JP2007326418A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of achieving compact design without degrading any properties such as durability. <P>SOLUTION: A pneumatic radial tire 10 includes: a dual crossing belt layer 3, of which the cord directions are intersected each other between layers, and which has a plurality of a rubberized layer of steel cord extending at an angle in the outer circumference of a crown portion of a carcass 2 with respect to an equatorial surface, and at least a single cap layer 4, of which the width is the same or longer than the total width of the dual crossing belt layer 3 and which has a rubberized layer of reinforced cord practically arranged along the tire circumference direction. The number of cords placed in the crossing belt layer 3 is set to be 25 pieces/50 mm, in addition, the elongation rate of the reinforced cord in the cap layer 4 is set to be 2% or less when a load of 1.5 kg is applied thereto and the number of the cords placed is set to be 30 pieces/50 mm or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic radial tire for a passenger car that is reduced in weight while ensuring durability and steering stability.

  In general, a pneumatic radial tire is provided with a so-called crossing belt in which at least two inclined belt layers intersecting each other are laminated on the outer periphery of a crown portion of a carcass. As a reinforcing material for such a crossing belt, a steel cord is usually used.

  In order to reduce the weight of such pneumatic radial tires, it is effective to reduce the amount of steel cords with high specific gravity, and by reducing the number of steel cords driven in the belt layer, the weight can be significantly reduced. It is known to be possible. However, if the number of steel cords to be driven is greatly reduced, the diameter growth at the time of internal pressure filling increases, and there is a concern in terms of durability.

On the other hand, from the viewpoint of weight reduction of the tire, for example, a technique using a belt including a single inclined belt layer and a circumferential belt layer using an organic fiber cord excellent in lightness has been proposed ( For example, disclosed in Patent Documents 1 and 2). Further, Patent Document 3 includes a band layer made of a composite cord having a predetermined elastic property, which is formed by twisting a high elastic filament and a low elastic filament outside the belt layer using a steel cord in the radial direction. A pneumatic tire is disclosed.
JP-A-62-152904 (Claims etc.) JP-A-4-163212 (Claims etc.) Japanese Patent No. 2757940 (Claims etc.)

  As described above, various studies have been made so far on techniques for achieving both tire weight reduction and other tire physical properties such as durability, but these are not sufficient, and these are more advanced. There was a need for a technology that could achieve both.

  Accordingly, an object of the present invention is to provide a pneumatic radial tire that achieves weight reduction without impairing other tire physical properties such as durability.

  As a result of intensive studies to solve the above problems, the present inventor has arranged a predetermined height against a cap layer that is disposed outside the steel crossing belt layer and is usually made of a low-elasticity cord, such as a nylon cord. It has been found that by using an elastic cord, it is possible to reduce the number of shots of the steel crossing belt layer while ensuring durability and to achieve weight reduction, and the present invention has been completed.

That is, the pneumatic radial tire of the present invention comprises a rubberized layer of a plurality of steel cords extending at an inclination with respect to the tire equatorial plane on the outer periphery of a crown portion of a carcass that forms a toroid shape straddling between a pair of bead cores. , Comprising at least two crossing belt layers whose cord directions intersect each other between the layers and a rubberized layer of reinforcing cords arranged substantially along the tire circumferential direction, and having a width dimension equal to or greater than the full width of the crossing belt layer In a pneumatic radial tire having at least one cap layer,
The number of driving of the crossing belt layer is 25/50 mm or less, the elongation of the reinforcing cord of the cap layer is 2% or less under a load of 1.5 kg, and the number of driving is 30/50 mm or more. It is characterized by being.

  In the present invention, it is preferable that the angle of the steel cord of the crossing belt layer is 35 ° or more with respect to the tire circumferential direction. The steel cord of the crossing belt layer is preferably a monofilament cord. Furthermore, the cap layer may be preferably two or more layers, and the angle of the crossing belt layer with respect to the tire circumferential direction of the steel cord is preferably larger in the inner layer than in the outer layer.

  Furthermore, the number of driving of the crossing belt layer is preferably within a range of 20 to 25 pieces / 50 mm, and the elongation of the reinforcing cord of the cap layer at a load of 1.5 kg is 1.0 to 1.5. %, And the number of implantations is preferably in the range of 40 to 55/50 mm.

  According to the present invention, by adopting the above-described configuration, it is possible to realize a pneumatic radial tire that achieves weight reduction without impairing other tire physical properties such as durability.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In FIG. 1, the schematic sectional drawing of the pneumatic radial tire of an example of this invention is shown. As shown in the figure, a pneumatic radial tire 10 according to the present invention includes a plurality of steel cords extending at an inclination to the tire equatorial plane on the outer periphery of a crown portion of a carcass 2 that forms a toroid straddling between a pair of bead cores 1. The rubber belt is composed of at least two crossing belt layers 3 whose cord directions intersect each other between the layers, and a rubberized layer of reinforcing cords arranged substantially along the tire circumferential direction. And at least one cap layer 4 having a width dimension equal to or greater than the entire width.

  In the tire of the present invention, the number of driving of the cross belt layer 3 is 25/50 mm or less, the elongation of the reinforcing cord of the cap layer 4 is 2% or less at a load of 1.5 kg, and the number of driving is 30 / It is characterized in that it is 50 mm or more.

  That is, it is possible to achieve a weight reduction of 7% or more as a tire weight by reducing the number of driving of the steel crossing belt layer 3 which is usually about 50 to 30/50 mm to 25/50 mm or less. became. The number of driving is preferably in the range of 20 to 25 pieces / 50 mm.

