Tires

Abstract

Tires (1), comprising: a pair of shoulder main grooves (21) extending in one direction around the circumference of the tire, and two or more center grooves (22) extending in the direction around the circumference of the tire; and a pair of shoulder bridge sections (31), a pair of middle bridge sections (32) and one or more rows of central bridge sections (33) defined and formed by the shoulder main grooves (21) and the middle grooves (22); wherein at least one of the middle web sections (32) has a plurality of continuous narrow grooves (321, 331) extending through the at least one of the middle web sections (32) in extending in the direction of tire width, comprising a plurality of central blocks (322) defined and formed by the continuous narrow grooves (321, 331) and non-continuous lug grooves (323), which open at one end to a boundary section on one side of the tire equatorial plane of a middle block (322) of the middle blocks (322) and end at another end in a central section of the middle block (322), wherein the central grooves (22) have a wave-like shape with an amplitude in the direction of tire width and the edge section on the side of the central groove (22) of the central block (322) has an arc shape that projects in the width direction of the central block (322), wherein a groove width (W23) of the non-continuous lug grooves (323) is in a range of 1.50 ≤ W23 / W21 ≤ 5.50 with respect to a groove width (W21) of the continuous narrow grooves (321, 331).

Description

Technical field

[0001] This invention relates to a tire and in particular to a tire that can provide, in a compatible manner, resistance to uneven wear and wet performance. State of the art

[0002] For tires used in regional operations, especially on highways, uneven wear is a common problem. At the same time, these tires must also provide adequate traction in wet conditions during local driving. The technology described in Patent Document 1 is known in the prior art as a tire addressing this issue. Patent Document 2 describes a high-performance tire that offers both high rolling resistance and wet grip. Patent Document 3 describes a pneumatic tire with improved rolling resistance, low noise, and wear resistance, while also exhibiting good wet grip. Patent Document 4 describes a pneumatic tire that effectively prevents the formation of cracks in the ribs. Patent Document 5 describes a pneumatic tire that reduces noise and provides good dry grip. List of literature on patent literature Patent document 1: JP 6088483 B Patent document 2: US 2016 / 0 297 254 A1 Patent document 3: US 10 471 778 B2 Patent document 4: EP 3 103 657 B1 Patent document 5: DE 20 2019 106 882 U1 Brief description of the invention: Technical problem

[0003] One object of the invention is to provide a tire that can provide resistance to uneven wear and wet performance in a compatible manner. Solution to the problem

[0004] To fulfill the above-described objective, a tire according to one embodiment of the invention includes a pair of main shoulder grooves extending in a tire circumferential direction, two or more center grooves extending in the tire circumferential direction, a pair of shoulder rib sections, a pair of center rib sections, and one or more rows of center rib sections defined and formed by the main shoulder grooves and the center grooves.At least one of the central rib sections includes a plurality of continuous narrow grooves extending through the at least one of the central rib sections in the tire width direction, a plurality of central blocks defined and formed by the continuous narrow grooves, and incomplete lug grooves that open at one end to form an edge section on one side of the tire's equatorial plane of a central block of the central blocks and terminate at the other end in a central section of the central block. The central grooves have a wave-like shape with an amplitude in the tire width direction. The edge section on the side of the central groove of the central block has an arc shape that projects in the width direction of the central block.A groove width W23 of the non-continuous lug grooves lies in a range of 1.50 ≤ W23 / W21 ≤ 5.50 in relation to a groove width W21 of the continuous narrow grooves. Advantageous effects of the invention

[0005] In the tire according to one embodiment of the invention, (1) the central block of the central rib section is defined and formed by the narrower, continuous grooves, thus increasing the stiffness of the central block in the circumferential direction of the tire. Accordingly, uneven wear of the central block can be suppressed, while the drainage function is ensured by the continuous, narrow groove. Additionally, (2) the edge section on the side of the central groove of the central block has an arc shape that projects in a lateral direction of the central block, thus increasing the stiffness of the central block in the lateral direction of the tire and suppressing uneven wear of the central block.Additionally (3), the central block incorporates the non-continuous lug groove, which opens only towards the edge section on the side of the tire's equatorial plane, thus improving the drainage characteristics of the central area of ​​the tread while ensuring the stiffness of the central block. Accordingly, an advantage is that the tire's resistance to uneven wear and its wet performance can be provided in a compatible manner. 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 top view showing a middle web section and a central web section of the in Fig. 2 illustrated tires. Fig. 4 is an enlarged top view showing the Fig. 3 illustrated middle bridge section. Fig. 5 is a cross-sectional view illustrating the middle web section and the central web section, which are shown in Fig. 3 are illustrated. Fig. 6 is a cross-sectional view showing a non-continuous groove of the in Fig. 3 illustrated middle bridge section. Fig. 7 is an enlarged top view showing the Fig. 3 illustrated central bridge section. Fig. 8 is an enlarged top view showing a Fig. 2. Shoulder groove illustrated. Fig.Figure 9 is a cross-sectional view along line A, which is shown in Fig. 8 illustrated shoulder groove illustrated. Fig. 10 is a cross-sectional view along line B, which is shown in Fig. 8 illustrated shoulder groove illustrated. Fig. Figure 11 is a top view, which is a modified example of the one in Fig. 2 illustrated tires. Description of embodiments

[0006] Embodiments of the invention are described in detail below with reference to the drawings. It should be noted that the invention is not limited to these embodiments. Furthermore, components of the embodiments include components that can be replaced and are clearly replacements while maintaining conformity with the embodiments of the invention. In addition, a plurality of modified examples described in the embodiments can be combined arbitrarily within the scope recognizable to a person skilled in the art. Tires

[0007] Fig.Figure 1 is a cross-sectional view in a tire meridional direction, illustrating a tire 1 according to an embodiment of the invention. The same drawing illustrates a cross-sectional view of a half-section in the tire radial direction. Additionally, in this embodiment, a high-performance radial pneumatic tire mounted on a steered wheel of a tractor is described as an example of the tire.

[0008] In the same drawing, a tire meridional cross-section is defined as a cross-section of the tire along a plane that includes a tire axis of rotation (not illustrated). A tire equatorial plane, CL, is defined as a plane passing through the center of the tire cross-sectional width as defined by the Japan Automobile Tyre Manufacturers Association Inc. (JATMA) and perpendicular to the tire axis of rotation. Additionally, a tire width direction is defined as a direction parallel to the tire axis of rotation, and the tire radial direction is defined as a direction perpendicular to the tire axis of rotation.

[0009] The tire 1 encloses a ring structure, with the tire axis of rotation being the center, 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).

[0010] The pair of bead cores 11, 11 each includes one or more bead wires made of steel and formed by multiple ring windings. The pair of bead cores 11, 11 is embedded in bead sections and forms the cores of the bead sections on the left and right. The pair of bead fillers 12, 12 each consists of a lower filler 121 and an upper filler 122. The pair of bead fillers 12, 12 is arranged on the outer circumferences of the pair of bead cores 11, 11 in the radial direction of the tire and reinforces the bead sections.

[0011] The carcass layer 13 comprises a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple layered carcass plies. The carcass layer 13 extends in a ring shape between the bead cores 11, 11 left and 11 right, forming the support structure of the tire. Furthermore, both end sections of the carcass layer 13 are wound and folded over to an outside in the tire width direction to encase the bead cores 11 and the bead fillers 12, and are fixed in place. The carcass layer 13 is formed by covering multiple carcass cord threads, made of steel, with coating rubber and by performing a rolling process on the carcass cord threads.The carcass layer of carcass layer 13 has a cord thread angle (defined as an inclination angle in a longitudinal direction of the carcass cord threads with respect to a tire circumferential direction) of 80 degrees or more and 90 degrees or less as an absolute value for a radial tire and 30 degrees or more and 45 degrees or less as an absolute value for a bias-ply tire.

