tire

Abstract

To provide a tire capable of achieving both low rolling resistance performance and wet performance under conditions of use at high internal pressure.SOLUTION: In a tire 1, a radial distance D3 from point P1 to point T3 is in a range of 0.05≤D3 / D1≤0.15 with respect to a radial distance D1 from point P1 to point T1 in a cross-sectional view in a tire meridional direction under no load with the tire 1 mounted on a specified rim and subjected to 230 [kPa]. Further, a radial distance D6 from point P1 to point T6 is in a range of 3.00≤D6 / D3≤6.00 with respect to the radial distance D3 from the point P1. Furthermore, a radius of curvature R1 of a first circular arc passing through points T3, T4, and T5 is in a range of 0.40≤R1 / R2≤1.00 with respect to a radius of curvature R2 of a second circular arc passing through points T1, T6, and T7.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire, and more particularly to a tire that can achieve both low rolling resistance and wet performance under conditions of use at high internal pressure. [Background technology]

[0002] In recent years, tires have adopted a structure in which the profile from the tread portion to the tire side portion is optimized in order to reduce the rolling resistance of the tire. A technology described in Patent Document 1 is known as a conventional tire adopting such a structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-113008 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, it has been expected that tires will be used with internal pressures higher than the specified internal pressure in order to reduce tire rolling resistance. Even under such high internal pressure conditions, it is necessary to ensure the tire's contact shape is appropriate and to ensure the tire's wet performance.

[0005] Therefore, the present invention has been made in view of the above, and has an object to provide a tire that can achieve both low rolling resistance performance and wet performance under use conditions at high internal pressure. [Means for solving the problem]

[0006] In order to achieve the above object, the tire according to the present invention is a tire including a carcass layer, a belt layer formed by laminating a pair of cross belts, a tread rubber, and a sidewall rubber, and in a cross section in the tire meridian direction when the tire is mounted on a specified rim and a pressure of 230 [kPa] is applied and no load is applied, the maximum diameter position of the tire profile is defined as point P1, the maximum width position of the tire profile is defined as point T1, the intersection of a straight line passing through point T1 and parallel to the tire width direction with the tire equatorial plane is defined as point T2, a position at 30 [%] of the distance from point T1 to point T2 is defined as point T3, a position at 20 [%] of the distance from point T1 to point T2 is defined as point T4, and a position that is 15% of the distance from point T1 to point T2 is defined as point T5, a position that is 10% of the distance from point T1 to point T2 is defined as point T6, and a position that is 3% of the distance from point T1 to point T2 is defined as point T7; a radial distance D3 from point P1 to point T3 is in the range of 0.05≦D3 / D1≦0.15 with respect to the radial distance D1 from point P1 to point T1; a radial distance D6 from point P1 to point T6 is in the range of 3.00≦D6 / D3≦6.00 with respect to the radial distance D3 from point P1; and a radius of curvature R1 of a first circular arc that passes through points T3, T4, and T5 is in the range of 0.40≦R1 / R2≦1.00 with respect to the radius of curvature R2 of a second circular arc that passes through points T1, T6, and T7. [Effects of the Invention]

[0007] The tire according to the present invention has the advantages of optimizing the ratios D3 / D1, D6 / D3, and R1 / R2 under high internal pressure conditions, thereby achieving both low rolling resistance and wet performance. Specifically, (1) the lower limit of the ratio D3 / D1 prevents the tire's rolling resistance from deteriorating due to excessive contact pressure in the tread shoulder region. The upper limit of the ratio D3 / D1 ensures the contact length of the tread shoulder region, thereby ensuring the tire's wet performance. The lower limit of the ratio D6 / D3 prevents the tire's contact area from decreasing due to excessive radial distance D3 from point P1 to point T3, thereby ensuring the tire's wet performance. The upper limit of the ratio D6 / D3 prevents the tire's rolling resistance from deteriorating due to excessive rubber volume in the buttress region. (3) The lower limit of the ratio R1 / R2 ensures uniformity in the distribution of contact pressure on the tire contact patch, reducing energy loss during tire rolling. This reduces tire rolling resistance. The upper limit of the ratio R1 / R2 ensures tension in the carcass layer 13, ensuring tire rigidity. This ensures an appropriate tire contact patch shape and ensures wet tire performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram showing the profile of the tire shown in FIG. [Figure 3] FIG. 3 is an enlarged view showing a main part of the tire profile shown in FIG. [Figure 4] FIG. 4 is an explanatory view showing the tread portion of the tire shown in FIG. [Figure 5] FIG. 5 is an explanatory diagram showing a modified example of the tire shown in FIG. [Figure 6] FIG. 6 is an enlarged view showing the tread portion of the tire shown in FIG. [Figure 7]FIG. 7 is a table showing the results of performance tests on the tire according to the embodiment of the present invention. [Figure 8] FIG. 8 is a table showing the results of performance tests on the tire according to the embodiment of the present invention. [Figure 9] FIG. 9 is a table showing the results of performance tests on the tire according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components of these embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. Furthermore, the multiple modifications described in these embodiments can be arbitrarily combined within the scope obvious to those skilled in the art.

