JP3578405B2 - heating furnace - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heating furnace used for heat-treating an article (object to be heated) such as a glass substrate for liquid crystal.
[0002]
[Problems to be solved by the invention]
2. Description of the Related Art In recent years, demand for liquid crystal display devices has been rapidly increasing. Main components thereof are manufactured through a process of performing a heat treatment on a glass substrate (hereinafter, referred to as an object to be heated) as a raw material. A heating furnace as shown in FIGS. 5 and 6 is used for the heat treatment of the object to be heated. Here, this conventional heating furnace will be briefly described. FIG. 5 is a schematic structural view of the heating furnace, and FIG. 6 is a cross-sectional view taken along line SS ′ in FIG.
[0003]
As can be seen from the drawing, the conventional heating furnace has a structure in which a gantry 12 is housed in a box-shaped case 11, and a plurality of panel heaters (heating means) 13 are arranged on the upper surface of the gantry 12 at appropriate intervals. It has become. In particular, the panel heaters 13 are arranged in a line in the transport direction of the object to be heated F ′, and a soaking plate 14 is placed on each panel heater 13 in contact therewith. Therefore, the object to be heated F ′ is heated by the panel heater 13 via the heat equalizing plate 14. In other words, the heat generated by the panel heater 13 is designed to be transmitted to the object to be heated F 'as uniformly as possible.
[0004]
Although not particularly shown, this conventional heating furnace is provided with a walking beam type conveying means. Together with the fixed beam, the moving beam constituting the transfer means intermittently moves as shown by the arrow in FIG. 5 (repeatedly ascending, advancing, descending, and retreating in this order). In FIG. 5, the sheet is conveyed from right to left. That is, the conveying means carries the object to be heated F ′ into the furnace from the opening 11 a provided on the side surface of the case 11 facing each other, places it on the soaking plate 14, and after a predetermined time elapses. The object F ′ to be heated is carried out of the furnace through the opening 11b.
[0005]
Now, in the conventional heating furnace having such a structure, the object to be heated F ′ set above the panel heater 13 is heated and dried by the heat generated by the panel heater 13 through the soaking plate 14. Will be done. However, in this conventional furnace, it is extremely difficult to realize a good temperature distribution of the object to be heated F ′.
[0006]
That is, although the soaking plate 14 is attached to the panel heater 13, the object to be heated F 'cannot be accurately and uniformly heated to the corners. The temperature distribution is such that the temperature gradually decreases toward. More specifically, the temperature distribution of the object to be heated F ′ during the heat treatment is non-uniform as shown in FIG. 7 (a conceptual diagram showing the temperature distribution of the object to be heated during the heat treatment).
[0007]
In the state shown in the figure, the central part temperature (Tc) is significantly higher than the edge part temperatures (Ts1 to Ts4), and the object to be heated F ′ has a temperature gradient with its center at the top. (Ts1 ≒ Ts2 ≒ Ts3 ≒ Ts4 <Tc). In such a situation, as a matter of course, the object to be heated F ′ is not accurately and uniformly heated, and it is difficult to achieve high quality.
[0008]
In order to solve such a problem, a heating furnace having a cross section shown in FIG. 8 has also been proposed. This heating furnace is characterized in that a panel heater 21 and a soaking plate 22 are further provided above the object to be heated F ′. When the heating furnace is configured in this way, the situation that causes the above-described inconvenience is improved, and a fairly uniform temperature distribution can be obtained. However, on the other hand, the number of panel heaters, which are heating means, must be doubled, so that the furnace becomes more expensive, and a large energy loss is involved, thereby significantly increasing the cost of the heating process. .
[0009]
Therefore, an object to be solved by the present invention is to provide a heating furnace capable of accurately performing a heating treatment on an object to be heated by a single heating means so as to have a uniform temperature distribution.
[0010]
[Means for Solving the Problems]
In the course of pursuing intensive research to solve the above-mentioned problems, the present inventor did not provide a panel heater but a metal material (heat ray reflector) that plays a role of reflecting heat rays (heat radiation) above the object to be heated. We thought about providing. That is, the object to be heated is sandwiched between the panel heater and the metal material from above and below so that heat from the panel heater is not unnecessarily dissipated. With this configuration, it is not necessary to install the panel heater above the object to be heated, so that the furnace does not become expensive and the processing cost does not increase. However, although the situation was somewhat improved than before, it was inevitable that the temperature distribution of the object to be heated would be non-uniform.
