JP2012217250A - Rotor and permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor and a permanent magnet motor in which rotation control of the rotor can be carried out precisely, by detecting the zero-cross point of an induction voltage waveform accurately.SOLUTION: The rotor includes flux barriers 12 for preventing short circuit of magnetic flux formed at both ends of a magnet embedment hole in a circumferential direction, a peripheral core 15 formed on the outer peripheral side of the embedment hole, a radially elongated slit 20 formed from the flux barriers 12 at the both ends of the peripheral core 15 to the peripheral inside, in parallel therewith, via a magnetic path d consisting of a magnetic part having a width corresponding to the plate thickness of the peripheral core 15. On the peripheral inside of a slit 20 formed near both ends of the peripheral core 15, one or more radially elongated slit may be formed furthermore via a magnetic path with a predetermined width.

Description

  The present invention relates to a rotor and a permanent magnet electric motor using the rotor.

  Conventionally, there has been a permanent magnet motor using a magnet-embedded rotor in which permanent magnets are embedded in a rotor core at predetermined intervals and a flux barrier is provided in the vicinity of both end portions of each permanent magnet. For example, a plurality of outer peripheral cores are arranged in contact with the stator side surface of the permanent magnet, and each outer peripheral core is rotated in a region sandwiched between each permanent magnet and the stator. A pair of through-holes penetrating in the axial direction of the child is opened. The pair of through holes are provided symmetrically on both sides with respect to the magnetic center line of the magnetic lines of force generated between each permanent magnet and the stator, and each has a long and narrow slit shape and is spaced from each other toward the stator. A permanent magnet motor is disclosed in which the shape of the taper is narrowed (see Patent Document 1).

  In addition to the above, the slit shape is formed on the rotor of a permanent magnet embedded motor (see Patent Document 2) having a plurality of slits elongated in the circumferential direction, or on the outer peripheral core of the permanent magnet accommodation hole. In addition, a permanent magnet motor or the like that is elongated in the radial direction and includes four or more slit holes that are spaced apart from each other along the permanent magnet housing hole is disclosed (see Patent Document 3).

JP 11-46464 A JP 2008-187778 A Japanese Patent No. 4248984

  In the conventional examples described in Patent Documents 1 to 3, when the rotation control of the motor is performed, a zero cross point where the induced voltage of the induced voltage waveform becomes “0 V” is detected, and the stator side is energized based on this. By switching the current flow, the rotating magnetic field is generated on the stator side, and the rotor can be rotated to follow the rotating magnetic field. However, in Patent Documents 1 to 3, since the induced voltage waveform lies at the zero cross point that is the current switching point, erroneous detection at the zero cross point is likely to occur, and the motor is controlled to rotate accurately. There was a problem that could not be.

  The present invention has been made in view of the above, and it is possible to accurately detect the zero-cross point of the induced voltage waveform, and to switch the flow of current to be supplied to the stator side based on the detected zero-cross point to rotate the An object of the present invention is to obtain a rotor and a permanent magnet electric motor capable of accurately controlling the rotation of the rotor.

  In order to solve the above-described problems and achieve the object, the present invention is a rotor in which magnet-embedded holes are formed in a circular shape at predetermined intervals, and are formed in a cylindrical shape with a magnetic material and in which plate-like permanent magnets are embedded. A permanent magnet embedded in the magnet embedding hole, a nonmagnetic portion for preventing magnetic flux short circuit formed at both circumferential ends of the magnet embedding hole, and an outer periphery formed on the outer peripheral side of the magnet embedding hole. Through a magnetic path consisting of a magnetic core having a width corresponding to the plate thickness of the outer peripheral core from the non-magnetic portion at both ends of the outer core to the inner side in the circumferential direction The hole includes a slit formed in parallel with the nonmagnetic portion.

  In the present invention, it is preferable that d ′ is formed with a width corresponding to the plate thickness of the magnetic part, where d ′ is the width of the magnetic path radially outward from the slit.

  Further, in the present invention, when the length in the radial direction of the slit is Ls and the length in the radial direction to the radially outer end of the nonmagnetic portion is Lf, the relationship Ls> Lf / 2 is satisfied. Preferably there is.

  In the present invention, the rotor, the rotor is disposed inside, and the tooth tip surface of the tooth portion extending inwardly from the annular yoke portion is formed between the magnetic pole portion and the interpolar portion of the rotor. And a concentrated winding stator facing at an interval of the same distance as at least one.

