DC induced heating device

Abstract

To provide a DC induction heating device that improves the productivity of heat treatment for objects to be heated. [Solution] The DC induction heating device 10 comprises a magnetic field generating unit 12 that generates a DC magnetic field, a rotating shaft 15 that intersects the DC magnetic field, and a holder 18 that rotates about the rotating shaft 15 as its central axis and holds a plurality of objects to be heated 16 at positions symmetrical to the rotating shaft 15.

Description

Technical Field

[0001] Embodiments of the present invention relate to a DC induction heating device that heats metal parts using a DC magnetic field.

Background Art

[0002] In the manufacturing site of metal parts, a high-frequency induction heating device (AC induction heating device) has been used for a long time as a heating means. This AC induction heating device applies an alternating magnetic field generated by flowing a high-frequency current through a coil to a metal part, and rapidly heats the metal part by heat generation due to eddy current loss and heat generation due to hysteresis loss caused by the electromagnetic induction action.

[0003] The heating efficiency of metal parts by an AC induction heating device is said to be 50 to 60%. Therefore, in an AC induction heating device, it is required to reduce the power consumption and further improve the heating efficiency while maintaining the metal heating quality.

[0004] On the other hand, a DC induction heating device applies a DC magnetic field generated by flowing a DC current through a coil to a metal part that is rotated by a motor or the like. Thus, by rotating the metal part, rapid heating similar to that of an AC induction heating device is achieved by heat generation due to eddy current loss and hysteresis loss.

[0005] The heating efficiency of metal parts by a DC induction heating device is said to be 80 to 90%. Therefore, in a DC induction heating device, it is expected to reduce the power consumption and improve the heating efficiency while maintaining the metal heating quality.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

[0007] Incidentally, AC induction heating systems are a continuous process in which metal parts to be heated are continuously transported on a conveyor belt while being heated. On the other hand, conventional DC induction heating systems transport metal parts to a heating position sandwiched between coils, place these metal parts on a gripping mechanism, and then rotate them to heat them. After that, the DC induction heating system stops rotating, removes the metal parts from the gripping mechanism, and transports them outside.

[0008] Conventional DC induction heating systems are batch processes and involve acceleration and deceleration during rotation. Therefore, compared to AC induction heating systems, DC induction heating systems have lower productivity in heating metal parts because they require attaching and detaching the gripping mechanism and accelerating and decelerating during rotation.

[0009] Embodiments of the present invention have been made in consideration of these circumstances, and aim to provide a DC induction heating device that improves the productivity of heat treatment for objects to be heated. [Means for solving the problem]

[0010] The DC induction heating apparatus according to this embodiment includes a magnetic field generating unit that generates a DC magnetic field, a rotating shaft that intersects the DC magnetic field, and a holder that rotates about the rotating shaft as its central axis and holds a plurality of objects to be heated at positions symmetrical to the rotating shaft. [Effects of the Invention]

[0011] According to embodiments of the present invention, a DC induction heating device is provided that improves the productivity of heat treatment for an object to be heated. [Brief explanation of the drawing]

[0012] [Figure 1] XY cross-sectional view of a DC induction heating device according to the first embodiment. [Figure 2] YZ perspective view of a DC induction heating device according to the first embodiment. [Figure 3]XY cross-sectional view of a DC induction heating device according to the second embodiment. [Figure 4] YZ perspective view of a DC induction heating apparatus according to the second embodiment. [Figure 5] XY cross-sectional view of a DC induction heating device according to the third embodiment. [Figure 6] (A)(B)(C) YZ perspective view showing the processing steps of the object to be heated in the DC induction heating apparatus according to the fourth embodiment. [Figure 7] (A)(B) YZ perspective view showing embodiments of holders applied to DC induction heating devices according to the first and fourth embodiments. [Figure 8] XY cross-sectional view of a DC induction heating device according to the fifth embodiment. [Figure 9] YZ perspective view of a DC induction heating apparatus according to the fifth embodiment. [Figure 10] (A)(B) YZ perspective view showing an embodiment of a holder applied to a DC induction heating device according to the fifth embodiment. [Modes for carrying out the invention]

