WO2013021771A1 - Liquid level detection device, glass manufacturing device, liquid level detection method, and glass manufacturing method - Google Patents

Abstract

A liquid level detection device (200) detects the level (L) of molten glass (102) contained within a melting tank (110). The liquid level detection device (200) comprises a camera (210) which captures the image of at least a part of each of the following objects: reference lines (151a, 152a) formed on the inner wall surface (150) of a glass melting furnace (100); the side wall section (111) of the melting tank (110); and the surface (103) of molten glass (102). The liquid level detection device (200) also comprises an image processing device (220) which processes an image (270P) captured by the camera (210). Thus the liquid level detection device (200) detects the positional relationship in the image (270P) between the reference lines (151a, 152a), the side wall section (111), and the surface (103) and then detects the level (L) on the basis of the detected positional relationship and of the actual positional relationship between the reference lines (151a, 152a).

Description

Liquid level detection device, glass manufacturing device, liquid level detection method, and glass manufacturing method

The present invention relates to a liquid level detecting device, a glass manufacturing apparatus, a liquid level detecting method, and a glass manufacturing method for detecting a liquid level of molten glass accommodated in a melting tank.

The glass melting furnace includes a melting tank for storing molten glass and a heating source for heating the inside of the melting tank. The glass raw material put into the liquid surface of the molten glass in the melting tank from above is heated by a heating source and gradually melts into the molten glass.

As a detection method to detect the height of the upper surface of the glass raw material layer floating on the molten glass, the upper surface of the glass raw material layer is irradiated with light from above, and the irradiated part (bright part) and the dark part around it are imaged. A method of binarizing a captured image has been proposed (see, for example, Patent Document 1). In this method, the center-of-gravity coordinates of the bright part in the image are obtained, and the amount of fluctuation in the height of the upper surface of the glass material layer is detected based on the amount of fluctuation of the center-of-gravity coordinates.

Japanese Unexamined Patent Publication No. 6-56432

By the way, in the glass melting furnace, it is required to keep the liquid level of the molten glass constant. When the liquid level changes, the flow rate of the molten glass flowing out from the glass melting furnace changes or the erosion of the melting tank is promoted.

Conventionally, the liquid level of molten glass has been measured by an electrode or visual inspection, but the measurement accuracy is not sufficient.

The present invention has been made in view of the above problems, and an object thereof is to provide a liquid level detecting device and a liquid level detecting method capable of accurately detecting the liquid level of molten glass.

In order to solve the above object, the present invention provides:
A liquid level detecting device for detecting a liquid level of molten glass contained in a melting tank of a glass melting furnace,
A plurality of reference lines formed on an inner wall surface of the glass melting furnace, a side wall of the melting tank, and a camera that images at least a part of the liquid level of the molten glass;
By performing image processing on the image captured by the camera, the positional relationship in the image of the plurality of reference lines, the side wall of the melting tank, and the liquid level of the molten glass is detected, and the detected There is provided a liquid level detecting device including an image processing device that detects the liquid level based on a positional relationship and an actual positional relationship of the plurality of reference lines.

The present invention also provides:
A liquid level detection method for detecting a liquid level of molten glass contained in a melting tank of a glass melting furnace,
Imaging at least a part of each of a plurality of reference lines formed on the inner wall surface of the glass melting furnace, a side wall portion of the melting tank, and a liquid level of the molten glass,
By performing image processing on the image captured by the camera, the positional relationship in the image of the plurality of reference lines, the side wall of the melting tank, and the liquid level of the molten glass is detected,
Provided is a liquid level detection method for detecting the liquid level based on the detected positional relationship and an actual positional relationship of the plurality of reference lines.

According to the present invention, there are provided a liquid level detecting device and a liquid level detecting method capable of accurately detecting the liquid level of molten glass.

Sectional drawing which shows the glass-melting furnace to which the liquid level detection apparatus by the 1st Embodiment of this invention and a liquid level detection apparatus are attached Sectional view along line II-II in FIG. Partial enlarged view of FIG. Another partially enlarged view of FIG. Sectional view along line VV in FIG. Schematic diagram showing an example of an image captured by the camera The schematic diagram which shows the change of the brightness | luminance in the vertical direction of the image of FIG. Sectional drawing which shows an example of the melting tank of the state eroded by the molten glass The schematic diagram which shows another example of the image imaged with a camera Schematic diagram showing the change in luminance in the vertical direction of the image of FIG. Sectional drawing which shows the structure of the glass manufacturing apparatus by the 2nd Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.

