JP2011162047A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire enhancing the durability by a different structure from a conventional one. <P>SOLUTION: The pneumatic tire includes a main groove extending in the tire circumferential direction with its width ≥8.0 mm, a plurality of sub grooves extending in the tire circumferential direction, and each having a narrow part with its width ≥1.5 mm and <4.0 mm, and a wide part with its width being ≥4.0 mm and <8.0 mm, and a plurality of lug grooves extending from the wide part of the first sub groove to the wide part of the second sub groove in an inclined manner with respect to the tire width direction while one of the pair of adjacent sub grooves out of the plurality of sub grooves is defined as the first sub groove, and the other is defined as the second sub groove. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with improved durability.

  Heavy duty tires used for buses and trucks are required to have excellent durability in order to run at high speeds under high loads. However, depending on the conditions of use of the tire, the groove bottom of the tire may crack, and the groove bottom of the tread rubber may be damaged. Further, heat is generated by a large interlaminar shear strain received by the edge portion of the belt layer, and the edge portion of the belt layer is peeled off by this heat. Furthermore, the adhesion between the tread rubber and the belt layer may deteriorate, and belt edge separation may occur in which the tread rubber is peeled off from the belt layer.

  In order to release the heat generated in the belt layer to the outside of the tire, a pneumatic tire is proposed in which a rubber layer made of a heat conductive rubber composition is interposed between the edge portion of the belt layer and the outermost carcass layer. (Patent Document 1).

JP 2004-359096 A

On the other hand, when the pneumatic tire contacts the road surface, compressive strain concentrates on the groove bottom of the pneumatic tire, and heat is also generated at the groove bottom of the pneumatic tire. It is considered that heat generated at the groove bottom of the pneumatic tire is also a factor that decreases durability.
However, according to the conventional pneumatic tire, the heat generated at the belt edge can be released to the outside of the tire, but the patent document does not consider the heat generated at the groove bottom of the pneumatic tire.

  An object of this invention is to provide the pneumatic tire which improves durability by the structure different from the past.

  The pneumatic tire of the present invention has a main groove extending in the tire circumferential direction and having a width of 8.0 mm or more, and a narrow portion extending in the tire circumferential direction and having a width of 1.5 mm or more and less than 4.0 mm. A plurality of sub-grooves having a width of 4.0 mm or more and less than 8.0 mm, and of the plurality of sub-grooves, one of the adjacent sub-grooves is a first sub-groove and the other is a first sub-groove. When the two sub-grooves are provided, a plurality of lug grooves extending from the wide portion of the first sub-groove to the wide portion of the second sub-groove inclining with respect to the tire width direction are provided.

Moreover, it is preferable that the width | variety of the said lug groove is 3 mm or more.
Moreover, it is preferable that the cross-sectional area of the said lug groove is 50% or more of the cross-sectional area of the said wide part.
The depth of the lug groove is preferably equal to the depth of the wide portion.
Moreover, it is preferable that the angle | corner which the said lug groove and the said secondary groove make is 20 to 85 degree | times.
The narrow portion and the wide portion are alternately formed in the sub-groove along the tire circumferential direction, and the wide portion of the first sub-groove and the wide portion of the second sub-groove are mutually in the tire circumferential direction. It is preferable to be positioned so as to be displaced.
Further, when the outer side of the main groove or the sub-groove formed on the outermost side in the tire width direction is a shoulder region, the interval between the pair of adjacent sub-grooves is not less than 1/4 of the width of the shoulder region. It is preferable that it is 1/2 or less.
It is preferable that at least two main grooves are provided.

  According to the pneumatic tire of the present invention, durability can be improved.

It is an expanded view showing an example of the tread pattern of the pneumatic tire of an embodiment. (A) is sectional drawing along the AA line shown in FIG. 1 at the time of non-grounding, (b) is sectional drawing along the AA line shown in FIG. 1 at the time of grounding. (A) is sectional drawing along the BB line shown in FIG. 1 at the time of non-grounding, (b) is sectional drawing along the BB line shown in FIG. 1 at the time of grounding. It is an expanded view which shows the tread pattern of the pneumatic tire of a prior art example. It is an expanded view which shows the tread pattern of the pneumatic tire of a comparative example and an example.

<Embodiment>
Hereinafter, the pneumatic tire of this embodiment will be described in detail.
The pneumatic tire of the present embodiment can be applied to heavy duty tires for trucks and buses defined in Chapter C of JATMA YEAR BOOK 2008 (Japan Automobile Tire Association Standard). In addition to heavy-duty tires, the present invention can also be applied to passenger car tires specified in Chapter A and small truck tires specified in Chapter B.

