JP6790547B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Pneumatic tires have a belt on the outside of the carcass. The belt reinforces the carcass. Belts usually have an inner layer and an outer layer. The inner layer and the outer layer each include a large number of cords and topping rubbers arranged in parallel. A typical cord material is steel.

The structure of the belt affects steering stability and ride comfort. The structure of the belt also affects the durability of the tire. Examples of studies on the structure of the belt are disclosed in JP-A-2006-341633 and JP-A-2015-131507.

Japanese Unexamined Patent Publication No. 2006-341633 JP 2015-131507

For tires with a large road index, further improvement in steering stability is required. Further, in a tire having a large road index, "BEL" may occur in which the cord is peeled from the rubber at the end of the belt due to insufficient strength of the belt. Belts are also required to have further improved durability.

In order to improve steering stability and durability, there are a method of increasing the number of cords per unit width (cord density) and a method of thickening the cords. As a result, the strength of the belt is improved. However, with these methods, the code spacing may be narrowed. Durability may be reduced due to the small amount of rubber between the cords. In addition, these methods increase the mass of the belt. Centrifugal force during high-speed driving may increase, and high-speed durability may decrease.

An object of the present invention is to provide a pneumatic tire in which good steering stability and durability are achieved.

The pneumatic tire according to the present invention includes a tread whose outer surface forms a tread surface, and a belt located inside the tread in the radial direction. The belt includes an inner layer and an outer layer laminated on the radial outer side of the inner layer. Each of the inner layer and the outer layer comprises a cord made of a large number of steels arranged in parallel. The ratio of the volume of the cord to the total volume of the belt is 11% or more and 14% or less.

Preferably, the cord of the inner layer and the cord of the outer layer are inclined with respect to the circumferential direction. The inclination direction of the inner layer with respect to the circumferential direction of the cord is opposite to the inclination direction of the outer layer with respect to the circumferential direction of the cord. In the inner layer, the absolute value of the inclination angle αi with respect to the circumferential direction of the cord in the center portion of the inner layer is smaller than the absolute value of the inclination angle βi with respect to the circumferential direction of the shoulder portion of the inner layer, and the angle αi. The difference between the angle βi and the angle βi is 1.5 ° or more and 2.5 ° or less. In the outer layer, the absolute value of the inclination angle αo with respect to the circumferential direction of the cord in the center portion of the outer layer is smaller than the absolute value of the inclination angle βo with respect to the circumferential direction of the shoulder portion of the outer layer, and the angle αo. The difference between the angle βo and the angle βo is 1.5 ° or more and 2.5 ° or less.

Preferably, in the inner layer, the width of the gap between the adjacent cords is 0.4 mm or more, and in the outer layer, the width of the gap between the adjacent cords is 0.4 mm or more.

Preferably, the width of the gap between the cord of the inner layer and the cord of the outer layer is 0.4 mm or more.

Preferably, each of the inner layer and the outer layer further comprises a topping rubber. The complex elastic modulus E ^* i of the topping rubber of the inner layer at 70 ° is 8 MPa or more and 12 MPa or less. The complex elastic modulus E ^* o at 70 ° of the topping rubber of the outer layer is 8 MPa or more and 12 MPa or less.

The inventors examined the structure of the belt in detail. As a result, it was found that the ratio of the volume of the belt to the volume of the cord contained in the belt has a great influence on the steering stability and durability. It has been found that good steering stability and durability can be achieved by appropriately setting these ratios. In this tire, the volume of the cord accounts for 11% or more and 14% or less of the total volume of the belt. By doing so, the tire has achieved good steering stability and durability.

FIG. 1 is a cross-sectional view showing a part of a tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing the structure of the belt of FIG. FIG. 3 is a schematic view showing the structure of the belt of FIG.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

FIG. 1 shows the pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equatorial plane except for the tread pattern.

