pneumatic tires

Abstract

To provide a pneumatic tire improved in on-ice gripping performance.SOLUTION: A pneumatic tire has at least one land part 3 on a tread surface 1. One or more connection body sipes 4 are disposed on at least one of the land parts 3. The connection body sipe 4 has a main part 4a extending in a first predetermined direction, and side parts 4b1 and 4b2 extending from the main part 4a to a side part of the main part 4a incliningly with respect to the first predetermined direction. The side part has a first side part 4b1 disposed on a side part on one side of the main part, and a second side part 4b2 disposed on a side part on the other side of the main part. The first side part 4b1 and the second side part 4b2 are alternately arranged in a tire circumferential direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Conventionally, in the tread land portion of pneumatic tires, especially studless tires, fine grooves called sipes have been provided to improve ice grip performance. By these sipes, water gushing out due to the melting of the ice road surface on the tire contact surface can be discharged outside the contact surface, thereby improving the ice grip performance.

[0003] A technique has been proposed to improve ice grip performance by arranging sipes at a high density while suppressing a decrease in the rigidity of the land portion (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, the compatibility between the rigidity of the land portion and the discharge of water by the sipes is not sufficient, and there is room for improvement in improving the ice grip performance.

[0006] Therefore, an object of the present invention is to provide a pneumatic tire with improved ice grip performance.

Means for Solving the Problems

[0007] The gist configuration of the present invention is as follows. (1) A pneumatic tire having at least one land portion on a tread surface, One or more connected sipes are placed on at least one of the aforementioned land portions. The connecting sipe has a main portion extending in a first predetermined direction, and a side portion extending from the main portion to the side of the main portion at an inclination with respect to the first predetermined direction. The side portion comprises a first side portion located on one side of the main portion and a second side portion located on the other side of the main portion. A pneumatic tire characterized in that the first side portion and the second side portion are arranged alternately in the circumferential direction of the tire.

[0008] Here, "tread surface" refers to the entire circumferential surface of the tread that comes into contact with the road surface when a pneumatic tire is mounted on the applicable rim, filled to the specified internal pressure, and subjected to the maximum load. Furthermore, "sipe" in "connected sipe" refers to a sipe whose width is 1 mm or less in an area of ​​50% or more of the sipe depth when the tire is mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Here, the sipe depth is measured in the direction perpendicular to the tread surface in the above condition, and the sipe width is measured in the direction parallel to the tread surface in a cross section perpendicular to the extension direction of the tread surface.

[0009] In this specification, "applicable rim" refers to the standard rim for the applicable size (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) which is an industrial standard valid in the region where the tire is produced and used, and which is listed or will be listed in the future in publications such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. (That is, the above "rim" includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of a "size to be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.) However, in the case of a size not listed in the above industrial standards, it refers to a rim with a width corresponding to the tire bead width. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in JATMA, etc. For sizes not listed in the above industrial standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, "maximum load capacity" refers to the load corresponding to the above maximum load capacity.

[0010] (2) The pneumatic tire described in (1) above, wherein at least one end of the main part terminates within the land portion.

[0011] (3) The main part extends in the circumferential direction of the tire, The side portion extends in the tire width direction or extends inclined in the tire width direction, as described in (1) or (2) above, a pneumatic tire.

[0012] (4) The pneumatic tire according to any one of (1) to (3) above, having the land portion in which the rows of the connecting sipes are arranged in a second predetermined direction.

[0013] (5) The side portions of the connecting body sizes of one of the columns and the side portions of the connecting body sizes of an adjacent column adjacent to the one column in the second predetermined direction are alternately arranged in the tire circumferential direction, and the two columns adjacent in the second predetermined direction are arranged with a phase shift in the tire circumferential direction. The pneumatic tire according to (4) above.

