JP2005073417A - Ac servo motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an AC servo motor wherein temperature rise in an anti-load-side bracket is reduced and thermal conduction between the anti-load-side bracket and an encoder is reduced. <P>SOLUTION: The AC servo motor comprises: a rotor having permanent magnets that constitute a plurality of magnetic poles; a stator having a load-side bearing and an anti-load-side bearing that rotatably support winding and the rotor, and a load-side bracket and the anti-load-side bracket that fix the load-side bearing and the anti-load-side bearing; and the encoder that detects the rotation angle of the rotor. The anti-load-side bracket is formed of resin, and a metal bearing cover is placed between the anti-load-side bracket and the anti-load-side bearing. Further, the encoder is positioned and fixed on the anti-load-side bracket. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an AC servo motor used for a drive shaft that performs high-speed and high-frequency positioning and high-precision constant-speed feeding in the FA field such as machine tools and semiconductor manufacturing apparatuses.

  Conventionally, an AC servo motor equipped with an encoder capable of detecting a high-resolution rotation angle is applied to high-speed and high-frequency positioning. Furthermore, from the viewpoint of requiring high-accuracy constant-speed feed, slotless AC servomotors that are extremely small in cogging torque causing the generation of speed ripple are being applied (for example, Patent Document 1, Patent Document 2, Patent Document 3).

FIG. 4 is a side sectional view of an AC servo motor to which a slotless type in the prior art is applied. In the figure, 1 is a rotor, 2 is a rotor yoke, 3 is a permanent magnet, 4 is a shaft, 10 is a stator, 11 is a stator yoke, 12 is an air core winding, 13 is a mold resin, 14 is a frame, 15 is a load side bearing, 16 is an anti-load side bearing, 17 is a load side bracket, 18a is an anti load side bracket, 19 is an encoder cover, 100 is an encoder, 101 is a rotary slit plate, 102 is a light emitting circuit board, 103 is a light receiving and signal processing board, 104 Is an encoder mounting plate spring, and 105 is an encoder mounting screw.
In FIG. 4, the rotor 1 includes a rotor yoke 2, a permanent magnet 3 having a plurality of magnetic poles attached to the surface of the rotor yoke 2, and a shaft 4. The rotor 1 is rotatably supported with respect to the stator 10 by a load side bearing 15 and an anti-load side bearing 16.
The stator 10 includes a hollow cylindrical stator yoke 11, an air core winding 12 disposed on the inner periphery of the stator yoke 11, a mold resin 13 that integrally fixes the air core winding 12 and the stator yoke 11, and the stator yoke 11. The frame 14 covers the outer periphery, the load side bearing 15 and the load side bracket 17 holding the anti load side bearing 16 and the anti load side bracket 18a. Here, the stator yoke 11 is a laminated silicon steel sheet, the mold resin 13 is a highly insulating epoxy mold resin, the frame 14 is aluminum having high thermal conductivity, and the load side bracket 17 and the anti-load side bracket 18a are the same. Aluminum with high thermal conductivity is used.
An encoder 100 that detects the rotation angle of the rotor 1 with high resolution is attached to the anti-load side bracket 18 a of the stator 10. The encoder 100 is an optical type, and includes a rotary slit plate 101 in which rotation angle information is engraved as a slit, a light emitting circuit board 102 having a light emitting unit that irradiates light to the rotary slit plate 101, and light that has passed through the rotary slit plate 101. The light receiving and signal processing board 103 for processing the encoder and the encoder mounting plate spring 104 and the encoder mounting screw 105 for mounting the encoder on the anti-load side bracket 18a. Furthermore, the encoder 100 is capped by an encoder cover 19 for preventing dust and water from entering.
In the AC servo motor configured as described above, a rotating magnetic field is generated in the gap portion between the rotor 1 and the stator 10 by causing a current corresponding to the magnetic pole of the rotor 1 to flow through the air core winding 12. Torque is generated in the rotor 1 by attraction and repulsion with the magnetic field generated by one magnetic pole. Furthermore, since it has a slotless structure, it is characterized in that no cogging torque is generated due to a change in permeance between the stator yoke 11 and the permanent magnet 3, and the speed ripple is small.
JP 58-58845 A JP 60-216746 A Japanese Patent Laid-Open No. 62-244251

