JP7283330B2 - pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of achieving both snow traction performance and uneven wear resistance performance of the tire.

Heavy-duty radial tires mounted on drive shafts of vehicles for long-distance transportation, such as trucks and buses, employ a block pattern with sipes in order to improve snow traction performance.

As a conventional pneumatic tire adopting such a structure, the technology described in Patent Document 1 is known.

JP-A-4-372506

On the other hand, conventional pneumatic tires have a problem of improving uneven wear resistance performance of the tire.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pneumatic tire that achieves both snow traction performance and uneven wear resistance performance of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention is divided into a plurality of main grooves extending in the tire circumferential direction, and shoulder main grooves located at the outermost side in the tire width direction among the main grooves. A pneumatic tire comprising a shoulder land portion and a middle land portion, wherein the shoulder land portion connects a single circumferential narrow groove extending in the tire circumferential direction with a tire ground contact edge and the circumferential narrow groove. a plurality of outer shoulder lug grooves connecting the shoulder main grooves and the circumferential narrow grooves; and a plurality of outer shoulders partitioned by the outer shoulder lug grooves and the circumferential narrow grooves. and a plurality of inner shoulder blocks partitioned by the inner shoulder lug grooves and the circumferential narrow grooves, wherein one outer shoulder block defines the circumferential narrow grooves for the three inner shoulder blocks. The maximum contact length L15 and the maximum contact width W15 of the inner shoulder blocks facing each other on both sides have a relationship of 1.10≦L15/W15≦1.50, and the maximum grooves of the circumferential narrow grooves The width W11 is characterized by having a relationship of 0.025≤W11/Wb1≤0.045 with respect to the maximum contact width Wb1 of the shoulder land portion . In addition, the pneumatic tire according to the present invention has a plurality of main grooves extending in the tire circumferential direction, and shoulder land portions and middle grooves which are partitioned into the outermost shoulder main grooves in the tire width direction among the main grooves. A pneumatic tire comprising a land portion, wherein the shoulder land portion comprises a single circumferential narrow groove extending in the tire circumferential direction and a plurality of outer shoulders connecting the tire contact edge and the circumferential narrow groove. a plurality of inner shoulder lug grooves connecting the shoulder main groove and the circumferential narrow groove; a plurality of outer shoulder blocks partitioned by the outer shoulder lug groove and the circumferential narrow groove; and the inner side. a plurality of inner shoulder blocks partitioned by shoulder lug grooves and said circumferential narrow grooves, wherein one said outer shoulder block faces three said inner shoulder blocks across said circumferential narrow grooves; The maximum contact length L15 and the maximum contact width W15 of the inner shoulder block have a relationship of 1.10≦L15/W15≦1.50, and the opening of the outer shoulder lug groove with respect to the circumferential narrow groove. The width W12 is characterized by having a relationship of 1.50≦W12/W13≦2.20 with respect to the opening width W13 of the inner shoulder lug groove with respect to the circumferential narrow groove. In addition, the pneumatic tire according to the present invention has a plurality of main grooves extending in the tire circumferential direction, and shoulder land portions and middle grooves which are partitioned into the outermost shoulder main grooves in the tire width direction among the main grooves. A pneumatic tire comprising a land portion, wherein the shoulder land portion comprises a single circumferential narrow groove extending in the tire circumferential direction and a plurality of outer shoulders connecting the tire contact edge and the circumferential narrow groove. a plurality of inner shoulder lug grooves connecting the shoulder main groove and the circumferential narrow groove; a plurality of outer shoulder blocks partitioned by the outer shoulder lug groove and the circumferential narrow groove; and the inner side. a plurality of inner shoulder blocks partitioned by shoulder lug grooves and said circumferential narrow grooves, wherein one said outer shoulder block faces three said inner shoulder blocks across said circumferential narrow grooves; The maximum contact length L15 and the maximum contact width W15 of the inner shoulder blocks have a relationship of 1.10≦L15/W15≦1.50, and the outer shoulder blocks are divided by sipes or grooves. It is characterized by having a continuous tread in the tire circumferential direction.

In the pneumatic tire according to the present invention, (1) the shoulder land portions have the outer shoulder lug grooves and the inner shoulder lug grooves, so that the edge components of the shoulder land portions are secured and the snow traction performance of the tire is improved. (2) Since the inner shoulder block faces the long outer shoulder block across the circumferential narrow groove, when the circumferential narrow groove is closed when the tire touches the ground, the inner shoulder block is positioned higher in the circumferential direction. It is supported by rigid outer shoulder blocks. This reinforces the inner shoulder blocks and suppresses heel-and-toe wear of the inner shoulder blocks (including uneven wear of block edges and uneven wear originating from sipes). In addition, (3) since the inner shoulder blocks have an elongated shape in the tire circumferential direction, the circumferential rigidity of the inner shoulder blocks is ensured, and heel-and-toe wear of the inner shoulder blocks is suppressed. As a result, there is an advantage that the uneven wear resistance performance of the tire and the snow traction performance are compatible.

FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the invention taken along the tire meridian line. 2 is a plan view showing the tread surface of the pneumatic tire shown in FIG. 1. FIG. FIG. 3 is an enlarged view showing the shoulder land portion and the middle land portion of the pneumatic tire shown in FIG. 4 is an enlarged view showing the shoulder land portion shown in FIG. 3. FIG. FIG. 5 is an enlarged view showing a main part of the shoulder land portion shown in FIG. 6 is a cross-sectional view of the shoulder land portion shown in FIG. 4. FIG. 7 is an enlarged view showing the middle land portion shown in FIG. 3. FIG. 8 is a cross-sectional view of the middle land portion shown in FIG. 7. FIG. FIG. 9 is a chart showing results of performance tests of the pneumatic tire according to the embodiment of the invention. FIG. 10 is a chart showing results of performance tests of the pneumatic tire according to the embodiment of the invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious to replace. Moreover, the multiple modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a cross-sectional view along the tire meridian line showing a pneumatic tire 1 according to an embodiment of the present invention. This figure shows a cross-sectional view of one side area in the tire radial direction. Also, FIG. 1 shows, as an example of the pneumatic tire 1, a heavy-duty radial tire mounted on a drive shaft of a vehicle for long-distance transportation such as a truck or a bus.

In the figure, the cross section in the tire meridian direction is defined as a cross section when the tire is cut along a plane including the tire rotation axis (not shown). Also, the tire equatorial plane CL is defined as a plane that passes through the midpoint of the measurement points of the tire cross-sectional width defined in JATMA and is perpendicular to the tire rotation axis. 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 around the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, and a tread rubber 15. , a pair of sidewall rubbers 16, 16 and a pair of rim cushion rubbers 17, 17 (see FIG. 1).

A pair of bead cores 11, 11 are formed by winding one or a plurality of steel bead wires in a ring-shaped manner, 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 composed of a lower filler 121 and an upper filler 122, and are arranged on the tire radial direction outer peripheries of the pair of bead cores 11, 11 to reinforce the bead portions.

