JP2007196894A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat tire devised to improve kinetic performance on an ice road surface in punctured travelling, especially a starting property while improving riding comfortability on a general road surface and steering stability on a snow road surface in non-punctured travelling. <P>SOLUTION: Three-layer belt layers 8, 9, 10 are arranged on the outer peripheral side of a carcass layer 6 on a tread part 4, cord angles α, β, γ of cords 8c, 9c, 10c constituting the belt layers 8, 9, 10 relative to the tire peripheral direction are set to α=15 to 30° on the innermost belt layer 8, β=40°or more on the intermediate layer 9 and γ=35 to 70° on the outermost belt layer 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a run-flat tire, and more particularly, while improving the riding comfort on a general road surface during non-puncture traveling and the handling stability on a snowy road surface, particularly the motion performance on an ice surface during a puncture travel, The present invention relates to a run-flat tire that improves startability.

  Conventionally, as a run-flat tire that can safely travel a fixed distance even if punctured, a tire rubber portion having a crescent-shaped hard rubber layer arranged on the tire sidewall is widely known (for example, patents) References 1 and 2). In this type of run-flat tire, when the tire is punctured and becomes zero pressure, a crescent-shaped hard rubber layer disposed on the sidewall portion runs while supporting the load of the vehicle.

  However, since this type of run-flat tire supports the vehicle load by the hard rubber on both the left and right sides as described above, the center portion in the width direction of the tread portion 4 buckles as shown in FIG. There is a problem that the area is reduced and the motion performance when traveling on a low friction road surface is lowered. In particular, in a tire designed to have low tread rigidity such as a studless tire, this tendency is prominent, and there is a problem that the tire slips on an icy road surface.

  As a countermeasure, a belt additional layer made of a cord extending at a high angle with respect to the tire circumferential direction is arranged on the outer peripheral side of the two belt layers arranged in the tread portion, so that the compression rigidity in the width direction in the tread portion is increased. There is a proposal (see Patent Document 3) that suppresses the buckling phenomenon by increasing it.

However, this proposal has a problem that the tread rigidity becomes too high due to the three layers of the belt layer, so that the riding comfort on a general road surface and the driving stability on a snowy road surface during non-puncturing are lowered. It was.
JP 2003-94912 A JP 2003-326924 A International Publication WO2003 / 024727

  An object of the present invention is to solve the above-described conventional problems, and while improving the riding comfort on a general road surface during non-puncture traveling and the handling stability on a snowy road surface, the road surface on ice during a puncture travel is provided. An object of the present invention is to provide a run-flat tire that improves the athletic performance, particularly the startability.

  In order to achieve the above object, a run flat tire of the present invention has a carcass layer mounted between bead cores embedded in a pair of left and right bead portions, and a hard rubber layer having a substantially crescent-shaped cross section on a sidewall portion. In the run flat tire in which three belt layers are arranged on the outer peripheral side of the carcass layer, the cord angle of the three belt layers with respect to the tire circumferential direction is set to 15 to 30 ° in the innermost belt layer, The gist is that the intermediate belt layer is set to 40 ° or more and the outermost belt layer is set to 35 ° to 70 °.

  According to the present invention, the cord angle of the three belt layers with respect to the tire circumferential direction is set to a low angle of 15 to 30 ° in the innermost belt layer, while 40 ° or more in the intermediate belt layer and 35 in the outermost belt layer. Since it is set to a high angle of ˜70 °, in order to enhance the compression rigidity in the width direction of the tread portion while suppressing the increase in the out-of-plane rigidity in the circumferential direction as the entire belt layer, While improving ride comfort and driving stability on a snowy road surface, it is possible to suppress a buckling phenomenon at the time of puncturing and to improve exercise performance (particularly, startability) on an iced road surface.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a plan view showing a part of the arrangement relationship between a tread surface and a belt layer of the tire shown in FIG.

  In FIG. 1, a pneumatic tire 1 includes a pair of left and right bead portions 2, 2, sidewall portions 3, 3 extending radially outward from the bead portions 2, 2, and radial directions of the sidewall portions 3, 3. And a cylindrical tread portion 4 that connects the outer sides.

