JP2005184872A - Stator core of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relatively inexpensive dust core exhibiting excellent magnetic characteristics, e.g. permeability. <P>SOLUTION: The stator core is formed by arranging electromagnetic steel plates in a core formed of magnetic powder along the circumferential direction of a stator and/or arranging the electromagnetic steel plates along the teeth direction of the core. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a stator core of various motors with improved efficiency, and more particularly to a technique for realizing a characteristic of high magnetic flux density and low iron loss over a wide frequency range in a motor stator.

There are many products using electromagnetism around us, such as transformers, motors, generators, speakers, induction heaters, and various actuators. In order to achieve higher performance and smaller size, it is essential to improve the performance of permanent magnets (hard magnetic materials) and soft magnetic materials. Below, the magnetic core (magnetic core) which is a kind of soft magnetic body among these magnets is demonstrated.
When the magnetic core is disposed in the magnetic field, the magnetic field lines can be concentrated to obtain a large magnetic flux density, and the electromagnetic device can be reduced in size and improved in performance. For example, the magnetic core is inserted into an electromagnetic coil (hereinafter simply referred to as a coil) to increase the local magnetic flux density, or interposed in a plurality of coils to form a magnetic circuit. .

  Such a magnetic core is required to have a high magnetic permeability in order to increase the magnetic flux density. In addition, since it is often used in an alternating magnetic field, it is also required that the high-frequency iron loss be small. High-frequency iron loss includes hysteresis loss and eddy current loss. Hysteresis loss is proportional to the frequency of the alternating magnetic field, whereas eddy current loss is proportional to the square of the frequency. Reduction is required. In order to reduce the eddy current loss, it is necessary to reduce the current flowing through the magnetic core due to the induced electromotive force. In other words, it is desired to increase the specific resistance of the magnetic core.

  Patent Document 1 discloses a technique in which teeth are formed of a unidirectional electrical steel sheet and the easy magnetization direction of the unidirectional electrical steel sheet is a radial direction. This document discloses that the iron loss in the teeth can be greatly reduced as compared with the case where the non-oriented electrical steel sheet is used. Further, as a method for omitting the step of laminating steel sheets and suppressing the cost, there is a method in which iron-based magnetic powder is sintered and used as a dust core.

In order to improve the efficiency of the electromagnetic motor, for example, increase the output torque of the three-phase synchronous motor and reduce the size of the shape, the iron loss in the teeth and the yoke must be further reduced. Manufacturing costs must also be kept down. Since the conventional dust core has a small specific resistance, it is mainly used only in a DC coil, and is rarely used in an AC coil. In order to increase the specific resistance, Patent Document 2 discloses that a magnetic core is manufactured by high-pressure molding of an iron-based magnetic powder coated with an insulating coating.
JP 7-067272 A JP-T-12-504785

  However, in Patent Document 2, the molding pressure at the time of pressure molding cannot be increased, and only a low-density powder magnetic core can be produced, and magnetic characteristics such as magnetic permeability are not always sufficient. Moreover, in the magnetic core formed of the electromagnetic steel sheet, the iron loss is low at a frequency of about 200 Hz or less. However, when the frequency is higher than this, the iron loss increases due to an increase in eddy current, and the iron loss becomes higher than that of the dust core. These problems are not limited to synchronous motors but are common to synchronous generators. Accordingly, it is an object of the present invention to provide a dust core having excellent magnetic properties such as magnetic permeability and relatively low cost.

Specific means of the present invention for solving the problems are as follows.
(1) A stator core for a motor, wherein an electromagnetic steel plate is disposed in a magnetic core formed using magnetic powder.
(2) The stator magnetic core of the motor according to (1), wherein electromagnetic steel plates are arranged along the circumferential direction of the magnetic core.
(3) The stator magnetic core of the motor according to (1) or (2), wherein electromagnetic steel sheets are arranged along the teeth direction of the magnetic core.
(4) A motor having a stator magnetic core comprising the magnetic powder according to any one of (1) to (3) and an electromagnetic steel plate.
(5) A vehicle comprising the motor according to (4).

  According to the present invention, by using a stator magnetic core formed by arranging magnetic steel sheets along the circumferential direction or the tooth direction and filling magnetic powder around them, the iron loss is low from low frequency to high frequency, and the efficiency is high. A high motor can be obtained.

