JP6940991B2 - Glass sheet manufacturing method - Google Patents

Description

The present invention relates to a method for producing a glass sheet for producing a glass sheet by molding molten glass.

Conventionally, a method of manufacturing a glass sheet by using a down draw method has been used. In the down draw method, after the molten glass is poured into the molded body, the molten glass is overflowed from the top of the molded body. The overflowed molten glass flows down along both side surfaces of the molded body and joins at the lower end of the molded body to form a sheet-shaped glass sheet. The glass sheet is then pulled down by a roller and cut to a predetermined length.
However, during the slow cooling process until the glass sheet is pulled downward and cut to a predetermined length, the glass sheet is thermally shrunk, which causes warpage and strain (residual stress). Such warpage and distortion cause display defects when the glass sheet is used, for example, as a liquid crystal display (LCD) substrate. Therefore, it is important to adjust the temperature of the glass sheet so that the glass sheet does not warp and strain (residual stress) during the slow cooling step. As for the temperature of the glass sheet, it is preferable to adjust the temperature distribution in the moving direction of the glass sheet in addition to the temperature distribution in the width direction of the glass sheet.

The temperature distribution in the moving direction of the glass sheet is controlled by a plurality of temperatures through which the glass sheet passes during the slow cooling process. By controlling the temperature of the divided space obtained by dividing the slow cooling space into a plurality of parts, the glass at each outlet of the divided space is controlled. The temperature of the sheet is often adjusted to the desired temperature.

For example, a technique is known in which the temperature of a glass sheet in each of the slow cooling spaces (divided space) is obtained from the amount of heat generated by the heater and the space temperature in the divided space using thermal fluid analysis software (). Patent Document 1).

WO2015 / 166792

However, the above technique reproduces the slow cooling device with a simulation model in which the divided space, the glass sheet, and the wall surrounding the divided space are divided into a plurality of meshes, and calculates the fluid analysis using the reproduced simulation model. It takes time to create a simulation model, and the temperature distribution cannot be easily obtained. In particular, when changing the shape and dimensions of the slow cooling device (for example, the length of the glass sheet in the divided space in the moving direction), it becomes necessary to recreate the entire simulation model, which takes a lot of time to create, which is efficient. bad.
Therefore, when designing a slow cooling device, after roughly determining the shape and dimensions of the slow cooling device using a simple model in advance, a detailed study should be conducted with a simulation model using the above thermal fluid analysis software. Is preferable.

In the present invention, the movement of the glass sheet can be easily performed by using a simulation model that reproduces the slow cooling device as in the conventional case, without calculating the temperature distribution in the movement direction of the glass sheet by using the analysis software of the thermal fluid. It is an object of the present invention to provide a method for manufacturing a glass sheet, which can calculate a temperature distribution in a direction and adjust the temperature of the glass sheet.

One aspect of the present invention is a method for producing a glass sheet. The manufacturing method is
The process of molding a glass sheet from molten glass,
It includes a step of cooling the molded glass sheet while moving it in the cooling space.
In the cooling space, a radiation source for radiating heat to the glass sheet is provided at a position facing the glass sheet moving path.
The temperature distribution in the moving direction of the glass sheet in the cooling space formed by receiving the radiant heat from the radiation source of the glass sheet is the temperature distribution formulated by using the model of the glass sheet and the radiation source. The cooling space is adjusted so that the temperature distribution in the moving direction of the glass sheet becomes a desired distribution using the estimated temperature distribution obtained by performing a calculation using an analytical formula.

Ｔは、前記冷却空間の前記ガラスシートの移動方向をＺ方向として、前記冷却空間における入り口及び出口のＺ方向における位置をｚ＝０及びｚ＝Ｈとして、前記冷却空間における位置ｚにおける前記ガラスシートの温度であり、
Ｄは、前記ガラスシートと前記放射板の間の離間距離であり、
Ｔｗは、前記放射板の加熱された温度であり、
σは、ステファンボルツマン定数であり、
ε_Ｇ及びε_Ｗは、前記ガラスシート及び前記放射板の放射率であり、
ρは、前記ガラスシートの密度であり、
Ｖは、前記ガラスシートの移動速度であり、
ｔは、前記ガラスシートの厚さであり、
Ｃｐは、前記ガラスシートの単位質量当たりの定圧比熱である。 The radiation source is a radiation plate arranged in parallel with the movement path of the glass sheet.
The analysis formula is preferably a differential equation represented by the following formula.

