JP3516742B2 - 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 a 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, ranging from 0.3 to ultra-flat tires also appear. [0003] When the tire cross section becomes flat, the tire width increases, and accordingly, the tread width is also set to be large. 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 easy to slip on a wet road, especially when traveling at 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 describes a tread structure in which a groove is divided into substantially uniform independent blocks by an inclined lug groove extending in a letter shape, and the ratio of the groove group to the entire tread, that is, the negative ratio is specified.
604. In the tread of the independent block type, when the block is stepped on a ground contact surface during traveling, a tapping sound hits a road surface at a corner of the block, and a vibration of the block generated due to 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 inevitable that steering stability is deteriorated due to insufficient rigidity peculiar to the independent block structure in consideration of drainage. Therefore, instead of the straight circumferential main groove and the lug groove, a large number of main grooves extending greatly in a V-shape from the center of the tread toward both ends in the axial direction are provided. Treads, which consist of land sections separated by main grooves, have recently attracted attention. And in this case,
For a land portion in the tread both-side area where a burden on a lateral force acting during cornering is large, by changing the inclined main groove in the axial direction while maintaining the same groove width in the both-side area of the tread (the shaft). Lug grooves of the same width parallel to the main grooves extending into the area, increasing the stiffness of the parts along the land grooves and consequently increasing the width of the undesired circumferential land part in that area. Are additionally arranged to form a fork-shaped subdivision. [0006] A tire provided with a V-shaped main groove in the tread is excellent in terms of steering stability and the above-mentioned noise when traveling straight while maintaining wet skid resistance. I can say On the other hand, the land portion extending in a V-shape divided by such a groove is hard to wear uniformly, and compared to the stepping side end portion of the land portion which comes in contact with the ground first during running, the ejection side which comes in contact with a delay. There is a problem in that the end portions are severely worn and heel-and-toe wear (uneven wear) occurs at a relatively early stage of traveling. This heel-and-toe wear is particularly severe at both ends of the tread extending at a reduced angle with respect to the axial direction of the land portion, and develops in both the depth and the spread as the traveling tongue advances. As a result, not only does the wear appearance of the tread deteriorate, but also the ground contact property deteriorates,
This will adversely affect performance such as vibration and ride comfort. The present invention has been made in view of such a problem, and an object of the present invention is to provide a pneumatic radial tire in which a heel and toe wear is reduced in a tread having a V-shaped inclined main groove. According to the present invention, a crown portion is connected between a pair of annular sidewalls, and a portion from one of the sidewalls through the crown portion to the other sidewall is formed by a radial arc. Further, a non-extensible belt layer and a tread portion are arranged on the outer periphery of the crown portion of the carcass to reinforce the tread portion. And a plurality of main grooves which are inclined from the central portion of the tread portion with respect to the circumferential direction, extend in a V-shape toward the ends of the main tread and extend into the auxiliary tread, and the main groove has an equatorial plane. In the pneumatic radial tire whose rotation direction is specified so as to sequentially contact the ground from the side, the main groove is formed at a central area corresponding to 20% of the main tread width W centered on the equatorial plane. And gradually turns around in the circumferential direction, further inverts, and connects to the adjacent main groove, a main portion extending linearly on both sides thereof in an intermediate area corresponding to 30% of the width W, A rear end portion extending in the end area between the tread end and narrowing the width in the axial direction,
The tread portion has a plurality of land portions divided by the plurality of main grooves, and the land portion is divided into a plurality of blocks by sipes and / or narrow grooves, and a tip portion, a main portion, And the rear end portion is formed such that one groove wall and the other groove wall are respectively 0 to 10 ° and 5 to 20 ° with respect to normals set on the main tread surface facing radially outward from the groove bottom. °, 5 to 15 °
At the same time exhibits a U-shape with flared inclined in opposite directions in the angle range, the main unit, and the groove wall of the rear end leading side within the angle range is tilted in the kicking side comparison larger angles It is a pneumatic radial tire characterized by the following. [0008] Here, the stepping side of the groove wall means a side of the two groove walls which first enters the ground contact surface during running, and a side which enters later with a kick-out side. The main tread is the area of the tread where the tire touches the ground when going straight.
