JP2012056445A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of markedly improving probability capable of being used as a base tire of retreading by hardly making a service life of a tire prior to retreading into sacrifice.SOLUTION: A pneumatic tire 1 is the pneumatic tire having a rise part 10 for providing a plurality of tread grooves on a tread part 2, and which is a tread wear indicator having a top face whose distance is x1 when being measured from an opening end position 5a of the groove to a radial direction of the tire on a groove bottom 5b of a first tread groove 5 out thereof has a projection part 20 on a groove wall 15c of a second tread groove 15 which is a prescribed width directional groove provided on a central region 3 of the tread part. A lower end 20a of the projection part is at a position of a distance x2 shorter than x1 when being measured from an opening end position 15a of the groove to the radial direction of the tire. The projection part 20 is a retreading indicator lost when the tread part is worn in a thickness part corresponding to the distance x2.

Description

  The present invention relates to a pneumatic tire, and in particular, even when only a portion of a tread portion, particularly a central region portion of the tread portion, is worn locally, the service life of the tire before retreading is not significantly sacrificed. The present invention relates to a pneumatic tire that has a significantly improved probability of being used as a retread base tire.

  As the pneumatic tire continues to roll load and the tread wears, the performance of the tire usually changes in a decreasing direction, especially when the drainage performance such as wet skid resistance is significantly reduced. It is. Therefore, the wear limit of the tread portion is displayed by the tread wear indicator. A general tread wear indicator has a groove bottom of a groove provided in a tread portion raised about a predetermined height from the groove bottom at about six places on the circumference. JIS D4230 stipulates that in the case of automobile tires (excluding tires for two-wheeled vehicles, agricultural machinery, industrial vehicles, and construction vehicles), the treadware indicator should be raised 1.6 mm above the groove bottom. Has been. In this case, the remaining groove becomes 1.6 mm due to wear, and when the tread wear indicator is exposed on the tread surface, the user can visually recognize the raised portion. Therefore, the tread wear indicator allows the user to replace the tire. It will be urging.

  In Patent Document 1, by providing two raised portions as tread wear indicators with a gap of 10 to 20 mm in the groove, a pumping sound is generated when they are exposed on the tread surface of the tread portion. A technique that encourages tire replacement by appealing to the sense of hearing is disclosed.

JP-A-8-207515

  By the way, in recent years, in order to consider environmental problems, the demand for recycling tires has increased. Recycled tires are widely known as retreaded tires. Generally, a retread tire is a tire obtained by removing a tread from a used tire to form a base tire, and a new material is attached to the base tire as a tread portion. This tire regeneration is also called “retread”.

  Conventionally, for example, in the case of aircraft tires, retreading has been performed after a specified number of uses. In the case of truck / bus tires, retreading was performed using the specified mileage. However, since the tire actually rolls under various road surface conditions, the degree of progress of wear due to the specified number of times or the specified travel distance is not constant. If the tire wears too much and even a portion of the tire belt layer is exposed, it may be impossible to use the tire as a base tire and retreading may not be possible.

  Thus, conventionally, there has been no effective means for recognizing the timing of retreading before it becomes unusable as a base tire, regardless of the conditions of use of the tire.

  Here, the present inventors have examined whether or not the treadwear indicator indicating the tire replacement time described in Patent Document 1 can also be used for the retreading time. That is, an attempt was made to use the treadwear indicator as an indication of the wear limit when retreading, as well as the wear limit suitable for tire replacement. However, even when trying to retread after the treadwear indicator that shows the wear limit suitable for tire replacement is exposed on the tread surface, the tire wears too much and it is found that there is a low probability that it can be used as a base tire. It was.

  Further, in order to ensure that the tire can be used as a pedestal tire, a means for observing the tread wear indicator and retreading it before it is exposed on the tread surface can be considered. However, it is difficult to accurately determine the wear amount of the tread rubber by such means. For example, it is assumed that the tire service life is extremely shortened by mistakenly judging that the tire should be replaced, even though it is not time to replace the tread rubber.

  Therefore, in view of the above problems, the present invention provides a pneumatic tire that can remarkably improve the probability that it can be used as a base tire of a retread without sacrificing the service life of the tire before the retread. Objective.

  According to the above examination by the present inventors, if there is some indicator indicating the wear limit when performing the tread before the tread wear indicator is exposed on the tread portion tread, the probability that it can be used as a base tire is increased. Can do. Furthermore, considering the specific circumstances when performing retreading, which will be described later, the optimum position for arranging this indicator was also examined. As a result, the following invention was completed.

That is, in view of the above problems, the gist of the present invention is as follows.
(1) A plurality of tread grooves are provided in the tread portion, and a tire is provided from the opening end position of the first tread groove to the groove bottom of the first tread groove which is a predetermined tread groove among the plurality of tread grooves. A pneumatic tire having a raised portion which is a treadwear indicator having a top surface whose distance when measured in the radial direction is x1,
The plurality of tread grooves include a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of width direction grooves extending in the tire width direction,
Of the plurality of widthwise grooves, the groove wall of the second tread groove that is a predetermined widthwise groove provided in the central region of the tread portion has a convex portion or a concave portion,
The lower end of the convex portion or the concave portion is a position at a distance x2 shorter than the x1 when measured in the tire radial direction from the opening end position of the second tread groove,
The pneumatic tire according to claim 1, wherein the convex portion or the concave portion is a retread indicator that disappears when the tread portion is worn by a thickness corresponding to the distance x2.

