JPH1178410A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a passenger car low in rolling resistance without lowering belt end separation resistance performance. SOLUTION: Belts 3 are arranged in parallel with each other in a inner-layer at an angle of about 10 to 30 degrees against the peripheral direction of a tire in a cord direction, they are formed of at least two layers made by burying a large number of metal cords 4 in rubber which are laminated so as to be in the opposite directions with each other with a tire equator line in the inter- layers, the metal cord is formed of a bundle paralleling two to six pieces of metal monofilaments 5 circular or roughly circular in cross-section and 0.20 to 0.35 mm in diameter by arranging them in the tire axial direction, and a cord interval of the metal cord layers arranged on the outside in the radial direction out of the two layers of the metal cord layers forming the belt is larger than a cord interval of the metal cord layers arranged on the inside in the radial direction on the pneumatic radial tire.

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 right and left bead portions, and extending from a crown portion to both bead portions via both side portions to form a bead. The present invention relates to a pneumatic radial tire for a passenger car, comprising a radial carcass wound around a core and moored to a bead portion, and a belt disposed radially outward of a crown portion of the radial carcass.

[0002]

2. Description of the Related Art A belt of a typical conventional pneumatic radial tire for a passenger car has a cord direction arranged at an angle of about 10 to 30 degrees with respect to a circumferential direction of the tire, and is arranged parallel to each other in a layer. In this example, at least two layers are formed by embedding a large number of metal cords in rubber so as to be opposite to each other with the tire equator interposed therebetween, and the metal cords are formed by twisting three to five metal filaments. 1 × 3, 1 × 4 or 1 × 5 stranded wire cord formed by
Alternatively, a stranded wire cord having a 2 + 7 structure formed by twisting two layers of metal filaments or the like has a diameter of 0.2 to 0.1 mm.
It was a twisted structure of a thin metal filament of about 3 mm.

[0003]

In recent years, due to social demands for resource saving and energy saving, the development of fuel-efficient tires, that is, tires with low rolling resistance, has also been required for pneumatic radial tires for passenger cars. In order to meet such a demand, conventionally, as disclosed in, for example, JP-A-63-19404, a metal cord for forming a tire belt has a diameter of 0.1 mm instead of the above-described stranded wire cord. It has been proposed to use a single wire metal cord with a circular cross section of 35 to 0.70 mm. However, when a belt is formed of a layer in which a large number of single-wire metal cords having a circular cross section having a diameter of 0.35 to 0.70 mm as described above are embedded in rubber, the rolling resistance of the tire certainly decreases,
Under operating conditions where the vehicle repeatedly turns sharply, such as running on a so-called zigzag path over a long distance, the single-wire metal cord forming the tire belt is broken, causing uneven wear of the tread and tire life. Is reduced. Therefore, if the diameter of the single-wire metal cord is simply reduced in order to alleviate the distortion that causes the breakage of the single-wire metal cord, the rigidity of the belt is insufficient and the steering stability is reduced. It is necessary to increase the number of cords to be driven, but as a result, there arises a problem that the performance against the separation generated from the crack of the belt end, that is, the belt end separation resistance decreases.

It is an object of the present invention to provide a pneumatic radial tire for a passenger car having a low rolling resistance without resolving the above-mentioned disadvantages of the prior art and without deteriorating the belt end separation resistance. .

[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 right and left bead portions, and a bead portion provided on both sides from a crown portion via both side portions. A radial carcass wound around the bead core and moored to the bead portion, and a belt disposed radially outside the crown portion of the radial carcass,
(1) The belts are laminated such that the cord direction is arranged at an angle of about 10 to 30 degrees with respect to the circumferential direction of the tire, in parallel in the layers, and in opposite directions with the tire equator interposed between the layers. (2) The metal cord has a circular or substantially circular cross section and a diameter of 0.20.
(3) formed of a bundle of 2 to 6 metal monofilaments of 0.3 to 0.35 mm arranged and aligned in the tire axial direction;
A passenger car characterized in that, of the two metal cord layers forming the belt, the cord interval between the metal cord layers arranged radially outside is larger than the cord interval between the metal cord layers arranged radially inside. It is a pneumatic radial tire.

