JP4299804B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire that can improve running performance on an icy road surface.

  Conventionally, various winter tires mainly intended to travel on icy and snowy roads such as studless tires have been proposed (see, for example, Patent Document 1 below). In these pneumatic tires, land portions such as blocks or ribs are provided in a tread portion, and incised siping having a small groove width is provided in the land portion. The effects of siping include, first, an increase in edge components, second, moderate softening of block rigidity, and third, improvement of frictional force by sucking water film on the ice road surface using capillary phenomenon etc. It is done.

JP-A-8-104111

  However, as shown in FIG. 12, in the conventional siping S, when the block B comes into contact with the road surface and receives the shearing force F, the siping wall surfaces are brought into close contact with each other at a portion A close to the road surface, thereby creating a siping space. It was found that the water film sucking effect was not sufficiently obtained due to the blockage.

  The present invention has been devised in view of the above circumstances. In the land portion, a siping-shaped narrow groove extending in a direction crossing the land portion is provided, and the siping-shaped narrow groove has a groove width of 2. Effectively moisture from the road surface based on the structure including a sipe part with a notch shape of 0 mm or less and a widened part that is continuous inward in the radial direction of the sipe part and the groove width is larger than 2.0 mm. It is an object of the present invention to provide a pneumatic tire that can improve the running performance on icy and snowy roads.

The invention according to claim 1 of the present invention is a pneumatic tire in which a plurality of longitudinal grooves extending in the tire circumferential direction are provided in a tread portion, and between the adjacent longitudinal grooves or between the longitudinal grooves and the tread. A sipe-like shape having a land portion between the ends, extending in a direction crossing the land portion, and having at least one end communicating with the longitudinal groove or tread end, and opening at a ground contact surface of the land portion A narrow groove is provided, and the sipe-shaped narrow groove has a sipe portion having a notch shape with a groove width of 2.0 mm or less, and a widening that is continuous inward in the radial direction of the sipe portion and the groove width is larger than 2.0 mm. And the widened portion is provided in a region not less than 20% and not more than 90% of the maximum depth of the siping-shaped narrow groove from the grounding surface, and the widened portion includes the groove width and / or The length in the tire radial direction is the width of the land. It expands toward the side edge side from the center side of direction .

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the widened portion has the groove width larger than the length in the tire radial direction.

  According to a third aspect of the present invention, in the widened portion, a ratio (w / h) between the groove width w and a length h in the tire radial direction is 1.2 to 2.5. It is a pneumatic tire.

According to a fourth aspect of the present invention, the siping-shaped narrow groove includes an outer widened portion provided on the ground contact surface side of the land portion and an inner widened portion provided on the inner side in the tire radial direction. 4. The outer widened portion according to any one of claims 1 to 3 , wherein the groove width and the length in the tire radial direction are smaller than the groove width of the inner widened portion and the length in the tire radial direction . It is a pneumatic tire.

The invention according to claim 5 is a pneumatic tire in which a plurality of longitudinal grooves extending in the tire circumferential direction are provided in the tread portion, and between the adjacent longitudinal grooves or between the longitudinal grooves and the tread ends. A sipe-like narrow groove extending in a direction crossing the land portion and having at least one end communicating with the longitudinal groove or the tread end and opening at a ground contact surface of the land portion. The siping-shaped narrow groove is provided with a sipe portion having a notch shape with a groove width of 2.0 mm or less, and a widened portion continuous inward in the radial direction of the sipe portion and having a groove width larger than 2.0 mm. And the widened portion is provided in a region of 20% to 90% of the maximum depth of the siping-shaped narrow groove from the grounding surface, and the widened portion is provided on the grounding surface side of the land portion. Widened outer part and the tire radial direction An inner widened portion provided on the inner side , and the outer widened portion has a groove width and a length in the tire radial direction, a groove width of the inner widened portion and a length in the tire radial direction. It is a pneumatic tire characterized by being smaller than this. Furthermore, in the invention according to claim 5, it is desirable that each widened portion has the groove width larger than the length in the tire radial direction, and further, the groove width w of each widened width and the length in the tire radial direction. It is desirable that the ratio (w / h) to the length h is 1.2 to 2.5.

