JP2003244873A - Stator core for motor with excellent noise characteristics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stator core and a material thereof contributing to generation of low noise, in a reluctance motor particularly in a switched reluctance motor. <P>SOLUTION: A stator core of a motor is formed with a teeth part and a core back part into a separate unit, to make the teeth part demountable with respect to this core back part. The stator core for the motor is preferable, to make the teeth part consist of a magnetic iron powder molded unit and the core back part consist of an ingot flat rolled magnetic steel sheet. The ingot magnetic steel sheet is preferable to have the characteristic of Si≥0.01 mass%, plate thickness≤1.0 mm, and Hv≥105. The stator core is preferably used for the motor utilizing reluctance torque. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an iron core for rotating equipment,
In particular, the present invention relates to a stator core that is suitable for a reluctance motor and has excellent noise characteristics.

[0002]

2. Description of the Related Art In recent years, with the increasing demand for energy saving, there has been an increasing trend toward increasing the efficiency of electrical equipment. Under such circumstances, steel sheet manufacturers have attempted to improve the iron loss characteristics of electromagnetic steel sheets used for electric devices by various means.

For example, the addition of Si to electromagnetic steel sheets is
This is the most effective means of increasing the specific resistance of the steel sheet and reducing the iron loss, and is a technique widely used in the field of electromagnetic steel sheets. On the other hand, Al is also known to be an element having the same effect as Si. For example, JP-A-53-66816 discloses positive addition of Al in order to increase the specific resistance of the steel sheet and to prevent the grain growth from being suppressed by the precipitation of fine AlN. Further, JP-A-55-73819 discloses that
By adding Al and adjusting the annealing atmosphere,
A technique for reducing the internal oxide layer on the surface of the steel sheet and achieving good high magnetic field characteristics is disclosed. Furthermore, JP-A-54-68716
JP-A-58-25427 and JP-A-58-25427 disclose a technique for improving the texture and reducing iron loss by adding Al and then adding REM and Sb in combination. It is disclosed.

In addition, in JP-A-61-87823, Al is added to control the cooling rate of a steel sheet during finish annealing, and in JP-A-3-274247, Al is added and B is added. ， S
By adding b and Sn together to prevent oxynitriding, in JP-A-3-294422, Al is added and cold rolling is controlled to reduce the characteristic difference between the L and C directions of the steel sheet. By
In JP-A-4-63252, by adding Mn and Al in combination, in JP-A-4-136138, Al is added to obtain an extremely low
There is disclosed a technique of improving magnetic properties by improving texture by adding Si and adding P and Sb.

By the way, recently, in the field of rotating equipment, in addition to high efficiency, recyclability has been required. DC motor, induction motor, brushless D
Generally, in C motors and the like, conductors such as aluminum and copper or magnets are used for the iron core of the rotor. Therefore, in order to recycle the iron core, it was necessary to separate these from the magnetic steel sheet.

On the other hand, since the reluctance motor uses the reluctance torque as its driving force, the rotor portion does not need a conductor or a magnet, and can be made of only an electromagnetic steel plate. Therefore, the reluctance motor has the features that it is highly recyclable, has a simple structure, is inexpensive, and is robust, and has been studied for a long time.

On the other hand, on the other hand, it has not been put to practical use because of problems such as difficulty in controlling the rotation and large noise during rotation. However, due to recent advances in semiconductor technology and control technology, these problems have been solved and are being adopted as motors for washing machines, vacuum cleaners and the like. Furthermore, recently, reluctance motors have been reviewed for their features such as having the above-mentioned recyclability, and have attracted attention for use in rotating machines used in automobiles and the like.

[0008]

However, since the operating conditions of the reluctance motor are greatly different from those of other motors, satisfactory characteristics cannot always be obtained even if the conventionally used magnetic steel sheet is used. Further, reluctance motors for automobiles and homes are required to be even quieter, and satisfactory progress in noise reduction cannot always be achieved only by the progress of conventional semiconductor technology and control technology.

An object of the present invention is to provide a stator core that contributes to noise reduction of a reluctance motor, especially a switched reluctance motor.

[0010]

[Means for Solving the Problems] The inventors have made detailed investigations on the cause of noise and a method of reducing the noise in an actual switched reluctance motor. As a result, in order to reduce the noise, it is effective to reduce the noise by dividing the stator into a tooth portion and a core back portion, and constructing each with a material having different characteristics. The present invention has been completed by finding that a combination of an iron powder compact and a core back portion made of a molten electromagnetic steel sheet is effective.

That is, according to the present invention, in a motor stator iron core, a tooth portion and a core back portion are formed as separate members, and the tooth portion is attached to the core back portion for a motor having excellent noise characteristics. It is a stator core.

