JP6798273B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire capable of suppressing a change in the outer diameter of the tire during inflation while improving steering stability.

In a pneumatic tire having a radial structure, a belt layer is formed on the radial outer side of the carcass in order to ensure excellent steering stability and durability. This belt layer is formed of a plurality of (for example, two) belt plies in which steel belt cords are inclined and arranged at an angle of, for example, 15 to 25 ° with respect to the tire circumferential direction. The belt plies are placed in different directions so that the belt cords intersect with each other. As a result, a truss structure is formed, the belt rigidity is increased, and the reinforcing effect is improved.

It is known that in such a pneumatic tire, by increasing the angle of the belt cord, the rigidity in the width direction (tire axial direction) is increased and the steering stability performance is improved. However, on the other hand, the tag effect is reduced and the binding force on the tread portion is reduced. As a result, there is a problem that the outer diameter of the tire after inflating (filling with internal pressure) is large and the tire width is small, which adversely affects durability and wear resistance.

It should be noted that, in order to suppress changes in the outer diameter of the tire during inflating, for example, it has been proposed in Patent Document 1 and the like that the carcass profile is defined and the internal pressure sharing ratio is made uniform, but the results are sufficiently satisfactory. Has not yet been obtained.

Japanese Unexamined Patent Publication No. 2015-066953

Therefore, an object of the present invention is to provide a pneumatic tire capable of suppressing a change in the outer diameter of the tire at the time of inflation by securing a binding force by the belt layer while improving steering stability.

The present invention is a carcass that extends from the tread portion through the sidewall portion to the bead portion.
A belt layer composed of a plurality of belt plies arranged outside the carcass in the radial direction of the tire and inside the tread portion.
A pneumatic tire provided with a belt cushion rubber having a triangular cross section arranged between the outer end portion of the belt layer in the tire axial direction and the carcass.
The belt width Wb of the belt layer is 90% or more of the tread ground contact width Wt.
The difference (Tc-T1) between the tread thickness Tc at the tire equator from the belt layer to the tread surface and the tread thickness T1 at the first position P1 separated from the tire equator by 35% of the tread contact width Wt. 0-1.2mm,
The thickness of the belt cushion rubber at the outer end in the tire axial direction of the belt ply adjacent to the belt cushion rubber is 2.0 mm or more.
Moreover, in each of the belt plies, the angle θc at the tire equator with respect to the tire circumferential direction of the belt cord is smaller than the angle θ1 at the first position P1, and the difference (θ1-θc) is 3.0 to 6. It is characterized by being in the range of 0 °.

In the pneumatic tire according to the present invention, the angle θc of the belt cord of the widest ply among the belt plies is preferably larger than the angle θc of the belt cords of the other belt plies.

In the pneumatic tire according to the present invention, the belt width Wb is preferably 110% or less of the tread ground contact width Wt.

In the pneumatic tire according to the present invention, the distance L from the tire equatorial line to the inner end of the belt cushion rubber in the tire axial direction is preferably 40% or less of the tread ground contact width Wt.

In the pneumatic tire according to the present invention, in the tire meridional cross section, the tread surface has a first arc having a radius of curvature R1 arranged inside in the tire axial direction and a radius of curvature R2 connected to this first arc on the outside in the tire axial direction. It is preferable that the radius of curvature R2 is 50% or less of the radius of curvature R1.

In the present invention, the "tread ground contact width Wt" is defined as the maximum width of the tread ground contact surface in the tire axial direction, which is grounded when a normal load is applied to a tire in a state where the rim is assembled on a regular rim and a normal internal pressure is applied. Will be done.

The "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATTA is a standard rim, TRA is "Design Rim", or ETRTO. If so, it means "Measuring Rim". The "regular internal pressure" is the air pressure defined for each tire by the standard, the maximum air pressure for JATTA, and the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. In the case of ETRTO, it means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The "regular load" is the load defined for each tire by the standard, and is the maximum load capacity for JATMA and the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. , ETRTO is "LOAD CAPACITY".

