Tire

Abstract

The present invention provides a tire that suppresses a decrease in handling stability on a dry road surface and improves performance on ice and snow, and the tire has a tread portion (2). The tread portion (2) includes circumferential grooves (3) and land portions (7). A first interrupted groove (33), a second interrupted groove (34), a first communication siped (37), a second communication siped (38), and a cross-cut siped (40) are provided on the tread surface (7s) of the land portion (7). The cross-cut siped (40) includes a first portion (41), a second portion (42), and a third portion (43). When observing the tread surface in a plan view, the first portion (41) overlaps a projection area obtained by extending the first communication siped (37) or the second communication siped (38) parallel to the tire axis.

Description

Technical Field

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

[0002] In Patent Document 1 below, a pneumatic radial tire is proposed in which longitudinal grooves and transverse grooves provided in the tread portion are connected in a substantially L shape. With the above-mentioned longitudinal grooves and above-mentioned transverse grooves, an improvement in snow-turning performance and snow-braking performance is expected for the above-mentioned tire.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-160055

[0004] Although the transverse grooves and the cuts provided in the tread portion of the tire contribute to improving the performance on ice and snow, there is a tendency for the rigidity of the tread portion to decrease, resulting in a decrease in handling stability on dry roads. Summary of the Invention

[0005] The present invention has been made in view of the above actual situation, and the main object thereof is to provide a tire that suppresses a decrease in handling stability on dry roads and improves the performance on ice and snow.

[0006] The present invention provides a tire having a tread portion, the tread portion including: a plurality of circumferential grooves continuously extending in the circumferential direction of the tire, and at least one tread portion divided by the circumferential grooves, the tread portion having a first circumferential edge, a second circumferential edge, and a tread surface between the first circumferential edge and the second circumferential edge, and provided on the tread surface are: a first interrupted groove extending from the first circumferential edge and having an interrupted end in the tread surface, a second interrupted groove extending from the second circumferential edge and having an interrupted end in the tread surface, a first connecting cut extending from the interrupted end of the first interrupted groove to the second circumferential edge, a second connecting cut extending from the interrupted end of the second interrupted groove to the first circumferential edge, and a cross-cut extending from the first circumferential edge to the second circumferential edge, the cross-cut including: a first portion inclinedly extending from the first circumferential edge, a second portion inclinedly extending from the second circumferential edge in the same direction as the first portion, and a third portion inclined at an angle different from the first portion and the second portion and connected to the first portion and the second portion, and when the tread surface is viewed from above, the first portion overlaps with a projection area obtained by extending the first connecting cut or the second connecting cut parallel to the tire axis.

[0007] In the tire of the present invention, it is preferable that the third portion is inclined in a direction opposite to the first portion and the second portion.

[0008] In the tire of the present invention, it is preferable that the above-mentioned second part overlaps with the projection area obtained by extending the above-mentioned first communication groove or the above-mentioned second communication groove parallel to the tire axis.

[0009] In the tire of the present invention, it is preferable that a first interrupted groove extending from the above-mentioned first circumferential edge and having an interrupted end within the above-mentioned tread is provided on the above-mentioned tread.

[0010] In the tire of the present invention, it is preferable that when the tread is viewed from above, the above-mentioned first interrupted groove overlaps with the projection area obtained by extending the above-mentioned first part parallel to the tire axis.

[0011] In the tire of the present invention, it is preferable that a second interrupted groove extending from the above-mentioned second circumferential edge and having an interrupted end within the above-mentioned tread is provided on the above-mentioned tread.

[0012] In the tire of the present invention, it is preferable that when the tread is viewed from above, the above-mentioned second interrupted groove overlaps with the projection area obtained by extending the above-mentioned second part parallel to the tire axis.

[0013] In the tire of the present invention, it is preferable that the angle of the above-mentioned first part with respect to the tire axis is 40 to 50°.

[0014] In the tire of the present invention, it is preferable that the angle between the above-mentioned first part and the above-mentioned third part is 90 to 110°.

[0015] In the tire of the present invention, it is preferable that the maximum depth of the above-mentioned first part is greater than the maximum depth of the above-mentioned first communication groove.

[0016] By adopting the above structure, the tire of the present invention can suppress the reduction of handling stability on dry roads and improve the performance on ice and snow. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a developed view of the tread portion of a tire according to an embodiment of the present invention.

[0018] Figure 2 is Figure 1 an enlarged view of the second land portion of

[0019] Figure 3 is Figure 2 an enlarged view of the transverse groove of

[0020] Figure 4 is Figure 2 a cross-sectional view taken along line D - D of

[0021] Figure 5 is Figure 1 an enlarged view of the first land portion of

[0022] Figure 6 is Figure 5 the sectional view taken along line A-A of

[0023] Figure 7 is Figure 5 the sectional view taken along line B-B of

[0024] Figure 8 is Figure 5 the enlarged top view of the first inclined cutter groove and the second inclined cutter groove of

[0025] Figure 9 is Figure 5 the sectional view taken along line C-C of

[0026] Figure 10 is Figure 1 the enlarged view of the third land portion of

[0027] Figure 11 the enlarged view of the second land portion of the tire of the comparative example

[0028] Description of reference numerals

[0029] 2... tread surface portion; 3... circumferential groove; 7... land portion; 7a... first circumferential edge; 7b... second circumferential edge; 7s... tread surface; 33... first interrupted groove; 34... second interrupted groove; 37... first communicating cutter groove; 38... second communicating cutter groove; 40... transverse cutter groove; 41... first portion; 42... second portion; 43... third portion. Detailed implementation manners

[0030] Hereinafter, based on the drawings, an embodiment of the present invention will be described.

