JP2006160106A - Pneumatic tire and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently assure driveability, high-speed durability, and external damage resistance while thinning a sidewall part, reducing the weight, and improving productivity. <P>SOLUTION: A pneumatic tire is equipped with a rubber reinforcing layer 13 made of hard rubber having rubber hardness of 70 to 110° and a fiber reinforcing layer 14 made of rubber-coated canvas fabric between a ply main body part 6a of a carcass 6 and a sidewall rubber Sg. The rubber reinforcing layer 13 extends from an overlapped part 20 overlapping with a bead apex rubber 8 outward in the radial direction, and interrupts at the range Ys from the maximum width position M of the tire to the outer end part of a belt layer 7. The fiber reinforcing layer 14 extends from an overlapped part 21 overlapping with the belt layer 7 inward in the radial direction, and interrupts at the range Y1 of 50 to 70% of a tire sectional height H. In the height range Y2 of 25 to 75% of the tire sectional height H, the total thickness T of the sidewall part 3 is within 3.0 to 5.0mm and the difference between the maximum thickness Tmax and the minimum thickness Tmin is set to be not more than 2.0mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire and a manufacturing method thereof that can reduce the weight and improve productivity by reducing the thickness of a sidewall portion, and can ensure steering stability and high-speed durability.

  Along with the recent strong demand for resource saving and fuel consumption reduction, further weight reduction is desired for tubeless tires.

  Therefore, as schematically shown in FIG. 12, the present inventor combined a thin sheet-like raw side wall rubber “b” on the outer surface of an unvulcanized raw carcass ply “a” in advance when forming a raw tire. Japanese Patent Application No. 2004-83206 proposes preparing a carcass ply c and winding the composite carcass ply c on a forming drum D to form a cylindrical composite carcass ply wound body e. The composite carcass ply wound body e is then set with bead apex rubber-attached bead cores f at both end portions e1 thereof, and the both end portions e1 are folded around, and the composite carcass ply winding is between the bead cores f and f. The rotating body e is swelled (shaped) in a toroidal shape and joined to the tread ring g to form a green tire.

  In such a manufacturing method, as in the prior art, a process of extruding raw sidewall rubber with a complicated cross-sectional shape using a rubber extruder and a separate winding and pasting process of raw sidewall rubber on a molding drum are performed. The manufacturing process can be simplified as unnecessary, and the production efficiency can be improved. For the manufacturing method in which the raw carcass ply a and the raw sidewall rubber b are handled in an integrated manner, it is necessary to form the raw sidewall rubber into a thin sheet having a thickness of 3 mm or less, for example. Thus, a great reduction in tire weight can be achieved.

  However, in such a tire, since the sidewall portion is thin, the rigidity of the tire is insufficient, the steering stability and high-speed durability are lowered, and the strength against scuffing and trauma with curbstones (trauma resistance) There is a problem of causing a decrease.

  Therefore, the present invention is based on the provision of a rubber reinforcing layer made of hard rubber and a fiber reinforcing layer made of canvas cloth in a predetermined area between the carcass ply and the side wall rubber, and the side wall portion is made thin and lightweight. It is an object of the present invention to provide a pneumatic tire and a method of manufacturing the same that can sufficiently ensure handling stability, high-speed durability, and resistance to trauma while improving productivity and productivity.

JP 2000-177308 A JP 2003-191720 A

The invention according to claim 1 of the present invention is a ply turn-up that is folded from the inner side to the outer side in the tire axial direction around the bead core to the ply main body part that extends from the tread part through the sidewall part to the bead core of the bead part. A bead core passing through between the ply body portion and the ply turn-up portion, a carcass made of a single carcass ply provided with a series of portions, a belt layer disposed inside the tread portion and radially outward of the carcass A pneumatic tire including a bead apex rubber extending radially outward from the sidewall rubber forming an outer surface of the sidewall portion,
The ply turn-up portion is interrupted radially inward from the outer end of the bead apex rubber, and is formed of a hard rubber having a rubber hardness of 70 to 110 ° between the ply main body portion and the side wall rubber. While providing a rubber reinforcement layer adjacent to the ply main body part and a fiber reinforcement layer made of rubberized canvas cloth and adjacent to the sidewall rubber,
The rubber reinforcing layer has an overlapping portion that overlaps the bead apex rubber on the inner side in the tire axial direction at the radially inner end portion, and the radial outer end extends from the tire maximum width position in the tire axial direction of the belt layer. Breaks in the area to the outer edge,
The fiber reinforcing layer has an overlapping portion that overlaps with the belt layer at the radially inner end thereof at the radially outer end portion, and the radial inner end portion has a radial height from the bead base line that is a tire cross section. In the region where the height H is 50 to 70% and the height in the radial direction from the bead base line is 25 to 75% of the tire cross-section height H, the total thickness T of the sidewall portion is The difference between the maximum thickness Tmax and the minimum thickness Tmin (Tmax−Tmin) in the range of 3.0 to 5.0 mm is characterized by being 2.0 mm or less.

