JPH11321237A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve all wear resistance, steering stability, tire noise and vibration performance by arranging a rubber more rigid than the inside one on the outside area of a tread part, imparting a specified hardness and a specified hardness different to each of the rubbers, and setting the interface position within the side wall surface of one vertical groove situated closer to the outside from the equatorial plane. SOLUTION: The tread pattern is formed closer to the tire outside area, when mounted on a vehicle, from the equatorial plane C of a tread part 1, and the tier outside part has an asymmetric pattern consisting of a rib pattern or highly rigid block pattern. The tread pattern 1 is formed by using rubbers having different hardness between the outside part from a main groove 2, which is one of vertical grooves situated close to the tire outside, and the inside part thereof. Namely, the rubber hardness of the outside rubber 1a is set to 60-70, and the hardness of the inside rubber 1b is set to 50-60, so that the hardness difference of the both is 6-15. According to this, the rigidity of the tire outside to which a large load is added in cornering can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire mainly used for minivans and one-box vehicles, the tread pattern having an asymmetric pattern.

[0002]

2. Description of the Related Art Minivans and one-box vehicles have a higher center of gravity than sedan-type vehicles, so that a heavy load is applied to the outside of the tire (outside when mounted on the vehicle) during cornering. . Therefore, the load of the pattern consisting of ribs and blocks outside the tire is large,
A phenomenon in which the wear of the rubber on the outer side of the tire is accelerated is likely to occur.

[0003] Further, if the block rigidity of the tread pattern is increased in order to correct these problems, the flexibility of the tire as a whole is reduced, and the ride comfort and the pattern noise may be deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and provides a combination of an asymmetrical tread pattern between the tire outer side and the tire inner side when mounted on a vehicle and an asymmetrical arrangement of rubber materials having different rigidities. Abrasion and steering stability,
An object of the present invention is to provide a pneumatic radial tire that can achieve both tire noise and vibration performance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 has a vertical groove extending in the tire circumferential direction on the outer periphery of the tread portion, and the tread pattern is more asymmetric than the asymmetric pattern. The tread portion is formed by arranging a rubber having higher rigidity than the inner side in an outer region of the tire when the vehicle is mounted, the outer rubber has a rubber hardness of 60 to 70, and the rubber of the inner rubber. Hardness is 50 ~
60, the hardness difference between the two is 6 to 15, and the interface position between the outer rubber and the inner rubber is set in the side wall surface of one longitudinal groove which is unevenly distributed to the outside of the tire from the crown center. It is characterized by the following.

According to the tire having the above configuration, the rigidity on the outside of the tire, which exerts a heavy load during cornering, is high, so that the progress of wear on the outside of the tire is suppressed,
Also, steering stability is well maintained. In addition, the rubber inside the tire from the portion of the vertical groove unevenly distributed on the outside of the tire has a lower rigidity than the outer rubber, whereby the flexibility of the entire tire can be secured, and the deterioration of ride comfort and the deterioration of pattern noise are reduced. Can be suppressed. In particular, when the rubber hardness and the hardness difference are in the ranges described above, each of the above-described properties can be satisfactorily secured.

The interface between the outer rubber made of the high-rigidity rubber and the inner rubber having a lower rigidity is located in the side wall surface of the vertical groove on the outer side of the tire. Since it is not present on the surface of the part or on the bottom of the vertical groove, there is no risk of step wear and cracking of the groove bottom due to the difference in rigidity.

The invention according to claim 2 is characterized in that the interface between the outer rubber and the inner rubber is inclined inward from the inner side wall surface of the vertical groove when the vehicle is mounted on the vehicle. Accordingly, the tread portion is made of two types of rubbers having different rigidities, so that the tire has good contact with the ground and good grip performance when traveling on a wet road surface.

According to a third aspect of the present invention, in the radial tire, the groove area ratio (S1) of the outer periphery of the tire and the groove area ratio (S2) of the inner side of the tire when the vehicle is mounted on the outer periphery of the tread portion.
And the ratio (S1 / S2) is 0.6 <(S1 / S2) <
It is set in the range of 1.0. As a result, the tread pattern forms an asymmetrical pattern with higher rigidity on the outer side of the tire when mounted on the vehicle, and this is combined with the effect of the high-rigidity outer rubber, thereby increasing the effect of suppressing the progress of wear.