[First Embodiment]
The present embodiment relates to a liquid level detecting device and a liquid level detecting method for detecting a liquid level of molten glass accommodated in a melting tank of a glass melting furnace.

FIG. 1 is a cross-sectional view showing a liquid level detecting device and a glass melting furnace to which the liquid level detecting device according to the first embodiment of the present invention is attached. In FIG. 1, the outer edge of the flame (frame) formed by the burner is indicated by a two-dot chain line. FIG. 2 is a sectional view taken along line II-II in FIG. In FIG. 2, the illustration of the frame and the tax tone is omitted to make the drawing easier to see. FIG. 3 is a partially enlarged view of FIG. FIG. 4 is another partially enlarged view of FIG. FIG. 5 is a sectional view taken along line VV in FIG.

(Glass melting furnace)
As shown in FIGS. 1 and 2, the glass melting furnace 100 includes a melting tank 110 that houses a molten glass 102. In the melting tank 110, the liquid level 103 of the molten glass 102 is a horizontal plane.

The melting tank 110 has a box shape opened upward, and includes front and rear side walls 111 to 114 and a bottom wall 115 as shown in FIGS. The inner side surfaces of the side wall portions 111 to 114 are vertical planes and are planes perpendicular to the liquid level 103.

In the glass melting furnace 100, upper side wall parts 121 to 124 disposed above the side wall parts 111 to 114 and an arched ceiling part 130 that covers the openings of the upper side wall parts 121 to 124 from above are integrally formed. Prepare.

As shown in FIG. 1, gaps are formed between the left side wall portion 111 and the left upper side wall portion 121, and between the right side wall portion 112 and the upper right side wall portion 122, respectively. In order to close this gap, a gap tile (tax tone) 140 is placed on the upper surface of each side wall 111, 112 and is in contact with the inner side surface of the corresponding upper side wall 121, 122.

The inner wall surface 150 of the glass melting furnace 100 has horizontal step surfaces 151 and 152 as shown in FIG. One step surface 151 is the upper surface of the tax tone 140. Another step surface 152 is a part of the upper surface of the left side wall portion 111 (a portion protruding from the tax tone 140 to the inside of the furnace). Inner edges 151 a and 152 a of the step surfaces 151 and 152 are straight lines parallel to the liquid surface 103 and parallel to the line 104 of intersection between the liquid surface 103 and the inner side surface 111 a of the left side wall 111.

The glass melting furnace 100 includes a burner 160 as a heating source for heating the inside of the melting tank 110 as shown in FIG. The burner 160 forms a flame (frame) F in an internal space surrounded by the liquid surface 103, the upper side wall portions 121 to 124, and the ceiling portion 130, and heats the inside of the melting tank 110 by radiant heat from the frame F. A plurality of burners 160 are provided on each of the pair of left and right upper side wall portions 121 and 122 at intervals in the front-rear direction (X direction in FIG. 2).

The glass melting furnace 100 includes a bubbler 170 that forms bubbles 106 in the molten glass 102. The bubbler 170 has a gas supply pipe 172 that penetrates the bottom wall 115 of the melting tank 110, and a gas (for example, nitrogen gas) is ejected from the gas supply pipe 172 to form a bubble 106. As the bubble 106 rises to the liquid level 103, an upward flow is formed in the molten glass 102, and the molten glass 102 is circulated. The gas supply pipe 172 is installed at a substantially central portion of the melting tank 110 in the front-rear direction (X direction in FIG. 2).

(Liquid level detector)
The liquid level detecting device 200 is a device that detects the liquid level L of the molten glass 102 accommodated in the melting tank 110 as shown in FIG. The liquid level detecting device 200 includes a camera 210 that captures the inside of the glass melting furnace 100 and an image processing device 220 that detects the liquid level L by performing image processing on an image captured by the camera 210.

The liquid level detecting device 200 includes a cylindrical water cooling box 230 disposed outside the glass melting furnace 100. The water cooling box 230 is disposed away from the glass melting furnace 100 and houses the camera 210 therein. The camera 210 images the inside of the glass melting furnace 100 through a viewing hole 180 formed through a furnace wall (for example, the upper right side wall portion 122) of the glass melting furnace 100.

The liquid level detection device 200 includes a cylindrical housing 240 attached to the outer surface of the glass melting furnace 100 so as to surround the viewing hole 180, and a transparent plate (for example, a quartz glass plate) that closes the opening of the housing 240 on the camera 210 side. ) 250. The camera 210 images the inside of the glass melting furnace 100 through the transparent plate 250, the internal space of the housing 240, and the viewing hole 180.

