JP2009234161A - Mold and forming apparatus and method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain temperatures at the center part and a peripheral part on a forming surface of the mold constant so as to become substantially equal to each other. <P>SOLUTION: A temperature measuring hole 25 for attaching a thermocouple is disposed on a position which is near a forming surface 19 and deviates to the peripheral part from the center part. A control part controls a heating capacity of a heating means based on a temperature signal provided from the thermocouple. The peripheral part of the mold 16 is near the heating means and has thermal response higher than the center part and, therefore, is controlled into a stable temperature without hardly causing hunting phenomenon. By controlling the temperature of a peripheral part into a stable temperature, the center part of the mold 16 can be maintained constant to be almost the same temperature as the peripheral part after a prescribed elapse of time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mold and a molding apparatus and method using the same.

  A lens molding apparatus for manufacturing an optical lens using press molding is known. In press molding, a molding material is placed between a pair of molds having a high-precision molding surface, the pair of molds and the molding element are heated to a temperature above the glass transition point by heating means, and then press molding is performed. The shape of the molding surface is transferred to mold the optical lens.

As a heating means, there are one using an induction heating method and one using an infrared lamp. A plurality of these are arranged in the press direction so as to surround the pair of molds. In press molding, when the molded lens is cooled, if there is a temperature difference between the upper mold and the lower mold, there is a problem in that internal stress is generated and quality defects such as cracks on the molding surface occur. For this reason, a temperature sensor such as a thermocouple is attached near the molding surface on the axis (center portion) of the pair of molds, the temperature near the molding surface is measured, and the pair of molds is predetermined based on the measured temperature The ability of each heating means is individually controlled so as to reach the target temperature (for example, Patent Document 1).
JP-A-6-263463

  However, when heating from the outer periphery of the mold, if the heating capability of the heating means is controlled so that the temperature at the center of the mold is constant, as shown in FIG. 5, it is closer to the heating means and more responsive than the center. A hunting phenomenon that fluctuates up and down occurs at a high temperature around the mold. For this reason, the mold periphery cannot be kept at the same temperature as the center. If a temperature distribution is generated in the molding surface, internal distortion may occur in the molded optical lens or the shape accuracy of the optical surface may be deteriorated.

  The present invention has been made in order to solve the above-described problems, and a mold capable of forming a high-quality molded product while maintaining the mold temperature at substantially the same temperature in the peripheral portion and the central portion, and It aims at providing the shaping | molding apparatus and method using this.

  In the present invention, a temperature measuring hole for attaching a temperature sensor is provided in a peripheral portion of the interior of the mold that constitutes a part of the mold that is outward from the mold center. And based on the temperature of the peripheral part inside a type | mold, the heating capability of a heating means is controlled so that the temperature of a type | mold may become predetermined temperature. When the heating means is controlled so that the temperature around the mold is constant based on the temperature around the mold, heat is transferred from the periphery of the mold to the center after the temperature around the mold becomes constant. Therefore, the temperature at the center of the mold becomes substantially equal to the temperature at the periphery after a predetermined time has elapsed. Thereby, the temperature gradient in the molding surface of the mold can be eliminated and maintained at a constant temperature.

  It is desirable to form the temperature measuring hole at a position close to the molding surface at a peripheral portion that is outward from the mold center. It is desirable to use a thermocouple as the temperature sensor because of its high heat resistance. The heating means is for heating the mold, and may be a heating means for heating a part of the mold or a heating means for heating the entire mold by surrounding the mold. As the latter heating means, it is desirable to use a means for heating without contact from the outer periphery of the mold, for example, a high frequency induction heating means or an infrared lamp.