  According to the present invention, the zero-cross point of the induced voltage waveform can be accurately detected, and the rotation control of the rotor can be accurately performed by switching the flow of current flowing to the stator side based on the detected zero-cross point. It is possible to obtain a rotor and a permanent magnet motor that can be performed in the same manner.

FIG. 1 is a plan view illustrating a configuration of a rotor according to a first embodiment of the present invention. FIG. 2 is an enlarged view of an outer peripheral core portion of the rotor of FIG. FIG. 3 is an induced voltage waveform diagram when the rotor of FIG. 1 rotates. FIG. 4 is a diagram for explaining the principle by which the rise of the induced voltage waveform at the zero cross point can be accurately detected when the rotor of the first embodiment rotates in the stator of the permanent magnet motor. FIG. 5 is a plan view showing the configuration of the rotor according to the second embodiment of the present invention. 6 is an enlarged view of the outer peripheral core portion of the rotor of FIG. FIG. 7 is an induced voltage waveform diagram when the rotor of FIG. 5 rotates. FIG. 8 is a plan view of a rotor of a comparative example compared with the rotor of the second embodiment. FIG. 9 is an enlarged view of the outer core portion of the rotor of FIG. FIG. 10 is an induced voltage waveform diagram when the rotor of FIG. 8 rotates.

  Embodiments of a rotor and a permanent magnet motor according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a plan view showing a configuration of a rotor according to a first embodiment of the present invention, FIG. 2 is an enlarged view of an outer peripheral core portion of the rotor of FIG. 1, and FIG. FIG. 4 is a diagram illustrating an induced voltage waveform at the time of rotation of the rotor, and FIG. 4 is a principle that can accurately detect the rising of the induced voltage waveform at the zero cross point when the rotor of the first embodiment rotates in the stator of the permanent magnet motor. FIG.

  As shown in FIG. 1, the rotor 10 according to the first embodiment is formed in a cylindrical shape by laminating a large number of thin silicon steel plates (magnetic bodies), and a rotor shaft 26 is inserted into the center of the rotor 10. Fixed. When a plurality of through holes are punched into the rotor 10 to form a slit, the punching process is performed by leaving at least a magnetic path having a width about the thickness of the magnetic body (silicon steel plate) around the slit. It is a limit. If the punching is performed while leaving a narrower magnetic path than that, the magnetic path will be inclined, making it difficult to laminate the steel plates.

  The six plate-like permanent magnets 14 are embedded in magnet embedding holes formed annularly at predetermined intervals near the outer periphery of the rotor 10 so as to form hexagonal sides with the rotor shaft 26 as the center. Is formed. And the flux barrier 12 as a nonmagnetic part for preventing the short circuit of magnetic flux is formed toward the outer periphery of the rotor 10 in the circumferential direction both ends of the magnet embedding hole of the rotor 10. The outer peripheral side of the rotor 10 surrounded by the permanent magnet 14 and the flux barrier 12 in the magnet embedded hole is the outer peripheral core 15, the center of which is the magnetic pole portion 22, and the portion where the flux barriers 12 at both ends are adjacent to each other. This is the inter-electrode portion 24. A characteristic configuration of the rotor 10 according to the first embodiment is that a slit 20 is formed by punching a radially elongated through hole in the vicinity of the inner side in the circumferential direction of the flux barrier 12 at both ends of the outer peripheral core 15. It is in.

  As shown in FIG. 2, the structure of the outer peripheral core 15 of the rotor 10 of the first embodiment has a thickness of the outer peripheral core 15 from the flux barriers 12 provided at both ends of the outer peripheral core 15 to the inner side in the circumferential direction. A slit 20 is formed so as to be parallel to the flux barrier 12 by punching a through hole having a shape elongated in the radial direction through a magnetic path width d formed of a magnetic part having a corresponding width.

  The rotor 10 of the first embodiment leaves a narrow magnetic path width d corresponding to the plate thickness of the outer peripheral core 15, which is the limit of normal punching, on the inner side in the circumferential direction of the flux barrier 12 at both ends of the outer peripheral core 15. Since the slit 20 is formed in the vicinity of the inside of the flux barrier 12 by punching, the magnetic part having the magnetic path width d is likely to cause magnetic saturation, and the amount of magnetic flux passing through the magnetic path width d can be reduced.