The housing 240 is formed of, for example, a heat resistant alloy. An annular seal member 260 is installed between the housing 240 and the outer surface of the glass melting furnace 100. The sealing member 260 closes a slight annular gap formed between the housing 240 and the glass melting furnace 100.

In the housing 240, gas supply ports 241 to 244 for supplying gas (for example, compressed air) into the housing 240 are formed as shown in FIGS. Each of the gas supply ports 241 to 244 is connected to a gas supply source such as a compressor via a pipe P provided with an on-off valve and a flow meter in the middle. When the gas supply source is activated and the on-off valve is opened, gas is supplied into the housing 240. The gas supplied into the housing 240 flows into the glass melting furnace 100 through the viewing hole 180. At this time, the gas flow in the viewing hole 180 is regulated in one direction as shown in FIG. This is because the opening on the camera 210 side of the viewing hole 180 is surrounded by the housing 240, and the opening on the camera 210 side of the housing 240 is closed by the transparent plate 250. In this way, the gas flow in the viewing hole 180 is regulated in one direction, so that the vapor of the volatile component (for example, boric acid) of the molten glass 102 can be prevented from flowing into the housing 240. Further, the fogging of the transparent plate 250 can be performed. Further, the influence of the heat of the frame F can be suppressed.

The gas supply ports 241 to 244 are slits that are long in the circumferential direction of the housing 240 as shown in FIG. 4, and form a gas curtain perpendicular to the central axis direction of the housing 240 as shown in FIG. The pair of gas supply ports 241 and 242 are arranged to face the rectangular tubular housing 240 so that the gas curtains collide with each other. Similarly, another set of gas supply ports 243 and 244 is disposed opposite to the rectangular tubular housing 240. One set of gas supply ports 241 and 242 is disposed closer to the camera 210 than the other set of gas supply ports 243 and 244.

(camera)
The camera 210 is, for example, a CCD camera or a CMOS camera. As shown in FIG. 1, the camera 210 images a part of the other side wall (for example, the left side wall 111) through a viewing hole 180 formed in one upper side wall (for example, the upper right side wall 122). To do. The optical axis A of the camera 210 is disposed substantially perpendicular to the inner side surface 111a of the left wall 111 when viewed from above. An angle θ formed by the optical axis A of the camera 210 and the horizontal plane B is, for example, 0 to 7 °. The distance H in the horizontal direction between the camera 210 (the center of the camera front surface) and the left side wall 111 is, for example, 5 m or more. Thus, by setting the angle θ to be 0 to 7 ° and the distance H5 m or more, an approximate expression can be used in the image processing described later. The vertical distance V between the camera 210 (the center of the camera front surface) and the left wall 111, the focal length and resolution of the camera 210, and the like are appropriately selected.

The camera 210 images at least a part of each of a plurality of reference lines formed on the inner wall surface 150 of the glass melting furnace 100, the left side wall portion 111 of the melting tank 110, and the liquid surface 103 of the molten glass 102. As the reference line, for example, inner end edges 151a and 152a of horizontal step surfaces 151 and 152 are used. Hereinafter, the inner end edges 151a and 152a are also referred to as reference lines 151a and 152a. These reference lines 151 a and 152 a are straight lines parallel to the liquid surface 103 and parallel to the intersection line 104 between the liquid surface 103 and the inner side surface 111 a of the left side wall 111.

In addition, although the reference lines 151a and 152a of this embodiment are the edges of the level | step difference surfaces 151 and 152, the joint between the bricks which comprise the furnace wall (for example, upper left side wall part 121) of the glass melting furnace 100 is shown. It may be a line or the like and is not particularly limited.

Further, the reference lines 151 a and 152 a of the present embodiment are straight lines parallel to the intersection line 104, but may be straight lines that are oblique to the intersection line 104 and straight lines perpendicular to the intersection line 104.

Further, as the reference line, two points may be captured and a line connecting the two points may be used as the reference line.

FIG. 6 is a schematic diagram illustrating an example of an image captured by the camera. FIG. 7 is a schematic diagram showing a change in luminance in the vertical direction of the image of FIG. In FIG. 7, the horizontal axis represents the distance from the upper edge of the image in FIG. 6, and the vertical axis represents the luminance.

