JP7560285B2 - Pneumatic tire and method for manufacturing pneumatic tire - Google Patents

Description

This disclosure relates to pneumatic tires and methods for manufacturing pneumatic tires.

Pneumatic tires are formed by placing a raw tire (an unvulcanized tire before vulcanization) in a mold and heating and vulcanizing it. As disclosed in Patent Document 1, the mold has a tread mold that forms the tire's tread and a side mold that forms the tire's sidewalls.

The tread mold and side mold are fitted together so that their molding surfaces are connected. However, rubber gets between the mating surfaces of the molds, leaving mating surface marks on the tire surface. The sidewall rubber that comes into contact with the mating surfaces of the tread mold and side mold is sucked in between the mating surfaces, so the sidewall rubber in the area that comes into contact with the mating surfaces tends to become thin. As a result, cracks are likely to occur in the thin parts of the sidewall rubber.

International Publication No. 2011/105390

This disclosure provides a pneumatic tire that suppresses the occurrence of cracks and a method for manufacturing a pneumatic tire.

The pneumatic tire disclosed herein comprises a tread rubber that forms the contact surface, and a sidewall rubber that covers the outer side of the tread rubber in the tire width direction, the sidewall rubber having a mating surface mark formed by the mating surface between the tread mold that forms the tire tread and the side mold that forms the tire sidewall, and the thickness of the sidewall rubber in the tire width direction at the portion where the mating surface mark is formed is 2 mm or more.

1 is a tire meridian cross-sectional view showing a pneumatic tire according to a first embodiment. FIG. FIG. 2 is an enlarged view of a main part of FIG. 1 . FIG. 2 is a cross-sectional view showing the relationship between the pneumatic tire of the first embodiment and a fitting surface of a mold. FIG. 6 is a tire meridian cross-sectional view showing a main portion of a pneumatic tire according to a second embodiment.

First Embodiment
Hereinafter, a pneumatic tire according to a first embodiment of the present disclosure will be described with reference to the drawings. In the drawings, "CD" means the tire circumferential direction, "WD" means the tire width direction, and "RD" means the tire radial direction. Each drawing shows the shape of a new tire.

1 and 4 are tire meridian cross-sections showing only one side in the tire width direction WD from the tire equator CL. As shown in FIG. 1, a pneumatic tire has a pair of beads 1, sidewalls 2 extending from each bead 1 to the tire radially outer side RD1, and a tread 3 connecting the tire radially outer side RD1 ends of the sidewalls 2. An annular bead core 1a made of a bundle of steel wire or the like and rubber-coated, and a bead filler 1b are arranged in the bead 1. The bead 1 is attached to a bead seat of a rim (not shown), and if the air pressure is a predetermined pressure (for example, the air pressure determined by JATMA), the tire fits appropriately to the rim flange due to the tire internal pressure, and the tire is fitted to the rim.

The tire also has a toroidal carcass 4 that extends from the tread 3 through the sidewall 2 to the bead 1. The carcass 4 is provided between a pair of beads 1, and its ends are secured in a rolled-up state via the bead core 1a. An inner liner rubber 5 is arranged on the inner periphery of the carcass 4 to maintain air pressure.

The tread 3 has tread rubber 31 that forms the contact surface 30. The tread rubber 31 has base rubber 31b arranged on the tire radial outer side RD1 of the carcass 4, and cap rubber 31a arranged on the tire radial outer side RD1 of the base rubber 31b. The cap rubber 31a has a contact surface 30. The contact surface 30 comes into contact with the road surface when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat road surface, and a standard load is applied. The contact edge LE is the end of the contact surface 30 on the outer side WD1 in the tire width direction. In a heavy-duty tire, as in this embodiment, this corresponds to the ridge line of the corner of the tread 3.