In the pneumatic tire according to claim 1 and claim 5 , the siping-shaped narrow groove is composed of a sipe portion having a small groove width and a widened portion having a large groove width, and the position of the widened portion is limited. Prevents siping-like narrow grooves from clogging and enhances the effect of sucking water from the road surface. Therefore, the running performance can be particularly remarkably improved on an icy road where a thin water film is formed on the surface. In particular, in the pneumatic tire according to claim 1, at the center portion in the width direction where the cross-sectional shape of the widened portion is relatively small, the capillary phenomenon is effectively generated, and on the side edge side, the drainage resistance is reduced, and thus the water sucked up. Can be discharged quickly. Therefore, such a configuration of the widened portion can exhibit two performances of water absorption and drainage from the road surface at a higher level, and a significant improvement in running performance on ice roads can be expected. Furthermore, the siping-shaped narrow groove like the pneumatic tire according to claim 5 reduces the outer widened portion close to the ground contact surface, effectively produces the capillary phenomenon, and reduces the rigidity of the land portion on the ground contact side. Can be suppressed. In addition, by providing a relatively large widened portion on the inner side of the land portion, even if the outer widened portion is temporarily blocked, the water film is formed using the pumping action of the inner widened portion. Can suck up surely.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 provided in the pneumatic tire (not shown) of the present embodiment. The pneumatic tire of the present embodiment is a studless tire for a passenger car, and the tread portion 2 extends in a direction intersecting with the plurality of vertical grooves 3 extending continuously in the tire circumferential direction and the vertical grooves 3. A plurality of lateral grooves 4 are provided.

  In the present embodiment, the vertical groove 3 includes a pair of central vertical grooves 3 a disposed on both sides of the tire equator C, and a pair of outer vertical grooves 3 b respectively disposed on both outer sides thereof. Each of the vertical grooves 3a and 3b has a groove width GW1 measured on the tread surface of 2.0% or more, more preferably 2.5% or more of the tread width TW in order to improve drainage or snow drainage. The upper limit is preferably 7.0% or less, more preferably 5.0% or less. Further, the depth of each of the longitudinal grooves 3a and 3b is preferably 5 mm or more, more preferably 8 mm or more, and the upper limit is preferably 25 mm or less, more preferably 20 mm or less. desirable. Each of the longitudinal grooves 3a and 3b is linear and extends in the tire circumferential direction, but may be wavy or zigzag-shaped.

  The tread width is a distance in the tire axial direction between the tread ends 2e and 2e in a normal state of the tire. The normal state is a no-load state in which the tire is assembled on the normal rim and filled with the normal internal pressure. Also, the tread end 2e is the edge when it is clearly shown by the edge, but when it is unclear, when the normal load is applied from the normal state and the tire and the plane are grounded at a camber angle of 0 ° The grounding end on the outermost side in the tire axial direction.

  The regular rim is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. If there is, “Measuring Rim”. In addition, “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. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars. Furthermore, “regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES". If ETRTO, the load is 88% of "LOAD CAPACITY".

  In this embodiment, the horizontal groove 4 includes a central horizontal groove 4a extending between the central vertical grooves 3a and 3a, and an intermediate horizontal groove 4b extending between the central vertical groove 3a and the outer vertical groove 3b. And an outer lateral groove 4c extending between the outer longitudinal groove 3b and the tread end 2e. About the groove width GW2 and groove depth of these horizontal grooves 4a-4c, it can determine similarly to the said vertical groove 3. FIG.

  And by such a vertical groove 3 and the horizontal groove 4, the tread portion 2 has a center block 5a between the central vertical grooves 3a and 3a, and a middle block between the central vertical groove 3a and the outer vertical groove 3b. A land portion including 5b and a shoulder block 5c between the outer vertical groove 3b and the tread end 2e is provided. In the present invention, the specific pattern shape is not limited to the illustrated one, and can be changed to various modes. Further, when the blocks 5a, 5b and 5c are collectively referred to without distinction, they are referred to as “block 5”.

