JP2010004663A - Permanent magnet synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet synchronous motor, using permanent magnets, each having a rectangular cross section in the circumference direction, capable of suppressing torque pulsations, during an energized rotation at a small level so that each of the frequency components is several percents or smaller, relative to a time-average torque. <P>SOLUTION: The permanent magnet synchronous motor is an outer rotor type motor. A rotor core 2a is formed with a groove, and a permanent magnet 1 is fit into and attached to the groove. The aperture angle τ<SB>pm</SB>of the permanent magnet 1 is 70 to 90 percents, relative to the polar pitch τ<SB>p</SB>of a rotor 3. On a stator 6 side, a slot 9 is an open slot, of which the aperture is completely open to a gap 7 between the rotor 3 and the stator 6. The end surface of each tooth 5 is an arc shape projecting toward the rotor 3, in the circumferential direction. The ratio of the curvature radius R<SB>st</SB>of the end surface to the outer diameter R<SB>t</SB>of the stator 6 is set at 5 to 40 percents. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a permanent magnet type synchronous motor used for industrial machines such as elevator hoisting machines.

  Permanent magnet synchronous motors are used in a wide variety of industrial products, and various characteristics and features are required for each product. One of them is the suppression of torque pulsation, especially low noise and vibration. For products that are strongly demanded, torque pulsation must be kept to an extremely small level.

  For example, a motor used in an elevator hoisting machine is an example. In particular, in the case of a direct drive type elevator hoisting machine that does not use a motor torque reduction mechanism, the motor torque is directly transmitted to the elevator car. Therefore, if there is a pulsation in the motor torque, the elevator car will vibrate up and down and the riding comfort will be significantly impaired, and it is therefore necessary to make the torque pulsation characteristic of this motor extremely small.

  On the other hand, in an elevator hoisting machine with a speed reduction mechanism to which a speed reducer is attached, since this speed reducer serves as a buffer material, the torque pulsation of the motor is reduced by this speed reducer and is difficult to transmit to the elevator car. The reduction gear is generally a gear reduction gear using a gear, and the reduction gear itself has a large vibration. For this reason, since the torque pulsation of the motor is sufficiently smaller than the vibration of the reduction gear itself, the torque pulsation of the motor is less likely to cause a problem in practice.

  By the way, as an elevator hoisting machine, a combination of a direct drive hoisting machine that does not use a speed reduction mechanism and a permanent magnet synchronous motor is used for the purpose of suppressing vibration of the elevator car (improvement of riding comfort). However, in such a configuration, the torque pulsation of the motor needs to be at a very small level, such as several percent or less, with respect to the time average torque with respect to all the frequency components. Further, in the motor for the direct drive type elevator hoisting machine, the maximum torque is approximately 200 to 300% with respect to the rated 100% torque, and the above-mentioned total load region from 0% torque to the maximum torque is described above. Thus, the level of torque pulsation must be kept very small. Although the magnitude of the maximum torque with respect to the rated torque varies depending on the type and application of the elevator, the numerical value of the maximum torque is a general numerical value.

  Conventionally, a technique shown in FIG. 10 is known as a method for reducing torque pulsation generated by a surface magnet type synchronous motor.

  FIG. 10 is a cross-sectional view showing a part of a cross section viewed from a plane perpendicular to the rotation axis (not shown) of an inner rotor type surface magnet synchronous motor in which the rotor is disposed inside the stator. 1 is a permanent magnet, 1a is an outer surface, 2 is a rotor core, 3 is a rotor, 4 is a stator core, 5 is a tooth (saliency pole), 6 is a gap (gap), and 7 is a skew.

  In FIGS. 2A and 2B, on the rotor 3 side, on the surface of the rotor core 2, along the circumferential direction of the surface (hereinafter referred to as the circumferential direction), the rotational axis direction (hereinafter referred to as the axial direction). A plurality of elongated permanent magnets 1 are arranged. On the stator 6 side, a plurality of teeth 5 projecting from the inner surface of the stator core 4, that is, the surface on the rotor 3 side, are provided, and windings (not shown) are placed in the slots between the teeth 5. Z) is wound around the teeth 5. A gap 7 is provided between the outer peripheral surface of the rotor core 2 on which the permanent magnet 1 is provided and the tip surface of the teeth 5 of the stator core 4, and 3 for each of the teeth 5 of the stator core 4. By flowing a corresponding phase current of the phase, a rotating magnetic field is generated in the gap 7 between the rotor 2 and the stator 6, and an electromagnetic force is applied to the permanent magnet 1 by the electromagnetic action between the rotating magnetic field and the permanent magnet 1. This occurs and the rotor rotates.

  In such an inner rotor type surface magnet type synchronous motor, conventionally, in order to reduce torque pulsation, as shown in FIG. 10A, the surface of the permanent magnet 1 on the stator 6 side, that is, the outer surface 1a is formed into a cylindrical surface. As shown in FIG. 10, the circumferential cross section of the permanent magnet 1 is shaped like a semi-cylindrical shape (hereinafter, the cross-sectional shape of the permanent magnet is called a semi-cylindrical permanent magnet), or as shown in FIG. A skew 7 is formed on the side surface of the teeth 5 of the stator. Alternatively, it is also known to form a skew on the rotor 3 side, or to combine the method shown in FIG. 10A and the method shown in FIG. It is also widely used in the surface magnet type synchronous motor.

  It is known that the torque pulsation decreases when the magnetic flux density distribution in the motor gap is approximated to a sine wave shape, and as shown in FIG. This is based on this. As shown in FIG. 10B, the provision of the skew 6 causes a phase difference (time difference) in the period of torque pulsation generated for each cross section of the motor in the axial direction. It is intended to counteract each other.

  On the other hand, a surface magnet type synchronous motor using a permanent magnet (hereinafter, referred to as a permanent magnet having a rectangular cross section in the circumferential direction) is also known (for example, a permanent magnet having a rectangular cross section in the circumferential direction) (for example, (See Patent Documents 1 and 2).

