JP2003104009A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain wet grip performance from lowering accompanied to progress of abrasion. SOLUTION: Tread rubber G includes a tread rubber main part 16, and an abrasion progressing rubber part 17 comprising abrasion progressive rubber having low rubber hardness and easy to be abraded. The abrasion-progressive rubber part 17 is provided with a rubber line part 19 extended continuously along a tire-circumferential direction in a height area Y between the deepest groove bottom height position Pb in a tread groove 11 and an intermediate height position Pa therein. When the tread rubber G is abraded, the rubber line part 19 is abraded more than the tread rubber main part 16 to form a vertical-groove-like recessed groove 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which deterioration of wet grip performance due to progress of wear is suppressed.

[0002]

2. Description of the Related Art In order to secure wet grip performance, a vertical groove in the circumferential direction along a streamline or a lateral groove for breaking a water film is used in a tread portion of a tire, Tread grooves of various patterns are formed.

However, the tread groove inevitably reduces the groove depth and the groove area as the wear progresses, thereby lowering the drainage property. In addition, since the tread rubber of the tire is hardened due to aging, road followability (ground contact) is impaired, and in combination with the above-mentioned deterioration of drainage performance, deterioration of wet grip performance is unavoidable. .

In view of the above, the present invention is based on the fact that a tread rubber is provided with a wear progressing rubber portion which is made of a soft rubber which is easily worn and which has one or more rubber strips extending continuously in the tire circumferential direction. When the rubber is worn, a large amount of the rubber strip portion is worn, so that a vertical groove can be newly appeared, and the reduction of the groove area, that is, the reduction of the drainage property is suppressed, and the tread rubber due to secular change. It is an object of the present invention to provide a pneumatic tire capable of suppressing the hardening of the tire and improving the wet grip performance by the synergistic effect of these.

[0005]

In order to achieve the above object, the invention of claim 1 is a pneumatic tire having a tread groove provided in a tread portion, wherein the tread rubber forming the tread portion is a tread. A rubber main part and a wear progressing rubber part made of wear progressing rubber having a rubber hardness smaller than that of the tread rubber main part and being easily worn, and the wear progressing rubber part is the deepest deepest part of the tread groove. A height region between the deep groove bottom height position Pb and the deepest groove depth intermediate height position Pa extends substantially continuously in the tire circumferential direction 1.
When the tread rubber is worn up to the height region by providing the above rubber strips, the rubber strips of the wear progressing rubber portion are worn more than the tread rubber main portion, resulting in a vertical groove-like recess. It is characterized by forming a groove.

According to the invention of claim 2, the tread groove has at least two vertical grooves extending in the tire circumferential direction to form a rib-like land portion between the vertical grooves, and the rubber strip portion. Is in the rib-shaped land portion, and the total width ΣWa of the rubber strip portion at the intermediate height position Pa is 0.5 mm or more and 1/3 or less of the width RW of the rib-shaped land portion, and the deepest groove bottom. The total width ΣWb of the rubber strip portion at the height position Pb is characterized in that it is not less than the total width ΣWa and not more than 1/2 of the width RW of the rib-like land portion.

Further, in the invention of claim 3, the wear progressing rubber portion has a plurality of rubber strips in the rib-shaped land portion.

In the invention of claim 4, the tread portion has a plurality of rib-shaped land portions, and the total widths ΣWa and ΣWb of the rubber strips in the rib-shaped land portion on the tire equator side are the ribs on the tread edge side. Width ΣWa, ΣW of the rubber strip in the land area
It is characterized by being larger than b.

According to a fifth aspect of the present invention, when the rib-shaped land portion is divided into a tire equator-side half width portion and a tread edge-side half width portion in the tire axial direction, it is included in the tire equator side half width portion. Width component ΣWa1 of width ΣWa, ΣWb,
ΣWb1 is the total width Σ included in the half width part on the tread edge side
It is characterized in that it is larger than the width components ΣWa2 and ΣWb2 of Wa and ΣWb.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. FIG. 1 is a meridional sectional view in the case where the pneumatic tire of the present invention is a passenger car tire, and FIG. 2 is a development view of the tread pattern thereof.

In FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a carcass 6 radially outside and inside the tread portion 2. Belt layer 7 arranged in
It is reinforced by a cord layer including and.

The carcass 6 is composed of at least one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 degrees with respect to the tire circumferential direction, in this example, one carcass ply 6A, and both ends of the carcass ply 6A. It is folded around and locked.

Further, the belt layer 7 is composed of a plurality of belt cords arranged in an angle of, for example, 15 ° to 35 ° with respect to the tire circumferential direction, in this example, two belt plies 7A and 7B. The plies intersect with each other to form a strong truss structure and reinforce the tread portion 2 with a hoop effect. Further, in this example, the belt layer 7 is covered with a band layer 9 in which organic fiber cords are arranged substantially parallel to the tire circumferential direction to improve high-speed durability. In the case of a heavy-duty tire, the belt layer 7 has a belt cord of 15 ° to 7 °.
It is usually formed with 3 to 4 belt plies arranged at an angle of 0 °.

Next, in this example, the tread portion 2 is
By providing the tread groove 11 including at least two vertical grooves 10 extending in the tire circumferential direction, the vertical grooves 10, 1
A rib type land portion 12 is formed between 0 to form a rib type, rib lug type, block type, or rib / block type tread pattern.

Particularly, in this embodiment, as shown in FIG. 2, a central vertical groove 10A extending on the tire equator C and vertical grooves 10B on both sides are provided, whereby the tread portion 2 is provided. Is divided into the rib-like land portion 12A inside the vertical grooves 10A and 10B and the rib-like land portion 12B outside between the side vertical groove 10B and the tread edge TE. The rib-shaped land portions 12A and 12B may be ribs 13 that extend substantially continuously in the tire circumferential direction, or may be block rows 15 divided into a plurality of blocks by lateral grooves 14, as in this example. Then, the rib-like land portion 12A inside is rib 13
The rib-block type tread pattern in which the outer rib-shaped land portion 12B is the block row 15 is illustrated.

In the present invention, the tread rubber G forming the tread portion 2 is composed of a tread rubber main portion 16 and a wear progressing rubber having a rubber hardness smaller than that of the tread rubber main portion 16 and easily worn. One of the features is that the wear progressing rubber portion 17 includes one or more rubber strip portions 19 that extend continuously in the tire circumferential direction in a predetermined height region Y while including the progressing rubber portion 17. Have one.

As shown in FIGS. 3 and 4, the wear-progressing rubber portion 17 is located below each rib-shaped land portion 12 and forms a radial inner surface of the tread rubber G in the present embodiment. It is formed of one or more, in this example, three (plural) rubber strips 19 extending outward in the radial direction from each base 18 at least over the height region Y.

Here, the height region Y means a region between the deepest deepest groove bottom height position Pb of the tread groove 11 and an intermediate height position Pa of the deepest groove depth. In other words, the height position Pb of the deepest groove bottom 11b of the tread groove 11 where the groove depth is the deepest, and the distance 0.5H from the height position Pb to 0.5 times the deepest groove depth H. Means a region in the radial direction between the position Pa and the position (intermediate height position) Pa. Generally, since the vertical groove 10 is formed deeper than the horizontal groove 14, the groove bottom of the vertical groove 10 corresponds to the deepest groove bottom 11b.

Each rubber strip 19 extends radially outward beyond the height region Y, and its outer end is interrupted in the rib-shaped land portion 12 or the tread surface (rib-shaped land portion 1).
2 radial outer surface) to form a part of this tread surface. In this example, a case where the outer end of each rubber strip portion 19 is interrupted in the rib-shaped land portion 12 is shown.

At this time, in the rubber strip portion 19 interposed in one rib-shaped land portion 12, the total width ΣWa of the rubber strip portion 19 at the intermediate height position Pa is 0.5 mm or more and the rib-shaped land portion is not less than 0.5 mm. 1/3 or less of the width RW of 12 and the total width ΣWb of the rubber strip portion 19 at the deepest groove bottom height position Pb is equal to or more than the total width ΣWa and equal to or less than 1/2 of the width RW of the rib-like land portion 12. It is preferable that It is preferable that each rubber strip 19 has a tapered shape with its width smoothly reduced outward in the radial direction.

