阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 原田俊也 于 2020-04-06 设计创作，主要内容包括：在该充气轮胎(1)中,多个第一陆部(3A)在轮胎周向上相邻地排列,多个第二陆部(3B)在轮胎周向上相邻地排列。另外,第一陆部(3A)及第二陆部(3B)沿着轮胎赤道面(CL)呈交错状排列。另外,第一陆部(3A)及第二陆部(3B)各自具备贯通陆部(3A、3B)并向所述一对倾斜主槽开口的多个贯通槽(41、42)和由这些贯通槽(41、42)划分而成的多个块(51～53)。最内中央块(51)被定义为块(51～53)中的最靠近轮胎赤道面(CL)的块。另外,最内中央块(51)的边缘部具有在倾斜主槽(2A、2B)的连接部开口的缺口部(61)。(In the pneumatic tire (1), a plurality of first land portions (3A) are arranged adjacently in the tire circumferential direction, and a plurality of second land portions (3B) are arranged adjacently in the tire circumferential direction. The first land portions (3A) and the second land portions (3B) are arranged in a staggered manner along the tire equatorial plane (CL). The first land portion (3A) and the second land portion (3B) each include a plurality of through grooves (41, 42) that penetrate the land portions (3A, 3B) and open to the pair of tilted main grooves, and a plurality of blocks (51-53) that are defined by the through grooves (41, 42). The innermost central block (51) is defined as the block closest to the tire equatorial plane (CL) among the blocks (51-53). In addition, the edge of the innermost center block (51) has a notch (61) that opens at the connection of the inclined main grooves (2A, 2B).)

1. A pneumatic tire is characterized by comprising:

a plurality of first inclined main grooves that extend obliquely in one direction with respect to the tire circumferential direction and that open at the tire equatorial plane and at one tire contact end;

a plurality of second inclined main grooves that extend obliquely to the other side with respect to the tire circumferential direction and that are open at the tire equatorial plane and the other tire contact end;

a plurality of first land portions that are defined by a pair of adjacent first inclined main grooves and 1 second inclined main groove and extend from a tire equatorial plane to the one tire ground contact end; and

a plurality of second land portions which are defined by a pair of adjacent second tilted main grooves and 1 first tilted main groove and which extend from the tire equatorial plane to the other tire contact end,

a plurality of the first land portions are arranged adjacently in the tire circumferential direction,

a plurality of the second land portions are adjacently arranged in the tire circumferential direction,

the first land portions and the second land portions are arranged in a staggered manner along the tire equator plane,

the first land portion and the second land portion each have a plurality of through grooves that penetrate the land portion and open to the pair of inclined main grooves, and a plurality of blocks that are partitioned by the through grooves,

the innermost central block is defined as the block closest to the tire equatorial plane among the blocks, and,

the edge of the innermost center block has a notch portion that opens at the connection portion of the inclined main groove.

2. A pneumatic tire according to claim 1,

the distance Ln from the corner of the innermost center piece to the opening position of the notch has a relationship of 0.40 & lt Ln/La1 & lt 0.60 with respect to the edge length La1 of the edge portion of the innermost center piece.

3. A pneumatic tire according to claim 1 or 2,

the extended length Wn of the notch portion has a relationship of 0.30 Wn/Wb1 '0.50 with respect to the width Wb 1' of the innermost center block at the position where the notch portion is disposed.

4. A pneumatic tire according to any one of claims 1 to 3,

the first land portion and the second land portion each include 2 or more and 4 or less through grooves and 3 or more and 5 or less blocks.

5. A pneumatic tire according to any one of claims 1 to 4,

1 of the first inclined main grooves is opened in a Y shape relative to 1 of the second inclined main grooves to form 1 main groove unit,

the second inclined main groove of the main groove unit opens in a Y-shape with respect to the first inclined main groove of another main groove unit adjacent in the tire rotation direction,

the plurality of main groove units are arranged in the tire circumferential direction.

6. A pneumatic tire according to any one of claims 1 to 5,

the groove widths of the through grooves monotonically increase from the through groove closest to the tire equatorial plane toward the tire width direction outer side in this order.

7. A pneumatic tire according to any one of claims 1 to 6,

the inclination angles of the through grooves with respect to the tire circumferential direction decrease monotonically from the inclination angle of the through groove closest to the tire equatorial plane toward the tire widthwise outer side in this order.

8. A pneumatic tire according to any one of claims 1 to 7,

an inclination angle of an innermost through groove closest to a tire equatorial plane among the through grooves with respect to a tire circumferential direction is in a range of 20deg to 40 deg.

9. A pneumatic tire according to any one of claims 1 to 8,

the ratio of the ground contact area of the innermost center block to the sum of the ground contact areas of the center blocks is in the range of 0.30 to 0.50.

10. A pneumatic tire according to any one of claims 1 to 9,

the contact area of the center block monotonically increases from the contact area of the innermost center block toward the outer side in the tire width direction.

11. A pneumatic tire according to any one of claims 1 to 10,

the ground contact area ratio of the adjacent center blocks is in the range of 1.01 to 1.50.

12. A pneumatic tire according to any one of claims 1 to 11,

the pneumatic tire is provided with a display unit for specifying the tire rotation direction,

an edge length of an edge portion on a rear land side in a tire rotation direction among edge portions on the inclined main groove side of the innermost center piece is longer than an edge length of an edge portion on a first land side.

13. A pneumatic tire according to any one of claims 1 to 12,

the projection amount Dp of the innermost center piece with respect to the tire equatorial plane has a relationship of 0 < Dp/TW ≦ 0.15 with respect to the tire ground contact width TW.

14. A pneumatic tire according to any one of claims 1 to 13,

the distance D1 from the end portion on the outer side in the tire width direction of the innermost center block to the tire equatorial plane has a relationship of 0.10. ltoreq. D1/TW. ltoreq.0.20 with respect to the tire ground contact width TW.

15. A pneumatic tire according to any one of claims 1 to 14,

the outermost center block is defined as a block located outermost in the tire width direction among the blocks in the tread portion center region, and,

the distance D2 from the end of the outermost center block on the outer side in the tire width direction to the tire equatorial plane has a relationship of 0.22. ltoreq.D 2/TW. ltoreq.0.35 with respect to the tire ground contact width TW.

