JP5205295B2 - Pneumatic radial tire - Google Patents

Description

  The present invention is a pneumatic radial tire for construction vehicles or a pneumatic radial tire for trucks and buses used for dump trucks and the like, and particularly relates to a pneumatic radial tire having excellent cut resistance.

  A pneumatic radial tire mainly used as a tire for a construction vehicle is a pair of small inclined belt layers that are disposed immediately above the carcass and rubber-coated with steel cords that are inclined at a relatively small angle with respect to the tire circumferential direction. A pair of large inclined belt layers, which are disposed on the outer side in the tire radial direction of the small inclined belt and are coated with rubber on a steel cord extending inclined at a relatively large angle with respect to the tire circumferential direction, and the large inclined belt It is common to provide a belt comprising a pair of protective belt layers disposed on the outer side in the tire radial direction and covered with a rubber covering an extensible steel cord extending at a relatively large angle with respect to the tire circumferential direction. .

  The large inclined belt layer ensures rigidity against deformation along the surface of the belt (hereinafter referred to as in-plane bending rigidity), and the small inclined belt layer provides tension in the tread circumferential direction by a cord arrangement with a small inclination angle. This reduces the tread diameter growth and prevents the crown shape from changing during travel.

  Further, as disclosed in Patent Document 1, for example, the belt is arranged such that the small inclined belt layer is arranged in a direction in which the cords of each layer intersect between adjacent layers in order to bear the tension in the tread circumferential direction, In order to increase the in-plane bending rigidity of the large inclined belt layer, the cords of each layer are arranged so as to intersect each other between adjacent layers, and even in the adjacent layer between the small inclined belt layer and the large inclined belt layer, In order to prevent strain concentration in the inclined belt layer, a technique has been developed in which the cords are arranged in an intersecting direction so that the cords constituting all the belt layers intersect each other between adjacent layers. Suppresses separation between the belt end in the tire width direction and the rubber in the vicinity of the belt, and further suppresses belt breakage caused by input when a step such as a stone is stepped on (hereinafter referred to as “cut input”). It is considered advantageous in terms of points (in terms of improving cut resistance).

  However, when the above-described technique is used, a crown-cut failure that has not occurred in the past has been found occasionally. When running on rough roads, the steel cords that make up the ply break or the rubber between the steel cords breaks due to the blunt input, causing separation of the small inclined belt layer or separation between the steel cords that make up the small inclined belt. It is a failure that occurs and a tire burst occurs. This failure is different from the conventional cut failure that occurs in the order of the protective belt layer, the large inclined belt layer, the small inclined belt layer, and the carcass ply after the tread is damaged. It is a cut failure from.

  Although tires with deep groove lug patterns to improve mine utilization rate and tire life in recent years have been put on the market, tires with sufficient grooves still have a cut failure from the inside in the tire radial direction. Accordingly, the tire life may be reduced, and as a result, the tire life may be reduced. Therefore, it is desired to develop a pneumatic tire that can cope with a cut failure from the inner side in the tire radial direction.

JP 2001-301420 A

  An object of the present invention is to provide a pneumatic radial tire that can effectively suppress a cut failure from the inner side in the tire radial direction against a blunt device input, in addition to the conventional cut failure from the tire radial direction against a projection input. Is to provide.

  The inventor has a belt composed of a plurality of belt layers on the outer peripheral side of a crown portion of a radial carcass composed of at least one ply in which a steel cord extending at an angle of 70 to 90 ° with respect to the tire circumferential direction is covered with rubber. As a result of repeated studies to solve the above-described problems with regard to pneumatic radial tires, it was found that the role of the carcass is important for cut failures from the inside in the tire radial direction. Further, earnest research was repeated, and a pair of narrow crossing belts, in which the belt is disposed immediately above the carcass and covered with a steel cord extending at a relatively small angle with respect to the tire circumferential direction, and the rubber coating, A pair of wide crossing belts, which are disposed on the outer side in the tire radial direction of the narrow crossing belt and are coated with rubber on a steel cord extending at a relatively large angle with respect to the tire circumferential direction, and the radial direction of the wide crossing belt The narrow cross belt, the wide cross belt, and the protection comprising a pair of protective belts disposed on the outside and covered with a rubber covering an extensible steel cord extending at a relatively large angle with respect to the tire circumferential direction. The steel cord extends at an angle opposite to the tire circumferential direction between adjacent layers, and the cord diameter of the ply is By optimizing it so that it is in the range of 70 to 90% of the cord diameter of the wide crossing belt, cut failure from the outside in the tire radial direction with respect to the protrusion input can be suppressed, and the ply is applied to the blunt input As a result of being able to absorb the deformation of the carcass due to the blunt input while suppressing the breakage of the constituting cord, it has been found that the cut failure from the inside in the tire radial direction can be effectively suppressed.