Next, the wear progressing rubber forming the wear progressing rubber portion 17 has its rubber hardness (durometer A hardness) Hs.
2 is a soft rubber that is easily worn by reducing 2 as compared with the rubber hardness Hs1 of the main rubber that forms the tread rubber main portion 16, and in this example, a reinforcing material included in the rubber composition, for example, It is made soft by reducing the blending amount of carbon black and silica. As the main rubber, for example, a conventional rubber that has a rubber hardness Hs1 of 55 to 70 degrees and is excellent in general wear resistance as a tread rubber can be preferably used.

In the tire according to the present embodiment, as shown in FIG.
As described above, when the tread rubber G is worn to at least the intermediate height position Pa, the rubber strip portion 19 is exposed on the tread surface. At this time, since the rubber strip portion 19 is formed of wear progressing rubber, it is worn more than the tread rubber main portion 16, and as a result, a vertical groove-like concave groove 20 appears at the position of the rubber strip portion 19. Can be made. This groove 2
Since 0 functions similarly to the conventional vertical groove, it is possible to compensate for the decrease in the groove area of the tread groove 11 due to the progress of wear,
It is possible to suppress deterioration of drainage.

Furthermore, due to secular change, tread rubber G
Even when the rubber is hardened, the abrasion-promoting rubber is a soft rubber, so that the flexibility is ensured and the road surface following property (grounding property) can be maintained. The synergistic effect of these can exert the effect of suppressing the deterioration of wet grip performance due to the progress of wear.

Here, the rubber hardness difference Hs1-Hs2 between the wear-promoting rubber and the main rubber is preferably 2 to 10 degrees. When the rubber hardness difference is less than 2 degrees, the wear difference becomes too small and the above-mentioned concave It becomes difficult to make the groove 20 appear. On the other hand, when the rubber hardness difference exceeds 10 degrees, not only the effect of suppressing the deterioration of wet grip performance reaches a ceiling, but also the wear progressing rubber portion 17 becomes a weak point, which tends to impair durability and strength. Therefore, the rubber hardness difference is more preferably 3 to 6 degrees.

Further, as described above, the total width ΣWa of the rubber strip portion 19 at the intermediate height position Pa is 0.5 mm or more and 1/3 or less of the width RW of the rib-shaped land portion 12, and the deepest groove bottom height. The total width ΣWb of the rubber strip portion 19 at the position Pb,
It is preferable that the total width ΣWa or more and half or less of the width RW of the rib-shaped land portion 12 be set.

The reason is that if the total widths ΣWa and ΣWb are less than 0.5 mm, the effect of suppressing the deterioration of wet grip performance cannot be exerted. Also, the total width ΣWa is 1 /
When it is larger than 3 × RW and the total width ΣWb is larger than 1/2 × RW, the block rigidity is out of balance, the wet grip performance tends to be impaired both when it is worn and when it is new, and when it is operated on a dry road surface. It is also a disadvantage to stability.
The "width RW of the rib-shaped land portion 12" is the width measured at the intermediate height position Pa.

Further, as described above, the cross-sectional shape of the rubber strip portion 19 is tapered outward in the radial direction, because the concave groove 20 formed by the rubber strip portion 19 is formed as the wear progresses. This is because it can be expected to increase drainage by widening the width. In addition, since the reduction of the ground contact area is suppressed such that the groove width of the concave groove 20 is minimized at the upper end of the groove, it is also useful for maintaining the grip performance on a dry road surface.

Further, it is preferable to provide three to four narrow rubber strips 19 rather than one wide strip.
Since the edge effect of the concave groove 20 can be expected, this is advantageous for the wet grip performance during turning when the total width is the same. It is also preferable in that the block rigidity is made uniform.

