JPS6158458A - Electric machine provided with permanent magnet - Google Patents

Abstract

PURPOSE:To enable the both pulsating torque and cogging torque to be reduced, by selecting various factors so that the ratio of cogging period to skew pitch of a permanent magnet section or an armature section may be fixed in the desired range. CONSTITUTION:On an electric machine wherein the greatest common divisor between the magnetic pole quantity P of a permanent magnet field magnet section 1 and the quantity m of salient poles 51-53 for windings is not P and wherein auxiliary grooves 8c1-8e3 are provided on the surface of the salient poles 51-53 for the windings, the ratio of the pitch of winding grooves 8a1-8b3 between the magnetic salient poles to the pitch of the auxiliary grooves 8c1-8e3 is shown roughly by integral numbers in the whole circumference. And if the least common multiple between the total number NR of the values and the magnetic pole quantity P of the permanent magnet field magnet section 1 is shown by L, the pitch of 1/L in the whole circumference is regarded as cogging period, and so when the skew pitch is set by 1/L in the whole circumference, various factors are selected so that the value 1/L may come to 0.5/L-1.5/L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electric machine equipped with a permanent magnet on either the fixed side or the movable side. More particularly, it relates to an electric machine having auxiliary grooves in addition to the main grooves on both sides of the salient poles in which windings are carried out.

The concept of the electric machine of the present invention includes electric motors and generators, and also includes those in which the movable side rotates relative to the fixed side and those that move in a linear direction.

[Background of the invention]

There are pulsating torques caused by electrical machines with salient poles, for example brushless and with non-constant .

In order to reduce the former cogging torque, Japanese Utility Model Application No. 50-32502 discloses that auxiliary +4s are arranged at equal intervals on the surface of the salient magnetic pole to increase the order of the cogging torque.

In order to reduce the latter pulsating torque, it is known that the salient poles or permanent magnets can be skewed by one slot angle to equalize the influence of the winding groove over the entire circumference. Since this pulsating torque changes approximately in proportion to the skew angle, it is desirable to make the skew angle as small as possible.

Unexamined Japanese Patent Publication No. 56-15 has been improved from this point of view.
There is one described in No. 3961.

In this method, main grooves for winding and magnetically equivalent auxiliary grooves are provided at equal intervals on the surface of a salient magnetic pole, and the skew angle is adjusted to match the groove spacing.

On the other hand, we inventors have conducted various studies on the skew angle of an electric machine in which the greatest common divisor of the number of magnetic poles P and the number m of salient poles for winding is different from P, and which has auxiliary grooves on the surface of the salient poles. It has been found that in machines, it is not necessary to match the skew angle to the groove spacing; in fact, it is more advantageous in terms of performance if the skew angle is smaller than the groove spacing.

[Purpose of the invention]

The present invention aims to reduce both cogging torque and pulsating torque in electrical machines with auxiliary grooves by appropriately selecting the skew angle.

[Summary of the invention]

The present invention provides a rotating electrical machine in which the greatest common divisor of the permanent magnet magnetic pole P and the winding salient pole m is different from the permanent magnet magnetic pole P, and
In electrical machines with auxiliary grooves on the surface of the winding salient poles,
The skew angle is specified as follows. The minimum skew angle for reducing cogging torque is the sum of the ratios of the pitches of the grooves between the winding salient poles and the auxiliary grooves over the entire circumference and Mt, Mz, M3...Ml. Then, the pitch of 1/L of the entire circumference becomes the cogging period. Therefore, when the pitch of the skew angle is smaller than the pitch of the winding groove and the auxiliary groove, that is, the skew pitch of the permanent magnet pole part or armature part is 1/S of the total circumference, 0.5/L<8<1 The selection of .5/L is a full feature. This selection provides a magnet motor with sufficient cogging torque and pulsating torque.

[Embodiments of the invention]

Hereinafter, the principle of the present invention will be explained with reference to the drawings.

