JP2007050596A - Tire vulcanizing/molding mold and vulcanizing/molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of a burr by the deformation of an inner mold or the protrusion of rubber by reducing the amount of a reduced cavity volume without making the structure of the inner mold complex during vulcanizing/molding by a core vulcanizing/molding method. <P>SOLUTION: The inner mold 3 regulating the inner surface shape of a tire is formed from a material having a thermal expansion coefficient smaller than that of iron or aluminum of an iron/nickel alloy or the like which can be cast. In this way, the amount of the reduced volume of the cavity 4 formed between the inner surface of an outer mold 2 and the outer surface of the inner mold 3 by a temperature increase is reduced by reducing the amount of the thermal expansion of the inner mold 3 associated with a temperature increase during vulcanizing/molding. The pressure increase of a green tire 5 housed in the cavity 4 is suppressed to reduce a pressure applied to each mold 2 or 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire manufacturing apparatus and manufacturing method, and in particular, a tire vulcanization mold and a vulcanization molding method for preventing deformation of an inner mold and protrusion of rubber during vulcanization molding by a core vulcanization molding method. About.

  In general, a pneumatic tire is formed into a predetermined shape by molding an unvulcanized green tire (raw tire) by combining various tire constituent members made of unvulcanized rubber or the like, and vulcanizing and molding the tire. Conventionally, as a manufacturing method of a pneumatic tire with high dimensional accuracy, after forming a green tire on a rigid inner mold (core) that defines the inner surface shape of the tire, the outer mold of the rigid body that defines the outer surface shape of the tire. There is known a so-called core vulcanization molding method in which vulcanization molding is carried out (see Patent Document 1).

FIG. 6 is a cross-sectional view of the main part of a tire vulcanization mold used in this core vulcanization molding method.
As shown in the drawing, this conventional vulcanization mold 80 includes an inner mold 81 composed of a plurality of segments for molding the inner surface of the tire, and an outer mold 85 composed of a plurality of segments 86 for molding the outer surface of the tire. Is provided. The outer surface 82 of the inner mold 81 is formed in a shape corresponding to the shape of the inner surface of the tire to be molded, and the interior 83 has a hollow structure for enclosing or circulating a heating / vulcanizing medium during vulcanization molding. On the other hand, the inner surface 87 of the outer mold 85 is formed in a shape corresponding to the outer surface shape such as a tread pattern of a tire to be molded. The inner mold 81 and the outer mold 85 are combined, and a product tire is interposed between them. A void 88 having substantially the same shape as the shape is formed.

  When manufacturing a product tire using such a vulcanization mold 80, first, an inner mold 81 is formed by assembling a plurality of segments, and a carcass ply, a belt, a tread rubber or the like is formed on the outer surface 82 thereof. The tire constituent members are sequentially bonded together to form a green tire close to the final shape of the product tire. Next, the green tire is preheated together with the inner mold 81 to a predetermined temperature (around 100 ° C.) at which rubber vulcanization does not start. At this time, the outer mold 85 is heated to a predetermined vulcanization temperature (around 180 ° C.) and held. Next, the segments 86 constituting the outer mold 85 are sequentially arranged around the green tire, the inner mold 81 and the outer mold 85 are combined, the vulcanization mold 80 is closed, and the green tire is placed in the cavity 88. Store. Thereafter, a heating / vulcanizing medium is sealed or circulated in the interior 83 of the inner mold 81 or the like, and vulcanized and molded to produce a product tire having a predetermined shape.

  After completion of the vulcanization molding, each segment 86 is opened and the vulcanized tire integrated with the inner die 81 is taken out from the outer die 85, the segments constituting the inner die 81 are disassembled, and the inner die 81 is removed from the vulcanized tire. Isolate. When a new tire is molded, the inner mold 81 cooled to near room temperature is reassembled and the above procedure is repeated.

  According to the core vulcanization molding method described above, the conventional methods using an inflatable bladder or the like having high accuracy in shape and dimensions since each of the dies 81 and 85 defining the final shape of the tire is made of a rigid body. Compared with the tire manufactured in (1), a pneumatic tire excellent in uniformity can be manufactured.

