Tire

Abstract

The purpose of the invention is to optimize the arrangement of chamfered sipes and non-chamfered sipes and to improve wet braking performance and wet steering stability performance. In this tire 1, first and second middle land parts have a plurality of sipe units constituted of non-chamfered sipes and chamfered sipes. Among chamfered sipes located on both sides of the non-chamfered sipes in the tire circumferential direction, chamfered sipes closer to the non-chamfered sipes are designated as proximate chamfered sipes, and a combination of a non-chamfered sipe and a proximate chamfered sipe is a sipe unit. The rib width W1 of the first middle land part and the rib width W2 of the second middle land part have the relationship of W1 < W2, and the distance D1 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the first middle land part and the distance D2 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the second middle land part have the relationship of D1 < D2.

Description

Tire

[0001] The present invention relates to a tire.

[0002] A technique is known in which a sipe unit combining chamfered sipes and non-chamfered sipes is arranged to effectively improve wet (hereinafter referred to as WET) braking performance (for example, Patent Document 1, Patent Document 2).

[0003] Japanese Patent No. 7167840 Japanese Unexamined Patent Application Publication No. 2022-54336

[0004] However, due to, for example, sipe collapse due to insufficient rigidity of the tread surface, the WET braking performance and WET handling stability performance may be insufficient. The present disclosure has been made in view of the above, and an object thereof is to optimize the arrangement of chamfered sipes and non-chamfered sipes and improve the WET braking performance and WET handling stability performance.

[0005] In order to solve the above-described problems and achieve the object, a tire according to an aspect of the present disclosure includes one or more center main grooves, a pair of shoulder main grooves provided outside the center main groove in the tire width direction, and a pair of shoulder lands and first and second middle lands partitioned by these main grooves. The first and second middle lands have a plurality of chamfered sipes having a sipe portion and a chamfer portion and non-chamfered sipes having no chamfer portion. The chamfered sipes and the non-chamfered sipes are alternately arranged in the tire circumferential direction. The first and second middle lands have a plurality of sipe units composed of the non-chamfered sipes and the chamfered sipes. Among the chamfered sipes located on both sides in the tire circumferential direction of the non-chamfered sipes, the chamfered sipe closer to the non-chamfered sipe is defined as a proximity chamfered sipe. The combination of the non-chamfered sipe and the proximity chamfered sipe is the sipe unit. A rib width W1 of the first middle land and a rib width W2 of the second middle land have a relationship of W1 < W2. An interval D1 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the first middle land has a relationship of D1 < D2 with respect to an interval D2 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the second middle land.

[0006] According to this disclosure, by optimizing the arrangement of chamfered sipes and non-chamfered sipes, block rigidity can be strengthened, chamfering of the sipes can be suppressed, and wet braking performance and wet handling stability can be improved.

[0007] Figure 1 is a meridional cross-sectional view of the pneumatic tire according to this embodiment. Figure 2 is a plan view of the tread portion of the pneumatic tire according to this embodiment. Figure 3 is an enlarged view of a portion of the first middle ground portion in Figure 2. Figure 4 is an enlarged view of a portion of the second middle ground portion in Figure 2. Figure 5 is a schematic diagram showing the cross-section of section A-A in Figure 3. Figure 6 is a schematic diagram showing the cross-section of section A-A in Figure 3 in a ground contact state. Figure 7 is a diagram showing a modified example of the first middle ground portion. Figure 8 is a diagram showing a modified example of the second middle ground portion. Figure 9A is a chart showing the results of a performance test of the tire according to this embodiment. Figure 9B is a chart showing the results of a performance test of the tire according to this embodiment. Figure 9C is a chart showing the results of a performance test of the tire according to this embodiment. Figure 9D is a chart showing the results of a performance test of the tire according to this embodiment. Figure 9E is a chart showing the results of a performance test of the tire according to this embodiment. Figure 9F is a chart showing the results of a performance test of the tire according to this embodiment. Figure 9G is a chart showing the results of the tire performance test according to this embodiment. Figure 9H is a chart showing the results of the tire performance test according to this embodiment. Figure 9I is a chart showing the results of the tire performance test according to this embodiment. Figure 9J is a chart showing the results of the tire performance test according to this embodiment. Figure 9K is a chart showing the results of the tire performance test according to this embodiment.

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following descriptions of each embodiment, the same or equivalent components as those in other embodiments will be denoted by the same reference numerals, and their descriptions will be simplified or omitted. The present invention is not limited by each embodiment. Furthermore, the components of each embodiment include those that are easily substituted or substantially identical to those that a person skilled in the art can substitute. In addition, the configurations described below can be combined as appropriate. Furthermore, configurations can be omitted, substituted, or modified without departing from the spirit of the invention.

[0009] [Pneumatic Tire] In the following description, pneumatic tire 1 will be used as an example of a tire relating to the present disclosure. Pneumatic tire 1, which is an example of a tire relating to the present disclosure, can be filled with air, an inert gas such as nitrogen, or other gases.

[0010] Figure 1 is a meridional cross-sectional view of a pneumatic tire according to this embodiment. Figure 2 is a plan view of the tread portion of the pneumatic tire 1 according to this embodiment. The pneumatic tire 1 according to this embodiment has an annular structure centered on the tire rotation axis. Figure 1 shows one side region in the radial direction of the tire. Also, Figure 1 shows a passenger car radial tire as an example of a pneumatic tire.

[0011] In the following explanation, the tire radial direction refers to the direction perpendicular to the rotation axis (not shown) of the pneumatic tire 1. The inner side of the tire radial direction refers to the side toward the rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the rotation axis. The tire width direction refers to the direction parallel to the rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the rotation axis of the pneumatic tire 1 and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the tire width direction center line, which is the center position of the pneumatic tire 1 in the tire width direction. The tire equatorial line is a line that lies on the tire equatorial plane CL and runs along the circumferential direction of the pneumatic tire 1. In this embodiment, it is denoted by the same symbol "CL" as the tire equatorial plane.

[0012] As shown in Figure 1, the pneumatic tire 1 of this embodiment has a tread portion 2, shoulder portions 3 on both sides thereof, and sidewall portions 4 and bead portions 5 that are sequentially continuous from each shoulder portion 3. The pneumatic tire 1 also includes a carcass layer 6, a belt layer 7, and a belt reinforcement layer 8.

[0013] The tread portion 2 is made of rubber material (tread rubber) and is exposed at the outermost edge in the radial direction of the pneumatic tire 1, with its outer surface forming the outline of the pneumatic tire 1. The outer surface of the tread portion 2 is mainly the surface that can come into contact with the road surface when driving, and is configured as the contact surface 10.

[0014] The shoulder portion 3 is the outermost part of the tread portion 2 in the tire width direction. The sidewall portion 4 is the outermost exposed part in the tire width direction of the pneumatic tire 1. The bead portion 5 has a bead core 15 and a bead filler 16. The bead core 15 is formed by winding a bead wire, which is a steel wire, into a ring shape. The bead filler 16 is a rubber material placed in the space formed when the tire width direction end of the carcass layer 6 is folded back at the position of the bead core 15.

[0015] The carcass layer 6 is formed by folding each end in the tire width direction from the inside to the outside in the tire width direction by a pair of bead cores 15, and wrapping around the tire circumferentially in a toroidal shape to form the tire's skeleton. This carcass layer 6 consists of multiple carcass cords (not shown) arranged in parallel at an angle in the tire circumferential direction that aligns with the tire meridian, and these cords are covered with a coating rubber. The carcass cords are made of organic fibers such as polyester, rayon, or nylon. This carcass layer 6 is provided in at least one layer.

