JP4946607B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. More specifically, the present invention relates to a pneumatic tire in which durability during run-flat running is stabilized and durability is improved while improving ride comfort during normal running.

  Various types of pneumatic tires for run-flat have been proposed so far that can travel safely over a certain distance even if the tire is punctured. Among these, there is one in which a reinforcing rubber layer made of hard rubber having a crescent cross section is disposed inside the tire sidewall portion. In this type of run-flat tire, when the tire is punctured to zero pressure, the crescent-shaped reinforcing rubber layer placed on the sidewall supports the load of the vehicle and runs. Since the same rim as a pneumatic tire can be used, it has become widespread.

  However, a tire in which a crescent-shaped reinforcing rubber layer is disposed on the sidewall portion has a problem that the riding comfort during normal running is deteriorated because the reinforcing rubber layer has high rigidity. Furthermore, when the tire is punctured and the filling internal pressure is reduced, the stress is concentrated on the thin portion of the reinforcing rubber layer due to the load of the vehicle, so that cracks are likely to occur, which grow and break the carcass layer. was there.

  Conventionally, there has been a proposal in which soft rubber is combined with a crescent-shaped reinforcing rubber layer in order to achieve both riding comfort during normal driving and durability during run-flat driving (see, for example, Patent Documents 1 and 2). ). However, in any proposal, although the ride comfort during normal driving is improved to some extent, the soft rubber cracks during run flat driving, and the durability has not been improved reliably. It was.

In addition, a reinforcing layer is placed inside the crescent-shaped reinforcing rubber layer to reduce strain due to load, and this reinforcing layer stabilizes run-flat durability by blocking the growth of cracks in the tire width direction. There is a proposal to make it (see Patent Document 3). However, since this proposal does not improve the riding comfort during normal running, it cannot be a measure for achieving both riding comfort during normal running and durability during run-flat running.
JP 2004-306791 A JP 2002-211116 A JP 2006-224837 A

  An object of the present invention is to solve the above-mentioned conventional problems, so as to stabilize the durability during run-flat running and improve the durability while improving the riding comfort during normal running. Is to provide a pneumatic tire.

  In order to achieve the above object, the pneumatic tire of the present invention is a run-flat pneumatic tire in which a hard reinforcing rubber layer having a crescent-shaped cross section is disposed inside a pair of left and right sidewall portions. A soft rubber having a lower hardness than the main rubber is inserted into a region including the maximum thickness position of the tire and extending from the inner side to the outer side in the tire width direction, and traverses in the tire radial direction on the outer side in the tire width direction of the soft rubber. In addition, a reinforcing layer that is continuous in the tire circumferential direction is disposed.

Moreover, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(8).
(1) The reinforcing layer is constituted by a cord layer, the arrangement direction of a plurality of cords constituting the cord layer is 0 to 45 ° with respect to the tire radial direction, and the arrangement interval is 0.5 to 3.0 mm. To do.
(2) The cross-sectional area ratio occupied by the soft rubber in the reinforcing rubber layer is 5 to 20%.
(3) The main body rubber has a JIS hardness (A type) of 71 to 90, and the soft rubber has a JIS hardness (A type) of 60 to 70.
(4) The hardness difference between the main rubber and the soft rubber is 5 to 20 in terms of JIS hardness (A type).
(5) The reinforcing layer is disposed adjacent to the soft rubber.
(6) The reinforcing layer is disposed on the outermost side of the reinforcing rubber layer in the tire width direction.
(7) The tire radial cross-sectional height of the soft rubber is gradually reduced from the inner side in the tire width direction toward the outer side.
(8) Both ends of the reinforcing layer in the tire radial direction are spaced from each other in the tire radial direction at the outer end in the tire width direction of the soft rubber by 5 to 40 mm with respect to the tire radial direction.

