JP3445348B2 - Pneumatic radial tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having an annular recess in a predetermined area in the width direction of a tread portion, which has excellent high-speed durability while suppressing an increase in tire weight and cost as much as possible. is there.

[0002]

2. Description of the Related Art Generally, a pneumatic radial tire having an annular concave portion in the width center of a tread portion is known to be excellent in drainage performance especially during high speed running. The depth of the recess of the annular recess of the tire is preferably large because the drainage becomes more advantageous as the volume of the recess is larger, but the thickness of the tread portion is restricted. Therefore, it is useful to recess the carcass and the belt along the tread circumference inward in the tire radial direction corresponding to the annular recess of the tread portion to further increase the recess depth of the annular recess. Radial tires are also known.

[0003]

In the pneumatic radial tire described above, the belt end and the center of the belt are easily expanded in the tire radial direction due to centrifugal force during high-speed running. There is a possibility that the belt separation may occur due to the interaction with the resulting deformation, and the high speed durability may be deteriorated. Therefore, as a member that reinforces the belt, a cap layer that covers the entire outer surface of the belt, a narrow layer-layer that covers the belt end, and a narrow belt auxiliary layer that covers the center of the belt must be arranged. Compared with a general tire that has a normal belt structure that does not include a cap layer and a layer layer, the tire weight increases by the amount of the member that reinforces the belt, so rolling resistance increases and fuel consumption deteriorates. Had. Further, since the belt structure becomes complicated, it is disadvantageous in terms of productivity and cost. Therefore, it is necessary for the tire to improve high-speed durability without deteriorating the weight and cost of the tire.

Therefore, the present invention has an excellent drainage property,
An object of the present invention is to provide a pneumatic radial tire having an annular recess in the width center of a tread portion with excellent high-speed durability while suppressing increase in tire weight and cost as much as possible.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a belt in which cord rubberized layers are cross-laminated on the outer periphery of a toroidal carcass and at least one cord rubber that substantially wraps the entire outer periphery of the belt. A tread portion reinforced with a belt and a hoop reinforcing layer, the tread portion having a carcass and a belt in a predetermined area in the width direction, and a tread circumference inward along the tire radial direction. In a pneumatic radial tire having a double crown configuration by having an annular recess recessed along the tread portion, the tread portion is changed to an annular recess having a concave curvature radially outward of the tire in a tire widthwise cross section. The area between the bending points is the central area, and at least the tire maximum of the double crown that extends from each inflection point to the outside in the tire width direction with a convex curvature. The area up to the radial position is divided into the intermediate area, and the area from the tire width direction outer end position of this intermediate area to each tread end position is divided into the lateral area, and the cord of the hoop reinforcement layer corresponding to these areas. In the pneumatic radial tire, the pre-stretch amount in the central region and the lateral regions is equal to or more than the pre-stretch amount in the intermediate region.

The amount of pre-stretch referred to here means the amount of elongation when the cord before molding is stretched with winding tension during molding and / or diameter expansion in the vulcanization mold. Further, it is preferable that the annular recess has a maximum depth position at a central portion when the tread portion is equally divided into a central portion and side portions in the tire width direction. Furthermore, if the cord of the hoop reinforcing layer is unstretched too much, the twist will return, and the permeability of rubber between the cord filaments will decrease, resulting in poor adhesion with rubber. The prestretch amount is preferably 5% or less regardless of each region of the tread portion. In addition, it is preferable from the viewpoint of manufacturing that the difference between the pre-stretch amount of the cord in the central region and the lateral region and the pre-stretch amount of the cord in the intermediate region is 2.5% or less.

Further, the tread portion has a smaller curvature in the middle region than in the central region and the lateral regions, and the hoop reinforcing layer is formed of a heat-shrinkable cord arranged substantially parallel to the tire equatorial plane. More preferably, it comprises a rubberized layer.

FIG. 1 shows a cross section in the width direction of a typical pneumatic radial tire according to the present invention. In the figure, 1 is a pneumatic radial tire, 2 is a carcass, 3 is a cord rubberized layer, 4 is a belt, and 5 is a belt. Hoop reinforcement layer, 6 is tread part,
Reference numeral 7 is an annular recess, 8 is a central area, 9 is an intermediate area, 10 is a lateral area, and 11 is a tread contact width.

The pneumatic radial tire 1 shown in FIG.
On the outer circumference of the toroidal carcass 2 consisting of 1 ply,
Belt 4 which is a cross-lamination of two cord rubber layers 3
And a single hoop reinforcement layer 5 made of a rubberized layer of a heat-shrinkable cord that substantially wraps the entire outer periphery of the belt 4 and is arranged substantially parallel to the equatorial plane of the tire. The tread portion 6 reinforced by the hoop reinforcing layer 5 is provided, and the tread portion 6 has an annular recessed portion 7 which is recessed along the circumference of the tread inward in the tire radial direction together with the carcass 2 and the belt 4 in the width center portion thereof. Has a double crown configuration.

