tire

Abstract

To provide a tire configured to effectively suppress a failure due to deflection of the tire and a failure due to flection between the tire and a rim flange to improve durability.SOLUTION: In a tire 10, whose cross section height SH is in a range of 50 mm-150 mm, under an unloaded condition that the tire 10 is assembled to a specific rim and is filled with a specific inner pressure, when an opening distance between the tire 10 and a rim flange 22 on a perpendicular line drawn on an outer surface of the tire 10 from an outermost point Tr in a radial direction of the rim flange 22 is defined as A, the opening distance A with respect to the cross section height SH satisfies a relational expression of 0.01≤A / SH≤0.16, and when a point at which a horizontal line in a tire width direction passing on the outermost point Tr in the radial direction of the rim flange 22 crosses the outer surface of the tire 10 is defined as P and when a point at which a rim width DW and a rim diameter DO of the specific rim 21 are specified is defined as Q, an angle α formed by a straight line connecting the point P to the point Q with respect to the horizontal line in the tire width direction is in a range of 50°≤α≤80°.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire suitable for situations where high load capacity is required, and more specifically, to a tire that effectively suppresses failures caused by tire bending and failures caused by rubbing between the tire and rim flange, thereby improving durability. [Background technology]

[0002] With the increase in vehicle weight due to the electrification of automobiles, etc., there is a demand for tires with high load capacity. However, if the deformation that occurs repeatedly from the sidewall to the bead when the tire rolls due to the increase in load increases, there is a problem that the durability of the tire deteriorates.

[0003] In response to this, it has been proposed to improve durability in heavy-duty tires by defining the shape of the bead portion relative to the shape of the rim flange (see, for example, Patent Document 1). However, simply defining the shape of the bead portion relative to the shape of the rim flange is not effective enough to improve durability, and there are still concerns that failures due to tire bending or rubbing between the tire and the flange may occur. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-34619 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a tire which effectively suppresses failures caused by tire bending and failures caused by rubbing between the tire and the rim flange, thereby improving durability. [Means for solving the problem]

[0006] In order to achieve the above object, the tire of the present invention has a section height SH in the range of 50 mm to 150 mm, When the tire is mounted on a specified rim and inflated to a specified internal pressure in an unloaded state, the opening distance A between the tire and the rim flange on a perpendicular line drawn from the radially outermost point of the rim flange to the outer surface of the tire satisfies the relationship of 0.01≦A / SH≦0.16 with respect to the cross-sectional height SH, the point where a horizontal line in the tire width direction passing through the radially outermost point of the rim flange intersects with the outer surface of the tire is defined as P, and a point defining the rim width and rim diameter of the specified rim is defined as Q, the angle α that the straight line connecting point P and point Q makes with the horizontal line in the tire width direction is in the range of 50°≦α≦80°. Effect of the Invention

[0007] As a result of extensive research by the inventors into the behavior of the bead portion of passenger vehicle tires with a cross-sectional height SH in the range of 50 mm to 150 mm, they discovered that since the cross-sectional height SH of the tire has a significant effect on the deflection of the tire, by appropriately specifying the opening distance A between the tire and the rim flange in relation to the cross-sectional height SH, and by appropriately specifying the angle α corresponding to the inclination angle of the bead portion, failures caused by the deflection of the tire and failures caused by rubbing between the tire and the flange can be effectively suppressed, which led to the present invention.

[0008] That is, in the present invention, when a tire is mounted on a specified rim and inflated to a specified internal pressure in an unloaded state, if the opening distance between the tire and the rim flange on a perpendicular line drawn from the radially outermost point of the rim flange to the outer surface of the tire is A, the opening distance A satisfies the relationship of 0.01≦A / SH≦0.16 with respect to the cross-sectional height SH, if the point where a horizontal line in the tire width direction passing through the radially outermost point of the rim flange intersects with the outer surface of the tire is P, and the point defining the rim width and rim diameter of the specified rim is Q, the angle α that the straight line connecting points P and Q makes with the horizontal line in the tire width direction is in the range of 50°≦α≦80°, thereby effectively suppressing failures caused by tire bending and failures caused by rubbing between the tire and the flange, and as a result, improving tire durability.

[0009] In the present invention, when the tire is mounted on a specified rim and inflated to a specified internal pressure in an unloaded state, and the point defining the total width of the tire is taken as L, it is preferable that the angle θ that the line connecting points P and Q makes with the line connecting points L and Q is in the range of 2°≦θ≦30°. This allows the opening distance A to be optimized with respect to the amount of deflection deformation, thereby enhancing the effect of improving durability.

[0010] In an unloaded state where a tire is mounted on a specified rim and inflated to a specified internal pressure, if the opening start point where the rim flange separates from the tire is defined as S, the radially outermost point of the rim flange is defined as Tr, and the point where a perpendicular line drawn from point Tr to the outer surface of the tire intersects with the outer surface of the tire, then it is preferable that the angle β that the line connecting points S and T makes with the line connecting points S and Tr is in the range of 15°≦β≦65°. This can enhance the effect of improving durability.

[0011] When a tire is mounted on a specified rim and inflated to a specified internal pressure in an unloaded state, and the point where the rim flange separates from the tire is defined as S, it is preferable that the horizontal distance B in the tire width direction between points Q and S satisfy the relationship 0.02≦B / SH≦0.18 with respect to the cross-sectional height SH. This brings the stress caused by repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0012] When the tire is mounted on a specified rim and inflated to a specified internal pressure in an unloaded state, and the opening start point where the rim flange separates from the tire is defined as S, the horizontal distance B in the tire width direction between points Q and S is preferably in the range of 3.0 mm≦B≦9.0 mm. This brings the stress caused by repeated deformation into an appropriate range, enhancing the effect of improving durability.

