JP2019182206A - tire - Google Patents

Abstract

To provide a tire capable of improving steering stability on a pavement and on-snow performance in good balance.SOLUTION: A tire comprises a tread portion 2. The tread portion 2 is provided with two middle land parts 4 interposing a tire equator. Each of the two middle lands 4 is provided with: multiple lug grooves 10 extending from a first end 61 and having an interrupted end in the middle land part 4; first sipes 11 extending in a tire circumferential direction between the lug grooves 10 adjacent to each other in the tire circumferential direction; second sipes 12 extending from the first end 61 to the first sipes 11; and third sipes 13 extending from the second end 62 to the first sipes 11. The third sipe 13 communicates with the first sipe 11 at the same position as that of the second sipe 12.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 2012-201335 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 tire having a tread portion, and the tread portion is provided with two middle land portions sandwiching the tire equator, and each of the two middle land portions has a middle land portion. A plurality of lug grooves extending from a first end that is one end in the tire axial direction and having a discontinuous end in the middle land portion, and a first sipe extending in the tire circumferential direction between the lug grooves adjacent in the tire circumferential direction And a second sipe extending from the first end to the first sipe and a third sipe extending from the second end, which is the other end in the tire axial direction of the middle land portion, to the first sipe. The third sipe communicates with the first sipe at the same position in the tire circumferential direction as the second sipe.

  In the tire according to the present invention, when the vehicle mounting direction is specified, the tread portion has an outer tread end positioned outside the vehicle when the vehicle is mounted and an inner tread end positioned inside the vehicle when the vehicle is mounted. The first end is preferably an end on the inner tread end side of the middle land portion.

  In the tire according to the present invention, the two middle land portions include an inner middle land portion located between the inner tread end and the tire equator, and an outer middle land portion located between the outer tread end and the tire equator. Preferably, the outer middle land portion has a larger tire axial width than the inner middle land portion.

  In the tire according to the present invention, it is preferable that a width of the outer middle land portion in the tire axial direction is 1.05 to 1.10 times a width of the inner middle land portion in the tire axial direction.

  In the tire of the present invention, the length in the tire axial direction of the lug groove disposed in the outer middle land portion is greater than the length in the tire axial direction of the lug groove disposed in the inner middle land portion. desirable.

  In the tire of the present invention, a dimensional ratio of a length in the tire axial direction of the lug groove provided in the outer middle land portion to a width in the tire axial direction of the outer middle land portion is provided in the inner middle land portion. The length of the lug groove in the tire axial direction is preferably 0.95 to 1.05 times the dimensional ratio of the inner middle land portion to the tire axial width.

  In the tire according to the present invention, the tread portion includes an outer shoulder main groove disposed between the tire equator and the outer tread end, and an outer shoulder land portion between the outer shoulder main groove and the outer tread end. The outer shoulder land portion is provided with an outer shoulder sipe extending from the outer shoulder main groove to the outer tread end, and the outer shoulder sipe has an end on the outer shoulder main groove side and the outer tread. It is desirable to have an intermediate shallow bottom with a raised bottom surface between the ends.

  In the tread portion of the tire of the present invention, two middle land portions are provided so as to sandwich the tire equator. Each of the two middle land portions is provided with a plurality of lug grooves extending from a first end that is one end in the tire axial direction of the middle land portion and having a discontinuous end in the middle 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. The lug groove has a discontinuous end in the middle land portion and does not completely cross the middle land portion. Therefore, the lowering of the rigidity of the middle land portion is suppressed as much as possible, and the deterioration of the steering stability on the paved road is prevented.

  According to the present invention, the first sipes extending in the tire circumferential direction between the lug grooves adjacent in the tire circumferential direction are provided. 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 middle 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 to the first sipe, and a third sipe extending from the second end, which is the other end in the tire axial direction of the middle land portion, to the first sipe, Is 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 while minimizing the rigidity deterioration of the middle land portion is minimized. Can be provided.