  According to a second aspect of the present invention, the rubber reinforcing layer has a thickness of 0.5 to 1.5 mm, and the sidewall rubber has a thickness of 0.5 to 1.5 mm.

  According to a third aspect of the present invention, the radially outer end of the fiber reinforcing layer is separated from the radially outer end of the rubber reinforcing layer by a distance L1 of 10 mm or more along the carcass ply.

  According to a fourth aspect of the present invention, the carcass ply includes an array of carcass cords and a topping rubber that covers both surfaces of the array, and the ply body portion forms a tire lumen surface, and the tire lumen The topping rubber portion on the surface side is formed of butyl rubber.

  In the invention of claim 5, the rubber reinforcing layer is characterized in that an overlapping width W1 along the carcass ply of the overlapping portion is set to 5 to 10 mm.

  In the invention of claim 6, the fiber reinforcing layer is characterized in that an overlapping width W2 along the carcass ply of the overlapping portion is 10 to 30 mm.

  In the invention of claim 7, the radially inner end of the sidewall rubber is in contact with the radially outer end of the bead apex rubber or spaced radially outward from the radially outer end. It is characterized by interruption.

  In the invention of claim 8, the radially inner end portion of the sidewall rubber overlaps with the bead apex rubber on the inner side in the tire axial direction and is interrupted.

  According to a ninth aspect of the present invention, the bead portion includes a chafer rubber that forms at least a bottom surface and an outer surface of the bead portion, and the chafer rubber includes the ply folded portion, the bead apex rubber, and a bead of sidewall rubber. It is characterized by covering these in contact with the part side in order.

The invention of claim 10 is a pneumatic tire manufacturing method for manufacturing the pneumatic tire according to any one of claims 1 to 9,
A composite carcass ply is formed by attaching a sheet-like raw rubber reinforcing layer, a raw fiber reinforcing layer, and a raw side wall rubber having a substantially constant thickness to the outer surface of the raw carcass ply before vulcanization of the carcass ply. A composite carcass ply forming step,
The composite carcass ply is wound around an outer peripheral surface of a forming drum to form a cylindrical composite carcass ply wound body, and a green tire forming step is included.

  In the invention of claim 11, in the composite carcass ply forming step, a sheet-shaped raw chafer rubber having a substantially constant thickness is formed on the inner surface of the raw carcass ply, and an outer end thereof is an end of the raw carcass ply. It includes a process of sticking with an overhanging portion protruding from the edge.

  Note that the dimensions of each part of the tire such as the tire cross-section height H are specified when the bead part is held in accordance with the rim width defined by the tire size in the non-rim assembled state unless otherwise specified. Value. Moreover, rubber hardness means the durometer A hardness measured based on JIS-K6253.

  Since the present invention is configured as described above, it is possible to sufficiently ensure steering stability, high-speed durability, and damage resistance while reducing the weight of the sidewall portion and improving productivity. .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a meridional sectional view showing a case where the pneumatic tire of the present invention is a tubeless tire for passenger cars.
In FIG. 1, a pneumatic tire 1 is disposed on a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, inside the tread portion 2 and radially outside the carcass 6. A belt layer 7 and a bead apex rubber 8 extending radially outward from the bead core 5 are provided. The pneumatic tire 1 includes a tread rubber Tg disposed outside the belt layer 7 and forming the outer surface of the tread portion 2, and a sidewall rubber Sg disposed outside the carcass 6 and forming the outer surface of the sidewall portion 3. A chafer rubber Cg disposed on the bead portion 4 and forming a bottom surface thereof and a tire axial direction outer surface is provided.

  The belt layer 7 includes at least two belt plies using a cord array in which high-strength belt cords such as steel cords are arranged at an angle of, for example, 10 to 45 ° with respect to the tire circumferential direction. 7A and 7B. The belt layer 7 enhances belt rigidity by crossing the belt cords with each other between the plies, and reinforces substantially the entire width of the tread portion 2 with a tagging effect.

  The carcass 6 is formed of a single carcass ply 6A using a cord array in which carcass cords are arranged at an angle of, for example, 75 to 90 degrees with respect to the tire circumferential direction. In this example, a polyester cord is used as the carcass cord. However, in addition to this, an organic fiber cord such as nylon, rayon, aramid, vinylon, or a steel cord can be used as necessary.

  The carcass ply 6 </ b> A includes a series of ply folding portions 6 b that are folded back from the inside in the tire axial direction around the bead core 5 on both sides of the ply main body portion 6 a that extends between the bead cores 5 and 5. In this example, the inner surface of the ply main body portion 6a is configured as a so-called inner linerless tire that forms a tire lumen surface.

