tire

Abstract

We offer Tire 2, which combines quietness with high-speed durability. [Solution] The tire 2 comprises a tire body 4 and a sound dampening element 6. The tire body 4 comprises a tread 8. The sound dampening element 6 is bonded to the inner surface of the tire body 4. The outer surface of the tread 8 comprises a crown portion 60, a pair of middle portions 62, and a pair of shoulder portions 64. The axial outer end PC of the bonding surface between the sound dampening element 6 and the tire body 4 is located axially inward of the boundary MS between the middle portion 62 and the shoulder portion 64. The axial distance from the equatorial plane to the axial outer end PC of the bonding surface is 90% or more of the axial distance from the equatorial plane to the boundary between the crown portion 60 and the middle portion 62. The radius TR1 of the arc representing the contour of the crown portion 60 is 1000 mm or more.

Description

Technical Field

[0001] The present invention relates to a tire. Specifically, the present invention relates to a tire mounted on a passenger car.

Background Art

[0002] There is road noise as a noise generated when the tire runs. Cavity resonance, that is, resonance vibration of air generated inside the tire is one of the factors causing road noise. A sound-absorbing body made of a sponge material is known as an item that can contribute to reducing road noise. The sound-absorbing body is provided inside the tire.

[0003] Long-time high-speed driving raises the internal temperature of the tire. The sound-absorbing body is a heat storage body. The temperature of the portion where the sound-absorbing body is joined tends to be higher than other portions. Providing the sound-absorbing body in the tire affects the high-speed durability of the tire.

[0004] Therefore, studies have been conducted aiming at establishing a technique capable of suppressing heat storage of the sound-absorbing body. For example, Patent Document 1 below proposes providing a heat radiation recess in the sound-absorbing body in order to suppress heat storage of the sound-absorbing body.

Prior Art Document

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a tire capable of achieving both quietness and high-speed durability.

Means for Solving the Problems

[0007] The tire according to the present invention is a HIGH LOAD CAPACITY type tire as defined in the ETRTO 2021 standard manual. The tire comprises a tire body and a sound-dampening body made of sponge material. The tire body comprises a tread that contacts the road surface and a belt located radially inward of the tread and including a number of parallel belt cords. The sound-dampening body is bonded to the inner surface of the tire body radially inward of the tread. The outer surface of the tread comprises a crown portion located in the axial center, a pair of middle portions located axially outward of the crown portion, and a pair of shoulder portions located axially outward of the middle portions. The axial distance from the equatorial plane of the tire to the boundary between the crown portion and the middle portion is 30% to 40% of the axial distance from the equatorial plane to the axial outer end of the tire. The axial distance from the equatorial plane to the boundary between the middle portion and the shoulder portion is 55% to 65% of the axial distance from the equatorial plane to the axial outer end of the tire. The axial outer end of the joint surface between the sound dampener and the tire body is located axially inward from the boundary between the middle section and the shoulder section. The axial distance from the equatorial plane to the axial outer end of the joint surface is 90% or more of the axial distance from the equatorial plane to the boundary between the crown section and the middle section. In the meridional cross-section of the tire, the contour of the crown section is represented by an arc centered on the equatorial plane, the contour of each middle section is represented by an arc tangent to the arc representing the contour of the crown section, and the contour of each shoulder section is represented by an arc tangent to the arc representing the contour of the middle section. The radius TR1 of the arc representing the contour of the crown section is greater than the radius TR2 of the arc representing the contour of the middle section. The radius TR2 of the arc representing the contour of the middle section is greater than the radius TR3 of the arc representing the contour of the shoulder section. The radius TR1 of the arc representing the contour of the crown section is 1000 mm or more. [Effects of the Invention]

[0008] According to the present invention, a tire can be obtained that achieves both quietness and high-speed durability. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a part of a tire relating to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing a portion of the cross-section in Figure 1. [Figure 3] This is a cross-sectional view illustrating the outline of the outer surface of the tread. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below, with reference to drawings as appropriate, based on preferred embodiments.

[0011] The tire of this invention is mounted on a rim. Air is filled inside the tire, and the internal pressure of the tire is regulated. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly comprises a rim and a tire mounted on this rim.

[0012] In this invention, the state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, and no load is applied to the tire is called the standard state.

[0013] In this invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured under normal conditions. The dimensions and angles of each part of the tire in the meridional cross-section, which cannot be measured when the tire is mounted on a standard rim, are measured at the tire's cross-section, obtained by cutting the tire along a plane containing the axis of rotation. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads in a tire mounted on a standard rim. The tire's structure, which cannot be confirmed when the tire is mounted on a standard rim, is confirmed at the aforementioned cross-section.

[0014] A genuine rim refers to a rim defined 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 considered genuine rims.

[0015] Regular tire pressure refers to the internal pressure specified in the tire's standard. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are all considered regular tire pressures.

[0016] The standard load refers to the load specified in the tire's specifications. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are all considered standard loads.

[0017] In this invention, unless otherwise specified, the load index (LI) is the load index for HIGH LOAD CAPACITY type tires (hereinafter referred to as HLC type tires) as defined in the ETRTO 2021 standard manual, and is an index that expresses the maximum mass that can be loaded onto the tire under specified conditions, i.e., the maximum load capacity, as an index.

[0018] In the present invention, crosslinked rubber is a crosslinked product of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is a material obtained by mixing rubber components with chemicals such as fillers in a kneading machine such as a Banbury mixer.

[0019] Examples of the rubber component include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), ethylene-propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and butyl rubber (IIR). Examples of the chemicals include reinforcing agents such as carbon black and silica, plasticizers such as aromatic oil, fillers such as zinc oxide, lubricants such as stearic acid, anti-aging agents, processing aids, sulfur, and vulcanization accelerators. The selection of the rubber component and chemicals, the content of the selected chemicals, etc. are appropriately determined according to the specifications of elements such as the tread, sidewall, etc. to which the rubber composition is applied.

[0020] In the present invention, among the elements constituting the tire, the loss tangent (tanδ) of the element made of crosslinked rubber is measured using a viscoelastic spectrometer in accordance with the provisions of JIS K6394. The measurement conditions are as follows. Initial strain = 10% Dynamic strain = ±1% Frequency = 10 Hz Mode = elongation mode Temperature = 30°C In this measurement, the test piece (length 40 mm × width 4 mm × thickness 1 mm) is sampled from the tire. The length direction of the test piece is made to coincide with the circumferential direction of the tire. When the test piece cannot be sampled from the tire, the test piece is sampled from a sheet-like crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressurizing and heating the rubber composition used for forming the element to be measured at a temperature of 170°C for 12 minutes. In the present invention, the loss tangent (tanδ) is represented by the loss tangent at 30°C.

