JP5615680B2 - tire - Google Patents

Description

  The present invention relates to a tire, and more particularly to a pneumatic tire that is suitably used for heavy-duty vehicles such as trucks and buses.

  In recent years, noise has been taken up as a pollution problem caused by automobiles. Noise generated while the tire travels is generated mainly with air exhausted from a groove provided in the tread between the tire tread and the road surface.

  In particular, in a tire having a wide circumferential groove in the tread portion, air column resonance occurs in the groove of the circumferential groove, which contributes to further noise deterioration. Air column resonance means that the groove width suddenly fluctuates due to the action of external force at the stepping-in / kick-out part during rolling contact with the tire, and high-frequency vibration is generated in the groove wall (or land wall). It vibrates the air in the circumferential groove on the ground contact surface, that is, the air in the pipe, and aggravates the noise by the acoustic resonance action based on it.

  In order to prevent the deterioration of noise due to this air column resonance, a flexible groove fence or barrier that extends in the direction of blocking the air flow from the groove wall or groove bottom, especially in heavy duty tires for trucks and buses An object is provided at a predetermined interval in the circumferential direction. A conventional groove fence generally has a shape as shown in the cross-sectional views of FIGS. 7 (a) and 7 (b). The groove fence 101a shown in FIG. 7 (a) is usually provided in a groove disposed in a central portion near the center line among the circumferential grooves of the tire. On the other hand, in the circumferential groove disposed in the shoulder portion, in order to suppress the occurrence of cracks from the groove bottom, a shape in which the groove bottom portion is usually notched as shown in FIG. The groove fence 101b which has is provided. In the figure, the groove fence is provided only on one groove wall in the groove, but usually a pair of symmetrical groove fences are provided on both sides of the groove wall, By closing the space between the groove fences, the effect of blocking the above air column resonance can be obtained.

  Further, for example, Patent Document 1 provides a heavy duty pneumatic tire that reduces air column resonance that causes noise problems during traveling by the groove fence and that does not cause cracks in the groove fence due to traveling. In order to achieve this, the groove fence part is composed of at least two protrusions extending from the groove wall and / or the groove bottom, and the gap between the protrusions is 0.5 in the tire width direction at normal internal pressure. A technique is disclosed that has a deviation of 0.4 to 3.0 mm in the circumferential direction so that the projections do not come into contact with each other when being loaded.

  Further, Patent Document 2 discloses a groove fence that protrudes toward a stepped land portion provided at a groove bottom portion of a circumferential groove at a predetermined interval in the extending direction of the circumferential groove on at least one of both groove walls of the circumferential groove. And a pneumatic tire having a thin wall portion having a shape in which a groove bottom side portion of the circumferential groove is notched as viewed in a cross section orthogonal to the circumferential groove. Furthermore, Patent Document 3 includes a tread including a plurality of circumferential grooves extending in the circumferential direction and land portions partitioned by the circumferential grooves, and having a groove fence portion extending in a direction blocking the grooves in the circumferential grooves. The groove fence portion is made of at least two protrusions extending from the groove wall and / or the groove bottom, and these protrusions are placed in the circumferential groove without being grounded. There is disclosed a tire arranged so that there is no gap between protrusions when viewed from the circumferential direction.

JP-A-11-105511 (Claims etc.) JP 2008-174198 A (Claims etc.) JP 2010-52699 A (Claims etc.)

  As described above, the groove fence is arranged in the circumferential groove for the purpose of reducing noise. However, in the shoulder portion where the circumferential groove is opened and closed, there is a risk of occurrence of cracks from the groove bottom. In addition, a groove fence 101b having a shape in which a groove bottom portion is cut out is usually used. However, in the groove fence 101b having such a shape, since the groove bottom portion is opened, the shielding effect of the groove cross section is small, and the noise reduction effect is reduced.

  Accordingly, an object of the present invention is to solve the problems in the above-described conventional technology and suppress the occurrence of cracks in the groove fence accompanying traveling, while reducing the air column resonance of the circumferential groove that causes noise problems during traveling. The object is to provide a tire with improved effects.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by providing a pair of protrusions having specific shapes asymmetric to each other in the circumferential groove, and has completed the present invention.

