JP2019006318A - tire - Google Patents

Abstract

To provide a tire improving the steering stability on a pavement and on-snow performance with well balance.SOLUTION: An objective pneumatic tire has at least one partitioned land part on a tread part 2. A plurality of lug grooves 10 extending from the first end 61 of the land part 6 and having a break end in the land part 6, a first sipe 11 extending between the adjacent lug grooves 10 along a tire circumferential direction, a plurality of second sipes 12 extending toward the first sipe 11 from the first end 61, and a plurality of third sipes 13 extending toward the first sipe 11 from the second end 62 of the land part 6 in a tire axial direction are provided on at least one land part 6. The second and third sipes 12 and 13 are arranged without crossing with the lug grooves 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire, and more particularly to a tire that can be suitably implemented as an all-season tire.

  All-season tires require basic driving performance not only on paved roads but also on snowy roads. In order to improve running performance on slippery snowy roads, tires are required to have a large snow column shearing force and a road surface scratching effect. The snow column shearing force is obtained by pressing the snow on the road surface with a horizontal groove and shearing it. Therefore, in order to improve the performance on snow, it is effective to provide many long lateral grooves in the tread portion. Further, the lateral groove and the edge of the sipe (that is, the ridge line where the tread surface and the groove wall or sipe wall intersect, the same applies hereinafter) improve the traction by scratching the pressed snow road. As a related technique, there is Patent Document 1 below.

JP 2012-2013335 A

  Cross grooves and sipes that completely cross the land area of the tread portion are useful for improving the performance on snow, but have a tendency to reduce the pattern rigidity of the tread portion and eventually deteriorate the steering stability on the paved road.

  The present invention has been devised in view of the above problems, and has as its main object to provide a tire capable of improving the steering stability on a paved road and the performance on snow in a well-balanced manner.

  The present invention is a pneumatic tire in which at least one land portion is divided into a tread portion, and the at least one land portion has a first end that is an end on one side of the land portion in the tire axial direction. A plurality of lug grooves extending from and having a discontinuous end in the land portion, a first sipe extending along the tire circumferential direction between the lug grooves adjacent in the tire circumferential direction, and from the first end to the first sipe A plurality of second sipes extending toward the first sipes from a second end that is the other end in the tire axial direction of the land portion, and a plurality of third sipes extending toward the first sipes. The two sipes and the third sipes are arranged without intersecting the lug grooves.

  In another aspect of the invention, the second sipe, the third sipe, and the lug groove may be inclined in the same direction with respect to the tire axial direction.

  In another aspect of the invention, the second sipe and the third sipe may be essentially connected to the first sipe.

  In another aspect of the invention, at least one end of the first sipe may be connected to the lug groove.

  In another aspect of the present invention, a plurality of the second sipes may be provided between the lug grooves adjacent in the tire circumferential direction.

  In another aspect of the present invention, a plurality of the third sipes may be provided between the lug grooves adjacent in the tire circumferential direction.

  In another aspect of the present invention, one end of a fourth sipe may be connected to the discontinuous end of each lug groove, and the other end of the fourth sipe may open to the second end.

  In another aspect of the present invention, the land portion is between the second sipe adjacent to each other in the tire circumferential direction and the first block partitioned between the lug grooves and the second sipe adjacent to the tire circumferential direction. And the second block divided into two. In this case, in the first block, at least a part of the edge extending in the tire circumferential direction on the first end side of the tread surface is more than the edge extending in the tire circumferential direction on the first end side of the tread surface of the second block. May be located on the inner side in the width direction of the land

  In another aspect of the present invention, the land portion includes a third block partitioned between the third sipe and the fourth sipe adjacent in the tire circumferential direction, and the third sipe adjacent in the tire circumferential direction. A fourth block divided in between may also be included. In this case, in the fourth block, at least a part of the edge extending in the tire circumferential direction on the second end side of the tread surface is more than the edge extending in the tire circumferential direction on the third end side of the tread surface of the third block. May also be located on the inner side in the width direction of the land.

  In another aspect of the present invention, the tread portion is formed by five main grooves extending continuously in the tire circumferential direction into five land portions including a crown land portion, a pair of middle land portions, and a pair of shoulder land portions. It may be divided. In this case, the at least one land portion may be one land portion of the pair of middle land portions.

  In another aspect of the invention, the tread portion may have a tread pattern in which a direction of mounting on the vehicle is specified. In this case, the at least one land portion is an inner middle land portion that is located on the inner side of the vehicle when a tire is mounted on the vehicle, and the first end is the inner middle portion. It may be the end of the land portion on the outer side in the tire axial direction.

