JPH03258601A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve C.B.U-resisting characteristic and wear resistance of a tire, respectively by specifying the strength and count of a cord for forming a tire innermost layer carcass ply. CONSTITUTION:A tire 30 comprises a carcass 22 formed by plural carcass plys having a specified cord, a tread 24, and a breaker 26 formed by plural breaker layers disposed therebetween. In this case, when the strength in a length of 10cm of a cord forming a tire innermost layer carcass ply 22a is let be T(kg) and the cord base yarn thickness x twisting number is let be N at least, the strength S (=Tx10<3>/D) of the above cord is set more than 8.9 (g/d). The cord count per a width of 25mm in the above carcass ply 22a is less than 23 in the case of a cord having a thickness of 1260d/2 and less than 18 in the case of a cord having a thickness of 1260d/3.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to pneumatic tires used for heavy-duty vehicles such as trucks and buses, and particularly to C, B, and U resistance on the inner peripheral surface thereof. This invention relates to an improved pneumatic tire for heavy loads.

(Prior Art) For example, as shown in FIG. 3, a heavy-duty pneumatic bias tire IO usually uses a cord made of aliphatic polyamide fiber such as nylon 6 or tenron 66 at an angle of 30° to the tire's equatorial plane. Carcass plies aligned in a substantially constant direction at an angle within the range of ~60° are stacked in 6 to 10 layers so that the respective cords intersect to form a carcass 12, and bead rings 14 are formed at both ends of the carcass ply. The tire is rolled up from the inside to the outside in the axial direction of the tire, and a tread l6 is provided on the crown portion of the carcass 12 to form a tire tread surface, and a breaker 18 is further provided between the carcass 12 and the tread 16. The structure protects the carcass 12 from impact caused by unevenness of the road surface and ensures adhesion between them.

(Problem to be Solved by the Invention) By the way, if the tire air pressure is poorly managed or if the tire is driven with the air pressure reduced due to some kind of malfunction, the tire will repeatedly undergo large deformations due to tire transfer, so In the part of the shoulder where the cords forming the carcass ply are located close to each other, the cords may separate from the rubber layer due to the relative displacement of the cords, or the cords may become locally high in temperature as they rub against each other. The result is C, B,
There was a problem in that a cord called U would break and eventually lead to a burst.

For this reason, in the conventional technology, the number of cords per unit width of the carcass ply is made as uniform as possible, and the interval between adjacent cords is made wider than that in a normal tire. Methods such as increasing the thickness of the rubber layer forming the inner peripheral surface have been taken.

However, increasing the distance between adjacent cords, that is, reducing the number of cords per unit width of the carcass ply, reduces the strength of the case. Increasing the thickness of the material is not a desirable method if heat generation is taken into account, and there is a limit to that.
Some kind of solution was needed.

The present invention was made in view of such problems, and an object of the present invention is to provide a heavy-duty pneumatic tire with excellent C, B, and U resistance characteristics.

(Means for Achieving the Object) In order to achieve this object, the present invention provides an aliphatic compound arranged in one direction obliquely intersecting the tire equatorial plane at an angle within a range of 30° to 60°. A carcass consisting of a plurality of carcass plies made of a polyamide fiber cord and wound from the inside to the outside in the axial direction of the tire at both ends through paired bead rings, and a tread forming the tread surface of the tire; In these heavy-duty pneumatic tires equipped with a carcass and a breaker consisting of a plurality of breaker layers arranged between the tread, the strength at least at a length of 10 cm of the cord forming the innermost carcass ply of the tire is T (kg), When the thickness of the cord yarn x the number of twisted strands is N, the strength of the cord is S (=Tx
lO''/D) is 8.9 (g/d) or more, and the number of cords inserted per 25 marks of carcass ply width is 1
For 260d/2 cord, 23 or less wires, thickness 18
For 90d/2 or 1260d/3 code, the number shall be 18 or less.

(Function) In such tires, the number of cords driven per predetermined width of the carcass ply is smaller than that of conventional tires.In other words, while increasing the distance between adjacent cords, each Since the strength of the cord is high, the strength of the case does not decrease even though the cord spacing increases, and therefore the C, B, and U resistance characteristics of the tire can be improved.

(Example) Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing half of a heavy-duty pneumatic tire 30 according to the present invention, including a shoulder portion 32, and the tire 30 is 30° with respect to its equatorial plane S.
Carcass plies having cords made of aliphatic polyamide fibers arranged in a certain direction at an angle within the range of ~60° are stacked in 6 to IO layers, and both ends are connected to the tire rotation axis through bead rings (not shown). A carcass 22 rolled up from the inner side to the outer side, a tread 24 forming the tire tread, and a cord made of fibers similar to the carcass ply disposed between the carcass and the tread with respect to the tire equatorial plane S. The breaker 26 includes a plurality of breaker layers arranged in a fixed direction at an angle within a range of 30° to 60°. Note that a plurality of grooves 28 are usually formed in the tread 24 forming the tire tread surface in order to improve the drainage performance of the tire.

5-6 - In the tire 20 of the present invention, at least the cords forming the carcass ply located inside the tire, that is, the innermost layer carcass ply 22a of the carcass 22 are selected so as to satisfy the following conditions.

