JP2008155672A - Pneumatic runflat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain enhancement of vibration riding comfortability and low vibration noise property while maintaining runflat durability. <P>SOLUTION: Side reinforcement rubber layers 25 having a cross section of crescent shape are arranged on an inner side of respective side wall parts 21 along an inner surface of a carcass layer 11 respectively, and at least any one of side reinforcement rubber 25 of the pair of side reinforcement rubber layers 25 is provided with: an outer rubber layer 27 comprising a high elastic rubber; and an inner rubber layer 29 comprising a high loss rubber arranged so as to be wrapped in the outer rubber layer 27 and having high loss characteristic. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic run-flat tire such as a pneumatic radial run-flat tire that can run flat for a certain distance even when the internal pressure suddenly decreases due to puncture.

  In recent years, various developments have been made on pneumatic run-flat tires, and the configuration of a general pneumatic run-flat tire will be briefly described as follows.

  That is, a general pneumatic run-flat tire has a pair of bead portions, and each bead portion has a bead core. Further, between the pair of bead cores, at least one carcass layer is provided so as to extend in a toroidal shape, and a tread portion is provided outside the crown region of the carcass layer in the tire radial direction. Further, sidewall portions are provided between one bead portion and the tread portion and between the other bead portion and the tread portion, respectively. A side reinforcing rubber layer having a crescent-shaped cross section is disposed along the inner surface of the carcass inside the pair of sidewall portions.

  Therefore, the load is mainly supported by the internal pressure of the pneumatic run-flat tire during normal traveling, but the load is mainly supported by the rigidity of the side reinforcing rubber layer instead of the internal pressure of the pneumatic run-flat tire during puncture. This makes it possible to run flat for a certain distance even during puncture.

  By the way, pneumatic run-flat tires have greater lateral rigidity than pneumatic tires that do not have a side reinforcing rubber layer, so that vibration due to road surface input during normal driving also increases, resulting in vibration ride comfort and low vibration. It is difficult to improve noise characteristics.

  Therefore, in order to improve the vibration ride comfort and low vibration noise characteristics, a pneumatic run flat tire as shown in Patent Document 1 (a pneumatic run flat tire according to the prior art) has been developed.

That is, the pneumatic run flat tire according to the prior art is different from a general pneumatic run flat tire, and the side reinforcing rubber layer has a multilayer structure in which rubber layers having different hardnesses are alternately laminated in the tire radial direction. ing. In other words, the side reinforcing rubber layer includes a rubber layer having a high hardness and a rubber layer having a low hardness. As a result, in the pneumatic run flat tire according to the prior art, the rigidity of the entire side-reinforcing rubber layer is sufficiently secured by the rigidity of the rubber layer having high hardness, and the elastic deformation of the rubber layer having low hardness is usually performed. It is possible to sufficiently absorb vibration caused by road surface input during traveling, and to improve vibration ride comfort and low vibration noise.
JP 2004-306791 A

  By the way, in the pneumatic run flat tire according to the prior art, although it is possible to improve the vibration ride comfort and the low vibration noise property as described above, the strain is concentrated on the rubber layer having low hardness in the side reinforcing rubber layer. Thus, cracks and the like are likely to occur. When a crack or the like is generated in the rubber layer having low hardness in the side reinforcing rubber layer, there is a problem that the rigidity of the side reinforcing rubber layer is drastically lowered during the run flat running and the run flat durability is deteriorated.

  That is, in the pneumatic run flat tire according to the prior art, there is a problem that it is extremely difficult to improve vibration ride comfort and low vibration noise performance while maintaining run flat durability.

  Therefore, an object of the present invention is to provide a run-flat pneumatic tire having a novel configuration that can solve the above-described conventional problems.

  A first feature of the present invention (a feature of the invention according to claim 1) is that a pair of bead portions each having a bead core and at least one carcass provided so as to extend in a toroid shape between the pair of bead cores. A tread portion provided on the outer side in the tire radial direction of the crown region of the carcass layer, and between the one bead portion and the tread portion and between the other bead portion and the tread portion. A pair of the side reinforcements in a pneumatic run-flat tire comprising a sidewall portion and a side reinforcing rubber layer having a crescent-shaped cross section disposed along the inner surface of the carcass layer inside each sidewall portion. The side reinforcing rubber layer of at least one of the rubber layers is encased in an external rubber layer made of highly elastic rubber and the external rubber layer And summary to become an inner rubber layer made of sea urchin disposed and having high loss characteristic high Rosugomu having a (high hysteresis loss characteristic) (low elasticity rubber).