[0031] Figure 1 is the developed view of the tread surface portion 2 of the tire 1 showing an embodiment of the present invention. The tire 1 of the present embodiment is suitable for use as a pneumatic tire for a passenger car for all seasons, for example. However, the present invention is not limited to such a manner, and can be applied to, for example, winter tires.

[0032] As Figure 1 shown, the tread surface portion 2 includes a plurality of circumferential grooves 3 continuously extending in the tire circumferential direction between two tread ends Te, and a plurality of land portions divided by the circumferential grooves 3.

[0033] The two tread ends Te respectively correspond to the outermost ground contact positions in the tire axial direction when the tire 1 in the normal state is loaded with the normal load and contacts the plane at a camber angle of 0°.

[0034] "Normal state" in the case of a pneumatic tire with various specified specifications refers to the state where the tire is assembled on a normal rim, filled with normal internal pressure, and is unloaded. In the case of a tire without specified various specifications or a non-pneumatic tire, the above normal state means a standard usage state corresponding to the usage purpose of the tire and an unloaded state. In this specification, unless otherwise specified, the dimensions, etc. of each part of the tire are values measured in the above normal state.

[0035] "Normal rim" refers to the rim specified for each tire in the specification system including the specifications on which the tire is based. For example, in the case of JATMA, it is the "standard rim"; in the case of TRA, it is the "Design Rim"; in the case of ETRTO, it is the "Measuring Rim".

[0036] "Normal internal pressure" refers to the air pressure specified for each tire in the specification system including the specifications on which the tire is based. For example, in the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is the "INFLATIONPRESSURE".

[0037] "Normal load" in the case of a pneumatic tire with various specified specifications refers to the load specified for each tire in the specification system including the specifications on which the tire is based. For example, in the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is the "LOAD CAPACITY". Additionally, in the case of a tire without specified various specifications or a non-pneumatic tire, "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The above "standard mounting state" refers to the state where the tire is mounted on a standard vehicle corresponding to the usage purpose of the tire and the vehicle is stationary on a flat road surface in a state where the vehicle can travel.

[0038] The circumferential groove 3 includes, for example, two tread circumferential grooves 4 and two shoulder circumferential grooves 5.

[0039] Two circumferential grooves 4 in the tread crown are arranged to sandwich the tire equator C. Two circumferential grooves 5 in the shoulder regions are arranged to sandwich the two circumferential grooves 4 in the tread crown. The distance L1 in the tire axial direction from the groove center line of the circumferential groove 4 in the tread crown to the tire equator C is, for example, 5% to 15% of the tread width TW. The distance L2 in the tire axial direction from the groove center line of the circumferential groove 5 in the shoulder region to the tire equator C is, for example, 20% to 35% of the tread width TW. In addition, the tread width TW is the distance in the tire axial direction from one tread end Te to the other tread end Te.

[0040] Each circumferential groove 3 extends linearly, for example, parallel to the tire circumferential direction. Each circumferential groove 3 may also extend in a serrated or wavy shape along the tire circumferential direction.

[0041] The groove width W1 of the circumferential groove 3 is preferably, for example, 3.0% to 6.0% of the tread width TW. The depth of the circumferential groove 3 (not shown) is preferably, for example, 5.0 to 15.0 mm. However, the circumferential groove 3 is not limited to such a manner.

[0042] The land portions of the present embodiment include a first land portion 6, a second land portion 7, and a third land portion 8. The first land portion 6 is divided between the two circumferential grooves 4 in the tread crown and is provided on the tire equator C. The second land portion 7 is divided between the circumferential groove 4 in the tread crown and the circumferential groove 5 in the shoulder region. In the present embodiment, two second land portions 7 sandwich the first land portion 6. The third land portion 8 includes the tread end Te and is divided outside the tire axial direction of the circumferential groove 5 in the shoulder region. In the present embodiment, two third land portions 8 sandwich one first land portion 6 and two second land portions 7.

[0043] Figure 2 An enlarged view of the second land portion 7 is shown. As Figure 2 shown, the second land portion 7 includes a first circumferential edge 7a, a second circumferential edge 7b, and a tread surface 7s therebetween.

[0044] A first interrupted groove 33, a second interrupted groove 34, a first connecting siped 37, a second connecting siped 38, and a transverse siped 40 are provided on the tread surface 7s of the second land portion 7. The first interrupted groove 33 extends from the first circumferential edge 7a and has an interruption end 33a within the tread surface 7s. The second interrupted groove 34 extends from the second circumferential edge 7b and has an interruption end 34a within the tread surface 7s. The first connecting siped 37 extends from the interruption end 33a of the first interrupted groove 33 to the second circumferential edge 7b. The second connecting siped 38 extends from the interruption end 34a of the second interrupted groove 34 to the first circumferential edge 7a. The transverse siped 40 extends from the first circumferential edge 7a to the second circumferential edge 7b.

