JP7783485B2 - Manufacturing method of magnetic member - Google Patents

Description

The present invention relates to a method for manufacturing a magnetic component made of electromagnetic steel sheet.

Magnetic components used in alternating magnetic fields are often made from laminates of electromagnetic steel sheets punched into a specified shape to form magnetic circuits, suppress eddy current loss (iron loss), ensure strength, etc. Furthermore, portions of the laminate may be demagnetized to improve performance and reduce loss (efficiency). Such demagnetization techniques are described, for example, in the following patent documents:

JP 2003-304670 Patent Publication No. 2011-6741

Patent Document 1 proposes demagnetizing the bridge portion of a rotor core made of laminated electromagnetic steel sheets by diffusing and penetrating a non-magnetic paint (e.g., [0018], [0019], [0022]). Patent Document 1 also proposes demagnetizing the bridge portion of the rotor core by introducing strain after laser welding (e.g., [0025]).

Patent Document 2 proposes forming localized nonmagnetic regions by irradiating a demagnetizing ink applied to an electromagnetic steel sheet (before lamination) before or after punching with an electron beam, thereby melting and alloying (austenitizing) the Fe in the electromagnetic steel sheet with the Cr-Ni in the demagnetizing ink ([0029]).

However, none of the patent documents provide any specific description or suggestion regarding the irradiation path (scanning trajectory) of the laser beam or electron beam.

The present invention was made in light of these circumstances, and aims to provide a new method for manufacturing magnetic components.

After extensive research, the inventors came up with and realized a new path for the high-energy beam used to demagnetize electromagnetic steel sheets. By further developing this, they were able to complete the present invention, which is described below.

<<Method for manufacturing magnetic member>>
(1) The present invention provides a method for manufacturing a magnetic component, comprising a modification process for demagnetizing a predetermined region of an electromagnetic steel sheet, the modification process including a specific irradiation process for scanning a high-energy beam along a specific trajectory and irradiating the electromagnetic steel sheet, the specific trajectory passing through a planned removal area and a planned remaining area that are set adjacent to each other on the electromagnetic steel sheet, and the start point and end point of the specific trajectory being within the same planned removal area.

(2) According to the present invention, when demagnetizing an electromagnetic steel sheet, it is possible to effectively utilize the electromagnetic steel sheet by minimizing areas where the electromagnetic steel sheet is sacrificed (wasted). In other words, it is possible to demagnetize specific areas of the electromagnetic steel sheet while improving the degree of freedom in the shape of the electromagnetic steel sheet when it is separated (punched, etc.) and the yield of the electromagnetic steel sheet.

The mechanism behind this is thought to be as follows: When a specific region (partial or even localized area) of an electromagnetic steel sheet is demagnetized by irradiating it with a high-energy beam (also simply referred to as a "beam"), the area near the start point (starting point) of the beam irradiation is likely to be insufficiently heated. For example, if an electromagnetic steel sheet is melted by beam irradiation, an unmelted area is likely to form near the starting point. On the other hand, thermal contraction is likely to occur near the end point (end point) of the beam irradiation. For example, if an electromagnetic steel sheet is melted by beam irradiation, shrinkage cavities are likely to form near the end point, and further, cracks are likely to form near the shrinkage cavities. On the other hand, such defects are usually unlikely to form halfway between the start and end points of the beam irradiation (the intermediate path connecting the start and end points).

In the present invention, the start and end points of the trajectory (path) of the beam irradiated onto the electromagnetic steel sheet are concentrated in a single removal area adjacent to the intended remaining area (or part thereof) to be demagnetized. As a result, defects that may arise due to beam irradiation are also concentrated in a single removal area, suppressing their dispersion (scattering) on the electromagnetic steel sheet. As a result, the area of the electromagnetic steel sheet required to remove defects can be reduced, increasing the degree of freedom in the shape of the pieces that can be taken from a single electromagnetic steel sheet and improving the yield of the electromagnetic steel sheet.

