JP2002345189A - Permanent magnet embedded synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce thermal loss by restraining concentration of eddy currents in a permanent magnet. SOLUTION: This synchronous motor has a stator 2, in which a coil part is formed and a rotor 3 in which permanent magnets 6 are embedded. The permanent magnet 6 is constituted of a pair of magnet segments 6-1, 6-2 which are arranged into a U-shape or a V-shape, where each magnetic pole protrudes toward an inner periphery of the rotor. Slits 11 are formed in part positions of the magnet segments which are adjacent to the outer periphery of the rotor. By enhancing the resistance of a part where the eddy current is apt to concentrate using the slit 11, the generation of an eddy current is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet embedded synchronous motor in which permanent magnets are embedded in a rotor.
More particularly, the present invention relates to a synchronous motor in which a coil is concentratedly wound around a stator, a magnetic field is generated in a direction in which a magnetic flux of a permanent magnet is weakened, and an operation region thereof is expanded.

[0002]

2. Description of the Related Art A permanent magnet embedded synchronous motor in which a permanent magnet is embedded in a rotor is provided with a magnet torque generated by the left-hand rule of Fleming, and an inductance of a rotor having a magnet and a magnet having no magnet. It is generally considered that the reluctance torque generated by the difference can be used, so that the output torque is large and the efficiency is high. Further, by performing a so-called field weakening in which a coil magnetic flux acts in a direction to weaken the permanent magnet, a wide range of operation is possible and a high output can be achieved, and these have been widely used in recent years.

[0003] Among them, a motor in which a coil is concentratedly wound around a stator has attracted attention because it can be reduced in size as compared with a motor in which the coil is wound in a distributed manner, the manufacturing process can be simplified, and the cost is low.

[0004] On the other hand, when the coil is concentratedly wound, the change in the linkage magnetic flux during rotation of the rotor becomes large. Therefore, the change in the magnetic flux density of the permanent magnet inside the rotor becomes large, and the vortex inside the permanent magnet. Heat is generated due to current,
There is a phenomenon that causes demagnetization.

To prevent this, for example, Japanese Patent Application Laid-Open
No. 0-245085.

In this method, the generation of eddy current is suppressed by dividing a permanent magnet embedded in the rotor into a plurality of parts and coating the divided magnet pieces with an insulating material to electrically insulate them. To prevent the heat generation and the thermal demagnetization caused thereby.

[0007]

However, in such a conventional structure, in order to effectively suppress the generation of eddy currents, when the permanent magnet is divided, each magnet piece must be made sufficiently small. Needed. This means that rotor pole 1
It means that the number of magnet pieces that make up the poles needs to be sufficiently large, and insulation treatment is applied to each of the magnet pieces,
Subsequent construction of one magnet for one pole inevitably results in a significant increase in cost.

Further, when the number of divisions is increased, the volume occupied by the magnet pieces and the insulating material interposed between the magnet pieces is increased, so that the apparent strength of the permanent magnet is reduced, and compared with the case where the magnet is not divided. As a result, there is a problem that the torque and output of the motor are reduced.

An object of the present invention is to solve such a problem.

[0010]

According to a first aspect of the present invention, there is provided a synchronous motor having a stator in which a coil portion is formed, and a rotor having a permanent magnet embedded therein. It is composed of a pair of magnet pieces arranged in a U-shape or a V-shape, which are convex, and slits are provided in portions of these magnet pieces that are close to the outer periphery of the rotor.

According to a second aspect of the present invention, in a synchronous motor having a stator having a coil portion formed therein and a rotor having a permanent magnet embedded therein, the permanent magnet has a U-shape in which each magnetic pole is convex toward the inner periphery of the rotor. It is composed of a pair of magnet pieces arranged in a mold or a V shape, and a conductive member is arranged on the outer periphery of these magnet pieces.

In a third aspect based on the second aspect, the conductive member is disposed on one surface of the magnet piece on the outer peripheral side of the rotor.

In a fourth aspect based on the second aspect, the conductive member is disposed only at a tip portion of the magnet piece near the rotor outer peripheral side.

In a fifth aspect based on the fourth aspect, a gap is provided between the conductive material and the magnet piece.

