tire

Abstract

To provide a tire that can achieve improvement in pinch-cut resistance.SOLUTION: A tire 2 has a nominal size of a cross sectional height which is 110 mm or less. The tire 2 comprises a tread, a pair of side walls, a pair of beads, a carcass, a belt and a band. The beads comprise cores and apexes. The belt comprises an inside layer and an outside layer. An end of the outside layer is positioned inside in an axial direction of an end of the inside layer. A ratio of a width in the axial direction of the outside layer to a cross sectional width of the tire 2 is 80% or less. A ratio of a length LCa of the carcass 12 from a position BW corresponding to an outer end PW in the axial direction of the tire 2 to a position BS corresponding to the end of the outside layer, to the cross sectional height of the tire 2 is 50% or more and 60% or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] When a tire passes over a bump, it is subjected to an impact. When a large load acts on the tire, the side of the tire bends significantly, and the bead portion fitted to the rim comes into contact with the tread portion at the end of the belt. At this time, a shear force is applied to the carcass. The carcass includes carcass cords. If a high shear force is applied to the carcass, there is a risk that the carcass cords will break. Damage that involves the breakage of the carcass cords is also called a pinch cut. Various studies have been conducted to prevent the occurrence of pinch cuts (for example, see Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-069901 Summary of the Invention [Problem to be solved by the invention]

[0004] Considering the impact on the environment, there has been an increase in the use of motors as a means of propulsion for vehicles. These vehicles are equipped with batteries. The weight of the vehicle increases compared to conventional vehicles. The load acting on the tires increases. Tires are required to have improved pinch cut resistance.

[0005] To improve pinch cut resistance, measures are usually taken, such as increasing the number of carcass plies that make up the carcass or replacing the carcass cords with cords that have higher rigidity. Low-profile tires with a nominal cross-section height of 110 mm or less have short sidewalls that contribute to absorbing impact when going over bumps. However, even with the above measures, low-profile tires used on vehicles equipped with batteries may not achieve the required pinch cut resistance.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tire that can achieve improved pinch cut resistance. [Means for solving the problem]

[0007] A tire according to one aspect of the present invention has a nominal section height of 110 mm or less. The tire includes a tread having a tread surface, a pair of sidewalls connected to edges of the tread and positioned radially inward of the tread, a pair of beads positioned radially inward of the sidewalls, a carcass positioned inward of the tread and the pair of sidewalls and spanning between a first bead and a second bead of the pair of beads, a belt laminated to the carcass on the inside of the tread, and a band positioned between the tread and the belt. The bead includes a core and an apex positioned radially outward of the core. The belt includes an inner layer and an outer layer positioned radially outward of the inner layer. An end of the outer layer is positioned axially inward of the end of the inner layer. The ratio of the axial width of the outer layer to the section width of the tire is 80% or less. The ratio of the length of the carcass from a position corresponding to an axially outer end of the tire to a position corresponding to an end of the outer layer to the section height of the tire is 50% or more and 60% or less.

[0008] Preferably, in this tire, the ratio of the length of the carcass from a position corresponding to the axial outer end of the tire to a position corresponding to the outer end of the apex to the section height of the tire is 18% or more and 23% or less.

[0009] Preferably, in the tire, in a meridian cross section, the region of the tread surface that includes the tire equator is the crown region. When the tire is mounted on a regular rim and the internal pressure of the tire is adjusted to 230 kPa, the outer diameter of the tire is the reference outer diameter, and the radius of the arc that represents the outline of the crown region is the reference radius. The ratio of the reference radius to the reference outer diameter is 55% or more and 70% or less.

[0010] Preferably, in the tire, the ratio of the tread thickness at the end of the outer layer to the tread thickness at the equator of the tire is equal to or greater than 55% and equal to or less than 75%.

[0011] Preferably, in this tire, a plurality of land portions arranged in parallel in the axial direction are formed by cutting circumferential grooves in the tread, and the land portions located axially outward among the plurality of land portions are shoulder land portions. A plurality of lateral grooves are cut into the shoulder land portions aligned in the circumferential direction, and the inner ends of the plurality of lateral grooves are located within the shoulder land portions, and the lateral grooves extend from the inner ends toward the edges of the tread surface. The band includes a full band covering the belt and a pair of edge bands spaced apart in the axial direction and covering the ends of the full bands. The inner ends of the edge bands are located axially inside the inner ends of the lateral grooves. [Effects of the Invention]

[0012] According to the present invention, a tire that can achieve improved pinch cut resistance can be obtained. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a part of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the contour of the carcass. [Figure 3] FIG. 3 is a cross-sectional view showing the contour of the tread surface. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0015] In this disclosure, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state. The state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to 180 kPa, and no load is applied to the tire is called the standard state. The state in which a tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire is called the reference state.

[0016] In this disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a standard state. The dimensions and angles of each part in a meridian cross section of the tire, which cannot be measured when the tire is mounted on a regular rim, are measured by cutting the tire along a plane including the rotation axis, and the distance between the left and right beads in the cross section is measured so that it matches the distance between the beads when the tire is mounted on a regular rim.

[0017] A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are all genuine rims.

[0018] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0019] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0020] In this disclosure, "nominal section height" refers to the value expressed in millimeters obtained by dividing the product of "nominal section width" and "nominal aspect ratio" by 100. "Nominal section width" and "nominal aspect ratio" are the "nominal section width" and "nominal aspect ratio" included in "tire designation" specified in JIS D4202 "Automobile tires - Designations and specifications."

[0021] In the present disclosure, the load index (LI) is defined, for example, in the JATMA standard, and is an index that indicates the maximum mass that can be loaded onto a tire under specified conditions, that is, the maximum load capacity.

