JP5956253B2 - Glass lump manufacturing apparatus, glass lump manufacturing method, and glass optical element manufacturing method - Google Patents

Description

  The present invention relates to a glass lump manufacturing apparatus and a glass lump manufacturing method for manufacturing a glass lump from molten glass using a mold, and a glass optical element manufacturing method for manufacturing a glass optical element such as a lens from the glass lump.

  2. Description of the Related Art There is known a glass lump manufacturing apparatus that forms molten glass flowing down from a molten glass supply unit into a glass lump (glass gob or preform) for precision press molding while receiving it in a floating state with a mold. A specific configuration of this type of apparatus is described in Patent Document 1, for example.

  In the glass lump manufacturing apparatus described in Patent Document 1, a plurality of molding dies are arranged on the turntable at equal intervals in the circumferential direction, and each molding die is set in a predetermined manner by rotating the turntable intermittently. Transfer sequentially to the stop position. Thereby, the supply (casting) of the molten glass to each shaping | molding die and the taking-out (takeout) of the glass lump shape | molded within the shaping | molding die are performed sequentially. A molding die used in this kind of glass lump manufacturing apparatus includes a molding surface having a plurality of pores (through holes) through which a floating gas (air or inert gas) is ejected, and the molding surface from the molten glass supply unit The molten glass flowing down is received in a floating state and molded while being cooled (hereinafter referred to as “floating molding”).

  Moreover, in the glass lump manufacturing apparatus of patent document 1, the descent | fall cutting method is used in order to cut | disconnect a molten glass lump from a molten glass flow. The descent cutting method is a method of separating a glass block having a predetermined weight from the molten glass flow by lowering the forming die at a speed faster than the flow rate of the molten glass after receiving the molten glass flow with the forming die.

  By the way, when performing floating molding, if the flow rate of the floating gas is set large, the lower end portion of the molten glass vibrates due to the wind pressure of the gas ejected from the pores of the molding mold at the initial stage of casting, and the shape of the glass lump is poor. Etc. may occur. Therefore, the glass lump manufacturing apparatus of Patent Document 1 is configured such that a gas with an extremely small flow rate is ejected from the mold while the mold is raised from the turntable and cast and descend cutting is performed. .

JP 2002-97023 A

  However, if a relatively heavy glass lump is produced using the glass lump manufacturing apparatus of Patent Document 1, it melts when the mold is accelerated or decelerated (for example, when the descent of the mold is stopped after descending cutting). Since a large inertial force acts on the glass lump, there is a problem that the molten glass is brought into close contact with the mold, and on the contrary, shape defects and quality defects are liable to occur.

  In addition, even when manufacturing a glass lump with a small weight, if the mold is moved at a high speed and a large acceleration in order to shorten the tact time of the glass lump production, a large inertial force is also exerted on the molten glass, and the molten glass lump is formed. There was a problem that shape defects and quality defects are likely to occur due to close contact with or in contact with the mold.

  A glass lump manufacturing apparatus according to an aspect of the present invention includes a mold that can eject gas from a molding surface so that the molten glass lump floats from the molding surface, and a molten glass supply unit that supplies a molten glass flow onto the mold A gas supply means for supplying gas to the mold, a mold drive means for driving the mold up and down when a molten glass flow is supplied onto the mold, and an acceleration acquisition for acquiring the acceleration of the mold And a gas supply means for controlling the supply of gas to the mold based on the acceleration of the mold.

  According to this configuration, when the mold is moved up and down at high speed by the mold driving means, the molten glass lump is prevented from coming into close contact with the molding surface due to inertial force, and the occurrence of shape defects and quality defects is suppressed. The

  Moreover, it is good also as a structure whose acceleration acquisition means is an acceleration sensor which detects the acceleration of a shaping | molding die.

  The acceleration acquisition means may acquire the acceleration of the molding die based on a parameter for controlling the driving of the molding die.

  According to this configuration, gas supply control to the mold based on the acceleration of the mold can be realized with a simple hardware configuration without providing an acceleration sensor.

  Further, the mold driving means may control the driving of the mold based on a predetermined drive waveform, and the acceleration acquisition means may acquire the acceleration of the mold by calculation based on the drive waveform.

  Further, the gas supply means may be configured to control the pressure or flow rate of the gas supplied to the mold based on the acceleration of the mold.

  Further, the gas supply means may control the supply of gas to the mold based on the acceleration of the mold when the mold driving means drives the mold up and down.

  According to this configuration, since the gas supply is controlled during casting that is largely driven up and down with the mold holding the molten glass, the occurrence of shape defects and quality defects can be more effectively suppressed.

  Further, when a predetermined amount of molten glass is supplied from the molten glass supply means to the mold, the mold driving means lowers the mold at a speed faster than the molten glass flow speed, thereby causing the mold to move from the molten glass flow. It is good also as a structure which drives a shaping | molding die so that the fall cutting which isolate | separates a molten glass lump may be performed.