  As one example, the surface magnet type motor described in Patent Document 1 covers a part of the surface of the permanent magnet provided on the rotor to cover the mold resin and firmly fixes the permanent magnet to the rotor. Yes, in the case of an inner rotor type motor in which the rotor is arranged inside the stator, the circumferential section is the narrowest distance from the sides on both sides of the rectangular permanent magnet to the stator, The center portion in the circumferential direction of the surface of the permanent magnet is covered with a mold resin so as not to come out of the envelope circle inscribed in the side portions on both sides (stator side).

  In the case of an outer rotor type surface magnet type synchronous motor in which the rotor is arranged outside the stator, the circumferential center of the permanent magnet having a rectangular cross section in the circumferential direction has the smallest distance to the stator. The side portions on both sides in the circumferential direction of the surface of the permanent magnet are covered with the mold resin so as not to come out of the envelope circle circumscribing the central portion (stator side).

  In this way, when the permanent magnet is fixed to the rotor with the mold resin, there are many portions that cover the permanent magnet with the mold resin, and thus the permanent magnet is more firmly fixed to the rotor. In this case, since the mold resin does not protrude from the envelope circle, it is necessary to increase the gap amount between the permanent magnet and the stator as compared with the case where the surface of the permanent magnet is not coated with the mold resin. Therefore, cogging torque and torque pulsation can be reduced.

The technique described in Patent Document 2 as the other example is to reduce the cogging torque when the motor power is off in an outer rotor type motor. Cogging torque is generated in a direction opposite to the rotational direction of the rotor due to the magnetic flux directed from the circumferential side of the permanent magnet when the side of the permanent magnet faces the slot opening between the teeth on the stator side. The technology described in Patent Document 2, which is generated by torque, is a magnet that can be removed from the circumferential side of the permanent magnet by attaching the permanent magnet in a groove provided in the rotor. Is increased to reduce the magnetic flux from the circumferential side to the slot opening, thereby reducing the cogging torque.
Japanese Patent Application No. 2004-222455 JP 2002-331986 A

  As shown in FIG. 10 (a), as a conventional technique for reducing torque pulsation by a surface magnet type synchronous motor, as shown in FIG. And a technique for providing a skew on the stator side, the rotor side, or both, as shown in FIG. 10 (b). Although it is used, it is disadvantageous with respect to the demagnetization resistance of the permanent magnet to make the circumferential cross section of the former permanent magnet disadvantageous, and the latter skew reduces the effective magnetic flux. In order to solve such a problem, there is a problem that an increase in the amount of magnet used (amount of material used to manufacture the magnet: mass) and an increase in the size of the motor are caused.

  Hereinafter, these will be described.

  The demagnetization resistance of a permanent magnet is determined by the physical properties and thickness of the permanent magnet itself. If the physical properties of the permanent magnet are the same, the permanent magnet is determined by the thickness of the magnet.

  With reference to FIG. 11 showing a cross section in the circumferential direction of the permanent magnet 1, the demagnetization resistance of the permanent magnet 1 having the kamaboko shape in the circumferential direction is compared with the circumferential side compared to the central portion B in the circumferential direction. Since the portion A is thin, the side A has a small demagnetization resistance. In order to obtain a certain degree of demagnetization resistance, the thickness of the magnet must be more than a certain level (generally, the physical properties of the permanent magnet, the magnitude of the reverse magnetic field applied to the permanent magnet by the stator, the temperature of the magnet, etc. In the case of a permanent magnet having a semi-cylindrical cross section in the circumferential direction, since it has a thin portion (side A), it is disadvantageous in terms of demagnetization resistance, and in the central portion B in the circumferential direction which is a thick portion, In many cases, there is a margin in the demagnetization resistance.

  By the way, in the surface magnet type synchronous motor, the relationship between the thickness of the permanent magnet and the output torque shows that a proportional relationship is established between the thickness of the magnet and the output torque, but the increase in the magnet thickness increases. The rate of increase in output torque is small relative to the rate.

  FIG. 12 shows the magnetic field analysis result regarding the relationship between the magnet thickness and the output torque in the inner rotor type 24-pole surface magnet type synchronous motor. As shown in the figure, the output increases as the magnet thickness increases. Although the torque also increases, it can be seen that the rate of increase in output torque is small relative to the rate of increase in magnet thickness.

  From this, it can be said that in a surface magnet type synchronous motor, a motor with a small magnet thickness is more efficient than a motor with a large magnet thickness when compared with an index of output torque per mass of the magnet. . That is, as long as the demagnetization performance permits, it is more efficient to reduce the magnet thickness because the amount of magnet use can be reduced.

  The permanent cross-sectional permanent magnet shown in FIG. 11 has a thick portion with a margin for demagnetization performance, but the increase in output torque due to this thickening cannot be expected so much. Rather, there is a problem in causing an increase in the amount of magnets used. As a method for solving this problem, as shown in FIG. 13, it is conceivable that the permanent magnet has a circular cross section in the circumferential direction. However, in this case, the torque in the circumferential direction is equivalent to that of a magnet having a semi-cylindrical shape. In the case of having a pulsation suppressing effect, it is possible to reduce the amount of magnet used compared to a magnet having a semi-circular cross section in the circumferential direction. However, such a permanent magnet having a cylindrical shape has a special shape compared to a permanent magnet having a rectangular cross section in the circumferential direction. Therefore, it takes time and effort to manufacture such a permanent magnet. When it is used for a large multi-pole motor, the positive creation of the magnet is remarkably impaired, and the shape of the stator core must be complicated according to the shape of the permanent magnet.

  FIG. 14 is a view showing a comparison between a permanent magnet 1A (solid line) having a rectangular cross section in the circumferential direction and a permanent magnet 1B (broken line) having a semi-cylindrical cross section in the circumferential direction.

  In the figure, a permanent magnet 1A having a rectangular cross section in the circumferential direction indicated by an arrow X and a permanent magnet 1B having a semi-cylindrical cross section in the circumferential direction are assumed to have the same thickness on the side 1b in the circumferential direction. The permanent magnet 1A having a rectangular cross section in the direction has a uniform thickness throughout, but the permanent magnet 1B having a semi-cylindrical cross section in the circumferential direction has a surface facing one of the stators (not shown). As indicated by a broken line, the arcuate shape rises from the peripheral portion 1b in the circumferential direction to the central portion 1c in the peripheral direction.

