tire

Abstract

This tire provides a balance of excellent wet and snow performance while maintaining good dry performance. [Solution] In a tire having a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape, a plurality of inclined grooves 10 are formed on both sides of the tire equator CL of the tread portion 1, and the inclined grooves 10 on both sides of the tire equator CL are connected to each other to form a zigzag groove portion 11 in the central region of the tread portion 1, and a plurality of circumferential narrow grooves 20 are provided in the land area partitioned by a pair of adjacent inclined grooves 10 in the circumferential direction of the tire on one side of the tire equator CL, thereby dividing it into at least three blocks 30, each circumferential narrow groove 20 having a single bending point, and the bending angle θ of the circumferential narrow groove 20 measured on the inside of the bending point in the tire width direction is obtuse.

Description

[Technical Field]

[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. [Background technology]

[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 (see, for example, Patent Document 1). In such tires, the contact edge side of the inclined grooves 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. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-054221 [Overview of the Initiative] [Problems that the invention aims to solve]

[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 performances. [Means for solving the problem]

[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. [Effects of the Invention]

[0006] In the present invention, since the tire has an indicating portion indicating the rotation direction of the tire and has the inclined grooves as described above in the tire with the rotation direction specified, drainage is promoted from the center side of the inclined grooves toward the tire width direction side as the tire rotates, and the wet performance can be improved. On the other hand, 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 tire circumferential direction in the central region of the tread portion. Since the land portion is partitioned by this zigzag groove portion and a pair of inclined grooves adjacent to each other in the tire circumferential direction on one side of the tire equator, an acute-angled corner portion is not formed on the land portion, and it becomes easier to secure the size of each block partitioned by the circumferential grooves described later. Therefore, a decrease in block rigidity can be suppressed, and dry performance can be maintained well. Further, a plurality of circumferential fine grooves are provided in the land portion, each of these circumferential grooves has a single bending point, and by making the bending angle θ of the circumferential fine groove measured inside the tire width direction of the bending point an obtuse angle, the shape of the circumferential fine groove becomes good, and the wet performance and snow performance can be improved. On the other hand, since the block shape partitioned by the circumferential fine grooves having the above-described shape also becomes good, it is advantageous for maintaining dry performance. By these collaborations, dry performance, wet performance, and snow performance can be highly compatible with each other.

[0007] In the present invention, it is preferable that the ratio Gs / Gd of the groove depth Gs of the circumferential fine groove to the groove depth Gd of the inclined groove satisfies the relationship of 0.3 ≦ Gs / Gd ≦ 0.7, and the bending angle θ satisfies the relationship of 90° < θ ≦ 175°. Thereby, since the shape of the circumferential fine groove becomes good, it is advantageous for achieving compatibility between dry performance, wet performance, and snow performance.

[0008] In the present invention, among the plurality of circumferential fine grooves included in one land portion, the bending angle at the bending point of the N-th circumferential fine groove from the tire equator is θ N When it is set as, the bending angle is θ N ≧θ N+1 It is preferable to satisfy the relationship of. Thereby, since the bending angle becomes good in each land portion, it is advantageous for achieving compatibility between dry performance and snow performance.

[0009] In the present invention, it is preferable that the bending angles of the circumferential narrow grooves adjacent to each other in the tire circumferential direction across the inclined groove are different from each other, and the circumferential narrow groove having a relatively small bending angle compared to the adjacent circumferential narrow groove and the circumferential narrow groove having a relatively large bending angle compared to the adjacent circumferential narrow groove are alternately arranged in the tire circumferential direction. Thereby, the balance between a plurality of circumferential narrow grooves arranged in the tire circumferential direction becomes good, which is advantageous for achieving both dry performance and snow performance.

[0010] In the present invention, it is preferable to adopt a specification in which a bottom-raising portion is provided in the zigzag groove portion. Thereby, the block rigidity of the land portion adjacent to the zigzag groove portion can be increased, which is advantageous for improving dry performance.

[0011] In the specification in which the bottom-raising portion is provided as described above, it is preferable that the ratio Gc / Gd of the groove depth Gc at the bottom-raising portion to the groove depth Gd of the inclined groove satisfies the relationship of 0.3 ≤ Gc / Gd ≤ 0.7. Thereby, even if a bottom-raising portion is provided, a sufficient groove volume can be ensured to secure drainage performance, so that while exhibiting good wet performance, an improvement in dry performance by the bottom-raising portion can be expected.