[0014] (6) Only one end of the main portion terminates within the land portion. One end of the main portion of the connecting body size of one of the columns on one side in the first predetermined direction terminates within the land portion, and the other end of the main portion of the connecting body size of an adjacent column adjacent to the one column in the second predetermined direction terminates within the land portion. The pneumatic tire according to (4) or (5) above, in which the ends terminating within the land portion are alternately arranged between the two columns adjacent in the second predetermined direction. [Advantages of the Invention]

[0015] According to the present invention, it is possible to provide a pneumatic tire with improved ice grip performance. [Brief Description of the Drawings]

[0016] [Figure 1] It is a figure which shows the tread pattern of the pneumatic tire which concerns on one Embodiment of this invention. [Figure 2] It is a top view which shows the structure of a connection body size. [Figure 3] It is a figure for demonstrating the dimension of a connection body size. [Figure 4] It is a table which showed the Example and the comparative example. [Figure 5] It is a figure which shows the relationship between block rigidity and actual contact area at the time of shearing. [Figure 6] It is a figure which shows the relationship between edge density and actual contact area. [Mode for Carrying Out the Invention]

[0017] Hereinafter, embodiments of the present invention will be exemplified and described in detail with reference to the drawings.

[0018] First, regarding the internal structure etc. of a pneumatic tire (hereinafter, also simply referred to as a tire), it can have the same structure as the conventional one. As an example, the tire can have a pair of bead parts, a pair of sidewall parts continuous with the pair of bead parts, and a tread part disposed between the pair of sidewall parts. Further, the tire can have a carcass straddling toroidally between the pair of bead parts, and a belt disposed on the outer side in the tire radial direction of the crown part of the carcass. Hereinafter, unless otherwise specified, dimensions etc. refer to the dimensions etc. when the tire is mounted on an applicable rim, filled with a specified internal pressure, and in an unloaded state.

[0019] FIG. 1 is a view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, this tire has one or more (4 in the illustrated example) circumferential main grooves 2 (2a to 2d) extending in the tire circumferential direction on the tread surface 1. Note that the number of the circumferential main grooves 2 is not limited to this example and can be changed as appropriate.

[0020] The groove width (opening width) of the circumferential main groove 2 is not particularly limited, but for example, it can be 4 to 15 mm, and the depth (maximum depth) of the circumferential main groove 2 is not particularly limited, but for example, it can be 6 to 20 mm. In the illustrated example, the circumferential main groove 2 extends straight in the tire circumferential direction, but it may extend in a zigzag shape or extend while bending. The circumferential main groove 2 may be inclined at an inclination angle of 5° or less with respect to the tire circumferential direction.

[0021] As shown in Figure 1, the circumferential main groove 2 and the tread edge TE divide the tire into multiple (five in the illustrated example) land areas 3 (3a to 3e). Specifically, land area 3a is divided by the tread edge TE and the circumferential main groove 2a, land area 3b is divided between the circumferential main grooves 2a and 2b, land area 3c is divided between the circumferential main grooves 2b and 2c, land area 3d is divided between the circumferential main grooves 2c and 2d, and land area 3e is divided by the tread edge TE and the circumferential main groove 2d. Thus, the tire has at least one land area 3.

[0022] Each of the land sections 3a to 3e has multiple widthwise grooves 5 extending in the tire width direction, spaced apart in the tire circumferential direction. In land sections 3a, 3c, 3d, and 3e, the widthwise grooves 5 are connected to two adjacent circumferential main grooves 2, and land sections 3a, 3c, 3d, and 3e are partitioned in a block-like manner. On the other hand, in land section 3b, one end of the widthwise groove 5 is connected to the circumferential main groove 2b, and the other end terminates within land section 3b, making land section 3b a rib-shaped land section (land section that is not completely separated in the circumferential direction depending on the widthwise groove 5). A widthwise sipe 6 extending in the tire width direction is connected to the other end of the widthwise groove 5, and the widthwise sipe 6 extends from the other end of the widthwise groove 5 and communicates with the circumferential main groove 2a.