[0021] In the present invention, the tread portion of the tire is the portion of the tire that contacts the road surface. The bead portion is the portion of the tire that is fitted to the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. The tire includes, as parts, a tread portion, a pair of bead portions, and a pair of sidewall portions.

[0022] [Practices that formed the basis of this invention] Due to environmental concerns, electric vehicles are becoming increasingly popular. Electric vehicles are equipped with batteries. Batteries that allow a vehicle to travel a distance of around 500 km are heavy. Electric vehicles tend to be heavier than conventional gasoline-powered vehicles. Therefore, the tires fitted to electric vehicles are subjected to a higher load than the tires fitted to gasoline-powered vehicles. In order to provide tires that can support high loads, the ETRTO standard has revised its load index, and the HIGH LOAD CAPACITY type (hereinafter referred to as HLC type) tire has been introduced as a new category. To qualify as an HLC-type tire, it must be able to support a higher load than conventional tires.

[0023] As the load acting on a tire increases, the deformation of the tire also increases. Since deformation promotes heat generation, the internal temperature of tires subjected to high loads, such as HLC type tires, is expected to rise even further. As mentioned earlier, sound-dampening materials, which are used to reduce road noise, are heat-storing materials. If sound-dampening materials are placed inside HLC-type tires, the temperature at the point where the sound-dampening materials are attached may rise excessively, potentially compromising the tire's high-speed durability.

[0024] Therefore, in order to achieve both quietness and high-speed durability, the inventors diligently studied technologies that can suppress heat generation in the tread section where the sound-dampening material is provided, and have completed the invention described below.

[0025] [Summary of Embodiments of the Invention] The present invention relates to a HIGH LOAD CAPACITY type tire as defined in the ETRTO 2021 standard manual, comprising a tire body and a sound-dampening body made of sponge material, wherein the tire body comprises a tread that contacts the road surface and a belt located radially inward of the tread and including a number of parallel belt cords, the sound-dampening body is bonded to the inner surface of the tire body radially inward of the tread, the outer surface of the tread comprises a crown portion located in the axial center, a pair of middle portions located axially outward of the crown portion, and a pair of shoulder portions located axially outward of the middle portions, the axial distance from the equatorial plane of the tire to the boundary between the crown portion and the middle portion being 30% or more and 40% or less of the axial distance from the equatorial plane to the axial outer end of the tire, the axial distance from the equatorial plane to the boundary between the middle portion and the shoulder portion being 55% or more and 65% or less of the axial distance from the equatorial plane to the axial outer end of the tire, and the sound-dampening body The axial outer end of the joint surface between the tire and the tire body is located axially inward of the boundary between the middle portion and the shoulder portion, the axial distance from the equatorial plane to the axial outer end of the joint surface is 90% or more of the axial distance from the equatorial plane to the boundary between the crown portion and the middle portion, in the meridional cross-section of the tire, the contour of the crown portion is represented by an arc centered on the equatorial plane, the contour of each middle portion is represented by an arc tangent to the arc representing the contour of the crown portion, the contour of each shoulder portion is represented by an arc tangent to the arc representing the contour of the middle portion, the radius TR1 of the arc representing the contour of the crown portion is greater than the radius TR2 of the arc representing the contour of the middle portion, the radius TR2 of the arc representing the contour of the middle portion is greater than the radius TR3 of the arc representing the contour of the shoulder portion, and the radius TR1 of the arc representing the contour of the crown portion is 1000 mm or more.

[0026] The tire of the present invention achieves both quietness and high-speed durability. Although the mechanism by which these effects are achieved has not been fully elucidated, it is presumed to be as follows.

[0027] HLC-type tires are used under heavy loads. Compared to tires used under normal loads, the input to the tire through the tread is greater. There is a concern that this will increase cavity resonance within the tire and increase road noise. However, this tire is equipped with a sound-dampening material made of sponge. The sound-dampening material suppresses cavity resonance, thus suppressing the increase in road noise. This tire can maintain good quietness. As mentioned earlier, if a sound-dampening material is placed inside an HLC-type tire, the temperature at the point where the sound-dampening material is attached may rise excessively, potentially impairing the tire's high-speed durability. However, in this tire, the contour of the crown is represented by a circular arc with a radius of 1000 mm or more. The crown is composed of a flat surface. This tire can reduce the contact pressure at the crown. Since mechanical fatigue of the tread is reduced, this tire can maintain good high-speed durability. Furthermore, in this tire, the axial outer end position of the joint surface between the sound-dampening material and the tire body is set considering the boundary position between the crown and middle sections. As a result, the sound-dampening material can effectively reduce road noise and suppress localized temperature increases. This tire can maintain good quietness while suppressing a decrease in high-speed durability. In this tire, the axial outer end of the joint surface between the sound-dampening element and the tire body is positioned axially inward at the boundary between the middle section and the shoulder section. This tire can suppress the sound-dampening element from exacerbating the heat generation in the shoulder section, which is prone to overheating. This tire can maintain good high-speed durability. This tire effectively reduces road noise while minimizing the decrease in high-speed durability caused by the inclusion of a sound-dampening material. This tire achieves a balance between quietness and high-speed durability.

[0028] Preferably, the ratio TR2 / TR1 of the radius TR2 of the arc representing the contour of the middle section to the radius TR1 of the arc representing the contour of the crown section is 0.45 or more and 0.55 or less. This allows the outer surface of the tread to effectively contribute to reducing the contact pressure at the crown section. Since the mechanical fatigue of the tread is effectively reduced, this tire can maintain good high-speed durability.

[0029] More preferably, the ratio TR3 / TR1 of the radius TR3 of the arc representing the contour of the shoulder portion to the radius TR1 of the arc representing the contour of the crown portion is 0.05 or more and 0.15 or less. This allows the outer surface of the tread to more effectively contribute to reducing the contact pressure at the crown portion. Since the mechanical fatigue of the tread is more effectively reduced, this tire can maintain good high-speed durability.

[0030] Preferably, the tread comprises a cap layer, an intermediate layer located radially inward of the cap layer, and a base layer located radially inward of the intermediate layer, wherein the loss tangent of the intermediate layer at 30°C is lower than that of the cap layer at 30°C and higher than that of the base layer at 30°C. This effectively suppresses heat generation in the tread. This tire can maintain good high-speed durability.