  When performing the lowering cutting, particularly the rapid lowering of the mold and the lowering stop are performed, and according to this configuration, the occurrence of shape defects and quality defects associated with the lowering cutting is effectively suppressed.

  In addition, after a predetermined amount of molten glass is supplied to the mold, the gas supply unit may start gas supply control to the mold based on the acceleration of the mold when descent cutting starts. .

  Further, the gas supply means may control the supply of gas to the mold according to the amount of molten glass supplied to the mold until a predetermined amount of molten glass is supplied to the mold. .

  According to this configuration, it is possible to effectively suppress the occurrence of defective shape and poor quality of the glass lump due to excessive supply of gas to the molten glass supplied to the mold.

  Moreover, the glass lump manufacturing method according to one aspect of the present invention is a glass lump that manufactures a glass lump by forming a gas melt from a molding surface of a mold and then cooling the molten glass lump while floating from the molding surface. In the manufacturing method, the method comprises a step of supplying a molten glass flow onto the mold, a step of supplying a gas to the mold, a step of driving the mold up and down, and a step of obtaining the acceleration of the mold. The step of supplying gas to the mold includes a step of controlling the supply of gas to the mold based on the acceleration of the mold.

  Further, the step of acquiring the mold acceleration may include a step of detecting the mold acceleration by an acceleration sensor.

  The step of acquiring the mold acceleration may include a step of acquiring the mold acceleration based on a parameter for controlling the driving of the mold.

  In the step of driving the mold up and down, the driving of the mold is controlled based on a predetermined drive waveform, and the acceleration of the mold is calculated based on the drive waveform in the step of acquiring acceleration. .

  In the step of supplying gas to the mold, the pressure or flow rate of the gas supplied to the mold may be controlled based on the acceleration of the mold.

  In addition, the step of controlling the gas supply to the mold based on the acceleration of the mold is performed on the mold when the mold is driven up and down by the process of driving the mold up and down. It is good also as a structure to be called.

  In addition, when the mold is moved up and down, when a predetermined amount of molten glass is supplied to the mold, the mold is lowered from the molten glass flow by lowering the mold at a speed faster than the molten glass flow speed. It is good also as a structure including the fall cutting process which isolate | separates a molten glass lump.

  Further, the step of controlling the supply of gas to the mold based on the acceleration of the mold may be configured to start with the start of the lowering cutting process after a predetermined amount of molten glass is supplied to the mold. .

  The step of supplying gas to the mold controls the gas supply to the mold according to the amount of molten glass supplied to the mold until a predetermined amount of molten glass is supplied to the mold. It is good also as a structure including the process to do.

  In addition, the method for manufacturing an optical element according to one aspect of the present invention includes a step of introducing the glass block manufactured by the above-described glass block manufacturing method into a precision press mold, and a glass block introduced into the precision press mold. And a step of precision press molding with a precision press mold in a softened state to obtain a glass optical element.

  In addition, a method for manufacturing a glass optical element according to an aspect of the present invention includes a step of heating and softening a glass block manufactured by the above-described glass block manufacturing method and introducing the glass block into a press mold, The glass lump is press-molded with a press mold in a softened state to obtain a press-molded product, and the step of obtaining a glass optical element by at least polishing the press-molded product.

  According to the glass lump manufacturing apparatus, the glass lump manufacturing method, and the glass optical element manufacturing method according to the embodiment of the present invention, the molten glass is melted by the inertial force applied to the molten glass as the molding die is driven at the time of forming the glass lump. Contact with the molding surface of the molding die is prevented, and it becomes possible to manufacture a glass lump and a glass optical element that are superior in shape and quality.

It is a side view of the glass lump manufacturing apparatus concerning the embodiment of the present invention. It is a top view of the glass lump manufacturing apparatus which concerns on embodiment of this invention. It is sectional drawing of the shaping | molding die and shaping | molding die base of the glass lump manufacturing apparatus which concerns on embodiment of this invention. It is sectional drawing of the shaping | molding die and shaping | molding die base of the glass lump manufacturing apparatus which concerns on embodiment of this invention. It is a figure which shows schematic structure of the gas supply system of the glass lump manufacturing apparatus which concerns on embodiment of this invention. It is a top view of the shaping | molding die of the glass lump manufacturing apparatus which concerns on embodiment of this invention. It is a figure which shows the procedure of a casting process. It is a timing chart explaining flow control of levitation gas.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Glass lump manufacturing apparatus and glass lump manufacturing method>
FIG.1 and FIG.2 is the side view and top view which show the structure of the glass lump manufacturing apparatus 1 which concerns on embodiment of this invention, respectively. As shown in FIGS. 1 and 2, the glass lump manufacturing apparatus 1 includes a control unit 101, a molten glass supply unit 104, a turntable 106, a direct drive motor 108, a heating furnace 110, a takeout means 112, a glass lump collection unit 114, and A molding die 120 is provided. The control unit 101 includes various operation switches for operating the glass lump manufacturing apparatus 1 and a control circuit for controlling the operation of each part of the glass lump manufacturing apparatus 1.

