JP2001071708A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve manipulability by increasing the rate occupying tread rubber of a rubber having highest dynamic modulus of elasticity in the other land part except for a center land part more on the tread end side of the land part than the tread center side thereof so that crushing force is utilized for increasing cornering power. SOLUTION: A tread rubber 1 is formed of a two-layer rubber comprising an inner layer rubber 2 and an outer layer rubber 3. The dynamic modulus of elasticity of the inner layer rubber 2 at about 30 deg.C and under distortion of about 1% is set smaller than that under the same condition of the outer layer rubber 3, and four circumferential grooves 4 are formed in the tread rubber 1 so as to partition five land parts 5, 6 in a tread part. In each land part 6 except for the center land part 5, the rate occupying the tread rubber 1 of the outer layer rubber 3 having high dynamic modulus of elasticity is increased more on the tread end side of the land part 6 than the tread center side thereof. Excess crushing force effectively contributes to increase of cornering power, and manipulability can be efficiently improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire provided with a tread rubber having at least two layers of rubber having different dynamic elastic moduli, and more particularly to improving the maneuverability.

[0002]

2. Description of the Related Art As a pneumatic tire having tread rubber comprising two layers of base rubber and cap rubber having different dynamic elastic moduli and having a land portion divided by a plurality of circumferential grooves, for example, JP-A-5-139127, JP-A-10-76809 and JP-A-10-76809
There is one disclosed in, for example, Japanese Patent No. 181311. Each of these pneumatic tires, under the action of tread rubber with a two-layer structure, simultaneously reduces both passing noise and acceleration noise generated from the tire, steering stability on wet road surfaces, and vibration riding comfort. An object of the present invention is to suppress the deterioration of each tire until the end of use thereof, and to improve both grip performance and tread rigidity of the two-wheeled tire, which are in conflict with each other.

[0003]

However, in such conventional tires, basically, the ratio of the inner and outer rubber layers to the tread rubber is made substantially constant over the entire tread width. Yes, therefore, under the action of the ridge provided on the vulcanizing mold, when forming a circumferential groove in the tread portion, in each of those inner and outer layer rubber,
Even if displacement flow occurs due to the ridge,
At each land portion separated by a circumferential groove, each rubber of the inner and outer layers will exhibit a substantially symmetric occupancy on each side of the land centerline.

[0004] For this reason, when the tire rolls, the tread land portion is compressed and horizontally expanded and deformed in the ground contact surface thereof due to being restrained by the road surface. The so-called crushing forces acting as the reaction forces acting inward in the width direction from the respective side edges of the land portion are both equal in magnitude, and the crushing forces are mutually offset in the land portion. Thus, in the conventional tire, the crushing force generated as described above cannot be effectively used to increase the cornering power of the tire during the turning operation of the vehicle and, consequently, to improve the maneuverability.

The present invention has been made in view of such a point of the prior art, and the crushing force generated on the tread land portion is asymmetrically occupied by two or more layers of rubber with respect to the land center line. Another object of the present invention is to provide a pneumatic tire that is effectively used for increasing cornering power, thereby improving the controllability.

[0006]

A pneumatic tire according to the present invention comprises a tread rubber having at least two layers of rubber having different dynamic elastic moduli, and is divided by a plurality of circumferential grooves. In the other land parts except the center land part, the ratio of the rubber with the highest dynamic elastic modulus to the tread rubber is larger on the tread end side than on the tread center side of the land part. Things.

In other pneumatic tires, the ratio of the rubber having the lowest dynamic elastic modulus to the tread rubber in the tread rubber, especially in the land portions other than the center land portion, is calculated from the tread center side of the land portion. It is smaller at the end.

In any of these pneumatic tires, the dynamic elastic modulus of the tread end portion of the land portion is higher than that of the tread center side, so that the rigidity of the tread end portion of the land portion is increased. Because it is higher than the center side,
When the tread, and eventually the compressive deformation of the land due to the ground contact, in the part of the land where the high rigidity rubber ratio is large,
Compressive deformation is mainly performed with low-rigid rubber having a small rubber ratio, and compressive deformation is concentrated on the low-rigid rubber to increase the amount of swelling deformation. As a result, the reaction force also increases. The crushing force of the high rigidity portion of the land portion is larger than the low stiffness portion of the land portion, so that the crushing force in the width direction of each land portion is better in the tread center side than in the opposite direction. In other words, an excessive crushing force directed toward the tread center is constantly generated on the land.

Incidentally, such a surplus crushing force is generated substantially symmetrically with respect to the tire equator when the vehicle is running straight, and is offset by each other. Has no effect.