  According to the present invention, the third sipe communicates with the first sipe at the same position in the tire circumferential direction as the second sipe. Thereby, since the 2nd sipe and the 3rd sipe become easy to open near the 1st sipe, it can provide a larger frictional force on a snowy road.

  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 an enlarged view 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 an enlarged view of the crown land part of FIG. (A) is the sectional view on the AA line of FIG. 7, (B) is the sectional view on the BB line of FIG. It is an enlarged view of the inner side shoulder land part of FIG. (A) is the sectional view on the AA line of FIG. 9, (B) is the sectional view on the BB line of FIG. 9, (C) is the sectional view on the CC line of FIG. . It is an enlarged view of the outer side shoulder land part of FIG. It is the DD sectional view taken on the line of FIG. It is an expanded view of the tread part of the tire of a comparative example.

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 1 of 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.

  In the case of a pneumatic tire, the inner tread end Te1 and the outer tread end Te2 are the contact positions on the outermost side in the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire 1 contacts the plane with a camber angle of 0 °. The normal state is a state in which the tire is assembled on the normal rim and is filled with the normal internal pressure, and further, there is no load. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in a normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, and “ETRTO” If there is "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JATMA” is the “highest air pressure”, TRA is the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JAMATA” is “Maximum load capacity”, TRA is “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  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. The width of the main groove 3 is, for example, 3.0% to 5.0% of the tread width. The tread width is a distance in the tire axial direction from the inner tread end Te1 to the outer tread end Te2 in the normal state. 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.

  The distance in the tire axial direction from the tire equator C to the groove center line of the inner crown main groove 3A and the distance in the tire axial direction from the tire equator C to the groove center line of the outer crown main groove 3B are respectively the tread width. 5% to 15% is desirable. The distance in the tire axial direction from the tire equator C to the groove center line of the inner shoulder main groove 3C and the distance in the tire axial direction from the tire equator C to the groove center line of the outer shoulder main groove 3D are respectively the tread width. It is desirable to be 20% to 30%.

  By the main grooves 3, two middle land portions 4 are provided in the tread portion 2 so as to sandwich the tire equator C. In the tread portion 2 of the present embodiment, two middle land portions 4 include an inner middle land portion 6 located between the inner tread end Te1 and the tire equator C, an outer tread end Te2 and the tire equator C. An outer middle land portion 7 located between them is provided. In addition to these, the tread portion 2 of the present embodiment includes a crown land portion 5, an inner shoulder land portion 8, and an outer shoulder land portion 9, and is divided into five land portions. However, the tread portion 2 of the tire 1 of the present invention is not limited to such an embodiment. For example, the two main land portions 4 and the two shoulder land portions 8 and 9 are separated by three main grooves 3. The so-called four ribs may be used.

  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 crown main groove 3A and the inner shoulder main groove 3C. The outer middle land portion 7 is divided between the outer crown 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.

  The middle land portion 4 has a first end 61 and a second end 62. The first end 61 is an end of the middle land portion 4 on the inner tread end Te1 side. The second end 62 is an end of the middle land portion 4 on the outer tread end Te2 side. For this reason, the first end 61 of the inner middle land portion 6 faces the inner shoulder main groove 3C, and the first end 61 of the outer middle land portion 7 faces the outer crown main groove 3B. The second end 62 of the inner middle land portion 6 faces the inner crown main groove 3A, and the second end 62 of the outer middle land portion 7 faces the outer shoulder main groove 3D.

  FIG. 2 shows an enlarged view of the inner middle land portion 6. Hereinafter, the configuration of the middle land portion 4 will be described by taking the inner middle land portion 6 as an example. However, the configuration of the inner middle land portion 6 can also be applied to the outer middle land portion 7.

  As shown in FIG. 2, in the present embodiment, the middle land portion 4 is provided with a lug groove 10, a first sipe 11, a second sipe 12, and a third sipe 13. 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.

