JP2007228800A - Permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce cogging torque of a servomotor, an electric motor-driven power steering-use motor, etc. <P>SOLUTION: The permanent magnet motor is constituted by including a rotor yoke 11, a rotor 10 made by including a plurality of permanent magnets (M1 to M10), a stator yoke 22, a salient magnetic pole 21, and a stator 20 made by including an armature winding 23. At least one of the permanent magnets is arranged in a regulation position moved at least in one of circumferential, diametrical, and axial directions of the rotor yoke from a reference position, of a plurality of the permanent magnets, the permanent magnet except the permanent magnet arranged in the regulation position is arranged in the reference position, the concerned regulation position is set in such a manner that the permanent magnet motor with at least one of a plurality of the permanent magnets arranged in the concerned regulation position has cogging torque smaller than that of the permanent magnet motor with all of a plurality of the permanent magnet motors arranged in the concerned reference position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a permanent magnet motor, and more particularly to a permanent magnet motor having a small cogging torque, such as a servo motor or an electric power steering motor.

  Servo motors and electric power steering motors are desired to be small and have low loss, and a motor with concentrated winding of armature windings on the stator salient poles is used to wind the stator end. The protrusion of the wire is reduced to reduce the motor length and the copper loss of the winding. In addition, there is a strong demand for reducing the cogging torque of the motor because of improved positioning accuracy and reduced noise and vibration.

  As a method for reducing the cogging torque of a concentrated winding permanent magnet motor, Patent Document 1 discloses that the relationship between the number of poles P of the rotor and the number M of salient stator poles is P = 6n ± 2, M = 6n (where n is 2). Or an integer of P = 3m ± 1, M = 3m (where m is an odd number of 3 or more). The permanent magnet motor has a pulsating cogging torque of the least common multiple of the number of poles P and the number of salient poles M per rotation of the rotor, and the magnitude of the cogging torque decreases as the number of pulsations increases. Based on this principle, the permanent magnet motor has a combination of the number of poles P and the number of salient poles so that the least common multiple of the number of poles P of the rotor and the number of salient poles M of the stator increases under the condition that three-phase winding is possible. M. Table 1 summarizes specific combinations of the number P of poles and the number M of salient poles.

  A permanent magnet motor having a combination of P = 10 and M = 12 in Table 1 was designed. FIG. 11 shows a schematic cross-sectional view of a 10 pole 12 slot permanent magnet motor in a plane perpendicular to the axis. FIG. 11 shows a rotor in which ten neodymium magnets (M1 to M10) having a residual magnetic flux density of 1.26 Tesla (Tesla) are arranged on the rotor yoke 11 of the low carbon steel S45C so that the polarities are alternately different at equal intervals in the circumferential direction. 10 and the stator yoke 22 of an isotropic silicon steel plate 35A300 facing the permanent magnet and having 12 salient poles 21 arranged at equal intervals in the circumferential direction, and concentratedly wound around the poles and connected in series in each phase. And a stator 20 having a 10-turn armature winding 23 in which a U-phase, a V-phase, and a W-phase are connected in three phases. In FIG. 11, the direction of magnetization of each permanent magnet is indicated by an arrow. The direction of rotation is indicated by an arrow at the center of the rotor. In addition, the permanent magnet was made into the shape where the thickness of both ends became thin. FIG. 12 shows a specific shape of the permanent magnet. In FIG. 12, Ri = 23 mm, Ro = 10 mm, D = 15 mm, and W = 12 mm. If the thickness of both ends of the permanent magnet is reduced, the magnetic flux density distribution in the air gap becomes smooth, and the cogging torque can be reduced. The axial length of the rotor and the stator is 40 mm, and the gap between the rotor magnet and the stator magnetic pole is 1 mm. In FIG. 11, the mark in the winding indicates the direction of the winding, the black circle mark (●) indicates the direction coming out of the paper surface, and the cross mark (×) indicates the direction entering the paper surface. The rated torque was set to 2 Nm (Newton meter) when driven by a sine wave current having an effective value of 20 A (ampere).

  When the cogging torque of the permanent magnet motor was calculated on the assumption that there was no variation in magnet characteristics and dimensions and all were in an ideal state, the peak value was 0.0003 Nm and a waveform with 60 pulsations per rotor rotation was obtained. . Since the cogging torque is expressed by the difference between the maximum and the minimum of the wave, the cogging torque in this case is 0.0006 Nm, which is a very small value of 0.03% of the rated torque. A permanent magnet motor for electric power steering or the like is desired to be 0.5% or less of the rated torque (0.01 Nm or less in this case) because a weak cogging torque affects the steering feeling.

  Next, as Comparative Example 1, the designed motor was actually manufactured and its cogging torque was measured. As the permanent magnet, a neodymium magnet obtained by filling a tile-shaped mold with magnet powder, sintering a magnetic field molded product, and heat-treating it with a grindstone with an accuracy of 0.05 mm or less was used. In addition, positioning of the permanent magnet to the rotor yoke was performed with an accuracy of 0.05 mm or less using a dedicated jig. The stator yoke was cut out from a 0.35 mm silicon steel plate into a predetermined shape by laser cutting, and stacked in a stacking method called parallel stacking in which the rolling directions were aligned in the same direction. After lamination, the outer peripheral portion of the stator yoke was fixed at 8 locations by laser welding, and the inner surface facing the permanent magnet was polished to improve the dimensional accuracy.