Technical Field

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire capable of improving wet performance and snow performance of the tire.

Background

In recent winter tires, high wet performance is required in addition to snow performance. As a conventional pneumatic tire related to such a problem, a technique described in patent document 1 is known.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2015-81076

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a pneumatic tire capable of improving the wet performance and the snow performance of the tire.

Means for solving the problems

In order to achieve the above object, a pneumatic tire according to the present invention includes: a plurality of first inclined main grooves that extend obliquely in one direction with respect to the tire circumferential direction and that open at the tire equatorial plane and at one tire contact end; a plurality of second inclined main grooves that extend obliquely to the other side with respect to the tire circumferential direction and that are open at the tire equatorial plane and the other tire contact end; a plurality of first land portions that are defined by a pair of adjacent first inclined main grooves and 1 second inclined main groove and extend from a tire equatorial plane to the one tire ground contact end; and a plurality of second land portions that are defined by a pair of adjacent second tilted main grooves and 1 first tilted main groove and extend from a tire equatorial plane to the other tire ground contact end, the plurality of first land portions being arranged adjacent to each other in the tire circumferential direction, the plurality of second land portions being arranged adjacent to each other in the tire circumferential direction, the first land portions and the second land portions being arranged in a staggered manner along a tire equatorial plane, the first land portions and the second land portions each having a plurality of through grooves that penetrate the land portions and open to the pair of tilted main grooves and a plurality of blocks that are defined by the through grooves, an innermost center block being defined as a block that is closest to the tire equatorial plane among the blocks, and an edge portion of the innermost center block having a notched portion that opens at a connecting portion of the tilted main grooves.

Effects of the invention

In the pneumatic tire of the present invention, (1) the first inclined main grooves and the second inclined main grooves extend from the tire contact edge to the tire equatorial plane, and therefore, the edge components of the tread portion increase to improve the snow braking performance of the tire, and the drainage property of the tread portion improves to improve the wet braking performance of the tire. Further, (2) since the land portions extending from the tire equatorial plane to the tire ground contact end are arranged adjacently in the tire circumferential direction, the arrangement efficiency of the tilted main grooves and the land portions is optimized, and the drainage property and the rigidity in the tire ground contact region are optimized, as compared with the structure in which the third land portion is arranged between these land portions. Further, (3) the first land portions and the second land portions are arranged in a staggered manner along the tire equator plane while reversing the longitudinal direction of each other, and therefore, the snow traction performance and the snow braking performance of the tire are improved. In addition, (4) the edge portion of the innermost center block has a notch portion opened at the connecting portion of the inclined main groove, and therefore, the drainage property in the center region of the tread portion is improved. This has the advantage of improving the snow performance and wet performance of the tire.

Drawings

Fig. 1 is a cross-sectional view showing a tire meridian direction of a pneumatic tire of an embodiment of the present invention.

Fig. 2 is a plan view showing a tread surface of the pneumatic tire illustrated in fig. 1.

Fig. 3 is an explanatory view showing the land portion shown in fig. 2.

Fig. 4 is an enlarged view showing a main portion of the pneumatic tire shown in fig. 2.

Fig. 5 is an enlarged view showing a main portion of the pneumatic tire shown in fig. 2.

Fig. 6 is a graph showing the results of a performance test of the pneumatic tire of the embodiment of the present invention.

Fig. 7 is a tread plan view showing a pneumatic tire of the conventional example.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited to the embodiment. The constituent elements of the present embodiment include elements that can be replaced and obviously replaced while maintaining the identity of the invention. The plurality of modifications described in the embodiment can be arbitrarily combined within a range that is obvious to those skilled in the art.

[ pneumatic tires ]

Fig. 1 is a cross-sectional view showing a tire meridian direction of a pneumatic tire of an embodiment of the present invention. This figure shows a cross-sectional view of a single side region in the tire radial direction. In addition, the figure shows a radial tire for a passenger car as an example of the pneumatic tire.

In the figure, a section in the tire meridian direction is defined as a section when the tire is cut along a plane including a tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane passing through the midpoint of the measurement point of the tire cross-sectional width defined by JATMA and perpendicular to the tire rotation axis. In addition, the tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis.

The pneumatic tire 1 has an annular structure centered on a tire rotation axis, and includes a pair of bead cores 11, a pair of bead fillers 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, and a pair of rim cushion rubbers 17, 17 (see fig. 1).

The pair of bead cores 11, 11 are cores in which 1 or more bead wires made of steel are annularly and multiply wound, and are embedded in the bead portions to constitute left and right bead portions. The pair of bead fillers 12, 12 are disposed on the outer peripheries of the pair of bead cores 11, 11 in the tire radial direction, respectively, to reinforce the bead portions.

The carcass layer 13 has a single-layer structure of 1 carcass ply or a multilayer structure of a plurality of carcass plies stacked, and is annularly stretched between the left and right bead cores 11, 11 to constitute a tire frame. Both ends of the carcass layer 13 are wound back to the outside in the tire width direction so as to enclose the bead core 11 and the bead filler 12, and are locked. The carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, or the like) with a covering rubber and calendering the covering rubber, and has a cord angle (defined as an inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction) of 80[ deg ] or more and 100[ deg ] or less.

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 142, and is wound around the outer periphery of the carcass layer 13. The belt plies 141 to 142 include a pair of intersecting belts 141, 142 and a belt cover 142.

The pair of cross belts 141, 142 are formed by coating a plurality of belt cords made of steel or an organic fiber material with a covering rubber and rolling the coated cords, and have a cord angle of 15 deg or more and 55 deg or less in absolute value. The pair of cross belts 141 and 142 have cord angles (defined as the inclination angles of the longitudinal directions of the belt cords with respect to the tire circumferential direction) of different signs from each other, and the longitudinal directions of the belt cords are stacked while crossing each other (so-called cross ply structure). The pair of cross belts 141, 142 are layered and arranged on the outer side of the carcass layer 13 in the tire radial direction.

