JP5445940B2 - Magnetic circuit of micro rotating electrical machine - Google Patents

Description

The present invention relates to a magnetic circuit of a micro rotating electric machine. More specifically, a magnetically isotropic magnetic film having a diameter of 2 mm or less and a remanent magnetization Mr 0.95 T or more composed of a nanoscale polycrystalline texture of a soft phase and a hard phase imparted with a nonmagnetic material. after a predetermined number of stacked, subjected to a pole pairs 2 or more multi-pole magnetized in the in-plane direction of the magnetic film, provided with a rotor magnet of a cylinder rotatably supported in the axial direction, opposite to the said rotor magnet The present invention relates to a magnetic circuit of a high torque type micro rotating electric machine having a gap permeance Pg of 8 or more with respect to a stator core having an exciting winding.

Regarding the downsizing of rotating electrical machines, for example, rotating electrical machines used for information communication equipment and the like have a market that is reduced in size and weight to about 100 mm ³ . It is known that the torque of these rotating electric machines has a power approximation based on the volume of the rotating electric machine and the scaling law, and there is a significant torque drop. However, a high-torque micro-rotating electric machine is required as a driving source for electric / electronic devices and robots in the fields of in-vehicle, information appliances, communication, precision measurement, medical welfare equipment.

  For example, Patent Document 1 uses a cylindrical main body having a conductive cylindrical wall provided with a slot as an excitation winding, and an intravascular ultrasonic scanning of a radial gap type brushless DC motor having an outer diameter of 1 mm or less and a length of 2 mm or less. Application to the system is disclosed. Patent Document 2 proposes a fluid-cooled radial gap type brushless DC motor having an outer diameter of 8 mm or less that can be introduced into the vascular system of the body in order to drive a blood pump located in the body. It is said that an output of 5 W can be obtained at 30,000 r / min by increasing the heat dissipation.

  As the micro rotating electric machine according to the above, for example, a discharge-processed Nd2Fe14B sintered magnet member is used as a two-pole rotor having an outer diameter of 0.76 mm, combined with a stator core, and an outer diameter of 1.6 mm and a length of 2 mm. Brushless DC motor [Non-Patent Document 1]. Further, H.C. Raisigel, M.M. By Nakano and Ito et al., Outer diameter 6 mm, length 2.2 mm [Non-patent document 2], outer diameter 5 mm, length 1 mm [non-patent document 3], and outer diameter 0.8 mm, long A micro-rotating electric machine having a thickness of 1.2 mm [Non-Patent Document 4] is known. However, in these micro rotating electric machines, significant torque reduction occurs due to volume reduction due to the scaling law [Non-Patent Document 5].

On the other hand, there are many proposals regarding the rotor magnet of the micro rotating electric machine as described above. For example, after an anisotropic Nd2Fe14B sintered magnet is ground to an outer diameter of 0.9 mm, a sputtered film of Dy, Tb, etc. is formed on the surface, and a heat treatment that promotes internal diffusion is applied. .35 T, coercive force HcJ = 1.34 MA / m, (BH) _max = 341 kJ / m ³ bulk rotor magnet [Patent Document 3], D.C. Hinz et al., An anisotropic Nd2Fe14B-based hot-working magnet with a die upset at 750 ° C. with residual magnetization Mr = 1.25 T, coercive force HcJ = 1.06 MA / m, (BH) _max = 290 kJ / m ³ Shows a magnet film having a thickness of 300 μm [Non-patent Document 6].

In addition, J.H. Delamere et al. Are a 16-pole magnetized Sm-Co-based rotor magnet and an opposing stator. When driven at 100,000 rpm, the torque is 10 μNm, or the generator is driven at 150,000 rpm. The power of W 2 is obtained [Non-patent Document 7]. Also, Topfer et al. Speriotis et al. Used a Nd2Fe14B bonded magnet film with a residual magnetization Mr 0.42 T, 15.8 kJ / m ³ , and a thickness of 500 μm printed on a 10 mm diameter Fe—Si substrate as a rotor, and a motor with a torque of 55 μNm. [Non-Patent Document 8].

