JPH09136512A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the turning performance of an oblate tire, particularly one with an oblateness of 60% or less, without deteriorating its durability, and to restrain degradation of its running performance due to heating (thermal sagging). SOLUTION: In a tire whose oblateness TH/TW is set to 60% or less, at least one fine groove 12 having a groove width Wg of less than 3.0mm and extending in the circumferential direction of the tire is formed in the outer surface S of a shoulder part 11 between a height position Q1 separate from a bead baseline L by a distance L0 that is 0.6 times the tire cross-sectional height TH and the height position Q2 of the grounded outer end E of the tread, the fine groove 12 having a circular wide part 12B at its lower end where it has a bottom groove width Dg larger than the groove width Wg; the groove depth Lg from the outer surface S of the shoulder part 11 to the deepest point of the wide part 12B is 0.2 to 0.6 times the shortest distance L1 from the outer surface S to a carcass 6 or a belt layer 7.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a flatness of 60 in particular.
% Of flat tires, in which the turning performance can be improved without impairing durability, and the deterioration of running performance (heat drop) due to heat generation can be suppressed.

[0002]

2. Description of the Related Art In recent years, as the performance and output of vehicles have increased, the rim diameter has to be increased in order to improve steering stability at high speeds even for tires. The flattening of tires with increased tread width is progressing.

However, particularly in a flat tire having an aspect ratio of 60% or less, a tread portion is reinforced over a wide range by a belt layer having a high modulus cord, and the tire as a whole is firmly restrained with a hoop effect. Due to this and the flat cross-sectional shape, the rigidity tends to be excessive at the shoulder portion from the tread outer end to the vicinity of the maximum width point of the side wall portion.

As a result, for example, as exaggeratedly shown in FIG. 9, when a lateral force F acts on the tire T at the time of turning, one end side a of the tread portion comes into contact with the ground contact shape S in such a direction as to rise from the road surface.
1 greatly changes, the turning area is reduced and the turning performance is impaired, and the characteristics of the tread rubber and tire cord deteriorate due to partial heat generation due to uneven contact pressure distribution, and the lap time deteriorates during continuous running etc. To do
There is a problem of causing so-called thermal sag.

Therefore, the invention according to claim 1 of the present invention is based on the fact that a fine groove extending along the tire circumferential direction is formed on the outer surface of the shoulder portion with a specific size and a specific shape. The purpose of the present invention is to provide a pneumatic tire that can improve the turning performance and the deterioration of running performance due to heat generation without deteriorating the performance.

In addition to the object of the invention described in claim 1, it is an object of the invention in claim 2 to provide a pneumatic tire capable of more reliably preventing a decrease in durability due to the formation of the narrow groove. It was done.

[0007]

[Means for Solving the Problems] Claim 1 of the present invention
The invention described has a carcass that folds around the bead core of the bead part from the tread part through the side wall part, and a belt layer arranged radially outside of the carcass and inside the tread part, and with respect to the tire width TW. A pneumatic tire having a flatness ratio TH / TW, which is a ratio of the tire cross-section height TH, of 60% or less, wherein the tire cross-section height TH is 0.6 outside the bead baseline of the bead portion in the tire radial direction. A height position Q1 which is a double distance L0,
At least one sipe-shaped narrow groove having a groove width Wg of less than 3.0 mm and extending along the tire circumferential direction is formed on the outer surface of the shoulder portion between the tread ground contact outer end and the height position Q2 and is substantially the same as the outer surface. The narrow groove is formed at a right angle, and the narrow groove has an arc-shaped wide portion having a bottom groove width Dg larger than the groove width Wg at its lower end, and from the outer surface of the shoulder portion where the narrow groove is provided, the wide portion is formed. The groove depth Lg up to the deepest point of is the shortest distance L1 from the outer surface to the carcass or the belt layer.
It is characterized by setting 0.2 to 0.6 times.

According to the second aspect of the present invention, the number of fine grooves formed is plural, and the interval P between adjacent fine grooves is 10.
It is characterized by being less than mm.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section of a tire that is mounted on a standard rim defined by JATMA and the like and is filled with an internal pressure of 0.5% of the standard internal pressure in a state of 0.5% internal pressure. , The aspect ratio TH / TW, which is the ratio of the tire cross-section height TH to the tire width TW, is 6
It is formed as a flat tire for passenger cars, which is 0% or less, 50% in this example. Incidentally, the tire shape in the 0.5% internal pressure state is generally substantially the same as the tire shape in the vulcanization mold.

The tire 1 has a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2.
And a bead portion 4 located at an inner end of each sidewall portion 3 in the radial direction of the tire. A toroidal carcass 6 is bridged between the bead portions 4 and 4 and a radial direction of the carcass 6 is provided. On the outside and inside the tread portion 2,
The belt layer 7 is wound.

