JP4499579B2 - Press molding apparatus and optical element molding method - Google Patents

Description

  The present invention uses a press molding apparatus for manufacturing an optical element having a predetermined shape by supplying a molding material such as a glass material between a pair of molds that can be opened and closed, and closing the mold, and the press molding apparatus is used. The present invention relates to a method for molding an optical element.

2. Description of the Related Art There is known a press molding apparatus that manufactures an optical element having a predetermined shape by supplying a glass material between a pair of molds that can be opened and closed, and closing the mold. In such a press molding apparatus, a combination of a servo motor and a ball screw / nut mechanism is known as a drive mechanism for moving an upper mold or a lower mold among a pair of upper and lower molds. For example, it is disclosed in the following Patent Documents 1, 2, and 3.
JP-A-63-95133 Japanese Utility Model Publication No. 7-6242 JP-A-3-265527

  The technique disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 63-95133) has a drawback that since the main shaft and the ball screw are not concentric, a moment is applied when a press load is applied, and the main shaft tends to tilt. If the main axis is tilted, the accuracy of decentration of the lens deteriorates.

  In the technique disclosed in Patent Document 2 (Japanese Utility Model Publication No. 7-6242), the main shaft and the ball screw are arranged in a straight line. Therefore, since no moment is generated when a press load is applied, tilting of the main shaft is unlikely to occur and lens tilt is unlikely to occur. However, since the length in the axial direction becomes the length obtained by adding the screw shaft to the main shaft and becomes longer, the position of the molding die becomes higher, the apparatus becomes larger, and the workability becomes worse.

  In the technique disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 3-265527), even if the main shaft and the ball screw are not in a straight line, the applied pressure is transmitted in a point contact state to the shaft center of the lower end surface of the holding shaft. The inclination of the holding shaft can be suppressed. However, since it is point contact, the pulling force at the time of mold release cannot be controlled.

  As described above, with respect to the press shaft (main shaft) and its drive mechanism used in the press molding apparatus for optical element manufacturing, the apparatus is downsized, the shaft is prevented from tilting, and the driving force (including tension) is controlled. There was no thing that could balance both.

  From this point of view, the inventor of the present application uses Japanese Patent Application No. 2003-341632 (filing date: Heisei Heisei) for a method of raising and lowering the spindle using two ball screws and two servomotors (this method is hereinafter referred to as “twin drive method”). (September 3, 2015).

  This twin drive type drive mechanism consists of left and right screw shafts (ball screws), two servo motors that rotate the screw shafts, and the left and right screw shafts. Elevating member (slider) that moves, one main shaft attached to the center of the slider, a lower base mold provided at the tip of the main shaft, a linear guide that guides the elevating of the slider, and a position every few milliseconds simultaneously And a control unit that controls the servo motor so that the left and right screw shafts are moved up and down in synchronization by repeating the control. In this drive mechanism, by controlling the drive so that the rotations of the two servo motors are always synchronized, the load applied to the main shaft by the press operation is evenly received by the two screw shafts to prevent the tilt of the main shaft. Can do. Further, the apparatus can be downsized.

  By the way, even if the control of raising and lowering the molding die during press molding is performed using a press molding apparatus that employs a twin drive system, if continuous press molding is performed, the lifting member ( It is completely unavoidable that the slider) is inclined.

  That is, in the process of continuous pressing, the temperature of the screw shaft may increase by several degrees Celsius to several tens of degrees Celsius. The main causes of the temperature rise are sliding heat at the screw engaging portion and heat transfer from the mold. In a twin drive type drive mechanism, if a temperature difference occurs between two screw shafts, a difference in thermal expansion occurs between these screw shafts, and even if the rotation of two servo motors is precisely controlled, the slider does not move. It will tilt slightly. For this reason, the main shaft attached to the slider is also tilted, and the parallelism of these molds during the approaching action of the upper mold and the lower mold is lost. If the parallelism between the upper and lower molds cannot be ensured, a tilt occurs between them, which leads to a horizontal misalignment between the axial positions when the upper and lower molds come into contact with each other.

