JP2021187188A - Pneumatic tire - Google Patents

Abstract

To secure sealing performance in a condition of being assembled to the wheel, as well as, to inhibit occurrence of molding defects due to shortage of rubber during molding.SOLUTION: A pneumatic tire 1 comprises an annular bead portion 30 having a base surface 37 inclined inward from an outer side of a tire width direction TW toward a tire radially inner side TRi. The base surface 37 comprises: an outer portion 38 including a first inclined portion 40 inclined at a first inclined angle α with respect to a tire axis TA; and an inner portion 41 including a second inclined portion 42 inclined at a second inclined angle β larger than the first inclined angle α with respect to the tire axis TA. A ratio that a width W3 in the tire width direction TW of the inner portion 41 accounts for a width W1 in the tire width direction TW of the base surface 37 is 5% to 25% inclusively.SELECTED DRAWING: Figure 3

Description

The present invention relates to a pneumatic tire.

The pneumatic tire includes a tread, a pair of sidewalls extending inward in the tire radial direction from both ends of the tread in the tire width direction, and a bead portion connected to the inside of the sidewall in the tire radial direction. The pneumatic tire disclosed in Patent Document 1 includes a base surface including an outer portion and an inner portion having different inclination angles at the tire radial inner end of the bead portion. The outer portion is tilted at a first tilt angle with respect to the tire axis, and the inner portion is tilted at a second tilt angle larger than the first tilt angle with respect to the tire axis. The inner part with a large tilt angle increases the fitting pressure between the rim and the base surface when assembled to the wheel to ensure sealing performance.

Japanese Unexamined Patent Publication No. 63-149207

Generally, tire vulcanization dies for molding this type of pneumatic tire include an annular sector mold that forms the outer surface of the tread and a pair of annular side plates that form the outer surface of the sidewall. , A pair of annular bead rings for molding the outer surface of the bead portion. During molding with this tire vulcanization die, the base surface is molded by flowing rubber from the outside to the inside in the tire width direction along the bead ring in the bead portion.

In the pneumatic tire of Patent Document 1, the inclination angle of the inner portion is larger than the inclination angle of the outer portion, and the inner portion occupies a large proportion of the entire base surface (30% or more). The amount of rubber required for molding the inner part including it is large. However, since the flow of rubber along the bead ring becomes weaker from the outside to the inside in the tire width direction, it is difficult to secure the amount of rubber required for molding the inner portion of the pneumatic tire of Patent Document 1, and rubber. Molding defects may occur due to insufficientness.

An object of the present invention is to provide a pneumatic tire that can secure a sealing property in a state of being assembled to a wheel and can suppress the occurrence of molding defects due to a lack of rubber during molding.

One aspect of the present invention includes an annular bead portion at the inner end in the tire radial direction having an annular bead portion having a base surface inclined inward in the tire radial direction from the outside in the tire width direction to the inside, and the base surface is a tire axis line. With respect to the outer portion including the first inclined portion inclined at the first inclined angle, and the outer portion located inside in the tire width direction at a second inclined angle larger than the first inclined angle with respect to the tire axis. It has an inner portion including an inclined second inclined portion, and the ratio of the width in the tire width direction of the inner portion to the width in the tire width direction of the base surface is 5% or more and 25% or less. Provide pneumatic tires.

In this embodiment, the base surface of the bead portion is an outer portion including a first inclined portion inclined at the first inclination angle and an inner portion including a second inclined portion inclined at a second inclination angle larger than the first inclination angle. In the state of being assembled to the wheel, the fitting pressure between the rim and the inner portion can be increased to ensure the sealing property. Further, although the inclination angle of the second inclined portion is made larger than the inclination angle of the first inclined portion, the ratio of the inner portion to the entire base surface is 25% or less, which is the inner portion as compared with the conventional case. Since the width of the tire is narrow, the amount of rubber required for molding the inner portion including the thickness in the tire radial direction can be reduced. Therefore, even if the flow of rubber becomes weaker from the outside to the inside in the tire width direction during molding, the amount of rubber required for molding the inner portion can be secured, and the occurrence of molding defects due to insufficient rubber can be suppressed.

The first tilt angle is 6 degrees or more and 14 degrees or less, and the second tilt angle is 12 degrees or more and 28 degrees or less.

The angle difference between the first inclination angle and the second inclination angle is 6 degrees or more and 14 degrees or less.

