JPH0694019B2 - Heater for drying oven - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heater for a drying oven, and more particularly to a heater provided on a reflector for a drying oven using near infrared rays.

(Prior Art) Conventionally, as a drying oven for drying an object to be dried or the like coated with various paints, a so-called hot air oven or a drying oven utilizing far infrared rays is known. The drying mechanism of these drying paths is understood as follows.

That is, first, the material to be dried, whose surface is coated with a solid coating material composed of a solvent and a resin such as an acrylic resin, is carried into the furnace. Next, hot air is blown or far infrared rays are irradiated. Then, the solvent on the surface of the coating applied to the material to be dried is first evaporated, and the surface loses fluidity and solidifies. When heat such as hot air propagates inside, that is, toward the base material side, the coating film solidifies due to overheating. Then, the solvent inside the surface penetrates the already solidified coating film surface and evaporates. Then, the trace of foaming remains on the surface and pinholes occur. Therefore, in the conventional hot air oven or the drying oven using far infrared rays,
Far infrared rays are radiated and hot air is blown so as to maintain a low temperature at which the solvent on the surface of the coating film does not foam and solidify immediately without rapid heating.

However, these conventional drying ovens have a problem that it takes time to dry because they are dried while maintaining a low temperature at which foaming does not occur. Further, far infrared rays and mid-infrared rays have a problem that the plastic coating film is difficult to penetrate and in the case of an object to be dried having a complicated shape, the shadow portion which is inevitably dried cannot be completely dried.

Therefore, a drying furnace utilizing near infrared rays has been proposed as a means for shortening the drying time of the material to be dried. For example, "Near infrared liquid, powder, coating, stove" (Actual Kaihei 1-151873), "Paint baking furnace dedicated light board"
(Actual Kaihei 2-43217), USP 4,863,375 "BAKING METHOD FO
R USE WITH LIQUID OR POWDER VARNISHING FURNACE ''
(Baking method for youth with liquid or powder varnishing furnish). In these conventional examples, a drying furnace using near infrared rays, or a drying method in which a high temperature portion and a low temperature portion are sequentially formed and dried in the drying furnace, or a ceramic reflection plate is provided behind the near infrared lamp, There is also a statement that a heater is provided in the ceramic reflector.

(Problems to be Solved by the Invention) However, it has been demanded to further improve the efficiency of a drying furnace using near infrared rays.

(Means for Solving the Problem) The present invention is directed to a near-infrared lamp 22 installed toward the inside of the drying furnace 11.
Installed on the back of the reflector 24 installed on the side of the
24 Drying furnace 11 characterized by heating the surface to maintain the temperature higher than the ambient temperature and above the dew point of paints, solvents, etc. used, and installed toward the inside of the drying furnace 11. Near infrared lamp 22
Installed on the back of the reflector 24 installed on the side of the
(24) A heater for a drying furnace, which is characterized in that the surface is heated and maintained at a temperature higher than the ambient temperature of the drying furnace at 3 to 5 ° C and above the dew point of the paint, solvent, etc. used.

(Function) The heater heats the reflection plate to maintain the surface of the reflection plate at a temperature higher than the ambient temperature in the drying furnace and above the dew point of the paint, solvent, etc. used. Alternatively, the heating is performed so that the temperature of the reflecting surface is 3 to 5 ° C. higher than that of the atmosphere of the drying oven and is maintained above the dew point of the paint, solvent, etc. used, so that the surface of the reflector plate is maintained above the dew point of the solvent gas. Therefore, it is possible to avoid the tar content in the solvent from sticking to the reflecting surface, and it is possible to avoid lowering the reflection efficiency of the reflecting surface of the reflecting plate.

(Embodiment) FIG. 1 showing a front center sectional view of an embodiment of the present invention,
FIG. 2 showing the same plan view, FIG. 3 showing a perspective view around the lamp, FIG. 4 showing the same plan view, FIG. 5 showing the same plan view of another embodiment, and a cross-sectional view of a near infrared lamp. The description will be given with reference to FIG. 6 showing the same and FIG. 7 showing a sectional view of another near-infrared lamp.

(11) is a drying oven. The drying oven (11) has a carry-in port (1
2) It is made of a metal hollow prism having an opening for the carry-out port (13). (14) is an introduction section, (15) is an effective section, and (16) is an unloading section. The carry-in port (12) and the carry-out port (13) are effective parts (1
It is installed lower than 5), and the introduction part (14) and the carry-out part (16) are installed at an angle. In this embodiment, the inner surface of the effective portion (15) is made of a metal plate having a surface with high reflection efficiency.
Mirror finishing may be performed. (17) is a conveyor. The conveyor (17) is installed so that it can be transported inside and outside the drying furnace (11). (18) is an article to be dried which is locked on the conveyor (17). The material to be dried (18) is, for example,
A 1-mm iron plate is coated with 30 μ of solvent and paint made of resin such as acrylic resin.

