JP2985630B2 - Heat supply method to paint baking drying oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying heat to a baking / drying oven, and more particularly, to a technique for preventing the occurrence of thermal deformation of an object to be coated in the oven when a painting line is temporarily stopped. About.

[0002]

2. Description of the Related Art Conventionally, as a paint baking drying oven used in an automobile painting process, a hot air circulation system (convection type) in which combustion gas generated from a heat source or air heated to a high temperature circulates in the drying oven, Many of them have been adopted at least for some of them. This hot air circulation system can averagely heat regardless of the shape of the object to be coated, and is suitable for a mass production line.

FIG. 5 schematically shows a heat supply system in an example of such a hot air circulation type paint baking / drying furnace. The coating baking / drying furnace 51 shown in FIG. 5 is a mountain furnace in which the floor 52 of the furnace is higher than the maximum height h of the entrance opening in order to reduce the outflow of hot air at the entrance / exit. The inside of the furnace 51 is divided into a heat-up zone 55 on the entrance 53 side and a keep zone 56 on the exit 54 side.

[0004] The supply of heated air to the furnace 51 is performed as follows. That is, the gas burner 57
The combustion gas obtained by the combustion of
Through the heat exchanger 59 and the heat exchanger 5
In 9, the return air sent from the furnace 51 through the return duct 60 is heated by heat exchange with the combustion gas to form heated air. Then, the heated air is sent into the furnace 51 through the heated air duct 61.
In this example, the heated air duct 61 is branched into two parts on the way, and opens into the heat-up zone 55 toward the inlet side of the furnace 51, and a keep zone 56 facing the outlet side of the furnace. And a second duct portion 61b that opens at the bottom. In the heating air duct 61, the first duct portion 61a and the second duct portion 61b
The portion closer to the heat exchanger 59 than the branching portion 62 that branches off is referred to as a main duct portion 61c. First duct 6
In the middle of 1a and the 2nd duct part 61b, the ventilation fans 63 and 64 were each installed. In FIG. 5,
Reference numeral 65 denotes a combustion air introduction line, reference numeral 66 denotes a combustion air suction fan, reference numeral 67 denotes a combustion gas circulation fan, reference numeral 6
Reference numeral 8 denotes a combustion gas discharge line, reference numeral 69 denotes a combustion gas circulation line, reference numeral 70 denotes a recirculation air outside lead-out line, reference numeral 71 denotes an exhaust fan, reference numeral 72 denotes an exhaust line, and reference numerals 73 and 74 denote switching dampers.

In general, in a paint baking / drying furnace, particularly in a furnace having a short furnace length, it is desirable to raise the temperature of a coating material that has entered the furnace to a required temperature in a relatively short time.
Side, the heat-up zone 55,
It is necessary to set the furnace temperature higher than the temperature on the side, that is, the keep zone 56.

Conventionally, as shown in FIG. 5, when the heated air heated by one heat exchanger is branched and supplied to both the heat-up zone 55 and the keep zone 56, the combustion gas is passed through the heat exchanger 59. , First duct section 6
1a flows from the left side (left side) to the second duct portion 61b side (right side), whereby the return air sent through the return duct 60 passes through the left side of the heat exchanger and passes through the right side. Heat to a higher temperature. In the main duct section 61c immediately after the heat exchanger 59, the heated air passing therethrough maintains the state in which the left side of the duct is hot and the right side is low temperature, and reaches the branch section 62, so that the heating air having a relatively high temperature is heated. Air can be sent into the first duct portion 61a, and the heat-up zone 55 is maintained at the desired set temperature as described above.

[0007] A coating object 50 such as a resin bumper or an automobile body, the surface of which is painted in a painting booth.
Is conveyed to a coating baking drying furnace 51 having the above-mentioned structure at a constant speed by a conveying means such as a conveyor, and the coating film is baked and dried.

