JP2005119384A - Run flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a side-reinforced type run flat tire for improving both of durability in run flat traveling and riding comfort with a normal inner pressure. <P>SOLUTION: In this run flat tire 1, a carcass 7 comprising plies 6a, 6b extending troidally is arranged across each of a pair of bead parts 3, a pair of side wall parts 4, and a tread part 5. Belt layers 9a, 9b, and a belt reinforced layer 10 are sequentially provided on an outer peripheral side of a crown part 8 of the carcass 7. An inner liner 11 is provided on an inner face side of the carcass 7, main grooves 17a-17c are formed on the tread part 5, and a reinforced rubber layer 12 is arranged at the side wall part 4. The belt reinforced layer 10 has a pair of narrow layers 14. The tire width direction distance d<SB>1</SB>between an inner end 15 and a tread grounding end 16 of the narrow layer 14 is 25% or more of a tread ground width TW, and a ratio of a groove depth h<SB>1</SB>of an outermost main groove 17a to a tire diameter direction distance h<SB>2</SB>between an deepest part 21 of the outermost main groove 17a and an inner face of the inner linear 11 is 1.0 or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  This tire relates to a so-called run-flat tire having a reinforcing rubber layer having a crescent-shaped cross section in a sidewall portion and capable of run-flat running even when the tire internal pressure is reduced by puncture or the like. To improve the durability.

  As a so-called run flat tire that can travel a certain distance even when the tire internal pressure is reduced by puncture or the like, a run flat tire having a reinforcing rubber layer having a crescent cross section in the sidewall portion, a so-called side reinforcing run Flat tires are known.

  In order to improve the durability of such side-reinforced run-flat tires during run-flat running, it is necessary to suppress deformation of the sidewalls when a load is applied while the tire internal pressure is reduced due to puncture or the like. However, for example, if the bending deformation is suppressed by increasing the thickness of the reinforcing rubber layer, problems such as an increase in tire weight and deterioration in riding comfort at normal internal pressure occur.

  For this reason, side-reinforced run-flat tires that simultaneously achieve high levels of durability, weight reduction, ride comfort at normal internal pressure, and improved steering stability during run-flat driving are desired. Various studies have been made on these matters.

  For example, Patent Document 1 discloses a side-reinforced runflat in which two pairs of reinforcing rubber layers are disposed on the sidewall portion, and a belt reinforcing layer made of a highly elastic aramid cord is disposed on the outer side in the radial direction of the belt layer. Tires are described. However, in this tire, the belt reinforcing layer is only provided for improving the performance at high speed of the tire, and is not optimized in consideration of suppressing the bending during the run-flat running.

JP-A-6-191244

  Therefore, the object of the present invention is to effectively suppress the bending during run-flat running without sacrificing other performance such as riding comfort during normal internal pressure by optimizing the belt reinforcement layer. An object of the present invention is to provide a side-reinforced run-flat tire with significantly improved durability.

  In order to achieve the above object, the present invention includes a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and each portion of a tread portion extending between both sidewall portions. A carcass composed of at least one ply extending in a toroid shape is provided, and at least one belt layer formed by rubber-covering a cord on the outer peripheral side of the crown portion of the carcass and a reinforcing element substantially in the tire circumferential direction Belt reinforcement layers arranged in parallel to each other, an inner liner on the inner surface side of the carcass, at least two main grooves extending along the tire circumferential direction in the tread portion, and a cross section in at least the sidewall portion In a run-flat tire having a crescent-shaped reinforcing rubber layer, the belt reinforcing layer has both end portions of the belt layer. Each having at least a pair of narrow layers covering each other, and the distance in the tire width direction between the inner end of the narrow layer and the tread ground contact end corresponding thereto is 25% or more of the tread ground contact width. The ratio of the depth of the outermost main groove, which is the outermost main groove, to the distance in the tire radial direction between the deepest portion of the outermost main groove and the inner surface of the inner liner is 1.0 or less. It is a flat tire.