(2) A plurality of tread grooves are provided in the tread portion, and the tire is provided from the opening end position of the first tread groove to the groove bottom of the first tread groove which is a predetermined tread groove among the plurality of tread grooves. A pneumatic tire having a raised portion which is a treadwear indicator having a top surface whose distance when measured in the radial direction is x1,
The plurality of tread grooves include a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of width direction grooves extending in the tire width direction,
Of the plurality of widthwise grooves, the groove wall of the second tread groove that is a predetermined widthwise groove provided in the central region of the tread portion has a convex portion or a concave portion,
The upper end of the convex portion or the concave portion is a position at a distance x2 shorter than x1 when measured in the tire radial direction from the opening end position of the second tread groove, and the lower end of the convex portion or the concave portion is the first 2 outside the tread groove bottom in the tire radial direction,
The pneumatic tire according to claim 1, wherein the convex portion or the concave portion is a retread indicator that is exposed on the tread surface when the tread portion is worn by a thickness corresponding to the distance x2.

  (3) The pneumatic tire according to (1) or (2), wherein a value of d1-x2 is 3.0 mm or more, where d1 is a depth of the first tread groove.

(4) The first tread groove is a circumferential groove provided in a central region of the tread portion,
The second tread groove is a width direction groove branched from a groove wall of the circumferential groove,
The convex portion or the concave portion is a position away from a branch position from the groove wall of the circumferential groove in a front view of the tread portion tread surface, and a groove wall line of the groove wall where the convex portion or the concave portion is provided. The pneumatic tire according to any one of (1) to (3), provided at a position within 15 mm in the groove wall line direction from an intersection with a groove width center line of the circumferential groove.

  (5) The pneumatic tire according to any one of (1) to (4), wherein the convex portion or the concave portion is provided in a range of 2 to 8 at a predetermined interval on the same tire circumference.

  (6) The maximum displacement y of the convex portion or the concave portion from the groove wall of the second tread groove is 1/10 or more and 1/5 or less of the groove width w of the second tread groove (1) The pneumatic tire according to any one of (5) to (5).

(7) The maximum displacement portion of the convex portion or the concave portion forms a plane,
The pneumatic tire according to any one of (1) to (6), wherein unevenness is further provided on the plane.

  (8) The pneumatic tire according to any one of (1) to (7), wherein the convex portion or the concave portion has a curved surface shape at a portion intersecting with a groove wall of the second tread groove.

  According to the present invention, before the tread wear indicator is exposed to the tread portion tread due to wear of the tread portion, the convex portion or the recess provided in the groove wall of the width direction groove in the central region disappears or is exposed to the tread portion tread. To encourage retreading. For this reason, it has become possible to remarkably improve the probability that the tire can be used as a retread base tire without significantly sacrificing the service life of the tire before retreading.

FIG. 3 is a development view of a part of a tread portion of a typical pneumatic tire according to the present invention. (A) is sectional drawing on the II line of the figure expanded and shown in the circle | round | yen enclosed with the broken line of FIG. 1, and shows the groove width direction cross section of a protruding part, (b) These are sectional drawings on the II-II line of the figure shown similarly in FIG. (A) is sectional drawing on the III-III line of the figure expanded and shown in the circle | round | yen enclosed with the broken line of FIG. 1, and shows the groove width direction cross section of the convex part 20 provided in the groove wall FIG. 4B is a cross-sectional view taken along the line IV-IV in the diagram similarly shown in FIG. 1. (A) is the expansion perspective view of the convex part 20 and the groove wall 15c which were shown in FIG. 3, (b) looked at the convex part 20 located in the 2nd tread groove 15 from the upper direction of the tread part tread. It is a top view at the time. It is a figure for demonstrating the suitable arrangement | positioning position of the convex part 20 in FIG. The convex part 20 which comprises another pneumatic tire according to this invention is shown, Comprising: (a) is an expansion perspective view of the convex part 20 and the groove wall 15c, (b) is a top view of the convex part 20 It is. The convex part 20 which comprises another pneumatic tire according to this invention is shown, Comprising: It is the width direction sectional drawing of a 2nd tread groove | channel. The convex part 20 which comprises another pneumatic tire according to this invention is shown, Comprising: (a) is width direction sectional drawing of a 2nd tread groove | channel, (b) is the 2nd tread groove | channel 15 and groove bottom position. It is sectional drawing when cut | disconnecting in a groove | channel extending direction. FIG. 9 shows a recess 30 constituting still another pneumatic tire according to the present invention, in which (a) is a cross-sectional view in the width direction of the second tread groove, and (b) is a view of the recess 30 from above the tread portion tread. FIG. The convex part 20 which comprises another pneumatic tire according to this invention is shown, Comprising: It is the width direction sectional drawing of a 2nd tread groove | channel.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. In principle, the same components are denoted by the same reference numerals, and description thereof is omitted.

