tire

Abstract

Provided is a tire that exhibits excellent wet performance and snow performance while maintaining good dry performance, and achieves all the performances. The tire comprises a tread part 1 extending in the tire circumferential direction to form an annular shape and has an indication part indicating the rotation direction of the tire. A plurality of inclined grooves 10 are formed on both sides of the tire center line CL of the tread part 1. A plurality of circumferential thin grooves 20 are provided in a land part, which is divided by a zigzag groove part 11 formed in a central region of the tread part 1 by connecting the inclined grooves 10 to each other on both sides of the tire center line CL and by pairs of inclined grooves 10 adjacent to each other in the tire circumferential direction on each side of the tire center line CL, to divide the land part into at least three blocks 30. Each of the circumferential thin grooves 20 has a single bending point, and the bending angle θ of each of the circumferential thin grooves 20 measured on the inner side of the bending point in the tire width direction is an obtuse angle.

Description

tire

[0001] The present invention relates primarily to a tire intended for use as an all-season 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] All-season tires, intended for use in various weather conditions throughout the year, are required to exhibit excellent driving performance not only on normal dry roads but also on wet roads during rainy weather and on snowy roads in winter. To improve the driving performance on wet roads (wet performance), it has been proposed to provide multiple inclined grooves (V-shaped inclined grooves) on both sides of the tire equator in the tread, extending inclined from the tire equator towards the contact edge, in tires with a specified direction of rotation (directional pattern) (see, for example, Patent Document 1). In such tires, the contact edge side of the inclined groove is inclined to be further back in the direction of rotation than the center side, so that drainage is promoted from the center side outward as the tire rotates, thereby improving wet performance. Furthermore, by dividing the land area partitioned by such V-shaped inclined grooves into blocks with circumferential grooves, the edge effect of the inclined grooves and circumferential grooves can be ensured, and an improvement in driving performance on snowy roads (snow performance) can also be expected. On the other hand, the land areas (blocks) demarcated by these V-shaped inclined grooves tend to have difficulty maintaining rigidity, especially in the center, making it difficult to maintain good driving performance on dry surfaces (dry performance). Therefore, there is a need to improve wet and snow performance while maintaining good dry performance in tread patterns based on V-shaped inclined grooves, 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, the outer end in the tire width direction of each inclined groove 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 extending 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.

[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. 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 in 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 maintains good dry performance. Furthermore, by providing multiple circumferential narrow grooves in the land area, and having each of these circumferential grooves have a single bending point, and by making the bending angle θ of the circumferential narrow groove measured on the inside of the bending point in the tire width direction obtuse, the shape of the circumferential narrow grooves is improved, improving both wet and snow performance. On the other hand, the block shape, which is partitioned by the aforementioned circumferential grooves, is also improved, which is advantageous for maintaining dry performance. Through the combined efforts of these factors, a high level of performance can be achieved in dry, wet, and snow conditions.

[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 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.

[0011] 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.

[0012] 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. N When 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.

[0013] In the present invention, one of the blocks may be provided with a bent sipe, which consists of a pair of straight sections extending linearly in the same direction as the inclined groove and a connecting section extending linearly to connect the ends of the pair of straight sections. By providing a sipe in this way, an edge effect from the sipe can be expected while maintaining block rigidity, which is advantageous for achieving both dry and snow performance. In particular, since the sipe has a bent shape consisting of a pair of straight sections extending linearly in the same direction as the inclined groove and a connecting section extending linearly to connect the ends of the pair of straight sections, it is possible to suppress the decrease in block rigidity caused by providing a sipe while expecting an increase in edge effect, thereby effectively achieving both dry and snow performance.

[0014] 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.

[0015] 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.

[0016] Figure 1 is a meridional 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. Figures 5(a) and 5(b) are explanatory diagrams showing enlarged parts of the tread surface of a tire according to another embodiment of the present invention.

[0017] The configuration of the present invention will be described in detail below with reference to the attached drawings.

[0018] 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.

[0019] 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.

[0020] As this invention relates to a tread pattern formed on the surface of the tread portion 1 of a tire, as described below, the internal structure (cross-sectional structure) of the tire is not limited to the general structure described above. Furthermore, it can be applied to various types of tires, including non-pneumatic tires, as long as they have a surface that contacts the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire).

