Tires

Abstract

Tires (1), comprising: a plurality of main grooves (21, 22) running in a circumferential direction of the tire; and five or more rows of web sections (31, 32, 33) defined by the main grooves (21, 22), wherein at least one row of the rib sections (31, 32, 33) comprises a plurality of continuous lug grooves (321, 331) extending in the tire width direction through the rib sections (31, 32, 33), wherein a pitch spacing length (P21, P31) of the continuous lug grooves (321, 331) is in a range of 7% or more to 14% or less of a maximum ground contact length (Lt) of the tire (1), and wherein a maximum groove depth (H21, H31) of the continuous tunnel grooves (321, 331) is in a range of 5% or more to 65% or less of a maximum groove depth (Hg1, Hg2) of the main grooves (21, 22).

Description

Technical field

[0001] The invention relates to a tire and in particular to a tire that can achieve acceleration performance on snow and performance with low rolling resistance in a compatible manner. State of the art

[0002] Conventional heavy-duty tires use a zigzag-shaped main groove to increase a tire's acceleration performance on snow. The technology described in JP 2017 154708 A is known as a conventional tire that uses this configuration.

[0003] EP 3 135 504 A1 discloses a tire with a plurality of main grooves extending in a circumferential direction; and five or more rows of rib sections defined by the main grooves, wherein at least one row of the rib sections has a plurality of continuous lug grooves extending through the rib sections in a tire width direction.

[0004] Other tires are known from EP 2 357 094 A2, DE 11 2017 006 789 T5 and JP H11 123 909 A. Brief description of the invention: Technical problem

[0005] On the other hand, with heavy-duty tires mounted on the steering axle of a vehicle, there is the problem that the rolling resistance of the tire should be reduced. Solution to the problem

[0006] To solve the problem described above, a tire according to one embodiment of the invention includes a plurality of main grooves extending in the circumferential direction of the tire and four or more rows of rib sections defined by the main grooves, wherein at least one row of the rib sections includes a plurality of continuous lug grooves extending through the rib section in the tire width direction, and a pitch spacing length of the continuous lug grooves that is in a range of 7% or more to 14% or less of a maximum ground contact length of the tire, and a maximum groove depth of the continuous lug grooves that is in a range of 5% or more to 65% or less of a maximum groove depth of the main grooves. Advantageous effects of the invention

[0007] In one embodiment of the invention, the tire offers the advantage of a suitably designed relationship between the pitch spacing and the maximum groove depth of the continuous lug grooves, thus achieving a compatible balance between acceleration on snow and low rolling resistance. Specifically, the range of pitch spacing of the continuous lug grooves defines a lower limit, and the range of maximum groove depths defines an upper limit. This ensures the stiffness of the rib section and prevents a deterioration in the tire's rolling resistance. Furthermore, the range of pitch spacing of the continuous lug grooves defines an upper limit, and the range of maximum groove depths defines a lower limit.As a result, the edge component of the bridge section is secured and the traction effect of the continuous stud grooves is ensured while driving on snow-covered road surfaces. Brief description of the drawings Fig. Figure 1 is a cross-sectional view in a tire meridian direction, illustrating a tire according to an embodiment of the invention. Fig. 2 is a top view showing a running surface of the in Fig. 1 illustrated tire illustrated. Fig. 3 is an enlarged view showing a central web section and a central web section of the in Fig. 2 illustrated tires. Fig. 4 is an enlarged view showing the Fig. 3 illustrated the middle section of the bridge. Fig. 5 is a cross-sectional view of the in Fig. 3 illustrated middle bridge section. Fig. 6 is a cross-sectional view of the in Fig. 3 illustrated middle bridge section. Fig. 7 is an enlarged view showing the Fig. 3 illustrated the central web section. Fig. 8 is an enlarged view showing the shoulder strap section of the Fig. 2 illustrated tires. Fig. 9 is an enlarged view showing a narrow, shallow groove of the Fig. 8 illustrated shoulder strap section. Fig. 10 is a cross-sectional view of the in Fig. 8 illustrated shoulder strap section. Fig. Figure 11 is an enlarged top view showing a grooved wall structure of the in Fig. 2 illustrated shoulder grooves. Fig. Figure 12 is an enlarged top view showing the groove wall structure of the in Fig. 2 illustrated shoulder grooves. Fig. 13 is a cross-sectional view in one groove depth direction of the in Fig. 2 illustrated shoulder groove. Fig. 14 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. 15 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. 16 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. 17 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. Figure 18 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. 19 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. Figure 20 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. Figure 21 is an explanatory diagram of a modified example of the in Fig. 9 illustrated narrow flat groove. Fig. Figure 22 is an explanatory diagram of a modified example of the one described in Fig. 9 illustrated narrow flat groove. Fig. Figure 23 is an explanatory diagram of a modified example of the one described in Fig. 9 illustrated narrow flat groove. Fig. Figure 24 is a table showing the results of performance tests of tires according to the embodiments of the invention. Fig. Figure 25 is a table showing the results of performance tests of tires according to the embodiments of the invention. Fig. 26 is an explanatory diagram showing a shoulder bridge section of the test tire of the in Fig. 25 illustrated comparative examples. Description of embodiments

[0008] Embodiments of the invention are described in detail below with reference to the drawings. However, the invention is not limited to these embodiments. Furthermore, components of the embodiments include elements that are interchangeable while maintaining conformity with the invention, as well as obviously interchangeable elements. Moreover, the modified examples described in the embodiments can be combined as needed within the scope of protection that is obvious to a person skilled in the art. Tires

[0009] Fig. Figure 1 is a cross-sectional view in a tire meridional direction, illustrating a tire according to one embodiment of the invention. The identical drawing illustrates a cross-sectional view of a half-section in the tire radial direction. In this embodiment, a heavy-duty radial pneumatic tire mounted on a steering axle of trucks and tractors is described as an example of the tire.

[0010] Referring to the same drawing, "cross-section in a tire meridian direction" refers to a cross-section of the tire along a plane that includes the tire's axis of rotation (not illustrated). The reference symbol CL denotes an equatorial plane of the tire and refers to a plane perpendicular to the tire's axis of rotation, passing through the tire's center point in the direction of the tire's axis of rotation. "Tire width direction" refers to the direction parallel to the tire's axis of rotation. "Tire radial direction" refers to the direction perpendicular to the tire's axis of rotation.

[0011] A tire 1 has a ring structure, the center of which is the tire rotation axis, 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 includes one or more bead wires made of steel, wound multiple times in a ring shape, and embedded in bead sections to configure the cores of the left and right bead sections. The pair of bead fillers 12, 12 is arranged in the tire radial direction on an outer circumference of the pair of bead cores 11, 11 and reinforces the bead sections.

[0013] The carcass layer 13 has a single-layer structure, consisting of a single carcass ply, or a multi-layer structure, consisting of multiple layered carcass plies, and extends between the left and right bead cores 11, 11 in a torus shape, thus forming the support structure of the tire. Furthermore, both end sections of the carcass layer 13 are bent back on an outside side in the direction of the tire width so that they are wrapped and fixed around the bead cores 11 and the bead fillers 12.The carcass layer of carcass layer 13 is also formed by rolling a plurality of carcass cord threads made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon or the like) covered with coating rubber and has a carcass angle (defined as the angle of inclination in the longitudinal direction of the carcass cord threads with respect to the tire circumferential direction) in the range of 80° or more to 100° or less in an absolute value.

[0014] The belt layer 14 is formed by stacking four layers of belt plies 141 to 144 and is arranged by wrapping them around the outer circumference of the carcass layer 13. The belt plies 141 to 144 are formed by rolling a plurality of belt cord threads made of steel or an organic fiber material coated with coating rubber and have a belt angle in the range of 15° or more to 55° or less in an absolute value. Furthermore, the belt plies 141 to 144 have belt angles (defined as the longitudinal angle of inclination of the belt cord threads with respect to the tire circumference) with opposite signs and are stacked such that the longitudinal directions of the belt cord threads intersect (so-called cross-ply structure).

[0015] The tread rubber 15 is arranged on an outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 and forms a tread section of the tire 1. The pair of sidewall rubbers 16, 16 are arranged on the outer side in the tire width direction of the carcass layer 13 and form a left and a right sidewall section. The pair of rim pad rubbers 17, 17 extend from an inner side in the tire radial direction of the left and right bead cores 11, 11 and the folded-over sections of the carcass layer 13 to an outer side in the tire width direction to form rim mating surfaces of the bead sections. Tread pattern

[0016] Fig. 2 is a top view showing a running surface of the in Fig. Figure 1 illustrates the tread surface of an all-season tire with the mud / snow marking "M+S". Referring to the same drawing, "tire circumference direction" refers to the direction of rotation around the tire's axis of rotation. A reference sign T denotes a contact edge of the tire, and a dimension symbol TW denotes a contact width of the tire.

[0017] As in Fig. As illustrated in Figure 2, the tire 1 includes a plurality of main circumferential grooves 21, 22 extending in the tire circumferential direction and a plurality of rib sections 31, 32, 33 defined in the main circumferential grooves 21, 22, wherein the plurality of main circumferential grooves 21, 22 and the plurality of rib sections 31, 32, 33 are provided in a tread surface.

[0018] “Main groove” refers to a groove where a wear indicator must be provided in accordance with JATMA and which has a maximum groove width of 7.0 mm or more and a maximum groove depth of 12 mm or more.

[0019] The groove width is measured as the distance between a left and a right groove wall at 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 rib section includes a recessed section or a chamfered section on its edge, the groove width is measured using the intersections between the tread contact surface and extension lines of the groove walls as measuring points, in a cross-sectional view with the groove length direction as a normal direction.

[0020] Groove depth is the distance from the tread contact surface to the groove bottom and is measured when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state. Additionally, in configurations where the grooves include an uneven section or sipes on the groove bottom, the groove depth is measured excluding these sections.

[0021] Here, "specified rim" refers to a "standard rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by 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 TRA, or "INFLATION PRESSURES" as defined by 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 of Fig. 2. The tire 1 exhibits an approximately point-symmetric tread pattern with a center point on the equatorial plane CL of the tire. However, no such restriction is intended, and, for example, the tire 1 may have a left-right axially symmetric tread pattern or a left-right asymmetric tread pattern around the equatorial plane CL of the tire, and may have a tread pattern with directional dependence in the direction of tire rotation (not illustrated).

[0023] Furthermore, the configuration of Fig. 2. The left and right areas, which are delimited by the equatorial plane CL of the tire, each have two main circumferential grooves 21, 22. These main circumferential grooves 21, 22 are arranged such that they are left-right symmetrical with respect to the equatorial plane CL of the tire. Five rows of rib sections 31 to 33 are defined by these main circumferential grooves 21, 22. Additionally, a rib section 33 is arranged on the equatorial plane CL of the tire.

[0024] However, no such restriction is intended, and three, five, or more major circumferential grooves can be arranged, or the major circumferential grooves can be arranged asymmetrically with respect to the equatorial plane CL of the tire (not illustrated). Additionally, the rib section can be positioned away from the equatorial plane CL of the tire, with one major circumferential groove located on the equatorial plane CL of the tire (not illustrated).

[0025] Furthermore, of the main circumferential grooves 21, 22, which are arranged in an area delimited by the equatorial plane CL of the tire, the main circumferential groove 21 on the outermost side in the tire width direction is defined as a shoulder main groove, and the main circumferential groove 22 on the side of the equatorial plane CL of the tire is defined as a middle main groove.

[0026] The rib section 31, located on the outer side in the tire width direction and defined in the main shoulder groove 21, is defined as a shoulder rib section. Shoulder rib section 31 is a rib section located on the outermost side in the tire width direction and at the ground contact edge T of the tire. Furthermore, rib section 32, located on the inner side in the tire width direction and defined in the main shoulder groove 21, is defined as a middle rib section. The middle rib section 32 is adjacent to shoulder rib section 31, with the main shoulder groove 21 located between them. Additionally, rib section 33, located closer to the side of the equatorial plane CL of the tire than the middle rib section 32, is defined as a middle rib section. The middle rib section 33 may be located 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).

