JP2016165934A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which suppresses uneven wear.SOLUTION: A profile of a tread 4 of a tire 2 has a circular arc TC1 located on a center of the tread 4 and a pair of circular arcs TC2 located on the axial direction outer side of the circular arc TC1. A curvature radius TR1 of the circular arc TC1 is larger than the curvature radius TR2 of the circular arc TC2. When an intersection between a radial direction outer surface of a second layer of a belt 14 and an equatorial plane is set as Pc, a pair of end points of the radial direction outer surface of the second layer is set as Pe, a virtual circular arc passing through three points of the intersection Pc and a pair of end points Pe is set as BC and a curvature radius of the circular arc BC is set as BR, the curvature radius BR is 900 to 1100 mm. A ratio (TR2/BR) of a curvature radius TR2 to the curvature radius BR is 0.38 to 0.63.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  In general, in a tire for a four-wheeled vehicle, the radius of curvature of the tread surface is increased at the center portion and decreased at the shoulder portion in order to achieve good steering stability. For this reason, the circumferential length of the ground contact shape (ground contact length) is shorter at the shoulder portion than at the center portion. Due to the difference in the contact length, the shoulder portion may be more worn than the center portion. In particular, wear is likely to be promoted at the axially outer portion in the shoulder portion. This wear promotion causes uneven wear. Uneven wear can shorten the life of the tire.

  Examinations for suppressing uneven wear of tires are reported in JP2013-060129A and JP2013-060131A. All of these suppress uneven wear by adjusting the shape of the tread.

JP2013-060129A JP2013-060131A

  Further, there is a demand for a tire that suppresses uneven wear. In addition to adjusting the shape of the tread, it is necessary to suppress uneven wear by examining the structure of other parts.

  An object of the present invention is to provide a pneumatic tire in which uneven wear is suppressed.

  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. In the cross section perpendicular to the circumferential direction, the tread profile includes a center arc TC1 positioned at the tread center and a pair of shoulder arcs TC2 positioned on the axially outer side of the center arc TC1. The radius of curvature TR1 of the center arc TC1 is larger than the radius of curvature TR2 of the shoulder arc TC2. When the intersection of the center arc TC1 and the shoulder arc TC2 is Px, in the axial direction, the ratio (Wx / Wt) of the width Wx from the equator plane to the intersection Px to the width Wt from the equator plane to the tread edge is 0.44 or more and 0.56 or less. The belt includes a first layer and a second layer laminated on a radially outer side of the first layer. The intersection between the radially outer surface of the second layer and the equator plane is defined as Pc, the pair of end points on the radially outer surface of the second layer is defined as Pe, and passes through the three points of the intersection Pc and the pair of endpoints Pe. When the virtual arc is BC and the curvature radius of the arc BC is BR, the curvature radius BR is 900 mm or more and 1100 mm or less. The ratio (TR2 / BR) of the curvature radius TR2 to the curvature radius BR is not less than 0.38 and not more than 0.63.

  Preferably, the tread includes a first main groove positioned on the equator plane and a pair of second main grooves each positioned between the first main groove and the tread end. The intersection point Px is located where the second main groove exists.

  Preferably, the thickness from the tread surface on the equator plane to the radially outer surface of the belt is G, and the point on the tread surface where the axial distance from the equator plane is 0.66 times the width Wt is Pg. When the thickness from the point Pg to the outer surface in the radial direction of the belt is Gg, the ratio of the thickness Gg to the thickness G (Gg / G) is 0.81 or more and 0.85 or less.

  Preferably, the ratio (Wb / Wt) of the axial width Wb from the equator plane to the end of the belt with respect to the width Wt is 0.96 to 1.01.

  Preferably, the tire further includes a band that covers the belt on a radially outer side of the belt. The band includes a cord made of nylon fiber.

  Preferably, the radius of curvature IR of the inner surface of the tire in the buttress portion is 55 mm or greater and 65 mm or less.

  The inventors examined the structure of a tire for suppressing uneven wear. As a result, it has been found that the shape of the belt affects the wear at the shoulder. It has been found that uneven wear due to accelerated wear at the shoulder portion can be suppressed by appropriately adjusting the shape of the belt and the shape of the tread.

