JPS61257303A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce the extent of wear in the center of a tread, by constituting it in setting up each thin nick, whose both ends are connected to main grooves, in each land part of a tread center part sandwiched between main grooves at the outermost side at the specified pitch, in case of the tread provided with more than two main grooves. CONSTITUTION:A tread 2 is divided into tread shoulders 5 and a tread center part 6 by plural numbers, for example, four main grooves 3. And, three land parts 6a-6c are formed in this tread part 6. Each nick 7 of about 0.3mm-1.5mm in thickness U, tilted at a tilt angle X of about 0-+ or -45 deg. to a tire turning axis O and of a circumferential pitch P of 5-15% in tread width is formed in these land parts 6a-6c so as connect three main grooves. With this constitution, wear in the tread center is prevented from occurring and, what is more, tire life against abrasion is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire with an improved tread pattern.

Traditionally, various tread patterns have been proposed according to the performance required of tires. For example, at least two
BACKGROUND ART Pneumatic tires are known in which a plurality of circumferentially extending land portions (ribs, lugs, blocks) are formed by forming more than one circumferentially extending main groove.

There is. However, with such pneumatic tires,
When the tire is mounted on the drive shaft and running, the ground pressure at the tread center between the outermost main grooves is equal to the ground pressure at the part of the tread shoulder between one end of the shoulder and the outermost main groove. As a result, center wear progresses and even if the tire is rotated, the wear life of the tire will eventually be reduced. Such problems are particularly noticeable in radial tires for heavy loads such as those for trucks and buses.

The problem with this type of octopus is that it is caught between the outermost main grooves.
A large number of linear thin cuts are formed in each land portion located in the tread center part, parallel to each other, and both ends connected to the main groove, and the circumferential pitch of the cuts is set from 5% to 15% of the tread width. This can be solved by setting the range to .

Since a large number of linear thin cuts are formed in each land part of the January tread center part, parallel to each other and both ends connected to the main groove, the rubber in the tread center part is divided into small pieces and easily deforms. , the rigidity of the tread center portion decreases. As a result, while the ground contact pressure at the tread center decreases, the total ground contact pressure of the tread remains almost constant, so the ground contact pressure at some tread shoulders increases, and therefore the ground contact pressure of the tread becomes uniform over the entire surface. As a result, the occurrence of center wear as described above is suppressed, and the wear life is improved.