[0011]
In view of such circumstances, as a result of further research, the present inventor has come up with the idea of using an appropriately devised cross-sectional shape as the above-mentioned heat ray reflector, which was merely a thin metal plate. That is, if the heat ray reflector is configured so that the thickness increases from the center toward the edge, the temperature distribution of the object to be heated becomes uniform during the heat treatment, in other words, the object to be heated is We thought that there would be no temperature difference inside and as a result high quality could be achieved. Then, they have found that the above problem is solved by actually realizing this idea.
[0012]
In other words, when the heating furnace is configured in this manner, the problem that the temperature distribution of the object to be heated becomes non-uniform during the heat treatment is eliminated by the action of the heat ray reflector having a unique cross-sectional shape, and the temperature distribution is It becomes uniform at every corner. Moreover, since the heat ray reflector is obtained by processing a metal material, the heat ray reflector is much cheaper than a panel heater, and the furnace does not become expensive. Generally speaking, the heating furnace of the present invention enables the object to be heated to be accurately heated by a single heating means so as to have a uniform temperature distribution.
[0013]
These effects are considered to be due to the following reasons. As described above, when the thickness of the heat ray reflector increases from the center to the edge, the heat capacity also increases from the center to the edge. Therefore, as a corollary, the heat ray reflector has a larger amount of heat ray reflected toward its edge. In the heating furnace according to the present invention, in addition to the heat from the panel heater serving as the heating means, a small amount of heat is further generated at the central portion of the object to be heated, while the heat is increased toward the edge. Heat is added. As a result, the temperature distribution of the object to be heated during the heat treatment is leveled, that is, the accuracy of the temperature distribution is improved, and a temperature difference that degrades the quality of the object to be heated does not occur.
[0014]
The present invention has been made based on such new findings, and the above-mentioned problems have been solved.
Heating means that serves to heat the object to be heated while being placed thereon,
Above the heating means, a heating furnace comprising a heat ray reflector provided so as to face the object to be heated placed thereon,
This is solved by a heating furnace, wherein the heat ray reflector is configured to increase in thickness from a central portion to an edge portion.
[0015]
The heat ray reflector constituting the heating furnace according to the present invention is provided with a recess on the upper surface side, and the heat ray reflector has a thickness from the center to the edge due to the presence of the recess. Preferably has a cross-sectional shape that gradually increases. In particular, it is desirable that the surface of the dent provided in the heat ray reflector is convex downward and is along a curve passing through the center of the heat ray reflector. By employing the heat ray reflector having such a cross-sectional shape, it is possible to realize a more uniform temperature distribution of the object to be heated.
[0016]
In addition, during the heat treatment, the temperature of the central portion of the object to be heated may be remarkably high, but in order to effectively cope with this, the heat ray reflecting ability of the central portion of the heat ray reflector, that is, It is necessary to lower the heat capacity of the central part more sufficiently than the peripheral part. For these reasons, it is preferable that a hollow portion (cavity) is provided at the center of the heat ray reflector. In this specification, “reflection” mainly means a phenomenon in which a heat ray once absorbed leaks out of the reflector when the temperature of the reflector sufficiently rises, that is, re-radiation.
[0017]
In addition, it is desirable that the surface of the heat ray reflector facing the object to be heated is subjected to a heat ray absorbing surface treatment in order to optimize the degree of heat absorption depending on the location. Specific examples of the heat ray absorbing surface treatment include black alumite treatment. This treatment is for improving the corrosion resistance and heat radiation performance of the aluminum surface, and is performed in the following procedure. First, an aqueous solution of oxalic acid, sulfuric acid, chromic acid, or the like is prepared, and an electrolytic process is performed using aluminum as an anode. Then, the surface of the aluminum is oxidized by oxygen generated at the anode, and as a result, a film of aluminum oxide is formed. The black alumite treatment is completed by blackening the surface by infiltrating a black dye into this.
[0018]
Furthermore, in order to enhance the processing efficiency, the heating furnace according to the present invention includes a heating object transporting unit that transports the heating object via an upper region of the heating unit, and a plurality of heating units that are configured to heat the heating object. It is preferable that the apparatus further comprises a gantry arranged in a line along the transport direction. In other words, ideally, a plurality of heating means are arranged in a row on the gantry, and it is ideally configured so that a plurality of objects to be heated can be heated at a time by the cooperative action with the transport means.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be specifically described with reference to FIGS. 1 is a schematic structural view of a heating furnace according to the present embodiment, FIG. 2 is a cross-sectional view taken along line SS ′ in FIG. 1, FIG. 3 is an enlarged cross-sectional view of a heat ray reflector, and FIG. It is a conceptual diagram which shows the temperature distribution of the to-be-heated processed object.
[0020]
The heating furnace according to the present embodiment (hereinafter, referred to as the main heating furnace) is used, for example, to heat and dry an article such as a glass substrate for a liquid crystal (hereinafter, referred to as an object to be heated).
