L u f t r e i f e n

Abstract

Pneumatic tires (1), comprising: a plurality of main grooves (21, 22) extending in a circumferential direction of the tire; and Bridge sections (31, 32, 33) defined by the adjacent main grooves (21, 22); wherein the rib section (32, 33) is a continuous rib in the circumferential direction of the tire and includes lug grooves (321, 322, 331, 332) with a semi-closed structure, of the main grooves (21, 22) that define the bridge section (32, 33), at least one main groove (21, 22) has a zigzag shape formed by alternating long sections and short sections, and a circumferential length (Lg2) of the long section exhibits a relationship 0.70 ≤ Lg2 / λ2 ≤ 0.90 with respect to a wavelength (λ2) of the zigzag shape, wherein the tunnel grooves (321, 322, 331, 332) are open at positions in an edge section of the bridge section (32, 33), wherein the positions are recessed in relation to the main groove (21), wherein the extension length in the tire width direction of the lug groove (321, 322, 331, 332) is in a range of 20% or more and 60% or less with respect to a maximum ground contact width of the rib section (32, 33).

Description

Technical field

[0001] The invention relates to a pneumatic tire and in particular to a pneumatic tire that can provide traction performance on snow and resistance performance of the tire to uneven wear in a compatible manner. State of the art

[0002] In a heavy-duty tire, which is primarily mounted on a vehicle's drive shaft, the tire's traction performance on snow is improved by arranging semi-closed lug grooves in ribs, while the tire's resistance to uneven wear is ensured based on a rib pattern.

[0003] The technology described in patent document 1 is known in the prior art as a pneumatic tire that uses such a structure. Patent document 2 describes a pneumatic tire having two central main grooves on an equatorial side of the tire and two shoulder main grooves on a side of the tire's ground contact area, extending in a circumferential direction of the tire, a central rib section between the two central main grooves, an intermediate rib section between the central main groove and the shoulder main groove, a shoulder rib section between the shoulder main groove and the ground contact area, and flat grooves on a surface of each of the rib sections. Patent document 3 describes a pneumatic tire provided with a row of shoulder blocks at an end section of a tread section in a tire width direction.The shoulder block row is configured such that a multitude of shoulder blocks, separated by lateral grooves between a main groove extending in one direction around the tire and a tire contact patch, are arranged in the tire's circumferential direction. The lateral groove between adjacent shoulder blocks has a shallow groove section in the tire's circumferential direction, positioned on one side near the main groove and having a shallower depth than the main groove.

[0004] Patent document 4 describes a pneumatic tire that offers improved driving performance on snow-covered roads while maintaining steering stability. Patent document 5 describes a pneumatic tire with a tread section provided with at least one main groove extending continuously in the circumferential direction, which main groove has a periodic zigzag pattern formed by repeatedly arranging a first inclined segment and a second inclined segment circumferentially as a repeating unit, defining a zigzag spacing, wherein the first inclined segment is designed without bending and wherein the second inclined segment is designed with a curve. List of literature on patent literature Patent document 1: JP 2019- 26 204 A Patent document 2: DE 10 2018 221 492 A1 Patent document 3: US 2018 / 0 001 712 A1 Patent document 4: JP 2015- 000 610 A Patent document 5: EP 3 199 375 A1 Brief description of the invention: Technical problem

[0005] One object of the invention is to provide a pneumatic tire that can provide both traction performance on snow and resistance to uneven wear in a compatible manner. Solution to the problem

[0006] To achieve the problem described above, a pneumatic tire according to one embodiment of the invention includes: a plurality of main grooves extending in a circumferential direction; and rib sections defined by the main grooves adjoining one another. The rib section is a continuous rib extending in the circumferential direction of the tire and includes a lug groove with a semi-closed structure. At least one of the main grooves defining the rib section has a zigzag shape formed by alternating long and short sections.A circumferential length Lg2 of the long section has a relationship 0.70 ≤ Lg2 / λ2 ≤ 0.90 with respect to a wavelength λ2 of the zigzag shape, wherein the lug grooves are open at positions in an edge section of the rib section, wherein the positions are recessed with respect to the main groove, and wherein an extent length in the tire width direction of the lug groove is in a range of 20% or more and 60% or less with respect to a maximum ground contact width of the rib section. Advantageous effects of the invention

[0007] In a pneumatic tire according to one embodiment of the invention, at least one of the main grooves defining the rib section has a zigzag shape formed by alternating the long and short sections. Compared to a configuration where both main grooves have a straight shape, this offers the advantage of improved traction on snow while maintaining the stiffness of the rib section. Furthermore, compared to a configuration where both main grooves have a zigzag shape formed by connecting linear sections of approximately identical length, this configuration ensures the stiffness of the rib section while improving the tire's resistance to uneven wear. Brief description of the drawings Fig.Figure 1 is a cross-sectional view in the tire meridian direction, illustrating a pneumatic tire according to an embodiment of the invention. Fig. 2 is a top view showing a running surface of the in Fig. 1 illustrated pneumatic tire illustrated. Fig. 3 is an enlarged view showing a shoulder strap section and a middle strap section of the in Fig. 2 illustrated tires. Fig. 4 is an enlarged view showing the middle web section and a central web section of the in Fig. 2 illustrated tires. Fig. 5 is an enlarged view showing the Fig. 3 illustrated shoulder strap section. Fig. 6 is an enlarged view showing the Fig. 3 illustrated middle bridge section. Fig.7 is a cross-sectional view of the in Fig. 6 illustrated middle bridge section. Fig. 8 is an enlarged view showing the one in Fig. 4 illustrated central bridge section. Fig. 9 is a cross-sectional view of the in Fig. 8 illustrated central bridge section. Description of embodiments

[0008] Embodiments of the invention are described in detail below with reference to the drawings. It should be noted that embodiments of the invention are not limited to the embodiments shown. Furthermore, components of the embodiments include components that can be replaced and are obviously replacements while maintaining consistency with the embodiments of the invention. In addition, a plurality of modified examples described in the embodiments can be combined arbitrarily within the scope recognizable to a person skilled in the art. pneumatic tires

[0009] Fig.Figure 1 is a cross-sectional view in the tire meridional direction, illustrating a pneumatic tire according to one embodiment of the invention. The same drawing illustrates a cross-sectional view of a half-section in the tire radial direction. As an example of a pneumatic tire, the same drawing illustrates a heavy-duty radial tire mounted on a drive shaft of a long-distance vehicle, such as a truck or bus.

[0010] In the same drawing, a tire meridional cross-section is defined as a cross-section of the tire along a plane that includes a tire axis of rotation (not illustrated). Furthermore, a tire equatorial plane CL is defined as a plane perpendicular to the tire axis of rotation through a midpoint between measurement points within a tire cross-sectional width defined by JATMA. Additionally, a tire width direction is defined as a direction parallel to the tire axis of rotation, and the tire radial direction is defined as a direction perpendicular to the tire axis of rotation.

[0011] A pneumatic tire 1 has a ring structure, the center of which is the tire's axis of rotation, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16 and a pair of rim pad rubbers 17, 17 (see Fig. 1).

[0012] The pair of bead cores 11, 11 each encloses one or more bead wires made of steel and produced by multiple ring windings. The pair of bead cores 11, 11 is embedded in bead sections and forms the cores of the bead sections on the left and right. The pair of bead fillers 12, 12 each consists of a lower filler 121 and an upper filler 122. The pair of bead fillers 12, 12 is arranged on the outer circumferences of the pair of bead cores 11, 11 in the radial direction of the tire and reinforces the bead sections.

[0013] The carcass layer 13 encloses a single-layer structure consisting of a single carcass ply or a multi-layer structure consisting of multiple layered carcass plies, and the carcass layer 13 extends between the left and right bead cores 11, 11 in a torus shape and forms the support structure of the tire. Furthermore, both end sections of the carcass layer 13 are wrapped and folded over to an outside in the tire width direction to enclose the bead cores 11 and the bead fillers 12, and are fixed in place.The carcass layer of carcass layer 13 is formed by covering a plurality of carcass cord threads made of steel with coating rubber and by carrying out a rolling process on the carcass cord threads and has a cord thread angle (defined as the angle of inclination in a longitudinal direction of the carcass cord thread with respect to the tire circumferential direction) which is 80° or more and 90° or less as an absolute value.

