JPH05138107A - Drying furnace for coating - Google Patents

Abstract

PURPOSE:To enable the heating up uniformly over the entire part of a work by providing plural far IR panel heaters for irradiating the work with far IR rays and plural air nozzles for discharging breezes of ordinary temp. to the work in such a manner that approximately the same sections of the work are irradiated with the IR rays and the breezes. CONSTITUTION:The hot wind past a burner 7 is introduced by a circulation fan 6 to heat radiating ducts 5 provided on the side walls of a drying furnace body 4 and the flank 1a of a vehicle body 1 is mainly heated up by radiation heat. On the other hand, the vinyl chloride resin applied on the rear 1b of the floor where the heating up is most difficult among the various parts of a vehicle body 1 is cured by the heat energy from the far IR panel heaters 2. The breezes are blown out of air nozzles 3 toward the sections approximately the same as the radiation sections of the far IR energy so that these sections are further uniformly irradiated with the far IR energy at the time of radiating the heat energy from the far IR panel heaters 2. Far IR panel heater units 8 are invertably provided on the floor surface 9 of the drying furnace by means of hinge members 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drying oven used in a painting process for automobiles and the like.

[0002]

2. Description of the Related Art Needless to say, the drying process of the coating film plays an important role in the coating process, but it is necessary to drain water after pretreatment, drain water after water polishing, or force putty or sealing material. A drying oven is also required for drying.

Various types of commonly used coating drying ovens are known depending on various conditions such as installation location.
For example, it can be classified into a tunnel type drying oven and a box type drying oven depending on its shape, and a radiation type drying oven and a convection type drying oven depending on the heat source. BACKGROUND ART As a coating drying oven for automobiles, a tunnel-type radiation drying oven, a convection drying oven, or a drying oven combining a radiation type and a convection type is widely used.

As shown in FIG. 8, a typical hot air circulating type drying oven has a hot air blowing duct 31 provided at the lower portion of the side wall of a drying oven main body 30, and a hot air suction duct 3 at the upper portion of the side wall.
Two are provided. The hot air in the furnace sucked from the hot air suction duct 32 is circulated by the circulation fan 33 to the combustion device 3
After being guided to No. 4 and heated to a predetermined temperature, it is again blown into the furnace from the hot air blowing duct 31. In addition, the combustion device 34
A fresh air for combustion is introduced by a fan 35 into the. On the other hand, the radiation type drying furnace is shown in FIG.
As shown in FIG. 3, a heat radiation duct 36 through which hot air circulates is provided on the side wall of the drying furnace main body 30, and the hot air that has passed through the combustion device 37 is guided into the heat radiation duct 36 by the circulation fan 38 and is irradiated from the surface of this heat radiation duct. The inside of the drying furnace main body 30 is heated by the radiant heat and is maintained at a predetermined temperature.

While such a convection drying oven is excellent in thermal efficiency, it has a drawback that dust in the oven adheres to the uncured coating surface to circulate the air in the oven, resulting in a coating film defect. ing. On the contrary, the radiant drying oven is inferior in thermal efficiency to the convection drying oven, but is excellent in preventing the above-mentioned coating film defects. Therefore, in the conventional drying oven for coating, radiant drying is used in an uncured state immediately after coating, and convection drying is used in a state where the coated surface is cured to some extent. That is, the inlet side zone of the drying furnace is of a radiant type and the outlet side zone is of a convective type so that the advantages of both drying methods can be utilized.

