JP5444385B2 - Rigid core for tire formation - Google Patents

Description

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

  In recent years, a tire forming method using a rigid core (hereinafter sometimes referred to as a core method) has been proposed in order to increase the formation accuracy of the tire (see, for example, Patent Documents 1 and 2). The rigid core includes 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. Then, by putting this raw tire together with the rigid core into the vulcanizing mold, the raw tire is vulcanized by being sandwiched between the inner core body and the outer vulcanizing mold. Molded.

  As shown in FIG. 7A, the core body a is composed of a plurality of core segments c that are divided in the circumferential direction so as to be disassembled and removed from the tire after vulcanization molding. Each core segment c has both end surfaces in the circumferential direction as mating surfaces cs, and the mating surfaces cs and cs adjacent in the circumferential direction are attached to each other, whereby the core body a is formed in an annular shape.

  Here, in the core method, it is desired to discharge air between the core body a and the raw tire during vulcanization molding in order to further improve the tire forming 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 inflowed rubber is thick and strong, and even if it is burned with the wall surface of the exhaust groove d. It is difficult to break, and 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.

  On the other hand, when the cross-sectional volume of the exhaust groove d is small, the inflowing rubber is thin and weak, so that it is burned onto the wall surface of the exhaust groove d and is easily broken. Therefore, after vulcanization, broken rubber tends to adhere to the wall surface of the exhaust groove d, the amount of adhesion increases as the number of vulcanizations increases, and the exhaust groove d is blocked to impair exhaust performance, or the broken rubber. The piece enters between the mating surfaces cs and cs, which causes a problem of impairing the tire forming accuracy, such as impairing the roundness of the core body a. Moreover, in order to prevent this, frequent cleaning of the core segment c is necessary, but this reduces the production efficiency of the tire.

  Accordingly, in the exhaust groove d, it is desirable to suppress the inflow of rubber by reducing the cross-sectional volume as much as possible. In that case, a sufficiently satisfactory effect is obtained such that the exhaust performance is reduced and the tire is deformed due to air accumulation. It has not reached.

  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, but since the large thermal expansion repeatedly occurs, the strength of the connecting portion becomes insufficient and the durability of the core segment is lowered. There is a problem. In addition, the inflow of rubber into the exhaust passage is still not taken into consideration.

JP 2011-161896 A JP 2011-167799 A

  Therefore, the present invention is based on devising the direction of inclination of the groove portion on the opening end side in the exhaust groove recessed in the mating surface, and ensures a sufficient cross-sectional volume of the exhaust groove to maintain sufficient exhaust performance. However, an object of the present invention is to provide a rigid core for forming a tire that can suppress the inflow of rubber into the exhaust groove and can solve the problems caused by the inflow of rubber.

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 whole green tire is put into a vulcanization mold. A rigid core that vulcanizes and molds the green tire between the vulcanization mold and the core body,
The vulcanization mold has a mold side tread molding surface portion that molds a tire tread outer surface by pressing inward in the tire radial direction, and a tread mold that is movable in and out of the tire radial direction;
It has a mold side molding surface part that molds the side outer surface of the tire by pressing inward in the tire axial direction, and includes a side mold that can move in and out of the tire axial direction,
The core-side tire molding surface has 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. While divided into a core side tread molding surface portion and a core side side molding surface portion outside the normal,
The core body is composed of a plurality of core segments divided in the circumferential direction,
And each core segment forms the said core main body by mutually adjoining the mating surfaces which adjoin each other in the circumferential direction by making the circumferential direction both ends into a mating surface,
On at least one mating surface of the mating surfaces adjacent in the circumferential direction, one end has an open end that opens at the core-side tire molding surface, and air between the core-side tire molding surface and the raw tire is cored At least one exhaust groove for exhausting inside the main body is recessed,
In addition, 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, and the side exhaust groove has an angle θ2 with respect to the tire axial direction line from the opening end. It has the feature that it has an inclined groove portion extending in an inclined manner.

  According to a second aspect of the present invention, the tread exhaust groove angle θ1 and the side exhaust groove angle θ2 are each in the range of 30 to 80 °.

  Further, in claim 3, the exhaust groove includes the tread exhaust groove and the side exhaust groove, and the tread exhaust groove includes a tread exhaust groove at an equator position whose opening end is disposed at a tire equator position, The side exhaust groove is characterized in that the open end includes a side exhaust groove at the maximum width position arranged at the maximum width position in the tire axial direction of the core side side molding surface portion.

According to a fourth aspect of the present invention, 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 formed 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 extending from the opening end thereof at an angle θ1 with respect to the tire radial line, and the side exhaust groove from the opening end to the tire axial line. It is formed with an inclined groove portion extending at an angle θ2.

