JP2015208858A - Rigid core for tire molding and tire production method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of the uniformity of tires by dispersing effects of the level difference between core segments in a circumferential direction.SOLUTION: A core body 2 consists of a first core segment 5A which increases in the circumferential-direction width between divided surfaces 6 and 6 toward the inner side in the radial direction, in an arbitrary cross-section K orthogonal to the tire axis i, and a second core segment 5B which decreases in the circumferential-direction width between the divided surfaces 6 and 6 toward the inner side in the radial direction. The outer periphery division line 7o on which the division surface 6 and the outer peripheral surface So of the core segment 6 intersect each other is inclined to the tire axial-direction line X.

Description

  The present invention relates to a rigid core for forming a tire that suppresses a decrease in tire uniformity due to a split surface of a core body, and a tire manufacturing method using the same.

  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 Document 1). The rigid core includes a core body having an outer shape that approximates the lumen of the vulcanized tire, and a tire component is sequentially affixed on the core body to form a raw tire. Further, by putting the green tire together with the rigid core into the vulcanization mold, the green tire is vulcanized and sandwiched between the core body and the vulcanization mold.

  On the other hand, as shown in FIG. 8 (A), the core body a is divided into a plurality of core segments b in the circumferential direction so that it can be disassembled and removed from the tire after vulcanization molding. Specifically, the core segment b includes a first core segment b1 in which the circumferential width between the divided surfaces s at both ends in the circumferential direction increases toward the inner side in the tire radial direction, and the circumferential width between the divided surfaces. Decreases inward in the tire radial direction, and the first core segment b1 includes second core segments b2 that are alternately arranged in the circumferential direction. Thereby, it can move one by one in the radial direction sequentially from the first core segment b1, and the core body a can be disassembled and removed from the tire.

  On the other hand, as shown exaggeratedly in FIG. 8 (B), in the core body a, the radial position between the core segments b1 and b2 due to the gap between the split surfaces s and s and thermal expansion during vulcanization. There is a tendency for deviation to occur, and this positional deviation becomes a step e and appears on the outer peripheral surface.

  However, in the conventional core segment b, the dividing surface s is formed as a plane parallel to the tire axis i. For this reason, the step e also appears along the tire axial direction on the outer peripheral surface. As a result, the influence on the uniformity in the tire circumferential direction is increased, and there arises a problem that the uniformity of the tire is lowered.

JP2013-006326A

  Therefore, the present invention can reduce the influence of a step between core segments in the circumferential direction, and can suppress the decrease in tire uniformity, and a tire forming rigid core, and a tire manufacturing method using the same It is an issue to provide.

The first invention of the present application includes an annular core body having a tire molding surface portion forming a green tire on the outer surface, and the raw tire is put into the vulcanization mold together with the vulcanization mold, A rigid core that vulcanizes and molds the green tire with the core body,
The core body is composed of a plurality of core segments divided in the circumferential direction by a dividing surface;
And the core segment is
In an arbitrary cross section orthogonal to the tire axis, the circumferential width between the divided surfaces at both ends in the circumferential direction increases toward the inner side in the tire radial direction, whereby the first pullable in the pulling direction toward the tire axis is performed. The core segment,
In an arbitrary cross section orthogonal to the tire axis, the circumferential width between the divided surfaces at both ends in the circumferential direction decreases toward the inner side in the tire radial direction, and the first segments are alternately arranged in the circumferential direction. The second core segment,
In addition, the outer peripheral dividing lines at which the dividing surfaces and the outer peripheral surfaces of the core segments intersect each other are inclined with respect to the tire axial direction line.

  In the rigid core for forming a tire according to the present invention, each of the outer circumferential dividing lines preferably has an angle θ with respect to a tire axial line in a range of 10 to 60 degrees.

  In the rigid core for forming a tire according to the present invention, it is preferable that each of the divided surfaces forms a straight line in an arbitrary cross section orthogonal to the tire axis.

  In the rigid core for forming a tire according to the present invention, it is preferable that each of the divided surfaces is a twisted surface.

  In the tire-forming rigid core according to the present invention, the end point on one side in the tire axial direction of one outer circumferential dividing line is the tire on the other outer circumferential dividing line in the other outer circumferential dividing line adjacent in the circumferential direction. It is preferable to be located on the tire axial line passing through the end point on the other side in the axial direction.

  2nd invention of this application is a manufacturing method of a tire, Comprising: The raw tire formation process which forms a raw tire using the rigid core of 1st invention, and vulcanized gold | metal | money with the rigid core formed said raw tire And a vulcanization step in which the raw tire is heated and vulcanized.

  In the present invention, as described above, the outer peripheral dividing line where the dividing surface and the outer peripheral surface of the core segment intersect is inclined with respect to the tire axial direction line. Therefore, when a step between core segments occurs on the outer peripheral surface of the core body, this step also appears inclined with respect to the tire axial line. That is, the steps appear continuously with a certain width in the circumferential direction. Therefore, the influence on the uniformity and roundness of the tread thickness can be mitigated in the circumferential direction, and a decrease in tire uniformity can be suppressed.

