Tire

Abstract

To provide a tire capable of improving on-ice performance.SOLUTION: A tire 1 includes a tread part 2 in which a plurality of blocks 3 are arranged in a tire circumferential direction. Each block 3 is separated from other blocks 3 by a plurality of grooves 5 that are wider than 1.5 mm. Each block 3 is divided into a plurality of block pieces Bi by a plurality of sipes 6. The plurality of sipes 6 include a circumferential sipe 8 and axial sipes 9. In each of the blocks 3, a difference (Sm-Sn) between a maximum value Sm and a minimum value Sn of a rigidity parameter S of each block piece Bi is 20% or less of the maximum value Sm.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The following Patent Document 1 describes a tire including a plurality of crown blocks in the tread portion. The tread surface of the crown block includes a first sipe, a second sipe, and a third sipe, and includes a first surface, a second surface, and a third surface divided by the first sipe, the second sipe, and the third sipe. In this tire, the areas of the first surface, the second surface, and the third surface are specified to suppress excessive deformation of the blocks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-62655 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for further improvement in tire performance on ice.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire capable of improving performance on ice. [Means for solving the problem]

[0006] The present invention relates to a tire including a tread portion, the tread portion including a block row in which a plurality of blocks are arranged in a tire circumferential direction, each of the plurality of blocks being separated from the other blocks by a plurality of grooves having a width greater than 1.5 mm, and each of the plurality of blocks being separated into a plurality of block pieces by a plurality of sipes, The plurality of sipes include circumferential sipes and axial sipes, Both ends of the circumferential sipe are connected to any of the plurality of grooves or are interrupted by a distance of 2.0 mm or less to any of the plurality of grooves, Both ends of the axial sipe are connected to any of the plurality of grooves or are disconnected from any of the plurality of grooves at a distance of 2.0 mm or less, and in each of the plurality of blocks, the difference (Sm-Sn) between the maximum value Sm and the minimum value Sn of the stiffness parameter S of each block piece calculated by the following formula (1) is 20% or less of the maximum value Sm. Stiffness parameter S=Ai / Di 3 …(1) Here, Ai is the tread area of ​​each block piece Bi, and Di is the average depth determined from the grooves and sipes surrounding each block piece. Effect of the Invention

[0007] By employing the above-mentioned configuration, the tire of the present invention can improve performance on ice. [Brief description of the drawings]

[0008] [Figure 1] 1 is a plan view of a tread portion showing one embodiment of a tire of the present invention. [Diagram 2] FIG. 2 is an enlarged view of a block in FIG. [Diagram 3] FIG. 2 is a plan view of the tread portion of FIG. [Figure 4] FIG. 4 is an enlarged view of the tread portion of FIG. [Diagram 5] 5A is a cross-sectional view taken along line AA in FIG. 4, and FIG. 5B is a cross-sectional view taken along line BB in FIG. [Figure 6] FIG. 4 is an enlarged view of the tread portion of FIG. [Figure 7] FIG. 13 is a plan view of a block according to another embodiment. [Figure 8] FIG. 13(A) is a plan view of a block according to still another embodiment, and FIG. 13(B) is a plan view of a block according to still another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings include exaggerated expressions and expressions different from the dimensional ratio of the actual structure in order to facilitate understanding of the present invention. In addition, when there are multiple embodiments, the same or common elements are given the same reference numerals throughout the specification, and duplicated explanations are omitted.

[0010] Fig. 1 is a plan view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The present invention is used in a pneumatic tire for a passenger vehicle that can also be driven on snowy and icy roads. However, the present invention may also be used in, for example, a pneumatic tire for heavy loads and a non-pneumatic tire that is not filled with compressed air.

[0011] In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in a normal state. In the case of a pneumatic tire for which various standards are established, the "normal state" refers to a state in which the tire 1 is mounted on a normal rim (not shown), inflated to a normal internal pressure, and unloaded. In the case of a tire for which various standards are not established, the normal state refers to a standard usage state according to the intended use of the tire, which is a state in which the tire is not mounted on a vehicle and is unloaded.

