Glass lens forming apparatus and forming method

Abstract

To provide a molding apparatus capable of improving or suppressing asymmetrical deformation caused in a glass material while molding a glass lens.SOLUTION: An apparatus for molding a glass lens according to the present disclosure holds a glass material using a pair of dies and performs a press molding step. The apparatus includes: a heating mechanism for heating the glass material through molding surfaces on which the dies contact the glass material; a press member for moving and pressing one of the pair of dies along a load axis toward the other die: a load detection device for detecting a load acting on the glass material in the load axial direction; and a load center calculation part for calculating the coordinate of the load center on an action surface where the glass material is orthogonal to the load axis on the basis of the detected load. The heating mechanism includes at least one heating element and a heating control part; and the heating control part controls the heating element on the basis of the coordinate of the calculated load center and changes a temperature distribution in a molding surface to heat the glass material.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a glass molding apparatus, and more specifically, to a glass lens molding apparatus and a molding method for mass-producing glass products such as lenses typified by optical elements by a molding technique using a mold.

Background Art

[0002] As a conventional glass lens molding apparatus, when press-molding a glass material softened by heating using a molding die member, due to structural reasons such as the inlet of the glass material with respect to the molding die, etc., regarding the circumferential direction of the die member, when there is a variation in the temperature distribution in the die member, there is an apparatus provided with temperature adjustment means capable of correcting this (see, for example, Patent Document 1).

[0003] In the configuration diagram of the conventional glass lens molding apparatus described in Patent Document 1 shown in FIG. 15, a body die 401 and die members 402 and 403 that are paired with each other are used. The glass material 404 is sandwiched between a lower die (lower punch) 403 and an upper die (upper punch) 402 and is heated by annular heater portions 405 installed vertically. In a softened state where the glass material 404 reaches a predetermined temperature, the upper die 402 and the lower die 403 are relatively moved closer to each other in the axial direction to be pressed, and by transferring the shape of the die member to the glass, the desired glass lens shape is obtained. Thereafter, the output of the heater 405 is adjusted to lower the temperature, and after the glass is solidified, the die members 402 and 403 are driven, and the molded glass lens is taken out, completing a series of glass molding processes.

[0004] In recent years, imaging optical lenses such as cameras have been able to meet various performance requirements such as aberration and resolution by combining multiple lenses. Lenses come in convex and concave shapes for the purpose of converging or diverging light. Among them, lenses with a shape where the peripheral part is thicker compared to the central part of the lens, such as concave meniscus lenses, are known to be sensitive to variations in the temperature of the mold member, particularly variations in the temperature distribution at the peripheral part of the mold member. As a result, there has been a problem that non-axisymmetric shape errors centered on the optical axis occur on the optical performance surface of the lens.

[0005] Therefore, in the glass lens molding apparatus described in Patent Document 1, an annular temperature control means 406 is provided around the vicinity of the molding surfaces of the upper and lower mold members (punches) 402 and 403. The temperature control means 406 can adjust the temperature for regions divided as required in the circumferential direction. In this way, when there are temperature variations in the circumferential direction of the mold member, by correcting this, temperature uniformity can be achieved and the occurrence of shape errors can be prevented.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the configuration of the conventional glass lens molding apparatus described above, temperature control is performed using temperature control means that surrounds the mold member so that the temperature in the peripheral region of the molding surface of the mold member divided in the circumferential direction becomes uniform. However, in this configuration, there is no measuring means for the molding surface of the mold member that directly affects the molding of the optical performance surface of the glass lens. As a result, there is a problem that a defective shape occurs on the molded lens surface because it is impossible to cope with a phenomenon in which the temperature of the molding surface of the mold member changes moment by moment during press molding. From the viewpoint of further suppressing defects in glass lens molding, the conventional configuration still has room for improvement.

[0008] The present invention solves the above-described conventional problems, and an object thereof is to provide a molding apparatus and a molding method capable of improving or suppressing an asymmetric deformation generated in a glass material during glass lens molding.

Means for Solving the Problems

[0009] In order to achieve the above object, a glass lens molding apparatus according to the present disclosure includes a heating mechanism that heats a glass material through a molding surface where a mold contacts the glass material, a press member that moves and presses one of a pair of molds along a load axis toward the other mold, a load detection device that detects a load in the load axis direction acting on the glass material, and a load center calculation unit that calculates coordinates of a load center on an action surface orthogonal to the load axis in the glass material based on the detected load. The heating mechanism includes at least one heating element and a heating control unit. The heating control unit controls the heating element based on the calculated coordinates of the load center, changes the temperature distribution in the molding surface, and heats the glass material.

Effects of the Invention

[0010] According to the glass lens molding apparatus and method of the present disclosure, it is possible to improve an asymmetric deformation during glass lens molding and provide a high-quality glass lens.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0012] According to a first aspect of the present disclosure, there is provided a glass lens molding apparatus that sandwiches a glass material using a pair of molds and performs press molding. The apparatus includes a heating mechanism that heats the glass material through a molding surface where the mold contacts the glass material, a press member that moves one of the pair of molds along a load axis toward the other mold and presses it, a load detection device that detects a load in the direction of the load axis acting on the glass material, and a load center calculation unit that calculates coordinates of the load center on an action surface orthogonal to the load axis in the glass material based on the detected load. The heating mechanism includes at least one heating element and a heating control unit. The heating control unit controls the heating element based on the calculated coordinates of the load center to change the temperature distribution within the molding surface and heat the glass material.

[0013] According to a second aspect of the present disclosure, the load detection device includes at least three load sensors. The load sensors are arranged axially symmetrically about the load axis within a plane orthogonal to the load axis, and each detects a load generated in the direction of the load axis. There is provided the glass lens molding apparatus according to the first aspect.

[0014] According to a third aspect of the present disclosure, the heating mechanism further includes a temperature measurement element that measures the heating temperature of the heating element, and the heating control unit controls the heating element based on the measured heating temperature of the heating element. There is provided the glass lens molding apparatus according to the first or second aspect.

