JPH0670520A - Synchronous motor - Google Patents

Abstract

PURPOSE:To provide a synchronous motor easy to fabricate with good characteristics in distribution of magnetic force and in eddy current at a rotor magnetic pole. CONSTITUTION:A rotor magnetic pole 22 is formed by providing a plurality of permanent magnetic members 24 in a circular line. Each permanent magnetic member 24 is electrically isolated through an insulating sheet 25, and a binding wire 26 is made of an insulating material. The permanent magnetic member 24 is so formed that residual magnetic-flux density is stronger at an intermediate part 24A and becomes weaker at the end part 24B. In this way, the larger rotor magnetic pole 22 is formed by using even the smaller permanent magnet members 24, and limitations on the fabricating method can be relaxed. Moreover, magnetic force distribution that meets a sinusoidal wave can be obtained. At the same time, the rotor magnetic pole 22 is divided electrically into small pole parts, and thereby an eddy current can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor using permanent magnets for rotor magnetic poles.

[0002]

BACKGROUND ART Conventionally, in a synchronous motor, an electromagnet is used as a stator magnetic pole and a permanent magnet is used as a rotor magnetic pole.

FIG. 5 shows a rotor 90 of a synchronous motor using permanent magnets. The rotor 90 is configured by alternately arranging a plurality of permanent magnets 92 and spacers 93 around a yoke 91 that is fixed through the rotation shaft, and magnetic poles 94 are formed by the permanent magnets 92 between the spacers 93.

The permanent magnet 92 is a substantially fan-shaped magnet piece corresponding to the width of the magnetic pole 94, and the permanent magnets 92 of the adjacent magnetic poles 94 are S poles or N poles alternately on the front side. Further, a plurality of permanent magnets 92 having the same pole are arranged in the axial direction on each magnetic pole 94 in accordance with the axial length of the rotor 90. A hot-rolled magnet is also used as the permanent magnet 92, but a molded sintered magnet is often used because it is easy to obtain a predetermined shape and can be made large.

On the outer circumferences of the permanent magnets 92 and the spacers 93, there are fixed bind wires for preventing scattering during rotation.
95 is wound, and the resin 96 is impregnated and applied thereon. As the bind wire 95, a tungsten wire, a carbon fiber, a glass fiber or the like is generally used, but since the glass fiber or the like has a low elastic modulus, a tungsten wire or a carbon fiber is mainly used.

In each magnetic pole 94, it is desirable that the waveform of the induced power generated during rotation in the stator magnetic field be close to a sine wave. Therefore, the permanent magnet 92 of each magnetic pole 94 has a magnetic flux distribution. Adjustments are made to weaken at the ends and stronger at the middle. To adjust the magnetic flux distribution as described above, a notch is formed at the end of the permanent magnet 92 as shown in FIG. 6 to reduce the magnetic force at the end, or as shown in FIG.
Is adopted so that the thickness of the end portion is gradually thinner than that of the middle portion.

[0007]

By the way, in the synchronous motor using the rotor 90 as described above, the rotor 90 is rotationally driven by the rotating magnetic field from the stator. On this occasion,
The magnetic field from the stator contains harmonic components due to the power inverter, etc., and each permanent magnet is a good electrical conductor.
Eddy current is generated on the surface of 92.

This eddy current generates heat when flowing through the respective permanent magnets 92, and this heat generation causes eddy current loss to lower the operating efficiency of the electric motor, and causes problems such as heat generation as the electric motor. is there.

In particular, like the rotor 90 described above, each electrode
If the surface area of the permanent magnet 92 that constitutes 94 is large, eddy currents are easily generated, and if a tungsten wire or carbon fiber that is an electrically good conductor is used for the bind wire 95, the entire electrode 94 is electrically There is a problem that the surface as a conductor is expanded by conduction, and an eddy current is more likely to be generated, and the above-mentioned decrease in efficiency and heat generation become remarkable.

On the other hand, as described above, the molded and sintered magnet that is often used for the permanent magnet 92 is brittle and is liable to be damaged or broken during the manufacturing process, etc., and rust is easily generated on the surface. As a result, there is a problem that the magnetic characteristics of the permanent magnet become unstable. Further, in the above-mentioned adjustment of the magnetic flux distribution of the permanent magnet 92, it is necessary to individually cut or change the forming die, which further complicates the manufacturing process.

