JP5545742B2 - 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. As a conventional groove fence, one having a shape as shown in the cross-sectional views of FIGS. 6A and 6B is generally used, and the groove fence 101a is usually closer to the center line in the circumferential groove of the tire. The groove fence 101b is usually provided in the groove disposed in the shoulder portion, and the groove fence 101b is provided in the groove disposed in the shoulder portion. In the figure, the groove fence is provided only on one of the groove walls in the groove, but normally, a pair of groove fences are provided on the groove walls on both sides, and the space between the pair of groove fences during load traveling. By closing, 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.)

  However, in the conventional groove fence, when the circumferential groove is closed at the time of ground contact, strain is concentrated on the edge portion X (the circled portion in FIG. 6A) that contacts the groove bottom of the groove fence X. Then, there is a possibility that a crack may occur from the end of this edge, that is, the root of the groove fence. Further, in the shoulder portion where the circumferential groove is largely closed, the groove fence 101b having the shape shown in FIG. 6B is usually used in order to avoid the above-described cracking. In this case, the groove bottom portion is opened. Therefore, the shielding effect of the groove cross section is smaller than that of the groove fence 101a, and there is a problem that the effect of reducing the air column resonance is reduced. Furthermore, in the groove fence 101b, it is necessary to make the angle of the portion Y surrounded by a circle in the drawing an obtuse angle in consideration of the ability of the mold to be removed.

  Therefore, the object of the present invention is to solve the problems in the conventional shape described above, to reduce the air column resonance of the circumferential groove that causes the noise problem during traveling, and to prevent cracks in the groove fence accompanying traveling. An object of the present invention is to provide a tire in which generation is suppressed.

  As a result of diligent study, the present inventor provided a groove fence composed of a protrusion protruding from one groove wall toward the other groove wall in the circumferential groove, and specifying the shape of the protrusion, The inventors have found that the above problems can be solved, and have 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 tire provided with a tread having a plate-like projection protruding from one groove wall of the circumferential groove toward the other groove wall in the circumferential groove,
The projecting portion shields at least the groove bottom portion of the circumferential groove, and has an opening portion that opens outward in the tire radial direction on the other groove wall side, and the other groove wall of the projecting portion The upper end P of the edge in contact with the tire is located on the outer side in the tire radial direction from the lower end of the groove wall having a linear cross section,
The protrusions are disposed in a pair between the groove walls on both sides of the circumferential groove, and the circumferential groove in the tire ground contact surface includes only one pair of the protrusions. To do.

  In the tire of the present invention, in the cross section of the circumferential groove, it is preferable that an angle α formed on the outer side in the tire radial direction between the protrusion at the upper end P of the protrusion and the other groove wall is an obtuse angle. . Moreover, it is preferable that the bottom part of the said opening part exhibits a substantially circular arc shape. Furthermore, in the tire according to the present invention, it is preferable that the circumferential groove does not have a see-through portion when the pair of projecting portions are close to each other in the tire width direction when the tire contacts the ground.

  According to the present invention, by disposing a protrusion that satisfies the above condition in the circumferential groove, it is possible to reduce the air column resonance of the circumferential groove that causes noise problems during traveling, It has become possible to realize a tire that suppresses the occurrence of cracks in the protrusions during traveling.

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. FIG. 3 is a partial development view of a tread surface portion showing an arrangement state of a pair of protrusions according to the tire of Example 1; (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.
In FIG. 1, sectional drawing which shows an example of the shape of the projection part which concerns on the tire of this invention is shown. 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, a plate-like protrusion 1 is provided in the circumferential groove 11 so as to protrude from one groove wall 11A toward the other groove wall 11B. In the present invention, as shown in the drawing, the protrusion 1 shields at least the groove bottom 11C of the circumferential groove 11 and has an opening 2 that opens outward in the tire radial direction on the other groove wall 11B side. . Moreover, the upper end P of the edge part which contact | connects the other groove wall 11B of the projection part 1 is located in the tire radial direction outer side rather than the upper end of the groove bottom part 11C. As described above, the protrusion 1 is shaped so as to completely shield the groove bottom 11C, and the end of the edge of the protrusion 1 is not present on the groove bottom 11C of the circumferential groove 11. It was possible to prevent the occurrence of cracks from the end portion X of the groove fence 101a present at the groove bottom, which was likely to occur in the conventional shape as shown in FIG. Further, since the protrusion 1 has a shape capable of shielding the groove bottom portion 11C, the effect of suppressing the air column resonance is higher than that of the conventional groove fence 101b shown in FIG. 6B, and the noise reduction effect can be obtained more favorably. Is.

  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 protrusions 1 are arranged according to the above conditions is important, and other points can be appropriately set according to a conventional method, and are particularly limited. Is not to be done.