The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of clinches 8, a pair of beads 10, a carcass 12, a belt 14, a band 16, an inner liner 18, and a chafer 19. This tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

The tread 4 has a shape that is convex outward in the radial direction. The tread 4 forms a tread surface 20 that is in contact with the road surface. A groove 22 is carved on the tread surface 20. A tread pattern is formed by the groove 22. The tread 4 has a base layer 24 and a cap layer 26. The cap layer 26 is located radially outside the base layer 24. The cap layer 26 is laminated on the base layer 24. The base layer 24 is made of crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 24 is a natural rubber. The cap layer 26 is made of crosslinked rubber having excellent wear resistance, heat resistance and grip.

Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents damage to the carcass 12.

Each clinch 8 is located approximately inside the sidewall 6 in the radial direction. The clinch 8 is located outside the bead 10 and the carcass 12 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. The clinch 8 comes into contact with the flange of the rim.

Each bead 10 is located axially inside the clinch 8. The bead 10 includes a core 28 and an apex 30 extending radially outward from the core 28. The core 28 is ring-shaped and includes a wound non-stretchable wire. A typical material for wire is steel. The apex 30 is tapered outward in the radial direction. Apex 30 is made of high hardness crosslinked rubber.

The carcass 12 is made of a carcass ply 32. The carcass ply 32 spans between the beads 10 on both sides and runs along the tread 4 and sidewall 6. The carcass ply 32 is folded around the core 28 from the inside to the outside in the axial direction. Due to this folding, the carcass ply 32 is formed with a main portion 34 and a folded portion 35.

Although not shown, the carcass ply 32 consists of a large number of parallel cords and topping rubber. The absolute value of the angle each code makes with respect to the equatorial plane is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord consists of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. The carcass 12 may be formed from two or more plies.

The belt 14 is located inside the tread 4 in the radial direction. The belt 14 is laminated with the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 is composed of an inner layer 36 and an outer layer 38. As shown in FIG. 1, in this embodiment, the width of the inner layer 36 is larger than the width of the outer layer 38. The belt 14 may have three or more layers.

The band 16 is located inside the tread 4 in the radial direction. The band 16 is located on the outer side in the radial direction of the belt 14. The band 16 is laminated on the belt 14. The band 16 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 16 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. The band 16 can contribute to the rigidity of the tire 2. The band 16 can suppress the influence of centrifugal force acting during traveling. This tire 2 is excellent in high-speed stability. The material of the cord is steel. Organic fibers may be used for the cord. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

The inner liner 18 is located inside the carcass 12. The inner liner 18 is joined to the inner surface of the carcass 12. The inner liner 18 is made of crosslinked rubber. Rubber having excellent air shielding properties is used for the inner liner 18. A typical base rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 holds the internal pressure of the tire 2.

Each chafer 19 is located in the vicinity of the bead 10. When the tire 2 is incorporated into the rim, the chafer 19 comes into contact with the rim. This contact protects the vicinity of the bead 10. In this embodiment, the chafer 19 comprises a cloth and rubber impregnated in the cloth. The chafer 19 may be integrated with the clinch 8. At this time, the material of the chafer 19 is the same as that of the clinch 8.

FIG. 2 is an enlarged cross-sectional view showing a part of the inner layer 36 of the belt 14. The inner layer 36 is composed of a large number of cords 40 arranged in parallel and a topping rubber 42. FIG. 2 is a cross section perpendicular to the extending direction of the cord 40. As shown in the figure, the topping rubber 42 covers the cord 40. The material of the cord 40 is steel. In this embodiment, the cord 40 has a structure in which two strands 43 made of steel are twisted together. Although not shown, the outer layer 38 has the same structure as the inner layer 36. That is, the outer layer 38 is composed of a large number of parallel cords and topping rubber. The material of the cord is steel. The cord has a structure in which two strands of steel are twisted together. In this embodiment, the structure of the cord 40 of the inner layer 36 and the structure of the cord of the outer layer 38 are the same. The structure of the cord 40 of the inner layer 36 and the structure of the cord of the outer layer 38 may be different. In this embodiment, the composition of the topping rubber 42 of the inner layer 36 and the composition of the topping rubber of the outer layer 38 are the same. The composition of the topping rubber 42 of the inner layer 36 and the composition of the topping rubber of the outer layer 38 may be different.

