Tire

Abstract

To provide a tire capable of exhibiting an excellent on-ice / snow performance while maintaining a dry performance.SOLUTION: The present invention relates to a tire having a tread part 2. The tread part 2 includes a circumferential direction groove 3 and a land part 4. The circumferential direction groove 3 includes a crown peripheral direction groove 5 and a shoulder peripheral direction groove 6. The land part 4 includes a middle land part 7. The middle land part 7 is provided with a communication sipe 10, an inside sipe 15, and an outside sipe 20. The communication sipe 10 includes a first communication sipe 11. The first communication sipe 11 includes a first straight portion 26 linearly extending from the crown peripheral direction groove 5, and a first curved part 27 extending so as to curve from an end portion of the first straight portion 26 to the shoulder peripheral direction groove 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Patent Document 1 below proposes a tire provided with first and second inclined sipes that extend linearly in the land portion of the tread. This tire is expected to improve steering stability on dry roads and performance on ice and snow by providing deep and shallow bottom portions in the first and second inclined sipes, respectively. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-064106 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the improvement in vehicle performance, there has been a demand for further improvement in tire performance on snow and ice. However, sipes that extend linearly over the entire range, such as those shown in Patent Document 1, tend to provide frictional force only in a specific direction, and there has been a demand for improvement in cornering performance (especially steering responsiveness) on snow and ice. On the other hand, even tires that run on snow and ice need to maintain their driving performance on dry roads (hereinafter referred to as "dry performance").

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that can exhibit excellent performance on ice and snow while maintaining dry performance. [Means for solving the problem]

[0006] The present invention provides a tire having a tread portion, the tread portion including a plurality of circumferential grooves extending continuously in the tire circumferential direction, and a plurality of land portions separated by the plurality of circumferential grooves, the plurality of circumferential grooves including a crown circumferential groove disposed on the tire equator side, and a shoulder circumferential groove adjacent to the crown circumferential groove on the tire axially outer side, the plurality of land portions including one middle land portion separated between the crown circumferential groove and the shoulder circumferential groove, the middle land portion including a plurality of communicating sipes extending from the crown circumferential groove to the shoulder circumferential groove, the tire is provided with a plurality of inner sipes that communicate with the crown circumferential groove, extending in the tire axial direction, but not communicating with the shoulder circumferential groove, and a plurality of outer sipes that communicate with the shoulder circumferential groove, extending in the tire axial direction, but not communicating with the crown circumferential groove, the plurality of communicating sipes including a plurality of first communicating sipes, each of the plurality of first communicating sipes including a first straight portion that extends linearly from the crown circumferential groove, and a first curved portion that extends curvedly from an end of the first straight portion toward the shoulder circumferential groove. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire of the present invention can exhibit excellent performance on ice and snow while maintaining dry performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the middle land area of ​​FIG. [Figure 3] 3 is an enlarged view of the first communicating sipe and its surroundings in FIG. 2. [Figure 4] 3 is an enlarged view of the second communicating sipe and its surroundings in FIG. 2. FIG. [Figure 5] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 6] FIG. 2 is an enlarged view of the crown land portion of FIG. [Figure 7]FIG. 7 is a cross-sectional view taken along line BB in FIG. 6. [Figure 8] FIG. 2 is an enlarged view of the shoulder land portion of FIG. [Figure 9] FIG. 2 is a development view of a tread portion of a tire of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the drawings. The drawings are intended to illustrate the features of the present invention, but may include exaggerated representations and representations that differ from the dimensional ratios of the actual structure to facilitate understanding of the present invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, well-known configurations may be appropriately adopted for configurations not described in this specification.

[0010] 1 is a development view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of this embodiment is used, for example, as a pneumatic tire for winter passenger cars. However, the present invention is not limited to this embodiment.

[0011] As shown in FIG. 1, the tread portion 2 includes a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between two tread ends Te, and a plurality of land portions 4 separated by the circumferential grooves 3.

[0012] The two tread edges Te correspond to the edges of the contact patch when the tire 1 in a normal state is loaded with 70% of the normal load and the tread portion 2 is brought into contact with a flat surface at a camber angle of 0°.

[0013] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0014] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0015] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0016] For pneumatic tires for which various standards are established, "normal load" refers to the load specified for each tire in the standard system including the standard on which the tire is based. For JATMA, this is "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is "LOAD CAPACITY." For tires for which various standards are not established, "normal load" refers to the maximum load that can be applied when using the tire in accordance with the above standards.

[0017] The circumferential grooves 3 include, for example, two crown circumferential grooves 5 and two shoulder circumferential grooves 6 .

[0018] The two crown circumferential grooves 5 are provided so as to sandwich the tire equator C. The two shoulder circumferential grooves 6 are provided so as to sandwich the two crown circumferential grooves 5. The axial distance L1 from the groove center line of the crown circumferential groove 5 to the tire equator C is, for example, 5% to 15% of the tread width TW. The axial distance L2 from the groove center line of the shoulder circumferential groove 6 to the tire equator C is, for example, 20% to 35% of the tread width TW. The tread width TW is the axial distance between the two tread ends Te in the normal state.

