JPH09113144A - Heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a glass thin plate to be prevented from being cracked within a heating furnace by a method wherein a transporting speed of a transporting set to transport a workpiece through a maximina furnace temperature gradient part at an interface between heater segments is set to be faster than that of another transporting set. SOLUTION: A plurality of upper heaters 1a, 1b, lower heaters 2a, 2b and the like are installed in a heating furnace. The heaters 1a, 2a and the heaters 1b, 2b are set in a pair, controlled by the same system and then one heater segment is formed. A workpiece transporting speed generated by a roller set 6c and a roller set 6e for use in transporting a workpiece 4 through a maxinmum furnace temperature gradient part placed at an interface between the heater segments is set to be faster than a transporting speed generated by another roller set. With such an arrangement as above, it is possible to prevent a glass thin plate of the workpiece 4 from being cracked in the furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace for heating and baking thin glass plates such as glass substrates for displays. More specifically, the present invention relates to a heating furnace that requires highly accurate temperature distribution characteristics, particularly plasma. The present invention relates to a continuous firing furnace used for a display panel production apparatus. In particular, the present invention relates to a firing furnace useful in a firing process after forming rib partition walls made of glass frit and various coatings on a substrate of a plasma display panel.

[0002]

2. Description of the Related Art Conventionally, as a conveying method for heating and firing a brittle work such as a thin glass plate, there are a so-called walking beam type and a continuous conveying type using rollers and belts.

The walking beam type is shown in FIG.
As shown in (1), the thin glass plate is conveyed by a walking beam conveyor. The walking beam conveyor comprises a fixed beam and a driving beam as shown in FIG. In the walking beam conveyor, as shown in FIG. 3B, the driving beam rotates in the vertical direction in accordance with the order of (1) to (4) in the figure, and the movement thereof conveys the thin glass plate.

In the continuous transfer type, as shown in FIG. 2 (a), the glass sheet is carried into the baking furnace, transferred into the baking furnace, and carried out from the baking furnace continuously by a belt conveyor or the like. It was done like this. As a material for the belt, a metal mesh, a metal band, or the like is used.

[0005]

In the walking beam type furnace, since the driving part for carrying is not outside the heating furnace, there is no difference in temperature between the atmosphere inside the furnace and the carrying jig. Therefore, there is an advantage that uneven heating due to such a temperature difference can be suppressed. However,
In the walking beam type furnace, the work is conveyed while moving up and down together with the drive beam, so it is necessary to make the front of the heating furnace wide and set the heater layout in consideration of the vertical temperature distribution in the heating furnace. There is a need to.

On the other hand, the continuous transfer system does not have such a drawback. However, recently, it has been found that when a larger and relatively thin glass plate is fired in a continuous-conveyance heating furnace such as for use as a substrate of a plasma display, glass plate cracking frequently occurs.

An object of the present invention is to avoid such in-furnace cracking of thin glass sheets.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a work is continuously conveyed in a heating furnace in which a plurality of heater sections, each of which is composed of one or more heaters controlled by the same system, are arranged in series to convey the work. In the heating furnace for heating, the work transfer mechanism for the work in the heating furnace consists of a plurality of transfer sets that can set different transfer speeds, and the work is transferred through the maximum temperature gradient inside the furnace at the boundary of the heater section. Provided is a heating furnace in which a transfer speed of a transfer set to be transferred is set to be higher than transfer speeds of other transfer sets.

As a result of investigating the cause of the above glass plate cracking, the present inventors found that the glass cracking was not caused by thermal distortion caused by the rapid heating or quenching of the temperature of the glass plate, but rather by a single sheet. It was found that the thermal stress due to the temperature distribution generated in the plane of the glass plate is the cause.

The present invention has been made on the basis of the above findings, and the work transfer mechanism for the work in the heating furnace is made up of a plurality of transfer sets capable of setting different transfer speeds, and the heater sections of the heater section are By setting the transfer speed of the transfer set that transfers the work through the maximum temperature gradient in the furnace at the boundary to be higher than the transfer speed of the other transfer sets, the temperature distribution generated in the plane of one glass plate can be reduced. However, the cracking of the substrate can be almost eliminated.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.

In this embodiment, a plurality of heaters are arranged in the heating furnace. .. are upper heaters, and 2a, 2b .. are lower heaters. The heaters 1a and 2a, the heaters 1b and 2b, ... Are paired and controlled by the same system to form one heater section. Since a constant in-furnace temperature that is a target for heating the work (glass thin plate) is set in each heater section, the temperature gradient becomes relatively high at the boundary between these heater sections.

On the other hand, the work is continuously (non-intermittently) conveyed by the rollers. The rollers for transportation are shown in FIG.
Like the rollers 6a to 6f shown in (a), the drive system is divided for each roller set consisting of several to several tens of rollers, and they are driven independently of each other. Therefore, the speed setting of each roller set can be arbitrarily set.

The speed setting of the roller set will be described. In this example, as shown in FIG. 1 (b), the set temperatures in the furnace between the heater sections 1c and 2c and the heater sections 1d and 2d and between the heater sections 1e and 2e and the heater sections 1f and 2f are set. Changes significantly, and therefore the ambient temperature in the furnace also changes rapidly. Heater section 1
The roller set that conveys the boundary between the c and 2c and the heater sections 1d and 2d is 6c, and the roller set that conveys between the heater sections 1e and 2e and the heater sections 1f and 2f is 6e.
It is.

