JP4381084B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. In particular, the present invention relates to a pneumatic tire that can reduce low-frequency road noise while maintaining high steering stability.

  Conventional pneumatic tires place an emphasis on improving steering stability in order to improve safety during vehicle travel. In order to improve the steering stability, it is known to increase the lateral spring constant and circumferential spring constant of the tire. As a method for increasing the lateral spring constant and the circumferential spring constant, it is conceivable to increase the hardness of the rubber forming the bead filler, increase the length of the bead filler in the tire radial direction, and increase the width of the bead filler. However, in these methods, in addition to the lateral spring constant and the circumferential spring constant, the longitudinal spring constant also increases. In the pneumatic tire, when the longitudinal spring constant is increased, low-frequency road noise is also increased, which is a cause of in-vehicle noise.

  Therefore, there is a type in which the length of the bead filler is suppressed to reduce the vertical spring constant, and a reinforcing layer is provided along the carcass material that is a forming member of the pneumatic tire (for example, see Patent Document 1). By suppressing the length of the bead filler in this way, the increase in the longitudinal spring constant is suppressed, and the lateral and circumferential spring constants that are decreased by suppressing the length of the bead filler are increased by providing a reinforcing layer. ing.

JP 2001-71715 A

  However, in the pneumatic tire described above, the proportion of the bead filler involved as the lateral spring constant is low, and the lateral spring constant is highly dependent on the reinforcing layer. For this reason, in order to further improve the steering stability, it is necessary to increase the lateral spring constant. That is, it is necessary to increase the rigidity of the reinforcing layer. As a method for increasing the rigidity, a method such as increasing the thickness of the reinforcing layer can be considered. However, when the rigidity is increased by such a method, the transverse spring constant increases and the longitudinal spring constant also increases. There is a fear. When the longitudinal spring constant increases, the low-frequency road noise also increases as described above. Therefore, it is difficult to reduce the low-frequency road noise while improving the steering stability.

  Therefore, the present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire that can improve steering stability and reduce low-frequency road noise.

In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention is a pneumatic tire having a reinforcing layer in a sidewall portion, wherein the reinforcing layer has a range of 0.2 mm to 2.0 mm. The plurality of rubber members are formed by being overlapped at least partially in the tire radial direction, and further, both ends of the reinforcing layer in the tire radial direction are formed. A hardness of the rubber member formed at the center is higher than a hardness of the rubber member formed at a central portion.

  In this invention, the reinforcing layer provided on the sidewall portion of the pneumatic tire is formed by a plurality of rubber members at least partially overlapped in the tire radial direction. Further, the hardness of the rubber member is set so that the rubber member at both ends in the tire radial direction is higher than the rubber member formed at the center. Thus, since the hardness of the rubber members at both ends in the tire radial direction is formed high, the lateral and circumferential rigidity of the pneumatic tire can be increased, whereby the lateral spring constant and the circumferential spring constant can be increased. Can be increased. Moreover, since the hardness of the rubber member in the central part is formed low, the rubber member serves as a cushioning material against the longitudinal impact on the pneumatic tire, and can absorb the impact. Thereby, the longitudinal spring constant is reduced. As a result, low frequency road noise can be reduced by reducing the longitudinal spring constant while increasing steering stability by increasing the lateral spring constant and the circumferential spring constant.

  Further, in the pneumatic tire according to the present invention, the plurality of rubber members are formed by sequentially stacking three rubber members along the tire radial direction, and a portion where the rubber members overlap is formed by three sheets. Of the rubber members, only two rubber members are stacked.

  In the present invention, the reinforcing layer is formed of three rubber members, and the three rubber members are sequentially stacked in the tire radial direction so as to partially overlap. At that time, only the two overlapping portions overlap each other. As a result, when the low-frequency road noise is reduced while improving the steering stability as described above, the side tread of the portion where the rubber member overlaps can be prevented from protruding in a convex shape in the tire width direction, and the aesthetic appearance is impaired. Can be prevented.

  Further, in the pneumatic tire according to the present invention, the portion where the rubber member overlaps is a rubber member provided on the inner side in the tire radial direction with respect to the rubber member provided on the outer side in the tire radial direction. Is provided so as to be on the tire equatorial plane side.

