JP2006327256A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing its anti-turnover characteristic. <P>SOLUTION: The pneumatic tire 1 has a cap tread rubber 51 constituting the tread surface of the tire and undertread rubber 52 installed as sub-layer of the cap tread rubber 51. In the region outside the vehicle more than the tire center line CL, the cap tread rubber 51 has an isotropic rubber part 511 to meet the condition M<SB>b</SB>/M<SB>a</SB>≤0.9, where Ma is the modulus at the 300-% tensile time applied in the tire circumferential direction (JIS-K 6251), and M<SB>b</SB>is the modulus at the 300-% tensile time applied in the tire width direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the rollover resistance of the tire.

  In recent years, with the increase in the center of gravity of a vehicle and the reduction in the flatness of a tire, there is a demand to improve the rollover resistance characteristics of the tire (tire characteristics for suppressing the rollover of the vehicle during a high-speed lane change, etc.). Such a rollover resistance is improved by moderately suppressing the maximum cornering force within a range that does not affect the steering stability and the like, and is generally optimized by adjusting the CF curve and the contact shape of the tire.

  In addition, the technique described in patent document 1 is known as a conventional pneumatic tire with a similar structure although a subject differs with respect to the pneumatic tire concerning this invention. In the conventional pneumatic tire, the tread pattern formed by grooves carved on the tread surface is asymmetric with respect to the tire equatorial plane, the tread rubber layer is the cap rubber, and the base rubber disposed under the cap rubber When the tire is mounted, the outer groove area S1 in the vehicle outer region and the inner groove area S2 in the vehicle inner region satisfy 0.6 <S1 / S2 <1.0. The cap rubber has a rebound resilience greater than 40% and less than 60%, and a high hardness rubber in the vehicle outer region of the cap rubber, and a low hardness rubber having a lower hardness than the vehicle outer region in the vehicle inner region. The cap rubber is disposed so that (the ground contact width of the high hardness rubber / the tire ground contact width) exceeds 0.4 and less than 0.6, and the rubber hardness of the high hardness rubber is Is less than 71 ° and the rubber hardness of the low hardness rubber is more than 55 ° and less than 63 °, the rubber hardness of the high hardness rubber and the rubber hardness of the low hardness rubber And the rubber hardness difference is 5 ° or more, the thickness of the base rubber is more than 1.0 mm and less than 3.0 mm, the rebound resilience of the base rubber is more than 64%, and 85 It is characterized by being less than%.

JP 2003-326917 A

  An object of the present invention is to provide a pneumatic tire that can improve the rollover resistance of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a cap tread rubber constituting a tread surface of the tire, and the cap tread rubber is located on the outer side of the vehicle with respect to the tire center line CL. In the region, the modulus M _a (JIS-K6251) at 300 [%] tension in the tire circumferential direction and the modulus M _b at 300 [%] tension in the tire width direction are M _b / M _a ≦ 0.9. It has the anisotropic rubber part which satisfy | fills this relationship, It is characterized by the above-mentioned.

Anisotropic In the pneumatic tire, a cap tread rubber, a vehicle outer side of the region, where the modulus M _b modulus M _a and the tire width direction of the tire circumferential direction satisfies a relationship of M _b / M _a ≦ 0.9 Since the rubber portion is provided, the region outside the vehicle is easily deformed in the tire width direction when the tire is in contact with the tire. As a result, the maximum cornering force at the time of a high slip angle or a high load is reduced, which has the advantage of improving the rollover resistance of the tire.

In the pneumatic tire according to the present invention, the modulus M _{a of the} anisotropic rubber portion in the tire circumferential direction is in the range of 5 [MPa] ≦ M _a ≦ 15 [MPa].

In this pneumatic tire, since the modulus M _{a in} the tire circumferential direction of the anisotropic rubber portion is optimized, there is an advantage that necessary tread rigidity is secured and the steering stability performance and braking performance of the tire are maintained. .

In the pneumatic tire according to the present invention, the modulus M _{b of the} anisotropic rubber portion in the tire width direction is in the range of 3 [MPa] ≦ M _b ≦ 13 [MPa].

