Induction heating device

Abstract

The goal is to improve the induction heating of the object being heated while also making it easier to assemble the cylindrical body. [Solution] The induction heating device 100 includes a rotor 1 and a rotation drive unit 10 for relative rotation of the object to be heated B, which is located inside the rotor 1, and the rotor 1. The rotor 1 includes a plurality of magnets 3 and a non-magnetic cylindrical frame 2 that holds the plurality of magnets 3. The plurality of magnets 3 are arranged in a Halbach arrangement along the circumferential direction of the frame 2 to increase the magnetic field strength toward the object to be heated B, which is located inside the rotor 1. The induction heating device 100 is configured to heat the object to be heated B by utilizing the fact that eddy currents flow in the object to be heated B when the rotor 1 and the object to be heated B are rotated relative to each other by the rotation drive unit 10.

Description

Technical Field

[0001] The present invention relates to an induction heating device using a magnet.

Background Art

[0002] Non-Patent Document 1 describes a technique for induction heating by rotating a billet, which is an object to be heated, disposed in a cylindrical body having a plurality of magnets annularly arranged in an N-S array along the circumferential direction and a plurality of back yokes respectively disposed outside two adjacent magnets along the circumferential direction and serving as magnetic paths of the two magnets.

Prior Art Documents

Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology described in Non-Patent Document 1 above, multiple back yokes are placed outside multiple magnets to concentrate the magnetic field inward rather than outward, thereby improving induction heating of the billet. However, when assembling a cylindrical body by arranging multiple magnets and back yokes, the magnets and back yokes tend to stick together, making it difficult to position them in the desired location. Furthermore, since the back yokes adjacent to the magnets become magnetized, tools and parts used for assembly tend to stick to the back yokes, making assembly difficult.

[0005] Therefore, the object of the present invention is to provide an induction heating device that improves the induction heating of the object to be heated while also being easy to assemble into a cylindrical shape. [Means for solving the problem]

[0006] The present invention provides an induction heating device for heating an object to be heated, comprising: a cylindrical body; and a rotation drive unit for relatively rotating the object to be heated and the cylindrical body, the cylindrical body being positioned inside the cylindrical body, the cylindrical body including a plurality of magnets and a non-magnetic cylindrical frame holding the plurality of magnets, the plurality of magnets being arranged in a Halbach arrangement along the circumferential direction of the frame to increase the magnetic field strength toward the object to be heated positioned inside the cylindrical body, and the device is configured to heat the object to be heated by utilizing the flow of eddy currents in the object to be heated when the cylindrical body and the object to be heated are rotated relative to each other by the rotation drive unit.

[0007] According to this design, because multiple magnets are arranged in a Halbach array, it is possible to increase the magnetic field strength directed towards the object being heated without providing a back yoke that acts as a magnetic path outside the multiple magnets. This makes it possible to improve the induction heating of the object being heated. Moreover, since there is no need for a back yoke, it becomes easier to attach the multiple magnets to the frame, and the cylindrical body containing multiple magnets becomes easier to assemble.

[0008] In the present invention, the invention further comprises a moving part for moving the object to be heated along the central axis direction of the cylindrical body, and a plurality of the cylindrical bodies are arranged along the central axis direction. Preferably, the rotational drive unit rotates the plurality of cylindrical bodies such that, in the first direction of movement in which the object to be heated is moved by the moving part, the rotational speed of the cylindrical bodies downstream of the plurality of cylindrical bodies is greater than that of the cylindrical bodies upstream. As a result, the downstream side of the object to be heated in the first direction of movement is heated more than the upstream side. Therefore, when extruding a heated object to be heated while moving it in the first direction of movement, it is possible to suppress the excessive heating of the upstream portion of the object to be heated in the first direction of movement due to processing heat generated by the deformation of the object to be heated during extrusion.

[0009] Furthermore, in the present invention, it is preferable that the rotation drive unit rotates two adjacent cylindrical bodies in opposite directions relative to each other in the direction of the central axis. As a result, when the cylindrical bodies are rotated, a force is generated in the object to be heated that tends to rotate along the direction of rotation of the cylindrical bodies, but because the two adjacent cylindrical bodies rotate in opposite directions, it is possible to reduce the rotational force generated in the object to be heated.