In the motor stator iron core of the present invention, it is preferable that the teeth portion is made of a magnetic iron powder compact and the core back portion is made of a molten electromagnetic steel plate.

The molten magnetic steel sheet of the present invention has Si ≧ 0.01.
It is preferable to have the characteristics of mass%, plate thickness ≤ 1.0 mm, and Hv ≥ 105.

Further, the stator core of the present invention is preferably used in a motor utilizing reluctance torque.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The inventors first obtained various commercially available switched reluctance motors and analyzed their noise characteristics. As a result, the following has become clear. A switched reluctance motor is a motor that rotates by using reluctance torque, and therefore, the smaller the air gap between the rotor teeth and the stator teeth when the rotor teeth and the stator teeth are close to each other, the smaller the rotor teeth and the stator teeth are. The difference in magnetic permeability between when the two are separated becomes large. Therefore, in the above-mentioned motor that uses the difference in magnetic permeability as the driving force, the greater the difference in magnetic permeability, the greater the rotational torque and the efficiency is improved. However, this large difference in magnetic permeability also causes a large change in the electromagnetic attractive force, increasing the amount of expansion and contraction of the stator, and as a result, increasing noise. As described above, the torque and noise of the reluctance motor are in a mutually contradictory relationship.

By the way, the above noise problem can be solved if the stator core does not expand or contract in response to a change in electromagnetic attraction force, or if the material or structure has a function of absorbing sound even if it expands or contracts. Should be. However, it is difficult to make the stator core into an iron core having a Young's modulus that does not expand or contract due to changes in magnetic permeability.

Therefore, the inventors examined the relationship between the structure of the stator core of the motor and the noise absorption performance using a switched reluctance motor rated at 300 W. As a result of the investigation and analysis, as shown in FIG. 1, a stator part which has been conventionally manufactured in an integrated structure using an electromagnetic steel plate is divided into a core back and a tooth, and these are manufactured separately. Was found to have a high noise absorption capacity. Next, we examined the materials of such core back and teeth separately, but found that using different materials gave better results than using the same material. In particular, for the core back of the stator, a normal electromagnetic steel sheet obtained by melting and rolling, that is, a molten electromagnetic steel sheet is used, while for the teeth portion, magnetic iron powder obtained by compacting magnetic iron powder. It has been found that the noise is further reduced when a molded body is used.

In this way, when the core core and the teeth are separately manufactured and the stator core formed by joining them to each other is used for the switched reluctance motor,
The reason why the noise performance is improved is considered as follows.
There are several methods for exciting the switched reluctance motor, but the one-sided excitation is the main method in which the magnetic poles of the teeth of the stator do not reverse. That is, for the iron core material, the BH loop is magnetized only above or below the so-called hysteresis loop. In this case, since the magnetization direction is not reversed and only the magnetic flux changes, the starting point in the magnetization process is the position of the residual magnetic flux density. But,
Since the motor has an air gap between the stator and the rotor, the residual magnetic flux density is not so large in an actual motor. Therefore, it has been difficult to further reduce the residual magnetic flux density.

However, according to the research conducted by the inventors, the air gap effect in the magnetic circuit is further increased and the residual magnetic flux density is reduced by making the stator part separate from the core back and the teeth. I found it to increase. That is, when the core back and the teeth are separately formed and then joined together, the change in magnetization is remarkably improved, and the noise is reduced. In particular, the presence of the divided portion of the core back and the teeth exerts the effect of absorbing electromagnetic vibration, which leads to further noise reduction.

The above-described effect of the present invention is not limited to simply forming and attaching the core back and the teeth separately, and
Further, when these are made of different materials, for example, when the stator teeth portion is a magnetic iron powder molded body, the aggregate of the iron powder, in addition to the residual magnetic flux reducing effect,
Since it also exhibits a noise absorbing effect, it is considered that further noise reduction will be achieved.

Although it is possible to use an iron powder molded body for the core back, it is preferable to use a molten electromagnetic steel sheet in order to secure the strength of the core. in this case,
For reinforcement, it is effective to apply a process such as winding an electromagnetic steel plate around the outermost peripheral portion. In addition, it is effective to embed a wire rod in the magnetic iron powder compact in the tooth portion to reinforce the strength.

Although the shape of the core is not particularly specified, the core back portion and the teeth portion of the separately formed stator core may be detachably attached as shown in FIG. The core back or the teeth portion itself may be formed by combining a plurality of pieces.

