JP2018083457A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which allows for improved steering stability and furthermore allows for suppression of tire shape change at inflation.SOLUTION: The pneumatic tire is provided in which a belt width Wb is 90% or more of a tread ground-contact width Wt; a difference (Tc-T1) of a tread thickness Tc at a tire equator Co and that T1 at a first position P1 is 1.2 mm or less; and the thickness tmax of a belt cushion rubber 9 is 2.0 mm or more. In the belt plies 7A, 7B, the angle θc of a belt cord at the tire equator Co is smaller than the angle θ1 at a first position P1, and a difference (θ1-θc) is in a range of 3.0 to 6.0°.SELECTED DRAWING: Figure 1

Description

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

  In a pneumatic tire having a radial structure, a belt layer is formed on the outer side in the radial direction 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 inclinedly arranged at an angle of, for example, 15 to 25 ° with respect to the tire circumferential direction. Each belt ply is placed with the belt cords in different directions so that the belt cords cross each other. As a result, a truss structure is formed, the belt rigidity is increased, and the reinforcing effect is improved.

  In such a pneumatic tire, it is known that 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 hoop 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 inflation (internal pressure filling) is large and the tire width is small, which adversely affects durability and wear resistance.

  In order to suppress a change in the outer diameter of the tire during inflation, for example, Patent Document 1 proposes to define a carcass profile and make the internal pressure distribution ratio uniform. I haven't come to get.

JP, 2015-066953, A

  Accordingly, an object of the present invention is to provide a pneumatic tire capable of securing a restraining force by a belt layer while improving steering stability and suppressing a change in the outer diameter of the tire during inflation.

The present invention is a carcass that extends from the tread portion to the bead portion through the sidewall portion,
A belt layer comprising a plurality of belt plies arranged on the outer side in the tire radial direction of the carcass and inside the tread portion;
And a pneumatic tire comprising a belt cushion rubber having a triangular cross section disposed between a tire axially outer end portion of the belt layer 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 at a distance of 35% of the tread ground contact width Wt from the tire equator. 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 belt ply, 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 3.0-6. It is characterized by a range of 0 °.

  In the pneumatic tire according to the present invention, it is preferable that the belt cord angle θc of the widest ply among the belt plies is 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 equator to the inner end in the tire axial direction of the belt cushion rubber 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 section, the tread surface has a first arc having a radius of curvature R1 disposed on the inner side in the tire axial direction, and a radius of curvature R2 continuous to the first arc on the outer side 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 contact width Wt” is defined as the maximum width in the tire axial direction of the tread contact surface that comes into contact when a normal load is applied to a tire assembled with a normal rim and filled with a normal internal pressure. Is done.

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

  In the present invention, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in a no-load state in which a rim is assembled on a normal rim and an internal pressure of 5% of the normal internal pressure is filled.

  As described above, according to the present invention, 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 The angle is 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 reduced. 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. Accordingly, it is possible to reduce the burden of the internal pressure sharing ratio of the belt layer on the shoulder side, and it is possible to suppress a change in the outer diameter of the tire during inflation as the whole tire.

  For this purpose, it is necessary that the belt layer bends 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 regulated to 1.2 mm or less.

  In the case of 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 low flat tire, a difference in the restraining force of the belt layer easily occurs between the center side and the shoulder side. Can function more effectively.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which expands and shows a belt cushion rubber. It is a conceptual diagram which expands and shows the arrangement | sequence state of a belt cord on 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 includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, the tire radial direction outer side of the carcass 6 and a tread portion. 2, and a belt cushion rubber 9 having a triangular cross section disposed between the outer end of the belt layer 7 in the tire axial direction and the carcass 6. In this example, the case where the pneumatic tire 1 is a low-flat passenger car tire with a flatness ratio of 60% or less is shown.

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

  Each bead portion 4 is provided with a bead apex rubber 8 having a triangular cross section extending radially outward from the bead core 5 through, for example, the ply main body portion 6a and the ply folding portion 6b. The wall part 3 is reinforced.

  The belt layer 7 includes a plurality of belt plies 7A and 7B in this example, in which high-elasticity belt cords 10 such as steel cords are inclinedly arranged at an angle θ (shown in FIG. 3) with respect to the tire circumferential direction. It is formed. The belt plies 7A and 7B are placed with the belt cords in different directions so that the belt cords cross each other.

  In this example, the radially inner belt ply 7A is formed 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 (in this example, the inner belt ply 7A) is set to 90% or more of the tread ground contact width Wt. Below 90%, the restraining force and the reinforcing effect of the belt layer 7 do not reach 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. If the upper limit is exceeded, belt end peeling or the like tends to occur.

