JP2003182310A - Tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire, of which the decrease of the wet performance is suppressed by securing the drainability of the tire during the middle to late period of wearing of the tread caused by traveling, and by achieving uniform wearing of the tread. <P>SOLUTION: The tire comprises a circularly formed tread, a pair of side walls arranged to extend inward from both ends of the tread in the radial direction of the tire, and beads extending inward continuous with the side walls in the radial direction of the tire. The tread comprises a treading surface having a plurality of block lines demarcated by a plurality of circumferential grooves 1a, 1b, 1c, 1d extending in the circumferential direction of the tire and by a plurality of lug grooves 4a, 4b intersecting the circumferential grooves and extending the width direction of the tire. When the tire is mounted on a vehicle, the groove area ratio of the tire is different between both areas divided by the central circumferential line of the tire, and the groove area ratio of the inner grounding side is larger than that of the outer grounding side, and the depth of the grooves formed on the inner grounding side is greater than that formed on the outer grounding side. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides drainage performance, braking performance, and hydroplaning resistance for a wet road surface in the middle and late stages of wear by ensuring drainage performance in the middle and latter stages of wear of the tread during running and achieving uniform wear. The present invention relates to a tire that suppresses a decrease in performance (generally referred to as “wet performance” hereinafter).

[0002]

2. Description of the Related Art Conventionally, in order to improve the wet performance of a tire tread, a pattern design is used to improve the drainage property, and at the same time, a rubber material of the tread is used to improve the friction coefficient μ with the road surface. Came.

For example, various tread pattern tires are known that are bilaterally asymmetrical with respect to the tire center line when mounted on a vehicle. Among them, the negative rate is different on both sides, and the side with the higher negative rate is the one. There is known a tire that is disposed on the inner side of the ground to ensure drainage, and the side with a low negative ratio is disposed on the outer side of the ground to ensure wear resistance.

Further, in order to suppress the deterioration of the wet performance in the middle and later stages of wear of the tread due to running, the rubber having a lower wear resistance than the tread rubber is exposed to the tread tread portion by the wear, and thereby a new groove is formed. A tire or the like has been proposed in which the volume reduction of the tread groove is complemented (JP-A-11-147403, etc.).

[0005]

However, in the conventional tire, as described in the above publication, a plurality of rubbers having different characteristics are not used in the tread,
At present, a technique capable of suppressing the deterioration of wet performance in the middle and latter stages of wear of the tread due to the improvement of the tread pattern has not been sufficiently established. For example, in the tire having the above-described left-right asymmetrical tread pattern, there is a problem that the drain groove is eliminated earlier on the side having a large negative ratio than on the side having a small negative ratio. For this reason, a decrease in wet performance was unavoidable in the middle and middle stages of tread wear.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional tire having an asymmetric tread block pattern, to secure drainage and uniform wear in the middle and latter stages of wear of the tread due to running, and to improve wet performance. An object of the present invention is to provide a tire whose reduction is suppressed.

[0007]

In order to solve the above-mentioned problems, the present inventor has made earnest studies by paying attention to the asymmetric tread block pattern and the groove depth, and as a result, achieved the above-mentioned object by the following constitution. They found that they could obtain the present invention and completed the present invention. That is, the present invention is as follows. (1) A tread portion formed in an annular shape, a pair of sidewall portions disposed inside both ends of the tread portion in the tire radial direction, and a bead portion connected to the inside of the sidewall portion in the tire radial direction. The tread portion of the tread portion has a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of block rows defined by a plurality of lug grooves that intersect the circumferential grooves and extend in the tire width direction. In a tire, when the vehicle is mounted on a vehicle, the negative ratio is different on both sides of the tire center line, the inner ground contact has a larger negative ratio than the outer ground contact, and the inner ground contact has a groove depth of the groove more than the outer ground contact. It is a tire characterized by deepness.

(2) In the tire of (1) above, the difference in groove depth between the inside of the ground and the outside of the ground is
The tire is provided so that the wear volumes due to running on the inside of the ground and the outside of the ground are substantially equal.

(3) In the tire of (2) above, the difference in groove depth between the inside of the ground and the outside of the ground is 0.5 to 2.5 mm.

(4) In the tire according to any one of (1) to (3), the negative ratio inside the ground is 35 to 4
The tire having a negative ratio of 5% and the outside of the ground is 25 to 35%, and the inside of the ground has a negative ratio of 5 to 15% larger than that of the outside of the ground.

(5) In the tire according to any one of (1) to (4), the tire has four circumferential main grooves extending in the tire circumferential direction, and the width of the circumferential main groove inside the ground is the ground. It is a tire that is larger than that on the outside.

Here, the "negative rate" means the following equation: The negative rate defined by The “ground contact area” in the “actual ground contact area of the tire” and the “area of the outer contour line in contact” shall refer to the ground contact area of the tread when a load is statically applied according to the following standards.

Here, the load is the maximum load (maximum load capacity) of a single wheel in the applicable size described in a predetermined industrial standard, and the internal pressure is the unit size in the applicable size described in the standard. It is the air pressure that corresponds to the maximum load (maximum load capacity) of the wheel, and the rim is the standard rim (or "in the applicable size" described in the same standard).
Applied Rim "," Recommende
d Rim "). As for such industrial standards, standards that are effective in the regions where tires are manufactured or used are defined, for example, in the United States," The Tire and Rim Associ ".
ation Inc. In Europe, "The Euro Book (including design guide)", "The Euro
pean Tire and Rim Technica
l Organization's Standards M
“Japan” and “JATMA Year Book” of the Japan Automobile Tire Manufacturers Association.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a partial plan development view of a tread of a tire having a rib lug type tread pattern according to an embodiment of the present invention. In the illustrated preferred example, four main grooves 1a, 1b, 1c, 1d that contribute to ensuring drainage are linearly extended in the circumferential direction on the tread surface of the tread, and these main grooves 1a, 1b, 1c are provided. By 1d, 3
A total of five ribs are defined, the book central ribs 2a, 2b, 2c and the two shoulder ribs 3a, 3b.

