JPS62152904A - Pneumatic radial tyre for heavy load - Google Patents

Abstract

PURPOSE:To enable durability of a tyre to be compatible with cornering power characteristics thereof, by a method wherein a belt, substantially surrounding a carcass throughout the total width of a tread part, is formed through combination of a main and an auxiliary belt layer, aligned at their respective specified cord angles with the quator of a tyre. CONSTITUTION:A case body, formed with a tread part T, side wall parts S, and bead part, is reinforced by a radial cord-aligned carcass C and a belt B formed with a cord layer in at least 2 layers substantially surrounding the carcass C throughout the total width of the tread part T. Flatness is set to 0.9 or less. In the radial tyre, the belt B is formed through combination of a main belt layer B1 in at least one layer spirally aligned at a cord angle of approxialmately 0 deg. with the quator of the tyre and an auxiliary belt layer B2 in a single layer inclinably aligned at a cord angle of 20-40 deg. with the quator radially internally of the tyre of the main belt layer B1.

Description

Detailed Description of the Invention (Industrial Application Field) A general heavy-duty pneumatic radial tire with a flatness ratio of 0.9 or less, which supports high loads and is used continuously for long periods of time. We propose improvements related to appropriate weight reduction of the belt structure.

The belt structure of this type of tire generally consists of interlaced layers of cords arranged at an angle with respect to the tire's equator. The strain is large, and there is a limit in terms of the internal pressure that must be applied against high loads.

(Prior art) In order to reduce strain at the belt end under high internal pressure, the belt is surrounded in the radial direction outward by an interlacing layer, and a spiral arrangement is formed at a cord angle close to Oo with respect to the equator of the tire. Adding multiple layers of eggplants is a special public interest rate of 11562%
Although it is known as stated in the official gazette, such additional layers increase the weight of the tire and are disadvantageous in terms of heat generation in the tread, and recently in Europe and the United States, penalties are imposed on heavier tires. Due to these trends, the need to reduce tire weight is now an important issue.

(Problem to be Solved by the Invention) Belt end separation can be effectively prevented without actually increasing the tire weight and without deteriorating the tire's maneuverability, especially cornering power, and thus improving the tire's durability. It is an object of the present invention to realize belt reinforcement that satisfies both cornering power and cornering power.

(Means for Solving the Problems) This invention provides a case body consisting of a tread portion, a sidewall portion, and a bead portion, and a carcass having a radial cord arrangement, and at least two carcass surrounding the carcass over substantially the entire width of the tread portion. In a radial tire with a flatness ratio of 0.9 or less reinforced by a belt consisting of a plurality of cord layers, the belt has at least one main layer in a spiral arrangement with a cord angle close to 0° with respect to the equator of the tire. 20° or more with respect to the equator within the belt layer and its tire radial direction 4
This is a heavy-duty pneumatic radial tire that is combined with a single sub-belt layer in an inclined arrangement with a cord angle of less than 0''.

There are two main belt layers here, and the belt is a metal cord.
It is particularly preferred that the main belt layer of the belt is made of an organic fiber cord such as Kevlar, which has a tensile modulus of elasticity of 2000 kgf/Tsuru2 or more at 1% elongation of one cord.

Now, in general flat heavy load radial tires with a flattening ratio of 0.9 or less, the so-called hoop effect of the belt must be sufficiently produced. ) is 60 to 80 degrees, the second layer is 10 to 30 degrees (but tilted in the same direction as the first layer), the third layer is tilted in the opposite direction at the same angle as the second layer, and the fourth layer is tilted in the opposite direction at the same angle as the second layer. In a belt structure in which the layers are inclined at the same angle and in the same direction, the radial growth of the tire is large, belt end separation is likely to occur, and it is difficult to obtain satisfactory durability. This problem is particularly serious when operating under more severe operating conditions in which a high load is supported by inflation due to high internal pressure.

On the other hand, when we tried to apply a so-called circumferential belt with a cord arrangement substantially parallel to the tire's equator, we found that the tire motion, especially the cornering power characteristics, were generally inferior compared to the normal belt structure mentioned above. Therefore, it is difficult to expect a tire to have both durability and cornering power, but with this invention, for the first time, a tire with cornering characteristics comparable to conventional tires with the above-mentioned normal belt structure,
A satisfactory improvement in durability could be achieved.

It has been confirmed that a single layer is necessary and sufficient for the sub-belt layer, especially in terms of cornering power. There is no disadvantage of increased weight or decreased heat generation durability as in the case of multiple layers.

FIG. 1 shows a cross-section of the main parts of a heavy-duty pneumatic radial tire having a belt structure according to the present invention, in which T is the tread, S is the sidewall, C is the carcass, and B is the belt.