[0014] The belt layer 14 is made from a plurality of belt layers 141 to 144, which are layered and arranged by wrapping them around an outer circumference of the carcass layer 13. The belt layers 141 to 144 include a large-angle belt 141, a pair of cross belts 142, 143, and a belt cover 144. The large-angle belt 141 is formed by coating a plurality of steel belt cord threads with coating rubber and performing a rolling process on the belt cord threads. The large-angle belt 141 has a cord thread angle (defined as an angle of inclination in the longitudinal direction of the belt cord threads with respect to the tire circumference) with a value in the range of 45 degrees to 70 degrees or less than an absolute value. The pair of cross belts 142, 143 is each formed by covering a plurality of belt cord threads made of steel with coating rubber and carrying out a rolling process on the belt cord threads.Each of the pair of cross belts 142, 143 has a cord thread angle of 10 degrees or more and 55 degrees or less as an absolute value. Furthermore, the pair of cross belts 142, 143 has cord thread angles that are opposite in sign, and the pair of cross belts 142, 143 is layered such that the belt cord threads overlap longitudinally (forming a so-called cross-layer structure). The belt cover 144 is formed by coating a plurality of belt cover cord threads, made of steel or an organic fiber material, with coating rubber and performing a rolling process on the belt cover cord threads. The belt cover 144 has a cord thread angle of 10 degrees or more and 55 degrees or less as an absolute value.

[0015] The tread rubber 15 is arranged on the outer circumferences of the carcass layer 13 and the belt layer 14 in the tire radial direction and forms a tread section of the tire. The pair of sidewall rubbers 16, 16 are arranged on the outer side of the carcass layer 13 in the tire width direction and each form a left and a right sidewall section. The pair of rim pad rubbers 17, 17 extend from an inner side of the bead cores 11, 11 in the tire radial direction, from left and right and folded-over sections of the carcass layer 13 to the outer side in the tire width direction to form rim mating surfaces of the bead sections. tread surface

[0016] Fig. 2 is a top view showing a running surface of the in Fig.Figure 1 illustrates a pneumatic tire. The same drawing illustrates the tread surface of an all-season tire. In the same drawing, "tire circumference direction" refers to the direction around the tire's axis of rotation. Additionally, the reference symbol T denotes a ground contact edge, and the dimension symbol TW denotes a tire ground contact width.

[0017] As in Fig. As illustrated in Figure 2, the pneumatic tire 1 includes in the tread surface a plurality of main grooves 21, 22 extending in the circumferential direction of the tire and a plurality of rib sections 31 to 33 defined by the main grooves 21, 22.

[0018] "Main groove" refers to a groove on which a wear indicator must be provided in accordance with JATMA and which has a groove width of 6.0 mm or more and a groove depth of 10 mm or more. Furthermore, the configuration of Fig.2 groove widths Wg1, Wg2 of the main grooves 21 and 22 respectively (see Fig. 2) in the range of 3% or more and 4% or less in relation to a ground contact width TW of the tire.

[0019] The groove width is measured as the distance between opposing groove walls within a groove opening section when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In a configuration where the groove opening section includes a recessed or chamfered section, the groove width is measured using the intersections of the tread contact surface and extensions of the groove walls as measuring points, in a cross-sectional view parallel to the groove width direction and the groove depth direction.

[0020] Groove depth is measured as the distance from the tread contact surface to the bottom of the groove when the tire is mounted on a specified rim, inflated to a specified internal pressure, and unloaded. Additionally, in a configuration where the groove bottom partially includes a raised section, sipe, or depression / raised section, the groove depth is measured only for the raised section, sipe, or depression / raised section.

[0021] According to the JATMA definition, "specified rim" refers to a "standard rim," a "design rim" as defined by the Tire and Rim Association (TRA), or a "measurement rim" as defined by the European Tyre and Rim Technical Organisation (ETRTO). Furthermore, "specified internal pressure" refers to a "maximum air pressure" as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by the TRA, or "INFLATION PRESSURES" as defined by the ETRTO. Furthermore, “specified load” refers to a “maximum load capacity” as defined by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” as defined by TRA, or “LOAD CAPACITY” as defined by ETRTO.However, in the case of a JATMA tire for a passenger car, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

[0022] For example, in the configuration according to Fig. 2 Four main grooves 21, 22 are arranged in a left-right symmetry around the equatorial plane CL of the tire. Five rows of rib sections are defined by the main grooves 21, 22. Additionally, a rib section 33 is arranged on the equatorial plane CL of the tire.

[0023] However, the configuration is not limited to this, and five main grooves can be arranged (not illustrated). Additionally, a rib section can be positioned at a distance from the equatorial plane CL of the tire (not illustrated).

[0024] Furthermore, of the main grooves 21, 22; 21, 22, which are arranged in each of the areas delimited by the equatorial plane CL of the tire, the main grooves 21, 21 on the outermost sides in the tire width direction are defined as shoulder main grooves, and the other main groove 22 is defined as a center main groove.

[0025] In the configuration of Fig. 2. A distance (dimension symbol omitted in the drawings) from the equatorial plane CL of the tire to a groove centerline of each of the shoulder main grooves 21, 21 left and right lies in a range of 26% or more to 32% or less of a ground contact width TW of the tire. A distance from the equatorial plane CL of the tire to a groove centerline of the center main grooves 22, 22 left and right lies in a range of 8% or more and 12% or less of a ground contact width TW of the tire.

[0026] The groove centerline is defined as an imaginary line that connects the centers of measurement points of a distance between opposing groove walls.

[0027] The ground contact width TW of the tire is measured as the maximum linear distance between a contact surface of the tire and a flat plate in the tire axial direction when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, placed vertically on the flat plate in a static state, and loaded with a load corresponding to a predetermined load.

[0028] A ground contact edge T of the tire is defined as a position of maximum width of the contact surface between the tire and a flat plate in the tire axial direction when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, placed vertically on the flat plate in a static state and loaded with a load corresponding to a predetermined load.

[0029] The rib sections 31, 31, located on the outer side in the direction of tire width, where the outer side is defined by the main shoulder grooves 21, 21, are defined as the shoulder rib sections. The shoulder rib sections 31, 31 are rib sections on the outermost sides in the direction of tire width and are located at the ground contact edges T of the tire. Furthermore, the rib sections 32, 32, located on an inner side in the direction of tire width, where the inner side is defined by the main shoulder groove 21, 21, are defined as the middle rib section. The middle rib sections 32, 32 are each adjacent to the shoulder rib section 31 across the main shoulder groove 21. Additionally, the rib section 33, which is located closer to one side of the equatorial plane CL of the tire than the middle rib sections 32, 32, is defined as a central rib section.The central rib section 33 can be arranged on the equatorial plane CL of the tire (see . Fig. 2) or may be located at a position away from the equatorial plane CL of the tire (not illustrated).

[0030] In a configuration that includes the four main grooves 21, 22, as in Fig. As illustrated in Figure 2, a pair of shoulder bridge sections 31, 31 and a pair of middle bridge sections 32, 32 and a single middle bridge section 33 are defined. Furthermore, for example, in a configuration that includes five or more main grooves, two or more rows of the central bridge sections are defined (not illustrated), and in a configuration that includes three main grooves, the middle bridge section also serves as the central bridge section (not illustrated).

[0031] In the configuration of Fig.2 The shoulder rib section 31 is a block row defined by the lug grooves 311 described below, and the middle rib section 32 and the central rib section 33 are ribs that are continuous in the circumferential direction of the tire.

[0032] In the configuration described above, the rib sections 32, 33 in the tread section's central area are continuous ribs in the tire's circumferential direction. This ensures the stiffness of the rib sections 32, 33, while also guaranteeing the tire's abrasion resistance and resistance to uneven wear. The rib sections 32, 33 in the tread section's central area enclose one pair of lug grooves 321, 322 and another pair of lug grooves 331, 332, the pairs of lug grooves having a semi-closed structure as described below, thus ensuring the tire's traction performance on snow.

