JP2001268868A - Switched reluctance motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide construction for achieving low noise and low vibration. SOLUTION: In a switched reluctance motor which comprises a rotor 2 having a plurality of poles 21, and a stator 1 having stator coils along with having a plurality of poles 11, a plurality of small teeth 12 are formed at the tip of each pole 11 of the rotor 2 or stator 1. Or in each pole 21 of the rotor 2, a magnetic air gap symmetrical with respect to an imaginary plane which passes the center axis of the rotor 2 and the center of each pole 21 as a reference is formed. Or the air gap has a height being a third of the height of the pole 21, along with having a width being a third of the circumferential breadth of the pole 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switched reluctance motor (hereinafter referred to as SR motor) including a rotor having a plurality of poles and a stator having a plurality of poles and having a stator winding. Abbreviated).

[0002]

2. Description of the Related Art SR motors are expected to be robust and inexpensive motors because they have a simpler structure than induction motors and permanent magnet synchronous motors.

[0003]

However, the SR motor has problems in torque ripple and noise caused by salient poles of the stator and the rotor, which hinders general use. Specifically, the radial force with respect to the torque is large, and the amount of deformation of the stator due to this force is large, which leads to an increase in vibration and noise.

Then, as a measure for reducing torque ripple, a method of finely adjusting the switching timing of the excitation phase {Ch}
arles Pollock, Chi-Yao W
u: "Acoustic Noise Cancell
ation Technologies for Switch
ched Reluctance Drives: At
tention to Mechanical Beh
aviour ", IEEE Trans. on I.C.
A. , Vol. 33, no. 2, pp. 477-
484 (1993) has been proposed, but it has a problem in versatility and has not been widely adopted.

In addition, a method of superimposing a third harmonic at an appropriate ratio on a drive current in consideration of a spatial harmonic of inductance to improve not only the torque ripple but also the torque / ampere ² is disclosed. Kosaka, Matsui:
"Consideration of improvement of current-torque characteristics of RM", see IEEJ rotating machine workshop RM-97-15 (1997).

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an SR motor having a structure capable of achieving low noise and low vibration.

[0007]

According to a first aspect of the present invention, there is provided an SR motor including a rotor having a plurality of poles, and a stator having a plurality of poles and having a stator winding. , A plurality of small teeth are provided at the tip of each pole of the rotor or the stator.

According to a second aspect of the present invention, there is provided an SR motor including a rotor having a plurality of poles, and a stator having a plurality of poles and having a stator winding. In addition, there is a symmetric magnetic air gap based on a virtual plane passing through the center axis of the rotor and the center of each pole.

According to a third aspect of the present invention, in the SR motor, the gap has a width of one third of a circumferential width of the pole.
The one having a height of 1/3 of the pole height is adopted.

[0010] In the SR motor according to claim 4, the gap has a width of 1/3 of a circumferential width of the pole.
A pole having a height 2/3 of the pole height is employed.

In the SR motor according to the present invention, the gap has a width of 2/3 of a circumferential width of the pole,
The one having a height of 1/3 of the pole height is adopted.

[0012]

According to the SR motor of the first aspect, since a plurality of small teeth are provided at the tip of each pole of the rotor or the stator, the torque is increased without changing the maximum value of the radial force so much. As a result, the ratio of torque / radial force can be maximized, and the noise and vibration of the SR motor can be reduced.

A further explanation will be given.

When the SR motor is excited, a radial force is generated together with the torque. Then, the radial force shrinks the stator, and the SR motor is deformed every time the excitation is switched, generating noise. Further, the radial force is generated in all portions where the excited stator pole and the rotor pole are opposed to each other, and the torque is generated intensively at the edge of the stator pole and the rotor pole. That is, the radial force decreases as the facing area between the stator pole and the radial pole decreases.

The noise evaluation function defined later can be improved in proportion to the increase in the number of small teeth.

Therefore, by providing a plurality of small teeth at the tip of each pole of the rotor or the stator, the edge portion can be increased to increase the torque, thereby maximizing the torque / radial force ratio. . As a result, low noise and low vibration of the SR motor can be achieved.

