JP2006151236A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing the performance in the initial service stage. <P>SOLUTION: A first curved shallow groove is formed in a substantially semi-circular shape projecting in the tire rotational direction with the radius thereof being about 1/4 of the tread width. The first curved shallow grooves 26 are arranged in the tire circumferential direction at the predetermined pitch, and one end thereof reaches a circumferential groove 14, and the other end reaches a tread end. A second straight shallow groove 27 forms a line extending from the circumferential groove 14 side located in a center of the tire width direction of a tread face to a tread end side backward of the tire rotational direction, and one end thereof reaches the circumferential groove 14 and the other end reaches the tread end. In other words, the second straight shallow groove 27 is formed in a V-shape with a forward portion in the tire rotational direction forming a top. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire having a plurality of land portions partitioned by a plurality of main grooves on a tread surface, and more particularly to a pneumatic tire with improved performance in the initial use of the tire.

  There is a so-called studless tire as a tire with improved performance on an icy and snowy road surface or a wet road surface. Studless tires are blended with various fillers to obtain an edge effect on the ice surface, and foam rubber is used to obtain the water absorption / edge effect of the foam layer during the period of use. There are things.

  However, in general, when rubber is vulcanized and cured, the filler and the foamed layer are not exposed on the surface of the tire that is in direct contact with the mold, and a film tends to be formed on the surface of the tire. As a result, in the initial use of the tire, the effect of the filler and the foam layer is not exhibited (or the effect is small).

  On the other hand, for example, Patent Document 1 and Patent Document 2 describe pneumatic tires for snowy and snowy roads that have improved braking / driving performance in the early stage of wear by forming narrow grooves on the tread surface. Patent Document 3 describes a pneumatic tire in which shallow grooves that form an angle of 0 ° to 40 ° with the tire circumferential direction are arranged side by side in the tire width direction in the ground contact portion of the tread.

However, in an actual use situation of a pneumatic tire, further performance improvement in the initial use is required.
JP 2004-34902 A JP 2004-34903 A Japanese Patent Laid-Open No. 7-186633

  In view of the above facts, an object of the present invention is to obtain a pneumatic tire capable of further improving performance in the initial use.

  The invention according to claim 1 has a plurality of land portions partitioned by a plurality of main grooves on the tread surface, and the land portions are divided by at least one sipe extending in the tire width direction to form sub-blocks. In the pneumatic tire, the land portion is shallower than the sipe, and at least one end thereof is a curved first curved shallow groove reaching one of the plurality of main grooves or tread ends, and shallower than the sipe. And at least one end portion reaching any one of the plurality of main grooves or tread ends, and a linear second straight shallow groove that intersects the first curved shallow groove.

  Here, examples of the “land portion” include blocks and ribs partitioned by main grooves. The “sipe” does not need to be continuous from one end to the other end in the tire width direction, and may have a structure in which adjacent sub-blocks are partially connected at discontinuous portions.

  In this pneumatic tire, a main groove, a sipe, a first curved shallow groove, and a second straight shallow groove (the first curved shallow groove and the second straight shallow groove are simply referred to as “shallow groove”) on the tread surface. Is formed. Various magnitudes and levels of force are applied to the pneumatic tire, but the edge effect of the main groove is applied to a relatively large force, and the sipe is applied to a relatively small force that remains at the deformation of the land. The edge effect is exerted, and the edge effect of the shallow groove is exhibited for a further minute force. In addition, the water absorption effect is also exhibited mainly in sipes and shallow grooves. Thereby, various forces can be received in a wider range, and the frictional force of the pneumatic tire can be effectively improved.

  In particular, in the present invention, the land portion has a curved first curved shallow groove in which at least one end reaches one of the plurality of main grooves or tread ends, and at least one end shallower than the sipe A linear second straight shallow groove that reaches one of the plurality of main grooves or tread ends and intersects the first curved shallow groove is formed. Since both shallow grooves have at least one end reaching the main groove, moisture can be transferred from the shallow groove to the main groove or the tread end, and the drainage effect can be further enhanced. Further, since the first shallow groove has a curved shape, the anisotropy of the edge effect is eliminated, and the on-ice performance can be improved particularly during cornering. Moreover, since the 2nd straight shallow groove is made into linear form, the outstanding drainage effect can be exhibited. In addition, since the shallow grooves intersect each other, the moisture in the shallow grooves can be moved through this intersection, and the water removal effect can be further enhanced.