  As described above, in order to improve the efficiency of the motor, increase the output torque, reduce the size of the shape, etc., iron loss has been reduced in the teeth and the yoke. The inventors of the present invention have conducted intensive research in order to effectively realize a technique that omits the laminating process of the magnetic steel sheets and does not deteriorate the magnetic characteristics as much as possible. As a result, when the stator was constructed by placing electromagnetic steel sheets in the yoke and teeth in the dust core, it was confirmed that the iron loss was reduced compared to the stator of the conventional dust core, and the conventional pressure was applied from low to high frequencies. It has been found as a knowledge that a stator core having a lower iron loss and a higher permeability can be obtained than a stator core composed only of a powder magnetic core or a magnetic steel sheet.

Next, the present invention will be described in more detail with reference to embodiments.
Although it is a magnetic powder, this specific resistance is an eigenvalue that does not depend on the shape. If the powder core has the same shape, the larger the specific resistance, the smaller the eddy current loss, and the specific resistance ρ is 0.7 μΩm. If it is less than 1, eddy current loss cannot be sufficiently reduced. Therefore, it is desirable to use magnetic powder of 0.7 μΩm or more. In the present invention, there is no need to stack the plates to make the magnetic steel plate a core and fix it by caulking, bolting or welding, etc. After the electromagnetic steel plate is placed, the surroundings are covered with magnetic powder and molded. is there.

Unlike a cast or sintered magnetic core, the dust core is made of a pressure-formed body of iron-based magnetic powder. The bonding of the particles of the powder is mainly mechanical bonding accompanying plastic deformation and not metallurgical bonding.
The iron-based magnetic powder is a ferromagnetic metal powder mainly composed of iron. For example, the iron-based magnetic powder is preferably an iron powder made of pure iron. This is because a high magnetic flux density can be easily obtained and hysteresis loss can be reduced due to a decrease in coercive force. The purity of the pure iron is preferably 99% or more, more preferably 99.5% or more, and 99.8% or more. As such iron powder, for example, ASC100.29 manufactured by Höganäs can be used. This iron powder has components other than Fe: C: 0.001, Mn: 0.02, O: 0.08 (unit: mass%) or less, and has very few impurities compared to other commercially available iron powders. Iron powder with excellent properties.

The iron-based magnetic powder may be a mixed powder composed of a plurality of powders suitable as a magnetic core material, or may be an alloy powder. The iron-based magnetic powder may be a granulated powder or a coarse powder. The type of iron oxide is not limited, but examples include α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and FeO. The specific resistance increases as the oxide film covers the entire particles of the iron-based magnetic powder and the film thickness increases. However, since the oxide film has a lower magnetism than iron, if the amount is too large, the magnetic flux density obtained in each magnetic field is also reduced.

  Since the magnetic flux flows in the circumferential direction of the motor in the yoke of the motor magnetic core, the longitudinal direction of the electromagnetic steel sheet is arranged along the circumferential direction. On the contrary, when the electromagnetic steel sheet is arranged perpendicular to the circumferential direction, an eddy current flows in the steel sheet surface and the loss increases. In the teeth, the same effect can be obtained by arranging the longitudinal direction of the electromagnetic steel sheet along the teeth direction.

  Next, in the magnetic powder filling step, the iron-based magnetic powder is put into a mold in which an electromagnetic steel plate is arranged. It is preferable that this filling step is a step of filling the heated iron-based magnetic powder and the heated molding die. When both the iron-based magnetic powder and the molding die are heated, the iron-based magnetic powder and the higher fatty acid-based lubricant react stably in the subsequent molding process, and a uniform lubricating film is formed between the two. Is easily formed. Therefore, for example, it is preferable to heat both to 100 ° C. or higher. Although it is a higher fatty acid-based lubricant, when this is applied to the inner surface of the molding die, filled with magnetic powder and processed warm, the lubricity between the inner wall of the molding die and the magnetic powder improves, It is possible to reduce the penetrating pressure from the mold to the pressure molding pair.

  In the molding process, pressure is applied warmly, and the magnetic powder is molded into a shape suitable for the mold. “Warm” in the molding process means molding under an appropriate heating condition in consideration of iron-based magnetic powder, higher fatty acid-based lubricant, molding pressure and the like. In order to promote the reaction between the iron-based magnetic powder and the higher fatty acid-based lubricant, the molding temperature is preferably set to 100 ° C. or higher, and in order to prevent deterioration of the higher fatty acid-based lubricant, the molding temperature is preferably set to 200 ° C. or lower.

