JP2006007796A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in on-ice performance without impairing traveling performance on a dry road surface by optimizing a compressive rigidity distribution within small land parts. <P>SOLUTION: In this tire, many block land parts 2 are divided and formed in a tread part 1, a plurality of sipes 3 for smaller sections are disposed in the block land parts 2, and thereby the block land parts 2 are sub-divided into the plurality of small land parts 4. At least one small land part 4 of the small land parts 4 has a plurality of small holes 5 in the section width center region c. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  According to the present invention, a plurality of block land portions are defined in the tread portion, and a plurality of sipes that are further subdivided are disposed on the block land portion, whereby the block land portions are divided into a plurality of small land portions. With respect to a pneumatic tire that is subdivided into parts, the performance on ice is improved without impairing the running performance on the dry road surface of such a tire.

  In conventional winter tires, a sipe extending in the direction crossing the tire equatorial plane is arranged on the block land section formed in the tread section in order to improve acceleration performance at the start on ice and braking performance at stoppage. Has been done. Increasing the number of sipe arrangements increases the so-called edge effect, which is the effect of the edge of the block land scratching the road surface, and the so-called drainage effect, which is the effect of sipe sucking up the water film present on the ice road surface. Increases performance on ice. However, the increase in the number of sipes disposed at the same time lowers the block rigidity and reduces the contact area on the ice, so the frictional force between the tire and the icy road surface (hereinafter referred to as “surface frictional force”) decreases. . And if the amount of decrease in surface friction force exceeds the amount of increase in edge effect and drainage effect, the effect of improving the performance on ice is lost. For this reason, there has been a limit to improving the performance on ice by arranging the sipes.

  For such problems, attempts have been made to improve the drainage effect by improving the tread rubber. For example, tires in which the tread portion is formed of a foamed rubber layer have been proposed (see Patent Documents 1 to 3). Such a tire improves the drainage effect by incorporating a water film on the road surface into many bubbles present in the foamed rubber layer. However, these tires improve the performance on ice along with the improvement of drainage performance in the temperature range near 0 ° C where water film is likely to occur, but the performance on ice is low in the low temperature region below 0 ° C where water film is difficult to occur. It cannot be improved as much as expected.

  In addition, improvement of the shape of the sipe that can suppress the reduction of the contact area and secure the surface friction force even when the number of sipe arrangements is increased has been studied. For example, there is an inclined portion in the middle part in the depth direction. A so-called three-dimensional sipe formed has been developed (see Patent Document 4). However, even when such a three-dimensional sipe is adopted, it is necessary to increase the number of sipe arrangements in order to improve the performance on ice, and the rigidity of the block land portion decreases due to the increase in the number of sipe arrangements. Since this is unavoidable, handling performance and wear performance on dry road surfaces are reduced.

JP-A-63-90403 JP-A 1-1118542 JP 7-242104 A JP 2000-6618 A

  Accordingly, an object of the present invention is to provide a pneumatic tire with improved performance on ice without impairing running performance on a dry road surface by optimizing the compression rigidity distribution in the small land.

  In order to achieve the above-described object, the present invention is configured such that a plurality of block land portions are defined in the tread portion, and a plurality of sipes that are further subdivided are disposed on the block land portion. In a pneumatic tire obtained by subdividing a land portion into a plurality of small land portions, at least one of the small land portions has a plurality of small holes in a central region of the section width. is there.

  Further, the section width central region is preferably an area of ± 20% of the section width of the small land portion measured along the section width direction from the center position of the section width of the small land portion.

  Further, it is preferable that the small holes are aligned on an imaginary line connecting the center positions of the section widths of the small land portions.

  In addition, the small holes are preferably aligned on at least two imaginary lines parallel to the imaginary line connecting the center positions of the section widths of the small land portions. However, it is more preferable that they are the same.

  In addition, it is preferable that the small holes are arranged at equal intervals on the same imaginary line.

  Moreover, it is preferable that the small hole has a helical spiral shape extending in the tire radial direction.

  Further, when the tread portion is divided into a tire width direction central region and both tire width direction side regions, the sipe is a lateral sipe extending substantially in the tire width direction in the block land portion of the tire width direction central region, and the tire width A longitudinal sipe extending substantially in the tire circumferential direction is preferable in the block land portion in the direction side area. Here, “substantially tire width direction” means a direction of ± 5 ° centered on the tire width direction, and “substantially tire circumferential direction” means a direction of ± 5 ° centered on the tire circumferential direction. .

  According to the present invention, by optimizing the compression rigidity distribution in the small land portion, a pneumatic tire having improved on-ice performance without increasing the number of sipe arrangements and thereby reducing the block rigidity of the tire. It became possible to provide.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a part of a tread portion of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 2 shows a block land portion of the tread portion shown in FIG. It is a perspective view when it sees.

