JPH1111108A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of ply cord layers and lighten a tire by forming the tire with a carcass in which two or more layers of many metallic cords are buried, which are arranged radially in parallel with each other across the equator line, and a belt with a radial cord layer with specified circumferential angle up to both ends of a crown. SOLUTION: This tire is equipped with a pair of right and left bead cores 1, a carcass 2 which is engaged with a right and left bead sections with being wound around the bead cores 1, and a belt 3 arranged radially outside of the crown section. The tire is formed with a pair of right and left radial cord layers which extend from the both bead sections to the both ends of the crown via both side parts, and terminate without exceeding a middle part of the crown section. The belt 3 whose cord direction is inclined about 20 degree (about 10-30 degree) circumferentially of the tire, is formed by the layer which is formed by burying a lot of metallic two-layer cords, which are stacked so that they are parallel each other in the layer and are relatively in the opposite direction on the both sides of the tire equator line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a bead core provided on a pair of left and right bead portions, and a carcass wound around the bead core and moored at the bead portion. , A belt disposed radially outward of the crown portion of the carcass, and a pneumatic radial tire for a passenger car.

[0002]

2. Description of the Related Art A carcass ply of a typical conventional pneumatic radial tire for a passenger car is formed by embedding a large number of organic fiber cords, which are arranged in parallel and radially with each other, in rubber, and one bead. It was formed of a radial cord layer extending continuously from the portion to the other bead portion via the side portion and the crown portion. As the ply cord layer, an organic fiber cord such as polyester cord or rayon cord is generally used. In a large-sized pneumatic radial tire for a car, two or more ply cord layers are used. Had been used.

[0003]

In recent years, due to social demands for resource saving and energy saving, development of fuel-efficient tires, that is, tires with low rolling resistance, by reducing the weight of pneumatic radial tires for passenger cars has been required. In order to respond to such demands, high-strength, high-elasticity organic fiber cords such as aramid fiber cords are used for the ply cord layer of the radial carcass, so that even large-sized pneumatic radial tires for passenger cars can have one layer. It has been proposed to form a carcass with a ply cord layer. However, high-strength, high-elasticity organic fiber cords have poor durability against input of compression and bending, and when they are new, they have high strength, but as the tires are used, the cord strength decreases,
Since it is difficult to maintain the strength of the tire due to breakage of the cord, the use of high-strength, high-elasticity organic fiber cord such as aramid fiber cord reduces the number of ply cord layers. The above proposal to reduce the weight of the tire has not been put to practical use.

An object of the present invention is to provide a pneumatic radial tire for a passenger car having a low rolling resistance, which has solved the above-mentioned disadvantages of the prior art, has reduced the number of ply cord layers, and has reduced the weight of the tire. It is to be.

[0005]

In order to achieve the above object, a pneumatic tire according to the present invention comprises a bead core provided on a pair of left and right bead portions, and a right and left bead wound around the bead core. In a pneumatic tire including a carcass moored at a bead portion and a belt disposed radially outward of a crown portion of the carcass, (1) the carcass includes a plurality of carcasses arranged in parallel with each other and in a radial direction. It is made by embedding a metal cord in rubber, extending from the bead part on both sides to at least both ends of the crown via both side parts,
(2) The belt is arranged parallel to each other within the layer at an angle of about 10 to 30 degrees with respect to the circumferential direction of the tire. Pneumatic radial for passenger cars, characterized by being formed of at least two layers of metal cords buried in rubber at least two layers laminated in opposite directions with respect to the tire equator line between the layers. Tires.

In order to achieve the above object, in the pneumatic tire of the present invention, the carcass extends from left and right bead portions to both ends of the crown via both side portions and terminates without crossing the crown center portion. Is preferably formed of the radial code layer. In this case, it is further preferable that the interval between the one end portion and the other end portion of the crown portion of the pair of left and right radial cord layers forming the carcass is 70 to 90% of the cross-sectional width of the belt. .

In order to achieve the above object, in the pneumatic tire according to the present invention, the carcass extends from the left and right bead portions to at least both end portions of the crown via both side portions, and terminates adjacent to each other at the crown portion. It is preferably formed of a pair of radial code layers.

In order to achieve the above object, in the pneumatic tire of the present invention, the carcass extends from the right and left bead portions to at least both ends of the crown via both side portions, and overlaps and terminates at the crown portion. It is preferable to be formed of a pair of left and right radial cord layers.

In order to achieve the above object, in the pneumatic tire of the present invention, the carcass is preferably formed of a radial cord layer formed by embedding a metal cord having a single twist structure in rubber.