[0015] According to a fourth aspect of the present disclosure, there is further provided a temperature adjustment determination unit. The temperature adjustment determination unit calculates, on the working surface, the amount of movement of the center of load relative to a predetermined reference position based on the coordinates of the center of load calculated by the center of load calculation unit, determines the temperature adjustment amount of the heating element based on the calculated amount of movement, and the heating control unit controls the heating element using the determined temperature adjustment amount of the corresponding heating element. There is provided a glass lens molding apparatus according to any one of the first to third aspects.

[0016] According to a fifth aspect of the present disclosure, there are a plurality of heating elements. The plurality of heating elements are arranged in a segmental shape, each heating a corresponding region of the molding surface at a heating temperature that can be adjusted independently of each other. The heating mechanism includes a plurality of temperature measurement elements paired with each heating element, and the plurality of temperature measurement elements measure the heating temperature of the heating elements that are paired with each other. There is provided a glass lens molding apparatus according to any one of the first to fourth aspects.

[0017] According to a sixth aspect of the present disclosure, there is provided a glass lens molding apparatus according to any one of the first to fifth aspects, wherein the heating element is a flat heater.

[0018] According to a seventh aspect of the present disclosure, there is provided a method for molding a glass lens by sandwiching a glass material using a pair of molds, the method including: heating the glass material through a molding surface where the mold contacts the glass material; moving one of the pair of molds along a load axis toward the other mold and pressing; detecting a load in the load axis direction acting on the glass material; calculating, based on the detected load, the coordinates of the center of load on a working surface orthogonal to the load axis in the glass material; and changing the temperature distribution within the molding surface and heating the glass material based on the calculated coordinates of the center of load.

[0019] According to an eighth aspect of the present disclosure, the step of heating the glass material by changing the temperature distribution within the forming surface based on the calculated coordinates of the center of load includes, based on the calculated coordinates of the center of load, on the working surface, calculating the amount of movement of the center of load relative to a predetermined reference position; determining an adjustment amount of the temperature for heating the glass material based on the calculated amount of movement; and controlling the temperature for heating the glass material using the determined adjustment amount of the temperature. A method for forming a glass lens according to the seventh aspect is provided.

[0020] According to a ninth aspect of the present disclosure, the step of calculating the amount of movement of the center of load relative to a predetermined reference position on the working surface based on the calculated coordinates of the center of load includes calculating the direction of movement of the center of load relative to the predetermined reference position on the working surface. The step of determining an adjustment amount of the temperature for heating the glass material based on the calculated amount of movement includes determining to relatively change the temperature of the region of the forming surface on the side toward the calculated direction of movement of the center of load and / or the temperature of the region of the forming surface on the side opposite to the calculated direction of movement of the center of load with respect to the temperature of other regions of the forming surface. A method for forming a glass lens according to the eighth aspect is provided.

[0021] According to a tenth aspect of the present disclosure, there is provided a method for forming a glass lens including a plurality of steps, the method including feeding back an adjustment amount of the temperature for heating the glass material determined in an upstream step to a downstream step; and in the downstream step, changing the temperature distribution within the forming surface to heat the glass material based on the fed-back adjustment amount of the temperature. A glass lens forming apparatus according to the eighth or ninth aspect is provided.

[0022] According to the eleventh aspect of the present disclosure, there is provided a method for forming a glass lens including a plurality of steps, wherein, among the plurality of steps, one or more steps include detecting a load in the load axis direction acting on a glass material, calculating coordinates of the load center on the working surface based on the detected load, and changing the temperature distribution in the forming surface and heating the glass material based on the calculated coordinates of the load center. The glass lens forming apparatus according to any one of the seventh to tenth aspects is provided.

[0023] <The process leading to the present invention> First, with reference to FIGS. 1 to 3, the process leading to the present invention will be described.

[0024] FIG. 1 is a diagram showing a glass lens forming apparatus 100 that continuously forms a glass lens by dividing the process into a plurality of steps and its forming process. The glass lens forming apparatus 100 shown in FIG. 1 can utilize a plurality of molds 1 simultaneously by dividing the forming process of the glass lens into a plurality of steps and continuously executing them, thereby enhancing productivity. As shown by the arrows in the figure, in the forming process shown in FIG. 1, each forming step proceeding from right to left is sequentially executed in the loading section 111, the heating section 112, the press forming section 113, the cooling section 114, the cooling section 115, and the unloading section 116. The mold 1 includes an upper mold (upper punch) 2, a lower mold (lower punch) 3, and a body mold 4. The upper mold 2 and the lower mold 3 are arranged opposite to each other and held by the body mold 4, and the glass material 5a to be formed into a lens is sandwiched therebetween. After the forming process starts, the mold 1, while sandwiching the glass material 5a, is fed into the loading section 111 of the forming apparatus 100 supported by a gantry 101 at regular intervals (e.g., every 10 minutes) by a feeding mechanism (not shown), and is transferred toward the unloading section 116. The glass material 5a is sequentially subjected to forming processes in each step. Each step will be described below.

[0025] In the loading process, in the loading section 111, the upper mold 2 is removed from the body mold 4, a glass material 5a serving as a lens is inserted, and then the upper mold 2 is inserted into the body mold 4. The mold 1 is assembled so that the lens material 5a is clamped between the lower mold 3 and the upper mold 2. Subsequently, the shutter 106a of the processing chamber 105 opens, and the mold 1 clamping the lens material 5a is slid and moved by a feeding mechanism and transferred between the upper and lower heater blocks 7a installed opposite each other in the heating section 112 in the processing chamber 105. The inside of the processing chamber 105 is generally in a vacuum or nitrogen atmosphere state to prevent oxidation of the mold.

[0026] In the heating process, the heater block 7a of the heating section 112 has a plurality of rod-shaped heaters 6a inserted therein and is controlled to maintain a predetermined preheating temperature. In the heating process, in order not to crack or damage the glass material 5a with a low temperature, the press member 10a moves the upper heater block 7a downward along the load axis 11a and abuts against the upper mold 2 so as not to apply a substantial load to the glass material 5a. The mold 1 immediately after being transferred to the heating section is lower than the set temperature of the heater block 7a. As the heater block 7a heats the glass material 5a through the mold 1, the glass material 5a reaches a temperature at which it can be sufficiently thermally deformed in the latter half of the heating process. After a predetermined time has elapsed, the mold 1 advances to the molding section 113 while clamping the glass material 5a that has reached the thermally deformable temperature, and in the heating section 112, the glass material fed in together with the next mold is heated.