The pneumatic tire of the present invention has the above-mentioned structure. In particular, the belt is formed of at least two layers of a plurality of metal cords buried in rubber. It is formed of a bundle in which two to six metal monofilaments of 20 to 0.35 mm are arranged and aligned in the tire axial direction without twisting, and the cord interval of the metal cord layer arranged radially outside is arranged radially inside. Since the distance between the cords of the metal cord layer is larger than that of the metal cord layer, it is possible to obtain a pneumatic radial tire for a passenger car having a low rolling resistance, in which the occurrence of a break in the cord of the belt is prevented or suppressed without deteriorating the belt end separation resistance. That is, as described above, under the use conditions in which the vehicle repeatedly turns sharply, such as running on a so-called zigzag path over a long distance, a large deformation occurs in the tire belt, and the single-wire metal cord forming the tire belt The pneumatic tire of the present invention has a diameter of 0.20 to 0.3 as described above.
Since a metal monofilament of 5 mm, preferably 0.20 to 0.33 mm is used, the strain applied to the metal cord forming the belt is alleviated, and it is possible to prevent a reduction in belt cord breaking performance. However, if the diameter of the metal monofilament is reduced as described above in order to reduce the distortion that causes the breakage of the metal cord, the rigidity of the belt is insufficient, so the number of single-wire metal cords to be driven must be increased by the reduced diameter. As a result, the spacing between the metal cords is reduced, and the belt end separation resistance is reduced. In order to solve such inconvenience, in the pneumatic tire of the present invention, as described above, the cord spacing of the metal cord layer arranged radially outside the cord spacing of the metal cord layer arranged radially inside. It is set to be larger. That is, in the belt end separation, first, a crack is generated at the end of the outer metal cord layer, and the crack propagates along the outer metal cord layer between the outer metal cord layer and the inner metal cord layer. In the pneumatic tire, as described above, the crack growth is suppressed by increasing the cord interval of the outer metal cord layer, while the cord ejection density of the inner metal cord layer is larger than the cord ejection density of the outer metal cord layer. By doing so, the shortage of the belt rigidity is resolved. In the pneumatic tire of the present invention, the cord interval of the outer metal cord layer is preferably 1.05 to 3 times the cord interval of the inner metal cord layer. As described above, the pneumatic tire of the present invention employs a metal monofilament having a diameter of 0.20 to 0.35 mm. However, if this value is smaller than 0.20 mm, it is necessary to compensate for the increase in the number of metal cords. This is because the belt stiffness is insufficient to the extent that it cannot be performed, and the steering stability performance of the tire is extremely reduced. On the other hand, if this value exceeds 0.35 mm, the riding comfort performance of the tire is reduced. Further, in the pneumatic tire of the present invention, as described above, the metal cord is formed of a bundle in which two to six metal monofilaments having a diameter of 0.20 to 0.35 mm are arranged and aligned in the tire axial direction without twisting. However, by not twisting the filaments, the rolling resistance of the tire is reduced. If the metal cord is formed of a single monofilament, the belt end separation resistance is reduced. This is because the workability is significantly reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tires of Examples 1 and 2, the conventional tires and the tires of Comparative Examples 1 to 10 according to the present invention will be described below with reference to the drawings. All tire sizes are PSR165SR13.

