JP3821185B2 - Permanent magnet motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inner rotor type permanent magnet motor used for a compressor or the like, and more specifically, to improve the effective use of reluctance torque to increase the total torque and to increase the strength of the rotor core (rotation). The present invention relates to a permanent magnet motor that has been devised in the configuration of the child.
[0002]
[Prior art]
The inner rotor of permanent magnet motor, for example, there is a structure shown in FIG. In FIG. 4, an embedded magnet field core (rotor core) 2 in the stator core 1 has one substantially permanent sector-shaped permanent magnet 3 embedded in one pole, and is arranged at equal intervals in the circumferential direction by the number of poles. In addition, the adjacent permanent magnets 3 have different polarities. Reference numeral 4 denotes a hole through which the shaft passes (center hole).
[0003]
Here, assuming that the magnetic flux distribution in the gap portion (between the teeth of the stator core and the permanent magnet) by the permanent magnet is sinusoidal, the torque T of the permanent magnet motor is T = Pn {Φa · Ia · cosβ− 0.5 (Ld−Lq) · I ² · sin 2β}. T is the output torque, Φa is the armature flux linkage by the permanent magnets on the d and q coordinate axes, Ld and Lq are d and q axis inductances, Ia is the amplitude of the armature current on the d and q coordinate axes, and β is The advance angle of the armature current on the d and q coordinate axes from the q axis, Pn, is the number of pole pairs. In the above formula, the first term is the magnet torque generated by the permanent magnet, and the second two terms are the reluctance torque generated by the difference between the d-axis inductance and the q-axis inductance.
[0004]
For details, see T.A. IEEE Japan, Vol. See 117-D, No. 7, 1997. In addition, according to the above paper, it is described that the reluctance torque is effectively used by forming a permanent magnet of each pole in a multilayer structure.
[0005]
For example, the rotor core in the stator core 1 has two permanent magnets having a circular arc cross section per pole, that is, has a two-layer structure. This is because the d-axis inductance Ld is small and the q-axis inductance Lq is greatly increased as compared with the case of one piece (one layer) per one pole described above, whereby the parameter inductance difference (Ld−Lq) in the above equation. ) Is large, resulting in a large motor torque T.
[0006]
Thus, if the reluctance torque is effectively used, the motor torque T can be increased, and if the permanent magnet per pole has a multilayer structure, the reluctance torque is more effectively used. For details, refer to the above paper.
[0007]
[Problems to be solved by the invention]
By the way, in the permanent magnet motor, the distance w between the substantially sectional fan-shaped permanent magnet 3 and the center hole 4 needs to be a minimum dimension in view of the strength of the rotor core (core sheet). There is a useless area (see solid arrow a in FIG. 4). Moreover, if the radius of curvature of the arc-shaped cross section is increased in order to increase the amount of permanent magnet used (magnet amount), the useless area becomes larger.
[0008]
As a result, the region between the permanent magnet 3 and the outer periphery of the rotor core 1 (see the solid line arrow b in FIG. 4) becomes smaller, the q-axis inductance becomes smaller, and the inductance difference from the d-axis becomes smaller. The reluctance torque is reduced, and therefore the motor efficiency cannot be improved. In addition, if the area of the execution arrow b in FIG. 4 is narrowed, it becomes difficult to form a caulking portion or pass through a rivet, and the strength of the rotor core 2 will be affected.
[0009]
Further, in the case of a rotor core having a multi-layered permanent magnet described in the above paper, the above-mentioned drawbacks can be solved, but since a plurality of permanent magnets are used per pole, manufacturing is possible. Cost increases. Therefore, in terms of manufacturing, it is preferable to use one permanent magnet per pole.
[0010]
The present invention has been made in view of the above problems, its object is to use one per pole one permanent magnet, while achieving the effective utilization of the magnet torque and the reluctance torque, increasing the motor efficiency, yet the strength of the rotor core An object of the present invention is to provide a permanent magnet motor that can improve the above.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is a permanent magnet motor in which an embedded magnet field core (rotor core) is disposed in a stator core, and a sectional bathtub curve shape per pole of the rotor core. one using a permanent magnet, buried base portion to the permanent magnet toward the center hole for the shaft insertion of the cross section bathtub curve shape at equal intervals only a small number of the circumferential direction of the rotor core, and A caulking portion is formed on the q-axis in a region between the permanent magnet and the central hole, and a rivet is inserted on the d-axis in a region between the permanent magnet and the outer periphery of the rotor core. It is characterized by.
