JP3170518B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a thin cut in a block for the purpose of improving a wet friction coefficient .mu ..

[0002]

2. Description of the Related Art Conventionally, in a pneumatic tire in which a block pattern having a large number of blocks defined by a circumferential groove of a tire and a transverse groove crossing the circumferential groove of the tire is formed on a tread surface of the tire, each block has There is a type in which a plurality of thin cuts, that is, sipes are provided in a direction intersecting the circumferential direction of the tire to improve the grounding performance of the block, and a braking performance is imparted by an edge effect of the tip of the sipe. As an example of this type, a sipe interval is defined to improve the braking performance on a low friction road, and the braking performance on an icy road or the like is improved while maintaining the driving performance of a pneumatic tire (for example, Japanese Patent Laid-Open No. 2
169307).

[0003]

It is common to cut a sipe into the land portion of the tread as described above, but if such a sipe is present in the tread, braking and braking during tire rotation will occur.
As a result of the driving force acting, the tread floats on the side that escapes from the ground contact surface in the rotation direction, and the contact surface area, which is an important element for securing the frictional force of the tire, is reduced. Then, the friction coefficient μ when wet was reduced, and the condition was poor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a side surface and a diameter facing a narrow groove of a succeeding portion connected to a leading portion obtained by cutting a sipe of a tire block through a narrow groove. By rounding only the portion where the outer surface intersects in the direction, the tread is prevented from floating on the side that escapes from the contact surface in the rotation direction of the subsequent portion during tire rotation, and the contact area is reduced. The purpose is to improve the wet friction coefficient.

[0005]

In order to achieve the above object, in the pneumatic tire of the present invention, the pneumatic tire is divided by a plurality of circumferential grooves, a large number of transverse grooves intersecting these circumferential grooves, and the above-mentioned groove group. An independent block, wherein the block has a leading portion that first contacts the ground during running and a trailing portion that subsequently contacts the road, the block includes at least one substantially axially extending sipe in the leading portion; The following portion of the block is connected to the preceding portion via a narrow groove extending in the axial direction, and has a rounded portion only at a portion where the side surface facing the narrow groove and the radially outer surface intersect. Is done.

[0006]

In the pneumatic tire configured as described above, the trailing portion and the leading portion of the block are connected via a narrow groove extending in the axial direction, and the side face of the trailing portion facing the narrow groove is formed. Since only the portion where the radially outer surface intersects is rounded, the contact pressure distribution on the tread surface during tire rotation shows a uniform tendency, and as a result, the block escapes from the contact surface in the rotation direction of the subsequent portion of the block. The floating on the side is small, and a decrease in the ground contact area can be prevented. Therefore, no decrease in the friction coefficient μ when wet is observed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a tread pattern according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA in FIG. FIGS. 3 and 4 show another embodiment of the present invention. FIG. 5 is an explanatory diagram of the operation state of the block according to the embodiment of the present invention. FIG. 6 is a sectional view of a conventional example.

In FIG. 1, a tread pattern T of a pneumatic tire according to an embodiment of the present invention has a rib 1 with an equatorial plane C interposed therebetween.
Extend symmetrically in the circumferential direction, and circumferential grooves 2 are formed on both sides of the rib 1. On the outside, a block 5 which forms one block by a leading portion 3 in which the tire rotates in the direction of the arrow and comes into contact with the ground and a trailing portion 4 via the narrow groove 7 is similarly continuously arranged in the circumferential direction. A plurality of sipes 6 (three in FIG. 1) are cut in the leading portion 3 in the horizontal direction. A rounded portion 8 is formed at the front end edge of the succeeding portion 4 that follows the leading portion 3 through a narrow groove 7 whose width is equal to or slightly larger than the width of the sipe. A block 5 'is provided in the circumferential direction like the block 5 via a circumferential groove 2' outside the blocks 5 continuously arranged in the circumferential direction. The block 5 'is composed of a leading part 3' and a succeeding part 4 ', like the block 5,
A sipe 6 ′ is cut into the leading portion 3 ′ inclining upward from the end of the plurality of circumferential grooves 2 ′ toward the tread end 9. Subsequent part 4 via narrow groove 7 'following preceding part 3'
An inclined rounded portion is formed at the front end edge of '.