However, the conventional AC servo motor has the following problems.
In the conventional AC servo motor, aluminum having high thermal conductivity is used for the anti-load side bracket, and the encoder temperature rises greatly as the winding temperature rises when copper loss occurs. As a result, malfunction and thermal damage of electronic components in the encoder occurred. This problem has been remarkably generated in a slotless permanent magnet type motor in which the torque decreases due to a decrease in gap magnetic flux density due to the wide gap structure, and the temperature rise of the winding increases.
In the prior art slotless permanent magnet type motor shown in FIG. 4, the temperature rise of the air core winding 12 increases with increasing copper loss, and the frame 14, load side bracket 17, and anti-load side bracket 18a, which are peripheral structures, are also heated. The temperature increased due to conduction. In particular, the temperature rise of the anti-load side bracket 18a is the largest due to the influence of the temperature rise of the internal air sealed with the peripheral structure. As a result, the temperature of the encoder 100 attached to the anti-load side bracket 18a rises, causing malfunctions and thermal damage of the integrated circuit components mounted on the light emitting circuit board 102 and the light receiving and signal processing circuit board 103. Furthermore, since the contact area between the encoder mounting location and the non-load side bracket is large, the amount of heat conducted there is also large, which promotes the above problem.
In response to the above problem, the current to the air-core winding 12 cannot be increased, and the torque and the size cannot be reduced.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an AC servo motor that eliminates the above problems and reduces the temperature rise of the anti-load side bracket and reduces the heat conduction between the anti-load side bracket and the encoder. .

In order to solve the above problem, the present invention of claim 1 is directed to a rotor having permanent magnets constituting a plurality of magnetic poles, a winding, a load-side bearing and an anti-load-side bearing that rotatably support the rotor, In an AC servomotor including a load side bracket that fixes a load side bearing and an antiload side bearing, a stator having an antiload side bracket, and an encoder that detects a rotation angle of the rotor,
The anti-load side bracket is made of resin,
A metal bearing cover was interposed between the anti-load side bracket and the anti-load side bearing, and the encoder was positioned and fixed to the anti-load side bracket.
According to the first aspect of the present invention, the temperature increase of the anti-load side bracket can be greatly reduced.
According to a second aspect of the present invention, a convex portion having a screw hole for attaching the encoder to the anti-load side bracket is integrally formed.
According to the present invention of claim 2, heat conduction between the anti-load side bracket and the encoder can be reduced.

