JP5824265B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

  The present invention relates to a pneumatic tire capable of reducing tire mass and manufacturing cost while maintaining internal pressure holding performance and durability, and a manufacturing method thereof.

  Conventionally, a pneumatic tire has a main body part extending from a tread part to a side wall part to a bead core of the bead part, and a folded part that extends from the main body part and is turned back from the inner side to the outer side in the tire axial direction. A carcass made of a carcass ply is provided. The carcass ply is formed including an array of carcass cords and a topping rubber that covers the array.

  In the pneumatic tire, an inner liner rubber forming a tire lumen surface on the inner surface of the carcass ply and a sidewall rubber forming an outer surface of the sidewall portion on the outer surface of the carcass ply are arranged. In such a pneumatic tire, the inner pressure of the tire is maintained by the inner liner rubber, and the rigidity and cut resistance of the sidewall portion are secured by the sidewall rubber, thereby maintaining the durability.

  However, in the pneumatic tire as described above, since the topping rubber, the inner liner rubber, and the sidewall rubber are formed from different rubbers, there is a problem that the tire mass and the manufacturing cost are likely to increase.

  Accordingly, a pneumatic tire is proposed in which air-impermeable butyl rubber is used as a topping rubber on the side of the tire lumen of the carcass ply. In such a pneumatic tire, since the topping rubber also has a function of maintaining the internal pressure of the tire, it is not necessary to provide the inner liner rubber separately from the carcass ply, and the tire mass and manufacturing cost can be reduced. Related literature includes the following.

JP 2005-262848 A

  However, in the pneumatic tire as described above, the tire mass and the manufacturing cost can be partially reduced, but there is room for further improvement.

  The present invention has been devised in view of the actual situation as described above, and the topping rubber of the carcass ply that reaches the bead core of the bead part from the tread part through the sidewall part and terminates without being folded back by the bead core, Based on the inner topping rubber made of butyl rubber that does not penetrate the air and is impervious to the tire, and the outer topping rubber that forms the outer surface of the sidewall portion and has a certain rubber thickness. The main object is to provide a pneumatic tire and a method for manufacturing the same that can reduce the mass and manufacturing cost of the tire while maintaining the internal pressure holding performance and durability.

The invention according to claim 1 of the present invention comprises a carcass consisting of a carcass ply that extends from a tread portion to a bead core of a bead portion through a sidewall portion and terminates without being folded back by the bead core, wherein the array of the carcass cord, and a topping rubber which covers the said sequence thereof, wherein the topping rubber in the sidewall portion, the inner topping consisting forms a tire cavity surface and the air-impermeable butyl rubber Rubber and an outer topping rubber disposed on the opposite side of the inner topping rubber with respect to the array and forming the outer surface of the sidewall portion, wherein the outer topping rubber is the outer surface of the sidewall portion. minimum rubber thickness 1.5~3.0mm der up the array from is, in the tire of the bead portion On the surface, contiguous to the inner topping rubber, a rubber sheet made of butyl rubber extending to bead toe is disposed, between the bead core and the rubber sheet is characterized in that the chafer rubber is disposed.

  According to a second aspect of the present invention, the bead core includes an inner core in which a bead wire is wound at least one round in the tire circumferential direction along an inner side surface in the tire axial direction of the array, and an outer surface of the outer topping rubber. The pneumatic tire according to claim 1, wherein the bead wire includes an outer core wound around at least one turn in the tire circumferential direction.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein a protector including a raised portion extending in a ring shape in a tire circumferential direction is formed on the outer surface of the sidewall portion. .

  According to a fourth aspect of the present invention, in the inner topping rubber, the shortest rubber thickness from the tire inner surface to the carcass cord is 0.5 to 1.0 mm. The pneumatic tire described.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein a short fiber for reinforcement is blended in the inner topping rubber and / or the outer topping rubber.

  Further, in the invention according to claim 6, the amount of sulfur in the outer topping rubber is 30 to 90% of the amount of sulfur in the inner topping rubber. Tire.