The belt cover 142 is formed by covering a belt cover cord made of steel or an organic fiber material with a cover rubber, and has a cord angle of 0[ deg ] or more and 10[ deg ] or less in absolute value. The belt cover 142 is, for example, a strip material in which 1 or a plurality of belt cover cords are covered with a cover rubber, and is configured by spirally winding the strip material around the outer circumferential surfaces of the intersecting belts 141, 142 a plurality of times in the tire circumferential direction.

The tread rubber 15 is disposed on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction, and constitutes a tread portion of the tire. The pair of sidewall rubbers 16, 16 are disposed on the outer sides of the carcass layer 13 in the tire width direction, respectively, to constitute left and right sidewall portions. The pair of rim cushion rubbers 17, 17 extend from the inside in the tire radial direction of the turnback portions of the left and right bead cores 11, 11 and the carcass layer 13 to the outside in the tire width direction, and constitute rim fitting surfaces of the bead portions.

[ Tread pattern ]

Fig. 2 is a plan view showing a tread surface of the pneumatic tire illustrated in fig. 1. The figure shows the tread surface of a winter tyre.

In fig. 2, the tire rotation direction is defined as a rotation direction in which the frequency of use of the tire is high when the tire is used, more specifically, as a rotation direction when the vehicle is traveling. In addition, a first landing side (so-called a step-in side or a toe side) and a rear landing side (so-called a kick-out side or a heel side) of the block at the time of tire ground contact are defined according to the tire rotation direction. The pneumatic tire further includes a rotation direction display unit (not shown) that indicates the rotation direction of the tire. The rotation direction display portion is configured by, for example, marks and/or projections and depressions attached to the sidewall portion of the tire.

The tire contact edge T is defined as a maximum width position in the tire axial direction in a contact surface between the tire and the flat plate when the tire is mounted on a predetermined rim (japanese: size リム) and a predetermined internal pressure (japanese: size) is applied thereto, and a load corresponding to a predetermined load (japanese: size load) is applied thereto while the tire is vertically placed on the flat plate in a stationary state.

The predetermined Rim means "adaptation リム (application Rim)" defined by JATMA, "Design Rim" defined by TRA, or "measurement Rim" defined by ETRTO. The predetermined internal pressure is a maximum value of "maximum air pressure (maximum air pressure)" defined by JATMA, "TIRE LOAD limit AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or "INFLATION pressure" defined by ETRTO. The predetermined LOAD is a maximum value of "maximum negative LOAD CAPACITY (maximum LOAD CAPACITY)" defined by JATMA, a maximum value of "TIRE LOAD LIMITS AT variable INFLATION PRESSURES" defined by TRA, or "LOAD CAPACITY" defined by ETRTO. However, in JATMA, in the case of a passenger vehicle tire, the internal pressure is defined as 180[ kPa ] and the load is defined as 88 [% ] of the maximum load capacity.

As shown in fig. 2, the pneumatic tire 1 includes first and second tilted main grooves 2A, 2B, and first and second land portions 3A, 3B defined by the tilted main grooves 2A, 2B.

The first inclined main groove 2A extends obliquely with respect to one direction (left side in the drawing) in the tire circumferential direction, and opens at the tire equatorial plane CL and one tire ground contact end T. In addition, the plurality of first inclined main grooves 2A are arranged at predetermined intervals in the tire circumferential direction. The second inclined main groove 2B extends obliquely to the other side (right side in the drawing) with respect to the tire circumferential direction, and opens to the tire equatorial plane CL and the other tire contact end T. In addition, the plurality of second inclined main grooves 2B are arranged at predetermined intervals in the tire circumferential direction. Specifically, the first and second tilted main grooves 2A, 2B are tilted from the tire equatorial plane CL toward the tire width direction outer side toward the opposite side of the tire rotation direction (i.e., the ground contact rear landing side). The first and second tilted main grooves 2A and 2B extend across the tire equatorial plane CL, respectively.

The first and second tilted main grooves 2A and 2B are grooves having a display obligation of a wear indicator defined by JATMA, and have a groove width of 2.5[ mm ] or more and a groove depth of 6.5[ mm ] or more (dimensional marks in the figure are omitted). In the configuration of fig. 2, the groove widths of the inclined main grooves 2A, 2B decrease monotonously from the tire contact end T toward the tire equatorial plane CL, and become minimum at the opening positions where the inclined main grooves 2B, 2A are opened with respect to the other inclined main grooves. In addition, the main groove 2A is inclined; the groove width of the main groove 2B is equal to that of the other inclined main grooves 2B from the side; the position of the 2A connection becomes the smallest.

The groove width is measured as the distance between the opposing groove walls at the groove opening in a no-load state in which the tire is mounted on a predetermined rim and a predetermined internal pressure is applied. In the structure having the notch portion or the chamfered portion at the groove opening portion, the groove width is measured using, as a measurement point, an intersection point of an extension line of the tread surface and an extension line of the groove wall in a cross-sectional view parallel to the groove width direction and the groove depth direction.

The groove depth is measured as the distance from the tread surface to the maximum groove depth position in a no-load state in which the tire is mounted on a predetermined rim and a predetermined internal pressure is applied. In the structure having a partial uneven portion or sipe at the groove bottom, the groove depth was measured with the exception of these portions.

Further, 1 first tilted main groove 2A is opened in a Y-shape with respect to 1 second tilted main groove 2B to constitute 1 main groove unit (unit constituted by a pair of tilted main grooves 2A and 2B; reference numeral in the figure is omitted). Specifically, 1 first tilted main groove 2A is connected to a second tilted main groove 2B from the side, and ends so as not to intersect with a second land portion 3B located on the extension line of the groove center line. The second inclined main groove 2B of the main groove unit opens in a Y-shape with respect to the first inclined main groove 2A of another main groove unit adjacent in the tire rotation direction. The second tilted main groove 2B is connected to the first land portion 3A from the side, and ends so as not to intersect the first land portion 3A located on the extension line of the groove center line. The plurality of main groove units (2A, 2B) are repeatedly arranged and connected in the tire circumferential direction. As a result, the first tilted main grooves 2A and the second tilted main grooves 2B are alternately connected in a Y-shape in the tire circumferential direction, and a tread pattern is formed by connecting the plurality of tilted main grooves 22A and 2B in the tire circumferential direction.

