JP2006347452A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the motion performance of the tire by setting the curvature of radius of a tread in a predetermined area (so called a shoulder area) from the ground contact end of the tread section asymmetrically in the right and left in a pneumatic tire having a plurality of air chambers. <P>SOLUTION: Since one side curvature of radius TRI is set larger than the other side curvature radius TRO in the curvature of radius of the tread 16A in the shoulder area 36, the ground contact length of the shoulder area 36 becomes asymmetrical (distribution of the ground contact pressure also becomes asymmetrical), and a lateral force F from the side having the curvature of radius TRI toward the side having the curvature of radius TRO is generated in straight running. The lateral force F is generated from the outside of the tire mounted to the vehicle toward the inside is generated and the operation stability becomes very excellent by making the side having the curvature of radius TRI be the inside of the tire mounted to the vehicle, and making the side having the curvature radius TRO be the outside of the tire mounted to the vehicle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a plurality of tire air chambers are formed when mounted on a rim.

The conventional tire chamber that can be filled with air obtained when a general tire is mounted on a rim has been one chamber, but at least one partition wall is provided on the inner side of the tire and is independent from the rim. Tires in which a plurality of tire air chambers are formed have also been developed (see Patent Document 1).
JP 2003-39914 A

  However, the above-described conventional example only discloses that a plurality of tire air chambers are formed by providing the partition walls, and there is nothing regarding the setting of the contact length in the so-called shoulder region of the tread portion. Not suggested.

  In consideration of the above fact, in the pneumatic tire having a plurality of tire air chambers, the radius of curvature of the tread surface within a predetermined range (so-called shoulder region) from the contact end of the tread portion is set to be asymmetric in the left-right direction. Thus, the object is to improve tire motion performance.

  In a pneumatic tire in which, for example, two partition walls are provided and three air chambers are formed when the rim is mounted, the main air chamber on the inner side in the tire width direction mainly shares the belt tension and is located on both sides in the tire width direction. The first auxiliary air chamber and the second auxiliary air chamber share the carcass tension of the sidewall portion, and the internal pressure of each air chamber can be set independently.

  For this reason, for example, by setting the internal pressure of the main air chamber to be lower than the normal internal pressure of the conventional tire and setting the internal pressure of the first sub air chamber and the second sub air chamber to be higher than the normal internal pressure of the conventional tire, It is possible to control the balance of tire stiffness, which is impossible with conventional tires, such as increasing the lateral stiffness (lateral spring) while lowering the stiffness (vertical spring).

  The three air chamber tire is a tire having such characteristics. However, as a result of further research, the left and right auxiliary air chambers (the first auxiliary air chamber and the second auxiliary air chamber) are set to different internal pressures. It has been newly verified that lateral force is generated mainly from the low pressure side to the high pressure side when going straight. This is because the tension stiffness of the left and right outer sidewalls and the left and right bulkheads is asymmetric on both sides of the tire equator, resulting in asymmetric contact pressure distribution. As a result, the lateral force (lateral force) when running straight Is considered to occur.

  In addition, when a normal tire rolls with a slip angle and a camber angle of 0, a price tear force and a consistency force are generated as uniformity components, but this time also when subtracting those contributions The existence of the generated lateral force was verified. Since this lateral force acts in the same direction as the lateral force generated when a negative camber angle is given to the tire, it will be referred to as “pseudo camber thrust” for convenience.

  Furthermore, in the case of a three-chamber internal pressure combination in which a sufficient lateral force is generated from the outside of the vehicle to the inside of the vehicle by a steering stability test conducted with tires attached to the test vehicle, the steering stability Is newly verified to be very good. This improvement in steering stability is almost the same as when the wheels are set to toe-in in terms of vehicle alignment, and the improvement in motion performance can be explained by a mechanism almost the same as that of toe-in.

