JP6363886B2 - Tire molding drum and method for producing run-flat tire using the same - Google Patents

Description

  The present invention relates to a tire forming drum for forming a cylindrical raw tire base for a run flat tire, and a method for producing a run flat tire using the same.

  Conventionally, a run flat tire having a side reinforcing rubber in a sidewall portion is known. Since such a run-flat tire has a sidewall portion whose rigidity is enhanced by the side reinforcing rubber, even if the air from the tire escapes due to puncture or the like, the run-flat tire can continuously run at a relatively high speed.

  A raw tire base for a run-flat tire is formed by, for example, winding tire constituent members sequentially on the outer peripheral surface of a cylindrical tire forming drum. For example, in the green tire base, a belt-like rubber strip is spirally wound on the outer peripheral surface to form an inner liner, and a side reinforcing rubber is wound on the outer surface thereof. Further, a sheet-like carcass ply is wound around the outside.

  For example, Patent Document 1 below proposes a tire molding drum for molding a raw tire base for a run-flat tire, in which a recess for arranging side reinforcing rubber is formed on the outer peripheral surface. Thereby, the outer surface of the whole green tire base | substrate is planarized.

Special table 2003-532566 gazette

  However, the outer diameter of the tire forming drum of Patent Document 1 is rapidly changing. When a belt-like rubber strip is spirally wound around the recess of such a tire molding drum, the rubber strip is likely to be drawn to the side having a larger outer diameter, and consequently the rubber strip cannot be wound at a uniform pitch. was there.

  The present invention has been devised in view of the actual situation as described above, and provides a tire molding drum capable of suppressing the winding failure of the inner liner on the basis of improving the shape of the concave portion of the outer peripheral surface of the tire molding drum. The main purpose is to do.

  The present invention relates to a cylindrical raw tire base having side reinforcing rubber for run flat running provided on each of a pair of sidewall portions, and an inner liner formed by winding a belt-like rubber strip in a spiral shape. The tire forming drum has a substantially cylindrical outer peripheral surface, and the outer peripheral surface has a first outer surface and an outer diameter smaller than the first outer surface. A second outer surface forming a circumferential recess for disposing the side reinforcing rubber, the second outer surface including a bottom portion and side wall surfaces on both sides thereof, and rotation of the tire molding drum In a meridian cross section including an axis, the side wall surface is connected to the first outer surface by an arc having a radius of curvature R1 of 20 to 200 mm, and an angle θ1 of the side wall surface with respect to the rotation axis is 30 ° or less. It is a symptom.

  In the tire molding drum of the present invention, it is desirable that the depth of the concave portion is 2 to 15 mm.

  In the tire molding drum of the present invention, the angle θ1 is desirably 15 ° or less.

  In the tire molding drum of the present invention, it is preferable that the radius of curvature R1 is 50 to 100 mm.

  In the tire forming drum of the present invention, it is preferable that the bottom portion extends along the rotation axis at a certain depth, and the side wall surface is connected to the bottom portion by an arc having a radius of curvature R2 of 20 to 200 mm.

  A second aspect of the present invention is a method for producing a run-flat tire, the step of forming a raw tire base with any of the tire forming drums described above, and the step of forming a raw tire using the raw tire base. And a step of vulcanizing the raw tire to obtain a run-flat tire.

  The tire molding drum of the present invention has a substantially cylindrical outer peripheral surface, and the outer peripheral surface has a first outer surface and an outer diameter smaller than the first outer surface, so that the side reinforcing rubber is disposed. And a second outer surface forming a circumferential recess. Thereby, the outer surface when the inner liner and the side reinforcing rubber are disposed on the tire molding drum is flattened, and, for example, the carcass ply is accurately wound around the outer surface.

  The second outer surface includes a bottom portion and a pair of side wall surfaces on both sides thereof. In the meridian cross section including the rotation axis of the tire forming drum, the side wall surface is connected to the first outer surface by an arc having a radius of curvature R1 of 20 to 200 mm, and the angle θ1 of the side wall surface with respect to the rotation axis is 30 ° or less. As a result, the outer diameter of the tire forming drum changes gradually. With such an outer peripheral surface, when a belt-like rubber strip is wound spirally as an inner liner and passes through the second outer surface, the rubber strip is disposed on the side wall surface with high accuracy without being displaced. . Therefore, the winding failure of the inner liner is suppressed.

It is the schematic of the tire shaping | molding apparatus containing the tire shaping | molding drum of this invention. It is sectional drawing of a run flat tire. (A) is a front view of a tire molding drum, (b) is a side view of a tire molding drum. (A) is sectional drawing of the tire shaping | molding drum by which the rubber strip was wound helically as an inner liner, (b) is sectional drawing of the tire shaping | molding drum in which the inner liner and the side reinforcement rubber were shape | molded. It is explanatory drawing when the winding defect of a rubber strip generate | occur | produces. It is an expanded sectional view of the 2nd outer surface.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic view of a tire forming apparatus 2 including a tire forming drum 1 of the present invention. The tire forming apparatus 2 in FIG. 1 is for forming a cylindrical raw tire base for a run-flat tire.