1 presentation 1 Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1.2, l is a toroidal pneumatic tire, for example a radial tire, and this pneumatic tire 1 has a tread 2. The tread 2 has at least two, in this embodiment four, zigzag main grooves 3 extending in the circumferential direction. here,
The main groove 3 is a circumferentially extending groove that does not close even when touching the ground, and preferably has a width V of 4% of the tread width W.
and 8%. The tread 2 has a tread shoulder portion 5 between the shoulder one end 4 and the main grooves 3a, 3b by the outermost main grooves 3a, 3b.
The tread center portion 6 is divided into two parts, and the tread center portion 6 is sandwiched between the amphibodi grooves 3a and 3b. A large number of thin cuts 7 are formed in each of the three land portions (ribs in this example) 6a, 6b, and 8c located in the tread center portion 8 in order to reduce their rigidity. Each cut 7 is substantially 1 at the time of ground contact.
The thickness is such that it closes, and preferably the thickness U is in the range of 0.3 mm to 1.5H. In addition, these notches 7
is preferably inclined at an angle X in the range of 0 degrees to ±45 degrees with respect to the tire rotation axis O. This is because when X is within the above-mentioned range, the circumferential rigidity of the tread center portion 8 is reduced and the shear stress in the kick-off region can be effectively alleviated. Since the cuts 7 are parallel to each other at least within the same land area, they are effective in alleviating the shear stress, and the rigidity in each region divided by the cuts is made uniform, thereby preventing uneven wear, etc. It has the effect of being difficult to produce. Moreover, the notch 7 is linear and both ends are connected to the main groove 3, and its depth D is preferably 30% to 10% of the depth E of the main groove 3.
The range is 0%. Therefore, the circumferential rigidity of the land portion located in the tread center portion 6 is effectively reduced. Furthermore, the circumferential pitch P of the cuts 7 is 5 of the tread width W.
% to 15%, preferably 8% to 10%. The reason for this is that when the pitch P is less than 5%, the rigidity of the tread center portion B decreases too much, and the ground contact pressure of the tread shoulder portion 5 becomes excessive, resulting in a ground contact pressure distribution of the entire tread that is good for wear. On the other hand, if the pitch P exceeds 15%, the rigidity of the tread center portion 6 will not decrease to an extent that prevents center wear. When the thin cut 7 is formed in the tread center portion B in this way, the tread center portion 6
The rigidity of the tread shoulder portion 5 decreases and the ground contact pressure decreases, while the ground contact pressure of the tread shoulder portion 5 increases accordingly. As a result, the ground contact pressures between the tread shoulder portion 5 and the tread center portion B become approximately equal, and even when the pneumatic tire 1 is mounted on the drive shaft, center wear is significantly reduced. However, when turning a corner while using the pneumatic tire 1 with such a notch 7 formed as a steering wheel, the ground contact pressure of the tread shoulder part 5 becomes particularly high as it approaches the shoulder end 4. There is a possibility that the outer shoulder portion 5 may be unevenly worn (edge drop, wave wear, shoulder drop, etc.) due to the force. Therefore, in this embodiment, the land portion (this In the example, a circumferential groove 8 extending in the circumferential direction is formed in each of the ribs 5a, and the ground pressure of the tread shoulder portion 5 raised by the notch 7 is dispersed and made uniform within the tread shoulder portion 5. . Here, each of the circumferential grooves 8 is a groove that substantially fills the ground when touching the ground, and preferably has a width S of 0.3% to 2% of the tread width W.
% range. In addition, since these circumferential grooves 8 are recessed from the outer surface of the substantially flat tread shoulder portion 5, there is no step between the tread shoulder portions 5 on both sides of the circumferential groove 8, resulting in good wear characteristics. is obtained. Moreover, each of the circumferential grooves 8 is located at a distance from one end 4 of the shoulder, that is, within a range of 6% to 12% of the tread width W, preferably slightly outward from the center in the width direction of the land portion 5a. Since the ground pressure is provided at the same position, the ground pressure can be effectively equalized.

These circumferential sides vIt8 may be zigzag-like or straight as in the embodiment, and two or more may be formed in each tread shoulder portion 5.

Next, the results of tests using conventional tires and tires of the present invention are shown in the attached table. Here, the tires used are TBRl
o, OOR2014P R, mileage is 50,000 km, and the conventional tire has no size (notch) formed in the tread, whereas the tire of Example 1 has a thin notch formed in the tread center part. Things, Example 2
This tire has a thin notch formed in the center of the tread and a circumferential groove formed in a portion of the tread shoulder.

In the above-mentioned embodiment, the case where the main groove 3 was formed with four trees was explained, but in this invention, the main groove may be formed with three trees as shown in FIG. 3, or two or five or more. In addition, the main groove 3 may be a straight one as shown in FIG. It may be divided into blocks.

As explained above, according to the present invention, it is possible to provide a pneumatic tire that hardly causes center wear even when mounted on a drive shaft and has an improved wear life.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the vicinity of the tread showing one embodiment of the present invention, FIG. 2 is a view taken along the line II in FIG. 1, and FIG. 3 is a plan view of the tread showing another embodiment of the invention. , FIG. 4 is a plan view of a tread showing still another embodiment of the present invention. 1... Pneumatic tire 2... Tread 3... Main groove 5... Tread shoulder part 6... Tread center part 7... Thin cut W... Tread width P... Circumference Directional Pitch Patent Applicant Brideston Co., Ltd. Agent Patent Attorney Tadashi 1) Toshio Figure 1 1...Pneumatic Tire 2 River Toledo 3...Main Groove 5...Tread Shoulder i6...Tread Center (7) ...Thin cut Tread width for w P...Circumferential pinch Fig. 2 3a 3 3 3b Fig. 3 Fig. 4

Claims (1)

[Claims] In a pneumatic tire in which the tread is divided into a plurality of land parts by at least two or more circumferentially extending main grooves, each land part located in the tread center part sandwiched between the outermost main grooves is parallel to each other and has both ends. 1. A pneumatic tire characterized by forming a large number of linear thin cuts connected to a main groove, and having a circumferential pitch of the cuts ranging from 5% to 15% of the tread width.