According to a fourth aspect of the present invention, an interface between the outer rubber and the inner rubber is set at a position at least 1.5 mm above a treadwear indicator on a side wall surface in the vertical groove.

The invention according to claim 5 is characterized in that the same high-rigidity rubber as the outer rubber is continuously provided as a base layer from the outer rubber portion under the inner rubber. . Thereby, the responsiveness of the tire is further improved. In particular, the interface between the base layer and the inner rubber on it,
If the tire is provided at a position above the treadwear indicator, high-rigidity rubber will be exposed over the entire tread at the end of tire wear, and good driving performance can be ensured to the end.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the embodiments shown in the drawings.

FIG. 1 is a partially developed plan view illustrating a tread pattern of a pneumatic radial tire (T) of the present invention, FIG. 2 is a schematic cross-sectional view of the tire in the width direction, and FIG.
Shows an enlarged sectional view of a part of the above.

As shown in FIG. 2, the radial tire (T) has a bead portion (1) having bead cores (11) on both sides.
2), a sidewall portion (13) extending radially outward from the bead portion (12), and a tread portion (1) connecting the upper end thereof, and both ends are folded back by a bead core (11) along the inner periphery thereof. Equipped with a supported carcass (14),
Further, a belt layer (15) is provided between the tread portion (1) and the carcass (14), and its reinforcing structure is the same as that of a general radial tire, so that detailed description is omitted.

In the figure, (2) is one main groove as a vertical groove formed on the outer peripheral surface of the tread portion (1) and extending linearly or zigzag in the tire circumferential direction, (3).
Is a horizontal groove in a direction crossing the main groove (1). In the case of the figure,
When the vehicle is mounted on the vehicle (the state in which the tire is mounted on the vehicle, the same applies hereinafter) than the main groove (2), a sub-groove (a vertical groove in the tire circumferential direction having a width smaller than the main groove (2)) is provided outside the tire. 4) is formed. (5) is an auxiliary groove connecting the horizontal grooves (3). 2 and 3, the grooves other than the main groove are omitted.

As shown in the figure, the tread pattern is such that the main groove (2) is formed so as to be unevenly distributed from the crown center (C) of the tread portion (1) to the tire outer region when the vehicle is mounted. The outer portion of the tire forms an asymmetric pattern composed of a rib pattern or a block pattern having high rigidity (a so-called high rigidity pattern).

For example, the outer periphery of the tread portion (1) when the vehicle is mounted is divided into an inner portion and an outer portion by a crown center (C), and a groove area ratio (S1) on the tire outer side and a groove area ratio (S2) on the tire inner side are determined. The ratio (S1 / S2) is 0.6 <(S1
/S2)<1.0, and the outside of the tire is a high rigidity pattern. The groove area (S1) (S2
) Is the ratio (groove area / contact area) between the groove area and the contact area on the outside and inside of the tire, respectively.

The tread portion (1) has a rubber portion outside the main groove (2), which is one of the longitudinal grooves that are unevenly distributed from the crown center (C) to the outside of the tire when the vehicle is mounted, and The rubber in the inner portion is made of a rubber compound having a different rigidity, so that the outer rubber (1
The rubber having a higher rigidity than the inner rubber (1b), that is, a rubber having a higher hardness as described later is disposed in a). In particular, the interface position (6a) that appears on the tire surface between the outer rubber (1a) and the inner rubber (1b) is set in the side wall surface (2a) of one main groove (2) unevenly distributed on the outer side of the tire. Have been.

The interface position (6a) is located in the main groove (2).
May be anywhere in the side wall surface (2a) from the boundary with the groove bottom (2b) to the boundary with the outer periphery of the tread portion (1), but is particularly preferably provided in the main groove (2). The treadwear indicator (7) is preferably provided at a position at least 1.5 mm above the treadwear indicator (7) (on the outer peripheral surface side of the tread).

That is, if the interface position (6a) is present on the surface of a land portion such as a block or a rib, a difference in rigidity tends to cause step wear, and the interface position (6a).
If a) is at the groove bottom (2b) of the main groove (2), cracks tend to occur at the groove bottom. If the interface position (6a) is located on the groove bottom side with respect to the treadwear indicator (7), the effect of increasing the grip property by the high-rigidity rubber when the wear progresses cannot be obtained. Therefore, it is preferable that the interface position (6a) is set within the above-mentioned range of the side wall surface (2a) of the main groove (2) as described above.