The carcass layer 13 has a single layer structure consisting of one carcass ply or a multilayer structure consisting of a plurality of laminated carcass plies. configure. Further, both ends of the carcass layer 13 are wound back outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12 and are locked. In addition, the carcass ply of the carcass layer 13 is configured by rolling a plurality of carcass cords made of steel coated with a coating rubber, and the absolute value of the cord angle is 80 [deg] or more and 90 [deg] or less (tire circumferential direction is defined as the longitudinal inclination angle of the carcass cord with respect to

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144 and is placed around the outer circumference of the carcass layer 13 . These belt plies 141 - 144 include a high angle belt 141 , a pair of cross belts 142 , 143 and a belt cover 144 . The high-angle belt 141 is configured by rolling a plurality of steel belt cords coated with a coating rubber, and has an absolute value of 45 degrees or more and 70 degrees or less of the cord angle (belt cord angle with respect to the tire circumferential direction). defined as the longitudinal tilt angle). The pair of cross belts 142 and 143 is formed by coating a plurality of steel belt cords with coat rubber and rolling the cords, and has a cord angle of 10 [deg] or more and 55 [deg] or less in absolute value. The pair of cross belts 142 and 143 have cord angles of opposite signs, and are laminated with the longitudinal directions of the belt cords crossing each other (having a so-called cross-ply structure). The belt cover 144 is formed by coating a plurality of belt cover cords made of steel or organic fiber material with coat rubber and rolling the cords, and has a cord angle of 10 [deg] or more and 55 [deg] or less in absolute value.

The tread rubber 15 is arranged on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to constitute the tread portion of the tire. A pair of sidewall rubbers 16, 16 are arranged outside the carcass layer 13 in the tire width direction, respectively, and constitute left and right sidewall portions. The pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction to the outer side in the tire width direction of the turn-up portions of the left and right bead cores 11, 11 and the carcass layer 13, and constitute rim fitting surfaces of the bead portions.

[Tread surface]
FIG. 2 is a plan view showing the tread surface of the pneumatic tire 1 shown in FIG. The figure shows the tread surface of an all-season tire. In the figure, the tire circumferential direction refers to the direction around the tire rotation axis. Further, reference character T is a tire contact edge, and dimension symbol TW is a tire contact width.

As shown in FIG. 2, the pneumatic tire 1 has a plurality of main grooves 21, 22 extending in the tire circumferential direction and a plurality of land portions 31 to 33 partitioned by the main grooves 21, 22. Prepare for the face.

The main groove is a groove required to display a wear indicator defined by JATMA, and has a groove width of 6.0 [mm] or more and a groove depth of 10 [mm] or more. 2, the groove widths Wg1 and Wg2 (see FIG. 2) of the main grooves 21 and 22 are in the range of 3% or more and 4% or less with respect to the tire contact width TW.

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

Groove depth is measured as the distance from the tread surface to the bottom of the groove when the tire is mounted on a specified rim and filled with a specified internal pressure in an unloaded state. In addition, in a configuration having a partial bottom portion, a sipe, or an uneven portion at the groove bottom, the groove depth is measured excluding these.

A specified rim means a "standard rim" specified by JATMA, a "design rim" specified by TRA, or a "measuring rim" specified by ETRTO. In addition, the prescribed internal pressure means the "maximum air pressure" prescribed by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" prescribed by TRA, or "INFLATION PRESSURES" prescribed by ETRTO. In addition, the specified load means the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. However, according to JATMA, in the case of passenger car tires, the specified internal pressure is 180 [kPa], and the specified load is 88 [%] of the maximum load capacity at the specified internal pressure.

For example, in the configuration of FIG. 2, four main grooves 21 and 22 are arranged symmetrically with the tire equatorial plane CL as a boundary. Five rows of land portions 31 to 33 are partitioned by these main grooves 21 and 22 . One land portion 33 is arranged on the tire equatorial plane CL.

However, the present invention is not limited to this, and three or five main grooves may be arranged (not shown). Also, the land portion may be arranged at a position away from the tire equatorial plane CL (not shown).

Here, of the main grooves 21 and 22 arranged in one region bounded by the tire equatorial plane CL, the outermost main groove 21 in the tire width direction is defined as the shoulder main groove, and the other main grooves 22 are defined as shoulder main grooves. is defined as the center main groove.

In the configuration of FIG. 2, the distance from the tire equatorial plane CL to the groove center lines of the left and right shoulder main grooves 21, 21 (dimension symbols omitted in the drawing) is 26% or more and 32% of the tire contact width TW. It is in the following range. Further, the distance from the tire equatorial plane CL to the groove centerlines of the left and right center main grooves 22, 22 is in the range of 8% or more and 12% or less of the tire contact width TW.

A groove centerline is defined as an imaginary line connecting the midpoints of the distance measurement points between opposing groove walls.

The tire contact width TW is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim, the specified internal pressure is applied, the tire is placed perpendicular to the flat plate in the stationary state, and the load corresponding to the specified load is applied. measured as the maximum linear distance in the axial direction of the tire.

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

Further, land portions 31, 31 on the outside in the tire width direction defined by the shoulder main grooves 21, 21 are defined as shoulder land portions. The shoulder land portions 31, 31 are the outermost land portions in the tire width direction and are located on the tire ground contact edge T. As shown in FIG. Also, the land portions 32, 32 on the inner side in the tire width direction defined by the shoulder main grooves 21, 21 are defined as middle land portions. The middle land portions 32 , 32 are adjacent to the shoulder land portion 31 with the shoulder main groove 21 interposed therebetween. Further, the land portion 33 located closer to the tire equatorial plane CL than the middle land portions 32, 32 is defined as the center land portion. The center land portion 33 may be arranged on the tire equatorial plane CL (see FIG. 2), or may be arranged at a position off the tire equatorial plane CL (not shown).

2, a pair of shoulder land portions 31, 31, a pair of middle land portions 32, 32, and a single center land portion 33 are defined. . Further, for example, in a configuration with five or more main grooves, two or more rows of center land portions are defined (not shown), and in a configuration with three main grooves, the middle land portion also serves as the center land portion ( not shown).

Further, in FIG. 2, the maximum contact widths Wb1, Wb2, Wb3 of the land portions 31, 32, 33 are in the range of 15% to 25% of the tire contact width TW. 2, the maximum ground contact width Wb1 of the shoulder land portion 31 is the widest, and the maximum ground contact width Wb3 of the center land portion 33 is the narrowest. Further, it is preferable that the maximum ground contact width Wb2 of the middle land portion 32 and the maximum ground contact width Wb1 of the shoulder land portion 31 have a relationship of 0.75≤Wb2/Wb1≤0.87, and 0.79≤Wb2/ It is more preferable to have a relationship of Wb1≦0.83.

The ground contact width of the land part is the width between the land part and the flat plate when the tire is mounted on the specified rim, the specified internal pressure is applied, and the load corresponding to the specified load is applied by placing the tire perpendicular to the flat plate in the stationary state. It is measured as a linear distance in the axial direction of the contact surface of the tire.

[Zigzag shape of main groove]
FIG. 3 is an enlarged view showing the shoulder land portion 31 and the middle land portion 32 of the pneumatic tire shown in FIG.

As shown in FIG. 3, the shoulder main groove 21 and the center main groove 22 have a zigzag shape with amplitude in the tire width direction.

