JP2013162557A - Electric rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric rotary machine capable of high quality rotary driving with excellent durability by effectively reducing demagnetization of a permanent magnet.SOLUTION: An electric rotary machine includes a stator 11 having a plurality of teeth 15 facing a rotor 12, and a plurality of slots 18 as spaces each for winding a coil around the teeth, the rotor having a pair of permanent magnets 16 for applying magnetic force to the teeth, the magnets being embedded in the rotor in a V shape. When a pair of the permanent magnets in the rotor, corresponding to six slots in the stator, is defined as one magnetic pole, there are formed adjustment grooves 21 in the middle of magnetic paths of magnetic fluxes produced by supplying power to the coil, the magnetic fluxes flowing to demagnetization regions A1 produced in the permanent magnets, as magnetic resistance increasing regions for increasing magnetic resistance, the grooves including deepest portions 21a positioned 56° (an electrical angle) equally away from a d-axis passing through the center of the one magnetic pole in forward and backward directions, so that a width of each of the grooves is equal to that of each of facing teeth.

Description

  The present invention relates to an electric rotating machine, and more particularly, to an electric rotating machine that realizes a high-quality rotating drive with high durability.

  Electric rotating machines mounted on various devices are required to have characteristics corresponding to the mounted devices. For example, they are mounted on a hybrid electric vehicle with an internal combustion engine as a driving source, or as a single driving source. In the case of a drive motor mounted on an electric vehicle (Electric Vehicle), it is required to have a wide variable speed characteristic at the same time as generating a large torque in a low rotation range.

As an electric rotating machine having such characteristics, it is effective to adopt a structure that can effectively use reluctance torque together with magnet torque, so that it becomes a V shape that opens toward the outer peripheral surface side, It has been proposed to adopt an IPM (Interior Permanent Magnet) structure in which a permanent magnet having a strong magnetic force is embedded in a rotor (for example, Patent Document 1).
In particular, hybrid vehicles and electric vehicles are required to have an electric rotating machine that is capable of high energy density output through weight reduction and miniaturization in response to the recent demand for improved energy efficiency (fuel consumption) as well as restrictions on mounting space. Therefore, neodymium magnets with high residual magnetic flux density are frequently used as embedded permanent magnets.

  This neodymium magnet is a rare earth (rare earth) magnet mainly composed of Nd—Fe—B, is expensive, and has a problem in heat resistance due to irreversible demagnetization at low temperatures and low coercive force. In order to solve this problem, it has been studied to improve the coercive force by adding dysprosium (Dy) or terbium (Tb), but these additives are also rare and expensive rare earths that are unevenly distributed locally. Therefore, there is a problem that the cost increases.

  Various proposals have been made to solve such problems. For example, from the viewpoint of materials, the amount of expensive dysprosium and terbium used can be determined by examining the production method together with additives added to dysprosium and terbium. There has been proposed a high-performance crystalline magnet that suppresses a decrease in residual magnetic flux density (irreversible demagnetization) while suppressing coercivity and increases coercive force (Patent Document 2).

  In addition to this material improvement, there is also a demand for improvement from a structural point of view. As a first structural improvement, for example, the permanent magnet is divided into two regions, the outer peripheral surface side and the inner side of the rotor. Thus, the outer peripheral surface side of the rotor including the region that is easily demagnetized is made a region made of an expensive material having a high coercive force, and the inside side is made a normal region, thereby reducing the amount of expensive material used. Thus, it has been proposed to prevent a significant increase in cost (Patent Document 3). However, demagnetization occurs only at the corners on both ends of the permanent magnet on the outer peripheral surface side of the rotor, and it is not necessary to set a region for increasing the coercive force on the entire surface of one side of the permanent magnet, and it is more than necessary. A sufficient cost reduction cannot be achieved due to the enhancement of the magnetic force.

  As another structural improvement, a demagnetizing field is formed and reduced by forming a short-circuit magnetic path made of a magnetic material in the resin disposed as a fixing member on both ends of the permanent magnet. It has been proposed to suppress magnetism (Patent Document 4). However, since the short-circuit magnetic path in the resin is narrow and easily magnetically saturated, the magnetic permeability decreases at a certain magnetic flux density and does not function as a short-circuit magnetic path. In order to ensure this function, if the width of the short-circuit magnetic path is widened, the amount of effective magnetic flux that contributes to torque decreases due to an increase in leakage magnetic flux. In addition, it functions as a short circuit for the magnetized magnetic flux, and a region having a low magnetization rate is generated locally, which causes demagnetization.

  As a third structural improvement, it has been proposed to increase the resistance to demagnetization by increasing the thickness in the magnetization direction on both ends of a permanent magnet that is easily demagnetized (Patent Document 5). However, since the volume of the magnet is increased, the cost is increased. In addition, when magnetizing, there is a region where the magnetized magnetic flux is concentrated (flows) and cannot be sufficiently magnetized in the high permeability internal region that is in contact with the magnet at thick portions in the magnetization direction on both ends. I cannot get the effect I expected. In addition, since the permanent magnet is formed in a concave shape, there is a problem in that processing costs are required when the permanent magnet is formed into one piece.

  On the other hand, in an electric rotating machine (motor) that adopts this IPM structure, reluctance torque is effectively achieved by embedding a permanent magnet in the rotor so as to be V-shaped and securing a q-axis magnetic path. Since it can be utilized, the ratio of the reluctance torque in this electric rotating machine becomes larger than the magnet torque, and the inductance ratio (Lq / Ld) of the q axis and d axis in the rotor in which the permanent magnet is embedded in the V shape. As a result, the salient pole ratio increases, and spatial harmonics are easily superimposed on the magnetic flux waveform. The d-axis is the direction of the magnetic flux created by the magnetic pole, that is, the central axis between the V-shaped permanent magnets, and the q-axis is an adjacent magnetic pole (permanent magnet) that is electrically and magnetically orthogonal to the d-axis. It becomes the central axis between.

