JP4998987B2 - Tire vulcanization molding apparatus and vulcanization molding method - Google Patents

Description

  The present invention relates to a pneumatic tire manufacturing apparatus and manufacturing method, and more particularly to a tire vulcanizing molding apparatus and a vulcanizing molding method for preventing deformation of an inner mold and protrusion of rubber during vulcanization molding by a core vulcanization molding method. .

  A pneumatic tire is generally formed into a predetermined shape by molding a 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. 5 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 inner surface shape of the tire to be molded, and the inner portion 83 has a hollow structure for enclosing or circulating a high-temperature / high-pressure 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.) before rubber vulcanization begins. 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 vulcanization medium is sealed or circulated inside the inner 83 of the inner die 81 and the outer side of the outer die 85, and the inner die 81 and the green tire are heated to raise the temperature from the preheating temperature to a predetermined vulcanization temperature. At this time, the outer mold 85, which is held at the vulcanization temperature in advance, does not change in temperature and does not thermally expand, whereas the inner mold 81 thermally expands at a temperature rise from the preheating temperature to the vulcanization temperature. As the temperature rises, the volume of the cavity 88 gradually decreases. At the same time, the green tire in the cavity 88 also expands greatly as the temperature rises, so that the pressure in the cavity 88 gradually increases.

  As a result, the green tire is pressurized and the rubber flows, and the cavity 88 is filled with the rubber, and the surface is pressed against the mold surfaces 82 and 87 to form the final shape of the product tire. Is done. Thereafter, the vulcanization mold 80 is maintained at a vulcanization temperature for a predetermined time, and a crosslinking reaction (vulcanization reaction) is advanced to cure the tire rubber, thereby producing a product tire having an appropriate elasticity.

  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, since the pressure applied to the tire at the time of vulcanization molding is generated only by the thermal expansion of the inner mold 81 and the tire rubber, if the volume of the tire is insufficient with respect to the volume of the cavity 88 at the vulcanization temperature, Cannot be completely filled with rubber, and there is a problem that a shrinkage nest, improper molding, or air accumulation (bearing) occurs. Even when the volume of the tire is larger than the cavity 88, if the difference is less than a predetermined value, the target vulcanization pressure cannot be obtained, and molding and air discharge become insufficient. As a result, there is a problem that an appearance defect such as air retention occurs in the tire after vulcanization.

  Accordingly, in such a vulcanization mold 80, the dimensions of the molds 81 and 85 are generally set so that the volume of the cavity 88 is smaller than the volume of the thermally expanding tire. However, in this case, when the tire volume exceeds a predetermined amount or the like, the pressure in the cavity 88 becomes excessive, and a large gap is generated between the molds 81 and 85 and between the segments 86, and rubber is generated from the gap. May protrude and cause burrs, or the inner mold 81 and the outer mold 85 may be deformed by pressure. If the rubber protrudes and burrs occur, the appearance and quality of the product tire will be impaired. Therefore, it is necessary to discard the vulcanized tire or remove the burrs, and the inner mold 81 and the outer mold 85 may be deformed. If it breaks down, it must be repaired or remanufactured, and there is a problem that the man-hours, costs, etc., 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. 6 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. 5, the inner mold 81 of the vulcanization mold 80 is an elastic material that expands the opening width to 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. . Thereby, since the volume of the cavity 88 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. it can.

  However, the inner mold 81 of the conventional vulcanization mold 80 is constantly used in the direction of expanding the width of the opening 84 and repeatedly deformed in the same direction every time vulcanization is performed. Accordingly, the dimensions and shape of the inner mold 81 may gradually change.

JP 2000-84937 A JP 2002-264134 A

  The present invention has been made in view of the above-described conventional problems, and its purpose is to suppress an excessive increase in pressure in the cavity during vulcanization molding by the core vulcanization molding method, and deformation or breakage of the mold. It is to improve the appearance quality of the tire by preventing the occurrence of burrs caused by air accumulation and rubber protrusion.