The carcass 6 is formed from one or more carcass plies, for example, two carcass plies, which are folded back from the inside to the outside around the bead core 5 of the bead portion 4 from the tread portion 2 to the side wall portion 3. The carcass ply has a radial or semi-radial arrangement in which carcass cords made of organic fibers such as nylon, polyester, and rayon are inclined at an angle of 75 to 90 degrees with respect to the tire equator C. The carcass 6 has a high turn-up structure in which the folded-back portion 6A of at least one carcass ply is terminated in the vicinity of the maximum width position of the tire.
Bead apex rubber 8 that rises radially outward from the
At the same time, the bead portion 4 is reinforced and the tire lateral rigidity is enhanced.

The belt layer 7 is a carcass 6 in this example.
Has a two-layer structure of an inner belt ply 7A that is adjacent to the outer side in the radial direction and an outer belt ply 7B that is placed on the outer side of the belt ply 7A and 7B. The plies are inclined at an angle of 10 to 30 degrees and are arranged so as to intersect each other between the plies. As the belt cord, a high modulus cord having a tensile elastic modulus of about 2500 kg / mm ² or more, for example, an aromatic polyamide fiber cord or a metal cord such as steel is used. The inner belt ply 7A is formed slightly wider than the outer belt ply 7B, and the maximum belt ply width BW, which is the width of the inner belt ply 7B, is made substantially equal to the tread ground width SW. , The tread portion 2 is reinforced over its entire width with a hoop effect,
The tire is restrained with a low flatness of 60% or less.

Here, the tread ground contact width SW is JA
This means the width in the tire axial direction of the contact area on the tread surface that comes into contact with the ground when a standard load is applied to a tire mounted on a standard rim defined by the tire standards such as TMA and filled with standard internal pressure, and this contact area The outer end of the tire in the axial direction is referred to as a tread contact outer end E.

On the outer side in the radial direction of the belt layer 7,
In this example, the band layer 10 is additionally provided for the purpose of suppressing the lifting of the belt layer 7 due to centrifugal force or the like. The band layer 10 covers the outer end portion of the belt layer 7 and prevents the peeling from the outer end portion, and the edge layer ply 10A covers substantially the entire width of the belt layer 7 together with the edge band ply 10A and is in the tread surface. Each ply 10A, 10B comprises a band cord having a small modulus of low modulus such as nylon and spirally wound at an angle of 0 to 5 degrees with respect to the tire equator C, for example. Formed by.

Further, in order to improve the ground contact property of the tire 1 during turning, in the 5% internal pressure state, a distance L0 of 0.6 times the tire cross-section height TH is separated from the bead base line L to the outer side in the tire radial direction. At least one sipe-shaped narrow groove 12 extending continuously in the tire circumferential direction is formed on the outer surface S of the shoulder portion 11 between the barrel height position Q1 and the height position Q2 of the tread ground contact outer end E. Form. The bead base line L is a line in the tire axial direction that passes through the tire axial direction outer end point of the bead bottom surface 4S and forms a reference line for selecting the rim diameter of the applicable rim.

As shown in the enlarged view of FIGS. 2 and 3, the narrow groove 12 has a groove width Wg from the outer surface S and extends at a substantially right angle to the outer surface S. Arc-shaped wide portion 1 having a bottom groove width Dg larger than the groove width Wg of 12A.
It has a flask-like shape with 2B. Also, the body 1
The groove width Wg of 2A is less than 3 mm, and the groove depth Lg from the position of the outer surface S where the narrow groove 12 is provided to the deepest point of the wide portion 12B is the shortest from the outer surface S to the carcass 6 or the belt layer 7. It is set to 0.2 times or more and 0.6 times or less of the distance L1.

As described above, since the narrow groove 12 having the flask-like shape and the dimension is provided in the region Y of the shoulder portion 11 between the height positions Q1 and Q2, the durability is impaired. Without the shoulder part 11
The bending rigidity can be moderately relaxed, the ground contact property of the tread portion 2 at the time of turning can be improved, and the turning performance can be improved. Generally, when a sipe or a narrow groove having a groove depth of 0.2 times or more of the shortest distance L1 is provided in the shoulder portion 11, durability is significantly impaired.
It was found that by providing the arc-shaped wide portion 12B at the lower end, it is possible to suppress deterioration of durability up to a depth of 0.6 times the shortest distance L1, and it is possible to achieve both relaxation of rigidity of the shoulder portion 11 and maintenance of durability. It was possible to achieve it.

The narrow groove 12 has the height positions Q1 and Q2.
It is necessary to provide it in the region portion Y between them in order to obtain the effect of improving the turning performance, and as shown in FIG. 2, preferably, the position R on the outer surface S where the volume of rubber is the largest is R.
From the position R on the outer surface S in the vicinity of the belt layer 7
It is a position where the distance Ls to the outer end portion and the distance Lc from the position R to the carcass 6 become substantially coincident with each other.