[0010] Furthermore, in the present invention, it is preferable that the magnetic body consists of multiple magnets. This makes it possible to construct a relatively large magnetic body. [Effects of the Invention]

[0011] According to the induction heating device of the present invention, since multiple magnets are arranged in a Halbach arrangement, it is possible to increase the magnetic field strength directed toward the object to be heated without providing a back yoke that forms a magnetic path outside the multiple magnets. This makes it possible to improve the induction heating of the object to be heated. Moreover, since there is no need to provide a back yoke, it becomes easier to attach the multiple magnets to the frame, and the cylindrical body having multiple magnets becomes easier to assemble. [Brief explanation of the drawing]

[0012] [Figure 1]This is a schematic plan view showing the main parts of an induction heating device according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view along the line II-II shown in Figure 1. [Figure 3] Figure 1 is a front view of the rotor as seen from the central axis direction. [Figure 4] Figure 3 is a magnified view of the magnetic body located in region IV. [Figure 5] Figure 3 is a diagram illustrating the magnetic field formed by the multiple magnets of the rotor shown. [Figure 6] (a) is a front view showing the rotor of the embodiment, (b) is a front view showing the rotor of the first comparative example, and (c) is a front view showing the rotor of the second comparative example. [Modes for carrying out the invention]

[0013] <Embodiment> First, with reference to Figures 1 and 2, the schematic configuration of an induction heating device according to one embodiment of the present invention will be described. As shown in Figures 1 and 2, the induction heating device 100 includes four cylindrical rotors 1, a rotation drive unit 10 that rotates the four rotors 1, a moving unit 20 that moves the object to be heated B, and a control unit 30 that controls the rotation drive unit 10 and the moving unit 20. The rotors 1 correspond to the "cylindrical body" of the present invention.

[0014] Each rotor 1 is formed in a cylindrical shape with a hollow portion 1A inside, as shown in Figure 2. Each rotor 1 is supported by a pair of support portions 9 so as to be circumferentially rotatable about its central axis C1. As shown in Figure 1, the pair of support portions 9 support both ends of the rotor 1 in the direction of the central axis C1. The four rotors 1 are arranged side by side in the direction of the central axis C1 with a predetermined gap H between them.

[0015] The rotation drive unit 10 has four drive sets 11. The four drive sets 11 respectively correspond to the four rotors 1, and each rotor 1 is configured to be rotatable. Each drive set 11 includes a motor 12, a pulley 13, and a belt 14. Note that the rotation drive unit 10 may have only one motor as a drive source and have a transmission mechanism that transmits the driving force of the motor to the pulley 13 corresponding to each rotor 1. Also, the rotation drive unit 10 may have any configuration as long as it can rotate each rotor 1.

[0016] The motor 12 is driven under the control of the control unit 30. The pulley 13 is connected to the drive shaft 12A of the motor 12. The pulley 13 is arranged such that its central axis C2 is parallel to the central axis C1 of the rotor 1. Also, the pulley 13 is arranged side by side with the corresponding rotor 1 in a direction orthogonal to the central axis C1.

[0017] As shown in FIG. 2, the belt 14 is an endless annular belt. Also, the belt 14 is spanned between the pulley 13 and the rotor 1, and when the pulley 13 rotates, the rotor 1 also rotates in the same rotation direction as the pulley 13.

[0018] In the present embodiment, the rotation drive unit 10 rotates the four rotors 1 such that their rotation speeds are different from each other. That is, the control unit 30 controls the driving of the four motors 12 such that the rotation speed of the rotor 1 downstream is higher in the first movement direction in which the object to be heated B moves by the moving unit 20. The first movement direction is the direction from one end (the left end in FIG. 1) to the other end (the right end in FIG. 1) in the direction of the central axis C1 of the object to be heated B. Note that among the four rotors 1, it is sufficient that the rotation speed of the rotor 1 downstream is higher than the rotation speed of the rotor 1 upstream of the rotor 1 in the first movement direction.