  As described above, the demagnetization resistance of the permanent magnet is substantially determined by the thickness and physical properties of the magnet, and the thickness at the peripheral portion 1b is set so that a predetermined demagnetization resistance can be obtained at the peripheral portion 1b. In the permanent magnet 1B having a semi-cylindrical cross section in the circumferential direction, the thickness of the circumferential central portion 1c is larger than the thickness of the peripheral portion 1b. Therefore, the demagnetization resistance at the circumferential central portion 1c is as follows. Is larger than the demagnetization resistance at the peripheral portion 1b. However, this is only a waste of the demagnetization resistance, and is essentially a wasteful cross section in the circumferential direction. It can be said that the permanent magnet 1B and the permanent magnet 1A having a rectangular cross section in the circumferential direction have substantially the same demagnetization resistance. Further, even if it is said that the circumferential cross section of the permanent magnet 1B has an increased thickness at the central portion 1c in the peripheral direction, as described with reference to FIG. The amount of magnet use (mass) of the permanent magnet 1B having a kamaboko-shaped cross section in the direction inevitably increases.

  On the other hand, the permanent magnet 1A having a rectangular cross section in the circumferential direction does not need to generate a portion having a margin in terms of demagnetization resistance, and is therefore less wasteful and necessary for obtaining a required output torque. The size of the magnet, that is, the amount of magnet used, can be reduced as compared with the permanent magnet 1B having a semicircular cross section in the circumferential direction. For the permanent magnet having a circular cross section in the circumferential direction shown in FIG. 13, the circumferential cross section has a simple shape such as a rectangular shape. The shape of the core is also simple, and its manufacturability is excellent.

  As described above, the permanent magnet 1A having a rectangular cross section in the circumferential direction has a greater amount of magnet usage and manufacturability than the permanent magnet 1B having a semi-cylindrical cross section in the circumferential direction and the permanent magnet having a circular arc cross section in the circumferential direction. However, when this is used for a surface magnet type synchronous motor, the generation of torque pulsation becomes a big problem, and it is necessary to suppress this.

  By the way, the surface magnet type synchronous motor using the permanent magnet 1A having a rectangular cross section in the circumferential direction is already known as described in Patent Documents 1 and 2, for example. .

  In the case of the surface magnet type motor described in Patent Document 1, in the case of the inner rotor type, the surface on the stator side of the permanent magnet protrudes outward from the envelope circle inscribed at the sides on both sides in the circumferential direction of the surface. In the case of the outer rotor type, the surface of the stator side of the permanent magnet is not covered with the mold resin so that it does not come out of the envelope circle circumscribed at the center in the circumferential direction of the surface. Covered, the gap between the permanent magnet and the stator side surface is the same size as when not covered with mold resin in this way, so that the permanent magnet can be firmly fixed to the rotor However, Patent Document 1 describes that this can sufficiently reduce cogging and torque pulsation.

  However, as described above, even if the surface of the permanent magnet is covered with the mold resin, the size of the gap between the permanent magnet and the surface of the stator does not change. Thus, it can be reduced to the same extent as in the case of not being coated with the mold resin, and since the surface of the permanent magnet is coated with the mold resin, cogging and torque pulsation are not further reduced.

  In the case of the inner rotor type, the gap between the permanent magnet and the stator is large at the circumferential central portion of the permanent magnet and small at both sides in the circumferential direction of the permanent magnet. It is clear that the distribution of magnetic flux density is not a sinusoidal waveform but a rectangular wave, and is not intended to reduce torque pulsation positively.

  The technique described in Patent Document 2 relates to a reduction in torque fluctuation during non-energization, so-called cogging torque, by fitting a permanent magnet into a groove provided in a rotor. It is not intended to reduce the torque pulsation at the time. For example, a motor for an elevator hoisting machine is rarely used without energization, but rather must suppress torque pulsation during energization rotation. Although there is a possibility that the frequency component of the cogging torque during energization rotation can be reduced by reducing the cogging torque, it is not possible to reduce other frequency components of torque fluctuation, especially for direct drive elevator hoisting machines. As a torque pulsation characteristic that needs to be suppressed by the motor, it is necessary to keep the level small so that each frequency component of torque pulsation during energization rotation is a level that is several percent or less of the time average torque, With the technique described in Patent Document 2, the torque pulsation characteristic cannot be suppressed to such a small level, and it is not intended to suppress it in this way.

  An object of the present invention is to eliminate such a problem and to use a permanent magnet having a rectangular cross section in the circumferential direction so that torque pulsation during energization rotation is less than several percent of each frequency component with respect to time average torque. Another object of the present invention is to provide an outer rotor type permanent magnet synchronous motor which can be suppressed to a small level.

  In order to achieve the above object, the present invention provides a stator in which a stator winding is disposed in a slot between teeth formed in a stator core, and the stator winding is wound around the tooth; A permanent magnet synchronous motor comprising a rotor on which a plurality of permanent magnets are arranged at equal intervals in the circumferential direction on a surface of the rotor core on the stator side, and the permanent magnet has a circumferential cross-sectional shape. A magnet having a rectangular shape, an outer rotor type motor in which a surface on the stator side protrudes from the surface of the rotor core and is disposed on the rotor core, and the rotor is disposed outside the stator. It is characterized by that.

  Further, the present invention is characterized in that a groove is provided on the surface of the rotor core, and the permanent magnet is fitted and pasted in the groove.

  Further, the present invention is characterized in that the slot of the stator is an open slot that is completely opened in the gap between the rotor and the stator.

  In addition, the present invention is characterized in that the stator winding is a concentrated winding wound around a tooth intensively.

  In the present invention, the ratio of the circumferential opening angle of the permanent magnet to the pole pitch of the rotor is 70% to 90%.

