JP2003011616A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of efficiently improving drainage performances, or defects when adopting a tread pattern of rib/lug pattern base, especially the drainage performance after a medium tread abrasion term, without impairing other performance. SOLUTION: At least, a circumferential groove 5 or 6 is disposed in, at least, one half section 3 or 4 of a tread part, a shoulder land part 8 is dividedly formed by a tread end 7 and the first circumferential groove 5 positioned closest thereto, and multiple lateral grooves 10 opened in the tread end 7 and extending from opening positions 9 toward the first circumferential groove 5 on the tire circumference at prescribed intervals apart from one another. The lateral groove 10 is characterized by having a terminal end 11 coming to a dead end inside the shoulder land part 8 without opened to the first circumferential groove 5 and having a groove bottom side part 12 positioned in the tire width direction inward of a tread side part 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a cross-sectional shape of a lateral groove arranged in a shoulder land portion of a tread portion of the tire, whereby the lateral groove is arranged. Improves pattern noise and heel-and-toe wear, which tends to be exacerbated by construction without sacrificing other performance.

[0002]

2. Description of the Related Art Generally, in a tread portion of a pneumatic tire, various tread grooves such as a circumferential groove extending along the tire circumferential direction and a lateral groove extending in the tire width direction are provided for the purpose of ensuring drainage performance. Are generally provided to form a so-called tread pattern.

As a tread pattern of a pneumatic tire, a so-called block pattern in which a plurality of blocks are defined by arranging a plurality of circumferential grooves and a plurality of lateral grooves open to these in a tread portion, In order to reduce pattern noise caused by large vibration of the tread due to impact (input) from the road surface, the lateral groove is arranged so that it does not open in the circumferential groove and terminates in the land portion. There is a so-called rib lug pattern in which a part of the rib has a rib shape continuously extending in the tire circumferential direction.

A tire having the above block pattern is
Although the drainage performance is generally good from the time of new product to the middle of tire wear or later, pattern noise is apt to occur due to impact sound of the block end at the time of tire load rolling or vibration due to it, and the block kick-out side part In addition, there is a drawback that uneven wear such as so-called heel and toe wear is likely to occur.

On the other hand, in the tire having the rib lug pattern, the land portion is not divided into complete blocks due to the arrangement of the lateral grooves, and a part of the land portion remains as a rib-shaped land portion. Pattern noise caused by impact sound at the block end or vibration due to it is improved, but especially in the tires after the middle stage of tread wear, the groove volume and the negative ratio (groove area ratio) are considerably reduced compared to new tires. Therefore, there is a drawback that sufficient drainage performance cannot be obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to make a tread pattern based on a rib rug pattern, and to drain the drainage performance which was a drawback of this pattern, especially the drainage performance after the middle period of tread wear, at the expense of other performances. It is to provide a pneumatic tire that can be effectively improved without performing.

[0007]

In order to achieve the above object, the pneumatic tire of the present invention has at least one half area when the tread portion is divided into both half areas by its pattern center. With a circumferential groove,
A shoulder land portion that continuously extends along the tire circumferential direction is defined by the tread end and the first circumferential groove that is the circumferential groove closest to the tread end, and the shoulder land portion has an opening at the tread end. A pneumatic tire having a plurality of lateral grooves extending from the opening position toward the first circumferential groove at predetermined intervals on the tire circumference, the lateral groove being the first circumferential groove. The tire has a dead end that does not open in the shoulder land portion, and the groove bottom side portion of the end is arranged more inward in the tire width direction than the tread side portion.

The term "tread edge" as used herein means the edge of the maximum width in the ground contact shape and the ground contact edge under the conditions of rim, load and internal pressure shown below. Here, "rim" means
Standard rim (or "Approved Rim", "Recommended Rim") in the applicable size listed in the following standards
The "load" is the maximum load (maximum load capacity) of a single wheel in the applicable size described in the standard below.
And the "internal pressure" is the air pressure corresponding to the maximum load (maximum load capacity) of a single wheel in the applicable size described in the following standard. The "standard" is defined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year
Book ”and in Europe,“ The European Tire and R
It is the "Standards Manual" of imTechnical Organization, and in Japan, "JATMA Year B" of the Japan Automobile Tire Association.
ook ”.

