JPH1075542A - Motor for driving compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce iron loss of a motor under conditions of high flux density by setting the thickness of silicon steel plate composing the stator core and the rotor core of a motor for driving a compressor comprising a stator and a rotor disposed oppositely through a predetermined gap at a specified dimension or below and setting the content of Si within a specified range. SOLUTION: The rotor core 2 and the stator core 9a of a motor are formed by laminating a large number of thin plates which are punched from one silicon steel plate in order to utilize the core material effectively. In this regard, a nonoriented electromagnetic steel plate of 0.35mm thick or less (e.g. 0.2mm) having content of Si in the range of 0.5-0.7wt.% is employed. This silicon steel plate can exhibit an appropriate hardness at the time of punching by combining the thickness and the content of Si appropriately and thereby the machinability is enhanced while suppressing abrasion of a punching die. Consequently, iron loss of a motor having high flux density can be decreased and power consumption of an airconditioner or the like can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for driving a compressor of a refrigerator or an air conditioner, and more particularly to a synchronous motor having a permanent magnet rotor.

[0002]

2. Description of the Related Art A general structure of a motor of this kind is shown in FIGS. 3 and 4 as a plan sectional view and a front sectional view, respectively. The stator core 2 and the rotor core 9 are formed by laminating a large number of thin plates formed by punching a silicon steel plate into a predetermined shape. And is fixed by well-known caulking clamp means 6, 11 which are fitted and fixed. A number of teeth 3 are provided in the inner peripheral portion of the stator core 2, and slots 4 are provided between the respective teeth. Is configured.

[0003] A plurality of holes provided inside the rotor core 9 are fitted with permanent magnets 10, and end plates 14 are fixed to both ends of the core 9 in the stacking direction by caulking pins 12 penetrating the core 9. Thus, the rotor 8 is configured. The rotor 8 is supported by a shaft 13 fitted into an iron core 9, and is opposed to the inner peripheral portion of the stator 1 via a predetermined gap 7 to constitute an electric motor.

[0004] The silicon steel sheet forming the stator core 2 and the rotor core 9 is a non-oriented electromagnetic steel sheet having a thickness of 0.2.
mm, 0.35 mm, 0.5 mm, 0.65 mm, etc., but in the motor for driving the compressor, the plate thickness is 0.5 mm and the Si (silicon) content is inexpensive and requires no laminating man-hour. 0.25 wt% (weight percent) is exclusively used.

The material of the permanent magnet 10 is as follows:
Ferrite magnet materials such as strontium ferrite are predominant, and the cross-sectional shape of the ferrite magnet is substantially the same as that shown in FIG. Are generally arc-shaped and the inner side is formed in a straight line, or the above-mentioned C-shaped one is mounted with the concave side facing the outer side. In addition to the permanent magnets shown in FIGS. 3 and 4 which are mounted inside the rotor core, the permanent magnets are mounted on the outer periphery of the rotor core and covered with a metal tube or the like to provide protection against scattering. Exists.

[0006]

The permanent magnet of the above-mentioned motor is selected from those having an appropriate performance in view of the relationship between the demagnetization resistance and the amount of magnetic flux, but the maximum energy product is about 4.6 MGOe.
(Mega Gauss Oersted), ferrite magnet materials used in compressor drive motors are:
Generally, those having a residual magnetic flux density of 0.4 to 0.45 T (tesla) are applied. On the other hand, Nd-Fe-B (neodymium-
In the case of a rare earth magnet material such as (iron-boron), the maximum energy product is about 30 to 40 MGOe, and a material having a residual magnetic flux density of 1.2 to 1.3 T is generally applied. Of the magnetic flux.

Conventionally, when a ferrite-based magnet material is used, the iron loss value has not been a problem because the air gap magnetic flux density of the motor is low. On the other hand, while the size is reduced, there is a disadvantage that the air gap magnetic flux density becomes high and the iron loss per unit weight becomes very large. In order to improve this problem, by increasing the Si content of the silicon steel plate as the iron core material, the electrical resistance increases and the iron loss value can be reduced. It is well known that eddy current loss in particular among iron losses can be reduced by reducing the plate thickness, for example, to 0.35 mm.

However, a commercially available plate thickness of 0.3
In the case of a high-grade silicon steel sheet having a thickness of 5 mm and a Si content of 2 wt%, the material is hardened due to a high Si content, so that the workability and continuous punching property at the time of punching are deteriorated, and the abrasion of the punching die is increased, resulting in an increase in gold. The number of mold polishing increases and the number of manufacturing steps increases, and the life of the mold is shortened. In addition, punch burrs become large due to mold wear, and dimensional accuracy is deteriorated, and eddy current loss accompanying the burrs is newly generated. Also, when the Si content is high, the magnetic flux density decreases, and when the magnetic flux density by the magnet is high, the leakage of the stator magnetic flux increases, and in order to compensate for this, the ampere-turn of the motor increases and copper loss increases. In particular, it has been difficult to apply the present invention to a motor having a high magnetic flux density using a rare earth magnet material.