[0023] The groove width (opening width, or maximum width if the groove width changes) of the widthwise groove 5 is not particularly limited, but can be, for example, 2 to 10 mm, and the depth (maximum depth) of the widthwise groove 5 is not particularly limited, but can be, for example, 5 to 20 mm. Furthermore, it is preferable that the widthwise groove 5 extends in the tire width direction or is inclined at an angle of more than 0° and 45° or less with respect to the tire width direction. The widthwise groove 5 can be arranged at equal intervals in the tire circumferential direction, or the pitch interval may be changed to reduce pattern noise. The width (opening width) of the widthwise sipe 6 is not particularly limited, but can be 0.3 to 1 mm, and the depth (maximum depth) of the widthwise sipe 6 is not particularly limited, but can be, for example, 3 to 10 mm. Furthermore, it is preferable that the widthwise sipe 6 extends in the tire width direction or is inclined at an angle of more than 0° and 45° or less with respect to the tire width direction. Furthermore, the land sections 3a and 3e are provided with multiple widthwise sipes 8 extending from the tread edge TE and terminating within the land section, at approximately equal intervals in the circumferential direction of the tire.

[0024] In this tire, one or more connecting sipes 4 are provided on at least one of the land sections 3 (all of the land sections 3 in the illustrated example). In the illustrated example, one or more connecting sipes 4 are provided on each block (or each section (or each part (or part (or part (or part (or part (or part (or part (or part (or part ( ())))) that are separated by the widthwise grooves 5 and the widthwise sipes 6))) that are separated by the widthwise grooves 5).

[0025] Figure 2 is a plan view showing the configuration of the connecting sipe 4. As shown in Figures 1 and 2, the connecting sipe 4 is a branch-shaped sipe having a main portion 4a extending in a first predetermined direction (the tire circumferential direction in the illustrated example) and side portions 4b1 and 4b2 extending from the main portion 4a to the side of the main portion 4a at an inclination with respect to the first predetermined direction (the tire circumferential direction in the illustrated example), and these are connected. The main portion 4a and the side portions 4b1 and 4b2 are sipe portions. The side portions have a first side portion 4b1 located on one side of the main portion 4a and a second side portion 4b2 located on the other side of the main portion 4a, and the first side portion 4b1 and the second side portion 4b2 are arranged alternately in the tire circumferential direction. In the illustrated example, the first side portion 4b1 extends to one side in the tire width direction (left side in the illustration) and terminates within the land portion 3, and the second side portion 4b2 extends to the other side in the tire width direction (right side in the illustration) and terminates within the land portion 3.

[0026] In the illustrated example, the main portion 4a1 extends in the tire circumferential direction, but it may also extend at an inclination angle of 15° or less with respect to the tire circumferential direction. In the illustrated example, the land portions 3a, 3c, 3d, and 3e are block-shaped land portions, and although land portion 3b is a rib-shaped land portion, it is partitioned by widthwise sipes 6. Therefore, the extending length of the main portion 4a is shorter than the tire circumferential length of the block (or block-shaped portion partitioned by widthwise sipes 6). Also, at least one end of the main portion 4a terminates within the land portion 3. In the illustrated example, only one end e1 of the main portion 3a in the first predetermined direction (tire circumferential direction in this example) terminates within the land portion 3, and the other end e2 communicates with the widthwise groove 5 or widthwise sipe 6. On the other hand, if the land portion 3 is a rib-shaped land portion, the main portion 4a can also extend continuously around the tire circumferential direction.

[0027] The side portions 4b1 and 4b2 may extend at an inclination angle of, for example, 45 to 90° with respect to a first predetermined direction which is the extension direction of the main portion 4a, although this is not particularly limited. Typically, the side portions 4b1 and 4b2 extend in the tire width direction or extend at an inclination angle with respect to the tire width direction (for example, the inclination angle can be 45° or less with respect to the tire width direction). In the illustrated example, both side portions 4b1 and 4b2 extend toward one side (one side in the tire circumferential direction) in the extension direction of the main portion 4a, but the first side portion 4b1 and the second side portion 4b2 may extend toward opposite sides in the extension direction of the main portion 4a (in this case, the side portion 4b1 may extend toward one side or the other).

