JP2006160100A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of improving the ground contact property of a run-flat tire in a regular traveling mode, and to enhance the steerability of a vehicle without sacrificing the ride quality performance by optimizing the distribution of the thickness of a side reinforcing rubber. <P>SOLUTION: Since the total thickness a of a wide wall part 14 at the position of the maximum thickness b of a side reinforcing rubber 18 is larger than the maximum total thickness c in an area (a thin-walled area 32) between the position of the maximum thickness b and a ground contact end 16A of a tread part 16, the transverse rigidity of the entire tire is increased, while the bending rigidity of the thin-walled area 32 is decreased. Thus, the bending moment of the side wall part 14 during the cornering is hardly transmitted to a ground contact surface of the tread part 16, the ground contact property of the tread part 16 is improved, and the cornering power is increased thereby. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire that can safely run flat for a predetermined distance even in a state where air pressure is lowered.

A crescent-shaped side reinforcement rubber is added to the sidewall of the run-flat tire that can continue running when the tire is punctured and the air pressure drops to zero. Some are arranged (see, for example, Patent Document 1).
JP-A-6-191243

  However, in the conventional side-reinforced type run-flat tire in which the side reinforcing rubber extends from the bead portion to the tread portion, the maximum width of the tire from the contact end of the tread portion of the total thickness of each portion in the tire cross section. The thickness of the region up to (buttress portion) is the largest, and the total thickness of the tread portion in the ground contact range is usually thinner than the buttress portion.

  For this reason, when the buttress part is subjected to bending deformation when a slip angle is added during normal driving (at normal air pressure) and the vehicle corners, the bending moment is easily transmitted to the contact surface of the tread part. There is a problem that the grounding property is deteriorated and sufficient cornering power cannot be obtained because the ground surface is lifted (buckle phenomenon) and the distribution of the ground pressure becomes remarkably non-uniform.

  On the other hand, when trying to obtain high cornering power in a normal tire that is not a run-flat tire, a reinforcing layer in which steel cords are arranged from the bead portion to the sidewall portion is arranged to increase the lateral rigidity of the tire and to the buttress portion. In order to improve the ground contact of the tread portion, the buttress portion is easily deformed without arranging a steel reinforcing layer.

  However, side-reinforced run-flat tires are disadvantageous in terms of ride comfort because they have hard side-reinforced rubber. Applying the above method to side-reinforced run-flat tires, If a reinforcing layer is arranged from the portion to the sidewall portion, the ride comfort performance of the run flat tire is further deteriorated.

  In consideration of the above-mentioned facts, the present invention optimizes the distribution of the thickness of the side reinforcing rubber to improve the ground contact property during normal driving in a run-flat tire without sacrificing riding comfort performance. The purpose is to improve the maneuverability of the vehicle.

  The invention of claim 1 includes a pair of bead portions, sidewall portions continuous to the bead portions, tread portions continuous to the sidewall portions on both sides, and thicknesses toward the bead portions and the tread portions, respectively. In a pneumatic radial tire provided with a side reinforcing rubber disposed on the inner surface side of the sidewall portion so as to gradually decrease, the total thickness of the sidewall portion at the position of the maximum thickness of the side reinforcing rubber is A grounding end that is attached to a standard rim and filled with air pressure corresponding to the maximum load capacity in the tire standard and loaded with 100% of the maximum load capacity, and the position of the maximum thickness of the side reinforcing rubber It is characterized by being thicker than the maximum total thickness in the area between.

  Here, when the rim guard part is formed in the sidewall part, the total thickness of the sidewall part means the total thickness based on the virtual contour line of the tire excluding the rim guard part.

  The tire standard is a standard issued by JATMA (Japan), TRA (US), ETRTO (Europe) and the like. The standard rim refers to a standard rim in an applicable size defined in YEAR BOOK issued by these organizations.

  In the pneumatic radial tire according to claim 1, the total thickness of the sidewall portion at the position of the maximum thickness of the side reinforcing rubber is a region (thin wall thickness) between the position of the maximum thickness and the ground contact end of the tread portion. The lateral stiffness of the entire tire is increased, but the bending stiffness of the thin-walled region is reduced. For this reason, it is difficult for the bending moment of the sidewall portion during cornering to be transmitted to the ground contact surface of the tread portion, thereby improving the ground contact property of the tread portion and increasing the cornering power.

