JPH06191212A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To reduce shearing distortion between a corrugated belt layer and the tread so as to prevent the generation of separation between them. CONSTITUTION:A pneumatic radial tire for heavy load is provided with at least two inclined belt layers 1, 2 formed of steel cords extended in the mutually crossed state on the outer peripheral side of the crown part of a carcass; at least one corrugated belt layer 3 formed of corrugated steel cords 4 extended substantially in the tire circumferential direction further on the outer peripheral side of the inclined belt layers 1, 2; and the tread 6 disposed on the outer peripheral side of the corrugated belt layer 3. A protecting belt layer 5 formed of linear steel cords extended being inclined in relation to the tire circumferential direction is provided between the corrugated belt layer 3 and the tread 6, and the side edge protruding length of the protecting belt layer 5 from the side edge of the corrugated belt layer 3 is to be 10mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for heavy loads, and more particularly to improvement of a belt structure.

[0002]

2. Description of the Related Art In recent years, particularly for the purpose of improving transportation efficiency, European truck manufacturers have been actively promoting the development of low-floor trucks.
There is an urgent need to develop heavy duty pneumatic radial tires with excellent durability and flatness of 70% or less.

Therefore, for the purpose of improving the belt durability, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-81706, it extends substantially in the tire circumferential direction between the inclined belt layer and the tread. A heavy-duty tire having a wavy belt layer made of a wavy steel cord is proposed,
According to such a tire, compared with the case where a protective layer made of a linear steel cord extending obliquely with respect to the tire circumferential direction is arranged on the outer peripheral side of the inclined belt layer, the tire is filled with internal pressure. In addition, it is said that it is possible to effectively prevent the tread from bulging outward in the radial direction when the tire rolls under load, thereby enhancing the durability of the belt.

[0004]

However, according to such a conventional technique, since the corrugated belt layer has a relatively large extensibility in the tire circumferential direction, the tire is filled with internal pressure and the tire is When rolling under load, the shear strain in the tire width direction between the wavy belt layer and the tread increases, and separation between them occurs due to shear strain, which reduces durability. It was

The present invention has been made as a result of studies aimed at solving such problems of the prior art, and an object of the present invention is to effectively make shear strain between the corrugated belt layer and the tread effective. It is intended to provide a pneumatic radial tire for heavy load, which is reduced in size to prevent the occurrence of separation due to shear strain and has a significantly improved durability.

[0006]

The pneumatic radial tire for heavy loads according to the present invention is provided with at least a pair of bead cores, and the end portions of the carcass are folded back around the bead cores and locked, and the crown portion of the carcass is secured. On the outer peripheral side, with respect to the tire circumferential direction, preferably disposed at least two inclined belt layers each made of steel cords that extend at an angle of 10 to 30 ° and extend to intersect each other, Further, on the further outer peripheral side of these inclined belt layers, at least one corrugated belt layer made of corrugated steel cords extending substantially in the tire circumferential direction is provided, and a tread is disposed as the outermost layer, the corrugated belt is formed. Between the belt layer and the tread, with respect to the tire circumferential direction, extending at an angle preferably in the range of 10 ~ 90 °, which also preferably high elongation With straight steel cord comprising at least provide a layer of protection belt layer, the side edges of the protection belt layer is a length of projection from the side edges of the corrugated belt layer that was 10mm or less. Here, it is also possible to position the side edge of the protective belt layer slightly inside the side edge of the wavy belt layer in the width direction. In this case, the amount of deviation from the side edge position of the wavy belt layer is preferably within 10 mm (-10 mm or more).

[0007]

In this heavy duty pneumatic radial tire, a protective belt layer is arranged between the corrugated belt layer and the tread, and the circumferential extension of the corrugated belt layer is effectively restrained by the protective belt layer. This makes it possible to effectively reduce the shear strain between the corrugated belt layer and the tread and between the protective belt layer and the tread, and as a result, effectively prevent the occurrence of separation between them. can do.