The tread portion 6 is an annular concave portion 7 having a concave curvature outward in the radial direction of the tire within a cross section in the tire width direction.
A central region 8 which is a region between inflection points, an intermediate region 9 which is a region from each inflection point to a tire maximum diameter position of a double crown extending with a convex curvature outward in the tire width direction, and an intermediate region A lateral area 10 which is an area from the tire width direction outer end position to the tread end position of the area 9 respectively.
It is divided into and. Central area 8, middle area 9, and lateral area 1
0 changes depending on the difference in the shape of the double crown, but the range of those regions 8, 9, 10 is the range in which the central region 8 occupies 20 to 35% of the tread contact width 11 and both outer ends of the intermediate region 9. The distance between the positions is 70 of the tread contact width 11 ~
It is preferable that the range that occupies 85%, and the distance between both outer end positions of the lateral area 10 occupies 100 to 105% of the tread ground contact width 11. The tread ground contact width 11 referred to here means the distance between the outer ends in the width direction of the ground contact portion of the tire tread when a tire inflated to a specified internal pressure is pressed against a flat ground with a specified load. The tread contact width 11 can be obtained if the tire standard is determined.

Further, the central region 8 and the lateral regions 10 of the cord of the hoop reinforcing layer 5 corresponding to these regions 8, 9 and 10.
The amount of pre-stretch in is set equal to or more than the amount of pre-stretch in the intermediate region 9. In FIG. 1, the lateral area 1
Although the embodiment in which the outer end position of 0 and the tread end position are the same has been shown, the present invention does not necessarily have to be the same. Further, although the annular concave portion 7 is arranged at the center of the tread width direction in FIG. 1, it may be arranged so as to be displaced in the width direction within a range in which drainage performance can be secured at the tread central portion.

The cord of the hoop reinforcing layer 5 is preferably a heat-shrinkable cord such as nylon. Hoop reinforcement layer 5
Is formed by spirally winding a ribbon with a rubberized cord in the width direction, or by winding a cord rubberized sheet having a width corresponding to each region 8, 9 and 10 while adjusting the tension in each region. It is preferably formed. When forming the hoop reinforcing layer 5 on a conventional flat BT drum, the ribbon is preferably wound while changing the winding tension in the width direction, while the BT having a shape corresponding to a double crown shape is used. When the hoop reinforcing layer 5 is formed on the drum, it is preferable to wind the hoop reinforcing layer 5 with a constant or adjusted winding tension in the width direction.

The number of hoop reinforcing layers 5 is preferably one in terms of weight and cost, but it can be slightly increased if necessary in consideration of high speed durability. In the case of a normal tread crown-shaped tire, the cord elongation of the hoop reinforcing layer 5 is such that the belt 4, the hoop reinforcing layer 5 and the tread rubber are attached to a flat BT drum to form a ring member, and this ring member is used as a green case. After being fitted to the outer periphery of the green case, the green case is expanded in the radial direction to be integrated, then vulcanized and cured to manufacture, and the shaping amount during this vulcanization molding is calculated and determined. In the case of the invention tire, since it has the double crown-shaped tread portion 6, it is manufactured by a method similar to the above on the BT drum corrugated corresponding to this shape, and each region 8 and 9 at the time of vulcanization molding 10 to calculate the shaping amount, or to determine the tension when the belt, the hoop reinforcing layer 5 and the tread rubber are attached to the flat BT drum. Determined by adjusting the width direction of the ram.

It is more preferable that the tread portion 6 has a smaller curvature in the intermediate region 9 than in the central region 8 and the lateral regions 10 in order to reduce the belt interlayer strain at the time of ground contact.
The carcass 2 preferably has its ply cords arranged substantially orthogonal to the tire equatorial plane. It is preferable that the cord rubberized layer 3 is formed by arranging cords having high elasticity so as to intersect the tire equatorial plane at relatively small angles, preferably 20 to 30 °, to form the belt 4.

[0015]

In the conventional pneumatic radial tire 1 having the double-crown tread portion, the inner liner and the carcass ply are attached to the drum and the bead cores are set at the ends of the inner liner and the carcass ply. To do. Separately from this, a ring member formed by laminating a belt, a hoop reinforcing layer, and a tread rubber on a flat BT drum different from the drum is fitted to the outer periphery of the green case, and then formed into a double crown structure tread shape. It was manufactured by vulcanization molding in a corresponding mold. In this manufacturing method, since the ring member is formed on the flat BT drum, the ring member has a cylindrical shape and the inner diameters thereof are substantially the same in the width direction, so that the tension at the time of laminating is substantially constant in the width direction. Is common. Therefore, after fitting the ring member into the green case, it is vulcanized and molded,
When forming a tread having a double crown structure, the diameter expansion ratio of the hoop reinforcement layer is different in the tire width direction, that is, the ratio of the diameter expansion is large in the middle area of the tread portion, and in the central area and side areas. Becomes smaller, and with it,
The amount of pre-stretch of the cord of the hoop reinforcement layer is also larger in the middle range than the state of being wound on the BT drum,
It becomes smaller in the central and lateral areas.

