JP4577597B2 - Method for bending glass plate and heating furnace for bending - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bending method and a bending furnace for bending a thin glass plate applied to a vehicle window glass.
[0002]
[Prior art]
When bending a glass plate applied to a rear glass or side glass of an automobile, the glass plate is heated to a temperature at which bending can be performed in a heating furnace before the bending. A roller hearth furnace known as a heating furnace has a conveyance roller in the furnace, and when the glass plate is placed on the conveyance roller and the glass plate is carried into the roller hearth furnace, the glass plate is located above the conveyance roller. Heated by the radiant heat of the upper heater provided, and heated by the radiant heat of the lower heater provided below the transport roller, and heated to a temperature at which bending can be performed at the outlet of the roller hearth furnace (for example, 600 to 650 ° C.). .
[0003]
By the way, since the lower surface of the glass plate is in contact with the conveying roller, the heat amount of the conveying roller is directly transmitted to the lower surface of the glass plate. For this reason, the temperature of the lower surface of a glass plate became higher than the temperature of an upper surface, and there existed a problem that a glass plate curved upwards.
[0004]
As an example for solving this problem, an annular groove is formed at a constant interval on the outer periphery of the transport roller to suppress the amount of heat directly transmitted from the transport roller to the lower surface side of the glass plate, and above the glass plate. A method of making the amount of heat absorbed by the lower surface and the upper surface of the glass plate uniform by injecting compressed air to cause convection above the glass plate and efficiently transmitting the radiant heat of the upper heater to the upper surface of the glass plate. Proposed.
[0005]
On the other hand, a glass plate applied to an automobile is required to be a thin plate (for example, a thickness of 3 mm or less) for the purpose of reducing the weight of the automobile. Even if such a thin glass plate is heated to the temperature at which it can be bent at the outlet of the roller hearth furnace, if it is taken out from the roller hearth furnace, the whole is immediately cooled naturally and it is difficult to strengthen. . Therefore, in the case of a thin glass plate, the temperature of the glass plate at the outlet of the roller hearth furnace is set higher than the temperature at which bending can be performed (for example, 680 to 695 ° C .: hereinafter referred to as “high temperature heating”). It was.
[0006]
[Problems to be solved by the invention]
However, when a glass plate is heated at a high temperature in a roller hearth furnace, the shape of foreign matter such as dust adhering to the surface of the transfer roller is transferred to the lower surface of the glass plate during high-temperature transfer. "Is abbreviated as") and the quality of the glass plate is lowered.
[0007]
In addition, in the conventional roller hearth furnace, the glass plate is heated at a high temperature by the convection heating method throughout the furnace in order to prevent the glass plate from warping. That is, a convection is generated by providing a large number of fans in the roller hearth furnace. As a result, the initial cost and running cost are enormous.
[0008]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a glass plate bending method and a bending furnace that can prevent the occurrence of RIP even when the glass plate is heated at a high temperature.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention bends a glass plate that is heated to a bending temperature by being conveyed by a plurality of conveying rollers disposed in a heating furnace and then bent into a predetermined shape. In the forming method, the glass plate is conveyed at a low speed on the upstream side in a heating furnace to be heated to a temperature at which bending can be performed , and is conveyed at a high speed on the downstream side to be heated to a temperature higher than the bendable temperature. And
[0010]
In order to achieve the above object, the present invention provides a glass comprising a plurality of conveying rollers for conveying a glass plate while supporting the lower surface of the glass plate, and a heating means for heating the glass plate being conveyed by the conveying roller. In a heating furnace for bending a plate, a convection heating furnace in which the conveying speed of the glass plate of the conveying roller arranged on the upstream side in the heating furnace is set to a low speed and the glass plate is heated to a bendable temperature. When the conveying speed of the glass plate of the conveyance roller disposed on the downstream side of the heating furnace, than the speed of the conveying rollers of the upstream is set faster than the bend moldable temperature the glass plate And a radiant heating furnace for heating to a higher temperature .
[0011]
According to the present invention, it is possible to sufficiently bend a glass plate by placing the glass plate on a conveying roller, carrying the glass plate into a heating furnace, and conveying the glass plate at a low speed upstream in the heating furnace. The glass plate is heated to a temperature, and the glass plate is conveyed at a high speed on the downstream side in the heating furnace and heated at a high temperature, and then bent into a predetermined shape. As described above, when the glass plate in which RIP is generated is heated at a high temperature, the glass plate is transported at high speed so as to minimize the time for the glass plate to pass through the furnace, so that the generation of RIP can be prevented.