The official rim is the rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, for JATMA, it is the standard rim, and for TRA and ETRTO, it is the "Measuring Rim." The official internal pressure is the air pressure that is specified for each tire by the standard system that includes 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." Note that if the tire is for passenger cars, it is 180 kPa, and if the tire is labeled "Extra Load" or "Reinforced," it is 220 kPa. The normal load is the load that each standard specifies for each tire in the standard system on which the tire is based. For JATMA, it is the maximum load capacity, for TRA, it is the maximum value listed in the table above, and for ETRTO, it is the "LOAD CAPACITY." However, if the tire is for passenger cars, it is 88% of the load that the internal pressure can support.

The sidewall 2 has a sidewall rubber 20 that forms the outer surface of the tire on the tire width direction outer side WD1 of the carcass 4. The sidewall rubber 20 covers the side surface of the tread rubber 31 on the tire width direction outer side WD1. That is, the tire of this embodiment has a SWOT (Side Wall On Tread) structure. As shown in FIG. 1, a mating surface trace 23 is formed on the sidewall rubber 20. The mating surface trace 23 is formed by the mating surface 83 of the tread mold 80 and the side mold 81. Specifically, as shown in FIG. 2, the mold 8 for molding the tire has a tread mold 80 that forms the tread 3 of the tire, a pair of side molds 81 that form the sidewall 2 of the tire, and a pair of bead molds 82 into which the bead 1 of the tire is fitted. The molding surface 80a of the tread mold 80 and the molding surface 81a of the side mold 81 are continuous, but a small gap is generated. When the tire is vulcanized, the sidewall rubber 20 penetrates between the fitting surface 83 of the tread mold 80 and the fitting surface 83 of the side mold 81, forming annular protrusions that are continuous in the tire circumferential direction. As shown in FIG. 3, the width of the protrusion in the tire radial direction is 1 mm or less, and the protrusion is in a sheet shape. In addition, the product is in a state where the protrusion is cut, and the amount of protrusion in the tire width direction of the protrusion in the cut state is 1 mm or less. The fitting surface trace 23 shown in FIG. 1 and FIG. 3 is a trace after the protrusion is cut. In addition, it is preferable that the fitting surface trace 23 is located on the tire radial direction outer side RD1 than the diameter φ2 that is 85% of the outer diameter φ1 of the tire (see FIG. 1). In this embodiment, the sidewall rubber 20 has an uneven portion 25 that is uneven in the tire circumferential direction for decorative purposes, on the tire radial direction inner side RD2 than the diameter φ2. These uneven portions 25 and the fitting surface trace 23 have different meanings.

The above diameters are determined when the tire is mounted on a standard rim and the standard internal pressure is applied in an unloaded state.

As shown in FIG. 1, in this embodiment, it is preferable that the thickness D1 in the tire width direction WD of the portion of the sidewall rubber 20 where the mating surface trace 23 is formed is 2 mm or more. The sidewall rubber 20 in the portion where the mating surface trace 23 is present is prone to becoming thin as the rubber is sucked between the mating surfaces 83, making it prone to cracks during use. Therefore, by making the thickness D1 of that portion 2 mm or more, it is possible to reduce the occurrence of cracks.

The sidewall rubber 20 has a first side rubber 21 arranged on the tire width direction outer side WD1 of the tread rubber 31, and a second side rubber 22 arranged on the tire width direction outer side WD1 of the first side rubber 21. The first side rubber 21 contacts the side surface of the tread rubber 31 on the tire width direction outer side WD1. The second side rubber 22 contacts the side surface of the first side rubber 21 on the tire width direction outer side WD1. It is preferable that the tire radial outer end 21a of the first side rubber 21 is arranged on the tire radial outer side RD1 than the tire radial outer end 22a of the second side rubber 22. As a result, the second side rubber 22 is expanded during molding and becomes thinner than the original member thickness before expansion, but even if the second side rubber 22 becomes thinner, it becomes easier to ensure the thickness of the sidewall rubber 20 including the first side rubber 21 and the second side rubber 22, and cracks can be suppressed. The first side rubber 21 is exposed to the tire surface.

