JP4621012B2 - Pneumatic tire - Google Patents

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 Literature 1 and Patent Literature 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. Furthermore, Patent Document 4, the first and small groove plurality of extending in the circumferential direction, that contains the tire was set to a grid pattern of small groove by the second small groove of the plurality extending in the tire axial direction.
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 JP 2000-25418 A

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

  In the first aspect of the present invention, the land portion is divided by at least one sipe extending in the tire width direction to form a sub-block having a plurality of land portions partitioned by a plurality of main grooves on the tread surface. In the pneumatic tire, a plurality of shallow grooves are formed in the land portion that are shallower than the sipe and define the plurality of micro land portions by dividing the land portion, and the shallow grooves are formed along the tire circumferential direction. A plurality of circumferential shallow grooves disposed in the tire width direction that are shallower than the circumferential shallow grooves and intersect with the circumferential shallow grooves. It is characterized by that.

  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, main grooves, sipes, and shallow grooves are formed on the tread surface. 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 land deformation. 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.

  Generally, in the tire circumferential direction, it is preferable to increase the drainage effect with respect to the road surface. However, in the tire width direction, it is preferable that the drainage effect can be maintained and the edge effect can be exhibited highly. The shallow groove of the present invention includes a plurality of circumferential shallow grooves arranged along the tire circumferential direction, and a plurality of shallow grooves arranged along the tire width direction that are shallower than the circumferential shallow grooves and intersect the circumferential shallow grooves. The circumferential direction shallow groove is relatively deeper than the width direction shallow groove, so that more water can be taken in and the drainage effect is sufficiently exhibited. On the other hand, since the shallow groove in the width direction is relatively shallower than the shallow groove in the circumferential direction, the rigidity of the edge portion is increased, and the edge effect can be enhanced. Thus, by making the shallow groove in the tire circumferential direction relatively deeper than the shallow groove in the tire width direction, the drainage effect and the edge effect can be achieved at a high level.

  In addition, since the plurality of shallow grooves (circumferential direction shallow grooves and width direction shallow grooves) intersect each other, moisture in the shallow grooves can be moved through the intersections, and the water removal effect can be further enhanced.

  According to a second aspect of the present invention, in the first aspect of the present invention, the shallow groove has a depth of 0.1 mm to 0.5 mm and a width of 0.1 mm to 1.0 mm. Features.

  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 the tread 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 circumferential shallow groove and the width shallow groove satisfy the condition that the depth is in the range of 0.1 mm to 0.5 mm, respectively, and the width shallow groove is formed shallower than the circumferential shallow groove.

In the invention described in claim 3, in the invention of claim 1 or claim 2, a plurality of micro land portions partitioned by a plurality of the shallow groove is set to tread area of 0.4 mm ² ～30Mm ² It is characterized by.

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.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the plurality of shallow grooves are arranged in a regular pattern.

  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 5 is the invention according to any one of claims 1 to 4, wherein the absolute value of the inclination angle measured from the acute angle side with respect to the tire equator plane is the circumferential shallow groove. 50 degrees or less and 40 degrees or more and 90 degrees or less in the said width direction shallow groove, It is characterized by the above-mentioned.

  In this way, by setting the inclination angle (the absolute value thereof) of the circumferential shallow groove to 50 degrees or less, it is possible to secure the component of the circumferential shallow groove in the tire circumferential direction and to reliably exert the drainage effect. It becomes possible. In addition, by setting the inclination angle (the absolute value thereof) of the width direction shallow groove to 40 degrees or more and 90 degrees or less, a component in the width direction of the tire in the tire width direction can be secured and the edge effect can be surely exhibited. Is possible.

  In the present invention, the circumferential shallow groove is relatively arranged along the tire circumferential direction rather than the widthwise shallow groove. Therefore, after satisfying the condition that the inclination angle of the circumferential shallow groove is smaller than the inclination angle of the width direction shallow groove, the inclination angle of the circumferential direction shallow groove and the width direction shallow groove is set within the above range.

The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein a difference in depth between the shallow groove in the width direction and the shallow groove in the circumferential direction is 0.3 mm or more. It is characterized by that.

