WO2013108537A1

WO2013108537A1 - Rigid core for tire formation

Info

Publication number: WO2013108537A1
Application number: PCT/JP2012/082953
Authority: WO
Inventors: 圭小原
Original assignee: 住友ゴム工業株式会社
Priority date: 2012-01-18
Filing date: 2012-12-19
Publication date: 2013-07-25
Also published as: JP2013146905A; JP5444385B2; CN103459131A; CN103459131B

Abstract

In order to suppress inflow of rubber to an exhaust groove, a core body comprises a plurality of core segments divided in the circumferential direction, and an exhaust grooves having an open end opening in a core-side tire molding face are arranged on the mating face of at least one of core segments adjacent in the circumferential direction. The exhaust groove comprises a tread exhaust groove, the open end of which opens in a portion of a core-side tread molding face, and/or a side exhaust groove which opens in a portion of a core-side side molding face. The tread exhaust groove has an inclined groove portion extending at an angle (θ1) in relation to the radial direction of the tire from the open end, and the side exhaust groove has an inclined groove portion extending at an angle (θ2) in relation to the axial direction of the tire from the open end.

Description

Rigid core for tire formation

The present invention relates to a rigid core for forming a tire in which exhaust grooves are formed on a mating surface of core segments.

Recently, a tire forming method using a rigid core (hereinafter sometimes referred to as a core method) has been proposed in order to improve the accuracy of tire formation (see, for example, Patent Documents 1 and 2). The rigid core includes a core body having an outer shape that matches a shape of a tire lumen surface of a vulcanized tire. And a raw tire is formed by affixing a tire structural member on this core main body one by one. This green tire is put together with a rigid core into a vulcanization mold, and is thereby sandwiched between an inner core body and an outer vulcanization mold so that the green tire is vulcanized. Molded.

As shown in FIG. 7A, in order to disassemble and remove the core body a from the tire after vulcanization, the core body a is divided into a plurality of core segments c divided in the circumferential direction. It is configured. The core main body a is formed in an annular shape by setting both end surfaces in the circumferential direction of each core segment c as mating surfaces cs and adjoining the mating surfaces cs and cs adjacent in the circumferential direction.

In the core method, it is desired to discharge air between the core body a and the green tire during vulcanization molding in order to further improve the tire formation accuracy. For this reason, the inventor has proposed that an exhaust groove d be provided in at least one of the mating surfaces cs of the core segment c as shown in FIG. 7B.

However, not only air but also rubber flows into the exhaust groove d. For example, when the cross-sectional volume of the exhaust groove d is large, the inflowing rubber is thick and strong. Therefore, the rubber is hardly broken even if it is burned with the wall surface of the exhaust groove d. Therefore, after vulcanization, the rubber can be taken out integrally with the tire without adhering to the wall surface of the exhaust groove d. However, since this rubber (spy) is thick and large, it can cause tire vibration.

Conversely, when the cross-sectional volume of the exhaust groove d is small, the inflowing rubber is thin and weak. For this reason, the rubber is easily burned by scorching on the wall surface of the exhaust groove d. Accordingly, after the vulcanization, the broken rubber adheres to the wall surface of the exhaust groove d, and the amount of adhesion increases as the number of vulcanizations increases. As a result, the exhaust groove d is blocked and exhaust performance is impaired. Further, when the broken rubber piece enters between the mating surfaces cs and cs, the roundness of the core body a is impaired, and the tire forming accuracy is lowered. Further, in order to prevent this, frequent cleaning of the core segment c is necessary, but this reduces the tire production efficiency.

Therefore, in the exhaust groove d, it is desired to reduce the cross-sectional volume as much as possible to suppress the inflow of rubber. However, in that case, the exhaust performance is also lowered, and the tire has a sufficiently satisfactory effect such as causing deformation due to air accumulation. I can't get it.

In Patent Document 1, each core segment is further divided into side segment pieces on both sides in the tire axial direction and intermediate segment pieces therebetween, and an exhaust passage for exhausting air is formed between the divided surfaces. It has been proposed. In this case, the side segment piece and the intermediate segment piece are integrally connected by a bolt. However, since large thermal expansion repeatedly occurs, there is a problem that the strength of the connecting portion becomes insufficient and the durability of the core segment is lowered. In addition, the inflow of rubber into the exhaust passage is still not taken into consideration.