In these aspects, by setting the first inclination angle and the second inclination angle to the numerical range or the angle difference, it is possible to suppress an excessive decrease in the rubber flow during molding. Therefore, it is possible to suppress the occurrence of molding defects on the base surface during molding. In addition, the sealing property between the rim and the inner part can be ensured when the pneumatic tire is assembled to the wheel.

A bead core is embedded in the bead portion, and the intersection of the first inclined surface and the second inclined portion is located between the center and the inner end of the bead core in the tire width direction. Here, the intersection of the first inclined surface and the second inclined portion is not limited to the intersection in a geometrically strict sense, and the intersection of the extension line of the first inclined surface and the extension line of the second inclined portion is not limited to the intersection. included.

If the intersection of the first inclined surface and the second inclined portion is arranged outside the center of the bead core in the tire width direction, the ratio of the second inclined portion becomes large, so that the amount of rubber required for molding the inner portion increases, and the molding is performed. Sometimes molding defects are likely to occur due to lack of rubber. On the other hand, if the intersection of the first inclined surface and the second inclined portion is arranged inside the inner end of the bead core in the tire width direction, the bead core cannot suppress the deformation of the inner portion outward in the tire radial direction. It becomes difficult to secure the sealing property between the rim and the inner part in the assembled state. In this embodiment, since the intersection of the first inclined portion and the second inclined portion is located between the center and the inner end of the bead core, it is possible to prevent inconvenience during molding and inconvenience in the state of being assembled to the wheel.

The outer portion includes an arcuate heel portion that is continuous with the outer end of the first inclined portion in the tire width direction and is curved outward in the tire radial direction from the inside to the outside in the tire width direction.

The inner portion includes an arcuate curved portion that is continuous with the inner end of the second inclined portion in the tire width direction and is curved inward in the tire radial direction from the outside in the tire width direction to the inside.

The first inclined portion and the second inclined portion are continuous via a connecting portion curved inward in the tire radial direction from the outside in the tire width direction to the inside. In this case, the intersection of the first inclined portion and the second inclined portion means the intersection of the extension lines of the first inclined portion and the second inclined portion.

In this embodiment, since the first inclined portion and the second inclined portion are continuous through the curved connecting portion, the inclination with respect to the tire axis gradually changes from the first inclination angle to the second inclination angle. That is, since it is possible to suppress a sudden change in the inclination angle of the base surface, it is possible to reduce the flow resistance of the rubber during molding. Therefore, it is possible to suppress the occurrence of molding defects due to lack of rubber.

In the pneumatic tire of the present invention, the sealing property can be ensured in the state of being assembled to the wheel, and the occurrence of molding defects due to insufficient rubber during molding can be suppressed.

FIG. 3 is a cross-sectional view taken along the meridian of the pneumatic tire according to the embodiment of the present invention. An exploded cross-sectional view showing the relationship between the bead and the rim of the wheel. Sectional drawing which shows the assembly state of the bead part to the rim of a wheel. FIG. 2A is an enlarged cross-sectional view of a portion III. An enlarged cross-sectional view of the IV portion of FIG. Sectional drawing of a tire vulcanization die for molding a pneumatic tire. An enlarged cross-sectional view of the VI portion of FIG. An enlarged cross-sectional view showing a modified example of the base surface of the bead portion.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a pneumatic tire (hereinafter, simply referred to as “tire”) 1 according to an embodiment of the present invention. Although only one side is shown with respect to the tire equatorial line CL in FIG. 1, the tire 1 includes a tread 10, a pair of sidewalls 20, and a pair of bead portions 30.

As shown in FIG. 1, the tread 10 has a cylindrical shape, extends in the tire width direction TW, and extends in the tire circumferential direction. Each of the pair of sidewalls 20 is an annular shape, is continuous with both ends (outer peripheral edges) of the tread 10 in the tire width direction TW, and extends toward the inner TRi in the tire radial direction. The pair of bead portions 30 are annular, and are connected to the inner ends of the pair of sidewalls 20 in the tire radial direction TR.

A bead core 31 and a bead filler 32 are embedded in the bead portion 30. The bead core 31 is composed of a large number of steel wires bundled in a ring shape. The bead filler 32 is ring-shaped and is made of rubber that is harder than the rubber constituting the tread 10 and the sidewall 20, and is arranged adjacent to the tire radial outer TRo of the bead core 31. The cross-sectional shape of the bead filler 32 in the meridian cross section is formed in a triangular shape that tapers toward the outer TRo in the tire radial direction. In this specification, the portion located on the outer diameter side is defined as the sidewall 20 and the portion located on the inner diameter side is defined as the bead portion 30 with reference to the outer end of the tire radial TR of the bead filler 32.