  The “inner end of the narrow layer” as used herein refers to an end edge located on the inner side in the tire width direction, of both end edges of the narrow layer. “Tread contact width” means that the tire is assembled to the standard rim specified by JATMA, the tire internal pressure is the highest air pressure specified by JATMA, and the load corresponding to 75% of the maximum load capacity in the applicable size / ply rating is applied. This is the distance in the tire width direction between the tread contact ends when loaded.

  Moreover, it is preferable that the inner end position of the narrow layer is on the inner side in the tire width direction than the center position of the groove width of the outermost main groove.

  Furthermore, it is preferable that the distance in the tire width direction between the center position of the groove width of the outermost main groove and the tread ground contact end corresponding thereto is 26% or more of the tread ground contact width.

  Here, the belt reinforcing layer may have a plurality of pairs of narrow layers. In such a case, of these narrow layers, the inner ends of the pair of narrow layers and the corresponding tread grounding ends. The width in the tire width direction is 25% or more of the tread contact width, and the distance in the tire width direction between the inner end of the other narrow layer and the corresponding tread contact end is 5 to 20% of the tread contact width. It is preferable that

  Further, the belt reinforcing layer may have a plurality of pairs of narrow layers, and in such a case, the inner end position of the pair of narrow layers among these narrow layers is the groove width of the outermost main groove. It is preferable that the inner end position of the other narrow layer is on the outer side in the tire width direction with respect to the center position of the outermost main groove.

  Furthermore, it is preferable that the belt reinforcing layer further has at least one wide layer covering the entire belt layer.

  Furthermore, at least one ply of the plies constituting the carcass is folded back around the bead core from the inner side to the outer side in the tire width direction, and the folded end is between the belt layer and the crown part of the carcass. It is preferable to have a so-called envelope structure, and the carcass is preferably composed of one ply.

  In addition, the reinforcing rubber layer is preferably located between the carcass inner surface and the inner liner.

  According to the present invention, it is possible to provide a side-reinforced run-flat tire that achieves both improved durability during run-flat travel and improved ride comfort during normal internal pressure.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a left half section in the width direction of a typical run-flat tire (hereinafter referred to as “tire”) according to the present invention.

  A tire 1 shown in FIG. 1 includes a pair of bead portions 3 in which a bead core 2 is embedded, a pair of sidewall portions 4 extending outward from the bead portion 3 in the tire radial direction, and a tread portion 5 extending between both sidewall portions 4. A carcass 7 including at least one ply extending in a toroidal shape over each portion, that is, two plies 6a and 6b in FIG. In addition, on the outer peripheral side of the crown portion 8 of the carcass 7, at least one belt layer formed by rubber-covering the cord, in FIG. 1, two belt layers 9a and 9b, and a reinforcing element are provided substantially in the tire circumferential direction. A belt reinforcing layer 10 formed in parallel is sequentially provided. In FIG. 1, the belt reinforcing layer 10 is composed of a single wide layer 14a covering the entire outer surface of the belt layers 9a and 9b and a pair of narrow layers 14b covering both ends of the belt layers 9a and 9b. An inner liner 11 is provided on the inner surface side of the carcass 7, and the tread portion 5 is provided with at least two main grooves extending along the tire circumferential direction, in FIG. 1, five main grooves 17 a to 17 c, and at least a sidewall portion. 4. In FIG. 1, a reinforcing rubber layer 12 having a crescent cross section is disposed from the bead portion 3 to a position immediately below the end of the belt layer, and has a so-called side-reinforced run-flat tire structure. FIG. 1 shows a case where the reinforcing rubber layer 12 is disposed between the inner surface of the carcass and the inner liner 11.

The main feature of the present invention is to optimize the outermost main groove 17a, which is the outermost main groove in the tire width direction of the narrow layer 14b constituting the belt reinforcing layer 10. More specifically, the belt reinforcing layer 10 has at least a pair of narrow layers 14b covering both ends of the belt layers 9a and 9b, and the inner end 15 of the narrow layer 14b and the tread grounding corresponding thereto. the tire width direction distance _{d 1} between the end 16 with a 25% or more of the tread ground-contact width TW, the groove depth _{h 1} of the outermost main groove 17a, the deepest portion 21 and the inner liner 11 inner surface of the outermost main groove 17a the ratio _h 1 / _{h 2} with respect to the tire radial distance _{h 2} between is to 1.0 or less.