[0012]
In this case, as described in claim 2, the bottom and both sides of the sectional bathtub curve of the permanent magnet are straightened, the corners are rounded, and one corner side of both end portions of the permanent magnet It is preferable to form a hole for a flux barrier on the other side and cut the other corner side at a predetermined angle.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 3. In the figure, the same parts as those in FIG.
[0014]
The permanent magnet motor of the present invention does not limit the shape of one permanent magnet per pole to a curved cross section (for example, a fan shape), but allows the rotor core to be used effectively, that is, adjacent permanent magnets having different polarities. Pay attention to the fact that the area between the permanent magnet and the outer periphery of the rotor core should be widened, for example, by making the cross-sectional shape along the bathtub curve adjacent to each other It is noted that the area between the permanent magnets can be reduced and the area between the permanent magnet and the outer periphery of the rotor core can be increased.
[0015]
Therefore, as shown in FIG. 1 and FIG. 2, the rotor core (embedded magnet field core; hereinafter referred to as the core) 10 of this three-phase four-pole permanent magnet motor is one permanent magnet having a bathtub-shaped cross section per pole. (For example, a ferrite magnet) 11 and the bottom (convex portion) of the bathtub-shaped cross section are arranged toward the center hole 4, and four permanent magnets 11 are embedded in the circumferential direction, and adjacent permanent magnets. 11 is buried in a different pole.
[0016]
Although the permanent magnet 11 has a sectional bathtub curve shape, the amount of use (magnet amount) of the permanent magnet 11 is approximately the same as that of the conventional sectional fan-shaped permanent magnet 3, and thus the thickness thereof is large. In other words, it can be said that the cross section of the deformed bathtub is curved. In addition, since the area corresponding to the solid line arrow a shown in FIG. 4 can be used effectively, the amount of permanent magnet used (magnet amount) is the same as or more than that in the past, and the magnet torque can be used effectively. Become.
[0017]
In this case, both oblique sides (side sides) of the permanent magnet 11 are substantially straight lines, and the oblique sides of the adjacent permanent magnets 11 are substantially parallel to each other, that is, the interval (the width including the q axis) is a predetermined value. (At least the thickness of the core sheet). Moreover, the interval is continuous, and a magnetic flux path (magnetic path) from the stator core 1 is secured, and the inner peripheral portion and the outer peripheral portion of the rotor core 10 are connected.
[0018]
Of the bathtub shape of the cross section of the permanent magnet 11, the bottom is straight and close to the center hole 4, but the distance is set to the minimum necessary value as described in the conventional example, and consideration is given to the strength of the rotor core 10. Further, since the bottom portion is linear, a substantially square region appears in the inner peripheral portion of the rotor core 10 due to the coupling between the bottom portion and both oblique sides, so that the region between the permanent magnet 11 and the center hole 4 The caulking portion 12 can be formed.
[0019]
The inner side of the sectional bathtub curve of the permanent magnet 11 is a recess, and a region c between the permanent magnet 11 and the outer periphery of the rotor core 10 (a region corresponding to the solid line arrow b shown in FIG. 4) is wide. Accordingly, the rivet 13 can be passed with a sufficient margin, and a magnetic flux path (magnetic path) from the stator core 1 can be secured, so that the value of the inductance difference (Ld−Lq) increases. A flux barrier hole 14 is formed at the end of the permanent magnet 11 (upper edge of the bathtub-shaped cross section) to prevent magnetic flux leakage and short circuit.
[0020]
By the way, as shown in FIG. 2, a flux barrier hole 14 is formed on one corner side (outer corner of the permanent magnet 11) at both ends of the permanent magnet 11 having a curved bathtub section, and the other corner side ( The inner angle of the permanent magnet 11 is cut at a predetermined angle (for example, an angle along the outer periphery of the rotor core 10) (see solid arrows d and e in the figure). Then, even if the thickness (width) of the permanent magnet 11 is increased, the other corner does not protrude from the rotor core 10. Therefore, the usage amount (magnet amount) of the permanent magnet 11 can be increased, and the same or more magnet torque as that of the prior art can be obtained.
[0021]
Further, although the hole for embedding the permanent magnet 11 and the hole for the flux barrier are angular, at least the angular area around the permanent magnet 11 (for example, corners f to m shown in FIG. 2) is given R. Good. That is, by rounding, the shape of the permanent magnet 11 also becomes a rounded bathtub-curve shape, and it is possible to prevent chipping of corners when the permanent magnet 11 is embedded.
[0022]
In the production of the rotor core 10, a core lamination method (automatic lamination method) is adopted in which an electromagnetic steel sheet is punched out by automatic press using a core press die and is integrally formed by caulking in the die.
