JP6374779B2 - Rigid core for tire formation - Google Patents

Description

  The present invention relates to a rigid core for forming a tire that can reduce the pulling-out force of a core segment from a vulcanized tire while maintaining the moldability of a green tire, and can expedite the operation of taking out and removing the core body.

  In recent years, a tire forming method using a rigid core (hereinafter sometimes referred to as “core method”) has been proposed in order to increase the formation accuracy of the tire (see, for example, Patent Documents 1 and 2). This rigid core has a core body having an outer shape that matches the shape of the tire lumen surface of the vulcanized tire, and a tire component is sequentially pasted on the core body to form a raw tire. Is done. The raw tire is inserted into the vulcanization mold together with the rigid core, so that the raw tire is vulcanized and molded between the inner core body and the outer vulcanization mold. Is done.

  7A and 7B, in the core method, the core body a is divided in the circumferential direction in order to take out the core body a from the tire T1 after vulcanization molding. And a plurality of core segments c. Then, the divided core segment c is pulled out inward in the radial direction one by one and taken out from the bead hole T1a of the tire T1.

  However, the inner surface Ts of the tire T1 after vulcanization is in close contact with the tire molding surface as which is the outer surface of the core body a. Therefore, a large force F is required for pulling out the core segment c. If the core segment c is pulled out forcibly, the tire T1 may be damaged or deformed, and the tire quality may be impaired. For this reason, conventionally, the number of divisions of the core segment c is increased to reduce the drawing force F per core segment c or to slowly draw out. However, in this case, the time required for disassembling and taking out the entire core body is increased, leading to a reduction in production efficiency.

  Therefore, the present inventor has proposed that a coating layer having rubber releasability is formed on the tire molding surface “as” of the core body “a” to improve the releasability from the tire T1 after vulcanization. However, the coating layer having rubber releasability generally exhibits high releasability even for unvulcanized rubber. Therefore, when the coating layer is formed on the tire molding surface as, it becomes difficult to adhere and hold an unvulcanized tire constituent member on the tire molding surface as at the time of raw tire formation, which impairs the moldability of the raw tire. New problems arise.

JP 2011-161896 A JP 2011-167799 A

  Accordingly, the present invention provides a tire after vulcanization while maintaining the moldability of the raw tire, based on the difference in rubber release properties of the coating layer between the tread molding surface portion and the side molding surface portion of the tire molding surface. It is an object of the present invention to provide a rigid core for forming a tire that can quickly disassemble and take out the core body and improve the production efficiency of the tire.

The present invention includes an annular core body having an outer surface having a tire molding surface for forming a green tire, and the raw tire is put into a vulcanization mold so that the vulcanization mold and the core body are provided. A rigid core for vulcanizing the green tire with
The core body is composed of a plurality of core segments divided in the circumferential direction,
And a coating layer having rubber releasability is formed on the tire molding surface,
The tire molding surface includes a tread molding surface portion that molds an inner surface of a tire tread portion, and side molding surface portions arranged on both sides thereof.
And the coating layer comprises a tread coating layer portion formed on the tread molding surface portion, and a side coating layer portion formed on the side molding surface portion,
In addition, the tread coating layer portion has a rubber release property larger than that of the side coating layer portion.

  In the present invention, as described above, a coating layer having rubber releasability is formed on the tire molding surface of the core body. Moreover, the coating layer includes a tread coating layer portion formed on the tread molding surface portion of the tire molding surface and a side coating layer portion formed on the side molding surface portion, and a rubber release of the tread coating layer portion. The property is greater than the rubber releasability of the side coating layer.

  The tread molding surface portion is substantially perpendicular to the drawing direction (radial direction) of the core segment and has a large contact area with the tire inner surface. Therefore, the influence on the extraction of the core segment is large. On the other hand, the side molding surface portion has a steep slope with respect to the radial line, so that it is difficult to adhere and hold an unvulcanized tire forming member when forming a green tire. That is, the influence on the moldability of the green tire is great.