The belt B is made up of at least two layers, a main belt layer Bl and a sub belt layer B2, which surround the carcass C over substantially the entire width of the tread portion T.

The main belt layer B1 has at least one layer spirally arranged at a cord angle close to 0° with respect to the equator of the tire, and the sub belt layer B2 has at least one layer radially inward of the main belt B and also with respect to the equator. Each layer is composed of two or more single layers arranged in an inclined manner with a cord angle of less than 40 degrees (particularly preferably 23 to 35 degrees).

Here, the width of the main belt layer/tread portion is 0.7 to 1.2, preferably 0.8 to 1.0, and the width of the sub belt layer/main belt layer is 0.6 to 1.3, preferably 0. The cord of the main belt layer has a tensile modulus of elasticity of 2 at 1% elongation.
XIO" kgf/mm2 or more metal or organic fiber cord such as Keppra, the cord of the sub belt layer is the same < I
It is preferable to use metal cords with a diameter of XIO'kgf/++n'' or more, and the cord spacing/cord diameter ratio is 0.1 to 3.0 for the main belt layer, preferably 0.3 to 1.5 for the sub belt layer. 0.1 to 4.0 preferably 0.3 to 1
．． It is 5.

(Function) The main belt layer B1 serves as a so-called circumferential belt.
-B increases the circumferential rigidity, and while the intersecting layers in the normal belt structure of conventional tires contribute to the balance of belt rigidity in the circumferential and radial directions, there is a disadvantage of increased outer diameter growth of the tire at high internal pressures. However, by combining a single sub-belt layer B2 with a cord arrangement inclined at a specific cord angle with respect to the equator of the tire, radially inward of the circumferential belt, This achieves a balance between belt rigidity and reduces outer diameter growth under high internal pressure.

(Example) Example 1 According to the place shown in Fig. 1, tire size 13/8
0 R20, internal pressure 7.95 kgf/cm”, load 3
With the specification of 650 kg, the sub belt layer Bt was varied variously between θ and 90 degrees with respect to the tire equator, and the main belt layer B
1 has a spiral arrangement of substantially 0° with respect to the tire equator, and all metal cords (subbelt: twisted structure 1 x 3 +
Tensile modulus at 9+15+1.1% elongation 1.3 XIO'
kg f/tm”, cord spacing/cord diameter ratio 0
．． 6. Main belt: Twisted structure IX3+9+15+1.1%
A test tire with a belt structure was made with a tensile modulus of elasticity at elongation of 1.3 Metal cords were used that were arranged at an angle of 65° to the right for the second layer, 20° to the right for the third layer, and 20° to the left for the fourth layer.

As shown in Figure 2, the influence of the cord angle of the sub-belt layer Bt on the cornering power is expressed as 20° in the index display where the cornering power of the conventional tire is set as 100.
By using the sub-belt B having a cord angle range of less than 40 degrees, cornering power equal to or greater than that of conventional tires can be achieved.

Example 2 A comparison was made with a belt structure according to the present invention in which two layers, each of which has a spiral arrangement with a cord angle close to 0°, are combined as the main belt layer B with a sub-belt layer B2 having a cord angle of 30''. Therefore, the cord angle of sub-belt layer B2 is (4)
The results of the test were as shown in Table 1 below, in which the comparative belt structure with a 5° angle was compared with the same belt structure as the conventional tire described in Example 1.

(Effects of the Invention) The belt structure of the present invention improves tire durability while simultaneously improving cornering power characteristics, and is also useful for reducing tire weight.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the embodiment, and FIG. 2 is a graph showing the relationship between the cord angle of the sub-belt layer and the cornering power. T...Tread part S...Sidewall part C...Carcass B...Belt B,...
・Main belt layer B2... Sub-belt layer Patent applicant Brideston Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] 1. A case body consisting of a tread portion, a sidewall portion, and a bead portion, and a carcass having a radial cord arrangement;
In a radial tire with a flattening ratio of 0.9 or less, which is reinforced with a belt consisting of at least two cord layers that surrounds the carcass over substantially the entire width of the tread, the belt is at an angle of 0° with respect to the equator of the tire. at least one main belt layer in a spiral arrangement with a cord angle close to
A heavy-duty pneumatic radial tire that is combined with a single sub-belt layer arranged at an angle with a cord angle of at least 40 degrees. 2. The tire according to claim 1, wherein the main belt layer is two layers. 3. Claim 1, wherein the belt is made of a metal cord.
Or 2, the tire described. 4. The tire according to claim 1 or 2, wherein the main belt layer is an organic fiber cord having a tensile modulus of elasticity of one cord at 1% elongation of 2000 kgf/mm^2 or more.