JP2014234134A - Tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire capable of not only suppressing the occurrence of distortion of a side part but also suppressing the formation and advance of an ozone crack.SOLUTION: A tire 1 includes a side part that has a recess 51 depressed inward in a tire width direction TW in a cross section along the tire width direction TW and a tire diameter direction TR. The recess 51 has inside and outside side rubber layers 55 and 54. An elastic modulus of the inside side rubber layer 55 is higher than that of the outside side rubber layer 54.

Description

  The present invention relates to a tire having a tread portion and a pair of side portions and configured to be assembled to a rim flange.

  2. Description of the Related Art Conventionally, in order to reduce the weight of a tire, a tire is proposed that includes a side portion having a concave portion that is recessed inward in the tire width direction in a cross section along the tire width direction and the tire radial direction. In such a tire, since the side portion is easily distorted by forming the concave portion, the organic fiber is disposed in the vicinity of the surface of the concave portion for the purpose of reinforcing the side portion.

JP 2010-1332075 A

  By the way, in the tire mentioned above, since the rubber | gum which comprises a recessed part is thin, an ozone crack may arise. However, only the point which suppresses generation | occurrence | production of the distortion of a side part is considered in the tire mentioned above.

  Therefore, the present invention has been made to solve the above-described problems, and in addition to suppressing the occurrence of distortion of the side portion, a tire that can suppress the occurrence and progress of ozone cracks. The purpose is to provide.

  The tire according to the first feature has a tread portion and a pair of side portions, and is configured to be assembled to a rim flange. The tire has a pair of bead cores and a toroidal shape straddling the pair of bead cores, and includes a carcass layer that forms a skeleton of the tread portion and the pair of side portions. Each of the pair of side portions has a recess that is recessed inward in the tire width direction in a cross section along the tire width direction and the tire radial direction. The recess includes an outer side rubber layer that forms a tire surface, and an inner side rubber layer that is positioned on the inner side of the outer side rubber layer in the tire width direction. The elastic modulus of the inner side rubber layer is higher than the elastic modulus of the outer side rubber layer.

  In the first feature, the lower end of the recess is based on the reference when the outer side in the tire radial direction is a positive region and the inner side in the tire radial direction is a negative region with respect to the upper end of the rim flange. On the other hand, it is located in the range of -5 mm or more and +10 mm or less.

  In the first feature, the elastic modulus of the outer side rubber is 2.0 MPa or more and 100 MPa or less and 2.4 MPa or less. The elastic modulus of the inner side rubber is 2.6 MPa or more and 3.0 MPa or less at 100% modulus.

  In the first feature, the inner side rubber has a length of 30 mm or more as a surface length along the tire surface in the tire radial direction.

  1st characteristic WHEREIN: The thickness of the said inner side rubber layer in the said tire width direction is the inside side rubber in the said tire width direction in the range of 10 mm or more and 30 mm or less toward the outer side of the said tire radial direction from the lower end of the said recessed part. 30% or more and 50% or more of the sum of the thickness of the layer and the thickness of the outer side rubber layer.

  1st characteristic WHEREIN: The said recessed part contains the most recessed part in which the said tire surface is dented in the innermost side with respect to the line which connects the upper end of the said recessed part, and the lower end of the said recessed part. The inner side rubber is thickest at the most recessed portion, and is thinner as it is away from the most recessed portion in the tire radial direction.

  ADVANTAGE OF THE INVENTION According to this invention, in addition to suppressing generation | occurrence | production of the distortion of a side part, the tire which makes it possible to suppress generation | occurrence | production and progress of an ozone crack can be provided.

FIG. 1 is a cross-sectional view showing a tire 1 according to the first embodiment. FIG. 2 is a cross-sectional view showing the tire 1 according to the first modification. FIG. 3 is a diagram showing the evaluation results.

  Hereinafter, a tire according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Outline of Embodiment]
The tire of the embodiment has a tread portion and a pair of side portions, and is configured to be assembled to a rim flange. The tire has a pair of bead cores and a toroidal shape straddling the pair of bead cores, and includes a carcass layer that forms a skeleton of the tread portion and the pair of side portions. Each of the pair of side portions has a recess that is recessed inward in the tire width direction in a cross section along the tire width direction and the tire radial direction. The recess includes an outer side rubber layer that forms a tire surface, and an inner side rubber layer that is positioned on the inner side of the outer side rubber layer in the tire width direction. The elastic modulus of the inner side rubber layer is higher than the elastic modulus of the outer side rubber layer.

