JPH10287437A - Heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arbitrarily control the temperature distribution on the surface of a glass plate. SOLUTION: This heating furnace is provided with a furnace main body 1 having plural burners 13 attached to the ceiling 12 and a transporting means 4 of a glass plate 2. The transporting means is placed in the furnace main body 1 and has a curved part 9 curved in the lateral direction 8 of the furnace and formed at least at the downstream side of the curved part 9. A heat- shielding plate 14 capable of controlling the temperature distribution of the glass plate 2 is placed between the ceiling 12 and the transporting means 4 in the furnace main body 1.

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 bending a glass sheet, and more particularly, to a heating furnace suitable for bending a window glass sheet for a vehicle into a desired curved shape. It relates to a heating furnace.

[0002]

2. Description of the Related Art Curved glass, for example, is generally used for automobile window glass. Curved glass is manufactured by bending a glass plate into a curved shape by bending.

[0003] In particular, a glass sheet for a side window or a rear window of an automobile is subjected to a cooling air blown by a cooling device after a bending process to rapidly cool the glass plate to generate a compressive stress on the surface. That is used.

[0004] The bending of the glass sheet is performed by heating the glass sheet to a temperature equal to or higher than the softening point and then press-molding the glass sheet with a press bending die, or placing the glass sheet on a ring mold and placing it in a heating furnace. A method of bending a glass sheet which has been carried in and heated and softened in a heating furnace by using its own weight has been proposed and has been actually implemented.

On the other hand, as a method for bending a glass sheet, when a glass sheet is transferred from an upstream side to a downstream side in a heating furnace, a transfer means provided in the heating furnace is provided with a predetermined curvature to soften the glass sheet. A method has been proposed in which a bent glass plate is bent so as to follow its curvature, thereby eliminating the need for a mold.

In the case of the bending by the above-mentioned method, the conveying means has a conveying surface having a curvature in a direction orthogonal to the conveying direction in plan view, that is, in a furnace width direction, and the glass plate has a curved conveying surface. Is transported.

The softened glass sheet hangs down by its own weight so as to follow the transfer surface having the above-mentioned curvature, and a curved glass having a curvature in the furnace width direction is obtained. As a conveying means, a roller hearth using a roller,
A gas hearth or the like in which heated air is blown onto the lower surface of the glass plate to levitate and transport the glass plate may be used.

In the above roller hearth, the central portion of the roller is curved downward, and a plurality of rollers generally form a downwardly protruding transport surface. The gas hearth is as shown in FIG. Here, FIG. 4 is a schematic perspective view showing a heating furnace used in the above method.

That is, inside the furnace body 1 of the heating furnace,
A conveying means called a hearth bed 4 having a plurality of holes 3 for heating and levitating an object to be heated such as a glass plate 2 by blowing heated air upward is provided.

The furnace body 1 has a length of about 30 m or more, and the furnace body 1 is long.
Is divided into a plurality of heating zones.

The conveying surface 6 of the hearth bed 4 has a flat surface 7 on the upstream side and a curved surface portion 9 having a curvature in the furnace width direction 8 on the downstream side. Then, near the position where the temperature of the glass plate 2 reaches the softening point in the middle of the hearth bed 4, the transport surface 6 gradually starts to change from the flat surface 7 to the curved surface portion 9, and the curved surface portion 9 moves to the downstream side. The curvature is gradually changed so that the curvature gradually increases.

Further, the transfer surface 6 of the hearth bed 4 is slightly inclined so that one side (upper side 10) of the furnace width direction 8 is higher than the other side (lower side 11). On the 11 side, a transport mechanism such as an endless chain (not shown) is extended in the transport direction 5 and a transport receiving tool is attached to the transport mechanism such as a chain at a predetermined interval.
The glass plate 2 levitated on the transfer surface 6 and moved to the lower side 11 by its own weight along the inclination of the transfer surface 6 is received by the transfer receiving tool to align the position of the glass plate 2 and to move the glass plate 2 downstream. They are transported.

Further, a ceiling 1 is provided in the furnace body 1 of the heating furnace.
2, a burner 13 for ejecting combustion gas downward is provided at a predetermined interval as a heating source.

