JPH03262710A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To eliminate cracks by forming a siping whose one end is extended to a lug groove and which is formed on the land section arranged on a tread with an end section having a specified depth and a main section which is shallower than the end section and inclining the bottom section of these sections and connecting to each other. CONSTITUTION:The tread T of a tire is provided with a plurality of peripheral direction grooves 10 to 12 in parallel with each other by which the land section is divided into a plurality of sections 20 to 23. A plurality of lug sections 30 and notches 31 are arranged so as to cross each peripheral direction grooves 10 to 12. In addition, at least the land section 23 is provided with a siping 40 at least one end of which is extended to a lug groove 30. In such structure, a siping 40 comprises tapered ends 40A and 40B having depth equal to the depth of the lug groove 30 next to itself or less and flat main sections 40C which are shallower than them. The bottom section is formed by inclining both ends 40A and 40B and the main sections and connecting them to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an improvement of a pneumatic tire, and more particularly, to a pneumatic tire with improved group crack resistance and excellent durability. It is something.

(Prior Art) Generally, the performance of pneumatic tires for automobiles is improved by forming various patterns on their treads.

That is, a plurality of grooves are provided in the tread portion of the tire in the circumferential direction of the tire, and a plurality of land portions are divided by these circumferential grooves.

In addition, lug grooves or notches are arranged at predetermined intervals in the circumferential direction in a direction that intersects with the circumferential groove, and furthermore, in order to adjust the rigidity of the tread portion, various lug grooves or notches are arranged in the circumferential direction or width direction. There are shaped sipes.

Appropriate rigidity is maintained particularly in the land portion on the tread end side by providing a sipe with at least one end communicating with the lug groove or notch.

That is, FIG. 3 is a partial cross-sectional view of the tread portion of a conventional pneumatic tire, where T is the tread portion, 1 is the lug groove, 2 is a linear circumferential sipe or narrow groove, and 3 is the lug groove 1. It shows a sipe cut so that one end and the other end communicate with the circumferential sipe 2.

Here, the sipe 3 is shallower than the lug groove 1 and the circumferential sipe 2, and its bottom 3A is formed flat with a constant depth.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional pneumatic tire, tensile strain concentrates on both ends 3B and 3C of the bottom 3A of the sipe 3, especially at the 3B position, especially during load transfer of the tire. , cracks are likely to occur in these parts.

There is a problem in that the cracks generated in these parts, especially at the 3B position, grow in length and width as the tire runs, leading to tire failure and impairing the durability of the tire.

Therefore, an object of the present invention is to solve the problems of the conventional pneumatic tires described above.

Therefore, it is an object of the present invention to provide a pneumatic tire that eliminates cracks caused by sipes formed particularly in the width direction of the tire and has excellent durability.

[Structure of the Invention] (Means for Solving the Problems) That is, the pneumatic tire of the present invention has a plurality of circumferential grooves, and grooves extending in a direction intersecting the circumferential grooves and spaced at approximately equal intervals in the circumferential direction. A tire comprising a tread including arranged lug grooves or notches, a land portion divided by the circumferential groove, and a sipe formed in the land portion, at least one end of which communicates with the lug groove or notch, The above-mentioned sipe consists of an end portion whose depth is up to the depth of the adjacent lug groove or notch, and a main portion shallower than the end portion, and the end portion and the bottom of the main portion are slanted and connected. shall be.

(Function) In the pneumatic tire of the present invention, the bottom of the sipe, which is formed in the land portion and at least one end of which communicates with the lug groove or notch, is connected to the bottom of the sipe at a depth that is up to the depth of the adjacent lug groove or notch. The main part is shallower than the end part, and the end part and the bottom part of the main part are connected to each other at an angle, so that the part of the bottom of the sipe that connects to the lug groove or notch is tapered. The tensile strain applied to this portion can be effectively alleviated, and the occurrence of cracks can be eliminated or the timing of their occurrence can be advantageously delayed.

(Example) Hereinafter, examples of the pneumatic tire of the present invention will be described in detail according to the drawings.