[0022] In the present disclosure, the complex modulus of an element made of crosslinked rubber, among elements constituting a tire, at a temperature of 70°C is measured in accordance with the provisions of JIS K6394 using a viscoelasticity spectrometer ("VES" manufactured by Iwamoto Seisakusho Co., Ltd.) under the following conditions: Initial strain = 10% Dynamic strain = 2% Frequency = 10 Hz Deformation mode = tension In this measurement, test specimens are sampled from tires. If it is not possible to sample test specimens from tires, test specimens are sampled from a sheet of crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressing and heating the rubber composition used to form the element to be measured at a temperature of 170°C for 12 minutes.

[0023] In this disclosure, the number of cords contained in a tire element, including parallel cords, per 5 cm width is expressed as the cord density (unit: ends) of the element. For example, if a tire element contains 30 cords per 5 cm width, the cord density of the element is expressed as 30 ends. Unless otherwise specified, the cord density is obtained in a cross section of the element obtained by cutting the element in a plane perpendicular to the length direction of the cords.

[0024] In this disclosure, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The side portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of side portions.

[0025] Fig. 1 shows a portion of a tire 2 according to one embodiment of the present invention. The tire 2 is a pneumatic tire for passenger cars. The tire 2 has a nominal section height of 110 mm or less. The tire 2 is a low aspect tire. FIG. 1 shows a portion of a cross section (hereinafter referred to as a meridian cross section) of the tire 2 taken along a plane including the rotation axis of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. The dashed-dotted line CL represents the equatorial plane of the tire 2.

[0026] The tire 2 is mounted on a rim R. The rim R is a regular rim. Air is filled inside the tire 2, and the internal pressure of the tire 2 is adjusted. The tire 2 mounted on the rim R is also called a tire-rim assembly. The tire-rim assembly includes the rim R and the tire 2 mounted on this rim R.

[0027] The rim R includes a seat RS and a flange RF. When the tire 2 is mounted on the rim R, the seat RS comes into contact with the bead portion from the radially inner side, and the flange RF comes into contact with the bead portion from the axially outer side.

[0028] In Fig. 1, the solid line BBL extending in the axial direction is the bead base line, which defines the rim diameter of the rim R (see JATMA, etc.).

[0029] The position indicated by the symbol PC in FIG. 1 is the intersection point between the outer surface of the tire 2 and the equatorial plane. The intersection point PC is also called the equator of the tire 2. When a groove is located on the equatorial plane, the equator PC is determined based on a virtual outer surface obtained assuming that no groove exists. The equator PC is also the radially outer end of the tire 2.

[0030] 1, the length indicated by the symbol SH is the radial distance from the bead base line to the equator PC. In this disclosure, the equator PC is specified for the tire 2 in a standard state. The radial distance SH is the cross-sectional height of the tire 2 (see JATMA, etc.).

[0031] 1, the length indicated by the symbol OD is the radial distance from the first equator PC to a second equator PC (not shown) located on the opposite side of the rotation axis. The radial distance OD is the outer diameter of the tire 2. In this disclosure, the outer diameter OD specified for the tire 2 in a reference state is the reference outer diameter ROD.

[0032] 1, the position indicated by the symbol PW is the axially outer end of the tire 2. If there is a decoration such as a pattern or lettering on the outer surface, the outer end PW is identified based on a virtual outer surface obtained assuming that there is no decoration. 1, the length indicated by the symbol WA is the axial width of the tire 2. The axial width WA is the axial distance from the first outer end PW to the second outer end PW. The axial width WA is the maximum width of the tire 2, and the outer end PW is the position at which the tire 2 exhibits the maximum width WA (hereinafter referred to as the maximum width position). In the present disclosure, the outer end PW is specified in the tire 2 in a standard state. The axial width WA is the cross-sectional width of the tire 2 (see JATMA, etc.).

[0033] 1, the length indicated by the symbol HW is the radial distance from the bead base line to the maximum width position PW. The radial distance HW is also referred to as the maximum width height. In the tire 2, the ratio (HW / SH) of the maximum width height HW to the cross-sectional height SH of the tire 2 is equal to or greater than 0.45 and is equal to or less than 0.55.

[0034] The tire 2 comprises, as elements, 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, a pair of chafers 18, and an inner liner 20.

[0035] The tread 4 comes into contact with the road surface at a tread surface 22. The tread 4 has a tread surface 22 that comes into contact with the road surface. The tread surface 22 forms a part of the outer surface SS of the tire 2. The tread surface 22 includes the equator PC described above. Grooves 24 are cut into the tread 4 of this tire 2. This forms a tread pattern.

[0036] The tread 4 comprises a tread body 26 and a pair of wings 28. Each wing 28 is located axially outward of the tread body 26. The wings 28 join the tread body 26 and the sidewall 6. The wings 28 are made of crosslinked rubber with adhesive properties taken into consideration.

[0037] The tread body 26 comprises a base portion 30 and a cap portion 32. The base portion 30 covers the band 16. The base portion 30 is made of cross-linked rubber that takes heat buildup into consideration. The cap portion 32 is located radially outward of the base portion 30. The cap portion 32 covers the base portion 30. The cap portion 32 is made of cross-linked rubber that takes wear resistance and grip performance into consideration.

[0038] Each sidewall 6 is continuous with an edge of the tread 4. The sidewall 6 is located radially inward of the tread 4. The sidewall 6 is made of crosslinked rubber in consideration of cut resistance.

[0039] Each clinch 8 is located radially inside the sidewall 6. The clinch 8 contacts the flange RF of the rim R. The clinch 8 is made of cross-linked rubber that is designed for wear resistance.