  According to the present invention, the land portion is provided with a plurality of lug grooves. The lug groove extends from a first end of the land portion and has a discontinuous end in the land portion. The lug groove generates a snow column shear force when traveling on snow, thereby increasing traction and braking force, and thus improving on-snow performance. Moreover, since the lug groove has a discontinuous end in the land portion, the lug groove does not completely cross the land portion. Therefore, a decrease in the rigidity of the land portion is suppressed as much as possible, and deterioration of steering stability on the paved road is prevented.

  According to the present invention, the first sipes extending along the tire circumferential direction are provided between the lug grooves adjacent in the tire circumferential direction. Since the first sipe has a width smaller than that of the groove, the first sipe provides a road surface scratching effect when a slip angle is given to the tire while preventing a decrease in rigidity of the land portion. Therefore, the first sipe increases the handling stability on a slippery snowy road.

  According to the present invention, a plurality of second sipes extending from the first end of the land portion toward the first sipes and a plurality of third sipes extending from the second end of the land portion toward the first sipes. And are provided. Since the second sipe and the third sipe are smaller in width than the groove, the road surface scratching effect on a snowy road over a wide range of the land portion is suppressed while minimizing the decrease in rigidity of the land portion. Can be provided.

  According to the present invention, the second sipe and the third sipe are arranged without intersecting with the inclined lug groove. The intersection between the groove and the sipe tends to decrease in rigidity locally. However, in the present invention, since the above-mentioned intersection portion is not formed in the land portion, a decrease in rigidity of the land portion is suppressed, and good steering stability on a paved road can be obtained.

  As described above, the tire of the present invention can exhibit good steering stability and performance on snow.

It is an expanded view of the tread part of the tire which shows one Embodiment of this invention. It is the elements on larger scale of the inner middle land part of FIG. It is the sectional view on the AA line of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2. FIG. 3 is a partially enlarged view of FIG. 2. (A) And (B) is the AA sectional view taken on the line of FIG. It is the elements on larger scale of the crown land part of FIG. (A) And (B) is the AA sectional view taken on the line of FIG. 7, and the BB sectional drawing.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of the tread portion 2 of the tire according to the present embodiment. The tire of this embodiment is configured as a pneumatic tire, for example. In the present embodiment, as a preferable aspect, an all-season tire intended for mounting on a passenger car or SUV is shown.

  As shown in FIG. 1, the tire has a tread portion 2. The tread portion 2 is a portion that contacts the road surface, and various tread patterns are formed. The tire 1 of this embodiment has a left-right asymmetric tread pattern. In order to maximize the characteristics of the tread pattern, the tire according to the present embodiment is designated for mounting on the vehicle. The direction of mounting on the vehicle is displayed, for example, in characters or graphics on the sidewall portion (not shown) of the tire.

  When the tire 1 is mounted on the vehicle, the tread portion 2 has an inner tread end Te1 positioned on the vehicle body center side of the vehicle, an outer tread end Te2 positioned outside the vehicle body, a plurality of main grooves 3, At least one (a plurality of land portions in this example) divided by them is formed.

  The main groove 3 continuously extends in the tire circumferential direction with a relatively large width and depth in order to discharge water on the road surface to the rear of the tire. In a preferred embodiment, the main groove 3 has a width and depth of 5 mm or more, more preferably 6 mm or more. Each main groove 3 extends straight along, for example, the tire circumferential direction. In another aspect, the main groove 3 may be non-linear such as zigzag or wavy.

  In the present embodiment, the tread portion 2 is provided with four main grooves 3. The four main grooves 3 include an inner crown main groove 3A and an outer crown main groove 3B arranged so as to sandwich the tire equator C. The main groove 3 includes an inner shoulder main groove 3C disposed between the inner crown main groove 3A and the inner tread end Te1, and an outer shoulder disposed between the outer crown main groove 3b and the outer tread end Te2. Main groove 3D.

  By each main groove 3, the land portion of the tread portion 2 is divided into five land portions: a crown land portion 5, an inner middle land portion 6, an outer middle land portion 7, an inner shoulder land portion 8, and an outer shoulder land portion 9. ing.

