JP2008001248A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for improving a high-speed durability while maintaining effect of reducing load noise. <P>SOLUTION: In the pneumatic radial tire 1, a belt cover layer 6 winding organic fiber cords around belt layers 4, 5 is formed in the tire circumferential direction. An expansion rate in loaded with 2.0 cN/dtex of the organic fiber cords composing the belt cover layer 6 is made to be 4.0 to 9.0% in an intermediate area A of the belt cover layer 6, and 1.5 to 3.5% in both ends areas B, B of the both sides. Highly elastic fiber cords 6b whose expansion rate is 1.5 to 3.5% are disposed at a central part C in the intermediate area A. <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 high-speed durability while maintaining the effect of reducing road noise.

  A belt cover layer in which a heat-shrinkable organic fiber cord such as nylon fiber is wound in the tire circumferential direction is formed on the outer peripheral side of the belt layer on the tread portion of the pneumatic radial tire for high-speed running. The belt cover layer formed in this way suppresses lifting due to the centrifugal force at both ends of the belt layer during high-speed running, thereby preventing peeling failure at the belt layer end and improving high-speed durability. By increasing the rigidity of the section, the natural frequency of the secondary section is increased to suppress vibration transmission to the vehicle interior, and the medium frequency road noise that is resonance sound in the vehicle interior is reduced.

  Conventionally, as a measure to satisfy both the improvement of high-speed durability and the reduction of road noise, polyketone fiber cords with higher elastic modulus than nylon fibers only in the width direction end regions (shoulder regions) of the belt cover layer described above There is a proposal to replace with (see Patent Document 1). However, with the recent high performance of vehicles, when super-high-speed running is performed, the belt layer layer has a lack of tagging effect in the intermediate region of the tread portion, particularly the central portion thereof, and high speed There was a problem that the tire outer diameter grew during running and durability was lowered.

As a countermeasure, attempts have been made to use high-elasticity fiber cords such as polyketone fiber cords not only at both ends (shoulder region) of the belt cover layer, but also throughout the belt cover layer. Then, since the high elastic fiber cord has low elongation, the high elastic fiber cord bites into the belt layer in the lift process during vulcanization molding, and the interlayer gauge between the belt cover layer and the belt layer becomes thin, resulting in high speed durability. Was found to be the cause of the decline.
JP 2004-306634 A

  An object of the present invention is to solve such a conventional problem and to provide a pneumatic radial tire in which high-speed durability is improved while reducing road noise.

  In order to achieve the above object, a pneumatic radial tire according to the present invention has a plurality of belt layers in which cord directions are crossed between layers on an outer periphery of a carcass layer in a tread portion, and an organic fiber cord is disposed on the outer periphery of the belt layer. Is formed in the tire circumferential direction, and a high elastic fiber cord is used as the organic fiber cord in both end regions of the belt cover layer, and the elastic modulus is lower in the middle region than the high elastic fiber cord. In a pneumatic radial tire using a low elastic fiber cord, a low elastic fiber cord having an elongation rate of 4.0 to 9.0% at a load of 2.0 cN / dtex is disposed in the intermediate region, The gist is that the high-elasticity fiber cords each having an extension ratio of 1.5 to 3.5% are arranged at the center of the intermediate region.

Furthermore, in the structure mentioned above, it is preferable to comprise as described in (1)-(4) below.
(1) The twist coefficient α defined by the following formula is set to 740 to 2100 in the low elastic fiber cord and 1000 to 2800 in the high elastic fiber cord.

α = N × (T / 1.111) ^1/2
However, N: Number of upper twists (times / 100 mm), T: Total fineness of cord (dtex)
(2) The winding width of the both end regions is W / 10 to W / 3 with respect to the maximum width W of the belt layer per side, and the winding width of the central portion is W / 20 to W / 4.
(3) The low elastic fiber cord is made of nylon fiber, and the high elastic fiber cord is made of polyketone fiber, polyester fiber or lyocell fiber.
(4) The end of the belt cover layer is positioned between 20 mm on the outer side in the tire width direction and 5 mm on the inner side in the tire width direction with respect to the end of the maximum width of the belt layer.

  According to the present invention, when both end regions of the belt cover layer are configured with high elastic fiber cords, and when the intermediate region is configured with low elastic fiber cords, the high elastic fiber cords are further disposed in the central portion of the intermediate region. Therefore, at high speed running, both ends of the belt layer prevent the belt end from rising due to the hook effect of the high elastic fiber cord that constitutes the belt cover layer, improving high speed durability and simultaneously suppressing road noise. In the central portion of the belt layer, the growth of the outer diameter of the tire can be suppressed and the high-speed durability can be improved by the hoop effect of the belt cover layer made of a highly elastic fiber cord.

  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, and FIG. 2 is a cross-sectional view schematically showing an arrangement relationship of a belt layer and a belt cover layer in the tire of FIG. is there.

