JP3226968B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having reduced tread uneven wear and improved durability, and more particularly to a heavy-duty pneumatic tire used for trucks and buses.

[0002]

2. Description of the Related Art Since pneumatic tires require different performance depending on the road surface conditions and weather conditions, the tread is provided with grooves, sipes, etc. having various shapes, widths, depths, etc., as necessary. are doing. In particular, the sipe is disposed on the tread mainly to improve the steering stability when traveling on a wet road surface.

[0003] The performance of a sipe is greatly affected by changes in the shape, width, depth, etc. of the cut.
There are mainly a method of cutting the tire after vulcanization molding with a knife and a method of forming the tire at the time of vulcanization molding.

For example, Japanese Patent Application Laid-Open No. 63-291705 discloses that a sipe extending parallel or inclined in the width direction of a tread is provided to improve steering stability on a wet road surface. It is disclosed that occurrence of uneven wear is suppressed.

[0005]

The effects of uneven sipe arrangement and sipe shape on uneven wear as described above still remain unclear. When the sipe is simply inclined in one direction on the tread divided in the width direction by the zigzag main groove, an acute corner is always formed on a portion of each land portion on the kick-out side. This corner portion is relatively flexible, so it is easy to move with respect to the road surface at the time of driving the tire, and because of its low rigidity, the contact pressure is small, and there is less wear than the remaining portion, and as a result, heel and toe wear is caused. Called step wear occurs. Further, the land block may partially develop into pumping wear or diagonal wear from which the land block is detached, which may deteriorate durability. In addition, pumping wear refers to a state in which blocks are separated one after another at intervals in the circumferential direction after one block is separated, and diagonal wear is
This refers to a state in which uneven wear regions are generated at intervals in the circumferential direction and the shape of the tire when viewed from the side is a polygon.

[0006] Further, by arranging the sipe crossing each land row between the tread ends in one direction, the shape of each land part defined by the main groove, the sipe and / or the tread end becomes a parallelogram, There is a difference in rigidity between the step-in side portion and the kick-out side portion located near the outer edge side of each land portion.
When a lateral force is applied, uneven wear tends to occur particularly on the land portion in the shoulder region.

It has been found that the provision of such a sipe tends to cause uneven wear. Therefore, it is an object of the present invention to improve the durability of a pneumatic tire by optimizing the shape and the like of the sipe so as to suppress occurrence of uneven wear.

[0008]

SUMMARY OF THE INVENTION The present invention provides a pair of central peripheral grooves extending in parallel on a tread with its central peripheral line interposed therebetween, and extends in parallel with the central peripheral grooves at a position close to an end of the tread. In a pneumatic tire having a plurality of land rows, in which the tread is divided in the width direction by the main groove and the tread edge, each land row extends from the tread circumferential line near the central circumferential groove toward the tread end. The sipe has a diverging arrangement of sipe that crosses the land row at an acute angle against the direction of rotation of the tire with respect to the plane including the tread circumferential line, and the sipe is located between the central circumferential groove and the tread end. A pneumatic tire having a blunt area in which an edge of a sipe arrangement to be sharpened is enlarged at an edge near a tread end side of a land row so that no sharp corner is formed.

Further, for a land row in which the dulling area of the sipe occupies a tread side area corresponding to within 0.3 times the tread width from the tread edge, an arcuate sipe shape having a radius of approximately 50 to 120 mm. The sipe of the divergent array has an acute angle of 4 ° at an angle that intersects a straight line connecting the start and end of each land row and a plane including the tread circumference at the end.
Within the range of 0 to 70 °, the one closer to the tread end side has a larger angle, and the sipe that crosses each land row between the main grooves has a locally shallow cut bottom whose cut depth has been reduced. That the sipe traversing the land row between the main groove and the tread edge is a sipe notch of decreasing depth toward the tread edge, and that the diverging sipe is adjacent to each other within the land row. Spacing within the range of 0.5 to 1.5 times the width of the land row, cutting width within the range of 0.5 to 1.5 mm, within the range of 0.5 to 1.0 times the main groove depth Having a sipe cutting depth of not more than 0.2 to 0.8 times the sipe cutting depth, and a sipe crossing each land row between the main grooves. In the land row between the central circumferential grooves, between the central circumferential groove and the main groove near both outer edges with respect to the center of the width In land row it is more desirable to have the notch bottom and shallow cut tread edge side to the center circumferential line side.

Hereinafter, the present invention will be described with reference to the drawings. The feature of the tire of the present invention is that the tread pattern is improved, and the internal structure of the tire does not need to be modified for a general radial tire, so that the present invention can be followed. FIG. 1 shows a part of a tread of the tire of the present invention developed.