[0012] The belt layer 14 is made from a plurality of belt plies 141 to 144, which are layered, and is arranged around an outer circumference of the carcass ply 13. These belt plies 141 to 144 include a large-angle belt 141, a pair of cross belts 142 and 143, and a belt cover 144. The large-angle belt 141 is formed by coating a plurality of steel belt cord threads with coating rubber and performing a rolling process on the belt cord threads. The large-angle belt 141 has a cord thread angle (defined as an angle of inclination in a longitudinal direction of the belt cord threads with respect to the tire circumference) of 45 degrees or more and 70 degrees or less as an absolute value. The pair of cross belts 142, 143 is each formed by covering a plurality of steel belt cord threads with coating rubber and carrying out a rolling process on the belt cord threads.Each of the pair of cross belts 142, 143 has a cord thread angle of 10 degrees or more and 55 degrees or less as an absolute value. Furthermore, the pair of cross belts 142, 143 has cord thread angles that are opposite in sign, and the pair of cross belts 142, 143 is layered by allowing the belt cord threads to overlap longitudinally (forming a so-called cross-layer structure). The belt cover 144 is formed by coating a plurality of belt cover cord threads, made of steel or an organic fiber material, with coating rubber and performing a rolling process on the belt cover cord threads. The belt cover 144 has a cord thread angle of 10 degrees or more and 55 degrees or less as an absolute value.

[0013] The tread rubber 15 is arranged on the 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 of the carcass layer 13 in the tire width direction and each form a left and a right sidewall section. The pair of rim cushion rubbers 17, 17 extend from an inner side in the tire radial direction of the bead cores 11, 11 left and right and folded-back sections of the carcass layer 13 to the outer side in the tire width direction and form rim mating surfaces of the bead sections. tread surface

[0014] Fig. 2 is a top view showing a running surface of the in Fig.Figure 1 illustrates tire 1. The same drawing illustrates the tread surface of the tire for regional use, primarily on highways. In the same drawing, "tire circumferential direction" refers to the direction around the tire's axis of rotation. Furthermore, the reference symbol T denotes a ground contact edge of the tire, and the dimension symbol TW denotes a ground contact width of the tire. Additionally, in the same drawing, tire 1 includes a tread surface that is substantially point-symmetrical, thus eliminating a section containing reference symbols for components in an area on the right side of the drawing.

[0015] As in Fig. As illustrated in Figure 2, the tire 1 includes four circumferential grooves 21, 22 and five rows of rib sections 31 to 33 in the tread section.

[0016] The circumferential grooves 21, 22 are formed from a pair of shoulder main grooves 21, 21 and two center grooves 22, 22. The circumferential grooves 21, 22 have an annular structure that extends continuously around the entire circumference of the tire. The shoulder main grooves 21 are defined as the main grooves located on the outermost side, in the tire width direction, of the majority of circumferential grooves 21, 22. "Main groove" refers to a groove where a wear indicator must be provided in accordance with JATMA. Furthermore, the pair of shoulder main grooves 21, 21 are arranged in left and right areas, between which the tire equatorial plane CL lies as the boundary. The center groove 22 is defined as a circumferential groove located further towards the tire equatorial plane CL than the shoulder main groove 21.

[0017] Furthermore, the shoulder groove 21 has a groove width Wg1 (see Fig. 2) of 5.0 mm or more and a groove depth Hg1 (see Fig.5, described below) of 10 mm or more. In addition, the center groove 22 has a groove width Wg2 (see Fig. 2) of more than 1.5 mm and a groove depth Hg2 (see Fig. 5, described below) of 10 mm or more. Furthermore, the groove width Wg2 of the central groove 22 is in the range of 0.10 ≤ Wg2 / Wg1 ≤ 1.00 with respect to the groove width Wg1 of the main shoulder groove 21 and is preferably in the range of 0.10 ≤ Wg2 / Wg1 ≤ 0.40. Additionally, the groove depth Hg2 of the central groove 22 is in the range of 0.70 ≤ Hg2 / Hg1 ≤ 1.30 with respect to the groove depth Hg1 of the main shoulder groove 21. In the configuration of Fig.2. The central groove 22 is a main groove on which a wear indicator must be provided in accordance with JATMA, and the central groove 22 has a groove width Wg2 that is smaller than the groove width Wg1 of the main shoulder groove 21, and a groove depth Hg2 that is equal to the groove depth Hg1 of the main shoulder groove 21. Accordingly, the drainage properties of the central area of ​​the tread section are ensured and its stiffness is increased.

[0018] The groove width is measured as the maximum distance between the opposing groove walls of a groove opening section on the tread contact patch when the tire is mounted on a specified rim, inflated to a specified internal pressure, and unloaded. In a configuration where the groove opening section includes a recessed section or a chamfered section, the groove width is measured by using as endpoints the intersection of an extension line of a tread contact patch and extension lines of the groove walls in a cross-sectional view parallel to a groove width direction and a groove depth direction.

[0019] Groove depth is measured as the maximum distance from the tread contact patch to the groove bottom when the tire is mounted on a specified rim, inflated to the specified internal pressure, and unloaded. Additionally, in configurations where the groove bottom partially includes depressions / protrusions or a sipe, the groove depth is measured excluding the partial depressions / protrusions or the sipe.

[0020] "Specified rim" refers to a "standard rim" as defined by JATMA, a "design rim" as defined by the Tire and Rim Association (TRA), or a "measurement rim" as defined by the European Tyre and Rim Technical Organisation (ETRTO). "Specified internal pressure" refers to a "maximum air pressure" as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by the TRA, or "INFLATION PRESSURES" as defined by the ETRTO. Furthermore, “specified load” refers to a “maximum load capacity” as defined by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” as defined by TRA, or “LOAD CAPACITY” as defined by ETRTO.However, in the case of a JATMA tire for a passenger car, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

[0021] The rib sections 31 to 33 are formed from a pair of shoulder rib sections 31, 31, a pair of middle rib sections 32, 32, and a series of central rib sections 33. The rib sections 31 to 33 are defined and formed by the circumferential grooves 21, 22 and form an annular road contact surface extending around the entire circumference of the tire. The shoulder rib section 31 is defined as a rib section located on the outside in the tire width direction, defined by the main shoulder groove 21. Furthermore, the pair of rib sections 31, 31 are located in the left and right areas, between which the tire equatorial plane CL lies as a boundary. The middle rib section 32 is defined as a rib section located on the inside in the tire width direction, defined by the main shoulder groove 21.Furthermore, the pair of middle rib sections 32, 32 are arranged in the left and right areas, between which the tire equatorial plane CL lies as a boundary. The central rib section 33 is defined as a rib section that is arranged further on the side of the tire equatorial plane CL than the middle rib sections 32, 32.

[0022] Furthermore, it lies in Fig.2. The ground contact width Wb1 of the shoulder rib section 31 is in the range of 0.05 ≤ Wb1 / TW ≤ 0.25, based on a ground contact width TW of the tire, and is preferably in the range of 0.15 ≤ Wb1 / TW ≤ 0.25. Furthermore, the ground contact width Wb2 of the middle rib section 32 is in the range of 0.10 ≤ Wb2 / TW ≤ 0.20, based on the ground contact width TW of the tire. Furthermore, the ground contact width Wb1 of the shoulder bridge section 31 is in the range of 1.10 ≤ Wb1 / Wb2 ≤ 1.60, relative to the ground contact width Wb2 of the middle bridge section 32. In such a configuration, the shoulder bridge section 31 has a wide structure, thus ensuring the stiffness of the shoulder bridge section 31 and effectively suppressing uneven wear of the shoulder bridge section 31.

[0023] The ground contact width of the rib section is measured as a maximum linear distance in the tire axial direction on a contact surface between the rib section and a flat plate when the tire is mounted on a specified rim, inflated to the specified internal pressure, placed vertically on the flat plate in a static state, and loaded with a load corresponding to the specified load.

[0024] The ground contact width 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.

[0025] The ground contact edge of the tire is defined as a position of maximum width 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 a predetermined load.