Further, in the present invention, unless otherwise specified, the dimensions and the like of each part of the tire shall be a value specified in a no-load state in which the rim is assembled on a regular rim and an internal pressure of 5% of the regular internal pressure is filled.

In the present invention, as described above, in the belt cord of each belt ply, the angle θc at the tire equator is smaller than the angle θ1 at the first position P1 on the shoulder side, and the difference (θ1-θc) is 3.0 to 3. It is set to 6.0 °.

That is, the steering stability can be improved by making the angle of the belt cord on the shoulder side relatively large. At this time, the binding force of the belt layer is lowered. However, in the present invention, the angle of the belt cord on the center side is relatively small, and the internal pressure sharing ratio of the belt layer on the center side is increased. Therefore, the burden of the internal pressure sharing ratio of the belt layer on the shoulder side can be reduced, and the tire as a whole can suppress changes in the outer diameter of the tire during inflating.

For that purpose, the belt layer needs to be curved along the contour shape of the tread surface. Therefore, the thickness of the belt cushion rubber at the outer end of the adjacent belt ply is set to 2.0 mm or more, and the difference between the tread thickness Tc and the tread thickness T1 is specified to be 1.2 mm or less.

Further, in a tire having a wide tread width in which the belt width Wb is 90% or more of the tread ground contact width Wt, particularly a tire having a low flatness, a difference in the binding force of the belt layer is likely to occur between the center side and the shoulder side. Can work more effectively.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which shows the belt cushion rubber enlarged. It is a conceptual diagram which shows the arrangement state of a belt cord in a plane.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the tread portion outside the tire radial direction of the carcass 6. A belt layer 7 arranged inside the tire tread 2 and a belt cushion rubber 9 having a triangular cross section arranged between the outer end portion of the belt layer 7 in the tire axial direction and the carcass 6 are provided. In this example, the case where the pneumatic tire 1 is a low flatness passenger car tire having a flatness of 60% or less is shown.

The carcass 6 is formed of one or more carcass cords arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire circumferential direction, or one carcass ply 6A in this example. The carcass ply 6A includes a ply main body portion 6a that spans the bead cores 5 and 5, and a ply folded portion 6b that is connected to the ply main body portion 6a and is folded back around the bead core 5.

A bead apex rubber 8 having a triangular cross section extending radially outward from the bead core 5 is arranged on each bead portion 4 through, for example, between the ply main body portion 6a and the ply folded portion 6b, and side from the bead portion 4. It is reinforced over the wall portion 3.

The belt layer 7 is composed of a plurality of highly elastic belt cords 10 such as steel cords inclined at an angle θ (shown in FIG. 3) with respect to the tire circumferential direction, and in this example, two belt plies 7A and 7B. It is formed. The belt plies 7A and 7B are placed in different directions so that the belt cords intersect with each other.

In this example, the inner belt ply 7A in the radial direction is formed to be wider than the outer belt ply 7B by, for example, about 10 to 20 mm. The belt width Wb defined as the ply width of the widest belt ply (inner belt ply 7A in this example) is set to 90% or more of the tread ground contact width Wt. If it is less than 90%, the binding force and reinforcing effect of the belt layer 7 do not reach almost the entire width of the tread portion 2, and the tire performance including steering stability, durability, wear resistance, etc. is exhibited at a high level. Becomes difficult. The upper limit of the belt width Wb is preferably 110% or less of the tread ground contact width Wt, and if it exceeds this, the belt end peeling tends to occur.

As shown in FIG. 3, in each of the belt plies 7A and 7B, the angle θc of the belt cord at the tire equator Co is smaller than the angle θ1 at the first position P1 on the shoulder side, and the difference (θ1-θc). ) Is in the range of 3.0 to 6.0 °. The first position P1 is defined as a position separated from the tire equator Co by a distance L ₃₅ of 35% of the tread contact width Wt. Specifically, the angle θ of the belt cord increases stepwise or continuously from the tire equator Co to the ply end.