FIG. 1 is a sectional view of the left half of the tire according to the first embodiment of the present invention. As shown in FIG. 1, the tire according to the first embodiment has a bead core 1 provided on a pair of right and left bead portions. A radial carcass 2 which extends from the crown portion to both bead portions via both side portions, is wound around the bead core 1 and is moored to the bead portion, and is disposed radially outward of the crown portion of the radial carcass 2. A pneumatic radial tire for a passenger car provided with a belt 3. The belts 3 are arranged such that the cord direction is at an angle of 20 degrees with respect to the circumferential direction of the tire, are arranged parallel to each other in the layers, and are stacked in such a manner that the directions are opposite to each other across the tire equator.
The layers are formed of layers 31 and 32 in which a number of metal cords 4 are embedded in rubber in parallel with each other. As shown in FIG. 2, three metal monofilaments 5 having a circular cross section and diameters d1 and d2 of 0.32 mm and 0.28 mm were arranged in the axial direction of the tire without twisting. It is formed of a bundle. Of the two metal cord layers 31 and 32 forming the belt 3, the cord interval D1 of the metal cord layer 31 arranged on the radially outer side is 1.03 mm, and the metal cord layer 32 arranged on the radially inner side is 1.03 mm. When the code interval D2 is 0.72 mm,
The former is 0.31 mm larger than the latter. Expressing this as the number of shots (number of wires / 50 mm), the number of code shots N1 = 50 / (3d1 + D1) of the metal code layer 31 arranged on the outside in the radial direction is 25.1 wires / 50m.
m, and the number of cords N2 = 50 / (3d2 + D2) of the metal cord layers 32 arranged on the inner side in the radial direction.
Is 32.0 lines / 50 mm.

In the tire according to the second embodiment, the metal cord layer 31 disposed radially outward has a metal cord having a diameter d1.
Is formed of five metal monofilaments of 0.28 mm, the cord interval D1 is 1.20 mm, the number of cords N1 is 19.2 / 50 mm, and the metal cord layer 32 arranged on the inner side in the radial direction is a metal cord. Is the diameter d2
Is formed of three metal monofilaments of 0.28 mm, the cord interval D2 is 0.72 mm, and the number of cords N2 is 32.0 cords / 50 mm. Is almost the same as

In the conventional pneumatic tire, the metal cord layer 31 arranged on the outside in the radial direction and the metal cord layer 32 arranged on the inside in the radial direction have three metal monofilaments having a diameter d1 of 0.28 mm. The air of Example 1 was formed except that the cord spacing D was 0.86 mm and the number of cords N was 32.0 / 50 mm. It is almost the same as a tire with a tire.

In the pneumatic tire of Comparative Example 1, the metal cord layer 31 disposed radially outward has a metal cord formed of three metal monofilaments having a diameter d1 of 0.16 mm and a cord interval D1 of 0.08 mm. The number N1 of cords is 88.9 / 50 mm, and the metal cord layer 32 disposed radially inward is formed of three metal monofilaments having a diameter d2 of 0.18 mm and a cord interval D2. It is almost the same as the pneumatic tire of Example 1 except that the number of cords N2 is 70.1 / 50 mm.

In the pneumatic tire of Comparative Example 2, the metal cord layer 31 arranged radially outward has a metal cord formed of three metal monofilaments having a diameter d1 of 0.45 mm and a cord interval D1 of 2.05 mm. The number N1 of cords is 14.7 cords / 50 mm, and the metal cord layer 32 disposed radially inward is formed of three metal monofilaments having a diameter d2 of 0.40 mm and a cord interval D2. It is almost the same as the pneumatic tire of Example 1 except that the number of cords N1 is 1.56 mm and the number of cords N2 is 18.1 / 50 mm.

In the pneumatic tire of Comparative Example 3, the metal cord layer 31 disposed radially outward has a metal cord formed of one metal monofilament having a diameter d1 of 0.28 mm and a cord interval D1 of 0.24 mm. The number N1 of cords to be implanted is 96.0 cords / 50 mm, and the metal cord layer 32 disposed radially inward is formed of one metal monofilament having a diameter d2 of 0.32 mm and a cord interval D2. It is almost the same as the pneumatic tire of the first embodiment except that the number of cords N2 is 75.4 / 50 mm.