  As shown in FIG. 3, the induced voltage waveform when the thus configured rotor 10 is rotated has a sine wave shape in the vicinity of the zero cross point B, and the induced voltage waveform and the horizontal axis representing the electrical angle Has crossed at a single point, it has been confirmed by experiments that the zero-cross point is not erroneously detected and the zero-cross point can be accurately detected.

  As shown in FIG. 4, when the rotor 10 of the first embodiment rotates in the direction of arrow C in the stator 36 of the permanent magnet motor, the rotor 10 moves from the position of FIG. As the rotation speed increases, the amount of magnetic flux flowing into the tooth portion 32 increases until the magnetic pole portion 22 of the outer peripheral core 15 and the tooth portion 32 of the stator 36 face each other. When the amount of magnetic flux flowing into the tooth portion 32 is maximized at the position where the magnetic pole portion 22 and the tooth portion 32 face each other, and then the rotor further rotates in the direction of arrow C, the magnetic pole portion 22 of the outer peripheral core 15, The amount of magnetic flux flowing into the teeth portion 32 decreases as the area where the teeth tip surface 40 of the teeth portion 32 of the stator 36 overlaps decreases.

  Considering this as the amount of change in magnetic flux flowing into the tooth portion 32 (that is, induced voltage), the point at which the amount of magnetic flux flowing into the tooth portion 32 is maximum corresponds to the point at which the induced voltage turns from plus to minus (zero cross point). . Specifically, as the rotor 10 rotates, when the slit 20 formed in the vicinity of the flux barrier 12 in the inter-electrode portion 24 moves to the next tooth portion 322 with the slot 38 as a boundary, Of the magnetic fluxes that have traveled from the magnetic pole part 22 toward the tooth part 321, the magnetic flux that first moves to the tooth part 322 becomes a magnetic flux that passes through the magnetic path width d between the flux barrier 12 and the slit 20. Since the magnetic path width d is narrowed to the processing limit, the amount of magnetic flux passing therethrough is reduced. Since the magnetic flux passing through the magnetic path width d of the slit 20 has a small amount of magnetic flux, the magnetic flux from the magnetic pole portion 22 toward the teeth portion 321 gradually moves toward the teeth portion 322. As a result, the amount of change in magnetic flux (starting voltage waveform near the zero cross point B) when the amount of magnetic flux flowing into the teeth portion 321 changes from increase to decrease becomes a sine wave, and the zero cross point can be detected accurately. Conceivable.

  Note that a magnetic path having a magnetic path width d ′ is provided on the outer peripheral side of the slit 20, and this magnetic path width d ′ is a limit value that allows the slit 20 to approach the outer peripheral side, that is, a punching limit. It is preferable that the thickness be approximately the same. If the magnetic path width d ′ is increased, a part of the magnetic flux flowing through the outer peripheral core 15 flows into the magnetic path width d via the magnetic path width d ′, and the magnetic flux flowing through the magnetic path width d is increased. This is because the amount increases. Furthermore, the radial length Ls of the slit 20 is preferably at least half or more than the radial length Lf of the adjacent flux barrier 12. This is because if Ls is shortened in the radial direction, a magnetic flux that flows into the stator across the slit 20 may be generated, and the effect of regulating the flow of magnetic flux by the slit 20 may not be obtained.

  On the other hand, the details of the comparative example shown in FIGS. 8 to 10 in which the magnetic path width e between the flux barrier 12 and the slit 20 is twice the magnetic path width d will be described later. As can be seen from the point G, the magnetic path width e is made wider than the magnetic path width d, and the amount of magnetic flux passing through the magnetic path width e is increased. Since the magnetic flux passing through the magnetic path width e has a large amount of magnetic flux, the magnetic flux from the magnetic pole portion 22 toward the teeth portion 321 cannot be gradually moved toward the teeth portion 322. As a result, the amount of change in magnetic flux (induced voltage waveform in the vicinity of the zero cross point G) when the amount of magnetic flux flowing into the tooth portion 321 changes from increasing to decreasing does not become a sine wave, and the zero cross point cannot be detected accurately. The rotor 10 of the first embodiment and the rotor 13 of the comparative example are different in the number and arrangement of slits, and therefore will be compared in detail with the rotor of the second embodiment having a similar rotor structure. To do.

  5 is a plan view showing a configuration of a rotor according to a second embodiment of the present invention, FIG. 6 is an enlarged view of an outer peripheral core portion of the rotor of FIG. 5, and FIG. 7 is a plan view of FIG. It is an induced voltage waveform figure at the time of rotation of a rotor.

