JP4834386B2 - Permanent magnet type motor and electric power steering device using the same - Google Patents

Description

  The present invention relates to a permanent magnet type motor having a permanent magnet attached to a rotor, and more particularly to a permanent magnet type motor which reduces distortion and cogging torque of an induced voltage waveform to reduce noise and vibration, and an electric power steering apparatus using the same. About.

  An electric power steering device may be provided to assist the vehicle driver's steering operation. This electric power steering device detects a steering torque applied to a steering shaft by a driver with a torque sensor, and generates a torque corresponding to the value by an electric motor and applies the torque to the steering shaft. The electric motor to be used is required to have less pulsation in the generated torque in order to realize a smooth steering operation.

  The pulsation included in the torque generated by a permanent magnet motor with a permanent magnet attached to the rotor is rotated by energization with the cogging torque generated when the rotor is turned even in a static state where no current flows through the motor. Torque ripple that is newly generated when

Of these, the cogging torque is based on the difference in the static magnetic attractive force between the rotor and the stator depending on the rotor position. In order to reduce the difference in magnetic attractive force, a closed slot-shaped slot 52 having no opening is employed as a slot for winding the stator winding around the stator core 51 of the stator 50 as shown in FIG. Sometimes. However, in the case of a closed slot-shaped occurs distortion in waveform of induced voltage when the magnetic flux leakage to short circuit between the magnetic pole teeth 54 adjacent in the coupling portion 53 of the closed slot is rotated because the rotor not a viable and torque ripple there is a ing big drawback.

  As a countermeasure, there is a structure in which a plurality of grooves 55 opened on the slot 52 side are arranged at non-equal intervals in the circumferential direction at a connecting portion 53 between adjacent magnetic pole teeth 54 as shown in FIG. The purpose of this is to reduce the magnetic flux leakage by increasing the magnetic resistance of the connecting portion 53 by providing the groove 55, and to reduce the combined cogging torque by arranging the grooves 55 at non-equal intervals to disperse the cogging torque. (See Patent Document 1). However, even if the groove 55 is provided, it is still a closed slot, and the magnetic flux leakage as a whole is large. Further, since the grooves 55 are arranged at unequal intervals, there is a problem that the number of processing steps increases.

On the other hand, in the case of a general open slot shape, since there is little magnetic flux leakage that short-circuits between the magnetic pole teeth, there is an advantage of less distortion of the induced voltage waveform. On the other hand, there is a drawback that the cogging torque increases because the magnetic energy change in the open slot portion becomes large. Further, in the case of the open slot shape, there is a risk that the winding of the stator winding jumps out of the opening of the slot and the rotor is locked, which becomes a problem in a severe safety application. In this respect, the closed slot shape is safe because there is no fear of the winding jumping out.
JP 2002-142391 A

  The present invention has been made to solve such problems, and the problem is to eliminate the risk that the winding of the stator winding jumps out of the stator core and locks the rotor. And providing a permanent magnet type motor with reduced noise and vibration by reducing torque pulsation during rotation.

According to a first aspect of the present invention, there is provided a stator including a rotor having a field permanent magnet attached thereto, and a stator iron core provided with a plurality of magnetic pole teeth and a stator winding slot. In the permanent magnet type motor, the stator core includes a stator core piece that is a closed slot by connecting the tip of the magnetic pole tooth to the tip of the adjacent magnetic pole tooth, and a stator that is an open slot without being connected. The stator core is configured by mixing and laminating iron core pieces, and the stator core is composed of a closed slot block in which one or more stator core pieces having the closed slots are laminated, and one or more stator core pieces having the open slots. The permanent magnet type motor is configured by stacking a plurality of open slot blocks stacked one on another, and the permanent magnet attached to the rotor is disposed only at a position facing the open slot block .

In the permanent magnet type motor having such a configuration, the stator core pieces having the closed slots are prevented from jumping out to the rotating portion of the stator windings, and at the same time, the stator core pieces having the open slots are mixed. The distortion of the induced voltage waveform is reduced and the torque ripple is reduced. Therefore, the safety and the noise and vibration can be reduced at the same time.
Further, if the permanent magnet is disposed only in the portion facing the block in which the stator core pieces having the open slots are laminated, the distortion of the induced voltage waveform can be reduced. Accordingly, the torque ripple is reduced and the noise and vibration are reduced.