[0026] Furthermore, the ground contact width Wb3 of the central rib section 33 is in the range of 0.10 ≤ Wb3 / TW ≤ 0.20, relative to the ground contact width TW of the tire. Additionally, the ground contact width Wb1 of the shoulder rib section 31 is in the range of 1.10 ≤ Wb1 / Wb3 ≤ 1.60, relative to the ground contact width Wb3 of the central rib section 33. In such a configuration, the shoulder rib section 31 has a wide structure, thus ensuring the stiffness of the shoulder rib section 31 and effectively suppressing uneven wear of the shoulder rib section 31. Furthermore, the ground contact width Wb3 of the central web section 33 is in the range of 1.00 ≤ Wb3 / Wb2 ≤ 1.50 with respect to the ground contact width Wb2 of the middle web section 32 and is preferably in the range of 1.00 ≤ Wb3 / Wb2 ≤ 1.20.In such a configuration, the central web section 33 has a wide structure, thus ensuring the stiffness of the central web section 33 and effectively suppressing uneven wear of the central web section 33.

[0027] Furthermore, tire 1 in the configuration of Fig.2 the pair of shoulder main grooves 21, 21 and the two middle grooves 22, 22, as described above, and thus the pair of shoulder rib sections 31, 31, the pair of middle rib sections 32, 32 and the single central rib section 33 are defined. However, such a restriction is not intended, and tire 1 may include one or three or more central grooves (not illustrated). In the former configuration, the central rib section is omitted, and in the latter configuration, two or more rows of central rib sections are defined. Furthermore, the central rib section 33 may be located on the tire equatorial plane CL (see Fig. 2) or be located at a position away from the tire equatorial plane CL (not illustrated).

[0028] Furthermore, the configuration of Fig.2. The tire 1 has a tread pattern that is point-symmetric with a center point on the tire equatorial plane CL. However, such a restriction is not intended, and the tire 1 may have an axisymmetric tread pattern with the tire equatorial plane CL as its center point, a tread pattern with directional dependence in the tire rotation direction, or a left-right asymmetric tread pattern (not illustrated).

[0029] Furthermore, the configuration of Fig.2. The main shoulder groove 21 has a straight shape, and the central groove 22 has a wave-like shape with an amplitude in the tire width direction. The wave-like shape of the groove must have an arc shape at least at the maximum projecting position in the direction of the side of the tire equatorial plane CL and includes, for example, a sinusoidal wave shape, a zigzag shape formed by connecting a plurality of linear sections with short arcs, and a continuous arc shape formed by uniformly connecting a plurality of arcs projecting in the direction of the side of the tire equatorial plane CL. Such a configuration is preferable insofar as it ensures the stiffness of the shoulder rib section 31, reduces uneven wear of the shoulder rib section 31, and simultaneously improves the drainage properties of the central area of ​​the tread section.However, no such restriction is intended, and the shoulder main groove 21 may have a wavy shape or the medial groove 22 may have a straight shape (not illustrated).

[0030] Furthermore, the central groove 22 in the configuration of Fig. 2 exhibits a wave-like shape, as described above, and now displays a transparent structure in the circumferential direction of the tire. In other words, the groove width of the central groove 22 is such that the edge sections of the left and right rib sections 32, 33, defined by the central groove 22, do not overlap when viewed in the circumferential direction of the tire. In particular, the transparency width Wst (see below) is Fig. 3) of the central groove 22 in the range of 0.5 mm ≤ Wst. Accordingly, the drainage properties of the central groove 22 are effectively ensured.

[0031] Furthermore, the configuration of Fig.2. Each of the rib sections 31 to 33 incorporates a plurality of multiple sipes 4. Each multiple sipe 4 is a short sipe that opens at one end towards the edge section of the rib sections 31 to 33 and terminates at the other end on the inside of the rib sections 31 to 33. The multiple sipe 4 has a width of 0.3 mm or more and 1.5 mm or less, a depth of 2.0 mm or more and 17 mm or less, and a length of 2.0 mm or more and 10 mm or less (dimensions have been omitted in the drawings). Furthermore, the plurality of multiple sipes 4 are arranged circumferentially along the edge sections on the sides of the circumferential grooves 21, 22. In addition, the pitch of the multiple sipe 4 is in the range of 0.1% or more and 0.6% or less of the tire circumference.In this configuration, the stiffness of the rib sections 31 to 33 is reduced by the multiple sipes 4, and thus the ground contact pressure of the edge sections of the rib sections 31 to 33 is reduced when the tire comes into contact with the ground. As a result, the occurrence of uneven wear (especially flow wear) is suppressed and the tire's resistance to uneven wear is improved. Middle section of the bridge

[0032] Fig. Figure 3 is an enlarged top view showing the middle web section 32 and the central web section 33 of the in Fig. 2 illustrated tires 1 illustrated. Fig. 4 is an enlarged top view showing the Fig. 3 illustrated middle bridge section 32 illustrated. Fig. Figure 5 is a cross-sectional view illustrating the middle web section 32 and the central web section 33, which are shown in Fig.Figure 3 illustrates a cross-section in which the web sections 32, 33 are cut along continuous narrow grooves 321, 331. Fig. 6 is a cross-sectional view showing a non-continuous tunnel groove 323 of the in Fig. Figure 3 illustrates the central web section 32. The same drawing illustrates a cross-sectional view perpendicular to the longitudinal direction of the non-continuous tunnel groove 323.

[0033] As in the Fig. 2 and Fig. As illustrated in Figure 3, the middle bridge section 32 includes a plurality of continuous narrow grooves 321, a plurality of medium blocks 322 and a plurality of non-continuous tunnel grooves 323.

[0034] As in Fig.As illustrated in Figure 3, the continuous narrow groove 321 extends through the central web section 32 in the tire width direction and connects with the left and right circumferential grooves 21, 22. Furthermore, the majority of continuous narrow grooves 321 are arranged at predetermined intervals in the tire circumferential direction. Additionally, there is an inclination angle θ21 (see Figure 3). Fig. 3) the continuous narrow groove 321 with respect to the tire circumference direction in the range of 45° ≤ θ21 ≤ 90°. In addition, there is a groove width W21 (see Fig. 4) the continuous narrow groove 321 in the range of 0.4 mm ≤ W21 ≤ 1.5 mm. In addition, there is a groove depth H21 (see Fig.5) the continuous narrow groove 321 in the range of 0.30 ≤ H21 / Hg2 ≤ 1.00 with respect to the groove depth Hg2 of the central groove 22, preferably in the range of 0.40 ≤ H21 / Hg2 ≤ 0.70. Furthermore, the continuous narrow groove 321 is a sipe. Because the groove width W21 is 1.5 mm or less and the groove depth H21 exceeds 2.0 mm, the continuous narrow groove 321 is preferably closed when the tire comes into contact with the ground.

[0035] The angle of inclination of the groove is measured as the angle of inclination with respect to the tire's circumferential direction of an imaginary straight line passing through both end sections of the groove when the tire is mounted on a given rim, inflated to a given internal pressure, and in an unloaded state.

[0036] Furthermore, the continuous narrow groove 321 in Fig. 4 a wave-like shape that includes three or more waves. In the configuration of Fig. In Figure 4, the continuous narrow groove 321 has a wave-like shape formed from eight curved points, thus exhibiting four waves. In such a configuration, compared to a configuration with straight or arcuate continuous narrow grooves (not illustrated), the traction properties of the central rib section 32 can be improved in wet conditions, while maintaining the stiffness of the central block 322. Furthermore, the wavelength λ21 of the wave-like shape of the continuous narrow groove 321 is in the range of 0.10 ≤ λ21 / Wb2 ≤ 0.50 with respect to the ground contact width Wb2 of the central rib section 32. Additionally, the amplitude A21 of the wave-like shape of the continuous narrow groove 321 is in the range of 0.6 mm ≤ A21 ≤ 2.5 mm.

[0037] The wave-like shape and number of waves in the groove, as well as the wavelength and amplitude of the groove, are identified by the wave-like shape of a groove centerline in a top view of the running surface. The groove centerline is defined as an imaginary line connecting the midpoints of the groove widths.