<Magnetic member>
The present invention can also be understood as a magnetic member obtained by the above-described manufacturing method. The term "magnetic member" as used herein may refer to either an intermediate product or a final product. An intermediate product is, for example, an intermediate material obtained by irradiating a portion of an electromagnetic steel sheet (raw material, raw material) with a beam to demagnetize it, or a work-in-progress that has undergone further processing (e.g., a separation process (e.g., punching), a shaping process (e.g., flattening, trimming), heat treatment, insulation treatment, etc.). A final product is, for example, a laminate (e.g., a core) obtained by stacking the electromagnetic steel pieces separated after the modification process, or an electromagnetic member (e.g., a field magnet or an armature) obtained by subjecting the laminate to another process or treatment or by adding other components (e.g., a magnet, a coil, etc.) to the laminate.

"others"
(1) In this specification, "modification" or "demagnetization" means making the electrical steel sheet (also referred to as "base material") less magnetizable (making it more difficult for magnetic flux to pass through) before modification. For example, a decrease in (initial) magnetic permeability, a decrease in saturation magnetic flux density, an increase in magnetic resistance, etc. correspond to modification or demagnetization. The ferromagnetic material that is the base material of electrical steel sheet usually undergoes a change in composition and structure through modification or demagnetization, becoming either a diamagnetic material, a paramagnetic material, or an antiferromagnetic material. A typical example of demagnetization is the austenitization of a ferrite phase or a martensite phase.

(2) The "trajectory" of the beam as referred to in this specification is determined based on the path of the beam center. Unless otherwise specified, it is sufficient to refer to the macroscopic path as the beam trajectory, rather than the microscopic path. Furthermore, the "starting point" and "ending point" of the trajectory should be set within the area to be removed, taking into consideration not only the beam diameter but also the heat-affected area associated with beam irradiation, etc.

(3) Unless otherwise specified, "x to y" in this specification includes a lower limit of x and an upper limit of y. Any numerical value included in the various numerical values or ranges described in this specification may be used as a new lower or upper limit to create a new range such as "a to b." Also, unless otherwise specified, "x to y mm" in this specification means x mm to y mm. The same applies to other unit systems.

FIG. 10 is a hypothetical diagram showing an example of division of an electromagnetic steel sheet. FIG. 1A to 1C are schematic diagrams showing an example of a modification step. 10 is a photograph showing an experimental example based on the embodiment. FIG. 10 is a schematic diagram showing a first comparative example of the modification process. 10 is a photograph showing an experimental example based on the first comparative example. FIG. 10 is a schematic diagram showing a second comparative example of the modification process. 10 is a photograph showing an experimental example based on the second comparative example. FIG. 2 is a schematic diagram showing an example of a specific trajectory of a laser beam. FIG. 10 is a schematic diagram showing another example of a specific trajectory of a laser beam. 3A and 3B are schematic diagrams illustrating non-magnetic portions provided in bridge regions of a rotor core. 10 is a schematic diagram illustrating a scanning trajectory of a laser irradiated onto the bridge region. FIG.

One or more components selected from the items described in this specification may be added to the above-described configuration of the present invention. Components related to the method may also be components related to the object (magnetic member, etc.). Which embodiment is best depends on the target, required performance, etc.

《Electromagnetic steel sheet》
The specific magnetic properties (such as magnetic permeability and saturation magnetization), composition, structure, thickness, shape, etc. of the electrical steel sheet are not important. A typical electrical steel sheet has, for example, a bcc crystal structure (ferrite phase) and is made of silicon steel (for example, an iron alloy containing 1 to 5 mass % Si). Its thickness is, for example, 0.1 to 1.0 mm, or even 0.2 to 0.7 mm. If the sheet is too thin, it will result in an increase in the number of laminations (increased costs), a decrease in the strength of the non-magnetic parts, and narrower beam irradiation conditions. If the sheet is too thick, it will result in increased iron loss and increased distortion due to the modification process.

The electrical steel sheet may be either oriented or non-oriented. For example, non-oriented electrical steel sheet is used in electric motors (including generators/simply referred to as "motors"). The electrical steel sheet is usually coated with an insulating film on at least one surface. However, if an insulating film is formed after the modification process, the insulating film before the modification process is not necessarily required.