  According to the present invention, since the temperature measuring holes are provided in the peripheral portion that is outward from the mold center, the temperature of the mold peripheral portion is constant based on the temperature signal obtained from the temperature sensor attached to the temperature measuring hole in the peripheral portion. When the heating means is controlled so that the temperature of the peripheral portion becomes constant, heat is transferred from the peripheral portion to the central portion, and after a predetermined time, the temperature of the mold central portion becomes substantially equal to the temperature of the peripheral portion. . Thereby, the temperature gradient in the molding surface of the mold can be eliminated and maintained at a constant temperature. Therefore, for example, it is possible to surely prevent inconveniences such as internal distortion in the optical lens and deterioration of the shape accuracy of the optical surface, and a high-quality molded product can be molded.

  As shown in FIG. 1, the lens molding apparatus 10 according to the embodiment of the present invention includes a mold 11, a heating unit 12, a control unit 14, and the like. The mold 11 includes upper and lower molds 15 and 16 and a body mold 17. Molding surfaces 18 and 19 for molding a molding material (for example, a preform glass material) are formed on the upper and lower molds 15 and 16 on opposite surfaces, respectively. The body mold 17 and the upper mold 15 are movable molds that move in the pressing direction, and the lower mold 16 is a fixed mold. The body mold 17 adjusts the center thickness of the molded product (optical glass) by aligning the centers of the upper and lower molds 15 and 16 and positioning the distance between the upper and lower molds 15 and 16. The heating means 12 is arranged so as to surround the pair of molds 15 and 16. In the present embodiment, a high-frequency induction heating type heating unit is used as the heating unit 12. Therefore, the heating means 12 has a configuration in which the induction coil is arranged so as to surround the upper and lower molds 15 and 16.

  The lower die 16 is formed with a step portion 20 in contact with the body die 17 on the outer periphery, and has a two-stage cylindrical shape including a first cylinder 21 having a large diameter and a second cylinder 22 having a smaller diameter. . A cavity 23 is formed inside the first cylinder 21 in order to reduce the thickness and improve the heat response. A temperature measuring hole 25 having a circular cross section is formed in the bottom of the cavity 23 in parallel with the pressing direction in order to attach the thermocouple 24. The temperature measuring hole 25 is formed near the molding surface 19 and at a position shifted from the center of the second cylinder 22 toward the periphery.

  The thermocouple 24 is a well-known sheathed thermocouple. When two types of metal wires having different thermoelectric power are joined at the ends, and two joint points are set at different temperatures, current flows in one direction, This is a temperature sensor using the Seebeck effect in which an electromotive force is generated.

  The thermocouple 24 has a front end portion (hot junction) inserted into the bottom of the temperature measuring hole 25, a conductive wire portion is taken out of the lower mold 16 through the hollow portion 23, and a rear end portion (cold junction) is the amplifier 27. It is connected to the control unit 14 via. The amplifier 27 amplifies the temperature signal obtained from the thermocouple 24. Based on the temperature signal obtained from the amplifier 27, the control unit 14 controls the capability of the heating means 12 via the high frequency power supply 28 so that the pair of molds 15 and 16 and the molding material have a predetermined target temperature. . The high frequency power supply 28 adjusts the power supplied to the heating means 12.

  The upper mold 15 has the same shape as the lower mold 16 except for the molding surface 18. Inside this, a temperature measuring hole 30 is provided near the periphery and near the molding surface 18, and a thermocouple 31 is attached to the temperature measuring hole 30. The rear end portion of the thermocouple 31 is connected to the control unit 14 via the amplifier 33.

  As shown in FIG. 2, the temperature measuring hole 25 is formed near the periphery of the second cylinder 22 and close to the molding surface 19. As shown in FIG. 3, the thermocouple 24 is attached with its tip 24 a contacting the bottom of the temperature measuring hole 25 in order to perform accurate measurement. The thermocouple 24 is housed in a protective tube 32 made of stainless steel or the like. In the present embodiment, the radial length L from the periphery to the bottom center of the temperature measuring hole 25 and the axial length H from the surface 19a on which the molding surface 19 is formed to the bottom of the temperature measuring hole 25 are lower. The temperature measuring hole 25 is formed at a position that is shorter than the radial length W from the central axis of the mold 16 to the bottom center of the temperature measuring hole 25. In FIG. 1, the upper and lower molds 15 and 16 are combined with the temperature measuring hole 25 being shifted by 180 degrees, but the upper and lower molds 15 and 16 are oriented so that the temperature measuring holes 25 face each other. You may combine.