As shown in FIG. 6, an image 270P captured by the camera 210 (hereinafter also referred to as “captured image 270P”) includes an image 121P of the upper left side wall 121, an image 140P of the tax tone 140, and a left side wall 111. Image 111 </ b> P and an image 103 </ b> P of the liquid surface 103. The captured image includes images 151aP and 152aP of a plurality of reference lines 151a and 152a and an image 104P of the intersection line 104. In the captured image 270P, the reference line images 151aP and 152aP and the intersecting line image 104P are straight lines parallel to each other.

As shown in FIG. 7, the luminance (brightness) of the pixels in the captured image 270P changes suddenly at the positions x1 and x2 of the reference line images 151aP and 152aP and the position x3 of the intersecting line image 104P. This is because, as shown in FIG. 3, the shape of the light reflecting surface suddenly changes in the actual reference lines 151a and 152a and the intersection line 104. The light reflecting surface is a surface that reflects light from a frame as a light source toward the camera.

Note that the change in luminance at the position x1 in the captured image 270P includes the influence of the shape change of the light reflecting surface at the outer edge 151b of the step surface 151. This is because the outer edge 151b and the inner edge 151a are located at substantially the same position in the captured image 270P. Similarly, the change in luminance at the position x2 in the captured image 270P includes the influence of the change in the shape of the light reflecting surface at the outer edge 152b of the step surface 152.

By the way, since the molten glass 102 accommodated in the melting tank 110 is obtained by melting a powdery or granular glass raw material, it contains bubbles inside.

The imaging area of the liquid surface 103 by the camera 210 is preferably in the peripheral areas 108 and 109 (see FIG. 2) of the area where the bubble 106 rises. Here, the “peripheral region” is a region (C1 = D1 = 10 mm, C2 = D2 = 1500 mm) whose distance in the front-rear direction (X direction in FIG. 2) with the gas supply pipe 170 is 10 to 1500 mm. means. Since the peripheral areas 108 and 109 are mirror surfaces substantially free of bubbles, there is almost no light scattering. Therefore, it is suitable for image processing to be described later for detecting a change in luminance of the pixels in the captured image 270P. Note that the imaging area of the liquid surface 103 by the camera 210 may be an area substantially free of bubbles, and is not limited to the peripheral areas 108 and 109 described above.

The captured image 270P is transmitted to the image processing device 220 via a signal line.

(Image processing device)
The image processing device 220 is a device that performs image processing on the captured image 270P and detects the liquid level L. The image processing apparatus 220 is configured as a computer including a CPU, a recording medium, and the like. The image processing apparatus 220 performs various processes described later by causing the CPU to execute various programs stored in the recording medium.

First, the image processing apparatus 220 identifies the positions x1 and x2 of the reference line images 151aP and 152aP and the position x3 of the intersection line image 104P based on the change in luminance of the pixels in the captured image 270P.

For example, the image processing device 220 detects a change in luminance for a pixel row composed of a plurality of pixels arranged in a predetermined direction (for example, a direction orthogonal to the intersecting line image 104P). This process is performed using, for example, a differential filter. The derivative is a first derivative or a second derivative (Laplacian). The pixel column used for this process is selected in advance by a test or the like.

It is preferable that detection of a change in luminance is performed using a plurality of pixel rows in one captured image 270P in order to improve accuracy. Further, the number of captured images 270P used for detection of a change in luminance is preferably two or more for suppressing errors, and it is preferable to capture images within 60 seconds for suppressing temporal fluctuations.

The image processing apparatus 220 identifies the places where the luminance of the pixels in the captured image 270P changes suddenly as the positions x1 and x2 of the reference line images 151aP and 152aP and the position x3 of the intersection line image 104P. The position is specified by sub-pixels (for example, about 0.1 pixel).

Next, the image processing apparatus 220 calculates the interval J1 (see FIG. 6) between the reference line images 151aP and 152aP and the interval J2 (see FIG. 6) between the one reference line image 152aP and the intersection line image 104P.

Further, the image processing apparatus 220 reads the actual interval K1 (see FIG. 1) between the reference lines 151a and 152a from the recording medium. The interval K1 is a distance in the vertical direction. Since the interval K1 does not vary with time, it is measured in advance and recorded on the recording medium.

Next, the image processing apparatus 220 calculates an actual interval K2 (see FIG. 1) between the one reference line 152a and the intersection line 104 based on the intervals J1, J2, and K1. The calculation of the interval K2 is performed using an approximate expression (K2 = K1 × J2 / J1). For calculating the interval K2, the arrangement information of the camera 210 (for example, the angle θ, the distance H, and the distance V shown in FIG. 1) may be used. The interval K2 is a distance in the vertical direction.