[0033] In Fig. 2. The maximum ground contact widths Wb1, Wb2, Wb3 of the rib sections 31, 32 and 33 respectively are in the range of 15% or more and 25% or less with respect to the ground contact width TW of the tire. In the configuration of Fig. 2. The maximum ground contact width Wb2 of the middle web section 32 is the smallest. The maximum ground contact width Wb3 of the central web section 33 preferably has the relationship 1.00 ≤ Wb3 / Wb2 ≤ 1.20 with respect to the maximum ground contact width Wb2 of the middle web section 32 and more preferably has the relationship 1.05 ≤ Wb3 / Wb2 ≤ 1.10.

[0034] The ground contact widths Wb of the rib sections are measured as a linear distance in the tire axial direction on a contact surface of the rib section and a flat plate when the tire is mounted on a predetermined rim, inflated to the predetermined internal pressure, placed perpendicular to the flat plate in a static state and loaded with a load corresponding to the predetermined load. Zigzag shape of the main groove

[0035] Fig. Figure 3 is an enlarged view showing a shoulder bridge section 31 and the middle bridge section 32 of the in Fig. 2 illustrated pneumatic tires. Fig. Figure 4 is an enlarged view showing the middle web section 32 and the central web section 33 of the in Fig. The two illustrated pneumatic tires are shown. In the drawings, a dash-dot line in a zigzag shape indicates a groove centerline of each of the main grooves 21, 22.

[0036] As in Fig. As illustrated in Figure 2, the shoulder main groove 21 and the central main groove 22 have a zigzag shape with an amplitude in the direction of tire width.

[0037] Furthermore, the shoulder main groove 21 has a zigzag shape formed by alternately connecting linear sections that are inclined in different directions with respect to the tire circumference. Fig.3 has a circumferential length Lg1 of the linear section preferably having the relationship 0.30 ≤ Lg1 / λ1 ≤ 0.70 with respect to a wavelength λ1 with a zigzag shape and more preferably having the relationship 0.35 ≤ Lg1 / λ1 ≤ 0.65. Accordingly, the shoulder main groove 21 preferably has a zigzag shape formed by connecting linear sections of substantially identical length. Furthermore, the amplitude A1 of the zigzag shape of the shoulder main groove 21 has the ratio 0.03 ≤ A1 / TW ≤ 0.05 with respect to the ground contact width TW of the tire.

[0038] The central main groove 22 has a zigzag shape, formed by alternating the connection of long and short sections, each inclined in different directions with respect to the tire's circumference. Fig.4. A circumferential length Lg2 of the long section with a zigzag shape has the relationship 0.70 Lg2 / λ2 ≤ 0.90 with respect to a wavelength λ2 with a zigzag shape and more preferably has the relationship 0.75 ≤ Lg2 / λ2 ≤ 0.85. Furthermore, an amplitude A2 of the zigzag shape has the ratio 0.03 ≤ A2 / TW ≤ 0.05 with respect to the ground contact width TW of the tire.

[0039] In the configuration described above, at least one of the main grooves 22, which define the rib sections 32, 33, has a zigzag shape formed by alternating long and short sections. This improves the tire's traction performance on snow compared to a configuration where both main grooves are straight, while ensuring the stiffness of the rib sections 32, 33. Furthermore, compared to a configuration where both main grooves have a zigzag shape formed by linear sections of approximately identical length, this configuration ensures the stiffness of the rib sections 32, 33 and improves the tire's resistance to uneven wear.

[0040] In Fig.3. The wavelengths λ1, λ2 of the zigzag shapes in the shoulder main groove 21 and the central main groove 22, respectively, exhibit the relationship 1.50 ≤ λ2 / λ1 ≤ 2.00. Furthermore, within the same pitch spacing, the wavelength λ2 in the central main groove 22 is preferably an integer multiple of the wavelength λ1 in the shoulder main groove 21. For example, in the configuration of Fig. 3 a ratio λ2 / λ1 of the wavelengths λ1, λ2 within the same division distance is set to twice the original value.

[0041] In Fig.4. The adjacent central main grooves 22, 22 have identical wavelengths λ2 and identical amplitudes A2. However, if the ratio of the wavelengths λ2 and the ratio of the amplitudes A2 of both main grooves are within ± 5%, the wavelengths and amplitudes are considered identical. Furthermore, a phase difference φ2 in the zigzag shapes of the adjacent central main grooves 22, 22 exhibits the relationship 0 ≤ φ2 / λ2 ≤ 0.10 with respect to the wavelength λ2 and the zigzag shape. Accordingly, the adjacent central main grooves 22, 22 are aligned with their zigzag phases.

[0042] In the configuration of Fig.2, as described above, the main shoulder groove 21 has a zigzag shape formed by connecting linear sections of substantially identical length, and the main center groove 22 has a zigzag shape formed by alternating long and short sections. In this configuration, the traction properties of the shoulder area in the tread section are improved, and the tire's snow performance is effectively enhanced. Furthermore, the stiffness of an edge section of the rib section 32 on the equatorial plane CL side of the tire is ensured, and mean wear of the rib section 32 is suppressed. Thus, the tire's snow performance and resistance to uneven wear are provided in a compatible manner.

[0043] However, no such restriction is intended, and both the main shoulder groove 21 and the middle shoulder groove 22 can exhibit the zigzag shape formed by alternating the long and short segments (not illustrated). In particular, in Fig. 2 the shoulder main groove 21 has an identical structure to the middle main groove 22, and thus the marginal sections to the left and right of the middle bridge section 32 can have an identical structure to the central bridge section 33.

[0044] Furthermore, the configuration of Fig.2, as described above, the shoulder main groove 21, with a shorter wavelength λ1 (< λ2), is positioned closer to a ground contact edge T of the tire than the center main groove 22, which has a longer wavelength λ2. In this configuration, the traction properties of the shoulder area in the tread section are improved, and the tire's snow performance is effectively enhanced. On the other hand, the center main groove 22, on the side of the equatorial plane CL of the tire, has a zigzag shape with the longer wavelength λ2, thus ensuring the stiffness of the central area of ​​the tread section and the tire's resistance to uneven wear. Therefore, the tire's snow performance and resistance to uneven wear are provided in a compatible manner.

[0045] However, no such restriction is intended, and the shoulder main groove 21 may have a zigzag shape with a longer wavelength than the mid main groove 22 (not illustrated), and the shoulder main groove 21 and the mid main groove 22 may have an identical wavelength and amplitude (not illustrated).

[0046] In the configuration of Fig. 2, as in Fig. As illustrated in Figure 3, the zigzag shape of the main shoulder groove 21, when viewed in the circumferential direction of the tire, exhibits a structure through which one can see. Thus, an edge section of the shoulder rib section 31 and an edge section of the middle rib section 32 do not overlap when viewed in the circumferential direction of the tire. Accordingly, a sufficient groove volume of the main shoulder groove 21 is ensured, and the tire's drainage properties are improved.

[0047] On the other hand, as in Fig.Figure 4 illustrates that the zigzag shape of the central main groove 22, when viewed in the circumferential direction of the tire, presents a structure through which it is less possible to see. Thus, the edge section of the central rib section 32 and an edge section of the central rib section 33 overlap when viewed in the circumferential direction of the tire. This improves the traction properties of the tire. Shoulder strap section

[0048] Fig. 5 is an enlarged view showing the Fig. 3 illustrates the shoulder bridge section 31. The same drawing illustrates a single shoulder block 312.

[0049] As in Fig. 2 and Fig. As illustrated in Figure 3, the shoulder bridge section 31 includes the shoulder stud grooves 311, the shoulder blocks 312, narrow circumferential grooves 313 and recess sections 314.

[0050] The shoulder lug groove 311 has a so-called open structure, runs through the shoulder rib section 31 in the tire width direction and is open towards the main shoulder groove 21 and the ground contact edge T of the tire. As in Fig. As illustrated in Figure 5, the shoulder lug groove 311 is open towards the ground contact edge T of the tire, at a position of maximum amplitude of the zigzag shape of the main shoulder grooves 21. Furthermore, a majority of the shoulder lug grooves 311 are arranged at a predetermined interval in the tire's circumferential direction. The maximum groove width (dimension symbol omitted in drawings) of the shoulder lug groove 311 is in the range of 10 mm or more and 25 mm or less. The maximum groove depth (not illustrated) of the shoulder lug groove 311 is in the range of 30% or more and 80% or less with respect to the maximum groove depth of the main shoulder groove 21. It should be noted that in the configuration of Fig.5 the shoulder stud groove 311 is flatter than the main shoulder groove 21 and thus, in a top view of the running surface, a boundary section between the shoulder stud groove 311 and the main shoulder groove 21 appears as a ridge line.