  For this reason, in such an electric rotating machine, torque ripple (torque ripple) which is a fluctuation range of torque increases. This increase in torque ripple causes an increase in vibration and electromagnetic noise of the electric rotating machine. Among these, the electromagnetic noise has a relatively higher frequency band than the noise caused by the drive of the internal combustion engine, and the electric rotating machine is installed. It is preferable to reduce the noise as much as possible because the sound is uncomfortable for the vehicle occupant.

For this reason, as an electric rotating machine of this type, for the purpose of suppressing torque ripple and the like, it has been proposed to form a groove extending in the axial direction on the outer peripheral surface of the rotor (for example, Patent Document 6). ~ 8).
However, in Patent Documents 6 to 8, it does not correspond to all the conditions of an electric rotating machine that employs a three-phase IPM motor structure, but how to determine the groove formation position. Important formation conditions such as whether the groove width should be good and what is necessary are unknown. For this reason, it cannot be applied to other structures. For example, the optimum conditions can be set according to various conditions such as permanent magnet installation conditions, the tip width of a tooth portion described later in the stator, and the opening width of the slot. Can not. In addition, the effect of suppressing the demagnetization of the permanent magnet cannot be obtained.

JP 2008-99418 A JP 2011-14668 A JP 2011-135638 A JP 2009-232525 A JP 2008-283823 A Japanese Patent Laid-Open No. 2004-328956 JP 2008-206308 A JP 2008-31316 A

  Therefore, the present invention provides an electric rotating machine capable of effectively suppressing demagnetization of a permanent magnet without causing a reduction in torque and the like and capable of high-quality rotation driving with excellent durability. It is an object.

  A first aspect of the invention relating to an electric rotating machine that solves the above problems includes a rotor that integrally rotates a rotating shaft of a shaft center, and a stator that rotatably accommodates the rotor, and the fixed The child wraps around the teeth portion, a plurality of teeth portions extending toward the outer peripheral surface that rotates around the rotor and facing the inner peripheral surface side to the outer peripheral surface, and a coil for inputting driving power. A plurality of slots formed between the teeth portions in a space, and the rotor is embedded with a plurality of permanent magnets so as to exert a magnetic force on the opposing surface of the teeth portions, The magnetic force generated when the coil is energized passes through the teeth part, the back side of the teeth part, and the rotor, and the reluctance torque that acts between the permanent magnet and the magnet of the attractive force or the repulsive force. An electric rotating machine that rotates the rotor in the stator by rotating the rotor, and the set of permanent magnets on the rotor side corresponds to the set of slots on the stator side. When the one set of permanent magnets has one magnetic pole, a magnetic resistance is provided in the middle of the magnetic path of the magnetic flux generated by energizing the coil toward the demagnetization point generated by the permanent magnet for each magnetic pole. A magnetic resistance increasing region to be enlarged is formed.

In addition to the specific matter of the first aspect, the second aspect of the invention related to the electric rotating machine that solves the above problem is, as the magnetic resistance increasing region, an outer peripheral surface facing the teeth portion of the rotor, An adjustment groove for adjusting the magnetic resistance is formed.
In the third aspect of the invention relating to the electric rotating machine that solves the above-described problem, in addition to the specific matter of the second aspect, the rotor side is opened in a V shape toward the outer peripheral surface side. The pair of permanent magnets is embedded in one pair to form the one magnetic pole, and the stator has six sets of the one slot on the stator side, and the adjustment groove is formed on both sides from the center of the one magnetic pole. Further, the tooth portion is formed so as to be parallel to the teeth portion with a width within the facing width facing the teeth portion which is equivalent to both sides.

According to a fourth aspect of the invention relating to the electric rotating machine that solves the above problem, in addition to the specific matter of the second or third aspect, the adjustment groove has an electric angle equal to 56 ° on both sides with respect to the center of the one magnetic pole. The position is formed so as to be the deepest part.
According to a fifth aspect of the invention relating to the electric rotating machine that solves the above-mentioned problems, in addition to the specific matter of any one of the second to fourth aspects, the inner peripheral surface of the teeth portion and the outer peripheral surface of the rotor And the depth F of the deepest portion of the adjustment groove is in a range of 0.2 ≦ F / D1 ≦ 0.4. It is.

According to a sixth aspect of the invention relating to the electric rotating machine that solves the above problem, in addition to the specific matter of the first aspect, as the magnetic resistance increasing region, an inner surface that forms a space for accommodating the permanent magnet, An adjustment gap for adjusting the magnetic resistance is formed between the outer surface of the permanent magnet.
The seventh aspect of the invention relating to the electric rotating machine that solves the above-described problem is such that, in addition to the specific matter of the sixth aspect, the rotor side opens in a V shape toward the outer peripheral surface side. The pair of permanent magnets is embedded to form the one magnetic pole, and the adjustment gap is formed on the side close to the outer peripheral surface of the rotor so as to be parallel to the teeth portion. It is what.

  Thus, according to the aspect of the present invention, when the magnetic flux generated by energizing the coil on the stator side passes from the teeth portion on the stator side to the facing rotor side, for each magnetic pole. In addition, it passes through a magnetic resistance increasing region having a large magnetic resistance in the middle of the magnetic path toward the demagnetized portion generated by the permanent magnet. Therefore, under the condition that the magnetic flux of the coil and the magnetic flux of the permanent magnet are reversed, the influence (demagnetization effect) that the high temperature region of the permanent magnet is demagnetized by the magnetic flux of the coil can be reduced, and the reliability is high. Efficient rotation drive can be continued.