[0012] The "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based, for example, "standard rim" in the case of JATMA, "Design Rim" in the case of TRA, and "Measuring Rim" in the case of ETRTO.

[0013] The "normal internal pressure" is the air pressure determined for each tire by each standard in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0014] As shown in FIG. 1, a tread portion 2 includes a block row 4 in which a plurality of blocks 3 are arranged in the tire circumferential direction.

[0015] Each of the blocks 3 is divided from the other blocks 3 by a plurality of grooves 5 having a width greater than 1.5 mm. Each of the blocks 3 is divided into a plurality of block pieces Bi by a plurality of sipes 6. The plurality of sipes 6 includes circumferential sipes 8 and axial sipes 9. This allows the blocks 3 to exhibit a large edge effect in multiple directions and to smoothly drain water melted by driving on icy roads. In this specification, the sipes 6 are notched recesses having a width of 1.5 mm or less, and are clearly distinguished from the grooves 5.

[0016] In this specification, the circumferential sipe 8 refers to a sipe 6 in which the angle θa of a virtual line v1 connecting both ends 8e, 8e with respect to the tire circumferential direction is 45 degrees or less. Also, the axial sipe 9 refers to a sipe 6 in which the angle θa of a virtual line v1 connecting both ends 9e, 9e with respect to the tire circumferential direction is more than 45 degrees.

[0017] Both ends 8e, 8e of the circumferential sipe 8 communicate with any one of the plurality of grooves 5. Also, both ends 9e, 9e of the axial sipe 9 communicate with any one of the plurality of grooves 5. Such circumferential sipes 8 and axial sipes 9 exert a greater edge effect and enhance the discharge function of the melted water.

[0018] In each of the blocks 3, the difference (Sm-Sn) between the maximum value Sm and the minimum value Sn of the stiffness parameter S of each block piece Bi calculated by the following formula (1) is 20% or less of the maximum value Sm. It is preferable that the difference (Sm-Sn) is 15% or less of the maximum value Sm. Stiffness parameter S=Ai / Di 3 …(1) Here, Ai is the area of ​​the tread surface Ba (shown in FIG. 2) of each block piece Bi, and Di is the average depth (not shown) determined from the grooves 5 and sipes 6 surrounding each block piece Bi. In this embodiment, the stiffness parameter S is rounded off to the first decimal place. The stiffness parameter S may be rounded off to the second decimal place. This reduces the difference in stiffness between the block pieces Bi in each of the multiple blocks 3, and the amount of collapse (deformation) of each block piece Bi when traveling on ice is similar to each other. This allows each block piece Bi to make uniform contact with the road surface, enhancing the edge effect of each block piece Bi and improving performance on ice.

[0019] The average depth Di of the block pieces Bi is calculated by the following formula (2). Di=(La×Da+Lb×Db) / (La+Lb)…(2) Where: La: The longitudinal length of the groove 5 surrounding the block piece Bi Da: Groove depth of groove 5 Lb: The longitudinal length of the sipe 6 surrounding the block piece Bi Db: Sipe 6 depth In addition, when the groove 5 surrounding the block piece Bi or the sipe 6 surrounding the block piece Bi has a plurality of different depths, the respective groove depths or lengths corresponding to the respective depths are used as the length in the longitudinal direction. Also, La+Lb is the length of the outer periphery (full circumference) of each block piece Bi.

[0020] FIG. 2 is a plan view of an example of the block 3 of this embodiment, and a method for calculating the average depth Di of each block piece Bi will be described using FIG. 2. For convenience, the cutout portion 30 (shown in FIG. 1) is removed from the block 3 in FIG. 2. As shown in FIG. 2, this block 3 includes six block pieces B1 to B6. Each of these block pieces Bi is surrounded by a groove 5 and a sipe 6. In this specification, the average depths D1, D4, and D5 of the block pieces B1, B4, and B5 will be specifically described as representatives. The average depths D2, D3, and D6 of the block pieces B2, B3, and B6 and the average depth Di of the block pieces Bi of other blocks 3 are calculated in the same manner.