The exposed portion of the interface 24 between the first side rubber 21 and the second side rubber 22 on the outer surface of the tire (the tire radial outer end 22a of the second side rubber 22) is preferably 5 mm or more away from the mating surface mark 23 in the tire radial direction RD. That is, the distance D2 in the tire radial direction RD from the mating surface mark 23 to the exposed portion 22a is preferably 5 mm or more. If the mating surface mark 23 and the exposed portion 22a are close to each other, a gap may be generated at the interface 24 due to the rubber being sucked by the mating surface 83, and this gap may cause cracks. If the distance D2 is 5 mm or more as described above, the occurrence of cracks can be reduced.

The rubber compounding of the first side rubber 21 and the second side rubber 22 may be the same or different. When the rubber compounding of the first side rubber 21 and the second side rubber 22 is different, it is preferable that the second side rubber 22 is made of a rubber that generates less heat than the first side rubber. In the embodiment shown in FIG. 1, the mating surface trace 23 is formed on the second side rubber 22. The mating surface trace 23 is located on the tire radial inner side RD2 of the exposed portion 22a.

The tire radial outer end 21a of the sidewall rubber 20 is located within 10 mm in the tire width direction WD from the tire width direction outer end LE (hereinafter also referred to as the ground contact end LE) of the ground contact surface 30. In other words, it is preferable that the distance D3 in the tire width direction WD from the ground contact end LE to the tire radial outer end 21a of the sidewall rubber 20 is 10 mm or less. With this configuration, the side of the tread rubber 31 is almost completely covered with the weather-resistant sidewall rubber 20, making it possible to improve durability.

[Manufacturing method of pneumatic tire]
The manufacturing method of the pneumatic tire includes a step of placing a green tire in a mold 8. As shown in FIG. 4, the green tire has a tread rubber 31 that forms a ground contact surface 30, and a sidewall rubber 20 that covers the side surface of the tread rubber 31. The sidewall rubber 20 has a first side rubber 21 that is arranged on the outer side WD1 of the tread rubber 31 in the tire width direction, and a second side rubber 22 that is arranged on the outer side WD1 of the first side rubber 21 in the tire width direction. The molding method of the green tire includes a step of molding a tread component in which an inner liner rubber 5, a carcass 4, a base rubber 31b, a cap rubber 31a, and the first side rubber 21 are laminated, a step of placing a bead core 1a and a bead filler 1b on the tread component and rolling up the end of the carcass 4 around the bead core 1a and the bead filler 1b, and a step of attaching a second side rubber 22 to the side surface of the tread component. Therefore, the first side rubber 21 and the second side rubber 22 are separate members in the manufacturing process of the green tire. 4, the tire radially outer end 21a of the first side rubber 21 is disposed on the tire radially outer side RD1 of the tire radially outer end 22a of the second side rubber 22. An exposed portion 22a of an interface 24 between the first side rubber 21 and the second side rubber 22 on the tire outer surface is disposed 5 mm or more away in the tire radial direction RD from the fitting surface 83. Once the placement of the green tire in the mold 8 is completed, the green tire is vulcanized by heating to produce a pneumatic tire.

Second Embodiment
5 is a tire meridian cross-sectional view showing a pneumatic tire of the second embodiment. In the second embodiment, the fitting surface trace 23 is formed on the first side rubber 21. The exposed portion 22a of the interface 24 between the first side rubber 21 and the second side rubber 22 is disposed on the tire radially inner side RD2 of the fitting surface trace 23. The other configurations are the same as those of the first embodiment. Specifically, the thickness D1 in the tire width direction WD of the portion where the fitting surface trace 23 is formed is 2 mm or more. The tire radially outer end 21a of the first side rubber 21 is disposed on the tire radially outer side RD1 of the tire radially outer end 22a of the second side rubber 22. The exposed portion 22a of the interface 24 between the first side rubber 21 and the second side rubber 22 on the tire outer surface is separated from the fitting surface trace 23 by 5 mm or more in the tire radial direction RD. An outer end 21 a in the tire radial direction of the sidewall rubber 20 is disposed within 10 mm in the tire width direction WD from an outer end LE in the tire width direction of the contact surface 30 .