The narrow groove 12 has a groove width Wg of 0.6.
To 2.5 mm, more preferably 1.2 to 2.0
When it is in the range of mm, the effect of relaxing the bending rigidity in the shoulder portion is high, which is desirable, but when it is 3.0 mm or more, the amount of deformation is remarkably increased such that the bending rigidity is excessively decreased, and turning performance is adversely affected. . The groove width Wg is 0.3 m
When it is less than m, it is difficult to form the fine groove 12 by vulcanization molding, which is not preferable.
As shown in Fig. 0 to 0 during vulcanization molding or after processing.
The sipe 13 of 0.3 mm may be formed, and thereafter, the flask-shaped cutter 14 may be moved along the sipe 13 to cut out the wide portion 12B to form the narrow groove 12 of a predetermined shape. In this case, the groove width Wg can be reduced to about 0 mm.

Further, the groove depth Lg is preferably 0.4 to 0.5 times the shortest distance L1 in order to improve the turning performance, but when it is less than 0.2 times, the effect of relaxing the bending rigidity is obtained. Insufficiently, especially the unevenness of the contact pressure distribution cannot be eliminated, thermal sagging cannot be suppressed, and if it exceeds 0.6 times, the durability will drop rapidly and crack damage from the groove bottom will be induced. Not suitable.

Further, in the narrow groove 12, the wide portion 12B is formed by an arc having a diameter d equal to the bottom groove width Dg as in the present embodiment, but as shown in FIG. Alternatively, it can be formed by an elliptical curve in which the length of the minor axis is set equal to the bottom groove width Dg, and an arc-shaped curve in which a plurality of arcs having different curvatures are smoothly connected, and further, FIG. As shown in C), the upper region of the wide portion 12B may be formed by parallel lines or inclined lines.

The number of the thin grooves 12 formed can be at least one, for example, two or three. At this time, the interval P between the groove centers of the adjacent small grooves 12 is 10 mm.
The following is assumed. In such a case, interference occurs between the narrow grooves 12 and the internal stress is dispersed in a wider range, so that the durability can be maintained more reliably. In order to disperse the stress, it is preferable that the shape of each of the fine grooves 12 be the same,
For example, as shown in FIG. 8C, the narrow grooves 12 having different shapes are formed.
May be combined. The lower limit of the interval P is the bottom groove width Dg.
It is preferable that the rubber thickness t between the wide portions 12B and 12B is 3.0 mm or more.

[0023]

EXAMPLE 1 As shown in FIGS. 6A to 6D, the fine groove 12 having the structure shown in FIG. 1 and having the specifications shown in Table 1 is provided with the height position Q2 of the tread grounding outer end E and the rubber volume. Near the maximum position R, a height position Q1 separated by 0.6 TH from the bead base line L, and 0.
Tires with different tire sizes of 225 / 50R16 92V, which were formed at different heights of 55TH, were prototyped, and the turning performance of each trial tire when dry and wet, heat sag performance during continuous running, durability performance The respective tires were measured and compared with each other by an index with the conventional tire having no narrow groove being 100.

A) Dry turning performance: A test tire was mounted on all wheels of a vehicle (3000 cc FR passenger car) under the standard rim (16 × 7JJ) and standard internal pressure (2.2 kg / cm ² ), and the load was applied. Under a condition equivalent to 360 kg per tire, the dry turning test path of the test course was turned at a speed of a course having a constant radius, and the limit speed at which the vehicle could safely turn at this time was indicated by an index. The higher the value, the higher the limit speed and the better the turning performance.

(A) Wet turning performance: The limit speed at which the vehicle was allowed to turn while running on the wet turning test road under the same conditions as in the above item (a) was displayed as an index. The larger the value, the better the turning performance.

C) Heat-resistant sag performance: The circuit course is continuously run under the same conditions as the above item a).
The lap time at that time was displayed as an index. The larger the value, the better the heat-resistant sag performance.

D) Durability The circuit course is continuously run under the same conditions as in the above item a),
The distance traveled until failure was displayed as an index. The higher the value, the better the durability.

[0028]

[Table 1]

As shown in Table 1, when a narrow groove is provided in the area portion Y between Q1 and Q2, the turning performance is improved, and particularly when it is provided at the maximum rubber volume position R, the improving effect is enhanced. Can be confirmed.

[0030]

[Example 2] Groove width Wg and bottom groove width D as specified in Table 2
A tire of the same size (225 / 50R16 92V) in which the narrow groove 12 having a different g was formed at the maximum position R of the rubber volume was prototyped, and the turning performance during dry and wet, heat-resistant sag, as in Example 1 above. The performance and the durability performance were compared by an index with the conventional tire as 100.