  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 outer side in the tire radial direction between the protrusion 1 and the other groove wall 11 </ b> B at the upper end P of the protrusion 1 may be an obtuse angle. preferable. Here, the angle α is substantially an angle formed by the tangent L of the upper edge of the protrusion 1 at the upper end P of the protrusion 1 and the groove wall 11B as shown in the figure. Thereby, generation | occurrence | production of the crack in the upper end P can be suppressed more effectively. The angle α can be set to 120 ° to 180 °, for example. Moreover, as shown in the drawing, the bottom of the opening portion 2 preferably has a substantially arc shape, and this can also improve the effect of suppressing the occurrence of cracks. Here, the substantially arc shape has the same meaning as described above. Therefore, in the present invention, the protrusion 1 having the shape as shown in FIG. 1 is used to more effectively suppress the concentration of distortion at the upper end P of the protrusion, and the conventional shape shown in FIG. The effect which avoids generation | occurrence | production of a crack in comparison is acquired.

  As described above, since the risk of cracking is particularly great in the circumferential groove located in the shoulder portion, conventionally, the groove fences 101a and 101b having different shapes in the circumferential groove in the central portion and the circumferential groove in the shoulder portion are used. However, in the protrusion according to the present invention, crack resistance is improved as compared with the groove fence 101a, so that the central portion and the shoulder portion can have a common protrusion shape. . Thereby, the effect which improves workability is also acquired on manufacture of a tire.

  Further, the protrusions according to the present invention are arranged in a pair between the groove walls 11A and 11B on both sides of the circumferential groove 11, and in the circumferential groove 11 in the ground contact surface formed when the tire is running, It is preferable that the protrusion is always included in only one place. The pair of protrusions 1A and 1B can be arranged in parallel with each other, for example, in the shape shown in the cross-sectional view of FIG. 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.

  Further, in the present invention, when a pair of projecting portions are arranged, the pair of projecting portions are adjacent to each other in the tire width direction and the circumferential groove has a see-through portion when the tire contacts the ground. It is preferable to form such that it does not. 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.

  The protrusions according to the present invention are preferably arranged in all circumferential grooves, but may be arranged only in some circumferential grooves, or may be used in combination with a conventional groove fence, In particular, it is effective to apply to the circumferential groove of the shoulder portion where the distortion of the groove bottom portion is large.

  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. Further, when a pair of protrusions are provided, the offset amount between the pair of protrusions can be set so 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. 6A, and the circumferential grooves 11a and 11d in the tire shoulder portion. The shape shown in FIG. 6 (b) is the shape shown in FIG. 6 (b), with each circumferential groove in the ground contact surface at the time of traveling having a pair of protrusions at substantially only one place at a circumferential interval 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.

<Example 1>
As shown in the enlarged view of FIG. 5, in each circumferential groove 11a to 11d, plate-like protrusions 1A and 1B projecting from one groove wall to the other groove wall of the circumferential groove are A tire of Example 1 was produced in the same manner as Comparative Example 2 except that a pair of groove walls on both sides of the directional groove was provided. As shown in FIG. 1, the protrusions 1A and 1B shield the groove bottom of the circumferential groove, and have an opening portion that opens outward in the tire radial direction on the other groove wall side, and the other groove The upper end P of the edge part which touches a wall had a shape located in a tire radial direction outer side rather than the upper end of a groove bottom part. In the cross section of the circumferential groove, an angle α formed between the protrusion at the upper end P of the protrusion and the other groove wall on the outer side in the tire radial direction was 160 °. In the tire of Example 1, the pair of protrusions were close to each other in the tire width direction at the time of tire contact, and the circumferential groove did not have a 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.

  As shown in the above table, in the test tire of Example 1, compared to the test tire of Comparative Example 2, the effect of shielding the circumferential grooves by the protrusions is improved, so that It was confirmed that the noise level was reduced without the occurrence of cracks.

1, 1A, 1B Protrusion 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 L Tangent P Upper end

Claims (4)

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 protruding from one groove wall of the circumferential groove toward the other groove wall,
The projecting portion shields at least the groove bottom portion of the circumferential groove, and has an opening portion that opens outward in the tire radial direction on the other groove wall side, and the other groove wall of the projecting portion The upper end P of the edge in contact with the tire is located on the outer side in the tire radial direction from the lower end of the groove wall having a linear cross section ,
The protrusions are disposed in a pair between the groove walls on both sides of the circumferential groove, and the circumferential groove in the tire ground contact surface includes only one pair of the protrusions. Tire.   2. The tire according to claim 1, wherein an angle α formed on the outer side in the tire radial direction between the protrusion at the upper end P of the protrusion and the other groove wall in the cross section of the circumferential groove is an obtuse angle.   The tire according to claim 2, wherein a bottom portion of the opening portion has a substantially arc shape. When the tire is ground by the pair of projecting portions is close to the tire width directions, the tire of any one of claims 1 to 3 becomes the said circumferential groove has no see-through portion.

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