[0027] The ground contact width TW of the tire is measured as the maximum linear distance in the tire axial direction of a contact surface between the tire and a flat plate 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 the predetermined load.

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

[0029] It should be noted that in a configuration where the four main circumferential grooves 21, 22, as in Fig. Figure 2 illustrates that a pair of shoulder bar sections 31, 31 and a pair of middle bar sections 32, 32 and a single middle bar section 33 are defined. Furthermore, for example, in a configuration that includes five or more main perimeter grooves, two or more rows of middle bar sections are defined (not illustrated). In a configuration that includes three main perimeter grooves, the middle bar section also serves as the middle bar section (not illustrated).

[0030] In the configuration of Fig. 2. The maximum ground contact width Wb1 of the shoulder rib section 31 has a relationship of 0.15 ≤ Wb1 / TW ≤ 0.25 with respect to the ground contact width TW of the tire. Furthermore, the maximum ground contact width Wb3 of the center rib section 33, which is closest to the equatorial plane CL of the tire, preferably has a relationship of 0.15 ≤ Wb3 / TW ≤ 0.25 with respect to the ground contact width TW of the tire, and more preferably has a relationship of 0.18 ≤ Wb3 / TW ≤ 0.23. Additionally, in a configuration that includes four main circumferential grooves 21, 22 and five rows of rib sections 31 to 33, as shown in Fig. Figure 2 illustrates that the maximum ground contact width Wb2 of the middle web section 32 is preferably somewhat narrower than the maximum ground contact width Wb1 of the shoulder web section 31 and is particularly preferably in a range of 0.85 ≤ Wb2 / Wb1 ≤ 0.95.

[0031] In the configuration of Fig. 2. The shoulder main groove 21 and the center main groove 22 have a zigzag or wave-like shape with an amplitude in the tire width direction. However, no such restriction is intended, and as described below, the shoulder main grooves 21 and the center main grooves 22 may have a straight shape at the groove opening section (not illustrated).

[0032] The shoulder rib section 31 is a rib with a continuous road contact surface in the circumferential direction of the tire and does not include any lug grooves. Additionally, the middle rib section 32 and the middle rib section 33 each enclose a plurality of continuous lug grooves 321, 331. The continuous lug grooves 321, 331 have an open structure that extends through the rib sections 32, 33 and are arranged at predetermined intervals in the circumferential direction of the tire. Consequently, the middle rib section 32 and the middle rib section 33 are divided in the circumferential direction of the tire by the continuous lug grooves 321, 331 to form a series of blocks.

[0033] In Fig. 2. A snow traction index (STI) in the direction of the tire circumference lies over the entire circumference of the tire 1 (so-called 0-degree snow traction index) in a range of 130 ≤ STI.

[0034] The Snow Traction Index (STI) is an empirical formula developed by Uniroyal, proposed by the Society of Automotive Engineers (SAE), and defined by the following mathematical formula (1). In the formula, Pg is a groove density (1 / mm) and is calculated as the ratio between the groove length (mm) of all grooves (all grooves except sipes) projecting in the tire's circumferential direction onto the tire's ground contact surface and the tire's ground contact area (product of the tire's ground contact width and the tire's circumferential length (mm^2)). Additionally, ρs is a sipe density (1 / mm) and is calculated as the ratio between the sipe length (mm) of all sipes projecting in the tire's circumferential direction onto the tire's ground contact surface and the tire's ground contact area (mm^2).Furthermore, Dg is an average value of the groove depth (mm) of all grooves that protrude in the circumferential direction onto the ground contact surface of the tire. STI=−6.8+2202×Pg+672×ρs+7.6×Dg Middle section of the bridge

[0035] Fig. Figure 3 is an enlarged view showing the central web section 32 and the central web section 33 of the in Fig. 2 illustrated tires 1 illustrated. Fig. 4 is an enlarged view showing the Fig. 3 illustrated middle bridge section 32 illustrated. Fig. 5 and Fig. 6 are cross-sectional views of the in Fig. 3 illustrated middle web section 32. In these drawings illustrated Fig. 5 a cross-sectional view of the middle web section 32 along a continuous tunnel groove 321A, which has a groove floor lamella 323, and Fig. Figure 6 illustrates a cross-sectional view of the middle web section 32 along a continuous tunnel groove 321B, which does not have a groove floor lamella.

[0036] In the configuration of Fig. 2, as in Fig. As illustrated in Figure 3, the groove opening sections of the shoulder main grooves 21 and the central main grooves 22 have a wave-like shape formed by connecting a plurality of arcs projecting towards the equatorial plane CL of the tire. Consequently, the left and right edge sections of the central rib section 32 have a wave-like shape formed by connecting a plurality of arcs projecting towards the equatorial plane CL of the tire.

[0037] Furthermore, there are in Fig. 4. The wavelengths λ2L, λ2R of the wave-like shapes of the edge sections of the central rib section 32 are in a range of 14% or more to 28% or less of the maximum ground contact length Lt of the tire (not illustrated). Additionally, the wave-like wavelengths λ2L, λ2R of the left and right edge sections are adjusted to be equal to each other.

[0038] The maximum ground contact length Lt of the tire is measured as the maximum linear distance in the tire's circumferential direction of a contact surface between the tire and a flat plate when the tire is mounted on a specified rim, inflated to a specified internal pressure, placed vertically on the flat plate in a static state, and loaded with a load corresponding to the specified load.

[0039] As in Fig. As illustrated in Figure 4, the circumferential length of the arc (dimension symbol omitted in drawings) is 80% or more, and preferably 85% or more, with respect to the wavelengths λ2L, λ2R of the wave-like shape. Furthermore, adjacent arcs are connected by short straight lines or bends. Accordingly, the edge section of the central web section 32 has a wave-like shape formed by connecting long bends projecting in the same direction. In such a configuration, uneven wear at the maximum projection position of the edge section is suppressed compared to a configuration in which the edge section has a zigzag or sinusoidal shape.

[0040] Furthermore, the amplitudes A2L, A2R of the wave-like shapes of the edge sections are in a range of 3.0% or more to 10% or less, and preferably in a range of 4.0% or more to 7.0% or less, with respect to the maximum ground contact width Wb2 of the central web section 32. Additionally, the amplitudes A2L, A2R are in a range of 1.0 mm or more to 15.0 mm or less, and preferably in a range of 1.2 mm or more to 10.0 mm or less. Moreover, the ratio of the amplitudes A2L, A2R of the wave-like shapes of the left and right edge sections is set to be in a range of 90% or more to 110% or less.

[0041] Furthermore, the phase ϕ2 of the wave-like shapes of the left and right boundary sections lies in a range of 10% or more to 40% or less with respect to the wavelength λ2L.

[0042] The wavelength, amplitude and phase of the wave-like shapes of the edge sections of the rib section are measured when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure and in an unloaded state.

[0043] As in Fig. As illustrated in Figure 3, the middle bridge section 32 includes a plurality of continuous tunnel grooves 321 and a plurality of blocks 322.

[0044] The continuous lug grooves 321 have an open structure that extends through the central rib section 32 in the tire width direction. Furthermore, the majority of the continuous lug grooves 321 are arranged at a predetermined pitch length P21 in the tire circumference direction. Additionally, the pitch length P21 of the continuous lug grooves 321 lies within a range of 7% or more to 14% or less of the maximum ground contact length Lt of the tire (not illustrated). For example, in the configuration of Fig. 3. The continuous lug grooves 321 are open at the positions of maximum amplitude of the wave-like shapes of the left and right edge sections of the central rib section 32. Furthermore, the pitch of the continuous lug grooves 321 is set to be twice the pitch of the wave-like shapes of the edge sections. Additionally, the pitch of the continuous lug grooves 321 is within a range of 100 or more to 200 or less across the entire circumference of the tire.

[0045] In Fig. 4 are the continuous lug grooves 321 of the middle web section 32 narrow flat grooves and have a maximum groove width W21 of 1.5 mm or more to 4.0 mm or less (preferably 3.0 mm or less) and a maximum groove depth H21 of 1.5 mm or more to 4.0 mm or less (preferably 3.0 mm or less) (see Fig. 5). Furthermore, it points out in Fig. 5 a maximum groove depth H21 of the continuous lug groove 321 a relationship of 0.05 ≤ H21 / Hg1 ≤ 0.65 and preferably a relationship of 0.10 ≤ H21 / Hg1 ≤ 0.30 with respect to the maximum groove depth Hg1 of the shoulder main groove 21.

[0046] In the configuration described above, the relationship between the pitch spacing P21 and the maximum groove depth H21 of the continuous lug grooves 321 is suitably designed, and the acceleration performance on snow and the low rolling resistance performance of the tire are achieved in a compatible manner. Specifically, the range of the pitch spacing P21 of the continuous lug grooves 321 has a lower limit, and the range of the maximum groove depth H21 of the continuous lug grooves 321 has an upper limit. As a result, the stiffness of the central rib section 32 is ensured, and a deterioration in the tire's rolling resistance is suppressed. Furthermore, the range of the pitch spacing P21 of the continuous lug grooves 321 has an upper limit, and the range of the maximum groove depth H21 of the continuous lug grooves 321 has a lower limit.As a result, the edge component of the middle rib section 32 is ensured and the traction effect of the continuous stud grooves 321 is ensured while driving on snow-covered road surfaces.

[0047] In Fig. 4. The inclination angle θ21 of the continuous lug grooves 321 with respect to the tire circumference direction is in the range of 60° ≤ θ21 ≤ 120°. In the configuration of Fig. 4 The wave-like shapes of the left and right edge sections of the central rib section 32 are arranged such that they are phase-shifted relative to each other, and the continuous lug grooves 321 are each open to the positions of maximum amplitude of the wave-like shapes of the left and right edge sections. As a result, the entire continuous lug grooves 321 are inclined with respect to the tire's circumferential direction.

[0048] The inclination angle θ21 of the continuous tread groove 321 is measured as an angle formed between an imaginary straight line connecting both end sections of the continuous tread groove 321 and the tire circumferential direction.

[0049] As in Fig. As illustrated in Figure 4, the continuous tunnel grooves 321 have a zigzag shape. Additionally, the amplitude of the zigzag shape of the continuous tunnel groove 321 is in the range of 2.0% or more to 7.0% or less with respect to the pitch spacing length P21 of the continuous tunnel groove 321. Furthermore, the wavelength of the zigzag shape of the continuous tunnel groove 321 is in the range of 16% or more to 22% or less with respect to the maximum ground contact width Wb2 of the central web section 32.

[0050] Additionally, as in Fig. As illustrated in Figures 3 to 6, the majority of continuous adit grooves 321 close a first continuous adit groove 321A (see Figure 3 to 6). Fig. 5) with a grooved bottom lamella 323 and a second continuous lug groove 321B without a grooved bottom lamella (see Fig. 6). As in Fig. As illustrated in Figure 6, the second continuous adit groove 321B has a structure in which the groove floor lamella 323 is in Fig. 5 from the first continuous lug groove 321A is omitted. Additionally, in the configuration of Fig. 3 The first continuous lug groove 321A and the second continuous lug groove 321B are arranged alternately in the circumferential direction of the tire. However, no such restriction is intended, and two or three second continuous lug grooves 321B may be arranged between adjacent first continuous lug grooves 321A, 321A (not illustrated).

[0051] The groove base sipe is a cut formed in the groove base of the lug groove, having a maximum sipe width of less than 1.0 mm and a sipe depth described later, and is closed when the tire comes into contact with the ground.