  As shown in FIG. 5, in the rotor 11 according to the second embodiment, two slits 18 and 16 are newly provided on both sides via a predetermined magnetic path in addition to the slit 20 according to the first embodiment. Is formed. Since the configuration of the slit 20 has been described in the first embodiment, a duplicate description is omitted.

  As shown in FIG. 6, the slit 18 is formed long in the radial direction, away from the inner side in the circumferential direction of the slit 20 by the magnetic path width c. Further, the slit 16 is formed long in the radial direction, away from the inner side in the circumferential direction of the slit 18 by the magnetic path width b. As described in the first embodiment, the action of the slit 20 is to make the induced voltage waveform in the vicinity of the zero cross point sinusoidal so that the zero cross point can be accurately detected. In the second embodiment, by adding the slits 18 and 16 in addition to the slit 20, the induced voltage waveform is brought closer to a smoother sine wave not only in the vicinity of the zero cross point but also at all electrical angles. The magnetic flux is concentrated at the center of the magnetic pole portion 22 and arranged so as to make it difficult to pass the magnetic flux as it goes to the interpolar portion 24 at both ends, thereby reducing the amount of magnetic flux.

  For example, as shown in FIG. 6, when the position of the slit is defined by the width of the magnetic path, the constant region at the center of the magnetic pole portion 22 of the outer peripheral core 15 is formed only by the magnetic portion without the slit, and the outer peripheral core. 15 is a magnetic path width a between the slits 16 as the first slits near the magnetic pole portion 22, a magnetic path width b is between the slits 16 and the slits 18 as the second slits, and the slit 20 as the third slit. When the magnetic path width d is defined between the flux barriers 12, the relationship is defined as a> b + c> d. Further, when it is considered that a part of the magnetic flux passing through the magnetic path width a of the slit 16 passes through the magnetic path width b ′ and merges with the magnetic flux of the magnetic path width b, a> b + b ′ + c> d It can also be specified that the relationship is

  Further, the position of each slit can be defined by the magnetic flux passing through the magnetic path. For example, the amount of magnetic flux passing through the magnetic path width a is defined as the first magnetic flux amount, the amount of magnetic flux passing through the magnetic path widths b, b ′, c between the slit 16 and the slit 18 is defined as the second magnetic flux amount, and the slit 20 and the flux When the amount of magnetic flux passing through the magnetic path width d with the barrier 12 is the third magnetic flux amount, the magnetic path width is defined so that the relationship of first magnetic flux amount> second magnetic flux amount> third magnetic flux amount is satisfied. May be.

  As described above, the rotor 2 according to the second embodiment concentrates the magnetic flux at the center of the magnetic pole portion 22 of the outer peripheral core 15, makes it difficult for the magnetic flux to pass as it goes to the interpolar portion 24 at both ends, and reduces the amount of magnetic flux. By adjusting the magnetic path width, as shown in FIG. 7, it becomes possible to make it closer to a sine wave than in FIG. 3, so that harmonic components and cogging torque can be reduced. Vibration and noise can be reduced, and efficiency reduction due to iron loss can be improved.

  Further, since the rotor 2 in the second embodiment is formed with the slit 20 similar to that in the first embodiment, as shown in FIG. 7, the induced voltage waveform at the zero cross point E can be raised. Since the zero cross point can be accurately detected without erroneous detection, the rotation control of the permanent magnet motor can be accurately performed.

[Comparison between Example 2 and Comparative Example]
In the following, in order to verify the effect of the rotor in the second embodiment, the magnetic path width d between the slit 20 and the flux barrier 12 is doubled without changing the positions of the slit 16 and the slit 18 in the second embodiment. A comparative example in which the magnetic path width e is changed is created and the effects are compared.

  FIG. 9 is a plan view of a rotor of a comparative example compared with the rotor of Example 2, FIG. 9 is an enlarged view of an outer peripheral core portion of the rotor of FIG. 8, and FIG. 10 is a view of the rotor of FIG. It is an induced voltage waveform figure at the time of rotation.

  The rotor 13 created as a comparative example of Example 2 is obtained by changing the magnetic path width d with the slit 21 adjacent to the flux barrier 12 to a double magnetic path width e as shown in FIG. Since it is the same as that of the rotor 11 of Example 2 about the structure other than that, duplication description is abbreviate | omitted.