Further, the present invention, the tip surface of the teeth, a circular arc-shaped surface in the circumferential direction protruding to the rotor side, the curvature radius R _t of the circumferential surface shape of the front end surface of the teeth, the stator R _t <R _st with _respect to the outer diameter R _{st of the} iron core.

Further, the ratio of the outer diameter R _st of the stator core of the curvature radius R _t of the teeth, characterized in that from 5% to 40%.

  The present invention is also characterized in that the motor is a thin motor having a cross-sectional width of the motor outer diameter larger than the axial length.

  Further, the present invention is characterized in that the number of magnetic poles of the rotor is 16 or more.

  According to the present invention, using a permanent magnet having a rectangular cross-sectional shape in the circumferential direction, torque pulsation is performed so that each frequency component is at a level of several percent or less with respect to the time average torque over the entire area. In addition, it is possible to reduce the magnet mass (amount of material used for one magnet) and improve the manufacturability.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  FIG. 1 is a partial sectional view showing a first embodiment of a permanent magnet type synchronous motor according to the present invention, wherein 1 is a permanent magnet, 2 is a rotor core, 2a is a magnet attachment surface, 3 is a rotor, 4 Is a back core, 5 is a tooth, 6 is a stator, 7 is a gap, 9 is a slot, and 10 is a stator winding.

  In the figure, the first embodiment is an outer rotor type permanent magnet synchronous motor in which a rotor 3 is arranged outside a stator 8, and here, a direct drive type elevator in which torque pulsation is a serious problem. Although a drive motor for a hoisting machine is assumed, it is not limited to this.

  The rotor 3 has a structure in which a plurality of permanent magnets 1 are arranged in the circumferential direction on the inner surface (surface on the gap 7 side) of the rotor core 2, that is, the magnet attaching surface 2a. These permanent magnets 1 have a rectangular cross section in the circumferential direction. Here, these permanent magnets 1 are S-pole and N-pole permanent magnets, and S-pole permanent magnets 1 and N-pole permanent magnets 1 are alternately arranged on the inner surface of the rotor core 2. The number of the S-pole permanent magnets 1 and the N-pole permanent magnets 1 arranged is equal, and is half the number of motor poles.

  On the magnet attachment surface 2a of the rotor core 2, grooves having a concave shape having a width equal to the width in the circumferential direction of the permanent magnet are provided at equal pitches in the circumferential direction, and each of these grooves is formed on the plane. A vertical line at the center point in the circumferential direction of the bottom surface is formed so as to face the rotation center axis of the permanent magnet type synchronous motor, and its side wall forms a vertical plane with respect to the bottom surface to provide a skew. The permanent magnet 1 is fitted and pasted in each of the grooves.

  FIG. 2 is a partial cross-sectional view showing the state in which the permanent magnet 1 is attached to the rotating iron core 2 in more detail. 1b is a circumferential side portion of the permanent magnet 1, 11 is the groove, and 12 is a side of the permanent magnet 1. The portions corresponding to those in FIG. 1 are assigned the same reference numerals, and redundant description is omitted. Is attached.

  In the figure, the groove 11 in which the permanent magnet 1 is fitted has a function of preventing the positional displacement of the permanent magnet 1, and further rotates the magnetic flux 12 from the circumferential side portion 1 b of the permanent magnet 1. It is also for leaking to the iron core 2 and making the magnetic flux density distribution in the gap 7 sinusoidal. The magnetic flux generated from the permanent magnet 1 tends to flow toward the magnetic body such as the rotor core 2 rather than in the gap (air), and the magnetic flux tends to flow in the direction in which it flows easily.

  Therefore, when the groove 11 is provided in the rotor core 2 and the permanent magnet 1 is fitted and pasted thereon, the circumferential side 1b of the permanent magnet 1 approaches the surface of the rotor core 2 made of a magnetic material. Accordingly, the amount of magnetic flux flowing from the side portion 1b to the rotor core 2 is increased, and the amount of magnetic flux flowing from the side portion 1b to the stator 6 is reduced. For this reason, the amount of magnetic flux flowing through the gap 7 from the circumferential central portion of the permanent magnet 1 is large, and the amount of magnetic flux flowing through the gap 7 from the side portion 1b is reduced. The distribution of the magnetic flux density in the gap 7 with the child 6 is sinusoidal.

  Returning to FIG. 1, teeth (saliency poles) 5 provided on the stator 6 are covered with an insulating material (not shown), and a stator winding 10 is disposed in a slot 9 between the teeth 5. Has been. The stator winding 10 is concentratedly wound on the side surface of the tooth 5 from above the insulating material covering the tooth 5 to form a concentrated winding. Here, the stator 6 has a configuration of, for example, 30 poles and 36 slots. Here, an insulating process is also performed by an insulating material at a portion where an insulating material other than the teeth 5 is required, for example, a contact portion of the stator 6 with the back core 4 or between adjacent stator windings 10 in the slot. Has been made.

  Note that no skew is provided in either the stator 6 or the rotor 3.

  Here, the characteristics of the outer rotor type surface magnet type synchronous motor using the permanent magnet 1 having a rectangular cross section in the circumferential direction and the inner rotor type surface magnet type synchronous motor will be compared.

  FIG. 3 is a partial cross-sectional view showing an outer rotor type surface magnet type synchronous motor using a permanent magnet 1 having a rectangular cross section in the circumferential direction. Parts corresponding to those in FIG. Omitted. The detailed shape on the stator 6 side is omitted.

  FIG. 4 is a partial cross-sectional view showing an inner rotor type surface magnet synchronous motor using a permanent magnet 1 having a rectangular cross section in the circumferential direction, and parts corresponding to those in FIG. Description is omitted. The detailed shape on the stator 6 side is omitted.

  In FIG. 3, the dimension of the gap 7 from the circumferential center 1 c to the stator 6 on the outer surface 1 a of the permanent magnet 1 is a, and from the circumferential side 1 b to the stator 6 on the outer surface 1 a of the permanent magnet 1. If the dimension of the gap 7 is b, a <b.

