JPH11334319A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively inhibit heel and tow wear in each block; and to inhibit cracks and partial desorption. SOLUTION: In each block 8 of a pneumatic tire 1, a kicking part K has earlier wear at linear driving rather than a tread part F. Where, to provide each block 8 with uniform wear contrary to the above fact at turning driving, earlier wear is to provide to the tread part F rather than the kicking part K in each block 8. To achieve this purpose, the width of the tread part F in each block 8 is widened compared with that of the kicking part K to increase the horizontal force burden of the tread part F at turning driving, exerting earlier wear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a block type pneumatic tire having a large number of blocks defined in a tread portion.

[0002]

2. Description of the Related Art In general, a pneumatic tire having a large number of blocks defined on a tread portion may cause uneven wear called heel-and-toe wear particularly at a tread end portion due to long-term running. Here, such heel-and-toe wear is caused by the fact that the input value from the road surface to each block during traveling is small at the stepped portion and conversely large at the kicked portion. This is a phenomenon in which each block wears in the circumferential direction in a saw-tooth fashion.

For this reason, conventionally, the pitch, arrangement, shape and the like of each block are variously changed to reduce the amount of deformation of each block, thereby preventing heel and toe wear. I have.

[0004]

However, such a conventional method can be expected to have a certain effect, but it is not sufficient. When the vehicle is driven for a long period of time, heel and toe wear still occurs.

[0005] It is an object of the present invention to provide a pneumatic tire that can effectively suppress heel and toe wear of a block.

[0006]

SUMMARY OF THE INVENTION The purpose of the invention is as follows.
In the tread portion, by forming a plurality of circumferential grooves spaced apart in the axial direction and a large number of lateral grooves intersecting the circumferential groove in the tread portion, a plurality of block rows including a plurality of blocks circumferentially separated from each other In the pneumatic tire in which the mounting direction with respect to the vehicle is defined, the width at the stepped portion of each block constituting the block row located at least at the tread end portion is made larger than the width at the kick-out portion,
By making the width direction shear rigidity of the stepped portion of each of these blocks larger than the width direction shear rigidity of the kicking portion,

Second, by forming a plurality of circumferential grooves spaced apart in the axial direction and a large number of lateral grooves intersecting the circumferential grooves in the tread portion, the tread portion is composed of a large number of blocks circumferentially separated from each other. In a pneumatic tire in which a plurality of block rows are defined and the mounting direction with respect to the vehicle is defined,
A plurality of narrow grooves extending in the circumferential direction and opening at the kick-out end are formed in the kick-out portion of each block constituting the block row located at least at the tread end portion, and the width-direction shear rigidity of the step portion of each block is kicked. This can be achieved by making the shear strength greater than the shear strength in the width direction of the projection.

First, the pneumatic tire of the present invention is mounted on a vehicle. At this time, the tread portion of each block is mounted so as to contact the ground before the kick-out portion during normal rotation of the pneumatic tire. Here, when a block row composed of blocks having a difference in the shear rigidity in the width direction is arranged only at one end of the tread, mounting is performed such that the block row is outside the mounting. Next, when running straight with such a pneumatic tire, the input value from the road surface to each block is small as described above, especially at the tread edge, which is small at the stepped portion, and conversely, large at the kicking portion,
The wear speed of the kick-out portion becomes larger than the wear speed of the step portion.

On the other hand, when turning with such a pneumatic tire, at least the width of the stepped portion of each block constituting the row of blocks located at the end of the tread is made wider than the width of the kick-out portion, or By forming a plurality of narrow grooves extending in the circumferential direction in the kick-out portion and opening at the kick-out end, the width-direction shear rigidity of the stepped portion of each of these blocks is greater than the width-direction shear rigidity of the kick-out portion. The stepped portion of the block bears a greater lateral force than the kick-out portion, and as a result, the wear speed of the stepped portion becomes higher than the wear speed of the kick-out portion.

[0010] Since the actual running of the pneumatic tire is a mixture of straight running and turning running, the two types of wear occur in each block, and the wear is substantially uniformized. In particular, the heel and toe wear of the block located at the end of the tread is effectively suppressed.

Here, in order to make the shear strength in the width direction of the stepped portion of each block larger than the shear rigidity in the width direction of the kicking portion, the kicking portion of each block is obliquely inclined with respect to the circumferential direction. May form a sipe that opens into the circumferential groove. However, in this case, a very small block piece having rigidity is defined by the sipe on the side of the kick-out end from the sipe. However, such a block piece is easily deformed by an external force, so that the groove of the sipe is formed when rolling. A large strain is repeatedly generated at the bottom, which may cause a crack at the bottom of the groove, and in some cases, a piece of the block may fall off.