[0038] As in the Fig. 2, Fig. 3 and Fig.As illustrated in Figure 4, the central block 322 is defined and formed by the adjacent continuous narrow grooves 321, 322. Furthermore, the majority of central blocks 322 are arranged in a row in the circumferential direction of the tire. Additionally, a circumferential length Le2 of the edge section on the side of the central groove 22 of the central block 322 is in the range of 0.80 ≤ Le2 / Wb2' ≤ 1.80 with respect to a ground contact width Wb2' of the central block 322 and is preferably in the range of 1.10 ≤ Le2 / Wb2' ≤ 1.50. Consequently, a form factor of the central block 322 is preferably determined such that the central block 322 is elongated in the circumferential direction of the tire. In such a configuration, compared to a configuration where the center block is extended in the tire width direction (not illustrated), the block stiffness in the tire circumference direction is ensured and uneven wear of the center block 322 is effectively suppressed.

[0039] The circumferential length Le2 of the edge section is measured as the distance in the tire's circumferential direction from the edge section facing the central groove 22 when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. Additionally, in a configuration where the corner section of the central block 322 has a chamfered section, the circumferential length Le2 is measured by using as an endpoint the intersection of a crest line of the edge section of the central rib section 32 and a crest line of the groove opening section of the continuous narrow groove 321 in the tread contact surface.

[0040] Furthermore, as shown in Fig.Figure 4 illustrates that the edge section on the side of the central groove 22 of the central block 322 has an arc shape that projects towards the side of the tire equatorial plane CL. In other words, the edge section on the side of the central groove 22 of the central block 322 projects towards the side of the tire equatorial plane CL in a region between the adjacent continuous narrow grooves 321, 322. Furthermore, the edge section as a whole has an arc shape with its center point located in the central block 322. Additionally, the continuous narrow groove 321 connects with the central groove 22 at the position of maximum amplitude towards the side of the tire's ground contact edge T (see Figure 4). Fig. 2) the wave-like shape of the central groove 22.

[0041] In the configuration described above (1), the central block 322 of the central rib section 32 is defined and shaped by the narrower continuous grooves 321, thus increasing the circumferential stiffness of the central block 322 compared to a configuration where the central block is defined by wider continuous lug grooves (not illustrated). Accordingly, uneven wear of the central block 322 can be suppressed, while the drainage function is ensured by the continuous narrow groove 321.Furthermore (2) the edge section on the side of the central groove 22 of the central block 322 has an arc shape that projects towards the side of the tire equatorial plane CL, and thus, compared to a configuration where the central block has an edge section with a recessed shape (not illustrated), the stiffness in the tire width direction of the central block 322 is increased and uneven wear of the central block 322 is suppressed. In addition (3) the central block 322 includes the non-continuous lug groove 323, which opens only towards the edge section on the side of the tire equatorial plane CL, and thus the drainage properties of the central area of ​​the tread section can be improved while ensuring the stiffness of the central block 322.Accordingly, the resistance to uneven wear and the wet performance of the tire can be provided in a compatible manner.

[0042] Furthermore, it lies in Fig. 4. The maximum projecting position relative to the side of the tire equatorial plane CL of the edge section of the central block 322 (a measuring point of the ground contact width Wb2' of the central block 322, reference symbol omitted in the drawings) in the central section of the edge section. In particular, the maximum projecting position is located at a distance of 35% or more and 65% or less from an end of the circumferential length Le2 of the edge section.

[0043] Furthermore, in Fig. 4 a circumferential length La2 of the arc shape of the edge section in the range of 0.50 ≤ La2 / Le2 ≤ 1.00 with respect to the circumferential length Le2 of the edge section of the middle block 322 and is preferably in the range of 0.90 ≤ La2 / Le2 ≤ 1.00.

[0044] The circumferential length La2 of the arc shape is measured as the distance between adjacent inflection points of the wave-like shape of the central groove 22, including the maximum projecting position of the edge section of the central block 322.

[0045] In the configuration of Fig. 2 The wave-like shape of the central groove 22, for example, has a continuous arc shape, which is elongated and projects towards the side of the tire equatorial plane CL, and which is formed by connecting a plurality of arcs. Furthermore, the continuous narrow groove 321 is connected to the connection point of the adjacent arcs. In other words, the continuous narrow grooves 321 are each connected to both ends of an arc. As a result, the entire edge section on the side of the central groove 22 of the central block 322 is formed from the single arc, and the ratio La2 / Le2 described above is 1.00.

[0046] Furthermore, in Fig. 4. The overhang Pe2 towards the side of the tire equatorial plane CL of the edge section of the central block 322 is in the range of 0.02 ≤ Pe2 / Wb2' ≤ 0.20 with respect to the ground contact width Wb2' of the central block 322 and is preferably in the range of 0.05 ≤ Pe2 / Wb2' ≤ 0.12. Furthermore, the overhang Pe2 is preferably in the range of 1.0 mm ≤ Pe2. The lower limit described above ensures the overhang of the edge section of the central block 322 and adequately increases the stiffness of the central block 322, thus suppressing uneven wear of the central block 322. The upper limit described above suppresses uneven wear of the central block 322 caused by an excessively large overhang of the edge section.

[0047] As in Fig.As illustrated in Figure 3, the non-continuous lug groove 323 opens at one end towards the edge section on the side of the tire equatorial plane CL of the central block 322 and terminates at another end in the central section of the central block 322. Furthermore, the majority of non-continuous lug grooves 323 are arranged at predetermined intervals in the tire's circumferential direction. Additionally, the extension length L23 in the tire width direction of the non-continuous lug groove 323 is in the range of 0.40 ≤ L23 / Wb2' ≤ 0.90 with respect to the ground contact width Wb2' of the central block 322 and is preferably in the range of 0.50 ≤ L23 / Wb2' ≤ 0.80. The lower limit described above ensures the drainage function of the non-continuous lug groove 323, and the upper limit described above ensures the stiffness of the central block 322. For example, in the configuration of Fig.3. The non-continuous lug groove 323 is connected to the central groove 22 at the position of maximum amplitude in the direction of the side of the tire equatorial plane CL of the wave-like shape of the central groove 22. Accordingly, the extension length L23 in the tire width direction of the non-continuous lug groove 323 is ensured.

[0048] Furthermore, in Fig. 3. An inclination angle θ23 with respect to the tire circumferential direction of the non-continuous lug groove 323 is in the range of -20° ≤ 821 - θ23 ≤ 20° with respect to an inclination angle θ21 of the continuous narrow groove 321 and is preferably in the range of -10° ≤ θ21 - θ23 ≤ 10°. Accordingly, the non-continuous lug groove 323 runs substantially parallel to the continuous narrow groove 321. Furthermore, in Fig.4. The groove width W23 of the non-continuous groove 323 is in the range of 1.50 ≤ W23 / W21 ≤ 5.50, relative to the groove width W21 of the continuous narrow groove 321, and is preferably in the range of 2.00 ≤ W23 / W21 ≤ 4.00. The groove width W23 of the non-continuous lug groove 323 is in the range of 1.5 mm ≤ W23 ≤ 5.0 mm.

[0049] Furthermore, it lies in Fig. 5. The groove depth H23 of the non-continuous adit groove 323 is in the range of 0.10 ≤ H23 / Hg2 ≤ 0.30 with respect to the groove depth Hg2 of the central groove 22. Furthermore, the groove depth H23 of the non-continuous adit groove 323 is smaller than the groove depth H21 of the continuous narrow groove 321. Moreover, in Fig.6. The groove width W23 and the groove depth H23 of the non-continuous tunnel groove 323 have a ratio of 1.00 ≤ W23 / H23 ≤ 1.50 and preferably a ratio of 1.20 ≤ W23 / H23 ≤ 1.50. Accordingly, the non-continuous tunnel groove 323 has a flat bottom and a wide structure. As a result, the stiffness of the central block 322 can be increased, while the drainage function of the non-continuous tunnel groove 323 is ensured. Furthermore, in Fig. 6 a groove wall angle α23 of the non-continuous trough groove 323 preferably in the range of 90° ≤ α23 ≤ 110°.

