JPH11235903A - Radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability in a radial tire for a heavy load used under a condition of high internal pressure and the high load. SOLUTION: A reinforcing belt 8 and a buffer belt 13 are provided between a crown part 3 of a radial carcass 2 and a tread 4, a width of all of narrow width cord tilt layers 11, 12 formed with the buffer belt 13 is in a range 20 to 60% a tread width in an tire width directional section under a prescribed condition, and an arrangement angle of a cord relating to a tire equator surface 5 is in a 15 deg. or less range, at least a pair of peripheral direction grooves 10a, 10b, extended along a tire circumference by interposing the tire equator surface 5 are arranged in a range of 15% or more and 75% or less of the tread width with the tire equator surface position 5 serving as the center in the tread 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for heavy loads which is used under high internal pressure and high load conditions and is particularly suitable for use in a construction vehicle mainly traveling on a rough terrain. In order to alleviate the effect of the pressure from the radial carcass due to the inflation pressure of the tire to which pneumatic pressure is applied to the reinforcing belt between the crown portion of the radial carcass and the normal reinforcing belt, at least one layer In particular, the envelope property of the tire having the belt structure in which the buffer belt including the width cord inclined layer is disposed is improved.

[0002] The "envelope property" here means
For example, when a tire stomps on a protrusion such as pebbles or rocks, it means the possibility of tread deformation that wraps around the protrusion, and the better the envelope property, the less the belt failure occurs, and the better the tire durability. In general, the envelope property and the tire durability are in a proportional relationship because of their superiority.

[0003]

2. Description of the Related Art A radial tire has a reinforcing belt formed of a wide cord inclined layer between a crown portion of a radial carcass and a tread to reinforce the tread and exhibit a so-called crimping effect. The cords of each wide cord sloping layer constituting the reinforcement belt are for the purpose of following the diameter growth during vulcanization molding, etc., and exerting the reinforcing effect by the so-called pantograph action with the ply cord of the radial carcass. The arrangement angle of the tire with respect to the equatorial plane of the tire is usually in the range of 20 to 40 °, and further, for the purpose of effectively enhancing the reinforcing effect, at least two of the wide cord inclined layers, Generally, a so-called intersecting belt that intersects with being sandwiched is used.

When the tire of the above configuration is filled with air and an internal pressure is applied, the radial carcass is in a state where no reinforcing belt is provided, that is, a radial surface contour in a state where the tire is not fastened, that is, a so-called natural equilibrium shape. Tend to approach.

However, since the above tire is generally fastened with a reinforcing belt, the carcass crown has a radius of curvature that is actually larger than the radius of curvature of the natural equilibrium shape. In order to approach the shape, the radius of curvature is reduced, that is, in order to deform in the direction of radial growth, especially the central portion of the width of the reinforcing belt is pressurized with the expansion of the carcass, while both ends of the reinforcing belt Parts tend to move away from the radial carcass in the radial direction of the tire, and in the case of a tire having both ends of such a reinforcing belt, the tire repeatedly undergoes large deformation when rolling on the tire load, thereby deteriorating the durability of the tire. This tendency is particularly remarkable in a heavy load radial tire to which a high internal pressure and a high load are applied.

[0006] As means for alleviating the pressing force from the carcass generated due to the inflation of the tire when the internal pressure is applied to the reinforcing belt, a cord is provided between the crown portion of the carcass and the reinforcing belt. Two layers of narrow-width cord layers are laminated so as to intersect with the tire equatorial plane interposed therebetween, and the angles of these cords with respect to the tire equatorial plane are greater than the angles of the cords of the wide-width cord inclined layers constituting the reinforcing belt. It is useful to provide a reduced buffer belt, which is disclosed in, for example, JP-A-54-126306 and JP-A-54-126308.

[0007]

However, when the inventor examined the durability of the tire having the belt structure described in the above-mentioned publication, the tire having this belt structure was found to have a large separation between the wide cord inclined layers. However, if the tire stomps on protrusions such as pebbles or rocks, the tread 104
As shown in FIG. 3, it is not possible to perform flexible deformation such as wrapping around the projection 114 while keeping the projection 114 on the projection 114, and the so-called envelope property is not sufficiently obtained.
As a result of the action force from 114 being concentrated on the specific portion 104a of the tread 104, the protrusion 114
4 and may reach the reinforcing belt 108 to cause belt destruction.
It turned out that there was a problem that the tread 104 could not sufficiently grip the road surface 115 and sufficient steering stability could not be obtained.

