JP2015000700A - Tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire capable of improving the wear resistance of a tread as well as steerability.SOLUTION: When the whole circumferential shear elasticity coefficient of a plurality of land part blocks 40 is represented by G, the circumferential shear elasticity coefficient of a center land part 40A is represented by G, that of a second land part 40B is represented by Gand that of a shoulder land part 40C is represented by G, a ratio, G/Gis 0.27 to 0.33, the ratio, G/Gis 0.12 to 0.18, and G/Gis 0.49 to 0.61.

Description

  The present invention relates to a tire including a tread portion having a tread contact surface.

  Conventionally, a tire having a pair of bead portions assembled to a rim flange, a pair of side portions continuous to the pair of bead portions on the outer side in the tire radial direction, and a tread portion having a tread ground contact surface that contacts the road surface. It has been known.

  In such a tire, the tread portion (tread contact surface) includes a plurality of circumferential grooves extending along the tire circumferential direction, a plurality of widthwise grooves extending along the tire width direction, a plurality of circumferential grooves, and a plurality of circumferential grooves. And a plurality of land blocks divided by the width direction grooves.

  The circumferential groove is continuous over the entire circumference in the tire circumferential direction, and has a zigzag shape having an amplitude in the tire width direction. The width direction groove communicates with a pair of circumferential grooves adjacent to each other, or opens at the tread grounding end while communicating with the circumferential groove. As a result, the land block has a pentagon or more polygon in the tread plan view.

  According to such a tire, uneven wear of the tread portion is suppressed by making the slip component in the tire circumferential direction and the slip component in the tire width direction uniform among the slip between the tread portion (tread contact surface) and the road surface. (For example, Patent Document 1).

JP 2007-145209 A

  However, as a result of intensive studies, the inventors have found that there is room for further improvement from the viewpoint of improving the wear resistance of the tread portion and improving the steering performance.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a tire that can improve wear resistance and steering performance of a tread portion.

The tire according to the first feature includes a tread portion having a tread ground contact surface that contacts the road surface. The tread portion includes a plurality of circumferential grooves extending along the tire circumferential direction, a plurality of width grooves extending along the tire width direction, a plurality of circumferential grooves, and a plurality of width direction grooves on the tread contact surface. A plurality of land blocks partitioned by. Each of the plurality of land blocks has a pentagon or more polygon in which the size in the tire circumferential direction is larger than the size in the tire width direction in a tread plan view. The plurality of land blocks include a center land portion straddling a tire equator line, a second land portion positioned on the outer side in the tire width direction with respect to the center land portion, and the tire with respect to the second land portion. And a shoulder land portion located outside in the width direction. Circumferential shear modulus of the whole of the plurality of land portion blocks is represented by G _ALL, circumferential shear modulus of the center land portion is represented by G _C, circumferential shear modulus of the second land portion , G _2nd , and the circumferential shear elastic modulus of the shoulder land portion is represented by G _SH . The ratio _G C _{/ G ALL} of the _{G ALL} and the _{G C} is 0.27 or more and 0.33 or less, the ratio _G 2nd _{/ G ALL} of the _{G ALL} and the _{G 2nd} 0.12 or more And the ratio G _SH / G _ALL between the G _ALL and the G _SH is 0.49 or more and 0.61 or less.

  1st characteristic WHEREIN: In the said tire width direction, the size of the said center land part and the said 2nd land part is 10% or more and 20% or less of a tread ground contact width. In the tire circumferential direction, the size of the center land portion and the second land portion is 15% or more and 35% or less of the tread contact length.

  In the first feature, the plurality of circumferential grooves include a first circumferential groove that divides the center land portion, a second circumferential groove that divides the center land portion and the second land portion, and the second groove. A third circumferential groove that divides the land portion and the shoulder land portion. The plurality of width direction grooves include a first width direction groove that divides the center land portion, a second width direction groove that divides the second land portion, and a third width direction groove that divides the shoulder land portion. including. The first circumferential groove has a zigzag shape having an amplitude in the tire width direction. The groove width of the first width direction groove is larger than the groove width of the first circumferential groove. The groove width of the second width direction groove is larger than the groove width of the first circumferential groove.

