JP2021078281A - Laminated iron core and manufacturing method thereof - Google Patents

Abstract

To provide a laminated iron core capable of preventing damage to a coil.SOLUTION: A laminated iron core 20 includes a plurality of teeth 23 extending radially from an annular yoke 22, is a member in which a plurality of electromagnetic steel sheets are laminated, and includes a carbon-based hard coating formed on both end surfaces in the stacking direction. A conductor (stator coil 24) having a carbon-based hard film formed on the surface can be wound around each of the teeth 23 to form a stator. A DLC film is preferably a hydrogenated amorphous carbon (a-C: H) film that is electrically stable and has high insulating properties.SELECTED DRAWING: Figure 5

Description

The present invention relates to a laminated iron core used for a stator of a brushless motor and the like, and a method for manufacturing the same.

In information equipment, industrial equipment, and the like, for example, an outer rotor type brushless motor having a structure in which a rotor is arranged outside the stator or an inner rotor type brushless motor having a structure in which a rotor is arranged inside the stator is used. The outer / inner rotor type brushless motor is used for the purpose of maintaining a constant rotation speed because the moment of inertia tends to be large. The inner rotor type brushless motor has the advantage that the moment of inertia is small and it is easy to control.

In a brushless motor, in order to reduce iron loss, for example, as described in Patent Document 2, a stator core (armature iron core) in which electromagnetic steel sheets, which are materials having high magnetic permeability, are laminated in the axial direction is used, and the height is high. Output is being achieved.

Furthermore, it has been proposed to use diamond-like carbon (DLC), which is a carbon-based hard film, as an insulating material in order to improve the insulation of the stator core around which the coil is wound to reduce the size and output of the motor. ing.

In Patent Document 1, the surface of an electromagnetic steel sheet is coated with an insulating film, the electromagnetic steel sheet on which an insulating film made of at least one of DLC or fullerene is formed is punched, and the processed electrical steel sheet is laminated. It is described that an insulating film is formed between the electromagnetic steel sheets. With this configuration, the insulating film can be formed at a low temperature, eliminating the need for large equipment, and since the insulating film contains carbon as the main component, it does not contain harmful substances and is advantageous in terms of environmental load. It is said that.

In Patent Document 2, a hard carbon film is used as an insulating material for a motor that insulates a stator core and a coil inserted into the slot, and DLC (hydrogen having a film thickness of 20 μm or more and 200 μm or less) is used as the hard carbon film. It is described that a modified amorphous carbon) is used. As a result, the heat dissipation of the coil can be improved, and the enamel coating can be prevented from being damaged when the coil is inserted.

In addition to this, although it is not a laminated core, Patent Document 3 states that a part of the surface of the dust core facing the winding (winding surface) is provided with an inorganic heat-resistant insulating film, for example, a DLC film or a ceramic film. It is described to form. According to this configuration, high heat resistance can be achieved, and especially in the case of a DLC film, it is said that the film forming property into a three-dimensional shape is improved.

Japanese Unexamined Patent Publication No. 2011-193622 Japanese Unexamined Patent Publication No. 2006-141130 Japanese Unexamined Patent Publication No. 2007-74851

However, when DLC is coated on each of the laminated electromagnetic steel sheets as described in Patent Document 1, there is a problem that the productivity is lowered and the cost is increased accordingly. Moreover, since DLC also has various structures and characteristics, it has not been easy to select DLC coating conditions applicable to the motor core.

As described in Patent Document 2, it is technically difficult to guarantee a film thickness of 20 μm or more because the film thickness of DLC used in practical use is about 0.1 to 3 μm, and productivity is also high. May have an adverse effect on.

Since the stator core described in Patent Document 3 uses a dust core as a substrate, it cannot be said that the mechanical strength is so high, and it requires a large-scale equipment for manufacturing, which has a drawback that the cost increases.

In view of the above problems, the present invention has a laminated iron core in which the coefficient of friction is reduced, the coil can be prevented from being damaged, and the thickness can be reduced including insulation by a carbon-based hard film without reducing the productivity. An object of the present invention is to provide a method for manufacturing the laminated iron core and the laminated iron core.

The laminated iron core according to the present invention is a laminated iron core provided with an annular yoke and a plurality of tooth portions extending radially from the yoke.
It is characterized in that carbon-based hard films are formed on both end faces in the stacking direction.