[0052] The distance H23' from the groove bottom of the continuous lug groove 321 to the position of maximum depth of the groove bottom lamella 323 is in a range of 0.06 ≤ H23' / Hg1 and preferably in a range of 0.10 ≤ H23' / Hg1 with respect to the maximum groove depth Hg1 of the shoulder main grooves 21. Furthermore, the distance H23 from the tread contact surface to the position of maximum depth of the groove bottom lamella 323 is in a range of H23 / Hg1 ≤ 1.00 and preferably in a range of H23 / Hg1 ≤ 0.50 with respect to the maximum groove depth Hg1 of the shoulder main grooves 21.

[0053] Block 322 is defined by the plurality of continuous lug grooves 321. Furthermore, block 322 has a shape that is elongated in the direction of the tire width. In particular, in Fig. 4 the pitch spacing length of the block 322 (equal to the pitch spacing length P21 of the continuous cleat grooves 321) in a range of 45% or more to 80% or less and preferably in a range of 50% or more to 75% or less with respect to the maximum ground contact width Wb2 of the middle web section 32. central section

[0054] Fig. 7 is an enlarged view showing the Fig. The central web section 33 is illustrated in section 3. The same drawing shows components that are the same as those in Fig. The three illustrated components are labelled with the same reference symbols, and their explanations are omitted.

[0055] In the configuration of Fig. 2, as in Fig. As illustrated in Figure 3, the groove opening sections of the left and right central main grooves 22, 22 have a wave-like shape formed by connecting a plurality of arcs projecting towards the equatorial plane CL of the tire. Consequently, the left and right edge sections of the central rib section 33 have a wave-like shape formed by connecting a plurality of arcs projecting towards the equatorial plane CL of the tire (in the same drawing, towards the inside in the width direction of the central rib section 33).

[0056] Furthermore, there are in Fig. 7. The wavelengths λ3L, λ3R of the wave-like shapes of the edge sections of the center rib section 33 are in a range of 14% or more to 28% or less of the maximum ground contact length Lt of the tire (not illustrated). Additionally, the wavelengths λ3L, λ3R of the wave-like shapes of the left and right edge sections are adjusted to be equal to each other. The wavelength λ3L of the edge section of the center rib section 33, defined by the central main grooves 22, is adjusted to be in a range of 90% or more to 110% or less with respect to the wavelength λ2R of the edge section of the center rib section 32 (see Fig. 4).

[0057] As in Fig. As illustrated in Figure 7, the circumferential length of the arc (dimension symbol omitted in drawings) is 80% or more, and preferably 85% or more, with respect to the wavelengths λ3L, λ3R of the wave-like shapes. Furthermore, adjacent arcs are connected by short straight lines or bends. Accordingly, the edge section of the central web section 33 has a wave-like shape formed by connecting long bends projecting in the same direction. In such a configuration, uneven wear at the maximum projection position of the edge section is suppressed compared to a configuration in which the edge section has a zigzag or sinusoidal shape.

[0058] Furthermore, the amplitudes A3L, A3R of the wave-like shapes of the edge sections are in a range of 3.0% or more to 10% or less, and preferably in a range of 4.0% or more to 7.0% or less, with respect to the maximum ground contact width Wb3 of the central web section 33. Additionally, the amplitudes A3L, A3R are in a range of 1.0 mm or more to 15.0 mm or less, and preferably in a range of 1.2 mm or more to 10.0 mm or less. Moreover, the ratio of the amplitudes A3L, A3R of the wave-like shapes of the left and right edge sections is set to be in a range of 90% or more to 110% or less.Furthermore, the amplitude A3L of the edge section of the central web section 33, defined by the central main groove 22, is set to be in a range of 90% or more to 110% or less with respect to the amplitude A2R of the edge section of the central web section 32 (see . Fig. 4).

[0059] Furthermore, the phase ϕ3 of the wave-like shapes of the left and right boundary sections lies in a range of 10% or more to 40% or less with respect to the wavelength λ3L.

[0060] As in Fig. As illustrated in Figure 3, the central bridge section 33 includes a plurality of continuous tunnel grooves 331 and a plurality of blocks 332.

[0061] The continuous lug grooves 331 have an open structure that extends through the central rib section 33 in the tire width direction. Furthermore, the majority of the continuous lug grooves 331 are arranged at a predetermined pitch length P31 in the tire circumference direction. The pitch length P31 of the continuous lug grooves 331 is in a range of 7% or more to 14% or less of the maximum ground contact length Lt of the tire (not illustrated). For example, in the configuration of Fig. 3. The continuous lug grooves 331 are open at the positions of maximum amplitude of the wave-like shapes of the left and right edge sections of the center rib section 33. Furthermore, the pitch of the continuous lug grooves 331 is set to be twice the pitch of the wave-like shapes of the edge sections. Additionally, the pitch of the continuous lug grooves 331 is within a range of 100 or more to 200 or less across the entire circumference of the tire. Furthermore, the pitch of the continuous lug grooves 331 of the center rib section 33 is equal to the pitch of the continuous lug grooves 321 of the center rib section 32.

[0062] As in Fig. As illustrated in Figure 3, the opening sections of the continuous lug grooves 331 of the central rib section 33 and the opening sections of the continuous lug grooves 321 of the central rib section 32 are arranged with respect to the central main groove 22 such that they face each other. In particular, the offset Da in the circumferential direction of the opening sections of the opposing continuous lug grooves 321, 331 is preferably in a range of 0 ≤ Da / λ2 ≤ 0.10 and more, preferably in a range of 0 ≤ Da / λ2 ≤ 0.05 with respect to the wavelength λ2 of the edge section of the central rib section 32.

[0063] In Fig. 7 The continuous grooves 331 of the central web section 33 are narrow, shallow grooves and have a maximum groove width W31 of 1.5 mm or more to 4.0 mm or less (preferably 3.0 mm or less) and a maximum groove depth H31 (not illustrated) of 1.5 mm or more to 4.0 mm or less (preferably 3.0 mm or less). The maximum groove depth H31 of the continuous grooves 331 has a relationship of 0.05 ≤ H31 / Hg2 ≤ 0.65 and preferably a relationship of 0.10 ≤ H31 / Hg2 ≤ 0.30 with respect to the maximum groove depth Hg2 of the central main groove 22 (not illustrated).

[0064] In the configuration described above, the relationship between the pitch spacing P31 and the maximum groove depth H31 of the continuous lug grooves 331 is suitably designed, resulting in a compatible balance between acceleration performance on snow and low rolling resistance. Specifically, the pitch spacing P31 of the continuous lug grooves 331 represents the lower limit, and the maximum groove depth H31 of the continuous lug grooves 331 represents the upper limit. Consequently, the stiffness of the center rib section 33 is ensured, and a deterioration in the tire's rolling resistance is suppressed. Furthermore, the pitch spacing P31 of the continuous lug grooves 331 represents the upper limit, and the maximum groove depth H31 of the continuous lug grooves 331 represents the lower limit.As a result, the edge component of the central web section 33 is ensured, and the traction effect of the continuous stud grooves 331 is ensured while driving on snow-covered road surfaces.

[0065] In Fig. 7. The inclination angle θ31 of the continuous lug grooves 331 with respect to the tire circumference direction lies within a range of 60° ≤ θ31 ≤ 120°. In the configuration of Fig. 7 The wave-like shapes of the left and right edge sections of the central rib section 33 are arranged such that they are phase-shifted relative to each other, and the continuous lug grooves 331 are each open to the positions of maximum amplitude of the wave-like shapes of the left and right edge sections. As a result, the entire continuous lug grooves 331 are inclined with respect to the tire's circumferential direction. Furthermore, as in Fig. Figure 3 illustrates the inclination direction of the continuous tunnel grooves 331 of the central bridge section 33 opposite to the inclination direction of the continuous tunnel grooves 321 of the central bridge section 32.

[0066] As in Fig. As illustrated in Figure 7, the continuous tunnel grooves 331 have a zigzag shape. Additionally, the amplitude of the zigzag shapes of the continuous tunnel grooves 331 ranges from 2.0% or more to 7.0% or less with respect to the pitch spacing length P31 of the continuous tunnel grooves 331. Furthermore, the wavelength of the zigzag shapes of the continuous tunnel grooves 331 ranges from 16% or more to 22% or less with respect to the maximum ground contact width Wb3 of the central web section 33.

[0067] Furthermore, as in Fig. 3 and Fig. As illustrated in Figure 7, the majority of continuous adit grooves 331 include a first continuous adit groove 331A with a groove floor lamella 333 and a second continuous adit groove 331B without a groove floor lamella. For example, in the configuration of Fig. 7. The first continuous lug groove 331A and the second continuous lug groove 331B are arranged alternately in the circumferential direction of the tire. However, no such restriction is intended, and two or three second continuous lug grooves 331B may be arranged between adjacent first continuous lug grooves 331A, 331A (not illustrated). Additionally, as shown in Fig. Figure 3 illustrates that the first continuous lug grooves 331A of the central rib section 33 with the groove base lamella 333 and the first continuous lug grooves 321A of the central rib section 32 with the groove base lamella 323 are arranged offset in the circumferential direction of the tire. In other words, the continuous lug grooves 321A, 321B, 331A, 331B of each of the rib sections 32, 33 are arranged such that the first continuous lug grooves 331A of the central rib section 33 with the groove base lamella 333 and the first continuous lug grooves 321A of the central rib section 32 with the groove base lamella 323 do not face each other via the central main groove 22.

[0068] Furthermore, the distance H33' (not illustrated) from the groove bottom of the continuous lug groove 331 to the position of maximum depth of the groove bottom lamella 333 is in a range of 0.06 ≤ H33' / Hg2 and preferably in a range of 0.10 ≤ H33' / Hg2 with respect to the maximum groove depth Hg2 (not illustrated) of the central main groove 22. Additionally, the distance H33 (not illustrated) from the tread contact surface to the position of maximum depth of the groove bottom lamella 333 is in a range of H33 / Hg2 ≤ 1.00 and preferably in a range of H33 / Hg2 to ≤ 0.50 with respect to the maximum groove depth Hg2 of the central main groove 22.

[0069] Block 332 is defined by the plurality of continuous lug grooves 331. Additionally, block 332 has a shape that is elongated in the direction of the tire width. In particular, in Fig. 7 the pitch spacing length of block 332 (equal to the pitch spacing length P31 of the continuous cleat grooves 331) in a range of 45% or more to 80% or less and preferably in a range of 50% or more to 75% or less with respect to the maximum ground contact width Wb3 of the central web section 33. Shoulder strap section

[0070] Fig. Figure 8 is an enlarged view showing the shoulder bridge section 31 of the in Fig. 2 illustrated tires 1 illustrated. Fig. Figure 9 is an enlarged view showing the narrow, shallow groove 311 of the in Fig. The shoulder bridge section 31 is illustrated in Figure 8. The same drawing illustrates a single narrow, shallow groove 311. Fig. 10 is a cross-sectional view of the in Fig. 8 illustrated shoulder bridge section 31. The same drawing illustrates a cross-sectional view of the shoulder bridge section 31 along the narrow flat groove 311.

[0071] In the configuration of Fig. As described above, the shoulder rib section 31 is a rib with a continuous road contact surface in the circumferential direction of the tire and is not divided in the circumferential direction by lug grooves or sipes. Furthermore, the edge section on the side of the main shoulder groove 21 of the shoulder rib section 31 has a wave-like shape formed by connecting a plurality of arcs that project towards the equatorial plane CL of the tire.

[0072] As in Fig. As illustrated in Figure 2, the shoulder bridge section 31 includes a plurality of narrow, shallow grooves 311.