Therefore, the tightening effect required in the central region and the lateral regions of the tread portion is insufficient, and the centrifugal force during high speed running tends to cause expansion in the tire radial direction. Therefore, in the case of the tire manufactured by the manufacturing method described above, a member for reinforcing the belt has to be provided at a position corresponding to the central region and the lateral region of the tread portion in order to secure high speed durability.

On the other hand, according to the present invention, at least one hoop reinforcing layer 5 that substantially envelops the entire outer periphery of the belt 4 is provided, and the expansion amount of the hoop reinforcing layer 5 is properly adjusted in the width direction of the belt. Adjust, specifically flat B
When attaching the hoop reinforcement layer 5 on the T drum,
Adjust the winding tension of a ribbon made of heat-shrinkable cord such as rubber-coated nylon, or
When the surface shape of the BT drum is a double crown shape close to the tread shape of the product, the winding tension is constant or the winding tension is adjusted in the same manner as the former, and the hoop reinforcing layer in the central region 8 and the lateral regions 10 is adjusted. By setting the pre-stretch amount of the cord of No. 5 to be equal to or more than the pre-stretch amount in the intermediate region 9, when a large centrifugal force is generated in the tire at high speed running, the central region 8 and the lateral regions of the tread portion 6 The radial expansion of the tire at 10 is suppressed. Here, instead of winding the ribbon described above, a cord rubber sheet having a width corresponding to each of the regions 8, 9 and 10 may be wound by adjusting the tension for each region. Further, since the central area 8 and the lateral areas 10 are reinforced as in the conventional case, it is not necessary to newly provide a narrow member for reinforcing the belt 4 at each position, so that the belt structure is not complicated. Further, by making the tread portion 6 have a smaller curvature in the intermediate region 9 than in the central region 8 and the lateral regions 10, the intermediate region 9 is further reduced.
At the time of grounding, the belt interlayer strain is reduced, and the durability can be improved.

[0018]

EXAMPLES Specific examples of the pneumatic tire according to the present invention will be described with reference to the drawings. -Example The invention tire shown in FIG. 1 has a tire size of 225/50.
R16, a belt 4 in which two cord rubberized layers 3 are cross-laminated on the outer periphery of a toroidal carcass 2 made of one ply of cord rubberized layers arranged at 90 ° with respect to the tire equatorial plane, The belt 4 and the hoop reinforcement are provided with a single hoop reinforcement layer 5 made of a rubberized layer of a heat-shrinkable cord that substantially wraps the entire outer periphery of the belt 4 and is arranged substantially parallel to the tire equatorial plane. A double crown is provided with a tread portion 6 reinforced with a layer 5, and the tread portion 6 has a carcass 2 and a belt 4 at the center of the width thereof and an annular recessed portion 7 that is recessed along the tread circumference inward in the tire radial direction. It will be composed. Tread section 6
Between the inflection points of the annular concave portion 7 having a concave curvature outward in the radial direction of the tire (the tread contact width 1
(33% of 1) is the central region 8, the region from each inflection point to the tire width direction outer side up to 80% of the tread contact width 11 is the intermediate region 9, and the region outside the intermediate region 9 in the tire width direction. Was classified as a lateral area 10. The amount of expansion of the hoop reinforcing layer 5 corresponding to these regions 8, 9, 10 is determined in each region of the belt, the hoop reinforcing layer, and the hoop reinforcing layer when the tread rubber is laminated on the BT drum to form a ring member. It was calculated from the outer peripheral length and the outer peripheral length after vulcanization and curing.

In the inventive tire 1, a ribbon obtained by rubberizing a nylon cord was spirally wound on a flat BT drum while controlling the winding tension of the cord in the tire width direction to form a hoop reinforcing layer 5. At this time, the pre-stretch amount was set to 4% for the central area 8, the intermediate area 9, and the lateral area 10.

The invention tire 2 uses a BT drum having a shape corresponding to the double crown shape, and the tire winding width is such that the cord winding tension is larger in the central region 8 and the lateral regions 10 than in the intermediate region 9. It was spirally wound in the direction. The pre-stretch amount at that time is the central area 8 and the lateral area 10.
At 3.5% and 2.0% in the middle range 9. Further, in the invention tires 1 and 2, the radius of curvature of the tread surface of the tread portion 6 in each of the regions 8, 9 and 10 is 30 mm in the central region 8, 300 mm in the intermediate region 9 and 150 mm in the lateral region 10, and cord rubberized. The layer 3 was formed by arranging the cords thereof so as to intersect the tire equatorial plane at 26 ° to form the belt 4.

