JP3009671B2 - Heavy duty pneumatic tires - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Industrial application field) The present invention relates to an improvement in the belt structure of a general pneumatic radial tire for heavy loads used for trucks, buses and the like, particularly for pneumatic tires.

(Prior Art) The belt structure of a conventional pneumatic tire of this type is as follows.
The main reinforcing means is at least two layers of so-called intersecting strips which intersect each other across the equator when the arrangement direction of the cords as the reinforcing elements is in an acute angle range of 15 to 25 ° with respect to the equatorial plane of the tire.

The reason for this is to maintain the radial Casas toroidal shape and to maintain a relatively flat tread, and to prevent the tire from cornering and to properly resist the lateral forces that occur when cornering. This is because the effect of obtaining the rigidity is expected for the belt.

However, in such a belt, a large tension is generated along the circumference due to an internal pressure applied to the tire, a load applied to the tire, and a centrifugal force caused by high-speed rotation, and the belt diameter tends to increase.

In the belt structure described above, since the cords of adjacent strips intersect with the equatorial plane of the tire at an acute angle of 15 to 25 ° C., the belt diameter is increased based on the tension, so that the strip ends at the belt end in the radial cross section. In this case, a large shear strain is generated, and after scanning for a long time, there is a possibility that a failure occurs.

Then, so as to cover the belt end of the cross strip,
An organic fiber cord or steel cord is arranged in parallel, and an additional reinforcing layer called a cap or layer is arranged along the circumference of the arrangement to reduce the belt tension during the action of centrifugal force on the tire. Measures have been taken to reduce and control the increase in the base belt diameter.

(Problems to be Solved by the Invention) However, the reinforcing effect of the textile cord is remarkably small because the internal pressure is extremely high when an additional reinforcing layer such as a cap or a layer is used for heavy loads such as trucks and buses. While the required durability cannot be obtained, steel cords cannot smoothly tolerate the expanding deformation of the tire from molding to vulcanization during tire manufacturing, which adds to manufacturing difficulties. The desired effect is difficult to obtain because the belt is wavy and the joints are exposed on the radial surface.

Accordingly, it is an object of the present invention to provide a pneumatic tire for heavy load, which does not require a combined use such as an additional reinforcing layer, and has a belt configuration improved so as to advantageously satisfy the required performance of the belt.

(Means for Solving the Problems) The present invention is based on a new idea which is radically departed from the conventional idea such as an additional reinforcing layer and is completely different from the conventional idea. The two functions required for the carcass, namely, the circumferential rigidity for maintaining the toroidal shape of the carcass and the shear rigidity for obtaining the resistance to the lateral force are separated into two types of reinforcements and individually borne. It is to try to make it.

That is, the present invention has a toroidal carcass moored by at least a pair of bead cores, and uses a large number of cords or filaments surrounding the crown of the toroidal carcass as a reinforcing element, and a polymer having a lower elastic modulus than this. A pneumatic tire having a belt made of four or five layers of strips coated with a material, wherein the belts are arranged in a corrugated or zigzag manner in the same strip, and are oriented along the equator of the tire. A first strip as a means of circumferential stiffness using a steel cord reinforcing element having an orientation of 30 ° to 60 ° with respect to the equatorial plane of the tire.
A pneumatic heavy load, characterized in that it has a stratified structure with two or three layers of second strips as shear stiffness means using steel cord reinforcing elements arranged in a linear array parallel to each other at an inclination angle of ゜. Tires.

In this tire, the reinforcing elements of each of the two or three-layer second strips are arranged so as to intersect with each other with the equator interposed therebetween, and the first strip becomes a layer occupying the radially inner side of the second strip. It is more appropriate that the first strip be a layer that occupies the radially outer side of the second strip.

FIG. 1 illustrates a specific example of a tire 1 according to the present invention, wherein 2 is a first strip, 3 is a second strip,
4 is a toroidal carcass and 5 is a bead core.

The first and second strips 2 and 3 have a layered structure shown in FIGS. 1A and 1C and function as belts for reinforcing the crown of the toroidal carcass 4.

In the figure, reference numeral 6 denotes a reinforcing element made of a steel cord which is aligned in a waveform (or zigzag shape) in each of the first strips 2 having two layers in this example, and is oriented along the equator of the tire 1. In this example, the steel cord reinforcing elements of the second strip also having two layers are arranged in a straight line parallel to each other at an inclination angle of 30 to 60 ° with respect to the equatorial plane of the tire 1.

It has been found that the layered structure of the belt still provides the desired effect under deformations as shown in several examples in FIG.

(Operation) The first strip 2 using the corrugated (or zigzag) steel cord reinforcing element functions as a circumferential rigid means according to the present invention.

That is, since there is no cord end at the strip end of the radial cross section of the tire 1 as in the conventional crossed belt having a small acute angle, even if circumferential tension is generated with respect to the belt, shear strain is generated there. No separation occurs.