  In the embodiment, the recess has an inner side rubber layer and an outer side rubber layer, and the elastic modulus of the inner side rubber layer is higher than the elastic modulus of the outer side rubber layer. Therefore, since the recess is reinforced by the inner side rubber layer having an elastic modulus higher than that of the outer side rubber layer, occurrence of distortion of the tire side portion (recess) is suppressed. Moreover, since the recess is reinforced by the inner side rubber layer having an elastic modulus higher than the elastic modulus of the outer side rubber layer instead of the arrangement of the organic fibers, resistance to ozone cracks is also improved.

  As described above, while reducing the weight by forming the concave portion, in addition to suppressing the occurrence of distortion of the side portion, the occurrence and progress of ozone cracks can be suppressed.

[First Embodiment]
(Tire composition)
Hereinafter, the tire according to the first embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a tire 1 according to the first embodiment. Specifically, FIG. 1 shows a cross section along the tire width direction TW and the tire radial direction TR.

  Here, the tire 1 has a pair of bead portions assembled to the rim flange, a side portion continuous to the pair of bead portions outside the tire radial direction TR, and a tread portion having a tire tread surface. However, in FIG. 1, a side part and a tread part are abbreviate | omitted and the bead part of one side is demonstrated among a pair of bead parts.

  As shown in FIG. 1, the tire 1 includes a pair of bead portions 10 (only the left side is shown in FIG. 1), a carcass layer 20, and a reinforcing layer 30. The tire 1 is configured to be assembled to a rim flange RF of a rim.

  Each bead unit 10 includes a bead core 12 and a bead filler 14. The bead core 12 is provided to fix the tire 1 to the rim flange RF. The bead core 12 is configured by a bead wire (not shown). The bead filler 14 is provided to increase the rigidity of the bead portion 10.

  In the first embodiment, the bead filler 14 includes a first bead filler 14A and a second bead filler 14B. The first bead filler 14 </ b> A covers the bead core 12 and is disposed adjacent to the bead core 12. The second bead filler 14B is disposed adjacent to the first bead filler 14A.

  The carcass layer 20 has a toroidal shape straddling between the pair of bead portions 10 (bead cores 12). The carcass layer 20 forms a skeleton of a tread portion and a side portion, and is folded back to the outside in the tire width direction TW by a bead core 12. Specifically, the carcass layer 20 is folded back while wrapping the bead core 12 and the bead filler 14. The carcass layer 20 turned back at the bead portion 10 extends along the tire radial direction TR.

  The reinforcing layer 30 is provided on the outer side of the carcass layer 20, and is folded back to the outer side in the tire width direction TW by the bead core 12. The reinforcing layer 30 reinforces the carcass layer 20.

  The side portions are formed at both ends of the tread portion in the tire width direction TW. Each side part has the recessed part 51 dented inside the tire width direction TW in the cross section along the tire width direction TW and the tire radial direction TR. In FIG. 1, the upper end of the recess 51 is represented by the upper end 51Ue and the lower end 51Le of the recess 51. The upper end 51Ue is a boundary between the tire surface in the region above the recess 51 and the tire surface of the recess 51 in the tire radial direction TR, and is a position where the curvature of the tire surface is reversed. Similarly, the lower end 51Le is a boundary between the tire surface in a portion below the recess 51 and the tire surface of the recess 51 in the tire radial direction TR, and is a position where the curvature of the tire surface is reversed.

  In the first embodiment, the lower end 51Le is based on the reference X when the upper end of the rim flange is a reference X and the outer side of the tire radial direction TR is a positive region and the inner side of the tire radial direction TR is a negative region. It is located in the range of −5 mm or more and +10 mm or less. Since the lower end 51Le is provided at a position of −5 mm or more with respect to the reference X, the gap between the rim flange RF and the bead portion 10 caused by the formation of the recess 51 does not become too large. Accordingly, the gap between the rim flange RF and the bead portion 10 is reduced by applying a load, and the bead portion 10 is prevented from falling. On the other hand, since the lower end 51Le is provided at a position of +10 mm or less with respect to the reference X, the length of the recess 51 in the tire radial direction TR can be sufficiently secured, and the weight of the tire 1 can be reduced.