  4, similarly, the dimension of the gap 7 from the circumferential central portion 1c to the stator 6 on the outer surface 1a of the permanent magnet 1 is a ′, and the circumferential side portion 1b on the outer surface 1a of the permanent magnet 1 is the same. A ′> b ′ where b ′ is a dimension of the gap 7 from the stator 6 to the stator 6.

  Here, when the outer rotor type surface magnet type synchronous motor shown in FIG. 3 and the inner rotor type surface magnet type synchronous motor shown in FIG. 4 are configured so that a = b ′ and a ′ = b, a ′> Although a and b ′ <b, the average dimensions of the gaps 7 are almost equal. However, in the case of the outer rotor type surface magnet type synchronous motor shown in FIG. 3, the portion where the gab dimension that contributes most to the torque is small is the circumferential central portion 1c on the outer surface 1a of the permanent magnet 1, and is shown in FIG. In the case of the inner rotor type surface magnet type synchronous motor, it is the side portions 1 b on both sides in the circumferential direction on the outer surface 1 a of the permanent magnet 1. In addition, as shown in FIG. 2, a part of the magnetic flux from the side portions 1b on the outer surface 1a of the permanent magnet 1 leaks into the stator core 2, or the adjacent permanent magnet 1 having a different polarity. However, the magnetic flux from the central portion 1c in the circumferential direction on the outer surface 1a of the permanent magnet 1 hardly leaks, and the effective magnetic flux is large. In particular, in the case of the outer rotor type surface magnet type synchronous motor shown in FIG. 3, the gap dimension a from the circumferential center 1c to the stator 6 on the outer surface 1a of the permanent magnet 1 having a large effective magnetic flux is the inner rotor type surface. It is smaller than the gap dimension a ′ from the circumferential central portion 1 c to the stator 6 on the outer surface 1 a of the permanent magnet 1 in the magnet type synchronous motor.

  As described above, the outer rotor type surface magnet type synchronous motor shown in FIG. 3 is more than the inner rotor type surface magnet type synchronous motor shown in FIG. 4 at the side portions 1b on both sides in the circumferential direction on the outer surface 1a of the permanent magnet 1. Although the gap dimension is large but the effective magnetic flux is small, the outer rotor type surface magnet synchronous motor shown in FIG. 3 has a larger effective magnetic flux than the inner rotor type surface magnet synchronous motor shown in FIG. Since the gap dimension is small at the circumferential central portion 1c on the outer surface 1a, the torque per magnet mass increases, and in this respect, the outer rotor type surface magnet synchronous motor shown in FIG. 3 is more advantageous. Therefore, the first embodiment is an outer rotor type surface magnet type synchronous motor.

  Further, in the outer rotor type surface magnet type synchronous motor shown in FIG. 3, the gap dimension “a” is small at the circumferential central portion 1 c on the outer surface 1 a of the permanent magnet 1, and the both sides in the circumferential direction on the outer surface 1 a of the permanent magnet 1. Since the gap dimension b is small at the side portion 1b, the permanent magnet 1 can obtain the same effect as the case where the circumferential cross section thereof has a semi-cylindrical shape, and a reduction in torque pulsation including cogging torque can be expected. It becomes. On the other hand, in the inner rotor type surface magnet type synchronous motor shown in FIG. 4, contrary to the kamaboko shape, the outer surface 1a of the permanent magnet 1 protrudes at the sides 1b on both sides in the circumferential direction, and the outer surface of the permanent magnet 1 Since the shape is recessed at the central portion 1c in the circumferential direction 1a, the distribution of the magnetic flux density in the gap 7 is rectangular, and torque pulsation increases.

  By the way, in the outer rotor type surface magnet type synchronous motor shown in FIG. 3, when used for a drive motor for an elevator hoisting machine, a torque pulsation characteristic necessary for this, that is, a full load region of 0% to maximum torque, In order to obtain a torque pulsation characteristic in which each frequency component of torque fluctuation is extremely small, that is, several percent or less of the time average torque, the shape of the rotor 3 and the shape of the stator 6 should be optimized. Is required.

  Hereinafter, such optimization will be described. First, optimization of the shape of the rotor 3 will be described.

  In order to reduce each frequency component of the torque fluctuation with respect to the entire load region as described above, as the shape of the rotor 3 is optimized, the circumferential opening of the permanent magnet 1 with respect to the pole pitch of the rotor 3 is increased. The corner ratio must be set appropriately.

FIG. 5 is a characteristic diagram showing the relationship between the opening angle τ _pm of the permanent magnet 1 shown in FIG. 1 and torque pulsation. FIG. 5A shows the state when the opening angle τ _pm is appropriate. FIG. 2B shows the state when the opening angle τ _pm is not appropriate. Specifically, FIG. 4A shows a state where the opening angle τ _pm of the permanent magnet 1 is 82% of the pole pitch τ _p of the rotor 3, and FIG. The state when τ _pm is 65% of the pole pitch τ _p of the rotor 3 is shown.

Here, in FIG.
Opening angle τ _pm of the permanent magnet 1: The rotation center of the motor is taken as the origin and viewed from this origin
Angle from one end of the circumferential width of the permanent magnet 1 to the other end
Every time. Here, the circumferential width of the permanent magnet 1 is determined.
The ends of “one end” and “other end” are the outer surface of the permanent magnet
1d is an end 1d in the circumferential direction on the surface opposite to 1a.
The

Pole pitch τ _p of the rotor 3: One of the widths per pole of the rotor 3 viewed from the origin
Angle from one end to the other. For example, the magnetic pole of the rotor 3
When the number is 30 poles, the pole pitch τ _{p of the} rotor 3
Is a mechanical angle of 360 ° / 30 = 12 °.

According to this definition of the opening angle τ _pm of the permanent magnet 1 and the pole pitch τ _p of the rotor 3, for example, the opening angle τ _pm of the permanent magnet 1 is 10 ° and the pole pitch τ _p of the rotor 3 is 12 °. Then, the ratio of the opening angle τ _pm of the permanent magnet 1 to the pole pitch τ _p of the rotor 3 is
10 ° x 100/12 ° = 83.33%
It becomes.