  The center block 5a, the middle block 5b, and the shoulder block 5c are each provided with at least one sipe-shaped fine groove 6 in the present embodiment. This siping-shaped narrow groove 6 divides the block 5 into a plurality of block small pieces 5P, exhibits the edge effect, and sucks up the water film on the icy road more effectively than in the past as will be described later. Increase the coefficient.

  FIG. 2 is a partial perspective view of the center block 5a for explaining the siping-shaped narrow grooves 6. FIG. 3 is an XX sectional view of FIG. 1, FIG. 4 is an AA sectional view of FIG. 3, and FIG. 5 is a BB sectional view of FIG.

  The siping-shaped narrow grooves 6 open at the ground contact surface 7 of each block 5 and have a depth inward in the tire radial direction. The siping-shaped narrow groove 6 of the present embodiment has a substantially constant maximum depth D. The maximum depth D of the siping-shaped narrow groove 6 is, for example, preferably 50% or more of the block maximum height BH, more preferably 80% or more, and the upper limit is preferably 100% or less, more preferably It is desirable that it is 90% or less. If the depth D is less than 50% of the block maximum height BH, a sufficient edge effect or the like cannot be exhibited on an icy and snowy road. Conversely, if the depth D exceeds 100%, the block rigidity tends to be excessively lowered. The block height BH is synonymous with the groove depth of the longitudinal groove 3.

  The siping-shaped narrow groove 6 extends in a direction crossing the block 5, and at least one end 6E forms an open end communicating with the longitudinal groove 3 or the tread end 2e. In other words, the siping-shaped narrow groove 6 is configured as full open or semi-open. For this reason, air or moisture taken into the siping-shaped narrow groove 6 can be discharged from the open end to the outside of the block. Each siping-shaped narrow groove 6 of the present embodiment is a full open type in which both ends 6E, 6E communicate with either the longitudinal groove 3 or the tread end 2e.

  Further, the siping-shaped narrow grooves 6 of the present embodiment extend substantially parallel to the tire axial direction and linearly. This is useful for exhibiting a high edge effect, particularly when traveling straight on an icy and snowy road. The siping-shaped narrow grooves 6 may be inclined with respect to the tire axial direction. However, considering the edge effect on the icy road, etc., the siping-shaped narrow groove 6 preferably has an angle with respect to the tire axial direction of 45 ° or less, more preferably 40 ° or less, and still more preferably 35 ° or less. In addition to the linear shape, various shapes such as a wave shape and a zigzag shape can be adopted as the shape of the siping-shaped fine groove 6.

  The siping-shaped narrow groove 6 includes a sipe portion 6a having a notch shape with a groove width of 2.0 mm or less, and a widened portion 6b which is continuous inward in the tire radial direction of the sipe portion 6a and has a groove width larger than 2.0 mm. It is comprised including. Here, each groove width is measured in a direction perpendicular to the direction in which the siping-shaped narrow grooves extend. In the present embodiment, the sipe portion 6a includes an outer sipe portion 6a1, an intermediate sipe portion 6a2, and an inner sipe portion 6a3 in the tire radial direction. The widened portion 6b includes an outer widened portion 6b1 and an inner widened portion 6b2 in the radial direction.

  As is apparent from FIG. 6, the siping-shaped narrow groove 6 of the present embodiment includes an outer sipe portion 6a1 that opens at the ground contact surface 7 of the block 5 and extends in the depth direction, and a tire radial direction of the outer sipe portion 6a1. An outer widened portion 6b1 continuous inward, an intermediate sipe portion 6a2 continuous inward in the radial direction of the outer widened portion 6b1, and an inner widened portion 6b2 continuous inward in the radial direction of the intermediate sipe portion 6a2. And an inner sipe portion 6a3 including the bottom portion 6T of the sipe-shaped narrow groove 6 that extends inward in the radial direction of the inner widened portion 6b2.

  Each sipe portion 6a is formed in a cut shape having a groove width g of 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less. In the present embodiment, the outer, middle and inner sipe portions 6a1, 6a2 and 6a3 all have substantially the same groove width g.