  The upper part of the molten glass supply unit 104 communicates with a stirring tank, a clarification tank, and a glass melting tank (not shown). Thereby, molten, clarified and homogenized molten glass G is continuously supplied to the molten glass supply unit 104. From the front end (outflow nozzle 104a) of the molten glass supply unit 104, the molten glass G controlled to a constant temperature flows down. The molten glass G flowing down from the outflow nozzle 104a receives the tip of the molten glass G by the molding die 120, and is separated so that the molten glass G has a desired weight, and has a predetermined shape (for example, a whip shape or a flat shape). ) Glass lump g.

  As shown in FIG. 2, a plurality of molds 120 are installed on the turntable 106 at equal intervals around the rotation center. For the turntable 106, for example, a lightweight and high-strength aluminum alloy disk is used. The turntable 106 is intermittently rotated clockwise by a direct drive motor 108 (FIG. 1). Thereby, each shaping | molding die 120 stops at the stop position (cast position) A and the stop position (takeout position) B for a predetermined time.

  A plurality of gas pipes 145 connected to the respective molds 120 are installed on the lower surface side of the turntable 106. Each gas pipe 145 supplies a levitation gas (described later) supplied from a gas supply source to the corresponding mold 120. In FIG. 2, the gas pipe 145 is indicated by an alternate long and short dash line for the sake of clarity.

  Next, a method for forming a precision press-molding glass block g (also referred to as gob or preform) by the glass block manufacturing apparatus 1 will be described. First, in order to separate (mold) a glass lump g having a predetermined weight from the molten glass G, the clarified and homogenized molten glass G is continuously flowed down from the outflow nozzle 104a at a constant speed. The molten glass G that has flowed down is successively received by the mold 120 that is sequentially transferred to the casting position A, and is cut by a descending cutting method (hereinafter, the molten glass G supplied onto the mold 120 is “melted”. "Glass lump g"). From the concave molding surface 120a (FIG. 3) of the molding die 120, the levitation gas supplied from the gas supply source via the gas pipe 145 is ejected. Therefore, the molten glass lump g is formed into, for example, a predetermined flat glass lump g while being supported in a state of being floated in each mold 120 by the jetting pressure of the levitation gas. Here, the levitation gas is adjusted to an ejection pressure that does not deform the lower surface of the molten glass lump g cast to the mold 120.

  In the heating furnace 110a, the molten glass lump g molded in the molding die 120 is gradually cooled to a temperature not higher than the glass transition point Tg until it is taken out. Next, the glass lump g in the mold 120 conveyed to the takeout position B is blown off radially outward of the turntable 106 by the gas blown out from the takeout means 112 and arranged on the outer peripheral portion of the turntable 106. It is collected by the substantially fan-shaped glass lump collection unit 114. Further, in the heating furnace 110b, the temperature of the forming die 120 is adjusted so as to be a temperature suitable for forming the glass lump g. Thus, in each shaping | molding die 120, according to rotation of the turntable 106, casting of the molten glass G, shaping | molding of the molten glass lump g, cooling of the molten glass lump g, and take-out of the glass lump g are performed in order. Each mold 120 is returned to the casting step after the glass lump g is taken out, and used repeatedly.

  Next, specific configurations of the mold base 130 and the mold 120 installed on the turntable 106 will be described. 3 and 4 are side sectional views of the mold 120 and the mold base 130, respectively. 3 shows a state where the mold 120 is lowered, and FIG. 4 shows a state where the mold 120 is raised. As shown in FIGS. 3 and 4, the mold base 130 includes a base portion 134 fixed to the turntable 106 and a movable portion 132 that can move up and down with respect to the base portion 134. The mold 120 is attached to the upper end of the movable part 132 and moves up and down together with the movable part 132. In the center of the base portion 134, a hole portion 134a that slidably holds the shaft portion 132a of the movable portion 132 extends in the vertical direction. The lower end portion of the shaft portion 132a protrudes downward from the lower end of the hole portion 134a. A spring 136 (compression spring) is wound around the lower end portion of the shaft portion 132a protruding from the hole portion 134a, and the movable portion 132 is always pushed downward by the elastic force of the spring 136.

