JP2785406B2 - Linear servo motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear servomotor suitable for precision positioning, high-speed conveyance, and the like.

[Conventional technology]

Among linear motors applied in various industrial fields, especially linear servo motors using permanent magnets for the field have servo characteristics with excellent positioning performance and speed performance. Used for

FIG. 5 is a sectional view of a conventional linear servomotor, and FIG. 6 is a top view of a field iron core of the linear servomotor. In these figures, reference numeral 1 denotes a field iron core, on which a plurality of permanent magnets 2 for the field are arranged at regular intervals so as to alternate with N poles and S poles. In addition, these permanent magnets 2
Have a skew structure in which each is arranged obliquely so that the spatial distribution of the field magnetic flux generated by itself becomes a sine wave. Reference numeral 3 denotes an armature core disposed with a gap between the field core 1 and a plurality of slots provided thereunder.
A coil 4 is wound around each of 3a. By the way, the field magnetic flux φ generated from the permanent magnet 2 reaches the armature core 3 via the gap as shown by a broken line in FIG. 2
And further passes through the field iron core 1 and returns to the original permanent magnet 2.
Return to A magnetic flux path interlinking with the coil 4 is formed by the field magnetic flux φ, and an induced voltage is generated in the coil 4 by the movement of the armature core 3.

Further, a detector (not shown) (not shown) for detecting the field magnetic flux φ is attached to the armature core 3. Reference numeral 5 denotes a control circuit for performing speed control, position control, and the like of the armature core 3, receives a detection signal of the detector, and supplies a control signal based on the input signal to a driver 6. And
The driver 6 supplies a drive current having the same phase as the induced voltage to the coil 4 via the conductor 7 and the brush 8 in accordance with the control signal. The coil 4 generates a magnetic flux according to the supplied drive current. Then, an interaction between the magnetic flux generated by the coil 4 and the field magnetic flux φ generated by the permanent magnet 2 generates a thrust in the armature core 3, and the armature core 3 is driven in any direction indicated by an arrow A in the drawing. .

[Problems to be solved by the invention]

By the way, the driving principle of a linear servomotor is the same as that of a general permanent magnet type AC servomotor, and for a linear servomotor, suppressing the speed fluctuation and the thrust fluctuation as much as possible determines the quality of the motor characteristics. This is an important matter. Then, in order to suppress the thrust fluctuation, it is necessary to make the spatial distribution of the field magnetic flux a sine wave, make the induced voltage a sine wave, and make the generated thrust a smooth constant value.

However, in the linear servomotor, the field magnetic flux is generated by the permanent magnet, so that the spatial magnetic flux distribution is closer to a rectangular wave than a sine wave. Therefore, conventionally, the sixth
As shown in the figure, a skew structure in which permanent magnets are arranged diagonally, or a slot in the field iron core is skewed,
Although the induced voltage was close to a sine wave, a sufficient effect was not obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a linear servomotor having excellent motor characteristics by making the spatial distribution of field magnetic flux a sine wave.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, a field magnetic flux is generated by a plurality of permanent magnets disposed on one surface of a field iron core, and the field magnetic flux interacts with a coil wound around an armature iron core. In the linear servomotor that generates a magnetic flux that moves and linearly moves the armature core, the permanent magnet has a longitudinal cross-sectional shape that is a part of two parallel circular arcs, two parallel elliptical arcs, or two parallel hyperbolas. Defined, protrusions that can align the inner peripheral surface of the permanent magnet are provided at equal intervals in the longitudinal direction on the surface of the armature core facing the field core, and the protrusion and the inner peripheral surface of the permanent magnet are provided. Be consistent.

(Operation)

In the present invention, since the cross-sectional shape of the permanent magnet is defined by two parallel arcs, elliptical arcs, or parts of hyperbolas, the gap length between the field iron core and the permanent magnet is the shortest at the center of the permanent magnet, It becomes longer toward the end, and is the longest between adjacent permanent magnets. Therefore, the permeance of the magnetic circuit is highest at the center of the permanent magnet, decreases toward the end, and lowest between adjacent permanent magnets.

From the viewpoint of the permanent magnet, it can be seen that the operating point of each part of the permanent magnet gradually decreases as the distance from the pole center increases, and that the amount of magnetic flux generated by the permanent magnet decreases. The spatial distribution of the magnetic flux approaches a sine wave, and the thrust applied to the field core becomes a smooth constant value.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of the first embodiment of the present invention. In this figure, the same reference numerals are given to the parts corresponding to those of the conventional example in FIG. 5, and the description is omitted.