[0012] In the present invention, when the area of the block located on the outermost side in the tire width direction among at least three blocks included in one land portion is Ao and the area of the Nth block from the tire equator side is A N it is preferable that the area A N satisfies the relationship of A N ≥ Ao, and the ratio A1 / A2 of the area A1 and the area A2 satisfies the relationship of 0.9 ≤ A1 / A2 ≤ 1.1. Thereby, the balance of at least three blocks included in one land portion becomes good, 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 edge" refers to both ends in the axial direction of the tire 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, including the standard on which the tire is based. For example, it is the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. "Standard internal pressure" refers to the air pressure specified for each tire in the standard system, including the standard on which the tire is based. For JATMA, it is the maximum air pressure. For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". For ETRTO, it is the "INFLATION PRESSURE". However, if the tire is for a passenger car, it is set to 180 kPa. "Regular load" refers to the load specified for each tire in the standards system, including the standard 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 CAPACITY." 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. [Brief explanation of the drawing]

[0016] [Figure 1] This is a meridian cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] This is a front view showing the tread surface of a tire according to an embodiment of the present invention. [Figure 3] This is an explanatory diagram showing an enlarged view of the main part of Figure 2. [Figure 4] This is an explanatory diagram showing an enlarged view of the main part of Figure 2. [Figure 5] This is an explanatory diagram showing an enlarged view of the main part of the tread surface of a tire according to another embodiment of the present invention. [Modes for carrying out the 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 toroidal basic 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 (2 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 (2 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] Since the present 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 from the tire equator CL side toward 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 can be set 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 tire circumferential direction in the central region of the tread portion 1. In other words, the inner end in the tire width direction of the inclined groove 10 on one side of the tire equator CL is connected to the middle part of the inclined groove 10 on the other side of the tire equator CL, and the inner end in the tire width direction of the inclined groove 10 on the other side of the tire equator CL is connected to the middle part of the inclined groove 10 on one side of the tire equator CL. In this way, the inclined groove 10 on one side of the tire equator CL and the inclined groove 10 on the other side are connected alternately, forming a zigzag groove portion 11 that extends in a zigzag pattern in the tire circumferential direction in the region between the inner end in the tire width direction of the inclined groove 10 on one side of the tire equator CL and the inner end 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 groove 10 (an element composed of multiple parts of the inclined groove 10 combined), but in the following explanation, these may be distinguished for convenience.

[0023] Focusing on the land area partitioned by a pair of adjacent inclined grooves 10 and zigzag groove sections 11 in the circumferential direction of the tire on one side of the tire equator CL, each land area is provided with multiple circumferential narrow grooves 20. These circumferential narrow grooves 20 partition each land area into at least three blocks 30 (three blocks in the illustrated example). Furthermore, focusing on the V-shaped land area partitioned by a series of grooves (V-shaped grooves) formed by the inclined grooves 10 on one side and the inclined grooves 10 on the other side of the tire equator CL, each V-shaped land area can be considered to be partitioned into at least six blocks 30 (six blocks in the illustrated example) by multiple circumferential narrow grooves 20 and a portion of the inclined grooves 10 (zigzag groove sections 11).

[0024] The circumferential grooves 20 are grooves provided on each land portion as described above, extending in the circumferential direction of the tire and having a groove width of less than half that of the inclined grooves 10. Each circumferential groove 20 has a "V" shape with a single bending point as shown in the figure. As shown in Figure 3, when the angle of the circumferential groove 20 measured on the inside of the bending point in the tire width direction is defined as the bending angle θ, this bending angle θ is always obtuse. The bending angle θ is measured based on the widthwise centerline of the circumferential groove 20 as shown in Figure 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 groove 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 on the land portion, 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. Therefore, 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] The circumferential narrow grooves 20 should, as mentioned above, have a groove width of less than half that of the inclined grooves 10, and preferably have a groove depth smaller than that of the inclined grooves 10. In particular, when the groove depth of the circumferential narrow grooves 20 is Gs and the groove depth (maximum 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 narrow 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 better the block rigidity tends to be, while the lower the ratio Gs / Gd, the better the block rigidity tends to be, but the lower the drainage performance tends to be. By considering these balances and setting the ratio Gs / Gd within the above appropriate range, it is possible to achieve a good balance between dry and wet performance.