In this example, the work transfer speed generated by the roller set 6c and the roller set 6e is made higher than the transfer speed generated by the other roller sets. Thus, as shown in FIG. 1B, it is possible to reduce the temperature difference between the front end portion, the central portion, and the rear end portion of the work in the traveling direction. This state is shown in FIG. The three curves in FIG. 1B are time histories of the temperatures of the front end portion, the central portion, and the rear end portion of the work in the traveling direction, respectively. As can be seen by paying attention to the circled portion A and the portion B, three curves are relatively dense in this portion. This means that the temperature difference between the front end portion, the central portion and the rear end portion of the work in the traveling direction does not become so large at this place.

FIG. 1 (c) schematically shows the temperature distribution in the work advancing direction. The horizontal axis of the rectangle in the figure shows the position inside the work (the right side is the direction of travel of the work).
The vertical axis represents temperature. The area of the hatched portion is a measure of the size of the temperature distribution. As shown in the figure, a very large temperature distribution does not occur in the work, and the occurrence of cracks during firing of the work in the furnace can be reduced.

On the other hand, in the case of the conventional method, since the moving speed of the work conveyed in the furnace is constant everywhere in the furnace, the temperature of the front end portion, the central portion and the rear end portion of the work in the traveling direction is kept constant. A large time difference occurs in the history.

FIG. 2 schematically shows such a state. In FIG. 2, the same atmospheric temperature in the furnace as in FIG. 1 is assumed. The three curves in FIG. 2B are time histories of the temperatures of the front end portion, the central portion, and the rear end portion of the work in the traveling direction, respectively. As can be seen by paying attention to the circled portion C and the portion D, three curves are relatively discrete in this portion. This means that at this location, the temperature difference between the front end portion, the central portion, and the rear end portion of the workpiece in the traveling direction is large.

As a result, the temperature distribution generated in the work is
The result is as shown in FIG. As shown by the area of the hatched portion, a steep temperature distribution is generated in the work advancing direction as compared with the case of FIG. Therefore, when a brittle glass thin plate such as glass is used as a work, cracks are likely to occur during firing in a furnace.

When the temperature distribution exceeds 30 ° C., cracking is likely to occur rapidly. Therefore, in the present invention, it is preferable to adjust the work transfer speed in the furnace so that the temperature distribution inside the work is suppressed to 30 ° C. or less. Particularly preferably, the temperature distribution is 20 ° C. or lower.

In this embodiment, the work is carried by the rollers, but the present invention can be applied to a heating furnace having another work carrying mechanism. For example, a belt may be used. In this case, a plurality of belts may be arranged in the furnace and each belt may be driven by an independent drive system. Further, the present invention can be applied to a method of supporting a work by an air float system and separately carrying a work together with thrust.

[0022]

Embodiments of the present invention will be described below. Of course, the present invention is not limited to the following examples.

[Example 1] Plate thickness 2.1 mm x 590 mm
(Sending direction) × 930 mm (width direction) soda lime silicate glass was placed on a low expansion crystallized glass having a plate thickness of 5 mm, and in a heating furnace in which heating conditions as shown in Table 1 were set, Table 2 Firing was performed at the transport speed shown. At this time, the temperature difference (the height of the hatched portion) as shown in (1) of FIG. 1 (c) at the location corresponding to A of FIG. 1 (b) in the glass traveling direction was 0 ° C.

The cracking probability in this case was almost 0%.

[0025]

[Table 1]

[0026]

[Table 2]

Comparative Example A work similar to that in Example 1 is fired in a furnace under the same heating conditions. However, when the transport speed is fixed at 60.0 mm / min, C in FIG.
The temperature difference as shown in (1) of FIG. 2 (c), which is generated in the glass advancing direction at the position corresponding to, was 35 ° C.

The cracking probability in this case was 0.4%.

[Examples 2 to 5] Firing was performed in the same manner as in Example 1 except that the work conveying speed was partially changed as shown in Table 3. Table 3 shows the transport speed conditions and the results.

[0030]

[Table 3]

[0031]

INDUSTRIAL APPLICABILITY The present invention has an excellent effect that a work can be stably produced in a heating and firing furnace for continuously firing thin glass plates and the like without cracking of the work in the furnace. In particular, since the operator can freely set an arbitrary speed setting to each roller set by separately driving the transport roller, the effect of being extremely user-friendly can be recognized.

Further, according to the present invention, even in a temperature range where a sufficient heating time is required, it is not necessary to allocate a large heating zone corresponding to the time, and there is an effect that the furnace becomes compact.

[Brief description of the drawings]

FIG. 1 (a) is a side sectional view showing an embodiment of the present invention,
(B) A graph showing the heater set temperature and the in-furnace work temperature history in Fig. 1 (a), and (c) a conceptual diagram showing the work temperature distribution in Fig. 1 (b).

2A is a side cross-sectional view showing an example of a conventional belt conveyor transport system, FIG. 2B is a graph showing heater set temperature and furnace work temperature history in FIG. 2A, and FIG. Explanatory drawing of temperature distribution in a work in (b).

3A and 3B are explanatory views showing details of a walking beam system.

[Explanation of symbols]

 1: Upper heater 2: Lower heater 3: Roller 4: Workpiece 5: Belt 6: Roller set

Claims (1)

[Claims] 1. A heating furnace for heating a work by continuously transporting the work in a heating furnace in which a plurality of heater compartments each including one or more heaters controlled by the same system are arranged in series. The work transfer mechanism for the work in the heating furnace consists of a plurality of transfer sets that can set different transfer speeds, and the transfer speed of the transfer set that transfers the work through the maximum furnace temperature gradient part at the boundary of the heater section is A heating furnace characterized by being set to a higher transfer speed than other transfer sets.