JP2008278551A - Stator core and motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stator core which enhances torque characteristics of a motor by restraining a rotating field generated by teeth of a stator effectively, thereby reducing iron loss, and to provide a motor having the stator core. <P>SOLUTION: The stator core 10 comprises an annular yoke 2 and a plurality of teeth 1, ... protruding radially inward from the yoke 2 and formed to have a predetermined height. In the teeth 1, slits 3, ... are formed to extend radially from the boundary between the yoke 2 and the teeth 1, i.e., the root of the teeth. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stator core and a motor, and more particularly, to a stator core that can effectively suppress a rotating magnetic field generated in a stator core that causes iron loss, and a motor including the stator core.

  In the automobile industry, with the aim of further improving the running performance of hybrid vehicles and electric vehicles, developments for drive motors with higher performance, lighter weight, and smaller size are in progress every day. In addition, home appliance manufacturers have no choice but to develop further miniaturization and higher performance of motors incorporated in various home appliances.

  In order to improve the motor performance, the problem is how to reduce various losses generated in the motor. For example, after electric input, copper loss due to conductor resistance loss occurs in the coil constituting the motor, and iron loss (or high frequency iron loss) due to eddy current loss and hysteresis loss occurs in the rotor and stator, Depending on these losses, motor efficiency and torque performance will be reduced. This eddy current loss is a loss caused by a change in magnetic flux density, and the hysteresis loss is a loss caused by the magnetic flux density waveform.

  By the way, the hysteresis loss described above is greatly influenced by the alternating magnetic field and the rotating magnetic field. The magnetic flux density waveform of the alternating magnetic field is a linear reciprocating waveform, whereas that of the rotating magnetic field is dispersed in the 360 degree direction. It is a waveform. Since magnetic flux density vectors other than the magnetic flux density vector in the linear reciprocating direction cause iron loss without being involved in the rotational performance of the motor, the rotational performance and torque performance of the motor are reduced by the generation of the rotating magnetic field. For example, as shown in a plan view in which a part of the stator a and the rotor b is taken out in FIG. It has been proved by experiments by the present inventors that a large amount occurs at the root portion of the tooth a in the B portion in the figure. Further, as shown in FIG. 10 based on Non-Patent Document 1, the iron loss due to the rotating magnetic field and the iron loss due to the alternating magnetic field at the time of motor rotation less than the saturation magnetic flux (the region less than 1.5 Tesla (T) in the figure) It has also been found that the former increases by 20 to 50% when compared. Therefore, how the generation of the rotating magnetic field can be suppressed in the stator leads to a reduction in iron loss, which in turn leads to an improvement in motor performance.

  As a conventional technique related to a stator core of a motor, Patent Document 1 shown below can be cited. The stator core disclosed in Patent Document 1 is provided with a slit at the tip of the tooth, and this configuration can suppress a rotating magnetic field at the tip of the tooth.

Journal of the Japan Society of Applied Magnetics, 130th Study Material (2003), “Recent Topics on Magnetic Field Analysis for Motor Performance Improvement”, Figure 16: Iron Loss under Rotating Magnetic Field JP 2003-319575 A

  According to the stator core of Patent Document 1, the rotating magnetic field generated at the tip of the teeth can be effectively suppressed. By the way, regarding the magnetic field generated in the teeth, the present inventors have obtained the time-dependent change of the magnetic flux for each part by analysis, and the results are shown in FIGS. Specifically, FIG. 11b shows a change in magnetic flux at a substantially central portion in the longitudinal direction (radial direction) of the tooth shown in FIG. 11a, and a magnetic flux change at the tip of the tooth shown in FIG. 12a (the rotor side portion of the tooth). 12b, and FIG. 13b shows the change in magnetic flux at the root of the tooth (near the boundary between the yoke and the tooth) shown in FIG. 13a.

  From FIG. 11b, in the central part in the longitudinal direction of the teeth, the magnetic flux changes in the direction along the longitudinal direction of the teeth (the y direction in FIG. 11a) while the flow direction changes with time. It shows that a magnetic field is generated.