[0028] 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.

[0029] When focusing on one land portion as shown in FIG. 3, the bending angle at the bending point of the Nth circumferential groove 20 from the tire equator side among the plurality of circumferential grooves 20 included in this land portion is θ N Let it be. At this time, the bending angle is θ N ≧θ N+1 It is preferable to satisfy the relationship of. For example, in the illustrated example, it includes two circumferential grooves 20, 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 θ1≧θ2. In this way, since the bending angle of the circumferential groove 20 on the tire equator CL side is large. It is possible to surely secure the block rigidity for the block on the tire equator CL side, which is advantageous for maintaining good dry performance. Also, due to the above-mentioned magnitude relationship of the bending angles, the balance of the bending shapes of the plurality of circumferential grooves 20 included in one land portion becomes good, and it is possible to balance the effect of ensuring the above-mentioned dry performance and the effect of ensuring the edge amount. When the bending angle does not satisfy the above relationship (θ N <θ N+1 ), the effect of securing the block rigidity on the tire equator CL side becomes limited.

[0030] Similarly, when focusing on one land portion, the tread area of the block 30 located on the outermost side in the tire width direction (ground contact end E side) among at least three blocks 30 included in this land portion is Ao, and the tread area of the Nth block 30 from the tire equator CL side is A N Let it be. Incidentally, the area Ao is the area of the portion within the ground contact area of the tread of the block 30 located on the outermost side in the tire width direction (inside the tire width direction from the ground contact end E). At this time, 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, 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 will be A N Preferably 0.9 ≤ A N / A N+1 It is good if 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 these grooves have different bending angles, and that circumferential grooves 20 with relatively smaller bending angles compared to adjacent circumferential grooves 20 and circumferential grooves 20 with relatively larger bending angles 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 are 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 ,θD 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) and circumferential grooves 20 suitable for ensuring edge size (with a relatively small bending angle), thus 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 that a raised portion 12 is provided 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), a raised portion 12 (shaded portion in the figure) that raises a part of the bottom of the zigzag groove portion 11 can also be provided. In the embodiment of Figure 5(b), a plurality of raised portions 12 are intermittently provided along the circumferential 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 a 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 a 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 presence of sipes, thus 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 section 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, even if it is an offset of the aforementioned curved sipe 41 or straight sipe 42. In other words, the sipe shape that appears on the tread surface (on the tread surface of the tread portion 1) may be a shape that is 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. [Examples]

[0039] The tire size is 205 / 55R16 94V, has the internal structure (cross-sectional structure) illustrated in Figure 1, has a tread pattern based on Figure 2, and on one side of the tire equator, there is a 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, and the number of blocks divided by circumferential grooves in one 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, the ratio of the groove depth Gc in the raised section to the groove depth Gd of the inclined groove Gc / Gd, and 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 fabricated for the Conventional Example, Comparative Examples 1-2, and Examples 1-14, with the following settings: the relative size of the areas, the ratio A1 / A2 of the area of ​​the first block A1 from the tire equator side, 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 where 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 "Magnitude of Bending Angle (Circumferential Direction)" column, if the bending angles of adjacent circumferential grooves in the tire circumferential direction, separated by an inclined groove, are different, and 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, this is indicated as "alternating." If the bending angles of adjacent circumferential grooves in the tire circumferential direction, separated by an inclined groove, are the same, this is indicated as "constant." If the bending angles of the circumferential grooves arranged in the tire circumferential direction are not "constant," and two circumferential grooves with relatively small bending angles and two circumferential grooves with relatively large bending angles are arranged alternately, this is indicated as "non-alternating." In the "Presence or Absence of Bending Sipes" column, "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] Dry performance Each test tire was mounted on a 16 x 6.5J rim wheel, inflated to 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 dry road surfaces. 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] Wet performance Each test tire was mounted on a 16 x 6.5J rim wheel, inflated to 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] Snow performance Each test tire was mounted on a 16 x 6.5J rim wheel, inflated to 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 higher index value indicates a shorter braking distance and superior snow performance (braking performance on snowy roads).

[0047] [Table 1]

[0048] [Table 2]

[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 suffered from reduced wet and snow performance due to the acute angle of the circumferential grooves. Comparative Example 2 had multiple bending points in the circumferential grooves, resulting in areas with low block rigidity and failing to improve dry performance. Furthermore, the zigzag bending of the circumferential grooves due to the multiple bending points made it difficult for water to flow within the grooves, resulting in reduced wet performance.