[0073] The narrow, flat grooves 311 have a U-shape (or a V-shape or a C-shape) with an opening section facing the road contact edge T of the tire. In other words, the narrow, flat grooves 311 have a continuous, one-sided opening shape with a closed section on the side of the equatorial plane CL of the tire and an opening section on the side of the road contact edge T of the tire. Furthermore, the narrow, flat grooves 311 have a closed structure that terminates at the road contact surface of the shoulder rib section 31. Therefore, the narrow, flat grooves 311 are not connected to the road contact edge T of the tire and the main shoulder grooves 21 and are arranged such that they are separated from the edge section of the road contact surface of the shoulder rib section 31. Additionally, the majority of the narrow, flat grooves 311 are arranged at predetermined intervals in the circumferential direction of the tire.Furthermore, adjacent narrow flat grooves 311 are arranged in such a way that they are separated from each other.

[0074] Furthermore, the maximum groove width Wn of the narrow, flat grooves is 311 (see Fig. 9) in a range of 0.1 mm ≤ Wn ≤ 5.0 mm and preferably in a range of 0.3 mm ≤ Wn ≤ 2.0 mm. Furthermore, the maximum groove depth Hn of the narrow, shallow grooves 311 (see Fig. 10) a relationship of 0.01 ≤ Hn / Hg ≤ 0.30 and preferably a relationship of 0.03 ≤ Hn / Hg ≤ 0.25 with respect to the maximum groove depth Hg of the shoulder main grooves 21. Since the narrow shallow grooves 311 have the maximum groove width Wn and the maximum groove depth Hn as described above, the narrow shallow grooves 311 function as open-open grooves when the tire contacts the ground.

[0075] In the configuration described above, (1) because the narrow flat grooves 311 have a U-shape, the acceleration performance of the tire on snow during vehicle travel is improved by the circumferential components of the narrow flat grooves 311 compared to a configuration featuring a plurality of I-shaped narrow grooves arranged circumferentially in the width direction (not illustrated). Furthermore, (2) because the narrow flat grooves 311 have a U-shape, with the opening section facing the contact edge T of the tire, the circumferential components of the narrow flat grooves in the area on the side of the contact edge T of the tire can be omitted compared to, for example, a configuration featuring narrow flat grooves with an annular structure (not illustrated).As a result, the noise performance of the tire is improved during vehicle operation, and uneven wear resulting from the narrow, flat grooves 311 is suppressed. Furthermore, (3) because the narrow, flat grooves 311 have a closed structure terminating in the ground contact surface of the rib section 31, the noise performance of the tire is improved compared to a configuration featuring narrow, flat grooves extending through the ground contact surface of the rib section in the tire width or circumferential direction (not illustrated).

[0076] Furthermore, it points out that Fig. 8 the width direction length W11 of the narrow flat grooves 311 a relationship of 0.40 ≤ W11 / Wb1 ≤ 0.90 and preferably a relationship of 0.50 ≤ W11 / Wb1 ≤ 0.80 with respect to the maximum ground contact width Wb1 of the shoulder rib section 31.

[0077] The width direction length W11 of the narrow flat grooves 311 is measured as the maximum extension length in the tire width direction of the narrow flat grooves 311 when the tire is mounted on a specified rim, inflated to the specified internal pressure and in an unloaded state.

[0078] Furthermore, it points out that Fig. 8 the circumferential length L11 of the narrow flat grooves 311 a relationship of 0.50 ≤ L11 / P11 ≤ 0.90 and preferably a relationship of 0.60 ≤ L11 / P11 ≤ 0.80 with respect to the pitch spacing length P11 of the narrow flat grooves 311.

[0079] The circumferential length L11 of the narrow flat grooves 311 is measured as the maximum extension length in the tire circumferential direction of the narrow flat grooves 311 when the tire is mounted on a specified rim, inflated to the specified internal pressure and in an unloaded state.

[0080] Furthermore, the pitch spacing Pn of the narrow flat grooves 311 is equal to the pitch spacing of the wave-like shapes of the edge sections of the shoulder rib section 31 and is in a range of 50 or more to 100 or less. Additionally, the spacing (not illustrated) of the adjacent narrow flat grooves 311, 311 is preferably ensured to be in a range of 10 mm or more.

[0081] Furthermore, it points out that Fig. 8 the distance D1 between the endpoints A1, A2 of the narrow flat grooves 311 in the tire circumferential direction a relationship of 0.30 ≤ D1 / P11 ≤ 0.70 and preferably a relationship of 0.40 ≤ D1 / P11 ≤ 0.60 with respect to the pitch distance length P11 of the narrow flat grooves 311.

[0082] Furthermore, it points out that Fig. 8 the distance D2 (see Fig. 9) between the endpoints A1, A2 of the narrow flat grooves 311 in the tire width direction a relationship of 0 ≤ D2 / Wb1 ≤ 0.70 and preferably a relationship of 0 ≤ D2 / Wb1 ≤ 0.50 with respect to the maximum ground contact width Wb1 of the shoulder rib section 31.

[0083] Furthermore, it points out that Fig. 8. The distance D3 between the narrow, flat groove 311 and the ground contact edge T of the tire has a relationship of 0.05 ≤ D3 / Wb1 and preferably a relationship of 0.10 ≤ D3 / Wb1 with respect to the maximum ground contact width Wb1 of the shoulder rib section 31. Likewise, the distance D4 between the narrow, flat groove 311 and the edge section of the shoulder rib section 31 has a relationship of 0.10 ≤ D4 / Wb1 and preferably a relationship of 0.15 ≤ D4 / Wb1 with respect to the maximum ground contact width Wb1 of the shoulder rib section 31. As a result, the stiffness of the edge section of the shoulder rib section 31 is ensured. It should be noted that the upper limit of the distances D3, D4 is not particularly restricted, but is limited by the relationship with the ratio W11 / Wb1 of the lateral direction length W11 of the narrow, shallow grooves 311 described above. Furthermore, in the configuration of Fig. 8 the measuring point of distance D3 is the endpoint A1, however the other endpoint A2 can be the measuring point of distance D3, depending on the shape of the narrow flat groove 311.

[0084] Furthermore, in Fig. 8 the width direction length W11 and the circumferential length L11 of the narrow flat grooves 311 have a relationship of 0.60 ≤ W11 / L11 ≤ 1.40 and preferably a relationship of 0.80 ≤ W11 / L11 ≤ 1.20.

[0085] Furthermore, in Fig. 8 in a configuration in which the shoulder rib section 31 has an edge section with a zigzag shape or a wave-like shape with an amplitude in the tire width direction, the distance D5 in the tire circumferential direction between the innermost point B in the tire width direction of the narrow flat groove 311 and the position of maximum amplitude P100 on the outside in the tire width direction of the edge section of the shoulder rib section 31 in a range of 0.30 ≤ D5 / λ1o_sh ≤ 0.70 and preferably in a range of 0.45 ≤ D5 / λ1o_sh ≤ 0.65 with respect to the wavelength λ1o_sh of the edge section. Accordingly, the innermost point B of the narrow, flat groove 311 is positioned such that it is separated from the position of maximum amplitude P100 on the outside in the tire width direction of the edge section of the shoulder rib section 31. As a result, the stiffness of the edge section of the shoulder rib section 31 is ensured.

[0086] As in Fig. As illustrated in Figure 9, the pair of endpoints A1, A2 of the narrow, flat grooves 311 and the innermost point B in the tire width direction are defined. An imaginary line L1 is defined that passes through the center point M and the innermost point B of the endpoints A1, A2. At this point, an angle θ11 between the imaginary line L1 and the tire circumference direction lies in a range of 45° ≤ θ11 ≤ 135° and preferably in a range of 50° ≤ θ11 ≤ 70°. Consequently, the opening direction of the U-shape of the narrow, flat grooves 311 is suitably designed.

[0087] Furthermore, the configuration of Fig. 9 The U-shape of the narrow, shallow grooves 311 comprises continuous width-direction sections Ra1, Ra2 with an inclination angle of 75° or more to 105° or less with respect to the tire circumference. The sum ΣLa of the width-direction lengths La1 to La4 of the width-direction sections Ra1, Ra2 (dimensional symbol omitted in drawings) exhibits a relationship of 1.00 ≤ ΣLa / W11 and preferably a relationship of 1.30 ≤ ΣLa / W11 with respect to the width-direction length W11 of the narrow, shallow groove 311. Furthermore, each of the lateral direction lengths La1 to La4 of the lateral direction profile sections Ra1, Ra2 preferably lies within a range of 25% or more with respect to the lateral direction length W11 of the narrow, shallow groove 311. Consequently, the lateral direction lengths La1 to La4 of the lateral direction profile sections Ra1; Ra2 are ensured.It should be noted that the upper limit of the ratio is not particularly restricted, but is limited by other conditions.

[0088] The inclination angle of the U-shape of the narrow flat groove 311 is measured as an angle between the tangent of the groove centerline of the narrow flat groove and the tire circumferential direction.

[0089] Furthermore, the configuration of Fig. 9. The U-shape of the narrow, shallow grooves 311 is provided with a continuous circumferential section Rb having an inclination angle of 0° or more to 15° or less with respect to the tire's circumferential direction. Furthermore, the circumferential length Lb1 (dimension symbol omitted in drawings) of the circumferential section Rb has a ratio of 0.50 ≤ Lb / L11 and preferably a ratio of 0.70 ≤ Lb / L11 with respect to the circumferential length L11 of the narrow, shallow groove 311. As a result, the circumferential length Lb1 of the circumferential section Rb is ensured. It should be noted that the upper limit of the ratio is not particularly restricted, but is limited by other conditions.

[0090] Furthermore, as in Fig. Figure 9 illustrates the U-shape of the narrow, flat grooves 311, preferably provided with a curved section (reference numeral omitted in the drawings) arranged in at least one of the regions between points A1, B and between points A2, B to connect adjacent width-direction sections Ra1, Ra1; Ra2, Ra2. The curved section has a crank shape or an S-shape. Furthermore, the distance D6 from the ground contact edge T of the tire to the center point C of the curved section preferably has a relationship of 0.30 ≤ D6 / Wb1 ≤ 0.70 and more preferably a relationship of 0.40 ≤ D6 / Wb1 ≤ 0.60 with respect to the maximum ground contact width Wb1 of the shoulder rib section 31. Thus, the curved section of the narrow, flat groove 311 is arranged in the width direction of the shoulder rib section 31 in the central section.

[0091] For example, in the configuration of Fig. 9 The pair of endpoints A1, A2 of the narrow, flat grooves 311 are arranged at substantially the same position in the tire width direction. Furthermore, the narrow, flat grooves 311 have a single innermost point B. The narrow, flat grooves 311 each enclose a pair of width-direction sections Ra1, Ra1; Ra2, Ra2, which extend substantially parallel to the tire width direction between points A1, B and between points A2, B', respectively. Additionally, two sets of width-direction sections Ra1, Ra1; Ra2, Ra2 are connected to each other by an S-shaped curved section. As a result, a groove section is formed that runs in a stepped shape in the tire width direction. Furthermore, the curved sections are inclined or bent in the same direction with respect to the tire circumference.Furthermore, the narrow, shallow grooves 311 have a single circumferential section Rb that extends substantially parallel to the tire's circumferential direction from the innermost point B. The circumferential section Rb also has a linear or slightly arc-shaped profile projecting towards the equatorial plane CL of the tire and is substantially L-shaped, connecting to the lateral-direction sections Ra1 and Ra2 at the innermost point B and the other endpoint B', respectively. Additionally, both endpoints B and B' of the pair of endpoints A1 and A2, and the circumferential section Rb, are arranged such that they are offset from each other in the tire's circumferential direction.

[0092] In the configuration of Fig. 9 The U-shape of the narrow flat grooves 311 consists of a single line that has no branching section. However, no such restriction is intended, and the U-shape of the narrow flat grooves 311 may have a branching section that diverges from the center (not illustrated).

