Induction heating coil and coating method

Abstract

To provide an induction heating coil that can be used to induction heat and quench-coat an aluminum-based workpiece.SOLUTION: An induction heating coil 1 for heating an aluminum-based workpiece 100 during a coating process has a spiral coil portion 5 and a flat coil portion 6. The induction heating coil 1 has a workpiece placement space 18 for placing a workpiece in the center. The spiral coil portion 5 has a conductive wire 10 wound in a spiral shape over a plurality of stages. Both ends of the spiral coil portion 5 is open. The spiral coil portion 5 has a roughly rectangular planar shape. The flat coil portion 6 is arranged at least on one side of the openings and has a conductive wire configuring a flat loop. The spiral coil portion 5 and the flat coil portion 6 are electrically connected in series.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an induction heating coil used when baking a workpiece made of an aluminum-based material, and also to a coating method for coating a box-shaped workpiece made of an aluminum-based material. [Background technology]

[0002] Baking coating is a widely known method for forming a coating film on metal. Baking coating involves applying a bake-hardening paint to a workpiece and then heating the paint to harden it. In baking paint, a heat source such as an electric heater is used to raise the temperature of the paint. That is, the workpiece coated with paint is brought close to an electric heater to heat and harden the paint. Furthermore, Patent Document 1 discloses a method of increasing the temperature of a workpiece by induction heating to heat and harden the paint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-200289 A Summary of the Invention [Problem to be solved by the invention]

[0004] The painting method disclosed in Patent Document 1 is intended for painting automobiles, and the material to be painted is an iron-based material. When an iron-based workpiece is exposed to high-frequency magnetic flux, eddy currents are generated inside the workpiece, and the workpiece is heated due to eddy current loss. In addition, when an iron-based workpiece is exposed to high-frequency magnetic flux, the workpiece is also heated due to hysteresis loss. Thus, iron-based materials are easily heated by induction. In Patent Document 1, an induction heating coil is moved around an object to be coated, and the paint applied to the object is baked.

[0005] In contrast, aluminum-based materials have no hysteresis loss and are therefore unsuitable for induction heating. Therefore, with an induction heating coil such as that disclosed in Patent Document 1, it is difficult to heat the workpiece to a temperature sufficient to harden the paint applied to the aluminum-based material.

[0006] In view of the above-mentioned problems, the present invention aims to provide an induction heating coil capable of induction heating an aluminum-based workpiece and hardening coating it. Another object of the present invention is to provide a coating method for baking coating a box-shaped workpiece made of an aluminum-based material. [Means for solving the problem]

[0007] An embodiment for solving the above problem is an induction heating coil for heating an aluminum-based workpiece during painting, This induction heating coil is characterized in that it has a helical coil section having a work placement space in the center for placing a workpiece, in which a conductive wire is wound in a spiral shape in multiple stages and has an approximately rectangular planar shape with both ends open, and a planar coil section that is arranged in at least one of the openings and in which the conductive wire forms a planar loop, and the helical coil section and the planar coil section are electrically connected in series.

[0008] The target workpiece is made of an aluminum-based material and is coated with paint. The workpiece is placed in the workpiece placement space. As a result, the peripheral surface of the workpiece is surrounded by the spiral coil portion of the induction heating coil. In addition, the end surface of the workpiece is covered by the planar coil portion. When an alternating current is passed through the induction heating coil, an alternating magnetic field is generated by the induction heating coil, and five surfaces of the workpiece are exposed to the alternating magnetic field generated by the induction heating coil of this embodiment. As a result, eddy currents are generated on each surface of the workpiece, causing the workpiece to heat up due to Joule heat, hardening the paint on the surface. The workpiece targeted by this embodiment is made of an aluminum-based material, and with the induction heating coil of this embodiment, eddy currents can be generated throughout the entire workpiece, allowing the workpiece to be heated to a temperature at which the paint will harden.

[0009] In the above aspect, it is preferable that the spiral coil portion is covered with an insulating material.

