Tire

Abstract

To improve various on-ice performances without reducing wet performance as much as possible by increasing rigidity of a whole land part.SOLUTION: In at least one of land parts (22), a sipe unit (28, 30, 32) including two sipes inclining to the opposite side of a tire circumferential direction (Dc) with respect to a tire radial direction (Dr) is formed. At least one sipe unit is formed in each of second to fourth regions, the second region (R2) being from a position of 5% to a position less than 20%, the third region (R3) being a position of 20% to a position less than 80%, and the fourth region (R4) being from a position of 80% to a position of less than 95%. Edges (E1 and E2) of the land part extending in a wire width direction are continuously present without breaks.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A tire has been disclosed in the past in which four sipes are provided in each of a plurality of land portions defined in the tread in order to reduce residual stress and improve straight-line stability without substantially affecting the land portion shape, pattern shape, etc., and one end of each sipe opens into a groove on each side of the land portion and the other end terminates within the land portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-138715 Summary of the Invention [Problem to be solved by the invention]

[0004] In the tire disclosed in Patent Document 1, one end of a sipe, in plan view of the tire, divides the edge of a land portion with a large tire width direction component and communicates with a groove, which may result in insufficient rigidity in the land portion near the groove. Also, in such a tire, there is no particular regulation regarding the positional relationship between sipes extending in the same direction in plan view of the tire, which may result in locally excessively high or low rigidity in the land portion.

[0005] In recent years, there has been a demand for the development of tires that improve various ice performances and also improve wear resistance without compromising wet performance by improving these locally different land stiffnesses.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a tire that improves various ice performances and also improves wear resistance without reducing wet performance by increasing the rigidity of the entire land portion where sipes are formed. [Means for solving the problem]

[0007] The tire of the present invention has a sipe unit formed in at least one of the land portions defined by a plurality of grooves, the sipe unit including two sipes inclined in opposite directions in the tire circumferential direction relative to the tire radial direction, The leading end of the land portion in the tire circumferential direction is defined as a 0% position, and the trailing end is defined as a 100% position, If the first region is from the 0% position to a position less than 5%, the second region is from the 5% position to a position less than 20%, the third region is from the 20% position to a position less than 80%, the fourth region is from the 80% position to a position less than 95%, and the fifth region is from the 95% position to the 100% position, At least one sipe unit is formed in each of the second region, the third region, and the fourth region, The edge of the land portion extending along the tire width direction is characterized by being continuous without any breaks. [Effects of the Invention]

[0008] In the tire according to the present invention, at least one sipe unit is formed in each of the second, third, and fourth regions that are divided in the tire circumferential direction of the land portion where the sipe units are formed, and the edges of the land portion extending along the tire width direction are continuously present without interruption. This not only locally increases or decreases the rigidity of the land portion where the sipes are formed, but also increases the rigidity of the tire circumferential end portions of the land portion in particular, thereby increasing the rigidity of the entire land portion where the sipes are formed in a balanced manner. As a result, various types of performance on ice can be improved without reducing wet performance, and wear resistance can also be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing both sides in the tire width direction with the tire equatorial plane as the reference in a plan view of a tire according to this embodiment as seen from the outer side in the tire radial direction. [Figure 2] FIG. 2 is an enlarged view showing the circled portion X in FIG. [Figure 3] FIG. 3 is a perspective view showing the land portion shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view in the tire circumferential direction showing the circled portion Y in FIG. [Figure 5] FIG. 5 is a perspective view showing the distance between two circumferentially adjacent sipe units (the distance between sipes) in the land portion shown in FIG. [Figure 6] FIG. 6 is a perspective view showing a modified example of the sipe unit shown in FIG. [Figure 7] FIG. 7 is a diagram showing both sides in the tire width direction with the tire equatorial plane as the reference in a plan view of a conventional tire as seen from the outer side in the tire radial direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Aspects of the present invention> The embodiments of the present invention relate to the following aspects.