T is the glass sheet at the position z in the cooling space, where the moving direction of the glass sheet in the cooling space is the Z direction, the positions of the inlet and outlet in the cooling space in the Z direction are z = 0 and z = H. Is the temperature of
D is the separation distance between the glass sheet and the radiation plate.
Tw is the heated temperature of the radiation plate.
σ is the Stefan-Boltzmann constant,
ε _G and ε _W are the emissivity of the glass sheet and the radiation plate.
ρ is the density of the glass sheet.
V is the moving speed of the glass sheet.
t is the thickness of the glass sheet.
Cp is the constant pressure specific heat per unit mass of the glass sheet.

The temperature of the glass sheet is preferably adjusted using at least one of the distance of the radiation source from the glass sheet and the heat generation temperature of the radiation source.

A plurality of divided spaces whose temperatures are separately controlled are provided in the cooling space along the moving direction of the glass sheet, and the glass sheet is moved and cooled in each of the divided spaces in order.
The estimated temperature of the glass sheet at the outlet in one of the divided spaces is given as an initial condition, and the temperature of the glass sheet at the entrance of the divided space adjacent to the downstream side in the moving direction of the glass sheet is given as an initial condition to move the glass sheet. It is preferable to estimate the temperature distribution in the direction by performing a calculation using the above analytical formula.

The step of forming the glass sheet is preferably performed by an overflow down draw method.

According to the above-mentioned glass sheet manufacturing method, the temperature distribution in the moving direction of the glass sheet is not calculated by using the thermal fluid analysis software using the simulation model that reproduces the slow cooling device as in the conventional case. , The temperature of the glass sheet can be adjusted by easily calculating the temperature distribution in the moving direction of the glass sheet.

It is a flow chart for demonstrating the process of the manufacturing method of the glass sheet of this embodiment. It is a schematic layout drawing of the apparatus used in the manufacturing method of the glass sheet of this embodiment. It is a schematic side view of the molding apparatus used in this embodiment. It is a control block diagram of the control device used in this embodiment. (A) is a diagram for explaining the positions of the heater, the radiation plate and the glass sheet, and (b) is a diagram for explaining the view factor in heat radiation. It is a figure which shows an example of the temperature distribution T (z) of the glass sheet obtained by calculating the analysis formula used in this embodiment.

Hereinafter, the method for manufacturing the glass sheet of the present embodiment will be described with reference to the drawings.

FIG. 1 is a partial flowchart of a glass sheet manufacturing method according to the present embodiment.
Hereinafter, a method for manufacturing a glass sheet will be described with reference to FIG.
As shown in FIG. 1, the glass sheet is manufactured through various steps including a melting step ST1, a clarification step ST2, a homogenization step ST3, a molding step ST4, a cooling step ST5, and a cutting step ST6. NS. Hereinafter, these steps will be described.

In the melting step ST1, the glass raw material is heated and melted. The glass raw material has a composition of, for example, SiO ₂ , Al ₂ O _{3, and the like.} The completely melted glass raw material becomes molten glass.
In the clarification step ST2, the molten glass is clarified. Specifically, the gas component contained in the molten glass is released from the molten glass, or the gas component contained in the molten glass is absorbed into the molten glass.
In the homogenization step ST3, the molten glass is homogenized. In this step, the temperature of the clarified molten glass is adjusted.
In the molding step ST4, a glass sheet is molded from the molten glass by a downdraw method (for example, an overflow downdraw method).

In the cooling step ST5, the glass sheet molded in the molding step ST4 is cooled while moving in the slow cooling space (cooling space). In the cooling step ST5, the glass sheet is cooled to near room temperature.
In the cutting step ST6, the glass sheet cooled to near room temperature is cut at predetermined length intervals.
The glass sheet cut to a predetermined length is then further cut and subjected to grinding / polishing, cleaning, and inspection to become a final product, which is used for a flat panel display such as a liquid crystal display.

FIG. 2 is a schematic view mainly showing the melting device 200. FIG. 3 is a schematic side view of the molding apparatus 300 included in the glass sheet manufacturing apparatus.

The glass sheet manufacturing apparatus mainly includes a melting apparatus 200 (see FIG. 2), a molding apparatus 300 (see FIG. 3), and a cutting apparatus 400 (see FIG. 3).

The melting device 200 is a device for performing the melting step ST1, the clarification step ST2, and the homogenization step ST3.
As shown in FIG. 2, the melting device 200 includes a melting tank 201, a clarification tank 202, a stirring tank 203, a first pipe 204, and a second pipe 205.
The melting tank 201 is a tank for melting the glass raw material. In the melting tank 201, the melting step ST1 is performed.