When the total volume of all the cords 40 of the inner layer 36 and all the cords of the outer layer 38 is CV, and the total volume of the belt 14 including the inner layer 36 and the outer layer 38 is BV, this tire 2 Then, the ratio of the volume CV to the volume BV (CV / BV) is 11% or more and 14% or less as a percentage. The thickness and spacing of the cord 40 of the inner layer 36 and the cord of the outer layer 38 are determined so that the ratio (CV / BV) is 11% or more and 14% or less. The sizes of the topping rubber 42 of the inner layer 36 and the topping rubber of the outer layer are determined so that the ratio (CV / BV) is 11% or more and 14% or less.

In this embodiment, the inner layer 36 and the outer layer 38 have the same structure. That is, when the total volume of all the codes 40 of the inner layer 36 is CVi and the total product of the inner layer 36 is BVi, the ratio of the volume CVi to the volume BVi (CVi / BVi) is 11% as a percentage. More than 14% or less. When the total volume of all the cords of the outer layer 38 is CVo and the total volume of the outer layer 38 is BVo, the ratio of the volume CVo to the volume BVo (CVo / BVo) is 11% or more and 14% as a percentage. It is as follows.

FIG. 3 is a schematic view showing the structure of the belt 14. In FIG. 3, the vertical direction is the circumferential direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the radial direction of the tire 2. As shown in FIG. 3, each cord 40 of the inner layer 36 and each cord 44 of the outer layer 38 are inclined with respect to the circumferential direction. The inclination direction of the cord 40 of the inner layer 36 with respect to the circumferential direction is opposite to the inclination direction of the cord 44 of the outer layer 38 with respect to the circumferential direction.

As shown in FIG. 3, in this embodiment, the inclination angle of the cord 40 of the inner layer 36 changes with a pair of virtual straight lines Li extending in the circumferential direction as a boundary. The portion between the pair of straight lines Li is the center portion Ci of the inner layer 36. The axially outer portion of the pair of straight lines Li is the shoulder portion Si of the inner layer 36. Reference numeral αi is an inclination angle of the inner layer 36 with respect to the circumferential direction in the center portion Ci of the inner layer 36. Reference numeral βi is an inclination angle of the inner layer 36 with respect to the circumferential direction of the cord 40 in the shoulder portion Si of the inner layer 36. In this embodiment, the absolute value of the tilt angle βi is larger than the absolute value of the tilt angle αi. The cord 40 of the inner layer 36 is inclined more in the circumferential direction than the center portion Ci in the shoulder portion Si of the inner layer 36.

In FIG. 3, the double-headed arrow Wi is the axial distance from the equatorial plane to the straight line Li. In FIG. 1, Wt is the axial distance from the equatorial plane to the tread end. The ratio of the distance Wi to the distance Wt (Wi / Wt) is 0.5 or more and 0.8 or less.

As shown in FIG. 3, in this embodiment, the inclination angle of the cord 44 of the outer layer 38 is changed with the pair of virtual straight lines Lo extending in the circumferential direction as boundaries. The portion between the pair of straight lines Lo is the center portion Co of the outer layer 38. The axially outer portion of the pair of straight lines Lo is the shoulder portion So of the outer layer 38. Reference numeral αo is an inclination angle of the outer layer 38 with respect to the circumferential direction at the center portion Co of the outer layer 38. Reference numeral βo is an inclination angle of the outer layer 38 with respect to the circumferential direction in the shoulder portion So of the outer layer 38. In this embodiment, the absolute value of the tilt angle βo is larger than the absolute value of the tilt angle αo. The cord 44 of the outer layer 38 is inclined more in the circumferential direction than the center portion Co in the shoulder portion So of the outer layer 38.

In FIG. 3, the double-headed arrow W is the axial distance from the equatorial plane to the straight line Lo. The ratio of the distance Wo to the distance Wt (Wo / Wt) is 0.5 or more and 0.8 or less.

In this embodiment, the difference between the absolute value of the angle αi and the absolute value of the angle αo outer layer 38 is within 2 °. The absolute values of the angles αi and αo range from 10 ° to 35 °.

The effects of the present invention will be described below.