  As described above, with respect to the rotor magnet of a micro rotating electric machine, a wide variety of magnetic characteristics in which the remanent magnetization Mr ranges from 0.42 to 1.35 T, and various forms from the magnet film to the bulk have been tried. Is the current situation.

  Below, the patent document shown in the column of background art and a nonpatent literature are described. In addition, patent documents and non-patent documents cited in the column of problems to be solved by the invention are described.

JP-T 9-501820 Japanese translation of PCT publication No. 2002-532047 JP 2005-210876 A

Sai Ohta, Takao Ohara, Yuki Karada, Munehisa Takeda, Mitsubishi Electric Technical Report Vol. 75, pp. 703-708 (2001) H. Raisigel, O .; Wiss, N.M. Achotte, O .; Cugat, J.A. Delamare, Proc. of 18th Int. workshop on high performance magnets and their applications, Annecy, France, pp. 942-944, (2004) M.M. Nakano, S .; Sato, R.A. Kato, H.C. Fukunaga, F.A. Yamashita, S .; Hoefinger and J.H. Fiddler, Proc. 18th Int. Workshop on High Performance Magnets and Their Applications, Annecy, France, pp. 723-726 (2004) Tetsuya Ito, Journal of Japan Society of Applied Magnetics, Vol. 18, pp. 922-927, (1994) Fumitoshi Yamashita, The Japan Society of Applied Magnetics, 143rd Meeting Material, Chuo Daisurugadai Memorial Hall (2005) D. Hinz, O .; Gutfleichech and K.C. H. Muller, Proc. 18th Int. Workshop on High Performance Magnets and Their Applications, Annecy, France, pp. 76-83 (2004) J. et al. Delamare, G.M. Reyne, O .; Cugat, Proc. of 18th Int. workshop on high performance magnets and their applications, Annecy, France, pp. 767-778, (2004) Topfer, B.M. Pawlowski, D.C. Schabbel, Proc. of 18th Int. workshop on high performance magnets and ther applications, pp. 942-944, (2004) H. Fukunaga, H. et al. Nakayama, M .; Nakano, M .; Ishimaru, M .; Itakura, and F.R. Yamashita, Intermag 2008, FG-06 Hirokazu Kanei, Satoshi Hirosawa, Journal of Japan Society of Applied Magnetics, vol. 22, pp. 385-387 (1998)

By the way, the torque T of the permanent magnet type rotating electrical machine is expressed by Equation 1 if the number of pole pairs is Pn, the current is I (Id, Iq), the inductance is L (Ld, Lq), and the flux linkage is Φa.
<Formula 1>
T = [Pn × Φa × Iq] + [Pn × (Ld−Lq) × Id]

  Here, the first term on the right side is the magnet torque, and the second term is the reluctance torque. In addition, the micro rotary electric machine which this invention makes object is 2 mm or less in diameter of a magnet rotor. Due to such actual size restrictions, the rotor targeted by the present invention is composed only of a permanent magnet and a rotating shaft of a nonmagnetic material, and does not have a rotor core. The torque T generated in such a micro-rotary electric machine with only a rotor magnet and no rotor core is only the magnet torque (Pn × Φa × Iq) in the first term on the right side, and there is no reluctance torque in the second term.

  From Equation 1, the magnet torque is proportional to the pole pair number Pn, the interlinkage magnetic flux density Φa, that is, the gap magnetic flux density Φg, and the energization current I of the stator excitation winding. Further, the torque constant Kt (Nm / A) of the motor is a torque gradient with respect to the energization current I of the stator excitation winding, and the greater the Kt, the greater the rotational driving force and the easier the current control. From this, as a means for suppressing the torque reduction accompanying the miniaturization of the rotating electrical machine and further increasing the rotational driving force and controllability by increasing Kt, 1) the number of pole pairs Pn is increased. 2) Increase the air gap permeance Pg to reduce the magnetic resistance. 3) Increasing the excitation current Iq or the number of turns n of the excitation winding increases the excitation force on the stator side.