  Here, it will be described what kind of tire ground contact shape is a satisfactory level that generally has no problem in motion performance. The ground contact shape with zero slip angle and camber is divided into three in the tire width direction, that is, the so-called center region and the left and right shoulder regions. Is slightly shorter than the ground contact length of the center region (generally about 10 to 20%). That is, it is considered that deterioration in tire ground contact causes a decrease in exercise performance even if the contact length of either one of the left and right shoulder regions is too short or too long.

  Accordingly, the invention of claim 1 includes a pair of left and right outer bead portions in which bead cores are embedded, a sidewall portion extending outward in the tire radial direction from the outer bead portion, a tread portion connected to the sidewall portion, The outer bead portion is provided between the pair of outer bead portions so as to be spaced apart in the tire width direction, and extends inward in the tire radial direction from a base portion on the tire inner surface side in at least one of the sidewall portion and the tread portion, One or more partitions that form a plurality of independent tire air chambers in the tire width direction between the inner bead portion provided at the inner end in the tire radial direction and the rim when the inner bead portion is attached to the rim; If the ground contact width of the tread portion is TW, the tires from the ground contact ends on both sides of the tire equatorial plane in the cross section in the tire axial direction. Among ranging equatorial plane, the curvature radius of the tread at least 20% of the ground contact width TW from the ground end, is characterized by one radius of curvature TRI is greater than the other radius of curvature TRO.

  Here, the range of at least 20% of the ground contact width TW from the ground contact end indicates a so-called shoulder region, and the range of the shoulder region is set in this way. This is because the magnitude of the lateral force (pseudo camber thrust) is insufficient to improve the exercise performance.

  The grounding end means that a pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (2004 edition, Japan Automobile Tire Association Standard), and the maximum load capacity (internal pressure) in the applicable size and ply rating in JATMA YEAR BOOK. -When the maximum load capacity is loaded by filling the internal pressure of 100% of the air pressure (maximum air pressure) corresponding to the bold load in the load capacity correspondence table. When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.

  TRI> TRO means that if TRI <TRO, the direction of the lateral force (pseudo camber thrust) is the direction from the radius of curvature TRI to the radius of curvature TRO even if the internal pressure of each tire chamber is the same. If the radius of curvature TRI is set to the inside of the vehicle and the radius of curvature TRO is set to the outside of the vehicle, a reduction in motion performance similar to that set to toe-out occurs in the case of vehicle alignment. Because it becomes.

  In the pneumatic tire according to claim 1, the curvature radius of the tread surface in the so-called shoulder region is set so that one curvature radius TRI is larger than the other curvature radius TRO, so that the contact length of the so-called shoulder region is left and right. It becomes asymmetric (the contact pressure distribution is also asymmetric), and a lateral force (pseudo camber thrust) from the curvature radius TRO side toward the curvature radius TRI is generated when going straight. Therefore, by setting the curvature radius TRI side as the vehicle mounting inner side and the curvature radius TRO side as the vehicle mounting outer side, this lateral force is generated from the vehicle mounting outer side to the inner side, so that the steering stability is very good.

  According to a second aspect of the present invention, in the pneumatic tire of the first aspect, the curvature radius TRO and the curvature radius TRI satisfy a relationship of 50 mm ≦ TRI-TRO ≦ 700 mm.

  Here, TRI-TRO ≧ 50 mm is set when TRI-TRO <50 mm, because the lateral force (pseudo camber thrust) is too small to improve the exercise performance, so a clear performance difference is not expressed. It is.

  Also, TRI-TRO ≦ 700 mm is set so that when TRI-TRO> 700 mm, the lateral force (pseudo camber thrust) for improving the exercise performance is sufficient, but the curvature has a large radius of curvature. This is because the ground contact length of the shoulder region on the radius TRI side is equal to or slightly longer than the ground contact length of the center region, and as a result, the ground contact property of the tire is deteriorated and the exercise performance is deteriorated.