[0051] The shoulder block 312 is formed by defining the shoulder rib section 31 in the tire circumference direction through the shoulder lug grooves 311. A single row of blocks is also formed. As in Fig.As illustrated in Figure 5, a marginal section of the shoulder block 312 on one side of the shoulder groove 21 has a zigzag shape along the shoulder groove 21. A marginal section of the shoulder block 312 also includes two raised sections projecting towards the shoulder groove 21 and one recessed section that is sunken relative to the shoulder groove 21. Furthermore, a maximum circumference L12 of the shoulder block 312 has the relationship 0.40 ≤ λ1 / L12 ≤ 0.70 with respect to the wavelength λ1 of the shoulder groove 21, where the wavelength λ1 exhibits the zigzag shape. The maximum circumference length L12 of the shoulder block 312 has the relationship 1.10 ≤ L12 / Wb1 ≤ 1.40 with respect to the maximum ground contact width Wb1 of the shoulder bridge section 31.

[0052] The narrow circumferential groove 313 runs through the shoulder block 312 in the direction of the tire's circumference and is open to the shoulder lug groove 311. As in Fig.As illustrated in Figure 5, the narrow circumferential groove 313 has a zigzag shape, and the amplitude (dimension symbol omitted in drawings) of the narrow circumferential groove 313 is smaller than the amplitude A1 (see Figure 5). Fig. 3) of the main shoulder groove 21. Furthermore, the maximum groove width (dimension symbol omitted in drawings) of the narrow circumferential groove 313 is in the range of 2% or more and 10% or less with respect to the maximum ground contact width Wb1 of the shoulder rib section 31. The maximum groove depth (not illustrated) of the narrow circumferential groove 313 is in the range of 30% or more and 80% or less with respect to the maximum groove depth of the main shoulder groove 21. A distance D13 from the ground contact edge T of the tire to the narrow circumferential groove 313 is in the range of 0.30 ≤ D13 / Wb1 ≤ 0.70 with respect to the maximum ground contact width Wb1 of the shoulder rib section 31.

[0053] The recess section 314 is formed in the edge section of the shoulder block 312 on the side of the main shoulder groove 21. The recess section 314 is arranged separately from the narrow circumferential groove 313. The recess section 314 is formed at the position of maximum amplitude of the zigzag shape of the main shoulder groove 21, towards the ground contact edge T of the tire. A single recess section 314 is also formed in the shoulder block 312. The opening width (dimension symbol omitted in drawings) of the recess section 314 with respect to the main shoulder groove 21 is in the range of 5.0 mm or more and 15 mm or less. The maximum depth (not illustrated) of the recess section 314 is in the range of 30% or more and 80% or less with respect to the maximum groove depth of the main shoulder groove 21.

[0054] Furthermore, as shown in Fig.Figure 5 illustrates that the shoulder block 312 comprises a plurality of sipes (reference symbols omitted in drawings). In particular, a single circumferential sipe is arranged in a region on the side of the ground contact edge T of the tire, the region being defined by the narrow circumferential groove 313, and extends in the tire's circumferential direction, with both end sections terminating within the shoulder block 312. Furthermore, a plurality of sipes are arranged in the tire's width direction in a region on the side of the main shoulder groove 21, the region being defined by the narrow circumferential groove 313, and extend in the tire's width direction, connecting the narrow circumferential groove 313 and the main shoulder groove 21 or the recess section 314.

[0055] "Lamella" refers to a cut formed in a tread contact surface, having a sipe width of less than 1.5 mm and a sipe depth of 2.0 mm or more, so that the sipe closes when the tire comes into contact with the ground.

[0056] The sipe width is measured as the maximum opening width of the sipe at the tread contact surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

[0057] Sipe depth is measured as the distance from the tread contact surface to the base of a sipe when the tire is mounted on a specified rim, inflated to a specified pressure, and unloaded. Additionally, in a configuration where the sipe partially includes a raised base section or a depression / protrusion section, the sipe depth is measured only for these sections. Middle section of the bridge

[0058] Fig. 6 is an enlarged view showing the Fig. Figure 3 illustrates the central web section 32. The same drawing is an extracted view of a single central web section 32. Fig. 7 is a cross-sectional view of the in Fig. Figure 6 illustrates the middle section of the bridge 32. The same drawing illustrates a cross-sectional view along a first middle tunnel groove 321.

[0059] As in Fig. 2 and Fig. As illustrated in Figure 3, the middle bridge section 32 includes the first middle tunnel groove 321 with a long length and a second middle tunnel groove 322 with a short length.

[0060] The first and second central lug grooves 321, 322 have a so-called semi-closed structure and are each open at one end section towards the main shoulder groove 21 and terminate at the other end section in the central rib section 32. Furthermore, all central lug grooves 321, 322 are open to an edge section of the central rib section 32 on the side of the ground contact edge T of the tire and do not open to an edge section on the side of the equatorial plane CL of the tire. Accordingly, the edge section of the central rib section 32 on the side of the equatorial plane CL of the tire has a flat structure that is not divided by lug grooves. In addition, both the first and the second central lug grooves 321, 322 are each open towards the equatorial plane CL of the tire at a position of maximum amplitude of the zigzag shape of the main shoulder groove 21.In other words, both the first and second central lug grooves 321, 322 are open at positions in the edge section of the central rib section 32, with the positions being recessed relative to the main shoulder groove 21. Additionally, the first central lug grooves 321 and second central lug grooves 322 are arranged at a predetermined interval in the circumferential direction of the tire.

[0061] In Fig.6 has a maximum length L21 of the first central lug groove 321 in the tire width direction preferably the relationship 1.30 ≤ L21 / L22 ≤ 2.30 with respect to a maximum length L22 of the second central lug groove 322 and preferably the relationship 1.40 ≤ L21 / L22 ≤ 2.00. Accordingly, the opening areas of the first and second central lug grooves 321, 322 are uniformly designed. The maximum length L21 of the first central lug groove 321 has the relationship L21 / Wb2 ≤ 0.60 with respect to the maximum ground contact width Wb2 of the central rib section 32. The maximum length L22 of the second middle lug groove 322 has the relationship 0.20 ≤ L22 / Wb2 with respect to the maximum ground contact width Wb2 of the middle rib section 32.There are no specific restrictions on the lower limit of an L21 / Wb2 ratio and on the upper limit of an L22 / Wb2 ratio, but they are subject to restrictions by the numerical ranges set out above by the L21 / L22 ratio.

[0062] The maximum length of a tunnel groove is the extension length of a tunnel groove body and is measured exclusively of a chamfered section and a recessed section formed in the tunnel groove.

[0063] In the configuration described above, the first and second lug grooves 321, 322 have maximum groove lengths L21, L22 that differ from each other, and thus, compared to a configuration in which the maximum groove lengths of the lug grooves are set uniformly, the resistance performance of the tire against uneven wear and the traction performance of the tire on snow can be efficiently provided in a compatible manner.

[0064] In the configuration of Fig.Figure 6 is the first adit groove 321, which has a long length (L21 > L22) and faces the long section of the zigzag shape of the central main groove 22, and the second adit groove 322, which has a short length, faces the short section of the zigzag shape of the central main groove 22. Specifically, an extension line of a groove centerline (not illustrated) of the first adit groove 321 intersects the long section of the zigzag shape of the central main groove 22, and an extension line of a groove centerline of the second adit groove 322 intersects the short section of the zigzag shape of the central main groove 22.

[0065] Furthermore, in the configuration of Fig.The first and second middle lug grooves 321, 322 each have a monotonous groove width from an opening section to the main shoulder groove 21 to a blind-ending end section in the middle rib section 32. Furthermore, the blind-ending end sections of the first and second middle lug grooves 321, 322 have a V-shape, formed by connecting a first and a second edge section with a linear or arc-shaped form. The first and second middle lug grooves 321, 322 have a narrower groove width in an identical direction around the circumference of the tire (in Fig. 6, top of the drawing).

