JPH09207510A - Air-filled radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-filled radial tire which improves straight advancing stability on an inclined road surface of a rut or the like by suppressing wondering. SOLUTION: A carcass layer 2 astride in a toroidal shape between a pair of bead cores comprises a main unit part and a fold back part, an end part of the fold back part of at least one layer of the carcass layer 2 is extended to a belt layer 3, a rubber layer 6 having a thickness larger than a tire radial direction thickness in the fold back part of the carcass layer 2 is arranged between end parts sandwiching a tire equator surface M, the belt layer 3 has a width direction sectional shape protruded in a tire diametric direction outside. In an air-filled radial tire 1, a groove 5 extended substantially in a tire peripheral direction is arranged in a corresponding tread 4 in the vicinity of an end part of the rubber layer 6, and in the vicinity of a shoulder side end part of the belt layer 3, at least a sheet of reinforced layer 7 having a width 0.1 to 0.3 times the width of a belt of the broadest width is arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses a complicated movement of a vehicle that is unpredictable by a driver, that is, so-called wandering, which occurs when a vehicle travels on a road surface having an inclined portion, for example, a road surface having unevenness such as a rut. The present invention relates to a pneumatic radial tire having improved straight running stability, particularly to a light truck tire and a light truck tire, a truck and bus tire.

[0002]

2. Description of the Related Art In recent years, not only passenger cars but also vehicles such as light trucks, light trucks, trucks and buses, so-called radial tires in which carcass cords are arranged in a direction substantially perpendicular to the tire equatorial plane are bias tires. It has been widely used because it is superior in wear resistance and steering stability compared to.

[0003]

With the increase in speed of vehicles, the adoption of radial tires has increased.
As vehicles have become routinely driven at high speeds due to the expansion and improvement of the road network, the occurrence of the wandering problem has increased. Since this wandering is a dangerous phenomenon that impairs the straight running stability of the vehicle, it has become a serious problem as the performance of tires is improved.

Therefore, an object of the present invention is to propose a pneumatic radial tire that suppresses wandering and improves straight running stability on a sloped road surface such as a rut.

[0005]

[Means for Solving the Problems] A carcass layer straddling in a toroidal shape between a pair of bead cores is composed of a main body portion and a folded portion, and a belt layer and a tread are sequentially arranged on the outer periphery of the crown portion, and the belt is formed. The layers are a stack of at least two belts, the ends of at least one turnback portion of the carcass layer extend to the belt layer, and the turnover of the carcass layer is between the end portions sandwiching the tire equatorial plane. A rubber radial layer having a thickness greater than the thickness in the tire radial direction is disposed, and the belt layer has a width-direction cross-sectional shape that is convex outward in the tire radial direction.

When a tire tries to cross an inclined road surface such as a rut or the like in a direction in which the tire rides up with an approach angle, as shown in FIG. 4, a reaction force FR from the road surface occurs on the tire and the inclined road surface. Lateral force F due to camber thrust FC
y works. Here, when the tire is made to be radial, the rigidity of the tire becomes high, and the reaction force F is higher than that of the bias tire.
Since R is large and the camber thrust FC is small, the lateral force Fy is also large, which makes it impossible to smoothly run over the rut and it was found that wandering occurs. Therefore, in order to suppress the wandering in the radial tire, the lateral force Fy can be increased by increasing the camber thrust FC.
It is effective to reduce

The camber thrust FC is generated by the bending deformation in the tire cross section of the tread when the tire is grounded on the inclined road surface and is flexibly deformed. That is, as shown in FIG. 5, the tread bending deformation bS near the tread ground contact end
It can be considered as the resultant force of the lateral force FCS generated by the above and the lateral force FCC generated by the tread bending deformation bc near the tire equatorial plane. Therefore, to increase the camber thrust FC, it is sufficient to increase the FCS and decrease the lateral force FCC.

According to the present invention, since the belt layer has a cross-sectional shape in the width direction that is convex outward in the radial direction of the tire, the bending deformation bs of the tread that tends to become flat with ground contact increases, and as a result, the tread ground contact end. Lateral force F generated near the section
CS can be increased. In order to have the convex cross-sectional shape in the width direction, the rubber layer having a thickness larger than the thickness in the tire radial direction than the carcass layer in the separated portion of the folded carcass layer is when the width of the widest belt layer is BW. To It is preferably in the range of 0.15 × BW to 0.50 × BW, and the thickness thereof is usually 1 to 5 mm at least in the tire equatorial plane.