Three central ribs 2a, 2b, 2c and 2
In the shoulder ribs 3a and 3b of the book, substantially V-shaped lug grooves 4a and 4b having a bending point on the central rib 2b are alternately communicated from one shoulder side to the other shoulder side. There is.

In the tread pattern of the tire according to the preferred embodiment of the present invention, the negative ratio is different on both sides of the tire center circumferential line M when the vehicle is mounted, and the inner side of the ground is more negative than the outer side of the ground. It is important that the rate is high. As a result, drainage is ensured inside the ground contact with a high negative ratio, and wear resistance is secured outside the ground contact with a low negative ratio. In order to make the drainage property and the wear resistance compatible with each other, it is preferable that the negative ratio inside the ground is 35 to 45.
%, The negative rate outside the ground is 25 to 35%, and the negative rate inside the ground is 5 to 5% lower than that outside the ground.
Make it 15% larger.

In the preferred embodiment shown in FIG. 1, the main grooves 1a and 1b on the inner side of the ground are wider than the main grooves 1c and 1d on the outer side of the ground in order to satisfy such conditions. Similarly, the width of the lug grooves 4a and 4b on the inside of the ground is wider than the width of the lug grooves 4a and 4b on the outside of the ground.

Further, in the present invention, it is important that the inside of the ground in the asymmetrical tread pattern has a greater groove depth than the outside of the ground. Preferably, the difference in groove depth between the inside of the ground and the outside of the ground,
It is provided so that the wear volumes due to running on the inside of the ground and the outside of the ground are substantially equal. Specifically, the difference in groove depth between the inside of the ground and the outside of the ground is set to 0.5 to 2.5 mm. As a result, the difference in friction volume between the inside and outside of the ground of the tire is reduced, more uniform wear can be secured, drainage is secured even in the middle and later stages of wear of the tread due to running, and deterioration of wet performance is suppressed. You can

The tread surface of the tire of the present invention may be appropriately provided with sipes and hot water grooves as needed. Further, the above-described preferred example is for a tire having a rib lug type tread pattern, but the present invention is similarly applicable to a tire having a rib type tread pattern, and the shape and circumferential direction of the tread portion of the block. The number of grooves and the like are not particularly limited.

[0020]

EXAMPLES The present invention will be specifically described below based on examples. A tire (size 245 / 45ZR17) having the tread pattern shown in FIG. 1 and under the conditions shown in Table 1 below was prototyped.

[0021]

[Table 1]

Using the rims (size: 8J × 17) thus obtained, the tires of Examples and Comparative Examples were mounted on an actual vehicle at an internal pressure of 240 kPa, and the running distance until the drainage groove depth became 1.6 mm was measured. did. The results obtained are shown in Table 2 below.

[0023]

[Table 2]

As can be seen from Table 2, in the tires of the examples, the wear speed of the tread was the same on the inside of the ground and the outside of the ground, and the tires were worn uniformly on both sides. The outer side was worn faster and the wear was uneven.

[0025]

As described above, according to the present invention, in a tire having an asymmetric tread block pattern, it is possible to secure drainage and uniform wear in the middle and latter stages of wear of the tread due to running, It is possible to suppress the deterioration of wet performance in the latter half of wear.

[Brief description of drawings]

FIG. 1 is a developed plan view of a tire according to an embodiment of the present invention.

[Explanation of symbols]

1a, 1b, 1c, 1d Circumferential main groove 2a, 2b, 2c Central rib 3a, 3b Shoulder rib 4a, 4b lug groove

Claims (5)

[Claims] 1. A tread portion formed in an annular shape, a pair of sidewall portions arranged inside the tire radial direction from both ends of the tread portion, and a bead portion connected to the inside of the sidewall portion in the tire radial direction. The tread portion of the tread portion, a plurality of circumferential rows extending in the tire circumferential direction, a plurality of block rows defined by a plurality of lug grooves intersecting these circumferential grooves and extending in the tire width direction When the vehicle is mounted on a vehicle, the negative ratio is different on both sides of the tire center line, the inner side of the ground has a larger negative ratio than the outer side of the ground, and the inner side of the ground has a greater groove ratio than the outer side of the ground. Tires with deep groove depth. 2. The difference in the groove depth between the inside of the ground and the outside of the ground is set so that the wear volumes due to running on the inside of the ground and the outside of the ground are substantially equal. tire. 3. The tire according to claim 2, wherein the groove depth difference between the inside of the ground and the outside of the ground is 0.5 to 2.5 mm. 4. The negative ratio inside the ground is 35 to 4
The tire according to claims 1 to 3, wherein the negative ratio on the outside of the ground is 5% and the negative ratio on the outside of the ground is 25 to 35%, and the negative ratio on the inside of the ground is 5 to 15% larger than the outside of the ground. 5. The tire according to claim 1, further comprising four circumferential main grooves extending in a tire circumferential direction, wherein a width of the circumferential main groove on the inner side of the ground is larger than that on the outer side of the ground. The tire described in the item.