[0013] Opening distance A is 1.5mm or less A It is preferable that the thickness is in the range of ≦8.0 mm. This brings the stress caused by repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0014] Furthermore, in an unloaded state where the tire is mounted on a specified rim and inflated to a specified internal pressure, if the opening start point where the rim flange separates from the tire is defined as S, the radially outermost point of the rim flange is defined as Tr, and the point where a perpendicular line drawn from point Tr to the outer surface of the tire intersects with the outer surface of the tire is defined as T, it is preferable that the arc of the tire passing through points S, P, and T has its center on the outer side in the tire width direction. This makes it less likely that compressive stress will be applied to the part of the tire that comes into contact with the rim flange, thereby enhancing the effect of improving durability.

[0015] In an unloaded state where a tire is mounted on a specified rim and inflated to a specified internal pressure, if the opening start point where the rim flange separates from the tire is defined as S, the radially outermost point of the rim flange is defined as Tr, the point where a perpendicular line drawn from point Tr to the tire's outer surface intersects with the tire's outer surface, and the point where a perpendicular line drawn from point P to the tire's outer surface intersects with the outer surface of the rim flange, then it is preferable that the radius of curvature Rr of the rim flange's arc passing through points S, Pr, and Tr and the radius of curvature Rb of the tire's arc passing through points S, P, and T satisfy the relationship 1.2≦Rb / Rr≦14.5. This makes it less likely that compressive stress will be applied to the part of the tire that comes into contact with the rim flange, thereby enhancing the effect of improving durability.

[0016] In a tire having multiple belt layers embedded in the tread portion, in a no-load state where the tire is mounted on a specified rim and inflated to a specified internal pressure, when the point where a horizontal line in the tire width direction passing through an edge portion of the belt layer located at the innermost side in the tire radial direction among the multiple belt layers intersects with the outer surface of the tire is defined as V, and the point defining the total width of the tire is defined as L, it is preferable that the angle γ that the straight line connecting point L and point V makes with the horizontal line in the tire width direction is in the range of 45°≦γ≦80°. This brings the stress due to repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0017] In an unloaded state in which a tire is mounted on a specified rim and inflated to a specified internal pressure, when a point W is on the outer surface of the tire at the center position in the tire radial direction between points L and V, it is preferable that the radius of curvature Rs of the tire's arc passing through points V, W, and L satisfies the relationship 0.3≦Rs / SH≦2.5 with respect to the cross-sectional height SH. This brings the stress due to repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0018] In the present invention, the dimensions measured in an unloaded state are measured in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure. On the other hand, the dimensions measured in a loaded state are measured in a state in which the tire is mounted on a specified rim, inflated to a specified internal pressure, and placed vertically on a flat surface and loaded with a load of 100% of the specified load capacity. Each dimension is the average value of measurements taken at four points on the tire circumference. The "specified rim" is a rim that is determined for each tire by a standard system including the standard on which the tire is based, for example, a standard rim for JATMA, a "Design Rim" for TRA, or a "Measuring Rim" for ETRTO. The "specified internal pressure" is an air pressure that corresponds to the maximum load capacity determined for each tire by each standard in the standard system including the standard on which the tire is based. The "specified load capacity" is the maximum load capacity determined for each tire by each standard in the standard system including the standard on which the tire is based. [Brief description of the drawings]

[0019] [Figure 1] 1 is a meridian half cross-sectional view showing a pneumatic tire (unloaded state) according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view showing a bead portion of the pneumatic tire (unloaded state) of FIG. 1. FIG. [Diagram 3] 2 is a cross-sectional view showing a bead portion and a sidewall portion of the pneumatic tire (unloaded state) of FIG. 1. [Figure 4] 2 is another cross-sectional view showing a bead portion of the pneumatic tire (in an unloaded state) of FIG. 1. FIG. [Diagram 5] 2 is another cross-sectional view showing a bead portion of the pneumatic tire (in an unloaded state) of FIG. 1. FIG. [Figure 6] 2 is another cross-sectional view showing a bead portion of the pneumatic tire (in an unloaded state) of FIG. 1. FIG. [Figure 7] 2 is another cross-sectional view showing a bead portion and a sidewall portion of the pneumatic tire (unloaded state) of FIG. 1. FIG. [Figure 8] 2 is another cross-sectional view showing a bead portion of the pneumatic tire (in an unloaded state) of FIG. 1. FIG. [Figure 9] 2 is a cross-sectional view showing a bead portion of the pneumatic tire (under 100% load) in FIG. 1. [Figure 10] 2 is another cross-sectional view showing a bead portion of the pneumatic tire (in an unloaded state) of FIG. 1. FIG. [Figure 11] 2 is another cross-sectional view showing a bead portion of the pneumatic tire (in an unloaded state) of FIG. 1. FIG. [Figure 12] FIG. 11 is a cross-sectional view showing a modified example of a bead portion (unloaded state). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. Figures 1 to 12 show a pneumatic tire according to an embodiment of the present invention. Figure 1 illustrates one side of the pneumatic tire bounded by the tire equator CL, and the pneumatic tire has a symmetrical or asymmetrical structure on both sides of the tire equator CL.

[0021] As shown in FIG. 1, the pneumatic tire 10 of this embodiment includes a tread portion 1 extending circumferentially around the tire to form an annular shape, a pair of sidewall portions 2, 2 arranged on either side of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0022] A carcass layer 4 is fitted between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5. The carcass layer 4 has a main portion 4A and a turned-up portion 4B, with the bead core 5 as the boundary.

