JPH0614780B2 - 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, it is desirable to directly drive the joints of such a robot with a brushless motor in consideration of the life of the brush of the DC motor and the speed reducer, or the maintenance of the lubricating oil. 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. 4 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 a stator and a rotor in a conventional pulse motor to form an outer rotor type, and to arrange a permanent magnet, which is conventionally on the rotor side, on the stator side.

In the figure, FIG. 4 (A) is a front view and FIG. 4 (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 . further,
These salient poles 11 _{1 to} 11 ₈ and 12 _{1 to} 12 ₈ are excited by a set of exciting coils 14 ₁ to 11 ₄ for each pair (11 ₁ and 12 ₁ , 11 ₂ and 12 ₂ , ...) Opposed via the permanent magnet 13. 14 ₈ is wound. Each of the four exciting coils (14 _{1 to} 14 ₄ and 14 _{5 to} 14 ₈ ) is connected in series.

Here, if the pitch of the teeth on the rotor 2 is P, the same pitch P is applied to the salient poles 11 _{1 to} 11 ₈ and 12 _{1 to} 12 ₈ of the magnetic bodies 11 and 12.
The teeth of adjacent salient poles (for example, 11 ₁ and 11 ₂ ) of the same magnetic body are provided with a phase shift of P / 4 from each other. Further, a phase shift of P / 2 is provided between the teeth of the salient poles (eg, 11 ₁ and 12 ₁ ) of the two magnetic bodies 11 and 12 which face each other.

In the pulse motor having such a configuration, if currents having 90 ° phase shifts 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 coils 14 ₁ to 1
And the magnetic flux due 4 ₈ is 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 structure, most of the manufacturing cost is occupied by expensive rare earth magnets, and the higher the efficiency of the magnet, the more the motor performance is improved, but the price is also expensive. turn into. Further, in the stator 1 and the rotor 2, the torque generated by one tooth is not a sine wave as shown in FIG. 5, but a distorted one. This is a cause of 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,
The holding torque characteristic of the motor as a whole is greatly distorted. In pulse motors used in robots, it is necessary for the motor to rotate smoothly.
The presence of such pulsating torque is undesirable.

The present invention eliminates the above-mentioned drawbacks of conventional devices, does not use a permanent magnet for driving a motor, eliminates pulsating torque, and has a simple configuration of a pulse motor capable of smoothly rotating a rotor. It is intended to be realized.

[Means for solving problems]

The pulse motor of the present invention eliminates the permanent magnets on the stator side by using the three-phase excitation method, and prevents the generation of pulsating torque by devising the pitch of the teeth provided on the salient poles on the stator side. It is something that is done. More specifically, focusing on the fact that the torque characteristics of each tooth as shown in FIG. 5 can be decomposed into higher harmonic components, the phase relationship between a plurality of salient poles is changed. Arrange half of the salient poles so that the specific harmonic components of the generated torque act on the remaining salient poles at different phases, cancel the harmonic components, and pulsate due to the harmonic components. It is designed to reduce the torque.

[Work]

Thus, if the excitation circuit of the pulse motor is configured without using permanent magnets, expensive parts can be omitted,
An inexpensive motor can be realized. If the torque of the harmonic component acting on the salient poles on the stator side is canceled between the teeth with different phases, the conventionally distorted torque characteristics can be approximated to a sine wave, and the motor rotation can be smoothed. be able to.

〔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. 4 are designated by the same reference numerals. As shown in the figure, the number of exciting coils is 6, and two exciting coils (14 ₁ and 14 ₂ ,
14 ₃ and 14 ₄ and 14 ₅ and 14 ₆ ) are connected in series or in parallel to form a three-phase excitation circuit. In this case, if the pitch of the teeth on the rotor 2 is P, to the salient poles 11 ₁ to 11 ₆ of the magnetic body 11 and the teeth are provided at the same pitch, the adjacent salient poles each other (e.g., 11 ₁ and each tooth 11 _2), P / 3 minutes by a phase shift is provided to each other.

In the pulse motor configured as described above, the three exciting coils 14 ₁ , 14 ₂ , 14 ₃ , 14 ₄ and 14 ₅ , 14 ₆ are separated from each other by 12
When exciting currents with a phase difference of 0 ° are applied, the magnetic velocities generated by the respective exciting coils 14 _{1 to} 14 ₆ give an attractive force to the rotor 2 in the gap between the stator 1 and the rotor 2 and the rotational torque Generate. 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.