[0016] The belt layer 7 has a multilayer structure consisting of at least two belts 7a and 7b stacked together. It is positioned on the outer circumference of the carcass layer 6 in the tread portion 2, in the radial direction of the tire, and covers the carcass layer 6 in the circumferential direction of the tire. The belts 7a and 7b consist of multiple cords (not shown) arranged side by side at a predetermined angle (for example, 20° to 30°) with respect to the circumferential direction of the tire, which are covered with a coating rubber. The cords are made of, for example, steel or organic fibers such as polyester, rayon, or nylon. The overlapping belts 7a and 7b are arranged so that their cords intersect.

[0017] The belt reinforcement layer 8 is positioned on the outer circumference of the belt layer 7, in the tire radial direction, and covers the belt layer 7 in the tire circumferential direction. The belt reinforcement layer 8 consists of multiple cords (not shown) arranged in parallel in the tire width direction, substantially parallel to the tire circumferential direction, and covered with coated rubber. The cords are made of, for example, steel, or organic fibers such as polyester, rayon, or nylon, and the angle of the cords is within ±5° with respect to the tire circumferential direction. The belt reinforcement layer 8 shown in Figure 1 is positioned to cover the entire belt layer 7. The configuration of the belt reinforcement layer 8 is not limited to the above, and although not explicitly shown in the figure, it may be configured to cover only the tire width direction end of the belt layer 7, or it may have, for example, two reinforcement layers, where the inner reinforcement layer in the tire radial direction is formed to be larger in the tire width direction than the belt layer 7 and is positioned to cover the entire belt layer 7, and the outer reinforcement layer in the tire radial direction is positioned to cover only the tire width direction end of the belt layer 7, or it may have, for example, two reinforcement layers, where each reinforcement layer is positioned to cover only the tire width direction end of the belt layer 7. In other words, the belt reinforcement layer 8 overlaps at least the tire widthwise end of the belt layer 7. Furthermore, the belt reinforcement layer 8 is provided by, for example, wrapping a strip material with a width of about 10 mm around the tire in the circumferential direction.

[0018] The internal structure of the pneumatic tire 1 described above is a typical example, but the internal structure is not limited to this example.

[0019] The pneumatic tire 1 of this embodiment has a specified mounting direction relative to the vehicle. That is, when the pneumatic tire 1 of this embodiment is mounted on a vehicle, its orientation relative to the outside and inside of the vehicle is specified in the tire width direction. The orientation is not explicitly shown in the figure, but is indicated, for example, by an indicator provided on the sidewall portion 4. Therefore, when mounted on a vehicle, the side facing outwards becomes the outside of the vehicle, and the side facing inwards becomes the inside of the vehicle. Note that the designation of outside and inside of the vehicle is not limited to when mounted on a vehicle. For example, when assembled on a rim, the orientation of the rim relative to the outside and inside of the vehicle is determined in the tire width direction. Therefore, when the pneumatic tire 1 is assembled on a rim, its orientation relative to the outside and inside of the vehicle is specified in the tire width direction.

[0020] [Tread section] The contact surface 10 of the tread section 2 has four circumferential main grooves 20 that extend in the circumferential direction of the tire and are continuous around the entire circumference of the tire, arranged in the width direction of the tire.

[0021] The circumferential main groove 20 is a groove that is required to display a wear indicator as specified by JATMA, and has a groove width of 3.0 mm or more and a groove depth of 6.0 mm or more.

[0022] The groove width, sipe width, and tread width described below are measured as the maximum value of the dimension in the tire width direction at both groove opening ends that open to the contact surface 10, under no-load conditions (specified load = 0) with the pneumatic tire 1 mounted on a specified rim and filled with the specified internal pressure. In configurations where notches or chamfers are formed on the groove opening edge, the groove width is measured including the notches or chamfers, with the groove opening end being the outer edge of the notches or chamfers. The groove depth and sipe depth are measured as the maximum value of the dimension from the contact surface 10 to the bottom of the groove under no-load conditions (specified load = 0) with the pneumatic tire 1 mounted on a specified rim and filled with the specified internal pressure.

[0023] A specified rim refers to the "standard rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO. Furthermore, the specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. Finally, the specified load refers to the "maximum load capacity" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

[0024] The circumferential main grooves 20 are arranged in pairs on the outer side in the tire width direction, with the tire equatorial plane CL as the boundary. On the inside of the vehicle, the circumferential main grooves 20 closer to the tire equatorial plane CL are called the inner center main groove (also called the center main groove) 21, and the circumferential main grooves 20 on the inner side in the tire width direction of the inner center main groove 21 are called the inner shoulder main groove (also called the shoulder main groove) 23. On the outside of the vehicle, the circumferential main grooves 20 closer to the tire equatorial plane CL are called the outer center main groove (also called the center main groove) 22, and the circumferential main grooves 20 on the outer side in the tire width direction of the outer center main groove 22 are called the outer shoulder main groove (also called the shoulder main groove) 24. The center land area 31 is divided by the inner center main groove 21 and the outer center main groove 22. In other words, the tread portion 2 comprises one or more center main grooves, a pair of shoulder main grooves provided on the outer side of the center main groove in the tire width direction, a center land portion 31 partitioned by these main grooves, a first middle land portion 32, a second middle land portion 33, and a pair of shoulder land portions 34, 35.

[0025] In Figures 1 and 2, the symbol "T" indicates the tire contact point. The tire contact point T is defined as the position of the maximum width in the axial direction of the tire at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed perpendicular to the flat plate in a stationary state with a load corresponding to a specified load applied.

[0026] [Center Land Section] Referring to Figure 2, the center land section 31 is located at a position that crosses the tire equatorial plane CL. The center land section 31 has sipes 71. Multiple sipes 71 are provided periodically in the circumferential direction of the tire. The sipes 71 extend in the circumferential direction and the width direction of the tire. One end of the sipes 71 communicates with the center main groove 21. The other end of the sipes 71 terminates at the center land section 31 without communicating with any groove. The sipes 71 are notches formed in the tread surface and close when the tire makes contact with the ground. The same applies to each sipe or sipe section described later.

[0027] [Middle section] The first middle section 32 has a plurality of chamfered sipes 43 and non-chamfered sipes 42. The chamfered sipes 43 and non-chamfered sipes 42 are arranged alternately in the circumferential direction of the tire. The non-chamfered sipes 42 do not have a chamfered portion. The chamfered sipes 43 have a sipe portion 431 and a chamfered portion 430. The chamfered sipes 43 are configured such that the chamfered portion 430 is connected to the sipe portion 431.

[0028] Furthermore, the first middle section 32 has a shallow bottom section 41. The shallow bottom section 41 has a V-shape with its top 410 facing in the circumferential direction of the tire. The shallow bottom section 41 of the first middle section 32 is connected to the non-chamfered sipe 42.

[0029] In the first middle section 32, a sipe unit 40 is defined, consisting of a non-chamfered sipe 42 and a chamfered sipe 43. Of the chamfered sipes 43 located on both sides of the non-chamfered sipe 42 in the tire circumferential direction, the chamfered sipe 43 closer to the non-chamfered sipe 42 is defined as the adjacent chamfered sipe, and the combination of the non-chamfered sipe 42 and the adjacent chamfered sipe constitutes the sipe unit 40. The first middle section 32 has multiple sipe units 40. Multiple sipe units 40 are provided in the tire circumferential direction in the first middle section 32.