  In addition, when a pair of upper and lower molds having molding surfaces are configured to contact and separate within a body mold that functions as a positioning member for obtaining the coaxiality, or support the upper and lower molds, respectively. When a positioning member provided with positioning pins and pin guide holes is provided on the opposing surface of the member (herein referred to as “upper and lower matrix”), these positioning members are provided on either the upper die or the lower die opposing surface. Usually provided protruding. Therefore, when the tilt or misalignment of the lower mold approaches the clearance between the trunk mold and the lower mold, or the clearance between the pin and its guide hole, the upper and lower molds approach and And the lower mold or rubbing between the positioning pin and its guide hole easily occur.

  If friction powder is generated due to rubbing of the mold, the lower mold surface may be stained and the appearance of the lens may be poor. Furthermore, if the main shaft is inclined too much, it may not be possible to assemble the body mold into which the upper mold is inserted and the lower mold.

  Further, if a part of the press load is taken away by the rubbing portion and an appropriate load is not applied to the pressed product, the surface accuracy of the lens may be deteriorated, or the lens thickness may be out of spec.

  Thus, even in the drive mechanism of the twin drive system, there is a problem that even when the components are set in the best state, rubbing is likely to occur during repeated pressing. Recently, there has been a demand for higher decentration accuracy of lenses, and it has become necessary to make the clearance between the barrel mold and the upper and lower molds less than 10 μm, more preferably 5 μm, and this problem has become serious.

  In view of these points, the object of the present invention is to correct the inclination generated in the upper die or the lower die during continuous press molding, etc., and to suppress the friction of the sliding portion between them and the deterioration of the eccentricity accuracy. The present invention is to propose a press molding apparatus and a method for molding an optical element using the press molding apparatus.

In order to solve the above problems, the present invention has a mold including an upper mold and a lower mold that are openable and closable having opposed molding surfaces, and at least one of the upper mold and the lower mold. In a press molding apparatus that press-molds a molding material by bringing the mold close to the other mold,
A main shaft supporting the mold on the moving side;
A lifting member supporting the main shaft;
An elevating mechanism for elevating the elevating member in the axial direction of the main shaft;
Control means for controlling the lifting operation by the lifting mechanism;
Detecting means for directly or indirectly detecting the state of inclination between the opposing surfaces of the mold at a predetermined point in the press cycle;
The elevating mechanism includes a plurality of rotating shafts that support the elevating member, and a plurality of rotation driving sources for rotationally driving each of the rotating shafts, and the rotational movement of each rotating shaft is performed by the elevating member. Each rotating shaft is engaged with the elevating member so as to be transmitted as the elevating movement of
The control means controls rotation of each rotational drive source based on the detected tilt state so that the opposing surfaces are parallel.

  In the press molding apparatus of the present invention, when each rotary shaft is thermally deformed in the axial direction, even if each rotary drive source is rotated the same, a difference occurs in the feed amount of the lifting member by each rotary shaft. Due to the difference in the feed amount, the elevating member is inclined, the moving mold supported by the elevating member is inclined with respect to the other mold, and is in a single-contact state when the mold is closed. In the present invention, the inclination states of the opposing surfaces of both molds are directly or indirectly monitored, and the rotation of each rotation drive source is controlled so that these inclinations are eliminated. That is, the rotation amount of each rotary drive source is controlled so that the feed amount of the elevating member by each rotary shaft is the same. Therefore, it is possible to avoid the occurrence of a single contact state between the upper die and the lower die, and it is possible to perform highly accurate press molding.

  Here, the detection means of the present invention includes at least one of an attitude of the elevating member, an attitude of the main shaft, an attitude of the molding die on the moving side, a rotation state of the rotation shaft, and a rotation state of the rotation drive source. It is characterized by detecting one. For example, in order to directly detect the amount of inclination of the opposing surfaces of both molds, the level of the molds may be detected using an optical sensor or the like. Or you may detect the relative angle of the opposing surface of both molds. Moreover, if the inclination of the main shaft is detected, the inclination of the mold supported by the main shaft can be indirectly detected.

  Further, when the moving mold hits the other mold, the mold does not move any further, and the load acting on the rotating shaft increases, and the rotation of the rotating shaft stops. If the rotation of each rotating shaft stops at the same time, it means that the opposing surfaces of the molds are parallel to each other. If the rotation does not stop at the same time, the mold is in a piece-to-piece state, that is, the mold It means that the mutually opposing surfaces are inclined. Therefore, the inclination of the opposing surfaces of the molds can be indirectly known from the rotation state of the rotating shaft.

