JPH05301727A - Method for forming optical element and forming apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain a press-formed optical element having accurate thickness and surface form and free from sink mark on the surface by mainly controlling the thickness of the element in the press-forming process and mainly controlling the pressure in the cooling and solidifying process. CONSTITUTION:A lower mold 3 and an upper mold 7 are placed opposite to each other. The lower mold 3 is held on the top of a vertically shifting mechanism composed of a motor 17 and a ball screw 16. The lower mold 3 is provided with a displacement sensor 18 and a pressure sensor 19. The vertical motion of the lower mold 3 is controlled by a controller 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method and a molding apparatus, and more particularly to an optical element molding method and a molding apparatus for pressure molding an optical element such as a glass lens.

[0002]

2. Description of the Related Art Conventionally, as a method for efficiently mass-producing optical elements such as lenses, there is a molding method using a pressing means such as a precise press molding machine. In the above method, a softened material block, for example, an optical material is supplied into a mold of a press molding machine, and pressure is applied in this state to obtain an optical element having a predetermined shape. In this case, the precision of the thickness of the molded optical element is extremely important in determining the precision of the optical element.

As a method for determining the wall thickness of an optical element molded by a press molding machine, for example, Japanese Patent Laid-Open No. 61-20563.
In order to prevent local shrinkage and shrinkage due to nonuniform volume shrinkage in the process of cooling and solidifying the optical element in the mold, the invention described in Japanese Patent Publication No. 0, in addition to a control mechanism such as a stopper, By interposing a pressure member (elastic member) between the pistons, the mold is configured to press the optical element in conjunction with the contraction of the optical element due to cooling and solidification.

The mold is fixed to the lower end of the piston of the pressurizing member (hydraulic cylinder), a stopper is provided in the middle of the piston, and the optical material shrinks due to cooling and solidification after pressure molding by the piston. The stopper is moved or removed so that the mold can press the optical element in conjunction with.

[0005]

Generally, in the case of molding an optical element, when it is attempted to accurately mold the inner wall of a glass molded product, the upper and lower molds are moved to a predetermined position in the press molding process, and the inner wall of the mold is moved. After securing the precision of the optical element, in the process of cooling and solidification, in order to prevent local shrinkage and sink of the optical element and obtain a highly precise surface shape, the optical element is linked with the shrinkage due to cooling and solidification, and the mold It is designed to apply pressure to the element.

However, the above-mentioned Japanese Patent Laid-Open No. 61-205630
When an elastic member is interposed between the mold and the piston as described in Japanese Patent Publication No. JP-A No. 2004-242, the pressure applied to the optical element for preventing sink marks during the cooling and solidifying process of the optical element is: Depends on the amount of deformation of the elastic member. The amount of deformation of the elastic member changes depending on the amount of medium thickness of the optical element in the molding process, and the amount of medium thickness is not constant as described above. Therefore, it is difficult to always keep the pressing force constant to prevent sink marks, and this also affects the variation in surface accuracy of the optical element after molding.

Further, in the case where the pressurizing member is interposed between the die and the piston, there is no means for detecting the start of cooling and solidification of the optical element, and therefore the pressure is applied before the cooling and solidification starts. If added, the thickness of the optical element is changed. Further, even if pressure is applied to the optical element after the cooling and solidification is started, the surface accuracy cannot be improved depending on the progress of the cooling and solidification, and a sink mark occurs. The starting point and progress of this cooling and solidification vary depending on the temperature of the heated molding material, the weight, the temperature of the mold used for molding, etc., and since it is not possible to measure the timing at which pressurization is started and apply pressure, It is not possible to suppress variations in the surface accuracy of the optical element.

Therefore, the present invention was developed in view of the problems in the above-mentioned prior art, and is not affected by the wall thickness of the optical element before molding, and its medium thickness and high accuracy after molding are achieved. An object of the present invention is to provide an optical element molding method and a molding apparatus capable of stably supplying the surface shape of the above.