Further, the lateral groove has a gouged groove portion having a tapered cross-sectional shape formed by the groove bottom and a groove bottom side portion of the terminal end, and the groove bottom portion forming the gouged groove portion is substantially parallel to the tread surface. It is preferable that the tread surface side portion of the terminal end has a cross-sectional shape that is convex outward in the tire width direction.

Further, when the position on the tread surface at the end of the lateral groove is measured from the tread end along the tire width direction,
The width of the shoulder land portion is preferably within the range of 20 to 70% of the distance when measured in the same direction.

Furthermore, the distance between the position on the tread surface and the innermost position in the tire width direction at the end of the lateral groove measured along the tire width direction is as follows: Of the distance when measured along the width direction
It is preferably in the range of 25 to 90%.

[0012] In addition, the distance when the maximum gouge height position of the gouged groove portion of the lateral groove is measured from the groove bottom position along the tire radial direction is within the range of 40 to 70% of the groove depth of the lateral groove. Is preferred.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Figure 1
1 shows a part of a tread pattern of a pneumatic tire according to the present invention, in which 1 is a tread portion, 2 is a pattern center, 3 and 4 are half areas, 5 and 6 are circumferential grooves, and 7 is a tread end. , 8 is a shoulder land portion and 10 is a lateral groove.

The pneumatic tire shown in FIG. 1 has at least one half area (two half areas 3 and 4 in FIG. 1) when the tread portion 1 is divided by the pattern center 2 into both half areas 3 and 4. , At least one circumferential groove (two circumferential grooves 5, 6 in each half-section 3, 4 in FIG. 1), which is the tread end 7 and the circumferential groove closest to it. First
A shoulder land portion 8 that continuously extends along the tire circumferential direction is defined by the circumferential groove 5.

In the shoulder land portion 8, a plurality of lateral grooves 10 which are open at the tread end 7 and extend from the opening position 9 toward the first circumferential groove 5 are provided at predetermined intervals on the tire circumference (see FIG. 1).
Are evenly spaced).

The "lateral groove" referred to here is not only a widthwise groove extending substantially parallel to the tire width direction, a so-called lug groove, but also a first circumferential groove inclined with respect to the tire width direction. Also included is a slanted groove that extends vertically.

The main structural features of the present invention are as follows.
The purpose is to optimize the lateral groove 10 disposed in the shoulder land portion 8, and more specifically, the terminal end 11 of the lateral groove 10 is set to the first
As a dead end in the shoulder land portion 8 without opening in the circumferential groove 5, the tread pattern is based on a rib lug pattern, and the groove bottom side portion 12 of the terminal end 11 is a tread side portion.
It is located in the tire width direction more inward than 13, and by adopting this configuration, drainage performance which was a drawback when adopting the rib rug pattern tone, especially drainage performance after the middle period of tire wear, Can be effectively improved without sacrificing performance.

Hereinafter, the process leading to the completion of the present invention will be described together with the operation. First, the inventor made the tread pattern a rib rug pattern basis which is advantageous for suppressing uneven wear such as pattern noise and heel-and-toe wear, and drainage performance which was a drawback of a tire having this rib lug pattern, particularly tread wear. A study was conducted to improve the drainage performance of tires from the middle period.

As a result, as means for improving the drainage performance of the tire after the middle period of tread wear, only the groove bottom side portion of the end of the lateral groove is opened to the first circumferential groove, and the tread side portion of the end is provided. It is effective to dispose a so-called tunnel-shaped land portion in the lateral groove, which is a dead end in the shoulder land portion, and the end side of the lateral groove and the tread side portion are continuous with the land portion portions adjacent to both sides. found.

However, when the tunnel-shaped land portion is arranged in the lateral groove, since the negative ratio increases as much as the tunnel-shaped land portion disappears after the middle period of tread wear, the drainage of the tire is improved, but It was clarified that the provision of the tunnel-shaped land portion causes a new problem that the rigidity on the circumference of the shoulder land portion becomes non-uniform and special uneven wear is likely to occur.

