JP5314327B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a plurality of blocks defined by circumferential grooves and lateral grooves are formed in a tread portion, and sipes are formed in the blocks.

  In winter tires called studless tires, snow and snow road performance is improved by providing several sipes in the block. In this block, a portion partitioned by sipes is referred to as a small block in this specification.

  When these tires are used while mounted on a vehicle, these blocks support a load in a direction perpendicular to the road surface, and at the same time, are subjected to a shearing force in a direction parallel to the road surface by braking / driving and turning. At this time, the block is deformed to collapse. It is widely known that due to this deformation, a part of the block ground contact surface is lifted, the ground contact area is reduced, and at the same time the ground contact pressure at the edge portion is increased.

  This phenomenon also occurs in summer tires, but is more pronounced in winter tires (studless tires). The reason is that, in order to keep the friction coefficient between the block rubber and the icy / snow road surface high, rubber having a low elastic modulus is used, and the rigidity of the block is lowered by providing many sipes and the like.

The increase in the edge pressure on the snowy and snowy road surface is important from the viewpoint of braking performance and driveability. For example, Patent Documents 1 and 2 disclose that the block surface pressure on the snowy and snowy road is effectively reduced by tapering the block surface. It is disclosed to raise.
JP 2003-25811 A Japanese Patent Laid-Open No. 2005-1621

  Regarding the friction coefficient of the icy road surface, two states are observed: a water film is generated between the block and the ice surface and the friction coefficient is very low, and there is no water film and the friction coefficient is relatively high. Yes. In the present specification, the former is defined as a state having a friction coefficient of 0.1 or less and is referred to as a low friction icy road, and the latter is defined as a road surface having a friction coefficient greater than 0.1 and is referred to as a high friction icy road.

  Conventionally, it is known that it is effective to eliminate the water film by using the edge pressure increase due to the collapse deformation in the low friction icy road with the water film. On the other hand, it is known that in a high friction icy road without a water film, it is effective to suppress a decrease in the contact area due to the above-described collapse deformation. Therefore, it has been difficult to improve both the increase in the edge pressure on the low friction icy and the suppression of the reduction of the block contact area on the high friction icy.

  In consideration of the above-mentioned facts, the present invention effectively improves both the increase in the edge pressure of the block on the low friction icy and the reduction of the contact area of the block on the high friction icy. It is an object to provide a tire.

In the first aspect of the present invention, a plurality of blocks defined by a circumferential groove and a lateral groove are formed in the tread portion, and all the blocks have sipes heading diagonally rearward in the slip direction during braking from the block surface. In the small block formed in the block by the sipe, the corner on the rear side in the sliding direction during braking is 30 to 70% of the small block width than the corner on the front side in the sliding direction during braking. Overhangs the outside in the tire radial direction.

Here, the slipping direction during braking is a direction in which a block that is in contact with the road surface slides with respect to the road surface during braking.
In the first aspect of the present invention, the sipe formed on the block is directed obliquely rearward in the sliding direction during braking from the block surface. As a result, in the case of a low friction icy road with a friction coefficient of 0.1 or less, the ground pressure at the sipe edge portion increases, and the water film can be effectively eliminated.
And in the small block formed in the block by the sipe , the tire radial direction is in the range of 30 to 70% of the small block width of the corner on the rear side in the sliding direction during braking than the corner on the front side in the sliding direction during braking. Projects outward. As a result, in the case of a high friction icy road having a friction coefficient larger than 0.1, the ground contact area is effectively increased by the small block falling down slightly.

  In addition, you may incline so that the ground-contact surface of a small block may become a taper shape with respect to a road surface. Thereby, the said effect can be efficiently acquired with a simple structure.

According to a second aspect of the present invention, the sipe is convexly curved in a direction opposite to the sliding direction during braking.
This makes it possible to more remarkably the effect obtained by inventions of claim 1.

In a third aspect of the invention, the ground contact surface of the small block is an inclined surface that is inclined in a range of 60 to 90 ° with respect to the tire radial direction.
This further increases the ground contact area more effectively on the high friction icy.

According to a fourth aspect of the present invention, the ground contact surface of the small block is concave.
Thereby, the contact pressure by the sipe edge portion and the block edge portion can be further increased.

  According to the present invention, it is possible to provide a pneumatic tire that effectively improves both the increase in the edge pressure of the block on the low friction icy road and the suppression of the decrease in the contact area of the block on the high friction icy road. it can.

Hereinafter, embodiments will be described and embodiments of the present invention will be described .

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, a pneumatic tire 10 according to the present embodiment is a studless tire for a passenger car, and includes a carcass 12 composed of one layer or a plurality of layers, each end of which is folded by a bead core 11. .

  On the outer side in the tire radial direction of the crown portion 12C of the carcass 12, a belt layer 14 in which a plurality of (for example, two) belt plies are stacked is embedded.