That is, the tire according to the present invention includes at least one circumferential groove including a pair of groove walls, a groove bottom portion connecting the lower ends of the pair of groove walls, and a land portion divided by the circumferential grooves. In the circumferential groove, plate-like protrusions that protrude from the groove wall of the circumferential groove toward the opposite groove wall and are disposed in pairs between the groove walls on both sides of the circumferential groove are provided. In a tire having a tread having,
The pair of protrusions have an asymmetric shape with respect to each other;
One of the pair of protrusions does not extend to the other groove wall, and the lower end A of the edge of the one protrusion that intersects the one groove wall is more tire than the upper end of the groove bottom. Located radially outside, and
When the other of the pair of protrusions is seen in a cross-section in the width direction of the circumferential groove, at least the groove bottom portion of the circumferential groove is covered, and the tire at the groove bottom portion on the one groove wall side. It has an opening part that does not cover the circumferential groove on the outer side in the radial direction, and the upper end B of the edge of the other protrusion that intersects the one groove wall is on the outer side in the tire radial direction than the upper end of the groove bottom part. It is characterized by being located.

  In the tire of the present invention, it is preferable that an edge portion of the one projecting portion that intersects the one groove wall has a substantially arc shape. Moreover, it is preferable that the edge part which cross | intersects said one groove wall of said other protrusion part exhibits a substantially circular arc shape. Furthermore, the tire radial distance from the lower end of the groove bottom to the lower end A of the one protrusion is preferably 2 to 5 mm, and the tire from the lower end of the groove bottom to the upper end B of the other protrusion The radial distance is preferably 2 to 5 mm.

  Furthermore, in the present invention, it is preferable that the circumferential groove in the tire contact surface includes only one pair of the pair of protrusions. Furthermore, in the tire of the present invention, it is preferable that the pair of protrusions are close to each other in the tire width direction and the circumferential groove does not have a see-through portion when the tire contacts the ground. Furthermore, in the present invention, it is preferable that the pair of protrusions is provided in the circumferential groove disposed at least on the shoulder portion.

  According to the present invention, by arranging the pair of protrusions satisfying the above conditions in the circumferential groove, it causes a noise problem during traveling while suppressing the occurrence of cracks in the protrusions during traveling. It has become possible to realize a tire that further improves the effect of reducing air columnar resonance in the circumferential groove.

It is sectional drawing which shows an example of the shape of the projection part which concerns on the tire of this invention. It is an expanded view of the tread part which shows the tread pattern of an example of the tire of this invention. It is sectional drawing which shows an example of the arrangement | positioning state of a pair of projection part which concerns on the tire of this invention. FIG. 6 is a partial development view of a tread surface portion showing an arrangement state of a pair of protrusions according to a tire of Comparative Example 2. 10 is a partial development view of a tread surface portion showing an arrangement state of a pair of protrusions according to a tire of Comparative Example 3. FIG. It is a partial expanded view of the tread part which shows the arrangement state of a pair of projection parts concerning the tire of an example. (A), (b) is sectional drawing which shows the shape of the conventional groove fence.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIGS. 1A and 1B are cross-sectional views showing an example of the shape of the protrusions according to the tire of the present invention. Moreover, in FIG. 2, the expanded view of the tread part which shows the tread pattern of an example of the tire of this invention is shown.

  As shown in FIG. 2, the tire of the present invention has one or more, in the illustrated example, four circumferential grooves 11a to 11d, and land portions 12a, 12b, 13a, which are divided by the circumferential grooves 11a to 11d. 13b and 14 are provided. Note that FIG. 2 shows an example of a tread pattern in the tire of the present invention, and therefore the description of the details of the pattern is omitted.

  As shown in FIG. 1, the circumferential groove 11 includes a pair of groove walls 11A and 11B and a groove bottom portion 11C that connects the lower ends of the pair of groove walls 11A and 11B. In the tread of the tire of the present invention, the circumferential groove 11 is provided so as to project from the groove walls 11A and 11B to the opposite groove walls 11B and 11A, and between the groove walls 11A and 11B on both sides of the circumferential groove. Plate-like protrusions 1A and 1B arranged in a pair are provided. As shown in the figure, the pair of protrusions 1A and 1B have asymmetric shapes.