  According to a second aspect of the present invention, in the permanent magnet type motor according to the first aspect, a stator core piece having the closed slot is laminated at both axial ends of the stator core. It is a permanent magnet type motor.

  The slots formed in the stator core pieces at both axial ends have a closed slot shape, which has a great effect on preventing the stator winding from jumping out to the rotating portion.

  According to a third aspect of the present invention, in the permanent magnet type motor of the first aspect, the opening width of the open slot in the stator core piece having the open slot is based on the winding diameter of the stator winding. It is a permanent magnet type motor characterized by being narrowed.

  If the opening width is narrower than the winding diameter, there is an effect that the risk of the stator winding jumping out from the opening of the open slot to the rotating portion is reduced.

  According to a fourth aspect of the present invention, in the permanent magnet type motor according to the first aspect, the thickness of the stator core piece having the closed slot is greater than the thickness of the stator core piece having the open slot. It is a permanent magnet type motor characterized by being made thin.

  If the thickness of the stator core piece having the closed slot is reduced in this way, the magnetic resistance of the connecting portion with the adjacent magnetic pole teeth increases, the leakage magnetic flux decreases, and the distortion of the induced voltage waveform decreases. . Therefore, the torque ripple is reduced and the noise and vibration are reduced.

  According to a fifth aspect of the present invention, in the permanent magnet type motor according to the first aspect, the total thickness of the stator core pieces having the open slots stacked on the stator core is the same as that of the stator core. The permanent magnet motor is characterized in that it is 80 to 95% of the total plate thickness, and the rest is a stator core piece having the closed slot.

  With such a configuration, the stator core piece having the closed slot prevents the stator winding from jumping to the rotating portion, and at the same time, the stator core piece having the open slot distorts the induced voltage waveform. The torque ripple is reduced. Therefore, the safety and the noise and vibration can be reduced at the same time.

According to a sixth aspect of the present invention, in the permanent magnet type motor according to the first aspect, the permanent magnet attached to the rotor is divided into a plurality of blocks in the axial direction, and a ging torque generated by each of the divided blocks is generated. A permanent magnet type motor characterized in that each block is shifted and fixed in the circumferential direction so as to cancel each other.

  If the cogging torque generated in a plurality of blocks is offset in the circumferential direction so as to cancel each other out in this way, the combined cogging torque is reduced, thereby reducing the vibration and noise when the motor rotates. Play.

Further, the invention according to claim 7, in the permanent magnet type motor according to claim 6, instead of fixing shifted circumferentially divided into a plurality of blocks of the permanent magnet in the axial direction, The permanent magnet motor is characterized in that the circumferential magnetic pole arrangement of the permanent magnet is continuously shifted in the circumferential direction as it advances in the axial direction so that the cogging torque cancels out as a whole.
With such a configuration, the combined cogging torque can be more effectively reduced, and vibration and noise when the motor rotates can be effectively reduced.

According to an eighth aspect of the present invention, in the permanent magnet type motor according to any one of the first to seventh aspects, a rotor core made of a magnetic material constituting the rotor is used instead of attaching the permanent magnet. A permanent magnet type motor characterized in that a surface layer portion is magnetized to constitute a magnet.
Thus, if a magnet is comprised by magnetization, a rotor can be manufactured at low cost.

According to a ninth aspect of the present invention, there is provided an electric power steering device for assisting a steering force of a vehicle steering, wherein the permanent magnet according to any one of the first to eighth aspects is used as an electric motor for generating the auxiliary steering force. An electric power steering apparatus using a mold motor.

  An electric power steering device using a permanent magnet type motor with little torque ripple has an effect of enabling a smooth steering operation.

  Hereinafter, an embodiment of a permanent magnet type motor according to the present invention will be described with reference to the drawings. The permanent magnet type motor of the present embodiment makes use of the advantages of the rotor core having the closed slot and the open slot as described in “Background Art”, and prevents the stator winding from jumping into the stator core. At the same time, distortion of the induced voltage waveform and cogging torque are reduced to reduce torque pulsation. In order to achieve this object, in the permanent magnet type motor of this embodiment, a rotor core is formed by mixing a closed slot and an open slot.

