Baking method and baking device

Abstract

To provide a baking method and a baking device in a powder baking coating of a heat exchanger which performs melting and hardening powdered paint for a short time to form a coating film and save space.SOLUTION: A baking method S includes a melting step S1, a temperature rising step S2, and a holding step S3. A blow device 20 disposed adjacent to a workpiece W, which is a heat exchanger having a fin at an end part of a nozzle 22, blows hot wind to the workpiece W to melt and harden powdered paint coated on the workpiece W to form a coating film. In the melting step S1, hot wind at a first wind speed H1 that does not blow off the powdered paint is blown to the workpiece W to melt the powdered paint. In the temperature rising step S2, hot wind at a second wind speed H2 larger than the first wind speed H1 is blown to the workpiece W to rapidly rise temperature of the powdered paint melted in the melting step S1. In the holding step S3, hot wind at the same second wind speed H2 is blown to the workpiece W to harden the powdered paint whose temperature is risen in the temperature rising step S2 to form the coating film on the surface of the workpiece W.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for firing a heat exchanger. [Background technology]

[0002] Conventionally, methods and devices for baking a painted workpiece have been known. For example, Patent Document 1 discloses a device that includes a baking chamber capable of accommodating the workpiece and a hot air supply means, and bakes the painted workpiece with hot air from the hot air supply means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-326205 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, to form a coating on a workpiece coated with powder paint, it was necessary to heat the workpiece for a long time while transporting it through a baking furnace that maintained a uniform temperature in order to melt and harden the powder paint without blowing it away. This also tended to require large equipment.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a space-saving baking method and baking device for powder baking coating of heat exchangers, which melts and hardens powder paint in a short time to form a coating film. [Means for solving the problem]

[0006] The baking method of the present invention is a baking method (S) in which the work (W) of a heat exchanger having a fin at the end of a nozzle (22) is blown with hot air by a blowing device (20) positioned close to the work (W) to melt and harden the powder coating applied to the work to form a coating film, and includes a melting step (S1), a heating step (S2), and a holding step (S3).

[0007] In the melting stage, the powder coating is melted by blowing hot air at a first air speed (H1) onto the workpiece, which does not blow the powder coating away.

[0008] In the temperature-raising stage, the workpiece is blown with hot air at a second air velocity (H2) that is greater than the first air velocity, thereby rapidly raising the temperature of the powder coating material that has been melted in the melting stage.

[0009] In the holding stage, the workpiece is further blown with hot air at the same second wind speed, hardening the powder paint heated in the heating stage and forming a coating on the surface of the workpiece.

[0010] The baking device of the present invention is a baking device (1) that melts and hardens powder paint applied to a workpiece (W) of a heat exchanger having fins to form a coating film, and is equipped with a baking furnace (10), a blowing device (20), and a condition setting section (30).

[0011] The firing furnace (10) has a conveying device (11) for conveying the workpiece.

[0012] The blowing device is provided inside the firing furnace, and the end of the nozzle (22) is positioned close to the workpiece to blow hot air onto the workpiece.

[0013] The condition setting unit variably sets the temperature and wind speed of the hot air blown by the blowing device.

[0014] The condition setting unit can set a first wind speed (H1) at which the powder paint is not blown away, and a second wind speed (H2) that is greater than the first wind speed.

[0015] With the above-described configuration, the baking method and baking apparatus of the present invention can melt and harden powder paint in a short time to form a coating film in powder baking coating of a heat exchanger, and can also save space. [Brief explanation of the drawings]

[0016] [Figure 1] An example of a workpiece is a heat exchanger with fins. [Figure 2]FIG. 2 is a schematic diagram showing fins of a workpiece. [Figure 3] FIG. 2 is a schematic diagram showing the fins of the workpiece in detail. [Figure 4] FIG. 1 is a schematic diagram showing a baking apparatus according to an embodiment. [Figure 5] FIG. 5 is a view taken in the direction of the arrow V in FIG. 4. [Figure 6] FIG. 1 is a schematic diagram illustrating a blowing device according to an embodiment. [Figure 7] FIG. 1 is a block diagram illustrating a baking method according to an embodiment. [Figure 8] 1 is a graph showing a temperature rise curve according to an embodiment. [Figure 9] FIG. 10 is a schematic diagram of a firing device of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (method and apparatus) of the present invention will now be described with reference to the accompanying drawings. This embodiment is intended for a corrugated fin type condenser work mounted on an automobile.