[0040] Each bead 10 is located axially inward of the clinch 8. The beads 10 are located radially inward of the sidewall 6. The bead 10 includes a core 34 and an apex 36. The core 34 extends in the circumferential direction. Although not shown, the core 34 includes a steel wire. The core 34 is formed by winding the wire multiple times in the circumferential direction. The apex 36 is located radially outward of the core 34. The apex 36 tapers radially outward. The apex 36 is made of crosslinked rubber with high rigidity.

[0041] 1, the length indicated by the symbol HA is the radial distance from the bead base line to the outer end of the apex 36. The radial distance HA is the apex height. In the tire 2, the ratio (HA / SH) of the apex height HA to the cross-sectional height SH of the tire 2 is equal to or greater than 25% and equal to or less than 40%.

[0042] In the tire 2, the complex modulus of elasticity of the apex 36 is preferably 20 MPa or more and 80 MPa or less. By setting the complex modulus of elasticity to 20 MPa or more, the apex 36 effectively increases the lateral rigidity of the tire 2. This enables improvement in the limit running performance of the tire 2. From this viewpoint, the complex modulus of elasticity is more preferably 30 MPa or more, and further preferably 40 MPa or more. Setting the complex modulus of elasticity to 80 MPa or less reduces the influence of the apex 36 on the ride comfort. From this viewpoint, the complex modulus of elasticity is more preferably 70 MPa or less, and further preferably 60 MPa or less.

[0043] The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of clinches 8. The carcass 12 bridges between the first bead 10 and the second bead 10 of the pair of beads 10. The carcass 12 includes at least one carcass ply 38.

[0044] The carcass 12 of this tire 2 is composed of two carcass plies 38. Although not shown, each carcass ply 38 includes a large number of carcass cords arranged in parallel. These carcass cords intersect with the equatorial plane. The carcass 12 of this tire 2 has a radial structure. In this tire 2, cords made of organic fibers are used as carcass cords. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0045] Of the two carcass plies 38, the carcass ply 38 located radially inner on the inner side of the tread 4 is a first carcass ply 40. The carcass ply 38 located radially outer of the first carcass ply 40 on the inner side of the tread 4 is a second carcass ply 42.

[0046] The first carcass ply 40 includes a first ply body 40a and a pair of first turned-up portions 40b. The first ply body 40a bridges between the first bead 10 and the second bead 10. Each of the first turned-up portions 40b is continuous with the first ply body 40a and is turned up from the inside toward the outside in the axial direction at each bead 10.

[0047] The second carcass ply 42 includes a second ply body 42a and a pair of second turned-up portions 42b. The second ply body 42a bridges between the first bead 10 and the second bead 10. Each of the second turned-up portions 42b is continuous with the second ply body 42a and is turned up from the inside toward the outside in the axial direction at each of the beads 10.

[0048] In this tire 2, the end of the first turned-up portion 40b is located radially outward from the outer end PW. The radial distance from the end of the first turned-up portion 40b to the outer end PW is 3 mm or more and 15 mm or less. The end of the second turned-up portion 42b is located radially inward from the outer end PW. The end of the second turned-up portion 42b is located radially between the outer end of the apex 36 and the core 34. The second folded portion 42b is located axially inward of the first folded portion 40b. The end of the second folded portion 42b is located between the apex 36 and the first folded portion 40b.

[0049] In this tire 2, the strength of each carcass ply 38 constituting the carcass 12 is preferably 7000 or more and 15000 or less. By setting this strength to 7000 or more, the carcass 12 balances the rigidity of the tire 2. In this tire 2, a good ride comfort is obtained. From this viewpoint, the strength of the carcass ply 38 is more preferably 8000 or more, and even more preferably 9000 or more. By setting the strength of the carcass ply 38 to 15000 or less, the effect of the carcass 12 on the mass of the tire 2 is suppressed. From this viewpoint, the strength of the carcass ply 38 is more preferably 14000 or less, and even more preferably 13000 or less.

[0050] In the present disclosure, the strength of the carcass ply 38 is expressed as the product of the cord density and the strength at break of the carcass cord. The strength at break of the carcass cord is measured in accordance with the provisions of JIS L1017, and its unit is Newton (N).

[0051] The belt 14 is laminated on the carcass 12 radially inward of the tread 4. The aforementioned equatorial plane intersects with the belt 14 at the center of the axial width of the belt 14. The belt 14 is made up of two layers 44 laminated in the radial direction. The belt 14 includes an inner layer 46 and an outer layer 48. The outer layer 48 is positioned radially outward of the inner layer 46. One or more layers 44 may be further provided between the inner layer 46 and the outer layer 48.

[0052] Although not shown, each layer 44 constituting the belt 14 includes a large number of belt cords arranged in parallel. These belt cords are inclined with respect to the equatorial plane. In this tire 2, the inclination direction of the belt cords included in the inner layer 46 is opposite to the inclination direction of the belt cords included in the outer layer 48. The belt cords are made of steel.

[0053] 1, the inner layer 46 is wider than the outer layer 48. An end of the outer layer 48 is located axially inward of an end of the inner layer 46. In the tire 2, the length from the end of the outer layer 48 to the end of the inner layer 46 is 3 mm or more and 10 mm or less.

[0054] In the tire 2, the strength of each layer 44 constituting the belt 14 is preferably 13,000 or greater and 28,000 or less. By setting the strength to 13,000 or greater, the belt 14 increases the rigidity of the tread portion. In the tire 2, good steering stability is obtained and uneven wear resistance is improved. From this viewpoint, the strength of the layer 44 is more preferably 14,000 or greater, and even more preferably 15,000 or greater. By setting the strength of the layer 44 to 28,000 or less, the impact of the belt 14 on the mass of the tire 2 is suppressed. From this viewpoint, the strength of the layer 44 is more preferably 27,000 or less, and even more preferably 26,000 or less.