Assemble the tire on the regular rim based on the O standard, fill the tire with the regular internal pressure, and make the area contact with the ground when 70% of the design maximum load is applied on the flat plate. The main tread, which is always in contact with the ground when traveling, is a center tire, a middle tire, and an end part, particularly in the case of a flat tire having a wide tread and an aspect ratio of 0.6 to 0.3. In the area, the functions of the main ditch and the land are different. In the present invention, in the central area, the front end of the main groove that is curved and continues to the adjacent main groove forms a pair of left and right circumferential grooves, and this portion is provided with a groove wall that is stood almost vertically at 0 to 10 °, The volume of the groove space is increased under limited geometrical conditions to improve drainage in the circumferential direction. [0011] The relatively large left and right intermediate areas are areas in which lateral force acting upon cornering in addition to drainage is taken into consideration. Therefore, the main groove group extending in a V-shape is wide, and the land portion divided by these main grooves has a lateral component unlike in the central area, so that the heel and toe wear is easily generated. However, in the present invention, the groove wall (which is also a land portion wall) is inclined at a larger angle range of 5 to 20 °, and the road surface on the tread side end side of the land portion which causes heel and toe wear is formed. By setting the slope of the kick-out side where the slip is large, the stepping-side inclination angle of the groove wall is larger, and for the land part, the land part wall of the kick-out side is set larger and the rigidity of that part is given. It suppresses front-rear deformation of the land kick-out part and balances the slip with the road surface. The relatively narrow end area near the end of the main tread is an area where a large lateral force acts during cornering. Therefore, the direction of the main groove is changed in the axial direction to form a land portion extending in the same direction. However, when such a land portion is provided in this area, heel and toe wear is significantly generated. In the present invention, the rigidity of the main groove is reduced by narrowing the width of the main groove and setting the inclination angle of the land portion wall to be larger at the kick-out end as in the case of the intermediate area in the angle range of the groove wall. To suppress heel and toe wear due to slippage due to local deformation in the front-rear direction. An embodiment will be described below with reference to the drawings. FIG. 1 is a tread plan development view of a tire showing one embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG.
FIG. 4 is a sectional view taken along the line CC in FIG. In the present invention, although not shown, the tire has a crown portion connected between a pair of annular sidewalls, and a radial arc extends from one of the sidewalls through the crown portion to the other sidewall. A non-extensible belt layer and a tread portion are reinforced around the crown portion of the carcass.
1 is placed and strengthened. Radial cascades use fiber codes represented by polyester and rayon as equatorial planes.
At least one of the plies arranged in a direction substantially orthogonal to
The belt layer has a well-known structure, and the belt layer also has a ply in which non-extensible cords such as steel cords are inclined at a shallow angle (15 to 35 °) with respect to the equatorial plane O. Of two or more, usually two, superposed so that their codes cross each other, and furthermore, a plurality of heat-shrinkable cords such as nylon are arranged around the entire periphery thereof, and a circumferentially spirally wound rubberized strip is used. This is a known structure including the formed cap layer. The tread portion 1 has a cylindrical main tread 1
_1, with consists auxiliary tread 1 ₂ followed with rounded on both sides, extends from a position close to the equatorial plane O of the tread portion inclined in a V-shape with respect to the axial direction to the respective main tread end E direction, further auxiliary number of the main groove continues to the tread 1 in the ₂ 2
And land portions 3 divided by these main grooves 2.
The main groove 2 has a main tread width W of 20 mm around the equatorial plane O.
% In the central area X, which gradually changes its direction in the circumferential direction and further reverses to connect to the adjacent main groove 2 and an intermediate area corresponding to 30% of the main tread width W on both sides thereof.
In Y, the main part y having a relatively large width b and extending linearly
And the end zone Z between these intermediate zones and the main tread edge
At a width c, a rear end portion z that extends substantially in the axial direction and turns. The groove walls 4 at the leading end x, the main part y, and the rear end z of the main groove are respectively radially outward from the groove bottom 5 with respect to the normal line n of the main tread surface to β · β ′.
Is 0 to 10 °, γ · γ ′ is 5 to 20 °, δ · δ ′ is 5
At the same time, it has a U-shape that expands in the range of 15 °
y, and the groove wall 4 at the rear end z, the stepping side 6 is the ejection side
7 It is inclined at an angle larger than the contrast, that is, γ ′> γ, δ ′> δ. In the embodiment of the 225 / 40ZR18 size shown in FIGS. 1 to 4, the main part y of the main groove extending into the middle area Y of the main tread has the widest width b of 11 mm and the inclination angle α with respect to the axial direction. 65 °, and the inclination angles γ (ejecting side) and γ ′ (stepping side) of the groove wall are 5 ° and 20 °, respectively. The leading end x of the main groove is gradually reduced in width a in the central area X to change its peeling in the circumferential direction, and is further inverted to be connected to the leading end x of the adjacent main groove. Therefore, this portion forms a pair of left and right circumferential grooves, and the endless rib 8 is partitioned between them. The inclination angles β and β ′ of the groove wall 4 are 2 ° and 2 °, respectively. The tip portion x can gradually approach the groove wall angles β and β ′ to the groove wall angles γ and γ ′ of the main portion y as the angle with respect to the axial direction is reduced. The rear end portion z of the main groove is squeezed width in the end zone Z, it continues further to the auxiliary tread 1 ₂ in different directions in the axial direction. The width c at the center of the zone Z is mm, and the inclination angles δ (kick-out side) and δ '(step-in side) of the groove wall 4 are 0, respectively.