Moreover, the shoulder main groove 21 has a zigzag shape formed by alternately connecting long portions and short portions that are inclined in different directions with respect to the tire circumferential direction. In FIG. 3, it is preferable that the circumferential length Lg1 of the zigzag elongated portion has a relationship of 0.60≤Lg1/λ1≤0.90 with respect to the wavelength λ1 of the zigzag shape, which is 0.65. It is more preferable to have a relationship of ≦Lg1/λ1≦0.80. Moreover, the amplitude A1 of the zigzag shape has a relationship of 0.02≦A1/TW≦0.04 with respect to the tire contact width TW.

The zigzag wave length and amplitude are measured using the groove centerline as the measuring point.

Further, the center main groove 22 has a zigzag shape formed by alternately connecting linear portions inclined in different directions with respect to the tire circumferential direction. In FIG. 3, the circumferential length Lg2 of these linear portions preferably has a relationship of 0.30≦Lg2/λ2≦0.70 with respect to the wavelength λ2 of the zigzag shape, and 0.35≦Lg2. /λ2≦0.65 is more preferable. Therefore, it is preferable that the center main groove 22 has a zigzag shape formed by connecting straight portions of approximately the same length. Also, the amplitude A2 of the zigzag shape of the center main groove 22 has a relationship of 0.02≦A2/TW≦0.04 with respect to the tire contact width TW. Also, the number of pitches of the zigzag shape of the center main groove 22 is equal to the number of pitches of the zigzag shape of the shoulder main grooves 21 .

In the configuration of FIG. 3, as described above, the shoulder main groove 21 has a zigzag shape in which long portions and short portions are alternately connected, and the center main groove 22 is a straight portion having substantially the same length. It has a zigzag shape formed by connecting With such a configuration, the rigidity of the edge portion of the center land portion 33 on the tire equatorial plane CL side is ensured, and uneven wear of the center land portion 33 is suppressed. On the other hand, the traction performance of the tread shoulder region is improved, effectively enhancing the snow performance of the tire. As a result, both snow performance and uneven wear resistance performance of the tire are achieved.

However, the present invention is not limited to this, and both the shoulder main groove 21 and the center main groove 22 may have a zigzag shape (not shown) in which long portions and short portions are alternately connected, or substantially the same. It may have a zigzag shape formed by connecting straight portions of length.

2, the zigzag shapes of the shoulder main groove 21 and the center main groove 22 have a see-through structure when viewed in the tire circumferential direction. Therefore, the edge portions of the adjacent land portions 31, 32; 32, 33 do not overlap each other when viewed in the tire circumferential direction. As a result, the groove volumes of the shoulder main grooves 21 and the center main grooves 22 are ensured, and the snow traction performance of the tire is improved.

[Shoulder land part]
FIG. 4 is an enlarged view showing the shoulder land portion 31 shown in FIG. FIG. 5 is an enlarged view showing a main portion of the shoulder land portion 31 shown in FIG. FIG. 6 is a cross-sectional view of the shoulder land portion 31 shown in FIG. This figure shows a sectional view in the groove depth direction along the outer shoulder lug groove 312 , the circumferential narrow groove 311 and the inner shoulder lug groove 313 .

As shown in FIG. 3 , the shoulder land portion 31 includes a single circumferential narrow groove 311 , a plurality of outer shoulder lug grooves 312 , a plurality of inner shoulder lug grooves 313 , a plurality of outer shoulder blocks 314 , and a plurality of outer shoulder blocks 314 . and an inner shoulder block 315 of.

The circumferential narrow groove 311 extends in the tire circumferential direction and continuously extends over the entire circumference of the shoulder land portion 31 . Further, the distance D11 from the tire contact edge T to the groove center line of the circumferential narrow groove 311 is in the range of 0.30≦D11/Wb1≦0.70 with respect to the maximum contact width Wb1 of the shoulder land portion 31, It is preferably in the range of 0.40≤D11/Wb1≤0.60. Therefore, the circumferential narrow groove 311 is arranged in the central portion of the shoulder land portion 31 in the tire width direction.

Further, in FIG. 4, the circumferential narrow groove 311 has a zigzag shape formed by connecting linear portions of approximately the same length. Further, the circumferential length L11 of the zigzag linear portion has a relationship of 0.30≦L11/λ11≦0.70 with respect to the wavelength λ11 of the zigzag shape, and 0.45≦L11/λ11≦0.45≦L11/λ11≦0.70. It is preferred to have 65 relationships. In addition, the zigzag amplitude of the circumferential narrow grooves 311 (dimension symbols omitted in the drawing) is smaller than the zigzag amplitude A1 of the shoulder main groove 21 (see FIG. 3). Also, the number of pitches of the zigzag shape of the circumferential narrow grooves 311 is equal to the number of pitches of the zigzag shape of the shoulder main grooves 21 (see FIG. 3).

4, the maximum groove width W11 of the circumferential narrow groove 311 and the maximum contact width Wb1 of the shoulder land portion 31 have a relationship of 0.025≦W11/Wb1≦0.045. Moreover, the maximum groove width W11 of the circumferential narrow groove 311 is in the range of W11≦3.0 [mm]. 6, the maximum groove depth H11 of the circumferential narrow groove 311 and the maximum groove depth Hg1 of the shoulder main groove 21 have a relationship of 0.55≦H11/Hg1≦0.75. As a result, the circumferential narrow grooves 311 are properly closed when the tire touches the ground, and the rigidity of the shoulder land portion 31 is ensured.

As shown in FIG. 3 , the outer shoulder lug grooves 312 extend in the tire width direction and connect the tire contact edge T and the circumferential narrow grooves 311 . Specifically, the outer shoulder lug groove 312 connects to the maximum amplitude position of the zigzag-shaped circumferential narrow groove 311 toward the tire ground contact edge T side. A plurality of outboard shoulder lug grooves 312 are arranged at predetermined intervals in the tire circumferential direction.

5, the opening width W12 of the outer shoulder lug groove 312 with respect to the circumferential narrow groove 311 is in the range of 12.0 [mm]≦W12≦18.0 [mm]. 6, the maximum groove depth H12 of the outer shoulder lug grooves 312 and the maximum groove depth Hg1 of the shoulder main grooves 21 have a relationship of 0.95≦H12/Hg1≦1.45.

As shown in FIG. 3 , the inner shoulder lug grooves 313 extend in the tire width direction and connect the shoulder main grooves 21 and the circumferential narrow grooves 311 . Specifically, the inner shoulder lug grooves 313 are arranged such that the zigzag-shaped maximum amplitude of the circumferential narrow grooves 311 toward the tire equatorial plane CL side and the zigzag-shaped maximum amplitude of the shoulder main groove 21 toward the tire ground contact edge T side. Connect with the position. A plurality of inner shoulder lug grooves 313 are arranged at predetermined intervals in the tire circumferential direction. Further, the opening position of the inner shoulder lug groove 313 with respect to the circumferential narrow groove 311 is offset in the tire circumferential direction with respect to the opening position of the outer shoulder lug groove 312 with respect to the circumferential narrow groove 311 .

3, the inclination angle θ13 of the inner shoulder lug groove 313 with respect to the tire circumferential direction is in the range of 73 [deg]≦θ13≦83 [deg]. In addition, in the configuration of FIG. 3 , the inner shoulder lug groove 313 is inclined in the opposite direction to the zigzag-shaped long portion of the shoulder main groove 21 in the tire circumferential direction.