On the other hand, when the width of the step portion of each block is wider than the width of the kick portion as described above, it is not necessary to provide the sipe as described above.
It is possible to prevent the generation of cracks due to the sipe and the falling off of the block pieces.

As described above, a plurality of narrow grooves extending in the circumferential direction at the kick-out portion of each block and opening at the kick-out end are formed by a plurality of the kick-out portions of each block in the axial direction. Just by being divided, the stepping side ends of these divided areas are continuous with the center of each block. For this reason, the rigidity of these divided areas is considerably larger than the above-mentioned block piece, and the deformation of each divided area during rolling is suppressed by contact with the divided areas on both sides,
Thereby, the generation of cracks due to the narrow grooves as described above,
The falling off of the block pieces is effectively suppressed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a pneumatic radial tire in which a mounting direction with respect to a vehicle is defined, and the tire 1 has a tread portion 2. A plurality of, here four, circumferential grooves 37 are formed on the outer surface of the tread portion 2 that contacts the road surface in contact with the road surface while bending in the circumferential direction (a direction parallel to the tire equatorial surface 3) while bending in a crank shape. The grooves 37 are separated from each other by a predetermined distance in the axial direction of the tire 1. Both tread ends 5, 6 and circumferential groove 37 of the tire 1
On the outer surface of the tread 2 between
A number of lateral grooves 7 intersecting 37 are formed, and these lateral grooves 7
Extend in the axial direction and are equidistant from each other in the circumferential direction.

As a result, these circumferential grooves 37
And a plurality of rows of a plurality of blocks 8 circumferentially separated from each other by a lateral groove 7, here, five block rows 9
Is defined. And these blocks 8 are tire 1
Is rotating in the normal direction (the direction of the arrow), the stepped portion F contacts the ground prior to the kick-out portion K.

Each block 8 constituting at least the block row 9 located at the end of the tread, in this embodiment, each block 8a, 8b, 8c, constituting each block row 9a, 9b, 9c, 9d, 9e The width of the stepped portion F of 8d and 8e is wider than the width of the kick-out portion K.
The plane shape of 8a, 8e is L-shaped, and each block 8b, 8
By making the planar shapes of c and 8d T-shaped, the shear strength in the width direction at the stepped portion F of each block 8 is made larger than the shear strength in the width direction at the kick-out portion K.

The widthwise shearing rigidity of the stepped portion F of each block 8 is equal to the widthwise shearing rigidity of the kick-out portion K, which is 1.
It is preferably at least 29 times. The reason is that when the ratio is less than 1.29 times, the lateral force load on the stepped portion F of each block 8 does not increase so much, and the effect of suppressing heel and toe wear is reduced. Here, the ratio between the shear strength in the width direction at the stepped portion F of each block 8 and the shear strength in the width direction at the kick-out portion K is determined by the radial outer end of the stepped portion F and the radial outer end of the kick-out portion K. The lateral deformation is measured by applying a lateral force of 2 kg per 1 cm in the circumferential direction, and the value of the former is divided by the value of the latter.

Next, the operation of the first embodiment of the present invention will be described. First, the tire 1 is mounted on a vehicle. At this time, the tire is mounted such that the stepped portion F of each block 8 comes into contact with the ground before the kick-out portion K when the tire 1 rotates normally. Next, when the vehicle travels straight with such a tire 1, the input value from the road surface to each block 8 is small at the stepped portion F and large at the kicked portion K, so that the wear speed of the kicked portion K is reduced. It becomes larger than the wear rate of F.
For this reason, in each block 8, especially the block 8a or 9e of the block row 9a or 9e located at the end of the tread on the outside of mounting.
It is considered that heel and toe wear occurs in 8e.

However, in this embodiment, the width of the steps 8a, 8b, 8c, 8d, 8e at the stepped portion F is made wider than the width at the kick-out portion K, so that the width direction of the stepped portions F of these blocks 8 is increased. Since the shear stiffness is set to be larger than the shear stiffness in the width direction of the kicking portion K, when the tire 1 turns, the stepped portion F of each block 8 becomes the kicking portion K.
Bears more lateral forces, and as a result these blocks 8
Is greater than the wear rate of the kick-out section K. When such straight running and turning running are mixed (generally, the actual running of the tire 1 is a mixture of straight running and turning running), the two forms of wear occur in each block 8. As a result, the wear of each block 8 is substantially uniform, and the heel and toe wear generated in all the blocks 8, especially the blocks 8a and 8e at the tread end, is effectively suppressed.

Here, in order to make the shear strength in the width direction of the stepped portion F of each block 8 greater than the shear strength in the width direction of the kicking portion K, the kicking portion of each block is inclined obliquely to the circumferential direction. However, it is also conceivable to form a sipe whose both ends open into the circumferential groove. However, in this case, a very small block piece having rigidity is defined by the sipe on the side of the kick-out end from the sipe. However, such a block piece is easily deformed by an external force, so that the groove of the sipe is formed when rolling. A large strain is repeatedly generated at the bottom, which may cause a crack at the bottom of the groove, and in some cases, a piece of the block may fall off.