  In this invention, since the pneumatic tire is formed in the outer direction in the tire width direction near the middle between the bead portion and the tread portion than in the vicinity of the bead portion, a reinforcing layer is formed in accordance with the shape. ing. That is, the reinforcing layer is sequentially formed while overlapping predetermined portions of the rubber member from the vicinity of the bead portion toward the tread portion, but the overlapping portion is more than the rubber member on the tread portion side, that is, on the outer side in the tire radial direction. The rubber member on the bead portion side, that is, the inner side in the tire radial direction is overlapped with the tire equatorial plane side that is the inner side in the tire width direction. As a result, the reinforcing layer can be formed without going against the shape of the tire, and a natural appearance can be obtained even when a side tread is provided outside the reinforcing layer.

  In the pneumatic tire according to the present invention, the rubber member is formed with a thickness in a range of 0.2 mm to 2.0 mm.

  In this invention, by forming the thickness of the rubber member within a range of 0.2 mm to 2.0 mm, the rubber member having higher hardness secures the rigidity in the transverse direction and the circumferential direction, and the transverse spring constant and The circumferential spring constant is increased, and the longitudinal spring constant is lowered by absorbing the impact in the longitudinal direction with the rubber member having the lower hardness. When the thickness of the rubber member having a higher hardness among the rubber members is less than 0.2 mm, the rubber member is too thin even if the hardness is high, so that the rigidity becomes insufficient and the effect as a rubber member is obtained. In the case where the thickness of the rubber member having the lower hardness among the rubber members is thicker than 2.0 mm, the rigidity becomes too high due to the thick formation even if the hardness is low. Also, the longitudinal spring constant becomes large and low frequency road noise cannot be reduced. Therefore, by forming the rubber member with the above thickness, both the lateral spring constant and the circumferential spring constant are increased and the longitudinal spring constant is decreased. As a result, low-frequency road noise can be reduced while improving steering stability.

  In the pneumatic tire according to the present invention, the thickness of the rubber member is formed so as to become thinner from at least a predetermined position toward the overlapping end.

  In the present invention, the thickness of the overlapped portions of the plurality of rubber members provided with the predetermined portions stacked is reduced toward the end portion. Thereby, even when the rubber members are stacked, it is possible to prevent the thickness from being increased only by that portion. As a result, when the side tread is provided outside the rubber member by thickening the part where the rubber members overlap, the side tread of that part is prevented from forming a convex shape, and a natural appearance is obtained. be able to.

  In the pneumatic tire according to the present invention, a plurality of rubber members having different hardnesses are provided as reinforcing layers provided in the sidewall portions. As for the arrangement, a rubber member having high hardness is provided in the vicinity of the bead portion, and a rubber member having low hardness is provided on the outer side in the tire radial direction of the rubber member. At that time, the rubber member and the rubber member are overlapped in a predetermined range. Furthermore, a rubber member having high hardness is provided on the outer side in the tire radial direction of the rubber member having low hardness. Also in this case, as described above, the predetermined range of the rubber member with high hardness and the rubber member with low hardness are overlapped. Thereby, a lateral spring constant and a circumferential spring constant increase with a rubber member with high hardness, and steering stability becomes high. In addition, since the rubber member with low hardness is provided between the rubber members with high hardness, the rubber member with low hardness becomes an interference material for the impact in the vertical direction, and the vertical spring constant can be reduced. Noise can be reduced. As a result, it is possible to achieve both improvement in steering stability and reduction in low-frequency road noise.

  Below, the example of the pneumatic tire concerning the present invention is described in detail based on a drawing. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  In the following description, the tire width direction refers to a direction parallel to a virtual rotation axis of the pneumatic tire. Further, the tire radial direction refers to a direction orthogonal to the rotation axis. In addition, a radial tire is assumed as an example of a pneumatic tire, but the pneumatic tire to which the present invention is applied may be a bias tire. FIG. 1 is a cross-sectional view showing a main part of a pneumatic tire according to an embodiment of the present invention. This pneumatic tire 1 is provided with a tread portion 2 at the outermost portion in the tire radial direction. Further, a sidewall portion 3 is provided from an end portion in the tire width direction of the tread portion 2 to a predetermined position on the inner side in the tire radial direction, and further, a bead portion 4 is provided on the inner side. Is provided.