  Each lug groove 10 extends partially across the middle land portion 4 from the first end 61 of the middle land portion 4, and has a discontinuous end 10 a in the middle land portion 4. That is, the lug groove 10 does not reach the second end 62 of the middle land portion 4. In the present embodiment, the lug groove 10 extends linearly from the first end 61 to the discontinuous end 10a. 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. Moreover, the lug groove 10 suppresses the deterioration of the rigidity of the middle land portion 4 as much as possible, and prevents the steering stability on the paved road from deteriorating.

  The width of each lug groove 10 is preferably 5% to 15% of the length of one pitch between the lug grooves 10 adjacent in the tire circumferential direction, for example. More specifically, the width of each lug groove 10 may be 8.0 mm or less, 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 middle land portion 4 in the tire axial direction. This helps to generate a snow column shear force in a wider range in the tire axial direction. In order to obtain a well-balanced snow column shear force while preventing deterioration in steering stability on a paved road, the length L1 of the lug groove 10 in the tire axial direction is the maximum width Lm of the middle land portion 4 in the tire axial direction. It is desirable to be 60% to 80%.

  In order to obtain a scratching effect in the tire axial direction while suppressing a decrease in lateral rigidity of the middle land portion 4, 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 50% to 70% 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. Is desirable.

  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 in the tire circumferential direction between the lug grooves 10 and 10 adjacent in the tire circumferential direction. In the present embodiment, the first sipe 11 extends linearly along the tire circumferential direction. 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. Since the first sipe 11 has a width smaller than that of the groove, the first sipe 11 provides a road surface scratching effect when a slip angle is given to the tire while preventing the rigidity of the middle land portion 4 from being reduced. Increase the driving stability.

  In a preferred embodiment, the first sipe 11 is provided on the center position of the maximum width Lm of the middle land portion 4. As a result, the rigidity deviation of the middle land portion 4 and, consequently, the deterioration of the steering stability can be further prevented.

  FIG. 3 shows a cross-sectional view of the first sipe 11. In order to suppress a decrease in rigidity of the middle land portion 4, 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 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 middle land portion 4 to 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 middle land portion 4 to 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 a preferred embodiment, the second sipe 12 and the third sipe 13 are arranged so as to equally divide the adjacent lug grooves 10 into substantially equal lengths in the tire circumferential direction (for example, the difference in length is within 5%). The Such an arrangement is useful for suppressing local rigidity reduction of the middle land portion 4 and improving steering stability on a paved road.

  The second sipe 12 and the third sipe 13 are at least essentially connected to the first sipe 11. 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. The second sipe 12 and the third sipe 13 of the present embodiment are in actual communication with 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.

  Since the second sipe 12 and the third sipe 13 have a smaller width than the groove, the road surface scratches on the snowy road over a wide range of the land portion while minimizing the rigidity reduction of the middle land portion 4. An effect can be provided.

  The third sipe 13 communicates with the first sipe 11 at the same position in the tire circumferential direction as the second sipe 12. Thereby, since the 2nd sipe 12 and the 3rd sipe 13 become easier to open in the 1st sipe 11 vicinity, it can provide a bigger frictional force on a snowy road. “Communicating at the same position in the tire circumferential direction” means that a first region in which one end of the sipe is extended along the tire axial direction and a first region in which the end of the other sipe is extended along the tire axial direction. A mode in which the minimum distance in the tire circumferential direction from the two regions is less than 2 mm is included. In a more desirable mode, it is desirable that the first region and the second region intersect each other. As a more desirable mode, in this embodiment, the edge of the second sipe 12 and the edge of the third sipe 13 are arranged in a straight line.

  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.

  Since the tire 1 of the present embodiment includes the inner middle land portion 6 and the outer middle land portion 7 having the above-described configuration, it can exhibit good steering stability and performance on snow.

  In a preferred embodiment, it is desirable that the second sipe 12 and the third sipe 13 are 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 middle land portion 4. The angle is preferably 5 to 45 °, more preferably 5 to 30 °, and still more preferably 5 to 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.