[0019] The circumferential grooves 3 extend linearly, for example, parallel to the tire circumferential direction. The groove width W1 of the circumferential grooves 3 is, for example, 3.0 mm or more. The groove width W1 of the circumferential grooves 3 is preferably, for example, 3.0% to 6.0% of the tread width TW. The depth (not shown) of the circumferential grooves 3 is, for example, 5.0 to 15.0 mm.

[0020] In this specification, when the numerical ranges of various parameters are described, unless otherwise specified, the numerical ranges refer to the average values ​​of the parameters. Therefore, the numerical ranges of the groove width and depth of the circumferential groove 3 refer to the average numerical ranges of the groove width and depth measured at various positions on the circumferential groove 3. The same applies to other parameters described later.

[0021] The land portion 4 includes at least a middle land portion 7. The middle land portion 7 is divided between the crown circumferential groove 5 and the shoulder circumferential groove 6. In this embodiment, the two middle land portions 7 are provided so as to sandwich the tire equator C therebetween.

[0022] In this embodiment, the land portion 4 includes, in addition to the above-mentioned middle land portion 7, two shoulder land portions 9 and one crown land portion 8. The shoulder land portion 9 is defined axially outward of the shoulder circumferential groove 6 and includes the tread edge Te. The crown land portion 8 is defined between the two crown circumferential grooves 5. As a result, the crown land portion 8 is adjacent to the middle land portion 7 via the crown circumferential groove 5. The crown land portion 8 is also provided on the tire equator C.

[0023] The tread portion 2 of this embodiment has a pattern that is point-symmetric with respect to a point on the tire equator C. Therefore, the features described for one middle land portion 7 can also be applied to the other middle land portion 7. The same applies to the two shoulder land portions 9.

[0024] Fig. 2 shows an enlarged view of the middle land portion 7 of Fig. 1. As shown in Fig. 2, the middle land portion 7 is provided with a plurality of communicating sipes 10, a plurality of inner sipes 15, and a plurality of outer sipes 20.

[0025] In this specification, the term "sipe" refers to a small-width notch in which, when a ground load acts on the tread portion 2, two sipe walls included in the sipe main body come into contact with each other, thereby maintaining the rigidity of the land portion. The sipe main body refers to a portion in which two sipe walls extend substantially parallel to each other (for example, at an angle of 10° or less) in the tire radial direction. From the viewpoint of achieving the above-described effect, the width between the two sipe walls in the sipe main body is, for example, 1.5 mm or less, preferably 0.4 to 1.2 mm, and more preferably 0.4 to 1.0 mm. The sipe of this embodiment extends with a constant width from its opening to its bottom. However, the sipe may have a chamfered edge. The sipe may also have a so-called flask bottom, which is wider at its bottom.

[0026] Unless otherwise specified, each groove in this specification is designed so that two groove walls do not come into contact with each other even when ground pressure acts, and a substantial drainage path can be maintained. From this perspective, the groove width of each groove is set to, for example, 2.0 mm or more.

[0027] The communicating sipes 10 extend from the crown circumferential groove 5 to the shoulder circumferential groove 6. The inner sipes 15 communicate with the crown circumferential groove 5 and extend in the tire axial direction, but do not communicate with the shoulder circumferential groove 6. The outer sipes 20 communicate with the shoulder circumferential groove 6 and extend in the tire axial direction, but do not communicate with the crown circumferential groove 5. Note that "a sipe communicates with a circumferential groove" includes a case where a space constituting another groove or recess is interposed between the end of the sipe and the circumferential groove. However, in this case, the axial length of the space must be 5 mm or less.

[0028] The plurality of communicating sipes 10 include a plurality of first communicating sipes 11. FIG. 3 shows an enlarged view of one first communicating sipe 11 and its surroundings. As shown in FIGS. 2 and 3, each of the plurality of first communicating sipes 11 includes a first straight portion 26 extending linearly from the crown circumferential groove 5 and an outer portion 24 extending from an end of the first straight portion 26 to the shoulder circumferential groove 6. The outer portion 24 also includes a first curved portion 27 extending in a curved manner from the end of the first straight portion 26 toward the shoulder circumferential groove 6. By employing the above-described configuration, the tire 1 of the present invention can exhibit excellent performance on snow and ice while maintaining dry performance. The reasons for this are as follows.

[0029] As shown in Figure 2, the middle land portion 7 of the tire 1 of the present invention is provided with the connecting sipes 10, outer sipes 20, and inner sipes 15, as described above. These sipes provide friction on icy and snowy roads. The outer sipes 20 and inner sipes 15 also help prevent excessive reduction in rigidity of the middle land portion 7 and maintain dry performance.