[0031] Preferably, the tire further comprises a band positioned radially between the tread and the belt, the band including a band cord that extends substantially circumferentially. This allows the band to restrain the belt. Since belt vibration is suppressed, heat generation in the tread is effectively suppressed. The tire can maintain good high-speed durability.

[0032] Thus, the tire of the present invention can achieve both quietness and high-speed durability. This will be explained in detail below using the tire shown in Figure 1 as an example.

[0033] [Details of the Embodiments of the Invention]

[0034] Figure 1 shows a part of a tire 2 according to one embodiment of the present invention. This tire 2 is a pneumatic tire for passenger cars. This tire 2 is a HIGH LOAD CAPACITY type tire as defined in the ETRTO 2021 standard manual. The tire 2 shown in Figure 1 is mounted on a rim R (regular rim).

[0035] Figure 1 shows a portion of the cross-section of tire 2 along a plane containing the axis of rotation of tire 2 (not shown). The cross-section shown in Figure 1 is also called a meridian cross-section. The direction indicated by the double arrow AD is the axial direction of tire 2. The axial direction of tire 2 means the direction parallel to the rotation axis of tire 2. The direction indicated by the double arrow RD is the radial direction of tire 2. The direction perpendicular to the plane of paper in Figure 1 is the circumferential direction of tire 2. The dashed line EL extending radially represents the equatorial plane of tire 2. Figure 2 shows a part of the cross-section shown in Figure 1. Figure 2 shows the tread portion T of tire 2.

[0036] In the axial direction, the direction away from the equatorial plane is the axial outward direction of tire 2, and the direction towards the equatorial plane is the axial inward direction of tire 2. The direction indicated by arrow RD1 is the radial outward direction of tire 2, and the direction indicated by arrow RD2 is the radial inward direction of tire 2.

[0037] In Figure 1, the position indicated by the symbol Eq is the intersection of the outer surface 2G of tire 2 (specifically, the tread surface, which will be described later) and the equatorial plane. Intersection point Eq is the equator of tire 2. If the groove is located on the equatorial plane, the equatorial Eq is determined based on the virtual outer surface obtained by assuming the absence of the groove. The equatorial Eq is the radial outer end of tire 2.

[0038] In Figure 1, the position indicated by the symbol PW is the axial outer end of tire 2 (hereinafter referred to as outer end PW). If there are decorations such as patterns or letters on the outer surface 2G, outer end PW is identified based on a virtual outer surface (the dashed line LV in Figure 1) obtained by assuming there are no decorations. In Figure 2, the length indicated by the double arrow WA is the axial distance from the equatorial plane to the axial outer end PW of tire 2. Twice this axial distance WA is the cross-sectional width of tire 2 (see JATMA, etc.). The cross-sectional width of tire 2 is also the maximum width of tire 2. The axial outer end PW is also called the maximum width position PW.

[0039] This tire 2 comprises a tire body 4 and a sound dampening element 6. Although not described in detail, the tire body 4 is obtained by vulcanizing the rubber composition of a green tire in a mold. This tire 2 is obtained by bonding the sound dampening element 6 to the inner surface 4N of the tire body 4. The outer surface 4G of the tire body 4 coincides with the outer surface 2G of the tire 2.

[0040] The tire body 4 comprises a tread 8, a pair of sidewalls 10, a pair of clinchers 12, a pair of beads 14, a carcass 16, a belt 18, a band 20, a pair of chafers 22, and an inner liner 24.

[0041] The tread 8 is located radially outward of the carcass 16. The tread 8 is made of cross-linked rubber. The tread 8 contacts the road surface at its tread surface 26. The tread 8 has a tread surface 26 that contacts the road surface. The outer surface 2G of the tire 2 includes the tread surface 26. Tread 8 has 28 grooves cut into it. This forms the tread pattern.

[0042] The tread 8 has a tread body 30 and a pair of wings 32. The tread body 30 is made of cross-linked rubber. The tread body 30 is the main component that comes into contact with the road surface. Each wing 32 is positioned between the tread body 30 and the sidewall 10. The tread body 30 and the sidewall 10 are joined via the wings 32. The wings 32 are made of cross-linked rubber with adhesive properties in mind.

[0043] Each sidewall 10 is connected to the tread 8. The sidewalls 10 are located on the axially outer side of the carcass 16. The sidewalls 10 are made of cross-linked rubber designed for cut resistance.

[0044] Each clinch 12 is located radially inward of the sidewall 10. The clinch 12 is in contact with the rim R. The clinch 12 is made of cross-linked rubber with wear resistance in mind.

[0045] Each bead 14 is located radially inward of the sidewall 10. The bead 14 is located axially inward of the clinch 12. The bead 14 comprises a core 38 and an apex 40. The core 38 extends circumferentially. Although not shown, the core 38 contains steel wires. The apex 40 is located radially outward of the core 38. The apex 40 is made of cross-linked rubber with high rigidity. The apex 40 tapers radially outward. The position indicated by the symbol PA is the outer end of the apex 40. The outer end PA of the apex 40 is located radially inward of the axial outer end PW of the tire 2. The outer end PA of the apex 40 is also the outer end of the bead 14.

[0046] The carcass 16 is located inside the tread 8, a pair of sidewalls 10, and a pair of clinches 12. The carcass 16 spans between a pair of beads 14.

[0047] The carcass 16 comprises at least one carcass ply 42. The carcass 16 of this tire 2 is composed of two carcass plies 42. Of the two carcass plies 42, the carcass ply 42 located on the inner side of the radially inner side of the tread 8 is the first carcass ply 44, and the carcass ply 42 located on the outer side is the second carcass ply 46.

[0048] The first carcass ply 44 is folded back axially from the inside to the outside at each bead 14. The first carcass ply 44 comprises a first ply body 44a and a pair of first folded portions 44b. The first ply body 44a spans between the pair of beads 14. Each first folded portion 44b is connected to the first ply body 44a and is folded back at each bead 14. The ends of the first folded portions 44b are located radially outward from the axial outer end PW of the tire 2.

[0049] The second carcass ply 46 is folded back axially from the inside to the outside at each bead 14. The second carcass ply 46 comprises a second ply body 46a and a pair of second folded portions 46b. The second ply body 46a spans between the pair of beads 14. Each second folded portion 46b is connected to the second ply body 46a and folded back at each bead 14. The ends of the second folded portions 46b are located radially inside the outer end PA of the apex 40. The ends of the second folded portions 46b are covered by the first folded portions 44b.