  At the casting position A of the molten glass G, below the molding die base 130, a molding die 120 and a molding die vertical drive unit 109 that drives the molding die base 130 up and down are installed. The molding die vertical drive unit 109 is a linear actuator composed of a servo motor (not shown) and a ball screw mechanism, and is configured such that a drive shaft 109a directly connected to the ball screw is driven up and down. Further, the drive shaft 109 a is coaxially disposed directly below the shaft portion 132 a of the mold base 130. When casting the molten glass G, the mold vertical drive unit 109 is operated, and the drive shaft 109a is lifted as shown in FIG. 4, and the movable part 132 (shaft part) of the mold base 130 is resisted against the force of the spring 136. 132a) is pushed up. As a result, the mold 120 is lifted up to the vicinity of the outflow nozzle 104a of the molten glass supply unit 104, and the molten glass G can be supplied. An acceleration sensor 109b is attached to the drive shaft 109a. The acceleration sensor 109b (acceleration acquisition means) detects the acceleration in the vertical direction of the drive shaft 109a (that is, the acceleration of the mold 120 that moves up and down together with the drive shaft 109a), and sends a signal indicating the detected acceleration to the control unit 101. . The control unit 101 controls the flow rate of the levitation gas according to the vertical acceleration of the drive shaft 109a. Details of the flow control of the levitation gas based on the acceleration of the drive shaft 109a will be described later.

  The glass lump manufacturing apparatus 1 according to the present embodiment employs a descending cutting method in order to accurately cut a molten glass lump g having a predetermined weight. When the molding die 120 is transferred to the casting position A by the turntable 106, the molding die vertical drive unit 109 operates as described above, and the drive shaft 109a pushes up the movable part 132 of the molding die base 130. In a state in which the movable part 132 of the mold base 130 is not pushed up by the drive shaft 109a, the movable part 132 is pushed downward by the spring 136 and abuts against the base part 134 to maintain a constant height. When the vertical drive unit 109 is operated, the movable unit 132 is lifted together with the molding die 120 against the elastic force of the spring 136, and the molding surface 120a of the molding die 120 is brought close to the outflow nozzle 104a. In addition, the movable portion 132 is strongly pressed against the drive shaft 109a by the elastic force of the spring 136 while being pushed up by the drive shaft 109a of the mold upper and lower drive portion 109. Therefore, the lower end of the movable portion 132 is the upper end of the drive shaft 109a. The movable portion 132 moves up and down integrally with the drive shaft 109a.

  Each of the molding dies 120 attached to the turntable 106 via the molding die base 130 is supplied with a molten glass lump g and a floating gas for floating the glass lump g. FIG. 5 shows a schematic configuration of a gas supply system that supplies the levitation gas to the mold 120. A levitation gas supplied from a gas supply source (not shown) is introduced into the multi-branch pipe 143 through the gas supply pipe 141 and the rotary joint 142 that penetrate the hollow portion 108a of the direct drive motor 108. The multi-branch pipe 143 is attached to a rotation shaft 108b of a direct drive motor 108 that rotates integrally with the turntable 106. By connecting the gas supply pipe 141 to the multi-branch pipe 143 through the rotary joint 142, it is possible to supply the floating gas to the multi-branch pipe 143 that rotates together with the turntable 106.

  The multi-branch pipe 143 has one input port and a plurality of output ports, and evenly distributes the levitation gas supplied from the input ports to the plurality of output ports. A gas supply pipe 141 is connected to an input port of the multi-branch pipe 143, and each forming die 120 is connected to each output port via a gas pipe 145. Each gas pipe 145 is provided with a mass flow controller 144 for controlling the flow rate of the levitation gas. The mass flow controller 144 adjusts the flow rate of the levitation gas in each gas pipe 145 based on the control of the control unit 101. In addition, the mass flow controller 144 sends a signal indicating the detected flow rate in each gas pipe 145 to the control unit 101.

  As shown in FIG. 3, the levitation gas is introduced into the space 132 b provided in the movable part 132 of the mold base 130 via the gas pipe 145 and communicates with the molding surface 120 a formed in the mold 120. It ejects from a plurality of gas ejection ports 121. The levitation gas ejected from the gas ejection port 121 is blown to the glass lump g on the molding surface 120a to float the glass lump g. As the levitation gas, air, an inert gas such as nitrogen, or a mixed gas thereof can be used.

  FIG. 6 is a plan view of the molding die 120 showing the arrangement configuration of the gas ejection ports 121. As shown in FIG. 6, in the present embodiment, the gas ejection ports 121 are arranged at regular intervals on the center of the molding surface 120 a and two concentric circles centering on the center, thereby forming the gas on the molding surface 120 a. The glass lump g is kept in a state where it is stably floated. However, the number of the gas outlets 121 is not limited to this, and may be one, or the molding surface may be formed of a porous material, and the levitation gas may be ejected from countless fine holes. May be. However, in order to stably float the molten glass G or the glass lump g, it is preferable to distribute the plurality of gas outlets 121 symmetrically around the central axis of the mold as in this embodiment. Moreover, it is preferable to distribute the gas ejection ports 121 evenly.