FIG. 2 illustrates an embodiment of the stator core according to the present invention. FIG. 2A shows a core back 2
On the other hand, this is an example of a structure in which a tenon having a substantially circular cross section is provided and a tenon having a substantially circular cross section is provided at the attachment end portion of the tooth portion 3 and these are fitted and joined together. This fitting form may be detachable, or may be firmly fitted by an adhesive or welding. FIG. 2B is an example of a structure in which a dovetail-shaped tenon is provided in the core back 2 and a dovetail-shaped tenon is provided at the attachment end of the tooth portion 3, and these are fitted and joined together. FIG. 2C shows an example in which the collared teeth are joined by the same joint structure as in FIG. 2A. This type of teeth has the effect of reducing spatial harmonic components. FIG. 2D shows the core back 2 itself.
An example is shown in which a plurality of pieces are used and these are joined by a tenon joint structure, and the teeth 3 are joined by the same joint structure to the core back 2.

Next, the material used for the stator core according to the present invention, particularly the core back portion, will be described. In the present invention, a molten electromagnetic steel sheet is used as the above material. It is desirable that this molten electromagnetic steel sheet contains Si in an amount of 0.01 mass% or more in order to reduce iron loss. However, excessive addition causes a decrease in saturation magnetic flux density and also impairs rollability and workability, so the upper limit is made 4.5 mass%. More preferably, it is 0.1 to 3.5 mass%.

Further, the thickness of this electromagnetic steel sheet is set to 1.0 mm or less in order to reduce iron loss under excitation accompanied by waveform distortion. If the thickness is more than this, the iron loss increases. It is preferably 0.65 mm or less.

The characteristics (workability) of this electromagnetic steel sheet are also important. That is, it is necessary to prevent sagging or crushing at the joint portion between the core back and the teeth portion, and to suppress the occurrence of burrs to suppress local distortion, thereby providing magnetic stability. As a characteristic of the electromagnetic steel sheet satisfying such requirements, Hv ≧ 105, preferably Hv: 120 to 250 is desirable.

The molten electromagnetic steel sheet may contain the following components in addition to Si. C is preferably 0.005 mass% or less so that the iron loss characteristics of the steel sheet do not cause aging deterioration. Al, like Si, is an effective element for increasing the specific resistance of steel and reducing iron loss.
% Or more. However, if its content is high,
At the time of continuous casting, the lubricity between molten steel and the mold deteriorates and casting becomes difficult, so the upper limit is preferably set to 2.5 mass%. However, when not used as a specific resistance element,
Addition of Al in the range of more than 0.01 mass% and less than 0.10 mass% hinders grain growth and deteriorates iron loss characteristics.
% Or less is preferable.

Mn also has the effect of increasing the specific resistance of steel and reducing iron loss, though not to the extent of Si and Al. Further, since it has an effect of improving hot rolling property, the lower limit is made 0.1 mass%. However, if it is contained excessively, the cold rolling property deteriorates, so the upper limit is preferably 2.5 mass%. P is also Si or Al
To a lesser extent, it has the effect of increasing the specific resistance of the steel and reducing iron loss, and also has the effect of improving the texture after cold rolling recrystallization by grain boundary segregation and improving the magnetic flux density, so addition Good. However, excessive grain boundary segregation hinders grain growth and deteriorates iron loss, so the upper limit is made 0.1 mass%. S forms precipitates and inclusions and inhibits grain growth. Therefore, S is an element that should be reduced as much as possible, and the upper limit is
It is preferably 0.01 mass%.

Sn and Sb not only improve the texture and magnetic flux density, but also suppress oxynitridation on the surface of the steel sheet and suppress the generation of surface fine grains to suppress the increase in surface hardness. , Improve punching workability. Furthermore, since it is an important element for reducing the residual magnetic flux density, it may be added. In this case, if the amount is less than 0.005 mass%, there is no effect, and if it is 0.12 mass% or more, grain growth is inhibited and the magnetism deteriorates. Therefore, it is preferable to add manually in the range of 0.005 to 0.12 mass%. Ni, Cu, Cr, etc. may be added because they are elements that increase the specific resistance, but their total amount is 10 mass%.
If it exceeds, rolling property deteriorates, so it is preferable to set the content to 10 mass% or less.

Next, a method of manufacturing the molten magnetic steel sheet and magnetic iron powder used for the stator core according to the present invention will be described. The manufacturing conditions of the magnetic steel sheet are not particularly specified,
The manufacturing method may be a combination of ordinary melting, rolling, recrystallization annealing and the like. The magnetic iron powder may be produced by any method other than transfer iron powder, atomized iron powder. In order to maintain the insulation between the iron powders and reduce the loss due to the eddy current, it is effective to subject the iron powders to an insulating coating treatment and then to perform powder compacting. This coating can be organic, inorganic,
Any of semi-organic materials may be used. The component of the magnetic iron powder may be pure iron, or the total amount of Si, Al, Mn, is 10 mass% or less in order to increase the electric resistance and reduce the eddy current loss.
It does not matter if P, Cu, Ni, etc. are added. Addition amount is 10
This is because if the mass% is exceeded, the magnetic flux density will decrease and the motor characteristics will deteriorate.