[0009]

According to the present invention, an optical material is carried in between a pair of upper and lower molds heated near the softening point temperature of the optical material, and the optical material is molded while being pressed by the mold. In the molding method of the optical element, in the press molding process, the relative position of the pair of upper and lower molds is detected to maintain the distance between the pair of upper and lower molds so that the optical material has a predetermined thickness, and after the press molding, In the cooling and solidifying process, the molding method is a method in which the pressure applied to the mold is detected and the constant pressure is always applied to the optical material that shrinks with the cooling and solidification.

Further, in a molding apparatus for an optical element that presses an optical material with a pair of upper and lower molds having a vertical movement mechanism section, the displacement of the mold provided on the side of the mold that moves up and down by the vertical movement mechanism section is measured. It is provided with a sensor, a sensor provided in either one of a pair of molds for detecting pressure applied to the mold, and a control means for controlling the vertical movement mechanism section by a detection signal from each sensor. ..

FIG. 1 is a conceptual diagram of the present invention. The lower mold 3 and the upper mold 7 are arranged so as to face each other, and the lower mold 3 is a motor 17
It is held at the upper end of a vertical movement mechanism composed of a ball screw 16 so as to be vertically movable. The lower mold 3 is on the lower side surface of the lower mold 3.
A displacement sensor 18 for detecting displacement of the lower mold 3 and a pressure sensor 19 for detecting pressure are arranged at the lower end of the lower mold 3.
A controller 20 that controls the vertical movement of the lower mold 3 based on the displacement of the lower mold 3 and the pressure applied to the lower mold 3 is provided.

In the molding apparatus having the above structure, the optical material 1 heated to a predetermined temperature is supplied between the upper mold 7 and the lower mold 3, and the lower mold 3 is elevated to perform pressure molding. At this time, the controller 20 receives a signal from the displacement sensor 18 that detects the displacement of the lower die 3, and moves the lower die 3 to a predetermined position.
Is controlled so that the inside of the optical material 1 is obtained. Thereafter, the pressure applied to the lower mold 3 is detected by the pressure sensor 19, and the optical material 1 is cooled and solidified while controlling the vertical movement of the lower mold 3 so as to apply a predetermined pressure. By this operation, an optical element having a highly precise surface shape in which sink marks are prevented can be obtained while ensuring the accuracy of the medium thickness.

[0013]

Embodiment 1 FIGS. 2 and 3 show this embodiment, FIG. 2 is a side view showing a cross section of a part showing a molding apparatus, and FIG. 3 is a flow chart. The molding chamber 22 is installed on the pedestal 21, and the molding chamber 22 is formed by the upper base 10, the lower base 6, and the cover 23. The upper die support 9 is fitted and fixed to the upper base 10. Further, the upper die 7 is fixed to the upper die support 9 via an upper die retainer 8 screwed to a threaded portion 9a at the end. Further, like the upper mold 7, the lower mold 3 also includes a lower mold holder 4 screwed to a screw portion 5a of a lower mold holder 5 held by a main shaft 11 slidable from a central opening 6a of the lower base 6. And is fixed to the lower die support 5. The lower die 3 is vertically held in the direction opposite to the upper die 7 by vertically moving the main shaft 11.

Further, the main shaft 11 of the lower base 6 can be moved through an opening 6a in the central portion, and the lower base 6 is arranged on a mount 21. A main bearing 24 is fixed to the lower end of the main shaft 11, and a pressure sensor 19 is fixed to the lower side of the main bearing 24, and a vertical movement mechanism is provided via the pressure sensor 19. Is fixed to the table 15. Further, a displacement sensor 18 is attached to the lower end of the main bearing 24 to measure the displacement of the lower mold 3, and its signal and the signal from the pressure sensor 19 are input to a controller 20 which controls the vertical movement of the main shaft 11. is doing.

The table 15 of the vertical movement mechanism is held slidably in the vertical direction by the guide 14, and is further moved in the vertical direction by the rotation of the ball screw 16. A motor 17 is attached to the lower end of the ball screw 16. The controller 20 controls the rotation of the motor 17 to control the positional displacement of the lower mold 3 and the pressure applied to the optical element.