[0045] In the present specification, a "groove" refers to a grooving element having a minute width, and the width between two groove walls facing each other is 1.5 mm or less. The above width of the groove is preferably 0.3 to 1.2 mm, more preferably 0.5 to 1.0 mm. The groove of the present embodiment extends throughout its entire depth so that the above width is within the above range. A chamfered opening portion or a flask bottom having a width larger than the above range may be connected to the groove.

[0046] Figure 3 An enlarged view of a cross-section of the groove 40 is shown. As Figure 3 shown, the cross-section of the groove 40 includes a first portion 41 that extends obliquely from a first circumferential edge 7a, a second portion 42 that extends obliquely from a second circumferential edge 7b in the same direction as the first portion 41, and a third portion 43 that is inclined at an angle different from those of the first portion 41 and the second portion 42 and is connected to the first portion 41 and the second portion 42. As a preferred embodiment, the third portion 43 of the present embodiment is inclined in a direction opposite to that of the first portion 41 and the second portion 42. Hereinafter, in the present specification, the inclination direction of the third portion 43 (lower on the left and higher on the right) is referred to as "inclined in a first direction with respect to the tire axial direction", and the inclination directions of the first portion 41 and the second portion 42 (higher on the left and lower on the right) are referred to as "inclined in a second direction with respect to the tire axial direction". In the present embodiment, the first interrupted groove 33, the second interrupted groove 34, the first communicating groove 37, and the second communicating groove 38 are inclined in the second direction with respect to the tire axial direction.

[0047] When the tread is viewed from above, the first portion 41 overlaps with a projection area 55 (colored in Figure 3 .) obtained by extending the first communicating groove 37 or the second communicating groove 38 parallel to the tire axial direction. In the present invention, by adopting the above structure, it is possible to suppress a decrease in handling stability on a dry road surface and improve performance on ice and snow. As a reason for this, the following mechanism is presumed.

[0048] In the present invention, the first interrupted groove 33 and the first communicating groove 37, and the second interrupted groove 34 and the second communicating groove 38 suppress a decrease in the rigidity of the second land portion 7 and provide an edge component. Thereby, a decrease in handling stability on a dry road surface is suppressed, and performance on ice and snow is improved.

[0049] In addition, the above cross-section of the groove 40 maintains performance on ice and snow by providing frictional force in multiple directions with its edge component. In addition, since the third portion 43 of the cross-section of the groove 40 is inclined at an angle different from those of the first portion 41 and the second portion 42, shear deformation along the length direction of the cross-section of the groove 40 is prevented when the groove walls come into contact, thereby improving braking performance on a dry road surface.

[0050] Also, in the present invention, since the first part 41 of the transverse cutter groove 40 overlaps with the above-mentioned projection area 55, each cutter groove provides a large frictional force in the tire axial direction through cooperation, thereby improving the turning performance on ice and snow. In the present invention, through such an effect, it is speculated that a decrease in handling stability on a dry road surface can be suppressed, and the performance on ice and snow can be improved.

[0051] As a more preferred embodiment, in the present embodiment, the third part 43 is inclined in a direction opposite to that of the first part 41 and the second part 42. In addition, the second part 42 overlaps with the projection area 55 (colored in Figure 3 .) obtained by extending the first communication cutter groove 37 or the second communication cutter groove 38 parallel to the tire axial direction. Thereby, the above-mentioned effects are further improved.

[0052] Hereinafter, a more detailed structure of the present embodiment will be described. In addition, each structure described below represents a specific embodiment of the present embodiment. Therefore, for the present invention, it goes without saying that even without the structures described below, the above-mentioned effects can be achieved. In addition, even if any one of the structures described below is applied alone to the tire of the present invention having the above-mentioned features, an improvement in performance corresponding to each structure can be expected. In addition, in the case where any one of the structures described below is applied in combination, a combined improvement in performance corresponding to each structure can be expected.

[0053] As Figure 2 shown, the angles of the first interruption groove 33 and the first communication cutter groove 37 with respect to the tire axial direction are, for example, 15 to 55°, preferably 30 to 50°. Such first interruption groove 33 and first communication cutter groove 37 equally improve the braking performance and turning performance on ice and snow.

[0054] The first interruption groove 33, for example, interrupts without crossing the center position of the second land portion 7 in the tire axial direction. The length of the first interruption groove 33 in the tire axial direction is smaller than the length of the first part 41 of the transverse cutter groove 40 in the tire axial direction. The length L9 of the first interruption groove 33 in the tire axial direction is, for example, 25% to 45% of the width W3 of the second land portion 7 in the tire axial direction, preferably 30% to 40%. Such first interruption groove 33 helps to equally improve the braking performance on a dry road surface and the performance on ice and snow.

[0055] The depth of the first interruption groove 33 is, for example, 60% to 80% of the depth of the crown circumferential groove 4. Thereby, the handling stability on a dry road surface (hereinafter, there are cases where it is simply referred to as "handling stability") and the performance on ice and snow are equally improved.