  The crown land portion 5 is divided between the inner crown main groove 3A and the outer crown main groove 3B. The inner middle land portion 6 is divided between the inner uranium main groove 3A and the inner shoulder main groove 3C. The outer middle land portion 7 is divided between the outer kuran main groove 3B and the outer shoulder main groove 3D. The inner shoulder land portion 8 is divided between the inner shoulder main groove 3C and the inner tread end Te1. The outer shoulder land portion 9 is divided between the outer shoulder main groove 3D and the outer tread end Te2.

  In the present embodiment, as one of the land portions 5, a lug groove 10, a first sipe 11, a second sipe 12, and a third sipe 13 are provided in the inner middle land portion 6. A plurality of these grooves 10 and sipes 11 to 13 are formed.

  In the present specification, “sipe” is defined as a thin notch having a width of 2.0 mm or less, preferably 0.5 to 2.0 mm. On the other hand, a “groove” is defined as a recess having a width greater than at least 2.0 mm.

  FIG. 2 shows a partially enlarged view of the inner middle land portion 6 of FIG. As shown in FIG. 2, the inner middle land portion 6 has a first end 61 and a second end 62. The first end 61 is the end of the tread surface facing the inner shoulder main groove 3C, and the second end 62 is the end of the tread surface facing the inner crown main groove 3A.

  Each lug groove 10 extends partially across the inner middle land portion 6 from the first end 61 of the inner middle land portion 6, and has a discontinuous end 10 a in the inner middle land portion 6. That is, the lug groove 10 does not reach the second end 62 of the inner middle land portion 6. In the present embodiment, the lug groove 10 extends linearly from the first end 61 to the discontinuous end. In other aspects, the lug groove 10 can include a bent portion to increase the groove length and edge component. The lug groove 10 generates a snow column shearing force when traveling on snow to enhance traction and braking force, thereby improving the performance on snow. Further, the lug groove 10 suppresses the decrease in rigidity of the inner middle land portion 6 as much as possible, and prevents the steering stability on the paved road from deteriorating.

  In a preferred embodiment, the width of each lug groove 10 may be 8.0 mm or less, and more preferably 4.0 to 8.0 mm. In the present embodiment, the width of each groove is measured in a direction orthogonal to the longitudinal direction of the groove. In a preferred embodiment, the groove width of each lug groove 10 gradually decreases toward the interrupted end 10a. In this case, the portion having a width of 2.0 mm or less is recognized as the interrupted end 10a.

  In the present embodiment, the discontinuous end 10a of each lug groove 10 is located closer to the second end 62 than the center position of the inner middle land portion 6 in the tire axial direction. This helps to generate a snow column shear force in a wider range in the tire axial direction. The length L1 of the lug groove 10 in the tire axial direction is the maximum width Lm of the inner middle land portion 6 in the tire axial direction in order to obtain a well-balanced snow column shear force while preventing deterioration in steering stability on the paved road. 30%, more preferably more than 50% and preferably 80% or less.

  In the present embodiment, each lug groove 10 is inclined with respect to the tire axial direction. In order to obtain a scratching effect in the tire axial direction while suppressing a decrease in lateral rigidity of the inner middle land portion 6, it is desirable that each lug groove 10 be inclined with respect to the tire axial direction. In a more preferred embodiment, each lug groove 10 is inclined at 5 to 45 °, more preferably 5 to 30 °, and still more preferably 5 to 20 ° with respect to the tire axial direction. In order to maximize the snow column shearing force and the road surface scratching effect with respect to traction, the lug groove 10 may include one extending along the tire axial direction.

  FIG. 3 is a cross-sectional view taken along line AA in FIG. In order to generate a large snow column shear force, the depth of the lug groove 10 (the maximum depth when the depth changes) d1 is, for example, 25% or more of the maximum depth D of the main groove 3 and It is desirable that it is 100% or less. In a more preferred embodiment, the depth d1 is set to be less than 100% of the maximum depth D of the main groove 3 in order to further suppress the decrease in rigidity of the inner middle land portion 6 while generating a snow column shear force. More preferably, it is 40 to 90%, and most preferably 40% to 60%.

  In a preferred embodiment, it is desirable that a shallow bottom portion 15 having a locally small depth is provided on the first end 61 side of the lug groove 10 (that is, the side communicating with the main groove 3). The depth d2 of the shallow bottom portion is, for example, about 40% to 60% of the maximum depth d1 of the lug groove 10.

  As shown in FIG. 2, the first sipe 11 extends between the lug grooves 10 and 10 adjacent in the tire circumferential direction along the tire circumferential direction. In the present embodiment, the first sipe 11 extends linearly. In another aspect, the first sipe 11 may include a bent portion in order to increase the edge component.