[0019] In this embodiment, the rotation drive unit 10 rotates two rotors 1 adjacent to each other in opposite directions in the direction of the central axis C1. That is, the control unit 30 controls the driving of the four motors 12 so that the rotation directions of the four motors 12 arranged in the direction of the central axis C1 are sequentially opposite. Among the four rotors 1, it is only necessary that any two adjacent rotors 1 rotate in opposite directions to each other. That is, among the four rotors 1, the two rotors 1 located at both ends in the direction of the central axis C1 may rotate in the same direction, and the two rotors 1 sandwiched between these two rotors 1 may rotate in a direction opposite to that of the two rotors 1 located at both ends. Also, among the four rotors 1, only the two rotors 1 located on the central side in the direction of the central axis C1 may rotate in opposite directions to each other.

[0020] As shown in FIG. 1, the moving unit 20 includes two air cylinders 21 and 22, a support base 23, an air cylinder 24, and a pair of guide rails 25. The air cylinders 21 and 22 in this embodiment are arranged vertically side by side, but they may be arranged in any manner. The air cylinder 21 is arranged above the air cylinder 22.

[0021] The air cylinder 21 has a U-shaped rod 21A having a pair of parallel portions 21A1 extending in a long shape in the direction of the central axis C1 of the rotor 1. The air cylinder 21 is configured to be movable in the direction of the central axis C1 with the rod 21A. One of the pair of parallel portions 21A1 of the rod 21A is arranged so as to be able to enter and exit the hollow portion 1A of the rotor 1. Also, at the tip of one of the parallel portions 21A1, there is a holding portion 21B for holding one end portion (the left end portion in FIG. 1) of the object to be heated B in the direction of the central axis C1.

[0022] The air cylinder 22 also has a U-shaped rod 22A having a pair of parallel sections 22A1 that extend elongated in the direction of the central axis C1 of the rotor 1. The air cylinder 22 is configured so that the rod 22A can move in the direction of the central axis C1. Of the pair of parallel sections 22A1 of the rod 22A, one parallel section 22A1 is positioned to move in and out of the hollow section 1A of the rotor 1. In addition, the tip of one of the parallel sections 22A1 has a holding section 22B that holds the other end (right end in Figure 1) of the object to be heated B in the direction of the central axis C1.

[0023] These air cylinders 21 and 22 are driven by the control unit 30. The control unit 30 controls the extension and retraction of the rods 21A and 22A of the air cylinders 21 and 22 so as to move the object to be heated B in the direction of the central axis C1 while holding the object to be heated B with the holding parts 21B and 22B.

[0024] The support base 23 supports the two air cylinders 21 and 22 from below. The support base 23 is positioned on a pair of guide rails 25 so as to be movable in the direction of the central axis C1. The pair of guide rails 25 extend parallel to the direction of the central axis C1 and are arranged side by side in a direction perpendicular to the central axis C1. The air cylinder 24 has a rod 24A that extends in the direction of the central axis C1. The tip of the rod 24A is connected via a mounting portion 23A provided at the end of the support base 23 in the direction of the central axis C1. The air cylinder 24 is also driven by the control unit 30. The control unit 30 controls the extension and retraction of the rod 24A of the air cylinder 24 so as to swing the support base 23 in the direction of the central axis C1 while the object to be heated B is held between the holding portions 21B and 22B. When the rod 24A of the air cylinder 24 is extended or retracted, the support base 23 swings in the direction of the central axis C1. This makes it possible to swing the object to be heated B, which is held between the two air cylinders 21 and 22 and the holding parts 21B and 22B, in the direction of the central axis C1, and as described later, the object to be heated B can be moved alternately in the first movement direction and in the second movement direction opposite to the first movement direction, thereby swinging the object to be heated B.

[0025] In this embodiment, the moving unit 20 has three air cylinders 21, 22, and 24, but it is not particularly limited and may have any configuration as long as it is possible to move the object to be heated B. For example, the moving unit 20 may use hydraulic or electric cylinders instead of air cylinders 21, 22, and 24. This makes it possible to miniaturize the moving unit 20. Note that if the object to be heated B is not oscillated, the moving unit 20 does not need to have a support base 23, air cylinders 24, and a pair of guide rails 25.