[0050] Furthermore, the non-continuous groove 323 in Fig. 4. A wave-like shape that has two or more waves. Furthermore, in the configuration of Fig.4. The non-continuous lug groove 323 has a wave-like shape formed from five curved points and thus exhibits two or three waves. In such a configuration, compared to a configuration including a non-continuous lug groove formed in a straight or arc shape (not illustrated), the traction properties in wet conditions of the central rib section 32 can be increased while maintaining the stiffness of the central block 322. A wavelength λ23 of the wave-like shape of the non-continuous lug groove 323 is in the range of 0.70 ≤ λ23 / λ21 ≤ 1.30 with respect to the wavelength λ21 of the wave-like shape of the continuous narrow groove 321 and is preferably in the range of 0.90 ≤ λ23 / λ21 ≤ 1.20.Furthermore, the amplitude A23 of the wave-like shape of the non-continuous tread groove 323 is in the range of 0.80 ≤ A23 / A21 ≤ 1.50 with respect to the amplitude A21 of the wave-like shape of the continuous narrow groove 321 and is preferably in the range of 1.20 ≤ A23 / A21 ≤ 1.50. Central section of the bridge

[0051] Fig. 7 is an enlarged top view showing the Fig. 3 illustrated central bridge section 33 illustrated.

[0052] As in the Fig. 2 and Fig. As illustrated in Figure 3, the central bridge section 33 includes a plurality of continuous narrow grooves 331 and a plurality of central blocks 332.

[0053] As in Fig.As illustrated in Figure 3, the continuous narrow groove 331 extends through the central web section 33 in the tire width direction and connects with the left and right circumferential grooves 22, 22. Furthermore, the majority of continuous narrow grooves 331 are arranged at predetermined intervals in the tire circumferential direction. Additionally, there is an inclination angle θ31 (see Figure 3). Fig. 3) with respect to the tire circumferential direction of the continuous narrow groove 331 in the range of 45° ≤ θ31 ≤ 90°. In addition, there is a groove width W31 (see Fig. 7) the continuous narrow groove 331 in the range of 0.4 mm ≤ W31 ≤ 1.5 mm. In addition, there is a groove depth H31 (see Fig.5) The continuous narrow groove 331 is in the range of 0.30 ≤ H31 / Hg2 ≤ 1.00 with respect to the groove depth Hg2 of the central groove 22 and is preferably in the range of 0.40 ≤ H31 / Hg2 ≤ 0.70. Furthermore, the continuous narrow groove 331 is a lamella. Because the groove width W31 is 1.5 mm or less and the groove depth H31 is 2.0 mm or more, the continuous narrow groove 331 is preferably closed when the tire comes into contact with the ground.

[0054] Furthermore, the continuous narrow groove 331 in Fig. 7 a wave-like shape which is in Fig.The continuous narrow groove 321 of the central web section 32 resembles the wave-like shape illustrated in Figure 4. In particular, the continuous narrow groove 331 of the central web section 33 has a wave-like shape with three or more waves, and one wavelength λ31 of it is in the range of 0.10 ≤ λ31 / Wb3 ≤ 0.50 with respect to the ground contact width Wb3 of the central web section 33. Furthermore, an amplitude A31 of the wave-like shape of the continuous narrow groove 331 is in the range of 0.7 mm ≤ A31 ≤ 2.5 mm.

[0055] Furthermore, the configuration of Fig.2. The continuous narrow groove 331 of the central rib section 33 is inclined in the circumferential direction of the tire relative to the continuous narrow groove 321 of the central rib section 32 in the opposite direction. As a result, the stiffness in the central area of ​​the tread section is increased. Furthermore, the continuous narrow groove 331 of the central rib section 33 and the continuous narrow grooves 321, 321 of the left and right central rib sections 32, 32 are inclined in opposite directions relative to each other relative to the circumferential direction of the tire. Furthermore, in Fig.3. A distance Dg in the circumferential direction of the tire between the connecting section of the continuous narrow groove 331 of the central rib section 33 to the central groove 22 and the connecting section of the continuous narrow groove 321 of the central rib section 32 to the central groove 22 in the range of 0 ≤ Dg / P21 ≤ 0.40 with respect to a pitch length P21 between the continuous narrow grooves 321 of the central rib section 32. Furthermore, the distance Dg is preferably in the range of 0 mm ≤ Dg ≤ 10 mm.Accordingly, a connecting groove formed by the continuous narrow groove 331 of the central rib section 33 and the continuous narrow grooves 321, 321 of the left and right central rib sections 32, 32, has a zigzag shape with a large wavelength, which has the position of maximum amplitude on the central groove 22 and extends over the central area of ​​the tread section and is connected to the left and right shoulder main grooves 21, 21. As a result, the drainage properties in the central area of ​​the tread section are improved.

[0056] As in the Fig. 2 and Fig. As illustrated in Figure 3, the central block 332 is defined and formed by the adjacent continuous narrow grooves 331, 332. Furthermore, the majority of central blocks 332 are arranged in a row in the circumferential direction of the tire. Moreover, in Fig.7. The circumferential length Le3 of the edge section of the central block 332 is in the range of 0.80 ≤ Le3 / Wb3' ≤ 1.80 with respect to a ground contact width Wb3' of the central block 332 and is preferably in the range of 1.10 ≤ Le3 / Wb3' ≤ 1.50. As a result, the form factor of the central block 332 is preferably determined such that the central block 332 is elongated in the tire circumferential direction. In such a configuration, compared to a configuration in which the central block is elongated in the tire width direction (not illustrated), the block stiffness in the tire circumferential direction is ensured and uneven wear of the block is suppressed.

[0057] Furthermore, as shown in Fig.Figure 7 illustrates that the edge section of the central block 332 has an arc shape that is recessed towards the side of the tire equatorial plane CL. Specifically, the central block 332 is located on the tire equatorial plane CL, and the left and right edge sections of the central block 332 have an arc shape that is recessed in the lateral direction of the central block 332 in a region between the adjacent continuous narrow grooves 331, 332. Furthermore, the continuous narrow groove 331 is aligned with the central groove 22 at the position of maximum amplitude towards the side of the tire's ground contact edge T (see Figure 7). Fig. 2) connected to the wave-like shape of the central groove 22.

[0058] Furthermore, in Fig.7 the maximum recessed position of the edge section of the central block 332 (a measuring point of the ground contact width Wb3' of the central block 332, reference symbol omitted in the drawings) in the middle section of the edge section. In particular, the maximum recessed position is located at a distance of 35% or more and 65% or less from an end of the circumferential length Le3 of the edge section.

[0059] Furthermore, in Fig. 7 a circumferential length La3 of the arc shape of the edge section in the range of 0.50 ≤ La3 / Le3 ≤ 1.00 with respect to the circumferential length Le3 of the edge section of the central block 332 and is preferably in the range of 0.90 ≤ La3 / Le3 ≤ 1.00.

[0060] In the configuration of Fig.2 The wave-like shape of the central groove 22, for example, has a continuous arc shape, which is formed in an elongated form projecting towards the side of the tire equatorial plane CL and is formed by connecting a plurality of arcs. Furthermore, the continuous narrow groove 331 is connected to the connection point of the adjacent arcs. In other words, the continuous narrow grooves 331 are each connected to both ends of an arc. As a result, the entire edge section on the side of the central groove 22 of the central block 332 is formed from the single arc, and the ratio La3 / Le3 described above is 1.00.

[0061] Furthermore, it lies in Fig.7. The indentation depth Pe3 of the edge section of the central block 332 is in the range of 0.02 ≤ Pe3 / Wb3' ≤ 0.20 with respect to the ground contact width Wb3' of the central block 332 and is preferably in the range of 0.05 ≤ Pe3 / Wb3' ≤ 0.12. Furthermore, the indentation depth Pe3 is preferably in the range of 1.0 mm ≤ Pe3. As a result, the edge section of the central block 332 has an arc shape that corresponds to the arc shape of the edge section of the middle block 322 described above.