In the laminated iron core according to the present invention, a conducting wire having a carbon-based hard film formed on its surface can be wound around the tooth.

In the laminated iron core according to the present invention, the conducting wire may have a rectangular cross-sectional view.

The method for manufacturing a laminated iron core according to the present invention is a method for manufacturing a laminated iron core including an annular yoke and a plurality of teeth extending radially from the yoke, and the yoke is punched out from a plurality of electromagnetic steel plates. A step of forming a processed body on which the teeth are formed, a step of stacking the processed bodies and crimping them to form a laminated body, and forming carbon-based hard films on both end surfaces of the laminated body in the stacking direction. It is characterized by having a process.

According to the present invention, a laminated iron core capable of reducing the friction coefficient, preventing damage to the coil, and being thinned including insulation by a carbon-based hard film without reducing productivity, and a laminated iron core thereof. A method for manufacturing an iron core can be provided.

It is the schematic sectional drawing of the brushless motor provided with the laminated iron core of this invention. It is a figure which shows the workpiece which constitutes the laminated iron core shown in FIG. 1, (a) is a perspective view, (b) is a front view. It is a figure which shows the material of the laminated iron core shown in FIG. 1, (a) is a perspective view, (b) is a side view. It is a figure which shows the laminated iron core shown in FIG. 1, (a) is a perspective view, (b) is a side view. It is a figure which shows the state which formed the carbon-based hard film on the laminated iron core shown in FIG. 1, (a) is a perspective view, (b) is a front view. It is sectional drawing of the tooth of the laminated iron core of this invention. It is sectional drawing which shows the other example of the teeth of the laminated iron core of this invention.

A mode for carrying out the present invention will be described with reference to FIGS. 1 to 5. The laminated iron core of the present invention can be used, for example, as a magnetic path forming member constituting a stator of a brushless motor.

The brushless motor shown in FIG. 1 is an outer rotor type motor in which a rotor 3 is rotatably provided on the outer peripheral side of the stator 2, and in the illustrated example, it is a 12-pole 9-slot type three-phase DC motor. The stator 2 has a laminated iron core 20 in which a plurality of electromagnetic steel sheets are laminated in the axial direction, and a stator coil 24 wound around a tooth portion 23 of the laminated iron core.

The rotor 3 has a yoke 31 made of a ferromagnet and a permanent magnet 32 having a plurality of magnetic poles on the surface, which is fixed to the inner peripheral surface of the yoke 31. The permanent magnet 32 can be manufactured by subjecting the outer peripheral surface of the ring magnet, which is integrally formed as a whole, to multi-pole magnetization. Not limited to this, it can be manufactured by fixing an arc segment magnet magnetized in the radial direction to the inner peripheral surface of the yoke 31 so that magnetic poles of different polarities are lined up along the circumferential direction.

The permanent magnet 32 can be formed of a known permanent magnet material, for example, a rare earth bond magnet, but in order to further increase the torque, an Nd-Fe-B-based sintered magnet (neodymium-based sintered magnet) having a high energy product is used. ) Can also be used.

In the stator 2, the stator coil 24 wound around the laminated iron core 31 is classified into three groups of U phase, V phase, and W phase according to the phase of the voltage applied from the controller (not shown). It is a coil, and it is a monofilament winding in which one coil 24 is wound around each tooth part. By connecting a drive circuit equipped with four switching elements and performing bipolar drive (full-wave energization), The utilization efficiency of the coil is improved, and a large torque can be obtained.

According to the above brushless motor, for example, the magnetic pole position of the rotor 3 is detected by three Hall elements (not shown), the sine wave voltage at the magnetic pole position is output, and the sine wave voltage is compared by the comparison circuit. A PWM signal is output from the control circuit, then a drive voltage having a different phase of 120 ° is output from the inverter circuit, and the three-phase coil is excited at an appropriate timing to drive a sine wave.

By selectively energizing the coils of each phase and changing the direction of the energizing current in this way, when energizing between two phases (for example, U phase and V phase), one of them depends on the strength of the generated magnetic flux. An N pole is formed at the tip of the laminated core 20 in the phase, and an S pole is formed at the tip of the laminated iron core 20 in the other phase. That is, when the U phase is energized from the V phase, the U phase is excited to the N pole and the W phase is excited to the S pole. Subsequently, the U phase is excited to the N pole and the W phase is excited to the S pole. When the W phase is energized to the U phase, the W phase is excited to the N pole and the U phase is excited to the S pole.