  The pneumatic tire of the present invention is a retread indicator for visually urging the user to retread, and is provided with a convex portion or a concave portion on a groove wall of a predetermined groove described later. Or the 1st pneumatic tire which shows the wear limit of a retread when a recessed part lose | disappears, and the 2nd pneumatic which shows the wear limit of a retread when a convex part or a recessed part is exposed to a tread part tread by wear of a tread part Including tires.

(First pneumatic tire)
The first pneumatic tire of the present invention has, in the tread portion, a plurality of tread grooves including a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction. Of the plurality of tread grooves, a predetermined width direction groove having a raised portion that is a tread wear indicator at the groove bottom of the first tread groove that is a predetermined tread groove and provided in a central region of the tread portion The groove wall of the second tread groove is a convex portion or a concave portion. The raised portion has a top surface whose distance is x1 when measured in the tire radial direction from the opening end position of the first tread groove. And the lower end of a convex part or a crevice is a position of distance x2 shorter than x1 when it measures in the tire diameter direction from the opening end position of the 2nd tread groove, and as a result, a tread part has a tread part. It is a retread indicator that disappears when worn by a thickness corresponding to the distance x2.

(First Pneumatic Tire—First Embodiment)
A typical pneumatic tire according to the first invention as described above will be described in detail with reference to FIGS. FIG. 1 is a development view of a part of a tread portion 2 of a pneumatic tire 1 according to a first embodiment of the present invention. The pneumatic tire 1 has four circumferential grooves 5, 6, 7 a, 7 b extending in the tire circumferential direction T in the tread portion 2, and a plurality of widthwise grooves extending substantially in the tire width direction W. 15, 16a, 16b. Of the four circumferential grooves 5, 6, 7a, 7b, the two circumferential grooves 5, 6 and the widthwise groove 15 located closer to the tire equator S define a block row 11 composed of a plurality of blocks. ing. Further, each of the circumferential rows 5, 6 and the two circumferential grooves 7a, 7b and the lateral grooves 16a, 16b adjacent to the outer side in the tire width direction define a block row 12a, 12b. A tread pattern based on the rows is formed. In addition, one side ribs (shoulder ribs) 13a and 13b defined by the circumferential grooves 7a and 7b located on the outer side in the tire width direction and the respective tread ends E are formed in both side regions 4 of the tread portion. ing.

  In the present embodiment, a raised portion 10 as a tread wear indicator is formed on the groove bottom 5b of the circumferential groove 5 provided in the central region 3 of the tread portion. In the present specification, the “central area of the tread portion” means an area of 50% of the tread width W centered on the tire equator S. The “side area” means an area other than the central area 3 of the tread portion.

  As shown in FIGS. 2 (a) and 2 (b), the raised portion 10 has a top surface whose distance is x1 when measured in the tire radial direction from the opening end position 5a of the circumferential groove 5 as the first tread groove. 10a. The groove depth of the circumferential groove 5 is d1, and the height of the raised portion is h1. In the case of automobile tires (excluding tires for motorcycles, agricultural machines, industrial vehicles, and construction vehicles), JIS D4230 stipulates that h1 is 1.6 mm. In this case, when the remaining groove becomes 1.6 mm due to wear and the raised portion 10 is exposed on the tread surface, the user can visually recognize the raised portion 10, so the raised portion 10 allows the user to replace the tire. It will be urging. Here, the height h1 of the raised portion is measured by measuring the depth x1 from the tread surface (open end position 5a) to the top surface 10a of the raised portion and the depth d1 of the first tread groove in which the raised portion is disposed. Then, it is determined by obtaining the difference. For example, when d1 = 8 mm, x1 is 6.4 mm.

  As shown in FIGS. 1, 3A, 3B, 4A, and 4B, the characteristic configuration of the present invention is a predetermined width direction provided in the central region 3 of the tread portion 2. A convex portion 20 is provided on the groove wall 15c of the second tread groove, which in this embodiment is the width direction groove 15, and the lower end 20a of the convex portion 20 is measured in the tire radial direction from the opening end position 15a of the width direction groove. The distance x2 is shorter than x1. The convex part 20 is a retread indicator, and the convex part is exposed to the tread part tread surface in the initial stage of use and can be visually recognized.If the tread part is worn by a thickness corresponding to the distance x2, the convex part 20 disappears. At this timing, retreading is promoted. The groove depth of the width direction groove 15 is d2, and the height from the groove bottom to the lower end 20a of the convex part is h2.

  Here, the process of adopting the above-described characteristic configuration to complete the present invention will be described including the effects. As already explained, as a technique for recognizing a suitable time for retreading before the tire becomes unusable due to excessive wear regardless of the conditions of use of the tire, the present inventors have similar to the treadwear indicator. In principle, the idea was to use an indicator that indicates the wear limit suitable for retreading. And in normal automobile tires, if a treadwear indicator with a height of 1.6 mm, which is a general treadwear indicator, is used until it is exposed on the tread surface, it will be The ratio that can be used as a base tire may be extremely low because the belt layer of the tire is exposed. That is, if a tire is used up to the wear limit that generally requires tire replacement, it often becomes impossible to retread. Therefore, at least on the premise that the tread portion is evenly worn, it is necessary to provide some indicator indicating the wear limit when performing the tread before the tread wear indicator is exposed to the tread surface. Protrusions 20 that disappear when worn by a thickness corresponding to a distance x2 shorter than x1 are provided on the groove wall.