  However, in this conventional vulcanization mold 80, as will be described below, the inner mold 81 is deformed or damaged during vulcanization molding, or a large gap is formed between the molds 81 and 85 or between the segments 86. May occur, or unvulcanized rubber may protrude from the gaps and burrs may occur.

  That is, as described above, when the vulcanization mold 80 is closed, the temperature of the inner mold 81 and the green tire is preheated to around 100 ° C., whereas the temperature of the outer mold 85 is almost the same as that during vulcanization. (Around 180 ° C.). When the heating medium is supplied to the inside 83 of the inner mold 81 in this state, the inner mold 81 is heated to about 80 ° C. from the preheating temperature to the vulcanization temperature, and greatly expands. The temperature does not change and thermal expansion does not occur. Accordingly, the volume of the cavity 88 decreases as the temperature of the inner mold 81 rises, and the green tire expands greatly as the temperature rises, so that the pressure of the rubber in the cavity 88 increases.

In addition, the outer mold 85 that does not need to be moved greatly and is maintained at a constant temperature may be made of iron that is relatively heavy and hardly changes in temperature, that is, relatively high in density and low in thermal conductivity. However, the inner mold 81 needs to be moved between the green tire molding device and the vulcanization molding device and heated up to the vulcanization temperature quickly by heat exchange with the vulcanization medium. Often, it is formed of aluminum or an aluminum-based material. This aluminum has a lower density than the iron (about 2.7 g / cm ³ to about 7.8 g / cm ³ of iron) for, is easy to handle such as carrying lightweight, and thermally conductive This is because the rate is high (at 100 ° C., it is 240 W / m · K with respect to 72 W / m · K of iron), so that the temperature can be raised quickly.

However, aluminum has a higher coefficient of thermal expansion than iron (2.2 × 10 ⁻⁵ twice that of iron 1.1 × 10 ^{−5 at} 20 ° C. to 200 ° C.). The tire (rubber) has a higher thermal expansion coefficient of 12.0 × 10 ^−5, and in this case, the amount of decrease in the volume of the cavity 88 due to the temperature rise described above is further increased, and the pressure in the cavity 88 is increased. Will rise further.

  Therefore, in this conventional vulcanization mold 80, due to excessive pressure in the cavity 88 at the time of vulcanization molding, gaps are formed between the molds 81, 85 and between the segments 86, and the rubber protrudes from there. Alternatively, the inner mold 81 may be deformed or damaged. When the rubber protrudes and burrs occur, the appearance of the product tire is impaired, so it is necessary to remove them, and when deformation or the like occurs in the inner mold 81, repair or remanufacturing, Alternatively, depending on the degree of deformation, it is necessary to discard the molded tire, which causes a problem that man-hours, costs, and the like are wasted.

  In order to solve the above problems, the vulcanization molding metal in which the volume of the cavity 88 is increased by decreasing the width of the inner mold 81 as the temperature rises, and the increase in the pressure in the cavity 88 is suppressed. A type is known (see Patent Document 2).

FIG. 7 is an enlarged cross-sectional view of a main part of the vulcanization mold 80.
In addition to the configuration of the conventional inner mold 81 shown in FIG. 6, the inner mold 81 of the vulcanization mold 80 is an elastic material that pushes the opening width into the opening 84 at the radially inner end of the inner 83. Means 90 are provided. Since the elastic means 90 expands the opening width of the opening 84 by the spring member 91 that reduces the elastic force as the temperature rises, the width of the inner mold 81 decreases as the temperature rises during vulcanization. . Accordingly, since the volume of the cavity 88 also increases as the temperature rises, the pressure received by each of the molds 81 and 85 can be reduced, and the above-described rubber protrusion and deformation of the inner mold 81 can be suppressed. .

  However, this conventional vulcanization mold 80 has a problem that the structure is complicated because a plurality of elastic means 90 must be arranged at predetermined intervals in the circumferential direction.

JP 2000-84937 A JP 2002-264134 A

  The present invention has been made in view of the above-described conventional problems, and the object of the present invention is to reduce the amount of cavity volume conventionally without complicating the structure of the inner mold during vulcanization molding by the core vulcanization molding method. It is less to suppress the generation of burrs due to deformation of the inner mold and protrusion of rubber.