As shown in FIG. 3, in each belt ply 7A, 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 °. Note the first position P1 is defined as a position spaced 35% of the distance _{L 35} of the tread ground-contact width Wt from the tire equator Co. Specifically, the angle θ of the belt cord increases stepwise or continuously from the tire equator Co to the ply end.

  Such a belt layer 7 can improve steering stability because the angle θ of the belt cord on the shoulder side is relatively large. At this time, although the binding force of the belt layer 7 is lowered, 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. Accordingly, 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 changes in the outer diameter of the tire during inflation as a whole tire.

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

  For this purpose, it is necessary that the belt layer 7 bends along the contour shape of the tread surface. For this purpose, 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 and extends, whereas the belt layer 7 extends along the contour shape of the tread surface 2S. Therefore, the outer end portion in the tire axial direction of the belt layer 7 is gradually separated from the carcass 6 as going outward in the tire axial direction. The belt cushion rubber 9 is disposed in 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. At the position of the tire axial direction outer end 7e of the adjacent belt ply (inner belt ply 7A in this example), the maximum thickness tmax is formed, and the maximum thickness tmax is set to 2.0 mm or more. The distance L from the tire equator Co to the inner end in the tire axial direction of the belt cushion rubber 9 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.

  As shown in FIG. 1, the tread thickness T from the belt layer 7 to the tread surface 2S is substantially constant. In particular, the tread thickness Tc at the tire equator Co and the tread at the first position P1 on the shoulder side. The difference (Tc−T1) from the thickness 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 share of the belt layer 7 on the side. When the difference in the tread thickness (Tc−T1) is out of the above range, the difference in the contour shape between the belt layer 7 and the tread surface 2S increases, and similarly, the internal pressure sharing ratio of the belt layer 7 on the shoulder side is increased. It becomes difficult to increase.

  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 on the inner side in the tire axial direction, and the tire axis on the first arc 21. A second arc 22 having a radius of curvature R2 that is smoothly connected outside in the direction is formed. In particular, for a double radius tire in which the radius of curvature R2 is 50% or less of the radius of curvature R1, changes in the outer diameter of the tire during inflation can be more effectively suppressed. In addition, the intersection of the 1st circular arc 21 and the 2nd circular arc 22 is located in a tire axial direction outer side rather than the 1st position P1 in this example.

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

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A pneumatic tire (215 / 50R18) for passenger cars having the basic structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and the shape change and steering stability during inflation of each sample tire were tested. The specifications other than those listed in Table 1 are substantially the same, 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 ground contact width Wt
・ Belt ply: 2 sheets ・ Belt cord: Steel cord ・ Cord angle: Listed in Table 1 (Each ply has the same configuration, and cords cross between plies)

(1) Shape change during inflation (change in tire outer diameter, change in total tire width)
The change in the tire outer diameter is indicated by an index obtained by measuring the tire outer diameter when the normal inner pressure is filled and setting the mold diameter as 100. The closer the value is to 100, the better the change during inflation.
The change in the total tire width is indicated by an index in which the total tire width when the normal internal pressure is filled is measured and the total mold width is 100. The closer the value is to 100, the better the change during inflation.

(2) Steering stability:
A sample tire is mounted on the four wheels of a vehicle (FF car with a displacement of 3000 cc) under the conditions of a rim (18 x 7.0) and internal pressure (220 kPa), and runs on a dry asphalt tire test course for stable operation. The property is indicated by an index with Comparative Example 1 being 100 depending on the driver's sensation. The larger the value, the better.

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

DESCRIPTION OF SYMBOLS 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 equator

Claims (5)

Carcass from the tread part through the sidewall part to the bead part,
A belt layer comprising a plurality of belt plies arranged on the outer side in the tire radial direction of the carcass and inside the tread portion;
And a pneumatic tire comprising a belt cushion rubber having a triangular cross section disposed between a tire axially outer end portion of the belt layer 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 at a distance of 35% of the tread ground contact width Wt from the tire equator. 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 belt ply, 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 3.0-6. A pneumatic tire characterized by being in a range of 0 °.   2. The pneumatic tire according to claim 1, wherein an angle θc of a belt cord of the widest ply among the belt plies is larger than an angle θc of a belt cord of another belt ply.   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 a distance L from a tire equator to an inner end in the tire axial direction of the belt cushion rubber is 40% or less of a tread ground contact width Wt.   In the tire meridional section, the tread surface is composed of a first arc having a radius of curvature R1 arranged on the inner side in the tire axial direction, and a second arc having a radius of curvature R2 connected to the first arc on the outer side in the tire axial direction, and The pneumatic tire according to any one of claims 1 to 4, wherein the curvature radius R2 is 50% or less of the curvature radius R1.

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