° and 10 °. The groove wall angle in this area can also be smoothed between the angles γ, γ ′ in the central area. Reference numerals 9 and 10 denote sipes and narrow grooves, which divide the land portion 3 into a plurality (four) of blocks 11 and form a block 11 having a large outermost surface area in the axial direction. Similar to the main groove 2, a narrow lug groove 12 is provided in parallel with the main groove, and the land portion is divided into a plurality of portions 13. As shown in FIG. 1, when the lug groove extends beyond the main tread end E and into the end area Z, the groove wall at that portion has the same angle as the angle δ, δ ′ of the rear end z of the main groove. Can be formed. The main groove leading to auxiliary tread 1 _2, and the same applies to the groove wall of the lug groove. [Effect] In order to confirm the effect of the tire according to the present invention,
Using 40ZR18 size radial tires for passenger cars,
A heel and toe abrasion test using an actual vehicle was performed together with a comparative example to evaluate. The tire used in the example had the shape shown in FIG. In this case, the angle α with respect to the axial direction of the main groove
65 °, groove wall angles β and β ′ are 0 ° and 0 °, γ and γ ′ are 5 ° and 20 °, and δ and δ ′ are 0 ° and 5 ° and the groove width
b and c were 11 mm and 4 mm. The tire of the comparative example was the same as the tire of the example except for the following differences. That is, the angle of the main groove in the end zone Z with respect to the axial direction is 20
°, and the width of the main groove was extended into the auxiliary tread with the width b in the middle area without being narrowed in the end area Z. The groove wall angles are the same for the stepped-in and kick-out sides through the zones X, Y, and Z. After the test tire is assembled on a rim of 18 × 8 size, it is filled with an internal pressure of 2.2 Kgf / Cm ² , and a speed of 50 to 150 km / H is provided in a course including a peripheral circuit of asphalt pavement and a general road. The hill and toe abrasion step after traveling was measured by traveling a distance of 4000 km with an actual vehicle in the range.
As a result of the measurement, the tire of the example had a 15 to 30% smaller wear step than the tire of the comparative example, and the appearance of wear was remarkably improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a developed plan view of a tread according to an embodiment. FIG. 2 is a sectional view taken along the line AA in FIG. FIG. 3 is a sectional view taken along the line BB in FIG. 1; FIG. 4 is a sectional view taken along the line CC in FIG. 1; [Description of Signs] 1 Tread 1 ₁ Main Tread 1 ₂ Auxiliary Tread 2 Main Groove 3 Land 4 Groove Wall 5 Groove Bottom 6 Groove Wall Tread Side 7 Groove Wall Ejection Side O Equatorial Plane W Main Tread Width X Central area Y Intermediate area Z End area x Main groove tip y Main groove main part z Main groove rear end

Claims (1)

(57) [Claims 1] A crown portion continues between a pair of annular sidewalls, and a radial arc extends from one of the sidewalls through the crown portion to the other sidewall, and A non-extensible belt layer and a tread portion are arranged and reinforced on the outer periphery of the crown portion of the carcass, and the tread portion is a cylindrical main tread that is grounded in a straight line.
A plurality of main grooves extending from the central portion of the tread portion to the circumferential direction and extending in a V-shape toward the ends of the main tread and extending into the auxiliary tread. In the pneumatic radial tire in which the rotation direction is specified so that the main groove is sequentially in contact with the equatorial plane side, the main groove is 20% of the main tread width W about the equatorial plane.
A tip portion which is gradually turned in the circumferential direction in a central area corresponding to the above and further inverted to continue to the adjacent main groove, and a main portion extending linearly on both sides thereof in an intermediate area corresponding to 30% of the width W, and In the end area between the intermediate area and the main tread end, the width is reduced and the rear end part extends while changing the direction in the axial direction, and the tread portion includes a plurality of land portions divided by the plurality of main grooves. The land portion is divided into a plurality of blocks by a sipe and / or a narrow groove, and a front end portion, a main portion, and a rear end portion of these main grooves are formed as one groove.
The wall and the other groove wall are respectively 0 to 10 ° with respect to a normal line standing on the main tread surface facing radially outward from the bottom of the groove, respectively.
5-20 °, 5-15 ° in opposite directions
The air is characterized by having a U-shape that is inclined and widened, and that the main portion and the groove wall of the rear end portion are inclined at an angle on the stepping side larger than that on the ejection side within the above angle range. Included radial tire.