JPS62138051A - Rotary electric machine of permanent magnet - Google Patents

Abstract

PURPOSE:To reconcile the reduction of cogging torque with the reduction of torque ripple, by organizing field spaces with concave sections on the central sections of salient magnetic poles. CONSTITUTION:Salient poles 51-53 for windings on the side of an armature 4 are provided with auxiliary grooves 8c1-8c3, 8d1-8d3, and the grooves are arranged near the both ends of the respective salient poles 51-53. Inside two auxiliary grooves 8c1-8c3, 8d1-8d3 of each salient poles 51-53, near the central sections of the respective salient poles 51-53, concave sections 81-83 with the variation due to the outer peripheral position of magnetic permeance be tween the salient poles and permanent magnets 2 facing each other via a space 9 in the diameter direction of the outer periphery which is more relaxed than the variation of the magnetic permeance on the auxiliary grooves 8c1-8c3, 8d1-8d3 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an armature core having a salient pole structure and a permanent magnet rotating electric machine that uses permanent magnets for the field.

[Background of the invention]

Torque fluctuations in rotating electric machines with salient magnetic poles, especially brushless motors, include cogging torque caused by the winding groove between the salient magnetic poles, pulsating torque caused by the DC component of the voltage induced in one winding being not constant, That is, there is a torque ripple. As a method of reducing cogging torque, it is possible to reduce the cogging torque by providing an auxiliary groove on the surface of the salient pole to increase the order of the cogging torque.
It is disclosed in the publication No. However, this method has a problem in that the torque ripple increases due to the auxiliary groove.

[Purpose of the invention]

The present invention aims to reduce cogging 1 herk and output torque 1-le ripple in an electric motor having a salient pole structure armature core and using a permanent magnet for the field.

[Summary of the invention]

The present invention uses auxiliary grooves and auxiliary salient poles to harmonically reduce or increase the order of cogging torque components, and also reduces the field magnetic permeance inside the magnetic poles to reduce the torque ripple of the composite torque.

This achieves both a reduction in cogging torque and a reduction in 1-leak ripple, which are difficult to achieve at the same time.

[Embodiments of the invention]

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

FIG. 1 shows a cross-sectional structure of an example of a motor to which the present invention is applied. A permanent magnet field section 1 of the rotor is composed of a ring-shaped permanent magnet 2 magnetized into four poles and a yoke section 3. The armature 4 includes winding salient poles 51°52.53 and auxiliary salient poles 61, 6.
2.63, and armature parts [71, 72, 73 are wound around the winding salient poles 51, 52, 53, respectively.

Here, 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 magnet.

If this motor is a brushless motor, one winding is 71.72 mm.
．． 73 is sequentially switched depending on the position of the rotor 1 to obtain continuous rotational force.

8aH8bt+8az*sb, 8a, 8bi are winding grooves located between the salient magnetic poles. This groove arrangement is
8 ax with a spacing of 1π (therefore M=2) in electrical angle
t 8 all 88. and 8b□, 8b2, 8b.

It consists of two groups.

The above is the magnet motor to which the present invention is applied. In addition, on the outer surfaces of the salient poles 51, 52, and 53 facing the magnet 2, there are auxiliary grooves 8 having approximately the same magnetic permeance as the winding grooves.
H8Qzg 8 C3,8dl H8dz+8d is provided.

The principle of generation of cogging torque in this type of motor will be explained below with reference to FIG. 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 change is the winding groove.

In Figure 2, (a) shows the air gap magnetic flux density, (b) shows the permanent magnet magnetic poles, (c) shows the developed view of the armature in the circumferential direction, and (
d) shows the armature section when the armature section has moved by θ.

In the drawings, for the sake of convenience, the armature section is assumed to move relative to the permanent magnet magnetic pole 2, contrary to the actual situation.

In the figure, cogging torque TC can generally be expressed by the following equation.

aθ where: 0: Movement angle of the armature with respect to the permanent magnet pole E(θ): Magnetic energy of the entire air gap Meanwhile, the magnetic energy ΔE(θ) per minute body dv at any angle ψ in the air gap is: 2 μ.

= 1・B, 2 (ψ, 0)・dψ ... (2
) where μ. : Magnetic permeability of air B, (ψ, θ): Magnetic flux density of the air gap 1: Constant, therefore, the magnetic energy E(θ) of the entire air gap is E(θ)”Klf 8g2(ψ, θ)dψ ・・・(3
) Here, P: Number of permanent magnet magnetic poles.