A comparative tire hoop reinforcing layer is laminated on a flat BT drum together with a belt and a tread rubber with a uniform tension in the width direction of the drum, and the hoop reinforcing layer is provided with narrow layers at both ends. The structure other than the above is almost the same as the invention tire used in the examples. Layer-
Nylon cords were used for the cords, and the cords were arranged at 0 ° with respect to the tire equatorial plane.

The structure is similar to that of the inventive tire used in the examples, except that the conventional tire hoop reinforcing layer is attached to the flat drum together with the belt and the tread rubber with a uniform tension in the width direction of the drum. is there.

Test method The test was carried out for high-speed durability, and also for tire weight and cost performance. High speed durability is 2.5k
A test tire inflated to an internal pressure of gf / cm ²
150 on a 3 m diameter drum under a load of 450 kgf
Run at a speed of km / h for 20 minutes, then 10 km / h every 20 minutes until tire breakage occurs.
The evaluation was performed by performing a high-speed drum endurance test in which the speed was gradually increased. Table 1 shows these results. Each of the numerical values in the table is an index ratio with the conventional tire as 100, and the higher the high-speed durability is, the better the tire weight and the lower the cost are.

[0024]

[Table 1]

From these results, invention tires 1 and 2
Both have the same tire weight and cost performance as those of conventional tires, and are excellent in high-speed durability. The invention tires 1 and 2 have the same high-speed durability as the comparative tires, but are excellent in terms of tire weight and cost performance. Therefore, inventive tires 1 and 2 are overall superior to conventional tires and comparative tires.

[0026]

According to the present invention, at least one hoop reinforcing layer 5 that substantially envelops the entire outer circumference of the belt 4 is provided, and the prestretch amount of the cord of the hoop reinforcing layer 5 is appropriate in the width direction of the belt 4. Adjustment, specifically, by increasing the pre-stretch amount in the central area 8 and the lateral area 10 to be equal to or greater than that in the intermediate area 9, when a large centrifugal force is generated in the tire during high-speed traveling, Since the radial expansion of the tire in the central region 8 and the lateral regions 10 of the portion 6 is suppressed, the occurrence of belt separation can be prevented, and as a result, high speed durability is improved.

Further, it is not necessary to additionally provide a narrow member for reinforcing the belt 4 at each position to reinforce the central area 8 and the lateral area 10 as before, and the belt structure is complicated. This is also advantageous in terms of productivity and cost.

Further, by making the tread portion 6 have a smaller curvature in the intermediate region 9 than in the central region 8 and the lateral regions 10, it is possible to further suppress belt interlayer strain in the ground contact region (intermediate region 9). Therefore, further improvement in high-speed durability can be expected.

The drainage property in the central region 8 of the tread portion 6 during high-speed traveling is also advantageous because radial expansion in the central region 8 is suppressed and the hollow volume of the annular recess 7 can be secured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the width direction of an inventive tire 1 used in Examples.

[Explanation of symbols]

1 Pneumatic radial tire 2 carcass 3 cord rubberized layer 4 belt 5 hoop reinforcement layer 6 Tread part 7 Annular recess 8 Central area 9 Middle range 10 lateral areas 11 tread width

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 9/22 B60C 3/00 B60C 11/00

Claims (3)

(57) [Claims] 1. A belt in which cord rubberized layers are cross-laminated on the outer periphery of a toroidal carcass, and a hoop reinforcement layer formed of at least one cord rubberized layer that substantially encloses the entire outer periphery of the belt. With a tread portion reinforced with a belt and a hoop reinforcing layer, the tread portion, in a predetermined region in the width direction thereof, an annular recess recessed along the tread circumference inward in the tire radial direction together with the carcass and the belt. In a pneumatic radial tire having a double-crown structure, the tread portion is located in the central area of the area between the inflection points of the annular concave portion having a concave curvature radially outward of the tire in the tire width direction cross section. And the area from the inflection point to the tire maximum diameter position of the double crown extending with a convex curvature outward in the tire width direction. And the region from the tire width direction outer end position to each tread end position of this intermediate region is divided into lateral regions, and the central region and lateral regions of the cord of the hoop reinforcement layer corresponding to these regions. The pneumatic radial tire is characterized in that the pre-stretch amount in (1) is equal to or more than the pre-stretch amount in the intermediate range. 2. The pneumatic radial tire according to claim 1, wherein the tread portion has a smaller curvature in an intermediate region than in the central region and the lateral regions. 3. The pneumatic radial tire according to claim 1, wherein the hoop reinforcing layer comprises a rubberized layer of heat-shrinkable cords arranged substantially parallel to the equatorial plane of the tire.