  The degree of "pressurization" in the molding process is also appropriately determined according to the required characteristics of the powder magnetic core, the type of iron-based magnetic powder, oxide film and higher fatty acid-based lubricant, the material of the molding die, the internal properties, etc. The However, in the case of the production method of the present invention, the molding can be performed under a molding pressure exceeding the conventional molding pressure. For example, the molding pressure can be 700 MPa or more.

The above is a method for producing a magnetic core using magnetic powder, and the present invention is characterized by combining this with an electromagnetic steel sheet. In a low frequency region such as 50 Hz, the magnetic flux flows through an electromagnetic steel sheet having a higher permeability than the magnetic powder. Therefore, the magnetic permeability of the motor core of the present invention is higher than that of the dust core alone, and the iron loss is reduced. Therefore, the torque is improved. In addition, since the periphery of the magnetic steel sheet is formed of magnetic powder having good high frequency characteristics, the iron loss at a higher frequency than that of the magnetic steel sheet motor core is reduced. Therefore, a motor with a low iron loss can be achieved at a higher rotational speed.
Hereinafter, the present invention will be described based on examples.

FIG. 1 is a sectional view of a stator of a permanent magnet motor to which the present invention is applied. In the motor stator of FIG. 1, the electromagnetic steel sheet is arranged along the yoke part, and the teeth part is also arranged in parallel in the radial direction toward the rotor center. The surroundings were wrapped with magnetic powder ASC 100.29 manufactured by Höganäs, and molded by pressing at a temperature of 200 ° C.
Here, the rotor was put in, and the iron loss was measured using a wattmeter with the current and voltage input from the outside. The frequency was 800 Hz, and the magnetic flux density of the yoke was 0-1.2T. As comparison objects, those formed only with a dust core and those made of a non-oriented electrical steel sheet were used.

The dust core had the highest iron loss, and it showed about 130 W / kg at 1.0T. On the other hand, what was produced with the non-oriented electrical steel sheet was about 50 W / kg. In the iron core of the present invention, the magnetic flux flows through the magnetic steel sheet through which the magnetic flux passes more easily than the dust core, so that the magnetic permeability increased and the iron loss decreased compared to the dust core alone (FIG. 2). The iron loss is higher than that of the non-oriented electrical steel sheet, which is an intermediate value between both cores. However, it is not necessary to laminate the steel sheets in the same manufacturing process as the dust core, and it is easier to manufacture.
Therefore, the torque is improved by the high magnetic permeability, and the efficiency is improved by the low iron loss. Moreover, since the circumference | surroundings of an electromagnetic steel plate are formed with the magnetic powder with a favorable high frequency characteristic, the iron loss in a frequency higher than an electromagnetic steel plate becomes low. Therefore, a motor with low iron loss could be formed even at higher rotational speeds.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 3 shows a cross-sectional view of a stator of a permanent magnet motor to which the present invention is applied. In the stator of the motor, only the magnetic powder is disposed in the yoke portion, and the electromagnetic steel plate is disposed in the central portion in the tooth portion. The surroundings are wrapped with magnetic powder and fixed by pressing. It was compression molded and formed at a temperature of 200 ° C.

A circular electromagnetic steel sheet was placed in the center of the magnetic core instead of the rotor, and the magnetic properties were measured. The magnetic flux flows through the magnetic steel sheet through which the magnetic flux passes more easily than the dust core. The magnetic permeability increased and the iron loss decreased compared to the magnetic core consisting only of the comparison material powder. Table 1 summarizes the magnetic properties. Coercive force Hc is the magnetic flux density _{B 50} in half of the magnetic powder core is 0.16T higher magnetic powder core. The iron loss at 1.0 T and 2 kHz is about 85% of the magnetic powder core.
Moreover, since the circumference | surroundings of an electromagnetic steel plate are formed with the magnetic powder with a favorable high frequency characteristic, the iron loss in a frequency higher than the electromagnetic steel plate magnetic core of a comparison material becomes low. Therefore, a motor with a lower iron loss at a higher rotational speed was obtained.

The example of the stator core of the present invention has been described above. Next, an embedded magnet synchronous motor (IPM) using the stator core of the present invention will be described as a third embodiment.
FIG. 4 shows a schematic configuration of the embedded magnet synchronous motor 1 of the present embodiment. The stator 2 includes an electromagnetic steel plate 3 embedded in the stator and a magnetic powder 4 that fixes the periphery thereof. The electromagnetic steel sheet is arranged with a curvature along the outer shape of the stator. Windings 5 are provided around the teeth formed of magnetic powder.
As described above, according to the stator magnetic core having a structure in which the magnetic steel sheet is fixed with the magnetic powder, it has high magnetic permeability and low iron loss characteristics in low frequency to high frequency excitation, and high efficiency can be achieved.
Since the structure of the rotor is the same as that of the conventional one, detailed description is omitted.

