JP2006347456A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the motion performance of the tire by setting rubber elastic modulus within a predetermined area from the ground contact end of the tread section asymmetrically in the right and left in a pneumatic tire having a plurality of tire air chambers. <P>SOLUTION: Since one side rubber elastic modulus TMI is set larger than the other rubber elastic modulus TMO for the rubber elastic modulus of the tread section 16 in a shoulder area 36, the distribution of the ground contact pressure of the shoulder area 36 becomes asymmetric and the lateral force F from the side having a tread rubber of the rubber elastic modulus TMO toward the side having the tread rubber of the rubber elastic modulus TMI is generated. The lateral force F is generated from the outside of the tire mounted to the vehicle toward the inside and the operation stability becomes very excellent by making the side having the tread rubber of the rubber elastic modulus TMI be the inside of the tire mounted to the vehicle and making the side having the tread rubber of the rubber elastic modulus TMO 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 wall, and the setting of the rubber elastic modulus in the so-called shoulder region of the tread portion. Nothing is suggested.

  In consideration of the above fact, in the pneumatic tire having a plurality of tire air chambers, by setting the rubber elastic modulus within a predetermined range (so-called shoulder region) from the contact end of the tread portion to be asymmetrical left and right, The purpose is to improve tire movement 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. Of the range up to the equator plane, the elastic modulus of the tread rubber in the range of at least 20% of the ground contact width TW from the ground contact edge is characterized in that one rubber elastic modulus TMI is larger than the other rubber elastic modulus TMO. Yes.

  Here, the range of 20% of the contact width TW from the contact end to the tire equatorial plane side refers to a so-called shoulder region, and the range of the shoulder region set in this way is less than 20%. This is because the asymmetry of the distribution is insufficient and the magnitude of the lateral force (pseudo camber thrust) is not so large as to improve the motion performance, which is not preferable.

  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.

  TMI> TMO is defined as TMI <TMO. Even if the internal pressure of each tire chamber is the same, the direction of the lateral force (pseudo camber thrust) is from the side having the tread rubber with the rubber elastic modulus TMI. When the tread rubber having the rubber elastic modulus TMI is the vehicle mounting inner side and the side having the tread rubber having the rubber elastic modulus TMO is the vehicle mounting outer side. This is because, when compared to vehicle alignment, the same movement performance as that set for toe-out occurs, which causes a safety problem.

  In the pneumatic tire according to claim 1, since the rubber elastic modulus TMI of the so-called shoulder region of the tread portion is set to be larger than the rubber elastic modulus TMO of the other, the rigidity in the shoulder region is It becomes asymmetrical, and the contact pressure distribution is also asymmetrical. Due to the asymmetrical contact pressure distribution, a lateral force (pseudo camber thrust) is generated from the side having the tread rubber having the rubber elastic modulus TMO toward the side having the tread rubber having the rubber elastic modulus TMI when traveling straight. Therefore, the side having the tread rubber having the rubber elastic modulus TMI is set as the vehicle mounting inner side, and the side having the tread rubber having the rubber elastic modulus TMO is set as the outer side of the vehicle mounting. Therefore, the steering stability is very good.

  According to a second aspect of the present invention, in the pneumatic tire of the first aspect, the rubber elastic modulus TMO and the rubber elastic modulus TMI satisfy a relationship of 1 MPa ≦ TMI−TMO ≦ 7 MPa.

  Here, TMI-TMO ≧ 1 MPa is set so that if TMI-TMO <1 MPa, the difference in rubber elastic modulus between the left and right shoulder regions is small, so the lateral force (pseudo camber thrust) is also small and clear maneuvering This is because it is difficult to improve the stability.

  Also, TMI-TMO ≦ 7 MPa is set so that when TMI-TMO> 7 MPa, the magnitude of the lateral force (pseudo camber thrust) for improving the exercise performance is sufficient, but the contact shape and contact pressure This is because the left-right asymmetry of the distribution becomes very large, and as a result, the ground contact property of the tire is deteriorated and the exercise performance is likely to be lowered.

