JP2008030656A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of keeping the block stiffness of a tire by making a shape of a block land part suitable, and further improving on-ice performance while keeping on-snow performance without impairing edge effect by a sipe. <P>SOLUTION: In the pneumatic tire, a plurality of circumferential grooves 4 extending in a generally tire circumferential direction, and a plurality of lateral grooves 5 communicating the adjacent two circumferential grooves 4 are arranged on a tread portion 1, thereby dividing at least one block land part line 2 composed of a large number of the block land parts. On the block land part 3, a plurality of first sipes 6 extending so as to intersect the tire circumferential direction is arranged. A pair of second sipes 7 extending in a direction intersecting the first sipes 6 is arranged on at lease one block land part 3. A sub block land part 8 is virtually divided by an extending line these first and second sipes 6, 7. Furthermore, a plurality of small holes 9 is provided in the sub block land part 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the tread portion, a plurality of block land portions are provided by disposing a plurality of circumferential grooves extending substantially in the tire circumferential direction and a plurality of lateral grooves communicating two adjacent circumferential grooves. A pneumatic tire, in particular, winter pneumatic, in which at least one block land portion row is formed and a plurality of sipes extending across the tire circumferential direction are disposed on the block land portion. The present invention relates to a tire, and aims to improve the running performance of the tire on an icy and snowy road surface.

  In order to eliminate dust pollution caused by spikes or studs protruding on the surface of the tread part, studless tires that do not have spikes and have excellent running performance on icy and snowy road surfaces have been developed.

  A feature that is almost common to studless tires is that the tread portion is divided into a large number of block land portions, and a large number of sipes are arranged. When such a sipe is provided, a so-called edge effect, which is an effect caused by the edge of the block land portion scratching the road surface, and a so-called drainage effect, which is an effect of the sipe sucking up a water film existing on the ice road surface, can be obtained. . Therefore, from the viewpoint of only the edge effect and the drainage effect, it is considered that the performance on ice is improved by increasing the number of sipe arrangements, but this simultaneously reduces the block rigidity and reduces the ground contact area due to the bending deformation of the block, Rather, the performance on ice is lowered, and at the same time, dry handling performance and wet handling performance are also lowered, and further, uneven wear of the block land portion may be caused. For example, Patent Document 1 describes a tire having a tread pattern in which sipes are arranged over the entire tread surface. In this tire, tire load rotation is reduced due to a decrease in rigidity of a block land portion. At the same time, there is a concern that excessive bending deformation of the block land near the sipe will occur, and not only the performance on ice and snow but also the dry handling performance and the wet handling performance will be degraded. In order to prevent such uneven wear, for example, Patent Document 2 includes the radius of curvature of the outer contour of the sub-block land portion formed by arranging sipes on the block land portion. There is described a tire with improved on-ice performance while ensuring on-snow performance without reducing the contact area with the road surface of the tread part tread at the same time as the tire load rolling by making it smaller than the radius of curvature of the outer contour of the tread part. Yes. Furthermore, Patent Document 3 describes a tire in which a plurality of small holes are provided in the block land portion to optimize the rigidity and improve the performance on ice.

JP-A-9-48216 Japanese Patent Application Laid-Open No. 10-244813 Japanese Patent Laid-Open No. 2006-7796

  However, the tire described in Patent Document 2 maintains the tire block rigidity and the performance on snow at a high level, and improves the performance on ice by preventing excessive fall of the sub-block land portion. Since the sipe movement is strongly suppressed at the same time, the edge effect is limited, and it cannot be said that the performance on ice is sufficiently improved. Patent Document 3 focuses on improving the performance on ice, and does not consider the optimization of the performance on snow.

Therefore, the object of the present invention is to optimize the shape of the block land portion, and to maintain the block rigidity of the tire, while maintaining the performance on the snow, without impairing the edge effect due to the sipe, the performance on the ice An object of the present invention is to provide a pneumatic tire that is further improved.