[0023] On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, a range of 10° to 40°. As the reinforcing cords of the belt layers 7, steel cords are preferably used. On the outer peripheral side of the belt layers 7, at least one belt cover layer 8 is arranged in which reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction for the purpose of improving high-speed durability. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0024] The above-mentioned tire internal structure shows a typical example of a pneumatic tire 10, but is not limited thereto. In Fig. 1, a tread rubber layer 11 is disposed in the tread portion 1, a sidewall rubber layer 12 is disposed in the sidewall portion 2, a rim cushion rubber layer 13 is disposed in the bead portion 3, and an inner liner rubber layer 14 is disposed along a carcass layer 4 on the inner surface of the tire 10. Also, a rim protector 15 for protecting a rim flange 22 is formed in the sidewall portion 2 so as to protrude outward in the tire width direction.

[0025] The above-mentioned tire 10 has a cross-sectional height SH in the range of 50 mm to 150 mm, and is mainly a tire for passenger cars. The following configuration is applied to such a tire 10. That is, as shown in Fig. 1 and Fig. 2, in a no-load state in which the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, when the opening distance between the tire 10 and the rim flange 22 on a perpendicular line drawn from the radially outermost point Tr of the rim flange 22 to the outer surface of the tire 10 is A (mm), the opening distance A satisfies the relationship of 0.01 ≦ A / SH ≦ 0.16 with respect to the cross-sectional height SH (mm), and when the point where the horizontal line in the tire width direction passing through the radially outermost point Tr of the rim flange 22 intersects with the outer surface of the tire 10 is P, and the point that specifies the rim width DW and rim diameter DO of the specified rim 21 is Q, the angle α that the straight line connecting point P and point Q makes with the horizontal line in the tire width direction is in the range of 50 ° ≦ α ≦ 80 °. In addition, when the rim flange 22 has a portion that extends parallel to the tire width direction at its radially outermost position, the radially outermost point Tr of the rim flange 22 is the widthwise innermost point of the rim flange 22 at the radially outermost position of the rim flange 22.

[0026] In the tire 10 described above, the opening distance A between the tire 10 and the rim flange 22 in an unloaded state satisfies the relationship 0.01≦A / SH≦0.16 with respect to the cross-sectional height SH, and the angle α corresponding to the inclination angle of the bead portion 3 is in the range of 50°≦α≦80°, so that the opening distance A is optimized with respect to the amount of flexural deformation of the tire 10, and failures caused by the flexure of the tire 10 and failures caused by rubbing between the tire 10 and the flange 22 can be effectively suppressed. This suppresses failures near the bead portion 3 and improves the durability of the tire 10. In particular, when the aspect ratio of the tire 10 is 55% or less, excellent durability is required, and in such a case, the effect of improving durability can be maximized.

[0027] Here, if the ratio A / SH is less than 0.01, the opening distance A becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 22 increases, leading to failure, while if it exceeds 0.16, the opening distance A becomes too large, making it more likely to cause failure due to rubbing between the tire 10 and the rim flange 22, and furthermore, making it easier for small stones and the like to get in, which may result in a significant deterioration in durability. In particular, it is desirable to satisfy the relationship 0.015≦A / SH≦0.14, and furthermore, to satisfy the relationship 0.02≦A / SH≦0.12.

[0028] Similarly, if the angle α is less than 50°, the opening distance A will be insufficient, and when the tire 10 flexes, the stress near the rim flange 22 will be large, leading to failure, and conversely, if it exceeds 80°, the opening distance A will be too large, making it more likely to cause failure due to rubbing between the tire 10 and the rim flange 22, and furthermore, making it easier for small stones and the like to get in, which may result in a significant deterioration in durability. In particular, it is desirable to satisfy the range of 55°≦α≦75°, and further to satisfy the range of 60°≦α≦70°.

[0029] In the tire 10, as shown in Fig. 1 and Fig. 3, in a no-load state in which the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, when a point that defines the total width TW of the tire 10 is L, the angle θ that the line connecting points P and Q makes with the line connecting points L and Q is preferably in the range of 2°≦θ≦30°. This allows the opening distance A to be optimized with respect to the amount of deflection deformation, and the effect of improving durability to be enhanced. The total width TW of the tire 10 is the total width of the tire 10 at the position where the carcass layer 4 bulges most outward in the tire width direction. In other words, the rim protector 15 for protecting the rim flange 22 is excluded from the total width TW.

[0030] Here, if the angle θ is less than 2°, the opening distance A becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 12 increases, leading to failure, whereas if it exceeds 30°, the opening distance A becomes too large, making failures more likely to occur due to rubbing between the tire 10 and the rim flange 22, and in either case, the effect of improving durability decreases. In particular, it is desirable to satisfy the range of 4°≦θ≦25°, and further to satisfy 6°≦θ≦20°.

[0031] 4, in the above tire 10, in an unloaded state where the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, when the opening start point where the rim flange 22 separates from the tire 10 is defined as S, the radially outermost point of the rim flange 22 is defined as Tr, and the point where a perpendicular line drawn from point Tr to the outer surface of the tire 10 intersects with the outer surface of the tire, it is preferable that the angle β that the line connecting points S and T makes with the line connecting points S and Tr is in the range of 15°≦β≦65°. This can enhance the effect of improving durability.

[0032] Here, if the angle β is less than 15°, the stress near the rim flange 22 increases when the tire 10 flexes, leading to breakdown, whereas if it exceeds 65°, breakdown is likely to occur due to rubbing between the tire 10 and the rim flange 22. It is particularly desirable to satisfy the range of 20°≦β≦60°, and further to satisfy the range of 25°≦β≦55°.

[0033] In the tire 10, it is preferable that the horizontal distance B (mm) in the tire width direction between points Q and S satisfies the relationship 0.02≦B / SH≦0.18 with respect to the section height SH (mm) as shown in Fig. 5. This brings the stress due to repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0034] Here, if the ratio B / SH is less than 0.02, failures due to rubbing between the tire 10 and the rim flange 22 are likely to occur, and conversely, if it exceeds 0.18, stress in the vicinity of the rim flange 22 increases when the tire 10 flexes, leading to failures, and in either case, the effect of improving durability decreases. In particular, it is desirable to satisfy the relationship 0.03≦B / SH≦0.15, and further to satisfy the relationship 0.04≦B / SH≦0.13.