[0011] [Aspect 1] A sipe unit consisting of two sipes inclined in opposite directions in the tire circumferential direction relative to the tire radial direction is formed in at least one of the land portions defined by the plurality of grooves, The leading end of the land portion in the tire circumferential direction is defined as a 0% position, and the trailing end is defined as a 100% position, If the first region is from the 0% position to a position less than 5%, the second region is from the 5% position to a position less than 20%, the third region is from the 20% position to a position less than 80%, the fourth region is from the 80% position to a position less than 95%, and the fifth region is from the 95% position to the 100% position, At least one sipe unit is formed in each of the second region, the third region, and the fourth region, A tire characterized in that the edges of land portions extending along the tire width direction are present continuously without any breaks. [Aspect 2] A tread surface position of the sipe in the tire radial direction is defined as a 0% depth position, and a bottom position of the sipe in the tire radial direction is defined as a 100% depth position, The tire according to aspect 1, wherein, when each of the sipe units is viewed from one side in the tire width direction, the intersection positions of the two sipes that make up each sipe unit in the second region and the fourth region are from a depth position greater than 50% to a depth position less than 100%. [Aspect 3] A tread surface position of the sipe in the tire radial direction is defined as a 0% depth position, and a bottom position of the sipe in the tire radial direction is defined as a 100% depth position, The tire according to aspect 1 or 2, wherein, when each of the sipe units is viewed from one side in the tire width direction, in the third region, the intersection position of the two sipes that constitute each sipe unit is at a depth position ranging from a depth position greater than 0% to a depth position of 50% or less. [Aspect 4] A tire according to aspect 1 or 2, wherein, when each of the sipe units is seen from one side in the tire width direction, the absolute value of the inclination angle of the sipe to each side in the tire circumferential direction with respect to the tire radial direction is 1° or more and 10° or less. [Aspect 5] A tire according to aspect 4, wherein the absolute values ​​of the inclination angles of the two sipes that make up the sipe unit are equal. [Aspect 6] A tire according to aspect 1 or 2, wherein, when each of the sipe units is viewed from one side in the tire width direction, the shortest distance in the tire circumferential direction between the sipes in adjacent sipe units, the shortest distance in the tire circumferential direction from the sipe in the second region to the leading-side edge of a land portion extending along the tire width direction, and the shortest distance in the tire circumferential direction from the sipe in the fourth region to the trailing-side edge of a land portion extending along the tire width direction are 2.0 mm or more. [Aspect 7] A tire according to any one of the preceding aspects, wherein the sipes have a depth that is 90% or less of the maximum groove depth. [Aspect 8] A tire according to aspect 1 or 2, wherein the sipes are any of flat sipes, two-dimensional sipes, and three-dimensional sipes. [Aspect 9] A tire according to aspect 1 or 2, wherein one end of the sipe in the tire width direction communicates with the groove, and the other end of the sipe in the tire width direction terminates within a land portion. [Aspect 10] A tire according to aspect 9, wherein one end of the sipe in the tire width direction communicates with the groove only at an outer portion in the tire radial direction.

[0012] <Definition> In the following description, the tire radial direction refers to the direction perpendicular to the tire's rotational axis, the tire radially inner side refers to the side toward the rotational axis in the tire radial direction, and the tire radially outer side refers to the side away from the rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the rotational axis as the central axis. The tire width direction refers to the direction parallel to the rotational axis, the tire widthwise inner side refers to the side toward the tire equatorial plane (tire equator line) in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane is a plane that is perpendicular to the tire's rotational axis and passes through the center of the tire width.

[0013] Similarly, in the following description, a regular rim refers to an "applicable rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO.

[0014] Similarly, in the following explanation, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Inflation Pressures" specified by ETRTO. Also, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Load Capacity" specified by ETRTO.

[0015] <Tire structure, etc.> Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described with reference to the drawings. Fig. 1 is a diagram showing both sides in the tire width direction with the tire equatorial plane as the tire according to the present embodiment in a plan view seen from the tire radial outside. Note that the figure shows the tire portion in a state where the tire is mounted on a rim and has a normal internal pressure applied, and is in an unloaded state. In Fig. 1, the symbol Dc denotes the tire circumferential direction, and the symbol Dw denotes the tire width direction (the same applies to other figures).

[0016] Although not shown in its entirety, the tire 10 of this embodiment has a meridian cross-sectional shape similar to that of a conventional pneumatic tire. That is, the tire 10 of this embodiment has, from the inner side to the outer side in the tire radial direction in a tire meridian cross-section (not shown), a bead portion, a sidewall portion, a shoulder portion, and a tread portion. The tire 10 also has, for example, a carcass layer extending from the tread portion to both bead portions in the tire meridian cross-section and wound around a pair of bead cores, and a belt layer and, in some cases, a belt cover layer on the tire radial direction outer side of the carcass layer.

[0017] The tire of this embodiment may or may not have a specified rotation direction. In the example shown in Fig. 1, the lower side of the paper (Fig. 1) is provisionally set to be the leading side S1 in the tire circumferential direction Dc, and the upper side of the paper is provisionally set to be the trailing side S2 in the tire circumferential direction Dc.

[0018] The tread portion 12 shown in FIG. 1 is made of rubber (tread rubber). The tread portion 12 has a tread surface 14 that comes into contact with the road surface when the vehicle is traveling. The tread surface 14 is annular, centered on the rotational axis of the tire 10, has a predetermined length in the tire width direction, and is continuous in the tire circumferential direction. A tread pattern of a predetermined design as shown in FIG. 1 is engraved on the tread surface 14. The tread pattern shown in FIG. 1 is symmetrical about a point on the tire equatorial plane CP (for example, the tire circumferential midpoint on the tire equatorial plane CP in FIG. 1) between both sides of the tire equatorial plane CP in the tire width direction Dw. In FIG. 1, the symbol EL denotes a contact edge line (a line connecting consecutive contact edges E in the tire circumferential direction).