A carcass ply 2 is wound around a pair of bead cores 31. The carcass ply 2 extends from the tread 10 through the pair of sidewalls 20 to the pair of bead portions 30, and is wound around the bead core 31 from the inside to the outside of the TW in the tire width direction. The carcass ply 2 of the present embodiment has a two-layer structure including a first ply 3 surrounding the outer surface of the bead core 31 and the bead filler 32, and a second ply 4 surrounding the outer surface of the first ply 3.

An inner liner 5 for holding air pressure in the state of being assembled to the wheel 50 (see FIG. 2B) is provided on the innermost peripheral surface of the tire 1 from the tread 10 to the pair of bead portions 30. The inner liner 5 is arranged so as to be overlapped with the inner TWi in the tire width direction of the second ply 4 located on the innermost side of the TW in the tire width direction among the laminated carcass plies 2.

A sidewall rubber 21 and a strip rubber 33 constituting the outer surface of the tire 1 are arranged on the outer TWo of the carcass ply 2 in the tire width direction. The pair of sidewall rubbers 21 are connected to both ends of the tread rubber (not shown) TW in the tire width direction of the tread 10, and form a part of the sidewall 20 and a part of the bead portion 30. The pair of strip rubbers 33 are connected to the inner ends of the tire radial TRs of the sidewall rubbers 21 to form a part of the bead portion 30. The strip rubber 33 is made of rubber having excellent wear resistance as compared with the sidewall rubber 21.

As shown in FIGS. 2A and 2B, by assembling the tire 1 to the wheel 50, the bead portion 30 is pressed against the regular rim (hereinafter, simply referred to as “rim”) 51. This prevents air from leaking through between the bead portion 30 and the rim 51.

The rim 51 includes a seat portion 52, a heel portion 53, and a flange portion 54 in order from the inside to the outside of the tire radial direction TR.

The seat portion 52 has a conical cylinder shape extending in the tire width direction TW with the tire axis TA as the center in the assembled state. The seat portion 52 is inclined inward TRi in the tire radial direction from the outside to the inside of the TW in the tire width direction. The inclination angle of the seat portion 52 with respect to the straight line (virtual line) L0 parallel to the tire axis TA (wheel axis) is γ.

The heel portion 53 is connected to the outer end of the tire width direction TW of the seat portion 52, and is curved from the inside to the outside of the tire width direction TW toward the tire radial outside TRo. The surface of the heel portion 53 facing the bead portion 30 has a center of curvature located on the outer side TRo in the radial direction of the tire and is curved with a predetermined radius of curvature R1.

The flange portion 54 includes a first portion 54a continuously extending to the outer TRo in the tire radial direction to the heel portion 53, and a second portion 54b continuously curved to the outer TWo in the tire width direction to the first portion 54a. Of the second portion 54b, the surface facing the bead portion 30 has a center of curvature located on the inner TRi in the radial direction of the tire and is curved with a predetermined radius of curvature R2.

The rim 51 is standardized for each tire standard, and is, for example, a "standard rim" for JATTA and a "Measuring Rim" for TRA and ETRTO. The rim 51 of the present embodiment to which the tire 1 having the tire size of 235 / 50R18 is assembled conforms to the flange symbol J (7.5J) of the 5 ° deep bottom rim specified in JATTA, and the inclination angle of the seat portion 52. γ is 5 ° ± 1 °, the radius of curvature R1 of the heel portion 53 is 6.5 mm, and the radius of curvature R2 of the second portion 54b is 9.5 mm. In the tire width direction TW, the seat width W0 from the inner end (not shown) of the seat portion 52 to the flange portion 54 is 19.5 mm.

Hereinafter, the bead portion 30 assembled to the rim 51 will be described more specifically. In the following description, the shape of each portion constituting the bead portion 30 is specified while looking at the cross section of the meridian.

As shown in FIGS. 2A and 2B, the bead portion 30 includes a rim protector 34 connected to the sidewall 20. Of the bead portion 30, the portion located on the inner TRi in the tire radial direction with respect to the rim protector 34 is the inner surface 35 located at the inner end of the tire width direction TW, the outer surface 36 located at the outer end of the tire width direction TW, and the outer surface 36. And is defined by a base surface 37 located at the inner end of the tire radial TR. Of these, the rim protector 34 is formed on the sidewall rubber 21 and the strip rubber 33, the inner side surface 35 is formed on the inner liner 5, and the outer surface 36 and the base surface 37 are formed on the strip rubber 33.

