JP2005075213A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing heel-and-toe abrasion even when a sipe is disposed in a rib to improve wet steering stability. <P>SOLUTION: In the pneumatic tire, the tread section 1 is provided with a plurality of circumferential grooves 2 and 3 extending continuously in the circumferential direction, the ribs 4 and 5 laid out between the circumferential grooves 2 and between a shoulder circumferential groove 3 and a tread edge, and a plurality of sipes 6 extending tiltingly with respect to the circumferential direction and crossing the rib 4 circumferentially at an interval in each of two rows of ribs 4 formed at least in a tread central region. In a corner on an obtuse angle side partitioned by each sipe 6 and a side edge of the rib 4, rib rigidity reducing sections 8 and 9 adjacent to the sipes are disposed over the range that is 1/2 times the sipe length or more and does not include the side edge of the rib of the corner on an acute angle side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire suitable for application to idler shafts such as trucks and buses, and more particularly to a heavy-duty pneumatic tire that achieves both wet handling stability performance and uneven wear resistance at a high level.

  Rib-based tires are generally used as tires for idler axles for trucks and buses. Such tires are described, for example, in JP-A-2002-254905 in order to improve wet steering stability. As shown in the figure, the rib is provided with a plurality of sipes extending across the rib to define an edge on the rib, and the edge cuts a water film formed between the tread and the tread on the wet road surface. The road surface grip is secured. However, such a sipe reduces the rigidity of the sipe in the vicinity of the rib, so heel and toe wear is likely to occur. If such heel and toe wear occurs, the noise on the road increases and the ride comfort is increased. In addition to the deterioration of the tire, there is a problem that the wear resistance performance of the tire is lowered and the tire is rejected at an early stage.

Further, in such a tire, there is a case where a shallow groove extending in the tread width direction is provided in the rib to ensure drainage performance at the time of cornering. As shown in Japanese Patent Laid-Open No. 2000-168317, a form in which a sipe is provided at the center of the groove width of the shallow groove is general. When the sipe and the shallow groove are arranged in this way, the side edges of the sipe and the rib Shallow grooves are present at both corners on the acute angle side formed between them, and the load supporting ability at the corners on the acute angle side is reduced. As a result, the obtuse angle corner located on the stepping side of the corner on the acute angle side in particular will bear an extra load, and the contact pressure locally increases at the obtuse angle corner and the wear energy increases. For this reason, there is a problem that uneven wear near the sipe on the kick-out side of the rib is promoted, and heel and toe wear is likely to occur.
JP 2002-254905 A JP 2000-168317 A

  The present invention has been made in order to solve such problems of the prior art, and the object of the present invention is to provide a heel and heel even when a sipe is provided on a rib for improving wet steering stability. The object is to provide a pneumatic tire capable of suppressing toe wear.

The invention according to claim 1 is provided with a plurality of circumferential grooves continuously extending in the circumferential direction on the tread tread portion, and ribs are defined between the circumferential grooves and between the shoulder circumferential groove and the tread tread edge. The pneumatic tire has a plurality of sipes extending at an angle with respect to the circumferential direction and crossing the ribs at intervals in the circumferential direction at least in each of the two rows of ribs formed in the tread central region. In addition, a rib rigidity reduction portion adjacent to the sipe is provided at a corner on the obtuse angle side defined by each sipe and the side edge of the rib, and the corner on the acute angle side is at least ½ of the sipe length. A pneumatic tire provided over a range not including the side edges of the ribs.
Here, the shoulder circumferential groove is a circumferential groove located closest to the tread tread edge side among the plurality of circumferential grooves.

  In a pneumatic tire in which a sipe that is inclined with respect to the circumferential direction is provided on the rib, the tire rotation direction is defined by the sipe and the side edge of the rib, the corner on the acute angle side and the corner on the obtuse angle side. Friction with the road surface becomes large at the corner on the acute angle side located on the kicking side, and the corner on the acute angle side is selectively worn, so-called heel and toe wear occurs.