For tires with a large road index, further improvement in steering stability is required. Tires with a large road index are also required to have improved durability. In particular, for tires with a road index of 85 or more, there is a strong demand for improved steering stability and durability.

The inventors examined the structure of the belt in detail. As a result, it was found that the ratio of the volume of the belt to the volume of the cord contained in the belt has a great influence on the steering stability and durability. It has been found that by appropriately setting these ratios, good steering stability and durability can be realized even in the tire 2 having a large road index.

In this tire 2, the ratio (CV / BV) of the volume CVs of the cords 40 and 44 to the total product BV of the belt 14 is 11% or more and 14% or less as a percentage. By setting the ratio (CV / BV) to 11% or more as a percentage, the belt 14 contributes to steering stability. Further, the belt 14 effectively reinforces the carcass 12. The tire 2 provided with the belt 14 has excellent durability. By setting the ratio (CV / BV) to 14% or less as a percentage, the generation of BEL caused by the reduction of rubber around the cords 40 and 44 is suppressed. This tire 2 has excellent durability. The tire 2 has good steering stability and durability.

In the tire 2, the rigidity of the tread 4 is properly maintained by setting the ratio (CV / BV) to 14% or less as a percentage. This effectively contributes to ride comfort. A good ride quality is realized with this tire 2. Further, the belt 14 having a ratio (CV / BV) of 14% or less is lightweight. The tire 2 provided with the belt 14 is lightweight. The belt 14 contributes to the reduction of rolling resistance of the tire 2.

From the viewpoint of achieving good steering stability and durability, the ratio (CV / BV) is more preferably 12% or more. The ratio (CV / BV) is more preferably 13.5% or less from the viewpoint of achieving good durability and riding comfort, and reducing the weight.

As described above, in the cord 40 of the inner layer 36, it is preferable that the inclination angle βi with respect to the circumferential direction in the shoulder portion is larger than the inclination angle αi with respect to the circumferential direction in the center portion. The belt 14 having a small inclination angle αi of the cord 40 at the center portion effectively contributes to the rigidity of the tread 4 in the circumferential direction. The tire 2 is excellent in steering stability and durability at high speeds. The belt 14 having a large inclination angle βi of the cord 40 at the shoulder portion effectively contributes to the lateral rigidity of the tread 4. The tire 2 is excellent in steering stability and durability during turning.

The difference between the tilt angle αi and the tilt angle βi is preferably 1.5 ° or more. By setting this difference to 1.5 ° or more, the belt 14 effectively contributes to the rigidity in the circumferential direction and the lateral direction. The tire 2 is excellent in steering stability and durability in straight running and turning running. The difference between the tilt angle αi and the tilt angle βi is preferably 2.5 ° or less. By setting the difference between the inclination angle αi and the inclination angle βi to 2.5 ° or less, it is possible to suppress a decrease in riding comfort due to a difference in rigidity between the center portion and the shoulder portion of the tread 4. This tire 2 is excellent in riding comfort.

As described above, in the cord 44 of the outer layer 38, it is preferable that the inclination angle βo with respect to the circumferential direction in the shoulder portion is larger than the inclination angle αo with respect to the circumferential direction in the center portion. The belt 14 having a small inclination angle αo of the cord 44 at the center portion effectively contributes to the rigidity of the tread 4 in the circumferential direction. The tire 2 is excellent in steering stability and durability at high speeds. The belt 14 having a large inclination angle βo of the cord 44 at the shoulder portion effectively contributes to the lateral rigidity of the tread 4. The tire 2 is excellent in steering stability and durability during turning.

The difference between the tilt angle αo and the tilt angle βo is preferably 1.5 ° or more. By setting this difference to 1.5 ° or more, the belt 14 effectively contributes to the rigidity in the circumferential direction and the lateral direction. The tire 2 is excellent in steering stability and durability in straight running and turning running. The difference between the tilt angle αo and the tilt angle βo is preferably 2.5 ° or less. By setting the difference between the inclination angle αo and the inclination angle βo to 2.5 ° or less, it is possible to suppress a decrease in riding comfort due to the difference in rigidity between the center portion and the shoulder portion of the tread 4. This tire 2 is excellent in riding comfort.