The clarification tank 202 is a tank for removing bubbles from the molten glass melted in the melting tank 201. By further heating the molten glass sent from the melting tank 201 in the clarification tank 202, defoaming of bubbles in the molten glass is promoted. In the clarification tank 202, the clarification step ST2 is performed.
The stirring tank 203 has a stirring device including a container for accommodating molten glass, a rotating shaft, and a stirring blade attached to the rotating shaft. As the container, the rotating shaft, and the stirring blade, for example, those made of a platinum group element such as platinum or an alloy of a platinum group element can be used, but the present invention is not limited thereto. When the rotating shaft is rotated by driving a driving unit (not shown) such as a motor, the stirring blade attached to the rotating shaft stirs the molten glass. In the stirring tank 203, the homogenization step ST3 is performed.
The first pipe 204 and the second pipe 205 are, for example, pipes made of a platinum group element or an alloy of a platinum group element. The first pipe 204 is a pipe that connects the clarification tank 202 and the stirring tank 203. The second pipe 205 is a pipe that connects the stirring tank 203 and the molding apparatus 300.

The molding apparatus 300 is an apparatus for performing the molding step ST4 and the cooling step ST5.
As shown in FIG. 3, the molding apparatus 300 includes a molded body 310, an atmosphere partition member 320, a cooling roller 330, a cooling unit 340, pulling rollers 350a to 350e, and heaters 360a to 360e. Hereinafter, these configurations will be described.

The molded body 310 is an apparatus for performing the molding step ST4.
As shown in FIG. 3, the molded body 310 is located above the molding device 300 and has a function of molding the molten glass flowing from the melting device 200 into a sheet-shaped glass sheet GS by the overflow down draw method. .. The molded body 310 has a wedge-shaped cross-sectional shape cut in the vertical direction, and is made of, for example, refractory brick.

The molded body 310 is formed with a supply port for supplying the molten glass to the molded body 310 on the upstream side in the flow path direction of the molten glass flowing from the melting device 200. Further, the molded body 310 is formed with a groove portion 312 opened upward along the longitudinal direction (the direction perpendicular to the paper surface in FIG. 3). The groove portion 312 is formed so as to gradually become shallower from the upstream side to the downstream side in the flow path direction of the molten glass.
The molten glass flowing from the melting device 200 toward the molding device 300 flows into the groove portion 312 of the molded body 310 through a supply port (not shown).
The molten glass that has flowed into the groove portion 312 of the molded body 310 overflows at the top of the groove portion 312 and flows down along both side surfaces 313 of the molded body 310. Then, the molten glass flowing down along both side surfaces 313 of the molded body 310 merges at the lower portion 314 of the molded body 310 to form a glass sheet GS.

As shown in FIG. 3, the atmosphere partition member 320 is a plate-shaped member arranged in the vicinity of the lower portion 314 of the molded body 310.
The atmosphere partition members 320 are arranged so as to be substantially horizontal on both sides of the glass sheet GS flowing down from the lower portion 314 of the molded body 310 in the thickness direction. The atmosphere partition member 320 functions as a heat insulating material. That is, the atmosphere partition member 320 suppresses the transfer of heat from the space above the atmosphere partition member 320 to the space below by partitioning the space above and below the atmosphere partition member 320. As shown in FIG. 3, the molding apparatus 300 includes a molded body accommodating portion 410 which is a space above the atmosphere partition member 320, a molding zone 42a which is a space directly below the atmosphere partition member 320, and a molding zone 42a below the molding zone 42a. It has a slow cooling zone 420 which is a space. The slow cooling zone 420 has a plurality of slow cooling spaces 42b, 42c, ..., 42f. The molding zones 42a and the slow cooling spaces 42b to 42f are arranged in series in this order from the upper side to the lower side in the vertical direction. By being surrounded by the furnace wall, a molding zone 42a and a slow cooling zone 420 (slow cooling space 42b to 42f) are formed, and the glass sheet GS forms the molding zone 42a and the slow cooling zone 420 (slow cooling space 42b to 42f). Moving.

The heat insulating member 41 is a plate-shaped heat insulating material arranged below the cooling roller 330, which will be described later, and on both sides of the glass sheet GS in the thickness direction in the slow cooling zone 420. By partitioning the space below the heat insulating member 41 and the atmosphere partition member 320, the molding zone 42a and the slow cooling spaces 42b to 42f are formed. For example, as shown in FIG. 3, the heat insulating member 41 forms a molding zone 42a and a slow cooling space 42b. Further, the heat insulating member 41 forms a slow cooling space 42b and a slow cooling space 42c. That is, the slow cooling spaces 42b to 42f are formed by being surrounded by the furnace wall and the heat insulating member 41. Each heat insulating member 41 suppresses heat transfer between the upper and lower spaces. For example, the heat insulating member 41 suppresses heat transfer between the molding zone 42a and the slow cooling space 42b, and the heat insulating member 41 suppresses heat transfer between the slow cooling space 42b and the slow cooling space 42c. .. That is, the slow cooling spaces 42b to 42f are a plurality of divided spaces in which the temperatures are separately controlled. These divided spaces are provided along the moving direction of the glass sheet GS, and the glass sheet GS moves in order in each of the divided spaces and is gradually cooled.

