tire

Abstract

Provided is a tire that exhibits excellent wet performance and snow performance while maintaining good dry performance, and achieves all of the performances simultaneously. The tire comprises an annular tread part 1 extending in the tire circumferential direction and has an indication part indicating the rotation direction of the tire. A plurality of inclined grooves 10 are formed on both sides of a tire equator CL of the tread part 1. A plurality of circumferential narrow grooves 20 each having a single bending point are provided in each of land parts partitioned by a zigzag groove part 11, formed in a central region of the tread part 1 by connecting the inclined grooves 10 on both sides of the tire equator CL to each other, and a pair of the inclined grooves 10, adjacent to each other in the tire circumferential direction on one side of the tire equator CL, thereby partitioning the land parts into at least three blocks 30. The bending angle θ of each of the circumferential narrow grooves 20 measured on the inside of the bending point in the tire width direction is obtuse. One of the blocks 30 is provided with a notch groove 21 that opens to the inclined groove 10 adjacent to the rear side in the rotation direction and terminates in the block 30.

Description

tire

[0001] The present invention relates primarily to a tire intended for use as a winter tire, and more specifically to a tire that exhibits excellent wet and snow performance while maintaining good dry performance, thereby achieving a balance of these performances.

[0002] So-called winter tires, designed for driving on snowy roads during winter, are required to have excellent driving performance on snowy surfaces (snow performance). On the other hand, even in winter, drivers may drive on dry roads when there is no snow, and on wet roads during rain or snowmelt, so they are required to exhibit excellent driving performance on these various road surfaces. To improve the driving performance on wet roads (wet performance) among these performances, it has been proposed to provide multiple inclined grooves (V-shaped inclined grooves) on both sides of the tire equator of the tread, sloping from the tire equator side toward the contact edge side (see, for example, Patent Document 1). In such a tire, the contact edge side of the inclined groove is inclined to be further back in the direction of rotation than the center side, so as the tire rotates, drainage is promoted from the center side toward the outside, improving wet performance. Furthermore, by dividing the land area, which is partitioned by such V-shaped inclined grooves, into blocks with circumferential grooves, the edge effect provided by the inclined grooves and circumferential grooves can be ensured, and an improvement in driving performance on snowy roads (snow performance) can be expected. On the other hand, it has been difficult to maintain rigidity in the land area (block) partitioned by such V-shaped inclined grooves, especially in the center, and it has been difficult to maintain good driving performance on dry roads (dry performance). Therefore, in tread patterns based on V-shaped inclined grooves, there is a need to improve wet and snow performance while maintaining good dry performance, and to achieve a high degree of balance between these performances.

[0003] Japanese Patent Application Publication No. 2003-054221

[0004] The objective of the present invention is to provide a tire that exhibits excellent wet and snow performance while maintaining good dry performance, thereby achieving a balance of these performance characteristics.

[0005] To achieve the above objective, the present invention provides a tire comprising a tread portion extending in the circumferential direction of the tire and forming an annular shape, and a portion indicating the direction of rotation of the tire, wherein a plurality of inclined grooves are formed on both sides of the tire equator of the tread portion, each inclined groove extending inclined from the tire equator side toward the contact end side, and each inclined groove is inclined such that its outer end in the tire width direction is located behind its inner end in the tire width direction in the direction of rotation, and the inclined grooves on both sides of the tire equator are connected to each other, forming a zigzag shape in the circumferential direction of the tire in the central region of the tread portion. An extended zigzag groove is formed, and on one side of the tire equator, a land area is provided which is partitioned by a pair of adjacent inclined grooves in the tire circumferential direction and the zigzag groove, and a plurality of circumferential narrow grooves are provided in the land area which is partitioned by the zigzag groove and the land area which is partitioned by at least three blocks, and each of the circumferential narrow grooves has a single bending point, and the bending angle θ of the circumferential narrow groove measured on the inner side of the bending point in the tire width direction is an obtuse angle, and one of the at least three blocks is provided with a notched groove that opens into the inclined groove adjacent to the rear side in the rotation direction and terminates within the block.

[0006] In this invention, the tire has a section indicating the direction of rotation, and in a tire with a specified direction of rotation, it is equipped with inclined grooves as described above. As the tire rotates, drainage is promoted from the center side of the inclined grooves toward the tire width direction, improving wet performance. Furthermore, these inclined grooves provide an excellent edge effect on snowy surfaces, improving snow performance. On the other hand, the inclined grooves on both sides of the tire equator are connected to each other, forming a zigzag groove section that extends in a zigzag pattern in the circumferential direction of the tire in the central region of the tread. The land area is divided by this zigzag groove section and a pair of adjacent inclined grooves in the circumferential direction of the tire on one side of the tire equator. As a result, no sharp corners are formed on the land area, and it becomes easier to secure the size of the individual blocks divided by the circumferential grooves described later. This suppresses a decrease in block rigidity and allows for good maintenance of dry performance. Furthermore, by providing multiple circumferential grooves in the land portion, each of which has a single bending point, and by making the bending angle θ of the circumferential groove obtuse, measured on the inner side of the tire width direction at the bending point, the shape of the circumferential grooves is improved, enhancing both wet and snow performance. On the other hand, the block shape partitioned by the aforementioned circumferential grooves is also improved, which is advantageous for maintaining dry performance. In addition, by providing notched grooves in the blocks, the edge effect and drainage provided by the notched grooves can be added, further improving snow and wet performance. Moreover, since the notched grooves terminate within the block without dividing it, the reduction in block rigidity is suppressed, and dry performance can be sufficiently maintained. Through the combined efforts of these factors, a high level of balance between dry, wet, and snow performance can be achieved.