  If the groove width g of the sipe portion 6a is larger than 2.0 mm, the rigidity of the block 5 is remarkably lowered, and the steering stability may be deteriorated. Moreover, the sipe part 6a can improve block rigidity and an edge effect, so that the groove width g is small. For this reason, the lower limit of the groove width of the sipe portion 6a is not particularly limited as long as it can be manufactured, but approximately 0.3 mm or more is preferable. It should be noted that the cut shape merely means a shape cut with a knife or the like, and it goes without saying that the actual processing includes a vulcanization molding method using a knife blade of a mold or the like.

  The widened portion 6b continues inward in the tire radial direction of the sipe portion 6a and has a groove width larger than 2.0 mm and a predetermined tire radial length. Therefore, the siping-shaped narrow groove 6 includes a portion where the groove width increases in the depth direction. In FIG. 6, a suffix a is attached to the groove width w and the tire radial length h of the outer widened portion 6b1, and a suffix b is attached to the lengths w and h of the inner widened portion 6b2. However, when the lengths w and h of the outer and inner widened portions 6b are simply collectively referred to, the symbols w and h are used as described above.

  Each widened portion 6b is provided in a region Y that is 20% or more and 90% or less of the maximum depth D of the siping-shaped narrow groove from the ground contact surface 7 of the block. As a result of various experiments, the inventors have found that most of the closed portion A of the siping space due to contact with the conventional siping surface occurs in the region Y.

  Accordingly, by providing at least one widened portion 6b in this region Y, as shown in FIG. 7, the siping-shaped narrow groove 6 accompanying the groove wall surface contact of the siping-shaped narrow groove 6 using the wide groove width portion is used. Can be blocked. For example, the siping-like space is maintained by different deformations and relative positional shifts of the widened portions 6b facing each other, and a capillary phenomenon can be exhibited. Further, the widened portion 6b is compressed and deformed by a load during traveling. At that time, the air of the widened portion 6b is exhausted from the end portion 6E at a stretch, and the road surface through the sipe portion 6a by the pumping action (negative pressure action). The water sucking action from water can be further enhanced. When a plurality of widened portions 6b are provided at a distance in the tire radial direction in one siping-shaped narrow groove 6 as in this embodiment, all the widened portions 6b are in the region Y. It is necessary to be included.

  As described above, the pneumatic tire of the present invention can sufficiently suck the water film on the road surface into the block through the sipe portion 6a and the widened portion 6b, so that the running performance on an icy road is improved. The sucked water can be discharged to the outside from the end 6E of the siping-shaped narrow groove 6, for example.

  When the widened portion 6b is provided in a region less than 20% of the groove depth D of the siping groove from the grounding surface 7, the opening of the siping groove 6 is remarkably increased due to the shearing force from the road surface. The water absorption effect cannot be obtained sufficiently. Conversely, if the widened portion 6b is provided in a region larger than 90% of the groove depth D of the siping-shaped narrow groove from the ground surface 7, a large strain acts on the bottom 6T of the siping-shaped narrow groove 6. There is a risk of causing damage such as rubber cracking. From such a viewpoint, the region Y is preferably 25% or more, more preferably 30% or more, and further preferably 33% or more of the groove depth D of the sipe-shaped narrow groove from the ground surface 7 and an upper limit. Is preferably 85% or less, more preferably 80% or less.

  For example, the widened portion 6b may have a circular cross section (a cross section in which a discontinuous portion is closed by an imaginary line), but is preferably formed in a non-circular shape as in this embodiment. In this embodiment, the groove width w of each widened portion 6b is formed in a flat and smooth ellipse or oval shape that is larger than the length h in the tire radial direction. That is, w> h is satisfied. Such a widened portion 6b is more likely to be deformed into a flat shape during tire load traveling, and the pumping action is easily obtained.

  As a particularly preferable aspect, the ratio (w / h) between the groove width w of the widened portion 6b and the length h in the tire radial direction is preferably 1.2 or more, more preferably 2.0 or more. On the other hand, even if the ratio (w / h) is too large, the rigidity of the widened portion 6b is likely to be greatly reduced, and the steering stability is likely to deteriorate. For this reason, the upper limit of the ratio (w / h) is, for example, 4.0 or less, more preferably 3.0 or less.

