JP2012086534A - Method for producing pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deformation of a projected and recessed shape in the outer face of a side wall part and improve the external appearance quality of the tire.SOLUTION: A method for producing a pneumatic tire includes a carcass formation step of sticking a plurality of rectangular ply pieces, each of which is obtained by covering each of carcass cord-arrayed bodies pulled/lined-up in the axial direction of the tire with topping rubber, successively on a rigid core body in the peripheral direction of the tire to form a toroidal carcass. The carcass is constituted in a tread part so that the adjacent rectangular ply pieces are arranged to be made adjacent to each other or be abutted on each other without superposing the side edge parts of the adjacent ply pieces on each other and constituted in the side wall part so that the side edge parts of the adjacent ply pieces are superposed on each other to form a superposed part. The carcass cord-arrayed body is constituted so that the modulus of an external carcass cord arrayed on the outermost side is made smaller than that of an internal carcass cord arrayed on the inside of the external carcass cord.

Description

  The present invention relates to a method for manufacturing a pneumatic tire including a carcass forming step of forming a toroidal carcass by sequentially attaching strip-like ply pieces on a rigid core body in the tire circumferential direction.

  In recent years, in order to improve tire uniformity, for example, a method of manufacturing a pneumatic tire using a rigid core body having an outer shape close to the tire lumen shape of a finished tire has been proposed (see Patent Document 1 below). . In this manufacturing method, for example, as shown in FIG. 7A, a strip sheet shape in which an array A of carcass cords A1 aligned in the tire axial direction is covered with topping rubber and the tire circumferential width L1 is small. The toroidal carcass D is formed by sequentially affixing the plurality of strip ply pieces B to the circumferential direction of the tire on the rigid core C as shown in FIG.

  At this time, in order to increase the uniformity of the tire, the strip ply pieces B are adjacent to or in contact with each other without overlapping in the tread portion Ta between the side edge portions Be and Be of the strip ply pieces B adjacent in the tire circumferential direction. Is arranged. As a result, in the sidewall portion Tb, a triangular overlapping portion J in which the side edge portions Be and Be overlap each other is inevitably formed.

  However, in this overlapping portion J, the outer carcass cords A1a and A1a located on the outermost side in the array A also overlap with each other as shown in FIG. Therefore, when the tire is inflated by being filled with the internal pressure, the carcass cord A1a is difficult to stretch in the overlapping portion J, the amount of expansion is locally reduced to become a concave, and the outer surface of the sidewall portion Tb is deformed in an uneven shape. There is a problem that the appearance quality of the tire is impaired.

JP-A-11-254906

  Therefore, the present invention is based on the principle that the modulus of the outer carcass cord arranged on the outermost side in the carcass cord array is smaller than the modulus of the inner carcass cord arranged on the inner side. It aims at providing the manufacturing method of the pneumatic tire which suppresses the uneven | corrugated deformation | transformation in the outer surface of this and improves the external appearance quality of a tire.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application is a method for manufacturing a pneumatic tire including a carcass extending from a tread portion to a bead portion on both sides through a sidewall portion,
Using a rigid core body, a plurality of strip ply pieces in the form of a strip sheet in which an array of carcass cords aligned in the tire axial direction is covered with a topping rubber and the width in the tire circumferential direction is small, the rigid core Including a carcass forming step of forming a toroidal carcass by sequentially pasting in the tire circumferential direction on the body,
In addition, the carcass is arranged in the tread portion so that the side edges of the strip ply pieces adjacent in the tire circumferential direction do not overlap with each other without being overlapped with each other, and in the sidewall portion, the overlapping portion where the side edges overlap. And having
The array of carcass cords is composed of an outer carcass cord disposed on the outermost side and an inner carcass cord disposed on the inner side thereof, and the modulus Mo of the outer carcass cord is changed to that of the inner carcass cord. It is characterized by being smaller than the modulus Mi.

  According to a second aspect of the present invention, the modulus Mo of the outer carcass cord is 20 to 80% of the modulus Mi of the inner carcass cord.

  The modulus of the carcass cord is an initial tensile resistance per cord determined in accordance with the chemical fiber tire cord test method of JIS L1017, and the “load-elongation of the cord determined in accordance with the test method” ”Means the slope of the tangent of the“ load-extension ”curve at the maximum point where the load change with respect to the extension change becomes maximum near the origin.