The invention according to claim 1 includes a rigid inner mold that defines the inner surface shape of the tire and a rigid outer mold that defines the outer surface shape of the tire, and is provided between the outer surface of the inner mold and the inner surface of the outer mold. A tire vulcanization mold in which a green tire is accommodated in a cavity formed in a vulcanization mold, and the coefficient of thermal expansion at 20 ° C. to 200 ° C. is 0.6 × 10 ⁻⁶ or more. It consists of a material of 5 × 10 ⁻⁶ or less.
According to a second aspect of the present invention, in the tire vulcanization mold according to the first aspect, the inner mold is made of a castable iron-nickel alloy.
The invention of claim 3 comprises a rigid inner mold that defines the inner surface shape of the tire, and a rigid outer mold that defines the outer surface shape of the tire, and is provided between the outer surface of the inner mold and the inner surface of the outer mold. A tire vulcanization molding method in which a green tire is accommodated in a cavity formed in a vulcanization molding method, and the coefficient of thermal expansion at 20 ° C. to 200 ° C. is 0.6 × 10 ⁻⁶ or more and 5 ×. A step of forming a green tire on the inner mold formed of a material of 10 ⁻⁶ or less, a step of combining the outer mold and the inner mold to form a cavity, and storing the green tire in the cavity And vulcanizing and molding the green tire in the cavity.
According to a fourth aspect of the present invention, in the tire vulcanization molding method according to the third aspect, the step of preheating the green tire formed on the inner mold to a predetermined temperature below the vulcanization temperature together with the inner mold, and the cavity Heating the green tire accommodated in the container to a predetermined vulcanization temperature, and maintaining the outer mold before forming the cavity at the predetermined vulcanization temperature.

  According to the present invention, since the inner mold of the tire vulcanization molding die is formed of a material having a lower thermal expansion coefficient than the conventional one, the cavity volume during vulcanization molding is reduced without complicating the structure of the inner mold. The amount can be made smaller than before, and the increase in pressure in the cavity can be suppressed. Therefore, it is possible to prevent the occurrence of gaps between the molds and deformation of the inner mold, and it is possible to suppress the occurrence of burrs due to the uncured rubber protruding.

Hereinafter, an embodiment of a tire vulcanization mold according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of a vulcanization mold 1 of this embodiment.

  This vulcanization mold 1 is used for molding a tire by the core vulcanization molding method, and, like the conventional vulcanization mold 80 shown in FIG. 6, an outer mold 2 that defines the outer shape of the tire, And an inner mold 3 which is accommodated in a recess formed in the inner peripheral portion of the outer mold 2 and defines the inner surface shape of the tire. As shown in FIG. 1, the vulcanization mold 1 forms a cavity 4 having substantially the same shape as that of the product tire between the inner surface of the outer mold 2 and the outer surface of the inner mold 3 when the mold is closed. The green tire 5 is placed in the cavity 4 and vulcanization molding is performed.

  The outer mold 2 is made of a rigid body of metal such as aluminum or iron, and includes a tread forming mold 21 disposed on the radially outer side, and an upper side mold 22 and a lower side mold 23 disposed above and below the mold 21. It has an annular shape in which the inner peripheral portion is formed in a concave shape as a whole.

  The tread forming mold 21 is formed of a large number of segments that are formed on the inner peripheral surface of the molding surface that forms the outer shape of the tread portion of the tire and that can move inward and outward in the radial direction. These segments are combined to form an annular shape as a whole and constitute the outer peripheral surface of the outer mold 2.

  The upper and lower side molds 22 and 23 each have an annular shape, and a molding surface forming a side surface shape such as a sidewall portion of a tire is an inner surface (the lower side mold 22 has a lower surface in the figure and the lower side mold 23 has an upper surface in the figure. ). These upper and lower side molds 22 and 23 each constitute a side surface of the outer mold 2, and at least one of the molds is provided to enable insertion of the green tire 5 into the cavity 4 and removal of the vulcanized tire. It can move in the opening direction.

The inner mold 3 is made of a metal rigid body having a toroidal cross section in which a molding surface forming the inner shape of the tire is formed on the outer surface.
FIG. 2 is a plan view of the inner mold 3, and FIG. 3 is a cross-sectional view taken along the line CC in FIG.