[0007] In the present invention, it is preferable that the ratio Gs / Gd of the groove depth Gs of the circumferential narrow groove to the groove depth Gd of the inclined groove satisfies the relationship 0.3 ≤ Gs / Gd ≤ 0.7, and that the bending angle θ satisfies the relationship 90° < θ ≤ 175°. This results in a good shape for the circumferential narrow groove, which is advantageous for achieving a balance between dry performance, wet performance, and snow performance.

[0008] In this invention, the bending angle at the bending point of the Nth circumferential groove from the tire equator among multiple circumferential grooves contained in a single land area is θ.N When the bending angle is θ N ≥θ N+1 It is preferable to satisfy this relationship. This results in a good bending angle in each land area, which is advantageous for achieving both dry and snow performance.

[0009] In the present invention, it is preferable that the bending angles of adjacent circumferential grooves in the tire circumferential direction, separated by an inclined groove, differ from each other, and that circumferential grooves with a relatively small bending angle compared to adjacent circumferential grooves and circumferential grooves with a relatively large bending angle compared to adjacent circumferential grooves are alternately arranged in the tire circumferential direction. This results in a good balance between the multiple circumferential grooves arranged in the tire circumferential direction, which is advantageous for achieving both dry and snow performance.

[0010] In the present invention, it is preferable that the notched groove is formed only in the innermost block in the tire width direction among at least three blocks included in one land portion, and that the angle α formed between the notched groove and the extension direction of another inclined groove connected to the open inclined groove is in the range of 0° to 45°. As a result, the notched groove and the other inclined groove facing each other on either side of the inclined groove extend in substantially the same direction, which promotes drainage by these grooves and is advantageous for improving wet performance.

[0011] In the present invention, it is preferable to provide a raised section in the zigzag groove. This increases the block rigidity of the land section adjacent to the zigzag groove, which is advantageous for improving dry performance.

[0012] In the specification with a raised base as described above, it is preferable that the ratio Gc / Gd of the groove depth Gc in the raised base to the groove depth Gd of the inclined groove satisfies the relationship 0.3 ≤ Gc / Gd ≤ 0.7. This ensures sufficient groove volume and drainage even with the raised base, thus allowing for good wet performance while also improving dry performance due to the raised base.

[0013] In this invention, Ao is the area of ​​the outermost block in the tire width direction among at least three blocks included in one land area, and A is the area of ​​the Nth block from the tire equator. NWhen this is the case, the area A N A N It is preferable that the relationship ≥ Ao is satisfied, and that the ratio of areas A1 and A2, A1 / A2, satisfies the relationship 0.9 ≤ A1 / A2 ≤ 1.1. This results in a good balance of at least three blocks contained in one land area, which is advantageous for improving dry performance.

[0014] In this invention, it is preferable that zigzag-shaped sipes are formed on all of the blocks. This is advantageous for improving snow performance because it adds an edge effect due to the sipes.

[0015] In this case, it is preferable that the angle β formed by the longitudinal direction of a sipe on the innermost block in the tire width direction among at least three blocks included in one land area, and the inclined groove adjacent to this block in the tire circumferential direction, satisfies the relationship 45° ≤ β ≤ 90°. This is advantageous for improving snow performance while maintaining dry performance, as it allows for an increase in the amount of edge due to the sipe while maintaining the rigidity of the innermost block in the tire width direction.

[0016] In this invention, "contact end" refers to both ends in the axial direction of the tire in the contact area formed when a tire is mounted on a standard rim, filled with standard internal pressure, placed vertically on a plane, and a standard load is applied. "Standard rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, it may be a standard rim for JATMA, a "Design Rim" for TRA, or a "Measuring Rim" for ETRTO. "Regular internal pressure" refers to the air pressure specified for each tire in the tire 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 "INFLATION PRESSURE," but for passenger car tires, it is set to 180 kPa. "Regular load" refers to the load specified for each tire in the standards system, including the standards on which the tire is based. For JATMA, it is the maximum load capacity; for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is "LOAD CAPACATY." However, if the tire is for a passenger car, it shall be a load equivalent to 88% of the above load.

[0017] The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, it can be filled with air, an inert gas such as nitrogen, or other gases.

[0018] Figure 1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. Figure 2 is a front view showing the tread surface of a tire according to an embodiment of the present invention. Figure 3 is an enlarged explanatory diagram showing the main part of Figure 2. Figure 4 is an enlarged explanatory diagram showing the main part of Figure 2. Figure 5 is an enlarged explanatory diagram showing the main part of Figure 2. Figures 6(a) and 6(b) are enlarged explanatory diagrams showing the main part of the tread surface of a tire according to another embodiment of the present invention.

[0019] The configuration of the present invention will be described in detail below with reference to the attached drawings.