The cooling roller 330 is arranged below the atmosphere partition member 320. Further, the cooling rollers 330 are arranged on both sides of the glass sheet GS in the thickness direction and facing both end portions in the width direction thereof. The cooling roller 330 is air-cooled by an air-cooled pipe passed through the inside. Therefore, when the glass sheet GS passes through the cooling roller 330, both side portions in the thickness direction and both end portions in the width direction in contact with the air-cooled cooling roller 330 are cooled. The cooling roller 330 also has a role of pulling the glass sheet GS downward by transmitting the driving force by the cooling roller drive motor 390 (see FIG. 4). The cooling roller 330 stretches the glass sheet GS to a predetermined thickness.

A cooling unit 340 is provided in the molding zone 42a. The cooling unit 340 is, for example, an air-cooled cooling device that cools the atmospheric temperature of the cooling roller 330 and the glass sheet GS passing below the cooling roller 330. Further, a plurality of cooling units 340 (for example, three) are arranged in the width direction of the glass sheet GS and a plurality of cooling units 340 are arranged in the flow direction thereof. Specifically, the cooling units 340 are arranged one by one so as to face the surfaces of both ends of the glass sheet GS, and one cooling unit is arranged so as to face the surface of the central region sandwiched between both ends. Has been done.

The tension rollers 350a to 350e are arranged below the cooling roller 330 at predetermined intervals in the flow direction of the glass sheet GS. Further, the pulling rollers 350a to 350e are arranged in the slow cooling space 42b to 42f on both sides of the glass sheet GS in the thickness direction and facing both ends in the width direction of the glass sheet GS, respectively. Then, the pulling rollers 350a to 350e pull the glass sheet GS downward while contacting both end portions in the thickness direction of the glass sheet GS whose viscosity has become a predetermined value or more by the cooling roller 330. The tension rollers 350a to 350e are driven by transmitting the driving force of the tension roller drive motor 391 (see FIG. 4). The peripheral speeds of the pulling rollers 350a to 350e are larger than the peripheral speeds of the cooling rollers 330. The peripheral speed of the pulling roller increases as it is arranged on the downstream side in the flow direction of the glass sheet GS. That is, among the plurality of tension rollers 350a to 350e, the peripheral speed of the tension roller 350a is the smallest, and the peripheral speed of the tension roller 350e is the largest.

As shown in FIG. 3, the cooling unit 340 and the heaters (temperature control units) 360a to 360e are arranged in the molding zone 42a and the slow cooling space 42b to 42f, respectively, and the molding zone 42a and the slow cooling space 42b, 42c, ... The temperature of the glass sheet GS at 42f is controlled. The heaters 360a to 360e function as a cooling device that controls the temperature of the glass sheet GS towed downward by the pulling rollers 350a to 350e by controlling the output of the heaters 360a to 360e by the control device 500 described later. Further, each of the heaters 360a to 360e may have a configuration having a plurality of (for example, three, six, etc.) heat generating portions arranged in the width direction.
Here, the temperature of the glass sheet GS pulled downward by the pulling rollers 350a to 350e is controlled by the temperature control of the heaters 360a to 360e, and the glass sheet GS changes from the viscous region to the viscoelastic region to the elastic region. ..

Further, in the vicinity of the heaters (temperature control units) 360a to 360e, thermocouple units 380 (see FIG. 4) for detecting the atmospheric temperature of each region of the glass sheet GS are arranged. The thermocouple unit 380 measures the atmospheric temperature of the slow cooling spaces 42b to 42f that change as the heaters 360a to 360e generate heat. The control device 500 acquires the atmospheric temperature measured by the thermocouple unit 380, and controls the amount of heat generated from the heaters 360a to 360e based on the acquired atmospheric temperature. Alternatively, the separation distance between the glass sheet GS of the radiation plate provided between the heaters 360a to 360e and the glass sheet GS and heated by the heaters 360a to 360e to uniformly radiate heat to the glass sheet GS is controlled. That is, in order to control the temperature of the glass sheet GS in the slow cooling spaces 42b, 42c, ..., 42f, either the calorific value of the heaters 360a to 360e and the separation distance between the radiation plate and the glass sheet GS are set. It is controlled according to the measurement results of the heaters 360a to 360e.