[0035] In the tire 10, it is preferable that the horizontal distance B is in the range of 3.0 mm≦B≦9.0 mm. This brings the stress due to repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0036] If the horizontal distance B is less than 3.0 mm, the tire 10 is more likely to break down due to rubbing against the rim flange 22, whereas if it exceeds 9.0 mm, the stress in the vicinity of the rim flange 12 increases when the tire 10 flexes, leading to a breakdown, and in either case the effect of improving durability decreases. In particular, it is preferable that the horizontal distance B is in the range of 3.2 mm≦B≦8.5 mm, and more preferably in the range of 3.4 mm≦B≦8.0 mm.

[0037] In the tire 10, the opening distance A is preferably in the range of 1.5 mm≦A≦8.0 mm, which can suppress stress caused by repeated deformation and enhance the effect of improving durability.

[0038] Here, if the opening distance A is less than 1.5 mm, the opening distance A becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 12 increases, leading to failure, whereas if it exceeds 8.0 mm, the opening distance A is too large, making it more likely to fail due to rubbing between the tire 10 and the rim flange 22, and in either case, the effect of improving durability decreases. In particular, it is preferable that the opening distance A is in the range of 1.8 mm≦A≦7.5 mm, and more preferably in the range of 2.0 mm≦A≦7.0 mm.

[0039] 6, in the above tire 10, when a perpendicular line drawn from the radially outermost point Tr of the rim flange 22 to the outer surface of the tire 10 intersects with the outer surface of the tire 10 at point T, it is preferable that an arc (with a curvature radius Rb) of the tire 10 passing through points S, P, and T has a center on the outer side in the tire width direction. This makes it difficult for compressive stress to be applied to the portion of the tire 10 that contacts the rim flange 22, thereby enhancing the effect of improving durability.

[0040] 6, if the point Pr is the point where a perpendicular line drawn from point P to the outer surface of the tire 10 intersects with the outer surface of the rim flange 22, it is preferable that the radius of curvature Rr (mm) of the arc of the rim flange 22 passing through points S, Pr, and Tr and the radius of curvature Rb (mm) of the arc of the tire 10 passing through points S, P, and T satisfy the relationship 1.2≦Rb / Rr≦14.5. This makes it difficult for compressive stress to be applied to the portion of the tire 10 that comes into contact with the rim flange 22, thereby enhancing the effect of improving durability.

[0041] If the ratio Rb / Rr is out of the above range, compressive stress is likely to be applied to the portion of the tire 10 that comes into contact with the rim flange 22, reducing the effect of improving durability. It is particularly desirable to satisfy the relationship 1.5≦Rb / Rr≦12.2, and more preferably 2.0≦Rb / Rr≦10.0.

[0042] In the tire 10, as shown in Fig. 7, in a no-load state in which the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, when a point where a horizontal line in the tire width direction passing through an edge portion of the belt layer 7 located at the innermost position in the tire radial direction among the multiple belt layers 7 intersects with the outer surface of the tire 10 is denoted as V, and a point defining the total width TW of the tire 10 is denoted as L, it is preferable that an angle γ that a straight line connecting points L and V makes with the horizontal line in the tire width direction is in the range of 45°≦γ≦80°. This brings the stress due to repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0043] Here, if the angle γ is out of the above range, the stress due to repeated deformation will be out of the appropriate range, and the effect of improving durability will decrease. In particular, it is preferable that the angle γ satisfies the range of 50°≦γ≦75°, and more preferably, the range of 55°≦γ≦70°.

[0044] 7, when a point W is on the outer surface of tire 10 at the center position in the tire radial direction between points L and V, it is preferable that the radius of curvature Rs of the circular arc of tire 10 passing through points V, W, and L satisfies the relationship 0.3≦Rs / SH≦2.5 with respect to the cross-sectional height SH. This brings the stress due to repeated deformation into an appropriate range, and the effect of improving durability can be enhanced.

[0045] If the ratio Rs / SH is out of the above range, the stress due to repeated deformation will be out of the appropriate range, and the effect of improving durability will decrease. In particular, it is preferable that the relationship 0.4≦Rs / SH≦2.3 is satisfied, and more preferably, the relationship 0.5≦Rs / SH≦2.0 is satisfied.

[0046] In the above tire 10, as shown in Figures 1 and 8, in an unloaded state where the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, when the protrusion amount W (mm) corresponds to half the difference between the total width TW of the tire 10 and the rim width DW of the specified rim 21, it is preferable that the opening distance A and the protrusion amount W satisfy the relationship 0.03≦A / W≦1.60.

[0047] In this way, by having the opening distance A between the tire 10 and the rim flange 22 in an unloaded state satisfy the relationship of 0.03≦A / W≦1.60 for the protrusion amount W equivalent to half the difference between the total width TW of the tire 10 and the rim width DW of the specified rim 21, the opening distance A can be optimized with respect to the amount of flexural deformation of the tire 10, and failures caused by flexure of the tire 10 and failures caused by rubbing between the tire 10 and the flange 22 can be effectively suppressed. This can suppress failures near the bead portion 3, and further enhance the effect of improving the durability of the tire 10.

[0048] Here, if the ratio A / W is less than 0.03, the opening distance A becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 22 increases, leading to failure, while if it exceeds 1.60, the opening distance A becomes too large, making it more likely to cause failure due to rubbing between the tire 10 and the rim flange 22, and furthermore, making it easier for small stones and the like to get in, which may result in a significant deterioration in durability. In particular, it is desirable to satisfy the relationship 0.035≦A / W≦1.5, and furthermore, to satisfy the relationship 0.04≦A / W≦1.4.

