JP2009055698A - Rotor for permanent magnet type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotor for a permanent magnet type motor capable of preventing degradation of cogging performance after the permanent magnet type motor which is configured to have small cogging is assembled in a casing. <P>SOLUTION: In this rotor for the permanent magnet type motor having a stator and the rotor, the rotor is fixed to a rotating shaft and rotatably supported to the shaft in the center of an inner diameter of the stator, a permanent magnet is disposed in the rotor, poles on the rotor surface have a skew structure which is obliquely magnetized by shifting in a continuous state or a step state, and the rotating shaft fixing the rotor can move in a rotating-shaft direction. Movement amount (L) in which the rotor moves in the rotating-shaft direction is at and less than non-pole width (D) between the adjacent poles of which the poles are skewed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotor of a permanent magnet motor that does not deteriorate the cogging torque performance of a permanent magnet motor designed for low cogging torque.

  In recent years, electric motors have been miniaturized, and high-output, high-torque electric motors have been demanded. In particular, electric motors and the like used for vehicle applications such as electric vehicles are required to be smaller and lighter from the vehicle mounting space. On the other hand, in such an electric motor, because of high output and high torque, cogging torque, sound, vibration, and the like due to the magnetic attraction generated between the stator and the rotor are generated. Various countermeasures have been studied in the past. For example, in a permanent magnet type rotor in which a cylindrical permanent magnet is attached to the surface of a rotor, skew magnetization is performed by twisting the rotation axis. Is used to reduce the cogging torque. However, this skew magnetized permanent magnet type rotor is inherently obtained when the motor is driven, because of the skew magnetization, the thrust force acts in the direction of the rotation axis and the rotor is pressed against one of the bearings. Reduction of power cogging torque and reduction of sound, vibration, etc. caused by it could not be performed reliably.

  In order to solve such a problem, as disclosed in Japanese Patent Application Laid-Open No. 8-298735 of Patent Document 1, it is divided into two at the center in the axial direction of the rotor to which a cylindrical permanent magnet is attached to form a V shape. A skew magnetized permanent magnet rotor is recalled.

JP-A-8-298735

  However, if stress from the load side is received due to the movement of the rotor itself and the connection with the load, the magnetic center of the stator and the rotor shifts, resulting in the reduction of the cogging torque assumed and the cogging torque. In some cases, sound, vibration, etc. could not be reduced. In particular, it is a problem when used for an electric motor for vehicles used for electric power steering or the like. In such an electric motor that dislikes the force acting on the rotor, for example, a bearing retainer that suppresses the axial movement of the bearing is provided on one of the bearings of the rotor so as not to forcibly move. Due to the assembly error such as the above, the magnetic center is fixed while being shifted. In addition, since a thrust force acts in the direction of the rotation axis and a force that presses the rotor against one of the bearings, the durability of the bearings and bearings also decreases.

The rotor has a stator and a rotor, and the rotor is fixed to a rotating shaft and is rotatably supported around the inner diameter of the stator. In the rotor of a permanent magnet type electric motor in which the magnetic pole of the magnet is skewed continuously or stepwise and magnetized obliquely, and the rotating shaft to which the rotor is fixed is movable in the rotating shaft direction.
A rotor of a permanent magnet type motor in which a moving amount (L) of a rotor fixed to a rotating shaft in the direction of the rotating shaft is less than or equal to a non-magnetic pole width (D) between adjacent magnetic poles skewed.

Note that the rotor has a movement amount (L) in the axial direction of the rotor, a non-magnetic pole width (D) between adjacent magnetic poles with the magnetic pole skewed, a displacement amount (d) between the magnetic poles, and a skew angle. (Θ)
d = L × tan (θ)
D ≧ d
It is.

  Such a rotor can be used for a rotor of a surface-attached type in which a permanent magnet is arranged on the surface, or a permanent magnet type electric motor of a permanent magnet embedded type in which a permanent magnet is arranged inside the rotor.