[0055] In the present disclosure, the strength of the layer 44 is expressed as the product of the cord density and the breaking load of the belt cord. The breaking load of the belt cord is measured in accordance with the JIS G3510 standard, and its unit is Newton (N).

[0056] The band 16 is located radially between the tread 4 and the belt 14. The band 16 is laminated on the belt 14 on the inside of the tread 4. The band 16 covers the entire belt 14. The band 16 is wider than the belt 14. The length from the end of the belt 14 to the end of the band 16 is 3 mm or more and 7 mm or less.

[0057] Although not shown, the band 16 includes a spirally wound band cord. The band cord extends substantially in the circumferential direction. Specifically, the angle that the band cord forms with the circumferential direction is 5° or less. The band 16 has a jointless structure. In the tire 2, a cord made of an organic fiber is used as the band cord. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0058] The band 16 includes a full band 50 and a pair of edge bands 52 . The full band 50 has opposite ends across the equator plane. The ends of the full band 50 are located axially outward of the ends of the belt 14. The full band 50 is laminated on the belt 14. The pair of edge bands 52 are arranged spaced apart in the axial direction across the equatorial plane. The edge bands 52 are laminated on the full band 50. The edge bands 52 cover the end portions of the full band 50. In this tire 2, the positions of the outer ends of the edge bands 52 coincide with the positions of the ends of the full band 50 in the axial direction. The outer ends of the edge bands 52 may be located outward from the ends of the full band 50 in the axial direction, or may be located inward from the ends of the full band 50 in the axial direction. In this case, the distance between the ends of the full band 50 and the outer ends of the edge bands 52 is set to 10 mm or less.

[0059] Each chafer 18 is located radially inside the bead 10. The chafer 18 is made of a cloth and rubber impregnated into the cloth. The chafer 18 comes into contact with the seat RS of the rim R.

[0060] The inner liner 20 is located inside the carcass 12. The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of crosslinked rubber that has excellent air barrier properties. The inner liner 20 maintains the internal pressure of the tire 2.

[0061] 1 is the width of the outer layer 48. The width WS of the outer layer 48 is the axial distance from the first end to the second end of the outer layer 48.

[0062] FIG. 2 shows the outlines of the carcass 12 and the inner layer 46 and outer layer 48 of the belt 14 in the meridian cross section shown in FIG. 1 . In this disclosure, the outline of the carcass 12 is represented by the outline of the ply body of the outermost carcass ply 38 among the carcass plies 38 constituting the carcass 12 located inside the tread 4. In the tire 2, the outline of the carcass 12 is represented by the outline of the second ply body 42a. This outline is represented by identifying the centers of the carcass cords included in the second ply body 42a. The outline of the carcass 12 is also referred to as a carcass line 54. The outline of the inner layer 46 is represented by identifying the centers of the belt cords included in the inner layer 46. The outline of the inner layer 46 is also referred to as an inner belt line 56. The outline of the outer layer 48 is represented by identifying the centers of the belt cords included in the outer layer 48. The outline of the outer layer 48 is also referred to as an outer belt line 58.

[0063] 2, the solid line indicated by the symbol SLW is a straight line extending in the axial direction and passing through the maximum width position PW of the tire 2. The symbol BW is the intersection point between the straight line SLW and the carcass line 54. In the present disclosure, this intersection point BW is a position on the carcass line 54 that corresponds to the axially outer end PW of the tire 2.

[0064] 2, the solid line indicated by the symbol SLS is a normal line to the inner surface of the tire 2 that passes through the end of the outer layer 48 (specifically, the end of the outer belt line 58). The symbol BS is the intersection point between the normal line SLS and the carcass line 54. In the present disclosure, this intersection point BS is a position on the carcass line 54 that corresponds to the end of the outer layer 48.

[0065] 2, the length indicated by the symbol LCa is the length of the carcass line 54 from the position BW to the position BS. In the present disclosure, this length LCa is the length of the carcass 12 from the position BW corresponding to the axially outer end PW of the tire 2 to the position BS corresponding to the end of the outer layer 48.

[0066] 2, the solid line indicated by the symbol SLA is a normal line to the inner surface of the tire 2 that passes through the outer end of the apex 36. The symbol BA is the intersection point between the normal line SLA and the carcass line 54. In the present disclosure, this intersection point BA is a position on the carcass line 54 that corresponds to the outer end of the apex 36.

[0067] 2, the length indicated by the symbol LCb is the length of the carcass line 54 from the position BW to the position BA. In the present disclosure, this length LCb is the length of the carcass 12 from the position BW corresponding to the axially outer end PW of the tire 2 to the position BA corresponding to the outer end of the apex 36.

[0068] As described above, the tire 2 is a low aspect tire having a nominal section height of 110 mm or less. The side portions of a low aspect tire are shorter than the side portions of a high aspect tire. Due to environmental considerations, an increasing number of vehicles are using motors as their drive means. These vehicles are equipped with batteries. These vehicles are heavier than vehicles that use engines as their drive means. Tires are subject to greater impact when going over bumps. Even if the carcass is made up of two carcass plies, as in tire 2, there is a risk that the carcass cords will break due to the impact when going over a bump.

[0069] In the tire 2, the ratio (WS / WA) of the width WS of the outer layer 48 to the cross-sectional width WA is 80% or less. In conventional tires, this ratio (WS / WA) exceeds 80%. The outer layer 48 of this tire 2 is narrower than that of conventional tires. The edge portions (hereinafter referred to as shoulder portions) of the tread 4 of this tire 2 are softer than those of conventional tires. These shoulder portions contribute to absorbing shock when going over bumps.