Conventionally, resin parts for automobiles such as resin bumpers are susceptible to deformation due to heat.
In a line separate from the car body, it was produced by baking and drying at a relatively low temperature, for example, about 120 ° C, using resin paint, but recently, due to the improvement in rigidity and heat resistance of resin parts In addition, it is possible to employ a paint for a steel sheet, and baking and drying is performed at a relatively high temperature, for example, about 140 ° C. By adopting the paint for steel sheet in this way, for example, advantages such as reduction in paint unit price, facilitation of color matching with the car body, and reduction in steps by simultaneous baking and drying with the car body are brought about.

[0009]

However, when baking and drying of a paint applied to the surface of a resin component is performed using such a baking and drying furnace, baking is performed at a relatively high temperature, particularly using a steel plate paint. In the case of drying, when the baking drying furnace is started up, a part of the resin component located in the furnace is heated and melted or deformed.

[0010] That is, the coating process is operated by a shift system such as a day shift system and a night shift system. During this shift, the line is temporarily stopped and the heat supply to the paint baking / drying furnace is also stopped. Is done. When restarting the line, the furnace temperature of the baking / drying furnace is lower than the set temperature.
The heating power of the gas burner is increased, and the reflux air is heated to a higher temperature than in the standard state and heat is sent into the furnace. However, in the conventional heat supply system, as described above, the high temperature is supplied to the first duct portion 61a. During the start-up, air having a temperature excessively higher than the set temperature temporarily flows near the outlet of the first duct portion in the heat-up zone. In addition, the above-described inconvenience occurs in the resin component located at the site when the line is stopped.

The occurrence of such a problem can be prevented as long as the object to be coated does not have to be transported into the furnace until the furnace temperature stabilizes at the set temperature. In the coating process, the transport means in the coating booth and the baking / drying oven are non-independent, so it is not possible to operate only the transporting means in the baking / drying oven between the systems, and the retention of objects to be coated in the furnace is not possible. It was inevitable.

Accordingly, an object of the present invention is to provide a method of supplying heat to a paint baking oven which prevents the above-mentioned problems from occurring when the paint baking oven is started.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a heating gas pipe which branches off into two or more sections from a heating section to reach a furnace and opens at two or more locations in the furnace. A method of supplying heat in a paint baking drying oven having: a divertable rectifying plate that controls a flow of a heated gas from the heating unit to each branch pipe at a branch of the pipe; when the drying oven temperature becomes lower than a predetermined temperature, the time of the furnace temperature to increase the output of the heating unit raised to a predetermined temperature, before
In the pipeline in front of the branch,
One branch pipe side is hot and the lower part of the baking drying oven
There is a bias in the temperature distribution where the other branch line toward
Of the heated gas in the state of
Excessive temperature of the heated gas passing through the first branch line by interrupting the flow by interfering with the flow straightening plate and distributing a large amount of heat to the other branch lines toward the lower temperature part of the baking / drying oven. Suppress the rise, increase the output of the blower fan provided on the first branch line, increase the flow rate of the heated gas passing through the first branch line, and reach the desired set temperature in a short time. And rise
And it is characterized in Rukoto is.

[0014]

As described above, according to the present invention, as the heat supply system,
In a hot air circulation type baking / drying furnace having a heating gas line which is branched into a plurality of parts on the way from one heating section and each of which opens to a predetermined position of the baking / drying furnace, the heating gas line is changed to a branching part. Since the flow rectifying plate is arranged freely, the angle of the flow rectifying plate is appropriately changed, and the flow of the heating gas having a temperature deviation in position flowing from the heating unit side is applied to the flow rectifying plate. This makes it possible to appropriately change the distribution of heat using the gas supplied from the heating unit as a medium to each branch pipe. Therefore, for example, it is possible to change the heat distribution to each branch line during the standard operation and the heat distribution to each branch line when the output of the heating unit is further increased, for example, at the time of furnace startup. The problem caused by almost the same distribution is that the heating gas at an unnecessarily high temperature is introduced at the time of furnace startup into a furnace part which is maintained at a relatively high temperature during standard operation, for example, a heat-up zone. As a result, the object to be coated, which has been stagnated in the furnace, is not deformed or melted.

