JP2015107593A - Tire manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the appearance of a crease while securing visibility of a relief mark.SOLUTION: In a predetermined area Y, an outer surface 11S of a side wall rubber member 11 before formation of a green tire forms an inclined plane 15 inclined in a direction in which the thickness T of the side wall rubber member 11 is reduced at a constant ratio to a bead side, and a difference Tp-Tq between a thickness Tp in an intersection-point equivalent position P1 and a thickness Tq in a separation position Q is in the range of 1-3 mm.

Description

  The present invention relates to a method for manufacturing a pneumatic tire having a raised mark formed on a sidewall portion.

  There has been proposed a pneumatic tire in which raised marks such as letters and lines are formed on the sidewall portions, and colored rubbers of different colors are exposed on the outer surface of the raised marks.

  In such a tire forming method, first, a raised mark is raised on a sidewall portion of a vulcanized tire by vulcanization molding. After that, the raised mark of the vulcanized tire is buffed and the black covering rubber layer covering the outer surface is removed, so that the colored rubber (for example, white rubber) embedded in the side wall rubber is buffed. It is exposed on the hanging surface.

  At this time, a rubber inflow recess for forming an embossing mark is formed on the tire molding surface of the vulcanization mold, and at the time of vulcanization molding, a part of the sidewall rubber of the raw tire is placed in the rubber inflow recess. By making it flow, the above-mentioned raised mark is formed. As the side wall rubber, a strip-like extruded product in which a colored rubber is embedded at a position corresponding to the raised mark and the surface of the colored rubber is covered with a thin coating rubber layer is used.

  However, in the prior art, the rubber flow into the rubber inflow recess becomes unstable. For example, as shown in FIG. 7A, the covering rubber layer b is formed at the root portion of the raised mark a, particularly at the bead side. A so-called crease c that is locally thick is generated, which tends to deteriorate the appearance. As a cause of the occurrence of the crease c, as conceptually shown in FIG. 7B, the rubber flow f1 along the tire molding surface out of the rubber flow into the rubber inflow recess d of the mold is poor, and the center Since the rubber flow f2 on the side becomes dominant, it is assumed that the rubber of the covering rubber layer b gathers at the root portion of the raised mark a and crease c is generated.

  Therefore, in the [0020] column of Patent Document 1 below, it is proposed to suppress the crease c by setting the radius of curvature of the root portion of the raised mark a as large as 3.0 to 8.0 mm. Has been.

  However, when the radius of curvature of the root portion is increased, there is a problem that the contour at the root portion of the raised mark a becomes inconspicuous and visibility is lowered. Therefore, there is a demand for a method that can suppress the generation of crease c while ensuring the visibility by suppressing the curvature radius of the root portion to 3.0 mm or less.

JP 2004-203227 A

  The present invention provides a tire manufacturing method capable of suppressing the occurrence of crease and improving the appearance while suppressing the curvature radius of the root portion of the raised mark to 3.0 mm or less and ensuring the visibility of the raised mark. The challenge is to do.

The present invention comprises a green tire forming process for forming a green tire,
A vulcanization step of vulcanizing the green tire with a vulcanization mold having a tire molding surface to form a vulcanized tire with raised marks on the outer surface of the sidewall portion;
A method of manufacturing a tire including a polishing step of exposing an internal colored rubber to a buffing surface by buffing an outer surface of a raised mark of the vulcanized tire,
In the green tire forming step, a sidewall portion of the green tire is formed using a belt-shaped side wall rubber member extruded by an extruder,
In addition, the vulcanization mold includes a rubber inflow recess for projecting the raised mark on the tire molding surface, and at least a bead side of the intersection P where the tire molding surface and the side wall surface of the rubber inflow recess intersect. The intersection P1 is removed by an arc-shaped chamfered portion having a curvature radius Ra of 0.8 to 3.0 mm,
The side wall rubber member covers a base rubber part, a color rubber part embedded in the base rubber part at a position corresponding to the raised mark, an outer surface of the color rubber part, and the base rubber part And a coating rubber layer having the same color and thickness of 0.5 to 1.0 mm,
The intersection point P1 on the bead side abuts on the outer surface of the sidewall rubber member when the green tire is put into the vulcanizing mold, and 10 mm from the position corresponding to the intersection point to the bead side along the outer surface. In the region between the separated positions Q that are separated by
The outer surface of the sidewall rubber member before forming the green tire has an inclined surface that is inclined in such a direction that the thickness T of the sidewall rubber member decreases at a constant rate toward the bead side, and the sidewall rubber member at the intersection-corresponding position P1. The difference Tp−Tq between the thickness Tp of the rubber member and the thickness Tq of the sidewall rubber member at the separation position Q is in the range of 1 to 3 mm.