[0056] From the same viewpoint, the depth of the first communication groove 37 is preferably less than the depth of the first interruption groove 33. For example, the depth of the first communication groove 37 is 40% to 55% of the depth of the circumferential groove 4 in the tread.

[0057] The second interruption groove 34 actually has the same structure as the first interruption groove 33, and the above-described structure of the first interruption groove 33 can be applied to the second interruption groove 34. The second communication groove 38 actually has the same structure as the first communication groove 37, and the above-described structure of the first communication groove 37 can be applied to the second communication groove 38.

[0058] The transverse groove 40 is located between the first interruption groove 33 and the second interruption groove 34. More specifically, the transverse groove 40 is provided between the first groove element 28 formed by the first interruption groove 33 and the first communication groove 37 and the second groove element 29 formed by the second interruption groove 34 and the second communication groove 38.

[0059] For example, the imaginary straight line connecting both ends of the transverse groove 40 is inclined in the second direction with respect to the tire axis. The angles of the first portion 41 and the second portion 42 with respect to the tire axis are, for example, 15 to 55°, preferably 40 to 50°. In the present embodiment, the angular difference between the first portion 41 and the first interruption groove 33 is 5° or less, and the angular difference between the second portion 42 and the second interruption groove 34 is 5° or less. Thereby, uneven wear of the second land portion 7 is suppressed.

[0060] The third portion 43, for example, intersects the central position in the tire axis direction of the second land portion 7. The length L10 of the third portion 43 in the tire axis direction is 10% to 25% of the width W3 of the second land portion 7 in the tire axis direction. The angle of the third portion 43 with respect to the tire axis is, for example, 40 to 60°, preferably 45 to 55°.

[0061] The angles between the first portion 41 and the third portion 43 and between the second portion 42 and the third portion 43 are each preferably 80° or more, more preferably 90° or more, preferably 120° or less, and more preferably 110° or less. Such a transverse groove 40 can suppress uneven wear of the second land portion 7 and effectively suppress deformation of the second land portion 7 when the groove walls come into contact with each other.

[0062] Figure 4 shows Figure 2 a cross-sectional view taken along line D - D of Figure 4As shown, the third part 43 of the transverse cutter groove 40 has a depth smaller than that of the first part 41 and the second part 42. The depth d6 of the third part 43 is, for example, 55% to 75% of the maximum depth d5 of the transverse cutter groove 40, preferably 60% to 70%. Such a third part 43 can suppress the excessive opening of the transverse cutter groove 40, suppress the uneven wear of the second land part 7, and improve the handling stability and performance on ice and snow.

[0063] In a more preferred embodiment, the maximum depth d7 of the first part 41 is greater than the maximum depth of the first connecting cutter groove 37. The maximum depth d7 of the first part 41 is 140% to 160% of the maximum depth of the first connecting cutter groove 37. Similarly, the maximum depth d8 of the second part 42 is greater than the maximum depth of the second connecting cutter groove 38. The maximum depth d8 of the second part 42 is 140% to 160% of the maximum depth of the second connecting cutter groove 38. Thereby, the edges of the first part 41 and the second part 42 can provide a large frictional force, thus improving the performance on ice and snow.

[0064] As Figure 2 and Figure 3 shown, the transverse cutter groove 40 alternately includes a first transverse cutter groove 40A and a second transverse cutter groove 40B along the tire circumferential direction. For the first transverse cutter groove 40A, more than 50% of the length of the first part 41 overlaps with the projection area 55, and more than 50% of the length of the second part 42 overlaps with the projection area 55. For the second transverse cutter groove 40B, less than 50% of the length of the first part 41 overlaps with the projection area 55, and less than 50% of the length of the second part 42 overlaps with the projection area 55. Thereby, the handling stability and the performance on ice and snow are improved in a balanced manner.

[0065] To reliably exhibit the above effects, in the present embodiment, for the first transverse cutter groove 40A, preferably more than 60%, more preferably more than 80% of the length of the first part 41 overlaps with the projection area 55. The same applies to the second part 42 of the first transverse cutter groove 40A. In addition, for the second transverse cutter groove 40B, preferably less than 40%, more preferably less than 30% of the length of the first part 41 overlaps with the projection area 55. The same applies to the second part 42 of the second transverse cutter groove 40B.

[0066] As Figure 2 shown, a first interrupted cutter groove 46 and a second interrupted cutter groove 47 are provided between the first cutter groove element 28 and the second cutter groove element 29 in the present embodiment. The first interrupted cutter groove 46 extends from the first circumferential edge 7a and has an interrupted end 46a within the tread surface 7s. The second interrupted cutter groove 47 extends from the second circumferential edge 7b and has an interrupted end 47a within the tread surface 7s. Such first interrupted cutter groove 46 and second interrupted cutter groove 47 contribute to maintaining the handling stability and improving the performance on ice and snow.