  ADVANTAGE OF THE INVENTION According to this invention, the tire which can aim at the improvement of the abrasion resistance of a tread part and the improvement of a steering property can be provided.

FIG. 1 is a diagram illustrating a tread contact surface of the tire 1 according to the first embodiment. FIG. 2 is a perspective view showing the land block 40 according to the first embodiment. FIG. 3 is a diagram for explaining the circumferential shear elastic modulus according to the first embodiment. FIG. 4 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]
A tire is provided with a tread part which has a tread grounding surface which contacts a road surface in an embodiment. The tread portion includes a plurality of circumferential grooves extending along the tire circumferential direction, a plurality of width grooves extending along the tire width direction, a plurality of circumferential grooves, and a plurality of width direction grooves on the tread contact surface. A plurality of land blocks partitioned by. Each of the plurality of land blocks has a pentagon or more polygon in which the size in the tire circumferential direction is larger than the size in the tire width direction in a tread plan view. The plurality of land blocks include a center land portion straddling a tire equator line, a second land portion positioned on the outer side in the tire width direction with respect to the center land portion, and the tire with respect to the second land portion. And a shoulder land portion located outside in the width direction. Circumferential shear modulus of the whole of the plurality of land portion blocks is represented by G _ALL, circumferential shear modulus of the center land portion is represented by G _C, circumferential shear modulus of the second land portion , G _2nd , and the circumferential shear elastic modulus of the shoulder land portion is represented by G _SH . The ratio _G C _{/ G ALL} of the _{G ALL} and the _{G C} is 0.27 or more and 0.33 or less, the ratio _G 2nd _{/ G ALL} of the _{G ALL} and the _{G 2nd} 0.12 or more And the ratio G _SH / G _ALL between the G _ALL and the G _SH is 0.49 or more and 0.61 or less.

In the embodiment, the ratio G _C / G _ALL is 0.27 or more, and the rigidity of the center land portion is high, so that the wear resistance of the center land portion is improved. Moreover, since the torsional rigidity of the center land portion is relatively increased, the cornering power is improved and the steering performance is improved. Along with this, it is necessary to reduce the ratio G _{2nd /} G _ALL, wear of the second land portion is promoted by the self-abrasion, there is a concern that partial wear such block punch occurs, the ratio G _{2nd /} G _By setting _ALL to 0.12 or more, such uneven wear can be suppressed.

As described above, in the embodiment, by optimizing the ranges of the ratio G _C / G _ALL , the ratio G _2nd / G _ALL and the ratio G _SH / G _ALL , the wear resistance of the tread portion and the steering performance are improved. Can be achieved. That is, in the embodiment, it is important to pay attention to optimization of the ranges of the ratio G _C / G _ALL , the ratio G _2nd / G _ALL, and the ratio G _SH / G _ALL .

[First Embodiment]
(Tire composition)
Hereinafter, the tire according to the first embodiment will be described. FIG. 1 is a diagram illustrating a tread contact surface of the tire 1 according to the first embodiment.

  Here, the tire 1 includes 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 tread ground contact surface that contacts the road surface. Have

  As shown in FIG. 1, the tire 1 has a tread portion 10 having a tread contact surface. The tread portion 10 (tread contact surface) includes a plurality of circumferential grooves 20 that extend along the tire circumferential direction TC, a plurality of width direction grooves 30 that extend along the tire width direction TW, and a plurality of circumferences on the tread contact surface. And a plurality of land blocks 40 defined by the direction grooves 20 and the plurality of width direction grooves 30.

  Each circumferential groove 20 is, for example, continuous over the entire circumference in the tire circumferential direction TC and has a zigzag shape having an amplitude in the tire width direction TW. Each widthwise groove 30 communicates with a pair of circumferential grooves 20 adjacent to each other, or opens to the tread grounding end 10 </ b> E while communicating with the circumferential groove 20. Each of the plurality of land blocks 40 has a pentagon or more polygon in which the size in the tire circumferential direction TC is larger than the size in the tire width direction TW in the tread plan view. Here, the plurality of land blocks 40 include a center land portion 40A that straddles the tire equator line CL, a second land portion 40B that is located on the outer side in the tire width direction with respect to the center land portion 40A, and a second land portion 40B. And a shoulder land portion 40C located outside in the tire width direction.

