Tire

Abstract

The present application provides a tire (2) capable of achieving an improvement in high-speed durability while suppressing an influence on rolling resistance. The tire (2) includes a tread (4) and a belt (16). An outer surface (4G) of the tread (4) includes a crown portion (64), a pair of intermediate portions (66), and a pair of shoulder portions (68). A radius (TR1) of a circular arc representing an outline of the crown portion (64) is 5 times or more and 7 times or less of an axial width (Wa) of a ground surface of the tire (2) in a standard state. The belt (16) includes a belt cord (56) composed of an organic fiber cord. A contraction rate (SRs) of the belt cord (56) at a position corresponding to a width of 70% of a maximum width (SW) of the tire (2) in the standard state is 70% or more and 130% or less of a contraction rate (SRc) of the belt cord (56) at an equatorial plane of the tire (2).

Description

Technical Field

[0001] This invention relates to tires. More specifically, this invention relates to tires mounted on passenger vehicles. Background Technology

[0002] For tires designed for use at speeds above 270 km / h, excellent high-speed durability is required.

[0003] For example, Patent Document 1 discloses a profile of the outer surface of a tread designed to improve high-speed durability.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-041563 Summary of the Invention

[0005] The purpose of this invention is to provide a tire that can improve high-speed durability while suppressing the effect on rolling resistance.

[0006] The tire according to the present invention comprises: a pair of beaded tires, a carcass disposed between the pair of beaded tires, a tread located radially outward of the carcass and in contact with the road surface, a belt located radially inward of the tread and radially outward of the carcass, and a belt located radially between the tread and the belt. The standard state of the tire is defined as follows: the tire is assembled onto a standard rim, the tire's internal pressure is adjusted to 92% of the standard internal pressure, and no load is applied to the tire. The outer surface of the tread comprises: a crown portion located axially at the center, a pair of intermediate portions located axially outward of the crown portion, and a pair of shoulder portions located axially outward of the intermediate portions. In the meridional cross-section of the tire in the standard state, the outline of the crown portion is represented by an arc having a center on the equatorial plane, the outline of each intermediate portion is represented by an arc tangent to the arc representing the crown portion, and the outline of each shoulder portion is represented by an arc tangent to the arc representing the intermediate portion. The position on the outer surface of the tire corresponding to the axial outer end of the tire's contact patch when the tire is subjected to a longitudinal load of 75% of the normal load in the tire under the aforementioned standard condition, causing the tire to contact a plane, is designated as the contact reference end. The axial distance from one contact reference end to the other contact reference end in the tire is defined as the axial width Wa of the contact patch. The radius TR1 of the arc representing the outline of the tire crown is at least 5 times and less than 7 times the axial width Wa. The belt has belt cords that are inclined relative to the circumferential direction. The belt cords are steel cords. The belt has belt cords that extend substantially circumferentially. The belt cords are organic fiber cords. The shrinkage rate of the belt cord at the position corresponding to 70% of the maximum width of the tire under the aforementioned standard condition is at least 70% and less than 130% of the shrinkage rate of the belt cord at the equatorial plane of the tire.

[0007] According to the present invention, a tire is obtained that can improve high-speed durability while suppressing the effect on rolling resistance. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view showing a portion of a tire according to one embodiment of the present invention.

[0009] Figure 2 It is an explanatory diagram illustrating the belt bundle and the structure of the belt bundle.

[0010] Figure 3 It is a cross-sectional view showing the outline of the outer surface of the tire tread.

[0011] Figure 4 This is a schematic diagram illustrating an example of the contact patch of a tire.

[0012] Figure 5 This is a three-dimensional view showing a portion of the strap used to form the strap.

[0013] Figure 6 It means Figure 3 A cross-sectional view of a portion of the outline of the outer surface shown.

[0014] Figure 7 This is an explanatory diagram illustrating the method for measuring the shrinkage rate of the belt cord.

[0015] Figure 8 This is an explanatory diagram illustrating the method for measuring the shrinkage rate of the belt cord.

[0016] Explanation of reference numerals in the attached figures

[0017] 2...Tire; 4...Tread; 10...Bead; 12...Carcass; 14...Belt; 16...Belt; 44, 46, 48...Belt cord; 50...Belt cord; 54...Full belt; 56...Belt cord; 60...Tread surface; 64...Crown; 66...Middle section; 68...Shoulder; 70...Corner. Detailed Implementation

[0018] The invention will now be described in detail with appropriate reference to the accompanying drawings and based on preferred embodiments.

[0019] The tire of this invention is assembled to a rim. Air is filled inside the tire to adjust its internal pressure. The tire assembled to the rim is also referred to as a tire-rim assembly. The tire-rim assembly comprises a rim and a tire assembled to that rim.

[0020] In this invention, the state in which a tire is assembled on a standard rim, the tire's internal pressure is adjusted to the standard internal pressure, and no load is applied to the tire is referred to as the standard state. The state in which a tire is assembled on a standard rim, the tire's internal pressure is adjusted to 92% of the standard internal pressure, and no load is applied to the tire is referred to as the standard state.

[0021] In this invention, unless otherwise specified, the dimensions and angles of the tire are measured under standard conditions.

[0022] The dimensions and angles of various parts of the tire's radial section, which cannot be measured when the tire is assembled on a standard rim, are measured in the cross-section of the tire obtained by cutting the tire along a plane including the axis of rotation. In this measurement, the tire is positioned such that the distance between the left and right bead sections is consistent with the distance between the bead sections in a tire assembled on a standard rim. Furthermore, the tire's structure, which cannot be determined when the tire is assembled on a standard rim, is determined in the aforementioned cross-section.

[0023] A standard rim refers to a rim specified in the tire's specifications. Standard rims are defined as "Standard Rim" in JATMA specifications, "Design Rim" in TRA specifications, and "Measuring Rim" in ETRTO specifications.

[0024] Standard internal pressure refers to the internal pressure specified in the tire's specifications. This includes the "maximum air pressure" in JATMA specifications, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA specifications, and "INFLATION PRESSURE" in ETRTO specifications.

[0025] Regular load refers to the load specified in the tire's specifications. The "maximum load capacity" in JATMA specifications, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA specifications, and "LOAD CAPACITY" in ETRTO specifications are all regular loads.

[0026] In this invention, the speed symbol refers to, for example, a symbol specified in the JATMA specification, indicating the highest speed a tire can travel under specified conditions with a mass represented by its load index. A tire with a speed symbol of W or higher means a tire with a speed symbol of W or Y.

[0027] Although described later, in the formation of the belt according to the present invention, the belt cords are wound into a spiral shape while a load is applied to them. The tension generated by applying the load to the belt cords acts as a binding force on the tire.

[0028] Within the tire's straps, the strap cords are under tension. Releasing the strap cords from the tire causes them to contract. The restraining force of the straps within the tire is reflected in the contraction rate of the strap cords.

[0029] In this invention, the shrinkage rate of the belt cord is measured as follows. Using... Figure 7 as well as Figure 8 This will explain the method for measuring shrinkage.

[0030] The tire's harness consists of harness cords wound in a spiral shape. Figure 7 The diagram schematically illustrates the state of the belt cord B in the tire's belt.

[0031] To determine the shrinkage rate, firstly, the tire tread is peeled off to expose the belt cords B. The length of the exposed belt cords B is measured, and a mark D indicating the reference length Lf (e.g., 100 cm) is marked on the belt cords B. Then, the belt cords B are peeled off from the tire and left to stand for 24 hours in an environment with a temperature adjusted between 20°C and 30°C. After standing, as... Figure 8 As shown, the distance between the marks on the belt cord B is measured to obtain the length La of the belt cord B after shrinkage. The shrinkage rate SR (in %) is calculated using the following formula.

