JPH11301221A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve run flat property to ensure a safer property, better rolling resistance to lower fuel consumption, and reduce road noise to improve a ride feeling. SOLUTION: The rubber layer, on at least a tire radius direction outer side out of a tread part 1, is blended by a reinforcing filler containing a silica of 50 wt.% or more, in a pneumatic radial tire equipped with a tread part 1, at least one layer carcass ply 2: where a reinforcing cord forms an actual angle of 90 deg. to a tire peripheral direction, and both the end parts are folded respectively toward the outer side from inner side of a tire around a pair of bead cores 7, at least two layer belts 3; arranged between the carcass ply 2 and the tread part 1, a reinforcing cord forms a given angle to the tire peripheral direction, and arranged so as to cross with each other, and a side wall part reinforcing layer 5 arranged on the inner side of the carcass ply 2, and having a crescent cross section extending in tread part and bead core directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire that can safely travel to a place where tires can be replaced even during a puncture, and more particularly to a pneumatic radial tire for a passenger car.

[0002]

2. Description of the Related Art As a pneumatic radial tire of a type having a reinforcing layer inside a sidewall portion, a carcass typically has a ply in which a reinforcing cord made of nylon, rayon, or polyester fiber is embedded.
The reinforcing layer of the sidewall portion is composed of a relatively hard rubber layer having a crescent-shaped cross-section and disposed substantially over the entire sidewall portion inside the carcass ply, and the belt is made of metal (steel). It is composed of multiple layers with embedded cords, and is reinforced to prevent punctures. In addition to these, a relatively large heat-shrinkable nylon cord substantially parallel to the tire circumferential direction, covering the entire width of the belt in the tire radial direction outside to improve high-speed durability in normal running. There is one in which one or two layers of cap plies in which the above-mentioned components are embedded are arranged. Since such a tire can support the load by the reinforcing layer provided on the sidewall portion, it can travel at a constant speed for several tens of kilometers even during a puncture, thereby allowing the tire to be replaced while in a punctured state. Travel to the place (run flat travel) becomes possible. Although such pneumatic tires have already been implemented, it is desired to further improve various performances.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to further improve the run flatness, and to improve the rolling resistance during normal running, which has been reduced due to the increase in weight due to the reinforcing layer in the sidewall portion. An object is to reduce the weight itself and further reduce vibration (road noise).

[0004]

In order to achieve the above object, the present invention improves the tread rubber itself,
It provides an optimal combination of a belt and a carcass ply.

[0005] The specific structure of the pneumatic tire of the present invention is as follows. (1) The (a) tread portion and (b) the reinforcing cord form an angle of substantially 90 degrees with respect to the tire circumferential direction, and both end portions are folded around a pair of bead cores from the inside to the outside of the tire. And (c) at least one carcass ply arranged between the carcass ply and the tread portion, wherein the reinforcing cords are arranged so as to form an angle of 20 to 30 degrees with respect to the tire circumferential direction and intersect with each other. In a pneumatic radial tire including a two-layer belt and (d) a sidewall reinforcing layer having a crescent-shaped cross section that is arranged inside the carcass ply and extends in the tread portion direction and the bead core direction, At least the rubber layer on the outer side in the tire radial direction
A reinforcing filler containing 0% by weight or more is compounded. (2) The reinforcing filler contains 90% by weight or more of silica. (3) The reinforcing cord of the belt is a polyamide fiber cord, specifically, Kevlar cord (Dupont: trade name)
It is characterized by being. (4) The reinforcing cord of the carcass ply is a steel cord having a filament diameter of 0.15 to 0.25 mm and a twist structure of 1 × n or 1 + n (n = 2 to 7, preferably 3 to 6), and after vulcanization. That is, the elongation under a 5 kgf load in the product is 2% or more. Preferably, the total elongation at break after vulcanization is at least 3.5%, more preferably at least 4.0%. (5) The reinforcing cord further includes a cap ply, which is an organic fiber cord substantially parallel to a tire circumferential direction, disposed outside the belt in a tire radial direction so as to cover the belt. In addition, in this specification, an organic fiber cord is used in a sense including a monofilament. (6) The organic fiber cord is polyethylene-2,6-
It consists of naphthalate fiber (hereinafter referred to as PEN fiber), has an elongation under a load of 1.4 gf / d at 50 ± 5 ° C. of 2.7% or less, and has an elongation of 0.7% at 170 ± 5 ° C.
The elongation under a load of 7 gf / d is 1.5 to 6.0%.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. An example of the pneumatic radial tire according to the present invention,
FIG. 1 is a partial sectional view. In the figure, 1 is a tread portion, 2 is a carcass ply, 3 is a belt, 4 is a sidewall portion,
5 is a sidewall reinforcing layer, 6 is a cap ply, 7
Is a bead core, 8 is a bead filler rubber, and 9 is an inner liner. In the present invention, at least the rubber layer on the outer side in the tire radial direction in the tread portion contains 50% by weight of silica.
It is characterized by blending the reinforcing filler contained above, but if it is less than 50% by weight, the effect of reducing rolling resistance is small. From the same viewpoint, preferably 90% by weight
That is all.