  In the tire manufacturing method according to the present invention, it is preferable that the rubber inflow recess has a depth D from the tire molding surface of 3.0 to 5.5 mm.

  As described above, according to the present invention, in the vulcanization mold, the bead side intersection P1 where the side wall surface of the rubber inflow recess for forming the raised mark intersects the tire molding surface has a curvature radius Ra of 0.8-3. Removed by arcuate chamfer of 0 mm. Thereby, the radius of curvature of the root portion of the raised mark can be suppressed to 3.0 mm or less, and the visibility of the raised mark can be ensured.

  Further, in a predetermined region of the side wall rubber member, the outer surface of the side wall rubber member is an inclined surface in which the thickness T of the side wall rubber member decreases at a certain rate toward the bead side, and the thickness Tp at the intersection equivalent position P1. And the difference Tp−Tq between the thickness Tq at the separation position Q is restricted to 1 to 3 mm. As a result, in the rubber flow into the rubber inflow recess, the rubber flow along the tire molding surface is smoothed, the balance with the rubber flow on the center side can be optimized, the occurrence of crease is suppressed, and Appearance can be improved.

It is a perspective view which shows one Example of the pneumatic tire formed by the tire manufacturing method of this invention. It is sectional drawing which expands and shows the protrusion mark. (A), (B) is a conceptual diagram explaining a green tire formation process. (A) is sectional drawing which shows the sidewall rubber member before green tire formation, (B) is sectional drawing which expands and shows the inclination of the outer surface in the area | region Y. It is sectional drawing which shows a vulcanization | cure process. (A) Partial enlarged sectional view showing the relationship between the raw tire and the vulcanizing mold at the time of charging, (B) is a partially enlarged sectional view showing the relationship between the vulcanized tire and the vulcanizing mold after vulcanization. . (A) is sectional drawing explaining a crease, (B) is a conceptual diagram which shows the generation | occurrence | production cause.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, a pneumatic tire 1 according to the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, a radially outer side of the carcass 6, and a tread portion. 2 and a belt layer 7 disposed inside.

  The carcass 6 is formed of one or more carcass plies 6A in this example, in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. The carcass ply 6 </ b> A includes a series of ply folding portions 6 b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the ply main body portion 6 a that extends between the bead cores 5 and 5. Reference numeral 8 in the drawing is a bead apex rubber for bead reinforcement, and reference numeral 14 is a clinching rubber for preventing rim slippage.

  The belt layer 7 is formed of at least two belt plies 7A and 7B in this example, in which belt cords are arranged at an angle of, for example, 10 to 45 ° with respect to the tire circumferential direction. In the belt layer 7, the belt cords cross each other between the plies, thereby increasing the belt rigidity and reinforcing the entire width of the tread portion 2.