  Specifically, the plurality of circumferential grooves 20 include a first circumferential groove 20A that divides the center land portion 40A, a second circumferential groove 20B that divides the center land portion 40A and the second land portion 40B, and a second land. And a third circumferential groove 20C that divides the portion 40B and the shoulder land portion 40C.

  As described above, the first circumferential groove 20A, the second circumferential groove 20B, and the third circumferential groove 20C have a zigzag shape having an amplitude in the tire width direction TW. The groove width of the first circumferential groove 20A is preferably smaller than the groove widths of the second circumferential groove 20B and the third circumferential groove 20C. Moreover, it is more preferable that the groove width of the first circumferential groove 20A is a groove width such that the groove walls of the land portion come into contact with each other at the time of grounding. The groove width of the second circumferential groove 20B is not particularly limited, but is substantially equal to the groove width of the third circumferential groove 20C. The amplitude of the first circumferential groove 20A is preferably larger than the amplitude of the second circumferential groove 20B and the third circumferential groove 20C. The amplitude of the second circumferential groove 20B is preferably larger than the amplitude of the third circumferential groove 20C.

  The plurality of width direction grooves 30 are a first width direction groove 30A that partitions the center land portion 40A, a second width direction groove 30B that partitions the second land portion 40B, and a third width direction that partitions the shoulder land portion 40C. Groove 30C.

  The first width direction groove 30A is preferably inclined with respect to the tire width direction TW. The groove width of the first width direction groove 30A is preferably larger than the groove width of the first circumferential direction groove 20A. Further, it is more preferable that the groove width of the first width direction groove 30A is a groove width that does not contact the groove wall of the land portion facing through the first circumferential groove 20A at the time of grounding. The second width direction groove 30B is preferably inclined with respect to the tire width direction TW. The groove width of the second width direction groove 30B is preferably larger than the groove width of the first circumferential groove 20A. The third width direction groove 30C may be substantially parallel to the tire width direction TW. The groove width of the third width direction groove 30C may be larger than the groove widths of the first width direction groove 30A and the second width direction groove 30B.

  In the first embodiment, a sipe 50 extending along the tire width direction TW may be formed in the center land portion 40A. The groove width of the sipe 50 is smaller than the groove width of the first circumferential groove 20A. The depth of the sipe 50 is smaller than the depth of the first circumferential groove 20A.

(Likubu Block)
The land block according to the first embodiment will be described below. FIG. 2 is a perspective view showing the land block 40 according to the first embodiment. It should be noted that the center land portion 40A is illustrated in FIG.

  As shown in FIG. 2, the land block 40 has a width BW as a size in the tire width direction TW, a length BL as a size in the tire circumferential direction TC, and a size in the tire radial direction TR. And has a depth d. As described above, the land block 40 has a polygon of a pentagon or more whose length BL is larger than the width BW in the tread plan view. In the first embodiment, the center land portion 40A and the second land portion 40B have a hexagonal shape, and the shoulder land portion 40C has a pentagonal shape.

  In the first embodiment, as shown in FIG. 1, the tread ground contact width is represented by W, and the tread ground contact length is represented by L. In a state where the tire 1 is mounted on a regular rim specified in JATMA, the internal pressure of the tire 1 is the normal internal pressure specified in JATMA, and the load of the tire 1 is 80% of the maximum load load specified in JATMA. The contact width W and the tread contact length L are measured.

  In the first embodiment, in the tire width direction TW, the width BW of the center land portion 40A is preferably 15% or more and 20% or less of the tread ground contact width W. In the tire circumferential direction TC, the length BL of the center land portion 40A is preferably 15% or more and 35% or less of the tread contact length L.