[0030] The second middle section 33 has multiple chamfered sipes 53 and non-chamfered sipes 52. The chamfered sipes 53 and non-chamfered sipes 52 are arranged alternately in the circumferential direction of the tire. The non-chamfered sipes 52 do not have a chamfered portion. The chamfered sipes 53 have a sipe portion 531 and a chamfered portion 530. The chamfered sipes 53 are configured such that the chamfered portion 530 is connected to the sipe portion 531.

[0031] Furthermore, the second middle section 33 has a shallow bottom 51. The shallow bottom 51 has a V-shape with its top 510 facing in the circumferential direction of the tire. The shallow bottom 51 of the second middle section 33 is connected to the non-chamfered sipe 52.

[0032] In the second middle section 33, a sipe unit 50 is defined, consisting of a non-chamfered sipe 52 and a chamfered sipe 53. Of the chamfered sipes 53 located on both sides of the non-chamfered sipe 52 in the tire circumferential direction, the chamfered sipe 53 closer to the non-chamfered sipe 52 is defined as the adjacent chamfered sipe, and the combination of the non-chamfered sipe 52 and the adjacent chamfered sipe constitutes the sipe unit 50. The second middle section 33 has multiple sipe units 50. Multiple sipe units 50 are provided in the second middle section 33 in the tire circumferential direction.

[0033] [Shoulder Land Section] The shoulder land section 34 is provided on the outer side in the tire width direction of the first middle land section 32. The shoulder land section 34 has lug grooves 61, sipes 62, and circumferential narrow grooves 63. The lug grooves 61 extend from inside the tire contact end T of the shoulder land section 34 outward in the tire width direction and terminate outside the tire contact end T. Multiple lug grooves 61 are provided in the tire circumferential direction. The sipes 62 extend from inside the tire contact end T of the shoulder land section 34 inward in the tire width direction and communicate with the shoulder main groove 23. Multiple sipes 62 are provided in the tire circumferential direction. The circumferential narrow grooves 63 extend in the tire circumferential direction within the shoulder land section 34, intersecting each lug groove 61 and each sipe 62.

[0034] The shoulder portion 35 is provided on the outer side in the tire width direction of the second middle portion 33. The shoulder portion 35 has lug grooves 64 and sipes 65. The lug grooves 64 extend from inside the tire contact end T of the shoulder portion 35 outward in the tire width direction and terminate outside the tire contact end T. Multiple lug grooves 64 are provided in the tire circumferential direction. The sipes 65 extend from inside the tire contact end T of the shoulder portion 35 inward in the tire width direction and communicate with the shoulder main groove 24. Multiple sipes 65 are provided in the tire circumferential direction.

[0035] Here, let W1 be the rib width (land width) of the first middle land section 32. Let W2 be the rib width (land width) of the second middle land section 33. In this case, the relationship W1 < W2 exists between the rib widths W1 and W2.

[0036] Furthermore, the distance between the non-chamfered sipe 42 and the chamfered sipe 43 of the sipe unit 40 in the first middle land section 32 is denoted as D1. The distance D1 is the distance along the tire circumferential direction between the center position of the opening of the non-chamfered sipe 42 into the shoulder main groove 23 and the center position of the opening of the sipe portion 431 of the chamfered sipe 43 into the shoulder main groove 23. The distance between the non-chamfered sipe 52 and the chamfered sipe 53 of the sipe unit 50 in the second middle land section 33 is denoted as D2. The distance D2 is the distance along the tire circumferential direction between the center position of the opening of the non-chamfered sipe 52 into the shoulder main groove 24 and the center position of the opening of the sipe portion 531 of the chamfered sipe 53 into the shoulder main groove 24. In this case, the relationship between the distance D1 and the distance D2 is D1 < D2.

[0037] In the land area with a narrow rib width (first middle land area 32), the block rigidity is lower, so the distance between sipes (spacing D1) of the sipe unit 40 is narrowed to secure the land area length between the sipe units 40 and increase the block rigidity. On the other hand, in the land area with a wide rib width (second middle land area 33), the block rigidity is higher, so the distance between sipes (spacing D2) of the sipe unit 50 is widened to shorten the land area length between the sipe units 50 and decrease the block rigidity. In this way, the block rigidity can be made uniform throughout the entire pattern of the tread section 2. By doing so, the effect of improving wet braking performance by adopting sipe units can be maintained while improving dry (hereinafter, DRY) handling stability and wet handling stability (hereinafter, sometimes referred to as DRY / WET handling stability). Note that if W1 < W2 and D1 > D2, the rigidity balance of the pattern becomes inappropriate, which may lead to a decrease in DRY / WET handling stability and is therefore undesirable.

[0038] The ratio W2 / W1 of the rib width W2 of the second middle land section 33 to the rib width W1 of the first middle land section 32 is preferably 1.1 or more and 1.6 or less. This range is optimal for maintaining the overall rigidity balance of the pattern. If the ratio W2 / W1 is greater than 1.6, the difference in rib rigidity becomes too large, resulting in insufficient improvement of dry / wet handling stability, which is undesirable. If the ratio W2 / W1 is less than 1.1, the effect of changing the rib width (i.e., changing the distance between sipes) becomes insufficient, which is undesirable. More preferably, the ratio W2 / W1 is 1.2 or more and 1.4 or less.

[0039] The ratio of the spacing D2 to the spacing D1, D2 / D1, is preferably between 1.2 and 2.0. This range is optimal for achieving the effect of improving wet performance through the close-proximity chamfered sipes and improving handling stability. If the ratio D2 / D1 is greater than 2.0, the distance between the sipes becomes too great, resulting in insufficient improvement in wet braking performance, which is undesirable. If the ratio D2 / D1 is less than 1.2, the effect of changing the distance between the sipes (changing the rib width) becomes insufficient, which is undesirable. More preferably, the ratio D2 / D1 is between 1.3 and 1.6.

[0040] Preferably, the ratio D1 / W1 of the spacing D1 to the rib width W1 is 0.2 or more and 0.8 or less, and the ratio D2 / W2 of the spacing D2 to the rib width W2 is 0.2 or more and 0.8 or less. The above range is optimal for exhibiting the effect of improving wet performance by closely spaced chamfered sipes and improving handling stability. If the ratio D1 / W1 and ratio D2 / W2 are less than 0.2, the distance between sipes is too narrow relative to the rib width, resulting in insufficient improvement of dry / wet handling stability, which is undesirable. If the ratio D1 / W1 and ratio D2 / W2 are greater than 0.8, the distance between sipes is too wide relative to the rib width, resulting in insufficient improvement of wet braking performance, which is undesirable. Furthermore, it is more preferable that the ratio D1 / W1 and ratio D2 / W2 are 0.3 or more and 0.6 or less.

[0041] It is preferable that the inclination angle θ1 of the chamfered sipe 43 of the sipe unit 40 in the first middle land section 32 with respect to the tire circumferential direction and the inclination angle θ2 of the chamfered sipe 53 of the sipe unit 50 in the second middle land section 33 have the relationship θ1 > θ2. By adjusting the inclination angle of the sipes in addition to the distance between the sipes, it becomes possible to achieve a higher level of balance between wet performance and handling stability. If the relationship of the inclination angles is θ1 ≤ θ2, the effect of improving dry / wet handling stability performance will be insufficient, which is undesirable. Note that the inclination angle θ1 only needs to be greater than the inclination angle θ2, and the inclination angle θ1 may be 90 [deg].

[0042] The inclination angles θ1 and θ2 are preferably between 30 degrees and 80 degrees. By setting the inclination angles of the chamfered sipes 43 and 53 within the above range, the effect of improving wet braking performance can be enhanced. If the inclination angles of the chamfered sipes 43 and 53 are less than 30 degrees or greater than 80 degrees, the effect of improving wet braking performance will be insufficient, which is undesirable. Furthermore, for inclination angles θ1 and θ2, it is more preferable that they be between 40 degrees and 75 degrees.