The tread 1 shown in FIG.
A plurality of land rows 5 divided in the width direction of the tread by a pair of central peripheral grooves 3 extending in parallel with each other and a main groove 4 extending parallel to the central peripheral grooves 3 at a position close to the tread edge. ~ 7. In the case of the tread 1 shown in FIG. 1, the number of the land rows is five. For convenience of explanation, the land portion row located at the center of the tread is the first land portion row 5, the land portion row between the central circumferential groove 3 and the main groove 4 is the second land portion row 6, and the land portion row between the main groove 4 and the tread end is located. Let the land row be the third land row 7.

Each of the land rows 5 to 7 is inclined at an acute angle from the tread circumferential line near the central circumferential groove 3 toward the tread end side with respect to a plane including the tread circumferential line against the tire rotation direction 14. The sipe 8 traverses the land row and forms a divergent arrangement. Sipe 8 of second and third land rows 6 and 7
Has a blunted area 19 in which the inclination angle of the sipe arrangement which sharpens at the edge near the tread end side of each land row 6, 7 is enlarged. When this blunted area 19 is divided by a sipe crossing the land row in an inclined manner, there is a sharp corner at the kick-out side, and the kick-out side is not worn as compared with the remaining part, so that the stepped wear is caused. Since so-called heel-and-toe wear occurs, the slope of the sipe at that portion is made obtuse so as not to form a sharp corner in order to prevent it. The sipe shape at this time is approximately 50 to 1
It has an arc shape with a radius of 20 mm, preferably 70-90 mm. If the radius of this arc is less than 50mm,
When the difference in the sipe angle between the edge near the center circumferential line of the land and the edge near the tread end becomes too large, the difference in rigidity between the land becomes too large, and uneven wear easily occurs. 120
If it exceeds mm, the angle difference of the sipe is insufficient and a sharp corner portion is formed on the kick-out side portion, and heel and toe wear is likely to occur. The sipe of the first land row may be straight or curved. In FIG. 1, the sipe of the first land part row is arranged in a linear shape that is symmetrical with respect to the central circumferential line, and the sipe of the second and third land part rows is arranged in a curved shape with a radius of 80 mm.

The sipe 8 of the divergent arrangement has an acute angle of intersection 40a, 9b, 9c between a straight line connecting the start end and the end in each land row and a plane including the tread circumference at the end. It is in the range of 70 °, preferably in the range of 45-60 °. The intersection angle increases from the first land row to the third land row (9a <9b <9c). If the crossing angle exceeds 70 °, heel-and-toe wear is likely to occur in the longitudinal direction of the extending sipe. If the crossing angle is less than 40 °, an acute angle portion is always formed on a part of the sipe section on the kicking side of the land. As a result, heel-and-toe wear occurs and the durability is deteriorated because the sharp portion does not wear as compared with the remaining portion.

Sipe 8 crossing each land row 5, 6 between the main grooves
The cut depth may be constant over the entire length of the sipe.However, it is preferable to prevent the occurrence of cracks and detachment of the land block due to the sipe cut, and to maintain the rigidity of the land portion, the cut depth is partially set. It is preferable to provide locally shallow cut bottoms 10 to 13 in which is reduced.

As shown in FIG. 2C, the sipe 8 crossing the land row 7 between the main groove 4 and the tread edge gradually reduces the sipe cutting depth toward the tread edge in order to maintain the land rigidity. Is preferred. When each sipe has two or more cut bottoms 10 to 13 in the land row between the main grooves,
In order to maintain the rigidity of the land portion, the first land portion row is configured such that the depth of the cut bottom 11 near both ends of the tread is made shallower than the depth of the cut bottom 10 near the center thereof, and the second land portion row is formed. It is preferable that the cutting depth of the cutting bottom 13 near the tread end is made shallower than the cutting depth of the cutting bottom 12 near the center circumferential line side. Note that making the cut bottom shallower means the same as making the cut bottom higher.

The spacing between sipes 8 adjacent to each other in each land row is within a range of 0.5 to 1.5 times the width of the land row 5 to 7 and the sipe cut width is 0.5 to 1.. 5 mm, the sipe cutting depth is 0.5 to 1.0 times the main groove depth, and the sipe cutting depth is 0.2 sipe cutting depth.
Although the ratio was set to 0.8 times, all of them are mainly optimized to prevent the occurrence of uneven wear.

FIG. 1 shows a tread pattern in which a large number of blocks 17 for preventing stone biting are arranged in a row on the central circumferential groove. Further, a shallow groove portion 15 having a wide sipe may be provided or not provided on the tread end side of the first land portion row 5 and the second land portion row 6 in order to improve drainage. Although the side grooves 16 are provided in FIG. 1 to make the land portion rigidity in the tread side region uniform, they may not be provided. The open end between the sipe and the central circumferential groove 3 and the main groove 4 may or may not have a V-shaped notch.