[0030] As shown in Figure 3, the first communicating sipe 11 of the present invention includes a first straight portion 26 and a first curved portion 27. The first straight portion 26 helps to improve traction performance on snow and ice. Meanwhile, the first curved portion 27 provides frictional force in multiple directions, improving steering responsiveness on snow and ice, and ultimately improving cornering performance on snow and ice. Due to this mechanism, the tire of the present invention can exhibit excellent performance on snow and ice while maintaining dry performance.

[0031] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to the tire 1 of the present invention having the above-described characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, an improvement in combined performance corresponding to those configurations can be expected.

[0032] The first straight portion 26 is inclined at an angle θ1 with respect to the tire axial direction, for example. The angle θ1 is, for example, 10 to 50°, and preferably 25 to 35°. The axial length L3 of the first straight portion 26 is, for example, 25% to 40% of the axial width W2 (shown in FIG. 2) of the tread surface of the middle land portion 7. This reliably improves traction performance on icy and snowy roads.

[0033] The first curved portion 27 is a portion whose angle θ2 with respect to the tire axial direction changes continuously from the end on the first straight portion 26 side toward the shoulder circumferential groove 6 (shown in FIG. 2). In this embodiment, the first curved portion 27 is arc-shaped with a single radius of curvature r1, but is not limited to this. The radius of curvature r1 is, for example, 30 to 50 mm, and preferably 33 to 40 mm.

[0034] The first communicating sipe 11 of this embodiment is bent between the first straight portion 26 and the first curved portion 27. In this embodiment, the first straight portion 26 is inclined toward one side in the tire circumferential direction toward the axially outer side of the tire (inclined upward to the left in FIG. 3), and the first curved portion 27 connected to the first straight portion 26 is curved in a direction that convexly faces axially inward and toward the one side in the tire circumferential direction (upper right in FIG. 3). As a result, the angle θ2 of the first curved portion 27 with respect to the tire axial direction decreases from the end on the first straight portion 26 side toward the shoulder circumferential groove 6 side.

[0035] The range of change of the angle θ2 is, for example, 25 to 75°. The angle θ3 between the first straight portion 26 and the first curved portion 27 is, for example, 90 to 160°, and preferably 130 to 140°. Such a first communicating sipe 11 can effectively suppress shear deformation of the middle land portion 7 when the two sipe walls are in contact with each other, thereby reliably maintaining dry performance.

[0036] It is desirable that the first curved portion 27 crosses the axial center of the tread surface of the middle land portion 7. This allows the first curved portion 27 to be formed over a wide area of ​​the middle land portion 7, further improving steering responsiveness on snowy and icy roads.

[0037] The outer portion 24 of the present embodiment includes a short straight portion 23 that extends linearly between the first curved portion 27 and the shoulder circumferential groove 6. However, the present invention is not limited to this aspect, and the outer portion 24 may be, for example, configured only with the first curved portion 27 from the first straight portion 26 to the shoulder circumferential groove 6.

[0038] As shown in FIG. 2 , the communicating sipes 10 of this embodiment include a plurality of second communicating sipes 12. In this embodiment, the first communicating sipes 11 and the second communicating sipes 12 are alternately arranged in the tire circumferential direction in the middle land portion 7. FIG. 4 shows an enlarged view of one second communicating sipe 12 and its surroundings in FIG. 2 . As shown in FIGS. 2 and 4 , each of the plurality of second communicating sipes 12 includes a second straight portion 28 extending linearly from the shoulder circumferential groove 6 and an inner portion 30 extending from an end of the second straight portion 28 to the crown circumferential groove 5. The inner portion 30 also includes a second curved portion 31 extending in a curved manner from an end of the second straight portion 28. Similar to the first communicating sipes 11, such second communicating sipes 12 can improve performance on snow and ice while maintaining dry performance.

[0039] The second straight portion 28 has the same characteristics as the first straight portion 26. Therefore, the above-described characteristics of the first straight portion 26 can be applied to the second straight portion 28, and the description thereof will be omitted here.

[0040] The second curved portion 31 is a portion whose angle θ4 with respect to the tire axial direction changes continuously from the end on the second straight portion 28 side toward the crown circumferential groove 5 side. The second curved portion 31 in this embodiment is an arc-shaped portion having a single radius of curvature r2, but is not limited to this. The radius of curvature r2 is, for example, 10 to 30 mm, and preferably 15 to 25 mm.

[0041] The second communicating sipe 12 of this embodiment is bent between the second straight portion 28 and the second curved portion 31. In this embodiment, the second straight portion 28 is inclined like the first straight portion 26 (inclined upward to the left in FIG. 4 ), and the second curved portion 31 connected to the second straight portion 28 is curved in a convex direction opposite to the first curved portion 27. As a result, the angle θ4 of the second curved portion 31 relative to the tire axial direction decreases from the end on the second straight portion 28 side toward the end on the crown circumferential groove 5 side. The change in the angle θ4 ranges, for example, from 25 to 75°. The angle θ5 between the second straight portion 28 and the second curved portion 31 is, for example, from 90 to 160°, and preferably from 130 to 140°. Such second communicating sipe 12 can reliably maintain dry performance.