  According to the first feature, during normal driving, the load is mainly supported by the internal pressure of the pneumatic run-flat tire, but at the time of puncture, instead of the internal pressure of the pneumatic run-flat tire, the side reinforcing rubber layer has a rigidity. Mainly supports the load. This makes it possible to run flat for a certain distance even during puncture (general operation of the pneumatic run-flat tire).

  In addition to the general operation of the pneumatic run-flat tire, the side reinforcing rubber layer includes the outer rubber layer made of highly elastic rubber and the inner rubber layer made of high loss rubber, so that the outer The rigidity of the entire side-reinforcing rubber layer is sufficiently ensured by the rigidity of the rubber layer, and vibration due to road surface input during normal traveling can be sufficiently absorbed by the elastic deformation of the internal rubber layer.

  In addition, since the inner rubber layer is disposed so as to be wrapped in the outer rubber layer, even if a crack or the like occurs in the inner rubber layer, the rigidity of the side reinforcing rubber layer during the run-flat running is reduced. Can be suppressed.

  A second feature of the present invention (a feature of the invention according to claim 2) is that, in addition to the first feature, the loss tangent tan δ of the high-loss rubber constituting the inner rubber layer is the high elasticity constituting the outer rubber layer. The gist is that it is larger than the loss tangent tan δ of rubber.

  According to a third feature of the present invention (a feature of the invention according to claim 3), in addition to the first feature or the second feature, the cross-sectional area of the external rubber layer is larger than the cross-sectional area of the internal rubber layer. It is a summary.

  According to a fourth feature (feature of the invention described in claim 4) of the present invention, in addition to any one of the first feature to the third feature, a plurality of the internal rubber layers are provided in the tire radial direction. The main point is that it is divided into

  According to the invention described in any one of claims 1 to 4, even if a crack or the like occurs in the internal rubber layer, the rigidity of the side reinforcing rubber layer is reduced during run flat running. As well as suppressing vibrations due to road surface input during normal driving due to elastic deformation of the internal rubber layer, it is possible to improve vibration ride comfort and low vibration noise while maintaining run-flat durability. it can.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  Here, FIG. 1 is a partial cross-sectional view of a pneumatic run-flat tire according to an embodiment of the present invention, and FIGS. 2 (a) to 2 (e) and 3 are other aspects of the embodiment of the present invention. It is a fragmentary sectional view of the pneumatic run flat tire which concerns.

  As shown in FIG. 1, a pneumatic run flat tire 1 according to an embodiment of the present invention (a passenger car pneumatic radial run flat tire in the embodiment of the present invention) is a pair of rims 3 that can be fitted. Each bead portion 5 includes a bead core 7 and a bead filler 9 disposed outside the bead core 7 in the tire radial direction R.

  Between the pair of bead cores 7, a two-layer carcass layer 11 is provided so as to extend in a toroid shape. The carcass layer 11 extends in the radial direction and has a plurality of steel cords or organic fiber cords (not shown). ), And both end portions of the carcass layer 11 are moored so as to be folded back to the bead core 7 in the corresponding bead portion 5. The carcass layer 11 may be one layer or three or more layers.

  A tread portion 13 is provided on the outer side of the crown region of the carcass layer 11 in the tire radial direction R, and a plurality of circumferential main grooves 15 extending in the tire circumferential direction C are formed on the surface of the tread portion 13. Has been. Further, between the tread portion 13 and the carcass layer 11, for example, two belt layers 17 that exhibit a so-called effect are provided, and the belt layer 17 is inclined with respect to the tire circumferential direction C. And a plurality of steel cords (not shown) are rubber-coated. Further, two belt reinforcing layers 19 are provided at both ends of the outer surface of the belt layer 17, respectively. The belt reinforcing layer 19 extends in the tire circumferential direction C and has a plurality of steel cords (not shown). Is formed by rubber coating. Instead of providing the two belt reinforcement layers 19 at both ends of the outer surface of the belt layer 17, the two belt reinforcement layers 19 may be provided on the entire outer surface of the belt layer 17.

  Side wall portions 21 are respectively provided between one bead portion 5 and the tread portion 13 and between the other bead portion 5 and the tread portion 13. Further, an inner liner 23 for preventing air leakage is provided on the inner surface of the carcass layer 11.

  Inside each side wall portion, a side reinforcing rubber layer 25 having a crescent-shaped cross section is disposed along the inner surface of the carcass layer 11, and each side reinforcing rubber layer 25 is covered with an inner liner 23. It has been broken. And the concrete structure of each side reinforcement rubber layer 25 is as follows.