  Therefore, forming a coating layer portion having a large rubber release property on the tread molding surface portion, and conversely forming a coating layer portion having a small rubber release property on the side molding surface portion, thereby forming a raw tire. It is possible to expedite the work of disassembling and removing the core body from the vulcanized tire while maintaining the properties, and the tire production efficiency can be improved.

It is sectional drawing which shows the use condition of the rigid core of this invention. It is a perspective view of a core main body. It is a side view of a core main body. It is sectional drawing explaining a tire molding surface. It is a conceptual diagram explaining the extraction method of the core segment from a vulcanized tire. (A), (B) is a conceptual diagram explaining the evaluation test which evaluates the rubber release property of a coating layer. (A), (B) is the side view explaining the problem of the conventional core main body, and sectional drawing.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the rigid core 1 for forming a tire according to the present embodiment includes an annular core body 2 having a tire molding surface S on the outer surface. Then, tire constituent members such as a carcass ply, a belt ply, a sidewall rubber, and a tread rubber are sequentially attached on the tire molding surface S, thereby forming a green tire T having substantially the same shape as the finished tire. Further, by putting the raw tire T together with the rigid core 1 into the vulcanizing mold B, the raw tire T is interposed between the core body 2 which is the inner mold and the vulcanizing mold B which is the outer mold. Is vulcanized. The tire molding surface S is formed in substantially the same shape as the inner surface shape of the finished tire.

  The rigid core 1 includes an annular core body 2 and a cylindrical core 3 that is inserted into the center hole 2H. Other than the core body 2, the rigid core 1 is conventionally known. The structure can be adopted. Therefore, only the core body 2 will be described below.

  The core body 2 of the present example has a hollow shape with a lumen portion 4 extending continuously in the circumferential direction in the inside thereof, for example, an electric heater that heats the raw tire T inside the lumen portion 4. Such heating means (not shown) are arranged.

  As shown in FIG. 2, the core body 2 is formed of a plurality of core segments 5 divided in the circumferential direction. Each core segment 5 has both end surfaces in the circumferential direction as mating surfaces 6, and the mating surfaces 6 adjacent to each other in the circumferential direction are attached to each other to form the core body 2 in an annular shape.

  In this example, the core segment 5 includes first and second core segments 5A and 5B that are alternately arranged in the circumferential direction. In the first core segment 5A, the mating surfaces 6A at both ends in the circumferential direction are inclined so that the circumferential width increases inward in the radial direction. On the other hand, in the second core segment 5B, the mating surfaces 6B at both ends in the circumferential direction are inclined in such a direction that the circumferential width decreases toward the inside in the radial direction. As a result, as shown in FIG. 3, the first core segment 5A can move inward in the radial direction in order, and after vulcanization molding, it can be sequentially disassembled and taken out from the bead hole of the vulcanized tire. The core 3 has a function of preventing the core segments 5 from moving inward in the radial direction and connecting the core segments 5 together.

  In the present invention, as shown in FIG. 4, a coating layer 11 having rubber releasability is formed on the tire molding surface S.

  As the coating layer 11, an organic material having excellent releasability such as a fluorine resin or a siloxane resin can be employed. However, a combination of the organic material and an inorganic material such as a metal, ceramics, or chemical conversion film can be suitably employed from the viewpoint of wear resistance, hardness, and releasability. As such a thing, a brand name Vicoat (Corporation Yoshida SKT) is mentioned, for example. This bicoat is a composite film in which organic materials such as fluorine-based resins and siloxane-based resins are dispersed and mixed in nickel-based metal coatings, chromium-based metal coatings, alumina coatings, chemical conversion coatings, and thermal spray coatings of metals and ceramics. It is formed. Specifically, the NYK series with a fluorine-based resin combined with a nickel-based metal film, the NOO series with a fluorine-based resin combined with a chromium-based metal film, and a fluorine-based film in a chemical conversion film reacted with iron ions in a metal substrate Examples include the TYS series in which a resin is fused, the NYN series in which a fluorine-based resin is combined with an alumina coating, and the CTT series in which a siloxane-based resin is combined with a metal coating.