[0042] It is desirable that the second curved portion 31 crosses the axial center of the tread surface of the middle land portion 7. This makes it easier for a large ground contact pressure to act on the second curved portion 31. This makes it easier for the second curved portion 31 to provide frictional force in multiple directions, further improving steering responsiveness on snowy and icy roads.

[0043] In this embodiment, the second curved portion 31 does not extend to the crown circumferential groove 5 (shown in FIG. 2 ). Therefore, the inner portion 30 includes a third straight portion 32 that extends linearly from the end of the second curved portion 31 to the crown circumferential groove 5. The third straight portion 32 is inclined, for example, in the same direction as the second straight portion 28, with the angle difference therebetween being 10° or less. In a preferred embodiment, the second straight portion 28 and the third straight portion 32 are arranged parallel to each other. The third straight portion 32 is also arranged closer to the shoulder circumferential groove 6 than the axial center of the middle land portion 7. The length of the third straight portion 32 (the so-called periphery length, hereinafter the same) is, for example, 30% to 45% of the overall length of the second communicating sipe 12. Such a third straight portion 32 helps improve traction performance on icy and snowy roads.

[0044] In another embodiment of the present invention, the entire inner portion 30 may be formed by the second curved portion 31 .

[0045] As shown in Fig. 2, it is desirable that the length L5 of the inner portion 30 in the tire circumferential direction be shorter than the length L4 of the outer portion 24 in the tire circumferential direction. Specifically, the length L4 of the outer portion 24 is 50% to 100% of the distance L6 in the tire circumferential direction from the first communicating sipe 11 to the second communicating sipe 12 on the longitudinal edge on the crown circumferential groove 5 side. The length L5 of the inner portion 30 is 50% to 80% of the distance L6. This improves traction performance and cornering performance on icy and snowy roads in a well-balanced manner.

[0046] Next, the characteristics of the cross-sectional shape along the length of the communicating sipe 10 will be described. In this regard, the characteristics will be described using the first communicating sipe 11 as an example, but these characteristics may also be applied to the second communicating sipe 12. FIG. 5 shows a cross-sectional view taken along line AA in FIG. 3. As shown in FIG. 5, the first communicating sipe 11 extends to a constant depth d2, except for the end portion on the shoulder circumferential groove 6 side. The depth d2 is, for example, 80% to 95% of the maximum depth d1 of the crown circumferential groove 5.

[0047] The first communicating sipe 11 of this embodiment has a reduced depth at the end portion on the shoulder circumferential groove 6 side. The depth d4 at this end portion is, for example, 20% to 35% of the maximum depth d6 of the shoulder circumferential groove 6. This effectively maintains the rigidity of the middle land portion 7, which helps to improve dry performance.

[0048] As shown in FIG. 2 , the inner sipes 15 include a first inner sipe 16 and a second inner sipe 17, each of which has a closed end on the shoulder circumferential groove 6 side. The first inner sipe 16 is inclined in the same direction as the first straight portion 26 with respect to the tire axial direction, and in a preferred embodiment, the difference between these angles is 10° or less. In a more preferred embodiment, the first inner sipe 16 and the first straight portion 26 are parallel to each other. Therefore, the angle θ7 of the first inner sipe 16 with respect to the tire axial direction is, for example, 10 to 50°, and preferably 25 to 35°. Such first inner sipes 16, together with the first straight portion 26, help improve traction performance on icy and snowy roads.

[0049] As shown in Fig. 3, the axial length L8 of the first inner sipe 16 on the tread surface 7s is desirably greater than the axial length L3 of the first straight portion 26. Specifically, the length L8 of the first inner sipe 16 is 35% to 50% of the axial width W2 (shown in Fig. 2) of the tread surface 7s of the middle land portion 7. Such a first inner sipe 16 improves dry performance and snow and ice performance in a well-balanced manner.

[0050] As shown in Fig. 2, in a plan view of the tread, at least a portion of the first inner sipe 16 overlaps with an imaginary region 25 (shown as dots in Fig. 2) that extends from the outer portion 24 parallel to the tire axial direction toward the crown circumferential groove 5. In a preferred embodiment, the entire first inner sipe 16 is disposed within the imaginary region 25. This allows the first inner sipe 16 and the first curved portion 27 to cooperate to provide a large frictional force, further improving performance on snow and ice.

[0051] From a similar viewpoint, it is desirable that the first inner sipe 16 and the outer portion 24 are disposed so as to satisfy the following relationship: In other words, when imaginary belt 29 (dotted in FIG. 2 ) is imagined, in a plan view of the tread, extending parallel to the first inner sipe 16 with a constant width W3 and disposed so as to cover the ends of the first inner sipe 16 and the outer portion 24 on the shoulder circumferential groove 6 side, it is desirable that the ends of the first inner sipe 16 and the outer portion 24 are disposed so that the width W3 is 10 mm or less.

[0052] The second inner sipe 17 has the same characteristics as the first inner sipe 16 in terms of the direction and angle of inclination relative to the tire axial direction. Therefore, the above-described characteristics regarding the angle of the first inner sipe 16 can be applied to the second inner sipe 17.