[0070] In this tire 2, the end of the outer layer 48 is located axially more inward than that of the conventional tire. The length LCa of the carcass 12 from the position BW corresponding to the axially outer end PW of the tire 2 to the position BS corresponding to the end of the outer layer 48 is longer than that of the conventional tire. In particular, in this tire 2, the ratio (LCa / SH) of the length LCa of the carcass 12 from the position BW corresponding to the axially outer end PW to the position BS corresponding to the end of the outer layer 48 to the cross-sectional height SH is 50% or more. In this tire 2, when the tire 2 receives a large impact when passing over a bump, the end portion of the belt 14 in the tread portion that comes into contact with the bead portion is more likely to move than in a conventional tire. The shear force acting on the carcass 12 is weakened. In this tire 2, even though the side portions are short, the occurrence of carcass cord breakage due to the impact when passing over a bump is suppressed. In this tire 2, pinch cut resistance performance is improved. From this viewpoint, it is preferable that this ratio (LCa / SH) is 53% or more.

[0071] If the end of the outer layer 48 is positioned closer to the equatorial plane, there is a concern that the end portion of the belt 14 may protrude radially outward, which may change the ground contact shape and reduce the uneven wear resistance of the tire 2.

[0072] In tire 2, the ratio (LCa / SH) is equal to or less than 60%. In tire 2, the end of the outer layer 48 is disposed at an appropriate position with respect to the equatorial plane. In tire 2, good uneven wear resistance is maintained. From this viewpoint, it is preferable that the ratio (LCa / SH) is equal to or less than 57%.

[0073] In this tire 2, improved pinch cut resistance is achieved while suppressing the effect on uneven wear resistance. In this tire 2, improved pinch cut resistance can be achieved while maintaining good uneven wear resistance.

[0074] In this tire 2, it is preferable that the ratio (LSb / SH) of the length LSb of the carcass 12 from the position BW corresponding to its axial outer end PW to the position BA corresponding to the outer end of the apex 36 to the cross-sectional height SH of the tire 2 is 18% or more and 23% or less.

[0075] By setting the ratio (LSb / SH) to 18% or more, the portion of the tire 2 from the maximum width position PW to the outer end of the apex 36 can contribute to reducing the shear force applied to the carcass 12 when passing over a step. In this tire 2, even though the side portions are short, the occurrence of carcass cord breakage due to impact when passing over a step is suppressed. From this viewpoint, the ratio (LSb / SH) is more preferably 19% or more. By setting the ratio (LSb / SH) to 23% or less, a decrease in the rigidity of the bead portion is suppressed. The tire 2 is excellent in limit running performance. From this viewpoint, the ratio (LSb / SH) is more preferably 22% or less.

[0076] Figure 3 shows a portion of the contour of the outer surface of the tire 2 in a meridian cross section of the tire 2 shown in Figure 1. This contour is obtained by mounting the tire 2 on the rim R, adjusting the internal pressure of the tire 2 to a predetermined pressure, and measuring the outer surface shape of the tire 2 with a displacement sensor in a state where no load is applied to the tire 2. The contour of the outer surface of the tire 2 is formed by connecting multiple contour lines consisting of straight lines or arcs, assuming that the measured outer surface shape does not include grooves 24, decorations, etc. In this disclosure, a contour line consisting of straight lines or arcs is simply referred to as a contour line. A contour line consisting of straight lines is referred to as a straight contour line, and a contour line consisting of arcs is referred to as a curved contour line. The radius of a curved contour line represents the radius of curvature of the outer surface in the corresponding area.

[0077] The contour of the outer surface shown in FIG. 3 includes the contour of the tread surface 22. The contour of the tread surface 22 includes a plurality of curved contour lines having different radii. Of the plurality of curved contour lines included in the contour of the tread surface 22, the curved contour line having the smallest radius is located at the end portion of the tread surface 22 and connects to the side surface 60. In this tire 2, of the plurality of curved contour lines included in the contour of the tread surface 22, the curved contour line consisting of an arc having the smallest radius and connecting to the side surface 60 is the shoulder contour line. In FIG. 3, the arrow indicated by the symbol Rh indicates the radius of this shoulder contour line. The region whose contour is represented by this shoulder contour line is also referred to as the shoulder region. The position indicated by the symbol TE is the boundary between the shoulder region and the side surface 60. In this tire 2, this boundary TE is the end of the tread surface 22.

[0078] In this tire 2, the contour of the tread surface 22, excluding the portion represented by the shoulder contour line, is divided into five regions arranged parallel to each other in the axial direction, specifically, a crown region Cr, a pair of middle regions Mi, and a pair of side regions Sd. The crown region Cr is located at the center in the axial direction. The crown region Cr includes an equator PC. Each middle region Mi is located outside the crown region Cr in the axial direction. Each side region Sd is located outside the middle region Mi in the axial direction.

[0079] In FIG. 3, the position indicated by the symbol CM is the boundary between the crown region Cr and the middle region Mi. The position indicated by the symbol MS is the boundary between the middle region Mi and the side region Sd. The symbol SE is the outer end of the side region Sd. The outer end SE is also the boundary with the aforementioned shoulder region.

[0080] As described above, the outline of the tread surface T includes a plurality of curved contours having different radii. The outline of each region is represented by a curved contour. In this tire 2, the curved contour representing the outline of the crown region Cr is the crown contour. The curved contour representing the outline of the middle region Mi is the middle contour. The curved contour representing the outline of the side region Sd is the side contour. The plurality of curved contours included in the outline of the tread surface 22 include a crown contour, a pair of middle contours, and a pair of side contours. The crown contour is the curved contour located in the center of the plurality of curved contours representing the outline of the tread surface 22.

