pneumatic tires

Abstract

It exerts great cornering force under high lateral G-force conditions. [Solution] In a pneumatic tire (1), a bead inclination line L is defined as a line connecting the midpoint BM of a line connecting intersections Po, Pi where an imaginary circle VC with a radius of 30 mm, centered on the cross-sectional center GC of a bead core (5), intersects with the tire outer surface and the tire inner surface, and the cross-sectional center GC of the bead core (5). In a tire meridian cross section in a first state in which the pneumatic tire (1) is mounted on a regular rim, adjusted to an internal pressure of 230 kPa, and is placed in contact with a horizontal plane (GL) at a camber angle of 0° while being subjected to a vertical load of 70% of the maximum load capacity of the 230 kPa internal pressure, the angle between the bead inclination line L and the horizontal plane (GL) is defined as α1. In a tire meridian cross section in a second state in which a lateral load of 50% of the vertical load is applied to the tire in the first state, the angle between the bead inclination line of the bead portion on the side of the bead portion in the lateral load application direction and the horizontal plane is defined as α2. The bead inclination angle change rate specified by (α1-α2) / α1 is 5% or less.

Description

[Technical Field]

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

[0002] Pneumatic tires with a low aspect ratio (for example, an aspect ratio of 45% or less) are often fitted to vehicles capable of high-speed driving, and are required to have excellent cornering performance in high-speed turning conditions (hereinafter sometimes referred to as high lateral G conditions) where they are subjected to large lateral acceleration (lateral G). Looking at this as a characteristic of the tire itself, it is necessary for the tire to exert a large cornering force in high lateral G conditions. Related technology is disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-078762 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional pneumatic tires, when large lateral G forces are applied, the shoulder side of the tread on the inside of a corner lifts up, reducing the contact area and preventing sufficient cornering force under high lateral G forces.

[0005] The present invention has been devised in view of the above problems, and has as its main object to provide a pneumatic tire that is capable of exerting a large cornering force under high lateral G conditions. [Means for solving the problem]

[0006] The present invention provides a pneumatic tire comprising a tread portion, a pair of sidewall portions, and a pair of bead portions each having a bead core disposed therein, wherein a bead inclination line is defined as a line connecting the midpoint of a line connecting the intersections where an imaginary circle having a radius of 30 mm and centered at the center of the cross section of the bead core intersects with the outer surface of the tire and the inner surface of the tire, and the line connecting the center of the cross section of the bead core, and the pneumatic tire is mounted on a regular rim, and the internal pressure is adjusted to 230 kPa, and the tire is capable of withstanding 70% of the maximum load capacity of the internal pressure of 230 kPa. In a tire meridian cross section in a first state in which a vertical load is applied and the tire is in contact with a horizontal surface at a camber angle of 0°, the angle between the bead inclination line and the horizontal plane is α1, and in a tire meridian cross section in a second state in which a lateral load that is 50% of the vertical load is applied in the first state, the angle between the bead inclination line of the bead portion of the pair of bead portions that is closer to the lateral load application direction is α2. The bead inclination angle change rate determined by (α1-α2) / α1 is 5% or less. [Effects of the Invention]

[0007] By adopting the above-described configuration, the pneumatic tire of the present invention is able to exert a large cornering force under high lateral G conditions. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a pneumatic tire showing one embodiment of the present invention. [Figure 2] 2 is a partial cross-sectional view of the pneumatic tire of FIG. 1 in a first state. [Figure 3] 2 is a partial cross-sectional view of the pneumatic tire of FIG. 1 in a second state. FIG. [Figure 4] FIG. 2 is a partial cross-sectional view of the pneumatic tire of FIG. 1 in a normal state. [Figure 5] FIG. 4 is an enlarged view of a main part of a bead portion in a first state. [Figure 6] FIG. 6 is an enlarged view of a portion VI in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The drawings include exaggerated representations and representations that differ from the dimensional ratios of the actual structure to facilitate understanding of the present invention. Furthermore, when there are multiple embodiments, the same or common elements are designated by the same reference numerals throughout the specification, and redundant explanations will be omitted.