[0010] [tire] 1 is a cross-sectional view in the tire meridian direction showing a tire 1 according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the tire radial direction. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire.

[0011] In the figure, the tire meridian cross section is defined as a cross section of the tire cut by a plane including the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire section width defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as the direction parallel to the tire rotation axis, and the tire radial direction is defined as the direction perpendicular to the tire rotation axis.

[0012] The tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair of rim cushion rubbers 17, 17 (see Figure 1).

[0013] The pair of bead cores 11, 11 are formed by winding one or more steel bead wires in an annular and multiple pattern and are embedded in the bead portions to form the cores of the left and right bead portions. The pair of bead fillers 12, 12 are disposed on the outer periphery of the pair of bead cores 11, 11 in the tire radial direction, respectively, to reinforce the bead portions.

[0014] The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally laid between the left and right bead cores 11, 11 to form the tire framework. Both ends of the carcass layer 13 are wrapped around and secured to the outside in the tire width direction so as to enclose the bead cores 11 and the bead fillers 12. The carcass ply of the carcass layer 13 is formed by covering multiple carcass cords made of steel or organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the carcass cords in the longitudinal direction relative to the tire circumferential direction) of 80 degrees or more and 100 degrees or less.

[0015] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 143, and is disposed by being wound around the outer periphery of the carcass layer 13. The belt plies 141 to 143 each include a pair of cross belts 141, 142 and a belt cover 143.

[0016] The pair of cross belts 141, 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and have a cord angle (defined as the inclination angle of the belt cords in the longitudinal direction with respect to the tire circumferential direction) of 15 degrees or more and 55 degrees or less in absolute value. The pair of cross belts 141, 142 have cord angles of opposite signs to each other, and are layered with the longitudinal directions of the belt cords crossing each other (so-called cross-ply structure). The pair of cross belts 141, 142 are layered and arranged on the outer side of the carcass layer 13 in the tire radial direction. Here, the cross belt 141 located on the inner side in the tire radial direction is defined as the inner cross belt, and the cross belt 142 located on the outer side in the tire radial direction is defined as the outer cross belt.

[0017] The belt cover 143 is configured by covering a belt cover cord made of steel or organic fiber material with coating rubber, and has a cord angle of 0 degrees or more and 10 degrees or less in absolute value. The belt cover 143 is, for example, a strip material configured by covering one or more belt cover cords with coating rubber, and is configured by winding this strip material spirally around the outer circumferential surfaces of the cross belts 141 and 142 multiple times in the tire circumferential direction. The belt cover 143 is disposed to cover the entire area of ​​the cross belts 141 and 142.

[0018] The tread rubber 15 is disposed on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to form the tread portion of the tire 1. A pair of sidewall rubbers 16, 16 are disposed on the outer sides of the carcass layer 13 in the tire width direction to form left and right sidewall portions. A pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction of the left and right bead cores 11, 11 and the turned-up portions of the carcass layer 13 to the outer side in the tire width direction to form the rim fitting surface of the bead portion.

[0019] [Tire Profile] Fig. 2 is an explanatory diagram showing the profile of the tire 1 shown in Fig. 1. The figure shows the profile from the tire equatorial plane CL to the tire maximum width position T1. Here, because the tire profile has a bilaterally symmetrical structure centered on the tire equatorial plane CL, only one side region bounded by the tire equatorial plane CL will be described in detail.

[0020] 1 and 2, in a cross-sectional view taken along the tire meridian in an unloaded state with a tire mounted on a specified rim and subjected to a pressure of 230 kPa, the maximum diameter position of the tire profile is defined as point P1, and the maximum width position of the tire profile is defined as point T1.

[0021] The specified rim refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure, described below, refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

[0022] A point P1 at the maximum diameter position of the tire profile is defined as an intersection point between the tire profile and the tire equatorial plane CL in a cross section seen in the tire meridian direction.

[0023] Point T1, which is the maximum width position of the tire profile, is defined as the end point of the tire section width DW. The radial distance D1 from point P1 to point T1 is in the range of 0.15≦D1 / (OD / 2)≦0.20 relative to the tire outer diameter OD (not shown).

[0024] The tire cross-sectional width DW is measured as the straight-line distance between the sidewalls, excluding any patterns or lettering on the side of the tire, when the tire is mounted on a specified rim, subjected to a pressure of 230 kPa, and in an unloaded state.

