JP2008296873A - Pneumatic run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a durable pneumatic run-flat tire capable of increasing a traveling distance during puncture without increasing the weight of the tire. <P>SOLUTION: The pneumatic run-flat tire comprises a radial carcass 3 consisting of one or more carcasses extending toroidally between bead cores 2a, 2b embedded in a pair of bead parts 1a, 1b, a tread part 5 arranged on the outer side in the tire radial direction of a crown part of the radial carcass 3, a pair of buttress parts 6a, 6b located on both ends of the tread part 5, a pair of side parts for connecting the buttress parts 6a, 6b to the bead parts 1a, 1b, and a pair of side reinforcing rubber layers 8a, 8b forming crescent-like sections arranged on the side parts 7a, 7b. The tread part 5 comprises a plurality of main grooves 9a-9c along the rotating direction of the tire, and a plurality of transverse grooves along the width direction of the tire. The mean depth h of the main groove 9a of the area located on the inner side R when the tire is fitted to a vehicle is smaller than the mean depth h1 of the main groove 9c of the area located on the outer side L when the tire is fitted to the vehicle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire that can run even in a punctured state, and intends to further improve the durability of the tire during puncture.

A run-flat tire is a tire that allows a tire to safely travel a certain distance without losing its load bearing capacity even when the internal pressure of the tire is reduced due to puncture or the like. It is common to adopt a structure that improves the rigidity of the side part by arranging a side reinforcing rubber layer with a relatively high crescent-shaped cross section inside the carcass of the part. Is prevented from excessively increasing (for example, Patent Document 1).
Japanese Unexamined Patent Publication No. 2000-264012

  By the way, in this type of tire, further improvement in the durability (travelable distance) of the tire at the time of puncture has been demanded, and measures are taken by changing the hardness and thickness of the side reinforcing rubber layer. However, there are disadvantages that increase the weight of the tire, increase the rolling resistance, and deteriorate the riding comfort, and there is a limit to improving the durability of the tire at the time of puncture.

  An object of the present invention is to propose a pneumatic run-flat tire with improved durability that can further extend the travel distance while ensuring safety even during puncture.

  The present invention relates to a radial carcass formed of one or more carcass plies extending in a toroidal manner between bead cores embedded in a pair of bead portions, and a radial carcass crown portion of the radial carcass arranged outside the radial direction of the tire. A tread portion provided, a pair of buttress portions located at both ends of the tread portion, a pair of side portions connecting the buttress portion and the bead portion, and a crescent arranged on the side portions In the pneumatic run flat tire provided with a pair of side reinforcing rubber layers having a cross section, the tread portion includes a plurality of main grooves along the tire rotating direction and a plurality of lateral grooves along the tire width direction. (The lug groove), and the main groove in the region located on the inner side when the vehicle is mounted has an average depth shallower than the average depth of the main groove in the region located on the outer side when the vehicle is mounted It is a pneumatic run-flat tire which is characterized.

  In the pneumatic run-flat tire having the above-described configuration, the main groove in the region located on the inner side when the vehicle is mounted is composed of a plurality of different average depths, and the average depth of the main groove closest to the side portion Is preferably the shallowest.

  Further, it is desirable that the main grooves in the region located outside when the vehicle is mounted have substantially the same average depth, and this average depth is the deepest among the main grooves in the entire tread portion.

  In the present invention, the width of the tread portion means that the tire is rim-assembled on a standard or design rim, such as JATMA, TRA, ETRTO, or the like, which is effective in the area where the tire is manufactured, sold, or used, which is effective in the region The tire width tread distance between the tire tread contact points when the air pressure to 100% internal pressure specified in the industrial standards, standards, etc. is filled and the load equivalent to the internal pressure is applied. It shall be said.

  Also, the load is the maximum load (maximum load capacity) of a single wheel in the applicable size described in the above standard, and the internal pressure is the maximum load (maximum load capacity) of a single wheel described in the above standard. The corresponding air pressure is further referred to as a rim, which is a standard rim in an applicable size described in the above standard.

  When driving in a puncture, the camber of the vehicle increases the internal deflection when the vehicle is mounted, and the side often breaks down, but the tire of the present invention has an average depth of the main groove in that region when the vehicle is mounted. It is shallower than the average depth of the main groove in the area located on the outside, and the bending is suppressed, which makes it possible to increase the rigidity without increasing the weight and further extend the mileage. The

  Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 1 is a diagram schematically showing, in section, an embodiment of a pneumatic run-flat tire according to the present invention.

  In the figure, reference numerals 1a and 1b are bead portions, 2a and 2b are bead cores embedded in the bead portion 1, and 3 is a radial carcass forming a tire skeleton. The radial carcass 3 is composed of one or more carcass plies extending in a toroid shape between the bead cores 2a and 2b.

  Reference numeral 4 denotes a belt layer disposed on the outer side in the tire radial direction of the crown portion of the radial carcass 3. This belt layer 4 is composed of a rubberized layer of cords extending at an angle (with an angle) to the tire equatorial plane, preferably a plurality of rubberized layers of steel cords, and the cords of each layer are mutually connected to the tire equatorial plane. Are stacked so as to cross each other.