As described above, in the molding zone 42a and the slow cooling space 42b to 42f, which are the regions below the lower portion 314 of the molded body 310, the cooling roller 330, the cooling unit provided in the molding zone 42a, and the heaters 360a to 360e (heating portions 361a to The step of cooling the glass sheet GS by 366a) is the cooling step ST5.

In the cutting device 400, the cutting step ST6 is performed. The cutting device 400 is a device that cuts the glass sheet GS flowing down in the molding device 300 from a direction perpendicular to the longitudinal surface thereof. As a result, the sheet-shaped glass sheet GS becomes a plurality of glass sheet GS having a predetermined length. The cutting device 400 is driven by a cutting device drive motor 392 (see FIG. 4).

FIG. 4 is a control block diagram of the control device 500.
The control device 500 is a computer composed of a CPU, a ROM, a RAM, a hard disk, and the like, and functions as a control unit that controls various devices included in the glass sheet manufacturing device 100.
As shown in FIG. 4, the control device 500 includes signals and input devices (for example, main power switch 381 and the like) by various sensors (for example, thermocouple unit 380 and the like) and switches (for example, main power switch 381 and the like) included in the glass sheet manufacturing apparatus. In response to an input signal from the operator via (not shown) or the like, the operations of the cooling unit 340, the heaters 360a to 360e, the cooling roller drive motor 390 that controls the operation of the cooling roller 330, and the operation of the pulling rollers 350a to 350e are controlled. The pulling roller drive motor 391, the cutting device drive motor 392 that controls the operation of the cutting device 400, the radiation plate moving motor 393, and the like are controlled.

In particular, as will be described later, the control device 500 is formed in the direction of movement of the glass sheet GS in which the glass sheet GS in the cooling zone 42a or the slow cooling spaces 42b to 42f receives radiant heat from a radiation source such as a radiation plate. The temperature distribution is estimated by performing a calculation using the analysis formula of the temperature distribution formulated using the glass sheet GS and the model of the radiation source. Using this estimated temperature distribution, the control device 500 adjusts the cooling zone 42a or the slow cooling spaces 42b to 42f so that the temperature distribution in the moving direction of the glass sheet GS becomes a desired distribution.
Specifically, in the estimation of the temperature distribution of the glass sheet GS in the control device 550, the temperature distribution in the moving direction of the glass sheet GS is calculated from the analytical formula using the measurement result at a specific position of the thermocouple unit 380. Here, the temperature measured by the thermocouple unit 380 is used as a boundary condition in the above analysis formula. The temperature at a specific position measured by the thermocouple unit 380 is preferably, for example, the temperature near the glass sheet GS at the inlet of the cooling zone 42a or the slow cooling spaces 42b to 42e. From the measurement result of this temperature, the temperature of the glass sheet GS at the inlet of the glass sheet GS is obtained, and the temperature of the glass sheet GS at this inlet is used to move the glass sheet GS in the cooling zone 42a or the slow cooling spaces 42a to 42e. Estimate the temperature distribution of.

FIG. 5A is a diagram illustrating the positions of the heater 360a and the glass sheet GS. As shown in FIG. 5A, a radiation plate 360a3 is provided in the slow cooling space 42b formed between the two heat insulating members 41 so as to face the glass sheet GS. In FIG. 5A, the radiation plate 360a3 and the heater 360a on one side of the glass sheet SG are shown, but the radiation plates 360a3 and the heater 360a are provided on both sides of the glass sheet SG. The radiation plate 360a3 receives a signal from the radiation plate moving motor 393, and the separation distance from the glass sheet GS to the radiation plate 360a3 is adjusted so as to approach or move away from the glass sheet GS. The heater 360a is provided with heat sources 360a1 and 360a2 at two locations in the moving direction of the glass sheet GS, and the heat sources 360a1 and 360a2 are configured to heat the radiation plate 360a3 so that the radiation plate 360a3 has an even temperature distribution. ing.

The glass sheet GS moves from top to bottom in FIG. 5A. This moving direction is defined as the Z direction, and the position in the Z direction is represented by z. In FIG. 5A, the position of the heat insulating plate 41 on the upper side of FIG. 5A in the height direction is set to z = 0. This position of z = 0 is the position of the entrance of the slow cooling space 42b. On the other hand, the position of the lower heat insulating plate 41 shown in FIG. 5A is the position of the outlet of the glass sheet GS, and in FIG. 5A, z = H. H is the length of the glass sheet GS in the slow cooling space 42b in the moving direction.
On the other hand, the radiation plate 360a3 is arranged parallel to the surface of the glass sheet GS, and the separation distance between the radiation plate 360a3 and the glass sheet GS is D.
Let Tw be the heated temperature of the radiation plate 360a3, and let T (z) be the temperature distribution in the moving direction (Z direction) of the glass sheet GS calculated using the following analysis formula.