  According to a second aspect of the present invention, in the first aspect of the invention, the second straight shallow groove extends from the center of the tread surface in the tire width direction toward the tread end toward the rear in the tire rotation direction. It is characterized by being a straight line.

  By setting it as the said structure, the water | moisture content taken in into the 2nd straight shallow groove can be efficiently drained to the tread end outer side.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, one of the main grooves is formed at the center of the tread surface in the tire width direction along the tire circumferential direction. The first circumferential shallow groove is formed in each of the tread half regions on both sides sandwiching the central circumferential groove with a radius of 1/4 or more of the tread width, and is convex in the tire rotation direction. A plurality of semicircular shallow grooves having a substantially semicircular shape are arranged in the tire circumferential direction.

  Thus, by arranging a plurality of semicircular shallow grooves, the density of the first curved shallow grooves formed in the vicinity of the tread edge and in the vicinity of the central circumferential groove is the same as that of the first straight shallow grooves formed in other portions. It can be greater than the density.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the first curved shallow groove and the second straight shallow groove have a depth of 0.1 mm to 0.5 mm, and The width is 0.1 mm to 1.0 mm.

  In this way, by setting the depth of the shallow groove to 0.5 mm or less, it is possible to suppress the deformation at the time of ground contact of the micro land portion partitioned by the shallow groove and reduce the wear. In addition, by setting the width of the shallow groove to 1.0 mm or less, it is possible to secure a tread surface area of the micro land portion and obtain high performance in the initial use.

  Furthermore, by setting the depth and width of the shallow groove to 0.1 mm or more, it is possible to secure a sufficient amount of water that can be taken into the shallow groove and obtain a high water removal effect.

The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein a plurality of micro land portions defined by the plurality of first curved shallow grooves and the second straight shallow grooves. but characterized in that it is a tread area of 0.4mm ² ~30mm ^2.

By setting the tread surface area of the micro land portion to 0.4 mm ² or more, it is possible to secure a ground contact area and obtain high performance in the initial use. In addition, by limiting to 30 mm ² or less, it is possible to secure a shallow groove region (negative rate) per unit area, so that a high water removal effect can be obtained by increasing the amount of water that can be taken into the shallow groove. Can do.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the plurality of first curved shallow grooves and second straight shallow grooves are arranged in a regular pattern. It is characterized by.

  Thereby, the local change of the performance by a shallow groove can be eliminated, and uniform performance can be obtained in the whole land part.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the rubber constituting the land portion includes a foam rubber layer on a radially outer side of the tire and a radially inner side. And an unfoamed rubber layer.

  Therefore, in this pneumatic tire, when the ground contact surface is worn by use, the foamed portion (foamed layer) of the foamed rubber layer is exposed, so the water absorption effect generated between the foamed portion and the road surface, and the road surface Edge effect can be obtained. Even when the foamed portion is not exposed in the initial use of the pneumatic tire, the water absorption effect and the edge effect can be obtained by the plurality of shallow grooves formed in the land portion.

  Further, the shape of the land portion can be stably maintained by the unfoamed rubber layer on the radially inner side.

  Since the present invention has the above-described configuration, it is possible to further improve the performance of the pneumatic tire at the initial stage of use.

  FIG. 1 shows a pneumatic tire 10 according to a first embodiment of the present invention. The pneumatic tire 10 has a predetermined rotational direction. In the drawings, this rotational direction is indicated by an arrow S, and the tire width direction orthogonal thereto is indicated by an arrow W. The circumferential direction of the pneumatic tire 10 is the rotational direction and the opposite direction.

  As shown in FIG. 2, the tread 12 of the pneumatic tire 10 includes an inner rubber layer 34 on the inner side in the tire radial direction and an outer rubber layer 36 on the outer side in the tire radial direction.

  The outer rubber layer 36 is a foamed rubber layer in which a large number of bubbles are present. When the pneumatic tire 10 is used, moisture between the tread 12 and the road surface is absorbed into the bubbles. The Moreover, the edge effect caught on the road surface by air bubbles is also exhibited. However, in general, in the initial stage of use of the pneumatic tire 10, bubbles are not exposed on the tire surface (tread surface) in direct contact with the tire molding die.