Therefore, as a result of further intensive studies by the inventor, the lateral groove 10 is a dead end in the shoulder land portion 8 without opening in the first circumferential groove 5, and the terminal end 11 is formed.
If the portion 12 on the groove bottom 15 side is arranged so as to be located more inward in the tire width direction than the portion 13 on the tread surface 16 side, it is possible to suppress the occurrence of the above-described special uneven wear on the circumference, and particularly the tread. The inventors have found that the drainage performance of tires after the middle stage of wear can be effectively improved, and have completed the present invention.

Further, the lateral groove 10 may have an undercut groove portion 14 having a tapered cross-section formed by the groove bottom 15 and the groove bottom side portion 12 of the terminal end 11, and the land portion 17 located directly above the undercut groove portion 14. It is preferable in that the decrease in the rigidity is suppressed.

Further, the lateral groove 10 has a cross-sectional shape in which the tread surface side portion 13 of the terminal end 11 has a convex shape outward in the tire width direction. It is preferable in that the decrease in rigidity is further suppressed.

Furthermore, the position on the tread of the terminal end 11 of the lateral groove 10
The distance W ₁ when 18 is measured along the tire width direction from the tread end 7 is within the range of 20 to 70% of the distance W ₀ when the width of the shoulder land portion 8 is measured in the same direction. Is preferable from the viewpoint of the performance balance of pattern noise, abrasion and drainage, and more preferably within the range of 30 to 60%.
This is because if the distance W ₁ is less than 20% of the distance W ₀ , the drainage performance may not be sufficiently obtained especially in the initial stage of wear, and if it exceeds 70%, the pattern due to the impact sound of the land portion may occur. This is because noise and heel and toe wear tend to deteriorate.

Incidentally, the "early wear" referred to here is, as shown in FIG. 2, specifically, from the time of a new article in which the groove depth of the lateral groove is h ₀ , the tread is worn and the groove depth of the lateral groove is increased. Means the stage until the distance becomes equal to the distance h ₁ .

Further, the distance W ₂ of the end 11 of the lateral groove 10 measured between the position 18 on the tread surface and the innermost position 19 in the tire width direction along the tire width direction is the tread of the end 11 of the lateral groove 10. It is preferable that the upper position 18 is within the range of 25 to 90% of the distance W ₁ when measured from the tread end 7 along the tire width direction in terms of pattern noise, wear, and drainage performance balance. This is because if the distance W ₂ is less than 25% of the distance W ₁ , the negative rate after the middle period of tread wear may be small and sufficient drainage performance may not be obtained, while if it exceeds 90%, Land rigidity becomes uneven on the circumference, special uneven wear is likely to occur on the circumference, and it is practically difficult to form a lateral groove of such shape using a normal manufacturing method. This is because it is necessary to apply a special manufacturing method.

Further, the distance h ₁ when the maximum gouge height position 20 of the gouging groove portion 14 of the lateral groove 10 is measured from the groove bottom position 15 along the tire radial direction is 40 to the groove depth h ₀ of the lateral groove 10. 70%
It is preferable that it is within the range from the viewpoint of performance balance. If the distance h ₁ is less than 40% of the groove depth h ₀ of the lateral groove 10, the wear rate
This is because the drainage performance after 40% may be inadequate, while if it exceeds 70%, problems may occur due to insufficient pattern rigidity at the initial stage of wear.

It should be noted that the maximum hollow height position 20 of the hollow groove portion 14
Is not a problem when it is clear, but as shown in FIG. 2, for example, the groove bottom side portion 12 of the terminal end 11 has an arcuate cross-sectional shape that is convex inward in the tire width direction, If the tread surface side portion 13 of the terminal end 11 has an arcuate cross-sectional shape that is convex outward in the tire width direction, and if the boundary position of these portions 12 and 13 is not clear, these inflections In the point position, and when the tread side portion 13 and the groove bottom side portion 12 are connected by a linear portion, the tread side portion
The inflection point position is the connection position between 13 and the linear part.

Although FIG. 1 shows the case where the pattern center 2 coincides with the tire equatorial plane position, the pattern center 2 may be slightly displaced from the tire equatorial plane position in the tire width direction. Furthermore, in FIG. 1, in order to further improve drainage and the like, there is shown a case where the inclined groove 21 and the sipe 22 are arranged between the pair of circumferential grooves 6 and 6 located on the pattern center 2 side. The arrangement and the like of these can be appropriately set as necessary. In addition, FIG. 1 shows a case where the lateral grooves 10, the inclined grooves 21, and the sipes 22 arranged in the respective half sections 3 and 4 are displaced by a half pitch in the tire circumferential direction. May be arranged line-symmetrically or asymmetrically.