  As described above, according to the present invention, the modulus Mo of the outer carcass cord disposed on the outermost side in the carcass cord array is smaller than the modulus Mi of the inner carcass cord disposed on the inner side. Therefore, the elongation of the carcass cord in the overlapping portion can be made closer to the elongation of the carcass cord in the non-overlapping portion. Therefore, in the internal pressure filling state, the amount of expansion at the overlapping portion can be locally reduced to prevent the concave portion from being depressed, and the unevenness on the outer surface of the sidewall portion can be suppressed to improve the appearance quality of the tire. be able to.

It is sectional drawing which shows one Example of the pneumatic tire formed by the manufacturing method of this invention. It is sectional drawing which shows a raw tire formation process. It is sectional drawing which shows a vulcanization | cure process. It is a perspective view which shows a strip ply piece. (A), (B) is explanatory drawing which shows a carcass shaping | molding process. It is sectional drawing which shows the overlap part of a strip ply piece. (A)-(C) are explanatory drawings which show the manufacturing method of the conventional pneumatic tire which used the rigid core body.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a cross-sectional view showing an example of a pneumatic tire 1 formed by the manufacturing method of the present invention. The pneumatic tire 1 has bead portions 4 on both sides through a sidewall portion 3 from a tread portion 2. 4, and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2.

  The carcass 6 is formed of one or more layers, in this example, one layer of carcass ply body 6A in which organic fiber carcass cords are radially arranged. The carcass ply body 6A has a toroid shape straddling the bead portions 4 and 4, and both ends of the carcass ply body 6A are not folded around the bead cores 5 arranged in each bead portion 4 in this example. 5 to be sandwiched and locked. Specifically, the bead core 5 is composed of inner and outer core pieces 5i and 5o in the tire axial direction, and both end portions of the carcass ply body 6A are sandwiched between the inner and outer core pieces 5i and 5o.

  The inner and outer core pieces 5i, 5o are formed by winding the non-extensible bead wire 5a a plurality of times in the tire circumferential direction. At this time, in the outer core piece 5o, the number of turns of the bead wire 5a is, for example, about 1.2 to 2.0 times larger than that of the inner core piece 5i, and the rigidity is larger than that of the inner core piece 5i. Is preferred. As a result, the bending rigidity of the bead portion 4 can be relatively increased while restricting the total number of turns of the bead wire 5a, which is useful for improving the steering stability. In addition, the code | symbol 8 in a figure is a bead apex which consists of hard rubber | gum whose rubber hardness is 80-100 degree | times, for example, rises from each core piece 5i, 5o in a taper shape, and raises bead rigidity. In addition, in this specification, rubber hardness means the durometer A hardness measured in a 23 degreeC environment by durometer type A based on JIS-K6253.

  The belt layer 7 is formed of two or more belt plies 7A and 7B, in this example, two or more in which high-elasticity belt cords such as steel cords are arranged at, for example, about 10 to 35 ° with respect to the tire circumferential direction. The In the belt layer 7, the belt cords cross each other between the plies, thereby increasing the belt rigidity, and substantially reinforcing the entire width of the tread portion 2 with a tagging effect. In this example, a band layer in which a band cord such as a nylon cord is spirally wound at an angle of 5 degrees or less with respect to the circumferential direction for the purpose of enhancing high-speed durability on the outer side in the radial direction of the belt layer 7. 9 is provided. As the band layer 9, a pair of left and right edge band plies that covers only the outer end of the belt layer 7 in the tire axial direction, and a full band ply that covers substantially the entire width of the belt layer 7 are used alone or in appropriate combination. Can be used. In the present example, the band layer 9 is composed of one full band ply.

  Further, a thin inner liner 10 that forms a tire cavity surface is disposed inside the carcass 6. The inner liner 10 is made of a non-air permeable rubber such as butyl rubber or halogenated butyl rubber, for example, and holds the air filled in the tire lumen in an airtight manner. A side wall rubber 11 forming the outer surface of the side wall portion 3 is disposed outside the carcass 6, and a tread rubber 12 forming the outer surface of the tread portion 2 is disposed outside the band layer 9 in the radial direction.