  FIG. 13 shows a measured waveform of cogging torque of the permanent magnet motor according to Comparative Example 1 (parallel stacked stator). The actually measured cogging torque waveform according to Comparative Example 1 was a waveform having 10 pulsations per one rotation of the rotor. The fact that the entire waveform is shifted to the minus side is a force against the rotation, which is called loss torque. This is caused by the hysteresis loss of the stator yoke. Since the cogging torque is represented by the difference between the maximum and the minimum of the wave, the cogging torque of Comparative Example 1 shown in FIG. 13 was 0.0274 Nm. FIG. 14 shows a result of dividing the cogging torque waveform according to Comparative Example 1 into components for each order of the waveform by Fourier analysis. Here, the order is the number of pulsations that appear when the rotor rotates once. For example, the 12th-order component is a component that pulsates 12 times when the rotor rotates once. The cogging torque components of Comparative Example 1 shown in FIG. 13 are 0.0061 Nm for the 10th order component, 0.0077 Nm for the 12th order component, 0.0016 Nm for the 20th order component, and 0.0007 Nm for the 24th order component. . It should be noted that the order component shown in FIG. 14 indicates the peak value of each component and is half the value of the cogging torque. By looking at the order component of the cogging torque waveform, it can be seen what the cogging torque is caused by. In the case of the permanent magnet motor according to Comparative Example 1, the 10th, 20th, and 30th orders corresponding to multiples of the number of poles are caused by variations in the stator yoke, and the 12th, 24th, and 36th orders corresponding to multiples of the number of salient poles are permanent magnets. It is thought that this was caused by the variation of. If there is no variation in the permanent magnets, the positional relationship between the stator yoke and the permanent magnets is rotationally symmetric with respect to the magnetic pole pitch angle, so the cogging torque due to the stator yoke variation has a waveform with a period of the number of poles per rotation as a fundamental wave. Similarly, if there is no variation in the stator, the positional relationship between the stator and the magnet is rotationally symmetric at the salient pole pitch angle, so the cogging torque due to the magnet variation has a waveform with the number of salient poles as the fundamental wave. . The 60th order of the least common multiple of the number of poles and the number of salient poles is a cogging torque when an ideal permanent magnet motor is used. The cogging torque of Comparative Example 1 shown in FIG. Even an isotropic steel sheet has a slight magnetic anisotropy in the rolling direction, and therefore magnetic anisotropy remains when the stator yokes are stacked in parallel in the rolling direction. This is considered to have caused cogging torque.

  In order to eliminate the magnetic anisotropy of the stator yoke, Non-Patent Document 1 uses a method of laminating so that the rolling direction called turn stacking rotates in order. As Comparative Example 2, a permanent magnet motor having a rotating stator was manufactured. The method of making the stator yoke other than the rotor and the lamination method is the same as in Comparative Example 1. FIG. 15 shows an actual measurement waveform of cogging torque of the permanent magnet motor according to Comparative Example 2 (turned stator). FIG. 14 shows a result of dividing the cogging torque waveform according to Comparative Example 2 into components for each order of the waveform by Fourier analysis. In Comparative Example 2, compared with Comparative Example 1, the 10, 20, and 30th order components were greatly reduced to 0.0002 Nm or less, and the cogging torque was 0.0122 Nm. In this way, the cogging torque caused by the stator yoke can be reduced.

  However, even with such a method, the 12th, 24th and 36th order components due to the permanent magnet cannot be eliminated. In particular, when a component with a low order is used in an electric power steering motor, the steering feeling is greatly affected. Therefore, it is desired to reduce the twelfth component.

  In order to eliminate the order (12th order in the comparative example) component of cogging torque caused by the permanent magnet, there is a method in which the permanent magnet of the rotor is divided into a plurality of parts in the axial direction and skewed. In this case, the skew angle is 360 ° / the number of salient poles (30 ° in the comparative example). However, in the case of a permanent magnet motor that has a low cogging torque due to the combination of the number of poles and the number of salient poles shown in Table 1, the difference between the number of poles and the number of salient poles is small, and when skewing, different magnetic poles exist on one salient pole. There is no driving torque because they face each other at the same time. As described above, there is no effective cogging torque reduction measure caused by the permanent magnet, and there is an industrial limitation in reducing the cogging torque by suppressing the variation of the magnet.

Japanese Patent No. 2135902 "Measurement of cogging torque of permanent magnet motor caused by magnetic anisotropy of non-oriented electrical steel sheet" Proceedings of the IEEJ National Conference 5-016

  An object of the present invention is to reduce the cogging torque of a servo motor, an electric power steering motor, etc., and to use a servo motor capable of positioning with high accuracy by eliminating the cogging torque component caused by a permanent magnet. It is to provide a permanent magnet motor that can realize an electric power steering with low vibration and good steering feeling.

  According to one aspect of the present invention, a rotor including a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke. A stator yoke that is spaced apart from the rotor, a salient pole that is opposed to the permanent magnet and that is disposed on the stator yoke at equal intervals in the circumferential direction, and a concentrated winding around the salient pole. And a stator including a three-phase-connected armature winding, wherein at least one of the permanent magnets is equally spaced with respect to the circumferential direction of the rotor yoke and with respect to the radial direction. Move from a reference position equidistant from the central axis and equidistant from the axial end surface of the rotor yoke in the axial direction to at least one of the circumferential direction, radial direction and axial direction of the rotor yoke. Of the plurality of permanent magnets, the permanent magnets other than the permanent magnets disposed at the adjustment position are disposed at the reference position, and at least one of the plurality of permanent magnets is disposed at the adjustment position. There is provided a permanent magnet motor in which the adjustment position is set so that the permanent magnet motor has a cogging torque smaller than that of the permanent magnet motor in which all of the plurality of permanent magnets are arranged at the reference position.

  According to another aspect of the present invention, a rotor including a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke. A stator yoke that is spaced apart from the rotor, a salient pole that is opposed to the permanent magnet and that is disposed on the stator yoke at equal intervals in the circumferential direction, and a concentrated winding around the salient pole. A method of adjusting cogging torque of a permanent magnet motor including a stator including a three-phase-connected armature winding, wherein the plurality of permanent magnets are related to the circumferential direction of the rotor yoke, etc. Arranged on the rotor yoke so that the polarities are alternately different in the circumferential direction at a reference position that is equidistant from the central axis in the radial direction and equidistant from the axial end surface of the rotor yoke in the axial direction. And a cogging torque adjusting method for a permanent magnet motor including adjusting the cogging torque by moving at least one of the permanent magnets in at least one of a circumferential direction, a radial direction and an axial direction of the rotor yoke. Provided.