  Furthermore, the present inventors have found that it is an important factor in which tread groove provided in the tread portion 2 the convex portion 20 is provided. Under actual use, the tread often wears unevenly. For example, when the tread contact surface is large, such as heavy duty tires, there is a tendency for the periphery of the tread to wear out quickly, whereas when the tread contact surface is small, the portion located in the center area of the tread wears out early. Tend to. First, when the tread central region wears out early, if the convex portion 20 is provided in the tread groove (for example, the circumferential grooves 7a and 7b) in the side region 4, when the convex portion 20 disappears from the tread surface of the tread portion, Further, the wear in the central region is more advanced, and there is a possibility that the tire becomes unusable as a base tire. Therefore, the convex portion 20 is arranged in the width direction groove provided in the central region 3.

  On the other hand, when the tread side region wears out early, if the convex portion 20 is provided in the width direction groove in the central region, the side portion of the tread portion disappears more when the convex portion 20 disappears from the tread surface. It will be advanced. However, when the pneumatic tire 1 is retreaded, it is a base tire in which the tread portion after wear is removed with a buff. However, since the tread rubber is generally thicker in the side region than in the central region, the belt in the side region is Exposure problems are less likely to occur. For this reason, it has been found that even when the convex portion 20 is disposed in the width direction groove provided in the central region, it is unlikely that the convex portion 20 is unusable as a base tire due to uneven wear in the lateral region.

  As described above, when retreading is performed, regardless of the uneven wear mode, if the convex portion 20 is disposed in the width direction groove provided in the central region, the retread before the wear becomes so advanced that it cannot be used as a base tire. The present inventors have found that a suitable time can be recognized more reliably and have completed the present invention.

  Thus, the convex part 20 can be used as an indicator for retreading to indicate that the time when the convex part 20 disappears from the tread due to wear of the tread part is the retreading time. By providing the above-described retread indicator indicating an appropriate retread time, the service life of the tire before the retread is not sacrificed as compared with the case where only the tread wear indicator is provided.

  The pneumatic tire 1 of this embodiment can freely select whether or not the user performs retreading. When retreading is performed, the retreading may be performed when the convex portion 20 disappears from the tread. When the retreading is not performed, the continuation of use is continued even when the convex portion 20 disappears from the treading, and the ridge 10 is used when exposed to the treading. Stop and change tires.

  In addition, it is normal to provide the protruding part 10 in the circumferential groove | channel, and it is provided in the circumferential groove | channel of the center area 3 of the tread part 2 in this embodiment. That is, in the present embodiment, the first tread groove is a circumferential groove in the central region 3 of the tread portion 2. On the other hand, disposing the protrusions 20 in the width direction grooves 15 is also preferable in that the drainage performance of the circumferential grooves 5 and 6 is not hindered.

With reference to FIG. 5, the preferable arrangement | positioning of the convex part 20 is demonstrated. The width direction groove 15 provided with the convex portion 20 is preferably a groove branched from the groove wall 5 c of the circumferential groove 5. Moreover, the convex part 20 is a position away from the branch position 17 from the groove wall 5c of the circumferential groove in a front view of the tread part tread surface, and a groove wall line of the groove wall 15c where the convex part 20 is provided. The circumferential groove 5 is preferably provided at a position within 15 mm (point Q) in the line direction of the groove wall 15c from the intersection P with the groove width center line 18. That the convex part 20 is separated from the branch position 17 means that the circumferential groove side end 20b ₁ of the convex part 20 is separated from the branch position 17. Since the wear of the tread portion proceeds from the corner of the block, when the convex portion 20 is in contact with the circumferential groove 5, the shape of the block optimized for the wear is broken, and uneven wear tends to occur. However, it can be suppressed by separating from the circumferential groove 5. Further, providing the convex portion 20 at a position within 15 mm from the intersection P means that the end 20b ₂ on the opposite side of the circumferential groove of the convex portion 20 is located on the circumferential groove side from the point Q. . By adopting this configuration, not only the occurrence of uneven wear is suppressed, but it is not too far away from the circumferential groove 5 as a starting point for determining the timing of retreading, and the optimum position can be determined and the appropriate retreading timing can be determined. (The final retreading time is determined by the convex portion 20, but since the retread is reliably performed when the convex portion 20 disappears, the wear amount of the circumferential groove may be observed from time to time before the disappearance.) .

  Normally, the side of the tire corresponding to the treadwear indicator is marked to make it easier to confirm the position of the indicator. It is preferable to mark also the side surface of the tire corresponding to the convex portion 20 which is a retread indicator. If it does in this way, the positional relationship of the circumferential direction of the protruding part 10 and the convex part 20 will not be specifically limited.

