornering characteristics, a tapered ply is provided between the main body part of the inner folded carcass ply 16B and its folded part 16b, extending from the bead core 5 to almost the entire length of the sidewall part 3. A bead apex 9 extending in a shape is provided.

- For example, as shown schematically in FIG. 4, the folding scraps 6 include a structure in which both ends of the body part passing through the folded carcass ply 16, the tread part 2, and the sidewall part 3 are above the one-dore core 5. It can be formed by combining an interrupted non-folded carcass ply 17, and the non-folded carcass ply 17 has both ends 17a terminated at a height l in the radial direction from the bead bottom of the bead portion 4 of 25 or less. It is also possible to terminate the cable at a length exceeding 25 m.

The belt layer 7 is made up of at least two belt plies 7A, 7B, and 7G in this example, and is arranged approximately parallel to the crown contour of the carcass 6 and approximately the same width as the carcass maximum width W2. By doing so, the hoop effect of the carcass case is increased, and the carcass case has a carcass flatness ratio H2/W2 which is the ratio of the carcass height H2 from the bead bottom of the bead portion 4 to the maximum carcass width W2. Constrain within the range of 0.75 or less.

In this example, the width of each belt ply of belt plies 7A, 7B, and 7G is gradually decreased toward the outside in the tire radial direction.
Belt edge peeling is reduced by differentiating the positions of each braai end, and the belt Ji of the narrowest belt ply, that is, the outermost belt ply 7C in this example.
The belt ply width BW in the tire axial direction along line 7 is set to be 0.35 times or more and 0.85 times or less of the tread width TW in the tire axial direction along the tread surface of the tread portion 2.

In addition, in this example, the belt cord used for each belt ply 7A to 7C has an initial tensile modulus of 400 to 800 kg.
An organic fiber cord with a low modulus of about /aJ, such as a nylon cord, is suitable, and is suitable for reducing stress concentration at both ends of the braai, which increases due to repeated deformation of the tread portion 2 due to contact/non-contact, especially due to a small radius of curvature. It is relaxed by the stretching action of the belt cord. In addition, bell) 7
The number of belt plies 17 can be adjusted by selecting different types of cord materials, such as rayon and polyester.

In addition, the belt cord needs to be set at a deeper angle than a normal belt cord, that is, at an angle of 10 to 25 degrees with respect to the tire equator.
It can moderately increase tread rigidity while maintaining the s*sum effect, envelope effect, etc.

In this example, the tire 1 is formed of a carcass 6 and a belt layer 7 in order to support the tire load P acting on the tread surface during ground contact with the tread portion 2 and the sidewall portion 3 in a well-balanced manner. In the tire structure 8, the strength balance coefficient γ determined by the following equation (1) is set to 0.
55 or more and 1.00 or less.

B: Breaking strength of belt cord.

α: Angle of the carcass cord with respect to the tire equator.

β: Angle of the belt cord with respect to the tire equator.

E. Number of carcass cords per 5cm.

F　i　Number of belt cords inserted per 5cm.

N1: Number of carcass plies (not including non-folded carcass ply 17 whose radial height l from the bottom of the carton exceeds 25 m and is interrupted at both ends).

N2: Number of belt plies.

The strength balance coefficient γ is shown in FIG.
As shown schematically, the ratio QT of the structure strength QT in the in-plane direction passing through the tire axis in the tread region T of the tire structure 8 to the structure strength QS in the in-plane direction in the sidewall region S. /QS, and the structure strength QT is the sum QT1+QT2 of the strength QTI of the carcass 6 disposed in the tread region T and the strength QT2 of the belt layer 7.
The structural strength QS is expressed by the strength QS of each carcass 6 arranged in the left and right sidewall regions S.
It is represented by the sum of I, QS 1 +QS 1.

That is, QT 1- N I X As1n (cr) ---
--(21QT 2 = N 2 XF/l!
s1n (β) (3) QS 1-N 1 xExAain
(cr) −=−−(4).

By regulating the strong balance coefficient T in this way and optimizing the balance between the structure strength QT in the tread region T of the tire structure 8 and the structure strength QS in the sidewall region S, it is possible to Moreover, it is possible to reduce the feeling of lack of tire rigidity, that is, the feeling of stiffness, which is likely to occur when cornering, and at the same time, it is possible to suppress the bumping up of the tire due to bumping up due to unevenness of the road surface.