Generally, the air gap magnetic flux density B (ψ) when 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,:B(ψ) and the following equation are defined as an energy function for the gap. (Fig. 2 (f)) S(ψ)=B”(ψ) =Σ S, (ψ) n=1 Here, S, (ψ): For the harmonics of S(ψ), (ψ) :
DC component of S, (ψ) S, : peak value of harmonic of S, (ψ) Here, the effect of the winding groove and auxiliary groove on the magnetic flux density is whether the air gap magnetic flux density above the groove decreases. Or, it may become zero. Therefore, the following function is defined in which only the position of the groove is used as a unit. (Figure 2 (e)) Here, by using a function greater than or equal to W: groove width, the existence of a groove can be determined by the following u
It can be expressed as t(θ).

ut(θ)=U(θ+α1)+u(θ+α2)+...+
u(010,)=ΣU(θ+α,)・・・・・・・・・
・・・・・・・・・・・・(7) n=1 where α0. α2...α1: Groove position level: number of grooves Therefore, the distribution of magnetic flux density including the grooves is: Bg(ψ, θ) = (1-u, (θ)) B(ψ)...(
8), and substituting equation (8) into equation (3),...
・・・・・・・・・・・・(9) is obtained. Since the first term of equation (9) is not a function of θ, (1
) clearly does not affect the cogging torque.

Therefore, the cogging torque Ta is aθ 8...
......(10), where S(ψ) represents the energy function when there is no groove, which further becomes: Therefore, the cogging torque T. As explained in Fig. 2, the energy function E(θ) shown in Fig. 2(f) is
The position function before movement (FIG. 2(e)) is represented by the fluctuation of the sum E1 of the energy functions indicating 1 and the sum E2 after movement.

Since it is difficult to directly find the fluctuation from Figure 2 (f), by further expanding equation (11), n=1 n1=
1 n=1 n1=1 n=1 n1=1 ・・・・・・・・・・・・・・・(12) Therefore, from equation (12), the cogging torque T is decomposed into each harmonic component. can do. This indicates that each harmonic component of the cogging torque is given as a variation in the sum of the groove position values of the energy function of the same harmonic.

Further, the above theory will be explained by an example using FIG. 3.

(a) is the air gap magnetic flux density Bg, (b) is the permanent magnet magnetic pole,
(c) shows the armature section with only the winding grooves.

(d) shows the groove position function, (C) and (f).

(g) shows the basic component of the energy function and the third
The harmonic component and the 6th harmonic component are shown. Here, the winding groove is composed of a group of 8a, 1aaZt8a, and a group of 8b, 8b, 8b3, which differ in phase by -π in electrical angle. for these two groups.

When applied to the fundamental wave component of equation (12), ΣSa, s
in:'1(0+αn1)n=1=constant. The first half in brackets [ ] in the above formula are grooves 8a1, 8a.

It corresponds to the group of 8a3, and the second half is) 18
This corresponds to the groups b1, 8b2, and 8b□, but the sum is constant and the cogging torque T.

does not occur.

In general, a group of three grooves with a groove spacing -M2C (M is an integer that is not a multiple of 3) produces cogging torque for the fundamental wave and 3n±1st harmonic from consideration using the same method as the above formula. It turns out there isn't.

On the other hand, if we consider the third harmonic.

Σ Sa 5in2 ・3 (θ+α, 1) n=1 =Sa, ・n−r sin 6 (θ)・・・・・・
(14) As shown in FIG. 3(f), the third harmonic of the energy distribution on each groove position becomes in phase, causing cogging.

It is effective to dispose the auxiliary grooves so that they are shifted by an amount (K is an integer) in order to eliminate the cogging torque generated by this third harmonic. As the simplest example, an auxiliary groove may be provided at the position indicated by the arrow in FIG. 3(f). As a result, equation (14) becomes . . . (15) and can be made zero. Note that the first term in equation (15) is a term for the winding groove, and the second term is a term for the auxiliary groove.

If the arrangement of the auxiliary grooves is limited to that shown in Figure 3, then
Any other position may also be used. However, the interval between the ten auxiliary grooves constituting the group shall be maintained at an electrical angle of -Mi (M is an integer that is not a multiple of 3). With this groove device, the cogging torque T becomes high order and can be reduced.

In the above arrangement of the winding groove and the auxiliary groove, the third harmonic component is removed, but the sixth harmonic component appears.

For the 6th harmonic component, the groove device shown in FIG.
...(16) This 6th harmonic component makes the group of winding grooves and auxiliary grooves different from other groups. An example of their arrangement is shown in Figure 3. Shown in (h).