[0043] The difference θ1 - θ2 between the inclination angle θ1 and the inclination angle θ2 is preferably 5 [deg] or more and 35 [deg] or less. By setting the difference in the sipe inclination angle within the above range, it is possible to achieve both excellent WET braking performance and improved DRY / WET handling stability. If the difference θ1 - θ2 between the inclination angle θ1 and the inclination angle θ2 is less than 5 [deg] or greater than 35 [deg], the effect of improving DRY / WET handling stability becomes insufficient, which is not preferable. Regarding the difference θ1 - θ2 between the inclination angle θ1 and the inclination angle θ2, more preferably, it is 10 [deg] or more and 30 [deg] or less.

[0044] The difference θ1 - θ1' between the inclination angle θ1' of the non-chamfered sipe 42 of the sipe unit 40 in the first middle land portion 32 and the inclination angle θ1 has a relationship of -10 [deg] ≤ θ1 - θ1' ≤ 10 [deg], and the difference θ2 - θ2' between the inclination angle θ2' of the non-chamfered sipe 52 of the sipe unit 50 in the second middle land portion 33 and the inclination angle θ2 has a relationship of -10 [deg] ≤ θ2 - θ2' ≤ 10 [deg]. That is, it is preferable that the chamfered sipe 43 and the non-chamfered sipe 42 of the sipe unit 40 are substantially parallel, and the chamfered sipe 53 and the non-chamfered sipe 52 of the sipe unit 50 are substantially parallel. When both are substantially parallel, the effect of improving WET braking performance can be enhanced. If the difference θ1 - θ1' or the difference θ2 - θ2' of the inclination angle is less than -10 [deg] or greater than 10 [deg], the effect of improving WET braking performance becomes insufficient, which is not preferable. Regarding the difference θ1 - θ1' and the difference θ2 - θ2' of the inclination angle, more preferably, it is -5 [deg] or more and 5 [deg] or less.

[0045] In Figure 2, let X1 be the tire width extension distance of the sipe portion 431 of the chamfered sipe 43 in the first middle land section 32. Preferably, the ratio X1 / W1 of distance X1 to rib width W1 has the relationship 0.40 ≤ X1 / W1 ≤ 0.90. Also, let X2 be the tire width extension distance of the sipe portion 531 of the chamfered sipe 53 in the second middle land section 33. Preferably, the ratio X2 / W2 of distance X2 to rib width W2 has the relationship 0.40 ≤ X2 / W2 ≤ 0.90. By setting the tire width extension distance of the sipe within the above range, the effect of improving wet braking performance can be enhanced. If the ratio X1 / W1 or ratio X2 / W2 is less than 0.4, the effect of improving wet braking performance will be insufficient, and if it is greater than 0.9, the effect of improving dry handling stability will be insufficient, which is undesirable. Furthermore, the ratio X1 / W1 or ratio X2 / W2 is more preferably 0.45 or more and 0.55 or less.

[0046] In Figure 2, it is preferable that the first middle section 32 is located on the inside of the vehicle mounting and the second middle section 33 is located on the outside of the vehicle mounting. By having a larger rib width (smaller main groove width) on the outside of the vehicle mounting and a smaller rib width (larger main groove width) on the inside of the vehicle mounting, it becomes possible to achieve a higher level of balance between dry handling stability and wet braking performance.

[0047] Here, Figure 3 is an enlarged view showing a portion of the first middle land section 32 in Figure 2. Figure 4 is an enlarged view showing a portion of the second middle land section 33 in Figure 2. Referring to Figures 2 and 3, as described above, the chamfered sipe 43 includes a sipe portion 431 and a chamfered portion 430. The chamfered portion 430 is provided only on the edge on the non-chamfered sipe 42 side of the edges on both sides of the sipe portion 431 that are perpendicular to the longitudinal direction. That is, the chamfered portion 430 is provided on the edge on the side closer to the non-chamfered sipe 42 of the edges on both sides of the sipe portion 431, and the chamfered portion is not provided on the edge on the side farther from the non-chamfered sipe 42.

[0048] FIG. 5 is a diagram schematically showing a cross-section of the A-A portion in FIG. 3. Referring to FIG. 5, a chamfered sipe 43 is provided adjacent to the non-chamfered sipe 42. The chamfered sipe 43 has a sipe portion 431 and a chamfered portion 430. The chamfered portion 430 is provided on the edge 431a closer to the non-chamfered sipe 42 among the edges on both sides of the sipe portion 431, and no chamfered portion is provided on the edge 431b farther from the non-chamfered sipe 42.

[0049] FIG. 6 is a diagram schematically showing a cross-section in the grounded state of the A-A portion in FIG. 3. Regarding the non-chamfered sipe 42, as indicated by reference numeral 42a in FIG. 6, the opening is crushed and closed when the tire is grounded. In contrast, since the chamfered sipe 43 has a chamfered portion 430, it does not close when the tire is grounded. Therefore, the drainage performance can be maintained. Thus, by providing the chamfered portion 430 only on the side closer to the non-chamfered sipe 43 in the chamfered sipe 43, the WET braking performance can be effectively enhanced.

[0050] Similarly, referring to FIGS. 2 and 4, the chamfered sipe 53 includes a sipe portion 531 and a chamfered portion 530. Among the edges on both sides orthogonal to the longitudinal direction of the sipe portion 531, the chamfered portion 530 is provided only on the edge on the non-chamfered sipe 52 side. That is, the chamfered portion 530 is provided on the edge closer to the non-chamfered sipe 52 among the edges on both sides of the sipe portion 531, and no chamfered portion is provided on the edge farther from the non-chamfered sipe 52. By providing the chamfered portion only on the non-chamfered sipe side in the chamfered sipe 53, the WET braking performance can be effectively enhanced.

[0051] Also, in FIG. 3, let the maximum width of the sipe portion 431 of the chamfered sipe 43 be Zs1, and the maximum width of the chamfered sipe 43 be Zm1. The ratio Zm1 / Zs1 of the maximum width Zm1 to the maximum width Zs1 satisfies the condition of 2.00 ≤ Zm1 / Zs1 ≤ 6.00, and it is preferable that the maximum width Zs1 satisfies the condition of 0.5 [mm] ≤ Zs1 ≤ 1.5 [mm].

[0052] Similarly, in Figure 4, the maximum width of the sipe portion 531 of the chamfered sipe 53 is denoted as Zs2, and the maximum width of the chamfered sipe 53 is denoted as Zm2. The ratio of the maximum width Zm2 to the maximum width Zs2, Zm2 / Zs2, satisfies the condition 2.00 ≤ Zm2 / Zs2 ≤ 6.00, and it is preferable that the maximum width Zs2 satisfies the condition 0.5 [mm] ≤ Zs2 ≤ 1.5 [mm].

[0053] The above relationship is preferable in order to improve drainage performance at the chamfered sipes 43 and 53. If the maximum width Zs1 is less than 0.5 [mm], the effect of improving drainage performance will be insufficient and undesirable. If the maximum width Zs1 is greater than 1.5 [mm], the effect of improving dry handling stability will be insufficient and undesirable. Furthermore, it is preferable that the ratio Zm1 / Zs1 satisfies the condition 2.00 ≤ Zm1 / Zs1 ≤ 4.00, and that the maximum width Zs1 is 0.5 [mm] ≤ Zs1 ≤ 1.0 [mm].

