pneumatic tires

Abstract

To provide a pneumatic tire that can suppress rolling resistance. [Solution] The pneumatic tire 1 has a pair of sidewall portions 3 and a pair of bead portions 4 connected to the pair of sidewall portions 3. Each of the pair of bead portions 4 is a bead cormorant The bead portion 4 includes the outer bead surface 43, which extends outward in the tire axial direction from 41, through the bead heel 42, to the sidewall portion 3. When assembled on a regular rim, filled with regular internal pressure, and subjected to regular load, the bead portion 4 has a contact area that contacts the regular rim, and in at least one of the pair of bead portions 4, the length of the contact area 44 along the outer bead surface 43 from the origin 0, which is located 16.5 mm inward in the tire axial direction from the reference line BWL for defining the rim width in the tire meridian cross-section, is 37 to 45 mm.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Conventionally, various proposals have been made regarding the structure of the bead portion of pneumatic tires (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a load is applied to a pneumatic tire, the bead portion is deformed with the rim flange as a fulcrum and generates heat, resulting in an increase in rolling resistance.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a pneumatic tire capable of suppressing rolling resistance.

Means for Solving the Problems

[0006] The present invention is a pneumatic tire having a pair of sidewall portions and a pair of bead portions continuous with the pair of sidewall portions, each of the pair of bead portions includes a bead outer surface that extends from the bead toe outward in the tire axial direction and reaches the sidewall portion through the bead heel, in a state where it is incorporated in a standard rim, filled with a standard internal pressure, and loaded with a standard load, the bead portion has a contact region that contacts the standard rim, In at least one of the pair of bead portions, the length of the contact area along the outer surface of the bead is 37 to 45 mm from the origin, which is located 16.5 mm inward in the tire axial direction from the reference line for defining the rim width in the tire meridian cross-section. [Effects of the Invention]

[0007] Since the green tire molding method of the present invention has the above configuration, rolling resistance can be easily suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view illustrating the procedure of one embodiment of the pneumatic tire of the present invention. [Figure 2] Figure 1 is an enlarged cross-sectional view of the bead portion of a pneumatic tire. [Figure 3] This is a cross-sectional view showing the pneumatic tire in Figure 1, mounted on a standard rim, filled with the standard internal pressure, and subjected to the standard load. [Figure 4] Figure 3 is an enlarged cross-sectional view of the bead portion of a pneumatic tire. [Figure 5] This graph shows the contact pressure distribution between the bead and the normal rim radius in the state shown in Figure 3. [Figure 6] Figure 1 is an enlarged cross-sectional view of the bead portion of a pneumatic tire. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire 1") showing one embodiment of the present invention. Figure 1 is a cross-sectional view of the tire in its normal state, including the axis of rotation. As shown in Figure 1, the tire 1 of this embodiment is suitably used, for example, as a pneumatic tire for a passenger car. However, the present invention is not limited to this embodiment and may be applied, for example, to a pneumatic tire for heavy loads.

[0010] "Normal condition" refers to the state in the case of pneumatic tires for which various standards are defined, where the tire is mounted on a normal rim, filled to the normal internal pressure, and under no load. In the case of tires for which various standards are not defined, the normal condition means the standard usage condition according to the intended use of the tire, where it is not mounted on a vehicle and under no load. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured under the normal condition. Furthermore, for components that cannot be measured under the normal condition (for example, the internal material of tire 1), the values ​​are measured with tire 1 in a state that approximates the normal condition as closely as possible.

[0011] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0012] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0013] The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 are connected to the axially oriented outer side of the tread portion 2 and extend in the radial direction of the tire. The bead portions 4 are connected to the radially oriented inner side of the sidewall portions 3. The tire 1 also includes a carcass 6. The carcass 6 extends between the pair of bead portions 4. In other words, the carcass 6 extends from one bead portion 4 through one sidewall portion 3, the tread portion 2, and the other sidewall portion 3 to the other bead portion 4.

[0014] Each bead portion 4 is embedded with a bead core 5. The bead core 5 is, for example, a ring-shaped body formed by winding bead wires (not shown) made of steel in multiple stages and multiple rows. On the outer side of the bead core 5 in the tire radial direction, a bead apex rubber 8 extending in a tapered shape is provided.

[0015] The carcass 6 is composed of, for example, a single carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a folded-back portion 6b. The main body portion 6a extends between, for example, two bead portions 4. The folded-back portion 6b is connected to the main body portion 6a and is folded back from the inner side to the outer side in the tire axial direction around the bead core 5.