  On the other hand, in FIG. 12b, the magnetic flux density vector at an arbitrary time swings left and right from the y direction in FIG. 12a to have an x direction component and has an 8-shaped locus. This indicates that not only an alternating magnetic field but also a rotating magnetic field (having a magnetic flux density vector other than the linear direction) is generated at the tip of the tooth, but the axial ratio (magnetic flux density x / magnetic flux density y). Is less than 0.1, the rotating magnetic field component is small.

  On the other hand, in the magnetic flux density vector shown in FIG. 13b, the locus exhibits an elliptical locus close to a circular locus. This means that the rotating magnetic field unnecessary for the rotational performance (or torque performance) of the motor is generated most in this portion. The present inventors have come to the conclusion that suppressing the rotating magnetic field in such a part leads to a reduction in iron loss and can effectively improve the torque performance of the motor.

  The present invention has been made in view of the above-described problems, and by effectively suppressing the rotating magnetic field generated in the teeth of the stator, the stator core can reduce the iron loss and improve the rotation efficiency of the motor. And a motor including the stator core.

  To achieve the above object, a stator core according to the present invention comprises an annular yoke and a plurality of teeth projecting radially inward from the yoke, and is a stator core formed at a predetermined height. A slit extending in the radial direction from the boundary between the yoke and the tooth is formed.

  The stator core of the present invention relates to a stator core applied to, for example, an inner rotor type motor, and in particular, is a stator core for the purpose of effectively reducing hysteresis loss. More specifically, hysteresis loss is reduced by changing the rotating magnetic field generated at the root of the teeth (near the boundary between the yoke and the teeth) to an alternating magnetic field, thereby improving the rotational efficiency of the motor and suppressing torque reduction. It is for the purpose.

  In order to achieve the above object, a slit extending from the boundary in the radial direction of the teeth and extending in the height direction of the stator core is formed near the root of the teeth, that is, in the vicinity of the boundary between the teeth and the yoke. It is. If the slit enters the yoke side, the magnetic flux flowing in the circumferential direction of the yoke is obstructed, so that the slit is preferably formed in the teeth. Here, as the slit to be formed, a form in which one slit is formed at the center in the width direction of the teeth, or a form in which two or three teeth are formed at regular intervals, for example, can be applied.

  Here, the stator core described above may be formed from a powder magnetic core, and may further be a steel sheet laminate formed by integrally stacking steel sheets.

  When the stator core is molded from a dust core, the dust core is obtained by pressure-molding soft magnetic powder, and the soft magnetic powder is composed of an aggregate of a plurality of soft magnetic particles. As the soft magnetic particles, metal magnetic particles covered with an insulating film are used. Examples of metal magnetic particles include iron, iron-silicon alloys, iron-nitrogen alloys, iron-nickel alloys, iron-carbon alloys, iron-boron alloys, iron-cobalt alloys, iron-phosphorous alloys. An alloy, an iron-nickel-cobalt alloy, an iron-aluminum-silicon alloy, or the like can be used. The insulating coating is formed, for example, by subjecting metal magnetic particles to phosphoric acid treatment. Preferably, the insulating coating contains an oxide. Insulating films containing this oxide include oxide phosphates such as manganese phosphate, zinc phosphate, calcium phosphate, silicon oxide, titanium oxide, aluminum oxide or zirconium oxide in addition to iron phosphate containing phosphorus and iron. Can be used. The insulating coating functions as an insulating layer between the metal magnetic particles. By covering the metal magnetic particles with an insulating coating, the electrical resistivity of the soft magnetic powder can be increased.

  On the other hand, when the stator core is formed from a steel plate, an electromagnetic steel plate, a cold-rolled steel plate, a hot-rolled steel plate, or the like can be used as the steel plate, and among them, it is preferable to use an electromagnetic steel plate. The electromagnetic steel plates and the like are laminated at a predetermined height, and the yokes of the respective steel plates are caulked and the like, so that the whole is integrally formed.