Moreover, here, the protruding length of the side edge of the protective belt layer from the side edge of the wavy belt layer is preferably -10 mm or more and 10 mm or less, particularly 5 mm or less, so that the protective belt layer It is possible to sufficiently exhibit the above-mentioned function of (1) and to suppress the generation of interlayer shear strain between the protective belt layer and the corrugated belt layer, and sufficiently prevent the occurrence of separation there. .

In other words, when the side edge of the protective belt layer is located inward in the width direction by more than 10 mm from the side edge position of the wavy belt layer, the side edge of the wavy belt layer is particularly The shear strain between the part and the tread cannot be effectively reduced, and conversely, when the protruding length of the side edge of the protective belt layer is set to be more than 10 mm, the end portion of the protective belt layer is Of the protective belt layer and the corrugated belt layer rapidly increase the interlaminar shear strain.

Here, the steel cord of the inclined belt layer is in the range of 10 to 30 ° with respect to the tire circumferential direction, and each of the linear steel cords of the protective belt layer is in the range of 10 to 90 ° with respect to the tire circumferential direction. When extended at an angle, if the inclined belt is less than 10 °, the rigidity in the circumferential direction becomes excessive and the impact resistance deteriorates, and it becomes impossible to secure the rigidity in the width direction.
If it exceeds 30 °, sufficient circumferential rigidity cannot be secured. If the protective belt is less than 10 °, the rigidity in the circumferential direction becomes excessive, the impact resistance deteriorates, and the rigidity difference with the tread becomes large, which may cause separation. Further, when the linear steel cord forming the protective belt layer is made of a highly extensible cord having a breaking elongation of 3% or more, the rigidity difference between the protective belt and the tread is reduced, and the separation between them is reduced. Occurrence can be suppressed. Further, when the swing width of the corrugated steel cord is a mm, the pitch of the waves is λ mm, and a / λ = 0.01 to 0.12.
It is possible to suppress the occurrence of separation between the tire and the protective belt during load rolling, and to effectively suppress outward bulging in the radial direction of the tire and prevent defects during manufacturing. . Here, when a / λ exceeds 0.12, the change in the wave during tire load rolling is large, separation between the tire and the protective belt, and further bulging in the tire radial direction cannot be suppressed. If it is less than 1, buckling is likely to occur.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a belt structure showing an embodiment of a tire having a size of 295/60 R22.5. In the figure, 1 indicates the inner side inclined belt layer, and 2 indicates the outer side inclined belt layer. Here, of the two inclined belt layers 1 and 2, the inner inclined belt layer 1 is provided.
Is formed of a steel cord that extends in a straight line at an angle of 20 ° to the tire circumferential direction and has a total width of 255 mm.
In addition, the outer layer side inclined belt layer 2 is inclined at an angle of 20 ° with respect to the tire circumferential direction, and the inner layer side inclined belt layer 1 is formed.
It has a total width of 235 mm and is formed by a straight steel cord of the same type that intersects the steel cord of the above.

Then, two corrugated belt layers 3 are disposed on the outer peripheral sides of the inclined belt layers 1 and 2. Each of these corrugated belt layers 3 has a corrugated steel cord 4 formed by molding a steel cord into a substantially sinusoidal shape having a swing width of 3 mm and a wave pitch of 32 mm (a / λ = 0.47).
It is formed by extending substantially in the tire circumferential direction, and both have a width of 195 mm.

By the way, these wavy belt layers 3 are
A bundle of rubberized steel cords having a total width of 5 mm can be formed by wrapping the inclined belt layers 1 and 2 once or twice, or one or more rubberized steel cords, or It is also possible to form a cord strip formed by aligning a plurality of corrugated steel cords 4 and rubber coating, and spirally winding the cord strip around the inclined belt layers 1 and 2.

Further, a protective belt layer 5 having the same width as that of the wavy belt layer 3 is provided on the outer peripheral side of the wavy belt layer 3, and the protective belt layer 5 is an inclined belt on the outer layer side with respect to the tire circumferential direction. It is formed by a straight steel cord with an elongation at break of 4%, inclined at an angle of 20 ° in the same direction as the steel cord of layer 2.