  As will be described in detail below, according to the present invention, the cogging torque due to the variation of the permanent magnets can be reduced, and a robot using a servo motor capable of high-accuracy positioning, or an electric power with low vibration and good steering feel. Steering can be realized.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below.

  As described above, according to the present invention, a rotation comprising a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke. A stator, a stator yoke that is spaced from the rotor, a salient pole that is opposed to the permanent magnet and is disposed on the stator yoke at equal intervals in the circumferential direction, and is concentrated on the salient pole A permanent magnet motor including a stator including a wound and three-phase armature winding, wherein at least one of the permanent magnets is equidistant with respect to a circumferential direction of the rotor yoke and is radially From a reference position that is equidistant from the central axis and is equidistant from the axial end surface of the rotor yoke in the axial direction. Among the plurality of permanent magnets, the permanent magnets other than the permanent magnets arranged at the adjustment position are arranged at the reference position, and at least one of the plurality of permanent magnets is at the adjustment position. There is provided a permanent magnet motor in which the adjustment position is set such that the arranged permanent magnet motor has a cogging torque smaller than that of the permanent magnet motor in which all of the plurality of permanent magnets are arranged at the reference position. .

  In the present invention, the permanent magnet motor can be configured in the same manner as a conventional permanent magnet motor except for the matters specifically described below, such as the position of the permanent magnet and the magnet holding means, so that detailed description thereof will be provided. Is omitted. The permanent magnet may be a samarium cobalt magnet, a ferrite magnet, or a bonded magnet thereof in addition to the neodymium magnet, and the material of the permanent magnet is not particularly limited. Further, low carbon steel or silicon steel can be used for the rotor yoke. The rotor yoke can be cylindrical with a circular opening at the center. A shaft having the same diameter as the opening is passed through the opening of the rotor yoke. Low carbon steel or the like can be used for the shaft.

  First, a plurality of permanent magnets are arranged on the rotor yoke at the reference position so that the polarities are alternately different in the circumferential direction. Here, the reference plane is equidistant from the circumferential direction of the rotor yoke, equidistant from the central axis in the radial direction, and equidistant from the axial end surface of the rotor yoke in the axial direction. In other words, the reference plane is a position where the permanent magnet is arranged in the conventional permanent magnet motor. When there is no variation in magnet characteristics and dimensions and all are in an ideal state, the cogging torque can be minimized when the permanent magnet is arranged at the reference position. The permanent magnet can be attached to the rotor yoke by the magnet's attractive force.

  Here, preferably, the plurality of permanent magnets are held at the reference position by the magnet holding means. The magnet holding means can hold preferably all of the permanent magnets at the reference position and the adjustment position as will be described below, and includes a magnet holding yoke and a magnet holder. Can do. The magnet holding yoke can be an annular shape having an opening having the same diameter as the shaft. Further, the magnet holding yoke has concentric circles having a radius equal to the distance between the rotor shaft and the permanent magnet, and the same number of tap holes as the permanent magnet at equal intervals in the circumferential direction. Note that the outer edge of the magnet holding yoke may be polygonal. A hexagon socket set screw or the like can be used as the magnet holder. The magnet holding yoke and the magnet holder are preferably made of a nonmagnetic material that does not affect the magnetic field, such as a resin material such as aluminum, stainless steel, or MC nylon. First, the magnet holding yoke is fixed to the shaft on each side of the rotor yoke by bolting or bonding. And about each permanent magnet arrange | positioned in the reference | standard position of the rotor yoke surface, a permanent magnet can be mechanically hold | maintained by pressing both ends of a permanent magnet with the magnet holder provided in the magnet holding yoke.

  Next, the cogging torque is adjusted by moving at least one of the permanent magnets in at least one of the circumferential direction, radial direction, and axial direction of the rotor yoke. Specifically, before adjusting the cogging torque, that is, when the permanent magnet is disposed at the reference position, the cogging torque is measured, and one of the permanent magnets is placed in the circumferential direction, radial direction and axial direction of the rotor yoke. The cogging torque when moved in at least one direction is measured, and further, based on the obtained measurement value, linear programming is used to move the permanent magnet and the permanent magnet to be moved so that the cogging torque becomes smaller. By determining the moving distance, the cogging torque can be adjusted. In other words, according to another aspect of the present invention, at least one of the permanent magnets is disposed at an adjustment position that is moved from the reference position in at least one of the circumferential direction, the radial direction, and the axial direction of the rotor yoke. Permanent magnets other than the permanent magnets arranged at the adjustment position among the magnets are provided with a permanent magnet motor arranged at the reference position. Here, the permanent magnet motor in which at least one of the plurality of permanent magnets is arranged in the adjustment position has a cogging torque smaller than that of the permanent magnet motor in which all of the plurality of permanent magnets are arranged in the reference position. The adjustment position is set.

  That is, as described in detail below, according to the present invention, by moving the permanent magnet on the rotor yoke, the cogging torque order (12th order in the above comparative example) component caused by the permanent magnet is significantly reduced. Can be reduced.

  When the permanent magnet on the rotor yoke is moved, the cogging torque changes. Here, as shown below, the change component of the cogging torque is the same as the order of the cogging torque caused by the permanent magnet (in the comparative example, a multiple of 12), most of which is the smallest of the orders ( In the comparative example, it is 12th order). Furthermore, the amount of change in cogging torque is proportional to the amount of movement. Moreover, the phase of the waveform of the change amount of the cogging torque is changed by changing the magnet position (θ) to be moved. The movement of the permanent magnet changes the component caused by the permanent magnet of the cogging torque (the twelfth order component in the comparative example), and the fact that the phase changes according to the position of the moved magnet is caused by the permanent magnet. This suggests that the cogging torque can be reduced by adjusting the position of the magnet to be moved and the amount of movement of the permanent magnet so as to cancel the cogging torque waveform.