In this way, the two-phase coils existing in the adjacent slots are excited in order, the magnetic flux passes between the two adjacent phases, and the magnetic flux moves to the adjacent phases in order to switch the excited state, whereby the laminated iron core 20 and the permanent magnet The 32 magnetic poles are attracted and repelled, and a rotational torque is generated in the motor.

In a brushless motor, the least common multiple of the number of magnetic poles and the number of slots is the frequency (number of peaks) of the cogging torque, so the 12-pole 9-slot configuration is the minimum compared to the 2-pole 3-slot or 4-pole 6-slot configuration. Since the common multiple is a large value, the cogging amplitude is canceled (distributed), so that the cogging torque is suppressed and the rotation can be performed smoothly.

The relationship between the number of magnetic poles and the number of slots is determined in consideration of the size, output, and cost of the motor. It is changed as appropriate depending on the overall shape and magnetic pole shape. The relationship between the number of magnetic poles and the number of slots may be, for example, 8 poles 9 slots, 10 poles 9 slots, 16 poles 9 slots, or 10 poles 12 slots.

The configuration and manufacturing method of the laminated iron core 20 will be described with reference to FIGS. 2 to 7. For the laminated iron core 20, a plurality of electromagnetic steel sheets having a predetermined thickness (for example, after applying an aqueous solution containing a phosphate or a chromium salt and a resin) are prepared and heated to form an insulating film), as shown in FIG. Each electromagnetic steel sheet is punched out by a press to produce a workpiece 21 having a yoke 22 and a plurality of teeth 23 extending radially from the yoke 22. As the electrical steel sheet, for example, non-oriented electrical steel sheet (NO) having a thickness of 0.35 mm or 0.5 mm can be used.

As shown in FIG. 3, the plurality of workpieces 21 are crimped in the thickness direction and integrated to form a material for the laminated iron core 20. Next, as shown in FIGS. 4 and 5, a carbon-based hard film (for example, a DLC film) is formed on the surface of the laminated iron core 20 to obtain the laminated iron core 20. The DLC film is formed on both end faces of the laminated iron core in the laminating direction as shown by hatching in FIG. That is, in the laminated iron core shown in FIG. 5, DLC films 220 are formed on both end surfaces of the teeth 23 as shown in FIG.

In the present invention, the present invention is not limited to this, and a DLC film may be formed at the corners of the teeth 23 of the laminated iron core as shown in FIG. In the present invention, since the surface of each electrical steel sheet is insulated, eddy currents are prevented from flowing between the laminated electrical steel sheets. In a plate-shaped material, the eddy current is proportional to the square of the thickness. Therefore, by forming the laminated structure in this way, the eddy current loss can be suppressed, and the iron loss is reduced. Moreover, since a DLC film is formed on the surface of the teeth 23 around which the coil is wound, damage to the coil can be prevented.

The thickness of the DLC film is preferably in the range of 0.2 to 1 μm. This is because 0.2 μm or more is required to ensure sufficient insulating properties, and if it exceeds 1 μm, the film forming time is significantly increased, which is not practical.

In the present invention, a round wire or a square wire can be used as the coil wound around the teeth 23 of the laminated iron core 20, but in order to improve the space factor, the coil is cut by slitting. An extra-fine slit wire (slit flat wire or slit square wire) can be used. A normal coil is an enamel wire in which the surface of a conducting wire is insulated, but in the present invention, a square wire having a DLC film formed on the surface of an ultrafine slit wire can be used. By using this square wire, it is possible to obtain a coil with a narrow wire width and excellent insulation withstand voltage and wear resistance, and the winding space factor can be significantly improved compared to ordinary enamel copper wire. Can be done.

As described above, in the present invention, a carbon-based hard film (DLC film) made of diamond-like carbon is used as an insulating film having a low coefficient of friction and excellent wear resistance. This DLC film is ^{a carbon film having an amorphous structure in which both sp 3} bonds (diamond chemical bonds) and sp ² bonds (graphite chemical bonds) are skeleton structures of carbon atoms.