  The tread portion 2 is provided with a cap tread 5 and a belt layer 6, and the sidewall portion 3 is provided with a side tread 7. The bead unit 4 is provided with a bead 10. A carcass 8 and an inner liner 9 are provided on the inner side in the tire radial direction from the belt layer 6 of the tread portion 2 and on the tire equatorial plane 40 side of the side tread 7 of the sidewall portion 3. Further, a bead filler 11 is provided on the outer side of the bead 10 in the tire radial direction. The carcass 8 is provided continuously on the tire equatorial plane 40 side surface in the tire width direction of the bead 10 and the inner side surface in the tire radial direction of the bead 10, and further from there the tire width of the bead 10. It is provided following the outer surface in the direction, and is also provided on the outer surface in the tire width direction of the bead filler 11.

  A reinforcing layer 21 is provided on the sidewall portion 3. The reinforcing layer 21 is provided on the outer surface of the carcass 8 of the sidewall portion 3 in the tire width direction, and the three rubber members have a predetermined range from the bead 10 direction to the outer side in the tire radial direction. These portions are formed by being sequentially stacked. Three reinforcing layers 21 are provided in both directions in the tire width direction as described above.

  The carcass 8 is formed on the outer side in the tire width direction in the vicinity of the center portion of the bead portion 4 and the tread portion 2 than in the vicinity of the bead portion 4. The bead filler 11 is formed along the carcass 8. For this reason, in the bead filler 11, the bead filler outer diameter portion 13 is formed on the outer side in the tire width direction than the bead filler inner diameter portion 12. Further, the width of the bead filler inner diameter portion 12 in the tire width direction is approximately the same as the width of the bead 10, but the bead filler outer diameter portion 13 is formed to be narrow. For this reason, the bead filler 11 is formed so as to become narrower while spreading outward in the tire width direction from the bead 10 direction toward the outer side in the tire radial direction.

  Further, the bead filler 11 is formed such that the bead filler outer diameter BD is larger than the outer diameter FD of the rim flange 18 of the wheel on which the pneumatic tire 1 is mounted. Further, the bead filler outer diameter BD is larger in the tire radial direction than the intermediate portion 14 of the tire cross-section height DH, which is ½ of the outer diameter OD of the pneumatic tire 1 and the outer diameter RD of the wheel rim 16. It is located on the inner side, that is, the bead filler outer diameter BD is formed smaller than the intermediate diameter AD that is the diameter of the intermediate portion. That is, when the height from the outer diameter portion 15 to the rim outer diameter portion 16 of the pneumatic tire 1 is assumed to be 1, the rim outer diameter portion 17 side is set to 0, and the outer diameter portion 15 side is set to 1, the bead filler The outer diameter portion 13 is formed between the rim flange outer diameter portion 19 from the position of the intermediate portion 14 which is 0.5 in the tire radial direction.

  FIG. 2 is a detailed view of a rubber member that forms the reinforcing layer 21. The three rubber members forming the reinforcing layer 21 include an upper reinforcing layer 22, a central reinforcing layer 25, and a lower reinforcing layer 28, all of which are made of a rubber material. Further, all three sheets are formed in a circular shape having a predetermined thickness and a predetermined thickness, and concentric circular holes are formed inside. The outer diameter of the circular shape and the inner diameter that is the diameter of the inner hole are different from each other. The inner diameter of the lower reinforcing layer 28 is formed to be larger than the outer diameter of the bead 6. The outer diameter of the central reinforcing layer 25 is larger than the outer diameter of the lower reinforcing layer 28, and the inner diameter of the central reinforcing layer 25 is smaller than the outer diameter of the lower reinforcing layer 28. The outer diameter of the upper reinforcing layer 22 is larger than the outer diameter of the central reinforcing layer 25, the inner diameter of the upper reinforcing layer 22 is smaller than the outer diameter of the central reinforcing layer 25, and the lower reinforcing layer 28 It is formed with a diameter larger than the outer diameter. In addition, the thickness is formed so that the thickness t in FIG. 2 is within the range of 0.2 mm to 2.0 mm.

  The hardness of the rubber forming these rubber members is different for each rubber member, and the hardness of the central reinforcing layer 25 is lower than the hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28. Specifically, the hardness of the rubber of the upper reinforcing layer 22 and the lower reinforcing layer 28 is about Hs 74 to 98 in JIS A hardness. The hardness of the rubber of the central reinforcing layer 25 is about Hs 50 to 85, and the hardness of the rubber of the central reinforcing layer 25 is higher than the rubber hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28. Is 2 or lower. The hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28 may be the same or different.

