JP2008307971A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire enhancing appearance property after development of friction while suppressing eccentric abrasion developed from a shoulder part end. <P>SOLUTION: The pneumatic tire is provided with a plurality of layers of belt layer 11; and a tread 12 arranged at an outer side in the tire radial direction and provided with a plurality of circumferential main grooves 1 on a crown part. A large number of sipes 2 directed to a tire radial direction are formed on a buttress part 13 continued to an end of the tread 12, and an upper end of the sipe 2 is positioned in a range of 30-100% of depth D of the circumferential main groove 1. Length h opened to a surface of the buttress part of the sipe 2 is 5-150% of the depth D of the circumferential main groove 1, and depth t of the sipe 2 is within a range of 0.5-10% of tread width. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter also simply referred to as “tire”), and more particularly to a heavy duty pneumatic tire used for trucks, buses, and the like.

  Suppressing uneven wear, particularly uneven wear (shoulder edge wear, hereinafter also referred to as “SEW”) in a pneumatic tire, particularly a so-called heavy duty pneumatic tire mounted on a truck, bus, etc. Various techniques have been studied in the past, for example, a technique is known in which a side groove that is continuous in the circumferential direction is arranged in the buttress part, or a multi-sipe that has appeared on the tread from the new article is arranged. (For example, refer to Patent Document 1).

In Patent Documents 2 and 3, heavy load air having a tread pattern with a rib base on the tread is provided for the purpose of effectively preventing the occurrence of uneven wear at the shoulder end without causing problems such as cracks. In a radial radial tire, a technology for providing a plurality of sipes inclined with respect to the tire radial direction in a buttress portion connected to a side edge of the tread, at least one narrow groove extending in the tire circumferential direction, and extending in the tire radial direction And the technique which provides the some sipe opened to this narrow groove is disclosed.
JP 2000-52713 A (Claims etc.) JP-A-7-17213 (Claims etc.) Japanese Patent Laid-Open No. 7-17214 (Claims etc.)

  As described above, SEW can be suppressed to some extent by using side grooves or multi-sipe. However, when a side groove is provided, as shown in FIG. 4, the upper wall end of the side groove 20 (a portion surrounded by an ellipse in the drawing. As shown in FIG. (Indicating changes in the tread surface), the appearance after wear often deteriorates. In addition, when the multi-sipe is adopted, the parts delimited by the multi-sipe may be heel-and-toe worn by running and become the core of uneven wear, and none of them is sufficient.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire that has improved appearance after the progress of friction while suppressing uneven wear that develops from the shoulder end.

As a result of intensive studies, the present inventors have found the following.
That is, normal SEW is generated and progresses by side force (SF) input to the shoulder end portion and braking force (BF) generated in the tread due to the diameter difference. In general, the occurrence of uneven wear nuclei is caused by SF, and the progress is caused by BF. In order to suppress these, it is considered effective to reduce the contact pressure at the shoulder end.

  From such a viewpoint, as a result of earnestly examining the means for reducing the ground pressure without causing appearance defects like conventional side grooves and multi-sipes, the present inventor has arranged a large number of sipes in the buttress part, It has been found that this problem can be solved by specifying the location of the sipes, and the present invention has been completed.

That is, the pneumatic tire of the present invention includes, in a crown portion, an air including a plurality of belt layers, and a tread that is disposed on the outer side in the tire radial direction of the belt layers and includes a plurality of circumferential main grooves. In entering tires,
A large number of sipes heading in the tire radial direction are formed in the buttress portion connected to the end portion of the tread, and the upper end of the sipe is located in a range of 30 to 100% of the depth of the circumferential main groove. The length opened on the surface of the part is 5 to 150% of the depth of the circumferential main groove, and the depth of the sipe is in the range of 0.5 to 10% of the tread width. It is what.

  In the present invention, the shortest distance between the sipe and the belt layer is preferably 10 mm or more. Moreover, the space | interval of the tire circumferential direction between the said many sipes exists in the range of 3-10 mm suitably. Furthermore, the width of the sipe is preferably in the range of 0.7 to 3.0 mm.