Further, on the downstream side of the heating furnace, a cooling air is blown to both sides of the heated glass sheet 2 to rapidly cool the glass sheet 2 to a temperature lower than its softening point. Is provided with a cooling device (not shown) for imparting tempered glass to tempered glass.

According to this configuration, heated air is ejected upward from the plurality of holes 3 formed in the transfer surface 6 of the hearth bed 4, and in this state, the heating air is blown from the upstream side of the furnace body 1. When the glass plate 2 is sent upward, the glass plate 2
Are levitated and supported by the jetted heated air.

At this time, the conveying surface 6 of the hearth bed 4
Since the side (upper side 10) of the furnace width direction 8 is slightly inclined so that one side (upper side 10) is higher than the other side (lower side 11), the glass plate 2 floated on the transfer surface 6 is inclined by the transfer surface 6. Is moved by its own weight to the lower side 11 side, and the position thereof is aligned by a transport mechanism such as an endless chain (not shown) extended in the transport direction 5 to the lower side 11 side of the hearth bed 4 and the transport mechanism such as a chain Is transported to the downstream side by the transport receiving tool attached at a predetermined interval.

Thus, the combustion gas is blown downward from the burner 13 attached to the ceiling portion 12 of the furnace body 1 at a predetermined interval to the glass plate 2 being conveyed to the downstream side in the furnace body 1. I do.

Then, convection heating is applied to the lower surface of the glass plate 2 by the heated air blown out from the plurality of holes 3 formed on the hearth bed 4 and radiant heating is applied to the lower surface of the glass plate 2 from the transfer surface 6 of the hearth bed 4. Further, the glass plate 2 is heated by radiant heating from a group of burners 13 appropriately arranged on the ceiling portion 12 of the furnace main body 1 of the heating furnace and each part of the furnace wall in the upper space of the furnace main body 1 to the upper surface of the glass plate 2. You.

At this time, since the floating distance between the glass plate 2 and the hearth bed 4 is very small, about 1 mm, the glass plate 2 and the hearth bed 4 mutually transmit the radiant heat while maintaining the mutual temperature distribution. It will be greatly affected.

When the glass plate 2 is heated to reach the softening point, the glass plate 2 softens and becomes a viscoelastic body, but the temperature of the glass plate 2 in the middle of the hearth bed 4 reaches the softening point. In the vicinity of the position, the conveying surface 6 starts to change from the flat surface 7 to the curved surface portion 9, and the curved surface portion 9 is gradually changed so that the curvature gradually increases toward the downstream side. The glass plate 2 which has become a body gradually hangs down so as to substantially follow the curved surface portion 9 and is bent into a desired shape.

When the glass sheet 2 thus bent leaves the furnace body 1 of the heating furnace, it is conveyed by a conveying mechanism such as a chain to a cooling device (not shown) arranged on the downstream side. Cooling air is blown to the surface to cool it to a temperature below the softening point, so that the shape is adjusted, and cooling air is blown to both surfaces to cool rapidly to the softening point or less. To give a tempered glass.

[0022]

The method of bending and forming the glass plate 2 by transferring the glass sheet 2 on the transfer surface 6 having the above-mentioned curved surface shape has a large heat capacity of the hearth bed 4 so that the furnace temperature fluctuation is small and a large amount of This is advantageous in that the glass plate 2 is stably produced.

However, on the other hand, once a non-uniform temperature field is formed in the furnace body 1 for some reason, there is a strong tendency that the non-uniform temperature field is maintained and continued as it is. There is a problem that a non-uniform temperature distribution is generated in all the glass plates 2.

The glass plate 2 thus non-uniformly heated is
Since the shape of the glass plate does not uniformly conform to the curvature of the hearth bed 4, an incompletely formed state called so-called non-uniformity R occurs, and the non-uniformity R causes the glass plate 2 to float during the levitating conveyance in the furnace body 1. There is a quality problem such as contact with the hearth bed 4 and contact flaws.