  According to the first aspect of the present invention, by providing the rib rigidity reducing portion adjacent to the sipe at the obtuse angle corner defined by the sipe and the side edge of the rib, the load supporting ability of the obtuse angle corner is provided. By intentionally increasing the load load of the corner on the acute angle side located on the kicking side across the sipe of the corner on the obtuse angle side, the wear energy of the corner on the acute angle side is increased. As a result, the wear on the acute angle corner is promoted, and the wear on the sharp angle corner on the opposite side across the sipe on the acute angle side is the same as in the past. Further, the wear amount at the corner on the opposite acute angle side can be made uniform to suppress heel and toe wear.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the rib rigidity reducing portion is constituted by a plurality of cuts or shallow grooves.
According to this, the function and effect of the first aspect can be realized by simpler means by providing the shallow groove or the notch with the function as the rib rigidity reducing portion. In addition, when the shallow groove | channel is provided in the rib, the drainage performance at the time of turning can be improved.

The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the shallow groove has an average width and depth of 1 to 5 mm.
According to this, while ensuring desired drainage performance, the rigidity of a rib can be secured. If the average width and depth are less than 1 mm, the required drainage performance cannot be obtained, and if it is greater than 5 mm, the required rib rigidity cannot be ensured.

  The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein each sipe adjacent in the circumferential direction is inclined in the opposite direction or the same direction with respect to the circumferential direction. Become.

In general, in tires in which the rotation direction is designated, the inclination directions of the sipe continuously provided in the circumferential direction are often the same as each other. However, in tires in which the rotation direction is not designated, adjacent sipe In some cases, the inclination directions with respect to the circumferential direction are opposite to each other.
According to the invention of claim 4, in any of these forms of a tire in which a sipe is provided on a rib, the rib rigidity reducing portion includes an obtuse angle side corner defined by the sipe and a side edge of the rib. By providing, heel and toe wear can be suppressed.

The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 3, wherein each sipe adjacent in the circumferential direction is inclined at an equal angle in the same direction with respect to the circumferential direction.
According to this, even when the inclination angle with respect to the circumferential direction of the sipe provided continuously in the circumferential direction is the same, heel and toe wear can be suppressed.

  The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein the sipe inclination angle with respect to the circumferential direction is 40 to 70 degrees.

  According to this, while ensuring the water film cutting function necessary for sipe, it is possible to prevent the stone from biting, and to ensure the rigidity of the rib and the corner on the acute angle side of the rib partitioned by the sipe. it can. If the width of the sipe is less than 0.3 mm, the water film cutting function becomes too small, and if it is larger than 2.0 mm, the stone biting becomes too remarkable. If the depth of the sipe is less than 50% of the depth of the circumferential groove, the water film cutting function will be too small, and if it is greater than 90%, there is concern about stone biting and the rigidity of the rib will be reduced. Too much.

  The invention according to claim 7 is the pneumatic tire according to any one of claims 1 to 6, wherein the width of the sipe is 0.3 to 2.0 mm, and the depth of the sipe is 50 to the depth of the circumferential groove. 90%.

  According to the invention which concerns on Claim 7, while ensuring the water film cutting | disconnection function required for a sipe, the rigidity of the corner part by the side of the acute angle of the rib divided by the rigidity of a rib can be ensured. If the inclination angle of the sipe with respect to the circumferential direction is less than 40 degrees, the rigidity of the corner on the acute angle side defined by the sipe becomes too small, and if it exceeds 70 degrees, there is a rigidity step between the ribs defined by the sipe. It gets bigger and the ride quality gets worse.