[0027] In the forming process, in the upper and lower heater blocks 7b of the forming section 113, a plurality of rod-shaped heaters 6b are inserted and are controlled to maintain a predetermined forming temperature. After the mold 1 is disposed between the upper and lower heater blocks 7b of the forming section, the press member 10b of the forming section 113 descends along the load axis 11b, bringing the forming surfaces of the mold 1 (the lower end surface of the upper mold 2 and the upper end surface of the lower mold 3) into contact with the glass material 5b, crushing and deforming the glass material 5a in a thermally deformable state. Then, while heating the glass material 5b deformed through the forming surface of the mold 1 by the heater block 7b, the lens shape is transferred to the glass material 5b. After a predetermined time has elapsed, the mold 1 holds the glass material 5b onto which the lens shape has been transferred and proceeds to the cooling section 114. In the forming section 113, the glass material fed in together with the next mold is press-formed.

[0028] In the first cooling process, in the upper and lower heater blocks 7c of the first cooling section 114, a plurality of rod-shaped heaters 6c are inserted and are controlled to maintain a cooling temperature slightly lower than the temperature of the heater block 7b of the forming section 113. After the mold 1 is disposed between the upper and lower heater blocks 7c of the first cooling section 114, the press member 10c of the first cooling section 114 descends along the load axis 11c, bringing the forming surface of the mold 1 into contact with the glass material 5b to maintain the glass material 5b at the cooling temperature. At this time, as the temperature of the glass material 5b decreases, it contracts, and in the process of contraction, the lens shape is completely transferred by the forming surfaces of the molds 2 and 3, and the surface shape of the lens to be formed is formed. After a predetermined time has elapsed, the mold 1 holds the glass material 5c after forming is completed and proceeds to the second cooling section 115. The first cooling section 114 forms the glass material fed in together with the next mold.

[0029] In the second cooling process, in the upper and lower heater blocks 7d of the second cooling section 115, a plurality of rod-shaped heaters 6d are inserted and are controlled to maintain the mold removal temperature. After the mold 1 is placed between the upper and lower heater blocks 7d of the second cooling section 115, the press member 10d of the second cooling section descends along the load axis 11d, brings the molding surface of the mold 1 into contact with the glass material 5c, and cools it until it reaches the second cooling temperature. The glass material 5c after the molding is completed is rapidly cooled and solidified while being sandwiched between the molds 2 and 3. After a predetermined time has elapsed, the shutter 106b of the processing chamber 105 opens, the mold 1 is sent out of the processing chamber 105, proceeds to the take-out section 116 while sandwiching the solidified glass material 5d, and in the second cooling section 115, the glass material fed in together with the next mold is cooled.

[0030] In the take-out process, the mold 1 is disassembled, the molded glass material 5d is taken out, and the molding process is completed. Thereafter, the mold 1 is transferred back to the input section 111, a new glass material is inserted, and each of the above-described processes is repeatedly executed.

[0031] Also, the glass lens molding process according to the present disclosure is not limited to the above-described processes. For example, the heating process may be performed in two stages, and similarly, the cooling process may be further divided into multiple stages. As described above, the set temperature of the heater block is different for each process, the preheating temperature of the heating section and the molding temperature of the molding section are high (not necessarily the same temperature), the first cooling temperature of the first cooling section is lower than the molding temperature, and the temperature of the second cooling section is the take-out temperature and is generally much lower than the first cooling temperature.

[0032] Note that it is also possible to increase productivity by automating the process of disassembling the mold to take out the molded glass material and the process of inserting a new glass material and assembling the mold, according to the production situation.

[0033] However, in the above molding process, asymmetric deformation of the glass material may occur. Hereinafter, the occurrence of asymmetric deformation of the glass material during press molding will be described.

[0034] <Occurrence of Asymmetric Deformation of Glass Material during Press Forming> FIG. 2 is a view showing the state of the outer peripheral surface of the glass material after the completion of the forming process by the glass lens forming apparatus of FIG. 1. After the glass lens is formed, the outer peripheral surface is processed along the centering planned line (5s1 shown in FIG. 2(a) or 5s2 shown in FIG. 2(b)). When the completed glass lens is assembled into the lens barrel, since the outer peripheral surface of the lens is held, if the center of the outer peripheral surface of the formed lens does not coincide with the optical axis optically, the optical performance cannot be fully exhibited.

[0035] The formed glass material 5d1 shown in FIG. 2(a) is in an axially symmetric formed state with respect to the optical axis perpendicular to the paper surface of FIG. 2, and the outer peripheral surface and the centering planned line 5s1 are concentric. On the other hand, the formed glass material 5d2 shown in FIG. 2(b) is in a non-axially symmetric formed state, the outer peripheral surface and the centering planned line 5s2 are non-concentric, and asymmetric deformation has occurred. In both cases of (a) and (b) in FIG. 2, if the outer peripheral surface is processed along the centering planned line, a lens having the same outer diameter can be finished. However, since the lens finished from the glass material 5d2 in FIG. 2(b) has asymmetric forming strain, sufficient optical performance cannot be achieved, and forming quality defects occur.

[0036] Regarding the cause of the occurrence of the asymmetric deformation generated in the glass material after the above press forming, it is examined with reference to FIG. 3. FIG. 3 is a view showing the state of the occurrence of asymmetric deformation during press forming. In FIG. 3(a) at the upper stage of FIG. 3, the glass material 5e is sandwiched between the upper die 2 and the lower die 3 at the center. While being held in this state, it is heated by a heater block (not shown), and after reaching the forming temperature, the upper die 2 is lowered along the load axis 11e by a press member (not shown).

[0037] In Figure 3(b) at the lower part of Figure 3, the glass material 5e is in a state where it is properly pressed and formed. As shown in Figure 3(b), the formed glass material 5f is evenly expanded around the center of the load axis. In this case, during the press forming, the center of gravity of the glass material does not move, and the load center 12f in the plane orthogonal to the glass material and the load axis is on the load axis 11f. In this case, the formed glass material 5f has a concentric outer peripheral surface with respect to the centering planned line as shown in Figure 2(a).