In the pneumatic tire of Comparative Example 4, the metal cord layer 31 disposed radially outward has seven metal monofilaments having a diameter d1 of 0.32 mm and a cord interval D1 of 2.39 mm. The number N1 of cords to be implanted is 10.8 / 50 mm, and the metal cord layer 32 disposed radially inward is formed of seven metal monofilaments having a diameter d2 of 0.28 mm and a cord interval D2. It is almost the same as the pneumatic tire of the above-mentioned Example 1 except that the number of cords N1 is 1.3.7 mm and the number of cords N2 is 13.7 / 50 mm.

In the pneumatic tire of Comparative Example 5, the metal cord layer 31 disposed radially outward has a metal cord formed of three metal monofilaments having a diameter d1 of 0.28 mm and a cord interval D1 of 0.72 mm. The number N1 of cords to be implanted is 32.0 / 50 mm, and the metal cord layer 32 arranged radially inward is formed of three metal monofilaments having a diameter d2 of 0.28 mm and a cord interval D2. It is almost the same as the pneumatic tire of Example 1 except that the number of cords N2 is 25.1 / 50 mm.

In the pneumatic tire of Comparative Example 6, the metal cord layer 31 disposed radially outside has three metal monofilaments having a diameter d1 of 0.16 mm and a cord interval D1 of 0.08 mm. The number N1 of cords to be implanted is 88.9 / 50 mm, and the metal cord layer 32 disposed radially inward is composed of five metal monofilaments having a diameter d2 of 0.18 mm and a cord interval D2. It is almost the same as the pneumatic tire of Example 1 except that it is 0.29 mm and the number of cords N2 is 42.1 / 50 mm.

In the pneumatic tire of Comparative Example 7, the metal cord layer 31 disposed radially outward has a metal cord formed of five metal monofilaments having a diameter d1 of 0.45 mm and a cord interval D1 of 3.43 mm. The number N1 of cords is 8.8 / 50 mm, and the metal cord layer 32 disposed radially inward is formed of three metal monofilaments having a diameter d2 of 0.40 mm and a cord interval D2. It is almost the same as the pneumatic tire of Example 1 except that the number of cords N1 is 1.56 mm and the number of cords N2 is 18.1 / 50 mm.

In the pneumatic tire of Comparative Example 8, the metal cord layer 31 disposed radially outward has a metal cord formed of one metal monofilament having a diameter d1 of 0.28 mm and a cord interval D1 of 0.24 mm. The number N1 of cords is 96.0 cords / 50 mm, and the metal cord layer 32 disposed radially inward is formed of three metal monofilaments having a diameter d2 of 0.28 mm and a cord interval D2. It is almost the same as the pneumatic tire of the first embodiment except that the number of cords N2 is 0.72 mm and the number of cords N2 is 32.0 / 50 mm.

In the pneumatic tire of Comparative Example 9, the metal cord layer 31 disposed radially outward has a metal cord formed of seven metal monofilaments having a diameter d1 of 0.28 mm and a cord interval D1 of 1.69 mm. The number N1 of cords to be implanted is 13.7 / 50 mm, and the metal cord layer 32 disposed radially inward is formed of five metal monofilaments having a diameter d2 of 0.28 mm and a cord interval D2. 1.20 mm, which is almost the same as the pneumatic tire of Example 1 except that the number of cords N2 is 19.2 / 50 mm.

In the pneumatic tire of Comparative Example 10, the metal cord layer 31 disposed radially outward has a metal cord formed of three metal monofilaments having a diameter d1 of 0.28 mm and a cord interval D1 of 0.72 mm. The number N1 of cords to be implanted is 32.0 / 50 mm, and the metal cord layer 32 disposed radially inward is formed of five metal monofilaments having a diameter d2 of 0.28 mm and a cord interval D2. 1.20 mm, which is almost the same as the pneumatic tire of Example 1 except that the number of cords N2 is 19.2 / 50 mm.