  As shown in FIGS. 2 and 3, the inner mold 3 is formed of a plurality of (10 in the figure) arc-shaped segments 31 and 32 that can move in the radial direction of the outer shape as a whole. ing. The segments 31 and 32 are composed of two types of segments having different shapes (a sector segment 31 and an equal-length segment 32), and are arranged in a state of being in close contact with each other in the circumferential direction to constitute the inner mold 2.

  The fan-shaped segment 31 has a shape in which the circumferential shape gradually increases toward the outer side in the radial direction, whereas the equal-length segment 32 has a shape in which the circumferential length gradually decreases toward the outer side in the radial direction or does not substantially change. Is formed. In order to remove the inner mold 3 composed of the segments 31 and 32 having such a shape from the inside of the vulcanized tire, first, the respective equal length segments 32 are sequentially moved inward in the radial direction so that the axis line extends from the circular hole at the center of the tire. Then, each sector segment 31 is sequentially moved inward in the radial direction and extracted in the axial direction.

  Moreover, as shown in FIG. 3, the interior 33 of each segment 31 and 32 has a hollow structure, and when the segments 31 and 32 are assembled, the interior 33 communicates to form a ring-shaped space. At the time of vulcanization molding, a heating medium is sealed or circulated in this space, and the inner mold 3 is heated to vulcanize and mold the green tire.

  Here, the outer mold 2 is made of a metal material such as aluminum or iron as in the conventional case, whereas the inner mold 3 is for suppressing the decrease in the volume of the cavity 4 due to the temperature rise during the vulcanization molding described above. These are formed of a metal material having a lower thermal expansion coefficient than those. Since the inner mold 3 has a complicated curved surface shape in accordance with the inner surface shape of the tire and the like, the inner mold 3 is often cast and molded in consideration of ease of manufacture. Therefore, the material of the inner mold 3 is a material that can be cast. It is preferable that

The inner mold 3 of the present embodiment is made of a castable iron / nickel alloy having a thermal expansion coefficient of 0.3 × 10 ⁻⁵ at 20 ° C. to 200 ° C., and is made of a conventional material (for example, a thermal expansion coefficient of 1.1 of iron). The coefficient of thermal expansion is lower than that of × 10 ⁻⁵ or aluminum (2.2 × 10 ⁻⁵ ). Therefore, the amount of expansion associated with the temperature rise is smaller than that of the conventional inner mold. Other physical properties of this alloy are a specific heat of 0.44 J / g · K, a density of 7.8 g / cm ³ , and a thermal conductivity at 100 ° C. of 72 W / m · K.

  A procedure for manufacturing a pneumatic tire using the vulcanization mold 1 having the above configuration will be described. First, the inner mold 3 is assembled cold (about room temperature), and tire constituent members such as a carcass ply, a belt, and a tread rubber are sequentially bonded to the outer surface of the inner mold 3 to form a green tire 5 close to the final shape of the product tire. Next, the molded green tire 5 is preheated together with the inner mold 3 to a predetermined temperature (about 80 ° C.) at which the rubber is not vulcanized.

  Next, after the inner mold 3 and the green tire on the surface thereof are arranged on the lower side mold 23, the upper side mold 22 and the tread forming mold 21 are closed to close the vulcanization mold 1. The green tire 5 is accommodated in the cavity 4. At this time, the temperatures of the molds 21, 22, and 23 constituting the outer mold 2 are kept at a predetermined vulcanization temperature (about 150 ° C.). Thereafter, a heating medium is supplied to the inside 33 of the inner mold 3 to start vulcanization. The heat of the vulcanization medium is transmitted from the inner surface of the inner mold 3 to the outer surface, and the green tire 5 in the cavity 4 is heated and vulcanized by this heat and heat from the outer mold 2.

  When the vulcanization molding is completed, the molds 21, 22, and 23 of the outer mold 2 are opened, the vulcanized tire and the inner mold 3 are taken out, and the inner mold 3 is disassembled and separated from the product tire. When molding a new tire, the inner mold 3 is cooled to near room temperature, then reassembled, and the above-described procedure is repeated.