[0019] 1, in a tire 10 according to this embodiment, four circumferential main grooves 16 and a plurality of lateral grooves 18 are formed on a tread surface 14. The lateral grooves 18 extend outward in the tire direction from near the tire equatorial plane CP, cross the two circumferential main grooves 16, 16, then bend and extend beyond the tread edge line EL outward in the tire width direction. This defines one center land portion 20 (rib-shaped land portion), a plurality of second land portions 22 (block-shaped land portions), and a plurality of shoulder land portions 24 (block-shaped land portions). Each shoulder land portion 24 is engraved with a pattern 26 extending in the tire circumferential direction.

[0020] Fig. 2 is an enlarged view showing the circled portion X in Fig. 1. The upper part of Fig. 2 is a plan view of the circled portion X, and the lower part is a perspective view from the side (i.e., from one side in the tire width direction) corresponding to the view shown in the upper part. In Fig. 2, the symbol Dr represents the tire radial direction (the same applies to other figures).

[0021] 2, three sipe units 28, 30, and 32 are provided in the land portion 22. The sipe unit 28 is made up of two sipes 28a and 28b that are inclined in opposite directions in the tire circumferential direction Dc relative to the tire radial direction Dr. Similarly, the sipe unit 30 is made up of two sipes 30a and 30b that are inclined in opposite directions in the tire circumferential direction Dc relative to the tire radial direction Dr, and the sipe unit 32 is made up of two sipes 32a and 32b that are inclined in opposite directions in the tire circumferential direction Dc relative to the tire radial direction Dr.

[0022] In this embodiment, a sipe refers to a recessed portion having a width of 1.5 mm or less on the tread surface and a depth from the tread surface of 100% or less of the maximum groove depth.

[0023] Here, the end of the land portion 22 on the leading side S1 in the tire circumferential direction Dc is defined as the 0% position, and the end of the land portion 22 on the trailing side S2 is defined as the 100% position. In the example shown in Fig. 2, the two edges E1 and E2 of the land portion 22 (the outer edges of the land portion 22 indicated by vertical lines in Fig. 2) extend parallel to the tire width direction Dw, but this embodiment is not limited to this case. Even if the two outer edges of the land portion 22 do not extend parallel to the tire width direction Dw, the method of determining the 0% position and the 100% position in the tire circumferential direction Dc is as described above.

[0024] As shown in FIG. 2, the areas of the land portion 22 are as follows: the first area R1 is from the 0% position to less than 5%; the second area R2 is from the 5% position to less than 20%; the third area R3 is from the 20% position to less than 80%; the fourth area R4 is from the 80% position to less than 95%; and the fifth area R5 is from the 95% position to the 100% position.

[0025] Under these conditions, at least one sipe unit (in the example shown in FIG. 2, as described above, sipe units 28, 30, and 32) is formed in each of the second region R2, third region R3, and fourth region R4 shown in Fig. 2. Furthermore, the edges of the land portion 22 extending along the tire width direction (specifically, the edge E1 on the leading side S1 and the edge E2 on the trailing side S2) exist continuously without interruption.

[0026] Here, the edges E1, E2 extending along the tire width direction means that the extension direction of the edges E1, E2 relative to the tire width direction in a plan view of the tire is at least −25° and not more than 25°.

[0027] Although not shown in FIG. 2, a plurality of sipe units may be formed in each of the second region R2, the third region R3, and the fourth region R4.

[0028] The tire 10 of this embodiment described above is obtained through each of the usual manufacturing steps, i.e., a tire material mixing step, a tire material processing step, a green tire molding step, a vulcanization step, and a post-vulcanization inspection step, etc. When manufacturing the tire of this embodiment, convex portions and concave portions corresponding to a predetermined tread pattern are formed on the inner wall of a vulcanization mold, and vulcanization is carried out using this mold.

[0029] (action, etc.) 1 and 2, the sipes 28a, 28b, 30a, 30b, 32a, and 32b constituting the sipe units 28, 30, and 32 are all inclined toward either side of the tire circumferential direction Dc with respect to the tire radial direction Dr. As a result, the sipe volume can be increased compared to when sipes that are not inclined with respect to the tire circumferential direction Dc are used (provided that the length in the tire radial direction Dr is the same), thereby improving drainage performance and wet performance.

[0030] 1 and 2, the sipes 28a, 28b constituting the sipe unit 28 are inclined in opposite directions in the tire circumferential direction Dc with respect to the tire radial direction Dr. The same applies to the sipes 30a, 30b constituting the sipe unit 30 and the sipes 32a, 32b constituting the sipe unit 32. Therefore, compared to using sipes that are not inclined with respect to the tire circumferential direction Dc or using a sipe unit consisting of two sipes inclined in the same direction with respect to the tire circumferential direction Dc, it is possible to prevent the land portion rigidity in the land portion 22 from being locally too high or too low (particularly with respect to the tire circumferential direction).