[0007] The reinforcing cord of the belt is characterized by a polyamide fiber cord, which is lighter in weight than a steel cord, so that the rolling resistance can be reduced. is there. Furthermore, when the belt is a separation belt having both width ends separated, the cord at the end of the belt easily moves following the road surface shape during run-flat running, so that the belt durability is improved, which is preferable.

Further, the present invention provides a reinforcing cord for a carcass ply, wherein the reinforcing cord is a steel cord having a filament diameter of 0.15 to 0.25 mm and a twist structure of 1 × n or 1 + n (n = 2 to 7). That is, 5k
It is characterized by an elongation under gf load of 2% or more, such as tire workability, carcass cord durability during running in a punctured state, riding comfort and steering stability during normal running, and the like. If the reinforcing cord is a steel cord, the rigidity of the carcass increases, so that when the tire internal pressure becomes zero, such as during a puncture, the bending and heat generation are reduced as compared with the conventional organic fiber reinforced cord. Further, the melting point of the steel cord is as high as 1500 ° C. or more, which is advantageous for melting the carcass cord due to heat, lowering the strength, lowering the adhesiveness of the cord, and improving the durability. In addition, from the same viewpoint, the total elongation at break after vulcanization is preferably 3.5% or more, more preferably 4.0% or more. In order to increase the total elongation at the time of cutting, the molding amount is increased with respect to the twist pitch length of the filament, or the filament is formed at a relatively low temperature of, for example, 380 to 430 ° C., or in the state of a twisted cord. Processing can be performed.

The present invention is further characterized by further comprising a cap ply covering the entire width of the belt, in order to improve high-speed durability. Further, the organic fiber cord is made of PEN fiber, and the elongation under a load of 1.4 gf / d at 50 ± 5 ° C. is 2.7% or less, and the elongation under a load of 0.7 gf / d at 170 ± 5 ° C. Is 1.5 to 6.0%. This is because a high-hardness reinforcing layer is disposed inside the sidewall portion, so that the rigidity of the tire as a whole does not include the reinforcing layer. In comparison with the above, it is not preferable from the viewpoint of road noise when the vehicle jumps over a protrusion or the like in normal driving, so that the use of the cord having the above-described physical properties with a relatively large elastic modulus improves road noise. is there.

When the reinforcing cord of the carcass ply is a steel cord, it preferably has the following characteristics. That is, in the image obtained as a plane by X-ray transmission (see FIGS. 2 and 3), the rubber-steel cord composite has a arbitrarily selected code axis direction (in both directions of arrows in FIGS. 2 and 3) for 15 mm ( The ratio of the filament area (F: equivalent to the total area of the black portions in FIG. 3) to the cord area (C: equivalent to the area of the hatched portion in FIG. 2) of the code area (indicated by L in FIGS. 2 and 3) (R: R = F / C = 0.45 to 0.90. The area occupancy R of the filament can be measured in the state of a tire as a product, or can be measured in a state where the filament is taken out of the tire. Further, the cord of the composite is preferably an open cord (filaments are not in contact with each other). By having the area occupancy R of the specific filament and making it an open cord, the contact area between each filament and rubber can be specified, and by increasing this contact area, the penetration of moisture into the steel cord In addition, friction (fretting) between filaments can be suppressed. Thereby, the corrosiveness due to these can be greatly improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below. In each case, the production was performed by producing a pneumatic tire having a tire size of P225 / 50R17. The composition of the tread rubber is as described in Table 1, and each structure is as follows. In addition, tire performance was measured by the following measurement method, and the results are also shown in Table 1. (I) In the case of a belt steel cord The belt has two layers as shown in FIG. 1, and the reinforcing cords are arranged so as to cross each other at an angle of 26 degrees with respect to the tire circumferential direction. Filament diameter: 0.225 mm Structure: 1 × 5 Elongation of cord after vulcanization under 5 kgf load: 0.18% Kevlar cord In the case of Kevlar cord, the belt is similarly separated into two layers, and the reinforcing cord is in the tire circumferential direction. They are arranged crossing each other at an angle of 24 degrees. Structure: 1500d / 3 (II) In the case of a carcass ply steel cord, the reinforcing cord forms an angle of 90 degrees with respect to the tire circumferential direction, and has a single layer, and the end folded around the bead core is extended to the lower side of the belt. Filament diameter: 0.15 mm Structure: 1 × 5 Elongation of cord after vulcanization under 5 kgf load: In the case of 3% rayon cord, the reinforcing cord forms an angle of 90 ° with respect to the tire circumferential direction, and two layers of bead core are used. The tire was turned around from inside to outside of the tire (turn-up ply), and one layer was covered with the turn-up ply from the outside. Both ends were located near the bead core without being turned back (down ply). Structure: 1650d / 3 (III) Sidewall Reinforcement Layer Both the conventional example and the embodiment were the same. Maximum thickness: 11 mm Shore A hardness: 84 degrees (IV) Cap ply In both the conventional example and the embodiment, ten cords are arranged at approximately equal intervals per 10 mm, and these are covered with rubber to form a ribbon-shaped piece (about 10 mm width). The belt is substantially adhered to the belt from the tire radial outer side so that the cord is substantially parallel to the tire circumferential direction, and two layers (one layer in FIG. 1) substantially cover the entire belt width. (Only shown). In the case of nylon cord, 6,6-nylon cord, 1260 d / 2 was used. In the case of the PEN cord, 100% polyethylene-2,6-naphthalate fiber cord, 1500 d / 3 was used. This cord has an elongation under a load of 1.4 gf / d at 50 ± 5 ° C. of 1.5%, and 0.7 g at 170 ± 5 ° C.
The elongation under f / d load is 2.7%.