That is, when the strength per 10 cm of the cord forming the innermost carcass ply 22a, determined based on JIS-L1017, is T (kg), and the cord yarn thickness x number of strands is N, S = T x 10”/
The strength S of the code given by D is 8.9 (g/d)
Based on the above, the number of cords driven per 25mm width of carcass ply is 23 or less for cords with a thickness of 1260d/2, and 1890d/2 or 1260d/3 in thickness.
The number of cords shall be selected to be 18 or less.

Here, the strength S of the cord of the innermost carcass ply 22a is
The reason for setting S to 8.9 (g/d) or more is to maintain the specified strength of the carcass even if the number of the cords is reduced.
(g/d) If a smaller cord is used, the incidence of failures such as cuts C, B, and U due to impact during driving on rough roads will increase.

On the other hand, the number of cords driven into the carcass ply 22a with a width of 25 mm is 23 or less when using a cord with a thickness of 1260d/2, and when using a cord with a thickness of 1890d/2 or 1260d/3. The reason why the number of cords is 18 or less is because if the number of cords exceeds the above value, the distance between the cords will become shorter, and due to the relative displacement of these cords, the cords may separate from the rubber layer or rub against each other, which is the problem mentioned above. This is because

Therefore, a comparative test was conducted to examine the C, B, and U resistance characteristics of the tire according to the present invention and a tire with a conventional structure. Each tire has the structure shown in Figure 1, and its size is 9.00-20, with a diameter of 5.
A carcass with six layers of carcass plies made of nylon cords arranged in one direction at an angle of 0 degrees, and a breaker layer made of nylon cords arranged in one direction at an angle of 50 degrees with respect to the tire equatorial plane. It includes breakers arranged in two layers.

◎Test tire: - Invention tire A: The cord thickness of the innermost carcass ply was 1260 d/2, and the cord strength (S) was 9.8 (g/d).
), and the driving number (N) is 22.0 (pieces/25mm
) tires.

・Invention tire B: The cord thickness of the innermost layer carcass ply is 1260 d/2 (or 1890 d/2), the cord strength (S) is 9.6 (g/d), and the number of inserted cords (N
) is 17.0 (pieces/25mm) Tie t0 ・Comparative tire l: The cord thickness of the innermost layer carcass ply is 12606/2, and the cord strength (S) is 8.0 (g/d
), and the driving number (N) is 23.7 (pieces/25mm
) tires.

・Comparison tire 2: The cord thickness of the innermost layer carcass ply is 1260 d/2, and the cord strength (S) is 8.0 (g/d).
), and the driving number (N) is 22.0 (pieces/25mm
) tires.

Comparison Tire 3: The cord thickness of the innermost carcass ply was 1260 d/2 (or 1890 d/2), and the cord strength (S) was 8. O (g/d), the number of shots (
Tires with N) of 19.4 (pieces/25 marks).

・Comparative tire 4: The cord thickness of the innermost layer carcass ply is 1260 d/2 (or 1890 d/2), the cord strength (S) is 8.0 (g/d), and the number of inserted cords (N
) is 17.0 (units/25 meters).

◎Test method: A test tire mounted on a regular rim was tested with a pressure of 3 kg/3 from the regular internal pressure.
cJI applied low internal pressure and pressed and rolled under the action of the regular load, C, B, [J due to the failure occurrence, the time required for removal, each test tire was installed alternately on the actual vehicle, 3000km After running, the presence or absence of 90C, B, and U and wear resistance were investigated.

Note that C, B, and U indicate the number of cords generated per 10 cords, and abrasion resistance was evaluated using an index.

◎Test results: The test results are shown in the table below.

According to this table, it can be seen that not only the C, B, and U resistance properties are improved, but also the wear resistance is maintained.

(Effects of the Invention) Thus, according to the present invention, it is possible to obtain a pneumatic tire for heavy loads that has excellent C, B, and U resistance properties and also has excellent wear resistance.

[Brief Description of the Drawings] Fig. 1 is an enlarged view of a part of the pneumatic tire for heavy loads according to the present invention, and Fig. 2 shows a conventional pneumatic tire for heavy loads 1-2. This is a diagram. 12.22 - Carcass 16.24 - Tread 28 - Groove 14 - Bead ring 18.26 - Breaker

Claims (1)

[Scope of Claims] 1. Consisting of cords of aliphatic polyamide fibers arranged in one direction obliquely at an angle within the range of 30° to 60° with respect to the tire equatorial plane, with beads forming a pair at both ends. A carcass consisting of a plurality of carcass plies rolled up from the inside to the outside in the axial direction of the tire through a ring, a tread forming the tread surface of the tire, and a plurality of breaker layers disposed between the carcass and the tread. In a heavy-duty pneumatic radial tire equipped with a breaker of
), the strength S (=T x 10^3/D) of the cord is 8.9, where N is the thickness of the cord yarn x number of strands twisted.
(g/d) or more, and the number of cords per 25mm width of the carcass ply is 23 or less for cords with a thickness of 1260d/2, and 12 or less for cords with a thickness of 1890d/2 or 12mm.
A heavy-duty pneumatic tire characterized by a 60d/3 code having 18 or less tires.