[0049] In the above tire 10, as shown in FIG. 9, when the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure while being loaded with a load of 100% of the specified load capacity, the opening distance between the tire 10 and the rim flange 22 on a perpendicular line drawn from the radially outermost point Tr of the rim flange 22 to the outer surface of the tire 10 is defined as A. 100 (mm), the opening distance A 100 is 0.003≦A for the cross-sectional height SH (mm) 100 It is recommended that the relationship / SH≦0.100 is satisfied. 100 The measurement position of the opening distance A is the same as the measurement position of the opening distance A when the tire 10 is deformed in this way. 100 By optimizing the above, the effect of improving durability can be enhanced.

[0050] Here, the ratio A 100 When / SH is less than 0.003, the opening distance A 100If the opening distance A is insufficient, the stress in the vicinity of the rim flange 12 increases when the tire 10 is bent, leading to failure. 100 Since A is too large, the tire 10 is more likely to be damaged due to friction between the tire 10 and the rim flange 22, and in either case, the effect of improving durability is reduced. 100 / SH≦0.070, and furthermore, 0.007≦A 100 It is desirable to satisfy the relationship / SH≦0.065.

[0051] In the tire 10, the opening distance A 100 (mm) is 0.010≦A for protrusion amount W(mm) 100 It is preferable to satisfy the relationship of / W≦1.000. This can enhance the effect of improving durability.

[0052] Here, the ratio A 100 When / W is less than 0.010, the opening distance A 100 If the opening distance A is insufficient, the stress in the vicinity of the rim flange 22 will increase when the tire 10 is bent, leading to failure. 100 Since A is too large, the tire 10 is more likely to be damaged due to friction between the tire 10 and the rim flange 22, and in either case, the effect of improving durability is reduced. 100 / W≦0.800 and 0.020≦A 100 It is desirable to satisfy the relationship: / W≦0.800.

[0053] In the above tire 10, the opening distance A (mm) and the opening distance A 100 (mm) is 0.20≦A 100 It is preferable that the relationship of / A≦0.80 is satisfied. This makes it possible to suppress the stress caused by repeated deformation and to enhance the effect of improving durability.

[0054] Here, the ratio A 100If / A is less than 0.20, the deformation in the vicinity of the rim flange 22 when the tire 10 is bent is significantly large, which may reduce the effect of improving durability. Conversely, if it exceeds 0.80, the deformation in a position away from the rim flange 22 when the tire 10 is bent is significantly large, which may reduce the effect of improving durability. In particular, 0.23≦A 100 / A≦0.75, and furthermore, 0.25≦A 100 It is desirable to satisfy the relationship: / A≦0.70.

[0055] In the tire 10, it is preferable that the opening distance A (mm) satisfies the relationship of 0.01≦A / SDH≦0.50 with respect to the height SDH (mm) in the tire radial direction up to the maximum width position (measurement position of the total width TW) of the tire 10. By specifying the opening distance A with respect to the height SDH, which has a large effect on the deformation of the bead portion 3, it is possible to suppress the stress caused by repeated deformation and to enhance the effect of improving durability.

[0056] Here, if the ratio A / SDH is less than 0.01, the opening distance A becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 12 increases, leading to failure, while if it exceeds 0.50, the opening distance A becomes too large, making failures more likely to occur due to rubbing between the tire 10 and the rim flange 22, and in either case, the effect of improving durability decreases. In particular, it is desirable to satisfy the relationship 0.02≦A / SDH≦0.45, and furthermore, to satisfy the relationship 0.03≦A / SDH≦0.40.

[0057] In the tire 10 described above, as shown in Figure 8, in an unloaded state in which the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, when the opening distance A' (mm) between the tire 10 and the rim flange 22 on a perpendicular line drawn from a midpoint Ur between the radially outermost point Tr of the rim flange 22 and an opening start point S where the rim flange 22 separates from the tire 10 to the outer surface of the tire 10, it is preferable that the opening distance A' and the cross-sectional height SH (mm) satisfy the relationship 0.006≦A' / SH≦0.150. This makes it possible to suppress stress caused by repeated deformation and enhance the effect of improving durability.

[0058] Here, if the ratio A' / SH is less than 0.006, the opening distance A' becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 12 increases, leading to failure, while if it exceeds 0.150, the opening distance A' becomes too large, making failures more likely to occur due to rubbing between the tire 10 and the rim flange 22, and in either case, the effect of improving durability decreases. In particular, it is desirable to satisfy the relationship 0.010≦A' / SH≦0.130, and further to satisfy the relationship 0.014≦A' / SH≦0.110.

[0059] In the tire 10, it is preferable that the opening distance A (mm) and the opening distance A' (mm) satisfy the relationship 0.50≦A' / A≦0.96. This makes it possible to suppress stress caused by repeated deformation and to enhance the effect of improving durability.

[0060] Here, if the ratio A' / A is less than 0.50, the opening distance A' becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 12 increases, leading to failure, while if it exceeds 0.96, the opening distance A' becomes too large, making failures more likely to occur due to rubbing between the tire 10 and the rim flange 22, and in either case, the effect of improving durability decreases. In particular, it is desirable to satisfy the relationship 0.53≦A' / A≦0.94, and furthermore, to satisfy the relationship 0.56≦A' / A≦0.92.

[0061] In the tire 10, the opening distance A' is preferably in the range of 1.0 mm≦A'≦7.5 mm, which can suppress stress caused by repeated deformation and enhance the effect of improving durability.