There are two methods for forming a sipe as described above. The method of cutting with a knife after vulcanization molding makes it possible to make a thin cut with substantially no groove width, and to reduce heel and toe wear. Although effective to some extent, as the tread wears, the sipe cuts become narrower, so stress tends to concentrate at the bottom of the sipe and cracks are more likely to occur, resulting in the detachment of the land block as a whole. Etc. are likely to occur. In order to prevent this, it was necessary to partially change the cutting depth and the shape of the sipe as necessary, or to change the extending direction of the sipe.However, these were cut with a knife after vulcanization molding. Very difficult to do. By forming a sipe by charging a blade during vulcanization molding, a complicated sipe shape can be formed relatively easily, and the above-described cut bottoms 10 to 13 and the like can be easily formed.

[0019]

[Effect] Between the central circumferential groove of the tread and the end of the tread, each land row divided by the inclined sipe has a sharp corner at the kicking-out side, but this is dulled to reduce the sipe. By eliminating the difference in rigidity of the land portion between the stepping-side portion and the kick-out side portion which are adjacent to each other, the wear of each portion becomes uniform, thereby suppressing the occurrence of uneven wear and improving the durability. In addition, by locally changing the cut depth of the sipe, the rigidity of the land portion can be maintained, and the occurrence of cracks due to the cut and the detachment of the land block can be prevented.

[0020]

The following is a description of comparative tests performed between the tire of the present invention and a conventional tire. ◎ Test tire ・ Invention tire This tire had a tread pattern shown in FIG. 1, the size was 11R24.5, and the tread width was 212 mm. The central peripheral groove 3 and the main groove 4 had a groove width of 12 mm and a groove depth of 15.2 mm. The stone biting prevention block 17 located on the central main groove is a parallelogram-shaped block having a side of 4 mm, a height of 4 mm, and an interval of 2 m.
m. The width of the land rows 5 to 7 divided by these grooves and / or tread ends is such that the first land row 5 has a width of 25 mm,
The second land row 6 is 29 mm, and the third land row 7 is 38 mm. The sipe 8 has a cut width of 0.8 mm, a cut depth of 12 mm, and an interval between sipe arrangements of 30 mm adjacent to each other in each land row. The extending shape of the sipe is a straight line symmetrical with respect to the central circumferential line in the first land part row 5, and the radius is approximately 80 mm in the second land part row 6 and the third land part row 7 having the blunted area 19. Arc. The intersection angles 9a, 9b, 9c between the straight line connecting the start and end of the sipe in each land row and the plane including the tread circumference at the end are defined by:
They are 45 °, 55 °, and 60 °, respectively. The sipe crossing each land row 5, 6 between the main grooves has a locally shallow cut bottom as shown in FIG. 2, and in the first land row 5, the cut depth of the cut bottom 10 near the width center thereof. 8 mm, the cutting depth of the cutting bottom 11 near both outer edges to 4 mm,
In the second land portion row 6, the cutting depth of the cutting bottom 12 on the central circumferential side was 8 mm, and the cutting depth of the cutting bottom 13 on the tread end side was 4 mm. Further, the sipe of the third land portion row 7 was arranged such that the cut depth was 5 mm on the tread end side and 12 mm on the main groove side, and the cut depth was changed as shown in FIG. The side groove 16 has a groove width of 2.
It was arranged in a waveform shape of 5 mm and the groove depth was 15.2 mm.
The shallow groove 15 provided in the first land part row and the second land part row to improve drainage has a cutting depth of 3 mm, the groove width is 3 mm in the first land part row 5, and the second land part row. 3.5m for 6
m.

Conventional tire 1 This tire has a tread pattern without a sipe as shown in FIG. 3, and the other structure is the same as that of the inventive tire. Conventional tire 2 This tire has a tread pattern having a sipe inclined in one direction as shown in FIG. 4, and the other structure is the same as the inventive tire.

Test Method Using each of the tires described above, a braking test was performed when the vehicle was running on a wet road surface, and an uneven wear amount generated on the tread during long-distance running was measured. In the braking test when traveling on a wet road surface, the above-described tires were mounted on an actual vehicle, and a braking distance was measured when braking was performed at a speed of 80 km / h under a normal internal pressure and a normal load. Table 1 shows the test results at that time. The numerical values in Table 1 are indicated by an index ratio with the performance of the conventional tire 1 being 100, and the larger the numerical value, the better the performance. The amount of uneven wear generated on the tread during long-distance running was measured by measuring the maximum width of uneven wear generated after running 150,000 km under a normal internal pressure and a normal load with each tire described above mounted on an actual vehicle. FIG. 5 is a plot of a value obtained by averaging the maximum width of uneven wear generated at that time with respect to the distance traveled by the actual vehicle.