[0032] SR(%)=(Lf-La) / Lf×100

[0033] The larger the shrinkage rate SR, the higher the restraining force of the strap; the smaller the shrinkage rate SR, the lower the restraining force of the strap.

[0034] In this invention, the tread portion of a tire refers to the part of the tire that contacts the road surface. The bead portion refers to the part of the tire that fits into the rim. The sidewall portion refers to the part of the tire that is positioned between the tread portion and the bead portion. A tire comprises a tread portion, a pair of bead portions, and a pair of sidewall portions.

[0035] The central part of the fetal tummy is also called the crown. The end part of the fetal tummy is also called the shoulder.

[0036] [Basic Insights of the Invention]

[0037] While a flat tread surface (hereinafter referred to as a flat tread) is beneficial for rolling resistance, it is detrimental to high-speed durability (hereinafter referred to as high-speed durability) when cambered. A tread surface with curvature (hereinafter referred to as a round tread) is beneficial for high-speed durability but detrimental to rolling resistance. Rolling resistance and high-speed durability have an inverse relationship, and it is difficult to balance both by controlling the profile of the tread's outer surface.

[0038] In a tire under driving conditions, repeated deformation and recovery occur. The radial position of the tread changes. This tread movement affects rolling resistance and high-speed durability.

[0039] The tire tread has a belt and a strap. The belt and strap are located radially inside the tread. The belt has belt cords made of steel cords and inclined relative to the circumference. The strap has strap cords made of organic fiber cords and extending substantially circumferentially. The belt and strap constrain the tread. This inhibits tread movement. The belt and strap help suppress the increase in rolling resistance and the decrease in high-speed durability caused by tread movement.

[0040] Despite employing a round tread pattern, which is beneficial for high-speed durability, there have been instances where the tire's high-speed durability has not reached the expected level. To clarify the reasons for this, the inventors investigated the belt harness and its restraint force. As a result, the inventors concluded that the restraint force in the end portion of the tread (hereinafter referred to as the shoulder portion) is tends to be lower than the restraint force in the central portion of the tread (hereinafter referred to as the crown portion), which affects the amount of improvement in high-speed durability.

[0041] Therefore, based on the above insights, the inventors have conducted thorough research on technologies that can improve high-speed durability while suppressing the impact on rolling resistance, and have thus completed the invention described below.

[0042] [Summary of Embodiments of the Invention]

[0043] The tire of the present invention comprises: a pair of beaded tires, a tire carcass disposed between the pair of beaded tires, a tread located radially outside the tire carcass and in contact with the road surface, a belt located radially inside the tread and radially outside the tire carcass, and a belt located radially between the tread and the belt. The standard state of the tire is defined as the tire being assembled on a standard rim, with the tire's internal pressure adjusted to 92% of the standard internal pressure, and without any load applied to the tire. The outer surface of the tread comprises: a crown portion located axially at the center, a pair of intermediate portions located axially outside the crown portion, and a pair of shoulder portions located axially outside the intermediate portions. In the meridional cross-section of the tire in the standard state, the outline of the crown portion is represented by an arc having a center on the equatorial plane, the outline of each intermediate portion is represented by an arc tangent to the arc representing the crown portion, and the outline of each shoulder portion is represented by an arc tangent to the arc representing the intermediate portion. The arc tangent to the arc represents the position on the outer surface of the tire corresponding to the axial outer end of the tire's contact surface obtained by applying a longitudinal load of 75% of the normal load to the tire in the standard state and causing the tire to contact the plane. The axial distance from one of the contact surface ends to the other of the tire's contact surface ends is the axial width Wa of the contact surface. The radius TR1 of the arc representing the outline of the tire crown is more than 5 times and less than 7 times the axial width Wa. The belt has belt cords that are inclined relative to the circumference. The belt cords are steel cords. The belt has belt cords that extend substantially in the circumference. The belt cords are organic fiber cords. The shrinkage rate of the belt cords at the position corresponding to 70% of the maximum width of the tire in the standard state is more than 70% and less than 130% of the shrinkage rate of the belt cords at the equatorial plane of the tire.

[0044] The tire of this invention can improve high-speed durability while suppressing the effect on rolling resistance. The mechanism by which this effect is achieved is not yet clear, but it is speculated to be as follows.

[0045] In the tire of the present invention, the radius TR1 of the arc representing the outline of the tread portion is set to be at least 5 times and less than 7 times the contact width Wa of the tire's contact surface. This results in a tread with a flat outer surface. As described above, a flat tread has an advantageous effect on rolling resistance. The tread of this tire helps to suppress the influence on rolling resistance.

[0046] On the other hand, a flat tread, as described above, negatively impacts high-speed durability. However, in this tire, the shrinkage rate of the belt cords at the shoulder portion of the tread portion is taken into account. Specifically, the shrinkage rate of the belt cords at a position corresponding to 70% of the maximum width of the tire in its standard state is set within a range of 70% to 130% of the shrinkage rate of the belt cords at the tire's equatorial plane. In this tire, the shrinkage rate of the belt cords at the shoulder portion is set to the same level as that of the belt cords at the crown portion. This sufficiently restrains the movement of the shoulder portion. The belt, together with the belt bundle in which steel cords are configured as belt cords, sufficiently contributes to restraining the movement of the tread portion.

[0047] The belt and belt of the present invention have a significant effect on tires intended for use at speeds of 270 km / h and above, in other words, tires with a speed rating of W or higher. This tire achieves improved high-speed durability.

[0048] Restraining the movement of the tread section also helps reduce rolling resistance. This tire achieves improved high-speed durability while suppressing the impact on rolling resistance.

[0049] Preferably, in the aforementioned tire contact surface, the ratio of the center contact length at the center of the contact width to the reference contact length at a position corresponding to 80% of the contact width is a shape index F80, wherein the shape index F80 is 1.10 or higher and 1.40 or lower. This constitutes a tire contact shape capable of suppressing the impact on high-speed durability and rolling resistance. The tire maintains good high-speed durability and low rolling resistance. Since wear at the tread portion is suppressed, the tire also maintains good wear resistance.

[0050] Preferably, the ratio of the radius TR2 of the arc representing the outline of the middle portion to the radius TR1 of the arc representing the outline of the crown portion, TR2 / TR1, is 0.35 or more and 0.40 or less, and the ratio of the radius TR3 of the arc representing the outline of the shoulder portion to the radius TR1 of the arc representing the outline of the crown portion, TR3 / TR1, is 0.09 or more and 0.13 or less. Therefore, the radius of the arc representing the shoulder portion is set to be smaller than the radius of the arc in conventional tires. In other words, the shoulder portion is set to be more rounded than conventional tire shoulders. When this tire uses a flat tread, it can suppress the increase in localized ground pressure at the contact point that may occur under conditions of high load on the shoulder portion, such as during extreme driving or high-speed driving. This tire can suppress wear at the contact point and reduce high-speed durability. This tire can suppress not only the influence on rolling resistance but also the influence on wear resistance, and can achieve improved high-speed durability.

[0051] Preferably, the ratio of the axial distance RW1 from the equatorial plane to the boundary between the tread portion and the intermediate portion to the axial width Wa of the contact patch, RW1 / Wa, is 0.15 or more and 0.25 or less; and the ratio of the axial distance RW3 from the boundary between the intermediate portion and the shoulder portion to the ground contact reference end, RW3 / Wa, to the axial width Wa, is 0.10 or more and 0.15 or less. Thus, in the outer surface profile of the tread, the flat profile of the tread portion effectively helps to reduce rolling resistance, and the curved profile of the shoulder portion effectively helps to suppress the increase of localized ground pressure at the contact patch end. This tire not only suppresses the impact on rolling resistance but also suppresses the impact on wear resistance, and achieves improved high-speed durability.