[0010] FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis (not shown) of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire 1") showing one embodiment of the present invention. The tire 1 of this embodiment is suitably used, for example, as a pneumatic tire for passenger cars. Pneumatic tires for passenger cars include at least tires of sizes listed in Chapter A "Passenger Car Tires" of the JATMA YEAR BOOK.

[0011] FIG. 1 is a cross-sectional view of a tire 1 in a normal state. In this specification, "normal state" refers to a state in which, in the case of a pneumatic tire for which various standards are established, the tire is mounted on a normal rim R, adjusted to a normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal state refers to a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in a normal state. Furthermore, for components that cannot be measured in a normal state (for example, internal structural materials of the tire 1), values ​​are measured by placing the tire 1 in a state as close to the normal state as possible.

[0012] In this specification, a "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which the tire is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0013] The regular rim R has a rim flange Rf. In this specification, the rim flange Rf is the portion of the regular rim R that is located radially outward from the bead base line BL. The bead base line BL is an imaginary straight line that extends parallel to the tire axial direction and defines the rim diameter Rr (see JATMA, etc.) of the regular rim R. The rim flange Rf in this embodiment includes a base portion Rf1 that extends almost straight outward in the tire radial direction from the bead base line BL, and a curved portion Rf2 that is connected to the radially outward side of the base portion Rf1 and curves in an arc that convex outward in the tire radial direction.

[0014] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0015] The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4 each having a bead core 5 disposed therein.

[0016] The tire 1 preferably has a low aspect ratio. A tire 1 with a low aspect ratio has a small tire section height and high lateral rigidity, which helps to generate a large cornering force. Although not particularly limited, the tire 1 preferably has an aspect ratio of 45% or less.

[0017] The aspect ratio of a tire 1 is the percentage of the ratio of the tire's section height to the tire's section width. The tire's section width is the width excluding the patterns, lettering, etc. on the tire's sidewall portions 3 from the total width of the tire. The total width of the tire is the linear distance in the tire axial direction between the sidewall portions 3, 3, including all patterns, lettering, etc. on the sidewall portions 3. The tire's aspect ratio is usually indicated on the sidewall portions 3.

[0018] A pair of sidewall portions 3 extend radially inward from the tread portion 2. A bead portion 4 is formed on the radially inner side of each sidewall portion 3.

[0019] A bead core 5 is embedded in each bead portion 4. The bead core 5 is made of a non-extensible material and serves to firmly mount the bead portion 4 of the tire 1 to a regular rim R. The bead core 5 of this embodiment is formed in a ring shape by winding steel wire in multiple rows and multiple layers.

[0020] In this embodiment, the tire 1 includes a carcass 6 extending toroidally between a pair of bead portions 4, 4, and a belt layer 7 arranged outside the carcass 6 in the tire radial direction and inside the tread portion 2.

[0021] The carcass 6 is made up of, for example, one or more carcass plies 6A. In this embodiment, the carcass 6 is made up of two carcass plies 6A. In another aspect, the carcass 6 may be made up of one carcass ply.

[0022] The carcass ply 6A includes a plurality of carcass cords and a topping rubber covering the cords (not shown). The carcass cords are made of organic fiber such as polyester, aramid, or rayon. The carcass cords are preferably arranged at an angle of 70 to 90 degrees, more preferably 80 to 90 degrees, relative to the tire equator Co. This gives the carcass 6 of this embodiment a radial structure.

[0023] In this embodiment, the carcass ply 6A includes, for example, a main body portion 6a and a pair of turned-up portions 6b. The main body portion 6a extends, for example, in a toroidal shape so as to straddle the pair of bead cores 5. Each turned-up portion 6b is, for example, connected to the main body portion 6a, turned around the bead core 5 from the axially inner side to the outer side, and further extends radially outward.

[0024] In this embodiment, the radially outer end of each turned-up portion 6b is located radially inward of the tire maximum width position M. The tire maximum width position M is specified as the outermost position in the tire axial direction of the main body portion 6a of the carcass ply 6A.

[0025] In each bead portion 4, a bead apex rubber 8 is disposed between the main portion 6a and the turned-up portion 6b of the carcass ply 6A. The bead apex rubber 8 is formed of, for example, a hard rubber composition, and extends in a tapered shape outward in the tire radial direction from the bead core 5. The bead apex rubber 8 helps to increase the bending rigidity of the bead portion 4.