[0067] The first interrupted cutter groove 46 is disposed on one side in the tire circumferential direction of the first part 41 of the transverse cutter groove 40, and the second interrupted cutter groove 47 is disposed on the other side in the tire circumferential direction of the second part of the transverse cutter groove 40. The first interrupted cutter groove 46 and the second interrupted cutter groove 47 are inclined, for example, in the second direction with respect to the tire axial direction. The angles of the first interrupted cutter groove 46 and the second interrupted cutter groove 47 with respect to the tire axial direction are, for example, 15 to 55°. The angle difference between the first interrupted cutter groove 46 and the first part 41 of the transverse cutter groove 40 is 5° or less, and in the present embodiment, they extend parallel to each other. The angle difference between the second interrupted cutter groove 47 and the second part 42 of the transverse cutter groove 40 is 5° or less, and in the present embodiment, they extend parallel to each other. Such first interrupted cutter groove 46 and second interrupted cutter groove 47 can suppress uneven wear of the second land part 7 and can evenly improve the traction performance and turning performance on ice and snow.

[0068] When the tread is observed from above, the first interrupted cutter groove 46 overlaps with the projection area obtained by extending the first part 41 parallel to the tire axial direction. In addition, the second interrupted cutter groove 47 overlaps with the projection area obtained by extending the second part 42 parallel to the tire axial direction. On the other hand, the second interrupted cutter groove 47 does not overlap with the projection area obtained by extending the first interrupted cutter groove 46 parallel to the tire axial direction. Thereby, the rigidity of the second land part 7 is maintained, and each cutter groove provides a large frictional force on ice and snow through cooperation.

[0069] The length of the first interrupted cutter groove 46 in the tire axial direction is, for example, less than the length of the first part 41 of the transverse cutter groove 40 in the tire axial direction, and preferably less than the length of the first interrupted groove 33 in the tire axial direction. Similarly, the length of the second interrupted cutter groove 47 in the tire axial direction is, for example, less than the length of the second part 42 of the transverse cutter groove 40 in the tire axial direction, and preferably less than the length of the second interrupted groove 34 in the tire axial direction. Specifically, the length L13 of the first interrupted cutter groove 46 or the second interrupted cutter groove 47 in the tire axial direction is 20% to 35% of the width W3 of the second land part 7 in the tire axial direction. Such first interrupted cutter groove 46 and second interrupted cutter groove 47 can effectively maintain the rigidity of the second land part 7 and particularly effectively maintain the braking performance on a dry road surface.

[0070] In order to maintain the handling stability and improve the performance on ice and snow, the maximum depth of the first interrupted cutter groove 46 is greater than the depth of the third part 43 of the transverse cutter groove 40 and is 90% to 110% of the maximum depth of the transverse cutter groove 40. In addition, the maximum depth of the first interrupted cutter groove 46 is less than the maximum depth of the first communicating cutter groove 37 and the maximum depth of the second communicating cutter groove 38.

[0071] Similarly, the maximum depth of the second interrupted cutter groove 47 is greater than the depth of the third part 43 of the transverse cutter groove 40 and is 90% to 110% of the maximum depth of the transverse cutter groove 40. In addition, the maximum depth of the second interrupted cutter groove 47 is less than the maximum depth of the first communicating cutter groove 37 and the maximum depth of the second communicating cutter groove 38.

[0072] Figure 5 An enlarged view of the first land portion 6 is shown. As Figure 5 shown, the first land portion 6 includes a first circumferential edge 6a, a second circumferential edge 6b, and a tread surface 6s therebetween.

[0073] A plurality of inclined cutter grooves 10 inclined in the first direction with respect to the tire axis are provided along the tire circumferential direction on the tread surface 6s of the first land portion 6. In addition, the inclined cutter grooves 10 include a first inclined cutter groove 11 and a second inclined cutter groove 12 adjacent to each other in the tire circumferential direction.

[0074] Figure 6 As a view showing a cross section of the first inclined cutter groove 11, a Figure 5 cross-sectional view taken along line A-A is shown. Figure 7 As a view showing a cross section of the second inclined cutter groove 12, a Figure 5 cross-sectional view taken along line B-B is shown. As Figure 6 shown, the first inclined cutter groove 11 includes a first deep bottom portion 16 disposed on the side of the first circumferential edge 6a and a first shallow bottom portion 17 disposed on the side of the second circumferential edge 6b and having a depth less than that of the first deep bottom portion 16. In addition, as Figure 7 shown, the second inclined cutter groove 12 includes a second deep bottom portion 21 disposed on the side of the second circumferential edge 6b and a second shallow bottom portion 22 disposed on the side of the first circumferential edge 6a and having a depth less than that of the second deep bottom portion 21.

[0075] Figure 8 An enlarged plan view of the first inclined cutter groove 11 and the second inclined cutter groove 12 is shown. In addition, in Figure 8 order to easily understand the features of the present embodiment, the first deep bottom portion 16 and the second deep bottom portion 21 are colored. As Figure 8 shown, the second deep bottom portion 21 is disposed at a position overlapping the projection area obtained by extending the first deep bottom portion 16 parallel to the tire axis.