JP 2011-161896 A JP 2011-167799 A

Accordingly, the present invention can suppress the inflow of rubber into the exhaust groove while maintaining a sufficient exhaust performance by securing a cross-sectional volume of the exhaust groove to some extent, and solves the above-mentioned problems caused by the inflow of rubber. An object of the present invention is to provide a rigid core for forming a tire.

In order to solve the above-mentioned problems, the invention of claim 1 of the present application includes an annular core body having a core-side tire molding surface for forming a green tire on the outer surface, and the raw tire is placed in a vulcanization mold. A rigid core that vulcanizes and molds the green tire between the vulcanization mold and the core body,
The vulcanization mold includes a tread mold that can move in and out of the tire radial direction, and a side mold that can move in and out of the tire axial direction,
The tread mold has a mold side tread molding surface portion that molds the outer surface of the tire tread by being pressed against the raw tire,
And the side mold has a mold side side molding surface part for molding the side outer surface of the tire by being pressed against the raw tire,
The core side tire molding surface is a normal line extending in a direction perpendicular to the core side tire molding surface through a boundary position between the mold side tread molding surface portion and the mold side side molding surface portion. Of the core side tread molding surface portion and the core side side molding surface portion outside the normal line,
The core body is composed of a plurality of core segments divided in the circumferential direction,
Each of the core segments forms an annular core body by attaching the circumferentially adjacent mating surfaces to each other with the circumferential ends of the core segment as mating surfaces.
On at least one mating surface of the mating surfaces adjacent in the circumferential direction, at least one exhaust groove extending on the mating surface is disposed,
The exhaust groove has an opening end that opens at the core-side tire molding surface, and exhausts air between the core-side tire molding surface and the raw tire from the opening end to the inside of the core body,
The exhaust groove includes a tread exhaust groove whose opening end opens at the core-side tread molding surface portion and / or a side exhaust groove which opens at the core-side side molding surface portion,
The tread exhaust groove has an inclined groove portion extending at an angle θ1 with respect to the tire radial direction line from the opening end,
Further, the side exhaust groove has an inclined groove portion that extends at an angle θ2 with respect to the tire axial direction line from the opening end.

Further, in claim 2, the angle θ1 of the tread exhaust groove is in the range of 30 to 80 °, and the angle θ2 of the side exhaust groove is in the range of 30 to 80 °.

According to a third aspect of the present invention, the exhaust groove includes the tread exhaust groove and a side exhaust groove, and the tread exhaust groove includes a tread exhaust groove whose opening end is disposed at a tire equator position, The exhaust groove includes a side exhaust groove in which the opening end is disposed at the maximum width position in the tire axial direction of the core side side molding surface portion.

In claim 4, the exhaust groove has a groove cross-sectional area perpendicular to the length direction of 0.03 mm 2 or less.

In the present invention, as described above, an exhaust groove is recessed in at least one of the mating surfaces of the core segments adjacent in the circumferential direction. The exhaust groove includes a tread exhaust groove having an open end in the core side tread molding surface portion and / or a side exhaust groove having an open end in the core side side molding surface portion. The tread exhaust groove has an inclined groove portion extending from the opening end thereof at an angle θ1 with respect to the tire radial direction line. The side exhaust groove has an inclined groove portion extending from the opening end thereof at an angle θ2 with respect to the tire axial direction line.

The vulcanization mold includes a tread mold that can move in and out of the tire radial direction and a side mold that can move in and out of the tire axial direction. At the time of vulcanization molding, the rubber of the raw tire is strongly pressed inward in the tire radial direction by the tread mold at a portion where the rubber comes into contact with the tread mold. Therefore, if the opening end side of the tread exhaust groove extends along the tire radial direction, the direction of the strong pressing force by the tread mold matches the direction of the exhaust groove. For this reason, the rubber easily flows into the exhaust groove. Similarly, the rubber of the raw tire is strongly pressed inward in the tire axial direction by the side mold at the portion that comes into contact with the side mold. Therefore, if the opening end side of the side exhaust groove extends along the tire axial direction, the direction of the strong pressing force by the side mold coincides with the direction of the exhaust groove. For this reason, the rubber easily flows into the exhaust groove.