  First, the tread pattern of the pneumatic tire of this embodiment will be described with reference to FIG. FIG. 1 is a development view showing an example of a tread pattern of the pneumatic tire of the present embodiment. The vertical direction in FIG. 1 indicates the tire circumferential direction. Moreover, the horizontal direction of FIG. 1 shows a tire width direction. CL indicates a tire equator line. As shown in FIG. 1, the pneumatic tire of this embodiment includes a plurality of circumferential grooves 10 and 20 extending in the tire circumferential direction and a plurality of lug grooves 30 extending in the tire width direction.

  In the following description, the tire circumferential direction is a direction that rotates around the rotation axis of the pneumatic tire as the center of rotation. The tire width direction is a direction parallel to the rotation axis of the pneumatic tire. Further, the outward in the tire width direction is a direction away from the tire equator line CL in the tire width direction. The inner side in the tire width direction is a direction approaching the tire equator line CL in the tire width direction.

In the following description, a groove having a width of 8.0 mm or more among the circumferential grooves is referred to as a “main groove”, and a groove having a width of less than 8.0 mm is referred to as a “sub-groove”. The pneumatic tire shown in FIG. 1 includes one main groove 10 and four sub grooves 20.
Here, the circumferential grooves are not limited to linear grooves parallel to the tire equator line CL as shown in FIG. The circumferential grooves include, for example, grooves that are inclined at an angle within ± 35 degrees with respect to the tire equator line CL.

  As shown in FIG. 1, the sub-groove 20 of the present embodiment includes a narrow portion 22 having a width of 1.5 mm or more and less than 4.0 mm, and a wide portion 24 having a width of 4.0 mm or more and less than 8.0 mm. And comprising. When attention is paid to one sub-groove 20, narrow portions 22 and wide portions 24 are alternately formed in the tire circumferential direction. Moreover, when paying attention to a pair of adjacent sub-grooves 20 (for example, two sub-grooves on the left side of the tire equator line CL in FIG. 1) among the plurality of sub-grooves 20, the tire circumferential direction in which the wide portion 24 is formed. A pair of adjacent sub-grooves are formed so that the positions of each other are shifted from each other.

  The lug groove 30 is inclined with respect to the tire width direction from the wide portion 24 of one of the adjacent subgrooves (first subgroove) to the wide portion 24 of the other subgroove (second subgroove). And extend. The angle formed by the lug groove 30 and the sub groove 20 is preferably 20 degrees or more and 85 degrees or less. For example, as shown in FIG. 1, when the secondary groove 20 is parallel to the tire equator line CL, the angle formed by the lug groove 30 and the tire circumferential direction is inclined at an angle of 20 degrees to 85 degrees. It is preferable. When the angle formed by the lug groove 30 and the sub-groove 20 is not less than 20 degrees and not more than 85 degrees, the wet performance is improved as described later.

  Moreover, it is preferable that the width | variety of the lug groove 30 is 3 mm or more. The cross-sectional area of the lug groove 30 is preferably 50% or more of the cross-sectional area of the wide portion 24. In addition, the depth of the lug groove 30 is preferably equal to the depth of the wide portion 24. When the lug groove 30 satisfies each of these conditions, the wet performance is improved as will be described later.

Moreover, it is preferable that the space | interval W of a pair of adjacent subgroove is 1/4 or more and 1/2 or less of the width | variety of shoulder region Ts.
Here, the shoulder region Ts is more outward in the tire width direction than the circumferential grooves 10 and 20 formed on the outermost side in the tire width direction, and more inward in the tire width direction than the ground contact end in the tire width direction. It is an area. The grounding end in the tire width direction is a pneumatic tire mounted on an applicable rim defined in JATMA YEAR BOOK 2008 (Japan Automobile Tire Association Standard). In a state where a load corresponding to 88% of the maximum load capacity is applied, the tread surface is an end portion that contacts the road surface. In the case of tires other than those for passenger cars, the tread surface is an end portion that contacts the road surface in a state where an air pressure corresponding to the maximum load capacity defined by JATMA and a load corresponding to the maximum load capacity are loaded.