[0028] Here, if we let w1 (mm) be the length of the connected sipe 4 in the tire width direction (length when projected in the tire width direction), and h (mm) be the depth (maximum depth) of the minute sipes (4a, 4b1, 4b2) that make up the connected sipe, then w1 × h = 150 (mm) 2 It is preferable that the w1 × h be less than or equal to 100 (mm). This is because reducing the size of the connecting sipes 4 allows for a higher density arrangement of the connecting sipes 4, which can further improve ice performance. For the same reason, w1 × h should be 100 (mm 2 It is more preferable that it be 50 (mm) or less. 2It is even more preferable that the following conditions apply: Furthermore, n is the number of connecting sipes 4 within the land section 3, BW (mm) is the maximum width of the land section 3 in the tire width direction, and the outer contour area of ​​the land section 3 (area enclosed by the outer contour) (mm) 2 When the "equivalent circumferential length of the tire on land" obtained by dividing ) by BW (mm) is defined as BL (mm), the equivalent number of sipes N (which is the number of sipes converted to transverse sipes that completely cross the land area) is defined as w1 × n / BW, the average sipe spacing in the circumferential direction of the tire is expressed as BL / (N+1), and the sipe density SD is defined as the reciprocal of the average sipe spacing in the circumferential direction of the tire, then when expressed as SD = (N+1) / BL = ((w1 × n / BW) + 1) / BL, it is preferable that SD be 0.15 (1 / mm) or more. This is because the performance on ice can be further improved by arranging the connected sipes at a high density. For the same reason, it is more preferable that the sipe density SD be 0.20 (1 / mm) or more, and even more preferable that it be 0.30 (1 / mm) or more. The number of interconnected sipes n, the maximum width BW in the tire width direction of the land portion, and the outer contour area of ​​the land portion shall be values ​​measured from a flat view of the tread surface. "Outer contour area" refers to the area enclosed by the outer contour when the tread surface is flat viewed, and therefore, even if non-contact areas such as sipes, small holes, and narrow grooves are located within the land portion, this area does not exclude the area of ​​such sipes, small holes, and narrow grooves. The following describes the effects and advantages of the pneumatic tire of this embodiment.

[0029] In the pneumatic tire of this embodiment, first, one or more connected sipes 4 are arranged on at least one of the land portion 3. Since the connected sipe 4 has a main portion 4a extending in a first predetermined direction and side portions 4b1 and 4b2 extending from the main portion 4a to the side of the main portion 4b at an angle to the first predetermined direction, the sipe portions cut the water film, the main portion 4a discharges the water in the first predetermined direction (in this example, the tire circumferential direction), and the side portions 4b1 and 4b2 connected to the main portion 4a also discharge the water to the side, thus enabling efficient removal of the water film. Furthermore, since the side portions consist of a first side portion 4b1 located on one side of the main portion 4a and a second side portion 4b2 located on the other side of the main portion 4a, which are arranged alternately in the tire circumferential direction, these side portions can be arranged at a high density, further enhancing the effect of removing the water film. On the other hand, since the side portions 4b1 and 4b2 terminate within the land portion 3, a decrease in the rigidity of the land portion 3 can be suppressed compared to, for example, a case where the block is completely divided in the circumferential direction of the tire by widthwise sipes extending between two circumferential main grooves, forming block pieces. As described above, the pneumatic tire of this embodiment can effectively remove the water film while suppressing a decrease in the rigidity of the land portion 3, thereby improving grip performance on ice.

