JP2574971B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which the vibration of a tire portion due to running is suppressed and the running noise is reduced by regulating the cross-sectional shape of the belt layer in the meridian section.

[0002]

2. Description of the Related Art With the rapid spread of automobiles, noise generated from automobiles is becoming a social problem. The noise generated by an automobile includes noise originating from tires in addition to noise emitted from the engine itself and intake and exhaust sounds.

[0003] Noise generated from a tire includes an air pumping sound based on a tread pattern of the tire, a pattern vibration sound, and a ground friction vibration sound. Among them, regarding the ground friction vibration noise, the tire comes into contact with the road surface and the tire is vibrated by the pattern and the unevenness of the road surface, but the vibration force causes the belt layer to vibrate and the vibration causes the sidewall portion to vibrate. It is known to generate noise by vibrating.

It is known that such vibration noise tends to occur particularly in a high-rigidity tire using a high modulus cord for a belt layer.

Conventionally, in order to reduce noise caused by such vibration, for example, a belt cord having a relatively low modulus has been employed, or a tire cavity has been filled with, for example, a foamable vibration damping material. For example, the vibration of the tire has been suppressed.

[0006]

However, with the above-mentioned structure, a satisfactory effect has not been obtained, and the adoption of a low modulus cord has a disadvantage in that the steering stability becomes insufficient, especially in the tread shoulder region. Those using the vibration damping material not only have poor ride comfort but also impair the weight balance of the tire and hinder smooth rolling of the tire.

Therefore, the inventor paid attention to the cross-sectional shape of the belt layer. Usually, the belt layer is formed by laminating two belt plies each having a belt cord arranged thereon, and is formed by a curved surface that forms an arc both in the circumferential direction and in the tire axial direction. It has been found that when such a cylindrical body is subjected to vibration, the difficulty of vibration, that is, the rigidity against vibration, differs depending on the magnitude of the curvature of the cylindrical body and the distribution of the curvature.

Therefore, by regulating this curvature,
The inventor has found that vibration of the belt layer can be suppressed and noise can be reduced, and the present invention has been completed.

According to the present invention, in the tire axial section of the belt layer, the inner and outer regions are formed by arcs having different radii of curvature, and the curvature radius ratio of the two arcs is regulated. The purpose of the present invention is to provide a pneumatic tire capable of reducing the passing noise of a tire, based on the basic rule that the height difference between the belt and the belt layer is determined and the axial cross-sectional shape of the shell formed by the belt layer is determined within a certain range. .

[0010]

SUMMARY OF THE INVENTION The present invention relates to a carcass that is folded from a tread portion through a sidewall portion and around a bead core of a bead portion, and a plurality of belts disposed inside the tread portion and outside the carcass. A pneumatic tire comprising: a belt layer on which plies are superimposed, wherein the belt layer has a superimposition at a superimposed portion where at least two belt plies overlap, the distance being an axial distance between edges of the superimposed portion. Virtually dividing into an inner area between the dividing points P, P, which separates a distance of 1/3 times the width W from the tire equatorial plane in the tire axial direction, and an outer area outside the dividing point P in the tire axial direction, In a normal state where a normal internal pressure is applied, the inner region is formed by a first arc having a radius of curvature R1 having a center on the tire equatorial plane, while the outer region is smoothly connected to the first arc. An equatorial point formed by a second arc having a radius of curvature R2 which is 0.7 times or more and 0.9 times or less the radius of curvature R1 of the first arc, wherein the belt layer intersects the tire equatorial plane; And a height difference D in the tire radial direction between 0.02 and 0.04 times the overlapping width W.

[0011]

In the belt layer, the radius of curvature R2 of the second arc forming the outer region is 0.7 times or more and 1.0 times or less of the radius of curvature R1 of the first arc forming the inner region. . The graph of FIG. 2 is a graph in which a noise test was conducted by making a prototype with different curvature radius ratios R2 / R1. According to the graph, when the curvature radius ratio R2 / R1 was 0.7 to 0.9, the noise was highest. It has been confirmed that it is small.