In the figure, reference numerals 61 and 62 denote notch portions of the blocks, and are distinguished from the inclined main grooves 2A and 2B. These notches 61 and 62 will be described later.

In the above-described configuration, the inclined main grooves 2A and 2B are connected to each other in a Y-shape and arranged in the tire circumferential direction, without penetrating the long land portions 3A and 3B extending from the tire equatorial plane CL to the tire ground contact edge T. This optimizes the arrangement efficiency of the tilted main grooves 2A and 2B and the long land portions 3A and 3B, and optimizes the drainage performance and rigidity in the tire ground contact area.

For example, in the structure of fig. 2, the first and second tilted main grooves 2A and 2B have a line-symmetric structure about the tire equatorial plane CL, and are arranged in a staggered manner in the tire circumferential direction. The first and second tilted main grooves 2A and 2B have a gently curved arc shape or a gently bent L shape. The inclination angles (dimensional symbols in the drawings are omitted) of the first and second inclination main grooves 2A, 2B monotonically increase from the tire equatorial plane CL toward the tire width direction outer side. This improves the drainage of the tire ground contact area.

The inclination angle of the inclined main grooves 2A, 2B is defined as an angle formed by a tangent to the groove center line of the inclined main groove and the opposite direction to the tire rotation direction. The groove center line of the tilted main groove is defined as a smooth curve connecting midpoints of left and right groove walls of the tilted main groove.

The first land portion 3A is defined by a pair of first inclined main grooves 2A, 2A and 1 second inclined main groove 2B adjacent to each other in the tire circumferential direction, and has a long-dimension structure extending from the tire equatorial plane CL to a tire ground contact end T on one side (left side in the drawing). Further, the plurality of first land portions 3A, 3A are adjacently arranged in the tire circumferential direction. Similarly, the second land portion 3B is defined by a pair of second oblique main grooves 2B, 2B adjacent to each other in the tire circumferential direction and 1 first oblique main groove 2A, and has a long structure extending from the tire equatorial plane CL to the tire contact end T on the other side (right side in the drawing). In addition, the plurality of second land portions 3B are adjacently aligned in the tire circumferential direction. The first land portions 3A and the second land portions 3B are arranged in a staggered manner along the tire equatorial plane CL with their longitudinal directions reversed.

For example, in the structure of fig. 2, the first and second land portions 3A and 3B have a line-symmetric structure with respect to the tire equatorial plane CL, and are arranged in a staggered manner in the tire circumferential direction. The first and second land portions 3A and 3B have a long shape that is gently curved or bent. The first and second land portions 3A, 3B are inclined in the longitudinal direction from the tire equatorial plane CL toward the tire widthwise outer side toward the opposite side to the tire rotation direction (i.e., the ground contact rear land side). The widths (dimension symbols in the drawings are omitted) of the first and second land portions 3A, 3B monotonically increase toward the tire width direction outer side from the tire equatorial plane CL. Thereby, the ground contact characteristics of the tire are improved.

The width of the land portions 3A, 3B is defined relative to the lengthwise direction of the land portions 3A, 3B, i.e., relative to the land portion 3A; 3B are divided into inclined main grooves 2A and 2B, and the width thereof in the direction perpendicular to the extending direction thereof.

In the above-described configuration, (1) the first inclined main grooves 2A and the second inclined main grooves 2B extend from the tire ground contact edge T to the tire equatorial plane CL, and therefore, the edge components of the tread portion increase to improve the snow braking performance of the tire, and the water drainage performance of the tread portion improves to improve the wet braking performance of the tire. Further, (2) the land portions 3A, 3B extending from the tire equatorial plane CL to the tire ground contact edge T are arranged adjacent to each other in the tire circumferential direction, and therefore, the arrangement efficiency of the inclined main grooves 2A, 2B and the land portions 3A, 3B is optimized and the drainage property and rigidity in the tire ground contact region are optimized as compared with a configuration in which the third land portion is arranged between these land portions 3A, 3B (see, for example, fig. 7). Further, (3) the first land portions 3A and the second land portions 3B are arranged along the tire equatorial plane CL in a staggered manner with the longitudinal directions thereof reversed, so that the snow traction performance and the snow braking performance of the tire are improved. This improves the snow performance and wet performance of the tire.

Fig. 3 is an explanatory view showing the land portion shown in fig. 2. This figure shows an enlarged view of the single land portion 3A (3B) extracted.

As shown in fig. 3, the 1 land portion 3A (3B) includes a plurality of through grooves 41 and 42 and a plurality of blocks 51 to 53 partitioned by the through grooves 41 and 42. Preferably, the number of through grooves in 1 land portion 3A (3B) is 2 or more and 4 or less, and the number of blocks is 3 or more and 5 or less.

The through grooves 41 and 42 have an open structure penetrating the land portion 3A (3B), and open to the adjacent pair of inclined main grooves 2A and 2A (2B and 2B). The plurality of through grooves 41 and 42 are arranged at predetermined intervals in the longitudinal direction of the land portion 3A (3B).

The through grooves 41 and 42 have groove widths W1 and W2 of 1.5 mm or more and groove depths (not shown) of 3.0 mm or more, and are opened when the tire contacts the ground to function as grooves. The groove widths W1, W2 of the through grooves 41, 42 have a relationship of W1. ltoreq.W 2. In a configuration (not shown) including 3 or more through grooves, the groove widths of the through grooves monotonically increase toward the tire width direction outer side in order from the innermost through groove 41 closest to the tire equatorial plane CL. In the structure of FIG. 2, the groove width W1 of the innermost penetration groove 41 is narrowest and is in the range of 1.5[ mm ] to W1 to 3.5[ mm ]. The outermost through groove 42 located on the outermost side in the tire width direction has a groove width W2 widest at 3.5[ mm ] to W2 to 6.0[ mm ].