[0076] The above-described first inclined cutter groove 11 and second inclined cutter groove 12 exert frictional force along the tire circumferential direction and the tire axial direction on an icy road surface, improving the braking performance and turning performance on ice and snow. On the other hand, the configurations of the first deep bottom 16 and the first shallow bottom 17 of the first inclined cutter groove 11, and the configurations of the second deep bottom 21 and the second shallow bottom 22 of the second inclined cutter groove 12 contribute to making the rigidity balance uniform in the tire circumferential direction and improving the straight running stability. And by having parts with high rigidity and low rigidity, it is easy to impart a slip angle, and thus smooth turning can be expected. Such an effect contributes to improving the handling stability on a dry road surface.

[0077] Moreover, in the present embodiment, since the second deep bottom 21 is arranged at a position overlapping the projection area obtained by extending the first deep bottom 16 parallel to the tire axial direction, when the first inclined cutter groove 11 and the second inclined cutter groove 12 come into contact with the ground, both the first deep bottom 16 and the second deep bottom 21 are opened, and large frictional force is provided by their edges. Thereby, the performance on ice and snow is further improved.

[0078] As Figure 5 shown, the inclined cutter groove 10 of the present embodiment extends from the first circumferential edge 6a to the second circumferential edge 6b and crosses the first land portion 6. However, it is not limited to such a manner, and the inclined cutter groove 10 may also be interrupted within the first land portion 6.

[0079] The inclined cutter groove 10 extends linearly, for example. Thereby, when the cutter groove walls facing each other in the inclined cutter groove 10 come into contact with each other, the first land portion 6 is easily sheared and deformed in the length direction of the inclined cutter groove 10. Such deformation can prevent snow from clogging the inside of the crown circumferential groove 4 and the inclined cutter groove 10.

[0080] The angle of the inclined cutter groove 10 with respect to the tire axial direction is, for example, 15 to 55°, preferably 30 to 50°. When the angle of the inclined cutter groove 10 is small, the interval between the inclined cutter grooves 10 arranged side by side in the tire circumferential direction becomes small. Therefore, it is preferable that the above-described second deep bottom 21 is arranged at a position overlapping the projection area of the first deep bottom 16. In addition, the first inclined cutter groove 11 and the second inclined cutter groove 12 are preferably inclined at angles close to each other. The angle difference between the first inclined cutter groove 11 and the second inclined cutter groove 12 is preferably 10° or less, more preferably 5° or less. As a further preferable manner, in the present embodiment, the first inclined cutter groove 11 and the second inclined cutter groove 12 are arranged parallel to each other. Thereby, the braking performance and turning performance on ice and snow are improved evenly.

[0081] The maximum distance L3 in the tire circumferential direction between the first inclined groove 11 and the second inclined groove 12 adjacent in the tire circumferential direction is, for example, 50% or less of the axial width W2 of the first land portion 6, preferably 20% to 45%, and more preferably 30% to 40%. Such an arrangement of the first inclined groove 11 and the second inclined groove 12 improves the handling stability and the performance on ice and snow in a balanced manner.

[0082] As Figure 6 shown, the first inclined groove 11 is between the first deep bottom portion 16 and the first shallow bottom portion 17, and includes a first depth change portion 18 in which the depth changes along the length direction of the groove. Accordingly, the first deep bottom portion 16 and the first shallow bottom portion 17 extend at a constant depth, respectively.

[0083] The depth d1 of the first deep bottom portion 16 is, for example, 60% to 80% of the depth of the crown circumferential groove 4. The axial length L4 of the first deep bottom portion 16 is 35% to 55% of the axial width W2 of the first land portion 6 ( Figure 5 as shown, the same applies hereinafter.).

[0084] The depth d2 of the first shallow bottom portion 17 is, for example, 50% or more of the depth d1 of the first deep bottom portion 16, preferably 55% to 75%, and more preferably 60% to 70%. Such a first shallow bottom portion 17 can maintain the rigidity of the first land portion 6 and improve the performance on ice and snow.

[0085] The axial length L5 of the first shallow bottom portion 17 is, for example, preferably 80% or more of the axial length L4 of the first deep bottom portion 16, more preferably 90% or more, preferably 120% or less, and more preferably 110% or less. Such a first deep bottom portion 16 and first shallow bottom portion 17 can suppress uneven wear of the first land portion 6 and improve the handling stability and the performance on ice and snow.

[0086] As Figure 7 shown, the second inclined groove 12 is between the second deep bottom portion 21 and the second shallow bottom portion 22, and includes a second depth change portion 23 in which the depth changes along the length direction of the groove. Accordingly, the second deep bottom portion 21 and the second shallow bottom portion 22 extend at a constant depth, respectively. The structures of the above-mentioned first deep bottom portion 16, first shallow bottom portion 17, and first depth change portion 18 can be respectively applied to the second deep bottom portion 21, second shallow bottom portion 22, and second depth change portion 23, and the description thereof is omitted here.

[0087] As Figure 8 shown, the circumferential length L12 of the overlapping region between the first deep bottom portion 16 and the second deep bottom portion 21 is preferably 30% or more of the circumferential length L11 of the first deep bottom portion 16, more preferably 50% or more, and in this embodiment, it is set to 60% to 80%. Thereby, the above-mentioned effects are reliably exhibited.