[0031] Furthermore, in the tire 10 shown in Figures 1 and 2, the edges E1 and E2 of the land portions 22 extending along the tire width direction Dw are continuous and uninterrupted. That is, there are no sipes that communicate with the lateral grooves 18 that contact the edges E1 and E2. This ensures a high level of rigidity in the land portions near the edges E1 and E2. As a result, these edges E1 and E2 suppress collapse of the land portions 22, particularly during braking, and improve grip (especially traction on ice) during acceleration.

[0032] In this way, the land portion rigidity in the land portion 22 is not locally too high or too low, and the land portion rigidity near the edges E1 and E2 can be maintained at a high level, thereby enhancing the so-called edge effect in the land portion 22, and as a result, not only can various ice performances (braking performance on ice and acceleration performance on ice) be improved, but wear resistance can also be improved.

[0033] As described above, in the tire of this embodiment, the above-mentioned characteristic sipe units are formed in the second region R2, the third region R3, and the fourth region R4, and the edges E1, E2 of the land portion 22 extending along the tire width direction are made to exist continuously along the tire width direction, thereby not only improving wet performance but also improving various ice performances (braking performance on ice and acceleration performance on ice), and further improving wear resistance.

[0034] (Suitable example 1) In the tire shown in Figures 1 and 2, the tread surface position of sipe 28a (similarly for sipes 28b, 30a, 30b, 32a, and 32b) in the tire radial direction is defined as the 0% depth position, and the bottom position of sipe 28a in the tire radial direction is defined as the 100% depth position.

[0035] Under these assumptions, in the tire according to this embodiment, when each of the sipe units 28, 30, 32 is viewed from one side in the tire width direction (see the lower diagram of Figure 2, and the same applies below), it is preferable that in the second region R2 and the fourth region R4, the intersection position of the two sipes 28a, 28b (32a, 32b) constituting the sipe unit 28 (32) is at a depth position between more than 50% and less than 100%.

[0036] 2, the 0% depth position and the 100% depth position are the same for the sipes 28a, 28b (32a, 32b) that make up the sipe unit 28 (32). However, if at least one of the 0% depth position and the 100% depth position differs between the sipes that make up a single sipe unit, the depth position of the sipe with the longer extension length in the tire radial direction Dr is used to determine the intersection position of the two sipes.

[0037] In this way, by setting the intersection position of the two sipes 28a, 28b (32a, 32b) constituting the sipe unit 28 (32) at a depth position between more than 50% and 100% or less, it is possible to increase the rigidity near the end of the land portion in the tire radial direction Dr, i.e., near the tread surface 14, and ensure particularly excellent rigidity for the land portion 22 until the depth of the sipe in the tire radial direction Dr becomes 50% due to wear. As a result, various on-ice performances (braking performance on ice and acceleration performance on ice) can be further improved, and wear resistance can also be further improved.

[0038] The intersection position can be, for example, from a depth position of more than 50% to a depth position of less than 60%, but the effect can be further enhanced by setting it at a depth position of more than 60% to a depth position of less than 65%, and the effect can be further enhanced by setting it at a depth position of more than 65% to a depth position of less than 100%.

[0039] (Preferable example 2) In the tire according to this embodiment, when each of the sipe units 28, 30, 32 is viewed from one side in the tire width direction (see the lower diagram in Figure 2), it is preferable that in the third region R3, the intersection position of the two sipes 30a, 30b that constitute the sipe unit 30 is at a depth position between more than 0% and 50% or less.

[0040] 2, the 0% depth position and the 100% depth position are the same for sipes 30a, 30b that make up sipe unit 30. However, if at least one of the 0% depth position and the 100% depth position is different for sipes 30a, 30b, the depth position of the sipe with the longer extension length in the tire radial direction Dr is used to determine the intersection position of the two sipes.

[0041] According to the inventor's findings, when two sipes 30a, 30b intersect in a side perspective (viewed from one side in the tire width direction) as shown in Fig. 2, the closer the intersection position is to the tread surface 14, the better the ease with which the tire can be removed from the mold (one of the indicators of vulcanization failure). Also, in general, with respect to the tire circumferential direction, the ease with which the tire can be removed from the mold is inferior in a region located relatively centrally of the land portion 22 (the third region R3 in the example shown in Fig. 2) than in regions located relatively at the ends of the land portion 22 (the second region R2 and the fourth region R4 in the example shown in Fig. 2).

[0042] Therefore, in order to improve the release properties in the third region R3, which is most likely to have poorer release properties from the mold among the second region R2 to the fourth region R4 that form the sipe unit, the intersection position of the two sipes 30a, 30b that make up the sipe unit 30 is set to a depth position ranging from a depth position greater than 0% to a depth position of 50% or less.

[0043] The intersection position can be, for example, from a depth position of more than 45% to a depth position of less than 50%, but the effect can be further enhanced by setting it at a depth position of more than 40% to a depth position of less than 45%, and the effect can be further enhanced by setting it at a depth position of more than 0% to a depth position of less than 40%.