The inclination angle of the lug groove is measured as an angle formed by a straight line parallel to the tire circumferential direction and an imaginary straight line connecting the center points of the left and right openings of the lug groove.

5, the opening width W13 of the inner shoulder lug groove 313 with respect to the circumferential narrow groove 311 is in the range of 6.0 [mm]≦W13≦10.0 [mm]. Further, the opening width W12 of the outer shoulder lug groove 312 with respect to the circumferential narrow groove 311 and the opening width W13 of the inner shoulder lug groove 313 with respect to the circumferential narrow groove 311 satisfy the relationship of 1.50≦W12/W13≦2.20. It is more preferable to have a relationship of 1.70≦W12/W13≦2.00.

6, the maximum groove depth H13 of the inner shoulder lug groove 313 and the maximum groove depth Hg1 of the shoulder main groove 21 have a relationship of 0.55≦H13/Hg1≦0.75. Also, the maximum groove depth H13 of the inner shoulder lug grooves 313 is shallower than the maximum groove depth H12 of the outer shoulder lug grooves 312 (H13<H12).

In addition, as shown in FIG. 6 , the inner shoulder lug groove 313 has a bottom upper portion 3131 formed at the connecting portion to the circumferential narrow groove 311 . Further, the distance H13′ from the tread surface of the shoulder land portion 31 to the top surface of the bottom portion 3131 of the inner shoulder lug groove 313 is 0.45≦H13′/Hg1≦with respect to the maximum groove depth Hg1 of the shoulder main groove 21. have a relationship of 0.65. Further, it is preferable that the distance H13' of the bottom portion 3131 and the maximum groove depth H11 of the circumferential narrow groove 311 have a relationship of 0.65≤H13'/H11≤0.90. Therefore, it is preferable that the distance H<b>13 ′ of the bottom portion 3131 is shallower than the maximum groove depth H<b>11 of the circumferential narrow groove 311 . This ensures the rigidity of the inner shoulder block 315 (see FIG. 4).

In addition, not limited to this, the bottom portion 3131 of the inner shoulder lug groove 313 may be omitted (not shown).

The outer shoulder blocks 314 are partitioned into outer shoulder lug grooves 312 and circumferential narrow grooves 311, as shown in FIG. A plurality of outboard shoulder blocks 314 are arranged at predetermined intervals in the tire circumferential direction.

Further, as shown in FIG. 4 , the edge portion of the outer shoulder block 314 on the side of the circumferential narrow groove 311 has a zigzag shape along the circumferential narrow groove 311 . Also, the edge portion of one outer shoulder block 314 on the side of the circumferential narrow groove 311 has a W shape with two convex portions and a single concave portion. Also, the maximum contact length L14 of the outer shoulder block 314 has a relationship of 1.45≦L14/λ11≦1.85 with respect to the zigzag-shaped wavelength λ11 of the circumferential narrow groove 311 .

Further, the maximum contact length L14 and the maximum contact width W14 of the outer shoulder blocks 314 have a relationship of 2.70≦L14/W14≦3.30. Further, the maximum contact width W14 of the outer shoulder block 314 and the maximum contact width Wb1 of the shoulder land portion 31 have a relationship of 0.40≦W14/Wb1≦0.60.

The maximum ground contact length and maximum contact width of the block are measured when the tire is mounted on the specified rim, the specified internal pressure is applied, and the block is placed vertically on a flat plate in a stationary state and a load corresponding to the specified load is applied. It is measured as the maximum linear distance in the tire circumferential direction and the tire axial direction at the contact surface between the tire and the flat plate.

Also, as shown in FIG. 4, the outboard shoulder block 314 has a single circumferential sipe 316 . Circumferential sipes 316 extend circumferentially of the tire and terminate at their ends in outboard shoulder blocks 314 . In addition, the length of the circumferential sipe 316 extending in the tire circumferential direction (dimension symbols omitted in the drawing) is 40% or more and 50% or less of the maximum circumferential length L14 of the outer shoulder block 314. in the range of On the other hand, the outer shoulder blocks 314 do not have sipes or grooves that connect to the circumferential grooves 311 . Therefore, the outboard shoulder blocks 314 are not divided by sipes or narrow grooves, and have tread surfaces that are continuous in the tire circumferential direction.

The sipe is a cut formed in the tread surface, and has a sipe width of less than 1.5 [mm] and a sipe depth of 2.0 [mm] or more, so that the sipe closes when the tire touches the ground.

The sipe width is measured as the maximum opening width of the sipe on the tread surface in a no-load state in which the tire is mounted on a specified rim and filled with a specified internal pressure.

The sipe depth is measured as the distance from the tread surface to the sipe bottom when the tire is mounted on a specified rim and filled with a specified internal pressure in an unloaded state. In addition, in a configuration in which the sipe has a partial bottom portion, an uneven portion, or an uneven portion on the sipe bottom, the sipe depth is measured excluding these portions.

As shown in FIG. 3, the inner shoulder blocks 315 are divided into inner shoulder lug grooves 313 and circumferential narrow grooves 311. A plurality of inner shoulder blocks 315 are arranged at predetermined intervals in the tire circumferential direction. Also, the number of pitches of the inner shoulder blocks 315 is equal to the number of pitches of the zigzag shape of the circumferential narrow grooves 311 and the shoulder main grooves 21 .

Further, as shown in FIG. 4, the left and right edge portions of the inner shoulder block 315 have a V-shape that protrudes toward the circumferential narrow groove 311 and the shoulder main groove 21 side. 4, the shoulder main groove 21 has a zigzag shape formed by alternately connecting the long portions and the short portions as described above. has an asymmetrical shape in the tire circumferential direction.

Also, three inner shoulder blocks 315 face one outer shoulder block 314 with the circumferential narrow groove 311 interposed therebetween. That is, one long outer shoulder block 314 extends in the tire circumferential direction across three short inner shoulder blocks 315 . 4, of the three inner shoulder blocks 315, the central inner shoulder block 315 faces the outer shoulder block 314 along the entire edge portion on the side of the circumferential narrow groove 311. . In addition, one inner shoulder block 315 arranged in front and behind in the tire circumferential direction faces two adjacent outer shoulder blocks 314 with the circumferential narrow groove 311 interposed therebetween.

In the above configuration, (1) the shoulder land portion 31 has the outer shoulder lug groove 312 and the inner shoulder lug groove 313, so that the edge component of the shoulder land portion 31 is secured and the snow traction performance of the tire is improved. (2) Since the inner shoulder block 315 faces the long outer shoulder block 314 with the circumferential narrow groove 311 interposed therebetween, when the circumferential narrow groove 311 is closed when the tire touches the ground, the inner shoulder block 315 are supported by outer shoulder blocks 314 with high circumferential stiffness. This reduces heel-and-toe wear of the inner shoulder block 315 . As a result, both the uneven wear resistance performance and the snow traction performance of the tire are achieved.

4, the maximum contact length L15 and the maximum contact width W15 of the inner shoulder block 315 have a relationship of 1.10≦L15/W15≦1.50, and 1.20≦L15/W15. It is preferred to have a relationship ≦1.40. Therefore, the inner shoulder block 315 has an elongated shape in the tire circumferential direction. Further, the maximum contact width W15 of the inner shoulder block 315 and the maximum contact width Wb1 of the shoulder land portion 31 have a relationship of 0.50≦W15/Wb1≦0.65.