On the other hand, when the width of the stepped portion F of each block 8 is wider than the width of the kick-out portion K as described above, it is not necessary to provide a sipe as described above. And the falling off of the block pieces can be prevented.

FIG. 2 is a view showing a second embodiment of the present invention. In this embodiment, the circumferential grooves 4a, 4b, 4c, and 4d are linearly extended in the circumferential direction, so that the tread portion 2 has a substantially rectangular shape (the width of the stepped portion F and the width of the kick-out portion K are substantially the same). ), And a plurality of narrow grooves (including sipes) 41 extending in the circumferential direction, which open at the kick-out end, are formed in the kick-out portion K of each block 8. When the narrow groove 41 is formed in the kick-out portion K of each block 8 in this manner, the shear rigidity in the width direction at the kick-out portion K decreases,
As a result, the shear rigidity in the width direction at the stepped portion F of each block 8 becomes greater than the shear rigidity in the width direction at the kick-out portion K, and the heel and toe wear of these blocks 8 is effectively suppressed as described above.

In this embodiment, the narrow groove 41 is formed in the kick portion K of each block 8 as described above. Only by being divided, the stepping-side ends of these divided areas 42 are continuous with the center of each block 8.
For this reason, the rigidity of these divided areas 42 is considerably larger than the block piece defined by the aforementioned sipe, and the deformation of each divided area 42 during rolling is suppressed by contact with the divided areas 42 on both sides. This effectively suppresses the occurrence of cracks and the falling off of the block pieces due to the narrow grooves as described above. Other configurations and operations are the same as those of the first embodiment.

[0024]

Next, test examples will be described. In this test, a comparative tire having a tread pattern obtained by removing the narrow groove 41 from the second embodiment, a test tire 1 having a tread pattern described in the first embodiment,
The test tire 2 having the tread pattern described in the embodiment was prepared. Here, the size of each tire is 11R2
It is 2.5 14 PR and the size of the rim to be installed is 8.25 × 22.
It was five.

Next, after assembling the above-mentioned tires into a rim, an internal pressure of 8.0 kg / cm ² is charged and 2D-4
It was mounted on the front wheels of a car and ran a total of 50,000 km on a general road (paved road). After running, the heel and toe wear amount of the block located outside the mounting of each tire, that is, the difference between the wear depth at the stepped portion and the wear depth at the kick-out portion of each block was determined. The result is 6.7 for the comparative tire.
mm, but 1.8mm for test tire 1 and 2 for test tire 2.
In 2.7mm, heel and toe wear was improved.

In the present invention, a block row composed of blocks having a difference in shear stiffness in the width direction may be arranged only at one end of the tread. In this case, the tire is mounted on the vehicle such that the block row is outside the mounting.

[0027]

As described above, according to the present invention, the heel-and-toe wear of the block can be effectively suppressed, and the occurrence of cracks and the partial detachment of the block can also be suppressed.

[Brief description of the drawings]

FIG. 1 is a development view of a tread portion showing a first embodiment of the present invention.

FIG. 2 is a development view of a tread portion showing a second embodiment of the present invention.

[Explanation of symbols]

 2 ... tread 7 ... lateral groove 8 ... block 9 ... block row 37 ... peripheral groove 41 ... narrow groove F ... stepped part K ... kick out part

Claims (2)

[Claims] 1. A plurality of rows of a plurality of blocks circumferentially separated from each other by forming a plurality of circumferential grooves separated in an axial direction and a plurality of transverse grooves intersecting the circumferential grooves in a tread portion. In the pneumatic tire in which the mounting direction with respect to the vehicle is defined, the width at the stepped portion of each block constituting at least the block line located at the tread end is made wider than the width at the kick-out portion, A pneumatic tire characterized in that the widthwise shearing rigidity of the stepped portion of each of these blocks is greater than the widthwise shearing rigidity of the kicking portion. 2. A plurality of rows comprising a plurality of blocks which are circumferentially separated from each other by forming a plurality of circumferential grooves separated in the axial direction and a plurality of transverse grooves intersecting the circumferential grooves in the tread portion. In the pneumatic tire in which the mounting direction with respect to the vehicle is defined, at least the extending portions of the blocks constituting the block line located at the tread end portion extend in the circumferential direction and open at the kicking end. A pneumatic tire, wherein a plurality of narrow grooves are formed, and the widthwise shearing rigidity of a stepped portion of each of these blocks is made larger than the widthwise shearing rigidity of a kicking portion.