  That is, each side reinforcing rubber layer 25 is provided with an external rubber layer 27 made of a highly elastic rubber, and a high loss rubber (which is disposed so as to be wrapped in the external rubber layer 27 and has a high loss characteristic (high hysteresis loss characteristic)). An inner rubber layer 29 made of a low-elasticity rubber, and the outer rubber layer 27 and the inner rubber layer 29 continuously extend in a ring shape in the tire circumferential direction C. The high-loss rubber refers to a rubber having a 30 ° loss tangent tan δ of 0.35 or higher, and the high-elastic rubber refers to a rubber having a dynamic elastic modulus of 13.5 MPa or higher.

  The loss tangent tan δ of the high-loss rubber constituting the inner rubber layer 29 is larger than the loss tangent tan δ of the high-elastic rubber constituting the outer rubber layer 27. Specifically, the loss tangent tan δ of the high-loss rubber is 0.35 or more, and the loss tangent tan δ of the highly elastic rubber constituting the outer rubber layer is 0.15 or less. Here, the loss tangent tan δ of the high loss rubber is made larger than the loss tangent tan δ of the high elastic rubber. If the loss tangent tan δ of the high loss rubber is equal to or less than the loss tangent tan δ of the high elastic rubber, the elastic deformation of the inner rubber layer 29 is performed. This is because vibration due to road surface input during normal traveling cannot be absorbed sufficiently. The loss tangent tan δ was measured using a viscoelastic spectrometer under conditions of a temperature of 30 ° C., a frequency of 50 Hz, an initial strain of 10%, and a dynamic strain of 1%.

  The sectional area of the outer rubber layer 27 is larger than the sectional area of the inner rubber layer 29. Specifically, the sectional area of the outer rubber layer 27 is 50 to 80% of the sectional area of the side reinforcing rubber layer 25. And the cross-sectional area of the internal rubber layer 29 is 15 to 50% of the cross-sectional area of the side reinforcing rubber layer 25. Here, the reason why the cross-sectional area of the external rubber layer 27 is larger than the cross-sectional area of the internal rubber layer 29 is that the cross-sectional area of the external rubber layer 27 is equal to or smaller than the cross-sectional area of the internal rubber layer 29. This is because the rigidity of the entire side reinforcing rubber layer 25 cannot be sufficiently secured due to the rigidity.

  As shown in FIG. 2A, the inner rubber layer 29 may be divided into a plurality of portions in the tire radial direction R. As shown in FIGS. The shape and arrangement of the rubber layer 29 may be changed as appropriate. As shown in FIG. 3, one side reinforcing rubber layer 25 (for example, the side reinforcing rubber layer 25 on the vehicle mounting inner side or the vehicle mounting outer side) of the pair of side reinforcing rubber layers 25 is an outer rubber layer 27 and an inner rubber. The other side reinforcing rubber layer 25 (for example, the side reinforcing rubber layer 25 on the vehicle mounting outer side or the vehicle mounting inner side) may be made of only highly elastic rubber.

  Next, the operation and effect of the embodiment of the present invention will be described.

  During normal running, the load is mainly supported by the internal pressure of the pneumatic run-flat tire, but at the time of puncture, the load is mainly supported by the rigidity of the side reinforcing rubber layer instead of the internal pressure of the pneumatic run-flat tire. Thereby, even at the time of puncture, it is possible to run flat for a certain distance (a general action of the pneumatic run-flat tire 1).

  In addition to the general action of the pneumatic run-flat tire 1, the side reinforcing rubber layer 25 includes an external rubber layer 27 made of high elastic rubber and an internal rubber layer 29 made of high loss rubber. With the rigidity of the layer 27, the rigidity of the entire side reinforcing rubber layer 25 is sufficiently ensured, and the vibration due to road surface input during normal traveling can be sufficiently absorbed by the elastic deformation of the internal rubber layer 29.

  Further, since the inner rubber layer 29 is disposed so as to be wrapped in the outer rubber layer 27, even if a crack or the like occurs in the inner rubber layer 29, the rigidity of the side reinforcing rubber layer 25 is reduced during run flat running. Can be suppressed.

  As described above, according to the embodiment of the present invention, even if a crack or the like occurs in the internal rubber layer 29, the rigidity of the side reinforcing rubber layer 25 during the run-flat traveling is suppressed, and the elastic deformation of the internal rubber layer 29 is suppressed. Therefore, it is possible to sufficiently absorb the vibration caused by road surface input during normal traveling, so that it is possible to improve vibration ride comfort and low vibration noise while maintaining run-flat durability.

  Further, since the outer rubber layer 27 and the inner rubber layer 29 continuously extend in the annular shape in the tire circumferential direction C, the outer rubber layer 27 and the inner rubber layer 29 are simultaneously formed by extrusion in the manufacturing process of the pneumatic run-flat tire 1. Thus, the side reinforcing rubber layer 25 can be manufactured, and the productivity of the pneumatic run-flat tire 1 can be improved.