[0052] Preferably, in the radial cross-section of the tire in the aforementioned standard state, the ratio of the radius TR1 of the arc representing the profile of the tread portion to the radius TRb of the arc having a center on the equatorial plane of the tire and passing through the equator and the ground contact reference end of the tire, TR1 / TRb, is 1.66 or more and 1.96 or less. Therefore, in the outer surface profile of the tread, the flat profile of the tread portion effectively helps to reduce rolling resistance, and the curved profile of the shoulder portion effectively helps to suppress the increase of localized ground pressure at the ground contact end. This tire not only suppresses the influence on rolling resistance but also suppresses the influence on wear resistance, and achieves improved high-speed durability.

[0053] Thus, the tire of the present invention can improve high-speed durability while suppressing the impact on rolling resistance. Furthermore, this tire is also expected to suppress not only the impact on rolling resistance but also the impact on wear resistance, and further improve high-speed durability. These aspects will be discussed below. Figure 1 The following is a detailed explanation using tire 2 as an example.

[0054] [Details of the embodiments of the present invention]

[0055] Figure 1 A portion of a tire 2 according to one embodiment of the present invention is shown. The tire 2 is a pneumatic tire for passenger vehicles. Figure 1 The tire 2 shown is in the state of being assembled on rim R (regular rim).

[0056] Figure 1 A portion of the cross-section of the tire 2 is shown, cut along a plane containing the axis of rotation of the tire 2 (not shown). Figure 1 The cross section shown is also known as the meridian section.

[0057] The double arrow AD indicates the axial direction of tire 2. The axial direction of tire 2 means the direction parallel to the axis of rotation of tire 2. The double arrow RD indicates the radial direction of tire 2. Relative to... Figure 1 The direction perpendicular to the paper is the circumferential direction of tire 2. The dotted line EL extending radially represents the equatorial plane of tire 2.

[0058] In the axial direction, the direction away from the equatorial plane is the axial outer side of tire 2, and the direction closer to the equatorial plane is the axial inner side of tire 2. Arrow RD1 indicates the radial outer side of tire 2, and arrow RD2 indicates the radial inner side of tire 2.

[0059] exist Figure 1 In the attached diagram, the location indicated by the reference numeral Eq is the intersection of the outer surface 2G of tire 2 (specifically, the tread surface described later) and the equatorial plane. The intersection point Eq is the equator of tire 2.

[0060] When the groove is located on the equatorial plane, the equatorial Eq is determined based on an imaginary outer surface obtained assuming there is no groove. The equatorial Eq is the radial outer end of tire 2.

[0061] exist Figure 1 In the attached diagram, the location indicated by reference numeral PW is the axial outer end of tire 2 (hereinafter referred to as the outer end PW). When patterns, text, or other decorations are located on the outer surface 2G, the outer end PW is based on an imaginary outer surface obtained assuming no decoration. Figure 1 The double-dotted line (LV) is used to determine this.

[0062] exist Figure 1In the diagram, the length indicated by the double arrow SW is the maximum width of tire 2. The maximum width SW of tire 2 is the axial distance from the outer end PW of one side to the outer end PW of the other side (not shown). The outer end PW is also referred to as the maximum width position. The maximum width SW obtained under normal conditions is the cross-sectional width of tire 2 (refer to JATMA et al.).

[0063] exist Figure 1 In the attached figure, the position indicated by reference numeral P70 is the position on the outer surface 2G of tire 2 corresponding to 70% of the maximum width SW of tire 2. Position P70 is determined in tire 2 under standard conditions. In tire 2 under standard conditions, the ratio of the axial distance from the equatorial plane to position P70 to the axial distance from the equatorial plane to the maximum width position PW is 70%.

[0064] Tire 2 has a tread 4, a pair of sidewalls 6, a pair of edge bead 8, a pair of bead 10, a carcass 12, belt 14, belt 16, a pair of anti-friction cloth 18, inner liner 20 and a pair of isolation layers 22.

[0065] The tread 4 is located radially outward of the carcass 12. The tread 4 is made of cross-linked rubber. The tread 4 is in contact with the road surface.

[0066] Grooves 24 are provided at the tread 4. This forms the tread pattern.

[0067] exist Figure 1 In the attached drawing, the location indicated by the reference numeral TS is the boundary between the tread 4 on the outer surface 2G of the tire 2 and the sidewall 6, which will be described later. The boundary TS is also the end of the outer surface 4G of the tread 4.

[0068] The tread 4 has a tread body 26 and a pair of side portions 28. The tread body 26 is in primary contact with the road surface. Each side portion 28 is located between the tread body 26 and the sidewall 6. The tread body 26 and the sidewall 6 are joined via the side portions 28. The side portions 28 are made of cross-linked rubber with adhesive properties considered.

[0069] The tread body 26 comprises a top layer 30 located radially outermost and a base layer 32 located radially innermost. The tread body 26 of this tire 2 consists of two layers: the top layer 30 and the base layer 32. The top layer 30 is made of cross-linked rubber that takes into account contact with the road surface, wear resistance, and grip performance. The base layer 32 is located radially inner of the top layer 30. The base layer 32 is covered by the top layer 30. The base layer 32 is made of cross-linked rubber with low heat generation.

[0070] Each sidewall 6 is connected to the tread 4. The sidewall 6 is located on the axially outer side of the carcass 12. The sidewall 6 is made of cross-linked rubber with cut resistance in mind.

[0071] Each edge portion 8 is located radially inside the tire sidewall 6. The edge portion 8 contacts the rim R. The edge portion 8 is made of cross-linked rubber with wear resistance in mind.

[0072] Each bead 10 is located radially inside the sidewall 6. The bead 10 is located axially inside the edge portion 8.

[0073] The bead 10 has a core 34 and a gusset 36. The core 34 extends circumferentially. Although not shown, the core 34 includes steel wires. The gusset 36 is located radially outward of the core 34. The gusset 36 is made of cross-linked rubber with high rigidity. The gusset 36 tapers radially outward.

[0074] The tire body 12 is located inside the tread 4, a pair of sidewalls 6, and a pair of beaded portions 8. The tire body 12 is mounted between a pair of beaded portions 10.

[0075] The tire carcass 12 has at least one carcass cord 38. The tire carcass 12 of the tire 2 is composed of two carcass cords 38. Of the two carcass cords 38, the carcass cord 38 located on the inner side of the radial inner side of the tread 4 is the first carcass cord 40, and the carcass cord 38 located on the outer side is the second carcass cord 42.

[0076] The first carcass ply 40 folds back from the axially inner side to the outer side at each bead 10. The first carcass ply 40 includes a first ply body 40a and a pair of first fold-back portions 40b. The first ply body 40a is positioned between the pair of bead 10. Each first fold-back portion 40b is connected to the first ply body 40a and folds back at each bead 10. The end of the first fold-back portion 40b is located radially outer of the axially outer end PW of the tire 2.

[0077] The second carcass cord 42 is folded back from the axially inward side to the outward side at each bead 10. The second carcass cord 42 has a second cord body 42a and a pair of second fold-back portions 42b. The second cord body 42a is positioned between the pair of bead 10. Each second fold-back portion 42b is connected to the second cord body 42a and folds back at each bead 10. The end of the second fold-back portion 42b is located radially inward to the outer end of the triangular rubber 36. The end of the second fold-back portion 42b is covered by the first fold-back portion 40b.