  In order to achieve the above object, according to the present invention, a plurality of circumferential grooves extending substantially in the tire circumferential direction and a plurality of transverse grooves communicating two adjacent circumferential grooves are disposed in the tread portion. The block land portion is divided into at least one row of block land portions, and a plurality of first sipes extending across the tire circumferential direction are provided on the block land portion. A sub-block in which a pair of second sipes extending in a direction intersecting with the first sipes is disposed in at least one block land portion in the entering tire, and virtually partitioned by an extension line of the first and second sipes. A pneumatic tire comprising a plurality of small holes in a land portion. With this configuration, the sub-block land portion of the block land portion prevents excessive bending deformation of the block land portion near the sipe, so that the performance on ice is sufficiently improved while maintaining the performance on snow, and the arrangement of the sipe With the moderate height of the block land portion rigidity, the wet handling performance and the dry handling performance are also maintained. Here, “substantially tire circumferential direction” means a direction in which an angle formed by an imaginary line connecting the center positions of the groove width and the tire circumferential direction becomes ± 5 °, and “small hole” means a tread portion tread surface. A small-diameter hole that opens and extends inward in the tire radial direction shall be referred to. Further, the “sub-block land portion virtually formed” means a land region surrounded by a pair of first sipes or their extension lines and a pair of second sipes or their extension lines. If this sub-block land part is completely separated from the other part of the block land part by the first and second sipes, a part of the sub-block land part is connected to the other part of the block land part. Including both.

  Moreover, it is preferable that a subblock land part is located in the center part of a block land part.

  Furthermore, it is preferable that the area of the sub-block land portion on the tread surface is 3 to 50% of the area of the block land portion including the sub-block land portion.

  Furthermore, the diameter of the opening of the small hole 11 is preferably 0.3 to 3.0 mm.

In addition, it is preferable to be arranged in the sub block land portion at an interval of 1 to 20 pieces / cm ² .

  In addition, it is preferable that the land portion of the sub-block on the tread surface is square.

  Moreover, it is preferable that the 1st sipe and the 2nd sipe are spaced apart in at least one corner | angular part of a rectangular subblock land part.

  Furthermore, it is preferable that the quadrangular sub-block land portion has two acute angle portions and two obtuse angle portions, and the first sipe and the second sipe are separated at least at the acute angle portion.

  Furthermore, the distance between the first sipe and the second sipe at the corner is preferably 0.1 to 2.5 mm. Here, the “separation distance” refers to a virtual line extending along the longitudinal direction at the center of the short sipe width of the first sipe and the second sipe, and the central line at the end of the first sipe. The distance from the end of the second sipe to the end of the center line at the end of the second sipe adjacent to the first sipe.

  According to this invention, as a result of suppressing the bending deformation of the block land portion by optimizing the shape of the block land portion, both on-ice performance and on-snow performance are achieved at a high level on the premise of maintaining the block rigidity of the tire. It is possible to provide a pneumatic tire.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a part of a block land portion row 2 of a tread portion 1 of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 2 is a view of the tread portion 1 shown in FIG. FIG. 3 and FIG. 4 are plan views of the block land portion 3 of the tread portion 1 of another typical tire according to the present invention.

  In the tire shown in FIG. 1, a plurality of circumferential grooves 4 extending substantially in the tire circumferential direction and a plurality of lateral grooves 5 communicating two adjacent circumferential grooves 4 are disposed in the tread portion 1. Then, at least one block land portion row 2 composed of a large number of block land portions 3 is partitioned. Thus, by arranging one or more block land portion rows 2, the groove area is increased and the negative rate is increased, so that basic performance on snow can be ensured.

  The block land portion 3 is provided with a plurality of first sipes 6 extending across the tire circumferential direction. As described above, when a plurality of sipes extending across the tire circumferential direction are arranged in the block land portion 3, the edge component of the block land portion 3 increases, so that basic performance on ice can be secured. it can.

  However, if sipe is excessively disposed on the block land portion 3, excessive bending deformation is caused in the block land portion 3 in the vicinity of the sipe, the contact area is reduced, and the performance on ice is rather deteriorated. In addition, wet handling performance and dry handling performance are also lowered. On the other hand, if the number of sipes provided is too small, a sufficient edge effect cannot be obtained, and the on-ice performance will not be sufficiently improved. On the other hand, in the tire of the present invention, a pair of second sipes 7 extending in a direction intersecting with the first sipes 6 are disposed in at least one block land portion 3, and the first sipes 6 and the second sipes 7 The performance on the ice and the performance on the snow are improved by virtually forming the sub-block land portion 8 by the extension line. This is because the sub-block land portion 8 of the block land portion 3 supports the block land portion 3 that bends and deforms to prevent excessive bending deformation of the block land portion 3 in the vicinity of the sipe. This is because that.