[0053] As shown in Fig. 4, the axial length L9 of the second inner sipe 17 is greater than the axial length L3 (shown in Fig. 3) of the first straight portion 26. The length L9 of the second inner sipe 17 is also greater than the length L8 (shown in Fig. 3) of the first inner sipe 16. Specifically, the length L9 of the second inner sipe 17 is 60% to 75% of the axial width W2 (shown in Fig. 2) of the tread surface 7s of the middle land portion 7. Such second inner sipes 17 improve dry performance and snow and ice performance in a well-balanced manner.

[0054] As shown in Fig. 2, in a plan view of the tread, at least a portion of the second inner sipe 17 overlaps with an imaginary region 33 (shown as dots in Fig. 2) that extends parallel to the tire axial direction from the inner portion 30 of the second communicating sipe 12 toward the crown circumferential groove 5. In a desirable embodiment, 10 to 50% of the entire length of the second inner sipe 17 overlaps with the imaginary region 33. This allows the second inner sipe 17 and the inner portion 30 to cooperate to provide a large frictional force, further improving performance on ice and snow.

[0055] The outer sipes 20 include a first outer sipe 21 and a second outer sipe 22. The first outer sipe 21 has a closed end on the crown circumferential groove 5 side. The second outer sipe 22 has a closed end on the crown circumferential groove 5 side that communicates with a first middle lateral groove 36, which will be described later. The first outer sipe 21 and the second outer sipe 22 each have similar characteristics to the first inner sipe 16 in terms of the direction and angle of inclination relative to the tire axial direction. Therefore, the above-mentioned characteristics regarding the angle of the first inner sipe 16 can be applied to the first outer sipe 21 and the second outer sipe 22.

[0056] The axial length L10 (shown in FIG. 3) of the first outer sipe 21 on the tread surface 7s is 35% to 50% of the maximum axial width W2 (shown in FIG. 2) of the tread surface 7s of the middle land portion 7. However, the first outer sipe 21 is not limited to this.

[0057] In a plan view of the tread, at least a portion of the first outer sipe 21 overlaps with an imaginary area 34 (dotted in FIG. 3 ) that extends from the outer portion 24 parallel to the tire axial direction toward the shoulder circumferential groove 6. In a preferred embodiment, the entire first outer sipe 21 is disposed within the imaginary area 34. This allows the first outer sipe 21 and the outer portion 24 to cooperate to provide a large frictional force.

[0058] The middle land portion 7 is provided with a plurality of middle lateral grooves 35. The middle lateral grooves 35 include first middle lateral grooves 36 and second middle lateral grooves 37. The first middle lateral grooves 36 communicate with the crown circumferential grooves 5 and extend in the tire axial direction, but do not communicate with the shoulder circumferential grooves 6. The second middle lateral grooves 37 communicate with the shoulder circumferential grooves 6 and extend in the tire axial direction, but do not communicate with the crown circumferential grooves 5. In the middle land portion 7 of this embodiment, the first middle lateral grooves 36 and the second middle lateral grooves 37 are provided alternately in the tire circumferential direction.

[0059] The first middle lateral grooves 36 and the second middle lateral grooves 37 have the same characteristics as the first inner sipes 16 in terms of the direction of inclination and the angle relative to the tire axial direction. Therefore, the above-described characteristics regarding the angle of the first inner sipes 16 can be applied to the first middle lateral grooves 36 and the second middle lateral grooves 37.

[0060] The first middle lateral grooves 36 cross the axial center of the tread surface of the middle land portion 7 and communicate with the second outer sipes 22. The axial length L11 of the first middle lateral grooves 36 is greater than the axial length L3 (shown in FIG. 3) of the first straight portion 26 of the first communicating sipe 11 and is also greater than the axial length L8 (shown in FIG. 3) of the first inner sipe 16. Such first middle lateral grooves 36 help improve performance on snow and ice while maintaining dry performance.

[0061] The edge of each first middle lateral groove 36 on one circumferential side (upper side in FIG. 2 ) extends in the longitudinal direction of the first middle lateral groove 36 (excluding the diamond cut at the end on the crown circumferential groove 5 side). Meanwhile, the edge of each first middle lateral groove 36 on the other circumferential side (lower side in FIG. 2 ) includes a portion extending in the longitudinal direction of the first middle lateral groove 36 and a portion curved in a direction that widens the groove width of the first middle lateral groove 36 toward the crown circumferential groove 5 side. As a result, the first middle lateral groove 36 includes a constant-width portion 36a extending with a constant groove width and a wide-width end portion 36b whose groove width widens toward the crown circumferential groove 5 side. This first middle lateral groove 36 facilitates the discharge of snow and ice particles that have entered the groove when driving on snowy and icy roads, thereby enabling the tire to continuously demonstrate excellent snow and ice performance.

[0062] The second middle lateral groove 37 has a shape point-symmetrical to the first middle lateral groove 36. Therefore, the second middle lateral groove 37 can apply the features of the first middle lateral groove 36 described above.

