Pneumatic tire

Abstract

In the pneumatic tire, a land portion (32) has a chamfer portion (321) formed at an edge portion on a tire ground end side of the land portion (32), and a transverse groove and a fine groove (323) disposed in correspondence with the chamfer portion (321). In addition, the chamfer portion (321) is formed at an edge portion on the tire ground end (T) side of the land portion (32), and widens a chamfer width (Wc) toward a tire circumferential direction on a tread surface of the land portion (32). In addition, the transverse groove terminates within the land portion (32) at one end portion, and opens at a central portion in a length direction of the chamfer portion (321) at the other end portion. In addition, the fine groove (323) opens at one end portion at an edge portion on a tire equatorial plane side of the land portion (32), and terminates at the other end portion in the vicinity of a maximum width position (3211) of the chamfer portion (321).

Description

[0001] This application is a divisional application of the Chinese Patent Application No. 201980043237.9, with the title of "Pneumatic Tire", filed on February 14, 2019. TECHNICAL FIELD

[0002] The present application relates to a pneumatic tire, and more particularly, to a pneumatic tire capable of balancing dry land handling stability and wet land handling stability. BACKGROUND

[0003] In recent years, in a pneumatic tire, there is a demand to improve the performance not only when running on a circular route, but also when running in an urban area and on an expressway. Therefore, there is a problem that the dry land performance and the wet land performance of the tire should be balanced. As a conventional pneumatic tire related to the problem, the technologies described in Patent Documents 1 and 2 are known.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent No. 4755709

[0007] Patent Document 2: Japanese Patent No. 5629283 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] An object of the present application is to provide a technology capable of balancing dry land handling stability and wet land handling stability.

[0010] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS

[0011] In order to achieve the above object, the pneumatic tire of the present application is characterized by comprising: a plurality of circumferential main grooves extending in a tire circumferential direction; and a land portion partitioned by the adjacent circumferential main grooves, wherein the land portion comprises: a chamfer portion formed at an edge portion of a tire grounding end side of the land portion; and a transverse groove and a fine groove disposed in correspondence with the chamfer portion, the chamfer portion is widened by a chamfer width in a tread surface direction of the land portion, with respect to the transverse groove, one end portion is terminated within the land portion, and the other end portion is opened at a central portion in a length direction of the chamfer portion, and with respect to the fine groove, one end portion is opened at an edge portion of a tire equatorial plane side of the land portion, and the other end portion is terminated in the vicinity of a position of maximum width of the chamfer portion or connected to the position of maximum width.

[0012] EFFECTS OF THE INVENTION

[0013] In the pneumatic tire of the present invention, the transverse grooves (Japanese: 横麝) opening in the center of the chamfered portion are wide transverse grooves, and the transverse grooves terminating or opening at the maximum width of the chamfered portion are narrow, thin grooves. This provides the following advantages: (a) Compared to a configuration in which all grooves arranged in the land portion are wide transverse grooves, the rigidity of the land portion is maintained, thereby ensuring the dry performance of the tire. Furthermore, (b) compared to a configuration in which all grooves arranged in the land portion are narrow, thin grooves or sipes, the drainage performance of the land portion 32 is improved, thereby improving the tire's wet handling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view taken along the tire meridian direction of a pneumatic tire according to an embodiment of the present invention.

[0015] Figure 2 It shows Figure 1 A plan view of the tread surface of the pneumatic tire described.

[0016] Figure 3 It shows Figure 2 An enlarged view of the second land portion and the shoulder land portion in the vehicle width direction inner region.

[0017] Figure 4 It shows Figure 3 An enlarged top view of the second land portion described.

[0018] Figure 5 It shows Figure 3 A cross-sectional view of the second land portion described.

[0019] Figure 6 It shows Figure 4 Explanatory diagram of a modified example of the transverse groove of the second land portion.

[0020] Figure 7 It shows Figure 4 Explanatory diagram of a modified example of the thin groove of the second land portion described above.

[0021] Figure 8 This is a graph showing the results of performance tests on pneumatic tires according to the embodiments of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited to this embodiment. The components of this embodiment include components that can be replaced while maintaining the identity of the invention, and where replacement is obvious. Furthermore, the various modifications described in this embodiment can be combined arbitrarily within the scope apparent to those skilled in the art.

[0023] [Pneumatic tire]

[0024] Figure 1 is a cross-sectional view of a tire meridian direction of a pneumatic tire showing an embodiment of the present application. This figure shows a cross-sectional view of a single-side region in a tire radial direction. In addition, as an example of a pneumatic tire, this figure shows a passenger car radial tire.

[0025] In this figure, the tire meridian direction cross-section refers to a cross-section when the tire is cut with a plane containing a tire rotation axis (omitted from the drawing). In addition, the reference sign CL is a tire equatorial plane, and refers to a plane passing through a center point of the tire in the tire rotation axis direction and perpendicular to the tire rotation axis. In addition, the tire width direction refers to a direction parallel to the tire rotation axis, and the tire radial direction refers to a direction perpendicular to the tire rotation axis.

[0026] In addition, the inboard and outboard in the vehicle width direction are defined as orientations with respect to the vehicle width direction when the tire is mounted to a vehicle. In addition, the regions to the left and right with the tire equatorial plane as a boundary are defined as the outboard region in the vehicle width direction and the inboard region in the vehicle width direction, respectively. In addition, the pneumatic tire is provided with a mounting direction display portion (omitted from the drawing) showing the tire mounting direction with respect to a vehicle. The mounting direction display portion is constituted by, for example, a mark or a concave-convex portion attached to a side portion of the tire. For example, ECE R30 (European Economic Commission Regulation 30) attaches an obligation that the side portion that becomes the outboard in the vehicle width direction in the vehicle mounted state should be provided with a display portion of the vehicle mounting direction.