  According to the study of the present inventor, as shown in an example described later, the tire has a tire size of 275 / 80R22.5, and the circumferential groove 5 (groove depth d1 = 15.8 mm) in the center region has a height h1. = In the all-season truck / bus tire provided with a raised portion of 1.6 mm, when the groove depth d2 of the widthwise groove 15 is 15.8 mm, the groove bottom 15b of the widthwise groove 15 and the lower end 20a of the convex portion The distance h2 is preferably 3.0 mm or more, and in the case of 3.2 mm, the ratio that can be used as a base tire has been greatly improved, and is the most preferable value.

  Furthermore, as a result of examination, with a different tire size (225 / 80R17.5), a raised portion having a height h1 = 1.6 mm is formed in the circumferential groove 5 (groove depth d1 = 14.7 mm) in the central region. In the provided truck tire, when the groove depth d2 of the width direction groove 15 is 14.7 mm, h2 = 3.0 mm or more is also preferable, and when h2 = 3.2 mm, the tire is used as a base tire. It has been found that the ratio that can be achieved is dramatically improved and is the most preferable value. At this time, when d2 was reduced by 1 mm to 13.7 mm, the most preferable value was obtained when h2 = 2.2 mm. From this, the position of the lower end 20a of the convex part 20 is most preferably a height of 3.2 mm on the basis of the groove bottom of the circumferential groove 5 provided with the tread wear indicator (raised part) regardless of the tire size. It has been found. Therefore, in this invention, it is preferable that the value of d1-x2 (distance from the groove bottom of the circumferential groove | channel 5 to the lower end of a convex part) is 3.0 mm or more, and 3.2 mm is the most preferable. Furthermore, as an upper limit of the value of d1-x2, it is preferable that it is 4.0 mm, and 3.5 mm is more preferable. If it is 3.0 mm or more, when the convex part 20 disappears from the tread surface, the wear does not progress excessively, and the probability that it can be used as a retread base tire is further increased. Even if it is larger than 4.0 mm, the retread is not likely to be used as a stand tire, and even if the retread is made too fast, the tire life is shortened, which is disadvantageous in terms of environment and cost. Therefore, it may be 4.0 mm or less. That is, if the value of d1-x2 is set to 3.0 mm or more and 4.0 mm or less, the effect of effectively increasing the availability of the retread as a stand tire can be expected without shortening the service life of the tire.

  The groove depth d1 of the circumferential groove 5 provided with the tread wear indicator (raised portion) varies depending on the tire size, but the remaining groove 1.6mm indicates the use limit of the tire. The groove to be provided is specified. And it discovered that the height on the basis of the groove bottom of the groove | channel in which a tread wear indicator is provided is a factor which influences the probability which can be used as a base tire of a retread. Note that the maximum groove depth of the main groove is described in TRA ENGINERING DESIGN INFORMATION 3-01 to 07.

  As described above, if the convex portion 20 disappears earlier from the tread portion tread surface, the probability that it can be used as a base tire increases. However, even if the convex portion 20 disappears too early, the tire life is shortened. . Therefore, in order to achieve the effect of effectively improving the probability that it can be used as a retread tire without shortening the service life of the tire, the contents of all the paragraphs are further generalized, and x2 / x1 is 0.84. It is preferable to set it to 0.91 or less. That is, if it is set to 0.91 or less, wear does not progress excessively when the convex portion 20 disappears from the tread surface, and the probability that it can be used as a retread tire is increased. Moreover, even if it is smaller than 0.84, the retread is not likely to be used as a base tire, and even if the retread is made too fast, the tire life is shortened, which is disadvantageous in terms of environment and cost. Therefore, it should be 0.84 or more.

  It is preferable to provide two or more protrusions 20 at a predetermined interval on the same tire circumference. If two or more are provided in the tire circumferential direction, even if one is hidden in the ground contact surface, the other can be surely visually recognized. Moreover, even if more than eight are provided in the tire circumferential direction, the visibility is not further improved, so the number may be eight or less. These are preferably provided at substantially equal intervals from the viewpoint of ensuring uniform visibility.

As shown in FIG. 4B, the maximum displacement amount y from the groove wall 15 c of the width direction groove of the convex portion 20 is 1/10 or more and 1/5 or less of the groove width w of the width direction groove 15. This is true. If it is 1/10 or more, the user can visually recognize the convex portion 20 more reliably, and if it is 1/5 or less, it does not affect the rigidity of the block, that is, the generation core of uneven wear. The function as a retread indicator can be exhibited.
FIG. 4B shows the maximum displacement amount y and the groove width w in a state where the tread portion is not worn. However, even during the process of wear, the distance from the opening end position 15a to 0.8 × x1 is shown. It is preferable to maintain the same relationship between the two.

Further, as clearly shown in FIGS. 4A and 4B, it is preferable that the convex portion 20 has a curved surface shape in the portions 20b ₁ and 20b ₂ intersecting the groove wall 15c of the width direction groove. In this case, since the convex part 20 is connected to the groove wall 15c via a gentle curved surface, it is possible to suppress the occurrence of cracks between the convex part 20 and the groove wall 15c.