<<Modification process>>
(1) The modification process involves demagnetizing a predetermined region of the electrical steel sheet by beam irradiation. Demagnetization occurs through changes in the structure, composition, etc. of the predetermined region, such as austenitization or transformation from a bcc structure (α phase) to an fcc structure (γ phase), or alloying of the base material of the electrical steel sheet with a γ-phase stabilizing element.

A typical example of a modification process is alloying, in which a modifier (agent) applied to an electromagnetic steel sheet and the electromagnetic steel sheet (such as silicon steel) are heated and melted (mixed and stirred) by beam irradiation, followed by cooling and solidification. In addition to melting and solidification, the modification process can also be carried out by changing the composition or structure through ablation. The application of the modifier can also be achieved by controlling the atmosphere in the beam irradiation area.

(2) The specific irradiation process is performed by scanning the beam along a specific trajectory. The specific trajectory can take any specific path as long as it passes through at least a portion of the intended remaining area (the intended modification portion) and its starting point and ending point are within the intended removal area adjacent to the intended remaining area.

The start and end points are determined within a continuous range (a range drawn in one stroke) that is continuously irradiated with the beam. Multiple specific trajectories (multiple pairs of start and end points) may be set for one area to be demagnetized. In this case, each pair of start and end points may be within the same area to be removed, or within different areas to be removed.

(3) High-energy beams are, for example, lasers or electron beams with high energy density (fluence). The type of laser (amplification medium, excitation source, optical resonator, etc.), output, energy density, irradiation area, overlap rate, etc. are selected and adjusted as appropriate. The laser may be a continuous wave laser or a pulsed laser. One example of a laser is a fiber laser (a type of solid-state laser) that uses an optical fiber (for example, a double-clad fiber with a rare earth element doped in the core) as the amplification medium. A fiber laser, for example, uses a semiconductor laser (LD) as the excitation source and has an optical reflective mirror on the input side and a low-reflection mirror on the output side as the optical resonator.

(4) Modifiers applied to the electromagnetic steel sheet include, for example, powder, ink (paste, slurry), sheet (film), etc. Powder is applied, for example, by leveling or the like to the designated area of the electromagnetic steel sheet to be demagnetized. Leveling is performed using a depression (recess) formed on the electromagnetic steel sheet corresponding to the designated area, or a form placed on the electromagnetic steel sheet. Ink (slurry) is applied to the designated area by, for example, screen printing or inkjet printing. Sheets (films) are, for example, formed (die-cut, etc.) into the desired shape in advance and then attached to the designated area.

《Other processes》
(1) When the irradiation marks of the beam (referred to as "beads" as appropriate) protrude from the base surface (unmodified surface) of the electromagnetic steel sheet, a shaping process may be carried out to make the bead lower than the base surface of the electromagnetic steel sheet (which may be flat or recessed). The shaping process may be carried out immediately after the modification process, or may be carried out in conjunction with the lamination process described below. The shaping process may also serve to remove thermal distortion, etc. of the electromagnetic steel sheet caused by beam irradiation.

(2) When the area near the surface irradiated with the beam becomes non-insulating, an insulating treatment process may be performed. The insulating treatment process may be performed, for example, by applying an insulating resin or by chemical conversion treatment (e.g., phosphate treatment). The insulating treatment process may also be a processing process that forms an insulating space between opposing surfaces when stacked. The processing process may also serve as the shaping process described above.

(3) After the modification process, the electromagnetic steel sheet is divided (sliced) to obtain electromagnetic steel pieces of the desired shape (separation process). The separation process is performed, for example, by press processing (punching), laser processing, etc. The separation process may be performed before or after the above-mentioned shaping process and/or insulation processing process. After the separation process, further trimming, finishing processes, etc. may be performed. During the separation process, it is preferable to also remove the areas to be removed, including the start and end points of the laser irradiation.

(4) The partially demagnetized electromagnetic steel pieces are stacked to form a laminate (stacking process). Multiple electromagnetic steel pieces are fixed together by crimping using press processing, welding, etc. The laminate may also be subjected to finishing processes to ensure dimensional accuracy.

