JPH0848115A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reduce the partial abrasion produced in a tread having a V-shaped inclined main groove of a pneumatic radial tire by letting both symmetrical inclined land parts, to be sectioned by this main groove, have plural pieces of specified blocks divided by a flask-form sipe whose bottom is expanded. CONSTITUTION:A tread 6 is formed into cylindrical form and continuous to a sidewall 2 via an auxiliary tread provided with roundness at both the sides. This tread 6 extends, in a V-shaped form, nearby an equatorial plane O from both the ends E at intervals in the circumferential direction, and its tip part G is curved and turned over, having a lot of inclined main grooves 8 adjacently ranging to one another, both symmetrical inclined land parts 9 sectioned by these inclined main grooves 8 and a central endless land part. In addition, this inclined land part 9 comprises two blocks 12 divided by a flask-form sipe 11, whose bottom is expanded, and when internal pressure is not added to a tire, each block 12 is formed into semicylindrical form, whereby a center land part 10 forms a ground surface 13 lower than these symmetrical inclined land parts 9 and 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire in which uneven wear of a tread having a V-shaped inclined main groove is reduced.

[0002]

2. Description of the Related Art In order to improve high-speed running performance of a pneumatic tire, a structure in which the base portion of the tread is reinforced with a non-extensible belt layer is generally used. The height ratio, that is, the flatness ratio has been reduced. About flatness ratio, 0.6
The degree is normally applied, and reaches 0.3, and even ultra-flat tires appear.

When the tire cross section becomes flat, the tire width becomes wider, and the tread width is accordingly set wider. In the case of such a tire, in terms of performance, steering stability on a dry road surface is improved, but It is known that the drainage property of the ground contact surface deteriorates, so that it is slippery on a wet road, especially when traveling at high speed. To improve the drainage property, a plurality of circumferential grooves (4 to 6) are provided, V crosses these circumferential grooves
A tread structure which is divided into substantially uniform independent blocks by inclined lug grooves extending in a letter shape, and a ratio of the groove groups to the entire tread, that is, a negative ratio is specified, is disclosed in JP-A-55-140.
Proposed in 604.

The above independent block type tread has a block striking sound at the corners of the block when the block is stepped on the ground surface during traveling, and a vibration of the block caused by friction with the road surface at the time of stepping and kicking. There is a problem of noise due to noise, and further, deterioration of steering stability due to insufficient rigidity peculiar to the independent block structure in consideration of drainage cannot be avoided. Therefore, instead of such a straight groove in the circumferential direction and a lug groove, a large number of main grooves extending from both ends of the tread toward the central portion in a V-shape with an acute angle with respect to the circumferential direction, and these main grooves. Recently, a tread consisting of land sections divided by has been attracting attention.

[0005]

It can be said that the tire having the V-shaped main groove in the tread is excellent in both noise and steering stability while maintaining wet skid resistance. On the other hand, however, this type of tire is applied to a wide tread, and it is not easy to obtain a uniform contact pressure distribution. By filling the internal pressure, the inclined main groove portions are subtly deformed, and the land portion formed between them is affected by the deformation depending on the position in the land portion. If the contact pressure distribution is not uniform, uneven wear (heel and toe wear) is likely to occur at a relatively early stage of running, and once uneven wear occurs, it develops three-dimensionally in terms of both depth and spread, resulting in a tread. Not only deteriorates the appearance of wear, but also impairs the grounding property of the tread and causes vibration. An object of the present invention is to provide a pneumatic radial tire in which uneven wear generated in a tread having a V-shaped inclined main groove is reduced.

[0006]

According to the present invention, a crown portion is formed between a pair of annular side walls, and a radial arc is provided between one of the side walls, the crown portion, and the other side wall. While reinforcing and arranging a non-stretchable belt layer and a tread on the outer circumference of the crown portion of this carcass, the tread is V-shaped from both ends thereof to the vicinity of the equatorial plane at intervals in the circumferential direction. A plurality of inclined main grooves extending in the direction of which the tip portion is curved and inverted and connected to each other next to each other, and the left and right inclined land portions divided by these main grooves,
And a tire having a central endless land portion, the slanted land portion includes a plurality of blocks divided by a flask-shaped sipe with a bulging bottom portion, and when no internal pressure is applied to the tire, the block has a semi-cylindrical shape with a raised central portion. A cross-section is a pneumatic radial tire characterized in that the central land portion forms ground contact surfaces lower than the left and right inclined land portions, respectively. Here, the tread refers to the area of the tread where the tire touches the ground when going straight. For convenience, the tire was assembled on the regular rim based on the ETRTO standard, the regular internal pressure was filled, and 70% of the maximum design load was applied on the flat plate. When this is the area to be grounded.