  According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, the maximum thickness of the side reinforcing rubber is 7 mm or more and 12 mm or less.

  Here, the lower limit of the maximum thickness of the side reinforcing rubber is set to 7 mm. If the lower limit is not satisfied, the lateral rigidity of the tire cannot be sufficiently increased, and the vehicle weight can be supported during run-flat running. This is because the upper limit is set to 12 mm. If the upper limit is exceeded, the tire mass increases significantly, so-called unsprung weight increases, and the riding comfort performance deteriorates.

  The range of the maximum thickness of the side reinforcing rubber corresponds to the tire for passenger cars, and is not limited to this numerical range in the case of tires other than those for passenger cars.

  In the pneumatic radial tire according to claim 2, since the maximum thickness of the side reinforcing rubber is optimized, the ride comfort is good and the maneuverability is excellent during normal running while having the run-flat running ability. ing.

  As described above, according to the pneumatic radial tire of the present invention, since the distribution of the thickness of the side reinforcing rubber is optimized, the ride comfort performance is not sacrificed and the normal running time in the run-flat tire is reduced. This improves the grounding performance of the vehicle and improves the controllability of the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The pneumatic radial tire 10 according to the present embodiment includes a bead portion 12, a sidewall portion 14, a tread portion 16, and a side reinforcing rubber 18 in FIGS. 1 and 2.

  The bead portions 12 each have an annular bead core 20 and are provided as a pair in the tire width direction. A carcass 22 is disposed between the pair of bead portions 12 in a toroidal shape.

  The carcass 22 includes, for example, two layers of down ply carcass 22A and one layer of down ply carcass 22B.

  For example, two belt layers 24 are disposed on the outer periphery of the crown portion of the carcass 22, and for example, two layers of the belt reinforcing layer 26 are wound along the outer periphery of the belt layer 24. The belt reinforcing layer 26 is, for example, a rubberized cord of an organic fiber.

  The structure of the carcass is not limited to the above, but, for example, a two-layer down-ply carcass is folded back at the bead core 20, and one end of the layer extends to the bottom of the belt layer 24, and terminates under the belt layer 24. You may let them.

  The sidewall portions 14 are respectively connected to the pair of bead portions 12 and constitute the side surfaces of the pneumatic radial tire 10.

  The tread portion 16 is configured to be connected to the sidewall portions 14 on both sides, and is further disposed on the outer peripheral side of the belt reinforcing layer 26.

  The side reinforcing rubber 18 is a hard rubber disposed on the inner surface side of the sidewall portion 14, for example, between the carcass 22 and the inner liner 26, so that the thickness gradually decreases toward the bead portion 12 and the tread portion 16. In this case, the vehicle (not shown) is supported during the run-flat running so that the running can be continued.

  The total thickness a of the sidewall portion 14 at the position of the maximum thickness b of the side reinforcing rubber 18 is 100% of the maximum load capacity that is attached to the standard rim and filled with air pressure corresponding to the maximum load capacity in the tire standard. It is configured to be thicker than the maximum total thickness c in the region between the ground contact end 16A when the load is applied and the position of the maximum thickness b of the side reinforcing rubber 18.

  Here, when the rim guard portion 30 is formed on the sidewall portion 14, the total thickness a of the sidewall portion 14 is based on the virtual contour line V of the pneumatic radial tire 10 excluding the rim guard portion 30. The total thickness.

  The maximum thickness b of the side reinforcing rubber 18 is 7 mm or more and 12 mm or less.

  Here, the lower limit of the maximum thickness b of the side reinforcing rubber 18 is set to 7 mm. If the lower limit is not satisfied, the lateral rigidity of the tire cannot be sufficiently increased, and the vehicle weight is supported during run-flat running. This is because the upper limit is set to 12 mm. If the upper limit is exceeded, the tire mass will increase significantly, so-called unsprung weight will increase, and riding comfort will deteriorate.

  The total thickness in the region closer to the bead portion 12 than the position of the maximum thickness b of the side reinforcing rubber 18 is also configured to be thinner than the total thickness a of the sidewall portion. This is to avoid deterioration in ride comfort.