《Application examples》
Examples of the magnetic member include rotor core pieces and stator core pieces of an electric motor (including a generator), or laminates thereof (rotor cores and stator cores).

When separating rotor core pieces and stator core pieces from a single electromagnetic steel sheet, for example, the slot area of the rotor core piece is the area to be removed, and the peripheral edge area of the rotor core piece adjacent to the stator core piece is the area to be left. Note that the outer peripheral edge area is the area to be left for inner rotor pieces, and the inner peripheral edge area is the area to be left for outer rotor pieces.

The non-magnetic portion formed in the peripheral edge region can have any configuration (shape, width, etc.) or arrangement, as long as it prevents the magnetic field lines from forming a closed loop (short-circuiting). For example, the non-magnetic portion may penetrate the bridge region (peripheral edge region), which forms the frame edge of the slot (magnet hole), in at least one location in an approximately radial direction.

The present invention will be specifically explained using the example of cutting rotor core pieces and stator core pieces used in manufacturing motor cores (laminations) from a single electromagnetic steel sheet.

"overview"
1A , consider the case where rotor core laminations 1 and stator core laminations 2 are punched out from a single electromagnetic steel sheet M. The rotor core laminations 1 and stator core laminations 2 are used to manufacture a rotor core (laminations/not shown) and a stator core (laminations/not shown) of an interior permanent magnet synchronous machine (referred to as an "IPM motor"). For ease of explanation, the same reference numerals are used in each drawing to designate parts of the electromagnetic steel sheet M before punching (imaginary parts shown by two-dot chain lines) and parts of the electromagnetic steel sheet M after punching (actual parts shown by solid lines).

As shown in Figure 1B, which is an enlarged view of part A in Figure 1A, rotor core piece 1 is for eight magnetic poles, and for each magnetic pole, approximately U-shaped slots 101, 102 into which bonded magnets are integrally molded are planned to be formed, with bridges 111, 112 formed on the outer periphery of these slots. The slots 101, 102 (slot areas) and shaft hole 10 before punching correspond to the areas to be removed, and the bridges 111, 112 (bridge areas) correspond to the areas to be left.

The stator core pieces 2 are for 48 poles, and each pole is planned to have comb-tooth-shaped teeth 211, 212 and slots 201, 202, 203 on either side of them. The slots 201, 202, 203 (slot areas) before punching correspond to the areas planned for removal, while the teeth 211, 212 (teeth areas) and yoke 21 correspond to the areas planned for remaining. For convenience, only representative parts of the rotor core pieces 1 and stator core pieces 2 will be explained, and explanations of the other parts that appear repeatedly around the circumference will be omitted.

Incidentally, the annular gap c that forms between the rotor core piece 1 and the stator core piece 2, which are punched out from a single electromagnetic steel sheet M, is reflected in the air gap of the IPM motor. Because the air gap affects motor performance, it is recommended that c be set to, for example, 0.2 to 1 mm, or even 0.3 to 0.7 mm.

<<Modification process>>
(1) An outline of the modification process for demagnetizing a portion of the regions of the electromagnetic steel sheet M before punching that are to become the bridges 111, 112 is shown in Figure 2A. First, modifier layers 311, 312 are provided in and around the regions (Step I). The modifier layers 311, 312 are made of, for example, Cr-Ni alloy powder and are formed by scraping or coating.

Next, a laser is applied from above the modifier layers 311, 312. The laser irradiation has a start point p0 and an end point p1 in the areas expected to become slots 101, 102, and the center of the laser beam is scanned along a trajectory t (specific trajectory) that passes through the areas expected to become bridges 111, 112 (Step II/Specific Irradiation Step). As a result, a bead b (laser irradiation mark/non-magnetic portion) is formed in the laser irradiation area, where the electromagnetic steel sheet M and the modifier layers 311, 312 are melted and mixed, cooled, and solidified.

Here, the trajectory t of the laser irradiation is set so that at least one bead b penetrates bridges 111, 112 in a substantially radial direction. Furthermore, the trajectory t is set so that the bead b formed on bridges 111, 112 does not extend beyond the gap c created during punching onto the stator core piece 2 side. Laser irradiation may be performed from both sides (front and back sides) of the electromagnetic steel sheet M. However, even if laser irradiation is performed only from one side of the electromagnetic steel sheet M, a bead extending from one side to the other side of the electromagnetic steel sheet M (a bead penetrating in the thickness direction) can be formed.

