JPH0195909A - Tread pattern suppressing uneven wear - Google Patents

Abstract

PURPOSE:To promote the prevention from shoulder dropping wear by forming a crown, defined by a radius of curvature in a tread width direction, in a tread surface larger in a shoulder area than in a center area further tilt grooves in the shoulder area. CONSTITUTION:A tread 1 provides two or more main grooves 2 extending along the peripheral direction. A tire respectively sets an area, interposed by both side shoulder parts 3 and outermost main grooves 4 being the main groove 2 most approaching the shoulder part 3, to a shoulder area 5 further an area in the tread central part, interposed by the outermost main grooves 4, to a center area 6. Here the shoulder area 5 parallelly forms many shallow tilt grooves 7 which extend in a width direction of the tread 1 gradually deepening toward the shoulder part 3. While forming a radius of curvature of the center area 6 in the section of diametric direction, when assumed Rc for crown further R1 for crown in a protrusive part 8 in the shoulder area 5, respectively, the radius of curvature is set to a relation where R1>Rc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tread pattern that can prevent shoulder drop wear of radial tires for passenger cars, trucks, buses, etc.

[Conventional technology]

When the shoulder parts of radial tires of passenger cars, trucks, buses, etc., especially heavy-duty vehicles, wear out prematurely, so-called shoulder drop wear occurs, the uneven wear of the shoulder parts gradually progresses toward the center of the trend, and the tire wears out. In addition to shortening the life of the tire, the appearance of the tire is also undesirable if shoulder drop wear occurs.

Conventionally, as a countermeasure for this shoulder drop wear of radial tires, Japanese Patent Publication No. 56-40044 and Japanese Patent Application Laid-open No. 58-19460 have been proposed.
As disclosed in No. 6, a minor groove is provided along the circumferential direction at a position close to the shoulder of the tire tread, and even if shoulder drop wear occurs on the shoulder of the tire, the uneven wear can be absorbed from the minor groove. A method is used to limit uneven wear to the outside and prevent uneven wear from progressing beyond the minor groove toward the center of the tread.

In addition, one way to proactively prevent tire shoulder drop wear is to provide a large number of sipes in the shoulder part of the tire that open to the buttress part between the shoulders. ,
There is a known method of increasing the ability of the rubber in the shoulder portion to follow the sliding force and eliminating the trigger for uneven wear in the shoulder portion.

(Problems to be Solved by the Invention) The above-mentioned method of providing a trend sub-groove along the shoulder portion can prevent shoulder drop wear occurring at the shoulder portion from progressing to the center of the tread; It is not possible to prevent the shoulder drop wear itself from occurring at the shoulder part, and due to the shoulder drop wear between the minor groove and the shoulder,
A step is created between that part and the center of the tread, which impairs the appearance.

Furthermore, although the above-mentioned method of providing an open sipe in the buttress portion has the effect of preventing shoulder drop wear to some extent, it is not sufficient and the occurrence of shoulder drop wear is often observed.

Therefore, an object of the present invention is to provide a tread pattern that can sufficiently prevent the occurrence of shoulder drop wear in radial tires.

[Means for solving problems]

To achieve the above objective, the inventors have conducted intensive research and found that uneven wear such as shoulder-drop wear starts with a small trigger, and once uneven wear begins, it spreads rapidly. We found that the most important thing is to eliminate the trigger, and if we can eliminate the initial trigger, uneven wear can be prevented.The causes that trigger shoulder drop wear are: a) Curvature of the crown part Therefore, the diameter of the center part of the trend is larger than that of the shoulder part, and the circumferential difference that arises between the two parts from this, b> Decrease in rigidity of the shoulder part in the width direction of the trend, 02 points are the main points.

For a), the difference in circumference can be reduced by increasing the radius of curvature in the trend width direction of the crown (hereinafter referred to as "crown R"), but the tread rubber at the shoulder becomes thicker, heat generation increases, and separation, etc. Another problem arises.

b) The belt width is made relatively wider than the tread width (by making the belt width relatively wider than the tread width, the stiffness in the width direction of the shoulder part can be increased, but if the belt is too close to the side part of the tire, the crank at the end of the belt, the belt Failures such as severance are likely to occur.