[0050] Although not shown in the diagram, the carcass ply 42 constituting the carcass 16 contains numerous parallel carcass cords. The carcass cords intersect with the equatorial plane. The carcass 16 of this tire 2 has a radial structure. The carcass cords are cords made of organic fibers (hereinafter referred to as organic fiber cords). Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0051] The belt 18 is located radially inward of the tread 8. The belt 18 is located radially outward of the carcass 16. In this tire 2, the belt 18 is laminated to the carcass 16 radially inward of the tread 8.

[0052] The belt 18 comprises a plurality of belt plies 48 arranged radially. The plurality of belt plies 48 include an inner belt ply 50 located on the innermost side and an outer belt ply 52 located on the outermost side. The belt 18 of this tire 2 consists of two belt plies 48, specifically an inner belt ply 50 and an outer belt ply 52. The inner belt ply 50 is laminated to the carcass 16 on the radially inner side of the tread 8. The outer belt ply 52 is laminated to the inner belt ply 50. The end of the outer belt ply 52 is located axially inward of the end of the inner belt ply 50. The outer belt ply 52 is narrower than the inner belt ply 50. The end of the inner belt ply 50 is the end of the belt 18.

[0053] Although not shown in the diagram, the belt plies 48 constituting the belt 18 contain numerous parallel belt cords. Each belt cord is inclined with respect to the equatorial plane. The direction of inclination of the belt cords contained in the outer belt plies 52 is opposite to the direction of inclination of the belt cords contained in the inner belt plies 50. The belt cords are made of steel cord.

[0054] Band 20 is laminated on the belt 18 inside the tread 8. Band 20 is located radially between the tread 8 and the belt 18. The ends of band 20 are located axially outward from the ends of the belt 18. Band 20 covers the belt 18.

[0055] Although not shown in the figures, band 20 includes a helically wound band cord. In band 20, the band cord extends substantially circumferentially. Specifically, the angle that the band cord makes with respect to the circumferential direction is 5° or less. Band 20 has a jointless structure.

[0056] Each chafer 22 is located radially inward of the bead 14. The chafer 22 is in contact with the rim R. The chafer 22 of this tire 2 consists of cloth and rubber impregnated into this cloth.

[0057] The inner liner 24 is located inside the carcass 16. The inner liner 24 constitutes the inner surface 4N of the tire body 4. The inner liner 24 is made of cross-linked rubber with excellent air shielding properties. The inner liner 24 maintains the internal pressure of the tire 2.

[0058] The sound dampening element 6 is bonded to the inner surface 4N of the tire body 4 on the radially inner side of the tread 8. In Figure 2, the position indicated by the symbol PC is the axial outer end of the bonding surface between the sound dampening element 6 and the tire body 4. The length indicated by the double arrow WS is the axial distance from the equatorial plane to the axial outer end PC of the bonding surface between the sound dampening element 6 and the tire body 4. The length indicated by the double arrow TS is the thickness of the sound dampening element 6. The thickness TS of the sound dampening element 6 is measured along the equatorial plane.

[0059] The sound dampening body 6 is made of sponge material. The sponge material is a porous structure resembling a sea sponge. Examples of sponge materials include so-called sponges themselves, which have open cells formed by foaming rubber or synthetic resin, as well as web-like structures made by intertwining and linking animal fibers, plant fibers, or synthetic fibers. The term "porous structure" includes not only those with open cells but also those with closed cells. The sound dampening body 6 of this tire 2 is made of an open-cell sponge material made of foamed polyurethane.

[0060] This tire 2 can suitably use synthetic resin sponges such as ether-based polyurethane sponge, ester-based polyurethane sponge, and polyethylene sponge, as well as rubber sponges such as chloroprene rubber sponge (CR sponge), ethylene propylene rubber sponge (EDPM sponge), and acrylonitrile butadiene rubber sponge (NBR sponge) as the sponge material. From the viewpoint of sound dampening, lightness, controllability of foaming, and durability, polyurethane-based sponges including ether-based polyurethane sponge or polyethylene sponge are preferred.

[0061] Figure 3 shows a portion of the contour line of the outer surface 2G of tire 2 in a meridian cross-section. The contour line of the outer surface 2G is represented by a virtual outer surface obtained by assuming that there are no grooves, patterns, letters, or other decorations. Although not described in detail here, in this invention the contour line of the outer surface 2G is obtained, for example, by measuring the outer surface shape of tire 2 in a normal state using a displacement sensor.

[0062] The outer surface 2G of this tire 2 comprises a tread surface 26 and a pair of side surfaces 58 connected to the tread surface 26. The tread surface 26 is divided into seven parts arranged in the axial direction. The seven parts of the tread surface 26 consist of a crown portion 60, a pair of middle portions 62, a pair of shoulder portions 64, and a pair of corner portions 66.

[0063] The crown portion 60 is located in the axial center. The pair of middle portions 62 are each located axially outside the crown portion 60. The position indicated by the symbol CM is the boundary between the crown portion 60 and the middle portion 62. The pair of shoulder portions 64 are each located axially outside the middle portion 62. The position indicated by the symbol MS is the boundary between the middle portion 62 and the shoulder portion 64. The pair of corner portions 66 are each located axially outside the shoulder portion 64. The position indicated by the symbol SC is the boundary between the shoulder portion 64 and the corner portion 66. The crown portion 60 is the part located in the axial center. The corner portion 66 is the part located on the outermost side in the axial direction. The middle portion 62 and the shoulder portion 64 are the parts located between the crown portion 60 and the corner portion 66.

[0064] As mentioned above, the corner section 66 is the outermost part in the axial direction. The corner section 66 connects to the side surface 58. The position indicated by the symbol CS is the boundary between the corner section 66 and the side surface 58. The boundary CS is also the edge of the tread surface 26. In Figure 3, the position indicated by the symbol BD is the boundary between the tread 8 and the sidewall 10 on the outer surface 2G of the tire 2, that is, the boundary between the outer surface of the tread 8 and the outer surface of the sidewall 10. In this tire 2, the outer surface of the tread 8 is included in the tread surface 26. The outer surface of the tread 8 includes a part of the corner portion 66. The outer surface 2G of the tire 2 may be configured such that the boundary BD between the outer surface of the tread 8 and the outer surface of the sidewall 10 coincides with the edge CS of the tread surface 26.