[0030] In particular, in this embodiment, since at least one end e1 of the main portion 4a terminates within the land portion 3, the reduction in rigidity of the land portion 3 can be further suppressed, and the ice grip performance can be further improved. From the viewpoint of suppressing the reduction in rigidity of the land portion 3, it is preferable that both ends of the main portion 4a terminate within the land portion 3, but from the viewpoint of effectively removing the water film, the other end 4e or both ends may be in communication with a widthwise groove or widthwise sipe. In this example, one end terminates within the land portion 3 and the other end is in communication with a widthwise groove 5 or widthwise sipe 6, so that the rigidity of the land portion is ensured at one end while effective removal of the water film is achieved at the other end.

[0031] Furthermore, by setting w1×h within the above range, the interconnected sipes can be arranged at a higher density, which can further improve ice grip performance. Also, by setting the sipe density SD within the above range, the interconnected sipes are arranged at a higher density, which can improve the effect of removing the water film and further improve ice grip performance.

[0032] Furthermore, in this embodiment, the main portion 4a extends in the tire circumferential direction, and the side portions 4b1 and 4b2 extend in the tire width direction or, as in this example, extend at an angle in the tire width direction. As a result, the main portion 4a can secure an edge component in the tire circumferential direction (edge ​​component relative to the tire width direction), thereby improving lateral grip performance during cornering. In addition, the side portions 4b1 and 4b2 can secure an edge component in the tire width direction (edge ​​component relative to the tire circumferential direction), thereby improving traction performance and braking performance on ice when driving straight.

[0033] Incidentally, as shown in Figure 1, the tire of this embodiment has land sections 3b, 3c, and 3d in which multiple rows of connecting sipes 4 (in the illustrated example, multiple connecting sipes 4 are arranged at intervals in the tire circumferential direction to form one row) are arranged in a second predetermined direction (in this example, the tire width direction). First, this enhances the effect of removing the water film compared to the case where only one row of connecting sipes 4 is arranged in each land section 3. Note that if the main section 4 extends continuously around the tire circumferential direction, one connecting sipe forms one row. Furthermore, the second predetermined direction may be inclined with respect to the tire width direction, for example, the inclination angle with respect to the tire width direction can be greater than 0° and 30° or less.

[0034] Furthermore, as shown in Figure 1, the sides (4b1 or 4b2) of the connecting sipes 4 in one row and the sides (4b2 or 4b1) of the connecting sipes 4 in the adjacent row adjacent to the first row in the second predetermined direction are arranged alternately in the tire circumferential direction, such that two adjacent rows in the second predetermined direction are arranged with a phase shift in the tire circumferential direction. This allows for a higher density arrangement of the connecting sipes 4 to further enhance the effect of removing the water film, and also balances the size of the land area partitioned by the sides. Moreover, as in this example, it is preferable that the sides (4b1 or 4b2) of the connecting sipes 4 in one row and the sides (4b2 or 4b1) of the connecting sipes 4 in the adjacent row adjacent to the first row in the second predetermined direction overlap each other when projected in the tire circumferential direction, thereby allowing for a higher density arrangement of the connecting sipes 4 and a more effective effect of removing the water film. In this example, the first side portion 4b1 and the second side portion 4b2 are inclined in the same direction in the circumferential direction of the tire and extend in the width direction of the tire, and the connecting sipe 4 of one row and the connecting sipe 4 of the adjacent row are symmetrical with respect to an axis along the width direction (vertically symmetrical in the figure). Therefore, when arranged in the manner described above, the size of the partitioned land area can be made uniform.

[0035] Furthermore, in this embodiment, as shown in Figure 1, only one end e1 of the main portion 4a terminates within the land portion 3. The ends e1 that terminate within the land portion 3 are arranged alternately (on one side and the other side in the circumferential direction) between two adjacent rows, such that one end 4a of the main portion 4a of the main portion 4a of the main portion 4a of the connecting sipe 4 of one row in a first predetermined direction terminates within the land portion 3, and the other end (opposite side) of the main portion 4a of the connecting sipe 4 of the adjacent row adjacent to the first row in a second predetermined direction terminates within the land portion 3. This allows for a balanced arrangement of areas where rigidity reduction is suppressed, preventing localized areas of reduced rigidity and improving ice performance.