  In FIG. 1, a pneumatic radial tire 1 includes a plurality of belt layers 4 and 5 (two layers in the figure) in which the cord directions intersect each other on the outer periphery of the carcass layer 3 in the tread portion 2, and the belt layer 5 A belt cover layer 6 in which an organic fiber cord is wound in the tire circumferential direction is formed on the outer periphery. As the organic fiber cord, a high elastic fiber cord 6b is used for both end regions B and B of the belt cover layer 6, and a low elastic fiber cord 6a having a lower elastic modulus than the high elastic fiber cord 6b is used for the intermediate region A. Has been.

  Furthermore, in the pneumatic radial tire 1 of the present invention, the high elastic fiber cord 6b is also disposed in the central portion C in the intermediate region A. The low elastic fiber cord 6a disposed in the middle region A has an elongation rate of 2.0 to 9.0% when loaded with 2.0 cN / dtex, and is disposed in both end regions B and B and the central portion C. The high elastic fiber cord 6b has an elongation rate of 1.5 to 3.5% when loaded with 2.0 cN / dtex.

  Thus, during high-speed running, the belt layers 4 and 5 can be prevented from rising at the both ends of the belt layers 4 and 5 due to the tagging effect of the high elastic fiber cord 6b to improve the high-speed durability. At the same time, road noise can be suppressed, and at the center of the belt layers 4 and 5, the growth of the tire outer diameter can be suppressed and the high-speed durability can be improved by the hoop effect of the belt cover layer 6 made of the high elastic fiber cord 6b.

  In the present invention, the organic fiber cord used for the belt cover layer 6 has a twist coefficient α defined by the following formula of 740 to 2100 in the low elastic fiber cord 6a and 1000 to 2800 in the high elastic fiber cord 6b. It is good to set so that

α = N × (T / 1.111) ^1/2
However, N: Number of upper twists (times / 100 mm), T: Total fineness of cord (dtex)
When the above-described twist coefficient α is less than the lower limit value of the above-described range, the durability of the organic fiber cord is reduced, and when the upper limit value is exceeded, the road noise reduction effect and the high-speed durability improvement effect are reduced. become.

  FIG. 2 is a cross-sectional view schematically illustrating the arrangement relationship of the belt layers 4 and 5 and the belt cover layer 6 in a flat shape, and the winding width of the highly elastic fiber cord 6b in the pneumatic radial tire 1 of the present invention is as follows. The winding width Wb of both end regions B and B is W / 10 to W / 3 with respect to the maximum width W of the belt layers 4 and 5 per side, and the winding width Wc of the central portion C is W / 20 to W / 4. It is good to set so that

  If the winding width Wb of the both end regions B and B described above is less than W / 10, the effect of reducing road noise and improving the high-speed durability is lowered, and the winding width Wb of both end regions B and B is W / 3. If it becomes super or the winding width Wc of the central portion C deviates from the above-described range, the effect of improving the high-speed durability is lowered. In addition, Wa in the figure has shown the winding width | variety of the low elastic fiber cord 6a in the intermediate | middle area | region A. FIG.

  In the present invention, nylon fiber is preferably used as the low elastic fiber cord 6a constituting the belt cover layer 6, and polyketone fiber, polyester fiber or lyocell fiber is preferably used as the high elastic fiber cord 6b.

Further, as shown in FIG. 3, the belt cover layer 6 has a terminal 6z that is 20 mm away from the maximum width terminal of the belt layers 4 and 5 (the terminal 4z of the belt layer 4 in the figure) outward in the tire width direction. It may be arranged so as to be located between (1) and a point Y that is 5 mm away from the inside in the tire width direction. In this case, the end of the belt layer other than the belt layer having the maximum width described above (the end 5z of the belt layer 5 in the figure) is preferably covered with the belt cover layer 6. As a result, it is possible to more reliably satisfy the road noise reduction effect and the high-speed durability improvement effect during high-speed driving.

  In the above-described embodiment, the high elastic fiber cord 6b arranged in the central portion C of the intermediate region A of the belt cover layer 6 is shown on the outer peripheral side of the low elastic fiber cord 6a in the intermediate region A. The high elastic fiber cord 6b disposed in the central portion C may be disposed on the inner peripheral side of the low elastic fiber cord 6a in the intermediate region A as shown in FIG. 4, or as shown in FIG. The arrangement of the low elastic fiber cord 6a in A may be divided into left and right, and the high elastic fiber cord 6b may be arranged therebetween. In the case shown in FIG. 5, it is preferable not to provide a gap between the low elastic fiber cord 6a and the high elastic fiber cord 6b.

  A conventional tire (conventional example) in which the tire size is 195 / 65R15 91H and the high elastic fiber cord 6b is not disposed in the central portion C of the intermediate region A, and the high elastic fiber is provided in the central portion C of the intermediate region A as shown in FIG. Tires of the present invention (Examples 1 to 3) and comparative tires (Comparative Examples 1 and 2) in which the cord 6b is arranged, and a comparative tire (Comparative Example 3) using the high elastic fiber cord 6b throughout the belt cover layer 6 , Respectively.