The invention according to claim 7 is a method for producing the pneumatic tire according to any one of claims 1 to 6,
Including a carcass ply attaching step of attaching the carcass ply to a core body having a toroidal outer peripheral surface;
The carcass ply sticking step includes a step of juxtaposing a plurality of strip ply pieces obtained by cutting the sheet-like carcass ply into small strips in the tire circumferential direction on the outer peripheral surface of the core body, and the tread portion side And a step of absorbing the difference in the tire circumferential length between the bead portion side by overlapping the edge side in the tire axial direction of the strip ply piece.

  The invention according to claim 8 is an inner core that forms the inner core of the bead core by winding a bead wire around the bead portion of the core body at least once in the tire circumferential direction prior to the carcass ply attaching step. A forming step and an outer core forming step of forming the outer core of the bead core by winding at least one bead wire in the tire circumferential direction along the outer surface of the carcass ply after the carcass ply sticking step. 7. A method for producing a pneumatic tire according to 7.

  In the present specification, unless otherwise specified, the dimensions of each part of the tire are values specified in a normal state in which a normal rim is assembled with a normal rim and filled with a normal internal pressure, and there is no load.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, and ETRTO is a standard rim. If present, it means "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Then, “INFLATION PRESSURE” is set, but when the tire is for a passenger car, the pressure is uniformly set to 180 kPa.

  The pneumatic tire according to the present invention includes a carcass made of a carcass ply that extends from a tread portion to a sidewall portion to a bead core of the bead portion and terminates without being folded back by the bead core. Such a carcass ply, for example, can reduce the material used for the carcass ply and reduce the mass of the tire compared to the one including the folded portion that is folded by the bead core. Can be reduced.

  The carcass ply includes an array of carcass cords and a topping rubber that covers the array. The topping rubber is arranged on the opposite side of the inner topping rubber from the inner topping rubber, which is formed on the sidewall portion of the tire and is made of air-impermeable butyl rubber. It consists of the outer topping rubber which makes the outer surface of a wall part.

  In such a carcass ply, the inner topping rubber also has the function of maintaining the internal pressure of the tire, and the outer topping rubber forms the outer surface of the side wall, so the inner liner rubber and the side wall rubber are separated from the carcass ply. Since it is not necessary to provide the tire, the tire mass and manufacturing cost can be reduced.

  The outer topping rubber is limited to a shortest rubber thickness from the outer surface of the sidewall portion to the array body of 1.5 to 3.0 mm. Thus, the outer topping rubber can suppress an increase in tire mass while ensuring the rigidity of the sidewall portion and maintaining the durability.

It is sectional drawing of the pneumatic tire of this embodiment. (A) is a fragmentary perspective view of a carcass ply, (b) is AA sectional drawing of (a). It is an enlarged view of the bead part of FIG. It is sectional drawing explaining the process of sticking a raw carcass ply. FIG. 5 is a perspective view of FIG. 4. It is sectional drawing which shows a green tire and a core. It is sectional drawing which expands and shows a protector.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is a carcass that extends from a tread portion 2 to a side wall portion 3 to a bead core 5 of a bead portion 4. 6 and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and on the inner side of the tread portion 2 are shown.

  The carcass 6 includes a single carcass ply 6A having a radial structure. The carcass ply 6 </ b> A reaches the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3, and terminates without being folded back by the bead core 5. Such a carcass ply 6A, for example, reduces the mass of the tire and the manufacturing cost by reducing the material used for the folded portion compared to the conventional one including the folded portion (not shown) folded by the bead core 5. sell.

  The belt layer 7 includes at least two belt plies 7A and 7B in which the belt cord is arranged at a small angle of, for example, 10 to 35 degrees with respect to the tire equator C. Are overlapped in the direction in which the belt cords cross each other. The belt cord of this embodiment employs a steel cord, but a highly elastic organic fiber cord such as aramid or rayon can also be used as necessary.

  And the carcass ply 6A of this embodiment is comprised including the array body 12 of the carcass cord 12a and the topping rubber 13 which coat | covers this array body 12, as FIG.1 and FIG.2 shows.

  The array body 12 has a radial structure in which the carcass cords 12a are arrayed at an angle of, for example, 75 to 90 degrees with respect to the tire equator C. As the carcass cord 12a, for example, an organic fiber cord such as polyester, nylon, rayon, or aramid, or a steel cord if necessary.