[0062] Here, if the opening distance A' is less than 1.0 mm, the opening distance A' becomes insufficient, and when the tire 10 flexes, the stress near the rim flange 12 increases, leading to failure, whereas if it exceeds 7.5 mm, the opening distance A' is too large, making it more likely to fail due to rubbing between the tire 10 and the rim flange 22, and in either case, the effect of improving durability decreases. In particular, it is preferable that the opening distance A' is in the range of 1.2 mm≦A'≦7.0 mm, and more preferably in the range of 1.4 mm≦A'≦6.5 mm.

[0063] In the tire 10 described above, as shown in FIG. 10, in a no-load state in which the tire 10 is mounted on a specified rim 21 and inflated to a specified internal pressure, the opening start point where the rim flange 22 separates from the tire 10 is defined as S, and the point where a perpendicular line drawn from the radially outermost point Tr of the rim flange 22 to the outer surface of the tire 10 intersects with the outer surface of the tire 10 is defined as T. When two perpendicular lines are drawn from point S and point T to the turned-up portion 4B of the carcass layer 4, the cross-sectional area Sr of the rubber portion R (shaded portion) included in the region surrounded by these two perpendicular lines and the turned-up portion 4B of the carcass layer 4 is 12 mm 2 ≦Sr≦101mm 2 It is preferable that the cross-sectional area Sr of the rubber portion R is the cross-sectional area of ​​the portion located outside the carcass cords that constitute the carcass layer 4.

[0064] In this way, the cross-sectional area Sr of the rubber portion R which performs the cushioning action for the rim flange 22 is 12 mm 2 ≦Sr≦101mm 2 By being in this range, the opening distance A can be optimized with respect to the amount of flexural deformation of the tire 10, and failures caused by flexure of the tire 10 and failures caused by rubbing between the tire 10 and the flange 22 can be effectively suppressed. This makes it possible to suppress failures near the bead portion 3 and further enhance the effect of improving the durability of the tire 10.

[0065] Here, the cross-sectional area Sr of the rubber part R is 12 mm 2 If the thickness is less than 101 mm, compressive stress is likely to be applied to the carcass layer 4 near the rim flange 22 when the tire 10 is bent, which may lead to failure.2 If the opening distance A is more than 14 mm, it becomes difficult to secure a sufficient opening distance A, and when the tire 10 is bent, the stress in the vicinity of the rim flange 22 becomes large, which leads to failure. 2 ≦Sr≦98mm 2 The range is satisfied, and furthermore, 16mm 2 ≦Sr≦93mm 2 It is desirable to satisfy the range of

[0066] 11, when the thickness of the rubber portion R on a perpendicular line drawn from point S to the turned-up portion 4B of the carcass layer 4 is Gl (mm) and the thickness of the rubber portion R on a perpendicular line drawn from point T to the turned-up portion 4B of the carcass layer 4 is Gu (mm), it is preferable that the thicknesses Gl and Gu satisfy the relationship 0.40≦Gl / Gu≦0.90. This ensures a good cushioning effect and enhances the effect of improving durability.

[0067] Here, if the ratio Gl / Gu is out of the above range, the cushioning effect is reduced, and the effect of improving durability is reduced. In particular, it is preferable that the relationship of 0.45≦Gl / Gu≦0.85 is satisfied, and more preferably, the relationship of 0.50≦Gl / Gu≦0.80 is satisfied. Moreover, it is preferable that the thickness Gl of the rubber portion R is in the range of 0.5 mm≦Gl≦4.0 mm, and more preferably, in the range of 1.5 mm≦Gl≦3.0 mm. The thicknesses Gl and Gu of the rubber portion R can also be measured on a cut sample of the tire 10.

[0068] In the tire 10, as shown in FIG. 11, in a no-load state in which the tire 10 is assembled to a specified rim 21 and inflated to a specified internal pressure, the point where a perpendicular line drawn from point S to the turned-up portion 4B of the carcass layer 4 intersects with the turned-up portion 4B of the carcass layer 4 is Sc, the point where a perpendicular line drawn from point T to the turned-up portion 4B of the carcass layer 4 intersects with the turned-up portion 4B of the carcass layer 4 is Tc, and the midpoint between points Sc and Tc is Uc, it is preferable that the arc (curvature radius Rc) of the carcass layer 4 passing through points Sc, Tc, and Uc has a center on the outer side in the tire width direction. This makes it difficult for compressive stress to be applied to the carcass layer 4 during tire deformation, thereby improving the durability. It is preferable that the arc of the carcass layer 4 passing through points Sc, Tc, and Uc has a center on the outer side in the tire width direction even when the tire 10 is in a state where it is not assembled to a rim alone or when 100% load is applied.

[0069] In particular, as shown in Figure 11, when the midpoint between points S and Tr is defined as Ur, it is preferable that the radius of curvature Rr (mm) of the arc of the rim flange 22 passing through points S, Tr, and Ur and the radius of curvature Rc (mm) of the arc of the carcass layer 4 passing through points Sc, Tc, and Uc satisfy the relationship 1 ≤ Rc / Rr ≤ 55. This makes it difficult for compressive stress to be applied to the carcass layer 4 when the tire deforms, thereby enhancing the effect of improving durability.

[0070] If the ratio Rc / Rr is out of the above range, compressive stress is likely to be applied to the carcass layer 4 during tire deformation, and the effect of improving durability is reduced. In particular, it is preferable that the relationship 2≦Rc / Rr≦50 is satisfied, and further, the relationship 3≦Rc / Rr≦45 is satisfied.