  Here, the vulcanization mold includes a tread mold that can move in and out in the tire radial direction and a side mold that can move in and out in 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 the portion that comes into contact with the tread mold. Therefore, if the opening end side of the tread exhaust groove extends along the tire radial direction, it matches the direction of the strong pressing force by the tread mold, so that 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 rubber tends to flow into the exhaust groove because it matches the direction of the strong pressing force by the side mold.

  However, in the present invention, the opening end sides of the tread exhaust groove and the side exhaust groove are inclined at the angles θ1 and θ2, respectively. That is, since the opening end side extends in a direction different from the strong pressing force, only the inflow of rubber can be suppressed without inhibiting the inflow of air. This is because the viscosity of rubber is much higher than that of air. By making the opening end side 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 viscosity Inflow of high rubber can be suppressed. Moreover, since it does not become a resistance against air having a low viscosity and does not inhibit the inflow thereof, the exhaust performance can be effectively exhibited.

  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 it is possible to suppress exhaust defects such as blocking the exhaust groove. It can also be suppressed that the roundness of the core body is impaired. 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)-(D) are sectional drawings which illustrate the cross-sectional shape of an 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. Then, a well-known tire constituent member such as a carcass ply, a belt ply, a sidewall rubber, and a tread rubber is sequentially attached on 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, and the raw tire T is heated between the core body 2 as the inner mold and the vulcanizing mold 20 as the outer mold. Vulcanization molding is performed by applying pressure.

  The vulcanization 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, and the tread outer surface Ta of the tire T is molded by pressing the mold side tread molding surface portion 21S inward in the tire radial direction. The side mold 22 has a mold side side molding surface portion 22S, and the side outer surface Tb of the tire T is molded by pressing the mold side side molding surface portion 22S inward in the tire axial direction.

  Next, the rigid core 1 includes an annular core body 2 and a cylindrical core 3 inserted into the center hole 2H. A 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 passes through a boundary position P between the mold-side tread molding surface portion 21S and the mold-side side molding surface portion 22S, and is orthogonal to the core-side tire molding surface 2S. By the normal lines N and N extending in the direction, the core side tread molding surface portion 2Sa between the normal lines N and N and the core side side molding surface portion 2Sb outside the normal line N are virtually divided.

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

  Moreover, the said core main body 2 is formed from the several core segment 5 divided | segmented into the circumferential direction, as shown to FIG. 2 (A), (B). Each core segment 5 has both end surfaces in the circumferential direction as mating surfaces 6 and the mating surfaces 6 and 6 adjacent in the circumferential direction are attached to each other to form the annular core body 2.

  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 6 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. On the other hand, in the second core segment 5B, the mating surfaces 6 at both ends in the circumferential direction are 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 in order 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 open end 12 having one end opened at the core-side tire molding surface 2S, and exhausts air between the core-side tire molding surface 2S and the raw tire T to the inside of the core body 2. . Note that the other end of the exhaust groove 11 communicates with the lumen portion 4 that conducts to the outside air in this example.

  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, and the tread exhaust groove 11A has a tread exhaust groove 11Ac at the equator position where the opening end 12 is disposed at the tire equator Co position. Further, it is desirable that the side exhaust groove 11B includes a side exhaust groove 11Bq at the maximum width position whose 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.

  Here, 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, and the side exhaust groove 11B extends from the opening end 12 to the tire. There is an inclined groove portion 14 that extends at an angle θ2 with respect to the axial line.

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

  The angles [theta] 1 and [theta] 2 are each preferably in the range of 30 to 80 [deg.], And if it is less than 30 [deg.], The resistance becomes small and the effect of suppressing rubber inflow cannot be sufficiently achieved. On the other hand, if the angle exceeds 80 °, the intersection between the core-side tire molding surface 2S and the exhaust groove 11 has a sword tip shape, which leads to a risk of lowering durability due to insufficient strength. 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.

  The exhaust groove 11 may be formed of only the inclined groove portion 14 as in the side exhaust groove 11B of this example, and the inclined groove portion 13 and the inclined groove portion 13 as in the tread exhaust groove 11A of this example. It can also be formed in the shape of a bent groove comprising a joint groove portion 15 that is continuous with the joint groove portion 15. In the case where the joint groove portion 15 is formed, it is not particularly limited, but it is preferably formed at the shortest distance toward the inside of the core body 2 (in this example, the lumen portion 4).

  The groove cross-sectional shape perpendicular to the length direction of the exhaust groove 11 may be, for example, a triangular cross section (FIG. 4A), a square cross section (FIGS. 4B and 4C), a semicircular arc shape ( Various shapes such as FIG. 4 (D) can be employed, but a triangular cross section 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 when the cross-sectional area is the same, and is preferable because the bottom m1 is the opening side and shorter than the other oblique sides m2. It is preferable 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.