Next, with reference to FIG. 2 and FIG. 3, the effect | action of the pneumatic tire of this embodiment is demonstrated. 2A is a cross-sectional view taken along the line AA shown in FIG. 1 when the pneumatic tire is not in contact with the road surface R (when not in contact with the road surface R), and FIG. FIG. 2 is a cross-sectional view taken along line AA shown in FIG. 1 when a tire is in contact with a road surface R (at the time of contact). 3A is a cross-sectional view taken along the line BB shown in FIG. 1 when not grounded, and FIG. 3B is a cross-sectional view taken along the line BB shown in FIG. 1 when grounded. It is.
As described above, in the pneumatic tire of the present embodiment, a pair of adjacent sub-grooves are formed so that the positions in the tire circumferential direction where the wide portion 24 is formed are shifted from each other. Therefore, as shown in FIG. 2A, the pair of adjacent sub-grooves 20 are formed such that the narrow portion 22 and the wide portion 24 are paired in a cross section along the tire width direction.

As shown in FIG. 2B, when the pneumatic tire contacts the road surface R, compression distortion occurs in the tire width direction due to the wiping action of the tire. In the present embodiment, since the pair of sub-grooves 20 are formed in the pneumatic tire, the distortion generated in the groove bottom can be dispersed in each sub-groove 20. Therefore, the strain energy generated at the groove bottom of the pneumatic tire is dispersed, and heat generation due to the strain energy is suppressed.
Moreover, in this embodiment, when the width | variety of the narrow part 22 of the subgroove 20 is 1.5 mm or more and less than 4.0 mm, when a pneumatic tire contacts the road surface R, the groove wall of the narrow part 22 is formed. It is possible to reduce distortion generated at the groove bottom of the pneumatic tire by contacting each other. Therefore, the strain energy to the groove bottom is dispersed, and heat generation due to the strain energy generated at the groove bottom of the pneumatic tire is suppressed.
In the present embodiment, since the width of the wide portion 24 of the sub-groove 20 is 4.0 mm or more and less than 8.0 mm, the groove walls of the wide portion 24 come into contact with each other when the pneumatic tire contacts the road surface R. And the groove does not collapse. Therefore, when the pneumatic tire contacts the road surface R, it is possible to suppress a decrease in drainage due to the crushing of the groove.

  As shown in FIG. 3A, in the cross section along the tire width direction, the narrow portion 22 of the pair of adjacent sub-grooves 20 (first sub-grooves) and the other sub-groove 20 (second sub-groove). There is a place where the narrow portion 22 of the groove) is formed in a pair. In such a place, the lug groove 30 is formed between the pair of narrow portions 22. Therefore, as described above, when the pneumatic tire contacts the road surface R, the groove of the lug groove 30 is crushed as shown in FIG. There is nothing. Therefore, it is possible to suppress a decrease in drainage due to the crushing of the groove when the pneumatic tire contacts the road surface R.

In particular, by setting the width of the lug groove 30 to 3 mm or more, it is possible to suppress a decrease in drainage due to the crushing of the groove when the pneumatic tire contacts the road surface R.
In addition, by setting the cross-sectional area of the lug groove 30 to 50% or more of the cross-sectional area of the wide part 24, water flowing through the wide part 24 can be efficiently drained into the lug groove 30. In addition, in order to improve drainage more, it is more preferable that the cross-sectional area of the lug groove 30 is 80% or more of the cross-sectional area of the wide portion 24.
In addition, by making the depth of the lug groove 30 equal to the depth of the wide portion 24, drainage can be effectively performed without stopping the flow of water at the portion where the wide portion 24 and the lug groove 30 are coupled. it can.
Moreover, when the angle formed by the lug groove 30 and the sub-groove 20 is 20 degrees or more and 85 degrees or less, the water flowing through the wide portion 24 can be efficiently drained into the lug groove 30.

  As described above, according to the pneumatic tire of the present embodiment, heat generated by the strain energy generated at the groove bottom of the pneumatic tire can be suppressed by dispersing the strain energy concentrated on the groove bottom. Further, according to the pneumatic tire of the present embodiment, even when the pneumatic tire contacts the road surface R and the groove walls of the narrow portion 22 contact each other, as shown by the arrows in FIG. And the drainage channel formed by the lug groove 30 can suppress a decrease in drainage.

  In the present embodiment, as shown in FIG. 1, an example in which one main groove 10 and four sub-grooves 20 are formed as circumferential grooves has been described. However, the number of circumferential grooves is as follows. It is not limited to this. For example, a plurality of main grooves 10 may be formed. Further, it is sufficient that at least two sub-grooves 20 are formed.