  In a preferred embodiment, at least one end of the first sipe 11 is connected to the lug groove 10. In a particularly preferable aspect, both ends of the first sipe 11 are connected to the lug groove 10. The 1st sipe 11 relieves the compressive distortion of the land part at the time of the inner middle land part 6 grounding. Further, the first sipe 11 provides a road surface scratching effect when a slip angle is given to the tire, and improves steering stability on a slippery snowy road.

  In a preferred embodiment, the first sipe 11 is provided on the center position of the maximum width Lm of the inner middle land portion 6. Thereby, the bias | inclination of the rigidity of the inner middle land part 6, and a deterioration of steering stability are further prevented further.

  FIG. 3 shows a cross-sectional view of the first sipe 11. In order to suppress a decrease in rigidity of the inner middle land portion 6, the depth of the first sipe 11 is preferably less than 100% of the maximum depth D of the main groove 3, more preferably 40 to 90%, Most preferably, it is 40% to 60%. The first sipe 11 of the present embodiment is formed with the same depth as the maximum depth d1 of the lug groove 10. This is useful for preventing the occurrence of uneven wear at the connection portion between the first sipe 11 and the lug groove 10.

  As shown in FIG. 2, the second sipe 12 extends from the first end 61 of the inner middle land portion 6 toward the first sipe 11. In the present embodiment, a plurality of second sipes 12 are provided between the lug grooves 10 and 10 adjacent in the tire circumferential direction. The third sipe 13 extends from the second end 62 of the inner middle land portion 6 toward the first sipe 11. In the present embodiment, a plurality of third sipes 13 are provided between the lug grooves 10 and 10 adjacent in the tire circumferential direction. In the present embodiment, the second sipe 12 and the third sipe 13 extend linearly. In another aspect, the second sipe 12 and the third sipe 13 may include bent portions in order to increase the edge component.

  The second sipe 12 and the third sipe 13 scratch the road surface on a snowy road, particularly at the first end 61 and the second end 62 of the inner middle land portion 6 while minimizing the decrease in rigidity of the inner middle land portion 6. An effect can be provided.

  Furthermore, in the present embodiment, the second sipe 12 and the third sipe 13 are arranged without intersecting the lug groove 10. The intersection of grooves and sipes tends to locally reduce the rigidity of the land. In this embodiment, since the above-mentioned intersection part is not formed in the inner middle land portion 6, the rigidity reduction is suppressed, and good steering stability on a paved road is obtained.

  As described above, the tire 1 of the present embodiment can exhibit good steering stability and on-snow performance. In particular, a large load acts on the inner middle land portion 6 and the outer middle land portion 7 not only when traveling straight but also when turning. Therefore, by applying the above-described arrangement of the lug groove 10 and the first to third sipes 11 to 13 to the inner middle land portion 6 and / or the outer middle land portion 7, the above action can be expressed more effectively. Can do. In particular, in the current situation where the negative camber penetration rate is high, it is particularly desirable to apply the above-described arrangement of the lug groove 10 and the first to third sipes 11 to 13 to the inner middle land portion 6 as in the above embodiment. In addition, it cannot be overemphasized that the said arrangement | positioning is not limitedly applied to the inner middle land part 6, and may be applied to another land part.

  In a preferred embodiment, the second sipe 12 and the third sipe 13 may be inclined with respect to the tire axial direction in order to obtain a scratching effect in the tire axial direction while suppressing a decrease in lateral rigidity of the inner middle land portion 6. Desirably, it is desirable to incline at 5-45 °, more preferably 5-30 °, and still more preferably 5-20 °. As a more preferable aspect, like the present embodiment, the second sipe 12 and the third sipe 13 are inclined in the same direction with respect to the lug groove 10 and the tire axial direction.

  In a particularly preferred embodiment, the second sipe 12, the third sipe 13 and the lug groove 10 extend essentially parallel to each other. “Essentially parallel” means that the tread portion 2 is a curved surface and that the tire is a rubber vulcanized molded product, and that “parallel” should not be interpreted as a strictly mathematical meaning. It is intended. In this sense, aspects that would be apparent to those skilled in the art as being parallel should be interpreted as being essentially parallel. For example, in a groove or sipe, an angle with respect to a tire axial direction of a straight line connecting both ends thereof is calculated, and an aspect in which the difference is about 10 ° or less, more preferably 5 ° or less is at least essentially parallel. It should be understood that. On the other hand, in the aspect of maximizing the road surface scratching effect, the second sipe 12 and the third sipe 13 may extend along the tire axial direction.

