JP2003285609A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more efficiently prevent a tire from causing cracks of the bottom of a grove than a conventional method that curvature radius of the bottom of the grove is enlarged in a cross section in the tread width direction or the like in a pneumatic tire. <P>SOLUTION: A peripheral groove 11 is arranged to continuously extend along the peripheral direction of the tread 10, and a land portion 12 adjacent to the peripheral groove 11 is partitioned. The tread 10 is provided with a belt 8 on the inner peripheral side thereof, and a reinforcing material 13 comprising a fiber member is arranged in the tread and a position of the reinforcing material 13 to correspond to the land portion 12 in the cross section in the tread width direction is located outwardly from the position to correspond to the peripheral groove 11. A position of the reinforcing member 13 to correspond to the bottom of a peripheral groove 14 is folded by curvature radius larger than two times or more of the minimum curvature radius at the bottom of the peripheral groove 14. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tires having relatively deep grooves such as studless tires and all-season tires for passenger cars and truck buses, and tires for mining vehicles. The present invention relates to a pneumatic tire that is suitable for use as a tire that is extremely large and that travels on rough roads.

[0002]

2. Description of the Related Art Studless tires and all-season tires of this kind having tread treads each having a circumferential groove extending continuously in the circumferential direction of the tread and having a relatively deep depth are used to block or rib the tire when rolling. Since the land portions such as the above are largely deformed in the direction of protruding into the circumferential groove, the groove bottom of the circumferential groove in the ground contact surface is repeatedly subjected to a large compressive force in the direction of reducing the groove width.

On the other hand, the circumference of the tread surface is
Since the length of the tread gradually decreases toward the tread side edge in the central part, the land part of the tread side region tends to be dragged by the land part of the central part in load rolling of the tire. Since a large circumferential shearing force is repeatedly applied to the groove bottom of the circumferential groove in the ground contact surface, cracks are likely to occur in the groove bottom at a relatively early stage.

The groove bottom crack thus generated is
When it reaches the belt as it travels inside the tread, it contributes to the belt separation, so it is advantageous to suppress the occurrence of groove bottom cracks as much as possible, which means that the load is large and the vehicle runs on rough roads. The same is true for tires for mining vehicles that are forced to do so.

[0005]

Therefore, conventionally, in order to suppress the occurrence of cracks at the groove bottom, the radius of curvature of the groove bottom in the cross section in the width direction of the tread is increased to concentrate stress on the groove bottom of the circumferential groove. Although prevention is widely performed in general, it is still not sufficient as a countermeasure, and there is still a high possibility that groove bottom cracks will occur when used under particularly severe conditions.

The present invention provides a pneumatic tire in which the occurrence of cracks in the groove bottom is improved more effectively than in the conventional method such as increasing the radius of curvature of the groove bottom in the cross section in the tread width direction. Is.

[0007]

In order to achieve the above object, the pneumatic tire of the present invention is provided with at least one circumferential groove continuously extending in the circumferential direction of the tread, and It divides the land area located adjacent to the circumferential groove,
A pneumatic tire having a belt arranged on the inner peripheral side of the tread, wherein a reinforcing material made of a woven or non-woven fabric made of a fibrous member is arranged in the tread, and within the widthwise cross section of the tread. The extending position of the portion of the reinforcing material corresponding to the land portion is radially outside of the extending position of the portion corresponding to the circumferential groove, and the portion of the reinforcing material corresponding to the circumferential groove bottom is defined as the groove bottom. It is characterized in that it is curved with a radius of curvature not less than twice the minimum radius of curvature in.