[0013] (First Embodiment) Embodiments of the present invention will be described below with reference to the attached drawings. Figure 1 is an XY cross-sectional view of a DC induction heating device 10A(10) according to the first embodiment. Figure 2 is a YZ perspective view thereof. As shown above, the DC induction heating device 10A includes a magnetic field generating unit 12 that generates a DC magnetic field 11, a rotating shaft 15 that intersects the DC magnetic field 11, and a holder 18 that rotates about the rotating shaft 15 as its central axis and holds a plurality of objects to be heated 16 at positions symmetrical to the rotating shaft 15.

[0014] With this configuration, the DC induction heating device 10 according to each embodiment dynamically applies a DC magnetic field 11 to the object to be heated 16, which is a metallic material such as a metal rod or metal tube. As a result, the object to be heated 16 is heated by Joule heating generated by the induced electromotive force.

[0015] The magnetic field generating unit 12 consists of a pair of coils 12a, and the rotation axis 15 is located in the space where the pair of coils 12a face each other. This magnetic field generating unit 12 is fixed to the holder 18 that rotates around the rotation axis 15 while maintaining a fixed and adjusted distance. In the first embodiment, the coil 12a, which is the magnetic field generating unit 12, employs an electromagnet made of a normal conducting wire material. However, as long as it can generate a DC magnetic field 11, there is no limitation in form, and a permanent magnet can also be employed.

[0016] The holder 18 is preferably made of a material with low electrical conductivity that is not heated due to eddy current loss, and further, a material with low thermal conductivity that does not dissipate the heat generated by the heated object 16, such as oxide ceramics such as alumina and magnesia.

[0017] And the holder 18 has a plurality (four in the figure) of hole portions 31 in the direction parallel to the rotation axis 15 that match the shape of the heated object 16. Thereby, the heated object 16 can be inserted into and removed from the holder 18 in the direction parallel to the rotation axis 15. Note that the heated object 16 loaded in the hole portion 31 is fixed to the holder 18 by a gripping mechanism (not shown in the figure) such as a chuck.

[0018] By loading the heated object 16 into this hole portion 31, a plurality of heated objects 16 are held at positions symmetric with respect to the rotation axis 15. Thereby, even if the holder 18 is rotated at high speed with the rotation axis 15 as the central axis, a stable balance can be ensured. By realizing the high-speed rotation of the holder 18 in this way, the heated object 16 can be heated at a high temperature at high speed.

[0019] The rotating shaft 15 has a drive unit 32 at one end for rotating the holder 18, and a bearing 33 at the other end to support it while it is rotating. It is desirable that this rotating shaft 15 be positioned perpendicular to the DC magnetic field 11. This allows the spacing between the pair of coils 12a to be narrowed in terms of the equipment layout, and a high-intensity DC magnetic field 11 can be generated in the space where the coils 12a face each other. The drive unit 32 is, for example, a rotating device such as a motor or a speed reducer, and can be appropriately used as long as it can rotate the object to be heated 16 around the rotating shaft 15.

[0020] The operation of the DC induction heating device 10A according to the first embodiment will now be described. First, multiple objects to be heated 16 are loaded through the opening 17 on the end face of the holder 18, and these objects to be heated 16 are fixed in place by a gripping mechanism (not shown) to prevent them from coming out of the holder 18. Next, the holder 18 is rotated around the rotation axis 15 by the drive unit 32, thereby rotating the objects to be heated 16.

[0021] The object to be heated 16 is subjected to a DC magnetic field from the magnetic field generating unit 12 and an AC magnetic field from the rotation of the drive unit 32. As a result, the object to be heated 16 is heated by Joule heating due to eddy currents. Since the object to be heated 16 is held symmetrically on the rotation axis 15, balance is maintained during rotation. Once heating of the object to be heated 16 is complete, the fixing by the gripping mechanism (not shown) is released, and the object to be heated 16 is removed from the opening 17 on the end face of the holder 18.