These seven types of tires were evaluated for road noise and high-speed durability by the following test methods, respectively, and the results are also shown in Table 1. In Table 1, 66N represents nylon 66 fiber, and POK represents polyketone fiber.
[Road noise]
Each tire is filled with an air pressure of 200 kPa and attached to the front and rear wheels of the vehicle (Mark ■, 2.0 Grande). The test course consisting of an asphalt road surface is run at an average speed of 60 km / h and attached to the backrest of the driver's seat. The sound pressure (decibel) in the 40 to 1000 Hz region was measured with a sound collecting 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.
[High-speed durability]
Each tire is filled with air pressure 210 kPa, and an indoor drum endurance test (drum diameter: 1707 mm) is loaded with a load corresponding to 88% of the maximum load capacity specified by JATMA, and the running speed is 81 km / h, and the load is adjusted for 120 minutes. After running, let cool for 3 hours, readjust the air pressure to 210 kPa, increase the initial speed to 121 km / h and increase the speed by 8 km / h every 30 minutes until the tire breaks Was measured. The result was displayed by the index | exponent which sets the conventional example to 100. The larger the value, the better the high-speed durability.

  From Table 1, it can be seen that the tires of the present invention (Examples 1 to 3) improve the high-speed durability while maintaining the road noise reduction effect as compared with the conventional tire (Conventional Example). In the comparative tire (Comparative Example 1), the extension ratio of the cord 6b in both end regions B and B was too large, so the tagging effect was insufficient and both road noise and high-speed durability deteriorated. Comparative tire (Comparative Example 2) Since the expansion rate of the cord 6a in the intermediate area A is too large, it can be seen that the tagging effect is insufficient and the road noise is deteriorated.

  On the other hand, in the comparative tire (Comparative Example 3) using high elastic fiber cords in the entire belt cover layer 6, the elongation ratio of the cords in the intermediate region A of the belt cover layer 6 was too small. It was confirmed that the high elastic fiber cords bite into the belt layer, the interlayer gauge between the belt cover layer and the belt layer was thinned, and the high-speed durability was lowered.

1 is a half sectional view showing a pneumatic radial tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the arrangement relationship between a belt layer and a belt cover layer in the tire of FIG. FIG. 2 is a partial cross-sectional view for explaining an arrangement relationship between end portions of a belt layer and a belt cover layer in the tire of FIG. 1. It is sectional drawing equivalent to FIG. 2 which shows the arrangement | positioning relationship of the belt layer and belt cover layer which consist of other embodiment of this invention. It is sectional drawing equivalent to FIG. 2 which shows the arrangement | positioning relationship of the belt layer which consists of further another embodiment of this invention, and a belt cover layer.

Explanation of symbols

l Pneumatic radial tire 2 Tread part 3 Carcass layer 4, 5 Belt layer 6 Belt cover layer 6a Low elastic fiber cord 6b High elastic fiber cord A Middle area B Both end area

Claims (5)

A belt cover layer is formed on the outer periphery of the carcass layer in the tread portion with a plurality of belt layers crossing the cord directions between the layers, and an organic fiber cord is wound around the outer periphery of the belt layer in the tire circumferential direction, and In a pneumatic radial tire using a high elastic fiber cord in both end regions of the belt cover layer as an organic fiber cord, and using a low elastic fiber cord having a lower elastic modulus than the high elastic fiber cord in an intermediate region,
A low elastic fiber cord having a stretch rate of 4.0 to 9.0% at a load of 2.0 cN / dtex is disposed in the intermediate region, and the stretch rate is 1 in each of the both end regions and the central portion of the intermediate region. A pneumatic radial tire in which a high elastic fiber cord of 5 to 3.5% is arranged. 2. The pneumatic radial tire according to claim 1, wherein a twist coefficient α defined by the following equation is 740 to 2100 in the low elastic fiber cord and 1000 to 2800 in the high elastic fiber cord.
α = N × (T / 1.111) ^1/2
However, N: Number of upper twists (times / 100 mm), T: Total fineness of cord (dtex)   The winding width of the both end regions is W / 10 to W / 3 with respect to the maximum width W of the belt layer per side, and the winding width of the central portion is W / 20 to W / 4. Pneumatic radial tires.   The pneumatic radial tire according to claim 1, 2 or 3, wherein the low elastic fiber cord is made of nylon fiber, and the high elastic fiber cord is made of polyketone fiber, polyester fiber or lyocell fiber. 5. The air according to claim 1, wherein the end of the belt cover layer is located between a tire width direction outer side 20 mm and a tire width direction inner side 5 mm with respect to a maximum width end of the belt layer. Entering radial tire.

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