[0038] On the other hand, Figure 3(c) shows a state where an asymmetric deformation has occurred and the glass material is not axisymmetrically formed. At this time, the glass material during the press forming does not spread uniformly with respect to the load axis 11g, and the spread progresses more in the m4 direction than in the m3 direction. As a result, the center of gravity of the formed glass material 5g moves, and the position of the load center 12g in the plane orthogonal to the glass material and the load axis is displaced by Δd1 with respect to the load axis 11g. The formed glass material 5g has a non-concentric outer peripheral surface with respect to the centering planned line as shown in Figure 2(b).

[0039] Thus, it has been found that the movement of the load center occurs with the occurrence of asymmetric deformation during the press forming. Therefore, a digital heating control mechanism applied to the glass lens forming apparatus has been developed, leading to the present invention. By applying the digital heating control mechanism according to the present disclosure to the glass lens forming apparatus, the asymmetric deformation in the glass material during forming is detected by measuring the movement of the load center during pressing, and the occurrence of asymmetric deformation can be improved by performing heating control accordingly.

[0040] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that all the embodiments described below show preferred specific examples of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions of the components, connection forms, etc. shown in the following embodiments are specific examples of the present disclosure and do not limit the present disclosure. Therefore, among the components in the following embodiments, the components not described in the independent claims indicating the highest concept of the present disclosure are described as optional components. Further, modifications can be made as appropriate without departing from the scope in which the effects of the present disclosure are achieved. Furthermore, combinations with other embodiments are also possible.

[0041] Note that each drawing shows a schematic diagram and is not necessarily drawn precisely. Also, in each drawing, substantially the same components are denoted by the same reference numerals, and overlapping descriptions are omitted or simplified.

[0042] (First Embodiment) <Configuration of the Digital Heating Control Mechanism According to the First Embodiment of the Present Disclosure> FIG. 4 is a configuration diagram of a digital heating control mechanism 200 according to the first embodiment of the present disclosure. The load detection and digital heating control mechanism 200 shown in FIG. 4 includes a pair of digital heaters 70 arranged vertically opposite to each other, a load detection device 20, an arithmetic device 30, and a heating control unit 40. The pair of digital heaters 70 includes a heating element 60 and a temperature measurement element 50 paired with the heating element 60. The heating element 60 heats a glass material (not shown) through the molding surface (not shown) of the mold 1, and the temperature measurement element 50 is used to measure the heating temperature of the paired heating elements. Below the digital heater 70, a load sensor 21 of the load detection device 20 is installed. These components will be described in detail below.

[0043] <Load Detection Device of the Digital Heating Control Mechanism According to the Embodiment of the Present Disclosure> As shown in FIG. 4, the load detection device 20 includes a load sensor 21 and an amplifier 22. The load sensor 21 is installed below the digital heater 70 and measures the load during pressing. The detected load value is amplified by the amplifier 22 and transmitted to the arithmetic unit 30. In order to protect the load sensor 21 from high temperatures and temperature changes, as will be described later, it can be installed via a heat insulating material below the heater block of the forming part (or the cooling part) of the glass lens forming device.

[0044] FIG. 5 is a diagram showing a configuration example of the planar arrangement of the load sensor 21 of the load detection device 20 according to the embodiment of the present disclosure. The load sensor 21 shown in FIG. 5 shows a configuration example using four uniaxial load sensors (21a1, 21a2, 21a3, 21a4) capable of measuring only the load in the pressing direction (Z-axis). This configuration is practical because it can be composed of only inexpensive uniaxial load sensors. As shown in FIG. 5, the four uniaxial load sensors 21a1 to 21a4 are installed at positions separated by ±m from the X-axis and ±n from the Y-axis in a plane orthogonal to the load axis. In this way, arranging the load sensors symmetrically with respect to the origin O of the X-Y coordinates is to facilitate the calculation of the coordinates of the load center described later. When the load sensors are not arranged symmetrically, the calculation of the coordinates of the load center becomes complicated. The virtual plane for deriving the position of the load center is defined as the working surface F1, and the plane of the X-Y coordinates shown in FIG. 5. When a press load occurs during press forming, the uniaxial load sensors 21a1 to 21a4 detect the loads z1, z2, z3, z4 on the Z-axis respectively, and the load on the Z-axis on the working surface F1 is the sum of z1 to z4.

[0045] When the four load sensors 21a1 to 21a4 respectively show the loads z1 to z4 on the Z-axis, the moment Mx about the X-axis and the moment My about the Y-axis with respect to the origin O of the X-Y coordinates are calculated by the following equations (1) and (2) respectively.

[0046]

Equation

[0047] The coordinates (a x1 , a y1 ) of the load center G1 on the working surface F1 can be obtained by the following equations (3) and (4).

[0048] [Number]

[0049] When the center position of the load axis coincides with the origin O of the X-Y coordinates of the working surface F1, from the start of press forming until the glass is expanded, when the formed glass material is in the state shown in Fig. 3(b), the load center G1 coincides with the origin O of the X-Y coordinates, and the calculation results of equations (3) and (4) are such that a x1 = a y1 ≈ 0 can be estimated. On the other hand, when the formed glass material is in the state shown in Fig. 3(c), asymmetric deformation occurs in the glass material during press forming, the load center G1 moves from the origin O of the X-Y coordinates, and the calculated values of the coordinates a x1 , a y1 of the load center G1 by equations (3) and (4) will not be zero.

[0050] In the configuration example of the load sensor 21 shown in Fig. 5, four uniaxial load sensors are arranged. However, if there are three or more load sensors 21, the coordinates of the load center can be calculated. When using three load sensors 21, the three load sensors 21 may be arranged at three locations that are not on a straight line. For example, the three load sensors 21 can be arranged in three of the four regions from the first quadrant to the fourth quadrant in the X-Y plane, respectively.

[0051] [Movement of the load center in the glass material during press forming] During the press forming of the glass lens, when asymmetric deformation as shown in Fig. 3(c) occurs as the press progresses, the load center will move within the X-Y plane. Hereinafter, with reference to Figs. 6-7, the movement pattern of the load center of the glass material during press forming and the cause of the movement will be described.