The above is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

[0031]

EXAMPLES Next, a pneumatic tire according to the present invention was prototyped and its performance was evaluated, which will be described below.

Examples Tires of Examples are pneumatic radial tires for passenger vehicles having a tread pattern shown in FIG. 1 and lateral grooves having a cross-sectional shape shown in FIG. 2, a tire size of 205 / 65R15, and the distance W ₀ , W ₁ and W ₂ are 25 mm and 10 m, respectively
m and 6 mm, and the distances h ₀ and h ₁ are 6.5, respectively.
mm and 4.0 mm, the radius of curvature of the cut groove is 1.5 m
m, and the radius of curvature of the tread side end portion was 1.5 mm.
The groove width and groove depth of the circumferential grooves 5 and 6 are both 8 mm.
And In addition, the carcass consists of a single carcass ply rubberized from a general polyester cord (1500d / 2) around a pair of bead cores so that the cords have a radial arrangement of 90 ° with respect to the tire circumferential direction. The structure was folded from the inside to the outside. The belt was constructed as a crossed belt in which two cord layers each made of rubberized 1 × 5 steel cord were laminated so as to cross each other at ± 23 ° with the tire equatorial plane sandwiched therebetween. Furthermore, on the outside of the belt, a nylon cord (1260d / 2) is rubberized for about 5
A single cap layer was arranged in which the cord extends substantially parallel to the tire circumferential direction by spirally winding a ribbon strip having a width of mm. The other tire structures were almost the same as those of a general pneumatic radial tire for passenger cars.

Comparative Example The tire of the comparative example is substantially the same as the tire of the example except that the lateral groove arranged in the shoulder land portion has a shape opening in a tunnel shape in the first circumferential groove. With the structure.

Conventional Example 1 The tire of Conventional Example 1 is an example except that the lateral groove arranged in the shoulder land portion is opened to the first circumferential groove to form the shoulder land portion with a plurality of blocks. The structure is almost the same as the tire.

Conventional Example 2 In the tire of Conventional Example 2, the lateral groove (extension length: 30 mm) arranged in the shoulder land portion has a dead end in the shoulder land portion without opening in the first circumferential groove. Except that it has the same structure as the tire of the example.

(Test Method) Each of the above-mentioned test tires was mounted on a standard rim (6JJ), and the pattern noise, drainage performance of the tire in the middle tread wear (at 60% wear), heel and toe wear, and circumferential deviation of the shoulder land portion were measured. A test was conducted to evaluate wear.

(1) Pattern noise evaluation test The pattern noise level was measured by an indoor drum tester. The test conditions are as follows: Tire pressure: 220k on a rotating drum with the surface covered with a safety walk.
Pa and tire load: Tires 110km under the condition of 4.61kN
/ H was coasted from a speed corresponding to the speed, the noise level was measured with respect to the decelerating speed, and the pattern noise was evaluated from these measured values. The microphone for measuring the noise level is JASO
Arranged according to the standard. Table 1 shows the evaluation results of pattern noise. The numerical values in Table 1 are shown as an exponential ratio with the value of Conventional Example 1 as 100, and the smaller the numerical value, the smaller the pattern noise.

(2) Evaluation test of drainage performance of tire after middle tread wear (at 60% wear) In order to approximate the middle condition of tread wear of the test tire,
After removing the tread rubber with a thickness equivalent to 60% of the groove depth of the circumferential groove of a new tire, this tire was mounted on all four wheels of a passenger car, and 60 km / km on a road surface with a constant water depth (2 mm).
After the vehicle was driven at h, the braking distance when the brake was applied suddenly was measured, and the drainage performance was evaluated from the measured value. Table 1 shows the evaluation results of drainage performance. The numerical values in Table 1 are shown as an index ratio with the value of Conventional Example 1 being 100. The smaller the numerical value, the shorter the braking distance and the better the drainage performance.