[0066] The first and second central lug grooves 321, 322 are inclined in the same direction with respect to the tire's circumference. The first and second central lug grooves 321, 322 and the long section of the central main groove 22, the long section having a zigzag shape, are inclined in the same direction with respect to the tire's circumference. Furthermore, the angle of inclination (not illustrated) of the groove centerline of each of the first and second central lug grooves 321, 322 with respect to the tire's circumference is between 45° or more and 90° or less.

[0067] In Fig.6 has a maximum groove width W22 of the second middle lug groove 322, which has the short length, preferably with the relationship 1.00 ≤ W22 / W21 ≤ 1.50 with respect to a maximum groove width W21 of the first middle lug groove 321, and more preferably with the relationship 1.05 ≤ W22 / W21 ≤ 1.35. Thus, the second middle lug groove 322 with the short length preferably has a wider structure than the first middle lug groove 321 with the long length. In such a configuration, the groove volumes of the first and the second middle lug grooves 321, 322 are uniform. Accordingly, the stiffness of the middle rib section 32 in the circumferential direction of the tire is uniform, and uneven wear of the middle rib section 32 is suppressed.

[0068] Furthermore, the maximum groove width W21 of the first central adit groove 321 with the long length is in the range of 5.0 mm ≤ W21, and the maximum groove width W22 of the second central adit groove 322 is in the range of W22 ≤ 15 mm. There are no specific upper limits to the maximum groove width W21 and a lower limit to the maximum groove width W22, but they are subject to limitations based on the numerical ranges defined above by the ratio W22 / W21.

[0069] In Fig.7 has a maximum groove depth H22 of the second middle lug groove 322 with the short length preferably the relationship 1.20 ≤ H22 / H21 ≤ 1.60 with respect to a maximum groove depth H21 of the first middle lug groove 321 with the long length and preferably the relationship 1.30 ≤ H22 / H21 ≤ 1.50. In such a configuration, the second middle lug groove 322 with the short length is deeper than the first middle lug groove 321 with the long length, and thus the groove volumes of the first and the second middle lug grooves 321, 322 are uniform. Accordingly, the stiffness of the middle rib section 32 in the circumferential direction of the tire is uniform and the uneven wear of the middle rib section 32 is suppressed.

[0070] Furthermore, it points out that Fig.7. The maximum groove depth H21 of the first middle lug groove 321 with the long length has the relationship 0.50 ≤ H21 / Hg1 with respect to a maximum groove depth Hg1 of the main shoulder groove 21, and the maximum groove depth H22 of the second middle lug groove 322 with the short length has the relationship H22 / Hg1 ≤ 0.95 with respect to the maximum groove depth Hg1 of the main shoulder groove 21. No upper limit or lower limit of a ratio H21 / Hg1 is subject to any specific restrictions, but they are subject to limitations by the numerical ranges set out above in the ratio H22 / H21. It should be noted that in Fig. 6 the middle lug grooves 321, 322 are flatter than the shoulder main groove 21, and thus a ridge line appears in a boundary section between each of the middle lug grooves 321, 322 and the shoulder main groove 21 in a running surface top view.

[0071] As in Fig.As illustrated in Figure 6, the central rib section 32 encloses a plurality of sipes 323, 324. Specifically, a first sipe 323 is open to the central lug groove 321 or 322 at one end section to extend the central lug groove 321 or 322, and is open to the central main groove 22 at the other end section. Furthermore, the first sipe 323 has a straight shape and is inclined in the same direction with respect to the first and second central lug grooves 321, 322. The second sipe 324 is arranged side by side between the first and second central lug grooves 321, 322 and extends through the central rib section 32 in the tire width direction to connect with the main grooves 21, 22 on the left and right. Furthermore, the second lamella 324 is inclined in an identical direction with respect to the first and the second middle tread groove 321, 322.The second lamella 324 has a zigzag shape and is inclined in the same direction with respect to the first and second middle lug grooves 321, 322. Furthermore, as in . Fig. Figure 7 illustrates a maximum depth H23 of the first lamella 323, which is connected to the first and second middle adit groove 321, 322, shallower than the maximum groove depths H21, H22 of the first and second middle adit groove 321, 322.

[0072] Furthermore, as shown in Fig.Figure 3 illustrates that the edge sections of the central rib section 32 each exhibit a zigzag shape parallel to the groove centerline of the shoulder main groove 21 or the central main groove 22. The central rib section 32 is a rib that is continuous in the tire's circumferential direction and does not include a continuous lug groove that divides the central rib section 32 in the tire's width direction. This differs from the shoulder rib section 31, which is a block row. It should be noted that the sipes 323, 324 are closed when the tire is in contact with the ground and do not impede the rib section's function as a rib. Central section of the bridge

[0073] Fig. 8 is an enlarged view showing the one in Fig. Figure 4 illustrates the central web section 33. The same drawing is an extracted view of a single central web section 33. Fig. 9 is a cross-sectional view of the in Fig. 8 illustrated central bridge section 33. The same drawing is a cross-sectional view along the central tunnel groove 331 (332).

[0074] As in Fig. 2 and Fig. As illustrated in Figure 4, the central bridge section 33 includes the first and second central tunnel grooves 331, 332.

[0075] The first and second central lug grooves 331, 332 have a so-called semi-closed structure, are open at one end section towards the central main groove 22, and terminate at the other end section in the central rib section 33. The first central lug groove 331 is formed in one edge section of the central rib section 33, and the second central lug groove 332 is formed in the other edge section of the central rib section 33. The first and second central lug grooves 331, 332 are each open towards the position of maximum amplitude, towards the equatorial plane of the tire CL, the zigzag shape of the central main groove 22. In other words, the first and second central lug grooves 331, 332 are open at positions in the edge section of the central rib section 33, with the positions being recessed relative to a corresponding central main groove 22. As in Fig.As illustrated in Figure 8, the opening positions of the first and second central lug grooves 331, 332 tend preferably towards the side of the long section of the zigzag shape of the central main grooves 22, 22. Furthermore, the first and second central lug grooves 331, 332 are arranged alternately offset in the circumferential direction of the tire.

[0076] In Fig. 8. The maximum groove widths W31, W32 of the first and second central adit grooves 331, 332 are in the range of 5.0 mm or more and 10 mm or less. Furthermore, the maximum groove widths W31, W32 of the first and second central adit grooves 331, 332 exhibit the relationship 0.90 ≤ W32 / W31 ≤ 1.10 and preferably the relationship 0.95 ≤ W32 / W31 ≤ 1.05. Thus, the first and second central adit grooves 331, 332 have a substantially identical maximum groove width.

[0077] Furthermore, in Fig.8 maximum lengths L31, L32 of the first and second central lug groove 331, 332 in the tire width direction have the relationships 0.20 ≤ L31 / Wb3 ≤ 0.60 and 0.20 ≤ L32 / Wb3 ≤ 0.60 with respect to the maximum ground contact width Wb3 of the central rib section 33 and preferably have the relationships 0.35 ≤ L31 / Wb3 ≤ 0.45 and 0.35 ≤ L32 / Wb3 ≤ 0.45. The maximum lengths L31, L32 of the first and second central adit grooves 331, 332 preferably exhibit the relationship 0.90 ≤ L32 / L31 ≤ 1.10 and more preferably exhibit the relationship 0.95 ≤ L32 / L31 ≤ 1.05. Thus, the first and second central adit grooves 331, 332 have an essentially identical maximum groove length.

[0078] In Fig.8 has an overlap Wr of the central lug grooves 331, 332, which are adjacent to each other when viewed in the circumferential direction of the tire, the relationship 0 ≤ Wr / Wb3 ≤ 0.30 with respect to the maximum ground contact width Wb3 of the central rib section 33 and preferably has the relationship 0.10 ≤ Wr / Wb3 ≤ 0.25.

[0079] Furthermore, in Fig. 8. The pitch spacing of each of the first and second central lug grooves 331, 332 is equal to the pitch spacing of the zigzag shape of the central main groove 22. Thus, a pair of central lug grooves 331, 332 is arranged within one pitch spacing of the central main groove 22. Furthermore, a distance D3 in the tire circumferential direction between the adjacent central lug grooves 331, 332 exhibits the relationship 0.20 ≤ D3 / λ2 ≤ 0.50 with respect to the wavelength λ2 of the zigzag shape in the central main groove 22.