  In the first embodiment, the recess 51 includes an outer side rubber layer 54 that forms the tire surface, and an inner side rubber layer 55 that is located on the inner side of the outer side rubber layer 54 in the tire width direction TW.

  The outer side rubber layer 54 is provided from the vicinity of the lower end 51Le of the recess 51 to the tread portion in the tire radial direction TR. The inner side rubber layer 55 is provided between the lower end 51Le of the recess 51 and the upper end 51Ue of the recess 51 in the tire radial direction TR. The elastic modulus of the inner side rubber layer 55 is higher than the elastic modulus of the outer side rubber layer 54.

  For example, the elastic modulus of the inner side rubber layer 55 is 2.6 MPa or more at 100% modulus and 3.0 MPa or less, and the elastic modulus of the outer side rubber layer 54 is 2.0 MPa or more at 100% modulus, and The pressure is preferably 2.4 MPa or less.

  Here, when the elastic modulus of the inner side rubber layer 55 is not less than 2.6 MPa at 100% modulus, the deflection of the side portion is suppressed and durability can be ensured. When the elastic modulus of the inner side rubber layer 55 is 100 MPa and 3.0 MPa or less, the exothermic deterioration is suppressed. When the elastic modulus of the outer side rubber layer 54 is 100 MPa and 2.0 MPa or more, cut resistance can be ensured. When the elastic modulus of the outer side rubber layer 54 is 100% modulus and 2.4 MPa or less, generation and progress of ozone cracks are suppressed.

  In the first embodiment, the inner side rubber layer 55 preferably has a length of 30 mm or more as a surface length along the tire surface in the tire radial direction TR. By arranging the inner side rubber layer 55 having a surface length of 30 mm or more, the occurrence of distortion of the side portion is effectively suppressed.

  In the first embodiment, the inner side rubber layer 55 in the tire width direction TW has a thickness in the range of 10 mm or more and 30 mm or less from the lower end 51Le of the recess 51 toward the outer side in the tire radial direction TR. It is preferably 30% or more and 50% or more of the sum of the thickness of the layer 55 and the outer side rubber layer 54 (hereinafter, the total thickness). When the thickness of the inner side rubber layer 55 is 30% or more of the total thickness, the side portion can be sufficiently reinforced, and the occurrence of distortion of the side portion can be suppressed. On the other hand, when the thickness of the inner side rubber layer 55 is 50% or less of the total thickness, the thickness of the outer side rubber layer 54 can be sufficiently maintained, and generation and progress of ozone cracks can be appropriately suppressed. .

  In the first embodiment, the recess 51 includes an indentation portion 51In in which the tire surface is recessed inwardly with respect to a line L connecting the upper end 51Ue of the recess 51 and the lower end 51Le of the recess 51. The inner side rubber layer 55 is preferably thickest at the most recessed portion 51In and thinner as it moves away from the most recessed portion 51In in the tire radial direction TR. That is, the thickness of the inner side rubber layer 55 is the thickest at the portion where the side portion is to be reinforced, and the rigidity step between the outer side rubber layer 54 and the inner side rubber layer 55 can be reduced at other portions.

(Function and effect)
In the first embodiment, the recess 51 has an inner side rubber layer 55 and an outer side rubber layer 54, and the elastic modulus of the inner side rubber layer 55 is higher than the elastic modulus of the outer side rubber layer 54. Accordingly, the concave portion 51 is reinforced by the inner side rubber layer 55 having an elastic modulus higher than the elastic modulus of the outer side rubber layer 54, and therefore, the occurrence of distortion of the side portion (the concave portion 51) is suppressed. In addition, since the concave portion 51 is reinforced by the inner side rubber layer 55 having an elastic modulus higher than that of the outer side rubber layer 54 instead of the arrangement of the organic fibers, the occurrence and progress of ozone cracks are suppressed.

  As described above, while reducing the weight by forming the recess 51, in addition to suppressing the occurrence of distortion of the side portion, the occurrence and progress of ozone cracks can be suppressed.

[Modification 1]
Hereinafter, Modification Example 1 of the first embodiment will be described. In the following, differences from the first embodiment will be described.