However, when the vehicle turns, each tire comes into contact with the outer part of the turn particularly strongly, while the contact pressure decreases in the inner part of the turn.
Since most of the roads tend to lift from the road surface, the land contraction on the ground contact surface becomes particularly large outside the turn, and the excess crushing force generated on each land and directed toward the tread center is reduced. The maneuverability is advantageously improved since it is much greater than a similar force in the inner part of the turn, which will effectively contribute to an increase in cornering power. Here, the cornering power is generally defined as the ratio of the cornering force to the slip angle in a small range of the slip angle.

In such a tire, preferably, a rubber having a low dynamic elastic modulus is provided in a large amount on the tread center side of the land portion other than the land portion at the center except for a rubber having a high dynamic elastic modulus. A large amount of rubber having a high dynamic elastic modulus is provided on the tread end side of the land portion with respect to a rubber having a low dynamic elastic modulus.

[0012] Preferably, the rubber having a high dynamic elastic modulus at a position 20% of the land width from the side edges of the tread center and the tread end side of the land other than the center land, The proportion of the tread rubber in the tread edge is larger than that in the tread center.

[0013] In this case, the ratio of the rubber having a high dynamic elastic modulus to the tread rubber particularly between the side edges of the tread center side and the tread end side and 20% of the land width. Is preferably gradually increased from the tread center side toward the tread end side.

According to the former, the position of 20% from the land side edge is specified, so that the influence of the flow of rubber when the circumferential groove is formed with the vulcanizing mold is advantageously removed, and the dynamic range is reduced. The arrangement ratio of the rubber having a high elastic modulus can be more objectively, specifically, and clearly compared.

According to the latter, local unevenness of rigidity can be suppressed and the production can be facilitated by gradually increasing the rubber having a high dynamic elastic modulus.

In these cases, the ratio of the rubber having a high dynamic modulus to the tread rubber at the position of 20% is 10% on the tread end side from the tread center side.
% Or more is preferable. According to this, the action or effect described above can be made more remarkable.

Preferably, the ratio of the rubber having a high dynamic elastic modulus to the tread rubber at a position 20% of the land width from the side edge on the tread center side is 10 to 30%, or The ratio of the rubber having a high dynamic elastic modulus to the tread rubber at a position 20% of the land width from the side edge on the end side is set to 40 to 60%.

In the former, when the proportion of the rubber having a high dynamic elastic modulus is less than 10%, the thickness of the rubber becomes too small, resulting in manufacturing instability. The compression difference between the rubber having a low dynamic elastic modulus and the tread end portion is reduced, and the difference in the crushing force is less likely to occur.

In the latter case, if the ratio of the rubber having a high dynamic elastic modulus is less than 40%, the difference in the crushing force is difficult to appear, and if it exceeds 60%, the thickness of the rubber having a low dynamic elastic modulus is too small. Therefore, instability in processing and manufacturing remains.

More preferably, the dynamic elastic modulus of the rubber having a low dynamic elastic modulus is 10 to 50% smaller than that of the rubber having a high dynamic elastic modulus under the condition of 1% strain at 30 ° C. .
According to this, it is easy to concentrate the deformation due to the compression on the rubber portion having a low elastic modulus and to create an imbalance in the surface deformation.

More specifically, a rubber having a low dynamic elastic modulus is disposed on the inner layer side, and a rubber having a high dynamic elastic modulus is disposed on the outer layer side. The dynamic elastic modulus under the condition of 1% strain was 5.0 to 11.0 MPa for the inner rubber and 10.0 for the outer rubber.
To 16.0 MPa, or a rubber having a low dynamic elastic modulus is disposed on the outer layer side, and a rubber having a high dynamic elastic modulus is disposed on the inner layer side.
The dynamic elastic modulus under the condition of 1% strain at 30 ° C. was 10.0 to 16.0 MPa for the outer layer rubber, and 11.0 to 11.0 for the inner layer rubber.
Preferably, the pressure is 24.0 MPa.

In the above case, the rubber having a low dynamic elastic modulus is disposed on the inner layer side and the rubber having a higher dynamic elastic modulus is disposed on the outer layer side, so that the compressive deformation of the surface rubber on the tread center side of the land can be reduced. The crushing force can be reduced, and the dynamic elastic modulus of the inner layer rubber is set to 5.0 to 11.0 MPa, and that of the outer layer rubber is set to 10.0 to 16.0 MPa, whereby the tread center side is reduced. Crushing deformation can be reduced by 20 to 60%.

In the latter case, a rubber having a low dynamic elastic modulus is disposed on the outer layer side and a rubber having a high dynamic elastic modulus is disposed on the inner layer side, so that the compression is concentrated on the surface rubber on the tread end side of the land portion. The lashing force can be increased, and the outer layer rubber has a dynamic elastic modulus of 10.0 to 16.0 MPa and the inner layer rubber has a dynamic elastic modulus of 11.0 to 24.0 MPa, so that crushing on the tread end side can be achieved. 20-60 deformation
% Can be increased.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the tread width direction showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a tread rubber, which is composed of two layers, an inner rubber 2 and an outer rubber 3.

