JP2006151231A - 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 plurality of circular shallow grooves 26 having the radius R determined so as to be closed in a sub block 28 are formed in a tread of a block 20. A large number of shallow grooves 26 are arranged so that the shallow grooves form a regular pattern and are not intersected with or brought into contact with each other. Since the rigidity of the tread is increased, the performance can be enhanced not only on an icy-snowy road but also on a dry road. <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.

  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. The pneumatic tire is characterized in that a plurality of shallow grooves, which are shallower than the sipe and are closed in the land portion, are formed in the land portion independently of each other without intersecting and contacting each other.

  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 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, the shallow groove of the present invention is shallower than the sipe in the land portion, and a plurality of shallow grooves formed in a closed shape in the land portion are independently formed without crossing or contacting each other. The “shape closed in the land” means a shape that can be drawn in the land without protruding from the land. By forming such a shallow groove, each of the shallow grooves has a groove component having a plurality of directions, so that the basic performance of the pneumatic tire is not directional and the so-called edge effect is enhanced.

  It should be noted that the plurality of shallow grooves only have to satisfy the condition of being closed in the land, and if this condition is satisfied, there is a shallow groove arranged or formed so as to protrude from the land. Also good.

  In addition, since the plurality of shallow grooves are independently formed without crossing or contacting each other, the rigidity of the tread surface of the pneumatic tire is ensured, so that traveling performance on a dry road can be ensured high.

  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 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.

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 basic unit has a circular shape having a constant radius when the land portion is viewed in plan. It is characterized by being.

  In this way, a regular pattern of shallow grooves can be formed with a simple structure in which the shallow grooves are circular. Further, by forming the circular shallow grooves in a regular pattern, uniform performance can be ensured over the entire tread surface.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the rubber constituting the land portion includes a foamed rubber layer on the 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 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 of the present embodiment is formed with a shape that becomes a circle when the tread surface of the block 20 is viewed in plan as a basic unit. 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 radius R of the circle, which is the basic unit of the shallow groove 26, is determined so as to be closed within the sub-block 28. As shown in detail in FIG. 4, this circular shape is independently arranged with a constant gap (interval D2) in the circumferential direction and the width direction of the pneumatic tire 10, and may intersect or contact each other. Not to be. Due to these circular shallow grooves 26, a large number of micro land portions 30 having a predetermined tread area are formed in a regular pattern on the tread. Thus, the aesthetic appearance of the pneumatic tire 10 is improved by forming a geometric pattern composed of a closed curve (shallow groove 26) and a small land portion 30 in a constant pattern on the tread.

  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.

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 shallow grooves 26 is preferably 0.3 mm to 0.5 mm. By setting the distance D2 to 0.3 mm or more, the rigidity of the tread can be maintained higher as will be described later. 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.

  In particular, in the present embodiment, the shallow grooves 26 of the basic unit (circular shape) closed in the sub-block 28 are arranged in a regular pattern with a constant interval in the tire circumferential direction and the tire width direction. Therefore, the anisotropy of the edge effect disappears, and the performance on ice especially at the cornering is improved.

  Further, in the present embodiment, the plurality of shallow grooves 26 are formed so as to be independent without intersecting or contacting each other, so that the rigidity of the tread surface of the pneumatic tire 10 is ensured. Therefore, when the pneumatic tire 10 of the present embodiment is used to travel on a dry road, it is possible to ensure a high traveling performance on the dry road.

  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 shallow groove 26 having the above-described circular shape as a basic unit. For example, a plurality of kinds of circles having different radii R may be combined. Further, as shown in FIG. 6 (A), a plurality of circular shallow grooves 26 are arranged at different intervals in the tire circumferential direction and the tire width direction, or a diamond-shaped shallow groove shown in FIG. 6 (B). 40, the triangular shallow groove 42 shown in FIG. 6C, the six-drawn shallow groove 44 shown in FIG. 6D, and a polygonal shape other than these, although not shown. Furthermore, these shapes may be combined. However, if the shallow groove is circular as in this embodiment, the tangent to the shallow groove continuously changes compared to the diamond-shaped, triangular, or polygonal shallow groove, so the anisotropy disappears. preferable.

  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 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 The water removal effect which is the original effect of 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. The radius of the circle constituting the shallow groove 26 was 1.5 mm.

  Moreover, as a comparative example, the pneumatic tire 70 shown in FIG. 7 was used, and the performance on ice and the handling stability on the dry road were also evaluated in the initial stage of use. As shown in FIG. 8, this pneumatic tire 70 is replaced with the shallow groove 26 of the pneumatic tire 10 of the embodiment, and forms a plurality of two directions in an angle of 45 ° with respect to the circumferential direction and intersecting each other. 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 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 used as a comparative example to evaluate the index. 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 during a constant speed of 20 km / h on ice was measured, and a comparative example was used as a comparative example to evaluate the index. The smaller the value, the better the braking performance.

・ Swivel performance (performance on ice)
The comparative example was evaluated as an index relative to 100 as a comparative example with the feeling of turning stability on ice by a test driver. The larger the value, the better the turning stability.

-Steering stability (dry road)
By comparatively setting the comparative example as 100, the examples were relatively index-evaluated by the feeling by the test driver on the handling stability on the dry road. The larger the value, the better the turning stability.

  From Table 1, it can be seen that the turning performance on ice is particularly improved in this embodiment as compared with the comparative example. In particular, smooth turning of the vehicle during turning was obtained, and a better feeling was obtained in terms of ease of handling. This is considered to be because the anisotropy of the edge effect is lost 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 a 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. (A)-(C) are all explanatory drawings which show the shape different from what is shown in FIGS. 1-5 of the shallow groove | channel applicable to 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

10 pneumatic tire 12 tread 14 circumferential groove 16 circumferential groove 18 lateral groove 20 block 22 sipe 24 lateral groove 26 shallow groove 28 sub-block 30 minute land portion 34 inner rubber layer 36 outer rubber layer 38 main groove 40 shallow groove 42 shallow groove 44 Shallow groove CL tire equator

Claims (6)

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,
A pneumatic tire characterized in that a plurality of shallow grooves that are shallower than the sipe and closed in the land portion are formed in the land portion independently of each other without intersecting and contacting each other.   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 pneumatic tire according to any one of claims 1 to 4, wherein the basic unit has a circular shape having a constant radius when the land portion is viewed in plan.   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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