  Further, the side wall portion 3 is formed with a raised mark 9 that protrudes from the outer surface 3S and displays, for example, a mark. The mark is a generic name including characters, symbols, and figures representing tire manufacturer names, product names, sizes, and the like. On the outer surface 9S of the raised mark 9, a color rubber G1 having a color different from that of the outer surface 3S of the sidewall portion 3 is exposed. In this example, as in the conventional tire, the outer surface 3S of the sidewall portion 3 is formed of black rubber G2, and the outer surface 9S of the raised mark 9 is formed of white colored rubber G1. It is.

  As shown in FIG. 2 in an enlarged manner, in the raised mark 9, the bead side side surface 9s1, in this example both the bead side and tread side surfaces 9s1, 9s2, have a curvature radius R of 0.8 to 0.8 respectively. The outer surface 3 </ b> S is smoothly connected via a 3.0 mm circular arc surface 10. Thus, since the curvature radius R of the root portion is small, the contour of the raised mark 9 can be made to stand out, and the visibility can be sufficiently secured.

  Next, a method for manufacturing the pneumatic tire 1 will be described. This manufacturing method includes a green tire forming step, a vulcanizing step, and a polishing step.

  As shown in FIGS. 3 (A) and 3 (B), the green tire forming step is a step of forming the green tire 1N, and the sidewall portion 3 of the green tire 1N is a strip-like shape formed by extrusion using an extruder. The side wall rubber member 11 is used.

Specifically, the raw tire formation process of this example is
(1) Step S1a for sequentially winding the sidewall rubber member 11, the carcass ply 6A and the like on the cylindrical tire forming drum 20 to form the cylindrical tire base 12, and
(2) Step S1b for setting the bead core 5 on the outer side in the tire axial direction of the cylindrical tire base 12;
(3) The tire base 12 is inflated between the bead cores 5 and 5 while being shaped close to the bead cores 5 and 5 and shaped into a toroid, and a tread ring 13 for forming a tread is separately formed in the inflated portion. Step S1c joined to the tire, thereby forming a raw tire 1N.

  FIG. 4A shows a cross section of the sidewall rubber member 11 before forming the raw tire (at the stage of extrusion molding). The side wall rubber member 11 covers a base rubber portion 11A, a colored rubber portion 11B embedded in the base rubber portion 11A at a position corresponding to the raised mark 9, and an outer surface of the colored rubber portion 11B. And a thin coated rubber layer 11C having a thickness of 0.5 to 1.0 mm. In the case of this example, the base rubber portion 11A and the covering rubber layer 11C are formed from a black rubber G2, and the color rubber portion 11B is formed from a white color rubber G1. Such a sidewall rubber member 11 can be formed using a multilayer extruder having a known structure. As the sidewall rubber member 11, an integrally extruded product further including clinch rubber 14 can be adopted as in this example.

  As shown in FIG. 5, in the vulcanization step, the raw tire 1N is vulcanized by a vulcanization mold 25 having a tire molding surface 25S. Thereby, the vulcanized tire 1 </ b> A in which the raised mark 9 is raised on the outer surface of the sidewall portion 3 is formed. At the stage of the vulcanized tire 1A, as shown in FIG. 6B, the outer surface 9S of the raised mark 9 is covered with a covering rubber layer 11C.

  The vulcanization mold 25 has a well-known structure, and a rubber inflow recess 26 for raising the raised mark 9 is provided on the tire molding surface 25S. As shown in FIG. 6 (A), in the vulcanization mold 25, at the intersection P1 where the tire molding surface 25S and the sidewall surface 26S of the rubber inflow recess 26 intersect, at least the intersection P1 on the bead side has a curvature radius Ra. It is removed by an arc-shaped chamfer 27 of 0.8 to 3.0 mm. In this example, the tread-side intersection point P <b> 2 is also removed by the chamfered portion 27. Thereby, the outline of the embossing mark 9 can be made to stand out and the visibility can be sufficiently secured. The depth D of the rubber inflow recess 26 from the tire molding surface 25S is preferably 3.0 to 5.5 mm.