[0078] The second cord body 42a is the outermost cord body among at least one cord body of the carcass 12.

[0079] Although not illustrated, the carcass ply 38 constituting the carcass 12 includes multiple carcass cords arranged side-by-side. The carcass cords intersect the equatorial plane. The carcass 12 of this tire 2 has a radial configuration. The carcass cords are 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.

[0080] Figure 2 This is an explanatory diagram illustrating the structure of belt 14 and belt 16. Figure 2 The double arrow CD indicates the circumferential direction of tire 2. The surface side of the paper represents the radially outward direction, and the back side represents the radially inward direction. (Use...) Figure 1 as well as Figure 2 To illustrate the structure of belt 14 and belt 16.

[0081] The belt 14 is located radially inside the tread 4. The belt 14 is located radially outside the tire body 12. The belt 14 of the tire 2 is stacked on the tire body 12 radially inside the tread 4.

[0082] The belt 14 has a plurality of belt cords 44 arranged radially. The plurality of belt cords 44 includes an innermost belt cord 46 located on the innermost side and an outermost belt cord 48 located on the outermost side. The belt 14 of the tire 2 is composed of two belt cords 44, specifically, an inner belt cord 46 and an outer belt cord 48.

[0083] The inner belt cord 46 is laminated on the tire carcass 12 radially inside the tread 4. The outer belt cord 48 is laminated on the inner belt cord 46.

[0084] The end of the outer belted curtain 48 is located axially inside the end of the inner belted curtain 46. The outer belted curtain 48 is narrower than the inner belted curtain 46. The end of the inner belted curtain 46 is the end of the belt 14.

[0085] The belted fabric 44 constituting the belted bundle 14 includes a plurality of belted cords 50 arranged in parallel. Figure 2 In the illustration, the cord 50 is represented by a solid line, but the cord 50 is covered by adhesive 52.

[0086] The belt cord 50 is made of steel cord. There are no special restrictions on the belt cord 50; steel cords commonly used as belt cords in tires are used as belt cords 50.

[0087] The individual belt cords 50 contained in the belt 14 are inclined relative to the circumferential direction. For example... Figure 2 As shown, the inclination direction of the belt cord 50 (hereinafter referred to as the outer belt cord 50s) included in the outer belt cord 48 is opposite to the inclination direction of the belt cord 50 (hereinafter referred to as the inner belt cord 50u) included in the inner belt cord 46.

[0088] The belt 14 has a belt cord 50, which is a steel cord and is inclined relative to the circumference.

[0089] The belt 16 is stacked on the belt 14 radially inside the tread 4. The belt 16 is located radially between the tread 4 and the belt 14. The end of the belt 16 is located axially outside the end of the belt 14. The belt 16 covers the belt 14.

[0090] The belt 16 of the tire 2 is a full belt 54. The belt 16 can also be a pair of edge belts configured to be axially separated across the equatorial plane and covering the end portions of the belt 14. The belt 16 can also consist of the full belt 54 and a pair of edge belts. Although not shown, in this case, the pair of edge belts are configured to be axially separated across the equatorial plane and cover the end portions of the full belt 54 from the radially outer side.

[0091] The entire belt 54 constituting the belt 16 includes belt cords 56 wound into a spiral shape. Figure 2 In the middle, for ease of explanation, the strap cord 56 is represented by a solid line, but the strap cord 56 is covered by adhesive 58.

[0092] The belt cord 56 in the belt 16 extends substantially circumferentially. Specifically, the angle between the belt cord 56 and the circumferential direction is 5° or less. The belt 16 has a seamless construction. The belt cord 56 is an organic fiber cord. Examples of organic fibers include nylon, rayon, polyester, and aramid fibers. There are no particular limitations on the belt cord 56; organic fiber cords commonly used as belt cords in tires are used as belt cords 56.

[0093] The belt 16 has belt cords 56, which are organic fiber cords and extend substantially circumferentially.

[0094] Each anti-friction cloth 18 is located radially inside the bead 10. The anti-friction cloth 18 contacts the rim R. The anti-friction cloth 18 of the tire 2 is composed of cloth and rubber impregnated in the cloth.

[0095] The inner liner 20 is located inside the tire carcass 12. The inner liner 20 forms the inner surface 2N of the tire 2. The inner liner 20 is made of cross-linked rubber with excellent air-shielding properties. The inner liner 20 maintains the internal pressure of the tire 2.

[0096] Each isolation layer 22 is located axially inside the sidewall 6. Specifically, the isolation layer 22 is laminated on the second cord body 42a axially inside the sidewall 6. In other words, the isolation layer 22 of the tire 2 is laminated on the outermost cord body of at least one cord body of the tire carcass 12 axially inside the sidewall 6.

[0097] One end of the isolation layer 22 is located axially inside the end of the belt 14. The other end of the isolation layer 22 is located radially inside the outer end of the triangular rubber 36.

[0098] The separator layer 22 is located radially inward at the end of the first fold-back portion 40b between the second cord body 42a and the first fold-back portion 40b, and radially inward at the outer end of the triangular rubber 36 between the second cord body 42a and the triangular rubber 36. The separator layer 22 is made of cross-linked rubber. The separator layer 22 is harder than the tire sidewall 6.

[0099] In the tire 2 of the present invention, the isolation layer 22 is not an essential element. It is also possible to omit the isolation layer 22 from the tire 2.

[0100] Figure 3 A portion of the outline of the outer surface 2G of the tire 2 is shown in a meridional cross-section. The outline of the outer surface 2G is represented by an imaginary outer surface assumed to be free of grooves, patterns, text, or other decorations. Although not described in detail, in this invention, the outline of the outer surface 2G is obtained, for example, by measuring the shape of the outer surface of the tire 2 using a displacement sensor while the tire 2 is assembled to the rim R, the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted.

[0101] Figure 3 The outline of the outer surface 2G shown represents the shape of the outer surface of the tire 2 in its standard state. The outline of the outer surface 2G, represented by the outline, has a shape that is symmetrical with respect to the equatorial plane.

[0102] The outer surface 2G of the tire 2 has a tread surface 60 and a pair of sidewalls 62 connected to the tread surface 60. The tread surface 60 is divided into seven parts arranged axially. The tread surface 60 has a crown portion 64, a pair of middle portions 66, a pair of shoulder portions 68, and a pair of corner portions 70 as the seven parts.

[0103] The crown portion 64 is located axially at the center. The equatorial plane intersects the crown portion 64. A pair of intermediate portions 66 are located axially outside the crown portion 64. The reference numeral CM indicates the boundary between the crown portion 64 and the intermediate portions 66. A pair of shoulder portions 68 are located axially outside the intermediate portions 66. The reference numeral MS indicates the boundary between the intermediate portions 66 and the shoulder portions 68. A pair of corner portions 70 are located axially outside the shoulder portions 68. The reference numeral SC indicates the boundary between the shoulder portions 68 and the corner portions 70.

[0104] The crown portion 64 is the part located at the center of the axial direction. The corner portion 70 is the part located at the outermost point of the axial direction. The middle portion 66 and the shoulder portion 68 are the portions located between the crown portion 64 and the corner portion 70.

[0105] As described above, corner 70 is the outermost portion located axially. Corner 70 connects to sidewall 62. The location indicated by reference numeral CS is the boundary between corner 70 and sidewall 62. Boundary CS is also the end of tread surface 60.

[0106] like Figure 3 As shown, the boundary TS between the outer surface 4G of the tread 4 and the outer surface 6G of the sidewall 6 is contained in the corner 70. In this tire 2, the outer surface 4G of the tread 4 is contained in the tread surface 60. The outer surface 2G of the tire 2 may also be configured such that the boundary TS between the outer surface 4G of the tread 4 and the outer surface 6G of the sidewall 6 coincides with the end CS of the tread surface 60.

