JPH083188Y2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention relates to a brushless motor having a permanent magnet field and adapted to energize a rectangular wave in an armature winding.

(Prior Art) This type of motor has been widely used in recent years in drive devices for industrial robots and machine tools, and in particular, reduction of rotational ripple has been attempted.

One of the causes of the rotational ripple in this type of motor is the cogging torque due to the change of the air gap permeance due to the influence of the slot opening of the armature core. In order to deal with this, as shown in Japanese Patent Publication No. 62-185545 and Japanese Patent Publication No. 62-185546, an auxiliary groove is provided in the tooth portion of the armature core,
A configuration is considered in which the arrangement of the permanent magnet field is shifted from the equidistant arrangement.

(Problems to be solved by the invention) However, in the above configuration, since no measure is taken for the torque ripple due to the interaction between the load current and the magnetic flux, which is another cause of the rotational ripple, the cogging torque is not taken. However, even if the torque ripple can be improved to some extent, it may adversely affect the torque ripple, and the reduction of the rotation ripple is still insufficient.

Therefore, an object of the present invention is to provide a brushless motor capable of not only improving the cogging torque but also suppressing the torque ripple, thereby greatly reducing the rotational ripple.

[Configuration of Device] (Means for Solving the Problem) The brushless motor of the present invention has an armature slot number of 3P.
The armature core is skewed at a 1 / n slot pitch, and the auxiliary groove is formed at the 1 / n slot pitch in the tooth portion of the armature core, and the central angle of each magnetic pole arc of the permanent magnet field is set to The feature is that it is set to 120 {2+ (1 / n)} / P] °.

(Function) The armature core is skewed at a 1 / n slot pitch, and the auxiliary groove is formed at the 1 / n slot pitch in the tooth part of the armature core. This is equivalent to a skew with a 1-slot pitch, and the cogging torque is suppressed.

Also, by setting the central angle of each magnetic pole arc of the field to [120 {2+ (1 / n)} / P] ° for an armature core having a slot number of 3P and a skew of 1 / n slot pitch, , The induced voltage of each phase winding is a trapezoidal wave that becomes flat in the electrical angle range of 120 °, so that no torque ripple occurs between the rectangular wave current of 120 ° in electrical angle.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

The armature winding has three phases and four poles, and the number of slots is 12, which corresponds to 3P when the number of poles is P. As shown in FIG. 2, each slot 2 of the armature core 1 has a 1/2 slot pitch (n
= 1 / n slot pitch) and the auxiliary groove 4 is also formed in the tooth portion 3 at a 1/2 (1 / n) slot pitch.

On the other hand, the field magnetic pole is composed of four permanent magnets 6 fixed to the outer circumference of the shaft 5 at equal intervals, and the central angle α of each magnetic pole arc is equivalent to [120 {2+ (1 / n)} / P] °. It is 75 °.

In the above-mentioned configuration, as shown in FIGS. 3 (A), (B) and (C), each phase winding of the armature winding has a rectangular wave current of 120 ° in electrical angle according to the rotational position of the field magnetic pole. Are flowed with a phase difference of 120 ° each, which causes the shaft 5 and thus the permanent magnet 6 to flow.
Rotates. In this case, since the armature core 1 is skewed, the overlapping portion of the magnetic field of each phase winding and the permanent magnet 6 gradually increases as the permanent magnet 6 rotates, and the induced voltage rises (second (Between a and b in the figure and FIG. 3). When all the permanent magnets 6 correspond to the magnetic fields of the windings of each phase, the induced voltage has a maximum constant value (b in FIG. 2 and thereafter, b → c in FIG. 3). After that, when the overlapping portion of the permanent magnet 6 and the magnetic field of each phase winding gradually decreases, the induced voltage decreases (between c and d in FIG. 3). Therefore, a trapezoidal wave-shaped induced voltage (see D, E, F in FIG. 3) is induced in each phase winding.
However, the arrow a in FIG. 2 indicates the direction of rotation of the permanent magnet 6.