[0010] According to this aspect, it is possible to prevent the conductive wire of the spiral coil portion from directly contacting the workpiece, and it is possible to reduce the distance between the workpiece and the spiral coil portion.

[0011] In each of the above-mentioned aspects, it is desirable that the coil assembly has a first power supply portion and a second power supply portion, the planar coil portion has straight portions arranged approximately in parallel and a connection portion connecting the ends of the straight portions, one of the straight portions being divided into an input line portion and an output line portion, the first power supply portion being connected to the input line portion by a first power supply line crossing one opening of the spiral coil portion, the output line portion being connected to one end of the spiral coil portion, and the other end of the spiral coil portion being connected to the second power supply portion by a second power supply line extending outside the spiral coil portion.

[0012] According to the induction heating coil of this embodiment, the temperature of the workpiece can be raised evenly.

[0013] It is desirable that two of the induction heating coils described above are disposed at positions facing each other, and that the workpiece is disposed so as to straddle the workpiece arrangement spaces of both induction heating coils.

[0014] According to this aspect, the entire periphery of the workpiece is covered with the induction heating coil.

[0015] An embodiment relating to a painting method includes applying paint to a box-shaped workpiece made of an aluminum-based material, placing the workpiece in a workpiece placement space of any of the induction heating coils described above, passing an alternating current through the induction heating coil to raise the temperature of the workpiece, and baking the paint onto the workpiece.

[0016] According to the coating method of this embodiment, a strong coating film can be formed on the surface of the workpiece. Effect of the Invention

[0017] According to the induction heating coil and painting method of the present invention, an aluminum-based workpiece can be induction heated and hardened and painted. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a perspective view of a workpiece and an induction heating coil according to the embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view of the induction heating coil of FIG. 1, divided into individual parts. [Diagram 3] 1 is a cross-sectional view showing a state in which a workpiece is placed in an induction heating coil. [Figure 4] FIG. 11 is a perspective view of a workpiece and an induction heating coil according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described. The workpiece 100 used in this embodiment is a box made of an aluminum-based material. As shown in Fig. 1, the workpiece 100 is a box made of aluminum or an alloy containing aluminum. The workpiece 100 is roughly a rectangular parallelepiped, with five faces covered and only one face open. For convenience, the workpiece 100 is referred to as a front plate 101, a back plate 102, left and right side plates 103 and 105, and a top plate 106. The workpiece 100 is a semi-finished product in the middle of being painted, and each surface is coated with paint 110. Note that the paint 110 is not limited to a liquid, and may be a powder.

[0020] The induction heating coil 1 is roughly divided into a main body 2 and a power supply side member 3. The main body 2 is composed of a spiral coil portion 5 and a planar coil portion 6. The power supply side member 3 is composed of a first power supply portion 30, a second power supply portion 32, a first power supply line 40, and a second power supply line 41.

[0021] The main body 2 is composed of a series of conductive wires 10. The conductive wires 10 constituting the main body 2 are all tubular and hollow inside. 2, the spiral coil portion 5 of the main body portion 2 has a three-dimensional shape that is approximately a rectangular parallelepiped and both ends are open. That is, the spiral coil portion 5 is covered on all four sides and is open on the top and bottom sides of the drawing. For ease of explanation, the opening on the top side of the drawing is referred to as the top opening 16, and the opening on the bottom side of the drawing is referred to as the bottom opening 17. The spiral coil portion 5 is formed by winding and stacking rectangular loop portions 11 each having the same size and shape, and its planar shape is a rectangle having a square opening 12 in the center. That is, the spiral coil portion 5 has a plurality of loop portions 11, each of which has a rectangular shape in a plan view, stacked vertically in multiple stages, and the loop portions 11 in each stage are electrically connected in series. 3, the conductive wire 10 of the spiral coil portion 5 is tubular and hollow as described above. An insulating material 15 is provided on the outside of the conductive wire 10 of the spiral coil portion 5. The loop portions 11 are overlapped with a small gap between them. The loop portions 11 may be overlapped closely with an insulating material 15 interposed therebetween. The spiral coil portion 5 has a space in the center, which functions as a work placement space 18 .