  According to the stator core of the present invention, the generation of the rotating magnetic field is effectively suppressed by the single or plural slits formed at the root portion of the tooth. Specifically, since a slit is provided at the root portion of the tooth, a plane space in which a rotating magnetic field is generated is restricted. Therefore, an alternating magnetic field flows predominantly in the tooth. As a result, the rotating magnetic field that is likely to be generated at the root portion is changed to an alternating magnetic field, whereby the hysteresis loss is reduced and the iron loss is reduced. Therefore, the iron loss due to the rotating magnetic field can be reduced as much as possible, and the motor efficiency (rotational performance) can be effectively increased.

  A preferred embodiment of the stator core according to the present invention is characterized in that when the width of the slit is t and the number of the slits is n, the expression t × n ≦ 0.5 (mm) is satisfied. To do.

  If the number of slits is too large or the slit width is too large, the interlinkage cross-sectional area of the magnetic flux in the teeth is reduced, and the torque is reduced. According to the analysis results of the present inventors, by designing the slits with the slit width and the number of slits that satisfy the above formula, it is possible to reduce the iron loss while suppressing the decrease in torque performance as much as possible. It was identified that the effect was enhanced.

  Further, according to the analysis by the present inventors, it is specified that the number of slits is preferably 3 in the above equation. That is, when t × n ≦ 0.5 (mm) and the number of slits is 3 (therefore, when the slit width is 0.17 mm or less), the torque effect reduction suppression effect and the iron loss reduction effect are the most. A high stator core can be obtained.

  Also, a preferred embodiment of the stator core according to the present invention is such that, in the stator core, L2 / L1 ≦ 0.2 when the radial length of the teeth is L1 and the radial length of the slit is L2. It is characterized by being.

  According to the analysis by the present inventors, it has been specified that the portion where the rotating magnetic field is most likely to occur is in the range of 0.2 times the tooth length from the boundary with the yoke at the root of the tooth.

  Therefore, by setting the slit length to a range that is 0.2 times the teeth length, and setting the width and number of slits to values that satisfy the above formula, it is optimal for the rotational performance of the motor, etc. A slit design can be realized.

  In addition, the motor according to the present invention is a motor having the above-described stator core, and by reducing the iron loss in the stator, it is possible to obtain a motor with improved rotational performance (motor efficiency) and high torque performance.

  Such motors of the present invention include, for example, various reluctance type (VR), permanent magnet type (PM), various motors including stepping motors including hybrid type (HB), next-generation SR motors for hybrid vehicles, It can be applied to various motors such as motors used in various home appliances and model playground equipment.

  As can be understood from the above description, according to the stator core of the present invention and the motor including the stator core, the rotating magnetic field generated in the teeth is effectively reduced by an extremely simple structure in which a slit is formed at the root of the teeth. Therefore, the rotational performance and torque performance of the motor can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are perspective views showing a part of an embodiment of a stator core of the present invention. FIG. 3 is a diagram for explaining the formation site and length of the slit, and FIG. 4 is a graph showing the analysis results regarding the slit length and the iron loss ratio. FIG. 5 is a diagram for explaining the slit width, and FIG. 6 is a graph for explaining the relationship between the slit width and the number of slits as analysis conditions. FIG. 7 is a graph showing an analysis result regarding the relationship between the number of slits and width and iron loss, and FIG. 8 is a graph showing an analysis result regarding the relationship between the number of slits and width and torque.

  FIG. 1 shows a stator core of the present invention. The stator core 10 is obtained by press-molding powder obtained by coating metal magnetic particles with an insulating coating. The metal magnetic particles include iron, iron-silicon alloy, iron-nitrogen alloy, iron-nickel alloy, iron-carbon alloy, iron-boron alloy, iron-cobalt alloy, iron-phosphorus alloy. Iron-nickel-cobalt alloys and iron-aluminum-silicon alloys can be used. In addition to iron phosphate containing phosphorus and iron, oxide insulators such as manganese phosphate, zinc phosphate, calcium phosphate, silicon oxide, titanium oxide, aluminum oxide, or zirconium oxide can be used as the insulating coating.