However, since the drive frequency required for rotation increases in proportion to the increase in the number of small teeth, it is preferable to select the optimum number of small teeth according to the purpose.

According to the SR motor of the present invention, each pole of the rotor has a symmetric magnetic gap with respect to a virtual plane passing through the center axis of the rotor and the center of each pole. Therefore, the radial force, which is a main factor for increasing the noise and vibration of the SR motor, can be reduced, and the noise and vibration of the SR motor can be reduced.

A further explanation will be given.

When the SR motor is excited, a radial force is generated together with the torque. Then, the radial force shrinks the stator, and the SR motor is deformed every time the excitation is switched, generating noise. Further, the radial force is generated in all portions where the excited stator pole and the rotor pole are opposed to each other, and the torque is generated intensively at the edge of the stator pole and the rotor pole. That is, the radial force decreases as the facing area between the stator pole and the radial pole decreases.

If a gap is provided in the rotor pole, the magnetically opposed area can be reduced equivalently, and the ratio of torque / radial force can be increased without increasing the output frequency of the driving power supply required for rotation. Can be improved. As a result, low noise and low vibration of the SR motor can be achieved.

According to a third aspect of the present invention, the gap has a width that is one-third the circumferential width of the pole and one-third the height of the pole. Therefore, in addition to the effect of the second aspect, the torque ripple can be minimized, and the radial force can be reduced by about 30%.

In the SR motor according to the present invention, the gap has a width which is 1/3 of a circumferential width of the pole and a height which is 2/3 of the height of the pole. Therefore, in addition to the function of claim 2, the torque ripple can be minimized, the radial force can be reduced by about 30%, and the weight of the rotor can be reduced, and the inertia can be reduced. The responsiveness of the motor can be improved.

According to a fifth aspect of the present invention, the gap has a width of 2/3 of the circumferential width of the pole and a height of 1/3 of the height of the pole. Therefore, in addition to the function of claim 2, the radial force is reduced by 70%.
%, And can be employed as a power source for applications where noise reduction due to radial force is particularly desired as compared with torque ripple.

[0025]

Embodiments of the SR motor according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic longitudinal sectional view showing an embodiment of the SR motor of the present invention, FIG. 2 is a schematic longitudinal sectional view showing another embodiment of the SR motor of the present invention, and FIG.
FIG. 10 is a schematic longitudinal sectional view showing still another embodiment of the motor. FIG. 4 is a schematic longitudinal sectional view showing an example of a conventional SR motor.

In the SR motor shown in FIG. 4, the number of salient poles of the rotor 2 is four and the number of salient poles of the stator 1 is six.

On the other hand, the SR motor shown in FIG.
Each of the six salient poles 11 of the stator 1 is provided with two small teeth 12 at the tip thereof, and the salient poles 21 of the rotor 2 are provided.
Is set to 10.

The SR motor shown in FIG.
Three small teeth 1 at the tip of each of the six salient poles 11
2 and the number of salient poles 21 of the rotor 2 is 1
6 is set.

Further, in the SR motor shown in FIG. 3, four small teeth 12 are provided at the respective ends of the six salient poles 11 of the stator 1 and the number of salient poles 21 of the rotor 2 is reduced to 22. Is set to

In the following description and drawings,
The SR motor shown in FIG.
4, the SR motor shown in FIG. 1 is represented by "small teeth 2" or "12-10", and the SR motor shown in FIG. 2 is represented by "small teeth 3" or "18-16". The SR motor indicated by No. 3 is represented by “number of small teeth 4” or “24-22”.

The operation of the SR motor shown in each of FIGS. 1 to 3 will be described.

First, the noise evaluation function NF is defined as follows.

Evaluation function NF = Average maximum torque / Maximum value of radial force (1) As this value increases, low noise can be expected at the same torque.

Next, the validity of the evaluation function NF will be described.