  On the other hand, the inner rubber layer 34 is an unfoamed rubber layer in which such bubbles do not exist, and has higher rigidity than the outer rubber layer 36. Thereby, the shape of the tread 12 can be stably maintained.

  As shown in FIG. 1, the tread 12 of the pneumatic tire 10 has a linear circumferential groove 14 formed on the tire equatorial plane CL, and circumferential grooves 16 are also formed on both sides of the tire equatorial plane CL in the tire width direction. ing. From both sides of the pneumatic tire 10 in the tire width direction, lateral grooves 18 that are curved toward the tire equatorial plane CL and intersect the circumferential grooves 16 are formed. The lateral groove 18 is bent in the rotational direction at an intermediate portion between the circumferential groove 16 and the circumferential groove 14, and further, a lateral groove 24 continuous to the circumferential groove 14 is formed from the substantially longitudinal center of the bent portion. Yes. The circumferential grooves 14 and 16 and the lateral grooves 18 and 24 are the main grooves 38 according to the present invention. By the main grooves 38, the tread 12 of the pneumatic tire 10 has a plurality of blocks 20 (land portions). It is defined.

The pneumatic tire 10 of the present embodiment is used as a winter studless tire, and the tread rubber forming the tread 12 has a hardness (0 ° C., JIS-A) of 50 degrees, The loss coefficient tan δ (peak position) is −45 ° C. and the dynamic elastic modulus (−20 ° C., 0.1% strain) is 180 kgf / cm ² , but the present invention is not limited to this.

The tread rubber used as a winter studless tire has a hardness (0 ° C., JIS-A) of 40 to 68 degrees, a loss coefficient tan δ (peak position) of −30 ° C. or less, and a dynamic elastic modulus ( −20 ° C., 0.1% strain) is preferably 300 kgf / cm ² or less.

Here, when the hardness of the tread rubber is less than 40 degrees, it is too soft and inferior in wear resistance, and when it is higher than 68 degrees, it is too hard and the contact area with the snowy and snowy road surface decreases, resulting in inferior braking performance and driving performance. Therefore, it is not preferable. Further, if the loss coefficient tan δ (peak position) is higher than −30 °, it is not preferable because it is too stiff on the snowy and snowy road surface and the contact area is reduced, resulting in poor braking performance and driving performance. Furthermore, if the dynamic elastic modulus is higher than 300 kgf / cm ² , it is not preferable because it is too stiff on the snowy and snowy road surface and the contact area is reduced, resulting in poor braking performance and driving performance.

  On the other hand, it is preferable that the circumferential grooves 14 and 16 and the lateral grooves 18 and 24 have a groove depth of 8 mm or more and a groove width of 3 mm or more from the viewpoint of drainage and life, and the negative ratio of the tread 12 tread 12 has the same drainage performance. From the point of the rigidity of the block 20, it is preferable to set it as 25 to 65%.

  Here, if the groove depth is less than 8 mm and the groove width is less than 3 mm, the drainage by the groove cannot be sufficiently exhibited, which is not preferable. Further, if the negative ratio is less than 25%, the drainage performance is lowered, which is not preferable. If the negative ratio is higher than 65%, the land block 20 becomes smaller and the rigidity is lowered, so that the braking performance and the driving performance are lowered. In some cases, wear resistance is also deteriorated, which is not preferable.

  As shown in FIG. 3, zigzag sipe 22 extending in the tire width direction (arrow W direction) is provided on the treads of these blocks 20, and each of the blocks 20 is between the main groove 38 and the sipe 22. Or, it is divided into a plurality of sub-blocks 28 between Sipe 22 and Sipe 22.

  Further, the tread surface of the block 20 is provided with a first curved shallow groove 26 and a second straight shallow groove 27 that can absorb water generated between the road surface and remove or reduce the water film. The first block shallow groove 26 and the second straight shallow groove 27 divide the sub-block 28 into the minute land portion 30.

