JP2007326439A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improving riding comfort without sacrificing steering stability, while reducing road noise. <P>SOLUTION: A belt cover layer 6 is made of a highly-elastic organic fiber cord having an elongation ratio of ≤3.5% at the time of 2.0cN/dtex load. A height H1 of an outer diameter of a bead filler 7 is set to be 22 to 55% of a tire cross section height SH. A tire radial direction height H2 from an outer peripheral end 7a of the bead filler 7 to a folded-back end 2a of a carcass layer 2 is set to be ≥11mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire that improves road comfort without sacrificing steering stability while reducing road noise.

  There is a strong demand to reduce medium-frequency road noise caused by transmission of vibrations during traveling along with the upgrading and quietness of automobiles. As a countermeasure, conventionally, the rubber of the tire tread portion has been softened, but there is a problem that the steering stability is deteriorated and the wear resistance is lowered.

  On the other hand, in order to improve high-speed durability, a belt cover layer in which a heat-shrinkable organic fiber cord such as nylon fiber is wound around the tire circumferential direction is generally provided on the tread portion of the pneumatic radial tire. Is formed. The belt cover layer formed in this manner increases the secondary natural frequency of the side portion to suppress the vibration transmission to the vehicle interior in order to increase the rigidity of the shoulder portion, and the medium frequency load that is a resonance sound in the vehicle interior. It is known to play a role in reducing noise.

  From such a background, conventionally, as a measure for further improving the effect of reducing the medium frequency road noise, there is a proposal to use an organic fiber cord such as polyketone fiber having a high elastic modulus for the belt cover layer described above. (For example, refer to Patent Documents 1 and 2).

However, it has been found that the use of an organic fiber cord having a high elastic modulus for the belt cover layer is advantageous in reducing road noise, but has a problem that riding comfort is lowered.
JP 2001-334811 A JP 2004-306634 A

  SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem, and to provide a pneumatic radial tire that improves road comfort without sacrificing steering stability while reducing road noise. There is.

  In order to achieve the above object, the pneumatic radial tire of the present invention extends the carcass layer from the tread portion to the bead portion through the left and right sidewall portions, and around the bead core embedded in the bead portion on the outer peripheral side thereof. A plurality of belt layers having cord directions intersecting between the layers at the outer periphery of the carcass layer in the tread portion, and at least the belt. A pneumatic radial tire in which a belt cover layer formed by winding a high-elasticity organic fiber cord having an elongation rate of 3.5% or less at a load of 2.0 cN / dtex on the outer periphery of both ends of the layer is provided. The outer diameter height H1 of the tire is 22 to 55% of the tire cross-section height SH, and the outer circumference end of the bead filler is Tire radial height H2 of up wrapping terminal of the scan layer and wherein the at 11mm or more.

Furthermore, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(3).
(1) The highly elastic organic fiber cord is polyketone fiber, polyester fiber, or lyocell fiber.
(2) The shrinkage stress at 150 ° C. of the highly elastic organic fiber cord is 10 to 20N.
(3) The number of high elastic organic fiber cords to be driven is 30 to 60/50 mm.

  According to the present invention, since the belt cover layer is made of an organic fiber cord having high elasticity, medium frequency road noise can be reduced by increasing the rigidity of the shoulder portion. Furthermore, the height of the bead filler and the height of the carcass layer are to be eliminated by properly maintaining the rigidity in the tire radial direction of the sidewall portion due to the use of the highly elastic organic fiber cord. Since the height in the tire radial direction of the joined portion of the carcass layer in the folded portion is adjusted within a range that does not impair the steering stability, the riding comfort can be improved without sacrificing the steering stability.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention.

  In FIG. 1, a pneumatic radial tire 1 includes a carcass layer 2 that extends from a tread portion 3 to bead portions 5 and 5 through left and right sidewall portions 4 and 4, and a bead core 6 embedded in the bead portions 5 and 5. 6 is configured to be folded back from the inside to the outside of the tire so as to wrap around the bead fillers 7 and 7 arranged on the outer peripheral side.