  Further, the tire according to the present invention has a plurality of small holes 9 in the sub-block land portion 8. By providing such a small hole 9, the rigidity of the sub-block land portion 8 is higher than that of providing a sipe in the sub-block land portion, so that bending deformation of the block land portion 3 can be sufficiently suppressed, and the sub-block land portion This is because the edge effect and water absorption effect of No. 8 are improved and the performance on ice is improved.

  Furthermore, the sub-block land portion 8 is preferably located at the center of the block land portion 3. For example, when the sub-block land portion 8 is unevenly located in the block land portion 3, a land portion that cannot support excessive bending deformation of the block land portion 3 near the sipe is formed. This is because the bending deformation cannot be sufficiently suppressed, and the edge effect cannot be secured, so that the performance on ice may not be sufficiently improved.

  In addition, the area of the sub-block land portion 8 on the tread portion 1 tread is preferably 3 to 50%, more preferably 5 to 40% of the area of the block land portion 3 including the sub-block land portion 8. Because, when the area of the sub-block land portion 8 on the tread portion 1 tread exceeds 50% of the area of the block land portion 3 including this, excessive bending deformation of the block land portion 3 near the sipe is suppressed. Since the area where the sipes in the block land portion 3 are disposed is reduced and the edge effect is reduced, the performance on ice may be lowered. On the other hand, the area of the sub block land portion 8 on the tread portion 1 tread surface Is less than 3% of the area of the block land portion 3 having this, the sub-block land portion 8 cannot sufficiently suppress excessive bending deformation of the block land portion 3 in the vicinity of the sipe, and the edge effect This is because the performance on ice may deteriorate due to the decrease in the temperature.

  In addition, the diameter of the opening of the small hole 9 is preferably 0.3 to 3.0 mm, more preferably 0.5 to 2.5 mm. This is because if the opening diameter is less than 0.3 mm, the rigidity of the block land portion 3 only decreases, and the water absorption effect and the edge effect are not exhibited, and there is a possibility that sufficient performance on ice cannot be obtained. On the other hand, when the opening diameter exceeds 3.0 mm, the water absorption effect is improved, but when the edge effect is applied, the ground contact area is reduced, and the performance on ice may be lowered. 1 to 4 show an embodiment in which the cross section of the small hole 11 in the tire width direction is circular, the cross sectional shape is not limited to this, and an elliptical cross section or a non-circular cross section may be used.

Further, it is preferable that the small hole 9 is disposed in the sub-block land portion 8 to 1 to 20 / cm ² interval, more preferably a 3 to 20 pieces / cm ² intervals. This is because when the spacing between the small holes 9 is less than 1 piece / cm ² , the rigidity of the block land portion 3 is maintained high, so that the edge effect is not sufficiently exhibited and the water absorption effect is also reduced. There is a possibility that the performance on ice may not be improved. On the other hand, when the interval between the small holes 9 exceeds 20 / cm ² , the water absorption effect is improved, but the rigidity of the sub-block land portion 8 is reduced. For this reason, excessive bending deformation of the block land portion 3 in the vicinity of the sipe cannot be suppressed, and the on-ice performance may be deteriorated.

The extending shape of the second sipe 7 is not limited to a linear shape, and may be curved or bent. Therefore, although illustration is omitted, the shape of the tread portion tread of the sub-block land portion 8 can be substantially elliptical, polygonal, or the like. A particularly preferable shape is a quadrangular shape as shown in the figure. Because, as shown below, various changes are made to the corners of the rectangular sub-block land portion 8 to prevent uneven wear of the sub-block land portion 8 and to adjust the rigidity of the desired block land portion 8 at the same time. This is because there is a possibility that it can be performed.

  Furthermore, as shown in FIGS. 1 and 2, the rectangular sub-block land portion 8 intersects the first sipe 6 and the second sipe 7 and is completely separated from other portions of the block land portion. However, some of them may be connected to other parts of the block land. In this case, it is preferable that the first sipe 6 and the second sipe 7 are separated from each other at at least one corner portion 10 of the sub-block land portion 8. Because bending deformation tends to concentrate on the corners of the sub-block land at the same time as the tire load rolling, by connecting the corner and other parts of the block land, parts other than the corner of the sub-block land This is because the rigidity can be increased while suppressing the reduction of the edge component rather than connecting the two. In addition, according to the required rigidity of the sub-block land portion, it is possible to appropriately change the presence / absence and distance of each corner portion. FIG. 3 is a plan view of the block land portion 3 in which the first sipe 6 and the second sipe 7 are separated from each other at all corner portions 10 of the sub-block land portion 8 according to the present invention.