FIG. 11 shows the first to sixth components of torque fluctuation.
Primary component: torque fluctuation frequency is 6 times the synchronous frequency Secondary component: torque fluctuation frequency is 12 times the synchronous frequency Tertiary component: torque fluctuation frequency is 18 times the synchronous frequency Quaternary component: torque fluctuation frequency Is 24 times the synchronization frequency. 5th order component: The frequency of torque fluctuation is 30 times the synchronization frequency. 6th order component: The frequency of torque fluctuation is 36 times the synchronization frequency.

  In the case of an ideal permanent magnet synchronous motor with no manufacturing dimensional error, the primary component is a basic component of torque pulsation generated when the motor is energized, and the secondary component here is a collision between the rotor 3 and the stator 6. It is a basic component of cogging torque determined by the number of poles. Further, the synchronization frequency is a value obtained from the number of poles and the rotation speed. If the number of poles is P and the rotation speed is N (r / min), the synchronization frequency = (N / 60) × (P / 2). (Hz).

  5 (a) and 5 (b), the horizontal axis represents the torque and the vertical axis represents the ratio of the torque fluctuation to the time average torque, but the torque pulsation when the torque is 0% is expressed as infinite. It will be omitted.

By the way, in order to sufficiently reduce the torque pulsation so as to obtain a torque pulsation characteristic in which each frequency component of the torque fluctuation is extremely small, that is, several percent or less of the time average torque, the opening angle τ _{pm of the} permanent magnet 1 is obtained. In addition to optimization, the shape of the stator 6 must also be optimized.

FIG. 5 shows the characteristics of torque pulsation when the shape of the stator 6 is also optimized. FIG. 5A shows the opening angle τ _pm of the permanent magnet 1 as described above. The ratio of the opening angle τ _pm of the permanent magnet 1 to the pole pitch τ _p is 82%, and FIG. 5 (b) shows that the opening angle τ _pm of the permanent magnet 1 is as described above. The ratio of the opening angle τ _pm of the permanent magnet 1 to the pole pitch τ _p of the rotor 6 is 65%, which is not optimized.

  In the torque pulsation characteristics shown in FIG. 5 (a), each frequency component of torque pulsation is suppressed to a considerably small level over the entire load region (approximately 0% to the entire region of the maximum torque). 0.8% or less.

On the other hand, although the shape of the stator 6 is also optimized, in the case of FIG. 5B in which the opening angle τ _pm of the permanent magnet 1 is not optimized, compared to FIG. It can be seen that the torque pulsation is large as a whole, and in particular, the secondary component is extremely large in the low load region (low torque region), and conversely, the primary component is extremely large in the high load region. The fundamental wave of cogging torque determined by the number of motor poles and the number of slots is included in the secondary component as described above.

Thus, although the shape of the stator 6 is also optimized, in the case of FIG. 5B in which the opening angle τ _pm of the permanent magnet 1 is not optimized, the deterioration of the torque pulsation characteristic is extremely large. Thus, the surface magnet type synchronous motor having such a deteriorated torque pulsation characteristic is inappropriate as a drive motor for an elevator hoisting machine.

In order to obtain an extremely small torque pulsation characteristic in which each frequency of torque fluctuation with respect to the entire load region is several percent or less with respect to the time average torque, the opening angle of the permanent magnet 1 with the shape of the stator 6 optimized. It is appropriate to set τ _pm to 70% to 90% with respect to the pole pitch of the rotor 3.

  Here, optimization of the shape of the stator 6 will be described.

  Here, in FIG. 1, when paying attention to the shape of the slot 9 in which the stator winding 10 is accommodated, the shape of the slot 9 is such that the opening on the gap 7 side is completely opened, and the slot 9 is opened. This is called a slot.

  On the other hand, FIG. 6 is a cross-sectional view showing a general shape of a semi-closed slot, in which 9 ′ is a slot, 13 is a protrusion, and portions corresponding to the previous drawings are given the same reference numerals and overlapped. Description to be omitted is omitted.

  In the same figure, a protrusion 13 is provided on the tip side of the tooth 5 so that the opening on the gap side of the slot 9 ′ is partially closed, and this slot 9 ′ has a general shape of a semi-closed slot. It is.

  In the case of such a semi-closed slot 9 ', the magnetic flux density tends to be extremely high in the peripheral portion due to the protrusion 13 at the tip of the tooth 5, and magnetic saturation is likely to occur. This is mainly due to the fact that the cross section of the magnetic path in the vicinity of the protrusion 13 is smaller than other parts, but the motor has a large output torque per volume of the motor, that is, is actively downsized. Since the motor often has a magnetic path cross section reduced as much as possible, the magnetic flux density becomes extremely high and magnetic saturation occurs remarkably. As for a drive motor for an elevator hoisting machine, downsizing is one important issue, and such characteristics tend to appear. In such a motor, the magnitude of torque pulsation is easily affected by the level of magnetic saturation, so that torque is applied not only to a specific load area but also to the entire load area as in a drive motor for an elevator hoisting machine. When pulsation needs to be suppressed, it is difficult to achieve both suppression of torque pulsation and downsizing. In addition, when the rotor or the stator is not provided with a skew that has a great effect on suppressing the torque pulsation, it becomes more difficult to achieve both the suppression of the torque pulsation and the miniaturization.

  Therefore, in the first embodiment, in order to suppress torque pulsation with respect to the entire load region, the shape of the stator 6 is such that the slot 9 is an open slot as shown in FIG. According to this, since there is no protrusion with a small magnetic path section at the tip of the tooth 5, there is no portion with extremely high magnetic flux density. Accordingly, the suppression and control of torque pulsation for the entire load region is easier than in the case of the semi-closed slot shown in FIG.

Moreover, in this 1st Embodiment, the front end surface of the teeth 5 is made into the circular arc shape which protruded to the rotor 3 side in the circumferential direction in FIG. Here, a circle (surrounding surface of the stator core) C centered on the rotation center (origin) of the motor in which the center portion in the circumferential direction that protrudes most on the rotor 3 side of the tip surface of each tooth 5 is inscribed is assumed. The radius of the circle C (the outer diameter (radius) of the stator core) is R _st . Further, the curvature radius of the arc in the circumferential direction of the distal end surface of the teeth 5 When R _t, and R _t <R _st. Thereby, the front end surface of the teeth 5 does not protrude from the circle C to the rotor 3 side.