[0016] The carcass ply 6A includes a plurality of carcass cords and topping rubber covering them (not shown). The carcass cords are, for example, organic fiber cords such as aramid and rayon. The carcass cords are preferably arranged at an angle of 70 to 90° with respect to the tire equator C.

[0017] On the inner side of the carcass 6 in the tire radial direction and the outer side in the tire axial direction, a clinch rubber 9 that adheres closely to the rim is provided.

[0018] The tread portion 2 of the present embodiment includes, for example, a belt layer 7 disposed on the outer side of the carcass 6 in the tire radial direction. However, the tread portion 2 is not limited to such a mode. The belt layer 7 includes a first belt ply 7A adjacent to the carcass 6 and a second belt ply 7B disposed on the outer side of the first belt ply 7A in the tire radial direction. Each of the first belt ply 7A and the second belt ply 7B includes a plurality of belt cords arranged at an angle of 15 to 45° with respect to the tire circumferential direction and topping rubber covering them. The belt cords of the first belt ply 7A and the belt cords of the second belt ply 7B are inclined in opposite directions with respect to the tire circumferential direction. Thereby, the tread portion 2 is effectively reinforced.

[0019] The length of the second belt ply 7B in the tire axial direction is preferably smaller than the length of the first belt ply 7A in the tire axial direction. As a result, the outer end of the second belt ply 7B in the tire axial direction is located on the inner side in the tire axial direction with respect to the outer end of the first belt ply 7A in the tire axial direction.

[0020] A belt layer may be provided on the outer side in the tire radial direction of the belt layer 7 and may be composed of a band ply. The band ply includes, for example, band cords arranged at an angle of 5° or less with respect to the tire circumferential direction and topping rubber covering the band cords. The band layer may be arranged to cover the entire belt layer 7, or may be arranged to locally cover a part of the belt layer 7, for example, the vicinity of the outer end of the belt layer 7 in the tire axial direction.

[0021] FIG. 2 shows the configuration of the bead portion 4. Each of the pair of bead portions 4 includes a bead outer surface 43 that extends outward in the tire axial direction from the bead toe 41, passes through the bead heel 42, and reaches the sidewall portion.

[0022] FIG. 3 shows the pneumatic tire 1 in a state where it is incorporated in a regular rim R, filled with a regular internal pressure, contacted with a plane G at a camber angle of zero, and loaded with a regular load (hereinafter referred to as a regular load loading state).

[0023] The "regular load" is the load determined for each tire in a standard system including the standard based on which the tire is based. In the case of JATMA, it is the "maximum load capacity", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY". When the tire is for a passenger car, for example, it is a load corresponding to 88% of the above load.

[0024] The bead portion 4 has a contact area 44 that contacts the regular rim R in the regular load loading state.

[0025] Figure 4 shows a magnified view of the bead portion 4 under normal load conditions. In the pneumatic tire 1 of the present invention, the length L1 of the contact area 44 in the tire meridian cross-section is 37 to 45 mm in at least one of the pair of bead portions 4. The length L1 of the contact area 44 is defined as the length along the outer surface 43 of the bead from the origin 0, which is located 16.5 mm inward in the tire axial direction from the reference line BWL for defining the rim width. Since the above position is the origin 0, an appropriate length L1 can be obtained even if the position of the bead toe 41 changes due to a change in the design of the bead sheet.

[0026] As already mentioned, in a pneumatic tire under load, bending deformation occurs from the sidewall portion 3 to the bead portion 4, with the rim flange as the pivot point. In the pneumatic tire 1 of the present invention, the length L1 of the contact area 44 is 37 mm or more, so that the sidewall portion 3 and the bead portion 4 are supported by the rim flange under normal load conditions, and the above bending deformation is suppressed. As a result, heat generation in the sidewall portion 3 and the bead portion 4 is suppressed, rolling resistance can be easily reduced, and fuel efficiency is improved. In addition, since the gap between the outer surface of the bead 43 and the rim flange is reduced, air resistance during driving is reduced, and fuel efficiency is improved.

[0027] To further enhance the above effects, the length L1 of the contact area 44 is preferably 39 mm or more.

[0028] On the other hand, by keeping the length L1 of the contact area 44 at 45 mm or less, the volume of the clinch rubber 9, which causes energy loss during running, is suppressed, and rolling resistance can be easily reduced.

[0029] To further enhance the above effects, the length L1 of the contact area 44 is preferably 43 mm or less in combination with any of the lower limits mentioned above.

[0030] For example, the length L1 of the contact area 44 is preferably 39 to 43 mm.