The invention of claim 1 includes a vulcanization mold having a rigid inner mold that defines an inner surface shape of a tire and a rigid outer mold that defines an outer surface shape of the tire, and the outer surface of the inner mold and the A tire vulcanization molding apparatus that accommodates a green tire in a cavity formed between an inner surface of an outer mold and vulcanizes the outer mold, and the outer mold is movable in a direction to increase the volume of the cavity. A plurality of molds including a mold, and provided with a means for moving the movable mold, the moving means having a predetermined pressure of 4 MPa or more and less than 6 MPa in the cavity during vulcanization molding When reaching the above, the movable mold is moved .
Invention 請 Motomeko 2, a tire vulcanization apparatus according to claim 1, wherein the outer mold has a tread mold for molding a tread portion shape of the tire, molding the sides shape of the tire The movable mold is composed of an upper side mold and a lower side mold, and the movable mold is the upper side mold and the lower side mold.
The invention of claim 3 includes a rigid inner mold that defines the inner surface shape of the tire, and an outer mold that includes a plurality of rigid molds that define the outer surface shape of the tire, and the outer surface of the inner mold includes: A tire vulcanization molding method in which a green tire is accommodated in a cavity formed between an inner surface of the outer mold and vulcanized and molded, the step of forming the green tire on the inner mold, and the outer mold And the inner mold are combined to form a cavity, the green tire is housed in the cavity, the vulcanization medium is supplied into the inner mold, and the pressure in the cavity is 4 MPa or more and 6 MPa. And increasing the volume of the cavity when a predetermined pressure of less than is reached.
According to a fourth aspect of the present invention, in the tire vulcanization molding method according to the third aspect , the predetermined pressure is a pressure for completing the shaping of the shape of the green tire .

(Function)
According to the present invention, in the vulcanization molding by the core vulcanization molding method, when the pressure in the cavity rises due to the thermal expansion of the inner mold and the green tire, a part of the mold constituting the outer mold is moved. Increase cavity volume and suppress excessive pressure rise in the cavity. In addition, a part of the mold constituting the outer mold is moved to maintain the pressure in the cavity at a predetermined vulcanization pressure, thereby suppressing the occurrence of air accumulation and improper molding.

  According to the present invention, it is possible to suppress an excessive increase in pressure in the cavity during vulcanization molding, and thus it is possible to prevent the generation of burrs due to the protrusion of rubber while preventing the occurrence of gaps between the molds. Deformation and damage can be prevented. In addition, it is possible to maintain the predetermined vulcanization pressure, suppress the occurrence of air accumulation and improper molding, and improve the appearance quality of the tire.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a tire vulcanization molding apparatus 10 according to the present embodiment.

  The vulcanization mold 1 of the tire vulcanization molding apparatus 10 is used for molding a tire by a core vulcanization molding method, and has the outer surface shape of the tire similar to the conventional vulcanization mold 80 shown in FIG. An outer die 2 to be defined and an inner die 3 which is accommodated in a recess formed in the inner peripheral portion of the outer die 2 and defines the inner surface shape of the tire are provided. 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 inner mold 3 is made of a rigid body made of a metal such as aluminum or iron, and is made of a toroidal member having a cross-section formed on the outer surface of the molding surface that forms the inner shape of the tire.
FIG. 2 is a plan view of the inner mold 3.

  As shown in FIGS. 1 and 2, the inner mold 3 is composed of a plurality of (10 in the figure) arc-shaped segments 31 and 32 that can move in the radial direction 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 where they are alternately in close contact with each other in the circumferential direction to constitute the inner mold 3.

  In the fan-shaped segment 31 having a substantially fan shape in plan view, the circumferential shape gradually increases toward the outer side in the radial direction, whereas the equal length segment 32 having a substantially rectangular shape in plan view gradually increases in the circumferential length toward the outer side in the radial direction. The shape is reduced or substantially unchanged. In order to remove the inner mold 3 including 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 radially inward from the circular hole 34 in the tire central portion. Extraction is performed in the axial direction, and thereafter, each fan-shaped segment 31 is sequentially moved inward in the radial direction and extracted in the axial direction.

  As shown in FIG. 1, the interior 33 of each segment 31, 32 has a hollow structure, and when the segments 31, 32 are assembled, the interior 33 communicates to form a ring-shaped space. After the inner mold 3 is housed in the outer mold 2, the supply passage 11 for the high-temperature / high-pressure vulcanizing medium is connected to the circular hole 34 at the center of one side (lower in FIG. 1), and the supply passage The rectifying plate 12 extending from the inner periphery of 11 is disposed up to the inside 33 thereof.