However, in the present invention, the opening end side portions of the tread exhaust groove and the side exhaust groove are inclined at the angles θ1 and θ2, respectively. That is, the portion on the opening end side extends in a direction different from the strong pressing force. Therefore, it is possible to suppress only the inflow of rubber without hindering the inflow of air. This occurs because the rubber has a much higher viscosity than air. By making the opening end side portion of the exhaust groove different from the direction in which a strong pressing force is applied, the difference in the direction becomes resistance, and the inflow of high viscosity rubber can be suppressed. Moreover, it does not become resistance to air with low viscosity, and the inflow is not hindered. Therefore, the exhaust performance can be exhibited effectively.

As a result, the amount of rubber adhering to the wall surface of the exhaust groove increases with an increase in the number of vulcanizations, and exhaust failure due to the exhaust groove being blocked can be suppressed. In addition, it is possible to suppress a decrease in the roundness of the core body caused by the adhering rubber being broken and entering between the mating surfaces. Moreover, since frequent cleaning of the intermediate segment pieces is not necessary, continuous production for a long time is possible. Moreover, since no thick spew is generated on the inner surface of the product tire, the tire quality can be maintained high.

It is sectional drawing which shows the use condition of one Example of the rigid core of this invention. (A), (B) is the perspective view and side view of a core main body. (A), (B) is the perspective view and front view which show the mating surface of a core segment with an exhaust groove. (A) to (D) are cross-sectional views illustrating the cross-sectional shape of the exhaust groove. (A), (B) is the perspective view which shows the other Example of a core segment, and a front view. (A), (B) is the perspective view and front view which show other Example of a core segment. (A) is a side view which shows the conventional core main body, (B) is a perspective view which shows exhaust grooves other than this invention.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the rigid core 1 of the present embodiment includes an annular core body 2 having a core-side tire molding surface 2S on the outer surface. A known tire component such as a carcass ply, a belt ply, sidewall rubber, and tread rubber is sequentially attached onto the core-side tire molding surface 2S, thereby forming a green tire T having substantially the same shape as the finished tire. Is done.

The raw tire T is put into the vulcanizing mold 20 together with the rigid core 1. The green tire T is heated and pressurized between the core body 2 that is the inner mold and the vulcanization mold 20 that is the outer mold, and vulcanized.

The vulcanizing mold 20 has a conventional well-known structure, and includes a tread mold 21 that can move in and out in the tire radial direction and

side molds

22 and 22 that can move in and out in the tire axial direction. The tread mold 21 has a mold side tread molding surface portion 21S. The tread outer surface Ta of the tire T is molded by pressing the mold side tread molding surface portion 21S toward the inner side in the tire radial direction. The side mold 22 has a mold side molding surface portion 22S. The side outer surface Tb of the tire T is molded by pressing the mold side molding surface portion 22S inward in the tire axial direction.

Next, the rigid core 1 includes the annular core body 2 and a cylindrical core 3 inserted into the center hole 2H. Other than the core body 2, a conventional well-known structure can be adopted. Therefore, only the core body 2 will be described below.

The core body 2 includes the core-side tire molding surface 2S on the outer surface thereof, which is substantially the same shape as the inner surface shape of the finished tire. As shown in FIG. 1, the core side tire molding surface 2S is virtually divided into a core side tread molding surface portion 2Sa and a core side side molding surface portion 2Sb by a normal line N. The normal line N is defined as a straight line extending in a direction orthogonal to the core-side tire molding surface 2S through a boundary position P between the mold-side tread molding surface portion 21S and the mold-side side molding surface portion 22S. And the part between the said normal lines N and N among the core side tire molding surfaces 2S is defined as the core side tread molding surface part 2Sa. Further, the portion outside the normal line N is defined as the core side side molding surface portion 2Sb.

In this example, the core body 2 has a hollow shape with a lumen 4 extending continuously in the circumferential direction, for example. A heating means (not shown) such as an electric heater for heating the raw tire T inside is disposed in the lumen 4.