  In addition to this, for example, Nidax (ULVAC Techno Co., Ltd.), which is a composite film in which fine pores of a nickel alloy layer are impregnated with a fluororesin and bonded firmly, and fine particles of fluororesin are uniformly distributed in the nickel film. The trade name Kaniflon (Nippon Kanisen Co., Ltd.), which is a composite film dispersed and co-deposited in the material, is also included.

  The tire molding surface S includes a tread molding surface portion S1 that molds the inner surface of the tread portion Ta of the tire T, and side molding surface portions S2 and S2 disposed on both sides thereof. The side molding surface portion S2 molds the inner surfaces of the sidewall portion Tb and the bead portion Tc of the tire T.

  A boundary Q1 between the tread molding surface portion S1 and the side molding surface portion S2 is located in a shoulder region Y1 defined below. Specifically, among the normal lines perpendicular to the tire molding surface S, the normal line having an angle α with respect to the radial line of 30 ° is defined as the reference line X1. Further, an intersection of the tire axial direction line passing through the maximum width point Pm where the tire molding surface S extends most outward in the tire axial direction and the reference line X1 is defined as a reference point P1. Among the straight lines passing through the reference point P1, an inner boundary line y1i inclined at an angle of 15 ° inward in the tire axial direction with respect to the reference line X1 and an outer boundary line inclined at an angle of 15 ° outward in the tire axial direction A region between y1o is referred to as the shoulder region Y1.

  Further, the side molding surface portion S2 of this example is divided into an outer side surface portion S2o on the radially outer side and an inner side surface portion S2i on the radially inner side. The boundary Q2 between the outer side surface portion S2o and the inner side surface portion S2i is located in a side region Y2 defined below. Specifically, a tire axial direction line passing through the maximum width point Pm is defined as a reference line X2, and a center point of curvature radius of the side molding surface portion S2 at the maximum width point Pm is defined as P2. Of the straight lines passing through the radius of curvature center point P2, an inner boundary line y2i inclined at an angle of 15 ° radially inward with respect to the reference line X2 and an outer boundary line inclined at an angle of 15 ° radially outward. A region between y2o is referred to as the side region Y2.

  As shown in FIG. 5, the tread molding surface portion S <b> 1 is substantially perpendicular to the drawing direction (radial direction) of the core segment 5 and has a large contact area with the tire inner surface. Accordingly, the influence on the withdrawal of the core segment 5 is great. On the contrary, since the side molding surface portion S2 has a steep slope with respect to the radial line, it is difficult to adhere and hold the unvulcanized tire forming member when the green tire T is formed. That is, the influence on the moldability of the raw tire is great.

  Therefore, in the present invention, the rubber releasability of the tread coating layer portion 11A formed on the tread molding surface portion S1 in the coating layer 11 is determined from the rubber releasability of the side coating layer portion 11B formed on the side molding surface portion S2. Also set to large. This makes it possible to achieve both the drawability of the core segment 5 and the green tire moldability. That is, while maintaining the formability of the green tire, the pulling force F of the core segment c from the vulcanized tire T1 can be reduced, and the work for disassembling and taking out the core body can be expedited to improve tire production efficiency. Can be made.

  As shown in FIG. 5, when the core segment 5 is taken out from the vulcanized tire T1, the core segment 5 is pulled out while pushing the bead portion Tc of the vulcanized tire T1 outward in the tire axial direction. Therefore, at the time of the drawing, the side coating layer portion 11B is strongly rubbed with the bead portion Tc, and the coating film is likely to be worn or peeled off. Therefore, the side coating layer portion 11B preferably includes a coating layer portion having a hardness higher than that of the tread coating layer portion 11A.