In this way, the heat distribution (heat per unit volume of the heated gas) to the first branch pipe toward the high temperature part of the furnace during the furnace startup is suppressed, so that this first If the flow rate of the heated air passing through the branch pipe is about the same as in the standard operation, the amount of heat required to raise the temperature to the predetermined set temperature in the high-temperature part may be less than Although there is a possibility that it will take a long time to ascend, in the present invention, together with the deflection of the rectifying plate, the output of the blower fan provided on the first branch pipe is increased,
By increasing the flow rate of the heated gas passing through the first branch pipe, the decrease in the heat distribution is compensated for, and the temperature can be increased to a desired set temperature in a short time.

[0016]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. FIG. 1 schematically shows a configuration of an example of a paint baking / drying furnace according to the present invention. The coating baking drying oven 11 shown in FIG. 1 is a tunnel type hot air circulation baking drying oven. In order to reduce the outflow of hot air at the entrance and exit, the floor surface 12 of the oven is placed at the maximum height of the entrance opening. H
This furnace has a higher height than that of the conventional baking / drying furnace 51 shown in FIG. 5, except that a baffle plate is provided in a heated air duct as described later. It should be noted that in FIG.
The reference numerals to which 0 is added indicate the corresponding parts in FIG.

In the baking / drying oven 11 shown in FIG. 1, the inlet 13 is divided into a heat-up zone 15 and the outlet 14 is divided into a keep zone 16, and heat is supplied to each zone by one heating unit. Is divided into two parts by a duct branched on the way.

A brief description of this heat supply system is as follows.
The paint baking / drying furnace 11 includes a gas burner 17 installed outside the furnace as a heating source.
7, a combustion air suction fan 2
6 is connected to a combustion air introduction line 25 and a combustion gas circulation line 29 so that the combustion air can be taken in from the outside or the combustion gas once burned together with the combustion air can be circulated again for use. Has become. On the other hand, a combustion gas line 18 is connected to the outlet side, and this combustion gas line 18 is connected to the inside of the heat exchanger 19 as a heating medium pipe, and passes through the inside of the heat exchanger 19 to the rear of the combustion gas line. After having the circulation fan 27, it branches into the combustion gas circulation line 29 and the combustion gas discharge line 28 at a branch portion provided with the switching damper 34. In addition, air outlets 3 provided at various parts in the furnace 11 are provided.
7, an air recirculation duct 20 is connected. The air recirculation duct 20 is extended to the heat exchanger 19, passes through the inside of the heat exchanger 19 as a medium pipe to be heated, and then is heated by a heating air duct. The reference numeral 21 extends into the furnace 11 again. The heating air duct 21 is branched into two parts on the way, and opens toward the inlet side of the furnace 11 and opens in the heat-up zone 15 (first heating air outlet 35). Keep zone 1 facing the side
6 and a second duct portion 21b that is opened (second heated air outlet 36). The heated air duct 2
1, the first duct portion 21a and the second duct portion 2
The portion closer to the heat exchanger 19 than the branch portion 22 that branches to the main duct 1b is referred to as a main duct portion 21c. In the middle of the first duct portion 21a and the second duct portion 21b, blower fans 23 and 24 are provided, respectively, and by operating these fans, the furnace 11 → the heating unit (heat exchanger 19) → A circulating flow of air is formed in the furnace 11. In this embodiment, the air recirculation duct 2
0, and has a return air outside lead-out line 30 branched from the middle of the switching damper 33, if necessary.
The exhaust fan 3 on the exhaust line 32 communicating with this line 30 and the combustion gas exhaust line 28
By operating 1, the return air can be exhausted to the outside of the system.