[0062] Furthermore, there are in Fig.3. The connecting section of the continuous narrow groove 331 of the central rib section 33 with the central groove 22 and the connecting section of the continuous narrow groove 321 of the central rib section 32 with the central groove 22 are essentially in the same position in the tire circumferential direction as described above. Accordingly, the wave-like shape of the edge section of the central rib section 33 is essentially in phase with the wave-like shape of the edge section of the central rib section 32. As a result, the recessed edge section of the central block 332 coincides with the protruding edge section of the central block 322, and the groove width of the central groove 22, which has a wave-like shape, is uniformly defined. Shoulder strap section

[0063] As in Fig.As illustrated in Figure 2, the shoulder rib section 31 is a rib that provides a continuous road contact surface in the tire's circumferential direction. Furthermore, the shoulder rib section 31 includes only the multiple sipes 4 and does not include any other grooves or sipes. As a result, the resistance to uneven wear of the shoulder rib section 31, where uneven wear is likely to occur, can be improved. However, no such limitation is intended, and the shoulder rib section 31 may have shallow sipes or shallow grooves with a depth of 15 mm or less (not illustrated). shoulder groove

[0064] Fig. 8 is an enlarged top view, which shows the Fig. 2. The main shoulder groove is illustrated. Fig. 9 and Fig. 10 are a cross-sectional view along line A ( Fig. 9) and a cross-sectional view along line B ( Fig.10), which are in Fig. 8 illustrated shoulder grooves.

[0065] As in the Fig.As illustrated in Figures 8 to 10, the ridge line of the connecting section between a groove bottom section of the main shoulder groove 21 and a groove wall section on the side of the shoulder rib section 31 of the main shoulder groove 21 has a wavy or zigzag shape with an amplitude in the tire width direction when viewed from above. Conversely, the ridge line of the connecting section between the groove bottom section of the main shoulder groove 21 and a groove wall section on the side of the middle rib section 32 of the main shoulder groove 21 has a straight shape. Such a configuration is preferable because it ensures the stiffness of the shoulder rib section 31, reduces uneven wear of the shoulder rib section 31, and simultaneously guarantees the drainage properties of the main shoulder groove 21.Furthermore, a groove wall angle φ1 (defined as an angle of inclination of the groove wall surface with respect to the normal line of the road contact surface of the tread) on the side of the shoulder rib section 31 of the main shoulder groove 21 is in the range of 0° ≤ φ1 - φ2 with respect to a groove wall angle φ2 on the side of the middle rib section 32 and is preferably in the range of 1° ≤ φ1 - φ2. Additionally, the groove wall angle φ1 on the side of the shoulder rib section 31 is in the range of 3° ≤ φ1 ≤ 20°. Furthermore, the radius of curvature (not illustrated) of the connecting section between the groove wall on the side of the shoulder bridge section 31 of the main shoulder groove 21 and the groove floor is equal to or greater than the radius of curvature of the connecting section between the groove wall on the side of the middle bridge section 32 of the main shoulder groove 21 and the groove floor. As a result, the stiffness of the shoulder bridge section 31 is increased. Modified examples

[0066] Fig. Figure 11 is a top view, which is a modified example of the one in Fig. 2 illustrated tire 1 illustrated. In the same drawing are components which are the same as those in Fig. The two illustrated components are labelled with the same reference symbols, and their explanations are omitted.

[0067] In the configuration of Fig. As described above, the groove width Wg2 of the central groove 22 is smaller than the groove width Wg1 of the main shoulder groove 21 and is in the range of 0.10 ≤ Wg2 / Wg1 ≤ 0.40. Such a configuration is preferable because it increases the stiffness of the central area of ​​the tread section, improves the tire's resistance to uneven wear, and reduces the tire's rolling resistance.

[0068] However, no such restriction is intended, and as in Fig. As illustrated in Figure 11, the central groove 22 can have a wide structure and thus a groove width corresponding to the groove width of the main shoulder groove 21. As a result, the wet performance of the tire is improved. Effect

[0069] As described above, the tire 1 includes the pair of shoulder main grooves 21, 21, which extend in the circumferential direction of the tire, and the two or more center grooves 22, 22, which extend in the circumferential direction of the tire, as well as the pair of shoulder rib sections 31, 31, the pair of center rib sections 32, 32, and one or more rows of central rib sections 33, which are defined and formed by the shoulder main grooves 21 and the center grooves 22 (see Fig.2). Furthermore, the central rib section 32 includes, at least on one side, the plurality of continuous narrow grooves 321 extending through the central rib section 32 in the tire width direction, and the plurality of central blocks 322, each defined and formed by the continuous narrow grooves 321, and the non-continuous lug grooves 323, each opening at one end to the edge section on the side of the tire equatorial plane CL of the central block 322 and terminating at another end in the central section of the central block 322. In addition, the central groove 22 has a wave-like shape with an amplitude in the tire width direction. Furthermore, the edge section on the side of the central groove 22 of the central block 322 has an arc shape projecting in the width direction of the central block 322.

[0070] In such a configuration (1), the central block 322 of the central rib sections 32 is defined and formed by the narrower continuous grooves 321, thus increasing the circumferential stiffness of the central block 322 compared to a configuration in which the central block is defined by wider continuous lug grooves (not illustrated). Accordingly, uneven wear of the central block 322 can be suppressed, while the drainage function is ensured by the continuous narrow groove 321.Furthermore (2) the edge section on the side of the central groove 22 of the central block 322 has an arc shape that projects in the width direction of the central block 322, thus increasing the stiffness in the tire width direction of the central block 322 and suppressing uneven wear of the central block 322 compared to a configuration in which the central block has a recessed edge section (not illustrated). In addition (3) the central block 322 encloses the non-continuous lug groove 323, which opens only to the edge section on the side of the tire equatorial plane CL, thus improving the drainage properties of the central area of ​​the tread section while ensuring the stiffness of the central block 322.Accordingly, one advantage is that the resistance to uneven wear and the wet performance of the tire can be provided in a compatible manner.

[0071] Furthermore, in tire 1, the maximum protruding position of the edge section of the middle block 322 is arranged at a distance of 35% or more and 65% or less from one end of the circumferential length Le2 of the edge section (see Fig. 4) Accordingly, an advantage is that the stiffness in the tire width direction of the middle block 322 can be effectively increased.

[0072] Furthermore, for tire 1, the protrusion Pe2 of the edge section of the middle block is in the range of 0.02 ≤ Pe2 / Wb2' ≤ 0.20 with respect to the ground contact width Wb2' of the middle block (see Fig.4) The lower limit described above ensures the overhang of the edge section of the central block 322 and appropriately increases the stiffness of the central block 322. This has the advantage of suppressing uneven wear of the central block 322. The upper limit described above has the advantage of suppressing uneven wear of the central block 322 caused by an excessively large overhang of the edge section.

[0073] Furthermore, the circumferential length Le2 of the edge section of the middle block 322 is in the range of 0.80 ≤ Le2 / Wb2' ≤ 1.80 with respect to the ground contact width Wb2' of the middle block 322 (see Fig.4) In such a configuration, block stiffness in the circumferential direction of the tire is ensured, in contrast to a configuration where the center block is elongated in the width direction of the tire (not illustrated). Thus, an advantage is that uneven wear of the center block 322 is effectively suppressed.

[0074] Furthermore, in tire 1, the circumferential length La2 of the arc shape of the edge section of the middle block 322 is in the range of 0.80 ≤ La2 / Le2 ≤ 1.00 with respect to the circumferential length Le2 of the edge section of the middle block 322 (see Fig. 4) Accordingly, the circumferential length La2 of the arc shape is ensured. Thus, an advantage lies in the fact that an increase in the stiffness of the central block 322, which is due to the fact that the edge section of the central block 322 has an arc shape projecting in the width direction of the central block 322, is adequately ensured.

[0075] Furthermore, the continuous narrow groove 321 in the tire 1 is a sipe that closes when the tire comes into contact with the ground. This increases the stiffness of the central block 322, thus improving the tire's resistance to uneven wear.