  Specifically, the carcass ply 6A has a well-known structure in which both sides of the array of carcass cords 10 are covered with a topping rubber 12 as shown in FIG. In the example, the topping rubber portion 12i on the tire lumen surface side is formed of butyl rubber. Since butyl rubber is excellent in air impermeability, the above-mentioned topping rubber portion 12i also functions as a conventional inner liner. Therefore, it is not necessary to provide an inner liner separately from the carcass ply 6A, and the tire weight can be reduced. Since butyl rubber tends to have a low adhesive force, non-butyl rubber is used for the outer topping rubber portion 12o in order to ensure bonding strength with other adjacent tire members.

  In the present specification, “butyl rubber” is a rubber containing 10 parts by weight or more of butyl rubber and / or a derivative thereof in 100 parts by weight of a rubber polymer, and “non-butyl rubber” Defined as rubber. Derivatives of butyl rubber (IIR) 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 not 10 parts by weight or more as described above, it is difficult to exert a sufficient internal pressure holding performance. From such a viewpoint, butyl rubber and / or its The content of the derivative is desirably 30 parts by weight or more. In the butyl rubber, the remainder of the rubber polymer may include one or more diene rubbers such as natural rubber (NR), butadiene rubber (BR), and styrene butadiene rubber (SBR). Similar to general topping rubber, various kinds of fillers (for example, reinforcing agents such as carbon black, vulcanizing agents, vulcanization accelerators, softening agents) are added to the rubber polymer. The non-butyl rubber is not particularly limited, but it is desirable to contain 95 parts by weight or more, more preferably 100 parts by weight of the diene rubber as a rubber polymer.

  Further, a bead apex rubber 8 made of hard rubber is provided between the ply main body portion 6a and the ply turn-up portion 6b of the carcass 6 and extends from the bead core 5 outward in the tire radial direction as shown in FIG. The portion 4 is reinforced and necessary bead rigidity is secured.

  Here, the bead apex rubber 8 is set such that the radial height h1 from the bead base line BL is as low as 5% to 35% of the tire cross-section height H. This is because in the tire 1 manufactured by the manufacturing method of the present invention, the height h2 in the radial direction of the chafer rubber Cg needs to be larger than the height h1. Therefore, if the height h1 exceeds 35% of the tire cross-section height H, the chafer rubber Cg approaches the maximum width position M where the surface distortion during tire deformation is large, so that the outer end of the chafer rubber Cg is cracked or the like. Tends to occur. Therefore, the height h1 is preferably 30% or less of the tire cross-section height H, and more preferably 25% or less. However, if it falls below 5% of the tire cross-section height H, the bead rigidity becomes too small to ensure the required steering stability.

  The bead apex rubber 8 has a rubber hardness Hsb in the range of 70 to 110 ° as in the conventional tire. The height h3 of the ply turn-up portion 6b from the bead base line BL is smaller than the height h1, and is preferably terminated radially inward from the upper end (not shown) of the rim flange. Thereby, the damage in the outer end of the ply folding | turning part 6b can be suppressed more effectively.

  Next, in the tire 1, in order to reduce the thickness of the sidewall portion 3 and reduce the weight of the tire, a height region Ys in which the radial height from the bead base line BL is 25 to 75% of the tire cross-sectional height H (see FIG. 1), the total thickness T of the sidewall portion 3 is set to be in a range of 3.0 to 5.0 mm and thinner than that in the case of a conventional tire (usually about 6.0 mm). . At this time, the difference in thickness (Tmax−Tmin) between the maximum thickness Tmax and the minimum thickness Tmin in the height region Ys is set to 2.0 mm or less to achieve uniform thickness. The total thickness T means an average value (Tmax + Tmin) / 2 of the maximum thickness Tmax and the minimum thickness Tmin.

  However, in the tire in which the sidewall portion 3 is thinned as described above, the rigidity of the sidewall portion 3 is not sufficient, and the steering stability and high-speed durability tend to be impaired. In particular, in the case of an inner linerless tire in which a butyl rubber is used as the topping rubber of the carcass 6, this tendency becomes strong because the butyl rubber is inferior in elastic characteristics. Therefore, in the present embodiment, a rubber reinforcing layer 13 adjacent to the ply main body portion 6a and a fiber reinforcing layer 14 adjacent to the side wall rubber Sg are provided between the ply main body portion 6a of the carcass 6 and the side wall rubber Sg. Provided.

  The sidewall rubber Sg is a soft rubber having a rubber hardness Hss in the range of 50 to 70 °, more preferably 50 to 65 °, as in the past, to impart flexibility to the sidewall surface and reduce surface distortion. Relax and absorb to prevent the occurrence of cracks. The thickness ts (shown in FIG. 3) of the sidewall rubber Sg is preferably in the range of 0.5 mm to 1.5 mm, and if it is 0.5 mm or less, the effect of preventing cracks and the like is insufficient. On the other hand, if the thickness ts exceeds 1.5 mm, the total thickness T increases, which impairs weight reduction or makes it difficult to ensure steering stability, such as forcing the thickness of the rubber reinforcing layer 13 to decrease.