The measuring method is as follows. (1) Run-flat running performance A load corresponding to the maximum mass in accordance with the 1998 TRA was applied to each tire (internal pressure 0) until the tire was broken at a speed of 89 km / h with an indoor drum (diameter 1.7 m). The distance was measured. (2) Rolling resistance According to the 1998 TRA, a load of 590 kgf corresponding to 200 kPa is applied to the tire, the internal pressure is 200 kPa, the indoor drum (diameter 1.7 m) is used, and the speed is 80 kPa.
It was practiced at m / h, and the rolling resistance of the tire at that time was measured. (3) Road noise On a test course that includes a road surface pattern that is likely to generate road noise, a measuring instrument is attached to the inner ear of a paneler, and a vehicle equipped with the tires of each example is driven in a certain mode.
The sound pressure at that time was measured.

[0013]

[Table 1]

From the results shown in Table 1, by changing the reinforcing filler of the tread rubber from the carbon black alone to the combined use with the silica, the rolling resistance can be greatly reduced, and the reinforcing cord of the belt is made of steel cord. By changing to Kevlar cord, the tire weight could be reduced and rolling resistance could be further reduced. Further, by changing the reinforcing cord of the carcass ply from a rayon cord to a specific steel cord, run-flat running performance was significantly improved. Further, by changing the reinforcing cord of the cap ply from the 6,6-nylon cord to the PEN fiber cord, the road noise could be greatly reduced.

[0015]

As described above, according to the present invention,
Improve run flatness, ensure more safety,
By improving the rolling resistance, fuel economy can be achieved, road noise can be reduced, and riding comfort can be improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a pneumatic radial tire according to the present invention.

FIG. 2 shows a steel cord X for reinforcing a carcass ply.
It is the figure image | photographed by line transmission, and shows code area (C).

FIG. 3 shows a steel cord X for reinforcing a carcass ply.
It is the figure image | photographed by line transmission, and shows a filament area (F).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 2 Carcass ply 3 Belt 4 Side wall part 5 Side wall part reinforcement layer 6 Cap ply 7 Bead core 8 Bead filler rubber 9 Inner liner

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 11/00 B60C 11/00 B 13/00 13/00 G

Claims (6)

[Claims] (A) a tread portion and (b) a reinforcing cord form an angle of substantially 90 degrees with respect to a tire circumferential direction;
At least one layer of carcass ply whose both ends are folded back from the inside to the outside of the tire around the pair of bead cores, and (c) are disposed between the carcass ply and the tread portion, and the reinforcing cord is arranged in the tire circumferential direction. 20-3
At least two layers of belts arranged at an angle of 0 degree and crossing each other, and (d) a side wall portion having a crescent-shaped cross-section disposed inside the carcass ply and extending in the tread portion direction and the bead core direction. A reinforcing layer,
A pneumatic radial tire comprising: a reinforcing filler containing 50% by weight or more of silica in at least a rubber layer on a radially outer side of the tread portion in the tread portion. 2. The pneumatic radial tire according to claim 1, wherein the reinforcing filler contains 90% by weight or more of silica. 3. The pneumatic radial tire according to claim 1, wherein the reinforcing cord of the belt is a polyamide fiber cord. 4. A reinforcing cord for a carcass ply is a steel cord having a filament diameter of 0.15 to 0.25 mm and a twist structure of 1 × n or 1 + n (n = 2 to 7) under a 5 kgf load after vulcanization. 4. The pneumatic radial tire according to claim 1, wherein the elongation is 2% or more. 5. The tire according to claim 1, further comprising a cap ply disposed over the belt in the tire radial direction and covering the belt, wherein the reinforcing cord is an organic fiber cord substantially parallel to the tire circumferential direction. Item 1, 2, 3 or 4
The described pneumatic radial tire. 6. The organic fiber cord is polyethylene-2,6.
-Consisting of naphthalate fibers, 1.50 at 50 ± 5 ° C.
Elongation under a load of 4 gf / d is 2.7% or less, and
The pneumatic radial tire according to claim 5, wherein the elongation under a load of 0.7 gf / d at 170 ± 5 ° C is 1.5 to 6.0%.