In the pneumatic tire, since the modulus M _b in the tire width direction of the anisotropic rubber portion is optimized, there is an advantage that耐転covering characteristics of the tire is more effectively improved. Further, since necessary tread rigidity is ensured, there is an advantage that the steering stability performance and braking performance of the tire are maintained.

In the pneumatic tire according to the present invention, a modulus M _b modulus M _a and the tire width direction of the tire circumferential direction of the anisotropic rubber portion satisfies the relation of 0.5 ≦ M _b / M _a.

In the pneumatic tire, because the ratio M _b / M _a and modulus M _b in the tire circumferential direction of the modulus M _a and the tire width direction of the anisotropic rubber portion is optimized, the outboard region (Anisotropic There is an advantage that steering stability is ensured by optimizing the rigidity ratio or rigidity difference between the tire circumferential direction and the tire width direction in the rubber property portion).

In the pneumatic tire according to the present invention, a tire circumferential direction of the modulus M _a of the anisotropic rubber portion, 300 [%] in the vehicle inner side region and the modulus M _a of time tensile, 0.7 ≦ M The relationship of _c / M _a ≦ 1.2 is satisfied.

In the pneumatic tire, the modulus M _a of the tire circumferential direction of the anisotropic rubber portion, 300 [%] of the vehicle inside the area since the modulus M _a when tension is optimized, the braking performance of the tire and There is an advantage that steering stability performance is ensured.

In addition, the pneumatic tire according to the present invention has a belt layer composed of a plurality of laminated belt materials, and among the plurality of belt materials, the innermost belt material in the tire radial direction is referred to as a first belt material. Sometimes, the ratio D ₀ / D of the width D ₀ of the anisotropic rubber part and the width D of the first belt material is in the range of 0.15 ≦ D ₀ /D≦0.40.

In this pneumatic tire, since the ratio D ₀ / D between the width D ₀ of the anisotropic rubber portion and the width D of the first belt material is optimized, the rollover resistance and steering stability of the tire are improved. There are advantages.

  In the pneumatic tire according to the present invention, the hardness of the cap tread rubber is substantially uniform in a region outside the vehicle and a region inside the vehicle.

  In this pneumatic tire, since the hardness of the cap tread rubber is substantially uniform in the area outside the vehicle and the area inside the vehicle, there is an advantage that the uneven wear resistance performance and the operation feeling performance of the tire are improved.

  In the pneumatic tire according to the present invention, short fibers are arranged and mixed in the tire circumferential direction in the anisotropic rubber portion.

  In this pneumatic tire, short fibers are arranged and mixed in the circumferential direction of the tire in the anisotropic rubber part, so that it is easy to achieve both rollover resistance and steering stability by controlling the anisotropy of the modulus. There are advantages.

Further, the pneumatic tire according to the present invention has an under tread rubber in a lower layer of the cap tread rubber, and the under tread rubber is located in a center region of the tire and a shoulder region portion positioned in a shoulder region. And the dynamic elastic modulus E _C of the center region portion and the dynamic elastic modulus E _S of the shoulder region portion have a relationship of E _C <E _S.

In this pneumatic tire, the undertread rubber has a center region portion located in the center region of the tire and a shoulder region portion located in the shoulder region, and the dynamic elastic modulus E _C and the shoulder region of the center region portion. The dynamic elastic modulus E _S of the part has a relationship of E _C <E _S. In such a configuration, since the dynamic elastic modulus E _C of the center region portion is smaller than the dynamic elastic modulus E _S of the shoulder region portion, the amount of change in the tire contact length at the time of high load becomes large. Thereby, there exists an advantage which the rollover-proof characteristic of a tire improves. In addition, since the tire rigidity of the shoulder region portion is larger than that of the center region portion, there is an advantage that steering stability performance is ensured.

