JP2001047812A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cut separation resistance by providing projections protruded with a layer itself outwardly in the tire radial direction along the peripheral direction of a tread section and recesses recessed inwardly in the radial direction repeatedly at least on the outermost layer of a specific number of steel cord cross layers of a belt. SOLUTION: This belt 3 is provided with three rubber-coated steel cord layers 3-1, 3-2, 3-3. The steel cords of adjacent two layers 3-1, 3-2 of the belt 3 and the steel cords of adjacent two layers 3-2, 3-3 form steel cord cross layers crossing across the tire equatorial plane E respectively. At least the outermost layer 3-3 itself of the outer two layers 3-2, 3-3 of the belt 3 repeatedly has projections 3-3R protruded outwardly in the radial direction of the tire and recesses 3-3D recessed inwardly in the radial direction along the peripheral direction of a tread section 1, thereby cut separation resistance is sharply improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic radial tire for heavy loads, and more particularly to a pneumatic radial tire for construction vehicles, and more particularly to a pneumatic radial tire for heavy loads excellent in cut separation resistance.

[0002]

2. Description of the Related Art Heavy-duty pneumatic radial tires used mainly for vehicles running on rough terrain, especially for construction vehicles, have an excellent cut resistance because the tread portion is constantly exposed to cuts during use. Is required. To meet this demand, a number of cut resistance improving means have been proposed.

[0003] The cut resistance improving means is roughly classified into a means using a material having excellent cut resistance, a means adopting a tire cross-sectional shape such as making the depth of a cut flaw as small as possible, and increasing a cutting energy as much as possible. It can be divided into means employing a belt structure to absorb.

[0004]

However, all of the above-mentioned means are intended to alleviate the degree of belt damage caused by cuts, and in any case, it is not possible to eliminate all cuts reaching the belt. . In the case of a cut flaw that has reached the belt, when a component in the tangential direction in the circumferential direction of the layer of the belt is large in the direction of the force acting on the belt, a crack grows from the end of the cut flaw in the circumferential direction of the layer.

This case is particularly applicable to pneumatic radial tires for driving wheels. That is, the driving force acting on the tire causes the crack to grow from the cut in the circumferential direction of the tread portion, eventually leading to a separation failure between the tread rubber and the outermost layer of the belt. Sometimes, foreign matter cuts the outermost layer of the belt, causing a separation failure between the outermost layer and its inner layer.

Therefore, the invention described in claims 1 to 8 of the present invention significantly suppresses the crack growth rate from the end of the cut, even when the belt is cut at least to the outermost layer of the belt. An object of the present invention is to provide a pneumatic radial tire for heavy loads excellent in cut separation resistance, which can advantageously avoid occurrence of separation failure.

[0007]

In order to achieve the above object, the invention described in claim 1 of the present invention is directed to a heavy load air comprising a belt of three or more rubber-coated steel cord cross layers for reinforcing a tread portion. In the filled radial tire, at least the outermost layer of the two steel cord crossing layers on the outer side of the belt has a convex portion projecting radially outward along the circumferential direction of the tread portion, and a convex portion extending from the convex portion. A heavy-duty pneumatic radial tire having a repetitive shape with a concave portion depressed inward in the tire radial direction.

[0008] Here, the code crossing layer of the belt refers to a layer configuration in which the cords of each layer in two adjacent layers cross each other across the tire equatorial plane.
In addition, the convex portions and the concave portions extend over the entire width of the belt layer.

According to the invention described in claim 1, claim 2 is provided.
As described above, the convex portion of the layer of the belt has a trapezoidal platform shape in cross section. Alternatively, as in the invention described in claim 3, the convex portion of the layer of the belt has a mountain-shaped cross-sectional shape.

According to the invention described in claims 1 to 3, as in the invention described in claim 4, the bottom surface of the concave portion of the belt layer is joined to an adjacent layer immediately below the layer, and the convex portion of the belt layer is formed by:
It has a rubber layer between it and the layer immediately below it.

According to the invention described in claims 1 to 4, as in the invention described in claim 5, each concave portion and each convex portion in the same layer of the belt are arranged so as to be inclined in the same direction with respect to the tire equatorial plane. It becomes.

According to the first to fifth aspects of the present invention, as in the sixth aspect of the present invention, each concave portion and each convex portion are arranged in the direction in which the steel cords of the layer having these concave portions and convex portions are arranged. It has a shape along.

Further, in addition to the inventions described in claims 5 and 6, the present invention relates to the inventions described in claims 1 to 4, and as in the invention described in claim 7, each concave portion and each convex portion are formed by a tire. The array is orthogonal to the equatorial plane.

With respect to the invention described in claims 1 to 7, in practice, as in the invention described in claim 8, the difference in height between the concave portion and the convex portion adjacent to each other in the same layer is the same as the steel of the layer. It is 50% or more of the diameter of the cord.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a left half essential part cross-sectional view of a heavy duty pneumatic radial tire according to the present invention, and FIG. 2 is a left half essential part sectional view of a heavy load pneumatic radial tire according to the present invention, which is different from FIG. Yes, FIG.
FIG. 4 is a partial perspective view of an outermost layer of the belt taken out of the tire shown in FIG. 1, and FIG. 4 is a partial perspective view of an outermost layer of the belt taken out of the tire shown in FIG.