  FIG. 1 is a perspective view showing a cross section of a stator core 1 of a permanent magnet type motor according to this embodiment, which is vertically divided into two. The stator core 1 is obtained by laminating a large number of stator core pieces 2 and 2a produced by punching magnetic steel plates such as silicon steel plates and caulking them in the axial direction. As for the slots of each stator core piece, for example, from the top of the figure, two are in a closed slot shape, 10 are in an open slot shape, 3 are in a closed slot shape, 10 are in an open slot shape, and 2 are in a closed slot shape Is formed.

  FIG. 2 shows an example of a planar shape of the stator core piece 2 having the closed slot 4, and FIG. 3 shows an example of a planar shape of the stator core piece 2a having the open slot 4a. Each of the stator core pieces 2, 2a is composed of an annular yoke portion 5 and a large number of magnetic pole teeth 6 projecting from the same toward the center at equal intervals. The slots 4, 4 a through which the stator winding 8 is passed are portions surrounded by the yoke portion 5 and the magnetic pole teeth 6. In the stator core piece 2 shown in FIG. 2, the closed slots 4 are formed by contacting the tip portions of adjacent magnetic pole teeth 6. In the stator core piece 2a shown in FIG. 3, the tip end portions of adjacent magnetic pole teeth 6 are opened to form an open slot 4a. The width of the opening 9 of the open slot 4a is narrower than the diameter of the winding 8 of the stator winding.

The stator core 1 is formed by stacking the stator core pieces 2 and 2a as shown in FIGS. 2 and 3. When the stator core 1 is actually manufactured, the unfolded stator as shown in FIG. 4 is first used. The iron core piece 10 is formed by punching a magnetic steel plate. This developed stator core piece 10 is divided by dividing the stator core pieces 2, 2 a of FIG. 2 and FIG. 3 into the number of magnetic pole teeth 6, and connected by an uncut portion 11 left on the outermost peripheral portion of the yoke portion 5. It is developed to the state. The tip portion 13 of the magnetic pole tooth 6 is formed in different shapes depending on whether it is an open slot or a closed slot. The development stator core pieces 10 are laminated to form a development stator core 15 as shown in FIG. 5, and the stator winding is wound around the magnetic pole teeth 6 first, and finally the whole is plastic in a cylindrical shape. A stator having the stator core 1 shown in the longitudinal sectional view of FIG. 1 is manufactured by deforming and joining both ends by welding or the like.

  As another method for manufacturing the stator core, there is a method in which the yoke portion 5 and the magnetic pole teeth 6 are separately manufactured and finally combined by fitting. In that case, first, the yoke part 5 as shown in FIG. 6 and the magnetic pole teeth 6 connected to the tip part are separately formed by stamping, and then they are laminated to form a laminated yoke part as shown in FIG. 5 and magnetic pole teeth 6 laminated. The magnetic pole teeth 6 of all the laminated layers are connected to the adjacent magnetic pole teeth 6 at their tips, and if they are attached inside the laminated yoke portion 5 as they are, all the layers will be in a closed slot shape. Therefore, in the state shown in FIG. 7, a cut for opening slot is made by machining from the outside in the layer requiring the opening slot shape. Thereafter, a stator winding is wound around the laminated magnetic pole teeth 6, and finally the whole is fitted and fixed in a dovetail groove 17 provided in the yoke portion 5, and a stator core 1a as shown in the longitudinal sectional view of FIG. Make a stator with.

  In the stator cores 1 and 1a configured as shown in FIGS. 1 and 8, two stator core pieces 2 each having a closed slot 4 are laminated at both ends in the axial direction and three at the center portion to thereby form the winding 8. Prevents jumping out of the slot. Further, even in the stator core piece 2a having the open slot 4a, the width of the slot opening 9 is made narrower than the diameter of the winding 8 so that the winding 8 hardly protrudes from the slot opening. Therefore, in the stator cores 1 and 1a configured as shown in FIGS. 1 and 8, there is a risk that the winding 8 of the stator winding may jump out to the inside (rotating portion) of the stator cores 1 and 1a in which the rotor is housed. The safety of this point is sufficiently secured.

  As described in “Background Art”, it is preferable that the slot has an open slot shape in order to reduce distortion of the induced voltage waveform and reduce torque ripple during energization to suppress vibration and noise. Considering this point, in the permanent magnet type motor of the present embodiment, the permanent magnet attached to the rotor is arranged only in a portion facing the portion where the open slot is formed in the stator core piece. FIG. 9 is a configuration example of a permanent magnet type motor 20 using a rotor in which permanent magnets are arranged in this way.