  A carcass layer 6 is mounted between the pair of left and right bead portions 2, 2, and a hard rubber layer 7 having a substantially crescent-shaped cross section is disposed on the inner side in the tire axial direction of the carcass layer 6 in the sidewall portion 3. On the outer peripheral side of the carcass layer 6 in the tread portion 4, three belt layers 8, 9, and 10 made of high-strength and high-elasticity organic fiber cords such as steel cords or aramid fibers are disposed. In the figure, reference numeral 5 denotes a belt cover layer made of an organic fiber cord such as nylon extending in the tire circumferential direction for suppressing the diameter expansion of the belt layers 8, 9, and 10 during high-speed running. Depending on the characteristics, it may not be arranged.

  FIG. 2 is a plan view showing the arrangement relationship between the tread surface and the belt layer of the tire of FIG. 1, and in this embodiment, the tread surface is formed in a block pattern in which a large number of blocks are arranged to constitute belt layers 8, 9, and 10. Cord angles α, β, and γ of the cords 8c, 9c, and 10c with respect to the tire circumferential direction are α = 15 to 30 ° in the innermost belt layer 8, and β = 40 ° or more, preferably 75 ° or less in the intermediate belt layer 9. In the outermost belt layer 10, γ is set to 35 to 70 °, preferably 40 to 65 °.

  Thus, while the cord angle α with respect to the tire circumferential direction of the belt layer 8 is set to a low angle, the cord angles β and γ with respect to the tire circumferential direction of the belt layers 9 and 10 are set to high angles, so that By optimizing the balance between the out-of-plane rigidity in the circumferential direction and the out-of-plane rigidity in the width direction and enhancing the compression rigidity in the width direction of the tread part, the ride quality on the general road surface and the snowy road surface during non-puncture driving While improving the steering stability of the vehicle, it is possible to improve the motion performance (particularly the startability) on the road surface on ice during puncture travel.

  When the cord angle α with respect to the tire circumferential direction of the innermost belt layer 8 is less than 15 °, the out-of-plane rigidity in the circumferential direction of the entire belt layer becomes too high, and riding comfort on the general road surface and on the snow during non-puncture traveling Steering stability on the road surface will be reduced.

  Further, when the cord angle β with respect to the tire circumferential direction of the intermediate belt layer 9 is less than 40 °, or the cord angle γ with respect to the tire circumferential direction of the outermost belt layer 10 is less than 35 °, as in the above case, The out-of-plane rigidity in the direction becomes too high, and riding comfort on a general road surface during non-puncture traveling and steering stability on a snowy road surface are deteriorated.

  Furthermore, when the cord angle γ with respect to the tire circumferential direction of the outermost belt layer 10 exceeds 70 °, the out-of-plane rigidity in the width direction of the entire belt layer becomes too large compared to the out-of-plane rigidity in the circumferential direction. The compression rigidity in the width direction in the vehicle becomes too high, and the riding comfort on the general road surface and the steering stability on the snowy road surface at the time of non-puncture traveling are lowered.

  The angle difference | β−γ | between the cords 9c and 10c constituting the intermediate belt layer 9 and the outermost belt layer 10 with respect to the tire circumferential direction β and γ is within 20 °, preferably within 10 °. It is good to set as follows. Thereby, since the difference in rigidity between the intermediate belt layer 9 and the outermost belt layer 10 is reduced, excessive twisting of the belt layer is suppressed, the steering wheel flow is suppressed, and the straight traveling performance is improved.

The cord material constituting each of the belt layers 8, 9, and 10 in the run-flat tire of the present invention is not particularly limited. As described above, the cord material is composed of a steel cord, and from the viewpoint of weight reduction, an aramid fiber and a polyketone fiber are used. , Polyethylene naphthalate fiber, polyparaphenylene benzobisoxazole fiber, or a composite fiber containing these, the tensile elastic modulus is 10,000 to 150,000 N / mm ² , preferably 20,000 to 100,000 N / mm An organic fiber cord having a high strength and high elasticity of mm ² is preferably used.