According to this, the compressive force, shearing force, etc., which is concentrated on the minimum radius of curvature of the bottom of the circumferential groove of the tire tread, is effectively made based on the support of the force by the fiber member of the reinforcing material. Since it can be relaxed, it is possible to effectively prevent the generation of cracks in the minimum radius of curvature.
Further, in disposing the reinforcing material, in order to efficiently exhibit the above effect of the reinforcing material along the minimum radius of curvature, rather than disposing the reinforcing material only in the groove bottom portion,
It is better to be located radially outside at least at one position closer to the land part from the groove bottom, and this makes it possible to efficiently cover the minimum radius of curvature with the reinforcing material. The arrangement position of is at the portion corresponding to the land portion and at the portion corresponding to the circumferential groove is outside in the tire radial direction.

Moreover, here, the reinforcing member is curved and extends with a radius of curvature larger than the minimum radius of curvature of the groove bottom, so that the curved portion is repeatedly subjected to the deformation of the land portion such as the block or rib. It is possible to improve durability of the reinforcing material itself, which receives an input such as bending deformation, to allow the reinforcing material to exhibit its original function for a long period of time, and to prevent the occurrence of groove bottom cracks more advantageously.

Here, although the reinforcing material can be made of a non-woven fabric, it is desirable that it be made of a woven fabric, especially a biaxial woven fabric. By the way, in this case, the extending form of the fiber member of the biaxial woven fabric can be appropriately selected as required. For example, each of the warp yarn and the weft yarn is arranged at an inclination of 45 degrees with respect to the circumferential direction of the tread. Alternatively, it is also possible to arrange them in a rectangular coordinate form of 0 degree and 90 degrees.

When the extending form of the fiber member is arranged at an inclination of 45 degrees with respect to the circumferential direction of the tread, both the compressive force and the shearing force can be dispersed and supported by the weft yarn and the warp yarn, respectively. In the case of the arrangement of orthogonal coordinates of 0 degree and 90 degrees with respect to the circumferential direction, for example, the compressive force can be supported by the weft thread and the shear force can be supported by the warp thread.

According to such a constitution of the reinforcing member, the widthwise compressive force and the shearing force applied to the groove bottom can be more effectively supported by the yarns in the longitudinal and transverse directions of the biaxial woven fabric. The deformation of the bottom can be suppressed more effectively. When the reinforcing material is composed of a triaxial woven fabric, the input to the groove bottom can be further alleviated by the distribution of the force based on the extending direction of the fiber member.

Also preferably, the fiber member is nylon,
It is formed by monofilament cords of organic fibers such as polyethylene terephthalate and aromatic polyamide, or metal fibers such as steel. This is because the compressive rigidity of the fiber member that contributes to the structure of the reinforcing material is important for supporting the compressive force at the bottom of the groove by the reinforcing material. This is because it is not possible to sufficiently bear the force, and in this respect, the monofilament cord can exhibit greater compression rigidity. Here, the organic fiber monofilament cord is advantageous in realizing weight reduction of the tire, and the metal fiber monofilament cord can enhance the ability to support compressive force and shear force. However, this is only desirable, and the reinforcing material can be made of non-woven fabric. In this case,
In particular, by using the unwoven cloth having the orientation, it is possible to reinforce in the direction in which the rigidity needs to be increased.

When the fiber member is a monofilament cord, the cord density of the monofilament cord and the number of cords per unit length in the extending direction of each cord in the case of a woven fabric are as follows. It is desirable that the portion corresponding to the bottom of the circumferential groove is larger than the portion corresponding to the central portion of the land portion such as the block or rib. This is because the part where the reinforcing material is likely to break is the part corresponding to the minimum radius part of the groove bottom, so it is effective to increase the density of the cords in that part to enhance the force support or load bearing capability. It is because it is a target. According to this, the durability of the reinforcing material is enhanced, and as a result, the occurrence of cracks at the groove bottom can be more advantageously prevented.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a widthwise sectional view showing an embodiment of the present invention with respect to a half portion of a tire, in which 1 is a tread portion and 2 is a side extending inward in a radial direction continuously from a side portion of the tread portion 1. The wall portion and reference numeral 3 denote a bead portion continuous with the inner end of the sidewall portion 2 in the radial direction.