  As shown in the figure, in the present invention, one protrusion 1A of the pair of protrusions does not extend to the other groove wall 11B, and the one protrusion wall 1A has one groove wall 11A. The lower end A of the intersecting edge portion is located on the outer side in the tire radial direction from the upper end of the groove bottom portion 11C. In addition, the protrusion 1B, which is the other of the pair of protrusions, covers at least the groove bottom 11C of the circumferential groove 11 when viewed in the cross-section in the width direction of the circumferential groove 11, and is on the one groove wall 11A side. Thus, the opening portion 2 that does not cover the circumferential groove 11 is provided on the outer side in the tire radial direction of the groove bottom portion 11C, and the upper end B of the edge portion of the protrusion 1B that intersects one groove wall 11A is the groove bottom portion 11C. It is located on the outer side in the tire radial direction from the upper end of the tire.

  As described above, one of the projecting portions 1A and 1B arranged asymmetrically has a shape in which a portion corresponding to the groove bottom portion 11C is cut out, and the other has a shape that covers the groove bottom portion 11C. The groove bottom portion that is likely to occur in the conventional shape as shown in FIG. 7A because the edge portions of the protrusions 1A and 1B do not exist in the groove bottom portion 11C of the circumferential groove 11. It is possible to prevent the occurrence of cracks from the end X of the groove fence 101a existing in the area. Moreover, since only one protrusion 11B of the pair of protrusions covers the groove bottom 11C, the opening and closing of the circumferential groove is not suppressed at the time of tire rolling. can get. In particular, by making the upper end B of the edge portion of the projection 11B covering the groove bottom portion 11C intersecting one groove wall 11A as far as possible in the tire radial direction, the opening and closing of the circumferential groove 11 is further suppressed. preferable.

  Furthermore, since the protrusion 1B has a shape covering the groove bottom portion 11C, the groove shielding effect can be sufficiently obtained and noise reduction can be further expected as compared with the case where both sides are notched corresponding to the groove bottom portion. Here, it is conceivable that both of the pair of protrusions have a shape covering the groove bottom, but in this case as well, a sufficient shielding effect can be obtained and effective in avoiding cracks in the protrusion. However, the rigidity of the bottom of the groove is increased, and the opening and closing of the groove at that portion is restricted, and stones are trapped and difficult to come out, which is disadvantageous in terms of stone-resistance. Moreover, since the movement of the adjacent land part is also restricted, it is considered disadvantageous with respect to uneven wear resistance. In the present invention, by combining the pair of protrusions with a shape that cuts out the portion corresponding to the groove bottom and a shape that covers the groove bottom, not only is it effective for avoiding cracking of the protrusion, While securing stone biting resistance and uneven wear resistance, a groove shielding effect can be sufficiently obtained, and a noise reduction effect can be further improved.

  Here, in the present invention, the groove bottom portion 11C refers to, for example, a portion having a substantially circular arc cross section that connects the lower ends of a pair of groove walls 11A and 11B having a linear cross section in the illustrated circumferential groove 11. In addition, the straight line shape means a substantially straight line shape within an allowable range for manufacturing, and the substantially arc shape means a shape in which the cross-sectional shape of the groove bottom part is a single arc or a plurality of arcs. It means that.

  In the present invention, with respect to one or more circumferential grooves 11, only the point at which the pair of protrusions 1A and 1B are arranged according to the above conditions is important, and other points can be appropriately set according to a conventional method. There is no particular limitation.