[0021] The tire of the present invention is a tire with a specified direction of rotation. The symbol R shown in Figure 2 represents the direction of tire rotation, with the tip of the arrow pointing forward (towards the foot-pushing side) and the opposite side pointing backward (towards the foot-pushing side). A tire with a specified direction of rotation generally has a marking (not shown) on the sidewall portion 2 indicating the direction of rotation.

[0022] As shown in Figure 2, the tire of the present invention has a plurality of inclined grooves 10 that extend inclined toward the contact end E from the tire equator CL side to the contact end E side on both sides of the tire equator CL of the tread portion 1. 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 to 6.5 mm to 9.0 mm. Each inclined groove 10 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 rotation direction R. In addition, 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 circumferential direction of the tire in the central region of the tread portion 1. In other words, the inner end of the inclined groove 10 on one side of the tire equator CL in the tire width direction connects to the middle of the inclined groove 10 on the other side of the tire equator CL, and the inner end of the inclined groove 10 on the other side of the tire equator CL in the tire width direction connects to the middle of the inclined groove 10 on one side of the tire equator CL. This alternating connection of the inclined grooves 10 on one side of the tire equator CL to the inclined groove 10 on the other side of the tire equator CL forms a zigzag groove portion 11 that extends in a zigzag pattern in the tire circumferential direction in the region between the inner end of the inclined groove 10 on one side of the tire equator CL and the inner end of the inclined groove 10 on the other side of the tire equator CL in the tire width direction. Strictly speaking, the zigzag groove portion 11 is a part of the inclined groove 10 (an element composed of multiple parts of the inclined groove 10 combined), but for convenience, they may be distinguished and explained separately in the following description.

[0023] When focusing on the land portions partitioned by a pair of circumferentially adjacent inclined grooves 10 and the zigzag groove portion 11 on one side of the tire equator CL, each of the land portions is provided with a plurality of circumferential narrow grooves 20. Each of the land portions is partitioned into at least three blocks 30 (three blocks in the illustrated example) by these circumferential narrow grooves 20. Furthermore, when focusing on the V-shaped land portion (V-shaped land portion) partitioned by a series of grooves (V-shaped grooves) formed by the inclined groove 10 on one side of the tire equator CL and the inclined groove 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 a part of the inclined groove 10 (zigzag groove portion 11).

[0024] 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 that is not more than half of that of the inclined grooves 10. Each circumferential narrow groove 20 has a shape in which a pair of straight portions are connected at a single bending point as illustrated. As shown in Fig. 3, when the angle of the circumferential narrow groove 20 measured on the inner side in the tire width direction of the bending point of the circumferential narrow groove 20 is defined as a bending angle θ, all of the bending angles θ are obtuse. The bending angle θ shall be measured based on the width-direction center line of the circumferential narrow groove 20 as shown in Fig. 3.

[0025] In the present invention, since the tire is equipped with the inclined groove 10 described above, wet performance can be improved. That is, since the tire of the present 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, so that 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. 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 portion 11 that extends in a zigzag shape in the tire circumferential direction in the central region of the tread portion 1, and the land portion is partitioned by this zigzag groove portion 11 and a pair of inclined grooves 10 adjacent to each other in the tire circumferential direction on one side of the tire equator, so that no sharp corners are formed in the land portion, and it is easier to secure the size of the individual blocks 30 partitioned by the circumferential grooves 20 described later, so that a decrease in block rigidity is suppressed and dry performance can be maintained well. In addition, multiple circumferential grooves 20 are formed in the land area, and each of these circumferential grooves 20 has a single bending point with an obtuse bending angle θ. This results in a good shape for the circumferential grooves 20, improving both wet and snow performance. On the other hand, the shape of the blocks 30 partitioned by the aforementioned circumferential grooves 20 is also good, which is advantageous for maintaining dry performance. Through the cooperation of these factors, a high level of balance between dry, wet, and snow performance can be achieved.

[0026] 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.