  The lens molding is roughly classified into a molding material supply process, a heating process, a pressing process, a slow cooling process, a rapid cooling process, and a molded product removal process. By repeating these series of cycles, a molded product is continuously formed. Although not shown, the lens molding apparatus 10 of the present embodiment is built in a molding chamber capable of maintaining the inside in an airtight state.

  In the molding material supply process, in the molding material supply process, the upper mold 15 is retracted upward, and the body mold 17 is incorporated in the lower mold 16. The shutter of the molding chamber is opened and the molding material is transferred to the molding surface 19 of the lower mold 16.

  In the heating step, the pair of molds 15 and 16 and the molding material are heated. At this time, the control unit 14 controls the heating capability of the heating unit 12 based on the temperature signal obtained from the pair of thermocouples 24 and 31. The pair of thermocouples 24 and 31 measure the temperature closer to the peripheral part than the center part of the pair of molds 15 and 16, and the control unit 14 is based on the temperature signal obtained from the pair of thermocouples 24 and 31. The heating capability of the heating means 12 is controlled so that the temperature near the periphery of the pair of molds 15 and 16 is constant.

  Thus, when the temperature of the peripheral part is controlled to a stable temperature with little hunting phenomenon on the basis of the temperature of the peripheral part of the molds 15 and 16, the peripheral part and the central part of the pair of molds 15 and 16 have an integrated structure. Therefore, the heat of the peripheral part is transmitted toward the central part, and as shown in FIG. 4, the temperature of the peripheral part and the central part of the pair of molds 15 and 16 becomes substantially the same after a predetermined time has elapsed. Thereby, the temperature gradient in the radial direction of the pair of molds 15 and 16 is eliminated, and the temperature of the pair of molds 15 and 16 can be kept constant.

  When the pair of molds 15 and 16 and the molding material reach the target temperature (temperature above the glass transition point), a pressing process is performed after a predetermined time. In the pressing step, the upper die 15 is lowered and incorporated into the body die 17, and the upper die 15 is pressurized toward the lower die 16 by a pressing means (not shown). Thereby, the shape of the molding surfaces 18 and 19 of the upper and lower molds 15 and 16 is transferred to the molding material, and a molded product is molded. In the heating / pressing process, the atmosphere in the molding chamber is kept in an inert gas atmosphere such as a nitrogen gas in order to prevent oxidation of the molds 15 to 17.

  In the slow cooling step, an inert gas is supplied to the pair of molds 15 and 16 and the periphery thereof, and the pair of molds 15 and 16 and the molded product are gradually cooled to a temperature below the glass transition point. In this slow cooling process, the cooling speed of the molding surfaces 18 and 19 varies depending on the shape of the molding surfaces 18 and 19 such as the radius of curvature. The temperature change during the slow cooling process is taken into the control unit 14 in real time by the thermocouples 24 and 31 built in the upper and lower molds 15 and 16, and the temperature of the pair of molds 15 and 16 is determined in advance for each elapsed time. The control unit 14 controls the heating capability of the heating means 12 and 13 so that the set temperature is reached.

  Also at this time, since the heating capability of the heating means 12 and 13 is controlled based on the measured temperature obtained from the thermocouples 24 and 31 mounted near the peripheral portions of the upper and lower molds 15 and 16, the stability of the hatching phenomenon is small. Can be controlled. For this reason, the pair of molds 15 and 16 can be gradually cooled while maintaining a state in which no temperature distribution occurs. This prevents the generation of internal stress caused by the temperature difference between the pair of molds 15 and 16 and the temperature difference inside each of the pair of molds 15 and 16, and manufactures a high-quality molded product having no cracks on the surface. can do. In the gradual cooling step, the inert gas may be tempered only by the heating capability of the heating means 12 and 13 so that the rate of temperature reduction is moderate without supplying the inert gas to the dies 15 and 16 and the surroundings. . Further, in order to maximize the temperature gradient, the heating means 12 and 13 may be stopped and the cooling may be performed only by supplying the inert gas. Further, the driving of the heating means 12 and 13 and the supply of the inert gas may be stopped to allow natural cooling.