  On the other hand, in tires whose belt circumferential rigidity has decreased due to a decrease in the number of shots, since the diameter growth at the time of internal pressure increases due to the circumferential tension of the belt, the strain between the belt layers increases and the belt durability deteriorates. There are concerns. Therefore, in the present invention, a highly elastic reinforcing cord having an elongation of 2% or less at a load of 1.5 kg is applied to the cap layer 4 provided on the steel crossing belt layer 3 so that the number of driving is 30 pieces / 50 mm or more. Thus, the cap layer ensures rigidity in the tire circumferential direction and suppresses the diameter growth at the time of internal pressure, thereby preventing the deterioration of durability. Preferably, the elongation of the cap layer reinforcing cord at a load of 1.5 kg is about 1.0 to 1.5%, and the number of driving is about 40 to 55/50 mm. it can.

  Note that it is possible to secure circumferential rigidity and suppress diameter growth during internal pressure by reducing the angle of the steel crossing belt layer 3 with respect to the tire circumferential direction. The in-plane shear rigidity of the belt for generating (side force (SF)) is insufficient, the cornering power (CP) is lowered, and the stability of the vehicle is remarkably impaired. Therefore, in the present invention, the in-plane shear rigidity is ensured by setting the angle of the steel cord of the crossing belt layer 3 to preferably 35 ° or more, more preferably about 35 to 40 ° with respect to the tire circumferential direction. be able to.

  In the present invention, it is also effective to apply a monofilament cord to the steel cord of the crossing belt layer 3 in order to achieve further weight reduction and cost reduction.

  Further, as a means for suppressing the diameter growth, it is effective to make the cap layer 4 two or more layers. However, in order to increase the weight, in this case, the cap layer has 1200 dtex or less, particularly 800 to 1100 dtex. It is preferable to use a fine thread cord of a degree.

  The material for the highly elastic reinforcing cord of the cap layer 4 in the present invention is not limited, but an organic fiber cord is preferable from the viewpoint of weight reduction. For example, aramid, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyamide (PA, nylon) and these composite twisted cords can be suitably used.

  In the present invention, it is also preferable that the angle of the crossing belt layer 3 with respect to the tire circumferential direction of the steel cord is larger in the inner layer than the outer layer, that is, in the inner layer.

  In the present invention, only the configuration of the crossing belt layer 3 and the cap layer 4 as described above is important, and other details of the tire structure, material, and the like can be appropriately configured according to a conventional method. There is no particular limitation. For example, as shown in the drawing, the tire of the present invention includes a pair of bead portions 11, a pair of sidewall portions 12 connected to the bead portions 11, and a tread portion 13 connected in a toroidal shape between the sidewall portions 12. Although not shown, a tread pattern is appropriately formed on the surface of the tread portion 13, and an inner liner is formed in the innermost layer.

Hereinafter, the present invention will be described in more detail with reference to examples.
A pneumatic radial tire having the structure shown in FIG. 1 having two steel crossing belt layers and one cap layer on the outer periphery of the crown portion of the carcass is shown in Table 1 below at a tire size of 195 / 65R15. It produced according to conditions.

  Each of the obtained test tires was assembled with a rim (rim size 6 JJ), filled with an internal pressure of 200 kPa and mounted on an actual vehicle, and a driver's feeling of steering stability performance was tested. The results were indexed with the comparative example as 100. Regarding steering stability, the larger the value, the better the result. Further, the weight of each test tire was indexed with a comparative example as 100. Regarding the weight, the smaller the value, the lighter the weight. These results are also shown in Table 1 below.

＊１）タイヤ周方向に対する角度を示す。

* 1) Indicates the angle with respect to the tire circumferential direction.

  As shown in Table 1 above, the number of driving of the cross belt layer is 25/50 mm or less, the elongation of the reinforcing cord of the cap layer is 2% or less at 1.5 kg load, and the number of driving is It was confirmed that the tires of Examples 1 to 3 having 30 pieces / 50 mm or more are lighter than the tires of Comparative Examples that do not satisfy these conditions, and are excellent in handling stability. .

1 is a schematic cross-sectional view of a pneumatic radial tire according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Crossing belt layer 4 Cap layer 10 Pneumatic radial tire 11 Bead part 12 Side wall part 13 Tread part

Claims (8)

At least two steel cord rubberized layers extending at an inclination to the tire equator plane on the outer periphery of a toroidal carcass crown straddling between at least a pair of bead cores, the cord directions intersecting each other between the layers An air having a cross belt layer of layers and at least one cap layer having a width dimension equal to or greater than the full width of the cross belt layer, which is formed of a rubberized layer of reinforcing cords arranged substantially along the tire circumferential direction. In entering radial tires,
The number of driving of the crossing belt layer is 25/50 mm or less, the elongation of the reinforcing cord of the cap layer is 2% or less under a load of 1.5 kg, and the number of driving is 30/50 mm or more. A pneumatic radial tire characterized by being.   The pneumatic radial tire according to claim 1, wherein the angle of the steel cord of the crossing belt layer is 35 ° or more with respect to the tire circumferential direction.   The pneumatic radial tire according to claim 1 or 2, wherein the steel cord of the crossing belt layer is a monofilament cord.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the cap layer has two or more layers.   The pneumatic radial tire according to any one of claims 1 to 4, wherein an angle of the steel cord of the crossing belt layer with respect to a tire circumferential direction is larger in the inner layer than in the outer layer.   The pneumatic radial tire according to any one of claims 1 to 5, wherein the number of driving of the crossing belt layers is in a range of 20 to 25 pieces / 50 mm.   The pneumatic radial tire according to any one of claims 1 to 6, wherein an elongation at a load of 1.5 kg of the reinforcing cord of the cap layer is in a range of 1.0 to 1.5%.   The pneumatic radial tire according to any one of claims 1 to 7, wherein a number of driving of the reinforcing cords of the cap layer is in a range of 40 to 55 pieces / 50 mm.

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