[0107] In this tire 2, in the radial section, the outlines of the crown portion 64, the middle portion 66, the shoulder portion 68, and the corner portion 70 are represented by arcs.

[0108] The outline of the crown portion 64 is represented by an arc centered on the equatorial plane. Figure 3 In the diagram, arrow TR1 represents the radius of the arc that outlines the crown portion 64.

[0109] The outline of the middle portion 66 is represented by an arc tangent to the arc representing the outline of the crown portion 64. Figure 3 In the diagram, arrow TR2 represents the radius of the arc representing the outline of the middle portion 66. The arc representing the outline of the middle portion 66 is tangent to the arc representing the outline of the crown portion 64 at the boundary CM. The boundary CM is the point of tangency between the arc representing the outline of the middle portion 66 and the arc representing the outline of the crown portion 64.

[0110] The outline of the shoulder portion 68 is represented by an arc tangent to the arc representing the outline of the middle portion 66. Figure 3 In the diagram, arrow TR3 represents the radius of the arc representing the outline of the shoulder portion 68. The arc representing the outline of the shoulder portion 68 is tangent to the arc representing the outline of the middle portion 66 at the boundary MS. The boundary MS is the point of tangency between the arc representing the outline of the shoulder portion 68 and the arc representing the outline of the middle portion 66.

[0111] The outline of corner 70 is represented by an arc tangent to the arc representing the outline of shoulder 68. Figure 3 In the diagram, arrow TRc represents the radius of the arc representing the outline of corner 70. The arc representing the outline of corner 70 is tangent to the arc representing the outline of shoulder 68 at boundary SC. Boundary SC is the point of tangency between the arc representing the outline of corner 70 and the arc representing the outline of shoulder 68. The arc representing the outline of corner 70 is tangent to the outline of sidewall 62 at boundary CS. Boundary CS is the point of tangency between the arc representing the outline of corner 70 and the outline of sidewall 62.

[0112] On the outline of the outer surface 4G of the tread 4, the arc representing the outline of the crown portion 64 is represented by the arc with the longest overlap with the outline, originating from the equator Eq. The arc representing the outline of the middle portion 66 is represented by the arc that is tangent to the end of the arc representing the outline of the crown portion 64, and has the longest overlap with the outline, originating from that end. The end of the arc representing the outline of the crown portion 64 is one end of the arc representing the outline of the middle portion 66, and is the boundary CM between the crown portion 64 and the middle portion 66. The arc representing the outline of the shoulder portion 68 is represented by the arc that is tangent to the other end of the arc representing the outline of the middle portion 66, and has the longest overlap with the outline, originating from that other end. The other end of the arc representing the outline of the middle portion 64 is one end of the arc representing the outline of the shoulder portion 68, and is the boundary MS between the middle portion 66 and the shoulder portion 68. The arc representing the outline of corner 70 is represented by an arc that is tangent to the other end of the arc representing the outline of shoulder 68, and has the longest overlap with the outline line from that other end. The other end of the arc representing the outline of shoulder 68 is the end of one of the arcs representing the outline of corner 70, and is the boundary SC between shoulder 68 and corner 70. The other end of the arc representing the outline of corner 70 is the end CS of tread surface 60, and is the boundary CS between tread surface 60 and sidewall 62.

[0113] In this tire 2, the radius TR1 of the arc representing the outline of the crown portion 64 is greater than the radius TR2 of the arc representing the outline of the middle portion 66. The radius TR2 of the arc representing the outline of the middle portion 66 is greater than the radius TR3 of the arc representing the outline of the shoulder portion 68. Furthermore, the radius TR3 of the arc representing the outline of the shoulder portion 68 is greater than the radius TRc of the arc representing the outline of the corner portion 70.

[0114] Of the seven portions constituting the tread surface 60, the arc representing the outline of the crown portion 64 located at the axial center has the largest radius TR1, and the arc representing the outline of the outermost corner portion 70 located at the axial center has the smallest radius TRc. Radius TRc is smaller than radius TR1. Specifically, the ratio of radius TRc to radius TR1, TRc / TR1, is 0.020 or more and 0.040 or less.

[0115] In two axially adjacent portions, the arc representing the outline of the portion located on the outer side of the axis has a smaller radius than the arc representing the outline of the portion located on the inner side of the axis.

[0116] Figure 4 An example of the contact patch of tire 2 is schematically shown. Figure 4In the diagram, the double arrows ADe indicate directions corresponding to the axial direction of tire 2. The double arrows CDe indicate directions corresponding to the circumferential direction of tire 2. Furthermore, for ease of explanation, the dimensions of the contact surface will be represented by the dimensions of tire 2 below.

[0117] The contact patch is obtained by applying a specified load to a tire 2, which is in a state where the tire 2 is assembled on the rim R, filled with air, and the internal pressure of the tire 2 is adjusted, and bringing the tire 2 into contact with a flat surface, using a tire contact patch shape measuring device (not shown), and tracing the contour of the contact patch. Figure 4 The image shown is of the ground plane. The shape of the ground plane is determined based on this image. In cases where the ground plane includes sections interrupted by trenches, these sections are connected with straight lines to trace the outline of the ground plane.

[0118] When the tire 2 reaches the contact patch, it is positioned with its axis parallel to the road surface. The aforementioned load is applied to the tire 2 in a direction perpendicular to the road surface. In other words, a longitudinal load is applied to the tire 2 with the camber angle set to 0°.

[0119] exist Figure 4 In the attached drawing, the location indicated by reference numeral CE is the axial outer end of the grounding surface (also referred to as the grounding end). In this invention, the axial outer end of the grounding surface (hereinafter referred to as the grounding end CE) is determined in the grounding surface between the tire 2 and the plane, obtained by applying a longitudinal load of 75% of the normal load to the tire 2 in its standard state and bringing the tire 2 into contact with the plane. The position on the outer surface 2G of the tire 2 corresponding to this grounding end CE is the grounding reference end. Figure 3 In the attached diagram, the location indicated by the PE symbol is the ground reference terminal.

[0120] exist Figure 4 In the diagram, the double arrow Wc indicates the grounding width of the grounding plane. The grounding width Wc is the axial distance from one grounding terminal CE to the other grounding terminal CE. Figure 3 The length measured along the tread surface 60 in the shown meridional section from the ground reference end PE on one side to the ground reference end PE on the other side is consistent with the ground width Wc.

[0121] exist Figure 3 In the diagram, the double arrow Wa represents the axial width of the contact patch in tire 2. The axial width Wa is the axial distance in tire 2 under standard conditions from one contact patch end PE to the other contact patch end PE. The tread surface 60 is curved in an outward bulging manner. The axial width Wa of the contact patch is shorter than the aforementioned contact patch width Wc.

[0122] like Figure 3As shown, the ground reference terminal PE is located between the aforementioned position P70 and the boundary SC of the shoulder portion 68 and the corner portion 70 (in other words, the outer end SC of the shoulder portion 68). Position P70 is located between the boundary MS of the middle portion 66 and the shoulder portion 68 (in other words, the inner end MS of the shoulder portion 68) and the ground reference terminal PE.

[0123] exist Figure 3 In the diagram, double arrow RW1 represents the axial distance from the equatorial plane to the boundary CM between the crown portion 64 and the intermediate portion 66. Double arrow RW2 represents the axial distance from the boundary CM between the crown portion 64 and the intermediate portion 66 to the boundary MS between the intermediate portion 66 and the shoulder portion 68. Double arrow RW3 represents the axial distance from the boundary MS between the intermediate portion 66 and the shoulder portion 68 to the ground reference end PE.