It is sectional drawing which shows the use condition of one Example of the rigid core of this invention. It is a perspective view of a core main body. It is a fragmentary sectional view which shows the arbitrary cross sections orthogonal to the tire axial center in a core main body. It is a perspective view which shows the 1st and 2nd core segment typically. (A)-(D) are the conceptual diagrams which show the upper surface, the cross section K1, the cross section K2, and the bottom face of the core main body 2 in FIG. It is a perspective view which shows the other example of a core main body. It is a perspective view which shows the core main body used for Example 1 of Table 1. FIG. (A) is a side view of the conventional core main body, (B) is a perspective view of the core main body exaggerating the level difference.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, a rigid core 1 for forming a tire according to this embodiment includes an annular core body 2 having a tire molding surface portion 2S 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 pasted on the tire molding surface portion 2S, thereby forming a green tire T having substantially the same shape as the finished tire. Further, the raw tire T is put together with the rigid core 1 into the vulcanization mold B, and the raw tire T is heated and pressurized between the core body 2 and the vulcanization mold B to perform vulcanization molding. Done.

  The rigid core 1 of this example includes the annular core body 2 and a cylindrical core 3 that is inserted into the center hole 2H. Since the conventional well-known structure can be adopted except for the core body 2, only the core body 2 will be described below.

  As shown in FIG. 2, the core body 2 includes a plurality of core segments 5 that are divided in the circumferential direction by the dividing surface 6, and the core segments 5 are first arranged alternately in the circumferential direction. , Second core segments 5A and 5B. In this example, an airtight chamber chamber 4 for heating (indicated by a one-dot chain line in FIG. 1) filled with a thermal fluid such as steam is formed inside each core segment 5A, 5B. Each chamber 4 is connected to a thermal fluid supply source (not shown) via an appropriate flow path. In addition to the thermal fluid, known heating means such as an electric heater can also be used.

  FIG. 3 shows a part of an arbitrary cross section K perpendicular to the tire axis i in the core body 2. As shown in FIG. 3, the first core segment 5A has a circumferential width between the dividing surfaces 6 and 6 at both ends in the circumferential direction at the inner side in the tire radial direction in an arbitrary cross section K orthogonal to the tire axis i. It is increasing towards. Accordingly, the first core segment 5A can be pulled out in the pulling direction F facing the tire axis i. That is, the core body 2 can be disassembled. The upper edge 6ju where the dividing surface 6 intersects the upper surface Su of the core body 2 is indicated by a one-dot chain line. In this example, a case where the drawing direction F passes on a bisector between the upper edges 6ju and 6ju is shown. 5A to 5D conceptually show the top surface, the cross section K1, the cross section K2, and the bottom surface of the core body 2 in FIG. In each surface, the circumferential width between the divided surfaces 6 and 6 at both circumferential ends of the first core segment 5A increases toward the inner side in the tire radial direction.

  In the second core segment 5B, in an arbitrary cross section K orthogonal to the tire axis i, the circumferential width between the dividing surfaces 6 and 6 at both ends in the circumferential direction decreases toward the inner side in the tire radial direction. Yes.

  FIG. 4 is a perspective view schematically showing a part of the core body 2, and as shown in FIGS. 2 and 4, an outer peripheral division in which the division surface 6 and the outer peripheral surface So of the core segment 5 intersect each other. Each of the lines 7o is inclined with respect to the tire axial line X. The tire axial direction line X means a line extending in the tire axial direction on the outer peripheral surface So of the core segment 5.

  Thus, the following effects are acquired when the outer periphery dividing line 7o inclines with respect to the tire axial direction line X. FIG. When a radial position shift occurs between the core segments 5A and 5B due to thermal expansion during vulcanization, the position shift appears as a step on the outer peripheral surface So. However, in the present invention, this level difference occurs obliquely along the outer peripheral dividing line 7o. That is, the steps appear continuously with a certain width W in the circumferential direction. Therefore, the influence on the uniformity and roundness of the tread thickness can be mitigated in the circumferential direction, and a decrease in tire uniformity can be suppressed.

  At this time, the angle θ of the outer circumferential dividing line 7o with respect to the tire axial direction line X is preferably in the range of 10 to 60 degrees. When the angle θ is less than 10 degrees, the effect of suppressing the decrease in uniformity is not sufficiently exhibited. If the angle θ exceeds 60 degrees, there is a possibility that the core body 2 cannot be disassembled by sequentially pulling it out from the first core segment 5A. The angle θ need not be constant and can vary within the range. In addition, in the outer peripheral dividing lines 7o and 7o adjacent in the circumferential direction, it is preferable from the viewpoint of suppressing reduction in uniformity to make the angle θ of one outer peripheral dividing line 7o different from the angle θ of the other outer peripheral dividing line 7o. .

  The dividing surface 6 may be a flat surface, but is preferably a twisted surface in order to increase the degree of design freedom. In the case where the dividing surface 6 is a twisted surface, it is preferable that the dividing surface 6 is a straight line in an arbitrary cross section K orthogonal to the tire axis i in order to improve the resolvability of the core body 2.