The rectifying plate 1 is arranged at the branch portion 22 of the heated air duct 21. The current plate 1 in this embodiment has the rotating shaft 2 on a straight line orthogonal to all of the axis of the first duct portion 21a, the axis of the second duct portion 21b, and the axis of the main duct portion 21c. , FIG. 2
As shown in the figure, this rotating shaft is connected to the driving device 3 provided outside the duct through the duct 21 airtightly, and the plate surface is turned around the rotating shaft in the direction of arrow k in the figure. It is possible to change to. However, in the present invention, the flow straightening plate does not substantially interfere with the flow of the heated air sent through the main duct portion 21c and branched into the first duct portion 21a and the second duct portion 21b. The size, shape, turning direction, and the like are not particularly limited as long as they can form a state capable of sufficiently interfering by turning.

The heat supply to the paint baking / drying furnace by the heat supply system having such a configuration is performed as follows.
That is, the combustion gas obtained by the combustion of the gas burner 17 is sent through the combustion gas line 18 to the heat exchanger 19, where the reflux gas sent from the furnace 11 through the reflux duct 20 is returned. The air is heated by heat exchange with the combustion gas to form heated air. Here, the combustion gas in the heat exchanger 19 is supplied to the first duct 2
Since it is configured to flow from the 1a side (left side) to the second duct portion 21b side (right side), the return air sent through the return duct 20 passes through the left side of the heat exchanger. It is heated to a higher temperature than what passes on the right.
In the main duct portion 21c immediately after the heat exchanger 19, the heated air passing therethrough reaches the branch portion 22 while maintaining the state in which the left side of the duct is hot and the right side is low temperature.

In the standard operation state, keep zone 1
In order to maintain the furnace temperature of the heat-up zone 15 set higher than that of the heat-up zone 6, the heat-up zone 1 is higher than the second duct portion 21b communicating with the keep zone 16.
It is necessary to feed heated air at a higher temperature (calorific value) to the side of the first duct portion 21a that communicates with the fifth duct 5. For this reason,
In the state where the temperature distribution is biased as described above,
In order to divide the flow of heated air that has reached the above without greatly disturbing the flow, the flow straightening plate 1 is oriented substantially along the pipe shape of the branch portion 22, for example, as shown in FIG. 3 (a) or (b), Orientation.

On the other hand, when the temperature inside the furnace falls below the set temperature after the coating line is temporarily stopped or the like, the heating power of the gas burner 17 is increased in order to raise the temperature inside the furnace to a predetermined temperature. The air is heated to a higher temperature than in the standard state. In this case, as in the standard operation state, heated air having a higher temperature (calorific value) is sent to the first duct portion 21a side than to the second duct portion 21b side. If this occurs, extremely high temperature heated air is blown out from the first blow-out port 35 that opens in the heat-up zone 15, and there is a possibility that the coating object 10 that has stayed in this portion may be thermally deformed or melted. is there. Therefore, in this embodiment, the
As described above, the heated air passing through the main duct portion 21c is
The left side of the duct is hot and the right side is low temperature.
Of the heated air reaching the branch portion 22
The flow of the air on the high temperature side (left side) interferes with the plate surface of the flow straightening plate 1, and the air on the high temperature side (left side) is increased more so that the second duct portion 21
In order to guide to the b side, the current plate 1 is oriented in a direction inclined toward the second duct portion 21b, for example, as shown in FIG.

In addition, since the temperature of the heated air flowing to the first duct portion 21a side is reduced by arranging the current plate 1 inclining in this manner, the temperature inside the furnace is reduced. In this case, the output of the blower fan 23 located on the first duct portion 21a is improved, and the flow rate of the heated air passing through the first duct portion 21a is increased, together with the inclined arrangement of the current plate. That is, if the flow rate is the same, it takes a longer time than in the case where the first duct portion 21a is not inclined to increase the in-furnace temperature in the heat-up zone 15 communicating with the first duct portion 21a to the set temperature, This is because there is a possibility that the predetermined baking and drying treatment cannot be performed sufficiently.

