JP3467081B2 - Pneumatic radial tire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire in which a tread having a V-shaped inclined main groove has reduced uneven wear. [0002] In order to improve high-speed running performance of a pneumatic tire, a structure in which a base portion of a tread is reinforced with a non-extensible belt layer is generally used. It has been practiced to reduce the ratio of the height to the width of the cross section, that is, the aspect ratio. About the aspect ratio, 0.6
The degree is commonly applied, with 0.3 and ultra-flat tires also appearing. [0003] When the tire cross section becomes flat, the tire width becomes wider, and accordingly the tread width is set wider. However, in the case of such a tire, the steering stability on a dry road surface is improved. It is known that the drainage property of the ground contact surface is deteriorated, so that it is slippery especially when traveling on a wet road at a high speed. In order to improve the drainage property, a plurality of circumferential grooves (4 to 6) are provided. V crossing these circumferential grooves
Japanese Patent Application Laid-Open No. 55-140 discloses a tread structure in which a substantially uniform independent block is divided by inclined lug grooves extending in the shape of a letter, and a ratio of the groove group to the entire tread, that is, a negative ratio is specified.
604. In the tread of the independent block type, when the block is stepped on the ground surface during running, the tapping sound hits the road surface at the corner of the block, and the vibration of the block generated due to the friction with the road surface when stepping or kicking out. There is a problem of noise due to noise and the like, and furthermore, it is not possible to avoid a decrease in steering stability due to insufficient rigidity peculiar to the independent block structure in consideration of drainage. Therefore, instead of such straight circumferential main grooves and lug grooves, a large number of main grooves extending in a V-shape that are inclined at an acute angle to the circumferential direction from both ends of the tread toward the center and extend in a V-shape. Treads, which consist of land sections, have recently been attracting attention. [0005] It can be said that a tire having a V-shaped main groove in a tread is excellent in both noise and handling stability while maintaining wet skid resistance. On the other hand, however, it is not easy to obtain a uniform contact pressure distribution because such a tire is applied to a wide tread. By filling the internal pressure, the inclined main grooves are slightly deformed, and the land formed between them is affected by the deformation depending on the position in the land. If the contact pressure distribution is not uniform, uneven wear (heel and toe wear) is likely to occur relatively early in the running, and once uneven wear occurs, it develops three-dimensionally in both depth and spread, resulting in tread. Not only does the abrasion appearance of the tire deteriorate, but it also impairs the tread's contact with the ground and causes vibration and the like. 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. According to the present invention, a crown portion is connected between a pair of annular side walls, and a radial dial extends from one side wall through the crown portion to the other side wall. A reinforcement is provided with a non-extensible belt layer and a tread on the outer periphery of the crown portion of the carcass, and the tread portion is reinforced by the tire equator.
On both sides of the tire from the center of the tread to the outside in the tire width direction.
Tread end
A plurality of main grooves that open in the tread portion of the tire
End of the main groove on the tread center side on both sides of the equatorial plane
Change the angle of inclination so that it follows the
Connected to the middle of the other main groove
A rib-shaped land portion arranged in the center of the pad and extending in the circumferential direction;
Inclined land portions arranged on both sides of the rib-shaped land portion are formed
In a pneumatic radial tire, the inclined land portion includes a plurality of blocks divided by a flask-type sipe whose bottom is inflated. The central land part is characterized by forming a lower contact surface than the left and right inclined land parts, respectively. Here, the tread refers to the area of the tread portion where the tire touches the ground when the vehicle goes straight ahead.
Assemble the tire on the regular rim according to the standard, fill it with the regular internal pressure, and set the area to contact the ground when 70% of the design maximum load is applied on the flat plate. A tread comprising a row of left and right sloping land portions and a circumferential endless land portion extending at a position sandwiched between the two is an advantageous structure for suppressing noise, but is particularly flat with a wide tread width. When this tread is applied to a radial tire, 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 remarkably narrow sipe, and the position of the inclined main groove is slightly deformed by filling the internal pressure, and these inclined main grooves are This means that the contact pressure on both sides of the adjacent land is higher than that on the center, and the contact pressure on the central land is generally higher on the inclined land on both sides of the trench. In the tire according to the present invention, when the tire is in a free state in which no internal pressure is applied, the land portion or the block divided into the inclined main grooves corresponding to the above-mentioned projection amount has a semi-cylindrical 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 an internal pressure is applied and a load is applied, whereby uneven wear can be advantageously suppressed. In addition, the flask-type sipe with a bulging bottom that re-partitions the sloped land,
It is also effective in preventing the reduction of wet skid resistance after abrasion has progressed, and the relative level reduction of the central land contact surface prevents local excessive heat generation in this part during high-speed driving, thereby resulting in high-speed durability It is also effective for improving the performance. An embodiment will be described below with reference to the drawings. FIG. 1 is a sectional view of a tire showing one embodiment of the present invention, and FIG. 2 is a tread plan view of the tire. In the present invention, tire 1 is
A pair of annular side walls 2 and a crown portion 3 extending between the two side walls 2, and a radial arc extending from one side wall 2 through the crown portion 3 to the other side wall 2. A non-extensible belt layer 5 and a tread are provided around the crown portion of the carcass.
6 is placed and strengthened. The carcass 4 has a known structure comprising at least one, usually two, plies in which fiber codes typified by polyester and rayon are arranged in a direction substantially orthogonal to the equatorial plane O. 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 through auxiliary treads 7 having rounded sides. Tread 6 is spaced circumferentially at both ends
A plurality of inclined main grooves 8 extending in a V-shape from E to near the equatorial plane O, and the tip end G is curved inversion and connected to each other, and left and right inclined land portions 9 divided by these inclined main grooves 8, And has a central endless land. And the slope land 9
Includes a plurality of blocks 12 divided by a flask-shaped sipe 11 with an inflated bottom.When no internal pressure is applied to the tires, the blocks 12 are in the shape of a semicircle, and the central land 10 is a lower ground contact than the left and right inclined land 9, The surface 13 is formed. In the present invention, the ratio H / S of the tire width S to the section height H is 0.1.
The present invention can be suitably applied to a flat radial tire for passenger cars of 3 to 0.6. In the embodiment shown in FIG. 2, the angle α of the inclined main groove 8 with respect to a 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 size of the tire, the pitch arrangement applied to the tread portion, and the like. The leading end G of the inclined main groove is narrowed, the width is changed in the circumferential direction, the direction is further reversed, and the adjacent inclined main groove 8 is rotated.
It is connected. Therefore, the left and right inclined land portions 9 and 9 and the central land portion 10 are independent of 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 14 can be applied in the range of v <w <3v. The depth of the sipe is preferably equal to or slightly smaller than the depth of the main groove. FIG. 4 is a sectional view taken along the line BB in FIG. In FIG. 4, the block 12 has both ends close to the main groove lower than the imaginary line k indicating the ground surface at the time of filling the internal or internal pressure (the drop height n at both ends is 0.5 mm). Although slightly, the central portion 15 of the block has a raised semicircular cross section. Drop height n is 0.3 ~
0.5 mm is preferred. FIG. 5 is a sectional view taken along the line CC in FIG. In FIG. 5, the central land portion 10 has a ground surface 13 which is lower by q than an imaginary line (also a level at the time of internal pressure filling) r connecting the surfaces of the blocks on both sides. The drop height q in this embodiment is about 0.5 mm, but can be applied in the range of 0.3 to 0.5 mm. By filling the tire thus formed with the used internal pressure, the drop heights n and q of the block and the central land portion are eliminated, and the ground contact surfaces substantially coincide with the imaginary lines k and r, respectively. [Effects] In order to confirm the effects of the tire according to the present invention, 29
Using a 5 / 35ZR18 size radial tire for a passenger car, an uneven wear test was carried out on a real vehicle using comparative examples and evaluated. 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. Regarding the tire of Example, the bottom width w of the sipe was made into a flask type in which the width was expanded by 2 mm.
In each case, the height n was 0.5 mm. 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 portion, and has a falling height q with respect to the central land portion and the block.
, N are each 0. The test tire was assembled on an 18 × 10.5J rim, filled with an internal pressure of 2.5 kgf / Cm ² and examined for the shape of the tread. According to the results, the tire of the example showed deformation at the position of the inclined main groove. The ground surface of the kamaboko block matches line k,
It was also found that the ground contact surface of the central land formed an ideal shape corresponding to the line r. On the other hand, in the tire of the comparative example, both ends of each block fall in the shape of a drum corresponding to the height n, and the center land portion also has a radially extending amount corresponding to the height q. The shape protruded outward. The test tires were run on an asphalt pavement circuit at a speed of 100 km / H for a distance of 10,000 km in a real vehicle, and the state of wear after running was measured. as a result,
In the tire of the comparative example, the central land portion wears on average 0.5 mm more than the level of the inclined land portion on both sides across the groove, and a step occurs,
In addition, uneven wear was found in the heel and toe wear of the block (inclined land portion), that is, the wear amount at the kick-out end of the block was 1.4 mm larger than that of the step-side end on average. On the other hand, in the tires of the examples, the wear step in 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 a flask-type sipe having an inflated bottom portion. The tire according to the invention, characterized in that it has a profiled section and that the central land has a lower contact surface than the left and right inclined lands, can advantageously solve the problem of uneven wear aimed.