  The topping rubber 13 is disposed on the side wall 3 on the opposite side of the inner topping rubber 13A and the inner topping rubber 13A forming the tire cavity surface 10 with respect to the array body 12, and on the outer surface of the side wall 3 It consists of an outer topping rubber 13B forming 3S. In FIG. 2, the boundary between the inner topping rubber 13A and the outer topping rubber 13B is indicated by reference numeral 13e.

  The inner topping rubber 13A is made of air-impermeable butyl rubber. Thus, the inner topping rubber 13A can ensure the function of holding the tire internal pressure (hereinafter sometimes simply referred to as “internal pressure holding performance”) without providing a conventional inner liner rubber separately.

  In the present specification, the “butyl rubber” is a rubber containing butyl rubber (IIR) and / or a derivative thereof in an amount of 10 parts by mass or more, more preferably 30 parts by mass or more in 100 parts by mass of a rubber polymer.

  Examples of the butyl rubber derivatives include chlorinated butyl rubber obtained by reacting butyl rubber with chlorine, bromine, and the like, and halogenated butyl rubber including brominated butyl rubber. In the butyl rubber, if the content of butyl rubber or a derivative thereof is less than 10 parts by mass, the internal pressure holding performance may not be sufficiently improved.

  The butyl rubber may contain one or more diene rubbers such as natural rubber (NR), butadiene rubber (BR), and styrene butadiene rubber (SBR) as the balance of the rubber polymer. For rubber polymers, as with general topping rubber, various fillers as required (for example, reinforcing agents such as carbon black, sulfur, zinc white, vulcanization accelerators, softening agents such as stearic acid) Is added.

  Furthermore, the amount Cv1 of sulfur in the inner topping rubber 13A is preferably 2 to 5 parts by mass. If the blending amount Cv1 is less than 2 parts by mass, the adhesiveness between the inner topping rubber 13A and the carcass cord 12a is lowered, and there is a possibility that the durability cannot be sufficiently maintained. On the contrary, when the blending amount Cv1 exceeds 5 parts by mass, the rubber hardness of the inner topping rubber 13A is increased, and the ride comfort may be deteriorated. From such a viewpoint, the blending amount Cv1 is more preferably 2.5 parts by mass or more, and more preferably 4.5 parts by mass or less.

  The shortest rubber thickness W1 from the tire inner cavity surface 10 of the inner topping rubber 13A to the carcass cord 12a is preferably 0.5 to 1.0 mm. If the shortest rubber thickness W1 is less than 0.5 mm, the internal pressure holding performance may not be sufficiently improved. On the contrary, if the shortest rubber thickness W1 exceeds 1.0 mm, there is a risk of increasing the tire mass or deteriorating the riding comfort. From such a viewpoint, the shortest rubber thickness W1 is more preferably 0.7 mm or more, and more preferably 0.9 mm or less.

  The outer topping rubber 13B is formed thicker than the inner topping rubber 13A, and the shortest rubber thickness W2 from the outer surface 3S of the sidewall portion 3 to the carcass cord 12a is set to 1.5 to 3.0 mm. The Such an outer topping rubber 13B can secure the rigidity and cut resistance of the sidewall portion 3 and maintain durability without providing a conventional sidewall rubber.

  As described above, the tire 1 of the present invention has the internal pressure holding performance and the rigidity of the side wall portion 3 as a component different from the carcass ply 6A without providing the conventional inner liner rubber and side wall rubber. Can be secured, and the tire mass can be reduced. Furthermore, the tire 1 of the present invention can simplify the manufacturing process and reduce intermediate inventory as the number of tire members decreases, and the manufacturing cost can also be reduced.

  In addition, when the shortest rubber thickness W2 of the outer topping rubber 13B is less than 1.5 mm, the rigidity of the sidewall portion 3 cannot be sufficiently secured, and the durability and the steering stability performance may be deteriorated. Conversely, if the shortest rubber thickness W2 exceeds 3.0 mm, the tire mass reduction effect cannot be obtained, and the ride comfort may be deteriorated. From this point of view, the shortest rubber thickness W2 is preferably 1.5 mm or more, more preferably 2 mm or more, and preferably 3 mm or less, more preferably 2.5 mm or less.