In addition, as for the 9y4th wave component, if you erase the 3rd harmonic, it will disappear automatically, and the 12th harmonic will remain as the other higher order, but you can adjust the skew according to the needs of this class of harmonics. If the skew is performed as necessary, the skew can be removed with the minimum skew angle.

Next, let's look at the torque ripple of the output torque.

FIG. 2(a) shows the magnetic flux distribution in the air gap 9.

Most of the magnetic flux emitted from the field magnet 2 is at the salient pole 5.
1,52,53. and absorbed by 61, 62°63,
The effective pitch of each of the salient pole portions 51, 52, 53 is - in mechanical angle and π in electrical angle. Since the magnetic flux interlinking with the windings 71, 72, 73 is equal to the magnetic flux flowing into the salient pole parts 51, 52, 53, the effective pitch of one winding is also π in electrical angle.
I can say that.

FIG. 4 is a schematic development diagram showing the relationship between the field section and the windings 71 (or 72, 73). The field part magnet 2 is developed in a plane, and the winding 71 is equivalently replaced with a one-turn winding 71S having an effective pitch of π. Here, a current i is applied to the winding 71S.
A rotational force M is generated by the electromagnetic interaction with the field section 1. This is because its size is proportional to the current and magnetic flux density according to Fleming's left-hand rule. That is, it can be seen that the rotational force M is proportional to both ends of the effective pitch of the winding.

Each volume for changes in rotation angle θ! ? Figure 5 (a) shows the change in the difference in magnetic flux density at both ends of each effective pitch of 1,72°73.
), in this case, a constant value of current 1t112113 is applied to each winding 71, 72 . . . according to the rotation angle as shown in FIG. 5(b).
73, the rotational force M becomes as shown in FIG. 5(c). Since the variation in the rotational force when a constant current is applied is torque ripple, it becomes ΔM in FIG. 5 CC>.

As is clear from the above explanation, each winding is 71°72.73°.
If the angular width F of the flat part of the magnetic flux density difference is increased, the torque ripple ΔM will decrease.
It can also be seen that if F is reduced to approach one magnetic pole pitch, F will expand and torque ripple will decrease. The auxiliary salient poles 61゜62.63 prevent unnecessary magnetic flux from interlinking with the windings, and bring the effective pitch of one winding close to the single magnetic pole pitch of the field section. For this type of motor, the rotational force is It is also disclosed in well-known motor theory that E is proportional to the product of the induced voltage E in the winding and the main current.

That is, both of FIGS. 5(a) and (Q) can be considered by replacing them with the in-winding induced electric current E.

Furthermore, the induced voltage in the winding can be calculated using Faraday's law, which is well known to be proportional to the rate of change in magnetic flux linkage over time, or it can also be calculated by It can also be obtained using Fleming's right hand side, which assumes that, and it is common knowledge that either method will reach the same conclusion, and the induced voltage waveform will be the same waveform as the magnetic flux wave cut by the winding side.

In other words, when we replace Figures 5(a) and 5(c) with the induced voltage E, its waveform is similar to the waveform of the air gap magnetic flux reference density Bg in Figures 2(a) and 3(a). It is understandable that

Here, as mentioned above, apart from the method of reducing sittle cripple by widening the flat part F by focusing on the effective pitch of the winding,
It turns out that there is a way to reduce torque ripple by paying attention to the magnetic flux distribution waveform.

The effective torque ripple can be evaluated by the variation with respect to the average of one rotational force M. Further, it is also effective to reduce the cogging torque by increasing the order of the cogging torque. For this purpose, the flat portion F in FIGS. 5(a) and 5(c) may be partially lowered in the ΔM direction within a range in which the value does not exceed ΔM. (
(8T in Figure 5(d)) It is easy to see that it is equally effective not only for one but for multiple shapes, even for shapes other than triangles.

The method for obtaining this ΔT is based on a device on the field 1 side.
It is thought that this is due to a device on the armature 4 side.

FIGS. 6(a) and 6(b) show an embodiment on the field 1 side. In a), the magnet 2 is provided with recesses of 11°, 12°, and 13°14, respectively. (b) shows that the inner diameter and outer diameter of the magnet 2 are both centered at point 0, R, and R2 in the example shown in Figure 1. It is constructed with a radius R, (R3<R), and has depressions 21°, 22, 23, and 24 in contrast to the former example shown by the broken line.

That is, in both (a) and (b), the armature 4 (
In this case, it is considered a cylinder with a uniform surface without grooves), whereas
The gap length is configured to be large so that the magnetic permeance is smaller at the inner side of the end faces 31 and 32 of the magnet 2 than at both ends. This attempts to form a depression 8T as shown in FIG. 5(d).