[0080] In the configuration of Fig.8 The first and second central adit grooves 331, 332 each face the long section of the zigzag shape of the central main groove 22. In particular, an extension line of a groove centerline (not illustrated) of both the first and the second central adit grooves 331, 332 intersects the long section of the zigzag shape of the central main groove 22.

[0081] Furthermore, in the configuration of Fig.8 The groove widths of the first and second central adit grooves 331, 332 each decrease monotonically from the opening section to the central main groove 22 to the blind-ending end section in the central web section 33. The opening section of each of the first and second central adit grooves 331, 332 is widened by having a partially chamfered section or a recessed section (reference symbols omitted in drawings) on one side thereof. The blind-ending end section of each of the first and second central adit grooves 331, 332 has a V-shape formed by connecting a first and a second edge section with a linear or arc-shaped form. Furthermore, the pair of first and second central adit grooves 331, 332 is each arranged on a long section of the zigzag shape of the central main groove 22, and the central adit grooves 331, 332 have curved shapes in opposite directions.

[0082] The first and second central lug grooves 331, 332 are inclined in the same direction with respect to the tire's circumference. The first and second central lug grooves 331, 332 and the long section of the zigzag shape of the central main groove 22 are inclined in opposite directions with respect to the tire's circumference. Furthermore, the angle of inclination (not illustrated) of the groove centerline of each of the first and second central lug grooves 331, 332 with respect to the tire's circumference is between 45° or more and 90° or less.

[0083] In Fig.9 The maximum groove depths H31, H32 of the first and second central adit grooves 331, 332 exhibit the relationships 0.70 ≤ H31 / Hg2 ≤ 1.00 and 0.70 ≤ H32 / Hg2 ≤ 1.00 with respect to a maximum groove depth Hg2 of the central main groove 22. Furthermore, the maximum groove depths H31, H32 of the first and second central adit grooves 331, 332 preferably exhibit the relationship 0.90 ≤ H32 / H31 ≤ 1.10. Thus, the first and second central adit grooves 331, 332 have substantially identical maximum groove depths. It should be noted that in the configuration of Fig. 8 the central tunnel grooves 331, 332 are shallower than the central main groove 22, and thus a ridge line appears in a boundary section between each of the central tunnel grooves 331, 332 and the central main groove 22 in a running surface top view.

[0084] As in Fig.As illustrated in Figure 8, the central rib section 33 encloses a plurality of sipes 333, 334. Specifically, the first sipe 333 is open to the central lug groove 331 or 332 at one end section to extend the central lug groove 331 or 332, and is open to the central main groove 22 at the other end section. The first sipe 333 has a straight shape and is inclined in the same direction with respect to the central lug grooves 331, 332. The second sipe 334 is positioned side by side between the first and second central lug grooves 331, 332 and extends through the central rib section 33 in the tire width direction to connect with the central main grooves 22, 234 on the left and right. The second sipe 334 is inclined in the same direction with respect to the central lug grooves 331, 332.The second lamella 334 also has a zigzag shape and is inclined in the same direction with respect to the central grooves 331, 332. As in . Fig. As illustrated in Figure 9, the maximum depth H33 of the first lamella 333, which is connected to the central tunnel groove 331 or 332, is shallower than the maximum groove depths H31, H32 of the central tunnel grooves 331 and 332, respectively.

[0085] Furthermore, as shown in Fig.Figure 4 illustrates that the outer edges of the central rib section 33 each exhibit a zigzag shape, parallel to the centerline of the central main groove 22 on the left and right. The central rib section 33 is a rib that is continuous in the tire's circumferential direction and does not include a continuous lug groove that divides the central rib section 33 in the tire's width direction. This differs from the shoulder rib section 31, which is a block row. It should be noted that the sipes are closed when the tire is in contact with the ground, thus not impeding the rib section's function as a rib. Effect

[0086] As described above, the tire 1 has a plurality of main grooves 21, 22 extending in the circumferential direction of the tire and a plurality of rib sections 32; 33 defined by the main grooves 21, 22; 22, 22 (see Fig.2). Furthermore, the rib sections 32; 33 are ribs that are continuous in the circumferential direction of the tire and enclose the lug grooves 321, 322; 331, 332, each with the semi-closed structure. Of the main grooves 21, 22; 22, 22 that define rib sections 32, 33, at least one of the main grooves 22 has the zigzag shape formed by alternating the connection of the long and short sections. In addition, the circumferential length Lg2 of the long section has the relationship 0.70 ≤ Lg2 / λ2 ≤ 0.90 with respect to the wavelength λ2 with the zigzag shape (see Fig. 3 and Fig. 4).

[0087] In such a configuration, (1) the rib sections 32; 33 are continuous ribs in the circumferential direction of the tire, which has the advantage of ensuring the stiffness of the rib sections 32; 33 while simultaneously ensuring the abrasion resistance and the resistance of the tire to uneven wear. Furthermore, (2) the rib sections 32; 33 enclose the lug grooves 321, 322; 331, 332 with the semi-closed structure, which has the advantage of ensuring the traction performance of the tire on snow.Furthermore, (3) at least one of the main grooves 22, which defines the rib sections 32, 33, has a zigzag shape formed by alternating the connection of long and short sections. Compared to a configuration in which both main grooves have a straight shape, this offers the advantage of improved traction on snow while maintaining the stiffness of the rib sections 32; 33. Additionally, compared to a configuration in which both main grooves have a zigzag shape formed by connecting linear sections of approximately identical length, this configuration offers the advantage of ensuring the stiffness of the rib sections 32; 33 and improving the tire's resistance to uneven wear.

[0088] Furthermore, in the pneumatic tire 1, both main grooves 22, 22, which define a rib section 33, have the zigzag shape that is produced by alternately connecting the long sections and the short sections (see Fig. 4) Thus, the edge section of the central rib section 33 has a zigzag shape, formed by alternating the connection of the long and short sections. This has the advantage of ensuring the stiffness of the tread section to improve the tire's resistance to uneven wear.

[0089] Furthermore, in the case of pneumatic tire 1, the amplitude A2 of the zigzag shape exhibits the relationship 0.03 ≤ A2 / TW ≤ 0.05 with respect to the ground contact width TW of the tire (see Fig. 3 and Fig. 4) This has the advantage that the amplitude A2 of the zigzag shape is appropriately adjusted.

[0090] Furthermore, in the case of the pneumatic tire 1, the main groove 22 with the zigzag shape, when viewed in the circumferential direction of the tire, exhibits a structure through which one can see less (see Fig. 4) This improves the tire's traction properties.

[0091] Furthermore, in the pneumatic tire 1, the lug grooves 321, 322; 331, 332 are open at positions in the edge sections of the rib sections 32 and 33 respectively, with the positions being recessed in relation to the main grooves 21, 22 (see Fig. 2) This has the advantage that the traction performance is achieved due to the lug grooves 321, 322; 331, 332, while the stiffness of the rib sections 32; 33 is ensured.

[0092] Furthermore, in pneumatic tire 1, the extension lengths L21, L22; L31, L32 of the lug grooves 321, 322; 331 and 332, respectively, lie in the tire width direction in the range of 20% or more and 60% or less with respect to the maximum ground contact width of the rib sections. This has the advantage that the traction performance is achieved due to the lug grooves 321, 322; 331, 332, while the stiffness of the rib sections 32; 33 is ensured.

[0093] Furthermore, in the pneumatic tire 1, the lug grooves 331, 332 are arranged in the edge sections to the left and right of the rib section 33 and offset in the tire circumferential direction (see Fig. 2 and Fig. 4) This has the advantage that the stiffness of the web section 33 becomes uniform and the uneven wear of the web section 33 is effectively suppressed.

[0094] Furthermore, in the case of the pneumatic tire 1, the overlap amount Wr of the adjacent lug grooves 331, 332, viewed in the circumferential direction of the tire, exhibits the relationship 0 ≤ Wr / Wb3 ≤ 0.30 with respect to the maximum ground contact width Wb3 of the tread section 33 (see Fig. 8) The lower limit described above offers the advantage of effectively maintaining the improved traction performance due to the lug grooves 331, 332. Furthermore, the upper limit described above offers the advantage of ensuring the stiffness of the web section 33.