  The rubber reinforcing layer 13 is a thin sheet-like body made of a hard rubber having a rubber hardness Hs1 of 70 to 110 ° and larger than the rubber hardness Hss, and as shown in FIG. In addition, the bead apex rubber 8 includes an overlapping portion 20 that overlaps the inside in the tire axial direction. Further, the radially outer end portion of the rubber reinforcing layer 13 terminates in a region Y1 (shown in FIG. 1) from the tire maximum width position M to the tire axial direction outer end portion 7E of the belt layer 7.

  Since such a rubber reinforcing layer 13 has an overlapping portion 20 with the bead apex rubber 8 in particular, a wide range from the bead portion 4 to the region Y1 can be reinforced in a well-balanced manner, and the thinning of the sidewall portion 3 is maintained. However, the bending rigidity can be sufficiently increased evenly. In particular, by increasing the bending rigidity uniformly, the heights h1 and h3 of the bead apex rubber 8 and the ply turn-up portion 6b are set low, and the maximum and minimum differences in the total thickness T in the height region Ys are reduced. Combined with keeping it low, sufficient and uniform tension can be applied to each part of the carcass cord 10. As a result, the load carrying capacity of the entire carcass 6 can be enhanced, for example, the original performance of the carcass cord can be maximized, and local deformation is suppressed and linearity is increased. Even with a small increase in rigidity, the steering stability can be sufficiently secured.

  Here, in the rubber reinforcing layer 13, the thickness t1 is preferably in the range of 0.5 to 1.5 mm, and the overlap width W1 along the carcass ply 6A of the overlap portion 20 is in the range of 5 to 10 mm. Is preferred.

  If the rubber hardness Hss is smaller than 70 ° and the thickness t1 is smaller than 0.5 mm, sufficient bending rigidity cannot be secured. Conversely, the rubber hardness Hss is larger than 110 ° and the thickness t1 is larger than 1.5 mm. On the other hand, the bending rigidity becomes excessive and the ride comfort is impaired. In addition, when the thickness t1 is larger than 1.5 mm, the total thickness T is increased and the weight reduction is hindered, or the thickness of the sidewall rubber Sg is forced to be reduced. If the overlap width W1 is smaller than 5 mm, the rigidity becomes uneven in the vicinity of the outer end of the bead apex rubber 8, for example, the rigidity becomes non-uniform, and the steering stability is lowered not only at high speed but also at normal speed. If it exceeds 10 mm, it is disadvantageous for weight reduction. From such a viewpoint, the lower limit value of the rubber hardness Hss is preferably 80 ° or more, more preferably 85 ° or more, and the upper limit value is preferably 100 ° or less. The rubber reinforcing layer 13 is preferably in contact with the bead apex rubber 8 as in this example from the viewpoint of the reinforcing effect. It is also preferable that the thickness t1 is in the range of 0.7 to 1.3 as a ratio t1 / ts with respect to the thickness ts of the sidewall rubber Sg.

  Next, the fiber reinforcement layer 14 is formed from a canvas cloth thinly rubberized, and, as shown in FIG. 4, an overlapping portion 21 that overlaps the belt layer 7 on the radially inner side is formed on the radially outer end portion thereof. Have. The radially inner end of the fiber reinforcement layer 14 terminates in a region Y2 (shown in FIG. 1) in which the radial height from the bead base line BL is 50 to 70% of the tire cross-section height H. The canvas cloth is a thin net-like body woven with organic fiber yarns such as nylon, polyester, rayon and aromatic polyamide as warp yarns and weft yarns. For example, warp yarns and weft yarns having a thickness of 300 to 800 dtex (for example, 490 dtex), A thickness of about 0.5 to 1.0 mm, preferably 0.7 to 0.9 mm, woven at a pitch interval of 20 to 50 lines / 5 cm (for example, 38 lines / 5 cm) can be suitably used.

  Such a fiber reinforcing layer 14 has a high reinforcing effect because warps and wefts are constrained to each other by weaving, and can effectively suppress deformation at the buttress portion that is most easily deformed while suppressing influence on bending rigidity. Since it has a particularly excellent hoop effect, it has a high effect of suppressing lifting in the region from the tread shoulder portion to the buttress portion, and the steering stability and high-speed durability can be enhanced by the synergistic action with the rubber reinforcing layer 13. In addition, since the fiber reinforcement layer 14 is also excellent in cut resistance, it is possible to effectively prevent the occurrence of deep trauma to the carcass 6, and compensates for the drawback of reduced trauma resistance due to the thinning of the sidewall rubber Sg.