FIG. 2 shows a cross-sectional structure of an electric motor, which is one of the objects of the present invention. In the figure, the moving side, that is, the permanent magnet field section 1 serving as the rotor is composed of a ring-shaped permanent magnet 2 magnetized into four poles and a yoke section 3.

The rotating side, that is, the armature 4 is for winding! 51,52゜53
and auxiliary salient poles 61, 62.53, and the winding salient pole 5
1, 52.53 have armature windings 71, 72.7, respectively.
3 is wound. Here, the object is a structure in which the number of poles of the so-called permanent magnet 2 and the number of salient poles for winding are 4 and 3, respectively, and the greatest common divisor thereof is different from the number of poles of the permanent magnet. If this electric motor is a brushless motor, the armature winding 7
1,72° 73 is sequentially switched depending on the position of the rotor 1 to obtain continuous rotational force.

8al * 8bt l 8a2 * ab2j 8a
318b3 is a winding groove located between salient magnetic poles;
In addition, salient poles 51° 52 for winding facing the permanent magnet magnetic pole 2
．． Auxiliary grooves 8C1°8 (11,8 et
l 8Cz l 8d2 # 8eZ *8c3.8d
3.8e3 are provided and these are arranged at approximately equal intervals including the grooves for the windings.

Below are the reasons for the cogging torque generation of this mallet motor! l!
is shown in Figure 3. FIG. 3 shows FIG. 2 expanded in the circumferential direction.

Generally, cogging torque is caused by a change in magnetic energy within the gap 9 as the permanent magnet pole 2 moves. The cause of this variation in magnetic energy is
Located in the winding groove and auxiliary groove.

In FIG. 3, (a) shows the permanent magnet magnetic poles, (b) shows a developed view of the armature in the circumferential direction, and (c) shows the air gap magnetic flux density. Although the air gap magnetic flux density generally has a trapezoidal shape, only the basic distribution is shown here. In this figure, for convenience, we will proceed assuming that the armature section 4 moves, contrary to the actual situation.

In the figure, cogging torque is generally expressed by the following equation.

Here, θ: Movement angle of the armature with respect to the permanent magnet poles E(: Magnetic energy of the entire air gap On the other hand, the microbody d at any angle ψ in the void.

The magnetic energy ΔE (θ) of this is “KIB! (ψ, θ)・dψ ・・・・・・・・・
・(2) Here, μ0: Magnetic permeability of air B, (ψ, θ): Magnetic flux density of air gap Kl: Constant In general, the air gap magnetic flux density B (ψ) in the case where there is no groove is decomposed into harmonic components and is expressed by the following equation.

Here, the peak value of the harmonic of B, 2B (ψ), and the following equation is defined as the energy function S (ψ) in the gap.

S (ψ) = 82 (ψ) = Σ S, (ψ a@1 = Σ (Km + S mm5112nψ) ・(5)
Roll l Here, S engineering (ψ): In the harmonic division of S (ψ), (ψ):
DC component of S, (ψ), s, : Peak value of harmonic of Sm (ψ) Here, the influence of the winding groove and auxiliary groove on the magnetic flux density is that the magnetic flux density on the groove part decreases or It is possible to set it to zero. Therefore, the following function is defined using only the position of the groove as a unit (shown in FIG. 3(d)).

......(6) Ox(-+,-<X where W: By using a function greater than or equal to the groove width, the existence of the groove can be expressed as the following us(
It can be displayed as θ).

u, (θ) = U (θ + αt) + u (θ + α2)...U
(θ+αn・)7 = Σ U(θ+α piece...
・・・・・・・・・(7)+I饋1 Here, C1lα2...αIl: Groove position Groove position Groove number Therefore, the distribution of magnetic flux density including the grooves is B bar ψ, θ)='(x-ut (θ) )B (ψ
) -C8) Substituting equation (8) into equation (3) gives E(θ)=Kt J' (1-ut (θ))"B"
(9+) dψ・・・・・・(9) Here, since the first term of equation (9) is not a function of θ, (1
) formula obviously has no effect on cogging torque. Therefore, the cogging torque is S (ψ) where S (ψ) indicates the energy relationship when there is no influence of the groove, and the fundamental wave, 3rd harmonic, and 15th harmonic are shown in Fig. 3 (c), (f), Shown in (g).