[0065] In Figure 3, the double-headed arrow WCM represents the axial distance from the equatorial plane to the boundary CM between the crown portion 60 and the middle portion 62. The double-headed arrow WMS represents the axial distance from the equatorial plane to the boundary MS between the middle portion 62 and the shoulder portion 64.

[0066] In this tire 2, the contours of the crown portion 60, middle portion 62, shoulder portion 64, and corner portion 66 are represented by arcs in its meridian cross-section.

[0067] The contour of the crown portion 60 is represented by a circular arc with its center on the equatorial plane. In Figure 3, arrow TR1 is the radius of the circular arc representing the contour of the crown portion 60. The contour of the middle section 62 is represented by an arc tangent to the arc representing the contour of the crown section 60. In Figure 3, arrow TR2 is the radius of the arc representing the contour of the middle section 62. The arc representing the contour of the middle section 62 is tangent to the arc representing the contour of the crown section 60 at boundary CM. Boundary CM is the point of tangency between the arc representing the contour of the middle section 62 and the arc representing the contour of the crown section 60. The contour of the shoulder portion 64 is represented by an arc tangent to the arc representing the contour of the middle portion 62. In Figure 3, arrow TR3 is the radius of the arc representing the contour of the shoulder portion 64. The arc representing the contour of the shoulder portion 64 is tangent to the arc representing the contour of the middle portion 62 at boundary MS. Boundary MS is the point of tangency between the arc representing the contour of the shoulder portion 64 and the arc representing the contour of the middle portion 62. The contour of the corner portion 66 is represented by an arc tangent to the arc representing the contour of the shoulder portion 64. In Figure 3, arrow TRc is the radius of the arc representing the contour of the corner portion 66. The arc representing the contour of the corner portion 66 is tangent to the arc representing the contour of the shoulder portion 64 at boundary SC. Boundary SC is the point of tangency between the arc representing the contour of the corner portion 66 and the arc representing the contour of the shoulder portion 64. The arc representing the contour of the corner portion 66 is tangent to the contour line of the side surface 58 at boundary CS. Boundary CS is the point of tangency between the arc representing the contour of the corner portion 66 and the contour line of the side surface 58.

[0068] In this tire 2, the radius TR1 of the arc representing the contour of the crown portion 60 is greater than the radius TR2 of the arc representing the contour of the middle portion 62. The radius TR2 of the arc representing the contour of the middle portion 62 is greater than the radius TR3 of the arc representing the contour of the shoulder portion 64. And the radius TR3 of the arc representing the contour of the shoulder portion 64 is greater than the radius TRc of the arc representing the contour of the corner portion 66. Among the seven parts that make up the tread surface 26, the arc representing the contour of the crown portion 60 located in the axial center has the largest radius TR1, and the arc representing the contour of the corner portion 66 located on the outermost axial side has the smallest radius TRc. In two adjacent parts in the axial direction, the arc representing the contour of the part located on the axial outer side has a smaller radius than the arc representing the contour of the part located on the axial inner side of that part. Radius TRc is smaller than radius TR1. Specifically, the ratio of radius TRc to radius TR1, TRc / TR1, is between 0.010 and 0.020.

[0069] As mentioned above, the sound dampening body 6 is made of sponge material and is bonded to the inner surface 4N of the tire body 4 on the radially inner side of the tread 8. The sound-dampening body 6, made of sponge material, reduces sound (cavity resonance energy) by converting the vibrational energy of vibrating air into thermal energy and dissipating it in the porous areas on its surface and inside. Since the sound-dampening body 6 suppresses cavity resonance, the increase in road noise is suppressed. Because the sound-dampening body 6 is made of sponge material, it is easily deformed, such as by shrinking and bending. Therefore, the sound-dampening body 6 does not substantially affect the deformation of the tire 2. As a result, this tire 2 can maintain good handling stability.

[0070] The radius TR1 of the arc representing the contour of the crown portion 60 is 1000 mm or more. The crown portion 60 is composed of a flat surface. This tire 2 can reduce the contact pressure at the crown portion 60. Since the mechanical fatigue of the tread 8 is reduced, this tire 2 can maintain good high-speed durability. From this viewpoint, the radius TR1 of the arc representing the contour of the crown portion 60 is preferably 1300 mm or more, and more preferably 1500 mm or more. From the viewpoint of preventing the crown portion 60 from being recessed radially inward and suppressing excessively high contact pressure at the shoulder portion 64, the radius TR1 is preferably 3000 mm or less, and more preferably 2500 mm or less.

[0071] In this tire 2, the axial distance WCM from the equatorial plane to the boundary CM between the crown portion 60 and the middle portion 62 is 30% to 40% of the axial distance WA from the equatorial plane to the axial outer end PW of the tire 2, and the axial distance WS from the equatorial plane to the axial outer end PC of the joint surface is 90% or more of the aforementioned axial distance WCM. In this tire 2, the position of the axial outer end PC of the joint surface between the sound dampening body 6 and the tire body 4 is set considering the boundary position between the crown portion 60 and the middle portion 62, so that the sound dampening body 6 can effectively reduce road noise and localized temperature rise is suppressed. This tire 2 can suppress a decrease in high-speed durability while maintaining good quietness. From this viewpoint, it is preferable that the ratio of the axial distance WS to the axial distance WCM, WS / WCM, is 120% or more.

[0072] In this tire, the axial distance WMS from the equatorial plane to the boundary MS between the middle section 62 and the shoulder section 64 is 55% to 65% of the axial distance WA from the equatorial plane to the axial outer end PW of the tire 2, and the axial outer end PC of the joint surface is located axially inward of the boundary MS between the middle section 62 and the shoulder section 64. This tire 2 can suppress the heat generation of the shoulder section 64, which is prone to heat generation, from being exacerbated by the sound dampening material 6. This tire 2 can maintain good high-speed durability. From this viewpoint, the ratio WS / WMS of the axial distance WS from the equatorial plane to the axial outer end PC of the joint surface to the aforementioned axial distance WMS is preferably 99% or less, and more preferably 82% or less.

[0073] This tire 2 can fully utilize the road noise reduction effect of the sound-dampening material 6 while suppressing the decrease in high-speed durability caused by the inclusion of the sound-dampening material 6. This tire 2 can achieve both quietness and high-speed durability.

[0074] In this tire 2, the axial distance WS from the equatorial plane to the axial outer end PC of the joint surface is 90% or more of the aforementioned axial distance WCM, and the axial outer end PC of the joint surface is located axially inward of the boundary MS between the middle section 62 and the shoulder section 64. Overall, this tire 2 can suppress heat generation. This tire 2 can achieve both quietness and high-speed durability while maintaining low rolling resistance.