[0124] Although not described in detail, Figure 1 The tire 2 shown is manufactured using a known manufacturing method. Although not shown, the tire 2 is prepared in an uncured state by combining components such as the tread 4 and sidewall 6. The tire 2 is obtained by pressurizing and heating the tire in a mold. The outer surface 2G of the tire 2 is shaped using a mold.

[0125] For the formation of the strap 16, use Figure 5 The shown is a strap 72. The strap 72 is strip-shaped. The strap 72 includes one or more strap cords 56. Figure 5 The belt strip 72 shown includes five belt cords 56. These belt cords 56 are arranged along the width direction of the belt strip 72 and extend along the length direction of the belt strip 72. The belt strip 72 is a cord arrangement formed by multiple belt cords 56.

[0126] The strap 72 is wound into a spiral shape to form the strap 16. Therefore, as described above, the strap 16 includes a strap cord 56 wound into a spiral shape.

[0127] During the formation of the belt 16, a specified load is applied to the belt cord 56 while the belt cord 56 is wound into a spiral shape. The tension generated by applying the load to the belt cord 56 acts as a restraining force on the tire 2, as described later.

[0128] In this tire 2, the radius TR1 of the arc representing the outline of the crown portion 64 is at least 5 times the axial width Wa of the contact patch in the tire 2. This results in a tread 4 with a flat outer surface 4G. This reduces the contact pressure at the crown portion 64, thereby reducing mechanical fatigue of the tread 4. The tread 4 also has a beneficial effect on rolling resistance. It helps to suppress the influence on rolling resistance. From this viewpoint, the radius TR1 is preferably at least 5.5 times the axial width Wa.

[0129] The radius TR1 is 7 times or less than the axial width Wa. This prevents the crown portion 64 from concave radially inward, thus suppressing excessive increase in contact pressure at the shoulder portion 68. The tire 2 can maintain good wear resistance. From this perspective, the radius TR1 is preferably 6.5 times or less than the axial width Wa.

[0130] As mentioned above, a flat tread surface is detrimental to high-speed durability. However, in this tire 2, the shrinkage rate of the belt cord 56 at the shoulder portion of the tread section T is taken into consideration. Specifically, the shrinkage rate SRs of the belt cord 56 at position P70, corresponding to 70% of the maximum width SW of the tire 2 in its standard state, is more than 70% and less than 130% of the shrinkage rate SRc of the belt cord 56 at the equatorial plane of the tire 2. In this tire 2, the shrinkage rate of the belt cord 56 at the shoulder portion is set to the same extent as the shrinkage rate of the belt cord 56 at the crown portion. The movement of the shoulder portion is sufficiently restrained. The belt 16, together with the belt 14 in which the steel cords are set as belt cords 50, can sufficiently help restrain the movement of the tread section T.

[0131] The belt 14 and belt 16 of this tire 2 have a significant effect on tires designed for use at speeds of 270 km / h and above, in other words, tires with speed ratings of W and above. This tire 2 can achieve improved high-speed durability.

[0132] Restraining the movement of the tread section T also helps reduce rolling resistance. This tire 2 can improve high-speed durability while suppressing the impact on rolling resistance.

[0133] As described above, the shrinkage rate SRs of the belt cord 56 at position P70 is 70% or more and 130% or less of the shrinkage rate SRc of the belt cord 56 at the equatorial plane of the tire 2. In other words, the ratio SRs / SRc of the shrinkage rate SRs of the belt cord 56 to the shrinkage rate SRc of the belt cord 56 is 70% or more and 130% or less. From the viewpoint that the belt 16 can effectively help restrain the tread T, the ratio SRs / SRc is preferably 80% or more and 120% or less, more preferably 90% or more and 110% or less, and even more preferably 95% or more and 105% or less.

[0134] In this invention, the shrinkage rate SRc of the band cord 56 at the equatorial plane is measured within the band cord 56 encompassing a region with an axial width of 5% of the maximum width SW centered on the equatorial plane. The shrinkage rate SRs of the band cord 56 at position P70 is measured within the band cord 56 encompassing a region with an axial width of 5% of the maximum width SW centered on position P70.

[0135] exist Figure 4The dotted line LP extending circumferentially is the centerline of the grounding width Wc of the ground plane. The centerline LP of tire 2 corresponds to the equatorial plane of tire 2. The double arrow C100 is the length of the intersection line between the plane including the centerline LP and the ground plane. The length of this intersection line C100 is the center grounding length at the center of the grounding width Wc of the ground plane.

[0136] The solid line LM is a straight line passing through the grounding terminal CE and parallel to the center line LP. The solid line L80 is a straight line located between LM and LP, and parallel to both LM and LP. The double arrow A100 is the axial distance from the center line LP to the straight line LM. Distance A100 is equivalent to half the grounding width Wc of the ground plane. The double arrow A80 is the axial distance from the center line LP to the straight line L80. Figure 4 In this context, the ratio of distance A80 to distance A100 is 80%. That is, the straight line L80 represents a position corresponding to 80% of the grounding width Wc. The double arrow C80 is the length of the intersection line between the plane including the straight line L80 and the grounding surface. In this tire 2, the length C80 of this intersection line is the reference grounding length at the position corresponding to 80% of the grounding width Wc of the grounding surface.

[0137] In the contact patch of tire 2 under standard conditions, the ratio of the center contact length C100 at the center of the contact patch width Wc to the reference contact length C80 at the position corresponding to 80% of the contact patch width Wc is the shape index F80.

[0138] The shape index F80 of the tire 2 is preferably 1.10 or higher and 1.40 or lower. This provides a contact patch shape for the tire 2 that can suppress the effects on high-speed durability and rolling resistance. The tire 2 maintains good high-speed durability and low rolling resistance. Since wear at the tread portion is suppressed, the tire 2 also maintains good wear resistance. From this viewpoint, the shape index F80 is more preferably 1.15 or higher and 1.35 or lower, and even more preferably 1.20 or higher and 1.30 or lower. A particularly preferred shape index F80 is 1.25.

[0139] The ratio TR2 / TR1, which represents the radius TR2 of the arc representing the outline of the middle portion 66, to the radius TR1 of the arc representing the outline of the crown portion 64, is preferably 0.35 or more and 0.40 or less. This results in a tread 4 having a flat outer surface 4G. This reduces the ground pressure at the crown portion 64, thereby reducing mechanical fatigue of the tread 4. The tread 4 has a beneficial effect on rolling resistance. It helps to suppress the influence on rolling resistance. From this viewpoint, a ratio TR2 / TR1 of 0.37 or more and 0.39 or less is more preferable.

[0140] The ratio TR3 / TR1, which is the radius TR3 of the arc representing the outline of the tire shoulder 68, to the radius TR1 of the arc representing the outline of the tire crown 64, is preferably 0.09 or more and 0.13 or less. This results in a curved tire shoulder 68. This suppresses the increase in localized ground pressure at the contact patch. The tire 2 can suppress wear at the contact patch and reduce high-speed durability. The tire 2 can suppress not only the impact on rolling resistance but also the impact on wear resistance, and can achieve improved high-speed durability. From this viewpoint, a ratio TR3 / TR1 of 0.10 or more and 0.12 or less is more preferable.

[0141] However, when a flat tread is used, under conditions of high load on the tire shoulder, such as during extreme driving or high-speed driving, there is a tendency for localized increases in ground contact pressure at the tire shoulder. In this situation, abnormal heating occurs in the tire shoulder, which may lead to wear at the ground contact point and reduced high-speed durability.