According to a sixth aspect of the present invention, in a synchronous motor having a stator having a coil portion formed therein and a rotor having a permanent magnet embedded therein, the permanent magnet has a U-shape in which each magnetic pole is convex toward the inner periphery of the rotor. Or a pair of magnet pieces arranged in a V-shape, the rotor core of the rotor is made of a laminated steel sheet, and a welded portion for fixing the laminated steel sheet is formed on the outer periphery of the rotor by the magnet piece being the most outer rotor outer periphery. It is a part approaching the side.

[0016]

According to the first aspect of the present invention, the electrical resistance of the material is partially increased by providing a slit at a portion closest to the outer periphery of the rotor where a large amount of eddy current generated in the permanent magnet is concentrated. The same effect can be obtained, whereby the generation of eddy current can be suppressed, and the accompanying heat loss can be suppressed.

In the second aspect, since the conductive member is arranged on the outer peripheral surface of the permanent magnet, the eddy current generated in the rotor is most frequently generated inside the conductive member. The eddy current generated in the conductive member is caused by its demagnetizing action.
Since the permeation of the magnetic field change into the permanent magnet on the inside is suppressed, the eddy current inside the permanent magnet can be reduced. Loss due to eddy currents occurs in the conductive member, but by making the volume of the conductive member sufficiently smaller than that of the permanent magnet, the amount of heat generated by the conductive member can be reduced and the loss can be reduced. .

In the third aspect, since the conductive member is arranged only on the outer peripheral surface of the rotor where eddy current is easily generated, the volume of the conductive member can be reduced, and the above-mentioned effect can be further enhanced.

According to the fourth aspect of the present invention, heat generation can be effectively suppressed with fewer members by arranging the conductive member at the tip of the permanent magnet.

According to the fifth aspect, since the conductive member is not brought into contact with the permanent magnet, the temperature rise of the permanent magnet can be effectively suppressed.

In the sixth aspect of the present invention, by specifying the welded portion of the laminated steel sheet of the rotor, substantially the same operation and effect as the arrangement of the conductive member can be obtained, and the configuration can be simplified.

[0022]

1 and 2 show a first embodiment of the present invention.

Referring to FIG. 1, a motor 1 includes a stator 2 and a rotor 3.

The stator 2 is composed of a plurality of magnetic steel sheets laminated on each other and fixedly wound around the teeth 7a of the stator piece 7 with a plurality of coils 8a and 8b arranged in a circumferential direction. It consists of.

On the other hand, the rotor 3 is provided with a plurality of magnet insertion holes 4a parallel to the rotor rotation axis inside a rotor core 4 formed by laminating a plurality of electromagnetic steel sheets. Of the permanent magnet pieces 6-1 and 6-2 are magnetized for one pole, and an even number of the permanent magnets 6 are embedded in the circumferential direction at regular intervals.

The reason why the number of the permanent magnets 6 is an even number is as follows.
Permanent magnet 6 so that the directions of adjacent magnetic poles are different from each other.
It is assumed that the permanent magnet pieces 6-1 and 6-2 have N poles that appear in the outer circumferential direction of the rotor. It is magnetized so that the S pole is on the outer peripheral side.

The rotor core 4 is fixed to a shaft 5 penetrating the center of the rotor core 4 so that its rotational force can be taken out of the shaft 5.

In this embodiment, a so-called 6-pole, 9-slot motor in which the number of magnetic poles of the permanent magnet 6 is 6 and the number of poles of the stator 2 is 9 is described as an example. The same applies to motors having a combination of configurations.

In the motor shown in FIG. 1, since the number of poles of the stator is 9, every third coil in the circumferential direction is connected in series or in parallel to form one phase coil. Assuming that certain three coils are U-phase, every other three coils are V-phase, and every other three coils are W-phase.
It becomes a phase and forms a three-phase coil.

On the other hand, the rotor 3 has a d-axis in which a permanent magnet 6 is embedded and a q-axis in a direction in which no magnet is provided. Generally, the magnetic permeability of the permanent magnet is sufficient compared to the steel sheet forming the rotor core 4. Since the magnetic flux is small, the magnetic flux from the stator 2 is difficult to pass in the d-axis direction, and conversely in the q-axis direction.
Therefore, when the inductance in the d-axis direction and the inductance in the q-axis direction are compared, the inductance in the d-axis direction is smaller.

For this reason, by controlling the three-phase coils of the stator 2 so that an optimal current is applied thereto, in addition to the magnet torque generated by the interaction between the magnetic flux generated by the magnet and the magnetic flux generated by the coil, moreover, A reluctance torque acting to shift to a magnetically stable direction acts, so that a relatively large torque can be obtained.