  The specific shape of the protrusion according to the present invention is not particularly limited as long as the above conditions are satisfied, but it is important to block the flow of air in the circumferential groove at the time of ground contact. For example, as shown in the figure, in the cross section of the circumferential groove 11, the angle α formed on the inner side in the tire radial direction between the protrusion 1 </ b> A and the groove wall 11 </ b> A at the lower end A of the protrusion 1 </ b> A is preferably an obtuse angle. Here, the angle α is substantially an angle formed between the tangent L1 of the lower edge of the protrusion 1A at the lower end A of the protrusion 1A and the groove wall 11A as shown in the figure. Thereby, generation | occurrence | production of the crack in the lower end A can be suppressed more effectively. Similarly, the angle β formed on the outer side in the tire radial direction between the protrusion 1B and the groove wall 11A at the upper end B of the protrusion 1B is preferably an obtuse angle. Here, the angle B is substantially an angle formed by the tangent L2 of the upper edge of the protrusion 1B at the upper end B of the protrusion 1B and the groove wall 11A as shown in the figure. Thereby, generation | occurrence | production of the crack in the upper end B can be suppressed more effectively. These angles α and β can be set to 120 ° to 180 °, for example.

  Further, as shown in the figure, the edge of the protrusion 1A that intersects the groove wall 11A preferably has a substantially arc shape, and the edge of the protrusion 1B that intersects the groove wall 11A also exhibits a substantially arc shape. It is preferable. Also by this, the effect of suppressing the occurrence of cracks can be improved. Here, the substantially arc shape has the same meaning as described above. Therefore, in the present invention, by using the protrusions 1A and 1B having the shapes as shown in FIG. 1, the strain concentration at the lower end A and the upper end B of the protrusion is more effectively suppressed, and cracks are more effectively cracked. Can be avoided.

  In the present invention, the distance in the tire radial direction from the lower end of the groove bottom 11C to the lower end A of the protrusion 11A is preferably 2 to 5 mm. If this distance is too small, the lower end A of the protrusion 11A approaches the groove bottom, so that there is a greater concern that cracks will occur at the lower end A. If it is too large, there is a concern that the rigidity of the protrusion will decrease and cracks will occur. Since it becomes large, neither is preferable. Further, the distance in the tire radial direction from the lower end of the groove bottom portion 11C to the upper end B of the projection portion 11B is preferably 2 to 5 mm. If this distance is too small, there is a greater concern that cracks will occur at the upper end B. If it is too large, opening and closing of the circumferential groove is suppressed, which is disadvantageous for stone biting resistance and uneven wear resistance, both of which are not preferable. .

  Note that, as described above, in particular, the circumferential groove located in the shoulder portion has a large distortion at the bottom of the groove and a large risk of cracking. Therefore, the pair of protrusions 1A and 1B according to the present invention is disposed at least on the shoulder portion. It is preferable to provide in the circumferential groove. In this case, a pair of protrusions according to the present invention may be used in combination with a conventional groove fence or the like. Moreover, a pair of projection part which concerns on this invention can also be arrange | positioned in all the circumferential grooves.

  Further, in the present invention, it is preferable that the circumferential groove 11 in the ground contact surface formed during tire traveling always includes only one pair of protrusions. The pair of protrusions 1A and 1B can be arranged, for example, in the shape shown in the cross-sectional view of FIG. As illustrated, the pair of protrusions 1A and 1B can be formed such that the opening of the protrusion 1B and the outer shape of the protrusion 1A itself have substantially the same shape. In this way, a pair of protrusions are arranged close to each other in the tire circumferential direction, and a plurality of pairs of protrusions are not included for each circumferential groove in the ground contact surface during tire rolling. Generation of a pumping sound when the compressed air is ejected can be avoided. In this case, the water flow in the circumferential groove is not substantially hindered when traveling on a wet road surface.

  Furthermore, in the present invention, it is preferable that the pair of protrusions be close to each other in the tire width direction and the circumferential groove does not have a see-through portion when the tire contacts the ground. That is, when the shape of the pair of protrusions is appropriately set and the circumferential groove is closed in the ground contact surface when the tire is in contact with the ground, the see-through portion is eliminated in the circumferential groove when viewed in the tire width direction cross section. By doing, the effect which suppresses air column resonance can be acquired.

  Further, in the present invention, the arrangement angle of the protrusion with respect to the circumferential groove is set, for example, in a range where the angle formed by the protrusion and the groove wall of the circumferential groove is 20 to 90 °, particularly 20 to 85 °. can do. If the disposition angle of the protrusion with respect to the groove wall is too small, it is not preferable because breakage tends to occur during traveling. Usually, the protrusion is provided in a direction forming 90 ° with respect to the groove wall of the circumferential groove. Furthermore, in the present invention, the offset amount between the pair of protrusions can be set such that the distance between the protrusions is 0.5 mm to 20 mm.