  In the vulcanization molding process described above, the outer mold 2 held at the vulcanization temperature does not change in temperature and does not thermally expand, whereas the inner mold 3 is heated from the preheating temperature to the vulcanization temperature. Due to thermal expansion, the volume of the cavity 4 gradually decreases as the temperature rises. At the same time, the green tire 5 also thermally expands greatly as the temperature rises, so that the green tire 5 is pressurized and the rubber flows in the cavity 4, and its surface is pressed against the molds 2 and 3 to form the product tire. Molded to final shape.

  However, when the pressure in the cavity 4 becomes excessive, the deformation of the inner mold 3 and the gap between the molds open as described above, and the rubber protrudes from the inner mold 3. Is made of a material having a lower thermal expansion coefficient than that of the prior art, and therefore, the amount of thermal expansion accompanying a rise in temperature and the amount of decrease in the volume of the cavity 4 associated therewith are smaller than before. Therefore, an excessive increase in the pressure in the cavity 4 is suppressed, and the occurrence of the above problems is also suppressed.

  FIG. 4 is a graph schematically showing a change in volume or volume (hereinafter, both referred to as volume) with respect to the temperature of the cavity 4 and the tire 5 in the vulcanization molding step.

This graph is calculated based on an example of vulcanizing and molding a radial tire for trucks and buses with a tire size of 275 / 80R22.5 defined by JATMA YEAR BOOK (2004, Japan Automobile Tire Association Standard). Each dimension of the molding die 1 was set so that the volume of the cavity 4 and the tire 5 coincided when the temperature was around 40 ° C. In addition, the figure also shows the volume change of the cavity 4 when the inner mold 3 made of aluminum (thermal expansion coefficient 2.2 × 10 ⁻⁵ ), which has been widely used for comparison, is used (the dashed line in the figure). Show.

  As shown in the figure, as the temperature rises, the volume of the tire increases linearly with a large inclination, whereas the volume of the cavity 4 decreases linearly with a small inclination. However, the rate of decrease is smaller when the inner mold 3 made of the iron / nickel alloy of the present embodiment is used than when made of the conventional aluminum. It can be seen that the volume reduction accompanying the temperature increase can be reduced as compared with the conventional case.

  Specifically, in the case of the inner mold 3 made of aluminum, the volume of the cavity 4 is larger than the volume of the tire 5 when it is cold near room temperature, for example, the cavity 4 is about 1. 0% (about 193cc) larger, but reverse at around 40 ° C, and at the preheating temperature (about 80 ° C), the cavity 4 becomes about 1.5% (about 261cc) smaller than the tire 5, and the vulcanization temperature (about 150 ° C.), the cavity 4 is smaller than the tire 5 by about 5.2% (about 942 cc).

  On the other hand, in the case of the inner mold 3 made of iron-nickel alloy of the present embodiment, the cavity 4 is also about 1.5% (about 261 cc) smaller than the tire 5 at the preheating temperature (about 80 ° C.). At the vulcanization temperature (about 150 ° C.), the cavity 4 is about 4.5% (about 807 cc) smaller than the tire 5. That is, the inner mold 3 can reduce the volume difference by a region indicated by the oblique lines in the figure than before. For example, at the vulcanization temperature, the volume of the cavity 4 is about 0.7% (about 135 cc) compared to that of aluminum. Therefore, the volume difference from the tire can be reduced accordingly.

  Note that a straight line T indicated by a one-dot chain line in the figure indicates the maximum cavity volume for obtaining a required vulcanization pressure, and when the volume of the cavity 4 is larger than this line, the difference from the volume of the tire 5 becomes small. The pressure in the cavity 4 becomes low, and a necessary vulcanization pressure cannot be obtained. Therefore, as shown in the drawing, at the vulcanization temperature (about 150 ° C.), in the case of the inner mold 3 made of aluminum, about 500 cc, the rubber is compressed and the pressure is increased, but the inner mold 3 is By using a nickel-based alloy, the amount of extra compressed rubber can be about 365 cc, and the pressure in the cavity 4 can be lowered.