4, it is preferable that the maximum contact length L15 of the inner shoulder block 315 and the maximum contact length L14 of the outer shoulder block 314 have a relationship of 0.45≦L15/L14≦0.65, It is more preferable to have a relationship of 0.50≦L15/L14≦0.60. Also, the total number of pitches of the inner shoulder blocks 315 is twice the number of pitches of the outer shoulder blocks 314 .

In the configuration of FIG. 4, one of the three inner shoulder blocks 315 facing one outer shoulder block 314 as described above, one inner shoulder block 315 arranged in front and behind in the tire circumferential direction Two adjacent outer shoulder blocks 314 , 314 are opposed to each other at a portion of the edge portion on the narrow groove 311 side.

At this time, as shown in FIG. 5, the sum of opposing lengths Ld1 and Ld2 in the tire circumferential direction between one inner shoulder block 315 and two adjacent outer shoulder blocks 314 is the circumferential length of the inner shoulder block 315. L15 preferably has a relationship of 0.40≦(Ld1+Ld2)/L15, and more preferably has a relationship of 0.50≦(Ld1+Ld2)/L15. Also, each of the facing lengths Ld1 and Ld2 is preferably 15% or more of the circumferential length L15 of the inner shoulder block 315. As shown in FIG. As a result, the inner shoulder block 315 is properly supported by the two outer shoulder blocks 314 when the circumferential narrow groove 311 is closed when the tire touches the ground. The upper limit of the ratio (Ld1+Ld2)/L15 is not particularly limited, but is restricted by the opening width W12 (see FIG. 5) of the outer shoulder lug grooves 312 with respect to the circumferential narrow grooves 311 .

5, the overlap amount Dd in the tire width direction between the outer shoulder block 314 and the inner shoulder block 315 has a relationship of 0.050≦Dd/W15 with respect to the maximum contact width W15 of the inner shoulder block 315. It is more preferable to have a relationship of 0.070≦Dd/W15. This ensures a contact width between the inner shoulder blocks 315 and the outer shoulder blocks 314 when the circumferential narrow grooves 311 are closed when the tire touches the ground. Although the upper limit of the ratio Dd/W15 is not particularly limited, it is restricted by the upper limit of the amplitude of the circumferential fine groove 311 .

4, the medial shoulder block 315 has a single open sipe 317 and a pair of closed sipes 318,318. The open sipe 317 is arranged in the central portion of the inner shoulder block 315 and penetrates the inner shoulder block 315 in the tire width direction. The pair of closed sipes 318 , 318 are arranged respectively in front and rear regions in the tire circumferential direction of the inner shoulder block 315 partitioned by the open sipe 317 , and both end portions terminate within the inner shoulder block 315 .

Note that in the configuration of FIG. 4, all of the sipes 316-318 have a wavy shape. However, not limited to this, some or all of the sipes may have a straight shape (not shown).

[Middle Land]
FIG. 7 is an enlarged view showing the middle land portion 32 shown in FIG. FIG. 8 is a cross-sectional view of the middle land portion 32 shown in FIG. This figure shows a sectional view in the groove depth direction along the middle lug groove 321A.

As shown in FIG. 3, the middle land portion 32 includes first and second middle lug grooves 321A and 321B and a plurality of middle blocks 322. As shown in FIG.

The first and second middle lug grooves 321</b>A, 321</b>B extend in the tire width direction, penetrate the middle land portion, and open into the shoulder main groove 21 and the center main groove 22 . The first and second middle lug grooves 321A, 321B have different groove depths. Specifically, the maximum groove depth H21A of the first middle lug groove 321A is deeper than the maximum groove depth H21B of the second middle lug groove 321B (H21B<H21A; see FIG. 8). This point will be described later.

Further, as shown in FIG. 3, the opening of the first middle lug groove 321A on the side of the tire contact edge T is arranged at a position offset from the outer shoulder lug groove 312 of the shoulder land portion 31 as viewed in the tire width direction. be. Further, the opening of the second middle lug groove 321B on the side of the tire contact edge T is arranged at a position overlapping the outer shoulder lug groove 312 of the shoulder land portion 31 as viewed in the tire width direction. In the configuration of FIG. 3, the first and second middle lug grooves 321A, 321B are alternately arranged in the tire circumferential direction.

In addition, the inclination angle θ21 of the first and second middle lug grooves 321A and 321B with respect to the tire circumferential direction is in the range of 50[deg]≦θ21≦80[deg]. In the configuration of FIG. 3, the first and second middle lug grooves 321A and 321B are inclined in the same direction in the tire circumferential direction with respect to the long zigzag-shaped portion of the shoulder main groove 21. 31 is slanted in the opposite direction to the inner shoulder lug groove 313 of 31 .

As shown in FIG. 7, the first and second middle lug grooves 321A and 321B have a shape in which the groove width narrows toward the tire equatorial plane CL side. In the configuration of FIG. 7, one (lower in the drawing) edge portion of the middle lug grooves 321A and 321B has a step shape, and the other (upper in the drawing) edge portion has a linear or arc shape. 321A and 321B have a shape in which the groove width is narrowed toward the tire equatorial plane CL side.

In FIG. 7, the opening width W21c of the middle lug grooves 321A and 321B on the tire equatorial plane CL side (that is, the center main groove 22 side) and the opening width W21t on the tire ground contact edge T side (that is, the shoulder main groove 21 side) are It is preferable to have a relationship of 0.30≦W21c/W21t≦0.60 and a relationship of 0.40≦W21c/W21t≦0.50. Further, it is preferable that the opening width W21c on the side of the tire equatorial plane CL is in the range of W21c≦4.0 [mm].

7, the extension length D21' of the narrow width portions (reference numerals omitted in the drawing) of the middle lug grooves 321A and 321B in the tire width direction is 0.00% with respect to the maximum contact width Wb2 of the middle land portion 32. It has a relationship of 20≤D21'/Wb2≤0.40. The narrow portions of the middle lug grooves 321A and 321B are defined as continuous regions having a groove width of 60% or less with respect to the opening width W21t on the tire contact edge T side. In the configuration of FIG. 7, the area from the opening of the middle lug grooves 321A, 321B on the tire equatorial plane CL side to the step-shaped raised portion is the narrow width portion.

Also, in FIG. 8, as described above, the maximum groove depth H21A of the first middle lug groove 321A is deeper than the maximum groove depth H21B of the second middle lug groove 321B (H21B<H21A). Therefore, the first middle lug groove 321A located in the central portion of the outer shoulder block 314 of the shoulder land portion 31 in the tire circumferential direction has a relatively deep groove depth. Specifically, the maximum groove depth H21B of the second middle lug groove 321B has a relationship of 0.60≦H21B/H21A≦0.80 with respect to the maximum groove depth H21A of the first middle lug groove 321A. Thereby, the circumferential rigidity of the shoulder land portion 31 and the middle land portion 32 is made uniform.

Further, the maximum groove depth H21A of the first middle lug groove 321A and the maximum groove depth Hg1 of the shoulder main groove 21 have a relationship of H21A/Hg1≦1.00, and a relationship of H21A/Hg1≦0.90. It is preferred to have Further, the maximum groove depth H21B of the second middle lug groove 321B and the maximum groove depth Hg1 of the shoulder main groove 21 have a relationship of 0.80≦H21B/Hg1 and a relationship of 0.70≦H21B/Hg1. is preferred. Although the lower limit of the ratio H21A/Hg1 and the upper limit of the ratio H21B/Hg1 are not particularly limited, they are restricted by the range of the ratio H21B/H21A.