The interface (6) between the outer rubber (1a) and the inner rubber (1b) extends inward from the inner side wall surface (2a) of the main groove (2) when mounted on the vehicle. 1
5) It is preferable to be inclined to the side. The interface (6) is not necessarily required to be linear, and may be one in which the outer rubber (1a) and the inner rubber (1b) enter each other and are deformed, or may be inclined as a whole. Accordingly, when the abrasion progresses beyond the interface position (6a) of the side wall surface (2a), the ratio of the outer rubber (1a) made of a high-rigidity rubber having a large friction coefficient to the total contact surface increases. As a result, the grip when traveling on a wet road surface is increased.

The outer rubber (1) made of the above-mentioned highly rigid rubber is used.
As a), a rubber compound having a higher rubber hardness and a higher friction coefficient (μ) than the inner rubber (1b) is used.

That is, the rubber hardness of the outer rubber (1a) is 60 to 70, and the rubber hardness of the inner rubber (1b) is 50 to 70.
60, so that the hardness difference between the two ranges from 6 to 15. When the hardness difference is smaller than the range,
If the outer rubber (1a) is made of a high-rigidity rubber, the effect cannot be sufficiently obtained, and if the hardness difference is larger than the above range, the uniformity of the tire may be reduced and the maneuverability may be deteriorated.

The range of the friction coefficient (μ) of the tread rubber (the ratio of the friction coefficient between the outer rubber and the inner rubber) is 100 to 1
It is preferably in the range of 15. For example, when the rubber hardness of the inner rubber and the outer rubber is 60:64, the friction coefficient ratio is
100: 107. Here, the tread rubber friction coefficient (μ) is the maximum value of the longitudinal force between 0 and 1 sec after the start of tire locking when a braking force is applied during running at a speed of 60 km / h.

In the above embodiment, when the main groove (2) and the sub-groove (4) exist as the vertical grooves in the tire outer region when the vehicle is mounted, the interface position is set in any of the vertical grooves. However, in practice, it is desirable to set it in the side wall surface of the main groove (2) as shown in the figure. When a plurality of main grooves (2) are provided outside the tire, the interface position may be set in any of the main grooves.

FIG. 4 shows an embodiment in which the inner rubber (1b) is used.
Below, there is shown a case where the same high-rigidity rubber as the outer rubber (1a) is provided as a base layer (1c) in a continuous form from the portion of the outer rubber (1a). The base layer (1c) has an interface (8) with the inner rubber (1b) on the base layer (1c) as long as the interface position (6a) on the side wall surface (2a) of the main groove (2) is equal to or less than the interface position (6a). It may have a thickness of at least 1.0 mm, but preferably has a thickness of at least 1.0 mm or more from the viewpoint of ensuring the responsiveness of the tire. In particular, the interface (8) is preferably provided so as to be located above the treadwear indicator (7), so that high-rigidity rubber is exposed throughout the tread at the end of tire wear. This means that good driving performance can be ensured until the end.

The base layer (1c) may be formed by extruding the corresponding rubber integrally with the outer rubber (1a) and then molding the same, or may be formed separately from the outer rubber (1a). It is also possible to arrange a sheet-like rubber over the entire tread portion, mount the outer rubber and the inner rubber on this, mold them, and integrate them by vulcanization.

The pneumatic radial tire (T) of the above-described embodiment is mounted on a wheel with the outer rubber (1a) made of high-rigidity rubber facing outward.

In this use, since the tread portion (1) is formed of a highly rigid rubber on the outside of the tire when the vehicle is mounted, this is combined with the pattern rigidity of the asymmetrical pattern, so that the tread portion (1) can sufficiently withstand a large load applied to the outside of the tire during cornering. Endurance, whereby the progress of wear on the outside of the tire is suppressed, and steering stability is well maintained. In addition, the inner rubber (1b) has a lower rigidity than the outer rubber (1a) with respect to the outer side of the tire, so that the flexibility of the tire as a whole can be sufficiently ensured, and the riding comfort and the pattern noise are deteriorated. Can also be suppressed.

In particular, the interface between the outer rubber (1a) and the inner rubber (1b) made of the high-rigidity rubber is located in the side wall surface of the vertical groove on the outer side of the tire, and blocks such as tread pattern blocks and ribs. Since it is not present on the land surface or on the bottom of the vertical groove, there is no risk of step wear and groove bottom cracking due to the difference in rigidity.