  In the pneumatic tire according to claim 2, since the range of the difference between the curvature radii TRI and TRO is appropriately set, the curvature radius TRI side is appropriately longer than the curvature radius TRO side with respect to the contact length of the shoulder region. This makes it possible to generate a sufficient lateral force (pseudo camber thrust) from the curvature radius TRO side toward the curvature radius TRI side in order to improve the exercise performance without deteriorating the ground contact property. Steering stability can be made favorable by setting the side as the vehicle mounting inner side and the curvature radius TRIO side as the vehicle mounting outer side.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the curvature radius TRO and the curvature radius TRI satisfy a relationship of 100 mm ≦ TRO <TRI ≦ 1000 mm. .

  Here, TRO ≧ 100 mm is set such that when TRO <100 mm, the lateral force (pseudo camber thrust) is relatively small, and the contact length of the left and right shoulder regions is 2 with respect to the contact length of the center region. This is because the tire ground contact property is deteriorated and the exercise performance is deteriorated because it may be shortened to about 10% or less.

  The reason why TRI ≦ 1000 mm is set is that when TRI> 1000 mm, the contact length of the shoulder region on the side of the curvature radius TRI having a large curvature radius is equal to or slightly longer than the contact length of the center region. This is because it deteriorates and lowers the exercise performance.

  The relationship between the curvature radii TRI and TRO is more preferably 200 mm <TRI-TRO <500 mm.

  In the pneumatic tire according to claim 3, since the ranges of the curvature radii TRI and TRO are appropriately set, the curvature radius TRI side is appropriately longer than the curvature radius TRO side with respect to the contact length of the shoulder region. Therefore, sufficient lateral force (pseudo camber thrust) can be generated from the curvature radius TRO side to the curvature radius TRI side to improve the exercise performance without deteriorating the ground contact property. Steering stability can be improved by setting the vehicle-mounted inner side and the curvature radius TRIO side as the vehicle-mounted outer side.

  According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the radius from the tire center to the rim base line of the outer bead portion is RO, and If the radius of the inner bead portion to the rim base line is RI, 0 <RO-RI <50 mm.

  When the relationship between the radius RO of the outer bead portion and the radius RI of the inner bead portion is RO = RI, the tall hump for preventing the inner bead portion formed on the partition wall from moving outward in the tire axial direction. It is necessary to use a rim provided with a portion, and the assembling work must be very difficult. Further, when RO-RI ≧ 50 mm, it is difficult and unrealistic to manufacture a tire using the current tire manufacturing method.

  Further, when the relationship between the radius RO of the outer bead portion and the radius RI of the inner bead portion becomes RO−RI ≧ 50 mm, the radius of the inner bead portion becomes too small with respect to the radius of the outer bead portion, and accordingly the rim As a result, the diameter of the brake that can be mounted inside the rim is reduced. This is not preferable because it may cause a decrease in vehicle motion performance.

  Therefore, it is preferable to satisfy 0 <RO-RI <50 mm because it is possible to prevent inconvenience as described above.

  According to a fifth aspect of the present invention, when the pneumatic tire according to any one of the first to fourth aspects is mounted on a vehicle, the side having the radius of curvature TRI is directed toward the inside of the vehicle, and the radius of curvature TRO is set. It is characterized in that it is mounted with its side facing the outside of the vehicle.

  In the pneumatic tire according to any one of claims 1 to 4, a lateral force (pseudo camber thrust) is generated from the side having the curvature radius TRO toward the side having the curvature radius TRI when traveling straight. When the pneumatic tire is mounted on the vehicle, the side having the radius of curvature TRI is directed to the inside of the vehicle and the side having the radius of curvature TRO is directed to the outside of the vehicle. When the vehicle is mounted facing, lateral force is generated from the vehicle mounting outer side toward the inner side, and as a result, the steering stability of the vehicle can be made very good.

  As described above, according to the pneumatic tire of the present invention, the tire running performance is improved by setting the radius of curvature of the tread tread within a predetermined range (so-called shoulder region) from the ground contact end of the tread portion to be asymmetrical to the left and right. It has the outstanding effect that it can be made to do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a pneumatic tire 10 according to this embodiment includes an outer bead portion 12, a sidewall portion 14, a tread portion 16 connected to the sidewall portion 14, a partition wall 18, an outer carcass 21, and an inner carcass. 22, and a belt layer 40 is disposed on the lower layer (inner side in the tire radial direction) of the tread portion 16 in the same manner as a general tire.

