JP2001191722A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing weight without impairing various performance of a tire, among others, maneuvering stability and low noise performance. SOLUTION: In this pneumatic tire for reinforcing a crown part of a carcass by a belt of at least one layer by using the carcass extening in a toroidal shape between a pair of bead parts as a skeleton, the carcass is provided with a defective part ranging over an area of 30 to 60% of an adjacent belt layer width with a tire equatorial surface as the center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a reduced weight without deteriorating its basic performance.

[0002]

2. Description of the Related Art In recent years, from the viewpoints of environmental protection and energy saving, automobiles have been reduced in fuel consumption, and accordingly, tires have been strongly required to be reduced in weight. In order to respond to this demand, recently, in the field of tires, various measures for weight reduction have been attempted.

That is, (a) reduction in tread rubber thickness,
Techniques such as (b) reduction of rubber thickness at the tire side, (c) reduction of bead filler rubber, (d) reduction of the number of cords inserted in the belt, and (e) removal of the belt reinforcement layer are known. .

[0004]

SUMMARY OF THE INVENTION
Since the methods (b) and (c) reduce the part that controls the reinforcement of the tire, the strength of the case is reduced, and as a result, the steering stability is deteriorated. Similarly, the above method (d) results in a decrease in the cornering power of the tire,
The steering stability will be degraded. (A) and
(e) In the method, since the input from the road surface is increased, tire noise of a kind particularly called road noise is easily generated.

[0005] As described above, there is a problem for each method. However, even when the above methods are combined, there is a serious problem that the effect of reducing the weight is limited. In particular, in small tires such as tires for passenger cars, there are few elements that can be reduced, and it has been difficult to significantly reduce the weight.

Accordingly, an object of the present invention is to provide a pneumatic tire which realizes weight reduction without sacrificing various tire performances, in particular, steering stability and low noise.

[0007]

SUMMARY OF THE INVENTION The present inventors have reviewed the basic structure of tires in order to achieve both steering stability, low noise, and light weight, and found that both the weight reduction and road noise reduction can be achieved. For this purpose, it is effective to remove the carcass under the belt, and at that time, it has been found that restricting the portion from which the carcass is removed is advantageous for suppressing a decrease in other performances, and completed the present invention. I came to.

That is, the gist of the present invention is as follows. (1) A pneumatic tire in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and a crown portion of the carcass is reinforced by at least one layer of a belt. A pneumatic tire characterized by having a notch, centered over an area of 30-60% of the width of an adjacent belt layer.

(2) In the above (1), the belt is a circumferential belt formed by winding an inclined belt layer made of a steel cord extending at an angle to the equatorial plane of the tire and an organic fiber cord in a circumferential direction of the tire. A pneumatic tire having a layer.

(3) In the above (2), the inclination angle of the steel cord of the inclined belt layer with respect to the equatorial plane of the tire is 30 to 30.
A pneumatic tire characterized by 40 °.

(4) The pneumatic tire according to (2) or (3), wherein the steel cord of the inclined belt layer is a monofilament.

(5) The pneumatic tire according to any one of the above (2) to (4), wherein the organic fiber cord of the circumferential belt layer is made of an aromatic polyamide.

(6) The pneumatic tire according to any one of the above (2) to (5), wherein the circumferential belt layer comprises two layers.

(7) The pneumatic tire according to any one of the above (1) to (6), wherein the tire has a case shape in which the width of the tire decreases when the internal pressure is charged.

(8) The pneumatic tire according to any one of the above (1) to (7), wherein the bead portion has a bead filler, and the length of the bead filler in the tire radial direction is 50 mm or more. .

(9) In any one of the above (1) to (8), the bead portion has a bead portion reinforcing layer formed by winding an organic fiber cord along a circumference around a rotation axis of the tire. A pneumatic tire, characterized in that:

(10) The pneumatic tire according to any one of the above (1) to (9), wherein the carcass has both ends fixed in the bead near the center of the thickness of the bead. .