(3) Heel and toe wear evaluation test A passenger car equipped with test tires was run at 100 km / h for 20000 km, and then heel and toe wear was evaluated according to the degree of wear of the land portion on the kicking side. Table 1 shows the evaluation results of heel and toe wear. The numerical values in Table 1 are shown as an index ratio with the value of Conventional Example 1 being 100. The smaller the numerical value, the smaller the difference in wear (step) and the less likely heel and toe wear occurs.

(4) Evaluation test of uneven wear on the shoulder land portion After running a passenger car equipped with test tires at 20,000 km at 100 km / h, the shoulder land portion was dented depending on the degree of depression of the shoulder land portion. The uneven wear on the circumference was evaluated. Table 1 shows the evaluation results of the uneven wear on the circumference. The numerical values in Table 1 indicate the amount of depression (mm) at the upper part of the lateral groove extension line (on the circumferential side of the shoulder land portion), and the smaller the numerical value, the less likely the uneven wear on the circumference occurs.

[0041]

[Table 1]

From the evaluation results shown in Table 1, the embodiment has lower pattern noise than the conventional example 1 and the heel-and-toe wear is suppressed, and moreover, as in the conventional example 2, the tread wear after the middle stage. The drainage performance of the tire is not deteriorated, and uneven wear around the shoulder land portion is not deteriorated as in the comparative example.

[0043]

According to the present invention, the rib lug pattern is adopted as the tread pattern, and the drainage performance which is a drawback of this pattern, particularly the drainage performance after the middle period of tread wear, is not sacrificed. It has become possible to provide pneumatic tires that can be effectively improved.

[Brief description of drawings]

FIG. 1 is a development view of (a part of) a tread portion of a pneumatic tire according to the present invention.

FIG. 2 is a sectional view taken along line I-I of FIG.

[Explanation of symbols]

1 tread section 2 pattern center 3, 4 and a half area 5 First circumferential groove (or circumferential groove) 6 circumferential groove 7 tread edge 8 shoulder land 9 Opening position 10 lateral groove 11 Lateral groove end 12 End groove bottom 13 Tread side of the end 14 Egg groove 15 Horizontal groove bottom 16 treads 17 Land part 18 Position on the tread at the end 19 Innermost position in the tire width direction at the end 20 Maximum hollow height position of the hollow groove 21 Inclined groove 22 Sipe

Claims (6)

[Claims] 1. At least one circumferential groove is provided in at least one half area when the tread portion is divided into both half areas by the pattern center, and the tread end and the circumference located closest to the end are provided. A shoulder land portion that continuously extends along the tire circumferential direction is defined by the first circumferential groove that is a directional groove, and the shoulder land portion is opened at the tread end and from this opening position to the first circumferential groove. In a pneumatic tire in which a plurality of lateral grooves extending toward each other are arranged at a predetermined interval on the tire circumference, the lateral grooves form a dead end in the shoulder land portion without opening in the first circumferential groove. A pneumatic tire having a terminating end, wherein a groove bottom side portion of the terminating end is located inward of a tread surface side portion in the tire width direction. 2. The pneumatic tire according to claim 1, wherein the lateral groove has a scooped groove portion having a tapered cross-sectional shape formed by a groove bottom and a groove bottom side portion of a terminal end. 3. The pneumatic tire according to claim 1 or 2, wherein the lateral groove has a cross-sectional shape in which a tread surface side end portion thereof is convex outward in the tire width direction. 4. The distance (W ₁ ) when the position on the tread at the end of the lateral groove is measured along the tire width direction from the tread end.
Is within the range of 20 to 70% of the distance (W ₀ ) when the width of the shoulder land portion is measured in the same direction. 5. The distance (W ₂ ) measured along the tire width direction between the position on the tread and the innermost position in the tire width direction at the end of the lateral groove is such that the tread at the position on the tread at the end of the lateral groove. Distance when measured along the tire width direction from the edge (W
The pneumatic tire according to any one of claims 1 to 4, which is in the range of 25 to 90% of ₁ ). 6. The distance (h ₁ ) when the maximum gouge height position of the gouging groove portion of the lateral groove is measured from the groove bottom position along the tire radial direction is 40 to 70 of the groove depth (h ₀ ) of the lateral groove. The pneumatic tire according to any one of claims 1 to 5, which is in the range of%.