[0142] However, in this tire 2, by setting the ratio TR2 / TR1 to 0.35 or higher and 0.40 or lower as described above, a tread 4 with a flat outer surface 4G is formed, which helps to suppress the influence on rolling resistance. By setting the ratio TR3 / TR1 to 0.09 or higher and 0.13 or lower, a curved shoulder 68 is formed, which helps to reduce wear at the contact patch and decrease high-speed durability. In particular, by setting the ratio TR2 / TR1 to 0.35 or higher and 0.40 or lower, and the ratio TR3 / TR1 to 0.09 or higher and 0.13 or lower, the radius TR3 of the arc representing the outline of the shoulder 68 in this tire 2 can be set to be smaller than that of conventional tires. In other words, the shoulder 68 is more rounded than conventional shoulders. This suppresses the increase in localized contact pressure at the contact patch. This tire 2 can suppress wear at the contact patch and decrease high-speed durability. This tire 2 not only suppresses the impact on rolling resistance but also suppresses the impact on wear resistance, and achieves improved high-speed durability. From this point of view, the ratio of TR2 / TR1 is 0.35 or higher and 0.40 or lower, the ratio of TR3 / TR1 is preferably 0.09 or higher and 0.13 or lower, the ratio of TR2 / TR1 is 0.37 or higher and 0.39 or lower, and the ratio of TR3 / TR1 is more preferably 0.10 or higher and 0.12 or lower.

[0143] The ratio RW1 / Wa of the axial distance RW1 from the equatorial plane to the boundary CM between the crown portion 64 and the intermediate portion 66, relative to the axial width Wa of the contact patch, is preferably 0.15 or more and 0.25 or less. Therefore, the flat profile of the crown portion 64 in the outline of the outer surface of the tread 4, i.e., the tread surface 60, effectively contributes to the reduction of rolling resistance. From this viewpoint, a ratio of RW1 / Wa of 0.18 or more and 0.22 or less is more preferable.

[0144] The ratio of the axial distance RW3 from the boundary MS between the middle portion 66 and the shoulder portion 68 to the ground reference end PE to the axial width Wa, RW3 / Wa, is preferably 0.10 or more and 0.15 or less. Therefore, in the profile of the tread surface 60, the curved profile of the shoulder portion 68 can effectively suppress the increase of localized grounding pressure at the grounding end. From this viewpoint, a ratio of 0.10 or more and 0.13 or less is more preferable than RW3 / Wa.

[0145] In this tire 2, a ratio of RW1 / Wa of 0.15 or higher and 0.25 or lower, and a ratio of RW3 / Wa of 0.10 or higher and 0.15 or lower are preferred. This allows the flat profile of the crown portion 64 in the tread surface 60 to effectively reduce rolling resistance, while the curved profile of the shoulder portion 68 effectively increases the localized ground pressure at the contact patch. This tire 2 not only suppresses the impact on rolling resistance but also suppresses the impact on wear resistance, and improves high-speed durability. From this viewpoint, a ratio of RW1 / Wa of 0.18 or higher and 0.22 or lower, and a ratio of RW3 / Wa of 0.10 or higher and 0.13 or lower are more preferred.

[0146] Figure 6 It shows Figure 3 Part of the outline. Figure 6 The solid line AR1 is the extension of the arc representing the outline of the crown portion 64. The extension AR1 is an arc with a center on the equatorial plane and a radius TR1 that passes through the equator Eq. The solid line ARb is an arc with a center on the equatorial plane and passes through the equator Eq and the ground reference end PE. Figure 6 The arrow TRb represents the radius of the arc shown by the solid line ARb.

[0147] In the radial cross-section of the tire 2 under standard conditions, the ratio TR1 / TRb of the radius TR1 of the arc representing the profile of the crown portion 64 to the radius TRb of the arc having a center on the equatorial surface of the tire 2 and passing through the equator Eq and the ground contact reference end PE of the tire 2 is preferably 1.66 or more and 1.96 or less. Therefore, in the profile of the tread surface 60, the flat profile of the crown portion 64 effectively contributes to reducing rolling resistance, and the curved profile of the shoulder portion 68 effectively helps to suppress the increase of localized ground pressure at the ground contact end. This tire 2 can not only suppress the influence on rolling resistance but also suppress the influence on wear resistance, and can achieve improved high-speed durability. From this viewpoint, a TR1 / TRb ratio of 1.70 or more and 1.90 or less is more preferred, and a ratio of 1.75 or more and 1.85 or less is even more preferred.

[0148] As can be seen from the above description, according to the present invention, a tire 2 can be obtained that can improve high-speed durability while suppressing the influence on rolling resistance. The present invention has a significant effect on tires 2 with a speed symbol of W or higher.

[0149] [Example]

[0150] The present invention will be further described in detail below through embodiments, etc., but the present invention is not limited to these embodiments.

[0151] [Examples and Comparative Examples]

[0152] Obtain Figure 1 The following are examples and comparative examples of tires with the basic structure shown and the specifications shown in Table 1. Two tires of different sizes were prepared for each example (tire size = 255 / 40ZR20 and 285 / 35R20).

[0153] In the comparative example, the belt cord is wound into a spiral shape while a load is applied to a flat roller to form a pre-formed belt. Then, the portion of the roller corresponding to the tire crown is expanded, and the portion corresponding to the tire shoulder is reduced in diameter to adjust the shape of the belt. The belt cord at position P70 is not under tension, and the shrinkage rate SRs is 0%.

[0154] In contrast, in this embodiment, a roller with a specific profile that takes into account the shape of the belt in the tire is used to wind the belt cords from one end to the other under a certain tension, thereby forming the belt. Thus, the belt is constructed in a manner that makes the shrinkage rate SRs of the belt cord at position P70 the same as the shrinkage rate SRc of the belt cord at the equatorial plane. The shrinkage rate SRc of the belt cord at the equatorial plane is the same as in the comparative example.

[0155] [Rolling resistance]

[0156] The rolling resistance coefficient (RRC) of a prototype tire (tire size = 285 / 35R20) was determined using a rolling resistance testing machine when traveling at a speed of 80 km / h on a roller under the following conditions. The results are shown in the "RRC" column of Table 1 below, with the comparative example being 100. The higher the value, the lower the rolling resistance of the tire.

[0157] Rim width: 20×10.0J

[0158] Internal pressure: 210 kPa

[0159] Longitudinal load: 6.28kN

[0160] [High-speed durability]

[0161] A prototype tire (tire size = 285 / 35R20) was assembled onto a rim (size = 20 × 10.5J) and inflated with air to a pressure of 200 kPa. The tire was mounted on a roller-type driving test machine with a camber angle set to 2 degrees. A longitudinal load of 4.86 kN was applied to the tire, and the tire was driven on the rollers (roller diameter = 5.0 m) with progressively increasing speeds until the tire could no longer move. The results are shown in the "High-Speed ​​Durability" column of Table 1 below, with Comparative Example 1 as 100. A higher value indicates better high-speed durability.

[0162] [Resistance to uneven wear]

[0163] A prototype tire (tire size = 255 / 40ZR20) was assembled onto a rim (size = 20 × 10.0J) and inflated with air to an internal pressure of 220 kPa. The tire was then mounted on a roller-type driving test machine. A longitudinal load of 7.20 kN was applied to the tire, and the tire was driven at 100 km / h on a roller (roller diameter = 5.0 m) with an asphalt surface. After 30 km of driving, the tread surface profile was measured using laser scanning, and the wear at the tire shoulder was measured. The results are shown in the "Uneven Wear Resistance" column of Table 1 below, with Comparative Example 1 as 100. A higher value indicates better high-speed durability.