[0006]

By the way, when the coating material is dried, it is necessary to raise the temperature uniformly over the entire coating surface. However, when the coating object having a complicated shape such as an automobile body is dried. Depending on the part, the temperature may not be sufficiently raised, or conversely, the temperature may be too high. It is necessary to hold the thermosetting paint at a predetermined temperature or higher for a predetermined time to dry it. For example, in the currently widely used top coat paint and intermediate coat paint, the temperature of 140 ° C. or higher is kept for 20 minutes or longer. There must be. If the temperature is not raised to 140 ° C or if the temperature is not raised to 140 ° C but the temperature is not maintained for 20 minutes or more, the drying condition is insufficient. As a result, the coating film performance is deteriorated and the coating film is peeled off. On the other hand, if the temperature of the coated surface rises too much, the curing rate of the coating resin will be faster than the evaporation rate of the solvent and the two cannot be balanced, and the coating surface will initially cure and the solvent vapor will escape from the inside. This causes a so-called "pinhole" that breaks through the surface when it evaporates and escapes to the outside. In the radiation type drying furnace described above,
The side surface of the vehicle body facing the side wall provided with the heat dissipation duct,
It was difficult to maintain a uniform temperature over the entire vehicle body because the temperature rising rate was greatly different in other parts, especially the underfloor, roof and hood. On the other hand, in the convection type drying oven, it is possible to maintain a uniform drying temperature over the entire vehicle body in order to circulate the air inside the oven, but as described above, the circulating air causes dust inside the oven to adhere to the coating surface. It was not possible to make up for the drawback of doing.

The present invention has been made in view of the problems of the prior art as described above, and makes it possible to uniformly raise the temperature of the entire work while preventing the dust in the furnace from adhering to the coated surface. Moreover, it is an object of the present invention to provide a coating drying oven having excellent thermal efficiency.

[0008]

The present invention for achieving the above object comprises a plurality of far infrared panel heaters for irradiating a work with far infrared rays and a plurality of air nozzles for discharging a breeze at room temperature to the work. In the coating drying furnace, the far infrared rays and the breeze are provided so as to irradiate substantially the same portion of the work.

[0009]

In the present invention thus constructed, the coating material or the like applied to the work is cured by the thermal energy from the far infrared panel heater. When the thermal energy is radiated from the far infrared panel heater, air is emitted. Since a slight breeze is blown from the nozzle toward the portion that is substantially the same as the far infrared energy radiating portion, the far infrared energy can be irradiated more uniformly, and a uniform temperature rise can be obtained over the entire work.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing a coating drying furnace according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a far infrared panel heater and an air nozzle according to the embodiment.

The drying oven for coating of this embodiment comprises a drying oven body 4
A radiating duct 5 is provided on the side wall of the drying furnace main body 4 in the longitudinal direction thereof.
The hot air that has passed through the heat dissipation duct 5 to the combustion device 7 again.
It is supposed to return to. The inside of the drying furnace main body 4 is heated by the radiant heat emitted from the surface of the heat radiation duct, and is maintained at a predetermined temperature. According to such a conventional radiant drying method, the temperature rise on the side surface 1a of the vehicle body 1 becomes sharp and the floor space,
In the present embodiment, the far-infrared panel heater unit 8 which irradiates heat to the underfloor, which has a particularly slow temperature rising rate, cannot be balanced against the temperature rise of the horizontal plane 1b such as the roof and the hood.
Is provided. This far infrared panel heater unit 8
Is a plurality of far-infrared panel heaters 2 provided on a substrate 11 which is provided on a floor 9 of a drying furnace through a hinge member 10.
And a plurality of air nozzles 3 provided between the far infrared panel heaters 2. Air nozzle 3
20 to 30 supplied from the air source 12 are installed substantially parallel to the radiation direction of the far infrared panel heater 2.
The normal temperature air at 0 ° C. is blown onto the object to be coated in a slight breeze of 0.5 to 1.0 m / s.