In the pneumatic tire according to the present invention, the dynamic elastic modulus E _C of the center region portion and the dynamic elastic modulus E _S of the shoulder region portion are 1.0 [MPa] ≦ E _C ≦ 5.0 [ MPa], 5.0 [MPa] ≦ E _S ≦ 15.0 [MPa], and 1.20 ≦ E _S / E _C.

In the pneumatic tire, since the dynamic elastic modulus E _S of the dynamic elastic modulus E _C and the shoulder region of the center region portion is optimized, there is an advantage that耐転covering properties and rolling resistance of the tire is ensured .

In addition, the pneumatic tire according to the present invention has a belt layer composed of a plurality of laminated belt materials, and among the plurality of belt materials, the innermost belt material in the tire radial direction is referred to as a first belt material. Sometimes, the ratio D _C / D between the width D _C of the center region and the width D of the first belt material is in the range of 0.30 ≦ D _C /D≦0.70.

In this pneumatic tire, since the ratio D _C / D of the width D _C of the center region portion and the width D of the first belt material is optimized, the steering stability of the tire is maintained and the rollover resistance is improved. There is an advantage to improve.

In the pneumatic tire according to the present invention, the ratio T _C / T between the thickness T _C of the center region portion in the tire radial direction and the thickness T of the cap tread rubber and the under tread rubber is 0.10. ≦ T _C /T≦0.50.

In this pneumatic tire, the ratio T _C / T between the thickness T _C of the center region with respect to the tire radial direction and the thickness T of the entire tread layer (cap tread rubber and under tread rubber) is optimized. There is an advantage that the rollover resistance can be improved while maintaining the rolling resistance of the tire.

In the pneumatic tire according to the present invention, the cap tread rubber, the vehicle outside the region, and the modulus M _b modulus M _a and the tire width direction of the tire circumferential direction satisfies a relationship of M _b / M _a ≦ 0.9 Since the anisotropic rubber portion is provided, the region outside the vehicle is easily deformed in the tire width direction when the tire contacts the ground. As a result, the maximum cornering force at the time of a high slip angle or a high load is reduced, which has the advantage of improving the rollover resistance of the tire.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to the present invention. FIG. 2 is an explanatory view showing a cap tread rubber of the pneumatic tire shown in FIG. 1. FIG. 3 is an explanatory view showing an under tread rubber of the pneumatic tire shown in FIG. 1. 4 and 5 are tables showing the results of performance tests of pneumatic tires.

  The pneumatic tire 1 includes a bead core (not shown), a carcass layer 3, a belt layer 4, a cap tread rubber 51, an under tread rubber 52, and a sidewall rubber 6. The bead core is configured as a pair of left and right. The carcass layer 3 is bridged between the left and right bead cores 2 and 2 in a toroidal shape. The belt layer 4 includes a plurality of stacked belt members 41 to 43 and is disposed on the outer periphery in the tire radial direction of the carcass layer 3. In addition, the belt material 41 arrange | positioned among the belt materials 41-43 at the innermost side (lowermost layer) of a tire radial direction is called a 1st belt material.

  The cap tread rubber 51 is disposed on the outer periphery in the tire radial direction of the belt layer 4 to constitute a tread surface of the tire. The under tread rubber 52 is disposed in a lower layer of the cap tread rubber 51 (a layer on the inner side in the tire radial direction. A layer between the cap tread rubber 51 and the belt layer 4). Note that the tread portion of the tire is composed of a plurality of types of rubber materials including a cap tread rubber 51, an under tread rubber 52, and a shoulder tread rubber 53. The sidewall rubber 6 is disposed on the outer side in the tire width direction of the carcass layer 3 and constitutes a sidewall portion of the tire.

  Moreover, in this pneumatic tire 1, the mounting direction with respect to the vehicle is defined. For example, the tread pattern is configured to be point symmetric or asymmetric with respect to the tire center line (not shown), and the direction with respect to the vehicle inner side (or vehicle outer side) is designated in the tire mounted state.

