JP2002144818A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of partial abrasion to a shoulder land part. SOLUTION: This pneumatic tire is provided with a plurality of circumferential grooves 6 in a tread surface 5 while a belt 2 and a tread 3 are successively arranged in an external peripheral side of a crown part of a carcass 1, and the tire is constituted by circularly annularly burying two layers of cord layers 8, 9 mutually crossing a cord between the layers as an attitude extending each cord in a surface almost in parallel to an equatorial surface of the tire in the vicinity of a rib surface in almost the central part in a width direction of a shoulder rib 7 partitioned in the vicinity of a side edge of the tread surface 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire,
Above all, a pneumatic radial tire for heavy loads for trucks and buses particularly improves the uneven wear resistance of a shoulder land portion, and in many cases, a shoulder rib.

[0002]

2. Description of the Related Art For example, as a pneumatic radial tire for heavy loads based on ribs, a radially extending radially extending tire between a pair of bead portions 21 and 21 is exemplified in FIG. A belt 23 and a tread 24 are sequentially disposed on the outer peripheral side of the crown portion of the carcass 22, and a plurality of circumferences extending continuously in the circumferential direction on the tread tread surface 25 to form a linear shape, a zigzag shape, or the like. Groove 26
And a plurality of ribs 27 are defined on the tread surface 25 by the circumferential grooves 26. 28 in the figure
Indicates sidewalls connected to the bead portions 21 from the respective tread side portions.

By the way, in such a tire, the tread surface 25 is generally formed in a cross-section as shown in the figure, and is formed in a curved surface shape composed of one or a plurality of circular arcs. In particular, it is located near the side edge of the tread surface 25. In the shoulder rib 27, the difference between the circumferential length on the side edge side of the tread surface 25 and the circumferential length on the tire equatorial plane side is large. There was a problem that early wear caused by dragging of the ribs 27 caused uneven wear called shoulder dropping wear.

[0004]

Therefore, by increasing the rubber thickness of the portion of the shoulder rib 27 on the side edge side of the tread surface 25 and increasing the circumferential length of the portion, the above-described occurrence of drag wear can be prevented. Although suppression has been done,
According to this, conversely, the circumferential length of the shoulder rib 27 on the tire equatorial plane side becomes relatively short, and this time, the circumferential groove is formed in the portion of the rib 27 adjacent to the circumferential groove 26. There is a high possibility that riverware which occurs along the inner surface 26 and proceeds to the inside of the rib 27 will be caused. In addition, this also causes a problem that uneven wear similar to the conventional one occurs after the wear of the rubber on the side edge side of the shoulder rib 27 whose thickness has been increased. Was not.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of the prior art. It is an object of the present invention to provide a method for unevenly abrading a shoulder land portion to a tread tread side edge portion. Pneumatic tires that can effectively suppress the occurrence of wear regardless of the state of wear of the shoulder land, and that do not generate river wear on the tire equatorial plane side of the shoulder land. To offer.

[0006]

According to the pneumatic tire of the present invention, a belt and a tread are sequentially arranged on a carcass extending toroidally between a pair of bead portions, for example, on an outer peripheral side of a crown portion of a radial carcass.
On the tread tread, a plurality of circumferential grooves extending continuously in the circumferential direction are provided, and at a shoulder land portion defined at a side edge portion of the tread tread, at a substantially central portion in the width direction,
Close to the land surface, two or more cord layers, with the cords intersecting each other between the layers and preferably extending substantially symmetrically,
Each cord is annularly buried as a posture extending in a plane substantially parallel to the tire equatorial plane.

[0007] In this tire, when the tire is filled with air pressure, particularly in the shoulder land portion where the cord layer is embedded, the circumferential length of the land portion and the cord layer both increase, so that a plurality of cord layers are formed. Are relatively displaced in the direction of decreasing their intersection angle, in other words, in the direction of falling down.

[0008] In this case, such a falling displacement of the cord layer cord is performed with a tread rubber near the surface of the land portion, which is vulcanized and bonded to the cord layer in the land portion in which the code layer is embedded, Thus, the surface of the shoulder land portion at the portion where the cord layer is buried and the vicinity thereof is depressed and deformed with respect to the other surface portion of the shoulder land portion, and a dent is generated there.