  Next, the flow control of the levitation gas ejected from the gas ejection port 121 of the mold 120 will be described. In the present embodiment, during the casting process, that is, while the mold 120 remains at the casting position A, the variable flow rate for supplying the mold 120 with a floating gas having a flow rate corresponding to the acceleration in the vertical direction of the mold 120. The flow rate of the levitation gas is controlled by the mode, and it is necessary to stably float the glass lump g on the molding surface 120a during other processes, that is, when the mold 120 is not stopped at the casting position A. The flow rate of the levitation gas is controlled to a constant amount by the constant flow mode for supplying a constant flow rate to the mold 120.

  FIG. 7 is a diagram illustrating a procedure of a casting process for supplying the molten glass G onto a mold. FIG. 8 is a timing chart for explaining the flow control of the levitation gas. FIG. 8A is a chart showing the timing of intermittent rotation driving of the turntable 106. FIGS. 8B and 8C are charts showing temporal changes in the height and acceleration in the height direction of the mold 120 driven up and down by the mold vertical drive unit 109, respectively. FIG. 8D is a chart showing the supply amount of the levitation gas supplied to the molding die 120 during casting.

FIG. 7A shows a state immediately after the mold 120 is transferred to the casting position A by the turntable 106. When the molding die 120 stops at the casting position A at time t ₁ , the flow rate control mode of the levitation gas supplied to the molding die 120 retained at the casting position A keeps the flow rate F (L / min) of the mass flow controller 144 constant. The constant flow mode maintained at the amount F _o is switched to the variable flow mode in which the flow rate of the mass flow controller 144 is changed according to the vertical acceleration of the mold 120. In the variable flow rate mode of the present embodiment, the control unit 101 controls the flow rate F of the mass flow controller 144 so as to be a value proportional to the acceleration A (m / s ² ) detected by the acceleration sensor 109b (however, , The sign of acceleration A is positive in the upward direction). Specifically, the target value of the flow rate F of the flow controller 144 is set to the value of the following equation (Equation 1).

（但し、ｇは重力加速度）

(Where g is the acceleration of gravity)

That is, when the acceleration A of the mold 120 is zero, the target value of the flow rate F of the flow controller 144 is the same value as the set flow rate F _O constant flow mode, the acceleration A of the mold 120 is the gravitational acceleration g (9 becomes a .8m / s ^2), the target value of the flow rate C becomes twice the set flow F _O constant flow mode (that is, the flow rate of the gas is increased). Further, the mold 120 is accelerated downward, the acceleration A is -g, supply of floating gas is stopped (i.e., the flow rate of the gas decreases the set flow rate F _O constant flow mode). When the mold 120 is driven at a downward acceleration larger than the gravitational acceleration (that is, A <−g), the glass block g is completely separated from the mold 120, and the glass block g is moved by the mold 120. Since molding cannot be performed, the vertical movement of the mold 120 by the mold vertical drive unit 109 is controlled so that the gravitational acceleration A of the mold 120 satisfies A ≧ −g.

  Next, the control unit 101 operates the mold upper / lower drive unit 109, pushes up the movable part 132 of the mold base 130 by the drive shaft 109a, and raises the mold 120 (FIG. 7B). In addition, the control part 101 is a drive waveform (for example, time change of the target position shown to FIG. 8 (B)) comprised from a cam curve so that an excessive jerk (time differentiation of the acceleration A) may not be added to the shaping | molding die 120. FIG. Accordingly, the molding die vertical drive unit 109 is driven at high speed. In the present embodiment, a cycloid curve is used as the cam curve, but other types of cam curves may be used.

When the molding surface 120a of the mold 120 is brought close to the outflow nozzles 104a (time _t 2), rise of the mold 120 is temporarily stopped. Waiting for the vibration of the molding die 120 generated during the stoppage to stop, the molding die 120 rises again at a low speed to the immediate vicinity of the outflow nozzle 104a (time t _{3 to} t ₄ ). The supply of the molten glass flow G to the molding surface 120a is started around the time when the molding die 120 reaches the immediate vicinity of the outflow nozzle 104a (FIG. 7C). When the mold 120 reaches the immediate vicinity of the outflow nozzle 104a (time t ₄ ), the driving direction of the mold 120 is reversed, and the mold 120 flows down while the molten glass G is supplied to the mold 120. It gradually descends at a constant speed according to the amount (t ₄ to t ₅ ). This is to prevent the tip of the outflow nozzle 104a from sinking into the molten glass G supplied to the mold 120 during casting and the molten glass G from getting wet to the tip of the outflow nozzle 104a.

When a predetermined time t _c elapses from the start of casting (time t ₅ ) and the molding die 120 receives a predetermined amount of the molten glass G, the molding die vertical drive unit 109 moves the drive shaft 109a down the molten glass flow G. pressing down instantly at a faster rate than the (time _t 5 _~t 6). At this time, the movable part 132 of the mold base 130 is suddenly lowered integrally with the drive shaft 109a and the mold 120 while being pressed against the drive shaft 109a by the spring 136 (FIG. 7D). As a result, the lower end g of the molten glass G supported by the molding die 120 also drops suddenly together with the molding die 120, and constriction occurs on the lower end g side of the molten glass G, and the lower end g of the molten glass G and the outflow nozzle 104a The molten glass G is separated by the surface tension.

