阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 高野宏和 于 2019-07-08 设计创作，主要内容包括：本发明的充气轮胎能够提高雪上行驶时的牵引性。充气轮胎(1)具有包括胎面端(Te)的胎肩陆地部(6)。胎肩陆地部(6)包括：从胎面端(Te)延伸的多个胎肩横沟(8)、被胎肩横沟(8)划分出的胎肩花纹块要素(9)、以及从胎肩陆地部(6)的轮胎轴向的外表面(6s)向轮胎轴向外侧隆起的凸部(10)。凸部(10)包括：多个沿轮胎径向延伸的第一凸部(12)、和在胎肩横沟(8)的轮胎径向内侧并且至少将两个第一凸部(12、12)的轮胎径向内侧部相互连结的第二凸部(13)。(The pneumatic tire of the present invention can improve traction during snow travel. The pneumatic tire (1) has a tire shoulder land portion (6) including a tread end (Te). The tire shoulder land portion (6) includes: a plurality of shoulder transverse grooves (8) extending from the tread end (Te), shoulder pattern block elements (9) divided by the shoulder transverse grooves (8), and convex parts (10) protruding from the outer surface (6s) of the shoulder land part (6) in the tire axial direction to the outer side in the tire axial direction. The convex part (10) comprises: the tire has a plurality of first protrusions (12) extending in the tire radial direction, and a second protrusion (13) located on the tire radial direction inner side of the shoulder lateral groove (8) and connecting at least the tire radial direction inner side portions of the two first protrusions (12, 12) to each other.)

1. A pneumatic tire having a tread portion, characterized in that,

the tread portion includes a shoulder land portion including a tread end,

the shoulder land portion includes: a plurality of shoulder transverse grooves extending from the tread end to the inner side of the tire axial direction, a plurality of shoulder pattern block elements divided by the shoulder transverse grooves, and a convex part protruding from the outer surface of the shoulder land part in the tire axial direction to the outer side of the tire axial direction,

the convex portion includes: first protrusions provided corresponding to the plurality of shoulder block elements, respectively, and extending in the tire radial direction; and a second convex portion extending in the tire circumferential direction on the inner side in the tire radial direction of the shoulder lateral groove and connecting the inner side portions in the tire radial direction of at least two of the first convex portions to each other.

2. A pneumatic tire according to claim 1,

the protruding portion is U-shaped when being observed from the front, and is composed of: two of the first convex portions, and one of the second convex portions connecting the two first convex portions.

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

the tire shoulder transverse groove comprises:

a first shoulder lateral groove having the second convex portion formed on the inner side in the tire radial direction; and

and a second shoulder lateral groove on the inner side of the tire radial direction of which the second convex part is not formed.

4. A pneumatic tire according to claim 3,

the first shoulder lateral grooves and the second shoulder lateral grooves are alternately arranged in the tire circumferential direction.

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

the first protrusion has a width in the tire circumferential direction smaller than a length in the tire circumferential direction of the shoulder block element.

6. A pneumatic tire according to claim 5,

the width of the first convex portion in the tire circumferential direction is 20% -60% of the length of the shoulder block element in the tire circumferential direction.

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

the height of the protrusion is 2.5-6.0 mm.

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

the side surface of the first convex portion bulges along a normal direction of the outer surface or bulges in a tapered shape at an angle of 45 ° or less with respect to the normal direction when viewed in a cross section along the tire circumferential direction.

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

the first protrusions connected to each other by the second protrusions have inner edges extending in the tire radial direction on the shoulder axial groove side,

the inner edge has an angle of 10 DEG or less with respect to the radial direction of the tire.

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

the first convex portion includes: the first convex portion of the same width that extends in the tire radial direction with the width of the tire circumferential direction being constant, and the first convex portion of the non-same width that makes the width of the tire circumferential direction change and extends in the tire radial direction.

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

the second convex portion and at least two of the first convex portions each have an inward edge disposed on the innermost side in the tire radial direction,

each of the inward-facing edges extends in the tire circumferential direction.

12. A pneumatic tire according to claim 11,

the inward edges of the second protrusions and the inward edges of at least two of the first protrusions form a curved line of a circular arc shape.

Technical Field

The present invention relates to a pneumatic tire suitable for snow travel.

Background

Patent document 1 proposes a pneumatic tire in which polygonal blocks are formed by dividing grooves in an outer surface region from a width-direction end portion of a tread surface to a side wall portion. Such a pneumatic tire provided with polygonal blocks can exhibit edge effects in a plurality of directions, and improve the turning performance on snow on a snowy road surface.