  The present invention relates to a permanent magnet rotor having a skew structure in which magnetic poles on a rotor surface of a permanent magnet rotor are continuously or stepwise shifted and magnetized obliquely, and a rotating shaft to which the permanent magnet rotor is fixed. Is movable in advance in the direction of the rotation axis, and the movement amount (L) that enables the rotor to move in the direction of the rotation axis is less than the non-magnetic pole width (D) between the adjacent magnetic poles with the magnetic pole skewing. When the rotor itself is moved or connected to the load, it receives stress from the load side and the magnetic center shifts between the stator and the rotor, or when the permanent magnet type rotor is assembled to the case or bearing. The cogging torque due to the deviation of the magnetic center such as the assembling error occurring in the sound, the sound, vibration, etc. due to the cogging torque can be reduced. In addition, since the amount of movement (L) is defined to be less than the non-magnetic pole width (D) of the permanent magnet rotor, the force with which the rotating shaft is pressed against one of the bearings is alleviated and the durability of the bearings and bearings is increased. You can also.

When the permanent magnet rotor is moved in the direction of the rotation axis (L), the magnetic pole is skewed to the non-magnetic pole width (D), the displacement between the magnetic poles (d), and the skew angle (θ) The relationship
d = L × tan (θ)
D ≧ d
It is.

  Such a rotor can be used for a rotor of a surface-attached type in which a permanent magnet is arranged on the surface or a permanent magnet type electric motor with a permanent magnet embedded in the rotor. Can do.

  The present invention will be described with reference to the drawings. In FIG. 1, a coil 3 is applied to a tooth portion of a stator 2, and a permanent magnet type rotor 1 that is rotatably supported by a bearing at the center of the inner diameter of the stator 2 is provided. The stator 2 is fixed to the case 5 by shrink fitting, press fitting, gap fitting or the like. The permanent magnet rotor 1 is fixed to the rotary shaft 8 by shrink fitting, press fitting, gap fitting or the like in the same manner as the stator 2. When the rotating shaft 8 is supported on both sides, the brackets 6a and 6b for supporting the rotating shaft 8 are provided on the brackets 4 on both sides, and the rotating shaft 8 is supported via the bearings 7a and 7b. Moreover, when supporting by one side, the rotating shaft 8 is supported by the bearing parts 6a and 6b of one of the brackets 4 via the bearings 7a and 7b.

  In such an electric motor, as described above, the stator 2 is shrink-fitted into the case 5 or the like and fixed by press-fitting, gap fitting, or the like, and the permanent magnet rotor 1 is also shrink-fitted onto the rotary shaft 8. As a result of the fixing by press fitting, gap fitting, etc., an assembly error occurs between each member. As shown in FIG. 1, bearings 7 a and 7 b attached to both sides of the rotating shaft 8 are inserted into bearing portions 6 a and 6 b provided on both sides of the bracket 4. A movable amount L is provided between the bearings 7a and 7b and the bearing portions 6a and 6b in consideration of some assembly error. A wave washer 9 or the like is inserted into this movable amount L of movement, and serves as a cushioning material between the bearing portions 6a and 6b and the bearings 7a and 7b.

  A permanent magnet rotor 1 in FIG. 1 is a surface-attached type permanent magnet rotor 1 in which a cylindrical ring magnet 10 is attached to the surface of a rotor core 100. The cylindrical ring magnet 10 is magnetized with a skew angle (θ) by an external magnetizing device or the like. The magnet in this case may be a ferrite magnet or a rare earth magnet.

  The permanent magnet rotor 1 of the permanent magnet motor shown in FIG. 1 will be described with reference to FIG. The direction in which the permanent magnet rotor 1 is rotationally driven is indicated by arrows in the figure. In this case, the permanent magnet type rotor 1 is magnetized so that magnetic poles can be alternately formed on the outer peripheral surface of the rotor, so that the adjacent magnetic poles are different from each other, and the gap between the poles and the vicinity thereof are magnetic. As a result, it is a neutral pole and a non-magnetic pole portion D.