Therefore, in a three-phase excitation type pulse motor,
Even if the permanent magnet in the exciting circuit is not provided, the rotating torque of the rotor can be applied, and the permanent magnet can be omitted.

Next, the phase shift provided between each salient pole in order to remove the harmonics of the torque acting on a plurality of salient poles 11 ₁ to 11 ₆ are determined as follows.

FIG. 2 shows the torque characteristic of FIG. 5 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.

Here, if it is assumed that the secondary torque has the largest effect as the component that generates the pulsating torque, the salient poles 11 ₁ to ₁ 1
The phase relationship in the arrangement of ₁₆ is devised so as to cancel this secondary torque.

That is, a plurality of salient poles 11 ₁ to 11 ₆ are disposed with a P / 4 becomes the phase shift of the salient pole 11 _{4-11 6} for half the remaining salient poles 11 ₁ to 11 _3. In this way, if half of the salient poles are shifted by P / 4 from the original phase, these salient poles 11 ₁ will be separated between the corresponding salient poles (for example, 11 ₁ and 11 ₄ ) in one excitation state. , 2 acting respectively 11 ₄
The following torque components are in opposite phase to each other and will be canceled.

FIG. 3 is a configuration diagram showing an arrangement state of salient poles whose phase relationship is defined as described above. The figure illustrates the phase relationship between the salient poles 11 ₁ and 11 ₄ with the teeth of the rotor 2 as a reference. As shown in the figure, the salient pole 11 ₁ and the salient pole 11 ₄ are arranged with a phase difference of P / 4 from the original phase (in-phase). Also, the other salient poles 11 ₂ and 11 ₅ and 11 ₃
And 11 ₆ have the same phase change. In this case, the adjacent salient poles are arranged with a phase shift of P / 3 as in the conventional case.

Thus, a plurality of salient poles 11 ₁ to 11 _6, when so arranged with P / 4 becomes the phase shift of the salient pole 11 _{4-11 6} of the radius for the remaining salient poles 11 ₁ to 11 ₃ Of the torques acting on the teeth of the salient poles, the second harmonic components can cancel each other, and the torque characteristic as a whole can be approximated to a sine wave. For this reason, the rotor can be smoothly rotated by the exciting currents having different phases, and the pulse motor suitable for driving the joint of the robot can be obtained.

In the above description, the case where the salient poles 11 _{4 to} 11 ₆ are displaced with respect to the salient poles 11 _{1 to} 11 ₃ is excited, but the selection of salient poles that are displaced in phase is limited to this. Not a thing. Further, in the above description, the case of removing the second-order harmonic component is illustrated, but the harmonic component to be removed may be of another order. In this case, the amount by which the salient pole is displaced depends on the order, and for example, in the case of the third order, P / 2
It becomes + P / 6. Further, the number of salient poles is not limited to six. Especially for large motors, 12 or 18 poles are reasonable. For example, in a 12-pole motor, there are four poles that are illustrated in the same phase. Therefore, two poles are arranged so as to remove the second harmonic component, and the remaining two poles are the third harmonic. When arranged so as to remove the wave component, a smoother rotation can be obtained.

〔The invention's effect〕

As described above, in the pulse motor of the present invention, the exemplary method is excited in three phases, and half of the plurality of salient poles are applied to the remaining salient poles so that a specific harmonic component has a different phase. Since they are arranged in the same manner, any harmonic components can be canceled out with each other, the torque characteristics as a whole can be made closer to a sine wave, and a permanent magnet is not used to drive the motor, and pulsation It is possible to realize a pulse motor with a simple structure that can eliminate the torque and smoothly rotate the rotor.

[Brief description of drawings]

1 to 3 are block diagrams showing an embodiment of the pulse motor of the present invention, and FIGS. 4 and 5 are block 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 poles, 13 ...... permanent magnets, 14 ₁ ~ 14 ₈
...... Excitation coil.

Claims (1)

[Claims] 1. A rotor provided with teeth of a constant pitch on its inner circumference, and teeth of the same pitch provided so as to face the teeth of the rotor in a part of an integer multiple of 3. A stator having a plurality of salient poles, and a plurality of exciting coils that excite the stator with three-phase exciting currents, and half of the plurality of salient poles with respect to the remaining salient poles. A pulse motor, which is arranged so as to operate in a phase in which a specific harmonic component of generated torque is canceled.