Patent document 1: japanese patent No. 6139843

However, in the pneumatic tire described above, there is room for further improvement in improvement of traction performance during straight running on snow.

Disclosure of Invention

The present invention has been made in view of the above problems, and a main object of the present invention is to provide a pneumatic tire capable of improving traction performance during snow traveling.

The pneumatic tire of the present invention has a tread portion, wherein the tread portion includes a shoulder land portion including a tread end, the shoulder land portion including: a plurality of shoulder lateral grooves extending inward in the tire axial direction from the tread end, a plurality of shoulder block elements partitioned by the shoulder lateral grooves, and a convex portion bulging outward in the tire axial direction from an outer surface of the shoulder land portion in the tire axial direction, the convex portion including: first protrusions provided corresponding to the plurality of shoulder block elements, respectively, and extending in the tire radial direction; and a second convex portion extending in the tire circumferential direction on the inner side in the tire radial direction of the shoulder lateral groove and connecting the inner side portions in the tire radial direction of at least two of the first convex portions to each other.

In the pneumatic tire according to the present invention, the convex portion is preferably U-shaped when viewed from the front, and includes: two of the first convex portions, and one of the second convex portions connecting the two first convex portions.

In the pneumatic tire according to the present invention described in claim 1 or 2, the shoulder lateral groove includes: a first shoulder lateral groove having the second convex portion formed on the inner side in the tire radial direction; and a second shoulder lateral groove on the inner side of the tire radial direction, wherein the second convex part is not formed.

In the pneumatic tire according to the present invention, the first shoulder lateral grooves and the second shoulder lateral grooves are preferably alternately arranged in the tire circumferential direction.

In the pneumatic tire according to the present invention, it is preferable that the first convex portion has a width in the tire circumferential direction smaller than a length of the shoulder block element in the tire circumferential direction.

In the pneumatic tire according to the present invention, it is preferable that the width of the first convex portion in the tire circumferential direction is 20% to 60% of the length of the shoulder block element in the tire circumferential direction.

In the pneumatic tire of the present invention, preferably, the height of the projection is 2.5 to 6.0 mm.

In the pneumatic tire according to the present invention, it is preferable that the side surface of the first convex portion bulges in a normal direction of the outer surface or bulges in a tapered shape at an angle of 45 ° or less with respect to the normal direction when viewed in a cross section along the tire circumferential direction.

In the pneumatic tire according to the present invention, it is preferable that the first protrusions connected to each other by the second protrusions have inner edges extending in the tire radial direction on the shoulder axial groove side, and an angle of the inner edges with respect to the tire radial direction is 10 ° or less.

In the pneumatic tire of the present invention, preferably, the first convex portion includes: the first convex portion of the same width that extends in the tire radial direction with the width of the tire circumferential direction being constant, and the first convex portion of the non-same width that makes the width of the tire circumferential direction change and extends in the tire radial direction.

In the pneumatic tire according to the present invention, it is preferable that the second convex portion and at least two of the first convex portions have inward edges disposed on the innermost side in the tire radial direction, and each of the inward edges extends in the tire circumferential direction.

In the pneumatic tire according to the present invention, it is preferable that the inward edge of the second convex portion and the inward edges of at least two of the first convex portions form a single arc-shaped curve.

The pneumatic tire of the present invention includes a convex portion that bulges outward in the tire axial direction from the outer surface of the tire shoulder land portion in the tire axial direction. The convex portion includes: the tire has a first convex portion extending in the tire radial direction, and a second convex portion connecting inner side portions in the tire radial direction of at least two of the first convex portions to each other. When such a pneumatic tire travels on snow, the tread portion sinks into the road surface on the snow, and therefore the first convex portion and the second convex portion enter the snow. The at least two first projections and the second projections joining them compact the snow of the road surface. This compacted snow mass is sheared by said first projection, whereby the tyre generates a greater traction. In addition, the second protrusion extends in the tire circumferential direction on the inner side in the tire radial direction of the shoulder lateral groove. Therefore, the snow column formed by the shoulder transverse groove and the snow block compacted by the convex part can be connected along the axial direction of the tire to form a large snow column, and further large traction force can be generated.

Drawings

Fig. 1 is a partial cross-sectional view showing one embodiment of a pneumatic tire of the present invention.