[0164] [Grounding voltage distribution]

[0165] A prototype tire (tire size = 255 / 40ZR20) was assembled onto a rim (size = 20 × 10.0J) and filled with air to achieve an internal pressure of 200 kPa. The tire was mounted on a ground pressure testing machine with a camber angle set to 2 degrees. The ground pressure distribution was measured under a longitudinal load of 6.40 kN. The total ground pressure in the ground width direction at the tire shoulder was obtained. The results are shown in the "Ground Pressure Distribution" column of Table 1 below, with Comparative Example 1 as 100. A smaller value indicates a lower total ground pressure.

[0166] [Table 1]

[0167]

[0168] As shown in Table 1, in the embodiments, not only was the impact on rolling resistance suppressed, but the impact on wear resistance was also suppressed, and high-speed durability was improved. Based on these evaluation results, the superiority of the present invention is evident.

[0169] [Industrial Applicability]

[0170] The technology described above, which can improve high-speed durability while suppressing the impact on rolling resistance, can be applied to various tires.

[0171] [Postscript]

[0172] The present invention includes the forms shown below.

[0173] [1] A tire comprising: a pair of beaded tires, a tire carcass disposed between the pair of beaded tires, a tread located radially outside the tire carcass and in contact with the road surface, a belt located radially inside the tread and radially outside the tire carcass, and a belt located radially between the tread and the belt, wherein the tire is in a standard state when it is assembled on a regular rim and the tire's internal pressure is adjusted to 92% of the standard internal pressure and no load is applied to the tire; the outer surface of the tread comprises: a crown portion located axially at the center, a pair of intermediate portions located axially outside the crown portion, and a pair of shoulder portions located axially outside the intermediate portions; in the radial section of the tire in the standard state, the outline of the crown portion is represented by an arc having a center on the equatorial plane, the outline of each intermediate portion is represented by an arc tangent to the arc representing the outline of the crown portion, and the outline of each shoulder portion is represented by an arc tangent to the arc representing the outline of the intermediate portion. The arc tangent to the arc represents the position on the outer surface of the tire corresponding to the axial outer end of the tire's contact surface obtained by applying a longitudinal load of 75% of the normal load to the tire in the standard state and causing the tire to contact the plane. The axial distance from one of the ground reference ends to the other ground reference end in the tire is the axial width Wa of the contact surface. The radius TR1 of the arc representing the outline of the tire crown is more than 5 times and less than 7 times the axial width Wa. The belt has belt cords that are inclined relative to the circumference. The belt cords are steel cords. The belt has belt cords that extend substantially in the circumference. The belt cords are organic fiber cords. The shrinkage rate of the belt cords at the position corresponding to 70% of the maximum width of the tire in the standard state is more than 70% and less than 130% of the shrinkage rate of the belt cords at the equatorial plane of the tire.

[0174] [2] According to the tire described in [1] above, in the ground contact surface of the tire, the ratio of the center ground contact length at the center of the ground contact width to the reference ground contact length at the position corresponding to 80% of the ground contact width of the ground contact surface is the shape index F80, and the shape index F80 is 1.10 or more and 1.40 or less.

[0175] [3] According to the tire described in [1] or [2] above, the ratio of the radius TR2 of the arc representing the outline of the middle part to the radius TR1 of the arc representing the outline of the crown part, TR2 / TR1, is 0.35 or more and 0.40 or less, and the ratio of the radius TR3 of the arc representing the outline of the shoulder part to the radius TR1 of the arc representing the outline of the crown part, TR3 / TR1, is 0.09 or more and 0.13 or less.

[0176] [4] The tire described in any one of [1] to [3] above, wherein the ratio of the axial distance RW1 from the equatorial plane to the boundary between the crown portion and the intermediate portion to the axial width Wa of the contact surface, RW1 / Wa, is 0.15 or more and 0.25 or less, and the ratio of the axial distance RW3 from the boundary between the intermediate portion and the shoulder portion to the ground reference end to the axial width Wa, RW3 / Wa, is 0.10 or more and 0.15 or less.

[0177] [5] According to any one of [1] to [4] above, in the meridional section of the tire in the above standard state, the ratio of the radius TR1 of the arc representing the outline of the crown portion to the radius TRb of the arc having a center on the equatorial plane of the tire and passing through the equator and the ground reference end of the tire, TR1 / TRb is 1.66 or more and 1.96 or less.

Claims

1. A tire comprising: a pair of beads, a carcass disposed between the pair of beads, a tread located radially outside the carcass and in contact with a road surface, a belt located radially inside the tread and radially outside the carcass, and a belt located radially between the tread and the belt, wherein, The standard condition of the tire is defined as follows: the tire is assembled on a standard rim, the tire's internal pressure is adjusted to 92% of the standard internal pressure, and no load is applied to the tire. The outer surface of the tread includes: a crown portion located at the axial center, a pair of intermediate portions located axially outside the crown portion, and a pair of shoulder portions located axially outside the intermediate portions. In the meridional section of the tire under the aforementioned standard condition, The outline of the tire crown is represented by an arc with a center on the equatorial plane. The outline of each of the intermediate portions is represented by an arc tangent to the arc representing the outline of the tire crown portion. The outline of each of the tire shoulders is represented by an arc tangent to the arc representing the outline of the middle portion. The position on the outer surface of the tire corresponding to the axial outer end of the tire's contact surface obtained by applying a longitudinal load of 75% of the normal load to the tire in the standard state, causing the tire to contact the plane, is the ground contact reference end. The axial distance from one ground contact reference end to the other ground contact reference end in the tire is the axial width Wa of the contact surface. The radius TR1 of the arc representing the outline of the tire crown is more than 5 times and less than 7 times the axial width Wa. The belt has belt cords that are inclined relative to the circumferential direction, and the belt cords are steel cords. The belt has belt cords that extend substantially circumferentially, and the belt cords are organic fiber cords. The shrinkage rate of the belt cord at a position corresponding to 70% of the maximum width of the tire in the standard state is more than 70% and less than 130% of the shrinkage rate of the belt cord at the equatorial plane of the tire.

2. The tire according to claim 1, wherein, In the tire's contact patch, the ratio of the center ground length at the center of the contact patch width to the reference ground length at a position corresponding to 80% of the contact patch width is a shape index F80. The shape index F80 is above 1.10 and below 1.

40.

3. The tire according to claim 1, wherein, The ratio of the radius TR2 of the arc representing the outline of the middle portion to the radius TR1 of the arc representing the outline of the crown portion, TR2 / TR1, is 0.35 or more and 0.40 or less. The ratio of the radius TR3 of the arc representing the outline of the tire shoulder to the radius TR1 of the arc representing the outline of the tire crown, TR3 / TR1, is 0.09 or more and 0.13 or less.

4. The tire according to claim 1, wherein, The ratio of the axial distance RW1 from the equatorial plane to the boundary between the crown portion and the intermediate portion to the axial width Wa of the contact surface, RW1 / Wa, is 0.15 or more and 0.25 or less. The ratio of the axial distance RW3 from the boundary between the middle portion and the shoulder portion to the ground reference end to the axial width Wa, RW3 / Wa, is 0.10 or more and 0.15 or less.

5. The tire according to claim 1, wherein, In the meridional section of the tire under the aforementioned standard condition, The ratio of the radius TR1 of the arc representing the outline of the tire crown to the radius TRb of the arc having a center on the equatorial plane of the tire and passing through the equator and the ground reference end of the tire, TR1 / TRb, is 1.66 or more and 1.96 or less.

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