[0050] This disclosure encompasses the following inventions: Invention [1] A tire having a tread portion that extends in the circumferential direction of the tire and forms an annular shape, and having a portion that indicates the direction of rotation of the tire, Multiple inclined grooves are formed on both sides of the tire equator of the tread portion, extending inclined from the tire equator side toward the contact edge side, and each of the inclined grooves 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 rotational direction. The inclined grooves on both sides of the tire equator are connected to each other to form a zigzag groove that extends in a zigzag pattern in the circumferential direction of the tire in the central region of the tread. Multiple circumferential narrow grooves are provided in the land area, which is partitioned by a pair of adjacent inclined grooves in the circumferential direction of the tire and the zigzag groove section on one side of the tire equator, and the land area is partitioned into at least three blocks. A tire characterized in that each of the circumferential grooves has a single bending point, and the bending angle θ of the circumferential groove, measured on the inner side of the bending point in the tire width direction, is obtuse. Invention [2] The tire according to Invention [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°. Invention [3] The angle of inflection at the inflection point of the Nth circumferential groove from the tire equator among the plurality of circumferential grooves included in one land portion is θ N When the bending angle is θ N ≥θ N+1 The tire according to the invention [1] or [2], characterized in that it satisfies the following relationship. Invention [4] A tire according to any one of Inventions [1] to [3], characterized in that the angles of bending of adjacent circumferential grooves in the circumferential direction of the tire, with respect to the inclined groove, are different from those of adjacent circumferential grooves, and circumferential grooves having a relatively small angle of bending compared to adjacent circumferential grooves and circumferential grooves having a relatively large angle of bending compared to adjacent circumferential grooves are alternately arranged in the circumferential direction of the tire. Invention [5] The tire according to Invention [1] to [4], characterized in that a raised portion is provided in the zigzag groove portion. Invention [6] The tire according to Invention [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. Invention [7] The area of ​​the outermost block in the tire width direction among the at least three blocks included in one land portion 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 is AN A tire according to any one of the inventions [1] to [6], characterized in that it satisfies the relationship ≥ Ao, and the ratio of areas A1 to A2, A1 / A2, satisfies the relationship 0.9 ≤ A1 / A2 ≤ 1.1. Invention [8] A tire according to any one of Inventions [1] to [7], characterized in that a bent sipe is formed in any of the blocks, the sipe comprising 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. [Explanation of symbols]

[0051] 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 Slant groove 11 Zigzag groove section 12. Raised base 20 Circumferential thin groove 30 blocks 40 sipes 41. Bent sipes 42 Straight Sipes CL Tire Equator E Ground end

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 portion that indicates the direction of rotation of the tire, Multiple inclined grooves are formed on both sides of the tire equator of the tread portion, extending inclined from the tire equator side toward the contact edge side, and each of the inclined grooves 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 rotational direction. The inclined grooves on both sides of the tire equator are connected to each other to form a zigzag groove that extends in a zigzag pattern in the circumferential direction of the tire in the central region of the tread. Multiple circumferential narrow grooves are provided in the land area, which is partitioned by a pair of adjacent inclined grooves in the circumferential direction of the tire and the zigzag groove section on one side of the tire equator, and the land area is partitioned into at least three blocks. A tire characterized in that each of the circumferential grooves has a single bending point, and the bending angle θ of the circumferential groove, measured on the inner side of the bending point in the tire width direction, is obtuse.

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 claim 1 or 2, characterized in that the angles of bending 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 angle of bending compared to adjacent circumferential grooves and circumferential grooves having a relatively large angle of bending compared to adjacent circumferential grooves are alternately arranged in the tire circumferential direction.

5. The tire according to claim 1 or 2, characterized in that a raised 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 at least three of the blocks included in one of the land portions, the area of the block located on the outermost side in the tire width direction is Ao, and the area of the Nth block from the tire equator side is A N When it is set as, area A N is A N satisfies the relationship of A 1 ≧ Ao, and the ratio A 2 of area A 1 / A 2 is 0.9 ≦ A 1 / A 2 ≦ 1.1, and the tire according to claim 1 or 2, characterized in that it satisfies this relationship.

8. The tire according to claim 1 or 2, 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.

Images