In FIGS. 1 and 2, a pneumatic radial tire for heavy loads (hereinafter referred to as a tire) has a tread 1
And a pair of sidewall portions (not shown) and a pair of bead portions (not shown) connected to both sides thereof. In addition, the tire has at least one ply that reinforces each part across a bead core (not shown) embedded in each bead part,
The illustrated example includes a one-ply carcass 2 and a belt 3 that strengthens the tread portion 1 at the outer periphery of the carcass 2. Belt 3
Is a tread rubber 4 on the outside in the tire radial direction. The illustration of the grooves formed in the tread rubber 4 is omitted.

The belt 3 has three rubber-coated steel cord layers 3-1, 3-2, 3-3. In the belt 3, the steel cord of each layer of the adjacent two layers 3-1 and 3-2 and the steel cord of each layer of the adjacent two layers 3-2 and 3-3 are:
A steel cord crossing layer intersecting the tire equatorial plane E is formed. For example, looking at the tire from the front,
The steel cords of the layer 3-1 are arranged right upward, the steel cords of the layer 3-2 are arranged left upward, and the steel cords of the layer 3-3 are arranged right upward.

Here, referring to FIGS. 3 and 4, at least the outermost layer 3 of the outer two layers 3-2 and 3-3 of the belt 3 will be described.
-3 is a convex portion 3-3R that the layer 3-3 itself projects outward in the tire radial direction along the circumferential direction of the tread portion 1.
And the concave portion 3 depressed inward in the tire radial direction from the convex portion 3-3R
-3D.

The projection 3-3R in the illustrated example has a platform shape with a trapezoidal cross section. In addition, although not shown, the case where the convex portion 3-3R has a chevron-shaped cross-sectional shape is also included. The convex portion 3-3R and the concave portion 3-3D are connected to the belt 3
, The entire width of the outermost layer 3-3 in the illustrated example.

As shown in FIG. 1, the bottom surface of the concave portion 3-3D has a repeating shape of the convex portion 3-3R and the concave portion 3-3D.
The convex portion 3-3R is bonded to the layer 3-2 immediately below the belt portion 3-2, and the belt-shaped rubber layer 5 having a trapezoidal cross section is interposed between the convex portion 3-3R and the layer 3-2 immediately below the convex portion 3-3R. When the convex portion 3-3R has a chevron-shaped cross-section, a belt-shaped rubber layer 5 having a chevron-shaped cross-section is interposed in accordance with this.

With the rubber layer 5 properly interposed, the convex portions 3-3R
When the unvulcanized tire is molded, the convex portion 3-3 is formed.
Using an unvulcanized member for the belt layer 3-3 having a convex shape corresponding to R, a rubber layer 5 is formed in a space below the shaped convex portion.
An unvulcanized belt-like rubber member or an unvulcanized cord-like rubber member to be set as follows. This unvulcanized tire is subjected to vulcanization molding to obtain a layer 3-3 of the belt 3.

The example of the layer 3-3 shown in FIG.
And the recess 3-3D are inclined in the same direction with respect to the tire equatorial plane E. This inclination is along the direction in which the steel cords of the layer 3-3 are arranged, for example, in the upwardly inclined arrangement direction. Further, the inclination angle between the convex portion 3-3R and the concave portion 3-3D is also the same as that of the layer 3-3.
Match the angle of the steel cord of No. 3. At this time,
The projection 3-3R and the recess 3-3D are formed by a manufacturing method described later.
Can be formed easily and with high precision.

The example of the layer 3-3 shown in FIG.
This is an example in which the recesses 3-3D face in a direction perpendicular to the tire equatorial plane E. FIG. 2 shows a left half section of the tire at this time. FIG. 2 is a cross-sectional view of the protrusion 3-3R of the layer 3-3.

FIG. 5 is a partial sectional view of the tire taken along a plane parallel to the tire equatorial plane E according to the present invention. The tread rubber 4 receives a cut wound K reaching the vicinity of the outermost layer 3-3 of the belt 3. This shows the state of the event. FIG. 6 shows FIG.
It is a fragmentary sectional view of the conventional tire which shows the same situation as (a).

5 and 6, when a rotational driving force in the direction of arrow F acts on the tread portions 1 and 11, the tread rubbers 4 and 14 having low rigidity and the outermost layers 3-3 and 13-3 having high rigidity are provided.
, A large shear strain occurs in the same direction as the arrow F direction. As a result, a crack C indicated by a broken line extends and grows in the direction of the arrow from the end of the cut K.

In the case of the conventional tire, the crack C grows rapidly in a short time because there is no obstacle in the direction of the growth and growth of the crack C. On the other hand, the crack C that grows from the concave portion 3-3D becomes a hindrance to growth because the transition between the concave portion 3-3D and the convex portion 3-3R is remarkably inclined with respect to the action direction of the shear strain. The growth stops almost once at the transition. The crack C moves from the projection 3-3R to the recess 3-
The same goes for 3D. Therefore, the growth rate of the crack C is significantly reduced, and the cut separation resistance is significantly improved.