However, the outer diameter of the rotor magnet of the micro rotating electric machine targeted by the present invention is 2.0 mm or less. In such a rotor magnet having an outer diameter of 2.0 mm or less, for example, in Patent Document 3, an anisotropic Nd ₂ Fe ₁₄ B-based sintered magnet having a residual magnetization Mr = 1.35 T, that is, a high residual magnetization Mr. Discloses a magnetic anisotropic bulk rotor magnet. However, in such a magnetic anisotropic magnet composed of one bulk having a diameter of 2.0 mm or less, the number of pole pairs Pn is limited to 1, and the number of pole pairs Pn cannot be increased. In addition, it is conceivable to divide the bulk for each magnetic pole and assemble this, but in this case, high mechanical dimensional accuracy, high accuracy of magnetic properties including the direction of high anisotropy, etc. are required. Considering these, it is clear that production on an industrial scale is difficult.

  Further, Patent Document 3 discloses that when the outer diameter of the magnetic anisotropic bulk rotor magnet is 1.2 mm and 0.9 mm, the outer diameter of the rotating electric machine is 2.0 mm and 1.7 mm, respectively. ing. Here, assuming that the thickness of the soft magnetic material (stator core) that also serves as a housing for fixing the slotless structure excitation winding is 0.1 mm, the rotor magnet including the storage space for the solenoid excitation winding The gap with the soft magnetic material (stator core) is 0.3 mm.

The residual magnetic flux density Br of the rotor magnet is 1.35 T, the reversible (recoil) permeability μr is 1.15, the rotor magnet outer diameter Do is 1.2 mm, and the rotor magnet inner diameter Di is 0.3 mm. When the child magnet length L is 4.8 mm and the magnetic pole angle θm of the rotor magnet having a pole pair of 1 is 180 degrees, the equivalent magnet length (thickness) Lm is (Do-Di) / 2 to 0.45 mm. Become. Furthermore, since the stator core is slotless, the facing angle θe is 360 degrees, the core inner diameter Da is 1.8 mm, the core length La is 5 mm, the leakage coefficient f is 1.1, and the magnetomotive force loss coefficient γ is 1. The equivalent cross-sectional area Am, air-gap cross-sectional area Ag, air-gap length Lg, and air-gap permeance coefficient Pg of a micro-rotary electric machine that constitutes a magnetic circuit with a slotless stator and a permanent magnet rotor are expressed by equations 2, 3, 4 respectively. 5 and the effective air gap magnetic flux density Φg was estimated from Equation 6. Then, the air gap permeance coefficient Pg is estimated to be 2.4, and the air gap magnetic flux density φg is estimated to be 4.7 × 10 ⁻⁶ Wb.

<Formula 2>
Am = ((Do + Di) / 2) × (π × θm / 360) × L
<Formula 3>
Ag = ((Di + Da) / 2) × (π × θe / 360) × La
<Formula 4>
Lg = (Da-Di) / 2
<Formula 5>
Pg = Lm × Ag × f / (Am × Lg × γ)
<Formula 6>

As a means for increasing the torque of a micro rotating electric machine that forms a magnetic circuit with the slotless stator and the permanent magnet rotor as described above, it is effective to further increase the residual magnetization Mr of the magnetic anisotropic bulk rotor magnet. It is. However, after the magnetic anisotropy Nd ₂ Fe ₁₄ B-based sintered magnet disclosed in Patent Document 3 is machined into a rotor magnet having a predetermined shape, Dy, Tb, etc. are physically deposited on the surface. The residual magnetization Mr after recovery of the magnetic properties by heat treatment is already 1.35 T. For this reason, it is difficult to obtain a high remanent magnetization Mr that greatly exceeds that value by surface modification. Also, assuming that an ideal magnet is obtained in which the theoretical value 1.6 T of the saturation magnetization Ms of the Nd ₂ Fe ₁₄ B intermetallic compound is the residual magnetization Mr, the gap magnetic flux density Φg is 5.5 × 10 ^−6. Estimated as Wb. That is, the theoretical limit of the magnetic anisotropy Nd ₂ Fe ₁₄ B sintered magnet with the number of pole pairs Pn applied to the rotor magnet set to 1 in the magnet torque (Pn × Φa × Iq) of the first term on the right side in Equation 1. Even if it is assumed that the remanent magnetization Mr is increased to the above, the improvement in the magnet torque due to the ratio of the gap magnetic flux density Φa of the micro rotating electric machine is less than 1.2 times.