[0025] The intersection of a line passing through point T1 and parallel to the tire width direction with the tire equatorial plane CL is defined as point T2. A position that is 30% of the distance from point T1 to point T2 is defined as point T3. A position that is 20% of the distance from point T1 to point T2 is defined as point T4. A position that is 15% of the distance from point T1 to point T2 is defined as point T5. A position that is 10% of the distance from point T1 to point T2 is defined as point T6. A position that is 3% of the distance from point T1 to point T2 is defined as point T7.

[0026] At this time, the radial distance D3 from point P1 to point T3 is in the range of 0.05≦D3 / D1≦0.15 relative to the radial distance D1 from point P1 to point T1, and preferably in the range of 0.10≦D3 / D1≦0.13.

[0027] Furthermore, the radial distance D6 from point P1 to point T6 is in the range of 3.00≦D6 / D3≦6.00 relative to the radial distance D3 from point P1, preferably in the range of 3.20≦D6 / D3≦5.00, and more preferably in the range of 3.50≦D6 / D3≦4.50.

[0028] The radius of curvature R1 of the first circular arc passing through points T3, T4, and T5, relative to the radius of curvature R2 of the second circular arc passing through points T1, T6, and T7, is in the range of 0.40≦R1 / R2≦1.00, preferably 0.45≦R1 / R2≦0.85, and more preferably 0.50≦R1 / R2≦0.70. The radius of curvature R1 is in the range of 20 mm≦R1≦50 mm, and more preferably 22 mm≦R1≦35 mm.

[0029] The above configuration optimizes the ratios D3 / D1, D6 / D3, and R1 / R2 under high internal pressure conditions, thereby achieving both low rolling resistance and wet performance. Specifically, (1) the lower limit of the ratio D3 / D1 prevents the tire's rolling resistance from deteriorating due to excessive contact pressure in the tread shoulder region. The upper limit of the ratio D3 / D1 ensures the contact length of the tread shoulder region, thereby ensuring the tire's wet performance. The lower limit of the ratio D6 / D3 prevents the tire's contact area from decreasing due to excessive radial distance D3 from point P1 to point T3, thereby ensuring the tire's wet performance. The upper limit of the ratio D6 / D3 prevents the tire's rolling resistance from deteriorating due to excessive rubber volume in the buttress region. (3) The lower limit of the ratio R1 / R2 ensures uniformity in the distribution of contact pressure on the tire contact patch, reducing energy loss during tire rolling. This reduces tire rolling resistance. The upper limit of the ratio R1 / R2 ensures tension in the carcass layer 13, ensuring tire rigidity. This ensures an appropriate tire contact patch shape and ensures wet tire performance.

[0030] 2, the radial distance D5 from point P1 to point T5 is in the range of 0.20≦D5 / D1≦0.40, and preferably 0.30≦D5 / D1≦0.35, relative to the radial distance D1 to point T1. This ensures an appropriate tire contact profile. Specifically, the lower limit prevents deterioration of tire rolling resistance due to excessive contact pressure in the tread shoulder region. The upper limit prevents a decrease in tire contact area due to an excessively large radius of curvature of the profile from point T3 to point T5, thereby ensuring wet tire performance.

[0031] Furthermore, when the above-mentioned 230 kPa and standard internal pressure are applied, the tire ground contact edge (reference numeral omitted in the figure) is located at a position that is 25% to 35% of the distance from point T1 to point T2, and preferably at a position that is 26% to 33% of the distance. Furthermore, the distance in the tire width direction from the tire ground contact edge to point T3 (reference numeral omitted in the figure) is preferably within a range of ±5% of the distance from point T1 to point T2. Therefore, it is preferable that the tire ground contact edge is located at approximately the same position as point T3. Furthermore, the tire ground contact edge may be located either inward or outward in the tire width direction from point T3 (not shown).

[0032] In order to obtain an appropriate profile at the internal pressure of 230 kPa, the tire 1 has the following profile at the specified internal pressure.

[0033] First, in a cross-sectional view in the tire meridian direction when the tire is mounted on a specified rim, pressurized to a specified internal pressure, and in an unloaded state, the maximum diameter position of the tire profile is defined as point P1' (not shown; see FIG. 2). The maximum width position of the tire profile is defined as point T1'. The intersection of a line passing through point T1' and parallel to the tire width direction with the tire equatorial plane CL is defined as point T2'. A position 30% of the distance from point T1' to point T2' is defined as point T3'. A position 20% of the distance from point T1' to point T2' is defined as point T4'. A position 15% of the distance from point T1' to point T2' is defined as point T5'. A position 10% of the distance from point T1' to point T2' is defined as point T6. A position 3% of the distance from point T1' to point T2' is defined as point T7'.

