JP5030545B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire suitable for use as a tire for a passenger car, and in particular, a technique for increasing out-of-plane bending rigidity in the width direction of the tread portion while suppressing an increase in circumferential rigidity of the tread portion. This is a proposal.

  For this type of pneumatic radial tire with steel cord belt layer, the inclination angle of each steel cord of the two belt layers with respect to the tire equatorial plane is intended to enhance the effect on the tread. Is set to a small angle of about 15 to 35 °, for example, and those steel cords are extended in opposite directions between the layers with respect to the tire equatorial plane.

  However, in such a radial tire, two steel cord belt layers are used, and the out-of-plane bending rigidity in the tread portion width direction, for example, in the tire load motion, the tread portion ground contact surface has a cross section in the tire width direction. As a result, it is difficult to increase the rigidity against the pushing force acting inward in the radial direction. Bending deformation with a small radius of curvature will occur, and this will cause concentration of contact pressure on the tread shoulder part, which will cause local premature wear on the tread shoulder part. was there.

  In order to cope with such early wear of the tread part, it is effective to suppress the occurrence of bending deformation with a small curvature radius on the tread shoulder part by increasing the out-of-plane bending rigidity in the width direction of the tread part. In order to achieve this, a third steel cord comprising a steel cord having an angular arrangement close to the meridian direction of the tire is further provided on the outer peripheral side of the two-layer steel cord belt layer that functions to ensure the effect on the tread portion. It is conceivable to arrange a belt layer.

  The steel cord of the third belt layer is located close to the tread portion ground contact surface when the tread portion is subjected to inward deformation in the radial direction, as seen in the cross section in the tire width direction, and is bent. Since it exists on the compression side from the neutral shaft, it functions to increase the out-of-plane bending rigidity in the cross-sectional view in the width direction of the tread part by exhibiting high compression rigidity in relation to their extending direction. be able to.

  However, the steel of the third belt layer that extends at an angle close to the meridian direction of the tire simply by adding the third steel cord belt layer to the conventional two-layer steel cord belt layer. The cord suppresses Poisson deformation against tensile in the circumferential direction to increase circumferential tensile rigidity and strengthens the effect, but the ground contact length in the center area of the tread portion is shortened, while the ground contact length of the tread shoulder portion is reduced. As a result, there is a problem that the tread shoulder portion protrudes and uneven wear occurs in the shoulder portion.

  An object of the present invention is to solve such problems of the prior art, and the object of the present invention is to effectively suppress an increase in tensile rigidity in the circumferential direction of the tread portion, while The third steel cord belt layer increases the out-of-plane bending stiffness in the width direction of the tread, which can greatly improve wear resistance without causing uneven wear on the tread shoulder. To provide radial tires.

The pneumatic radial tire according to the present invention includes a tread portion, a pair of sidewall portions connected to the respective side portions of the tread portion, and a bead portion continuous to the inner peripheral side of each sidewall portion, A carcass extending in a toroidal manner between a pair of bead portions, and a belt comprising three steel cord belt layers disposed on the outer peripheral side of the crown region of the carcass to reinforce the tread portion. Furthermore, it is possible to dispose a belt auxiliary layer such as a so-called cap or layer on the outer peripheral side, and each steel cord of the two belt layers of the innermost layer belt layer and the intermediate layer belt layer, Inclined in opposite directions to each other at an angle in the range of 20 to 45 ° with respect to the tire equator plane, for example, extends symmetrically with respect to the equator line, and The steel cord of the coat layer, extend inclined at an angle in the range of 45 to 90 ° with respect to the tire equatorial plane, the circumferential tensile rigidity of the entire belt consisting of three layers of the belt layer, in a range of 500kPa~3000kPa It will be.

More preferably in such tires, in each of the respective steel cord belt layers of the three layers, the number of implantation of the steel cord consisting of three to eight filaments, shall be the 10 to 40 pieces of range per 50 mm.

  Here, the “belt circumferential tensile stiffness” is a belt member having a thickness of 3 mm and a width of 30 mm cut out from the tread portion of the tire (in this case, all three belt layers are included in the thickness of 3 mm). Steel cord)), the stress when 1% strain is generated in the circumferential direction, and here, in order to reproduce the belt rigidity in the tire, the belt member is deformed out of plane when pulled It shall be the value when the measurement is carried out while restraining from the outside so as not to occur.