  In the present embodiment, a plurality of (for example, two) second sipes 12 are arranged between the lug grooves 10 and 10 adjacent in the tire circumferential direction. In a preferred embodiment, the second sipe 12 is disposed so as to equally divide between adjacent lug grooves 10 with a substantially equal length in the tire circumferential direction (for example, the difference in length is within 5%). Such an arrangement is useful for suppressing local rigidity reduction of the inner middle land portion 6 and improving steering stability on a paved road.

  In the present embodiment, the second sipe 12 and the third sipe 13 are arranged so as to be aligned in a straight line via the first sipe 11. In a particularly preferred embodiment, the second sipe 12 and the third sipe 13 are essentially connected to the first sipe 11. Thereby, an essentially continuous edge from the first end 61 to the second end 62 of the inner middle land portion 6 can be provided, and the road surface scratching effect can be further enhanced. Note that two sipes are “essentially connected” as well as a mode in which the two sipes are actually connected (communication), but the two sipes are not actually connected, but 1 mm or less. It is assumed to include a state in which they are arranged close to each other through a gap.

  4 shows a cross-sectional view taken along line BB of FIG. As shown in FIG. 4, the second sipe 12 of the present embodiment extends from the first end 61 toward the first sipe 11, and the depth d3 gradually decreases in the vicinity of the end 12a on the first sipe 11 side. Yes. In this example, the end portion 12 a of the second sipe 12 coincides with the edge of the first sipe 11 on the first end 61 side. Similarly, the third sipe 13 extends from the second end 62 toward the first sipe 11, and the depth d4 gradually decreases in the vicinity of the end 13a on the first sipe 11 side. In this example, the end 13 a of the third sipe 13 coincides with the edge of the first sipe 11 on the second end 62 side. In such an aspect, the inner middle land portion 6 provides a long edge that is essentially continuous from the first end 61 to the second end 62 while sufficiently maintaining the rigidity of the central portion in the width direction, and the road surface. The scratching effect can be further improved.

  In order to improve the steering stability on the paved road, the second sipe 12 has the largest depth d3, and from there to the end portion 12b on the first end 61 side and the end portion 12a on the first sipe 11 side. The depth gradually decreases toward each. In the second sipe 12 of the present embodiment, the depth of the end 12b is greater than the depth at the end 12a. Particularly preferably, the depth of the end 12a is zero as described above. Further, in the second sipe 12, the depth at the end 12 b is preferably smaller than the depth of the first sipe 11.

  Similarly, the third sipe 13 has the largest depth d4, and the depth gradually decreases from the third sipe 13 toward the end portion 13b on the second end 62 side and the end portion 13a on the first sipe 11 side. . In the 3rd sipe 13 of this embodiment, the depth of the edge part 13b is larger than the depth in the edge part 13a. Particularly preferably, the depth of the end portion 13a is zero as described above. In the third sipe 13, the depth at the end 13 b is preferably smaller than the depth of the first sipe 11.

  Furthermore, it is desirable that the depth d3 of the second sipe 12 and the depth d4 of the third sipe 13 are larger than the depth of the first sipe 11. In particular, the depths d3 and d4 are desirably 50% or more and 100% or less, more preferably 60 to 80%, of the maximum depth D of the main groove 3, for example.

  According to the configuration of the present embodiment, the second sipe 12 and the third sipe 13 are located near the positions of the first end 61, the second end, and the first sipe 11 of the inner middle land portion 6 when the tire is running. The opening amount when touching the ground can be reduced, and the handling stability on the paved road can be improved. Further, when traveling on a snowy road, for example, the opening amount can be relatively increased at the center position in the length direction of each of the second sipe 12 and the third sipe 13 to further enhance the road surface scratching effect.

  As shown in FIGS. 1 to 3, in the preferred embodiment, the inner middle land portion 6 is further provided with a plurality of fourth sipes 14.

  The fourth sipe 14 is connected to the interrupted end 10 a of the lug groove 10. In a preferred embodiment, the fourth sipe 14 extends to the second end 62. In such an aspect, a long edge extending from the first end 61 to the second end 62 is provided while suppressing a decrease in rigidity of the inner middle land portion 6. Therefore, the performance on snow is further enhanced without impairing the steering stability on the paved road. In particular, since the groove width of the interrupted end 10a of the lug groove 10 is gradually reduced, the change in rigidity at the connection position with the fourth sipe 14 can be reduced.

