JP2016097586A - Heavy-duty tire molding drum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy-duty tire molding drum capable of preventing generation of ply cord waving by preventing contact between a bead core and a carcass ply.SOLUTION: The case molding drum includes, in its outer drum surface, a parallel part 201 parallel to a drum axis in the center, a first circular arc part 202 continuous in the axial outside of the outer most end P1 of the parallel part and extending along a first curvature radius R1 to a drum diameter direction inside, and a second circular arc part 203 continuous in the axial outside of the outermost end P2 of the first circular arc part and extending along a second curvature radius R2 to the drum diameter direction inside. A molding drum height DH is 0.30 to 0.40 times larger than a nominal application rim diameter RD, the first and second curvature radiuses are respectively 0.58 to 0.62 times larger and 0.19 to 0.23 times larger than the drum height DH, and a distance W1 from an axial center C to the outermost end P1 of the parallel part and a distance W2 from the center to the outermost end P2 of the first circular arc part are respectively 0.62 to 0.72 times larger than a drum half width DHW and 0.953 to 0.993 times larger than DHW.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a molding drum used for molding a green case of a heavy duty tire such as a radial tire (ORR) for construction and mining vehicles.

  Conventionally, a heavy-duty tire may be manufactured through processes as described below (for example, Patent Document 1). First, a cylindrical band including an inner liner and a carcass ply is molded on a band drum (band molding). After that, on the primary molding drum, bead cores are driven into both ends of the band in the axial direction, the carcass ply is folded around the bead core, and another tire constituent member (sidewall rubber or the like) is attached from above. A cylindrical green case is molded (primary molding). Then, while narrowing the gap between the bead cores of the green case on the secondary molding drum, the green case is expanded (expanded) by the bladder, and additional tire components (belts and tread rubber) are formed on the outer peripheral surface of the green case. Etc.) to complete the green tire (secondary molding). Thereafter, the green tire is vulcanized in a mold (vulcanization process) to obtain a final product tire.

Japanese Patent Laid-Open No. 2003-211555

In heavy duty tires, in order to meet the demand for high durability of the bead portion, there is a case where a middle turn-up structure is adopted in which the folded portion of the carcass reaches the vicinity of the maximum width position of the tire in the final product tire. However, in order to obtain a middle turnup structure, when the length of the carcass folded portion of the green case is sufficiently secured in the primary molding, it occurs at the time of expansion of the green case in the secondary molding or deformation in the vulcanization process. When the carcass ply is pulled out from the bead portion or when the folded portion is compressed, the folded portion is left over, particularly in the vicinity of the rim line portion, a ply cord wave that appears curved in the circumferential direction at the folded portion may occur. there were. And there existed a problem that durability of a bead part fell by such a ply cord wave of a return part.
On the other hand, as a measure for suppressing the ply cord wave, for example, by reducing the drum width of the primary molding drum, the expansion rate of the green case in the secondary molding is increased, and as a result, the carcass ply pull-out amount is increased. It is conceivable to increase However, in this case, there is a problem that the tightening amount of the carcass ply with respect to the bead core is increased, and the bead core and the carcass ply are in contact with each other, which may cause the ply cord to be cut and consequently to cause a failure of the bead portion.

  An object of the present invention is to provide a heavy duty tire molding drum capable of preventing the occurrence of a ply cord wave while avoiding contact between a bead core and a carcass ply. To do.

A molding drum for a heavy duty tire according to the present invention is a molding drum for molding a green case of a heavy duty tire. In the central portion of the direction, a parallel portion extending in parallel to the drum axis direction and an outermost end P1 of the parallel portion in the drum axis direction are continuous, and an arc having a first radius of curvature R1 toward the outside in the drum axis direction A first arc portion extending inward in the drum radial direction along the drum and an outermost end P2 in the drum axis direction of the first arc portion, and an arc having a second radius of curvature R2 toward the outer side in the drum axis direction And a second arc portion extending inward in the drum radial direction and reaching the outermost end DE in the drum axial direction of the molding drum, and the drum height DH of the molding drum is The nominal rim diameter of a tire manufactured using the molding drum is 0.30 to 0.40 times the nominal RD, and the first radius of curvature R1 is 0.58 to 0.62 times the drum height DH. The second radius of curvature R2 is 0.19 to 0.23 times the drum height DH, and extends from the drum axial center C of the molding drum to the outermost end P1 of the parallel portion in the drum axial direction. The drum axis direction distance W1 is 0.62 to 0.72 times the drum half width DHW, and the drum axis direction center C of the molding drum to the drum axis direction outermost end P2 of the first arc portion is a drum. The axial distance W2 is 0.953 to 0.993 times the drum half width DHW.
According to the molding drum of this invention, generation | occurrence | production of a ply cord wave can be prevented, avoiding a contact with a bead core and a carcass ply.

  According to the present invention, it is possible to provide a heavy duty tire molding drum capable of preventing the occurrence of ply cord waves while avoiding contact between the bead core and the carcass ply.