Thus, in the first embodiment, the torque pulsation is reduced by setting R _t <R _st as one of the shapes on the stator 6 side.

FIG. 7 is a characteristic diagram showing torque pulsation when R _t = R _st , and parts corresponding to those in FIG.

In this figure, in this case, the tip end surface of the tooth 5 coincides with the circle C. Here, the shape of the rotor 3 is the same as in the case of FIG. 5A, and is optimized, but in FIG. 5A, the tip surface of the tooth 5 with respect to the radius _{Rst of the} circle C is shown. circumferential direction of the arc of curvature radius R _t may be those that are optimized, the shape of the rotor 3 are also the shape of the stator 6 it is also optimized.

When the characteristic diagram shown in FIG. 7 is compared with the characteristic diagram shown in FIG. 5 (a), the magnitude of torque pulsation increases as a whole. In particular, in the low load region, the secondary component becomes extremely large. Yes. Since the secondary component includes the fundamental frequency of the cogging torque, by setting R _t <R _st , the change of the magnetic field when the rotor 3 rotates becomes smooth, and the gogging torque is reduced. Such torque pulsation can also be reduced.

Here, in order to optimize the radius of curvature R _t of the arc in the circumferential direction of the distal end surface of the tooth 5, the upper limit of the ratio of the curvature radius R _t to the radius R _st of the circle C to 40%. When this upper limit is exceeded, it becomes difficult to suppress torque pulsation over the entire load region, and in particular, as shown in FIG. 7, torque pulsation at low load increases.

FIG. 8 is a characteristic diagram showing torque pulsation when the ratio of the radius of curvature R _t to the radius R _st of the circle C is 4.5%, and other conditions are the same as those in FIG. 7, corresponding to FIG. The same reference numerals are assigned to the parts to be repeated, and the duplicate description is omitted.

Reducing the ratio of the curvature radius R _t to the radius R _st of the circle C, compared with the characteristic shown in FIG. 7, the torque ripple at full load region is a torque pulsation in low load is small is gradually reduced, the If the ratio becomes too small, as shown in FIG. 8, the primary component of torque pulsation at the time of high load increases rapidly. When the shape of the rotor 3 is not optimized, this tendency appears more prominently and becomes an inappropriate characteristic as a drive motor for an elevator hoisting machine.

In order to reduce the torque pulsation in a high load from the characteristic shown in FIG. 8, may be Takamere the ratio of the curvature radius R _t to the radius R _st of the circle C, by the lower limit of this ratio is 5%, Torque pulsation is not increased at low and high loads, and characteristics with reduced torque pulsation are obtained so that each frequency component of torque fluctuation is less than a few percent of time average torque over the entire load range. It is.

As described above, the first embodiment is an outer rotor type surface magnet type synchronous motor. On the rotor 3 side, the rotor core 2 is provided with a groove 11 (FIG. 2) without skew, and this The permanent magnet 1 having a rectangular cross section in the circumferential direction is fitted and fixed in the groove 11, and the opening angle τ _pm of the permanent magnet 1 is set to 70% to the pole pitch of the rotor 3 as the shape of the rotor 3. By setting the ratio to 90%, the shape of the rotor 3 is optimized, and on the stator 6 side, the slot 9 is an open slot, and as the shape of the stator 6, the tip surface of the teeth 5 protrudes toward the rotor 3 side. in the circumferential direction is an arc shape, by the ratio of the outer diameter R _t of the stator 6 of the radius of curvature R _st of the distal end face 5 to 40% is to optimize the shape of the stator 6.

  As described above, a surface magnet type synchronous motor with a small torque pulsation can be realized, but when used for a drive motor for a direct drive type elevator hoisting machine, the motor shape is made flat (thin). In addition, since it is flat, it is necessary to provide a multipole motor having a large number of magnetic poles in the rotor.

  The elevator hoisting machine is installed in the machine room or elevator hoistway. Generally, the floor area (cross-sectional area) in the space where the elevator hoisting machine is installed is small, and the allowable space in the height direction is the floor area. It is often larger than that. Therefore, the elevator hoisting machine tends to have a smaller sectional seat (floor area) and a larger height direction. This is because the place where elevator equipment is installed is a dead zone in the building, and the dead zone is oriented not in the horizontal direction but in the height direction so that the residential area and commercial area of the building can be expanded. It is by aiming.

  The same applies to the drive motor for the elevator hoisting machine. In particular, as the external shape of the drive motor for the direct drive type elevator hoisting machine, the axial length is more than the outer diameter width. It is often a small flat motor. This means that an elevator hoisting machine with a large motor shaft length requires a larger floor area, whereas an elevator hoisting machine with a smaller motor shaft length requires an elevator hoisting machine. This is because the floor area can be reduced.

  However, if the motor shaft length is reduced, the torque generated by the motor is reduced accordingly. On the other hand, since the torque required for the motor does not change, it is necessary to increase the outer diameter of the motor in order to interpolate the amount by which the shaft length of the motor is reduced. This is the main reason why there are many flat motors for elevator hoisting machines.

  From the above, the drive motor for the direct type elevator hoisting machine is generally a large-diameter flat motor (large-diameter thin motor). According to past results, the motor outer diameter is 400 mm. This is often the case, and some of the larger ones exceed 1500 mm. Although the shaft length of the motor is various, an ultra-thin motor having an axial length of approximately 1/10 or less of the outer diameter is sometimes used.

  Normally, the number of magnetic poles of the rotor increases in proportion to the outer diameter of the motor. However, since the drive motor for the elevator hoisting machine has a large outer diameter as described above, it has 16 poles, 24 poles, Multipole motors such as 30 poles, 40 poles, and 60 poles are used, and the minimum number of poles is 16 poles as a result.

  The first embodiment described above can also be a thin motor having such a large diameter, and thus can be a drive motor for a direct type elevator hoisting machine.