  The local premature wear of the tread shoulder portion of the conventional tire caused by the indentation deformation of the tread surface when the tire is in contact with the ground is low in the out-of-plane bending rigidity of the tread portion in the cross section in the width direction. In order to suppress the occurrence of such local deformation of the tread shoulder portion, as described above, the width direction of the tread portion is caused by the portion being deformed with a small radius of curvature. It is effective to increase the out-of-plane bending rigidity in the cross section.

  That is, the tread portion ground contact surface that has a convex curve shape radially outward in the cross section in the width direction of the tread portion is a flat surface that is subjected to a radially inward out-of-plane indentation deformation at the time of ground contact due to tire rolling. Therefore, exhibiting high rigidity against such out-of-plane bending deformation is effective for improving wear resistance.

  Therefore, in the tire according to the present invention, with respect to the out-of-plane bending deformation of the tread portion, the steel is located near the tread portion grounding surface, which is positioned on the compression side from the neutral axis of bending, with respect to the tire equator surface. The outermost belt layer in which the cord extends at a large angle in the range of 45 to 90 ° is disposed, and the steel cord exhibits a high compression resistance, thereby effectively increasing the out-of-plane bending rigidity. Collateral.

  By the way, when the steel cord belt layer of the outermost layer is simply added to the steel cord belt layers of the innermost layer and the intermediate layer, which have sufficient effects on the tread portion, as described above, the belt In the present invention, there is a possibility that uneven wear occurs in the tread shoulder due to an increase in the rectangular ratio due to suppression of Poisson deformation due to excessively high circumferential tensile rigidity of the steel. In order to make the circumferential tensile rigidity of the belt composed of two layers equal to that of a conventional belt composed of two steel cord belt layers, the steel cords of the innermost layer and the intermediate layer of each belt layer with respect to the tire equatorial plane By increasing the tilt angle to 20-45 °, which is larger than that of the conventional technology, the belt's circumferential tensile rigidity can be increased. It has won.

  And in this pneumatic radial tire, in addition to the above, the circumferential tensile rigidity of the belt is the number of steel cords driven by three to eight filaments for each of the three steel cord belt layers. By making the range from 10 to 40 per 50 mm, it can be more effectively suppressed.

  By the way, in the pneumatic radial tire of size 205/55 R16, the belt is composed of two steel cord belt layers, and the steel cord twist structure is 1 × 5 × 0.23, and the tire equator of each steel cord In contrast to the conventional structure in which the inclination angle with respect to the surface is 25 ° and the number of steel cords driven in each belt layer is 36/50 mm, the inclination angle of the steel cord of the innermost layer and the intermediate layer with respect to the tire equatorial plane is 33 °, the inclination angle of the steel cord of the outermost layer belt layer with respect to the tire equator plane is 90 °, and the number of steel cords of the belt layers of each of the three layers is 18/50 mm, the same Under the application of a steel cord having a twisted structure, the circumferential tensile rigidity of the belt can be made substantially equal.

  As described above, tires with a size of 205/55 R16 have been described as an example. However, with respect to tires of other sizes, conventionally, the inclination angle of the steel cord of the belt structure having two belt layers is mostly In the belt structure according to the present invention, which is a three-layer belt, the cord inclination angles of the innermost layer and the intermediate layer are set to 20 to 45 °. By adjusting within the range, it is possible to effectively cope with an increase in the circumferential tensile rigidity of the belt.

  By the way, when the number of steel cords to be driven is increased under the belt structure composed of three belt layers according to the present invention, the cord inclination angles of the belt layers of the innermost layer and the intermediate layer are made larger. It is possible to easily achieve the circumferential tensile rigidity equivalent to the conventional technology. Conversely, when reducing the number of steel cords to be driven, it is necessary to reduce the inclination angle of the belt layer cord with respect to the tire equatorial plane. Can do. And in any of these cases, it is possible to cope with the change of the twist structure of the steel cord.

Also, in any of these cases, when the circumferential tensile rigidity of the belt composed of three belt layers is set in the range of 500 to 3000 kPa, the tread shoulder portion is prevented from being deformed and excellent. It is possible to ensure the high wear resistance and uneven wear.
On the other hand, when the rigidity exceeds 3000 kPa, the tread shoulder portion is greatly deformed and uneven wear occurs in the shoulder portion. On the other hand, if it is less than 500 kPa, the tire shape cannot be maintained, and not only the wear resistance is deteriorated but also the durability is lowered.