  This neutral pole, that is, the non-magnetic pole portion D can be consciously adjusted by the magnetizing yoke 20 when the permanent magnet 10 is magnetized. The magnetization that constitutes the non-magnetic pole portion D is shown in FIG. When magnetizing the permanent magnet rotor 1b provided with the cylindrical ring magnet 10b facing the magnetizing yoke 20 of FIG. 3, the cylindrical shape is opposed to the magnetizing yoke 20 as shown. The teeth of the magnetized yoke extend on the surface of the permanent magnet rotor 1b provided with the ring magnet 10b. Since the width of the opening between the tips of the teeth around which the magnetizing coil 30 of the magnetizing yoke 20 is wound becomes the non-magnetic pole portion D, the width of the non-magnetic pole portion D can be adjusted. A cylinder facing this tooth portion by passing a magnetizing current through a magnetizing coil 30 wound around the tooth portion of the magnetizing yoke 20 so that adjacent tooth portions of the magnetizing yoke 20 have different polarities. Shaped ring magnet 10b can be magnetized. On the other hand, the portion of the cylindrical ring magnet 10b that is not opposed to the magnetizing yoke 20 has a weak magnetic force and the adjacent poles have different polarities, so the magnetic force is canceled and a non-magnetic pole portion D is formed. This makes it possible to consciously create this non-magnetic pole portion D.

  In such a permanent magnet type motor using the permanent magnet rotor 1b, cogging torque is generated due to the saliency associated with the magnetic force of the cylindrical ring magnet 10b, and sound, vibration, etc. due to the cogging torque are also generated. ing. To solve this problem, as shown in FIG. 4, a cylindrical ring magnet 10a affixed to the rotor core 100a is skewed at an appropriate angle to form a magnetic pole that is magnetized obliquely. As a result, the cogging torque can be reduced, and sound, vibration, and the like resulting from the cogging torque can also be reduced.

  However, when the permanent magnet type rotor 1 is rotationally driven in the direction of the arrow shown in FIGS. 1 and 2, the permanent magnet type rotor 1 has a magnetic thrust acting in the axial direction (FIGS. 1 and 2). Then, the rotor moves to the bearing portion 6b side where the wave washer 9 is inserted), the position where the skew magnetization is performed shifts, and the cogging torque that should be originally obtained can be reduced, and the sound caused by the cogging torque, Reduction of vibration or the like cannot be achieved.

  This is because the stator 2 and the permanent magnet rotor 1 are skewed obliquely because the positional relationship between the armature composed of the stator 2 and the permanent magnet rotor 1 constituting the field is shifted in the axial direction. This is because the positional relationship with the magnetic pole magnetized by magnetization is lost and the cogging torque is deteriorated. As can be seen from this, the skew of the permanent magnet type rotor 1 applied to reduce the cogging torque is based on the relationship between the movable amount (L) necessary for movement in the axial direction and the non-magnetic pole portion width (D). I understand that it holds.

  When the relationship between the amount of movement (L) and the non-magnetic pole part width (D) is applied to the armature structure on the stator side, the skew width is the equivalent non-magnetic path width between the excitation poles (between the tooth parts). This is established by providing a skew at (non-magnetic pole portion (D)). In this case, since the skew is applied by the armature on the stator side, it is not necessary to take the skew on the rotor side, and the permanent magnet can be magnetized by forming a non-magnetic pole portion parallel to the axial direction. On the other hand, if the equivalent non-magnetic path width (non-magnetic pole part D) is provided between the excitation poles (between teeth) of the stator and the assumed skew angle cannot be taken, It is also possible to take the skew angle that could not be removed.