[0021] Table 1 shows the length Lai of the groove 5 surrounding the block pieces B1, B4, B5, the groove depth of the groove 5, the length Lbi of the sipe 6 surrounding the block pieces B1, B4, B5, and the depth of the sipe 6.

[0022] [Table 1]

[0023] From Table 1, the average depths D1, D4, and D5 can be determined as follows. D1:(40×13+15×13+12×12+37×12) / (40+15+12+37)=12.5mm D4:(18×13+15×14+28×7+15×5) / (18+15+28+15)=9.4mm D5:(33×13+13×1+22×5.5) / (33+13+22)=8.2mm

[0024] In this manner, the average depths D1 to D6 are calculated. Table 2 shows the calculated values ​​of the tread area Ai, average depth Di, and stiffness parameter S of the block pieces B1 to B6. From Table 2, it can be seen that for block 3 in Fig. 2, Sm = Sn = 0.3 (1 / mm), and the difference in stiffness parameter S (Sm - Sn) is 20% or less of the maximum value Sm.

[0025] [Table 2]

[0026] Fig. 3 is a plan view of the tread portion 2. As shown in Fig. 3, in this embodiment, the block row 4 includes a pair of crown block rows 4A, 4A positioned on either side of the tire equator C, and a pair of shoulder block rows 4B, 4B arranged between each crown block row 4A and a tread edge Te. Each crown block row 4A is formed of crown blocks 3A arranged in the tire circumferential direction. Each shoulder block row 4B is formed of shoulder blocks 3B arranged in the tire circumferential direction.

[0027] The tread end Te is the axially outermost contact position when the tire 1 in the normal state is loaded with a normal load and contacts the ground on a flat surface with a camber angle of 0°. The axial length between both tread ends Te, Te is defined as the tread width TW.

[0028] In the case of a pneumatic tire for which various standards are established, the "normal load" is the load that is established for each tire by each standard in the standard system including the standard on which the tire is based, and is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In addition, in the case of a tire for which various standards are not established, the "normal load" refers to the maximum load that can be applied when using the tire according to the above-mentioned standards.

[0029] Each crown block row 4A is formed with first crown blocks 11 and second crown blocks 12, each having a smaller maximum width W2 in the tire axial direction than the first crown blocks 11, arranged alternately in the tire circumferential direction. Each of the first crown blocks 11 and the second crown blocks 12 is provided with circumferential sipes 8 and axial sipes 9. Each of the first crown blocks 11 and the second crown blocks 12 is divided into a plurality of block pieces Bi.

[0030] Each shoulder block row 4B is formed with first shoulder blocks 13 including the tread edge Te and second shoulder blocks 14 located axially inward of the tread edge Te, which are alternately arranged in the circumferential direction of the tire. Each of the first shoulder blocks 13 and the second shoulder blocks 14 is provided with circumferential sipes 8 and axial sipes 9. Each of the first shoulder blocks 13 and the second shoulder blocks 14 is divided into a plurality of block pieces Bi.

[0031] In this embodiment, the difference (Sm-Sn) in the stiffness parameter S is set to 20% or less of the maximum value Sm in the block pieces Bi of the first crown block 11. Also, for example, it is preferable that the difference (Sm-Sn) in the stiffness parameter S is set to 20% or less of the maximum value Sm in the block pieces Bi of the second crown block 12. Furthermore, it is even more preferable that the difference (Sm-Sn) in the stiffness parameter S is set to 20% or less of the maximum value Sm in the block pieces Bi of each shoulder block 3B.