[0026] Next, referring to Figures 3 to 5, the rotor 1 will be described below. As shown in Figure 3, the rotor 1 has a frame 2 and 16 magnets 3. The frame 2 is formed in a cylindrical shape with a hollow portion 1A inside. The belt 14 described above is stretched across the outer circumferential surface 2A of the frame 2. The frame 2 is made of a non-magnetic material. In this embodiment, the frame 2 is made of, for example, SUS303 stainless steel, but any non-magnetic material such as metal or synthetic resin may be used.

[0027] The 16 magnet bodies 3 are arranged along the circumferential direction of the frame 2. Each magnet body 3 consists of nine magnets 4, as shown in Figure 4. The magnets 4 are permanent magnets whose pole positions and magnetic force do not change. There are no particular limitations on the type of permanent magnet used for the magnets 4. Each magnet 4 is inserted into a hole 2B formed in the frame 2. Furthermore, each magnet 4 has the same length as the frame 2 in the direction of the central axis C1, and is formed to be elongated.

[0028] The nine magnets 4 that make up the magnetic body 3 are arranged so that their magnetization direction (direction of the arrow in Figure 4) matches the magnetization direction (direction of the arrow in Figure 3) of the corresponding magnetic body 3 shown in Figure 3. As a result, each magnetic body 3 has a structure in which a first core 3N forming the north pole and a second core 3S forming the south pole are appropriately arranged.

[0029] The 16 magnets 3 are arranged in a ring shape to form a Halbach arrangement that optimizes the magnetization direction of the magnets 3, thereby increasing the magnetic field strength toward the central axis C1. This arrangement of the 16 magnets 3 generates a magnetic field on the inner surface of the rotor 1, as shown in Figure 5, resulting in a high magnetic field strength on the inner surface of the rotor 1. In other words, a small magnetic field (not shown) is generated on the outer surface of the rotor 1, but its strength is extremely low. With the object to be heated B placed within the hollow portion 1A of the rotor 1, the rotor 1 rotates relative to the object to be heated B. This causes eddy currents to flow through the conductive object to be heated B, counteracting the increase in magnetic flux according to the law of electromagnetic induction. These eddy currents generate Joule heat, causing the object to be heated B itself to heat up.

[0030] As described above, the induction heating device 100 in this embodiment is configured to heat the object to be heated B by utilizing the flow of eddy currents in the object to be heated B. In particular, by using a plurality of magnets 3 arranged in a Halbach array and increasing the magnetic field strength so that the magnetic field is concentrated on one side of the radial direction of the rotor 1 toward the object to be heated B, the heating of the object to be heated B can be promoted compared to when a Halbach array is not used, and this is effective in increasing the heating efficiency of the object to be heated B. In other words, the induction heating of the object to be heated B can be improved.

[0031] Next, the method for heating the object B using the induction heating device 100 will be explained. First, the object B is held between the four rotors 1 on the outside (upstream side in the first movement direction) in the direction of the central axis C1 by the moving part 20. After this, the moving part 20 moves the object B so that it is positioned inside the hollow part 1A of the four rotors 1 as shown in Figure 1.

[0032] Next, the control unit 30 controls the drive of the four motors 12 so that the rotation speed of the rotor 1 downstream increases in the first direction of movement of the object to be heated B. At the same time, the control unit 30 controls the drive of the four motors 12 so that the rotation directions of the four motors 12, which are aligned in the direction of the central axis C1, are sequentially opposite. As a result, each rotor 1 rotates relative to the object to be heated B, and eddy currents flow through the object to be heated B. Then, Joule heat is generated by these eddy currents, causing the object to be heated B itself to heat up and become heated.

[0033] Next, the control unit 30 controls the air cylinder 24 to move the object to be heated B alternately in a first movement direction and a second movement direction opposite to the first movement direction, thereby causing the object to be heated B to oscillate. At this time, the object to be heated B oscillates within a range approximately equal to the gap H between two adjacent rotors 1 in the direction of the central axis C1. This allows the object to be heated B to be heated effectively along its entire length.