[0076] Furthermore, in the tire 1, the non-continuous lug groove 323 is connected to the central groove 22 at the position of maximum amplitude in the direction of the side of the tire equatorial plane CL of the wave-like shape. Accordingly, the extension length L23 in the tire width direction of the non-continuous lug groove 323 can be increased, and thus the advantage lies in the fact that the traction properties in wet conditions can be improved in the central area of ​​the tread section.

[0077] Furthermore, the continuous narrow groove 321 in the tire 1 has a wave-like shape, and the wavelength λ21 of the wave-like shape of the continuous narrow groove 321 is in the range of 0.10 ≤ λ21 / Wb2 ≤ 0.50 with respect to the ground contact width Wb2 of the middle rib section 32 (see Fig. 4) The lower limit described above ensures the wavelength λ21 of the wave-like shape, thus offering the advantage of suppressing uneven wear generated by the bending point of the continuous narrow groove 321. The upper limit described above ensures the number of waves of the wave-like shape, thus offering the advantage of ensuring the improved drainage properties provided by the continuous narrow groove 321.

[0078] Furthermore, for tire 1, the inclination angle θ23 with respect to the tire circumferential direction of the non-continuous lug groove 323 is in the range of -20° ≤ θ21 - θ23 ≤ 20° with respect to the inclination angle θ21 of the continuous narrow groove 321 (see Fig. 3) Accordingly, the stiffness of the central block 322 in the circumferential direction of the tire is provided uniformly in an area between the non-continuous lug groove 323 and the continuous narrow groove 321, and thus an advantage is that uneven wear of the central block 322 is suppressed.

[0079] Furthermore, in tire 1, the groove width W23 of the non-continuous lug groove 323 is in the range of 1.50 ≤ W23 / W21 ≤ 5.50 with respect to the groove width W21 of the continuous narrow groove 321 (see Fig.4) The advantage of the lower limit described above is that the wider, non-continuous lug groove 323 ensures improved traction properties in wet conditions for the central tread section 32. The advantage of the upper limit described above is that the narrower, continuous groove 321 ensures increased stiffness of the central tread section 32.

[0080] Furthermore, the non-continuous lug groove 323 of the tire 1 has a wave-like shape, and the wavelength λ23 of the wave-like shape of the non-continuous lug groove 323 is in the range of 0.70 ≤ λ23 / λ21 ≤ 1.30 with respect to the wavelength λ21 of the wave-like shape of the continuous narrow groove 321. Accordingly, the wavelength λ23 of the wave-like shape of the non-continuous lug groove 323 is essentially equal to the wavelength λ21 of the wave-like shape of the continuous narrow groove 321, and the stiffness of the central block 322 in the area between the non-continuous lug groove 323 and the continuous narrow groove 321 is provided uniformly. Thus, an advantage is that uneven wear of the central block 322 is suppressed.

[0081] Furthermore, in tire 1, the continuous narrow groove 331 of the central rib section 33 is inclined in the circumferential direction with respect to the continuous narrow groove 321 of the middle rib section 32 (see Fig. 2) Accordingly, one advantage is that the stiffness of the central area of ​​the tread section is increased. Application object

[0082] Furthermore, tire 1 is a high-performance radial pneumatic tire mounted on a steered wheel of a tractor. Such a tire is an application object, and thus wet performance and resistance to uneven tire wear can be effectively provided in a compatible manner.

[0083] Furthermore, a pneumatic tire is described as an example of the tire in the embodiments. However, no such limitation is intended, and the configurations described in the embodiments can also be applied arbitrarily to other tires within the scope of protection obvious to those skilled in the art. Examples of other tires include a flat tire and a solid tire. Examples

[0084] The following tables show the results of performance tests of tires according to embodiments of the invention. Comparative example Example 1 Example 2 Shape of the edge section of the middle block Deepened Above Above Pe2 / Wb2' 0,07 0,07 0,02 Le2 / Wb2' 0,95 0,95 0,95 La2 / Le2 1,00 1,00 1,00 W21 (mm) 1,0 1,0 1,0 W23 (mm) 2,0 2,0 2,0 W23 / W21 2,00 2,00 2,00 Shape of the continuous narrow groove Bow Bow Bow Shape of the middle lug groove Bow Bow Bow λ21 / Wb2 - - - A21 (mm) - - - λ23 / λ21 - - - A23 / A21 - - - WB2 / TW 0,15 0,15 0,15 WB3 / WB2 1,00 1,00 1,00 Traction performance in wet conditions 100 101 101 Resistance to uneven wear 100 101 101 Example 3 Example 4 Example 5 Example 6 Shape of the edge section of the middle block Above Above Above Above Pe2 / Wb2' 0,20 0,07 0,07 0,07 Le2 / Wb2' 0,95 0,80 1,38 1,80 La2 / Le2 1,00 1,00 1,00 1,00 W21 (mm) 1,0 1,0 1,0 1,0 W23 (mm) 2,0 2,0 2,0 2,0 W23 / W21 2,00 2,00 2,00 2,00 Shape of the continuous narrow groove Bow Bow Bow Bow Shape of the middle lug groove Bow Bow Bow Bow λ21 / Wb2 - - - - A21 (mm) - - - - λ23 / λ21 - - - - A23 / A21 - - - - WB2 / TW 0,15 0,15 0,15 0,15 WB3 / WB2 1,00 1,00 1,00 1,00 Traction performance in wet conditions 101 101 102 102 Resistance to uneven wear 101 101 101 100 Example 7 Example 8 Shape of the edge section of the middle block Above Above Pe2 / Wb2' 0,07 0,07 Le2 / Wb2' 1,38 1,38 La2 / Le2 1,00 1,00 W21 (mm) 1,0 1,0 W23 (mm) 1,0 5,5 W23 / W21 1,00 5,50 Shape of the continuous narrow groove Bow Bow Shape of the middle lug groove Bow Bow λ21 / Wb2 - - A21 (mm) - - λ23 / λ21 - - A23 / A21 - - WB2 / TW 0,15 0,15 WB3 / WB2 1,00 1,00 Traction performance in wet conditions 103 102 Resistance to uneven wear 102 103 Example 9 Example 10 Example 11 Example 12 Shape of the edge section of the middle block Above Above Above Above Pe2 / Wb2' 0,07 0,07 0,07 0,07 Le2 / Wb2' 1,38 1,38 1,38 1,38 La2 / Le2 1,00 1,00 1,00 1,00 W21 (mm) 1,0 1,0 1,0 1,0 W23 (mm) 2,0 2,0 2,0 2,0 W23 / W21 2,00 2,00 2,00 2,00 Shape of the continuous narrow groove wave-like wave-like wave-like wave-like Shape of the middle lug groove wave-like wave-like wave-like wave-like λ21 / Wb2 0,10 0,22 0,50 0,22 A21 (mm) - - - 1,2 λ23 / λ21 - - - 1,00 A23 / A21 - - - 1,00 WB2 / TW 0,15 0,15 0,15 0,15 WB3 / WB2 1,00 1,00 1,00 1,00 Traction performance in wet conditions 104 104 103 104 Resistance to uneven wear 102 102 103 103 Example 13 Example 14 Example 15 Example 16 Shape of the edge section of the middle block Above Above Above Above Pe2 / Wb2' 0,07 0,07 0,07 0,07 Le2 / Wb2' 1,38 1,38 1,38 1,38 La2 / Le2 1,00 1,00 1,00 1,00 W21 (mm) 1,0 1,0 1,0 1,0 W23 (mm) 2,0 2,0 2,0 2,0 W23 / W21 2,00 2,00 2,00 2,00 Shape of the continuous narrow groove wave-like wave-like wave-like wave-like Shape of the middle lug groove wave-like wave-like wave-like wave-like λ21 / Wb2 0,22 0,22 0,22 0,22 A21 (mm) 2,0 2,5 2,0 2,0 λ23 / λ21 1,00 1,00 0,70 1,30 A23 / A21 1,00 1,00 1,00 1,00 WB2 / TW 0,15 0,15 0,15 0,15 WB3 / WB2 1,00 1,00 1,00 1,00 Traction performance in wet conditions 105 104 105 106 Resistance to uneven wear 103 104 103 103 Example 17 Example 18 Example 19 Example 20 Shape of the edge section of the middle block Above Above Above Above Pe2 / Wb2' 0,07 0,07 0,07 0,07 Le2 / Wb2' 1,38 1,38 1,38 1,38 La2 / Le2 1,00 1,00 1,00 1,00 W21 (mm) 1,0 1,0 1,0 1,0 W23 (mm) 2,0 2,0 2,0 2,0 W23 / W21 2,00 2,00 2,00 2,00 Shape of the continuous narrow groove wave-like wave-like wave-like wave-like Shape of the middle lug groove wave-like wave-like wave-like wave-like λ21 / Wb2 0,22 0,22 0,22 0,22 A21 (mm) 2,0 2,0 2,0 2,0 λ23 / λ21 1,00 1,00 1,00 1,00 A23 / A21 0,85 1,15 1,45 1,15 WB2 / TW 0,15 0,15 0,15 0,15 WB3 / WB2 1,00 1,00 1,00 1,14 Traction performance in wet conditions 106 107 106 107 Resistance to uneven wear 103 103 103 103