[0020] The tire of the present invention, when it is a pneumatic tire as shown in Figure 1, comprises a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In Figure 1, the symbol CL indicates the tire equator, and the symbol E indicates the contact end. Although not depicted in Figure 1 because it is a meridian cross-sectional view, the tread portion 1, sidewall portions 2, and bead portions 3 each extend in the circumferential direction of the tire and form an annular shape, thereby forming the basic toroidal structure of the pneumatic tire. The following explanation using Figure 1 is basically based on the illustrated meridian cross-sectional shape, but each tire component extends in the circumferential direction of the tire and forms an annular shape.

[0021] A carcass layer 4 is mounted between a pair of left and right bead sections 3. The carcass layer 4 includes multiple reinforcing cords extending in the tire radial direction and is folded back from the inside to the outside in the tire width direction around the bead core 5 located in each bead section 3. A bead filler 6 is also placed on the outer circumference of the bead core 5, and this bead filler 6 is enclosed by the main body and folded portion of the carcass layer 4. On the other hand, multiple belt layers 7 (two layers in Figure 1) are embedded on the outer circumference side of the carcass layer 4 in the tread section 1. Each belt layer 7 includes multiple reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10° to 40°. Furthermore, at least one belt reinforcement layer 8 (two layers in Figure 1) is provided on the outer circumference side of the belt layer 7. The belt reinforcement layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcement layer 8, the organic fiber cords are set to an angle of, for example, 0° to 5° with respect to the circumferential direction of the tire.

[0022] As described below, the present invention relates to a tread pattern formed on a surface of a tire tread portion 1, and therefore the internal structure (cross-sectional structure) of the tire is not limited to the general structure described above. Furthermore, the present invention can be applied to various tires including non-pneumatic tires, as long as the tire has a surface that comes into contact with the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire).

[0023] The tire of the present invention is a tire with a specified rotation direction. Reference sign R shown in FIG. 2 represents the tire rotation direction, wherein the tip of the arrow is the front (stepping side) in the rotation direction, and the opposite side is the rear (kick-out side) in the rotation direction. A tire with a specified rotation direction generally includes, typically provided with an indication portion (not shown) showing the rotation direction on the sidewall portion 2.

[0024] As shown in FIG. 2, the tire of the present invention has a plurality of inclined grooves 10 which are provided on both sides of the tire equator CL of the tread portion 1 and extend while being inclined from the tire equator CL side toward the ground contact edge E side, respectively. The inclined grooves 10 are grooves that bear the main drainage function, and the maximum groove width can be set to, for example, 5.0 mm to 12.0 mm, and the maximum groove depth can be set to 6.5 mm to 9.0 mm. Each inclined groove 10 is inclined such that the outer end portion in the tire width direction is located rearward in the rotation direction R relative to the inner end portion in the tire width direction. Further, the inclined grooves 10 on both sides of the tire equator CL are connected to each other to form a zigzag groove portion 11 that extends in a zigzag shape in the tire circumferential direction in the central region of the tread portion 1. In other words, the inner end portion in the tire width direction of the inclined groove 10 on one side of the tire equator CL is connected to the middle portion of the inclined groove 10 on the other side of the tire equator CL, and the inner end portion in the tire width direction of the inclined groove 10 on the other side of the tire equator CL is connected to the middle portion of the inclined groove 10 on one side of the tire equator CL. By alternately connecting the inclined grooves 10 on one side of the tire equator CL and the inclined grooves 10 on the other side of the tire equator CL in this manner, the zigzag groove portion 11 that extends in a zigzag shape in the tire circumferential direction is formed in the region between the inner end portion in the tire width direction of the inclined groove 10 on one side of the tire equator CL and the inner end portion in the tire width direction of the inclined groove 10 on the other side of the tire equator CL. Strictly speaking, the zigzag groove portion 11 is a part of the inclined grooves 10 (an element constituted by combining portions of the plurality of inclined grooves 10), but for convenience, these may be distinguished and described in the following description.

[0025] Focusing on the land portions partitioned by a pair of circumferentially adjacent inclined grooves 10 and zigzag groove portions 11 on one side of the tire equator CL, a plurality of circumferential narrow grooves 20 are provided in each land portion. Each land portion is partitioned into at least three blocks 30 (three blocks in the illustrated example) by these circumferential narrow grooves 20. When focusing on a V-shaped land portion (V-shaped land portion) partitioned by a series of grooves (V-shaped grooves) formed by the inclined grooves 10 on one side of the tire equator CL and the inclined grooves 10 on the other side, it can be considered that each V-shaped land portion is partitioned into at least six blocks 30 (six blocks in the illustrated example) by a plurality of circumferential narrow grooves 20 and part of the inclined grooves 10 (zigzag groove portions 11).

[0026] The circumferential narrow grooves 20 are grooves provided in each land portion as described above, extend in the tire circumferential direction, and have a groove width equal to or less than half that of the inclined grooves 10. As illustrated, each circumferential narrow groove 20 has a shape in which a pair of straight portions are connected at a single bending point. As shown in Fig. 3, when the angle of the circumferential narrow groove 20 measured on the tire width direction inner side of the bending point of the circumferential narrow groove 20 is defined as the bending angle θ, the bending angle θ is all obtuse. The bending angle θ shall be measured based on the width-direction centerline of the circumferential narrow groove 20, as shown in Fig. 3.