  In the fiber reinforcement layer 14, the overlap width W2 of the overlap portion 21 along the carcass ply 6A is preferably 10 to 30 mm, and if it is less than 10 mm, the effect of suppressing lifting to the belt layer 7 becomes insufficient. If it is larger than 30 mm, it becomes excessive quality, which is disadvantageous for cost and weight reduction. Further, the radially outer end of the fiber reinforcing layer 14 is preferably separated from the radially outer end of the rubber reinforcing layer 13 by a distance L1 of 10 mm or more along the carcass ply 6A, and the distance L1 is smaller than 10 mm. If it becomes, durability will deteriorate by the stress concentration in an edge part. Further, in the fiber reinforcing layer 14, even when the radially inner end portion of the fiber Y ends beyond the region Y2 in the radially inward direction, the quality becomes excessive quality, which is disadvantageous in terms of cost and weight reduction. When terminated in the radially outward direction, the lifting suppressing effect and the damage resistance cannot be sufficiently exhibited. For steering stability, the rubber reinforcing layer 13 preferably extends radially outward beyond the region Y2, and the rubber reinforcing layer 13 overlaps the fiber reinforcing layer 14 at this time. Forming part.

  In addition, in the fiber reinforcement layer 14, if both warp and weft are arranged in the direction which cross | intersects a tire peripheral direction, the inclination angle in particular will not be controlled. In the unvulcanized state, the fiber reinforced layer 14 can be freely expanded and contracted by warp and weft being deformed into a pantograph shape, so that there is no occurrence of wrinkles and the tire moldability is not hindered. In particular, a sufficient tension is applied to the fiber reinforcement layer 14 due to the inner linerless structure, the carcass 6 made of a single ply, and the sidewall portion 3 being thin. For this reason, the fiber reinforcement layer 14 can be easily expanded and contracted at the time of tire molding, which is preferable for tire moldability and tire quality. Moreover, in the tire after vulcanization, since a uniform tension acts on the fiber reinforcing layer 14, a higher tagging effect can be exhibited. For example, a conventional band layer can be formed while ensuring high driving stability and high speed durability. This makes it possible to further reduce weight and improve productivity.

  In the sidewall rubber Sg, as shown in FIG. 4, the radially outer end portion extends beyond the outer end portion of the fiber reinforcing layer 14 inward in the tire axial direction, and extends along the carcass ply 6A. It is preferable to secure a length L2 of 10 mm or more. As a result, the shearing force acting on the outer end of the belt layer 7 and the outer end of the fiber reinforcement layer 14 can be alleviated by the soft sidewall rubber Sg, and end peeling can be suppressed. The upper limit of the extension length L2 is preferably 25 mm or less from the viewpoint of cost and weight reduction.

  Further, in this example, the radially inner end portion of the sidewall rubber Sg terminates in contact with the radially outer end portion of the bead apex rubber 8 as shown in FIG. This is because, according to the manufacturing method of the present invention, it is difficult to overlap the radially inner end of the sidewall rubber Sg with the bead apex rubber 8 on the outer side in the tire axial direction. Therefore, in this example, the end of the bead apex rubber 8 is terminated in contact with the outer end of the bead apex rubber 8, thereby minimizing a decrease in rigidity at the outer end of the bead apex rubber 8. However, as schematically shown in FIG. 5 (A), the radially inner end of the sidewall rubber Sg can also be terminated away from the radially outer end of the bead apex rubber 8 in the radially outward direction. In that case, it is preferable to set the separation distance L3 to 10 mm or less. Further, as schematically shown in FIG. 5B, the radially inner end portion of the sidewall rubber Sg may be overlapped with the bead apex rubber 8 on the inner side in the tire axial direction and terminated.

  Next, the chafer rubber Cg for preventing rim displacement is made of rubber that is harder than the side wall rubber Sg and has excellent wear resistance and cut resistance. The chafer rubber Cg is in contact with the radially inner end portion of the ply main body portion 6a, the ply folded portion 6b, the bead apex rubber 8 and the bead portion side of the sidewall rubber Sg as shown in FIG. Protect the coating. In particular, in this chafer rubber Cg, the rubber hardness Hsc is substantially the same as the difference | Hs1-Hsc | of the rubber reinforcement layer 13 from the rubber hardness Hs1 of 10 ° or less. It is preferable to suppress a decrease in rigidity at the outer end portion of the apex rubber 8.

  Next, a method for manufacturing such a pneumatic tire 1 will be described. In this manufacturing method, the composite carcass ply forming step (FIG. 8), the winding step (FIG. 10), the bead core setting step (FIG. 10), the bulging / folding step (FIG. 11), and the joining step (FIG. 11) shown below. The tire 1 shown in FIG. 1 is manufactured by forming the raw tire 38 (FIG. 11) by a raw tire molding process including a) and vulcanizing and molding the raw tire 38 with a vulcanization mold as in the prior art. To do.