  In the first embodiment, the carcass layer 20 is folded while wrapping the bead core 12 and the bead filler 14, and the carcass layer 20 folded at the bead portion 10 extends along the tire radial direction TR.

  On the other hand, in the first modification, as shown in FIG. 2, the carcass layer 20 is folded while wrapping the bead core 12, and the carcass layer 20 folded by the bead portion 10 is wound around the bead core 12.

  FIG. 2 is a cross-sectional view showing the tire 1 according to the first modification. Specifically, FIG. 2 shows a cross section along the tire width direction TW and the tire radial direction TR, as in FIG. In FIG. 2, a side part and a tread part are abbreviate | omitted and the bead part of one side is demonstrated among a pair of bead parts.

[Evaluation results]
Hereinafter, the evaluation results will be described. Specifically, the samples shown below are prepared, and for each sample, the measured strain value (index), the ozone crack level measured value (index), the BF drum distance measured value (index), and the RR measured value (index). It was measured.

  As each sample, a sample according to a conventional example, a sample according to comparative example 1, and a sample according to example 1-9 were prepared. The sample which concerns on a prior art example is a tire which does not have the recessed part mentioned above. Although the sample which concerns on the comparative example 1 has the recessed part mentioned above, it does not have inner side rubber | gum, but is a tire which reinforced the recessed part with the organic fiber. The sample according to Example 1-9 is a tire having the above-described recess and inner side rubber. Each parameter according to Example 1-9 is as illustrated in FIG.

  The tire size of each sample is 295 / 75R22.5 / 14PR, and the applicable rim width of each sample is 8.25 inches.

(Strain measurement)
Each sample was pressed against the test drum, and the test drum was rotated under the condition of the dry road surface, and the distortion of the side portion was measured. The measurement result was represented by an index with the sample according to the conventional example as 100. Here, the larger the index, the smaller the distortion. Here, a case where the internal pressure of each sample is an internal pressure of 650 KPa and no load is applied (at the time of internal pressure), and a case where the internal pressure of each sample is an internal pressure of 650 KPa and a normal load is applied (at the time of load) About, the distortion of the side part was measured.

(Ozone crack level measurement)
Each sample was mounted on a vehicle (trailer) and the vehicle was run for 10 months to measure the ozone crack level. Since the road surface condition depends on the weather and the like, it is a dry road surface or a wet road surface. The measurement result was represented by an index with the sample according to the conventional example as 100. Here, the larger the index, the less the occurrence of ozone cracks. The ozone crack level is an area where ozone cracks occur in a certain area of the side portion.

(BF drum distance measurement)
Each sample was pressed against the test drum, the test drum was rotated under dry road conditions, and the travel distance until the bead portion was broken was measured. In addition, the load applied to each sample was increased stepwise. The measurement result was represented by an index with the sample according to the conventional example as 100. Here, the greater the index, the longer the travel distance.

(RR measurement value)
Each sample was pressed against the test drum, and the test drum was rotated under dry road conditions to measure rolling resistance. The measurement result was represented by an index with the sample according to the conventional example as 100. Here, the larger the index, the smaller the rolling resistance.

(Summary)
The test results described above are as shown in FIG. As shown in FIG. 3, in the comparative example 1, the strain measurement value (at the time of a load) improved by reinforcing a recessed part with an organic fiber compared with the prior art example. However, in Comparative Example 1, the strain measurement value (when loaded) and the ozone crack level measurement value were deteriorated as compared with the conventional example.

  On the other hand, in Example 1- Example 9, compared with the comparative example 1, a distortion measured value (at the time of load) and an ozone crack level measured value are more than an equivalent level. That is, in a sample according to an example having an inner side rubber layer having an elastic modulus higher than that of the outer side rubber layer in comparison between samples that are reduced in weight by forming a concave portion, the distortion (load) of the side portion is reduced. It was confirmed that generation and progress of ozone cracks can be suppressed in addition to suppressing occurrence of

  Here, in Example 2, since the elastic modulus of the inner side rubber layer is less than 2.6 MPa, the measured strain value (at the time of load) is 82, which is compared with the other Examples 1, 4, 5, 7, and 9. It was confirmed that the improvement of the measured strain value (at the time of loading) was insufficient. That is, the elastic modulus of the inner side rubber layer is preferably 2.6 MPa or more.