[0021]
As can be seen from FIGS. 1 and 2, the present heating furnace includes, as main components, a box-shaped case 1, a long gantry 2 housed therein, and a plurality of Panel heater (heating means) 3, a heat equalizing plate 4 placed on the panel heater 3, and provided above the heat equalizing plate 4 so as to face the heat equalizing plate 4 (therefore, the panel heater 3). And a plurality of heat ray reflectors 5.
[0022]
Although not particularly shown, the present heating furnace includes a heated object transfer means for transferring an object to be heated (indicated by F in the figure) via an area above the panel heater 3. In the present embodiment, the most common walking beam type is employed as the transport means.
[0023]
The transport means of the present method generally includes a fixed beam and a movable beam, of which the movable beam intermittently moves as shown by an arrow in FIG. As a result, the object to be heated F is intermittently conveyed from right to left in FIG. That is, the transporting means of the walking beam type transports the workpieces F to be heated one by one into the furnace from the openings 1 a provided on the mutually facing side surfaces of the case 1 and places them on the heat equalizing plate 4. I do. After a lapse of a predetermined time, the objects F to be heated are carried out one by one from the other opening 1b of the case 1 to the outside of the furnace.
[0024]
More specifically, when focusing on a specific object to be heated F, it is first loaded into the furnace through the opening 1a, and is located above the panel heater 3 closest to the opening 1a (actually, the heat equalizing plate). 4). In this state, after a heat treatment is performed for a predetermined time, another object to be heated F is carried into the furnace in the same manner. It is lifted from the place where it was placed and transferred onto the panel heater 3 located at the center. Further, after this operation is repeated once, the heated object F to be heated is carried out of the furnace through the opening 1b. However, any other method may be used as the transfer means.
[0025]
Among the above components, the panel heater 3 is a flat plate, and in the present embodiment, corresponds to the shape (square) of the object to be heated F placed thereon via the soaking plate 4. And a square shape is used. Further, a plurality of the panel heaters 3 exist as described above. They are arranged in a line at predetermined intervals on the long gantry 2 along the transport direction of the object to be heated F, and serve to heat the object to be heated F via the soaking plate 4. Fulfill. On the other hand, the heat equalizing plate 4 functions so that heat from the panel heater 3 is transmitted to the object to be heated F as uniformly as possible. The panel heater 3 and the soaking plate 4 each have a sufficiently larger area than the object F to be heated.
[0026]
Now, the heat ray reflector 5 forming the main heating furnace together with the above-mentioned components faces directly above the heat equalizing plate 4 (therefore, above the panel heater 3) and the object to be heated F placed thereon. It is provided as follows. That is, the same number of heat ray reflectors 5 as the panel heaters 3 are present in the case 1, and the object to be heated F is heated while being sandwiched between them. The heat ray reflector 5 is fixed in the case 1 by supporting means (not shown).
[0027]
As shown in FIG. 3, the heat ray reflector 5 is configured so that its thickness increases from the center to the edge. That is, a depression 5 a is provided on the upper surface side of the heat ray reflector 5. The depression 5a has a circular shape when viewed from above, and the presence of the depression 5a causes the heat ray reflector 5 to have a cross-sectional shape such that the thickness gradually increases from the center to the edge.
[0028]
More specifically, the surface of the depression 5a provided in the heat ray reflector 5 has a smooth curved surface except for the central portion (the central portion is a flat surface). That is, the surface of the depression 5a is convex downward and follows a curve passing through the center of the heat ray reflector 5 (indicated by a dashed line L in FIG. 3). The curve L adopted in the present embodiment is obtained by setting the x-axis and the y-axis as shown in FIG.
y = (1/750) x ² + (1/30) x + 0.8
Is a part of a parabola as represented by Note that, naturally, the cross-sectional shape of the heat ray reflector 5 is symmetric with respect to the y-axis.
[0029]
At the center of the heat ray reflector 5, a hollow portion 5b is provided. The hollow portion 5b serves to locally and slightly reduce the heat capacity of the heat ray reflector 5 to suppress the amount of heat rays reflected by the heat ray reflector 5 to an appropriate value. Here, the heat ray reflector 5 is configured by sandwiching a ring-shaped main body 5c from above and below with a curved metal thin plate 5d and a flat metal thin plate 5e, and the through hole of the main body 5c is formed in the hollow portion. It plays the role of 5b. In the present embodiment, the surface of the heat ray reflector 5 facing the object to be heated F is subjected to a heat ray absorbing surface treatment, specifically, a black alumite treatment. The thickness of the oxide film formed by this treatment is about 10 to 30 μm.