  In the polishing step (not shown), as in the prior art, the outer surface 9S of the raised mark 9 of the vulcanized tire 1A is buffed, and the covering rubber layer 11C on the outer surface 9S is removed, The colored rubber G1 is exposed on the buffing surface K (shown in FIGS. 1 and 2).

  And in this invention, as shown to FIG. 4 (A), in the predetermined area | region Y, the inclination degree of the outer surface 11S of the sidewall rubber member 11 is controlled.

  As shown in FIG. 6A, the predetermined area Y is defined as follows. When the raw tire 1N is put into the vulcanizing mold 25, when the intersection-corresponding position where the bead-side intersection point P1 abuts on the outer surface 11S of the sidewall rubber member 11 is 11P, the intersection-corresponding position 11P A region between a separation position Q that is separated by a distance L of 10 mm on the bead side along the outer surface 11S and the intersection equivalent position 11P is defined as the region Y.

As shown in FIGS. 4A and 4B, the outer surface 11S of the sidewall rubber member 11 before forming the raw tire has a constant thickness T of the sidewall rubber member 11 on the bead side in the region Y. The inclined surface 15 which inclines in the direction reduced with a ratio is formed. Moreover, Tp−Tq, which is the difference ΔT between the thickness Tp of the sidewall rubber member at the intersection equivalent position P1 and the thickness Tq of the sidewall rubber member at the separation position Q, is in the range of 1 to 3 mm. That is, the inclined surface 15 has an angle α (α = sin ⁻¹ (1/10) to sin ⁻¹ (3/10)) with respect to a reference plane X parallel to the inner surface of the sidewall rubber member 11. It is inclined at an angle.

  Thus, by forming the outer surface 11S in the region Y with the inclined surface 15 having the angle α, in the rubber flow into the rubber inflow recess 26, the rubber flow along the tire molding surface 25S is smoothed, and the center side It is possible to optimize the balance with the rubber flow. As a result, the occurrence of crease can be suppressed and the appearance of the raised mark 9 can be improved.

  When the thickness difference ΔT is less than 1 mm, the effect of suppressing crease becomes insufficient. Conversely, if it exceeds 3.0 mm, the variation in the extrusion shape tends to be large, and the target thickness tends not to be obtained. For example, when the sidewall rubber member 11 becomes thinner than the target, due to deterioration over time after mounting on the vehicle, A problem of brown discoloration of the color rubber G1 occurs due to the migration of the anti-aging agent to the color rubber G1. Further, when the sidewall rubber member 11 becomes thicker than intended, an appearance defect due to insufficient vulcanization (under cure) occurs.

  Since there is no flow of rubber in the raw tire forming process, the thickness distribution of the sidewall rubber member 11 at the time of extrusion molding is directly the thickness distribution from the carcass 6 to the outer surface 3S of the sidewall portion 3 in the raw tire 1N. appear. Therefore, by regulating the shape of the outer surface 11S of the sidewall rubber member 11 at the time of extrusion molding before forming the raw tire, the same effect as that of regulating the shape of the outer surface 3S in the raw tire 1N can be obtained. It is possible to improve the rubber flow into the rubber inflow recess 26 in the tire 1N.

  Here, if the depth D of the rubber inflow recess 26 is less than 3.0 mm, the raised height of the raised mark 9 becomes insufficient and the visibility is lowered. On the contrary, when the depth D exceeds 5.5 mm, the carcass 6 sucks up as the amount of rubber inflow into the rubber inflow recess 26 increases, so that the carcass is likely to meander.

  On the other hand, if the thickness of the covering rubber layer is less than 0.5 mm, the white rubber G1 is exposed at a position other than the buffing surface K, which tends to cause poor white rubber exposure. On the other hand, when the thickness exceeds 1.0 mm, the ratio of the exposed area of the colored rubber G1 to the buffing surface K becomes small, and the colored rubber G1 becomes less conspicuous and the visibility is lowered.