  That is, in the conventional side-reinforced run-flat tire 101, as shown in FIG. 4, in the run-flat running state where the tire internal pressure is reduced, the sidewall portion 103 provided with the crescent-shaped reinforcing rubber layer 102 is While being greatly bent by pressing from the bead part 104, the tread part 105 is buckling deformed toward the inner side in the tire radial direction and is lifted with respect to the road surface. As a result, the deformation of the sidewall part 103 is further promoted. When repeated large bending deformations such that the tread portion 105 bends during run-flat running, stress concentrates on the tread portion 105, particularly the tread rubber portion near the 25% position of the tread ground contact width, and cracks are generated. In some cases, the cracks easily develop and eventually reach the belt layer 106 to cause a failure such as a cord breakage.

Therefore, in the tire 1 of the present invention, the tire width direction distance d ₁ between the tread ground-contact end 16 corresponding thereto and the inner end 15 of the narrow layer 14b of the belt reinforcing layer 10 or 25% of the tread width TW As a result, the buckling deformation of the tread portion 5 can be effectively suppressed by reinforcing the portion where the bending deformation of the tread portion 5 is large. Further, since the buckling deformation is generated starting from the outermost main groove 17a, the groove depth h ₁ of the outermost main groove 17a, the tire radial direction between the deepest portion 21 and the inner liner 11 inner surface of the outermost main groove 17a By ensuring that the ratio h ₁ / h ₂ to the distance h ₂ is 1.0 or less and the rigidity of the tire portion corresponding to the outermost main groove 17a is secured, buckling deformation of the tread portion 5 can be more effectively suppressed. . As a result, as shown in FIG. 3, bending deformation of the sidewall portion 4 is also suppressed, and as a result, the durability of the entire tire can be improved.

  In addition, the inner end position 15 of the narrow layer 14b of the belt reinforcing layer is located on the inner side in the tire width direction from the center position 18 of the groove width of the outermost main groove 17a, thereby suppressing buckling of the tread portion 5. Is preferable. That is, in a tire having a main groove disposed in the tread portion, local deformation occurs centering on the outermost main groove 107, stress is concentrated on the groove bottom of the outermost main groove 107, and cracks easily occur. Although the inner end position 15 of the narrow layer 14b of the belt reinforcing layer is the inner side in the tire width direction from the center position 18 of the groove width of the outermost main groove 17a, a portion in the vicinity of the outermost main groove 17a is This is because the local deformation of the tread portion 5 around the outermost main groove 17a can be further suppressed by reinforcing.

Further, it is preferred that the tire width direction distance d ₂ between the tread ground-contact end 16 corresponding thereto and the center position 18 of the groove width of the outermost main groove 17a is not less than 26% of the tread ground-contact width TW. As described above, since the outermost main groove 17a is a starting point for occurrence of buckling deformation, the outermost main groove 17a is disposed on the inner side in the tire width direction from the position of 25% of the tread ground contact width where stress is concentrated. This is because the local deformation of the tread portion 5 around the outermost main groove 17a can be further suppressed by reducing the stress applied to the outermost main groove 17a.

The belt reinforcing layer 10 may be constituted by only a pair of narrow layers 14b, but a plurality of pairs of narrow layers 14b may be provided. In this case, of these narrow layers, the distance d _{1 in} the tire width direction between the inner end 15 of the pair of narrow layers 14b and the corresponding tread ground contact end 16 is 25% or more of the tread ground contact width TW. In addition, it is preferable that the distance in the tire width direction between the inner end of the other narrow layer and the tread ground contact end corresponding thereto is 5 to 20% of the tread ground contact width TW. This is because buckling deformation of the tread portion 5 can be effectively suppressed without significantly increasing the tire weight. Alternatively, among these narrow layers, the inner end position 15 of the pair of narrow layers 14b is on the inner side in the tire width direction with respect to the center position 18 of the groove width of the outermost main groove 17a, and the inside of the other narrow layers The end position is preferably on the outer side in the tire width direction from the center position 18 of the groove width of the outermost main groove 17. This is because buckling deformation of the tread portion 5 can be effectively suppressed without significantly increasing the tire weight.