[0075] The thickness TS of the sound dampening body 6 is preferably between 20 mm and 40 mm. By setting the thickness TS of the sound-dampening material 6 to 20 mm or more, the sound-dampening material 6 can contribute to reducing road noise. This tire 2 has good quietness. From this perspective, it is more preferable that the thickness TS of the sound-dampening material 6 be 25 mm or more. By setting the thickness TS of the sound-dampening element 6 to 40 mm or less, the temperature rise caused by the sound-dampening element 6 is suppressed. This tire 2 has good high-speed durability. From this viewpoint, it is more preferable that the thickness TS of the sound-dampening element 6 be 35 mm or less.

[0076] As mentioned above, the radius TR1 of the arc representing the contour of the crown portion 60 is larger than the radius TR2 of the arc representing the contour of the middle portion 62. More specifically, the ratio TR2 / TR1 of the radius TR2 of the arc representing the contour of the middle portion 62 to the radius TR1 of the arc representing the contour of the crown portion 60 is preferably between 0.45 and 0.55. This allows the tread surface 26 to effectively contribute to reducing the contact pressure at the crown portion 60. Since the mechanical fatigue of the tread 8 is effectively reduced, this tire 2 can maintain good high-speed durability. From this viewpoint, a ratio TR2 / TR1 of 0.47 or more and 0.53 is more preferable.

[0077] As mentioned above, the radius TR2 of the arc representing the contour of the middle section 62 is larger than the radius TR3 of the arc representing the contour of the shoulder section 64. Since the radius TR1 of the arc representing the contour of the crown section 60 is larger than the radius TR2 of the arc representing the contour of the middle section 62, the radius TR3 of the arc representing the contour of the shoulder section 64 is smaller than the radius TR1 of the arc representing the contour of the crown section 60. In particular, the ratio TR3 / TR1 of the radius TR3 of the arc representing the contour of the shoulder section 64 to the radius TR1 of the arc representing the contour of the crown section is preferably 0.05 or more and 0.15 or less. This allows the tread surface 26 to more effectively contribute to reducing the contact pressure at the crown section 60. Since the mechanical fatigue of the tread 8 is more effectively reduced, this tire 2 can maintain good high-speed durability. From this viewpoint, it is more preferable that the ratio TR3 / TR1 is 0.07 or more and 0.13 or less.

[0078] As described above, the band 20 of this tire 2 is located radially between the tread 8 and the belt 18 and includes a band cord that extends substantially circumferentially. The band 20 restrains the belt 18. This suppresses vibration of the belt 18. Heat generation in the tread 8 is effectively suppressed. This tire 2 can maintain good high-speed durability. From this viewpoint, it is preferable that the tire 2 further comprises a band 20 located radially between the tread 8 and the belt 18, and that this band 20 includes a band cord that extends substantially circumferentially.

[0079] The band cord of this tire 2 is an organic fiber cord. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. A hybrid cord may be used as the band cord, which is made by twisting together filaments of two types of organic fibers with different stiffnesses. Examples of hybrid cords include a hybrid cord of polyester fibers and nylon fibers, a hybrid cord of aramid fibers and polyester fibers, and a hybrid cord of aramid fibers and nylon fibers.

[0080] In this tire 2, a hybrid cord is preferred as the band cord. This allows the band 20 to effectively restrain the belt 18. Since vibration of the belt 18 is suppressed, heat generation in the tread 8 is effectively suppressed. This tire 2 can maintain good high-speed durability. From this viewpoint, if the band cord is a hybrid cord, it is preferable that the band cord is a hybrid cord of aramid fibers and nylon fibers.

[0081] The band 20 of this tire 2 comprises a full band 54 and a pair of edge bands 56. The full band 54 covers the entire belt 18. A pair of edge bands 56 are positioned axially spaced apart on either side of the equatorial plane. Each edge band 56 is located radially outward from the full band 54. The edge bands 56 cover the ends of the full band 54. This band 20 may consist only of the full band 54. A band 20 comprising a full band 54 and a pair of edge bands 56 effectively restrains the belt 18 compared to a band 20 composed of only a full band 54. Vibration of the belt 18 is sufficiently suppressed. Heat generation in the tread 8 is more effectively suppressed. This tire 2 can maintain good high-speed durability. From this viewpoint, it is preferable that the band 20 comprises a full band 54 and a pair of edge bands 56.

[0082] The tread 8 of this tire 2, more specifically the tread body 30, comprises a cap layer 68, an intermediate layer 70, and a base layer 72. The cap layer 68 constitutes the radially outer portion of the tread body 30. The base layer 72 constitutes the radially inner portion of the tread body 30. The intermediate layer 70 is located radially inward of the cap layer 68, and the base layer 72 is located radially inward of the intermediate layer 70. The tread body 30 is composed of three layers, the cap layer 68, the intermediate layer 70, and the base layer 72, which are arranged radially. This tread 8 is also called a three-layer tread. This tread body 30 may also be composed of two layers, the cap layer 68 and the base layer 72, which are arranged radially. In this case, this tread 8 is also called a two-layer tread.

[0083] The three layers, the cap layer 68, the intermediate layer 70, and the base layer 72, have a generally uniform thickness in the axial direction. In Figure 2, the double arrow Tc represents the thickness of the cap layer 68. The double arrow Tm represents the thickness of the intermediate layer 70. The double arrow Tb represents the thickness of the base layer 72. The double arrow TA represents the thickness of the tread 8. Thicknesses Tc, Tm, Tb, and TA are measured along the equatorial plane. If a groove 28 is provided on the equatorial plane, thicknesses Tc, Tm, Tb, and TA are measured along the normal to the tread surface 26 at the width center of the land portion adjacent to the groove 28 on the equatorial plane.

[0084] In this tire 2, the ratio Tc / TA of the thickness Tc of the cap layer 68 to the thickness TA of the tread 8 is between 0.2 and 0.4. The ratio Tb / TA of the thickness Tb of the intermediate layer 70 to the thickness TA of the tread 8 is between 0.4 and 0.6. The ratio Tb / TA of the thickness Tb of the base layer 72 to the thickness TA of the tread 8 is between 0.1 and 0.3. If the tread 8 is a two-layer tread, the ratio Tc / TA of the thickness Tc of the cap layer 68 to the thickness TA of the tread 8 is between 0.7 and 0.9. The ratio Tb / TA of the thickness Tb of the base layer 72 to the thickness TA of the tread 8 is between 0.1 and 0.3.