The rim protector 34 is provided to protect the rim 51. In the assembled state with the wheel 50, the rim protector 34 is located on the outer TRo in the tire radial direction with respect to the rim 51, and protrudes to the outer TWo in the tire width direction. Referring to FIG. 1, the rim protector 34 is located on the inner TWi in the tire width direction with respect to the tire maximum width position Pw. The maximum width position Pw is the position farthest from the tire equatorial line CL in the tire width direction TW in the tire 1 (sidewall 20).

The inner side surface 35 extends from the outer end 31a side of the bead core 31 in the tire radial direction TR to the inner end 31b beyond the inner end 31b in the tire width direction inner TWi of the bead core 31 to the tire radial inner TRi.

The outer side surface 36 is connected to the top 34a, which is the inner end of the tire radial TR of the rim protector 34, in the tire width direction outer TWo of the bead core 31, and extends to the tire radial inner TRi. The inner end 36a of the tire radial TR of the outer side surface 36 is located between the outer end 31a and the inner end 31b of the bead core 31 in the tire radial TR.

The outer side surface 36 has a curved surface shape that is recessed in the inner TWi in the tire width direction, and its radius of curvature R3 is larger than the radius of curvature R2 of the second portion 54b of the flange portion 54. In the assembled state with the rim 51, the inner end 36a side of the outer surface 36 is pressure-welded (surface contact) to the flange portion 54 due to the elastic deformation of the strip rubber 33. The outer end 36b side of the outer side surface 36 gradually separates from the flange portion 54 from the inside to the outside of the tire radial direction TR.

The base surface 37 extends in the tire width direction TW at the inner end of the tire radial TR of the tire 1, and is inclined toward the tire radial inner TRi from the outside to the inside of the tire width direction TW. Here, the inclination is not limited to the configuration extending linearly as long as the configuration is directed toward the inner TWi in the tire width direction and the inner TRi in the tire radial direction, and may include an element extending in a curved shape.

The base surface 37 includes an outer portion 38 located on the outer TWo in the tire width direction and an inner portion 41 located on the inner TWi in the tire width direction.

Referring to FIG. 3, the outer portion 38 includes a heel portion 39 located on the outermost side of the tire width direction TW on the base surface 37, and a first inclined portion 40 connected to the heel portion 39.

The heel portion 39 has an arc shape whose center of curvature is located on the tire radial outer side TRo, and is curved from the inner side to the outer side of the tire width direction TW toward the tire radial outer side TRo. The heel portion 39 is connected to the inner end 36a of the outer surface 36 and extends from the outer TWo in the tire width direction of the bead core 31 to the inner TRi in the tire radial direction.

The outer end 39a of the heel portion 39 in the tire width direction TW is located between the outer end 31a and the inner end 31b of the bead core 31 in the tire radial direction TR in the tire width direction outer TWo of the bead core 31. The inner end 39b of the heel portion 39 in the tire width direction TW is located between the outer end 31c and the center 31e of the bead core 31 in the tire width direction TW in the tire radial inner TRi of the bead core 31.

The radius of curvature R4 of the heel portion 39 is substantially the same as the radius of curvature R1 of the heel portion 53 of the rim 51. In the present embodiment, the radius of curvature R1 of the heel portion 53 of the rim 51 is 6.5 mm, so that the radius of curvature R4 of the heel portion 39 of the bead portion 30 is set to 6.5 mm in the present embodiment. The heel portion 39 configured in this way is pressed against the heel portion 53 of the rim 51 by elastic deformation of the strip rubber 33 in a state of being assembled to the rim 51.

The first inclined portion 40 has a linear shape and is inclined with a uniform gradient from the outside of the TW in the tire width direction to the inside TRi in the tire radial direction from the outside to the inside. The first inclined portion 40 is connected to the inner end 39b of the heel portion 39 in the tire radial inner TRi of the bead core 31, and extends to the inner TWi in the tire width direction.

The outer end 40a of the first inclined portion 40 in the tire width direction TW is located between the outer end 31c and the center 31e of the bead core 31 in the tire width direction TW. The inner end 40b of the first inclined portion 40 in the tire width direction TW is located between the inner end 31d and the center 31e of the bead core 31 in the tire width direction TW.

The first inclination angle of the first inclination portion 40 with respect to the straight line (virtual line) L1 parallel to the tire axis TA is α. The first tilt angle α in the non-assembled state to the rim 51 is larger than the tilt angle γ (5 degrees) of the seat portion 52 including no tolerance (± 1 degree). In the assembled state with the rim 51, the first inclined portion 40 is pressed against the sheet portion 52 by the elastic deformation of the strip rubber 33.