[0036] It is preferable that each of the above effects be obtained in each land area, and therefore, it is preferable that all land areas 3 (whether block-shaped or rib-shaped) have the above-mentioned connecting sipes 4.

[0037] Except when the main portion 4b1 extends continuously in the circumferential direction, the connecting sipes 4 can be arranged in a row in the circumferential direction of the tire. In this case, as shown in Figure 1, it is preferable to place one connecting sipe 4 in each block (or block-shaped land area partitioned by the widthwise sipes 6) in each row. This is because arranging the connecting sipes 4 at a high density can further enhance the effect of removing the water film.

[0038] As shown in Figure 1, each land section 3 has multiple sub-sipes 7 arranged at intervals from the connecting sipe 4. In this example, the sub-sipes 7 are formed by connecting a long side and a short side. The long side of the sub-sipe 7 has a point-symmetrical configuration with the sides 4b1 and 4b2 of the connecting sipe 4, and the short side of the sub-sipe 7 has a point-symmetrical configuration with a part of the main part 4a of the connecting sipe 4. The long side of the sub-sipe 7 extends in the tire width direction or extends at an angle to the tire width direction, and the short side of the sub-sipe 7 extends in the tire circumferential direction. The sub-sipe 7 and a part of the main part 4a and the side 4b1 (4b2) of the connecting sipe 4 are arranged to face each other with an offset in the tire width direction, forming a pair of sipes. This allows for a higher density arrangement of sipes. In this example, the angle between the long side and the short side of the sub-sipe 7 is obtuse. The ratio of the extended length of the long side to the extended length of the short side is preferably 1 to 15. This is because setting the ratio to 15 or less ensures sufficient length of the short side to effectively guide drainage, while setting the ratio to 1 or more allows for a moderately short length of the short side, enabling a high-density arrangement of sipes. As shown in the figure, multiple sub-sipes 7 are arranged in the circumferential direction of the tire (for example, at equal intervals), and their short sides are located on the same straight line. The ratio of the circumferential length of the sipes to the widthwise length is preferably 0.1 to 2.6. This is because setting the ratio to 0.1 or more ensures sufficient distance between sipes to secure block rigidity, while setting the ratio to 2.6 or less ensures that φ is not excessively large and that the widthwise length is not too short, thereby providing sufficient effect on braking and driving forces.

[0039] Figure 3 is a diagram illustrating the dimensions of the connecting sipe 4. Here, as shown in Figure 3, let a (mm) be the extended length of the side portions 4b1 and 4b2 of the connecting sipe 4, let d (mm) be the length of the side portions 4b1 and 4b2 in the tire width direction (projected length in the tire width direction), let s (mm) be the distance in the tire width direction between the end of the side portion 4b1 (4b2) of one connecting sipe (the end that terminates in the land portion) and the main portion 4a of a connecting sipe adjacent to one connecting sipe, and let φ be the inclination angle of the side portions 4b1 and 4b2 with respect to the tire width direction. In this case, d can be expressed as d = a × cosφ. Here, it is preferable that s be 1.5 mm or more. This is because setting s to 1.5 mm or more further suppresses the decrease in block rigidity. It is also preferable that d > s. This is because the side portions overlap when projected in the circumferential direction of the tire, further enhancing the effect of removing the water film by the sipe portions on the sides. Furthermore, when the circumferential pitch between the side portions 4b1 (or 4b2) is p (mm), and the circumferential distance between the side portion 4b1 (4b2) of one connecting sipe and the side portion 4b2 (4b1) of an adjacent connecting sipe is q (mm) and r (mm) (q ≤ r), then p can be expressed as p = q + r. Also, the circumferential distance c (mm) between the connection point between the main portion 4a and the branch portion 4b1 of one connecting sipe and the connection point between the main portion 4a and the branch portion 4b2 of an adjacent connecting sipe is, c = α(d+s) - q, α = tanφ, It can be expressed as follows. Here, when q = α × (d + s), c = 0, and the circumferential positions of the branching points of adjacent sipe rows align in the width direction. This ensures continuity in the sipe density of the branches in response to the tire width direction input, suppressing circumferential fluctuations in block stiffness and enabling stable lateral grip performance. For this reason, a range of q = α × (d + s) × 0.8 to α × (d + s) × 1.2 is desirable. In particular, when q = p / 2, r = q, and all sipes included in the sipe row are arranged at equal intervals in the tire circumferential direction. For this reason, it is preferable to set q in the range of P / 2 × 0.8 to p / 2 × 1.2, and more preferably to set q to p / 2, which makes it possible to uniformize the sipe density in the tire circumferential direction on the block's land portion. [Examples]