  For example, as the magnetic resistance increasing region, an adjustment groove for adjusting the magnetic resistance is formed so as to extend in parallel with the outer peripheral surface facing the teeth portion of the rotor, or an adjustment gap for adjusting the magnetic resistance is adjacent to the permanent magnet. And may be formed so as to extend in parallel. In the case of a structure in which one magnetic pole on the side of a pair of permanent magnets corresponds to one set of six slots, the adjustment groove is positioned at an electrical angle of 56 ° equivalent to both sides with one tooth portion on both sides from the center of one magnetic pole. The deepest portion is formed so as to extend in parallel with the width within the facing width to the teeth portion, and the deepest portion with respect to the facing distance D1 between the inner peripheral surface of the teeth portion and the outer peripheral surface of the rotor By forming the ratio of the depth F to be in the range of 0.2 to 0.4, torque ripple and the like can be effectively reduced even in the structure, and high quality with less loss along with vibration and noise. Rotational drive can be realized.

It is a figure which shows 1st Embodiment of the electric rotary machine which concerns on this invention, and is a top view which shows the basic structure. It is a top view which shows the generation | occurrence | production situation of the magnetic flux generation | occurrence | production when there is no magnetic pole in the rotor side. It is a partially expanded plan view explaining the subject of the present invention. FIG. 4 is a partially enlarged plan view in a use environment different from FIG. 3 for explaining the problem of the present invention. It is a partially expanded plan view which shows the structure of the embodiment. It is a partially expanded plan view which shows the structural conditions of the embodiment. It is a graph of the magnetic flux waveform explaining the solution of the problem in the basic structure. It is a graph explaining the condition determination of the structure of the embodiment. It is a graph different from FIG. 8 explaining condition determination of the configuration of the embodiment. It is a graph which verifies the effect by the structure. It is a graph different from FIG. 8 which verifies the effect by the structure. FIG. 10 is a graph different from FIGS. 8 and 9 for verifying the effect of the configuration. FIG. It is a figure which shows 2nd Embodiment of the electric rotary machine which concerns on this invention, and is a partially expanded plan view which shows the structure of the embodiment. It is a partially expanded plan view which shows the structural conditions of the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 12 are views showing a first embodiment of an electric rotating machine according to the present invention.
In FIG. 1, an electric rotating machine (motor) 10 includes a stator (stator) 11 formed in a substantially cylindrical shape, and a rotating shaft 13 that is rotatably housed in the stator 11 and coincides with an axis. For example, in a hybrid vehicle or an electric vehicle, it has a performance suitable for mounting as a drive source similar to an internal combustion engine or in a wheel wheel. ing.

  The stator 11 is formed with a plurality of stator teeth 15 extending in the normal direction of the axial center so that the outer peripheral surface 12a of the rotor 12 faces the inner peripheral surface 15a via the gap G. . The stator teeth 15 are wound with three-phase windings constituting a coil for generating magnetic flux (not shown) for rotationally driving the rotor 12 confrontingly accommodated therein by distributed winding.

  The rotor 12 is manufactured to have an IPM (Interior Permanent Magnet) structure in which a pair of permanent magnets 16 are embedded as one magnetic pole so as to be V-shaped to open toward the outer peripheral surface 12a. The rotor 12 includes a space 17a in which a corner portion 16a of a flat plate-like permanent magnet 16 extending in the front and back direction of the drawing is fitted in a facing state and accommodated in a stationary state, and both sides in the width direction of the permanent magnet 16 A V-shaped space 17 that forms a space 17b (hereinafter also referred to as a flux barrier 17b) that functions as a flux barrier that restricts the wraparound of the magnetic flux is formed so as to face the outer peripheral surface 12a. A center bridge 20 that connects and supports the permanent magnets 16 is formed between the V-shaped spaces 17 so that the permanent magnets 16 can be positioned and held against centrifugal force during high-speed rotation.

  In this electric rotating machine 10, the space between the stator teeth 15 constitutes a slot 18 for forming a coil by winding it through a winding, and six stator teeth are provided on each of the eight sets of permanent magnets 16. It is constructed so that 15 slots face each other, in other words, 6 slots 18 correspond to one magnetic pole formed on the pair of permanent magnets 16 side. That is, the electric rotating machine 10 is wound with 8 poles (4 pole pairs), 48 slots, single-phase distributed winding 5 pitches, with the N and S poles of the permanent magnet 16 alternately arranged for each adjacent magnetic pole. It is made to a wired three-phase IPM motor. In addition, the display of the N pole and the S pole in the figure does not exist on the surface of the member, but is shown for explanation.

  Thus, the electric rotating machine 10 attracts the permanent magnet 16 when the coil in the slot 18 of the stator 11 is energized and the magnetic flux is passed through the rotor 12 facing from the stator teeth 15. In addition to the magnet torque caused by the repulsive force, it can be rotationally driven by a total torque including the reluctance torque that attempts to minimize the magnetic path through which the magnetic flux passes, and the rotating shaft 13 that rotates integrally with the rotor 12. It is possible to output the electrical energy energized and input as mechanical energy.

  Here, as shown in FIG. 2, the electric rotating machine 10 enters the rotor 12 from the stator 11 for each of a plurality of stator teeth 15 corresponding to a pair of permanent magnets 16 constituting one magnetic pole. The winding 18 is formed by distributed winding in the slot 18 so that the magnetic path of the passing magnetic flux m is evenly arranged. In other words, the formation of the magnetic flux m is not hindered along the magnetic path. Thus, a V-shaped space 17 for accommodating the permanent magnet 16 is formed. Note that the stator 11 and the rotor 12 are screwed by using a bolt hole 19 or the like by superposing thin sheets of electromagnetic steel plate material such as silicon steel in the axial direction so as to have a thickness corresponding to a desired output torque. It is produced by.

  Further, the permanent magnet 16 is magnetized so as to have a magnetic moment aligned in the magnetization direction from the S pole to the N pole in the internal magnetic domain (see FIG. 5). As a result, the magnetic force may be weakened by being disturbed by a thermal influence (disturbance), and when the temperature exceeds the Curie temperature, an irreversible region in which the magnetic domain cannot be maintained is generated, and a so-called demagnetized portion is formed. In addition, the magnetic moment in the magnetic domain of the permanent magnet 16 is susceptible to magnetic influence during heating, and by aligning with the magnetization direction of the external magnetism, it can return to the original magnetization direction even if the influence of the external magnetism is eliminated. Instead, a so-called demagnetization point is formed.