  First, an unvulcanized raw carcass ply 30 for forming the carcass ply 6A is formed as shown in FIG. In this raw carcass ply 30, the inner surface side of the array of carcass cords 10 is covered with the raw topping rubber 32 i made of the butyl rubber also serving as an inner liner, and the outer surface side is covered with the raw topping rubber 32 o of non-butyl rubber. It is formed by. Therefore, the preparation process of the inner liner rubber different from the carcass ply, the winding process around the molding drum, and the like are not required, and the manufacturing process can be simplified.

  In this example, the thickness ti of the butyl raw topping rubber 32i and the thickness to of the non-butyl raw topping rubber 32o are formed to be substantially the same. As shown in FIG. 7, the thicknesses ti and to can be different. In the example of FIG. 7, since only the raw topping rubber 32o having excellent adhesiveness is in contact with the array of the carcass cord 10, damage such as rubber peeling of the carcass cord 10 can be prevented, and the durability of the carcass 6 is improved. To help. The sum of the thicknesses ti and to (ti + to) is preferably 2 times or more, more preferably 2.5 times or more of the outer diameter d of the carcass cord 10, and the upper limit thereof is 5 times or less, more preferably 4 times or less is desirable. If the sum of the thicknesses (ti + to) exceeds 5 times the outer diameter d of the carcass cord 10, it is disadvantageous for weight reduction. Conversely, if it is less than 2 times, the ply strength tends to be insufficient. Further, the thickness ti of the raw topping rubber 32i is preferably 0.5 mm or more, and more preferably 0.6 mm or more in order to improve air impermeability. However, if the thickness ti is too large, the weight is increased, so the upper limit is preferably 1.4 mm or less, and more preferably 1.2 mm or less.

  Next, as shown in FIG. 8, on the outer surface of the sheet-like raw carcass ply 30, a sheet-like unvulcanized raw rubber reinforcing layer 33, a raw fiber reinforcing layer 34, and a raw fiber reinforcing layer 33 having a substantially constant thickness are formed. Sidewall rubber Nsg is affixed to form composite carcass ply 31 (composite carcass ply forming step).

  The raw rubber reinforcing layer 33, the raw fiber reinforcing layer 34, and the raw sidewall rubber Nsg have thicknesses of 0.5 to 1.5 mm, 0.5 to 1.0 mm, and 0.5 to 1. It is a 5 mm sheet body and is affixed to a symmetrical position with the center line CL of the raw carcass ply 30 as the center. At this time, as shown in FIG. 9, on the outer end side in the drum axial direction, the raw rubber reinforcing layer 33 protrudes outward in the drum axial direction from the raw sidewall rubber Nsg so that the overlapping portion 20 can be formed. On the inner end side in the drum axial direction, the raw fiber reinforcing layer 34 projects the distance L1 inward in the drum axial direction from the raw rubber reinforcing layer 33 so that the overlapping portion 21 can be formed. The rubber Nsg further protrudes the distance L2 inward in the drum axial direction from the raw fiber reinforcing layer 34.

  Further, in this example, the composite carcass ply forming step includes a process of attaching uncured raw chafer rubber Ncg for forming chafer rubber Cg to the inner surface of the raw carcass ply 30. The raw chafer rubber Ncg is also made of a sheet body having a substantially constant thickness, and has a protruding portion 23 that protrudes outward from the edge of the raw carcass ply 30 from the edge of the raw carcass ply 30 in the drum axial direction. Affixed to the carcass ply 30.

  In this composite carcass ply forming step, the raw carcass ply 30, the raw rubber reinforcing layer 33, the raw fiber reinforcing layer 34, the raw side wall rubber Nsg, and the raw chafer rubber Ncg are each a thin sheet body having a constant thickness, and thus are well known in advance. And the integrated composite carcass ply 31 can be easily and collectively wound around the forming drum D. Therefore, unlike the conventional case, it is not necessary to manually stick the raw sidewall rubber and the raw chafer rubber to the raw carcass ply wound in a cylindrical shape, thereby improving the productivity. Furthermore, the raw sidewall rubber Nsg and the raw chafer rubber Ncg are not extrusion molding having a complicated cross-sectional shape as in the past, but are made of a sheet body having a constant thickness by calendering, etc., so the molding process itself is greatly simplified. This can improve productivity further. If the raw side wall rubber has a thick and complicated cross-sectional shape as in the past, even if the raw side wall rubber is preliminarily pasted and integrated with the raw carcass ply, It is difficult to wind well and easily.

  Next, as shown in FIG. 10, the composite carcass ply 31 is wound around the outer peripheral surface of the forming drum D (one turn) to form a cylindrical composite carcass ply wound body 42 (winding step). . In this example, the forming drum D is a so-called single stage type drum, and the winding step, bead core setting step, bulging / folding step, and joining step are performed on this one drum D. Although illustrated, a so-called two-stage system can also be adopted.