Note that when the strength balance coefficient γ exceeds 1.00,
As shown by the dashed line in FIG. 5, the sidewall region S is more easily deformed than the tread region T, which worsens the feeling of stiffness and increases the bounce. If the strength balance coefficient T is less than 0.55, the tread area tends to deform, as shown by the two-dot chain line in the figure, and although it suppresses the jump, it worsens the feeling of stiffness.

Further, a block-shaped tread pattern formed by recessing grooves 11 is provided on the surface of the tread portion 2 of the tire l including such a tire structure 8, and the tread pattern has a surface area of the block portion 13. The area ratio L/S of the ground contact area S, which is the sum of the areas of the grooves 11, and the non-ground contact area S, which is the sum of the areas of the grooves 11, is set to 0.3 or less.

Note that such a small area ratio can be achieved by appropriately improving the tread rigidity by the belt layer 7.

Furthermore, the tire 1 of the present invention has the carcass aspect ratio H2/
W2 is 0.75 or less, and the tire aspect ratio H1/Wl, which is the ratio of the tire height Hl from the bead bottom to the tire maximum height and the tire maximum width W1, is 0.9 or less, and the carcass Since the tread portion 2 is formed with a high tread gauge thickness t, the height ratio H2/H1, which is the ratio between the height N2 and the tire height Hl, is 0.8 or less,
It is possible to form a deeper groove 11, and the area ratio L/S
In combination with the achievement of

Furthermore, by setting the tread gauge thickness t, it is possible to suppress rubber separation between the belt layer and the tread rubber, and by increasing durability, it is possible to adopt a radial structure in motocross tires used under harsh conditions. becomes. In addition, when forming the deep groove part 11 in the tread part 2 having such a high tread gauge thickness t, especially in the case of a radial structure, as shown in FIG. 3, for example, as shown in FIG. The block portion 13 and the groove portion 11 have different rubber thicknesses.
Meandering tends to occur in the belt layer 7 and the carcass 6 between the belt layer 7 and the carcass 6. This occurs because the carcass cord with a radial structure has a lower binding force than the carcass cord with a bias structure that intersects in a pantograph shape. External damage may cause a decrease in durability and a decrease in gauge thickness may cause the cord to peel off. Therefore, in this embodiment, the meandering is prevented, and the thickness tl of cefsilane in the block part 13 and the thickness t2 of cefsilane in the groove part 11 are made uniform, and in particular, t 1/l 2 is set to 0.9.
5 to 1.0, the belt layer 7 and carcass 6 are meandered in a reverse direction in advance of vulcanization molding.

Also, the distance M between the groove bottom 11a of the groove portion 11 and the end of the belt layer 7
It is preferable that C is 4W or more and 6fi or less, and 4
If it is less than 1 day, distortion will occur at the belt edge, and if it exceeds 6 fl, it will promote rubber heat generation and cause separation of the belt layer edge, resulting in a decrease in durability. [Example 1] A tire with a tire size of 110/90R19, which was prototyped based on the specifications in Table 1, has a displacement of 1.
The test piece was attached to the rear wheel of a 25cc motorcycle, and an actual vehicle running test was conducted, and the feeling evaluation at that time was expressed as an index and shown in Table 1.

Note that the same carcass and bell 71 are used for the experimental product 1.2 and comparative products 1 and 2, respectively, and only the carcass oblateness and section thickness ratio are different.

Note that the above index is an average value obtained by five test drivers and a comparative value with the conventional tire set as 100, and the larger the index, the better. The test conditions are shown in Table 2.
As shown in the table, the tire according to the embodiment 1.2 of the present invention has excellent gap running performance and
Improves controllability and handling stability. Furthermore, the road surface tracking ability is increased, which improves grip performance and shortens ramp time. Furthermore, by employing a belt layer and regulating the gauge thickness t1 and the section thicknesses t1 and t2, the tire case durability can be improved.

[Specific Example 2] Also, based on the specifications in Table 3, tire sizes with the same tire flatness ratio H1/W2, carcass flatness ratio H2/W2, and height ratio H2/H1 and different strength balance coefficients γ are 1.
A prototype tire of 10/90R19 was manufactured and subjected to an actual vehicle running test based on the test conditions shown in Table 2.