Here, a carcass, for example, a radial carcass 5 extending in a toroidal manner to reinforce each of the above-mentioned parts 1, 2 and 3 between bead cores 4 arranged in each bead part 3, is formed by at least one carcass ply. At the same time, the side portion of the radial carcass 5 is rolled up outward in the radial direction around the bead core 4, and on the outer peripheral side of the crown portion of such a radial carcass 5,
The belt 8 is provided with two or more layers, in the figure, two belt layers 6 and 7, and the belt layer cords intersect each other between the layers. A belt auxiliary layer 9 made of an organic fiber cord that extends substantially in the tire circumferential direction can be disposed further on the outer peripheral side of the belt 8. This belt reinforcement layer 9
Can be formed, for example, by spirally winding one or a plurality of organic fiber cords from one side portion of the belt 8 toward the other side portion.

Further, here, the tread surface of the tread 10 is provided with circumferential grooves 11 extending continuously in the circumferential direction, and blocks, ribs, and the like are provided between the circumferential grooves and between the circumferential groove 11 and the tread side edge. The land portion 12 that can be formed is sectioned. Further, a reinforcing material 13 is provided in the tread on the outer peripheral side of the belt auxiliary layer 9, and here, the tread 10 is used.
In the cross section in the width direction of, the distance R1 of the portion of the reinforcing material 13 corresponding to the land portion 12 from the tire central axis is calculated from the distance R2 of the portion of the reinforcing material 13 corresponding to the groove bottom 14 to the tire central axis. In addition, as is clear from FIG. 2 showing a cross section in the tread width direction, the radius of curvature r1 of the portion of the reinforcing member 13 corresponding to the groove bottom 14 is increased.
Is at least twice the minimum radius of curvature r2 of the groove bottom itself. As a result, the minimum radius of curvature of the groove bottom 14 is
The reinforcing material 13 enables efficient coverage. In addition, in FIG. 1, the reinforcing material 13 is arranged over almost the entire tread width, but the reinforcing material 13 can be partially arranged in any of the circumferential grooves. Yes, this too can bring about the desired effects.

According to this, the minimum radius of curvature of the circumferential groove groove bottom 14 of the tire tread and the section in the tread width direction shown in FIG. Since compressive stress, shear stress, etc. can be effectively suppressed and relaxed based on the support of the force of the fiber member of the reinforcing member 13, it is possible to effectively prevent the occurrence of cracks in the minimum radius of curvature. it can. In addition, here, the reinforcing material 1
By making the distance R1 of the portion corresponding to the land portion 12 of the tire 3 to the tire center axis line larger than the distance R2 of the portion of the reinforcing member 13 corresponding to the groove bottom axis 14 to the tire center axis line, the minimum of the groove bottom 14 is obtained. The radius of curvature can be efficiently covered by the reinforcing material 13. Further, by bending and extending the reinforcing material 13 with a radius of curvature r1 that is at least twice as large as the minimum radius of curvature r2 of the groove bottom 14, it is possible to sufficiently enhance the durability of the reinforcing material itself. Therefore, even if the reinforcing member 13 is repeatedly bent and deformed at the curved portion due to the deformation of the land portion 12 such as the block and the rib, it is possible to prevent the occurrence of the groove bottom crack with excellent durability. You can

By the way, such an extending manner of the portion corresponding to the groove bottom of the reinforcing member 13 is also applied to the case where the entire groove bottom 14 is formed by only a curved line as shown in FIG. 2 (b). Even in such a case, even in such a case, the minimum curvature radius r3 of the groove bottom 14 such as compressive stress and shear stress is set by setting the curvature radius r3 of the reinforcing member 13 to be twice or more the minimum curvature radius r4 of the groove bottom 14. Since the concentration on the radius portion can be effectively suppressed and relaxed based on the support of the force of the fiber member of the reinforcing member 13, it is possible to effectively prevent the occurrence of the crack on the minimum curvature radius portion. .