[0027] As described above, the circumferential fine groove 20 not only has a groove width equal to or less than half that of the inclined groove 10, but also preferably has a groove depth smaller than that of the inclined groove 10. In particular, when Gs is the groove depth of the circumferential fine groove 20 and Gd is the groove depth (maximum groove depth) of the inclined groove 10, the ratio Gs / Gd thereof preferably satisfies the relationship of 0.3≦Gs / Gd≦0.7, and more preferably satisfies the relationship of 0.4≦Gs / Gd≦0.6. Optimizing the groove depth of the circumferential fine groove 20 in this manner is advantageous for achieving both dry performance and wet performance. That is, as the ratio Gs / Gd increases, drainage performance improves while block rigidity tends to decrease, and as the ratio Gs / Gd decreases, block rigidity can be ensured while drainage performance tends to decrease. Therefore, by setting the ratio Gs / Gd within the above appropriate range in consideration of the balance between these, both dry performance and wet performance can be achieved in a well-balanced manner.

[0028] As described above, the bending angle θ of the circumferential fine groove 20 is an obtuse angle, and preferably satisfies the relationship of 90°<θ≦175°, more preferably 130°≦θ≦160°. This improves the bent shape of the circumferential fine groove 20, which is advantageous for improving dry performance and snow performance. That is, as the bending angle θ increases, block rigidity can be ensured while the edge amount tends to decrease, and as the bending angle θ decreases, the edge amount can be ensured while block rigidity tends to decrease. Therefore, by setting the bending angle θ within the above appropriate range in consideration of the balance between these, both dry performance and snow performance can be achieved in a well-balanced manner.

[0029] When focusing on one land portion as shown in Fig. 3, among the plurality of circumferential fine grooves 20 included in this land portion, the bending angle at the bending point of the N-th circumferential fine 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 fine grooves 20 are included, and the bending angle θ thereof NThe angles θ1 and θ2 are defined as the bending angles θ1 and θ2 from the tire equator side, and these bending angles satisfy the relationship θ1 ≥ θ2. In this way, the large bending angle of the circumferential groove 20 on the tire equator CL side ensures that block rigidity is reliably secured for the block 30 on the tire equator CL side, which is advantageous for maintaining good dry performance. Furthermore, the above relationship of bending angles results in a good balance of the bending shapes of the multiple circumferential grooves 20 contained in one land area, allowing for a balance between the effect of securing dry performance and the effect of securing edge amount. If the bending angle does not satisfy the above relationship (θ N <θ N+1 ), the effect of ensuring block rigidity on the tire's equator CL side becomes limited.

[0030] Similarly, when considering one land area, the area of ​​the tread surface of the outermost block 30 in the tire width direction (contact end E side) among the at least three blocks 30 included in this land area is Ao, and the area of ​​the tread surface of the Nth block 30 from the tire equator CL side is A N Let's assume that area Ao is the area of ​​the part of the tread surface of the outermost block 30 in the tire width direction that is in the contact area (inside the contact edge E in the tire width direction). N Preferably A N It 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).

[0031] 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.

[0032] As shown in Figure 4, 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 DThese 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.

[0033] 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 5(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 5(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 5(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.

[0034] 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.

[0035] In the present invention, each block 30 can also be provided with a sipe 40. By providing the sipe 40, the edge effect provided by the sipe 40 can be expected while maintaining block rigidity, which is advantageous for achieving both dry and snow performance. The sipe 40 is a fine groove with a groove width of, for example, 0.3 mm to 1.0 mm. When providing the sipe 40 in this way, it is preferable to provide a bent sipe (hereinafter referred to as a "bent sipe 41") on at least one block 30, which consists of a pair of straight sections extending linearly in the same direction as the inclined groove 10 on the tread surface of the block 30 and a connecting section extending linearly to connect the ends of the pair of straight sections. For example, in the illustrated example, bent sipes 41 are provided on the block 30 on the tire equator side and the block 30 on the contact end side, respectively, of the three blocks 30 shown in an enlarged view in Figure 3. The bent sipe 41, due to its bent shape, can efficiently increase the amount of edge while suppressing the reduction in block rigidity caused by the provision of sipes 40, thereby effectively achieving both dry and snow performance. The aforementioned bent sipe 41 has advantages in terms of manufacturing (the mold for forming the bent sipe 41 has high strength), so it is preferable to provide it on the shoulder portion of the block 30 (the block 30 on the ground-contacting end side), where sipe breakage tends to occur during manufacturing.