Next, the image processing apparatus 220 reads the actual distance K0 (see FIG. 1) between the one reference line 152a and the inner bottom surface of the melting tank 110 from the recording medium. The distance K0 is a distance in the vertical direction. Since the distance K0 does not vary with time, it is measured in advance and recorded on the recording medium.

Finally, the image processing apparatus 220 calculates the liquid level L based on the distance K0 and the interval K2 (L = K0−K2). In addition, although the reference surface of the liquid level L in this embodiment is the inner bottom surface of the melting tank 110, it may be the upper surface of the melting tank 110. In this case, L = K2, and the data of K0 is unnecessary. It is.

In this way, the image processing apparatus 220 performs image processing on the captured image 270P, thereby the positional relationship (interval J1) in the captured image 270P among the plurality of reference lines 151a and 152a, the left side wall portion 111, and the liquid surface 103. , J2). Further, the image processing apparatus 220 detects the liquid level L of the molten glass 102 based on the detected positional relationship and the actual positional relationship (distance K1) of the plurality of reference lines 151a and 152a.

In the present embodiment, since the liquid level L is detected using the plurality of reference lines 151a and 152a formed on the inner wall surface 150 of the glass melting furnace 100, the actual positional relationship between the plurality of reference lines 151a and 152a is referred to. Thus, the liquid level L can be detected with high accuracy.

Further, in the present embodiment, since one reference line 152a is a straight line parallel to the liquid surface 103, in the captured image 270P, the one reference line image 152aP and the intersecting line image 104P become parallel. Therefore, since the positional relationship between one reference line 152a and the intersection line 104 is determined by one parameter (interval J2), it is easy to specify the positional relationship.

[Modification of First Embodiment]
This modification relates to image processing when the side wall 111 of the melting tank 110 is eroded by the molten glass 102.

FIG. 8 is a cross-sectional view showing an example of a melting tank in a state of being eroded by molten glass. FIG. 9 is a schematic diagram illustrating another example of an image captured by the camera. FIG. 10 is a schematic diagram showing a change in luminance in the vertical direction of the image of FIG. In FIG. 10, the horizontal axis represents the distance from the upper edge of the image in FIG. 9, and the vertical axis represents the luminance.

As shown in FIG. 8, a recess 116 is formed on the inner side surface 111 a of the left wall portion 111 due to the influence of erosion by the molten glass 102. The liquid level 103 extends to the inside of the concave part 116, and the inner wall surface of the concave part 116 has a shadow part 117 where the light from the frame F as a light source does not reach above the liquid level 103. Since the shadow 117 is reflected on the liquid surface 103, a dark dark portion 118 is formed on the liquid surface 103.

As shown in FIG. 9, the captured image 270AP includes an image 121P of the upper left side wall 121, an image 140P of the tax tone 140, an image 111P of the left side wall 111, and an image 103P of the liquid level 103. In addition, the captured image includes images 151aP and 152aP of a plurality of reference lines 151a and 152a, an image 117P of a shadow portion 117, and an image 118P of a dark portion 118. The shadow part image 117P and the dark part image 118P are continuously connected to form a strip-like image 262P having a low luminance.

An image 104AP of an intersection line 104A between the extended surface of the inner side surface 111a of the left side wall 111 and the liquid surface 103 is hidden between both side edges of the belt-like image 262P. The actual intersection line 104A is a virtual line.

One side edge of the belt-like image 262P is an image 117aP of the upper edge 117a of the shadow 117. The other side edge of the belt-like image 262P is an image 118aP of the leading edge 118a of the dark part 118.

The reference line images 151aP and 152aP, both side edges of the belt-like image 262P, and the intersection line image 104AP are straight lines parallel to each other.

As shown in FIG. 10, the luminance (brightness) of the pixels in the captured image 270AP changes suddenly at positions x5 and x6 on both side edges of the belt-like image 262P in addition to the positions x1 and x2 of the reference line images 151aP and 152aP.

First, the image processing apparatus 220 detects a change in luminance for a pixel row composed of a plurality of pixels arranged in a predetermined direction (for example, a direction orthogonal to the belt-like image 262P), and determines the location where the luminance changes suddenly as a reference line image 151aP, It is specified as positions x1 and x2 of 152aP and positions x5 and x6 on both side edges of the belt-like image 262P.