[0027] The pneumatic tire 10 has a ring-like configuration with the tire rotation axis as the center, and is provided with 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 side rubbers 16, 16, and a pair of rim cushion rubbers 17, 17 (refer to Figure 1 ).

[0028] The pair of bead cores 11, 11 are formed by winding one or a plurality of bead wires composed of steel in a ring shape and in multiple layers, and are embedded in the bead portions to constitute the cores of the left and right bead portions. The pair of bead fillers 12, 12 are disposed at the tire radial direction outer peripheries of the pair of bead cores 11, 11 to reinforce the bead portions.

[0029] The carcass layer 13 has a single-layer structure consisting of a single carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together. It is toroidally arranged between the left and right bead cores 11, 11, forming the tire's skeleton. The two ends of the carcass layer 13 are rolled outward and secured in the tire width direction, enclosing the bead core 11 and bead filler 12. The carcass ply of the carcass layer 13 is formed by covering and calendering multiple carcass cords made of steel or an organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with a covering rubber. The carcass angle (defined as the inclination angle of the carcass cord's longitudinal direction relative to the tire's circumferential direction) is 80 degrees or more and 95 degrees or less in absolute value.

[0030] The belt layer 14 is formed by laminating a pair of cross belts 141 and 142 and a belt cover 143, and is wound around the outer circumference of the carcass layer 13. The pair of cross belts 141 and 142 are formed by covering a plurality of belt cords made of steel or organic fiber material with a rubber cover and then calendering them, resulting in a belt angle of 20 degrees or more and 55 degrees or less in absolute terms. Furthermore, the pair of cross belts 141 and 142 have belt angles (defined as the inclination angle of the belt cords' longitudinal direction relative to the tire circumferential direction) of opposite signs, and are laminated so that the belt cords' longitudinal directions intersect with each other (a so-called cross-ply structure). The belt cover 143 is formed by covering the belt cover cords made of steel or organic fiber material with a rubber cover, resulting in a belt angle of 0 degrees or more and 10 degrees or less in absolute terms. The belt cover 143 is, for example, a belt material formed by covering one or more belt cover cords with a covering rubber, and can be constructed by spirally winding the belt material multiple times in the tire circumferential direction around the outer peripheral surfaces of the cross belts 141 and 142 .

[0031] Tread rubber 15 is disposed on the tire radially outer periphery of carcass layer 13 and belt layer 14 to form the tire's tread portion. A pair of sidewall rubbers 16, 16 are disposed on the tire widthwise outer side of carcass layer 13 to form the left and right sidewall portions. A pair of rim cushion rubbers 17, 17 are disposed on the tire radially inner side of the left and right bead cores 11, 11 and the turned-up portion of carcass layer 13 to form the rim-engaging surface of the bead portion.

[0032] [Tread pattern]

[0033] Figure 2 It shows Figure 1 A top view of the tread surface of a pneumatic tire. This figure shows the tread pattern of an all-weather tire. In this figure, the tire circumferential direction refers to the direction around the tire's axis of rotation. The reference symbol T represents the tire's contact patch, and the dimension symbol TW represents the tire's contact patch width.

[0034] like Figure 2 As shown, the pneumatic tire 10 includes, on the tread surface, a plurality of circumferential main grooves 21 to 23 and a circumferential narrow groove 24 extending in the tire circumferential direction, and a plurality of land portions 31 to 35 defined by these circumferential grooves 21 to 24 .

[0035] Main grooves are grooves that display wear indicators as specified by JATMA and generally have a groove width of 3.0 mm or greater and a groove depth of 6.0 mm or greater. Transverse grooves, described later, extend transversely across the tire width and function as grooves when the tire is in contact with the ground. Sipes, described later, are cuts formed in the tread surface and are distinguished from transverse grooves in that they remain closed when the tire is in contact with the ground.

[0036] The groove width is measured as the maximum value of the distance between the left and right groove walls at the groove opening, in the unloaded state, with the tire mounted on a specified rim and filled to a specified internal pressure. For tires with notches and / or chamfers at the edges of the land portions, the groove width is measured at the intersection of the tread surface and the extended lines of the groove walls, viewed in a cross-section with the groove length as the normal. For tires with grooves extending in a zigzag or wavy pattern along the tire circumference, the groove width is measured at the centerline of the groove wall's amplitude.

[0037] Groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom in an unloaded state, with the tire mounted on a specified rim and filled to a specified internal pressure. If the groove has localized concave and convex portions and / or sipes on the groove bottom, these are excluded from the measurement.

[0038] The "specified rim" refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. Furthermore, the "specified internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. Furthermore, the "specified load" (Japanese: Specified Load) refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, in the case of tires for passenger cars, the prescribed internal pressure is an air pressure of 180 [kPa], and the prescribed load is 88 [%] of the maximum load capacity.

[0039] For example, in Figure 2 In this structure, the pneumatic tire 10 has a bilaterally asymmetric tread pattern centered on the tire equatorial plane CL. Furthermore, the vehicle widthwise inner region, bounded by the tire equatorial plane CL, comprises two circumferential main grooves 21 and 22, while the vehicle widthwise outer region comprises one circumferential main groove 23 and one circumferential narrow groove 24. Furthermore, these circumferential grooves 21, 22; 23, 24 are arranged bilaterally symmetrically about the tire equatorial plane CL. Furthermore, these circumferential grooves 21-24 define five rows of land portions 31-35. Furthermore, one land portion 33 is located on the tire equatorial plane CL.

[0040] Furthermore, the land portions 31 and 35 on the outer side in the tire width direction, defined by the outermost circumferential main groove 21 in the vehicle width direction inner region or the circumferential narrow groove 24 in the vehicle width direction outer region, are defined as shoulder land portions. The shoulder land portions 31 and 35 are the outermost land portions in the tire width direction and are located at the tire contact edge T. Furthermore, the land portions 32 and 34 on the inner side in the tire width direction, defined by the outermost circumferential main groove 21 or the circumferential narrow groove 24, are defined as second land portions. Therefore, the second land portions 32 and 34 are adjacent to the shoulder land portions 31 and 35 across the outermost circumferential main groove 21 and 24. Furthermore, the land portion 33 located closer to the tire equatorial plane CL than the second land portions 32 and 34 is defined as a center land portion.