[0012]
In addition, according to the present invention, since the convection method is adopted as the heating method on the upstream side in the heating furnace in which the glass plate is conveyed at a low speed, it is possible to prevent the warp that occurs when the glass plate is heated. And since the radiation system was employ | adopted as a heating system of the downstream in the heating furnace in which a glass plate is conveyed at high speed, initial cost and running cost can be reduced rather than a convection system. Therefore, the initial cost and the running cost can be reduced as compared with the conventional heating furnace adopting only the convection heating.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a glass sheet bending method and a bending furnace according to the present invention will be described below in detail with reference to the accompanying drawings.
[0014]
A heating furnace 10 according to the embodiment shown in FIGS. 1 and 2 is a heating furnace that is heated at a high temperature in order to bend a thin glass plate 12 that is applied to a rear glass and a side glass of an automobile. The heating furnace 10 is separated into an upstream heating furnace and a downstream heating furnace. The upstream heating furnace is a convection heating furnace 14 using a convection heating method, and the downstream heating furnace is a radiation heating furnace 16 using a radiant heating method. It is configured. Moreover, these heating furnaces 14 and 16 are partitioned by a partition plate 18 so that each atmosphere temperature does not adversely affect the atmosphere temperature of the adjacent heating furnace.
[0015]
Further, in the heating furnaces 14 and 16, a large number of conveying rollers 20, 20... Are arranged at a predetermined interval along the conveying direction of the glass plate 12. The glass plate 12 placed on the conveyance rollers 20, 20... Near the inlet 15 of the convection heating furnace 14 is carried into the convection heating furnace 14 from the inlet 15 of the convection heating furnace 14 by the rotation of the conveyance rollers 20, 20. Is done. Here, the glass plate 12 is sufficiently heated to the temperature at which bending can be performed, then passes through the passage hole 19 of the partition plate 18 and is carried into the radiation heating furnace 16 where it is heated at high temperature. And the glass plate 12 heated at high temperature is carried out of the furnace 17 from the exit 17 of the radiation heating furnace 16 and conveyed to a bending apparatus (not shown) where it is bent into a predetermined shape. An example of the forming apparatus is a bending apparatus provided with a pressing support ring that supports the peripheral surface of the glass plate and an upper mold that is pressed against the glass plate 12 supported by the pressing support ring. The present applicant has proposed such a bending apparatus according to Japanese Patent Laid-Open No. 11-263634.
[0016]
2 are provided with heating heaters (corresponding to heating means) 22, 22... Below the conveying rollers 20, 20... Of the convection heating furnace 14 shown in FIG. Gas burners for heating (corresponding to heating means) 24 and 24 are provided. In the present embodiment, the electric heater 22 is used as the lower heating means, but the glass plate 12 may be heated using a gas burner.
[0017]
Further, a convection heating device 26 is provided above the transport rollers 20, 20. The convection heating device 26 includes a casing 28, a fan 30, and blowing nozzles 32, 32. The casing 28 has an opening hole (not shown) formed on the upper surface, and the air outlets (not shown) of the heating gas burners 24, 24.
[0018]
A suction port (not shown) is formed in the center of the lower surface of the casing 28, and a fan 30 is rotatably provided in the casing 28 above the suction port. When the fan 30 is rotated by the motor 34, the intake air sucked from the convection heating furnace 14 through the suction port is diffused into the casing 28. As a result, the intake air sucked from the suction port and the heated air blown from the outlet of the heating gas burner 24 are mixed in the casing 28, and this mixed air is directed from the blow nozzles 32, 32. Blown out. Therefore, convection is generated on the upper surface of the glass plate 12, and the upper surface of the glass plate 12 is heated. The lower surface of the glass plate 12 is heated by the radiant heat of the electric heater 22. As such a convection heating furnace 14, the applicant of the present application discloses an example in Japanese Patent Application Laid-Open No. 7-126026.
[0019]
On the other hand, heating heaters (corresponding to heating means) 36, 36,... Are provided below the conveying rollers 20, 20,. Electric heaters (corresponding to heating means) 38, 38... Are provided. In the present embodiment, the electric heaters 36 and 38 are used as heating means, but the glass plate 12 may be heated using a gas burner. However, in consideration of running costs, an electric heater is preferable to a gas burner.