  Further, 5 is a tread portion disposed on the outer side in the tire radial direction of the belt layer 4, 6a and 6b are buttress portions positioned at the width end of the tread portion 5, 7a and 7b are buttress portions 6a and 6b and bead portions 1a and 1b. The crescent moons 8a and 8b are connected from the buttress parts 6a and 6b to the side parts 7a and 7b (disposed between the carcass ply and the liner rubber of the radial carcass 3). It is a side reinforcement rubber layer which makes a cross section.

Reference numerals 9a to 9c denote main grooves shown in three examples provided in the tread portion 5 along the direction in which the tire rotates. The main grooves 9a to 9c are regions of the region located on the inner side R when the vehicle is mounted when the right side of the drawing is the vehicle mounting inner side R and the left side of the drawing is the vehicle mounting outer side L with respect to the center 0 of the width of the tread portion 5. the average depth h of the main groove 9a has shallower than the average depth h ₁ of the main groove 9b region located on the vehicle when mounted outside L (h <h _1).

  Further, 10a and 10b in the figure are bead fillers, and 11 is a belt reinforcing layer covering the end of the belt layer 5.

  When the tire is punctured, if the side wall part bends, the tread part will also be deformed at the same time. Especially, in the part where the main groove is provided, the thickness of the tread part will be thin and the deformation will be large, which is the deformation of the side part. It becomes the cause which enlarges. In the present invention, the average depth h of the main groove 9a in the region located on the inner side R when the vehicle is mounted is reduced to suppress the deformation of the main groove that affects the deformation of the side portion, thereby improving the durability at the time of puncture. It is intended.

  The deformation state of a tire having a main groove 9c having a normal depth and a tire having a main groove 9a having a shallow depth are shown in comparison with FIGS. 2 (a) and 2 (b), respectively.

  Looking closely at the deformed parts as shown in Fig. 2 (a) and (b) above, the belt layer is actually located just below the main groove (if the belt layer consists of two layers, it becomes the second belt layer) Will cause a deformation that causes the entire tread part including the belt layer to bend into a "<" shape (hereinafter referred to as a bending deformation), but the depth of the main groove in this part will be reduced. This means that the groove bottom of the main groove is pulled away from the bending fulcrum, and the present invention reduces the depth of the main groove 9a on the inner side R when the vehicle is mounted, thereby increasing the bending rigidity of the tread portion. .

  Although the above bending deformation occurs at the groove bottom of each main groove, the tread portion is deformed the most in the main groove located on the innermost side of the vehicle, and then the next main groove and then the next main groove. In order to cope with this situation, in the present invention, as shown in FIG. 3, the average depth of the main groove closest to the side portion is made the shallowest and the main adjacent to it is reduced. The groove is slightly deeper than the main groove closest to the side portion. When two or more main grooves are provided, the average depth is gradually increased toward the center of the tread portion.

  The main groove in the region located on the outer side L when mounted on the vehicle is not necessarily affected by the above bending deformation at the time of puncture, but from the viewpoint of ensuring hydroplaning properties on the wet road surface, the main groove of the tread portion 5 Of these, the main groove is preferably the deepest and has a certain average depth.

Example A tire of size 285 / 35R19, which has an asymmetric cross section as shown in Fig. 1 and has the specifications shown in Table 1, was assembled on a rim of size 10J and rim-assembled at a constant speed of 90km / h. By (actual vehicle durability test), the tread flexure (index) and travel distance (index) were investigated. The results are also shown in Table 1.

  As is clear from Table 1, it was confirmed that the conforming tire according to the present invention had less deflection than the comparative tire and greatly extended the travel distance.

  It is possible to provide a highly durable pneumatic run-flat tire that can extend the mileage during puncture without increasing the weight of the tire.

1 is a cross-sectional view schematically showing an embodiment of a pneumatic run-flat tire according to the present invention. (A) (b) is the figure which showed the deformation | transformation condition of the tire in a puncture state. It is sectional drawing which showed typically other embodiment of the pneumatic run-flat tire according to this invention.

Explanation of symbols

1a, 1b Bead part
2a, 2b bead core
3 Carcass ply
4 Belt layer
5 Tread
6a, 6b Buttress
7a, 7b Side part
8a, 8b Side reinforcement rubber layer
9a to 9c main groove
h Average depth
h ₁ average depth

Claims (3)

A radial carcass composed of one or more carcass plies extending in a toroidal shape between bead cores embedded in a pair of bead portions, and a tread disposed on the outer side in the tire radial direction of the crown portion of the radial carcass A pair of buttress portions located at both ends of the tread portion, a pair of side portions connecting the buttress portion and the bead portion, and a crescent-shaped cross section disposed on the side portions. In a pneumatic run flat tire provided with a pair of side reinforcing rubber layers,
The tread portion includes a plurality of main grooves along the direction of rotation of the tire, and a plurality of lateral grooves along the width direction of the tire,
A pneumatic run-flat tire characterized in that a main groove in a region located on the inner side when the vehicle is mounted has an average depth shallower than an average depth of a main groove in a region located on the outer side when the vehicle is mounted.   2. The pneumatic runflat according to claim 1, wherein the main groove in the region located on the inner side when the vehicle is mounted is composed of a plurality of different average depths, and the average depth of the main groove closest to the side portion is the shallowest. tire.   3. The pneumatic runflat according to claim 2, wherein the main grooves in the region located outside when the vehicle is mounted have substantially the same average depth, and the average depth is the deepest among the main grooves in the tread portion. tire.

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