[0044] (Suitable example 3) Fig. 3 is a perspective view showing the land portion shown in Fig. 2. In the land portion 22 shown in Fig. 3, when each of the sipe units 28, 30, 32 is seen through from one side in the tire width direction, it is preferable that the absolute value of the inclination angle θ of the sipes 28a, 28b, 30a, 30b, 32a, 32b toward each side in the tire circumferential direction with respect to the tire radial direction Dr is 1° or more and 10° or less.

[0045] In FIG. 3, when the outer portion of each sipe in the tire radial direction Dr is located closer to the trailing side S2 in the tire circumferential direction Dc than the inner portion, the inclination angle θ is considered to be a positive value, and when the outer portion of each sipe in the tire radial direction Dr is located closer to the leading side S1 in the tire circumferential direction Dc than the inner portion, the inclination angle θ is considered to be a negative value. According to this definition, in FIG. 3, the inclination angle θ of sipes 28a, 30a, and 32a is a negative angle, and the inclination angle θ of sipes 28b, 30b, and 32b is a positive angle.

[0046] By setting the absolute value of the inclination angle θ of the sipes 28a, 28b, 30a, 30b, 32a, and 32b to each side in the tire circumferential direction with respect to the tire radial direction to 1° or more, the length of the sipe in the extension direction becomes longer compared to when the sipe inclination angle is 0°, i.e., when the sipes extend in the tire radial direction Dr. This allows the sipe volume to be relatively large, thereby further improving wet performance.

[0047] On the other hand, by setting the absolute value of the inclination angle θ of the sipes 28a, 28b, 30a, 30b, 32a, and 32b to each side in the tire circumferential direction with respect to the tire radial direction to 10° or less, collapse of the land portions near the sipes when a load is applied to the tire can be suppressed. As a result, various ice performances (braking performance on ice and acceleration performance on ice) and wear resistance can be further improved. In addition, setting the absolute value to 10° or less can further improve the ease with which the tire can be released from the mold.

[0048] By setting the absolute value of the inclination angle to 1.5° or more and 9.5° or less, the above effect can be further enhanced, and by setting it to 2.0° or more and 9.0° or less, the above effect can be further enhanced.

[0049] (Suitable example 4) Fig. 4 is a tire circumferential cross-sectional view showing the circled portion Y in Fig. 3, and particularly shows a case where the inclination angle θ1 of the sipe 28a in the tire circumferential direction Dc with respect to the tire radial direction Dr is equal to the inclination angle θ2 of the sipe 28b in the tire circumferential direction Dc with respect to the tire radial direction Dr. As shown in Fig. 4, it is preferable that the absolute values ​​of the inclination angles θ1 and θ2 of the two sipes 28a and 28b constituting the sipe unit 28 are equal.

[0050] By making the absolute values ​​of the inclination angles θ1 and θ2 equal in the two sipes 28a and 28b, it is possible to prevent the land portion 22 from collapsing to either side in the tire circumferential direction when a load is applied to the tire, thereby suppressing uneven wear such as heel-and-toe wear. Note that the relationship between the absolute values ​​of the inclination angles θ1 and θ2 is also the same for the sipes 30a and 30b (32a and 32b) that constitute the sipe unit 30 (32).

[0051] (Suitable example 5) 5 is a perspective view showing the distance between two circumferentially adjacent sipe units (more specifically, the distance between sipes) in the land portion shown in FIG. 5. As shown in FIG. 5, when each of the sipe units 28, 30, and 32 is seen from one side in the tire width direction, The shortest distances D1, D2 between the sipes in the tire circumferential direction between adjacent sipe units (the sipe unit 28 and the sipe unit 30, or the sipe unit 30 and the sipe unit 32), The shortest distance D3 in the tire circumferential direction from the sipe 28b in the second region to the edge E1 on the leading side S1 of the land portion extending along the tire width direction, and The shortest distance D4 in the tire circumferential direction from the sipe 32a in the fourth region to the edge E2 of the trailing side S2 of the land portion extending along the tire width direction However, it is preferable that each of them is 2.0 mm or more.

[0052] Here, the shortest distances D1, D2 in the tire circumferential direction between sipes in adjacent sipe units are the distances between sipes located on the same side in the tire width direction in the two sipe units. For example, the shortest distance D1 between sipes in sipe unit 28 and sipe unit 30 may be the distance between sipes 28a, 30a located on the near side of the paper in Fig. 5 (one side in the tire width direction), or may be the distance between sipes 28b, 30b located on the far side of the paper in Fig. 5 (the other side in the tire width direction).

[0053] Furthermore, the shortest circumferential distance D3 from a sipe in the second region to the edge E1 of the leading side S1 of a land portion extending along the tire width direction is determined by using the sipe 28b, which is closer to edge E1, of the sipes 28a, 28b included in the second region. Similarly, the shortest circumferential distance D4 from a sipe in the fourth region to the edge E2 of the leading side S2 of a land portion extending along the tire width direction is determined by using the sipe 32a, which is closer to edge E2, of the sipes 32a, 32b included in the fourth region.