[0027] A notch groove 21 is formed in any one of the at least three blocks 30 partitioned as described above. In the illustrated example, the notch groove 21 is formed in the innermost block 30 in the tire width direction among the three blocks 30 (may be referred to as "innermost block 31" in the following description). Each notch groove 21 has a shape in which one end opens into the inclined groove 10 adjacent to the rear side in the rotation direction of the block 30, and the other end terminates inside the block 30. Although the dimensions of the notch groove 21 are not particularly limited, the groove depth of the notch groove 21 can be set to, for example, 20% to 80% of the groove depth of the inclined groove 10, and the maximum groove width of the notch groove 21 can be set to, for example, 20% to 80% of the groove width of the inclined groove 10.

[0028] In this invention, the inclined groove 10 as described above can improve wet performance. Specifically, since the tire of this invention is a tire with a specified rotation direction R, the inclined groove 10 is inclined such that the outer end of the inclined groove 10 in the tire width direction is located behind the inner end in the tire width direction in the rotation direction R. As the tire rotates, drainage is promoted from the center side of the inclined groove 10 toward the tire width direction, thereby improving wet performance. Furthermore, these inclined grooves 10 can provide an excellent edge effect on snowy road surfaces, thus improving snow performance. On the other hand, the inclined grooves 10 on both sides of the tire equator CL are connected to each other to form a zigzag groove section 11 that extends in a zigzag pattern in the circumferential direction of the tire in the central region of the tread section 1. Since the land area is partitioned by this zigzag groove section 11 and a pair of adjacent inclined grooves 10 in the circumferential direction of the tire on one side of the tire equator, no sharp corners are formed in the land area, and it becomes easier to secure the size of the individual blocks 30 partitioned by the circumferential grooves 20 described later, thereby suppressing a decrease in block rigidity and maintaining good dry performance. In addition, multiple circumferential fine grooves 20 are formed in the land area, and each of these circumferential grooves 20 has a single bending point, and the bending angle θ is obtuse, so the shape of the circumferential fine grooves 20 is good, and wet performance and snow performance can be improved. On the other hand, the shape of the blocks 30 partitioned by the circumferential fine grooves 20 of the aforementioned shape is also good, which is advantageous for maintaining dry performance. Furthermore, by providing notched grooves 21 in the block 30, the edge effect and drainage provided by the notched grooves 21 can be added, thereby improving snow performance and wet performance. Since the notched grooves 21 terminate within the block 30 and do not further divide the block 30, a decrease in block rigidity is suppressed, and dry performance can be sufficiently maintained. Through the combined efforts of these factors, a high level of balance between dry performance, wet performance, and snow performance can be achieved.

[0029] As mentioned above, the circumferential groove 20 has a single bending point. If the number of bending points is two or more, the circumferential groove 20 bends in a zigzag pattern, making it difficult to maintain the rigidity of the partitioned block, and thus making it impossible to ensure sufficient dry performance. As mentioned above, the circumferential groove 20 is a groove with a groove width of less than half that of the inclined groove 10, so when the groove width of the circumferential groove 20 is Ws and the groove width (maximum groove width) of the inclined groove 10 is Wd, the ratio Ws / Wd satisfies the relationship Ws / Wd ≤ 0.5, but preferably satisfies the relationship 0.3 ≤ Ws / Wd ≤ 0.4.

[0030] The circumferential grooves 20, as described above, should not only have a groove width of less than half that of the inclined grooves 10, but preferably also have a groove depth smaller than that of the inclined grooves 10. In particular, when the groove depth of the circumferential grooves 20 is Gs and the groove depth of the inclined grooves 10 is Gd, it is preferable that the ratio Gs / Gd satisfies the relationship 0.3 ≤ Gs / Gd ≤ 0.7, and more preferably 0.4 ≤ Gs / Gd ≤ 0.6. Optimizing the groove depth of the circumferential grooves 20 in this way is advantageous for achieving both dry and wet performance. That is, the larger the ratio Gs / Gd, the better the drainage performance tends to be, but the lower the ratio Gs / Gd, the more block rigidity can be ensured, but the lower the drainage performance tends to be. By considering these balances and setting the ratio Gs / Gd within the above-mentioned appropriate range, it is possible to achieve a good balance between dry and wet performance.

[0031] As mentioned above, the circumferential groove 20 has an obtuse bending angle θ, but preferably satisfies the relationship 90° < θ ≤ 175°, and more preferably 130° ≤ θ ≤ 160°. This results in a good bending shape of the circumferential groove 20, which is advantageous for improving both dry and snow performance. In other words, a larger bending angle θ tends to ensure block rigidity but reduce the amount of edge, while a smaller bending angle θ tends to ensure the amount of edge but reduce block rigidity. By considering these balances and setting each bending angle θ within the above appropriate range, it is possible to achieve a good balance between dry and snow performance.