[0022] According to the first embodiment, if the loading / unloading of the object to be heated 16 into / from the hole 31 is achieved by providing a slidable rail or guide (not shown) along the rotating shaft 15, the holder 18 can be permanently fixed to the rotating shaft 15. This speeds up the loading / unloading of the object to be heated 16 compared to the conventional case where the object to be heated 16 was loaded onto the rotating shaft individually, contributing to improved production efficiency.

[0023] According to this embodiment, by holding multiple objects to be heated 16 in the holder 18 symmetrically with respect to the rotation axis 15, multiple objects to be heated 16 can be heated simultaneously at high speed. As a result, when the number of objects to be heated 16 held in the holder 18 is n, the processing time per object can be reduced to 1 / n compared to the conventional method in which each object to be heated 16 is rotated individually, contributing to improved production efficiency.

[0024] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figures 3 and 4. Figure 3 is an XY cross-sectional view of the DC induction heating device 10B(10) according to the second embodiment. Figure 4 is a YZ perspective view thereof. In Figures 3 and 4, parts having the same configuration or function as those in Figures 1 and 2 are indicated by the same reference numerals, and redundant explanations are omitted.

[0025] The DC induction heating device 10B of the second embodiment differs from the first embodiment described above in that the magnetic field generating unit 12 is a superconducting coil 12b made by winding a superconducting wire. For this purpose, the DC induction heating device 10B includes a refrigerator 20 that supplies cold air to bring the superconducting coil 12b to a critical temperature, and a heat transfer member 25 that transfers the cold air from the refrigerator 20 to the superconducting coil 12b.

[0026] In this second embodiment, the magnetic field generating unit 12 is a superconducting magnet, and in order to maintain the critical temperature, the superconducting coil 12b is connected to the refrigerator 20 via a heat transfer member 25 and is further insulated inside the insulated tank 26. The insulated tank 26 is vacuum insulated inside, preventing heat transfer by convection of air or the like.

[0027] Thus, the superconducting coil 12b and the heat transfer member 25 need to be kept below the critical temperature for superconductivity transition, and are therefore housed in an insulated tank 26. This insulated tank 26 further incorporates a radiation shield 27 to reduce the effects of heat intrusion from the environment in which the DC induction heating device 10 is installed (room temperature: approximately 300K). The weight of the radiation shield 27 and the heat transfer member 25 is supported from the insulated tank 26 by support members (not shown).

[0028] The superconducting coil 12b is a coil made from low-temperature superconducting wires such as Nb-Ti alloys or Nb3Sn, or high-temperature superconducting wires such as rare-earth or bismuth alloys. Below the critical temperature, the superconducting coil 12b has almost zero electrical resistance, virtually no power loss due to current flow, and can conduct current at high current densities, thus enabling it to continuously generate a high-intensity magnetic field.

[0029] The refrigerator 20 is exemplified as a GM refrigerator. The first stage 21 of this GM refrigerator 20 is connected to the radiation shield 27, and the second stage 22 is connected to the heat transfer member 25. Due to the adiabatic compression effect of the working gas (He gas, etc.) sealed into the GM refrigerator 20 from the compressor (not shown), the radiation shield 27 is cooled to about 40K and the heat transfer member 25 is cooled to about 4K.

[0030] The refrigerator 20 used is not limited to the GM refrigerator described above. Any refrigerator that can supply the cooling necessary to bring the superconducting coil 12b to a critical temperature may be used as appropriate, such as a pulse tube refrigerator, Claude refrigerator, or Stirling refrigerator.

[0031] The heat transfer member 25 is made of a material that has high mechanical rigidity, does not magnetize, and has high thermal conductivity, such as copper, copper alloy, aluminum, or aluminum alloy. The heat transfer member 25 is supported from the inside of the insulated tank 26 by a support member (not shown) and receives cold energy from the refrigerator 20 in contact with it. This cold energy supplied from the refrigerator 20 is transferred to the superconducting coil 12b fixed to the heat transfer member 25.

[0032] According to the DC induction heating device 10B of the second embodiment, the superconducting coil 12b can generally generate a higher DC magnetic field 11 and further reduce power consumption compared to the normal conducting coil 12a (Figure 1; first embodiment). This improves the heating efficiency of the object to be heated 16.