Fig. 2 is a perspective view of the shoulder land portion.

Fig. 3 is a schematic view of the convex portion as viewed from the front.

Fig. 4 is a sectional view taken along line a-a of fig. 2.

Fig. 5 is a development view of a shoulder land portion of another embodiment.

Description of reference numerals: 1 … pneumatic tire; 6 … shoulder land portion; 6s … outer surface; 8 … shoulder transverse grooves; 9 … shoulder block elements; 10 … protrusions; 12 … a first protrusion; 13 … second projection; te … tread end.

Detailed Description

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a radial cross-sectional view of a tire in a right half portion including a tire rotation axis (not shown) in a normal state of a pneumatic tire (hereinafter, sometimes simply referred to as "tire") 1 according to the present embodiment. In the present embodiment, a tire for a passenger car is shown as a preferable embodiment. However, the present invention includes a light truck tire and a heavy truck tire, and can be applied to other types of tires 1.

The "normal state" is a state in which the tire 1 rim is assembled to a normal rim (not shown) and is filled with normal internal pressure and no load. In the present specification, unless otherwise specified, the dimensions and the like of each portion of the tire 1 are values measured in this normal state.

The "regular Rim" is a Rim that defines the specification for each tire in a specification system including the specification that the tire 1 conforms to, and is, for example, "standard Rim" in the case of JATMA, "Design Rim" in the case of TRA, and "Measuring Rim" in the case of ETRTO.

The "normal internal pressure" is an air pressure specified for each TIRE in a specification system including the specification which the TIRE 1 conforms to, and is "maximum air pressure" in case of JATMA, the maximum value described in the table "TIRE LOAD limitor pressure inside TIREs" in case of TRA, and "INFLATION pressure" in case of ETRTO.

The tire 1 of the present embodiment includes: the tire has a tread portion 2 and a pair of side wall portions 3 extending inward in the tire radial direction from both end portions of the tread portion 2. The tire 1 is reinforced by, for example, a carcass 4 extending in a ring shape and a belt layer 5 disposed on the outer side of the carcass 4 in the tire radial direction and inside the tread portion 2.

In the present embodiment, the tread portion 2 includes a shoulder land portion 6. The shoulder land portion 6 of the present embodiment includes a tread end Te, and is formed on the outer side in the tire axial direction of the shoulder main groove G adjacent to the tread end Te. In the present embodiment, the shoulder land portions 6 are provided on both sides of the tread portion 2. The shoulder land portion 6 includes, for example, a tread surface 6a that contacts the road surface and an outer surface 6s in the tire axial direction. The outer surface 6s of the present embodiment extends from the tread end Te toward the inner side in the tire radial direction while being connected to the tread surface 6 a.

The "tread end Te" is set to a ground contact position on the two outermost sides in the tire axial direction when a normal load is applied to the tire 1 in a normal state and ground contact is made at a 0 degree camber angle as a plane.

The "normal LOAD" is a LOAD for each TIRE, which is defined in the above specification, and is a maximum LOAD CAPACITY in case of JATMA, a maximum value described in a table "TIRE LOAD conditions AT variatus color requirements" in case of TRA, and a "LOAD CAPACITY" in case of ETRTO.

Fig. 2 is a perspective view of the shoulder land portion 6. As shown in fig. 2, the shoulder land portion 6 includes a plurality of shoulder lateral grooves 8, a plurality of shoulder block elements 9 partitioned by the shoulder lateral grooves 8, and a convex portion 10 that bulges outward in the tire axial direction from an outer surface 6s of the shoulder land portion 6. In the present embodiment, a plurality of shoulder lateral grooves 8, shoulder block elements 9, and protrusions 10 are provided on the shoulder land portions 6, 6 on both sides, respectively.

The convex portion 10 of the present embodiment includes: a plurality of first convex portions 12 extending in the tire radial direction, and a second convex portion 13 connecting inner side portions of at least two first convex portions 12 in the tire radial direction to each other. When the tire 1 runs on snow, the tread portion 2 sinks into the snow road surface. Therefore, the first convex portions 12 and the second convex portions 13 enter snow, and the two first convex portions 12 and the second convex portions 13 connecting the two first convex portions 12 compact the snow on the road surface. In particular, the second projections 13 apply a load in the vertical direction to the snow as indicated by reference numeral F in the drawing, and therefore the snow can be strongly compacted. The compacted snow mass is sheared by the first projections 12 extending in the radial direction of the tyre, so that the tyre 1 generates a greater traction.