  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 middle land portion 4 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 outer middle land portion 7. 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, a 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, it is desirable that the middle land portion 4 is provided with a chamfered portion 17 in which a part of a tread surface and a side corner portion of the land portion is recessed. The chamfered portion 17 includes a first chamfered portion 18 that connects the lug groove 10 and the second sipe 12 on the first end 61 side. The first chamfered portion 18 forms a large snow column together with the lug groove 10, makes it easy to discharge the snow in the lug groove 10, and can continuously exhibit excellent performance on snow. In a desirable mode, chamfering part 18 contains the 2nd chamfering part 19 which connects between two 3rd sipes 13 on the 2nd end 62 side, for example. The second chamfered portion 19 can further enhance the performance on snow together with the first chamfered portion 18.

  In order to improve the steering stability and the performance on snow in a well-balanced manner, the length of the first chamfered portion 18 in the tire circumferential direction is preferably 0.30 to 0.50 times the pitch length of the lug grooves 10. .

  FIG. 6A shows a cross-sectional view taken along line AA of FIG. 5 and 6A, in this embodiment, the depth d6 of the chamfered portion 17 is, for example, 30% to 100% of the maximum depth D of the main groove 3 (shown in FIG. 3). Preferably, it is desirable to be 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.

  As shown in FIG. 6B, as another aspect, the chamfered portion 17 may be formed to include, for example, a linear slope.

  As shown in FIGS. 3 and 4, the first chamfered portion 18 and the second chamfered portion 19 desirably have a depth larger than that of the first sipe 11, for example. Further, it is desirable that the first chamfered portion 18 and the second chamfered portion 19 have a depth greater than that of the lug groove 10. Such a chamfer 17 can provide a large snow column shear force.

  As shown in FIG. 5, it is desirable that the angle between the lug groove 10 and the first chamfered portion 18 is an obtuse angle in the tread plan view. Thereby, the snow in the lug groove 10 and the 1st chamfer part 18 becomes easy to be discharged | emitted integrally at the time of driving | running | working on snow, and the outstanding on-snow performance is exhibited continuously.

  It is desirable that the first chamfered portion 18 and the second chamfered portion 19 are 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.

  The region where the second chamfered portion 19 extends to the first end 61 side along the tire axial direction preferably intersects with a part of the first chamfered portion 18. Such arrangement of the chamfered portion 17 can further improve the performance on snow.

  The middle land portion 4 includes a plurality of first blocks 21 and a plurality of second blocks 22 by providing the lug grooves 10 and the sipes described above.

  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. The edge e1 of the first block 21 is located on the inner side in the width direction of the middle land portion 4 than the edge e2 of the second block 22. The edge e1 of the first block 21 is formed by, for example, the first chamfered portion 18.

  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. The edge e4 of the fourth block 24 is located on the inner side in the width direction of the middle land portion 4 than the edge e3 of the third block 23. The edge e4 of the fourth block 24 is formed by, for example, the second chamfer 19.

  As shown in FIG. 1, the outer middle land portion 7 desirably has a larger width in the tire axial direction than the inner middle land portion 6. The width of the outer middle land portion 7 in the tire axial direction is preferably 1.05 to 1.10 times the width of the inner middle land portion in the tire axial direction, for example. Such an outer middle land portion 7 has high rigidity and can improve steering stability.

  The length in the tire axial direction of the lug groove 10 disposed in the outer middle land portion 7 is desirably larger than the length in the tire axial direction of the lug groove 10 disposed in the inner middle land portion 6.

  In a more desirable mode, the dimensional ratio of the length in the tire axial direction of the lug groove 10 provided in the outer middle land portion 7 to the width in the tire axial direction of the outer middle land portion 7 is provided in the inner middle land portion 6. The length of the lug groove 10 in the tire axial direction is preferably 0.95 to 1.05 times the dimensional ratio of the inner middle land portion 6 to the width in the tire axial direction. Thereby, the partial wear of the inner middle land portion 6 and the outer middle land portion 7 is suppressed.

  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 inclined at 5 °, more preferably 5-30 °, and still 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 be subjected to a relatively large contact pressure, the length of the crown block 32 in the tire circumferential direction is equal to the length of each block of the inner middle land portion 6 in the tire circumferential direction. It is larger than 1.0 times, particularly preferably 1.3 times or more, more preferably 1.4 times or more.