  FIG. 2 shows a cross-sectional view of the run flat tire 22. As shown in FIG. 2, the run flat tire 22 includes a carcass 11 extending from the tread portion 23 through the sidewall portion 24 to the bead portion 25, an inner liner 9 that forms a tire lumen surface, and a pair of sidewall portions. 24 and the side reinforcing rubber 10 provided in each. For example, the side reinforcing rubber 10 is provided between the carcass 11 and the inner liner 9.

  As shown in FIG. 1, the tire forming device 2 includes, for example, a tire forming drum 1, a drum rotating device 3 that supports the tire forming drum 1 in a cantilevered manner, and a tire forming drum 1. And a supply device 4 for continuously supplying a belt-like or sheet-like rubber member 5 to a predetermined position.

  FIG. 3A shows a front view of the tire molding drum 1. FIG. 3B shows a side view of the tire molding drum 1. As shown in FIG. 3A, the tire molding drum 1 has a substantially cylindrical outer peripheral surface 8. For example, the outer peripheral surface 8 of the tire molding drum 1 is formed of a plurality of segments 13.

  As shown in FIG. 3B, each segment 13 has an outer surface with a substantially arc-shaped cross section, and is supported by a rotating cylinder 7 positioned at the center of the tire molding drum 1. Between each segment 13 and the rotating cylinder 7, a diameter reducing means 14 for moving each segment 13 inward in the radial direction of the drum is provided.

  As shown in FIG. 1, for example, the rubber member 5 is supplied from the supply device 4 to the outer peripheral surface 8 of the rotating tire forming drum 1. The supplied rubber member 5 is wound around the outer peripheral surface 8 of the tire molding drum 1. Thereby, a cylindrical raw tire base (described later) is formed on the outer peripheral surface 8 of the tire forming drum 1.

  4A and 4B are cross-sectional views of the tire forming drum 1 for explaining a process of forming the raw tire base 6. As shown in FIG. 4A, a belt-like rubber strip 17 having a small width is spirally wound around the outer peripheral surface 8 of the tire molding drum 1 to form an inner liner 9. After the inner liner 9 is formed, as shown in FIG. 4B, the side reinforcing rubber 10 is wound around the outer side and the region corresponding to the sidewall portion. The side reinforcing rubber 10 may be formed by, for example, a belt-shaped rubber strip having a small width wound spirally, or may be formed by winding a wide rubber sheet.

  Conventionally, as shown in FIG. 5, when the rubber strip c is wound around the recess b of the tire molding drum a, the rubber strip c is easily drawn to the side having the larger outer diameter, and the winding pitch of the portion becomes small. There is a problem that the thick part d is generated or the rubber strip is easily wrinkled.

  As shown in FIG. 3A, the tire molding drum 1 of the present invention has the first outer surface 15 and the second outer surface 16 to solve the above-described problems.

  For example, the first outer surface 15 forms the entire outer peripheral surface 8 excluding the second outer surface 16. The first outer surface 15 of the present embodiment is a cylindrical surface having a constant outer diameter. The first outer surface 15 is not limited to this. For example, the first outer surface 15 may be gently inclined with respect to the rotating shaft 1a of the drum.

  The second outer surface 16 is provided on each side of the center line 1c of the tire forming drum corresponding to the tire equator. The second outer surface 16 has an outer diameter smaller than that of the first outer surface 15, thereby forming a circumferential recess 18 for arranging the side reinforcing rubber 10. As a result, as shown in FIG. 4B, the outer surface when the inner liner 9 and the side reinforcing rubber 10 are arranged on the tire molding drum 1 is flattened. For example, the carcass ply is accurately placed on the outer surface. Wrapped.

  FIG. 6 shows an enlarged cross-sectional view of the second outer surface 16. As shown in FIG. 6, the second outer surface 16 includes a bottom portion 20 and side wall surfaces 21 on both sides thereof.

  The bottom 20 extends along a rotating shaft 1a of the drum (shown in FIG. 3 (a), and so on) at a constant depth.

  The side wall surface 21 forms between the bottom portion 20 and the first outer surface 15. The side wall surface 21 connects between the outer edge 15e of the first outer surface 15 and the outer edge 20e of the bottom portion 20, for example.

  In the cross section including the rotation axis of the drum, the side wall surface 21 includes an outer arc portion 28 formed of an arc having a large curvature radius R1 of 20 to 200 mm on the first outer surface 15 side. The outer arc portion 28 is continuous with the first outer surface 15. Such an outer circular arc portion 28 makes the change of the outer diameter from the first outer surface 15 to the second outer surface 16 gentle. Therefore, when a strip-shaped rubber strip is wound from the first outer surface 15 to the second outer surface 16 to form the inner liner, the rubber strip is wound at a uniform pitch without being displaced.

  In order to further exert the above-described effects, the radius of curvature R1 is preferably 50 mm or more, more preferably 80 mm or more, preferably 150 mm or less, more preferably 100 mm or less.

