JPH03506A - Pneumatic tire whose shoulder portion partial wear is reduced - Google Patents

Abstract

PURPOSE:To prevent a shoulder drop wear and improve the qualities of anti- wear and operation stability at a heavy load tire, by forming a number of sipes in a tire diameter direction from the buttress portion of a tread side surface and in a predetermined depth separation from a tread surface portion. CONSTITUTION:A number of sipes 7 which open at the buttress portion 6 of a tread side surface on the outer side than a ground contact portion 5 and which extend in a tire breadth direction, are provided at a shoulder portion 4. A sipe 7 is not almost opened at the tread surface portion 3 of a tread 2, and is formed at a portion separated from the tread surface portion 3 radially as much as a depth h which is more than one third of the depth H of a main groove 1. Also, a sipe 7 depth D which is from the surface of the buttress portion 6 toward the tire breadth direction, is set at a depth which is about 0.2-1.5 times the depth H of the main groove 1. As a result, the prevention of a shoulder drop wear, the improvement of anti-wear and the improvement of operation stability are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty radial tire that suppresses uneven wear such as drop-off wear on a portion of the shoulder.

[Conventional technology]

In heavy-duty tires with high rigidity, due to the difference in height between the center of the tread and part of the shoulder, there is a large amount of slippage in the part of the shoulder, and the part of the shoulder tends to wear out in a step-like manner at an early stage, so-called shoulder drop wear.

One way to prevent uneven wear on a part of the shoulder, especially shoulder drop wear, is to provide a large number of short sipes that extend in the width direction of the tire from the contact edge toward the center of the tread and open on the tread surface. A method of reducing the rigidity of the nearby tread rubber to make it easier for the tread edge to follow the slippage on the road surface, reducing the amount of slippage on part of the shoulder and preventing uneven wear. A method of reducing the rigidity of a part of the shoulder by providing a narrow sub-groove extending in the circumferential direction (JP-A-63-232007, JP-A-63-
240403) etc. are widely practiced, and a method combining these methods (Japanese Patent Laid-Open No. 63-25203) is also known.

[Problem that the invention seeks to solve]

Among the methods for preventing shoulder drop wear mentioned above, the method of providing a large number of sipes on the surface of the tread surface of the shoulder part is that if short sipes are applied, shoulder drop wear can be prevented in the siped area, but Significant wear occurs near the center of the tread, and if the sipes are lengthened, toe-and-heel wear is likely to occur in the small area sandwiched between the sipes, and there is also a risk of cranking from the sipes.

If a thin minor groove extending in the circumferential direction of the tire is provided along the contact edge of the tire, the area outside of the minor groove to the contact edge will hardly contribute to the wear resistance of the tread, and the wear resistance of the tire will decrease. . Further, the stiffness of the tire in the width direction near the tread contact edge is greatly reduced, and the steering stability of the tire may be impaired.

Therefore, the present invention eliminates the risk of toe-and-heel wear and cracks caused by the sipes in the shoulder part, prevents the rigidity of the shoulder part from decreasing too much, prevents shoulder drop wear, and improves the wear resistance of the tire. The purpose of the present invention is to provide a tire with excellent handling stability.

[Means for solving problems]

In order to achieve the above object, as a result of extensive research, the inventor of the present invention found that a cut is made in a part of the shoulder of the tire from the side of the tread outside the ground contact edge toward the center of the tread, without opening in the tread. By providing the sipes at a certain distance from the tread surface, the sipes do not appear on the tread surface in the early stages of tread wear, but appear on the tread surface only after the tread wears out more than -100 cm, which eliminates the above-mentioned drawbacks. The present invention was completed based on this discovery.

That is, in a pneumatic radial tire having tread grooves on the tread circumferential surface, a large number of sipes made of thin grooves are cut from the buttress portion of the tread side surface outside the ground contacting end of the tread along the radial cross section of the tire, Most of the sipes are spaced apart from the tread surface in the radial direction of the tire by at least 173 cm, which is the depth of the deepest tread groove among the tread grooves. The gist is a pneumatic tire with reduced weight.

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

FIG. 1 is a partially sectional perspective view of the tire of the present invention, and FIG. 2 is a detailed sectional view of a part of the shoulder of FIG. 1 near the ground contact end. (1) is the tread surface (3) of the tire tread (2).
) is a main groove provided approximately along the circumferential direction of the tire, and a sipe (4) extending in the width direction of the tire opens in a buttress part (6) of the tread side surface outside the ground contact edge (5) in the shoulder part (4). 7). Sipe (η is tread (2
) has almost no opening in the tread (3), and its sipe (7)
Most of the parts are located deeper than a certain depth from the tread surface (3). The preferable depth h is 1/3 or more of the depth H of the main groove (1). The entire portion of the sipe (7) does not need to be at least this depth from the tread portion (3), for example, as shown in FIGS. 2 and 3, a portion of the sipe (7) may
3) may be located at a shallower position, or a portion may be opened above the tread portion (3).

However, at a point where the depth d measured from the surface of the buttress portion (6) in the tire width direction is 0.2 times the depth H of the main groove (1), the tread portion of the sipe (7) It is necessary that the depth h from (3) is 173 or more of the depth H of the main groove (1). .

The depth h of this sipe (7) from the tread portion (3) is the main groove (
If it is shallower than 1/3 of the depth H in 1), the sipe (7) will open into the tread (3) early in the tire wear, and the rigidity of the shoulder part (4) will decrease too much. There is a risk of reduced steering stability and toe and heel wear.