  Next, the control means of the present invention controls the rotation of the rotational drive source based on the amount of inclination detected in the previous press cycle so that the facing surfaces are parallel in the next press cycle. It is a feature.

  In addition, the detecting means detects a stop rotation position at the time when the rotation of the rotation drive source or the rotation shaft stops when the load exceeds a predetermined value when the upper mold and the lower mold are close to each other, The control means obtains a difference between the detected stop rotation position and one of the remaining stop rotation positions on the basis of one of the detected stop rotation positions, and each rotation drive source or each The rotation amount of each rotation drive source is corrected based on the difference so that the rotation of the rotation shaft stops simultaneously.

  When the molding die falls into a piece contact state, the movement of the part of the elevating member corresponding to the part that is in contact with the piece stops, the load acting on the rotating shaft that supports this part increases, and the rotation stops. . However, since the load acting on the remaining rotating shaft is small, the rotation continues and the feeding operation of the corresponding lifting member portion continues. Therefore, by comparing the stop rotational positions of the respective rotary shafts or the respective rotary drive sources connected to the respective rotary shafts, the inclination state of the opposing surfaces of the molds can be known. In the present invention, the rotation amount of each rotation drive source is corrected so that there is no difference between the respective stop rotation positions. In other words, the feed amount of the elevating member by each rotation shaft connected to each rotation drive source Therefore, the opposing surfaces of the molds can be brought close to each other in parallel.

Next, a typical configuration of the press molding apparatus of the present invention is as follows.
The rotary shaft includes first and second feed screw shafts,
The rotary drive source includes a first servo motor connected to the first feed screw shaft and a second servo motor connected to the second feed screw shaft,
The detection means includes a first rotational position detector that detects a rotational position of the first servomotor and a second rotational position detector that detects a rotational position of the second servomotor, and the upper mold And the first and second stop rotation positions at the time when the rotation of the first and second servo motors stops due to the load exceeding a predetermined value when the lower mold is in proximity,
The control means obtains a difference between the detected first and second stop rotational positions, and when the upper die and the lower die are close to each other in the next press cycle, based on the difference, the position of at least one of the servo motors It is characterized by correcting the target value of control.

  In the press molding apparatus of the present invention, in order to prevent a moment from being generated in the main shaft, a plurality of rotating shafts supporting the elevating member that supports the main shaft are positioned at equal distances from the axis of the main shaft. It is desirable to arrange so that.

  On the other hand, the present invention is a method for molding an optical element using the press molding apparatus having the above-described configuration, wherein a heating step for heating the molding die to a predetermined temperature in advance, and a heat-softened molding material are conveyed, The method includes a supply step of supplying the molding material to a lower die of the molding die, and a pressure molding step of pressure-molding the molding material by bringing the molding die close to each other.

  Here, in the pressure molding step, the main shaft is moved at a first moving speed to a predetermined position before the molding material supplied to the lower mold contacts the upper mold, and passes through the predetermined position. After that, it is desirable to move the spindle at a second movement speed that is slower than the first movement speed.

  In the press molding apparatus of the present invention, the inclinations of the opposing surfaces of the molds are grasped, and the rotary shafts for raising and lowering the lifting members supporting the main shaft supporting the molds are eliminated so that the inclination is eliminated. The rotation is controlled.

  Therefore, according to the present invention, when the rotary shafts supporting the elevating member are thermally deformed in the axial direction, etc., the feed amount varies, in other words, when the elevating member is inclined. Even if it exists, the rotation amount of each rotating shaft is corrected so as to eliminate the variation (inclination). Therefore, the elevating member can always be held in a predetermined posture, and the main shaft supported here can be held in a predetermined posture. Therefore, the mold supported by the main shaft can be held so as to be always parallel to the other mold. Therefore, according to the present invention, it is possible to increase the molding accuracy, particularly the eccentricity accuracy of the press-molded product (to suppress molding tilt and molding shift).