[0031] In the pneumatic tire 1 of the present invention, it is desirable that the length L1 of the contact area 44 in the tire meridian cross-section of the other bead portion 4 of the pair of bead portions 4 is 37 to 45 mm.

[0032] The numerical range for further enhancing the above-mentioned effects is the same as the preferred numerical range for one of the bead sections 4. The following describes one of the bead sections 4, but the same applies to the other bead section 4.

[0033] Figure 5 shows the distribution of contact pressure between the bead portion 4 and the normal rim R under a normal load condition in the pneumatic tire 1 of the present invention. The horizontal axis represents the length in the direction from the bead toe 41 to the outer surface 43 of the bead, and the vertical axis represents the contact pressure (please specify the unit).

[0034] As shown in Figure 5, it is desirable that the contact pressure between the bead portion 4 and the normal rim R under normal load conditions has at least three peaks P1, P2, and P3 in the direction from the bead toe 41 to the outer surface 43 of the bead.

[0035] The first peak P1 is a peak that occurs at a first position on the radially inward side of the bead core 5. In the pneumatic tire 1 of this embodiment, the first peak P1 is the maximum value of the contact pressure between the bead portion 4 and the regular rim R.

[0036] The second peak P2 is a peak that occurs at a second position where the bead core 5 contacts the flange side surface F1 of the normal rim R (see Figures 3 and 4) on the radially outer side of the tire. A first bottom B1 exists between the first peak P1 and the second peak P2.

[0037] The third peak P3 is the peak that occurs at the third position, which is the outermost axially of the tire in the contact area and makes contact with the flange surface F2 of the normal rim R (see Figures 3 and 4). A second bottom B2 exists between the second peak P2 and the third peak P3.

[0038] The ratio of the third peak P3 to the second peak P2, P3 / P2, should ideally be between 0.70 and 1.20.

[0039] A P3 / P2 ratio of 0.70 or higher ensures that the sidewall portion 3 and bead portion 4 are effectively supported by the rim flange under normal load conditions, thereby suppressing the aforementioned bending deformation. This reduces heat generation in the sidewall portion 3 and bead portion 4, easily lowering rolling resistance and improving fuel efficiency.

[0040] To further enhance the above effects, the ratio P3 / P2 is preferably set to 0.95 or higher.

[0041] By keeping the ratio P3 / P2 at 1.20 or less, wear of the clinch rubber 9 is suppressed.

[0042] To further enhance the above effects, the ratio P3 / P2 is preferably 1.10 or less in combination with any of the lower limits mentioned above.

[0043] For example, the length L1 of the contact area 44 is preferably 39 to 43 mm.

[0044] The ratios P1 / P2 and P1 / P3 between the first peak P1, the second peak P2, and the third peak P3 are preferably between 0.75 and 0.85. By keeping the ratios P1 / P2 and P1 / P3 below 0.75, wear of the clinch rubber 9 is suppressed.

[0045] Figure 6 shows a magnified view of the bead portion 4 in its normal state, assembled on a normal rim and filled with the normal internal pressure.

[0046] The pneumatic tire 1 of this embodiment has a bead outer surface 43 which includes a bead base surface 45 extending from the bead toe 41 to the bead heel 42, a bead outer surface 46 extending radially outward from the bead heel 42 and in contact with the flange side surface F1, and a flange receiving surface 47 that is connected to the bead outer surface 46 and curves outward in the tire axial direction, and curves to follow the flange surface F2 of the regular rim.

[0047] It is desirable that the radius of curvature R1 of the flange mounting surface 47 in the normal state, when assembled into the normal rim and filled with the normal internal pressure, be between 8.5 and 15.0 mm.

[0048] The radius of curvature R1 of the flange receiving surface 47 is 8.5 to 15.0 mm, which makes it easier for the flange receiving surface 47 to conform to the flange surface F2 under normal load conditions. This allows the sidewall portion 3 and bead portion 4 to be supported more effectively by the rim flange, thereby suppressing the bending deformation described above.

[0049] To further enhance the above effects, the radius of curvature R1 of the flange receiving surface 47 is preferably 9.5 mm or more. In addition, the radius of curvature R1 of the flange receiving surface 47 is preferably 14.0 mm or less in combination with any of the lower limits mentioned above.

[0050] For example, the radius of curvature R1 of the flange receiving surface 47 is preferably 9.5 to 14.0 mm.

