JPH0742667B2 - Radial tires for passenger cars - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for passenger cars having improved rolling resistance and riding comfort without impairing other performances, and more specifically, a plurality of untwisted cross-sections for reinforcing belt layers. Relates to a radial tire for passenger cars, which not only improves performance but also improves productivity by using a circular metal wire.

[0002]

2. Description of the Related Art In recent years, as the performance of passenger cars has improved, tires have shifted from a bias structure to a radial structure, and the cords used in the belt layers of radial tires are made of organic fibers because of their wear resistance and puncture resistance. It is shifting from cord to steel cord. The characteristics required for tires are
In order to improve the fuel economy of passenger cars, rolling resistance must be small, and riding comfort and cost must be low. In order to reduce rolling resistance, the tread portion has a two-layer structure and rubber having a small heat generation is used for the inner layer. In addition, in order to improve the riding comfort, it has been attempted to reduce the elastic modulus of the inner rubber layer of the two-layer tread.

As a reinforcing steel cord, for example, a plurality of strands are not twisted but the strands are arranged in parallel on the same plane, and the strands are bundled by wrapping so that the relative positions of all strands are not changed. Japanese Patent Application Laid-Open No. 62-149929 discloses a method in which the bending rigidity of the above has a directional property.

[0004]

As described above, there is a limit to improvement from the tread portion of the tire. For example, if the elastic modulus of the inner rubber layer of the multi-layer tread is too small, cracks are likely to occur at the bottom of the pattern groove. It causes a problem in durability. Further, if the heat generation property of the tread rubber is made too small in order to reduce the rolling resistance, the frictional force with the road surface will be reduced and the grip performance will be reduced.

In order to reduce rolling resistance in the belt layer, it has already been proposed to use a steel single wire for the belt cord (Japanese Utility Model Application No. 61-113799). However, with such a tire, even if there is no problem when traveling straight ahead, the belt buckles when it receives repeated sharp turns or when it travels a long distance on a zigzag road. It turned out to occur. When a large number of belt cord breaks occur, a partial recess is formed on the tread surface, causing abnormal wear and a decrease in the durability life.
In addition, the strength of the belt portion is reduced, and thus the safety is reduced. In some cases, the broken steel cord penetrates the inner liner layer, causing a decrease in internal pressure, resulting in catastrophic failure due to low internal pressure running.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a radial tire for a passenger car, which is improved in rolling resistance and riding comfort.

[0007]

As a result of various studies for solving the above-mentioned problems, the present inventor has found that it is effective to use a plurality of steel wires having a circular cross section without twisting as a belt reinforcing material. And has arrived at the present invention.

That is, according to the present invention, preferably two or more and five or less metal wires having a circular cross-section, each having a wire diameter of 0.05 mm to 0.35 mm, are aligned without being substantially twisted into one unit. A radial tire for passenger cars having a belt ply in which a number of these units are arranged in parallel and embedded in rubber, wherein the metal wire units are flat in the thickness direction of the belt layer in the radial cross section of the tire. , The degree of flatness (converging diameter (Dt) in belt layer thickness direction of belt layer cross section / converging diameter (Dl) in belt layer width direction) is 1 / n
Provided is a radial tire for a passenger vehicle, characterized by having a ratio of 2/3 or less to 60% or more.

Here, for a metal wire having a circular cross section, generally a steel wire, two or more and five or less wires are aligned to form one unit. 6
If the number is more than this, the metal filaments will be significantly overlapped with each other, the rubber will not permeate between the filaments, and will easily become a fracture nucleus of the rubber, and the belt layer separation (peeling) will be easily caused, which is not preferable. Further, the metal wires are not substantially twisted, but twists having a twist pitch of 30 mm or more may be included. The metal wire unit is flattened in the thickness direction of the belt layer in the radial cross section of the tire, and the flatness degree is the convergence diameter (Dt) in the thickness direction of the belt layer cross section / the convergence diameter in the width direction of the belt layer cross section ( 1 / n expressed as the ratio of Dl)
More than 2/3 or less, 60% or more, preferably 7
It occupies 0 to 90%. Here, n means the number of metal wires in aligned metal units.

FIGS. 1 (a) to 1 (h) are sectional views showing an example of a metal wire focusing unit in a tire belt ply when four metal wires are aligned and a belt ply is manufactured.
(A)-(k) is sectional drawing which shows the example of five bundle focusing. FIG. 3 is a partially enlarged view of the radial cross section of the belt ply, and defines the focusing diameter Dt in the thickness direction of the belt layer cross section and the focusing diameter Dl in the width direction of the belt layer cross section for each metal wire. d
Is the diameter of the metal wire forming the metal wire unit. FIG. 4 shows a cross section of a conventional metal wire unit.

[0011]

In the present invention, since the metal wire having the circular cross section is used, the bending deformation of the wire becomes uniform, and the cord bendability is improved without causing the local deformation as seen in the metal wire having the flat cross section. . Further, in the case of a single wire, since the wire diameter is made thick in order to maintain the strength of the belt, the constant wire strain increases the surface diameter of the single wire and reduces the fatigue property, but in the present invention, since a plurality of metal wires are used, the strength is also improved. Fatigue does not cause any problems.

If the wire diameter is less than 0.005 mm, the wire drawing workability is extremely deteriorated and the productivity is reduced, and if it exceeds 0.35 mm, the fatigue resistance is deteriorated due to the surface strain of the metal wire.
The strength improvement due to the degree of wire drawing becomes small, and therefore, in order to maintain the belt strength at a predetermined level, the amount of metal wire used increases and rolling resistance increases, so the wire diameter of the metal wire is 0.0
It is preferably in the range of 5 to 0.35 mm.