[0032] Each of the blocks 3 is divided into 6 to 8 block pieces Bi. Such blocks 3 can enhance the edge effect of the sipes 6 and ensure uniform ground contact of the block pieces Bi while suppressing a decrease in the rigidity of the block pieces Bi. In this embodiment, the first crown block 11 and the second crown block 12 are divided into 6 to 8 block pieces Bi. The first shoulder block 13 and the second shoulder block 14 are divided into a smaller number of block pieces Bi than the crown blocks 11 and 12, for example. It is preferable that the first shoulder block 13 and the second shoulder block 14 are divided into 4 to 6 block pieces Bi. Such shoulder blocks 3B maintain a higher rigidity of the block pieces Bi of each shoulder block 3B, which is subjected to a relatively large lateral force during cornering, and allow the block pieces Bi to contact the ground more uniformly.

[0033] One end 9e of the axial sipe 9 of each shoulder block 3B on the tread end Te side is, for example, discontinued without communicating with the groove 5. In this embodiment, the one end 9e of the axial sipe 9 of each shoulder block 3B is located between the circumferential sipe 8 and the tread end Te. As a result, each shoulder block 13, 14 is divided into a block piece Bs that is closest to the tread end Te and a plurality of block pieces Bb that are adjacent to the block piece Bs on the inner side in the tire axial direction. The tread area of ​​the block piece Bs is formed larger than the tread area of ​​each block piece Bb. In this embodiment, the block piece Bs of the shoulder block 3B is located on the tread end Te side from the circumferential sipe 8.

[0034] FIG. 4 is an enlarged view of the tread portion 2 of FIG. 1. As shown in FIG. 4, the tread surface 3a of each of the blocks 3 is surrounded by 6 to 13 edges (first edges) E1. In each of the blocks 3, at least one tread surface Ba of the block pieces Bi is surrounded by six or more edges (second edges) E2. Such blocks 3 and block pieces Bi exhibit edge effects in multiple directions and improve on-ice performance by suppressing a decrease in rigidity of each block 3. Each tread surface Ba of the block pieces Bi is surrounded by eight or less second edges E2. The first edge E1 is formed by an outer edge e1 (shown in FIG. 5) that is continuous with the outer ends of the grooves 5 in the tire radial direction. The second edge E2 is formed by the outer edge e1 of the grooves 5 and the outer edge e2 that is continuous with the outer ends of the sipes 6 in the tire radial direction. In this specification, the number of the first edges E1 and second edges E2 is defined as one when they extend linearly. The term "linear" includes not only a straight line but also an arc with a curvature radius of 100 mm or more in a plan view of the tread. In addition, the term "tread surface" in this specification refers to a surface that is in contact with the plane under the normal load condition.

[0035] In this embodiment, each of the tread surfaces 11a-14a of the crown blocks 11, 12 and shoulder blocks 13, 14 is surrounded by six to thirteen first edges E1. Also, in each of the crown blocks 11, 12 and shoulder blocks 13, 14, at least one tread surface Ba of the multiple block pieces Bi is surrounded by six to ten second edges E2.

[0036] It is desirable that the maximum value Am of each area Ai of each block piece Bi of the block 3 is 5 times or less than the minimum value An of each area Ai. Since the maximum value Am is 5 times or less than the minimum value An, the difference in rigidity of each block piece Bi can be reduced, and uniform ground contact with the road surface can be achieved, thereby improving the performance on ice. If the maximum value Am is greater than 1 time the minimum value An, uniform ground contact with the road surface can be achieved in each block piece Bi. In this embodiment, in the second crown block 12, the maximum value Am of each area Ai is 4 to 5 times the minimum value An of each area Ai.

[0037] Fig. 5(A) is a cross-sectional view taken along line AA in Fig. 4. As shown in Figs. 4 and 5(A), the shoulder block 3B includes a block wall 16 that contacts one of the grooves 5 that divide the shoulder block 3B. At least one block wall 16a of the shoulder blocks 3B extends in a stepped manner in the tire radial direction. Such a block wall 16a can increase the snow column shear force. In this embodiment, the stepped block wall 16a extends in the tire circumferential direction and is located adjacent to the first crown block 11. However, the block wall 16a is not limited to this position.

[0038] In this embodiment, the groove depth Da of the groove 5 is preferably 10 mm or more, and preferably 15 mm or less. Since the groove depth Da is 10 mm or more, large snow pillars can be formed, and the drainage effect of melted water during driving on icy roads can be improved. Since the groove depth Da is 15 mm or less, excessive deformation of the block 3 during driving is suppressed, and an appropriate edge effect is exhibited.