[0026] The belt layer 7 is disposed adjacent to the outer side in the tire radial direction of the carcass 6. The belt layer 7 of the present embodiment includes an outer belt ply 7A and an inner belt ply 7B located inward in the tire radial direction of the outer belt ply 7A.

[0027] Each of the outer belt ply 7A and the inner belt ply 7B includes a plurality of belt cords arranged at an angle of, for example, 15 to 45 degrees with respect to the tire circumferential direction, and a topping rubber covering the cords (not shown). As the belt cords, for example, steel cords are suitable.

[0028] Each of the outer belt ply 7A and the inner belt ply 7B extends, for example, further outward in the tire axial direction than the tread ground contact edge Te.

[0029] In this specification, the "tread edge" Te is defined as the axially outermost edge of the contact surface 2s of the tread portion 2 in a first state of the tire 1. The axial distance between a pair of tread edges Te, Te is the tread width TW, and the midpoint therebetween is the tire equator Co. In the tread portion 2, the side of the tread edge Te is the shoulder region, and the side of the tire equator Co is the crown region. The "first state" of the tire 1 is a state that statically and simply reproduces the straight-ahead running state of the tire 1, in which the tire 1 is mounted on a regular rim R, adjusted to an internal pressure of 230 kPa, and is placed in contact with a horizontal surface at a camber angle of 0° with a vertical load of 70% of the maximum load capacity of the internal pressure of 230 kPa. The tire 1 in this first state is partially shown in FIG. 2.

[0030] A band layer 9 may be provided radially outward of the belt layer 7 and inward of the tread portion 2. The band layer 9 includes, for example, band cords 9A made of organic fibers aligned at an angle of 5° or less with respect to the tire circumferential direction. In a more preferred embodiment, the band cords 9A are wound spirally in the tire circumferential direction. Such a band layer 9 serves to suppress deformation of the tread portion 2 during high-speed running and ensure stable high-speed running performance.

[0031] Fig. 2 shows a tire meridian cross section of the right side and ground contact side of the tire 1 in a first state. For ease of explanation, the normal rim R is not depicted in Fig. 2. In this specification, a bead inclination line L is defined to identify the state of deformation of the bead portion 4 of the tire 1.

[0032] The bead tilt line L is an imaginary line connecting the cross-sectional center GC of the bead core 5 with the midpoint BM of a line connecting the intersection points Pi and Po where an imaginary circle VC with a radius of 30 mm, centered at the cross-sectional center GC of the bead core 5, intersects with the tire outer surface and the tire inner surface. The radius of the imaginary circle VC is set to 30 mm in order to identify the deformation state of the bead portion 4 at a position radially outward of the height of the rim flange Rf of the regular rim R. For convenience, the cross-sectional center GC of the bead core 5 may be defined as the intersection point of a tire radial line passing through the center of the maximum width in the axial direction of the cross section of the bead core 5 and a tire axial line passing through the center of the maximum width in the radial direction of the bead core 5.

[0033] The angle α1 between the bead inclination line L and the horizontal plane GL (in FIG. 2, the acute angle between the bead inclination line L and a straight line GL' parallel to the horizontal plane GL) corresponds to the inclination of the bead portion 4 of the tire 1. Therefore, the angle α1 in the first state virtually indicates the deformation state of the bead portion 4 when the tire 1 is traveling straight.

[0034] Next, a second state is set in which a lateral load F that is 50% of the vertical load is applied to the tire 1 in the first state. FIG. 3, which corresponds to FIG. 2, shows a tire meridian cross section of the right side and ground contact side of the tire 1 in the second state, and the imaginary line indicates the outline of the bead portion 4 in the first state. The second state is a static and simplified reproduction of a high lateral G state in which a lateral acceleration of about 0.5 G acts on the tire.

[0035] In the second state of Fig. 3, the angle between the bead inclination line L of one of the pair of bead portions 4 on the side of the load direction of the lateral load F (see the arrow) and the horizontal plane GL (in Fig. 3, the acute angle between the bead inclination line L and a straight line GL' parallel to the horizontal plane GL) is set to α2. Therefore, the angle α2 in the second state virtually represents the deformation state of the bead portion 4 of the tire 1 in a high lateral G state.