  FIG. 9 is a partial cross-sectional view showing a second embodiment of a permanent magnet type synchronous motor according to the present invention, wherein 14 is a gap, and the same reference numerals are given to the portions corresponding to the previous drawings, and the description is repeated. Omitted.

  In the same figure, this 2nd Embodiment is the edge part (namely, surface side on the opposite side to the outer surface 1a of the permanent magnet 1) of the circumferential direction both sides of the groove | channel 11 in which the permanent magnet 1 in the rotor 3 was engage | inserted. The gap 14 is provided in the part where the sides on both sides in the circumferential direction face each other.

  By providing the gap 14 in the side portion of the portion fitted in the groove 11 of the permanent magnet 1, the magnetic resistance of this portion is increased, so that the effective magnetic flux in the side portion is reduced, and the prior art shown in FIG. As in the case of the surface magnet type synchronous motor, the same effect as that obtained by using a permanent magnet having a semicircular cross section in the circumferential direction can be obtained, and torque pulsation can be reduced.

  In the second embodiment, the stator 6 may have a conventional general structure as shown in FIG. 6, for example, but may have a structure as shown in FIG. In FIG. 1, a gap 14 similar to the second embodiment may be provided in the groove 11 (FIG. 2).

  In addition, the second embodiment can also be a thin motor having such a large diameter, and thus can be a drive motor for a direct type elevator hoisting machine.

  As described above, in each of the above embodiments, by using the permanent magnet 1 having a rectangular cross section in the circumferential direction, the mass of the magnet can be reduced as compared with the case where the above-described kamaboko shaped permanent magnet is used. It has excellent manufacturability and can effectively reduce torque pulsation characteristics to realize a surface magnet type synchronous motor with good torque characteristics. For example, a drive motor for an elevator hoisting machine It is most suitable for.

1 is a partial cross-sectional view showing a first embodiment of a permanent magnet type synchronous motor according to the present invention. It is a fragmentary sectional view which shows the attachment state to the rotating iron core of the permanent magnet in FIG. 1 in detail. 1 is a partial cross-sectional view showing an outer rotor type surface magnet type synchronous motor using a permanent magnet 1 having a rectangular cross section in the circumferential direction. It is a fragmentary sectional view showing an inner rotor type surface magnet type synchronous motor using permanent magnet 1 whose section in the peripheral direction is a rectangle. FIG. 2 is a characteristic diagram showing a relationship between an opening angle τ _pm of the permanent magnet 1 shown in FIG. 1 and torque pulsation. It is sectional drawing which shows the general shape of a semi-closed slot. FIG. 3 is a characteristic diagram showing torque pulsation when R _t = R _st in FIG. 1. FIG. 6 is a characteristic diagram showing torque pulsation when the ratio of the radius of curvature R _t to the radius R _st of the circle C in FIG. 1 is 4.5%. It is a fragmentary sectional view showing a 2nd embodiment of a permanent magnet type synchronous motor by the present invention. It is sectional drawing which shows a part of cross section seen in the surface perpendicular | vertical to the rotating shaft of the conventional inner rotor type surface magnet type synchronous motor. It is sectional drawing which shows the permanent magnet whose cross section of the circumferential direction of a motor is kamaboko shape. It is a figure which shows the magnetic field analysis result regarding the relationship between the thickness of a magnet in an inner rotor type | mold 24 pole surface magnet type synchronous motor, and output torque. It is a fragmentary sectional view of a motor using a permanent magnet whose section in the circumferential direction is an arc. It is a figure which compares and shows the permanent magnet whose cross section of a circumferential direction is a rectangle, and the permanent magnet whose cross section of a circumferential direction is a semi-cylindrical shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Permanent magnet 1a Outer surface 1b Circumferential side part 1c Circumferential center part 1d Circumferential end part 2 Rotor core 2a Magnet attachment surface 3 Rotor 4 Back core 5 Teeth 6 Stator 7 Gap 9 Slot 10 Stator winding 11 Groove 12 Magnetic flux 13 Protrusion 14 Air gap

Claims (9)

A stator winding is disposed in a slot between teeth formed on the stator core, the stator winding is wound around the teeth, and a circumferential direction on the surface of the rotor core on the stator side And a permanent magnet type synchronous motor provided with a rotor in which a plurality of permanent magnets are arranged at equal intervals.
The permanent magnet is a magnet having a rectangular cross-sectional shape in the circumferential direction, and the stator side surface protrudes from the surface of the rotor core and is disposed on the rotor core.
A permanent magnet type synchronous motor, wherein the rotor is an outer rotor type motor having the rotor arranged outside the stator. In claim 1,
A permanent magnet type synchronous motor, wherein a groove is provided on the surface of the rotor core, and the permanent magnet is fitted and pasted in the groove. In claim 1 or 2,
The permanent magnet type synchronous motor according to claim 1, wherein the slot of the stator is an open slot completely opened in a gap between the rotor and the stator. In claim 1, 2 or 3,
The permanent magnet type synchronous motor according to claim 1, wherein the stator winding is concentrated winding wound around the teeth. In claim 1, 2, 3 or 4,
A permanent magnet synchronous motor, wherein a ratio of a circumferential opening angle of the permanent magnet to a pole pitch of the rotor is 70% to 90%. In any one of Claims 1-5,
The tip end surface of the teeth is a circumferentially arcuate surface protruding toward the rotor side,
The radius of curvature R _t in the circumferential direction of the surface shape of the front end surface of the teeth, to the outer diameter R _st of the stator core, a permanent magnet synchronous motor, which is a R _t <R _st. In claim 6,
The ratio of the outer diameter R _st of the stator core is a permanent magnet type synchronous motor, characterized in that from 5% to 40% of the curvature radius R _t of the teeth. In any one of Claims 1-7,
A permanent magnet type synchronous motor, characterized in that the motor outer diameter is a thin motor having a cross-sectional width larger than an axial length. In any one of Claims 1-8,
A permanent magnet type synchronous motor, wherein the number of magnetic poles of the rotor is 16 or more.

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