As a result, both the tread tread side edge side portion and the tire equatorial plane side portion of the shoulder land portion have a long circumference, and receive a sufficiently large contact pressure when the tire is rolling. Both parts will be effectively protected from premature wear due to drag.

[0010] The fact is that even if the side edge portion of the shoulder land portion wears due to the continuous use of the tire, the tire layer continues to function due to the original function of the belt layer and the occurrence of drag wear on the concave portion. Therefore, the uneven wear resistance of the shoulder land portion is greatly improved as compared with the prior art.

By the way, the exposed portion of the cord layer itself on the land surface is worn away with the wear of the recessed portion. However, the cord layer remains as long as the cords cross each other. The function can be sufficiently exhibited to contribute to the appearance of the dent.

Here, considering such abrasion of the cord layer due to the road surface, the cord of the cord layer is made of an organic fiber cord, compared to the case where the cord layer is made of a steel cord or the like. It is preferable in reducing the influence.

More preferably, in such a tire, the ratio of the amount of depression of the cord layer buried portion to the width of the shoulder land portion in the state where the tire is filled with the maximum air pressure (according to JATMA YEAR BOOK) is 0.004. And the same ratio under the condition that the tire internal pressure is the atmospheric pressure is set to 0.004 or less. That is, if the ratio of the air pressure at the time of filling is 0.004 or less, the uneven wear resistance cannot be improved to the expected degree due to the insufficient dent amount, while the tire internal pressure is large. If the ratio at the time of the atmospheric pressure is more than 0.004, the amount of depression at the time of filling the air pressure becomes too large, so that the cord layer buried portion cannot be sufficiently grounded, and the grounding in the shoulder land portion is performed. There is a possibility that the variation of the pressure becomes large, the road surface grip force is reduced, and the required drag wear cannot be brought to the concave portion.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged cross-sectional view showing a main part. In this tire shown in a state where the maximum air pressure is filled in a rim-assembled tire, reference numeral 1 denotes a radial carcass extending toroidally between bead portions (not shown). , 2, and 3 respectively indicate a belt and a tread sequentially arranged on the outer peripheral side of the crown portion of the radial carcass 1. Reference numeral 4 in the figure denotes a sidewall connecting the tread 3 and a bead (not shown).

Here, a plurality of circumferential grooves 6 extending linearly or zigzag continuously in the tread circumferential direction are provided on the tread tread surface 5, so that the circumferential grooves 6 and the circumferential grooves can be interposed. A plurality of land portions, for example, ribs 7 are defined between the groove 6 and the side edge of the tread surface 5.

Of the ribs 7, the shoulder ribs 7 defined near the side edges of the tread tread surface 5 have at least two layers of cords near the rib surface at substantially the center in the width direction thereof. The layers 8 and 9 are positioned in a plane substantially parallel to the tire equatorial plane XX and are buried in an annular shape. Each of the cords forming the code layers 8 and 9 is shown in FIG. As shown in the perspective view, the layers extend in directions intersecting each other between the layers, preferably substantially symmetrically with respect to a virtual circumferential line passing through the intersection.

In such a tire, the end faces of the cord layers 8, 9 which are preferably formed of the organic fiber cord, at the end of the vulcanization molding, have a rib surface as shown in a schematic plan view in FIG. And can be slightly embedded in the ribs.

In any of these cases, the embedding of the cord layers 8 and 9 as described above is performed, for example, as shown in FIG. The shoulder rib 7
Is divided in the width direction at a position corresponding to the central portion of the above, and between the divided portions, two separately prepared cord layers 8, 9 are preferably attached to a rubber sheet, or
This can be performed by placing the tread rubber divided portions 11a on the tread rubber main body portion 11b via the cord layers 8 and 9, and then placing the tread rubber divided portions 11a through the cord layers 8 and 9. By subjecting such a tread rubber 11 containing a rubber material to general tire molding on a molding drum, the cord layers 8 and 9 are provided at predetermined positions of the green tire, and eventually the product tire after vulcanization molding. It can be arranged as you did.