The rolling resistance of the pneumatic tires of Examples 1 and 2 according to the present invention, the pneumatic tire of the conventional example, and the pneumatic tires of Comparative Examples 1 to 10 were determined as follows:
Comparative tests on belt end separation performance, ride comfort performance of tires and calendering workability were conducted. The test results are shown in Tables 1, 2 and 3.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

The comparative test for the rolling resistance was conducted according to SAE J1.
The rolling resistance was measured in accordance with the test method of No. 269, and was indicated by an index with the rolling resistance of the pneumatic tire of the above-mentioned conventional example being 100.

Since the belt end separation resistance is largely governed by the length of the crack at the belt end, the crack length is used as a substitute measure for the belt end separation. The comparative test of the belt end separation resistance was carried out by mounting the tires of Examples 1 and 2 above, the conventional tires and the tires of Comparative Examples 1 to 10 on an actual vehicle, and after traveling 60,000 km on a general road at a filling internal pressure of 150 kPa, The tire was dissected to measure the length of a crack generated at the edge of the main belt 4, and the result was indicated by an index with the crack length of the above-described conventional pneumatic tire being 100. The smaller the number is, the smaller the crack length is, indicating that the belt end separation resistance is excellent.

The comparative test of the riding comfort performance of the tire is a test by an indoor drum test, and the above Examples 1 and 2
, A conventional tire, and the tires of Comparative Examples 1 to 10 were loaded with a predetermined load on a drum tester having a protrusion of 2 cm in width and 1 cm in height attached to one place on a drum having an outer diameter of 2 m. Rotate the drum and measure the vertical vibration when the tire passes over this protrusion as the force of the tire mounting shaft with an accelerometer, and measure the amplitude of the first week from the vertical vibration waveform, The index was represented by an index with the amplitude of the pneumatic tire of the conventional example being 100. The smaller the number is, the smaller the amplitude is, indicating that the ride comfort performance of the tire is excellent.

The calendering workability comparison test was conducted on the tires of Examples 1 and 2, the conventional tire and Comparative Example 1.
For the tires of Nos. 1 to 10, the ease of preparation of the cord and the ease of calendering before manufacturing the composite of cord and rubber were evaluated by the feeling of the worker, and the ease of calendering of the above-described conventional pneumatic tire was evaluated. Displayed in comparison with.

[0029]

From the above evaluation results, the pneumatic tire of the embodiment based on the present invention has improved belt end separation performance, ride comfort of the tire and ease of calendering work as compared with the conventional pneumatic tire. It can be seen that the tire has excellent rolling resistance without lowering.

[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.

FIG. 2 is a schematic partial cross-sectional view of a metal cord layer.

[Explanation of symbols]

 1 Bead Core 2 Radial Carcass 3 Belt 4 Metal Cord 5 Metal Filament

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 9/22 B60C 9/22 G

Claims (1)

[Claims] 1. A bead core provided on a pair of left and right bead portions, and a radial core extending from the crown portion to both bead portions via both side portions, wound around the bead core and moored to the bead portion. In a pneumatic tire including a carcass and a belt disposed radially outward of a crown portion of the radial carcass, (1) the belt has a cord direction of about 10 to 30 degrees with respect to a circumferential direction of the tire. At least two layers are arranged parallel to each other within the layer at an angle, and are stacked so as to be opposite to each other across the tire equator between the layers. 2) The metal cord is formed of a bundle of 2 to 6 metal monofilaments having a circular or nearly circular cross section and a diameter of 0.20 to 0.35 mm arranged side by side in the tire axial direction. (3) forming the belt 2
A pneumatic radial tire for a passenger car, wherein, among the metal cord layers of the layers, a cord interval of a metal cord layer arranged radially outside is larger than a cord interval of a metal cord layer arranged radially inside.