The present invention has been made based on such findings, and the gist thereof is as follows.
(1) Air having a belt made of a plurality of belt layers on the outer peripheral side of a crown portion of a radial carcass made of at least one ply in which a steel cord extending at an angle of 70 to 90 ° with respect to the tire circumferential direction is covered with rubber. A pair of narrow crossing belts formed by rubber-covering steel cords that are disposed immediately above the carcass and extend at a relatively small angle with respect to the circumferential direction of the tire; A pair of wide crossing belts, which are disposed on the outer side in the tire radial direction of the narrow crossing belt and are coated with rubber on a steel cord extending at a relatively large angle with respect to the tire circumferential direction, and the radial direction of the wide crossing belt A pair of protective belts that are placed on the outside and covered with an extensible steel cord that extends at a relatively large angle with respect to the tire circumferential direction. The narrow crossing belt, the wide crossing belt, and the protective belt extend in such a manner that the steel cords are inclined at opposite angles across the tire circumferential direction between adjacent layers, and the cord diameter of the ply is A pneumatic radial tire characterized by being in the range of 70 to 90% of the cord diameter of the wide crossing belt.

(2) The pneumatic radial tire according to (1), wherein a treat tensile strength of the ply is in a range of 40 to 70% of a treat breaking strength of the wide cross belt.

(3) The pneumatic radial tire according to (1) or (2), wherein an inclination angle of a steel cord constituting the narrow crossing belt is in a range of 4 to 10 ° with respect to a tire circumferential direction.

(4) The pneumatic radial tire according to any one of (1) to (3), wherein the width of the narrow crossing belt is in a range of 20 to 50% of a tire cross-sectional width.

(5) The pneumatic radial tire according to any one of (1) to (4), wherein an inclination angle of a steel cord constituting the wide cross belt is in a range of 15 to 40 ° with respect to a tire circumferential direction. .

(6) The pneumatic radial tire according to any one of (1) to (5), wherein a width of the wide crossing belt is in a range of 50 to 75% of a tire cross-sectional width.

  According to the present invention, a pneumatic radial tire that can effectively suppress a cut failure from the inner side in the tire radial direction with respect to the blunt input, in addition to suppressing a cut failure from the outer side in the tire radial direction with respect to the projection input according to the present invention. It became possible to provide.

1 is a perspective view schematically showing a part of a pneumatic radial tire of the present invention. 1 is a cross-sectional view in the width direction schematically showing a part of a pneumatic radial tire of the present invention. It is sectional drawing to which one of the steel cords which comprise the carcass ply in FIG. 1 was expanded. It is a mimetic diagram for explaining tire center part driving.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1, 2, and 3.
FIG. 1 is a cutaway perspective view schematically showing a part of the pneumatic radial tire of the present invention, and FIG. 2 schematically shows a cross section in the width direction of a part of the pneumatic radial tire of the present invention. FIG. 3 is an enlarged view of a cross section of a steel cord constituting the carcass ply in FIG.

  In the present invention, as shown in FIGS. 1 and 2, at least one ply 10 (one in FIGS. 1 and 2) in which a steel cord 11 extending at an angle of 70 to 90 ° with respect to the tire circumferential direction is covered with rubber is covered. A radial radial tire 1 including a belt 20 including a plurality of belt layers 30, 40, 50 on the outer peripheral side of a crown portion of the radial carcass 10, and the belt 20 is disposed immediately above the carcass 10. A pair of narrow cross belts 30 formed by rubber coating steel cords 31 and 32 extending at a relatively small angle with respect to the tire circumferential direction, and disposed on the outer side in the tire radial direction of the narrow cross belt 30; A pair of wide cross belts 40 formed by covering steel cords 41 and 42 extending at a relatively large angle with respect to the tire circumferential direction, and tires of the wide cross belts 40 It disposed outward, made extensible steel cords 51 and 52 extending obliquely at a relatively large angle with respect to the tire circumferential direction from the pair of the protection belt 50. formed by a rubber coating.