[0036] In the tire 1 of the present invention, the bead inclination angle change rate specified by (α1−α2) / α1 using the angles α1 and α2 is set to 5% or less.

[0037] The inventors focused on the rate of change in the angle of the bead inclination line L before and after the application of a lateral load F as a parameter that affects lifting of the shoulder region of the tread portion 2 under high lateral G-forces. Specifically, they found that when a lateral force acts on the tread portion 2 during high-speed cornering, the greater the bending deformation of the bead portions 4 and the radially inner portions of the sidewall portions 3 (hereinafter referred to as "bead portions, etc.") in the tire's tire surface, the more likely the shoulder region of the tread portion 2 is to lift off the road surface. Therefore, the inventors newly defined the bead inclination angle change rate (α1-α2) / α1 as a parameter that represents the amount of bending deformation of the bead portions, etc. under high lateral G-forces. After conducting various experiments, they confirmed that by limiting the bead inclination angle change rate to 5% or less, lifting of the shoulder side of the tread portion 2 under high lateral G-forces is suppressed, thereby generating a large cornering force. In a particularly preferred embodiment, the bead inclination angle change rate may be 4% or less, or even 3% or less.

[0038] On the other hand, if the bead inclination angle change rate is too small, deformation of the bead portion and the like during tire running is extremely suppressed, and as a result, the impact input to the tread portion 2 is excessively transmitted to the regular rim R, which may result in a deterioration in ride comfort when going over a protrusion. Therefore, from this perspective, it is desirable that the bead inclination angle change rate be 1% or more, and more preferably 2% or more.

[0039] As an example, the bead inclination angle change rate may be preferably in the range of 1% to 5%, more preferably in the range of 1% to 3%, and particularly preferably in the range of 2% to 3%.

[0040] In FIG. 3, the bead inclination angle change rate is explained assuming that the lateral load F is applied to the right side. However, even if the lateral load F is applied to the left side, the left and right bead portions 4 are configured so that the same bead inclination angle change rate as in the example on the right side can be obtained.

[0041] The tire 1 of the present invention is not particularly limited in its specific configuration as long as it has such a bead inclination angle change rate. Preferred examples of specific configurations of the tire 1 of the present invention will be described below.

[0042] [Rim protector] 1 and 3, the tire 1 is provided with a rim protector 10 that protrudes axially outward and extends circumferentially in the tire, in the bead portion 4 on the side facing the load direction of the lateral load F. As shown in Fig. 1, the tire 1 of this embodiment is provided with a rim protector 10 in the bead portion 4 on both sides.

[0043] Figure 4 shows a meridian cross section of the tire bead portion 4 in a normal state. As shown in Figure 4, the rim protector 10 protrudes axially outward from the axially outer end RfT of the rim flange Rf of the normal rim R. The rim protector 10 prevents the rim flanges Rf from coming into contact with each other and being damaged when rim-mounted tires 1 are stacked on top of each other, and also helps prevent damage to the rim flange Rf from coming into contact with a curb or the like.

[0044] [Rim protector protrusion amount B] The rim protector 10 of this embodiment has an apex 11 that protrudes most outward in the axial direction of the tire. The rim protector 10 also has the largest rubber gauge at the apex 11. The rubber gauge is the thickness of the rubber portion measured from the outer surface of the carcass 6 in a direction perpendicular to the outer surface. Furthermore, the rim protector 10 of this embodiment is configured so that the rubber gauge continuously decreases from this apex 11 toward both the outer and inner sides in the radial direction of the tire.

[0045] The rim protector 10 has a protrusion amount B relative to the rim flange Rf. The protrusion amount B is the axial distance from the axial outer end RfT of the rim flange Rf to the apex 11 of the rim protector 10. The protrusion amount B of the rim protector 10 is preferably in the range of 1 to 10 mm, for example. If the protrusion amount B of the rim protector 10 is less than 1 mm, there is a risk that the rim flanges Rf will come into contact with each other and damage the genuine rim R when pneumatic tires assembled to genuine rims R are stacked together. On the other hand, if the protrusion amount B of the rim protector 10 exceeds 10 mm, the rubber volume of the rim protector 10 will be excessively large, which may deteriorate the rolling resistance of the pneumatic tire 1. From this perspective, the protrusion amount B of the rim protector 10 is more preferably 3 mm or more, and even more preferably 7 mm or less. In other words, the protrusion amount B is preferably 3 mm≦B≦7 mm.