In addition, since the tire has a corrugated shape (zigzag shape), it hardly hinders the expansion of the belt diameter during tire production, so that the tire can be easily produced by the molding and vulcanizing technique according to the conventional practice.

Moreover, since a steel cord reinforcement element is used,
Regardless of whether the internal pressure of the tire is high or the centrifugal force acting on the belt is large, an excellent reinforcing effect is always provided, and the durability of the tire can be greatly improved.

On the other hand, the second strip 3 serves only as a means of shear rigidity in the axial direction of the tire. Therefore, the second strip 3 does not need to have circumferential rigidity.

The shear stiffness is a stiffness against a shear force F as shown in FIG. 3 (b), and is calculated to be extremely high in the range of 30 ° to 60 ° as shown in FIG. 3 (a). Shear rigidity can be obtained.

In the present invention, two or three layers of the second strip are used, and in this case, with a constant circumferential tension, FIG.
As shown in FIG. 3 (b), a cross section taken along the line AA 'in FIG. 3 (a), the shear angle is required to be 30 [deg.] Or more in order for shear strain to occur between the strip end layers as shown in FIG. 4 (a). In this way, separation at the side end of the second strip 3 can be completely prevented.

In the case of a radial tire such as a large truck or bus expected in the present invention, at least two layers must be used because a single layer of the second strip 3 has insufficient shear rigidity due to heavy load. .

Furthermore, the larger the tire pressure, the higher the internal pressure, and therefore the greater the circumferential rigidity. Therefore, it is necessary to use a plurality of layers for the first strip 2 as well, and the examples shown in FIGS. 1 and 2 are preferable.

(Example) A prototype tire having a size of 1000R20 is prepared, and cornering power (internal pressure: normal internal pressure (7.25 kg / cm ² ), load: normal load (2425 g)) and durability (with a load twice the normal load) Distance to failure when running at 80km / h on drum)
And the results in the following table were obtained.

The belt structure of each test tire in the above table is as follows, and the reinforcement structure except for the belt was common throughout the test tires.

Embodiment In a laminated structure of three layers of first strips 2 and two layers of second strips 3 according to FIG. 2 (d), the corrugated reinforcing element 6 comprises a steel cord, while the second strip 3
For the steel cord reinforcing element 7, the crossing strips having an inclination angle of 45 ° with respect to the equatorial plane and intersecting each other with the equatorial plane interposed therebetween were used.

On the other hand, in the comparative example, according to the conventional technique, a five-layered crossed belt that intersects the tire at an inclination angle of 18 ° with respect to the equatorial plane with the equator interposed therebetween is used.

(Effects of the Invention) According to the present invention, the belt performance required for heavy-duty pneumatic tires such as trucks and buses can be advantageously realized without using an additional reinforcing layer, which has conventionally been indispensable. Can significantly contribute to the improvement of the properties.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to the present invention, a development view of a tread and a belt, FIG. 2 is a schematic view of a lamination procedure of a belt, FIG. 3 is a relation diagram between a shear rigidity and a cord angle, and FIG. FIG. 4 is a diagram illustrating a relationship between distortion and a cord angle. DESCRIPTION OF SYMBOLS 1 ... Tire 2 ... 1st strip 3 ... 2nd strip 4 ... Toroidal carcass 5 ... Bead core

Continuation of the front page (56) References JP-A-62-152904 (JP, A) JP-A-57-201704 (JP, A) JP-A-47-20807 (JP, A) JP-A-61-178204 (JP, A) , A) Japanese Patent Publication No. 54-11562 (JP, B2)

Claims (4)

(57) [Claims] 1. A toroidal carcass anchored by at least one pair of bead cores, and a plurality of cords or filaments surrounding a crown of the toroidal carcass is used as a reinforcing element, and has a lower elastic modulus than the reinforcing element. A pneumatic tire having a belt composed of four or five layers of strips coated with a molecular material, wherein the belts are arranged in a corrugated or zigzag shape in the same strip and oriented along the equator of the tire. A first strip as a means of circumferential rigidity using a steel cord reinforcement element oriented in the following manner, and a steel cord reinforcement element arranged in a linear arrangement parallel to each other at an inclination angle of 30 to 60 ° with respect to the equatorial plane of the tire. Characterized in that the used two or three layers have a stratified structure with a second strip as a shear rigidity means, characterized in that it is a pneumatic container for heavy load. Unpleasant. 2. The tire according to claim 1, wherein the reinforcing elements of each of the two or three layers of the second strip are arranged so as to intersect each other with the equator interposed therebetween. 3. The tire according to claim 1, wherein the first strip is a layer occupying the radially inner side of the second strip. 4. The tire according to claim 1, wherein the first strip forms a layer occupying the radially outer side of the second strip.