JP2017185984A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having achieved an excellent steering stability and high durability.SOLUTION: A tire 2 comprises: multiple cords made of steel arranged in parallel on respective inner layer 36 and outer layer 38 of a belt 14. Volumes of the cords account for 11-14% of the whole volume of the belt 14. An absolute value of an inclining angle αi of the code 40 in a circumferential direction at a center part of the inner layer 36 is preferably less than an absolute value of an inclining angle βi of the code 40 in a circumferential direction at a shoulder part of the inner layer 36; and the difference between the angle αi and the angle βi is between 1.5° and 2.5°. An absolute value of an inclining angle αo of the code 44 in a circumferential direction at a center part of the outer layer 38 is less than an absolute value of an inclining angle βo of the code 44 in a circumferential direction at a shoulder part of the outer layer 38; and the difference between the angle αo and the angle βo is between 1.5° and 2.5°.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire.

  The pneumatic tire includes a belt outside the carcass. The belt reinforces the carcass. Usually the belt has an inner layer and an outer layer. Each of the inner layer and the outer layer includes a large number of cords and a topping rubber arranged in parallel. A typical cord material is steel.

  The structure of the belt affects the handling 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 Japanese Patent Laid-Open Nos. 2006-341633 and 2015-131507.

JP 2006-341633 A JP2015-131507A

  Further improvements in handling stability are required for tires with a large road index. Further, in a tire having a large road index, “BEL” in which the cord is peeled off from the rubber at the end of the belt may occur due to insufficient strength of the belt. The belt is also required to be further improved in durability.

  In order to improve steering stability and durability, there are a method of increasing the number of cords (cord density) per unit width and a method of thickening the cords for the belt. As a result, the strength of the belt is improved. However, in these methods, the code interval may be narrowed. Due to the small amount of rubber between cords, durability may be reduced. Furthermore, these methods increase the mass of the belt. Centrifugal force during high-speed running increases, and high-speed durability may be reduced.

  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 positioned radially inward of the tread. The belt includes an inner layer and an outer layer laminated on a radially outer side of the inner layer. Each of the inner layer and the outer layer includes a cord made of a plurality 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 cord in the shoulder portion of the inner layer. 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 cord in the shoulder portion of the outer layer. 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 at 70 ° of the topping rubber of the inner layer 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 has been found that the ratio between the volume of the belt and the volume of the cord included in the belt greatly affects the handling stability and durability. It has been found that by appropriately setting these ratios, good steering stability and durability can be realized. In this tire, the ratio of the cord volume to the total volume of the belt is 11% or more and 14% or less. By doing in this way, favorable steering stability and durability are realized in this tire.

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 sectional view showing the structure of the belt of FIG. FIG. 3 is a schematic diagram showing the structure of the belt of FIG.

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

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial 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 circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern.

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

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

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

  Each clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located outside the beads 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 contacts the flange of the rim.

  Each bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 28 and an apex 30 that extends radially outward from the core 28. The core 28 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 30 is tapered outward in the radial direction. The apex 30 is made of a highly hard crosslinked rubber.

  The carcass 12 includes a carcass ply 32. The carcass ply 32 is bridged between the beads 10 on both sides, and extends along the tread 4 and the sidewall 6. The carcass ply 32 is folded around the core 28 from the inner side to the outer side in the axial direction. By this folding, a main portion 34 and a folding portion 35 are formed in the carcass ply 32.

  Although not shown, the carcass ply 32 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord is made of organic fiber. Examples of preferable 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 on the inner side in the radial direction of the tread 4. The belt 14 is laminated with the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes 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 greater than the width of the outer layer 38. The belt 14 may include three or more layers.

  The band 16 is located on the inner side in the radial direction of the tread 4. The band 16 is located on the radially outer side of the belt 14. The band 16 is laminated on the belt 14. The band 16 is made 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 that acts during traveling. The tire 2 is excellent in high speed stability. The cord material is steel. An organic fiber may be used for the cord. Examples of preferable 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 a crosslinked rubber. For the inner liner 18, rubber having excellent air shielding properties is used. A typical base rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 maintains 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. By this contact, the vicinity of the bead 10 is protected. In this embodiment, the chafer 19 is made of 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 sectional view showing a part of the inner layer 36 of the belt 14. The inner layer 36 includes a plurality of cords 40 and a topping rubber 42 arranged in parallel. 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 cords arranged in parallel and a topping rubber. The cord material 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, the tire 2 Then, the ratio (CV / BV) of the volume CV to the volume 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 cords 40 of the inner layer 36 is CVi and the total volume of the inner layer 36 is BVi, the ratio of the volume CVi to the volume BVi (CVi / BVi) is 11% in percentage. It is 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 diagram 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 inner layer 36 with respect to the circumferential direction of the cord 40 is opposite to the inclination direction of the outer layer 38 with respect to the circumferential direction of the cord 44.