  As is apparent from the above description, according to the present invention, heel and toe wear can be effectively suppressed in a pneumatic tire in which a sipe is provided on a rib for improving wet steering stability. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread pattern in which a rotation direction indicated by an arrow is designated, showing an embodiment of the present invention in a front view of a mounting posture on a vehicle.
Here, the tread tread portion 1 is provided with a circumferential groove 2 continuously extending in a straight line in the circumferential direction on the tire equator line C, symmetrically positioned across the tire equator line C, and linear in the circumferential direction. A pair of shoulder circumferential grooves 3 extending continuously are provided, the rib 4 is defined by the circumferential groove 2 and the shoulder circumferential groove 3, and the rib 5 is defined by the shoulder circumferential groove 3 and the tread tread edge.
The ribs 4 and 5 are provided with linear sipes 6 that are inclined by an angle α with respect to the circumferential direction and at a predetermined interval in the circumferential direction.
The wedge-shaped shallow grooves 7 and 8 are provided at corners on the obtuse angle side defined by the sipe 6 and the side edges of the ribs 4 so as to include the corners and reach the apex on the acute angle side.

FIG. 2 is a development view of a tread pattern showing another embodiment of the present invention in a front view of a mounting posture on a vehicle.
Here, the tread tread surface portion 21 is provided with a circumferential groove 22 that extends continuously in a straight line in the circumferential direction on the tire equator line C, is located symmetrically across the tire equator line C, and is linear in the circumferential direction. A pair of shoulder circumferential grooves 23 extending continuously are provided, the ribs 24 are defined by the circumferential grooves 22 and the shoulder circumferential grooves 23, and the ribs 25 are defined by the shoulder circumferential grooves 23 and the tread tread edge.
A straight sipe 26 is inclined on the rib 24 and the rib 25 by an angle α with respect to the circumferential direction, and the inclined directions of adjacent sipe in the circumferential direction are opposite to each other at a predetermined interval in the circumferential direction. Provided.
A wedge-shaped shallow groove 27 having an obtuse angled corner defined by the sipe 26 and the side edge of the rib 24 and including the corner and having a length approximately half the length of the sipe 26; 28 is provided.

FIG. 3 is a partially enlarged view of a tread pattern showing another embodiment of the portion A of FIG.
In FIG. 3 (a), in a form including an obtuse angle corner section defined by the sipe 6 and the side edge of the rib 4, the sipe 6 has a length approximately ½ and parallel to the sipe 6. Shallow grooves 7 and 8 are provided.
In FIG. 3B, the sipe 6 is bent in a crank shape substantially at the center of the rib 4, and includes the corner on the obtuse angle side defined by the sipe 6 and the side edge of the rib 4. 6, and shallow grooves 7 and 8 are provided in parallel to the sipe 6.
In FIG. 3 (c), in a form including an obtuse angle side corner sectioned by the sipe 6 and the side edge of the rib 4, the sipe 6 has a length approximately ½ and parallel to the sipe 6. In place of the rib groove as the rib rigidity reducing portion, cuts 7a and 8a are provided.

For the purpose of evaluating the effect of suppressing the heel and toe wear of the pneumatic tire according to the present invention, Example tires 1 to 3 having the dimensions shown in Table 1 having a size of 315/80 R225 and Comparative tires 1 to 6 are used. Was mounted on a rim of 9.00 × 22.5, filled with an internal pressure of 850 kPa, mounted on a test vehicle and subjected to a field test, and the uneven wear step at 50% wear was measured. The results are shown in Table 1.
Here, the uneven wear level difference indicates the height difference in the tire radial direction between the stepping edge and the kicking edge in the tire circumferential cross section of each rib defined by the sipe.

The sipe and shallow groove form of the comparative tires 1 to 6 are shown in FIG.
FIG. 4 is a partially enlarged view of a tread pattern showing another form of the portion A in FIG. 1, and none of them is included in the present invention.
In FIG. 4 (a), the shallow groove 7 is provided over the entire length of the sipe 6 only in the illustrated lower side of the sipe 6 in parallel with the sipe 6.
In FIG. 4B, the shallow grooves 7 and 8 are provided over the entire length of the sipe in a form including acute corners defined by the sipe 6 and the side edges of the ribs 4.
In FIG. 4 (c), the shape includes an acute-angled corner section defined by the sipe 6 and the side edge of the rib 4, and has a length approximately half that of the sipe 6 and is parallel to the sipe 6. Shallow grooves 7 and 8 are provided.