[0032] When focusing on one land portion as shown in Figure 3, among the plurality of circumferential narrow grooves 20 included in this land portion, the bending angle at the bending point of the N-th circumferential narrow groove 20 from the tire equator side is θ N . In this case, the bending angle satisfies θ N ≧θ N+1 . It is preferable to satisfy this relationship. For example, in the illustrated example, two circumferential narrow grooves 20 are included, and the bending angles θ N are defined as bending angles θ1 and θ2 from the tire equator side, and these bending angles satisfy the relationship of θ1≧θ2. Since the bending angle of the circumferential narrow groove 20 on the tire equator CL side is large in this way, the block rigidity can be reliably ensured for the blocks 30 on the tire equator CL side, which is advantageous for maintaining good dry performance. In addition, according to the magnitude relationship of the above bending angles, the balance of the bending shapes of the plurality of circumferential narrow grooves 20 included in one land portion becomes good, and the balance between the aforementioned effect of ensuring dry performance and the effect of ensuring the edge amount can be achieved. When the bending angle does not satisfy the above relationship (θ N <θ N+1 ), the effect of ensuring block rigidity on the tire equator CL side becomes limited.

[0033] Similarly, when focusing on one land portion, among at least three blocks 30 included in this land portion, let Ao be the area of the tread surface of the block 30 located on the outermost side in the tire width direction (on the ground contact edge E side), and let A be the area of the tread surface of the N-th block 30 from the tire equator CL side N . In addition, the area Ao is the area of the portion within the ground contact region of the tread surface of the block 30 located on the outermost side in the tire width direction (inside the ground contact edge E in the tire width direction). In this case, the area A N is preferably A NIt is preferable that the relationship ≥ Ao is satisfied, and that the ratio of area A1 to area A2 A1 / A2 is preferably 0.9 ≤ A1 / A2 ≤ 1.1, and more preferably 0.95 ≤ A1 / A2 ≤ 1.05. This results in a good balance of the sizes of at least three blocks 30 contained in one land area, which is advantageous for improving dry performance. In particular, the above-mentioned size relationship allows for sufficient area of ​​the block 30 on the tire equator CL side, thereby improving the rigidity of the block 30 on the tire equator CL side and achieving the effect of improving dry performance (especially steering performance).

[0034] In the illustrated example, one land area is divided into three blocks 30, so the areas of these blocks 30 are A1, A2, and Ao. However, if, for example, it is divided into four or more blocks 30 (including areas A3, A4, etc.), the area of ​​block 30 is A N Preferably 0.9 ≤ A N / A N+1 It is desirable that the relationship ≤ 1.1 is satisfied. This gives the area A of block 30. N Since the size is roughly the same regardless of the position (value of N) from the tire equator CL side, it is advantageous for ensuring sufficient rigidity of each block 30 and improving dry performance.

[0035] As shown in Figure 4, it is preferable to provide the notched groove 21 only in the innermost block 30 (innermost block 31) located on the innermost side in the tire width direction (tire equator CL side) of the at least three blocks 30 included in one land area. That is, as described above, the inclined groove 10 on one side of the tire equator CL and the inclined groove 10 on the opposite side are connected alternately, so another inclined groove 10 (the inclined groove 10 on the opposite side of the tire equator CL) will be connected to the portion of the inclined groove 10 adjacent to the rear side of the innermost block 31 in the tire circumferential direction. When the notched groove 21 is provided in the innermost block 31, the other inclined groove 10 (the inclined groove 10 on the opposite side of the tire equator CL) and the notched groove 21 are arranged to face each other with one inclined groove 10 in between, so the cooperation of these grooves can effectively improve wet performance and snow performance. In particular, from the viewpoint of drainage, it is preferable that the opening of the notch 21 and the opening of another inclined groove 10 (the inclined groove 10 on the opposite side of the tire equator CL) overlap at least partially along the extension direction of the one inclined groove 10 (i.e., the virtual grooves extended from each groove touch or overlap each other).

[0036] As described above, when a notched groove 21 is provided in the innermost block 31, the angle α formed by the notched groove 21 and the other inclined groove 10 facing each other across one inclined groove 10 is preferably 0° to 45°, more preferably 0° to 15°. Here, one inclined groove 10 refers to the inclined groove 10 through which the notched groove 21 and the other inclined groove 10 each open. The angle α is the acute angle formed by the straight line passing through the widthwise center of the notched groove 21 and the straight line passing through the widthwise center of the other inclined groove 10, as shown in the figure. As a result, the notched groove 21 and the other inclined groove 10 facing each other across one inclined groove 10 extend in substantially the same direction, which promotes drainage by these grooves and is advantageous for improving wet performance. When the angle α exceeds 45°, the extension direction of the notched groove 21 becomes close to the extension direction of the aforementioned inclined groove 10 (the inclined groove 10 through which both the notched groove 21 and the other inclined groove 10 open), thus limiting the drainage through the notched groove 21 and the other inclined groove 10 that are opposite each other across the inclined groove 10.