[Brief description of the drawings] FIG. 1 is a sectional view of a tire according to an embodiment. FIG. 2 is a plan view of a tread of the embodiment. FIG. 3 is a sectional view taken along line AA in FIG. 2; FIG. 4 is a sectional view taken along the line BB in FIG. 2; FIG. 5 is a sectional view taken along the line CC in FIG. 2; [Explanation of symbols] 1 tire 2 Side wall 3 Crown 4 Carcass 5 Belt layer 6 tread 8 Inclined main groove 9 Inclined land 10 Central Land 11 Sipe 12 blocks 13 Central Land Surface 14 Sipe bottom

Claims (1)

(1) A crown portion extends between a pair of annular side walls, and a radial arc extends from one side wall through the crown portion to the other side wall. With a non-extensible belt layer and a tread placed around the crown of the carcass and reinforced,
The above tread is located on the center of the tread on both sides of the tire equatorial plane
The same direction from the tire width direction to the outside in the tire width direction
It has a number of main grooves that extend at an
For example, the above treads on both sides of the tire equatorial plane
The tread center side end of the main groove is inclined so as to follow the circumferential direction
Change the angle to connect to the middle part of another circumferentially adjacent main groove.
By being tied, it is located at the center of the tread and
A rib-shaped land portion extending in the direction of
Pneumatic radial tires with a sloping sloping land
In addition, the inclined land portion includes a plurality of blocks divided by a flask-type sipe whose bottom is inflated, and when no internal pressure is applied to the tire, the block has a semi-cylindrical cross section with a raised central portion. Are pneumatic radial tires, each having a lower contact surface than the left and right inclined land portions.