The present invention can obtain the following effects.
(1) According to the first embodiment of the present invention, the anti-load side bracket is made of resin, and a metal bearing cover is interposed between the anti-load side bracket and the anti-load side bearing. With such a configuration, the temperature rise of the anti-load side bracket can be reduced as compared with the prior art, and as a result, malfunctions and circuit element damage due to the temperature rise of the encoder can be prevented.
(2) According to the second embodiment of the present invention, the convex portion having a screw hole for attaching the encoder to the anti-load side bracket is integrally formed. With such a configuration, the heat conduction to the encoder can be reduced, and the temperature rise of the encoder can be further reduced than in (1).
(3) Due to the effects of (1) and (2), the winding current, that is, the generated torque can be increased to within the allowable temperature rise of the encoder. Further, the AC servo motor can be reduced in size by keeping the generated torque as it is and increasing the copper loss to within the allowable temperature rise of the encoder.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view of a slotless AC servo motor according to a first embodiment of the present invention. Hereinafter, the same components as those of the prior art are denoted by the same reference numerals and the description thereof is omitted, and only different points will be described.
In the figure, reference numeral 18a denotes an anti-load side bracket according to the first embodiment of the present invention, and 20 denotes a bearing cover.
The difference between the present invention and the prior art is that the anti-load side bracket 18a is molded from resin, and a metal bearing cover 20 is interposed between the anti-load side bracket 18a and the anti-load side bearing 16. is there. For example, PPS resin or the like is used as the resin of the anti-load side bracket 18a. The thermal conductivity of PPS resin is about 1 W / (m · K), which is 1/200 of aluminum. That is, the anti-load side bracket 18a has a structure in which heat hardly flows.
The bearing cover 20 is made of a metal such as aluminum as in the prior art, and fixes the anti-load side bearing 16 with sufficient strength and accuracy. The fixing of the bearing cover 20 and the non-load side bracket is realized by providing a non-rotating pin as described in, for example, Japanese Utility Model Laid-Open No. 1-64016, in order to suppress the rotation of the bearing cover 20 in addition to fixing with an adhesive. ing.
With such a configuration, it is possible to suppress an increase in temperature of the anti-load side bracket, which has been a problem in the prior art, and as a result, it is possible to significantly reduce an increase in the temperature of the encoder. As a result of conducting a temperature rise test in an experimental machine in which the present invention is implemented, it has been confirmed that the temperature rise of the anti-load side bracket and the encoder can be reduced by 25% compared to the prior art.

Next, a second embodiment will be described.
FIG. 2 is a side sectional view showing the vicinity of the encoder portion of the AC servo motor in the second embodiment of the present invention.
In the figure, reference numeral 18c denotes an anti-load side bracket according to the second embodiment of the present invention. FIG. 3 is a front view of the anti-load side bracket 18c as viewed from the encoder side.
The present invention is different from the prior art and the first embodiment in that a convex portion 21 having a screw hole for attaching the encoder 100 to the anti-load side bracket 18c is integrally formed.
The convex portion 21 can reduce the contact area with the encoder mounting plate spring 104 and can greatly reduce the heat conduction to the encoder 100. Furthermore, since the anti-load side bracket 18c is molded with resin and the convex portion 21 can be integrally molded, it is not necessary to cut out and the production time can be shortened.

  In the above embodiments, the slotless type motor is shown, but it goes without saying that the effects of the present invention can also be achieved even with a slotted motor widely used as an AC servomotor.

1 is a side sectional view of an AC servomotor showing a first embodiment of the present invention. Side sectional view around the encoder of the AC servo motor showing the second embodiment of the present invention Front view of the anti-load side bracket showing the second embodiment of the present invention Side sectional view of an AC servo motor in the prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor 2 Rotor yoke 3 Permanent magnet 4 Shaft 10 Stator 11 Stator yoke 12 Air core winding 13 Mold resin 14 Frame 15 Load side bearing 16 Anti load side bearing 17 Load side bracket 18a, 18b, 18c Anti load side bracket 19 Encoder cover 20 Bearing Cover 21 Convex 100 Encoder 101 Rotating slit plate 102 Light emitting circuit board 103 Light receiving and signal processing board 104 Encoder mounting plate spring 105 Encoder mounting screw

Claims (2)

A rotor having permanent magnets constituting a plurality of magnetic poles; a winding; a load-side bearing and an anti-load-side bearing that rotatably support the rotor; a load-side bracket that fixes the load-side bearing and the anti-load-side bearing; In an AC servo motor configured by a stator having a non-load-side bracket and an encoder that detects a rotation angle of the rotor,
The anti-load side bracket is made of resin,
An AC servomotor characterized in that a metal bearing cover is interposed between the anti-load side bracket and the anti-load side bearing, and the encoder is positioned and fixed to the anti-load side bracket. 2. The AC servo motor according to claim 1, wherein a convex portion having a screw hole for attaching the encoder to the counter load side bracket is integrally formed.

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