[0007]

The tread consisting of the left and right slanted land portions and the circumferential endless land portion extending between the two is an advantageous structure for noise suppression, but especially for a flat radial tire with a wide tread width. When this tread is applied, it tends to be difficult to obtain a uniform contact pressure distribution. Specifically, the dividing means that further blocks the inclined land portion may be a sipe with a significantly narrow width, and the position of the inclined main groove is subtly deformed by filling the internal pressure. The ground contact pressure is higher on both sides of the adjacent land part than on the center part, and the center land part is generally higher in ground contact pressure than the inclined land parts on both sides of the groove.

In the tire according to the present invention, when it is in a free state in which no internal pressure is applied, it is apparent that the land portion or the block divided into the inclined main grooves corresponding to the above-mentioned protruding amount has a kamaboko-shaped cross section, and at the same time, By providing a relatively low contact surface to the central endless land, the contact pressure distribution becomes uniform when the internal pressure is applied and a load is applied, which can advantageously suppress uneven wear. In addition, the flask type sipe with a bulged bottom that re-divides the inclined land part,
It is also effective in preventing the deterioration of wet skid resistance after wear has progressed, and the relative leveling down of the ground contact surface in the central land area prevents local excessive heat generation in this area during high-speed running, which results in high-speed durability. It is also effective for improving sex.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. FIG. 1 is a sectional view of a tire showing an embodiment of the present invention, and FIG. 2 is a tread plan view of the tire. In the present invention, the tire 1 is
A pair of annular sidewalls 2 and a crown portion 3 are formed across both sidewalls 2, and the radial portion extends from one sidewall 2 through the crown portion 3 to the other sidewall 2. Reinforced with the dregs 4, the non-stretchable belt layer 5 and the tread around the crown of this
6 are placed and strengthened. The carcass 4 has a known structure composed of at least one, usually two plies in which fiber cords represented by polyester and rayon are arranged in a direction substantially orthogonal to the equatorial plane O, and Belt layer 5 also
Steel - Turkey - inextensible co such de - a plurality of plies 5 ₁ inclined arranged at a shallow angle de to the equatorial plane O (15 to 35 °), the two normal, their co - de intersection superimposed to further heat-shrinkable co such as nylon its entire periphery - a de plurality of side by side is formed by the circumferential direction helically wound rubberized strips, a known structure including a cap layer 5 _2.

The tread 6 has a cylindrical shape and continues to the side wall 2 via an auxiliary tread 7 having rounded sides. Tread 6 is circumferentially spaced at both ends
A large number of inclined main grooves 8 extending from E to the vicinity of the equatorial plane O, the tip G of which is curved and inverted and connected to each other next to each other, and the left and right inclined land portions 9 divided by these inclined main grooves 8. And has a central endless land area. And the sloped land 9
Includes a number of blocks 12 divided by a flask-shaped sipe 11 with an inflated bottom, the blocks 12 have a semi-cylindrical shape when no internal pressure is applied to the tires, and the central land portion 10 has a ground contact lower than the left and right inclined land portions 9 and 9. Forming surface 13. In the present invention, the ratio H / S of the tire width S to the sectional height H is 0.
It can be suitably applied to flat passenger car radial tires of 3 to 0.6.

In the embodiment shown in FIG. 2, the angle α of the inclined main groove 8 with respect to the line j parallel to the equator O is about 28 °.
However, the angle α can be applied in the range of 15 to 55 ° depending on the tire size and the pitch arrangement provided on the tread portion. The tip portion G of the inclined main groove is turned to the circumferential direction of the aperture and further inverted to make an adjacent inclined main groove 8
It is in a row. Therefore, the left and right inclined land sections 9 and 9 and the central land section 10 are independent from each other.

FIG. 3 is a sectional view taken along the line AA in FIG. In FIG. 3, the sipe 11 dividing the block 12 has a width v
Is about 1 mm, and the width w of the bulged bottom 14 is about 2 mm. The width of the bottom portion 14 can be applied in the range of v <w <3v. The depth of the sipe is preferably equal to or slightly shallower than the depth of the main groove.

FIG. 4 is a sectional view taken along line BB in FIG. In FIG. 4, the block 12 has both ends close to the main groove, which is lower than the imaginary line k that indicates the ground contact surface when the inner or inner pressure is filled (falling height n at both ends is 0.5 mm). As a result, the center part 15 of the block has a slightly raised kamaboko-shaped cross section. Falling height n is 0.3 ~
0.5 mm is preferable.