In particular, in the case of a tire for a construction vehicle that mainly travels on a rough terrain, the tread 104 is
4 The frequency of stepping on the tire often increases the envelope, but this tire has a rather thick tread rubber and the rigidity of the tread rubber itself is quite high, so the tread 104 is flexible enough to wrap the protrusion 114. In many cases, such deformation cannot be performed, and the above-described problem is likely to occur.

As a result, the inventor has further studied to solve the above-mentioned problem. As a result, if at least one pair of circumferential grooves is provided at an appropriate position of the tread, when the protrusions such as pebbles and rocks are depressed, In addition, the tread deforms flexibly so as to envelop the protrusions, increasing the envelope properties,
As a result, they found that the durability of the tire was improved (see FIG. 2).

[0010] It is an object of the present invention to provide a cushioning belt between a crown portion of a radial carcass and a reinforcing belt, which has an appropriate width dimension and a cord arrangement angle, and at least a tread at a proper position of a tread. By arranging a pair of circumferential grooves, separation between the wide-width cord inclined layers constituting the reinforcing belt is unlikely to occur, and a heavy-duty radial tire having excellent envelope properties and excellent durability, particularly on rough terrain. It is an object of the present invention to provide a heavy duty radial tire suitable for use in a traveling construction vehicle.

[0011]

In order to achieve the above object, the present invention provides a radial carcass crown portion extending in a toroidal shape between a pair of bead cores and a tread.
A reinforcing belt comprising at least one wide-width cord inclined layer in which the cord extends inclining with respect to the tire equatorial plane, and the reinforcing belt is located radially inward of the reinforcing belt, and the cord inclines with respect to the tire equatorial plane. In a heavy duty radial tire having at least one layer of a narrow-width cord inclined layer and a shock absorbing belt, the tire is mounted on a design rim specified in TRA, and a cross section in a width direction of the tire to which an air pressure corresponding to a maximum load is applied. Each of the narrow cord inclined layers forming the cushioning belt has a width in the range of 20 to 60% of the tread width around the tire equatorial plane, and the angle at which the cords are arranged with respect to the tire equatorial plane is 15 °. Within the following range, and within the range of 15% or more and 75% or less of the tread width of the tread with respect to the tire equatorial plane position, preferably the narrow width forming the buffer belt. At least one extending along the tire circumference across the tire equatorial plane within a range corresponding to 10% of the tread width centered on the width end position of the width cord inclined layer.
It is a radial tire for heavy load characterized by providing a pair of circumferential grooves.

Further, the cushioning belt may be formed by laminating two layers of narrow-width cords intersecting each other across the equatorial plane of the tire, or may be formed by one layer of narrow-width cords. preferable.

[0013] The term "wide cord inclined layer" herein means a cord inclined layer having a width in the range of 65 to 85% of the tread width, and the "design rim based on TRA" means. "DESIGN RIM" specified in "YEAR BOOK (1997)" issued by "THE TIRE and RIM ASSOCIATION INC."
And "maximum load" means "maximum load" defined in TRA. In addition, the circumferential groove
The tread arrangement position is determined based on the tread opening width center position. In addition, "the buffer belt
The term “13 width end positions” specifically means the width end positions of the narrower narrowed cord layers, which are wider, of the narrower cord layers constituting the buffer belt.

The term "tread width" as used herein means that a tire is mounted on a design rim, an air pressure corresponding to the maximum load is applied, the tire is placed perpendicular to a flat plate in a stationary state, and the maximum load is applied. And the line segment length when these ground end positions are connected along the tire width direction on a tire in a no-load state.

[0015] In addition, the reinforcing belt has a crossed belt constituted by two wide cord inclined layers laminated so that cords intersect with the tire equatorial plane interposed therebetween, and the wide cord inclined layer constituting the crossed belt is provided. The arrangement angle of the cord with respect to the tire equatorial plane is in the range of 10 to 40 °, and, between the tread and the reinforcing belt, covers the entire surface of the reinforcing belt, and is 15 to 40 with respect to the tire equatorial plane. It is more preferable to provide a protective layer composed of a rubberized layer of a highly extensible cord extending at an angle of °.

[0016]

FIG. 1 shows a cross section in the width direction of a typical crown portion of a heavy-duty radial tire according to the present invention. In the drawing, 1 is a heavy-load radial tire, 2 is a radial carcass, 3 is a crown portion, 4 is a tread, 5 is a tire equatorial plane, 8 is a reinforcement belt, and 13 is a buffer belt.