  In addition, the quadratic sub-block land portion 8 has two acute angle portions and two obtuse angle portions, and the first sipe 6 and the second sipe 7 are separated from each other at least at the acute angle portion. preferable. This is because the first sipe 6 and the second sipe 7 are separated at the acute angle portion as shown in FIG. 4 rather than the first sipe 6 and the second sipe 7 are separated at the obtuse angle portion. However, because of the shape, the sub-block land portion 8 becomes easier to move simultaneously with the tire load rolling, and the small hole 9 in the sub-block land portion 8 also becomes easier to move, so that the on-ice performance and the water absorption performance are efficiently improved. This is because there is a possibility that uneven wear at an acute angle portion where bending deformation tends to concentrate more than at an obtuse angle portion can be prevented at the same time. Of course, when high rigidity is required for the sub-block land portion, the first sipe 6 and the second sipe 7 of the obtuse angle portion are separated from the first sipe 6 and the second sipe 7 of the acute angle portion. The rigidity may be increased.

  In addition, the distance between the first sipe 6 and the second sipe 7 in the corner portion 10 is preferably 0.1 to 2.5 mm, and more preferably 0.3 to 2.0 mm. Because, when the separation distance between the first sipe 6 and the second sipe 7 at the corner portion 10 exceeds 2.5 mm, the rigidity of the sub-block land portion 8 becomes too high and the movement in the vicinity of the small hole 9 is suppressed. If the distance between the first sipe 6 and the second sipe 7 at the corner 10 is less than 0.1 mm, the first sipe 6 and the second sipe 7 This is because there is a possibility that a decrease in rigidity due to the separation of the two hardly occurs.

  The block land portion 3 shown in FIG. 1 can be appropriately changed according to the required performance on ice and snow. For example, the block land portion 3 may be arranged at intervals of several. It may be arranged in all rows as in the tire of the embodiment according to the invention shown. In addition, as shown in FIG. 1, FIG. 3 or FIG. 4, the shape of the block land portion 3 when viewed in plan is a quadrangle, but it can be appropriately changed to various shapes used for conventional tires. May be.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention.

  Next, the tire of the present invention having the tread pattern shown in FIG. 5 (Example) and the tire having the tread pattern of the prior art tire shown in FIG. 6 (conventional example) were respectively prototyped and subjected to performance evaluation. Therefore, it will be described below.

  The tire of the embodiment having the tread pattern shown in FIG. 5 is arranged on the tread portion 3 on the central land portion 12 and on the outer side in the tire width direction by arranging four circumferential grooves 11a, 11b, 11c, and 11d. A first shoulder land portion 13 and a second shoulder land portion 14 that are provided, and a first intermediate land portion 15 and a second intermediate land portion 16 that are disposed between the land portions are defined. Further, by arranging a plurality of transverse grooves 5, the first shoulder land portion 13, the second shoulder land portion 14, the first intermediate land portion 15 and the second intermediate land portion 16 are each made up of a large number of block land portions 3. It is divided into. These block land portions 3 are provided with a plurality of first sipes 6 extending so as to intersect the tire circumferential direction. Further, as shown in the figure, the first shoulder land portion 13 is provided with a second sipe 7 extending in a direction intersecting the first sipe 6, and a sub-block land portion 8 is defined, and a plurality of small holes are formed therein. 9 is disposed.

  Further, the conventional tire having the tread pattern shown in FIG. 6 has basically the same configuration as the tire of the embodiment except that it does not have the sub-block land portion and the small hole.

Each of these prototype tires is a 205 / 65R15 passenger car radial tire, and has the following specifications.
Negative rate: 27.6% (Example), 27.4% (Conventional example)
Sipe 6 tire circumferential width: 0.4 mm
Groove width of tire circumferential groove 11c: 9.5 mm
Groove width of tire circumferential groove 11b: 3.0 mm
Tire circumferential groove 11a, 11d groove width: 5.5mm
Tire circumferential width of the first and second shoulder land portions: 31.0 mm
Width in the tire width direction of the first shoulder land: 37.0 mm
Width in the tire width direction of the second shoulder land: 31.0mm
Tire circumferential direction groove width of the lateral groove 5 of the first and second shoulder land portions: 6.0 mm