[0020]
By the way, in the heating furnace 10 of this Embodiment, the conveyance speed of the glass plate 12 in the convection heating furnace 14 is controlled to low speed, and the conveyance speed of the glass plate 12 in the radiation heating furnace 16 is controlled to high speed.
[0021]
In the configuration enabling such control, the conveying rollers 20, 20... Are distinguished into convection heating furnace conveying rollers 20A, 20A... And radiant heating furnace conveying rollers 20B, 20B. This can be achieved by driving the rollers 20A, 20A... And the conveying rollers 20B, 20B. That is, the sprocket 44 is fixed to both ends of the conveying roller 20A, and the endless chain 46 is engaged with the sprocket 44, and the drive sprocket 48 (FIG. 1) of the motor 40 is engaged with the chain 46. As a result, when the driving force of the motor 40 is transmitted to the chain 46 via the drive sprocket 48, the chain 46 moves around and the transport rollers 20A, 20A,... Rotate at a predetermined rotational speed. The glass plate 12 is conveyed at a predetermined low speed. The motor 40 and the chain 46 are disposed on both sides of the transport rollers 20A, 20A.
[0022]
A sprocket 50 is also fixed to both ends of the conveying roller 20B shown in FIG. 3, and an endless chain 52 is meshed with the sprocket 50, and a drive sprocket 54 (FIG. 1) of the motor 42 is meshed with the chain 52. . As a result, when the driving force of the motor 42 is transmitted to the chain 52 via the drive sprocket 54, the chain 52 moves around, and accordingly, the transport rollers 20B, 20B... Rotate at a predetermined rotational speed. The glass plate 12 is conveyed at a predetermined high speed. The motor 42 and the chain 52 are arranged on both sides of the transport rollers 20B, 20B... As shown in FIG.
[0023]
Acceleration conveyance rollers 20C, 20C,... Are arranged between the conveyance roller 20A and the conveyance roller 20B. In order to smoothly transfer the glass plate 12 conveyed at a low speed by the conveyance roller 20A to the conveyance roller 20B for high-speed conveyance, the conveyance roller 20C changes the glass plate 12 from a low speed by the conveyance roller 20A to a high speed by the conveyance roller 20B. It is a conveyance roller for accelerating the conveyance speed. These conveying rollers 20C, 20C,... Are arranged at the lower part of the partition plate 18 shown in FIG.
[0024]
Also, the sprocket 56 shown in FIG. 1 is fixed to both ends of the conveying roller 20 </ b> C, and an endless chain 58 is engaged with the sprocket 56, and a drive sprocket 62 of the motor 60 is engaged with the chain 58. Therefore, as the rotational speed of the drive sprocket 62 is increased by the motor 60, the rotational speed of the chain 58 increases, and the rotational speed of the transport rollers 20C, 20C,. The plate 12 is transported at a speed increased from a low speed by the transport roller 20A to a high speed by the transport roller 20B. The motor 60 and the chain 58 are arranged on both sides of the transport rollers 20C, 20C... As shown in FIG.
[0025]
Next, the operation of the heating furnace 10 configured as described above will be described.
[0026]
For example, the conveyance path length ratio between the convection heating furnace 14 and the radiation heating furnace 16 is set to 1: 1, and the conveyance speed ratio between the convection heating furnace 14 and the radiation heating furnace 16 is set to 1: 2.
[0027]
And while driving all the conveyance rollers 20A, 20C, and 20B, the glass plate 12 before a heating is mounted in the conveyance rollers 20A, 20A ... arrange | positioned in the vicinity of the inlet part 15 of the convection heating furnace 14. FIG. As a result, the glass plate 12 is carried into the convection heating furnace 14 and is sufficiently heated to a formable temperature by the convection heating device 26 and the electric heater 22 by the low-speed conveyance here.
[0028]
Next, the sufficiently heated glass plate 12 is transferred from the conveying rollers 20A to 20C, and is increased to the speed of the conveying roller 20B by the conveying rollers 20C, and then smoothly transferred to the conveying roller 20B of the radiation heating furnace 16. Delivered. The glass plate 12 is heated at a high temperature by the electric heaters 36 and 38 in the radiation heating furnace 16 while being transported at a speed twice that of the convection heating furnace 14, and then transported to the outside of the furnace from the outlet 17 of the radiation heating furnace 16. Then, it is bent into a predetermined shape by a bending apparatus (not shown).