[0081] Although not shown, the center of the crown contour is located on the equatorial plane. In FIG. 3, the arrow indicated by the symbol Rc is the radius of the crown contour. The middle contour is in contact with the crown contour at the boundary CM. In FIG. 3, the arrow indicated by the symbol Rm is the radius of the middle contour. The side contour is in contact with the middle contour at the boundary MS. In FIG. 3, the arrow indicated by the symbol Rs is the radius of the side contour.

[0082] In the present disclosure, among the arcs having a center on the equatorial plane and including the equator PC, the arc that has the longest overlap length with the contour of the tread surface 22 is identified as the crown contour line, and the end of this arc is identified as the boundary CM, and the radius of this arc is used as the radius Rc of the crown contour line. Among the arcs having a center on a line passing through the boundary CM and the center of the crown contour line, the arc that has the longest overlap length with the contour of the tread surface 22 is identified as the middle contour line, and the outer end of this arc is identified as the boundary MS, and the radius of this arc is used as the radius Rm of the middle contour line. Among the arcs having a center on a line passing through the boundary MS and the center of the middle contour line, the arc that passes through the boundary MS and the boundary SE is identified as the side contour line, and the radius of this arc is used as the radius Rs of the side contour line.

[0083] In this disclosure, the contours of the tread surface 22 are specified in both the reference state and the standard state. Of the radius Rc of the crown contour line, the radius Rm of the middle contour line, and the radius Rs of the side contour line in the reference state, the radius Rc of the crown contour line is used as the reference radius RR of this tire 2. The radius Rc of the crown contour line in the standard state is expressed as the standard radius SRc, the radius Rm of the middle contour line is expressed as the standard radius SRm, and the radius Rs of the side contour line is expressed as the standard radius SRs.

[0084] In this tire 2, it is preferable that the ratio (RR / ROD) of the radius Rc of the arc representing the outline of the crown region in the reference state, i.e., the reference radius RR, to the outer diameter OD of the tire 2 in the reference state, i.e., the reference outer diameter ROD, is 55% or more and 70% or less. By setting the ratio (RR / ROD) to 55% or more, the portion of the tire 2 from the maximum width position PW to the outer end of the apex 36 can contribute to reducing the shear force applied to the carcass 12 when passing over a step. In this tire 2, even though the side portions are short, the occurrence of carcass cord breakage due to impact when passing over a step is suppressed. From this viewpoint, the ratio (RR / ROD) is more preferably 60% or more. By setting the ratio (RR / ROD) to 70% or less, the contour of the tread surface 22 is configured with an appropriate shape. Since the contact shape can be stabilized, good resistance to uneven wear can be maintained in the tire 2. From this viewpoint, the ratio (RR / ROD) is more preferably 65% ​​or less.

[0085] In this tire 2, the ratio (SRm / SRc) of the radius Rm of the arc representing the outline of the middle region in the standard state, i.e., the standard radius SRm, to the radius Rc of the arc representing the outline of the crown region in the standard state, i.e., the standard radius SRc, is preferably 0.47 or greater and 0.57 or less. This allows the outline of the tread surface 22 to be configured with an appropriate shape. Since the contact shape is stabilized, this tire 2 maintains good resistance to uneven wear. From this viewpoint, this ratio (SRm / SRc) is more preferably 0.49 or greater, and even more preferably 0.51 or greater. This ratio (SRm / SRc) is more preferably 0.55 or less, and even more preferably 0.53 or less.

[0086] In this tire 2, the ratio (SRs / SRc) of the radius Rs of the arc representing the profile of the side region in a standard state, i.e., the standard radius SRs to the standard radius SRc, is preferably 0.17 or greater and 0.27 or less. This allows the profile of the tread surface 22 to be configured with an appropriate shape. Since the contact shape is stabilized, this tire 2 maintains good resistance to uneven wear. From this viewpoint, this ratio (SRs / SRc) is more preferably 0.19 or greater, and even more preferably 0.21 or greater. This ratio (SRs / SRc) is more preferably 0.25 or less, and even more preferably 0.23 or less.

[0087] In the tire 2, a ratio (SRc / SH) of the standard radius SRc to the section height SH of the tire 2 is preferably equal to or greater than 6.0 and is preferably equal to or less than 8.0. By setting the ratio (SRc / SH) to 6.0 or greater, the portion of the tire 2 from the maximum width position PW to the outer end of the apex 36 can contribute to reducing the shear force applied to the carcass 12 when passing over a bump. In this tire 2, even though the side portions are short, the occurrence of carcass cord breakage due to impact when passing over a bump is suppressed. From this perspective, it is more preferable that the ratio (SRc / SH) be 6.5 or greater. By setting the ratio (SRc / SH) to 8.0 or less, the contour of the tread surface 22 is configured with an appropriate shape. Since the contact shape can be stabilized, good resistance to uneven wear can be maintained in the tire 2. From this viewpoint, the ratio (SRc / SH) is more preferably 7.5 or less.

[0088] In Fig. 1, the length indicated by the symbol TC is the thickness of the tread 4 at the equator PC of the tire 2. This thickness TC is measured along the equatorial plane. In Fig. 1, the solid line indicated by the symbol LTS is a normal line to the inner surface of the tire 2 that passes through the end of the outer layer 48. The length indicated by the symbol TC is the thickness of the tread 4 measured along this normal line LTS. In the present disclosure, this thickness TC is the thickness of the tread 4 at the end of the outer layer 48.

[0089] In this tire 2, the ratio (TS / TC) of the thickness TS of the tread 4 at the end of the outer layer 48 to the thickness TC of the tread 4 at the equator PC of the tire 2 is preferably 55% or more and 75% or less. This allows the contour of the tread surface 22 to be configured with an appropriate shape. Since the contact shape is stabilized, this tire 2 maintains good resistance to uneven wear. From this viewpoint, this ratio (TS / TC) is more preferably 58% or more, and even more preferably 61% or more. This ratio (TS / TC) is more preferably 72% or less, and even more preferably 69% or less.