[0034] In this case, the radial distance D3' from point P1' to point T3' is in the range of 0.05≦D3' / D1'≦0.15, preferably 0.08≦D3' / D1'≦0.13, relative to the radial distance D1' from point P1' to point T1' (not shown). Also, the radial distance D6' from point P1' to point T6' is in the range of 3.20≦D6' / D3'≦5.00, preferably 3.20≦D6' / D3'≦4.50, relative to the radial distance D3' from point P1' to point T3'. Furthermore, the radius of curvature R1' of the first circular arc passing through points T3', T4', and T5', relative to the radius of curvature R2' of the second circular arc passing through points T1', T6', and T7', is in the range of 0.20≦R1' / R2'≦0.80, preferably 0.25≦R1' / R2'≦0.75, and more preferably 0.28≦R1' / R2'≦0.58 (not shown). This ensures an appropriate tire profile at the high internal pressure of 230 kPa.

[0035] FIG. 3 is an enlarged view showing a main part of the tire profile shown in FIG.

[0036] In FIG. 2, the radial distance Da from point T3 to point T4, relative to the radial distance Db from point T4 to point T5, is in the range of 0.20≦Da / Db≦1.30, preferably 0.40≦Da / Db≦1.10. This ensures an appropriate tire contact shape. Specifically, as shown in FIG. 3, the smaller the ratio Da / Db, the smaller the radius of curvature R1 (see FIG. 2) of the first circular arc formed by points T3, T4, and T5, and the higher the contact pressure in the tread shoulder region. Therefore, the lower limit of the ratio Da / Db prevents excessive contact pressure in the tread shoulder region, ensuring a uniform contact pressure distribution in the tire contact patch. This prevents a deterioration in the tire's rolling resistance. On the other hand, the larger the ratio Da / Db, the larger the radius of curvature R1 of the first circular arc, and the smaller the tire's contact area. Therefore, the above upper limit of the ratio Da / Db ensures the tire's contact area and wet performance. It is also preferable that the radial distance Da is in the range of 2.0 mm≦Da≦7.0 mm.

[0037] Fig. 4 is an explanatory diagram showing a tread portion of the tire 1 shown in Fig. 1. Fig. 5 is an explanatory diagram showing a modified example of the tire 1 shown in Fig. 4.

[0038] 1, the tire 1 has multiple circumferential main grooves 2c, 2s in the ground contact region of the tread surface. Of these circumferential main grooves 2c, 2s, the circumferential main groove 2c closest to the tire equatorial plane CL is defined as the center main groove, and the circumferential main grooves located on the outermost sides in the tire width direction are defined as shoulder main grooves.

[0039] In the configuration shown in Fig. 1, the center main groove 2c is located on the tire equatorial plane CL, as shown in Fig. 4. However, the present invention is not limited to this, and the center main groove 2c may be located at a position deviated from the tire equatorial plane CL, as shown in Fig. 5.

[0040] 1, the tire 1 has three circumferential main grooves: a single center main groove 2c and a pair of shoulder main grooves 2s. However, the tire 1 is not limited to this, and may have four or more circumferential main grooves (not shown). For example, the pair of center main grooves 2c may be disposed on either side of the tire equatorial plane CL, or a middle main groove may be disposed between the center main groove 2c and the shoulder main grooves 2s (not shown).

[0041] As shown in FIG. 4, an intersection P2 is defined between a line passing through point P1 and parallel to the tire width direction and a line passing through intersection point T5 and parallel to the tire radial direction.

[0042] In this case, the groove cross-sectional area Ac of the center main groove 2c in a cross section taken along the tire meridian is in the range of 0.30≦Ac / At≦1.00, preferably 0.40≦Ac / At≦0.70, relative to the area At of the region enclosed by points P2, T3, T5, and the first arc passing through the above-mentioned points T3, T4, and T5. This optimizes the groove cross-sectional area Ac of the center main groove 2c. That is, the smaller the groove cross-sectional area Ac of the center main groove 2c, the smaller the groove area of ​​the tire contact patch, resulting in poor wet tire performance. Furthermore, the larger the area At of the region, the larger the curvature radius R1 (see FIG. 2 ) of the first arc formed by points T3, T4, and T5, resulting in non-uniform contact pressure distribution in the tire contact patch and poor tire rolling resistance. Therefore, the lower limit of the ratio Ac / At ensures the tire's wet performance and reduces the tire's rolling resistance. Furthermore, as the groove cross-sectional area Ac of the center main groove 2c increases, the contact area in the tread center region decreases, resulting in a deterioration in the rolling resistance of the tire. Furthermore, as the area At of the center main groove 2c decreases, the curvature radius R1 of the first circular arc formed by points T3, T4, and T5 decreases, which increases the contact pressure in the tread shoulder region and worsens the rolling resistance of the tire. Therefore, the upper limit of the ratio Ac / At prevents the tire from experiencing a deterioration in rolling resistance.