  In the present invention, at least one of the cords constituting the intermediate belt layer 9 and the outermost belt layer 10 may be constituted by a steel cord. As a result, the compression rigidity in the width direction of the tread portion 4 can be appropriately and reliably increased, so that the buckling phenomenon at the time of puncture traveling is reliably suppressed, and the motion performance on the ice road surface (particularly, startability). Can be further improved.

  As shown in FIG. 2, the cords 8c, 9c, and 10c constituting the belt layers 8, 9, and 10 are arranged so that the cord directions of the innermost belt layer 8 and the intermediate belt layer 9 are different from each other with respect to the tire equatorial plane. It is good to arrange | position so that it may become an opposite direction, and it may arrange | position so that the cord direction of the intermediate | middle belt layer 9 and the outermost belt layer 10 may become the same direction with respect to a tire equator surface. As a result, it is possible to improve the riding comfort on the general road surface during non-puncture traveling and the steering stability on the road surface on snow and the motion performance on the road surface on ice during the puncture travel in a well-balanced manner.

  The arrangement relationship between the intermediate belt layer 9 and the outermost belt layer 10 described above depends on the size of the tire and the required characteristics, as shown in FIG. 3, the cord directions of the intermediate belt layer 9 and the outermost belt layer 10 are In some cases, the tires are arranged in opposite directions with respect to the equator plane.

  In the present invention, the total cross-sectional area of the cords 9 c and 10 c in at least one of the intermediate belt layer 9 and the outermost belt layer 10 is 1.2 to 1.5 of the total cross-sectional area of the cord 8 c in the innermost belt layer 8. It is better to set it to be double. As a result, the compression rigidity in the width direction of the tread portion 4 can be reliably increased, so that the buckling phenomenon at the time of puncture traveling can be more reliably suppressed, and the motion performance (particularly, startability) on the ice surface can be further increased. Can be improved. Here, the total cross-sectional area of the cord means the total sum of the cross-sectional areas of the cord per unit width in the cross section including the tire axis of the belt layer.

  As described above, in the run flat tire of the present invention, three belt layers are arranged outside the carcass layer in the tread portion, and the cord angles of these belt layers with respect to the tire circumferential direction are set to 15 to 30 in the innermost belt layer. ° By increasing the intermediate belt layer to 40 ° or more and the outermost belt layer of 35 to 70 °, while improving the riding comfort on the general road surface and the driving stability on the snowy road surface during non-puncturing, It suppresses the buckling phenomenon at the time of puncture traveling and improves the motion performance on the icy road surface, and is particularly preferably applied as a studless tire traveling on an icy and snowy road surface.

<Conventional Examples, Comparative Examples 1 and 2 and Examples 1 to 7>
The tire size (205 / 55R16), the tire structure (FIG. 1) and the tread pattern (FIG. 2) are used in common, and the cord angles of the cords in the belt layers 8, 9, and 10 with respect to the tire circumferential direction, and the tire equatorial plane Conventional tires (conventional examples), comparative tires (comparative examples 1 and 2), and tires of the present invention (Examples 1 to 7) were manufactured with different cord directions as shown in Table 1.

  In each tire, the belt layer cord is steel cord, the innermost belt layer width is 190 mm, the intermediate belt layer width is 180 mm, the outermost belt layer width is 170 mm, and the total cords in each belt layer are The cross-sectional area was made common.

  For these 10 types of tires, the following test methods were used to evaluate the riding comfort on the general road surface during non-puncture driving, the steering stability on the snow road surface, and the startability on the ice road surface during the puncture driving, respectively. The results are also shown in Table 1.

[Riding comfort on general roads]
Each tire is installed in the rim, filled with air pressure of 230 kPa, mounted on the front and rear four wheels of a 2500cc rear-wheel drive vehicle, and run on a test course consisting of an asphalt road surface at an average speed of 60 km / h. Sensory evaluation was performed by a driver. The result was displayed by the index | exponent which sets the prior art example to 100. The larger the value, the better the riding comfort.