The present inventors have investigated the cause of the above-mentioned contact flaw. As a result, the abnormally heated portion of the glass plate 2 was locally deformed at a high temperature because the glass plate 2 was heated unevenly in the furnace body 1. It was found that the non-uniform heating factor and the non-uniform distribution of the amount of heat removal in the furnace caused by the shape of the glass plate.

This is because when a glass plate 2 having a non-rectangular shape such as a side door glass of an automobile is continuously charged into a furnace body 1 having a uniform temperature field before the start of production, Since the amount of heat removal in the furnace is different between a portion where the size of the glass plate 2 in the transport direction 5 is large and a portion where the size is small, a heat removal amount distribution occurs in the furnace main body 1, thereby forming an uneven temperature distribution on the upper surface of the hearth bed 4. Further, since the lower surface of the glass plate 2 receives secondary non-uniform radiation from the non-uniform temperature distribution on the upper surface of the hearth bed 4 thus formed, an in-plane temperature distribution occurs in the glass plate 2. .

In addition, when the glass after heating is cooled by the cooling device on the downstream side, and the shape is adjusted by the balance control of the cooling capacity of the upper and lower surfaces of the glass, the unevenness R generated in the heating furnace causes the cooling during cooling. There has been a problem in terms of shape adjustment of the glass plate 2 such that the shape adjustment range is narrowed.

On the other hand, in the above-mentioned heating mode for the glass sheet 2, when the non-uniform temperature distribution of the glass sheet 2 generated as described above is to be improved, the temperature of the glass sheet 2 in the group of burners 13 is increased. The only adjusting means is to extinguish the burner 13 in the high part of the burner 13.

However, in this case, the burner 13 must be provided separately from the hearth bed 4 so that the hearth bed 4 can be replaced according to the change of the glass plate 2 to be formed. Due to structural restrictions, a desired glass temperature distribution cannot be obtained even if a part of the burners 13 is extinguished.

That is, the burner 13 and the hearth bed 4
Is considerably large, and even if some of the burners 13 are extinguished, the effect of radiant heat from the burners 13 provided at adjacent positions becomes relatively large. The effect of lowering the temperature is hardly obtained.

Therefore, the fire extinguishing of the burner 13 has a disadvantage that the temperature distribution of the glass sheet 2 cannot be arbitrarily controlled for various glass sheet shapes.

The operation of igniting or extinguishing the burner 13 is rather complicated as the operation of the equipment, and has hardly been adopted as a practical temperature distribution adjusting means during production.

The present invention provides a heating furnace which can easily avoid such a non-uniform temperature distribution of a glass sheet in the heating furnace and can form an arbitrary temperature distribution as required. It is intended to provide.

[0034]

According to the present invention, there is provided a furnace body 1 having a plurality of heating means 13 mounted on a ceiling portion 12 and disposed in the furnace body 1 at least downstream in a furnace width direction 8. Conveying means 4 for glass plate 2 having a curved surface portion 9 having a curvature formed thereon
In the heating furnace provided with the above, a heat shield plate 14 capable of adjusting the temperature distribution of the glass plate 2 is disposed at a position between the ceiling portion 12 and the transfer means 4 in the furnace main body 1. It depends on the heating furnace.

In this case, the heat shield plate 14 may be arranged in the vicinity of the position where the temperature of the glass plate 2 reaches the softening point in the furnace main body 1.

Further, the heat shield plate 14 may be arranged above the portions 20 to 22 of the glass plate 2 in which the dimension in the transport direction 5 is short to face.

Further, the heat shield plate 14 may be provided so as to be adjustable in position in the furnace width direction 8.

According to the above configuration, the following operation can be obtained. The glass plate 2 is conveyed from the upstream side to the downstream side in the furnace main body 1 by the conveying means 4, and the ceiling 12
The heating means 13 is heated and softened by radiant heating by a plurality of heating means 13 attached thereto, and is bent so as to follow a curved surface portion 9 having a curvature in the furnace width direction 8 of the conveying means 4.

At this time, if there is a portion 20 to 22 or a long portion of the glass plate 2 having a short dimension in the conveying direction 5, a difference occurs in the amount of heat removed in the furnace. As a result, the glass plate 2 is heated to an uneven temperature. This may cause an incompletely formed state or a contact flaw with the conveying means 4 due to local bending.