  Similarly, in the tire width direction TW, the width BW of the second land portion 40B is preferably 10% or more and 15% or less of the tread ground contact width W. In the tire circumferential direction TC, the length BL of the second land portion 40B is preferably 15% or more and 20% or less of the tread contact length L.

  The width BW and length BL of the shoulder land portion 40C are not particularly limited, but are the same as the width BW and length BL of the center land portion 40A or the width BW and length BL of the second land portion 40B. There may be.

(Circumferential shear modulus)
Hereinafter, the circumferential shear elastic modulus according to the first embodiment will be described. FIG. 3 is a diagram for explaining the circumferential shear elastic modulus according to the first embodiment. It should be noted that the center land portion 40A is illustrated in FIG.

  As shown in FIG. 3, when the land block 40 is d, the area of the wall surface of the land block 40 adjacent to the widthwise groove 30 is A, and a load F is applied to the land block 40, Consider a case where the deformation amount of the land block 40 in the tire circumferential direction TC is Δx.

  In such a case, the shear strain γ is expressed by γ = Δx / d. The shear stress τ is expressed by τ = W / A. The circumferential shear elastic modulus G is expressed by G = τ / γ.

Here, the circumferential shear modulus of the whole of the plurality of land portion blocks 40 is represented by G _ALL, circumferential shear modulus of the center land portion 40A is represented by G _C, circumferential shearing second land portion 40B modulus _is represented by _{G 2nd,} circumferential shear modulus of the shoulder land portion 40C _is represented by _{G SH.}

In such _cases, the ratio _G C _{/ G ALL} the _{G ALL} and _{G C} is 0.27 or more and 0.33 or _less, the ratio _G 2nd _{/ G ALL} the _{G ALL} and _{G 2nd} is 0. It is 12 or more and 0.18 or less, and the ratio G _SH / G _ALL between G _ALL and G _SH is 0.49 or more and 0.61 or less.

(Function and effect)
In the first embodiment, the ratio G _C / G _ALL is 0.27 or more, and the rigidity of the center land portion 40A is high, so the wear resistance of the center land portion 40A is improved. Further, since the torsional rigidity of the center land portion 40A is relatively high, the cornering power is improved and the steering performance is improved. Along with this, it is necessary to reduce the ratio G _{2nd /} G _ALL, wear of the second land portion 40B is promoted by self-abrasion, there is a concern that partial wear such block punch occurs, the ratio G _2nd / By setting G _ALL to be 0.12 or more, such uneven wear can be suppressed.

As described above, in the embodiment, by optimizing the ranges of the ratio G _C / G _ALL , the ratio G _2nd / G _ALL and the ratio G _SH / G _ALL , the wear resistance of the tread portion 10 is improved and the steering performance is improved. Improvements can be made. That is, in the embodiment, it is important to pay attention to optimization of the ranges of the ratio G _C / G _ALL , the ratio G _2nd / G _ALL, and the ratio G _SH / G _ALL .

Specifically, when the ratio G _C / G _ALL is 0.27 or more, the slippage amount at the time of kicking is reduced, and the corresponding wear resistance is improved. In particular, center wear that occurs in the case where the tire 1 is mounted on the drive shaft is effectively suppressed. In addition, since the torsional rigidity of the center land portion 40A is relatively high, lateral input is reduced, and shoulder wear that occurs in the case where the tire 1 is mounted on the steering shaft is effectively suppressed.

Here, it should be noted that the lower limit of the ratio G _SH / G _ALL is determined from the viewpoint of suppressing uneven wear of the shoulder land portion 40C. It should be noted that the upper limits of the ratio G _C / G _ALL and the ratio G _SH / G _ALL are determined by the balance of the circumferential shear elastic modulus of each land block 40. That is, if the upper limit of the ratio G _C / G _ALL or the ratio G _SH / G _ALL is too large, the circumferential shear elastic modulus (G _2nd ) becomes too small.