A tire 1 having a crown portion shown in FIG. 1 is provided between a crown portion 3 of a radial carcass 2 and a tread 4 extending in a toroidal shape between a pair of bead cores (not shown).
A reinforcing belt 8 including at least one wide cord inclined layer 6, 7 (two wide cord inclined layers are shown in FIG. 1) in which the cord extends obliquely with respect to the tire equatorial plane 5; The cord is located on the inner side 9 in the tire radial direction of the reinforcing belt 8 and the cord extends at least one narrow cord inclined layer with respect to the tire equatorial plane 5 (in FIG. 1, two narrow cord inclined layers are formed). And a buffer belt 13).

The buffer belt is a belt having the highest rigidity among the existing belts, and may be constituted by at least one narrow cord inclined layer, for example, three or more narrow cord inclined layers. When the buffer belt is composed of layers,
There is a concern that the stiffness is too high, such as a decrease in the envelope property, and there is a tendency that the inconvenience that the belt end distortion increases becomes large. Therefore, in the case of a current tire, particularly a heavy load tire, it is more preferable that the number of narrow-width cord inclined layers constituting the cushioning belt is one or two.

The main feature of the present invention is that a cushioning belt is provided between the crown portion 3 of the radial carcass 2 and the reinforcing belt so as to optimize the width and the angle at which the cords are arranged.
It is an essential feature of the present invention to dispose the at least one pair of circumferential grooves 10a and 10b at an appropriate position of the tread 4.

Specifically, the above-mentioned specific features of the invention are as follows. Each of the narrow cord inclined layers 11 and 12 constituting the buffer belt 13 has a width of 20 to 60% of the tread width around the tire equatorial plane 5. And the angle at which the cords are arranged with respect to the tire equatorial plane 5 is within a range of 15 ° or less, whereby the pressing force from the carcass 2 caused by the expansion of the tire when the internal pressure is applied. Can be effectively prevented from acting on the reinforcing belt 8, and the separation between the wide cord inclined layers 6 and 7 constituting the reinforcing belt 8 can be effectively suppressed. As a result, tire durability is improved.

The reason why the width of the narrow cord inclined layers 11, 12 is limited to the range of 20 to 60% of the tread width around the tire equatorial plane 5 is that the width of the narrow cord inclined layers 11, 12 is as follows. If the width is larger than the above range, the strain at the end of the cord inclined layer increases sharply.If the width is smaller than the above range, the pressure from the carcass when applying the internal pressure acting on the reinforcing belt is sufficient. This is because it is impossible to reduce the number of times.

The reason why the arrangement angle of the cords of the narrow cord inclined layers 11 and 12 is limited to the range of 15 ° or less is that when the arrangement angle of the cords is larger than the range, the cords are tightened. This is because the effect is weak, and the pressure from the carcass when applying the internal pressure acting on the reinforcing belt cannot be sufficiently reduced.

Specifically, the above-mentioned invention-specific matter specifically relates to the tire circle with the tire equatorial plane 5 interposed between 15% and 75% of the tread width of the tread 4 centered on the tire equatorial plane position 5. At least one pair of circumferential grooves extending along the circumference
10a, 10b.

FIG. 2 shows the deformed state of the tread 4 and the belts 8 and 13 when the inventive tire having the circumferential grooves 10a and 10b arranged at appropriate positions on the tread 4 steps on the protrusion 14 on the road surface 15. 2 (solid line). Note that the two-dot chain line in FIG. 2 shows the tire shape when traveling on a flat road surface.

As is apparent from a comparison between FIG. 2 and FIG.
In the conventional tire shown in FIG. 3, when the protrusion 114 is stepped on, the tread 104 is not deformed so as to wrap the protrusion 114 while being stretched on the protrusion 114 (bending deformation in the direction of arrow 17). In contrast to the case where the envelope property is not obtained, the inventive tire shown in FIG. 2 has a low rigidity at the tread portion where the circumferential grooves 10a and 10b are arranged at appropriate positions when the protrusion 14 is stepped on. Accordingly, the circumferential grooves 10a,
10b can be largely bent and deformed, and as a result, a deformation (arrow 17
Direction bending deformation) easily occurs, and sufficient envelope properties can be obtained.

Although FIG. 3 shows a tire in which the circumferential groove is not provided, deformation in which the protrusion 14 is wrapped may also occur when the circumferential groove is provided under conditions that do not satisfy the invention specific items. Difficulty is similar to the tire shown in FIG.