When the radius ratio is less than 0.7, the outer region has higher rigidity than the inner region, and the inner region sandwiched between the outer regions is easily vibrated. On the other hand, if the curvature radius ratio R2 / R1 exceeds 1.0, the belt layer becomes almost flat, and the entire belt layer is likely to vibrate.

The belt layer has a height difference D between an equatorial point and an edge of a superimposed portion where two belt plies overlap each other.
0.02 times or more and 0.04 times or less. FIG.
Is a graph showing the relationship between the height difference D and noise, and shows that the noise level is the lowest in a range where the height difference D is 0.02 to 0.04 times the overlapping width W.

If the height difference D is less than 0.02 of the superimposition width W, the belt layer is almost flat, and the entire belt layer is easily vibrated and noise increases. Conversely, if it exceeds 0.04, the rigidity of the belt layer becomes excessive and the whole tire is likely to vibrate.

As described above, according to the present invention, by restricting the shape of the cross section of the belt layer in the tire axial direction to a limited range, the vibration of the tire generated during running can be suppressed and the passing noise can be reduced.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 includes a tread portion 2
And a pair of bead portions 4, 4 located radially inward of the sidewall portions 3, 3 extending inward in the tire radial direction from both ends of the bead portions 4, 4. A toroidal carcass 6 that passes through the sidewall portions 3 and 3 and the tread portion 2 is bridged between the bead cores 5 and 5 that are provided in the tread portion 2. I have.

In the present embodiment, the carcass 6 is formed by laminating one or more carcass plies in a so-called radial or semi-radial direction in which carcass cords are arranged at an angle of 60 to 90 degrees with respect to the equator C of the tire. In the present embodiment, it is formed of one carcass ply. As the carcass cord, a fiber cord such as nylon, polyester, rayon, or aromatic polyamide is used. In this example, the main body 6a of the carcass 6 is located outside the belt core.
A bead apex 8 extending in a tapered shape and made of hard rubber is disposed between the bead apex 8 and the folded portion 6b.

In the present embodiment, the belt layer 7 is composed of an inner belt ply 7A arranged on the carcass 6 side and an outer belt ply 7B arranged outside and narrower than the inner belt ply 7A. It is formed as a layer structure. Each belt ply 7
A and 7B are the same as the carcass 6, organic fibers such as nylon, polyester, rayon, and aromatic polyamide, and a belt cord using a steel cord are arranged at an angle of 0 to 30 degrees with respect to the tire equator C. Are arranged so as to cross each other between the plies.

The belt layer 7 has an overlapping portion 9 where the inner and outer belt plies 7A and 7B overlap, and an overlapping width which is a distance between the edges F of the overlapping portion 9 in the tire axial direction. W is set to 0.8 to 1.1 times the tread width TW in this embodiment.

Further, the belt layer 7 has two section points P, P, which are separated from the tire equator plane CO by a distance of の of the superposed width W on both sides in the tire axial direction.
In addition to the virtual division into an inner region 10 located between P and an outer region 11 located on the outer side in the tire axial direction of the division point P, in each of the inner, outer and regions 10 and 11, the respective radii of curvature are set. It is formed by a circular arc.

The inner region 10 is composed of a first arc S1 having a center at the tire equatorial plane CO, and has a radius of curvature R1 of:
In this embodiment, the overlap width W is set to be 1.0 times or more and 2.5 times or less, while the outer area 11 is set to the first arc S
1 and a radius of curvature R of the first arc S1.
1 is formed by a second circular arc S2 having a radius of curvature R2 which is 0.7 times or more and 0.9 times or less thereof.

The reference line defining the radius of curvature of each of the first and second arcs S1 and S2 is a center line passing through the center in the thickness direction of the overlapping portion 9 of the belt layer 7.

In the belt layer 7, the edge F of the overlapping portion 9 is located radially inward in the tire radial direction with respect to the equator point A where each belt layer 7 intersects the tire equatorial plane CO. F
And the height difference D in the tire radial direction between 0.02 and 0.04 times the overlapping width W.