As described above, the belt 14 of the tire 2 has a ratio (CV / BV) of 11% or more and 14% or less. For the belt 14 satisfying this, as described above, the inclination angle of the cord 40 in the shoulder portion Si of the inner layer 36 is made larger than the inclination angle of the cord in the center portion Ci, and the inclination angle of the cord 44 in the shoulder portion So of the outer layer 38. The belt 14 contributes particularly effectively to steering stability and durability by making the angle of inclination of the cord 44 in the center portion Co larger than that of the cord 44. By combining these, a tire 2 having excellent steering stability and durability can be realized.

As described above, in the inner layer 36 of the belt 14, the difference between the inclination angle αi and the inclination angle βi is 1.5 ° or more and 2.5 ° or less. In the inner layer 36, the difference in the inclination angle of the cord 40 is appropriately suppressed between the center portion Ci and the shoulder portion Si. In the outer layer 38 of the belt 14, the difference between the inclination angle αo and the inclination angle βo is 1.5 ° or more and 2.5 ° or less. In the outer layer 38, the difference in the inclination angle of the cord 44 is appropriately suppressed between the center portion Co and the shoulder portion So. The belt 14 can be realized by adjusting the circumference of the drum in the molding process and the shape of the cavity surface of the mold in the vulcanization process. In the manufacture of the tire 2, no special step is required for changing the inclination angles of the cords 40 and 44 at the center portion and the shoulder portion of each of the inner layer 36 and the outer layer 38. Good productivity is maintained in this tire 2.

In FIG. 2, the double-headed arrow Di is the width of the gap between adjacent cords 40 in the inner layer 36. The width Di is preferably 0.4 mm or more. In the inner layer 36 having a width Di of 0.4 mm or more, even when the belt 14 is distorted by a load, the adjacent cords 40 are prevented from coming into contact with each other. In the inner layer 36, damage to the cord 40 due to contact with the cord 40 is prevented. The tire 2 provided with the inner layer 36 has excellent durability. From this viewpoint, the width Di is more preferably 0.45 mm or more.

Although not shown, the double-headed arrow Do is the width of the gap between adjacent cords 44 in the outer layer 38. The width Do is preferably 0.4 mm or more. In the outer layer 38 having a width Do of 0.4 mm or more, even when the belt 14 is distorted by a load, the adjacent cords 44 are prevented from coming into contact with each other. In the outer layer 38, damage to the cord 44 due to contact with the cord 44 is prevented. The tire 2 provided with the outer layer 38 has excellent durability. From this viewpoint, the width Do is more preferably 0.45 mm or more.

Although not shown, the double-headed arrow Dio is the width of the gap between the cord 40 of the inner layer 36 and the cord 44 of the outer layer 38 adjacent thereto. The width Dio is preferably 0.4 mm or more. In the belt 14 having a width Dio of 0.4 mm or more, even when the belt 14 is distorted by a load, the cord 40 of the adjacent inner layer 36 and the cord 44 of the outer layer 38 are prevented from coming into contact with each other. In this belt 14, damage to the cords 40 and 44 due to contact with the cords is prevented. The tire 2 provided with the belt 14 has excellent durability. From this viewpoint, the width Dio is more preferably 0.45 mm or more.

The characteristics of the topping rubber of the belt affect the performance of the tire. The hard topping rubber contributes to the rigidity of the belt. Tires with hard topping rubber have excellent steering stability. However, hard topping rubber reduces the shock absorption of the tire. This tire is inferior in riding comfort. Tires with soft topping rubber are comfortable to ride, but inferior in steering stability. The inventors have found that for tires in which the ratio of volume CV to volume BV (CV / BV) is 11% or more and 14% or less, the complex elastic modulus of the topping rubber is adjusted to improve steering stability and ride comfort. I found that it could be improved.