  A pair of outer bead portions 12 are provided on the left and right sides of the tire equatorial plane CL, and the bead cores 30 are embedded therein. The sidewall portions 14 are formed so as to extend outward from the pair of left and right outer bead portions 12 in the tire radial direction.

  The partition walls 18 are provided between the pair of left and right outer bead portions 12 so as to be spaced apart from the outer bead portions 12 in the tire width direction, for example, on the left and right sides of the tire equatorial plane CL. At least one is formed to extend inward in the tire radial direction from the base portion 20 on the tire inner surface side. When the pneumatic tire 10 is mounted on the rim 26 and the inner bead portion 24 provided at the inner end in the tire radial direction is brought into contact with the rim 26, the partition wall 18 is independent of the tire rim 26. Chambers (a total of three air chambers including the main air chamber 28 and the first sub air chamber 31 and the second sub air chamber 32 on both sides thereof) are formed in the tire width direction.

  The inner carcass 22 is disposed in a toroidal shape between inner bead portions 24 formed at inner ends in the tire radial direction of the pair of left and right partition walls 18, with respect to the bead core 34 disposed on the inner bead portion 24. Each end is rolled back from the inside to the outside. The inner carcass 22 may be wound around the bead core 34 from the outside to the inside.

  The outer carcass 21 is disposed so as to straddle between the outer bead portions 12, and is wound around the bead core 30 disposed in the outer bead portion 12 from the inner side to the outer side and terminates.

  As shown in the figure, the outer carcass 21 is disposed so as to cover the outer side of the inner carcass 22 in the tire radial direction, and is a lower layer of the tread portion 16 between the pair of left and right partition walls 18 (more specifically, a lower layer of the belt layer 40). ) And the inner carcass 22. Note that the arrangement of the carcass is not limited to this.

  Assuming that the contact width of the tread portion 16 is TW, the curvature radius of the tread tread surface 16A in the range of 20% of TW from the contact ends 16B and 16C to the tire equatorial plane CL side in the tire axial cross section TRI is formed larger than the radius of curvature TRO outside the vehicle. Here, the grounding end 16B is a grounding end inside the vehicle mounting, and the grounding end 16C is a grounding end outside the vehicle mounting. The range of 20% of TW from the ground contact ends 16B and 16C toward the tire equatorial plane CL indicates a so-called shoulder region 36. The range of the shoulder region 36 is set in this way because, if it is less than 20%, the asymmetry of the contact pressure distribution is insufficient, so that the lateral force F (pseudo camber thrust) is used to improve the motion performance. This is because the size of is insufficient. A portion from the grounding end 16B to the circumferential main groove 42 closest to the grounding end 16B and a portion from the grounding end 16C to the circumferential main groove 44 closest to the grounding end 16C may be used as shoulder regions 36, respectively. Good.

  TRI> TRO (the radius of curvature TRI is greater than the radius of curvature TRO outside the vehicle) If TRI <TRO, even if the internal pressures of the tire chambers 31, 28, 32 are all the same, the lateral force This is because the direction of F (pseudo camber thrust) is the direction from the inside to the outside of the vehicle, and if it is compared to the alignment of the vehicle, the same movement performance as that set to toe-out occurs, which causes a safety problem. .

  The relationship between the curvature radius TRO and the curvature radius TRI is set so as to satisfy at least one condition of 50 mm ≦ TRI-TRO ≦ 700 mm and 100 mm ≦ TRO <TRI ≦ 1000 mm. Here, the reason why TRI-TRO ≧ 50 mm is that when TRI-TRO <50 mm, the lateral force F is too small to improve the exercise performance, so that a clear performance difference is not expressed.