[0054] Furthermore, in Figure 3, the ratio Za1 / Zs1 of the distance Za1 from the non-chamfered sipe 42 to the sipe portion 431 of the chamfered sipe 43 in the sipe unit 40 to the maximum width Zs1 of the sipe portion 431 of the chamfered sipe 43 is preferably Za1 / Zs1 ≤ 30. If the ratio Za1 / Zs1 is greater than 30, the effect of improving wet braking performance will be insufficient, which is undesirable. It is more preferable that the ratio Za1 / Zs1 ≤ 20. It is preferable to satisfy the above relationship in order to improve drainage performance by proximity sipes.

[0055] Regarding the distance Zb1 from the non-chamfered sipe 42 to the end of the chamfered portion 430 of the chamfered sipe 43, it is preferable that the condition Zb1 ≥ 3.0 [mm] is satisfied. It is preferable to satisfy the above relationship in order to improve drainage performance by the proximity of the sipes. If the distance Zb1 is less than 3.0 [mm], the effect of improving wet braking performance will be insufficient and it is undesirable. Regarding the distance Zb1, it is preferable that 20.0 [mm] ≥ Zb1 is satisfied. If the distance Zb1 is greater than 20.0 [mm], the effect of the sipe unit will not be obtained and it is undesirable. Regarding the distance Zb1, it is preferable that 20.0 [mm] ≥ Zb1 ≥ 3.0 [mm] is satisfied, and it is more preferable that 15.0 [mm] ≥ Zb1 ≥ 5.0 [mm] is satisfied.

[0056] Similarly, in Figure 4, the ratio Za2 / Zs2 of the distance Za2 from the non-chamfered sipe 52 to the sipe portion 531 of the chamfered sipe 53 in the sipe unit 50 to the maximum width Zs2 of the sipe portion 531 of the chamfered sipe 53 is preferably Za2 / Zs2 ≤ 30. If the ratio Za2 / Zs2 is greater than 30, the effect of improving wet braking performance will be insufficient, which is undesirable. More preferably, the ratio Za2 / Zs2 ≤ 20. It is preferable to satisfy the above relationship in order to improve drainage performance by proximity sipes.

[0057] Regarding the distance Zb2 from the non-chamfered sipe 52 to the end of the chamfered portion 530 of the chamfered sipe 53, it is preferable that the condition Zb2 ≥ 3.0 [mm] is satisfied. It is preferable to satisfy the above relationship in order to improve drainage performance by the proximity of the sipes. If the distance Zb2 is less than 3.0 [mm], the effect of improving wet braking performance will be insufficient, which is undesirable. Regarding the distance Zb2, it is preferable that 20.0 [mm] ≥ Zb2 is satisfied. If the distance Zb2 is greater than 20.0 [mm], the effect of the sipe unit will not be obtained, which is undesirable. Regarding the distance Zb2, it is preferable that 20.0 [mm] ≥ Zb2 ≥ 3.0 [mm] is satisfied, and it is more preferable that 15.0 [mm] ≥ Zb2 ≥ 5.0 [mm] is satisfied.

[0058] In this disclosure, distances Za1 and Za2 may be collectively referred to as "distance Za." In this disclosure, distances Zb1 and Zb2 may be collectively referred to as "distance Zb." In this disclosure, maximum widths Zm1 and Zm2 may be collectively referred to as "maximum width Zm." In this disclosure, maximum widths Zs1 and Zs2 may be collectively referred to as "maximum width Zs."

[0059] Referring to Figure 3, and focusing on the non-chamfered sipes 42 of the sipe unit 40, a single non-chamfered sipe 42 is positioned between a pair of adjacent chamfered sipes 43a and 43b in the circumferential direction of the tire. Of the pair of chamfered sipes 43a and 43b, we define the adjacent chamfered sipe 43a, which is positioned close to the non-chamfered sipe 42, and the distant chamfered sipe 43b, which is positioned farther from the non-chamfered sipe 42. For the sake of explanation, the groove width of the distant chamfered sipe 43b is depicted wider to make the center line clearer. In reality, the groove width of the distant chamfered sipe 43b is equivalent to the groove width of the other sipes. In the first middle ground section 32, it is preferable that the ratio Dbmax1 of the maximum value of the circumferential distance Db from the center line of the sipe portion 431 of the distant chamfered sipe 43b to the center line of the non-chamfered sipe 42, with respect to the maximum value of the circumferential distance Da from the center line of the sipe portion 43a of the nearby chamfered sipe 43a to the center line of the non-chamfered sipe 42, is in the range of 1.50 ≤ Dbmax1 / Damax1 ≤ 4.00. This range is appropriate for improving wet braking performance. If the ratio Dbmax1 / Damax1 is less than 1.50, the improvement effect on dry and wet handling stability performance will be insufficient and undesirable. If the ratio Dbmax1 / Damax1 is greater than 4.00, the improvement effect on wet braking performance will be insufficient and undesirable.

[0060] Referring to Figure 4, and focusing on the non-chamfered sipes 52 of the sipe unit 50, a single non-chamfered sipe 52 is positioned between a pair of adjacent chamfered sipes 53a and 53b in the circumferential direction of the tire. Of the pair of chamfered sipes 53a and 53b, we define the adjacent chamfered sipe 53a, which is positioned close to the non-chamfered sipe 52, and the distant chamfered sipe 53b, which is positioned farther from the non-chamfered sipe 52. For the sake of explanation, the groove width of the distant chamfered sipe 53b is depicted wider to make the center line clearer. In reality, the groove width of the distant chamfered sipe 53b is equivalent to the groove width of the other sipes. In the second middle ground section 33, it is preferable that the ratio Dbmax2 of the maximum value of the tire circumferential distance Db from the center line of the sipe portion 531 of the distant chamfered sipe 53b to the center line of the non-chamfered sipe 52, with respect to the maximum value of the tire circumferential distance Da from the center line of the sipe portion 431 of the nearby chamfered sipe 53a to the center line of the non-chamfered sipe 52, is in the range of 1.20 ≤ Dbmax2 / Damax2 ≤ 3.00. The above range is appropriate for improving wet braking performance. If the ratio Dbmax2 / Damax2 is less than 1.20, the effect of improving dry and wet handling stability performance will be insufficient and is undesirable. If the ratio Dbmax2 / Damax2 is greater than 3.00, the effect of improving wet braking performance will be insufficient and is undesirable.

[0061] The groove width of the non-chamfered sipes 42 and 52 is preferably 0.5 mm or more and 1.5 mm or less. The groove depth of the non-chamfered sipes 42 and 52 is preferably 2.0 mm or more and less than or equal to the maximum groove depth of the circumferential main groove 20. The above dimensional range is preferred in order to enhance the effect of improving wet braking performance and dry steering stability performance. If the maximum width of the non-chamfered sipes 42 and 52 is less than 0.5 mm and the maximum groove depth is less than 2.0 mm, the drainage performance will be insufficient and this is undesirable. If the maximum width of the non-chamfered sipes 42 and 52 is greater than 1.5 mm and the maximum groove depth is deeper than the circumferential main groove 20, the effect of improving dry steering stability performance will be insufficient and this is undesirable. More preferably, the maximum width of the non-chamfered sipes 42 and 52 is 0.5 mm or more and 1.0 mm or less, and the maximum groove depth is 3.0 mm or more and 6.0 mm or less. The same applies to the sipe portion 431 of the chamfered sipe 43 and the sipe portion 531 of the chamfered sipe 53.