  In addition, when one molding die is close to the other molding die as described above, the pressing process is performed in which the opposing surfaces are made parallel to each other and the opposing surfaces are brought into close contact with each other to apply a load. Since the inclination of the spindle due to the generation of moment can be avoided, the occurrence of eccentricity can be suppressed consistently in the molding process.

  Embodiments of a press molding apparatus and an optical element molding method to which the present invention is applied will be described below with reference to the drawings.

  FIG. 1 is a schematic plan view showing an example of a glass optical element manufacturing apparatus using the press molding apparatus of the present invention. The manufacturing apparatus of this example is for manufacturing four small lenses at the same time by heat-softening a spherical glass material and press-molding it with a molding die processed with high accuracy.

  As shown in FIG. 1, the manufacturing apparatus 50 includes a heating chamber 100 and a molding chamber 200, and both chambers 100 and 200 communicate with each other through a passage 130 having an opening / closing valve 131. The heating chamber 100 is an area for preheating the glass material to a temperature suitable for pressing, a supply unit 111 for supplying the glass material to the heating chamber 100 from the outside, and a conveyance unit for conveying the supplied glass material. 112 and a heating means 113 for heating the glass material in advance. The heating means 113 is a resistance heating furnace having upper and lower heaters.

  The conveying means 112 includes a two-part divided plate 112d and an arm 112c, and can be opened and closed in the horizontal direction. Furthermore, the glass material on the tray 112d can be floated by blowing gas from the bottom of the tray 112d. Further, the conveying means 112 includes a drive base 112b that supports the arm 112c and a sliding portion 112a for sliding the drive base 112b. The arm 112c can rotate in the horizontal direction around the drive base 112b, and can move forward and backward in the horizontal direction together with the drive base 112b.

  The conveying means 112 having this configuration receives the glass material supplied to the heating chamber 100 by the dish 112d, can be heated while floating there, moves to the molding chamber 200, and opens the arm 112c, thereby preheated glass. The raw material can be dropped and supplied onto a lower mold described later installed in the molding chamber 200.

  Next, the molding chamber 200 is an area for press-molding a preheated glass material with a preheated mold, and the press molding apparatus 1 and the press product after molding are automatically sent from the press molding apparatus 1. An unloading means 220 for taking out and conveying to the unloading means 230 is arranged. As will be described below, the press molding apparatus 1 includes a mother mold that holds a mold, a main shaft, and a high-frequency heating coil for preheating the mold.

  FIG. 2 is a schematic cross-sectional view showing the main configuration of the press molding apparatus 1, and shows a state during the press. The press molding apparatus 1 includes a molding unit 2 disposed in the molding chamber 200 and a drive unit 3 disposed on the lower side of the molding chamber 200. In the molding part 2, an upper mold 22 and a lower mold 23 having a pair of molding surfaces and a sleeve 24 that slidably guides these are disposed as a mold. The upper die 22 and the sleeve 24 are slidably accommodated in the upper mother die 25, and the lower die 23 is slidably accommodated in the lower mother die 26. The clearance between the upper and lower dies 22 and 23 and the sleeve 24 that determines the alignment accuracy of the upper die 22 and the lower die 23 affects the eccentricity accuracy of the press product, so that it is required to be 10 μm or less. In FIG. 2, a pair of molding dies are shown. However, a plurality of pairs (four pairs in FIG. 1) of the molding dies may be arranged on the mother die and a plurality of press moldings may be performed simultaneously. .

  The upper mother die 25 is fixed to the ceiling of the molding chamber 200 via the upper main shaft 27, and the lower mother die 26 is supported on the upper end of the lower main shaft 28. The lower main shaft 28 vertically penetrates the bottom surface of the molding chamber 200 in a rotatable state and extends toward the lower drive unit 3, and a lower end thereof is vertically moved in the drive unit 3. It is supported by the member 31. The elevating member 31 is supported along the linear guide 32 so as to be movable up and down.

  The elevating member 31 is raised and lowered by an elevating mechanism disposed in the drive unit 3. The lifting mechanism of this example is configured as follows. First, the elevating / lowering member 31 is supported by a first feed screw shaft 33 and a second feed screw shaft 34 that are vertically disposed at a portion that is symmetrical with respect to the axis 28 a of the lower main shaft 28. That is, nut portions 31a and 31b are formed at the left and right portions of the elevating member 31, and the first and second feed screw shafts 33 and 34 are screwed into these from below.