  In the pneumatic tire according to claim 2, since the range of the difference between the rubber elastic moduli TMI and TMO is appropriately set, the contact pressure distribution can be made moderately asymmetric, thereby deteriorating the contact property. Without generating a force, a sufficient lateral force (pseudo camber thrust) is generated from the side having the tread rubber having the rubber elastic modulus TMO toward the side having the tread rubber having the rubber elastic modulus TMI. The side having the tread rubber having the rubber elastic modulus TMI is set as the vehicle mounting inner side, and the side having the tread rubber having the rubber elastic modulus TMO is set as the vehicle mounting outer side, the steering stability can be improved.

  The invention of claim 3 is characterized in that, in the pneumatic tire according to claim 1 or 2, the rubber elastic modulus TMO and the rubber elastic modulus TMI satisfy a relationship of 1 MPa ≦ TMO <TMI ≦ 10 MPa. .

  Here, when TMO ≧ 1 MPa, if TMO <1 MPa, the average value of the rubber elastic modulus in the tire width direction of the tread portion becomes considerably thin. As a result, the input when getting over a small protrusion or the like on the road surface This is because it becomes larger and the vibration ride comfort is deteriorated.

  The reason why TMI ≦ 10 MPa is that when TMI> 10 MPa, the average value of the rubber elastic modulus in the tire width direction of the tread portion becomes considerably thick. This is because the absolute level becomes small, and as a result, even if the rubber elastic modulus is changed on the left and right, it is difficult to clearly improve the handling stability.

  In the pneumatic tire according to claim 3, since the ranges of the rubber elastic moduli TMI and TMO are appropriately set, the contact pressure distribution can be made moderately asymmetric, thereby deteriorating the contact property. In addition, a sufficient lateral force (pseudo camber thrust) for improving motion performance can be generated from the side having the tread rubber having the rubber elastic modulus TMO toward the side having the tread rubber having the rubber elastic modulus TMI. By setting the side having the tread rubber having the rubber elastic modulus TMI as the vehicle mounting inner side and setting the side having the tread rubber having the rubber elastic modulus TMO as the vehicle mounting outer side, it is possible to improve the steering stability.

  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 tread rubber having the rubber elastic modulus TMI is directed toward the inner side of the vehicle. It is characterized in that the side having the tread rubber having the rubber elastic modulus TMO is mounted toward the outside of the vehicle.

  In the pneumatic tire according to any one of claims 1 to 4, a lateral force (simulated) from a side having a tread rubber having a rubber elastic modulus TMO toward a side having a tread rubber having a rubber elastic modulus TMI when traveling straight. When the pneumatic tire is mounted on the vehicle as in the method of mounting the pneumatic tire according to claim 5, the side having the tread rubber having a rubber elastic modulus TMI is placed on the inner side of the vehicle. If the side having the tread rubber having the rubber elastic modulus TMO is attached to the outside of the vehicle, a lateral force is generated from the outside of the vehicle to the inside, and as a result, the steering stability of the vehicle is very good. be able to.

  As described above, according to the pneumatic tire of the present invention, by setting the rubber elastic modulus within a predetermined range (so-called shoulder region) from the ground contact end of the tread portion to improve the tire motion performance. It has an excellent effect of being able to.

  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 ground contact width of the tread portion 16 is TW, in the cross section in the tire axial direction, in the range from the ground contact ends 16B, 16C to the tire equatorial plane CL, in the range of at least 20% of the ground contact width TW from the ground contact ends 16B, 16C. As for the elastic modulus of the tread rubber, the rubber elastic modulus TMI inside the vehicle is set larger than the rubber elastic modulus TMO 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 the contact width TW from the contact ends 16B, 16C to the tire equatorial plane CL side indicates a so-called shoulder region 36. The range of the shoulder region 36 is set in this way, and if it is less than 20%, the asymmetry of the contact pressure distribution is insufficient, so the magnitude of the lateral force F (pseudo camber thrust) is the exercise performance. This is because it is not so large that it is not preferable. A portion between the left and right shoulder regions 36 is a center region 38 of the tread portion 16. When the circumferential main groove is formed in the tread portion 16, a portion extending from the ground end 16B to the circumferential main groove 42 closest to the ground end 16B, and a circumferential direction closest to the ground end 16C from the ground end 16C. The portions reaching the main groove 44 may be used as shoulder regions 36, respectively.