  When the electric rotating machine 10 has an IPM structure in which the permanent magnets 16 are embedded in the rotor 12, the corners 16a of the pair of permanent magnets 16, particularly the outer corners 16ao on the outer peripheral surface 12a side of the rotor 12 and the inner side. A region A1 where the corner 16ai faces the vector direction mv of the magnetic flux m generated by energizing the winding coil formed in the slot 18 on the stator 11 side (see FIGS. 3 and 5). It is easily affected by the magnetization direction. Further, the region A2 (see FIGS. 4 and 5) on the opposite side of the outer corner 16ao and the inner corner 16ai of the permanent magnet 16 is not opposed to the vector direction mv of the magnetic flux m, but only on one side. It is easily affected by the magnetization direction.

  For this reason, as shown in FIG. 3, the permanent magnet 16 is driven by rotating the rotor 12 in the counterclockwise (CCW) direction by energizing the coil in the slot 18 of the stator 11, for example, another motor. When the temperature rises to 190 ° C. before the heat resistance temperature of the component parts, a strong demagnetization point is generated in the outer corner 16ao of the region A1 facing the magnetic flux m entering the rotor 12 from the stator teeth 15, and the inner side Some demagnetization was also observed at the corner 16ai. Further, as shown in FIG. 4, for example, when the temperature of the permanent magnet 16 is increased to 200 ° C., which is set as the heat resistant temperature of other motor components, the outer corner portion 16ao and the inner corner portion 16ai of the region A1. In addition, the demagnetization of the inner corner 16ai of the opposite region A2 is increased, and a slight demagnetization is also observed in the outer corner 16ao. In other words, the permanent magnet 16 needs some countermeasures because the demagnetization appears strongly at the outer corner 16ao of the region A1 facing the magnetic flux m within the operating temperature range. The outer corner portion 16ao and the inner corner portion 16ai of the permanent magnet 16 are more demagnetized toward the tip side because of the difference in the influence of the strength of the adjacent magnetic force.

  Therefore, in the electric rotating machine 10, as shown in FIG. 5, the concave adjustment groove 21 is close to the outer peripheral surface 12 a of the rotor 12 in order to adjust the gap G between the stator teeth 15 and the inner peripheral surface 15 a. The adjustment groove 21 is formed so as to extend in parallel with the inner peripheral surface 15a of the stator teeth 15 and to face each other. The adjusting groove 21 serves as a magnetic resistance increasing region, which can slightly increase the magnetic resistance by lowering the magnetic permeability between the stator tooth 15 and the inner peripheral surface 15a, and suppresses the strength of the magnetic flux m entering the magnetic force. The influence is reduced and the occurrence of demagnetization is suppressed.

Therefore, the electric rotating machine 10 can continue the rotation drive with high reliability and efficiency by forming the adjustment groove 21 on the outer peripheral surface 12a of the rotor 12 so that a demagnetization point is hardly generated in the permanent magnet 16. Can do.
In addition, the adjustment groove 21 can suppress particularly the harmonic torque due to the nth-order spatial harmonics by slightly increasing the magnetic resistance to the magnetic flux m interlinking with the specific stator teeth 15, as will be described later. It is possible to obtain a high-quality torque waveform by adjusting the superimposed harmonic component. In FIG. 5, the size of the adjustment groove 21 is deformed to be larger than the actual ratio so that it can be easily determined (the same applies to FIG. 6).

  The adjustment groove 21 is determined by performing an electromagnetic field analysis by a finite element method to determine the optimum position and shape to be formed on the outer peripheral surface 12a of the rotor 12, and the inner side (d-axis side) slope 21b and the outer side The formation position of the deepest portion 21a sandwiched between the inclined surfaces 21c and the optimum conditions for the depth are determined.

  First, when the electric rotating machine 10 has an IPM structure in which the permanent magnet 16 is embedded in the rotor 12, the change in magnetic flux in one tooth of the stator tooth 15 of the stator 11 approximates a rectangular wave as shown in FIG. can do. By superimposing low-order spatial harmonics such as the fifth and seventh orders on this magnetic flux waveform, iron loss and torque ripple, which is the fluctuation range of torque, increase, resulting in a decrease in efficiency due to waste as thermal energy. This is a cause of vibration and noise. Iron loss can be divided into hysteresis loss and eddy current loss. Hysteresis loss is the product of frequency and magnetic flux density, and eddy current loss is the product of the square of frequency and magnetic flux density, so the loss can be reduced by suppressing spatial harmonics, and the input of electrical energy Drive efficiency can be improved. In FIG. 7, the vertical axis is the field magnetic flux, the horizontal axis is time, and there is no magnetic flux linkage between L1 and the magnetic flux is forward / reversely linked between L2 with respect to one stator tooth 15. , An approximate rectangular wave of the magnetic flux waveform in one electrical angle period T (4L1 + 2L2) is illustrated.

  The electromagnetic noise of the motor (electric rotating machine) is generated by the vibration of the stator due to the electromagnetic force acting on the stator (stator) side. The electromagnetic force acting on the stator is the same as that of the rotor (rotor). There are radial electromagnetic force due to the magnetic coupling of the stator and circumferential electromagnetic force due to torque. When the motor is approximated by a linear magnetic circuit for each stator tooth 15, the radial electromagnetic force is considered to be magnetic flux φ, magnetic energy W, radial electromagnetic force fr, magnetic resistance Rg, magnetic flux density B, magnetic flux. Assuming that the interlinkage area S, the distance x between the air gaps G, and the magnetic path permeability μ, the magnetic energy W and the radial electromagnetic force fr can be expressed by the following equations (1) and (2).

  Therefore, when the magnetic flux density B is expressed as the following equation (3) in consideration of the spatial harmonics, the radial electromagnetic force fr includes the square of the magnetic flux density B, so that the superposition of the spatial harmonics is radial. This increases the electromagnetic force fr. That is, it has been clarified by earnest research and study that reduction of spatial harmonics can realize reduction of torque ripple and, in turn, reduction of motor electromagnetic noise and improvement of driving efficiency.