Here, the dynamic elastic modulus of the inner rubber 2, more precisely, the dynamic elastic modulus under a strain of 1% at 30 ° C. is made smaller than the similar dynamic elastic modulus of the outer rubber 3. With
The tread rubber 1 has a plurality of circumferential grooves 4 in the figure.
Is formed to divide the five-article land portions 5 and 6 into tread portions.

Here, the outer layer having a high dynamic modulus of elasticity in each of the land portions 5 except for the center land portion 5 located on the tire equatorial plane among the land portions 5 and 6 thus classified. The ratio of rubber 3 to tread rubber 1 is calculated as
At the tread end side than at the tread center side. In other words, in each land portion 6, the ratio of the inner rubber 4 having a low dynamic elastic modulus to the tread rubber 1 is larger on the tread center side of the land portion 6 than on the tread end side.

In this case, it is preferable that the dynamic elastic modulus of the inner rubber 2 be lower than that of the outer rubber 3 by 10 to 50%. More specifically, the dynamic elastic modulus of the inner rubber 2 is 5%. It is preferable that the pressure be in the range of 0.0 to 11.0 MPa and that of the outer layer rubber 3 be in the range of 10.0 to 16.0 MPa.

Preferably, as shown in an enlarged sectional view of one land portion 6 in FIG. 2, the land portion 6 has a land portion width WR of 2 mm from the side edges of the tread center side and the tread end side.
In each of the 0% positions, the ratio of the outer rubber 3 to the tread rubber 1 at the tread end side from the tread center side is increased by 10% or more, and more preferably, between the two positions. Increase the ratio gradually.

More preferably, the ratio of the outer layer rubber 3 to the tread rubber 1 at a position 20% of the land width WR from the side edge of the land portion 6 on the tread center side is 10%.
Preferably, the ratio of the outer rubber layer 3 to the tread rubber 1 at a position 20% of the land width WR from the side edge of the tread rubber end side of the land portion 6 to the tread rubber 1 is 40 to 60%.
% Range.

FIG. 3 is a sectional view similar to FIG. 1 showing another embodiment. This is because the inner rubber layer 12 constituting the tread rubber 11 is a rubber having a high dynamic elastic modulus, while the outer rubber layer 13 is a rubber having a low dynamic elastic modulus.
In this case, the dynamic elastic modulus of the inner rubber 12 is set to 11.0 to
It is preferable that the pressure is in the range of 24.0 MPa and the dynamic elastic modulus of the outer rubber 13 is in the range of 10.0 to 16.0 MPa. Other preferred embodiments are the same as those described above.

According to the tire configured as described above,
The crushing force in each direction based on the contraction of the land portion 6 in the width direction, which is generated on the ground contact surface when the tire is rolling, is enlarged in FIG. 4A using the embodiment shown in FIG. 3 as an example. As shown, the portion facing the tread center side is larger than the portion facing the tread end side, so that the surplus crushing force F facing the tread center side always acts on each land portion 6 in the ground contact surface. Will be.

Therefore, when the vehicle turns, the surplus crushing force F of the land portion 6 located outside the turn effectively contributes to an increase in cornering force and, consequently, an increase in cornering power. Drivability is advantageously improved.

On the other hand, in the prior art in which the inner and outer two layers of rubber having different dynamic elastic moduli are arranged at a substantially uniform ratio over the entire width of the land portion, as shown in FIG. Since the crushing forces f generated in the width direction of the land portion and having different directions are substantially the same in magnitude, there is no room for the generation of the surplus crushing force F as described above. We can't hope for more power.

[0034]

EXAMPLE 1 The tire size was 195/65 R14, the applicable rim was 6 J, the air pressure was 200 KPa, and the load was 40.
When the cornering power is set to 00N, the speed is 50km.
/ H, and the difference in lateral force at a slip angle of 0 ° and 1 ° was measured and evaluated by an index. The result was as shown in Table 1. The larger the index value, the better the result. Table 1
Each of the example tire and the comparative tire 1 has the configuration and specifications shown in FIGS. 5 (a) and 5 (b).

The comparative tire 2 has a tread structure shown in FIG. 4 (b). The dynamic elastic modulus of the inner rubber is 14.0 MPa, and that of the outer rubber is 11.0 MPa.
The comparative tire 3 has a dynamic elastic modulus of the inner and outer rubber layers opposite to that of the comparative tire 2.