  In a preferred mode, it is desirable that the crown land portion 5 is provided with a chamfered portion 33 in which a part of the corner portion on the tread surface and the side surface is recessed. For example, the chamfered portion 33 is longer in the tire circumferential direction than 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 chamfer 33 has the same configuration and preferable range as the chamfer 17 provided in the middle land portion 4.

  It is desirable that the chamfered portion 33 provided in the crown land portion 5 has a smaller tire circumferential length than the chamfered portion 17 provided in the middle land portion 4, for example. Thereby, the partial wear of the crown land portion 5 is suppressed.

  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, the chamfered portion 33 is desirably 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 30B in which the chamfered portion 33 is not connected to both ends. Including. 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 being lowered, 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.

  FIG. 9 shows an enlarged view of the inner shoulder land portion 8. As shown in FIG. 9, the inner shoulder land portion 8 includes, for example, a plurality of inner shoulder lateral grooves 41, a chamfered portion 43 in which a part of a tread surface and a side corner portion of the land portion is recessed, and a plurality of inner shoulder portions. A sipe 45 is provided.

  For example, the inner shoulder lateral groove 41 desirably extends from the inner shoulder main groove 3C to the inner tread end Te1. The inner shoulder lateral groove 41 of the present embodiment extends, for example, with a constant groove width. The groove width of the inner shoulder lateral groove 41 is preferably larger than the groove width of the lug groove 10 provided in the inner middle land portion 6.

  For example, the inner shoulder lateral groove 41 is preferably inclined in the same direction as the lug groove 10 provided in the inner middle land portion 6 with respect to the tire axial direction. For example, the inner shoulder lateral grooves 41 are arranged at an angle of 5 to 15 ° with respect to the tire axial direction.

  FIG. 10A shows a cross-sectional view taken along line AA of FIG. As shown in FIG. 10A, it is desirable that a shallow bottom portion 41a having a locally small depth is provided on the inner shoulder main groove 3C side of the inner shoulder lateral groove 41. The depth d10 of the shallow bottom portion 41a is preferably 40% to 60% of the maximum depth d9 of the inner shoulder lateral groove 41, for example.

  As shown in FIG. 9, the chamfered portion 43 is provided between the inner shoulder lateral grooves 41 arranged in the tire circumferential direction, for example. The chamfered portion 43 of the present embodiment has, for example, substantially the same cross-sectional shape as the chamfered portion 17 disposed on the inner middle land portion 6. The chamfered portion 43 of the present embodiment is not connected to any of the inner shoulder lateral grooves 41 located on both sides in the tire circumferential direction. Such a chamfered portion 43 can improve the performance on snow.

  The length in the tire circumferential direction of the chamfered portion 43 provided in the inner shoulder land portion 8 is preferably larger than the length in the tire circumferential direction of the chamfered portion 17 provided in the inner middle land portion 6. Such a chamfered portion 43 makes the progress of wear uniform between the inner shoulder land portion 8 and the inner middle land portion 6 and provides excellent wear resistance.

  The inner shoulder sipe 45 includes, for example, a first inner shoulder sipe 46 that completely crosses the inner shoulder land portion 8, and a second inner shoulder that extends from the inner tread end Te1 toward the tire equator C and is interrupted in the inner shoulder land portion 8. And Sipe 47.

  It is desirable that the first inner shoulder sipe 46 communicates with the chamfered portion 43, for example. In the present embodiment, two first inner shoulder sipes 46 are arranged between the inner shoulder lateral grooves 41 adjacent in the tire circumferential direction, and communicate with the end portions of the chamfered portion 43 in the tire circumferential direction. Such a first inner shoulder sipe 46 helps to increase traction on snow.

  FIG. 10B is a sectional view taken along line BB in FIG. As shown in FIG. 10B, the first inner shoulder sipe 46 desirably has a shallow bottom portion 46 a with a groove bottom raised at the chamfered portion 43, for example. Such a 1st inner side shoulder sipe 46 can improve steering stability and on-snow performance with sufficient balance.