[0093] It should be noted that the edge section on the side of the main shoulder groove 21 of the shoulder bridge section 31 may have multiple fine lamellae (reference symbol omitted in drawings). These lamellae have a width of less than 1.0 mm and a length of less than 5.0 mm. These lamellae suppress uneven wear of the edge section in the shoulder bridge section 31. Grooved wall structure of the shoulder joint

[0094] Fig. Figures 11 to 13 are enlarged top views ( Fig. 11 and Fig. 12) and a cross-sectional view in the groove depth direction ( Fig. 13), which defines the groove wall structure of the in Fig. The shoulder groove 21 is illustrated in two drawings. Fig. 11 in particular the groove wall structure on the outside in the tire width direction of the main shoulder groove 21, and Fig. Figure 12 illustrates in particular the groove wall structure on the inside in the direction of tire width. Fig. Figure 13 illustrates a cross-sectional view at the position of maximum amplitude of the shoulder main groove 21 on the outside in the tire width direction.

[0095] In the configuration of Fig. 2, as in Fig. As illustrated in Figure 11, both the groove opening section 211 and the groove bottom section 212 of the shoulder main groove 21 have a zigzag or wave-like shape with an amplitude in the tire width direction. However, no such restriction is intended, and the groove opening section 211 of the shoulder main groove 21 may have a straight shape (not illustrated).

[0096] In this process, the outer edge section and the inner edge section are defined in the direction of tire width within both the groove opening section and the groove bottom section of the main groove. Furthermore, in each of the outer edge and inner edge sections, a position of the outer maximum amplitude, projecting towards the outside in the direction of tire width, and a position of the inner maximum amplitude, projecting towards the inside in the direction of tire width, are defined.

[0097] The edge section of the groove opening section is defined by an imaginary line that marks the intersection point (see, for example, Fig. 13) of the groove wall and the tread profile in a cross-sectional view in the groove depth direction over the entire area in the tire circumference direction. In a configuration where the edge section includes a chamfered section, the edge section of the groove opening section is connected to an intersection point (not illustrated) of the extension line of the groove wall and the tread profile to create an imaginary line.

[0098] The edge section of the groove bottom section is defined as an imaginary line connecting the endpoints of the position of maximum groove depth in the cross-sectional view, in the groove depth direction, across the entire area in the tire circumference direction. If the groove bottom section of the main groove is a flat, straight line at the position of maximum groove depth (see, for example, Fig. 13), the outer edge section and the inner edge section of the groove bottom section are defined at both endpoints of the flat straight line. If, on the other hand, the groove bottom section of the main groove has an arc shape or a funnel shape (not illustrated), the position of maximum groove depth is a point, and the edge section of the groove bottom section is defined by a point. Therefore, the outer edge section and the inner edge section of the groove bottom section described above are located at the same position. The position of maximum groove depth of the main groove is defined by excluding any raised bottom sections formed within the groove bottom section of the main groove.

[0099] In the configuration of Fig. 11 and Fig. 12 The groove opening section 211 of the main shoulder groove 21 has a wave-like shape with an amplitude in the tire width direction at each of the outer edge section 211o on the side of the shoulder rib section 31 and the inner edge section 211i on the side of the middle rib section 32. In addition, the groove bottom section 212 of the main shoulder groove 21 has a zigzag shape with an amplitude in the tire width direction at each of the outer edge section 212o on the side of the shoulder rib section 31 and the inner edge section 212i on the side of the middle rib section 32.

[0100] As in Fig. As illustrated in Figure 11, the position of the outer maximum amplitude P100 of the outer edge section 2110 of the groove opening section 211 of the shoulder main groove 21 is at the same position in the tire circumferential direction with respect to the position of the outer maximum amplitude P200 of the outer edge section 2120 of the groove bottom section 212. In particular, Fig. 11 the offset amount ϕoo_sh of the positions of the outer maximum amplitude P1oo, P2oo of the groove opening section 211 of the shoulder main groove 21 and the outer edge sections 211o, 212o of the groove bottom section 212 has a relationship of 0 ≤ ϕoo_sh / λ10o_sh ≤ 0.10 and more preferably a relationship of 0 ≤ ϕoo_sh / λ1o_sh ≤ 0.05 with respect to the wavelength λ1o_sh of the outer edge section 211o of the groove opening section 211.

[0101] The offset of the positions of maximum amplitude is the distance in the tire circumferential direction of the positions of maximum amplitude in a tread plan view when the tire is mounted on a given rim, inflated to the given internal pressure and in an unloaded state.

[0102] Likewise, as in Fig. Figure 12 illustrates the position of the outer maximum amplitude P1io of the inner rim section 211i of the groove opening section 211 of the shoulder main groove 21 at the same position in the tire circumferential direction with respect to the position of the outer maximum amplitude P2io of the inner rim section 212i of the groove bottom section 212. In particular, in Fig. 12 the offset amount ϕio_sh of the positions of the outer maximum amplitude P1io, P2io of the groove opening section 211 of the shoulder main groove 21 and the inner edge sections 211i, 212i of the groove bottom section 212 a relationship of 0 ≤ ϕio_sh / λ1i_sh ≤ 0.10 and more preferably a relationship of 0 ≤ ϕio_sh / λ1i_sh ≤ 0.05 with respect to the wavelength λ1i_sh of the inner edge section 211i of the groove opening section 211.

[0103] As in Fig. As illustrated in Figure 11, the position of the outer maximum amplitude P1oo of the outer edge section 211o and the position of the outer maximum amplitude P1io of the inner edge section 211i of the groove opening section 211 of the shoulder main groove 21 are located at the same position in the tire circumferential direction. In particular, the offset δ_sh between the position of the outer maximum amplitude P1oo of the outer edge section 211o and the position of the outer maximum amplitude P1io of the inner edge section 211i in the groove opening section 211 of the shoulder main groove 21 has a relationship of 0 ≤ δ_sh / λ1o_sh ≤ 0.10, and more preferably a relationship of 0 ≤ δ_sh / λ1o_sh ≤ 0.05 with respect to the wavelength λ1o_sh of the outer edge section 211o of the groove opening section 211.

[0104] Furthermore, in Fig. 11 The wavelength λ1o_sh of the outer edge section 211o of the groove opening section 211 of the shoulder main groove 21 is adjusted such that it is essentially equal to the wavelength λ2o_sh of the outer edge section 212o of the groove bottom section 212. In particular, the wavelengths λ1o_sh, λ2o_sh of the groove opening section 211 and of the groove bottom section 212 lie in a range of 0.90 ≤ λ2o_sh / λ1o_sh ≤ 1.10.

[0105] Likewise, in Fig. 12 The wavelength λ1i_sh of the inner edge section 211i of the groove opening section 211 of the shoulder main groove 21 is adjusted such that it is essentially equal to the wavelength λ2i_sh of the inner edge section 212i of the groove bottom section 212. In particular, the wavelengths λ1i_sh, λ2i_sh of the groove opening section 211 and of the groove bottom section 212 lie in a range of 0.90 ≤ λ2i_sh / λ1i_sh ≤ 1.10.

[0106] Furthermore, the wavelength λ2_sh (λ2o_sh, λ2i_sh) of the groove bottom section 212 of the shoulder main groove 21 exhibits a relationship of 0.10 ≤ λ2_sh / TW ≤ 0.35 with respect to the ground contact width TW of the tire.

[0107] Furthermore, it points out that Fig. 11 The maximum distance L1o_sh in the tire circumferential direction between the position of the outer maximum amplitude P1oo and the position of the inner maximum amplitude P1oi of the outer edge section 211o of the groove opening section 211 of the shoulder main groove 21 has a relationship of 0.50 ≤ L1o_sh / λ1o_sh ≤ 0.60, and preferably a relationship of 0.50 ≤ L1o_sh / λ1o_sh ≤ 0.55 with respect to the wavelength λ1o_sh of the outer edge section 211o. As a result, the stiffness of the tread contact surface, when the tire is new, is uniform in the tire circumferential direction.

[0108] The maximum distance in the tire circumference direction between the position of the outer maximum amplitude and the position of the inner maximum amplitude is measured as the larger of the distances in the tire circumference direction between the adjacent positions of the outer maximum amplitude and a given position of the inner maximum amplitude between the positions of the outer maximum amplitude.

[0109] The wavelength λ1o_sh of the outer edge section 211o of the groove opening section 211 of the shoulder main groove 21 is only defined if the shoulder main groove 21 has a zigzag or wave-like shape, and is not defined if the shoulder main groove 21 has a straight shape.

[0110] Similarly, in Fig. 12 the maximum distance L1i_sh in the circumferential direction of the tire between the position of the outer maximum amplitude P1io and the position of the inner maximum amplitude P1ii of the inner edge section 211i of the groove opening section 211 of the shoulder main groove 21 a relationship of 0.50 ≤ L1i_sh / λ1i_sh ≤ 0.60 and preferably a relationship of 0.50 ≤ L1i_sh / λ1i_sh ≤ 0.55 with respect to the wavelength λ1i_sh of the inner edge section 211i.

[0111] Furthermore, it points out that Fig. 11. The maximum distance L2o_sh in the tire circumferential direction between the position of the outer maximum amplitude P2oo and the position of the inner maximum amplitude P2oi of the outer edge section 212o of the groove bottom section 212 of the shoulder main groove 21 exhibits a relationship of 0.50 ≤ L2o_sh / λ2o_sh ≤ 0.60 and preferably a relationship of 0.50 ≤ L2o_sh / λ2o_sh ≤ 0.55 with respect to the wavelength λ2o_sh of the outer edge section 212o. Accordingly, the position of the outer maximum amplitude P2oo and the position of the inner maximum amplitude P2oi of the groove bottom section 212 of the shoulder main groove 21 are arranged at substantially equal intervals in the tire circumferential direction.

[0112] Similarly, in Fig. 12 the maximum distance L2i_sh in the tire circumferential direction between the position of the outer maximum amplitude P2io and the position of the inner maximum amplitude P2ii of the inner edge section 212i of the groove bottom section 212 of the shoulder main groove 21 a relationship of 0.50 ≤ L2i_sh / λ2i_sh ≤ 0.60 and preferably a relationship of 0.50 ≤ L2i_sh / λ2i_sh ≤ 0.55 with respect to the wavelength λ2i_sh of the inner edge section 212i.

[0113] Furthermore, it points out that Fig. 11 The amplitude A1o_sh of the outer edge section 211o of the groove opening section 211 of the shoulder main groove 21 has a relationship of 1.20 ≤ A2o_sh / A1o_sh ≤ 2.00, more preferably a relationship of 1.30 ≤ A2o_sh / A1o_sh ≤ 1.80 with respect to the amplitude A2o_sh of the outer edge section 212o of the groove bottom section 212. Accordingly, the amplitude A2o_sh of the zigzag shape of the groove bottom section 212 is set larger than the amplitude A1o_sh of the wave-like shape of the groove opening section 211.

[0114] Similarly, in Fig. 12 the amplitude A1i_sh of the inner margin section 211i of the groove opening section 211 of the shoulder main groove 21 a relationship of 1.20 ≤ A2i_sh / A1i_sh ≤ 2.00 and more preferably a relationship of 1.30 ≤ A2i_sh / A1i_sh ≤ 1.80 with respect to the amplitude A2i_sh of the inner margin section 212i of the groove bottom section 212.

[0115] In the configuration described above, (1) because the amplitudes A1o_sh, A1i_sh of the groove opening section 211 of the main shoulder groove 21 are set small, the uneven wear of the edge section of the rib sections 31, 32, which is likely to occur at the position of maximum amplitude P1io, P1oi on the side of the main shoulder groove 21, is suppressed. Furthermore, (2) because the amplitudes A2o_sh, A2i_sh of the groove bottom section 212 of the main shoulder groove 21 are set large, the stiffness of the rib sections 31, 32 is ensured, and the tear strength of the tire is guaranteed. As a result, the tire's resistance to uneven wear and its tear strength performance are achieved in a compatible manner.Furthermore, (3) since the groove opening section 211 of the shoulder main groove 21 has a zigzag or wave-like shape with an amplitude in the tire width direction, the edge component of the rib sections 31, 32 is increased and the acceleration performance of the tire on snow is improved.