[0046] [Height of rim protector peak C] The apex 11 of the rim protector 10 has a height C in the tire radial direction from the bead baseline BL. The height C of the apex 11 is preferably 20 mm or more, for example. If the height C of the apex 11 of the rim protector 10 is less than 20 mm, the step between the apex 11 and the rim flange Rf becomes too steep, and air flowing from the tread portion 2 may generate vortices around the rim flange Rf while the tire is running, which may worsen air resistance. On the other hand, if the height C of the apex 11 of the rim protector 10 is excessively large, the air flowing from the tread portion 2 may separate prematurely near the apex 11 while the tire is running, which may worsen air resistance. From this perspective, the height C of the apex 11 of the rim protector 10 is preferably equal to or less than the tire maximum width height HM, which is the tire radial height from the bead baseline BL to the tire maximum width position M. As an example, the height C of the apex 11 of the rim protector 10 is preferably 30 mm ± 5 mm.

[0047] [Length of rim protector contact area A] FIG. 5 shows an enlarged view of a main portion of the bead portion 4 in a meridian cross section of the tire in a first state. However, in FIG. 5, the rim flange Rf is drawn with imaginary lines. As shown in FIG. 5, the rim protector 10 has a contact area 20 that comes into contact with the rim flange Rf. In this embodiment, the contact area 20 includes a first area 21 that comes into contact with the base Rf1 of the rim flange Rf, and a second area 22 that comes into contact with the curved portion Rf2 of the rim flange Rf. In this way, the contact area 20 has a profile that follows the rim flange Rf.

[0048] The contact area 20 also has a contact edge 23, which is the axially outermost position of the tire. In this embodiment, the contact area 20 is in contact with the rim flange Rf continuously from the bead base line BL to the contact edge 23. The contact edge 23 of the contact area 20 is located on the curved portion Rf2 of the rim flange Rf, but is located axially more inward than the axially outer edge RfT of the rim flange Rf.

[0049] In a preferred embodiment, the contact end 23 of the contact region 20 is located axially outward of the tire at a distance A of 9.5 to 15.0 mm from the tire radial line RWL that passes through the rim width position of the regular rim R. In other words, the contact region 20 of the rim protector 10 can contact the rim flange Rf over a range of at least 9.5 mm in the tire axial direction.

[0050] In high lateral G-force conditions, the bead portion 4 of the tire 1 tends to undergo large bending deformation with the rim flange Rf as the fulcrum. However, the rim protector 10 of this embodiment has a contact area 20 in the first state that contacts the rim flange Rf over an axial range of at least 9.5 mm, so that the bead portion 4 is effectively supported by the rim flange even during high G-force cornering, suppressing bending deformation of the bead portion 4. This makes it possible to keep the rate of change of the bead inclination angle small, and ultimately to generate a large cornering force in high lateral G-force conditions.

[0051] If the distance A of the contact end 23 is excessively large, the rubber volume of the bead portion 4 and the sidewall portion 3 increases, which may deteriorate the rolling resistance of the tire 1. From this perspective, the distance A of the contact end 23 is set to 15.0 mm or less, and more preferably 11.0 mm or less. As an example, the distance A is preferably set to 9.5 mm≦A≦11.0 mm.

[0052] In this way, the tire 1 of this embodiment employs a profile that follows the rim flange Rf, thereby making it possible to suppress bending deformation of the bead portion, etc. Furthermore, this method makes it possible to suppress bending deformation of the bead portion, etc. without adding any internal structural material to the tire, and therefore makes it possible to suppress deterioration in durability due to damage to the internal structural material.

[0053] [Rim protector apex radius] Fig. 6 is an enlarged view of part VI in Fig. 4. As shown in Fig. 6, in a meridian cross section of the tire in a normal state, the vertex 11 of the rim protector 10 is chamfered with a curvature radius r. The curvature radius r is preferably in the range of 1.5 to 25 mm, for example.