  At the time of vulcanization molding, the inner hole 33 is sealed by closing the circular hole 34 at the center of the other side (upper in FIG. 1) of the inner mold 3, and the vulcanization medium is passed through the outside of the current plate 12 at the inner periphery of the supply passage 11. Supply to the inside 33 of the inner mold 3. As indicated by the arrows in FIG. 1, the vulcanization medium moves below the rectifying plate 12 radially outward, rises along the inner peripheral surface of the inner mold 3, and rises above the rectifying plate 12. It wraps around, moves upward in the radial direction on the upper side of the rectifying plate 12, passes through the inner side of the rectifying plate 12 in the inner periphery of the supply passage 11, and is discharged to the outside. Thus, the inner mold 3 heats the green tire 5 by circulating the vulcanization medium in the interior 33.

  The outer mold 2 is made of a rigid body of metal such as aluminum or iron, and as shown in FIG. 1, a tread mold 21 disposed on the radially outer side, an upper side mold 22 and a lower side disposed above and below the tread mold 21. The mold 23 is provided and has an annular shape in which the inner peripheral portion is formed in a concave shape as a whole.

  The tread mold 21 has a molding surface that forms the outer shape of the tread portion of the tire on the inner peripheral surface, and is composed of a number of segments 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 them (upper upper side mold 22 in the figure) inserts and adds the green tire 5 and the like into the cavity 4. In order to enable removal of the vulcanized tire, it is movable in the mold opening direction.

  Further, the vulcanization molding apparatus 10 includes a lower base 40 fixed below the outer mold 2, and a disk on which an vulcanization medium is supplied to the upper surface of the lower base 40 during vulcanization molding. The lower platen 41 is fixed, and the lower side mold 23 is provided on the upper surface of the lower platen 41.

  On the other hand, on the lower surface of the lower base 40, a plurality of piston / cylinder mechanisms 42 are arranged at equal intervals along the circumferential direction of the lower side mold 23 (two in the figure), and the piston rod 43 faces upward. It is fixed. The piston rod 43 passes through a through hole 44 that penetrates the lower base 40 and the lower platen 41 in the vertical direction, and the tip thereof is attached to the lower surface of the lower side mold 23. An annular recess 41 a that can accommodate a lower portion of the lower side mold 23 is formed in a portion facing the lower surface of the lower side mold 23 on the upper surface of the lower platen 41.

  FIG. 3 shows the tire vulcanization molding apparatus 10 in a state where the piston / cylinder mechanism 42 is operated and the lower side mold 23 is moved downward. In the figure, the upper side mold 22 is also moved upward by the mechanism described later. The state moved in the direction is shown.

  As shown in FIGS. 1 and 3, the lower side mold 23 can be moved in and out of the recess 41 a (up and down direction in the figure) by operating a plurality of piston / cylinder mechanisms 42 in conjunction with each other. It is possible to move between an upper position (see FIG. 1) that contacts the molds 2 and 3 and a lower position (see FIG. 3) in which the lower portion is accommodated in the recess 41a. That is, the lower side mold 23 can be moved from the closed position of the mold 1 in the direction of increasing the volume of the cavity 4, and the volume of the cavity 4 is changed by changing its position. In this embodiment, the movement amount of the lower side mold 23 is about 1 mm at the maximum, and the depth of the recess 41a is at least more than that, for example, about 2 mm to 5 mm.

  Further, as shown in FIG. 1, an upper base 50 that can be moved up and down by a driving means (not shown) is installed above the outer mold 2, and a vulcanizing medium is formed on the lower surface of the lower die 2 in the same manner as the lower platen 41 during vulcanization molding. A disk-shaped upper platen 51 is fixed to the inside. Further, an outer ring 52 is fixed to a radially outer end of the upper platen 51 on the lower surface of the upper base 50, and an inner peripheral surface 52a thereof is formed on an inclined surface (a part of a conical surface) whose diameter increases downward. Has been. On the radially inner side of the outer ring 52 and on the lower side of the upper platen 51, a vulcanization molding die 1, an upper plate 53, a sector segment 54, and the like, which will be described later, are disposed.