[0052] FIG. 6 is a diagram showing an example of the change in the position of the load center in the glass material during press molding detected by the load detection device according to the embodiment of the present disclosure. FIG. 7 is a diagram showing the relationship between the change in the position of the load center in the glass material and the temperature distribution on the molding surface of the mold. The X-Y coordinates in FIGS. 6 and 7 are the same as the X-Y coordinates of the working surface F1 shown in FIG. 5, that is, they represent the coordinates of the load center.

[0053] In the example shown in FIG. 6, in the molding process of the glass lens molding process of FIG. 1, immediately after the mold 1 moves to the molding part 113, since the upper heater block 7b is above, no press load is generated (only the weight of the mold acts on the glass material 5b). Thereafter, when the press member 10b descends and comes into contact with the mold 1, a press load is generated. The starting point A1 (the ■ position shown in FIG. 6) shown in FIG. 6 indicates the position of the load center acting on the glass material on the working surface F1 when the press load reaches 10 N, for example. Thereafter, the load center is detected at each set sampling timing, and as the press molding progresses, the load center moves along the locus Q1 and becomes A2 (the ● position shown in FIG. 6) which is the farthest from the origin O at the end of the molding process.

[0054] Examine the cause of the movement of the load center as the press molding progresses. In the molding process, the setting of the heater block for controlling the molding temperature varies depending on the type of glass used. Generally, the molding temperature is set near the yield point (At point) higher than the glass transition point (Tg point). When the heater block heats the glass material being molded through the molding surface of the mold, even a slight difference of, for example, only 1 or 2 °C in the temperature distribution on the molding surface of the mold causes a large change in the viscosity of the glass material. Specifically, on the side where the temperature of the molding surface is high, the viscosity of the glass material is low and the deformation progresses faster. As a result, although the press load is applied only in the load axis (Z-axis) direction, the deformation of the glass in the X-Y plane becomes non-uniform and asymmetric deformation occurs. Thus, when measuring the press load by the load sensor 21, as in the example shown in FIG. 6, it is found that the movement of the load center is caused by the non-uniform temperature distribution on the molding surface of the mold.

[0055] Figure 7 shows the temperature distribution of the molding surface of the mold when the center of the load moves from the origin O (center of the load axis) of the X-Y coordinates of the working surface F1 to B1 (the ● position shown in Figure 7). In this example, the moving direction Q2 of the center of the load is the direction rotated γ° clockwise from the X-axis. On the side facing the moving direction, there is a region where the temperature of the molding surface of the mold is slightly higher (the "H" region in the figure). The value of the movement amount Δd2 of the center of the load (correspondingly Δd1 shown in Figure 3(c)) depends on the size of the lens to be molded and the molding conditions. For a lens with a diameter of about 30 mm, it is at most 1 to 2 mm, and usually 0.5 mm or less. When the value of this Δd2 is large, asymmetric strain remains on the molded lens surface, resulting in defects. How large the value of Δd2 should be to cause defects may be appropriately determined according to the lens shape and quality standards.

[0056] <Configuration of the digital heater in the digital heating control mechanism according to the embodiment of the present disclosure> The configuration of the digital heater in the digital heating control mechanism according to the present disclosure will be described in order to improve the asymmetric deformation of the glass material caused by the non-uniform temperature distribution on the molding surface of the mold during press molding.

[0057] FIG. 8 is a diagram showing a comparison between a digital heater 70 of a digital heating control mechanism according to an embodiment of the present disclosure and a conventional heater block 7. As shown in the upper part of FIG. 8, the configuration of the heater block 7 of the general glass lens molding apparatus 100 shown in FIG. 1 uses a rod-shaped heater 6, and is configured such that the heating surface of the heater block (the surface that contacts the mold) has a uniform temperature. However, as shown in FIG. 1, the glass lens molding process is executed such that the mold 1 slides and proceeds to each step sequentially. In such a case, even if the heating surface of the heater block has a uniform temperature, the molding surface of the mold (the surface that contacts the glass material) does not necessarily have a uniform temperature. This is because, for example, when a minute foreign object is caught between the lower surface of the lower mold 3 and the heating surface of the lower heater block and the mold slightly lifts, or when the heating surface of the heater block wears due to long-term use and the contact state becomes non-uniform, even if the heater block has a uniform temperature, heat is not uniformly transferred, so a non-uniform temperature distribution occurs on the molding surface of the mold.

[0058] In view of such a situation, the digital heater 70 developed is shown in the lower part of FIG. 8. The digital heater 70 includes one or more heating elements 60 arranged in a segmented manner along the heating surface, and temperature measurement elements 50 paired with each of the heating elements 60. The heating element 60 is preferably a small planar heater having a flat plate shape (for example, Sakaguchi Denki Co., Ltd. MS-1000R, MS-1000-10), but is not limited thereto. The one or more heating elements 60 are each configured to heat a corresponding region of a mold (not shown) at a heating temperature that can be independently adjusted for each other. The temperature measurement element 50 may be, for example, a thermocouple, and forms individual heating segments with the heating elements 60 that are paired with each other.

[0059] FIG. 9 is a diagram showing a control method for the heating temperature of a digital heater 70 of a digital heating control mechanism according to an embodiment of the present disclosure. As shown in the figure, in the digital heater 70, each heating segment is configured such that a pair of heating elements 60 and a temperature measuring element 50 are connected to a temperature control unit 40 and can be temperature-controlled independently of each other. In this way, by changing the temperature distribution on the heating surface of the digital heater 70, the temperature distribution on the molding surface of the mold can be appropriately adjusted, and the glass material can be heated.

[0060] Theoretically, an arbitrary temperature distribution can be formed on the heating surface of the digital heater 70 by a plurality of heating elements 60. However, since the plurality of heating elements 60 are adjacent to each other and affect each other, a temperature distribution of about 10° C. at most can be formed at an arbitrary location. As described above, even if the conventional heater block realizes a uniform temperature distribution on the heating surface, it is difficult to uniformly transfer heat to the glass material through the molding surface of the mold. By using the digital heater according to the present disclosure, it is possible to form an arbitrary temperature distribution on the heating surface, make the temperature distribution on the molding surface of the mold uniform, and uniformly transfer heat to the glass material during molding.