  Further, even if the groove width w of the widened portion 6b is too large, the block rigidity is greatly reduced, or the knife blade is liable to fall out in the case of vulcanization molding using a mold. From such a viewpoint, the groove width w of the widened portion 6b is preferably 8 mm or less, more preferably 6 mm or less, and further preferably 4 mm or less.

  Furthermore, if the length h in the tire radial direction of each widened portion 6b is too small, the widened portion 6b is easily closed by a vertical load from the road surface, and a sufficient water absorption effect may not be obtained. If it is too much, the block rigidity is lowered, and there is a possibility that the basic steering stability cannot be obtained. From such a viewpoint, the length h in the tire radial direction of each widened portion 6b is preferably 1.0 mm or more, more preferably 1.5 mm or more, and the upper limit is preferably 6.0 mm or less. More preferably, it is 4.0 mm or less.

  As shown in FIGS. 4 and 5, the widened portion 6 b of the present embodiment has a groove width w and a tire radial length h from the center side in the width direction of the block 5 toward the side edge side. A mode of expanding in a shape is shown. Thereby, in the width direction center part where the cross-sectional shape of the widened part 6b is relatively small, the capillary phenomenon is effectively generated, the drainage resistance is reduced on the side edge side, and the sucked-up water can be quickly discharged. Therefore, such a configuration of the widened portion 6b can exhibit two performances of water absorption and drainage from the road surface at a higher level, and a significant improvement in traveling performance on ice roads can be expected.

  As a particularly preferred embodiment, the ratio (w2 / w1) between the minimum groove width w1 on the center side of the widened portion 6b and the maximum groove width w2 on the side edge side, and the minimum on the center side of the length h in the tire radial direction The ratio (h2 / h1) between the length h1 and the maximum length h2 on the side edge side is preferably 120% or more, more preferably 130% or more, and the upper limit is preferably 250% or less, more preferably Is preferably 230% or less.

  In addition, one siping-like narrow groove 6 includes at least one widened portion 6b, but it is particularly preferable that a plurality of, more preferably two to three widened portions 6b are included as in the present embodiment. Thereby, sufficient space which can prevent obstruction | occlusion of the siping-shaped narrow groove 6 as a whole is securable, reducing the cross-sectional area etc. of each wide part 6b. Therefore, a high water absorption effect can be exhibited while preventing a decrease in block rigidity. In addition, it is not preferable that one siping-shaped narrow groove 6 includes more than three widened portions 6b because block rigidity tends to be lowered.

  Further, when a plurality of widened portions 6b are provided in one siping-shaped narrow groove 6, the groove width wa of the outer widened portion 6b1 and the length ha in the tire radial direction are the inner widened portion. It is preferable to be smaller than the groove width wb of 6b2 and the length hb in the tire radial direction. That is, wa <wb and ha <hb are desirable.

  Such siping-like narrow grooves 6 can downsize the outer widened portion 6b1 close to the grounding surface 7, effectively exhibit a capillary phenomenon, and suppress a decrease in rigidity on the grounding side of the block 5. Further, by providing a relatively large widened portion 6b2 inside the block 5, even if the outer widened portion 6b1 is temporarily closed, the pumping action of the inner widened portion 6b2 is utilized. The water film can be sucked up reliably.

  For example, as shown in FIG. 8, in the winter tire, a platform 8 is provided between the blocks 5 and 5 so as to rise at a height (0.5 GD) that is half the groove depth GD of the lateral groove 4. A tire in which the platform 8 appears as a contact surface with the wear of the tread portion 2 cannot be used as a winter tire, but can be used as a summer tire. For this reason, the outer widened portion 6b1 is positioned outward in the tire radial direction from the height 0.5GD of the platform 8, and the inner widened portion 6b2 is positioned radially inward from the height 0.5GD of the platform 8. By providing it, the water absorption effect of the siping-shaped narrow groove 6 using the widened portion 6b can be exhibited not only as a winter tire but also when used as a summer tire.