  The rubber hardness of the outer topping rubber 13B is preferably 50 to 75 degrees. If the rubber hardness is less than 50 degrees, sufficient cut resistance of the sidewall portion 3 cannot be ensured, and durability may be reduced. On the contrary, if the rubber hardness exceeds 75 degrees, the flexibility of the sidewall portion 3 cannot be ensured sufficiently and the ride comfort may be deteriorated. From such a viewpoint, the rubber hardness is more preferably 55 degrees or more, and more preferably 70 degrees or less. In the present specification, the “rubber hardness” is a hardness according to durometer type A in an environment at a temperature of 23 ° C. in accordance with JIS-K6253.

  Further, it is desirable that the outer topping rubber 13B is made of a non-butyl rubber other than the butyl rubber. Such non-butyl rubber tends to have higher adhesive strength than butyl rubber, and is excellent in peel resistance. The non-butyl rubber is not particularly limited, but a rubber polymer containing 95 parts by mass or more, more preferably 100 parts by mass of the diene rubber as a rubber polymer is desirable.

  Moreover, it is desirable that the sulfur blending amount Cv2 of the outer topping rubber 13B is set to be larger than the conventional sidewall rubber and smaller than the blending amount Cv1 of the inner topping rubber 13A. Accordingly, the outer topping rubber 13B can maintain the adhesiveness with the carcass cord 12a while ensuring the flexibility of the sidewall portion 3.

  In order to effectively exhibit such an action, the ratio (Cv2 / Cv1) of the blending amount Cv2 of the outer topping rubber 13B and the blending amount Cv1 of the inner topping rubber 13A is desirably 30 to 90%. If the ratio (Cv2 / Cv1) is less than 30%, the adhesion with the carcass cord 12a may not be maintained. On the other hand, if the ratio (Cv2 / Cv1) exceeds 90%, the rubber hardness of the outer topping rubber 13B increases, and the flexibility of the sidewall portion 3 may not be sufficiently maintained. From such a viewpoint, the ratio (Cv2 / Cv1) is more preferably 40% or more, and more preferably 80% or less.

  The inner topping rubber 13A and / or the outer topping rubber 13B is preferably blended with reinforcing short fibers (not shown). Such short fibers can reinforce the inner topping rubber 13 </ b> A and / or the outer topping rubber 13 </ b> B to increase rigidity and improve durability and the like. In particular, the outer topping rubber 13B is useful for improving cut resistance and trauma resistance and improving durability.

  The short fiber is preferably a non-metallic material having excellent adhesion to rubber, for example, an organic material such as nylon, polyester, aramid, rayon, vinylon, aromatic polyamide, cotton, cellulose resin, or crystalline polybutadiene. Short fibers and inorganic short fibers such as boron, glass fibers or carbon fibers are preferred. Particularly preferred is a nylon fiber excellent in water resistance. Moreover, a short fiber may be used individually or in combination of 2 or more types.

  The content of the short fibers is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber polymer. When the content of the short fiber is excessively reduced, the above effects cannot be expected sufficiently. On the other hand, if the content of the short fiber is excessively large, the tear resistance and the like are reduced, and cracking is likely to occur. In addition, durability may be deteriorated, and the rigidity of the inner and outer topping rubbers 13A and 13B. May increase the ride comfort. From such a viewpoint, the content of the short fibers is preferably 25 parts by mass or less, more preferably 18 parts by mass or less.

  In addition, the average fiber length of the short fibers can be set as appropriate, but if it becomes too small, the above effects cannot be sufficiently expected. On the other hand, if the average fiber length is excessively large, the adhesion of the inner and outer topping rubbers 13A and 13B to the carcass cord 12a is lowered, and the wear resistance and crack resistance may not be sufficiently improved. From such a viewpoint, the average fiber length is preferably 20 μm or more, more preferably 100 μm or more, and preferably 2 mm or less, more preferably 800 μm or less.

  Furthermore, it is preferable that the short fibers are oriented in the sidewall portion 3 along the tire circumferential direction. Thereby, the circumferential direction rigidity of the side wall part 3 increases, and durability and steering stability performance can be improved. “Oriented along the tire circumferential direction” means that 90% or more of the short fibers are oriented in an angular range of ± 20 degrees or less with the tire circumferential direction as the center.