FIG. 5 is a sectional view taken along the line CC in FIG. In FIG. 5, the central land portion 10 has a ground contact surface 13 that is dropped by q from an imaginary line (which is also a level at the time of filling with internal pressure) r connecting the surfaces of the blocks on both sides. The drop height q in this embodiment is about 0.5 mm, but it can be applied in the range of 0.3 to 0.5 mm. By filling the internal pressure of the tire thus formed, the drop heights n and q of the block and the central land are eliminated, and the ground contact surfaces substantially coincide with the virtual lines k and r, respectively.

[0015]

[Effect] To confirm the effect of the tire according to the present invention 29
Using radial tires for passenger cars of 5 / 35ZR18 size, a partial wear test was performed on an actual vehicle with a comparative example and evaluated. The test tires having the shapes shown in FIGS. 1 and 2 were commonly used. In this case, the width v of the sipe 11 was 1 mm. For the tires of the examples, a flask type in which the bottom width w of the sipe was inflated by 2 mm was used in the block 12 before the internal pressure filling.
Therefore, a drop-shaped height n was set to 0.5 mm to form a kamaboko shape. Central land area
The drop height q of 10 is 0.5 mm. On the other hand, the sipe applied to the tire of the comparative example has a normal shape that does not inflate the bottom part, and the falling height q with respect to the central land part and the block.
, N is 0, which is a normal shape.

The test tire was assembled on an 18 × 10.5J rim, filled with an internal pressure of 2.5 Kgf / Cm ^2, and the shape of the tread was examined. According to the results, the tire of the example was deformed at the position of the inclined main groove. The grounding surface of the kamaboko-shaped block coincides with the line k,
It was also confirmed that the ground contact surface of the central land also formed an ideal shape that coincided with the line r. On the other hand, in the tire of the comparative example, both ends of each block are bulged outward in the radial direction by the amount corresponding to the drop height n, and the central land portion also similarly has the entire amount corresponding to the drop height q in the radial direction. It had a shape protruding to the outside.

The test tires were run on an asphalt pavement peripheral circuit at a speed of 100 km / H for a distance of 10,000 knots in actual vehicles, and the state of wear after running was measured. as a result,
In the tire of the comparative example, the central land portion was worn by 0.5 mm more than the level of the inclined land portions on both sides of the groove, resulting in a step difference.
Further, heel-and-toe wear of the block (inclined land portion), that is, uneven wear in which the amount of wear at the end on the kicking side of the block is 1.4 mm on average rather than the end on the stepping side occurs. On the other hand, in the tires of the examples, the wear level difference at the central land portion was not substantially recognized, and the heel and toe wear was 0.5 mm on average.

As described above, the V-shaped inclined land portion includes a plurality of blocks divided by the flask-type sipe whose bottom portion is inflated, and when no internal pressure is applied to the tire, the block has a kamaboko with a raised central portion. The tire of the present invention, which is characterized by a profiled section and a ground contact surface lower than the left and right inclined land portions, can advantageously solve the problem of uneven wear.

[Brief description of drawings]

FIG. 1 is a sectional view of a tire according to an embodiment.

FIG. 2 is a plan view of the tread of the embodiment.

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

FIG. 4 is a sectional view taken along line BB in FIG.

5 is a cross-sectional view taken along the line CC of FIG.

[Explanation of symbols]

 1 Tire 2 Sidewall 3 Crown 4 Carcass 5 Belt layer 6 Tread 8 Inclined main groove 9 Inclined land 10 Central land 11 Sipe 12 Block 13 Ground contact surface of central land 14 Sipe bottom

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B60C 11/12 A 7504-3B C 7504-3B 7504-3B B60C 11/08 A

Claims (1)

[Claims] 1. A crown portion is connected between a pair of annular sidewalls, and a portion extending from one of the sidewalls through the crown portion to the other sidewall is reinforced by a radial arcus, and While arranging a non-stretchable belt layer and a tread on the outer circumference of the crown portion for reinforcement,
The above-mentioned tread extends in a V-shape from both ends thereof at intervals in the circumferential direction to the vicinity of the equator plane, and the tip portion is curved and inverted to form a large number of inclined main grooves which are adjacent to each other, and are divided by these main grooves. In a tire having left and right slanted land portions and a center endless land portion, the slanted land portion includes a plurality of blocks divided by a flask-type sipe with a bulging bottom portion, and when no internal pressure is applied to the tire, the block is a center portion. A pneumatic radial tire characterized in that each of the central land portions has a ground contact surface lower than that of the inclined land portions on the left and right sides, and a raised kamaboko-shaped cross section.