On the other hand, the reason why the far infrared panel heater is adopted in this embodiment is as follows. That is, when the paint is dried, a method of irradiating the effect of the coating film with an electron beam or ultraviolet rays is applied, but these are not the coating film curing by heat, and the coating components are respectively affected by the electron beam or ultraviolet ray. It uses a special paint that polymerizes or crosslinks. On the other hand, infrared rays can be directly applied to thermosetting paint drying,
Far-infrared rays (wavelength 4 μm or more) are particularly effective for drying the thermosetting coating material. Generally, the resin that forms the paint is 4
It has a property of well absorbing a wavelength of μm or more. The molecules of the paint activate their molecular motion by absorbing such energy, and frictional heat is generated between the molecules.
On the other hand, the absorption of energy causes intense collisions between molecules and progresses the volatilization of solvents etc., and at the same time, a phenomenon of connecting other molecules with each other, that is, a cross-linking reaction occurs, and when this becomes a polymer substance, Has dried and cured. When heated in a convection-type drying oven, heat gradually penetrates from the outside to the inside of the coating film, not only does it take a considerable amount of time to dry, but if only the surface is initially cured, When the solvent vapor evaporates, it breaks through the surface and escapes to the outside, which may cause coating defects such as pinholes, but when irradiated with far infrared rays, energy is absorbed even inside the coating and heating is done at once. Since it is performed, the heating time is shortened and uniform heating is possible.
Far infrared heaters include far infrared tube type heaters, far infrared lamp type heaters, and far infrared panel heaters.
In this embodiment, a far infrared panel heater is used. In this far infrared panel heater, a nichrome wire resistance heating element is built in a planar radiation surface, and a far infrared radiation element is applied or baked on the radiation surface of the outer surface thereof. This radiating element is mainly formed of a semiconductor titanium oxide obtained by reducing titanium oxide as a main component. The far-infrared tube heater and the far-infrared lamp heater each have a heating surface of a high temperature, so that a certain distance (usually 350 mm or more) needs to be provided in order to uniformly radiate heat to the heat-receiving surface. However, since the radiation intensity weakens in inverse proportion to the square of the distance, in this embodiment, the far-infrared panel which can be arranged close to the object to be coated and which can radiate heat uniformly It uses a heater.

Although the surface of the far infrared panel heater 2 is curved in this embodiment, this reflects energy radiated at an angle nearly parallel to the radiating surface and again reflects the energy to the object to be coated 1. This is to radiate the light at an angle close to vertical, whereby more energy can be concentratedly radiated to the object to be coated 1.

According to the coating drying oven of this embodiment having such a configuration, the side surface 1a of the vehicle body 1 is mainly heated by the radiant heat from the heat radiation duct 5 provided on the side wall of the drying oven main body 4, and With respect to the underfloor 1b of the vehicle body 1 which is the most difficult to heat up, the vinyl chloride resin or the like applied to the underfloor can be cured by the thermal energy from the far infrared panel heater 2. In radiating the thermal energy from the far infrared panel heater 2, since a slight breeze is blown from the air nozzle 3 to a site substantially the same as the site where the far infrared energy is radiated, the far infrared energy can be more uniformly radiated. It is possible to obtain a uniform temperature rise over the entire floor space. Further, since the far infrared panel heater unit 8 is foldably installed on the floor surface 9 of the drying oven via the hinge member 10, the far infrared panel heater unit 8 is used when performing cleaning work or inspection in the drying oven. The heater unit 8 can be erected and does not interfere with the work.

The present invention is not limited to the above-mentioned embodiments and can be modified in various ways. FIG. 3 is a vertical sectional view showing a coating drying furnace according to another embodiment of the present invention, and FIG. 4 is a horizontal sectional view of the same embodiment.

The present embodiment is a specific example applied to a drying oven for coating the automobile bumper 1, in which an air pipe 13 connected to an air source 12 is attached inside the drying oven main body 4. An air nozzle 3 is provided from the air pipe 13 to blow room temperature air at 20 to 30 ° C. to the bumper 1 transported in the drying furnace main body 4 in a slight breeze state of 0.5 to 1.0 m / s. Further, the far infrared panel heater 2 is attached between the air nozzles 3. Then, as shown in FIG. 4, a plurality of sets of such far infrared panel heater units 8 are provided in the drying furnace body. Even in the drying oven according to the present embodiment configured as described above, the coating material applied to the bumper 1 can be cured by the thermal energy from the far infrared panel heater 2, but the far infrared panel heater 2 When radiating the thermal energy, a slight breeze is blown from the air nozzle 3 toward a portion substantially the same as the far infrared energy radiating portion, so that the far infrared energy can be evenly radiated and uniform over the entire bumper surface. A temperature rise can be obtained.