[0039] FIG. 5(B) is a cross-sectional view of line BB in FIG. 4. As shown in FIG. 5(B), the depth Db of each of the sipes 6 is preferably 30% or more of the groove depth Da of each of the grooves 5 that divide the block 3 in which the sipes 6 are provided. In other words, the minimum value of the depth Db of the sipes 6 arranged in one block 3 is preferably 30% or more of the maximum value of the groove depth Da of the grooves 5 that divide the block 3. Such sipes 6 can enhance the drainage effect of the melted water. The depth Db of each of the sipes 6 is preferably 100% or less of each groove depth Da. In FIG. 5(B), the depth Db1 of the axial sipe 9 of the first crown block 11 is shown as an example.

[0040] FIG. 6 is an enlarged view of the tread portion 2 of FIG. 1. As shown in FIG. 6, one circumferential sipe 8 is provided in each block 3. One circumferential sipe 8 is provided in each of the first crown block 11, the second crown block 12, the first shoulder block 13, and the second shoulder block 14. A plurality of axial sipes 9 are provided in each block 3. Two to three axial sipes 9 are provided in each of the first crown block 11 and the second crown block 12, and two axial sipes are provided in this embodiment. In this embodiment, the number of axial sipes 9 provided in the first shoulder block 13 and the second shoulder block 14 is greater than that of the first crown block 11. For example, three to four axial sipes 9 are provided in each of the first shoulder block 13 and the second shoulder block 14, and three axial sipes are provided in each of the first shoulder block 13 and the second shoulder block 14.

[0041] The circumferential sipes 8 include, for example, a portion inclined with respect to the tire circumferential direction. Such circumferential sipes 8 can also exert an edge effect in the tire circumferential direction. Each of the circumferential sipes 8 of the crown blocks 11 and 12 of this embodiment is formed of a first circumferential portion 8A inclined at the same angle with respect to the tire circumferential direction. Each of the first circumferential portions 8A extends linearly. The circumferential sipes 8 of the shoulder blocks 13 and 14 of this embodiment are formed of a second circumferential portion 8B extending parallel to the tire circumferential direction. Such a second circumferential portion 8B exerts a large edge effect in the tire axial direction, improving cornering performance when traveling on ice.

[0042] The circumferential sipes 8 intersect with the axial sipes 9, for example. The circumferential sipes 8 desirably intersect with the longitudinal center portion 9c of the axial sipes 9. This reduces the difference in area of ​​the tread surfaces Ba of the block pieces Bi located on either side of the circumferential sipe 8, and thus each of the block pieces Bi can be uniformly grounded on the road surface, thereby improving the performance on ice. The "center portion" includes, for example, a position spaced apart from one end 9e of the axial sipe 9 by 40% to 60% of the longitudinal length Ld of the axial sipe 9. In this embodiment, the circumferential sipes 8 of each of the first crown block 11 and the second crown block 12 intersect with the central portion 9c of at least one of the two axial sipes 9. The circumferential sipes 8 of the first shoulder block 13 intersect with the central portions 9c of all the axial sipes 9.

[0043] The axial sipes 9 include, for example, a portion inclined with respect to the tire axial direction. The axial sipes 9 of the first crown block 11 of this embodiment include a first axial portion 9A inclined at the same angle with respect to the tire axial direction, and a second axial portion 9B inclined at an angle larger than that of the first axial portion 9A and at the same angle. The first axial portion 9A and the second axial portion 9B each extend linearly. The axial sipes 9 of the second crown block 12 are formed, for example, only by the first axial portion 9A. The axial sipes 9 of each shoulder block 13, 14 of this embodiment are each formed by the first axial portion 9A and a third axial portion 9D that is located outside the first axial portion 9A in the tire axial direction and extends parallel to the tire axial direction.