Note that Topfer et al. And T.W. When the magnetically isotropic remanent magnetization Mr 0.42 T magnet [Non-patent Document 8] of Speriotis et al. Is applied to the rotor, the resulting magnetic flux density Φa remains at about 1.4 × 10 ⁻⁶ Wb. . For this reason, the corresponding magnet torque cannot be obtained unless the number of pole pairs Pn is 4 or more. For example, when the number of pole pairs is 4 with a rotor magnet having a diameter of 1.2 mm, the distance between the poles is less than 0.5 mm. Such multipolar saturation magnetization with a distance between magnetic poles of less than 0.5 mm is difficult. Further, when the number of pole pairs is 5, it can be expected that the magnet torque obtained with the anisotropic Nd ₂ Fe ₁₄ B-based sintered magnet rotor having the number of pole pairs 1 can be improved by about 1.2 times. However, the distance between the magnetic poles is less than 0.4 mm, and multipolar saturation magnetization becomes more difficult. In addition, in the brushless DC motor as in Patent Document 5, an increase in the number of slots is unavoidable, so that the configuration of the stator becomes extremely complicated, and the configuration of the magnetic circuit of the micro rotating electric machine becomes difficult.

The present invention relates to a magnetic circuit of a high torque micro rotating electric machine. Specifically, after stacking a predetermined number of isotropic magnet films having an outer diameter of 2 mm or less and comprising a nanoscale polycrystalline texture of a soft phase and a hard phase imparted with a non-magnetic material, the isotropic magnet It has a cylindrical rotor magnet that is magnetized in the in-plane direction of the film to a pole pair number of 2 or more. A magnetic circuit of a micro-rotating electric machine having a configuration in which an average air gap permeance coefficient Pg between the rotor magnet and a stator core having an exciting winding facing the rotor magnet is 8 or more is basically used.

As a preferable magnetic film for constituting the rotor magnet according to the present invention, R-TM-B (R is Nd, Pr, TM is Fe, Co) type alloy, or Sm-Fe type molten alloy is rapidly solidified. After film formation of the substrate by the physical deposition method, they are appropriately crystallized or nitrided as required, and further, a nonmagnetic metal is appropriately added to the surface of the magnet film by physical deposition as necessary. A magnetic film composed of a nanoscale polycrystalline texture with -B, αFe soft phase, R ₂ TM ₁₄ B, and Sm ₂ Fe ₁₇ N ₃ hard phase. Further, as a more preferable magnet film, it has a spring back characteristic in which the magnetization of 90% or more of the residual magnetization Mr is recovered even when about 50% of the residual magnetization Mr is reversed, and the residual magnetization Mr 0.95 T or more in the in-plane direction. And a magnetic film having a coercive force HcJ of 150 kA / m or more.

  The rotor magnet according to the present invention has a structure in which a predetermined number of magnet films are laminated so that the magnet space factor is 70% or more in the rotation axis direction, and the stator facing the rotor magnet according to one of the present invention. A magnetic circuit of a micro rotary electric machine having a configuration in which the iron core tip shape is formed on an arc surface along the outer peripheral surface of the rotor magnet and the respective excitation windings are formed in parallel to each other is preferable.

  As described above, the micro rotary electric machine including the micro rotor according to the present invention includes a slot type radial gap type brushless DC motor, a PM stepping motor, a generator, and the like as information equipment, medical equipment, industrial equipment. Furthermore, as a device for driving micromachines such as various lens driving devices for endoscopes and self-propelled inspection robots in narrow tubes, it can contribute to improving the performance of small electric and electronic devices from the viewpoint of higher output and lower current consumption than conventional devices.