As a result of analyzing the radial force f _R and the tangential force f _T generated on the excited stator poles of the 6-4 type SR motor by the finite element method, the analysis results shown in FIG. 5 were obtained. . The range of analysis is a mechanical angle of −30 ° to + 30 °, and the total magnetomotive force is 600 A (300 A × 2 poles). The upper thick mesh line in FIG. 5 indicates the position of the stator pole, and the lower thick mesh line indicates the position of the rotor pole. It should be noted that the values of the tangential force are shown inverted to facilitate the distinction between the radial force and the tangential force.

The reference position (θ = 0 °) of the rotor is
A state in which the center of the stator pole coincides with the center of the concave portion of the rotor pole, and a rotor position of 45 ° (mechanical angle) indicates a state in which the stator pole and the rotor pole completely overlap. .

The radial force is generated at all portions of the excited stator and rotor poles facing each other, and the tangential force is generated at the edge where the stator and rotor poles overlap. You can see that.

The radial force f _{R obtained} by integrating the radial force f _R is the radial force F _R generated at the stator pole. The tangential force f _T in the rotational direction is integrated to obtain the rotor radius (= D _r / 2). And the number of excitation poles (= 2 poles) is the static torque T.

FIG. 6 shows the radial force F _R and the static torque T. FIG. 6 shows that the measured value and the calculated value of the static torque match well. Radial force could not be measured due to the structure of the rotating machine, but the static torque was also calculated from Maxwell's stress, and since the static torque was calculated accurately, the radial force was also calculated accurately. I can guess.

The power level of the radiated sound is proportional to the square of the vibration speed u of the radiating surface {Fukuda et al .: "(Japan) Society of Mechanical Engineers, Machine Noise Handbook", Sangyo Tosho (1991)}. Since the main factor of vibration speed is radial force,
The vibration velocity is measured under the condition of constant torque, and the validity of the evaluation function is examined. For comparison, 6-4 type (type with 6 stator salient poles and 4 rotor salient poles) ｛(A) in FIG.
Reference type and 12-8 type (type with 12 stator salient poles and 8 rotor salient poles) (see FIG. 8B).

The measuring device is as shown in FIG. 7. On the surface plate 30, the output shaft of an SR motor 31 is connected to a load 33 via a torque converter 32, and a piezoelectric acceleration pickup 34 is attached to the SR motor 31. The output from the piezoelectric acceleration pickup 34 is supplied to the FFT 36 through the charge amplifier 35. And the torque converter 32
Is connected to a dynamic strain measuring device 37.

The measurement points are shown in FIG.
The 60 ° range shown in FIG. 8B is divided into 1 cm squares as shown in FIG. The vibration speed at each measurement point was measured at a rotation speed of 20 rps and a torque of 15 kg · cm. No significant difference was observed at any of the measurement points, but the average of the measured values was as shown in Table 1.

[0044]

[Table 1]

The vibration speed ratio of the 6-4 type is 2.30 times that of the 12-8 type. Since the power level of the radiated sound is proportional to the square of the vibration speed u, the noise level can be calculated as 10 log (2.30) ² ≒ 7.23 from the vibration speed ratio.
It can be expected that the 12-8 type is about 7 dB lower.

Here, since the comparison is made with the torque being fixed at 15 kg · cm, the calculated value when the total magnetomotive force is 1200 A is used for the 6-4 type. In addition, in the 12-8 type 1200A, the average maximum torque is 15 kg · c.
m, and the torque when saturation is ignored is proportional to the square of the magnetomotive force. Therefore, the total magnetomotive force is 2 ^1/2 times 1
The comparison was made at 200 × 2 ^1/2 A. The calculated values are shown in Table 2 and FIG.

[0047]

[Table 2]

When the ratio of the vibration velocity in Table 1 to the reciprocal (1 / evaluation function) ratio of the evaluation function in Table 2 is almost the same, the validity of the evaluation function can be understood.

Next, the operation of the SR motor will be described.

As shown in FIG. 5, since the torque is generated at each edge portion of the rotor and the stator, it is extremely effective to increase the torque by increasing the number of poles. here,
Verify quantitatively, including the relationship with radial force.