[0095] In the case of the pneumatic tire 1, the distance D3 in the tire circumferential direction between the adjacent tread grooves 331, 332 has the ratio 0.20 ≤ D3 / λ2 ≤ 0.50 with respect to the wavelength λ2 with the zigzag shape (see Fig. 8). This has the advantage that the distance D3 between the adjacent cleat grooves 331, 332 is appropriately adjusted.

[0096] Furthermore, in the case of the pneumatic tire 1, the inclination direction of each of the tread grooves 331, 332 with respect to the tire circumferential direction is opposite to the inclination direction of the long section of the zigzag shape of the main groove 22 (see Fig. 8) This has the advantage that the stiffness of the web section 33 becomes uniform and the uneven wear of the web section 33 is suppressed.

[0097] Furthermore, in the case of pneumatic tire 1, the maximum groove depths H31, H32 of the lug grooves 331 and 332 are in the range of 70% or more and 100% or less with respect to the maximum groove depth Hg2 of the main groove 22 (see Fig. 9) In such a configuration, the lug grooves 331, 332 each have maximum groove depths H31, H32, which are equivalent to those of the main groove 22, and this has the advantage that the traction performance of the tire on snow is ensured after intermediate stages of wear.

[0098] Furthermore, in the pneumatic tire 1, of the main grooves 21, 22 that define the rib section 32, the main groove 22 on the side of the equatorial plane CL of the tire has the zigzag shape formed by alternating connection of the long sections and the short sections, and the main groove 21 on the side of the ground contact edge T of the tire has the zigzag shape formed by connecting the linear sections of substantially identical length (see Fig. 2 and Fig. 3) The circumferential length Lg1 of the linear section of the main groove 21 on the side of the ground contact edge T of the tire has the relationship 0.30 ≤ Lg1 / λ1 ≤ 0.70 with respect to the wavelength λ1 with the zigzag shape (see Fig.3) Such a configuration has the advantage that the stiffness of the edge section of the rib section 32 on the side of the equatorial plane CL of the tire is ensured and the mean wear of the rib section 32 is suppressed.

[0099] Furthermore, in the case of the pneumatic tire 1, the wavelength λ1 of the main groove 21 on the side of the ground contact edge T of the tire and the wavelength λ2 of the main groove 22 on the side of the equatorial plane CL of the tire exhibit the relationship 1.50 ≤ λ2 / λ1 ≤ 2.00 (see Fig. 3) The lower limit described above offers the advantage of ensuring the increased stiffness of the edge section of the rib section 32 on the side of the equatorial plane CL of the tire due to the longer wavelength λ2. The upper limit described above offers the advantage of reducing the stiffness difference between the edge sections to the left and right of the rib section 32.

[0100] Furthermore, the pneumatic tire 1 is a heavy-duty tire mounted on a vehicle's drive shaft. Applying it to such a heavy-duty tire offers the advantage of significantly improving traction performance on snow and the tire's resistance to uneven wear. Examples

[0101] The following tables show the results of performance tests of pneumatic tires according to embodiments of the invention. Example of the state of the art Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Main groove shape Straight Zigzag Zigzag Zigzag Zigzag Zigzag Zigzag λ2 / λ1 - 1,00 1,00 1,00 1,55 1,70 1,85 Lg1 / λ1 - 0,60 0,60 0,60 0,60 0,60 0,60 Lg2 / λ2 - 0,70 0,80 0,90 0,80 0,80 0,80 A1 / TW - 0,02 0,02 0,02 0,02 0,02 0,02 A2 / TW - 0,02 0,02 0,02 0,04 0,04 0,04 L21 / Wb2 0,75 0,75 0,75 0,75 0,75 0,75 0,75 L22 / Wb2 0,75 0,75 0,75 0,75 0,75 0,75 0,75 L21 / L22 1,00 1,00 1,00 1,00 1,00 1,00 1,00 L31 / Wb3 0,25 0,25 0,25 0,25 0,25 0,25 0,25 L32 / WB3 0,25 0,25 0,25 0,25 0,25 0,25 0,25 Wr / Wb3 -0,50 -0,50 -0,50 -0,50 -0,50 -0,50 -0,50 H21 / Hg1 0,65 0,65 0,65 0,65 0,65 0,65 0,65 H22 / Hg1 0,65 0,65 0,65 0,65 0,65 0,65 0,65 H22 / H21 1,00 1,00 1,00 1,00 1,00 1,00 1,00 H31 / Hg2 0,65 0,65 0,65 0,65 0,65 0,65 0,65 H32 / Hg2 0,65 0,65 0,65 0,65 0,65 0,65 0,65 Traction performance on snow 100 110 108 106 113 111 109 Resistance to uneven wear 100 90 92 94 99 101 103 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Main groove shape Zigzag Zigzag Zigzag Zigzag Zigzag Zigzag λ2 / λ1 1,70 1,70 1,00 1,70 1,70 1,70 Lg1 / λ1 0,50 0,40 0,50 0,50 0,50 0,50 Lg2 / λ2 0,80 0,80 0,80 0,80 0,80 0,80 A1 / TW 0,02 0,02 0,02 0,02 0,02 0,02 A2 / TW 0,04 0,04 0,04 0,04 0,04 0,04 L21 / Wb2 0,75 0,75 0,75 0,55 0,45 0,35 L22 / Wb2 0,75 0,75 0,75 0,25 0,25 0,25 L21 / L22 1,00 1,00 1,00 2,20 1,80 1,40 L31 / Wb3 0,25 0,25 0,25 0,25 0,25 0,25 L32 / WB3 0,25 0,25 0,25 0,25 0,25 0,25 Wr / Wb3 -0,50 -0,50 -0,50 -0,50 -0,50 -0,50 H21 / Hg1 0,65 0,65 0,65 0,65 0,65 0,65 H22 / Hg1 0,65 0,65 0,65 0,65 0,65 0,65 H22 / H21 1,00 1,00 1,00 1,00 1,00 1,00 H31 / Hg2 0,65 0,65 0,65 0,65 0,65 0,65 H32 / Hg2 0,65 0,65 0,65 0,65 0,65 0,65 Traction performance on snow 114 115 110 120 117 114 Resistance to uneven wear 100 98 100 105 106 107 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Main groove shape Zigzag Zigzag Zigzag Zigzag Zigzag Zigzag λ2 / λ1 1,70 1,70 1,00 1,00 1,70 1,70 Lg1 / λ1 0,50 0,50 0,50 0,50 0,50 0,50 Lg2 / λ2 0,80 0,80 0,80 0,80 0,80 0,80 A1 / TW 0,02 0,02 0,02 0,02 0,02 0,02 A2 / TW 0,04 0,04 0,04 0,04 0,04 0,04 L21 / Wb2 0,45 0,45 0,45 0,45 0,45 0,45 L22 / Wb2 0,20 0,30 0,25 0,25 0,25 0,25 L21 / L22 2,25 1,50 1,80 1,80 1,80 1,80 L31 / Wb3 0,25 0,25 0,50 0,60 0,60 0,60 L32 / WB3 0,25 0,25 0,50 0,60 0,60 0,60 Wr / Wb3 -0,50 -0,50 0 0,20 0,20 0,20 H21 / Hg1 0,65 0,65 0,65 0,65 0,65 0,65 H22 / Hg1 0,65 0,65 0,65 0,65 0,80 0,85 H22 / H21 1,00 1,00 1,00 1,00 1,23 1,31 H31 / Hg2 0,65 0,65 0,65 0,65 0,65 0,65 H32 / Hg2 0,65 0,65 0,65 0,65 0,65 0,65 Traction performance on snow 111 116 123 125 130 132 Resistance to uneven wear 108 105 108 110 112 110 Example 19 Example 20 Example 21 Example 22 Example 23 Example 24 Main groove shape Zigzag Zigzag Zigzag Zigzag Zigzag Zigzag λ2 / λ1 1,70 1,70 1,70 1,70 1,00 1,00 Lg1 / λ1 0,50 0,50 0,50 0,50 0,60 0,60 Lg2 / λ2 0,80 0,80 0,80 0,80 0,80 0,80 A1 / TW 0,02 0,02 0,02 0,02 0,02 0,02 A2 / TW 0,04 0,04 0,04 0,04 0,04 0,04 L21 / Wb2 0,45 0,45 0,45 0,45 0,45 0,45 L22 / Wb2 0,25 0,25 0,25 0,25 0,25 0,25 L21 / L22 1,80 1,80 1,80 1,80 1,80 1,80 L31 / Wb3 0,60 0,60 0,60 0,60 0,60 0,60 L32 / WB3 0,60 0,60 0,60 0,60 0,60 0,60 Wr / Wb3 0,20 0,20 0,20 0,20 0,20 0,20 H21 / Hg1 0,65 0,60 0,55 0,50 0,55 0,55 H22 / Hg1 0,90 0,80 0,80 0,80 0,8 0,8 H22 / H21 1,38 1,33 1,45 1,60 1,45 1,45 H31 / Hg2 0,65 0,65 0,65 0,65 0,85 0,95 H32 / Hg2 0,65 0,65 0,65 0,65 0,85 0,95 Traction performance on snow 135 133 130 128 135 133 Resistance to uneven wear 108 110 112 114 117 115