[0033] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Figure 5. Figure 5 is an XY cross-sectional view of the DC induction heating device 10C(10) according to the third embodiment. The DC induction heating device 10C of the third embodiment has a configuration in which an iron core 30 is further added to the configuration of the first and second embodiments described above. In Figure 5, parts that have the same configuration or function as those in Figures 1 to 4 are indicated by the same reference numerals, and redundant explanations are omitted.

[0034] This iron core 30 penetrates each of the pair of coils 12 from the outside, and has opposing end faces 35a and 35b formed on its inside, sandwiching the holder 18. With the iron core 30 arranged in this way, the ferromagnetic iron core 30 becomes magnetized, making it possible to generate an even stronger DC magnetic field 11.

[0035] (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to Figures 6 and 7. Figures 6(A), 6(B), and 6(C) are YZ perspective views showing the processing steps for the object to be heated in the DC induction heating device 10D(10) according to the fourth embodiment. The DC induction heating device 10D of the fourth embodiment has a configuration in which the holder 18 is separated from the rotating shaft 15 to load / remove the object to be heated 16, compared to the configuration of the first embodiment described above. In Figures 6 and 7, parts that have the same configuration or function as those in Figures 1 and 2 are indicated by the same reference numerals, and redundant explanations are omitted.

[0036] In the DC induction heating device 10D, openings 17 for loading the object to be heated 16 are provided on the end faces 18a and 18b of the holder 18, and the rotating shaft 15 is configured to detachably support the holder 18 at both end faces 18a and 18b.

[0037] In the fourth embodiment, the rotating shafts 15 (15a, 15b) are separated into a rotating shaft 15a on the drive unit 32 side and a rotating shaft 15b on the bearing 33 side. A flange 36 (36a, 36b) is provided at the tip of each rotating shaft 15 (15a, 15b) on the holder 18 side. A projection 37 (37a, 37b) is provided on the main surface of each flange 36 (36a, 36b) that engages with the opening 17 of the hole 31 of the holder 18.

[0038] The operation of the DC induction heating device 10D according to the fourth embodiment will now be described. First, as shown in Figure 6(A), multiple objects to be heated 16 are loaded into the separated holder 18, and these objects to be heated 16 are fixed in place by a gripping mechanism (not shown) so that they do not come out of the holder 18. Next, the holder 18 is moved to a position where the openings 17 on the end faces 18a and 18b face the projections 37a and 37b on the flanges 36a and 36b.

[0039] Next, as shown in Figure 6(B), the holder 18 is connected by sliding either the rotating shaft 15a or 15b in the axial direction. Then, the holder 18 is rotated around the rotating shaft 15 by the drive unit 32, thereby applying an alternating magnetic field and heating the object to be heated 16 by Joule heating caused by eddy currents.

[0040] Next, as shown in Figure 6(C), once the heating of the object to be heated 16 is complete, the holder 18 is separated by sliding either the rotating shaft 15a or 15b in the opposite direction. Then, the object to be heated 16 is removed from the holder 18.

[0041] According to the fourth embodiment, by preparing at least three holders 18, the loading of the object to be heated 16 into the separated holders 18, heating of the object to be heated 16 by rotating the holders 18, and removal of the object to be heated 16 from the separated holders 18 can be performed simultaneously. This reduces the time consumed solely for loading / removing the object to be heated 16, contributing to improved production efficiency.

[0042] Figures 7(A) and 7(B) are YZ perspective views showing embodiments of holders 18 applied to DC induction heating devices 10A and 10D (10) according to the first and fourth embodiments. As shown above, in the first and fourth embodiments, a heat insulating material 19 (19a, 19b) is placed on at least one of the inner circumferential surface of the hole into which the object to be heated is loaded and the outer circumferential surface of the holder 18.

[0043] The thermal insulation material 19 (19a, 19b) is made of, for example, ceramics or rock wool, and is provided on the outer circumference of the holder 18 and at the interface that comes into contact with the object to be heated 16. This suppresses the temperature rise of the holder 18 and the temperature drop of the object to be heated 16 caused by heat transfer from the object to be heated 16 to the holder 18 during heating. As a result, energy loss during heating is reduced and the efficiency of the heat treatment is improved. Furthermore, deterioration of the holder 18 can be prevented and the durability of the device can be improved.