[0051] In the normal state, the height H from the bead baseline BL to the inner end of the flange receiving surface 47 in the tire radial direction is preferably 10.0 to 14.5 mm. In this embodiment, since the flange receiving surface 47 is formed in conjunction with the outer bead surface 46, the inner end of the flange receiving surface 47 in the tire radial direction is the position where the outer bead surface 46 switches to the flange receiving surface 47, and is also the outer end of the outer bead surface 46 in the tire radial direction.

[0052] The height H of the flange receiving surface 47 to the inner edge in the tire radial direction is 10.0 to 14.5 mm, so that the flange receiving surface 47 contacts the rim flange over a wide area, even in an unloaded state, and the bead portion 4 is effectively supported by the rim flange.

[0053] To further enhance the above effects, the height H from the flange receiving surface 47 to the inner end in the tire radial direction is preferably 11.5 mm or more. In addition, the height H from the flange receiving surface 47 to the inner end in the tire radial direction is preferably 13.0 mm or less in combination with any of the lower limits mentioned above.

[0054] As an example, the height H from the flange mounting surface 47 to the inner end in the tire radial direction is preferably 11.5 to 13.0 mm.

[0055] In the normal state, the axial length L2 of the tire from the outer surface 46 of the bead to the outer end of the flange receiving surface 47 in the tire axial direction is preferably 7.0 to 12.0 mm.

[0056] By having a length L2 of 7.0 mm or more from the outer surface 46 of the bead to the outer end of the flange receiving surface 47 in the tire axial direction, the flange receiving surface 47 contacts the rim flange over a wide area under normal load conditions, and the concentration of pressure at the outer end of the flange receiving surface 47 in the tire axial direction is mitigated.

[0057] To further enhance the above effects, the length L2 from the outer surface 46 of the bead to the outer end of the flange receiving surface 47 is preferably 8.5 mm or more.

[0058] By keeping the length L2 from the outer surface 46 of the bead to the outer end of the flange receiving surface 47 in the tire axial direction 12.0 mm or less, the rubber volume of the bead portion 4 is suppressed, heat generation in the bead portion 4 is suppressed, and rolling resistance can be easily reduced.

[0059] To further enhance the above effects, the length L2 from the outer surface 46 of the bead to the outer end of the flange receiving surface 47 is preferably 10 mm or less in combination with any of the lower limits mentioned above.

[0060] For example, the length L2 from the outer surface 46 of the bead to the outer end of the flange receiving surface 47 is preferably 8.5 to 10.0 mm.

[0061] In this embodiment, the outer bead surface 43 is connected to the flange receiving surface 47 and includes a top surface 48 that extends radially outward in the tire direction.

[0062] The radius of curvature R2 of the top surface 48 in the normal state should preferably be between 0.3 and 5.0 mm.

[0063] The radius of curvature R2 of the top surface 48 is 0.3 mm or more, which mitigates localized pressure concentration on the top surface 48.

[0064] To further enhance the above effects, the radius of curvature R2 of the top surface 48 is preferably 0.4 mm or more.

[0065] Because the radius of curvature R2 of the top surface 48 is 5.0 mm or less, the flange receiving surface 47 can easily conform to the flange surface F2, the sidewall portion 3 and the bead portion 4 are more effectively supported by the rim flange, and the bending deformation described above is suppressed.

[0066] To further enhance the above effects, the radius of curvature R2 of the top surface 48 is preferably 3.0 mm or less in combination with any of the lower limits mentioned above.

[0067] For example, the radius of curvature R2 of the top surface 48 is preferably 0.4 to 3.0 mm.

[0068] Although the method for forming a green tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiments described above and can be implemented in various modified forms.

[0069] [Note] The present invention includes the following embodiments.