FIG. 3 is a diagram illustrating an extending mode of a fiber member forming the reinforcing material 13 when the reinforcing material 13 is made of a biaxial woven fabric, and FIG. 3 (a) is a warp as a fiber member. 15 (b) and the weft thread 16 are arranged at an angle of 45 degrees with respect to the circumferential direction of the tread, and FIG. 3 (b) shows the warp thread 15 and the weft thread 16 of the biaxial woven fabric in the circumferential direction. On the other hand, the case where they are arranged in a rectangular coordinate system with angles of 0 degree and 90 degrees is shown. When the longitudinal and transverse yarns 15 and 16 are arranged at an angle of 45 degrees with respect to the tread circumferential direction, both the compressive force and the shearing force are dispersed and supported by the warp yarn 15 and the weft yarn 16, respectively. On the other hand, when the yarns 15 and 16 are arranged in the orthogonal coordinate directions of 0 ° and 90 ° with respect to the circumferential direction of the tread, the compressive force is mainly the weft yarn 16 and the shear force is the warp yarn 1
It will be supported by 5.

In any of these cases, the widthwise compressive force and the shearing force applied to the groove bottom 14 are sufficiently effectively supported by the yarns 15 and 16 in the longitudinal and transverse directions of the biaxial woven fabric. The deformation of the bottom 14 can be effectively suppressed by the biaxial woven fabric as the reinforcing material 13.

Further, preferably, the fiber member forming the biaxial woven fabric or the like is a monofilament cord of an organic fiber such as nylon, polyethylene terephthalate or aromatic polyamide, or a metal fiber such as steel. This is the groove bottom 1
In order to make the reinforcing material 13 bear the compression input of 4, it is important to increase the compressive rigidity of the reinforcing material 13, and thus of the fiber member, and the monofilament cord exhibits a sufficiently high compressive rigidity as compared with the twisted cord. It depends on what you can do. In addition,
In this case, the use of the organic fiber monofilament cord is advantageous in reducing the weight of the tire, and the use of the metal fiber monofilament cord is advantageous in improving the supporting ability of the compressive force and the shearing force.

When the fiber member is a monofilament cord as described above, it is more preferable that the driving density of the monofilament cord, that is, the driving density in the tread width direction as shown in FIG. Then, the portion corresponding to the groove bottom 14 is made large. According to this, the cord density is increased at the portion corresponding to the minimum radius of curvature of the groove bottom 14 where the reinforcing material 13 is likely to be broken, and the total support or load bearing capacity of the force is increased to increase the individual cord strength. Since the load on the cord can be reduced and the durability of the cord, and by extension, the reinforcing material 13, can be increased,
As a result, cracking of the groove bottom 14 can be prevented for a long period of time.

[0024]

EXAMPLE A size of 245/40 R18, each of two belt layers is formed of a steel cord having a constitution of 1 × 5 × 0.23, and the cord is set to 38 cords / 50 mm. , The cords of the inner side belt layer extend 28 degrees to the right when the tire is viewed from the front, and the cords of the outer side belt layer extend 28 degrees to the left when viewed from the same side. A pneumatic tire having a basic structure formed by spirally winding a nylon cord at a density of 10 wires / 12 mm from the side portion to the other side portion, and the pneumatic tire having the specifications of Table 1 was prepared by applying a filling air pressure to the tire. A drum test was performed in which rolling was performed under the conditions of 230 kPa, a speed of 89 km / h, and a load of 5.10 kN, and the traveling distance until cracks were generated at the groove bottom on the outermost side in the width direction. As the test tire, the presence or absence of a reinforcing material, the type of fiber member and the driving density, whether the driving density of the portion corresponding to the groove bottom was changed, the radius of curvature r1 of the portion corresponding to the groove bottom of the reinforcing material, and the groove Table 1 shows that four types of example tires and two types of comparative example tires were prepared by combining the curvature radius ratios r1 / r2 of the minimum radius of curvature r2 of the bottom, and the above-mentioned test was performed for each. I got the result.