The outer rubber (1) is placed under the inner rubber (1b).
When the base layer (1c) made of the same high rigidity rubber as in a) is provided, the steering stability is further improved.

(Embodiment) Table 1 below shows a comparison test of each performance of abrasion, crack, steering stability, riding comfort, and pattern noise for each tire of the embodiment and the comparative example set under the following tire conditions. Is shown. The tire used for the test had a tire size of 215.
/ 65R15 96H, two steel belt tires. The evaluation of each performance is indicated by an index with Comparative Example 1 being a conventional symmetrical pattern tire being 100, excluding cracks, and the larger the numerical value, the better the performance.

The test vehicle was a domestic minivan 2400
cc and the tire internal pressure were 230 kPa. Each performance test was performed by the following method.

The wear (outside shoulder drop, step) and cracks were evaluated after traveling 1200 km on a general road, and the steering stability and riding comfort and the pattern noise were evaluated by the sensory evaluation of the driver.

[0035]

[Table 1] As described above, the tires of Examples 1 and 2 of the present invention are different from the comparative examples in that the wear performance and steering stability are suppressed while suppressing the deterioration of ride comfort and pattern noise without generating step wear and cracks. The performance has been greatly improved. In particular, the tire of Example 2 in which a base layer made of a high-rigidity rubber was provided under the inner rubber had further improved steering stability.

[0036]

As described above, according to the present invention, it is possible to increase the rigidity of the outer side of the tire subjected to a large load at the time of cornering, to improve the steering stability and the uneven wear resistance performance, and to improve the tire as a whole. As a result, it is possible to suppress the deterioration of the ride comfort and the deterioration of the pattern noise by ensuring a high degree of flexibility, and there is no possibility of the occurrence of step wear and cracks.

[Brief description of the drawings]

FIG. 1 is a schematic development plan view of a tread pattern of a pneumatic radial tire according to the present invention.

FIG. 2 is a schematic cross-sectional view of the tire in the circumferential direction.

FIG. 3 is an enlarged sectional view of a part of the above.

FIG. 4 is a partial cross-sectional view showing another embodiment.

[Explanation of symbols]

 (T) Pneumatic radial tire (1) Tread portion (1a) Outer rubber made of high rigidity rubber (1b) Inner rubber (1c) Base layer (2) Main groove (2a) Side wall surface (2b) Groove bottom (3) Lateral groove (4) Secondary groove (5) Auxiliary groove (6) Interface (6a) Interface position (7) Treadwear indicator (8) Interface between base layer and inner rubber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 11/24 B60C 11/04 H 11/06 B

Claims (6)

[Claims] 1. A pneumatic radial tire having a vertical groove extending in a tire circumferential direction on an outer periphery of a tread portion and having a tread pattern formed of an asymmetric pattern, wherein the tread portion is higher than the inner side on the tire outside when the vehicle is mounted. The outer rubber has a rubber hardness of 60 to 70, the inner rubber has a rubber hardness of 50 to 60, and the hardness difference between the two is 6 to 15. A pneumatic radial tire, wherein an interface position between the tire and the crown center is set in a side wall surface of one longitudinal groove which is located outside the tire from the crown center. 2. The air according to claim 1, wherein an interface between the outer rubber and the inner rubber is slanted inward from an inner side wall surface of the vertical groove when the vehicle is mounted on the vehicle. Included radial tire. 3. The ratio (S1 / S2) of the groove area ratio (S1) outside the tire to the groove area ratio (S2) inside the tire when the vehicle is mounted on the outer periphery of the tread portion is 0.6 <(S1 / S2). ) <1.
The pneumatic radial tire according to claim 1, wherein the radial tire is set to 0. 4. An interface between the outer rubber and the inner rubber, wherein:
The pneumatic radial tire according to any one of claims 1 to 3, wherein the pneumatic radial tire is set at least 1.5 mm above a treadwear indicator on a side wall surface in the vertical groove. 5. The lower part of the inner rubber is provided with the same high-rigidity rubber as the outer rubber as a base layer continuously from the outer rubber part.
The pneumatic radial tire according to any one of the above items. 6. The pneumatic radial tire according to claim 5, wherein an interface between the base layer and the inner rubber on the base layer is provided at a position above a treadwear indicator.