  In the tire shown in FIG. 1, a block land portion 2 is formed by partitioning a plurality of block land portions 2 in the tread portion 1 and arranging a plurality of sipes 3 further subdivided in the block land portion 2. Is divided into a plurality of small land portions 4.

  The main feature of the structure of the present invention is that at least one of the small land portions 4 (all five in FIGS. 1 and 2) has a plurality (6 in FIGS. 1 and 2) in the central region c of the section width. ) Has a small hole 5.

  The small land portion 4 has a section width direction y as a direction perpendicular to the extending direction x of the sipe 3 forming the section, a section width w as a length measured along the section width direction y, and a section width. A region having a predetermined width including the center position M of w is referred to as a section width central region c.

  Next, the operation of the present invention will be described with reference to FIG. 6 showing an example of deformation and contact pressure distribution during rolling with the block land portion of the conventional tire and the block land portion of the tire of the present invention.

  When the conventional tire rolls on the icy road surface, as shown in FIG. 6A, the small land portion 101 falls down toward the stepping-in side In, so that the edge portion 102 of the kicking-out Out The ground pressure (hereinafter referred to as “edge pressure”) increases. The edge effect is generated by the edge portion 102 scratching the ice surface according to the edge pressure. Therefore, in order to improve the edge effect, it is considered that the edge pressure of the small land portion 101 should be increased. Here, when the tire load and the internal pressure condition are the same, it is known that the average contact pressure in the tread contact area is substantially equal. For this reason, in order to increase the edge pressure, the ground pressure in the central region of the section width of the small land portion 101 is lowered, and an uneven ground pressure distribution is generated in the small land portion 101, so that the edge pressure is relatively increased. It is considered to be effective. Further, the ground contact pressure of the block land portion 100 depends on the compression stiffness, and the portion with high compression stiffness has high ground pressure, and the portion with low compression stiffness has low ground pressure. Therefore, the edge pressure can be increased by reducing the compression rigidity of the section width center region c of the small land portion 101.

  In the present invention, as shown in FIG. 6 (b), a plurality of small holes 5 are provided in the section width central region c of the small land portion 4 in order to reduce the compression rigidity of the section width central region c of the small land portion 4. Yes. Thereby, the compression rigidity in the edge part 6 can be increased, reducing only the compression rigidity of the division width center area | region c of the small land part 4. FIG. Compared with the sipe 3, the small hole 5 can minimize the influence on the bending rigidity of the small land portion 4 in the falling direction, and therefore can prevent a reduction in the ground contact area due to excessive falling deformation. Moreover, since the small hole 5 sucks up the water film in the contact area, the drainage effect can be improved. In this way, the block land portion 2 of the tire of the present invention increases the edge pressure to enhance the edge effect, suppress the reduction of the contact area, and enhance the drainage effect. As a result, compared to the conventional tire The performance on ice can be remarkably improved.

  As shown in FIG. 2, the section width central region c is measured along the section width direction from the center position M of the section width w of the small land portion 4 and is ± 20% of the section width w of the small land section 4. A region is preferred. This is because if the small hole 5 is disposed outside this region, the compression rigidity of the edge portion 6 of the small land portion 4 is lowered, so that a sufficient increase in the edge effect may not be obtained. A more preferable range is an area of ± 10% of the section width w of the small land portion 4.

  Furthermore, since the depth of the small hole 5 affects the effect of taking in the water film and the compression rigidity of the small land portion 4, it is preferably set to 50 to 100% of the depth of the sipe 3. When this depth is less than 50%, the small hole volume is small, and it is difficult to obtain the expected effect of taking up the water film. This is because the expected performance cannot be maintained. If it exceeds 100%, the effect of taking up the water film is sufficient, but the running performance on dry and wet roads decreases due to the decrease in compression rigidity. The water taken into the small hole in the contact area is difficult to completely drain out of the small hole outside the contact area due to the centrifugal force at the time of rolling. This is because the performance on ice decreases in any case.

  Further, the small holes 5 are preferably aligned on the virtual line I connecting the section width center positions M of the small land portions 4. Thus, by arranging the small hole 5 on the imaginary line I connecting the section width center position M, the portion where the compression rigidity is reduced can be limited to the section width central region c of the small land portion 4. This is because the compression rigidity in the vicinity of the edge portion 6 can be secured and the edge effect can be improved.