[0043] Furthermore, the groove cross-sectional area Ac of the center main groove 2c in a cross-section taken along the tire meridian direction is set to a value relative to the groove cross-sectional area As of the shoulder main groove 2s in the range of 1.05≦Ac / As≦1.80, preferably 1.05≦Ac / As≦1.55. This optimizes the groove cross-sectional area ratio Ac / As of the center main groove 2c and the shoulder main groove 2s. Since the center main groove 2c contributes significantly to drainage, the larger the groove cross-sectional area Ac of the center main groove 2c, the better the tire's wet performance. On the other hand, the larger the groove cross-sectional area Ac of the center main groove 2c, the smaller the contact patch in the center region of the tread, resulting in a deterioration in the tire's rolling resistance. Furthermore, the larger the groove cross-sectional area As of the shoulder main grooves 2s, the more non-uniform the contact pressure distribution in the tire's contact patch, resulting in a deterioration in the tire's rolling resistance. Therefore, the above lower limit ensures the groove cross-sectional area Ac of the center main groove 2c, which contributes significantly to drainage, thereby ensuring the tire's wet performance. Furthermore, the above upper limit prevents the groove cross-sectional area As of the shoulder main groove 2s from becoming excessively large, thereby preventing the rolling resistance of the tire from deteriorating.

[0044] The groove cross-sectional areas Ac and As of the main grooves 2c and 2s are measured as the area of ​​the region surrounded by the groove wall surfaces of the main grooves and the tire profile when viewed in cross section in the tire meridian direction with the tire mounted on a specified rim and under an unloaded condition with a pressure of 230 kPa applied. In a configuration in which the main grooves have chamfered portions at the groove openings (not shown), the area of ​​the chamfered portions is added to calculate the groove cross-sectional areas Ac and As. On the other hand, in a configuration in which the main grooves have decorative irregularities on the groove walls (not shown), the groove cross-sectional areas Ac and As are calculated using the groove wall surfaces excluding these irregularities. In a configuration in which the groove area of ​​the main grooves varies circumferentially (not shown), the maximum groove cross-sectional areas around the tire are used as the groove cross-sectional areas Ac and As.

[0045] Fig. 6 is an enlarged view showing the tread portion of the tire 1 shown in Fig. 1. The drawing shows the tread portion of one side region bounded by the tire equatorial plane CL.

[0046] In Figure 6, the distance Ds from the tire equatorial plane CL to the shoulder main groove 2s, relative to the tire cross-sectional width DW, is in the range of 0.03 ≦ Ds / DW ≦ 0.20, preferably 0.10 ≦ Ds / DW ≦ 0.20. This optimizes the position of the shoulder main groove 2s. Specifically, the above lower limit ensures rigidity in the tread center region and reduces tire rolling resistance. The above upper limit ensures drainage by the shoulder main groove 2s and ensures wet tire performance.

[0047] The distance Ds to the shoulder main groove 2s is measured with the center line of the shoulder main groove 2s as the endpoint when the tire is mounted on a specified rim, a pressure of 230 kPa is applied, and no load is applied.

[0048] The groove center line of the shoulder main groove 2s is defined as an imaginary line connecting the midpoints of the groove width endpoints. In a configuration in which the groove center line has a zigzag or wavy shape, the imaginary groove center line is defined as a straight line passing through the center line of the amplitude and parallel to the tire equatorial plane.

[0049] Further, the tire section width DW is in the range of DW / OD≦0.40, and preferably DW / OD≦0.35, relative to the tire outer diameter OD (not shown).

[0050] 1, the belt width Wb1 of the wider cross belt (inner diameter side cross belt 141 in FIG. 1) of the pair of cross belts 141, 142 is in the range of 0.60≦Wb1 / DW≦0.90, preferably 0.70≦Wb1 / DW≦0.85, relative to the tire cross section width DW. This optimizes the belt width Wb1.

[0051] The width Wb1 of the belt ply is the distance in the tire width direction between the left and right ends of the belt ply (more specifically, the belt cords located outermost in the tire width direction), and is measured with the tire mounted on a specified rim, with 230 kPa applied, and in an unloaded state.

[0052] For example, in the configuration shown in Fig. 1, the inner diameter side cross belt 141 and the outer diameter side cross belt 142 of the belt layer 14 have a symmetrical structure with respect to the tire equatorial plane CL. The inner diameter side cross belt 141 is wider than the outer diameter side cross belt 142. As shown in Fig. 6, the edge portion of the inner diameter side cross belt 141 is located between points T3 and T4 in the tire width direction.

[0053] 6, the gauge Ga3 from point T3 to the outer diameter side cross belt 142 is in the range of 0.70≦Ga3 / Ga1≦0.98, and preferably 0.80≦Ga3 / Ga1≦0.98, relative to the gauge Ga1 from point P1 to the outer diameter side cross belt 142. This optimizes the tread gauge in the shoulder region of the tread portion, thereby reducing the rolling resistance of the tire.