[0034] Next, after the object to be heated B has been heated to a predetermined temperature, the control unit 30 controls the rotation drive unit 10 to stop the rotation of the four rotors 1. At this time, the control unit 30 also controls the air cylinder 24 to stop the oscillation of the object to be heated B. The temperature of the object to be heated B may be detected by a temperature sensor (not shown) or estimated by the driving time for rotating the rotors 1.

[0035] Next, the control unit 30 controls the two air cylinders 21 and 22 to move the object to be heated B outwards from the hollow portion 1A of the four rotors 1 in the first movement direction. In this way, the heating of the object to be heated B by the induction heating device 100 is completed.

[0036] Next, we will explain the results of calculations regarding the Joule heat generated in the heated object and the effective utilization of the magnets when the rotor 101 of the embodiment, the rotor 201 of the first comparative example, and the rotor 301 of the second comparative example are used in the induction heating device 100. As shown in Figure 6(a), the rotor 101 has 16 magnets (or magnetic bodies) arranged in a ring shape, and these magnets are arranged in a Halbach arrangement, similar to the embodiment described above.

[0037] As shown in Figure 6(b), rotor 201 has 16 magnets (or magnetic bodies) arranged in a ring, and these magnets are arranged in an N-S configuration. As shown in Figure 6(c), rotor 301 has 6 magnets (or magnetic bodies) arranged in a ring, and these magnets are arranged in an N-S configuration. In addition, rotors 201 and 301 have annular ferromagnetic bodies positioned radially outside the magnets. The ferromagnetic bodies are connected to the outer surfaces of each magnet, forming a magnetic path.

[0038] Two-dimensional transient response analysis was used for the calculation method. The analysis conditions for each rotor 101, 201, and 301 are shown below. The outer diameter of the annular arrangement of magnets in rotors 101, 201, and 301 is φ390 mm, and the inner diameter is φ290 mm. The outer diameter of the ferromagnetic material in rotor 201 and 301 is φ490 mm. The object to be heated has a cylindrical shape, with an outer diameter of φ254 mm and a length of 200 mm. The air gap between the magnet and the object to be heated is 18 mm. The electrical resistivity of the object to be heated is 5.43 × 10⁻⁶. -8 The magnetic field strength is Ωm. Each magnet is a permanent magnet, specifically a samarium-cobalt magnet, with a magnet temperature of 20°C, a specific gravity of 8.4, and a residual magnetic flux density of 1.00 (T). The total mass of magnets used in each rotor 101, 201, and 301 is 89.7 kg. The rotational speed of each rotor 101, 201, and 301 is 900 rpm.

[0039] Based on the analysis conditions described above, the Joule heat generated in the object being heated by rotor 101 was 105,392 J, by rotor 201 it was 38,567 J, and by rotor 301 it was 94,084 J. This shows that rotor 101 in the example heats the object being heated more effectively than rotors 201 and 301 in the comparative examples.

[0040] Furthermore, the efficiency of the magnets was calculated by dividing the Joule heat generated by each rotor 101, 201, and 301 by the mass of the magnets used. As a result, the efficiency of the magnets in each rotor 101, 201, and 301 was 1175 J / Kg, 430 J / Kg, and 1049 J / Kg, respectively. This also shows that the rotor 101 in the example has a higher efficiency of magnet utilization than the rotors 201 and 301 in each comparative example.

[0041] As described above, in the induction heating device 100 of this embodiment, since the multiple magnets 3 are arranged in a Halbach arrangement, it is possible to increase the magnetic field strength directed toward the object to be heated B without providing a ferromagnetic material (back yoke) that forms a magnetic path outside the multiple magnets 3. This makes it possible to improve the induction heating of the object to be heated B. Moreover, since there is no need to provide a back yoke, it becomes easier to attach the multiple magnets 3 to the frame 2, and the rotor 1 having the multiple magnets 3 becomes easier to assemble.

[0042] The rotary drive unit 10 rotates the four rotors 1 such that the rotational speed increases with each rotor 1 located downstream in the first direction of movement of the object to be heated B. As a result, the downstream side of the object to be heated B in the first direction of movement is heated more than the upstream side. Therefore, when extruding the heated object to be heated B while moving it in the first direction of movement, it is possible to suppress the excessive heating of the upstream portion of the object to be heated B in the first direction of movement due to processing heat generated by the deformation of the object to be heated B during extrusion.