[Evaluation results]
Hereinafter, the evaluation results will be described. Specifically, samples with different ratios G _C / G _ALL (R _C ), ratios G _2nd / G _ALL (R _2nd ), and ratios G _SH / G _ALL (R _SH ) are created, and the center land portion 40A Wear (C / L wear), wear of the second land portion 40B (2nd wear), and wear of the shoulder land portion 40C (SHO wear) were measured. C / L wear, 2nd wear, and SHO wear are expressed by indices, and the index means that the larger the index value, the better the result (result of less wear) was obtained.

  The test conditions are as shown below.

・ Tire size: 11R22.5
・ Rim wheel size: 7.50 × 22.5
・ Tire type: Heavy duty tire ・ Vehicle: General cargo (fixed volume state)
・ Test tire mounting position: Steering shaft and drive shaft ・ Travel distance at the time of final evaluation: approx. 100,000 km
・ Traveling road surface: general road The evaluation results are shown in Fig.4. As shown in FIG. 4, in the example in which the ratio G _C / G _ALL is 0.27 or more, the 2nd wear and the SHO wear increase compared to the comparative example in which the ratio G _C / G _ALL is less than 0.27. It was confirmed that C / L wear was reduced while suppressing the above.

[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, in the tread plan view, the center land portion 40A and the second land portion 40B have a hexagon, and the shoulder land portion 40C has a pentagon. However, the embodiment is not limited to this. For example, the center land portion 40A and the second land portion 40B may be octagonal. In addition, the top (corner) of the land block 40 may be chamfered in the tread plan view.

  DESCRIPTION OF SYMBOLS 1 ... Tire, 10 ... Tread part, 20A ... 1st circumferential groove, 20B ... 2nd circumferential groove, 20C ... 3rd circumferential groove, 30A ... 1st width direction groove, 30B ... 2nd width direction groove, 30C ... 3rd width direction groove, 40 ... Land block, 40A ... Center land part, 40B ... Second land part, 40C ... Shoulder land, 50 ... Sipe

Claims (3)

A tire including a tread portion having a tread contact surface that contacts the road surface,
The tread portion includes a plurality of circumferential grooves extending along the tire circumferential direction, a plurality of width grooves extending along the tire width direction, a plurality of circumferential grooves, and a plurality of width direction grooves on the tread contact surface. And a plurality of land blocks divided by
Each of the plurality of land blocks has a pentagon or more polygon larger in size in the tire circumferential direction than in the tire width direction in a tread plan view,
The plurality of land blocks include a center land portion straddling a tire equator line, a second land portion positioned on the outer side in the tire width direction with respect to the center land portion, and the tire with respect to the second land portion. Including a shoulder land portion located outside in the width direction,
Circumferential shear modulus of the whole of the plurality of land portion blocks is represented by G _ALL, circumferential shear modulus of the center land portion is represented by G _C, circumferential shear modulus of the second land portion , G _2nd , the circumferential shear elastic modulus of the shoulder land portion is represented by G _SH ,
The ratio _G C _{/ G ALL} with the _{G ALL} and the _{G C} is 0.27 or more and 0.33 or less,
The ratio G _2nd / G _ALL between the G _ALL and the G _2nd is 0.12 or more and 0.18 or less,
A ratio G _SH / G _ALL between the G _ALL and the G _SH is 0.49 or more and 0.61 or less. In the tire width direction, the size of the center land portion and the second land portion is 10% or more and 20% or less of the tread contact width,
2. The tire according to claim 1, wherein in the tire circumferential direction, the size of the center land portion and the second land portion is 15% or more and 35% or less of a tread contact length. The plurality of circumferential grooves include a first circumferential groove that divides the center land portion, a second circumferential groove that divides the center land portion and the second land portion, the second land portion, and the shoulder land. A third circumferential groove that divides the portion,
The plurality of width direction grooves include a first width direction groove that divides the center land portion, a second width direction groove that divides the second land portion, and a third width direction groove that divides the shoulder land portion. Including
The first circumferential groove has a zigzag shape having an amplitude in the tire width direction,
The groove width of the first width direction groove is larger than the groove width of the first circumferential groove,
The tire according to claim 1, wherein the groove width of the second width direction groove is larger than the groove width of the first circumferential groove.

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