In such a belt layer 7, the steering stability can be improved by making the angle θ of the belt cord on the shoulder side relatively large. At this time, the binding force of the belt layer 7 is lowered, but the angle θ of the belt cord on the center side is relatively small, and the internal pressure sharing ratio of the belt layer 7 on the center side is increased. Therefore, the burden of the internal pressure sharing ratio of the belt layer 7 on the shoulder side can be reduced. As a result, it is possible to suppress a change in the outer diameter of the tire at the time of inflating the tire as a whole.

In particular, in a low flat tire having a flatness of 60% or less, even when the angle θc of the belt cord is 25 ° or more, the change in the outer diameter of the tire during inflation is suppressed while improving the steering stability. It becomes possible.

For that purpose, the belt layer 7 needs to be curved along the contour shape of the tread surface. Therefore, the belt cushion rubber 9 is formed and the tread thickness T is made uniform.

Specifically, as shown in FIG. 1, the carcass 6 is curved in an arc shape and extends, whereas the belt layer 7 extends along the contour shape of the tread surface 2S. Therefore, the outer end portion of the belt layer 7 in the tire axial direction gradually separates from the carcass 6 toward the outside in the tire axial direction. The belt cushion rubber 9 is arranged on the separated portion K.

As shown in FIG. 2, the thickness t of the belt cushion rubber 9 gradually increases from the inner end in the tire axial direction of the belt cushion rubber 9 toward the outer side in the tire axial direction. Then, at the position of the outer end 7e in the tire axial direction of the adjacent belt ply (inner belt ply 7A in this example), the maximum thickness tmax is formed, and this maximum thickness tmax is set to 2.0 mm or more. The distance L from the tire equatorial line Co to the inner end of the belt cushion rubber 9 in the tire axial direction is preferably 45% or less, more preferably 40% or less of the tread ground contact width Wt. Such a belt cushion rubber 9 stably holds the belt layer 7 in an appropriate contour shape.

Further, as shown in FIG. 1, the tread thickness T from the belt layer 7 to the tread surface 2S is substantially constant, particularly the tread thickness Tc at the tire equator Co and the tread at the first position P1 on the shoulder side. The difference from the thickness T1 (Tc-T1) is set to 0 to 1.2 mm.

Here, when the thickness tmax of the belt cushion rubber 9 is less than 2.0 mm and the distance L exceeds 45% of the tread ground contact width Wt, the contour shape of the belt layer 7 becomes too close to the carcass 6 and the shoulder It becomes difficult to increase the internal pressure sharing ratio of the belt layer 7 on the side. Further, when the difference in tread thickness (Tc-T1) is out of the above range, the difference in contour shape between the belt layer 7 and the tread surface 2S becomes large, and similarly, the internal pressure sharing ratio of the belt layer 7 on the shoulder side is increased. It becomes difficult to raise.

In this example, the contour shape of the tread surface 2S, particularly the contour shape in the range of the tread ground contact width Wt, is the first arc 21 having a radius of curvature R1 arranged inside in the tire axial direction, and the tire shaft on the first arc 21. It is formed from a second arc 22 having a radius of curvature R2 that is smoothly connected outside the direction. Further, in particular, for a double radius tire in which the radius of curvature R2 is 50% or less of the radius of curvature R1, it is possible to more effectively suppress a change in the outer diameter of the tire during inflating. In this example, the intersection of the first arc 21 and the second arc 22 is located outside the tire axial direction from the first position P1.

In order to suppress changes in the outer diameter of the tire during inflating while improving steering stability, the angle θc of the belt cord of the widest belt ply (inner belt ply 7A in this example) is set to 25 °. The above is preferable, and it is more preferable that the angle θc of the belt cord of another belt ply (outer belt ply 7B in this example) is larger than the angle θc. At this time, the difference in angle θc is more than 0 and preferably 1.5 ° or less.

