JPH088764B2 - Permanent magnet field type brushless motor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a permanent magnet field type brushless motor.

[Background of the Invention]

Small motors for audio equipment such as VTR capstan motors are desired to have high output and small cogging torque. In general, most of the motors of this type are coreless type motors having no salient poles, but coreless motors have no cogging torque, but have a problem that it is difficult to obtain a large output motor. On the other hand, the core type is easy to obtain a high output, but has a drawback that the cogging torque becomes large because it has saliency. In order to improve the cogging torque in a core type motor, it is disclosed in Japanese Patent Publication No. Sho 49-8568 that the number of permanent magnet poles is made larger than the number of salient pole magnets.

The cogging torque is a pulsating torque that is the least common multiple of the number M of salient poles and the number P of permanent magnet magnetic poles per rotation, and the magnitude of cogging torque is inversely proportional to the number of pulsations.

A conventional permanent magnet rotor type brushless motor of this type will be described with reference to FIG. 4 and Table 1. The stator 1 has salient pole poles 3 in which armature windings 29 are intensively wound around the outer circumference.
Is provided. On the outer periphery of the stator 1, a rotor 6 having permanent magnets 4 magnetized into N and S at equal intervals and a yoke 5 for passing magnetic flux
Is rotatably supported via a gap. Japanese Patent Sho 49
In the example of No. 8568, the pulsation number of the cogging torque is increased by setting the relationship between the number P of permanent magnet magnetic poles of the m-phase configuration and the number M of salient poles to P: M = m + 2: m + 1.
It is proposed to reduce the magnitude of cogging torque. Further, the armature winding 2 is intensively wound around the salient pole 3 to improve winding workability.

Table 1 shows three phases and the number P of permanent magnet magnetic poles and the number M of salient poles.
When the ratio of P is P: M = 4: 3, the pulsation number of cogging torque and the winding utilization rate are summarized. The number of permanent magnet magnetic poles P is 16 and the number of salient poles M is
In the 12 examples, the pulsation number of the cogging torque reaches 48, and a small cogging torque can be obtained. Also mechanically 90
Since the salient pole magnetic poles 3 having a phase of 3 degrees are electrically in phase, the utilization factor of the armature winding 2 is good, and further, the pulsation of the induced voltage, which is a factor of the pulsating torque, can be reduced. ing.

However, in this type of motor, further reduction of cogging torque and improvement of utilization efficiency of the armature winding are desired.
The cogging torque can be reduced by increasing the number of phases m, but in the brushless motor, the number of magnetic pole position detection elements and switching elements of the rotor used for controlling the armature winding current increases. However, the structure becomes complicated and expensive. In order to improve the utilization rate of the armature winding 2, there is also a method of providing an auxiliary salient pole having no armature winding between the salient pole magnetic poles 3 so that the armature winding utilization rate becomes 1.
If a large number of auxiliary salient poles are provided, the workability of winding is reduced, and the number of grooves between the auxiliary magnetic poles is increased, which causes a cogging torque to increase.

[Object of the Invention]

An object of the present invention is to provide a permanent magnet field type brushless motor having a simple structure, a small cogging torque, and a relatively large output.

[Outline of Invention]

According to the present invention, the relationship between the number P of permanent magnet magnetic poles of the permanent magnet field and the number M of salient poles of the stator is set to P: M = 6n ± 2: 6n (where n is an integer of 2 or more). , Improved winding coefficient (improved output)
While reducing the magnitude of the cogging torque.

Example of Invention

 An embodiment will be described with reference to FIGS. 1 and 2.

The stator 1 is provided with twelve salient poles 3 on the outer circumference, and the armature windings 2 are concentratedly wound around the salient poles 3.
The number of salient poles 3 corresponding to 1 is 4, and salient poles 3 _U1 , 3 _U2 , 3 _U3 ,
The armature winding 2 wound around 3 _U4 is connected to the same phase to form the U phase. That is, as the U-phase is based on the salient pole center 3 _U1 (can be set to any), an electrical angle 180K (K is an integer) ~180K + 60 degrees less than the range of salient poles 3 wound on of the armature Consists of winding 2. V and W phases are salient poles 3 _v1 and 3 _w1 mechanically separated from the U phase magnetic pole by 120 degrees and 240 degrees (-120 degrees).
The armature windings (not shown) wound around the salient pole magnetic poles 3 in the range of 180K to less than 180 + 60 degrees.

The permanent magnet rotor 6 is alternately magnetized into N and S, is arranged inside the yoke 5, and faces the salient poles 3.
It is equipped with 14 permanent magnet magnetic poles 4.

According to the permanent magnet field type brushless motor as described above, the cogging torque pulsation number per rotation is 84, which is the least common multiple of 14 permanent magnet magnetic poles and 12 salient pole magnetic poles, and the cogging torque is reduced. It

On the other hand, regarding the winding utilization factor (winding coefficient), the short pitch winding coefficient is cos30 / 2 = 0.966, and the coefficient due to the distribution of salient poles is also cos30 / 2 = 0.966.
66 = 0.933, which is better than the conventional one. Similar results can be obtained by setting the number of permanent magnet magnetic poles P to 10 and the number of salient pole magnetic poles M to 12.