The complex elastic modulus E ^* i of the topping rubber 42 of the inner layer 36 is preferably 8 MPa or more. By setting the complex elastic modulus E ^* i to 8 MPa or more, the topping rubber 42 effectively contributes to the rigidity of the belt 14. This tire has excellent steering stability. From this point of view, the complex elastic modulus E ^* i is more preferably 9 MPa or more. The complex elastic modulus E ^* i is preferably 12 MPa or less. By setting the complex elastic modulus E ^* i to 12 MPa or less, the rigidity of the belt 14 is appropriately suppressed. This tire is comfortable to ride. From this viewpoint, the complex elastic modulus E ^* i is more preferably 11 MPa or less.

The complex elastic modulus E ^* o of the topping rubber of the outer layer 38 is preferably 8 MPa or more. By setting the complex elastic modulus E ^* o to 8 MPa or more, this topping rubber effectively contributes to the rigidity of the belt 14. This tire has excellent steering stability. From this point of view, the complex elastic modulus E ^* o is more preferably 9 MPa or more. The complex elastic modulus E ^* o is preferably 12 MPa or less. By setting the complex elastic modulus E ^* o to 12 MPa or less, the rigidity of the belt 14 is appropriately suppressed. This tire is comfortable to ride. From this viewpoint, the complex elastic modulus E ^* o is more preferably 11 MPa or less.

In the present invention, the complex elastic moduli E ^* i and E ^* o are viscoelastic spectrometers (trade name "VESF-3" manufactured by Iwamoto Seisakusho Co., Ltd.) under the following measurement conditions in accordance with the provisions of "JIS K 6394". ") Is measured.
Initial distortion: 10%
Amplitude: ± 2.0%
Frequency: 10Hz
Deformation mode: tension
Measurement temperature: 70 ° C

In the present invention, the dimensions and angles of each member of the tire 2 are measured in a state where the tire 2 is incorporated in the regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. As used herein, the term "regular rim" means a rim defined in the standard on which Tire 2 relies. The "standard rim" in the JATTA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims. As used herein, the normal internal pressure means the internal pressure defined in the standard on which the tire 2 relies. The "maximum air pressure" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures. In the case of the passenger car tire 2, the dimensions and the angle are measured in a state where the internal pressure is 180 kPa.

Hereinafter, the effects of the present invention will be clarified by Examples, but the present invention should not be construed in a limited manner based on the description of these Examples.

[Example 1]
A tire of Example 1 having the structure shown in FIG. 1 was obtained. The size of the tire was "205 / 60R16 96VL". Table 1 shows the specifications of the belt for this tire.

[Comparative Example 1-3 and Example 2-4]
The tires of Comparative Example 1-3 and Example 2-4 were obtained in the same manner as in Example 1 except that the width Di and the width Do were changed and the ratio (CV / BV) was as shown in Table 1-2.

[Example 5]
The tires of Example 5 were obtained in the same manner as in Example 1 except that the width Dio was changed and the ratio (CV / BV) was as shown in Table 2.

[Example 6-9]
The tires of Example 6-9 were obtained in the same manner as in Example 1 except that the angles αi and αo were as shown in Table 3.

[Example 10-13]
The tires of Examples 10-13 were obtained in the same manner as in Example 1 except that the complex elastic modulus E ^* i and the complex elastic modulus E ^* o were as shown in Table 4.

[Maneuvering stability and ride comfort]
The tire was incorporated into a regular rim (size: 6.5J), and the tire was filled with air so that the internal pressure was 250 kPa. This tire was attached to the rear wheel of the vehicle. The driver was allowed to drive this vehicle on a test course to evaluate steering stability and ride comfort. This result is shown in Table 1-4 below in a graded evaluation with a perfect score of 10. The larger the value, the more preferable.

[durability]
The tire was incorporated into a regular rim (size: 6.5J), and the tire was filled with air to set the internal pressure to 290 kPa. This tire was mounted on a drum type running tester, and a vertical load of 10.27 kN was applied to the tire. The tire was run at a speed of 80 km / h on a drum with a radius of 1.7 m. The mileage until damage was confirmed on the tire was measured. This result is shown as an index in Table 1-4 below. The larger the value, the more preferable.