  Further, as shown in FIG. 2A, when the inner rubber layer 29 is divided into a plurality of portions in the tire radial direction R, the rigidity balance of the side reinforcing rubber layer 25 is changed to improve the steering stability and the like. The range of performance tuning can be expanded.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, In addition, it can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

(Comparative example)
First, before describing specific contents of the example, a pneumatic run flat tire (control pneumatic run flat tire) according to a comparative example will be briefly described with reference to FIG. Here, FIG. 4 is a partial cross-sectional view of a pneumatic run-flat tire according to a comparative example.

  As shown in FIG. 4, in the pneumatic run flat tire 31 according to the comparative example, unlike the pneumatic run flat tire 1 according to the embodiment of the present invention, each side reinforcing rubber layer 25 is composed of only high elastic rubber. In other words, each side reinforcing rubber layer 25 does not include the internal rubber layer 29. Of the plurality of components in the pneumatic run flat tire 31 according to the comparative example, those corresponding to the components in the pneumatic run flat tire 1 according to the embodiment of the present invention are denoted by the same reference numerals in the drawing. Thus, the description is omitted.

(Specific contents of the example)
The pneumatic run-flat tire 1 according to the embodiment of the present invention shown in FIG. 1 and the pneumatic run-flat tire 31 according to the comparative example shown in FIG. 4 are used as invention products and comparative products under a predetermined tire size (PC225 / 45R18). Respectively. Then, the following riding comfort test, vibration noise test, and run flat durability test were performed on the inventive product and the comparative product, respectively.

(i) Ride Comfort Test The ride comfort test is performed by comparing the PP (Peak to Peak value) of the axial force in the vertical direction of the tire when it passes over a rectangular cleat installed on a smooth drum. The results of the ride comfort test are summarized as shown in Table 1 below. In addition, it shows that riding comfort is so favorable that the numerical value of riding comfort is high.

(ii) Vibration noise test The vibration noise test is performed by measuring the sound in the car and measuring the near-ear sound of the driver while driving on the road noise test road. The results of the vibration noise test are summarized as shown in Table 1 below.

(iii) Run-flat endurance test The run-flat endurance test is performed until the tire breaks down under conditions specified by ISO standards (room temperature: 38 °, load: 65% of normal load, speed: 80 km / h). This is done by measuring the distance. The results of the run flat durability test are summarized as shown in Table 1 below. In addition, it has shown that run flat durability is so high that the numerical value of run flat durability is high.

即ち、表１に示すように、発明品は、比較品と同等のランフラット耐久性を維持しつつ、比較品に比べて振動乗り心地性及び低振動騒音性を向上を図ることができることが確認された。

In other words, as shown in Table 1, it is confirmed that the invention product can improve the vibration ride comfort and the low vibration noise property compared with the comparative product while maintaining the run flat durability equivalent to the comparative product. It was done.

1 is a partial cross-sectional view of a pneumatic run flat tire according to an embodiment of the present invention. FIG. 2A to FIG. 2E are partial cross-sectional views of a pneumatic run-flat tire according to another aspect of the embodiment of the present invention. It is a fragmentary sectional view of a pneumatic run flat tire concerning other modes of an embodiment of the present invention. It is a fragmentary sectional view of the pneumatic pneumatic run flat tire concerning a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic run-flat tire 5 Bead part 7 Bead core 11 Carcass layer 13 Tread part 21 Side wall part 25 Side reinforcement rubber layer 27 External rubber layer 29 Internal rubber layer

Claims (4)

A pair of bead portions each provided with a bead core, at least one carcass layer provided so as to extend in a toroid shape between the pair of bead cores, and a tread provided on the outer side in the tire radial direction of the crown region of the carcass layer Along the inner surface of the carcass layer on the inside of each side wall part, and between the one bead part and the tread part and between the other bead part and the tread part. In a pneumatic run flat tire provided with a side reinforcing rubber layer having a crescent-shaped cross section disposed respectively,
The at least one side reinforcing rubber layer of the pair of side reinforcing rubber layers is an external rubber layer made of highly elastic rubber, and is disposed so as to be wrapped in the external rubber layer and has a high loss characteristic. A pneumatic run-flat tire comprising an internal rubber layer made of loss rubber.   2. The pneumatic run-flat tire according to claim 1, wherein a loss tangent tan δ of the high-loss rubber constituting the inner rubber layer is larger than a loss tangent tan δ of the high-elastic rubber constituting the outer rubber layer. .   The pneumatic run-flat tire according to claim 1 or 2, wherein a cross-sectional area of the outer rubber layer is larger than a cross-sectional area of the inner rubber layer.   The pneumatic run-flat tire according to any one of claims 1 to 3, wherein the inner rubber layer is divided into a plurality of portions in a tire radial direction.

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