[0054] In this way, by making all of the tire circumferential distances D1 to D4 2.0 mm or more, it is possible to further increase the rigidity of the land portions 22 without excessively shortening the distance between the sipes or the distance between the sipes and the lateral grooves 18. As a result, it is possible to further improve various on-ice performances (braking performance on ice and acceleration performance on ice) and wear resistance (particularly performance related to heel-and-toe wear).

[0055] By making each of the shortest distances in the tire circumferential direction 2.5 mm or more, the above effect can be further enhanced, and by making each of the shortest distances 3.0 mm or more, the above effect can be further enhanced.

[0056] (Suitable example 6) The depth of the sipes 28a, 28b, 30a, 30b, 32a, and 32b shown in Figures 1 to 5 is preferably 90% or less of the depth of the deepest groove. In the tread pattern shown in Figure 1, the deepest grooves are the four circumferential main grooves 16. The depth of the circumferential main grooves 16 shown in Figure 1 can be 5 mm or more and 20 mm or less.

[0057] By setting the depth of the sipes 28a, 28b, 30a, 30b, 32a, and 32b to 90% or less of the depth of the circumferential main groove 16, it is possible to suppress breakage starting from these sipes. This makes it possible to prevent exposure of the belt layer or belt cover layer (not shown) located on the radially lower side of the tread rubber, thereby improving the durability of the tire.

[0058] Similarly, by making the depth of sipes 28a, 28b, 30a, 30b, 32a, and 32b 90% or less of the depth of the deepest groove, collapse of the land portion 22 in the vicinity of where the sipes are formed can be suppressed, and as a result, uneven wear such as heel-and-toe wear can be further suppressed.

[0059] By making the sipe depth 85% or less of the depth of the deepest groove, the above effect can be further enhanced, and by making it 80% or less, the above effect can be further enhanced.

[0060] (Suitable example 7) 1 to 5 can be any of flat sipes, two-dimensional sipes, and three-dimensional sipes, and it is particularly preferable to use sipes of the same type (for example, flat sipes) within the same sipe unit. Here, flat sipes refer to sipes that are not curved in any direction, two-dimensional sipes refer to sipes that are curved in one direction (for example, the tire width direction), and three-dimensional sipes refer to sipes that are curved in two directions (for example, the tire width direction and the tire radial direction).

[0061] 1 to 5 are limited to flat sipes, two-dimensional sipes, and three-dimensional sipes, which limits the change in rigidity of the land portion 22, particularly between sipes within a sipe unit (i.e., between the sipes located closest to each other), and further prevents the rigidity of the land portion from becoming locally too high or too low. As a result, various ice performances (braking performance on ice and acceleration performance on ice) and abrasion resistance (particularly performance related to heel-and-toe abrasion) can be further improved while maintaining the drainage improvement effect of the sipes.

[0062] (Suitable example 8) In the tire according to the present embodiment, there is no particular limitation as to whether or not the tire width direction ends of the sipes (described above) communicate with a groove. However, as shown in Figures 1 and 2, it is preferable that one end of each sipe in the tire width direction communicates with a groove (the circumferential main groove 16 shown in Figure 1) and the other end of each sipe in the tire width direction terminates within the land portion 22. In the example shown in Figures 1 and 2, sipes 28a, 28b, 30a, 30b, 32a, and 32b are shown as such suitable examples.

[0063] As shown in Figures 1 and 2, by connecting one end of the sipe in the tire width direction to the groove, not only can drainage performance and therefore wet performance be improved, but also the release of the tire from the mold can be improved.

[0064] In addition, by terminating the other end of the sipe in the tire width direction within the land portion 22, the rigidity of the land portion 22 can be increased, thereby improving various ice performances (braking performance on ice and acceleration performance on ice) and wear resistance.

[0065] (Suitable example 9) Fig. 6 is a perspective view showing a modified example of the sipe unit shown in Fig. 3. As shown in Fig. 6, three sipe units 36, 38, and 40 are provided in the land portion 34. The sipe unit 36 ​​is made up of two sipes 36a and 36b that are inclined in opposite directions in the tire circumferential direction Dc relative to the tire radial direction Dr. Similarly, the sipe unit 38 is made up of two sipes 38a and 38b that are inclined in opposite directions in the tire circumferential direction Dc relative to the tire radial direction Dr, and the sipe unit 40 is made up of two sipes 40a and 40b that are inclined in opposite directions in the tire circumferential direction Dc relative to the tire radial direction Dr.

[0066] In Fig. 6, the sipes 36a, 38a, and 40a are inclined at an angle θ3 (a positive angle) with respect to the tire radial direction Dr, and the sipes 36b, 38b, and 40b are inclined at an angle θ4 (a negative angle) with respect to the tire radial direction Dr. However, in Fig. 6, the angle θ3 is applied only to the sipe 36a, and the angle θ4 is applied only to the sipe 40b.