(A) (b) Conceptual diagram showing nanoscale polycrystalline texture of two types of soft phase and hard phase (A) Definition of magnetization springback, (b) its characteristic diagram Perspective view showing an analysis model of a micro rotating electromechanical magnetic circuit (A) (b) Characteristic diagram showing distribution of air gap permeance coefficient Pg Characteristic diagram showing the relationship between the magnet space factor in the rotation axis direction (stacking direction) and the air gap permeance coefficient Pg Cross-sectional configuration diagram showing an example of a micro rotating electric machine (A) Conceptual diagram of magnet torque generation, (b) Characteristic diagram showing relationship between dimensional ratio L / D and magnet torque (A) Characteristic diagram showing relative magnet torque distribution, (b) Characteristic diagram showing relative torque constant

The present invention relates to a magnetic circuit of a high torque micro rotating electric machine. Specifically, after laminating a predetermined number of isotropic magnet films having an outer diameter of 2 mm or less and comprising a nanoscale polycrystalline texture of a soft phase and a hard phase imparted with a nonmagnetic material, the surface of the magnet film It has a cylindrical rotor magnet that is magnetized in the inward direction to have two or more pole pairs. And it applies to the magnetic circuit of the micro rotary electric machine of the structure which makes the average space | gap permeance coefficient Pg with the stator core provided with the exciting winding facing the said rotor magnet 8 or more.

First, an isotropic magnet film composed of a nanoscale polycrystalline texture of a soft phase and a hard phase provided with a nonmagnetic material according to the present invention will be described. If a soft phase such as αFe of high saturation magnetization Ms that exchange-couples with R ₂ TM ₁₄ B (R is Nd among rare earth elements, or Pr, TM is Fe or Co among transition metal elements) as a hard phase, Under the magnetic field, the magnetization is reversed first from the soft phase, and a high coercive force HcJ cannot be obtained. However, if the size of the soft phase is suppressed to be equal to or smaller than the domain wall width, nonuniform magnetization reversal in a reverse magnetic field is suppressed. As a result, the coercive force HcJ is dominated by the magnetic anisotropy Ha of the hard phase, and a decrease in the coercive force HcJ is suppressed. Furthermore, in order to obtain a higher magnetic flux from the soft phase, it is necessary to increase the volume ratio of the soft phase in the magnet. For this purpose, the size of the hard phase is made as small as possible. The size of the hard phase may be equal to or less than the domain wall width, but if it is too small, it is difficult to maintain the coercive force HcJ, and therefore the hard phase is suppressed to about the domain wall width. The domain wall width is estimated by π (A / Ku) 1/2 (A: exchange stiffness constant, Ku: magnetic anisotropy energy).

For example, when the soft phase is αFe and the hard phase is Nd ₂ Fe ₁₄ B, the thickness is about 60 nm and several nm, respectively. That is, as shown in FIG. 1A, the magnetic film having a multilayer structure in which the size of αFe of the soft phase 12 is set to 60 nm or less and the hard phase 11 smaller than the αFe is alternately deposited with the soft phase 12 by 10 ³ or more. Alternatively, it refers to a magnetically isotropic magnet film composed of a random polycrystalline texture of soft phase 12 and hard phase 11 as shown in FIG. In addition, as an isotropic magnet film having a residual magnetization Mr 1 T or more having the configuration of FIG. 1A according to the present invention, αFe and Nd ₂ Fe ₁₄ B by PLD (pulse laser deposition) are nonmagnetic such as Ta. A magnet film on a substrate can be exemplified [Non-Patent Document 9]. An example of the isotropic magnet film having a residual magnetization Mr 1 T or more having the configuration shown in FIG. 1B is a magnet film of Fe ₃ B and Nd ₂ Fe ₁₄ B by rapid solidification of a molten alloy. [Non-Patent Document 10] In this case, a non-magnetic film such as Al is provided on one surface of the magnet film by physical volume means such as ion plating and sputtering as in FIG. Such a composite with a non-magnetic metal material having excellent spreadability is indispensable for improving the shear workability of the magnet film.

By the way, the remanence enhancement of the magnetic film according to the present invention, which is a magnetically isotropic magnetic film composed of a polycrystalline texture in which the sizes of the soft phase and the hard phase are optimized to about 20 nm, can be easily obtained. T or more. One coercive force HcJ reaches 400 kA / m. In particular, according to a detailed computer analysis in which sufficient magnetic coupling is imparted at the contact interface between αFe and Nd ₂ Fe ₁₄ B, and the thickness of each is controlled to a nanoscale structure about the domain wall width, If a uniform nanocomposite structure of about 10 nm can be formed, the (BH) _max of a magnetically isotropic magnet film can be expected to about 200 kJ / m ³ .