The first protrusion 12 is provided corresponding to each of the shoulder block elements 9. Specifically, at least one, in the present embodiment, one first protrusion 12 is provided for each shoulder block element 9. In this way, in the present embodiment, since the convex portions 10 are provided over the entire circumference of the tire, the traction force during snow travel can be effectively improved.

The second protrusion 13 extends in the tire circumferential direction on the inner side in the tire radial direction of the shoulder lateral groove 8. Thus, the snow column formed by the shoulder transverse groove 8 and the snow lump compacted by the convex portion 10 can be connected in the tire axial direction to form a large snow column. Therefore, a larger traction force can be generated.

In the present embodiment, the protruding portion 10 has a U-shape in front view, and includes: two first protrusions 12, and one second protrusion 13 connecting the two first protrusions 12. Such a convex portion 10 can shear a snow lump by an arbitrary first convex portion 12, regardless of the tire rotation direction. Such a convex portion 10 can also suppress an excessive increase in the mass of the tire 1 due to the convex portion 10, and can improve the running performance. The convex portion 10 is not limited to this form, and may be formed in a lateral E-shape (not shown) in front view, for example, by three first convex portions 12 and two second convex portions 13 connecting the three first convex portions 12.

In the present embodiment, the convex portion 10 includes: a wall surface 15 rising from the outer surface 6s, and an outward surface 16 surrounded by the wall surface 15 and facing outward in the tire axial direction. In the present embodiment, the wall surface 15 includes: a side surface 17 extending in the tire radial direction, and a circumferential surface 18 extending in the tire circumferential direction.

Fig. 3 is a schematic view of the projection 10 as viewed from the front. Fig. 3 shows the tread end Te curved in the tire circumferential direction in a straight line for convenience of explanation. As shown in fig. 3, the side surface 17 of the first convex portion 12 includes: a first side surface 19 connected to the second convex portion 13, and a second side surface 20 disposed on the outermost side of the convex portion 10 in the tire circumferential direction. The circumferential surface 18 of the first convex portion 12 includes: a first circumferential surface 21 on the tread end Te side, and a second circumferential surface 22 disposed on the tire radial direction inner side of the first circumferential surface 21. The circumferential surface 18 of the second convex portion 13 includes: a third circumferential surface 23 connecting the second circumferential surfaces 22, 22 and a fourth circumferential surface 24 connecting the first side surfaces 19, 19.

The first circumferential surface 21 preferably extends, for example, in the tire circumferential direction in order to smoothly shear snow. In addition, the fourth circumferential surface 24 preferably extends, for example, in the tire circumferential direction in order to effectively compact the snow lump. In the present embodiment, the first circumferential surface 21 and the fourth circumferential surface 24 extend along the tread end Te and in the tire circumferential direction.

In the present embodiment, the first projecting portion 12 is formed such that the width W1 in the tire circumferential direction is smaller than the length L1 in the tire circumferential direction of the shoulder block element 9. This can ensure a large volume of the snow lump formed by the first convex portion 12 and the second convex portion 13, and thus can generate a large traction force. In addition, an excessive increase in the mass of the tire 1 due to the convex portion 10 can be suppressed.

If the width W1 of the first convex portion 12 is excessively reduced, the rigidity of the first convex portion 12 is reduced, and the shearing force against snow may be reduced. Therefore, the width W1 of the first protrusion 12 is preferably 20% to 60% of the length L1 of the shoulder block element 9.

As shown in fig. 2, the first convex portion 12 and the second convex portion 13 have inward edges 12e and 13e, respectively, which are disposed on the innermost side in the tire radial direction. These respective inward edges 12e, 13e extend in the tire circumferential direction. Such inward edges 12e, 13e suppress an excessive increase in the mass of the tire 1. In the present specification, the inward edge 12e is an edge between the outer surface 6s and the second circumferential surface 22, and the inward edge 13e is an edge between the outer surface 6s and the third circumferential surface 23. In the present embodiment, the inward edges 12e, 13e extend parallel to the tread end Te.

In the present embodiment, the inward edges 12e, 12e of the two first convex portions 12 forming the convex portion 10 and the inward edge 13e of the second convex portion 13 form a single arc-shaped curve. Thereby more effectively performing the above-described functions. The inward edges 12e and 13e are not limited to this form, and may be displaced in the tire radial direction (not shown), for example.