  The reinforcing layer 21 made of these rubber members is provided on the outer surface of the carcass 8 in the tire width direction as described above. First, the lower reinforcing layer 28 is provided on the outer surface of the carcass 8. Further, the central reinforcing layer 25 is provided from the outside. Since the inner diameter of the central reinforcing layer 25 is smaller than the outer diameter of the lower reinforcing layer 28, the range of the difference between the inner diameter of the central reinforcing layer 25 and the outer diameter of the lower reinforcing layer 28 of the central reinforcing layer 25. Overlaps the outside of the lower reinforcing layer 28, and the other part of the central reinforcing layer 25 is provided outside the carcass 8. Further, the upper reinforcing layer 22 is provided from the outside. Since the inner diameter of the upper reinforcing layer 22 is smaller than the outer diameter of the central reinforcing layer 25, there is a range of difference between the inner diameter of the upper reinforcing layer 22 and the outer diameter of the central reinforcing layer 25 of the upper reinforcing layer 22. The other part of the upper reinforcing layer 22 is provided outside the carcass 8 so as to overlap the outer side of the central reinforcing layer 25. In addition, since the inner diameter of the upper reinforcing layer 22 is larger than the outer diameter of the lower reinforcing layer 28, the upper reinforcing layer 22 and the lower reinforcing layer 28 do not overlap in the tire width direction. Three reinforcing layers 21 do not overlap in the tire width direction.

  When the three rubber members forming the reinforcing layer 21 are provided on the outer surface in the tire width direction of the carcass 8 as described above, the diameter of the lower reinforcing layer inner diameter portion 30 is larger than the outer diameter of the bead 10. It is larger and smaller than the diameter of the point on the bead filler outer diameter portion 13 side among the three equally divided points of the bead filler outer diameter portion 13 and the bead filler inner diameter portion 12. The diameter of the lower reinforcing layer outer diameter portion 29 is larger than the diameter of the bead filler outer diameter portion 13 and smaller than the intermediate diameter AD.

  The diameter of the upper reinforcing layer inner diameter portion 24 is equal to the diameter of the lower reinforcing layer outer diameter portion 29. Further, the diameter of the upper reinforcing layer outer diameter portion 23 is larger than the intermediate diameter AD, and from the vicinity of the end portion of the carcass 8 on the side where the reinforcing layer 21 of the belt layer 6 is provided. Among the four equally divided points along the shape of the carcass 8 up to the vicinity of the outer diameter portion of the 8 beads 10, the diameter is smaller than the point closest to the belt layer 6 side. The central reinforcing layer 25 overlaps the upper reinforcing layer 22 and the lower reinforcing layer 28, and the length of the overlapping portion in the tire radial direction is 5 mm or more, and the center of the central reinforcing layer 25 is The length from the part reinforcing layer outer diameter part 26 to the central part reinforcing layer inner diameter part 27 is ½ or less. In addition, the length of the overlapping portion is preferably 10 mm or less.

  Hereinafter, the performance evaluation test performed on the conventional pneumatic tire 1 and the pneumatic tire 1 of the present invention will be described. The evaluation conditions were 205 / 60R16 pneumatic tire 1 mounted on a 16 × 6-1 / 2JJ wheel, air pressure set to 200 kPa, mounted on a passenger car with a displacement of 2500 cc, noise performance evaluation and steering stability evaluation. Carried out. The noise performance was measured on a rough road surface at 60 km / h on a test course, and the level (dB) was measured at a sound pressure of 80 to 160 Hz with a microphone attached to the driver seat window side position of the passenger car. Compared with. Steering stability was measured by a paneler feeling test on the test course, and the result was expressed as an index with a conventional pneumatic tire as 100. The larger this value, the better the steering stability. Table 1 shows the results obtained by the evaluation test.

  In the evaluation test, two types of conventional examples are used as conventional pneumatic tires. Conventional Example 1 in Table 1 is a tire without a reinforcing layer, and Conventional Example 2 is a tire in which the reinforcing layer is formed by a single rubber member. In addition, as comparative examples for the present invention, evaluation tests of Comparative Examples 1 and 2, which are two types of comparative examples in which the hardness of the reinforcing layer is changed, are performed and compared with the present invention.