Further, the torque ripple of the three-phase motor having the IPM structure is based on the 6f-order (f = 1, 2, 3,...) At the electrical angle θ due to the spatial harmonics of the single-phase one-pole magnetic flux and the time harmonics included in the phase current.・: Natural number) It was found by intensive research and examination that it occurs in components.
Specifically, each phase induced voltage E _u (t), E _v (t), E _w (t), UVW phase currents I _u (t), I _v (t), I, UVW, angular velocity ω _m , UVW _{When w} (t), the three-phase output P (t) and the torque τ (t) can be expressed as the following equations (4) and (5).

P (t) = E _u (t) I _u (t) + E _v (t) I _v (t) + E _w (t) I _w (t) = ω _m · τ (t) (4)
τ (t) = [E _u (t) I _u (t) + E _v (t) I _v (t) + E _w (t) I _w (t)] / ω _m (5)
The three-phase torque is the sum of the torques of the U-phase, V-phase, and W-phase, where m represents the harmonic component of the current, n represents the harmonic component of the voltage, and the U-phase voltage E _u (t) Is represented by the following equation (6) and the U-phase current I _u (t) is represented by the following equation (7), the U-phase torque τ _u (t) can be represented by the following equation (8).

Here, since the phase current I (t) and the phase voltage E (t) are both symmetrical waves, “n” and “m” are only odd numbers, and the V-phase torque other than the U-phase and the W-phase The torque is a phase difference of “+ 2π / 3 (rad)” and “−2π / 3 (rad)” with respect to the U-phase induced voltage E _u (t) and the U-phase current I _u (t), respectively. The overall torque is canceled (offset) so that only the term of the coefficient “6” remains,
6f = n ± m (f: natural number), s = nα _n + mβ _m , t = nα _n −mβ _m
Then, it can be expressed as the following formula (9).

  In addition, since the induced voltage can be obtained by time-differentiating the magnetic flux, the same order component is generated in the harmonic order contained in each induced voltage and the harmonic contained in the 1-phase 1-pole magnetic flux. As a result, in the three-phase AC motor, when the combination of the spatial harmonic order n included in the magnetic flux (induced voltage) and the time harmonic order m included in the phase current is 6f, the torque ripple of the 6f-order component is It was found that this occurred.

  By the way, as described above, the torque ripple of the three-phase motor is obtained when n ± m = 6f (f: natural number) in the space harmonic n in the magnetic flux waveform in one phase and one pole and the time harmonic m in the phase current. Therefore, for example, in the case of approximating a sine wave with only the time harmonic m = 1 of the phase current, torque ripple is generated when the superposition of the orders of the spatial harmonics n = 5, 7, 11, 13 occurs. It will be.

In the case of this three-phase IPM structure, as shown in FIG. 7, the magnetic flux waveform in which the field magnetic flux interlinks with one stator tooth 15 is a substantially rectangular wave. The next spatial harmonic n (6f order = sixth harmonic) is easily superimposed and difficult to reduce.
Note that one electrical angle (360 °) corresponds to the N pole / S pole of the pair of permanent magnets 16 facing the outer peripheral surface 12a side of the rotor 12, in other words, one magnetic pole (a pair including the flux barrier 17b). This corresponds to twice the opening angle θ1 with respect to the rotation center of each permanent magnet 16). In the structure of the 8-pole 48-slot motor of this electric rotating machine 10 (structure in which 6 slots correspond to 1 magnetic pole), 2 cycles of 8 poles are 1 cycle, so that 1 cycle of the mechanical angle of the rotor 12 is 1 cycle. 360 ° rotation corresponds to 4 electrical angles.

  Further, in the case of a three-phase IPM motor in which six slots 18 per magnetic pole correspond to the electric rotating machine 10, twelve slots 18 correspond to one magnetic pole pair, and one cycle of the electrical angle. Inside, the magnetic resistance is increased at 12 locations due to the low magnetic flux permeability in the air in the slot open (gap between the tips of the stator teeth 15 serving as the coil insertion opening). The eleventh and thirteenth spatial harmonics n are superimposed on the magnetic flux waveform by the magnetic resistance of the twelve slots 18.

  The eleventh and thirteenth spatial harmonics n are generally called slot harmonics and have, for example, a skew angle twisted about the axis according to the installation position of the permanent magnet 16 in the axial direction. Thus, the 11th and 13th orders can be reduced by shifting the timing of the magnetic resistance in the slot 18. However, in the method of providing the skew angle on the rotor 12 side, there is a problem that a step is present between the adjacent permanent magnets 16 and the magnetization rate is lowered as described above.

  On the other hand, in the electric rotating machine 10, as shown in FIG. 6, a concave adjustment groove 21 that adjusts the gap G between the inner peripheral surface 15 a of the stator teeth 15 and the outer peripheral surface 12 a of the rotor 12 is provided. Is formed. The adjusting groove 21 is formed on the outer peripheral surface 12a of the rotor 12 facing the inner peripheral surface 15a of the stator tooth 15 to reduce the magnetic permeability, thereby reducing the magnetic resistance to the magnetic flux interlinked with the stator tooth 15. High harmonic torque components can be adjusted to suppress high harmonic torque caused by the fifth, sixth, eleventh, and thirteenth spatial harmonics n and to obtain high-quality torque waveforms. I have to.