  The stator core 1 is the same as that shown in FIG. 8, and a longitudinal section divided into two is shown in a perspective view. A stator winding wound around the stator core 1 is omitted. The rotor 21 has a substantially cylindrical shape and is rotatably housed inside the stator core 1. The rotating shaft and the support mechanism are omitted. The rotor 21 has a surface magnet structure in which a permanent magnet 23 is attached to the surface of a cylindrical rotor core 22, but may have a magnet embedded structure embedded in the rotor core 22. Further, instead of attaching the permanent magnet 23, the surface layer portion of the rotor core 22 may be magnetized to constitute a magnet.

  The induced voltage generated by the rotation of the rotor core 22 is generated in a stator winding portion (not shown) facing the stuck permanent magnet 23. In the structure of the permanent magnet type motor 20 shown in FIG. 9, all the slots formed in the stator core 1 in the portion facing the stuck permanent magnet 23 have an open slot shape. For this reason, distortion of the induced voltage is reduced. Therefore, the torque ripple generated when a sinusoidal alternating current is passed through the stator winding is reduced, and the vibration and noise are reduced.

  FIG. 10 shows a permanent magnet type motor 20a in which the permanent magnet type motor 20 shown in FIG. 9 is improved so as to reduce the cogging torque. In this permanent magnet type motor 20a, the permanent magnets 23 attached to the rotor 21a are divided in the axial direction and arranged so as to be shifted from each other in the circumferential direction so as to provide a so-called skew. Cogging torque is periodically generated by the least common multiple of the number of poles of the rotor and the number of slots of the stator during one rotation of the rotor 21a. In other words, the mechanical angle obtained by dividing 360 ° by the least common multiple is periodically generated with the time for the rotor 21a to rotate as one period.

  The magnitude of the cogging torque during one period changes in a positive and negative manner with a waveform similar to a sine wave, and the waveform of the first half cycle and the waveform of the second half cycle are substantially positive and negative symmetrical waveforms. Accordingly, when the angle shifted in the circumferential direction is set to ½ of the mechanical angle obtained by dividing 360 ° by the least common multiple, the cogging torques generated in the two divided portions cancel each other and the combined cogging torque can be reduced. . In the permanent magnet type motor 20a shown in FIG. 10, the rotor 21a has 4 poles and the number of slots of the stator core 1 is 6, so that the shifting angle is 15 ° in mechanical angle. With such a configuration, it is possible to reduce the distortion of the induced voltage and also reduce the cogging torque.

  10 shows a case where the permanent magnet 23 is divided into two in the axial direction, that is, a case where a two-step skew is provided, the number of steps of this division may be further increased. In this case, the shift angle per stage is an angle obtained by dividing the mechanical angle corresponding to one cycle of the cogging torque by the number of stages.

  Furthermore, instead of dividing, the circumferential magnetic pole arrangement of the permanent magnets 23 may be continuously shifted in the circumferential direction as it advances in the axial direction so that the cogging torque cancels out as a whole. In this case, the machine angle corresponding to one period of the cogging torque is continuously shifted. Thus, if the number of division stages is increased or continuously shifted, the cancellation accuracy can be improved and the cogging torque can be reduced more effectively.

  FIG. 11 shows a change in the ratio of the number of stator core pieces provided with open slots and stator core pieces provided with closed slots in a permanent magnet type motor using a rotor provided with the skew. In this case, the distortion of the induced voltage waveform is measured. The vertical axis represents the distortion rate (%) of the induced voltage waveform, and the horizontal axis represents the ratio (%) of the stator core piece provided with the open slot.

  As can be seen in the figure, the distortion rate (%) of the induced voltage waveform decreases as the proportion of the stator core piece provided with the open slot increases. Further, the distortion rate does not decrease any more when the ratio of the stator core piece provided with the open slot is about 85%. If the ratio of the stator core piece provided with the open slot is set to 100%, as described above, the risk of the winding of the stator winding jumping out of the open slot portion increases. Also, the cogging torque is a large value. Therefore, it is possible to ensure safety by setting the ratio of the stator core piece provided with the open slot to 80 to 95% (the ratio of the stator core piece provided with the closed slot is set to 20 to 5%). It is preferable in terms of suppressing vibration and noise.