FIG. 5 is another example showing the volume change of each part with respect to the temperature change at the time of tire vulcanization molding. For comparison, the inner mold 3 is made of aluminum (thermal expansion coefficient 2.2 × 10 ⁻⁵ ) and spherical graphite. It also shows the case of producing with cast iron (FCD) (coefficient of thermal expansion 1.1 × 10 ^{−5 to} 1.2 × 10 ⁻⁵ ).

  The numerical values in this figure are calculated by vulcanizing and molding radial tires for trucks and buses of tire size 275 / 70R22.5 as defined by JATMA YEAR BOOK (2004, Japan Automobile Tire Association Standard). Each dimension of the vulcanization mold 1 was set so that the volume of the cavity 4 and the tire 5 coincided when the temperature was cold (around 25 ° C.). Therefore, as shown in the drawing, the tire rubber volume and the cavity 4 volume (the value obtained by subtracting the volume of the inner mold 3 from the inner volume of the outer mold 2) are both 19450 cc, and the difference (balance) as shown in the figure. Is 0 cc.

  Also, each volume (cc) at the time of internal mold preheating and vulcanization in the figure is shown by the difference between the respective volumes at the time of cold, and the figure shows the volume of tire rubber or cavity volume at the time of cold (in the figure) The ratio (%) to 19450 cc) is also shown. Here, each value is indicated by plus (+) for a change in the rubber excess direction with respect to the cold volume, that is, the expansion of the rubber or the decrease direction of the cavity 4, and the change in the rubber shortage direction, The reduction of the rubber or the change in the expansion direction of the cavity 4 is indicated by minus (−).

  As shown in the figure, during the inner mold preheating, the inner mold 3 and the green tire 5 are heated to the preheating temperature (80 ° C.), so that the tire rubber expands by 490 cc (2.52%). Each inner mold 3 also expands, but the expansion amount is 13 cc (0.07%) for the iron-nickel alloy compared to 70 cc (0.36%) for aluminum and 35 cc (0.18%) for FCD. ) And smaller.

  On the other hand, since the outer mold 2 is heated to the vulcanization temperature (150 ° C.), it expands by 580 cc (2.9%) in the direction of increasing the cavity 4. Therefore, in the inner mold 3 made of aluminum and FCD, the cavity 4 is 20 cc (0.10%) and 55 cc (0.28%) larger than the tire rubber, respectively, whereas the iron / nickel alloy It can be seen that the inner mold 3 made of the cavity 4 is 77 cc (0.40%) larger than the tire rubber, and the volume of the cavity 4 is the largest.

  Further, at the time of vulcanization, the inner mold 3 and the green tire 5 are heated by about 70 ° C. from the preheating temperature to the vulcanization temperature (150 ° C.), so that the tire rubber expands by 1140 cc (5.86%) with respect to the cold time. Each inner mold 3 also expands, but the expansion amount is 25 cc (0.13%) for iron / nickel alloy, compared to 160 cc (0.82%) for aluminum and 80 cc (0.41%) for FCD. ) And smaller.

  On the other hand, since the outer mold | type 2 is hold | maintained at the vulcanization temperature (150 degreeC), the expansion amount with respect to the time of cold does not change with 580cc (2.9%). Therefore, in the inner mold 3 made of aluminum and FCD, the cavity 4 is 720 cc (3.7%) and 640 cc (3.3%) smaller than the tire rubber, respectively. In the manufactured inner mold 3, the cavity 4 is 585 cc (3.0%) smaller than the tire rubber, and it can be seen that the volume difference between the cavity 4 and the tire rubber is the smallest.

  Thus, by making the inner mold 3 made of the iron / nickel alloy of the present embodiment, the volume reduction amount of the cavity 4 accompanying the temperature rise can be reduced as compared with the conventional inner mold 3, and the rubber in the cavity 4 can be reduced. It can be seen that an increase in pressure can be suppressed.

In addition, the volume reduction amount of the cavity 4 accompanying a temperature rise can be made smaller as the thermal expansion coefficient of the inner mold 3 is smaller. However, if the thermal expansion coefficient at 20 ° C. to 200 ° C., which is the use temperature, is 5.0 × 10 ⁻⁶ or less, the volume expansion of the inner mold 3 accompanying the temperature rise becomes sufficiently smaller than the conventional material, and the temperature rise Thus, the volume reduction amount of the cavity 4 can be effectively suppressed, and the effects of the present invention can be sufficiently obtained.