In the molding method using the optical element molding apparatus having the above-described structure, the barrel mold 2 is heated to a temperature equal to or higher than the softening point temperature of the optical material 1 in a heating furnace (not shown) arranged outside the molding chamber 22. The placed optical material 1 is heated. Next, the optical material 1 and the barrel die 2 are conveyed by the conveying member (not shown) between the upper die 7 and the lower die 3 which are heated to around the softening point temperature of the optical material 1. Then, the motor 17 is rotated to raise the table 15 to raise the lower die 3 and press-mold the optical material 1 with the upper die 7 and the lower die 3.

A change in relative position between the lower mold 3 and the upper mold 7 is measured by a displacement sensor 18, and a pressure applied to the lower mold 3 is measured by a pressure sensor 19. At this time, the motor 17 for raising the lower mold 3 is controlled according to the flow shown in FIG. That is, a rotation command is output to the motor 17 so as to raise the lower mold 3 until the relative position between the lower mold 3 and the upper mold 7 falls within a predetermined position range (the thickness accuracy of the optical element).

When the relative position between the upper mold 7 and the lower mold 3 is within a predetermined position range, the value input from the pressure sensor 19 is within a predetermined pressure range (amount of pressurization due to cooling of the optical element). ) Is supported so as to apply a torque from the motor 17 so that the motor 17 can enter. Then, after a sufficient cooling and solidifying time of the optical element has passed, the lower mold 3 descends and is discharged to the outside of the molding chamber 22 by a conveying member (not shown). During this time, a uniform pressure is applied during the cooling and solidification process of the optical element.

According to the present embodiment, in the process of pressing the optical element, the displacement sensor 18 for detecting the displacement of the lower mold 3 is provided to control the relative position between the upper mold 7 and the lower mold 3, thereby making it possible after molding. The accuracy of the inner wall thickness of the optical element is ensured, and in the process of cooling and solidifying the optical element, the same driving mechanism controls the pressure force evenly by the pressure sensor 19 that detects the pressure applied to the lower mold 3, thereby The sink mark of the optical element can be prevented, and the optical element having a highly precise surface shape can be stably molded.

The same effect can be obtained by installing the pressure sensor 19 on the upper die 7 or the upper die support 9. Even if the output torque of the motor 17 is detected instead of the pressure sensor 19 and the same control is performed, the same effect as described above can be obtained.

[0021]

Second Embodiment FIG. 4 is a flow chart showing this embodiment. The molding apparatus used in the molding method of this embodiment is the same as the molding apparatus of the first embodiment, and will be described with reference to FIG. The optical material 1 heated to a temperature equal to or higher than the softening point temperature of the optical material 1 is conveyed between the upper mold 7 and the lower mold 3 heated near the softening point temperature of the optical material 1, and the lower mold 3 rises. By press molding. At this time, if the motor 17 is controlled so that the measured value of the displacement sensor 18 obtains only the relative position between the predetermined upper die 7 and the lower die 3, the optical material 1 and the upper die 7 and the lower die 7 are controlled before entering the predetermined position range. Cooling and solidification of the optical material 1 starts by heat exchange with the mold 3, the positional displacement does not increase with respect to the movement instruction amount of the motor 17, and the pressure of the lower mold 3 increases.

If the lower die 3 is further raised in this state, not only a pressure greater than the amount of pressure required when the optical material 1 is cooled and solidified is applied to the optical material 1, but also the motor 17 is overloaded. Become. Therefore, in addition to the displacement of the lower mold 3, the pressure applied to the lower mold 3 is processed by the controller 20,
A pressure above the limit value is detected during the control of the pressing process, or the variation amount of the deviation of the displacement amount of the lower die 3 (the variation amount of the displacement amount per unit time) is below the limit value and is added to the lower die 3. When the amount of change in pressure deviation (the amount of change in pressure per unit time) exceeds the limit value, it is determined that the optical material 1 has entered the cooling and solidifying process, and the position control of the lower mold 3 in the pressing process is performed. Upon completion, the control shifts to the cooling and solidifying process for controlling the pressure applied to the lower mold 3.

Regarding the control of the cooling and solidifying process, similarly to the control of the pressing process, the pressure applied to the optical material 1 becomes constant after the setting of the predetermined lower die 3 and upper die 7 intervals is completed in the pressing process. Even if a torque is generated in the motor 17, if the cooling of the optical element has not started,
The pressure applied to the lower mold 3 does not increase, but the position displacement increases.