  In this tire, the profile of the tread includes a center arc TC1 located at the tread center and a pair of shoulder arcs TC2 located outside the center arc TC1 in the axial direction. A virtual arc passing through the intersection of the radially outer surface of the belt and the equatorial plane and three end points of the radially outer surface of the belt is defined as BC, and when the radius of curvature of this arc BC is defined as BR, the radius of curvature is BR is 900 mm or more and 1100 mm or less. The ratio (TR2 / BR) of the curvature radius TR2 of the arc TC2 to the curvature radius BR is not less than 0.38 and not more than 0.63. This structure contributes to suppression of wear at the shoulder portion. In this tire, uneven wear is suppressed.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a tread portion of the tire of FIG. 1.

  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. In FIG. 1, the vertical direction is the radial direction of the tire, the horizontal direction is the axial direction of the tire, and the direction perpendicular to the paper surface is the circumferential direction of the tire. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire. The shape of the tire is symmetrical with respect to the equator plane except for the tread pattern. In this figure, the tire is mounted on the rim R.

  In the present invention, the dimension and angle of each member of the tire are measured in a state where the tire is incorporated in a regular rim and the tire is filled with air so as to have a regular internal pressure. During the measurement, no load is applied to the tire. In this specification, the normal rim means a rim defined in a standard on which a tire depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In this specification, the normal internal pressure means an internal pressure defined in a standard on which the tire depends. “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 this specification, the normal load means a load defined in a standard on which the tire depends. “Maximum value” published in “Maximum load capacity” in the JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “LOAD CAPACITY” in the ETRTO standard are normal loads.

  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 pair of chafers 20. The tire 2 is a tubeless type. The tire 2 is mounted on a small truck. The tire 2 corresponds to a small truck tire 2 which is a target of Chapter B of the JATMA standard.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 22 that contacts the road surface. The tread 4 has a groove. A tread pattern is formed by this groove. In this embodiment, the tread 4 includes a first main groove 24 positioned on the equator plane, and a pair of second main grooves 28 positioned between the first main groove 24 and the tread end 26. . In the tread 4, a region partitioned by the first main groove 24 and the second main groove 28 is referred to as a rib 30. A plurality of ribs 30 are formed on the tread 4. In this embodiment, four ribs 30 are formed on the tread 4. The tread 4 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  In this embodiment, as described above, a total of three main grooves are provided by combining the first main groove 24 and the second main groove 28. The number of main grooves is not limited to three. The tread 4 may have 2 or less main grooves. The tread 4 may not include the main groove. The tread 4 may include four or more main grooves.

  Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. A radially outer portion of the sidewall 6 is joined to the tread 4. The radially inner portion of the sidewall 6 is joined to the clinch 8. The sidewall 6 is located on the outer side in the axial direction than the carcass 12. 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 radially inward of the sidewall 6. The clinch 8 is located on the outer side in the axial direction of the bead 10 and the carcass 12. 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 32 and an apex 34 that extends radially outward from the core 32. The core 32 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 34 is tapered outward in the radial direction. The apex 34 is made of a highly hard crosslinked rubber.

  The carcass 12 includes a first ply 12a and a second ply 12b. The first ply 12 a and the second ply 12 b are bridged between the beads 10 on both sides, and extend along the tread 4 and the sidewall 6. The first ply 12 a is folded around the core 32 from the inner side toward the outer side in the axial direction. By this folding, a main portion 36 and a folding portion 38 are formed in the first ply 12a. The second ply 12b is folded around the core 32 from the inner side to the outer side in the axial direction. By this folding, a main portion 40 and a folding portion 42 are formed in the second ply 12b. The end of the folded portion 38 of the first ply 12a is located outside the end of the folded portion 42 of the second ply 12b in the radial direction.

  Each of the first ply 12a and the second ply 12b 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 a single ply.

  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. In this embodiment, the belt 14 includes a first layer 14a and a second layer 14b. The second layer 14b is located outside the first layer 14a in the radial direction. Although not shown, each of the first layer 14a and the second layer 14b is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the first layer 14a with respect to the equator plane is opposite to the inclination direction of the cord of the second layer 14b with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord. The belt 14 may include three or more layers.