Although the particularly preferable embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be modified into various embodiments.

Pneumatic tires (215 / 50R18) for passenger cars having the basic structure shown in FIG. 1 were prototyped with the specifications shown in Table 1, and the shape change and steering stability of each sample tire during inflation were tested. The specifications are substantially the same except those listed in Table 1, and the common specifications are as follows.
<Carcass>
・ Carcass ply: 1 sheet ・ Carcass cord: Polyester cord ・ Cord angle; 90 °
<Belt layer>
-Belt width Wb: 97% of tread grounding width Wt
・ Belt ply: 2 sheets ・ Belt cord: Steel cord ・ Cord angle: Listed in Table 1 (each ply has the same configuration, and the cord intersects between plies)

(1) Shape change during inflating (change in tire outer diameter, change in total tire width)
The change in the tire outer diameter is expressed as an index with the mold diameter as 100 by measuring the tire outer diameter when the normal internal pressure is applied. The closer the value is to 100, the smaller the change during inflation, and the better.
The change in the total tire width is expressed as an index with the total width of the mold as 100 by measuring the total tire width when the normal internal pressure is applied. The closer the value is to 100, the smaller the change during inflation, and the better.

(2) Steering stability:
The sample tires are mounted on the four wheels of the vehicle (FF vehicle with a displacement of 3000cc) under the conditions of rim (18 x 7.0) and internal pressure (220kPa), and run on a dry asphalt tire test course to stabilize steering. The sex is expressed as an index with Comparative Example 1 as 100 according to the sensory nature of the driver. The larger the number, the better.

As shown in the table, it can be confirmed that the tires of the examples can suppress the shape change of the tire at the time of inflating while improving the steering stability.

1 Pneumatic tire 2S Tread surface 2 Tread part 3 Side wall part 4 Bead part 6 Carcass 7A, 7B Belt ply 7 Belt layer 9 Belt cushion rubber 21 1st arc 22 2nd arc Co Tire equatorial line

Claims (5)

Carcass from the tread part to the bead part through the sidewall part,
A belt layer composed of a plurality of belt plies arranged outside the carcass in the radial direction of the tire and inside the tread portion.
A pneumatic tire provided with a belt cushion rubber having a triangular cross section arranged between the outer end portion of the belt layer in the tire axial direction and the carcass.
The belt width Wb of the belt layer is 90% or more of the tread ground contact width Wt.
The difference (Tc-T1) between the tread thickness Tc at the tire equator from the belt layer to the tread surface and the tread thickness T1 at the first position P1 separated from the tire equator by 35% of the tread contact width Wt. 0-1.2mm,
The thickness of the belt cushion rubber at the outer end in the tire axial direction of the belt ply adjacent to the belt cushion rubber is 2.0 mm or more.
Moreover, in each of the belt plies, the angle θc at the tire equator with respect to the tire circumferential direction of the belt cord is smaller than the angle θ1 at the first position P1, and the difference (θ1-θc) is 3.0 to 6. Pneumatic tires characterized by a range of 0 °. The pneumatic tire according to claim 1, wherein the angle θc of the belt cord of the widest ply among the belt plies is larger than the angle θc of the belt cords of the other belt plies. The pneumatic tire according to claim 1 or 2, wherein the belt width Wb is 110% or less of the tread ground contact width Wt. The pneumatic tire according to any one of claims 1 to 3, wherein the distance L from the tire equatorial line to the inner end of the belt cushion rubber in the tire axial direction is 40% or less of the tread ground contact width Wt. In the tire meridional cross section, the tread surface is composed of a first arc having a radius of curvature R1 arranged inside in the tire axial direction and a second arc having a radius of curvature R2 connected to the first arc on the outside in the tire axial direction. The pneumatic tire according to any one of claims 1 to 4, wherein the radius of curvature R2 is 50% or less of the radius of curvature R1.

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