[0040] Examples will be described below with reference to Figure 4. Figure 4 is a table showing examples and comparative examples.

[0041] Finite element method (FEM) simulations were performed on the tires of Examples 1-3 and Comparative Examples 1-3 shown in Figure 4. Block stiffness and contact area were evaluated under conditions where a vertical load was applied, calculated by multiplying the contact area of ​​the block's land surface under no load by the standard contact pressure of a passenger car tire (230 kPa). In Examples 1-3 and Comparative Examples 1-3, the evaluation was performed assuming that the block's land surface had a maximum length of 30 mm in the circumferential direction and a width of 27 mm in the tire's width direction, with sipes as shown in the sipe shape diagrams of Figure 4. All sipes had a width of 0.4 mm, a depth of 6.7 mm, and a tip radius of 0.2 mm.

[0042] Figure 5 shows the relationship between block stiffness and the actual contact area during shear. Figure 6 shows the relationship between edge density and the actual contact area. Here, block stiffness Kx (N / mm) is the shear input value in the same direction when the lateral displacement in the circumferential direction of the tire is 1 mm, and the actual contact area Ar (mm) during shear. 2) represents the remaining contact area when partial lift occurs, where the shear input in the circumferential direction of the tire is 0.3 times the above-mentioned vertical load. As shown in Figure 5, it can be seen that in Examples 1 to 3, both block rigidity and actual contact area are achieved compared to Comparative Examples 1 to 3. As shown in Figure 6, it can be seen that in Examples 1 to 3, the actual contact area is increased compared to Comparative Examples 1 to 3, given the same edge density. [Explanation of Symbols]

[0043] 1: Tread surface, 2: Circumferential main groove, 3: Rikube, 4: Connecting sipe, 5: Width direction groove, 6: Widthwise sipes, 7: Subsidiary sipes, 8: Widthwise sipes, CL: Tire equatorial plane, TE: Tread edge

Claims

1. A pneumatic tire in which the tread surface has one or more circumferential main grooves formed along the circumferential direction of the tire, and the space between adjacent circumferential main grooves, or the space between the tread edge and the adjacent circumferential main groove, functions as a land area, At least one of the land portions has one or more connected sipes formed therein. The aforementioned connecting sipe is The main part is aligned with the circumferential direction of the tire, A side portion extending from the main portion toward the side of the main portion so as to be inclined with respect to the tire circumferential direction and terminating within the land portion, It has, The side portion comprises a first side portion located on one side of the main portion and a second side portion located on the other side of the main portion. The first side portion and the second side portion are arranged alternately in the circumferential direction of the tire. A pneumatic tire characterized in that both ends of the main part terminate within the land portion.

2. The pneumatic tire according to claim 1, having the land portion in which the rows of the connecting sipes are arranged in multiple rows in the tire width direction.

3. The pneumatic tire according to claim 2, wherein two adjacent rows in the tire width direction are arranged with a phase difference in the tire width direction so that the side portion of the connecting sipe of one row and the side portion of the connecting sipe of an adjacent row adjacent to the first row in the tire width direction are arranged alternately in the tire width direction.

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