  Therefore, we analyzed which cogging torque can be reduced by moving what magnet and how much using mathematical programming. Here, as described above, since the amount of change in cogging torque is proportional to the amount of movement, it is preferable to use linear programming as the mathematical programming. If the cogging torque adjustment is expressed as a linear programming problem, it becomes “minimize (1) under condition (2)”, and by solving this, the position of the magnet to be moved and the amount of movement of the permanent magnet are determined. can do. The magnet position is for specifying each of a plurality of permanent magnets arranged on the rotor yoke. For example, in the above comparative example, there are 10 magnet positions, each of which has each permanent magnet. To represent.

Ｃ₀とＣ₁は、磁石の移動量とコギングトルクとのバランスで設定される係数で、Ｃ₀は０以上の数、Ｃ₁は０より大きい数である。すなわち、Ｃ₀とＣ₁は、Ｂ、Ｘ_j、ｔｏｌｅおよびＷのバランスで決定される。Ｃ₀とＣ₁を変えると線形計画法の解が変化し、これらの係数を調整しながら計算を行う。作業者は、できるだけ小さい磁石総移動量（ΣＸ_j）で目標のコギングトルクを達成するように、Ｃ₀とＣ₁の値を調整しながら、複数回の計算を行うことで、最適な移動量Ｘ_jを求めることができる。具体的には、特に限定されるものではないが、まず、Ｃ₀／Ｃ₁＝０として計算を行い、各磁石の移動量Ｘ_jを求める。ここで、磁石の総移動量（ΣＸ_j）をより小さくすることが望まれる場合には、Ｃ₀／Ｃ₁を大きくして、例えば、Ｃ₀／Ｃ₁＝０．００１としてさらに計算を行い、各磁石の移動量Ｘ_jを求める。この過程を繰り返すことで、できるだけ小さい磁石移動量で目標のコギングトルクを達成することができる。 In the formula, what each character represents is as follows.
B represents the number of magnets.
i represents a measurement point of cogging torque. That is, each i represents each rotor rotation angle (0 to 360 °) that is a measurement point of cogging torque.
j represents a magnet position. That is, j takes an arbitrary integer between 1 and the number B of permanent magnets, and each j represents each permanent magnet.
X _j is the movement amount of the j-th magnet.
T _i is the cogging torque at the i-th point before adjusting the cogging torque. As T _i, measurement data before adjustment of the cogging torque is inputted.
a _ij is the amount of change in the cogging torque at the i-th point per moving amount of the magnet when the j-th magnet is moved. Specifically, for each i-th point, a _ij can be obtained by dividing the measured value of the change amount of the cogging torque when the j-th magnet is moved by the magnet movement amount.
T _l is a loss torque before adjusting the cogging torque. T _l can be an average value of measured values of cogging torque before adjustment.
Tole is a target cogging torque. The tole can be arbitrarily determined according to the target to which the permanent magnet motor is applied. In particular, when applied to a servo motor, an electric power steering motor, or the like, the tole is preferably set to 0.5% or less of the rated torque.
W is the difference between the target cogging torque (tole) and the calculated value of the cogging torque after moving the permanent magnet. Specifically, W is represented by the following formula (3).

C ₀ and C ₁ are coefficients set by the balance between the moving amount of the magnet and the cogging torque. C ₀ is a number greater than or equal to 0, and C ₁ is a number greater than 0. That is, C ₀ and C ₁ are determined by the balance of B, X _j , tole and W. Changing C ₀ and C ₁ changes the solution of the linear programming method, and performs calculations while adjusting these coefficients. The operator performs a plurality of calculations while adjusting the values of C ₀ and C ₁ so as to achieve the target cogging torque with the smallest possible total magnet movement (ΣX _j ). X _j can be obtained. Specifically, although not particularly limited, first, calculation is performed with C ₀ / C ₁ = 0 to obtain the movement amount X _j of each magnet. Here, when it is desired to further reduce the total moving amount (ΣX _j ) of the magnet, C ₀ / C ₁ is increased, and for example, further calculation is performed with C ₀ / C ₁ = 0.001. Then, the movement amount X _j of each magnet is obtained. By repeating this process, the target cogging torque can be achieved with the smallest possible magnet movement.

  By inputting the cogging torque data before adjustment and the cogging torque variation data when each permanent magnet is moved in the circumferential direction, etc. into the linear programming method, the cogging torque is reduced by the above linear programming problem. The amount of movement of each permanent magnet can be calculated.

  When the position of the magnet to be moved and the amount of movement of the permanent magnet are determined by mathematical programming, the permanent magnet is moved accordingly. At this time, the movement of the permanent magnet can be performed using a dedicated jig as in the case where the permanent magnet is arranged at the reference position. The movement of the permanent magnet is preferably performed with the same accuracy as when the permanent magnet is arranged at the reference position. When the permanent magnet is moved, it is preferable to hold the plurality of permanent magnets at the adjustment position by the magnet holding means.

  A first embodiment according to the present invention will be described with reference to FIG. FIG. 1 shows a schematic front view of a rotor from a direction perpendicular to the axis of the rotor according to the first embodiment. In the rotor 10 according to the first embodiment, as described above, a plurality of permanent magnets (M1 to M10) are arranged at the reference position on the rotor yoke 11 through which the shaft 12 is passed, and the magnet holding yoke 14 and For the permanent magnet motor that holds the plurality of permanent magnets at the reference position from both sides of the rotor yoke 11 by the magnet holding means 13 including the magnet holder 15, one of the permanent magnets (M1) is placed in the circumferential direction of the rotor yoke. To adjust the cogging torque, and each permanent magnet is held at the adjustment position by the magnet holding means. In the figure, the moving direction of the magnet is indicated by an arrow.