The cogging torque of the permanent magnet type motor described in FIGS. 1 to 4 designed as described above obtains a result as shown in FIG. FIG. 5 shows a state where the cogging torque fluctuates with respect to the displacement of the permanent magnet rotor 1 in the rotation axis direction. As can be seen from FIG. 5, when the moving amount (L) of the rotor in the direction of the rotation axis is equal to or less than the non-magnetic pole width (D), the fluctuation of the cogging torque is stable with a very slight fluctuation. I understand. On the contrary, the cogging torque increases abruptly when it becomes wider than the non-magnetic pole width (D). In other words, the amount of movement (L) of the rotor that can be moved in the direction of the rotation axis should be less than or equal to the non-magnetic pole width (D) in the distance in the rotation direction formed by the magnetic pole skew on the magnetic pole surface of the rotor.
Accordingly, the cogging torque is obtained by setting the movable movement amount (L) in consideration of the assembly error between the bearing 7b and the bearing portion 6b so as to be equal to or less than the non-magnetic pole width (D) of the magnetized skew of the rotor. In addition, noise and vibration caused by cogging torque can be reduced.

  Conversely, the non-magnetic pole width (D) between the adjacent magnetic poles skewed by the magnetic poles is set to be equal to or larger than the movement amount (L) in the axial direction of the rotor, that is, the non-magnetic pole width ( The same effect can be obtained by setting D) to be equal to or greater than the distance in the rotation direction formed by the skew of the magnetic poles according to the movement of the movement amount (L) set in the rotation axis direction. However, if the width is made larger than necessary, the non-magnetic pole width (D) increases and the amount of magnetic flux decreases, so it goes without saying that the range is allowed in terms of the performance of the permanent magnet motor.

The contents described above will be described with mathematical expressions using the symbols shown in FIG.
As described above, the non-magnetic pole width (D) is a non-magnetic pole portion or a non-magnetized portion between the magnetic poles. A skew angle (θ) for reducing the cogging torque by forming a magnetic pole on the rotor, a movable amount (L) that the rotor can move in the direction of the rotational axis, and a movable amount that can move the rotor in the direction of the rotational axis When the displacement (d) is the displacement (d) between the poles when moved (L), the equations (1) and (2) are obtained.
d = L × tan (θ) (1)
D ≧ d (2)

1 to 5 have been described with respect to a surface-attached type rotor in which the cylindrical ring magnet 1 is attached to the surface of the rotor core 100, other embodiments will be described with reference to the drawings.
FIG. 6 shows a permanent magnet type rotor that is a permanent magnet type rotor similar to the surface sticking type described in FIGS. 1 to 5, but in which a plurality of permanent magnets 10 f to 10 k are stacked in multiple stages. As shown in the detailed view, the permanent magnets 10fa, 10fb,... And 10ga, 10gb,. There is no permanent magnet between the poles and the non-magnetic part (D1). In the rotation axis direction of the rotor, permanent magnets 10fa and 10ga, 10fb and 10gb, which are adjacent to each other and having the same polarity, are attached so that there is no gap as much as possible. The permanent magnets 10fa, 10ga, 10fb, and 10gb adjacent to each other in the axial direction are stacked stepwise so as to have a skew angle (θ). The skew angle (θ) between the magnetic poles is between the equivalent poles.

  FIG. 7 shows a permanent magnet embedded rotor in which permanent magnets 10c (10ca, 10cb) are arranged inside the rotor. Inside the rotor, magnet accommodation holes 40c (40ca, 40cb) for embedding the plate permanent magnets 10c (10ca, 10cb) are provided in each pole to form four poles. Since each pole has the same configuration, only one pole will be described, and description of other poles will be omitted. The magnet housing hole 40ca is provided with an outer iron core portion 100e between the rotor outer periphery and the magnet housing hole 40ca, and an inner iron core portion 100f is provided between the magnet housing hole 40ca and the rotor inner diameter. Further, both end portions of the magnet housing hole 40ca face the rotor outer periphery, and a gap 50ca is provided between the flat plate permanent magnet 10ca and the rotor outer periphery. Between the gap 50ca and the outer periphery of the rotor, a bridge portion 60ca is provided in which the width of the rotor core is reduced to such an extent that magnetic flux does not leak. The bridge portion 60ca is connected to the outer core portion 100e of the magnet accommodation hole 40ca by a rib 70c provided so as to be sandwiched between the gap 50ca of the magnet accommodation hole 40cb adjacent to the gap 50ca of the magnet accommodation hole 40ca. The permanent magnet 10ca is embedded up to the boundary between the outer core portion 100e between the outer periphery of the rotor of the magnet housing hole 40ca and the magnet housing hole 40ca and the bridge portion 60ca at the end of the magnet housing hole 40ca.