[0041] [Inner area in vehicle width direction]

[0042] Figure 3 It shows Figure 2 An enlarged view of the second land portion and the shoulder land portion in the vehicle width direction inner region.

[0043] exist Figure 2 In the structure, the vehicle width direction inner side area bounded by the tire equatorial plane CL includes two circumferential main grooves 21 and 22, and the shoulder land portion 31, the second land portion 32 and the center land portion 33 defined by these circumferential main grooves 21 and 22.

[0044] The two circumferential main grooves 21 and 22 have a straight shape with a constant groove width. Furthermore, the distance Dm from the tire equatorial plane CL to the groove centerline of the outermost circumferential main groove 21 is within a range of 8% to 12% relative to the tire contact patch width TW. Furthermore, the distance Dn from the tire equatorial plane CL to the groove centerline of the other circumferential main groove 22 is within a range of 26% to 32% relative to the tire contact patch width TW.

[0045] The groove centerline of the circumferential main groove is defined as a straight line that passes through the midpoint of the left and right measurement points of the groove width of the circumferential main groove and is parallel to the tire circumferential direction.

[0046] The tire contact patch width TW is measured as the maximum linear distance in the tire axial direction at the contact surface between the tire and the flat plate when the tire is mounted on a predetermined rim, a predetermined internal pressure is applied, the tire is placed vertically relative to the flat plate in a stationary state, and a load corresponding to a predetermined load is applied.

[0047] The tire ground contact edge T is defined as the maximum axial width position of the tire in the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, a specified internal pressure is applied, and the tire is placed vertically relative to the flat plate in a stationary state and a load corresponding to a specified load is applied.

[0048] The circumferential main grooves 21 and 22 have a groove width in the range of 5.0 mm to 25.0 mm, and a groove depth in the range of 5.0 mm to 12.0 mm (dimension symbols are omitted in the drawings).

[0049] [Inner shoulder land portion]

[0050] like Figure 3 As shown, the shoulder land portion 31 includes a transverse groove 311 and a narrow groove 312. The transverse groove 311 and the narrow groove 312 terminate within the shoulder land portion 31 at one end, without penetrating the entire portion. They extend in the tire width direction and intersect with the tire contact patch T. Consequently, the outermost circumferential edge of the shoulder land portion 31, on the main groove 21 side, has a planar structure without groove or sipe openings and extends continuously in the tire circumferential direction. This improves the tire's noise performance.

[0051] The distance D11 between the transverse grooves 311 and the narrow grooves 312 and the edge of the shoulder land portion 31 preferably satisfies the relationship of 0.10≤D11 / Wb1≤0.40, and more preferably satisfies the relationship of 0.15≤D11 / Wb1≤0.25, relative to the contact patch width Wb1 of the shoulder land portion 31 .

[0052] The ground contact width of the land portion is measured as the maximum straight-line distance in the tire axial direction in the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, a specified internal pressure is applied, and the tire is placed vertically relative to the flat plate in a stationary state and a load corresponding to a specified load is applied.

[0053] Furthermore, the contact patch width Wb1 of the shoulder land portion 31 preferably satisfies the relationship of 0≤Wb1 / TW≤0.30 with respect to the tire contact patch width TW.

[0054] In addition, Figure 3 In the configuration, the transverse grooves 311 and the narrow grooves 312 have gently curved arc shapes along the tire circumferential direction. However, this is not limiting; the transverse grooves 311 and the narrow grooves 312 may also have straight lines extending substantially parallel to the tire width direction (illustration omitted). Furthermore, the plurality of transverse grooves 311 and the narrow grooves 312 are alternately arranged at predetermined intervals along the tire circumferential direction. However, this is not limiting; the plurality of narrow grooves 312 may also be arranged between adjacent transverse grooves 311, 311 (illustration omitted).

[0055] [Second inner land portion]

[0056] Figure 4 and Figure 5 It shows Figure 3 An enlarged top view of the second land portion ( Figure 4 ) and sectional view ( Figure 5 ).

[0057] like Figure 3 As shown, the second land portion 32 includes a chamfered portion 321 and a transverse groove 322 and a narrow groove 323 (first and second transverse grooves) having different groove widths.

[0058] The chamfered portion 321 is formed on the edge of the second land portion 32 on the tire ground contact end T side (i.e., on the outermost circumferential main groove 21 side), connecting the tread of the second land portion 32 to the groove wall surface of the outermost circumferential main groove 21 with a flat surface or a curved surface. In addition, the chamfered portion 321 has a chamfer width Wc that widens toward the tire circumferential direction on the tread of the second land portion 32 (see Figure 4 ) shape. In addition, a plurality of chamfered portions 321 are arranged at predetermined intervals in the tire circumferential direction. By increasing the groove volume of the outermost circumferential main groove 21 through these chamfered portions 321, the wet performance of the tire is improved.

[0059] The maximum width Wc of the chamfered portion 321 preferably satisfies the relationship of 0.05≤Wc / Wb2≤0.30 with respect to the maximum width Wb2 of the second land portion 32 , and more preferably satisfies the relationship of 0.15≤Wc / Wb2≤0.25.

[0060] The width of the chamfered portion is measured as the distance in the tire width direction from the edge of the land portion to the ridgeline of the chamfered portion on the tread of the land portion. The edge of the land portion is defined as the intersection of the extended line of the groove wall of the circumferential main groove and the tread of the land portion. The ridgeline of the chamfered portion is defined as the boundary between the wall surface of the chamfered portion and the tread of the land portion.