As shown in FIGS. 3 and 4, the inner portion 41 has a second inclined portion 42 connected to the first inclined portion 40 via the connecting portion 44, and a curvature located on the innermost side of the tire width direction TW on the base surface 37. A unit 43 is provided.

The second inclined portion 42 has a linear shape and is inclined with a uniform gradient from the outside of the TW in the tire width direction to the inside TRi in the tire radial direction from the outside to the inside. The second inclined portion 42 is connected to the inner end 44b of the connecting portion 44 in the tire radial inner TRi of the bead core 31, and extends to the inner TWi in the tire width direction.

Since the second inclined portion 42 is connected to the first inclined portion 40 (outer portion 38) via the connecting portion 44, both the outer end 42a and the inner end 42b of the second inclined portion 42 in the tire width direction TW are bead cores. It is located on the inner TWi in the tire width direction with respect to the inner end 31d of 31.

The second inclination angle of the second inclination portion 42 with respect to the straight line L1 parallel to the tire axis TA is β. The second tilt angle β is larger than either the tilt angle γ of the seat portion 52 or the first tilt angle α of the first tilt portion 40. In the assembled state with the rim 51, the second inclined portion 42 is pressed against the sheet portion 52 by the elastic deformation of the strip rubber 33.

The curved portion 43 has an arc shape whose center of curvature is located on the inner TRi in the tire radial direction and is in contact with the second inclined portion 42, and is curved from the outer side to the inner side in the tire width direction toward the inner TRi in the tire radial direction. The curved portion 43 is located on the inner end TW in the tire width direction of the bead core 31 in the tire radial inner TRi of the bead core 31 with respect to the inner end 31d of the tire width direction TW of the bead core 31.

The outer end 43a of the curved portion 43 in the tire width direction TW is connected to the inner end 42b of the second inclined portion 42. The inner end 43b of the curved portion 43 in the tire width direction TW is connected to the inner end of the inner side surface 35 in the tire radial direction TR. The inner end 43b of the curved portion 43 is the innermost end of the tire 1 in the tire radial direction TR. In the assembled state with the rim 51, the curved portion 43 is pressed against the sheet portion 52 by the elastic deformation of the strip rubber 33.

The connection portion 44 has an arc shape in which the center of curvature is located on the inner TRi in the tire radial direction and is in contact with both of the inclined portions 40 and 42, and is curved from the outer side to the inner side in the tire width direction TW toward the inner TRi in the tire radial direction. There is. The connecting portion 44 is connected to the inner end 40b of the first inclined portion 40 and the outer end 42b of the second inclined portion 42, and extends to the inner TWi in the tire width direction in the tire radial inner TRi of the bead core 31.

The outer end 44a of the connecting portion 44 in the tire width direction TW is located between the inner end 31d and the center 31e of the bead core 31 in the tire width direction TW. In the tire width direction TW, the inner end 44b of the connecting portion 44 is located on the inner end TWi in the tire width direction with respect to the inner end 31d of the bead core 31. In the assembled state with the rim 51, the connecting portion 44 is pressed against the sheet portion 52 by elastic deformation of the strip rubber 33.

The radius of curvature R5 of the connecting portion 44 is set to 10 mm or more and 25 mm or less. If the radius of curvature R5 is made excessively small, the angle change from the first inclined portion 40 to the second inclined portion 42 becomes steep. In this case, since the flow resistance of the rubber becomes large during molding, which will be described later, the amount of rubber required for molding the inner portion 41 including the thickness of the tire radial direction TR cannot be secured, and molding defects due to lack of rubber are likely to occur. If the radius of curvature R5 is made excessively large, the second inclined portion 42 cannot be molded, so that it becomes difficult to secure the sealing property between the second inclined portion 42 and the seat portion 52 in the assembled state with the wheel 50. In order to prevent these inconveniences, the radius of curvature R5 is preferably set in the above range, and is set to 20 mm in the present embodiment.

In the tire width direction TW, the outer half of the connecting portion 44 is included in the outer portion 38, and the inner half of the connecting portion 44 includes the inner portion 41. More specifically, the outer portion 44c located on the outer TWo in the tire width direction from the intersection Pi with reference to the intersection Pi of the extension line 40'of the first inclined portion 40 and the extension line 42'of the second inclined portion 42. Is included in the outer portion 38, and the inner portion 44d located on the inner TWi in the tire width direction with respect to the intersection Pi is included in the inner portion 41.