  In the present embodiment, the fourth sipe 14 extends linearly. In another aspect, the fourth sipe 14 may include a bent portion in order to increase the edge component. In a particularly preferred embodiment, the fourth sipe 14 extends essentially parallel to the third sipe 13. “Essentially parallel” is as described above. On the other hand, as a mode for maximizing the road surface scratching effect, the fourth sipe 14 may extend along the tire axial direction.

  When the fourth sipe 14 is provided, as shown in FIG. 3, the maximum depth d5 is formed to be smaller than the depths of the first sipe 11, the second sipe 12, and the third sipe 13. desirable. In the present embodiment, the depth d5 of the fourth sipe 14 is configured to be substantially constant. In other aspects, the depth d5 may vary.

  FIG. 5 shows a further partial enlarged view of the inner middle land portion 6. As shown in FIG. 5, the inner middle land portion 6 includes a plurality of first blocks 21 and a plurality of second blocks 22.

  The first block 21 is divided between the second sipe 12 and the lug groove 10 adjacent in the tire circumferential direction. The first block 21 has an edge e1 extending in the tire circumferential direction on the first end 61 side of the tread surface.

  The second block 22 is divided between the second sipes 12 and 12 adjacent in the tire circumferential direction. The second block 22 has an edge e <b> 2 extending in the tire circumferential direction on the first end 61 side of the tread surface.

  In a preferred aspect, in at least one of the first blocks 21, at least a part of the edge e <b> 1 (in this embodiment, all of the edge e <b> 1) is in the width direction of the inner middle land portion 6 with respect to the edge e <b> 2 of the second block 22. Located inside.

  According to the said aspect, the 1st end 61 side of the inner middle land part 6 is made uneven, and the edge component increases. This enhances the road surface scratching effect on slippery road surfaces. Further, the step formed between the edges e1 and e2 adjacent in the tire circumferential direction generates a snow column shear force. Furthermore, by making the edge e1 of the first block 21 communicate with the lug groove 10, for example, snow in the lug groove 10 is easily discharged to the main groove 3 side, and the self-cleaning function of the lug groove 10 is improved. Therefore, according to the above aspect, the performance on snow can be further improved.

  FIG. 6A shows a cross-sectional view taken along line AA of FIG. As shown in FIGS. 5 and 6A, in the present embodiment, the edge e1 of the first block 21 is provided by, for example, providing the chamfered portion 17 on the first end 61 side of the first block 21. ing. For example, the chamfered portion 17 is formed as a concave arc-shaped recess with respect to the outer surface of the land. In order to improve the steering stability on the paved road and the performance on snow with a good balance, the depth d6 of the chamfered portion 17 is, for example, 30% to 100% of the maximum depth D (shown in FIG. 3) of the main groove 3; Preferably it is 50 to 100%. Similarly, it is desirable that the width W of the chamfered portion 17 in the tire axial direction is, for example, 0.5 to 5 mm. Furthermore, it is particularly desirable that the chamfered portion 17 is formed over the entire length of the first block 21 in the tire circumferential direction.

  As shown in FIG. 6B, as another aspect, for example, the edge e1 of the first block 21 is provided with a chamfered portion 17 formed of a linear slope on the first end 61 side of the first block 21. May be provided at.

  As shown in FIG. 5, the inner middle land portion 6 further includes a plurality of third blocks 23 and a plurality of fourth blocks 24.

  The third block 23 is divided between the third sipe 13 and the lug groove 10 (and the fourth sipe 14) adjacent in the tire circumferential direction. The third block 23 has an edge e3 extending in the tire circumferential direction on the second end 62 side of the tread surface.

  The fourth block 24 is divided between the third sipes 13 and 13 adjacent in the tire circumferential direction. The fourth block 24 has an edge e4 extending in the tire circumferential direction on the second end 62 side of the tread surface.

  In a preferred aspect, in at least one of the fourth blocks 24, at least a part of the edge e <b> 4 (in this embodiment, all of the edge e <b> 4) is wider than the edge e <b> 3 of the third block 23 in the width direction of the inner middle land portion 6. Located inside. According to this aspect, the same operation as described above can be obtained. The edge e4 of the fourth block 24 may be provided by providing the chamfered portion 17 as described above, as shown in FIGS. 6 (A) and 6 (B).