ここで、Ｔは、ガラスシートＧＳの温度分布Ｔ（ｚ）である。
また、σは、ステファンボルツマン定数であり、ε_Ｇ及びε_Ｗは、ガラスシートＧＳ及び放射板３６０ａ３の放射率であり、ρは、ガラスシートＧＳの密度であり、Ｖは、ガラスシートＧＳの移動速度であり、ｔは、ガラスシートＧＳの厚さであり、Ｃｐは、ガラスシートＧＳの単位質量当たりの定圧比熱である。また、Ｈは、徐冷空間のＺ方向の長さである。 In the arrangement of the radiation plate 360a3 and the glass sheet GS as shown in FIG. 5A, assuming that the temperature distribution of the glass sheet GS is formed by receiving the radiant heat of the radiation plate 360a3, the temperature distribution T (z) The analytical equation for obtaining is a differential equation expressed by the following equation.

Here, T is the temperature distribution T (z) of the glass sheet GS.
Further, σ is a Stefan-Boltzmann constant, ε _G and ε _W are the emissivity of the glass sheet GS and the radiation plate 360a3, ρ is the density of the glass sheet GS, and V is the movement of the glass sheet GS. The velocity, t is the thickness of the glass sheet GS, and Cp is the constant pressure specific heat per unit mass of the glass sheet GS. Further, H is the length of the slow cooling space in the Z direction.

Such an analytical formula can be determined by using thermal radiation based on Stefan-Boltzmann's law and a view factor FG _{→ W that anticipates the radiation plate 360a3 at each position of the glass sheet GS.} FIG. 5B is a diagram illustrating a view factor in heat radiation.
As for the view factor FG _{→ W} , the angle at which the radiation plate 360a3 is expected at the position z is φ1 (φ1 <0) to φ2 (0 <φ2), so that the view factor FG _{→ W} is 1/2 · cosφ. Is the integrand, and the integration range is φ1 to φ2. Therefore, the view factor FG _{→ W} is 1/2 · (sinφ2-sinφ1).

On the other hand, the amount of heat dQ received by the minute portion dz of the glass sheet GS is expressed as _{dQ = fs · σ · (T w} ^4- T (z) ^{4) dz using Stefan-Boltzmann's law.}
Here, the radiation coefficient fs = FG _{→ W} · ε _G · ε _W / {1-FG _{→ W} · _{FW → G} · (1-ε _G ) · (1-ε _W )}. _{FW → G} is a view factor that anticipates the glass sheet GS from the radiation plate 360a3, and since _{FW → G} = dz / H · FG _{→ W} , the radiation coefficient fs ≒ FG _{→ W} · ε _G · ε _W.
On the other hand, dQ gives a temperature change dT to the glass sheet GS and can be expressed as dQ = ρ, V, t, Cp, dT.
From the above, by summarizing dQ = ρ, V, t, Cp, dT and dQ = FG _{→ W} , ε _G , ε _W , σ, (T _w ^4- T (z) ⁴ ) dz, the following analysis It can be expressed by an expression. Sinfai1 and Sinfai2 the view factor F _{G → W} ^{is, sinφ1 = -z / (z 2} + D 2) is ^{(1/2), sinφ2 = (H} -z) / {(H-z) 2 + D 2} ( ^1/2) .

The above-mentioned analytical equation is a differential equation in which the temperature T of the glass sheet GS is represented by a function of z, and the above-mentioned differential equation cannot obtain an analytical solution, but can obtain a numerical solution. The temperature distribution of the glass sheet GS can be estimated based on the temperature distribution T (z) which is a numerical solution.
At this time, since the differential equation is a first-order differential equation, it is necessary to input the initial conditions. In the present embodiment, z = 0, that is, the measured temperature of the thermocouple unit 380 at the inlet of the slow cooling space 42b is the temperature of the glass sheet GS at the inlet, and this temperature is given as the initial condition of the first-order differential equation. In this case, the thermocouple unit 380 is provided at the portion of the heat insulating member 41 as close as possible to the glass sheet GS, so that the temperature measurement result can be regarded as the temperature of the glass sheet GS with a small error. preferable.
FIG. 6 is a diagram showing an example of the temperature distribution T (z) of the glass sheet GS calculated from the analysis formula. In FIG. 6, H = 600 mm, and the temperature (initial condition) of the glass sheet GS at the inlet is 1100 ° C.