Conversely, if the sheet thickness is reduced to, for example, 0.35 mm and the Si content is set to be as low as 0.2 to 0.3 wt%, which is as low as that of a conventional low-grade silicon steel sheet having a sheet thickness of 0.5 mm, Due to the softness of the material, punching distortion increases.
This punching distortion is recovered by annealing, and the hysteresis loss is reduced.However, the eddy current loss increases due to the crystal being too large. Since iron increases in proportion to the square of the frequency, iron loss tends to worsen.

In addition, a normal material having a thickness of 0.5 mm and a thickness of 0.1 mm are used.
Japanese Patent Laying-Open No. 57-156641 has proposed a structure in which high-grade materials of 35 mm are alternately laminated to obtain both effects of reducing the iron loss value and increasing the magnetic flux density. Such a configuration has the disadvantage of requiring a large number of manufacturing steps.In addition, in the case of caulking clamp means for automatically caulking and fixing each thin plate constituting the iron core in a mold at the same time as punching with a punching projection, a single Since only plate materials can be used, a method of alternately laminating different materials cannot be applied.

[0011]

SUMMARY OF THE INVENTION The present invention has a stator core and a rotor core obtained by stamping and stacking a silicon steel sheet into a predetermined shape, and a stator is formed by attaching windings to the stator core. A permanent magnet is mounted on the rotor core to form a rotor, and the stator and the rotor are arranged to face each other with a predetermined gap therebetween. Not more than 0.35 mm, and S
The i content is in the range of 0.5 to 0.7 wt%. In the case where annealing is performed on the iron core after lamination, a sufficient effect can be expected by annealing only the stator iron core. When a rare earth magnet material is used as the permanent magnet, the effect becomes more remarkable because the air gap magnetic flux density increases.

[0012]

The electric resistance is increased by reducing the thickness of the silicon steel sheet to 0.35 mm or less and the Si content to 0.5 to 0.7 wt%, and the eddy current loss is reduced. The loss is greatly reduced. Further, when punching a steel sheet having a thickness of 0.35 mm or less, the workability is set to a favorable state in order to form an appropriate hardness in which the Si content is not too hard and not too soft. Further, since the Si content is not as high as that of the conventional high-grade silicon steel sheet, the magnetic flux density does not decrease, and the ampere-turn of the electric motor is reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS By applying the present invention to an electric motor using a ferrite magnet material as shown in FIGS. 3 and 4, the workability at the time of punching an iron core is good and the iron loss is reduced. Although the above-described electric motor can be constructed, the effect of the present invention is most remarkably exhibited when a rare earth magnet material as shown in FIG. 1 is used. The electric motor shown in FIG. 1 is different from FIG. 3 only in the material and shape of the permanent magnet 10a, and the other parts are not much different. Therefore, the same or corresponding parts as those in FIG. The description of the overlapping portions will be omitted.

The permanent magnet 10a in the motor of FIG.
For example, it is preferable to use inexpensive magnets such as Nd-Fe-B magnets among rare earth magnets. In this case, since the residual magnetic flux density of the permanent magnet is 1.2 to 1.3T, the air gap magnetic flux density of the electric motor is very high. When using other rare-earth magnet materials, it is necessary to adjust the magnetic flux density of the motor to an appropriate point by appropriately changing the motor physique or the amount of permanent magnets used in accordance with their residual magnetic flux density. It is advantageous in terms of cost to configure a small physique as a high magnetic flux density.

The permanent magnet 10a is formed in a plate shape because this shape can be manufactured at a low cost. Therefore, the iron core 9a of the rotor 8a is provided with a plurality of holes having a shape capable of accommodating the permanent magnet 10a. The plurality of permanent magnets 10a are fitted into the holes,
In the case of the configuration shown in the figure, the adjacent ones are magnetized so as to have mutually different polarities to form a four-pole field. In the drawing, reference numeral 16 denotes a hole portion connected to the hole portion to prevent a magnetic flux short circuit between the poles. 11a is a laminated iron core 9a
Caulking clamp means for fixing
Is a caulking pin which penetrates the iron core 9a in the laminating direction and fixes and holds the end plates at both ends.

The stator core 2 and the rotor core 9a in the electric motor shown in FIG. 1 are formed by laminating a number of thin plates punched from the same silicon steel plate in order to use the core material effectively. As the silicon steel sheet, a non-oriented electrical steel sheet having a thickness of 0.35 mm and a Si content of 0.5 to 0.7 wt% is used. As the board thickness,
For example, it may be 0.2 mm.