  According to the present invention, the above configuration makes it possible to realize a pneumatic tire capable of suppressing uneven wear that develops from the end of the shoulder portion without impairing the appearance after the progress of friction. It was.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an enlarged partial cross-sectional view ((a) in the drawing) and a schematic side view ((b) in the drawing) showing a portion from a tread end portion to a buttress portion of a preferred example of the pneumatic tire of the present invention. ). As shown in the figure, the pneumatic tire of the present invention has a plurality of layers, two belt layers 11 in the illustrated example, and a plurality of circumferential main grooves 1 arranged on the outer side in the tire radial direction in the crown portion. And a tread 12 provided.

  In the tire of the present invention, as shown in the figure, a number of sipes 2 directed in the tire radial direction are provided in a buttress portion 13 connected to an end portion of the tread 12. Since the sipe 2 is formed facing the tire radial direction, even if wear progresses, a normal multi-sipe only appears on the tread surface, and troubles such as tread peeling do not occur. Therefore, it is possible to effectively reduce the ground contact pressure of the shoulder end portion and suppress uneven wear without causing problems such as the appearance deterioration with the progress of wear as in the case of conventional side grooves. Become. The reason for forming the sipe 2 in the radial direction of the tire is that if the formation direction of the sipe 2 is inclined, directionality occurs in the sipe deformation, and this directionality may cause directionality in the road surface deformation. This is because deformation with the property sometimes causes uneven wear.

  The sipe 2 according to the present invention needs to be provided so that the upper end (position of the depth d) is located in a range of 30 to 100% of the depth D of the circumferential main groove 1. 2 does not appear on the tread when new. As described above, when there is a multi-sipe on the tread from the beginning of wear, heel-and-toe wear may occur between the multi-sipe, and the SEW itself may become the core of SEW. Since 30% of the height does not appear on the tread until the wear rate becomes 30% or more, the rib (block) rigidity itself increases, so the multi-sipe according to the present invention appears in the buttress portion, Even if the heel and toe wear causes uneven wear, it is difficult to progress. On the other hand, if the upper end position of the sipe 2 exceeds 100% of the depth D, the effect of suppressing the contact pressure is lost, so in the present invention, the upper end depth d of the sipe 2 is in the above range.

  The length h opened on the surface of the buttress portion of the sipe 2 is 5 to 150% of the depth D of the circumferential main groove 1. When the opening length h of the sipe 2 is less than 5%, the effect of suppressing the contact pressure becomes insufficient. If the lower end of the opening of the sipe 2 is deeper than the main groove depth D, the effect of suppressing the contact pressure can be obtained until the end of wear, but if the opening length h is too long, there is no further effect.

  Furthermore, the depth t of the sipe 2 is in the range of 0.5 to 10% of the tread width. If the sipe depth t is less than 0.5% of the tread width, the effect of reducing the contact pressure is low. If the sipe depth t exceeds 10%, the contact pressure of the entire shoulder portion decreases and the contact pressure at the shoulder end relatively increases. End up. Moreover, if it is deeper than that, a crack will occur from the bottom of the sipe, and it will easily lead to failure.

  Furthermore, it is preferable that the sipe 2 is disposed so that the shortest distance from the belt layer 11 is 10 mm or more. That is, as illustrated, the distance r from the end of the nearest belt layer 11 is set to 10 mm or more. Thereby, the effect which suppresses the crack from the sipe bottom by keeping away the sipe 2 from the distortion which generate | occur | produces in the belt layer 11 is acquired. The distance r is 10 mm or more, and the larger the distance r, the better.

  Furthermore, the width of the sipe 2 is preferably in the range of 0.7 to 3.0 mm. If the width of the sipe 2 is too narrow, there is a possibility that cracks and baldness may occur due to strain generated at the sipe bottom. On the other hand, if the width is too wide, an effect similar to that of a side groove can be obtained. On the other hand, as with the case where the side groove is applied, there is a risk that the side groove may be worn away.