  In Conventional Example 1, which is one of the conventional examples, since the reinforcing layer 21 is not provided, the lateral spring constant and the peripheral spring constant are low, and thus steering stability is poor. In the evaluation test, the low-frequency road noise of Conventional Example 1 is used as a reference.

  In Conventional Example 2, one rubber member is provided as the reinforcing layer 21, and the hardness of the rubber member is set to Hs93 in JIS A hardness. Since the reinforcing layer 21 has a high hardness as described above, the lateral spring constant and the circumferential spring constant are increased, so that the steering stability is improved. At the same time, since the longitudinal spring constant increases, the low-frequency road noise also increases, which is 1.0 dB higher than that of the conventional example 1.

  As an example of the present invention, three rubber members forming the reinforcing layer 21 are provided at the positions as described above, the hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28 is Hs93, and the hardness of the central reinforcing layer 25 is Hs75. What is used. In the present invention, since the upper reinforcing layer 22 and the lower reinforcing layer 28 are high in hardness, the lateral spring constant and the circumferential spring constant are increased, so that the steering stability is improved. On the other hand, since the intermediate reinforcing layer 25 is made of a rubber material having a low hardness, the longitudinal spring constant is reduced and low-frequency road noise is also reduced. Specifically, the low-frequency road noise is reduced by 0.2 dB compared to the conventional example 1.

  In Comparative Example 1, which is one of the comparative examples, the hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28 is Hs75, and the hardness of the central reinforcing layer 25 is Hs93. As described above, when the hardness of the three rubber members is opposite to that of the present invention and the hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28 is lowered and the hardness of the central reinforcing layer 25 is increased, the upper reinforcing layer 22 Since the hardness of the layer 22 and the lower reinforcing layer 28 is low, the transverse spring constant and the longitudinal spring constant do not increase. For this reason, the steering stability does not improve, and the steering stability is poor as in the first conventional example. In addition, since the upper reinforcing layer 22 and the lower reinforcing layer 28 are low in hardness as described above, the reinforcing layer 21 does not function as the reinforcing layer 21, so the low-frequency road noise is similar to that in the conventional example 1. ± 0 dB.

  In Comparative Example 2, the upper reinforcing layer 22 and the lower reinforcing layer 28 have a hardness of Hs93, and the central reinforcing layer 25 has a hardness of Hs92. In Comparative Example 2, since the upper reinforcing layer 22 and the lower reinforcing layer 28 are high in hardness, the lateral spring constant and the circumferential spring constant are increased, so that the steering stability is improved. On the other hand, the hardness of the intermediate reinforcing layer 25 is lower than the hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28. However, if the numerical difference in JIS A hardness is only 1, the intermediate reinforcing layer 25 Cannot play the role of cushioning material. For this reason, the low-frequency road noise is increased by 1.0 dB compared to the conventional example 1.

  As is clear from the above evaluation test, when only one rubber member having a high rubber hardness formed as in Conventional Example 2 is used when the reinforcing layer 21 is provided on the pneumatic tire 1, the steering stability is increased. However, low frequency road noise cannot be reduced. Further, as in Comparative Example 1, even when three rubber members are provided, the hardness of the rubber forming the upper reinforcing layer 22 and the lower reinforcing layer 28 is lowered, and the hardness of the rubber forming the central reinforcing layer 25 is decreased. If it is increased, the steering stability cannot be improved. Further, as in Comparative Example 2, when the hardness of the central reinforcing layer 25 of the three reinforcing layers 21 is lower than the hardness of the upper reinforcing layer 22 and the lower reinforcing layer 28, the difference is small. In this case, low frequency road noise cannot be reduced.

  On the other hand, by providing three rubber members with appropriate thicknesses at appropriate positions as the reinforcing layer 21 as in the present invention, and forming the upper reinforcing layer 22 and the lower reinforcing layer 28 with rubber having high hardness, Since the rigidity in the direction and the circumferential direction is increased, the lateral spring constant and the circumferential spring constant are increased. Thereby, when the vehicle equipped with the pneumatic tire 1 is run, the steering stability is improved. Further, by making the hardness of the rubber forming the central reinforcing layer 25 lower than the hardness of the rubber forming the upper reinforcing layer 22 and the lower reinforcing layer 28, the central reinforcing layer 25 can withstand the longitudinal impact of the tire. It plays the role of a cushioning material and the longitudinal spring constant decreases. This reduces low frequency road noise. As a result, by providing the pneumatic tire 1 with the reinforcing layer 21 as in the present invention, low-frequency road noise can be reduced while improving steering stability.