  According to the present invention, the cross section disposed inside the sidewall portion includes the maximum thickness position in the crescent-shaped hard reinforcing rubber layer, and traverses in the tire radial direction to the region from the inner side to the outer side in the tire width direction. In addition, a soft rubber having a hardness lower than that of the main rubber is inserted, and a reinforcing layer that is transverse to the tire radial direction and continuous in the tire circumferential direction is disposed outside the soft rubber in the tire width direction. In some cases, stress is concentrated on the soft rubber to make it easy to generate cracks, and the progress of the cracks toward the outside in the tire width direction is blocked by a reinforcing layer arranged on the outside, thereby stabilizing run flat durability. Run-flat durability can be improved.

  In addition, when the tire is not punctured, the soft rubber disposed substantially at the center of the reinforcing rubber layer absorbs vibrations in the tire radial direction, so that it is possible to improve riding comfort during normal running.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing a pneumatic tire according to an embodiment of the present invention, and FIGS. 2A and 2B are explanatory views showing an embodiment of a reinforcing rubber layer in the tire of FIG.

  In FIG. 1, a pneumatic tire 1 includes a pair of left and right bead portions 2, 2, sidewall portions 3, 3 extending radially outward from the bead portions 2, 2, and radial directions of the sidewall portions 3, 3. And a cylindrical tread portion 4 that connects the outer sides.

  A carcass layer 6 is mounted between the pair of left and right bead portions 2 and 2, and bead fillers 8 and 8 are wrapped around bead cores 7 and 7 embedded in the bead portions 2 and 2, respectively. The tire is folded from the inside to the outside. A belt layer 9 and a belt cover layer 10 are disposed on the outer peripheral side of the carcass layer 6 of the tread portion 4, and a hard reinforcing rubber layer 5 having a crescent-shaped cross section is formed in the tire radial direction inside the sidewall portions 3 and 3. Is arranged.

  In the pneumatic tire 1 of the present invention, as shown in FIGS. 2 (a) and 2 (b), from the inner side to the outer side in the tire width direction centering on the maximum thickness position Q (shown by a dotted line) of the reinforcing rubber layer 5. A soft rubber 5a having a hardness lower than that of the main body rubber 5b is inserted in a region toward the main body, and a reinforcing layer 11 that is transverse to the tire radial direction and continuous in the tire circumferential direction is disposed outside the soft rubber 5a in the tire width direction. ing.

  As a result, when the tire is punctured, stress is concentrated on the soft rubber 5a to easily generate a crack, and the progress of the crack toward the outer side in the tire width direction is blocked by the reinforcing layer 11 arranged on the outer side. The flat durability can be stabilized, and as a result, the run flat durability can be improved.

  In addition, when the tire is not punctured, the soft rubber 5a disposed at the substantially central portion of the reinforcing rubber layer 5 absorbs vibrations in the tire radial direction, so that it is possible to improve riding comfort during normal running.

  The stabilization of the run-flat durability mentioned above refers to a state in which the tire does not suddenly break during puncturing, and a state in which a certain amount of time or traveling distance can be secured from the occurrence of puncture to the destruction of the tire. Say.

  The reinforcing layer 11 in the present invention plays a role of preventing the crack generated in the soft rubber 5a from propagating to the main rubber 5b or the carcass layer 6, and its configuration is not particularly limited. A woven fabric or cord layer made of an organic, inorganic or metal cord, preferably made of a metal cord, or a sheet made of a resin or rubber harder than the main rubber 5b is used.

  When the reinforcing layer 11 is constituted by a cord layer, the arrangement direction of a plurality of cords constituting the cord layer is set to 0 to 45 ° with respect to the tire radial direction, and the arrangement interval is set to 0.5 to 3.0 mm. It is good to adjust to. The reason is that cracks generated in the soft rubber 5a usually progress at an angle of about 90 ° with respect to the tire radial direction. In order for the reinforcing layer 11 to reliably block the cracks, the arrangement angle of the cords and The arrangement interval is set within this range to prevent cracks from passing between a plurality of cords.

  In the present invention, the cross-sectional area occupied by the soft rubber 5a may be adjusted to 5 to 20%, preferably 10 to 15% with respect to the total cross-sectional area of the reinforcing rubber layer 5. As a result, it is possible to balance the riding comfort during normal traveling and the durability during run-flat traveling in a well-balanced manner. In other words, if the cross-sectional area ratio occupied by the soft rubber 5a is less than 5%, the riding comfort during normal running will be reduced, and if it exceeds 20%, it will be difficult to support the load of the vehicle during puncture. Durability will be reduced.