[0063] In this embodiment, the middle land portion 7 is provided with a circular recess 40 that opens onto the tread surface 7s. The diameter of the circular recess 40 is, for example, 1.5 to 2.5 mm. The depth of the circular recess 40 is, for example, 1.0 to 2.0 mm. In this embodiment, the circular recess 40 is continuous with the first curved portion 27 of the first communicating sipe 11 and the second curved portion 31 of the second communicating sipe 12. Such a circular recess 40 provides friction in multiple directions, further improving performance on snow and ice.

[0064] FIG. 6 shows an enlarged view of the crown land portion 8 in FIG. 1. As shown in FIG. 6, the crown land portion 8 includes a tread surface 8s divided into two crown circumferential grooves 5, a side surface 8a on one side in the tire axial direction, and a side surface 8b on the other side in the tire axial direction. The crown land portion 8 also includes a plurality of first recesses 41, a plurality of second recesses 42, and a plurality of crown connecting sipes 45. The first recesses 41 are open at the tread surface 8s and the side surface 8a on one side. The second recesses 42 are open at the tread surface 8s and the side surface 8b on the other side. The crown connecting sipe 45 extends from the first recesses 41 to the second recesses 42 on the tread surface 8s. The first recesses 41, the second recesses 42, and the crown connecting sipes 45 help improve performance on snow and ice.

[0065] The crown communicating sipe 45 is disposed so that an imaginary line (not shown) connecting both ends of the crown communicating sipe 45 faces in the opposite direction to that of the inner sipe 15 (shown in FIG. 2). The crown communicating sipe 45 includes an S-shaped portion 47 formed by two arc portions 46 that are convex in opposite directions and are connected to each other. The crown communicating sipe 45 extends linearly from the end of the S-shaped portion 47 to the first recessed portion 41 or the second recessed portion 42. Such a crown communicating sipe 45 prevents shear deformation of the crown land portion 8 when the two sipe walls come into contact with each other, thereby effectively maintaining dry road performance.

[0066] Fig. 7 shows a cross-sectional view taken along line BB in Fig. 6. As shown in Fig. 7, the crown communicating sipe 45 has a greater depth than the first recessed portion 41 and the second recessed portion 42. The crown communicating sipe 45 has a constant depth d7 throughout. The depth d7 is 65% to 80% of the maximum depth d6 of the crown circumferential groove 5. Such a crown communicating sipe 45 helps to improve dry performance and performance on snow and ice in a well-balanced manner.

[0067] As shown in FIG. 6 , the crown land portion 8 is provided with a plurality of linearly extending first crown sipes 51, a plurality of second crown sipes 52, and a plurality of third crown sipes 53. The first crown sipes 51 extend from one crown circumferential groove 5 to the other crown circumferential groove 5. The second crown sipes 52 extend from one crown circumferential groove 5 and have a closed end within the tread surface 8s. The third crown sipes 53 extend from the other crown circumferential groove 5 and have a closed end within the tread surface 8s. All of these sipes cross the axial center position of the crown land portion 8. This sipe arrangement reliably improves performance on ice and snow.

[0068] The first crown sipes 51, the second crown sipes 52, and the third crown sipes 53 are each inclined in the opposite direction to the inner sipes 15 (shown in FIG. 2). The angle θ8 of these sipes with respect to the tire axial direction is, for example, 20 to 30°. This improves traction performance and cornering performance on icy and snowy roads in a well-balanced manner.

[0069] Fig. 8 shows an enlarged view of the shoulder land portion 9. As shown in Fig. 8, the shoulder land portion 9 is provided with a plurality of communicating sipes 54, a plurality of shoulder lateral grooves 55, a plurality of first shoulder sipes 56, and a plurality of second shoulder sipes 57.

[0070] The communicating sipes 54 extend from the shoulder circumferential grooves 6 and are discontinued within the shoulder land portion 9. The shoulder lateral grooves 55 extend from the communicating sipes 54 to at least the tread edge Te. Such communicating sipes 54 and shoulder lateral grooves 55 can improve wet performance while suppressing an excessive decrease in rigidity of the shoulder land portion 9.

[0071] The first shoulder sipes 56 extend obliquely from the shoulder circumferential groove 6 and have closed ends within the shoulder land portion 9. The second shoulder sipes 57 are adjacent to the first shoulder sipes 56 on the axially outer side of the tire and extend at least to the tread edge Te. The gap between the first shoulder sipes 56 and the second shoulder sipes 57 is, for example, 3 mm or less. Such a sipe arrangement helps to maintain the rigidity of the shoulder land portion 9. In another embodiment, the first shoulder sipes 56 and the second shoulder sipes 57 may be connected to form a single sipe.

[0072] In this embodiment, the first shoulder sipes 56 and the second shoulder sipes 57 each extend in a zigzag pattern. This allows the two sipe walls of these sipes to mesh with each other and come into contact. This ensures that the rigidity of the shoulder land portion 9 is maintained, resulting in excellent dry performance. However, these sipes are not limited to this configuration and may extend in a straight line.