When the motor 17 is further controlled to apply torque in this state, the position of the lower mold 3 is raised and the inner wall of the optical material 1 is reduced. Therefore, in addition to the pressure applied to the lower mold 3, the displacement of the lower mold 3 is processed by the controller 20,
When the deviation of the displacement of the lower die 3 is equal to or more than the limit value and the deviation of the pressure applied to the lower die 3 is equal to or less than the limit value during the control of the cooling and solidifying process, the optical material 1 is not in the cooling and solidifying process. Judgment is made, and the control is returned to the pressing process for obtaining the inside thickness of the optical material 1.

According to the present embodiment, even if the optical material before molding having a large variation in thickness is molded, the accuracy of the thickness of the optical element after molding is ensured, and the optical element having a highly accurate surface shape is formed. The element can be stably molded.

[0026]

[Third Embodiment] FIG. 5 shows a molding apparatus used in this embodiment.
It is a partial side view which carried out the section of the part. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. A holder 25 is installed on the lower surface of the upper base 10, and a lower holder 28 is installed on the lower base 6. Further, a capacitance type lower displacement gauge 26 and an upper displacement gauge 29 having heat resistance are installed on the upper holder 25 and the lower holder 28, respectively. Then, the upper mold plate 8 is attached to the upper mold plate 8 and the lower mold plate 4 respectively.
7 and the lower die plate 30 are fixed, and the upper die displacement gauge 29 and the lower die displacement gauge 26 are configured to detect the positional displacements of the upper die 7 and the lower die 3, respectively. Others are the same as those in the first embodiment.

In the molding method using the molding apparatus having the above-described structure, in the pressing process of the optical material 1, the difference between the outputs of the upper mold displacement meter 29 and the lower mold displacement meter 26 is taken to obtain the upper mold 7.
The relative position displacement between the lower mold 3 and the
The motor 17 is driven so as to obtain the precision of the inside meat. After that, the motor 17 is driven so that the pressure applied to the lower mold 3 becomes a pressurization amount accompanying a predetermined cooling and solidification.

According to this embodiment, in the process of detecting the relative position between the upper die 7 and the lower die 3, the displacement amount can be measured in a same atmosphere as the die at a position closer to the die. Therefore, the influence of expansion due to heat is small and accurate measurement is possible. Therefore, it is possible to obtain an optical element having a highly accurate inner wall.

[0029]

As described above, according to the optical element molding method and molding apparatus of the present invention, the thickness of the optical material to be press-molded is mainly determined by the thickness in the press-molding process. It is possible to control and mainly press force in the cooling and solidifying process to control the press forming. Therefore, the accuracy of the wall thickness is good and there is no sink mark on the surface.
An optical element having a highly precise surface shape can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the present invention.

FIG. 2 is a side view showing a cross section of part 1 showing the first embodiment.

FIG. 3 is a flowchart showing a first embodiment.

FIG. 4 is a flowchart showing a second embodiment.

FIG. 5 is a partial side view showing a part of the third embodiment in section.

[Explanation of symbols]

 1 Optical material 3 Lower mold 7 Upper mold 16 Ball screw 17 Motor 18 Displacement sensor 19 Pressure sensor 21 Controller

Claims (2)

[Claims] 1. A method of molding an optical element in which an optical material is carried between a pair of upper and lower molds heated near the softening point temperature of the optical material, and the optical material is molded while being pressed by the mold, in a pressure molding step. Detects the relative position of the pair of upper and lower molds and maintains the distance between the pair of upper and lower molds so that the optical material has a predetermined thickness, and shrinks with cooling and solidification in the cooling and solidifying process after press molding. A method for molding an optical element, characterized in that the pressure applied to the mold is detected by applying a constant pressure to the optical material. 2. An optical element molding apparatus for pressing an optical material by a pair of upper and lower molds having a vertical movement mechanism section,
A sensor that measures the displacement of the mold provided on the mold side that moves up and down by the vertical movement mechanism section, and a sensor that detects the pressure applied to the mold provided on either one of the pair of molds,
A molding device for an optical element, comprising: a control unit that controls a vertical movement mechanism unit according to a signal from each sensor.