JPH09175113A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain wandering and ensure linear movement stability by laminating a belt layer with at least three belts, dividing the belt of the innermost layer with the equatorial surface of a tire put between, disposing them at an interval, and making the other belt layers own a protruding cross-section in a width direction outside in the radial direction of the tire. SOLUTION: A belt is made to own a protruding cross-section in a width direction outside in the radial direction of the tire in the central part of a tread by disposing a rubber layer 6 at a separated part between a carcass 2 and the first belt 3-1 and includes a tire equatorial surface M. A width center of the rubber layer 6 substantially meet the tire equatorial surface M. The second and third belt plies have stepping-off and owns the protruding cross-section in a width direction outside in the radial direction of the tire because the cross-section of the rubber layer 6 is of roughly rectangle shape. It is thus possible to attain a more wandering restraint effect by disposing a groove 5-1 of the equatorial surface side of the tire at a distance of 16mm from the equatorial surface of the tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses complicated movement of a vehicle, which is unpredictable by a driver, that is, so-called wandering, which occurs when traveling 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 Recently, not only passenger cars but also light trucks,
Even in vehicles such as small trucks, trucks and buses, so-called radial tires in which carcass cords are arranged in a direction substantially orthogonal to the tire equatorial plane are often used because they are superior in wear resistance and steering stability to bias tires. Has been done.

[0003]

The adoption of radial tires has increased as the speed of vehicles 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 which suppresses wandering and improves straight running stability on a sloped road surface such as a rut.

[0005]

A belt and a tread are sequentially arranged on the outer circumference of a crown portion of a carcass straddling in a toroidal shape between a pair of bead cores, and the belt is a stack of at least three belts. The innermost belt among the belts is divided with the equatorial plane of the tire in between, and is spaced apart, and the belt that is not divided with the equatorial plane in between has a widthwise cross-sectional shape that is convex outward in the tire radial direction. It is a pneumatic radial tire characterized by.

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 two undivided belt layers have a convex cross-sectional shape in the width direction on the outer side in the radial direction of the tire, the bending deformation bs of the tread, which tends to become flat with ground contact, increases. As a result, the lateral force FCS generated near the tread ground contact end 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 divided belt layer in the separated portion of the divided belt layer has the width of the widest belt layer as BW. sometimes. 0.15 x BW-0.
It is preferably in the range of 50 × BW, and its thickness is
Usually, 1 to 5 mm is used.

Further, in comparison with the separated portion in the vicinity of the tire equatorial plane of the innermost layer belt, in the belt end region other than that,
Great rigidity is obtained by the truss effect of the three belt layers. Therefore, while maintaining the rigidity of the entire belt moderately, the mutual binding force between the belt layers is relatively weak in the vicinity of the equatorial plane of the tire, and the mutual binding force between the belt layers is strong in the other belt end regions. 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 19 according to the structure shown in FIG.
A 5 / 85R16 114 / 112LT pneumatic radial tire 1 for small trucks was prototyped according to the specifications in Table 1 with the groove arrangement changed. In FIG. 1, the carcass 2 is constituted by laminating three rubber-coated plies in which a large number of polyester cords are arranged in the radial direction, and a belt 3 and a tread 4 are arranged on the outer periphery of the carcass 2. 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), the belt 3-1 The belts 3-2 (hereinafter also referred to as the second belt) and 3-3 (hereinafter also referred to as the third belt) arranged on the outer periphery of the cord and having a relatively small inclination angle with respect to the tire equatorial plane are the cords. The tires are laminated so that they cross each other with the equatorial plane in between.

[0013]

EXAMPLES Examples will be shown below. The first belt has a cord inclination angle of 52 ° and a separation width of 4 near the tire equatorial plane.
A total of two belts having a width of 40 mm are arranged across 5 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
It is a belt, and its width is BW. 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 at a position including the tire equatorial plane M at the distance between the carcass 2 and the first belt 3-1, the belt is moved to the center of the tread. The portion has a width-direction cross-sectional shape that is convex outward in the tire radial direction. 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 44 mm
Was 0.33 × BW 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. However, the cross-sectional shape of the rubber layer 6 is not limited to this, and may be, for example, 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 Example 1 is that the first belt is a belt having a width of 125 mm, which is not divided with the tire equatorial plane sandwiched, and the rubber layer 6 is not provided. That is, the center portion of the tread does not have a widthwise sectional shape that is convex outward in the tire radial 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 the 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

Claims (3)

[Claims] 1. A belt layer and a tread are sequentially arranged on the outer circumference of a crown portion of a carcass straddling in a toroidal shape between a pair of bead cores, and the belt layer is a laminate of at least three belts. The innermost belt among the belts is divided with the tire equatorial plane in between, and separated from each other,
A pneumatic radial tire characterized in that the belt layers other than the above have a width-direction cross-sectional shape that is convex outward in the tire radial direction. 2. A rubber layer having a thickness larger than the radial thickness of the tire in the radial direction of the tire is arranged in a separated portion of the divided belt layer, and the tread corresponding to the vicinity of the end portion of the rubber layer is substantially The pneumatic radial tire according to claim 1, wherein a groove extending in the tire circumferential direction is arranged. 3. The 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 shoulder side end of the belt layer. Pneumatic radial tire.