[0073] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0074] A pneumatic tire of size 215 / 55R17 having the basic pattern shown in FIG. 1 was prototyped. As a comparative example, a tire having a tread pattern shown in FIG. 9 was prototyped. The comparative tire does not have a first communicating sipe including a first curved portion as in the present invention, but rather has a communicating sipe b extending linearly in the middle land portion a, as shown in FIG. 9. Except for the above-mentioned features, the comparative tire has substantially the same configuration as the tire shown in FIG. 1. The dry performance and ice / snow performance of each test tire were tested. The common specifications and test methods for each test tire are as follows. Rim: 17 x 7J Tire pressure: All wheels: 250kPa Test vehicle: 2500cc, front-wheel drive Tire mounting position: All wheels

[0075] <Dry performance> The driving performance of the test vehicle when driven on a dry road surface was evaluated by the driver. The results were given as a rating indicating the driving performance, with a higher rating indicating better dry performance.

[0076] <Performance on ice and snow> The driving performance of the test vehicle when driven on snowy and icy roads was evaluated by the driver. The results were given as a rating indicating the driving performance, with a higher rating indicating better performance on snow and ice. The test results are shown in Table 1.

[0077] [Table 1]

[0078] As shown in Table 1, it can be confirmed that the tires of the examples have significantly improved dry performance and snow and ice performance. In other words, it has been confirmed that the tires of the present invention exhibit excellent snow and ice performance while at least maintaining dry performance.

[0079] [Note] The present invention includes the following aspects.

[0080] [Invention 1] A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction and a plurality of land portions separated by the plurality of circumferential grooves, the plurality of circumferential grooves include a crown circumferential groove disposed on the tire equator side and a shoulder circumferential groove adjacent to the crown circumferential groove on an outer side in the tire axial direction, the plurality of land portions include one middle land portion partitioned between the crown circumferential groove and the shoulder circumferential groove, The middle land portion has: a plurality of communicating sipes extending from the crown circumferential groove to the shoulder circumferential groove; a plurality of inner sipes that communicate with the crown circumferential groove, extend in the tire axial direction, and do not communicate with the shoulder circumferential groove; a plurality of outer sipes are provided, the outer sipes communicating with the shoulder circumferential grooves and extending in the tire axial direction, but not communicating with the crown circumferential grooves, the plurality of communicating sipes include a plurality of first communicating sipes, Each of the plurality of first communicating sipes includes a first straight portion extending linearly from the crown circumferential groove and a first curved portion extending curvedly from an end of the first straight portion toward the shoulder circumferential groove. tire. [Invention 2] the plurality of communicating sipes include a plurality of second communicating sipes, each of the plurality of second communicating sipes includes a second linear portion extending linearly from the shoulder circumferential groove and an inner portion extending from an end of the second linear portion to the crown circumferential groove; The tire according to Invention 1, wherein the inner portion includes a second curved portion that curves and extends from an end of the second straight portion. [Invention 3] each of the plurality of first communicating sipes includes an outer portion extending from an end of the first linear portion to the shoulder circumferential groove; the outer portion includes the first curved portion, The tire according to aspect 2, wherein the length of the inner portion in the tire circumferential direction is smaller than the length of the outer portion in the tire circumferential direction. [Invention 4] a length in the tire circumferential direction of the outer portion is 50% to 100% of a distance in the tire circumferential direction from the first communicating sipe to the second communicating sipe on a longitudinal edge on the crown circumferential groove side, The tire according to invention 2 or 3, wherein the length of the inner portion in the tire circumferential direction is 10% to 50% of the distance in the tire circumferential direction. [Invention 5] The tire according to any one of claims 2 to 4, wherein the inner portion includes a third straight portion that extends linearly from an end of the second curved portion to the crown circumferential groove. [Invention 6] The tire according to any one of claims 1 to 5, wherein the first communicating sipe is bent between the first straight portion and the first curved portion. [Invention 7] The tire according to any one of claims 1 to 6, wherein the first curved portion crosses the axial center position of the tread surface of the middle land portion. [Invention 8] the outer sipe includes a first outer sipe having a closed end on the crown circumferential groove side, The tire according to any one of claims 1 to 7, wherein, in a plan view of the tread, the first outer sipe is disposed within a virtual area obtained by extending the first curved portion toward the shoulder circumferential groove side in parallel to the tire axial direction. [Invention 9] The inner sipe includes a first inner sipe having a closed end on the shoulder circumferential groove side, The tire according to any one of claims 1 to 8, wherein, in a plan view of the tread, the first inner sipe is disposed within a virtual area obtained by extending the first curved portion toward the crown circumferential groove side in parallel to the tire axial direction. [Invention 10] the inner sipe includes a second inner sipe whose end on the shoulder circumferential groove side is closed, The tire according to the present invention 9, wherein the axial length of the second inner sipe is greater than the axial length of the first inner sipe. [Invention 11] the plurality of circumferential grooves include two of the crown circumferential grooves arranged on either side of the tire equator, the plurality of land portions include one crown land portion partitioned between two of the crown circumferential grooves, the crown land portion includes a tread surface divided by the two crown circumferential grooves, a side surface on one side in the tire axial direction, and a side surface on the other side in the tire axial direction, The crown land portion has A plurality of first recesses opening on the tread surface and the one side surface; A plurality of second recesses opening on the tread surface and the other side surface; The tire according to any one of claims 1 to 10, further comprising a plurality of crown-interconnecting sipes extending from the first recessed portion to the second recessed portion on the tread surface. [Invention 12] 12. The tire according to claim 11, wherein the crown connecting sipe includes one S-shaped portion formed by connecting two arcuate portions that are convex in opposite directions. [Explanation of symbols]