The feature of the present invention lies in the structure of the permanent magnet 6 embedded in the rotor 3.

First, the whole or a part of the permanent magnet 6 is made to approach the outer periphery of the rotor, and for each magnetic pole, a pair of permanent magnet pieces 6-1 and 6-2 are projected toward the center axis of the rotor. V-shaped or U-shaped.

As a result, the center of the magnetic pole (V-shaped or U-shaped valley) which is relatively far from the outer periphery of the rotor is not significantly affected by the magnetic field from the stator 2 and the magnetic flux density change in that portion is relatively small. The eddy current generated is small.

On the other hand, portions near the outer periphery of the rotor (both ends of the V-shape and U-shape) receive a large magnetic field from the stator 2, and the magnetic flux density change inside the permanent magnet at that time naturally increases. Therefore, as shown in FIG. 2A, a plurality of mutually parallel slits 11 are provided near the end where the magnet is closest to the outer periphery of the rotor. They are provided in parallel.

The permanent magnet pieces 6-1 and 6-
By inserting the rotor 2 into the magnet insertion hole 4a provided in the rotor core 4 to constitute the rotor 3, it is possible to effectively suppress the generation of eddy current in the magnet.

Hereinafter, the reason will be described.

In general, in a permanent magnet embedded synchronous motor in which a concentrated winding coil is applied to a stator, a rotor receives more than a distributed winding motor in which one coil is wound so as to sandwich a plurality of stator teeth. There is a characteristic that a change in magnetic flux from the stator becomes extremely large. This is because, compared to a distributed winding motor, a concentrated winding motor has a smaller number of stator teeth, increases the distance between adjacent magnetic poles and the adjacent teeth are always out of phase, so the spatial magnetic field This is because the distribution has a shape far from the ideal sine wave.

Therefore, in an ideal synchronous motor, while the magnetic field viewed from the synchronously rotating rotor is constant,
In the concentrated winding motor, the magnetic field acting on the rotor changes greatly. Furthermore, in the case of performing so-called field-weakening control, in which control is performed so that current flows through the coils of the stator in the direction of weakening the magnetic flux of the permanent magnet for the purpose of expanding the operating speed range, the permanent magnet in the rotor generates The magnetic field that tries to weaken the magnetic flux, for the reasons described above,
It will work with large fluctuations according to the rotation.

At this time, when the permanent magnet is located relatively far from the outer periphery of the rotor (the magnet is embedded in a deep position), the distance between the magnetic field generated by the stator and that of the permanent magnet acts on each other. Therefore, it is known that the change in magnetic flux density occurring directly inside the permanent magnet can be suppressed to a relatively small value. However, if the magnet is buried deep from the outer periphery of the rotor, the N
A large amount of magnetic flux forms a loop between the poles and the S pole or between adjacent magnets of the other pole, and these are completed in the rotor, so that they do not affect the rotor surface. That is, it is the same as the appearance of the permanent magnet that has become weaker. Therefore, in order to obtain a desired torque and output as a motor, the volume of the permanent magnet must be increased.

Therefore, the permanent magnet 6 like the shape of the present invention is used.
It is necessary to make the whole or a part of the rotor close to the outer periphery of the rotor to reduce the ineffective magnetic flux as described above as much as possible.

At this time, if the arrangement of the pair of permanent magnet pieces 6-1 and 6-2 of each permanent magnet 6 is V-shaped or U-shaped convex toward the center axis of the rotor, the outer periphery of the rotor can be reduced. The V-shaped and U-shaped valleys, which are the center portions of the magnetic poles at a relatively long distance from the magnetic pole, are not greatly affected by the magnetic field from the stator 2 and the change in the magnetic flux density at that portion is relatively small. The eddy current amount can be reduced.

On the other hand, portions near the outer periphery of the rotor (both ends of the V-shape and U-shape) receive a large magnetic field from the stator 2, and the magnetic flux density change inside the permanent magnet at that time naturally becomes large.

However, as shown in FIG. 2 (a), if the slit 11 is provided at the end (corresponding to the V-shaped end) of the permanent magnet piece 6-1 (6-2), the electricity of the material is partially This has the same effect as increasing the resistance, and it is possible to suppress the generation of eddy current and the loss accompanying it.