It is effective that the amount of the height difference δ between the convex portion 3-3R and the concave portion 3-3D is as large as possible, and the layer forming these concave and convex portions, in this case, the outermost layer 3-3. 50% or more of the diameter of the steel cord. If it is less than 50%, the effect is small and practicality is lacking. Convex part 3-3R and concave part 3-3
The number of repetitions N with D is preferably as large as possible. In practice, the number of repetitions N is 200 mm in circumference of the outermost layer 3-3.
A range of 1 to 10 is suitable. Further, it is preferable that the circumferential length of the convex portion 3-3R and the circumferential length of the concave portion 3-3D are substantially equal.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One type of radial ply tire for construction vehicles, the size of which is 37.00R57, and the belt 3 is composed of six rubber-coated steel cord layers. The outer three layers of the belt 3 are regarded as the layers 3-1 to 3-3 shown in FIG. 1, and a convex portion 3-3R and a concave portion 3-3D shown in FIGS. 1 and 3 are formed on the outermost layer. The inclination angle between 3-3R and recess 3-3D was adjusted to the steel cord arrangement inclination angle of outermost layer 3-3. The amount of the height difference δ is 100% of the diameter of the steel cord of the outermost layer 3-3, and the number N of repetitions of the protrusions 3-3R and the recesses 3-3D is 2 per 200 mm of the circumference of the outermost layer 3-3. And

With the exception of the outermost layer 3-3, all conventional tires were prepared in accordance with the example tires, and the following tests were performed using these tires as test tires. In other words, two positions A and B on the circumference of the tread portion are previously provided with a cut of 10 cm in width and a cutting position in the depth direction of the outermost layer 3-3 and a cut in the direction of the axis of rotation of the tire in the depth direction. The tires were dissected and the length of crack propagation at positions A and B, ie, the length of separation growth was measured.

Results of Separation Propagation Length Measurement: (1) Conventional Example Tire: Position A Length 150 cm, Position B
215cm in length. (2) Example tire: position A length 30 cm, position B length 35 cm. From the above results, it can be seen that the outermost layer having the repeated height difference portions of the convex portions 3-3R and the concave portions 3-3D has excellent cut separation resistance.

[0031]

According to the invention as set forth in claims 1 to 8 of the present invention, the air for heavy load in which the cut separation resistance is greatly improved only when the outer one or two layers of the belt have repeated height difference portions. It is possible to provide a radial tire containing the tire.

[Brief description of the drawings]

FIG. 1 is a sectional view of a left half of a tire according to the present invention.

FIG. 2 is a sectional view of a left half main part of another tire of the present invention.

FIG. 3 is a partial perspective view of the outermost layer of the belt of the tire shown in FIG. 1;

4 is a partial perspective view of an outermost layer of the belt of the tire shown in FIG.

FIG. 5 is an explanatory diagram of the progress of cut separation of the tire of the present invention.

FIG. 6 is an explanatory diagram of progress of cut separation of a conventional tire.

[Explanation of symbols]

 Reference Signs List 1 tread portion 2 carcass 3 belt 3-2 adjacent layer of outermost layer of belt 3-3 outermost layer of belt 3-3R convex portion 3-3D concave portion 4 tread rubber 5 rubber layer E tire equatorial plane δ Height difference

Claims (8)

[Claims] 1. A heavy-duty pneumatic radial tire having a belt of three or more rubber-coated steel cord cross layers for reinforcing a tread portion, wherein at least the outermost layer of the two steel cord cross layers outside the belt is formed of a rubber cord. The pneumatic device for heavy loads, characterized in that the layer itself has a repetitive shape of a convex portion protruding outward in the tire radial direction along the circumferential direction of the tread portion and a concave portion depressed inward in the tire radial direction from the convex portion. Radial tire. 2. The tire according to claim 1, wherein the convex portion of the layer of the belt has a trapezoidal platform in cross section. 3. The tire according to claim 1, wherein the convex portion of the layer of the belt has a chevron cross-sectional shape. 4. The belt according to claim 1, wherein the bottom surface of the concave portion of the belt layer is joined to an adjacent layer immediately below the belt layer, and the convex portion of the belt layer has a rubber layer between itself and the immediately lower layer. The tire described in one item. 5. The tire according to claim 1, wherein each of the concave portions and the convex portions in the same layer of the belt has an arrangement inclined in the same direction with respect to the tire equatorial plane. 6. The tire according to claim 1, wherein each of the concave portions and the convex portions has a shape along the direction of arrangement of the steel cords of the layer having the concave portions and the convex portions. 7. The tire according to claim 1, wherein each of the concave portions and the convex portions is arranged in an array orthogonal to the tire equatorial plane. 8. The tire according to claim 1, wherein the height difference between the concave portion and the convex portion adjacent to each other in the same layer is 50% or more of the diameter of the steel cord in the layer.