  Next, in order to evaluate the performance of the embedded magnet synchronous motor of this embodiment, an embedded magnet synchronous motor with an output of 60 kW class was manufactured. As a comparative example, a stator magnetic core made only of magnetic powder having the same shape except that there is no electromagnetic steel sheet in the stator was manufactured, and the performance of a motor in which a rotor was incorporated at the center of the stator was evaluated. And the performance of the internal magnet synchronous motor of this embodiment and the motor as a comparative example were compared.

  Specifically, when the efficiency at 10,000 rpm (rotation / min) and 60 kW was compared, the efficiency of the embedded magnet synchronous motor of this embodiment was higher than that of the comparative example. The main cause of such a result is that the magnetic permeability from the low frequency to the high frequency (50-2000 Hz) by the stator core embedded with the magnetic steel sheet is high, the iron loss is low, and the copper loss of the winding is also reduced. I understood it.

  In the above description, the embedded magnet synchronous motor of FIG. 4 has been described as an example. However, it is apparent that the present invention can be applied to an embedded magnet type rotating machine. That is, the present invention can be applied to electric motors other than synchronous motors, and can also be applied to generators that require high-speed rotation.

  As described above, according to the present embodiment, a stator magnetic core that is highly resistant to centrifugal force and can be rotated at high speed can be realized. Further, according to the embedded magnet synchronous motor of the present embodiment, it is possible to realize a motor capable of high-speed rotation without deteriorating performance.

Next, the vehicle of the present invention will be described. A vehicle equipped with the rotor of the present invention is an EV (electric vehicle), HEV (hybrid electric vehicle), or FCV (fuel cell vehicle). In the present embodiment, an explanation will be given by taking EV as an example.
FIG. 5 schematically shows an EV according to the present embodiment. An EV (electric vehicle) 21 shown in FIG. 6 drives a tire 24 by distributing torque via a transmission 22 and a differential gear 23 by an embedded magnet synchronous motor 20 having a stator magnetic core described in the third embodiment. ing.

However, the vehicle of the present invention is not limited to this case. Used for various types of vehicles, such as a type that does not have a transmission machine, a type that drives two wheels independently with two motors, and a type that independently drives tires with a wheel-in motor with a motor installed inside the wheels. Of course you can.
According to the vehicle of this embodiment, since the embedded magnet type motor with high high-speed rotation performance is used as the driving force source, the drive portion has excellent mechanical strength and can easily perform output operation over a wide range including the high-speed rotation region. A vehicle that achieves the above can be provided.

As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these cases, and it goes without saying that various additions or modifications can be made by those skilled in the art.
For example, in the above description, the case where the magnetic powder ABC100, 20 manufactured by Höganäs is used as the stator material is shown, but the present invention is not limited to this case. For example, the present invention can also be applied when using Mitsubishi Materials MBS100 or the like.

It is a figure which shows the stator magnetic core which has arrange | positioned the electromagnetic steel plate in the yoke part. It is a figure which shows the iron loss of the stator magnetic core of this invention. It is a figure which shows the stator magnetic core which has arrange | positioned the electromagnetic steel plate in the teeth part. It is a figure which shows an example of the interior magnet synchronous motor (IPM) which has a stator magnetic core of this invention. It is a figure which shows an example of the vehicle of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Embedded magnet synchronous motor 2 Stator 3 Magnetic steel plate 4 Magnetic powder 5 Winding 20 Embedded magnet synchronous motor 21 EV (electric vehicle) 22 Transmission 23 Differential gear 24 Tire

Claims (5)

A stator core for a motor, wherein an electromagnetic steel plate is disposed in an iron core formed using magnetic powder. 2. A stator core for a motor according to claim 1, wherein an electromagnetic steel plate is disposed along a circumferential direction in a yoke portion of the iron core motor. The stator magnetic core of the motor according to claim 1 or 2, wherein an electromagnetic steel sheet is disposed along a tooth direction in a tooth portion of the iron motor. A motor comprising a stator magnetic core of a motor comprising the magnetic powder according to claim 1 and a magnetic steel sheet. A vehicle comprising the motor according to claim 4.

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