  Here, according to the researches of the inventors, the rollover resistance characteristics of the tire (tire characteristics for suppressing the rollover of the vehicle at the time of a high-speed lane change, etc.) are the compound physical properties of the rubber material constituting the tread portion (particularly 300 It has been found that it greatly depends on [%] modulus during tension) and side wall rigidity. For example, according to the multiple correlation analysis regarding the rollover resistance, it has been found that the compound physical properties of the cap tread rubber 51 have a high contribution rate to each parameter (maximum cornering force) regarding the rollover resistance.

In view of this point, in the pneumatic tire 1, the cap tread rubber 51 has an anisotropic rubber portion 511 in a region outside the vehicle with respect to the tire center line CL (see FIG. 1). This anisotropic rubber part 511 has a modulus M _a (JIS-K6251) of 300 [%] tension applied in the tire circumferential direction and a modulus M _{b of} 300 [%] tension applied in the tire width direction of M _b / It consists of a rubber material (compound) having a relationship of M _a ≦ 0.9. That is, the anisotropic rubber portion 511, the modulus M _b in the tire width direction is smaller than the modulus M _a of the tire circumferential direction (M _a> M _b). Therefore, the cap tread rubber 51 is configured so that a portion (region outside the vehicle) that comes into contact with the vehicle during cornering is easily deformed.

  Note that the cap tread rubber 51 only needs to have the anisotropic rubber portion 511 in at least a part of the region outside the vehicle. Further, the vehicle outer side or the vehicle inner side is defined with reference to a state in which the pneumatic tire 1 is mounted on the vehicle.

On the other hand, in the cap tread rubber 51, a rubber part (hereinafter referred to as other rubber part) 512 other than the anisotropic rubber part 511 is formed of a normal rubber material. For example, the other portion 512 has a uniform modulus M _c with respect to the tire circumferential direction and the tire width direction.

  Specifically, the cap tread rubber 51 is composed of an anisotropic rubber part 511 and another rubber part 512 (multi-tread structure), and the anisotropic rubber part 511 and other rubbers in a sectional view in the tire meridian direction. The boundary with the portion 512 is located in a region outside the vehicle with respect to the tire center line CL. Accordingly, a region outside the vehicle from the boundary between the rubber portions 511 and 512 is configured by an anisotropic rubber material, and a region inside the vehicle from the boundary is configured by a normal rubber material. The cap tread rubber 51 may have a portion other than the anisotropic rubber portion 511 and the other rubber portion 512.

[effect]
In the pneumatic tire 1, a cap tread rubber 51, the vehicle outer side area, and modulus M _b modulus M _a and the tire width direction of the tire circumferential direction satisfies a relationship of M _b / M _a ≦ 0.9 different Since it has the isotropic rubber portion 511, the region outside the vehicle is likely to be deformed in the tire width direction when the tire contacts the ground. As a result, the maximum cornering force at the time of a high slip angle or a high load is reduced, which has the advantage of improving the rollover resistance of the tire.

[Modification 1]
In the pneumatic tire 1, the modulus M _{a of} the anisotropic rubber portion 511 in the tire circumferential direction is preferably in the range of 5 [MPa] ≦ M _a ≦ 15 [MPa]. As a result, necessary tread rigidity is ensured, and there is an advantage that the steering stability performance and braking performance of the tire are maintained.

In addition, the modulus M _{b of} the anisotropic rubber portion 511 in the tire width direction is preferably in the range of 3 [MPa] ≦ M _b ≦ 13 [MPa]. As a result, since the deformation amount in the tire width direction of the vehicle outer region at the time of tire contact is optimized, there is an advantage that the rollover resistance of the tire is more effectively improved. Further, since necessary tread rigidity is ensured, there is an advantage that the steering stability performance and braking performance of the tire are maintained.

Further, the modulus M _b modulus M _a and the tire width direction of the tire circumferential direction of the anisotropic rubber portion 511, the relationship of 0.5 ≦ M _b / M _a (lower), or, 1 ≦ M _a -M It is preferable to satisfy the relationship of _b ≦ 8 (rigidity difference). As a result, the rigidity ratio or the difference in rigidity between the tire circumferential direction and the tire width direction in the region outside the vehicle (anisotropic rubber portion 511) is optimized, so both rollover resistance and steering stability are compatible. There are advantages.