In this case, it is not necessary to divide and insulate the permanent magnet 6 over the entire volume, and since the slit 11 is provided only at the portion where the eddy current is originally concentrated, the cost is relatively low. It is possible to increase the proportion of the magnet in the volume.

The shape of the slit provided in the magnet at this time is not limited to the direction shown in FIG.
As shown in (b), the same effect can be expected even if a plurality of slits 11 are provided in the vertical direction.

Next, another embodiment will be described.

FIG. 3 is a diagram showing a second embodiment of the present invention.

In this embodiment, in the rotor 3 having the structure shown in the embodiment of FIG. 1, the outer peripheral surface of the permanent magnet 6 is made of a relatively high-conductivity thin plate material represented by copper or aluminum. Is provided.

In this case, the slits 11 as shown in FIG. 2 may or may not be provided in the permanent magnet pieces 6-1 and 6-2. The conductive member 12 is formed of a thin plate member different from the permanent magnet 6, but is different from the thin plate member.
May be provided with a conductive coating. Further, the conductive member 13 is not directly attached to the permanent magnet 6,
It can be arranged on the inner peripheral surface of the magnet insertion hole 4a along the outer peripheral surface of the permanent magnet 6.

When the motor having the rotor 3 having such a configuration is driven, the influence of the eddy current does not cause much problem in a region where the rotation is relatively low because the speed (frequency) of the magnetic field change acting on the rotor 3 is low. .

However, when the conductive member 12 is made of a non-magnetic material, the portion is similar to the air gap existing on the magnetic circuit viewed from the permanent magnet 6, and in that sense, the conductive member 12 The thickness is preferably as thin as possible. Even if the thickness is sufficiently small, the effect of the eddy current has a skin effect that is concentrated on the surface as the frequency increases, so that the effect described later is not adversely affected.

On the other hand, when the operating speed of the motor is relatively high, the frequency of the magnetic field change acting on the rotor 3 is also high, and an eddy current is generated in the rotor. However, since the conductive member 12 is disposed on the outer peripheral surface of the permanent magnet 6, the eddy current is most frequently generated inside the permanent magnet. The eddy current generated inside the conductive member 12 suppresses the permeation of a magnetic field change into the permanent magnet 6 located inside the conductive member 12 due to the demagnetizing action thereof. No more problems.

Conversely, a loss due to eddy current occurs in the conductive member 12 and the conductive member 12 itself generates heat. The amount of heat (loss) is determined by the volume (area in the figure) of the thin plate of the conductive member 12. By making) sufficiently smaller than the volume of the permanent magnet 6, it is possible to make the loss smaller than the loss generated in the permanent magnet 6 when the conductive member 12 is not provided.

FIG. 4 shows a third embodiment.

In the present embodiment, in the rotor 3 having the structure shown in the embodiment of FIG. 1, along the one surface on the rotor outer peripheral side of the permanent magnet 6, a relatively conductive thin plate material such as copper or aluminum is used. Conductive member 13 is disposed.

The conductive member 13 can be directly attached to the permanent magnet 6, or can be arranged on the inner peripheral surface of the magnet insertion hole 4a along the outer peripheral surface of the permanent magnet 6.

Since the conductive member 13 is provided only on one surface of the permanent magnet 6, the magnetic resistance viewed from the permanent magnet 6 during low rotation can be made relatively small, and a decrease in motor torque can be suppressed. As described in the above embodiment, the effect of reducing the loss due to heat generation can be obtained.

FIG. 5 shows a fourth embodiment.

In the region where the motor rotates relatively low,
As described above, it is preferable that the thickness of the conductive member is as thin as possible. However, in order to more sufficiently generate the effect, the volume of the conductive member needs to be extremely small.

Therefore, in the present embodiment, of the permanent magnet pieces 6-1 and 6-2 arranged in a V-shape or a U-shape, the magnet, which is the site where the eddy current is generated most, is the one where the magnet approaches the outer periphery of the rotor. The conductive member 14 is arranged only on the outer peripheral side of the tip.

By doing so, the effect of suppressing the above-described thermal loss due to the eddy current can be enhanced without substantially impairing the magnetic flux generated by the permanent magnet 6.

FIG. 6 is a diagram showing a fifth embodiment.