  Further, FIG. 9 shows a position corresponding to the AA cross section of FIG. 3 as another embodiment of the present invention. In this embodiment, the widened portions 6b1 and / or 6b2 are formed in a non-linear shape. As the non-linear shape, various shapes such as a smooth V-shape in a front view of FIG. 9 or an inverted V-shape (not shown) opposite to this, and a zigzag shape or a wave shape can be adopted.

  FIG. 10A shows a development view (left half) of the tread portion 2 as another embodiment of the present invention, and FIG. 10B shows a YY cross section thereof. In this embodiment, the shoulder block 5c is provided with siping-shaped narrow grooves 6 extending in the tire circumferential direction, and the rest is the same as the pattern of FIG.

  In the contact surface of the tread portion 2, each block mainly receives a force toward the contact center. Therefore, the center block 5a is greatly deformed in the tire circumferential direction, while the shoulder block 5c is largely deformed in the tire axial direction toward the tire equator. For this reason, in this embodiment, the siping-shaped fine grooves 6 extending in the tire circumferential direction are arranged on the shoulder block 5c, and an edge effect suitable for deformation of the shoulder block 5c is given, and the widened portion 6b of the siping-shaped fine grooves 6 is provided. This prevents the sipe portion from being blocked and can exhibit a water absorption effect.

  Although the embodiment of the present invention has been described above, the land portion may be a rib, and the present invention is not limited to the above embodiment, and can be implemented in various aspects.

  Studless tires for passenger cars (size 195 / 65R15) having the tread pattern shown in FIG. 1 were manufactured based on the specifications in Table 1 and tested for braking performance on ice and cornering performance on icy and snowy roads. FIG. 11 shows a schematic diagram of a block of each test example. The outline of the pattern of each test example is as follows.

(Reference Example 1, Example 2)
In Reference Example 1 and Example 2, semi-open type siping-shaped narrow grooves in which the dimension X in FIG. 11A is 0.7 times the block width BW are provided in all the blocks. Further, in Reference Example 1 , one widened portion is provided in one siping-shaped narrow groove, and in Example 2, two widened portions are provided. The widened portions are all disposed in the region Y.

(Reference Example 2, Examples 4 to 6)
In Reference Example 2 and Examples 4 to 6 , all the blocks are provided with fully open type siping-shaped narrow grooves in which the dimension X in FIG. 11A is 1.0 times the block width BW. . Further, in Reference Example 2 , one widened portion is provided in one siping-shaped narrow groove, in Examples 4 and 5, two widened portions are provided, and in Example 6, three widened portions are provided. Furthermore, about Example 5, the widening part is diameter-expanded in the trumpet shape from the width direction center side of a block toward the side edge side. The widened portions are all disposed in the region Y.

(Conventional example, Comparative Examples 1 and 2)
In the conventional example, a siping having no widened portion is provided. The layout of siping is the same as the layout of the siping-shaped narrow grooves in each embodiment. Comparative Example 1 is based on Example 1, but the widened portion is provided outside the region Y, and Comparative Example 2 is the widened portion provided radially inward of the region Y.

The common specifications of each example are as follows.
Block height BH: 10.0mm
Maximum depth of siping groove: D = 8.0mm
Maximum depth of siping (conventional example): 10.0mm
Groove width g of sipe part: 1.0 mm
The test method is as follows.

<Ice braking ability>
After each test tire was assembled in a rim (15 x 6.5), filled with 200 kPa of internal pressure, mounted on all wheels of a rear-wheel drive vehicle with a displacement of 2000 cc, and run for about 100 km on a dry pavement The internal pressure was adjusted again to 200 kPa, and a braking test on an icy road was conducted. In the braking test, the vehicle is run at a speed of 30 km / h on the test road surface, sudden braking with 4 wheels locked is applied, the braking distance until the car stops is measured 5 times for each tire, and the average value is calculated. Was done. The evaluation is indicated by an index with the average braking distance of the conventional example being 100. The larger the value, the shorter the braking distance and the better the performance.

<Cornering performance on icy and snowy roads>
Using the above vehicle, the vehicle traveled on a snowy road under an environment of -5 ° C and a mirror-burn-like frozen road, and the cornering performance at that time was evaluated by a 10-point method by feeling by a driver. The larger the value, the better.