[0018] 1 to 3 show an example of a workpiece W of a heat exchanger (condenser) having fins F to which one embodiment is applied. Fig. 1 is a front view during assembly. The workpiece W is a substantially rectangular parallelepiped with a horizontally long rectangular front and a certain depth.

[0019] 2 shows the details of the workpiece W. The workpiece W has fins F and has a multi-layer structure in which a plurality of tubes T and fins F are alternately stacked.

[0020] In this embodiment, the tubes T are made of a material with a wall thickness of about 0.3 mm, and the fins F are made of a material with a wall thickness of 0.1 mm or less. The width wT of the tubes T is about 1.5 mm, and the width wF of the space between adjacent tubes T formed by the fins F is about 5 to 8 mm.

[0021] Fig. 3 shows the details of the fins F. The fins F have many slit holes (louvers L) to ensure ventilation and heat dissipation.

[0022] 4 and 5 show a baking apparatus 1 of this embodiment. The baking apparatus 1 melts and hardens a powder coating applied to a workpiece W of a heat exchanger having fins F to form a coating film. The purpose of the coating is to prevent rust and improve the appearance. The baking apparatus 1 includes a baking furnace 10, a transport device 11 for transporting the workpiece, a blowing device 20, and a condition setting unit 30.

[0023] The workpiece W coated with the powder paint is conveyed on the conveying device 11 in a conveying direction dW in a lying state, and is blown by the blowing device 20 in a blowing direction dH.

[0024] 6 shows the blowing device 20 together with the transfer device 11 and the workpiece W. The blowing device 20 is provided inside the firing furnace 10. The blowing device 20 has a muffle 21 and a nozzle 22.

[0025] As shown in Figures 5 and 6, the nozzle 22 is shaped to extend in a direction perpendicular to the conveying direction dW so as to ensure that air is ventilated thoroughly into the gaps formed by the fins F of the workpiece W that is laid on its side.

[0026] 4 to 6, the end of the nozzle 22 is positioned close to the workpiece W, and hot air is blown onto the workpiece W. A clearance C between the tip of the nozzle 22 from which the hot air is blown and the workpiece W is maintained at a short distance of approximately 100 mm, which increases the efficiency of heating by the hot air.

[0027] 4 variably sets the temperature and wind speed of the hot air blown by the blowing device 20. It is also possible to set a first wind speed H1, which is a wind speed that is suppressed to a level that does not blow away the powder paint, and a second wind speed H2, which is a wind speed greater than the first wind speed.

[0028] With the above configuration, when the workpiece W is transported on the transport device 11 and is subjected to hot air blown from above by the blowing device 20, the complex fin structure of the workpiece W causes the hot air to blow through the gaps in the louvers L of the fins F, for example, along the path R shown in Figure 3.

[0029] Many different hot air paths are formed, overlapping randomly and intricately, resulting in the hot air forming a turbulent current. This allows the hot air to transfer heat evenly to the entire workpiece W, improving the heat transfer rate and achieving high-speed heating.

[0030] 7 shows a baking method S of this embodiment. In the baking method S, the end of a nozzle 22 is blown onto the workpiece W of a heat exchanger having fins F by a blowing device 20 arranged close to the workpiece W, and the powder coating applied to the workpiece W is melted and hardened to form a coating film.

[0031] The firing method S includes a melting stage S1, a temperature-raising stage S2, and a holding stage S3. Fig. 8 shows a temperature-raising curve according to the firing method S of this embodiment. The following description will also refer to Fig. 4.

[0032] In the melting stage S1, the workpiece W is blown with hot air at a first air velocity H1, which is an air velocity at which the powder coating is not blown away, to melt the powder coating.

[0033] In this embodiment, the first air velocity H1 is 2 m / sec, and the air is blown at this air velocity for 30 seconds (Fig. 8), which melts the powder coating applied to the workpiece surface and changes it into a state where it can be rapidly heated at a higher air velocity.

[0034] In this embodiment, during the melting stage S1, both the ambient temperature and the surface temperature of the workpiece W rise to around 200°C, and thereafter, throughout the heating stage S2 and the holding stage S3, this ambient temperature and the surface temperature of the workpiece W are maintained at approximately 200°C.

[0035] In the temperature raising stage S2, the workpiece W is blown with hot air at a second air velocity H2, which is faster than the first air velocity, to rapidly raise the temperature of the powder coating material melted in the melting stage.

[0036] In this embodiment, the second air velocity H2 is 10 m / sec, and the air is blown at this air velocity for 40 seconds (FIG. 8). The powder paint and the workpiece W, which have melted on the surface of the workpiece in the melting stage S1 and are no longer blown away, are further blown at an increased air velocity to rapidly raise the temperature.