  As shown in an enlarged view in FIG. 3, the bead core 5 of the present embodiment includes an inner core 5 </ b> A in which the bead wire 5 c is wound at least one turn in the tire circumferential direction along the inner surface 12 i in the tire axial direction of the array body 12. And an outer core 5B in which a bead wire 5c is wound at least one turn in the tire circumferential direction along the outer surface 13Bo of the outer topping rubber 13B. Moreover, the steel cord which has big intensity | strength is used for the bead wire 5c of this embodiment.

  Since the inner core 5A and the outer core 5B can hold the inner end 6Ae side of the carcass ply 6A, the carcass ply 6A can be prevented from being blown through without having a conventional carcass ply folded portion. sell.

  In the present embodiment, the inner core 5A and the outer core 5B are arranged over a wide range of the bead portion 4 in the tire radial direction. As a result, the inner core 5A and the outer core 5B can reinforce the bead portion 4 without providing the conventional bead apex rubber, so that the tire mass and manufacturing cost can be reduced.

  In order to effectively exhibit such an action, the ratio L1 / the maximum length L1 of the inner core 5A in the tire radial direction and the tire cross-sectional height H1 (shown in FIG. 1) from the bead base line BL. H1 is preferably 6.5 to 18%. If the ratio L1 / H1 is less than 6.5%, the bead portion 4 cannot be sufficiently reinforced and the durability may not be maintained. On the other hand, if the ratio L1 / H1 exceeds 18%, the rigidity of the bead portion 4 is excessively increased, which may cause deterioration in ride comfort and increase in tire mass. From such a viewpoint, the ratio L1 / H1 is more preferably 8% or more, and more preferably 15% or less. The bead base line BL means a tire axial direction line passing through a rim diameter position of a regular rim (not shown).

  Similarly, the ratio L2 / H1 between the maximum length L2 of the outer core 5B in the tire radial direction and the tire cross-sectional height H1 is preferably 6.5% or more, more preferably 8% or more, Preferably it is 18% or less, more preferably 15% or less.

  In addition, the outer core 5B of the present embodiment is disposed on the outer side in the tire axial direction of the first outer core 5Ba along the outer surface 13Bo of the outer topping rubber 13B, and the first outer core 5Ba. The second outer core 5Bb is smaller in height in the tire radial direction than the core 5Ba. Since such an outer core 5B can increase the rigidity of the bead portion 4 on the outer side in the tire axial direction, it can suppress problems such as rim displacement.

  Further, a chafer rubber 14 made of hard rubber is disposed on the bead portion 4. Such chafer rubber 14 can suppress problems such as damage due to friction with the rim and rim displacement.

The chafer rubber 14 includes a base portion 14a having a substantially L-shaped cross section disposed on the inner side in the tire axial direction of the inner core 5A, and on the inner side in the tire radial direction of the inner core 5A and the outer core 5B, and the tire shaft of the outer core 5B. And a sub-part 14b disposed on the outer side in the direction. Further, on the tire lumen surface 10 side of the base portion 14a of the present embodiment, a rubber sheet 11 that is in contact with the edge 13At of the inner topping rubber 13A and made of butyl rubber is disposed.

  Such a rubber sheet 11, together with the inner topping rubber 13 </ b> A, can span an air-impermeable rubber between the bead portions 4, 4 of the tire lumen surface 10, so that the internal pressure retaining performance is reliably retained. sell.

Next, a method for manufacturing the tire 1 will be described.
In the manufacturing method of this embodiment, as shown in FIGS. 4 and 6, a raw tire 1 </ b> L is formed by using a raw tire molding core 16 having a toroidal outer peripheral surface 16 s. A tire molding step and a vulcanization step of vulcanizing the raw tire 1L together with the core body 16 using a vulcanization mold (not shown) that forms the outer surface of the raw tire 1L are included.

  The core body 16 of this embodiment is constituted by, for example, a plurality of divided pieces (not shown) that can be divided in the tire circumferential direction, and by assembling these divided pieces, a three-dimensional shape that approximates the inner shape of the tire. An outer peripheral surface 16s and a pair of flange surfaces 16f that are connected to the bead-side end of the outer peripheral surface 16s and extend outward in the axial direction are formed. The core body 16 is formed of a metal material such as duralumin that can withstand heat and pressure during vulcanization.