[0054] By making the radius of curvature r of the apex 11 1.5 mm or more, it is possible to prevent abrupt changes in the rubber thickness of the rim protector 10. It also alleviates the concentration of local strain at the apex 11 while the tire is running. Furthermore, by making the radius of curvature r of the apex 11 25 mm or less, it is possible to prevent the rubber volume of the rim protector 10 from becoming excessively large, thereby suppressing a deterioration in rolling resistance. In a particularly preferred embodiment, the radius of curvature r of the apex 11 may be set to 10 mm≦r≦20 mm.

[0055] [Tread rubber] As shown in FIG. 1 , a tread rubber 2G is disposed in the tread portion 2. The tread rubber 2G is disposed radially outward of the belt layer 7 and the band layer 9. In this embodiment, the thickness d of the tread rubber 2G at the tire equator Co is preferably 5 to 8 mm. If grooves extending in the tire circumferential direction are provided at the tire equator Co, the thickness d of the tread rubber 2G is set to a virtual thickness that fills the grooves. If the thickness of the tread rubber 2G at the tire equator Co is large, the shear rigidity of the tread rubber 2G will be small, which may result in a decrease in cornering force under high lateral G forces. From this perspective, the thickness d of the tread rubber 2G is set to 8 mm or less. On the other hand, if the thickness d of the tread rubber 2G is small, the depth of the grooves formed in the tread rubber 2G will have to be shallow, which will result in a deterioration in drainage performance, etc. From this perspective, the thickness d of the tread rubber 2G is set to 5 mm or more.

[0056] The rubber hardness of the contact surface 2s of the tread rubber 2G is preferably 67 to 75. In this specification, "rubber hardness" refers to the Shore hardness (Hs) measured in accordance with JIS K 6253-3:2012 using a durometer type A at a temperature of 23°C. A sample for measuring Shore hardness is prepared by cutting out a piece from the tread portion 2 so that the thickness direction is the tire radial direction. The measurement is performed by pressing a measuring tool against the sample from the contact surface side of the hardness measurement sample.

[0057] If the rubber hardness of the contact surface 2s of the tread rubber 2G becomes smaller, the shear rigidity of the tread rubber 2G becomes smaller, which may result in a decrease in cornering force under high lateral G forces. From this perspective, it is more desirable that the rubber hardness of the tread rubber 2G be 68 or greater. On the other hand, if the rubber hardness of the tread rubber 2G becomes larger, input from the road surface may be more easily transmitted to the vehicle interior via the rim, which may result in a deterioration in ride comfort. From this perspective, it is more desirable that the rubber hardness of the tread rubber 2G be 72 or less.

[0058] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways. [Example]

[0059] Test tires with the basic structure shown in Figure 1 were prototyped based on the specifications in Table 1. Various performance characteristics of the test tires were then tested. The test methods and common specifications of each test tire are as follows: Tire size: 275 / 35R19 Rim size: 19 x 9.5

[0060] <Contact area when lateral load is applied> The contact area of ​​the tread portion was measured in the second state shown below. The results are expressed as an index, with the contact area of ​​Comparative Example 1 being 100. The larger the value, the smaller the reduction in contact area under high lateral G (equivalent to approximately 0.5 G) and the greater the cornering force generated. Internal pressure: 230kPa Vertical load: 70% of maximum load capacity at 230kPa Lateral load: 50% of vertical load

[0061] <High speed durability> Each test tire was mounted on a rim and the internal pressure was adjusted to 230 kPa. A durability test was conducted using an indoor drum tester in accordance with the load / speed performance test specified by ECE30 using the step speed method, and the running distance until the tire broke was measured. The results are expressed as an index, with Example 1 being 100. The higher the value, the better the durability.

[0062] <Air resistance> When each test tire was mounted on the front wheels of a vehicle, the air resistance coefficient was calculated by aerodynamic simulation. The results are expressed as an index with Comparative Example 1 being 100, with a larger value indicating lower (better) air resistance.