  TMI> TMO (the rubber elastic modulus TMI is larger than the rubber elastic modulus TMO on the outside of the vehicle). If TMI <TMO, even if the internal pressures of the tire chambers 31, 28, 32 are all the same, The direction of the lateral force F (pseudo camber thrust) is from the inside to the outside of the vehicle, and if compared to the alignment of the vehicle, the same movement performance degradation as that set for toe-out occurs, causing a safety problem. It is.

  The relationship between the rubber elastic modulus TMO and the rubber elastic modulus TMI is set so as to satisfy at least one condition of 1 MPa ≦ TMI−TMO ≦ 7 MPa and 1 MPa ≦ TMO <TMI ≦ 10 MPa. Here, the reason TMI-TMO ≧ 1 MPa is that when TMI-TMO <1 MPa, the difference in rubber elastic modulus between the left and right shoulder regions 36 is small, so the lateral force F (pseudo camber thrust) is also small. This is because it is difficult to improve the handling stability.

  Also, TMI-TMO ≦ 7 MPa is set so that when TMI-TMO> 7 MPa, the lateral force F is sufficient to improve the exercise performance, but the ground contact shape and the left-right asymmetry of the contact pressure distribution are sufficient. This is because as a result of this becoming extremely large, the ground contact property of the tire is deteriorated and the exercise performance is likely to be lowered.

  The reason why TMO ≧ 1MPa is that when TMO <1MPa, the average value of the rubber elastic modulus in the tire width direction of the tread portion 16 becomes considerably thin, and as a result, the input when getting over small protrusions on the road surface becomes large. This is because the vibration ride comfort is deteriorated.

  The reason why TMI ≦ 10 MPa is that when TMI> 10 MPa, the average value of the rubber elastic modulus in the tire width direction of the tread portion 16 becomes considerably thick. This is because, as a result, it is difficult to clearly improve the handling stability even if the rubber elastic modulus is changed on the left and right sides.

  In addition, about the value of rubber elastic modulus TMI and TMO, a more preferable range is TMO ≧ 2 MPa and TMI ≦ 5 MPa. The rubber elastic moduli TMI and TMO are determined by assembling the tire to the rim 26 corresponding to the normal rim, and adjusting 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). ) And in an unloaded condition.

  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.

  Further, in the pneumatic tire 10, the rubber elastic modulus TMI on the vehicle mounting inner side is set larger than the rubber elastic modulus TMO on the vehicle mounting outer side with respect to the rubber elastic modulus of the tread portion 16 in the shoulder region 36. The abutment pressure distribution becomes asymmetric, 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.

  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 settings of the rubber elastic moduli TMI and TMO in the present embodiment, when the internal pressure of the first auxiliary air chamber 31 on the inner side of the vehicle is set to be appropriately larger than the internal pressure of the second auxiliary air chamber 32 on the outer side of the vehicle. 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 further effectively improved.

(Test example)
The tires according to the conventional examples shown in Tables 1 and 2 and Comparative Examples 1 to 3 and Examples 1 to 3 were mounted on an actual vehicle, and tests on steering stability and vibration ride comfort were 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 and vibration ride comfort were evaluated by scoring the driving feeling during actual vehicle driving by 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 each comparative example, the steering stability or the vibration ride comfort is lower than the conventional example, but in each example, good results are obtained without any lower than the conventional example. ing.

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

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 in that one rubber elastic modulus TMI is larger than the other rubber elastic modulus TMO. The rubber elastic modulus TMO and the rubber elastic modulus TMI are
1 MPa ≦ TMI−TMO ≦ 7 MPa,
The pneumatic tire according to claim 1, wherein the relationship is satisfied. The rubber elastic modulus TMO and the rubber elastic modulus TMI are
1 MPa ≦ TMO <TMI ≦ 10 MPa,
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.   5. When the pneumatic tire according to claim 1 is mounted on a vehicle, the tread rubber having the rubber elastic modulus TMO is directed toward the vehicle inner side with the tread rubber having the rubber elastic modulus TMI facing the inside. A method for mounting a pneumatic tire, characterized in that the tire is mounted with its side facing the outside of the vehicle.

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