In the tire, from the viewpoint of wet grip performance, higher drainage performance is desired on the tire equator side than on the tread edge side. Therefore, the total widths ΣWa and ΣWb of the rubber strips 19 in the inner rib-shaped land portion 12A are equal to the total widths ΣWa and ΣWb of the rubber strips 19 in the outer rib-shaped land portion 12B.
It is preferable to increase the drainage performance on the equator side of the tire.

Similarly, in one rib-shaped land portion 12, a higher drainage performance is desired on the tire equator side than on the tread edge side. Therefore, as illustrated in FIG. 6, when the rib-shaped land portion 12 is divided into a half width portion J1 on the tire equator side and a half width portion J2 on the tread edge side, the total width ΣWa included in the half width portion J1 on the tire equator side, Width component of ΣWb ΣW
It is preferable to make a1 and ΣWb1 larger than the width components ΣWa2 and ΣWb2 of the total widths ΣWa and ΣWb included in the half-width portion J2 on the tread edge side to enhance drainage performance on the tire equator side.

7 to 9 show another example of the wear-promoting rubber portion 17. In the wear progressing rubber portion 17 of FIG.
8 forms a base rubber layer 22 extending over substantially the entire width of the tread rubber G. That is, in this example, the tread rubber G has a two-layer structure including a base rubber layer 22 made of wear-progressing rubber and a cap rubber layer 23 formed by the tread rubber main portion 16 arranged radially outside thereof. The rubber strip 19 is formed so as to extend radially outward from the base rubber layer 22.

FIG. 8 shows a case in which the base portion 18 is eliminated and the wear progressing rubber portion 17 is formed only by the independent rubber strip portion 19. At this time, each rubber strip 1
9 extends outward in the radial direction from the inner surface of the tread rubber G.

In FIG. 9, in the structure of FIG. 8, the tread rubber main portion 16 has a base rubber layer 22 and a cap rubber layer 2.
The case of forming a two-layer structure with No. 3 is shown.

In the present invention, the tread groove may be of various sizes without restricting the groove width and groove depth, and various tread patterns may be adopted. Above, a particularly preferred embodiment of the present invention has been described in detail, but the present invention is not limited to the illustrated embodiment and can be carried out by being modified into various aspects.

[0035]

EXAMPLE A passenger car tire having a tire size of 185 / 70R14 having the basic structure or tread pattern shown in FIGS. 1 and 2 was prototyped according to the specifications shown in Table 1, and the wet grip performance (braking performance, steering performance) of each test tire was prototyped. Stability), riding comfort and wear appearance were tested, and the results are shown in Table 1. The rubber composition of the tread rubber used in Table 1 is shown in Table 2.

(1) Abrasion resistance: According to JISK6264, using a Lambourn abrasion tester, a load of 2.0 kg,
The values measured under the condition of the slip ratio of 40% were compared by an index with the rubber A being 100. The larger the index value,
It has excellent wear resistance.

(2) Wet grip performance (braking performance);
At the internal pressure (220 kPa) of the sample tire, the passenger car (20
The tires were mounted on four wheels (00 cc), and the braking distance from a speed of 60 km / h was measured on a wet asphalt road surface, and comparison was made using an index with the conventional tire as 100. The larger the index value, the better the wet grip performance. In addition, "when new" means running in with new tires (for example, 100km)
The "medium wear stage" means the state of being worn to the intermediate height position Pa.

(3) Wet grip performance (driving stability), riding comfort; driving stability (braking performance, acceleration performance, cornering performance) when traveling on a wet asphalt road surface using the passenger car used in the braking performance test. (Characteristics, etc.) are displayed by a 10-point method by the sensory evaluation of the driver. The larger the value, the better.

(4) Riding comfort: Using the passenger car used in the braking test, the riding comfort when running on dry asphalt road surface during the middle period of wear is displayed by a 10-point method by the sensory evaluation of the driver. . The larger the value, the better.

(5) Appearance of wear: The appearance of the tire in the middle stage of wear is visually inspected, and is displayed by a 10-point method by sensory evaluation. The larger the value, the better.