  The lower end of the first feed screw shaft 33 is coaxial and is connected to a first servo motor M1 disposed below the first feed screw shaft 33. Similarly, the lower end of the second feed screw shaft 34 is coaxially connected to a second servo motor M2 disposed below the second feed screw shaft 34. When the first and second servo motors M1, M2 are driven to rotate the first and second feed screw shafts 33, 34, nut portions 31a screwed into the feed screw shafts 33, 34, The elevating member 31 provided with 31 b moves up and down along the linear guide 32. Therefore, the lower main shaft 28 supported by the elevating member 31 moves up and down in the direction of the axis 28a, and the lower base mold 26 and the lower mold 23 attached to the upper end of the lower main shaft 28 are fixed to the upper base mold 25 on the fixed side. And it moves up and down with respect to the upper mold 22.

  A high frequency coil 37 for heating is arranged in a state surrounding the upper mother die 25 and the lower mother die 26 on the moving side. The upper and lower mother dies 25, 26 are induction-heated by the high-frequency coil 37, and the forming dies (upper die 22, sleeve 24, lower die 23) are heated by heat conduction from the upper and lower mother dies 25, 26. Accordingly, the upper and lower mother dies 25 and 26 are easily induction-heated, and a material having high temperature strength, for example, a tungsten alloy is preferable. Although not shown, a pin and its guide hole can be provided around the upper and lower mother dies in order to align the upper and lower mother dies.

  Here, in order to raise and lower the lower die 23 (lower mother die 26) coaxially without tilting with respect to the upper die 22 (upper mother die 25), it is effective to synchronize the rotations of the two feed screw shafts 33 and 34. It is. In this example, the rotational positions of the servo motors M1 and M2 are detected, and the position control of both servo motors M1 and M2 is performed in a short cycle of about several milliseconds so as to rotate them synchronously. Such position control is performed until the press is completed, that is, until the lower mold 23 is completely pushed. Since the two feed screw shafts 33 and 34 usually have a slight difference in screw pitch, etc., use a ball screw or a guide rail with weak or no preload to move it up and down smoothly. Is preferred.

The press cycle of the press molding apparatus 1 of this example will be described. In the press cycle, a heating process, a supply process, a pressure molding process, a cooling process, and a take-out process are set as one cycle. In the heating process, the molds 22, 23 and 24 are preheated by the high frequency coil 37. In the supplying step, immediately after the preheating is completed, the glass material preheated in the heating chamber 100 by the conveying means 112 is dropped and supplied onto the molding surface of the lower mold 23. The glass material is preferably heated to a temperature equal to or higher than the softening temperature (for example, a glass viscosity corresponding to 10 ⁶ to 10 ⁹ poise), and the mold is heated to a temperature corresponding to a glass material viscosity of 10 ¹⁰ to 10 ⁸ poise. The heating temperature of the glass material is preferably higher than the heating temperature of the mold.

  In the pressure molding process, the conveying means 112 is retracted into the heating chamber 100 and the lower mold 23 is raised by driving by position control. By rapidly raising the lower mold 23 to a position close to the upper mold 22, the cooling of the glass material can be minimized. The glass material is press-molded while repeating position control in a short period (for example, 4 ms) in accordance with the viscosity of the glass material from the close position. The glass material can be pressed at a speed of several mm / second.

Immediately after the press molding is completed, the cooling process is started with the upper and lower dies 22 and 23 closed. The cooling process may be started in the middle of press molding. When the molding dies 22 and 23 are cooled to a predetermined temperature equal to or lower than the temperature equivalent to 10 ^12.5 poises by the viscosity of the glass material, the process proceeds to an extraction step. In the take-out process, the lower mold 23 is lowered to the press product take-out position. Next, the press product is taken out from the lower mold 23 by the take-out means 230. Thereafter, the lower mold 23 is moved up and down to the preheating position, and the next press cycle is started.