  In the green tire forming step, an inner core forming step for forming the inner core 5A of the bead core 5, a carcass ply attaching step for attaching the carcass ply 6A to the core body 16, and an outer core forming for forming the outer core 5B. Process.

  In the inner core forming step, as shown in FIG. 4, prior to the formation of the inner core 5A, the air non-permeable rubber sheet 11 and the outer peripheral surface 16s and the flange surface 16f of the core body 16 and the inner core 5A are formed. A base portion 14a of the chafer rubber 14 is wound in a ring shape. The bead wire 5c is wound around the outer circumferential surface of the base portion 14a at least once in the tire circumferential direction. As a result, the bead wires 5c are stacked in the tire radial direction from the base portion 14a to form the inner core 5A.

  Next, in the carcass ply sticking step, as shown in FIGS. 4 and 5, the first step of juxtaposing the strip ply piece 21 on the outer peripheral surface 16 s of the core body 16, and the tire axial direction of the strip ply piece 21 Including a second step of overlapping the end edge 21t side. The strip ply piece 21 is formed by cutting a sheet-like carcass ply 6A into a narrow strip shape in the tire circumferential direction.

  In the first step, the strip ply piece 21 has the inner topping rubber 13A directed toward the outer peripheral surface 16s side of the core body 16, and the side edge 21e of the strip ply piece 21 is abutted to the tire circumferential direction. It is pasted side by side. Further, the edge 21 t of the strip ply piece 21 is terminated by the base portion 14 a of the chafer rubber 14 without being folded back by the bead core 5.

  In the second step, the edge 21t side of the strip ply piece 21 is overlapped with the strip ply pieces 21 adjacent in the tire circumferential direction, and an overlapping portion 22 is formed on the carcass ply 6A. Thereby, the strip ply piece 21 can absorb the difference in the tire circumferential direction length between the tread portion 2 side and the bead portion 4 side of the core body 16, and toroidal carcass ply 6 </ b> A without generating wrinkles or the like. Can be formed.

  As shown in FIG. 6, in the outer core forming step, the bead wire 5c is wound from the base portion 14a of the chafer rubber 14 along the outer surface 6Ao of the carcass ply 6A in the tire circumferential direction by at least one turn. A core 5B is formed. In the present embodiment, after the first outer core 5Ba is formed along the outer surface 6Ao of the carcass ply 6A, the bead wire 5c is wound outside the first outer core 5Ba so that the second outer core 5Bb It is formed.

  Further, the sub-portion 14b of the chafer rubber 14 is attached to the outer side of the outer core 5B in the tire axial direction, and the buttress rubber 23, the belt layer 7, the tread rubber 2G, and the like are sequentially attached to the inside. A raw tire 1 </ b> L is formed on the child body 16.

  As described above, in the raw tire forming process of the present embodiment, the step of turning the carcass ply 6A with the bead core and the step of attaching the sidewall rubber can be eliminated, so that the manufacturing process can be simplified and the manufacturing cost can be reduced. .

  In the vulcanization step, the tire 1 is manufactured by vulcanizing the raw tire 1L together with the core body 16 using the vulcanization mold (not shown).

FIG. 7 shows a tire 1 according to another embodiment.
In the tire 1 of this embodiment, a protector 18 is formed on the outer surface 3 </ b> S of the sidewall portion 3. The protector 18 is an annular ridge extending in the tire circumferential direction. Such a protector 18 can partially increase the rubber thickness of a buttress portion or the like where the side wall portion 3 is likely to be damaged, and the tire mass is excessively increased while improving the cut resistance and the damage resistance. The increase can be suppressed. Further, the protector 18 makes the undulation that the rubber portions of the sidewall portion 3 and the buttress portion undulate along the carcass cord 12a inconspicuous, and can also suppress deterioration in the appearance of the tire 1.