  The second inner shoulder sipe 47 is preferably provided between the two first inner shoulder sipes 46 described above, for example. FIG. 10C shows a cross-sectional view taken along the line CC of FIG. As shown in FIG. 10C, it is desirable that the groove depth of the second inner shoulder sipe 47 is gradually reduced toward the discontinuous end.

  FIG. 11 shows an enlarged view of the outer shoulder land portion 9. As shown in FIG. 11, the outer shoulder land portion 9 includes, for example, a plurality of outer shoulder lateral grooves 51, a chamfered portion 53 in which a part of a tread surface and a side corner portion of the land portion is recessed, and a plurality of outer shoulder portions. A sipe 55 is provided.

  The outer shoulder lateral groove 51 desirably extends from the outer shoulder main groove 3D to the outer tread end Te2, for example. The outer shoulder lateral groove 51 of the present embodiment includes, for example, an outer groove portion 51a on the outer tread end Te2 side and an inner groove portion 51b on the outer shoulder main groove 3D side. The inner groove portion 51b has a smaller groove width and groove depth than the outer groove portion 51a. Such outer shoulder lateral grooves 51 can improve the performance on snow while maintaining steering stability on a paved road.

  The chamfered portion 53 provided in the outer shoulder land portion 9 has substantially the same cross-sectional shape as the chamfered portion 17 disposed in the middle land portion 4, for example. Moreover, it is desirable that the chamfered portion 53 provided in the outer shoulder land portion 9 communicates with the inner groove portion 51b of the outer shoulder main groove 3D, for example. The chamfered portion 53 disposed in the outer shoulder land portion 9 of the present embodiment has a greater tire circumferential length than the chamfered portion 17 disposed in the middle land portion 4, for example.

  The outer shoulder sipe 55 extends, for example, from the outer tread end Te2 to the outer shoulder main groove 3D. For example, the outer shoulder sipe 55 may communicate with the chamfered portion 53.

  FIG. 12 is a cross-sectional view of the outer shoulder sipe 55 of the present embodiment taken along line DD. As shown in FIG. 12, the outer shoulder sipe 55 of the present embodiment includes, for example, an end-side shallow bottom portion 56 in which the bottom surface of the end portion on the outer shoulder main groove 3D side is raised, and an end portion on the outer shoulder main groove 3D side. And an intermediate shallow bottom portion 57 having a raised bottom surface between the outer tread end Te2 and the outer tread end Te2. Such end-side shallow bottom portion 56 and intermediate shallow bottom portion 57 can suppress the outer shoulder sipe 55 from opening excessively, and can exhibit excellent on-snow performance while suppressing a decrease in steering stability.

  In order to improve the steering stability and the performance on the snow in a well-balanced manner, the depth d12 of the end shallow portion 56 or the intermediate shallow portion 57 is, for example, 0.40 to 0.60 of the maximum depth d11 of the outer shoulder sipe 55. Is double. Specifically, the maximum depth d11 is, for example, 4.0 to 5.5 mm, and the depth d12 is, for example, 2.1 to 2.6 mm.

  The distance L2 in the tire axial direction from the edge of the outer shoulder land portion 9 (which means an edge ignoring the chamfered portion 53) to the center position in the tire axial direction of the intermediate shallow portion 57 is, for example, the tire of the outer shoulder land portion 9 It is desirable to be 0.35 to 0.55 times the axial width W1 (shown in FIG. 11, the same applies hereinafter). Such an intermediate shallow bottom portion 57 can effectively prevent the outer shoulder sipe 55 from opening.

  The width W2 of the middle shallow bottom portion 57 in the tire axial direction is, for example, 0.15 to 0.25 times the width W1 of the outer shoulder land portion 9. The angle with respect to the tire radial direction of the first inclined portion 57a on the outer shoulder main groove 3D side of the intermediate shallow portion 57 is, for example, 30 to 45 °. The angle of the second inclined portion 57b on the outer tread end Te2 side of the intermediate shallow portion 57 with respect to the tire radial direction is, for example, 15 to 45 °. Such a middle shallow bottom portion 57 can improve steering stability and performance on snow in a well-balanced manner.