  Next, FIG. 3 is a schematic block diagram showing a drive control system of the lifting mechanism of the press forming apparatus 1 of this example. The drive control system is configured around a control unit 41 formed of a microcomputer. The control unit 41 controls the drive of the servo motors M1 and M2 via the motor drivers 42 and 43 by executing a control program stored and held in a built-in ROM. A memory 44 is connected to the control unit 41, and various drive conditions such as a target position for position control necessary for press forming operations by the servo motors M <b> 1 and M <b> 2 are stored and held in advance in the memory 44. The motor drivers 42 and 43 are based on commands from the control unit 41, actual rotational positions detected by rotational position detection units 45 and 46 such as motor encoders, and load torque detected by the torque detection units 47 and 48. A drive current is generated to drive each of the servo motors M1 and M2.

  Further, the control unit 41 obtains a difference between stop rotation positions where the rotation of the servo motors M1 and M2 stops when the lower mold 23 is raised in the pressure molding process, and based on the difference, the position of each servo motor M1 and M2 Correct the target position for control. In this example, as described below, the target position of the servo motor M2 is corrected.

  FIG. 4 is a flowchart showing the operation of the press molding process by the press molding apparatus 1. The press process from when the preheated glass material is supplied by dropping until the lower mold 23 is pushed will be described according to this flowchart. In addition, description of a heating, conveyance, etc. is abbreviate | omitted.

  First, after a glass material is dropped and supplied onto the molding surface of the lower mold 23, a start signal for starting press is issued (step ST1). Thereafter, the control unit 41 starts position control (servo control) at a fixed cycle. That is, the control unit 41 takes in the rotational position information and the target position information of the servo motors M1 and M2, calculates the difference between the detected rotational position (current position) and the target position, and controls to eliminate this. Then, the target position of the position control and the control amount are sent to the motor drivers 42 and 43 at the same time. The motor drivers 42 and 43 drive the servo motors M1 and M2 based on them (step ST2).

  The rotational positions of the servo motors M1 and M2 are detected by the rotational position detectors 45 and 46, and these detection signals are taken into the motor drivers 42 and 43 and the controller 41 at a constant sampling period (step ST3, 4). The control unit 41 calculates the height position of the lower mold 23 from the detected rotational positions of the servo motors M1 and M2, respectively, and determines whether or not the predetermined position has been reached (step ST5). If the predetermined position has not been reached, the process returns to step ST2, and position control is executed again.

  Such feedback control is preferably performed at a cycle as short as possible, for example, at intervals of several milliseconds, in order to maintain the parallelism of the lower die with respect to the upper die at the time of press molding with high accuracy.

  When the position of the lower mold 23 reaches a predetermined position, the process proceeds to the next position control (step ST6). The predetermined position can be a position immediately before pressing, for example, when the glass material on the lower mold 23 comes close to the molding surface of the upper mold 22 in the ascending process of the lower mold 23 after the glass material is supplied. Ascending by position control every short time can be performed quickly before approaching and at a slow speed according to the viscosity of the glass material after approaching.

  Here, when the two feed screw shafts 33 and 34 are thermally deformed and there is a difference in the amount of expansion in the axial direction, the screw pitch also expands at the same ratio. Even if the same amount of rotation is performed in synchronism, a slight difference occurs in the feed amount, and the elevating member 31 is inclined. As a result, the lower main shaft 28 supported thereon is also inclined, and the lower mother die 26 and the lower die 23 attached thereon are inclined with respect to the upper mother die 25 and the upper die 22. If the lower mother die 26 and the lower die 23 are raised in this state, the upper mother die 25 and the upper die 22 are in a one-to-one contact state.

  FIG. 5 is an explanatory diagram showing the occurrence of a one-sided state, in which the molds 22, 23, and 24 are omitted. As shown in this figure, when a one-side contact state occurs in which the left end portion of the lower mother die 26 first hits the upper mother die 25, the raising of the left end portion of the elevating member 31 stops, and the first supporting portion is supported here. A large load acts on the side of the first servo motor M1 that rotationally drives one feed screw shaft 33, and the rotation of the servo motor M1 is stopped by the action of a built-in torque limiter or the like. On the other hand, the rotation of the other second servo motor M2 continues until the position where the right end portion of the lower mother die 26 hits the upper mother die 25, and then the rotation similarly stops.