[0037] As a result, as shown in FIG. 8, the temperature inside the workpiece (1) also rises to around 200° C., and the curing reaction of the powder paint progresses.

[0038] Throughout the melting stage S1 and the temperature rising stage S2, the temperature gradually rises even in areas where it is difficult to raise the temperature, such as the inside of the work (2), and finally rises to over 180°C.

[0039] In the holding stage S3, the workpiece is further blown with hot air at the same second air velocity, hardening the powder coating material heated in the temperature-raising stage S2 and forming a coating film on the surface of the workpiece.

[0040] In this embodiment, in the holding step S3, hot air is blown for an additional 50 seconds at the same air speed as in the temperature increase step S2, thereby hardening the powder coating material applied to the workpiece W throughout, including the inside of the workpiece where the temperature does not easily increase, and completing the formation of the coating film.

[0041] Figure 9 shows a conventional baking device (comparison example). Conventionally, when forming a coating by melting and hardening a workpiece coated with a powder coating such as an anti-rust coating, it was common to melt and harden the workpiece over a long period of time in a baking furnace maintained at a relatively low temperature. For this reason, in order to improve work efficiency, measures such as placing five workpieces on one tray were required, which made it easy for the equipment to become large.

[0042] On the other hand, the workpiece W targeted in this embodiment is a heat exchanger having fins F, and is a component composed of a large number of fins F having louvers L. Therefore, by devising a method for blowing hot air, it is possible to create turbulent air and blow it through, which is thought to enable high-speed heating that distributes heat evenly throughout the workpiece.

[0043] Therefore, in this embodiment, by combining hot air heating control (melting and hardening by two-stage air speed control) with the product characteristics of a high thermal conductivity configuration, the work surface is placed very close to the hot air outlet, creating a turbulent hot air flow that speeds up melting and hardening, significantly reducing the time required for these processes.

[0044] Specifically, in the conventional one-tray five-piece system, it took about 15 minutes per tray, but in this system, even though only one workpiece is fed at a time, it is possible to form a coating film per workpiece in about two minutes, so even with five workpieces, coating formation can be completed in about 10 minutes.

[0045] Furthermore, the conventional technology shown in Figure 9 required a large facility area of, for example, 14 meters x 4.5 meters, and was also tall due to the need to use five trays per tray. On the other hand, in this embodiment, the facility area is only 7.8 meters x 1.8 meters, and the height is kept down by using a one-workpiece flow system.

[0046] (Other embodiments) In the above embodiment, the nozzle 22 shown in Figure 6 is used, and the blowing device 20 is a so-called sirocco fan (Figures 4-5), but the nozzle configuration and blowing means are not limited to these and can be changed depending on the situation as long as it is possible to blow hot air by close placement.

[0047] The temperature and wind speed conditions set by the condition setting unit 30 are not limited to fixed conditions, and may be feedback controlled so that the conditions are changed as needed based on parameters such as the actual work temperature detected by a temperature sensor.

[0048] As described above, the present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0049] 20: Blow device, 22: Nozzle, H1: First wind speed, H2: Second wind speed, S: Firing method S1: Melting stage, S2: Heating stage, S3: Holding stage, W: Workpiece

Claims

1. A baking method (S) in which a workpiece (W) of a heat exchanger having a fin at an end of a nozzle (21) is blown with hot air by a blowing device (20) arranged close to the workpiece, and a powder coating applied to the workpiece is melted and hardened to form a coating film, a melting step (S1) of melting the powder coating by blowing hot air onto the workpiece at a first air velocity (H1) at which the powder coating is not blown away; a heating step (S2) in which hot air having a second wind speed (H2) greater than the first wind speed is blown onto the workpiece to rapidly heat up the powder coating material melted in the melting step; a holding step (S3) in which the workpiece is further blown with hot air at the second air velocity to harden the powder coating heated in the temperature raising step, thereby forming a coating film on the surface of the workpiece; A baking method comprising:

2. A baking device (1) for melting and hardening a powder coating applied to a workpiece (W) of a heat exchanger having fins to form a coating film, a baking furnace (10) having a conveying device (11) for conveying the workpiece; a blowing device (20) provided inside the firing furnace, the end of a nozzle (22) being positioned close to the work, for blowing hot air onto the work; a condition setting unit (30) for variably setting the temperature and wind speed of the hot air blown by the blowing device; Equipped with The baking device, wherein the condition setting unit is capable of setting a first wind speed (H1) at which the powder coating material is not blown away, and a second wind speed (H2) that is greater than the first wind speed.

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