Further, as shown in FIG. 8 (C), at the initial stage of sudden drop of the mold 120, the lower end g of the molten glass G received by the mold 120 and the mold 120 is a large downward acceleration near the gravitational acceleration − It descends while accelerated by A _1. Thereby, a large upward inertia force is applied to the molten glass lump g. Therefore, the weight of the molten glass lump g in the inertial system of the mold 120 is extremely small. In this state, if a large flow rate of levitation gas is ejected from the molding surface 120 a of the mold 120, the lower end g of the molten glass G may be blown off from the mold 120. In the variable flow mode of the present embodiment, the flow rate of the levitation gas is adjusted (reduced) according to the acceleration of the mold 120 according to the equation shown in the above equation 1, so that the flow rate of the levitation gas is extremely high at the initial stage of the sudden drop. It is controlled to a small value, and the lower end g of the molten glass G is prevented from being blown off from the mold 120 by the levitation gas.

Further, the mold vertical drive unit 109 causes the movable part 132 of the mold base 130 that descends at a high speed on the turntable 106 after the mold 120 is rapidly lowered to cut the molten glass lump g from the molten glass flow G. The lowering of the mold 120 is suddenly stopped so as not to crash into the fixed base 134. At this time, it received was the molten glass gob g to the mold 120 and the mold 120, joined by a large acceleration A ₂ upward, also, thereby, a large inertial force downward is applied to the molten glass gob g. The acceleration A ₂ is the gravitational acceleration and whether the same level, which can lead to more dimensions. Therefore, the weight of the molten glass lump g in the inertial system of the mold 120 is extremely large. In this state, the set flow rate F _O of flying gas in the constant flow mode, is insufficient to float the molten glass gob g from the forming surface 120a, and a molten glass gob g is in close contact with the molding surface 120a, formed There is a possibility that quality defects such as shape defects and striae of the glass lump g to be generated may occur. In the present embodiment, the levitation gas is adjusted according to the acceleration of the mold 120 according to the equation shown in the above formula 1 (the mold 120 is suddenly stopped, the molten glass lump g is subjected to acceleration A when the downward inertial force accompanying the deceleration of ₂ is applied, the flow rate of the floating gas so as not to generate quality defects sufficiently and molten glass gob g to floating the molten glass gob g to the magnitude of the acceleration a ₂ Therefore, adhesion of the molten glass lump g to the molding surface 120a is prevented. This significantly reduces the occurrence of defective shapes and poor quality, particularly in the formation of a glass lump having a relatively large capacity (for example, 20 g or more). Incidentally, as shown in FIG. 8 (D), after the upward acceleration A ₂ applied to the molten glass gob g _(downward inertial force) is maximized, the acceleration A ₂ is gradually reduced, the acceleration A ₂ reduced to reduce the flow rate of the floating gas to match, eventually controlled so that the flow rate F _O.

  With the lowering speed of the mold 120 sufficiently lowered, the movable part 132 of the mold base 130 is placed on the base part 134, and from the shaft part 132a of the movable part 132 to the drive shaft 109a of the mold upper and lower drive part 109. And the vertical movement of the mold 120 by the mold vertical drive unit 109 is completed (FIG. 7E).

<Manufacture of glass optical elements>
A precision press-molding glass block g (preform) molded using the glass block forming apparatus 1 according to the embodiment of the present invention is introduced into a precision press mold (not shown) and heated together with the precision press mold. Then, it is precision press-molded in a softened state, and the surface shape of the molding surface of the precision press-molding die is transferred to the precision press-molding glass block g. The precision press-molding glass block g is cooled while being pressurized in the precision press-molding die, and then taken out from the precision press-molding die (isothermal press molding). Thereby, an aspherical lens to which the surface shape of the molding surface of the precision press mold is transferred is obtained. The aspherical lens thus manufactured is subjected to various coatings such as centering processing, chamfering processing, dyeing processing, antireflection and UV cut to obtain a glass optical element. As another precision press molding method, precision press molding can be performed by introducing a pre-heated and softened glass lump g (preform) into a precision press mold (non-isothermal press molding). ).

  The above is the description of an example of the embodiment of the present invention. However, the present invention is not limited to the configuration of the above embodiment, and is within the scope of the technical idea indicated by the description of the scope of claims. Various modifications are possible.

  For example, in the above embodiment, a configuration is adopted in which the flow rate of the levitation gas is controlled based on the acceleration of the mold 120 detected by the acceleration sensor 109b. Alternatively, the acceleration of the mold 120 may be calculated from the drive waveform and the flow rate of the levitation gas may be controlled based on the calculated acceleration. For example, when the drive waveform of the mold upper and lower drive unit 109 is given as a time function of the target position, the second derivative of the drive waveform (target position) is calculated, and the flow rate of the levitation gas is calculated based on this value. It is good also as a structure to control.