Therefore, in the present invention, a heat shield plate 14 is provided at a position between the ceiling 12 and the transfer means 4 in the furnace main body 1 so as to adjust the temperature distribution of the glass plate 2. I have.

As described above, by adjusting the temperature distribution of the glass plate 2 by the heat shield plate 14, the glass plate 2 can be heated to a uniform temperature, so that a good molding state can be obtained. The local bend can be eliminated, and the contact flaw with the conveying means 4 can be prevented.

In this case, the heat shield plate 14 may be provided in a desired heating zone in the furnace main body 1.
Preferably, the glass plate 2 is provided at a portion immediately before the temperature reaches the softening point, a portion immediately after the temperature reaches the softening point, or the like.

By arranging the heat shield plate 14 on the portions 20 to 22 of the glass plate 2 where the dimension in the transport direction 5 is short, an effect of heating the glass plate 2 to a uniform temperature can be obtained.

Further, by adjusting the position of the heat shield plate 14 in the furnace width direction 8, the temperature distribution on the glass plate 2 can be finely adjusted, or the temperature distribution can be adjusted on various glass plates 2 having different shapes. The function can be optimized.

[0045]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 (a), (b),
(C) is an example of an embodiment of the present invention, FIG. 1 is a schematic perspective view of a heating furnace, FIG. 2 is a view taken along the line II-II of FIG. 1, and FIGS. 3 (a) and (b). And (c) is a schematic plan view showing a heat shielding range for glass plates of various shapes.

The basic configuration of the heating furnace is as follows.
Since the configuration is the same as that of FIG. 4, the same portions are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, the ceiling 1 in the furnace body 1
A heat shield plate 14 capable of adjusting the temperature distribution of the glass plate 2 is provided at a position between the glass plate 2 and the glass plate 2.

The heat shield plate 14 may be provided in a desired heating zone in the furnace main body 1;
It is provided in a heating zone immediately before the temperature of the glass plate 2 reaches the softening point, a heating zone immediately after the temperature reaches the softening point, and the like.

As the heat shield plate 14, for example, a heat insulating material such as kao wool sandwiched between two stainless steel thin plates is used.

The heat shield plate 14 is a slide guide member 1 extending in the furnace width direction 8 fixed via a support member 15 at a position avoiding the burner 13 on the ceiling 12 of the heating furnace.
6, the suspension is supported via the slide portion 17 and the suspension member 18 so as to be adjustable in the furnace width direction 8.

The lower surface of the heat shield plate 14 is
To be arranged close to the upper surface of the. The distance 19 between the lower surface of the heat shield plate 14 and the upper surface of the glass plate 2 is, for example, 80 to 150 mm.

The heat shield plate 14 is formed as shown in FIG.
(B) and (c) as shown in FIG.
Are arranged so as to oppose each other over the short portions 20 to 22 having the short dimensions.

Next, the operation will be described.

The process of heating and softening the glass plate 2 in a heating furnace and bending the glass plate 2 so as to follow the curved surface portion 9 of the hearth bed 4 is the same as in FIG.

When the glass plate 2 is heated by the heating furnace, if the glass plate 2 has a portion having a large dimension in the conveying direction 5 and a small portion, the amount of heat removed in the furnace is distributed, and the temperature in the furnace body 1 becomes uneven. A field is formed.

Once a non-uniform temperature field is formed in the furnace main body 1, since the heating furnace has a large heat capacity, the non-uniform temperature field tends to be maintained and continued as it is. Although a non-uniform temperature distribution will be generated in the glass plate 2, in the present invention, since the heat shield plate 14 is disposed in the furnace main body 1, by optimizing the position of the heat shield plate 14, The amount of radiation heat received by the glass plate 2 in the heating furnace can be partially controlled so that the entire glass plate 2 can be heated to a substantially uniform temperature.

That is, by providing the heat shield plate 14, the burner 13 group appropriately arranged on the ceiling 12 of the furnace main body 1 of the heating furnace, and the various parts of the furnace wall in the upper space of the furnace main body 1 from the upper surface of the glass plate 2. Since the radiant heating to the glass plate 2 can be partially blocked, the temperature of the portion is lowered by disposing the heat shield plate 14 above the locally high temperature portion of the glass plate 2, and the temperature of the glass plate 2 is reduced. Has a substantially uniform temperature as a whole.