  The non-magnetic pole portion D2 of the permanent magnet embedded rotor 1c is formed of a rib 70c from the boundary between the outer core portion 100e between the outer periphery of the rotor and the magnet accommodation hole 40ca and the bridge portion 60ca at the end of the magnet accommodation hole 40ca. The non-magnetic pole portion (D2) extends from the bridge portion 60cb at the end of the magnet receiving hole 40cb of the adjacent magnetic pole to the boundary between the outer periphery of the rotor and the outer core portion 100e between the magnet receiving hole 40cb. The non-magnetic part (D2) is stacked stepwise so that the adjacent permanent magnets in the direction of the rotation axis have a skew angle (θ) as in the case of a surface-attached type permanent magnet rotor. The skew angle (θ) between the magnetic poles is between the equivalent poles.

FIG. 8 shows a permanent magnet embedded rotor similar to FIG. Magnet housing holes 40d (40da, 40db) for inserting the permanent magnet 10d (10da, 10db) are provided in each pole to form four poles. Since each pole has the same configuration, only one pole will be described, and description of the other magnet receiving holes 40d (40dc, 40dd) will be omitted. In this case, the permanent magnet 10da is embedded in the magnet housing hole 40da before the boundary between the outer core portion 100g between the outer periphery of the rotor and the magnet housing hole 40da and the bridge portion 60da at the end of the magnet housing hole 40da. Has not reached.
Even in this case, the gap between the equivalent poles of the non-magnetic pole part (D3) is the rib 70d from the boundary between the outer core part 100g between the rotor outer periphery and the magnet accommodation hole 40da and the bridge part 60da at the end of the magnet accommodation hole 40da. The non-magnetic pole portion (D3) extends from the bridge portion 60db at the end of the magnet housing hole 40db of the adjacent magnetic pole to the boundary between the outer periphery of the rotor and the outer core portion 100g between the magnet housing hole 40db. The permanent magnet type rotor 1d configured as described above is stacked in a stepped manner so that adjacent permanent magnets in the axial direction have a skew angle (θ). The skew angle (θ) between the magnetic poles is between the equivalent poles.

  FIG. 9 shows a permanent magnet embedded rotor similar to that shown in FIGS. Magnet accommodating holes 40e (40ea, 40eb) for inserting permanent magnets 10e (10ea, 10eb) are provided in an arc shape along the outer periphery of the rotor inside the rotor. In FIG. 9, magnet accommodation holes 40e (40ea, 40eb) for embedding the arc-shaped permanent magnet 10e (10ea, 10eb) in the rotor are provided in each pole to form four poles. Since each pole has the same configuration, only one pole will be described, and description of the other magnet receiving holes 40e (40ec, 40ed) will be omitted. The outer periphery of the rotor of the arc-shaped magnet housing hole 40ea is provided along the outer periphery of the rotor and is configured by a bridge portion 60ea. An inner core portion 100i is provided between the arc-shaped magnet housing hole 40ea and the rotor inner diameter. A gap 50ea is provided at the end of the permanent magnet 10ea embedded in the arc-shaped magnet housing hole 40ea. A rib 70e extending between the rotor inner diameter and the magnetic pole between the magnetic pole 50eb and the gap 50eb at the end of the permanent magnet 10eb embedded in the arc-shaped magnet housing hole 40eb of the adjacent magnetic pole. Is provided. The rib 70e and the bridge portion 60ea are connected.