  In addition, TRI-TRO ≦ 700 mm is set so that when TRI-TRO> 700 mm, the lateral force F for improving the exercise performance is sufficient, but the shoulder region on the inner side of the vehicle having a large curvature radius. This is because the ground contact length (not shown) of 36 is equal to or slightly longer than the contact length (not shown) of the center region 38, resulting in deterioration of the ground contact performance of the tire and lowering the exercise performance. .

  The reason TRO ≧ 100 mm is that when TRO <100 mm, the lateral force (pseudo camber thrust) is relatively small and the contact length of the left and right shoulder regions 36 is 20% of the contact length of the center region 38. This is because the tire ground contact property is deteriorated and the exercise performance is deteriorated because it may be shortened to a degree or less.

  The reason why TRI ≦ 1000 mm is set is that when TRI> 1000 mm, the contact length of the shoulder region 36 on the inner side of the vehicle having a large curvature radius is equal to or slightly longer than the contact length of the center region 38. This is because the performance deteriorates and exercise performance decreases.

  The relationship between the curvature radii TRI and TRO is more preferably 200 mm <TRI-TRO <500 mm. Further, the radii of curvature TRI and TRO are obtained by assembling the tire to the rim 26 corresponding to the normal rim, and applying the internal pressure corresponding to the normal internal pressure to each tire air chamber (the main air chamber 28, the first sub air chamber 31 and the second sub air chamber 32). In a no-load state. The numerical values of the curvature radii TRI and TRO are assumed to be general passenger car tires, and are not limited to these numerical ranges in the case of other types of tires.

  In the pneumatic tire 10, the inner diameter of the inner bead portion 24 is smaller than the inner diameter of the outer bead portion 12. Specifically, assuming that the radius from the tire center (not shown) to the rim base line BLO of the outer bead portion 12 is RO and the radius from the tire center to the rim base line BLI of the inner bead portion 24 is RI, 0 <RO− RI <50 mm.

  When the relationship between the radius RO of the outer bead portion 12 and the radius RI of the inner bead portion 24 is RO = RI, the inner bead portion 24 formed on the partition wall 18 is prevented from moving outward in the tire axial direction. A rim provided with a tall hump part must be used, and the assembly work must be very difficult. Further, when RO-RI ≧ 50 mm, it is difficult and unrealistic to manufacture a tire using the current tire manufacturing method.

  Furthermore, when the relationship between the radius RO of the outer bead portion 12 and the radius RI of the inner bead portion 24 is RO−RI ≧ 50 mm, the radius of the inner bead portion 24 becomes too small with respect to the radius of the outer bead portion 12, Accordingly, the radius of the rim is reduced, and as a result, the diameter of the brake that can be mounted on the inner side of the rim is reduced. This is not preferable because it may cause a decrease in vehicle motion performance.

  Therefore, it is preferable to satisfy 0 <RO-RI <50 mm because it is possible to prevent inconvenience as described above.

  In the pneumatic tire 10, since the inner bead portion 24 has an inner diameter smaller than the inner diameter of the outer bead portion 12, the rim 26 for mounting the pneumatic tire 10 has the pneumatic tire 10. It is necessary to be configured so that the tire 10 can be correctly attached.

  For this reason, the rim 26 is provided with a pair of left and right outer bead seats 26A that respectively contact the inner peripheral surfaces of the pair of left and right outer bead portions 12, and a step portion 26D on the inner side in the rim axial direction of each of the outer bead sheets 26A. A pair of left and right inner bead sheets 26B which are set to have a smaller diameter than the outer bead sheet 26A and come into contact with the inner peripheral surfaces of the pair of left and right inner bead parts 24, and one of the pair of left and right inner bead sheets 26B. A drop portion 26C provided between the other and set to have a smaller diameter than the inner bead sheet 26B is provided.

  The configuration of the rim 26 will be described in more detail. The outer bead sheet 26 </ b> A is formed according to the inner diameter of the outer bead portion 12, and the inner bead sheet 26 </ b> B is formed according to the inner diameter of the inner bead portion 24. In this example, as described above, since the inner diameter of the outer bead portion 12 is larger than the inner diameter of the inner bead portion 24, the inner bead sheet 26B is set to have a smaller diameter than the outer bead sheet 26A. Has been.