  An upper plate 53 is provided at a position directly below the upper platen 51 and in contact with the lower surface thereof. The upper plate 53 is connected to the tip of a piston rod 58 of a piston / cylinder mechanism (not shown), and can be moved up and down separately from the upper base 50 by operating the piston / cylinder mechanism. An upper side mold 22 is provided on the lower surface of the upper plate 53, and a plurality of arc-shaped sector segments 54 arranged side by side in the circumferential direction are slidably attached to the outer side in the radial direction. Yes.

  A plurality of segments constituting the above-described tread mold 21 are fixed to the inner peripheral surface of each sector segment 54, and at the time of vulcanization molding, a vulcanization medium is supplied to heat the tread mold 21. It is like that. Further, the outer peripheral surface 54a of each sector segment 54 is formed on an inclined surface (a part of a conical surface) having the same gradient as the inclined surface of the inner peripheral surface 52a of the outer ring 52, and both surfaces 52a and 54a are provided by a groove joint or the like. While being connected, they are slidably engaged.

  As a result, when the outer ring 52 moves up and down with respect to the upper plate 53, the sector segment 54 and the tread mold 21 are supported in the upper plate 53 by the wedge action between the inner peripheral surface 52 a and the outer peripheral surface 54 a. It is designed to move in sync with. Further, when the upper plate 53 is lowered until the lower surface of the sector segment 54 comes into contact with the upper surface of the lower base 40, and when the upper base 50 is lowered until the lower surface of the upper platen 51 comes into contact with the upper surface of the upper plate 53, 54 and the segments of the tread mold 21 are in close contact with each other to form a ring shape as a whole. At this time, the vulcanization mold 1 is closed, and a cavity 4 for hermetically storing the green tire 5 is formed between the outer mold 2 and the inner mold 3.

  On the other hand, on the upper surface of the upper base 50, a plurality of piston / cylinder mechanisms 55 (two in the figure) are arranged at equal intervals along the circumferential direction of the upper side mold 22, and the piston rod 56 is directed downward. It is fixed. The piston rod 56 passes through a through hole 57 that penetrates from the upper surface of the upper base 50 to the lower surfaces of the upper platen 51 and the upper plate 53, and the tip thereof is attached to the upper surface of the upper side mold 22. In addition, an annular recess 53 a that can accommodate an upper portion of the upper side mold 22 is formed in a portion facing the upper surface of the upper side mold 22 on the lower surface of the upper plate 53.

  Accordingly, as shown in FIGS. 1 and 3, the upper side mold 22 is operated in an inward / outward direction of the recess 53 a by operating a plurality of piston / cylinder mechanisms 55 in conjunction with the lower side mold 23 described above (see FIG. It can be moved in the vertical direction in the figure, and thereby, between a lower position (see FIG. 1) that contacts the other molds 2 and 3 and an upper position (see FIG. 3) in which the upper portion is accommodated in the recess 53a. It is possible to move with. That is, the upper side mold 22 can be moved from the closed position of the mold 1 in the direction of increasing the volume of the cavity 4, and the volume of the cavity 4 is changed by changing its position. In the present embodiment, the movement amount of the upper side mold 22 is about 1 mm at the maximum, and the depth of the recess 53a is at least more than that, for example, about 2 mm to 5 mm.

  A procedure for manufacturing a pneumatic tire using the tire vulcanization molding apparatus 10 configured as described above will be described. First, the segments 31, 32 are assembled to form the inner mold 3, and the final shape of the product tire is obtained by sequentially laminating tire components such as carcass plies, belts, and tread rubber on the outer surface while rotating around the axis. The green tire 5 close to is molded.

  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. At this time, the tire vulcanization molding apparatus 10 is in a state where the upper base 50 and the upper plate 53 are raised, that is, each sector segment 54 and the tread mold 21 are expanded in the radial outer position, and the upper side mold The mold 22 is raised and the outer mold 2 is kept open.