[0043] The rotary drive unit 10 rotates two adjacent rotors 1 in opposite directions relative to each other in the direction of the central axis C1. As a result, when the rotors 1 rotate, a force is generated in the object to be heated B that tends to rotate along the direction of rotation of the rotors 1. However, because the two adjacent rotors 1 rotate in opposite directions, it is possible to reduce the rotational force generated in the object to be heated B.

[0044] The magnetic body 3 consists of nine magnets 4. This makes it possible to construct a relatively large magnetic body 3. The magnetic body 3 may also be composed of 1 to 8 or 10 or more magnets.

[0045] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible as long as they are within the scope of the claims.

[0046] Although the rotor 1 in the above-described embodiment has a cylindrical shape, it may have any cylindrical shape, such as a triangle, a square, or other polygon, or an ellipse. In this case as well, it is sufficient that multiple magnets (including those consisting of one magnet) are arranged in an annular Halbach arrangement along the circumferential direction of the cylindrical body so that the magnetic field strength directed toward the object to be heated, which is located inside the cylindrical body, is higher than that directed toward the outside. Furthermore, the induction heating device 100 in the above-described embodiment may have 1 to 3 or 5 or more rotors 1. When the induction heating device 100 has multiple rotors 1, it is sufficient to rotate the necessary rotors 1 as appropriate, depending on the length of the object to be heated B in the direction of the central axis C1. For example, if there are four rotors 1, and the length of the object to be heated B in the direction of the central axis C1 is such that it spans two adjacent rotors 1, then it is sufficient to rotate only the two adjacent rotors 1.

[0047] The rotary drive unit 10 may rotate each rotor 1 in the same direction. Alternatively, the rotary drive unit 10 may rotate each rotor 1 at the same rotational speed. Furthermore, the induction heating device 100 may have a sensor for detecting the temperature of the object to be heated B. In this case, when heating the object to be heated B, the control unit 30 may control the rotary drive unit 10 based on the temperature of the object to be heated B detected by the sensor. In other words, the control unit 30 can control at least one of the rotational speed, rotational direction, or driving time of each rotor 1 so that the temperature of the object to be heated B detected by the sensor reaches a desired temperature.

[0048] In the above embodiment, the rotary drive unit 10 rotates the rotor 1, but the object to be heated B, or both the object to be heated B and the rotor 1, may be rotated, causing the rotor 1 and the object to be heated B to rotate relative to each other. [Explanation of symbols]

[0049] 1 rotor 2 frames 3. Magnetic body 4 Magnets 10 Rotary drive unit 20 Mobile Unit 100 Induction heating device B Heated object C1 center axis

Claims

1. An induction heating device for heating an object to be heated, A cylindrical body, The system includes a rotational drive unit for relative rotation between the object to be heated and the cylindrical body, which is positioned inside the cylindrical body. The cylindrical body is Multiple magnetic bodies, It includes a non-magnetic cylindrical frame that holds the plurality of magnets, The plurality of magnets are arranged in a Halbach arrangement along the circumferential direction of the frame to increase the magnetic field strength directed toward the object to be heated, which is located inside the cylindrical body. An induction heating device characterized in that it is configured to heat the object to be heated by utilizing the fact that eddy currents flow in the object to be heated when the cylindrical body and the object to be heated are rotated relative to each other by the rotation drive unit.

2. The system further includes a moving part for moving the object to be heated along the central axis direction of the cylindrical body, Multiple cylindrical bodies are arranged along the central axis direction, The induction heating apparatus according to claim 1, characterized in that the rotation drive unit rotates the plurality of cylindrical bodies such that, in the first direction of movement in which the object to be heated is moved by the moving unit, the rotation speed of the cylindrical bodies downstream of the plurality of cylindrical bodies is greater than that of the cylindrical bodies upstream.

3. The induction heating apparatus according to claim 2, characterized in that the rotational drive unit rotates two cylindrical bodies adjacent to each other in the direction of the central axis in opposite directions.

4. The induction heating apparatus according to any one of claims 1 to 3, characterized in that the magnetic body consists of a plurality of magnets.

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