[0044] In the first shoulder block 13, the third axial portion 9D intersects with the circumferential sipe 8. The circumferential sipe 8 of the first shoulder block 13 intersects with the third axial portion 9D axially inward of the longitudinal center of the third axial portion 9D. In the second shoulder block 14, the circumferential sipe 8 intersects with the connection position K between the first axial portion 9A and the third axial portion 9D.

[0045] The axial sipes 9 are preferably arranged at equal intervals in the longitudinal direction of the circumferential sipes 8. Such axial sipes 9 reduce the difference in rigidity of each block piece Bi in the circumferential direction of the tire, and allow each block piece Bi to contact the road surface more uniformly. In this specification, the term "arranged at equal intervals in the longitudinal direction" refers to arranging both ends 8e, 8e of the circumferential sipes 8 at equal intervals. In other words, the distance Lx between one end 8e of the circumferential sipe 8 and the axial sipe 9 adjacent to this end 8e, and the distance Ly between the adjacent axial sipes 9 are each exactly the same. In this specification, the term "same" refers to a state in which the distances Lx and Ly are the same, and the difference between the maximum and minimum values ​​thereof is 3 mm or less. In this embodiment, the axial sipes 9 are arranged at equal intervals in the longitudinal direction of the circumferential sipes 8 in each crown block 11, 12.

[0046] In this embodiment, the distances Ly between the adjacent axial sipes 9 are the same in each shoulder block 13, 14. Even in such an embodiment, the above-mentioned effect is exerted. In this specification, "the distances Ly between the adjacent axial sipes 9 are the same" includes an embodiment in which the difference between the distances Ly and Ly is 3 mm or less.

[0047] It is desirable that the axial sipe 9 is parallel to any one of the multiple first edges E1 of the block 3 on which the axial sipe 9 is provided. This makes it possible to reduce the difference in rigidity between the block pieces Bi, suppress excessive collapse of the block pieces Bi, and maintain high performance on ice. In this specification, the term "parallel" means that the absolute value |α1-α2| of the difference between the angle α1 of the axial sipe 9 and the angle α2 of any one of the first edges E1 with respect to the tire axial direction is not only 0 degrees, but also 3 degrees or less.

[0048] In this embodiment, the land ratio of the tread portion 2 is desirably 60% to 65%. Since the land ratio is 60% or more, the area of ​​the grooves 5 is secured, and snow column shear force can be exerted. Since the land ratio is 65% or less, the rigidity of each block 3 is secured, and the edge effect can be exerted. In this specification, the land ratio is the area of ​​the tread surface of the tread portion 2 relative to the area of ​​the virtual tread surface obtained by filling the grooves and sipes.

[0049] The area of ​​the tread surface 3a of the block 3 (shown in FIG. 4) is 1300 mm 2 More than 1600mm is preferable. 2 More than 2300mm is more preferable. 2 Less than 2000mm is preferable. 2 The following is even more desirable:

[0050] Fig. 7 is an enlarged view of the block 3 shown in Fig. 1. As shown in Fig. 7, both ends 8e, 8e of the circumferential sipe 8 may be terminated at a distance Le of 2.0 mm or less into any of the plurality of grooves 5. Also, both ends 9e, 9e of the axial sipe 9 may be terminated at a distance Le of 2.0 mm or less into any of the plurality of grooves 5. The block 3 shown in Fig. 7 is also divided into block pieces B1 to B6, which can effectively improve performance on ice.

[0051] Fig. 8(A) is a plan view of a block 3 according to another embodiment, and Fig. 8(B) is a plan view of a block 3 according to yet another embodiment. Fig. 8 shows a crown block 3A, more specifically, a first crown block 11. As shown in Fig. 8, it is desirable that the width Wb of each of the multiple sipes 6 decreases from the groove 5 side that divides the block 3 toward the center of the block 3.

[0052] 8(A), the sipe 6 may have a shape in which the width Wb continuously decreases (tapered) from one end 6e toward a central portion 6c of the sipe 6. The maximum width Wbm of the sipe 6 is desirably 1.5 to 2.5 times the minimum width Wbn.