  Next, a raw bead core assembly 35 in which a raw bead apex rubber Nbg is previously bonded to the bead core 5 is inserted into the composite carcass ply wound body 42 from both outer end sides in the drum axial direction. The joined body 35 is set at the position of the overlapping region 24 between the raw carcass ply 30 and the raw chafer rubber Ncg (bead core setting step).

  After that, as shown in FIG. 11, the composite carcass ply wound body 42 includes an extending portion 25 that protrudes outward in the drum axial direction from the raw bead core assembly 35, including the raw chafer rubber overhang portion 23. A folded portion 26 that is folded around the bead core assembly 35 is formed, and the bead cores 5 and 5 are bulged in a toroidal shape to form a raw tire main portion 36 (bulging / folding step).

  At this time, a raw tread ring 37 made of a tread member including a raw belt layer and a raw tread rubber Ntg waits in advance on the radially outer side of the composite carcass ply wound body 42 to bulge into the toroidal shape. Accordingly, the raw tire main portion 36 and the raw tread ring 37 are joined by pressure welding to form a raw tire 38 (joining step). And the tire 1 can be manufactured by vulcanizing-molding this raw tire 38 with a vulcanization mold according to a custom.

  As described above, the particularly preferable embodiment of the present invention has been described in detail. However, the present invention is not limited to the illustrated embodiment, and can be applied not only to passenger cars but also to various categories of tires such as motorcycles and trucks. However, the present invention can be implemented with various modifications. Further, the butyl-based topping rubber portion 12i does not need to be disposed on the entire inner surface side of the array of the carcass cords 10, but is limited to the range that forms the tire cavity surface, and other portions are non-butyl-based. Rubber can also be used.

  A radial tire for a passenger car (size: 195 / 65R15) having the basic structure shown in FIG. 1 is manufactured according to the method of the present invention and with the specifications shown in Table 1 (Example tire), and the manufacturing cost, tire weight, and steering stability of the sample tire are also shown. Performance, high-speed durability, and general durability were evaluated. In the examples and comparative examples, the inner topping rubber portion of the carcass is formed of butyl rubber. In the conventional example, the inner liner of the butyl rubber is formed by a sheet different from the carcass ply, and the side wall rubber and the chafer rubber are sequentially wound on the drum to form a raw tire.

Common specifications other than those in Table 1 are as follows.
Number of carcass plies: 1 Carcass cord: Polyester, 1100 dtex / 2
Number of drives: 61 (5 / 5cm)
Carcass cord angle: 90 degrees (against tire equator)
Belt layer: Two plies of steel cord Side wall rubber: Rubber hardness Hss (60 degrees)
Bead apex: Rubber hardness Hsb (92 degrees)
Chafa rubber: rubber hardness Hsc (70 degrees)
The test method is as follows.

(1) Manufacturing cost:
The manufacturing cost required to manufacture one tire is indicated by an index with the conventional example being 100. The smaller the numerical value, the smaller the manufacturing cost and the better.

(2) Tire weight:
The weight per tire was measured.

(3) Steering stability:
Each test tire is mounted on all wheels of a 2000cc domestic FF passenger car under the conditions of rim (6 x 15 JJ) and internal pressure (200 kPa), running on a dry paved road test course, straight running, turning Stability, vehicle behavior during braking, etc. were comprehensively determined by a 10-point method based on sensory evaluation by a professional driver. The larger the value, the better.

(4) High speed durability:
Using a drum tester, the speed is increased by 10 km / h every 10 minutes from the initial speed of 170 km / h based on the conditions of rim (6 × 15 JJ), internal pressure (260 kPa), and load load (5.0 KN). The speed and time (minutes) when the tire was damaged were measured.

(5) General durability:
Using a drum testing machine, based on the conditions of rim (6 × 15JJ), internal pressure (200 kPa), and load load (7.0 KN), the vehicle was run at a speed of 80 km / h. It was measured.

(6) Internal pressure retention:
The test tire was assembled on a rim (6 × 15 JJ), filled with an internal pressure of 200 kPa and allowed to stand for 30 days, and the reduction rate (%) of the internal pressure was examined. The smaller the value, the better the internal pressure retention performance.

It is sectional drawing which shows one Embodiment of the pneumatic tire of this invention. It is the AA sectional view. It is sectional drawing which expands and shows a bead part. It is sectional drawing which expands and shows a tread part. (A), (B) is sectional drawing which shows the structure of the inner-end part of sidewall rubber. It is sectional drawing which shows an example of a raw carcass ply. It is sectional drawing which shows the other example of a raw carcass ply. It is a fragmentary perspective view which shows an example of a composite carcass ply. It is sectional drawing which expands and shows a part of composite carcass ply. It is a diagram explaining a winding process and a bead core setting process. It is a diagram explaining a swelling / folding process and a joining process. It is sectional drawing explaining background art.