Alternatively, as shown in FIG. 3, the small hole 5 has at least two imaginary lines parallel to the imaginary line I connecting the section width center positions M of the small land portions 4, and in FIG. 3, two imaginary lines L1 and L2 It is preferable to line up. In this way, by arranging the small holes 5 in alignment on two or more imaginary lines, the portion where the compression rigidity is reduced can be limited to the section width central region c of the small land portion 4, and the small hole diameter This is because the compression rigidity can be reduced by the small holes 5 and the effect of sucking up the water film in the contact area can be increased, and the edge effect and the drainage effect can be improved. Here, the reason why the small hole diameter is not increased is that when the small hole diameter is increased, the bending rigidity in the direction in which the small land portion 4 falls down during rolling is greatly decreased, and the contact area may be decreased. In this case, in the same small land portion, the alignment position of the small holes 5 is the same in any of the virtual lines L1, L2, that is, the small holes 5 are aligned even when viewed in the section width direction y. preferable. By aligning the small holes 5 also in the section width direction y, when the small land portion 4 is viewed in the section width direction at the time of rolling, the portion where the small holes 5 exist can be minimized, and due to excessive collapse deformation This is because the reduction of the contact area can be prevented more effectively. That is, since the portion where the small hole 5 does not exist mainly bears the bending rigidity in the section width direction, the effect of the small hole 5 being arranged to increase this portion has an influence on the bending rigidity in the direction in which the small land portion 4 falls. This is because the reduction of the ground contact area due to excessive collapse deformation can be more effectively prevented.
The number of imaginary lines is preferably 3 or less, more preferably 2.

  Furthermore, it is preferable to arrange the small holes 5 at equal intervals on the same virtual line. As a result, the ground pressure is uniformly distributed in the extending direction x of the sipe 3, so that local wear of the edge portion 6 can be prevented. More preferably, the arrangement interval of the small holes 5 is set to 3 to 6 mm.

  FIG. 4 is a perspective view of a block land portion of another tire according to the present invention. As shown in FIG. 4, the small hole 5 preferably has a helical spiral shape extending in the tire radial direction. When the extension shape of the small hole 5 is a spiral spiral shape, the volume of the small hole per the same diameter and the same extension distance is larger than when it is linear, so the water film in the contact area is more efficiently formed. This is because the drainage can be further improved as a result of being sucked up.

  The extending direction of the sipe 3 disposed in the small land portion 4 is not particularly limited, and the direction of deformation applied to the block land portion 2 during traveling at an arbitrary angle in the range of 0 to 90 ° with respect to the tire equator plane E. Can be determined in consideration of For example, as shown in FIG. 5, when the tread portion 1 is divided into a tire width direction central region 7 and both tire width direction side regions 8, 8 ′, the collapse deformation in the circumferential direction of the tire becomes dominant. A lateral sipe 9 extending substantially in the tire width direction is disposed in the block land portion 2 in the tire width direction central region 7, and the tire width direction side regions 8, 8 ′ in which the deformation in the tire width direction is dominant. The block land portion 2 is preferably provided with a vertical sipe 10 extending substantially in the tire circumferential direction. By adopting such a sipe arrangement pattern, the block land portion 2 in the center region 7 in the tire width direction exhibits driving and braking on the icy road surface, and the block land in the tire width direction side regions 8 and 8 '. In part 2, it is possible to share the role for each block so that cornering performance on the icy road surface is exhibited. As a result, it becomes possible to achieve both driving / braking performance and cornering performance on the icy road surface at a high level. Because.

  In addition, the place mentioned above only showed a part of embodiment of this invention, and can add a various change in a claim. For example, FIGS. 1 to 5 show an example in which the shape of the block land portion is a rectangle when the tread portion is viewed in plan, but the shape of the block land portion is a rhombus, hexagon, octagon, circle, oval The shape of various block land portions used in conventional tires, such as a substantially U shape, can be used.

Moreover, it is preferable that the small hole 5 makes the opening area in the surface of the block land part 2 into the range of 0.2-10 mm < ² >. If the opening area is less than 0.2 mm ² takes effect and edge effect of the water film is not sufficiently exhibited, is because the improvement of on-ice performance may be insufficient, when it exceeds 10 mm ² This is because the actual ground contact area of the small land portion 4 is reduced, and the improvement on the ice performance may be insufficient. A more preferable range is 0.7 to ⁵ mm ² .

  Next, a pneumatic tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

  The tires of Examples 1 to 3 are radial tires for passenger cars having a tire size of 195 / 65R15, and the shapes shown in FIGS. 2 (Example 1), 3 (Example 2), and 4 (Example 3), respectively. These block land portions are arranged as shown in FIG. This block land portion has a tire circumferential direction length of 40 mm, a tire width direction length of 30 mm, and a height of 9 mm, and four sipes having a depth of 7.5 mm extending along the tire width direction are arranged at intervals of 8 mm. Set up. In each of the small land portions of the tires of Examples 1 and 3, six small holes having a diameter of 1 mm and a depth of 6 mm were arranged at equal intervals on a virtual line connecting the center positions of the section widths. A small hole having a diameter of 1 mm and a depth of 6 mm is formed in each small land portion of the tire of Example 2 in parallel with an imaginary line connecting the section width center positions and 2 mm across the imaginary line connecting the section width center positions. Six pieces were arranged at equal intervals on two spaced apart virtual lines.