  The band 16 is located on the radially outer side of the belt 14. In the axial direction, the width of the band 16 is larger than the width of the belt 14. Although not shown, 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, further 2 ° or less. Since the belt 14 is restrained by this cord, lifting of the belt 14 is suppressed. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 14 and the band 16 constitute a reinforcing layer. The reinforcing layer may be formed only from the belt 14.

  The inner liner 18 is located inside the carcass 12. In the vicinity of the equator plane, the inner liner 18 is joined to the inner surface of the carcass 12. The inner liner 18 is made of a crosslinked rubber having excellent air shielding properties. 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 20 is located in the vicinity of the bead 10. The chafer 20 contacts the rim R. By this contact, the vicinity of the bead 10 is protected. In this embodiment, the chafer 20 is made of cloth and rubber impregnated in the cloth. The chafer 20 may be integrated with the clinch 8. In this case, the material of the chafer 20 is the same as that of the clinch 8.

  FIG. 2 is an enlarged cross-sectional view of the tread 4 portion of the tire 2 of FIG. In FIG. 2, 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.

  The contour of the outer surface of the virtual tire 2 obtained without the projections and grooves for the characters and patterns provided on the grooves of the tread 4 and the side surface of the tire 2 is referred to as a profile. As shown in the figure, the profile of the tread 4 includes a center arc TC1 positioned at the center of the tread 4 and a pair of shoulder arcs TC2 positioned outside in the axial direction of the center arc TC1. In this embodiment, the profile of the tread 4 includes a center arc TC1 and a pair of shoulder arcs TC2. The center arc TC1 and the shoulder arc TC2 are in contact at the intersection Px. In this specification, the radius of curvature of the center arc TC1 is referred to as a center radius of curvature TR1. The radius of curvature of shoulder arc TC2 is referred to as shoulder radius of curvature TR2. In the tire 2, the center curvature radius TR1 is larger than the shoulder curvature radius TR2. In this embodiment, the center radius of curvature TR1 is not less than 340 mm and not more than 1000 mm. In the present invention, the dimensions and angles relating to this profile are based on the cavity surface of the mold.

  In the figure, a double-headed arrow Wt is an axial width from the equator plane CL to the tread end 26. A double-headed arrow Wx is an axial width from the equator plane CL to the intersection point Px. In the tire 2, the ratio (Wx / Wt) of the width Wx to the width Wt is 0.44 or more and 0.56 or less.

  In the tire 2, the profile of the tread 4 may include other small arcs and straight lines in addition to the center arc TC1 and the shoulder arc TC2. Here, “small arcs and straight lines” mean arcs or straight lines in which a profile including them can be regarded as equivalent to a profile not including them. In this sense, in the tire 2, the profile of the tread 4 substantially includes a center arc TC1 and a pair of shoulder arcs TC2. When a small arc or straight line exists between the center arc TC1 and the shoulder arc TC2, the intersection point Px is an arc obtained by extending the arc length of the center arc TC1 and an arc obtained by extending the arc length of the shoulder arc TC2. Is the intersection of In the tread 4, a portion of the profile substantially constituted by the center arc TC <b> 1 is referred to as a center portion, and a portion substantially constituted by the shoulder arc TC <b> 2 is referred to as a shoulder portion.

  In FIG. 2, a point Pc is an intersection of the radially outer side surface of the second layer 14b and the equator plane. The point Pe is an end point of the radially outer surface of the second layer 14b. In FIG. 2, only one of the pair of end points Pe is shown. In this specification, a virtual arc passing through the three points of the intersection Pe and the pair of end points Pe is referred to as a belt virtual arc BC. The belt virtual arc BC has a shape protruding outward in the radial direction. The curvature radius of the belt virtual arc BC is referred to as a belt curvature radius BR. In the tire 2, the belt curvature radius BR is not less than 900 mm and not more than 1100 mm. In the tire 2, a ratio (TR2 / BR) of the shoulder curvature radius TR2 to the belt curvature radius BR is 0.38 or more and 0.63 or less.

  The effects of the present invention will be described below.