  In the above embodiment, the flow rate is controlled so that the flow rate of the levitation gas changes in proportion to the acceleration of the mold 120. However, the flow rate of the levitation gas is changed nonlinearly with respect to the acceleration. It is good also as a structure. The relationship between the acceleration of the mold 120 and the flow rate of the levitation gas can be appropriately set according to the weight, shape, etc. of the glass lump.

  Further, in the above embodiment, a configuration is adopted in which the flow rate of the levitation gas supplied to each mold 120 is controlled by the mass flow controller 144, but each gas pipe 145 is provided with a pressure sensor and a flow rate adjustment valve. The throttle of the flow rate adjusting valve can be controlled based on the pressure of the levitation gas detected by the pressure sensor.

  In the above embodiment, the flow control of the levitation gas is always performed based on the acceleration of the mold 120 during the casting process, but a predetermined time elapses after the mold 120 starts to receive the molten glass G (molding mold). Until the molten glass G received by 120 reaches a predetermined amount), the flow rate of the levitation gas is set to zero or a relatively small predetermined amount, and a predetermined time has elapsed (the molten glass G received by the mold 120 is a predetermined amount). The flow rate control of the levitation gas based on the acceleration of the mold 120 may be performed later. Further, during casting, depending on the amount of the molten glass G received by the mold 120 (that is, the flow rate of the floating gas increases as the amount of the molten glass G received by the mold 120 increases). It is good also as composition which performs flow control of gas. In the initial stage of casting when the amount of molten glass G received by the mold 120 is small, increasing the flow rate of the floating gas increases the wind pressure of the floating gas (the non-uniform pressure that the molten glass tip g receives from the floating gas). May cause defective quality such as shape defects and striae in the glass lump. By suppressing the flow rate of the levitation gas at the initial stage of casting, a glass lump having excellent quality can be manufactured more stably.

  Moreover, the suitable value of the flow rate of the levitation gas varies depending on the weight of the glass block to be formed. Therefore, a load sensor is provided in the mold base 130, the weight of the molten glass G received by the mold 120 is detected by the load sensor, and in addition to the acceleration of the mold 120, the load glass floats according to the weight of the molten glass G. It is good also as a structure which controls the flow volume of gas.

  Further, in the above embodiment, the descending cutting method is adopted as a method for separating a molten glass lump of a predetermined weight from the molten glass flow.For example, other separating methods such as a method using a sandwiched cutter are used. May be used.

  Further, in the above embodiment, the flow rate of the levitation gas is controlled according to the vertical acceleration of the mold 120, but also according to the horizontal acceleration (for example, the acceleration in the vertical direction and the horizontal acceleration). A configuration may be adopted in which the flow rate of the levitation gas is controlled (in accordance with the vector sum).

  In the above embodiment, the position of the mold 120 (drive shaft 109a) is controlled, and the drive control of the mold vertical drive unit 109 is performed. However, the speed and acceleration of the mold 120 are controlled. It is also possible to perform drive control of the mold vertical drive unit 109.

  In the above embodiment, the drive control of the mold vertical drive unit 109 is performed based on a predetermined drive waveform. However, the predetermined drive parameters (for example, speed, acceleration, moving distance, moving time, etc.) are set. A configuration may be adopted in which drive control of the mold vertical drive unit 109 is performed by sequence control based thereon. In this case, the control unit 101 may be configured to control the flow rate of the levitation gas in accordance with the acceleration of the molding die 120 calculated based on the driving parameter of the molding die vertical driving unit 109.

  In addition, the above embodiment is an example of molding a glass lump (preform) that is a press material for precision press molding for producing a final product, but with the same configuration, a shape that approximates a lens that is a final product It is also possible to mold a press material for press-molding into a lens blank (press-molded product) having a slab, or a press material for reheat press.

  In the case of producing a glass optical element by reheat pressing, first, the press material (glass lump such as glass gob or preform) manufactured by the method of the above embodiment is subjected to barrel polishing and then softened by heating. The press material is press-molded (reheat press) with a press mold. Depending on the glass material (for example, when a glass material that is difficult to be fused to the mold is used), the press material can be directly pressed without barrel polishing. Further, the press material is subjected to a centering process and a chamfering process as necessary before the barrel polishing. A glass optical element such as a spherical lens can be obtained by subjecting a press-molded product obtained by the reheat press to a polishing process and, if necessary, a dyeing process or a coating process.