(11) A method for manufacturing a pneumatic tire, wherein the tire according to (10) is manufactured according to a core manufacturing method.

[0018]

FIG. 1 shows a cross section of a pneumatic radial tire for a passenger car according to the present invention, wherein 1 is a bead core, 2 is a carcass, 3 is a belt made up of at least two layers of belt layers 3a and 3b, and 4 is a tread.

The carcass 2 is composed of at least one ply made of, for example, an organic fiber cord and arranged in a radial direction across a pair of bead cores 1.
It is essential that the crown has a missing portion 5 in the crown portion. That is, by removing the crown portion of the carcass 2 and reducing the amount of the carcass material, it is possible not only to significantly reduce the weight, but also to reduce the road noise, particularly the road noise having a peak around 250 Hz. That is,
Road noise around 250Hz is caused by cavity resonance inside the tire.A detailed analysis of this mechanism revealed that the vibration mode in the cross section in the tire width direction could be changed by providing a cutout in the carcass crown. For example, it became clear that cavity resonance inside the tire can be significantly reduced.

Here, the missing portion 5 may have a length D in the tire width direction of 30 to 60% of the maximum width L of the belt layer 3 a adjacent to the carcass 2 with the tire equatorial plane O as the center. It is vital. If the length D of the missing portion 5 is less than 30%, the effect of reducing the weight of the carcass material and the effect of reducing the road noise cannot be sufficiently obtained. On the other hand, if the length D exceeds 60%, the carcass as a carcass holding the air pressure of the tire is not obtained. This is because the role is hindered, and the durability of the tire is reduced.

Since the portion of the carcass 2 where the notch 5 is provided hits the inner side in the radial direction of the belt, and the load ratio of the tension is smaller than the other carcass portions, the notch 5 is provided here. The decrease in tire stiffness due to the above is almost negligible.

Further, in the example shown in FIG. 1, the belt 3 is formed by winding an inclined belt layer 3a made of a steel cord extending inclining with respect to the equatorial plane O of the tire and an organic fiber cord in the circumferential direction of the tire. It has a two-layer structure of the circumferential belt layer 3b. In this belt structure, the number of the inclined belt layers made of steel cords is reduced as compared with a conventional two-layer structure of inclined belt layers made of steel cord or a structure in which a reinforcing layer is added to the two layers. Effectively contributes to

In this belt 3, the inclined belt layer 3a
It is advantageous to arrange the steel cord at an inclination angle of 30 to 40 ° with respect to the equatorial plane O of the tire to increase cornering power. Now, in the conventional two-layer structure of the inclined belt layer made of the steel cord, the in-plane bending rigidity of the belt becomes maximum at an inclination angle of the cord of 20 to 30 °.
However, in the belt structure according to the present invention, the radial carcass is arranged inside the inclined belt layer 3a and the circumferential belt layer is arranged outside the inclined belt layer 3a, and the cords of the carcass 2, the inclined belt layer 3a and the circumferential belt layer 3b are laminated. In order to form a triangle, the steel cord of the inclined belt layer 3a is
When arranged at an inclination angle of 30 to 40 °, the in-plane bending stiffness is maximized, and the cornering power can be increased.

Further, the use of a solid monofilament for the steel cord constituting the inclined belt layer 3a reduces the weight per cord unit length and the thickness of the coating rubber, thereby reducing the tire thickness. This is advantageous for achieving weight reduction. On the other hand, it is advantageous that the organic fiber cord of the circumferential belt layer 3b is made of an aromatic polyamide. This is because the use of the aromatic polyamide increases the circumferential tension, reduces the input from the road surface, and reduces road noise.