[0085] In this tire 2, the loss tangent LTm of the intermediate layer 70 at 30°C is lower than the loss tangent LTc of the cap layer 68 at 30°C, and higher than the loss tangent LTb of the base layer 72 at 30°C. The cap layer 68, intermediate layer 70, and base layer 72 are each made of cross-linked rubber having different heat generation properties. Specifically, the cap layer 68 generates the most heat, and the base layer 72 generates the least heat. The intermediate layer 70 has a heat generation property between that of the cap layer 68 and that of the base layer 72.

[0086] In this tire 2, the intermediate layer 70 can contribute to suppressing heat generation in the tread 8. In this tread 8, heat generation is suppressed compared to when the tread 8 is composed of two layers: a cap layer 68 and a base layer 72. In other words, by constructing the tread 8 with three layers: a cap layer 68, an intermediate layer 70, and a base layer 72, heat generation in the tread 8 is effectively suppressed. This tire 2 can maintain good high-speed durability. From this viewpoint, it is preferable that the tread 8 comprises a cap layer 68, an intermediate layer 70 located radially inward of the cap layer 68, and a base layer 72 located radially inward of the intermediate layer 70, and that the loss tangent LTm of the intermediate layer 70 at 30°C is lower than the loss tangent LTc of the cap layer 68 at 30°C and higher than the loss tangent LTb of the base layer 72 at 30°C.

[0087] As mentioned above, in this tire 2, the loss tangent Ltm of the intermediate layer 70 at 30°C is lower than the loss tangent LTc of the cap layer 68 at 30°C. Specifically, the ratio (LTm / LTc) of the loss tangent LTm of the intermediate layer 70 at 30°C to the loss tangent LTc of the cap layer 68 at 30°C is preferably between 40% and 90%. By setting the ratio (LTm / LTc) to 40% or more, the intermediate layer 70 can secure the necessary rigidity. Tire 2 can maintain good handling stability. From this viewpoint, a ratio (LTm / LTc) of 50% or more is more preferable, and 60% or more is even more preferable. By setting the ratio (LTm / LTc) to 90% or less, the intermediate layer 70 can effectively contribute to suppressing heat generation. This tire 2 can maintain good high-speed durability. From this viewpoint, a ratio (LTm / LTc) of 80% or less is more preferable, and 70% or less is even more preferable.

[0088] The loss tangent LTc of the cap layer 68 at 30°C is preferably 0.15 or higher. This is because the cap layer 68 can contribute to improved handling stability. From this viewpoint, a loss tangent LTc of 0.16 or higher is more preferable, and 0.17 or higher is even more preferable. The cap layer 68 is in contact with the road surface. From the viewpoint of improving handling stability, a higher loss tangent LTc is preferable. However, a high loss tangent LTc leads to heat generation. There is a concern that the heated cap layer 68 will raise the temperature of the intermediate layer 70 more than expected. From the viewpoint of enabling the tire 2 to maintain a stable temperature state for the entire tread 8 and maintain good high-speed durability, the loss tangent LTc of the cap layer 68 at 30°C is preferably 0.30 or lower, more preferably 0.28 or lower, and even more preferably 0.27 or lower.

[0089] In this tire 2, from the viewpoint that the intermediate layer 70 can effectively contribute to improving high-speed durability, the loss tangent Ltm of the intermediate layer 70 at 30°C is preferably 0.15 or less, more preferably 0.14 or less, and even more preferably 0.13 or less. From the viewpoint of maintaining good handling stability, the loss tangent Ltm of the intermediate layer 70 at 30°C is preferably 0.10 or more, and more preferably 0.11 or more.

[0090] In this tire 2, the loss tangent LTb of the base layer 72 at 30°C is lower than the loss tangent LTm of the intermediate layer 70 at 30°C. Specifically, the loss tangent LTb of the base layer 72 at 30°C is preferably 0.10 or less, because the base layer 72 can effectively contribute to maintaining good high-speed durability. From this viewpoint, it is more preferable that the loss tangent LTb of the base layer 72 is 0.09 or less. Since a smaller loss tangent LTb of the base layer 72 is preferable, no preferred lower limit is set.

[0091] As is clear from the above description, according to the present invention, a tire 2 can be obtained that achieves both quietness and high-speed durability. [Examples]

[0092] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0093] [Examples 1-7 and Comparative Examples 1-2] We obtained tires (tire size = 245 / 35R20) for Example 1-7 and Comparative Example 1-2, which have the basic configuration shown in Figure 1 and the specifications shown in Table 1 below. The axial distance WCM from the equatorial plane to the boundary CM between the crown and middle sections was set to 33% of the axial distance WA from the equatorial plane to the outer axial end PW of the tire. The axial distance WMS from the equatorial plane to the boundary MS between the middle and shoulder regions was set to 61% of the aforementioned axial distance WA. An ether-based polyurethane sponge was used as the sound dampening material. In Table 1, "Y" in the sound dampening column indicates that a sound dampening element is present, and "N" indicates that a sound dampening element is not present. In the "Band Cord" column, "N" indicates that nylon fiber cord was used as the band cord, and "HB" indicates that a hybrid cord of aramid fiber and nylon fiber was used as the band cord. In the "Band Structure" column, "1F" indicates that the band consists only of full bands, while "1F+1E" indicates that the band consists of full bands and a pair of edge bands.

[0094] Comparative Example 1 does not have a sound dampening element. In Examples 1-4 and Comparative Example 1-2, a two-layer tread was used for the tread, while in Example 5-7, a three-layer tread was used for the tread. In Examples 1-5 and Comparative Example 1-2, nylon fiber cords were used as band cords, while in Examples 6-7, a hybrid cord of aramid fiber and nylon fiber was used as a band cord. In Examples 1-6 and Comparative Examples 1-2, the band consists only of a full band, while in Example 7, the band consists of a full band and a pair of edge bands.

[0095] [High speed durability] A prototype tire with an internal pressure of 250 kPa was mounted on a drum testing machine, and the condition of the tire's internal structure was evaluated after driving 30,000 km at 120 km / h under a load of 6.6 kN. The results are expressed as an index with Comparative Example 1 set to 100, where a higher value indicates a better condition of the tire's internal structure and superior high-speed durability.