  A tread portion 16 provided with a groove is formed on the outer side of the belt layer 14 in the tire radial direction. As shown in FIG. 2, the tread portion 16 is formed with a plurality of circumferential grooves (main grooves) 22 along the tire circumferential direction U on the tire equatorial plane CL and on both sides thereof. The tread portion 16 is formed with a plurality of lateral grooves 24 that intersect the tire circumferential direction U. In the present embodiment, the lateral groove 24 is formed along the tire width direction V. Both end portions of each lateral groove 24 communicate with the circumferential groove 22 or extend beyond the tread end T so as to be drained outward in the tire width direction.

  Here, the tread end means that a pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (2006 edition, Japan Automobile Tire Association Standard), and the maximum load in the applicable size and ply rating in JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to the capacity (internal pressure-load capacity correspondence table) as the internal pressure, and indicates the outermost contact portion in the tire width direction when the maximum load capacity is applied. In addition, when TRA standard and ETRTO standard are applied in a use place or a manufacturing place, it follows each standard.

  As shown in FIG. 2, a large number of blocks 26 are formed in the tread portion 16 by the circumferential grooves 22 and the lateral grooves 24.

  As shown in FIGS. 2 and 3, three sipes 28 are formed in each block 26, and four small blocks 27 </ b> A to 27 </ b> D are formed in each block 26 by the three sipes 28. Each sipe 28 is inclined with respect to the rear side of the sipe depth direction G in the sliding direction F during braking. That is, each sipe 28 is directed obliquely rearward in the sliding direction F during braking from the block surface. As a result, as shown in FIG. 4, in the low friction icy road SL having a friction coefficient of 0.1 or less, the ground contact pressure at the sipe edge portion on the rear side in the sliding direction F particularly increases during braking, thereby effectively Can be eliminated.

  The ground contact surfaces 30 of the small blocks 27A to 27D are inclined surfaces that gradually protrude outward in the tire radial direction as they become rearward in the sliding direction F during braking. Therefore, the rear corner portion 29P in the braking slip direction F protrudes outward in the tire radial direction from the front corner portion 29Q in the braking slip direction. Thereby, as shown in FIG. 5, in the high friction icy road SH having a friction coefficient larger than 0.1 (particularly, the high friction icy road having a friction coefficient in the range of 0.1 to 0.2), the small blocks 27A to 27A When D falls down slightly, the ground contact area effectively increases.

  That is, the pneumatic tire 10 according to the present embodiment exhibits stable high performance in various road surface conditions such as the low friction ice path SL and the high friction ice path SH regardless of the presence or absence of a water film on the road surface. Note that this effect becomes more prominent if the sipe 28 is curved convexly in the direction opposite to the sliding direction F during braking.

  Further, in each of the small blocks 27A to 27D, the corner 29P on the rear side in the braking slip direction F has a small block width W (see FIG. 3) of 30 compared to the corner 29Q on the front side in the braking slip direction F. It protrudes outward in the tire radial direction in a range of ˜70%. This further increases the ground contact area more effectively on the high friction icy.

  Furthermore, in this embodiment, the ground contact surfaces 30 of the small blocks 27A to 27D are in a range of θ = 60 to 90 ° (see FIG. 3) with respect to the tire radial direction D, that is, in a range of 0 to 30 ° with respect to the road surface. The inclined surface is inclined at This further increases the ground contact area more effectively on the high friction icy.

  In the present embodiment, the ground contact surface 30 of the block 26 is concave. Thereby, the contact pressure by the sipe edge portion and the block edge portion can be further increased.

[ Reference form ]
Next, reference embodiments not included in the present invention will be described. In this reference embodiment, as compared with the first embodiment, as shown in FIGS. 6 to 8, the block 26 (see FIG. 6) block 46 in place (see FIG. 3) are formed in the tread portion.

  In this block 46, a sipe 48 orthogonal to the ground contact surface 50 is formed, and the sipe 48 forms small blocks 47 </ b> A to 47 </ b> D in the block 46. And in the small blocks 47A-D, the recessed part 52 is formed in the sipe wall 49 of the front side of the sliding direction F at the time of braking. The recess 52 is formed so as to straddle a half of the sipe depth H (see FIG. 6).

  As a result, as shown in FIG. 7, in the low friction icy road SL having a friction coefficient of 0.1 or less, the small blocks 47A to 47D are bent at the concave portions 52, thereby increasing the contact pressure of the sipe edge portion and the block edge portion. And effectively eliminate the water film. As shown in FIG. 8, in the high friction icy road SH having a friction coefficient larger than 0.1 (particularly, the high friction icy road having a friction coefficient in the range of 0.1 to 0.2), the sipe wall 49 has a recess. Since 52 is formed, the small block 47 falls down slightly and the ground contact area is effectively increased.

  As in the first embodiment, the sipe 48 may be convexly curved in a direction opposite to the sliding direction F during braking. Thereby, this effect becomes more remarkable.