In the example shown in FIG. 1, the belt 3 has a two-layer structure of the inclined belt layer 3a and the circumferential belt layer 3b. However, as shown in FIG. 2, the circumferential belt layer 3b has two layers. It is also possible to have a total of three layers. By forming the circumferential belt layer 3b into two layers, the circumferential rigidity of the belt is increased and the input from the road surface is reduced, so that road noise, particularly road noise having a peak near 160 Hz can be reduced. .

Next, providing the tire with a case shape in which the width of the tire decreases when the internal pressure is applied is advantageous for increasing the belt tension and the tension of the tire side portion to reduce road noise. Specifically, by reducing the outer shape of the tire, particularly the curvature of the side portion, a tension load distribution is provided that increases the belt tension load and reduces the tension load on the side portion when the tire is filled with air. Then, the belt tension and the tension of the tire side portion can be increased, and the input from the road surface is reduced, so that the road noise is reduced.

The bead filler disposed at the bead portion of the tire, that is, the bead filler 6 disposed radially outside the bead core 1 in the example shown in FIGS. 1 and 2, has a tire radial length h of 50 mm or more. Is advantageous for improving the steering stability. That is, when the length h of the bead filler 6 is 50 mm or more, that is, 45% or more of the tire cross-sectional height, only the torsional rigidity can be effectively increased while the longitudinal springs of the tire are almost equal. Therefore, an improvement in steering stability is achieved while maintaining ride comfort.

Further, as shown in FIGS. 2 and 3, the organic fiber cord is formed along the outer periphery of the bead filler mainly along the tire width direction and along the circumference around the rotation axis of the tire. Arranging the wound bead reinforcing layer 7 is advantageous for improving the steering stability. That is,
When the bead portion reinforcing layer 7 is provided, the tire bead portion is prevented from falling down and lateral rigidity is increased, so that steering stability is improved.

When the so-called hybrid cord in which an aromatic polyamide cord and a nylon cord are twisted is used as the organic fiber cord constituting the bead portion reinforcing layer 7, the aromatic polyamide cord secures rigidity, The application of such cords is recommended because nylon cords ensure elongation.

The tire shown in FIG. 1 to FIG.
In this example, the carcass ply has a bead structure in which the carcass ply is wound around the bead core 1 from the inside to the outside of the tire so that the folded portion extends outward in the tire radial direction. As shown in FIG. By adopting a bead portion structure in which the portion is fixed in the bead portion near the center of the thickness of the bead portion, it is possible to further reduce the carcass ply and reduce the weight.

In the structure shown in FIG. 4, in order to fix both end portions of the carcass ply in the vicinity of the center of the thickness of the bead portion, the fixing layers 8a and 8b sandwiching the end portions of the carcass ply from both sides in the tire width direction are provided. It is preferable to arrange them. The fixed layers 8a and 8b are formed by spirally winding a bead wire around a rotation axis of a tire.

The tire shown in FIG. 4 can be manufactured according to a so-called core manufacturing method. That is, FIG.
As shown in the figure, using a substantially donut-shaped inner mold 10 made of a rigid body, firstly, a rubberized cord is radially wound around the inner surface of the inner mold 10, turned around at the inner peripheral edge of the mold, and wound again in the radial direction. The carcass ply 11 is formed on the peripheral surface of the inner mold 10 repeatedly, and then a rubberized cord is spirally wound around the carcass ply 11 in the circumferential direction of the inner mold 10 to form a belt ply 12, and the belt ply 12 is further formed. Ply 12
A raw tire 13 is formed by winding raw rubber 13 serving as a tread thereon. Next, the inner mold 10 with the green tires adhered thereto is carried into the vulcanized outer mold as it is, and vulcanization molding is performed. The tire thus obtained has the structure shown in FIG. 4 in which the carcass ply is fixed near the center of the thickness of the bead portion.