The control device 500 estimates the temperature distribution T (z) obtained by calculating the analysis formula as the temperature distribution of the glass sheet GS. In this estimation result, for example, an intermediate position in the slow cooling space 360a (for example, When the temperature in (z = 100 to 500 mm range) deviates from the desired temperature, the control device 500 adjusts the temperature distribution so that it becomes the target temperature distribution. Adjustable parameters that affect the temperature distribution T (z) are the temperature Tw of the radiation plate 360a3 and the separation distance D, as well as the moving speed of the glass sheet V and the moving direction of the glass sheet GS in the slow cooling space 360a. However, it is preferable to adjust the calorific value of the heat sources 360a1 and 360a2 or to adjust the separation distance D. By these adjustments, the temperature of the glass sheet GS at the intermediate position can be adjusted even if the temperature of the glass sheet GS at the inlet and the outlet in the slow cooling space 42b is substantially the same. In this way, the control device 500 can adjust the temperature of the glass sheet GS at an intermediate position between the inlet and the outlet in the slow cooling space 360a, so that the warp and strain (residual stress) of the glass sheet GS can be reduced. Contribute to.
Further, in the present embodiment, the temperature distribution in the moving direction of the glass sheet is not calculated by using the thermal fluid analysis software, and the above-mentioned analysis formula (differential equation) is used. Therefore, the temperature distribution of the glass sheet GS is analyzed. It can be easily estimated from the temperature distribution T (z) calculated from the equation.

As described above, the temperature distribution of the glass sheet GS can be adjusted by the plurality of adjustment parameters described above. Among them, the distance D of the radiation source such as the radiation plate 360a3 from the glass sheet GS and the radiation. It is preferable to adjust using at least one of the exothermic temperature of the source, that is, the temperature T _w , in order to adjust the temperature at an intermediate position between the inlet and the outlet of the slow cooling space of the temperature distribution of the glass sheet GS. ..

The estimated temperature of the glass sheet GS at the outlet of one of the cooling zones 42a and the slow cooling spaces 42b to 42f, which are the cooling spaces, is the temperature of the glass sheet GS at the inlet of the slow cooling space adjacent to the downstream side in the moving direction of the glass sheet GS. Is given as an initial condition, and it is preferable to estimate the temperature distribution in the moving direction of the glass sheet GS by performing a calculation using the above-mentioned analytical formula. As a result, as shown in FIG. 3, when the cooling zone 42a and the slow cooling spaces 42b to 42f are continuously arranged in series in the moving direction of the glass sheet GS, the glass sheet GS at the entrance of the slow cooling zone 42a By simply setting the temperature as the initial condition, the temperature distribution in the moving direction of the glass sheet GS can be estimated from the temperature distributions T (z) in the cooling zone 42a and the slow cooling spaces 42b to 42f, and the calculation efficiency is high.
Such estimation of the temperature of the glass sheet GS is suitable in the slow cooling step performed by the overflow down draw method in which the glass sheet GS is cooled while moving while suppressing warpage and distortion.

In the above-described embodiment, the temperature distribution T (z) calculated using the above-mentioned analysis formula is used as the estimated temperature distribution itself of the glass sheet GS, but if necessary, the temperature distribution T (z) is used. ) May be used as the estimated temperature distribution in the moving direction of the glass sheet GS. As a correction method, the simulation result of the temperature distribution in the moving direction of the glass sheet using the thermal fluid analysis software and the calculation result of the temperature distribution T (z) calculated using the analysis formula of the glass sheet GS under the same state and conditions. It is preferable to obtain a deviation from the above in advance, establish a correction formula capable of correcting the calculation result of the temperature distribution T (z) to the simulation result, and use this correction formula to correct the calculation result of the analysis formula.

When the above analysis formula is a differential equation, in the above embodiment, when calculating the temperature distribution of the glass sheet GS, the measurement result of the temperature of the glass sheet GS at the entrance of the slow cooling space is used as an initial condition (boundary condition). However, the temperature of the measurement result by the thermocouple unit 380 may be corrected based on a predetermined correction equation and used as the temperature at the inlet of the glass sheet SG. Further, the temperature of the glass sheet SG used as the initial condition (boundary condition) is not limited to the temperature at the inlet, and may be the temperature at the outlet or the temperature at the specified intermediate position.