[0061] FIG. 9 shows an example of a digital heater composed of 9 heating segments arranged in a 3×3 grid in the vertical and horizontal directions, but the present disclosure is not limited to this. If the number of heating segments constituting the digital heater 70 is increased from the example of FIG. 9, such as to 4×4, 5×5, or 4×5, more precise temperature control becomes possible. On the other hand, even if the number of heating segments is increased, since the temperature itself is transmitted analogously with a time delay, increasing the number of heating segments unnecessarily will result in an increase in the cost of the heating control unit 40 shown in FIG. 4.

[0062] In order to improve the asymmetric deformation of the glass material during forming, it becomes effective for the first time by combining the control of the heating temperature by the digital heater 70 described above and the detection of the movement of the load center during forming by the load detection device 20. The cooperation between the digital heater 70 and the load detection device 20 is realized through the determination of the heating temperature adjustment amount by the arithmetic unit 30 of the digital heating control mechanism shown in FIG. 4. Hereinafter, in the heating control mechanism 200 of the present disclosure, the determination of the heating temperature adjustment amount by the arithmetic unit 30 will be described.

[0063] <Arithmetic unit 30 (computer device)> FIG. 10 is a block diagram showing a configuration example of the arithmetic unit 30 of the digital heating control mechanism shown in FIG. 4. The arithmetic unit 30 is, for example, a computer device. As this computer device, a general-purpose computer device can be used. For example, as shown in FIG. 10, it includes a processing unit 31, a storage unit 32, and a display unit 33. Note that it may further include an input device, a storage device, an interface, and the like. The arithmetic unit 30 can perform arithmetic processing based on the measurement data of the load during press forming detected by the load detection device 20.

[0064] <Processing unit 31> The processing unit 31 may be, for example, a central processing operator (CPU), a microcomputer, or a processing device capable of executing instructions executable by a computer.

[0065] <Storage unit 32> The storage unit 32 may be, for example, at least one of ROM, EEPROM, RAM, flash SSD, hard disk, USB memory, magnetic disk, optical disk, magneto-optical disk, etc.

[0066] The storage unit 32 includes a program 35. When the arithmetic unit 30 is connected to a network, the program 35 may be downloaded from the network as necessary.

[0067] <Program 35> The program 35 can include a load center calculation unit 35a and a temperature adjustment determination unit 35b. The load center calculation unit 35a and the temperature adjustment determination unit 35b are read from the storage unit 32 and executed by the processing unit 31 during execution. The load center calculation unit 35a and the temperature adjustment determination unit 35b calculate the position of the load center of the glass material during press molding, and further, based on the movement of the load center, the adjustment amount of the heating temperature of the digital heater that heats the glass material can be determined.

[0068] <Display unit 33> The display unit 33 can display, for example, the results obtained when the program 35 is executed by the processing unit 31.

[0069] Referring to FIG. 11, a determination program for determining the adjustment amount of the temperature for heating the glass material by calculating the load center will be described. FIG. 11 is a flowchart of the program 35 of the arithmetic unit 30 in FIG. 10. As shown in FIG. 11, the program 35 of the arithmetic unit 30 consists of the following three steps. The load center calculation unit 35a corresponds to step S11, and the temperature adjustment determination unit 35b corresponds to steps S12 and S13. (1) Based on the load detected by the load detection device, calculate the coordinates of the load center of the formed glass material (S11). (2) Next, based on the calculated coordinates of the load center, calculate the movement amount of the load center, and determine the adjustment amount of the heating temperature of the heating element in the digital heater so as to reduce the calculated movement amount of the load center (S12). (3) Then, transmit the determined adjustment amount of the heating temperature to the heating control unit 40 (S13).

[0070] <Heating control of the digital heating control mechanism according to the embodiment of the present disclosure> The heating control unit 40 can control the heating temperature of the digital heater 70 based on the adjustment amount of the heating temperature determined by the arithmetic unit 30, and adjust the temperature distribution within the molding surface of the mold to heat the glass material. Referring to FIG. 12, an example of the heating temperature control of the digital heater 70 of the present disclosure will be described.

[0071] FIG. 12 is a diagram showing an example of the heating control by the heating control unit 40 according to the embodiment of the present disclosure, and shows the X-Y coordinates of the working surface F1 of FIG. 5 as viewed from directly above a digital heater 70 composed of 3×3 heating segments in the vertical and horizontal directions. The mold 1 (outer shape) is arranged at the center. The movement of the load center described with reference to FIG. 7 is shown superimposed. As described above, when the load center moves from the center O of the load axis to B1, it is considered that there is a slightly higher temperature region on the side in the moving direction, that is, on the extension line of OB1. At this time, for example, the heating control unit 40 can control the temperature of the heating elements of the heating segments (3, 1) of the digital heater 70 to be relatively lowered with respect to other heating segments. The specific temperature adjustment amount can be determined based on the analysis or mapping data using parameters such as the moving speed from point O to point B1, the moving amount Δd2, the material of the mold, and the shape of the lens to be molded and the material type of the glass material. In this way, by performing temperature control, the moving amount Δd2 of the load center shown in FIG. 12 can be reduced. As a result, the asymmetric deformation generated in the glass material during molding can be improved, and high-precision lenses can be produced with good yield.

[0072] Note that the calculation of the moving amount of the load center during molding is not limited to being based on the center position of the load axis. In the working surface F1, the moving amount of the load center may be calculated with respect to an arbitrarily determined reference position, or during molding, the moving amount of the load center in the working surface F1 may be calculated based on the coordinates of the load center continuously calculated by the arithmetic unit 30.

[0073] (Second Embodiment) <Configuration of the Digital Heating Control Mechanism According to the Second Embodiment of the Present Disclosure> FIG. 13 is a configuration diagram of a digital heating control mechanism 200a according to a second embodiment of the present disclosure. In this embodiment, the digital heating control mechanism 200a transfers the adjustment amount of the heating temperature of the digital heater 70a determined based on the movement of the load center in the molding section 113a to the cooling section 114a downstream of the mold 1, and feeds back the adjustment amount to the digital heater 70b in the cooling section 114a to control the temperature distribution on the heating surface of the digital heater 70b.