  In the pneumatic radial tire 10, the total thickness a of the sidewall portion 14 at the position of the maximum thickness b of the side reinforcing rubber 18 is an area between the position of the maximum thickness b and the ground contact end 16 </ b> A of the tread portion 16. Since it is thicker than the maximum total thickness c in (thin region 32), the lateral stiffness of the entire tire is increased, but the bending stiffness in the thin region 32 is decreased.

  For this reason, the bending moment generated in the sidewall portion 14 during cornering is absorbed by the deformation of the thin region 32 and is difficult to be transmitted to the ground contact surface 16B of the tread portion 16, thereby improving the ground contact property of the tread portion 16. Increases cornering power.

Further, in the pneumatic radial tire 10, since the maximum thickness b of the side reinforcing rubber 18 is optimized, the ride comfort is good and the maneuverability is excellent during the normal running while having the run flat running ability. Yes.
(Test example)
As shown in Table 1, pneumatic radial tires according to conventional examples, comparative examples, examples 1 and 2 were prototyped and tested for lateral stiffness, cornering power and drum durability.

  Each tire size is 255 / 40R20, and includes a two-layer carcass in which cords are arranged in the radial direction, a two-layer steel belt layer, and a two-layer belt reinforcing layer made of organic fiber cords. The end of one layer of carcass penetrates and terminates under the steel belt layer.

  The rims used are all 9.5 JJ × 20.

  The tires according to Example 1 and Example 2 have a crescent-shaped side reinforcing rubber inside the sidewall part, and the dimensions of each part are as shown in Table 1.

  In the tire according to the conventional example, the maximum thickness b of the side reinforcing rubber, the total sidewall portion thickness a, and the thin wall region maximum thickness c are different from those of the examples, and the thin wall region maximum thickness c is particularly thick. ing.

  Since the tire according to the comparative example is a normal tire that is not run-flat, it does not have side reinforcing rubber, but has a reinforcing layer in which steel cords are arranged from the bead portion to the sidewall portion.

  The lateral rigidity test was evaluated by the value of the spring constant at the time when the air pressure was 220 kPa and the load was 5 kPa in the lateral direction.

  The cornering power test was performed on the drum under the conditions of an air pressure of 220 kPa and a load of 5 kPa, and was evaluated by the value of the lateral force when the slip angle (SA) was 1 °.

  Drum durability was evaluated using a drum tester, running under conditions of air pressure 0 kPa, load 7 kN, speed 50 km / h until the tire broke down, and the running distance.

  As shown in Table 2, the test results are represented by an index with the conventional example set to 100, and the larger the number, the better the result.

  Regarding the lateral rigidity, Example 1 and Example 2 are improved by 3% over the conventional example. In the comparative example, the lateral stiffness is improved by 10%, and the effect of side steel reinforcement appears.

  As for the cornering power, the improvement equal to or higher than that of the comparative example can be seen in both Example 1 and Example 2.

  In terms of drum durability, Examples 1 and 2 are improved by 2 to 3% over the conventional example.

It is sectional drawing shown about the left half of the tire equatorial plane CL in a pneumatic radial tire. It is an expanded sectional view of a pneumatic radial tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic radial tire 12 Bead part 14 Side wall part 16 Tread part 16A Grounding end 18 Side reinforcement rubber

Claims (2)

A pair of bead portions; a sidewall portion continuous with the bead portion; a tread portion continuous with the sidewall portions on both sides; and the sidewalls such that the thickness gradually decreases toward the bead portion and the tread portion. In a pneumatic radial tire provided with a side reinforcing rubber disposed on the inner surface side of the part,
The total thickness of the side wall portion at the position of the maximum thickness of the side reinforcing rubber is attached to a standard rim and filled with air pressure corresponding to the maximum load capacity in the tire standard, and a load of 100% of the maximum load capacity is loaded. Being thicker than the maximum total thickness in the region between the ground contact edge when being done and the position of the maximum thickness of the side reinforcing rubber;
Pneumatic radial tire characterized by.   The pneumatic radial tire according to claim 1, wherein the maximum thickness of the side reinforcing rubber is 7 mm or more and 12 mm or less.

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