[0067] Here, in the land portion 34 shown in Fig. 6, each position in the tire circumferential direction (0% position and 100% position) and each position in the tire radial direction (0% depth position and 100% depth position) are the same as each position described in the example shown in Fig. 2. Also, the sipe unit 36 ​​is formed in the second region R2 shown in Fig. 2, the sipe unit 38 is formed in the third region R3 shown in Fig. 2, and the sipe unit 40 is formed in the fourth region R4 shown in Fig. 2.

[0068] Under these conditions, in the example shown in FIG. 3 described above, one end of each sipe in the tire width direction (the rear end of the paper in FIG. 3 for sipes 28a, 30a, and 32a shown in FIG. 3, and the front end of the paper in FIG. 3 for sipes 28b, 30b, and 32b) communicates with a groove (circumferential main groove 16) in the entire region in the tire radial direction Dr. On the other hand, in the example shown in FIG. 6, one end of each sipe in the tire width direction (the front end of the paper in FIG. 6 for sipes 36a, 38a, and 40a shown in FIG. 6, and the rear end of the paper in FIG. 6 for sipes 36b, 38b, and 40b) communicates with a groove (circumferential main groove 16) only in the outer portion in the tire radial direction Dr. That is, in the land portion 34 shown in FIG. 6, each sipe forms a bottom upper portion (a portion where the bottom of the sipe is partially raised).

[0069] By connecting one end of each sipe in the tire width direction to a groove (circumferential main groove 16) only in the outer portion in the tire radial direction Dr, the sipe volume is secured in the outer portion in the tire radial direction Dr, drainage is maintained, and an extreme decrease in wet performance can be prevented. Furthermore, with this configuration, the sipes and grooves are not connected in any portion other than the outer portion in the tire radial direction Dr, so the rigidity of the land portion 34 is increased, various performances on ice (such as braking performance on ice) are further improved, and wear resistance can also be further improved.

[0070] In order to achieve a good balance between wet performance, various ice performances, and wear resistance, it is preferable that the radially inner position of the radially outer portion of the sipe at one end in the tire width direction (the radially outermost position of the bottom-up portion) is located at a depth position of 20% to 80% or less, more preferably 30% to 70% or less, and extremely preferably 40% to 60% or less. [Example]

[0071] Tires of Examples 1 to 10 were manufactured, each having a tire size of 195 / 65R15 91Q (specified by JATMA), a common tread pattern as shown in Fig. 1, and satisfying the conditions shown in Table 1. Note that the terms in Table 1 all correspond to the terms explained in this embodiment.

[0072] In response to this, a reference tire was produced, which had a tire size of 195 / 65R15 91Q, a tread pattern as shown in Fig. 7 (a diagram showing both sides in the tire width direction with the tire equatorial plane as the reference in a plan view of a conventional tire seen from the outside in the tire radial direction), and satisfied the various conditions shown in Table 1. Note that, among the reference symbols in Fig. 7, the same symbols as those in Fig. 1 indicate the same components as those shown in Fig. 1.

[0073] Next, each test tire (each invention example tire and reference example tire) was mounted on a 15x6.5J rim, and the front and rear tires were inflated to 250 kPa, and the tires were mounted on a vehicle with an engine displacement of 1200 cc. All test tires were evaluated for wet braking performance, braking performance on ice, acceleration performance on ice, wear resistance, and mold release properties according to the following procedures.

[0074] (Wet braking performance evaluation method) A vehicle equipped with each test tire was driven on an asphalt road sprayed with 1 mm of water, and the braking distance from an initial speed of 40 km / h was measured and the reciprocal of the measured value was calculated. Based on the calculation results, an index evaluation was performed with the reference example as the standard (100). The evaluation results are also shown in Table 1. The higher the index, the better the wet braking performance.

[0075] (Method for evaluating braking performance on ice) Using a vehicle fitted with each test tire, the braking distance was measured while driving at a speed of 20 km / h on an icy test course (skating rink), and the reciprocal of the measured value was calculated. Based on the calculated results, an index rating was then given, with the reference example being assigned a standard rating of 100. The evaluation results are also shown in Table 1. The higher the index, the better the braking performance on ice.

[0076] (Evaluation method for acceleration performance on ice) Using a vehicle fitted with each test tire, the time it took to reach a speed of 20 km / h from a standstill on an icy test course (skating rink) was measured, and the reciprocal of the measured value was calculated. Based on these calculation results, an index was then evaluated, with the reference example being assigned a standard value of 100. The evaluation results are also shown in Table 1. The higher the index, the better the acceleration performance on ice.

[0077] (Evaluation method for wear resistance) After a vehicle fitted with each test tire was driven 50,000 km on a dry road (paved road), the depth of so-called step wear on the edge of the land portion was measured and the reciprocal of the measured value was calculated. Based on the calculation results, an index evaluation was performed with the reference example set as the standard (100). The evaluation results are also shown in Table 1. The higher the index, the higher the wear resistance.