In FIG. 4D, the sipe 6 is bent in a crank shape substantially at the center of the rib 4 and includes a sharp corner defined by the sipe 6 and the side edge of the rib 4. 6, and shallow grooves 7 and 8 are provided in parallel to the sipe 6.
In FIG. 4 (e), the shallow groove 7 is provided over the entire length of the sipe 6 in parallel with the sipe 6 only on the upper side of the sipe 6 in the drawing.
In FIG. 4F, shallow grooves 7 and 8 are provided on the upper side and the lower side of the sipe 6 in parallel with the sipe 6 over the entire length of the sipe 6.

According to the data in Table 1, it can be seen that the example tires 1 to 3 can achieve suppression of heel and toe wear as compared with the comparative tires 1 to 6. In particular, the tire of Example 1 has a small uneven wear step, includes an obtuse angled corner defined by a sipe and a rib, and does not include an acute angle apex. It has been shown that the configuration in which the shallow grooves are provided over the entire area is the most effective in suppressing heel and toe wear.
In addition, the comparative example tire 1 has a smaller uneven wear step than the example tire 1 during the reverse rotation and the comparative example tire 5 during the normal rotation. This is because a shallow groove is provided only on the stepping side of the sipe. This is because the wear of the rib on the sipe kick-out side is promoted, and the heel and toe wear is promoted during the normal rotation in the comparative example tire 1 and during the reverse rotation in the comparative tire 5, which is also not preferable.

  The present invention is effective when applied to a pneumatic tire suitable for use on idler shafts such as trucks and buses.

It is an expanded view of the tread pattern which shows one Embodiment of this invention. It is an expanded view of the tread pattern which shows other one Embodiment of this invention. It is the elements on larger scale of the tread pattern which show one Embodiment of this invention. It is the elements on larger scale of the conventional tread pattern.

Explanation of symbols

1 tread surface 2 circumferential groove 3 shoulder circumferential groove 4 rib 5 rib 6 sipe 7 shallow groove 8 shallow groove 7a notch 8a notch 21 tread tread 22 circumferential groove 23 shoulder circumferential groove 24 rib 25 rib 26 sipe 27 shallow groove 28 shallow groove

Claims (7)

A plurality of circumferential grooves extending continuously in the circumferential direction are provided in the tread tread portion, and ribs are defined between the circumferential grooves and between the shoulder circumferential groove and the tread tread edge, and are formed at least in the central region of the tread. Each of the two rows of ribs is a pneumatic tire having a plurality of sipes extending at an angle with respect to the circumferential direction and crossing the ribs at intervals in the circumferential direction,
A rib rigidity reduction portion adjacent to the sipe is provided at a corner on the obtuse angle side defined by each sipe and the side edge of the rib, and the rib at the corner on the acute angle side is at least ½ of the sipe length. A pneumatic tire provided over a range not including the side edges.   The pneumatic tire according to claim 1, wherein the rib rigidity reduction portion is constituted by a plurality of cuts or shallow grooves.   The pneumatic tire according to claim 1 or 2, wherein the shallow groove has an average width and depth of 1 to 5 mm.   The pneumatic tire according to any one of claims 1 to 3, wherein each sipe adjacent in the circumferential direction is inclined in the opposite direction or the same direction with respect to the circumferential direction.   The pneumatic tire according to any one of claims 1 to 3, wherein each sipe adjacent in the circumferential direction is inclined at the same angle in the same direction with respect to the circumferential direction.   The pneumatic tire according to any one of claims 1 to 5, wherein the width of the sipe is 0.3 to 2.0 mm, and the depth of the sipe is 50 to 90% of the depth of the circumferential groove.   The pneumatic tire according to any one of claims 1 to 6, wherein an inclination angle of the sipe with respect to a circumferential direction is set to 40 to 70 degrees.

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