A tread 6 is provided on the outer peripheral side of the belt structure constructed as described above, as shown by the phantom line in the figure, to construct a heavy-duty pneumatic radial tire together with components not shown.

According to such a heavy-duty pneumatic radial tire, particularly on the basis of the action of the protective belt layer 5,
As described above, it is possible to effectively reduce the shear strain between the corrugated belt layer 3 and the tread 6, and to effectively prevent the occurrence of separation between the corrugated belt layer 3 and the tread 6. It is also possible to effectively suppress the occurrence of interlayer shear strain between the outer side corrugated belt layer 3 and the occurrence of separation there.

FIG. 2 is a graph showing this, according to which the side edge of the protective belt layer 5 is made to correspond to the corrugated belt layer 3.
When it is located more than 10 mm inward in the width direction from the side edge position of the, the shear strain between the exposed side end portion of the wavy belt layer 3 and the tread 6 is increased as shown on the right side of the graph. On the other hand, when the protrusion length of the side edge of the protective belt layer 5 from the side edge of the wavy belt layer 3 exceeds 10 mm, which is not preferable because it increases sharply, it is on the left side of the graph. As shown, it is clear that the interlayer shear strain between the protective belt layer 5 and the outer layer side inclined belt layer 2 sharply increases.

[Test Example] Hereinafter, a comparative test concerning the heat generation durability of the invention tire, the comparison tire, and the conventional tire, in other words, the durability until separation occurs due to heat generation due to shear strain will be described. To do.

◎ Test tire Size 295/60 R 22.5 tire ◎ Invention tire 1 A tire having a belt structure having the structure and dimensions shown in FIG. Inventive tire 2 A tire similar to inventive tire 1 except that the widths of the wavy belt layer and the protective belt layer were both 215 mm. ◎ Comparative tire The width of each wavy belt layer is 195 mm and the width of the protective belt layer is 215 mm, which is 20 mm wider than that.
A tire similar to Inventive Tire 1 except that ◎ Conventional tire A tire similar to the invention tire 1 except that the protective belt layer is omitted.

◎ Test method The durability was evaluated by a drum test, and the running distance until the occurrence of separation at the belt end was measured and evaluated.

◎ Test Results When the results of the above-mentioned tests are shown as an index with the conventional tire as a control, invention tire 1 170, invention tire 2 170, comparative tire 140 and conventional tire 100 were obtained. The larger the index value, the better the result.

[0022]

As is apparent from the above-mentioned test examples, according to the present invention, the shear strain between the wavy belt layer and the tread and the protection are caused by the action of the protective belt layer covering the wavy belt layer. It is possible to effectively reduce both the interlaminar shear strain between the belt layer and the outer side corrugated belt layer, and effectively prevent the occurrence of separation due to the shear strain.

[Brief description of drawings]

FIG. 1 is a schematic line sectional view showing an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a side edge position of a protective belt layer and shear strain and interlayer shear strain.

[Explanation of symbols]

 1, 2 inclined belt layer 3 corrugated belt layer 4 corrugated steel cord 5 protective belt layer 6 tread

Claims (1)

[Claims] 1. A pair of bead cores, a carcass whose end portions are folded back and locked around each bead core, and respective steel cords extending to intersect each other on the outer peripheral side of the crown portion of the carcass. At least two slanted belt layers, at least one corrugated belt layer made of corrugated steel cords extending substantially in the tire circumferential direction further on the outer peripheral side of these slanted belt layers, and on the outer peripheral side of this corrugated belt layer. A heavy duty pneumatic radial tire comprising a tread arranged, wherein a protective belt layer made of a linear steel cord extending obliquely to the tire circumferential direction is provided between the wavy belt layer and the tread. Along with this, the heavy-duty pneumatic lathe in which the protruding length of the side edge of the protective belt layer from the side edge of the wavy belt layer is 10 mm or less. Giar tire.