  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. A 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 sign α i represents an inclination angle of the inner layer 36 with respect to the circumferential direction of the cord 40 at the center portion Ci. Reference sign βi is an inclination angle of the shoulder portion Si of the inner layer 36 with respect to the circumferential direction of the cord 40 of the inner layer 36. In this embodiment, the absolute value of the inclination angle βi is larger than the absolute value of the inclination angle αi. The cord 40 of the inner layer 36 is greatly inclined with respect to the circumferential direction in the shoulder portion Si of the inner layer 36 rather than the center portion Ci.

  In FIG. 3, a double arrow Wi is an axial distance from the equator plane to the straight line Li. In FIG. 1, Wt is the axial distance from the equator plane to the tread end. The ratio (Wi / Wt) of the distance Wi to the distance 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 changes with a pair of virtual straight lines Lo extending in the circumferential direction as a boundary. A 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. The symbol αo is an inclination angle of the outer layer 38 with respect to the circumferential direction of the cord 44 at the center portion Co of the outer layer 38. The symbol βo is an inclination angle of the shoulder portion So of the outer layer 38 with respect to the circumferential direction of the cord 44 of the outer layer 38. In this embodiment, the absolute value of the inclination angle βo is larger than the absolute value of the inclination angle αo. The cord 44 of the outer layer 38 is inclined more greatly in the circumferential direction than the center portion Co in the shoulder portion So of the outer layer 38.

  In FIG. 3, a double-headed arrow Wo is an axial distance from the equator plane to the straight line Lo. The ratio (Wo / Wt) of the distance Wo to the distance 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 are 10 ° to 35 °.

  Below, the effect of this invention is demonstrated.

  Further improvements in handling stability are required for tires with a large road index. Tires with a large road index are also required to have improved durability. In particular, in a tire having a road index of 85 or more, there is a strong demand for improvement in handling stability and durability.

  The inventors examined the structure of the belt in detail. As a result, it has been found that the ratio between the volume of the belt and the volume of the cord included in the belt greatly affects the handling 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 the tire 2, the ratio (CV / BV) of the volume CV of the cords 40 and 44 to the total volume BV of the belt 14 is 11% or more and 14% or less as a percentage. By making the ratio (CV / BV) 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 including the belt 14 is excellent in durability. By setting the ratio (CV / BV) to 14% or less as a percentage, generation of BEL due to a decrease in rubber around the cords 40 and 44 is suppressed. The tire 2 is excellent in durability. In the tire 2, good steering stability and durability are realized in the tire 2.

  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. In the tire 2, a good ride comfort is realized. Furthermore, the belt 14 having a ratio (CV / BV) of 14% or less is lightweight. The tire 2 including the belt 14 is lightweight. The belt 14 contributes to a reduction in 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 realizing good durability and riding comfort and weight reduction.

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

  The difference between the inclination angle αi and the inclination angle βi is preferably 1.5 ° or more. By making this difference 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 handling stability and durability in straight running and turning. The difference between the inclination angle αi and the inclination 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, a decrease in riding comfort due to a difference in rigidity between the center portion and the shoulder portion of the tread 4 can be suppressed. The tire 2 is excellent in ride comfort.

  As described above, in the cord 44 of the outer layer 38, the inclination angle βo with respect to the circumferential direction in the shoulder portion is preferably 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 in the center portion effectively contributes to the circumferential rigidity of the tread 4. The tire 2 is excellent in handling stability and durability in high speed running. The belt 14 having a large inclination angle βo of the cord 44 in the shoulder portion effectively contributes to the lateral rigidity of the tread 4. The tire 2 is excellent in handling stability and durability in turning.

  The difference between the inclination angle αo and the inclination angle βo is preferably 1.5 ° or more. By making this difference 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 handling stability and durability in straight running and turning. The difference between the inclination angle αo and the inclination 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, a decrease in riding comfort due to a difference in rigidity between the center portion and the shoulder portion of the tread 4 can be suppressed. The tire 2 is excellent in ride comfort.

  As described above, in the belt 14 of the tire 2, the ratio (CV / BV) is 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 is obtained. Is made larger than the inclination angle of the cord 44 at the center portion Co, so that the belt 14 contributes particularly effectively to steering stability and durability. By combining these, the tire 2 excellent in 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 not less than 1.5 ° and not more than 2.5 °. 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 not less than 1.5 ° and not more than 2.5 °. 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 process is required for changing the inclination angle of the cords 40 and 44 between the center portion and the shoulder portion of each of the inner layer 36 and the outer layer 38. In the tire 2, good productivity is maintained.