  In the present invention, the hardness of the main rubber 5b constituting the reinforcing rubber layer 5 is 71 to 90, preferably 73 to 80 in terms of JIS hardness (A type), and the hardness of the soft rubber 5a is JIS hardness (A type). ) 60-70, preferably 63-68.

  Furthermore, the hardness difference between the main rubber 5b and the soft rubber 5a may be adjusted so as to be 5 to 20, preferably 10 to 15 in terms of JIS hardness (A type). If the hardness difference is less than 5, the stability of run-flat durability cannot be secured and the effect of improving riding comfort during normal driving will be insufficient, and if it exceeds 20, it will be difficult to support the load of the vehicle during puncture. Run-flat durability will be reduced.

  In the pneumatic tire 1 of the present invention, the reinforcing layer 11 described above may be disposed adjacent to the soft rubber 5a as shown in FIG. Thereby, the crack generated in the soft rubber 5a during puncture travel can be directly blocked by the reinforcing layer 11 without propagating to the main rubber 5b, and the run-flat durability can be stabilized.

  More preferably, the reinforcing layer 11 is disposed on the outermost side in the tire width direction of the reinforcing rubber layer 5 as shown in FIG. Thereby, since the inhibitory force with respect to the bending of the reinforced rubber layer 5 is reduced, it is possible to prevent deterioration in riding comfort during normal traveling.

  In the present invention, the tire radial direction cross-sectional height h of the soft rubber 5a may be gradually decreased from the inner side to the outer side in the tire width direction. In this way, by making the cross-sectional height h of the soft rubber 5a the largest on the inner side in the tire width direction, it is possible to reliably generate a crack at the position of the soft rubber 5a during run-flat running. Further, by reducing the cross-sectional height h on the outer side in the tire width direction, it is possible to reliably receive the crack propagated in the soft rubber 5a toward the outer side of the tire with the reinforcing layer 11.

  In the pneumatic tire 1 of the present invention, the upper and lower ends 11a and 11b in the tire radial direction of the reinforcing layer 11 are respectively connected to the tire radial direction from the upper and lower ends 5x and 5y in the tire radial direction at the outer end in the tire width direction of the soft rubber 5a. 5 to 40 mm, preferably 10 to 15 mm. That is, in FIGS. 2A and 2B, the interval between the upper end 11a of the reinforcing layer 11 and the upper end 5x of the soft rubber 5a is h1, and the interval between the lower end 11b of the reinforcing layer 11 and the lower end 5y of the soft rubber 5a is h2. In this case, the distances h1 and h2 may be adjusted so as to satisfy 5 mm ≦ h1 and h2 ≦ 40 mm. If the distances h1 and h2 are less than 5 mm, cracks propagated from the soft rubber 5a may propagate to the main rubber 5b side and hinder the stability of the run-flat durability. Will drop.

  As described above, the pneumatic tire of the present invention inserts a soft rubber having a hardness lower than that of the main body rubber into the maximum thickness position of the reinforcing rubber layer having a crescent-shaped cross section disposed inside the sidewall portion. By arranging a reinforcement layer on the outside, it stabilizes run-flat durability during puncture and improves ride comfort during non-puncture, because it has an excellent effect while having a simple configuration It can be widely applied to various run flat tires.

  The tire size is 225 / 45R18 91W, the tire structure is as shown in FIG. 1, and all the specifications except for the reinforcing rubber layer 5 arranged on the side wall 3 are common, and the form of the reinforcing rubber layer 5 and the main rubber 5b are soft. Conventional tires (conventional examples), comparative tires (comparative examples 1 and 2), and tires of the present invention (examples 1 and 2) were produced by varying the rubber hardness of the rubber 5a as shown in Table 1.