[0010] The pneumatic tire of the present invention has the above-described structure. In particular, a metal cord having higher strength is used in place of an organic fiber cord such as polyester or rayon which has been generally used in the past. Therefore, it is possible to reduce the number of ply cord layers and reduce the weight of the tire, thereby providing a pneumatic radial tire for passenger cars with low rolling resistance. The pneumatic tire of the present invention is configured as described above, and in particular, the carcass extends from the left and right bead portions to at least both ends of the crown via both side portions, and terminates at the crown portion. In other words, the radial cord layer forming the carcass is not continuously extended from one bead portion to the other bead portion as in the prior art, but is divided by the crown portion. Occurrence of buckling is suppressed or prevented. This means that the chance of inputting compression and bending applied to the cord decreases, and the strength of the cord that was high when new is reduced as the tire is used, and the cord breaks due to breakage etc. This eliminates the problem of forming a carcass with a high-strength cord layer, which makes it difficult to maintain the strength of the tire. At the same time, the steering stability at the time of cornering when turning sharply with a high slip angle is improved,
The occurrence of uneven wear such as wavy wear is prevented.

[0011] The pneumatic tire of the present invention, as described above,
Preferably, the carcass is formed of a pair of left and right radial cord layers extending from left and right bead portions to both end portions of the crown via both side portions and terminating without exceeding the central portion of the crown. It is further preferable that the interval between one end portion and the other end portion of the crown portion of the pair of left and right radial cord layers forming the above is 70 to 90% of the cross-sectional width of the belt. If this value is less than 70%, buckling of the carcass is likely to occur, and uneven wear such as wavy wear is likely to occur, and at the same time, there occurs a problem that steering stability at the time of running at the limit is reduced, while 90% Exceeding the threshold value may cause a radial cord to fall out to form a carcass, and the internal pressure at break of the tire may be extremely reduced.

[0012] In the pneumatic tire of the present invention, as described above, the carcass is preferably formed of a radial cord layer formed by embedding a metal cord having a single twist structure in rubber. This is because the metal cord having a single twist structure has a certain degree of elongation without a decrease in strength due to fretting.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, tires of Examples 1 to 3, a conventional tire and a comparative tire according to the present invention will be described with reference to the drawings. All tire sizes are PSR205 / 65R15.

FIG. 1 is a schematic cross-sectional view of a left half of a tire according to a first embodiment of the present invention. As shown, the tire according to the first embodiment includes a bead core 1 provided on a pair of right and left bead portions. A pneumatic radial tire for a passenger car, comprising a carcass 2 wound around a bead core 1 and moored to left and right bead portions, and a belt 3 disposed radially outward of a crown portion of the carcass 2. The carcass 2 is formed by embedding a large number of metal cords arranged in parallel and in the radial direction in rubber, extending from the right and left bead portions to both ends of the crown via both side portions, without passing over the center portion of the crown. It is formed of a pair of left and right radial cord layers that terminate. The distance W1 from one end to the other end of the crown of the carcass 2 is 1
25 mm, which is 80 mm of the sectional width W2 of the belt 3.
%. The code forming the carcass 2 is 1 × 5 ×
0.20 steel cord. The belt 3 is a two-layered belt in which the cord direction is arranged at an angle of 20 degrees with respect to the circumferential direction of the tire, and is arranged parallel to each other in the layers, and is interposed between the layers in opposite directions with respect to the tire equator. The cord is formed of a layer of a large number of metal cords embedded in rubber, and the cord is a 1 × 5 × 0.20 steel cord.

The pneumatic tire of the second embodiment has a carcass 2
Except that it is formed of a pair of left and right radial cord layers extending from the left and right bead portions to the crown portion via both side portions and terminating adjacently at the center portion of the crown so as to abut each other. It is almost the same as the pneumatic tire of Example 1.

The pneumatic tire of the third embodiment has a carcass 2
Except that it is formed of a pair of left and right radial cord layers extending from the left and right bead portions to the crown portion via both side portions and overlapping each other over a width of 50 mm at the center portion of the crown and terminating with each other. This is almost the same as the pneumatic tire of the first embodiment.

The conventional pneumatic tire has a carcass 2
Is formed by embedding a large number of 1500 d / 2 polyester fiber cords in rubber, which are arranged in parallel and in the radial direction, continuously from one bead portion to the other bead portion via a side portion and a crown portion. It is almost the same as the pneumatic tire of the above embodiment, except that it is formed of two extending radial cord layers.

The pneumatic tire of the comparative example has a carcass 2
Are arranged in parallel with each other and in the radial direction.
A 5 × 0.20 steel cord is embedded in a large number of rubbers, and is formed of one radial cord layer extending continuously from one bead portion to the other bead portion via a side portion and a crown portion. Except for this, it is almost the same as the pneumatic tire of the above embodiment.

The pneumatic tires of Examples 1 to 3 according to the present invention, the pneumatic tire of the conventional example, and the pneumatic tire of the comparative example all have a strength per unit width of the carcass 2 of 2275 kgf / 5 cm. The number of code hits has been adjusted to give the same value.