DLC film, high hardness (Hv 1000 or higher), low coefficient of friction (about 0.1 or less), high insulation ^{(10 4 ~10 14 Ω · cm} ), high chemical stability, those having characteristics such as high gas barrier properties Since the surface is flat and a film can be formed at a relatively low temperature of about 500 ° C. from room temperature, it has been conventionally applied to cutting tools, automobile parts, optical parts and the like. The mechanical properties, electrical properties, etc. of the DLC film vary depending on the composition, structure, manufacturing process, and the like.

The ratio of the diamond structure (sp ³ bond) in the ^{DLC film (sp 3} / sp ³ + sp ² ) is 10 to 90%, and further contains 0 to 50 atm.% Of hydrogen, so that it has a wide range of physical properties. Approximately four non-doped DLC films {tetrahedral amorphous carbon (hereinafter referred to as "ta-C"), tetrahedral hydride amorphous carbon (hereinafter referred to as "ta-C: H"), amorphous carbon (hereinafter referred to as "a-"). It is classified into "C") and hydrogenated amorphous carbon (hereinafter referred to as "a-C: H").

ta-C: H, a-C: H is a film produced by, for example, a plasma CVD method (DC plasma CVD, RF plasma CVD, etc.) and intentionally containing hydrogen, and is usually 10 atm. Contains% or more hydrogen. The a-C type has an sp3 bond of more than 20%, less than 50%, and an H of 5 atm. % Or less. The ta-C and a-C are formed by, for example, a PVD method (sputtering method, arc ion plating method, laser vapor deposition method, etc.). The ta-C film is often used with a film thickness of 0.1 to 0.5 μm, and other DLC films are often used with a film thickness of 1 to 3 μm.

The sp ² / sp ³ ratio of the DLC film and the hydrogen content taken in during the film formation process are important structural factors of the DLC film, and the hydrogen content is 15 to 50 atm. It changes in the range of%.
When the hydrogen content in the DLC film increases, the bonds of the carbon skeleton in the unit volume decrease, so that the DLC film becomes soft, and since the CH group is not conductive, the electrical conductivity decreases, and the bond dissociation energy further decreases. Is small, so the heat resistance is reduced. The hydrogen content can be detected by ERDA (elastic recoil detection analysis), which is known as a method for detecting hydrogen in a thin film with high accuracy.

When the abundance ratio of carbon atoms having sp2 bonds is large, the film is soft and has high electrical conductivity. Therefore, in the present invention, the film forming conditions are selected so that the abundance ratio of carbon atoms having sp3 bonds is large. is required. The sp2 / sp3 ratio can be analyzed by, for example, UV Raman spectroscopy or NEXAFS (X-ray absorption fine structure near the absorption edge).

In the present invention, hydrogenated amorphous carbon (a-C:) which is electrically stable as a DLC film in order to be used as a protective film for a laminated iron core which is a component for a motor by utilizing excellent wear resistance and insulating properties. It is preferable to use H).

a-C: H can be produced by a chemical vapor deposition method (CVD method) in a vacuum vessel. That is, a film is formed from a hydrocarbon-based gas such as _{methane (CH 4} ), acetylene (C ₂ H ₂ ), and ethylene (C ₂ H _{4) by an ionic process.} For example, by applying energy to this gas raw material by electric discharge (DC, high-frequency ion source, electron beam laser) to generate positive ions containing carbon, this ion is accelerated by an electric field and supplied onto the cathode substrate. , A DLC film is formed on the surface of the substrate. Specifically, the cleaned substrate is mounted on the substrate holding member, the substrate holding member is set in a vacuum chamber with a built-in heater, and vacuum exhaust, heating, and bombard (the surface of the substrate is etched by Ar ions). Cleaning), (intermediate layer formation), DLC film formation, cooling / exhaust procedure.

In the present invention, for example, it is preferable to form a DLC film by a plasma CVD method, and an example of the film forming conditions for the DLC film in that case is as follows.
Substrate voltage: 300 to 600 V, vacuum degree: 0.1 to 0.2 Pa, Ar flow rate: 20 to 50 sccm, CH ₄ flow rate: 50 to 150 sccm, film formation time: 10 to 120 min.

(Example 1)
Non-oriented electrical steel sheets (applied with an aqueous solution containing phosphate and resin, heated to form an insulating film, thickness 0.5 mm) are punched out with a press to create eight workpieces (see Fig. 2). , These are crimped in the thickness direction to prepare a material for the laminated iron core (see FIG. 3), and then this material is processed as follows to prepare a laminated iron core having a DLC film on the surface (see FIG. 5). did.