  Further, in the present embodiment, as illustrated in FIG. 1, the example in which the main groove 10 is formed on the tire equator line CL and the pair of sub grooves 20 is formed on both sides of the main groove 10 has been described. The arrangement of the main groove 10 and the sub-groove 20 is not limited to this. For example, a pair of sub-grooves 20 may be formed near the tire equator line CL, and the main groove 10 may be formed outward of the pair of sub-grooves 20 in the tire width direction.

  Further, in the present embodiment, as shown in FIG. 1, the wide portion 24 of one sub-groove (first sub-groove) of the pair of adjacent sub-grooves to the wide portion of the other sub-groove (second sub-groove). Although the example in which the lug groove 30 extending obliquely with respect to the tire width direction has been described has been described, the groove extending in the tire width direction is not limited thereto. In addition to the lug grooves 30 described in the present embodiment, grooves and sipes extending in the tire width direction may be further formed.

  The test which confirms the effect of this invention was done using the various pneumatic tires. The tire size is 1100R20.

(durability)
Each tire was prepared with a JATMA prescribed rim and air pressure at maximum load, and each tire was attached to an indoor drum testing machine (drum diameter: 1707 mm). The vehicle was run for 2 hours at a load corresponding to 85% of the maximum load capacity specified by JATMA at a speed of 45 km / h at an ambient temperature of 30 ° C. Thereafter, a slip angle of ± 2 ° (0.1 Hz sin wave) was applied, the load was increased stepwise by 5% every 24 hours, and the travel distance until the failure occurred was measured. The evaluation results are indicated by an index with the conventional example being 100. The larger the index value, the better the durability.

(Wet performance)
Each tire is mounted on the front wheel of a 2-D vehicle, and full braking is applied at a speed of 45 km / h on a wet road surface test course under the pneumatic conditions specified in JATMA YEAR BOOK 2008 (Japan Automobile Tire Association Standard). The distance to stop was measured. The evaluation results are indicated by an index with the conventional example being 100. It means that wet performance is excellent, so that this index value is large.

(Conventional example, Comparative examples 1 and 2, Examples 1 to 3)
The effect of changing the width of the narrow portion 22 was examined using the conventional examples, comparative examples 1 and 2, and examples 1 to 3.
First, a conventional pneumatic tire will be described with reference to FIG. FIG. 4 is a development view showing a tread pattern of a conventional pneumatic tire. The vertical direction in FIG. 4 indicates the tire circumferential direction. Moreover, the horizontal direction of FIG. 4 shows a tire width direction. As shown in FIG. 4, the conventional pneumatic tire includes a main groove 10 extending in the tire circumferential direction and a sub-groove 20. 4 has a width of 207 mm, a width of the main groove 10 of 13 mm, a width of the sub-groove 20 of 3.0 mm, a distance between a pair of adjacent sub-grooves 20 of 15 mm, and a width of the shoulder region Ts of 36 mm. . The depth of the main groove 10 is 14 mm, and the depth of the sub-groove 20 is 14 mm.

Next, with reference to FIG. 5, the pneumatic tire of each comparative example and each example will be described. FIG. 5 is a development view showing a tread pattern of each comparative example and each example. The vertical direction in FIG. 5 indicates the tire circumferential direction. Moreover, the horizontal direction of FIG. 5 shows a tire width direction. The basic tread pattern of each comparative example and each example is the same as that of the embodiment described with reference to FIG.
The width of the tread shown in FIG. 5 is 207 mm, the width of the main groove 10 is 13 mm, the distance between a pair of adjacent sub-grooves 20 is 15 mm, and the width of the shoulder region Ts is 36 mm. The depth of the main groove 10 is 14 mm, and the depth of the sub-groove 20 is 14 mm.
The width of the lug groove 30 is 4 mm, and the angle formed by the lug groove 30 and the auxiliary groove 20 is 31 degrees. The depth of the lug groove 30 is 14 mm.
The width W1 of the narrow portion 22 and the width W2 of the wide portion 24 differ depending on each comparative example and each example. The length of the narrow portion 22 in the tire circumferential direction is 82 mm, and the width of the wide portion 24 in the tire circumferential direction is 42 mm.

The widths of the wide portions 24 in Comparative Examples 1 and 2 and Examples 1 to 3 are all 6.0 mm.
The width of the narrow portion 22 of Comparative Example 1 is 1.0 mm.
The width of the narrow portion 22 of Example 1 is 1.5 mm.
The width of the narrow portion 22 of Example 2 is 3.0 mm.
The width of the narrow portion 22 of Example 3 is 4.0 mm.
The width of the narrow portion 22 of Comparative Example 2 is 4.5 mm.