[0071] FIG. 12 shows a modified example of the bead portion. In FIG. 12, the main body portion 4A and the turned-up portion 4B of the carcass layer 4 contact each other without a bead filler, forming a closed region that encloses the bead core 5. In other words, the carcass layer 4 is wound up around the bead core 5 from the inside to the outside of the tire, and is arranged so that the main body portion 4A and the turned-up portion 4B are in close contact with each other at the upper end position of the bead core 5. By adopting such a turned-up structure of the carcass layer 4, it is possible to move the carcass layer 4 away from the rim flange 22 at the contact portion with the rim flange 22, so that the compressive stress applied to the carcass layer 4 can be significantly reduced and the durability can be improved. The rubber occupancy rate of the closed region formed by the carcass layer 4 is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less. The rubber occupancy rate referred to here is the percentage of the rubber portion (for example, the insulation rubber of the bead wire and small bead fillers) that occupies the closed region formed by the carcass layer 4 in the tire meridian cross section.

[0072] In the structure of FIG. 12, the durability can be improved by disposing a secondary bead filler 9 on the outer side of the turned-up portion 4B of the carcass layer 4 in the tire width direction or by thickening the rim cushion rubber layer 13. In this case, the cross-sectional area Sr of the rubber portion R is 36 mm 2 ≦Sr≦101mm 2 In particular, the range can be set to 42 mm. 2 ≦Sr≦98mm 2 The range is satisfied, and furthermore, 48 mm 2 ≦Sr≦93mm 2 It is desirable to satisfy the range of

[0073] In the above tire 10, when the tire 10 has a rim cushion rubber layer 13 arranged in an area that contacts the rim flange 22 and a sidewall rubber layer 12 arranged radially outward of the rim cushion rubber layer 13 as shown in Fig. 10, in an unloaded state in which the tire 10 is mounted on a specified rim and inflated to a specified internal pressure, it is preferable that the boundary point X between the rim cushion rubber layer 13 and the sidewall rubber layer 12 on the outer surface of the tire 10 is located radially outward of point T. In other words, it is preferable that the rim cushion rubber layer 13 extends from the underside of the bead core 5 toward the radially outward side of the tire at least to the position of point T. This makes it difficult for compressive stress to be applied to the carcass layer 4 when the tire deforms, thereby enhancing the effect of improving durability.

[0074] The hardness of the rim cushion rubber layer 13 at 20°C is preferably 55 or more and 80 or less. This improves the durability of the rim cushion rubber layer 13. If the hardness of the rim cushion rubber layer 13 falls outside the above range, the effect of improving durability decreases. The hardness is a durometer hardness measured at a temperature of 20°C using a type A durometer in accordance with JIS-K6253.

[0075] The 100% modulus of the rim cushion rubber layer 13 at 20°C is preferably 2.0 MPa or more and 9.5 MPa or less. This improves the durability of the rim cushion rubber layer 13. If the 100% modulus of the rim cushion rubber layer 13 falls outside the above range, the effect of improving durability decreases. The 100% modulus is the tensile stress at a specified elongation measured at a temperature of 20°C in accordance with JIS-K6251.

[0076] The loss tangent (tan δ) of the rim cushion rubber layer 13 at 20°C is preferably 0.05 or more and 0.35 or less. This makes it possible to suppress an increase in rolling resistance while ensuring the thickness (durability) of the rim cushion rubber layer 13. Here, if the loss tangent of the rim cushion rubber layer 13 exceeds 0.35, the rolling resistance will increase. The loss tangent (tan δ) is measured in accordance with JIS-K6394 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho) under conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ±2%, and a temperature of 60°C.

[0077] The intermediate elongation of the carcass cord constituting the carcass layer 4 under a load of 1.5 cN / dtex is preferably 3.3% or more and 6.2% or less. This can enhance the effect of improving durability. If the intermediate elongation of the carcass cord constituting the carcass layer 4 under a load of 1.5 cN / dtex is out of the above range, the effect of improving durability decreases. In particular, the intermediate elongation of the carcass cord under a load of 1.5 cN / dtex is preferably 3.8% or more and 5.9% or less. The intermediate elongation is measured by carrying out a tensile test on the carcass cord taken out from the sidewall portion of the tire 10 under the conditions of a gripping distance of 250 mm and a tensile speed of 300±20 mm / min in accordance with JIS-L1017.

[0078] The carcass cords constituting the carcass layer 4 are preferably organic fiber cords. When, for example, high modulus rayon cords are used as the carcass cords, durability is improved. The total thickness of the carcass layer 4 is preferably 0.8 mm or more and 1.5 mm or less. In the case of rayon cords, the cord diameter is preferably 0.6 mm or more and 1.1 mm or less, and the cord placement density is preferably 43 / 50 mm or more and 59 / 50 mm or less. Polyester cords, which have excellent fatigue resistance, are also suitable as the carcass cords. In the case of polyester cords, the cord diameter is preferably 0.7 mm or more and 1.2 mm or less, and the cord placement density is preferably 44 / 50 mm or more and 60 / 50 mm or less.

[0079] The angle of the carcass cords constituting the carcass layer 4 with respect to the tire circumferential direction can be set in the range of 75° to 90°. In particular, when the angle of the carcass cords is set to less than 88°, tire rigidity is increased, improving durability. It is preferable that the turned-up portion 4B of the carcass layer 4 extends beyond the maximum tire width position to a position where it overlaps with the edge portion of the belt layer 7. By adopting such a turned-up structure, tire rigidity is increased, improving durability. EXAMPLES

[0080] For a tire size of 285 / 35R20 (SH=95 mm), pneumatic tires of Comparative Examples 1-2 and Examples 1-9 were manufactured with A / SH, angle α, angle θ, angle β, B / SH, horizontal distance B, opening distance A, center position of the tire arc (Rb) passing through points S, P, and T, Rb / Rr, radius of curvature Rb, radius of curvature Rr, angle γ, and Rs / SH set as shown in Table 1. Regarding the center position of the arc (Rb), the case where the center position of the arc is on the inner side in the tire width direction is indicated as "inner side", and the case where the center position of the arc is on the outer side in the tire width direction is indicated as "outer side".