[0062] Referring to Figure 2, the chamfered sipes 43 and non-chamfered sipes 42 in each of the multiple sipe units 40 of the first middle land section 32 communicate with the shoulder main groove 23. In other words, the chamfered sipes 43 and non-chamfered sipes 42 communicate with the same shoulder main groove 23, rather than being arranged in a staggered pattern that alternately communicates with different main grooves. Similarly, the chamfered sipes 53 and non-chamfered sipes 52 in each of the multiple sipe units 50 of the second middle land section 33 communicate with the shoulder main groove 24. In other words, the chamfered sipes 53 and non-chamfered sipes 52 communicate with the same shoulder main groove 24, rather than being arranged in a staggered pattern that alternately communicates with different main grooves. By arranging each sipe to communicate with one end of the same rib in this way, it becomes possible to achieve a higher level of both dry and wet handling stability.

[0063] Referring to Figure 2, the chamfered sipes 43 and non-chamfered sipes 42 in each of the multiple sipe units 40 of the first middle land section 32 communicate with the shoulder main groove 23, which is the outer main groove in the tire width direction, rather than the inner main groove in the tire width direction. That is, the chamfered sipes 43 and non-chamfered sipes 42 communicate with the shoulder main groove 23, which is the outer main groove, rather than in a staggered arrangement where they alternately communicate with the inner and outer main grooves in the tire width direction. Similarly, the chamfered sipes 53 and non-chamfered sipes 52 in each of the multiple sipe units 50 of the second middle land section 33 communicate with the shoulder main groove 24, which is the outer main groove in the tire width direction, rather than the inner main groove in the tire width direction. That is, the chamfered sipes 53 and non-chamfered sipes 52 communicate with the shoulder main groove 24, which is the outer main groove, rather than in a staggered arrangement where they alternately communicate with the inner and outer main grooves in the tire width direction. In this way, each sipe communicates with the outer main groove adjacent to the land section, making it possible to further improve dry and wet handling stability.

[0064] Referring to Figure 2, each shallow bottom portion 41 of the first middle land portion 32 is arranged so that the V-shaped tops 410 of each shallow bottom portion 41 are facing the same direction in the tire circumferential direction. Similarly, each shallow bottom portion 51 of the second middle land portion 33 is arranged so that the V-shaped tops 510 of each shallow bottom portion 51 are facing the same direction in the tire circumferential direction. The V-shaped tops 410 of each shallow bottom portion 41 of the first middle land portion 32 and the V-shaped tops 510 of each shallow bottom portion 51 of the second middle land portion 33 are arranged so that they are facing opposite directions in the tire circumferential direction. That is, the tops 410 face upwards in Figure 2, and the tops 510 face downwards in Figure 2. Within the first middle land portion 32, the tops 410 of adjacent shallow bottom portions 41 in the circumferential direction are not arranged so that they are facing the same direction alternately, but rather so that they are facing the same direction. Within the second middle land section 33, the tops 510 of adjacent shallow bottom sections 51 in the circumferential direction are not arranged alternately in opposite directions, but rather in the same direction in the circumferential direction. Furthermore, the tops 410 of the shallow bottom section 41 in the first middle land section 32 and the tops 510 of the shallow bottom section 51 in the second middle land section 33 are not in the same direction in the circumferential direction, but are in opposite directions. By arranging the V-shaped shallow grooves in this way, the rigidity of the first middle land section 32 and the second middle land section 33 is ensured, and deformation of each land section can be suppressed. This contributes to improving the dry and wet handling stability performance.

[0065] [Modifications] Figure 7 shows a modified version of the first middle-distance track and field section. Figure 8 shows a modified version of the second middle-distance track and field section.

[0066] Referring to Figure 7, the first middle land section 32a has a closing groove 44 provided in the direction of extension of the chamfered sipe. The closing groove 44 has approximately the same width as the chamfered portion 430 of the chamfered sipe 43. The closing groove 44 is not connected to the chamfered sipe 43 and is independent.

[0067] Referring to Figure 8, the second middle land section 33a has a closure groove 54 provided in the direction of extension of the chamfered sipe. The closure groove 54 has approximately the same width as the chamfered portion 530 of the chamfered sipe 53. The closure groove 54 is not connected to the chamfered sipe 53 and is independent.

[0068] By providing occluding grooves 44 and 54 at the sipe ends where stress is concentrated during rolling, stress concentration can be mitigated and crack propagation can be suppressed. In other words, even if cracks occur, they can be terminated at the occluding grooves 44 and 54, thereby suppressing crack propagation. Furthermore, by using independent, short, and shallow occluding grooves, a decrease in tread rigidity can be prevented, thus preventing a decrease in dry performance.

[0069] Furthermore, it is also possible to provide only one of the blocking grooves, instead of both the blocking groove 44 in the first middle land section 32a and the blocking groove 54 in the second middle land section 33a. In the middle land sections provided with blocking grooves 44 and 54, as described above, stress concentration can be alleviated and crack propagation can be suppressed.

[0070] [Example] Figures 9A to 9K are diagrams showing the results of performance tests of the tire according to this embodiment. In this performance test, wet braking performance, wet handling stability performance, dry handling stability performance, and crack propagation resistance performance were evaluated for multiple types of test tires. A test tire with tire size 215 / 55R17 98W 17×7J was mounted on a JATMA-specified rim, and the JATMA-specified internal pressure and load were applied to this test tire. The test tire was also mounted on all wheels of a passenger car, which was the test vehicle.

[0071] (1) The evaluation of wet braking performance involves the test vehicle driving on an asphalt road that has been sprayed with water to a depth of 1 mm, and measuring the braking distance from an initial speed of 80 km / h. Based on the measurement results, an index evaluation is performed with Comparative Example 1 as the baseline (100). In terms of evaluation, a higher numerical value is preferable.

[0072] (2) The evaluation of wet handling stability performance involves the test vehicle driving on a wet test course, and a professional test driver performing a subjective evaluation of lane change performance, cornering performance, etc. This evaluation is performed using an index evaluation with Comparative Example 1 as the baseline (100). A higher numerical value is preferable.

[0073] (3) The evaluation of dry handling stability performance involves the test vehicle driving on a dry test course, and a professional test driver performing a subjective evaluation of lane change performance, cornering performance, etc. This evaluation is performed using an index evaluation with Comparative Example 1 as the baseline (100). A higher numerical value is preferable.

[0074] (4) The evaluation of crack propagation resistance was conducted by investigating cracks during a 30,000 km road test. The conventional example was used as the baseline (100), and the crack occurrence rate and crack growth rate were expressed as an index. A higher value is preferable.

[0075] The test tires of each embodiment have the configuration shown in Figures 1 and 2. The conventional tire is a tire without sipe units. The tire of Comparative Example 1 has sipe units, and the rib width W1 of the first middle section and the rib width W2 of the second middle section are equal. The tires of Comparative Examples 2 and 3 have sipe units, and the rib width W2 of the second middle section is larger than the rib width W1 of the first middle section.

[0076] As the test results show, the test tires for each embodiment showed good results in terms of wet braking performance, wet handling stability performance, dry handling stability performance, and crack propagation resistance.