[0102] In the performance tests, a plurality of test tire types were evaluated for (1) snow performance and (2) abrasion resistance performance. The test tires, with a tire size of 11R22.5, were mounted on JATMA-specified rims, and JATMA-specified inflation pressure and load were applied to the test tires. Furthermore, the test tires were each mounted on a drive shaft of a towing head of a 2-D (two-wheeled vehicle), which served as the test vehicle. (1) To assess traction performance on snow, the test vehicle is driven on a snow-covered road surface of a test track with a snow-covered road, and the acceleration time from 5 km / h to 20 km / h is measured. The measurement results are expressed and evaluated as index values, with the prior art example (100) being assigned as a reference. Higher values ​​are preferred in this evaluation. (2) In assessing resistance performance to uneven wear, the test vehicle is driven 30,000 km on a predetermined paved road, and then the degrees of wear on the heel and toe are measured and expressed as index values ​​and evaluated. The results of the evaluation are expressed as index values ​​and assessed by determining the prior art as a reference value (100). In this evaluation, higher values ​​are to be preferred. Even if the value is 90 or higher, the performance is deemed to be adequately ensured.

[0103] The test tires of examples are equipped with the configurations of Fig. 1 and Fig.The rim is provided with 2 and includes four main grooves 21, 22 with a zigzag shape and five rows of rib sections 31 to 33, which are defined by the main grooves 21, 22. Furthermore, the maximum groove widths Wg1, Wg2 of the main grooves 21 and 22 are each 9.0 mm, and the maximum groove depths Hg1, Hg2 of the main grooves 21 and 22 are each 21 mm. The wavelength λ1 of the zigzag shape of the shoulder main groove 21 is 40 mm. The ratio of the maximum ground contact width Wb2 of the middle rib section 32 and the maximum ground contact width Wb3 of the central rib section 33 with respect to the ground contact width TW of the tire is 20%. The ground contact width TW of the tire is 240 mm.

[0104] The test tire of the state-of-the-art example includes, in the configuration of Fig. 1 and Fig. Two main grooves 21, 22, which have a straight shape.

[0105] As can be seen from the test results, the test tires of the examples provide both traction performance on snow and resistance to uneven wear in a compatible manner. [List of reference symbols] 1 pneumatic tire 11 bead core 12 bead fillers 121 Lower pen 122 Upper fountain pen 13 Carcass layer 14 Belt layer 141 Belts with a large angle 142, 143 Cross belt 144 Belt cover 15 tread rubber 16 side wall rubber 17 Rim pad rubber 21 Shoulder groove 22 Medial groove 31 Shoulder strap section 311 Shoulder stud groove 312 Shoulder block 313 Narrow circumferential groove 314 Recess section 32 Middle section of the bridge 321 First middle groove 322 Second middle lug groove 323 First lamella 324 Second lamella 33 Central Bridge Section 331 First central tunnel groove 332 Second central tunnel groove 333 First lamella 334 Second lamella

Claims

[1] Pneumatic tires (1), comprising: a plurality of main grooves (21, 22) extending in a circumferential direction of the tire; and Bridge sections (31, 32, 33) defined by the adjacent main grooves (21, 22); wherein the rib section (32, 33) is a continuous rib in the circumferential direction of the tire and includes lug grooves (321, 322, 331, 332) with a semi-closed structure, of the main grooves (21, 22) that define the bridge section (32, 33), at least one main groove (21, 22) has a zigzag shape formed by alternating long sections and short sections, and a circumferential length (Lg2) of the long section exhibits a relationship 0.70 ≤ Lg2 / λ2 ≤ 0.90 with respect to a wavelength (λ2) of the zigzag shape, wherein the tunnel grooves (321, 322, 331, 332) are open at positions in an edge section of the bridge section (32, 33), wherein the positions are recessed in relation to the main groove (21), wherein the extension length in the tire width direction of the lug groove (321, 322, 331, 332) is in a range of 20% or more and 60% or less with respect to a maximum ground contact width of the rib section (32, 33). [2] Pneumatic tire (1) according to claim 1, wherein both main grooves (21, 22) defining the rib section (32, 33) have the zigzag shape formed by connecting the long sections and the short sections. [3] Pneumatic tire (1) according to claim 1 or 2, wherein an amplitude (A2) of the zigzag shape has a ratio of 0.03 ≤ A2 / TW ≤ 0.05 with respect to the ground contact width (TW) of the tire. [4] Pneumatic tire (1) according to one of claims 1 to 3, wherein the edge section of the middle rib section (32) and an edge section of the central rib section (33) overlap when viewed in the circumferential direction of the tire. [5] Pneumatic tire (1) according to any one of claims 1 to 4, wherein the lug grooves (321, 322, 331, 332) are arranged in the edge sections to the left and right of the rib section (32, 33) and are arranged offset in the circumferential direction of the tire. [6] Pneumatic tire (1) according to claim 5, wherein an overlap amount Wr of the lug grooves (321, 322, 331, 332) which are adjacent to each other when viewed in the circumferential direction of the tire has a relationship 0 ≤ Wr / Wb3 ≤ 0.30 with respect to a maximum ground contact width (Wb3) of the rib section (32, 33). [7] Pneumatic tire (1) according to claim 5 or 6, wherein a distance (D3) in the circumferential direction of the tire between the adjacent tread grooves (321, 322, 331, 332) has a relationship 0.20 ≤ D3 / λ2 ≤ 0.50 with respect to the wavelength (λ2) of the zigzag shape. [8] Pneumatic tire (1) according to claim 6 or 7, wherein an inclination direction of the tread groove (321, 322, 331, 332) is opposite to an inclination direction of the long section of the main groove (21, 22) with respect to the tire circumferential direction, wherein the long section has the zigzag shape. [9] Pneumatic tire (1) according to any one of claims 6 to 8, wherein a maximum groove depth of the lug groove (321, 322, 331, 332) is in a range of 70% or more and 100% or less with respect to a maximum groove depth of the main groove (21, 22). [10] Pneumatic tire (1) according to any one of claims 1 to 9, wherein of the main grooves (21, 22) defining the rib section (32, 33), the main groove (21, 22) on one side of the equatorial plane of the tire has the zigzag shape formed by alternating connecting the long sections and the short sections, the main groove (21, 22) on a ground contact edge side of the tire has a zigzag shape formed by connecting linear sections of approximately identical length, and the linear section of the main groove (21, 22) on the ground contact edge side of the tire has a circumferential length Lg1 which has a relationship 0.30 ≤ Lg1 / λ1 ≤ 0.70 with respect to a wavelength λ1 of the zigzag shape. [11] Pneumatic tire (1) according to claim 10, wherein the wavelength (λ1) of the main groove (21, 22) on the side of the ground contact edge of the tire and the wavelength (λ2) of the main groove (21, 22) on the side of the equatorial plane of the tire have a relationship 1.50 ≤ λ2 / λ1 ≤ 2.

00. [12] Pneumatic tire (1) according to any one of claims 1 to 11, wherein the pneumatic tire (1) is a heavy-duty tire mounted on a drive shaft of a vehicle.

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