In the present embodiment, an air gap 17 is provided between the conductive member 14 and the permanent magnet 6 in the embodiment shown in FIG. 5, so that they do not directly contact each other. By doing so, when an eddy current is generated in the conductive member 14 and heat is generated, the heat is first transmitted to the rotor core 4 without being directly transmitted to the permanent magnet 6.
Further, since the portion where the conductive member 14 is provided is very close to the outer periphery of the rotor 3, it can be expected that the rotor 3 rotates and is efficiently cooled by the air on the outer periphery of the rotor 3. Therefore, the temperature of the permanent magnet 6 can be further effectively suppressed.

Here, the air gap 17 is provided between the conductive member 14 and the permanent magnet 6.
For example, a similar effect can be obtained by using an adhesive or a resin layer for fixing the permanent magnet 6.

FIG. 7 shows a sixth embodiment.

In the present embodiment, when the rotor cores 4 formed by laminating electromagnetic steel sheets are fixed to each other by welding, in the rotor circumferential direction, the portion where the permanent magnet 6 embedded therein comes closest to the outer peripheral surface. The weld 1
5 is assumed.

At the welded portion 15, the laminated steel plates are electrically connected to each other to be in a conductive state. Therefore, the same effect as when a conductive member having the same thickness as the welding depth is provided in this portion is produced. Therefore, the same effects as those of the above-described embodiment can be obtained. In addition, since the welded portion 15 is on the outer periphery of the rotor and is always in contact with the outside air, the heat generated in that portion by the rotation of the rotor 3 is effectively reduced. It is possible to suppress the temperature of the permanent magnet 6 being cooled.

Further, the end of the permanent magnet 6 is closest to the outer periphery of the rotor. In the rotor core portion a in the figure, the magnetic flux generated by the permanent magnet 6 is short-circuited between the N pole and the S pole of the same magnet 6. Since the aperture becomes an aperture that suppresses the occurrence of the reduction (the magnetic resistance is increased), by using this portion as the welded portion 15, the magnetic properties of the steel sheet partially decrease due to heat at the time of welding. And the advantage that the torque and output can be improved.

The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible within the scope of the technical idea of the present invention described in the appended claims.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIGS. 2A and 2B are perspective views showing the same permanent magnet piece.

FIG. 3 is a sectional view of a main part showing a second embodiment.

FIG. 4 is a sectional view of a main part showing a third embodiment.

FIG. 5 is a sectional view of a main part showing a fourth embodiment.

FIG. 6 is a sectional view of a main part showing a fifth embodiment.

FIG. 7 is a sectional view of a main part showing a sixth embodiment.

[Explanation of symbols]

 Reference Signs List 1 motor 2 stator 3 rotor 4 rotor core 4a magnet insertion hole 6 permanent magnet 6-1 permanent magnet piece 6-2 permanent magnet piece 11 slit 12 conductive member 13 conductive member 14 conductive member 15 weld 17 air gap

Claims (6)

[Claims] In a synchronous motor having a stator having a coil portion formed therein and a rotor having a permanent magnet embedded therein, the permanent magnet has a U-shape or a V-shape in which each magnetic pole is convex toward the inner circumference of the rotor. A synchronous motor comprising a pair of magnet pieces arranged in a mold, wherein a slit is provided in a portion of the magnet pieces approaching the outer periphery of the rotor. 2. A synchronous motor having a stator having a coil portion formed therein and a rotor having a permanent magnet embedded therein, wherein the permanent magnet has a U-shaped or V-shaped configuration in which each magnetic pole is convex toward the inner periphery of the rotor. A synchronous motor comprising a pair of magnet pieces arranged in a mold, and a conductive member arranged on the outer periphery of these magnet pieces. 3. The synchronous motor according to claim 2, wherein the conductive member is disposed on one surface of the magnet piece on the outer peripheral side of the rotor. 4. The synchronous motor according to claim 2, wherein the conductive member is disposed only at a tip of the magnet piece near the outer periphery of the rotor. 5. The synchronous motor according to claim 4, wherein a gap is provided between said conductive material and said magnet piece. 6. A synchronous motor having a stator having a coil portion formed therein and a rotor having a permanent magnet embedded therein, wherein the permanent magnet has a U-shape or a V-shape in which each magnetic pole is convex toward the inner periphery of the rotor. On the other hand, the rotor core of the rotor is formed of a laminated steel plate, and a welded portion for fixing the laminated steel plate is arranged on the outer periphery of the rotor such that the magnet piece is closest to the outer periphery of the rotor. A synchronous motor characterized in that it is a part that is in the same position.