  Therefore, when the opposing surfaces of the molds are inclined, the stop rotation positions at which the rotations of both servo motors M1 and M2 stop are different. In this example, based on detection signals from the rotational position detectors 45 and 46, a stop rotational position where the rotation of both the servomotors M1 and M2 stops is detected, and based on the difference between them, a target position for position control of the servomotor M2 is detected. In the next press cycle, the servo motors M1 and M2 are controlled to stop rotating simultaneously. In other words, the occurrence of the one-sided state is eliminated.

  Returning to the flowchart of FIG. 4 again, the control unit 41 samples the rotational position at the same cycle as the cycle of position control (steps ST7 and ST8), and the lower die 23 comes close to the upper die 22. Thereafter, the sampled rotational positions are sequentially compared to determine whether or not these values are the same (steps ST9 and ST10). Then, when the servo motors M1 and M2 stop rotating, the feeding operation of the lower mold 23 is stopped.

  For example, if the rotational positions of both servo motors M1 and M2 do not change over 10 cycles (a time width corresponding to several tens of milliseconds in total), a push-off state has occurred, that is, the upper and lower master dies 25 , 26 is in a state of complete contact, and the rotation position at the press-cutting completion position, that is, the stop rotation position is read, and the difference S (rotation speed of servo motor M2−rotation speed of servo motor M1) is calculated. Calculate (step ST11). Next, the calculated difference S is added to the target position of the second servo motor M held in the memory 44 to correct the target position (step ST12).

In order to prevent an excessive torque from being applied after the push-off, the torque limiter is set to operate automatically or switched to an appropriate torque control in advance. The press load can be set to several kg / cm ² to several hundred kg / cm ² .

At this point, press forming of the glass material is completed (step ST13), and the mold closing is maintained while being pressurized with the torque limiter value, and the process proceeds to the cooling process. During this cooling step, a load of less than 1 kg / cm ² to several kg / cm ² can be applied to the mold.

  In the next press cycle, the position of the second servomotor M2 is controlled by specifying the corrected target position. For example, when the one-side contact state as shown in FIG. 5 occurs, the rotation speed of the second servo motor M2 slightly increases, and the amount of feed of the elevating member 31 by the second feed screw shaft 34 increases. Thus, the level of the elevating member 31 is ensured. As a result, the verticality of the main shaft 28 is maintained, the lower base die 26 and the lower die 23 are raised in a horizontal state, and the contact between the molds is eliminated.

  It is also possible to set another predetermined position from the start of pressing of the glass material to the press-off, and to change the position control so that the cooling is started when the position is reached and the press speed or the applied pressure is loosened. In this way, multistage pressurization is also possible.

  As described above, in this example, when the press molding is performed by controlling the position of the twin drive type press molding apparatus 1, the press is performed until the upper and lower mother dies 25 and 26 come into contact with each other. The stop rotational position, which is the rotational position of the left and right servomotors M1, M2 when they are pushed out every cycle, is detected, and the difference S (the rotational position of the first servomotor M1−the rotational position of the second servomotor M2). Is calculated. Further, the control unit 41 adds the difference S to the target position of the second servo motor M2 written in the memory 44, and corrects the target position. In the next press cycle, position control when the lower mold 23 is raised is performed based on the corrected target position.

  By repeating this control operation for each press operation of each press cycle, it is possible to perform the press operation while always maintaining the elevating member 31 horizontally, that is, maintaining the lower main shaft 28 vertical. Therefore, it is possible to prevent the upper and lower molds 22 and 23, the sleeve 24, and the guide pin from being rubbed, and to prevent the upper and lower molds 22 and 23 from being tilted, so that a highly accurate optical element can be molded.

  The present invention is particularly advantageous in a multi-piece molding apparatus capable of simultaneously press-molding a plurality of molding materials. This is because the arrangement of a plurality of molding dies increases the opposing area of the pair of molding dies, which can easily cause a one-to-one contact state, and the resulting variation in the shape of individual molded bodies can be effectively suppressed.