  In order to effectively exhibit such an action, the length L3 of the protector 18 in the tire radial direction between the inner end 18i and the outer end 18o in the tire radial direction and the tire cross-sectional height from the bead base line BL are described. The ratio L3 / H1 to the height H1 (shown in FIG. 1) is preferably 10 to 45%. In addition, when the ratio L3 / H1 is less than 10%, the cut resistance and the damage resistance as described above may not be sufficiently improved, and the appearance deterioration may not be sufficiently suppressed. On the other hand, if the ratio L3 / H1 exceeds 40%, there is a risk of increasing the tire mass or deteriorating riding comfort. From such a viewpoint, the ratio L3 / H1 is more preferably 15% or more, and more preferably 40% or less.

  From the same viewpoint, the ratio L4 / W2 between the protrusion length L4 of the protector 18 from the outer surface 3S and the shortest rubber thickness W2 of the outer topping rubber 13B is preferably 50% or more, more preferably 100. % Or more is desirable, preferably 300% or less, more preferably 250% or less.

  The protector 18 is preferably formed with a plurality of concave grooves 19 extending in the tire circumferential direction. Such a concave groove 19 facilitates the deformation of the protector 18, absorbs the impact received from the road surface, and can suppress the deterioration of the riding comfort.

  In order to effectively exhibit such an action, the ratio D1 / L4 between the groove depth D1 of the concave groove 19 and the protruding length L4 is preferably 20 to 90%. If the ratio D1 / L4 is less than 20%, the protector 18 may not be sufficiently deformed. Conversely, when the ratio D1 / L4 exceeds 90%, the function as the protector 18 may not be sufficiently obtained. From such a viewpoint, the ratio D1 / L4 is more preferably 30% or more, and more preferably 80% or less.

  From the same viewpoint, the ratio W3 / H1 of the groove width W3 of the recessed groove 19 and the tire cross-section height H1 is preferably 1% or more, more preferably 2% or more, and preferably 10% or less. More preferably, 8% or less is desirable.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Tires having the basic structure shown in FIG. 1 and having the carcass ply shown in Table 1 were manufactured and evaluated. For comparison, a conventional tire (Comparative Example 1) in which an inner liner rubber and a sidewall rubber are arranged and a tire including a folded portion of a carcass ply (Comparative Example 2) were also tested in the same manner. The common specifications are as follows.
Tire size: 175 / 65R14
Rim size: 5 × 14
Tire cross-section height H1: 113 (mm)

The blending of the inner and outer topping rubbers is shown in Table 2. Details are as follows.
Natural rubber (NR): RSS # 3
Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd.
Butyl halide: 2255 manufactured by LANXESS
Carbon (N326): Diamond Black LH manufactured by Mitsubishi Chemical Corporation
Carbon (N660): Diamond Black G manufactured by Mitsubishi Chemical Corporation
Process oil: Dyna process oil PA-32 manufactured by Idemitsu Kosan Co., Ltd.
Anti-aging agent 6C: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Paraffin wax: OZOACE0355 manufactured by Nippon Seiwa Co., Ltd.
Stearic acid: Agate made by Nippon Oil & Fats Co., Ltd. Zinc flower: Zinc flower No. 2 manufactured by Mitsui Kinzoku Co., Ltd. Sulfur: Powdered sulfur produced by Karuizawa Sulfur Co., Ltd. Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide)
Short fiber: Paper fiber (cellulose)
The test method is as follows.

<Mass of carcass ply>
The mass of the carcass ply per each test tire was measured and displayed as an index with Comparative Example 1 being 100. The smaller the value, the better.

<Tire mass>
The mass of each test tire is measured and displayed as an index with Comparative Example 1 being 100. The smaller the value, the better.

<Steering stability>
Each test tire was assembled on the rim, filled with an internal pressure of 200 kPa, mounted on all wheels of a domestic FF vehicle with a displacement of 1000 cc, and run on a dry asphalt road test course. Then, through a sensory evaluation by a professional driver, a straight evaluation, stability during turning, vehicle behavior during braking, etc. were comprehensively evaluated and evaluated by a 10-point method. The larger the value, the better.

<Ride comfort>
Each test tire was assembled on the rim under the above conditions and mounted on the vehicle, and was run on a stepped road, a Belgian road, and a Bitzmann road on a dry asphalt road surface. The sensation by a professional driver was comprehensively evaluated for ruggedness, push-up, and damping, and was evaluated by a 10-point method. The larger the value, the better.