  A second embodiment according to the present invention will be described with reference to FIG. FIG. 2 shows a schematic cross-sectional view of a permanent magnet motor in a plane passing through the axis of the rotor according to the second embodiment. In addition to the rotor, FIG. 2 also shows a stator 20 having salient poles arranged to face the magnet. Unlike the first embodiment, the permanent magnet motor according to the second embodiment adjusts the cogging torque by moving one of the permanent magnets (M1) in the radial direction of the rotor yoke. When the permanent magnet is moved in the radial direction, a non-magnetic shim 16 having a calculated thickness is sandwiched between the permanent magnet (M1) and the rotor yoke 11 so that the permanent magnet is moved in the radial direction. The permanent magnet is preferably held by the magnet holding means 13 after being moved. In the figure, the moving direction of the magnet is indicated by an arrow.

  A third embodiment according to the present invention will be described with reference to FIG. FIG. 3 shows a schematic cross-sectional view of a permanent magnet motor in a plane passing through the axis of the rotor according to the third embodiment. FIG. 3 also shows a stator yoke having salient poles arranged to face the magnet in addition to the rotor. Unlike the first embodiment, the permanent magnet motor according to the third embodiment is one in which one of the permanent magnets (M1) is moved in the axial direction of the rotor yoke 11 to adjust the cogging torque. . In the figure, the moving direction of the magnet is indicated by an arrow.

  For the direction of movement, select the one with the fewest number of magnets to be adjusted as a result of calculation by mathematical programming. In the first to third embodiments, the cogging torque is adjusted by moving the permanent magnet independently in the circumferential direction, the radial direction, and the axial direction, but the cogging torque is adjusted by combining them. You can also Which direction of the circumferential direction, the radial direction, the axial direction, or a combination thereof can be determined can be determined as follows. That is, if the amount of movement is obtained by mathematical programming for each direction, and the movement is made in the adjustment direction where the number of magnets to be adjusted is small, adjustment can be performed with less error. When the value of the cogging torque after adjustment does not satisfy the target, readjustment can be performed by the same method from the state after adjustment. The readjustment direction may be different from the previous adjustment direction, and does not move in either direction.

  In addition, the upper limit of the movement amount of a permanent magnet is until it hits an adjacent permanent magnet, when moving in the circumferential direction. In the case of moving in the radial direction, since the rotor and the permanent magnet do not rotate when they collide with each other, it is preferable that the gap between the inner surface of the stator and the permanent magnet is at least 0.1 mm. In the case of moving in the axial direction, it is until the permanent magnet hits the holding mechanism.

  Further, the plurality of permanent magnets can be fixed at the adjustment position by an adhesive. In this case, the magnet holding means can be removed after fixing the permanent magnet. FIG. 4 shows a schematic front view of the rotor from a direction perpendicular to the axis of the rotor according to the fourth embodiment. As shown in FIG. 4, the magnet holding mechanism may be removed if the permanent magnet is fixed by attaching an adhesive 17 around the magnet after the permanent magnet is moved. In this case, the magnet holding mechanism can be used for adjusting the cogging torque of another permanent magnet motor.

In order to eliminate the magnetic anisotropy of the stator yoke, it is preferable that the stator yoke is formed by rolling. Further, it is preferable that the number P of the rotor and the number M of the salient stator poles satisfy the following formula 1 or formula 2. Specifically, a combination of the number of poles P and the number of stator salient poles M shown in Table 1 is preferable. This is because the cogging torque can be reduced by using a permanent magnet motor having a relationship between the number of poles P of the rotor satisfying the formula 1 or the formula 2 and the number M of the salient stator poles. In addition, the present invention has the same effect even in a permanent magnet motor that satisfies the following expression 3 which is a relationship of a normal concentrated winding motor.
P = 6n ± 2, M = 6n Equation 1
(However, n is an integer of 2 or more.)
P = 3m ± 1, M = 3m Equation 2
(However, m is an odd number of 3 or more.)
P = 2k, M = 3k Equation 3
(However, k is an integer of 1 or more.)

  Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the examples described below.

  As shown in Comparative Example 2, the influence of the stator yoke can be eliminated by carrying out stacking (see FIGS. 14 and 15). In Comparative Example 2, the cogging torque was 0.0122 Nm. . However, as described above, the cogging torque is desired to be 0.5% or less of the rated torque (0.01 Nm or less in this case), and this is not achieved in Comparative Example 2. For this reason, in the following examples, the cogging torque was adjusted for the permanent magnet motor shown in Comparative Example 2.

[Example 1]
The permanent magnet motor according to the example 1 has the same configuration as the permanent magnet motor according to the comparative example 2 except for the matters specifically described below such as the position of the permanent magnet and the magnet holding means (see FIG. 11). . The shaft of the same material was passed through the center of the low-carbon steel rotor yoke. In Example 1, as shown in FIG. 1, the permanent magnet was held by the magnet holder after the permanent magnet was moved in the circumferential direction. Here, as the magnet holding means, a magnet holding yoke having a tapped hole and a hexagon socket set screw as a magnet holder were used. Moreover, the stator yoke was created by rolling.

  First, the amount of change in cogging torque when the permanent magnet was moved in the circumferential direction was measured. Specifically, the amount of change in cogging torque generated when the magnet 1 in FIG. 11 was moved in the circumferential direction was measured, and the change component of cogging torque was analyzed by Fourier analysis in the same manner as in the comparative example. FIG. 5 shows the result of dividing the waveform of the change amount of the cogging torque when the permanent magnet is moved in the circumferential direction into components for each order of the waveform by Fourier analysis. In addition, the waveform of the amount of change in cogging torque when each of magnet 1 to magnet 5 in FIG. 11 was moved 1.25 ° in the same direction was measured. FIG. 6 shows a measured waveform of the amount of change in cogging torque when the permanent magnets at different magnet positions are moved in the circumferential direction.