[0070] [Invention 1] A pneumatic tire having a pair of sidewall portions and a pair of bead portions connected to the pair of sidewall portions, Each of the pair of bead portions includes the outer surface of the bead, extending outward from the bead toe in the tire axial direction, through the bead heel, and reaching the sidewall portion. When assembled into a regular rim, filled with regular internal pressure, and subjected to regular load, the bead portion has a contact area that contacts the regular rim. In at least one of the pair of bead portions, the length of the contact area along the outer surface of the bead is 37 to 45 mm from the origin, which is located 16.5 mm inward in the tire axial direction from the reference line for defining the rim width in the tire meridian cross-section. Pneumatic tires. [2nd Invention] The pneumatic tire according to the present invention 1, wherein the contact pressure between the bead portion and the regular rim when the regular load is applied has at least three peaks in the direction from the bead toe along the outer surface of the bead. [Invention 3] Each of the pair of bead portions includes a bead core. The pneumatic tire according to the present invention 2, wherein the at least three peaks include a first peak P1 at a first position on the radially inward side of the bead core, a second peak P2 at a second position on the radially outward side of the bead core where it contacts the flange side surface of the normal rim, and a third peak P3 at the outermost axially outward side of the contact region. [4th Invention] The pneumatic tire according to the present invention, wherein the ratio P3 / P2 of the third peak P3 to the second peak P2 is 0.70 to 1.20. [5th ​​Invention] The pneumatic tire according to Invention 1, wherein the outer surface of the bead includes an outer surface of the bead extending radially outward from the bead heel and in contact with the flange side surface, and a flange receiving surface that is continuous with the outer surface of the bead and curves outward in the tire axial direction and curves along the flange surface of the regular rim. [Invention 6] The pneumatic tire according to invention 5, wherein the radius of curvature of the flange receiving surface when assembled to a regular rim and filled to the regular internal pressure is 8.5 to 15.0 mm. [7th Invention] The pneumatic tire according to claim 5 of the present invention, wherein the height from the bead baseline to the inner end of the flange receiving surface in the tire radial direction is 10.0 to 14.5 mm. [8th Invention] The pneumatic tire according to claim 5 of the present invention, wherein the axial length of the tire from the outer surface of the bead to the outer end of the flange receiving surface in the tire axial direction is 7.0 to 12.0 mm. [Invention 9] The outer surface of the bead is connected to the flange receiving surface and includes a top surface that extends radially outward in the tire direction. The pneumatic tire according to claim 5 of the present invention, wherein the radius of curvature of the top surface is 0.3 to 5.0 mm. [Explanation of Symbols]

[0071] 1: Pneumatic tire 3: Sidewall section 4: Bead section 5: Bead core 41: Bead Toe 42: Bead Heel 43: Outer surface of the bead 44: Contact area 46: Outer surface of the bead 47: Flange mounting surface 48:Top surface BL: Bead Baseline F1: Flange side F2: Flange surface H: Height P1: Peak P1: First peak P2: Second peak P2: Peak P3: Third Peak P3: Peak R: Regular rim R1: radius of curvature R2: radius of curvature

Claims

1. A pneumatic tire having a pair of sidewall portions and a pair of bead portions connected to the pair of sidewall portions, Each of the pair of bead portions includes the outer surface of the bead, extending outward in the tire axial direction from the bead toe, through the bead heel, to the sidewall portion. When assembled into a regular rim, filled with regular internal pressure, and subjected to regular load, the bead portion has a contact area that contacts the regular rim. In at least one of the pair of bead portions, the length of the contact area along the outer surface of the bead is 37 to 45 mm from the origin, which is located 16.5 mm inward in the tire axial direction from the reference line for defining the rim width in the tire meridian cross-section. Pneumatic tires.

2. The pneumatic tire according to claim 1, wherein the contact pressure between the bead portion and the regular rim when the regular load is applied has at least three peaks in the direction from the bead toe along the outer surface of the bead.

3. Each of the pair of bead portions includes a bead core. The pneumatic tire according to claim 2, wherein the at least three peaks include a first peak P1 at a first position on the radially inward side of the bead core, a second peak P2 at a second position on the radially outward side of the bead core where it contacts the flange side surface of the regular rim, and a third peak P3 at the outermost axial position of the contact area.

4. The pneumatic tire according to claim 3, wherein the ratio P3 / P2 of the third peak P3 to the second peak P2 is 0.70 to 1.

20.

5. The pneumatic tire according to claim 1, wherein the outer surface of the bead includes an outer surface of the bead extending radially outward from the bead heel and in contact with the flange side surface, and a flange receiving surface that is continuous with the outer surface of the bead and curves outward in the tire axial direction and curves along the flange surface of the regular rim.

6. The pneumatic tire according to claim 5, wherein the radius of curvature of the flange receiving surface when assembled to a regular rim and filled to the regular internal pressure is 8.5 to 15.0 mm.

7. The pneumatic tire according to claim 5, wherein the height from the bead baseline to the inner end of the flange receiving surface in the tire radial direction is 10.0 to 14.5 mm.

8. The pneumatic tire according to claim 5, wherein the tire axial length from the outer surface of the bead to the outer end of the flange receiving surface in the tire axial direction is 7.0 to 12.0 mm.

9. The outer surface of the bead is connected to the flange receiving surface and includes a top surface that extends radially outward in the tire direction. The pneumatic tire according to claim 5, wherein the radius of curvature of the top surface is 0.3 to 5.0 mm.

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