[0023]

[Table 1]

The results of a braking test when traveling on a wet road surface show that the tread has excellent performance regardless of the shape of the sipe extending, etc. In addition, the tire of the present invention is superior to the others at any distance in the amount of uneven wear of the tread during long distance running, but the conventional tire 2 in which the sipe is inclined in one direction and disposed on the tread.
Is inferior in performance to the conventional tire 1 having no sipe.
From the above results, it can be seen that the tire of the present invention is superior to any of the conventional tires.

[0025]

According to the pneumatic tire, the sipe provided on the tread has an appropriate shape in which the sipe extends, so that the steering stability in traveling on a wet road surface is secured and the uneven wear of the tread is reduced. Generation can be suppressed and durability can be greatly improved. Properly setting the cut depth of the sipe has the effect of suppressing the occurrence of uneven wear, can also maintain the rigidity of the land, and makes it difficult for the land block to be detached by the cut.

[Brief description of the drawings]

FIG. 1 is a part of a development view of a tread 1 of a tire according to the present invention.

FIG. 2A is a cross-sectional view of the tread 1 shown in FIG. 1 in which a sipe of a first land row is cut along XX.
(B) is sectional drawing which cut | disconnected the sipe of the 2nd land part row | line by YY, and (c) is sectional drawing which cut | disconnected the sipe of the 3rd land part row | line by ZZ.

FIG. 3 is a part of a development view of a tread 20 of the conventional tire 1 having no sipe.

FIG. 4 is a part of a development view of a tread 21 of a conventional tire 2 having a sipe inclined in one direction.

FIG. 5 is a diagram showing a relationship between a traveling distance during long-distance traveling and a maximum width of uneven wear occurring at that time.

[Explanation of symbols]

 1 Tread 2 Central perimeter line 3 Central perimeter groove 4 Main groove 5 First land row 6 Second land row 7 Third land row 8 Sipe 9a, 9b, 9c Intersection angle 10, 11 Cut bottom 12, 13 Cut bottom 14 Tire rotation direction 15 Shallow groove 16 Side groove 17 Stone biting prevention block 18 Main groove 19 Blunt area 20, 21 Tread

Claims (8)

(57) [Claims] 1. A pair of central peripheral grooves extending in parallel with each other on the tread with its central peripheral line interposed therebetween, a main groove extending parallel to the central peripheral groove at a position close to the tread end, and a tread end. In a pneumatic tire having a plurality of land portions arranged in the width direction of the tread, each land portion row extends from a tread circumferential line near the central circumferential groove toward a tread end side with respect to a plane including the tread circumferential line. Crossing the land row at an acute angle against the direction of rotation of the tire has a sipe in a divergent arrangement, crossing the land row, the sipe is located on the tread end side of each land row located between the central circumferential groove and the tread end A pneumatic tire having a blunt area in which a sharp edge is increased at a near edge by increasing a slope angle of a sharpened sipe arrangement. 2. An arcuate sipe having a radius of approximately 50 to 120 mm per land row where the dulling area of the sipe occupies a side area of the tread corresponding to within 0.3 times the tread width from the tread edge. The pneumatic tire according to claim 1, wherein the pneumatic tire has a shape. 3. A diverging sipe having an acute angle between a straight line connecting the start and end of each land row and a plane including a tread circumference at the end within a range of 40 to 70 °.
The pneumatic tire according to claim 1 or 2, wherein the closer to the tread end, the larger the angle. 4. The pneumatic pneumatic pump as claimed in claim 1, wherein the sipe traversing each land row between the main grooves has a locally shallow cut bottom with a reduced cut depth. tire. 5. The sipe notch which crosses the land row between the main groove and the tread edge is a sipe notch whose depth is gradually reduced toward the tread edge. The pneumatic tire as described. 6. The diverging arrays of sipes are adjacent to each other in the land row and have a spacing in the range of 0.5 to 1.5 times the width of the land row, in the range of 0.5 to 1.5 mm. 6. A sipe cutting depth in the range of 0.5 to 1.0 times the depth of the main groove and the depth of the main groove.
A pneumatic tire according to claim 1. 7. The pneumatic tire according to claim 4, wherein the cut depth of the locally shallow cut bottom is within a range of 0.2 to 0.8 times the sipe cut depth. 8. The sipe crossing each land row between the main grooves, but in the land row between the central peripheral grooves, the notches near both outer edges are shallower in the vicinity of the center of the width, and between the central peripheral groove and the main groove. The pneumatic tire according to claim 4 or 7, wherein the land portion row has a locally shallow cut bottom in which a cut at a tread end side is made shallow with respect to a center circumferential line side.