The core body 2 is formed of a plurality of core segments 5 divided in the circumferential direction, as shown in FIGS. 2 (A) and 2 (B). Each core segment 5 has both end surfaces in the circumferential direction as mating surfaces 6, and the mating surfaces 6, 6 adjacent in the circumferential direction are attached to each other, whereby the annular core body 2 is formed.

In this example, the core segment 5 is composed of first and

second core segments

5A and 5B that are alternately arranged in the circumferential direction. The mating surface 6 of the first core segment 5A is inclined in the direction in which the circumferential width decreases toward the inside in the radial direction. On the other hand, the mating surface 6 of the second core segment 5B is inclined in a direction in which the circumferential width increases inward in the radial direction. Thereby, it can move to the inner side in the radial direction sequentially from the second core segment 5B, and can be sequentially taken out from the bead hole of the finished tire T after vulcanization molding. The core 3 prevents the core segments 5 from moving inward in the radial direction and connects the core segments 5 together.

In the present invention, at least one exhaust groove 11 is recessed on at least one of the mating surfaces 6 adjacent in the circumferential direction, as shown in FIGS. The The exhaust groove 11 has an opening end 12 that opens at the core-side tire molding surface 2S. The air between the core side tire molding surface 2S and the raw tire T is exhausted from the opening end 12 through the exhaust groove 11 to the inside of the core body 2. The other end of the exhaust groove 11 communicates with the lumen portion 4 in this example, and the lumen portion 4 conducts to the outside air.

Specifically, the exhaust groove 11 includes a tread exhaust groove 11A whose opening end 12 opens at the core side tread molding surface portion 2Sa and / or a side exhaust groove 11B which opens at the core side side molding surface portion 2Sb.

Preferably, the exhaust groove 11 is formed of a tread exhaust groove 11A and a side exhaust groove 11B. More preferably, the tread exhaust groove 11A includes an equatorial tread exhaust groove 11Ac, and the side exhaust groove 11B includes a maximum width position side exhaust groove 11Bq. The tread exhaust groove 11Ac at the equator position means the tread exhaust groove 11A in which the opening end 12 is disposed at the position of the tire equator Co. The side exhaust groove 11Bq at the maximum width position means the side exhaust groove 11B in which the opening end 12 is disposed at the maximum width position Q in the tire axial direction of the core side side molding surface portion 2Sb.

In this example, the exhaust groove 11 is composed of one tread exhaust groove 11A and two side exhaust grooves 11B, and this one tread exhaust groove 11A is formed as a tread exhaust groove 11Ac at the equator position. Moreover, the case where the two side exhaust grooves 11B are formed as the side exhaust grooves 11Bq at the maximum width position is shown.

The tread exhaust groove 11A has an inclined groove portion 13 extending from the opening end 12 at an angle θ1 with respect to the tire radial direction line. The side exhaust groove 11B has an inclined groove portion 14 extending from the opening end 12 with an angle θ2 with respect to the tire axial direction line.

As described above, the tread exhaust groove 11A includes the inclined groove portion 13 on the opening end 12 side, and the inclined groove portion 13 is inclined at an angle θ1 with respect to the tire radial direction which is a direction of a strong pressing force by the tread mold 21. Therefore, the angle θ1 becomes a resistance, and the inflow of rubber having a high viscosity can be suppressed. Similarly, the side exhaust groove 11B includes an inclined groove portion 14 on the opening end 12 side, and the inclined groove portion 14 is inclined at an angle θ2 with respect to the tire axial direction that is a direction of a strong pressing force by the side mold 22. Therefore, the angle θ2 becomes a resistance, and the inflow of rubber having a high viscosity can be suppressed.

The angles θ1 and θ2 are each preferably in the range of 30 to 80 °. If the angles [theta] 1 and [theta] 2 are less than 30 [deg.], The resistance becomes small and the rubber inflow suppressing effect cannot be sufficiently achieved. Conversely, when it exceeds 80 °, the intersection of the core-side tire molding surface 2S and the exhaust groove 11 has a sword tip shape. As a result, the crossing portion is insufficient in strength, which may lead to a decrease in durability. From such a viewpoint, the lower limit values of the angles θ1 and θ2 are more preferably 45 ° or more, and the upper limit value is more preferably 70 ° or less.