[Modification 2]
In the pneumatic tire 1, the modulus M _a tire circumferential direction of the anisotropic rubber portion 511, 300 [%] in the vehicle inner side region and the modulus M _a of time tensile, 0.7 ≦ M _c / It is preferable to satisfy the relationship of M _a ≦ 1.2. Further, it is more preferable that these satisfy the relationship of 0.9 ≦ M _c / M _a ≦ 1.1. As a result, the modulus difference between the region outside the vehicle (anisotropic rubber portion 511) and the region inside the vehicle is optimized, and there is an advantage that the braking performance and steering stability performance of the tire are ensured.

[Modification 3]
In the pneumatic tire 1, the ratio D ₀ / D between the width D ₀ of the anisotropic rubber portion 511 and the width D of the first belt member 41 is in a range of 0.15 ≦ D ₀ /D≦0.40. It is preferable to be within. In such a configuration, since the width D ₀ of the anisotropic rubber portion 511 is optimized with respect to the width D of the first belt material 41, there is an advantage that the rollover resistance and the steering stability of the tire are improved. Specifically, when the ratio D ₀ / D is D ₀ /D<0.15, the maximum cornering force is not effectively reduced, and the rollover resistance of the tire is not improved. Further, when the ratio D ₀ / D is 0.40 <D ₀ / D, the rigidity of the tread portion is lowered and steering stability is deteriorated.

[Modification 4]
In the pneumatic tire 1, it is preferable that the hardness of the cap tread rubber 51 is substantially uniform in the vehicle outer region and the vehicle inner region. That is, it is preferable that the hardness of the anisotropic rubber part 511 and the hardness of the other rubber part 512 are substantially equal. Thereby, there is an advantage that the uneven wear resistance performance and the operation feeling performance of the tire are improved.

[Modification 5]
In the pneumatic tire 1, it is preferable that short fibers are arranged and mixed in the anisotropic rubber portion 511 in the tire circumferential direction. Thereby, there is an advantage that it is easy to achieve both rollover resistance and steering stability by controlling the anisotropy of the modulus.

  The types of short fibers include, for example, polyamide fibers, polyester fibers, PVA fibers (vinylon fibers), polypropylene fibers, polyethylene fibers, polyacryl fibers, aramid fibers and other organic fibers, glass fibers, carbon fibers and other inorganic fibers. Or cotton, hemp or other natural fibers. However, the kind of short fiber is not limited to these. The short fibers preferably have a thickness of 5 [dtex] to 15 [dtex] and a length of 3 [mm] to 50 [mm]. The anisotropic rubber portion 511 is formed by, for example, blending short fibers with an unvulcanized rubber material and extruding it into a plate while kneading it in an extruder.

[Modification 6]
In this pneumatic tire 1, the undertread rubber 52 has a center region portion 521 located in the center region of the tire and a shoulder region portion 522 located in the shoulder region, and the dynamic of the center region portion 521 It is preferable that the elastic modulus E _C and the dynamic elastic modulus E _S of the shoulder region portion 522 have a relationship of E _C <E _S (see FIGS. 1 and 2). For example, the undertread rubber 52 includes a center region portion 521 and a pair of shoulder region portions 522 and 521, and the shoulder region portions 522 and 521 are disposed on both outer sides in the tire width direction with the center region portion 521 as the center. The undertread rubber 52 may have a single structure in which the center region portion 521 and the shoulder region portion 522 are integrated, or may have a structure divided into the center region portion 521 and the shoulder region portion 522. You may do it.

In such a configuration, since the dynamic elastic modulus E _C of the center region portion 521 is smaller than the dynamic elastic modulus E _S of the shoulder region portion 522, the amount of change in the tire contact length at the time of high load increases. Thereby, there exists an advantage which the rollover-proof characteristic of a tire improves. Further, since the tire rigidity of the shoulder region portion 522 is larger than that of the center region portion 521, there is an advantage that steering stability performance is ensured. In this way, by changing the dynamic elastic moduli E _C and E _S of the under tread rubber 52 in the tire width direction (the center region portion 521 and the shoulder region portion 522), the average contact length of the tire can be optimized or the tread portion. It is possible to adjust the out-of-plane bending rigidity.