[0031]

[Table 2]

As shown in Table 2, when the groove width Wg is less than 3 mm, the effect of improving the turning performance is exhibited, and in particular, 0.6 to
2.5 mm range, more preferably 1.2-2.0 m
It can be seen that the improvement effect is enhanced in the range of m.

[0033]

[Embodiment 3] As shown in Table 3, the groove width Wg is constant (1.2
mm), only the bottom groove width Dg is different, FIG. 3, FIG. 7 (A),
A tire of the same size (225 / 50R16 92V) in which the narrow groove 12 shown in (B) is formed at the maximum position R of the rubber volume was made as an experimental product, and the durability was set to 100 as that of the conventional tire, as in Example 1. I compared them with each other.

[0034]

[Table 3]

As shown in Table 3, since the arc-shaped wide portion is provided at the lower end of the narrow groove, it can be confirmed that the durability is maintained.

[0036]

[Embodiment 4] As shown in Table 4, the groove width Wg is constant (0.6
mm) and the bottom groove width Dg is constant (1.2 mm) and the groove depth Lg.
A tire of the same size (225 / 50R16 92V) in which the narrow groove 12 having a different shape is formed at the maximum position R of the rubber volume was manufactured as a trial, and the turning performance at the time of dry and wet and the heat-resistant sag were obtained as in Example 1. The performance and the durability performance were compared by an index with the conventional tire as 100.

[0037]

[Table 4]

As shown in Table 4, when the groove depth Lg is 0.2 to 0.6 times the shortest distance L1, the effect of improving the turning performance is exhibited, and the groove depth Lg exceeds 0.6L1 and becomes 0. It can be seen that the durability is significantly reduced when reaching 0.7L1.

[0039]

Fifth Embodiment As shown in FIGS. 8A) to 8C), a tire of the same size (225 / 50R16 92V) provided with a narrow groove having the specifications of Table 5 in the vicinity of the maximum position R of the rubber volume was manufactured. Similar to Example 1, the turning performance, the heat-resistant sag performance, and the durability performance during dry and wet were compared by an index with the conventional tire as 100.

[0040]

[Table 5]

As shown in Table 5, a plurality of narrow grooves can be provided, and the effect of improving the turning performance and the heat-resistant sag performance is exhibited even when the narrow grooves having different shapes are combined.

[0042]

Since the pneumatic tire of the present invention is constructed as described above, especially in a flat tire having an aspect ratio of 60% or less, the turning performance can be improved without impairing the durability and the heat generated by heat generation. It is possible to suppress deterioration of running performance (heat drop).

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a shoulder portion thereof.

FIG. 3 is an enlarged cross-sectional view showing a narrow groove.

FIG. 4 is a schematic view showing an example of forming a fine groove.

5 (A), (B) and (C) are cross-sectional views showing another embodiment of the narrow groove.

6 (A), (B), (C), and (D) are the first embodiment.
3 is a schematic cross-sectional view showing the fine groove formation position of the trial tire in FIG.

7 (A) and 7 (B) are cross-sectional views showing a narrow groove shape of a prototype tire in Example 3. FIG.

8 (A), (B), and (C) are schematic cross-sectional views showing narrow grooves of a prototype tire in Example 5. FIG.

FIG. 9 is a schematic cross-sectional view exaggeratingly showing a deformed state of the flat tire during turning.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 11 shoulder part 12 narrow groove 12B wide part E tread outer edge L bead base line S outer surface of shoulder part

Claims (2)

[Claims] 1. A carcass which passes from a tread portion to a side wall portion and folds around a bead core of a bead portion, and a belt layer arranged radially outside the carcass and inside the tread portion, and with respect to a tire width TW. A pneumatic tire having a flatness ratio TH / TW, which is a ratio of the tire cross-section height TH, of 60% or less, wherein the tire cross-section height TH is 0.6 in the tire radial direction from a bead baseline of the bead portion. A height position Q1 that is twice the distance L0, and a height position Q of the tread outer contact end
Groove width Wg is 3.0m on the outer surface of the shoulder between 2 and
at least 1 that is less than m and extends along the tire circumferential direction
A sipe-shaped narrow groove is formed substantially at right angles to the outer surface, and the narrow groove has an arc-shaped wide portion having a bottom groove width Dg larger than the groove width Wg at the lower end thereof, and the narrow groove. The pneumatic tire in which the groove depth Lg from the outer surface of the shoulder portion to which is provided to the deepest point of the wide portion is 0.2 to 0.6 times the shortest distance L1 from the outer surface to the carcass or the belt layer. 2. A plurality of the fine grooves are provided on the outer surface of the shoulder portion, and an interval P between the fine grooves adjacent to each other is 10 mm.
The pneumatic tire according to claim 1, wherein: