JP2008120270A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively improve driving force when a vehicle turns on snow. <P>SOLUTION: A pneumatic tire has at least a raw of blocks BL1-BL4, in a tread portion 2, in which a plurality of blocks B are lined up in the tire circumferential direction by providing a plurality of longitudinal grooves Gm and Gs continuously extending in the tire circumferential direction and a plurality of transverse grooves g1-g4 crossing the longitudinal grooves. At least one of the blocks B is sectioned into main block pieces Bm on both sides in the tire circumferential direction, and a sub-block piece Bs which is approximately a wedge shape in a plan view formed between the main block pieces Bm, and a length in the tire circumferential direction of which gradually decreases from one side to another side in the tire axial direction, by a pair of sipings S1 and S2 oppositely extending with each other in the tire axial direction. A width of the sub-block piece Bs in the tire axial direction is smaller than a width of the main block piece Bm in the tire axial direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can improve turning performance on snow.

For example, a pneumatic tire such as a winter tire, a snow tire, or a studless tire having improved performance on snow has a large number of blocks defined by vertical grooves and horizontal grooves in the tread portion. And in this kind of tire, the drive property and turning performance on snow can be improved by raising the reaction force at the time of shearing the snow column compressed in those grooves. Patent Document 1 below has been proposed as an attempt to improve running performance on snow.
JP-A-2003-118321 discloses a block provided with a plurality of sipings extending substantially in parallel. Such siping can improve the performance on ice by removing the water film on the road surface by a wiping effect or a capillary phenomenon. However, the block provided with such siping is merely deformed in the lateral direction when a lateral force acts, and cannot obtain an effect of pressing the snow column in the lateral groove. In other words, it does not fully contribute to the turning performance on snow.

  The present invention has been devised in view of the above problems, and a block included in a block row is provided with a pair of sipings extending in opposite directions with respect to the tire axial direction and crossing the block. Based on the fact that the sub-block pieces in a plan view are roughly divided between sipings, when the lateral force is applied, this sub-block piece acts like a wedge to compress the snow column in the horizontal groove and turn on the snow. The main purpose is to provide a pneumatic tire capable of effectively increasing the driving force at the time.

  The invention according to claim 1 of the present invention is that the tread portion is provided with a plurality of vertical grooves extending continuously in the tire circumferential direction and a plurality of horizontal grooves crossing between the vertical grooves, whereby a plurality of blocks are formed. A pneumatic tire having at least one block row arranged in a tire circumferential direction, wherein at least one of the blocks extends in a direction opposite to each other with respect to the tire axial direction and crosses the block, thereby causing a tire circumferential direction. The main block pieces on both sides and the sub-block pieces that are formed between the main block pieces and have a tire circumferential direction length that gradually decreases from one side to the other side in the tire axial direction in a plan view and substantially wedge-shaped. In addition, the width of the sub-block piece in the tire axial direction is smaller than the width of the main block piece in the tire axial direction.

  According to a second aspect of the present invention, the sub-block piece includes an outer side wall surface that is located on the tread grounding end side and has a large tire circumferential length, and a tire equatorial side that is located on the tire equator side and the outer side wall surface. And a tire circumferential direction length of the sub-block piece gradually decreases from the outer side wall surface side toward the inner side wall surface side. 1. The pneumatic tire according to 1.

  According to a third aspect of the present invention, the main block piece has an outer side wall surface located on the tread grounding end side, and the outer side wall surface of the sub block piece is more tread than the side wall surface of the main block piece. The pneumatic tire according to claim 2, which is provided on a ground contact end side.

  According to a fourth aspect of the present invention, the outer side edge of the sub-block piece is substantially V-shaped or substantially trapezoidal and protrudes toward the tread grounding end side in plan view. Tire.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein the siping extends linearly and is inclined at an angle of 15 to 40 ° with respect to a tire axial direction.

  The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein a width of the lateral groove is 2.5 to 7.5% of a tread ground contact width.

  In the invention according to claim 7, the aspect ratio of the main block piece is 0.3 to 0.8, and the aspect ratio of the sub block piece is 0.2 to 0.7. The pneumatic tire according to any one of 6.

  In the present invention, at least one block provided in the tread portion is formed between a main block piece on both sides in the tire circumferential direction and a pair of the main block pieces by a pair of sipings extending in opposite directions with respect to the tire axial direction. The tire circumferential direction length is divided into sub-block pieces having a substantially wedge shape in a plan view that gradually decreases from one side in the tire axial direction toward the other side. Since the width of the sub-block piece in the tire axial direction is smaller than the width of the main block piece in the tire axial direction, the lateral rigidity is relatively small. Therefore, when receiving the lateral force, the sub-block piece can be deformed in the tire axial direction and be interrupted like a wedge between the main block pieces. Thereby, the main block piece can be pressed to the lateral groove side which each faces. By such an action, the snow column in the lateral groove is pressed, and as a result, the driving force during turning is increased.

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

  FIG. 1 shows a cross-sectional view of a normal state of the pneumatic tire 1 of the present embodiment. The normal state uniquely defines the posture of the tire, and is defined as an unloaded state in which the tire 1 is incorporated in the normal rim J and filled with the normal internal pressure. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA, “Design Rim” for TRA, and ETRTO If there is, “Measuring Rim”. Furthermore, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA and the table “TIRE LOAD LIMITS AT” is TRA. The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” if it is ETRTO, but if the tire is for passenger cars, it is uniformly 180 kPa.

  A pneumatic tire 1 includes a carcass 6 having at least one carcass ply 6A that is folded and locked by a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3, and a tire radial direction of the carcass 6 The belt layer 7 disposed outside and inside the tread portion 2 is shown in this embodiment for heavy loads used in heavy vehicles such as trucks and buses.

  In the present embodiment, the carcass 6 is formed from one carcass ply 6A. The carcass ply 6A is formed by covering a carcass cord with a topping rubber. Moreover, although a steel cord is used for the carcass cord, an organic fiber such as nylon, polyester, rayon, or aromatic polyamide may be used as necessary or depending on the tire category. It is desirable that the carcass cord is arranged to be inclined with respect to the tire equator C at an angle of 75 to 90 degrees, more preferably 80 to 90 degrees.

  The belt layer 7 includes, for example, a first belt ply 7A disposed on the innermost side in the tire radial direction in which a steel cord is inclined with respect to the tire equator C at an angle of, for example, about 40 to 70 °, and the tire equator C. On the other hand, the belt cord is composed of a plurality of belt plies composed of second to fourth belt plies 7B, 7C and 7D inclined at a small angle of 10 to 30 °.

  FIG. 2 shows a development view of the tread portion 2. The tread portion 2 is provided with a plurality of vertical grooves Gm, Gs extending continuously in the circumferential direction and a plurality of horizontal grooves g crossing between the vertical grooves, so that a large number of blocks B are partitioned.

  In the present embodiment, the vertical groove includes a main vertical groove Gm having a relatively large groove width GW1 and a sub-vertical groove Gs having a relatively small groove width GW2. The groove width GW1 measured in the tire axial direction of the main longitudinal groove Gm is not particularly limited, but preferably 2 of the tread ground contact width TW in order to form a large snow column on the snow road and ensure sufficient driving force. While 5% or more, more preferably 3.0% or more is desirable, it is preferably 10.0% or less, more preferably 7.0% or less. On the other hand, the groove width GW2 of the auxiliary vertical groove Gs is not particularly limited, but preferably 0.5% of the tread grounding width TW in order to secure the grounding area of the tread portion 2 while forming a minimum snow column. While more preferably 1.0% or more, more preferably 3.0% or less, and even more preferably 2.0% or less.

  Here, the “tread contact width” TW is a tire axial distance between the tread contact ends E, E of the tread portion 2. The “grounding end” E is a grounding end portion when a normal load is applied to the tire 1 in the normal state and pressed against a flat surface with a camber angle of 0 °. The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

  In the present embodiment, the main longitudinal groove Gm is a pair of first main longitudinal grooves Gm1 and Gm1 extending on both sides of the tire equator C, and a pair of second main grooves Gm1 extending outward in the tire axial direction. It consists of a main longitudinal groove Gm2. The sub-vertical groove Gs is a second sub-groove extending between the first sub-vertical groove Gs1 extending on the tire equator C, the first main vertical groove Gm1 and the second main vertical groove Gm2, and substantially in the middle thereof. Of the secondary vertical groove Gs2. In the present embodiment, each of the longitudinal grooves Gm and Gs extends in a zigzag shape in the tire circumferential direction, but is not limited to such an embodiment.

  The horizontal groove g includes a first horizontal groove g1 that defines a block B between the first sub vertical groove Gs1 and the first main vertical groove Gm1, and the first main vertical groove Gm1 and the second sub vertical groove Gm1. A second horizontal groove g2 that partitions the block B between the vertical groove Gs2, and a third horizontal groove g3 that partitions the block B between the second sub-vertical groove Gs2 and the second main vertical groove Gm2, It consists of the 4th horizontal groove g4 which divides the block B between the 2nd main vertical groove Gm2 and the tread grounding end E. As shown in FIG.

  Each of the lateral grooves g1 to g4 is spaced apart in the tire circumferential direction at a pitch equal to one zigzag pitch of the longitudinal grooves Gm and Gs. Further, both ends of each of the lateral grooves g1 to g4 communicate with the zigzag peak position (corner position) of the longitudinal groove Gm or Gs. Further, the lateral grooves that are adjacent to each other in the tire axial direction (for example, the first lateral groove g1 and the second lateral groove g2) are arranged so that the positions in the tire circumferential direction are shifted by shifting the arrangement phase of each other by a half pitch. Is done. In other words, the lateral grooves g1 to g4 are provided without being directly connected to each other. This increases the dispersibility of the lateral grooves g1 to g4 and helps to ensure a uniform driving force on the snowy road.

  Further, when traveling on a snowy road, it is possible to increase the driving force by forming a large snow column inside the lateral grooves g1 to g4 and shearing it. From such a viewpoint, the groove width GW3 measured in the tire circumferential direction of each of the lateral grooves g1 to g4 is preferably 2.5% or more, more preferably 3.0% or more, more preferably 4 of the tread contact width TW. 0.0% or more is desirable.

  On the other hand, if the groove width GW3 of the lateral groove g is too large, the pattern rigidity of the tread portion 2 is reduced, and uneven wear resistance performance, block chipping, etc. are likely to occur. There is a risk of worsening the running performance. In addition, there is a tendency that the snow pillars in the groove tend to collapse. From such a viewpoint, the groove width GW3 of the lateral grooves g1 to g4 is preferably 7.5% or less, more preferably 6.0% or less, and further preferably 5.0% or less of the tread ground contact width TW. The groove width GW3 may be constant or may be changed as appropriate. Further, the groove width GW3 may be different for each of the lateral grooves g1 to g4.

  The lateral grooves g1 to g3 of the present embodiment are inclined at a relatively small angle, for example, greater than 0 ° and less than 20 ° with respect to the tire circumferential direction. This not only helps to improve the driving force described above, but also increases the rigidity of each block, which in turn helps to suppress uneven wear during running on dry asphalt roads.

  In the present embodiment, the first to third lateral grooves g1, g2, and g3 include two types having different inclination directions with respect to the tire circumferential direction. Specifically, in FIG. 2, a lateral groove gr extending upward and a lateral groove gl extending downward are included, and the lateral grooves gr and gl are alternately arranged in the tire circumferential direction. This prevents so-called single flow caused by the pattern, improves straight running stability, and helps to ensure a uniform driving force even when turning on a snowy road.

  In FIG. 3, the elements on larger scale of the tread part 2 are shown. The block B includes a siping block Bd provided with a pair of sipings S1 and S2 extending in opposite directions with respect to the tire axial direction and crossing the block. Thereby, the block Bd with siping is formed between the main block piece Bm on both sides in the tire circumferential direction and the main block piece Bm by the sipings S1 and S2, and the tire circumferential length is one side in the tire axial direction. Are divided into sub-block pieces Bs that are substantially wedge-shaped in a plan view and gradually decrease toward the other side. Moreover, the siping block Bd is formed such that the width BWs of the sub-block piece Bs in the tire axial direction is smaller than the width BWm of the main block piece Bm in the tire axial direction. Here, the width in the tire axial direction of each block piece Bm and Bs is the maximum width sandwiched between a pair of parallel tire circumferential lines as shown in FIG.

  The operation of the block Bd with siping will be described by taking the third block row BL3 as an example. For example, when turning on a snowy road, when the lateral force SF indicated by an arrow acts on the block Bd with siping, the sub-block piece Bs having relatively lower rigidity than the main block piece Bm has a lateral force SF. Accordingly, the second auxiliary vertical groove Gs2 is deformed in the tire axial direction. At this time, since the sub-block piece Bs has a wedge shape, the movement of the sub-block piece Bs in the tire axial direction passes through the sipings S1 and S2 to the main block pieces Bm and Bm to the lateral grooves g3 and g3 that they face. It is converted into a circumferential movement and transmitted. As a result, the snow column in the lateral groove g3 is more strongly pressed and solidified by the main block piece Bm, so that a large driving force is applied to the tire when shearing it. Therefore, the pneumatic tire 1 of the present invention improves the turning performance on snowy roads. Note that if the width BWs of the sub-block piece Bs in the tire axial direction becomes excessively small, there is a risk that uneven wear is likely to occur in the portion, and therefore preferably a ratio with the width BWm of the main block piece Bm in the tire axial direction ( BWs / BWm) is preferably 0.7 to 0.9.

  The operation as described above can be obtained if at least one of the blocks B of the tread portion 2 is the siping block Bd as described above. However, it is preferable that all of the blocks in at least one block row are formed by the above-mentioned blocks Bd with siping, and more preferably, as shown in FIG. The attached block Bd is desirable.

  The shapes of the sipings S1 and S2 are not particularly limited. However, when the sipings S1 and S2 are formed in a zigzag shape, depending on the zigzag shape, the sub block piece Bs and the main block piece Bm may be engaged with each other, and relative slippage may not occur smoothly between them. . This hinders the wedge action described above. From this point of view, the sipings S1 and S2 are preferably linear and cross the block B, and both ends thereof are connected to the longitudinal grooves Gs or Gm.

  Further, the inclination angles θ1, θ2 (absolute values and opposite directions) of the sipings S1, S2 with respect to the tire axial direction are preferably 8 ° or more, more preferably 10 ° or more, preferably 40 It is desirable that the angle is not more than 0 °, more preferably not more than 30 °. If the angle θ1 or θ2 is less than 8 degrees, the above-mentioned wedge action is small, and therefore there is a possibility that the effect of improving the turning performance on snow cannot be expected sufficiently. Conversely, if the angle θ1 or θ2 exceeds 40 degrees, the main block piece Bm In addition to excessively increasing the amount of deformation, the durability of the block may be deteriorated, and the edge effect of siping on an icy road may be reduced. Note that the siping S1 and the siping S2 are opposite to each other with respect to the tire axial direction, that is, the siping S1 is inclined to the right and the siping S2 is inclined to the right, but these angles θ1 and θ2 are substantially equal. It is desirable that they are the same.

  The width GW4 of the sipings S1 and S2 is not particularly limited, but if it is too large, the block rigidity may be lowered, and the steering stability on the dry road surface may be deteriorated. It becomes difficult to obtain a wedge action. From such a viewpoint, the width GW4 of the sipings S1 and S2 is preferably 2.0 mm or less, and more preferably 0.5 to 1.5 mm.

  Further, the depth Ds of the sipings S1 and S2 (shown in FIG. 1) is not particularly limited, but if the depth Ds is too small, the deformation amount of the sub-block piece Bs is limited to be small, so that the above-described wedge action is sufficient. However, if it is too large, the overall rigidity of the block B may be lowered, and the durability and uneven wear resistance may be deteriorated. From such a viewpoint, the depth Ds of the sipings S1 and S2 is preferably 55% or more, more preferably 65% or more of the groove depth Dy of the lateral groove of the block row to which the block belongs, while preferably 95%. Below, 85% or less is more desirable.

  Further, at the time of turning, a lateral force SF is generated from one of the tread ground contact ends E toward the tire equator C. Therefore, in order to effectively apply the lateral force SF to the sub-block piece Bs, the sub-block piece Bs is positioned on the tread ground contact end E side and the outer side wall surface Wso having a large tire circumferential length BL1. And an inner side wall surface Wsi which is located on the tire equator C side and has a tire circumferential direction length BL2 smaller than the outer side wall surface Wso, and the length of the sub-block piece Bs in the tire circumferential direction. However, it is desirable to include a siping block Bd that gradually decreases from the outer side wall surface Wso side toward the inner side wall surface Wsi side.

  In the present embodiment, the above-mentioned siping blocks Bd are provided on the both sides of the tire equator C in the first to third block rows BL1 to BL3 every other one in the tire circumferential direction. Such a block arrangement is useful for uniformly including the above-mentioned siping block Bd in the ground plane, and can improve the turning performance on snow more efficiently. If the length BL2 of the side wall surface Wsi of the side wall surface Wsi in the sub-block piece Bs is reduced, the rigidity of the sub-block piece Bs is excessively reduced, and the wedge action is reduced. May cause uneven wear. From such a viewpoint, the length BL2 of the inner side wall surface Wsi in the tire circumferential direction is preferably 4.0 mm or more, and more preferably 5.0 mm or more.

  Moreover, in this embodiment, the main block piece Bm of another block is arrange | positioned adjacent to the tire equator C side of the main block piece Bm via the sub vertical groove Gs. Therefore, when a large lateral force is applied, the sub-vertical groove Gs is closed and the adjacent main block pieces Bm and Bm are apparently integrated to enhance lateral rigidity, thereby further improving steering stability during turning. On the other hand, since the lateral groove g1 or g2 is arranged on the tire equator side of the sub-block piece Bs, a space in which the sub-block piece Bs can move to the tire equator side can be sufficiently provided.

  Further, as shown in FIG. 3, it is desirable that the outer side wall surface Wso of the sub block piece Bs is provided closer to the tread grounding end E side than the outer side wall surface Wmo of the main block piece Bm on both sides thereof. As shown in FIG. 4A, the outer side wall surface Wso of the present embodiment is formed in a substantially V shape and protrudes toward the tread grounding end E side, but as shown in FIG. In addition, a substantially trapezoidal shape that projects in a tapered shape toward the tread grounding end side in a plan view can be preferably employed.

  Since such a sub-block piece Bs is closer to the tread ground contact E, it is more easily affected by the lateral force SF, so that the aforementioned wedge effect can be further enhanced. In addition, since the outer side wall surface Wso of the sub-block piece Bs includes the slope Z that is inclined with respect to the tire circumferential direction, the snow column compressed in the zigzag main longitudinal groove Gm2 is formed. When the side wall surface Ws outside the sub-block piece Bs is pressed in the tire circumferential direction, the force is converted in the tire axial direction by the slope Z. This is desirable because it further promotes the wedge effect. In this sense, it is desirable that the side wall surface Wso outside the sub-block piece Bs is disposed so as to face the main longitudinal groove Gm having a large groove width.

Although not particularly limited, as shown in FIG. 3, the main block piece Bm is used in order to more effectively apply the lateral force and the pressure from the snow column in the main longitudinal groove Gm to the sub-block piece Bs. The protrusion amount F of the outer side wall surface Wso of the sub block piece Bs from the outer side wall surface Wmo to the outer side in the tire axial direction is preferably 5 to 25% of the width BWm of the main block piece Bm in the tire axial direction. .

In order to effectively exhibit the wedge action of the sub block piece Bs, the aspect ratio of the main block piece Bm is preferably 0.3 or more, more preferably 0.4 or more, preferably 0.8 or less. More preferably, 0.7 or less is desirable. Here, the aspect ratio is the ratio (BL3 / BWm) of the length BL3 in the tire circumferential direction of the main block piece Bm (the length sandwiched between two parallel tire axial directions) and the width BWm in the tire axial direction. Defined by Since the main block piece Bm having such an aspect ratio is more easily deformed in the tire circumferential direction than in the tire axial direction, the direction in which the lateral groove g is effectively compressed by the movement of the sub block piece Bs toward the tire equator side. It is possible to form a solid snow column by efficiently compressing and solidifying the snow column in the lateral groove. When the aspect ratio is less than 0.3, the rigidity in the tire circumferential direction of the main block piece Bm tends to be excessively lowered, and as a result, the main block piece Bm is likely to have partial wear such as chipping and heel and toe wear. On the other hand, if the aspect ratio exceeds 0.8, the tire circumferential rigidity is excessively increased, and the effect of compressing the snow columns in the lateral grooves tends to decrease.

  The aspect ratio (BL1 / BWs) of the sub block piece Bs is preferably 0.2 or more, more preferably 0.3 or more, preferably 0.7 or less, more preferably 0.6 or less. desirable. When the aspect ratio (BL1 / BWs) of the sub-block piece Bs is less than 0.2, the rigidity in the tire circumferential direction of the sub-block piece Bs tends to be reduced, and the sub-block piece Bs is chipped and heel-and-toe wear as described above. Uneven wear is likely to occur. Conversely, when the aspect ratio (BL1 / BWs) exceeds 0.7, the rigidity in the tire circumferential direction of the sub-block piece Bs is excessively increased, and the sub-block piece Bs becomes difficult to move in the tire axial direction. There is a tendency that the wedge action described above is difficult to obtain.

  Although the embodiment of the present invention has been described above by taking the heavy load tire as an example, it goes without saying that the present invention can also be applied to a passenger car tire or the like.

  The on-snow performance and on-ice performance of a heavy duty radial tire of size 11R22.5 made according to the specifications of FIGS. 1, 2 and Table 1 were tested. Further, as shown in FIG. 5, the same test was performed on tires of the same size (comparative example) having patterns in which sipings are arranged in parallel. The common specifications are as follows.

Tread contact width TW: 220mm
Main vertical groove width GW1: 7.0mm
Groove width GW2 of sub vertical groove: 2.0mm
Horizontal groove width GW3: 7.0 mm
Siping width GW4: 1.0mm
Note that the outer contour of the block was the same in both the example and the comparative example. Further, except for Example 4, the length BL2 in the tire circumferential direction of the side wall surface in the sub-block piece was unified to 5.0 mm, and only BL1 was changed by changing the angles of sipings S1 and S2. In Example 4, the length BL2 was set to 3.0 mm. The test method is as follows.
<Snow performance>
Each test tire was mounted on the vehicle under the following conditions, and the critical speed at which the vehicle began to skid when the vehicle was traveling on a downward curve was measured. The higher the limit speed, the better the turning performance on snow.

Internal pressure: 700 kPa
Rims: 8.25 x 22.5
Test vehicle: 2-D vehicle with a load capacity of 8t (constant load, test tires are mounted on all wheels)
Test course surface: Snowy road Road slope: 4%
Curvature radius of curvature: 60R
Traveling speed (initial speed): 40km / H
<Performance on ice>
Using the above vehicle, the braking distance was measured when a sudden lock braking (without an antilock system) was applied from a speed of 30 km / h on a minus 4 ° C. ice road. The results are displayed as an index with Comparative Example 1 as 100. The larger the value, the shorter the braking distance and the better the braking performance on ice.
<Evaluation of uneven wear and chipped blocks>
Each test tire traveled on an asphalt road surface for 20000 km, and the uneven wear amount was measured as a step between blocks, so-called heel and toe wear amount, to evaluate the presence or absence of block chipping and cracks in the siping bottom.
The results of the test are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire of the example had significantly improved turning performance on snow. It was also confirmed that the performance on ice and uneven wear resistance were comparable to the conventional ones.

It is sectional drawing of the pneumatic tire which shows one Embodiment of this invention. It is an expanded view of the tread part. It is an enlarged plan view which shows a part of block. (A), (b) is a fragmentary perspective view of a block. It is an expanded view of the tread part of a comparative example.

Explanation of symbols

1 Pneumatic tire B Block Gs Main vertical groove Gm Sub vertical groove g Horizontal groove BL1-BL4 Block row Bm Main block piece Bs Sub block pieces S1, S2 Siping E Tread grounding end

Claims (7)

The tread portion is provided with a plurality of vertical grooves extending continuously in the tire circumferential direction and a plurality of horizontal grooves crossing between the vertical grooves, thereby having at least one block row in which the plurality of blocks are arranged in the tire circumferential direction. A pneumatic tire,
The at least one block is formed between a main block piece on both sides in the tire circumferential direction by a pair of sipings extending in opposite directions with respect to the tire axial direction and crossing the block. The direction length is divided into a substantially wedge-shaped sub-block piece in plan view that gradually decreases from one side of the tire axial direction toward the other side,
Moreover, the pneumatic tire is characterized in that the width of the auxiliary block piece in the tire axial direction is smaller than the width of the main block piece in the tire axial direction. The sub-block piece is located on the tread contact end side and has an outer side wall surface having a large length in the tire circumferential direction, and is located on the tire equator side and has a smaller tire circumferential direction length than the outer side wall surface. The pneumatic tire according to claim 1, further comprising: an inner side wall surface, and a length of the sub-block piece in a tire circumferential direction gradually decreasing from the outer side wall surface side toward the inner side wall surface side.   The main block piece has an outer side wall surface located on the tread ground end side, and the outer side wall surface of the sub block piece is provided closer to the tread ground end side than the side wall surface of the main block piece. The described pneumatic tire.   4. The pneumatic tire according to claim 2, wherein an outer side edge of the sub-block piece has a substantially V shape or a substantially trapezoidal shape protruding in a tread grounding end side in a plan view.   The pneumatic tire according to any one of claims 1 to 4, wherein the siping extends in a straight line and at an angle of 15 to 40 ° with respect to a tire axial direction.   The pneumatic tire according to any one of claims 1 to 5, wherein a width of the lateral groove is 2.5 to 7.5% of a tread contact width.   The pneumatic block according to any one of claims 1 to 6, wherein the main block piece has an aspect ratio of 0.3 to 0.8, and the sub block piece has an aspect ratio of 0.2 to 0.7. tire.