Next, the image processing device 220 approximately specifies the center positions of the positions x5 and x6 on both side edges of the specified belt-like image 262P as the position of the intersection image 104AP. The location information of the camera 210 (for example, the angle θ, the distance H, and the distance V shown in FIG. 1) may be used for specifying the position of the intersection line image 104P.

Thereafter, the image processing apparatus 220 detects the liquid level L in the same manner as in the first embodiment. Therefore, the liquid level L can be detected with high accuracy as in the first embodiment.

[Second Embodiment]
The present embodiment relates to a glass manufacturing apparatus including a liquid level detecting device and a glass manufacturing method using the liquid level detecting method.

FIG. 11 is a cross-sectional view showing the configuration of the glass manufacturing apparatus according to the second embodiment of the present invention.

In addition to the glass melting furnace 100 and the liquid level detecting device 200, the glass manufacturing apparatus 1000 predetermines a charging device 300 for charging the glass raw material G into the glass melting furnace 100 and a molten glass 102 supplied from the glass melting furnace 100. And a forming apparatus 400 for forming the shape.

The charging device 300 includes, for example, a blanket feeder 320 for charging the glass raw material G dropped from the hopper 310 into the glass melting furnace 100, and a drive source 330 such as a motor for driving the blanket feeder 320.

Note that the charging device 300 may include, for example, a screw feeder, and the feeder system is not particularly limited. Further, the charging method may be a batch type or a continuous type.

Liquid level detection device 200 controls the amount of glass material G charged by charging device 300 based on the detected liquid level L. Control of the input amount of the glass raw material G may be performed by the image processing apparatus 220 as shown in FIG. 11, or may be performed by a dedicated computer. Control of the input amount of the glass raw material G is performed by controlling the drive source 330.

According to the present embodiment, since the detection accuracy of the liquid level L is high, the fluctuation of the liquid level L is suppressed by controlling the input amount of the glass raw material G based on the detected liquid level L. Therefore, erosion of the melting tank 110 can be delayed.

The forming apparatus 400 is, for example, a float forming apparatus, and includes a float bath 410 that accommodates molten metal (for example, molten tin) 402. The forming apparatus 400 forms the glass ribbon by forming the molten glass 102 supplied from the glass melting furnace 100 into a strip shape by flowing in a predetermined direction on the molten metal 402.

By the way, the flow rate of the molten glass 102 supplied from the glass melting furnace 100 to the molding apparatus 400 is a difference in height between the liquid surface 103 of the molten glass 102 in the glass melting furnace 100 and the liquid surface of the molten metal 402 in the float bath 410. Mainly determined.

According to this embodiment, since the fluctuation of the liquid level L in the glass melting furnace 100 is reduced, the fluctuation of the flow rate of the molten glass 102 flowing into the forming apparatus 400 is suppressed. Therefore, since the thickness of the glass ribbon is stabilized, a product having a uniform thickness can be obtained.

The molding apparatus 400 may be a fusion molding apparatus, for example, and is not particularly limited.

Further, a defoaming device (not shown) for defoaming bubbles in the molten glass 102 produced in the glass melting furnace 100 may be installed between the molding apparatus 400 and the glass melting furnace 100. Examples of the defoaming device include a vacuum degassing device.

The glass ribbon formed into a strip shape by the forming apparatus 400 is cooled while flowing in the float bath 410 in a predetermined direction. The glass ribbon is lifted from the molten metal 402 by the lift-out roll 500 installed near the outlet of the float bath 410 and conveyed to the slow cooling device 600.

The slow cooling device 600 slowly cools the glass formed by the forming device 400. The slow cooling apparatus 600 includes, for example, a tunnel furnace 610 having a heat insulating structure and a transport roller 620 that transports glass in the tunnel furnace 610. A plurality of transport rollers 620 are arranged at intervals in the transport direction. When the transport roller 620 is rotationally driven by a motor or the like, the glass is transported horizontally on the transport roller 620. The glass carried out from the slow cooling apparatus 600 is cut into a predetermined size and shape by a cutting machine to become a product.

The glass produced by the glass production apparatus 1000 is not particularly limited, but may be a glass substrate or cover glass for a flat panel display (FPD) such as a liquid crystal display (LCD), a plasma display (PDP), or an organic EL display. .