  Next, the inner mold 3 and the green tire 5 on the surface thereof are carried into the outer mold 2 and placed on the lower side mold 23 so that the radial direction is in the lateral direction. At this time, the lower side mold 23 is moved to the closing position of the mold 1 (above the concave portion 41a) (see FIG. 1). Further, the vulcanization medium is supplied to the upper and lower platens 51 and 41 and the sector segment 54, and the upper and lower side molds 22 and 23 and the tread mold 21 are kept at a predetermined vulcanization temperature (about 150 ° C.).

  Next, in a state where a predetermined distance is maintained between the lower surface of the upper platen 51 and the upper surface of the upper plate 53, that is, in a state where each sector segment 54 is expanded radially outward, the upper base 50 and the upper plate 53. Move down in conjunction with. At this time, the upper side mold 22 is moved to the closing position of the mold 1 (a position below the recess 53a) (see FIG. 1). In this state, the descent continues, and when the lower surface of the sector segment 54 comes into contact with the upper surface of the lower base 40 and the upper side mold 22 comes into contact with the green tire 5, the lowering of the upper plate 53 is stopped.

  Thereafter, only the upper base 50 is continuously lowered. At this time, the piston / cylinder mechanism 55 fixed to the upper surface of the upper base 50 is interlocked so that the position of the upper side mold 22 does not change. By operating, the piston rod 56 is housed in the cylinder by the lowering amount of the upper base 50. In this way, the upper base 50 is brought close to the upper plate 53, and the sector segment 54 and the tread mold 21 are brought radially inward by the wedge action between the inner peripheral surface 52a of the outer ring 52 and the outer peripheral surface 54a of the sector segment 54. Move in sync.

  When the upper base 50 is lowered to the lower limit and the upper platen 51 and the upper plate 53 come into contact with each other, the sector segment 54 moves to the movement limit on the radially inner side, and the vulcanization mold 1 is closed. The green tire 5 is housed in the container. Next, the upper base 50 is pressed downward by a driving means (not shown) to apply a large clamping force, and then a vulcanization medium is supplied to the interior 33 in the inner mold 3 to start vulcanization molding. The heat of the vulcanizing 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 by this heat and the heat from the outer mold 2.

  At this time, the outer mold 2 that is held in advance at the vulcanization temperature (around 150 ° C.) does not change in temperature and does not thermally expand, whereas the inner mold 3 increases the temperature from the preheating temperature to the vulcanization temperature. Therefore, the volume of the cavity 4 gradually decreases as the temperature rises. At the same time, the green tire 5 in the cavity 4 also expands greatly as the temperature rises, so that the pressure in the cavity 4 gradually increases. As a result, the green tire 5 is pressurized and the rubber flows, and the cavity 4 is filled with rubber, and the surface is pressed against the molds 2 and 3 to form the final shape of the product tire. Is done. Thereafter, the vulcanization mold 1 is maintained at the vulcanization temperature for a predetermined time, and a crosslinking reaction (vulcanization reaction) is advanced to cure the tire rubber, thereby producing a product tire having an appropriate elasticity.

  However, when the pressure in the cavity 4 becomes excessive, as described above, the molds 2 and 3 are deformed or damaged, or gaps between the molds are opened, and rubber protrudes therefrom. Therefore, in the tire vulcanization molding apparatus 10 according to the present embodiment, the upper side mold 22 is moved upward with the concave portion 53a in accordance with an increase in pressure in the cavity 4 while the positions of the sector segment 54 and the tread mold 21 are fixed. And the lower side mold 23 is moved into the recess 41a in the downward direction (see FIG. 3), and the volume of the cavity 4 is increased to absorb the thermal expansion of the tire rubber and suppress an excessive increase in pressure. To do.

  FIG. 4 is a graph schematically showing an example of pressure change in the cavity 4 at the time of vulcanization molding, where the horizontal axis indicates the time (seconds) from when the mold 1 is closed, and the vertical axis indicates the time at that time. Indicates pressure. Note that the pressure in the cavity 4 has a certain width in the region indicated by the oblique lines in the figure, because the pressure varies depending on each part of the tire, such as the tread portion, the shoulder portion, and the sidewall portion.