  A flange 26F that prevents the outer bead portion 12 from being pushed outward in the tire width direction is formed on the outer side in the axial direction of the outer bead sheet 26A, and is formed between the inner bead sheet 26B and the outer bead sheet 26A. Is formed with a step portion 26D that functions to prevent the inner bead portion 24 from being pushed outward in the tire width direction.

  Further, at the center in the axial direction of the rim 26, a drop portion (well) 26C in which the diameter of the groove bottom is smaller than that of the inner bead sheet 26B is provided.

  Although not shown, the rim 26 has an air valve for filling the first auxiliary air chamber 31 with gas, an air valve for filling the second auxiliary air chamber 32 with gas, and the main air chamber 28. Air valves for filling the gas are provided.

  The tire / rim assembly 51 is configured by mounting the pneumatic tire 10 on the rim 26.

(Function)
In the rim 26 in the tire / rim assembly 51, the radius RO of the outer bead portion 12 is set larger than the radius RI of the inner bead portion 24, and the drop portion 26C is provided in the middle portion. When the tire 10 is mounted, the outer bead portion 12 and the inner bead portion 24 can be dropped into the drop portion 26C, and the pneumatic tire 10 is assembled to the rim 26 in the same manner as the conventional pneumatic tire assembly. Work is easy.

  Further, the tire width of the inner bead portion 24 is determined by the difference in diameter between the outer bead seat 26A to which the outer bead portion 12 is attached and the inner bead seat 26B to which the inner bead portion 24 is attached. Since the step portion 26D that prevents the movement outward in the direction is formed, the inner bead portion 24 is caught when the rim is assembled, and the tall hump portion that deteriorates workability is placed outside the inner bead portion 24 in the tire width direction. There is no need to form the rim, and rim assembly is facilitated.

  Further, as a basic function of the tire / rim assembly 51 of the present embodiment, a first auxiliary air chamber 31, a main air chamber 28, which are partitioned by a partition wall 18 between the pneumatic tire 10 and the rim 26, In addition, since the second auxiliary air chamber 32 is formed in the tire width direction, any of the puncture on the ground contact surface due to the nailing of the tread portion 16 or the puncture of the sidewall portion 14 due to curb rubbing, etc. Since the two unpunctured air chambers support the load, although the tire height is slightly reduced, the steering stability and the vibration ride are slightly deteriorated, the vehicle can continue to travel safely without problems.

  In the pneumatic tire 10, the curvature radius TRI of the tread tread surface 16 </ b> A in the shoulder region 36 is set to be larger than the curvature radius TRO of the vehicle mounting inner side than the curvature radius TRO of the vehicle mounting outer side. Becomes laterally asymmetric (the ground pressure distribution is also asymmetrical), and a lateral force F is generated from the outside toward the inside in the vehicle width direction when traveling straight. When such a lateral force F is generated, the steering stability becomes very good. In terms of vehicle alignment, this improvement in steering stability is almost the same as if the wheels were set to toe-in, and almost the same mechanism as toe-in (stability during high-speed straight travel was ensured, and the steering wheel (It is not staggered and a firm response is obtained), which improves exercise performance.

  In addition, since the ranges of the curvature radii TRI and TRO are appropriately set, the vehicle mounting inner side is appropriately longer than the vehicle mounting outer side with respect to the ground contact length of the shoulder region 36. Sufficient lateral force F can be generated to improve exercise performance.

  If the conventional one-chamber tire (not shown) tries to improve the exercise performance, the radius of curvature of the shoulder area of the tread portion needs to be changed considerably on the left and right, but the tire has been used for a long time. In this case, a difference in wear occurs due to a difference in ground pressure between the left and right shoulder regions, and the desired lateral force F cannot be generated, or other performance such as vibration riding comfort deteriorates due to the progress of uneven wear. There is concern.