It is a schematic plane block diagram which shows the manufacturing apparatus of the optical element to which this invention is applied. It is a schematic block diagram which shows the press molding apparatus integrated in the manufacturing apparatus of FIG. It is a schematic block diagram of the control system in the press molding apparatus of FIG. It is a schematic flowchart which shows operation | movement of the press process of the press molding apparatus of FIG. It is explanatory drawing which shows the one part contact state resulting from the thermal deformation in the press molding apparatus of a twin drive system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Press molding apparatus 2 Molding part 3 Drive part 22 Upper mold 23 Lower mold 24 Sleeve 25 Upper master mold 26 Lower master mold 27 Upper main spindle 28 Lower main spindle 31 Lifting member 32 Linear guide 33, 34 Feed screw shaft 31a, 31b Nut 41 Control unit 42, 43 Motor driver 44 Memory 45, 46 Rotation position detector 50 Manufacturing apparatus 100 Heating chamber 111 Supplying unit 112 Conveying unit 113 Heating unit 130 Passage 131 Valve 200 Molding chamber 220 Unloading unit 230 Unloading unit M1, M2 Servo motor

Claims (8)

It has a mold including an upper mold and a lower mold that can be opened and closed having opposite mold surfaces, and presses the molding material by bringing at least one of the upper mold and the lower mold close to the other mold. In a press molding device for molding,
A main shaft supporting the mold on the moving side;
A lifting member supporting the main shaft;
An elevating mechanism for elevating the elevating member in the axial direction of the main shaft;
Control means for controlling the lifting operation by the lifting mechanism;
Detecting means for directly or indirectly detecting the state of inclination between the opposing surfaces of the mold at a predetermined point in the press cycle;
The elevating mechanism includes a plurality of rotating shafts that support the elevating member, and a plurality of rotation driving sources for rotationally driving each of the rotating shafts, and the rotational movement of each rotating shaft is performed by the elevating member. Each rotating shaft is engaged with the elevating member so as to be transmitted as the elevating movement of
The said control means controls the rotation of each rotational drive source so that the said opposing surface may become parallel based on the detected said inclination state, The press molding apparatus characterized by the above-mentioned. In claim 1,
The detecting means detects at least one of a posture of the elevating member, a posture of the main shaft, a posture of the mold on the moving side, a rotating state of the rotating shaft, and a rotating state of the rotation drive source. A press molding apparatus characterized by the above. In claim 1 or 2,
The control means controls the rotation of the rotation drive source based on the tilt state detected in the previous press cycle so that the opposing surfaces of the mold are parallel in the next press cycle. Press molding equipment. In any one of claims 1 to 3,
The detecting means detects a stop rotation position at the time when the rotation of the rotary drive source or the rotary shaft stops due to the load exceeding a predetermined value when approaching the mold,
The control means obtains a difference between the detected stop rotation position and one of the remaining stop rotation positions on the basis of one of the detected stop rotation positions, and each rotation drive source or each A press molding apparatus, wherein the amount of rotation of each rotational drive source is corrected based on the difference so that the rotational axes stop simultaneously. In any one of claims 1 to 3,
The rotary shaft includes first and second feed screw shafts,
The rotary drive source includes a first servo motor connected to the first feed screw shaft and a second servo motor connected to the second feed screw shaft,
The detection means includes a first rotational position detector that detects a rotational position of the first servomotor and a second rotational position detector that detects a rotational position of the second servomotor, and the upper mold And the first and second stop rotation positions at the time when the rotation of the first and second servo motors stops due to the load exceeding a predetermined value when the lower mold is in proximity,
The control means obtains a difference between the detected first and second stop rotational positions, and at the time of approaching the mold in the next press cycle, based on the difference, a target for position control of at least one of the servo motors A press molding apparatus for correcting a value. In any one of claims 1 to 5,
The press molding apparatus according to claim 1, wherein the rotation shaft is disposed at an equal distance from an axis of the main shaft. An optical element molding method using the press molding apparatus according to any one of claims 1 to 6,
A heating step of heating the mold in advance to a predetermined temperature;
A supply step of conveying the heat-softened molding material and supplying the molding material to the lower mold of the molding dies;
A molding method for an optical element, comprising: a pressure molding step of pressure molding the molding material by bringing the molding die close to each other. In claim 7,
In the pressure molding step, the spindle is moved at a first moving speed to a predetermined position before the molding material supplied to the lower mold contacts the upper mold, and after passing through the predetermined position, A method of molding an optical element, wherein the spindle is moved at a second movement speed that is slower than the first movement speed.

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