  In Example 8, since the elastic modulus of the outer side rubber layer is less than 2.0 MPa, the measured strain value (at the time of loading) is 81, and compared with the other Examples 1, 4, 5, 7, and 9, the strain It was confirmed that the measurement value (at the time of loading) was insufficiently improved. In Example 8, it was also confirmed that the measured BF drum distance deteriorated. That is, the elastic modulus of the outer side rubber layer is preferably 2.0 MPa or more.

  In Example 3, the thickness of the inner side rubber layer is 30% or less of the sum of the thickness of the inner side rubber layer and the outer side rubber layer in the range of 10 mm or more and 30 mm or less from the lower end of the recess toward the outer side in the tire radial direction. Therefore, the measured strain value (at the time of loading) is 79, and it is confirmed that the improvement of the measured strain value (at the time of loading) is insufficient compared to the other Examples 1, 4, 5, 7, and 9. It was. That is, the thickness of the inner side rubber layer is preferably 30% or more of the sum of the thickness of the inner side rubber layer and the outer side rubber layer.

  In Example 6, the thickness of the inner side rubber layer is 50% or less of the sum of the thickness of the inner side rubber layer and the outer side rubber layer in the range of 10 mm to 30 mm from the lower end of the recess toward the outer side in the tire radial direction. Therefore, the ozone crack level measured value was 88, and it was confirmed that the improvement of the ozone crack level measured value was insufficient as compared with other Examples 1-5, 7, and 8. That is, the thickness of the inner side rubber layer is preferably 50% or less of the sum of the thickness of the inner side rubber layer and the thickness of the outer side rubber layer.

  In Example 7, since the inner side rubber layer has a length of 30 mm or more as the surface length along the tire surface in the tire radial direction, the strain measurement value (at the time of internal pressure) is improved, and good results are also obtained with other characteristics. Obtained.

[Other Embodiments]
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment, the case where the inner side rubber layer 55 is constituted by one rubber layer is illustrated. However, the embodiment is not limited to this. The inner side rubber layer 55 may be composed of two or more rubber layers having different elastic moduli.

  DESCRIPTION OF SYMBOLS 1 ... Tire, 10 ... Bead part, 12 ... Bead core, 14 ... Bead filler, 20 ... Carcass layer, 30 ... Reinforcement layer, 51 ... Recessed part, 51Ue ... Upper end, 51Le ... Lower end, 51In ... Most recessed part

Claims (6)

A tire having a tread portion and a pair of side portions and configured to be assembled to a rim flange;
A pair of bead cores,
Having a toroidal shape straddling between the pair of bead cores, and comprising a carcass layer forming a skeleton of the tread portion and the pair of side portions,
Each of the pair of side portions has a recess recessed inward in the tire width direction in a cross section along the tire width direction and the tire radial direction,
The concave portion has an outer side rubber layer that forms a tire surface, and an inner side rubber layer that is positioned inside the outer side rubber layer in the tire width direction,
The tire according to claim 1, wherein an elastic modulus of the inner side rubber layer is higher than an elastic modulus of the outer side rubber layer.   The lower end of the recess is -5 mm or more and +10 mm with respect to the reference when the outer side in the tire radial direction is a positive region and the inner side in the tire radial direction is a negative region with respect to the upper end of the rim flange. The tire according to claim 1, which is located in the following range. The elastic modulus of the inner side rubber is not less than 2.0 MPa and not more than 2.4 MPa at 100% modulus,
The tire according to claim 1 or 2, wherein the elastic modulus of the outer side rubber is 2.6 MPa or more and 3.0 MPa or less at 100% modulus.   The tire according to any one of claims 1 to 3, wherein the inner side rubber has a length of 30 mm or more as a surface length along the tire surface in the tire radial direction.   The thickness of the inner side rubber layer in the tire width direction is within the range of 10 mm to 30 mm from the lower end of the recess toward the outer side in the tire radial direction. The tire according to any one of claims 1 to 3, wherein the tire is 30% or more and 50% or more of a sum of thicknesses of the side rubber layers. The concave portion includes an innermost recessed portion where the tire surface is recessed inwardly with respect to a line connecting the upper end of the concave portion and the lower end of the concave portion,
The tire according to any one of claims 1 to 5, wherein the inner side rubber is thickest at the most recessed portion and is thinner as it is away from the most recessed portion in the tire radial direction.

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