  In the above embodiment, the rubber member forming the reinforcing layer 21 is formed with a constant thickness, but the thicknesses of the upper reinforcing layer 22, the central reinforcing layer 25, and the lower reinforcing layer 28 are as shown in FIG. As shown in FIG. 4, the thickness may be reduced toward the end of the radial direction when the rubber member is mounted on the pneumatic tire 1 or the end of the overlapping portion of the rubber members. For example, as shown in FIGS. 4-1 to 4-5, any one or all of the upper reinforcing layer 22, the central reinforcing layer 25, and the lower reinforcing layer 28 are formed so as to decrease in thickness toward the end portion. When the rubber members are stacked as described above, even when the rubber members are stacked, it is possible to prevent the overlapping portions from becoming thick by stacking the portions having a small thickness. Therefore, when the side tread 7 is provided outside the reinforcing layer 21 made of the rubber member, the overlapping portion of the rubber member pushes out the side tread 7 formed on the outer side, and only that portion rises in a convex shape. Can be prevented. As a result, even when low-frequency road noise is reduced while improving steering stability, it is possible to prevent the appearance from deteriorating and to obtain a natural appearance. In this case, the thickness of the rubber member is the thickness t of the thickest part.

  In the above description, the overlapping portion of the rubber member is provided with the central reinforcing layer 25 inside the upper reinforcing layer 22 and the lower reinforcing layer 28 inside the central reinforcing layer 25, as shown in FIG. As described above, the central reinforcing layer 25 may be provided outside the upper reinforcing layer 22, and the lower reinforcing layer 28 may be provided outside the central reinforcing layer 25. Even if the overlapping method is different, by providing the central reinforcing layer 25 having a low hardness between the upper reinforcing layer 22 and the lower reinforcing layer 28 having a high hardness, the central reinforcing layer 25 has an impact in the longitudinal direction of the tire. It can serve as a cushioning material. As a result, it is possible to achieve both improvement in steering stability and reduction in low-frequency road noise.

It is a partial cross section figure which shows the Example which concerns on this invention. It is detail drawing of the rubber member which forms the reinforcement layer shown in FIG. It is a figure which shows the modification of the shape of the reinforcement layer of the pneumatic tire of an Example. It is detail drawing of the modification of the reinforcement layer of the pneumatic tire of an Example. It is detail drawing of the modification of the reinforcement layer of the pneumatic tire of an Example. It is detail drawing of the modification of the reinforcement layer of the pneumatic tire of an Example. It is detail drawing of the modification of the reinforcement layer of the pneumatic tire of an Example. It is detail drawing of the modification of the reinforcement layer of the pneumatic tire of an Example. It is a figure which shows the modification of arrangement | positioning of the reinforcement layer of the pneumatic tire of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Cap tread 6 Belt layer 7 Side tread 8 Carcass 9 Inner liner 10 Bead 11 Bead filler 15 Outer part 16 Rim 17 Rim outer part 18 Rim flange 19 Outer rim flange Diameter 21 Reinforcement layer 22 Upper reinforcement layer 25 Center reinforcement layer 28 Lower reinforcement layer

Claims (4)

In a pneumatic tire having a reinforcing layer in the sidewall portion,
The reinforcing layer is formed of a plurality of rubber members formed with a thickness within a range of 0.2 mm to 2.0 mm ,
The plurality of rubber members are formed by overlapping at least a part in the tire radial direction, and the hardness of the rubber members formed at both ends of the reinforcing layer in the tire radial direction is formed in the center portion. A pneumatic tire characterized by being higher in hardness than a rubber member. The plurality of rubber members are formed by sequentially stacking three rubber members along the tire radial direction,
2. The pneumatic tire according to claim 1, wherein in the portion where the rubber member overlaps, only two rubber members of the three rubber members are overlapped.   The portion where the rubber member overlaps is provided such that the rubber member provided on the inner side in the tire radial direction is on the tire equatorial plane side with respect to the rubber member provided on the outer side in the tire radial direction. The pneumatic tire according to claim 1, wherein the pneumatic tire is provided. The thickness of the rubber member, at least a predetermined position, as claimed in any one of claim 1 to 3, characterized in that it is thinner toward the end portion of the overlapping and side air Enter tire.

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