  The belt reinforcing layer 10 preferably further includes at least one wide layer 14a covering the entire belt layers 9a and 9b. This is because the rigidity of the tread portion 5 is increased and the buckling deformation can be further suppressed.

  Further, of the plies 6a and 6b constituting the carcass 7, at least one ply 6a is folded around the bead core 2 from the inner side to the outer side in the tire width direction, and the folded end 19 is connected to the belt layer 9a. It is preferable to have a so-called envelope structure positioned between the crown portion 8 of the carcass 7. This is because the sidewall portion 4 can be effectively reinforced by adopting such an envelope structure. In this case, it is preferable that the carcass 7 is composed of one ply in terms of weight reduction. FIG. 2 shows an example of another run-flat tire of the present invention in which the carcass 7 is constituted by a single ply 6 and the ply 6 has an envelope structure.

  Furthermore, the reinforcing rubber layer 12 can be disposed between the plies of the carcass 7, between the main body portion and the folded portion of the carcass 7, and in particular, disposed between the inner surface of the carcass 7 and the inner liner 11. It is preferable to provide it in terms of efficiently improving durability and load support efficiency.

  As described above, in the tire according to the present invention, the bending deformation of the sidewall portion 4 during the run-flat running is suppressed, so that the durability equivalent to that of the conventional tire can be maintained even if the reinforcing rubber layer 12 is thinned. In addition, it is possible to reduce the weight of the tire and improve the riding comfort during normal internal pressure by reducing the thickness. In this case, it is preferable that the maximum thickness of the reinforcing rubber layer 12 is 4 to 8 mm.

  The belt reinforcing layer 12 of the present invention is formed by, for example, a method of forming a single reinforcing element coated with rubber, for example, an organic fiber cord by spirally winding a plurality of times in the tire circumferential direction, or aligning in the tire width direction. Further, it can be formed using a known method such as a method in which a belt-like member in which a plurality of reinforcing elements are embedded in rubber is wound on the outer surface of the belt layer 9 in the tire radial direction. As the material of the reinforcing element, for example, organic fibers such as nylon 66, polyethylene terephthalate, and polyethylene naphthalate can be used, but polyethylene naphthalate is particularly preferable from the viewpoint of reducing road noise.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

  Next, a run-flat tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

  Each of the tires of Examples 1 to 3 has a tire size of 215 / 45ZR17, and the carcass is composed of a single ply having a folded structure in which the folded end is in the vicinity of the tire maximum width position. Is disposed between the carcass and the inner liner, each includes two belt layers having steel cords extending at an angle of ± 26 ° with respect to the tire circumferential direction and intersecting each other. It is composed of a wide layer and two pairs of narrow layers. Both the wide layer and the narrow layer are formed by spiral winding of a single PEN cord, and their outer end positions are both from the end of the belt layer. This is a run-flat tire for a passenger car that is disposed on the outer side in the tire width direction, provided with a rim guard on the outer surface of the sidewall portion, and having the specifications shown in Table 1.

  For comparison, a run flat tire (Comparative Examples 1 to 3) in which the inner end position of the belt reinforcing layer is out of the scope of the present invention was also prototyped.

  The durability during run-flat driving is as follows. Each test tire is assembled to a standard rim (7JJ) defined by JATMA to form a tire wheel, and the air pressure is 0 kPa (relative pressure), the tire load is 4.17 kN, and the running speed is 90 km / h. Running on the drum test machine under the conditions, the running distance until the tire broke down was measured and evaluated by this measured value. The riding comfort was evaluated by measuring the maximum displacement (longitudinal spring index) in the tire radial direction by grounding on a flat plate at an air pressure of 230 kPa and a test load of 3.7 kN. The evaluation results are shown in Table 1. The durability in Table 1 is indicated by an index ratio when the durability and riding comfort of Comparative Example 2 are set to 100. The larger the value, the better the riding comfort. Yes.