The intersection Pi of the first inclined portion 40 and the second inclined portion 42 is located between the center 31e and the inner end 31d of the bead core 31 in the tire width direction TW. More specifically, the intersection Pi is located near the inner end 31d of the bead core 31. In other words, the formation positions of the first inclined portion 40 and the second inclined portion 42 and the inclination angles α and β are arranged so that the intersection Pi is located between the center 31e and the inner end 31d of the bead core 31 in the tire width direction TW. It is set.

In the base surface 37 configured in this way, the distance of the tire width direction TW from the outer end 39a of the heel portion 39 to the inner end 43b of the curved portion 43, that is, the width of the tire width direction TW of the base surface 37 is W1. be. The width W1 of the base surface 37 is smaller than the seat width W0 (19.5 mm) of the rim 51, for example, 16.5 mm.

The width of the tire width direction TW of the outer portion 38 is W2, and the width of the tire width direction TW of the inner portion 41 is W3. The ratio of the width W3 of the inner portion 41 to the width W1 of the base surface 37 is smaller than the ratio of the width W2 of the outer portion 38. More specifically, the ratio of the width W2 of the outer portion 38 to the width W1 of the base surface 37 is 75% or more and 95% or less, and the width W3 of the inner portion 41 with respect to the width W1 of the base surface 37. The percentage is 5% or more and 25% or less.

The tilt angle γ of the seat portion 52, the first tilt angle α of the first tilt portion 40, and the second tilt angle β of the second tilt portion 42 are larger in the order of γ, α, and β (γ <α <β). .. Of these, the first tilt angle α is preferably set to 6 degrees or more and 14 degrees or less, and the second tilt angle β is preferably set to 12 degrees or more and 28 degrees or less. If the inclination angles α and β are made excessively small, it is difficult to secure the sealing property between the outer portion 38 and the seat portion 52 and the sealing property between the inner portion 41 and the seat portion 52 in the assembled state with the wheel 50. become. If the inclination angles α and β are excessively increased, the amount of rubber required for molding the inner portion 41 increases, so that molding defects due to insufficient rubber are likely to occur during molding. In order to prevent these inconveniences, the tilt angles α and β are preferably set within the predetermined range, and in the present embodiment, the tilt angle α is set to 8 degrees and the tilt angle β is set to 18 degrees.

The angle difference between the first tilt angle α of the first tilt portion 40 and the second tilt angle β of the second tilt portion 42 is preferably set to 6 degrees or more and 14 degrees or less. If the angle difference is made excessively small, it becomes difficult to secure the sealing property with the seat portion 52 in the assembled state with the wheel 50. If the angle difference is excessively large, the amount of rubber required for molding the inner portion 41 increases, so that molding defects due to insufficient rubber are likely to occur during molding. In order to prevent these inconveniences, the angle difference between the inclination angles α and β is preferably set within the above-defined range, and is set to 10 degrees in this embodiment.

The tire 1 configured in this way is molded by arranging a green tire in a tire vulcanization mold and vulcanizing it.

FIG. 5 shows an example of the tire vulcanization die 60. As shown in FIG. 5, the tire vulcanization die 60 includes a sector mold 61 for molding the outer surface of the tread 10, a pair of side molds 63 for molding the outer surface of the sidewall 20 and the outer surface of the bead portion 30, and a pair of side molds 63. A bladder 66 for molding the inner surface of the tire 1 is provided.

The sector mold 61 has a cylindrical shape and is arranged so that the axis extends in the vertical direction. The sector mold 61 is composed of a plurality of sectors 62 divided in the circumferential direction. The individual sectors 62 are movable in the radial direction about the axis of the sector mold 61.

The pair of side molds 63 are arranged above and below the sector mold 61, respectively. Each side mold 63 is annular and includes a side plate 64 and a bead ring 65. The side mold 63 located below the sector mold 61 is immovably fixed. The side mold 63 located above the sector mold 61 is movably arranged along the axis of the sector mold 61.

The bladder 66 is arranged in the sector mold 61 and can be expanded and contracted by an air supply device (not shown).

With the sector mold 61 open, the green tire is placed on the lower side mold 63. Subsequently, the bladder 66 is inflated to hold the inner surface of the green tire, the plurality of sectors 62 are moved toward the inner diameter side, and the upper side mold 63 is moved downward. When the sector 62 and the upper side mold 63 are moved to a fixed position to complete the mold clamping, the green tire is housed in the cavity 67 of the tire vulcanization mold 60 and vulcanization is started.