Reference numeral 10 denotes a lug groove. Here, an operation state of a pneumatic tire having such a tread pattern T on a wet road will be described with reference to FIG.
Now, when the block slides on the wet water film as shown in FIG. 5, the contact pressure at the block edge and the sipe edge increases, and the drainage is good, while the contact pressure at the portion decreases by rounding the edge of the subsequent portion. The surface shows a tendency to be uniform without performing, and as a result, there is little decrease in the contact area and little decrease in the friction coefficient μ. In the above-mentioned embodiment, the block 5 is composed of one block of the leading part 3 and the trailing part 4. FIG. 3 shows that the trailing part is provided behind the trailing part 4 through a narrow groove, and the leading edge is provided. The configuration is such that a rounded portion is provided in the portion.

The above-described embodiment of FIGS. 2 and 3 is an embodiment in the case where the rotation direction is specified. However, when the rotation direction is not specified, FIG. 4 shows one block shown in FIG. To a tip portion 3 and a subsequent portion 4 following the narrow portion.
And a structure corresponding to the leading portion 3 in which the sipe 6 is further cut through a narrow groove is disposed behind the groove. FIG. 6 shows a conventional example in which a block is simply provided with a sipe.

Next, the sipe has a tread pattern T shown in FIG. 1, and has a sipe width b = 0.5 mm in the first, second and comparative examples shown in FIGS. 2, 4 and 6 shown in FIG. A sipe having a depth of d = 7 mm and a pitch between sipe of P = 3 mm was formed, applied to a tire having a tire size of 185 / 6bR14, a test tire was prototyped, mounted on a passenger car, and allowed to run on a wet road surface. . The results are shown as follows when the performance at the time of driving and braking is expressed as an evaluation index, with the index of the conventional example being 100.

[0012]

[0013]

As described in detail above, the pneumatic tire of the present invention is constituted and has a block consisting of a preceding portion that first comes into contact with the ground while the tire is running, and a subsequent portion that subsequently contacts the ground. At least one substantially axially extending sipe, and the succeeding portion is connected to the preceding portion via an axially extending narrow groove, and only at a portion where the side facing the narrow groove and the radially outer surface intersect. The roundness prevents the tread from lifting on the side that escapes from the ground contact surface in the direction of rotation of the subsequent portion during tire rotation, and reduces the decrease in the contact area, and as a result, the coefficient of friction There is almost no decrease in μ, and it is possible to improve the braking / driving performance of the tire on a wet road surface.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tread pattern according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a sectional view of a block showing another embodiment of the present invention.

FIG. 4 is a sectional view of a block showing still another embodiment of the present invention.

FIG. 5 is a diagram showing an operating state during rotation of the block of the pneumatic tire of the present invention.

FIG. 6 is a sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rib 2 Circumferential groove 2 'Circumferential groove 3 Leading part 3' Leading part 4 Trailing part 4 'Trailing part 5 Block 5' Block 6 Sipe 6 'Sipe 7 Narrow groove 7' Narrow groove 8 Rounded part 9 Tread edge 10 Lug groove T Tread pattern

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-147409 (JP, A) JP-A-4-310408 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11 / 11,11 / 12

Claims (2)

(57) [Claims] 1. A vehicle comprising: a plurality of circumferential grooves; a plurality of lateral grooves intersecting with the circumferential grooves; and an independent block separated by the group of grooves, wherein the block is connected to a preceding portion that first comes into contact with the ground during traveling. In a tire having a trailing portion that contacts the ground, the block comprises at least one generally axially extending sipe in the leading portion, and the trailing portion of the block communicates with the leading portion via an axially extending groove. A pneumatic tire having a roundness only at a portion where a side surface facing the narrow groove and a radially outer surface intersect. 2. The pneumatic tire according to claim 1, wherein a plurality of sipes are provided at a leading portion of the block.