<Drum durability performance>
Each test tire was assembled on the rim under the above conditions and traveled on a drum testing machine at a speed of 80 km / h, and the travel distance until the tire broke was examined. In the evaluation, the travel distance was displayed as an index with Comparative Example 1 as 100. The larger the value, the better.

<Manufacturing cost>
The manufacturing cost required to manufacture one tire was indicated by an index with Comparative Example 1 as 100. The smaller the value, the lower the manufacturing cost and the better the productivity.

<Internal pressure retention performance>
Each test tire was assembled on the rim, filled with an internal pressure of 200 kPa and allowed to stand for 30 days, and the rate of decrease in internal pressure (%) was measured. As a result, the reciprocal of the rate of decrease in internal pressure was expressed as an index with Comparative Example 1 as 100. The larger the value, the better.

<Cut resistance>
A pendulum side wall impact test was adopted. This is a wedge-shaped blade attached to the weight at the lower end of the pendulum, impacting the tire sidewall by a free fall method, and determining the breaking energy of the tire sidewall from the weight and the drop height, Comparative Example 1 is indicated by an index of 100. It shows that the cut resistance of a side wall part is excellent, so that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tire of the example can reduce the tire mass and the manufacturing cost while maintaining the internal pressure holding performance and the durability.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 6A Carcass ply 13A Inner topping rubber 13B Outer topping rubber

Claims (8)

Comprising a carcass consisting of a carcass ply that extends from the tread portion through the sidewall portion to the bead core of the bead portion and terminates without being folded back at the bead core;
The carcass ply includes an array of carcass cords and a topping rubber that covers the array.
The topping rubber, in the side wall portion, and an inner topping rubber consisting forms a tire cavity surface and the air-impermeable butyl rubber,
An outer topping rubber disposed on the opposite side of the inner topping rubber with respect to the array and forming the outer surface of the sidewall portion;
It said outer topping rubber, shortest rubber thickness from the outer surface of the sidewall portion to the array is Ri 1.5~3.0mm der,
The tire inner surface of the bead portion is connected to the inner topping rubber, and a rubber sheet made of butyl rubber extending to the bead toe is disposed,
A pneumatic tire characterized in that a chafer rubber is disposed between the rubber sheet and the bead core .
The bead core is an inner core around which at least one bead wire is wound in the tire circumferential direction along the inner surface of the array body in the tire axial direction;
The pneumatic tire according to claim 1, comprising a bead wire and an outer core wound around at least one round in the tire circumferential direction along an outer surface of the outer topping rubber.   The pneumatic tire according to claim 1 or 2, wherein a protector including a raised portion extending in a ring shape in a tire circumferential direction is formed on the outer surface of the sidewall portion.   The pneumatic tire according to any one of claims 1 to 3, wherein the inner topping rubber has a shortest rubber thickness of 0.5 to 1.0 mm from the tire lumen surface to the carcass cord.   The pneumatic tire according to any one of claims 1 to 4, wherein a short fiber for reinforcement is blended in the inner topping rubber and / or the outer topping rubber.   The pneumatic tire according to any one of claims 1 to 5, wherein a blending amount of sulfur in the outer topping rubber is 30 to 90% of a blending amount of sulfur in the inner topping rubber. A method for producing the pneumatic tire according to any one of claims 1 to 6,
Including a carcass ply attaching step of attaching the carcass ply to a core body having a toroidal outer peripheral surface;
The carcass ply sticking step includes a step of juxtaposing a plurality of strip ply pieces in which the sheet-like carcass ply is cut into a narrow strip in the tire circumferential direction on the outer peripheral surface of the core body, and the tread portion side And a step of absorbing the difference in the tire circumferential length between the bead portion side and the edge side in the tire axial direction of the strip ply piece in a superimposed manner. Prior to the carcass ply sticking step, an inner core forming step of forming the inner core of the bead core by winding a bead wire around the bead portion of the core body at least once in the tire circumferential direction;
8. The outer core forming step of forming an outer core of the bead core by winding at least one bead wire in the tire circumferential direction along the outer surface of the carcass ply after the carcass ply attaching step. A method of manufacturing a pneumatic tire.

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