Further, since the end of the folded portion of at least one of the carcass layers extends to the belt layer, the belt end region has a large rigidity due to the truss effect of the two belt layers and the carcass layer. Is obtained. Therefore,
While maintaining the rigidity of the entire belt moderately, the mutual restraining force between the belt layers is weakened relatively near the equatorial plane of the tire,
In addition, in other belt end regions, the mutual restraining force between the belt layers can be strengthened, and the lateral force FCC generated in the tread can be reduced.

By arranging a groove extending substantially in the tire circumferential direction in the tread corresponding to the vicinity of the end portion of the rubber layer, the bending deformation bS of the tread becomes larger and occurs near the tread ground contact end portion. Lateral force FCS can be further increased. Further, at the time of vulcanization molding, the groove can prevent the rubber layer from flowing outward in the width direction, and the convex shape can be further strengthened.

In addition, by disposing at least one reinforcing layer having a width of 0.1 to 0.3 times the width of the widest belt near the end of the belt layer on the shoulder side, the internal pressure filling Since the convex shape can be further strengthened and the belt rigidity of the portion can be increased, the bending deformation bS of the tread can be significantly increased. The width of 0.1 to 0.3 times the width of the widest belt is 0.1
If it is less than twice, the convex shape cannot be strengthened sufficiently, and 0.
If it is more than 3 times, the bending deformation bS is improved, but the convex shape cannot be strengthened, and in any case, the sufficient improvement effect due to the disposition of the reinforcing layer cannot be obtained. Further, the reinforcing layer can be expected to improve the bending deformation bS regardless of whether the reinforcing layer is arranged on the outer side in the radial direction of the belt layer, inside the belt layer, or on the inner side in the radial direction of the belt layer, but since the convex shape is further strengthened. It is preferable to arrange it on the outer side in the radial direction of the belt layer.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Size according to the structure shown in FIG.
195 / 85R16 114 / 112LT pneumatic radial tire 1 for small trucks was prototyped according to the specifications in Table 1 by changing the groove layout. In FIG. 1, the carcass 2 is composed of one rubber-coated ply in which a plurality of polyester cords are arranged in the radial direction, and a belt is provided around the carcass 2.
3 and tread 4 are placed. Although the carcass 2 is composed of one sheet, since the end of the folded portion of at least one of the carcass layers extends to the belt layer, not only can the rigidity substantially the same as that of the two carcass layers be secured,
Excellent productivity. The belt 3 is composed of three steel belts, and is adjacent to the carcass, and has a relatively large inclination angle of the cord with respect to the tire equatorial plane 3-1 (hereinafter also referred to as the first belt). -1 is a belt disposed on the outer periphery of the cord and having a relatively small inclination angle of the cord with respect to the tire equatorial plane. 3-2 (hereinafter also referred to as a second belt) and 3-3 (hereinafter also referred to as a third belt) are The cords are laminated so as to intersect each other with the tire equatorial plane sandwiched therebetween.

[0013]

EXAMPLES Examples will be shown below. The first belt has a cord inclination angle of 52 ° and a width of 120 mm, the second belt has a cord inclination angle of 24 ° and a width of 135 mm, and the third belt has a cord inclination angle of 24 ° and a width of 120 mm. Of the three belts, the widest belt is the second belt, and this width is BW. Further, an end portion of at least one folded portion of the carcass layer extends to the belt layer, and a separation distance thereof is 60 mm. The tread is provided with four grooves 5 extending substantially continuously in the tire circumferential direction. Illustration of the vicinity of the bead core is omitted.