  The stator core 10 includes a yoke 2 that forms a ring-shaped columnar body on the outer periphery thereof, and teeth 1, 1,... Protruding radially inward from the yoke 2.

  A predetermined number of slits 3 having a predetermined length and a predetermined width are formed from the root portion of each tooth 1, that is, from the boundary between the tooth 1 and the yoke 2 in the longitudinal direction (radial direction) of the tooth. The slit 3 extends in the length (thickness) direction of the stator core.

  The method of forming the slits 3,... Described above may be a method of in-mold molding by previously providing a slit forming ridge on a molding die used when the stator core 1 is pressed. The method of shape | molding by the cutter cutting | disconnection to the teeth base part of the stator core after press work may be sufficient.

  On the other hand, FIG. 2 shows another embodiment of the stator core. The stator core 10A includes a ring-shaped yoke 2A and a plurality of electromagnetic steel plates punched out in a plan view having teeth 1A,... Projecting therefrom, and laminated at a predetermined height. In this stator core, for example, a plurality of slits 3,... Are formed at the root of the teeth. In addition, when manufacturing this stator core 10A, since the distortion has arisen in the inside at the time of the punching of an electromagnetic steel plate, it is desirable to remove this internal distortion by finally annealing.

[Analysis results on slit length and iron loss ratio]
FIG. 3 is an enlarged plan view of the teeth of the stator core 10. As shown in the drawing, a slit 3 having a rectangular plan view and a slit length of 1 is formed at the root of the tooth 1 (from the boundary point O with the yoke to the inside of the tooth). The total length of the teeth is L.

  The inventors made an analysis model of three equally spaced slits (slit width 0.17 mm) with a teeth width of 8 mm, and changed the ratio of slit length: 1 and teeth length: L in FIG. The loss ratio, that is, the reduction rate of iron loss was calculated. The result is shown in FIG. In this analysis, there was no torque fluctuation even when the ratio of slit length: 1 and teeth length: L was changed.

  From the analysis result of FIG. 4, the iron loss reduction effect is large until the slit length: 1 is about 10% of the teeth length: L, and the iron loss reduction effect reaches a peak at about 20%. When the slit length is 10% of the teeth length, the iron loss is reduced to 85%. When the slit length is 20%, the iron loss is reduced to 80%.

  Therefore, it can be concluded that the slit length is preferably set to about 10 to 20% of the teeth length.

[Analysis results on number of slits, width and iron loss ratio]
Next, the present inventors conducted analysis on the number of slits, width, and iron loss. FIG. 5 is a diagram schematically showing the slit width: t with respect to the teeth width: W and the width of the non-slit portion: w. In the analysis, W = 8 mm is set. FIG. 6 is a graph showing variations of a predetermined total slit width (one slit width: t × number of slits: n). As an assumed effective combination, a case where t × n is 1 mm ( The combinations of the number of slits and the slit width are shown for each of the graph X1), the case where t × n is 0.5 mm (graph X2), and the case where t × n is 0.3 mm (graph X3). Note that the iron loss ratio is calculated as follows: iron loss ratio = 1−0.2 × {(W−w) / W} where the iron loss reduction ratio when changing the rotating magnetic field to an alternating magnetic field is 0.2. Can be expressed as

  FIG. 7 shows an analysis result regarding the iron loss ratio when the number of slits is a variable in the above three cases.

  From the figure, it is obvious that the iron loss is the largest when there is no slit and the cross-link cross-sectional area is 100%. However, in either case, the effect of reducing iron loss is the highest when the number of slits is one. Thus, an iron loss reduction effect of about 90% of the total iron loss reduction with the number of slits up to 3 can be obtained.

  Increasing the number of slits leads to problems such as an increase in manufacturing labor and a decrease in the strength of the stator core. From this analysis result, it can be concluded that the number of slits is preferably set to about 3.