In general, the number of teeth of the rotor with respect to the number of teeth of the stator of the concentrated winding SR motor is determined in consideration of the following conditions.

(1) Since two poles are excited symmetrically about the center, the number of rotor teeth is even.

(2) Divisors and multiples of the number of poles at which the rotor and the stator mesh with each other are not taken.

(3) (angle required per pole) ×
(Number of poles) must not exceed 360 °.

(4) It is necessary that (the width of one concave portion of the rotor tooth)> (the width of one convex portion of the rotor tooth).

In consideration of the above, the number of rotor teeth in the SR motor with six poles of the stator to be examined this time is actually obtained.

Let n be the number of small teeth per stator pole and m be the number of rotor teeth to be determined.

The total tooth width θ per stator pole (0 <θ
<60 °) is fixed, and from the conditions (3) and (4), 360n · (n−1) / (60n−θ) <m <180n / θ (2) Therefore, in this example, θ = 30 ° and condition (1)
It suffices to find m and n that satisfy Expression (1) under (2). From this, the stator tooth width [delta] _s, the rotor poles width [delta] _r is determined.

The equipment constants of the SR motor shown in FIGS. 1 to 4 are as shown in Table 3.

[0060]

[Table 3]

The torque, radial force characteristics, evaluation function, and vector diagram of the SR motor shown in FIGS. 1 to 4 when the magnetomotive force is 600 A are shown in FIGS.
(C) As shown in (D).

When the number of small teeth is increased, the torque generation section becomes narrower and the torque increases. However, it can be seen that the maximum value of the radial force does not change much.

Next, at a magnetomotive force of 600 A, 12-10
The state of occurrence of torque and radial force in each part of the model is as shown in FIG. It can be seen that the torque is generated at the stator and rotor edge portions, and the radial force is generated at the overlapping portion between the stator teeth and the rotor teeth. It should be noted that the torque is reversed for easy viewing.

When the number of small teeth increases, the edge portion increases, and the torque increases. On the other hand, the maximum value of the radial force hardly changes because the total opposing area does not change even if the number of the small teeth increases.

The maximum radial force tends to decrease slightly when the number of small teeth of the stator is increased while the magnetomotive force is constant.

From the above results, the torque increases almost in proportion to the number of small teeth of the stator poles, and the radial force generates substantially the same force. Therefore, the merit of increasing the number of small teeth of the stator is as follows. Is more effective in increasing torque than in reducing radial force. Therefore, it can be seen that under the same torque condition, a motor having a smaller number of teeth has a lower noise. However, the torque generation section becomes shorter with the rotor tooth width in proportion to the smaller teeth, and the output frequency of the drive power supply required for rotation increases. Therefore, it is necessary to select an optimum number of smaller teeth according to the purpose.

When the small teeth are provided as described above, the evaluation function NF
Is improved, but the output frequency of the driving power supply is increased. Considering that the torque is generated at the edge and the radial force is generated at the portion where the stator teeth and the rotor teeth are opposed, for example, a gap is provided at the center of the rotor teeth of the 6-4 model SR motor. A method for equivalently reducing the magnetically opposed area while securing a magnetic flux path near the edge by using the method will be discussed.

As the examination procedure, examination is performed in three stages of (1) the size of the gap shape, (2) the position, and (3) the height and the width.

The shape of the space to be provided can be geometrically determined in various dimensions. Here, in order to obtain an approximate direction, a basic shape will be examined.

FIG. 12 is an enlarged view showing the shape of the tip of the rotor teeth of the SR motor. Table 4 shows the specifications of the 6-4 model SR motor.

[0071]

[Table 4]

However, the stator pole inner diameter, rotor pole outer diameter, and yoke thickness are the same as those of the 6-4 model SR motor shown in FIG. The gap 22 (T) in FIG.
Based on the height y1 of the type A), the gap 22 (Type B) in FIG. 12B is twice as large, and the gap 22 (Type C) in FIG. 12C is three times as large as an extreme example. did. In any case, the air gap has a symmetrical shape with respect to a virtual plane passing through the center axis of the rotor 2 and the center of the rotor pole 21.

