JPH0614778B2 - Pulse motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a pulse motor used for driving a joint of a multi-joint type robot or the like.

[Conventional technology]

A drive system using a DC motor and a speed reducer is often used in applications that require high torque at low speed, such as joint drive of an articulated robot. However, DC
Considering the life of the motor brush and reducer, the maintenance of the lubricating oil, and the like, it is desirable that the joint of such a robot be directly driven by a brushless motor.
Further, since the torque generated by the motor is proportional to the square of the magnetic flux density in the gap between the stator and the rotor, it is advantageous to use a pulse motor having a larger magnetic flux density due to its structure.

The applicant of the present application has already applied for a pulse motor as shown in FIG. 7 as a pulse motor that is lightweight and capable of generating high torque for use in such applications (Practical application Sho 58-79109). ). This is to reverse the positional relationship between the stator and the rotor in the conventional pulse motor to form an outer rotor type, and to arrange the permanent magnet on the rotor side and the stator side in the related art.

In the figure, FIG. 7 (A) is a front view and FIG. 7 (B) is a sectional view. In the figure, 1 is a magnetic body 11, 12 and a permanent magnet 13.
The stator 2 made up of is a rotor arranged outside the stator 1. The magnetic bodies 11 and 12 have salient poles 11 on their outer circumferences.
Has ₁ to 11 _8, 12 ₁ to 12 ₈ is joined on both sides so as to sandwich the permanent magnet 13. Similar teeth are provided on the inner circumference of the rotor 2 so as to face the teeth provided on the salient poles 11 _{1 to} 11 ₈ and 12 _{1 to} 12 ₈ . In addition, these salient poles 11 _{1 to} 11 ₈ and 12 _{1 to} 12 ₈ have permanent magnets.
For each pair facing through 13 (11 ₁ and 12 ₁ , 11 ₂ and 12 ₂ ,
Excitation coils 14 _{1 to} 14 ₈ are wound around (...). Each of these exciting coils is four (14 _{1 to} 14 ₄ and 14 _{5 to} 14 ₈ )
It is connected in series.

Here, assuming that the pitch of the teeth in the rotor 2 is P, the salient poles 11 _{1 to} 11 ₈ and 12 _{1 to} 12 ₈ of the magnetic bodies 11 and 12 are also provided with teeth at the same pitch P, and the same magnetic property. The teeth of adjacent salient poles (eg, 11 ₁ and 11 ₂ ) of the body are offset from each other by P / 4. In addition, the two magnetic bodies 11,
There is a phase shift of P / 2 between each tooth of the 12 opposing salient poles (eg, 11 ₁ and 12 ₁ ).

In the pulse motor configured as described above, if currents having a 90 ° phase shift are applied to the exciting coils 14 _{1 to} 14 ₄ and 14 _{5 to} 14 ₈ , the magnetic flux generated by the permanent magnet 13 and the exciting coil 14 ₁
And the magnetic flux due to 14 ₈ are added or subtracted alternately in the gap between the stator 1 and the rotor 2, to generate a torque on the rotor 2 rotates it. This rotation direction is determined by the advance or delay of the phase of the exciting current, and can be arbitrarily switched by controlling the phase relationship.
Further, since the rotor 2 is provided outside the stator 1, the radius of the tooth portion of the rotor 2 can be increased, and a much larger torque can be obtained as compared with a motor of the same volume.

[Problems to be solved by the invention]

However, in the pulse motor having such a configuration, when the rotor 2 is rotated, the torque acting on the rotor 2 does not change sinusoidally but has some distortion.

FIG. 8 shows how the torque acting on the teeth of the stator changes with the relative position of the teeth of the rotor. Ideally, this torque characteristic changes sinusoidally, but in reality, it has a distorted waveform as shown in the figure due to the non-linearity of the magnetic path.

Since the torque acting on one salient pole is the sum of the torques acting on all the teeth provided on that salient pole, the torque acting on one salient pole is applied to the salient pole side as in the pulse motor shown in FIG. In the case where the pitch of the teeth to be provided is equal to the peach of the teeth on the rotor side, all the teeth in one salient pole face the teeth on the rotor side in the same phase relationship, The same torque is applied to all teeth, and the torque is added. Therefore, the torque characteristic at the salient pole becomes equal to the torque characteristic at one tooth as shown in FIG.