As the exhaust groove 11, the entire length can be formed only by the inclined groove portion 14 as in the side exhaust groove 11B of this example. Further, like the tread exhaust groove 11 </ b> A of this example, it can also be formed in a bent groove shape including an inclined groove portion 13 and a joint groove portion 15 connected to the inclined groove portion 13. When the joint groove portion 15 is formed, it is not particularly restricted, but it is preferably formed at the shortest distance toward the inside of the core body 2 (in this example, the lumen portion 4).

Examples of the groove cross-sectional shape perpendicular to the length direction of the exhaust groove 11 include, for example, a cross-sectional triangle shape (FIG. 4A), a cross-sectional square shape (FIGS. 4B and 4C), and a semicircular arc shape (FIG. 4 (D)) can be employed. However, the cross-sectional triangle shape is preferable from the viewpoint of workability. In the case of a triangular cross section, an isosceles triangular shape is preferable to an equilateral triangle with less rubber inflow when the cross sectional area is the same. In particular, it is preferable that the base m1 is the opening side and is shorter than the other oblique sides m2 in order to stably suppress the inflow of rubber. In addition, in the case of a rectangular cross section, a rectangular shape is more suitable than a square when the cross-sectional area is the same. This is preferable.

The effect of suppressing the inflow of rubber by the

inclined groove portions

13 and 14 is also limited, and if the groove cross-sectional area is too large, the effect of suppressing the effect is not sufficiently exhibited. Therefore, the groove cross-sectional area is preferably 0.03 mm ² . On the other hand, if the groove cross-sectional area is too small, an advanced processing technique is required and exhaust performance is reduced. Accordingly, the lower limit of the groove cross-sectional area is preferably 0.02 mm ² or more. At this time, it is preferable that the length of any one side in the cross-sectional shape (the length of the oblique side m2 and the long side n2 in this example) is 0.1 mm or more.

The exhaust groove 11 may be provided on at least one of the mating surfaces 6 adjacent in the circumferential direction. In addition, when forming the exhaust groove 11 in both the mating surfaces 6, it is preferable to make the position of the opening end 12 mutually different.

FIGS. 5 and 6 show another embodiment of the core segment 5. In FIG. 5, the end surfaces 18 on both sides in the circumferential direction of the core segment 5 include an edge surface portion 18A along the outer periphery, and a recessed surface portion 18B surrounded by the edge surface portion 18A and recessed from the edge surface portion 18A in a step shape. It is formed as a stepped surface. In this case, the mating surface 6 is constituted by the edging surface portion 18A. Further, the exhaust groove 11 is formed in the edge surface portion 18A. In the present example, the other end of the exhaust groove 11 is electrically connected to the recessed surface portion 18B, and the recessed surface portion 18B is electrically connected to the outside air.

In FIG. 6, the core segment 5 has the entire end face 18 on both sides in the circumferential direction as the mating face 6. In this example, the other end of the exhaust groove 11 communicates with the radially inner end 18e of the end face 18, and the radially inner end 18e is electrically connected to the outside air.

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 195 / 65R15 was prototyped based on the specifications shown in Table 1. And when a pneumatic tire is formed using this core body, the rubber flows into the exhaust groove, the seized state in which the rubber that has flowed in adheres to the groove wall surface, and the exhaust performance decreases due to seizure. The state of occurrence of air pockets was evaluated.

Each core body is made of aluminum (coefficient of thermal expansion = 23.1 × 10 ⁻⁶ / degree), and is divided into 10 core segments as shown in FIG. A green tire is formed on the core body at room temperature (20 ° C.). The inside of the vulcanization mold is heated to a high temperature of 150 ° C. Except as described in Table 1, the specifications are substantially the same. The test method was as follows, and each evaluation was performed in the tread exhaust groove at the equator position.

(1) Rubber flowing in:
The amount of spew (rubber amount) generated on the tire side by the inflow of rubber into the exhaust groove is compared. Specifically, vulcanization was carried out 1000 times continuously, and the amounts of spews at the first, 300th, 600th, and 1000th times were quantified and evaluated. A numerical value shows that there are few inflows and it is so favorable that it is large.

(2) Burn-in condition:
The amount of seizure of the rubber that has flowed into the exhaust groove and sticks to the groove wall surface is compared. Specifically, vulcanization was performed continuously 1000 times, and the amount of seizure in the first, 300th, 600th, and 1000th times was quantified and evaluated. The larger the numerical value, the smaller the amount of image sticking and the better.