Incidentally, the difference E _S -E _C with dynamic elastic modulus E _C of the dynamic elastic modulus E _S and the center region portion 521 of the shoulder region 522 is preferably _{2 [MPa] ≦ E S -E} C More preferably, 5 [MPa] ≦ E _S −E _C. Thereby, there exists an advantage which the rollover-proof characteristic of a tire improves more effectively.

In the above configuration, the dynamic elastic modulus E _C of the center region portion 521 and the dynamic elastic modulus E _S of the shoulder region portion 522 are 1.0 [MPa] ≦ E _C ≦ 5.0 [MPa], 5 It is preferable that 0.0 [MPa] ≦ E _S ≦ 15.0 [MPa] and 1.20 ≦ E _S / E _C (E _S is 20 [%] or higher than E _C ). In such a configuration, the dynamic elastic modulus E _S of the center region portion 521 and the shoulder region 522, since E _C are optimized, there is an advantage that耐転covering properties and rolling resistance of the tire is ensured. For example, when the dynamic elastic modulus E _C of the center region portion 521 is 5.0 [MPa] <E _C , the tire contact length becomes insufficient and the rollover resistance is not improved. Further, when the dynamic elastic modulus E _S of the shoulder region portion 522 is 15.0 [MPa] <E _S , the rollover resistance and rolling resistance are deteriorated.

In the above configuration, the width D _C and the ratio D _C / D of the width D of the first belt member 41 of the center region 521 is within the range of 0.30 ≦ D _C /D≦0.70 Is preferred (see FIG. 3). In such a configuration, the width D _C of the center region 521 is optimized, there is an advantage that耐転covering properties are improved with steering stability of the tire is maintained. For example, if the width of the center region portion 521 is too narrow and D _C /D<0.30, the amount of change in the tire contact length at high loads becomes small, and the rollover resistance is not improved. Further, when 0.70 <D _C / D, the steering stability is deteriorated.

In the above configuration, the ratio T _C / T between the thickness T _C of the center region portion 521 with respect to the tire radial direction and the thickness T of the entire tread layer (the cap tread rubber 51 and the under tread rubber 52) is 0.00. It is preferable to be within the range of 10 ≦ T _C /T≦0.50. In such a configuration, since the thickness T _C of the center region portion 521 is optimized, there is an advantage that the rollover resistance can be improved while maintaining the rolling resistance of the tire. For example, when the thickness T _C of the center region portion 521 is small and T _C /T<0.10, the change in rigidity in the tire width direction is reduced, and the rollover resistance is not improved. On the other hand, if the thickness T _C of the center region 521 is too thick, an increase in tire weight and deterioration of rolling resistance occur.

Similarly, the ratio T _S / T of the thickness T _S of the shoulder region portion 522 to the tire radial direction and the thickness T of the entire tread layer is in the range of 0.1 ≦ T _S /T≦0.4. It is preferable that it exists in. There is an advantage that the rollover resistance can be improved while maintaining the rolling resistance of the tire.

[Performance test 1]
In this example, performance tests on (1) rollover resistance, (2) steering stability performance, and (3) braking performance were performed on a plurality of types of pneumatic tires having different cap tread rubber configurations (FIG. 4). reference). In this performance test, a pneumatic tire having a tire size of 185 / 60R15 85H is mounted on a regular rim defined by JATMA, and a normal internal pressure and a normal load are applied to the pneumatic tire.

  (1) In the performance test related to the rollover resistance, a double lane change (ISO 3888-2: Elk test) was performed with a pneumatic tire mounted on a 1300 [cc] class domestic small car. The rollover resistance is evaluated based on whether or not the wheels are lifted up when the vehicle is running. In the evaluation result, a circle is given when the wheel does not lift up.