[Table 1]

Comparing the example tires with the comparative example tires, in all of the example tires, the cracking distance is increased more than that of the comparative example tire, and the reinforcing material is bent so that r1 / r2 is double or more. It can be seen that the effect of preventing the occurrence of cracks at the groove bottom can be obtained by arranging the same as above. Comparing Comparative Example 2 with Example 1, r1 / r2
It can be seen that by setting the ratio of 2 to 2 times or more, the crack generation distance is extended by about 12,000 km even with the same implantation density with the same cord. In addition, comparing Example 1 and Example 2, it can be seen that when the cord is a steel monofilament cord, the crack generation distance is further extended by 80,000 km or more even when the number of driving is reduced as compared with the nylon monofilament cord. Furthermore, comparing Example 2 with Example 3, even if the nylon monofilament cord is left as it is, the number of cords to be driven is made dense at the portion corresponding to the groove bottom, and it is 0.8 like the steel filament cord.
You can see that it extends over 10,000 km. In Example 4, since the reinforcing material is a nylon twisted cord, it can be seen that the effect of extending the crack generation distance is slightly lower than in other Examples.

[0026]

As is apparent from the above description, according to the present invention, in particular, a reinforcing member made of a fiber member is provided in the tread, and the reinforcing member is provided in the widthwise cross section of the tread. The extending position of the portion of the material corresponding to the land portion is radially outside of the extending position of the portion corresponding to the circumferential groove, and the portion of the reinforcing material corresponding to the circumferential groove bottom is the minimum in the groove bottom. By curving with a radius of curvature that is at least twice the radius of curvature, it is possible to prevent the occurrence of groove bottom cracks more effectively than conventional methods, such as increasing the radius of curvature of the groove bottom in the tread width direction cross section. it can.

[Brief description of drawings]

FIG. 1 is a tread width direction sectional view of a tire half portion showing an embodiment of the present invention.

FIG. 2 is a schematic enlarged view showing a cross section in the tread width direction.

FIG. 3 is a development view illustrating an extending mode of a fiber member of a biaxial woven fabric.

FIG. 4 is a cross-sectional view similar to FIG. 2, illustrating a mode of variation in the driving density of the monofilament cord.

[Explanation of symbols]

1 tread section 2 Side wall part 3 bead part 4 bead core 5 radial carcass 6,7 Belt layer 8 belts 9 Belt auxiliary layer 10 treads 11 circumferential groove 12 Land 13 Reinforcement material 14 groove bottom 15 Warp 16 weft 17 Reinforcing material that corresponds to the center of the land

Claims (4)

[Claims] 1. A tread is provided with at least one circumferential groove continuously extending in the circumferential direction thereof, and a land portion adjacent to the circumferential groove is defined to define an inner circumferential side of the tread. A pneumatic tire having a belt disposed in the tread, wherein a reinforcing material made of a woven or non-woven fabric made of a fibrous member is arranged in the tread, and the land of the reinforcing material is The extension position of the part corresponding to the part,
Radially outside the extending position of the portion corresponding to the circumferential groove,
A pneumatic tire in which a portion of the reinforcing material corresponding to the groove bottom of the circumferential groove is curved with a radius of curvature that is at least twice the minimum radius of curvature of the groove bottom. 2. The pneumatic tire according to claim 1, wherein the reinforcing material is a biaxial woven fabric. 3. The fiber member as a monofilament cord made of organic fiber or metal fiber.
Pneumatic tire described in. 4. The air according to claim 3, wherein the monofilament cord has a higher impact density of the cord than the portion corresponding to the groove bottom of the circumferential groove and the portion corresponding to the central portion of the land portion. Included tires.