(First Pneumatic Tire—Second Embodiment)
Another pneumatic tire according to the first aspect of the present invention will be described with reference to FIG. In the first embodiment, the maximum displacement portion of the convex portion 20 is a flat plane. However, in the pneumatic tire of this embodiment, the convex portion 21 is further provided on the plane 20c. By providing the convex portion 21 on the flat surface 20c of the maximum displacement portion, the flat surface 20c of the convex portion 20 can be shaded when the width direction groove 15 is viewed, and the visibility of the convex portion 20 can be further enhanced. Moreover, it may replace with the convex part 21 and may provide a recessed part (not shown). In the present embodiment, the contents other than the above are the same as those described in the first embodiment. As a suitable protrusion degree of the convex part 21, in FIG.6 (b), both the protrusion amount y1 from the plane 20c and the width | variety z1 of the direction along the width direction groove | channel 15 of the convex part 21 are 0.3 mm-0. 5 mm is preferable. This is because it is difficult to recognize the shadow if the convex portion 21 is too large or too small.

(First Pneumatic Tire—Third Embodiment)
In the first embodiment, the convex portion 20 extends to the tread portion tread surface, but as shown in FIG. 7, even if the upper end 20d of the convex portion 20 is located on the inner side in the tire radial direction than the tread portion tread surface. good. In this case, although the convex portion 20 is not exposed on the tread portion tread at the initial use of the tire, the convex portion 20 is exposed on the tread portion tread as the wear progresses, and disappears when the tread portion is worn by a thickness corresponding to the distance x2. To do. Other points are the same as those in the first and second embodiments.

(First Pneumatic Tire—Fourth Embodiment)
In the first to third embodiments, the case where the longitudinal direction of the convex portion extends in the tire radial direction as seen in the cross-sectional view along the groove extending direction is shown, but in the groove extending direction as shown in FIG. The convex part 20 in which the longitudinal direction of the convex part extends may be used. Furthermore, it does not have to be a rectangular convex portion as shown in FIG.

(First Pneumatic Tire—Fifth Embodiment)
In 1st-4th embodiment, although the convex part 20 was provided in the groove wall 15c of the width direction groove | channel 15 as a retread indicator, you may replace with the convex part 20 and provide the recessed part 30 as shown in FIG. In this case, since the lower end 30a of the concave portion 30 is located at the position x2 when measured in the tire radial direction from the opening end position 15a of the width direction groove 15, the concave portion 30 disappears when the tread portion is worn by a thickness corresponding to the distance x2. To do. Other points are the same as in the first to third embodiments. As shown in FIG. 8B, reference numerals 30b ₁ and 30b ₂ are portions where the concave portion 30 intersects the groove wall 15c, and the protrusion width of the convex portion 30 toward the land portion is defined as the maximum displacement amount y. Yes.

(First Pneumatic Tire—Other Embodiments)
In the present invention, the internal structure of the tire is not particularly limited. Since the belt layer tends to become unusable as a retread pedestal tire by exposing the belt layer, the present invention can be suitably applied to a pneumatic tire in which the belt layer is arranged inside the tread rubber.

  The pneumatic tire of the present invention can be used for tires of any application including tires for passenger cars, but can be more effective when used as an all-season truck / bus tire. In recent years, the use of environmentally friendly parts in the truck and bus industry has attracted attention as retread tires that not only reduce waste tires but also reduce tire costs. The present invention is effective.

  In the first to fifth embodiments, the tread pattern based on the block row has been described, but the present invention is applicable to a pneumatic tire having an arbitrary tread pattern. For example, a tread pattern in which a center rib is provided and a plurality of width direction grooves are provided on the center rib may be used. Moreover, the width direction groove | channel does not need to open to the circumferential direction groove | channel like this embodiment.

  The pneumatic tire of the present invention can be manufactured by providing a pattern corresponding to the first and second raised portions on a mold during vulcanization and performing vulcanization molding.

(Embodiment of the second pneumatic tire)
The second pneumatic tire of the present invention has, in the tread portion, a plurality of tread grooves including a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire width direction. Of the plurality of tread grooves, a predetermined width direction groove having a raised portion that is a tread wear indicator at the groove bottom of the first tread groove that is a predetermined tread groove and provided in a central region of the tread portion The groove wall of the second tread groove is a convex portion or a concave portion. The raised portion has a top surface whose distance is x1 when measured in the tire radial direction from the opening end position of the first tread groove. And the upper end of a convex part or a recessed part is a position of distance x2 shorter than x1 when it measures in the tire radial direction from the opening end position of the 2nd tread groove, As a result, a convex part or a recessed part has a tread part. It is a retread indicator that is exposed on the tread surface when worn by a thickness corresponding to the distance x2. Further, the retread indicator of the present invention is not a form in which a raised portion is provided at the groove bottom like the tread wear indicator 10, but is a convex portion or a concave portion provided at the bottom of the groove to the last. It exists in the tire radial direction outer side from the groove bottom of 2 tread grooves.

  An example of such a pneumatic tire is shown in FIG. In FIG. 10, the convex part 20 is provided in the groove wall 15c of the width direction groove | channel 15 as a 2nd tread groove | channel. Since the upper end 20d of the convex portion is located at a position x2 in the tire radial direction from the opening end position 15a of the width direction groove, the convex portion 20a is exposed to the tread portion tread when the tread portion is worn by a thickness corresponding to the distance x2. The projection 20 is used as a retread indicator to indicate that this time is the retread time.