<Test example>
In order to confirm the effect of the present invention, the inventor has an example of a pneumatic tire according to the first embodiment (hereinafter referred to as a tire of Example 1) and an example of a pneumatic tire according to a reference mode (hereinafter referred to as a comparative example). And an example of a conventional pneumatic tire (see FIG. 9 and FIG. 10; hereinafter referred to as a conventional tire), a braking performance test is performed on an icy road, and a braking performance (braking performance) is prepared. Evaluated.

  Here, as shown in FIGS. 8 and 9, the conventional tire is a tire in which a sipe 88 is arranged so as to be orthogonal to the ground contact surface (tread surface). The tire of Example 1 is a tire in which the sipe 28 is inclined by θ = 80 ° with respect to the tire radial direction D, that is, a tire in which the sipe 28 is inclined by 10 ° with respect to the road surface.

  The block dimensions were the same for each tire. In addition, the same condition was set such that the width of the small block sandwiched between the sipes was 3 mm and the sipe depth was 3 mm. The elastic modulus of rubber constituting each tire is about 3 Mpa.

  In this test example, all tires were tested by actual vehicle running with a tire size of 195 / 65R15, mounted on a regular rim, attached to a passenger car, and an average contact pressure of 300 kPa. Here, the “regular rim” refers to a standard rim in an applicable size defined in the 2007 YEAR BOOK issued by JATMA, for example.

In this test example, the test was performed on a low friction icy ice and a high friction icy ice. In any case, the braking distance from the initial speed of 30 km / h until full braking was applied to the stationary state was measured, and the average deceleration was calculated from the initial speed and the braking distance. Then, the evaluation index 100 based on the average deceleration of the tire of the conventional example was used, and the evaluation index for relative evaluation was calculated for the tires of Example 1 and the comparative example . The evaluation results are shown in Table 1.

表１の評価結果では評価指数が大きいほど氷上性能が高いこと、すなわち制動距離が短くて制動性能に優れていることを示す。表１から判るように、低摩擦氷路、高摩擦氷路の何れであっても、実施例１のタイヤでは従来例のタイヤよりも評価指数が高く、比較例のタイヤでは更に評価指数が高いという結果になった。

The evaluation results in Table 1 indicate that the larger the evaluation index, the higher the performance on ice, that is, the shorter the braking distance and the better the braking performance. As can be seen from Table 1, the evaluation index of the tire of Example 1 is higher than that of the conventional tire, and the evaluation index of the comparative example tire is higher than that of the tire of the conventional example. It became the result.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. It goes without saying that the scope of rights of the present invention is not limited to these embodiments.

It is tire radial direction sectional drawing of the pneumatic tire which concerns on 1st Embodiment. It is explanatory drawing which shows the block arrangement of the tread part of the pneumatic tire which concerns on 1st Embodiment in a planar state. It is a side view which shows the block of the pneumatic tire which concerns on 1st Embodiment (no-load state). It is a side view which shows the block of the pneumatic tire which concerns on 1st Embodiment (the shear state in a low friction ice road). It is a side view which shows the block of the pneumatic tire which concerns on 1st Embodiment (shearing state in a high friction icy road). It is a side view which shows the block of the pneumatic tire which concerns on a reference form (no-load state). It is a side view which shows the block of the pneumatic tire which concerns on a reference form (the shear state in a low friction ice road). It is a side view which shows the block of the pneumatic tire which concerns on a reference form (the shear state in a high friction icy road). It is a side view which shows the block of the conventional pneumatic tire used by the test example (no-load state). It is a side view which shows the block of the conventional pneumatic tire used by the test example (the shear state in a high friction ice road).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 16 Tread part 22 Circumferential groove 24 Lateral groove 26 Block 27A-D Small block 28 Sipe 29P The corner | angular part on the back side
29Q Front side corner 30 Grounding surface 46 Blocks 47A to D Small block 48 Sipe 49 Sipe wall 50 Grounding surface 52 Recess 88 Sipe D Tire radial direction F Slip direction during braking G Sipe depth direction H Sipe depth W Small block width

Claims (4)

A plurality of blocks defined by the circumferential groove and the lateral groove are formed in the tread portion,
In all the blocks, a sipe is formed from the block surface toward the diagonally rear side in the sliding direction during braking,
Further, in the small block formed in the block by the sipe, the tire has a corner in the rear side in the sliding direction during braking in a range of 30 to 70% of the small block width than the corner in the front side in the sliding direction during braking. A pneumatic tire that protrudes radially outward. The pneumatic tire according to claim 1, wherein the sipe is convexly curved in a direction opposite to a sliding direction during braking. The pneumatic tire according to claim 1 or 2, wherein the ground contact surface of the small block is an inclined surface inclined in a range of 60 to 90 ° with respect to a tire radial direction. The pneumatic tire according to any one of claims 1 to 3, wherein a contact surface of the small block is concave.

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