  In particular, the inner side surface portion S2i is more rubbed with the bead portion Tc than the outer side surface portion S2o. Therefore, in the side coating layer portion 11B, the hardness of the inner side coating layer portion 11Bi formed on the inner side surface portion S2i is set larger than the hardness of the outer side coating layer portion 11Bo formed on the outer side surface portion S2o. Is preferred.

  That is, in this example, the coating layer 11 is divided into a tread coating layer portion 11A disposed on the tread molding surface portion S1 and a side coating layer portion 11B disposed on the side molding surface portion S2, and the side coating layer portion 11B is divided. The inner side coating layer portion 11Bi disposed on the inner side surface portion S2i and the outer side coating layer portion 11Bo disposed on the outer side surface portion S2o are divided.

  The rubber release property of the tread coating layer portion 11A is made larger than the rubber release property of the side coating layer portion 11B. In the side coating layer portion 11B, the hardness of the inner side coating layer portion 11Bi is larger than the hardness of the outer side coating layer portion 11Bo. In general, a coating film having a high hardness tends to be inferior in rubber releasability as compared with a coating film having a low hardness. Therefore, in this example, the rubber release property of the inner side coating layer portion 11Bi is smaller than that of the outer side coating layer portion 11Bo. This is also suitable for adhering and holding an unvulcanized tire forming member on the inner side surface portion S2i when forming a raw tire.

  The hardness of the coating layer is compared with a value measured according to “Micro Vickers Hardness Test” described in “Vickers Hardness Test—Test Method” of JIS Z2244.

The rubber peelability of the coating layer can be evaluated by the following peel test. As shown in FIG. 6A, upper and lower molds 30 and 31 are used. A concave portion 31a having a depth of about 15 mm is provided on the upper surface of the lower mold 31, and a convex portion 30a that fits into the concave portion 31a is provided on the lower surface of the upper mold 30. A metal sample piece 32 having a coating layer on the surface and having a thickness of about 10 mm is disposed on the bottom surface of the recess 31a. In this example, a plurality of sample pieces 32 having different coating types are arranged. An unvulcanized rubber sheet 33 having a thickness of about 2 mm is laid on the upper surface of the sample piece 32. The sample piece 32 and the rubber sheet 33 are sandwiched between the upper and lower molds 30 and 31, and heat vulcanization is performed while pressing. The vulcanization conditions are, for example, a temperature of 170 ° C., a time of 12 minutes, and a pressure of about 22 kg / cm ² .

  After vulcanization, as shown in FIG. 6B, the peelability when the rubber sheet 33 after vulcanization is peeled off from the sample piece 32 by hand is evaluated by the operator's sense. In the coating layer, the evaluation order of peelability from rubber after vulcanization and the evaluation rank of peelability from unvulcanized rubber are substantially the same.

  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.

DESCRIPTION OF SYMBOLS 1 Rigid core 2 Core body 5 Core segment 11 Coating layer 11A Tread coating layer part 11B Side coating layer part B Vulcanization mold S Tire molding surface S1 Tread molding surface part S2 Side molding surface part T Raw tire

Claims (1)

An annular core body having a tire molding surface for forming a green tire is provided on the outer surface, and the raw tire is inserted into the vulcanization mold so that the vulcanization mold and the core body A rigid core for vulcanizing the green tire,
The core body is composed of a plurality of core segments divided in the circumferential direction,
And a coating layer having rubber releasability is formed on the tire molding surface,
The tire molding surface includes a tread molding surface portion that molds an inner surface of a tire tread portion, and side molding surface portions arranged on both sides thereof.
And the coating layer comprises a tread coating layer portion formed on the tread molding surface portion, and a side coating layer portion formed on the side molding surface portion,
Moreover, the tire tread coating layer portion has a rubber release property greater than that of the side coating layer portion.

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