[0036]

[Table 1]

Example 2 The cornering power was measured in the same manner as in Example 1, and the cross-section height was 10 m on a 1.7 m diameter tram.
m, a cleat having a width of 15 mm was attached, and the P-P values of the vertical force generated on the tire shaft when the cleat was laid at 50 km / h were measured. . Regarding the PP values in the table, the smaller the index value, the better the result. The example tire and the comparative tire are shown in FIGS. 6 and 5, respectively.
It had the specifications shown in (b).

[0038]

[Table 2]

[0039]

Thus, according to the present invention, the tread rubber is constituted by a plurality of inner and outer rubber layers having different dynamic elastic moduli, and the occupation ratio of each rubber in the width direction of each land portion is appropriately selected. By doing so, the cornering power of the tire can be effectively increased, and the maneuverability can be advantageously improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in a tread width direction showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an arrangement of an inner rubber and an outer rubber.

FIG. 3 is a sectional view similar to FIG. 1, showing another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a state in which an excess crushing force is generated.

FIG. 5 is a view showing dimensions of an example tire and a comparative tire.

FIG. 6 is a view showing dimensions of another example tire.

[Explanation of symbols]

 1,11 Tread rubber 2,12 Inner layer rubber 3,13 Outer layer rubber 4 Circumferential groove 5,6 Land F Excessive crushing force

Claims (11)

[Claims] 1. A pneumatic tire comprising a tread rubber having at least two inner and outer rubber layers having different dynamic elastic moduli, and having land portions divided by a plurality of circumferential grooves. A pneumatic tire in which the ratio of the rubber having the highest dynamic elastic modulus to the tread rubber in the land portion other than the land portion is larger on the tread end side than on the tread center side of the land portion. 2. A pneumatic tire comprising a tread rubber having at least two layers of rubber having different dynamic elastic moduli, and having a land portion divided by a plurality of circumferential grooves. A pneumatic tire in which the ratio of the rubber having the lowest dynamic elastic modulus to the tread rubber in the tread rubber is smaller on the tread end side than on the tread center side of the land portion other than the land portion. 3. In a land portion other than the center land portion, a large amount of rubber having a low dynamic elastic modulus is disposed on the tread center side of the land portion with respect to rubber having a high dynamic elastic modulus. 3. The pneumatic tire according to claim 1, wherein a large amount of rubber having a high dynamic elastic modulus is disposed on the tread end side with respect to the rubber having a low dynamic elastic modulus. 4. A tread rubber of a rubber having a high dynamic elastic modulus at a position 20% of a land width from each side edge of a tread center and a tread end side of a land portion other than a center land portion. The pneumatic tire according to any one of claims 1 to 3, wherein a ratio of the pneumatic tire is larger on a tread end side than on a tread center side. 5. A rubber having a high dynamic elastic modulus between 20% of a land portion width from a tread center side and a tread edge side of each of the other land portions except the center land portion, The pneumatic tire according to claim 4, wherein the proportion of the tread rubber is gradually increased from the tread center side toward the tread end side. 6. A tread rubber of a rubber having a high dynamic elastic modulus at a position of 20% of a land width from a tread center and a side edge of a tread end side of a land other than a center land. 6. The pneumatic tire according to claim 4, wherein a ratio of the pneumatic tire to the tread edge is greater than the tread center side by 10% or more. 7. The proportion of the rubber having a high dynamic elastic modulus in the tread rubber at a position 20% of the land width from the side edge of the tread center side of the land except the center land is 10 to 30.
%. The pneumatic tire according to any one of claims 4 to 6, wherein 8. The proportion of rubber having a high dynamic elastic modulus in the tread rubber at a position 20% of the land width from the side edge of the tread end side of the land except the center land is 40 to 60. %. The pneumatic tire according to any one of claims 4 to 7, wherein 9. The dynamic elastic modulus of a rubber having a low dynamic elastic modulus,
The pneumatic tire according to any one of claims 1 to 8, which is 10 to 50% smaller than that of a rubber having a high dynamic modulus under the condition of 1% strain at 30 ° C. 10. A rubber having a low dynamic elastic modulus is provided on an inner layer side and a rubber having a high dynamic elastic modulus is provided on an outer layer side, and the respective rubbers are subjected to a condition of 1% strain at 30 ° C. Dynamic elastic modulus of the inner layer side rubber is 5.0 to 11.0M
The pneumatic tire according to any one of claims 1 to 9, wherein Pa and the outer layer side rubber have a pressure of 10.0 to 16.0 MPa. 11. A rubber having a low dynamic elastic modulus is provided on an outer layer side and a rubber having a high dynamic elastic modulus is provided on an inner layer side, and the respective rubbers are subjected to a condition of 1% strain at 30 ° C. Dynamic elastic modulus in the outer layer side rubber is 10.0 to 16.0.
The pneumatic tire according to any one of claims 1 to 9, wherein the inner layer rubber has a pressure of 11.0 to 24.0 MPa.