The belt layer may be formed by overlapping three or more belt plies. In this case, the overlapping portion is in a range where at least two belt plies overlap. Further, the configuration of the belt layer may be a tire having a bias arrangement, and the present invention can be modified into various aspects.

[0025]

[Specific example] A tire having a tire size of 225 / 50R16 was mounted on a 7JJ × 16 rim, an internal pressure of 2.5 kgf / cm ^{2 was} applied, and test tires having the same specifications were mounted on front and rear wheels of a real vehicle, and noise was generated. Tested.

The method of the noise test is as follows. A vehicle equipped with test tires was tested on a test road at 60 km /
h and coasting at a speed of h and 7.5 m away from the center of the vehicle in a direction perpendicular to the direction of travel and 1.2 m
A microphone was installed at the height of the car and the noise level was measured.

FIG. 2 shows the results of the change in the noise level by varying the curvature radius ratio R2 / R1 stepwise, and FIG. 3 shows the results of the change in the noise level varying the height difference D.

Further, in FIG. 4, the results of frequency analysis of the tire according to the present application are shown by solid lines, and the results of frequency analysis of the tire according to the conventional configuration in which the entire belt layer has a single radius of curvature are shown by broken lines. From the graph of FIG. 4, it was confirmed that the noise level of the configuration of the present application was lower than that of the conventional configuration, and that the noise level was significantly reduced particularly in the peak region generated at 1 kHz.

[0029]

As described above, the pneumatic tire of the present invention has the following features.
In the overlapping portion of the belt ply, the shape of the belt layer in the axial direction of the tire is regulated so as to be divided into an inner region and an outer region, so that vibration of the tire due to running can be suppressed and running noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the radius of curvature of the inner and outer regions and the noise level.

FIG. 3 is a graph showing a relationship between a height difference between an equatorial point of a belt layer and an edge of a superimposed portion and a noise level.

FIG. 4 is a graph showing a result of a frequency analysis of a tire noise level.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 7A, 7B Belt ply 9 Overlapping part 10 Inner area 11 Outer area A Equatorial point C Tire equator CO Tire equatorial plane D Height difference F Edge P Partition point R1, R2 Radius of curvature S1 First arc S2 Second arc W Overlap width

Continuation of the front page (56) References JP-A-1-141104 (JP, A) JP-A-4-123905 (JP, A) JP-A-4-163208 (JP, A) JP-A-63-188502 (JP) JP-A-59-75807 (JP, A) JP 8-9282 (JP, B2) JP 6-51441 (JP, B2) JP 6-53441 (JP, B2) 57-17723 (JP, B2) JP-B-58-2845 (JP, B2) JP-B, 1-23323 (JP, B2)

Claims (1)

(57) [Claims] 1. A carcass which is folded from a tread portion through a sidewall portion and around a bead core of a bead portion, and a belt layer which is disposed inside the tread portion and outside of the carcass and in which a plurality of belt plies are overlapped. In the pneumatic tire, the belt layer is formed such that, at an overlapping portion where at least two belt plies overlap, the overlapping width W, which is the distance in the tire axial direction between the edges of the overlapping portion, is 1 /.
A virtual internal pressure was added while a virtual division was made between an inner area between the dividing points P, P which separated the tire equatorial plane by three times the distance in the tire axial direction, and an outer area outside the dividing point P in the tire axial direction. In the normal state, the inner region is formed by a first arc having a radius of curvature R1 centered on the tire equatorial plane, while the outer region is smoothly connected to the first arc and has a first arc.
A second arc having a radius of curvature R2 that is 0.7 times or more and 0.9 times or less the radius of curvature R1 of the arc, and between the equatorial point where the belt layer intersects the tire equatorial plane and the edge. Height difference D in the tire radial direction is 0.02 of the superposed width W
A pneumatic tire characterized by being at least twice and at most 0.04 times.