  Table 1 shows other examples of castable iron / nickel alloys having such a thermal expansion coefficient.

As the material of the inner mold 3, an iron / nickel alloy having such physical properties can also be used. As shown in Table 1, the thermal expansion coefficient has a minimum value of 0.6 of that of the alloy 1. × 10 ⁻⁶ and the maximum value is 3 to 4 × 10 ^{−6 of} alloys 4 and 5. Therefore, the thermal expansion coefficient of the inner mold 3 is preferably 0.6 × 10 ⁻⁶ or more and 5.0 × 10 ⁻⁶ or less at 20 ° C. to 200 ° C.
In the present invention, the castable iron / nickel-based alloy refers to an alloy having the above-described physical property values or the respective physical property values representatively shown in Table 1.

  As described above, the vulcanization mold 1 according to the present embodiment is formed of a material having a smaller thermal expansion coefficient than that of a conventional cast iron / nickel alloy or the like. The amount of expansion of the inner mold 3 can be reduced as compared with the prior art. Therefore, without complicating the structure of the inner mold 3, the amount of decrease in the volume of the cavity 4 at the time of vulcanization molding can be reduced as compared with the prior art, and an increase in the pressure in the cavity 4 can be suppressed. As a result, the pressure received by the molds 2 and 3 can be reduced, the deformation of the inner mold 3 can be suppressed, and the formation of gaps between the molds 2 and 3 and the segments can be prevented. It is possible to suppress the generation of burrs due to the protrusion of slag.

It is sectional drawing which shows schematic structure of the tire vulcanization molding metal mold | die of this embodiment. It is a top view of the inner mold of the tire vulcanization mold of this embodiment. It is CC sectional view taken on the line of FIG. It is a graph which shows typically the volume (volume) change with respect to the temperature of a cavity and a tire in a vulcanization molding process. It is a figure which shows the volume change with respect to the temperature change at the time of tire vulcanization molding. It is principal part sectional drawing of the conventional tire vulcanization molding die used for a core vulcanization molding method. It is an expanded sectional view of the principal part of the conventional vulcanization molding die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vulcanization molding die, 2 ... Outer die, 3 ... Inner die, 4 ... Cavity, 5 ... Green tire, 21 ... Tread formation die, 22 .... -Upper side mold, 23 ... Lower side mold, 31 ... Fan segment, 32 ... Equal length segment, 33 ... Inside.

Claims (4)

A rigid inner mold that defines the inner surface shape of the tire and a rigid outer mold that defines the outer surface shape of the tire, and a cavity formed between the outer surface of the inner mold and the inner surface of the outer mold A tire vulcanization mold that houses and vulcanizes green tires,
The tire vulcanization mold, wherein the inner mold is made of a material having a thermal expansion coefficient of 0.6 × 10 ⁻⁶ or more and 5 × 10 ⁻⁶ or less at 20 ° C. to 200 ° C. In the tire vulcanization mold according to claim 1,
The tire vulcanization mold, wherein the inner mold is made of a castable iron-nickel alloy. A rigid inner mold that defines the inner surface shape of the tire and a rigid outer mold that defines the outer surface shape of the tire, and a cavity formed between the outer surface of the inner mold and the inner surface of the outer mold A tire vulcanization molding method for storing and vulcanizing a green tire,
The inner mold is formed of a material having a thermal expansion coefficient at 20 ° C. to 200 ° C. of 0.6 × 10 ⁻⁶ or more and 5 × 10 ⁻⁶ or less,
Forming a green tire on the inner mold;
Combining the outer mold and the inner mold to form a cavity, and storing the green tire in the cavity;
Vulcanizing and molding the green tire in the cavity;
A tire vulcanization molding method comprising: In the tire vulcanization molding method according to claim 3,
Preheating the green tire formed on the inner mold to a predetermined temperature below the vulcanization temperature together with the inner mold;
Heating the green tire housed in the cavity to a predetermined vulcanization temperature,
A tire vulcanization molding method, wherein the outer mold before forming the cavity is maintained at the predetermined vulcanization temperature.

Images