[0061] Furthermore, the contact patch width Wb2 of the second land portion 34 relative to the contact patch width Wb1 of the shoulder land portion 35 preferably satisfies the relationship of 0.70 ≤ Wb2 / Wb1 ≤ 1.20, and more preferably satisfies the relationship of 0.90 ≤ Wb2 / Wb1 ≤ 1.00. This optimizes the contact patch widths Wb1 and Wb2 of the left and right land portions 31 and 32 defined by the circumferential main grooves 21 and 22.

[0062] In addition, Figure 4 The maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 is relative to the pitch length Pc of the chamfered portion 321 (see Figure 3 ) preferably has a relationship of 0.60 ≤ Lc / Pc ≤ 1.00, and more preferably has a relationship of 0.80 ≤ Lc / Pc ≤ 0.95. This ensures that the widened area of ​​the chamfer width Wc is appropriately ensured. Furthermore, chamfered portions 321, 321 adjacent to each other in the tire circumferential direction may be connected or separated, provided that the aforementioned Lc / Pc ratio is satisfied.

[0063] In addition, Figure 5 The maximum depth Hc of the chamfered portion 321 preferably satisfies the relationship of 0.20≤Hc / Hg1≤0.70 with respect to the maximum depth Hg1 of the circumferential main groove 21 , and more preferably satisfies the relationship of 0.30≤Hc / Hg1≤0.50.

[0064] For example, in Figure 4 and Figure 5 In the structure, the chamfered portion 321 has a triangular pyramid shape with the minimum width position 3212 as the vertex. Figure 4 As shown, the chamfered portion 321 has a triangular shape formed by connecting a long portion (Japanese: long-length portion) (a portion consisting of reference numerals 3213 and 3214) and a short portion (Japanese: short-length portion) (reference numerals omitted in the figure) on the tread surface of the second land portion 32, and the chamfered width of the chamfered portion 321 gradually increases toward one direction of the tire circumferential direction in the long portion. Figure 5As shown, the chamfered portion 321 is a C-chamfer, connecting the tread of the second land portion 32 to the groove wall of the outermost circumferential main groove 21 with a flat surface. However, this is not limiting; the chamfered portion 321 may also be an R-chamfer, connecting the tread of the second land portion 32 to the groove wall of the outermost circumferential main groove 21 with a curved surface. Furthermore, adjacent chamfered portions 321 are arranged continuously without any gaps between them. As a result, the ridgeline of the chamfered portion 321 has a zigzag shape extending along the edge of the second land portion 32 in the tire circumferential direction.

[0065] The transverse groove 322 is a first transverse groove configured corresponding to the chamfered portion 321. Figure 3 As shown, one end portion terminates in the second land portion 32 , and the other end portion opens at the center portion in the longitudinal direction of the chamfered portion 231 and communicates with the outermost circumferential main groove 21 .

[0066] In addition, Figure 4 The tire widthwise extension length D22 of the transverse groove 322 preferably satisfies the relationship of 0.20 ≤ D22 / Wb2 ≤ 0.80, and more preferably 0.40 ≤ D22 / Wb2 ≤ 0.60, relative to the maximum width Wb2 of the second land portion 32. Therefore, the transverse groove 322 preferably terminates substantially in the center of the second land portion 32.

[0067] The extending length of the transverse groove is measured as the distance in the tire width direction from the edge of the land portion on the circumferential main groove side to the terminal end of the transverse groove.

[0068] Furthermore, the maximum groove width W22 of the transverse groove 322 preferably satisfies the relationship of 0.03 ≤ W22 / Lc ≤ 0.10, and more preferably 0.04 ≤ W22 / Lc ≤ 0.07, relative to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321. Furthermore, the maximum groove width W22 of the transverse groove 322 preferably falls within the range of 2.5 mm ≤ W22 ≤ 6.5 mm.

[0069] The maximum groove width of the transverse groove is measured as the maximum width of the transverse groove in the tread surface of the land portion. When the transverse groove is a chamfered sipe as described below, the maximum groove width is measured as the maximum width including the chamfered portion.

[0070] Furthermore, the inclination angle θ22 of the transverse groove 322 with respect to the tire circumferential direction is preferably in the range of 30 [deg] ≤ θ22 ≤ 85 [deg], and more preferably in the range of 50 [deg] ≤ θ22 ≤ 70 [deg].

[0071] The inclination angle of the transverse groove is measured as an angle formed by an imaginary line connecting both ends of the transverse groove and the tire circumferential direction.

[0072] Furthermore, the distance L22 in the tire circumferential direction from the maximum width position 3211 of the chamfered portion 321 to the opening position of the transverse groove 322 relative to the chamfered portion 321 preferably has a relationship of 0.35 ≤ L22 / Lc ≤ 0.65, and more preferably has a relationship of 0.40 ≤ L22 / Lc ≤ 0.60, relative to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321. Therefore, the transverse groove 322 opens at the center portion in the longitudinal direction of the chamfered portion 321.

[0073] In addition, Figure 5 In the embodiment, the maximum groove depth H22 of the transverse groove 322 preferably satisfies the relationship of 0.40≤H22 / Hg1≤0.85 with respect to the maximum depth Hg1 of the circumferential main groove 21, and more preferably satisfies the relationship of 0.50≤H22 / Hg1≤0.75. Figure 5 As shown, the maximum groove depth H22 of the transverse groove 322 is set to be larger than the maximum depth Hc of the chamfered portion 321 .

[0074] For example, in Figure 4 and Figure 5 In this configuration, the transverse groove 322 has a short straight line or gently arcuate shape and opens at the center of the long portion 3213 of the chamfered portion 321. Furthermore, the number of transverse grooves 322 is the same as the number of chamfered portions 321, with a single transverse groove 322 opening into one chamfered portion 321. Thus, the long portion 3213 of the chamfered portion 321 is divided and separated in the tire circumferential direction by the transverse groove 322. Furthermore, the inclination angle φ1 of the transverse groove 322 relative to the ridgeline of the long portion 3213 of the chamfered portion 321 is within the range of 35 degrees ≤ φ1 ≤ 80 degrees.