Such a distortion of the torque characteristic in the salient pole causes a pulsating torque generated when the rotor 2 is rotated, and when the permanent magnet 13 is used in the exciting circuit, this distortion becomes larger. Therefore, the holding torque characteristic of the motor as a whole is significantly distorted. In the pulse motor used in the robot, it is necessary that the motor rotates smoothly, and the presence of such pulsating torque is not preferable.

An object of the present invention is to eliminate the drawbacks of the conventional device as described above, eliminate the pulsating torque accompanying the rotation of the rotor, and realize a pulse motor that can smoothly rotate the rotor with a simple configuration. It is what

[Means for solving problems]

The pulse motor of the present invention is designed to prevent the generation of pulsating torque by devising the pitch of the teeth provided on the salient poles on the stator side. In detail, changing the arrangement (phase) of the teeth provided in one salient pole, paying attention to the fact that the torque characteristics in each tooth as shown in FIG. 8 can be decomposed into higher harmonic components. By applying the harmonic components of torque to each tooth in different phases, this harmonic component is canceled out from the torque acting on the salient pole as the sum of the torques acting on each tooth, and This is to eliminate the resulting pulsating torque.

[Work]

In this way, by canceling the torque of the harmonic component that acts on the salient poles on the stator side between the teeth with different phases, the torque characteristics of salient poles that were conventionally distorted can be made sinusoidal. The rotation can be smoothed.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the pulse motor of the present invention. In the figure, FIG. 1 (A) is a front view and FIG. 1 (B) is a sectional view. In the figure, components similar to those in FIG. 7 are designated by the same reference numerals. The pulse motor shown in the figure is one in which the permanent magnet on the stator side is eliminated by using a three-phase excitation method. Therefore, the number of exciting coils is 6, and two exciting coils (14 ₁ and 1
4 ₂ , 14 ₈ and 14 ₄ , 14 ₅ and 14 ₆ ) are respectively connected in series or in parallel to form a three-phase excitation circuit.
Further, if the pitch of the teeth on the rotor 2 by P, is provided with similar teeth on the salient poles 11 ₁ to 11 ₆ of the magnetic body 11,
The teeth of adjacent salient poles (for example, 11 ₁ and 11 ₂ ) are provided with a phase shift of P / 3 from each other.

Here, the pitch (arrangement state) of the teeth provided on one salient pole is determined as follows.

FIG. 2 shows the torque characteristic of FIG. 8 divided into high-order harmonic components. Here, only the harmonic components up to the third order are shown. As shown in the figure, if the state where any tooth on the salient pole on the stator side completely faces the tooth on the rotor is the state of 0 phase, this tooth will rotate by P / 2. The torque shown in the figure acts.
At this time, the secondary and tertiary torque components cause pulsating torque.

Now, assuming that the number of teeth provided on each of the salient poles 11 _{1 to} 11 ₆ is 4, with reference to the tooth pitch P in the rotor 2,
A phase shift of P / 4 is provided between the first tooth and the second tooth and between the third tooth and the fourth tooth to form two pairs. Here, focusing only on the second-order harmonic component of the torque acting on the first to fourth teeth, the magnitude of the second-order harmonic component of the torques T1 to T4 acting on these four teeth is the first. The relationship is as shown in FIG. Note that FIG. 3 shows the relationship of the generated torque based on the tooth phase difference as a positional relationship on the characteristic curve. As is clear from the figure, the torque T1 acting on the first tooth and the torque acting on the second tooth
T2 has the same magnitude and opposite direction to T2, and the combined torques acting on the salient poles provided with the first and second teeth cancel each other out and become zero. The same can be said between the torque T3 acting on the third tooth and the torque T4 acting on the fourth tooth. That is, when the four teeth are arranged in the above relationship, the second harmonic component of the generated torque can be canceled in each pair.