Fig. 4 is a sectional view taken along line a-a of fig. 2. Line A-A is along the tire circumferential direction. As shown in FIG. 4, the protrusion 10 preferably has a height h of 2.5 to 6.0 mm. In the case where the rise height h of the convex portion 10 is less than 2.5mm, the volume of the snow lump is reduced, so that it is possible to reduce the traction force. When the bulge height h exceeds 6.0mm, the mass of the tire 1 increases, and the running performance may be deteriorated.

The first side surface 19 is preferably raised in the normal direction n of the outer surface 6s or raised in a tapered shape at an angle α 1 of 45 ° or less with respect to the normal direction n, whereby snow lumps compacted by the first convex portion 12 and the second convex portion 13 can be smoothly sheared, and a large traction force can be generated, and further, during running on snow, snow enters between the second side surfaces 20, 20 facing each other in the tire circumferential direction of the adjacent convex portions 10, 10 in the tire circumferential direction, and the snow lumps are formed, and for smoothly shearing the snow lumps, the second side surface 20 is also preferably raised in the normal direction n of the outer surface 6s or raised in a tapered shape at an angle α 2 of 45 ° or less with respect to the normal direction n.

As shown in fig. 3, the first protrusions 12 connected to each other by the second protrusions 13 have inner edges 25 extending in the tire radial direction on the shoulder lateral groove 8 side. The angle θ 1 of the inner edge 25 with respect to the tire radial direction is preferably 10 ° or less. In the case where the angle θ 1 of the inner edge 25 exceeds 10 °, the shearing force with respect to the snow lump compacted by the first convex portion 12 and the second convex portion 13 is reduced, and there is a possibility that a large traction force cannot be generated. The inner edge 25 is an edge of the first side surface 19 connected to the outer surface 6 s.

From the same viewpoint, the angle θ 2 of the outer edge 26 of the first convex portion 12 extending in the tire radial direction with respect to the tire radial direction is preferably 10 ° or less. The outer edge 26 is the edge where the second side surface 20 is connected to the outer surface 6 s.

The tire radial direction length Lm of the convex portion 10 is preferably 28% to 35% of the tire cross-sectional height (not shown). The height Lm is preferably the same at the projections 10 of the shoulder land portions 6 on both sides. This makes the load applied to the convex portions 10 of the shoulder land portions 6 on both sides uniform, and thus vehicle slip can be suppressed. The "tire section height" described above is a value calculated by using the product of "the general term of section width" and "the general term of the deviation ratio/100" indicated in the tire size expression.

The tire radial direction length L2 of the first side surface 19 is preferably 0.5 times or more, more preferably 1.5 times or more, and still more preferably 2.0 times or more the tire radial direction length L3 of the second convex portion 13. The tire radial direction length L2 of the first side surface 19 is preferably 5.0 times or less, more preferably 4.5 times or less, and still more preferably 4.0 times or less the tire radial direction length L3 of the second convex portion 13. This allows the first convex portion 12 and the second convex portion 13 to effectively compact the snow lump and smoothly shear the snow lump by the first convex portion 12.

When the tire circumferential direction length (shortest length) L5 between the convex portions 10, 10 adjacent in the tire circumferential direction is small, for example, the volume of snow formed between the convex portions 10, 10 is reduced, and a large traction force may not be generated. When the length L5 is large, for example, the width W1 of the first convex portion 12 is reduced, and there is a possibility that the shearing force against the snow lump is reduced. Therefore, the length L5 is preferably 70% or more, more preferably 80% or more, further preferably 130% or less, and more preferably 120% or less of the width W1 of the first convex portion 12.

In the present embodiment, the convex portion 10 is formed at a position further inward in the tire radial direction than the tread end Te. This prevents the convex portion 10 from coming into contact with the road surface during running on an asphalt road surface, for example, and therefore, the wear of the convex portion 10 can be suppressed. The distance La in the tire radial direction between the outer end (first circumferential surface 21)10e of the convex portion 10 in the tire radial direction and the tread end Te is preferably about 5mm or less, for example. The projection 10 is not limited to this form, and may be formed to extend from the tread end Te toward the inner side in the tire radial direction, for example.

The shoulder lateral groove 8 of the present embodiment extends inward in the tire axial direction from the tread end Te. In the present embodiment, the shoulder transverse groove 8 includes: a first shoulder lateral groove 8A having a second convex portion 13 formed on the inner side in the tire radial direction, and a second shoulder lateral groove 8B having no second convex portion 13 formed on the inner side in the tire radial direction. Such a tire 1 can maintain high running performance because an increase in mass thereof can be suppressed.

In the present embodiment, the shoulder lateral groove 8 is formed by alternately arranging the first shoulder lateral groove 8A and the second shoulder lateral groove 8B in the tire circumferential direction. This enables the above-described effects to be more effectively exhibited.

As shown in fig. 2, in the present embodiment, the shoulder lateral groove 8 is connected to the shoulder main groove G. Such shoulder lateral grooves 8 can form a large snow column in the groove, and therefore can improve traction force when running on snow. In this case, the shoulder block element 9 is formed as a shoulder block 9A. The shoulder lateral groove 8 is not limited to this form, and may be formed so as to have a terminal end in the shoulder land portion 6 without being connected to the shoulder main groove G, for example.

In the present embodiment, the shoulder lateral groove 8 includes: a pair of first lateral groove portions 8a, 8a disposed on both sides in the tire axial direction, and a second lateral groove portion 8b sandwiched by the pair of first lateral groove portions 8a, 8a and inclined at a larger angle with respect to the tire axial direction than the first lateral groove portion 8 a. Such a shoulder lateral groove 8 can cancel the air column resonance transmitted from the shoulder main groove G by the groove wall of the second lateral groove portion 8b, for example, and therefore can improve the noise performance. The shoulder lateral groove 8 is not limited to this form, and may extend straight, for example.

As shown in fig. 3, in the present embodiment, the groove bottom 8s of the shoulder lateral groove 8 is located inward in the tire radial direction from the first circumferential surface 21. Thus, the shearing force of the first projecting portion 12 acts not only on the snow lump compacted by the first projecting portion 12 and the second projecting portion 13 but also on the snow pillar formed by the shoulder lateral groove 8 connected thereto, and these snow lumps can be sheared more effectively.

The shoulder transverse groove 8 is not particularly limited, but the width Wg thereof is preferably about 4.5 to 9.0mm, and the depth Hg thereof is preferably about 7.5 to 9.5 mm.

Fig. 5 is a developed view of the shoulder land portion 6 of the tire 1 according to another embodiment of the present invention. The same components as those of the tire 1 of the present embodiment are denoted by the same reference numerals, and the description thereof is omitted. As shown in fig. 5, in this embodiment, the first convex portion 12 of the convex portion 10 includes: the first convex portion 30 of the equal width extending in the tire radial direction with the width in the tire circumferential direction being constant, and the first convex portion 31 of the unequal width extending in the tire radial direction with the width in the tire circumferential direction being varied. The first convex portions 30 of the same width constitute the first convex portions 12 on one side (right side in the figure) of the convex portions 10 in the tire circumferential direction, and the first convex portions 31 of different widths constitute the first convex portions 12 on the opposite side (left side in the figure) to the first convex portions 30 of the same width. The equal-width first convex portion 30 and the unequal-width first convex portion 31 are not limited to such an arrangement.

In this embodiment, the uniform-width first convex portions 30 are inclined toward the tire radial direction outer side and away from the non-uniform-width first convex portions 31. Such a constant-width first convex portion 30 facilitates the discharge of the snow mass compacted by the first convex portion 12 and the second convex portion 13 toward the road surface side. In this embodiment, the first side surface 19 and the second side surface 20 of the equal-width first convex portion 30 are inclined linearly toward the tire radial direction outer side.

In this embodiment, the width W1 in the tire circumferential direction of the unequal-width first convex portion 31 increases toward the tire radial direction outer side. Since the rigidity of the portion of the first convex portion 31 having such unequal width on the outer side in the tire radial direction near the road surface is increased, the shearing force can be increased, and therefore, the snow lump compacted by the first convex portion 12 and the second convex portion 13 can be sheared and discharged efficiently. The first side surfaces 19 of the first protrusions 31 having unequal widths extend linearly, for example, along the tire radial direction. The second side surface 20 of the unequal-width first convex portion 31 extends in a crank shape, for example, inclined outward in the tire radial direction in a direction away from the equal-width first convex portion 30. In this embodiment, the crank portions 31a of the second side surfaces 20 of the first protrusions 31 having different widths are arranged further outward in the tire radial direction than the fourth circumferential surfaces 24 of the second protrusions 13.

While the above description has been made of the particularly preferred embodiment of the present invention, the present invention is not limited to the illustrated embodiment, and can be modified into various embodiments.