Further, as shown in FIG. 8, the middle lug grooves 321A and 321B have a bottom portion 3211 on the groove bottom portion on the tire equatorial plane CL side. Specifically, the bottom portion 3211 is formed in the narrow portion described above. Further, the distance H21' from the tread surface of the middle land portion 32 to the top surface of the bottom portion 3211 of the middle lug grooves 321A and 321B is 0.50≤H21'/Hg1≤ with respect to the maximum groove depth Hg1 of the shoulder main groove 21. have a relationship of 0.65.

As shown in FIG. 3, the middle block 322 is partitioned into adjacent first and second middle lug grooves 321A and 321B. A plurality of middle blocks 322 are arranged at predetermined intervals in the tire circumferential direction. Also, the number of pitches of the middle blocks 322 is equal to the number of pitches of the inner shoulder blocks 315 of the shoulder land portion 31 .

Further, as shown in FIG. 7, the left and right edge portions of the middle block 322 have a V-shape that protrudes toward the shoulder main groove 21 side and the center main groove 22 side. In addition, in the configuration of FIG. 7, the shoulder main groove 21 has a zigzag shape formed by alternately connecting the long portions and the short portions as described above. The V shape has an asymmetrical shape in the tire circumferential direction.

7, the maximum contact length L22 and the maximum contact width W22 of the middle block 322 have a relationship of 1.10≤L22/Wb2≤1.40, and 1.20≤L22/Wb2≤1.40. It is preferred to have a relationship of 1.30. Therefore, the middle block 322 has an elongated shape in the tire width direction.

Also, as shown in FIG. 7, the middle block 322 has a single open sipe 323 and a pair of closed sipes 324,324. The open sipe 323 is arranged in the central portion of the middle block 322 and penetrates the middle block 322 in the tire width direction. The pair of closed sipes 324 , 324 are arranged respectively in front and rear regions in the tire circumferential direction of the middle block 322 partitioned by the open sipe 323 , and both end portions terminate within the middle block 322 .

[Center Rikubu]
As shown in FIG. 2, the center land portion 33 includes a plurality of center lug grooves 331 penetrating the center land portion 33 in the tire width direction, and a plurality of center blocks 332 partitioned by the center lug grooves 331. Prepare. Also, the direction of inclination of the center lug groove 331 with respect to the tire circumferential direction is opposite to the direction of inclination of the middle lug grooves 321A and 321B of the middle land portion 32 . Further, the opening position of the center lug groove 331 with respect to the center main groove 22 is offset in the tire circumferential direction with respect to the opening positions of the middle lug grooves 321A and 321B of the middle land portion 32 . Further, in the configuration of FIG. 2, the center lug groove 331 has a stepped bent shape.

Also, as shown in FIG. 2, the center block 332 has a single open sipe and a pair of closed sipes (reference numerals omitted in the drawing). The open sipe is arranged in the central portion of the center block 332 and penetrates the center block 332 in the tire width direction. The pair of closed sipes are arranged in front and rear regions in the tire circumferential direction of the center block 332 partitioned by the open sipe, and both end portions of the closed sipes terminate within the center block 332 .

[effect]
As described above, the pneumatic tire 1 is divided into a plurality of main grooves 21, 22 extending in the tire circumferential direction and the shoulder main groove 21, which is the outermost of the main grooves 21, 22 in the tire width direction. A shoulder land portion 31 and a middle land portion 32 are provided (see FIG. 2). In addition, the shoulder land portion 31 includes a single circumferential narrow groove 311 extending in the tire circumferential direction, a plurality of outer shoulder lug grooves 312 connecting the tire contact edge T and the circumferential narrow groove 311, and shoulder main grooves. 21 and the circumferential narrow grooves 311, a plurality of outer shoulder blocks 314 partitioned by the outer shoulder lug grooves 312 and the circumferential narrow grooves 311, the inner shoulder lug grooves 313 and the circumferential narrow grooves 311. and a plurality of inner shoulder blocks 315 defined by directional slots 311 (see FIG. 3). Also, one outer shoulder block 314 faces three inner shoulder blocks 315 with the circumferential narrow groove 311 interposed therebetween. Also, the maximum contact length L15 and the maximum contact width W15 of the inner shoulder block 315 have a relationship of 1.10≦L15/W15≦1.50 (see FIG. 4).

In the above configuration, (1) the shoulder land portion 31 has the outer shoulder lug groove 312 and the inner shoulder lug groove 313, so that the edge component of the shoulder land portion 31 is secured and the snow traction performance of the tire is improved. (2) Since the inner shoulder block 315 faces the long outer shoulder block 314 with the circumferential narrow groove 311 interposed therebetween, when the circumferential narrow groove 311 is closed when the tire touches the ground, the inner shoulder block 315 are supported by outer shoulder blocks 314 with high circumferential stiffness. As a result, the inner shoulder blocks 315 are reinforced, and heel-and-toe wear of the inner shoulder blocks 315 (including uneven wear of block edges and uneven wear originating from sipes) is suppressed. (3) Since the inner shoulder blocks 315 have an elongated shape in the tire circumferential direction, the circumferential rigidity of the inner shoulder blocks 315 is ensured, and heel-and-toe wear of the inner shoulder blocks 315 is suppressed. . As a result, there is an advantage that the uneven wear resistance performance of the tire and the snow traction performance are compatible.

Further, in the pneumatic tire 1, the maximum groove width W11 of the circumferential narrow groove 311 has a relationship of 0.025≤W11/Wb1≤0.045 with respect to the maximum contact width Wb1 of the shoulder land portion 31 (Fig. 4). There is an advantage that the function of the circumferential narrow groove 311 as a groove is ensured by the above lower limit. With the above upper limit, there is an advantage that the circumferential narrow groove 311 is properly closed when the tire touches the ground, and the reinforcing action of the inner shoulder block 315 by the outer shoulder block 314 is ensured.

Further, in the pneumatic tire 1, the circumferential narrow grooves 311 have a zigzag shape with amplitude in the tire width direction (see FIG. 4). In such a configuration, when the circumferential narrow grooves 311 are closed when the tire touches the ground, meshing force is generated in the tire circumferential direction, so there is an advantage that the reinforcing effect of the outer shoulder blocks 314 on the inner shoulder blocks 315 is effectively enhanced. In addition, there is an advantage that edge components in the tire circumferential direction of the circumferential narrow grooves 311 are increased and the snow traction of the tire is improved.

In the pneumatic tire 1, the opening width W12 of the outer shoulder lug groove 312 with respect to the circumferential narrow groove 311 is 1.50≦W12/1.50≦W12/ It has a relationship of W13≦2.20 (see FIG. 5). As a result, there is an advantage that the sum of the groove opening widths of the regions on the tire ground contact edge T side defined by the circumferential narrow grooves 311 and the sum of the groove opening widths on the tire equatorial plane CL side are balanced.

In addition, in the pneumatic tire 1, the inner shoulder lug groove 313 has a bottom upper portion 3131 formed at a connecting portion to the circumferential narrow groove 311 (see FIG. 6). This has the advantage of reinforcing the rigidity of the inner shoulder block 315 .