[0075] The narrow groove 323 is a second transverse groove arranged corresponding to the chamfered portion 321. One end portion of the narrow groove 323 opens at the edge portion of the second land portion 32 on the tire equatorial plane CL side, and the other end portion terminates near the maximum width position 3211 of the chamfered portion 321. As described later, the narrow groove 323 may be connected to the maximum width position 3211 of the chamfered portion 321 at the other end portion.

[0076] In addition, Figure 4 The maximum groove width W23 of the narrow groove 323 preferably satisfies the relationship 0<W23 / W22≤0.80, and more preferably 0<W23 / W22≤0.50, relative to the maximum groove width W22 of the transverse groove 322. Therefore, the groove width of the narrow groove 323 is set sufficiently narrow relative to the groove width of the transverse groove 322.

[0077] The maximum groove width W23 of the narrow groove 323 is preferably in the range of 0.4 mm ≤ W23 ≤ 1.5 mm, more preferably in the range of 0.5 mm ≤ W23 ≤ 1.0 mm. Furthermore, the narrow groove 323 is preferably a sipe that is closed when the tire contacts the ground.

[0078] Furthermore, the inclination angle θ23 of the narrow groove 323 with respect to the tire circumferential direction is preferably in the range of 30 [deg] ≤ θ23 ≤ 85 [deg], and more preferably in the range of 50 [deg] ≤ θ23 ≤ 70 [deg].

[0079] The maximum groove depth H23 of the narrow groove 323 preferably satisfies the relationship 0.20 ≤ H23 / Hg1 ≤ 0.70, and more preferably 0.40 ≤ H23 / Hg1 ≤ 0.60, relative to the maximum depth Hg1 of the circumferential main groove 21. Furthermore, the maximum groove depth H23 of the narrow groove 323 is set smaller than the maximum groove depth H22 of the transverse groove 322.

[0080] For example, in Figure 4 and Figure 5 In this structure, the thin groove 323 has a short straight line shape or a gently arcuate shape. Furthermore, the number of thin grooves 323 is the same as the number of chamfered portions 321, with each thin groove 323 positioned opposite one chamfered portion 321. Furthermore, the inclination angle φ2 of the thin groove 323 relative to the ridgeline of the long portion 3213 of the chamfered portion 321 is within the range of 35 degrees ≤ φ2 ≤ 80 degrees.

[0081] In addition, if Figure 4 As shown, the groove 323 terminates near the maximum width position 3211 of the chamfered portion 321. Furthermore, the distance Gs between the terminal end of the groove 323 and the maximum width position 3211 of the chamfered portion 321 is within the range of Gs ≤ 1.5 [mm]. This structure is preferred for reducing vulcanization failures caused by air accumulation because it allows a small gap to be formed between the forming blades of the groove 323 and the forming blades of the chamfered portion 321 in a tire forming mold (not shown) during tire vulcanization. The lower limit of the distance Gs is not particularly limited, but if it is 0.3 [mm] or greater, the air flow path is ensured, thereby ensuring the aforementioned effect of reducing vulcanization failures.

[0082] In addition, if Figure 4 As shown, only the narrow grooves 323 open at the edge of the second land portion 32 on the tire equatorial plane CL side, while the other wide transverse grooves do not open at the edge of the second land portion 32 on the tire equatorial plane CL side. This ensures the rigidity of the edge of the second land portion 32 on the tire equatorial plane CL side, improving the tire's dry performance.

[0083] [Modification]

[0084] Figure 6 It shows Figure 4 This figure shows a cross-sectional view of a transverse groove 322 in the groove depth direction.

[0085] exist Figure 4 In the structure, the transverse groove 322 has a U-shaped cross-section (omitted from the figure), and has a substantially constant groove width from the initial to the middle stage of wear. However, this is not limited to this, and the transverse groove 322 may also be Figure 6 That is, the transverse groove 322 may be composed of a narrow sipe portion 3221 that is closed when the tire contacts the ground, and a chamfered portion 3212 formed at the opening of the sipe portion 3221 and extending the groove width W22.

[0086] Figure 7 It shows Figure 4 This figure illustrates a modified example of the thin groove of the second land portion. This figure shows the positional relationship between the other end of the thin groove 323 and the maximum width position 3211 of the chamfered portion 321.

[0087] exist Figure 4 In the structure, as described above, the thin groove 323 is not connected to the chamfered portion 321 but terminates inside the second land portion 32. In addition, the gap (distance Gs) between the terminal end of the thin groove 323 and the maximum width position 3211 of the chamfered portion 321 is appropriately ensured. However, this is not limited to this. Figure 7 As shown, the thin groove 323 may be connected to the maximum width position 3211 of the chamfered portion 321. Furthermore, if the connection point between the thin groove 323 and the chamfered portion 321 is within a distance of 2.5 mm from the maximum width position 3211 of the chamfered portion 321, the thin groove 323 can be said to be connected to the maximum width position 3211 of the chamfered portion 321.

[0088] [Additional matters]

[0089] like Figure 3 As shown, the chamfered portion 321 and the transverse groove 322 of the second land portion 32 are arranged at substantially the same position in the tire circumferential direction relative to the transverse groove 311 of the shoulder land portion 31. Specifically, the entire transverse groove 311 of the shoulder land portion 31 in the tire contact patch is within the circumferential length Lc of the long portion 3213 of the chamfered portion 321 of the second land portion 32 (see FIG. Figure 4 ) range. As a result, the drainage performance of the tire is improved.