[0078] (Method for evaluating releasability from mold) When manufacturing each tire of the invention example, after the vulcanization process, the vulcanization mold was removed from the tire and the state of damage due to rubber chipping in the circumferential main groove 16, where the sipes formed in the land portion 22 shown in FIG. 1 communicate with the circumferential main groove 16, was visually observed. Similarly, when manufacturing a tire of the reference example, after the vulcanization process, the state of damage due to rubber chipping in the circumferential main groove 16, where the sipes formed in the land portion 52 shown in FIG. 7 communicate with the circumferential main groove 16, was visually observed when the vulcanization mold was removed from the tire. Note that these observations were performed on 10 tires of each type, and the average number of rubber chips was recorded. The reciprocal of this was calculated as an evaluation index. The evaluation results are also shown in Table 1. In this evaluation, a higher index indicates better wear resistance.

[0079] [Table 1]

[0080] According to Table 1, it can be seen that the tires of Invention Examples 1 to 10, which fall within the technical scope of the present invention (i.e., at least one sipe unit is formed in each of the second region R2, the third region R3, and the fourth region R4, and the edges of the land portions extending along the tire width direction are continuous without interruption), all have improved performance on ice in various conditions and also improved wear resistance without reducing wet performance compared to the reference tire, which does not fall within the technical scope of the present invention. [Explanation of symbols]

[0081] 10, 50 tires 12 Tread section 14 Tread surface 16 Circumferential main groove 18 Yokomizo 20 Center Land Section 22, 34, 52 (Second) Land Section 24 Shoulder Land Section 26 Pattern 28, 30, 32, 36, 38, 40 sipe units 28a, 28b, 30a, 30b, 32a, 32b, 36a, 36b, 38a, 38b, 40a, 40b Sipe CP tire equatorial plane Dc Circumferential direction of tire Dr Tire radial direction Dw Tire width direction D1, D2, D3, D4 Shortest distance around the tire El ground terminal wire E1, E2 edges R1 First Region R2 Second Region R3 The third region R4 The Fourth Region R5 The Fifth Region S1 Stepping side S2 kicking side X, Y circled part θ, θ1, θ2, θ3, θ4 angle

Claims

1. a sipe unit including two sipes inclined in opposite directions in the tire circumferential direction relative to the tire radial direction is formed in at least one of the land portions defined by the plurality of grooves; a leading-side end of the land portion in the tire circumferential direction is defined as a 0% position, and a trailing-side end of the land portion is defined as a 100% position, If the first region is from the 0% position to a position less than 5%, the second region is from the 5% position to a position less than 20%, the third region is from the 20% position to a position less than 80%, the fourth region is from the 80% position to a position less than 95%, and the fifth region is from the 95% position to the 100% position, At least one sipe unit is formed in each of the second region, the third region, and the fourth region, A tire characterized in that the edges of land portions extending along the tire width direction are present continuously without any breaks.

2. A tread surface position of the sipe in the tire radial direction is defined as a 0% depth position, and a bottom position of the sipe in the tire radial direction is defined as a 100% depth position, 2. The tire according to claim 1, wherein, when each of the sipe units is viewed from one side in the tire width direction, in the second region and the fourth region, the intersection position of the two sipes that constitute each sipe unit is at a depth position of more than 50% to 100% or less.

3. A tread surface position of the sipe in the tire radial direction is defined as a 0% depth position, and a bottom position of the sipe in the tire radial direction is defined as a 100% depth position, 3. The tire according to claim 1, wherein, when each of the sipe units is viewed from one side in the tire width direction, in the third region, the intersection position of the two sipes constituting each sipe unit is at a depth position ranging from a depth position exceeding 0% to a depth position of 50% or less.

4. 3. The tire according to claim 1, wherein, when each of the sipe units is seen from one side in the tire width direction, an absolute value of an inclination angle of the sipe to each side in the tire circumferential direction with respect to the tire radial direction is 1° or more and 10° or less.

5. The tire according to claim 4 , wherein the absolute values ​​of the inclination angles of the two sipes that make up the sipe unit are equal.

6. 3. The tire according to claim 1, wherein, when each of the sipe units is viewed from one side in the tire width direction, the shortest distance in the tire circumferential direction between the sipes in adjacent sipe units, the shortest distance in the tire circumferential direction from the sipe in the second region to a leading-side edge of a land portion extending along the tire width direction, and the shortest distance in the tire circumferential direction from the sipe in the fourth region to a trailing-side edge of a land portion extending along the tire width direction are 2.0 mm or more.

7. 3. The tire according to claim 1, wherein the depth of the sipe is 90% or less of the depth of the maximum groove.

8. The tire according to claim 1 or 2, wherein the sipe is any one of a flat sipe, a two-dimensional sipe, and a three-dimensional sipe.

9. The tire according to claim 1 or 2, wherein one end of the sipe in the tire width direction communicates with the groove, and the other end of the sipe in the tire width direction terminates within a land portion.

10. The tire according to claim 9 , wherein one end of the sipe in the tire width direction communicates with the groove only at an outer portion in the tire radial direction.

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