[Analysis results on number of slits, width and torque ratio]
Next, the torque corresponding to the number of slits is calculated in the above three cases, and the result is shown in FIG. It is self-evident that the torque value is maximum when there is no slit and therefore the cross-sectional area is 100%.

  As a result of the analysis, the graph X1 and the graph X2 have a high torque reduction suppression effect, and both have a slit number of 1 or more and the torque value does not change. In graph X1 (case of t × n = 0.3), the torque value is slightly over 96% of the case without slit, and in graph X2 (case of t × n = 0.5), the torque value is without slit. Of 94%.

  From this analysis result and the analysis result regarding the iron loss ratio described above, it is concluded that it is desirable to design the slit with the width and number of slits satisfying slit width: t × number of slits: n ≦ 0.5 (mm). It can be concluded that, more desirably, the number of slits is set to 3 (thus, the slit width is 0.17 mm or less).

  From the above analysis results, the rotating magnetic field is suppressed by forming slits whose length, width, and number are set to predetermined values at the root of the teeth, and as a result, iron loss is reduced to less than the saturation magnetic flux. The motor rotation performance (motor efficiency) in the magnetic flux region can be improved. Moreover, since the torque reduction inhibiting effect is high, a high torque motor can be obtained.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention. For example, it is possible to suppress both the rotating magnetic field generated at the root portion and the rotating magnetic field generated at the tip portion by forming a concave groove extending in the thickness direction of the stator core at the tip portion as well as the root portion of the tooth. Is possible. In this case, the width, length, and number satisfying the above relational expression at the root and tip of the teeth (for example, the width is 0.17 mm, the length is 0.1 or 0.2 times the teeth, and the number is 3). ) Slits and grooves.

It is the perspective view which showed a part of one Embodiment of the stator core of this invention. It is the perspective view which showed a part of other embodiment of the stator core of this invention. It is a figure for demonstrating the formation site | part and length of a slit. It is the graph which showed the analysis result regarding a slit length and an iron loss ratio. It is a figure for demonstrating a slit width. It is the graph explaining the relationship between the slit width which is analysis conditions, and the number of slits. It is the graph which showed the analysis result regarding the relationship between the number of slits, width, and iron loss. It is the graph which showed the analysis result regarding the relationship between the number of slits, width, and torque. It is a top view explaining the site | part which a rotating magnetic field produces in teeth. It is the graph which compared the iron loss by a rotating magnetic field and the iron loss by an alternating magnetic field at the time of motor rotation below saturation magnetic flux. (A) is the figure explaining the site | part of the center part of teeth, (b) is the figure which showed the time-dependent change of the magnetic flux density in the site | part of (a). (A) is the figure explaining the site | part of the teeth front-end | tip part, (b) is the figure which showed the time-dependent change of the magnetic flux density in the site | part of (a). (A) is the figure explaining the site | part of the teeth base part, (b) is the figure which showed the time-dependent change of the magnetic flux density in the site | part of (a).

Explanation of symbols

  1, 1A ... Teeth, 2, 2A ... Yoke, 3 ... Slit, 10, 10A ... Stator core

Claims (7)

A stator core comprising an annular yoke and a plurality of teeth projecting radially inward from the yoke, and molded to a predetermined height,
In the teeth, a slit extending in the radial direction from a boundary between the yoke and the teeth is formed. 2. The stator core according to claim 1, wherein when the width of the slit is t and the number of slits is n, the following expression is satisfied.
t × n ≦ 0.5 (mm) The stator core according to claim 2,
A stator core having three slits. The stator core according to any one of claims 1 to 3, wherein the following expression is satisfied, where L1 is a length in the radial direction of the teeth and L2 is a length in the radial direction of the slit.
L2 / L1 ≦ 0.2   The stator core according to claim 1, wherein the stator core is formed from a dust core.   The stator core according to claim 1, wherein the stator core is formed of a laminated steel plate.   A motor comprising at least the stator core according to claim 1 and a rotor.

Images