[0041]

[Table 1]

[0042]

[Table 2]

In the conventional example, the wet grip performance (braking performance, steering stability) deteriorates with the progress of wear. Comparative Example 1
Although the wet grip performance itself is highly evaluated, it deteriorates as the wear progresses, and the wear appearance also becomes poor.

On the other hand, in Examples 1 and 2, the wet grip performance hardly deteriorates with the progress of wear,
It can also be expected to improve riding comfort. In the case where the wear-promoting rubber portion is excessively arranged as in Example 3, the wet grip performance is not deteriorated as the wear progresses, but the balance of the block rigidity is lost, so that the wet grip performance itself is evaluated low. Also, the wear appearance deteriorates.

[0045]

Since the present invention is constructed as described above,
When the tread rubber wears, a vertical groove can be newly appeared, which suppresses the reduction of the groove area, that is, the deterioration of the drainage property, while suppressing the hardening of the tread rubber due to aging, and the progress of wear. It is possible to suppress deterioration of the wet grip performance that accompanies it.

[Brief description of drawings]

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

FIG. 2 is a development view showing the tread pattern.

FIG. 3 is a cross-sectional view of a tread rubber illustrating a wear progressing rubber portion.

FIG. 4 is a partially enlarged view thereof.

FIG. 5 is a cross-sectional view of the rib-like land portion in the middle stage of wear showing the effects of the present invention.

FIG. 6 is a cross-sectional view showing another example of a rubber strip portion.

FIG. 7 is a cross-sectional view showing another example of a wear progressing rubber portion.

FIG. 8 is a cross-sectional view showing still another example of the wear progressing rubber portion.

FIG. 9 is a cross-sectional view showing still another example of the wear progressing rubber portion.

[Explanation of symbols]

2 tread section 10 flutes 11 tread groove 12 Rib-shaped land 16 Tread rubber main part 17 Wear progress rubber part 19 Rubber strip 20 groove G tread rubber Y height area

Claims (5)

[Claims] 1. A pneumatic tire having a tread groove provided in a tread portion, wherein the tread rubber forming the tread portion has a tread rubber main portion and a rubber hardness smaller than that of the tread rubber main portion and wears. And a wear progressing rubber portion made of wear progressing rubber, wherein the wear progressing rubber portion is between the deepest deepest groove bottom height position Pb of the tread groove and the intermediate height position Pa of the deepest groove depth. By providing one or more rubber strips extending substantially continuously in the tire circumferential direction in the height region, when the tread rubber is worn to the height region, the rubber strips of the wear progressing rubber part are provided. The pneumatic tire is characterized in that a vertical groove is formed by abrading more than the main portion of the tread rubber. 2. The tread groove has at least two vertical grooves extending in the tire circumferential direction to form a rib-shaped land portion between the vertical grooves, and the rubber strip portion is provided in the rib-shaped land portion. And the total width ΣWa of the rubber strip portion at the intermediate height position Pa is 0.5 mm or more and 1/3 or less of the width RW of the rib-shaped land portion, and the rubber at the deepest groove bottom height position Pb. The total width ΣWb of the strip is the total width Σ
The pneumatic tire according to claim 1, wherein the width is not less than Wa and not more than 1/2 of the width RW of the rib-shaped land portion. 3. The pneumatic tire according to claim 2, wherein the wear-progressing rubber portion has a plurality of rubber strips in the rib-shaped land portion. 4. The tread portion has a plurality of rib-shaped land portions, and the total widths ΣWa, ΣWb of the rubber strip portions in the rib-shaped land portion on the tire equator side are the rubber strips in the rib-shaped land portion on the tread edge side. The pneumatic tire according to claim 2, wherein the total width of the portion is larger than ΣWa and ΣWb. 5. When the rib-shaped land portion is divided into a tire equator side half width portion and a tread edge side half width portion in the tire axial direction, a total width ΣW included in the tire equator side half width portion.
The width components ΣWa1 and ΣWb1 of ΣWb are the width components Σ of the total widths ΣWa and ΣWb included in the half width portion on the tread edge side.
It is larger than Wa2 and ΣWb2, The pneumatic tire according to any one of claims 2 to 4 characterized by things.