  Further, a plurality (two layers in the figure) of belt layers 8 and 9 whose cord directions intersect each other are arranged on the outer periphery of the carcass layer 2 in the tread portion 3, and 2.0 cN on the outer periphery of the belt layers 8 and 9. A belt cover layer 10 is provided which is formed by winding a highly elastic organic fiber cord having an elongation rate of 3.5% or less, preferably 1.5% or more when / dtex is applied. Although the figure shows a case where the belt cover layer 10 is disposed over the entire width of the outer periphery of the belt layers 8, 9, the belt cover layer 10 may be disposed only on the outer periphery of both end portions of the belt layers 8, 9. is there.

  Thus, since the belt cover layer 10 is composed of an organic fiber cord having high elasticity, the rigidity of the shoulder portion can be reliably increased, and thereby, the medium frequency road noise can be efficiently reduced.

  Further, in the pneumatic radial tire 1 of the present invention, the height H1 of the outer diameter of the bead filler 7 is set to 22 to 55% of the tire cross-section height SH, and the carcass layer 2 is folded back from the outer peripheral end 7a of the bead filler 7. The tire radial height H2 up to the terminal 2a is set to 11 mm or more, preferably 12 mm or more.

  In this way, the bead filler 10 is used to eliminate the deterioration factor of the riding comfort associated with the use of the high elastic fiber cord for the belt cover layer 10 by appropriately maintaining the rigidity of the sidewall portion 4 in the tire radial direction. Since the height H1 of the tire and the height H2 in the tire radial direction of the joint portion of the carcass layers 2 and 2 in the folded portion of the carcass layer 2 are adjusted within a range not impairing the steering stability, the steering stability is sacrificed. Riding comfort can be improved without any.

  The above-described height H1 of the outer diameter of the bead filler 7 refers to 1/2 of the difference between the outer diameter and the rim diameter at the outer peripheral end 7a of the bead filler 7, and the tire cross-section height SH refers to the outside of the tire. One half of the difference between the diameter and the rim diameter.

  Further, the position of the folded terminal 2 a of the carcass layer 2 may be extended to the outer diameter direction of the sidewall portion 4 and extended to the inner peripheral surfaces of the belt layers 8 and 9. Therefore, the tire radial direction height H2 of the joint portion of the carcass layers 2 and 2 described above is set to at least 11 mm.

  In the present invention, polyketone fibers, polyester fibers or lyocell fibers are preferably used as the highly elastic organic fiber cords constituting the belt cover layer 10.

  Furthermore, the shrinkage stress at 150 ° C. of the highly elastic fiber cord may be adjusted to 10 to 20 N, preferably 12 to 15 N. As a result, medium frequency road noise can be reliably reduced.

  The highly elastic fiber cord constituting the belt cover layer 10 is a narrow band-shaped body in which a plurality of cords are arranged in parallel and covered with rubber, and the angle between the band-shaped body and the tire circumferential direction is 0 to 10 °, preferably 0. It is wound around the outer periphery of the belt layers 8 and 9 in a spiral shape so as to be ˜5 °.

  The number of high elastic fiber cords driven in the belt cover layer 10 may be adjusted to 30 to 60/50 mm, preferably 35 to 45/50 mm. If the number of high-elastic fiber cords driven is less than 30/50 mm, the effect of reducing medium frequency road noise cannot be obtained sufficiently. Cause a decline in sex.

  As described above, the pneumatic radial tire of the present invention reduces the medium-frequency road noise by using a high-elasticity organic fiber cord for the belt cover layer. This is solved by appropriately maintaining the rigidity of the tire in the radial direction of the tire, and is particularly preferably used as a tire for passenger cars.