  However, in the case of a three-chamber tire such as the pneumatic tire 10 according to the present embodiment, the first auxiliary air chamber 31 does not change the internal pressure of the main air chamber 28, that is, without changing the tire basic performance. Further, by finely adjusting the internal pressure of the second auxiliary air chamber 32, it is possible to continuously generate the lateral force F from the initial stage of wear to the end stage and continue to obtain the merit of improving the exercise performance.

  In addition to the setting of the curvature radii TRI and TRO in the present embodiment, when the internal pressure of the first auxiliary air chamber 31 inside the vehicle is set to be appropriately larger than the internal pressure of the second auxiliary air chamber 32 outside the vehicle, A lateral force from the outside to the inside of the vehicle due to the differential pressure is also generated, and the steering stability can be improved more effectively.

(Test example)
The tires according to the conventional examples shown in Tables 1 and 2 and Comparative Examples 1 to 4 and Examples 1 to 4 were mounted on an actual vehicle, and a test on steering stability was performed. The tire size is 255 / 55R17, and the tire structure is as shown in FIG. The internal pressure of all three chambers was 200 kPa.

  Steering stability was evaluated by scoring the driving feeling during driving with a plurality of test drivers and calculating the average value. The result shown in Table 1 is an index when the scoring average value of the conventional example is set to 100, and the larger the value, the better the result.

  According to this test example, in Comparative Examples 1 and 3, the steering stability was lower than that in the conventional example, and Comparative Example 2 was evaluated as the same as the conventional example. On the other hand, in Examples 1-4, the evaluation which exceeds all conventional examples is obtained.

1 is a cross-sectional view of a tire / rim assembly in which a pneumatic tire is mounted on a rim.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Outer bead part 14 Side wall part 16 Tread part 16A Tread tread 16B Grounding end 16C Grounding end 18 Bulkhead 20 Base 21 Outer carcass 24 Inner bead part 26 Rim 28 Main air chamber (tire air chamber)
30 Bead core 31 First auxiliary air chamber (tire air chamber)
32 Second auxiliary air chamber (tire air chamber)
34 Bead Core BLI Rim Baseline BLO Rim Baseline CL Tire Equatorial Surface TRI Curvature Radius TRO Curvature Radius

Claims (5)

A pair of left and right outer bead parts with embedded bead cores;
Sidewall portions extending outward from the outer bead portion in the tire radial direction,
A tread portion connected to the sidewall portion;
The outer bead portion is provided between the pair of left and right outer bead portions so as to be spaced apart in the tire width direction, and extends inward in the tire radial direction from a base portion on the tire inner surface side in at least one of the sidewall portion and the tread portion. The inner bead portion provided at the inner end in the tire radial direction contacts the rim, and at least one partition wall that forms a plurality of independent tire air chambers in the tire width direction between the inner rim and the rim when the inner bead is attached to the rim. A pneumatic tire having
Assuming that the ground contact width of the tread portion is TW, in the cross section in the tire axial direction, the tread in the range from the ground contact end to at least 20% of the ground contact width TW in the range from the ground contact edge on both sides of the tire equator surface to the tire equator surface. A pneumatic tire characterized by having a curvature radius TRI of one tread surface larger than a curvature radius TRO of the other. The curvature radius TRO and the curvature radius TRI are:
50 mm ≦ TRI-TRO ≦ 700 mm,
The pneumatic tire according to claim 1, wherein the relationship is satisfied. The curvature radius TRO and the curvature radius TRI are:
100 mm ≦ TRO <TRI ≦ 1000 mm,
The pneumatic tire according to claim 1, wherein the relationship is satisfied. When the radius from the tire center to the rim baseline of the outer bead portion is RO, and the radius from the tire center to the rim baseline of the inner bead portion is RI,
The pneumatic tire according to any one of claims 1 to 3, wherein 0 <RO-RI <50 mm.   When the pneumatic tire according to any one of claims 1 to 4 is mounted on a vehicle, a side having the curvature radius TRI is directed toward the inside of the vehicle, and a side having the curvature radius TRO is directed toward the outside of the vehicle. A method for attaching a pneumatic tire, characterized in that

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