Then, the electromagnetic steel sheet M, from which the excess modifier layers 311, 312 have been removed, is punched using a mold of a predetermined shape (Step III). This results in a rotor core piece 1 having nonmagnetic portions 121, 122 in part of the bridges 111, 112, along with a stator core piece 2. During the punching process, defects (unmelted portions, shrinkage cavities, etc.) that occur at the start point p0 and end point p1 of the laser irradiation are removed as the slots 101, 102 are formed.

(2) Figure 2B shows an example of an experiment in which laser irradiation along the above-mentioned trajectory t was performed on an electrical steel sheet to which a modifier had been added. The electrical steel sheet used was 50HXT780T (thickness: 0.5 mm) manufactured by Nippon Steel Corporation. The modifier used was Cr-50% Ni alloy powder (Wellpowder manufactured by Nippon Welding Rod Co., Ltd.). The modifier was added to the electrical steel sheet by scraping off the powder on a thin plate (thickness: 0.4 mm) placed on the electrical steel sheet. Laser irradiation was performed using a single-type fiber laser (laser oscillator: YLS-2000-SM manufactured by IPG Corporation, fiber core diameter: 24 μm, optical system: 3D galvanometer scanner manufactured by Yaskawa Electric Corporation, focusing diameter: 36 μm) at 340 W, 11 mm/s, amplitude width: 0.6 mm, and Ar flow conditions.

Note that the trajectory t shown in Figure 2B is shown as a roughly U-shaped path for convenience, but in reality it is a roughly linear, reciprocating path of approximately 4 mm. Also, one division (minimum division) of the scale shown in Figure 2B is 0.5 mm.

As can be seen from Figure 2B, an unmelted area was formed near the starting point p0 of the laser irradiation, and a shrinkage cavity was formed near the end point p1. More specifically, the location where the shrinkage cavity occurred was slightly before the end point p1 (upper side of Figure 2B).

The bead (non-magnetic portion) formed in the intermediate path between the start point p0 and the end point p1 was good. This experimental example confirmed that, for example, defective portions of the bead (unmelted portions, shrinkage cavities) can be removed when forming the slot 101, while leaving a good bead portion as the non-magnetic portion 121 of the bridge 111. It was also confirmed that the end of the bead can be contained within the gap c, preventing it from crossing over onto the stator core piece 2 side.

Comparative Example
(1) As a first comparative example, a case where laser irradiation was performed along the trajectory t shown in FIG. 3A was shown. An experimental example of this case is shown in FIG. 3B. The trajectory t shown in FIG. 3B was a substantially linear path of approximately 10 mm. For convenience, the same reference numerals are used for the components and parts already described, and detailed descriptions thereof are omitted (the same applies below). In addition, the electromagnetic steel sheets and laser irradiation conditions used in the experiment were the same as those already described for the experimental example shown in FIG. 2B (the same applies below).

The trajectory t shown in Figure 3A has a start point p0 in the planned area of slots 101, 102, passes through the planned area of bridges 111, 112, and has an end point p1 on the outer periphery. In this case, a defect (shrinkage cavity) that occurs just before end point p1 does not fit within gap c and extends into the area that could become stator core laminations 2. Considering the removal of such defects, it is clear that rotor core laminations 1 and stator core laminations 2 cannot be simultaneously separated from a single electromagnetic steel sheet M.

(2) As a second comparative example, a case where laser irradiation was performed along the trajectory t shown in Figure 4A was shown. An experimental example of this is shown in Figure 4B. In this comparative example, laser irradiation was performed on rotor core pieces 1 that had been punched out first from electromagnetic steel sheet M, and bridges 111, 112 were modified (demagnetized). The trajectory t of laser irradiation was the same as in the example (see Figure 2A).