FIG. 4 schematically shows the structure of a paint baking drying oven used in an experiment conducted to confirm the effect of the present invention. This furnace has its effective length (AA)
') Is about 36 m, and seven trolleys on which resin bumpers as objects to be coated are mounted can be mounted between A-A'. In this baking drying oven 11,
The opening (first outlet 35) of the first duct portion 21a is A-
When seven trolleys are placed between A's, they are present at the positions where the second and third trolleys are located from the A end side. In this experiment, temperature measurement was performed at point X, which is a position near the opening of the first duct portion 21a, and at point Y (the center of the duct), which was an intermediate position between the main duct portions 21c, and the flow rate was measured by the rectifying plate arrangement. The effect was confirmed. The set temperature of the heat-up zone 15 during the standard operation is 165 ° C., and the temperature measured at the point X at this time is 155 ° C. At this time, the ratio of the flow rate passing through the first duct section 21a to the total flow rate (m ³ / min) of the heating air passing through the heating air duct 21 is about 45.7%, and the flow rate passing through the second duct section 21b. Was about 54.3%.

Here, first, the output of the gas heater is increased from the state in which the ambient temperature in the heat-up zone 15 is 55 ° C. in a configuration in which the current plate is not disposed in the branch portion 22 (conventional example), Was brought up to the standard operating condition. At this time, the ratio of the flow rate passing through the first duct portion 21a and the flow rate passing through the second duct portion 21b to the total flow rate (m ³ / min) of the heating air passing through the heating air duct 21 was the same as in the standard operation. As a result, of the seven trucks left between A-A 'at the time of the start-up operation, the side portions of the resin bumper mounted on the trucks located on the second and third trucks from the A end side (The horizontal distance between the side portion of the bumper and the first outlet 35 in the furnace is about 20 mm), causing a problem of melting. During the start-up operation, the maximum value of the temperature measured at the Y point of the main duct is about 200 ° C., the average value is about 190 ° C., and the temperature measured at the X point of the first duct is Maximum value is 1
70 ° C, average value was about 165 ° C. It took about 30 minutes to raise the ambient temperature in the heat-up zone 15 to the set temperature.

Next, a rectifying plate is arranged at the branch portion 22, and FIG.
Orientation as shown in (c) (Example of the present invention), the output of the gas heater was increased from the state in which the ambient temperature in the heat-up zone 15 was 55 ° C. It was put into operation. At this time, the ratio of the flow rate passing through the first duct portion 21a to the total flow rate (m ³ / min) of the heating air passing through the heating air duct 21 is about 6%.
8.5%, and the ratio of the flow rate passing through the second duct portion 21b was 31.5%. As a result, no trouble occurred in any of the resin bumpers placed on each of the carts left in the furnace during the start-up operation, and the coating was baked and dried well. During the start-up operation, the temperature measured at the point Y of the main duct section has a maximum value of about 200 ° C. and an average value of about 1 as in the case of the conventional example.
Although it was 90 ° C., the maximum value of the temperature measured at point X of the first duct portion was 165 ° C., and the peak value did not increase as in the conventional example. The average value of the temperature measured at the point X was almost the same as that of the conventional example. Further, the time required to raise the ambient temperature in the heat-up zone 15 to the set temperature was reduced to about 15 minutes.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the configuration of the illustrated embodiment. For example, in the above-described embodiment, the heated air duct is branched into two in the middle. However, a duct having a shape of three or more branches can be similarly applied, and the heating air duct can be changed to a branch part. By arranging the rectifying plates that can be freely directed, the distribution of heat supplied from one heating unit to each branch path can be controlled. In addition, as described above, the size and shape of the current plate are not particularly limited, and the current plate is not limited to a flat plate, but may be a curved plate.
Further, in the above-described embodiment, the heating unit is of an indirect heating type using a gas burner and a heat exchanger, but it is possible to adopt a heating source other than a gas burner, and it is also possible to employ a direct heating type. It may be something. In the above embodiment, the baking and drying furnace is a mountain furnace, but may be a flat furnace. In addition, the baking drying oven
If the heating booth of the hot air circulation system for supplying heat to a plurality of parts from one heating unit as described above is provided in a part thereof, for example, a structure such as a combination of a dark infrared furnace and a hot air circulation furnace is used. And the like.