As described above, the pneumatic tires of the first and second embodiments include the tread rubber 31 that forms the contact surface 30, the sidewall rubber 20 that covers the side surface of the tread rubber 31 on the outer side WD1 in the tire width direction, and the mating surface trace 23 formed in the sidewall rubber 20 by the mating surface 83 between the tread mold 80 that forms the tire tread 3 and the side mold 81 that forms the tire sidewall 2, and it is preferable that the thickness D1 in the tire width direction WD of the part of the sidewall rubber 20 where the mating surface trace 23 is formed is 2 mm or more.

As in this embodiment, the method for manufacturing a pneumatic tire includes a step of placing a raw tire in a mold 8 having a tread mold 80 that forms the tread 3 of the tire and a side mold 81 that forms the sidewall 2 of the tire. The raw tire includes a tread rubber 31 that forms the contact surface 30, and a sidewall rubber 20 that covers the side surface of the tread rubber 31 on the outer side WD1 in the tire width direction. The sidewall rubber 20 is a first sidewall rubber 20 that is arranged on the outer side WD1 in the tire width direction of the tread rubber 31. The tire includes a first side rubber 21 and a second side rubber 22 arranged on the tire width direction outer side WD1 of the first side rubber 21, the tire radial outer end 21a of the first side rubber 21 is arranged on the tire radial outer side RD1 of the tire radial outer end 22a of the second side rubber 22, and the exposed portion 22a of the interface 24 between the first side rubber 21 and the second side rubber 22 on the tire outer surface is preferably arranged 5 mm or more away in the tire radial direction RD from the mating surface 83 between the tread mold 80 and the side mold 81.

The sidewall rubber 20 in contact with the mating surface 83 is easily sucked in and penetrates into the gaps of the mating surface 83. The rubber that penetrates into the mating surface 83 is left as a protrusion and is cut off during finishing after vulcanization to become the mating surface trace 23. The area where the mating surface trace 23 is located is easily thinned by suction, and because it is thin, cracks are likely to occur when the tire is used. Therefore, by making the thickness D1 of the relevant area 2 mm or more, it is possible to prevent cracks from occurring.

Although not particularly limited, as in the first and second embodiments, the sidewall rubber 20 includes a first side rubber 21 arranged on the tire width direction outer side WD1 of the tread rubber 31, and a second side rubber 22 arranged on the tire width direction outer side WD1 of the first side rubber 21, and it is preferable that the tire radial direction outer end 21a of the first side rubber 21 is arranged on the tire radial direction outer side RD1 than the tire radial direction outer end 22a of the second side rubber 22.

The second side rubber 22 expands during molding and becomes thinner than its original thickness before expansion. However, if the tire radial outer end 21a of the first side rubber 21 is positioned radially outward RD1 of the second side rubber 22, it becomes easier to ensure the thickness of the sidewall rubber 20, which is the combined thickness of the first side rubber 21 and the second side rubber 22, even if the second side rubber 22 becomes thinner, and cracks can be suppressed.

Although not particularly limited, as in the first and second embodiments, the sidewall rubber 20 includes a first side rubber 21 arranged on the outer side WD1 of the tread rubber 31 in the tire width direction, and a second side rubber 22 arranged on the outer side WD1 of the first side rubber 21 in the tire width direction, and it is preferable that the exposed portion 22a of the interface 24 between the first side rubber 21 and the second side rubber 22 on the tire outer surface is 5 mm or more away from the fitting surface trace 23 in the tire radial direction RD.

If the exposed portion 22a of the interface 24 between the first side rubber 21 and the second side rubber 22 on the outer surface of the tire is close to the mating surface mark 23, the rubber may be sucked into the mating surface 83, creating a gap at the interface 24, which may cause cracks to occur. Therefore, by keeping the distance 5 mm or more as described above, it is possible to reduce the occurrence of cracks.