  When the temperature of the pair of molds 15 and 16 and the molded product is equal to or lower than the glass transition point, the slow cooling process is terminated and the rapid cooling process is performed. In the rapid cooling step, an inert gas is supplied to the pair of molds 15 and 16 and the periphery thereof to cool to a temperature at which the pair of molds 15 and 16 and the molded product can be taken out (temperature at which the molded product is released from the mold). At the end or after the cooling step, the upper die 15 and the barrel die 17 are sequentially retreated upward. In the molded product removal step, the shutter of the molding chamber is opened, and the molded product is removed from the molding surface 19 of the lower mold 16 by the robot arm.

  In the embodiment described above, the lower mold 16 is fixed, and the body mold 17 and the upper mold 15 are moved. However, the body mold 17 may be fixed and the upper and lower molds 15, 16 may be moved. A structure in which the upper die 15 is fixed and the barrel die 17 and the lower die 16 are moved may be employed. Further, although a mold including a pair of molds 15 and 16 and a trunk mold 17 is used, the trunk mold 17 may be omitted and a mold including only the pair of molds 15 and 16 may be used for molding. . Furthermore, although the heating means 12 and 13 are used as a heating means, an infrared lamp etc. may be used. Furthermore, the temperature measuring hole 25 is formed in each of the upper and lower molds 15 and 16, but only one of the molds is formed, and the heating capability of the heating means is based on the temperature sensor provided in the temperature measuring hole. May be controlled. Further, in order to improve the heating responsiveness, the cavity portion 23 is formed inside the first cylinder 21, but in order to further improve the heating responsiveness, a cavity portion may be provided also in the inside of the second cylinder 22. Good. In this case, the temperature measuring hole 25 may be formed in the pressing direction within the thickness of the side surface connected to the molding surface 19 of the second cylinder 22.

  In each of the above embodiments, a glass molded product is obtained from a glass material. However, the present invention is not limited to this. For example, a molding apparatus that obtains a resin molded product using a resin material may be used. Other than the lens may be used. Furthermore, the present invention can also be used for thermoforming.

It is sectional drawing which shows the structure of the lens shaping | molding apparatus which is embodiment of this invention. It is a perspective view which shows a lower mold | type, and has broken and shown half. It is an expanded sectional view which shows the bottom part of a temperature measuring hole. It is a graph which shows the type | mold temperature at the time of performing temperature control by this invention. It is a graph which shows the mold temperature at the time of performing temperature control with the lens shaping | molding apparatus demonstrated by the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lens shaping | molding apparatus 15 Upper mold | type 16 Lower mold | type 12 Heating means 14 Control part 18, 19 Molding surface 24, 31 Thermocouple 25, 30 Temperature measuring hole

Claims (3)

In the molding method for controlling the heating capability of the heating means based on the temperature signal obtained from the temperature sensor arranged inside the mold so that the temperature of the mold becomes a predetermined temperature,
A molding method characterized in that the heating capability of the heating means is controlled on the basis of the temperature of the peripheral part of the interior of the mold that is outward from the mold center.   In a mold to which a temperature sensor used for controlling the heating capability of the heating means is set so that the temperature of the mold becomes a predetermined temperature, in the periphery of the inside of the mold that is away from the mold center. A mold having a temperature measuring hole for mounting the temperature sensor. In a molding apparatus for controlling the heating capability of the heating means based on a temperature signal obtained from a temperature sensor arranged inside the mold so that the temperature of the mold becomes a predetermined temperature,
A molding apparatus, wherein a temperature measuring hole for attaching the temperature sensor is provided in a peripheral portion of the interior of the mold that is outward from the mold center.

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