[0029]
As described above, according to the heating furnace 10 of the present embodiment, when the glass plate 12 is heated at a high temperature, the glass plate 12 is transported at a high speed at twice the speed of the convection heating furnace 14, so that the conventional high temperature heating is performed at a low speed. The generation of RIP can be sufficiently suppressed as compared with the above heating furnace.
[0030]
In addition, according to the heating furnace 10 of the present embodiment, since the convection method is adopted as the heating method on the upstream side of the heating furnace 10 in which the glass plate 12 is conveyed at a low speed, it is possible to prevent warping that occurs when the glass plate 12 is heated. . And since the radiation system was employ | adopted as a heating system of the downstream of the heating furnace in which the glass plate 12 is conveyed at high speed, initial cost and running cost can be reduced rather than a convection system. Therefore, the initial cost and running cost of the heating furnace 10 can be reduced as compared with a conventional heating furnace that employs only convection heating.
[0031]
【The invention's effect】
As described above, according to the method for bending a glass plate and the heating furnace for bending according to the present invention, the glass plate is conveyed at a low speed on the upstream side in the heating furnace and heated to a bendable temperature. Since it is conveyed at a high speed on the downstream side of the inside and heated at a high temperature and then bent into a predetermined shape, the occurrence of RIP can be prevented.
[0032]
In addition, according to the present invention, since the convection method is adopted as the heating method on the upstream side in the heating furnace, it is possible to prevent the warp that occurs when the glass plate is heated, and the downstream side in the heating furnace in which the glass plate is conveyed at high speed. Since the radiation method is adopted as the side heating method, the initial cost and running cost can be reduced as compared with the convection method, and the overall length of the heating furnace can be reduced. Therefore, the initial cost and running cost of the heating furnace can be reduced and the heating furnace can be downsized as compared with a conventional heating furnace that employs only convection heating.
[Brief description of the drawings]
FIG. 1 is an overall perspective view of a glass sheet bending furnace according to the present embodiment seen through. FIG. 2 is a cross-sectional view of the glass sheet bending furnace according to the present embodiment. Plan view showing the structure of the transport roller of the heating furnace for bend forming glass plates
DESCRIPTION OF SYMBOLS 10 ... Heating furnace, 12 ... Glass plate, 14 ... Convection heating furnace, 16 ... Radiation heating furnace, 18 ... Partition plate, 20, 20A, 20B, 20C ... Conveyance roller, 22, 36, 38 ... Electric heater for heating, 24 ... Gas burner for heating, 26 ... Convection heating device, 28 ... Casing, 30 ... Fan, 32 ... Blowing nozzle, 34 ... Motor

Claims (4)

In the method of bending a glass plate, the glass plate is heated by a plurality of transfer rollers disposed in a heating furnace and heated to a bending temperature, and then bent into a predetermined shape.
The glass plate is heated at a low speed on the upstream side in a heating furnace to be heated to a bendable temperature, and is conveyed at a high speed on the downstream side to be heated to a temperature higher than the bendable temperature. Bending method.   The glass plate conveyed at low speed on the upstream side in the heating furnace is heated by convection, and the glass plate conveyed at high speed on the downstream side in the heating furnace is heated by radiation. Item 2. A method for bending a glass sheet according to Item 1.   The glass plate bending method according to claim 1 or 2, wherein the glass plate has a thickness of 3 mm or less. In a glass plate bending furnace comprising a plurality of transport rollers for transporting a glass plate while supporting the lower surface of the glass plate, and heating means for heating the glass plate being transported by the transport roller,
A convection heating furnace in which the conveyance speed of the glass plate of the conveyance roller disposed on the upstream side in the heating furnace is set at a low speed, and the glass plate is heated to a bendable temperature;
The conveyance speed of the glass plate of the conveyance roller arranged on the downstream side in the heating furnace is set to be higher than the velocity of the conveyance roller on the upstream side, and the glass plate is made higher than the bend forming temperature. A heating furnace for bending a glass sheet, comprising: a radiation heating furnace for heating to a temperature of

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