(3) Air accumulation occurrence state:
The state of occurrence of air pockets due to the rubber sticking to the groove wall surface due to seizure and lowering the exhaust performance is compared. Specifically, vulcanization was continuously performed 1000 times, and the deformation state of the tire caused by air accumulation was numerically evaluated in each of the first, 300th, 600th, and 1000th times. The larger the numerical value, the better the less air accumulation.

As shown in Table 1, the rigid core of the example is provided with an inclined groove portion of a predetermined angle in the exhaust groove, so that the rubber can be prevented from flowing into the exhaust groove, and the occurrence of spew on the tire. It can be confirmed that the seizure of rubber in the exhaust groove and the clogging of the exhaust groove due to this can be effectively suppressed. Further, it can be confirmed that the groove cross-sectional shape is excellent in the order of FIG. 4 (A)> FIG. 4 (B)> FIG. 4 (D) ≧ FIG.

DESCRIPTION OF SYMBOLS 1 Rigid core 2 Core body 2S Core side tire molding surface 2Sa Core side tread molding surface part 2Sb Core side side molding surface part 5 Core segment 6 Matching surface 11 Exhaust groove 11A Tread exhaust groove 11Ac Tread exhaust groove 11B at the equator position Side exhaust Groove 11Bq Side exhaust groove 12 at maximum width

position Open end

13, 14 Inclined groove 20 Vulcanizing mold 21S Mold side tread molding surface 21 Tread mold 22S Mold side side molding surface 22 Side mold N Normal line P Boundary position T tire

Claims

An annular core body having a core-side tire molding surface for forming a green tire is provided on the outer surface, and the vulcanized mold and the core body are inserted into the vulcanization mold together with the green tire A rigid core that vulcanizes and molds the green tire,
The vulcanization mold includes a tread mold that can move in and out of the tire radial direction, and a side mold that can move in and out of the tire axial direction,
The tread mold has a mold side tread molding surface portion that molds the outer surface of the tire tread by being pressed against the raw tire,
And the side mold has a mold side side molding surface part for molding the side outer surface of the tire by being pressed against the raw tire,
The core side tire molding surface is a normal line extending in a direction perpendicular to the core side tire molding surface through a boundary position between the mold side tread molding surface portion and the mold side side molding surface portion. Of the core side tread molding surface portion and the core side side molding surface portion outside the normal line,
The core body is composed of a plurality of core segments divided in the circumferential direction,
Each of the core segments forms an annular core body by attaching the circumferentially adjacent mating surfaces to each other with the circumferential ends of the core segment as the mating surfaces.
On at least one mating surface of the mating surfaces adjacent in the circumferential direction, at least one exhaust groove extending on the mating surface is disposed,
The exhaust groove has an opening end that opens at the core-side tire molding surface, and exhausts air between the core-side tire molding surface and the raw tire from the opening end to the inside of the core body,
The exhaust groove includes a tread exhaust groove whose opening end opens at the core-side tread molding surface portion and / or a side exhaust groove which opens at the core-side side molding surface portion,
The tread exhaust groove has an inclined groove portion extending at an angle θ1 with respect to the tire radial direction line from the opening end,
The side exhaust groove has an inclined groove portion extending at an angle θ2 with respect to the tire axial line from the opening end, and is a rigid core for tire formation.
The tire forming rigidity according to claim 1, wherein the tread exhaust groove angle θ1 is in a range of 30 to 80 °, and the side exhaust groove angle θ2 is in a range of 30 to 80 °. Child.
The exhaust groove includes the tread exhaust groove and a side exhaust groove, and the tread exhaust groove includes a tread exhaust groove whose opening end is disposed at a tire equator position,
The said side exhaust groove contains the side exhaust groove in which the said open end is distribute | arranged to the tire axial direction maximum width position of the core side side molding surface part, The rigidity for tire formation of Claim 1 or 2 characterized by the above-mentioned. Child.
The rigid core for forming a tire according to any one of claims 1 to 3, wherein the exhaust groove has a groove cross-sectional area perpendicular to the length direction of 0.03 mm 2 or less.