[0116] Furthermore, in Fig. 12. The amplitude A1o_sh of the outer edge section 211o of the groove opening section 211 of the shoulder main groove 21 is adjusted such that it is substantially equal to the amplitude A1i_sh of the inner edge section 211i. In particular, the amplitude A1o_sh of the outer edge section 211o has a relationship of 0.90 ≤ A1o_sh / A1i_sh ≤ 1.10 and more preferably a relationship of 0.95 ≤ A1o_sh / A1i_sh ≤ 1.05 with respect to the amplitude A1i_sh of the inner edge section 211i.

[0117] Furthermore, the amplitudes A1o_sh, A1i_sh of the groove opening section 211 of the shoulder main groove 21 lie in a range of 0 mm or more to 15.0 mm or less, and preferably in a range of 2.0 mm or more to 10.0 mm or less. If the amplitudes A1o_sh, A1i_sh are 0 mm, the groove opening section 211 of the shoulder main groove 21 has a straight shape.

[0118] Furthermore, the amplitudes A2o_sh, A2i_sh of the groove bottom section 212 of the shoulder main groove 21 are in a range of 2.5 mm or more to 15.0 mm or less and preferably in a range of 4.0 mm or more to 12.0 mm or less.

[0119] As in Fig. As illustrated in Figure 13, the groove wall angle α100 at the position of the outer maximum amplitude P100 of the outer border section 2110 of the groove opening section 211 of the main shoulder groove 21 exhibits a relationship of α100 < α10i with respect to the groove wall angle 010i at the position of the inner maximum amplitude P10i of the outer border section 2110. Likewise, the groove wall angle 0100 at the position of the outer maximum amplitude P100 of the inner border section 211i of the groove opening section 211 of the main shoulder groove 21 exhibits a relationship of α1ii < α100 with respect to the groove wall angle α1ii at the position of the inner maximum amplitude P1ii of the inner border section 211i.Therefore, the groove wall angles α1oi, α1io of the main shoulder grooves 21 are set large at the position where the marginal section of the groove opening section of the main shoulder groove 21 projects towards the main shoulder groove 21 (the position of the inner maximum amplitude P1oi of the outer marginal section 211o and the position of the outer maximum amplitude P1io of the inner marginal section 211i in . Fig. 11). As a result, the stiffness of the web sections 31, 32 is ensured at the positions of maximum amplitude P1oi, P1io.

[0120] Furthermore, as in Fig. Figure 11 illustrates that the entire groove bottom section 212 of the main shoulder groove 21 is arranged such that it is pre-stressed towards the inside in the tire width direction with respect to the entire groove opening section 211. Therefore, the mean value of the groove wall angle of the inner edge section 211i of the main shoulder groove 21 is set to be greater than the mean value of the groove wall angle of the outer edge section 211o. Thus, the stiffness of the narrow central rib section 32 (see Figure 11) is increased. Fig. 2) ensured.

[0121] Furthermore, it points out that Fig. 13 The maximum width Wg2_sh of the groove bottom section 212 of the main shoulder groove 21 has a relationship of 0 ≤ Wg2_sh / Wg1_sh ≤ 0.60 and preferably a relationship of 0.35 ≤ Wg2_sh / Wg1_sh ≤ 0.45 with respect to the maximum width Wg1_sh of the groove opening section 211 (that is, the maximum groove width of the main shoulder groove 21). If the groove bottom section of the main groove has an arc shape or a funnel shape (not illustrated), the maximum width Wg2_sh of the groove bottom section 212 is approximately 0.

[0122] Furthermore, the configuration of Fig. 11 both the outer edge section 211o and the inner edge section 211i of the groove opening section 211 of the shoulder main groove 21 form a wave-like shape by connecting a plurality of arcs that project towards the inside in the direction of the tire width (i.e. towards the equatorial plane CL of the tire, see Fig. 2). Furthermore, the circumferential length of the arc (dimension symbol omitted in drawings) is 80% or more, and more preferably 85% or more, with respect to the wavelength λ1o_sh of the outer edge section 211o. Adjacent arcs are also connected by short straight lines or arcs. In such a configuration, it is desirable that, compared to a configuration in which the edge section has a zigzag or sinusoidal shape, uneven wear at the maximum protrusion position of the edge section is suppressed.

[0123] However, no such restriction is intended, and the groove opening section 211 of the shoulder main groove 21 may have a linear shape or a zigzag shape as described above, or may have a sinusoidal wave-like shape (not illustrated).

[0124] Furthermore, the configuration of Fig. 11 Both the outer edge section 212o and the inner edge section 212i of the groove base section 212 of the shoulder main groove 21 have a zigzag shape, which is formed by connecting linear sections of essentially the same length in the tire's circumferential direction. In addition, the circumferential length of the groove base section 212 (in Fig. 11 the circumferential length is essentially equal to the maximum distance L2o_sh in the tire circumferential direction between the positions of maximum amplitude P2oo, P2oi of the outer edge section 212o) preferably in a range of 40 % or more to 60 % or less with respect to the wavelength λ2o_sh of the outer edge section 212o.

[0125] However, no such restriction is intended, and the groove floor section 212 of the shoulder main groove 21 may have a wave-like shape as described above (not illustrated). Modified example of narrow, shallow grooves

[0126] Fig. Figures 14 to 23 are explanatory diagrams that show modified examples of the information in Fig. Figure 9 illustrates the narrow, flat groove 311. The same drawing shows components that are the same as those in Fig. The 9 illustrated components are labelled with the same reference symbols and their explanations are omitted.

[0127] In the configuration of Fig. 9 The circumferential profile section Rb has a linear or slightly arc-shaped profile inclined with respect to the tire's circumferential direction, with the narrow, shallow grooves 311 having a single innermost point B'. Furthermore, the innermost point B' is located at the connecting section between the lateral direction profile section Ra1 and the circumferential profile section Rb of the narrow, shallow groove 311.

[0128] In contrast, in the configuration of Fig. 14 The circumferential section Rb is formed by a straight line parallel to the tire's circumferential direction. In this case, the center point of a region of the groove section of the narrow, shallow groove 311 is on the innermost side in the tire width direction (in Fig. 14 the entire circumferential section Rb) is defined as the innermost point B' of the narrow shallow groove 311. Furthermore, in the configuration of Fig. 15 The left and right lateral direction section Ra1; Ra2 are connected by an arc-shaped groove section that projects towards the equatorial plane CL of the tire. Furthermore, the raised section, with its arc shape, encloses the innermost point B' and the circumferential direction section Rb of the narrow, shallow grooves 311.

[0129] Furthermore, the configuration of Fig. 9 the narrow flat grooves 311 a pair of width direction progression sections Ra1, Ra1; Ra2, Ra2 which extend essentially parallel to the tire width direction between points A1, B and between points A2, B respectively.

[0130] In contrast, the configuration of Fig. 16 the narrow flat grooves 311 a pair of latitude-direction-profile sections Ra1, Ra1 between points A1, B and a single latitude-direction-profile section Ra2 between points A2, B. In addition, the latitude-direction-profile section Ra2 and the innermost point B on the side of point A2 are connected by an extended arc that includes a short and S-shaped curved section and the circumferential profile section Rb.

[0131] In the configuration of Fig. 9 are the pair of endpoints A1, A2 of the narrow, flat grooves 311 arranged at essentially the same position in the tire width direction. Therefore, the distance D2 between the endpoints A1, A2 in the tire width direction is approximately zero.

[0132] In contrast, the configuration of Fig. 17 The pair of endpoints A1, A2 of the narrow flat grooves 311 are arranged such that they are offset from each other in the tire width direction. In such a configuration, since the angle θ11 of the narrow flat grooves 311 lies in the range described above, it can be assumed that the narrow flat grooves 311 have opening sections that face the ground contact edge T of the tire.

[0133] Furthermore, the configuration of Fig. 9 the opening section of the U-shape of the narrow flat grooves 311 is configured such that the width direction sections Ra1, Ra2 have a linear shape or a slight arc shape, and these width direction sections Ra1, Ra2 have the endpoints A1, A2 of the narrow flat grooves 311.

[0134] In contrast, in the configuration of Fig. 18 The opening section of the U-shape of the narrow, flat grooves 311 is curved in a direction that narrows the opening width towards the endpoints A1, A2. Furthermore, in the configuration of Fig. 19 The S-shaped curved sections connecting the adjacent width-direction-progression sections Ra1, Ra1; Ra2, Ra2 are curved in a direction that narrows the opening width of the U-shape. As described above, the U-shape of the narrow flat grooves 311 can have a shape with a narrow opening width.

[0135] Furthermore, the configuration of Fig. 9 the narrow flat grooves 311 each the pair of width direction progression sections Ra1, Ra1; Ra2, Ra2 which extend substantially parallel to the tire width direction between points A1, B and between points A2, B respectively, wherein each of the two sets of width direction progression sections Ra1, Ra1; Ra2, Ra2 are connected to each other via an S-shaped curved section.

[0136] In contrast, the configuration of Fig. 20 The narrow, flat grooves 311 have a single latitude-direction profile section Ra1 between points A1 and B and a pair of latitude-direction profile sections Ra2 and Ra2 between points A2 and B. Furthermore, points A1 and B are connected by the long and linear latitude-direction profile section Ra1. Additionally, in the configuration of Fig. 21. A pair of latitude-direction profile sections Ra1, Ra1 is provided between points A1, B, and one latitude-direction profile section is not provided between points A2, B. In addition, points A2, B are connected by a long and arc-shaped groove section.

[0137] Furthermore, the configuration of Fig. 22 and Fig. 23 the narrow, flat grooves 311 form a single long width-direction profile section Ra1; Ra2 between points A1, B and between points A2, B respectively. In particular, in the configuration of Fig. 23 the points A1, B and the points A2, B are connected by the latitude direction section Ra1; Ra2. Impact 1

[0138] As described above, the tire 1 includes a plurality of main grooves 21, 22 extending in the circumferential direction of the tire and four or more rows of rib sections 31 to 33 defined by the main grooves 21, 22 (see Fig. 2). In addition, at least one series of bridge sections (in Fig. 2 the middle rib section 32 and the middle rib section 33) a plurality of continuous lug grooves 321; 331 which run through the rib section 32; 33 in the tire width direction (see Fig. 3) The pitch spacing length P21; P31 of the continuous lug grooves 321; 331 is in a range of 7% or more to 14% or less of the maximum ground contact length Lt of the tire (not illustrated). Furthermore, the maximum groove depth H21 (see Fig. 5); H31 (not illustrated) of the continuous adit grooves 321, 331 in a range of 5% or more to 65% or less of the maximum groove depth Hg1, Hg2 of the main groove 21; 22.

[0139] In such a configuration, an advantage lies in the suitably designed relationship between the pitch spacing λ2; λ3 and the maximum groove depth H21; H23 of the continuous lug grooves 321; 331, thus achieving compatible acceleration performance on snow and low rolling resistance tire performance. Specifically, the pitch spacing range P21; P31 of the continuous lug grooves 321; 331 defines the lower limit, and the maximum groove depth range H21; H31 of the continuous lug grooves 321; 331 defines the upper limit. Consequently, the stiffness of the rib section 32; 33 is ensured, and a deterioration in the tire's rolling resistance is suppressed. Furthermore, the pitch spacing range P21; P31 of the continuous lug grooves 321; 331 defines the upper limit, and the maximum groove depth range H21; H31 of the continuous tunnel grooves 321; 331 the lower limit.As a result, the edge component of the bridge section 32; 33 is ensured, and the traction effect of the continuous stud grooves 321; 331 is ensured while driving on snow-covered road surfaces.