  Furthermore, in the present invention, it is preferable that the protrusions are provided with a phase difference in the tire circumferential direction between the circumferential grooves. When the protrusions are provided with a phase difference, noise peaks between the circumferential grooves are dispersed, that is, the noise frequency band can be shifted. Further, when the pair of protrusions are arranged close to each other in the tire circumferential direction, it is possible to obtain a higher air vibration propagation suppression effect in the groove.

  Furthermore, it is preferable that the maximum height of the protrusion is 70% or more and less than 100% of the circumferential groove depth. Air column resonance occurs when high-frequency vibration of the circumferential groove wall (or land wall) during tire rolling propagates to the air in the circumferential groove. For this reason, if the maximum height of the protrusion is 100% of the circumferential groove depth, the vibration of the circumferential groove wall (or land wall) propagates to the protrusion, Since the air is vibrated, a sufficient noise suppression effect cannot be obtained, and it is difficult to ensure sufficient circulation of water in the circumferential groove, which may impair wet skid resistance. On the other hand, if the maximum height of the protrusion is less than 70% of the circumferential groove depth, the effect of preventing the deterioration of noise due to air column resonance may not be sufficiently obtained.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Comparative Example 1>
At tire size 275 / 80R22.5, as shown in FIG. 2, four circumferential grooves 11a-11d extending in a zigzag shape in the tire circumferential direction, and a land portion 12a divided by these circumferential grooves 11a-11d , 12b, 13a, 13b and 14 were produced as tires of Comparative Example 1 having a tread.

<Comparative example 2>
As shown in the enlarged view of FIG. 4, the pair of protrusions are formed in the circumferential grooves 11b and 11c in the tire central portion in the shape shown in FIG. 7A, respectively, and in the circumferential grooves 11a and 11d in the tire shoulder portion. The shape shown in FIG. 7 (b) is the shape shown in FIG. 7 (b), with each circumferential groove in the ground contact surface at the time of traveling having a circumferential interval in which only one pair of protrusions is always included substantially at one place with respect to the groove wall of the circumferential groove. A tire of Comparative Example 2 was produced in the same manner as Comparative Example 1 except that it was provided in the vertical direction.

<Comparative Example 3>
As shown in the enlarged view of FIG. 5, the pair of protrusions arranged in the circumferential grooves 11a and 11d of the tire shoulder portion are the same as in Comparative Example 2 except that the shape shown in FIG. A tire of Comparative Example 3 was produced.

<Example>
As shown in the enlarged view of FIG. 6, the pair of protrusions disposed in the circumferential grooves 11 a and 11 d of the tire shoulder portion are asymmetrical shapes composed of combinations of the shapes shown in FIGS. 1 (a) and (b). Example tires were produced in the same manner as in Comparative Example 2 except for the above. As shown in FIG. 1, the protrusion 1A of the pair of protrusions does not extend to the groove wall 11B, and the lower end A of the edge of the protrusion 1A that intersects the groove wall 11A is higher than the upper end of the groove bottom 11C. Also had a shape located on the outer side in the tire radial direction. Further, the protrusion 1B covers the groove bottom 11C of the circumferential groove when viewed in the cross section in the width direction of the circumferential groove, and covers the circumferential groove on the groove wall 11A side on the outer side in the tire radial direction of the groove bottom. The upper end B of the edge portion of the protrusion 1B intersecting the groove wall 11A is located outside the upper end of the groove bottom portion 11C in the tire radial direction. Further, in the cross section of the circumferential groove, the edge of the protrusion 1A that intersects the groove wall 11A and the edge of the protrusion 1B that intersects the groove wall 11A all had a substantially arc shape. Further, the distance in the tire radial direction from the lower end of the groove bottom 11C to the lower end A of the protrusion 1A is 3.2 mm, and the distance in the tire radial direction from the lower end 11C of the groove bottom to the upper end B of the protrusion 1B is 3.7 mm. there were. In the tire of this example, at the time of tire contact, the pair of protrusions are close to each other in the tire width direction, and the circumferential groove has no see-through portion.