[0044] (Fifth embodiment) Next, a fifth embodiment of the present invention will be described with reference to Figures 8 and 9. Figure 8 is an XY cross-sectional view of the DC induction heating device 10E(10) according to the fifth embodiment. Figure 9 is a YZ perspective view thereof. Figures 10(A) and 10(B) are YZ perspective views showing an example of a holder 18 applied to the DC induction heating device 10E according to the fifth embodiment. In Figures 8, 9, and 10, parts having the same configuration or function as those in Figures 1 and 2 are indicated by the same reference numerals, and redundant explanations are omitted.

[0045] In the fifth embodiment of the DC induction heating device 10E, the object to be heated 16 is loaded through an opening 24 provided on the outer circumferential surface of the holder 18, instead of the opening 17 (Figure 2) provided on the end face of the holder 18 in the first embodiment described above. A cover portion 28 is provided for the opening 24.

[0046] Here, the lid 28 does not need to close the entire opening 24; it is sufficient to close at least a portion of it so that the object to be heated 16 does not detach due to centrifugal force during rotation. The lid 28 can also be configured such as one side being hinged to the edge of the opening 24 and the other side open, as shown in Figure 8, or as being detachable from the opening 24, as shown in Figure 10(B).

[0047] Furthermore, the DC induction heating device 10E includes a loading section 38 for loading the object to be heated 16 into the uppermost opening 24a, and an unloading section 39 for unloading the object to be heated 16 removed from the lowermost opening 24b. In this manner, the loading section 38 loads the object to be heated 16 before heat treatment into the holder 18 from a direction perpendicular to the rotation axis 15, along the direction of the rotation axis 15. Then, the unloading section 39 unloads the heat-treated object to be heated 16, which has been allowed to fall naturally by gravity by opening the lid section 28, to the outside of the holder 18.

[0048] The loading unit 38 is, for example, a lifting device such as a belt conveyor or elevator, and can transport the object to be heated 16 to the opening 24 of the holder 18 in a direction perpendicular to the rotating shaft 15. Such a loading unit 38 is installed around the holder 18 and operates by a separate drive mechanism (not shown) from the drive unit 32 of the rotating shaft 15 so as not to affect the rotation of the rotating shaft 15. Although Figure 8 shows a loading unit 38 that transports the object to be heated 16 in a vertical direction, the transport direction of the object to be heated 16 is not particularly limited as long as the object to be heated 16 can be transported to the opening 24 of the holder 18 in a direction perpendicular to the rotating shaft 15.

[0049] The unloading section 39 is, for example, a ramp, which allows the object to be heated 16, removed from the holder 18, to be transported perpendicular to the rotating shaft 15. The unloading section 39 is installed below the rotating shaft 15 and operates by a separate drive mechanism (not shown) from the drive unit 32 of the rotating shaft 15, so as not to affect the rotation of the rotating shaft 15. The device may be configured using either the loading section 38 or the unloading section 39, or using both.

[0050] The operation of the DC induction heating device 10E according to the fifth embodiment will be described (see Figures 8 and 9). First, the holder 18 is left empty (see Figure 10(B)). Next, the lid 28a of the opening 24a facing the loading section 38 is opened, the untreated object to be heated 16 is loaded into the holder 18, and the lid 28a is closed again to prevent the object to be heated 16 from coming loose.

[0051] Next, the holder 18 is rotated to bring the opening 24a, which does not yet contain the object to be heated 16, opposite the loading section 38, and the same operation is repeated. Once all the openings 24 have been loaded with the objects to be heated 16, the drive unit 32 rotates the holder 18 around the rotation axis 15.

[0052] The object to be heated 16 is subjected to a DC magnetic field by the magnetic field generating unit 12 and an AC magnetic field by rotation by the drive unit 32. As a result, the object to be heated 16 is heated by Joule heating due to eddy currents. Once the heating of the object to be heated 16 is complete, the lid 28b of the opening 24b facing the discharge unit 39 is opened, and the processed object to be heated 16 is discharged from the holder 18.