As described above, the magnet film according to the present invention is a substrate film formed by physical deposition of an R-TM-B (R is Nd, Pr, TM is Fe, Co) -based alloy, or Sm-Fe-based molten alloy. Alternatively, after rapid solidification of the molten alloy, they are appropriately crystallized or nitrided as necessary, and a soft phase of Fe-B or αFe in which a nonmagnetic metal is added to the surface of the magnet film by physical deposition. , R ₂ TM ₁₄ B, Sm ₂ Fe ₁₇ N ₃ based hard phase and a magnetic film composed of a nanoscale polycrystalline texture.

  Next, as a more preferable characteristic of the magnetic film according to the present invention, the springback characteristic of magnetization will be described with reference to FIGS. First, the definition of the springback characteristic of magnetization referred to in the present invention will be described with reference to FIG. As shown in the figure, a demagnetizing field -H is applied from the residual magnetization Mr, and the magnetization is reversed to an arbitrary magnetization M. Thereafter, when the magnetization when the demagnetizing field -H is removed is Mr ', the magnetization reversal rate is Mr' / Mr and the magnetization restoration rate is (Mr-M) / Mr.

FIG. 2 (b) shows the magnetization reversal rate and the recovery rate of an isotropic magnet film comprising a nanoscale polycrystalline texture of a soft phase (Fe ₃ B) and a hard phase (Nd ₂ Fe ₁₄ B) according to the present invention. It is a characteristic view which shows a relationship. The comparative example is a single-phase magnet film having only a hard phase (Nd ₂ Fe ₁₄ B). As is apparent from the figure, the magnet film according to the present invention has a strong springback characteristic in which the magnetization of 90% or more of the residual magnetization Mr is recovered even when about 50% of the residual magnetization Mr is reversed. Such a strong springback characteristic is such that in the magnetic circuit of the micro rotating electrical machine according to the present invention, when the rotating shaft is constrained for some reason, the rotor is exposed to the reverse magnetic field -dH of the exciting winding. It is effective to secure the demagnetization resistance of the magnet.

  Next, the gap permeance coefficient Pg between the rotor core and the stator core configured by laminating a predetermined number of magnetically isotropic magnet films according to the present invention as described above is set to 8 or more. A magnetic circuit of a micro rotating electric machine will be described with reference to the drawings. However, in this case, the magnet space factor in the rotation axis direction of the rotor magnet in which a predetermined number of isotropic magnet films having in-plane residual magnetization Mr 1 T and coercive force HcJ 400 kA / m are stacked is 10 to 90%, the number of pole pairs Is 2.

  FIG. 3 is a 3-D FEM analysis model obtained by dividing the micro rotating electromechanical magnetic circuit according to the present invention into 803220 elements. However, in the figure, 31 is an outer diameter of 1 mm, an inner diameter of 0.3 mm, and a thickness of 100 μm according to the present invention having the nanoscale structure of FIG. 1 (a) or (b). This is a rotor magnet in which 15 hollow disk-shaped magnet films (including a substrate) are laminated and bonded and fixed. Further, 32 is a stator core, and 33 is a gap with the stator core 32 for making the rotor magnet 31 rotatable. Reference numeral 323 denotes a fluctuation range of the gap 33 due to a change in the inner diameter of the stator core 32.

4A and 4B show the results of computer analysis by the 3-D FEM model of FIG. 3 in comparison with a conventional configuration example. However, in the conventional example, an anisotropic Nd ₂ Fe ₁₄ B-based sintered magnet having a remanent magnetization Mr 1.3 T and a reversible (recoil) permeability μr 1.035 limited to the number of pole pairs 1 is a rotor magnet. These are the results of computer analysis when the gap is 50 μm. A micro rotating electric machine using an anisotropic Nd ₂ Fe ₁₄ B sintered magnet as a rotor magnet has a slotless stator structure, and therefore the gap is estimated to be about 0.3 mm. According to this, the gap permeance coefficient Pg is about 2.4 at most, and Patent Document 3 specifies the minimum value of Pg as 1.4. In addition, even if the gap is narrowed to 50 μm as shown in FIGS. 4 (a) and 4 (b), the Pg is less than 5 from the results of this computer analysis. On the other hand, Pg exemplified in the magnetic circuit of the micro rotating electric machine according to the present invention reaches 18 as an average value as is apparent from the drawing.