[0081] The strain resistance and abrasion resistance of these test tires were evaluated by the following test methods, and the results are shown in Table 1.

[0082] Strain resistance: Each test tire was mounted on a wheel with a rim size of 20x10J and attached to a testing machine with a drum diameter of 1707mm, the air pressure was set to 290kPa, the speed was set to 81km / h, the initial load was set to 88% of the maximum load capacity, and the load was increased by 13% every two hours, and the running distance until the tire broke down was measured. The evaluation results were shown as an index with Comparative Example 2 being 100. The higher the index value, the better the strain resistance performance.

[0083] Abrasion resistance: Each test tire was mounted on a wheel with a rim size of 20×10J and attached to a test machine with a drum diameter of 1707 mm, and a running test of 2500 km was performed with an air pressure of 290 kPa, a speed of 81 km / h, an initial load of 88% of the maximum load capacity, and an increase in load of 13% every 2 hours. The rubber thickness from the outer surface of the tire to the carcass layer at a position corresponding to the radially outermost point of the rim flange was measured before and after the test, and the change in the rubber thickness was calculated. The evaluation results were expressed as an index using the reciprocal of the change in rubber thickness, with Comparative Example 1 being set to 100. The higher the index value, the better the abrasion resistance performance.

[0084] [Table 1]

[0085] As can be seen from Table 1, in comparison with Comparative Examples 1 and 2, the tires of Examples 1 to 9 were improved in both strain resistance and abrasion resistance, and had excellent durability. [Explanation of symbols]

[0086] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt cover layer 10 Tires 11 Tread rubber layer 12 Sidewall rubber layer 13 Rim cushion rubber layer 14 Inner liner layer 15 Rim protector 21 Regulation rim 22 Rim flange

Claims

1. In a tire having a section height SH in the range of 50 mm to 150 mm, A tire characterized in that, in an unloaded state when the tire is mounted on a specified rim and inflated to a specified internal pressure, when an opening distance between the tire and the rim flange on a perpendicular line drawn from the radially outermost point of the rim flange to the outer surface of the tire is A, said opening distance A satisfies the relationship of 0.01≦A / SH≦0.16 with respect to the cross-sectional height SH, when a point P is a point where a horizontal line in the tire width direction passing through the radially outermost point of the rim flange intersects with the outer surface of the tire, and a point Q is a point defining the rim width and rim diameter of the specified rim, the angle α that a straight line connecting point P and point Q makes with the horizontal line in the tire width direction is in the range of 50°≦α≦80°.

2. 2. The tire according to claim 1, characterized in that, when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state, a point defining the total width of the tire is defined as L, and an angle θ between a line connecting the point P and the point Q and a line connecting the point L and the point Q is in the range of 2°≦θ≦30°.

3. 3. A tire as claimed in claim 1 or 2, characterized in that in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when S is the opening start point where the rim flange separates from the tire, Tr is the radially outermost point of the rim flange, and T is the point where a perpendicular line drawn from point Tr to the outer surface of the tire intersects with the outer surface of the tire, the angle β that a straight line connecting point S and point T makes with a straight line connecting point S and point Tr is in the range of 15°≦β≦65°.

4. 4. A tire according to any one of claims 1 to 3, characterized in that in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when an opening start point where the rim flange separates from the tire is defined as S, a horizontal distance B in the tire width direction between said point Q and said point S satisfies the relationship 0.02≦B / SH≦0.18 with respect to a cross-sectional height SH.

5. 5. A tire according to any one of claims 1 to 4, characterized in that in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when the opening start point at which the rim flange separates from the tire is defined as S, the horizontal distance B in the tire width direction between point Q and point S is in the range of 3.0 mm≦B≦9.0 mm.

6. The tire according to any one of claims 1 to 5, characterized in that the opening distance A is in the range of 1.5 mm≦A≦8.0 mm.

7. 7. A tire as claimed in any one of claims 1 to 6, characterized in that in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when the opening start point where the rim flange separates from the tire is defined as S, the radially outermost point of the rim flange is defined as Tr, and the point where a perpendicular line drawn from point Tr to the outer surface of the tire intersects with the outer surface of the tire, an arc of the tire passing through point S, point P, and point T has its centre on the outer side in the tire width direction.

8. 8. The tire according to any one of claims 1 to 7, characterized in that in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when S is the opening start point where the rim flange separates from the tire, Tr is the radially outermost point of the rim flange, T is the point where a perpendicular line drawn from point Tr to the outer surface of the tire intersects with the outer surface of the tire, and Pr is the point where a perpendicular line drawn from point P to the outer surface of the tire intersects with the outer surface of the rim flange, Rr is the radius of curvature of the rim flange's arc passing through points S, Pr, and Tr, and Rb is the radius of curvature of the tire's arc passing through points S, P, and T satisfies the relationship 1.2≦Rb / Rr≦14.

5.

9. In a tire having a plurality of belt layers embedded in a tread portion, The tire according to any one of claims 1 to 8, characterized in that in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when a point where a horizontal line in the tire width direction passing through an edge portion of a belt layer located at the innermost side in the tire radial direction among the multiple belt layers intersects with an outer surface of the tire is defined as V, and a point defining a total width of the tire is defined as L, an angle γ that a straight line connecting the point L and the point V makes with the horizontal line in the tire width direction is in a range of 45°≦γ≦80°.

10. 10. The tire according to claim 9, characterized in that, in an unloaded state in which the tire is mounted on a specified rim and inflated to a specified internal pressure, when a point W is on the outer surface of the tire at a radially central position between the point L and the point V, a radius of curvature Rs of an arc of the tire that passes through the point V, the point W, and the point L satisfies a relationship of 0.3≦Rs / SH≦2.5 with respect to the cross-sectional height SH.

Images