As shown in Table 3, for tires with the same height ratio H2/H1, etc., the feeling of stiffness can be improved by setting the strength balance coefficient γ in the range of 0.55 or more and 1.00 or less. It is possible to suppress jump while improving driving performance.

Therefore, by further regulating the strength balance coefficient T in the tire of the present invention, gap running performance, controllability, steering stability, etc. can be further improved.

[Effects of the Invention] As described above, the motorcycle tire of the present invention has the following features in regulating the carcass aspect ratio, tire aspect ratio, and height ratio.
This makes it possible to adopt a radial structure in motocross tires that are used under harsh conditions. In addition, this prevents an excessive increase in longitudinal stiffness due to flattening, improving ride comfort, and optimizing tread stiffness with the belt layer suppresses tire bounce, improves road tracking performance and improves trough sill resistance. improve. Moreover, by optimizing the tread rigidity and regulating the height ratio, it is possible to form a tread pattern with a low area ratio, that is, a large driving force, and many effects such as a greater improvement in trough silane properties can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a plan view showing a part of the tread pattern, Fig. 3 is a cross-sectional view explaining the meandering of the carcass, and Fig. 4 is a cross-sectional view showing the carcass and other parts. FIG. 5 is a simplified diagram showing the tire structure. 6...-carcass 7--belt layer, 7A, 7B, 7C,--belt ply, 11...-groove, 16---folded carcass ply, 17--non-folded carcass ply, BW--belt Ply width, TW...-Tread width.

Claims (1)

[Scope of Claims] 1. A carcass that is secured around the bead core of a pair of left and right bead portions with both ends folded back, passes through the sidewall portion and tread portion, and is arranged at an angle of 70 to 90° with respect to the tire equator. a carcass including a folded carcass ply having a cord; and a belt ply having a belt cord disposed inside the tread portion and radially outside the carcass and arranged at an angle of 10 to 25 degrees with respect to the tire equator. and a belt layer consisting of a belt layer, and a groove is provided in the tread part, and the area ratio L/S, which is the ratio of the ground contact area L of the tread surface of the tread part to the non-ground contact area S formed by the groove part, is 0. .3 or less, and the carcass aspect ratio H2/W2, which is the ratio of the carcass height H2 from the bead bottom of the bead portion to the maximum carcass width W2, is 0.75 or less, and the bead The tire aspect ratio H1/W1, which is the ratio of the tire height H1 from the bottom to the maximum tire width W1, is 0.9 or less, and the carcass height H2 and the tire height H1 are A motorcycle tire having a height ratio H2/H1 of 0.8 or less. 2. The motorcycle tire according to claim 1, wherein the belt layer has a distance C between a belt end and the groove bottom of 3 mm or more and 6 mm or less. 3. The motorcycle tire according to claim 1, wherein the belt layer comprises at least two belt plies. 4. The carcass includes the folded carcass ply,
The carcass ply may include a non-folded carcass ply that passes through the tread portion and the sidewall portion and is terminated at both ends above the bead core, and has a height of 25 m in the radial direction from the bead bottom to the folded carcass ply.
2. The motorcycle tire according to claim 1, wherein the sum of the non-folded carcass ply whose both sides are interrupted within m is at least 1 or more. 5. The motorcycle tire according to claim 4, wherein the carcass includes the folded carcass ply and the non-folded carcass ply. 6 The belt layer has a belt ply width in the axial direction of the tire along the belt layer of the belt ply that is the narrowest among the belt plies, and a tread width in the axial direction of the tire along the tread surface of the tread portion. .35 or more and 0
．． 4. The motorcycle tire according to claim 3, wherein the tire has a particle diameter of 85 or less. 7. The motorcycle tire according to claim 1, wherein the carcass and belt layer have a strength balance coefficient γ determined by the following equation (1) of 0.55 or more and 1.00 or more. γ=N1×Asin(α)+N2×F/E×Bsin(
β)/2×N1×Asin(α)...(1) A: Breaking strength of carcass cord, B: Breaking strength of belt cord, α: Angle of carcass cord with respect to tire equator, β: Belt cord with respect to tire equator Angle, E: Number of carcass cords per 5 cm, F: Number of belt cords per 5 cm, N1: Number of carcass plies (unfolded, where the radial height from the bead bottom exceeds 25 mm and both ends are interrupted) (does not include carcass plies), N2; Number of belt plies,