[Steering stability on snowy road surface]
The above-mentioned vehicle was driven 10 km at an average speed of 40 km / h on a test course (temperature: -3 to -8 ° C, snow temperature: -4 to -8 ° C) consisting of a road surface on snow. Was done. The result was displayed by the index | exponent which sets the prior art example to 100. The larger the value, the better the steering stability.

[Startability on ice surface]
Of the tires mounted on the vehicle described above, the air pressure of the front wheel on the driver side is set to zero (0 kPa), and the running condition of the vehicle when starting the test course consisting of the road surface on ice is observed to evaluate the startability. did. The result was displayed by the index | exponent which sets the prior art example to 100. The larger the value, the better the startability.

  From Table 1, the tires of the present invention (Examples 1 to 7) are compared to the conventional tires and comparative tires in terms of riding comfort on a general road surface and driving stability on a snowy road surface during puncture travel, and puncture travel. It can be seen that the startability on the ice surface at the time is improved in a well-balanced manner.

<Examples 8 and 9>
Of the outermost belt layer and the intermediate belt layer in the tire of Example 1, the total cross-sectional areas of the cords in one of the belt layers were varied as shown in Table 2 to produce Examples 8 and 9, respectively. In addition, about the total cross-sectional area of the code | cord | chord, it displayed with the index | index which makes the total cross-sectional area of the code | cord | chord in the conventional tire (conventional example) mentioned above 100.

For these two types of tires, the same test method as above was used to evaluate the riding comfort on the general road surface during non-puncture driving, the driving stability on the snow road surface, and the startability on the ice road surface during the puncture driving, The results are shown in Table 2 together with the results of the conventional tire (conventional example) in Table 1.

  From Table 2, the tires of the present invention (Examples 8 and 9) are compared to the conventional tires in terms of riding comfort on a general road surface during non-puncture traveling, driving stability on a snowy road surface, and on ice during puncture travel. It can be seen that the startability on the road surface is improved in a more balanced manner.

It is sectional drawing which shows the pneumatic tire by embodiment of this invention. It is a top view which fractures | ruptures and shows a part explaining the arrangement | positioning relationship between the tread surface of the tire of FIG. 1, and a belt layer. FIG. 3 is a plan view corresponding to FIG. 2 according to another embodiment of the present invention. It is sectional drawing explaining the deformation | transformation condition of the tread part at the time of the puncture driving | running | working of the conventional run flat tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Side wall part 4 Tread part 5 Belt cover layer 6 Carcass layer 7 Hard rubber layer 8 Innermost belt layer 9 Intermediate | middle belt layer 10 Outermost belt layer 8c, 9c, 10c Code (alpha), (beta), (gamma) Cord angle

Claims (6)

A carcass layer is mounted between bead cores embedded in a pair of left and right bead portions, a hard rubber layer having a substantially crescent-shaped cross section is disposed on the sidewall portion, and a three-layer belt is disposed on the outer peripheral side of the carcass layer. In run flat tires with layers,
Run-flat tires in which the cord angles of the three belt layers with respect to the tire circumferential direction are 15 to 30 ° in the innermost belt layer, 40 ° or more in the intermediate belt layer, and 35 to 70 ° in the outermost belt layer, respectively.   The run-flat tire according to claim 1, wherein an angle difference between a cord angle with respect to a tire circumferential direction in the intermediate belt layer and a cord angle with respect to a tire circumferential direction in the outermost belt layer is set to 20 ° or less.   The run flat tire according to claim 1 or 2, wherein the cord constituting the intermediate belt layer and / or the outermost belt layer is a steel cord.   The cord directions of the innermost belt layer and the intermediate belt layer are arranged opposite to each other with respect to the tire equator plane, and the cord directions of the intermediate belt layer and the outermost belt layer are the same direction with respect to the tire equator plane. The run-flat tire according to claim 1, 2, or 3 arranged in the above.   The total cross-sectional area of the cord in the intermediate belt layer and / or the outermost belt layer is 1.2 to 1.5 times the total cross-sectional area of the cord in the innermost belt layer. The described run-flat tire.   The run-flat tire according to any one of claims 1 to 5, wherein the run-flat tire is a studless tire for running on an icy and snowy road.

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