[0088] As Figure 5 shown, in the present embodiment, a plurality of groove pairs 14 of the first inclined groove 11 and the second inclined groove 12 are arranged side by side in the tire circumferential direction, and a third inclined groove 13 is provided between these groove pairs 14. The structure of the third inclined groove 13 when observing the tread from above can apply the structure of the above-mentioned first inclined groove 11 or second inclined groove 12.

[0089] Figure 9 shows a Figure 5 C-C line cross-sectional view. As Figure 9 shown, the third inclined groove 13 of the present embodiment includes a central shallow bottom portion 26 provided at the central portion in its longitudinal direction, and an outer deep bottom portion 27 provided between the central shallow bottom portion 26 and the crown circumferential groove 4.

[0090] The central shallow bottom portion 26 is arranged, for example, in the central region when the third inclined groove 13 is equally divided into three in its longitudinal direction, and includes the center position in the tire axial direction of the third inclined groove 13. The tire axial length L7 of the central shallow bottom portion 26 is, for example, 30% to 45% of the tire axial width W2 of the first land portion 6. Such a central shallow bottom portion 26 can suppress the third inclined groove 13 from opening excessively, so that uneven wear of the first land portion 6 can be suppressed, and handling stability is improved. In addition, the above-mentioned length L7 of the central shallow bottom portion 26 is measured, for example, at the center position in its height direction.

[0091] The depth d3 of the central shallow bottom portion 26 is, for example, 40% to 55% of the depth of the crown circumferential groove 4. In the present embodiment, the central shallow bottom portion 26, the first shallow bottom portion 17, and the second shallow bottom portion 22 are formed with the same depth as each other. Thereby, the above-mentioned effects are exerted, and uneven wear of the first land portion 6 is further suppressed.

[0092] When observing the tread from above, the central shallow bottom portion 26 is preferably arranged at a position overlapping the projection area obtained by extending the first shallow bottom portion 17 or the second shallow bottom portion 22 parallel to the tire axial direction.

[0093] The depth d4 of the outer deep bottom portion 27 is, for example, 60% to 80% of the depth of the crown circumferential groove 4. In the present embodiment, the outer deep bottom portion 27, the first deep bottom portion 16, and the second deep bottom portion 21 are formed with the same depth as each other.

[0094] As Figure 5As shown, a plurality of inclined groove groups 15 each composed of five inclined grooves 10 are provided in the first land portion 6 of the present embodiment along the tire circumferential direction. The inclined groove group 15 includes two groove pairs 14 each composed of a first inclined groove 11 and a second inclined groove 12, and includes one third inclined groove 13 disposed therebetween. In addition, between two adjacent inclined groove groups 15 along the tire circumferential direction, a first short groove 31 extending from the first circumferential edge 6a and interrupted within the first land portion 6, and a second short groove 32 extending from the second circumferential edge and interrupted within the first land portion 6 are provided. In addition, a connecting groove 30 extending from the first short groove 31 to the second short groove 32 is provided in the first land portion 6.

[0095] The first short groove 31 and the second short groove 32 are inclined in the second direction with respect to the tire axial direction. The angles of the first short groove 31 and the second short groove 32 with respect to the tire axial direction are, for example, 15 to 55°, preferably 30 to 50°. Thereby, a large frictional force can be exerted in a direction different from that of the inclined groove 10 on ice and snow, so that the turning performance and braking performance on ice and snow are improved.

[0096] The first short groove 31 and the second short groove 32 are interrupted, for example, without crossing the center position of the first land portion 6 in the tire axial direction. The axial length L8 of the first short groove 31 and the second short groove 32 in the tire axial direction is, for example, 15% to 35% of the axial width W2 of the first land portion 6 in the tire axial direction, preferably 20% to 30%. The first short groove 31 and the second short groove 32 configured in this way improve the handling stability and performance on ice and snow in a balanced manner.

[0097] The depths of the first short groove 31 and the second short groove 32 are, for example, 60% to 80% of the depth of the crown circumferential groove 4. The depths of the first short groove 31 and the second short groove 32 in the present embodiment are the same as the depth of the first deep bottom portion 16.

[0098] The connecting groove 30 is inclined in the first direction with respect to the tire axial direction, for example. The angle of the connecting groove 30 with respect to the tire axial direction is, for example, 15 to 55°, preferably 30 to 50°. The angle difference between the connecting groove 30 and the inclined groove 10 in the present embodiment is 5° or less, and in a more preferred embodiment, it extends parallel to the inclined groove 10. The connecting groove 30 configured in this way, together with the inclined groove 10, improves the braking performance and turning performance on ice and snow.

[0099] The maximum depth of the connecting groove 30 is less than the maximum depths of the first deep bottom portion 16 and the second deep bottom portion 21. The above depth of the connecting groove 30 is, for example, 40% to 55% of the depth of the crown circumferential groove 4, and in the present embodiment, it is the same as the depths of the first shallow bottom portion 17 and the second shallow bottom portion 22. Thereby, uneven wear of the first land portion 6 is suppressed.

[0100] Figure 10An enlarged view of the third land portion 8 is shown. As Figure 10 shown, a plurality of transverse grooves 49 that cross the third land portion 8 and a plurality of serrated cutter grooves 50 that extend in a serrated shape are provided in the third land portion 8.