[0028]

As described above, according to the present invention, the heating section is branched into two or more parts on the way to reach the furnace, and the heating is performed through the heating gas pipe which is opened at two or more parts in the furnace. When introducing the gas into the paint baking drying oven, a deflectable rectifying plate for controlling the flow of the heated gas from the heating unit to each of the branch conduits is disposed at the branch of the conduit, so that the direction of the rectifier plate is Can be changed according to the situation, so that the heat distribution to each branch pipeline can be changed. For this reason, for example, in a coating line in which a resin component is coated using a coating material for a steel sheet and baked and dried at a relatively high temperature, the amount of heat supplied (total amount) must be increased when the furnace is started up as compared with that during normal operation. Even in the situation, by appropriately changing the heat distribution to each branch line, it is possible to prevent the problem of blowing out the heated gas that is too hot from the first branch line toward the high temperature part of the furnace. As a result, problems such as thermal deformation and heat melting of the resin component staying in the furnace are solved, and a good baking and drying process can be performed. Further, in conjunction with the deflecting operation of the rectifying plate, in order to increase the output of the blower fan provided on the first branch line and increase the flow rate of the heated gas passing through the first branch line, Such a decrease in heat distribution makes it possible to raise the temperature to the set temperature in a short time without causing a problem such as the inability to raise the temperature to the set temperature in the high temperature part of the furnace or requiring a long service life. is there.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of a heat supply system in one embodiment of a coating baking drying oven according to the present invention;

FIG. 2 is a partially cutaway perspective view showing an arrangement of a current plate in one embodiment of the present invention;

FIGS. 3A to 3C are schematic diagrams each showing a turning direction of a current plate;

FIG. 4 is a schematic diagram showing the configuration of a baking / drying furnace used in the experiment.

FIG. 5 is a schematic diagram showing a configuration of a heat supply system in an example of a conventional paint baking / drying furnace.

[Explanation of symbols]

1 ... current plate, 2 ... rotating shaft,
3 ... Drive device, 11 ... Paint baking drying oven, 12 ...
Hearth floor, 13: furnace inlet, 14: furnace outlet,
15 heat up zone, 16 keep zone, 17 gas burner, 18 combustion gas line, 19 heat exchanger, 20 reflux duct, 21 heated air duct, 21a first duct part, 21b second Duct portion, 21c: trunk duct portion, 22: branch portion, 23, 24: blower fan,
25 ... combustion air introduction line, 26 ... combustion air suction fan, 27 ... combustion gas circulation fan, 28 ... combustion gas discharge line, 29 ... combustion gas circulation line, 30 ... recirculation air outside lead-out line, 31 ... exhaust fan 32: exhaust line, 33, 34: switching damper, 35: first heated air outlet, 36: second heated air outlet, 37: air outlet.

Claims (1)

(57) [Claims] 1. A method for supplying heat in a paint baking / drying furnace having a heating gas pipeline having two or more branches from a heating section on the way to a furnace and opening to two or more parts in the furnace. A rectifying plate that controls the flow of heated gas from the heating section to each branch pipe is disposed at a branch of the pipe, and when the temperature in the paint baking / drying furnace falls below a predetermined temperature,
When increasing the output of the heating unit to raise the temperature in the furnace to a predetermined temperature, the pipeline is directed toward the high-temperature portion of the baking / drying furnace in the pipeline before the branch portion.
The first branch line side is hot, and the lower temperature of the baking oven
The temperature distribution where the other branch pipe side toward the
Of the heated gas in a certain state, the high temperature side that has reached the branch
Interfering with the flow straightening plate, interrupting the flow, distributing a large amount of heat to the other branch lines toward the lower temperature part of the baking / drying furnace, and causing excessive heating gas passing through the first branch line. Suppress the temperature rise, increase the output of the blowing fan provided on the first branch line, increase the flow rate of the heated gas passing through the first branch line, and set the desired set temperature in a short time. To above
Heat supply methods to paint baking drying furnace, wherein Rukoto raising.