[0090] In addition, if Figure 3As shown, the groove centerlines of the transverse grooves 322 of the second land portion 32 and the groove centerlines of the transverse grooves 311 of the shoulder land portion 31 are inclined in the same direction and are staggered relative to each other in the tire circumferential direction. Specifically, when defining the intersection points P1 and P2 of the groove centerlines of the transverse grooves 311 and 322 with the groove centerline of the outermost circumferential main groove 21, respectively, the distance Dp in the tire circumferential direction between these intersection points P1 and P2 relative to the pitch length Pc of the chamfered portion 321 of the second land portion 32 is preferably within the range of 0 ≤ Dp / Pc ≤ 0.50, and more preferably within the range of 0.10 ≤ Dp / Pc ≤ 0.40. Furthermore, the pitch number of the transverse grooves 311 of the shoulder land portion 31 and the pitch number of the transverse grooves 322 of the second land portion 32 are the same, ranging from 20 to 80.

[0091] [Effect]

[0092] As described above, the pneumatic tire 10 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, and land portions 32 defined by adjacent circumferential main grooves 21 and 22 (see FIG. Figure 3 ). In addition, the land portion 32 includes a chamfered portion 321 formed at the edge portion of the tire ground contact end side of the land portion 32, and a transverse groove 322 and a fine groove 323 arranged corresponding to the chamfered portion 321 (see Figure 4 ). In addition, the chamfered portion 321 is formed at the edge portion of the land portion 32 on the tire ground contact end T side, and the chamfer width Wc is widened toward the tire circumferential direction on the tread of the land portion 32. In addition, the transverse groove 322 ends at one end in the land portion 32, and opens at the center portion in the longitudinal direction of the chamfered portion 321 at the other end. In addition, the fine groove 323 opens at one end at the edge portion of the land portion 32 on the tire equatorial plane CL side, and ends at the other end near the maximum width position 3211 of the chamfered portion 321 (refer to Figure 4 ), or connected to the maximum width position 3211 (refer to Figure 7 ).

[0093] In this structure, (1) the land portion 32 includes a chamfered portion 321 and a transverse groove 322 formed at the edge portion on the tire ground contact end T side, thereby improving the drainage performance of the land portion 32 and improving the wet handling stability of the tire. In addition, (2) the transverse groove 322 does not penetrate the land portion 32, thereby ensuring the rigidity of the land portion 32 and ensuring the dry handling stability of the tire. In addition, (3) the transverse groove 322 opens at the center portion in the longitudinal direction of the chamfered portion 321, thereby improving the drainage performance of the land portion 32 and improving the wet handling stability of the tire.

[0094] Further, (4) the lateral groove opened at the center of the chamfer portion 321 is a wide-width lateral groove 322, and the lateral groove terminated or opened at the maximum width position 3211 of the chamfer portion 321 is a narrow-width fine groove 323, and thus has the following advantages. That is, (a) compared with a structure in which all the grooves provided in the land portion 32 are wide-width lateral grooves (omitted illustration), the rigidity of the land portion 32 is ensured, and the dry performance of the tire is ensured. Further, (b) compared with a structure in which all the grooves provided in the land portion 32 are narrow-width fine grooves or sipes (omitted illustration), the drainability of the land portion 32 is improved, and the wet handling stability performance of the tire is improved. Further, (c) compared with a structure in which the wide-width lateral groove is opened at the maximum width position of the chamfer portion, and the narrow-width fine groove or sipe is terminated or opened at the center of the chamfer portion (omitted illustration), the drainability from the lateral groove 322 to the chamfer portion 321 is ensured, and the rigidity of the land portion 32 at the maximum width position 3211 of the chamfer portion 321 is ensured, and thus has the advantage that the dry handling stability performance and the wet handling stability performance of the tire can be balanced.

[0095] Further, in the pneumatic tire 10, the maximum width Wc of the chamfer portion 321 has a relationship of 0.05 ≤ Wc / Wb2 ≤ 0.30 with respect to the maximum width Wb2 of the land portion 32 (refer to Figure 4 ). There is the advantage that, by the lower limit, the improvement effect of the drainability based on the chamfer portion 321 is ensured, and by the upper limit, the rigidity of the land portion 32 is ensured.

[0096] Further, in the pneumatic tire 10, the maximum length Lc in the tire circumferential direction (refer to Figure 4 ) from the maximum width position 3211 to the minimum width position 3212 of the chamfer portion 321 has a relationship of 0.60 ≤ Lc / Pc ≤ 1.00 with respect to the pitch length Pc (refer to Figure 3 ) of the chamfer portion 321. There is the advantage that, by the lower limit, the improvement effect of the drainability based on the chamfer portion 321 is ensured, and by the upper limit, the planar shape of the chamfer portion 321 is appropriately adapted.

[0097] Further, in the pneumatic tire 10, the chamfer portion 321 has a triangular shape (refer to Figure 3 ) in which a long dimension portion and a short dimension portion are connected on the tread surface of the land portion 32. Thus, there is the advantage that the drainability based on the chamfer portion 321 is improved.

[0098] Further, in the pneumatic tire 10, the extension length D22 in the tire width direction of the lateral groove 322 has a relationship of 0.20 ≤ D22 / Wb2 ≤ 0.80 with respect to the maximum width Wb2 of the land portion 32 (refer to Figure 4). This has the following advantages: by setting the lower limit, the drainage improvement effect of the transverse grooves 322 can be ensured, and by setting the upper limit, the rigidity of the land portion 32 can be ensured.

[0099] In the pneumatic tire 10, the maximum groove width W22 of the transverse groove 322 has a relationship of 0.03≤W22 / Lc≤0.10 with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 (see FIG. Figure 4 ). This has the following advantages: by setting the lower limit, the drainage improvement effect of the transverse grooves 322 can be ensured, and by setting the upper limit, the rigidity of the land portion 32 can be ensured.

[0100] In the pneumatic tire 10, the inclination angle θ22 of the transverse groove 322 relative to the tire circumferential direction is in the range of 30 [deg] ≤ θ22 ≤ 85 [deg] (see Figure 4 ). This has the advantage of making the inclination angle θ22 of the transverse groove 322 appropriate.