  In a preferred embodiment, the chamfered portion 17 on the first end 61 side and the chamfered portion 17 on the second end 62 side are desirably provided at different positions in the tire circumferential direction. As a result, the chamfered portions 17 are alternately brought into contact with the road surface at the first end 61 and the second end 62 of the inner middle land portion 6 when the tire is running, and a snow column shear force can be obtained with a good balance.

  FIG. 7 shows a partially enlarged view of the crown land portion 5 of FIG. The crown land portion 5 is provided with a plurality of crown sipes 30. In the present embodiment, each crown sipe 30 extends linearly. As another aspect, in order to increase the edge component, each crown sipe 30 may include a bent portion.

  In a preferred embodiment, the crown sipe 30 is desirably inclined with respect to the tire axial direction, preferably 5 to 45 in order to obtain a scratching effect in the tire axial direction while suppressing a decrease in lateral rigidity of the crown land portion 5. It is desirable to incline at an angle of 5 °, more preferably 5-30 °, and even more preferably 5-20 °. As a more preferable aspect, as in this embodiment, the crown sipe 30 is inclined in the opposite direction to the second sipe 12, the third sipe 13, and the lug groove 10 with respect to the tire axial direction.

  In a preferred embodiment, each crown sipe 30 extends over the entire width of the crown land portion 5. As a result, the crown land portion 5 is divided into crown blocks 32. Since the crown land portion 5 tends to have a relatively large contact pressure, the length P in the tire circumferential direction of the crown block 32 is set to the first to fourth blocks 21 to 24 of the inner middle land portion 6 described above. Is greater than 1.0 times the length in the tire circumferential direction, particularly preferably 1.3 times or more, and more preferably 1.4 times or more.

  In a preferred embodiment, the crown land portion 5 is desirably provided with a chamfered portion 33. The chamfered portion 33 is a recess whose length in the tire circumferential direction is larger than the length in the tire axial direction. In the present embodiment, the chamfered portions 33 are respectively provided at both ends of the crown land portion 5 in the tire axial direction. Each chamfer 33 generates a snow column shear force at that portion, and can further improve the performance on snow. Each chamfered portion 33 has the same configuration and preferred range as the chamfered portion 17 provided in the inner middle land portion 6.

  In a preferred embodiment, chamfered portions 33 are provided on both ends of the crown land portion 5 in the tire axial direction. In this case, it is desirable that the chamfered portion 33 is provided so as to communicate with the crown sipe 30.

  In this embodiment, the crown sipe 30 includes a first crown sipe 30A in which the chamfered portion 33 is connected to at least one end (both ends in the present embodiment), and a second crown sipe in which the chamfered portion 33 is not connected to both ends. 30B. In a preferred embodiment, the first crown sipe 30A and the second crown sipe 30B are alternately provided in the tire circumferential direction. As a result, the performance on snow is further improved while suppressing a decrease in steering stability on the paved road.

  FIG. 8A shows a cross-sectional view taken along line AA of FIG. As shown in FIG. 8A, the first crown sipe 30A is formed with a constant depth d7, for example. In order to improve on-snow performance while preventing the rigidity of the crown land portion 5 from decreasing, it is desirable that the depth d7 of the first crown sipe 30A be formed smaller than the depth of the chamfered portion 33, for example. In a preferred embodiment, the depth d7 is 30% or less of the maximum depth D of the main groove 3, more preferably about 10 to 30%.

  FIG. 8B shows a cross-sectional view taken along line BB in FIG. As shown in FIG. 8B, the depth of the second crown sipe 30B of the present embodiment changes in three stages. The second crown sipe 30B of the present embodiment includes a first portion 35, a second portion 36, and a third portion 37 in order of increasing depth.

  The first portion 35 is formed at both ends of the second crown sipe 30B in the tire axial direction. The depth of the first portion 35 coincides with the depth d7 of the first crown sipe 30A, for example. The second portion 36 is provided at the center portion of the second crown sipe 30B in the tire axial direction. The third portion 37 is provided between the first portion 35 and the second portion 36. In order to improve the performance on snow while preventing the rigidity of the crown land portion 5 from being lowered, the depth d8 of the third portion 37 of the second crown sipe 30B is, for example, 50% or more of the maximum depth D of the main groove 3 Preferably about 65 to 80% is desirable.

  As shown in FIG. 1, in the present embodiment, the outer middle land portion 7, the inner shoulder land portion 8, and the outer shoulder land portion 9 are respectively formed by an outer middle lateral groove 40, an inner shoulder lateral groove 41, and an outer shoulder lateral groove 42, respectively. It is divided into an outer middle block, an inner shoulder block and an outer shoulder block. These land portions 7 to 9 are preferably provided with sipes and chamfered portions as appropriate.