  Next, when a predetermined number of magnet films having the above-described configuration are laminated to form a rotor magnet, the preferred space factor of the magnet from the viewpoint of shape magnetic anisotropy is calculated using the 3-D FEM model of FIG. This will be explained based on the analysis. FIG. 5 is a characteristic diagram showing the relationship between the magnet space factor in the rotation axis direction (stacking direction) and the air gap permeance coefficient Pg. As shown in the figure, when the space factor of the magnet exceeds 70% under the condition that the gap is constant, the Pg is improved. Such an improvement in Pg is the effect of reducing the magnetic resistance in the magnetic circuit of the micro rotating electrical machine according to the present invention, in other words, the condition that the shape magnetic anisotropy is remarkably exhibited is that the space factor of the magnet is 70%. It can be explained that.

  Next, a preferred configuration example of the magnetic circuit of the micro rotating electrical machine according to the present invention will be described with reference to the drawings. In the present invention, for example, as shown in FIG. 6, a stator core tip shape facing the rotor magnet is formed on an arc surface along the outer peripheral surface of the rotor magnet, and each excitation winding is formed in parallel to each other. It is preferable to take the magnetic circuit of a rotating electrical machine. However, in the figure, 61 is the rotor magnet according to the present invention, 62 is the stator core, 621 is the tip of the stator core 62, 622 is the excitation winding of the stator core 62, and 63 is the rotor magnet and stator core. And the gap. Here, a three-phase (UVW) drive 4-pole 6-slot brushless DC motor is illustrated as a micro rotating electric machine according to the present invention. In this case, the rotational drive is performed by detecting the position of the magnet rotor 61 (not shown) and controlling the timing of energizing the excitation windings 622 of each phase of UVW according to the position of the magnet rotor 61. A magnetic field is generated from the stator 62 to rotationally drive the rotor 61.

  The shape of the stator core according to the present invention is an area that should be left to the design philosophy of the micro-rotary electric machine. However, by adopting the shape of the stator core shown in FIG. 6, the dimension in the Y-axis direction can be made extremely thin. It is.

  The present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

Table 1 shows a residual magnetization Mr 1.03 T composed of a nanoscale polycrystalline texture of a soft phase (Fe ₃ B) and a hard phase (Nd ₂ Fe ₁₄ B) according to the present invention, and a coercive force HcJ 330 kA / m. An isotropic magnet film having an outer diameter of about 1 mm and a predetermined number of layers are stacked, and then the dimensions of the columnar magnet magnetized to the pole pair number 1 in the in-plane direction are shown together with the magnet occupation ratio in the stacking direction (rotating axis direction). A comparative example is an anisotropic Nd ₂ Fe ₁₄ B-based sintered magnet having a residual magnetization of 1.3 T and a coercive force HcJ> 1 MA / m. In all cases, pulse magnetization of 4.8 MA / m is performed in the radial direction.

  As shown in FIG. 7A, it is assumed that a dipole cylindrical magnet as shown in Table 1 is exposed to a uniform external magnetic field Hex. Here, when the counterclockwise direction in the rotation direction (torque generation direction) is positive, and the center of the S pole of Hex (rotating magnetic field from the stator) rotates counterclockwise from directly above the N pole of the dipole cylindrical magnet. Think. Then, when the S pole center of Hex is directly above the N pole of the sample, the torque is zero, and when the S pole center of Hex rotates counterclockwise, the magnet torque gradually increases, and at a position rotated 90 degrees. Maximum torque. With further rotation, the torque gradually decreases again and becomes zero at 180 degrees.