[0030]
In the heating furnace configured as described above, a heat ray reflector 5 that plays a role of reflecting heat rays is provided above the object to be heated F, not a panel heater. The object to be heated F can be heated by being sandwiched between the heat ray reflector 5 and the panel heater 3 on the gantry 2 from above and below. Further, in the present embodiment, the heat ray reflector 5 having a characteristic cross-sectional shape, that is, the heat ray reflector 5 having a thickness gradually increasing from the center to the edge is used. In this case, since the heat capacity of the heat ray reflector 5 increases from the center to the edge, the reflection amount of the heat ray also increases toward the edge.
[0031]
In this heating furnace, in this way, in addition to the heat from the panel heater 3 as the heating means, a small amount of heat is further located in the center of the object to be heated F, while the periphery is near the edge. More heat is added to the part. As a result, the temperature distribution of the object to be heated F during the heat treatment is leveled and becomes uniform as shown in FIG. That is, the edge temperatures (Ts1 to Ts4) and the central temperature (Tc) are substantially equal, and a temperature gradient, that is, a temperature difference does not occur in the object F to be heated, with the center at the top ( Ts1 ≒ Ts2 ≒ Ts3 ≒ Ts4 ≒ Tc).
[0032]
Generally speaking, the heating furnace can accurately and uniformly heat the object to be heated F by a single panel heater 3 to every corner, and can achieve high quality. Moreover, since the heat ray reflector 5 is obtained by processing a metal material, the heat ray reflector 5 is much cheaper than a panel heater, and the furnace does not become expensive.
[0033]
Here, the description has been given on the assumption that the object to be heated is a square, but the shape of the object to be heated is not limited to this. For example, an object to be heated having various shapes such as a rectangle and a circle may be a target of the heat treatment. For reference, for example, in a furnace corresponding to a rectangular object to be heated, the cross-sectional shape in the width direction and the cross-sectional shape in the transport direction of the heat ray reflector constituting the furnace are not the same. The optimum cross-sectional shape of the heat ray reflector in each of the width direction and the transport direction is selected in consideration of the planar shape of the object to be heat-treated, so that the temperature distribution becomes uniform. Further, the contour line of the depression of the heat ray reflector is not limited to a curve, and a straight line having a certain gradient may be adopted. That is, the shape of the depression of the heat ray reflector may be an inverted truncated cone.
[0034]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the heating furnace which concerns on this invention, a to-be-processed object can be precisely heat-processed by a single heating means so that it may become a uniform temperature distribution, and high quality can be implement | achieved.
[Brief description of the drawings]
FIG. 1 is a schematic structural view of a heating furnace according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line SS ′ in FIG. 1 of the heating furnace according to the embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of a heat ray reflector constituting the heating furnace according to the embodiment. FIG. 4 is a conceptual diagram showing a temperature distribution of an object to be heated during a heating process using the heating furnace according to the embodiment of the present invention. FIG. 6 is a schematic structural view of a conventional heating furnace. FIG. 6 is a cross-sectional view of the conventional heating furnace taken along line SS ′ in FIG. 5. FIG. FIG. 8 is a conceptual diagram showing a temperature distribution of an object to be heated. FIG. 8 is a cross-sectional view of another conventional heating furnace.
1 case 1a, 1b case opening 2 gantry 3 panel heater (heating means)
4 Heat equalizing plate 5 Heat ray reflector 5a Heat ray reflector recess 5b Heat ray reflector hollow part 5c Heat ray reflector main body parts 5d, 5e Metal sheet F Heated object

Claims (6)

Heating means that serves to heat the object to be heated while being placed thereon,
Above the heating means, a heating furnace comprising a heat ray reflector provided so as to face the object to be heated placed thereon,
The heating furnace, wherein the heat ray reflector is configured to increase in thickness from a central portion to an edge portion. A depression is provided on the upper surface side of the heat ray reflector, and the heat ray reflector has a cross-sectional shape such that the thickness gradually increases from the center toward the edge due to the presence of the depression. The heating furnace according to claim 1, characterized in that: The heating furnace according to claim 2, wherein the surface of the depression provided in the heat ray reflector is convex downward and is along a curve passing through the center of the heat ray reflector. . The heating furnace according to any one of claims 1 to 3, wherein a hollow portion is provided at the center of the heat ray reflector. The heating furnace according to any one of claims 1 to 4, wherein a surface of the heat ray reflector facing the object to be heated is subjected to a heat ray absorbing surface treatment. The apparatus further includes a heated object transporting unit that transports the heated object via an upper region of the heating unit, and a pedestal in which the plurality of heating units are arranged in a line in a transport direction of the heated object. The heating furnace according to any one of claims 1 to 5, characterized in that:

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