  As mentioned above, although embodiment of this invention was described in detail, it cannot be overemphasized that this invention can be changed in various aspects, without being limited to said embodiment.

  In order to confirm the effect of the present invention, 245 / 60R18 pneumatic tires having the basic pattern of FIG. 1 were prototyped based on the specifications in Table 1, and on-snow performance and steering stability were tested. The configuration other than the inner middle land is the same. The maximum depth D of the main groove was 7.9 mm. The test method is as follows.

<Snow performance>
A test driver ran a four-wheel drive vehicle with each sample tire mounted on the four wheels on a snowy road, and the driver's feelings comprehensively evaluated traction, turning performance, braking ability, and the like. Evaluation shows that it is so favorable that a numerical value is large.

<Steering stability>
A test driver ran a four-wheel drive vehicle with each sample tire mounted on the four wheels on a dry paved road, and the driver's feeling was comprehensively evaluated for handle response, rigidity, grip, etc. . Evaluation shows that it is so favorable that a numerical value is large.

  The results of the test are shown in Table 1. As is clear from Table 1, it can be confirmed that the tires of the examples improved the steering stability on the paved road and the performance on snow in a well-balanced manner as compared with the tires of the comparative examples.

2 tread portion 3 main groove 5 crown land portion 6 inner middle land portion 7 outer middle land portion 8 outer shoulder land portion 9 inner shoulder land portion 10 lug groove 11 first sipe 12 second sipe 13 third sipe 14 fourth sipe 17 Chamfered portion 21 First block 22 Second block 23 Third block 24 Fourth block 61 First end 62 Second end

Claims (11)

A pneumatic tire in which at least one land portion is divided into a tread portion,
The at least one land portion includes
A plurality of lug grooves extending from a first end that is one end of the land portion in the tire axial direction and having a discontinuous end in the land portion;
A first sipe extending along the tire circumferential direction between the lug grooves adjacent in the tire circumferential direction;
A plurality of second sipes extending from the first end toward the first sipes;
A plurality of third sipes extending from the second end, which is the other end in the tire axial direction of the land portion, to the first sipes,
The tire in which the second sipe and the third sipe are arranged without intersecting the lug groove.   The tire according to claim 1, wherein the second sipe, the third sipe, and the lug groove are inclined in the same direction with respect to a tire axial direction.   The tire according to claim 1 or 2, wherein the second sipe and the third sipe are essentially connected to the first sipe.   The tire according to any one of claims 1 to 3, wherein at least one end of the first sipe is connected to the lug groove.   The tire according to any one of claims 1 to 4, wherein a plurality of the second sipes are provided between the lug grooves adjacent in the tire circumferential direction.   The tire according to any one of claims 1 to 5, wherein a plurality of the third sipes are provided between the lug grooves adjacent in the tire circumferential direction.   7. One end of a fourth sipe is connected to the discontinuous end of each lug groove, and the other end of the fourth sipe is open to the second end. Tires. The land portion includes a first block partitioned between the second sipe and the lug groove adjacent in the tire circumferential direction, and a second block partitioned between the second sipe adjacent in the tire circumferential direction. Including
In the first block, at least a part of an edge extending in the tire circumferential direction on the first end side of the tread surface is more land than an edge extending in the tire circumferential direction on the first end side of the tread surface of the second block. The tire according to claim 1, which is located on the inner side in the width direction. The land portion includes a third block divided between the third sipe and the fourth sipe adjacent in the tire circumferential direction, and a fourth block divided between the third sipe adjacent in the tire circumferential direction. Including
In the fourth block, at least a part of the edge extending in the tire circumferential direction on the second end side of the tread surface is more land than the edge extending in the tire circumferential direction on the third end side of the tread surface of the third block. The tire according to claim 7, which is located on the inner side in the width direction. The tread portion is divided into five land portions including a crown land portion, a pair of middle land portions, and a pair of shoulder land portions by four main grooves extending continuously in the tire circumferential direction.
The tire according to any one of claims 1 to 9, wherein the at least one land portion is one land portion of the pair of middle land portions. The tread portion has a tread pattern in which the direction of mounting on the vehicle is specified,
The at least one land portion is an inner middle land portion located on the vehicle inner side when a tire is mounted on the vehicle, out of the pair of middle land portions,
The tire according to claim 10, wherein the first end is an end on the outer side in the tire axial direction of the inner middle land portion.

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