  (2) In the performance test for handling stability, a pneumatic tire is mounted on a test vehicle, and the test vehicle travels on a test course having a flat circuit around 60 [km / h] to 100 [km / h]. Drive at speed. A sensitivity evaluation is performed by three specialized panelists regarding the steering performance during lane change and cornering and the stability during straight travel. The evaluation result is indicated by an index value based on the conventional example as a reference (100), and the larger the index, the better.

  (3) In the performance test related to braking performance, a pneumatic tire is mounted on a test vehicle, and a braking distance from a traveling speed of 100 [km / h] is measured on a test course having a smooth road surface. And this measured value is implemented 5 times for each pneumatic tire, and the average of the measured values is evaluated. The evaluation result is indicated by an index value based on the conventional example as a reference (100), and the larger the index, the better.

In the pneumatic tire of Conventional Example 1, the cap tread rubber is made of a single rubber material, and the modulus of the area inside the vehicle and the area outside the vehicle are equal. The pneumatic tire of the invention examples 1 and 2, has an anisotropic rubber portion 511 to the outboard region of the cap tread rubber 51, the modulus M _b is the tire circumferential direction of the tire width direction of the anisotropic rubber portion 511 Is smaller than the modulus M _a (M _a > M _b ). Moreover, the anisotropic rubber part 511 is comprised by the mixing | blending of the polyamide fiber. These pneumatic tires have the same JIS hardness of their tread compounds.

As shown in the test results in FIG. 4, it can be seen that in the pneumatic tires of Invention Examples 1 and 2, the rollover resistance of the tire is improved. Also, comparing the pneumatic tires of the invention Examples 1 and 2 and Comparative Example 1, by modulus ratio M _b / M _a in the tire width direction and the tire circumferential direction are optimized, can耐転covering properties of the tire improve I understand that Further, when the pneumatic tires of Invention Example 1 and Invention Example 5 are compared, the tread width ratio D ₀ / D of the anisotropic rubber portion 511 is optimized, so that the rollover resistance of the tire is improved. I understand.

[Performance test 2]
Further, in this example, performance tests on (1) rollover resistance, (2) steering stability performance, and (3) rolling resistance were performed on a plurality of types of pneumatic tires having different configurations of the undertread rubber ( (See FIG. 5). In this performance test, a pneumatic tire having a tire size of 185 / 60R15 85H is mounted on a regular rim defined by JATMA, and a normal internal pressure and a normal load are applied to the pneumatic tire.

  (1) The performance test concerning the rollover resistance is performed by the same test method as the performance test 1 described above.

  (2) In the performance test for steering stability, the CP value (cornering power at a running speed of 10 [km / h] and a slip angle of ± 1 [deg]) of a pneumatic tire was measured with a flat belt. Based on the above, index evaluation using the conventional example as a reference (100) is performed. A larger index is more preferable.

  (3) In the performance test concerning rolling resistance, a constant load is applied to the pneumatic tire on the rotating drum, and the rolling resistance of the tire is measured. Based on this measured value, index evaluation is performed with the reciprocal of the measured value of the conventional example as a reference (100). A larger index is more preferable.

In the pneumatic tires of Conventional Examples 2 and 3, the under tread rubber is made of a single rubber material and has a uniform dynamic elastic modulus. In the pneumatic tires of Invention Examples 3 and 4, a difference (E _C <E _S ) is provided between the dynamic elastic moduli E _C and E _S of the center region portion 521 and the shoulder region portion 522 of the under tread rubber. These pneumatic tires have the same JIS hardness of their tread compounds.

As shown in the test results of FIG. 5, it can be seen that in the pneumatic tires of Invention Examples 6 and 7, the rollover resistance of the tire is improved, and the steering stability performance and the rolling resistance are maintained. Further, when the pneumatic tires of Invention Example 6 and Comparative Example 2 are compared, it can be seen that the steering stability performance of the tire is improved by optimizing the tread width ratio D _C / D of the center region portion 521.