[0037] As shown in Figure 5, focusing on the circumferential grooves 20 adjacent to each other in the tire circumferential direction with respect to the inclined groove 10, it is preferable that their bending angles θ differ from each other, and that circumferential grooves 20 with a relatively small bending angle θ compared to adjacent circumferential grooves 20 and circumferential grooves 20 with a relatively large bending angle θ compared to adjacent circumferential grooves 20 be arranged alternately in the tire circumferential direction. For example, in Figure 4, four arbitrary circumferential grooves 20 adjacent to each other in the tire circumferential direction with respect to the inclined groove 10 are extracted and shown, and their bending angles θ are respectively θ A , θ B , θ C , θ D Therefore, the bending angle θ B The adjacent bending angle θ A , θ C It is larger in comparison, and the bending angle θ C The adjacent bending angle θ B , θ D It is smaller in comparison. In other words, the bending angle θ is relatively large compared to the adjacent circumferential grooves 20. B , θ D The bending angle θ is relatively small compared to the adjacent circumferential groove 20. A , θ C These are arranged alternately in the circumferential direction of the tire. At this time, the bending angle θ B The bending angle θ is relatively small compared to A and the bending angle θ C These angles may be different from each other, and the bending angle θ C The bending angle θ is relatively large compared to B and the bending angle θ D These angles may be different from each other. This arrangement allows for a good balance of the shapes of the multiple circumferential grooves 20 arranged in the circumferential direction of the tire, which is advantageous for achieving both dry and snow performance. In more detail, as mentioned above, a larger bending angle θ ensures block rigidity, while a smaller angle ensures edge size. Therefore, the above arrangement allows for a good balance between circumferential grooves 20 suitable for ensuring block rigidity (with a relatively large bending angle θ) and circumferential grooves 20 suitable for ensuring edge size (with a relatively small bending angle θ), thereby achieving a high level of both dry and snow performance.

[0038] In the present invention, the zigzag groove portion 11 is a portion of the inclined groove 10 formed by a part of the alternatingly intersecting inclined grooves 10, and it is preferable to provide a raised portion 12 at the bottom of the groove. By providing the raised portion 12 in this way, the block rigidity of the land portion adjacent to the zigzag groove portion 11 can be increased, which is advantageous for improving dry performance. As shown in Figure 6(a), the raised portion 12 can be a raised portion 12 (shaded portion in the figure) that raises the entire bottom of the zigzag groove portion 11. Alternatively, as shown in Figure 6(b), the raised portion 12 (shaded portion in the figure) can be a raised portion 12 that raises a part of the bottom of the zigzag groove portion 11. In the embodiment of Figure 6(b), a plurality of raised portions 12 are provided intermittently along the extension direction of the zigzag groove portion 11 so as to avoid the points where the inclined groove 10 on one side connects to the inclined groove 10 on the other side, and the points where the inclined groove 10 on the other side connects to the inclined groove 10 on the other side.

[0039] When the raised section 12 is provided as described above, the ratio Gc / Gd of the groove depth Gc in the raised section 12 to the groove depth Gd of the inclined groove 10 preferably satisfies the relationship 0.3 ≤ Gc / Gd ≤ 0.7, and more preferably 0.4 ≤ Gc / Gd ≤ 0.6. This ensures sufficient groove volume and drainage even when the raised section 12 is provided, thus allowing for improved dry performance due to the raised section 12 while maintaining good wet performance. If the ratio Gc / Gd is less than 0.3, the additional effects of providing the raised section 12 cannot be fully expected. If the ratio Gc / Gd exceeds 0.7, sufficient groove volume cannot be secured for the zigzag groove section 11, resulting in limited drainage performance based on the zigzag groove section 11.

[0040] In the present invention, each block 30 can also be provided with sipes 40. By providing sipes 40, the edge effect provided by the sipes 40 can be expected while maintaining block rigidity, which is advantageous for achieving both dry performance and snow performance. A sipe 40 is a fine groove with a groove width of, for example, 0.3 mm to 1.0 mm. When sipes 40 are provided in this way, the tread surface shape of each sipe 40 (shape viewed from the tread surface of the tread portion 1) is preferably a zigzag shape, as shown in the illustrated example. On the other hand, the shape of the sipe 40 in the depth direction is not particularly limited, and the sipe shape that appears on the tread surface (on the tread surface of the tread portion 1) may be constant along the sipe depth direction (a so-called two-dimensional sipe), or the sipe shape that appears on the tread surface may change along the sipe depth direction (a so-called three-dimensional sipe). Providing such a zigzag-shaped sipe 40 can efficiently increase the amount of edge, which is advantageous for improving snow performance.

[0041] At this time, the angle β formed between the longitudinal direction of the sipe 40 provided on the innermost block 30 (innermost block 31) in the tire width direction among at least three blocks 30 included in one land area, and the inclined groove 10 adjacent to this block 30 (innermost block 31) in the tire circumferential direction, preferably satisfies the relationship 45°≦β≦90°, and more preferably 55°≦β≦65°. The longitudinal direction of the sipe 40 is the direction of extension of the straight line connecting the ends of the sipe 40, as shown in Figure 4, and the angle β is the angle formed between this and the inclined groove 10 (more precisely, the boundary line between the inclined groove 10 and the block 30 as shown in the figure) on the inside in the tire width direction. By setting the angle β in this way, it is possible to increase the amount of edge provided by the sipe 40 while maintaining the rigidity of the innermost block 31, which is advantageous for improving snow performance while maintaining dry performance. If the angle β is less than 45°, the longitudinal direction of the sipe 40 approaches the extension direction of the inclined groove 10, thus limiting the effect of suppressing the reduction in rigidity when the sipe 40 is provided. If the angle β exceeds 90°, the longitudinal direction of the sipe 40 approaches the circumferential direction of the tire, thus limiting the edge effect with respect to the rotational direction of the tire.

[0042] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples.