The present invention provides a crown R in the shield area of the tread.
is larger than the crown R on the inner side to reduce the difference in circumference between the center part of the tread and the shoulder part, and at the same time, in the shoulder area, a shallow inclined groove with a pattern that gradually deepens towards the shoulder is created in the width direction of the tire. By arranging a large number of tires approximately parallel to each other, it improves heat dissipation.Furthermore, by providing a narrow sipe at the bottom of the sloping groove with one end opening to the buntless part, it improves the followability of the shoulder part in the tire circumferential direction. This eliminates the cause of shoulder drop wear between the shoulders.

Next, the content of the present invention will be explained in detail with reference to the drawings.

Fig. 1 is a developed view of a tread pattern that suppresses uneven wear according to the present invention, Fig. 2 is a radial cross-sectional view of the same, Fig. 3 is a perspective view of an example of the shield area of the tread pattern, and Fig. 4 is the same. It is an enlarged sectional view.

The tread (11 is a plurality of main grooves (2) extending along the circumferential direction
), and the area sandwiched between the shoulder portions (3) on both sides and the outermost main groove (4), which is the main groove (2) closest to the shielder part (3), is called the shielder area (5), 2 The central area of the tread (1) sandwiched between the outermost main grooves (4) of the book is defined as the center area (6). Part (3)
A large number of wedge-shaped shallow slanted grooves (7) are arranged in parallel, the grooves becoming gradually deeper toward the surface. As a result, in the shoulder region (5), convex portions (8) sandwiched between the inclined grooves (7) and recessed portions (9) formed by the inclined grooves (7) are alternately arranged in parallel.

The radius of curvature of the center region (6) in the radial cross section, the crown R is Re, and the convex part (
When the crown R of 8) is R1, it is determined so that R1>Rc. (The bottom surface α of the IJi oblique groove (7) has a radius of curvature R2 smaller than the crowns R and R1 of the surface (shoulder region < 5). R2 can be approximately equal to Rc.

The width of the convex part (8) and the concave part (9) is 5 to 20 a+m, respectively.
The height difference between the convex part (8) and the concave part (9) is preferably the greatest at the ground contact end of the shoulder part (3), but the height difference in this part is 1.0 to 1.0. 4.0-■ is desirable.

A sipe aD consisting of one or more narrow grooves is provided in the bottom surface OI) of the inclined groove (7) in the width direction of the tread (1), with one end opening into the buttress portion Q4). It is preferable that the sipe αυ be provided along both sides of the inclined groove (7) that are in contact with the convex portion (8). 8 of W
~50%, the average depth h of which is 50% of the depth H of the main groove (2)
~150% is appropriate. The average depth h of the sipe αD here is the length of the side area of the sipe Qυ! It is divided by .

[Effect]

According to the tread pattern of the present invention, (11) the crown R and R1 of the shielder region (5) are made larger than the crown R% Rc of the center region (6), and (11) the surface body is formed to have a constant crown R. In some cases, by raising the shoulders of the shoulder region (5), the difference in diameter and circumference between the shoulder region (5) and the center region (6) becomes smaller, and as a result, the slippage of the shoulder portion (3) is reduced.

(2) By providing unevenness in the shield area (5), the ground contact area becomes smaller, the pressure on the ground contact surface becomes higher, the frictional force increases, and the resistance to soaking increases.

(3) By providing the recess (9) with a size Qυ, the movement of the convex part (8) in the circumferential direction is facilitated, and from the beginning to the end of contact, shearing force is applied to the tread rubber surface based on the difference in circumference. (Resistance to relative soaking) Improves followability and prevents slipping.

Comparing the road surface conditions of the tread pattern of the present invention and a conventional tire with only sipes Qυ provided in the shield area (5), as shown in FIG. 5, the conventional tread pattern shown in FIG. As shown in the figure, there is a wide sliding area Oa and a small adhesion area (2), especially a wide sliding area aδ on the ground contact surface of the shield area (5), whereas the present invention shown in FIG. In the tread pattern, the soaking area (b) is small (, the sillage area (5)
Therefore, in the tread pattern of the present invention, only the sagging in the sillder region (ω) does not become larger compared to the center region (6).