It is a figure for demonstrating an example of the manufacturing method of the tire using the molding drum of the heavy duty tire which concerns on one Embodiment of this invention, Fig.1 (a) is band molding, FIG.1 (b) is primary. Molding, FIG. 1 (c) shows secondary molding, respectively. It is sectional drawing which shows the principal part of the molding drum of the heavy duty tire which concerns on one Embodiment of this invention along a drum axial direction.

  Hereinafter, an embodiment of a heavy duty tire molding drum according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram for explaining an example of a method for manufacturing a heavy duty tire that can suitably use the molding drum of the present embodiment. The molding drum of this embodiment (hereinafter referred to as “primary molding drum 20”) is used for molding a green case of a heavy duty tire such as a radial tire (ORR) for construction and mining vehicles. It is.

  First, in the band molding shown in FIG. 1A, a cylindrical band 50 including an inner liner 41 and a carcass ply 40 on the outer peripheral side thereof is molded on the band molding drum 10. At this time, the outer diameter of the band 50 is made smaller than the inner diameter of the predetermined bead core 42 in the final product tire. Here, although not shown, a rubber chafer 46 (see FIGS. 1B and 1C) may be disposed.

  Next, in the primary molding shown in FIG. 1B, the band 50 is expanded in diameter by the band molding drum 10 or the primary molding drum 20 or the like, and is arranged around the primary molding drum 20. In the primary molding drum 20, the outer diameter of the central portion in the drum axial direction (same as the drum width direction; the left-right direction in FIG. 1) is larger than the outer diameter of the end in the drum axial direction. It is larger than the inner diameter of the bead core 42. The bead core 42 is driven on the carcass ply 40 at both ends in the drum axial direction of the primary molding drum 20, and the ends of the carcass ply 40 in the tire width direction (same as the drum axial direction) are folded around the bead core 42. . At this time, a portion of the carcass ply 40 that extends between the bead cores 42 is a carcass ply main body portion 40a, and a portion that is continuous from the carcass ply main body portion 40 and is folded around the bead core 42 is folded back into the carcass ply. The portion 40b is assumed. Thereafter, another tire constituent member (sidewall rubber 45 or the like) is attached to the outer peripheral side of the carcass ply 40 to mold the cylindrical green case 60.

  Next, in the secondary molding shown in FIG. 1 (c), the green case 60 is disposed around the secondary molding drum 30 to reduce the interval in the tire width direction between the bead cores 42 and on both sides of the tire width direction. The green case 60 is expanded by a bladder (not shown) while the carcass ply 40 is rotated around the bead core 42 toward the outer side in the tire width direction. Further, the remaining tire constituent members (the belt 43, the tread rubber 44, etc.) are provided on the outer peripheral side of the green case 60 to complete the green tire 70. Thereafter, the green tire 70 is vulcanized in a mold to obtain a final product tire.

  The primary molding drum 20 as the molding drum of the present invention according to the present embodiment is not limited to the above-described manufacturing method, and in any heavy load tire manufacturing method involving the expansion of the green case, It can be suitably used for molding.

  FIG. 2 is a cross-sectional view along the drum axial direction showing the half width and radius of the primary molding drum 20 of FIG. The outer peripheral surface of the primary molding drum 20 includes a parallel portion 201 that extends in parallel to the drum axial direction, and a parallel portion 201 at a central portion of the primary molding drum 20 in the drum axial direction (left-right direction in FIG. 2). A first arc portion 202 that is continuous with the outermost end P1 in the drum axis direction and extends inward in the drum radial direction along the arc of the first radius of curvature R1 toward the outer side in the drum axis direction; 202, which is continuous to the outermost end P2 in the drum axial direction, extends inward in the drum radial direction along the arc of the second curvature radius R2 toward the outer side in the drum axial direction, and extends in the drum axial direction of the primary molding drum 20 And a second arc portion 203 reaching the outermost end DE. Note that the center of curvature of each of the first radius of curvature R1 in the first arc portion 202 and the second radius of curvature R2 in the second arc portion 203 is inside the drum from the outer peripheral surface of the primary molding drum 20. Is located.

In the present embodiment, the drum height DH of the primary molding drum 20 is 0.30 to 0.40 times the nominal RD of the nominal rim diameter of a tire manufactured using the primary molding drum 20. Here, the drum height DH is defined by DH = DD / 2−RD / 2, where DD is the maximum outer diameter of the primary molding drum 20.
In the present embodiment, the first curvature radius R1 of the first arc portion 202 is 0.58 to 0.62 times the drum height DH, and the second curvature radius R2 of the second arc portion 203 is the drum height. It is 0.19 to 0.23 times DH.
Furthermore, in this embodiment, the drum axial distance W1 from the drum axial center C of the primary molding drum 20 to the drum axial outermost end P1 of the parallel portion 201 is 0.62 to. 72 times. The drum half width DHW indicates the distance in the drum axial direction from the drum axial center C of the primary molding drum 20 to the outermost end DE of the primary molding drum 20 in the drum axial direction.
In the present embodiment, the drum axial distance W2 from the drum axial center C of the primary molding drum 20 to the drum axial outermost end P2 of the first arc portion 202 is 0.953 to the drum half width DHW. It is 0.993 times.