  FIG. 1 is a cross-sectional view in the width direction of a pneumatic radial tire showing an embodiment of the present invention, in which 1 is a tread portion and 2 is a radial direction continuously to each side portion of the tread portion 1. A pair of sidewall portions extending inwardly, and 3 indicates a bead portion continuous on the inner peripheral side of each sidewall portion.

  In the figure, reference numeral 4 denotes a bead core embedded in each bead portion 3, and reference numeral 5 denotes a radial structure carcass comprising one or more carcass plies extending toroidally between the bead cores to form a tire skeleton. Each side portion of the carcass 5 is wound around and fixed around each bead core 4.

  Here, on the outer peripheral side of the crown region of the carcass 5, a belt 9 composed of three steel cord belt layers 6, 7, 8 and contributing to reinforcement of the tread portion is disposed. Both side portions are covered from the outer peripheral side by one or more layers as a belt auxiliary layer, in the drawing, two layers 10.

  Further, as shown in the figure, the widths of the belt layers 6, 7, and 8 are sequentially made narrow toward the outer side in the radial direction, and the main parts are illustrated in a partially developed plan view in FIG. The steel cords 6a, 7a of the innermost layer belt layer 6 and the intermediate layer belt layer 7 are inclined in opposite directions at an angle in the range of 20 to 45 ° with respect to the tire equatorial plane, for example, FIG. The steel cord 8a of the outermost layer belt layer 8 is inclined and extended at an angle in a range of 45 to 90 ° with respect to the tire equator plane E.

  In the belt 9 composed of the three steel cord belt layers 6, 7, 8, in particular, by setting the inclination angle of the steel cord 8 a of the outermost belt layer 8 with respect to the tire equatorial plane E to such a large angle, the tire As shown in the cross-sectional view in the width direction in FIG. 3, the tread portion ground contact surface is flattened radially inward in the direction of the imaginary line under the action of the road surface reaction force F. The outermost belt layer 8, which is positioned closest to the ground contact surface of the tread portion 1 and on the compression side from the neutral axis of the bend of the tread portion 1, Since the steel cord 8a provides a sufficiently large compressive drag, the out-of-plane bending rigidity in the width direction of the tread portion 1 is effectively increased. As a result, the tread shoulder portion is moved to the tread shoulder portion. , So that the premature wear due to the generation of a small radius of curvature local bending deformation is effectively prevented.

  In addition, here, the inclination angle of the steel cords 6a, 7a of the belts 6, 7 of the innermost layer and the intermediate layer with respect to the tire equatorial plane E is set to a large angle of 20 to 45 °, so that three belt layers 6, In addition, as a belt structure to be 7 or 8, the increase in the circumferential tensile rigidity of the belt 9 and hence the tread portion 1 with respect to the prior art is effectively suppressed, and uneven wear on the shoulder portion 11 of the tread portion 1 is prevented. Can also be effectively prevented.

In such a tire, more preferably, the number of driven steel cords 6a, 7a, 8a composed of three to eight filaments of the three steel cord belt layers 6, 7, 8 is 10 per 50 mm. The range is ˜40.
Incidentally, the circumferential tensile rigidity of the belt 9, the range of 500～3000KPa.

Pneumatic radial tires having a size of 205/55 R16 and having the specifications shown in Table 1 were prototyped and various performances were evaluated. Table 1 also shows the evaluation effect.
Note that the steel cord twist structures used were all 1 × 5 × 0.23.

  In the table, 1 belt, 2 belts and 3 belts are obtained by counting the belt layers in order from the inner layer side.

  “Tread part width direction out-of-plane bending stiffness” in the table is when a cut sample cut out in a length of 3 cm in the circumferential direction at the tread part is subjected to 10 mm out-of-plane bending deformation inward in the radial direction. The load is indicated by an index using the conventional tire as a control.

  Further, “belt circumferential tensile rigidity” indicates a stress value (kPa) when a belt member is cut out with a thickness of 3 mm and a width of 30 mm and is distorted by 1% in the circumferential direction.

  “Tire outer diameter” indicates the tire outer diameter at the time of air pressure filling of 230 kPa, and “Rectangular ratio” is measured from a footprint when a load of 3.92 kN is applied in an internal pressure state of 230 kPa. Indicates the value.