In recent years, thinning of FPD has progressed, and thinning of FPD plate glass has progressed. As the thickness of FPD plate glass, a thickness of 3 mm or less is required, and a thickness of 2 mm or less. May be required. The thickness of the plate glass for LCD or organic EL is 1.3 mm or less, preferably 1.0 mm or less, more preferably 0.7 mm or less, further preferably 0.5 mm or less, particularly preferably 0.3 mm or less, and more particularly Preferably it is 0.1 mm or less.

According to this embodiment, since the thickness of the glass ribbon is stabilized, the FPD plate glass having a thickness in the above range can be manufactured with high accuracy.

Although the kind of glass manufactured with the glass manufacturing apparatus 100 is not specifically limited, For example, it may be an alkali free glass. The alkali-free glass is a glass that substantially does not contain an alkali metal oxide (Na ₂ O, K ₂ O, Li ₂ O) (that is, does not contain an alkali metal oxide except for inevitable impurities). The total content (Na ₂ O + K ₂ O + Li ₂ O) of the alkali metal oxide content in the alkali-free glass may be, for example, 0.1% or less. The chemical composition of the glass is measured with a fluorescent X-ray analyzer.

The alkali-free glass is, for example, expressed in terms of mass percentage based on oxide, SiO ₂ : 50 to 73%, preferably 50 to 66%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 8%, CaO: 0 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, ZrO ₂ : 0 to 5%, MgO + CaO + SrO + BaO: 8 to It is 29.5%, preferably 9 to 29.5%.

The alkali-free glass has a high strain point, and in consideration of solubility, it is preferably expressed in terms of mass percentage based on oxide, SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5 to 12%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 3 to 12.5%, BaO: 0 to 2%, MgO + CaO + SrO + BaO: 9 to 18%.

The alkali-free glass is preferably SiO ₂ : 50 to 61.5%, Al ₂ O ₃ : 10.5 to 18%, B ₂ , particularly in terms of mass percentage based on oxide, in consideration of solubility. O ₃ : 7 to 10%, MgO: 2 to 5%, CaO: 0 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, MgO + CaO + SrO + BaO: 16 to 29.5%. .

In particular, when considering a high strain point, the alkali-free glass is preferably expressed as an oxide-based mass percentage, and SiO ₂ :
56-70%, Al ₂ O ₃ : 14.5-22.5%, B ₂ O ₃ : 0
-2%, MgO: 0-6.5%, CaO: 0-9%, SrO: 0-15.5%, BaO: 0-2.5%, MgO + CaO + SrO + BaO: 10-26%.

When alkali-free glass has a particularly high strain point and solubility is considered, it is preferable to express SiO ₂ : 54 to 73% and Al ₂ O ₃ : 10.5 to 22.2. 5%, B ₂ O ₃ : 1.5 to 5.5%, MgO: 0 to 6.5%, CaO: 0 to 9%, SrO: 0 to 16%, BaO: 0 to 2.5%, MgO + CaO + SrO + BaO : 8 to 25%.

As mentioned above, although the liquid level detection apparatus and the liquid level detection method were demonstrated by embodiment etc., this invention is not limited to said embodiment etc., The range of the summary of this invention described in the claim Various modifications and improvements are possible.

This application claims priority based on Japanese Patent Application No. 2011-174210 filed with the Japan Patent Office on August 9, 2011. The entire contents of Japanese Patent Application No. 2011-174210 are incorporated herein by reference. Incorporate.

DESCRIPTION OF SYMBOLS 100 Glass melting furnace 102 Molten glass 103 Liquid surface 104 Intersection line 106 Bubble 110 Melting tank 111 Left side wall part 122 Upper right side wall part 150 Inner wall surface 151 of a glass melting furnace Step surface 151a Inner edge (reference line)
152 Stepped surface 152a Inner edge (reference line)
170 Bubbler 180 Peeping hole 200 Liquid level detection device 210 Camera 220 Image processing device 240 Housing 241 to 244 Gas supply port 250 Transparent plate 260 Seal member 270P Image 300 Input device 400 Molding device 1000 Glass manufacturing device

Claims (17)