Further, the salient poles 3 of the same phase, for example, 3 _U1 , 3 _U2 , 3 _U3 , 3 _U4
Are distributed, and the induced voltage of the armature winding 2 wound around this is close to a sine wave. Therefore, the induced voltage is controlled by applying a sine wave current suitable for this. There is an effect that the torque pulsation due to the voltage harmonic component is corrected.

In the above, the case where M is 12 and P = M ± 2 is taken as an example, and it is stated that the cogging torque and the winding coefficient are comparable to each other. It will be described below that an effect peculiar to the brushless motor, which is not described above, can be obtained as compared with the case of making it larger.

In the brushless motor, the current is distributed to the three-phase windings based on the signal from the position detection element of the permanent magnet magnetic pole provided every 120 electrical degrees, but the mounting error of the position detection element ( As for the influence on the control accuracy by every 120 degrees, the smaller the number P of the magnetic poles of the permanent magnet is, the smaller the error in the electrical angle is. Therefore, the torque ripple generated by this error can be reduced.

Table 2 shows the number of permanent magnet magnetic poles P in the vertical direction and the number M of salient poles in the horizontal direction, and shows the pulsation number of the cogging torque and the winding coefficient for the combination of the two. The winding coefficient is the product of the short pitch winding coefficient and the distributed winding coefficient. The fractional winding coefficient is calculated by sin (90P / M), and the distributed winding coefficient is calculated from the distribution of salient poles of the same phase. In the case of a conventional motor of this type, M = (3/4) P
Alternatively, at M = (3/2) P, the distributed winding coefficient is 1, but the short winding coefficient is 0.866.

From Table 2, the number P of permanent magnet magnetic poles and the number M of salient poles can be calculated as (2 /
3) If M <P <(4/3) M, it is clear that both the cogging torque and the winding coefficient are improved. But M
In case of = P, it is necessary to satisfy M ≠ P because three-phase connection cannot be made.

In the example of Table 2, when P = M ± 1, M = 3 m (where m is an odd number larger than 2), the pulsation number of cogging torque is the largest and the torque pulsation is the smallest.

In FIG. 3, the number P of permanent magnet magnetic poles is 16, and the number M of salient poles is 15.
As shown in Table 2, this combination has better cogging torque pulsation rate and winding coefficient than any combination. However, it can be seen that the decreasing tendency of the winding coefficient increases as P increases. In the figure, a winding method different from those of FIGS. 1 and 2 up to now is described as the armature winding method regardless of the combination of P and M. The salient poles 3 around which the armature windings 2 of the same phase are wound are unevenly distributed in one place, so that a voltage imbalance is likely to occur between the phases unless the air gap lengths are made uniform.

On the other hand, in the example shown in Table 2, by setting the relationship between the number P of permanent magnet magnetic poles and the number M of salient poles to be 6n ± 2: 6n (where n is an integer of 2 or more), the pulsation number of cogging torque is increased. , The armature windings 2 wound around the salient poles 3 at mechanically different positions by nearly 180 degrees can be selected in the same phase, so that it is possible to obtain a motor in which the influence of air gap imbalance is small.

The winding coefficient becomes the largest when the armature winding 2 wound around the salient pole 3 located in the range of 180K + 0 to 60 degrees (K is an integer) in electrical angle is connected as an in-phase. 2 shows the best winding coefficient based on this idea.

Although the above embodiment has been described on the assumption that the armature winding 2 is wound around all the salient poles 3, part of the salient poles 3 is an auxiliary salient pole (the armature winding is not wound). ) Is also possible.

The present invention can also be applied to a linear motor. In this case, the width 1 / P of the permanent magnet and the width 1 / M of the salient poles are set to 2/3 <P / M <4/3.

〔The invention's effect〕

As described above, according to the present invention, by appropriately selecting the relationship between the number P of permanent magnet magnetic poles and the number M of salient poles, the permanent magnet having a small cogging torque while improving the winding coefficient (improving the output). A field type brushless motor can be provided. Furthermore, by selecting in-phase the armature windings that are wound around salient poles at mechanically different positions (symmetrical positions) about 180 degrees from the center of the motor, the influence of air gap imbalance is reduced and vibration is reduced. Can provide a small motor.

[Brief description of drawings]

1 and 3 are side views of a motor showing each embodiment of the present invention, FIG. 2 is a development view of the motor shown in FIG. 1, and FIG.
The figure is a side view of a conventional motor. 1 ... Stator, 2 ... Armature winding, 3 ... Salient pole magnetic pole, 4 ... Permanent magnet magnetic pole, 6 ... Rotor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Konno 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Taga factory (56) Reference JP-A-54-72410 (JP, A)

Claims (1)

[Claims] 1. A permanent magnet field having P permanent magnet magnetic poles arranged at equal intervals, M salient pole magnetic poles arranged at equal intervals, and concentratedly wound on the salient pole magnetic poles. An armature having armature windings connected in three phases, and a permanent magnet that generates torque in the permanent magnet field by controlling the armature winding current according to the moving position of the permanent magnet field. In the field type brushless motor, the relation between the number P of permanent magnet magnetic poles and the number M of salient poles is set to P: M = 6n ± 2: 6n (where n is an integer of 2 or more). Magnet field type brushless motor.