[0101] The serrated cutter groove 50 includes a first serrated cutter groove 51 that extends from the shoulder circumferential groove 5 and terminates within the third land portion 8, and a second serrated cutter groove 52 that extends from the tread end Te and terminates within the third land portion. Such a first serrated cutter groove 51 and a second serrated cutter groove 52 contribute to improving the apparent rigidity of the third land portion 8 when the cutter groove walls facing each other come into contact with each other, thereby evenly improving the handling stability and performance on ice and snow.

[0102] As described above, the pneumatic tire according to one embodiment of the present invention has been described in detail, but the present invention is not limited to the above-described specific embodiments and can be implemented in various ways.

[0103]

Example

[0104] A pneumatic tire of size 215 / 60R16 having a Figure 1 basic tread pattern was trial-produced. As a comparative example, a tire having a second land portion a shown in Figure 11 was trial-produced. In the second land portion a of the comparative example, a transverse cutter groove d that is inclined in the same direction as a whole with respect to the tire axis is provided between the first interrupted groove b1 and the first communicating cutter groove c1 and the second interrupted groove b2 and the second communicating cutter groove c2. The tread portion of the tire of the comparative example is the same as the Figure 1 specification shown except for the above matters. The handling stability on a dry road surface, the braking performance on a dry road surface, and the performance on ice and snow of each test tire were tested. The common specifications and test methods of each test tire are as follows.

[0105] Mounting rim: 16×6J

[0106] Tire internal pressure: 240 kPa

[0107] Test vehicle: A front-wheel drive vehicle with a displacement of 2400 cc

[0108] Tire mounting position: All wheels

[0109] <Handling stability and braking performance on a dry road surface>

[0110] The handling stability and braking performance when driving on a dry road surface using the above test vehicle were evaluated by the driver's senses. The results are expressed as a score with the above handling stability or braking performance of the comparative example being 100, and the larger the value, the more excellent the handling stability or braking performance on a dry road surface.

[0111] <Performance on ice and snow>

[0112] The snow and ice performance during driving on snow and ice using the above test vehicle was evaluated by the driver's sensory evaluation. The results are expressed as scores with the comparative example being 100, and the larger the value, the more excellent the snow and ice performance.

[0113] The test results are shown in Table 1.

[0114]

Table 1

[0115]

[0116] As a result of the test, it was confirmed that the tires of the examples suppress the deterioration of handling stability on dry roads and improve the snow and ice performance.

Claims

1. A tire having a tread surface, characterized in that, the tread surface includes: a plurality of circumferential grooves continuously extending along the circumferential direction of the tire, and at least one land portion divided by the circumferential grooves, the land portion has a first circumferential edge, a second circumferential edge, and a tread surface between the first circumferential edge and the second circumferential edge, on the tread surface, there are provided: a first interrupted groove extending from the first circumferential edge and having an interrupted end within the tread surface, a second interrupted groove extending from the second circumferential edge and having an interrupted end within the tread surface, a first connecting sipe extending from the interrupted end of the first interrupted groove to the second circumferential edge, a second connecting sipe extending from the interrupted end of the second interrupted groove to the first circumferential edge, and a transverse sipe extending from the first circumferential edge to the second circumferential edge, the transverse sipe includes: a first portion inclinedly extending from the first circumferential edge, a second portion inclinedly extending from the second circumferential edge in the same direction as the first portion, and a third portion inclined at an angle different from those of the first portion and the second portion and connected to the first portion and the second portion, when observing the tread surface from above, the first portion overlaps with a projection area obtained by extending the first connecting sipe or the second connecting sipe parallel to the tire axis, and the third portion overlaps with a projection area obtained by extending the first connecting sipe or the second connecting sipe parallel to the tire axis.

2. The tire according to claim 1, characterized in that, the third portion is inclined in a direction opposite to those of the first portion and the second portion.

3. The tire according to claim 1 or 2, characterized in that, the second portion overlaps with a projection area obtained by extending the first connecting sipe or the second connecting sipe parallel to the tire axis.

4. The tire according to claim 1 or 2, characterized in that, on the tread surface, there is provided a first interrupted sipe extending from the first circumferential edge and having an interrupted end within the tread surface.

5. The tire according to claim 4, characterized in that, when observing the tread surface from above, the first interrupted sipe overlaps with a projection area obtained by extending the first portion parallel to the tire axis.

6. The tire according to any one of claims 1, 2, and 5, characterized in that, on the tread surface, there is provided a second interrupted sipe extending from the second circumferential edge and having an interrupted end within the tread surface.

7. The tire according to claim 6, characterized in that, when observing the tread surface from above, the second interrupted sipe overlaps with a projection area obtained by extending the second portion parallel to the tire axis.

8. The tire according to any one of claims 1, 2, 5, and 7, characterized in that, the angle of the first portion with respect to the tire axis is 40 to 50°.

9. The tire according to any one of claims 1, 2, 5, and 7, characterized in that, the angle between the first portion and the third portion is 90 to 110°.

10. The tire according to any one of claims 1, 2, 5, and 7, characterized in that the maximum depth of the first part is greater than the maximum depth of the first communicating groove.

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