A liquid level detecting device for detecting a liquid level of molten glass contained in a melting tank of a glass melting furnace,
A plurality of reference lines formed on an inner wall surface of the glass melting furnace, a side wall of the melting tank, and a camera that images at least a part of the liquid level of the molten glass;
By performing image processing on the image captured by the camera, the positional relationship in the image of the plurality of reference lines, the side wall of the melting tank, and the liquid level of the molten glass is detected, and the detected A liquid level detecting device comprising: an image processing device that detects the liquid level based on a positional relationship and an actual positional relationship of the plurality of reference lines. 2. The liquid level detecting device according to claim 1, wherein the one reference line is a straight line parallel to the liquid level. 3. The liquid level detecting device according to claim 2, wherein the one reference line is an edge of a step surface parallel to the liquid surface or a joint line between bricks constituting a furnace wall of the glass melting furnace. . The camera is installed outside the glass melting furnace, images the inside of the glass melting furnace through a viewing hole formed through the furnace wall of the glass melting furnace,
The liquid level detection device is:
A cylindrical housing attached to the outer surface of the glass melting furnace so as to surround the peephole,
A transparent plate that closes the camera-side opening of the housing;
The liquid level detection device according to any one of claims 1 to 3, wherein a gas supply port for supplying gas into the housing is formed in the housing. In the top view, the optical axis of the camera is arranged substantially perpendicular to the inner side surface of the side wall portion imaged by the camera,
The angle between the optical axis of the camera and the horizontal plane is 0-7 °,
The liquid level detecting device according to any one of claims 1 to 4, wherein a distance in a horizontal direction between the inner side surface of the side wall portion imaged by the camera and the camera is 5 m or more. 6. The liquid level detection device according to claim 1, wherein an imaging area of the liquid level by the camera is an area substantially free of bubbles. The glass melting furnace includes a bubbler that forms bubbles in the molten glass,
The liquid level detection apparatus according to claim 6, wherein an imaging area of the liquid level by the camera is in a peripheral area of an area where the bubble rises. The liquid level detecting device according to any one of claims 1 to 7, the glass melting furnace, a charging device for charging a glass raw material into the glass melting furnace, and a melting supplied from the glass melting furnace In a glass manufacturing apparatus comprising a molding apparatus for molding glass into a predetermined shape,
The liquid level detection device is a glass manufacturing apparatus that controls the amount of charging by the charging device based on the detected liquid level. A liquid level detection method for detecting a liquid level of molten glass contained in a melting tank of a glass melting furnace,
Imaging at least a part of each of a plurality of reference lines formed on the inner wall surface of the glass melting furnace, a side wall portion of the melting tank, and a liquid level of the molten glass,
By performing image processing on the image captured by the camera, the positional relationship in the image of the plurality of reference lines, the side wall of the melting tank, and the liquid level of the molten glass is detected,
A liquid level detection method for detecting the liquid level based on the detected positional relationship and an actual positional relationship of the plurality of reference lines. 10. The liquid level detection method according to claim 9, wherein the one reference line is a straight line parallel to the liquid level. 11. The liquid level detection method according to claim 10, wherein the one reference line is an edge of a step surface parallel to the liquid surface or a joint line between bricks constituting a furnace wall of the glass melting furnace. . The camera is installed outside the glass melting furnace, images the inside of the glass melting furnace through a viewing hole formed through the furnace wall of the glass melting furnace,
A cylindrical housing is attached to the outer surface of the glass melting furnace so as to surround the viewing hole, and the opening on the camera side of the housing is closed with a transparent plate,
The liquid level detection method according to any one of claims 9 to 11, wherein gas is supplied into the housing. In the top view, the optical axis of the camera is arranged substantially perpendicular to the inner side surface of the side wall portion imaged by the camera,
The angle between the optical axis of the camera and the horizontal plane is 0-7 °,
The liquid level detection method according to any one of claims 9 to 12, wherein a distance in a horizontal direction between the inner side surface of the side wall portion imaged by the camera and the camera is 5 m or more. The liquid level detection method according to any one of claims 9 to 13, wherein an imaging area of the liquid level by the camera is an area substantially free of bubbles. The glass melting furnace includes a bubbler that forms bubbles in the molten glass,
The liquid level detection method according to claim 14, wherein an imaging area of the liquid level by the camera is in a peripheral area of an area where the bubble rises. A step of controlling the amount of glass raw material charged into the glass melting furnace based on the liquid level of the molten glass detected by the liquid level detection method according to any one of claims 9 to 15;
Forming a molten glass supplied from the glass melting furnace into a predetermined shape. The glass to be produced is an alkali-free glass, and the alkali-free glass is expressed in terms of mass percentage based on oxide, SiO ₂ : 50 to 73%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 8%, CaO: 0 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, ZrO ₂ : 0 to 5% The method for producing glass according to claim 16, wherein MgO + CaO + SrO + BaO: 8 to 29.5%.

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