Although not particularly limited, as in the first and second embodiments, it is preferable that the tire radial outer end 21a of the sidewall rubber 20 is located within 10 mm in the tire width direction WD from the tire width direction outer end LE of the contact surface 30.

With this configuration, the sides of the tread rubber 31 are almost entirely covered with the weather-resistant sidewall rubber 20, improving durability.

Although the embodiments of the present disclosure have been described above with reference to the drawings, the specific configuration should not be considered to be limited to these embodiments. The scope of the present disclosure is indicated not only by the description of the above embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

The structures employed in each of the above embodiments can be employed in any other embodiment. The specific configurations of each part are not limited to the above-mentioned embodiments, and various modifications are possible without departing from the spirit of this disclosure.

<Modification>
(1) In the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 5, the tire radial direction outer end 21a of the first side rubber 21 is disposed on the tire radial direction outer side RD1 than the tire radial direction outer end 22a of the second side rubber 22, and thus a part of the first side rubber 21 is exposed to the tire surface, but this configuration is not limited to this. For example, all of the first side rubber 21 may be covered by the second side rubber 22. In that case, the tire radial direction outer end 21a of the first side rubber 21 and the tire radial direction outer end 22a of the second side rubber 22 may be disposed at the same height in the tire radial direction. In addition, the tire radial direction outer end 22a of the second side rubber 22 may be disposed on the tire radial direction outer side RD1 than the tire radial direction outer end 21a of the first side rubber 21.

(2) In the first and second embodiments, the sidewall rubber 20 has a first side rubber 21 and a second side rubber 22, but the sidewall rubber 20 does not have to be divided into the first side rubber 21 and the second side rubber 22.

20: sidewall rubber, 21: first side rubber, 22: second side rubber, 23: mating surface trace, 30: ground contact surface, 31: tread rubber, 8: mold, 80: tread mold, 81: side mold

Claims (4)

A tread rubber that forms the contact surface;
and a sidewall rubber covering the outer side surface of the tread rubber in the tire width direction,
the sidewall rubber has a mating surface mark formed by a mating surface between a tread mold that forms a tread of the tire and a side mold that forms a sidewall of the tire,
The pneumatic tire has a thickness in the tire width direction of a portion of the sidewall rubber where the fitting surface trace is formed being 2 mm or more. The sidewall rubber includes a first side rubber disposed on an outer side of the tread rubber in the tire width direction, and a second side rubber disposed on an outer side of the first side rubber in the tire width direction ,
The first side rubber and the second side rubber have different rubber compositions,
an outer end in the tire radial direction of the first side rubber is disposed outer in the tire radial direction than an outer end in the tire radial direction of the second side rubber,
The pneumatic tire according to claim 1 , wherein a portion of the interface between the first side rubber and the second side rubber exposed on the outer surface of the tire is spaced 5 mm or more from the fitting surface trace in the tire radial direction . The pneumatic tire according to claim 1 or 2 , wherein an outer end in a radial direction of the tire of the sidewall rubber is disposed within 10 mm in the tire width direction from an outer end in the tire width direction of the contact surface. placing the green tire in a mold having a tread mold for forming the tread of the tire and a side mold for forming the sidewalls of the tire ;
a vulcanization step of vulcanizing the raw tire by heating after the placing step ,
The raw tire includes a tread rubber that forms a contact surface, and a sidewall rubber that covers a side surface of the tread rubber on an outer side in a tire width direction, the sidewall rubber including a first side rubber that is disposed on the outer side of the tread rubber in the tire width direction, and a second side rubber that is disposed on the outer side of the first side rubber in the tire width direction,
an outer end in the tire radial direction of the first side rubber is disposed outer in the tire radial direction than an outer end in the tire radial direction of the second side rubber,
a portion of the interface between the first side rubber and the second side rubber exposed to the outer surface of the tire is positioned 5 mm or more in the tire radial direction from a fitting surface between the tread mold and the side mold.

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