In the pneumatic radial tire 1 of the present invention, as shown in FIG. 1, the narrow cross belt 30, the wide cross belt 40, and the protection belt 50 are respectively disposed between adjacent steel cords 31, 32. , 41, 42, 51, 52 extend with an inclination at opposite angles across the tire circumferential direction.
By adopting the above configuration, the tire shape maintaining effect by the narrow cross belt 30, the improvement of the tire lateral rigidity and cut resistance by the wide cross belt 40, and the breakage / damage to the projection input by the protective belt 50 are achieved. Each suppression can be realized. In addition, by making the steel cords 31, 32, 41, 42, 51, 52 extend at an angle opposite to each other across the tire circumferential direction between adjacent layers, belt durability (belt It is possible to greatly improve the suppression of end separation and the suppression of cut failures from the outside in the tire radial direction.

  The relatively small inclination angle with respect to the tire circumferential direction when the steel cords 31 and 32 constituting the narrow cross belt 30 extend is smaller than that of the steel cords constituting the wide cross belt 40. Any angle may be used, and specifically, it is preferably in the range of 4 to 10 ° with respect to the tire circumferential direction. If the angle of inclination with respect to the tire circumferential direction is less than 4 °, the angle of inclination is too small, so the diameter growth of the tread part can be suppressed and the tire shape can be maintained, but the shear strain at the time of tire load rolling becomes too large. This is because, as a result of excessive concentration of stress on the tire width direction end 30a of the narrow cross belt 30, separation with the rubber in the vicinity of the tire width direction end 30a may occur. If the inclination angle exceeds 10 °, the inclination angle is too large, so that the stress concentration at the end 30a can be considered, but the tension in the tire circumferential direction cannot be fully borne, and the tread portion grows in diameter. This is because the tire shape cannot be maintained.

  Further, the width W1 of the narrow cross belt 30 is preferably in the range of 20 to 50% of the tire cross-sectional width W as shown in FIG. When the width W1 of the narrow crossing belt 30 is less than 20% of the tire cross-sectional width W, the area where the narrow crossing belt 30 is disposed becomes too small and the range in which the tension in the tire circumferential direction can be borne. This is because the diameter growth of the tread portion cannot be suppressed and the tire shape cannot be maintained. On the other hand, the width W1 exceeds 50% of the tire cross-sectional width W. As a result, the shear strain of the narrow cross belt 30 during rolling of the tire is excessively increased, and stress is excessively concentrated on the tire width direction end 30a of the narrow cross belt 30. As a result, the narrow cross belt 30 is in the vicinity of the tire width direction end 30a. This is because separation with rubber may occur. Here, when the widths of the belts constituting the pair of narrow width crossing belts 30 are different from each other, the width W1 is preferably in the range of 20 to 50% of the tire cross-sectional width W.

  A relatively large inclination angle with respect to the tire circumferential direction when the steel cords 41 and 42 constituting the wide crossing belt 40 extend is larger than that of the steel cords constituting the narrow crossing belt 30. Any angle may be used, and specifically, it is preferably in the range of 20 to 50 ° with respect to the tire circumferential direction. When the inclination angle with respect to the tire circumferential direction is less than 20 °, because the inclination angle is too small, the lateral rigidity at the time of tire load rolling cannot be ensured sufficiently, so that the steering stability may be greatly reduced. On the other hand, when the inclination angle exceeds 50 °, similarly, the stress load at the time of tire load rolling is transferred to the narrow cross belt 30 and the stress is excessively concentrated on the end 30a in the tire width direction of the narrow cross belt 30. This is because there is a risk of separation from the rubber in the vicinity of the tire width direction end 30a.

  Further, the width W2 of the wide cross belt 40 is preferably in the range of 50 to 75% of the tire cross-sectional width W as shown in FIG. When the width W2 of the wide crossing belt 40 is less than 50% of the tire cross-sectional width W, the region where the wide crossing belt 40 is disposed becomes too small, so that sufficient lateral rigidity at the time of tire load rolling is ensured. This is because there is a risk that the steering stability may be greatly reduced because it cannot be performed. On the other hand, if the width W2 exceeds 75% of the tire cross-sectional width W, when a step such as a stone is stepped on when rolling the tire, Although it can effectively resist the input from the protrusions, the shear strain of the wide cross belt 40 becomes excessively large and stress is excessively concentrated on the end 40a of the wide cross belt 40 in the tire width direction. This is because there is a risk of separation from the rubber in the vicinity of the width direction end 40a. Here, when the width W2 of each belt which comprises a pair of said wide cross belt 40 is different, it is preferable that each width W2 is the range of 50 to 75% of the tire cross-sectional width W.

  A relatively large inclination angle with respect to the tire circumferential direction when the extensible steel cords 51 and 52 constituting the protective belt 50 extend is larger than that of the steel cord constituting the narrow cross belt 30. There is no particular limitation as long as it is an inclination angle. Further, the extensible steel cord is a steel cord having extensibility in the extending direction as compared with a normal steel cord, and the elongation to break is 5 to 8% or more of the total elongation. Say. For example, specifically, there is a wavy steel cord having a predetermined amplitude.