Further, in the pneumatic tire 1, the outer shoulder block 314 has a tread that is continuous in the tire circumferential direction and is not divided by sipes or grooves. This has the advantage of ensuring the rigidity of the outer shoulder blocks 314 .

Further, in the pneumatic tire 1, the maximum contact length L14 and the maximum contact width W14 of the outer shoulder block 314 have a relationship of 2.70≦L14/W14≦3.30 (see FIG. 4). As a result, there is an advantage that the outer shoulder blocks 314 are secured in the circumferential direction, and the heel-and-toe wear of the outer shoulder blocks 314 is suppressed.

Also, in the pneumatic tire 1, the facing length in the tire circumferential direction between one inner shoulder block 315 and two adjacent outer shoulder blocks 314, which are arranged in the front and rear in the tire circumferential direction among the three inner shoulder blocks 315, is The sum of Ld1 and Ld2 has a relationship of 0.40≦(Ld1+Ld2)/L15 with respect to the circumferential length L15 of the inner shoulder block 315 (see FIG. 5). This has the advantage that one inner shoulder block 315 is properly supported by two adjacent outer shoulder blocks 314 when the tire touches the ground.

In the pneumatic tire 1, the overlap amount Dd between the outer shoulder blocks 314 and the inner shoulder blocks 315 in the tire width direction is 0.050≦Dd/W15 with respect to the maximum contact width W15 of the inner shoulder blocks 315. (see Figure 5). Thereby, there is an advantage that the contact width between the inner shoulder block 315 and the outer shoulder block 314 is ensured when the circumferential narrow groove 311 is closed when the tire touches the ground.

Further, in the pneumatic tire 1, the middle land portion 32 includes a plurality of middle lug grooves 321A and 321B penetrating the middle land portion 32 in the tire width direction (see FIG. 2). Also, the middle lug grooves 321A and 321B have a shape in which the groove width narrows toward the tire equatorial plane CL (see FIG. 7). Further, the opening width W21c of the middle lug grooves 321A and 321B on the tire equatorial plane CL side and the opening width W21t on the tire ground contact edge T side have a relationship of 0.30≦W21c/W21t≦0.60. In such a configuration, the middle lug grooves 321A and 321B have a shape in which the groove width narrows toward the tire equatorial plane CL side, so that the rigidity of the middle block 322 is appropriately reinforced and heel-and-toe wear of the middle block 322 is prevented. has the advantage of being suppressed.

Further, in the pneumatic tire 1, the middle land portion 32 includes first and second middle lug grooves 321A and 321B penetrating the middle land portion 32 in the tire width direction (see FIG. 3). Further, the opening of the first middle lug groove 321A on the side of the tire contact edge T is arranged at a position offset from the outer shoulder lug groove 312 of the shoulder land portion 31 as viewed in the tire width direction. Further, the opening of the second middle lug groove 321B on the side of the tire contact edge T is arranged at a position overlapping the outer shoulder lug groove 312 of the shoulder land portion 31 as viewed in the tire width direction. Also, the maximum groove depth H21A of the first middle lug groove 321A has a relationship of H21B<H21A with respect to the maximum groove depth H21B of the second middle lug groove 321B. With such a configuration, the maximum groove depths H21A and H21B of the first and second middle lug grooves 321A and 321B are optimized according to the positional relationship with the wide outer shoulder lug grooves 312. There is an advantage that the circumferential rigidity of the land portion 32 is made uniform.

Further, in the pneumatic tire 1, the maximum contact width Wb2 of the middle land portion 32 and the maximum contact width Wb1 of the shoulder land portion 31 have a relationship of 0.75≦Wb2/Wb1≦0.87 (see FIG. 2). reference). As a result, there is an advantage that the maximum contact width Wb2 of the middle land portion 32 is optimized.

Further, in the pneumatic tire 1, the shoulder main groove 21 has a zigzag shape formed by alternately connecting long portions and short portions. Also, the circumferential length Lg1 of the elongated portion has a relationship of 0.60≦Lg1/λ1≦0.90 with respect to the wavelength λ1 of the zigzag shape (see FIG. 3). As a result, there is an advantage that the rigidity of the trend portion shoulder region is increased and the heel-and-toe wear of the land portions 31 and 32 is suppressed.

Further, in this pneumatic tire 1, the center main groove 22 has a zigzag shape formed by connecting straight portions of approximately the same length, and the circumferential length Lg2 of the straight portions is 0.30≦Lg2/λ2≦0.70 (see FIG. 3). As a result, there is an advantage that the traction performance of the tread portion shoulder region is improved and the snow traction performance of the tire is effectively enhanced.

Also, this pneumatic tire 1 is a heavy-duty tire mounted on a drive shaft of a vehicle (see FIG. 1). By applying such a heavy-duty tire, there is an advantage that the effect of improving snow traction performance and uneven wear resistance performance of the tire can be effectively obtained.

9 and 10 are charts showing the results of performance tests of the pneumatic tire according to the embodiment of the invention.

In this performance test, multiple types of test tires were evaluated for (1) snow traction performance and (2) uneven wear resistance performance. Also, a test tire having a tire size of 11R22.5 is mounted on a JATMA specified rim, and the JATMA specified internal pressure and load are applied to the test tire. Also, the test tire is mounted on the drive shaft of the 2-D (two-wheel drive) tractor head, which is the test vehicle.

(1) Snow traction performance is evaluated by running a test vehicle on a snowy road surface of a snow road test site and measuring the acceleration time from 5 [km/h] to 20 [km/h]. Then, based on this measurement result, index evaluation is performed with the conventional example as the standard (100). This evaluation is so preferable that the numerical value is large.

(2) Evaluation of uneven wear resistance performance is performed by measuring the heel-and-toe wear amount after the test vehicle has traveled 30,000 [km] on a predetermined paved road and performing an index evaluation. This evaluation is performed by index evaluation with the conventional example as a standard (100), and the larger the value, the better.

The test tire of the example has the configuration shown in FIGS. and The maximum groove widths Wg1 and Wg2 of the main grooves 21 and 22 are 8.3 [mm], and the maximum groove depths Hg1 and Hg2 of the main grooves 21 and 22 are 21.4 [mm]. Further, the tire contact width TW is 240 [mm], and the maximum contact width Wb1 of the shoulder land portion 31 is 53.5 [mm]. Also, the zigzag-shaped wavelength λ1 of the shoulder main groove 21 is 45.1 [mm]. Also, the maximum groove depth H21A of the first middle lug groove 321A is 12.4 [mm].

1 and 2, the conventional test tire has a structure in which the inner shoulder block 315 of the shoulder land portion 31 is elongated in the tire width direction.

As can be seen from the test results, the test tires of the examples have both snow traction performance and uneven wear resistance performance.