An object of the present invention is to provide a synchronous motor which has good characteristics such as eddy current and magnetic force distribution of rotor magnetic poles and is easy to manufacture.

[0012]

The present invention is characterized in that a rotor magnetic pole is composed of a plurality of permanent magnet pieces arranged in the circumferential direction.

At this time, it is desirable that the permanent magnet pieces are joined in an electrically insulated state, and that the shatterproof binding wire wound on the outer peripheral side is a silicon carbide fiber.
Further, it is preferable that each of the permanent magnet pieces is set so that the residual magnetic flux density of the magnet piece at the middle portion of the array is high and the residual magnetic flux density of the magnet piece at the end portion of the array is low.

[0014]

[Operation] In the present invention as described above, the rotor magnetic pole is composed of a plurality of permanent magnet pieces arranged in the circumferential direction,
That is, each magnetic pole is divided into a plurality of pieces in the circumferential direction. Therefore, it is possible to form a large magnetic pole even if each individual permanent magnet piece is small, and it is possible to easily manufacture a large rotor magnetic pole.

By joining the permanent magnet pieces in an electrically insulated state, the magnetic poles are electrically divided into small sections, which greatly reduces the generation of eddy currents and the rotor. The characteristics as a magnetic pole can be improved. At this time, the silicon carbide fiber has a high electric insulation and a sufficient strength, and eddy current due to electric conduction through the bind wire can be prevented.

Furthermore, by selecting the strength of the residual magnetic flux density of each permanent magnet piece according to the arrangement, the magnetic force distribution of the magnetic poles can be made to correspond to a sine wave while using each permanent magnet piece of the same outer shape, and rotation is possible. The characteristics as a child magnetic pole can be improved. Therefore, by arranging a plurality of permanent magnet pieces in the circumferential direction as in the present invention to form the rotor magnetic poles, it is possible to facilitate the manufacture and improve the characteristics, thereby achieving the above object.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a synchronous motor 10 includes a stator 11 fixed to an outer peripheral portion, and a rotor 20 that rotates integrally with a rotation shaft (not shown; only a rotation center is shown by a chain line) inside the stator 11. .

The stator 11 is an electromagnet composed of a coil 12 wound in the circumferential direction, and forms a rotating magnetic field inside by a current from an external AC power source. The rotor 20 has a rotor magnetic pole 22 on the peripheral surface of a yoke 21 mounted on a rotating shaft (not shown), and is rotationally driven by a rotating magnetic field generated by the stator 11.

In FIG. 2, the rotor 20 comprises a plurality of rotor magnetic poles 22 and spacers 23 arranged alternately around the yoke 21.
Is equipped with. The rotor magnetic poles 22 adjacent to each other with each spacer 23 sandwiched between the spacers 23 are S poles or N poles.
Is a member made of bakelite with cloth. The rotor magnetic pole 22 is formed by arranging a plurality of strip-shaped hot-rolled permanent magnet pieces 24 each extending in the axial direction of the rotor 20 in the circumferential direction so that the surface sides thereof have the same polarity.

As shown in FIG. 3, among the permanent magnet pieces 24 arranged as the rotor magnetic poles 22, a rare earth magnet 24A such as praseodymium-iron-boron having a high residual magnetic flux density is arranged in the middle of the arrangement. The ferrite magnet 24B having a low residual magnetic flux density is arranged at the end of the array. These permanent magnet pieces 24 are joined to each other by an adhesive in an electrically insulated state with an insulating sheet 25 such as Nomex paper sandwiched therebetween.

Returning to FIG. 2, silicon carbide fiber bind wires 26 are multiply wound around the outer peripheral surfaces of the rotor magnetic poles 22 and the spacers 23, and a resin 27 is impregnated and applied thereon. End rings 28 are attached to both ends of the rotor 20, and the coating of the bind wire 26 and the resin 27 wound on the outer peripheral surface is applied to a part of the end rings 28.

In this embodiment thus constructed, the rotating magnetic field formed by the coil 12 of the stator 11 acts on the rotor magnetic poles 22 of the rotor 20 to rotate the rotor 20.