[0022] The planar coil portion 6 is a one-turn coil having an oval planar shape. That is, the planar coil portion 6 has a first straight portion 20 and a second straight portion 21 arranged substantially parallel to each other, and has arc-shaped connection portions 23 and 25 that connect the ends of the first straight portion 20 and the second straight portion 21. The planar coil portion 6 is disposed in a position covering one opening (upper opening 16) of the spiral coil portion 5. That is, the planar coil portion is in a position to cover one opening (upper opening 16) of the spiral coil portion 5.

[0023] The first straight portion 20 of the planar coil portion 6 is divided into two portions, one of which is an input line portion 27 and the other of which is an output line portion .

[0024] The first power supply part 30 and the second power supply part 32 are both copper plates and face each other with an insulating material 33 interposed therebetween. The first power feed line 40 and the second power feed line 41 are both tubular and hollow. The first power feed line 40 and the second power feed line 41 are connected to pipe connection members 43 and 45, respectively. The first feed line 40 is a member that connects the first feed portion 30 and the input line portion 27 of the planar coil portion 6. That is, the first feed line 40 is connected to the input line portion 27 by crossing one opening (the upper opening 16) of the spiral coil portion 5. The second power supply line 41 is a member that connects the lower end of the spiral coil portion 5 and the second power supply portion 32. The second power supply line 41 protrudes outside the spiral coil portion 5 and does not overlap with the opening (lower opening 17) of the spiral coil portion 5.

[0025] Electrically, the induction heating coil 1 is configured such that a planar coil portion 6 and a spiral coil portion 5 are connected in series between a first power supply portion 30 and a second power supply portion 32 . That is, the first power supply section 30 is connected to the input line section 27 of the planar coil section 6 by the first power supply wire 40, the input line section 27 is connected to one end of the connection section 23 and to one end of the second straight section 21 of the connection section 23, the other end of the second straight section 21 is connected to one end of the connection section 25, and the other end of the connection section 25 is connected to one end of the output line section 28. In addition, the other end of the output line portion 28 is connected to the upper end of the spiral coil portion 5, the lower end of the spiral coil portion 5 is connected to one end of the second power supply line 41, and the other end of the second power supply line 41 is connected to the second power supply portion 32.

[0026] Next, a coating method using the induction heating coil 1 will be described. The surface of the workpiece 100 is coated with paint 110 in a separate coating process. Then, the workpiece 100 is placed in the workpiece placement space 18 of the induction heating coil 1. In practice, the induction heating coil 1 is held by a lifting device (not shown) and moves up and down. Then, the workpiece 100 is placed under the induction heating coil 1, and the induction heating coil 1 is lowered to place the workpiece 100 in the work placement space 18. In this embodiment, since there is an opening (lower opening 17) at the bottom of induction heating coil 1, induction heating coil 1 will not collide with workpiece 100 when induction heating coil 1 is lowered.

[0027] 3, the workpiece 100 is accommodated in the workpiece arrangement space 18 of the induction heating coil 1, with the inner surface of the spiral coil portion 5 of the induction heating coil 1 closely facing the front plate 101, back plate 102, and left and right side plates 103, 105 of the workpiece 100. In addition, the planar coil portion 6 of the induction heating coil 1 faces the top plate 106 of the workpiece 100. In this embodiment, since the conductive wire 10 constituting the spiral coil portion 5 has an insulating material 15, the conductive wire 10 of the induction heating coil 1 does not come into direct contact with the front plate 101, rear plate 102, left and right side plates 103, 105 of the workpiece 100, and therefore no short circuit occurs. Therefore, the distance between the spiral coil portion 5 and the workpiece 100 can be made extremely small.