1 pneumatic tire; 11 bead core; 12 bead filler; 121 lower filler; 122 upper filler; 13 carcass layer; Rubber; 17 rim cushion rubber; 21 shoulder main groove; 22 center main groove; 31 shoulder land portion; 311 circumferential narrow groove; 312 outer shoulder lug groove; 32 middle land part; 33 center land part; 321A first middle lug groove; 321B second middle lug groove; 3211 bottom upper part; 322 middle block; Lug groove; 332 center block

Claims (16)

A pneumatic tire comprising a plurality of main grooves extending in the tire circumferential direction, and a shoulder land portion and a middle land portion defined by the outermost shoulder main grooves in the tire width direction of the main grooves. ,
The shoulder land portion includes a single circumferential narrow groove extending in the tire circumferential direction, a plurality of outer shoulder lug grooves connecting the tire contact edge and the circumferential narrow groove, the shoulder main groove and the circumferential narrow groove. a plurality of inner shoulder lug grooves connecting the narrow grooves; a plurality of outer shoulder blocks partitioned by the outer shoulder lug grooves and the circumferential narrow grooves; and a plurality of outer shoulder blocks partitioned by the inner shoulder lug grooves and the circumferential narrow grooves. a plurality of inner shoulder blocks consisting of
one of the outer shoulder blocks faces the three inner shoulder blocks across the circumferential narrow groove ;
The maximum contact length L15 and the maximum contact width W15 of the inner shoulder blocks have a relationship of 1.10≦L15/W15≦1.50, and
A pneumatic tire , wherein the maximum groove width W11 of the circumferential narrow groove has a relationship of 0.025≦W11/Wb1≦0.045 with respect to the maximum ground contact width Wb1 of the shoulder land portion. The pneumatic tire according to claim 1 , wherein the circumferential narrow grooves have a zigzag shape with amplitude in the tire width direction. The opening width W12 of the outer shoulder lug groove with respect to the circumferential narrow groove has a relationship of 1.50≦W12/W13≦2.20 with respect to the opening width W13 of the inner shoulder lug groove with respect to the circumferential narrow groove. The pneumatic tire according to claim 1 or 2 . The pneumatic tire according to any one of claims 1 to 3 , wherein the inner shoulder lug groove has a bottom portion formed at a connecting portion to the circumferential narrow groove. The pneumatic tire according to any one of claims 1 to 4 , wherein the outer shoulder blocks have a continuous tread in the tire circumferential direction that is not divided by sipes or grooves. The pneumatic tire according to any one of claims 1 to 5 , wherein the maximum contact length L14 and the maximum contact width W14 of the outer shoulder blocks have a relationship of 2.70≤L14/W14≤3.30. The sum of opposing lengths Ld1 and Ld2 in the tire circumferential direction between one inner shoulder block and two adjacent outer shoulder blocks, which are arranged fore and aft in the tire circumferential direction among the three inner shoulder blocks, is the inner shoulder The pneumatic tire according to any one of claims 1 to 6 , having a relationship of 0.40≤(Ld1+Ld2)/L15 with respect to the circumferential length L15 of the block. The overlap amount Dd between the outer shoulder blocks and the inner shoulder blocks in the tire width direction has a relationship of 0.050≦Dd/W15 with respect to the maximum contact width W15 of the inner shoulder blocks. A pneumatic tire according to any one of the above. the middle land portion includes a plurality of middle lug grooves penetrating the middle land portion in the tire width direction;
The middle lug groove has a shape with a groove width narrowing toward the tire equatorial plane side,
The middle lug groove according to any one of claims 1 to 8 , wherein an opening width W21c on the tire equatorial plane side and an opening width W21t on the tire grounding edge side of the middle lug groove have a relationship of 0.30≤W21c/W21t≤0.60. Pneumatic tires as described. the middle land portion includes first and second middle lug grooves penetrating the middle land portion in the tire width direction,
the opening of the first middle lug groove on the side of the tire grounding edge is arranged at a position offset from the outer shoulder lug groove of the shoulder land portion as viewed in the tire width direction,
The opening of the second middle lug groove on the side of the tire contact edge is arranged at a position overlapping the outer shoulder lug groove of the shoulder land portion as viewed in the tire width direction, and
The pneumatic tire according to any one of claims 1 to 9 , wherein the maximum groove depth H21A of the first middle lug grooves has a relationship of H21B<H21A with respect to the maximum groove depth H21B of the second middle lug grooves. . The maximum contact width Wb2 of the middle land portion and the maximum contact width Wb1 of the shoulder land portion are in a relationship of 0.75≦Wb2/Wb1≦ 0.87 . pneumatic tires. The shoulder main groove has a zigzag shape in which long portions and short portions are alternately connected, and the circumferential length Lg1 of the long portion is 0.60 with respect to the wavelength λ1 of the zigzag shape. The pneumatic tire according to any one of claims 1 to 11 , having a relationship of ≤Lg1/λ1≤0.90. The center main groove has a zigzag shape formed by connecting straight portions of substantially the same length, and the circumferential length Lg2 of the straight portion is 0.30≦Lg2/ with respect to the wavelength λ2 of the zigzag shape. 13. The pneumatic tire according to claim 12 , having a relationship of λ2≦0.70. The pneumatic tire according to any one of claims 1 to 13 , which is a heavy-duty tire mounted on a drive shaft of a vehicle. A pneumatic tire comprising a plurality of main grooves extending in the tire circumferential direction, and a shoulder land portion and a middle land portion defined by the outermost shoulder main grooves in the tire width direction of the main grooves. ,
The shoulder land portion includes a single circumferential narrow groove extending in the tire circumferential direction, a plurality of outer shoulder lug grooves connecting the tire contact edge and the circumferential narrow groove, the shoulder main groove and the circumferential narrow groove. a plurality of inner shoulder lug grooves connecting the narrow grooves; a plurality of outer shoulder blocks partitioned by the outer shoulder lug grooves and the circumferential narrow grooves; and a plurality of outer shoulder blocks partitioned by the inner shoulder lug grooves and the circumferential narrow grooves. a plurality of inner shoulder blocks consisting of
one of the outer shoulder blocks faces the three inner shoulder blocks across the circumferential narrow groove ;
The maximum contact length L15 and the maximum contact width W15 of the inner shoulder blocks have a relationship of 1.10≦L15/W15≦1.50, and
The opening width W12 of the outer shoulder lug groove with respect to the circumferential narrow groove has a relationship of 1.50≦W12/W13≦2.20 with respect to the opening width W13 of the inner shoulder lug groove with respect to the circumferential narrow groove. A pneumatic tire characterized by: A pneumatic tire comprising a plurality of main grooves extending in the tire circumferential direction, and a shoulder land portion and a middle land portion defined by the outermost shoulder main grooves in the tire width direction of the main grooves. ,
The shoulder land portion includes a single circumferential narrow groove extending in the tire circumferential direction, a plurality of outer shoulder lug grooves connecting the tire contact edge and the circumferential narrow groove, the shoulder main groove and the circumferential narrow groove. a plurality of inner shoulder lug grooves connecting the narrow grooves; a plurality of outer shoulder blocks partitioned by the outer shoulder lug grooves and the circumferential narrow grooves; and a plurality of outer shoulder blocks partitioned by the inner shoulder lug grooves and the circumferential narrow grooves. a plurality of inner shoulder blocks consisting of
one of the outer shoulder blocks faces the three inner shoulder blocks across the circumferential narrow groove ;
The maximum contact length L15 and the maximum contact width W15 of the inner shoulder blocks have a relationship of 1.10≦L15/W15≦1.50, and
A pneumatic tire , wherein the outer shoulder block has a tread that is continuous in the tire circumferential direction and is not divided by sipes or grooves .

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