Further, from the viewpoint of decomposability, as shown in FIG. 3, it is necessary to satisfy the following condition A in an arbitrary cross section K orthogonal to the tire axis i. That is,
Pi, Pi, the inner peripheral dividing points on both sides where the dividing surfaces 6, 6 on both sides of the first core segment 5A intersect the inner peripheral surface Si of the core segment 5A
-Po and Po are the outer peripheral dividing points on both sides where the dividing surfaces 6 and 6 on both sides intersect the outer peripheral surface So of the core segment 5A.
-When the reference lines parallel to the drawing direction F through Po and Po through the outer peripheral dividing points on both sides are J and J,
The inner peripheral dividing points Pi and Pi need to be located outside the reference lines J and J on both sides. Thus, the first core segment 5A can be pulled out in the pulling direction F, and the core body 2 can be disassembled. The inner circumferential dividing line 7i where the dividing surface 6 and the inner circumferential surface Si intersect is not particularly restricted as long as the condition A is satisfied.

  FIG. 6 shows another example of the core body 2. In this example, in the other peripheral dividing line 7o1, 7o2 adjacent in the circumferential direction, an end point EL on one side (lower side in this example) of one outer peripheral dividing line 7o1 is the other outer peripheral dividing line. 7o2 is located on the tire axial direction line X passing through the end point EU on the other side in the tire axial direction (upper side in this example). Thereby, the outer periphery dividing line 7o is continuously arranged over the circumference. As a result, the reduction in uniformity can be more effectively exhibited.

  The tire manufacturing method includes a green tire forming process and a vulcanizing process. In the green tire forming process, tire constituent members such as carcass ply, belt ply, sidewall rubber, and tread rubber are sequentially pasted on the tire molding surface portion 2S of the core body 2 in the rigid core 1 to obtain a finished tire. A green tire T having substantially the same shape is formed. In the vulcanization step, the raw tire T is put together with the rigid core 1 into the vulcanization mold B, and the raw tire T is heated and pressurized between the core body 2 and the vulcanization mold B. Vulcanization molding is performed.

  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.

  In order to confirm the effect of the present invention, a core body for forming a pneumatic tire having a tire size of 205 / 65R15 was prototyped based on the specifications shown in Table 1. And the uniformity of the pneumatic tire manufactured using this core main body was tested, and it mutually compared. In each core body, the number of divisions of the core segment is 8, and the position of the upper edge of the dividing surface is the same in each core body. Except for the description in Table 1, the specifications are substantially the same.

(1) Uniformity:
Using a uniformity testing machine, the radial force variation (RFV) of the sample tires (10 tires each) was measured in accordance with JASO C607: 2000 uniformity testing conditions, and the average values were compared with each other. The measurement conditions are a rim (15 × 6 J), an internal pressure (200 kPa), and a speed (120 km / h).

  As shown in the table, it can be confirmed that the tires of the examples have reduced RFV and improved uniformity.

DESCRIPTION OF SYMBOLS 1 Rigid core 2 Core body 2S Tire shaping | molding surface part 5 Core segment 5A 1st core segment 5B 2nd core segment 6 Split surface 7o Peripheral parting line B Vulcanization metal mold EU, EL End point F Pull-out direction i Tire axis K, K1, K2 Cross section So Outer peripheral surface T Raw tire X Tire axial line

Claims (6)

An annular core body having a tire molding surface portion for forming a raw tire on the outer surface is provided, and the raw tire is inserted into the vulcanization mold so that the vulcanization mold and the core body are interposed between 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 by a dividing surface;
And the core segment is
In an arbitrary cross section orthogonal to the tire axis, the circumferential width between the divided surfaces at both ends in the circumferential direction increases toward the inner side in the tire radial direction, whereby the first pullable in the pulling direction toward the tire axis The core segment,
In an arbitrary cross section orthogonal to the tire axis, the circumferential width between the divided surfaces at both ends in the circumferential direction decreases toward the inner side in the tire radial direction, and the first segments are alternately arranged in the circumferential direction. The second core segment,
In addition, the tire-forming rigid core is characterized in that the outer peripheral dividing lines where the dividing surface and the outer peripheral surface of the core segment intersect with each other are inclined with respect to the tire axial direction line.   2. The rigid core for forming a tire according to claim 1, wherein each of the outer circumferential dividing lines has an angle θ of 10 to 60 degrees with respect to a tire axial line.   The rigid core for forming a tire according to claim 1 or 2, wherein each of the dividing surfaces forms a straight line in an arbitrary cross section perpendicular to the tire axis.   The rigid core for forming a tire according to claim 3, wherein each of the divided surfaces includes a twisted surface.   In the other peripheral dividing line adjacent in the circumferential direction, the end point on one side in the tire axial direction of one outer peripheral dividing line is positioned on the tire axial line passing through the end point on the other side in the tire axial direction of the other outer peripheral dividing line The rigid core for forming a tire according to any one of claims 1 to 4, wherein: A raw tire forming step of forming a raw tire using the rigid core according to claim 1, and the formed raw tire together with the rigid core is placed in a vulcanization mold to heat the raw tire. A tire manufacturing method comprising: a vulcanizing step of vulcanizing.

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