  The first pneumatic tire and the second pneumatic tire are different in terms of means for indicating the wear limit of the retread when the convex portion or the concave portion disappears from the tread tread surface or when exposed to the tread portion tread surface. Only. Therefore, the other description about the 2nd pneumatic tire is the same as what was performed with the 1st pneumatic tire.

Next, in order to further clarify the effects of the present invention, the following (A) and (B) two types of size tires were compared and evaluated using pneumatic tires according to examples and comparative examples. explain. Items common to each pneumatic tire are as follows.
Tire size: (A) 275 / 80R22.5 (truck / bus tire), (B) 225 / 80R17.5 (truck tire)
Tread pattern: block pattern shown in FIG. 1 The circumferential grooves 5, 6, 7a, 7b have groove width = (A) 11-14 mm, (B) 8-11 mm, groove depth d1 = (A) 15.8 mm, (B) 14.7 mm
The width direction grooves 15, 16a, 16b are groove width w = (A) 7-9 mm, (B) 5.5-6.5 mm, groove depth d2 = (A) 15.8 mm, (B) 14.7 mm.
Tire internal structure: radial tire with a pair of crossed belts
(Cord angle 74 °, 1 carcass)
Raised part:
A treadwear indicator is provided in the circumferential groove 5 (groove depth d1 = (A) 15.8 mm, (B) 14.7 mm) in the central region, with one raised portion having a height h1 = 1.6 mm in the circumferential direction. It was. (Thus, x1 = (A) 14.2 mm, (B) 13.1 mm)

Convex part (retread indicator):
The comparative tire 1 was not provided with a convex portion (retread indicator).
Further, in the comparative example tires 2 and 3, the convex portions of the first embodiment at various x2 shown in Table 1 are provided in the lateral region of the width direction groove 16 a (branch position from the circumferential groove 7 a). 20 was provided. In addition, the groove width center line of the circumferential grooves 7a and 7b is 0.325 W away from both the tire equator (A) and (B), and the groove width center line of the circumferential grooves 5 and 6 is from the tire equator (A ) And (B) are 0.13 W apart.
In Example tires 1-4, the convex part 20 of 1st Embodiment was provided in the width direction groove | channel 15 in a center area by various h2 shown in Table 1. In FIG. In the arrangement described with reference to FIG. 5, the circumferential groove side end of the convex portion is 2 mm away from the branch position where the width direction groove branches from the circumferential groove, and the opposite end is from the intersection P (A). At 12.4 mm and at (B) at 10.9 mm.
About the convex part of Comparative Examples 2 and 3 and Examples 1-4, it is y = 1.5mm and z = 5mm.

(Evaluation of the ratio that can be used as a base tire)
Each tire is mounted on an applicable rim (rim width: (A) 7.50, (B) 6.00) defined in the JATMA standard, internal pressure (A) 900 kPa, (B) 700 kPa, load (A) 1.6 t, (B) For Comparative Example 1, when the raised portion is exposed to the tread surface of the tread portion, Comparative Example 2, 3 and Examples 1 to 4 have the convex portion from the tread surface of the tread portion. It was removed when it disappeared, and it was examined whether it could be used as a retread base tire. For each comparative example and example, an experiment was performed with 110 tires in (A) and 160 tires in (B), and the ratios that can be used as stand tires are shown in Table 1 as evaluation results.

(Evaluation of service life before retreading)
Further, the time from the start of running until the convex part disappears from the tread part tread (the time until the raised part is exposed in Comparative Example 1) is measured, and the index display with Comparative Example 1 as 100 indicates “the service life of the tire. (Primary life exhaustion feeling) "was evaluated and shown in Table 1. In addition, it shows that the service life of a tire is excellent, so that a numerical value is large.

(Evaluation of secondary life)
Further, among the 110 tires in (A) and 160 tires in (B), the tires that could be retreaded were retreaded until the failure occurred or if no failure occurred, the remaining grooves 1. Further running was performed until the 6 mm tread wear indicator was exposed (secondary life running). And, for tires that were not retreaded, the primary life running time was calculated for the tires that were retreaded, and the sum of the primary life running time and the primary life running time was calculated, and the average value of all tires was taken. The service life (secondary life) of the tire including after retreading was calculated and is shown in Table 1 in index notation with Comparative Example 1 as 100. This secondary life shows that it is so excellent that a numerical value is large.

  Comparing Comparative Example 1 and Examples 1 to 4, it is possible to increase the ratio that can be used as a base tire by providing an indicator for retreading as the convex portion 20 that disappears earlier than the treadwear indicator is exposed. It was. Here, the service life (primary) of the tire is naturally an index smaller than that of the comparative example 1, but is a minimum of 83 when the comparative example 1 is 100, and is within a range in which there is no problem in consideration of subsequent retreading. . Since the primary service life of the tire is shorter when the primary life is terminated early in order to reliably retread without providing the retread indicator, Examples 1 to 5 are retreads. The probability of being able to be used as a retreaded base tire could be improved without sacrificing the service life of the previous tire.