  In the conventional example, the reinforcing rubber layer 5 is configured only by the main rubber 5b as shown in FIG. 3A, and in the first comparative example, the maximum thickness position Q of the main rubber 5b is shown in FIG. 3B. A soft rubber 5a is inserted into the region centered on the rubber member, and in the comparative example 2, as shown in FIG. 3 (c), a reinforcing layer 11 is disposed that traverses in the tire radial direction about the maximum thickness position Q of the main rubber 5b. did. In each tire, the maximum thickness of the reinforcing rubber layer 5 is 8 mm, and the reinforcing layer 11 in Comparative Example 2, Examples 1 and 2 is a braided cord layer made of steel (cord arrangement direction and arrangement angle: tire diameter). 40 ° with respect to the direction, and the arrangement interval: 1 mm).

  These five types of tires were evaluated for ride comfort and run-flat durability during normal running by the following test methods, and the results are shown in Table 1 using an index with the conventional tire as 100. The larger the value, the better.

[Riding comfort during normal driving]
Each tire is assembled in a rim (size: 18 x 7.5 JJ), filled with air pressure 220 kPa, mounted on the front and rear four wheels of a 3000 cc four-wheel drive vehicle, and an asphalt road test course with an average speed of 50 km / h The vehicle was run for 10 km at h, and sensory evaluation was performed by three test drivers.

[Run-flat durability]
Of the above tires, the air travel of the front wheel on the driver side is zero (0 kPa), the test course consisting of the asphalt road surface is run at an average speed of 90 km / h, and the travel distance until the tire with zero air pressure breaks down Was measured. This was repeated 5 times, and the result was evaluated.

  From Table 1, it can be seen that the tire according to the present invention has a well-balanced improvement in ride comfort and run-flat durability during normal running as compared with the conventional tire.

It is sectional drawing which shows the pneumatic tire by embodiment of this invention. (A) And (b) is explanatory drawing which shows embodiment of the reinforced rubber layer in the tire of FIG. 1, respectively. (A)-(c) is a figure equivalent to FIG. 2 which shows the structure of the reinforced rubber layer in the tire each evaluated in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Side wall part 5 Reinforcement rubber layer 5a Soft rubber 5b Body rubber 11 Reinforcement layer Q The maximum thickness position of a reinforcement rubber layer

Claims (9)

In a pneumatic tire for a run flat in which a hard reinforcing rubber layer having a crescent cross section is arranged inside a pair of left and right sidewall portions,
A soft rubber having a hardness lower than that of the main rubber is inserted into a region including the maximum thickness position of the reinforcing rubber layer and extending from the inner side to the outer side in the tire width direction, and the tire diameter on the outer side in the tire width direction of the soft rubber. A pneumatic tire in which a reinforcing layer that crosses in the direction and continues in the tire circumferential direction is disposed.   The reinforcing layer comprises a cord layer, the arrangement direction of a plurality of cords constituting the cord layer is 0 to 45 ° with respect to the tire radial direction, and the arrangement interval is 0.5 to 3.0 mm. Pneumatic tire described in 2.   The pneumatic tire according to claim 1 or 2, wherein a cross-sectional area ratio of the soft rubber in the reinforcing rubber layer is 5 to 20%.   The pneumatic tire according to claim 1, 2 or 3, wherein the main rubber has a JIS hardness (A type) of 71 to 90 and the soft rubber has a JIS hardness (A type) of 60 to 70.   The pneumatic tire according to claim 1, 2, 3 or 4, wherein the hardness difference between the main rubber and the soft rubber is 5 to 20 in terms of JIS hardness (A type).   The pneumatic tire according to claim 1, wherein the reinforcing layer is disposed adjacent to the soft rubber.   The pneumatic tire according to claim 1, 2, 3, 4, 5, or 6, wherein the reinforcing layer is disposed on the outermost side in the tire width direction of the reinforcing rubber layer.   The pneumatic tire according to claim 1, 2, 3, 4, 5, 6 or 7, wherein a cross-sectional height of the soft rubber in a tire radial direction is gradually decreased from an inner side in a tire width direction toward an outer side.   The both ends in the tire radial direction of the reinforcing layer are spaced from each other in the tire radial direction at the outer end in the tire width direction of the soft rubber by 5 to 40 mm with respect to the tire radial direction. The pneumatic tire according to 5, 6, 7 or 8.

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