[0096] [Quietness] A prototype tire, with its internal pressure adjusted to 250 kPa, was mounted on a drum test machine installed in an anechoic chamber. Sound pressure was measured when the machine was driven at 120 km / h under a load of 6.6 kN. Quietness was evaluated using an index where the smaller the cavity resonance peak value, the higher the index value. The results are expressed as an index with Comparative Example 1 set to 100, and a higher index value indicates a smaller cavity resonance peak value and superior quietness.

[0097] [Table 1]

[0098] As shown in Table 1, the embodiments demonstrate a balance between quiet operation and high-speed durability. This evaluation clearly demonstrates the superiority of the present invention. [Industrial applicability]

[0099] The technology described above, which achieves both quietness and high-speed durability, can be applied to various types of tires.

[0100] [Note] The present invention includes the following embodiments.

[0101] [1] A HIGH LOAD CAPACITY type tire as defined in the ETRTO 2021 standard manual, comprising a tire body and a sound dampening body made of sponge material, wherein the tire body comprises a tread that contacts the road surface and a belt located radially inward of the tread and including a number of parallel belt cords, the sound dampening body is bonded to the inner surface of the tire body radially inward of the tread, the outer surface of the tread comprises a crown portion located in the axial center, a pair of middle portions located axially outward of the crown portion, and a pair of shoulder portions located axially outward of the middle portions, wherein the axial distance from the equatorial plane of the tire to the boundary between the crown portion and the middle portion is 30% or more and 40% or less of the axial distance from the equatorial plane to the axial outer end of the tire, and the axial distance from the equatorial plane to the boundary between the middle portion and the shoulder portion is 55% or more and 65% or less of the axial distance from the equatorial plane to the axial outer end of the tire, and the sound dampening body A tire in which the axial outer end of the joint surface between the sound body and the tire body is located axially inward of the boundary between the middle portion and the shoulder portion, the axial distance from the equatorial plane to the axial outer end of the joint surface is 90% or more of the axial distance from the equatorial plane to the boundary between the crown portion and the middle portion, in the meridional cross-section of the tire, the contour of the crown portion is represented by an arc centered on the equatorial plane, the contour of each middle portion is represented by an arc tangent to the arc representing the contour of the crown portion, the contour of each shoulder portion is represented by an arc tangent to the arc representing the contour of the middle portion, the radius TR1 of the arc representing the contour of the crown portion is greater than the radius TR2 of the arc representing the contour of the middle portion, the radius TR2 of the arc representing the contour of the middle portion is greater than the radius TR3 of the arc representing the contour of the shoulder portion, and the radius TR1 of the arc representing the contour of the crown portion is 1000 mm or more. [2] The tire as described in [1] above, wherein the ratio TR2 / TR1 of the radius TR2 of the arc representing the contour of the middle portion to the radius TR1 of the arc representing the contour of the crown portion is 0.45 or more and 0.55 or less. [3] The tire as described in [2] above, wherein the ratio TR3 / TR1 of the radius TR3 of the arc representing the contour of the shoulder portion to the radius TR1 of the arc representing the contour of the crown portion is 0.05 or more and 0.15 or less. [4] The tire according to any one of [1] to [3] above, wherein the tread comprises a cap layer, an intermediate layer located radially inward of the cap layer, and a base layer located radially inward of the intermediate layer, wherein the loss tangent of the intermediate layer at 30°C is lower than the loss tangent of the cap layer at 30°C and higher than the loss tangent of the base layer at 30°C. [5] The tire according to any one of the above [1] to [4], further comprising a band located radially between the tread and the belt, wherein the band includes a band cord substantially extending in the circumferential direction. [Explanation of Symbols]

[0102] 2... Tires 4. Tire body 6...Sound damping body 8...Tread 18... belt 20 bands 26...Tread surface 30...Tread body 48, 50, 52... Belt ply 54...Full Band 56. Edge Band 60... Crown section 62... Middle Section 64... Shoulder section 66... ​​Corner section 68... Cap layer 70...Middle class 72...Base layer

Claims

1. A tire of the HIGH LOAD CAPACITY type as defined in the ETRTO 2021 standard manual, It comprises a tire body and a sound-dampening element made of sponge material. The tire body comprises a tread that contacts the road surface and a belt located radially inward of the tread and including a number of parallel belt cords, The sound dampening element is bonded to the inner surface of the tire body on the radially inner side of the tread. The outer surface of the tread comprises a crown portion located in the axial center, a pair of middle portions located axially outside the crown portion, and a pair of shoulder portions located axially outside the middle portions. The axial distance from the equatorial plane of the tire to the boundary between the crown portion and the middle portion is 30% or more and 40% or less of the axial distance from the equatorial plane to the outer axial end of the tire. The axial distance from the equatorial plane to the boundary between the middle portion and the shoulder portion is 55% or more and 65% or less of the axial distance from the equatorial plane to the outer axial end of the tire. The axial outer end of the joint surface between the sound dampening body and the tire body is located axially inward of the boundary between the middle portion and the shoulder portion. The axial distance from the equatorial plane to the axial outer end of the joint surface is 90% or more of the axial distance from the equatorial plane to the boundary between the crown portion and the middle portion. In the meridional cross-section of the aforementioned tire, The contour of the crown portion is represented by an arc having its center on the equatorial plane, The contour of each middle section is represented by an arc tangent to the arc representing the contour of the crown section, The contour of each shoulder portion is represented by an arc tangent to the arc representing the contour of the middle portion, The radius TR1 of the arc representing the contour of the crown portion is greater than the radius TR2 of the arc representing the contour of the middle portion. The radius TR2 of the arc representing the contour of the middle portion is greater than the radius TR3 of the arc representing the contour of the shoulder portion. The radius TR1 of the arc representing the outline of the crown portion is 1000 mm or more. tire.

2. The ratio TR2 / TR1 of the radius TR2 of the arc representing the contour of the middle portion to the radius TR1 of the arc representing the contour of the crown portion is 0.45 or more and 0.55 or less. The tire according to claim 1.

3. The ratio TR3 / TR1 of the radius TR3 of the arc representing the contour of the shoulder portion to the radius TR1 of the arc representing the contour of the crown portion is 0.05 or more and 0.15 or less. The tire according to claim 2.

4. The tread comprises a cap layer, an intermediate layer located radially inward of the cap layer, and a base layer located radially inward of the intermediate layer. The loss loss tangent of the intermediate layer at 30°C is lower than the loss loss tangent of the cap layer at 30°C, and higher than the loss loss tangent of the base layer at 30°C. The tire according to claim 1.

5. The system further comprises a band located radially between the tread and the belt, The band includes a band code that extends substantially in the circumferential direction. The tire according to claim 1.

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