LU100489A1 - HYBRID WIRED AS CARCASE REINFORCEMENT IN DIAGONAL TIRES - Google Patents

Abstract

A diagonal tire carcass reinforced with hybrid cords consisting of a ply of aramid yarn (1) and a ply of nylon yarn (2), and the nylon content within the cord is between 45 and 65 % the nylon content of the yarn within this range improves the fatigue strength and reduces the sidewall gauge with respect to a diagonal reference tire having a nylon carcass; in one embodiment of the present invention, a tire tire diagonal tire carcass having reinforcing layers comprising hybrid cords consisting of a ply which is made of aramid yarns and a ply which is made of yarns. nylon with a nylon content of 45 to 65% by weight, which are balanced twisted cords.

Description

HYBRID WIRED AS A CARCASE REINFORCEMENT IN DIAGONAL TIRES

FIELD OF THE INVENTION

The present invention relates generally to pneumatic tires and more specifically to hybrid cables as carcass reinforcements in diagonal tires.

BACKGROUND OF THE INVENTION

Diagonal ply tires have a carcass formed of an even number of layers or plies of wired fabric. They are also known as "diagonal folds" or "cross folds". The reinforcing cords of each layer run diagonally across the tire from one bead portion to another bead portion. The angle of inclination of the cable tray relative to the axial direction of the tire is greater than 15 degrees. The carcass cords extend in opposite directions in each successive layer (or successive ply) of reinforcing material, which results in a crisscross pattern. Top plies are additional layers of reinforcing material or plies that can be included for additional reinforcement of the tire, these layers covering the top area of the tire to further strengthen the tread region. The cords of these reinforcements do not extend to the bead portions of the tire.

The other type of tire structure is the radial tire. In a radial tire, the carcass cords extend from bead to bead on either side of the top of the tire substantially in radial planes crossing the axis of rotation of the tire. Radiation towards the outside of the fold or folds under the tread is a high modulus belt made up of one or more layers of cords, the angles of the belt cords being relatively small, for example from 15 to 25 degrees relative to the equatorial plane (circumferential direction) of the tire. The present invention does not relate to radial tires.

In pneumatic diagonal tires for heavy vehicles, a carcass composed of layers of rubberized pleats has been provided so far, each containing relatively fine nylon cords, for example, from 940 dtex / 2 to about 1,400 dtex / 2. Tires are usually formed by laminating 8 or more carcass plies on top of each other in order to cross them with each other at a predetermined cable angle.

In order to reduce the number of folds in the carcass, thicker nylon cords such as 2 100/2 and 2 100/3 are also available. But such applications do not improve the flatness behavior and do not eliminate the need for a post-curing tire inflation process.

On the other hand, hybrid cable structures containing high tenacity / high modulus wire with nylon have been proposed and used widely as a tire reinforcement in tire technology. Some examples can be given as follows.

In documents US 2007/0235116 and US 2010/0024948, the three-ply hybrid cable comprising two plies of aramid yarns and one ply of nylon yarns (aramid 3,300 dtex / 2 + nylon 1,880 dtex, nylon content of 22%) with different twist levels has been proposed as radial carcass reinforcements in aircraft tires.

In the document US Pat. / 1

AR 1100 dtex / 3 + NY 940 dtex / 1 etc., with nylon contents of 18%,%, and 22% respectively) have been proposed as a fold / cushion damping reinforcement in pneumatic tires.

In document US Pat. 39%), have been proposed for use as a folded and unfolded belt reinforcement in radial aircraft tires.

In US 7,222,481, hybrid cables having a low modulus rod (less than 900 cN / tex) and a high modulus casing (greater than 1,300 cN / tex) which is produced with a rod insertion technique have have been disclosed and offered as crown reinforcement in pneumatic tires.

SUMMARY OF THE INVENTION

The invention provides hybrid aramid / nylon cords with a high nylon content for diagonal carcass reinforcement in pneumatic tires. The tires are preferably truck and aircraft tires.

In order to reduce the weight and flatness of the tire and to eliminate post-curing inflation, but also to improve endurance in diagonal tires, hybrid cables made of aramid / nylon 66 with a content (percentage by weight ) made of high nylon 66 are offered as carcass ply reinforcement.

While an aramid ply in a hybrid cord provides high strength and modulus, nylon 66 provides robust grip and improved flexibility fatigue resistance. The nylon / aramid ratio is an important parameter regulating the dynamic adhesion and the resistance to flexibility fatigue for a given level of twist in hybrid cable.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, two-ply aramid / nylon hybrid cables which have one ply which consists of aramid yarns and the other ply which consists of nylon yarns, these yarns having a twist in a direction prior to twisting. (may also be called wiring), and the plurality of wires being twisted together with a twist in the opposite direction to form the cord, the twist of the wires being at least equal to the twist of twisting (wiring), the twists of said wires and twisting (wiring) being of such a nature as to give a balanced twisted cord with an optimum nylon content, improve the endurance of a diagonal tire and make it possible to eliminate a post-hardening inflation process. In two-ply hybrid cable structures, aramid and nylon plies (wires within a cable) have a smooth contact surface with each other at the interface. In the case of a number of folds of three or more, semicircular fold cross sections become triangular, which gives rise to an increased contact surface and a higher degree of friction at the interface in dynamic conditions. On the other hand, interface filaments of each ply wire are much more deformed due to triangular cross sections. Therefore, two-ply hybrid cable structures are provided in our invention.