(21) is a near infrared irradiation device. Two near infrared irradiation devices (21) are installed in this embodiment, but three or more near infrared irradiation devices (21) may be installed at equal intervals. Near-infrared irradiation device (21),
It has a near-infrared lamp (22), a lamp bank (23), and a reflector (24). The infrared rays emitted from the near infrared lamp (22) are 1-1,8μ, preferably 1-1,5μ.
Near-infrared light having a peak at is effective. The nine near-infrared lamps (22) are installed vertically, but the number is not limited. The near-infrared lamp (22) may have a circular cross section as shown in FIG. 6 or a parabolic curved surface as shown in FIG.
Install a reflector (26) on the back of 5). The lamp bank (23) has a near-infrared lamp (22) fixed on the front surface, and the surface on the near-infrared lamp (22) side is made of a metal having a mirror surface treatment or a metal having a high reflection efficiency. The reflection plate (24) has a mirror-finished surface, but may be made of a metal having good reflection efficiency, and is made of a plate-like body having a curved tip. The reflection plate (24) may further have a flat plate shape that is not curved.
(27) is the reflector rotation axis. Reflector rotation axis (27)
As shown in FIG. 4, the lamp banks (23) are vertically mounted on the lamp banks (23) side of the two reflectors (24) as shown in FIG. 4, but as shown in FIG. , The reflectors (24), (24) are integrally formed, and the lamp bank (2
3) You may install one on the back of the part. (31) is a motor for driving the rotary shaft (27) of the reflector plate. The drive motor (31) rotates in the forward and reverse directions to rotate the reflecting plate rotation shaft (27) and move the tip of the reflecting plate (24) toward the center of the drying oven (11) or the wall surface. Reference numeral (32) is a control device including a micro computer or the like, which controls driving of the driving motor. (33) is a non-contact type sensor, which is installed on the upstream side of the conveyor (17) of the near-infrared irradiation device (21),
Detects the proximity of the object to be dried (18). (34) is a conveyor drive motor. Both the sensor (33) and the conveyor drive motor (34) are connected to the control device (32). The near infrared ray irradiation device may be fixed.

In the embodiment shown in FIG. 9, the reflection plate (24) does not follow the movement of the object to be dried (18), and the reflection rotation axis (27).
The reflection plate (24) is rotated with the center of rotation as the center of rotation, and the direction of light collection is set in advance.

(41) is a heater. The heater (41) is an electric heater and is installed on the back surface of the reflection plate (24). Heater (4
In 1), the reflector (24) is heated to maintain the surface of the reflector (24) at a temperature higher than the ambient temperature of the drying furnace (11). Although the dew point of the paint, solvent, etc. used varies depending on the component, the heating of the paint, solvent, etc., whose temperature on the reflecting surface is higher than the temperature of the drying furnace (11) atmosphere by 3 to 5 ° C It suffices that the temperature is at the dew point or higher, and the high temperature of 5 ° C. or higher is not always necessary.

Next, the operation of the embodiment will be described. Items to be dried (18)
Is coated with a solvent and a resin such as acrylic resin in the previous step, and is locked to the conveyor (17). The conveyor (17) is driven by the conveyor drive motor (34). The material to be dried (18) is conveyed to the conveyor (17), enters the drying furnace (11) through the carry-in port (12), and reaches the effective section (15). Then, in the embodiment shown in FIGS. 4 and 5, the proximity of the material to be dried (18) is detected by the sensor (33). When the sensor (33) detects it, it sends a signal to the controller (3
2) Transmit to. The control device (32) has a drive motor (3
1) is driven to rotate each reflection plate (25) to the a side.
The control device (32) is also connected to the conveyor driving motor (34), and the conveyor drive speed signal is also transmitted. The control device (32) synchronizes the reflection plate (25) with the driving speed of the conveyor by the input driving speed signal of the conveyor.
It is moved in the direction b, that is, in the moving direction of the object to be dried (18) according to the moving speed. As the downstream sensor (33) sequentially senses, the near-infrared irradiation device (21) on the downstream side is also sequentially activated. When the material to be dried (18) is out of the irradiation range of the near infrared irradiation device, for example, the sensor (33)
After a lapse of a certain period of time after the detection by the control device (32), the drive motor (31) is driven by the control device (32) and the reflecting plate rotation shaft (27) is directed to the front again.

The reflection of the near infrared lamp (22) by the reflector (25)
The energy density of the near-infrared lamp (22) when passing through the near-infrared lamp (22) before the object to be dried (18) increases, and the surface temperature of the object to be dried (18) increases. Further, since the reflection plate (25) moves in synchronization with the conveyance speed of the material to be dried (18), the irradiation time of the near infrared lamp (22) is extended.