[0140] Furthermore, the maximum groove width W21; W31 of the continuous lug grooves 321; 331 of tire 1 lies in a range of 1.5 mm or more to 4.0 mm or less. Consequently, an advantage lies in the fact that the maximum groove width W21; W31 of the continuous lug grooves 321; 331 is appropriately designed.

[0141] In tire 1, the continuous lug grooves 321; 331 have a zigzag shape ( Fig. 3) Furthermore, the amplitude (not illustrated) of the continuous lug grooves 321; 331 is in the range of 2.0% or more to 7.0% or less with respect to the pitch spacing length (not illustrated) of the continuous lug grooves 321; 331. In addition, the wavelength of the continuous lug grooves 321; 331 is in the range of 16% or more to 22% or less with respect to the maximum ground contact width Wb2; Wb3 of the rib section 32; 33. Consequently, an advantage is that the zigzag shape of the continuous lug grooves 321; 331 is suitably designed and the effect of the improvement in tire traction performance due to the continuous lug grooves 321; 331 is ensured.

[0142] Furthermore, in tire 1, the inclination angle θ21; θ31 of the continuous lug grooves 321; 331 with respect to the tire circumferential direction lies in a range of 60° or more to 120° or less (see Fig. 4 and Fig. 7) The lower limit offers the advantage that the effect of the improvement in traction performance due to the continuous lug grooves 321; 331 is ensured, and the upper limit offers the advantage that the stiffness of the rib section 32; 33 is adequately ensured.

[0143] Furthermore, in tire 1, a section 321A; 331A of the majority of continuous lug grooves 321; 331 has a groove base lamella 323; 333 (see Fig. 4 and Fig. 7) Furthermore, the continuous lug grooves 321A; 331A with the groove base lamella 323; 333 and at least one continuous lug groove 321B; 331B without the groove base lamella are arranged alternately in the circumferential direction of the tire. Since, in such a configuration, the continuous lug grooves 321A; 331A have the groove base lamella 323; 333, an advantage is that the acceleration performance of the tire on snow is improved. Since, in addition, the continuous lug grooves 321A; 331A with the groove base lamella 323; 333 and the continuous lug grooves 321B; 331B without the groove base lamella are arranged alternately in the circumferential direction of the tire, an advantage is that the stiffness of the rib section 32; 33 is ensured and the rolling resistance of the tire is reduced.

[0144] Furthermore, the distance H23' is located in tire 1 (see Fig. 5); H33' from the groove bottom of the continuous lug grooves 321; 331 to the position of maximum depth of the groove bottom lamella 323; 333 is in a range of 6% or more with respect to the maximum groove depth Hg1; Hg2 of the main groove 21; 22. Furthermore, the distance H23; H33' from the tread contact surface to the position of maximum depth of the groove bottom lamella 323; 333 is in a range of 100% or less with respect to the maximum groove depth Hg1; Hg2 of the main groove 21; 22. Therefore, an advantage is that the depth of the groove bottom lamella 323; 333 is appropriately designed. In particular, the lower limit offers the advantage that the effect of the improved acceleration performance on snow due to the groove bottom lamella 323; 333 is ensured and the upper limit offers the advantage that the stiffness of the rib section 32; 33 is ensured and the rolling resistance of the tire is reduced.

[0145] Furthermore, in tire 1, the adjacent rib sections 32, 33 each enclose the continuous lug groove 321, 331 (see Fig. 3) Additionally, one continuous lug groove 321A; 331A of the pair of continuous lug grooves 321, 331, which face each other and with the main groove 22 arranged between them, has the groove base lamella 323; 333, and the other continuous lug groove 331B; 323B does not have a groove base lamella. As a result, an advantage is that the stiffness between adjacent rib sections 32, 33 is made uniform and the rolling resistance of the tire is reduced.

[0146] Furthermore, for tire 1, the maximum ground contact width Wb2; Wb3 of the rib section 32; 33 is in a range of 15% or more to 25% or less with respect to the ground contact width TW of the tire (see Fig. 2) As a result, an advantage exists in that the bridge section 32; 33 is suitably designed.

[0147] Furthermore, in the tire 1, the first and second edge sections of the rib section 32; 33 have a zigzag or wave-like shape with an amplitude in the tire width direction and are arranged such that they are phase-shifted in the tire circumferential direction (see Fig. 3) Furthermore, the continuous lug grooves 321; 331 are inclined with respect to the tire's circumferential direction to connect the positions of maximum amplitude of the first and second edge sections. Since, in such a configuration, the edge sections of the rib section 32; 33 have a zigzag or wave-like shape, the tire's acceleration performance on snow is improved compared to a configuration where the edge sections of the rib section have a straight shape (not illustrated). Additionally, since the continuous lug grooves 321; 331 are open to the position of maximum amplitude of the edge sections of the rib sections, uneven wear of the rib section 32; 33 is reduced compared to configurations where the grooves are open to other positions.

[0148] Furthermore, in tire 1, the first and second edge sections of the rib section 32; 33 have a wave-like shape, which is formed by connecting a plurality of arcs with an amplitude in the tire width direction (see Fig. 3) Additionally, the circumferential length of the arc (not illustrated) lies within a range of 80% or more with respect to the wavelength λ2; λ3 of the wave-like shape. With such a configuration, an advantage is that uneven wear of the web section 32; 33 is suppressed compared to a configuration where the web section has an edge section with a zigzag or sinusoidal shape.

[0149] Furthermore, in tire 1, the wave-like shape of the first and second edge sections of the rib section 32; 33 is formed by connecting a plurality of arcs that project towards the equatorial plane CL of the tire (see Fig. 3) As a result, an advantage is that the uneven wear of the web section 32; 33 is effectively suppressed. Impact 2

[0150] The tire 1 includes 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 (see Fig. 2). In addition, at least one series of bridge sections (in Fig. 2 left and right shoulder rib sections 31, 31) a plurality of narrow flat grooves 311 which have a U-shape with an opening section which faces the ground contact edge T of the tire and terminates blindly in the ground contact surface of the rib section 31 (see Fig. 8).

[0151] In such a configuration, (1) since the narrow flat grooves 311 have a U-shape, there is an advantage in that the acceleration performance of the tire on snow while the vehicle is in motion is improved due to the circumferential components of the narrow flat grooves 311 compared to a configuration that includes a plurality of narrow, I-shaped grooves arranged circumferentially in the width direction (not illustrated). Furthermore, (2) since the narrow flat grooves 311 have a U-shape, with the opening section facing the ground contact edge T of the tire, the circumferential components of the narrow flat grooves in the area on the side of the ground contact edge T of the tire can be omitted compared to, for example, a configuration that includes narrow flat grooves with an annular structure (not illustrated).As a result, one advantage is that the noise performance of the tire is improved during vehicle operation and uneven wear resulting from the narrow, shallow grooves 311 is suppressed. Furthermore, (3) since the narrow, shallow grooves 311 have a closed structure that terminates blindly at the ground contact surface of the rib section 31, there is an advantage in that the noise performance of the tire is improved compared to a configuration featuring narrow, shallow grooves extending through the ground contact surface of the rib section in the tire width or circumferential direction (not illustrated).

[0152] Furthermore, in the tire 1, the rib section 31, which includes the narrow flat grooves 311, is a rib with a road contact surface that runs continuously in the circumferential direction of the tire (see Fig. 8) As a result, one advantage is that the stiffness of the rib section 31 is ensured and the tire's acceleration performance on snow is improved. Another advantage is that the tire's noise performance is improved compared to a configuration featuring narrow, shallow grooves running across the tire's width through the ground contact surface of the rib section (not illustrated).

[0153] Furthermore, the maximum groove width Wn is specified for tire 1 (see Fig. 9) the narrow, flat grooves 311 in a range of 0.1 mm ≤ Wn ≤ 5.0 mm and the maximum groove depth Hn (see Fig. 10) The narrow, shallow grooves 311 exhibit a relationship of 0.01 ≤ Hn / Hg1 ≤ 0.30 with respect to the maximum groove depth Hg1 of the shoulder main grooves 21. Consequently, an advantage is that the maximum groove width Wn and the maximum groove depth Hg1 of the narrow, shallow grooves 311 are suitably designed.

[0154] Furthermore, in the tire 1, the lateral direction length W11 of the narrow, flat grooves 311 exhibits a relationship of 0.40 ≤ W11 / Wb1 ≤ 0.90 with respect to the maximum ground contact width Wb1 of the rib section 31 (see Fig. 8) The lower limit offers the advantage that the edge component of the narrow, shallow grooves 311 is ensured in the tire's circumferential direction, thus guaranteeing the improved acceleration performance of the tire on snow. The upper limit offers the advantage that the distances D3, D4 (see Fig. 8) between the narrow flat grooves 311 and the edge sections of the web sections 31 is ensured and the stiffness of the web sections 31 is ensured.

[0155] Furthermore, in tire 1, the circumferential length L11 of the narrow flat grooves 311 exhibits a relationship of 0.50 ≤ L11 / P11 ≤ 0.90 with respect to the pitch distance length P11 of the narrow flat grooves 311 (see Fig. 8) The lower limit offers the advantage of ensuring the circumferential component of the U-shape of the narrow, flat grooves 311 and thus guaranteeing the tire's acceleration performance on snow while driving. The upper limit offers the advantage of suppressing a deterioration in the tire's noise performance due to excessive circumferential components of the narrow, flat grooves 311.

[0156] Furthermore, in tire 1, the distance D1 between the pair of endpoints A1, A2 of the narrow flat grooves 311 in the tire circumferential direction exhibits a relationship of 0.30 ≤ D1 / P11 ≤ 0.90 with respect to the pitch distance length P11 of the narrow flat grooves 311 (see Fig. 8) The lower limit offers the advantage of ensuring the opening width of the U-shape of the narrow, flat grooves 311 and suppressing the deterioration of the tire's noise performance. The upper limit offers the advantage of ensuring the distance between the endpoints A1, A2 of adjacent narrow, flat grooves 311, 311.

[0157] Furthermore, the distance D2 on tire 1 (see Fig. 9) between the pair of endpoints A1, A2 of the narrow flat grooves 311 in the tire width direction a relationship of 0 ≤ D2 / Wb1 ≤ 0.70 with respect to the maximum ground contact width Wb1 of the rib section 31 (see Fig. 8) Since, in such a configuration, the pair of endpoints A1, A2 of the narrow flat grooves 311 are located at the same position in the tire width direction, an advantage is that the stiffness of the shoulder rib section 31 is uniformly designed and resistance of the shoulder rib section 31 to uneven wear is suppressed.

[0158] Furthermore, if, in tire 1, the pair of endpoints A1, A2 of the narrow flat grooves 311 and the innermost point B in the tire width direction are defined, and the imaginary line L1 passing through the center point M and the innermost point B of the endpoints A1, A2 is defined, the angle θ11 between the imaginary line L1 and the tire circumference direction lies in a range of 45° ≤ θ11 ≤ 135° (see Fig. 9) As a result, one advantage is that the opening direction of the U-shape of the narrow flat grooves 311 is suitably designed and the noise performance of the tire is improved while driving the vehicle.

[0159] Furthermore, in the tire 1, the U-shape of the narrow, flat grooves 311 has at least one width-direction section Ra1, Ra2 with an inclination angle of 75° or more up to 105° or less with respect to the tire circumference direction (see Fig. 9) The sum ΣLa of the lateral direction lengths La1 to La4 of the lateral direction sections Ra1, Ra2 exhibits a relationship of 1.00 ≤ ΣLa / W11 with respect to the lateral direction length W11 of the narrow, shallow groove 311. Since, in such a configuration, the total length ΣLa of the lateral direction sections Ra1, Ra2, which run essentially perpendicular to the tire circumference, is ensured, an advantage is that the effect of the improved acceleration performance on snow during straight-line driving of a vehicle due to the narrow, shallow grooves 311 is efficiently ensured.