The torque, radial force characteristics, evaluation function, and vector diagram for each rotor shape in the case of a magnetomotive force of 600 A are as shown in FIGS. 13A to 13D.

As can be seen from FIGS. 13A and 13B,
The torque in the case where the gaps 22 of Type B and C are formed has a larger ripple than that of the basic model Type A. Further, the maximum radial force is reduced to about 60 to 70% of the basic model Type A in each of the models Type B and C. Above all, in the basic model Type A, the radial force smoothly changes as the rotor moves from the position where the maximum radial force is generated.

In general, as shown in FIG. 13 (D), the noise can be reduced as the vector approaches the lower right. However, when the torque ripple and the like are comprehensively considered, the basic model Type
A or model Type B is suitable for noise reduction.

Next, the relationship between the torque and the radial force when the gap 22 is moved by r in the radial direction without changing the shape of the gap 22 will be examined by taking the basic model Type A as an example. Note that the shape of the tip of the rotor tooth of the SR motor is enlarged in FIG.
4 and the specifications are shown in Table 5.

[0077]

[Table 5]

The torque, radial force characteristics, evaluation function, and vector diagram for each rotor shape when the magnetomotive force is 600 A are as shown in FIGS.

As can be seen from FIGS. 15A and 15B,
The more the air gap is located at the tip of the rotor pole, the more the torque ripple increases, but the radial force decreases.

As can be seen from FIGS. 15C and 15D,
As the air gap inside the rotor pole approaches the tip, the maximum radial force is reduced and the noise evaluation function is improved. However, in consideration of the effect of magnetic saturation, the arrangement at the pole tip has a problem.

The case where r = 3 [mm] will be described below in consideration of the torque profile shown in FIG.

(A), (B), and (C) in FIG.
It is the schematic which shows the front-end | tip shape of the rotor pole 21 in the state which was set to [mm] and changed the size and shape of the space | gap 22. In FIG. 16 (A) (Type D), the gap width X _{1 is set} to L / 3 and the height y ₁ is set to d / 3, and in FIG. 16 (B) (Type E), The width X ₁ of the gap is set to L / 3, and the height y ₁ is set to 2d / 3. In FIG. 16 (C) (Type F), the width X ₁ of the gap is set to 2L / 3, the height y ₁ is set to d / 3.

Then, the torque, the radial force characteristic, the evaluation function, and the vector evaluation in the case where the air gap shape in each rotor pole was adopted at the magnetomotive force of 600 A were obtained. (C) As shown in (D).

As can be seen from FIGS. 17A and 17B,
The influence of the air gap height on the torque and the radial force is hardly seen, and the evaluation functions and the vector diagrams are almost the same for both types D and E. However, the influence of the gap width is great, and Ty
Both the peF torque and the radial force are reduced, and the evaluation function is improved, but the torque at the same exciting current is significantly reduced.

As can be seen from FIGS. 17C and 17D, the evaluation functions of Type D and Type E are almost the same. However, Type E is excellent in terms of weight reduction of the rotor.

Although only the case where either the small teeth or the gap is provided has been described above, it is considered that an SR motor with lower noise can be obtained by using both of them.

The same low noise effect can be obtained for other combinations of pole numbers not exemplified by the method of the present invention, for example, the 8-6 type, and the strength of the rotor is increased. The same low noise effect can be obtained by filling the gap with a non-magnetic resin, for example.

[0088]

According to the first aspect of the present invention, the torque can be increased without changing the maximum value of the radial force so much, and as a result, the ratio of the torque / radial force can be maximized. This has a specific effect that the noise and vibration of the SR motor can be reduced.

According to the second aspect of the present invention, the radial force, which is a main factor for increasing the noise and vibration of the SR motor, is reduced.
A unique effect is achieved in that low noise and low vibration of the motor can be achieved.

According to the invention of claim 3, in addition to the effect of claim 2, torque ripple can be minimized.
This has a specific effect that the radial force can be reduced by about 30%.