In this comparative example, defects (unmelted areas, shrinkage cavities, etc.) formed at the start point p0 and end point p1 of the laser irradiation are removed by forming slots 101 and 102. However, defects due to shrinkage cavities and other defects caused by the laser irradiation occurred in the narrow bridges 111 and 112 on the outer peripheral end side of the rotor core piece 1.

《Trajectory》
(1) As long as the predetermined region can be demagnetized and the desired electromagnetic steel pieces can be separated with a good yield from the electromagnetic steel sheet after the modification process, various trajectories for scanning the beam are possible. For example, the substantially U-shaped trajectory t shown in Fig. 2A may be changed to a substantially square-shaped (substantially U-shaped) trajectory t1 shown in Fig. 5A, or to a substantially linear (reciprocating) trajectory t2 shown in Fig. 5B.

Unless otherwise specified, the trajectory referred to in this embodiment and this specification is the general main path that the beam center traces on the electromagnetic steel plate. When observed in detail, the beam center may, for example, trace a secondary path that intersects or oscillates with respect to the main path. A specific example is a trajectory that traces a zigzag secondary path ts when viewed microscopically, but traces a linear main path tm when viewed macroscopically (see Figure 6B).

(2) As shown in Figure 6A, the slot 101 of the rotor core piece 1 is composed of, for example, two slots 1011 and 1012 divided into left and right halves. At this time, non-magnetic portions 1211 and 1212 are formed in the bridges 1111 and 1112 located in the outer peripheral end regions of the slots 1011 and 1012 by the modification process described above.

It is also desirable to form non-magnetic portions 1213 in the bridge 1113 formed between slots 1011 and 1012 (non-peripheral edge region). The non-magnetic portions 1213 may be formed by irradiating the laser along the linear trajectory (main path tm) shown in Figure 6B. This trajectory may also include microscopic zigzag secondary paths ts.

Of course, non-magnetic portion 1213 may be formed in the same manner as non-magnetic portions 1211 and 1212 (see Figures 2A and 2B). In other words, non-magnetic portion 1213 may be formed by scanning a laser along a trajectory with a start point p0 and an end point p1 in either slot 1011 or slot 1012 (the area to be removed) (specific irradiation process).

Furthermore, the nonmagnetic portion 1213 may be formed along multiple specific trajectories. For example, the nonmagnetic portion 1213 may be formed by scanning a laser along a first trajectory having a start point p0 and an end point p1 in the slot 1011 (area to be removed) and a second trajectory having a start point p0 and an end point p1 in the slot 1012 (area to be removed) (specific irradiation process). This also applies to the nonmagnetic portion 121 (1211, 1212). For example, the nonmagnetic portion 121 may be formed by scanning a laser along a first trajectory having a start point p0 and an end point p1 in the slot 101 (area to be removed) and a second trajectory having a start point p0 and an end point p1 in the slot 202 (area to be removed; see Figure 1B) on the stator core piece 2 side (specific irradiation process).

t Locus p0 Start point p1 End point M Electromagnetic steel sheet 1 Rotor core piece 2 Stator core piece 101 Slot 111 Bridge 121 Non-magnetic portion 311 Modifier layer

Claims (6)

a modification step of demagnetizing a predetermined region of the electromagnetic steel sheet,
the modification step includes a specific irradiation step of irradiating the electromagnetic steel sheet with a high-energy beam by scanning it along a specific trajectory,
The specific trajectory passes through a planned removal area and a planned remaining area that are set adjacent to each other on the electromagnetic steel sheet, and has a start point and an end point within the same planned removal area. The method for manufacturing a magnetic component according to claim 1, wherein the specific irradiation process melts at least a portion of the intended remaining area. A method for manufacturing a magnetic component according to claim 1 or 2, wherein rotor core pieces and stator core pieces are to be separated from one electromagnetic steel sheet after the modification process. A method for manufacturing a magnetic component according to claim 3, wherein the intended remaining area is a peripheral end area of the rotor core piece adjacent to the stator core piece. The method for manufacturing a magnetic member according to claim 4, wherein the modification process forms a non-magnetic portion that penetrates approximately radially through at least a portion of the peripheral edge region. A method for manufacturing a magnetic component according to any one of claims 3 to 5, wherein the intended removal area is a slot area of the rotor core piece.