  From the results shown in Table 1, the tires of Examples 1, 3 and 4 maintain the same level of riding comfort as compared with the tires of Comparative Examples 1, 2 and 3 in which the maximum thickness of the reinforcing rubber layer is the same. However, it turns out that durability is remarkably excellent. Moreover, it turns out that the tire of Example 2 is excellent in riding comfort compared with the tire of the comparative example 2 with the same durability.

1 is a left half sectional view in a width direction of a typical run-flat tire according to the present invention. FIG. 6 is a left half sectional view in the width direction of another typical run-flat tire according to the present invention. 1 is a half-sectional view in the width direction of a typical run-flat tire according to the present invention in a run-flat running state. FIG. 5 is a half-sectional view in the width direction of a conventional side-reinforced run-flat tire in a run-flat running state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead core 3 Bead part 4 Side wall part 5 Tread part 6, 6a, 6b Ply 7 Carcass 8 Crown part 9, 9a, 9b Belt layer 10 Belt reinforcement layer 11 Inner liner 12 Reinforcement rubber layer 13 Belt layer edge part 14a Narrow Wide layer 14b Wide layer 15 Narrow layer inner end 16 Tread grounding end 17 Outermost main groove 18 Groove width center position 19 of outermost main groove Carcass ply folded end 20 Outer radial position 21 of reinforcing rubber layer in the tire radial direction Deepest part of the groove

Claims (9)

A pair of bead portions in which bead cores are embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and at least one ply extending in a toroid shape over each portion of the tread portion extending between both sidewall portions. A carcass is disposed, and at least one belt layer formed by rubber-covering a cord on the outer peripheral side of the crown portion of the carcass, and a belt reinforcing layer formed by arranging reinforcing elements substantially in parallel in the tire circumferential direction in order. Provided with an inner liner on the inner surface side of the carcass, provided with at least two main grooves extending along the tire circumferential direction in the tread portion, and provided with a reinforcing rubber layer having a crescent cross section in at least the sidewall portion. In run-flat tires,
The belt reinforcing layer has at least a pair of narrow layers respectively covering both ends of the belt layer,
The tire width direction distance between the inner end of the narrow layer and the corresponding tread contact end is 25% or more of the tread contact width,
The ratio of the groove depth of the outermost main groove, which is the outermost main groove located in the tire width direction, to the distance in the tire radial direction between the deepest portion of the outermost main groove and the inner surface of the inner liner is 1.0 or less. Run-flat tire characterized by.   2. The run-flat tire according to claim 1, wherein an inner end position of the narrow layer is on an inner side in a tire width direction than a center position of a groove width of the outermost main groove.   The run flat tire according to claim 1 or 2, wherein a distance in a tire width direction between a center position of a groove width of the outermost main groove and a tread ground contact end corresponding to the center position is 26% or more of a tread ground contact width.   The belt reinforcing layer has a plurality of pairs of narrow layers, and among these narrow layers, the distance in the tire width direction between the inner ends of the pair of narrow layers and the corresponding tread ground contact ends is 25 of the tread ground contact width. The tire width direction distance between the inner end of the other narrow layer and the tread ground contact end corresponding to this is 5 to 20% of the tread ground contact width. The described run-flat tire.   The belt reinforcing layer has a plurality of pairs of narrow layers, and among these narrow layers, the inner end positions of the pair of narrow layers are on the inner side in the tire width direction than the center position of the groove width of the outermost main groove, The run-flat tire according to any one of claims 1 to 4, wherein the inner end position of the other narrow layer is located on the outer side in the tire width direction with respect to the center position of the groove width of the outermost main groove.   The run flat tire according to any one of claims 1 to 5, wherein the belt reinforcing layer further includes at least one wide layer covering the entire belt layer.   Among the plies constituting the carcass, at least one ply is folded back around the bead core from the inner side to the outer side in the tire width direction, and the folded end is between the belt layer and the crown part of the carcass. The run-flat tire according to any one of claims 1 to 6, which has a so-called envelope structure.   The run-flat tire according to claim 7, wherein the carcass is constituted by a single ply.   The run-flat tire according to any one of claims 1 to 8, wherein the reinforcing rubber layer is positioned between a carcass inner surface and an inner liner.

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