  The first curved shallow groove 26 has a radius that is about ¼ of the tread width, and has a substantially semicircular shape that is convex in the tire rotation direction. The first curved shallow grooves 26 are arranged at a predetermined pitch in the tire circumferential direction, and one end reaches the circumferential groove 14 and the other end reaches the tread end.

  As described above, by arranging a plurality of first curved shallow grooves 26, the density of the first curved shallow grooves 26 formed near the tread end and in the vicinity of the circumferential groove 14 can be made larger than that of other portions. Moreover, drainage can be efficiently performed by making it a substantially semicircular shape in the tire rotation direction.

  The second straight shallow groove 27 is a straight line extending from the circumferential groove 14 side located at the center in the tire width direction of the tread surface to the tread end side toward the rear in the tire rotation direction, and one end reaches the circumferential groove 14. The other end reaches the tread end. In other words, the second straight shallow groove 27 has a V shape with the front in the tire rotation direction as the top. The inclination angle of the second straight shallow groove 27 with respect to the tire circumferential direction is preferably in the range of 0 ° to 90 ° in consideration of the relationship between the tire rotation direction and drainage.

  The width W1 (see FIG. 4) of the first curved shallow groove 26 and the second straight shallow groove 27 is at least narrower than the width W2 of the sipe 22 (see FIG. 3). W1 may be wider than W2.

  As shown in FIG. 4, the first curved shallow groove 26 and the second straight shallow groove 27 have a substantially rectangular cross section, and the depth D1 is preferably in the range of 0.1 mm to 0.5 mm. The width W1 is preferably in the range of 0.1 mm to 1.0 mm. By setting the depth D1 and the width W1 to 0.1 mm or more, it is possible to secure a sufficient amount of water that can be taken into the first curved shallow groove 26 and the second straight shallow groove 27 and to obtain a high water removal effect. . Further, by setting the depth D1 to 0.5 mm or less and the width W1 to 1.0 mm or less, the deformation of the micro land portion 30 at the time of ground contact can be suppressed and wear can be reduced.

As the tread area of the small land portion 30, it is preferable to 0.4mm ² ~30mm ^2. By setting the tread surface area to 0.4 mm ² or more, it is possible to secure a ground contact area and obtain high performance in the initial use of the pneumatic tire 10. Further, by limiting to 30 mm ² or less, it is possible to secure a sufficient amount of water that can be taken into the first curved shallow groove 26 and the second straight shallow groove 27 and to obtain a high water removal effect.

  The first curved shallow groove 26 and the second straight shallow groove 27 can be formed on the inner surface of a mold for vulcanizing and molding the pneumatic tire 10 by cutting, electric discharge machining, etching, or the like.

  Further, the first curved shallow groove 26 and the second straight shallow groove 27 can be formed on a molded tire or a tire whose surface has been worn to some extent by running. In such a tire, knife cutting or It can be formed by surface buffing with sandpaper or the like.

  Next, the effect | action of the pneumatic tire 10 of this embodiment is demonstrated.

  The tread 12 of the pneumatic tire 10 includes an inner rubber layer 34 (unfoamed rubber layer) on the inner side in the tire radial direction and an outer rubber layer 36 (foamed rubber layer) on the outer side in the tire radial direction. In the initial stage of use, the bubbles of the outer rubber layer 36 are not exposed on the tread.

  When the pneumatic tire 10 in the initial use state travels on an icy and snowy road, water is generated due to pressure, friction, and the like when the tread 12 contacts the ice or snow. This water that causes a reduction in frictional force is taken into the first curved shallow groove 26 and the second straight shallow groove 27 provided on the tread surface of the block 20, and through this groove portion (or further through the sipe 22). D) Since the water is discharged to the circumferential grooves 14 and 16 and the lateral grooves 18 and 24, the water film between the tread surface and the road surface is removed.

  For this reason, the pneumatic tire 10 according to the present embodiment has a braking performance / drive on an icy and snowy road surface in the initial use compared to a tire in which the first curved shallow groove 26 and the second straight shallow groove 27 are not formed on the tread. The performance is improved and the wet performance is also improved on the wet road surface by the drainage effect of the first curved shallow groove 26 and the second straight shallow groove 27.