  That is, if the circumferential shallow groove is slightly deeper than the width shallow groove, the effect of the present invention can be obtained. However, by making the depth difference 0.3 mm or more, the edge effect of the width shallow groove is reliably obtained. At the same time, the drainage effect in the shallow groove in the width direction can be kept high. Moreover, necessary and sufficient accuracy can be obtained at low cost as the working accuracy when forming the circumferential shallow grooves and the width shallow grooves.

  In the invention according to claim 7, in the invention according to any one of claims 1 to 6, the rubber constituting the land portion includes a foamed 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 at the initial use of the pneumatic tire.

  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 shallow groove 26 that absorbs moisture generated between the block 20 and the road surface to remove or reduce the water film. The shallow groove 26 according to the present embodiment includes a circumferential shallow groove 26A arranged along the tire circumferential direction and a widthwise shallow groove 26B arranged along the tire width direction when the tread surface of the block 20 is viewed in plan view. (Hereinafter, when it is necessary to distinguish between them, they are referred to as a circumferential shallow groove 26A and a width direction shallow groove 26B, and when there is no need to distinguish them, they are simply referred to as shallow grooves 26). Although the width W1 of the shallow groove 26 (see FIG. 5) is at least narrower than the width W2 of the sipe 22 (see FIG. 3), these widths may be the same, or W1 may be wider than W2.

  The plurality of circumferential shallow grooves 26A are arranged with a constant interval D2 in the tire width direction, and the width direction shallow grooves 26B are arranged with a constant interval D3 in the tire circumferential direction. The circumferential shallow groove 26A and the widthwise shallow groove 26 intersect at a plurality of intersections, and the shallow grooves 26 are arranged in such a regular pattern, whereby a rectangular micro land having a predetermined tread surface area is obtained. Many portions 30 are formed in a regular pattern on the tread. And the aesthetics of the pneumatic tire 10 are also improved by forming the geometric pattern which consists of the closed curve (shallow groove 26) and the micro land part 30 of a fixed pattern in this way on the tread. In the present embodiment, as an example, the distances D2 and D3 are equal, and the micro land portion 30 is square.

  As shown in FIG. 5, the shallow groove 26 has a substantially rectangular cross-sectional shape, and its depth D1 is preferably in the range of 0.1 mm to 0.5 mm, and the width W1 is 0.1 mm to 1.0 mm. The range of is preferable. By setting the depth D1 and the width W1 to 0.1 mm or more, it is possible to secure an amount of moisture that can be taken into the shallow groove 26 and 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.

  And in this embodiment, after each depth of the circumferential direction shallow groove 26A and the width direction shallow groove 26B is made into the said range, as shown to FIG. 2 (A) and (B), the width direction The shallow groove 26B is formed so as to be shallower than the circumferential shallow groove 26A.

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, the amount of moisture that can be taken into the shallow groove 26 is ensured, and a high water removal effect can be obtained.

  The distance D2 between the circumferential shallow grooves 26A and the distance D3 between the widthwise shallow grooves 26B are preferably 0.3 mm to 0.5 mm. By setting the distances D2 and D3 to 0.3 mm or more, the rigidity of the tread can be maintained higher. Moreover, the arrangement density of the shallow groove | channel 26 can be made high by setting it as 0.5 mm or less, and it becomes possible to fully exhibit the water removal effect.

  The shallow groove 26 can be formed on the inner surface of a mold for vulcanizing the pneumatic tire 10 by cutting, electric discharge machining, etching, 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 a shallow groove 26 provided on the tread surface of the block 20, and the circumferential grooves 14, 16, and lateral grooves are passed through this groove portion (or further via the sipe 22). Since it is discharged to 18, 24, the water film between the tread and the road surface is removed.

  For this reason, the pneumatic tire 10 of the present embodiment has improved braking performance and driving performance on the icy and snowy road surface in the initial use as compared with a tire in which the shallow groove 26 is not formed on the tread surface, and also on the wet road surface, The wet performance is improved by the drainage effect of the shallow groove 26.