  As a result of the test, it was confirmed that the performance on ice was improved for the tire of the example. There was no deterioration in cornering performance on icy and snowy roads.

It is an expanded view of the tread part which shows embodiment of this invention. It is a perspective view of a center block. It is XX sectional drawing of FIG. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. FIG. 4 is a partially enlarged view of FIG. 3. It is a side view which shows an example of the deformation | transformation state of the block in load driving | running | working. It is sectional drawing along the tire peripheral direction of the block which shows other embodiment of this invention. It is sectional drawing equivalent to the AA cross section of FIG. 3 which shows other embodiment of this invention. (A) is the expanded view of the tread part which shows other embodiment of this invention, (B) is the YY sectional drawing. It is a figure explaining the siping-shaped narrow groove of an Example, (A) is a top view of a block, (B) thru | or (D) is the AA sectional drawing. It is a side view which shows an example of the deformation | transformation state of the block during the conventional load driving | running | working.

Explanation of symbols

2 tread portion 2e tread end 3 vertical groove 4 land portion 5 block 6 siping-shaped narrow groove 6a sipe portion 6b widened portion 6b1 outer widened portion 6b2 inner widened portion 7 land contact surface D maximum depth of siping-shaped narrow groove g Groove width of the sipe part w Groove width of the wide part h Length of the wide part in the tire radial direction

Claims (7)

A pneumatic tire provided with a plurality of longitudinal grooves extending in the tire circumferential direction in the tread portion,
Between adjacent vertical grooves or between the vertical grooves and tread ends,
The land portion is provided with a sipe-like narrow groove extending in a direction crossing the land portion and having at least one end communicating with the longitudinal groove or the tread end, and opening at a ground contact surface of the land portion,
The siping-shaped narrow groove includes a sipe portion having a notch shape having a groove width of 2.0 mm or less, and a widened portion continuous inward in the radial direction of the sipe portion and having a groove width larger than 2.0 mm.
In addition, the widened portion is provided in a region of 20% or more and 90% or less of the maximum depth of the siping-shaped narrow groove from the ground contact surface ,
The pneumatic tire according to claim 1, wherein the widened portion has a groove width and / or a length in a tire radial direction that is enlarged from a center side in a width direction of a land portion toward a side edge side .   The pneumatic tire according to claim 1, wherein the widened portion has the groove width larger than a length in a tire radial direction.   The pneumatic tire according to claim 2, wherein the widened portion has a ratio (w / h) of the groove width w to a length h in the tire radial direction of 1.2 to 2.5.   The siping-shaped narrow groove includes an outer widened portion provided on the ground contact surface side of the land portion, and an inner widened portion provided on the inner side in the tire radial direction,
  The air according to any one of claims 1 to 3, wherein the outer widened portion has the groove width and the tire radial length smaller than the inner widened groove width and the tire radial length. Enter tire. A pneumatic tire provided with a plurality of longitudinal grooves extending in the tire circumferential direction in the tread portion,
Between adjacent vertical grooves or between the vertical grooves and tread ends,
The land portion is provided with a sipe-like narrow groove extending in a direction crossing the land portion and having at least one end communicating with the longitudinal groove or the tread end, and opening at a ground contact surface of the land portion,
The siping-shaped narrow groove includes a sipe portion having a notch shape having a groove width of 2.0 mm or less, and a widened portion continuous inward in the radial direction of the sipe portion and having a groove width larger than 2.0 mm.
In addition, the widened portion is provided in a region of 20% or more and 90% or less of the maximum depth of the siping-shaped narrow groove from the ground contact surface,
The widened portion includes an outer widened portion provided on the ground contact surface side of the land portion and an inner widened portion provided on the inner side in the tire radial direction , and the outer widened portion is the groove width. A pneumatic tire characterized in that a length in the tire radial direction is smaller than a groove width of the inner widened portion and a length in the tire radial direction .   The pneumatic tire according to claim 5, wherein each of the widened portions has a groove width larger than a length in a tire radial direction.   6. The pneumatic tire according to claim 5, wherein each of the widened portions has a ratio (w / h) of the groove width w to a length h in the tire radial direction of 1.2 to 2.5.

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