[0090] In this tire 2, the grooves 24 constituting the tread pattern include circumferential grooves 62 that extend continuously in the circumferential direction. In this tire 2, a plurality of circumferential grooves 62 that are parallel to each other in the axial direction are cut into the tread 4. In the tire 2 shown in FIG. 1, three circumferential grooves 62 are cut into the tread 4. Of the three circumferential grooves 62, the circumferential groove 62 located on the outer side in the axial direction is the shoulder circumferential groove 62s. The circumferential groove 62 located axially inward of the shoulder circumferential groove 62s is the middle circumferential groove 62m.

[0091] In this tire 2, there are no particular limitations on the arrangement, groove depth, and groove width of the circumferential grooves 62 cut in the tread 4. The arrangement, groove depth, and groove width of the circumferential grooves 62 of the tire 2 are generally applicable to this tread 4.

[0092] In this tire 2, circumferential grooves 62 are formed in the tread 4, thereby forming a plurality of land portions 64 in the tread 4. As described above, four circumferential grooves 62 are formed in the tire 2 shown in FIG. 1 . This results in five land portions 64. Of these land portions 64, the land portion 64 located on the outer side in the axial direction is the shoulder land portion 64s. The land portion 64 located on the inner side in the axial direction of the shoulder land portion 64s is the middle land portion 64m. The land portion 64 located on the inner side in the axial direction of the middle land portion 64m is the center land portion 64c. In this tire 2, the center land portion 64c is the land portion 64 located in the center of the five land portions 64, and is located on the equatorial plane.

[0093] In this tire 2, a plurality of circumferentially aligned lateral grooves 66 are formed in the shoulder land portion 64s. These lateral grooves 66 are spaced apart in the circumferential direction. An inner end 66e of each lateral groove 66 is located within the shoulder land portion 64s. The lateral grooves 66 extend from the inner end 66e toward the edge TE of the tread surface 22.

[0094] The lateral grooves 66 reduce the rigidity of the shoulder land portions 64s. As described above, in this tire 2, the ends of the outer layer 48 are positioned closer to the equatorial plane. In this tire 2, the ends of the belt 14 are prone to protruding radially outward. If the ends of the belt 14 protrude radially outward, there is a concern that the contact pressure will increase locally at the ends of the contact patch. In this case, there is a risk that the uneven wear resistance of the tire 2 will decrease.

[0095] As described above, the tire 2 is provided with an edge band 52 that covers the end of the full band 50. The edge band 52 includes a spirally wound band cord. Moreover, the inner end of the edge band 52 is located axially inside the inner end 66e of the lateral groove 66. The edge band 52 is disposed so as to overlap with the lateral groove 66 in the radial direction. In the tire 2, the edge band 52 effectively suppresses the end portions of the belt 14 from protruding radially outward. In the tire 2, the contact shape is stabilized, thereby maintaining good uneven wear resistance.

[0096] 1, the length indicated by the symbol DE is the axial distance from the inner end of the edge band 52 to the inner end 66e of the lateral groove 66. From the viewpoint of enabling the edge band 52 to effectively contribute to improving uneven wear resistance, the axial distance DE is preferably 3 mm or more and 7 mm or less.

[0097] As described above, the present invention provides a tire 2 that can achieve improved pinch-cut resistance while minimizing the impact on uneven wear resistance. In particular, the present invention is particularly effective for a tire 2 that has a nominal section height of 110 mm or less and a load index of 85 or greater and 105 or less. [Example]

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0099] [Example 1] A pneumatic tire for passenger cars (tire nominal size: 215 / 50R17 91V) was obtained having the basic configuration shown in Figure 1 and the specifications shown in Table 1. The specifications of Example 1 were based on the specifications of Comparative Example 2 described below, with the tread surface contour and the width of the outer layer being adjusted mainly.

[0100] In this Example 1, the nominal cross-sectional height is 108 mm. The ratio (WS / WA) of the axial width WS of the outer layer to the tire's section width WA was 76%. The ratio (LCa / SH) of the carcass length LCa from the position BW corresponding to the outer end PW to the position BS corresponding to the end of the outer layer to the tire's section height SH was 53%. The ratio (LCb / SH) of the carcass length LCb from the position BW corresponding to the outer end PW to the position BA corresponding to the outer end of the apex to the tire's section height SH was 21%. The ratio (RR / ROD) of the reference radius RR to the reference outer diameter ROD was 62%. The ratio (TS / TC) of the tread thickness TS at the end of the outer layer to the tread thickness TC at the tire's equator PC was 63%. The ratio (HA / SH) of the apex height HA to the tire cross-sectional height SH was 32%. The inner end of the edge band was located axially inside the inner end of the lateral groove, and the axial distance DE from the inner end of the edge band to the inner end of the lateral groove was 4 mm. The ratio (SRc / SH) of the standard radius SRc to the section height SH of tire 2 was 7.1.

[0101] [Comparative Example 1] Comparative Example 1 is a conventional tire (tire nominal size: 215 / 55R17 94V). The specifications of Comparative Example 1 are as shown in Table 1 below. The tread thickness TC at the equator is the same as that of Example 1. The inner end of the edge band was located axially outward of the inner end of the lateral groove, and the axial distance DE between the inner end of the edge band and the inner end of the lateral groove was 13 mm. The ratio (SRc / SH) of the standard radius SRc to the section height SH of tire 2 was 7.4.

[0102] Comparative Example 2 A tire of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the tire nominal size was set to "215 / 50R17 91V" and the cross-sectional height SH was changed. The inner end of the edge band was located axially outward of the inner end of the lateral groove, and the axial distance DE between the inner end of the edge band and the inner end of the lateral groove was 13 mm. The ratio (SRc / SH) of the standard radius SRc to the section height SH of tire 2 was 8.1.