  As shown in FIG. 5, the change component of the cogging torque is a multiple of 12 and almost the 12th order, and the change amount is proportional to the movement amount. As shown in FIG. 6, the phase of the waveform changed by changing the magnet position (θ). As described above, it is understood that the cogging torque can be reduced by adjusting the position of the magnet to be moved and the moving amount of the permanent magnet so as to cancel the cogging torque waveform caused by the permanent magnet.

  In the first embodiment, in order to adjust the cogging torque, by solving the linear programming problem “minimizing (1) under condition (2)”, the position of the magnet to be moved and the amount of movement of the permanent magnet It was determined. Specifically, in Example 1, the cogging torque was adjusted by moving the permanent magnet in the circumferential direction. First, the cogging torque data before adjustment and the change data of the cogging torque when each permanent magnet is moved in the circumferential direction are input to the linear programming method. Was calculated. Specifically, the calculation was performed by inputting the following data for each character in formulas (1) and (2).

In formula (1), B = 10, C ₀ = _0, 0.0001, 0.001, 0.01, C ₁ = 1.
In equation (2), i = 1 to 600, tole = 0.001, T _i = torque waveform shown in FIG. 15 at measurement point i (T ₁ = −0.01268, T ₂ = −0.01285, T ₃ = −0.01346,..., A _ij = the waveform of the change amount of the cogging torque shown in FIG. 6 divided by the movement amount 1.25 ° (a ₁₁ = 0.00203, a ₂₁ = 0.00195 , A ₃₁ = 0.00184, ... a ₁₂ = 0.00043, a ₂₂ = 0.00023, ...).

Table 2 shows the magnet movement amount X _i and cogging torque at each C ₀ / C ₁ .

  From the calculation results, it was found that the cogging torque can be optimized by moving the magnet 3 in the same circumferential direction by 1.0 ° and the magnet 4 by 2.2 °. According to this calculation result, the permanent magnet was moved, the cogging torque waveform was measured as in the comparative example, and the change component of the cogging torque was analyzed by Fourier analysis. FIG. 7 shows an actual measurement waveform of cogging torque of the permanent magnet motor according to the first embodiment. FIG. 8 shows a result of dividing the cogging torque waveform according to Comparative Example 2 and Example 1 into components for each order of the waveform by Fourier analysis. As shown in FIG. 8, in Comparative Example 2, the 12th-order component (peak value) was 0.0053 Nm, but in Example 1, it was greatly reduced to 0.0004 Nm. Further, as shown in FIG. 7, in Comparative Example 2, the total cogging torque was 0.0122 Nm, but in Example 1, it was 0.0036 Nm. Thus, in Example 1, the target cogging torque of 0.01 Nm or less (0.5% or less of the rated torque) could be achieved.

[Example 2]
As shown in FIG. 2, Example 2 was the same as Example 1 except that the permanent magnet was moved in the radial direction. First, the amount of change in cogging torque when the permanent magnet was moved in the radial direction was measured. Note that nonmagnetic SUS was used as the nonmagnetic shim. Specifically, the amount of change in cogging torque generated when the magnet 1 in FIG. 11 was moved in the radial direction was measured, and the change component of cogging torque was analyzed by Fourier analysis in the same manner as in the comparative example. FIG. 9 shows the result of dividing the waveform of the change amount of the cogging torque when the permanent magnet is moved in the radial direction into components for each order of the waveform by Fourier analysis. As in the case of moving the permanent magnet in the circumferential direction, the change component of the cogging torque is a multiple of 12 and most of it is the 12th. Further, the amount of change in cogging torque was proportional to the amount of movement. From this, it can be seen that, even when the permanent magnet is moved in the radial direction, the amount of movement of the permanent magnet in the radial direction for reducing the cogging torque can be obtained by linear programming as in the first embodiment. .

  As in the first embodiment, the cogging torque data before adjustment and the cogging torque variation data when each permanent magnet is moved in the radial direction are input to the linear programming method so that the cogging torque is reduced. The amount of movement of the permanent magnet was calculated. From the calculation results, it was found that the cogging torque can be optimized by moving the magnet 1 and the magnet 6 in the diameter direction of 0.52 mm, the magnet 4 and the magnet 9 in the direction of 0.26 mm, and the magnet 5 and the magnet 10 in the diameter direction of 0.22 mm. . According to this calculation result, the permanent magnet was moved, the cogging torque waveform was measured as in the comparative example, and the change component of the cogging torque was analyzed by Fourier analysis. In Comparative Example 2, the 12th-order component (peak value) was 0.0053 Nm, but in Example 2, it was greatly reduced to 0.0018 Nm. In Comparative Example 2, the overall cogging torque was 0.0122 Nm, but in Example 2, it was 0.0068 Nm. Thus, in Example 2, the target cogging torque of 0.01 Nm or less (0.5% or less of the rated torque) could be achieved.

[Example 3]
As shown in FIG. 3, Example 3 was the same as Example 1 except that the permanent magnet was moved in the axial direction. First, the amount of change in cogging torque when the permanent magnet was moved in the axial direction was measured. Specifically, the amount of change in cogging torque generated when the magnet 1 in FIG. 11 was moved in the axial direction was measured, and the change component of cogging torque was analyzed by Fourier analysis in the same manner as in the comparative example. FIG. 10 shows a result of dividing the waveform of the amount of change in cogging torque when the permanent magnet is moved in the axial direction into components for each order of the waveform by Fourier analysis. As in the case where the permanent magnet is moved in the circumferential direction and the radial direction, the cogging torque components are almost all twelfth. Further, the amount of change in cogging torque was proportional to the amount of movement. From this, even when the permanent magnet is moved in the axial direction, the amount of axial movement of the permanent magnet for reducing the cogging torque can be obtained by linear programming as in the first and second embodiments. I understand.