When there are glass plates 2 of various shapes as shown in FIGS. 3 (a), 3 (b) and 3 (c), the portions Since the amount of internal heat removal is small and the temperature is likely to be locally high, the heat shield plate 14 is arranged above and opposed to the portions 20 to 22.

At this time, if the heat shield plate 14 is arranged close to the glass plate 2, a high heat shield effect can be obtained. In particular, the distance 1 between the lower surface of the heat shield plate 14 and the upper surface of the glass plate 2
9 is preferably, for example, 80 to 150 mm.

The heat shield plate 14 may be provided in a desired heating zone in the furnace main body 1, but may be provided in a heating zone immediately before the temperature of the glass plate 2 reaches the softening point or in a heating zone immediately after the temperature reaches the softening point. It is preferable to provide the heat shield plate 14 locally in a portion where the highest effect is obtained, such as a heating zone.

Further, the supporting member 1 is mounted on the ceiling 12 of the heating furnace.
5 with respect to the slide guide member 16 fixed via
By displacing the slide portion 17 and adjusting the position of the heat shield plate 14 in the furnace width direction 8 via the suspending member 18, the position of the heat shield plate 14 is optimized with respect to the glass plates 2 of various shapes. It becomes possible.

As described above, the temperature of the entire glass plate 2 becomes substantially uniform, so that the bending accuracy of the glass plate 2 at the curved surface portion 9 of the hearth bed 4 can be improved, and
Contact flaws due to the contact of the glass plate 2 with the hearth bed 4 can be eliminated. The position of the heat shield plate 14 is roughly adjusted in advance according to the shape of the glass plate 2 before the operation of the heating furnace,
Fine adjustment can be made externally during operation.

Alternatively, the heat shield plate 14 may be replaced with a portion other than the above,
For example, by moving to the lower side 11 side and simultaneously increasing the amount of radiant heating of the burner 13, a glass temperature distribution in which only the lower side 11 side is suppressed can be formed. The glass temperature distribution can be arbitrarily controlled as needed.

[0064]

Embodiments of the present invention will be described below. First,
In each heating zone, a heating furnace set to the heating conditions shown in Table 1 is used.

[0065]

[Table 1]

Example 1 As Example 1, of the heating zones provided in the heating furnace in the transport direction 5 and divided into 12 zones, the downstream heating zone (the 8th heating zone from the upstream side)
(Threeth zone) to the tenth heating zone, thickness 50 mm, furnace width direction 8 length 250 m
A comparison was made between the case where the heat shield plates 14 of m and 400 mm were installed and the case where they were not installed.

In the experiment, soda lime glass having a plate thickness of 3.5 mm, a maximum dimension of 1044 mm in the conveying direction 5, and a maximum dimension of 527 mm in the furnace width direction 8 having the shape shown in FIG. 3A was used.

As a result, a maximum temperature difference as shown in Table 2 was obtained between the upper side 10 and the lower side 11 of the glass plate 2.

[0069]

[Table 2]

The area covered by the heat shield plate 14 indicates the distance from the upper side 10 of the hearth bed 4.

According to Table 2, the shielding range of the heat shield plate 14 is 0.
mm, the glass temperature distribution at the outlet of the heating furnace is such that the maximum temperature difference in the furnace width direction 8 is 17.5 ° C.
Was unevenly heated, and at this time, a contact flaw occurred at the corner of the upper side 10 of the glass plate 2.

Heat shield plate 1 having a length of 250 mm in furnace width direction 8
4 is installed, the maximum temperature difference in the furnace width direction 8 is 1
It was kept at 0.5 ° C. In addition, the length in the furnace width direction 8 is 40
In the case of Example 1 in which the heat shield plate 14 of 0 mm was installed, the maximum temperature difference in the furnace width direction 8 of the glass temperature distribution at the heating furnace outlet was suppressed to 10.0 ° C.