[0054] The gauges Ga1 and Ga3 to the outer diameter side cross belt 142 are measured as the lengths of perpendicular lines drawn from points P1 and T3 on the tire profile to the outer surface of the outer diameter side cross belt 142. The outer surface of the outer diameter side cross belt 142 is defined as an imaginary line (not shown) connecting the outer ends of the belt cords that make up the outer diameter side cross belt 142.

[0055] 6, the gauge Gb3 from point T3 to the tire inner surface is in the range of 0.80≦Gb3 / Gb1≦1.10, and preferably 0.90≦Gb3 / Gb1≦1.10, relative to the gauge Gb1 from point P1 to the tire inner surface. This optimizes the total gauge in the shoulder region of the tread, reducing the rolling resistance of the tire.

[0056] 6, the gauge Gb4 from point T4 to the tire inner surface is in the range of 0.70≦Gb4 / Gb3≦1.10, and preferably 0.75≦Gb4 / Gb3≦1.05, relative to the gauge Gb3 from point T3 to the tire inner surface. This optimizes the contact shape of the tread shoulder region, improving the wet performance of the tire and reducing the rolling resistance of the tire.

[0057] The gauges Gb1, Gb3, and Gb4 to the tire inner surface are measured as the lengths of perpendicular lines drawn from points P1 and T3 on the tire profile to the tire inner surface.

[0058] [effect] As described above, [1] the tire 1 includes the carcass layer 13, the belt layer 14 formed by laminating a pair of cross belts 141, 142, the tread rubber 15, and the sidewall rubber 16 (see FIG. 1). In addition, when tire 1 is mounted on a specified rim and under an unloaded condition with 230 kPa applied, the maximum diameter position of the tire profile is defined as point P1, the maximum width position of the tire profile is defined as point T1, the intersection of a line passing through point T1 and parallel to the tire width direction with the tire equatorial plane is defined as point T2, a position that is 30% of the distance from point T1 to point T2 is defined as point T3, a position that is 20% of the distance from point T1 to point T2 is defined as point T4, a position that is 15% of the distance from point T1 to point T2 is defined as point T5, a position that is 10% of the distance from point T1 to point T2 is defined as point T6, and a position that is 3% of the distance from point T1 to point T2 is defined as point T7 (see Figure 2). In this case, the radial distance D3 from point P1 to point T3 is in the range of 0.05≦D3 / D1≦0.15 relative to the radial distance D1 from point P1 to point T1. The radial distance D6 from point P1 to point T6 is in the range of 3.00≦D6 / D3≦6.00 relative to the radial distance D3 from point P1. The radius of curvature R1 of the first circular arc passing through points T3, T4, and T5 is in the range of 0.40≦R1 / R2≦1.00 relative to the radius of curvature R2 of the second circular arc passing through points T1, T6, and T7.

[0059] This configuration optimizes the ratios D3 / D1, D6 / D3, and R1 / R2 under high internal pressure conditions, resulting in the tire's low rolling resistance and wet performance. Specifically, (1) the lower limit of the ratio D3 / D1 prevents the tire's rolling resistance from deteriorating due to excessive contact pressure in the tread shoulder region. The upper limit of the ratio D3 / D1 ensures the contact length of the tread shoulder region, thereby ensuring the tire's wet performance. (2) The lower limit of the ratio D6 / D3 prevents the tire's contact area from decreasing due to excessive radial distance D3 from point P1 to point T3, thereby ensuring the tire's wet performance. The upper limit of the ratio D6 / D3 prevents the tire's rolling resistance from deteriorating due to excessive rubber volume in the buttress region. (3) The lower limit of the ratio R1 / R2 ensures uniformity in the distribution of contact pressure on the tire contact patch, reducing energy loss during tire rolling. This reduces tire rolling resistance. The upper limit of the ratio R1 / R2 ensures tension in the carcass layer 13, ensuring tire rigidity. This ensures an appropriate tire contact patch shape and ensures wet tire performance.

[0060] [2] In the tire 1, in the above [1], the radial distance D5 from point P1 to point T5 is in the range of 0.20≦D5 / D1≦0.40 relative to the radial distance D1 from point P1 to point T1 (see FIG. 2). This has the advantage of ensuring an appropriate tire contact patch shape.

[0061] [3] In the tire 1, in the above [1] or [2], the radial distance Da from point T3 to point T4 and the radial distance Db from point T4 to point T5 are in the range of 0.20≦Da / Db≦1.30 (see FIG. 2). This has the advantage of ensuring an appropriate tire contact patch shape.

[0062] [4] In addition, in the tire 1, in any one of the above [1] to [3], the radius of curvature R1 of the first circular arc is in the range of 20 mm≦R1≦50 mm (see FIG. 2). This has the advantage of ensuring an appropriate tire contact shape.