After ultrasonic cleaning of the above material with acetone, a DLC film (a-C: H) having a thickness of 1 μm was formed by a plasma CVD method.

The above insulating film (DLC film) was evaluated as follows.
(A) Evaluation of Insulation The dielectric breakdown voltage of the DLC film produced in the present invention was measured using a two-point probe method. In each measurement, the surface of the insulating film of the steel sheet was used as the measurement target. Before applying the voltage, the surface of the insulating film was washed with a cotton swab containing ethanol to prevent creeping discharge. A voltage was applied at a constant rate to determine and evaluate the voltage at which dielectric breakdown occurs.
(B) Slidability evaluation When the laminated iron core and the insulated wire are wound at high speed, the insulated wire may be scratched or damaged, and problems such as short circuit or cutting may occur. Therefore, mechanical slidability is also required for the laminated iron core and the insulating film on the surface of the electric wire. The coefficient of friction of the prepared DLC film was evaluated by a ball-on-disc test. Using a ball-on-disc tester, the coefficient of friction of the insulating film was determined using SUJ2 balls of φ6 as the mating material.
(C) Heat resistance evaluation The amount of heat generated inside electrical equipment is increasing as the performance increases. The high temperature generated by electrical equipment may affect the insulation performance of the insulating material. Therefore, the produced DLC film is left in a constant temperature bath at a constant temperature of about 200 ° C. for 168 hours, the degree of deterioration of the insulating film surface of the electrical steel sheet at that time is determined, and the heat resistance is judged based on the determination. went. No decrease in insulation was observed even after 168 hours of indwelling (○), 30% decrease in insulation (Δ), and 50% decrease in insulation (×). Evaluated as.
(D) Chemical resistance evaluation Considering the atmosphere in which electrical equipment is used, the insulating film may come into contact with acid or alkaline solutions due to liquid leakage from the battery, so it is required to have chemical resistance as well. The chemical resistance of the prepared DLC film is judged based on the degree of decrease in film hardness of the insulating film after immersing the insulating film in a strong acid (sulfuric acid) and strong alkali (sodium hydroxide) solution for one day. Was done. Those in which no decrease in film hardness was observed even after immersion (○), those in which the film hardness decreased by 30% (Δ), and those in which the film hardness decreased by 50% were evaluated as (×). did.

(Comparison example)
For comparison, a laminated iron core similar to that of Example 1 was prepared except that a laminated iron core coated with an epoxy resin conventionally used as an insulating film was produced, and an insulating film was formed under the same conditions as in Example 1. evaluated.

The evaluation results of Example 1 and Comparative Example are shown in Table 1 below. Table 1 also shows the film thickness of the insulating film.

From Table 1, according to the present invention, the film thickness can be reduced by about 1/150 times, the dielectric breakdown voltage can be improved by about 8 times, and the slidability can be reduced by about 35% as compared with the conventional insulating film. I understand. From the above, it goes without saying that the motor can be made smaller. In addition, the DLC film is excellent in heat resistance and chemical resistance, and can be applied even in a harsher usage environment.

Further, in this description, a laminated iron core having a shape composed of a ring and a tooth has been described, but the same effect can be obtained even with a laminated iron core composed of a rectangular processed body having no ring and consisting only of the teeth.

1: Brushless motor,
2: stator,
20: Laminated iron core, 21: Work piece (electromagnetic steel plate), 22: Yoke, 23: Teeth, 24: Stator coil, 210: End face, 220: DLC film 3: Rotor, 31: Yoke, 32: Permanent magnet

Claims (4)

A laminated iron core including an annular yoke and a plurality of teeth extending radially from the yoke.
A laminated iron core characterized in that carbon-based hard films are formed on both end faces in the lamination direction. The laminated iron core according to claim 1, wherein a conducting wire having a carbon-based hard film formed on its surface is wound around the tooth. The laminated iron core according to claim 2, wherein the conducting wire has a rectangular cross-sectional view. A method for manufacturing a laminated iron core including an annular yoke and a plurality of teeth extending radially from the yoke.
A step of punching out a plurality of electromagnetic steel plates to form a workpiece in which the yoke and the teeth are formed, a step of stacking the workpieces and crimping them to form a laminate, and both ends of the laminate in the lamination direction. A method for manufacturing a laminated iron core, which comprises a step of forming a carbon-based hard film on a surface.

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