[0036] It is also possible to use sipes 40 with tread surface shapes other than the curved sipes 41 in combination. For example, in the illustrated example (three blocks 30 shown enlarged in Figure 3), three straight sipes (straight sipes 42) are provided on the blocks 30 excluding the innermost block 30 and the outermost block 30 in the tire width direction, that is, the second block 30 from the tire equator CL side. More specifically, there is one straight sipe 42 that opens into the circumferential narrow groove 20 on the inner side in the tire width direction and terminates within the block 30, and two straight sipes 42 that open into the circumferential narrow groove 20 on the outer side in the tire width direction and terminate within the block 30. By using a combination of curved sipes 41 and sipes 40 of other shapes (for example, straight sipes 42) in this way (mixing blocks 30 with curved sipes 41 and blocks 30 with straight sipes 42), an edge effect in various directions can be expected, which is advantageous for improving snow performance.

[0037] When sipes 40 are provided as described above, the shape of each sipe 40 in the depth direction is not particularly limited, and can be either the curved sipe 41 or the straight sipe 42 described above. In other words, 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).

[0038] 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.

[0039] 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, and on one side of the tire equator, it is divided into a single land area by a pair of adjacent inclined grooves and a zigzag groove (or main groove) in the circumferential direction of the tire, and the number of blocks divided by circumferential grooves in that land area, the presence or absence of zigzag grooves, the number of inflection points of the circumferential 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 of the circumferential groove to the groove depth of the inclined groove, and of the multiple circumferential grooves contained in one land area, the first circumferential groove from the tire equator. The relationship between the bending angle θ1 at the bending point of a directional groove and 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 an inclined groove (see "Magnitude of Bending Angle (Circumferential Direction)" in Table 1 below), the presence or absence of a raised section in the zigzag groove section, the ratio of the groove depth Gc in the raised section to the groove depth Gd of the inclined groove Gc / Gd, 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. N The relationship between the two (in Table 1 below, "Land area (Ao, A) N Pneumatic tires (test tires) were manufactured for the Conventional Example, Comparative Examples 1-2, and Examples 1-14, with the following settings: the relationship between the size of the areas A1 and A2 blocks from the tire equator, the ratio A1 / A2 of the area of ​​the second block, and the presence or absence of a bent sipe (bent sipe) consisting of a pair of straight sections extending linearly in the same direction as the inclined groove and a connecting section extending linearly to connect the ends of the pair of straight sections, as shown in Table 1.

[0040] 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.

[0041] For the bending angle θ, the maximum and minimum values ​​are provided. In the column for "Magnitude of Bending Angle (Circumferential Direction)," "Alternating" indicates that the bending angles of adjacent circumferential grooves in the tire circumferential direction, separated by an inclined groove, are different, and that circumferential grooves with relatively small bending angles compared to adjacent circumferential grooves and circumferential grooves with relatively large bending angles compared to adjacent circumferential grooves are arranged alternately in the tire circumferential direction. "Constant" indicates that the bending angles of adjacent circumferential grooves in the tire circumferential direction, separated by an inclined groove, are the same. "Non-alternating" indicates that the bending angles of circumferential grooves arranged in the tire circumferential direction are not "constant," and that two circumferential grooves with relatively small bending angles and two circumferential grooves with relatively large bending angles are arranged alternately. In the column for "Presence or Absence of Bending Sipes," "None" means that straight sipes are formed in all blocks and no bending sipes are provided, and "Present" means that bending sipes are provided (however, as shown in Figure 2, straight sipes are also used).

[0042] 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.

[0043] 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.

[0044] 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).

[0045] 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).

[0046] 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).

[0047]

[0048]

[0049] As is clear from Tables 1-2, the tires of Examples 1-14 showed improved dry performance, wet performance, and snow performance compared to conventional examples, achieving a good balance of these performances. On the other hand, Comparative Example 1 had a sharp bending angle in the circumferential grooves, resulting in reduced wet performance 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.

[0050] 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 30. 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, the outer end in the tire width direction of each inclined groove is inclined such that it 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.

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 a raised base portion is provided in the zigzag groove portion.

6. The tire according to claim 5, 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.

7. 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 6, 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.

8. The tire according to any one of claims 1 to 7, characterized in that one of the blocks has a bent sipe formed thereon, which consists of a pair of straight sections extending linearly in the same direction as the inclined groove and a connecting section extending linearly to connect the ends of the pair of straight sections.

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