[0101] In the pneumatic tire 10, the distance L22 in the tire circumferential direction from the maximum width position 3211 of the chamfered portion 321 to the opening position of the transverse groove 322 relative to the chamfered portion 321 has a relationship of 0.35≤L22 / Lc≤0.65 with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 (see FIG. Figure 4 In this structure, since the transverse groove 322 opens at the center portion in the longitudinal direction of the chamfered portion 321, there is an advantage that the drainage effect based on the combination of the transverse groove 322 and the chamfered portion 321 is further improved.

[0102] In the pneumatic tire 10, the inclination angle θ23 of the narrow groove 323 relative to the tire circumferential direction is in the range of 30 [deg] ≤ θ23 ≤ 85 [deg] (see Figure 4 ). This has the advantage of making the inclination angle θ23 of the narrow groove 323 appropriate.

[0103] Furthermore, in the pneumatic tire 10, the maximum groove width W23 of the narrow grooves 323 is related to the maximum groove width W22 of the transverse grooves 322 by the relationship 0<W23 / W22≤0.80. This configuration optimizes the groove width ratio between the transverse grooves 322 and the narrow grooves 323, thereby achieving an optimal balance between the drainage enhancement effect of the transverse grooves 322 and the land portion rigidity reinforcement effect of the narrow grooves 323.

[0104] In the pneumatic tire 10, the maximum groove width W22 of the transverse groove 322 is within the range of 2.5 [mm] ≤ W22 ≤ 6.5 [mm] (see Figure 4). This has the following advantages: by setting the lower limit, the drainage improvement effect of the transverse grooves 322 can be ensured, and by setting the upper limit, the rigidity of the land portion 32 can be ensured.

[0105] In the pneumatic tire 10, the maximum groove width W23 of the narrow groove 323 is within the range of 0.4 [mm] ≤ W23 ≤ 1.5 [mm] (see Figure 4 ). This has the following advantages: by setting the lower limit, the drainage improvement effect of the fine groove 323 is ensured, and by setting the upper limit, the rigidity of the land portion 32 is ensured.

[0106] In the pneumatic tire 10, the distance Gs (see FIG. 1 ) between the other end of the narrow groove 323 and the maximum width position 3211 of the chamfered portion 321 is Figure 4 and Figure 7 ) is in the range of Gs≤1.0 [mm]. As a result, the extension length of the fine groove 323 is ensured, and the effect of improving the drainage performance by the fine groove 323 is ensured.

[0107] In the pneumatic tire 10, the other end of the narrow groove 323 is arranged to be separated from the maximum width position 3211 of the chamfered portion 321 (see FIG. Figure 4 In this structure, during tire vulcanization forming, a small gap can be formed between the forming blade of the fine groove 323 and the forming blade of the chamfered portion 321 in the tire forming mold (not shown), thereby having the advantage of being able to reduce vulcanization failures caused by air accumulation.

[0108] In the pneumatic tire 10, only the narrow groove 323 opens at the edge portion of the land portion 32 on the tire equatorial plane CL side, and other wide transverse grooves (for example, the transverse groove 322) do not open at the edge portion of the land portion 32 on the tire equatorial plane CL side (see FIG. Figure 4 ) This has the advantage that the rigidity of the edge portion of the land portion 32 on the tire equatorial plane CL side is ensured, and the dry performance of the tire is improved.

[0109] Example

[0110] Figure 8 This is a graph showing the results of performance tests on pneumatic tires according to the embodiments of the present invention.

[0111] In this performance test, various test tires were evaluated for (1) dry handling stability and (2) wet handling stability. Test tires with a tire size of 245 / 40R1897Y were mounted on rims with a rim size of 18×8.5J, and the JATMA specified internal pressure and load were applied to the test tires. Furthermore, the test tires were mounted on all wheels of a passenger car used as the test vehicle.

[0112] (1) In the evaluation relating to the dry land maneuvering stability performance, the test vehicle was driven on a test course of a dry road surface having a flat circular road at 60 [km / h] to 100 [km / h]. Then, the test driver made a sensory evaluation with respect to the steering performance at the time of lane change and at the time of turning, and the stability at the time of straight running. The evaluation was made by an index evaluation with the past example 2 as a reference (100), and the larger the value, the more preferable. In addition, if the evaluation was 98 or more, it can be said that the dry land performance was maintained.

[0113] (2) In the evaluation relating to the wet land maneuvering stability performance, the test vehicle was driven on a predetermined test course under rain conditions, and the one lap time was measured. Then, an index evaluation was made based on the measurement result. The evaluation was made by an index evaluation with the past example 2 as a reference (100), and the larger the value, the more preferable.

[0114] The test tire of Examples 1 to 14 has a structure of Figures 1-3 , and has two circumferential main grooves 21, 22 and a shoulder land portion 31 and a second land portion 32 in the inner side region in the tire width direction with the tire equatorial plane CL as a boundary. In addition, the second land portion 32 has a chamfer portion 321 and first and second transverse grooves (a wide non-penetrating transverse groove 322 and a narrow fine groove 323) disposed in correspondence with the chamfer portion 321. In addition, in Figure 2 , the tire width TW is 200 [mm], the distance Dm of the circumferential main groove 21 on the tire ground contact end T side is 60.0 [mm], and the distance Dn of the circumferential main groove 22 on the tire equatorial plane CL side is 25.0 [mm]. In addition, the groove width of the circumferential main grooves 21, 22 is 15.0 [mm], the width Wb1 of the shoulder land portion 31 is 36.0 [mm], and the width Wb2 of the second land portion 32 is 27.0 [mm]. In addition, the pitch length Pc of the chamfer portions 321 is 73 [mm], and the number of pitches is 30. In addition, the distance Ga of the chamfer portion 321 from the terminal end portion of the fine groove 323 is 0 [mm] (see Figure 7 ).