According to the invention of claim 4, in addition to the effect of claim 2, torque ripple can be minimized,
Radial force can be reduced by about 30%.
Reduce the weight of the rotor and thus the inertia to reduce
This has a specific effect that the responsiveness of the R motor can be improved.

According to the fifth aspect of the present invention, in addition to the effect of the second aspect, the radial force can be reduced by about 70%, and as a power source for applications where it is desired to reduce noise caused by the radial force as compared with the torque ripple. It has a unique effect that it can be adopted.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing one embodiment of an SR motor of the present invention.

FIG. 2 is a schematic longitudinal sectional view showing another embodiment of the SR motor of the present invention.

FIG. 3 is a schematic longitudinal sectional view showing still another embodiment of the SR motor of the present invention.

FIG. 4 is a schematic longitudinal sectional view showing an example of a conventional SR motor.

FIG. 5 shows a radial force f generated at an excited stator pole.
And _R and tangential force f _T is a graph showing the results of analysis by the finite element method.

FIG. 6 is a diagram showing a radial force F _R and a static torque T.

FIG. 7 is a schematic diagram showing an apparatus for measuring vibration acceleration and dynamic strain.

FIG. 8 is a schematic diagram illustrating measurement points.

FIG. 9 is a diagram showing a calculation result of an evaluation function and a vector diagram.

10 is a diagram showing a torque, a radial force characteristic, an evaluation function, and a vector diagram of the SR motor of FIGS. 1 to 4;

FIG. 11 is a diagram showing distribution of radial force and torque.

FIG. 12 is a diagram showing a state in which a gap is provided in a rotor pole.

13 is a diagram showing a torque, a radial force characteristic, an evaluation function, and a vector diagram of the SR motor corresponding to each gap shown in FIG. 12;

FIG. 14 is a diagram illustrating a gap position in a rotor pole.

FIG. 15 shows the torque and radial force characteristics of the SR motor when the distance from the rotor pole tip to the air gap is changed;
It is a figure which shows an evaluation function and a vector diagram.

FIG. 16 is a diagram showing the shape of the gap in a state where the distance from the rotor pole tip to the gap is set to 3 mm.

17 is a diagram showing a torque, a radial force characteristic, an evaluation function, and a vector diagram of the SR motor corresponding to each gap shown in FIG. 16;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Rotor 11 Salient pole 12 Small tooth 21 Salient pole 22 Air gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeo Morimoto 1-5-2-2-407, Mitsuishidai, Hashimoto City, Wakayama Prefecture (72) Inventor Nobuyuki Matsui 7-12-3, Oshizawadai, Kasugai City, Aichi Prefecture (72) Invention Person Noriaki Okabe 23 Ono Shiba-cho, Sakai City, Osaka Prefecture Seiryo Dormitory A-7 F-term (reference) 5H002 AA04 AE07 5H619 AA10 BB01 BB15 PP01 PP02 PP05

Claims (5)

[Claims] A switched reluctance motor including a rotor (2) having a plurality of poles (21) and a stator (1) having a plurality of poles (11) and having a stator winding. 3. The switch reluctance motor according to claim 1, wherein a plurality of small teeth (12) are provided at the tip of each pole (11) of the rotor (2) or the stator (1). 2. A switched reluctance motor including a rotor (2) having a plurality of poles (21) and a stator (1) having a plurality of poles (11) and having a stator winding. In each of the poles (21) of the rotor (2), a symmetric magnetic air gap (22) based on a virtual plane passing through the center axis of the rotor (2) and the center of each pole (21) is provided. A switched reluctance motor comprising: 3. The air gap (22) has a width of 1/3 of a circumferential width of the pole (21) and a height of 1/3 of a height of the pole (21). The switched reluctance motor according to claim 2. 4. The gap (22) has a width of 1/3 of a circumferential width of the pole (21) and a height of 2/3 of a height of the pole (21). The switched reluctance motor according to claim 2. 5. The gap (22) has a width of ２ of a circumferential width of the pole (21) and a height of １ ／ of a height of the pole (21). The switched reluctance motor according to claim 2.