This depression 11, 12, 13, 14 or 21.2
2, 23, and 24, even if each magnet has a plurality of them or whatever their shape, they are smaller than ΔM of one rotational force or the induced voltage corresponding to it, as described above, and
It is obvious that any device that generates the rotational force ΔT within the flat portion F or the induced voltage corresponding thereto may be used. However, even if it is outside the 2nd section, there is some effect as long as it is within the switching point T of the winding current i□912j 1m.

FIG. 7 shows a modification on the armature 4 side according to the present invention. There are auxiliary grooves 8 on the winding protrusions 51, 52, and 53.
cl, 8c, 8c, and 8d, 8d2
8d, which are arranged near both ends of each salient pole according to the theory described above.

The two auxiliary grooves 8 c, ~ of each salient pole 51, 52, 53
8 C3, 8d1 to 8d, inside each salient pole 51 to 5
In the vicinity of the center of 3, there is an auxiliary groove 8 C1+ 8 czp8 c, , 8 where the magnetic permian with the opposing permanent magnet 2 across the radial gap 9 on the outer periphery varies depending on the outer circumferential position.
Recesses 81, 82, and 83 are formed in shapes that are gentler than those of di, 8d, and 8d.

Based on this theory, the depression ΔT shown in FIG. 5(d) is created.

〔Effect of the invention〕

According to the above configuration, it is possible to reduce cogging torque and torque ripple, which are difficult to achieve at the same time.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of an electric motor to which the present invention is applied, Fig. 2 is an explanatory diagram of the principle of cogging torque generation, Fig. 3 is an explanatory diagram of cogging torque reduction corresponding to Fig. 1, Figs. 4 and 5. (a
) to d) and FIGS. 6(a) and 6(b) are diagrams showing the principle of torque ripple generation and reduction methods, respectively, and FIG. 7 is a configuration diagram showing one embodiment of the present invention. 1... Permanent magnet field part, 2... Permanent magnet magnetic pole, 3...
... Yoke part, 4... Armature, 51, 52, 53...
・Salient pole for winding, 61, 62.63... Auxiliary salient pole, 71
,72゜73-...armature winding, 8 alp 8 a2
e 8 a3t 8 bit8b2, 8b3... Winding groove, 8C work, 8c,, 8c3°8di, 8d2, 8
d,...Auxiliary groove, 9...Gap, 11°12.13,
14... Recess in magnet 2, 21°22.23.24
... Recess in magnet 2, 31° 32 ... End of magnet 2, 81, 82, 83 ... Salient pole for winding, 51.52.
A depression formed near the center of 53 where the magnetic permeance gradually changes.

Claims (1)

[Claims] 1. An armature consisting of a permanent magnet field part and a salient magnetic pole in which an armature winding is wound around all or a part of the salient pole, and the surface of the salient magnetic pole is In a permanent magnet machine in which an auxiliary groove is provided in a permanent magnet field part or an armature part is configured to be rotatable relative to the other, the field part is provided with a concave shape in the center of the salient magnetic pole. A permanent magnet rotating electric machine characterized in that magnetic permeance between the permanent magnet field portion and the armature is smaller inside the salient magnetic pole than at both ends of the salient magnetic pole by forming a magnetic air gap. 2. In the item described in claim 1, an auxiliary salient pole portion is provided between the main salient pole portions of the armature core so as to face the field portion, and the effective pitch of the armature winding is A permanent magnet rotating electrical machine characterized by having field poles that are almost equally pitched. 3. In the item described in claim 1, the number of field poles is P, the number of armature winding salient poles is m, the greatest common divisor of both is different from P, and the electrical angle is It has one or more groups of winding grooves with an interval of 2/3Mπ (M is an integer that is not a multiple of 3), and the electrical angle is 2/3K+π/6 (K is A permanent magnet rotating electrical machine characterized by having auxiliary grooves of the same number as winding grooves provided on the surface of a salient magnetic pole at positions separated by an integer. 4. In the product described in claim 3, one group of winding grooves and auxiliary grooves in which the distance between the winding grooves and the auxiliary grooves is separated by π/3K+π/6 is separated from the other group. A permanent magnet rotating electric machine characterized in that the permanent magnet rotating electric machine is arranged so as to be shifted by an electrical angle of L·π/2 (L is an integer) with respect to the group. 5. The device according to claim 1, wherein continuous rotational force is obtained by switching energization to a plurality of armature windings according to the position of the magnetic field, and the magnetic permeance is A permanent magnet rotating electric machine characterized in that the drop causes a depression in the composite induced voltage within the winding switching, and the depression is not smaller than the depression at the winding switching point.