The sheet thickness is 0.35 mm and the Si content is 0.5
The above-mentioned silicon steel sheet of up to 0.7 wt% has a moderate hardness that is not too hard and not too soft at the time of punching due to the combination of the sheet thickness and the Si content. The wear of the mold is small, the number of times of mold polishing, mold life, and product accuracy are 0.5 mm
A state almost equivalent to the case where the silicon steel sheet is used is obtained.
Further, the punching strain also works to recover the good state by annealing and improve the characteristics. For these effects to be expected, a necessary condition is that the Si content is in the range of 0.5 to 0.7 wt%. For example, an iron loss value W15 / at a point of 50 Hz and 1.5 T of a silicon steel sheet having a sheet thickness of 0.35 mm and a Si content of 0.55 wt%.
50 is an annealed product having a thickness of 2.5 to 3 W / Kg and a thickness of 0.5
mm, the content is significantly reduced as compared with 4.5 to 5 W / Kg in a conventional silicon steel sheet having a Si content of 0.25 wt%.
This is mainly because the eddy current loss is reduced substantially in proportion to the square of the thickness by setting the thickness of the silicon steel sheet to 0.35 mm or less, and at the same time, the Si content is set to 0.5 to 0.7 wt%. This is due to the fact that the electrical resistance is increased and the eddy current loss is reduced.

FIG. 2 shows the measured DC magnetization characteristics (BH curves) of a 25 cm Epstein specimen of a silicon steel sheet after annealing in the rolling direction and the perpendicular direction.
Is a steel sheet of the present invention having a thickness of 0.35 mm and a Si content of 0.55 wt%, a broken line b is a high-grade steel sheet having a thickness of 0.35 mm and a Si content of 2 wt%, and a dashed line c is a thickness of 0.5
mm and a conventionally used steel sheet having a Si content of 0.25 wt% are shown. As is apparent from the figure, the silicon steel sheet a in the present invention has a lower magnetic flux density because the Si content is not as high as that of the conventional high-grade steel sheet b. It is almost the same ampere turn. Therefore, even in the motor having a high magnetic flux density using the rare-earth magnet material shown in FIG. 1, the leakage of the stator magnetic flux does not increase, so that the ampere-turn does not increase extremely and the increase in the copper loss of the motor is suppressed. Will be.

Incidentally, in the case of the synchronous motor as shown in FIGS. 1, 3 and 4, since the ratio of iron loss generated in the stator core due to the field magnetic flux of the rotor is large, after the lamination, In the case where the core is annealed, a sufficient iron loss reduction effect can be obtained by annealing only the stator core 2 so that the rotor cores 9 and 9a are not subjected to annealing so as to save the manufacturing cost. It is desirable to configure.

[0020]

According to the present invention, the silicon steel plate constituting the iron core in the motor for driving a compressor is made not more than 0.35 mm in thickness and the Si content is 0.5 to 0.7 wt%.
, The mold life, product accuracy, and punching workability are not deteriorated.
A 0.35 mm steel plate or the like can be used instead of the 5 mm steel plate, and the iron loss of the electric motor can be significantly reduced, and the power consumption of an air conditioner and the like can be reduced. Also, in a motor having a high magnetic flux density, such as when a rare earth magnet material is used, an increase in copper loss can be suppressed, so that the motor has a feature of achieving downsizing and high efficiency of the motor.

[Brief description of the drawings]

FIG. 1 is a sectional plan view of an electric motor showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing DC magnetization characteristics of a silicon steel sheet.

FIG. 3 is a plan sectional view illustrating a general configuration of the electric motor.

FIG. 4 is a front sectional view of the electric motor of FIG. 3;

[Explanation of symbols]

 2 Stator core 6,11,11a Caulking clamp means 7 Air gap 9,9a Rotor core 10,10a Permanent magnet

Claims (3)

[Claims] 1. A stator having a stator core and a rotor core formed by punching and stacking a silicon steel sheet into a predetermined shape, a stator is formed by mounting a winding on the stator core, and a stator is formed on the rotor core. In a compressor driving motor in which a rotor is formed by mounting a permanent magnet and the stator and the rotor are arranged to face each other with a predetermined gap therebetween, the thickness of the silicon steel plate is set to 0.35.
mm or less and a silicon content of 0.5 to 0.7
An electric motor for driving a compressor, wherein the amount is in the range of wt%. 2. The electric motor according to claim 1, wherein the stator core is annealed. 3. The electric motor according to claim 1, wherein a rare earth magnet material is used as the permanent magnet.