<Indoor noise test>
About each obtained tire, the noise evaluation test of 1/3 octave (dBA) was done on condition of 30.89 kN (7.50 rim, 900 kPa) and speed 60 km / h under normal temperature. The result was expressed as an index with the air column resonance frequency band value of Comparative Example 2 as 100. It shows that a noise level is so large that a numerical value is large. The results are shown in the table below.

<Crack resistance test>
Each of the obtained test tires was subjected to a crack resistance test (drum test) under normal temperature conditions of 30.89 kN (7.50 rim, 900 kPa) and a speed of 60 km / h. The results were obtained by confirming the presence or absence of cracks and the crack level in each test tire when running 100,000 km on the Long Grand Ram. A case where no crack was generated was indicated by ◯, a case where the crack was less than 2 mm was indicated by Δ, and a case where the crack was 2 mm or more was indicated by ×. The results are shown in the table below.

<Evaluation of stone biting resistance (stone separation)>
Each test tire obtained was assembled on a rim of size 7.50 × 22.5, filled with an internal pressure of 900 KPa, and loaded on the vehicle under a load equivalent to the maximum load specified in JATMA. The test course was run with stones fitted into the pair of protrusions. As the vehicle, 2-D · 4 was used, and each test tire was mounted on all wheels. The running distance was 25 km. After running, the number of stones remaining was expressed as a ratio to the number of stones fitted. The smaller this ratio, the better the stone-releasability and the better. The results are shown in the table below.

  As shown in the above table, in the test tires of the examples, by improving the groove shielding effect by the protrusions, the air column resonance can be reduced, and the stone biting resistance is deteriorated and cracks are reduced. It was confirmed that the noise level was reduced without any occurrence.

1A, 1B Projection part 2 Opening part 11A, 11B Groove wall 11C Groove bottom part 11, 11a-11d Circumferential groove 12a, 12b, 13a, 13b, 14 Land part 101a, 101b Groove fence A Lower end B Upper end L1, L2 Tangent

Claims (8)

Including at least one circumferential groove formed of a pair of groove walls and a groove bottom portion connecting the lower ends of the pair of groove walls, and a land portion partitioned by the circumferential groove, and in the circumferential groove, In a tire provided with a tread having a plate-like protrusion that is provided so as to protrude from the groove wall of the circumferential groove toward the opposite groove wall and is disposed between the groove walls on both sides of the circumferential groove,
The pair of protrusions have an asymmetric shape with respect to each other;
One of the pair of protrusions does not extend to the other groove wall, and the lower end A of the edge of the one protrusion that intersects the one groove wall is more tire than the upper end of the groove bottom. Located radially outside, and
When the other of the pair of protrusions is seen in a cross-section in the width direction of the circumferential groove, at least the groove bottom portion of the circumferential groove is covered, and the tire at the groove bottom portion on the one groove wall side. It has an opening part that does not cover the circumferential groove on the outer side in the radial direction, and the upper end B of the edge of the other protrusion that intersects the one groove wall is on the outer side in the tire radial direction than the upper end of the groove bottom part. A tire characterized by being located.   2. The tire according to claim 1, wherein an edge portion of the one projecting portion that intersects the one groove wall has a substantially arc shape.   The tire according to claim 1 or 2, wherein an edge portion of the other projection portion that intersects the one groove wall has a substantially arc shape.   The tire according to any one of claims 1 to 3, wherein a distance in a tire radial direction from a lower end of the groove bottom to a lower end A of the one protrusion is 2 to 5 mm.   The tire according to any one of claims 1 to 4, wherein a distance in a tire radial direction from a lower end of the groove bottom portion to an upper end B of the other projection portion is 2 to 5 mm.   The tire according to any one of claims 1 to 5, wherein the circumferential groove in the tire contact surface includes only one pair of the pair of protrusions.   The tire according to any one of claims 1 to 6, wherein the pair of protrusions are close to each other in the tire width direction when the tire contacts the ground, and the circumferential groove does not have a see-through portion.   The tire according to any one of claims 1 to 7, wherein the pair of protrusions is provided in the circumferential groove disposed at least on a shoulder portion.

Images