  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.

A pneumatic tire of size 245 / 60R18 having the basic tread pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire having a tread pattern shown in FIG. 13 was prototyped. In the tread pattern of FIG. 13, a lateral groove b and a sipe c that completely cross the land portion are provided in the outer middle land portion a. Further, the land portion a is not provided with a sipe extending in the tire circumferential direction. The tread pattern shown in FIG. 13 is substantially the same as the pattern shown in FIG. 1 except for the configuration of the outer middle land portion a. Each test tire was tested for snow performance and handling stability. The common specifications and test methods for each test tire are as follows.
Test vehicle: displacement 3600cc, four-wheel drive vehicle Test tire mounting position: all wheels Rim: 18 x 7.5J
Tire internal pressure: 240kPa

<Snow performance>
The running performance when running on a snowy road with the test vehicle was evaluated by the driver's sensuality. A result is a score which makes a comparative example 100, and shows that performance on snow is excellent, so that a numerical value is large.

<Steering stability>
The driving stability of the test vehicle when traveling on a dry paved road was evaluated by the driver's sensuality. A result is a score which makes a comparative example 100, and shows that steering stability is excellent, so that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples were improved in a well-balanced manner in handling stability on the paved road and performance on snow.

2 tread portion 4 middle land portion 10 lug groove 11 first sipe 12 second sipe 13 third sipe 61 first end 62 second end

Claims (7)

A tire having a tread portion,
The tread part is provided with two middle land parts sandwiching the tire equator,
In each of the two middle land sections,
A plurality of lug grooves extending from a first end which is one end in the tire axial direction of the middle land portion and having a discontinuous end in the middle land portion;
A first sipe extending in the tire circumferential direction between the lug grooves adjacent in the tire circumferential direction;
A second sipe extending from the first end to the first sipe;
A third sipe extending from the second end, which is the other end in the tire axial direction of the middle land portion, to the first sipe;
The third sipe communicates with the first sipe at the same position in the tire circumferential direction as the second sipe.
tire. By specifying the direction of vehicle mounting, the tread portion has an outer tread end positioned outside the vehicle when mounted on the vehicle, and an inner tread end positioned inside the vehicle when mounted on the vehicle,
The tire according to claim 1, wherein the first end is an end of the middle land portion on the inner tread end side. The two middle land portions include an inner middle land portion located between the inner tread end and the tire equator, and an outer middle land portion located between the outer tread end and the tire equator,
The tire according to claim 2, wherein the outer middle land portion has a larger width in the tire axial direction than the inner middle land portion.   The tire according to claim 3, wherein a width of the outer middle land portion in the tire axial direction is 1.05 to 1.10 times a width of the inner middle land portion in the tire axial direction.   The length in the tire axial direction of the lug groove disposed in the outer middle land portion is greater than the length in the tire axial direction of the lug groove disposed in the inner middle land portion. tire.   The dimensional ratio of the length in the tire axial direction of the lug groove provided in the outer middle land portion to the width in the tire axial direction of the outer middle land portion is determined by the ratio of the lug groove provided in the inner middle land portion. The tire according to any one of claims 3 to 5, wherein the tire axial length is 0.95 to 1.05 times the dimensional ratio of the inner middle land portion to the tire axial width. The tread portion has an outer shoulder main groove disposed between a tire equator and the outer tread end, and an outer shoulder land portion between the outer shoulder main groove and the outer tread end,
The outer shoulder land portion is provided with an outer shoulder sipe extending from the outer tread end to the outer shoulder main groove,
The tire according to any one of claims 2 to 6, wherein the outer shoulder sipe has an intermediate shallow bottom portion whose bottom surface is raised between an end portion on the outer shoulder main groove side and the outer tread end.

Images