  Further, from Examples 1 to 4, a preferable result is obtained when the value of d1-x2 is 3.0 mm or more. Particularly, when 3.2 mm is set (Example 1), the probability that it can be used as a base tire is remarkably increased. I understand. This tendency was the same in the case of different tire sizes as in Examples 5-8.

(Example tire 9)
Example 2 is the same as Example tire 9 in the case where the circumferential groove side end portion of the convex portion is made coincident with the branch position with respect to the arrangement of the second raised portions described in FIG. The experiment was conducted. The ratio that can be used as a base tire was the same as in Example 2, but some uneven wear occurred starting from the convex portion, and the tire life until the retread was slightly reduced.

(Example tire 10)
A similar experiment was conducted using the pneumatic tire provided with projections and depressions of 0.3 to 0.5 mm shown in FIG. 6 as the example tire 10 under the same conditions as the example tire 1. The ratio that can be used as the base tire is the same as in Example 2. When the retread indicator was observed, it was confirmed that the visibility of the convex portion was higher.

  Similar results are obtained for the second pneumatic tire.

  According to the present invention, before the tread wear indicator is exposed to the tread portion tread due to wear of the tread portion, the convex portion or the recess provided in the groove wall of the width direction groove in the central region disappears or is exposed to the tread portion tread. To encourage retreading. For this reason, it has become possible to remarkably improve the probability that the tire can be used as a retread base tire without significantly sacrificing the service life of the tire before retreading.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Central area of tread part 5 Circumferential groove | channel (1st tread groove)
5a Opening end position of circumferential groove 5b Groove bottom of circumferential groove 6, 7a, 7b Circumferential groove 10 Raised portion 10a Top surface of raised portion 15 Width direction groove (second tread groove)
15a Opening end position of width direction groove 15b Width direction groove bottom 15c Width direction groove groove wall 16a, 16b Width direction groove 20 Convex part 20a Convex part lower end 20d Convex part upper end 30 Concave part 30a Concave bottom part

Claims (8)

A plurality of tread grooves are provided in the tread portion. Among the plurality of tread grooves, on the groove bottom of the first tread groove, which is a predetermined tread groove, from the opening end position of the first tread groove in the tire radial direction. A pneumatic tire having a raised portion that is a treadwear indicator having a top surface with a measured distance of x1,
The plurality of tread grooves include a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of width direction grooves extending in the tire width direction,
Of the plurality of widthwise grooves, the groove wall of the second tread groove that is a predetermined widthwise groove provided in the central region of the tread portion has a convex portion or a concave portion,
The lower end of the convex portion or the concave portion is a position at a distance x2 shorter than the x1 when measured in the tire radial direction from the opening end position of the second tread groove,
The pneumatic tire according to claim 1, wherein the convex portion or the concave portion is a retread indicator that disappears when the tread portion is worn by a thickness corresponding to the distance x2. A plurality of tread grooves are provided in the tread portion. Among the plurality of tread grooves, on the groove bottom of the first tread groove, which is a predetermined tread groove, from the opening end position of the first tread groove in the tire radial direction. A pneumatic tire having a raised portion that is a treadwear indicator having a top surface with a measured distance of x1,
The plurality of tread grooves include a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of width direction grooves extending in the tire width direction,
Of the plurality of widthwise grooves, the groove wall of the second tread groove that is a predetermined widthwise groove provided in the central region of the tread portion has a convex portion or a concave portion,
The upper end of the convex portion or the concave portion is a position at a distance x2 shorter than x1 when measured in the tire radial direction from the opening end position of the second tread groove, and the lower end of the convex portion or the concave portion is the first 2 outside the tread groove bottom in the tire radial direction,
The pneumatic tire according to claim 1, wherein the convex portion or the concave portion is a retread indicator that is exposed on the tread surface when the tread portion is worn by a thickness corresponding to the distance x2.   The pneumatic tire according to claim 1 or 2, wherein a value of d1-x2 is 3.0 mm or more, where d1 is a groove depth of the first tread groove. The first tread groove is a circumferential groove provided in a central region of the tread portion,
The second tread groove is a width direction groove branched from a groove wall of the circumferential groove,
The convex portion or the concave portion is a position away from a branch position from the groove wall of the circumferential groove in a front view of the tread portion tread surface, and a groove wall line of the groove wall where the convex portion or the concave portion is provided. The pneumatic tire according to any one of claims 1 to 3, provided at a position within 15 mm in the groove wall line direction from an intersection with a groove width center line of the circumferential groove.   5. The pneumatic tire according to claim 1, wherein two or more of the convex portions or the concave portions are provided at a predetermined interval on the same tire circumferential line.   The maximum displacement amount y of the convex portion or the concave portion from the groove wall of the second tread groove is 1/10 or more and 1/5 or less of the groove width w of the second tread groove. A pneumatic tire given in any 1 paragraph. The maximum displacement part of the convex part or the concave part forms a plane,
The pneumatic tire according to any one of claims 1 to 6, wherein unevenness is further provided on the plane.   The pneumatic tire according to any one of claims 1 to 7, wherein the convex portion or the concave portion has a curved surface shape at a portion intersecting with a groove wall of the second tread groove.