  The inventors examined the structure of a tire for suppressing uneven wear. As a result, it has been found that the shape of the belt affects the wear at the shoulder. It has been found that by appropriately adjusting the shape of the belt and the shape of the tread, occurrence of uneven wear due to accelerated wear at the shoulder portion can be suppressed.

  In the tire 2, the profile of the tread 4 is substantially composed of a center arc TC1 and a shoulder arc TC2. In the tire 2, the belt radius of curvature BR is not less than 900 mm and not more than 1100 mm. The ratio (TR2 / BR) of the shoulder curvature radius TR2 to the belt curvature radius BR is not less than 0.38 and not more than 0.63. In the structure of the tread 4 and the belt 14, by setting the ratio (TR2 / BR) to 0.38 or more, the ground contact length (the length in the circumferential direction of the ground contact surface) between the axially inner portion and the outer portion in the shoulder portion. ) Difference can be reduced. Thereby, the difference of the abrasion loss of the axial direction inner side part in a shoulder part and an outer side part can be made small. In the tire 2, it is effectively suppressed that the wear of the outer portion in the shoulder portion is accelerated. By setting the ratio (TR2 / BR) to 0.63 or less, the load applied to the shoulder portion when the vehicle turns can be moderately reduced. In the tire 2, it is effectively suppressed that the wear of the shoulder portion is accelerated. In the tire 2, uneven wear is suppressed.

  As described above, in the embodiment of FIG. 2, the tread 4 includes the first main groove 24 and the pair of second main grooves 28. The tread 4 is composed of four ribs 30. When the tread 4 has this structure, the intersection Px between the center arc TC1 and the shoulder arc TC2 is preferably located where the second main groove 28 exists. If the intersection point of the center arc TC1 and the shoulder arc TC2 having different curvature radii is on the rib 30, when the tread 4 is deformed during traveling, distortion may be concentrated in the vicinity of the intersection point. In this embodiment, since the intersection point Px is located where the second main groove 28 exists, the concentration of distortion is suppressed even if the tire 2 is greatly deformed. The tread 4 is not easily damaged. The tire 2 is excellent in durability.

  In FIG. 2, a double-headed arrow G is the thickness in the radial direction from the tread surface 22 to the radially outer surface of the belt 14 on the equator plane. A symbol Pg is a point on the tread surface 22 whose axial distance from the equator plane is 0.66 times the width Wt. A double-headed arrow Gg is the thickness in the radial direction from the point Pg to the radially outer surface of the belt 14.

  The ratio (Gg / G) of the thickness Gg to the thickness G is preferably 0.81 or more. By setting the ratio (Gg / G) to 0.81 or more, the difference in contact length between the axially inner portion and the outer portion in the shoulder portion can be reduced. Thereby, the difference of the abrasion loss of the axial direction inner side part in a shoulder part and an outer side part can be made small. In the tire 2, it is effectively suppressed that the wear of the outer portion in the shoulder portion is accelerated. Furthermore, the tire 2 has a sufficient ground contact width by setting the ratio (Gg / G) to 0.81 or more. The tire 2 is excellent in handling stability. The ratio (Gg / G) is preferably 0.85 or less. By setting the ratio (Gg / G) to 0.85 or less, the load applied to the shoulder portion when the vehicle turns can be moderately reduced. In the tire 2, it is effectively suppressed that the wear of the shoulder portion is accelerated. In the tire 2, uneven wear is suppressed.

  In FIG. 2, a double-headed arrow Wb is an axial width from the equator plane to the axially outer end of the belt 14. When the belt 14 has a plurality of layers, the width Wb is an axial width from the equator plane to the end located on the outermost side in the axial direction among the ends of these layers. In this embodiment, the width Wb is an axial width from the equator plane to the end of the first layer 14a.

  The ratio (Wb / Wt) of the width Wb to the width Wt is preferably 0.96 or more. By setting the ratio (Wb / Wt) to 0.96 or more, the belt 14 restrains the carcass 12 to the vicinity of the tread end 26. The deformation of the tire 2 near the tread end 26 during traveling is reduced. This prevents the curvature of the shoulder arc TC2 from increasing during traveling. The contact length on the outside of the shoulder portion is maintained. In the tire 2, it is effectively suppressed that the wear of the outer portion in the shoulder portion is accelerated. The ratio (Wb / Wt) is preferably 1.01 or less. By setting the ratio (Wb / Wt) to 1.01 or less, it is possible to suppress stress from being concentrated on the end of the belt 14 when the tread 4 is deformed during traveling. Damage is unlikely to occur near the end of the belt 14. This tire 2 is excellent in durability.