[0115] The test tires of the past examples 1, 2, and the comparative example differ from the test tire of Example 1 in the structure of the inner side region in the tire width direction. Specifically, the past example 1 does not have the first transverse groove (transverse groove 322) opening at the central portion of the chamfer portion 321 in the test tire of Example 1, and has a wide penetrating transverse groove instead of the second transverse groove (narrow fine groove 323) opening at the maximum width position 3211 of the chamfer portion 321. The past example 2 does not have the first transverse groove (transverse groove 322) opening at the central portion of the chamfer portion 321 in the test tire of Example 1, and has only the second transverse groove (narrow fine groove 323) opening at the maximum width position 3211 of the chamfer portion 321.

[0116] As shown in the test results, it is understood that the dry handling stability performance and wet handling stability performance of the tires of Examples 1 to 14 are improved.

[0117] Description of Reference Numerals

[0118] 10 pneumatic tire; 11 bead core; 12 bead filler; 13 carcass layer; 14 belt layer; 141, 142 cross belts; 143 belt cover; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 21-23 circumferential main grooves; 24 circumferential fine grooves; 31 shoulder land portion in the inner area; 311 transverse grooves; 312 fine grooves; 32 second land portion in the inner area; 321 chamfered portion; 3211 maximum width position; 3212 minimum width position; 3213 long dimension portion; 322 transverse grooves; 3221 sipe portion; 3222 chamfered portion; 323 fine grooves.

Claims

1. A pneumatic tire comprising: a plurality of circumferential main grooves extending in the tire circumferential direction; and shoulder land portions and second land portions, the land portions being defined by adjacent circumferential main grooves, wherein: The second land portion includes: a chamfered portion formed at an edge portion of the second land portion on the tire ground contact end side; and a transverse groove and a narrow groove arranged corresponding to the chamfered portion. The chamfered portion has a wider chamfer width in the tire circumferential direction on the tread surface of the second land portion. The transverse groove terminates in the second land portion at one end and opens at the center of the chamfered portion in the longitudinal direction at the other end. The narrow groove opens at one end portion toward the edge portion of the second land portion on the tire equatorial plane side, and terminates at the other end portion near the maximum width position of the chamfered portion or connects to the maximum width position. The contact patch width Wb2 of the second land portion and the contact patch width Wb1 of the shoulder land portion have a relationship of 0.70≤Wb2 / Wb1≤1.

20. The shoulder land portion includes a transverse groove having a groove centerline inclined in the same direction as a groove centerline of the transverse groove of the second land portion. Intersection points P1 and P2 of the groove centerline of the transverse groove of the shoulder land portion and the groove centerline of the transverse groove of the second land portion with the groove centerline of the circumferential main groove dividing the shoulder land portion and the second land portion are defined respectively, and The distance Dp in the tire circumferential direction between the intersection points P1 and P2 relative to the pitch length Pc of the chamfered portion of the second land portion is in the range of 0.10≤Dp / Pc≤0.

40. The maximum groove width W22 of the transverse groove is in the range of 2.5 mm ≤ W22 ≤ 6.5 mm.

2. The pneumatic tire according to claim 1, wherein: The maximum width Wc of the chamfered portion and the maximum width Wb2 of the second land portion have a relationship of 0.05≤Wc / Wb2≤0.

30.

3. The pneumatic tire according to claim 1 or 2, wherein: A maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion relative to a pitch length Pc of the chamfered portion satisfies a relationship of 0.60≤Lc / Pc≤1.

00.

4. The pneumatic tire according to any one of claims 1 to 3, wherein: The chamfered portion has a triangular shape connecting a long portion and a short portion on a tread surface of the second land portion.

5. The pneumatic tire according to claim 1, wherein: An extension length D22 of the transverse groove in the tire width direction has a relationship of 0.20≤D22 / Wb2≤0.80 with respect to the maximum width Wb2 of the second land portion.

6. The pneumatic tire according to any one of claims 1 to 5, characterized in that: The maximum groove width W22 of the transverse groove and the maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion satisfy the relationship of 0.03≤W22 / Lc≤0.

10.

7. The pneumatic tire according to any one of claims 1 to 6, wherein: The inclination angle θ22 of the transverse groove with respect to the tire circumferential direction is in the range of 30 degrees ≤ θ22 ≤ 85 degrees.

8. The pneumatic tire according to any one of claims 1 to 7, wherein: A distance L22 in the tire circumferential direction from the maximum width position of the chamfered portion to the opening position of the transverse groove relative to the chamfered portion has a relationship of 0.35≤L22 / Lc≤0.65 with respect to a maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion.

9. The pneumatic tire according to any one of claims 1 to 8, characterized in that An inclination angle θ23 of the narrow groove relative to the tire circumferential direction is in the range of 30 degrees ≤ θ23 ≤ 85 degrees.

10. The pneumatic tire according to any one of claims 1 to 9, wherein: The maximum groove width W23 of the narrow groove and the maximum groove width W22 of the transverse groove have a relationship of 0<W23 / W22≤0.

80.

11. The pneumatic tire according to any one of claims 1 to 10, wherein: The maximum groove width W23 of the thin groove is in the range of 0.4 mm ≤ W23 ≤ 1.5 mm.

12. The pneumatic tire according to any one of claims 1 to 11, characterized in that: A distance Gs between the other end of the narrow groove and the maximum width position of the chamfered portion is in a range of Gs≦1.0 mm.

13. The pneumatic tire according to claim 12, wherein: The other end portion of the narrow groove is arranged to be spaced apart from a maximum width position of the chamfered portion.

14. The pneumatic tire according to any one of claims 1 to 13, wherein: Only the narrow groove opens at the edge portion of the second land portion on the tire equatorial plane side, and the other wide transverse grooves do not open at the edge portion of the land portion on the tire equatorial plane side.

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