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 6A Carcass ply 6a Ply main body portion 6b Ply folded portion 7 Belt layer 8 Bead apex rubber 12 Topping rubber portion 13 in topping rubber 12i Rubber reinforcing layer 14 Fiber reinforcing layer 20 , 21 Overlap portion 23 Overhang portion 31 Composite carcass ply 42 Composite carcass ply wound body Cg Chafer rubber M Tire maximum width position Ncg Raw chafer rubber Sg Side wall rubber Ys, Y1, Y2 region

Claims (11)

From a single carcass ply provided with a series of ply turn-up portions that are turned back from the inside to the outside in the tire axial direction around the bead core in the ply body portion extending from the tread portion through the sidewall portion to the bead core of the bead portion. A bead apex rubber extending radially outward from the bead core through the space between the ply body portion and the ply turn-up portion, and A pneumatic tire comprising a sidewall rubber forming the outer surface of the sidewall portion,
The ply turn-up portion is interrupted radially inward from the outer end of the bead apex rubber, and is formed of a hard rubber having a rubber hardness of 70 to 110 ° between the ply main body portion and the side wall rubber. While providing a rubber reinforcement layer adjacent to the ply main body part and a fiber reinforcement layer made of rubberized canvas cloth and adjacent to the sidewall rubber,
The rubber reinforcing layer has an overlapping portion that overlaps the bead apex rubber on the inner side in the tire axial direction at the radially inner end portion, and the radial outer end extends from the tire maximum width position in the tire axial direction of the belt layer. Breaks in the area to the outer edge,
The fiber reinforcing layer has an overlapping portion that overlaps with the belt layer at the radially inner end thereof at the radially outer end portion, and the radial inner end portion has a radial height from the bead base line that is a tire cross section. In the region of 50 to 70% of the height H, it breaks,
In a region where the radial height from the bead baseline is 25 to 75% of the tire cross-section height H, the total thickness T of the sidewall portion is in the range of 5.0 to 3.0 mm and its maximum thickness. A pneumatic tire characterized in that a difference (Tmax-Tmin) between a thickness Tmax and a minimum thickness Tmin is 2.0 mm or less.   2. The pneumatic tire according to claim 1, wherein the rubber reinforcing layer has a thickness of 0.5 to 1.5 mm, and the sidewall rubber has a thickness of 0.5 to 1.5 mm.   3. The pneumatic tire according to claim 1, wherein a radially outer end of the fiber reinforcing layer is separated from a radially outer end of the rubber reinforcing layer by a distance L <b> 1 of 10 mm or more along the carcass ply.   The carcass ply includes an array of carcass cords and a topping rubber that covers both sides of the array, and the ply body portion forms a tire lumen surface, and a topping rubber portion on the tire lumen surface side. The pneumatic tire according to claim 1, wherein the tire is made of butyl rubber.   The pneumatic tire according to any one of claims 1 to 4, wherein the rubber reinforcing layer has an overlapping width W1 along the carcass ply of the overlapping portion of 5 to 10 mm.   The pneumatic tire according to any one of claims 1 to 4, wherein the fiber reinforcement layer has an overlap width W2 of 10 to 30 mm along the carcass ply of the overlap portion.   A radially inner end portion of the sidewall rubber is cut off in contact with a radially outer end portion of the bead apex rubber or spaced apart radially outward from the radially outer end portion. The pneumatic tire in any one of -6.   The pneumatic tire according to any one of claims 1 to 6, wherein an inner end portion in the radial direction of the sidewall rubber overlaps with the bead apex rubber on the inner side in the tire axial direction and is interrupted.   The bead portion includes a chafer rubber that forms at least a bottom surface and an outer surface of the bead portion, and the chafer rubber is in contact with the ply folded portion, the bead apex rubber, and the bead portion side of the sidewall rubber in this order. The pneumatic tire according to any one of 1 to 8, wherein the tire is coated. A pneumatic tire manufacturing method for manufacturing the pneumatic tire according to claim 1,
A composite carcass ply is formed by attaching a sheet-like raw rubber reinforcing layer, a raw fiber reinforcing layer, and a raw side wall rubber having a substantially constant thickness to the outer surface of the raw carcass ply before vulcanization of the carcass ply. A composite carcass ply forming step,
A method for producing a pneumatic tire comprising a green tire molding step including a winding step of winding the composite carcass ply around an outer peripheral surface of a molding drum to form a cylindrical composite carcass ply wound body .   The composite carcass ply forming step has a sheet-like raw chafer rubber having a substantially constant thickness on the inner surface of the raw carcass ply, and an overhanging portion that protrudes from the edge of the raw carcass ply. The manufacturing method of the pneumatic tire of Claim 10 including the process to stick and stick.

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