Tread portion T of the pneumatic tire of the present invention shown in FIG.
In this embodiment, two zigzag-shaped circumferential grooves 11 and 12 are provided in parallel to the circumferential direction on both sides of the zigzag-shaped central circumferential groove 10 along the circumferential center line,
As a result, the tread portion T is divided into land portions 20.21°, 22, and 23.

Further, the circumferential grooves 10 are provided in both side areas of the lower part of the tread.
．． 11.12, a plurality of lug grooves 30 are provided at predetermined intervals in the circumferential direction, and the circumferential grooves 10.11-112 are provided with cuts in the direction intersecting with these circumferential grooves. Notches 31 are provided at predetermined intervals in the circumferential direction.

Note that the circumferential grooves 10, 11, and 12 may have a zigzag shape parallel to the circumferential direction as shown in the figure, but they may also have a straight line shape, and their groove width and depth are determined according to the groove group. It is the widest and deepest of all.

In addition, the lug grooves 30 are inclined at an appropriate angle from both sides of the tire to the center, usually at an angle of 50 to 70 degrees, and these may also be linear instead of ramp-shaped as shown in the figure.
The groove width and depth are equal to or less than the circumferential groove.

Similarly, the notches 31 are formed at a moderate angle, usually 50 mm, from each circumferential groove] 0.11.12 to both sides or the center of the tire.
The grooves are inclined at an angle of ~70 degrees, and in addition to being linear as shown, they may also be clamp-shaped, and the width and depth of the grooves are equal to or smaller than the lug grooves.

Furthermore, 13, ]4, ]5 and 16 in the drawings are circumferential straight sipes or narrow grooves (hereinafter referred to as sipes) provided to adjust the rigidity of the lower part of the tread, and the width of these sipes is It is designed to be so spacious that it can practically be heard in areas that come into contact with the area.

Further, 32 and 33 in the drawings similarly indicate sipes (sipes) provided as necessary to adjust the rigidity of the tread portion T.
Hereinafter referred to as sipes (2), these do not communicate with the lug grooves 30 or the notches 31, and their groove widths are also set narrow.

In the pneumatic tire of the present invention, sipes (sipes) formed mainly in the width direction of the land portion, at least one end of which passes through the lug groove 30, and in this embodiment also through the notch 31.
The bottom structure of 40.41 (hereinafter referred to as Sipe ■) is constructed as follows.

That is, in FIG. 1, the sipe 140 has one end connected to the lug groove 30 as an extension thereof, and the other end connected to the sipe nlB, 1.
6, respectively, and are inclined at an angle of 45 to 90 degrees with respect to the circumferential direction, and the groove width is 0.5 to 1.51 cm, and the depth is from the above lug *30 and sipe 1113. It is also formed shallowly.

In addition, the sipe 141 has one end connected to the notch 31 as an extension thereof, and the other end connected to the sipe 113.14.15.16, respectively, and is similarly inclined at an angle of 45 to 90 degrees with respect to the circumferential direction. In addition, its width is narrower in this example than the sipe 140, and its depth is shallower than the notch 31 and the sipe [13].

Here, to specifically explain the sipe 140, as shown in FIG.
and tapered end portions 4 which are shallower than the sipe Ir1B and whose bottom has a depth that is limited to the depth of the adjacent lug groove 30.
0A (the part leading to the lug groove 30), 40B (the part leading to the sipe T13), and a flat main part 40C shallower than the end part, and these end parts 40A, 40B and the main part 4
The bottom portion is formed by a series of 0Cs being inclined.

The degree of tapered inclination of the ends 40A and 40B in the above-mentioned Sipe I40 is such that the relationship b/a between length a and depth b of each end 40A and 40B is 0.25 to 1.0, particularly 0.5 to 1.0. A range with a relationship of 0.75 is preferable.

It goes without saying that the sipe 141 should also have the same bottom structure as above (＼.

As described above, in the pneumatic tire of the present invention in which the bottoms of the sipes I40 and 41 are composed of tapered end portions and a substantially flat main portion, the sipes I are formed into lug grooves or cuts when the tire rolls under load. It is possible to effectively disperse the tensile strain applied to the part that communicates with the crack, and it is possible to effectively eliminate the occurrence of group cracks or to effectively delay their occurrence, and it is possible to improve the tire durability life. .