  As shown in FIG. 1, the tire 2 preferably includes a band 16 that covers the belt 14. The cord of the band 16 is particularly preferably made of nylon fiber. The band 16 provided with a cord made of nylon fiber effectively contributes to an improvement in the binding force of the belt 14. This prevents the curvature of the shoulder arc TC2 from increasing during traveling. The contact length on the outside of the shoulder portion is maintained. In the tire 2, it is effectively suppressed that the wear of the outer portion in the shoulder portion is accelerated.

  In FIG. 1, reference numeral P <b> 1 is a point on the inner surface of the tire 2 that is axially inner than the end of the belt 14 and has an axial distance B <b> 1 from the end of the belt 14 of 20 mm. Reference symbol P2 is a point on the inner surface of the tire 2 that is axially outside the end of the belt 14 and has an axial distance B2 from the end of the belt 14 of 10 mm. A portion from the point P1 to the point P2 on the inner surface of the tire 2 is referred to as a buttress portion. The curvature radius of the inner surface of the tire 2 in the buttress portion is referred to as a buttress curvature radius IR.

  The buttress curvature radius IR is preferably 55 mm or greater and 65 mm or less. By setting the buttress curvature radius IR to 55 mm or more and 65 mm or less, the position of the belt 14 in the shoulder portion can be appropriately maintained even during traveling. The end of the belt 14 is prevented from being deformed inward in the radial direction during traveling. This prevents the curvature of the shoulder arc TC2 from increasing during traveling. The contact length on the outside of the shoulder portion is maintained. In the tire 2, it is effectively suppressed that the wear of the outer portion in the shoulder portion is accelerated.

  As shown in the figure, the carcass 12 preferably has two plies. The cord of the ply is particularly preferably made of polyester fiber. The carcass 12 reduces deformation of the shoulder portion during traveling. The end of the belt 14 is prevented from being deformed inward in the radial direction during traveling. This prevents the curvature of the shoulder arc TC2 from increasing during traveling. The contact length on the outside of the shoulder portion is maintained. In the tire 2, it is effectively suppressed that the wear of the outer portion in the shoulder portion is accelerated.

  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]
The tire shown in FIG. 1-2 was manufactured. The specifications of the tire are shown in Table 1. The size of this tire is “175 / 75R15 103 / 101L”. The tire includes a first main groove and a pair of second main grooves. The intersection point Px between the center arc TC1 and the shoulder arc TC2 is located where the second main groove exists. The ratio (Wx / Wt) was 0.50. The center curvature radius TC1 was 850 mm. The thickness G was 13.5 mm. The cord of this band is made of nylon fiber. The cords of the first ply and the second ply of the carcass are made of polyester fibers.

[Comparative Example 1-2]
A tire of Comparative Example 1-2 was obtained in the same manner as in Example 1 except that the belt curvature radius BR was changed and the ratio (TR2 / BR) was changed as shown in Table 1.

[Example 2-4 and Comparative Example 3-4]
Example 2-4 and Comparative Example 3-4 were the same as Example 1 except that the belt curvature radius BR was 900 mm, the shoulder curvature radius TR2 was changed, and the ratio (TR2 / BR) was as shown in Table 2. I got a tire.

[Example 5-6 and Comparative Example 5-6]
Tires of Example 5-6 and Comparative Example 5-6 were obtained in the same manner as Example 1 except that the shoulder curvature radius TR2 was changed and the ratio (TR2 / BR) was changed as shown in Table 3.

[Example 7-9 and Comparative Example 7-8]
Example 7-9 and Comparative Example 7-8 were the same as Example 1 except that the belt curvature radius BR was 1100 mm, the shoulder curvature radius TR2 was changed and the ratio (TR2 / BR) was as shown in Table 4. I got a tire.