  In particular, in the present embodiment, one end of the first curved shallow groove 26 and the second straight shallow groove 27 reaches the circumferential groove 14 and the other end reaches the tread end portion. Moisture can be transferred from the shallow groove 27 to the circumferential groove 14 or the outer side of the tread, and the drainage effect can be further enhanced. The drainage effect can be improved as long as at least one end of each of the first curved shallow groove 26 and the second straight shallow groove 27 reaches one of the main grooves 38 or the tread end.

In addition, since the first curved shallow groove 26 has a curved shape, the anisotropy of the edge effect is eliminated, and the on-ice performance particularly during cornering is improved. Since the second straight shallow groove 27 is straight, drainage is also improved. Also, since the first curved shallow groove 26 and the second straight shallow groove 27 intersect, both pass through this intersection. The movement of moisture in the shallow groove becomes possible, and the water removal effect can be further enhanced.

  In addition, the 1st curve shallow groove | channel and 2nd curve shallow groove | channel which concern on this invention are not limited to the shape as described in the said embodiment. As shown in FIG. 5, the first curved shallow groove 26 of the above embodiment may be combined with a second straight shallow groove 50 that is parallel to the tire circumferential direction. Moreover, as shown in FIG. 6, it is good also as a shape which combined the 2nd straight shallow groove 50 of the tire circumferential direction, and the elliptical 1st curve shallow groove 52 inclined by the predetermined angle with respect to the tire circumferential direction. Furthermore, as shown in FIG. 7, it is good also as a shape which combined the 1st curve shallow groove 54 of the wave shape inclined by the predetermined angle with respect to the tire circumferential direction, and the 2nd straight shallow groove 27 of the said embodiment. .

  The first curved shallow groove and the second straight shallow groove do not necessarily have to be arranged in a regular pattern as in the present embodiment. However, if the regular pattern is formed, the structure becomes simple and the tread surface It is preferable because uniform performance can be ensured throughout.

  In the present embodiment, the pneumatic tire 10 in which the sipe 22 is formed in the block 20 is taken as an example. However, the present invention is applied to a pneumatic tire in which the sipe 22 is not formed, and the first curved shallow groove 26 is applied. It is also possible to form the second straight shallow groove 27 in the block 20. In this case, if the first curved shallow groove and the second straight shallow groove are shallower and narrower than at least the circumferential grooves 14 and 16 and the lateral grooves 18 and 24, the basic curve of the pneumatic tire is reduced to the first curved shallowness. The influence of the groove 26 and the second straight shallow groove 27 can be reduced, and the water removal effect that is the original effect of the first curved shallow groove and the second straight shallow groove can be maintained.

  Further, not only the pneumatic tire 10 in which the block 20 is formed by the main groove 38 but also a pneumatic tire in which a rib is formed, for example, a pneumatic tire according to the present invention is formed by forming a shallow groove in the rib. Is possible.

  Moreover, it replaces with the outer rubber layer comprised with the foamed rubber layer as the block 20 (or rib), and may be comprised with the rubber with which the filler was filled in order to improve on-ice performance. Even in this configuration, it is assumed that the filler is not exposed on the tread at the initial use of the pneumatic tire, but by using the shallow groove as in this embodiment, the initial use of the pneumatic tire The performance at can be improved.

  Next, the present invention will be described in more detail with reference to examples.

  In this example, the pneumatic tire 10 of this embodiment shown in FIGS. 1 to 4 was mounted on a passenger car, and the performance on ice in the initial use was evaluated. The radius of the first curved shallow groove 26 was ¼ of the tread width, and the inclination angle of the second straight shallow groove 27 with respect to the tire circumferential direction was 45 °.

  Further, as a comparative example, the performance on ice in the initial use was similarly evaluated using a pneumatic tire 70 shown in FIG. As shown in FIG. 9, this pneumatic tire 70 is replaced with a shallow groove 26 of the pneumatic tire 10 of the embodiment, and forms a plurality of two-direction crossing at an angle of 45 ° with respect to the circumferential direction. This is different from the pneumatic tire 10 in that the shallow grooves 72 (interval: 1.09 mm) are formed. The rest of the basic configuration is the same as that of the pneumatic tire 10 of the embodiment, and the same parts in FIG.

  Table 1 shows the basic configuration of the pneumatic tires 10 and 70 and the evaluation of the performance on ice.