  FIG.7 (b) shows the magnet torque measured with the magnetic torque meter which set the column magnet shown by the example of this invention of Table 1 to Hex24kA / m. The magnet torque exhibits good linearity with respect to the dipole cylindrical magnet length L (the number of stacked layers is different), and a small magnet torque can be accurately measured. The magnet torque (M × Hex sin θ) with respect to the load angle θ in FIG. 7A is the magnet torque (Pn × Φa × Iq) in the first term on the right side of Equation 1. Here, Pn and Φa are applied to the rotor magnet M, and Iq is applied to Hex. Therefore, in order to normalize the measured magnet torque with a diameter of 1 mm (L / D = 1.5), the circumference of the dipole cylindrical magnet is corrected with the stacking length, and the rotation shaft insertion hole is set to 0.3 mm. When this was done, the magnet torque was corrected by the ratio of the integral value of the surface magnetic flux density distribution at the number of pole pairs 1 and 2 and the number of pole pairs. In this way, the relative magnet torque distribution at the pole pair number 2 according to the present invention was calculated.

FIG. 8A is a characteristic showing the relative magnet torque distribution expressed by the corrected rotor magnet according to the example of the present invention with the number of pole pairs of 2, together with a comparative example of the anisotropic Nd ₂ Fe ₁₄ B-based sintered magnet with the number of pole pairs of 1. FIG. As is apparent from the figure, the maximum magnet torque value of the present invention example was 1.7 times the maximum magnet torque value of the comparative example.

FIG. 8B is a characteristic diagram showing the relative magnet torque at a diameter of 1 mm (L / D = 1.5) with respect to Hex when the external magnetic field Hex is 8, 24, and 40 kA / m. As is apparent from the figure, Hex and the relative magnet torque can be approximated by a linear function. The slope of the regression equation shown in the figure, dT / dH (μNm / kA / m), was 2.037 in the present invention example and 1.2368 in the comparative example. This value corresponds to a torque constant (μNm / A) in a magnetic circuit of a micro rotating electric machine constituted by a permanent magnet rotor and a stator core. Therefore, it is meant that the torque constant according to the present invention of the micro rotating electric machine having the same magnetic circuit configuration is improved 1.86 times compared with the comparative example. As described above, according to the present invention, the means for increasing the residual magnetization Mr of the anisotropic Nd ₂ Fe ₁₄ B-based sintered magnet having the pole pair number of 1 shown as the comparative example and increasing the torque of the micro rotating electric machine is provided. It is clear that a much higher effect can be obtained.

11: Hard phase, 12: Soft phase, 31: Rotor magnet, 32: Stator core, 323: Air gap fluctuation range, 61: Rotor magnet, 62: Stator core, 621: Stator core tip, 622 : Excitation winding, 63: Air gap

Claims (5)

After laminating a predetermined number of isotropic magnet films having an outer diameter of 2 mm or less and comprising a nanoscale polycrystalline texture of a soft phase and a hard phase imparted with a nonmagnetic material, in the in- plane direction of the isotropic magnet film A micro-rotating electric machine comprising a cylindrical rotor magnet magnetized with two or more pole pairs , and having an average air gap permeance Pg of 8 or more between the rotor magnet and a stator core having an exciting winding facing the rotor magnet Magnetic circuit. After the magnet film is formed by rapid solidification of an R-TM-B (R is Nd, Pr, TM is Fe, Co) -based alloy, or Sm-Fe-based molten alloy, or a physical film deposition method is used. If necessary, it is crystallized or nitrided, and if necessary, a non-magnetic metal is appropriately added to the surface of the magnet film by physical deposition. Fe-B, αFe soft phase, R ₂ TM ₁₄ B The magnetic circuit of a micro rotating electric machine according to claim 1, wherein the magnetic circuit is a magnetic film made of a nanoscale polycrystalline texture with a hard phase of Sm ₂ Fe ₁₇ N ₃ . 2. The micro-rotation electricity according to claim 1, wherein the magnet film has a spring back characteristic of magnetization that recovers magnetization of 90% or more of the residual magnetization Mr even if about 50% of the residual magnetization Mr is reversed. The magnetic circuit of the machine. 2. The minute number according to claim 1, wherein a predetermined number of magnet films having a residual magnetization Mr 0.95 T or more in the in-plane direction and a coercive force HcJ 150 kA / m or more are laminated with an axial space factor of 70% or more. Magnetic circuit of a rotating electrical machine. To claim 1, wherein the tip shape of the stator core opposing the rotor magnet is formed in a circular arc surface along the outer peripheral surface of the rotor magnet and each excitation winding portion in parallel to form one another the magnetic circuit of the micro rotary electric machine according.