At the time of mold clamping, the molded portion of the tread 10 is pressed toward the inner TRi in the tire radial direction by the sector mold 61. Further, the molded portion of the sidewall 20 and the molded portion of the bead portion 30 are pressed from the outside to the inside of the TW in the tire width direction by the side mold 63. By this pressing, the rubber constituting the base surface 37 flows from the outside to the inside of the tire radial direction TR in FIG. At this time, the air interposed between the molded surface of the bead ring 65 and the rubber (base surface 37) also moves to the inner TWi in the tire width direction together with the rubber and is discharged to the outside of the tire vulcanization die 60. ..

However, since the pressing force for flowing the rubber in the tire width direction TW becomes weaker from the outside to the inside, if the amount of rubber required for molding the inner portion 41 is excessively large, molding defects due to insufficient rubber are likely to occur. .. Further, when the air between the molded surface and the rubber cannot be discharged, a bear which is a rubber defect due to the residual air is likely to occur.

On the other hand, in the present embodiment, the ratio of the inner portion 41 to the entire base surface 37 is 25% or less, and the width of the inner portion 41 is narrower than that of the conventional case (30% or more). Therefore, the amount of rubber required for molding the inner portion 41 including the thickness of the tire radial direction TR can be reduced. As a result, the amount of rubber required for molding the inner portion 41 can be secured, so that the occurrence of molding defects due to insufficient rubber can be suppressed. In addition, the exhaustability between the molded surface and the rubber can be improved as compared with the conventional case, and the generation of bears, which are rubber defects due to residual air, can be suppressed.

The pneumatic tire 1 configured in this way has the following features.

The base surface 37 of the bead portion 30 has an outer portion 38 including a first tilt portion 40 tilted at a first tilt angle α with respect to the tire axis TA and a second tilt angle β larger than the first tilt angle α. It includes an inner portion 41 including an inclined second inclined portion 42. Therefore, the fitting pressure between the rim seat portion 52 and the inner portion 41 can be increased in the assembled state to the wheel 50 to ensure the sealing property.

The second tilt angle β of the second tilt portion 42 is larger than the first tilt angle α of the first tilt portion 40, but the ratio of the inner portion 41 to the entire base surface 37 is 25% or less. The width of the inner portion 41 is narrower than that of the conventional one. Therefore, since the amount of rubber required for molding the inner portion 41 including the thickness of the tire radial direction TR can be reduced, even if the rubber flow becomes weaker from the outside to the inside of the tire width direction TW during molding, the inner portion. The amount of rubber required for molding 41 can be secured. As a result, it is possible to suppress the occurrence of molding defects in the inner portion 41 due to lack of rubber, and it is possible to suppress the occurrence of bears, which are rubber defects due to residual air.

The first tilt angle α of the first tilt portion 40 is 6 degrees or more and 14 degrees or less, and the second tilt angle β of the second tilt portion 42 is 12 degrees or more and 28 degrees or less. Further, the angle difference between the first inclination angle α and the second inclination angle β is 6 degrees or more and 14 degrees or less. Therefore, since it is possible to suppress an excessive decrease in the rubber flow during molding, it is possible to suppress the occurrence of molding defects on the base surface 37. Further, when the tire 1 is assembled to the wheel 50, the sealing property between the rim seat portion 52 and the inner portion 41 can be ensured.

Since the intersection Pi of the first inclined portion 40 and the second inclined portion 42 is located between the center 31e and the inner end 31d of the bead core 31 in the tire width direction TW, molding defects occur due to insufficient rubber and assembly is performed. It is possible to suppress the deterioration of the sealing property in the state. Specifically, when the intersection Pi of the first inclined portion 40 and the second inclined portion 42 is arranged on the outer TWo in the tire width direction from the center 31e of the bead core 31, the ratio of the second inclined portion 42 (inner portion 41) is large. Therefore, the amount of rubber required for molding the inner portion 41 increases, and molding defects due to insufficient rubber are likely to occur during molding. On the other hand, when the intersection Pi of the first inclined portion 40 and the second inclined portion 42 is arranged on the inner TWi in the tire width direction from the inner end 31d of the bead core 31, the bead core 31 suppresses the deformation of the inner portion 41 to the outer TRo in the tire radial direction. Since no action is obtained, it becomes difficult to secure the sealing property between the rim seat portion 52 and the inner portion 41 in the state of being assembled to the wheel 50. However, in the present embodiment, since the intersection Pi of the first inclined portion 40 and the second inclined portion 42 is located between the center 31e and the inner end 31d of the bead core 31, inconveniences at the time of molding and in the assembled state can be suppressed. .. The deformation suppressing action means that the bead core 31 having high rigidity composed of a large number of steel wires suppresses excessive deformation of the inner portion 41 toward the outer TRo in the tire radial direction.