  Next, a method for manufacturing the pneumatic tire 1 will be described. In this manufacturing method, as schematically shown in FIG. 2, a toroid-shaped rigid core body 20 having an outer shape substantially matching the tire lumen shape of the pneumatic tire 1 is used, and the rigid core body 20 is used. A raw tire forming step S1 for forming the raw tire 1N by sequentially affixing unvulcanized tire constituent members to the outer surface of the tire, and as shown schematically in FIG. A vulcanization step S2 is performed, in which the entire body 20 is put into a vulcanization mold 21 and vulcanized.

  In the raw tire forming step S1, an inner liner forming step for attaching a member for forming the inner liner 10 to the rigid core body 20, a carcass forming step for attaching a member for forming the carcass 7, and a member for forming the bead core 5 are attached. A bead core forming step for attaching, a bead core forming step for attaching a member for forming bead apex 8, a belt forming step for attaching a member for forming belt layer 7, a band forming step for attaching a member for forming band layer 9, a sidewall rubber 11 includes a sidewall forming process for attaching a member for forming 11, a tread forming process for attaching a member for forming tread rubber 12, and the like.

  Among these, in the raw tire forming step S1, other than the carcass forming step and the vulcanizing step S2, various known types using the rigid core body 20 can be appropriately employed. Only the carcass forming step will be described below.

  In the carcass forming step, as shown in FIG. 4, a plurality of strip sheet-like sheets in which an array 31 of carcass cords 30 aligned in the tire axial direction is covered with a topping rubber 32 and the tire circumferential width L1 is small. The strip ply pieces 13 and the plurality of strip ply pieces 13 are sequentially attached in the tire circumferential direction on the rigid core body 20 as shown in FIGS. A toroidal carcass 6 is formed. At this time, the side edge portions 13e and 13e of the strip ply pieces 13 and 13 adjacent in the tire circumferential direction are arranged in the tread portion 2 so as to be close to or in contact with each other without overlapping each other. Therefore, in the tread portion 2, the cord density of the carcass cord 30 becomes substantially uniform, and a high tire uniformity can be secured. On the other hand, in the side wall part 3, the triangular overlapping part J where the said side edge parts 13e and 13e mutually overlap is inevitably formed. Therefore, in this overlapping portion J, the code density of the carcass cord 30 increases locally.

  Therefore, in the present invention, among the carcass cords 30 arranged on the strip ply piece 13, the modulus Mo of the outer carcass cord 30a arranged on the outermost side is changed to the modulus of the inner carcass cord 30b arranged on the inner side. It is set smaller than Mi. As a means for making the cord moduli different, for example, the outer carcass cord 30a and the inner outer carcass cord 30b are made of different cord materials, different cord thicknesses, and / or different cord twist numbers. These can be mentioned alone or in combination with each other. From the viewpoint of productivity and production cost, the cord material is preferably the same, and the cord thickness is more preferably different from the viewpoint of accuracy and ease of control. In this example, the carcass cords 30 are arranged at substantially equal pitch intervals P in the strip ply piece 13.

  With such a configuration, as shown in FIG. 6, since the low modulus carcass cord 30a overlaps in the overlapping portion J, the elongation of the carcass cord 30a is made closer to the elongation of the carcass cord 30b in the non-overlapping portion. Can do. Therefore, the appearance quality can be improved by reducing the difference in expansion amount between the overlapping portion J and the non-overlapping portion in the internal pressure filling state.

  For this purpose, the modulus Mo of the outer carcass cord 30a is preferably in the range of 20 to 80% of the modulus Mi of the inner carcass cord 30b, more preferably in the range of 30 to 70%, further 40 to 60%. It is more preferable to set the range.

  If the width L1 of the strip ply piece 13 in the tire circumferential direction is too large, when the strip ply piece 13 is bent from the tread portion 2 to the sidewall portion 3 inward in the tire radial direction, wrinkles are generated and cord disturbance occurs. It becomes easy. In addition, since the overlap width Wj in the circumferential direction at the overlap portion J is also widened, the number of carcass cords that overlap at the overlap portion J is also increased, and the effects of the present invention are not fully exhibited. On the contrary, if the width L1 in the tire circumferential direction is too small, the number of man-hours for affixing the strip ply piece 13 increases and the affixing efficiency is reduced. Therefore, the width L1 is preferably in the range of 10 to 30 mm, and the number of carcass cords 30 in the array 31 is preferably 10 to 30.