DESCRIPTION OF SYMBOLS 1 Glass lump manufacturing apparatus 101 Control part 104 Molten glass supply part 104a Outflow nozzle 106 Turntable 108 Direct drive motor 109 Mold upper / lower drive part 109b Accelerometer 110 Heating furnace 112 Take-out means 114 Glass lump collection part 120 Mold 130 Mold base 141 Gas supply pipe 142 Rotary joint 143 Multi-branch pipe 144 Mass flow controller 145 Gas pipe

Claims (18)

A molding die capable of ejecting gas from the molding surface so that the molten glass lump floats from the molding surface;
Molten glass supply means for supplying a molten glass flow onto the mold;
Gas supply means for supplying gas to the mold,
When a molten glass flow is supplied onto the mold, a mold drive means for driving the mold up and down;
Acceleration acquisition means for acquiring the acceleration of the mold;
With
The gas supply means to control the pressure or flow rate of the gas supplied to the forming die on the basis of the acceleration of the mold,
A glass lump manufacturing apparatus characterized by that. The acceleration acquisition means is an acceleration sensor for detecting an acceleration of the mold;
The glass lump manufacturing apparatus according to claim 1. The acceleration acquisition means acquires the acceleration of the mold based on a parameter for controlling the driving of the mold;
The glass lump manufacturing apparatus according to claim 1 or 2, characterized in that The mold driving means controls the driving of the mold based on a predetermined drive waveform;
The acceleration acquisition means acquires the acceleration of the mold by calculation based on the drive waveform;
The glass lump manufacturing apparatus according to claim 1 or 2, characterized in that The gas supply means controls the supply of gas to the mold based on the acceleration of the mold when the mold drive means drives the mold up and down;
The glass lump manufacturing apparatus according to any one of claims 1 to 4 , wherein the glass lump manufacturing apparatus is characterized. The mold driving means lowers the mold at a speed faster than the flow rate of the molten glass when a predetermined amount of molten glass is supplied from the molten glass supply means to the mold. Driving the mold to perform a down cut to separate the molten glass mass from the molten glass stream;
The glass lump manufacturing apparatus according to claim 5 . After the predetermined amount of molten glass is supplied to the mold, the gas supply means starts control of gas supply to the mold based on the acceleration of the mold when the descent cutting starts. The glass lump manufacturing apparatus according to claim 6 . The gas supply means controls the supply of gas to the mold according to the amount of molten glass supplied to the mold until the predetermined amount of molten glass is supplied to the mold.
The glass lump manufacturing apparatus according to claim 6 or 7 , wherein In the glass lump production method for producing a glass lump by forming a molten glass lump while jetting gas from the molding surface of the mold and floating from the molding surface,
Supplying a molten glass stream on the mold;
Supplying gas to the mold;
Driving the mold up and down;
Obtaining the acceleration of the mold;
With
Supplying a gas into the mold, comprising the step of controlling the pressure or flow rate of the gas that be supplied to the molding mold based on the acceleration of the mold,
The glass lump manufacturing method characterized by the above-mentioned. The step of acquiring the acceleration of the mold includes the step of detecting the acceleration of the mold by an acceleration sensor.
The method for producing a glass lump according to claim 9 . The step of acquiring the acceleration of the mold includes the step of acquiring the acceleration of the mold based on a parameter that controls the driving of the mold.
The glass lump manufacturing method according to claim 9 or 10 , wherein the glass lump is produced. In the step of driving the mold up and down, the driving of the mold is controlled based on a predetermined drive waveform,
In the step of acquiring the acceleration, the acceleration of the mold is calculated based on the driving waveform.
The glass lump manufacturing method according to claim 9 or 10 , wherein the glass lump is produced. The step of controlling the supply of gas to the mold based on the acceleration of the mold is performed when the mold is driven up and down by the step of driving the mold up and down. Done,
The method for producing a glass lump according to any one of claims 9 to 12 , wherein: In the step of driving the mold up and down, when a predetermined amount of molten glass is supplied to the mold, the molten glass is lowered by lowering the mold at a speed faster than the flow rate of the molten glass. Including a descent cutting process to separate the molten glass mass from the stream,
The glass lump manufacturing method according to claim 13 . The step of controlling the supply of gas to the mold based on the acceleration of the mold is started together with the start of the descent cutting process after the predetermined amount of molten glass is supplied to the mold. The method for producing a glass lump according to claim 14 . The step of supplying gas to the mold is to supply gas to the mold according to the amount of molten glass supplied to the mold until the predetermined amount of molten glass is supplied to the mold. Including the step of controlling,
The method for producing a glass lump according to claim 14 or 15 , wherein the glass lump is produced. Introducing the glass mass produced by the glass mass production method according to any one of claims 9 to 16 into a precision press mold;
And a step of precision press molding the glass lump introduced into the precision press mold with the precision press mold in a softened state to obtain a glass optical element. A step of heating, softening and introducing the glass lump produced by the glass lump production method according to any one of claims 9 to 16 into a press mold,
A step of obtaining a press-molded product by press-molding the glass lump introduced into the press-molding die with the press-molding die in a softened state;
And a step of obtaining a glass optical element by polishing at least the press-molded product.

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