  In addition, crack property can be improved further by making the bottom part of the sipe 2 into a flask shape, and it is suitable.

  Further, the interval w in the tire circumferential direction between the plurality of sipes 2 is preferably in the range of 3 to 10 mm. If the interval w is too narrow, the land portion sandwiched between the sipe 2 may be peeled off.

  In the tire of the present invention, only the point that the sipe 2 is provided in the buttress portion 13 is important, and other details of the tire structure, tread pattern, and the like can be appropriately determined according to a conventional method as desired. There is no particular limitation. The pneumatic tire of the present invention is particularly suitable as a heavy-duty pneumatic tire used for trucks, buses, etc. In this case, the belt layer 11 can be preferably provided in 3 to 6 layers.

Hereinafter, the present invention will be described in more detail with reference to examples.
A pneumatic tire having two belt layers and a tread having three circumferential main grooves disposed on the outer side in the tire radial direction at a crown portion is referred to as a tire size 11R22.5 14PR (tread width). : 210 mm, circumferential direction main groove depth D: 16.0 mm).

  A tire in which the sipe is not provided in the buttress portion 13 as the conventional example 1 (FIG. 2A, no processing), and a tire in which the side groove 3 continuous in the circumferential direction is provided in the buttress portion 13 as the conventional example 2 (FIG. 2B). ), A tire (FIG. 2 (c)) provided with a multi-sipe 4 that has appeared on the tread from the time of a new article in the buttress portion 13 as a conventional example 3, and a large number of sipes 2 directed toward the tire radial direction in the buttress portion 13 as an example. Each of the tires (FIG. 2 (d)) formed was formed. The formation conditions of the sipe 2 according to the example are shown in Table 1 below.

Each test tire was mounted on a vehicle (2D4), the mounting position was fixed, and rotation was performed between the vehicles, and the following evaluation items were evaluated. The results are shown in Table 2 below.
(1) SEW uneven wear amount in actual driving (SEW drop height A × width B, see FIG. 3): The evaluation result of the uneven wear amount is an index with the test tire of Conventional Example 1 as a control (100). . The smaller the value, the better.
(2) Appearance at the end of wear (feeling evaluation): Good to poor were evaluated as 5 to 1.

  As shown in Table 2 above, in the tire of the example in which the sipe directed in the tire radial direction is provided in the buttress portion in a specific arrangement, when uneven wear is satisfactorily suppressed and the conventional side groove or multi-sipe is provided. In comparison, it was confirmed that the appearance after wear could be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged partial cross-sectional view showing a portion from a tread end portion to a buttress portion and (b) a side view of a preferred example of the pneumatic tire of the present invention. (A)-(d) is an expanded partial sectional view which shows the structure of the buttress part of each test tire in an Example. It is explanatory drawing which shows the evaluation method of the SEW uneven wear amount in an Example. It is explanatory drawing which shows the buttress part at the time of providing the conventional side groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circumferential main groove 2 Sipe 3,20 Side groove 4 Multi sipe 11 Belt layer 12 Tread 13 Buttress part

Claims (4)

In a pneumatic tire comprising a crown portion, a plurality of belt layers, and a tread that is disposed on the outer side in the tire radial direction of the belt layers and provided with a plurality of circumferential main grooves,
A large number of sipes heading in the tire radial direction are formed in the buttress portion connected to the end portion of the tread, and the upper end of the sipe is located in a range of 30 to 100% of the depth of the circumferential main groove. The length opened on the surface of the part is 5 to 150% of the depth of the circumferential main groove, and the depth of the sipe is in the range of 0.5 to 10% of the tread width. And pneumatic tires.   The pneumatic tire according to claim 1, wherein the shortest distance between the sipe and the belt layer is 10 mm or more.   The pneumatic tire according to claim 1 or 2, wherein an interval in the tire circumferential direction between the plurality of sipes is in a range of 3 to 10 mm.   The pneumatic tire according to any one of claims 1 to 3, wherein a width of the sipe is in a range of 0.7 to 3.0 mm.

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