  In addition, the number N of overlapping carcass cords 30 in the overlapping portion J is preferably 1 to 2, particularly 1 in the tire maximum width position Qm. Therefore, the width L1 of the strip ply pieces 13 and the interval between the side edge portions 13e of the strip ply pieces 13 adjacent in the tire circumferential direction in the tread portion 2 are set in advance so that the overlapping number N falls within the above range. The

  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.

  A passenger car tire (tire size 175 / 65R14) having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1 using a rigid core, and the appearance of each sample tire (sidewall portion, buttress portion) And tested for uniformity.

  In the conventional example, a cylindrical carcass ply is formed by winding one carcass ply in the circumferential direction on a cylindrical forming drum without using a rigid core, and this cylindrical carcass ply is connected between bead cores. It is formed by the conventional general manufacturing method which has the expansion | swelling process which expands by and shapes in toroid form. In both the comparative example and the example, a rigid core was used.

  Except as described in Table 1, the specifications are substantially the same. The strip ply pieces share the inner carcass cord, and in the first to fifth embodiments, the modulus Mo is changed with respect to the modulus Mi of the inner carcass cord by changing the thickness of the outer carcass cord. ing. In the sixth embodiment, the modulus Mo is changed with respect to the modulus Mi of the inner carcass cord by changing the number of twists of the outer carcass cord. In the seventh embodiment, the modulus Mo is changed with respect to the modulus Mi of the inner carcass cord by changing the material of the outer carcass cord. Further, in Comparative Example 2, the distance between adjacent strip ply pieces is increased in the buttress portion Bs (shown in FIGS. 1 and 5) to the same extent as the pitch distance P of the carcass cord, so that the carcass at the tire maximum width position Qm is obtained. The number of overlapping codes N is 0.

Strip ply piece ・ Circumferential width L1 --- 20mm,
・ Inside carcass cord --- polyester cord, 1670 dtex / 2,
・ Number of cords --- 20

(1) Appearance:
Tires are assembled on the rim under conditions of rim (5.5 J × 14) and internal pressure (200 kPa), and the surface of the sidewall and buttress portion Bs (shown in FIGS. 1 and 5) is visually inspected for deformation. In addition, the index of the conventional example is 100. The smaller the value, the better.

(2) Uniformity:
Using a tire uniformity tester, RFV was measured in accordance with JASO C607: 2000 “Uniformity test method for automobile tires” and displayed as an index with a conventional example of 100. The smaller the value, the better. The measurement conditions were a rim (5.5 J × 14), internal pressure (200 kPa), tire rotation speed (60 rpm), and longitudinal load (3.54 kPa).

  As shown in the table, it can be confirmed that the tires of the examples can improve the appearance performance while ensuring excellent uniformity.

2 Tread portion 3 Side wall portion 4 Bead portion 6 Carcass 13 Strip ply piece 13e Side edge portion 20 Rigid core body 30 Carcass cord 30a Carcass cord 31 in the outer carcass cord 30b Array 32 Topping rubber J Overlap portion

Claims (2)

A pneumatic tire manufacturing method comprising a carcass extending from a tread portion to a side wall portion to bead portions on both sides,
Using a rigid core body, a plurality of strip ply pieces in the form of a strip sheet in which an array of carcass cords aligned in the tire axial direction is covered with a topping rubber and the width in the tire circumferential direction is small, the rigid core Including a carcass forming step of forming a toroidal carcass by sequentially pasting in the tire circumferential direction on the body,
In addition, the carcass is arranged in the tread portion so that the side edges of the strip ply pieces adjacent in the tire circumferential direction do not overlap with each other without being overlapped with each other, and in the sidewall portion, the overlapping portion where the side edges overlap. And having
The array of carcass cords is composed of an outer carcass cord disposed on the outermost side and an inner carcass cord disposed on the inner side thereof, and the modulus Mo of the outer carcass cord is changed to that of the inner carcass cord. A method for manufacturing a pneumatic tire, characterized by being smaller than the modulus Mi.   2. The method for manufacturing a pneumatic tire according to claim 1, wherein the modulus Mo of the outer carcass cord is 20 to 80% of the modulus Mi of the inner carcass cord.

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