  Here, in general, it is preferable to obtain a high drainage effect with respect to the road surface in the tire circumferential direction, but in the tire width direction, it is preferable that the drainage effect can be maintained while exhibiting a high edge effect. The shallow groove 26 of the present embodiment includes a plurality of circumferential shallow grooves 26A arranged along the tire circumferential direction, and a widthwise shallow groove 26B arranged along the tire width direction and shallower than the circumferential shallow groove 26A. , Is composed of. Since the circumferential shallow groove 26A is relatively deeper than the widthwise shallow groove 26B, more water can be taken in and the drainage effect is sufficiently exhibited. On the other hand, since the width direction shallow groove 26B is relatively shallower than the circumferential direction shallow groove 26A, the rigidity of the edge portion is increased, and the edge effect can be further enhanced. In this way, by making the circumferential shallow groove 26A relatively deep with respect to the widthwise shallow groove 26B, the drainage effect and the edge effect can be achieved at a high level.

  In the present embodiment, since the plurality of shallow grooves are arranged at constant intervals D2 and D3 in the tire circumferential direction and the tire width direction, anisotropy of the edge effect is eliminated, and performance on ice particularly during cornering. Will improve.

  Furthermore, in the present embodiment, the circumferential shallow grooves 26A and the widthwise shallow grooves 26B are arranged so as to intersect each other, so that moisture can be moved between the respective shallow grooves 26 through the intersections. The water effect can be further enhanced.

  In addition, when the air bubbles of the outer rubber layer 36 are exposed by using the pneumatic tire 10, a water removal effect and an edge effect on the road surface are exhibited by the air bubbles.

  The shallow groove according to the present invention is not limited to the linear groove described above. For example, it may be formed in a zigzag shape or a wave shape. In this case, if the longitudinal direction is arranged along the tire circumferential direction as a whole, the circumferential shallow groove 26A is arranged along the tire width direction. Then, the shallow groove 26B in the width direction is formed.

  The direction of the circumferential shallow groove 26A may be a direction having a main component in the tire circumferential direction, and in particular, a direction in which the absolute value of the inclination angle measured from the acute angle side with respect to the tire equatorial plane is 50 degrees or less. If it arrange | positions by, it becomes possible to ensure the component to the tire circumferential direction of 26 A of circumferential direction shallow grooves, and to exhibit the drainage effect reliably, and is preferable. Further, the direction of the width direction shallow groove 26B may be a direction having a main component in the tire width direction, and in particular, the absolute value of the inclination angle measured from the acute angle side with respect to the tire equator plane is 40 degrees or more and 90 degrees. If it is arranged in a direction that is less than or equal to the degree, it is possible to secure a component in the tire width direction of the widthwise shallow groove 26B and to reliably exhibit the edge effect, which is preferable.

  In addition, after satisfying the condition that the inclination angle of the circumferential shallow groove 26A is smaller than the inclination angle of the width direction shallow groove 26B, the inclination angle of the circumferential direction shallow groove and the width direction shallow groove is set within the above range. The

  The depth ratio of the width direction shallow groove 26B to the circumferential direction shallow groove 26A is not particularly limited. If the circumferential direction shallow groove 26A is slightly deeper than the width direction shallow groove 26B, the effect of the present invention is achieved. By making the difference 0.3 mm or more, the edge effect of the widthwise shallow groove 26B can be obtained reliably and the drainage effect in the widthwise shallow groove can be maintained high. Moreover, necessary and sufficient accuracy can be obtained at low cost as the working accuracy when forming the circumferential shallow groove 26A and the width shallow groove 26B.

  The shallow grooves do not necessarily have to be arranged in a regular pattern as in the present embodiment, but regular patterning simplifies the structure and ensures uniform performance over the entire tread surface. ,preferable.

  In this 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 shallow groove 26 is formed in the block 20. It is also possible to form it. In this case, if the shallow groove 26 is shallower and narrower than at least the circumferential grooves 14 and 16 and the lateral grooves 18 and 24, the influence of the shallow groove 26 on the basic performance of the pneumatic tire can be reduced, and the shallow groove 26 is shallow. The water removal effect that is the original effect of the groove 26 can also 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 the present embodiment shown in FIGS. 1 to 5 was mounted on a passenger car, and the performance on ice in the initial stage of use and the handling stability on a dry road were evaluated. Both the distance D2 between the circumferential shallow grooves 26A and the distance D3 between the widthwise shallow grooves 26B were 1.0 mm.

