Patent Application
20110156521
The present application claims priority from Japanese patent application serial no. 2009-291702, filed on Dec. 24, 2009, the content of which is hereby incorporated by reference into this application.
The present invention relates to a permanent magnet type rotating electric machine and more particularly to a permanent magnet type rotating electric machine suitable for the type having a permanent magnet in a rotor core.
With regard to permanent magnet type rotating electric machines, as described in TOSHIBA REVIEW Vol. 55 No. 9 (2000) and ELECTRIC MACHINES 2007.6, p. 12-14, there is known, for example, a surface magnet type rotating electric machine having a rotor structure in which plural magnets are attached to an outer periphery of a rotor core formed by laminating silicon steel plates in an axial direction of the rotor core, and a interior permanent magnet type rotating electric machine in which slots are formed near an outer periphery of a rotor core so as to be extended in the axial direction of the rotor core and permanent magnets are inserted into the slots respectively.
In the former, since an induced voltage increases in proportion to the rotational speed, it has a disadvantage in that a maximum rotational speed must be limited to a certain rotational speed at which the induced voltage does not exceed a power supply voltage. On the other hand, the latter does not have such a disadvantage.
One drawback of the permanent magnet is that it is a fragile material in point of strength. In addition, each insertion slot for the permanent magnet in the rotor core since is formed by axially aligning holes formed by respectively punching silicon steel plates to be laminated, asperities trend to present on the slot in the axial direction due to tolerances of holes.
Therefore, the insertion of a permanent magnet may become impossible due to a large frictional force induced at the time of insertion of the magnet caused by the asperities due to the tolerances of holes. To avoid this inconvenience, a large slot relative to the shape of a magnet is formed, thereby causing a clearance to be formed between the magnet and the slot.
Accordingly, it is desired to surely fix the fragile material such as a permanent magnet into the rotor core without permitting movement of the magnet through the slot due to the clearance during operation not to cause cracking of the magnet and without deteriorating magnetic characteristics.
For fixing the permanent magnet to the rotor, an adhesive is used mainly in small-sized rotating electric machines which are not so strictly required to satisfy high strength and high reliability. However, the adhesive has a disadvantage in that the adhesive force thereof deteriorates due to, for example, aged deterioration. In the case of an induction motor having rotor bars inserted into slots of a rotor core and an end ring attached to front ends of the rotor bars, a natural frequency of torsional vibration induced by those rotor bars and end ring is likely to be lowered. As a method for preventing such a lowering of the natural frequency, JP 2000-341891A shows a technique of adopting a structure in which the rotor bars are constantly pressed against a side where the rotor bars are pressed with a rotary force of the rotor during rotation thereof.
With regard to a conventional interior permanent magnet type rotating electric machine as shown in
As described above, each slot for insertion therein of a permanent magnet of the rotor is formed by axially aligned holes formed by respectively punching silicon steel plates to be laminated, asperities may present on the slot in the axial direction due to tolerances on holes. Due to the asperities caused by the tolerances, therefore, it is likely that a frictional force induced at the time of inserting the permanent magnet into the slot will become large, making it impossible to effect the insertion of the magnet. To avoid this inconvenience, a large slot (holes) relative to the shape of a magnet is formed, thus causing a clearance to be formed between the magnet and the slot. In this case, however, since the permanent magnet is a fragile material in point of strength, the presence of a clearance between the magnet and the magnet insertion slot is likely to cause cracking due to vibration or the like.
The present invention has been accomplished in view of the above-mentioned point and it is an object of the invention to provide a permanent magnet type rotating electric machine in which a permanent magnet, though fragile in point of strength, does not move through a slot of a rotor core under, for example, vibration during operation and is hence not cracked by vibration or the like.
In order to achieve the above-mentioned object, a permanent magnet type rotating electric machine of the present invention is characterized as follows basically. It is comprised of a rotor and a stator opposed to each other keeping a predetermined clearance therebetween, the rotor having a rotor core formed by silicon steel plates being laminated in an axial direction of the rotor core, slots being formed near an outer periphery of the rotor core in the rotor core so as to be open at the outer periphery of the rotor core, permanent magnets being inserted into the slots respectively, and a non-magnetic sleeve covering the outer periphery of the rotor core, wherein each of the slots has inclined side faces outwardly broadening the slot in a radial direction of the rotor core, and each of the permanent magnets is fixed into the slot with a force applied from the sleeve so as to directing toward a center of the rotor core and an pressure applied from the inclined side faces of the slot.
According to the present invention, it is possible to provide a permanent magnet type rotating electric machine which is able to easily insert a permanent magnet into a slot because of the slot outwardly broadening in the radial direction of the rotor core, and prevent rattling of the permanent magnet within the slot even if the permanent magnet is formed of a fragile material in point of strength.
Embodiments of the present invention will be described below with reference to the drawings.