As shown in Table 1-4, the tires of Examples are superior in value to the tires of Comparative Examples. From this evaluation result, the superiority of the present invention is clear.

The tire according to the present invention can be mounted on various vehicles.

2 ... Tire 4 ... Tread 6 ... Sidewall 8 ... Clinch 10 ... Bead 12 ... Carcass 14 ... Belt 16 ... Band 18 ... Inner liner 19 ...・ Chafer 20 ・ ・ ・ Tread surface 22 ・ ・ ・ Groove 24 ・ ・ ・ Base layer 26 ・ ・ ・ Cap layer 28 ・ ・ ・ Core 30 ・ ・ ・ Apex 32 ・ ・ ・ Carcass ply 34 ・ ・ ・ Main part 35・ ・ ・ Folded part 36 ・ ・ ・ Inner layer 38 ・ ・ ・ Outer layer 40 ・ ・ ・ Inner layer cord 42 ・ ・ ・ Topping rubber 43 ・ ・ ・ Wire 44 ・ ・ ・ Outer layer cord

Claims (8)

It has a tread whose outer surface is a tread surface and a belt located inside the tread in the radial direction.
The belt has an inner layer and an outer layer laminated on the radial outer side of the inner layer.
Each of the inner layer and the outer layer has a cord made of a large number of steels arranged in parallel.
Each cord has a structure in which two strands of steel are twisted together.
The structure of the cord of the inner layer and the structure of the cord of the outer layer are the same, and the width of the gap between the adjacent cords in the inner layer and the width of the gap between the adjacent cords in the outer layer. Is the same, the cord of the inner layer and the cord of the outer layer are inclined with respect to the circumferential direction, and the inclination direction of the cord of the inner layer with respect to the circumferential direction is the above of the outer layer. It is the opposite of the direction of inclination of the cord with respect to the circumferential direction.
A pneumatic tire in which the volume of the cord is 11.3 % or more and 13.4 % or less of the total volume of the belt. In the above SL inner layer, the absolute value of the inclination angle αi with respect to the circumferential direction of the cord in the center portion of the inner layer is smaller than the absolute value of the inclination angle βi to the circumferential direction of the cord in the shoulder portion of the inner layer,
The difference between the angle αi and the angle βi is 1.5 ° or more and 2.5 ° or less.
In the outer layer, the absolute value of the inclination angle αo with respect to the circumferential direction of the cord in the center portion of the outer layer is smaller than the absolute value of the inclination angle βo with respect to the circumferential direction of the shoulder portion of the outer layer.
The tire according to claim 1, wherein the difference between the angle αo and the angle βo is 1.5 ° or more and 2.5 ° or less. In the inner layer, the ratio (Wi / Wt) of the distance Wi from the equatorial plane to the boundary between the center portion and the shoulder portion to the distance Wt from the equatorial plane to the end of the tread is 0.5 or more and 0.8. The tire according to claim 2, which is as follows. In the outer layer, the ratio (Wo / Wt) of the distance Wo from the equatorial plane to the boundary between the center portion and the shoulder portion to the distance Wt from the equatorial plane to the end of the tread is 0.5 or more and 0.8. The tire according to claim 2 or 3, which is as follows. Claims 1 to 4 in which the width of the gap between the adjacent cords in the inner layer is 0.41 mm or more, and the width of the gap between the adjacent cords in the outer layer is 0.41 mm or more. Tires listed in any of . Any of claims 1 to 5 in which the width of the gap between the adjacent cords in the inner layer is 0.61 mm or less and the width of the gap between the adjacent cords in the outer layer is 0.61 mm or less. Tires listed in Crab. The tire according to any one of claims 1 to 6 , wherein the width of the gap between the cord of the inner layer and the cord of the outer layer is 0.4 mm or more. Each of the inner layer and the outer layer further includes a topping rubber.
A claim that the complex elastic modulus E ^* i of the inner layer of the topping rubber at 70 ° is 8 MPa or more and 12 MPa or less, and the complex elastic modulus E ^* o of the outer layer of the topping rubber at 70 ° is 8 MPa or more and 12 MPa or less. Item 4. The tire according to any one of Items 1 to 7 .

Images