Moreover, the sub block land part of the tire of an Example becomes the following specification.
The circumferential width of the sub-block land area: 7.5mm
Sub-block land width in the tire width direction: 12.5mm
The gap between the sub-block land and the adjacent first sipe: 0.2 mm
Small holes: 8 on each sub-block land, diameter: 1.2 mm, depth: 7.0 mm

Each of these test tires is attached to a rim having a size of 15 × 6.5J to form a tire wheel. The tire is mounted on a test vehicle so that the first shoulder land portion 13 is on the outside of the vehicle. An additional load of 470 kN was applied and the following evaluations were made.
Feeling on snow: A professional driver comprehensively evaluated the braking performance, starting performance, straight running performance, and cornering performance when driving on a snowy road test course.
On-snow braking performance: The braking distance when full braking was performed from a speed of 40 km / h on a pressure snow road surface was measured and evaluated based on the measurement result.
Feeling on ice: A professional driver comprehensively evaluated the braking performance, startability, straightness, and cornering on an ice road test course.
Braking on ice: A braking distance was measured when full braking was performed at a speed of 20 km / h on an ice road surface, and the measurement result was evaluated.
Dry road handling: When driving on a dry road test course in various driving modes, handling was evaluated by a professional driver.
Wet road surface handling: Handling was evaluated by a professional driver when driving on a wet road test course in various driving modes.

  Table 1 shows the evaluation results of these tests. In addition, the evaluation result of Table 1 is shown by the index ratio when the tire evaluation result of a conventional example is set to 100, and performance is excellent, so that a numerical value is large.

  As shown in the results of Table 1, the tires of the examples had improved performance on snow, performance on ice, wet handling performance, and dry handling performance as compared to the conventional tire.

  As is clear from the above invention, by optimizing the shape of the block land portion, a pneumatic tire that achieves both on-ice performance and on-snow performance at a high level on the premise of maintaining the tire block rigidity. It became possible to provide.

It is a top view of a part of block land part row | line | column of the tread part of the typical tire according to this invention. It is a perspective view which extracts and shows one of the block land parts shown in FIG. It is a top view of the other typical block land part according to this invention. It is a top view of the other typical block land part according to this invention. FIG. 3 is a development view of a part of a tread portion of a tire according to an embodiment. FIG. 6 is a development view of a part of a tread portion of a conventional tire.

Explanation of symbols

1 tread portion 2 block land portion row 3 block land portion 4 circumferential groove 5 transverse groove 6 first sipe 7 second sipe 8 sub block land portion 9 small hole 10 corner portions 11a, 11b, 11c, 11d circumferential groove 12 central land portion 13 First shoulder land portion 14 Second shoulder land portion 15 First intermediate land portion 16 Second intermediate land portion

Claims (9)

By arranging a plurality of circumferential grooves extending substantially in the tire circumferential direction and a plurality of lateral grooves communicating with two adjacent circumferential grooves in the tread portion, at least one comprising a plurality of block land portions. In the pneumatic tire formed by partitioning the block land portion row of the row and arranging a plurality of first sipes extending across the tire circumferential direction in the block land portion,
A pair of second sipes extending in a direction intersecting with the first sipe are disposed in at least one of the block land portions, and the sub-block land portion virtually formed by an extension line of the first and second sipes is provided. A pneumatic tire comprising a plurality of small holes.   The pneumatic tire according to claim 1, wherein the sub-block land portion is located at a central portion of the block land portion.   The pneumatic tire according to claim 1 or 2, wherein an area of the sub-block land portion on the tread surface is 3 to 50% of an area of the block land portion including the sub-block land portion.   The pneumatic tire according to any one of claims 1 to 3, wherein the aperture of the small hole has a diameter of 0.3 to 3.0 mm. The eyelets are arranged in the sub-block land portion in 1-20 / cm ² interval, the pneumatic tire according to any one of claims 1-4.   The pneumatic tire according to any one of claims 1 to 5, wherein the sub-block land portion has a quadrangular shape on the tread portion tread surface.   The pneumatic tire according to claim 6, wherein the first sipe and the second sipe are separated from each other at at least one corner of the rectangular sub-block land portion.   The quadratic sub-block land portion has two acute angle portions and two obtuse angle portions, and the first sipe and the second sipe are separated from each other at least at the acute angle portion. The described pneumatic tire.   The pneumatic tire according to any one of claims 6 to 8, wherein a separation distance between the first sipe and the second sipe at the corner is 0.1 to 2.5 mm.

Images