The through grooves 41, 42 have inclination angles θ 1, θ 2 of 10[ deg ] to 90[ deg ], and are inclined outward in the tire width direction toward the tire rotation direction. The inclination angles theta 1 and theta 2 of the through grooves 41 and 42 are in a relationship of theta 1 ≧ theta 2. In a configuration (not shown) including 3 or more through grooves, the inclination angles of the through grooves monotonically decrease toward the tire width direction outer side in order from the innermost through groove 1. In the structure of FIG. 2, the inclination angle θ 1 of the innermost through groove 41 with respect to the tire circumferential direction is in the range of 20[ deg ] ≦ θ 1 ≦ 40[ deg ]. The inclination angle theta 2 of the outermost through groove 42 is in the range of 10 deg.C to 30 deg.C.

The inclination angles θ 1 and θ 2 of the through grooves 41 and 42 are measured as angles formed by virtual straight lines connecting the left and right openings of the through grooves 41 and 42, which are opened with respect to the inclined main grooves 2A and 2B, and the opposite direction to the tire rotation direction.

In the structure of fig. 2, a plurality of outermost through grooves 42 are arranged in the tire circumferential direction, and these outermost through grooves 42 have the above-described inclination angle θ 2, thereby opposing the inclined main grooves 2A; the openings of the 2B openings are arranged so as to be shifted from each other. Thereby, the outermost through groove 42 and the inclined main groove 2A are formed; 2B are formed by alternately connecting a part of the circumferential grooves in the tire circumferential direction.

The blocks 51 to 53 are divided by a plurality of through grooves 41 and 42, and are arranged in a row along a pair of inclined main grooves 2A and 2A (2B and 2B) that divide the land portion 3A (3B). In the structure of fig. 3, 1 land portion 3A (3B) includes 3 blocks 51 to 53. Further, the blocks 51 to 53 in the tread portion center region have a trapezoidal shape having the edge portions on the pair of inclined main grooves 2A, 2A (2B, 2B) sides as substantially parallel opposite sides. Further, the blocks 51 and 52 in the tread portion center region have acute corner portions on the first land side in the tire rotation direction and on the outer side in the tire width direction.

The tread portion center region CE (see fig. 2) is defined as a region on the inner side in the tire width direction with respect to the outermost through groove 42 located on the outermost side in the tire width direction. The tread shoulder region SH is defined as a region on the outer side in the tire width direction with the outermost through groove 42 as a boundary.

Further, the innermost center block 51 closest to the tire equatorial plane CL is disposed on the tire equatorial plane CL. The amount of projection Dp (see FIG. 3) of the innermost center piece 51 with respect to the tire equatorial plane CL is preferably in a relationship of 0 < Dp/TW 0.15 with respect to the tire ground contact width TW, and more preferably in a relationship of 0.01 Dp/TW 0.10. The amount of projection Dp of the innermost center block 51 is preferably in the range of 0.5[ mm ] Dp.ltoreq.5.0 [ mm ], more preferably in the range of 1.0[ mm ] Dp.ltoreq.4.0 [ mm ].

In the center blocks 51 and 52 located in the tread portion center region, distances D1 and D2 from the tire equatorial plane CL to the corner portions on the outer side in the tire width direction of the center blocks 51 and 52 have a relationship of D1 < D2. In a configuration (not shown) including 3 or more center blocks, the distance to the corner of the center block increases from the innermost center block 51 closest to the tire equatorial plane CL toward the tire width direction outer side in this order. In addition, the distance D1 of the corner portion of the innermost center piece 51 has a relationship of 0.10. ltoreq. D1/TW. ltoreq.0.20 with respect to the tire ground contact width TW. In addition, the distance D2 of the corner portion of the outermost center block 52 located on the outermost side in the tire width direction has a relationship of 0.22. ltoreq.D 2/TW. ltoreq.0.35 with respect to the tire ground contact width TW.

In addition, the ground areas S1, S2 of the center blocks 51, 52 have a relationship of S1 ≦ S2. In a configuration (not shown) including 3 or more center blocks, the contact area of the center block monotonically increases from the innermost center block 51 toward the outer side in the tire width direction. The ratio S2/S1 of the ground contact areas S1, S2 of the adjacent center blocks 51, 52 is preferably in the range of 1.01 to 1.50, more preferably 1.05 to 1.30. Further, the ratio S1/Σ ce between the ground area S1 of the innermost center block 51 and the sum Σ se of the ground areas S1 and S2 of the center blocks 51 and 52 is in the range of 0.30 to 0.50. Further, the ratio S2/Σ ce of the ground area S3 of the outermost center block 52 to the sum Σ se of the ground areas S1 and S2 of the center blocks 51 and 52 is in the range of 0.50 to 0.70. In the structure of fig. 3, the land area of the shoulder block 53 located in the shoulder region of the tread portion is larger than the land area of the outermost center block 52.

In the above-described structure, the edge component of the block in the region near the tire equatorial plane CL becomes relatively large, and the snow traction in the tire ground contact region is improved. On the other hand, the rigidity of the land portions 3A, 3B in the region close to the tire ground contact edge T increases, and the wet braking performance in the tire ground contact region improves. Therefore, the snow performance and the wet performance of the tire are considered at the same time.

In addition, the inclined main grooves 2A, 2A of the center blocks 51, 52; of the edge portions on the 2B and 2B sides, the edge lengths La1 and La2 of the edge portion on the rear land side in the tire rotation direction are longer than the edge lengths Lb1 and Lb2 of the edge portion on the front land side (Lb1 < La1 and Lb2 < La 2). The ratios of these edge lengths La1/Lb1 and La2/Lb2 are preferably in the range of 1.01 to 1.15, more preferably 1.03 to 1.10. In addition, the edge lengths La1, La2 (and Lb1, Lb2) of the center block 51 have a relationship of La 1. ltoreq. La2 (and Lb 1. ltoreq. Lb 2). In a configuration (not shown) including 3 or more center blocks, the edge length of the center block also monotonically increases from the innermost center block 51 toward the tire width direction outer side. The edge lengths La1 and La2 are measured as linear distances between both ends of the edge of the blocks 51 and 52.