  As described above, the pneumatic tire according to the present invention is useful in that it can improve the rollover resistance of the tire.

It is sectional drawing of the tire meridian direction which shows the pneumatic tire concerning this invention. It is explanatory drawing which shows the cap tread rubber of the pneumatic tire described in FIG. It is explanatory drawing which shows the under tread rubber | gum of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of a pneumatic tire. It is a graph which shows the result of the performance test of a pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Carcass layer 4 Belt layer 41 First belt material 51 Cap tread rubber 511 Anisotropy rubber part 512 Other rubber part 52 Under tread rubber 53 Shoulder tread rubber 6 Side wall rubber 521 Center area part 522 Shoulder Area part

Claims (12)

A pneumatic tire having a cap tread rubber constituting a tread surface of the tire,
The cap tread rubber, a vehicle outer side region from the tire centerline CL, 300 [%] according to the tire circumferential direction modulus M _a (JIS-K6251) and applied to the tire width direction 300 when tension [%] when the tensile a pneumatic tire and modulus M _b of and having an anisotropic rubber portion satisfies the relationship M _b / M _a ≦ 0.9. 2. The pneumatic tire according to claim 1, wherein a modulus M _{a in} the tire circumferential direction of the anisotropic rubber portion is in _{a range} of 5 [MPa] ≦ M _a ≦ 15 [MPa]. 3. The pneumatic tire according to claim 1, wherein a modulus M _{b of the} anisotropic rubber portion in a tire width direction is in a range of 3 [MPa] ≦ M _b ≦ 13 [MPa]. The modulus M _{a in} the tire circumferential direction of the anisotropic rubber portion and the modulus M _{b in the} tire width direction satisfy _a relationship of 0.5 ≦ M _b / M _a . Pneumatic tire. The tire circumferential direction of the modulus M _a of the anisotropic rubber portion, 300 [%] in the vehicle inner side region and the modulus M _a of time tensile, the relationship _{0.7 ≦ M c / M a ≦} 1.2 The pneumatic tire according to any one of claims 1 to 4, which is satisfied. When having a belt layer composed of a plurality of laminated belt materials and calling the innermost belt material in the tire radial direction among the plurality of belt materials as a first belt material,
The ratio D ₀ / D between the width D ₀ of the anisotropic rubber portion and the width D of the first belt member is in the range of 0.15 ≦ D ₀ /D≦0.40. The pneumatic tire according to any one of the above.   The pneumatic tire according to any one of claims 1 to 6, wherein the hardness of the cap tread rubber is substantially uniform in a region outside the vehicle and a region inside the vehicle.   The pneumatic tire according to claim 1, wherein short fibers are arranged and mixed in the tire circumferential direction in the anisotropic rubber portion. Under tread rubber under the cap tread rubber,
The under tread rubber has a center region portion located in the center region of the tire and a shoulder region portion located in the shoulder region, and the dynamic elastic modulus E _C of the center region portion and the movement of the shoulder region portion. The pneumatic tire according to claim 1, wherein the elastic modulus E _S has a relationship of E _C <E _S. The dynamic elastic modulus E _C of the center region portion and the dynamic elastic modulus E _S of the shoulder region portion are 1.0 [MPa] ≦ E _C ≦ 5.0 [MPa], 5.0 [MPa] ≦ E The pneumatic tire according to claim 9, wherein _S ≦ 15.0 [MPa] and 1.20 ≦ E _S / E _C. When having a belt layer composed of a plurality of laminated belt materials and calling the innermost belt material in the tire radial direction among the plurality of belt materials as a first belt material,
11. The ratio D _C / D between the width D _C of the center region portion and the width D of the first belt member is in a range of 0.30 ≦ D _C /D≦0.70. Pneumatic tire. The ratio T _C / T of the thickness T _C of the center region with respect to the tire radial direction and the thickness T of the cap tread rubber and the under tread rubber is in the range of 0.10 ≦ T _C /T≦0.50 The pneumatic tire according to claim 9, wherein the pneumatic tire is inside.

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