  In this case, in the non-magnetic pole part (D4), almost no magnetic flux flows in the bridge part 60ea having a narrow width between the rotor outer peripheral part and the arc-shaped magnet housing hole 40ea provided along the rotor outer peripheral part. Therefore, the outer core portion of the rotor is not affected by the flow of magnetic flux, so that the arc shape of the adjacent magnetic pole is sandwiched from the end of the permanent magnet 10ea embedded in the arc-shaped magnet housing hole 40ea with the rib 70e interposed therebetween. A portion up to the end of the permanent magnet 10eb embedded in the magnet housing hole 40eb is the non-magnetic pole portion (D4). This non-magnetic pole portion (D4) is stacked stepwise so that the adjacent permanent magnets 10e in the axial direction have a skew angle (θ), like the permanent magnet type rotors of FIGS. The skew angle (θ) between the magnetic poles is between the equivalent poles.

In the permanent magnet type rotor described above, the permanent magnets adjacent to each other in the axial direction are stacked stepwise so as to have a skew angle (θ), and are set between the equivalent poles of the skew angle (θ). It may be configured.
For example, the permanent magnet can be configured to have a skew angle (θ) with a single permanent magnet without being divided in the axial direction. Further, the magnetic orientation of the permanent magnet of the permanent magnet type rotor may be a radial orientation or a parallel orientation, and a polar anisotropic ring magnet can be used particularly for a cylindrical permanent magnet.

The figure which assembled | attached the rotor of the permanent magnet type motor in this embodiment to the case. The rotor of the permanent magnet type electric motor explained in FIG. Magnetization of the rotor of a permanent magnet motor. A rotor of a permanent magnet motor using a cylindrical ring magnet with skew magnetization. The graph which showed the fluctuation | variation of the cogging torque with respect to the shift | offset | difference of the rotating shaft direction of the permanent magnet type rotor which gave the skew magnetization like FIG. The rotor of the permanent magnet type electric motor which showed another embodiment. The rotor of the permanent magnet type electric motor which showed another embodiment. The rotor of the permanent magnet type electric motor which showed another embodiment. The rotor of the permanent magnet type electric motor which showed another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c, 1d, 1e ... Permanent magnet type rotor 2 ... Stator 3 ... Coil 4 ... Bracket 5 ... Case 6a, 6b ... Bearing part 7a, 7b ... Bearing 8 ... Rotating shaft 9 ... Wave washer 10, 10a-10k, 10ca-10ea, 10cb-10eb, 10fa, 10fb, 10ga, 10gb ... Permanent magnet 20 ... For magnetization Yoke 30 ... Magnetizing coils 40, 40a to 40e, 40ca to 40ea, 40cb to 40eb ... Magnet housing holes 50ca to 50ea, 50cb to 50eb ... Gaps 60ca to 60ea, 60cb to 60eb ... Bridges Part 70c-70e ... rib part 100, 100a, 100b ... rotor core 100e, 100g ... outer core part 100f, 100h, 100i ... the inner core part D, D1~D4 ··· non-magnetic pole portion

Claims (4)

A rotor having a stator and a rotor, the rotor being fixed to a rotation shaft and rotatably supported at the center of the inner diameter of the stator, wherein a permanent magnet is disposed on the rotor and rotated; The magnetic pole on the child surface is a skew structure that is magnetized diagonally, shifted continuously or stepwise,
In the rotor of the permanent magnet type motor in which the rotating shaft that fixed the rotor is movable in the rotating shaft direction,
A rotor of a permanent magnet type electric motor characterized in that a moving amount (L) of the rotor moving in the direction of the rotation axis is not more than a non-magnetic pole width (D) between adjacent magnetic poles skewed by magnetic poles. . The rotor has a movement amount (L) in the axial direction of the rotor, a non-magnetic pole width (D) between adjacent magnetic poles with the magnetic pole skewed, a displacement amount (d) between the magnetic poles, and a skew angle ( θ)
d = L × tan (θ)
D ≧ d
The rotor of a permanent magnet type electric motor according to claim 1, wherein The rotor of a permanent magnet type electric motor according to claim 1 or 2, wherein the rotor is a surface-attached type in which permanent magnets are arranged on the surface. The rotor of a permanent magnet type electric motor according to claim 1, wherein the rotor is a permanent magnet embedded type in which a permanent magnet is disposed inside the rotor.

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