  As in the first embodiment, the cogging torque data before adjustment and the cogging torque variation data when the respective permanent magnets are moved in the axial direction are input to the linear programming method so that the cogging torque is reduced. The amount of movement of the permanent magnet was calculated. From the calculation results, it was found that the cogging torque can be optimized by moving the magnet 2 in the axial direction by 2.3 mm and the magnets 3 and 8 in the axial direction by 3.8 mm. According to this calculation result, the permanent magnet was moved, the cogging torque waveform was measured as in the comparative example, and the change component of the cogging torque was analyzed by Fourier analysis. In Comparative Example 2, the twelfth-order component (peak value) was 0.0053 Nm, but in Example 3, it was greatly reduced to 0.0017 Nm. In Comparative Example 2, the overall cogging torque was 0.0122 Nm, but in Example 3, it was 0.0064 Nm. Thus, in Example 3, the target cogging torque of 0.01 Nm or less (0.5% or less of the rated torque) could be achieved.

  According to another aspect of the present invention, the following embodiments are provided.
  [Embodiment 1]
  A rotor comprising a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke;
  A stator yoke arranged at a space from the rotor, salient poles facing the permanent magnet and arranged on the stator yoke at equal intervals in the circumferential direction, and a concentrated winding on the salient poles. A stator comprising phase-connected armature windings;
  A permanent magnet motor comprising:
  At least one of the permanent magnets is equidistant in the circumferential direction of the rotor yoke, equidistant from the central axis in the radial direction, and from the reference position that is equidistant from the axial end surface of the rotor yoke in the axial direction. The permanent magnets are arranged at the adjustment position moved in at least one of the radial direction and the axial direction, and the permanent magnets other than the permanent magnets arranged at the adjustment position among the plurality of permanent magnets are arranged at the reference position,
  The adjustment position such that a permanent magnet motor having at least one of a plurality of permanent magnets disposed at the adjustment position has a cogging torque that is less than a permanent magnet motor at which all of the plurality of permanent magnets are disposed at the reference position. Is set with permanent magnet motor.
  [Embodiment 2]
  The permanent magnet motor according to embodiment 1, further comprising magnet holding means capable of holding the permanent magnet at the reference position and / or the adjustment position.
  [Embodiment 3]
  The permanent magnet motor according to embodiment 1, wherein the plurality of permanent magnets are fixed by an adhesive at the adjustment position.
  [Embodiment 4]
  The permanent magnet motor according to any one of Embodiments 1 to 3, wherein the rotor pole number P and the stator salient pole number M satisfy Formula 1 or Formula 2 below.
  P = 6n ± 2, M = 6n Equation 1
(However, n is an integer of 2 or more.)
  P = 3m ± 1, M = 3m Equation 2
(However, m is an odd number of 3 or more.)
  [Embodiment 5]
  A rotor comprising a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke;
  A stator yoke arranged at a space from the rotor, salient poles facing the permanent magnet and arranged on the stator yoke at equal intervals in the circumferential direction, and a concentrated winding on the salient poles. A stator comprising phase-connected armature windings;
  A method for adjusting the cogging torque of a permanent magnet motor comprising:
  The plurality of permanent magnets are alternately spaced in the circumferential direction at reference positions that are equidistant in the circumferential direction of the rotor yoke, equidistant from the central axis in the radial direction, and equidistant from the axial end surface of the rotor yoke in the axial direction. Arranging on the rotor yoke to be different from each other,
  Adjusting the cogging torque by moving at least one of the permanent magnets in at least one of a circumferential direction, a radial direction and an axial direction of the rotor yoke;
  Cogging torque adjustment method for permanent magnet motor including
  [Embodiment 6]
  The step of adjusting the cogging torque includes
  Measuring the cogging torque before adjusting the cogging torque;
  Measuring a cogging torque when one of the permanent magnets is moved in at least one of a circumferential direction, a radial direction and an axial direction of the rotor yoke;
  Determining a permanent magnet to be moved and a moving distance of the permanent magnet based on the obtained measurement value using linear programming so that the cogging torque becomes smaller; and
  Embodiment 6. The method of embodiment 5 comprising:
  [Embodiment 7]
  Holding the plurality of permanent magnets at the reference position by a magnet holding means; and / or
  The step of holding the plurality of permanent magnets at the adjusted position after the movement by the magnet holding means.
  The method according to embodiment 5 or 6, further comprising:
  [Embodiment 8]
  Fixing the plurality of permanent magnets at the adjustment position with an adhesive; and
  Removing the magnet holding means after fixing the permanent magnet;
  The method of embodiment 7, further comprising:
  [Embodiment 9]
  Embodiment 9. The method according to any of embodiments 5-8, wherein the linear programming is to minimize (1) under condition (2).

(Where
  B represents the number of magnets.
  i represents a measurement point of cogging torque.
  j represents a magnet position.
  X _j Is the amount of movement of the j-th magnet.
  T _i Is the i-th point cogging torque before adjusting the cogging torque.
  a _ij Is the amount of change in cogging torque at the i-th point per amount of movement of the magnet when the j-th magnet is moved.
  T _l Is the loss torque before adjusting the cogging torque.
  Tole is a target cogging torque.
  W is the difference between the target cogging torque and the calculated value of the cogging torque after moving the permanent magnet.
  C ₀ And C ₁ Is a coefficient set by the balance between the moving amount of the magnet and the cogging torque. )
  [Embodiment 10]
  A permanent magnet motor having a cogging torque adjusted by the method according to any one of Embodiments 5 to 9.