  Further, the side wall surface 21 includes a linear portion 30 that is continuous with the outer arc portion 28 and extends in a planar shape. An angle θ1 of the linear portion 30 of the side wall surface 21 with respect to the rotation shaft 1a of the tire molding drum 1 is 30 ° or less. Thereby, the outer diameter of the tire molding drum 1 changes more gradually. When the rubber strip is wound spirally by the outer peripheral surface 8 and passes through the second outer surface 16, the rubber strip is disposed on the side wall surface 21 with high accuracy without being displaced. Accordingly, the winding failure of the inner liner is effectively suppressed.

  In order to further exhibit the above-described effects, the angle θ1 is preferably 20 ° or less, more preferably 15 ° or less.

  The depth d1 of the recess 18 is preferably 2 mm or more, more preferably 5 mm or more, preferably 15 mm or less, more preferably 10 mm or less. Such a recess 18 can secure the thickness of the side reinforcing rubber 10 while suppressing a sudden change in the outer diameter of the tire molding drum 1.

  The side wall surface 21 desirably includes, for example, an inner circular arc portion 29 having a curvature radius R2 of 20 to 200 mm on the bottom 20 side of the linear portion 30. The inner arc portion 29 continues to the bottom portion 20. The radius of curvature R2 of the inner arc portion 29 is preferably 50 mm or more, more preferably 80 mm or more, preferably 150 mm or less, more preferably 100 mm or less. Thereby, when the rubber strip is wound spirally and reaches from the side wall surface 21 to the bottom portion 20, the rubber strip is wound with high accuracy without being displaced.

  The curvature radius R2 is preferably equal to the curvature radius R1. Thereby, the rubber strip is wound around the side wall surface 21 and the bottom portion 20 at a uniform pitch, and the thickness of the inner liner becomes uniform.

  As mentioned above, although the especially preferable form 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 run-flat tire of size 235 / 50R18 with side reinforcing rubber was molded with a tire molding drum based on the specifications in Table 1. The molded tire was tested for the wound state, uniformity, and appearance defect rate of the rubber strip wound as an inner liner. The test method is as follows.

<Wound state of rubber strip>
The presence or absence of thick portions and wrinkles on the rubber strip shown in FIG. 5 was confirmed with the naked eye. When the rubber strip was tightly wound to generate a thick part, the maximum thickness t1 of the thick part was measured. A smaller maximum wrinkle thickness indicates that the rubber strip is wound at a uniform pitch.

<Uniformity>
With respect to the molded tire, RFV was measured using a tire uniformity tester according to JASOC 607: 2000 “Uniformity test method for automobile tire”. A result is an index | exponent which sets the comparative example 1 to 100, and shows that uniformity is so favorable that a numerical value is small. Detailed measurement conditions are as follows.
Internal pressure: 200kPa
Longitudinal load: 4.88kN
Tire rotation speed: 60rpm

<Appearance defect rate>
The appearance defect of the tire due to the winding failure of the inner liner was visually confirmed, and the occurrence rate (%) was calculated. The appearance defect is, for example, a Bron rubber in which a dent in the tire lumen surface due to a poor winding of the rubber strip shown in FIG.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tire molding drum of the present invention suppressed the winding failure of the inner liner and increased the tire uniformity.

DESCRIPTION OF SYMBOLS 1 Tire molding drum 6 Raw tire base | substrate 8 Outer peripheral surface 9 Inner liner 10 Side reinforcement rubber 15 1st outer surface 16 2nd outer surface 18 Recessed part 20 Bottom 21 Side wall surface

Claims (6)

To form a cylindrical green tire base body having side reinforcing rubber for run flat running provided on each of the pair of sidewall portions and an inner liner formed by winding a belt-like rubber strip in a spiral shape Tire molding drum
The tire molding drum has a substantially cylindrical outer peripheral surface,
The outer peripheral surface includes a first outer surface and a second outer surface that has a smaller outer diameter than the first outer surface to form a circumferential recess for arranging the side reinforcing rubber,
The second outer surface includes a bottom portion and side wall surfaces on both sides thereof.
In the meridian cross section including the rotation axis of the tire molding drum,
The side wall surface is connected to the first outer surface by an arc having a curvature radius R1 of 20 to 200 mm,
An angle θ1 of the side wall surface with respect to the rotation axis is 30 ° or less.   The tire forming drum according to claim 1, wherein the depth of the concave portion is 2 to 15 mm.   The tire forming drum according to claim 1 or 2, wherein the angle θ1 is 15 ° or less.   The tire forming drum according to any one of claims 1 to 3, wherein the curvature radius R1 is 50 to 100 mm. The bottom extends along the axis of rotation at a constant depth;
The tire forming drum according to any one of claims 1 to 4, wherein the side wall surface is connected to the bottom portion by an arc having a radius of curvature R2 of 20 to 200 mm.   A step of forming a green tire base with the tire forming drum according to any one of claims 1 to 5, a step of forming a green tire using the green tire base, and a run flat tire obtained by vulcanizing the green tire The method of manufacturing a run flat tire characterized by including the process of obtaining.

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