Next, the temperature rising effect of the coating drying oven according to the present invention will be described in comparison with a conventional drying oven.
FIG. 5A is a schematic diagram when the embodiment of the present invention is applied, where “Y, Z” are test pieces, “2” is a far infrared panel heater, “3” is an air nozzle, and “A, B, C,
“D” indicates the measurement points. In addition, FIG.
Is a graph showing a temperature rise curve at measurement points A, B, C, and D. FIG. 6 is a schematic view when only a conventional far infrared panel heater is used as a comparative example of the embodiment shown in FIG. 5, where “Y, Z” are test pieces, “2” is a far infrared panel heater, “A, B, C, D” respectively indicate measurement points. Further, FIG. 6B is a graph showing a temperature rising curve at the measurement points A, B, C and D. FIG. 7 is a schematic view when a conventional hot air heater is used as a comparative example of the embodiment shown in FIG. 5, where “Y, Z” are test pieces and “1”.
4 "is a heater for generating hot air, and" A, B, C, D "are measurement points. Further, FIG. 7B shows the measurement point A,
It is a graph which shows the temperature rising curve in B, C, and D. As is clear from this result, when only the far-infrared panel heater shown in FIG. 6 is used, the positions A and B close to the panel heater rise in temperature relatively quickly, but the positions C and D far from the panel heater are relatively high. Is slowed down, and as a result, the temperature of the entire work is not uniform. Further, according to the convection drying shown in FIG. 7, although the temperature is raised more uniformly than in the comparative example shown in FIG. 6, variations due to parts are observed in the initial temperature rise. On the other hand, according to the present embodiment shown in FIG. 5, even in the initial temperature rise, the variation due to the site is not observed, and the uniform temperature rise can be obtained over the entire work.

[0018]

As described above, according to the present invention, a plurality of far-infrared panel heaters for irradiating a work with far-infrared rays and a plurality of air nozzles for discharging a breeze at room temperature to a work are provided. Since the and are provided so as to irradiate almost the same part of the work, it is possible to prevent the dust in the furnace from adhering to the coating surface, and to enable a uniform temperature rise over the entire work, and a coating with excellent thermal efficiency. A drying oven can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a coating drying oven according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a far infrared panel heater and an air nozzle according to the embodiment.

FIG. 3 is a longitudinal sectional view showing a coating drying furnace according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of the same embodiment.

FIG. 5 is a schematic diagram and a graph showing a temperature rise curve when the embodiment of the present invention is applied.

FIG. 6 is a schematic diagram and a graph showing a temperature rise curve when only a conventional far infrared panel heater is used as a comparative example of the embodiment shown in FIG.

FIG. 7 is a schematic diagram and a graph showing a temperature rising curve when a conventional hot air heater is used as a comparative example of the embodiment shown in FIG.

FIG. 8 is a vertical cross-sectional view showing a conventional convection drying oven.

FIG. 9 is a vertical sectional view showing a conventional radiation type drying furnace.

[Explanation of symbols]

1 ... Work, 2 ... Far infrared panel heater, 3 ... Air nozzle, 4 ... Drying oven main body.

Claims (1)

[Claims] 1. A far-infrared panel heater for irradiating a work with far-infrared rays and a plurality of air nozzles for ejecting a breeze at room temperature onto the work, the far-infrared rays and the breeze irradiating substantially the same portion of the work. A drying oven for painting, which is provided as described above.