Example 1 As shown in FIG. 1, by arranging the rubber layer 6 between the first belt 3-1 and the second belt 3-2 at a position including the tire equatorial plane M, the belt Has a width-direction cross-sectional shape that is convex outward in the tire radial direction at the tread central portion. Here, in the prototype tire, the width center of the rubber layer 6 was arranged so as to substantially coincide with the tire equatorial plane M. The width of the rubber layer is 50
It corresponds to 0.37 × BW in mm, and the thickness was 3 mm. Moreover, since the rubber layer 6 has a substantially rectangular cross-sectional shape, the second and third belt plies have a width-direction cross-sectional shape that is convex outward in the tire radial direction with a step. But,
However, the cross-sectional shape of the rubber layer 6 is not limited to this, and may be a convex lens cross-sectional shape. When the convex lens has a cross-sectional shape, a wandering suppressing effect can be expected especially when the vehicle is empty or when the camber angle is small. Here, the circumferential groove depth was 9.5 mm near the tire equatorial plane and 12 mm near the ground contact end. Further, an example is shown in which the groove 5-1 on the tire equatorial plane side is located at a distance of 16 mm from the tire equatorial plane and is arranged in the tread corresponding to the vicinity of the end portion of the rubber layer 6. The more effective the layout, the greater the effect of suppressing wandering.

Example 2 Example 2 is almost the same as Example 1 except that the groove 5-1 on the tire equatorial plane side is located at a distance of 25 mm from the tire equatorial plane.

Example 3 In Example 3, as shown in FIG. 2, a width of 20 mm, which is 0.15 times the width of the widest belt, is radially outside the belt layer in the vicinity of the belt layer shoulder side end. Example 2 is substantially the same as Example 2 except that two nylon reinforcing layers 7 having

Conventional Example As a conventional example, a tire of the above size having the structure shown in FIG. 3 was prepared. The difference from the first embodiment is that the carcass is 2
The end of the folded-back part is located inside the tire maximum width position in the tire radial direction.Because there is no rubber layer 6, the belt has a tire radial outside on the center part of the tread compared to the carcass 2 shape. That is, it does not have a convex cross-sectional shape in the width direction.

After filling these tires with a specified internal pressure of 6.0 kgf / cm ² , a small truck of 2 tons loading (rear wheel is a double-wheel type)
The test driver was run on a paved road including a rut in a state where the specified maximum load was applied to the small truck, and straight running stability was sensory evaluated. The results are also shown in Table 1 in the index evaluation with the conventional example being 100 (the larger the index, the better). From the table, it is clear that the straight running stability of the tire according to the present invention is remarkably improved.

[0019]

[Table 1]

That is, according to the present invention, it is possible to suppress the wandering of the pneumatic radial tire and improve the straight running stability on an inclined road surface such as a rutted road.

[Brief description of drawings]

FIG. 1 is a tire width direction sectional view of a pneumatic radial tire according to the present invention.

FIG. 2 is a sectional view in the tire width direction of the pneumatic radial tire according to the present invention.

FIG. 3 is a sectional view in the tire width direction of a conventional example.

FIG. 4 is a schematic view showing a state in which a tire is in contact with a sloped road surface.

FIG. 5 is a schematic diagram showing deformation and lateral force when a tire is in contact with a sloped road surface.

[Explanation of symbols]

 1 Pneumatic radial tire 2 Carcass 3 Belt 4 Tread 5 Groove 6 Rubber layer 7 Reinforcement layer M Tire equatorial plane

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B60C 11/04 B60C 11/06 Z

Claims (3)

[Claims] 1. A carcass layer straddling in a toroidal shape between a pair of bead cores is composed of a main body portion and a folded portion, and a belt layer and a tread are sequentially arranged on the outer circumference of the crown portion,
The belt layer has a stack of at least two belts, the end of the folded portion of at least one layer of the carcass layer extends to the belt layer, and the carcass is provided between the ends sandwiching the tire equatorial plane. A pneumatic radial tire, wherein a rubber layer having a thickness larger than a tire radial direction thickness of a folded portion of the layer is arranged, and the belt layer has a widthwise cross-sectional shape that is convex outward in a tire radial direction. 2. The pneumatic radial tire according to claim 1, wherein a groove substantially extending in a tire circumferential direction is arranged in a tread corresponding to an end portion of the rubber layer. 3. The air according to claim 1, wherein at least one reinforcing layer having a width of 0.1 to 0.3 times the width of the widest belt is arranged near the end of the belt layer. Radial tires with.