In order to provide the fixed layers 8a and 8b for sandwiching the end portion of the carcass ply in the bead portion, as shown in FIG.
10 After the rubberized cord is spirally wound several times along the inner peripheral edge to form the fixed layer 8b, the carcass ply
Then, a rubberized cord is spirally wound around the end of the carcass ply 11 a plurality of times to form a fixed layer 8a. Thereafter, the belt ply 12 and the raw rubber 13 are wound in the same manner as described above. Should be performed.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the structure shown in FIGS.
175 / 70R14 size radial tires for passenger cars were prototyped under the various specifications shown in (1). In addition, the number of the inclined belt layers 3a of the belt 3 was 30/50 mm, and the number of the peripheral belt layers 3b was 40/50 mm. Also, the tire shown in FIG. 6, that is, a conventional tire having a continuous carcass without a missing portion, was prototyped in the same size.

Each of the tires thus obtained was subjected to each test of tire weight, rolling resistance coefficient (RRC), riding comfort, steering stability and road noise. The measurement and test results are also shown in Table 1.

Here, the tire weight is indicated by an index when the weight of each tire is set to 100 in the comparative example, and the smaller the index is, the lighter the tire is.

The rolling resistance coefficient (RRC) is obtained by measuring the rolling resistance and dividing the measured value by the applied load. The result is shown as an index when the result of the comparative example is set to 100. ing.

The ride comfort test, steering stability and road noise were evaluated by feeling when a test tire was mounted on an actual vehicle and the test driver ran on a predetermined course. The score is shown by an index when the result of the comparative example is set to 100, and the larger the index, the better.

[0039]

[Table 1]

[0040]

According to the present invention, weight reduction can be realized without sacrificing various tire performances such as steering stability and low noise.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tire structure of the present invention.

FIG. 2 is a diagram showing a tire structure of the present invention.

FIG. 3 is a view showing a tire structure of the present invention.

FIG. 4 is a diagram showing a tire structure of the present invention.

FIG. 5 is a diagram illustrating a tire manufacturing procedure of the present invention.

FIG. 6 is a view showing a structure of a comparative tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 4 Tread 5 Missing part 6 Bead filler 7 Bead part reinforcing layer 8a 8b Fixed layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 15/00 B60C 15/00 15/06 15/06 BN // B29D 30/10 B29D 30/10 B60C 9/02 B60C 9/02 A

Claims (11)

[Claims] 1. A pneumatic tire in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and a crown portion of the carcass is reinforced by at least one layer of a belt. A pneumatic tire having a cutout extending over an area of 30 to 60% of the width of an adjacent belt layer around a surface. 2. The belt according to claim 1, wherein the belt is formed by winding a single inclined belt layer made of a steel cord extending at an angle to an equatorial plane of the tire and an organic fiber cord in a circumferential direction of the tire. A pneumatic tire having a belt layer. 3. The tire according to claim 2, wherein the angle of inclination of the steel cord of the inclined belt layer with respect to the equatorial plane of the tire is 30 to 40.
°, a pneumatic tire. 4. The pneumatic tire according to claim 2, wherein the steel cord of the inclined belt layer is a monofilament. 5. The method according to claim 2, wherein
A pneumatic tire, wherein the organic fiber cord of the circumferential belt layer is made of an aromatic polyamide. 6. The method according to claim 2, wherein
A pneumatic tire, wherein the circumferential belt layer comprises two layers. 7. The method according to claim 1, wherein
A pneumatic tire having a case shape in which the width of the tire decreases when the internal pressure is charged. 8. The method according to claim 1, wherein
A pneumatic tire having a bead filler at a bead portion, wherein a length of the bead filler in a tire radial direction is 50 mm or more. 9. The method according to claim 1, wherein
A pneumatic tire comprising a bead portion reinforcing layer formed by winding an organic fiber cord along a circumference around a rotation axis of the tire in a bead portion. 10. The pneumatic tire according to claim 1, wherein both ends of the carcass are fixed in the bead near the center of the thickness of the bead. 11. A method for manufacturing a pneumatic tire, wherein the tire according to claim 10 is manufactured according to a core manufacturing method.