With respect to the pneumatic tires of Examples 1 to 3 according to the present invention, the pneumatic tire of the conventional example, and the pneumatic tire of the comparative example, the strength of the tire, the weight of the radial cord layer forming the carcass, and the rolling. A comparative test of resistance, buckling resistance and tire durability was performed.

In the tire strength comparison test, a test tire was assembled on a rim, a hose was connected to a valve from a hydraulic pump, and the water pressure was gradually increased to measure the pressure at which the tire was destroyed.
When the strength of the pneumatic tires of Examples 1 to 3 and the pneumatic tire of the comparative example are 100, the strength of the pneumatic tires of Examples 1 to 3 and the comparative example is 100. Met.

The comparative test for the rolling resistance was conducted according to SAE J1.
269 was measured according to the test method. When the rolling resistance of the pneumatic tire of the conventional example is represented by an index with the rolling resistance being 100, the rolling resistances of the pneumatic tires of Examples 1 to 3 are 120, 105, and 105, and the rolling resistance of the pneumatic tire of the comparative example is Was 110.
The larger the number, the smaller the rolling resistance of the tire.

The weight of the radial cord layer forming the carcass is 1891 kg for the conventional pneumatic tire.
Thus, the pneumatic tires of Examples 1 to 3 are 1175k
g, 1568 kg, and 1786 kg, and the air intake of the comparative example was 1568 kg.

The comparative test of the anti-buckling performance was performed by measuring the contact pressure distribution while rotating the test tire at a slip angle of 9 degrees, and measuring the area where buckling occurred in the contact surface. The ratio of occurrence of rings is 0% in the conventional pneumatic tires, and 0%, 0% and 5% in the pneumatic tires of Examples 1 to 3.
In the comparative example, the pneumatic tire was 20%.

The comparative test of the durability performance of the tire is carried out by measuring the strength of a radial cord forming a carcass after mounting a test tire on an actual vehicle and traveling 20,000 km on a general road, and measuring the strength of the cord when new. The ratio of the strength of the cord after traveling 20,000 km to the strength of the cord was compared with the cord strength retention rate expressed as a percentage. The cord pneumatic tire of the above-described conventional example has a cord strength retention of 95%, the pneumatic tires of Examples 1 to 3 each have 90%, and the pneumatic tire of the comparative example has a cord strength retention of 3%.
It was 0%.

The results of the above evaluation tests are shown in Table 1 together with the outlines of the test tires.

[0026]

[Table 1]

[0027]

From the above evaluation results, the pneumatic tire of the embodiment based on the present invention maintains the tire strength, buckling resistance and tire durability almost equal to those of the conventional pneumatic tire. However, it can be seen that the weight of the radial cord layer forming the carcass is reduced and the rolling resistance is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of the left half of a pneumatic tire according to the present invention.

[Explanation of symbols]

 1 Bead core 2 Radial carcass 3 Belt

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI B60C 9/20 B60C 9/20 E

Claims (6)

[Claims] 1. A bead core provided in a pair of left and right bead portions, a carcass wound around the bead core and moored in the left and right bead portions, and a carcass portion disposed radially outward of a crown portion of the carcass. (1) The carcass is formed by embedding a large number of metal cords arranged in parallel and in a radial direction in rubber in rubber and passing through both side portions from right and left bead portions. (2) a pair of right and left radial cord layers extending at least to both ends of the crown and terminating at the crown;
The belt has a cord direction of 10 to the circumferential direction of the tire.
A layer formed by embedding a large number of metal cords in rubber at least two layers, which are arranged parallel to each other in the layer at an angle of about 30 degrees and are opposite to each other across the tire equator line between the layers. A pneumatic radial tire for a passenger car, characterized by being formed of: 2. The carcass is formed of a pair of left and right radial cord layers extending from left and right bead portions to both ends of the crown via both side portions and terminating without exceeding the center portion of the crown. The pneumatic radial tire for a passenger car according to claim 1. 3. A distance between one end and the other end of the crown portion of the pair of right and left radial cord layers forming the carcass is 70 to 90% of a cross-sectional width of the belt. The pneumatic radial tire for a passenger car according to claim 2, characterized in that: 4. A pair of left and right radial fins extending from the left and right bead portions via both side portions to at least both ends of the crown, and terminating adjacent to each other at the crown portion.
The pneumatic radial tire for a passenger car according to claim 1, wherein the tire is formed of a cord layer. 5. The carcass is formed of a pair of left and right radial cord layers extending from left and right bead portions through at least both side portions to at least both end portions of the crown, and overlapping and terminating at the crown portion. The pneumatic radial tire for a passenger car according to claim 1, wherein: 6. The pneumatic radial tire for a passenger car according to claim 1, wherein the carcass is formed of a radial cord layer formed by embedding a metal cord having a single twist structure in rubber. .