In the above-described structure, the edge component of the block is relatively large on the tire equatorial plane CL side and on the rear land side in the tire rotation direction, and snow traction in the tire contact patch is improved. Further, since the edge length of the center block increases monotonously from the innermost center block 51 toward the tire width direction outer side, the drainage of the tire contact patch is improved. Therefore, the snow performance and the wet performance of the tire are considered at the same time.

Each of the blocks 51 to 53 has a plurality of sipes (reference numerals in the figure are omitted). The sipe is a cut formed on the tread surface, and has a sipe width of less than 1.5[ mm ] and a sipe depth of 2.0[ mm ] or more, thereby being closed when the tire is grounded.

Fig. 4 and 5 are enlarged views showing a main portion of the pneumatic tire shown in fig. 2. In these figures, fig. 4 shows the arrangement of the land portions 3A, 3B near the tire equatorial plane CL, and fig. 5 shows the single block 51 closest to the tire equatorial plane CL.

In the configuration of fig. 2, as described above, the first tilted main grooves 2A and the second tilted main grooves 2B extend across the tire equatorial plane CL, and the first tilted main grooves 2A and the second tilted main grooves 2B are alternately arranged in the tire circumferential direction so as to intersect each other in a Y-shape. The first land portions 3A and the second land portions 3B defined by the first tilted main grooves 2A and the second tilted main grooves 2B are arranged in a staggered manner along the tire equatorial plane CL.

At this time, as shown in fig. 4, the intersection points (reference numerals in the drawing are omitted) of the groove center lines of the first tilted main grooves 2A and the second tilted main grooves 2B are arranged in a staggered manner in the tire circumferential direction with respect to the tire equatorial plane CL. Thus, zigzag-shaped main grooves formed by parts of the first tilted main grooves 2A and the second tilted main grooves 2B are formed on the tire equatorial plane CL. The innermost center blocks 51 of the first land portion 3A and the second land portion 3B have treads on the tire equatorial plane CL, and the innermost center blocks 51 of the first land portion 3A and the innermost center blocks 51 of the second land portion 3B are arranged in a staggered manner in the tire circumferential direction with the tire equatorial plane CL therebetween.

In FIG. 5, the aspect ratio Wb1/Lb1 of the innermost center block 51 is preferably in the range of 1.50. ltoreq. Wb1/Lb 1. ltoreq.3.00, and more preferably in the range of 1.80. ltoreq. Wb1/Lb 1. ltoreq.2.50. The dimension Lb1 is the inclined main groove 2A; 2B, the dimension Wb1 is the maximum length of the block 51 in the extending direction of the inclined main groove 2A; 2B in the direction orthogonal to the extending direction of the block 51.

[ notched part of block ]

As shown in fig. 2, each of the center blocks 51, 52 has a first notch portion 61 or a second notch portion 62.

The first notch 61 is formed in the inclined main groove 2A of the innermost center block 51; 2B side and opens at the connection part of the left and right inclined main grooves 2A, 2B. Specifically, the first notch portion 61 is formed in one of the inclined main grooves 2A; 2B inclined main grooves 2B from the side to the other; 2A is opened at the position connected in a Y shape, and is arranged in one inclined main groove 2A; 2B on an extension of the groove center line (see fig. 4). The first notch 61 is formed in the edge portion of the innermost center block 51 on the rear landing side in the tire rotation direction. On the other hand, the edge portion on the first land side in the tire rotation direction of the innermost center block 51 does not have a notched portion.

The notch is defined as a stepped recess (i.e., a step) having a bottom surface parallel to the tread surface of the land portion. Alternatively, a short horizontal groove may be formed instead of the notch portion.

The second notch 62 is formed in the inclined main groove 2A of the other center block 52; 2B side edge portion, and in the inclined main groove 2A; 2B and the communication groove 41 are open. Specifically, the second notch 62 is disposed in the communication groove 41 with respect to the tilted main groove 2A; 2B, the opening of the substrate. Further, the second notch 62 is formed at the edge portion on the rear land side in the tire rotation direction of the center block 52. On the other hand, the edge portion of the center block 52 on the land first side in the tire rotation direction does not have a notch portion.

It is preferable that the opening widths (dimensional symbols in the drawings are omitted) of the first and second notch portions 61 be in the range of 1.5[ mm ] to 3.0[ mm ], and be equal to or smaller than the opening widths of the opposing inclined main grooves 2A and 2B or the communication groove 41. It is preferable that the maximum depth (not shown) of the first and second notches 61 is in a range of 2.0[ mm ] to 7.0[ mm ], and the groove depth with respect to the inclined main grooves 2A and 2B is in a range of 20 [% ] to 90 [% ].

In the above configuration, the connection portion of the inclined main grooves 2A and 2B is widened by the first notch portion 61, and the drainage property in the tread portion center region is improved. Further, the snow traction is improved by the edge component of the first notch portion 61. This improves the wet performance and snow performance of the tire.

In FIG. 5, the distance Ln from the corner of the innermost central block 51 to the opening position of the first notch 61 is preferably in a relationship of 0.40. ltoreq. Ln/La 1. ltoreq.0.60, more preferably in a relationship of 0.45. ltoreq. Ln/La 1. ltoreq.0.55, with respect to the edge length La1 of the edge portion of the innermost central block 51. That is, the first notch 61 is disposed in the center of the edge of the innermost center block 51. Further, as described above, since the first notch portion 61 opens at the connecting portion of the left and right tilted main grooves 2A, 2B, the connecting portion of the left and right tilted main grooves 2A, 2B is located at the center portion of the edge portion of the innermost center block 51 (see fig. 4). As shown in fig. 2, the second notch 62 is also disposed in the center of the edge of the center block 52, similarly to the first notch 61.

The distance Ln of the first notch 61 is measured as a distance from the measurement point of the edge length La1 of the block 51 to the center of the opening of the first notch 61.

In addition, in FIG. 5, the extended length Wn of the first notch portion 61 preferably has a relationship of 0.30. ltoreq. Wn/Wb1 '. ltoreq.0.50, more preferably 0.35. ltoreq. Wn/Wb1 ' 0.45 with respect to the width Wb1 ' of the innermost center block 51 at the position where the first notch portion 61 is disposed. Therefore, the first notch portion 61 has a structure shorter than the through grooves 41 and 42 of the through land portions 3A and 3B. Thereby, the rigidity of the block 51 is ensured. As shown in fig. 2, the second notch 62 also has a short structure having the same size as the first notch 61.