  For comparison, a conventional tire having a block land portion having the same shape as that of the tires of Examples 1 to 3 except that the tire size is the same as that of Examples 1 to 3 and no small holes are provided.

  Each of the test tires was attached to a rim of size 6JJ to form a tire wheel. The tire wheels were mounted on a test vehicle, and the following tests were performed by applying air pressure: 200 kPa (relative pressure) and tire load load: 4.0 kPa.

(Performance on ice)
An acceleration test, a deceleration test, and a feeling test were performed on the icy road surface. In the acceleration test, the average acceleration index calculated from the initial speed, the final speed and the acceleration time is measured by measuring the time (acceleration time) to reach the final speed of 45 km / h when the accelerator is fully opened from the running state of the initial speed of 10 km / h. Was evaluated. Further, in the deceleration test, sudden braking was performed from the initial speed of 40 km / h, the braking distance until the stationary state was reached was measured, and the average deceleration index calculated from the initial speed and the braking distance was evaluated. Furthermore, in the feeling test, professional drivers comprehensively evaluated the driving performance when driving on an ice road test course. Table 1 shows the evaluation results of the acceleration test, deceleration test and feeling test.

(Dry performance)
Regarding dry performance, professional drivers comprehensively evaluated the driving performance when driving on a dry road test course. The evaluation results are shown in Table 1.

  In addition, all the evaluation results in Table 1 are shown as index ratios when the evaluation result of the conventional example is set to 100, and the performance of these evaluation results is better as the numerical value is larger.

  From the evaluation results shown in Table 1, all of the tires of Examples 1 to 3 are superior in driving performance on ice road surfaces while having the same driving performance on dry road surfaces as compared to conventional tires. I understand.

  According to the present invention, it is possible to provide a pneumatic tire with improved performance on ice without impairing the running performance on the dry road surface by optimizing the compression rigidity distribution in the small land portion. .

1 is a development view of a part of a tread portion of a typical pneumatic tire according to the present invention. It is a perspective view of the block land part of the tread part shown in FIG. 1, and shows in the state which saw through the small hole. It is a perspective view of the block land part of the other pneumatic tire according to this invention, and shows the state which looked through the small hole. It is a perspective view of the block land part of the other pneumatic tire according to this invention, and shows the state which looked through the small hole. FIG. 6 is a development view of a part of a tread portion of another pneumatic tire according to the present invention. It is a figure for demonstrating the improvement of the edge effect by arrangement | positioning of a small hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Block land part 3 Sipe 4 Small land part 5 Small hole 6 Edge part of a small land part 7 Tire width direction center area 8, 8 'Tire width direction side area 9 Horizontal sipe 10 Vertical sipe

Claims (8)

The block land portion is divided into a plurality of small land portions by forming a plurality of block land portions in the tread portion and arranging a plurality of sipes to be further subdivided in the block land portion. In the pneumatic tire
The pneumatic tire according to claim 1, wherein at least one of the small land portions has a plurality of small holes in a central region of the section width.   2. The pneumatic tire according to claim 1, wherein the section width central region is an area that is ± 20% of the section width of the small land portion as measured along the section width direction from the position of the section width center of the small land portion. .   The pneumatic tire according to claim 1 or 2, wherein the small holes are aligned on an imaginary line connecting the center positions of the section widths of the small land portions.   3. The pneumatic tire according to claim 1, wherein the small holes are aligned on at least two imaginary lines parallel to an imaginary line connecting the section width center positions of the small land portions.   The pneumatic tire according to claim 4, wherein the alignment positions of the small holes are the same in any virtual line in the same small land portion.   The pneumatic tire according to any one of claims 3 to 5, wherein small holes are arranged at equal intervals on the same imaginary line.   The pneumatic tire according to any one of claims 1 to 6, wherein the small hole has a spiral spiral shape extending in the tire radial direction.   When the tread portion is divided into a tire width direction central region and both tire width direction side regions, the sipe is a lateral sipe extending substantially in the tire width direction in the block land portion of the tire width direction central region, and the tire width direction The pneumatic tire according to any one of claims 1 to 7, which is a longitudinal sipe extending substantially in the tire circumferential direction in the block land portion in the lateral region.

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