The positions of the circumferential grooves 10a and 10b are
15% of the tread width around the tire equatorial plane position 5
The range of 75% or less is limited to the circumferential grooves 10a and 10a.
If the arrangement position of b is inside or outside the tire width direction from this range, it is difficult to deform the projection 14 so as to cover the projection 14 when the projection 14 is stepped on. If it is necessary to further improve the envelope property, the position of the circumferential grooves 10a and 10b corresponds to 10% of the tread width centered on the width end position of the buffer belt 13. It is preferable to dispose within the range.

It should be noted that, as is clear from FIG. 2, the deformation surrounding the projection 14 cannot be achieved with a single circumferential groove, but along the tire circumference with the tire equatorial plane 5 interposed therebetween. It is necessary to provide at least one pair of circumferential grooves 10a, 10b extending therefrom. Although FIGS. 1 and 2 show the case where only one pair of the circumferential grooves 10a and 10b are arranged with the tire equatorial plane 5 interposed therebetween, it is needless to say that the present invention is not limited to this configuration. That is.

Further, since the heavy duty tire of the present invention is used under conditions of high internal pressure and high load, the reinforcing belt 8
As shown in FIG. 1, two wide cord inclined layers 6 and 7 stacked so that cords intersect with the tire equatorial plane interposed therebetween.
It is preferable to have a cross belt constituted by:

At this time, the tire equatorial plane 5 of the cords 6a, 7a of the wide cord inclined layers 6, 7 constituting the cross belt is used.
The arrangement angle with respect to the tire is such that when the tire stomps on a protrusion such as pebbles or rocks existing on the road surface, the protrusion imparts mobility when the protrusion penetrates the tread and reaches the reinforcing belt, thereby providing the tire with mobility. From the viewpoint of preventing a failure from occurring, it is more preferable that each of the angles is in the range of 10 to 40 °.

When it is necessary to protect the reinforcing belt 8 from the above-mentioned protrusions, the entire surface of the reinforcing belt 8 is covered between the tread 4 and the reinforcing belt 8 so that the reinforcing belt 8 is 15 to 40 ° with respect to the tire equatorial plane. It is more preferable to provide a protective layer composed of a rubberized layer of a highly extensible cord that extends at an angle of. As the highly extensible cord, for example, a cord having an elongation at break of 4.0% or more is preferably used.

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

[0033]

EXAMPLES Next, a heavy-duty radial tire according to the present invention was prototyped, and a test for evaluating durability was performed. The test will be described below. The tires of Examples 1 to 5 are tires for construction vehicles having a tire size of 37.00 R57 (tread width: 840 mm), and the cord inclined layers 11 and 12 forming the cushioning belt 13 (However, in the fifth embodiment, the cord inclined Layer (one layer), the width (mm) of the cords 11a and 12a, the laying angle (°), the width (mm) of the cord inclined layers 6 and 7 forming the reinforcing belt 8, and the cord.
Table 1 shows the arrangement angle (°) of 6a and 7a, the width (mm) of the protective layer 16, the arrangement angle (°) of the cord, and the circumferential grooves 10a and 10b. The radial carcass 2 was composed of one ply, the ply cord 2a had a cord diameter of 3.2 mm, and the cord material was steel. Other tire structures used were substantially the same as those of general construction vehicle radial tires. Incidentally, for reference, a conventional example having no reinforcing belt composed of four wide-width cord inclined layers without the provision of the buffer belt, Comparative Example 1 in which the circumferential groove was not disposed on the tread,
Table 1 also shows comparative examples 2 to 5 in which a circumferential groove is provided in the tread but not provided within an appropriate range of the tread.

[0034]

[Table 1]

(Evaluation of Durability) The durability was evaluated by performing a test in accordance with a tire strength (breaking energy) test specified in JIS D 4230, and evaluating the test results. Attach the tire to the design rim (rim contour: 27.00 inches, rim width: 27.00 inches, rim diameter: 57 inches) and increase the tire pressure to 70.
At 0kPa, fix the unloaded tire wheel to the plunger device, and attach a plunger with a hemispherical tip (φ19mm) to the plunger.
Push the plunger vertically into the tire crown center position at ± 2.5mm / min. Perpendicular to the tire axis, and move the plunger P (cm) from when the plunger touches the tire until the tire breaks, and Plunger pushing force F
(kgf), the breaking energy W was calculated according to the following equation: W = 0.5 × P × F (kgf · cm), and the envelope property was evaluated from the magnitude of the measured value of the plunger movement amount P at this time. Table 2 shows the results of the envelope property and the breaking energy. The numerical values in Table 2 are all shown as index ratios with Comparative Example 1 being 100, and the larger these numerical values are, the better.