[Example 10-13]
Tires of Examples 10-13 were obtained in the same manner as Example 1, except that the thickness Gg was changed and the ratio (Gg / G) was changed as shown in Table 5.

[Examples 14-16]
Tires of Examples 14-16 were obtained in the same manner as Example 12 except that the shoulder curvature radius TR2 was not provided and the ratio (TR2 / BR) was changed as shown in Table 6.

[Examples 17-20]
Tires of Examples 17-20 were obtained in the same manner as Example 12 except that the width (Wb) was changed and the ratio (Wb / Wt) was changed as shown in Table 7.

[Examples 21-24]
Tires of Examples 21-24 were obtained in the same manner as in Example 12 except that the buttress curvature radius IR was changed as shown in Table 8.

[Abrasion resistance evaluation]
The tire was incorporated into a standard rim (size = 15 × 5.0 J) and mounted on a commercially available truck. The internal pressure of this tire was 600 kPa. On a general road, the vehicle was driven until the travel distance reached 150 km. The amount of wear on the shoulder portion of the tire was measured. The reciprocal of this value is an index value with the reciprocal of the target wear amount being 100, and is shown in Table 1-8 below. Higher values indicate longer tire life against wear. Larger values are preferred.

  As shown in Tables 1 to 8, the tire of the example has a higher evaluation than 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 ... Tire 4 ... Tread 6 ... Sidewall 8 ... Clinch 10 ... Bead 12 ... Carcass 12a ... First ply 12b ... Second ply 14 ... Belt 14a ... first layer 14b ... second layer 16 ... band 18 ... inner liner 20 ... chafer 22 ... tread surface 24 ... first main groove 26 ... tread End 28 ... Second main groove 30 ... Rib 32 ... Core 34 ... Apex 36, 40 ... Main part 38, 42 ... Folded part

Claims (6)

It has a tread whose outer surface forms a tread surface and a belt located inside the tread in the radial direction,
In a cross section perpendicular to the circumferential direction, the profile of the tread includes a center arc TC1 positioned at the tread center and a pair of shoulder arcs TC2 positioned outside the center arc TC1 in the axial direction.
The radius of curvature TR1 of the center arc TC1 is larger than the radius of curvature TR2 of the shoulder arc TC2,
When the intersection of the center arc TC1 and the shoulder arc TC2 is Px,
In the axial direction, the ratio (Wx / Wt) of the width Wx from the equator plane to the intersection Px to the width Wt from the equator plane to the tread edge is 0.44 or more and 0.56 or less,
The belt comprises a first layer and a second layer laminated radially outward of the first layer;
The intersection point between the radially outer surface of the second layer and the equator plane is defined as Pc, the pair of end points of the radially outer surface of the second layer is defined as Pe, and passes through the intersection point Pc and the pair of endpoints Pe. When the virtual arc is BC and the radius of curvature of the arc BC is BR,
The radius of curvature BR is 900 mm or more and 1100 mm or less,
A pneumatic tire in which a ratio (TR2 / BR) of the curvature radius TR2 to the curvature radius BR is 0.38 or more and 0.63 or less. A first main groove on which the tread is positioned on the equator plane, and a pair of second main grooves each positioned between the first main groove and the tread end;
The tire according to claim 1, wherein the intersection point Px is located where the second main groove is present.   The thickness from the tread surface on the equator plane to the radially outer surface of the belt is G, and the point on the tread surface where the axial distance from the equator plane is 0.66 times the width Wt is Pg. The ratio (Gg / G) of the thickness Gg to the thickness G when the thickness from Pg to the outer surface in the radial direction of the belt is Gg is 0.81 or more and 0.85 or less. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 3, wherein a ratio (Wb / Wt) of the axial width Wb from the equator plane to the end of the belt with respect to the width Wt is 0.96 or more and 1.01 or less. . A band that covers the belt on the outer side in the radial direction of the belt;
The pneumatic tire according to any one of claims 1 to 4, wherein the band includes a cord made of nylon fiber.   The pneumatic tire according to any one of claims 1 to 5, wherein a radius of curvature IR of an inner surface of the tire in the buttress portion is 55 mm or greater and 65 mm or less.

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