The depth D of the sipe (7) from the surface of the buttress R (6) in the tire width direction is 0.2 to 1.5 of the depth H of the main groove (1).
Double is desirable. If the depth D of this sipe (7) is too large, the rigidity of the shoulder part (4) will be too small, resulting in a decrease in steering stability and other problems, and if the depth D is too small, it will not be effective in preventing uneven wear. is small.

The radius W of the sipe (7) in the tire circumferential direction is 0.2 to 1.5 m.
About m is preferable. Further, the length of the sipe (7) in the tire radial direction is suitably 1 to 4 times the depth of the main groove [1]. The pitch P at which the sipes (7) are arranged on the shoulder part (4) is not particularly limited, and varies depending on the length and depth D of the sipes (7), but is usually desirably about 3 to 12M.

FIG. 5 is a perspective view of another embodiment of the tire of the present invention. A narrow portion along the peripheral edge (9) of the sipe (7) other than the opening (8) is widened in the tire circumferential direction to provide a U-shaped enlarged portion αQ. The width of the enlarged portion αQ in the tire circumferential direction is 1.5 to 8 times the width W of the sipe (7).

Further, as shown in FIG. 5, between the sipes (7) of the shoulder portion (4) of the tire of the present invention, sipes (6) that open to the conventional tread portion (3) may be intermixed.

The present invention is applicable to any radial tire with rib pattern, block pattern, lug pattern, rib-lug pattern, etc.

[Effect]

According to the pneumatic tire of the present invention, the buttress portion (6)
Due to the sipe (7) cut in the width direction of the tire, the base of the ribs, blocks, etc. near the ground contact end (5) of the shoulder part (4) is cut in the width direction, reducing the rigidity in the circumferential direction. It becomes easier to move in response to the tangential force caused by the frictional force with the road surface when it touches the ground, has a high ability to follow slippage, and can prevent uneven wear.

In the early stages of tire wear, the sipes (4) on the shoulder part (4)
7) has almost no opening in the tread portion (3), so the stiffness of the shoulder portion (4) does not become too small, and there is little deterioration in steering stability. When the tread (2) wears to a depth h, the sipes (7) will open in the tread (3), but at that time the main groove (1) has already become shallow and the tread (2) will open.
) has high rigidity, so even if the rigidity of the shoulder part (4) decreases due to the sipe (7), it will not decrease too much, and the sipe (7) opened in the tread (3)
The stiffness of the shoulder portion (4) is moderately reduced, and uneven wear is suppressed. At this time, the thickness of the rubber of the tread portion (3) is considerably reduced compared to the initial thickness, so there is no risk of deterioration of steering stability due to the opening of the sipe (7).

〔Example〕

Tire size 10 having the tread pattern shown in Fig. 1 and having a carcass layer surface of one britain made of steel cord and a belt layer (2) of three plies made of steel cord.
．． A 0OR20 tire of the present invention was manufactured, mounted on the front wheel of a truck, and ran on a paved road for 17,000 km to conduct a wear test. The results are shown in Table 1 as Examples 1 and 2. Further, similar tests were conducted on the same tires with different positions and depths of the sipes (7), and the results are similarly shown in Table 1 as Comparative Examples 1 to 3.

In Table 1, the amount of shoulder drop wear is calculated by applying a gauge that matches the curvature of the center of the tread to the tread of a worn tire, and measuring the extension of the curve (b) and the contact edge (5) as shown in Figure 7.
) was measured. The handling stability was evaluated using a 10-point evaluation method using Comparative Example 1 as a control by performing a sensory test on the test tires by attaching them to the four wheels of a truck after buff-grinding them for 3 years and using Comparative Example 1 as a control.

Table 1 [Effects of the Invention] According to the pneumatic tire of the present invention in which uneven wear of a part of the shoulder is reduced, 1. Uneven wear such as drop-off wear on a part of the shoulder can be prevented, and there is no possibility that the steering stability and wear resistance of the tire will deteriorate.

[Brief explanation of drawings]

FIG. 1 is a partially sectional perspective view of an example of the pneumatic tire of the present invention, FIG. 2 is an enlarged sectional view of the same portion, and FIGS. 3 and 4 are other embodiments of the pneumatic tire of the present invention. 5 and 6 are perspective views of alternative embodiments of the invention,
FIG. 7 is an explanatory diagram of a method for measuring shoulder drop wear amount. (1) Main groove, (3) Tread, (5) - Ground contact edge, (7) - Sipe, (9) ... Peripheral part, ■ - Sipe, Side belt layer, (2) Tread, (4) - Shoulder part, (6) Buttress part, (8)° opening, αQ° ampullae, beaten/carcass layer, α curve. Figure 2 Figure Otsu Figure 7 Tomi Figure 1 Figure 3 Figure 5

Claims (1)

[Claims] (1) In a pneumatic radial tire that has tread grooves on the tread circumference, a number of sipes are provided that are made up of thin grooves cut approximately along the radial cross section of the tire from the buttress portion of the tread side surface outside the ground contacting edge of the tread. , most of the sipes are spaced apart from the tread surface of the tread in the radial direction of the tire by at least 1/3 of the depth of the deepest tread groove among the tread grooves. Pneumatic tires that reduce uneven wear.