[0103] [Pinch cut resistance] The prototype tire was mounted on a rim (17 x 7.0J) and inflated to an internal pressure of 230 kPa. This tire was mounted on a test vehicle (a domestically produced FR automobile with a 2500 cc engine displacement). One driver was in the test vehicle. A 200 mm high protrusion was placed on the road surface of the test course, and the test vehicle was driven over the protrusion with its front wheel. The tire was visually inspected to determine whether pinch cut damage had occurred. The vehicle speed was started at 40 km / h and increased in steps of 0.5 km / h, and the speed at which tire damage occurred was measured. The results are shown in Table 1 below, where Comparative Example 1 is indexed to 100. The higher the index, the better the pinch cut resistance.

[0104] [Resistant to uneven wear] The prototype tire was mounted on a rim (17 x 7.0J) and inflated to an internal pressure of 240 kPa. This tire was then mounted on a wear energy measuring device. The camber angle was set to 0° and the slip angle to 0°, and the tire's wear energy was measured. The ratio (Ec / Es) was calculated as an index of uneven wear resistance from the wear energy Ec of the rear side of the center land portion and the wear energy Es of the rear side of the shoulder land portion. The results are shown in Table 1 below, where Comparative Example 1 is set to an index of 100. The higher the value, the better the uneven wear resistance.

[0105] [Table 1]

[0106] As shown in Table 1, in the examples, improvement in pinch cut resistance was achieved while minimizing the effect on uneven wear resistance. From these evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0107] The above-described techniques for achieving improved pinch-cut resistance can be applied to various types of tires. [Explanation of symbols]

[0108] 2. Tires 4. Tread 6. Sidewall 10 Bead 12. Carcass 14. Belt 16...Band 22 Tread surface 34 cores 36 Apex 40 First carcass ply 42 Second casing 40a···First ply body 40b First folded part 42 Second carcass ply 42a Second ply body 42b Second folded part 46...inner layer 48...outer layer 50...Full Band 52 Edge band 54···Carcass line 60···Side surface 62, 62s, 64m...Circumferential groove 64, 64s, 64m, 64c...Land 66 Yokomizo 66e···Inner end of horizontal groove 66

Claims

1. A tire having a nominal section height of 110 mm or less, a tread having a tread surface; a pair of sidewalls connected to the ends of the tread and positioned radially inward of the tread; a pair of beads located radially inside the sidewall; a carcass located inside the tread and the pair of sidewalls and spanning between a first bead and a second bead of the pair of beads; a belt laminated on the carcass on the inside of the tread; a band positioned between the tread and the belt; Equipped with The bead includes a core and an apex located radially outward of the core, The belt includes an inner layer and an outer layer positioned radially outward of the inner layer, an end of the outer layer located axially inward of an end of the inner layer; a ratio of the axial width of the outer layer to the section width of the tire is 80% or less; a ratio of a length of the carcass from a position corresponding to an axially outer end of the tire to a position corresponding to an end of the outer layer to a section height of the tire is 50% or more and 60% or less, a ratio of the tread thickness at the end of the outer layer to the tread thickness at the equator of the tire is 55% or more and 75% or less; tire.

2. a ratio of a length of the carcass from a position corresponding to an outer end of the tire in the axial direction to a position corresponding to an outer end of the apex to a section height of the tire is 18% or more and 23% or less; 2. The tire of claim 1.

3. In a meridian cross section of the tire, a region of the tread surface that includes an equator of the tire is a crown region, the outer diameter of the tire when the tire is mounted on a regular rim and the internal pressure of the tire is adjusted to 230 kPa is a reference outer diameter, and the radius of the arc representing the outline of the crown region is a reference radius; a ratio of the reference radius to the reference outer diameter of the 3. The tire according to claim 1 or 2.

4. A plurality of land portions arranged in parallel in the axial direction are formed by forming circumferential grooves in the tread, Among the plurality of land portions, a land portion located on an outer side in the axial direction is a shoulder land portion, A plurality of lateral grooves are formed in the shoulder land portion and aligned in the circumferential direction, an inner end of each of the plurality of lateral grooves is located within the shoulder land portion, and the lateral grooves extend from the inner end toward an edge of the tread surface; The band includes a full band that covers the belt, and a pair of edge bands that are spaced apart in the axial direction and cover the ends of the full band, The inner end of the edge band is located axially inside the inner end of the lateral groove. A tire according to any one of claims 1 to 3.

5. A tire having a nominal section height of 110 mm or less, a tread having a tread surface; a pair of sidewalls connected to the ends of the tread and positioned radially inward of the tread; a pair of beads located radially inside the sidewall; a carcass located inside the tread and the pair of sidewalls and spanning between a first bead and a second bead of the pair of beads; a belt laminated on the carcass on the inside of the tread; a band positioned between the tread and the belt; Equipped with The bead includes a core and an apex located radially outward of the core, The belt includes an inner layer and an outer layer positioned radially outward of the inner layer, an end of the outer layer located axially inward of an end of the inner layer; a ratio of the axial width of the outer layer to the section width of the tire is 80% or less; a ratio of a length of the carcass from a position corresponding to an axially outer end of the tire to a position corresponding to an end of the outer layer to a section height of the tire is 50% or more and 60% or less, In a meridian cross section of the tire, a region of the tread surface that includes an equator of the tire is a crown region, the outer diameter of the tire when the tire is mounted on a regular rim and the internal pressure of the tire is adjusted to 230 kPa is a reference outer diameter, and the radius of the arc representing the outline of the crown region is a reference radius; a ratio of the reference radius to the reference outer diameter of the tire.

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