[0081] 2 Tread section 3 Circumferential groove 4 Land 5 Crown circumferential groove 6 Shoulder circumferential groove 7 Middle Track 10 Interconnected sipes 11 First connecting sipe 15 inner sipe 20 outer sipes 26 1st straight section 27 First curved section

Claims

1. A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction and a plurality of land portions separated by the plurality of circumferential grooves, the plurality of circumferential grooves include a crown circumferential groove disposed on the tire equator side and a shoulder circumferential groove adjacent to the crown circumferential groove on an outer side in the tire axial direction, the plurality of land portions include one middle land portion partitioned between the crown circumferential groove and the shoulder circumferential groove, The middle land portion has: a plurality of communicating sipes extending from the crown circumferential groove to the shoulder circumferential groove; a plurality of inner sipes that communicate with the crown circumferential groove, extend in the tire axial direction, and do not communicate with the shoulder circumferential groove; a plurality of outer sipes are provided, the outer sipes communicating with the shoulder circumferential grooves and extending in the tire axial direction, but not communicating with the crown circumferential grooves, the plurality of communicating sipes include a plurality of first communicating sipes, each of the plurality of first communicating sipes includes a first straight portion extending linearly from the crown circumferential groove and a first curved portion extending in a curved manner from an end of the first straight portion toward the shoulder circumferential groove; tire.

2. the plurality of communicating sipes include a plurality of second communicating sipes, each of the plurality of second communicating sipes includes a second linear portion extending linearly from the shoulder circumferential groove and an inner portion extending from an end of the second linear portion to the crown circumferential groove, The tire according to claim 1 , wherein the inner portion includes a second curved portion extending in a curved manner from an end of the second straight portion.

3. each of the plurality of first communicating sipes includes an outer portion extending from an end of the first linear portion to the shoulder circumferential groove; the outer portion includes the first curved portion, The tire according to claim 2 , wherein the inner portion has a circumferential length smaller than the circumferential length of the outer portion.

4. a length in the tire circumferential direction of the outer portion is 50% to 100% of a distance in the tire circumferential direction from the first communicating sipe to the second communicating sipe on a longitudinal edge on the crown circumferential groove side, The tire according to claim 3, wherein the length of the inner portion in the tire circumferential direction is 10% to 50% of the distance in the tire circumferential direction.

5. The tire according to claim 4 , wherein the inner portion includes a third straight portion that extends linearly from an end of the second curved portion to the crown circumferential groove.

6. The tire according to claim 1 , wherein the first communicating sipe is bent between the first straight portion and the first curved portion.

7. The tire according to claim 1 , wherein the first curved portion crosses an axial center position of the tread surface of the middle land portion.

8. the outer sipe includes a first outer sipe having a closed end on the crown circumferential groove side, 6. The tire according to claim 1, wherein, in a plan view of the tread, the first outer sipe is disposed within a virtual region in which the first curved portion extends parallel to the tire axial direction toward the shoulder circumferential groove side.

9. the inner sipe includes a first inner sipe having a closed end on the shoulder circumferential groove side, 6. The tire according to claim 1, wherein, in a tread plan view, the first inner sipe is disposed within a virtual region in which the first curved portion extends parallel to the tire axial direction toward the crown circumferential groove side.

10. the inner sipe includes a second inner sipe whose end on the shoulder circumferential groove side is closed, The tire according to claim 9 , wherein the axial length of the second inner sipe is greater than the axial length of the first inner sipe.

11. the plurality of circumferential grooves include two of the crown circumferential grooves arranged on either side of the tire equator, the plurality of land portions include one crown land portion partitioned between two of the crown circumferential grooves, the crown land portion includes a tread surface divided by the two crown circumferential grooves, a side surface on one side in the tire axial direction, and a side surface on the other side in the tire axial direction, The crown land portion has a plurality of first recesses opening on the tread surface and the one side surface; A plurality of second recesses opening on the tread surface and the other side surface; The tire according to claim 1 , further comprising a plurality of crown-interconnecting sipes extending from the first recessed portion to the second recessed portion on the tread surface.

12. The tire according to claim 11 , wherein the crown connecting sipe includes one S-shaped portion formed by connecting two arcuate portions that are convex in opposite directions.

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