[0160] Furthermore, in the tire 1, the U-shape of the narrow, flat grooves 311 has a pair of adjacent lateral direction-of-flow sections Ra1, Ra1; Ra2, Ra2 and a crank-shaped or S-shaped curved section (reference symbol is omitted in drawings) that connects the pair of lateral direction-of-flow sections Ra1, Ra1; Ra2, Ra2 (see Fig. 9) connects. As a result, one advantage is that the circumference components of the narrow, flat grooves 311 are increased, and the noise performance of the tire is improved while driving the vehicle.

[0161] Furthermore, in the tire 1, the U-shape of the narrow, flat grooves 311 has a continuous circumferential section Rb with an inclination angle of 0° or more to 15° or less with respect to the tire circumferential direction (see Fig. 9) Furthermore, the circumferential length Lb of the circumferential section Rb exhibits a relationship of 0.50 ≤ Lb / L11 with respect to the circumferential length L11 of the narrow, shallow grooves 311. In such a configuration, the length Lb of the circumferential section Rb, which extends substantially parallel to the tire's circumferential direction, is ensured. Consequently, an advantage is that the effect of the narrow, shallow grooves 311 on the improved acceleration performance on snow while driving the vehicle is efficiently ensured. Application object

[0162] Furthermore, tire 1 is a heavy-duty tire mounted on a vehicle's steering axle. Using such a tire as the application object offers the advantage of effectively improving resistance to uneven wear and tear resistance, while also meeting the acceleration performance requirements for all-season tires on snow.

[0163] Additionally, in this embodiment, a pneumatic tire is described as an example of a tire. However, no such limitation is intended, and the configuration described in this embodiment can be applied to other tires within the scope of protection obvious to those skilled in the art. Examples of other tires include airless tires, solid tires, and the like. Example 1

[0164] Fig. Figure 24 is a table showing the results of performance tests of tires according to the embodiment of the invention.

[0165] The performance tests evaluate (1) acceleration performance on snow and (2) low rolling resistance performance for a variety of test tire types. The test tires, size 315 / 70R22.5, are mounted on rims measuring 22.5×9.00, and an internal pressure of 900 kPa and a specified JATMA load are applied. The test tires are mounted on the steering axle of the 4×2 tractor.

[0166] (1) The assessment of acceleration performance on snow shall be carried out by measuring the distance required to accelerate from a predetermined initial speed to a final speed under test conditions that comply with ECE (Eastern Commission for Europe) Regulation No. 117-2 (Revision 2). Higher values ​​shall be preferred in this assessment.

[0167] (2) For the evaluation of low rolling resistance performance, a drum testing machine with a drum diameter of 1707 mm is used, and the rolling resistance coefficients of the test tires are calculated under conditions of a load of 33.3 kN, an air pressure of 900 kPa, and a speed of 80 km / h in accordance with ISO 28580. The results of the evaluation are expressed as index values ​​and assessed, with the prior art example assigned as a reference value (100). Higher values ​​are preferred in this assessment.

[0168] In the test tire of example 1, in which in Fig. 1 and Fig. In the illustrated configuration 2, the edge sections of the shoulder main grooves 21 and the center main grooves 22 have a zigzag shape. Furthermore, the groove depth of the shoulder main grooves 21 and the center main grooves 22 is 14.6 mm, and the groove width is 15.3 mm. Each of the continuous lug grooves 321, 331 has a zigzag shape and an inclination angle θ21, θ31 of 75° with respect to the tire's circumferential direction. Additionally, the ground contact width TW of the tire is 268 mm, the maximum ground contact width Wb1 of the shoulder rib section 31 is 49.5 mm, the maximum ground contact width Wb2 of the center rib section 32 is 36.0 mm, and the maximum ground contact width Wb3 of the center rib section 33 is 36.0 mm. The test tires of other examples are modified examples of the test tire from Example 1.

[0169] In the test tires of the comparison example, the pitch spacing lengths P21, P31 of the continuous lug grooves 321, 331 of the middle rib section 32 and the middle rib section 33 are set so that they are larger than those of the test tires of example 1.

[0170] As can be seen from the test results, the acceleration performance on snow and the low rolling resistance tire performance are achieved in a compatible manner in the test tires of examples. Example 2

[0171] Fig. Figure 25 is a table showing the results of performance tests of tires according to the embodiment of the invention. Fig. 26 is an explanatory diagram showing a shoulder bridge section of the test tire of the in Fig. 25 illustrated comparative examples.

[0172] In the performance tests, (1) acceleration performance on snow and (2) pass-by noise performance are evaluated for a variety of test tire types. The test tires, size 315 / 70R22.5, are mounted on rims with a rim size of 22.5×9.00, and an internal pressure of 900 kPa and a specified load from JATMA are applied to the test tires. The test tires are mounted on the steering axle of the 4×2 tractor.

[0173] (1) The assessment of acceleration performance on snow is carried out by measuring the distance required to accelerate from a predetermined initial speed to a final speed under test conditions that comply with ECE (Eastern Commission for Europe) Regulation No. 117-2 (Revision 2). Higher values ​​are to be preferred in this assessment. Furthermore, if the value is 96 or higher, the performance is deemed to be adequately ensured.

[0174] (2) When assessing pass-by noise performance, the pass-by noise is measured under test conditions that comply with ECE Regulation R117-2. The decibel difference is then calculated based on the measurement results, with the comparison example being assigned as the reference value (0). Lower values ​​are preferred.

[0175] The test tire of example 16 has the configuration of Fig. 1, Fig. 2 and Fig. 8. Furthermore, the groove depth of the main shoulder grooves 21 and the main center grooves 22 is 14.6 mm, and the groove width is 15.3 mm. The continuous lug grooves 321 and 331 also have a maximum groove width W21 of 2.1 mm and a maximum groove depth H21 of 2.5 mm. The tire's ground contact width TW is 268 mm, the maximum ground contact width Wb1 of the shoulder rib section 31 is 49.5 mm, the maximum ground contact width Wb2 of the center rib section 32 is 36.0 mm, and the maximum ground contact width Wb3 of the center rib section 33 is 36.0 mm. Additionally, the pitch of the zigzag pattern of the groove opening sections 211 and 221 of the main grooves 21 and 22 ranges from 50 or more to 100 or less. The test tires in other examples are modified examples of the test tire from Example 16.

[0176] The test tire in the comparison example is the test tire from example 16, in which the narrow, flat groove has a straight shape and runs through the shoulder rib section (see Fig. 26).

[0177] As can be seen from the test results, the test tires of examples can improve the pass-by noise performance while driving the vehicle, while maintaining the tire's acceleration performance on snow. List of reference symbols 1 tire; 11. Bead core; 12 bead fillers; 13 Carcass layer; 14 Belt layer; 141, 142 Cross girdle; 15 tread rubber; 16 side wall rubber; 17 Wheel rim pad rubber; 21 Shoulder groove; 22. Midline groove; 31 Shoulder bridge section; 311 Narrow shallow groove; 32 Middle web section; 32 Middle section of the bridge; 321, 321A, 321B Continuous cleat groove; 322 Block; 323 Grooved floor lamella; 33 Central web section; 331, 331A, 331B Continuous cleat groove; 332 Block; 333 Grooved floor lamella

Claims

[1] Tires (1), comprising: a plurality of main grooves (21, 22) running in a circumferential direction of the tire; and five or more rows of web sections (31, 32, 33) defined by the main grooves (21, 22), wherein at least one row of the rib sections (31, 32, 33) comprises a plurality of continuous lug grooves (321, 331) extending in the tire width direction through the rib sections (31, 32, 33), wherein a pitch spacing length (P21, P31) of the continuous lug grooves (321, 331) is in a range of 7% or more to 14% or less of a maximum ground contact length (Lt) of the tire (1), and wherein a maximum groove depth (H21, H31) of the continuous tunnel grooves (321, 331) is in a range of 5% or more to 65% or less of a maximum groove depth (Hg1, Hg2) of the main grooves (21, 22). [2] Tires (1) according to claim 1, wherein a maximum groove width of the continuous lug grooves (321, 331) is in a range of 1.5 mm or more to 4.0 mm or less. [3] Tires (1) according to claim 1 or 2, wherein the continuous adit grooves (321, 331) have a zigzag shape, the amplitude of the continuous adit grooves (321, 331) is in a range of 2.0% or more to 7.0% or less with respect to the pitch spacing length (P21, P31) of the continuous adit grooves (321, 331), and a wavelength of the continuous tunnel grooves (321, 331) lies in a range of 16% or more to 22% or less with respect to a maximum ground contact width (Wb1, Wb2, Wb3) of the bridge sections (31, 32, 33). [4] Tire (1) according to any one of claims 1 to 3, wherein an inclination angle (θ21) of the continuous tread grooves (321, 331) with respect to the tire circumferential direction is in a range of 60° or more to 120° or less. [5] Tire (1) according to any one of claims 1 to 4, wherein a section of the plurality of continuous lug grooves (321, 331) comprises a groove base lamella (323, 333), and the continuous lug grooves (321, 331) which include the groove base lamella (323, 333) and at least one of the continuous lug grooves (321, 331) which does not include the groove base lamella (323, 333) are arranged alternately in the circumferential direction of the tire. [6] Tires (1) according to claim 5, wherein a distance from a groove bottom of the continuous tunnel grooves (321, 331) to a position of maximum depth of the groove bottom lamella (323, 333) is in a range of 6% or more with respect to the maximum groove depth (Hg1, Hg2) of the main grooves (21, 22), and a distance from a tread contact surface to the position of maximum depth of the groove bottom lamella (323, 333) is in a range of 100% or less with respect to the maximum groove depth (Hg1, Hg2) of the main grooves (21, 22). [7] Tires (1) according to any one of claims 1 to 6, wherein the adjacent bridge sections (31, 32, 33) each comprise the continuous tunnel grooves (321, 331), and a continuous adit groove (321, 331) of a pair of continuous adit grooves (321, 331) facing each other, wherein the main grooves (21, 22) are arranged between them, includes the groove floor lamella (323, 333) and another continuous adit groove (321, 331) of the pair of continuous adit grooves (321, 331) does not include the groove floor lamella (323, 333). [8] Tire (1) according to any one of claims 1 to 7, wherein a maximum ground contact width (Wb1, Wb2, Wb3) of the rib sections (31, 32, 33) is in a range of 15% or more to 25% or less with respect to a ground contact width of the tire (1). [9] Tires (1) according to any one of claims 1 to 8, wherein a first edge section and a second edge section of the rib sections (31, 32, 33) have a zigzag shape or a wave-like shape with an amplitude in the tire width direction and are arranged phase-shifted in the tire circumferential direction, and the continuous tread grooves (321, 331), while inclined with respect to the tire circumference direction, run such that they connect positions of maximum amplitude of the first and second edge sections. [10] Tires (1) according to any one of claims 1 to 9, wherein a first edge section and a second edge section of the rib sections (31, 32, 33) have a wave-like shape formed by connecting a plurality of arcs with an amplitude in the tire width direction, and a circumferential length of the arcs lies within a range of 80% or more with respect to a wavelength of the wave-like shape. [11] Tire (1) according to claim 10, wherein the wave-like shape of the first and second edge sections of the rib sections (31, 32, 33) is formed by connecting the plurality of arcs projecting towards the equatorial plane of the tire (1). [12] Tire (1) according to any one of claims 1 to 11, wherein the tire (1) is a heavy-duty tire mounted on a steering axle of a vehicle.

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