From the above definition, the following equation is derived.

(11) In the above equation JJ, the cogging torque can be decomposed into each harmonic component. This shows that each harmonic component of the cogging torque can be given by a variation in the sum of the groove position values of the energy function of the same harmonic.

For example, considering the cogging torque caused by the fundamental wave of the energy distribution, the value at each groove position is S11+S1□, as shown in FIG. 3(e).

813...5laff (indicated by arrows in the figure), and the total sum is constant, not a function of θ, when the grooves are arranged at equal intervals with a ratio of 1:5. Therefore, the cogging torque should be set to zero. Similarly, the second energy function
From the harmonics to the 14th harmonic, the sum is zero. However, for the 15th harmonic = na S atss
in 2.15 (θ+αl) However, α1=48°α
2=96°...9, which becomes a function of θ and produces cogging torque. As is clear from Fig. 3(g), all groove positions of the 15th harmonic are in phase, and θ
becomes a function of

As a result of the above, the frequency of shogging torque is 15X4=6
It can be found as 0. Pitch 1/S of this cogging torque =
1/60 is clearly smaller than the groove pitch of 1/15.

Therefore, by reducing the skew pitch to 1/60, the same effect can be obtained with one skew pitch smaller than 1/15. Pulsating torque can also be reduced by selecting a small skew pitch.

In general, when the number of permanent magnet poles is P and the total number of grooves nα is the same pitch and groove distribution, the order n of the energy function that causes cogging torque is as shown in Fig. 3 (g), Pπ Krc na n Therefore, n= □・K K: Any integer (however, n can be an integer) Therefore, the cogging number nrc for one revolution is H7 (=H*p
==(-K) ++p() The expression in which the numbers in parentheses are integers or more indicates that nτC is the least common multiple of the number of grooves nα and the number of permanent magnet magnetic poles P.

Therefore, the cogging frequency nTe is higher than na. The minimum necessary skew pitch S may be set to the pitch 1/L of the harmonic order n of the energy function that causes cogging torque. Therefore, by selecting this skew angle, the conventional skew pitch 1/nayp can also be selected to be small, so that the pulsating torque component can be made small.

To summarize the above, the skew pitch 1/S of the permanent magnet field or armature is the total number of grooves and the number of permanent magnet poles P.
The cogging torque can be reduced the most at the minimum skew angle when the pitch is approximately equal to the pitch 1/L of the reciprocal of the value of the greatest common multiple of . On the other hand, the skew angle is not only when the two match, but generally 0.5/L < 1/
8 (If it is 1,5/L, the effect will be produced. Fig. 1 shows the main part configuration of an embodiment of the present invention. Number of grooves na = 15
, the number of permanent magnet magnetic poles is 4, and the pitch of the skew angle is 1 of the entire circumference.
760, and the groove spacing is smaller than 1/15.

Another embodiment of the invention is shown in FIG. In the figure, i.
The configuration is the same as in FIG. 1 except for the pitch and number of grooves of the auxiliary grooves. FIG. 5 shows a principle explanatory diagram expanded from FIG. 4 in the circumferential direction. Here, the winding groove 8a1゜31)l, 8a
2 + 8bz, 8a3.8ba and auxiliary 1'
48 c 1 r act, l 8c
z l na2, 3c3.

The pitch of 8d is shown as a function of groove position in FIG. 5(d).