[0074] As shown in FIG. 13, the basic configuration of the digital heating control mechanism 200a is the same as that of the digital heating control mechanism 200 described above, and thus detailed description thereof is omitted. The heating control unit 40a is connected to both the digital heater 70a in the molding section 113a and the digital heater 70b in the cooling section 114a to perform heating control. Hereinafter, a heating control method for feeding back the adjustment amount of the heating temperature determined in the molding process to the cooling process will be described.

[0075] In the glass lens molding process, when the press of the mold 1 moved from the heating section (not shown) to the molding section 113a is started, the load detected by the load sensor 21a below the digital heater 70a is transmitted to the arithmetic unit 30 via the amplifier 22a, and the movement amount of the load center is calculated. Based on the calculated movement amount of the load center, the arithmetic unit 30 determines the adjustment amount 1 of the heating temperature of the digital heater and transmits it to the heating control unit 40. The temperature control unit 40 controls the heating temperature of the digital heater 70a in the molding section 113a based on the received adjustment amount 1 of the heating temperature.

[0076] Next, after the molding process is completed, the mold 1 is transferred to the cooling unit 114a in the downstream process. At the same time, the temperature control unit 40 controls the heating temperature of the digital heater 70b of the cooling unit 114a with the adjustment amount 2 of the heating temperature based on the adjustment amount 1 of the heating temperature determined in the molding unit 113a. However, the adjustment amount 2 of the heating temperature used for controlling the heating temperature of the digital heater 70b of the cooling unit 114a is not necessarily the same as the adjustment amount 1 of the heating temperature determined in the molding unit 113a. Desirably, the adjustment amount 2 of the heating temperature is an adjustment amount of the heating temperature suitable for the cooling unit 114a derived based on the adjustment amount 1 of the heating temperature.

[0077] Specifically, if, for example, an adjustment amount with a temperature 5°C lower than the adjustment amount of the heating temperature obtained in the molding unit is an adjustment amount of the heating temperature suitable for the cooling unit 114a, then the suitable adjustment amount of the heating temperature is used as the adjustment amount 2 of the heating temperature to control the heating temperature of the digital heater 70b of the cooling unit 114a. Note that the derivation of the adjustment amount 2 of the heating temperature based on the adjustment amount 1 of the heating temperature is not limited to the above simple subtraction.

[0078] Deriving the adjustment amount 2 of the heating temperature based on the adjustment amount 1 of the heating temperature and controlling the digital heater 70b of the cooling unit 114a is because, as described above, the molding temperature of the molding unit 113a and the cooling temperature of the cooling unit 114a are different. Generally, since the heat capacity of each heating element of the digital heater 70b of the cooling unit 114a itself is small, it changes steeply to the commanded temperature, and the heating surface of the digital heater 70b also gradually reaches that temperature. The mold 1 immediately after being transferred from the molding unit 113a has a zero load during movement, so it is fed into the cooling unit 114a in a state where the thermal deformation has once recovered. The temperature of the glass material after the molding process in the mold 1 immediately after being fed remains the heating temperature of the molding unit 113a, and it may have changed significantly with thermal deformation recovery. When the pressing in the cooling unit 114a starts, the glass material begins to deform again along the molding surface of the mold. At this time, by making the temperature distribution of the heating surface with the adjustment amount 2 of the heating temperature derived based on the adjustment amount 1 of the heating temperature obtained in the molding unit, it becomes possible to mitigate the asymmetric deformation of the molded glass lens.

[0079] Furthermore, as shown in FIG. 13, in the same manner as the forming unit 113a, a load sensor 21b is installed in the cooling unit 114a, and the press load is detected. During the first cooling step, based on the press load measured by the load sensor 21b, the arithmetic unit 30 determines the adjustment amount of the new heating temperature of the digital heater 70b, and the heating temperature of the digital heater 70b set based on the adjustment amount 2 of the heating temperature can be further controlled according to the forming state of the cooling unit 114a.

[0080] <Glass lens molding apparatus to which the digital heating control mechanism according to the present disclosure is applied> FIG. 14 is a diagram showing a glass lens molding apparatus 300 to which the digital heating control mechanism according to the embodiment of the present disclosure is applied and its molding process. In the glass lens molding apparatus 300, the digital heating control mechanism 200a shown in FIG. 13 is applied to the forming unit 313 and the first cooling unit 314 to control the heating temperature of the digital heater 70 during press molding. As shown in FIG. 14, in the forming unit 313 and the first cooling unit 314, a set of four uniaxial load detectors 21 are installed below the lower digital heater 70 via a heat insulating material 8. In the loading unit 311, the heating unit 312, the second cooling unit 315, and the unloading unit 316, since no press load is applied to the glass material, it is the same as the glass lens molding apparatus 100 shown in FIG. 1, and the conventional heater block 7 is installed.

[0081] In the molding process of the glass lens molding apparatus 300 shown in FIG. 14, the method for controlling the heating temperature by the digital heating control mechanism of the present disclosure is particularly advantageous. In the molding process of the glass lens of the glass lens molding apparatus 300, the process time of the entire process is constant, and the molds move simultaneously during the process execution. The control of the heating temperature by the digital heating control mechanism of the present disclosure is very effective when the process time is long, for example, 3 minutes or more. On the contrary, when the process time is shorter than 3 minutes, even if the heating temperature of the digital heater is controlled, it takes time for heat conduction to the mold, and during that time, the process time may reach the set time, and the temperature control may not be effectively realized. Further, as shown in FIG. 13, by feeding back the adjustment amount of the heating temperature obtained in the molding part to the digital heater in the cooling part 1, when the mold moves to the cooling part 1, since the heating temperature of the digital heater in the cooling part 1 has already been set, an optimal temperature distribution can be formed on the heating surface without delay.

[0082] In addition, in the embodiments of the present disclosure described above, heating control is performed so as to make the temperature distribution on the molding surface of the mold uniform, but the present disclosure is not limited thereto. Depending on the application, heating control that deliberately makes the temperature distribution on the molding surface non-uniform is also possible.