[0053] Also, as shown in FIG. 8(B), the width Wb of the sipe 6 may be gradually reduced. In this embodiment, the sipe 6 includes a pair of first portions 6A, 6A including both ends 6e, 6e, and a second portion 6B connected to the pair of first portions 6A, 6A. The width Wbm of the first portion 6A is preferably 1.5 to 2.5 times the width Wbn of the second portion 6B. In this embodiment, the circumferential sipe 8 and the axial sipe 9 are formed by the first portion 6A and the second portion 6B. Also, the sipe 6 as shown in FIG. 8 may be provided in the second crown block 12, or may be provided in each of the shoulder blocks 3B (not shown).

[0054] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and carried out in various forms. EXAMPLES

[0055] Pneumatic tires having the basic pattern shown in Fig. 1 were prototyped. Each test tire was then tested for its performance on ice and on snow. The test method was as follows.

[0056] <Ice performance> The test tires were fitted to all wheels of a test vehicle, and the characteristics relating to driving stability and cornering were evaluated by the test driver on an icy test course. The results were scored based on a score of 100 for Comparative Example 1, with a higher score indicating better performance on ice. The results of the tests are shown in Table 3. Tire size: 185 / 85R16 Rim: 16×5.0J The Sm and Sn in Table 3 are for the first crown block. The second crown block and the shoulder block all have the same sipe depth. Groove depth: 10mm Test vehicle: 660cc four-wheel drive passenger vehicle

[0057] [Table 3]

[0058] As a result of the test, it is understood that the tire of the embodiment has better performance on ice than the tire of the comparative example. Furthermore, other tests confirmed that the performance on ice can be further improved by making the difference between the maximum and minimum stiffness parameters of each block piece 20% or less of the maximum value, as in the present invention, also in the second crown block and shoulder block.

[0059] [Note] The present invention includes the following aspects.

[0060] [Invention 1] A tire including a tread portion, The tread portion includes a block row in which a plurality of blocks are arranged in a tire circumferential direction, Each of the plurality of blocks is separated from the other blocks by a plurality of grooves having a width of more than 1.5 mm; Each of the plurality of blocks is divided into a plurality of block pieces by a plurality of sipes, The plurality of sipes include circumferential sipes and axial sipes, Both ends of the circumferential sipe are connected to any of the plurality of grooves or are interrupted by a distance of 2.0 mm or less to any of the plurality of grooves, Both ends of the axial sipe communicate with any one of the plurality of grooves or are interrupted by a distance of 2.0 mm or less to any one of the plurality of grooves, In each of the plurality of blocks, a difference (Sm-Sn) between a maximum value Sm and a minimum value Sn of the stiffness parameter S of each block piece calculated by the following formula (1) is 20% or less of the maximum value Sm. tire. Stiffness parameter S=Ai / Di 3 …(1) Here, Ai is the tread area of ​​each block piece Bi, and Di is the average depth of the grooves and sipes surrounding each block piece. (Please define briefly in the text.) [Invention 2] 2. The tire according to claim 1, wherein the circumferential sipes intersect with the axial sipes. [Invention 3] 3. The tire according to claim 2, wherein the circumferential sipe intersects with a longitudinal center portion of the axial sipe. [Invention 4] The tire according to any one of claims 1 to 3, wherein a width of each of the plurality of sipes decreases from a side of the groove dividing the block toward a center side of the block. [Invention 5] The tire according to any one of claims 1 to 4, wherein each of the plurality of blocks is divided into 6 to 8 block pieces. [Invention 6] The tire according to any one of claims 1 to 5, wherein a maximum value Am of each area Ai of each of the block pieces is 5 times or less a minimum value An of each area Ai. [Invention 7] The tire according to any one of claims 1 to 6, wherein the depth of each of the plurality of sipes is 30% or more of the groove depth of each of the plurality of grooves that divide the block in which the plurality of sipes are provided. [Invention 8] The tire according to any one of claims 1 to 7, wherein the land ratio of the tread portion is 60% to 65%. [The present invention 9] The tire according to any one of claims 1 to 8, wherein the axial sipes are arranged at equal intervals in the longitudinal direction of the circumferential sipes. [The present invention 10] the plurality of blocks includes a plurality of shoulder blocks, the shoulder blocks each include a block wall that is in contact with any one of the grooves that divide the shoulder block, The tire according to any one of claims 1 to 9, wherein at least one block wall of the plurality of shoulder blocks extends in a stepped manner in the tire radial direction. [The present invention 11] Each of the plurality of blocks has a tread surface surrounded by 6 to 13 edges, The tire according to any one of claims 1 to 10, wherein in each of the plurality of blocks, the tread surface of at least one of the plurality of block pieces is surrounded by six or more edges. [The present invention 12] The circumferential sipe includes a portion inclined with respect to the tire circumferential direction, 12. The tire according to any one of claims 1 to 11, wherein the axial sipe includes a portion inclined with respect to the tire axial direction. [Explanation of symbols]