[0028] In this state, high frequency current is applied to the induction heating coil 1 via the first power supply part 30 and the second power supply part 32, and cooling water is passed through the induction heating coil 1 via the piping connection members 43, 45. As a result, a high-frequency magnetic field is generated in the induction heating coil 1, which generates eddy currents and heats the internal workpiece 100. The paint 110 on the surface of the workpiece 100 is then heated and hardened.

[0029] Since the induction heating coil 1 of this embodiment is close to the workpiece 100, it can heat the surface of the workpiece 100 even if the workpiece is made of aluminum, because the induction heating coil 1 of this embodiment can simultaneously heat the five surfaces of the workpiece 100 (front plate 101, back plate 102, left and right side plates 103 and 105, and top plate 106), so that even if there are areas where direct heating is insufficient, this is compensated for by heat conduction from the surroundings, and the entire workpiece can be brought to a temperature where it can be hardened and painted.

[0030] In the embodiment described above, the temperature of the workpiece 100 is increased by one induction heating coil 1, but the temperature of the workpiece 100 may be increased by two induction heating coils 1 as shown in FIG. A heating device 50 shown in FIG. 4 has two induction heating coils 1 arranged opposite to each other, and the two induction heating coils 1 can be moved closer to or farther apart by a moving device (not shown). 4, the workpiece 100 is arranged across the workpiece arrangement spaces 18 of both induction heating coils 1. That is, about half of the area of ​​the workpiece 100 is in the workpiece arrangement space 18 of the induction heating coil 1, and the other half of the area of ​​the workpiece 100 is in the workpiece arrangement space 18 of the other induction heating coil 1. According to this embodiment, the planar coil portion 6 of one induction heating coil 1 and the planar coil portion 6 of the other induction heating coil 1 are positioned to face each other, and six sides of the workpiece 100 are covered with the induction heating coils 1. 4, the two induction heating coils 1 have the same size, but they may be different in size. That is, the number of turns of the spiral coil portion 5 of one induction heating coil 1 may be different from the number of turns of the spiral coil portion 5 of the other induction heating coil 1.

[0031] In the embodiment described above, the planar coil portion 6 is a one-turn coil having an oval planar shape, but it may be a spiral coil. [Explanation of symbols]

[0032] 1 Induction heating coil 5 Spiral coil section 6 Planar coil section 10 Conductive wire 15 Insulation materials 16 Upper side opening 17 Lower side opening 18 Work placement space 20 First straight section 21 Second straight section 23 Connection 25 Connection 27 Input line section 28 Output line section 30 First power feeding section 32 Second power feed section 40 First feeder line 41 Second feeder line 100 Work 110 Paint

Claims

1. An induction heating coil for heating an aluminum workpiece during painting, An induction heating coil comprising: a helical coil section having a work placement space in the center for placing a workpiece, in which a conductive wire is wound in a spiral shape over multiple stages and has a generally rectangular planar shape with both ends open; and a planar coil section arranged in at least one of the openings, in which the conductive wire forms a planar loop, the helical coil section and the planar coil section being electrically connected in series.

2. 2. The induction heating coil according to claim 1, wherein the spiral coil portion is covered with an insulating material.

3. A first power feed and a second power feed, 2. The induction heating coil according to claim 1, wherein the planar coil portion has straight portions arranged approximately in parallel and a connection portion connecting ends of the straight portions, one of the straight portions being divided into an input line portion and an output line portion, the first power supply portion is connected to the input line portion by a first power supply line crossing one opening of the spiral coil portion, the output line portion is connected to one end of the spiral coil portion, and the other end of the spiral coil portion is connected to the second power supply portion by a second power supply line extending outside the spiral coil portion.

4. 2. An induction heating coil comprising: two induction heating coils according to claim 1 arranged at opposing positions; and a workpiece arranged across the workpiece arrangement spaces of both induction heating coils.

5. A coating method comprising the steps of: applying paint to a box-shaped workpiece made of an aluminum-based material; placing the workpiece in a workpiece arrangement space of the induction heating coil described in claim 1; passing an alternating current through the induction heating coil to raise the temperature of the workpiece; and baking the paint onto the workpiece.

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