  Tire size: 195 / 65R15 91H, tire structure: FIG. 1, cord material for belt reinforcement layer, height of bead filler outer diameter H1 / tire cross-section height SH, and tire from bead filler outer peripheral edge to carcass layer folding end All the specifications except for the radial height H2 are used in common, the cord material of the belt reinforcing layer, the outer diameter height of the bead filler H1 / the tire cross-section height SH (in Table 1, simply referred to as “H1 / SH”) , And the tire radial direction height H2 from the outer peripheral edge of the bead filler to the carcass layer folding end (simply referred to as “height H2” in Table 1), as shown in Table 1, respectively, Invention tires (Examples 1, 2) and comparative tires (Comparative Examples 1, 2) were prepared. In the tire of Example 2, the cord material of the belt reinforcing layer was made different between the central region and both end regions of the belt reinforcing layer, and the cord material in the central region was nylon fiber.

  In Table 1, POK refers to a polyketone fiber with an elongation rate of 2.2% when loaded with 2.0 cN / dtex, and 66N refers to a nylon fiber with an elongation rate of 7.5% when loaded with 2.0 cN / dtex. Say.

  These five types of tires were evaluated for road noise, riding comfort and handling stability by the following test methods, respectively, and the results are also shown in Table 1.

[Road noise]
Each tire is filled with an air pressure of 220 kPa, mounted on the front and rear wheels of a vehicle (2000 cc, sedan type), and collected on the driver's seat window side while running on a test course consisting of asphalt at an average speed of 60 km / h. The sound pressure (decibel) in the 0 to 2.5 kHz region was measured with a microphone. The result was displayed by the index | exponent which sets the conventional example to 100. It shows that the reduction effect of road noise is excellent, so that a numerical value is large.

[Riding comfort and handling stability]
Each tire was filled with an air pressure of 220 kPa, mounted on the front and rear wheels of a vehicle (2000 cc, sedan type), and a test course consisting of an asphalt road surface was run at an average speed of 60 km / h, and a sensory evaluation was performed by a skilled test driver. . The result was displayed by the index | exponent which sets the conventional example to 100. It shows that riding comfort and handling stability are excellent, so that a numerical value is large.

  From Table 1, the tires of the present invention (Examples 1 and 2) are more comfortable than the conventional tires (Conventional Examples) while maintaining the road noise reduction effect and without reducing the driving stability. It turns out that it is improving. The comparative tire (Comparative Example 1) has an H2 value that is too small to improve riding comfort, and the comparative tire (Comparative Example 2) has an H1 / SH value that is too small to deteriorate steering stability. Admitted to do.

It is sectional drawing which shows the pneumatic radial tire which consists of embodiment of this invention.

Explanation of symbols

l Pneumatic radial tire 2 Carcass layer 2a Folding terminal of carcass layer 3 Tread part 4 Side wall part 5 Bead part 6 Bead core 7 Filler 7a Filler upper end 8, 9 Belt layer 10 Belt auxiliary layer

Claims (4)

The carcass layer is extended from the tread part to the bead part through the left and right sidewall parts, and the bead core embedded in the bead part is folded back from the inside to the outside so as to wrap the bead filler arranged on the outer peripheral side. In the tread portion, a plurality of belt layers having cord directions intersecting between the layers are arranged on the outer periphery of the carcass layer in the tread portion, and at least the outer periphery of both end portions of the belt layer is extended at a load of 2.0 cN / dtex. In a pneumatic radial tire provided with a belt cover layer formed by winding a highly elastic organic fiber cord having a rate of 4.0% or more,
The outer diameter height H1 of the bead filler is 22 to 55% of the tire cross-section height SH, and the tire radial height H2 from the outer peripheral end of the bead filler to the folded terminal of the carcass layer is 11 mm or more. Pneumatic radial tire.   The pneumatic radial tire according to claim 1, wherein the highly elastic organic fiber cord is made of polyketone fiber, polyester fiber, or lyocell fiber.   The pneumatic radial tire according to claim 1 or 2, wherein the highly elastic organic fiber cord has a shrinkage stress of 10 to 20 N at 150 ° C.   4. The pneumatic radial tire according to claim 1, wherein the number of driven highly elastic organic fiber cords is 30 to 60/50 mm.

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