  As shown in the figure, the pressure in the cavity 4 increases with time, that is, with increasing temperature. However, after about 1500 seconds have passed since the vulcanization mold 1 is closed and the temperature approaches the vulcanization temperature and the pressure exceeds 5 MPa, the thermal expansion amount of the inner mold 3 and the green tire 5 also decreases. The pressure also gradually increases within 5-6 MPa. In the present embodiment, for example, the pressure is measured by a pressure gauge (not shown), and when the pressure in the cavity 4 reaches about 5 MPa, the upper and lower side molds 22 and 23 start to move, and the volume of the cavity 4 is set to the pressure. Increase as you rise. Since the tire rubber thereafter thermally expands toward the portion where the upper and lower side molds 22, 23 move and the volume increases, the pressure in the cavity 4 becomes constant at about 5 MPa, as indicated by the dotted line in the figure. An excessive increase in pressure is suppressed.

  Here, the vulcanization molding of the tire includes a first stage in which a crosslinking reaction proceeds while the green tire 5 is molded into a predetermined shape, and a second stage in which predetermined physical properties are imparted to the tire. In the first stage, the tire rubber has plasticity and flows in the cavity 4. On the other hand, when the second stage is reached, the crosslinking reaction proceeds, the rubber is cured, the plasticity is lost, and the rubber does not easily flow. Become. In the example of FIG. 4, the boundary between the first and second stages is the time when the pressure increase amount in the cavity 4 reaches about 5 MPa. A shape is formed. After that, even if the tire expands thermally, the rubber does not flow easily. Therefore, even if the shape of the cavity 4 changes slightly and the tire deforms accordingly, the final shape of the product tire is less affected. Tires maintain the product shape.

  In the present embodiment, as described above, after the pressure in the cavity 4 reaches about 5 MPa, that is, after the molding of the tire is completed, the upper and lower side molds 22 and 23 are moved to change the shape of the cavity 4. Further, deformation of the tire shape due to rubber flow can be prevented. Therefore, while maintaining the final shape of the product tire, an excessive increase in pressure in the cavity 4 can be suppressed to prevent the molds 2 and 3 from being deformed or damaged, or protruding from the rubber.

  In addition, the start time of the movement of the upper and lower side molds 22 and 23 may be after the tire molding is completed, and depending on the size and type of the tire to be manufactured or the design dimensions of the molds 2 and 3, You may start at other times. That is, when the pressure in the cavity 4 reaches a predetermined pressure other than about 5 MPa, the volume of the cavity 4 may be increased and the pressure maintained.

  However, when the pressure of the cavity 4 is less than 4 MPa, the vulcanization pressure is insufficient, and as described above, the molding and the exhaust of air become insufficient, resulting in poor appearance such as air accumulation in the tire. There is a fear. On the other hand, when the pressure is 6 MPa or more, the pressure applied to the molds 2 and 3 is increased, and deformation or breakage occurs in them, or a gap is generated between the molds 2 and 3 to cause burrs due to protrusion of rubber. May occur. Accordingly, the pressure in the cavity 4 is preferably maintained at 4 MPa or more and less than 6 MPa, that is, about 5 MPa.

  In addition, the upper and lower side molds 22 and 23 may be interlocked and moved in the same amount in the opposite direction to increase the volume of the cavity 4 in the vertical direction, and are not interlocked separately depending on the pressure of each part. It may be moved to. Further, a driving gas having a predetermined pressure (about 5 MPa in the present embodiment) is supplied to the plurality of piston / cylinder mechanisms 42 and 55 that drive the upper and lower side molds 22 and 23, and the pressure in the cavity 4 becomes the predetermined pressure. When the pressure is exceeded, the piston rods 43 and 56 are pushed by the pressure and retracted into the cylinders to suppress an excessive increase in the pressure in the cavity 4 and to maintain a predetermined pressure. .

  Vulcanization molding is performed as described above, and after a predetermined time has elapsed, the outer mold 2 is opened by an operation reverse to the above procedure, and the vulcanized tire integrated with the inner mold 3 is taken out from the outer mold 2. Thereafter, the segments 31 and 32 constituting the inner mold 3 are disassembled and taken out from the vulcanized tire, and the vulcanized tire is separated from the inner mold 3. When a new tire is molded, the inner mold 3 cooled to near room temperature is reassembled and the above-described procedure is repeated.