  As described above, the permanent magnet type motors 20 and 20a shown in FIG. 9 or FIG. 10 have less distortion of the induced voltage and a small cogging torque, so that torque pulsation during rotation is reduced. Therefore, if such a permanent magnet type motor is used as an electric motor of an electric power steering apparatus, a smooth steering operation can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS The cross section which divided the stator core of the permanent magnet type motor which concerns on one Embodiment of this invention into 2 vertically is shown with the perspective view. It is an example of a planar shape of a stator core piece having a closed slot. It is an example of a planar shape of a stator core piece having an open slot. It is an example of a shape of an expansion | deployment stator core piece. It is an example of the shape of the expansion | deployment stator core formed by laminating | stacking an expansion | deployment stator core piece. It is the example of a shape of the stator core piece which forms a yoke part and a magnetic pole tooth separately. It is an example of the shape of the iron core which laminated | stacked the yoke part and magnetic pole tooth shown in FIG. It is another example of a shape of a stator core. It is an example of composition of a permanent magnet type motor concerning one embodiment of the present invention. It is another example of composition of a permanent magnet type motor concerning one embodiment of the present invention. It is a graph which shows the relationship between the ratio of the open slot shape stator core piece which occupies for a stator core, and distortion of an induced voltage waveform. It is an example of the stator core which has a closed slot which concerns on a prior art. It is another example of the stator core which has a closed slot which concerns on a prior art.

Explanation of symbols

  In the drawings, 1, 1a is a stator core, 2, 2a is a stator core piece, 4 is a closed slot, 4a is an open slot, 5 is a yoke portion, 6 is a magnetic pole tooth, 8 is a winding, 9 is an opening, 10 Is a developed stator core piece, 15 is a developed stator core, 23 is a permanent magnet, 20 and 20a are permanent magnet type motors, and 21 and 21a are rotors.

Claims (9)

In a permanent magnet type motor comprising a rotor having a permanent magnet for field, and a stator having a stator core provided with a plurality of magnetic pole teeth and a slot for stator winding,
The stator core has a laminated stack of a stator core piece that is a closed slot by connecting the tip of the magnetic pole tooth to the tip of an adjacent magnetic pole tooth, and a stator core piece that is not connected and is an open slot to configure,
The stator core includes a plurality of closed slot blocks in which one or more stator core pieces having the closed slots are stacked, and an open slot block in which one or more stator core pieces having the open slots are stacked. Stack up and configure
A permanent magnet motor , wherein the permanent magnet attached to the rotor is disposed only at a position facing the open slot block .   The permanent magnet type motor according to claim 1, wherein a stator core piece having the closed slot is laminated at both axial ends of the stator core.   2. The permanent magnet motor according to claim 1, wherein an opening width of the open slot in the stator core piece having the open slot is narrower than a winding diameter of the stator winding. .   2. The permanent magnet type motor according to claim 1, wherein a thickness of the stator core piece having the closed slot is made thinner than a thickness of the stator core piece having the open slot. .   2. The permanent magnet type motor according to claim 1, wherein a total thickness of the stator core pieces having the open slots stacked on the stator core is 80 to 95% of a total thickness of the stator core, and the rest Is a stator core piece having the closed slot. 2. The permanent magnet motor according to claim 1, wherein the permanent magnet attached to the rotor is divided into a plurality of blocks in the axial direction, and the blocks are arranged in the circumferential direction so that ging torques generated by the divided blocks cancel each other. A permanent magnet type motor characterized by being fixed to be shifted to 7. The permanent magnet type motor according to claim 6 , wherein instead of fixing the permanent magnet into a plurality of blocks in the axial direction and shifting and fixing in the circumferential direction, the circumferential magnetic pole arrangement of the permanent magnet is set in the axial direction. A permanent magnet motor characterized by being arranged so that cogging torque cancels out as a whole by continuously shifting in the circumferential direction as it advances . The permanent magnet type motor according to any one of claims 1 to 7 , wherein a magnet is formed by magnetizing a surface layer portion of a rotor core made of a magnetic material constituting the rotor instead of attaching the permanent magnet. permanent magnet motor, characterized in that configuration was. An electric power steering device for assisting a steering force of a vehicle steering, wherein the permanent magnet type motor according to any one of claims 1 to 8 is used as an electric motor for generating an auxiliary steering force. Electric power steering device.

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