Further, in the present embodiment, the slow cooling space is adjusted according to the temperature measurement result by the thermocouple unit 380 during the manufacturing operation of the glass sheet of the slow cooling device 300 arranged in advance, but at the design stage of the device. When examining whether or not the designed slow cooling device 300 operates properly and the temperature of the glass sheet GS reaches the target temperature, it is possible to use the estimation of the temperature distribution in the moving direction of the glass sheet GS. can.
For example, when considering optimizing the shape and dimensions to be determined at the design stage, such as the length H in the slow cooling space 360a shown in FIG. 5 (a), the temperature in the moving direction of the glass sheet GS in the slow cooling space. The distribution can be calculated to determine whether the calculated temperature distribution is close to the target temperature distribution. After that, using a simulation model using the determined shape and dimensions, the slow cooling space can be adjusted by detailed analysis using thermal fluid analysis software, and the development of an efficient slow cooling device 300 is efficient. It is preferable because it is often done.

In the present embodiment, a radiation plate is used as a radiation source for giving heat to the glass sheet GS, but the radiation plate is not limited to the radiation plate, and a heater or the like can be used. In this case, when the heater radiates heat uniformly in a plane, the above-mentioned view factor FG _{→ W} is 1/2 · (sinφ2-sinφ1). However, when a point-shaped heater is used, the above-mentioned view factor FG _{→ W} is formulated as a point-shaped radiation source, unlike 1/2 · (sinφ2-sinφ1).

Although the method for producing a glass sheet of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and changes may be made without departing from the gist of the present invention. Of course.

100 Glass sheet manufacturing equipment 200 Melting equipment 201 Melting tank 202 Clearing tank 203 Stirring tank 204 1st pipe 205 2nd pipe 300 Molding equipment 310 Molded body 312 Groove 313 Side surface 314 Lower part 320 Atmosphere partition member 330 Cooling roller (roller)
350a-350e Pulling roller (roller)
360a to 360e Heaters 360a1, 360a2 Heat source 360a3 Radiant plate 400 Cutting device 410 Mold accommodating part 420 Slow cooling zone 41 Insulation member 41
42a Molding zone 42b to 42f Slow cooling space SG glass sheet

Claims (5)

It is a manufacturing method of glass sheets.
The process of molding a glass sheet from molten glass,
It includes a process of cooling the molded glass sheet while moving it in the cooling space.
In the cooling space, a radiation source for radiating heat to the glass sheet is provided at a position facing the glass sheet moving path.
Using a simulation model, the temperature distribution in the moving direction of the glass sheet in the cooling space formed by receiving the radiant heat from the radiation source of the glass sheet can be measured by using thermal fluid analysis software. Without calculating the temperature distribution in the moving direction, it was estimated by performing a calculation using the analysis formula of the temperature distribution formulated using the glass sheet and the model of the radiation source, and the estimated temperature distribution was used. A method for producing a glass sheet, wherein the cooling space is adjusted so that the temperature distribution of the glass sheet in the moving direction becomes a desired distribution. The radiation source is a radiation plate arranged in parallel with the movement path of the glass sheet.
The method for manufacturing a glass sheet according to claim 1, wherein the analysis formula is a differential equation represented by the following formula.

T is the glass sheet at the position z in the cooling space, where the moving direction of the glass sheet in the cooling space is the Z direction, the positions of the inlet and outlet in the cooling space in the Z direction are z = 0 and z = H. Is the temperature of
D is the separation distance between the glass sheet and the radiation plate.
Tw is the heated temperature of the radiation plate.
σ is the Stefan-Boltzmann constant,
ε _G and ε _W are the emissivity of the glass sheet and the radiation plate.
ρ is the density of the glass sheet.
V is the moving speed of the glass sheet.
t is the thickness of the glass sheet.
Cp is the constant pressure specific heat per unit mass of the glass sheet. The method for producing a glass sheet according to claim 1 or 2, wherein the temperature of the glass sheet is adjusted by using at least one of the distance of the radiation source from the glass sheet and the heat generation temperature of the radiation source. A plurality of divided spaces whose temperatures are separately controlled are provided in the cooling space along the moving direction of the glass sheet, and the glass sheet is moved and cooled in each of the divided spaces in order.
The estimated temperature of the glass sheet at the outlet in one of the divided spaces is given as an initial condition, and the temperature of the glass sheet at the entrance of the divided space adjacent to the downstream side in the moving direction of the glass sheet is given as an initial condition to move the glass sheet. The method for manufacturing a glass sheet according to any one of claims 1 to 3, wherein the temperature distribution in the direction is estimated by performing a calculation using the above analytical formula. The step of forming the glass sheet is performed by an overflow down draw method.
The method for producing a glass sheet according to any one of claims 1 to 4.

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