[0063] [5] The tire 1 has a plurality of circumferential main grooves 2c, 2s (see FIG. 1) in any one of [1] to [4] above. When defining an intersection point P2 between a line passing through point P1 and parallel to the tire width direction and a line passing through point T5 and parallel to the tire radial direction, the groove cross-sectional area Ac of the center main groove 2c in a cross section taken along the tire meridian is in the range of 0.30≦Ac / At≦1.00, where At is the area of ​​the region surrounded by the intersection point P2, point T3, point T5, and the first circular arc. This has the advantage of optimizing the groove cross-sectional area Ac of the center main groove 2c.

[0064] [6] In the tire 1, in the above [5], the groove cross-sectional area Ac of the center main groove 2c in a cross section taken along the tire meridian direction is in the range of 1.05≦Ac / As≦1.80 relative to the groove cross-sectional area As of the shoulder main grooves 2s (see FIG. 4). This has the advantage of optimizing the groove cross-sectional area ratio Ac / As of the center main groove 2c and the shoulder main grooves 2s.

[0065] [7] In addition, in the tire 1, in any one of the above [1] to [6], the distance Ds (see FIG. 6) from the tire equatorial plane CL to the shoulder main groove 2s is in the range of 0.03≦Ds / DW≦0.20, relative to the tire cross-sectional width DW (see FIG. 1). This has the advantage of optimizing the position of the shoulder main groove 2s. The above lower limit ensures rigidity in the tread center region and reduces the rolling resistance of the tire. The above upper limit ensures drainage by the shoulder main groove 2s and ensures wet performance of the tire.

[0066] [8] In the tire 1, in any one of the above [1] to [7], the tire section width DW (see FIG. 1) is in the range of DW / OD≦0.40 relative to the tire outer diameter OD. This has the advantage of optimizing the tire section width DW.

[0067] [9] In the tire 1, in any one of the above [1] to [8], the belt width Wb1 of the wider cross belt (inner diameter side cross belt 141 in FIG. 1) of the pair of cross belts 141, 142 is in the range of 0.60≦Wb1 / DW≦0.90 with respect to the tire cross-sectional width DW. This has the advantage of optimizing the belt width Wb1.

[0068]

[10] In the tire 1, in any one of the above [1] to [9], the gauge Ga3 from the point T3 to the outer diameter side cross belt 142 of the pair of cross belts 141, 142 is in the range of 0.70≦Ga3 / Ga1≦0.98 relative to the gauge Ga1 from the point P1 to the outer diameter side cross belt 142 (see FIG. 6). This has the advantage of optimizing the tread gauge in the shoulder region of the tread portion.

[0069]

[11] In addition, in any one of the above [1] to

[10] , the gauge Gb3 from point T3 to the tire inner surface is in the range of 0.80≦Gb3 / Gb1≦1.10 relative to the gauge Gb1 from point P1 to the tire inner surface (see FIG. 6). This has the advantage of optimizing the total gauge in the shoulder region of the tread portion.

[0070]

[12] In addition, in any one of the above [1] to

[11] , the tire 1 has a gauge Gb4 from point T4 to the tire inner surface, and a gauge Gb3 from point T3 to the tire inner surface, which is in the range of 0.70≦Gb4 / Gb3≦1.10 (see FIG. 6). This has the advantage of optimizing the contact shape of the tread shoulder region. [Example]

[0071] 7 to 9 are tables showing the results of performance tests of the tires according to the embodiments of the present invention.

[0072] In this performance test, several types of test tires were evaluated for (1) low rolling resistance performance and (2) wet performance.

[0073] (1) For the evaluation of low rolling resistance performance, a test tire with a tire size of 195 / 65R15 was mounted on a rim with a rim size of 15x6, and an internal pressure of 230 kPa and a load of 4.82 kN were applied to the test tire. A drum testing machine with a drum diameter of 1707 mm was used, and the reciprocal of the rolling resistance coefficient of the test tire was calculated and evaluated in accordance with ISO 28580 at a speed of 80 km / h. This evaluation was performed using an index evaluation with the comparative example as the standard (100), with the higher the value, the better.

[0074] (2) For the evaluation of wet performance, a test tire with a tire size of 195 / 65R15 was mounted on a rim with a rim size of 15x6, and an internal pressure of 230 kPa and a load of 4.1 kN were applied to the test tire. The test vehicle was then driven on an asphalt road sprayed with water at a depth of 1 mm, and the braking distance from an initial speed of 40 km / h was measured. Based on the measurement results, an index rating was then given, with the comparative example being assigned a standard value of 100. The higher the rating, the better.

[0075] The test tires of the example and comparative examples have the configurations shown in Figures 1 and 2. The tire outer diameter OD (not shown) is 640 mm, the tire section width DW (see Figure 1) is 211 mm, and the radial distance D1 from point P1 to point T1 is 63 mm.