The stator iron core of the present invention which provides low noise and highly efficient motor characteristics can exert its effect more effectively when applied to a reluctance motor, especially a switched reluctance motor. The reason for this is that the noise especially in switched reluctance motors is higher than in other reluctance motors.

[0032]

Example 1 Six kinds of steel materials having symbols A to F having the composition shown in Table 1 were heated and then hot rolled.
2.5mm hot rolled sheet, then cold rolled to final sheet thickness 0.5
It was a 0 mm cold rolled sheet. After annealing the cold rolled sheet, a semi-organic insulating coating was applied to the surface. This steel plate was punched to form a stator core back of a 300 W switched reluctance motor. The hardness of each of the steel sheets was in the range of 120 to 250. The teeth of the stator core are made by punching the above steel plate, and Si: 0.1mass%, Al: 0.001mass%, Mn: 0.08mass.
%, P: 0.01 mass%, the balance was Fe, and magnetic iron powder having a composition of inevitable impurities was press-molded to prepare two types, which were then wound and then combined with a stator core back. For comparison, a conventional type stator core integrated with an electromagnetic steel plate was also manufactured.

Motor efficiency and noise were measured using these motor cores. The motor efficiency is measured using a system consisting of a torque meter, a load meter, and a power meter, and the maximum value of the motor efficiency (= output / input × 100%) is calculated by varying the number of rotations of the motor. It was The noise was measured by installing a microphone 30 cm away from the motor.

Table 2 shows the measurement results of the materials and the motor characteristics. By using the stator core having the split structure of the present invention, the motor efficiency is improved and the noise is reduced as compared with the conventional stator core integrated with an electromagnetic steel plate. In particular, the effect is remarkable when the core back part is made of molten electromagnetic steel sheet and the teeth part is made of magnetic iron powder.

[0035]

[Table 1]

[0036]

[Table 2]

Example 2 Six types of steel materials, steels A to F, having the composition shown in Table 1 were heated and then hot rolled.
2.5mm hot rolled sheet, then cold rolled to final sheet thickness
It was a cold rolled sheet of 0.35 mm. After annealing the cold rolled sheet, a semi-organic insulating coating was applied to the surface. This steel plate was punched to form a stator core back of a 400 W switched reluctance motor. The hardness of the steel sheet is
All were in the range of 120-210. On the other hand, the teeth part has Si: 0.2 mass%, Al: 0.001 mass%, Mn: 0.2 mass%,
P: 0.01 mass%, the magnetic iron powder having the composition of the balance Fe and unavoidable impurities was press-molded to be produced, wound, and then combined with the stator core back. In addition, the teeth portion was manufactured from the electromagnetic steel plate manufactured from the steel D by punching. For comparison, a conventional type stator core integrated with an electromagnetic steel plate was also manufactured. Using these motor cores, motor efficiency and noise were measured in the same manner as in Example 1.

Table 3 shows the measurement results of the motor characteristics.
In the switched reluctance motor, the motor efficiency improving effect and the noise reducing effect of the stator core iron core of the present invention are clear.

[0039]

[Table 3]

[0040]

As described above, according to the present invention,
By making the stator of the reluctance motor separate from the teeth part and the core back part, it is possible to achieve low noise and high efficiency of the motor. Furthermore, by making the teeth part a magnetic iron powder molded body and the core back part a combination of molten electromagnetic steel plates, it is possible to further reduce noise and improve efficiency. This stator is particularly effective when applied to a switched reluctance motor.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the structure of a stator core and noise.

FIG. 2 is a schematic diagram illustrating a mounting structure of a stator core.

[Explanation of symbols]

1: Stator core (iron core) 2: Core back part 3: Teeth part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Naomichi Nakamura             1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama             Shi) Kawasaki Steel Co., Ltd. Mizushima Steel Works F-term (reference) 5H002 AA04 AB01 AB06 AC01                 5H619 AA01 BB01 PP01 PP05 PP06

Claims (4)

[Claims] 1. In a stator core of a motor, a tooth portion and a core back portion are formed as separate bodies, and
A stator core for a motor that has excellent noise characteristics by attaching its teeth to the core back. 2. The stator core for a motor according to claim 1, wherein the teeth portion is made of a magnetic iron powder compact, and the core back portion is made of a molten electromagnetic steel plate. 3. The stator core for a motor according to claim 2, wherein the molten magnetic steel sheet has characteristics of Si ≧ 0.01 mass%, plate thickness ≦ 1.0 mm, and Hv ≧ 105. 4. The stator core is used in a motor utilizing reluctance torque.
The stator core for a motor according to any one of 3 above.