Although the motor configuration shown in FIG. 4 is different from that shown in FIG. 1, and the grooves are not spaced evenly, the principle of cogging is the same. Below, when the sum of the groove positions is calculated for each harmonic order of the energy key function, the basic distribution (Figure 5 (C)) Σ8tsin2(θ+a, ) = constl1l
l However, α1 to α1□ are the groove positions shown in FIG. 5(d).

Similarly, the values for the 2nd to 5th harmonics are zero (for the 3rd harmonic, see Figure 5 (as shown by 0, the groove position of V4υ and 1
Since they are at 80 degrees different positions, the sum is obviously constant).

On the other hand, regarding the 6th harmonic, the 6th harmonic (Fig. 5(f)) Σ51 sin16 (θ+am) = 125tsin 2.6 (θ+α1) 4 CO
Therefore, the frequency of the cogging torque is 24, which is the product of the harmonic order 6 and the number of poles 4, and it is sufficient to skew at a pitch of 1/24 all around the circumference. This means that the groove pitch is 60:3.
If 0:120:30:・・・・・・・・・:30 is roughly converted into an integer and set to 2:1:4:1:・・・・・・・・・=1, the value will be 24. , the least common multiple of this value and the number of poles, 24, is the cogging frequency9, and it is sufficient to skew according to this pitch. Generally, the groove pitch is α1:α2
:・・・・・・・・・：When expressed as α, convert it into an approximate integer and get Mt r Mz + Ms...
......M, the total sum Nm=ΣMn
It is preferable to perform the skewing at a period equal to the least common multiple of the permanent magnet magnetic poles P.

Although the two examples above have been shown, the idea of the present invention is not limited to the above examples, but is effective even when the number of poles, the number of grooves, the groove spacing, etc. are changed, or whether or not there are auxiliary salient poles. . In particular, according to the present invention, similar actions and effects can be obtained even when the grooves are arranged at uneven intervals in the groove positions.

〔Effect of the invention〕

As described above, according to the present invention, by selecting the minimum appropriate skew angle, both cogging torque and pulsating torque can be reduced, and an extremely high-performance electric machine can be provided. .

[Brief explanation of drawings]

FIG. 1 is a developed cross-sectional view of the main parts showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of the main parts of a brushless motor to which the present invention is applied,
FIG. 3 is a diagram illustrating the generation KW of cogging torque, FIG. 4 is a sectional view of a main part showing another embodiment, and FIG. 5 is a diagram illustrating the principle of the example shown in FIG. 4. 1... Permanent magnet field part, 2... Permanent magnet, 3...
Yoke part, 4... Armature, 51, 52.53... Salient pole for winding, 61.62.63... Auxiliary salient pole, 71°7
2.73-%, machine winding, 8a1+8az+8
a'3 l8bt +sb2. sb, ... winding groove,
8c4.8c2.謬 l 口

Claims (1)

[Claims] 1. A permanent magnet field part having P magnetic poles, and an armature part composed of salient magnetic poles having m armature windings on all or part of the salient poles. The permanent magnet pole P and the winding salient pole m having the armature winding have a structure in which the greatest common divisor is different from P, and the salient pole has an auxiliary groove on the surface, In one in which either the permanent magnet field part or the armature part moves relative to the other, the pitch ratio between the winding groove and the auxiliary groove between the salient magnetic poles is adjusted over the entire circumference. Roughly convert it into integers, M_1, M_2, M_3...M
When _n_a (na: total number of grooves), the total sum N_R
=Σ^n^a_R_=_1 When the least common multiple of M_R and permanent magnet pole P is L, and the skew pitch of the permanent magnet field or armature is 1/S of the entire circumference, 0.5/L<1/
An electric machine equipped with a permanent magnet, characterized in that S<1.5/L. 2. In the thing described in claim 1 above, N_
When the least common multiple of R and P is L, and the skew pitch of the permanent magnet field part or armature part is 1/S of the entire circumference, then 1
An electric machine equipped with a permanent magnet, characterized in that /S and 1/L have the same value.