  The shape of the slit 21 is the same as the slit 20 of FIG. 6 as shown in the enlarged view of FIG. 9, but the magnetic path width e of the comparative example is twice the width of the magnetic path width d of the second embodiment. ing. For this reason, when the rotor 13 of the comparative example is incorporated and rotated in the stator of the permanent magnet motor, the amount of magnetic flux passing through the magnetic path width e is larger than the amount of magnetic flux passing through the magnetic path width d of the second embodiment. . As a result, for example, as shown in FIG. 4, in the positional relationship of the rotor with respect to the stator, the tooth portion 32 into which the magnetic flux that has passed through the magnetic path width d of the slit 20 of the second embodiment flows flows with the slot 38 as a boundary. When switching from the part 321 to the next tooth part 322, the tooth part 32 into which the magnetic flux that has passed through the magnetic path width e of the slit 21 of the comparative example flows flows from the tooth part 321 to the next tooth part 322 with the slot 38 as a boundary. Compared with the case of switching, the magnetic flux passing through the magnetic path width e has a large amount of magnetic flux, so that the magnetic flux that has been directed from the magnetic pole part 22 toward the tooth part 321 cannot be gradually directed toward the tooth part 322. As a result, the induced voltage waveform in the vicinity of the zero cross point is not a sine wave in the comparative example than in the second embodiment. Specifically, the induced voltage waveform in the vicinity of the zero cross point G shown in FIG. 10 does not have a sine wave shape, whereas the induced voltage waveform in the vicinity of the zero cross point E shown in FIG. It can be seen that the points can be detected.

  Thus, since the difference in the configuration of the rotor between Example 2 and the comparative example is only the difference in the magnetic path width between the slit 20 or 21 and the flux barrier 12, the slit 20 or 21 and the flux barrier 12 It is clear that the magnetic path width of A has an effect on the slope of the induced voltage waveform at the zero cross point.

  The rotors according to the first and second embodiments configured as described above are incorporated in the stator of a permanent magnet motor, and reduce the harmonic components of the induced voltage when driven by 180-degree sine wave energization. As a result, torque ripple is reduced, vibration and noise during rotation are reduced, and a highly efficient permanent magnet motor can be obtained due to the effect of reducing iron loss. Moreover, when driving with 120-degree rectangular wave energization, by reducing the harmonic component of the induced voltage, detection of the zero cross point is facilitated, and a permanent magnet motor that can suppress false detection can be obtained. .

  As described above, the electric motor according to the present invention is useful as a rotor and a permanent magnet electric motor used for a compressor motor or the like capable of performing accurate rotation control.

10, 11, 13 Rotor 12 Flux barrier (non-magnetic part)
14 Permanent magnet 15 Outer peripheral iron core 16, 18, 20, 21 Slit
22 Magnetic pole part 24 Inter-polar part 26 Rotor shaft 32 Teeth part 34 Yoke part 36 Stator 38 Slot 40 Teeth tip surface a, b, b ', c, d, e Magnetic path width

Claims (4)

A rotor in which magnet-embedding holes, which are formed in a cylindrical shape by a magnetic body and in which plate-like permanent magnets are embedded, are annularly formed at predetermined intervals,
A permanent magnet embedded in the magnet embedding hole;
A nonmagnetic portion for preventing magnetic flux short circuit formed at both circumferential ends of the magnet embedding hole;
An outer peripheral core formed on the outer peripheral side of the magnet embedding hole;
Through holes that are elongated in the radial direction from the non-magnetic portions at both ends of the outer peripheral portion iron core to the inner side in the circumferential direction through magnetic paths having magnetic portions having a width corresponding to the plate thickness of the outer peripheral iron core. A slit formed in parallel with the magnetic part;
A rotor characterized by comprising:   2. The rotor according to claim 1, wherein d ′ is formed with a width corresponding to a plate thickness of the magnetic part, where d ′ is a width of a magnetic path radially outward from the slit. . When the length in the radial direction of the slit is Ls and the length in the radial direction to the radially outer end of the nonmagnetic portion is Lf, the relationship is expressed by the following formula (1). The rotor according to claim 1 or 2.
Ls> Lf / 2 (1) The rotor according to any one of claims 1 to 3,
The rotor is disposed inside, and a tooth tip surface of a tooth portion extending inwardly from an annular yoke portion is concentrated opposite to at least one of the magnetic pole portion or the inter-pole portion of the rotor at the same distance. A winding stator,
A permanent magnet electric motor comprising:

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