[0023]
In this pressing process, the center hole 4, the embedding hole of the permanent magnet 11, the caulking portion 12, the hole for passing the rivet 13 and the hole 14 for the flux barrier are punched out and automatically pressed as shown in FIG. The rotor core 10 is formed by laminating the sheets 10a. The buried hole of the permanent magnet 11 and the flux barrier hole 14 are integrated holes.
[0024]
Thereafter, a low-cost ferrite magnet formed in the hole of the permanent magnet 11 is embedded, and the permanent magnet 11 is magnetically oriented in the thickness direction (the radial direction of the rotor core 10) and magnetized. Moreover, as shown in FIG. 3, after covering both ends of the rotor core 10, the rivet 14 is caulked to complete the manufacture of the rotor core 10.
[0025]
Referring additionally to FIG. 1, this is a case where the permanent magnet motor is a three-phase four-pole motor, and the 24-slot stator core 10 is provided with U-phase, V-phase and W-phase armature windings, The outer armature winding is U-phase, the inner armature winding is W-phase, and the middle armature winding is V-phase, but the number of slots and the number of armature windings are different. Also good.
[0026]
Moreover, by utilizing the rotor core 10 described above in brushless DC motors, for example, it is applied to a compressor of an air conditioner or the like, the performance up of the air conditioner, the improvement of the reliability improved.
[0027]
【The invention's effect】
As described above, according to the invention described in 請 Motomeko 1, in the permanent magnet motor formed by arranging the rotor core in the stator core, one permanent magnet of one pole per sectional bathtub curve shape of the rotor core used, the since the bottom portion of the cross section bathtub curve shape toward the center hole for the shaft insertion formed by embedding the permanent magnets at equal intervals only a small number of the circumferential direction of the rotor core, the rotor core by cross bathtub curve shape Effective use of magnet torque and reluctance torque without reducing the amount of permanent magnet used (magnet amount) and securing the path of magnetic flux from the stator core (magnetic path) This has the effect of improving the motor efficiency. Further, a caulking portion is formed on the q axis in a region between the permanent magnet and the central hole, and a rivet is inserted on the d axis in a region between the permanent magnet and the outer periphery of the rotor core. As a result, there is an effect that the formation of the caulking portion and the rivet passage can be afforded, and the strength of the rotor core can be maintained.
[0028]
According to the invention described in claim 2, Oite to claim 1, wherein the base and inclined sides of the cross bathtub curve shape of the permanent magnet linear, rounded the corners, one of the ends of the permanent magnet Since the hole for flux barrier is formed on the corner side and the other corner side is cut at a predetermined angle, in addition to the effect of claim 1 , the corner of the corner when the permanent magnet is embedded in the rotor core by rounding the corner Chipping and the like can be prevented, and flux leakage and short circuit can be prevented by the flux barrier. Further, by cutting one corner, there is an effect that the thickness (width) of the sectional bathtub curve shape can be increased to increase the amount of permanent magnet used (magnet) and increase the magnet torque.
[Brief description of the drawings]
Schematic plan view showing an embodiment of a permanent magnet motor according to the invention; FIG.
Schematic top view of a one pole of the permanent magnet included in the embodiment of the present invention; FIG.
Schematic sectional view showing a rotor core included in the embodiment of the present invention; FIG.
Schematic plan view showing the Figure 4 prior art permanent magnet motor.
[Explanation of symbols]
1 Stator core 4 Center hole (for shaft)
10 Rotor core (embedded magnet field core)
11 Permanent magnet (of rotor core 10)
12 Caulking part 13 Rivet 14 Hole (for flux barrier)

Claims (2)

In a permanent magnet motor in which a magnet-embedded field core (rotor core) is disposed in a stator core,
Using one of the permanent magnets of one pole per sectional bathtub curve shape of the rotor core, the pole the permanent magnet toward the bottom portion of the cross section bathtub curve shape in the center hole of the shaft inserted in the circumferential direction of the rotor core It is embedded at equal intervals for several minutes , and a caulking portion is formed on the q-axis in a region between the permanent magnet and the central hole, and d in a region between the permanent magnet and the outer periphery of the rotor core. A permanent magnet electric motor comprising a rivet inserted on a shaft . The bottom and both sides of the permanent magnet sectional bathtub curve are straightened, the corners are rounded, and a flux barrier hole is formed on one corner of both ends of the permanent magnet, and the other corner is The permanent magnet motor according to claim 1 , wherein the permanent magnet motor is cut at a predetermined angle.

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