The reason why a plurality of metal wires are not twisted in the present invention is as follows. As shown in FIG. 2, since the aggregate shape of the metal wire units is flattened in the rubber thickness direction by being crushed by rubber during calendaring and the belt ply gauge becomes thin, the out-of-plane bending rigidity of the belt layer becomes small. As a result, rolling resistance and riding comfort are improved. However, as shown in FIG.
As shown in (c), when the metal wires are arranged in a line in the belt width direction, that is, when Dl / Dt = 1 / n, the out-of-plane rigidity of the belt is extremely reduced and the rolling resistance at high speed is increased. It also becomes large and the adhesiveness with rubber is reduced, and the durability is reduced.

Therefore, in order to avoid a state where the metal wires are arranged in a line in the width direction of the belt ply, the metal wire tension at the time of calendering when manufacturing the belt ply is increased to reduce the crushing, or the metal wires are removed. It is achieved by aligning and then winding a material having a stretchable surface, for example, an organic fiber monofilament, or by applying a sweet twist of 5 to 20 turns / m to a plurality of metal wires. But Dt / Dl
When the ratio exceeds 2/3, the same value may be obtained even in the conventional twisted steel cord, and the effect of improving the rolling resistance of the tire is small. That is, the focusing unit of (the focusing diameter in the belt ply thickness direction / the focusing diameter in the belt width direction of the focusing unit of the metal wire of the belt layer) exceeding 1 / n and not more than 2/3 becomes the focusing unit of the belt layer. By occupying 60% or more, the reduction of rolling resistance becomes remarkable.

[0015]

EXAMPLES The present invention will now be described in more detail with reference to examples. Preparation of Belt Layer Five wires having a wire diameter of 0.23 mm were aligned and set as one unit, and rubber was coated with a calender roll through a guide such that the number of shots was 38 units / 5 cm. At this time, the calender was calendered by applying a tension of 1 kg per wire so that the five wires were not crushed by the rubber when passing through the calender roll and were not lined up in a row in the width direction. The rubber-coated steel wire fabric was cut at an angle of 70 ° with respect to the axial direction of the wire arrangement to form a belt ply.

Preparation of tire The tire was molded and vulcanized by a conventional method with a PSR 165 SR 13 size 1-ply carcass 2-belt ply structure.

Test method (1) Rolling resistance: Measured in accordance with SAE J 1269. From the rolling resistance value thus obtained, the rolling resistance index was calculated according to the following formula. Rolling resistance index = rolling resistance × 100 rolling resistance / Target tire of Conventional tire

(2) Riding comfort 2 cm wide and 1 c high at one place on an iron drum with an outer diameter of 2 m
Mount the protrusion of m and press the tire on the drum with a regular load to rotate the drum. The vertical vibration when the tire passed over the protrusion was measured by the accelerometer as the force of the tire mounting shaft. From the waveform recorded at this time, the amplitude of the first cycle was used as the hit index, and the ride comfort index was calculated using the following formula. I asked. Riding Comfort Index = indicates that good larger the riding comfort of per index × 100 index per index / Target tire of Conventional tire.

(3) Cord Fracture Property of Belt Layer After the tire was filled with the normal internal pressure, it was evaluated in an actual vehicle. The running condition was that the tire was dissected after running 20,000 km on a constant winding road at a speed of 60 km, the belt cord was sampled from the belt layer, and the number of swings was evaluated. Resistant belt cord breakage resistance index = fold larger the cords of the belt cord breakage number × 100 Index of belt cord breakage number / Target tire of Conventional tire is excellent in less durability.

(4) Appearance rate of flatness degree in the belt layer% Flatness degree appearance rate = 1 / n <Dt / Dl ≦ 2/3 Belt layers in a focusing unit satisfying the condition: Number per 50 mm / total number per 50 mm of belt layer Number of bundle units × 100 (5) Belt layer separation property The same evaluation method as the above-mentioned (3) belt layer cord foldability is used.
Therefore, it was expressed as an index as in the following formula. Belt separation index = belt separation of the tire of the present invention
Length / Belt separation length of target tire
X 100

[0021]

[Table 1]

In addition to the above-described tire performance, cornering power self-lining torque and high-speed durability by a drum were also evaluated as indoor steering stability, but no difference from conventional tires was observed. Next, we have 6 wires
(Comparison tire 2) and layer twist structure (Comparison
Table 2 shows comparison data with the tire 3). Starting from this
Light tires have excellent riding comfort and belt separation.
I know that

[Table 2]

[0023]

INDUSTRIAL APPLICABILITY In the radial tire for a passenger car according to the present invention, since rolling resistance can be reduced, fuel consumption can be improved and riding comfort can be improved.

[Brief description of drawings]

1 (a) to 1 (h) are cross-sectional views each showing an example of a focusing unit composed of four metal wires in a belt ply of a tire.

2 (a) to 2 (k) are cross-sectional views each showing an example of focusing five pieces.

FIG. 3 is a partially enlarged view of a radial cross section of a belt ply of a tire.

4 (a) to 4 (d) are cross-sectional views of a conventional metal wire focusing unit, respectively.

Claims (1)

[Claims] 1. Two or more and five metal wires having a circular cross section
A radial tire for passenger cars having a belt ply in which a large number of these units are arranged in parallel and buried in rubber without being substantially twisted together, and the metal wire unit is a tire. Is flat in the thickness direction of the belt layer in the radial cross section, and the degree of flatness (converging diameter in the thickness direction of the belt layer cross section / focusing diameter in the width direction) is 1 /
Radial tires for passenger cars characterized by occupying 60% or more of 2/3 or less exceeding n (n is the number of aligned metal wires).