[0085] In the performance tests, a number of test tire types were evaluated for (1) wet performance and (2) resistance to uneven wear. The test tires, with a tire size of 11R22.5, were mounted on rims specified by JATMA, and JATMA-specified inflation pressure and load were applied. Furthermore, each test tire was mounted on a 2D tractor unit, which serves as a test vehicle.

[0086] (1) To assess wet traction performance, the test vehicle is driven on an asphalt road covered with 1 mm of water, and the driving time from a speed of 5 km / h to a speed of 20 km / h is measured. The results are then expressed as index values ​​and evaluated, with the comparison example assigned as the reference (100). Higher values ​​are preferred in this evaluation.

[0087] (2) When assessing resistance to uneven wear, after the test vehicle has been driven 150,000 km on a predetermined paved road, the depth of the step wear on the edge section of the rib section is considered, expressed as index values, and evaluated. The results are expressed as index values ​​and evaluated, with the comparison example (100) assigned as the reference. Higher values ​​are preferred in the evaluation.

[0088] Each of the test tires from the examples includes the ones in the Fig. 1 and Fig.The configurations illustrated in Figure 2 are included. The central rib section 32 includes the continuous narrow grooves 321, the central blocks 322, and the non-continuous lug grooves 323. The central grooves 22 have a wave-like shape with an amplitude in the tire width direction. Furthermore, the edge section on the side of the central groove 22 of the central block 322 has an arc shape that projects towards the side of the tire equatorial plane CL. Additionally, the groove width Wg1 of the main shoulder groove 21 is 13.0 mm, and the groove depth Hg1 of the main shoulder groove 21 is 16.2 mm. Furthermore, the groove width Wg2 of the central groove 22 is 3.6 mm, and the groove depth Hg2 of the central groove 22 is 16.7 mm. Furthermore, the ground contact width TW of the tire is 215 mm, and the ground contact width Wb1 of the shoulder rib section 31 is 43.5 mm.

[0089] The tire of the comparison example is configured such that the edge section on the side of the central groove 22 of the central block 322 of the test tire of example 1 has an arc shape that is recessed in the width direction of the central block 322.

[0090] As can be seen from the test results, the test tires of the examples provide both traction performance in wet conditions and resistance to uneven wear in a compatible manner. List of reference symbols 1 tire 11 bead core 12 bead fillers 121 Lower pen 122 Upper fountain pen 13 Carcass layer 14 Belt layer 141 Belts with a large angle 142, 143 Cross belt 144 Belt cover 15 tread rubber 16 side wall rubber 17 Rim pad rubber 21 Shoulder groove 22 Center groove 31 Shoulder strap section 32 Middle section of the bridge 321 Continuous narrow groove 322 Middle Block 323 Non-continuous lug groove 33 Central Bridge Section 331 Continuous narrow groove 332 Central Block 4 Multi-lamella

Claims

[1] Tires (1), comprising: a pair of shoulder main grooves (21) extending in one direction around the circumference of the tire, and two or more center grooves (22) extending in the direction around the circumference of the tire; and a pair of shoulder bridge sections (31), a pair of middle bridge sections (32) and one or more rows of central bridge sections (33) defined and formed by the shoulder main grooves (21) and the middle grooves (22); wherein at least one of the middle web sections (32) has a plurality of continuous narrow grooves (321, 331) extending through the at least one of the middle web sections (32) in extending in the direction of tire width, comprising a plurality of central blocks (322) defined and formed by the continuous narrow grooves (321, 331) and non-continuous lug grooves (323), which open at one end to a boundary section on one side of the tire equatorial plane of a middle block (322) of the middle blocks (322) and end at another end in a central section of the middle block (322), wherein the central grooves (22) have a wave-like shape with an amplitude in the direction of tire width and the edge section on the side of the central groove (22) of the central block (322) has an arc shape that projects in the width direction of the central block (322), wherein a groove width (W23) of the non-continuous lug grooves (323) is in a range of 1.50 ≤ W23 / W21 ≤ 5.50 with respect to a groove width (W21) of the continuous narrow grooves (321, 331). [2] Tire (1) according to claim 1, wherein a maximum protruding position of the edge section of the central block (322) is at a distance of 35% or more and 65% or less from an end of a circumferential length (Le2) of the edge section. [3] Tire (1) according to claim 1 or 2, wherein an overhang amount (Pe2) of the edge section of the middle block (322) is in a range of 0.02 ≤ Pe2 / Wb2' ≤ 0.20 with respect to a ground contact width (Wb2') of the middle block (322). [4] Tire (1) according to any one of claims 1 to 3, wherein a circumferential length (Le2) of the edge section of the middle block (322) is in a range of 1.10 ≤ Le2 / Wb2' ≤ 1.50 with respect to a ground contact width (Wb2') of the middle block (322). [5] Tire (1) according to any one of claims 1 to 4, wherein a circumferential length (La2) of the arc shape of the edge section of the middle block (322) is in a range of 0.50 ≤ La2 / Le2 ≤ 1.00 with respect to a circumferential length (Le2) of the edge section of the middle block (322). [6] Tire (1) according to any one of claims 1 to 5, wherein the continuous narrow grooves (321, 331) are sipes which are closed when the tire (1) comes into contact with a ground. [7] Tire (1) according to any one of claims 1 to 6, wherein the non-continuous lug grooves (323) are connected to the respective central grooves (22) at a position with maximum amplitude in the direction of the side of the tire equatorial plane of the wave-like shape. [8] Tire (1) according to any one of claims 1 to 7, wherein the continuous narrow grooves (321, 331) have a wave-like shape and a wavelength (λ21) of the wave-like shape of the continuous narrow grooves (321, 331) is in a range of 0.10 ≤ λ21 / Wb2 ≤ 0.50 with respect to a ground contact width (Wb2) of the central rib section (32). [9] Tire (1) according to any one of claims 1 to 8, wherein an inclination angle (θ23) with respect to the circumferential direction of the non-continuous lug grooves (323) is in a range of -20° ≤ θ21 - θ23 ≤ 20° with respect to an inclination angle (θ21) of the continuous narrow grooves (321, 331). [10] Tire (1) according to any one of claims 1 to 9, wherein the non-continuous lug grooves (323) have a wave-like shape and a wavelength (λ23) of the wave-like shape of the non-continuous lug grooves (323) is in a range of 0.70 ≤ λ23 / λ21 ≤ 1.30 with respect to a wavelength (λ21) of a wave-like shape of the continuous narrow grooves (321, 331). [11] Tire (1) according to any one of claims 1 to 10, wherein the central rib section (33) comprises a plurality of continuous narrow grooves (321, 331) extending through the central rib section (33) in the tire width direction, and the continuous narrow grooves (321, 331) of the central rib section (33) are inclined in a opposite direction in the tire circumferential direction with respect to the respective continuous narrow grooves (321, 331) of the central rib section (32).

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