[0063] <Rolling resistance> The rolling resistance was measured in accordance with ECE R117-02 (ECE Regulation No. 117 Revision 2). Specifically, the test tire was run on a simulated road surface using an indoor drum testing machine under the following conditions, and the rolling resistance value was measured. The results are expressed as an index, with the reciprocal of the rolling resistance value of Comparative Example 1 set to 100, and the larger the index, the smaller the rolling resistance. Vertical load: 4.6kN Speed: 80km / h

[0064] <Ride comfort> A set of four test tires from each group was mounted on all wheels of a 2000cc domestic front-wheel drive vehicle, and a test driver drove the vehicle on a test course with a dry asphalt road surface equipped with protrusions. The test driver then evaluated the magnitude of the shock when going over a single protrusion and the magnitude of vibration during driving. The results are shown as a score, with Comparative Example 1 being given a score of 100. The higher the score, the better the ride comfort performance. The test results are shown in Tables 1 and 2. [Table 1]

[0065] The test results showed that the tires of Examples 1 to 9 had a contact patch that was increased by 5% or more when a lateral load was applied compared to Comparative Example 1. Therefore, the tires of Examples 1 to 9 are expected to have a large cornering force that is correlated with the contact patch under high lateral G conditions.

[0066] [Note] The present invention includes the following aspects.

[0067] [Invention 1] A pneumatic tire, A tread portion; A pair of sidewall portions; a pair of bead portions each having a bead core disposed therein; a bead inclination line is defined as a line connecting the midpoint of a line connecting points where an imaginary circle having a radius of 30 mm and centered at the center of the cross section of the bead core intersects with the tire outer surface and the tire inner surface, and the line connecting the center of the cross section of the bead core; In a tire meridian cross section in a first state in which the pneumatic tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 230 kPa, a vertical load of 70% of the maximum load capacity of the internal pressure of 230 kPa is applied, and the tire is in contact with a horizontal surface at a camber angle of 0°, the angle between the bead inclination line and the horizontal plane is defined as α1, In a tire meridian cross section in a second state in which a lateral load that is 50% of the vertical load is applied in the first state, when the angle between the bead inclination line of one of the pair of bead portions on the side in the application direction of the lateral load and the horizontal plane is α2, The bead inclination angle change rate specified by (α1-α2) / α1 is 5% or less. Pneumatic tires. [Invention 2] The pneumatic tire according to invention 1, having an aspect ratio of 45% or less. [Invention 3] 3. The pneumatic tire according to claim 1 or 2, wherein the bead inclination angle change rate is 3% or less. [Invention 4] 4. The pneumatic tire according to any one of aspects 1 to 3, wherein the bead inclination angle change rate is 1% or more. [Invention 5] 5. The pneumatic tire according to any one of claims 1 to 4, wherein the bead inclination angle change rate is 2% or more. [Invention 6] the bead portion on the side facing the lateral load direction is provided with a rim protector that protrudes axially outward and extends circumferentially of the tire, The pneumatic tire according to any one of Inventions 1 to 5, wherein when the pneumatic tire is mounted on the regular rim, adjusted to the regular internal pressure, and in a normal state where no load is applied, the rim protector protrudes axially outward from the axially outer end of the rim flange of the regular rim by a protrusion amount B of 1 to 10 mm. [Invention 7] 7. The pneumatic tire according to claim 6, wherein the protrusion amount B is in the range of 3 to 7 mm. [Invention 8] In the first state, the rim protector has a contact area that comes into contact with the rim flange of the regular rim, A pneumatic tire according to Invention 6 or 7, wherein the contact edge, which is the outermost position in the axial direction of the contact area, is located axially outward of the tire at a distance A of 9.5 to 15.0 mm from a tire radial line passing through the rim width position of the regular rim. [Invention 9] The rim protector has an apex located on the outer side in the tire axial direction, 9. The pneumatic tire according to any one of inventions 6 to 8, wherein the height C of the apex in the tire radial direction from the bead base line is 20 mm or more and is equal to or less than the maximum width height of the tire. [Invention 10] 10. The pneumatic tire according to claim 9, wherein in the tire meridian cross section in a normal state, the apex is chamfered with a curvature radius r, and the curvature radius r is in the range of 1.5 to 25 mm. [Invention 11] 11. The pneumatic tire according to claim 10, wherein the radius of curvature r is 10 to 20 mm. [Invention 12] A tread rubber is disposed in the tread portion, 12. The pneumatic tire according to any one of claims 1 to 11, wherein the thickness of the tread rubber at the tire equator is 5 to 8 mm. [Invention 13] 13. The pneumatic tire according to claim 12, wherein the rubber hardness of the contact surface of the tread rubber is 67 to 75. [Explanation of symbols]