[0077] This disclosure encompasses the following inventions: [1] A tire comprising one or more center main grooves, a pair of shoulder main grooves provided on the outer side of the center main groove in the tire width direction, a pair of shoulder land portions and first and second middle land portions partitioned by these main grooves, wherein the first and second middle land portions have a plurality of chamfered sipes having a sipe portion and a chamfered portion, and non-chamfered sipes not having a chamfered portion, the chamfered sipes and the non-chamfered sipes are arranged alternately in the circumferential direction of the tire, the first and second middle land portions have a plurality of sipe units composed of the non-chamfered sipes and the chamfered sipes, the chamfered sipes located on both sides of the non-chamfered sipe in the circumferential direction of the tire that are closer to the non-chamfered sipe are designated as proximity chamfered sipes, and the combination of the non-chamfered sipe and the proximity chamfered sipe constitutes the sipe unit. A tire in which the rib width W1 of the first middle land section and the rib width W2 of the second middle land section have the relationship W1 < W2, and the distance D1 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the first middle land section has the relationship D1 < D2 with respect to the distance D2 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the second middle land section. [2] The tire according to [1], wherein the distance Zb from the non-chamfered sipe to the end of the chamfered portion of the chamfered sipe is 20.0 [mm] or less. [3] The tire according to [1] or [2], wherein the ratio W2 / W1 of the rib width W2 to the rib width W1 is 1.1 or more and 1.6 or less. [4] The tire according to any one of [1] to [3], wherein the ratio D2 / D1 of the interval D2 to the interval D1 is 1.2 or more and 2.0 or less. [5] The tire according to any one of [1] to [4], wherein the ratio D1 / W1 of the spacing D1 to the rib width W1 is 0.2 or more and 0.8 or less, and the ratio D2 / W2 of the spacing D2 to the rib width W2 is 0.2 or more and 0.8 or less.[6] A tire according to any one of [1] to [5], wherein the inclination angle θ1 of the chamfered sipe of the sipe unit in the first middle land section with respect to the tire circumferential direction and the inclination angle θ2 of the chamfered sipe of the sipe unit in the second middle land section with respect to the tire circumferential direction are in the relationship θ1 > θ2. [7] A tire according to [6], wherein the inclination angles θ1 and θ2 are 30 [deg] or more and 80 [deg] or less. [8] A tire according to [6], wherein the difference θ1 - θ2 between the inclination angle θ1 and the inclination angle θ2 is 5 [deg] or more and 35 [deg] or less. [9] The tire according to [6], wherein the inclination angle θ1' of the non-chamfered sipe of the sipe unit in the first middle land portion has a relationship of -10 [deg] ≤ θ1 - θ1' ≤ 10 [deg] with respect to the tire circumferential direction and the inclination angle θ2' of the non-chamfered sipe of the sipe unit in the second middle land portion has a relationship of -10 [deg] ≤ θ2 - θ2' ≤ 10 [deg].

[10] The tire according to any one of [1] to [9], wherein the ratio X1 / W1 of the tire width extension distance X1 of the chamfered sipe in the first middle land portion to the rib width W1 is 0.40 ≤ X1 / W1 ≤ 0.90, and the ratio X2 / W2 of the tire width extension distance X2 of the chamfered sipe in the second middle land portion to W2 is 0.40 ≤ X2 / W2 ≤ 0.90.

[11] The tire according to any one of [1] to

[10] , wherein the first middle land portion is located on the inside of the vehicle mounting.

[12] The tire according to any one of [1] to

[11] , wherein the chamfered sipe includes a sipe portion and a chamfered portion, and the chamfered portion is provided only on the edge on the non-chamfered sipe side of the edges on both sides of the sipe portion.

[13] A tire according to any one of [1] to

[12] , wherein the ratio Zm / Zs of the maximum width of the chamfered sipe to the maximum width Zs of the sipe portion of the chamfered sipe satisfies the condition 2.00 ≤ Zm / Zs ≤ 6.00, and the maximum width Zs satisfies the condition 0.5 [mm] ≤ Zs ≤ 1.5 [mm].

[14] A tire according to any one of [1] to

[13] , wherein the ratio Za / Zs of the distance Za from a non-chamfered sipe to the sipe portion of the chamfered sipe in the sipe unit to the maximum width Zs of the sipe portion of the chamfered sipe is Za / Zs ≤ 30, and the distance Zb from the non-chamfered sipe to the end of the chamfered portion of the chamfered sipe is Zb ≥ 3.0 [mm].

[15] A single non-chamfered sipe is positioned between a pair of adjacent chamfered sipes in the circumferential direction of the tire, and a close chamfered sipe is defined as the pair of chamfered sipes positioned closer to the non-chamfered sipe, and a distant chamfered sipe is defined as the pair of chamfered sipes positioned further away from the non-chamfered sipe, and in the first middle land section, the ratio Dbmax1 of the maximum value of the circumferential distance Db from the center line of the sipe portion of the distant chamfered sipe to the center line of the non-chamfered sipe to the maximum value of the circumferential distance Da from the center line of the sipe portion of the close chamfered sipe to the center line of the non-chamfered sipe, Dbmax1 / Damax1, is in the range of 1.50 ≤ Dbmax1 / Damax1 ≤ 4.00, and in the second middle land section, A tire according to any one of [1] to

[14] , wherein the ratio Dbmax2 of the maximum value of the tire circumferential distance Db from the center line of the sipe portion of the remote chamfered sipe to the center line of the non-chamfered sipe to the maximum value of the tire circumferential distance Da from the center line of the sipe portion of the nearby chamfered sipe to the center line of the non-chamfered sipe, Dbmax2 / Damax2, is in the range of 1.20 ≤ Dbmax2 / Damax2 ≤ 3.00.

[16] A tire according to any one of [1] to

[15] , wherein the groove width of the non-chamfered sipe is 0.5 [mm] or more and 1.5 [mm] or less, and the groove depth of the non-chamfered sipe is 2.0 [mm] or more and less than or equal to the maximum groove depth of the main groove.

[17] The tire according to any one of [1] to

[16] , wherein the chamfered sipes and the non-chamfered sipes in each of the multiple sipe units of the first middle land section communicate with the same main groove, and the chamfered sipes and the non-chamfered sipes in each of the multiple sipe units of the second middle land section communicate with the same main groove.

[18] The tire according to any one of [1] to

[17] , wherein the chamfered sipes and the non-chamfered sipes in each of the plurality of sipe units of the first middle land section communicate with the main groove on the outside in the tire width direction, and the chamfered sipes and the non-chamfered sipes in each of the plurality of sipe units of the second middle land section communicate with the main groove on the outside in the tire width direction.

[19] The tire according to any one of [1] to

[18] , wherein the first middle land portion and the second middle land portion each further include a shallow bottom portion having a V shape with its top facing in the circumferential direction of the tire, the shallow bottom portion of the first middle land portion being connected to the non-chamfered sipe of the first middle land portion, the shallow bottom portion of the second middle land portion being connected to the non-chamfered sipe of the second middle land portion, the tops of the V shape of the shallow bottom portion of the first middle land portion being in the same direction in the circumferential direction of the tire, and the tops of the V shape of the shallow bottom portion of the first middle land portion and the tops of the V shape of the shallow bottom portion of the second middle land portion being in opposite directions in the circumferential direction of the tire.

[20] A tire according to any one of [1] to

[19] , having a closed groove in the direction of extension of the chamfered sipe in at least one of the first middle land portion and the second middle land portion, wherein the closed groove is not connected to the chamfered sipe.