  In detail, the adjustment groove 21 is, for example, the edge of the inclined surfaces 21b and 21c matched with the groove depth Rt from the outer peripheral surface 12a to the deepest portion 21a of the rotor 12 and the facing width of the inner peripheral surface 15a of the stator teeth 15. The formation position is determined by performing electromagnetic field analysis by the finite element method with the gap groove width Ts being constant, and the d axis (center line between the pair of permanent magnets 16) of one magnetic pole of the rotor 12 is the center. The angle of displacement θ2 of the amount of deviation in the forward / reverse direction of the position of the deepest portion 21a is used as a parameter facing the stator teeth 15 at the symmetrical position. In this embodiment, the groove width Ts of the adjustment groove 21 is made to coincide with the facing width with the inner peripheral surface 15a of the stator teeth 15, but may be adjusted to be smaller than the facing width as appropriate. It is effective to adjust the magnetic resistance over the entire facing width through which the magnetic flux passes.

  In the electromagnetic field analysis by the finite element method, when the torque ripple rate and the spatial harmonic content rate in the torque waveform by the 11th and 13th spatial harmonics n are derived, the result shown in the graph of FIG. 8 is obtained. From the graph of FIG. 8, the displacement angle θ2 in the forward / reverse direction with respect to the d-axis is 56 ° (electrical angle), and the torque ripple rate and the content of the 11th and 13th spatial harmonics n are set to the lowest level. It can be seen that it is the optimum value. That is, the adjustment groove 21 is located at a position facing the inner circumferential surface 15a of the symmetrically adjacent stator teeth 15 with one tooth centered on the stator teeth 15 that coincide with the d axis of one magnetic pole of the rotor 12. The deepest portion 21a is formed so as to be displaced by 56 ° (displacement angle θ2) in the forward and reverse directions from the d-axis, and the inner peripheral surface 15a of the stator tooth 15 and the outer peripheral surface 12a of the rotor 12 are formed. The magnetic resistance in the air gap G at the gap interval xL is adjusted. The torque ripple rate here is calculated by the following equation.

Torque ripple rate (%) = ((maximum torque−minimum torque) / average torque) × 100
Further, the adjustment groove 21 changes the groove depth Rt while leaving the groove width Ts as it is, and the gap interval (opposing surface) of the gap G between the outer peripheral surface 12a of the rotor 12 and the inner peripheral surface 15a of the stator teeth 15 is changed. Using the ratio σ (Rt / xL) of the groove depth Rt to the (inter-distance) xL as a parameter, the electromagnetic field analysis is performed by the finite element method to determine the groove depth Rt.

  In the electromagnetic field analysis by the finite element method, when the torque ratio with respect to the configuration in which the adjustment groove 21 is not formed and the sixth and twelfth harmonic torque ratios superimposed on the torque are derived, as shown in the graph of FIG. Results are obtained. In the graph of FIG. 9, on the basis of σ = 0 (without the adjustment groove 21), the torque ratio is stabilized to the extent that it gradually decreases without increasing substantially as the groove depth Rt is increased (the ratio is increased). When the ratio σ (Rt / xL) is 40% or more, the ratio abruptly decreases. On the other hand, the torque ratio of the sixth-order spatial harmonic n in the torque waveform is stabilized to the extent that it gradually increases without increasing substantially as the groove depth Rt is increased, and the ratio σ (Rt / xL) is stable. If it exceeds 40%, it will rise rapidly. Furthermore, the torque ratio of the 12th-order spatial harmonic n in the torque waveform, on the contrary, changes substantially as the groove depth Rt increases and the ratio σ (Rt / xL) reaches 20% or more. However, if the ratio σ (Rt / xL) becomes 40% or more after being stabilized to the extent that it slowly rises, it will rise rapidly. From this, the ratio σ (Rt / xL) of the air gap G of the stator teeth 15 to the gap interval xL (D1) falls within the range of the following condition 1 so that the torque is not greatly reduced, and the 12th order In addition, the 12th harmonic torque can be further reduced by narrowing it within the range of the following condition 2, and further the following condition 3 The 12th-order harmonic torque can be more effectively reduced by narrowing down to the range.

Condition 1: 20% ≦ σ (Rt / xL) ≦ 40%
Condition 2: 20% ≦ σ (Rt / xL) ≦ 30%
Condition 3: 20% ≦ σ (Rt / xL) ≦ 25%
In this electric rotating machine 10, for example, by adjusting the depth Rt of the adjustment groove 21 formed in the outer peripheral surface 12a of the stator 11 so as to be within the range of the above condition 3, as shown in FIG. It is possible to reduce the content of the fifth and seventh spatial harmonics, which is a factor of the sixth harmonic torque superimposed on the induced voltage, and to effectively reduce the difficult sixth harmonic torque. I understand. Since iron loss generally tends to increase when many spatial harmonics are superimposed, iron loss can also be reduced by reducing the contained spatial harmonics.

Further, in the electric rotating machine 10, as shown in FIG. 11, the torque ripple that the driver or the like feels uncomfortable because the torque fluctuates greatly and suddenly in a short period is further suppressed and adjusted to a stable torque output with gentle fluctuation. I understand that I can do it. For example, it can be seen from FIG. 11 that the torque pulsation can be reduced by about 30% compared to the case without the adjustment groove 21.
Moreover, in this electric rotating machine 10, as shown in FIG. 12, the effect of the adjustment groove 21 can be clearly confirmed by developing and confirming the Fourier series of the torque waveform, and the harmonic torque can be confirmed. It can be seen that the 6th order component can be reduced and the 12th order component of the harmonic torque can be greatly reduced.

  Therefore, in this electric rotating machine 10, the rotation facing the inner peripheral surface 15 a of the stator tooth 15 at a symmetrical position adjacent to one another is centered on the stator tooth 15 that coincides with the d axis of one magnetic pole of the rotor 12. An adjustment groove 21 is formed on the outer peripheral surface 12a of the child 12 so that the deepest portion 21a is 56 ° (electrical angle θ2) in the forward / reverse direction of the d-axis. Preferably, 20% ≦ σ (Rt / xL) ≦ 30%, more preferably 20%, so as to be within a range of 20% ≦ σ (Rt / xL) ≦ 40%. Only by forming so as to satisfy the condition of ≦ σ (Rt / xL) ≦ 25%, the torque ripple can be effectively reduced by greatly reducing the sixth and twelfth components of the harmonic torque.