[0061] 1 Tire 2 Tread section 3 Blocks 5 grooves 6 Sipe 8 Circumferential sipes 9 Axial sipes Bi block piece S stiffness parameter Sm Maximum Sn minimum value

Claims

1. A tire including a tread portion, The tread portion includes a block row in which a plurality of blocks are arranged in a tire circumferential direction, Each of the plurality of blocks is separated from the other blocks by a plurality of grooves having a width of more than 1.5 mm; Each of the plurality of blocks is divided into a plurality of block pieces by a plurality of sipes, The plurality of sipes include circumferential sipes and axial sipes, Both ends of the circumferential sipe are connected to any of the plurality of grooves or are interrupted by a distance of 2.0 mm or less to any of the plurality of grooves, Both ends of the axial sipe communicate with any one of the plurality of grooves or are interrupted by a distance of 2.0 mm or less to any one of the plurality of grooves, In each of the plurality of blocks, a difference (Sm-Sn) between a maximum value Sm and a minimum value Sn of the stiffness parameter S of each block piece calculated by the following formula (1) is 20% or less of the maximum value Sm. tire. Stiffness parameter S=Ai / Di ３ …(1) Here, Ai is the tread area of ​​each block piece Bi, and Di is the average depth determined from the grooves and sipes surrounding each block piece.

2. The tire of claim 1 , wherein said circumferential sipes intersect said axial sipes.

3. The tire of claim 2 , wherein the circumferential sipe intersects a longitudinal center portion of the axial sipe.

4. The tire according to claim 1 , wherein a width of each of the plurality of sipes decreases from a side of the groove dividing the block toward a center side of the block.

5. 4. The tire according to claim 1, wherein each of the plurality of blocks is divided into six to eight block pieces.

6. 4. The tire according to claim 1, wherein a maximum value Am of each area Ai of each block piece is not more than five times a minimum value An of each area Ai.

7. 4. The tire according to claim 1, wherein a depth of each of the plurality of sipes is 30% or more of a depth of each of the plurality of grooves that divide the block in which the plurality of sipes are provided.

8. 4. The tire according to claim 1, wherein the land ratio of the tread portion is 60% to 65%.

9. 4. The tire according to claim 1, wherein the axial sipes are arranged at equal intervals in a longitudinal direction of the circumferential sipes.

10. the plurality of blocks includes a plurality of shoulder blocks, the shoulder blocks each include a block wall that is in contact with any one of the grooves that divide the shoulder block, The tire according to claim 1 , wherein at least one block wall of the plurality of shoulder blocks extends in a stepped manner in the tire radial direction.

11. The tread surface of each of the plurality of blocks is surrounded by 6 to 13 edges; 4. The tire according to claim 1, wherein in each of the plurality of blocks, at least one tread surface of the plurality of block pieces is surrounded by six or more edges.

12. The circumferential sipe includes a portion inclined with respect to the tire circumferential direction, The tire according to claim 1 , wherein the axial sipe includes a portion inclined with respect to the tire axial direction.

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