Further, in the pneumatic radial tire 1 of the present invention, as shown in FIG. 3, a diameter X of a steel cord 11 (hereinafter referred to as “ply cord 11”) constituting the ply 10 is set to the wide cross belt 40. The steel cords 41 and 42 (hereinafter, referred to as “broad crossing belt cords 41 and 42”) constituting the steel wire have a diameter of 70 to 90%.
The role of the radial carcass 10 is important for the cut failure from the inside in the tire radial direction due to the blunt input when traveling on a rough road. Specifically, (1) the breakage of the ply cord 11 with respect to the blunt input is suppressed. And (2) flexibility for blunt input to suppress breakage of the small inclined belt layer 30 and separation between the steel cords 31 and 32 constituting the small inclined belt 30. Necessary. Therefore, in the present invention, by optimizing the diameter X of the ply cord 11, both the performances (1) and (2) of the carcass 10 described above are achieved, and a cut failure from the inside in the tire radial direction is effectively prevented. It becomes possible to suppress.

  Here, the ply cord 11 is a cord formed by bundling a plurality of steel fibers 12, as shown in FIG. The reason why the diameter X of the ply cord 11 is limited to the range of 70 to 90% of the diameter of the wide cross belt cords 41 and 42 is that if the diameter X of the ply cord 11 is less than 70%, the diameter is too small. For this reason, the breakage of the ply cord 11 cannot be sufficiently suppressed. On the other hand, if the diameter X exceeds 90%, the rigidity of the carcass ply 10 becomes too large. This is because the ply cord 11 does not break and the ply cord 11 does not break, but as a result of the occurrence of the rubber tear between the ply cords 11, the cut failure from the inner side in the tire radial direction cannot be sufficiently suppressed.

  Further, the treat tensile strength of the ply 10 is preferably in the range of 40 to 70% of the treat breaking strength of the wide cross belt 50. If the treat tensile strength of the ply 10 is less than 40% of the treat breaking strength of the wide cross belt 50, the strength of the ply 10 becomes too small, so that the breaking of the ply cord 11 cannot be sufficiently suppressed, There is a possibility that cut failure from the inner side in the tire radial direction cannot be suppressed. On the other hand, if the treat tensile strength of the ply 10 exceeds 70% of the treat breaking strength of the wide cross belt 50, the rigidity of the ply 10 becomes too large. This is because the radial carcass 10 is not sufficiently flexible with respect to the blunt input, and as a result of rubber tearing between the ply cords, there is a possibility that cut failures from the inside in the tire radial direction cannot be sufficiently suppressed. Here, the treat tensile strength means the tire center portion driving (as shown in FIG. 4, the number of cords per unit length of 50 mm in the direction perpendicular to the cord extending direction) and the cord after vulcanization. This is the product of the tensile rupture strengths in the axial direction.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

Next, a pneumatic radial tire according to the present invention was prototyped and its performance was evaluated, which will be described below.
(Examples 1-6 and Comparative Examples 1-2)
As an example, as shown in FIG. 2, a belt 20 composed of a plurality of belt layers is provided on the outer peripheral side of a crown portion of a radial carcass 10 composed of a single carcass ply 10 extending at an angle of 90 ° with respect to the tire circumferential direction. A radial tire for a construction vehicle (tire size: 53 / 80R63, rim used: 36.00 / 5.0), wherein the belt is disposed immediately above the carcass 10 and is 5 ° to the tire circumferential direction, − A pair of narrow cross belts 30 formed by rubber coating steel cords 31 and 32 extending at an angle of 5 °, and steel cords 41 and 42 extending at an angle of 28 ° and −18 ° to the tire circumferential direction, respectively, are covered with rubber. A pair of wide belts 40 and a pair of protective belts 50 formed by rubber coating stretchable steel cords 51 and 52 extending at an angle of −30 ° to −23 ° with respect to the tire circumferential direction, respectively. The narrow cross belt 30, the wide cross belt 40, and the protective belt 50 are pneumatic radials in which the steel cord extends at an angle opposite to each other across the tire circumferential direction between adjacent layers. A tire was produced.
It should be noted that the cord diameter (mm) of the steel cords 31, 32, 41, 42, 51, and 52 constituting the narrow cross belt 30, wide cross belt 40 and carcass ply 10 and the carcass ply 10 and wide cross belt. The treat tensile strength index of 40 is shown in Table 1.