In this drawing, reference numeral 10 denotes a field iron core, which comprises a plurality of electric iron plates 10a, 10a,... Shown in FIG. On one side in the longitudinal direction of the electric iron plate 10a, arc-shaped protrusions 11 formed by punching or the like are provided at regular intervals, and the field iron core 10 is formed by laminating the electric iron plates in the same direction. Have been. Also, by laminating as described above, arc-shaped projections 11, 11,...
Are formed at regular intervals. On the other hand, permanent magnet 13
As shown in FIG. 2, its longitudinal cross-sectional shape is defined by two parallel arcs, and its inner peripheral surface 13a is
It is aligned with the protrusion 11 of 0. The permanent magnet 13 is arranged such that the magnetic poles appearing at the top of the permanent magnet 13 appear alternately with the N pole and the S pole.

As described above, by providing the field magnet 10 with the permanent magnet 13 having a sectional shape defined by two parallel arcs, the permeance (reciprocal of the magnetoresistance) of the gap between the field iron core 10 and the armature core 3 is reduced. It is not constant and has a predetermined spatial distribution. That is, the permeance of the air gap is highest at the center of the magnetic pole and lowest at the switching point of the magnetic pole as shown by the solid line in FIG. 3, and the distribution of the field magnetic flux Φ approaches from a rectangular wave to a sine wave. (Note that the one-dot chain line in FIG. 3 indicates the distribution of the field magnetic flux Φ of the conventional linear servomotor shown in FIG. 5.) Therefore, the armature core 3 is driven by the drive current supplied from the driver 6. Drives smoothly.

Next, FIG. 4 shows a sectional view of a linear servomotor according to a second embodiment of the present invention. This embodiment is exactly the same as the first embodiment, except that the projection 11 of the field iron core 10 is elliptical, and the longitudinal sectional shape of the permanent magnet 13 is defined by two parallel elliptical arcs. Also in this example, as in the embodiment of FIG. 1, the permeance of the air gap is the highest at the center of the magnetic pole and the lowest at the switching point of the magnetic pole, and the distribution of the field magnetic flux Φ approaches a sine wave. Therefore, the armature core 3 is smoothly driven by the drive current supplied from the driver 6.

The shape of the permanent magnet 13 is not limited to the above-described one, and the gap length between the armature iron core and the permanent magnet is the longest at the center of each permanent magnet, and becomes shorter toward the end. Thus, the shape of the permanent magnet may be determined, that is, the longitudinal cross-sectional shape may be defined by a part of two parallel hyperbolas, and the protrusion may be formed so as to match the inner surface of the permanent magnet. In other words, the permeance distribution should be the highest at the center of the magnetic pole, the lowest at the magnetic pole switching point, and the spatial harmonics should be minimized in correlation with the air gap length of the motor.

〔The invention's effect〕

As described above, the present invention uses a permanent magnet whose longitudinal cross-sectional shape is defined by two parallel arcs / elliptical arcs or a part of a hyperbola, and provides the inner peripheral surface of the permanent magnet in a field core. Since the gap is aligned with the protrusion, the permeance distribution of the air gap can be set to be the highest at the center of the magnetic pole of the permanent magnet and the lowest at the magnetic pole switching point, and the spatial distribution of the field magnetic flux can be made closer to a sine wave . As a result, the generated thrust can be made constant, and a linear servomotor having excellent characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a first embodiment of the present invention,
FIG. 2 is a perspective view showing the structure of the field core and the permanent magnet of the embodiment, FIG. 3 is a magnetic flux density curve diagram showing the field magnetic flux generated by the permanent magnet of the embodiment, and FIG. FIG. 5 is a sectional view of a conventional linear servomotor, and FIG. 6 is a top view of a field core of the linear servomotor. 3 ... armature iron core, 10 ... field iron core, 11 ... protrusion, 13 ... permanent magnet.

Claims (1)

(57) [Claims] 1. A field magnetic flux is generated by a plurality of permanent magnets disposed on one surface of a field iron core, and a magnetic flux interacting with the field magnetic flux is generated by a coil wound around an armature iron core. In the linear servomotor for linearly moving the armature core, the permanent magnet has a longitudinal sectional shape of 2 mm.
A protrusion that is defined by two parallel arcs, two parallel elliptical arcs or two parallel hyperbolas, and that allows the inner peripheral surface of the permanent magnet to be aligned with the surface of the field core facing the armature core. A linear servomotor, which is provided at equal intervals in the longitudinal direction, and wherein the protrusion and the inner peripheral surface of the permanent magnet are aligned.