  In FIG. 2, the double-headed arrow Di is the width of the gap between the 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, the adjacent cords 40 are prevented from contacting each other even when the belt 14 is distorted by a load. In the inner layer 36, the cord 40 is prevented from being damaged due to the cord 40 coming into contact therewith. The tire 2 including the inner layer 36 is excellent in durability. In this respect, 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 the adjacent cords 44 in the outer layer 38. The width Do is preferably 0.4 mm or more. The outer layer 38 having a width Do of 0.4 mm or more prevents the adjacent cords 44 from contacting each other even when the belt 14 is distorted by a load. In the outer layer 38, the cord 44 is prevented from being damaged by the cord 44 coming into contact. The tire 2 including the outer layer 38 is excellent in durability. In this respect, the width Do is more preferably 0.45 mm or more.

  Although not shown, the double 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 contacting each other. In this belt 14, the cords 40 and 44 are prevented from being damaged due to the cords coming into contact with each other. The tire 2 including the belt 14 is excellent in durability. In this respect, the width Dio is more preferably 0.45 mm or more.

  The characteristics of the belt topping rubber affect the performance of the tire. A hard topping rubber contributes to the rigidity of the belt. A tire having a hard topping rubber has excellent steering stability. However, a hard topping rubber reduces the impact absorption of the tire. This tire is inferior in ride comfort. A tire provided with a soft topping rubber is excellent in ride comfort, but inferior in handling stability. The inventors of the present invention have improved steering stability and ride comfort by adjusting the complex elastic modulus of the topping rubber in a tire having a ratio of volume CV to volume BV (CV / BV) of 11% to 14%. I found that it can 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 is excellent in handling stability. In this respect, 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 excellent in ride comfort. In this respect, 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, the topping rubber effectively contributes to the rigidity of the belt 14. This tire is excellent in handling stability. In this respect, 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 excellent in ride comfort. In this respect, 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 determined according to the following measurement conditions in accordance with the provisions of “JIS K 6394” (trade name “VESF-3 manufactured by Iwamoto Seisakusho Co., Ltd.). )).
Initial strain: 10%
Amplitude: ± 2.0%
Frequency: 10Hz
Deformation mode: Tensile
Measurement temperature: 70 ° C

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a 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. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures. In the case of the passenger car tire 2, the dimensions and angles are measured in a state where the internal pressure is 180 kPa.

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

[Example 1]
A tire of Example 1 having the structure shown in FIG. 1 was obtained. The tire size was “205 / 60R16 96V L”. Table 1 shows the specifications of the tire belt.

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

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

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

[Example 10-13]
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 assembled in a regular rim (size: 6.5 J), and the tire was filled with air so that the internal pressure was 250 kPa. This tire was mounted on the rear wheel of the vehicle. The driver was allowed to drive the vehicle on a test course to evaluate the handling stability and ride comfort. This result is shown in the following Table 1-4 in a step evaluation with 10 being a perfect score. Larger numbers are preferable.

[durability]
The tire was assembled in a regular rim (size: 6.5 J), and the tire was filled with air to adjust the internal pressure to 290 kPa. This tire was mounted on a drum-type running test machine, and a longitudinal load of 10.27 kN was applied to the tire. This tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The travel distance until the tire was confirmed to be damaged was measured. The result is shown as an index in Table 1-4 below. A larger numerical value is preferable.

  As shown in Table 1-4, the tire of the example is superior in value to the tire of the comparative example. 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 ... tyre 4 ... tread 6 ... side wall 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 ... Strand 44 ... Outer layer cord

Claims (5)

It has a tread whose outer surface forms a tread surface, and a belt located inside the tread in the radial direction,
The belt comprises an inner layer and an outer layer laminated radially outward of the inner layer;
Each of the inner layer and the outer layer includes a cord made of a plurality of steels arranged in parallel,
A pneumatic tire in which a ratio of a volume of the cord to a total volume of the belt is 11% or more and 14% or less. 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 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 cord in 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 not less than 1.5 ° and not more than 2.5 °.   The width of the gap between the adjacent cords in the inner layer is 0.4 mm or more, and the width of the gap between the adjacent cords in the outer layer is 0.4 mm or more. Tires.   The tire according to any one of claims 1 to 3, wherein a width of a 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 comprises a topping rubber,
The complex elastic modulus E ^* i at 70 ° of the topping rubber of the inner layer is from 8 MPa to 12 MPa, and the complex elastic modulus E ^* o of the topping rubber of the outer layer at 70 ° is from 8 MPa to 12 MPa. Item 5. The tire according to any one of Items 1 to 4.

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