  As described above, in this embodiment, the adjustment groove 21 having the same width or less as the inner peripheral surface 15a of the stator teeth 15 of the stator 11 is formed so as to effectively function as a magnetic resistance increasing region if possible. The adjustment groove 21 is located symmetrically with one tooth from the stator teeth 15 that coincides with the d-axis of one magnetic pole of the rotor 12, and a position with an electrical angle of 56 ° equal to both sides from the d-axis is the deepest portion 21a. Thus, the ratio σ (Rt / xL) of the groove depth Rt to the gap interval xL of the air gap G of the stator teeth 15 is in the range of 20% to 40%. Thereby, the magnetic resistance to the magnetic flux of the coil entering in the opposite direction toward the magnetic flux in the corner portion 16a of the permanent magnet 16 from the stator teeth 15 during the rotation driving, the space of the air gap G is adjusted to the adjustment groove (magnetic resistance increasing region) 21. Therefore, the demagnetization of the corner portion 16a of the permanent magnet 16 due to the magnetic flux of the coil can be reduced.

Further, sixth and twelfth harmonic torque superimposed on the torque waveform can be reduced to suppress torque ripple, and torque fluctuation can be reduced.
Therefore, the electric rotating machine 10 can be rotated at high quality with less vibration and noise, and can be rotated at high efficiency with little loss, and the rotation driving with high reliability and efficiency can be continued. it can.

Next, FIG. 13 and FIG. 14 are views showing a second embodiment of the electric rotating machine according to the present invention. Here, since the present embodiment is configured in substantially the same manner as the above-described embodiment, the same components are denoted by the same reference numerals and the characteristic portions will be described.
In FIG. 13, the electric rotating machine 10 includes a stator 11, a rotor 12, and a rotating shaft 13. In this embodiment, in place of the adjustment groove 21 in the above embodiment, the magnetic resistance is increased. An adjustment gap 31 is formed as a region. The adjustment gap 31 is formed at a symmetrical position around the d-axis of one magnetic pole as in the above-described embodiment, and is not particularly referred to in the above-described embodiment in addition to counterclockwise (CCW). However, a case where the adjustment gap 31 for adjusting the balance of the magnetic flux (magnetic path) in one magnetic pole is formed by limiting the generation of the demagnetization region A1 when rotating in the clockwise (CW) direction. It is shown.

  As shown in FIG. 14, the adjustment gap 31 includes a V-shaped space 17 (spaces 17 a and 17 b) that accommodates the permanent magnet 16 in the rotor 12 and also functions as a flux barrier, and is a plane in the width direction of the permanent magnet 16. It is formed by retreating the wall surface facing the outer corner 16ao sandwiched between 16b and the thickness direction plane 16c in the separation direction. The adjustment gap 31 is formed in a shape including an extended wall surface 17d extending from the base wall surface 17c forming the flux barrier 17b to a region facing the width direction plane 16b of the permanent magnet 16, and exists as a gap space. It functions as a magnetic resistance increasing region that restricts (suppresses) the entrance of magnetic flux together with the flux barrier 17b.

  Specifically, in the adjustment gap 31, the dimension and shape of the extended wall surface 17 c are set by electromagnetic field analysis by a finite element method so as to function effectively as a magnetic resistance increasing space, and with respect to the thickness Lm of the permanent magnet 16. The dimensions of the facing width Rw of the extended wall surface 17d facing the width direction plane 16b of the permanent magnet 16 and the separation height Rh spaced from the width direction plane 16b are determined as follows.

  Since the coercive force of the permanent magnet 16 increases in proportion to the thickness Lm, the separation height Rh for ensuring the demagnetization resistance against the reverse magnetic flux is inversely proportional to the thickness Lm. For example, as shown in FIG. 4, the width direction of the demagnetization region A1 generated in the outer corner portion 16ao of the permanent magnet 16 having a thickness Lm of 6 mm when the rotor 12 is driven up to 200 ° C. by rotational driving. When the demagnetization width Dw in the plane 16b is 1.3 mm, the facing width Rw is matched with the demagnetization width Dw, and the electromagnetic field analysis is performed using the separation height Rh as a variable. The occurrence of irreversible demagnetization that becomes unrecoverable at 0.5 mm is no longer observed. From this, when the thickness Lm of the permanent magnet 16 is 6 mm and the demagnetization width Dw is 1.3 mm, the adjustment gap 31 is formed in the following dimension shape, whereby the outer corner portion 16ao of the permanent magnet 16 is obtained. It is possible to avoid occurrence of irreversible demagnetization in.

Face width Rw = 1.3mm or more, separation height Rh = 3 / Lm
The internal eddy current in the permanent magnet 16 flows through the outer end portion under the influence of the skin effect, and heat loss is concentrated in the outer end portion. The demagnetization width Dw changes according to the length Lb of the permanent magnet 16. Further, the reverse magnetic field vector toward the outer corner 16ao of the permanent magnet 16 greatly depends on the positional relationship between the inner peripheral surface 15a of the stator teeth 15 and the magnet opening degree θ1, and also the permanent magnet 16 itself. Since it depends on the characteristics, it is easy to derive the shape dimension of the adjustment gap 31 by electromagnetic field analysis.

  The above conditions presented here are neodymium magnets having a residual magnetic flux density Br of about 1.25 T (Tesla) at 20 ° C., a coercive force Hcb of 965.75 kA / m, and a thickness Lm of 6 mm. Therefore, while the coercive force is 5795 A, the reverse magnetic field of the rotating magnetic field generated by applying a maximum current value of 500 Apk (effective value (500 / √2) ≈353.6 Arms) with four coil turns arranged in parallel in 10 rows Is the optimum shape in the driving environment where the fundamental wave component is 884A ((effective value / 4) × 10). In addition, the above condition is derived in consideration of the temperature increase of the rotor 12 of 200 ° C., but since this temperature depends on the allowable heat-resistant temperature of the components of other motors, it is not necessary to limit to this temperature. It is a parameter that can be set as appropriate.