The results of the disk fatigue laboratory are given below. According to laboratory results, a two-ply hybrid cable with the same helix angle and even the same nylon content gives better fatigue resistance results (resistance retention after fatigue) than three-ply hybrid cable.

Table 1. Fatigue analysis results on disk

Cable structure AR 3 340 + NY 2 800 AR 1 670/2 + NY 2 800/1 AR 1 670/2 +1 400 Number of folds 2 3 3 Content nylon (%) 45.6 45.6 29.5 Cable twist 335 335 380 Helix angle 46 ° 46 ° 46 ° Resistance retained after fatigue on disc * 85 81 74 * 3.6 mi cycle lions (2.0% extension and compression of e 14%)

The results on tire confirm the laboratory results. The reference is a diagonal truck tire from 10.00 to 20 with a 1,400/2 nylon carcass with 8 plies. Based on equal carcass strength, using AR / NY hybrid cables, the number of carcass plies was reduced from 8 to 4. Using AR 3,340 + NY 2,800 as carcass reinforcement, overload endurance has been improved by approximately 40% compared to 10 AR 1 670/2 + NY 1 400/1 (4-ply carcass) and nylon 6, 1 400/2 ( pleated carcass).

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and other advantages of the invention will be better understood with reference to the description of a nonlimiting example, to which the drawings are associated;

Figure 1a. Radial cross section of a two-ply hybrid cable in which,

1. Aramid fold (semi-circular)

2. Nylon fold (semi-circular)

3. Aramid and nylon ply contact surface (interface)

Figure 1b. Radial cross section of a three-ply hybrid cable in which,

4. Aramid fold (triangular)

5. Nylon fold (triangular)

6. Aramid and nylon ply contact surface (interface)

Nylon has a dual function, that is, it functions as a lubricant or cushion in conjunction with an aramid yarn by improving resistance to dynamic fatigue, and another function is to increase the overall adhesion of a cord hybrid (aramid + nylon). As is well known, the inactive surface of aramid filaments gives poor adhesion retention under flexion. Nylon filaments with more active sites (functional groups) on their surface give superior adhesion even with conventional RFL adhesives.

An optimum nylon content of said hybrid cable is preferably between 45 and 65%, more preferably between 50 and 60%. If the nylon content of said hybrid cable is less than 45%, the retention of fatigue strength of flexibility and adhesion after bending becomes poorer, and if the nylon content of said hybrid cable is more than 65%, the module effective and toughness become weaker. With higher nylon contents, the cable diameters become larger, which leads to a higher rubber gauge and a lower cable to cable distance (rivet area) between parallel cables within the layer of carcass. A weaker rivet area between the cables can easily initiate the crack between the cables under bending conditions.

A high nylon surface on hybrid cables improves resistance to cable-rubber separation under dynamic conditions, i.e. against inter-laminate stresses between carcass plies due to triangulation displacements.

In the present invention, the total linear density value of said hybrid cable is preferably between 4,000 and 12,000 dtex, more preferably between 6,000 and 9,000 dtex. The linear density value of total hybrid cable can be obtained by adding the nominal linear density values of the aramid and nylon yarns used in hybrid cable (for example, the total linear density value for AR 3 340 + NY 2 800 is 6 140 dtex).

In the invention in its preferred form, the level of twist of the hybrid cable varies between 150 and 400 turns per meter (rpm).

The most preferred embodiment of the present invention relates to a diagonal tire carcass for pneumatic tires which have reinforcing layers comprising hybrid cords consisting of a ply which is made of aramid yarns and a ply which is made nylon yarns with a nylon content of 50 to 60% by weight, which are balanced twisted cords, the total linear density value of said hybrid cord being between 6,000 and 9,000 dtex.

In order to increase the breaking strength (simultaneous rupture of nylon and aramid pleats in the hybrid cord), an overload of aramid ply of up to 3% can be applied during the twisting process (the length of aramid wire in hybrid twisted cable can be up to 3% longer than that of nylon wire).

Claims (6)

1. Diagonal carcass for pneumatic tires comprising a plurality of two-ply hybrid cables characterized in that said two-ply hybrid cables consist of a ply of aramid wires (1) and a ply of nylon wires (2 ), and said hybrid cables have a nylon content of 45 to 65% by weight and a total linear density value of between 6,000 and 9,000 dtex and torsion levels of 150 to 400 rpm. 2. Diagonal carcass for pneumatic tires comprising a plurality of two-ply hybrid cables according to the preceding claims wherein said two-ply hybrid cables have a nylon content of 50 to 60% by weight. 3. Diagonal carcass for pneumatic tires comprising a plurality of two-ply hybrid cables according to the preceding claims wherein said two-ply hybrid cables are balanced twisted cables. 4. A diagonal carcass for pneumatic tires comprising a plurality of two-ply hybrid cables according to the preceding claims wherein said nylon thread of said two-ply hybrid cable is polyamide 66. 5. Diagonal carcass for pneumatic tires comprising a plurality of two-ply hybrid cables according to the preceding claims wherein said nylon wire of said two-ply hybrid cable is polyamide 6. 6. Diagonal carcass for pneumatic tires comprising a plurality of two-ply hybrid cables according to the preceding claims wherein said aramid wire of said two-ply hybrid cable has a boost of up to 3%.