Here, the rotor magnetic pole 22 is composed of a plurality of permanent magnet pieces 24 arranged in the circumferential direction of the rotor 20, and each permanent magnet piece 24 is electrically insulated from each other by an insulating sheet 25. Since the bind wire 26 connecting each is also electrically non-conductive, each rotor magnetic pole 22 is electrically divided into small sections. Therefore, even if there is a harmonic component in the magnetic field from the stator 11, eddy current is unlikely to be generated in each rotor magnetic pole 22, and inconveniences such as eddy current loss or heat generation can be eliminated.

Further, the rotor magnetic pole 22 has a high residual magnetic flux density in the rare earth magnet 24A at the middle of the array and a low residual magnetic flux density in the ferrite magnet 24B at the end of the array. , 24B, the magnetic flux distribution of the rotor magnetic pole 22 can be approximated to a curve corresponding to a sine wave (see FIG. 4).

Further, even with a large rotor magnetic pole 22,
Since each of the permanent magnet pieces 24 constituting the same can be made small, the individual permanent magnet pieces 24 can be easily and inexpensively hot-rolled, and the hot-rolling can cause defects and defects in the permanent magnet pieces 24. It is possible to prevent rust and the like.

The present invention is not limited to the above embodiment, and the following modifications and the like are also included in the present invention. That is, in the above embodiment, the rotor magnetic pole 22
24 different pieces of permanent magnets in the middle and end of the array
Although the magnetic force distribution was adjusted in two steps by using, the magnet material for increasing the strength is not limited to the combination of the rare earth magnet 24A such as praseodymium-iron-boron and the ferrite magnet 24B, but the same material Different magnets or the like may be used, and those having an appropriate magnetic force may be selected for implementation.

Further, the adjustment of the magnetic force distribution of the rotor magnetic pole 22 is not limited to the two steps as in the above embodiment, but may be three steps or more. If the magnetic force distribution does not need to be adjusted, the same permanent magnet piece 24 may be used.

Further, the permanent magnet pieces 24 are not limited to those produced by hot rolling, but may be produced by other production methods.

On the other hand, in the above-mentioned embodiment, the permanent magnet pieces 24 are bonded with an adhesive by sandwiching an insulating sheet 25 such as Nomex paper, but other means is used to obtain insulation between the adjacent permanent magnet pieces 24. Alternatively, for example, another sheet may be used, and the insulating sheet 25 may be omitted if the insulating property can be obtained only by the adhesive.

Further, the bind wire 26 may be made of another material as long as it has sufficient insulation and strength.

[0031]

As described above, according to the present invention,
Since the rotor magnetic poles are composed of a plurality of permanent magnet pieces arranged in the circumferential direction, characteristics such as eddy current and magnetic force distribution can be improved, and manufacturing can be facilitated.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing the rotor of the embodiment.

FIG. 3 is an enlarged view showing a rotor magnetic pole of the embodiment.

FIG. 4 is a schematic diagram showing a magnetic force distribution of a rotor magnetic pole of the embodiment.

FIG. 5 is an exploded perspective view showing a conventional rotor.

FIG. 6 is a schematic view showing a conventional permanent magnet.

FIG. 7 is a schematic view showing another conventional permanent magnet.

[Description of symbols] 10 Synchronous motor 11 Stator 20 Rotor 22 Rotor magnetic pole 24 Permanent magnet piece 24A Rare earth magnet with high residual magnetic flux density 24B Ferrite magnet with low residual magnetic flux density 25 Insulation sheet 26 Bind wire

Claims (3)

[Claims] 1. A synchronous motor, wherein a rotor magnetic pole is composed of a plurality of permanent magnet pieces arranged in a circumferential direction. 2. The synchronous motor according to claim 1, wherein the permanent magnet pieces are joined in an electrically insulating state, and the shatterproof binding wire wound around the outer peripheral side is a silicon carbide fiber. Characteristic synchronous motor. 3. The synchronous motor according to claim 1, wherein each permanent magnet piece has a high residual magnetic flux density in a magnet piece at an intermediate portion of the array and a residual magnetic flux density in a magnet piece at an end portion of the array. The synchronous motor is characterized by being set low.