  As described above, the tire vulcanization molding apparatus 10 according to the present embodiment responds to the pressure when the pressure in the cavity 4 increases due to thermal expansion of the inner mold 3 and the green tire 5 during tire vulcanization molding. Since the upper and lower side molds 22 and 23 are moved to increase the volume of the cavity 4, the thermal expansion of the tire can be absorbed to prevent an excessive increase in pressure in the cavity 4. In addition, the upper and lower side molds 22 and 23 are moved after the molding of the tire is completed and the rubber loses its plasticity, so that the flow of the rubber is prevented and the deformation of the tire shape is suppressed, and the final shape of the product tire is reduced. Can be maintained.

  In this way, since the pressure received by the molds 2 and 3 can be suppressed, deformation and breakage of the molds 2 and 3 can be prevented, and a gap can be formed between the molds 2 and 3 or between the sector segments 54. It is possible to prevent the occurrence of burrs due to the protrusion of rubber. Moreover, since the pressure in the cavity 4 can be maintained at a predetermined vulcanization pressure, it is possible to suppress the occurrence of air accumulation and improper molding. Therefore, the appearance quality of the product tire can be improved, the tire disposal due to the appearance defect, the removal work of burrs and the like can be reduced, and the molds 2 and 3 can be used for a long time, so that the manufacturing cost can be reduced.

It is sectional drawing which shows schematic structure of the tire vulcanization molding apparatus of this embodiment. It is a top view of the inner mold of the tire vulcanization mold of this embodiment. This is a tire vulcanization molding apparatus in a state where the upper and lower side molds are moved to increase the volume of the cavity. It is a graph which shows typically an example of pressure change in a cavity at the time of 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 mold, 3 ... Inner mold, 4 ... Cavity, 5 ... Green tire, 10 ... Tire vulcanization molding apparatus, 11 ...・ Supply passage, 12 ... rectifier plate, 21 ... tread mold, 22 ... upper side mold, 23 ... lower side mold, 31 ... fan segment, 32 ... etc Segments 33 ... inside 34 ... circular hole 40 ... lower base 41 ... lower platen 41a ... recessed portion 42 ... piston / cylinder mechanism 43 ... piston Rod, 44 ... through hole, 50 ... upper base, 51 ... upper platen, 52 ... outer ring, 52a ... inner peripheral surface, 53 ... upper plate, 53a ... Recess, 54 ... Sector segment, 54a ... Outer peripheral surface, 55 ... Piston / cylinder mechanism, 6 ... the piston rod, 57 ... through hole, 58 ... piston rod.

Claims (4)

A vulcanization mold having a rigid inner mold that defines an inner surface shape of a tire and a rigid outer mold that defines an outer surface shape of the tire is provided between the outer surface of the inner mold and the inner surface of the outer mold. A tire vulcanization molding apparatus for accommodating and molding a green tire in a cavity formed in
The outer mold is composed of a plurality of molds including a mold movable in a direction to increase the volume of the cavity,
Means for moving the movable mold,
The moving means moves the movable mold when the pressure in the cavity during vulcanization reaches a predetermined pressure of 4 MPa or more and less than 6 MPa. . In the tire vulcanization molding apparatus according to claim 1,
The outer mold is composed of a tread mold that molds the shape of the tread portion of the tire, and an upper side mold and a lower side mold that mold both side surface shapes of the tire,
The tire vulcanization molding apparatus, wherein the movable molds are the upper side mold and the lower side mold . A rigid inner mold that defines the inner surface shape of the tire, and an outer mold that includes a plurality of rigid molds that define the outer surface shape of the tire, and 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 housed in a cavity formed therebetween and vulcanized,
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;
Supplying a vulcanization medium into the inner mold;
Increasing the volume of the cavity when the pressure in the cavity reaches a predetermined pressure of 4 MPa or more and less than 6 MPa;
Tire vulcanization method comprising Rukoto to have a. Te tire vulcanization method odor according to claim 3,
Wherein the predetermined pressure is a tire vulcanization wherein the pressure der Rukoto when completing an embossed shape of the green tire.

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