[0053] Next, the holder 18 is rotated to position the opening 24b containing the objects to be heated 16 facing the discharge section 39, and the same operation is repeated. Once all the objects to be heated 16 have been discharged from the openings 24, the process returns to its original position and the unprocessed objects to be heated 16 are loaded into the holder 18.

[0054] According to the fifth embodiment, the object to be heated 16 can be moved in and out perpendicular to the rotating shaft 15, and the loading and unloading of the object to be heated 16 are separate and independent processes. Therefore, even if the object to be heated 16 is heavy, the work efficiency is not reduced, and it contributes to the safety and speed of the work. Furthermore, the occupied area of ​​the device is reduced, making it more compact. In addition, since the heat treatment of the object to be heated 16 can be carried out continuously, the time other than heating can be significantly reduced, contributing to improved productivity.

[0055] According to the DC induction heating apparatus of at least one embodiment described above, by having a holder that holds multiple objects to be heated at positions symmetrical with respect to the rotation axis, it is possible to improve the productivity of the heating process for the objects to be heated.

[0056] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, modifications, and combinations are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0057] 10 (10A, 10B, 10C, 10D, 10E)... DC induction heating device, 11... DC magnetic field, 12 (12a, 12b)... Magnetic field generator, 12a (12)... Normal conducting coil, 12b (12)... Superconducting coil, 15 (15a, 15b)... Rotating shaft, 16... Object to be heated, 17... Opening on the end face of the holder, 18... Holder, 18a... End face of the holder, 19... Insulation material, 20... Refrigeration unit 21...First stage, 22...Second stage, 24(24a,24b)...Opening on the outer surface of the holder, 25...Heat transfer member, 26...Insulation tank, 27...Radiation shield, 28...Lid, 30...Iron core, 31...Hole, 32...Drive unit, 33...Bearing, 35a,35b...Both end faces of the iron core, 36(36a,36b)...Flange, 37(37a,37b)...Protrusion, 38...Loading unit, 39...Discharge unit.

Claims

1. A magnetic field generating unit that generates a DC magnetic field, A rotating shaft intersecting the aforementioned DC magnetic field, A DC induction heating device comprising a holder that rotates about the aforementioned rotation axis as its central axis and holds a plurality of objects to be heated at positions symmetrical to the rotation axis.

2. In the DC induction heating apparatus according to claim 1, The aforementioned magnetic field generating unit consists of a pair of coils, A DC induction heating device in which the rotating shaft is located in a space where a pair of the coils face each other.

3. In the DC induction heating apparatus according to claim 2, The aforementioned coil is a superconducting coil, A refrigerator that supplies cold air to bring the superconducting coil to a critical temperature, A DC induction heating device comprising a heat transfer member that transfers the aforementioned cold energy from the refrigerator to the superconducting coil.

4. In the DC induction heating apparatus according to claim 2 or claim 3, A DC induction heating device comprising an iron core that penetrates each of the pair of coils from the outside, with opposing end faces formed on the inside, sandwiching the holder.

5. In the DC induction heating apparatus according to claim 2 or claim 3, An opening for loading the object to be heated is provided on the end face of the holder. The rotating shaft is configured to detachably support the holder at both end faces of the DC induction heating device.

6. In the DC induction heating apparatus according to claim 5, A DC induction heating device in which an insulating material is placed on at least one of the inner circumferential surface of the hole into which the object to be heated is loaded and the outer circumferential surface of the holder.

7. In the DC induction heating apparatus according to claim 2 or claim 3, An opening for loading the object to be heated is provided on the outer circumferential surface of the holder. A DC induction heating device having a lid that closes at least a portion of the opening.

8. In the DC induction heating apparatus according to claim 7, The uppermost opening is a loading section for loading the object to be heated, A DC induction heating apparatus comprising: an unloading section for unloading the object to be heated, which has been removed from the lowest opening; and a DC induction heating apparatus.

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