In addition, there is a limit to the effect of suppressing the inflow of rubber by the inclined groove portions 13 and 14, and if the groove cross-sectional area is too large, the above-described suppression effect cannot be 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 the exhaust performance is lowered. Therefore, the lower limit 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.

  5 and 6 show another embodiment of the core segment. In FIG. 5, side surfaces 18 at both ends 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. At this time, the mating surface 6 is constituted by the edge surface portion 18A, and the exhaust groove 11 is formed in the edge surface portion 18A. In the present example, the other end of the exhaust groove 11 communicates with a recessed surface portion 18B that conducts to the outside air.

  In FIG. 6, the core segment 5 is formed as a mating surface 6 with the entire side surfaces 18 at both ends in the circumferential direction. In this example, the other end of the exhaust groove 11 communicates with the radially inner end 18e of the side surface 18 that conducts 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 state of rubber flowing into the exhaust groove, the seized state in which the rubber that has flowed in adheres to the groove wall surface, and the air pool caused by the deterioration of the exhaust performance due to seizure The occurrence state of each 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. The core body is heated to a high temperature state of 150 ° C. in the vulcanization mold while a green tire is formed at normal temperature (20 ° C.). Except as described in Table 1, the specifications are substantially the same. The test method was as follows, and the evaluation was performed in the tread exhaust groove at the equator position.

(1) Rubber flowing in:
This is a comparison of the amount of spew (rubber amount) generated on the tire side due to the rubber flowing into the exhaust groove. The vulcanization is performed 1000 times in succession, and the amount of spew at the first, 300th, 600th and 1000th times, respectively 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:
This is a comparison of the amount of seizure of the rubber that has flowed into the exhaust groove and adheres to the wall surface of the groove. The vulcanization is performed 1000 times in succession, and the amount of seizure in the first, 300th, 600th and 1000th times is calculated. Each was evaluated numerically. The larger the numerical value, the smaller the amount of image sticking and the better.

(3) Condition of air accumulation:
This is a comparison of the occurrence of air pockets due to the rubber sticking to the groove wall surface due to seizure and lowering the exhaust performance. The vulcanization is performed 1000 times continuously, the first time, the 300th time, the 600th time, the 1000th time. In FIG. 2, the deformation state of the tire caused by air accumulation was quantified and evaluated. The larger the numerical value, the better the less air accumulation.

  As shown in Table 1, since the rigid core of the example has an inclined groove portion of a predetermined angle formed in the exhaust groove, it is possible to suppress the inflow of rubber into the exhaust groove, and the occurrence of spew to the tire, exhaust It can be confirmed that the seizure of rubber in the groove and the clogging of the exhaust groove due to the seizure can be effectively suppressed. Moreover, 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 portion 2Sb Core side side molding surface portion 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 part 20 Vulcanization mold 21S Mold side tread molding surface part 21 Tread mold 22S Mold side side molding surface part 22 Side mold N Normal line P Boundary position T Raw tire

Claims (4)

An annular core body having a core-side 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 are A rigid core for vulcanizing and molding the green tire,
The vulcanization mold has a mold side tread molding surface portion that molds a tire tread outer surface by pressing inward in the tire radial direction, and a tread mold that is movable in and out of the tire radial direction;
It has a mold side molding surface part that molds the side outer surface of the tire by pressing inward in the tire axial direction, and includes a side mold that can move in and out of the tire axial direction,
The core-side tire molding surface has 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. While divided into a core side tread molding surface portion and a core side side molding surface portion outside the normal,
The core body is composed of a plurality of core segments divided in the circumferential direction,
And each core segment forms the said core main body by mutually adjoining the mating surfaces which adjoin each other in the circumferential direction by making the circumferential direction both ends into a mating surface,
On at least one mating surface of the mating surfaces adjacent in the circumferential direction, one end has an open end that opens at the core-side tire molding surface, and air between the core-side tire molding surface and the raw tire is cored At least one exhaust groove for exhausting inside the main body is recessed,
In addition, 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, and the side exhaust groove has an angle θ2 with respect to the tire axial direction line from the opening end. A rigid core for forming a tire, characterized in that it has an inclined groove portion extending in an inclined manner.   2. The rigid core for forming a tire according to claim 1, wherein the angle [theta] 1 of the tread exhaust groove and the angle [theta] 2 of the side exhaust groove are in a range of 30 to 80 [deg.], Respectively. The exhaust groove includes the tread exhaust groove and a side exhaust groove, and the tread exhaust groove includes a tread exhaust groove at an equator position where an opening end is disposed at a tire equator position,
3. The tire forming tire according to claim 1, wherein the side exhaust groove includes a side exhaust groove at a maximum width position where an opening end is disposed at a maximum width position in a tire axial direction of the core side side molding surface portion. Rigid core. 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.

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