(Evaluation)
(1) Cut resistance against sharp projection input For each sample of the example and comparative example, the TRA regular internal pressure and the regular rim are used to attach to the rear position, and the same use conditions (travel route, travel speed, tire load: Table 1 shows the results of measuring the running time until 10 out of 100 t), measuring the time taken for 5 of them to be scrapped due to the tread cut caused by sharp tread input, and evaluating it with an index. The numerical values in Table 1 are indices when the traveling time of Example 5 is set to 100, and the larger the numerical value, the longer the traveling time and the better the results. It can be said that there is sex. Whether or not the failure is caused by a sharp projection input is confirmed by analyzing the tire by anatomical analysis and by the sharp tread input.

(2) Cut resistance against blunt input For each sample of the examples and comparative examples, using a TRA regular internal pressure and a regular rim, a diameter of 40 cm so that a blunt protrusion with a height of 20 cm is formed at one location on the outer peripheral surface. Using a 7m diameter drum fitted with a sphere and running straight with 100% load, cut failure from the inside in the tire radial direction (caused by ply cord breakage or rubber tear between ply cords) The tire travel time until tire swell) was measured and evaluated by an index. The numerical values in Table 1 are indices when the traveling time of Example 1 is set to 100. Larger values mean longer traveling time and better results. Tires with an index of 75 or more are marketed. It can be said that there is sex. Since the frequency of occurrence of cut failures due to blunt input is lower than the frequency of occurrence of cut failures due to sharp projection input, evaluation is performed by drum tests in order to improve evaluation accuracy.

  From the results of Table 1, the pneumatic radial tires of Examples 1 to 6 in which the ply cord diameter was optimized have excellent resistance to both a cut failure due to sharp protrusion input and a cut failure due to blunt input. I understood it. Furthermore, it was found that Examples 1 to 4 in which the treatment tensile strength of the carcass ply was optimized were further cut resistant. On the other hand, Comparative Example 1 with a small ply cord diameter has low cut resistance against sharp protrusion input, and Comparative Example 2 with large ply cord diameter has low cut resistance against blunt input, both satisfying marketability. I knew it was n’t there.

  According to the present invention, a pneumatic radial tire that can effectively suppress a cut failure from the inner side in the tire radial direction with respect to the blunt input, in addition to suppressing a cut failure from the outer side in the tire radial direction with respect to the projection input according to the present invention. Can be provided.

DESCRIPTION OF SYMBOLS 1 Pneumatic radial tire 10 Carcass, carcass ply 20 Belt 30 Narrow crossing belt 40 Wide crossing belt 50 Protection belt

Claims (6)

A pneumatic radial tire having a belt made of a plurality of belt layers on the outer peripheral side of a crown portion of a radial carcass made of at least one ply in which a steel cord extending at an angle of 70 to 90 ° with respect to the tire circumferential direction is covered with rubber. Because
The belt is disposed immediately above the carcass, and a pair of narrow cross belts formed by rubber coating steel cords extending at a relatively small angle with respect to the tire circumferential direction, and the tire diameter of the narrow cross belt A pair of wide cross belts formed by rubber coating steel cords extending at a relatively large angle with respect to the tire circumferential direction, and disposed on the tire radial outside of the wide cross belt. It consists of a pair of protective belts made of rubber-coated extensible steel cords that extend at a relatively large angle with respect to the direction,
The narrow crossing belt, the wide crossing belt, and the protection belt extend in such a manner that the steel cords are inclined at opposite angles across the tire circumferential direction between adjacent layers, and the cord diameter of the ply is the wide belt A pneumatic radial tire characterized by being in the range of 70 to 90% of the cord diameter of the cross belt.   2. The pneumatic radial tire according to claim 1, wherein a treat tensile strength of the ply is in a range of 40 to 70% of a treat breaking strength of the wide cross belt.   The pneumatic radial tire according to claim 1 or 2, wherein an inclination angle of a steel cord constituting the narrow crossing belt is in a range of 4 to 10 ° with respect to a tire circumferential direction.   The pneumatic radial tire according to any one of claims 1 to 3, wherein a width of the narrow-width crossing belt is in a range of 20 to 50% of a tire cross-sectional width.   The pneumatic radial tire according to any one of claims 1 to 4, wherein an inclination angle of a steel cord constituting the wide crossing belt is in a range of 15 to 40 ° with respect to a tire circumferential direction.   The pneumatic radial tire according to any one of claims 1 to 5, wherein a width of the wide intersection belt is in a range of 50 to 75% of a tire cross-sectional width.

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