Table 1 shows test results of durability and wet performance in the conventional examples, comparative examples 1 and 2, and examples 1 to 3.

From the results in Table 1, it can be seen that the durability is improved when the width of the narrow portion 22 is narrowed. Moreover, it turns out that wet performance improves, when the width | variety of the narrow part 22 becomes large. In each of the examples and comparative examples, durability and wet performance were improved as compared with the conventional example. However, in order to further improve the durability, the width of the narrow portion 22 is preferably less than 4.0 mm. . In addition, if the width of the narrow portion 22 is excessively narrowed, cracks may occur at the bottom of the sub-groove 20, so the width of the narrow portion 22 is preferably 1.5 mm or more.

(Conventional example, Comparative examples 3 and 4, Examples 2, 4 and 5)
Using conventional examples, comparative examples 3 and 4, and examples 2, 4 and 5, the effect of changing the width of the wide portion 24 was examined.
The widths of the narrow portions 22 in Comparative Examples 3 and 4 and Examples 2, 4 and 5 are all 3.0 mm.
The width of the wide portion 24 of Comparative Example 3 is 3.5 mm.
The width of the wide portion 24 of Example 4 is 4.0 mm.
The width of the wide portion 24 of Example 2 is 6.0 mm.
The width of the wide portion 24 of Example 5 is 8.0 mm.
The width of the wide portion 24 of Comparative Example 4 is 9.0 mm.

Table 2 shows the test results of durability and wet performance in the conventional examples, comparative examples 3 and 4, and examples 2, 4 and 5.

From the results of Table 2, it can be seen that the durability is improved when the width of the wide portion 24 is narrowed. It can also be seen that the wet performance improves as the width of the wide portion 24 increases. In any of the examples and comparative examples, durability and wet performance were improved as compared with the conventional example. However, in order to further improve the wet performance, the width of the wide portion 24 is preferably set to 4.0 mm or more. In addition, if the width of the wide portion 24 is excessively widened, the width of the land portion between a pair of adjacent sub-grooves 20 is relatively narrow, so that the rigidity of the land portion is reduced and uneven wear is likely to occur. . For this reason, the width of the wide portion 24 is preferably less than 8.0 mm.

  From the results shown in Tables 1 and 2, it was found that the pneumatic tire of the present invention improves durability while suppressing a decrease in wet performance.

10 Main groove 20 Sub groove 22 Narrow part 24 Wide part 30 Lug groove R Road surface Ts Shoulder region

Claims (8)

A main groove extending in the tire circumferential direction and having a width of 8.0 mm or more;
A plurality of sub-grooves that extend in the tire circumferential direction and include a narrow portion having a width of 1.5 mm or more and less than 4.0 mm and a wide portion having a width of 4.0 mm or more and less than 8.0 mm;
Of the plurality of sub-grooves, when one of a pair of adjacent sub-grooves is a first sub-groove and the other is a second sub-groove, the tire extends from the wide portion of the first sub-groove to the wide portion of the second sub-groove. A plurality of lug grooves extending inclined with respect to the width direction;
A pneumatic tire comprising:   The pneumatic tire according to claim 1, wherein a width of the lug groove is 3 mm or more.   The pneumatic tire according to claim 1 or 2, wherein a cross-sectional area of the lug groove is 50% or more of a cross-sectional area of the wide portion.   The pneumatic tire according to claim 1, wherein a depth of the lug groove is equal to a depth of the wide portion.   The pneumatic tire according to any one of claims 1 to 4, wherein an angle formed by the lug groove and the auxiliary groove is 20 degrees or more and 85 degrees or less. The narrow portion and the wide portion are alternately formed in the sub-groove along the tire circumferential direction,
The pneumatic tire according to any one of claims 1 to 5, wherein the wide portion of the first sub-groove and the wide portion of the second sub-groove are positioned so as to be shifted from each other in the tire circumferential direction.   When the shoulder region is outside the main groove or the sub-groove formed on the outermost side in the tire width direction, the interval between the pair of adjacent sub-grooves is not less than 1/4 of the width of the shoulder region. The pneumatic tire according to any one of claims 1 to 6, which is 2 or less. The pneumatic tire according to any one of claims 1 to 7, comprising at least two main grooves.