The extension length Wn of the first notch portion 61 is measured as the extension distance of the first notch portion 61 in the direction of the width Wb1 of the innermost center block 51.

[ Effect ]

As described above, the pneumatic tire 1 includes: a plurality of first inclined main grooves 2A extending obliquely in one direction with respect to the tire circumferential direction and opening at the tire equatorial plane CL and at the tire ground contact end T on one side; a plurality of second inclined main grooves 2B extending obliquely to the other side with respect to the tire circumferential direction and opening at the tire equatorial plane CL and the other tire contact end T; a plurality of first land portions 3A, each of the first land portions 3A being defined by a pair of adjacent first inclined main grooves 2A, 2A and 1 second inclined main groove 2B and extending from the tire equatorial plane CL to one of the tire contact ends T; and a plurality of second land portions 3B each of which is defined by a pair of adjacent second tilted main grooves 2B, 2B and 1 first tilted main groove 2A and extends from the tire equatorial plane CL to the other tire contact end T (see fig. 2). Further, the plurality of first land portions 3A are arranged adjacent to each other in the tire circumferential direction, and the plurality of second land portions 3B are arranged adjacent to each other in the tire circumferential direction. The first land portions 3A and the second land portions 3B are arranged in a staggered manner along the tire equatorial plane CL. The first land portion 3A and the second land portion 3B each include a plurality of through grooves 41 and 42 that penetrate the land portions 3A and 3B and open to the pair of inclined main grooves, and a plurality of blocks 51 to 53 (see fig. 3) partitioned by the through grooves 41 and 42. The innermost central block 51 is defined as the block closest to the tire equatorial plane CL among the blocks 51 to 53. Further, the edge portion of the innermost center block 51 has a notch portion 61 (see fig. 4) that opens at the connection portion of the inclined main grooves 2A, 2B.

In this structure, (1) the first inclined main grooves 2A and the second inclined main grooves 2B extend from the tire ground contact edge T to the tire equatorial plane CL, and therefore, the edge components of the tread portion increase to improve the snow braking performance of the tire, and the water drainage performance of the tread portion improves to improve the wet braking performance of the tire. Further, (2) the land portions 3A, 3B extending from the tire equatorial plane CL to the tire ground contact edge T are arranged adjacent to each other in the tire circumferential direction, and therefore, the arrangement efficiency of the inclined main grooves 2A, 2B and the land portions 3A, 3B is optimized and the drainage property and rigidity in the tire ground contact region are optimized as compared with a configuration in which the third land portion is arranged between these land portions 3A, 3B (see, for example, fig. 7). Further, (3) the first land portions 3A and the second land portions 3B are arranged in a staggered manner along the tire equatorial plane CL with their longitudinal directions reversed, so that the snow traction performance and the snow braking performance of the tire are improved. Further, (4) the edge portion of the innermost center block 51 has the notch portion 61 opened at the connecting portion of the inclined main grooves 2A, 2B, so that the drainage property in the tread portion center region is improved. This has the advantage of improving the snow performance and wet performance of the tire.

In the pneumatic tire 1, the distance Ln from the corner of the innermost center block 51 to the opening position of the cutout 61 is in a relationship of 0.40 ≦ Ln/La1 ≦ 0.60 with respect to the edge length La1 of the edge portion of the innermost center block 51 (see fig. 5). In this configuration, since the notch 61 is disposed at the center portion in the longitudinal direction of the innermost center block 51, there is an advantage that the rigidity of the block is appropriately secured.

In addition, in the pneumatic tire 1, the extended length Wn of the notch portion 61 has a relationship of 0.30. ltoreq. Wn/Wb1 '. ltoreq.0.50 with respect to the width Wb 1' of the innermost center block 51 at the position where the notch portion 61 is disposed (see fig. 5). In this configuration, the notch portion 61 has a short-sized structure, so that the rigidity of the block is suitably ensured.

In the pneumatic tire 1, the first land portion 3A and the second land portion 3B each include 2 or more and 4 or less through grooves 41 and 42 and 3 or more and 5 or less blocks 51 to 53 (see fig. 3). This has the advantage that the number of the through grooves 41, 42 and the blocks 51 to 53 is optimized, and the drainage property and rigidity in the tire ground contact region are optimized.

In the pneumatic tire 1, 1 first tilted main groove 2A is opened in a Y-shape with respect to 1 second tilted main groove 2B to constitute 1 main groove unit (see fig. 2). The second tilted main groove 2B of the main groove unit opens in a Y-shape with respect to the first tilted main groove 2A of another main groove unit adjacent in the tire rotation direction. The plurality of main groove units are arranged in the tire circumferential direction. In this configuration, the inclined main grooves 2A and 2B are disposed so as to be connected to each other without penetrating the land portions 3A and 3B extending from the tire equatorial plane CL to the tire ground contact edge T. This has the advantage that the arrangement efficiency of the inclined main grooves 2A, 2B and the land portions 3A, 3B is optimized, and the drainage performance and rigidity in the tire ground contact area are optimized.

In the pneumatic tire 1, the groove widths of the through grooves 41 and 42 are monotonically increased toward the tire width direction outer side in order from the through groove 41 or 42 closest to the tire equatorial plane CL (W1 ≦ W2) (see fig. 3). This has the advantage of achieving both drainage and rigidity in the tire contact patch.

In the pneumatic tire 1, the inclination angles θ 1 and θ 2 of the through grooves 41 and 42 with respect to the tire circumferential direction decrease monotonically toward the tire width direction outer side in order from the inclination angle of the through groove 41 closest to the tire equatorial plane CL (θ 1 ≧ θ 2) (see fig. 3). This has the advantage of achieving both drainage in the tire contact patch and snow traction.

In the pneumatic tire 1, the inclination angle θ 1 with respect to the tire circumferential direction of the innermost through groove 41 closest to the tire equatorial plane CL of the through grooves 41, 42 is in the range of 20[ deg ] to 40[ deg ]. This has the advantage of improving snow traction in the tread portion center region.