  If the radius of curvature Ra of the chamfered portion is less than 0.8 mm, cracks are likely to occur. Conversely, if the radius of curvature Ra exceeds 3.0 mm, the outline of the base of the raised mark 9 becomes inconspicuous and visibility is improved. Reduce.

  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.

  Using the manufacturing method of the present invention, a pneumatic tire (LT265 / 75R16) having the structure shown in FIG. Then, the visibility, crack resistance, and appearance of the raised marks in each sample tire were tested.

(1) Visibility:
After the polishing step, the visibility of the raised mark was evaluated by an index with Comparative Example 1 being 100 by visual inspection. The larger the value, the better the visibility. In the visual inspection, the degree of conspicuousness of the outline of the raised mark and the ratio of the exposed area of the colored rubber G1 to the buffing surface were evaluated.

(2) Crack resistance:
Running on the drum at a speed (100 km / h) under the conditions of rim (16 x 7.5 J), internal pressure (550 kPa), and load (maximum allowable load), cracks occur around the raised mark. The travel distance was evaluated by an index with Comparative Example 1 as 100. The larger the value, the better the crack resistance.

(3) Appearance:
By visual inspection, crease defects, colored rubber exposure defects, brown discoloration, and insufficient vulcanization in the embossed marks were evaluated using indices of Comparative Example 1 as 100, respectively. The larger the value, the better the appearance.

  As shown in the table, it can be confirmed that the embodiment can suppress the occurrence of crease while ensuring the visibility of the embossed mark, and can also suppress the adverse effect on the appearance other than the crease.

1A Vulcanized tire 1N Raw tire 3 Side wall portion 3S Outer surface 9 Raised mark 9S Outer surface 11 Side wall rubber member 11A Base rubber portion 11B Colored rubber portion 11C Equivalent position 11S Outer surface 15 Inclined surface 25 Vulcanization mold 25S Tire molding surface 26 Rubber inflow recess 26S Side wall surface 27 Chamfer G1 Colored rubber K Buffing surface Y Region

Claims (2)

A raw tire forming process for forming a raw tire;
A vulcanization step of vulcanizing the green tire with a vulcanization mold having a tire molding surface to form a vulcanized tire with raised marks on the outer surface of the sidewall portion;
A method of manufacturing a tire including a polishing step of exposing an internal colored rubber to a buffing surface by buffing an outer surface of a raised mark of the vulcanized tire,
In the green tire forming step, a sidewall portion of the green tire is formed using a belt-shaped side wall rubber member extruded by an extruder,
In addition, the vulcanization mold includes a rubber inflow recess for projecting the raised mark on the tire molding surface, and at least a bead side of the intersection P where the tire molding surface and the side wall surface of the rubber inflow recess intersect. The intersection P1 is removed by an arc-shaped chamfered portion having a curvature radius Ra of 0.8 to 3.0 mm,
The side wall rubber member covers a base rubber part, a color rubber part embedded in the base rubber part at a position corresponding to the raised mark, an outer surface of the color rubber part, and the base rubber part And a coating rubber layer having the same color and thickness of 0.5 to 1.0 mm,
The intersection point P1 on the bead side abuts on the outer surface of the sidewall rubber member when the green tire is put into the vulcanizing mold, and 10 mm from the position corresponding to the intersection point to the bead side along the outer surface. In the region between the separated positions Q that are separated by
The outer surface of the sidewall rubber member before forming the green tire has an inclined surface that is inclined in such a direction that the thickness T of the sidewall rubber member decreases at a constant rate toward the bead side, and the sidewall rubber member at the intersection-corresponding position P1. A tire manufacturing method, wherein a difference Tp-Tq between a thickness Tp of the tire and a thickness Tq of the sidewall rubber member at the separation position Q is in a range of 1 to 3 mm. The tire manufacturing method according to claim 1, wherein the rubber inflow recess has a depth D of 3.0 to 5.5 mm from the tire molding surface.

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