At this time, the partial change in the radius of curvature of the glass plate 2 in the furnace width direction 8 is compared with the case where the shielding range is set to 0 mm and the case where the shielding range is set to 400 mm. The change amount ΔR becomes ΔR = 200 mm,
When the heat shield plate 14 was provided, the shape of the glass plate was improved in a direction in which the heat shield plate 14 was adapted to the hearth bed 4. From the above, the effect of the heat shield plate 14 was confirmed.

[Embodiment 2] As Embodiment 2, as in Embodiment 1, of the heating zones divided into 12 zones in the heating furnace, from the eighth heating zone on the downstream side to the tenth heating zone, 50m thickness over 3 zones
The comparison was made between a case where the heat shield plate 14 having a length of 400 mm and a length of 500 mm in the furnace width direction 8 was installed and a case where the heat shield plate 14 was not installed.

In the experiment, the plate thickness was 3.5 mm, the maximum dimension in the transport direction 5 was 1044 mm, and the maximum dimension in the furnace width direction 8 was 527 m.
m, soda lime glass, plate thickness 3.5 mm, maximum dimension 1062 mm in transport direction 5, maximum dimension 49 in furnace width direction 8
8 mm soda lime glass, thickness 4.0 mm, maximum dimension 821 mm in transport direction 5, maximum dimension 5 in furnace width direction 8
79 mm soda lime glass was used. Note that these shapes are all shapes as shown in FIG.

As a result, a maximum temperature difference as shown in Table 3 was obtained between the upper side 10 and the lower side 11 of the glass plate 2. Note that the result partially overlaps with Example 1.

[0077]

[Table 3]

The range covered by the heat shield plate 14 indicates the distance from the upper side 10 of the hearth bed 4.

From Table 3, it can be seen that there is an optimum arrangement condition for uniform heating in the arrangement of the heat shield plate 14, and the condition is the heat shield plate 1
It was confirmed that the value changed depending on the size and material of No. 4.

The present invention is not limited to the above-described embodiments and examples. In particular, in the above-described embodiment, the case where the gas hearth is used as the transfer means is described, but a roller hearth may be used.

In the above example, a burner is used as the heating means. However, various heating means such as an electric heater can be used. When the glass plate is levitated and conveyed using a hearth head as the conveying means, a burner using a combustion gas is also preferable because the combustion gas is mixed with the heated air and ejected from the hearth head.

[0082]

According to the present invention, in a glass heating furnace in which radiant heating is dominant, an excellent effect that glass can be arbitrarily controlled to a desired temperature distribution and user-friendly can be obtained.

Further, since the shape of the glass plate conforms to the hearth bed and a desired glass temperature distribution can be obtained, cooling air is blown to one side of the heated glass plate to cool the glass plate to a temperature not lower than the softening point. Thus, there is an effect that the control of the shape of the glass plate can be facilitated.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a heating furnace according to an example of an embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrows II-II in FIG.

FIGS. 3A, 3B, and 3C are schematic plan views showing heat shielding ranges for glass sheets of various shapes, respectively.

FIG. 4 is a schematic perspective view showing a general heating furnace.

[Description of Signs] 1: Furnace main body 2: Glass plate 4: Hearth bed (conveying means) 8: Furnace width direction 9: Curved surface part 12: Ceiling part 13: Burner (heating means) 14: Heat shield plate 20 to 22: part

Claims (4)

[Claims] 1. A furnace body having a plurality of heating means mounted on a ceiling portion, and a glass plate provided in the furnace body and having a curved surface portion having a curvature in a furnace width direction at least on a downstream side. Wherein a heat shield plate capable of adjusting the temperature distribution of the glass plate is provided at a position between the ceiling portion in the furnace main body and the transfer means. 2. The heating furnace according to claim 1, wherein the heat shield plate is arranged in a portion near a position where the temperature of the glass sheet reaches the softening point in the furnace main body. 3. The heating furnace according to claim 1, wherein the heat shield plate is disposed above and opposed to a portion of the glass plate having a short dimension in the transport direction. 4. The heat shield plate is provided so as to be adjustable in position in the furnace width direction.
The heating furnace as described.