In the pneumatic tire 1, the ratio S1/(S1+ S2) between the contact area S1 of the innermost center block 51 and the sum of the contact areas S1 and S2 of the center blocks 51 and 52 is in the range of 0.20 to 0.30. This has the advantage that the ground contact area S1 of the innermost center block 51 is appropriately ensured.

In the pneumatic tire 1, the contact patch areas S1, S2 (dimensional symbols in the drawing are omitted) of the center blocks 51, 52 located in the tread portion center region among the blocks 51 to 53 monotonically increase toward the tire width direction outer side from the innermost center block 51 closest to the tire equatorial plane CL (S1 ≦ S2) (see fig. 3). In this structure, the edge component of the block in the region near the tire equatorial plane CL is relatively large and the snow traction in the tire ground contact region is improved, while the rigidity of the land portions 3A, 3B in the region near the tire ground contact end T is increased and the wet braking performance in the tire ground contact region is improved. Therefore, the snow tire has the advantages of taking the snow performance and the wet performance of the tire into consideration.

In the pneumatic tire 1, the contact area ratio S2/S1 between the adjacent center blocks 51 and 52 is in the range of 1.01 to 1.50. This has the advantage that the ground area ratio of the center blocks 51 and 52 is optimized.

The pneumatic tire 1 is provided with a display unit (not shown) for designating the tire rotation direction. In addition, the inclined main grooves 2A, 2A of the center blocks 51, 52; of the edge portions on the 2B and 2B sides, the edge lengths La1 and La2 of the edge portion on the rear land side in the tire rotation direction are longer than the edge lengths Lb1 and Lb2 of the edge portion on the front land side (Lb1 < La1 and Lb2 < La 2). This has the advantage of improving the traction performance of the center blocks 51, 52 and improving the snow performance of the tire.

In addition, in this pneumatic tire 1, the projection amount Dp of the innermost center block 51 with respect to the tire equatorial plane CL has a relationship of 0 < Dp/TW < 0.15 with respect to the tire ground contact width TW. This provides the advantage that the rigidity balance of the innermost center piece 51 is appropriately balanced, and the snow performance and the wet performance of the tire are both achieved.

In the pneumatic tire 1, the distance D1 (see fig. 3) from the end portion on the tire width direction outer side of the innermost center block 51 to the tire equatorial plane CL has a relationship of 0.10 ≦ D1/TW ≦ 0.20 with respect to the tire ground contact width TW (see fig. 2). This provides the advantage that the rigidity balance of the innermost center piece 51 is appropriately balanced, and the snow performance and the wet performance of the tire are both achieved.

In addition, in this pneumatic tire 1, the outermost center block 52 is defined as the block located on the outermost side in the tire width direction among the blocks 51, 52 in the tread portion center region. The distance D2 from the end of the outermost center block 52 on the outer side in the tire width direction to the tire equatorial plane CL has a relationship of 0.22. ltoreq.D 2/TW. ltoreq.0.35 with respect to the tire ground contact width TW. This provides the advantage that the rigidity balance of the outermost center block 52 is appropriately balanced, and the snow performance and the wet performance of the tire are both achieved.

Examples

Fig. 6 is a graph showing the results of a performance test of the pneumatic tire of the embodiment of the present invention. Fig. 7 is a tread plan view showing a pneumatic tire of the conventional example.

In this performance test, evaluations concerning (1) wet braking performance and (2) snow braking performance were performed on a plurality of test tires. Further, a test tire having a tire size of 205/55R 1691H was mounted on a rim having a rim size of 16 × 6.5J, and predetermined loads specified by internal pressures of 200[ kPa ] and JATMA were applied to the test tire. The test tire was mounted on an FF (Front engine Front drive) type passenger vehicle having an exhaust gas volume of 1500[ cc ] as a test vehicle.

(1) In the evaluation relating to the snow braking performance, the test vehicle was run on a snow road surface of a snow test site, and the braking distance from the running speed of 40[ km/h ] was measured. Then, based on the measurement results, an index evaluation was performed using the conventional example as a reference (100). The larger the value of the evaluation, the more preferable.

(2) In the evaluation of the wet braking performance, the test vehicle was run on an asphalt road sprayed with water at a depth of 1[ mm ], and the braking distance from the running speed of 85[ km/h ] was measured. Then, based on the measurement results, an index evaluation was performed using the conventional example as a reference (100). The larger the value of the evaluation, the more preferable.

The test tire of the example has the structure shown in fig. 1 and 2, and long land portions 3A and 3B extending from the tire equatorial plane CL to the tire ground contact end T are arranged adjacent to each other in the tire circumferential direction and arranged in a staggered manner along the tire equatorial plane CL. The inclined main grooves 2A and 2B have a groove width of 5.0 mm and a groove depth of 8.5 mm, respectively. The through groove 41 on the tire equatorial plane CL side has a groove width of 3.0 mm and a groove depth of 4.5 mm, and the through groove 42 on the tire width direction outer side has a groove width of 5.0 mm and a groove depth of 4.5 mm. Further, the tire ground contact width TW is 160[ mm ]. The notches 61 and 62 have an opening width of 2.5[ mm ] and a maximum depth of 4.5[ mm ].

The test tire of the conventional example has the structure of fig. 7, and is different from the test tire of the example in particular in that a short land portion not extending to the tire equatorial plane CL is inserted between adjacent long land portions, and that the land portion has 4 communication grooves (having inclination angles θ 1 to θ 4) and 4 center blocks (having contact patch areas S1 to S4).

As shown in the test results, the snow braking performance and the wet braking performance of the tires were improved in the test tires of the examples as compared with the test tires of the conventional examples.

Description of the reference numerals

1 a pneumatic tire; 11 a bead core; 12 bead filler; 13 a carcass layer; 14 belt layers; 141. 142 crossing the belt; 142 a belt cover; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 2A, 2B inclined main grooves; 3A, 3B land portions; 41. 42 through the slot; 51. 52 a central block; 53 shoulder blocks; 61. 62 gap part