  According to Table 1, in the example tire and the comparative example tires 1 and 2 having three steel cord belt layers, the out-of-plane bending rigidity in the tread portion width direction is greatly increased. It can be seen that the change in the inclination angle of the above does not greatly affect the rigidity.

  Further, in the comparative example tire 1 in which the 1 and 2 belt cord inclination angles are reduced to 18 °, the belt circumferential tensile rigidity is extremely increased, the diameter growth (tire outer diameter) on the tire equator line is suppressed, and the rectangular ratio 109%, and the tread shoulder portion is in a protruding state, whereas in the comparative example tire 2 in which the 1 and 2 belt cord inclination angle is increased to 47 °, the circumferential tensile rigidity is extremely reduced. It can be seen that the tire diameter growth is greatly increased due to the lowering of the belt effect.

  However, in the example tires in which the 1 and 2 belt cord inclination angle is 33 °, the tensile strength in the belt circumferential direction is equivalent to that of the conventional tire having a belt structure having two belt layers. It can be made equivalent to a tire, and it can be seen from the rectangular ratio that the protrusion of the shoulder portion of the tread portion is effectively suppressed.

  Among the prototype tires as described above, the conventional tire, the example tire, and the comparative tire 1 were evaluated for wear resistance, actual vehicle stability, and high-speed durability. The results shown in Table 2 were obtained.

Here, “wear resistance” is the reciprocal of the amount of wear after a tire is mounted on a standard rim as defined by the JATMA standard, filled with the maximum air pressure corresponding to the maximum load capacity and mounted on a passenger car, and running on a paved road for 10,000 km. Indicates the index value when the conventional tire is 100,
“Actual vehicle maneuverability” means that after a tire is mounted on a standard rim defined by the JATMA standard, the maximum air pressure corresponding to the maximum load capacity is filled, and the tire is driven on a dry road by a vehicle mounted on four wheels. The driver's feeling is an index of steering stability.
“High-speed durability” means that after a tire is mounted on a standard rim defined by JATMA standard, the tire is loaded on a drum under conditions of 300 kPa and a load of 5.3 kN, and every 20 minutes. The drum rotation speed was increased by 10 km / h, and the time until failure occurred was measured and indexed.

  The index values in the table indicate better results as the conventional tire is used as a control.

  According to Table 2, in the example tire and the comparative example tire 1 having three steel cord belt layers, wear resistance is improved as a result of suppressing local bending deformation of the tread shoulder portion. This is remarkable in the example tire in which the tension in the belt circumferential direction is equal to that of the conventional tire and the tread shoulder portion is prevented from protruding.

  Further, in the example tire, the tread shoulder portion has improved local vehicle stability due to the effect of suppressing local bending deformation with a small curvature radius, and at the same time, the tread portion caused by the projecting deformation of the shoulder portion. By suppressing the heat generation, high-speed durability can also be improved.

  In short, in the example tire, the wear resistance can be greatly improved based on the uniform contact pressure, and the actual vehicle stability and high-speed durability can also be effectively improved.

It is sectional drawing of the width direction which shows embodiment of this invention. It is a partial expansion top view which illustrates cord arrangement of each steel cord belt layer. It is explanatory drawing which shows the effect | action of a belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 5 Carcass 6, 7, 8 Steel cord belt layer 6a, 7a, 8a Steel cord 9 Belt 10 Layer 11 Shoulder part E Tire equatorial surface

Claims (2)

A tread portion, a pair of sidewall portions that are continuous to the side portions of the tread portion, and a bead portion that is continuous on the inner peripheral side of each sidewall portion, and a carcass that extends toroidally between the pair of bead portions; and A pneumatic radial tire comprising a belt composed of three steel cord belt layers disposed on the outer peripheral side of the crown region and reinforcing a tread portion,
The steel cords of the two belt layers of the innermost layer belt layer and the intermediate layer belt layer are inclined and extended in directions opposite to each other at an angle in a range of 20 to 45 ° with respect to the tire equator plane, The steel cord of the outermost belt layer is inclined and extended at an angle in the range of 45 to 90 ° with respect to the tire equator plane ,
A pneumatic radial tire in which the circumferential tensile rigidity of the belt is in the range of 500 to 3000 kPa .   2. The pneumatic radial tire according to claim 1, wherein the number of steel cords composed of three to eight filaments in each of the three steel cord belt layers is within a range of 10 to 40 per 50 mm.

Images