[0043] The tire size is 205 / 55R16 94V, and it has the internal structure (cross-sectional structure) illustrated in Figure 1, and the tread pattern is based on Figure 2. On one side of the tire equator, in a single land area that is divided by a pair of adjacent inclined grooves and a zigzag groove (or main groove) in the circumferential direction of the tire, the number of blocks divided by circumferential grooves, the presence or absence of zigzag grooves, the number of inflection points of the circumferential grooves, the presence or absence of notched grooves, the inflection angle θ of the circumferential groove measured on the inner side of the inflection point in the tire width direction, the ratio Gs / Gd of the groove depth Gs of the circumferential groove to the groove depth Gd of the inclined groove, and the inflection angle θ1 at the inflection point of the first circumferential groove from the tire equator among multiple circumferential grooves contained in a single land area. The relationship between the bending angle θ2 at the bending point of the second circumferential groove (see "Magnitude of Bending Angle (Width Direction)" in Table 1 below), the relationship between the bending angles of adjacent circumferential grooves in the tire circumferential direction, separated by the inclined groove (see "Magnitude of Bending Angle (Circumferential Direction)" in Tables 1-3 below), the angle α between the extension direction of another inclined groove connected to the inclined groove where the notched groove opens and the notched groove, the presence or absence of a raised section in the zigzag groove section, the ratio Gc / Gd of the groove depth Gc in the raised section to the groove depth Gd of the inclined groove, the area Ao of the outermost block in the tire width direction among the blocks included in one land area and the area A of the Nth block from the tire equator side. N The relationship between the two (in Tables 1-3 below, "Land area (Ao, A)" N Conventional examples, comparative examples 1-2, and examples 1-21 (test tires) were fabricated by setting the following parameters: the relative size of the areas A1 and A2 from the tire equator, the ratio A1 / A2 of the area of ​​the first block A1 from the tire equator, the shape of the sipes formed in each block, and the angle β between the longitudinal direction of the sipes and the inclined grooves, as shown in Tables 1-3.

[0044] The Conventional Example and Comparative Examples 1-2 are examples without zigzag grooves (examples in which the inclined grooves on both sides of the tire equator are not connected to each other, and no zigzag grooves are formed in the central region of the tread). In these cases, a single main groove (of the same depth as the inclined grooves) is provided on the tire equator, extending linearly in the circumferential direction of the tire, and the inclined grooves on both sides of the tire equator are connected to this linear main groove. As a result, on one side of the tire equator, the land area is divided by a pair of adjacent inclined grooves and the main groove in the circumferential direction of the tire, and blocks are divided by providing circumferential narrow grooves on this land area. In other words, the Conventional Example and Comparative Examples 1-2 can be said to be examples of tread patterns having a tread pattern in which the zigzag grooves in Figure 2 are replaced by a single main groove extending linearly in the circumferential direction of the tire on the tire equator.

[0045] In the "Presence or Absence of Notched Grooves" column, the arrangement of blocks with notched grooves was also noted. Specifically, if the notched groove was located on the outermost block in the tire width direction (innermost block) within a single land area, it was indicated as "innermost," and if it was located on the second block from the tire equator, it was indicated as "second." The maximum and minimum values ​​for the bending angle θ were also provided. In the "Magnitude of Bending Angle (Circumferential Direction)" column, the bending angles of adjacent circumferential grooves in the tire's circumferential direction, separated by an inclined groove, are different. When circumferential grooves with relatively small bending angles and circumferential grooves with relatively large bending angles are arranged alternately in the tire's circumferential direction, this is indicated as "alternating." When the bending angles of adjacent circumferential grooves in the tire's circumferential direction, separated by an inclined groove, are the same, this is indicated as "constant." When the bending angles of circumferential grooves arranged in the tire's circumferential direction are not "constant," and two pairs of circumferential grooves with relatively small bending angles and two pairs of circumferential grooves with relatively large bending angles are arranged alternately, this is indicated as "non-alternating." In the "Sipe Shape" column, in all examples, multiple sipes are provided in every block. Sipes that extend in a straight line are indicated as "straight," and sipes that extend in a zigzag shape are indicated as "zigzag."

[0046] In Comparative Example 2, since each circumferential groove has multiple (two) bending points, it is not possible to compare the bending angles of adjacent circumferential grooves in the width direction or circumferential direction in the same way as in the other examples. Therefore, the columns for "Magnitude of Bending Angle (Width Direction)" and "Magnitude of Bending Angle (Circumferential Direction)" in Comparative Example 2 were left blank. On the other hand, the minimum and maximum values ​​of the bending angle θ for Comparative Example 2 were also included as reference values.

[0047] These test tires were evaluated for dry performance, wet performance, and snow performance using the evaluation method described below, and the results are shown in Table 1.

[0048] For the dry performance test, each test tire was mounted on a rim size 16 x 6.5J wheel, inflated to an air pressure of 250 kPa, and mounted on a test vehicle (a 1500cc front-wheel-drive passenger car). Braking tests were then conducted on a test track consisting of dry road surface. Specifically, the braking distance was measured from a speed of 100 km / h until the vehicle came to a complete stop. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional value set to 100. A larger index value indicates a shorter braking distance and superior dry performance (braking performance on dry road surfaces).

[0049] For the wet performance test, each test tire was mounted on a rim size 16 x 6.5J wheel, inflated to an air pressure of 250 kPa, and mounted on a test vehicle (a 1500cc front-wheel-drive passenger car). Braking tests were conducted on a test track consisting of a wet surface with a water depth of 1.0 mm. Specifically, the braking distance was measured from a speed of 80 km / h until the vehicle came to a complete stop. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional value set to 100. A larger index value indicates a shorter braking distance and superior wet performance (braking performance on wet surfaces).