[0083] The present disclosure is fully described in connection with the preferred embodiments with reference to the accompanying drawings, but various modifications and corrections will be apparent to those skilled in this technology. Such modifications and corrections should be understood to be included within the scope of the claims of the present invention as long as they do not depart from the scope of the present invention according to the appended claims.

Industrial Applicability

[0084] The glass lens molding apparatus of the present invention can improve the quality defects due to asymmetric deformation during the glass lens molding, and further can efficiently produce high-precision glass lenses. Further, it can be similarly used in the molding of resin lenses having significantly different temperature ranges of use.

Explanation of Reference Numerals

[0085] 1 Glass lens molding die (whole) 2 Upper die 3 Lower die 4 Sleeve 5 Glass material 5a Glass material before press molding 5b Glass material after press molding 5c, 5d, 5e Glass material during press molding 6 Heater, 6a: Rod-shaped heating element, 6b: Plate-shaped heating element 7 7a Heater block, 7b (by plate-shaped heating element) 8 Heat insulation plate 10 Press member 11 Load axis (drive axis) 20 Load detection device 21 Load sensor 21a1, 21a2, 21a3, 21a4 1-axis load sensor 22 Amplifier 30 Arithmetic unit 31 Arithmetic section 32 Memory section 33 Display section 35 Program 40 Heating control section 50 Temperature measurement element 60 Heating element 70 Digital heater 100 Glass lens molding device 101 Stand 105 Processing chamber 106a Loading section shutter 106b Unloading section shutter 111, 311 Loading section 112, 312 Heating section 113, 313 Molding section 114, 314 Cooling section 1 115, 315 Cooling section 2 116, 316 Unloading section 200, 200a Digital heating control mechanism 300 Glass lens molding device to which digital heating control mechanism is applied 401 Body mold 402 Upper punch 403 Lower punch 404 (Glass lens during forming) 405 Heater section 406 Temperature control means

Claims

1. A glass lens forming apparatus that sandwiches a glass material using a pair of molds and performs press forming, comprising: a heating mechanism that heats the glass material through a molding surface where the mold contacts the glass material; a press member that moves and presses one of the pair of molds along a load axis toward the other mold; a load detection device that detects a load in the direction of the load axis acting on the glass material; a load center calculation unit that calculates coordinates of a load center on an action surface orthogonal to the load axis in the glass material based on the detected load; and the heating mechanism includes a plurality of heating elements and a heating control unit, and the heating control unit controls the heating elements based on the calculated coordinates of the load center, changes a temperature distribution within the molding surface, and heats the glass material. A glass lens forming apparatus.

2. The load detection device includes at least three load sensors, and the load sensors are arranged axially symmetrically about the load axis in a plane orthogonal to the load axis, and each detects a load generated in the direction of the load axis. The glass lens forming apparatus according to claim 1.

3. The heating mechanism further includes a temperature measurement element, the temperature measurement element measures a heating temperature of the heating element, and the heating control unit controls the heating element based on the measured heating temperature of the heating element. The glass lens forming apparatus according to claim 1 or 2.

4. further comprising a temperature adjustment determination unit, and the temperature adjustment determination unit Based on the coordinates of the load center calculated by the load center calculation unit, calculate the amount of movement of the load center relative to a predetermined reference position on the working surface, and determine the temperature adjustment amount of the heating element based on the calculated amount of movement. The heating control unit controls the heating element using the determined temperature adjustment amount of the corresponding heating element. The glass lens molding apparatus according to any one of claims 1 to 3.

5. A plurality of the heating elements are arranged in a segmented manner, each heating a corresponding region of the molding surface at a heating temperature that can be adjusted independently of each other. The heating mechanism includes a plurality of temperature measurement elements paired with each of the heating elements. A plurality of the temperature measurement elements each measure the heating temperature of the paired heating element. The glass lens molding apparatus according to any one of claims 1 to 4.

6. The heating element is a flat heater, and the glass lens molding apparatus according to any one of claims 1 to 5.

7. A method for molding a glass lens by sandwiching a glass material using a pair of molds and performing a press molding process, heating the glass material through a molding surface where the mold contacts the glass material; moving one of the pair of molds along the load axis toward the other mold and pressing; detecting the load in the direction of the load axis acting on the glass material; calculating the coordinates of the load center on the working surface orthogonal to the load axis in the glass material based on the detected load; changing the temperature distribution within the molding surface and heating the glass material based on the calculated coordinates of the load center; including a method for molding a glass lens.

8. The step of heating the glass material by changing the temperature distribution within the forming surface based on the calculated coordinates of the load center is Based on the calculated coordinates of the load center, calculating, on the acting surface, the amount of movement of the load center relative to a predetermined reference position; Determining an adjustment amount of the temperature for heating the glass material based on the calculated amount of movement; Controlling the temperature for heating the glass material using the determined adjustment amount of the temperature; including The method for forming a glass lens according to claim 7.

9. The step of calculating, on the acting surface, the amount of movement of the load center relative to a predetermined reference position based on the calculated coordinates of the load center is including calculating, on the acting surface, the direction of movement of the load center relative to the predetermined reference position; The step of determining an adjustment amount of the temperature for heating the glass material based on the calculated amount of movement is determining to relatively change the temperature of the region of the forming surface on the side toward the calculated direction of movement of the load center and / or the temperature of the region of the forming surface on the side opposite to the calculated direction of movement of the load center with respect to the temperature of the other regions of the forming surface; The method for forming a glass lens according to claim 8.

10. A method for forming a glass lens including a plurality of steps, feeding back an adjustment amount of the temperature for heating the glass material determined in an upstream step to a downstream step; In the downstream step, changing the temperature distribution within the forming surface based on the fed-back adjustment amount of the temperature to heat the glass material; including The method for forming a glass lens according to claim 8 or 9.

11. A method for forming a glass lens including a plurality of steps, Among the plurality of steps, one or more steps include: Detecting a load in the load axis direction acting on the glass material; Calculating coordinates of a load center on the working surface based on the detected load; Changing a temperature distribution in the forming surface based on the calculated coordinates of the load center to heat the glass material; and The method for forming a glass lens according to any one of claims 7 to 10.

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