In the armature core 1 having the number of slots of 3P and the skew of 1 / n slot pitch, one slot pitch is an electrical angle expressed by the formula (A). Therefore, the skew angle θ _S of the 1 / n slot pitch (see FIG. 2) is the electrical angle as shown in equation (B).

However, electrical angle = (P / 2) × mechanical angle.

(360 ° / 3P) × (P / 2) = 60 ° …… (A) θ _S = (1 / n) × 60 ° …… (B) Also, the polar arc angle of the permanent magnet 6 is α in mechanical angle. If
The polar arc angle of the permanent magnet 6 is an electrical angle (P · α / 2). Therefore, the upper side of the induced voltage in the trapezoidal wave (b → c)
Is expressed by the following equation (C).

b → c = P · α / 2−θ _S = P · α / 2−60 ° / n (C) When formula (C) is rearranged with respect to α, formula (D) is obtained,
Substituting b → c = 120 ° into equation (D) and rearranging (E)
The formula is obtained. Then, by substituting n = 2 and P = 4 into the equation (E), α = 75 ° is obtained.

α = (2 / P) (b → c + 60 ° / n) …… (D) = [120 {2+ (1 / n)} / P] …… (E) Then, the central angle of the magnetic pole arc of the permanent magnet 6 Is set to 75 °, an induced voltage as shown in (D), (E), and (F) of the same figure is induced in each phase winding. Since this induced voltage waveform is a waveform corresponding to the field magnetic flux interlinking each phase winding,
It is clear that each phase torque based on the interaction between the field magnetic flux and each phase current is as shown in (G), (H) and (I) of the same figure. Therefore, the combined torque output from the shaft 5 is a constant torque that does not include ripples, as shown in FIG.

On the other hand, since the armature core 1 is skewed with a 1/2 slot pitch, and the tooth portion 3 is also formed with the auxiliary groove 4 with a 1/2 slot pitch, as shown in FIG. The air gap permeance seen from the magnetic pole is equivalent to one slot skew, and cogging torque is not generated.
Therefore, in addition to suppressing the torque ripple as described above, the generation of cogging torque can also be suppressed, so that the rotation ripple can be sufficiently suppressed.

In the above embodiment, the skew of 12 slots and 1/2 slot pitch is shown, but the present invention is not limited to this, and the skew of 1/3, 1/4, 1/5 ... Can also be applied to the case of 1 / 3,1 / 4,1 / 5 ……
It is sufficient to form auxiliary grooves having a slot pitch of, and set the center angles of the magnetic pole arcs to 70 °, 67.5 °, 66 °, ... Also, 6
The same configuration can be applied to the case of 18 poles, 8 poles, 24 slots, 10 poles, 30 slots, etc.

[Advantage of the Invention] As described above, the present invention eliminates the torque ripple between the induced voltage of each phase winding as a trapezoidal wave that becomes flat in the electrical angle range of 120 ° and a 120 ° rectangular wave current. In addition, it is possible to make the change of the permeance of the air gap equivalent to the skew of one slot pitch and suppress the cogging torque, so that it is possible to significantly reduce the rotational ripple.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a longitudinal sectional view, FIG. 2 is a developed view of an armature core, and FIG. 3 is a waveform diagram showing current, voltage and torque of each phase. In the drawing, 1 is an armature winding, 2 is a slot, 3 is a tooth portion, 4
Is an auxiliary groove, and 6 is a permanent magnet.

Claims (1)

[Scope of utility model registration request] 1. A permanent magnet field and a three-phase P-pole armature winding, wherein a rectangular wave current of 120 ° in electrical angle is passed through each phase winding of the armature winding. In the above, the number of armature slots is set to 3P, and the armature core is skewed at a 1 / n slot pitch, and the auxiliary groove is formed at the 1 / n slot pitch in the tooth portion of the armature core. A brushless motor characterized in that the center angle of each magnetic pole arc is set to [120 {2+ (1 / n)} / P] °.