[0050] Each snow performance test tire was mounted on a rim size 16 x 6.5J wheel, inflated to an air pressure of 250 kPa, and mounted on a test vehicle (a 1500cc front-wheel-drive passenger car). Braking tests were conducted on a test track consisting of snow. Specifically, the braking distance was measured from a speed of 30 km / h until the vehicle came to a complete stop. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional value set to 100. A larger index value indicates a shorter braking distance and superior snow performance (braking performance on snowy roads).

[0051]

[0052]

[0053]

[0054] As is clear from Tables 1 to 3, the tires of Examples 1 to 21 improved snow and wet performance while maintaining dry performance compared to conventional examples, achieving a good balance between these performances. On the other hand, Comparative Example 1 had a sharp bending angle in the circumferential grooves, resulting in reduced wet and snow performance. Comparative Example 2 had multiple bending points in the circumferential grooves, which resulted in areas with low block rigidity and failed to improve dry performance. Furthermore, the presence of multiple bending points caused the circumferential grooves to bend in a zigzag pattern, making it difficult for water to flow within the grooves, thus reducing wet performance.

[0055] 1 Tread section 2 Sidewall section 3 Bead section 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 10 Inclined groove 11 Zigzag groove section 12 Raised bottom section 20 Circumferential narrow groove 21 Notched groove 30 Block 31 Innermost block 40 Sipe 41 Bent sipe 42 Straight sipe CL Tire equator E Contact edge

Claims

1. A tire having a tread portion that extends in the circumferential direction of the tire and forms an annular shape, and having a marking portion that indicates the direction of rotation of the tire, wherein a plurality of inclined grooves are formed on both sides of the tire equator of the tread portion, each inclined groove extending inclined from the tire equator side toward the contact end side, and each inclined groove is inclined such that the outer end in the tire width direction is located behind the inner end in the tire width direction in the direction of rotation, the inclined grooves on both sides of the tire equator are connected to each other to form a zigzag groove portion that extends in a zigzag shape in the circumferential direction of the tire in the central region of the tread portion, a plurality of circumferential fine grooves are provided in a land area partitioned by a pair of adjacent inclined grooves in the circumferential direction of the tire and the zigzag groove portion on one side of the tire equator, the land area is partitioned into at least three blocks, each of the circumferential fine grooves has a single bending point, and the bending angle θ of the circumferential fine groove measured on the inner side of the bending point in the tire width direction is an obtuse angle. A tire characterized in that at least one of the three blocks is provided with a notched groove that opens into the inclined groove adjacent to the rear side in the direction of rotation and terminates within the block.

2. The tire according to claim 1, characterized in that the ratio Gs / Gd of the groove depth Gs of the circumferential narrow groove to the groove depth Gd of the inclined groove satisfies the relationship 0.3 ≤ Gs / Gd ≤ 0.7, and the bending angle θ satisfies the relationship 90° < θ ≤ 175°.

3. The angle of inflection at the inflection point of the Nth circumferential groove from the tire equator among the multiple circumferential grooves included in one of the land portions is θ. N When the bending angle is θ N ≥θ N+1 A tire according to claim 1 or 2, characterized in that it satisfies the relationship.

4. The tire according to any one of 1 to 3, characterized in that the bending angles of adjacent circumferential grooves in the tire circumferential direction, with respect to the inclined groove, are different from those of adjacent circumferential grooves, and circumferential grooves having a relatively small bending angle compared to adjacent circumferential grooves and circumferential grooves having a relatively large bending angle compared to adjacent circumferential grooves are alternately arranged in the tire circumferential direction.

5. The tire according to any one of claims 1 to 4, characterized in that the notched groove is formed only in the innermost block in the tire width direction among at least three blocks included in one of the land portions, and the angle α formed between the notched groove and the extension direction of another inclined groove connected to the open inclined groove is in the range of 0° to 45°.

6. The tire according to any one of claims 1 to 5, characterized in that a raised portion is provided in the zigzag groove portion.

7. The tire according to claim 6, characterized in that the ratio Gc / Gd of the groove depth Gc in the raised portion to the groove depth Gd of the inclined groove satisfies the relationship 0.3 ≤ Gc / Gd ≤ 0.

7.

8. Of the at least three blocks included in one of the land portions, the area of ​​the outermost block in the tire width direction is Ao, and the area of ​​the Nth block from the tire equator is A N When this is the case, the area A N A N A tire according to any one of claims 1 to 7, characterized in that it satisfies the relationship ≥ Ao, and the ratio of area A1 to area A2, A1 / A2, satisfies the relationship 0.9 ≤ A1 / A2 ≤ 1.

1.

9. The tire according to any one of claims 1 to 8, characterized in that zigzag-shaped sipes are formed on all of the blocks.

10. The tire according to claim 9, characterized in that the angle β formed by the longitudinal direction of the sipe provided on the innermost block in the tire width direction among at least three blocks included in one of the land portions, and the inclined groove adjacent to this block in the tire circumferential direction satisfies the relationship 45° ≤ β ≤ 90°.

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