  Therefore, also in the present embodiment, the electric rotating machine 10 is similar to the above-described embodiment in that the outer corner 16ao of the permanent magnet 16 on the rotor 12 side is formed only by forming the adjustment gap 31 inside the rotor 12. The magnetic permeability around the stator teeth 15 on the stator 11 side can be increased by lowering the magnetic permeability around the stator 11, and the permanent magnet 16 is unlikely to generate a demagnetization point and is reliable and efficient. Driving can be continued.

  As described above, in the present embodiment, the adjustment gap 31 that covers the region A1 where the demagnetization is generated by the permanent magnet 16 on the rotor 12 side is formed. The adjustment gap 31 can effectively function as a magnetic resistance increasing region with respect to the magnetic flux of the coil entering in the opposite direction toward the outer corner portion 16ao of the permanent magnet 16, and the corner of the permanent magnet 16 by the magnetic flux of the coil. Demagnetization of the portion 16ao can be reduced. Therefore, the electric rotating machine 10 can be rotationally driven with high efficiency with little loss, and reliable and efficient rotational driving can be continued.

  Here, in the electric rotating machine 10 of the above-described embodiment, it is sufficient that the allowable heat-resistant temperature of the components of the motor is 200 ° C. and functions effectively in a driving environment of 190 ° C. The case where the adjustment groove 21 and the adjustment gap 31 are formed only for the corner portion 16ao will be described as an example. However, the present invention is not limited to this, and the inner corner portion 16ai may be formed for the use environment. Accordingly, the adjustment grooves and adjustment gaps may be formed similarly.

  In the above-described two embodiments, the case where the permanent magnet 16 is formed in a V shape and embedded in the rotor 12 will be described as an example. However, the present invention is not limited to this. The present invention can also be applied to the case of a flat plate arrangement embedded in a state facing a flat plate shape with respect to the outer peripheral surface 12a, and similar effects can be obtained. In addition, an electric rotating machine 10 having an 8-pole 48-slot motor configuration is taken as an example, and an angle corresponding to one cycle (360 °) of one magnetic pole pair will be described as an electrical angle. However, the present invention is not limited to this. The present invention can also be applied to other motor structures in which 6 slots correspond to the magnetic poles. For example, the present invention can also be applied to a motor structure having 6 poles, 36 slots, 4 poles, 24 slots, and 10 poles and 60 slots.

  The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but also includes all embodiments that provide equivalent effects to those intended by the present invention. Further, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but may be defined by any desired combination of particular features among all the disclosed features. .

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 10 Electric rotating machine 11 Stator 12 Rotor 12a Outer peripheral surface 13 Rotating shaft 15 Stator teeth 15a Inner peripheral surface 16 Permanent magnet 16a Corner portion 16ai Inner corner portion 16ao Outer corner portion 17 V-shaped space 17b Flux barrier 18 Slot 20 Center bridge 21 Adjustment groove 21a Deepest part 21b, 21c Slope 31 Adjustment gap A1, A2 Demagnetization region G Air gap Rt Groove depth Ts Groove width xL, xS Gap spacing θ1 Opening angle θ2 Displacement angle

Claims (7)

A rotor that integrally rotates the rotation shaft of the shaft center, and a stator that rotatably accommodates the rotor,
The stator includes a plurality of teeth portions that extend toward the outer peripheral surface that rotates around the rotor and faces the outer peripheral surface to the inner peripheral surface side, and a coil that inputs driving power to the teeth portion. A plurality of slots formed between the teeth portions in a space for winding,
In the rotor, a plurality of permanent magnets are embedded so as to exert a magnetic force on the opposing surface of the teeth portion,
The reluctance torque generated when the magnetic flux generated when the coil is energized passes through the teeth portion, the back side of the teeth portion, and the rotor, and the attractive or repulsive magnet torque acting between the permanent magnets. An electric rotating machine that rotationally drives the rotor in the stator,
When one set of the permanent magnets on the rotor side corresponds to one set of the slots on the stator side, and the one set of permanent magnet side is one magnetic pole, the one for each magnetic pole An electric rotating machine, wherein a magnetic resistance increasing region for increasing a magnetic resistance is formed in the middle of a magnetic path of the magnetic flux generated by energizing the coil toward a demagnetized portion generated by a permanent magnet.   2. The electric rotating machine according to claim 1, wherein an adjustment groove for adjusting the magnetic resistance is formed on an outer peripheral surface of the rotor facing the teeth portion as the magnetic resistance increasing region. On the rotor side, the one magnetic pole is configured by embedding the pair of permanent magnets so as to open in a V shape toward the outer peripheral surface side,
On the stator side, the one set of slots is composed of six,
The adjustment groove is formed so as to be parallel to the teeth portion with a width within a facing width facing the teeth portion equivalent to both sides with one tooth placed on both sides from the center of the one magnetic pole. The electric rotating machine according to claim 2, characterized in that:   4. The electric rotating machine according to claim 2, wherein the adjustment groove is formed such that a position at an equal electrical angle of 56 ° on both sides with respect to the center of the one magnetic pole is a deepest portion. 5. The facing distance D1 between the inner peripheral surface of the teeth portion and the outer peripheral surface of the rotor, and the depth F of the deepest portion of the adjustment groove,
0.2 ≦ F / D1 ≦ 0.4
The electric rotating machine according to any one of claims 2 to 4, wherein the electric rotating machine is formed so as to fall within a range of.   The adjustment air gap for adjusting the magnetic resistance is formed between the inner surface forming the space for accommodating the permanent magnet and the outer surface of the permanent magnet as the magnetic resistance increasing region. The electric rotating machine according to 1. On the rotor side, the one magnetic pole is configured by embedding the pair of permanent magnets so as to open in a V shape toward the outer peripheral surface side,
The electric rotating machine according to claim 6, wherein the adjustment gap is formed on a side close to the outer peripheral surface of the rotor so as to be parallel to the teeth portion.

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