  In addition, as a comparative example, the pneumatic tire 70 shown in FIG. 6 was used, and the performance on ice and the handling stability on the dry road in the initial use were also evaluated. In this pneumatic tire 70, shallow grooves 72 having the same pattern as that of the shallow grooves 26 of the pneumatic tire 10 of the embodiment are formed in a plan view. However, as shown in FIG. It differs from the pneumatic tire 10 in that the shallow groove 72A and the width direction shallow groove 72B are made equal. The other basic configuration is the same as that of the pneumatic tire 10 of the embodiment, and the same parts in FIG. 6 are denoted by the same reference numerals as those in FIG.

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

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 taken as a comparative example and index evaluation was relatively performed. The larger the value, the better the acceleration performance.

・ Brake distance (performance on ice)
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 smaller the value, the better the braking performance.

-Steering stability (dry road)
The steering stability on the dry road was relatively index-evaluated with the comparative example as 100 by the feeling of the test driver. The larger the value, the better the turning stability.

  From Table 1, it can be seen that both the acceleration on ice and the turning performance are particularly improved in the present embodiment as compared with the comparative example. Regarding acceleration on ice, in this embodiment, it is considered that the drainage effect is enhanced by making the circumferential shallow groove 26A relatively deeper than the widthwise shallow groove 26B. Regarding the turning performance, it is considered that the anisotropy of the edge effect disappears because the plurality of shallow grooves 26 are arranged in a regular pattern in this embodiment.

  Also, in this example, higher evaluation than the comparative example was obtained in terms of steering stability on the dry road. This is considered to be because the rigidity of the tread surface is maintained high by arranging the plurality of shallow grooves 26 independently so as not to cross or contact each other.

It is a top view which shows the tread of the pneumatic tire of one Embodiment of this invention. It is sectional drawing which expands and shows the block of the pneumatic tire of one Embodiment of this invention. It is a top view which expands and shows the tread of the pneumatic tire of one embodiment of the present invention partially. It is explanatory drawing which takes out and shows only the shallow groove | channel formed in the tread of the pneumatic tire of one Embodiment of this invention. It is explanatory drawing which shows the depth and width | variety of the shallow groove | channel formed in the tread of the pneumatic tire of one Embodiment of this invention. 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

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential groove 16 Circumferential groove 18 Horizontal groove 20 Block 22 Sipe 24 Lateral groove 26 Shallow groove 28 Sub block 30 Inner rubber layer 36 Outer rubber layer 38 Main groove 40 Shallow groove 42 Shallow groove 44 Shallow groove CL tire equator

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 is shallower than the sipe, and a plurality of shallow grooves that form a plurality of micro land portions by dividing the land portion are formed,
A plurality of circumferential shallow grooves arranged along the tire circumferential direction, and a plurality of width directions intersecting the circumferential shallow grooves arranged along the tire width direction shallower than the circumferential shallow grooves. A pneumatic tire comprising a shallow groove.   The pneumatic tire according to claim 1, wherein the shallow groove has a depth of 0.1 mm to 0.5 mm and a width of 0.1 mm to 1.0 mm. The pneumatic tire according to claim 1 or claim 2 the plurality of minute land portions partitioned by a plurality of the shallow groove, characterized in that there is a tread area of 0.4mm ² ~30mm ^2.   The pneumatic tire according to any one of claims 1 to 3, wherein the plurality of shallow grooves are arranged in a regular pattern.   The absolute value of the inclination angle measured from the acute angle side with respect to the tire equator plane is 50 degrees or less in the circumferential shallow groove and 40 degrees or more and 90 degrees or less in the width shallow groove. The pneumatic tire according to any one of claims 1 to 4. The pneumatic tire according to any one of claims 1 to 5, wherein a difference in depth between the circumferential shallow groove and the width shallow groove is 0.3 mm or more.   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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