The effects of the present invention are particularly noticeable in radial tires used for heavy-duty vehicles such as trucks and buses.

Next, the structure and effects of the pneumatic tire of the present invention will be explained in more detail using test examples.

(Test example) Tire size: 215/75R16613, rim used:
The tread pattern shown in FIGS. 1 and 2 described above was formed on the tread portion of a radial tire of 15×6J J with an air pressure of 1.3 kg/cd, and this tire was evaluated.

Note that other structures such as the radial carcass and belt layer of the tire and manufacturing conditions were similar to those of conventional tires, so details will be omitted.

That is, in Fig. 1, the width of the tread portion T = 14C)
am, groove width of circumferential groove 10.11.12: 6°5Il1
m, depth: 11.5m111. Groove width of lug groove 30: 5°0°, depth: 11.5°, groove width of notch 31: 5°0°, depth: 8.0°, groove width of Sipe I40: 2°Owrm
% depth = 6.0mm, depth of both bottom ends 40A and 40B +7.0mm, width in width direction: 2.0+nm, depth of main part 40C: 6. Omm, Width in width direction: 8. Omm, Sipe I
4.1 groove width: 1. Om+i, depth: 2. Oam.

Depth of both bottom ends 40A and 40B +3.0+n, width in width direction: 2. Omm, depth of main part 40C: 2.0+am.

Width in width direction: 2. A tread pattern of Omm was formed to obtain a tire of the present invention.

On the other hand, for comparison, the depths of Sipe I40 and 41 were set to 6.0 mm and 2.0 mm, respectively, and the entire bottom was made flat without providing a tapered portion at both ends of the bottom. A conventional tire consisting of the following configuration was obtained.

The following table shows the results of evaluating the occurrence of group cracks in the sipe 1 portion of these two types of tires through an indoor drum test.

From the results shown in the table above, the pneumatic tire of the present invention does not cause group cracks even when running for a long time, and has extremely improved tire durability.

[Effects of the Invention] As described above in detail, the pneumatic tire of the present invention has the bottom part of the sipe formed in the land portion, at least one end of which communicates with the lug groove or notch, connected to the adjacent lug groove or notch. The shape consists of an end with a depth up to the depth of the sipe, and a main part shallower than the end, and these ends and the bottom of the main part are connected to each other at an angle, so that the lug groove or The portion that passes through the notch is tapered, so that the tensile strain applied to this portion can be effectively dispersed, and the occurrence of group cracks can be eliminated or the timing of their occurrence can be considerably delayed.

Furthermore, since the main part of the sipe (bottom central part) remains flat, the appearance of the tire will not be impaired even if the tire wears.

Therefore, according to the pneumatic rear tire of the present invention, the occurrence of group cracks can be effectively eliminated or delayed, and the tire durability life can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a developed view of the tread portion showing an example of the pneumatic tire of the present invention, Fig. 2 is an explanatory cross-sectional view taken along the line a-a in Fig. 1, and Fig. 3 is a partial cross-section of the tread portion of a conventional pneumatic tire. It is an explanatory diagram. T...Tread section 10...Circumferential main groove 11...〃 12.../1 13...Sipe ■( Circumferential straight sipe) 14
・・・・・・ // 15・・・・・・ 〃 16・・・・・・ 〃 20・・・・・・Land part 21・・・・・・／/ 22・・・・・・〃 23...〃 0...Lag groove 1...Notch 2...Sipe ■ (radial sipe) 3...
・〃 0... Sipe I (sipe of the present invention) 1...
〃 OA...bottom both ends OB.../1 0C...main part (flat part)

Claims (1)

[Claims] A plurality of circumferential grooves, lug grooves or notches extending in a direction intersecting these circumferential grooves and arranged at approximately equal intervals in the circumferential direction, a land portion divided by the circumferential groove, and the land portion In a tire equipped with a tread, the sipe includes a sipe at least one end of which is formed in the lug groove or notch, and the sipe has an end portion whose depth is limited to the depth of the adjacent lug groove or notch; Consisting of a main part shallower than the end part,
A pneumatic tire characterized in that these end portions and the bottom of the main portion are sloped and connected.