[0076] As the test results show, the test tires of the examples can achieve both low rolling resistance and wet performance under conditions of use at high internal pressure. [Explanation of symbols]

[0077] 1 tire; 2s shoulder main groove; 2c center main groove; 11 bead core; 12 bead filler; 13 carcass layer; 14 belt layer; 141 inner diameter side cross belt; 142 outer diameter side cross belt; 143 belt cover; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber

Claims

1. A tire comprising a carcass layer, a belt layer formed by laminating a pair of cross belts, a tread rubber, and a sidewall rubber, When viewed in a cross section in the tire meridian direction with the tire mounted on a specified rim and in an unloaded state with a pressure of 230 kPa applied, the maximum diameter position of the tire profile is defined as point P1, the maximum width position of the tire profile is defined as point T1, the intersection of a straight line passing through point T1 and parallel to the tire width direction with the tire equatorial plane is defined as point T2, a position that is 30% of the distance from point T1 to point T2 is defined as point T3, a position that is 20% of the distance from point T1 to point T2 is defined as point T4, a position that is 15% of the distance from point T1 to point T2 is defined as point T5, a position that is 10% of the distance from point T1 to point T2 is defined as point T6, and a position that is 3% of the distance from point T1 to point T2 is defined as point T7. a radial distance D3 from the point P1 to the point T3 is in a range of 0.05≦D3 / D1≦0.15 with respect to a radial distance D1 from the point P1 to the point T1; A radial distance D6 from the point P1 to the point T6 is in the range of 3.00≦D6 / D3≦6.00 with respect to a radial distance D3 from the point P1, and A tire characterized in that a radius of curvature R1 of a first circular arc passing through points T3, T4, and T5, relative to a radius of curvature R2 of a second circular arc passing through points T1, T6, and T7, is in the range of 0.40≦R1 / R2≦1.

00.

2. 2. The tire according to claim 1, wherein a radial distance D5 from point P1 to point T5 is in the range of 0.20≦D5 / D1≦0.40 relative to a radial distance D1 from point P1 to point T1.

3. 3. The tire according to claim 1, wherein the radial distance Da from point T3 to point T4 and the radial distance Db from point T4 to point T5 are in the range of 0.20≦Da / Db≦1.

30.

4. The tire according to claim 1, wherein the radius of curvature R1 of the first circular arc is in a range of 20 mm≦R1≦50 mm.

5. a plurality of circumferential main grooves; Among the plurality of circumferential main grooves, the circumferential main groove closest to the tire equatorial plane is defined as a center main groove, An intersection point P2 between a line passing through point P1 and parallel to the tire width direction and a line passing through point T5 and parallel to the tire radial direction is defined, and 2. The tire according to claim 1, wherein a groove cross-sectional area Ac of the center main groove in a cross section taken along the tire meridian direction is in a range of 0.30≦Ac / At≦1.00, relative to an area At of a region surrounded by intersection point P2, point T3, point T5, and the first arc.

6. The circumferential main groove located at the outermost side in the tire width direction among the plurality of circumferential main grooves is defined as a shoulder main groove, and 6. The tire according to claim 5, wherein a groove cross-sectional area Ac of the center main groove in a cross section taken along the tire meridian direction is in a range of 1.05≦Ac / As≦1.80 relative to a groove cross-sectional area As of the shoulder main groove.

7. 2. The tire according to claim 1, comprising a plurality of circumferential main grooves, wherein the circumferential main grooves located outermost in the tire width direction among the plurality of circumferential main grooves are defined as shoulder main grooves, and a distance Ds from the tire equatorial plane to the shoulder main groove, relative to a tire cross-sectional width DW, is in a range of 0.03≦Ds / DW≦0.

20.

8. 2. The tire according to claim 1, wherein the tire section width DW and the tire outer diameter OD are in the range of DW / OD≦0.

40.

9. 2. The tire according to claim 1, wherein a belt width Wb1 of the wider one of the pair of cross belts is in a range of 0.60≦Wb1 / DW≦0.90 relative to the tire cross section width DW.

10. 2. The tire according to claim 1, wherein a gauge Ga3 from point T3 to the outer diameter side cross belt of the pair of cross belts is in a range of 0.70≦Ga3 / Ga1≦0.98 relative to a gauge Ga1 from point P1 to the outer diameter side cross belt.

11. 2. The tire according to claim 1, wherein a gauge Gb3 from point T3 to the tire inner surface is in the range of 0.80≦Gb3 / Gb1≦1.10 relative to a gauge Gb1 from point P1 to the tire inner surface.

12. 2. The tire according to claim 1, wherein a gauge Gb4 from point T4 to the tire inner surface is in the range of 0.70≦Gb4 / Gb3≦1.10 relative to a gauge Gb3 from point T3 to the tire inner surface.

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