[0036]

[Table 2]

From the results shown in Table 2, it can be seen that Examples 1 to 5 have better envelope properties, are less likely to break the tire, and have higher durability than the conventional examples and Comparative Examples 1 to 5.

[0038]

According to the present invention, a heavy-duty radial tire for heavy load, which is excellent in durability, in which separation between the wide cord inclined layers 6 and 7 constituting the reinforcing belt 8 is unlikely to occur and which has excellent envelope properties. It has become possible to provide a heavy-duty radial tire suitable for use in a construction vehicle that mainly travels.

When the reinforcing belt 8 has a cross belt, the wide cord inclined layers 6 and 7 constituting the cross belt are provided.
If the angle at which the cords 6a and 7a are arranged with respect to the tire equatorial plane 5 is within the range of 10 to 40 °, when the tire steps on the projection 14 such as pebbles or rocks on the road surface, the projection Since the mobility when the object 14 penetrates the tread 4 and reaches the reinforcing belt 8 can be imparted, tire failure is more unlikely to occur.

Further, between the tread 4 and the reinforcing belt 8, a rubberized layer of a highly extensible cord covering the entire surface of the reinforcing belt 8 and extending at an angle of 15 to 40 ° with respect to the tire equatorial plane 5 is provided. The provision of the protective layer 16 can effectively prevent the protrusions 14 from penetrating the tread 4 and reaching the reinforcing belt 8.

[Brief description of the drawings]

FIG. 1 is a widthwise cross-sectional view diagrammatically showing a characteristic portion of a heavy-duty radial tire according to the present invention.

FIG. 2 is a diagram schematically showing a deformed state of the inventive tire when a protrusion such as pebbles on a road surface is stepped on.

FIG. 3 is a diagram schematically showing a deformed state of a conventional tire when a protrusion such as pebbles on a road surface is stepped on.

[Explanation of symbols]

 1 Radial tire for heavy loads 2 Radial carcass 3 Crown 4 Tread 5 Tire equatorial plane 6,7 Wide cord slope layer 8 Reinforcement belt 9 Tire radial inside 10a, 10b Circumferential groove 11,12 Outside narrow cord slope layer 13 Buffer belt 14 Projection 15 Road surface 16 Protective layer 17 Arrow direction

Claims (6)

[Claims] 1. A reinforcing belt comprising at least one wide cord inclined layer in which a cord extends obliquely to a tire equatorial plane between a crown portion of a radial carcass and a tread extending in a toroidal shape between a pair of bead cores. And a shock-absorbing belt comprising at least one narrow-width cord-inclined layer, which is located inside the reinforcing belt in the tire radial direction and whose cord is inclined with respect to the equatorial plane of the tire, comprising: At the cross section in the width direction of the tire applied to the design rim specified in the above and applying the air pressure corresponding to the maximum load, the width of each of the narrow cord inclined layers forming the shock absorbing belt is centered on the tire equatorial plane. Tread width 20 ~
60% of the range, and the angle at which the cord is arranged with respect to the tire's equatorial plane is within 15 °, and the tread is within the range of 15% to 75% of the tread width centered on the tire's equatorial plane. A heavy load radial tire, wherein at least one pair of circumferential grooves extending along the tire circumference with the tire equatorial plane interposed therebetween is provided. 2. The heavy duty radial tire according to claim 1, wherein the cushioning belt is formed by laminating two narrow-width cord inclined layers whose cords intersect each other across the equatorial plane of the tire. 3. The heavy-duty radial tire according to claim 1, wherein the buffer belt comprises one layer of a narrow cord inclined layer. 4. The at least one pair of circumferential grooves disposed on both sides of the tire equator are disposed within a range corresponding to 10% of a tread width centered on a width end position of the buffer belt. The radial tire for heavy load described in 1, 2, or 3. 5. The reinforcing belt has a crossed belt composed of two wide cord inclined layers laminated so that the cords cross each other across the tire equatorial plane, and the cord of the wide cord inclined layer constituting the crossed belt is provided. 5. The radial tire for heavy load according to claim 1, wherein an arrangement angle of the tire with respect to the tire equatorial plane is in a range of 10 to 40 °. 6. A protection comprising a rubberized layer of a highly extensible cord between the tread and the reinforcing belt, covering the entire surface of the reinforcing belt and extending at an angle of 15 to 40 ° with respect to the tire equatorial plane. The heavy load radial tire according to any one of claims 1 to 5, wherein a layer is provided.