The permanent magnet type rotating electric machine of this embodiment shown in
In this embodiment, each of the slots 4 being open at the outer periphery surface of the rotor core 2 has inclined side faces 4a (which are inclined with respect to a vertical center line of the slot 4) outwardly broadening (e.g. fanning out) the slot 4 in the radial direction of the rotor core 2. Each of the permanent magnets 3 has a wedge-shaped form and is fixed into the slot 4 with a force C applied from the sleeve 7 (the force C directing toward a center of the rotor core 2) and an pressure applied from the inclined side faces 4a of the slot 4 as shown in black allows D in
In comparison with the present embodiment, a conventional permanent magnet type rotating electric machine as shown in
On the other hand, in the case of the present embodiment of
Thus, since the permanent magnet 3 is surely borne with the initial surface applied thereto, no clearance is formed between the permanent magnet 3 and the slot 4 and there is no fear of the permanent magnet 3 moving through the slot 4 to develop a crack even under vibration of the rotor 1 while being able to easily inserting the permanent magnet 3 into the slot 4 by a provisional insertion in advance of the interference fit or tight fit with the non-magnetic sleeve 7.
As shown in
As described above already, each insertion slot 4 for the permanent magnet 3 is formed by axially aligning holes formed by respectively punching silicon steel plates to be laminated, asperities may present on the slot in the axial direction. Even at a small tolerance, therefore, a frictional force developed upon insertion of the permanent magnet becomes large, the insertion of a permanent magnet may become impossible due to a large frictional force induced at the time of insertion of the magnet. To avoid this inconvenience, in the conventional art, a large slot (aligned holes) relative to the shape of the permanent magnet is formed, thereby causing a clearance between the permanent magnet and the slot.
In the embodiment of
With this configuration, in addition to the effect obtained by the configuration of the first embodiment, there is obtained an effect that the permanent magnet 3 can be still further easily inserted into the slot 4 by decreasing a frictional force induced at the time of inserting the permanent magnet into the slot.
As shown in
In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
The present embodiment's features different from the above-mentioned other embodiments are as follows. The present embodiment has parallel (opposed) side faces 4a′ of each slot 4′ in place of outwardly broadening inclined side faces 4a of the slot 4 described in the first to fifth embodiments, and has parallel both faces of each non wedge-shaped permanent magnet 3′ inserted into the slot 4′. In the parallel side faces 4a′ of the slot 4′ of the present embodiment, one parallel side face (indicated by numeral 9b′), which is opposite to another parallel side face subjected to a pressure of the permanent magnet 3′ with a resultant force of both a centrifugal force of the rotor 1 and an electromagnetic force generated by the stator (not shown), is provided with a cut face 9b′ increasing a clearance between the one parallel side face 4a′ and the permanent magnet 3′ so as to be greater than the manufacturing tolerance. The one side face 4a′ as the cut face 9b′ is shorter than another side face 4a′, and an inclined side face 9a′is provided between the cut face 9b′ and the bottom of the slot 4′.
In the case of the permanent magnet 3′ not having an inclination like a wedge, the inclined side face 9a′ near a slot's one end portion (at bottom side and the rotor core center side) is also located on the side opposite to another inclined side face 4a′ subjected to the pressure of the permanent magnet 3′ with the resultant force of both the centrifugal force of the rotor 1 and the electromagnetic force.
According to such a configuration, the permanent magnet 3′ is applied with a force pressing the permanent magnet 3′ into the slot 4 by the sleeve 7, and thereby one corner of the permanent magnet 3′ is pressed against the inclined side face 9a′. Therefore, the permanent magnet 3′ is surely fixed by the force pressing the magnet 3′ into the slot 4′ by the sleeve 7, the force (stress) applied to the permanent magnet 3′ from the inclined side faces 9a′, and the force pressing the permanent magnet 3′ against the another side face 4a′ with the resultant force of both the centrifugal force of the rotor 1 and the electromagnetic force.
With this configuration, even when adopting the slot 4′ having non broadening side faces (parallel side faces) 4a′ with the cut face 9b′ and non wedge-shaped permanent magnet 3′, it is possible to surely bear the permanent magnets 3′ in the slot 4′ during ration of the rotor 3′ and of course, it is possible to obtained the effect that the permanent magnet 3′ can be still further easily inserted into the slot 4′ by decreasing a frictional force induced at the time of inserting the permanent magnet into the slot.
As shown in
In the present embodiment, an elastic member 11 is inserted between the sleeve 7 and a slot open-side end portion of each permanent magnet 3 thereby to allow the elastic member 11 to keep a force pressing the permanent magnet 3 toward the rotor core center side of each slot 4′.
With this configuration, in addition to the effect obtained by the configuration of the first embodiment, the following effect is obtained. That is, even if the interference effect at the slot-open side end portion of the permanent magnet 3 is gone due to a thermal deformation difference such as a thermal expansion difference, the permanent magnet 3 can be surely held with a reaction force of the elastic member 11. In addition, since the elastic member 11 is interposed between the slot open-side end portion of the permanent magnet 3 and the sleeve 7, it can be not necessary to machine the slot open-side end portion of the permanent magnet in conformity with the outer periphery of the rotor and the sleeve 7.
This embodiment is a modified example of the seventh embodiment and the technical matter different from the seventh embodiment is as follows. In the present embodiment, a slot-side end portion of a permanent magnet 3 is cut by a predetermined thickness with respect to the outer periphery of a rotor and an elastic member 11 having a predetermined uniform thickness is inserted into the thus-cut space namely between the slot open-side end portion of the permanent magnet 3 and the sleeve 7.
With this configuration, a uniform surface pressure can be applied to the slot-side end portion of the permanent magnet 3.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-291702 | Dec 2009 | JP | national |