これら実施例及び比較例では、共通の条件として、
・タイヤサイズ：１９５／６５Ｒ１６
・使用リム ：６Ｊ−１５
・使用内圧 ：２１０ｋＰａ（フロント、リヤ同じ）
とした。

In these examples and comparative examples, as common conditions,
・ Tire size: 195 / 65R16
・ Rim used: 6J-15
・ Internal pressure: 210 kPa (same for front and rear)
It was.

<Test method and evaluation method>
-Acceleration on ice The time required to accelerate from 5 km / h to 15 km / h on ice was measured, and a comparative example was used as a comparative example to evaluate the index. The larger the value, the better the acceleration performance.

-Braking distance The braking distance required to decelerate to 0 km / h by brake lock while driving at a constant speed of 20 km / h on ice was measured. The larger the value, the better the braking performance.

-Turning performance The turning stability on ice was evaluated by feeling by a test driver. The larger the value, the better the turning stability.

  From Table 1, it can be seen that the present example is superior to the comparative example in the acceleration performance on ice and the turning performance. This is considered to be because the first curved shallow groove 26 is curved in this embodiment.

It is a top view which shows the tread of the pneumatic tire of this embodiment. It is sectional drawing which expands and shows the block of the pneumatic tire of this embodiment. It is a top view which expands and shows the tread of the pneumatic tire of this embodiment partially. It is explanatory drawing which shows the depth and width | variety of the 1st curve shallow groove and the 2nd curve shallow groove formed in the tread of the pneumatic tire of this embodiment. It is a top view which shows the modification of the tread of the pneumatic tire of this embodiment. It is a top view which shows the other modification of the tread of the pneumatic tire of this embodiment. It is a top view which shows the other modification of the tread of the pneumatic tire of this embodiment. It is a top view which shows the tread of the pneumatic tire of a comparative example. It is explanatory drawing which takes out and shows only the shallow groove | channel formed in the tread of the pneumatic tire of the comparative example.

Explanation of symbols

10 tire 14 circumferential groove 20 block 22 sipe 26 first curve shallow groove 27 second straight shallow groove 28 sub-block 30 minute land portion 34 inner rubber layer 36 outer rubber layer 38 main groove 50 second straight shallow groove 52 first Curve shallow groove 54 First curve shallow groove

Claims (7)

In a pneumatic tire having a plurality of land portions partitioned by a plurality of main grooves on a tread surface, and the land portions are divided by at least one sipe extending in the tire width direction to form sub-blocks,
The land portion has a curved first curved shallow groove that is at least one end shallower than the sipe and reaches one of the plurality of main grooves or tread ends, and at least one end shallower than the sipe. A linear second straight shallow groove that reaches one of the plurality of main grooves or tread ends and intersects the first curved shallow groove;
A pneumatic tire characterized by comprising:   2. The pneumatic according to claim 1, wherein the second straight shallow groove is a straight line extending from a center portion of the tread surface in the tire width direction toward the tread end portion toward the rear in the tire rotation direction. tire. One of the main grooves is a central circumferential groove formed along the tire circumferential direction at the center of the tread surface in the tire width direction,
The first curved shallow groove is formed in each of the tread half regions on both sides sandwiching the central circumferential groove with a radius of 1/4 or more of the tread width, and has a substantially semicircular shape that is convex in the tire rotation direction. The pneumatic tire according to claim 1 or 2, wherein a plurality of the semicircular shallow grooves formed are arranged in the tire circumferential direction.   The first curved shallow groove and the second straight shallow groove have a depth of 0.1 mm to 0.5 mm and a width of 0.1 mm to 1.0 mm. 4. The pneumatic tire according to any one of 3 above. Claims 1 in which a plurality of micro land portions partitioned by a plurality of said first curved shallow groove and the second linear shallow groove, characterized in that there is a tread area of 0.4 mm ² ～30Mm ² The pneumatic tire according to any one of 4.   The pneumatic tire according to any one of claims 1 to 5, wherein a plurality of the first curved shallow grooves and the second straight shallow grooves are arranged in a regular pattern.   The rubber constituting the land portion is composed of a foam rubber layer on the outer side in the radial direction of the tire and an unfoamed rubber layer on the inner side in the radial direction. The pneumatic tire according to item 1.

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