The typical front view of the rotor from a direction perpendicular | vertical to the axis | shaft of a rotor concerning 1st Embodiment is shown. The typical sectional view of the permanent magnet motor in the plane which passes along the axis of a rotor concerning a 2nd embodiment is shown. The typical sectional view of the permanent magnet motor in the plane which passes along the axis of a rotor concerning a 3rd embodiment is shown. The typical front view of the rotor from the direction perpendicular | vertical to the axis | shaft of a rotor concerning 4th Embodiment is shown. The result of dividing the waveform of the change amount of the cogging torque when the permanent magnet is moved in the circumferential direction into components for each order of the waveform by Fourier analysis is shown. The measured waveform of the variation | change_quantity of a cogging torque when the permanent magnet of a different magnet position is moved to the circumferential direction is shown. The measured waveform of the cogging torque of the permanent magnet motor concerning Example 1 is shown. The result of having divided the cogging torque waveform concerning the comparative example 2 and Example 1 into the component for every order of a waveform by Fourier analysis is shown. The result of dividing the waveform of the amount of change in cogging torque when the permanent magnet is moved in the radial direction into components for each order of the waveform by Fourier analysis is shown. The result of dividing the waveform of the change amount of the cogging torque when the permanent magnet is moved in the axial direction into components for each order of the waveform by Fourier analysis is shown. The typical sectional view in the field perpendicular to the axis of the 10 pole 12 slot permanent magnet motor used in the example and the comparative example is shown. Specific shapes of the permanent magnets used in Examples and Comparative Examples are shown. The measured waveform of the cogging torque of the permanent magnet motor concerning the comparative example 1 (parallel stacked stator) is shown. The result of having divided the cogging torque waveform concerning the comparative examples 1 and 2 into the component for every order of a waveform by Fourier analysis is shown. The measured waveform of the cogging torque of the permanent magnet motor concerning the comparative example 2 (rotation stacking stator) is shown.

Explanation of symbols

M1 to M10: permanent magnet 10: rotor 11: rotor yoke 12: shaft 13: magnet holding means 14: magnet holding yoke 15: magnet holder 16: shim 17: adhesive 20: stator 21: salient pole 22: stator Yoke 23: Armature winding

Claims (10)

A rotor comprising a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke;
A stator yoke arranged at a space from the rotor, salient poles facing the permanent magnet and arranged on the stator yoke at equal intervals in the circumferential direction, and a concentrated winding on the salient poles. A permanent magnet motor comprising: a stator comprising armature windings connected in phase;
At least one of the permanent magnets, at equal intervals in the circumferential direction of the rotor yoke, equidistant from the central axis in the radial direction, from the reference position is equidistant from the axial end surface of the rotor yoke with respect to the axial direction, radial direction of the rotor yoke And a permanent magnet other than the permanent magnets arranged at the adjustment position among the plurality of permanent magnets is arranged at the reference position.
The adjustment position is such that a permanent magnet motor having at least one of a plurality of permanent magnets disposed at the adjustment position has a smaller cogging torque than a permanent magnet motor at which all of the plurality of permanent magnets are disposed at the reference position. Is set with permanent magnet motor.   The permanent magnet motor according to claim 1, further comprising magnet holding means capable of holding the permanent magnet at the reference position and / or the adjustment position.   The permanent magnet motor according to claim 1, wherein the plurality of permanent magnets are fixed by an adhesive at the adjustment position. The permanent magnet motor according to any one of claims 1 to 3, wherein the number of poles P of the rotor and the number of salient stator poles M satisfy Formula 1 or Formula 2 below.
P = 6n ± 2, M = 6n Equation 1
(However, n is an integer of 2 or more.)
P = 3m ± 1, M = 3m Equation 2
(However, m is an odd number of 3 or more.) A rotor comprising a rotor yoke and a plurality of permanent magnets arranged on the side surface of the rotor yoke at predetermined intervals so that the polarities are alternately different in the circumferential direction of the rotor yoke;
A stator yoke arranged at a space from the rotor, salient poles facing the permanent magnet and arranged on the stator yoke at equal intervals in the circumferential direction, and a concentrated winding on the salient poles. A stator comprising a phase-connected armature winding and a cogging torque of a permanent magnet motor comprising:
The plurality of permanent magnets are alternately spaced in the circumferential direction at reference positions that are equidistant in the circumferential direction of the rotor yoke, equidistant from the central axis in the radial direction, and equidistant from the axial end surface of the rotor yoke in the axial direction. Arranging on the rotor yoke to be different from each other,
Adjusting the cogging torque by moving at least one of the permanent magnets in at least one of the radial direction and the axial direction of the rotor yoke , and adjusting the cogging torque of the permanent magnet motor. The step of adjusting the cogging torque includes
Measuring the cogging torque before adjusting the cogging torque;
Measuring a cogging torque when one of the permanent magnets is moved in at least one of a circumferential direction, a radial direction and an axial direction of the rotor yoke;
The method according to claim 5, further comprising: using a linear programming method to determine a permanent magnet to be moved and a moving distance of the permanent magnet based on the obtained measurement value so as to reduce the cogging torque. The method further comprises the steps of: holding the plurality of permanent magnets at the reference position by the magnet holding means; and / or holding the plurality of permanent magnets at the adjusted position after the movement by the magnet holding means. The method according to 5 or 6. Fixing the plurality of permanent magnets at the adjustment position with an adhesive; and
The method according to claim 7, further comprising: removing the magnet holding means after fixing the permanent magnet. 9. A method according to any of claims 5 to 8, wherein the linear programming is to minimize (1) under condition (2).

(Where
B represents the number of magnets.
i represents a measurement point of cogging torque.
j represents a magnet position.
X _j is the movement amount of the j-th magnet.
T _i is the cogging torque at the i-th point before adjusting the cogging torque.
a _ij is the amount of change in the cogging torque at the i-th point per moving amount of the magnet when the j-th magnet is moved.
T _l is a loss torque before adjusting the cogging torque.
Tole is a target cogging torque.
W is the difference between the target cogging torque and the calculated value of the cogging torque after moving the permanent magnet.
C ₀ and C ₁ are coefficients set by a balance between the moving amount of the magnet and the cogging torque. )   A permanent magnet motor in which cogging torque is adjusted by the method according to claim 5.

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