[0068] 1 tire 1 pneumatic tire 2 Tread section 2G tread rubber 2s ground plane 3 Sidewall 4 Bead section 5 bead core 10 Rim Protector 11 Vertex 20 contact area 23 Contact end L Bead inclination line VC Virtual Circle Pi intersection Po intersection R Genuine rim Rf rim flange

Claims

1. A pneumatic tire, A tread portion; A pair of sidewall portions; a pair of bead portions each having a bead core disposed therein; a bead inclination line is defined as a line connecting the midpoint of a line connecting points where an imaginary circle having a radius of 30 mm and centered at the center of the cross section of the bead core intersects with the tire outer surface and the tire inner surface, and the line connecting the center of the cross section of the bead core; In a tire meridian cross section in a first state in which the pneumatic tire is mounted on a regular rim, the internal pressure of the tire is adjusted to 230 kPa, a vertical load of 70% of the maximum load capacity of the internal pressure of 230 kPa is applied, and the tire is in contact with a horizontal surface at a camber angle of 0°, the angle between the bead inclination line and the horizontal plane is defined as α1, In a tire meridian cross section in a second state in which a lateral load that is 50% of the vertical load is applied in the first state, when the angle between the bead inclination line of one of the pair of bead portions closer to the application direction of the lateral load and the horizontal plane is defined as α2, The bead inclination angle change rate specified by (α1-α2) / α1 is 5% or less, the bead portion on the side facing the lateral load direction is provided with a rim protector that protrudes axially outward and extends circumferentially of the tire, In the first state, the rim protector has a contact area that comes into contact with the rim flange of the regular rim, The contact edge, which is the outermost position in the tire axial direction of the contact area, is located axially outward at a distance A of 9.5 to 15.0 mm from a tire radial line passing through the rim width position of the regular rim. Pneumatic tires.

2. The pneumatic tire according to claim 1, wherein the aspect ratio is 45% or less.

3. The pneumatic tire according to claim 1 , wherein the bead inclination angle change rate is 3% or less.

4. The pneumatic tire according to claim 1 , wherein the bead inclination angle change rate is 1% or more.

5. The pneumatic tire according to claim 1 , wherein the bead inclination angle change rate is 2% or more.

6. A pneumatic tire as described in any one of claims 1 to 5, wherein when mounted on the regular rim, adjusted to the regular internal pressure, and in a normal state where there is no load, the rim protector protrudes axially outward from the axial outer end of the rim flange of the regular rim by a protrusion amount B of 1 to 10 mm.

7. 7. The pneumatic tire according to claim 6, wherein the protrusion amount B is in the range of 3 to 7 mm.

8. A pneumatic tire as described in claim 1, wherein in the first state, the contact area is in contact with the rim flange continuously from the bead baseline to the contact end.

9. A pneumatic tire as described in claim 8, wherein when mounted on the normal rim, adjusted to the normal internal pressure, and in a normal state where there is no load, the outer surface of the bead portion contacts both the base portion of the rim flange extending in the tire radial direction and the curved portion curved in an arc shape that is convex outward in the tire radial direction.

10. The rim protector has an apex located on the outer side in the tire axial direction, 2. The pneumatic tire according to claim 1, wherein a height C of the apex from a bead base line in the tire radial direction is 20 mm or more and is equal to or less than a maximum width height of the tire.

11. A pneumatic tire as described in claim 10, wherein in the tire meridian cross section in the normal state, the vertex is chamfered with a radius of curvature r, and the radius of curvature r is in the range of 1.5 to 25 mm.

12. A pneumatic tire as described in claim 11, wherein the radius of curvature r is 10 to 20 mm.

13. A tread rubber is arranged in the tread portion, 2. The pneumatic tire according to claim 1, wherein the thickness of the tread rubber at the tire equator is 5 to 8 mm.

14. A pneumatic tire as described in claim 13, wherein the rubber hardness of the contact surface of the tread rubber is 67 to 75.

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