The first inclined portion 40 and the second inclined portion 42 are continuous via the curved connecting portion 44. Therefore, the inclination with respect to the tire axis TA (straight line L1) gradually changes from the first inclination angle α to the second inclination angle β depending on the connecting portion 44. That is, since it is possible to suppress a sudden change in the inclination angle on the base surface 37, it is possible to reduce the flow resistance of the rubber during molding. As a result, it is possible to suppress the occurrence of molding defects due to lack of rubber.

The pneumatic tire 1 of the present invention is not limited to the configuration of the above embodiment, and various modifications can be made.

For example, as shown in FIG. 7, the first inclined portion 40 and the second inclined portion 42 may be connected to each other without providing the connecting portion 44 between the outer portion 38 and the inner portion 41.

If the intersection Pi of the first inclined portion 40 and the second inclined portion 42 is arranged between the center 31e and the inner end 31d of the bead core 31, the shape of the bead core 31 can be changed as needed. The inner portion 41 may be composed of only the second inclined portion 42 without providing the curved portion 43.

1 Pneumatic tire 2 Carcass ply 3 1st ply 4 2nd ply 5 Inner liner 10 Tread 20 Sidewall 21 Sidewall rubber 30 Bead part 31 Bead core 31a Tire radial outer end 31b Tire radial inner end 31c Tire width direction Outer end 31d Inner end in tire width direction 31e Center 32 Bead filler 33 Strip rubber 34 Rim protector 34a Top 35 Inner side surface 36 Outer side surface 36a Inner end 36b Outer end 37 Base surface 38 Outer part 39 Heel part 39a Outer end 39b Inner end 40 1st inclined part 40'extension line 40a outer end 40b inner end 41 inner part 42 2nd inclined part 42'extension line 42a outer end 42b inner end 43 curved part 43a outer end 43b inner end 44 connection part 44a outer end 44b inner End 44c Outer part 44d Inner part 50 Wheel 51 Rim 52 Seat part 53 Heel part 54 Flange part 54a First part 54b Second part 60 Tire smelting mold 61 Sector mold 62 Sector 63 Side mold 64 Side plate 65 Bead ring 66 Bladder 67 Cavity α 1st tilt angle β 2nd tilt angle W1 Base surface width W2 Outer width W3 Inner width Pi Intersection of 1st and 2nd tilt TR Tire radial direction TW Tire width direction CL Tire equatorial Line TA Tire axis L1 Straight line parallel to the tire axis

Claims (7)

An annular bead portion having a base surface inclined inward in the tire radial direction from the outside to the inside in the tire width direction is provided at the inner end in the tire radial direction.
The base surface is
The outer portion including the first inclined portion inclined at the first inclined angle with respect to the tire axis, and the outer portion.
The outer portion is located inside in the tire width direction and has an inner portion including a second inclined portion inclined at a second inclined angle larger than the first inclined angle with respect to the tire axis.
The ratio of the width in the tire width direction of the inner portion to the width in the tire width direction of the base surface is 5% or more and 25% or less.
Pneumatic tires. The first inclination angle is 6 degrees or more and 14 degrees or less.
The second inclination angle is 12 degrees or more and 28 degrees or less.
The pneumatic tire according to claim 1. The pneumatic tire according to claim 1 or 2, wherein the angle difference between the first inclination angle and the second inclination angle is 6 degrees or more and 14 degrees or less. A bead core is embedded in the bead portion.
The intersection of the first inclined portion and the second inclined portion is located between the center and the inner end of the bead core in the tire width direction.
The pneumatic tire according to any one of claims 1 to 3. Claims 1 to 4 include an arcuate heel portion connected to the outer end of the first inclined portion in the tire width direction and curved outward in the tire radial direction from the inside to the outside in the tire width direction. The pneumatic tire according to any one of the above items. Claims 1 to 5 include an arcuate curved portion that is continuous with the inner end of the second inclined portion in the tire width direction and is curved inward in the tire radial direction from the outside in the tire width direction to the inside. The pneumatic tire according to any one of the above items. One of claims 1 to 6, wherein the first inclined portion and the second inclined portion are continuous via a connecting portion curved inward in the tire radial direction from the outside in the tire width direction to the inside. Pneumatic tires listed in.

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