[0078] 1. Pneumatic tire 2. Tread section 3. Shoulder section 4. Sidewall section 5. Bead section 6. Carcass layer 7. Belt layer 7a, 7b. Belt 8. Belt reinforcement layer 10. Contact surface 15. Bead core 16. Bead filler 20. Circumferential main groove 21, 22. Outer center main groove 23. Inner shoulder main groove 24. Outer shoulder main groove 31. Center land section 32, 32a. First middle land section 33, 33a. Second middle land section 34, 35. Shoulder land section 40, 50. Sipe unit 41, 51. Shallow bottom section 42, 52. Non-chamfered sipe 43, 43a, 43b, 53, 53a, 53b. Chamfered sipe 44, 54. Closed groove 61, 64. Lug groove 62, 65, 71. Sipe 63 Circumferential narrow groove 430, 530 Chamfered portion 431, 531 Sipe portion

Claims

1. The tire comprises one or more center main grooves, a pair of shoulder main grooves provided on the outer side of the center main groove in the tire width direction, a pair of shoulder land sections and first and second middle land sections partitioned by these main grooves, the first and second middle land sections each having a plurality of chamfered sipes having a sipe portion and a chamfered portion, and non-chamfered sipes not having a chamfered portion, the chamfered sipes and non-chamfered sipes are arranged alternately in the circumferential direction of the tire, the first and second middle land sections each having a plurality of sipe units composed of the non-chamfered sipes and the chamfered sipes, the chamfered sipes located on both sides of the non-chamfered sipe in the circumferential direction of the tire that are closer to the non-chamfered sipe are designated as proximity chamfered sipes, and the combination of the non-chamfered sipe and the proximity chamfered sipe constitutes the sipe unit. A tire in which the rib width W1 of the first middle section and the rib width W2 of the second middle section have the relationship W1 < W2, and the distance D1 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the first middle section has the relationship D1 < D2 with respect to the distance D2 between the non-chamfered sipe and the chamfered sipe of the sipe unit in the second middle section.

2. The tire according to claim 1, wherein the distance Zb from the non-chamfered sipe to the end of the chamfered portion of the chamfered sipe is 20.0 [mm] or less.

3. The tire according to claim 1 or 2, wherein the ratio of the rib width W2 to the rib width W1, W2 / W1, is 1.1 or more and 1.6 or less.

4. The tire according to claim 1 or 2, wherein the ratio of the interval D2 to the interval D1, D2 / D1, is 1.2 or more and 2.0 or less.

5. The tire according to claim 1 or 2, wherein the ratio D1 / W1 of the spacing D1 to the rib width W1 is 0.2 or more and 0.8 or less, and the ratio D2 / W2 of the spacing D2 to the rib width W2 is 0.2 or more and 0.8 or less.

6. The tire according to claim 1 or 2, wherein the inclination angle θ1 of the chamfered sipe of the sipe unit in the first middle land portion with respect to the tire circumferential direction and the inclination angle θ2 of the chamfered sipe of the sipe unit in the second middle land portion with respect to the tire circumferential direction are in the relationship θ1 > θ2.

7. The tire according to claim 6, wherein the inclination angles θ1 and θ2 are 30 degrees or more and 80 degrees or less.

8. The tire according to claim 6, wherein the difference between the inclination angle θ1 and the inclination angle θ2, θ1 - θ2, is 5 [deg] or more and 35 [deg] or less.

9. The tire according to claim 6, wherein the inclination angle θ1' of the non-chamfered sipe of the sipe unit in the first middle land portion has the relationship -10 [deg] ≤ θ1 - θ1' ≤ 10 [deg] with respect to the tire circumferential direction, and the inclination angle θ2' of the non-chamfered sipe of the sipe unit in the second middle land portion has the relationship -10 [deg] ≤ θ2 - θ2' ≤ 10 [deg].

10. The tire according to claim 1 or 2, wherein the ratio X1 / W1 of the tire width extension distance X1 of the chamfered sipe in the first middle land portion to the rib width W1 is 0.40 ≤ X1 / W1 ≤ 0.90, and the ratio X2 / W2 of the tire width extension distance X2 of the chamfered sipe in the second middle land portion to W2 is 0.40 ≤ X2 / W2 ≤ 0.

90.

11. The tire according to claim 1 or 2, wherein the first middle land portion is located on the inside of the vehicle.

12. The tire according to claim 1 or 2, wherein the chamfered sipe includes a sipe portion and a chamfered portion, and the chamfered portion is provided only on the edge on the non-chamfered sipe side of the edges on both sides of the sipe portion.

13. The tire according to claim 1 or 2, wherein the ratio Zm / Zs of the maximum width of the chamfered sipe to the maximum width Zs of the sipe portion of the chamfered sipe satisfies the condition 2.00 ≤ Zm / Zs ≤ 6.00, and the maximum width Zs satisfies the condition 0.5 [mm] ≤ Zs ≤ 1.5 [mm].

14. The tire according to claim 1 or 2, wherein the ratio Za / Zs of the distance Za from a non-chamfered sipe to the sipe portion of the chamfered sipe in the sipe unit to the maximum width Zs of the sipe portion of the chamfered sipe is Za / Zs ≤ 30, and the distance Zb from the non-chamfered sipe to the end of the chamfered portion of the chamfered sipe is Zb ≥ 3.0 [mm].

15. A single non-chamfered sipe is positioned between a pair of adjacent chamfered sipes in the circumferential direction of the tire, and a close chamfered sipe is defined as the pair of chamfered sipes positioned closer to the non-chamfered sipe, and a distant chamfered sipe is defined as the pair of chamfered sipes positioned further away from the non-chamfered sipe, and in the first middle land section, the ratio Dbmax1 of the maximum value of the circumferential distance Db from the center line of the sipe portion of the distant chamfered sipe to the center line of the non-chamfered sipe to the maximum value of the circumferential distance Da from the center line of the sipe portion of the close chamfered sipe to the center line of the non-chamfered sipe, Dbmax1 / Damax1, is in the range of 1.50 ≤ Dbmax1 / Damax1 ≤ 4.00, and in the second middle land section, The tire according to claim 1 or 2, wherein the ratio Dbmax2 of the maximum value of the tire circumferential distance Db from the center line of the sipe portion of the remote chamfered sipe to the center line of the non-chamfered sipe to the maximum value of the tire circumferential distance Da from the center line of the sipe portion of the nearby chamfered sipe to the center line of the non-chamfered sipe, Dbmax2 / Damax2, is in the range of 1.20 ≤ Dbmax2 / Damax2 ≤ 3.

00.

16. The tire according to claim 1 or 2, wherein the groove width of the non-chamfered sipe is 0.5 mm or more and 1.5 mm or less, and the groove depth of the non-chamfered sipe is 2.0 mm or more and less than or equal to the maximum groove depth of the main groove.

17. The tire according to claim 1 or 2, wherein the chamfered sipes and the non-chamfered sipes in each of the multiple sipe units of the first middle land section communicate with the same main groove, and the chamfered sipes and the non-chamfered sipes in each of the multiple sipe units of the second middle land section communicate with the same main groove.

18. The tire according to claim 1 or 2, wherein the chamfered sipes and the non-chamfered sipes in each of the plurality of sipe units of the first middle land portion communicate with the main groove on the outside in the tire width direction, and the chamfered sipes and the non-chamfered sipes in each of the plurality of sipe units of the second middle land portion communicate with the main groove on the outside in the tire width direction.

19. The tire according to claim 1 or 2, wherein the first middle land portion and the second middle land portion each further include a shallow bottom portion having a V-shape with its top facing in the circumferential direction of the tire, the shallow bottom portion of the first middle land portion being connected to the non-chamfered sipe of the first middle land portion, the shallow bottom portion of the second middle land portion being connected to the non-chamfered sipe of the second middle land portion, the tops of the V-shape of the shallow bottom portion of the first middle land portion being in the same direction in the circumferential direction of the tire, and the tops of the V-shape of the shallow bottom portion of the first middle land portion and the tops of the V-shape of the shallow bottom portion of the second middle land portion being in opposite directions in the circumferential direction of the tire.

20. The tire according to claim 1 or 2, wherein at least one of the first middle land portion and the second middle land portion has a closed groove provided in the direction of extension of the chamfered sipe, the closed groove not connected to the chamfered sipe.

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