(Example) Tires with a tire size of 12R24514PR having the tread pattern shown in Figs. 3 and 4 were installed on the front wheels of an intercity bus in the metropolitan area, and a 100% paved road was covered with 80,000 yen.
The vehicle was driven for 1 km, and shoulder drop wear Δh was measured. The results are shown in Table 1.

Similarly, a tire of the same size has a tread pattern with a circumferential minor groove (2) without raised shoulders, unevenness, or sipes in the shoulder area (5) shown in Figure 6, and a shoulder area (5) shown in Figure 7. Raised shoulder, no unevenness, sipe α
Comparative Example 1.2 and Table 1 also show the results of a similar test for a tire of the same size provided with only D.

Table 1 Shoulder drop wear Δh is calculated from the center area (
6) is indicated by the distance between the extended surface of the surface and the surface of the shoulder region (5).

〔Effect of the invention〕

According to the tread pattern that suppresses uneven wear of the present invention,
The slip area in the shoulder area is reduced, there is no difference in the amount of wear between the shoulder area and the center area, and it is possible to prevent shoulder drop wear in which only the shoulder area wears out prematurely.

[Brief explanation of the drawing]

Fig. 1 is a developed view of the tread pattern that suppresses uneven wear according to the present invention, Fig. 2 is a radial cross-sectional view of the same, Fig. 3 is a perspective view of the shoulder region of the same tread pattern, and Fig. 4 is an enlarged cross-section of the same. It is a diagram. FIG. 5 is an explanatory diagram of the ground contact conditions of tires with conventional and inventive tread patterns, FIGS. 6 and 7 are developed views of tread patterns of comparative tires, and FIG. 8 is a method for measuring debris wear. FIG. (ll---) Red, (2) -Main groove, (
3)...shoulder part, (4)--outermost main groove, (5)--shoulder region, (6)--center region, (7)--slanted groove, +8) -Convex part, (9)--Concave part, (II--Bottom surface,
a toe sipe, 0 - slip area, α3-1
a Wearing area Q41 - buttress part, +19 - circumferential minor groove. Patent applicant: Toyo Rubber Industries Co., Ltd. Agent: Yoshi Koyama, patent attorney 2 Figure 2 (1)... Toshirad (2)... Main groove (3)...
... Shoulder part (4) ... Outermost main groove (5) ...
・Shoulder area (6)...Center area (7)・
・・Slanted groove (14)... Buttress part (15)
Circumferential minor groove Fig. 7 Fig. 5 σ b d No. 8; Fig. 3 Fig. 4 Fig. 6 Sunosfn7v! J

Claims (4)

[Claims] (1) In the tread pattern of a radial tire that has two or more main grooves extending in the circumferential direction, the ground contact part of the tread is the two outermost main grooves, which are the main grooves closest to the shoulders, and the shoulder parts on both sides. The crown R, which is defined by the radius of curvature of the tread surface in the tread width direction, is composed of two shoulder regions sandwiched by the ground contact edges and a center region sandwiched between the two outermost main grooves. The crown R of the tread is larger than the crown R of the center region, and a large number of shallow inclined grooves are provided in the shoulder region substantially parallel to the width direction of the tread that gradually deepen from the outermost main groove toward the shoulder contact end. A tread pattern that suppresses uneven wear, characterized in that the bottom surface of the inclined groove is provided with a sipe that opens at the ground contact end of the shoulder portion to a buttress portion on the side surface of the shoulder portion. (2) The difference in height between the surface of the convex portion sandwiched between the inclined grooves in the shoulder region and the bottom surface of the inclined grooves is 1.0 to 4.0 mm at the ground contact end of the tread portion. Tread pattern that suppresses uneven wear as described in section. (3) The tread pattern that suppresses uneven wear according to claim 1, wherein the width of the inclined grooves and the interval between adjacent inclined grooves are each 5 to 20 mm. (4) A tread pattern that suppresses uneven wear according to claim 1, wherein the sipes are arranged along both sides of the bottom surface of each inclined groove.