The tire constructed as described above is used in a JATM
When the rim is assembled to the applicable rim in accordance with the provisions of A YEAR BOOK and the maximum air pressure is filled into the tire, the tread 3 will be expanded and deformed over the entire surface of the tread 3 due to the air pressure. The length also becomes longer.

Such an increase in the circumferential length of the shoulder rib 7 causes the respective cord layers 8 and 9 embedded therein to expand and deform, and as a result, the cords forming the cord layers 8 and 9 fall in the direction in which they fall. The surface of the rib 7 is depressed and deformed in the vicinity of the portion where the cord layers 8 and 9 are provided and in the vicinity thereof by the accompanying deformation of the tread rubber integral with the cord layer cord. Is formed over the entire circumference of the recess.

Here, such a concave portion 10 shown in an enlarged manner in FIG. 5 preferably has a depth exceeding 0.004 times the width w of the shoulder rib 7 when the tire is filled with the maximum air pressure. And the depth is 0.004 times or less when the tire internal pressure is set to the atmospheric pressure. Note that the depth of the concave portion here refers to the depth at the embedding position of the cords 8 and 9 with respect to a line segment connecting both side edges of the shoulder rib 7 as illustrated.

According to the tire configured as described above, since the recess 10 is present when the tire is filled with the maximum air pressure, the peripheral lengths of both side edges of the shoulder rib 7 and the vicinity thereof are both reduced. Since the length can be balanced, the ribs 7 of the tire 7
Either side edge portion can be effectively protected from drag wear, and the occurrence of shoulder wear on the shoulder ribs 7 and uneven wear such as river wear can be sufficiently suppressed.

In addition, even if the wear of the side edges of the ribs 7 progresses, the cord layers 8 and 9 can sufficiently exhibit their original functions, and the recesses 1
Since 0 is worn early by the occurrence of sliding wear, the occurrence of uneven wear on the ribs 7 is suppressed for a long time even if the ribs 7 are worn.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For trucks and buses, size 315 /
The tire of 80R22.5 is mounted on the rim of 9.00, and the tire is filled with 825 kPa of air pressure,
The tire is mounted on a front wheel of a truck having a loading capacity of 98 kN in a 2-D4 format (two front wheels, four drive wheels and four idle wheels), and is mounted on a highway (80 km / h) and a general road (5 km).
0 km / h) at a ratio of 6: 4 for a total of 60,000 km, and the average wear of the inner and outer ends of the shoulder rib was measured. The results shown in Table 1 were obtained.

[0025]

[Table 1]

According to Table 1, it is clear that Examples 1, 2 and 3 can greatly improve uneven wear resistance as compared with conventional tires.

[0027]

As described above, according to the present invention, the local wear of the shoulder land portion, which is particularly severely generated in the steering wheel tire, can be greatly reduced, and the uneven wear resistance can be effectively improved.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional perspective view showing an embedding mode of a code layer.

FIG. 3 is a schematic plan view showing an exposed state of a cord end;

FIG. 4 is a view showing a process of disposing a cord layer on an unvulcanized tread rubber.

FIG. 5 is an enlarged sectional view showing a recess.

FIG. 6 is a cross-sectional view showing a conventional tire.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 carcass 2 belt 3 tread 4 sidewall 5 tread tread 6 circumferential groove 7 rib 8, 9 cord layer 10 recess w rib width d depth

Claims (3)

[Claims] 1. A belt and a tread are sequentially disposed on an outer peripheral side of a crown portion of a carcass extending toroidally between a pair of bead portions, and a plurality of circumferences extending continuously in a circumferential direction on a tread tread surface. A tire provided with grooves, two layers where cords cross each other between the layers near the surface of the land in the widthwise center of the shoulder land section defined near the side edge of the tread tread. A pneumatic tire in which each of the above-mentioned cord layers is embedded in an annular shape such that each cord extends in a plane substantially parallel to the tire equatorial plane. 2. A state in which the ratio of the depression amount of the cord layer buried portion to the width of the shoulder land portion in the state where the tire is filled with the maximum air pressure is set to a value exceeding 0.004 and the tire internal pressure is set to the atmospheric pressure. A similar ratio under 0.00
The pneumatic tire according to claim 1, wherein the number is 4 or less. 3. The pneumatic tire according to claim 1, wherein the cord of the cord layer is an organic fiber cord.