Next, if the phase shift between each pair is P / 6 while keeping the phase relationship in each pair as it is, the torque T1
The relationship between the magnitudes of the second harmonic components of T4 is as shown in FIG. Here, as in the case of FIG. 3 described above,
It can be seen that the second harmonic component can be canceled. In addition, focusing on the third harmonic component of the torque acting on each tooth in such an arrangement, the relationship between the harmonic components of the torques T1 to T4 acting on each tooth is as shown in FIG. There is. As is clear from the figure, in this case, the torque T1 acting on the first tooth and the torque T3 acting on the third tooth are equal in magnitude, opposite in direction, and cancel each other out. The torque T2 acting on the teeth and the torque T4 acting on the fourth teeth cancel each other out, and by arranging each tooth in this way, the third harmonic component can be made zero.

Thus, based on a pair of two teeth having a phase shift of P / 4 (combination state), and arranging two pairs in such a state with a phase shift of P / 6, each tooth The second- and third-order harmonic components of the torque acting on the torque can be canceled out with each other, and the torque characteristic at the salient pole, which is the sum of these torques, can be approximated to a sine wave. Therefore, the rotor can be smoothly rotated by the exciting currents having different phases,
A pulse motor suitable for driving a robot joint can be obtained.

FIG. 6 is a block diagram showing an example of the state of the teeth whose phase relationship is defined as described above. In the figure, S1 to S4
Are four teeth provided on the salient pole 11 ₁ , and here S1
Corresponds to the first tooth, similarly, S2 corresponds to the third tooth, S3 corresponds to the second tooth, and S4 corresponds to the fourth tooth. That is, the tooth S4 (fourth tooth) has a phase shift of P / 4 with respect to the tooth S2 (third tooth) and the phase shift of P / 6 with respect to the tooth S3 (second tooth). have. Adjacent salient poles 11 ₂ have the same tooth arrangement as salient poles 11 ₁ and are disposed with a phase shift of P / 3 with respect to this salient pole 11 ₁ .

In the above description, the number of teeth provided on one salient pole is 4
However, the number of teeth provided on the salient pole is not limited to this. For example, if eight teeth are used, four teeth are provided.
Even the next higher harmonic component can be removed, and if 16 teeth are used, even the fifth higher harmonic component can be removed. That is, if 2 n power teeth are used, (n +
1) It is possible to remove up to the next harmonic component. Here, for example, when eight teeth are used, the four teeth having the positional relationship as shown in FIG. 4 or FIG.
It is considered that one reference pair is formed, and two pairs in such a state may be arranged with a phase shift (P / 8) so as to cancel the fourth harmonic component. In other words,
When 2 n-th teeth are provided on one salient pole, all the teeth are P / 4, ..., P / 2 respectively with any other teeth.
It is arranged so as to have a phase relationship of n. Further, in the above description, the permanent magnet provided in the exciting circuit is eliminated, and the pulse motor configured so that the rotor is arranged outside the stator has been exemplified, but the type of the pulse motor is not limited to this. However, the rotor may be arranged inside the stator, for example.

〔The invention's effect〕

As described above, in the pulse motor of the present invention, the arrangement (phase) of the teeth provided in one salient pole is changed so that the harmonic components of the torque act on the respective teeth at different phases. Therefore, the harmonic components of the torque acting on each tooth can be canceled out, and the torque characteristics at the salient poles that were distorted in the past can be made sinusoidal. It is possible to realize a pulse motor that can be rotated in a simple manner with a simple configuration.

[Brief description of drawings]

1 to 6 are configuration diagrams showing an embodiment of a pulse motor of the present invention, and FIGS. 7 and 8 are configuration diagrams showing an example of a conventional pulse motor. 1 ... Stator, 2 ... Rotor, 11, 12 ... Magnetic material, 11 ₁
~ 11 ₈ , 12 ₁ ~ 12 ₈ ...... salient pole, 13 ...... permanent magnet, 14 ₁ ~ 14
₈ …… Excitation coil.

Claims (1)

[Claims] 1. A rotor having teeth with a constant pitch on its inner or outer circumference, and 2 n powers (n is a number) such that a part of a plurality of salient poles faces the teeth of the rotor, respectively. 2 or more integer)
, And a phase relation in which all the teeth provided on one salient pole are respectively P / 2i with respect to any of the other teeth (P is the pitch of the teeth in the rotor, i Is an integer from 2 to n).