  The above-mentioned “nominal rim diameter nominal RD” refers to the diameter of the applicable rim. “Applicable rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA YEAR BOOK of JATMA (Japan Automobile Tire Association), and in Europe, ETRTO (The European Tire and Rim Technical Organization). STANDARDDS MANUAL of), standard rims for applicable sizes (Measuring Rim for STANDARDDS MANUAL of ETRTO), YEARM BOG for TRA) Point to.

By configuring the outer peripheral surface of the primary molding drum 20 as described above, the arrangement of the carcass ply main body portion 40a and the carcass ply turn-up portion 40b in the raw tire obtained through the primary molding and the secondary molding is vulcanized. More close to their placement in the final product tire obtained after the process. Thereby, generation | occurrence | production of the ply cord wave of the carcass ply folding | turning part 40b in the rim line part vicinity can be prevented, and the durability of a bead part can be improved by extension.
Further, since it is not necessary to prevent the ply cord wave as described above, that is, to increase the carcass ply pull-out amount, the bead core 42 induced by the increase in the carcass ply pull-out amount Contact with the carcass ply 40 can be avoided, and consequently failure of the bead portion can be avoided.

The drum axis direction distance W1 from the drum axis direction outermost end P1 of the parallel portion 201 to the drum axis direction outermost end DE of the primary forming drum 20 is 0.53 to 0.57 times the drum height DH. Preferably there is.
The drum height DH is preferably 0.44 to 0.67 times the drum half width DHW.

  In the example of FIG. 2, the tangent of the first arc portion 202 at the innermost end (P1) in the drum axis direction of the first arc portion 202 is parallel to the drum axis direction. Further, the tangent of the second arc portion 203 at the outermost end (DE) in the drum axis direction of the second arc portion 203 is parallel to the drum radial direction. Moreover, in the example of FIG. 2, the 1st circular arc part 202 and the 2nd circular arc part 203 are smoothly connected in these connection positions (P2).

(Example)
The molding drums of the comparative example and the example were respectively produced, and heavy load tires of the tire size ORR2700R49 were produced using these respectively. The incidence of contact with the carcass ply was evaluated. The molding drums of the comparative example and the example have a drum height DH of 15 inches (381.0 mm), a drum half width DHW of 740 mm, and a drum maximum outer diameter DD of 1625.6 mm. In addition, the specifications of the molding drums of the comparative example and the example are as shown in Table 1.

  As can be seen from Table 1, by using the molding drum of the example, it is possible to prevent the occurrence of the ply cord wave while avoiding the contact between the bead core and the carcass ply.

  The molding drum of the present invention can be used for molding heavy load tires such as radial tires (ORR) for construction and mining vehicles.

  10: Band molding drum, 20: Primary molding drum (molding drum), 30: Secondary molding drum, 40: Carcass ply, 40a: Carcass ply main body part, 40b: Carcass ply folding part, 41: Inner liner, 42: Bead core, 43: belt, 44: tread rubber, 45: sidewall rubber, 46: rubber chafer, 50: band, 60: green case, 70: green tire, 201: parallel part, 202: first arc part, 203 : Second arc part

Claims (1)

A molding drum for molding the green case of heavy duty tires,
In the cross section along the drum axial direction of the molding drum, the outer peripheral surface of the molding drum has a parallel portion extending in parallel to the drum axial direction at the central portion in the drum axial direction, and the drum axial direction of the parallel portion A first arc portion that is continuous with the outermost end P1 and extends inward in the drum radial direction along the arc of the first curvature radius R1 toward the outer side in the drum axis direction, and the drum axis direction of the first arc portion Continuing to the outermost end P2 and extending inward in the drum radial direction along the arc of the second radius of curvature R2 toward the outer side in the drum axial direction, reaching the outermost end DE in the drum axial direction of the molding drum. A second arc portion,
The drum height DH of the molding drum is 0.30 to 0.40 times the nominal RD of the nominal rim diameter of a tire manufactured using the molding drum,
The first curvature radius R1 is 0.58 to 0.62 times the drum height DH,
The second radius of curvature R2 is 0.19 to 0.23 times the drum height DH.
The drum axis direction distance W1 from the drum axis direction center C of the molding drum to the drum axis direction outermost end P1 of the parallel part is 0.62 to 0.72 times the drum half width DHW,
The drum axial distance W2 from the drum axial center C of the forming drum to the drum axial outermost end P2 of the first arc portion is 0.953 to 0.993 times the drum half width DHW. A heavy duty tire molding drum.

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