In the embodiment shown in FIG. 9, the light collecting direction is determined by the preset position of the reflecting plate (24),
The temperature becomes higher in the light collecting direction. Therefore, it becomes possible to increase the difference between the high temperature and the low temperature in the furnace as compared with the case where the reflector is not used.

When the near-infrared rays are irradiated to the material to be dried, most of the near-infrared rays penetrate the coating film, are absorbed at the position of 1 to 2 nm from the surface of the metal plate, the temperature of the metal surface rises, and the coating film is heated from inside. Then, the curing starts near the metal surface. Therefore, rapid heating is performed before the fluidity of the coating film surface is reduced, the solvent is blown away, and solvent bubbling and pinholes are not generated after the fluidity of the coating film surface is lost. Therefore, curing can be performed in a short time, and the drying furnace itself can be downsized.

The heater (41) heats the reflection plate (24) and maintains the surface of the reflection plate (24) at a temperature higher than the ambient temperature of the drying furnace (11). As for heating, the temperature of the reflecting surface is 3 to 5 than the atmosphere of the drying oven (11).
By maintaining the temperature at a high temperature above the dew point of the paint, solvent, etc. used, the surface of the reflector (25) is maintained above the dew point of the solvent gas. That is, although the near-infrared irradiation device (21) is attached to the wall surface of the drying furnace (11), the temperature of the wall surface tends to be lower than the ambient temperature, but is heated by the heater (41). Therefore, it is possible to prevent tar and the like in the solvent from sticking to the reflecting surface, and to avoid a decrease in the reflection efficiency of the reflecting surface of the reflecting plate (24).

Example 1 A drying oven having a shape as shown in FIGS. 1 and 2 was used, a near-infrared irradiation device was fixed, and a temperature change on the surface of an object to be dried was measured depending on the presence or absence of a reflector. .

Effective part (15) 5,000mm Effective part transit time 10 minutes Near infrared irradiation device 2 units Near infrared irradiation device interval 2,800mm Distance from end of effective part to near infrared irradiation device center 1,600m
m Iron plate thickness (bonded steel plate) 2 mm Atmosphere temperature 160 ° C Fig. 8 shows a with and without a reflector. Reference numeral c is a reflector mounting portion, I is an introduction portion, and II is an effective portion.

When the reflector is attached, the energy density of infrared rays is concentrated in front of the lamp, and the energy density at the furnace end is reduced, so the initial temperature is higher when the reflector is not installed than when the reflector is attached. However, the ascending point is slow,
The surface temperature reverses at a point of about 4 minutes from the effective part entrance. In the vicinity of the lamp bank, the temperature rise gradient becomes larger with the reflection plate, intersects with the temperature curve without the reflection plate in front of the lamp bank, and thereafter the surface temperature with the reflection plate becomes higher. This indicates that the material to be dried is rapidly irradiated with the temperature in front of the lamp and the temperature rises rapidly, the temperature of the coating film rises rapidly, the crosslinking reaction of the resin is promoted as the evaporation of the solvent progresses, and the degree of crosslinking increases. It is possible to increase.

(Effect of the Invention) Therefore, in the present invention, it is possible to avoid a decrease in the reflection efficiency of the reflection surface of the reflection plate.

[Brief description of drawings]

FIG. 1 is a front central sectional view of an embodiment of the present invention, FIG. 2 is a plan view of the same, FIG. 3 is a perspective view of the vicinity of a lamp, FIG. 4 is a plan view of the same, and FIG. 5 is another embodiment. FIG. 6 is a sectional view of a near-infrared lamp, FIG. 7 is a sectional view of another near-infrared lamp, FIG. 8 is a temperature change diagram of an embodiment, and FIG. 9 is a further embodiment. FIG. (11) …… drying oven, (21) …… near infrared irradiation device, (2
2) …… Near infrared lamp, (24) …… Reflector for drying oven,
(41) …… Heater for drying oven.

Claims (2)

[Claims] 1. The drying furnace 11 is installed on the back of a reflector 24 installed on the side of a near-infrared lamp 22 installed toward the inside of the drying furnace 11, and the surface of the reflector 24 is heated to a temperature higher than the ambient temperature of the drying furnace 11. A heater for a drying furnace, characterized in that it is maintained above the dew point of paints, solvents, etc. used in 2. The drying furnace 11 is installed on the back side of a reflecting plate 24 installed on the side of a near-infrared lamp 22 installed toward the inside of the drying furnace 11, and the surface of the reflecting plate 24 is heated to 3 to 3 times the ambient temperature of the drying furnace.
A heater for a drying furnace, which is maintained at a high temperature in the range of 5 ° C and above the dew point of paints, solvents, etc. used.