KR100377783B1 - Yoke structure of brushless linear motor - Google Patents

Abstract

The linear motor includes a movable part having a winding coil and a fixing part extending in a long direction along the moving direction of the movable part. The fixing part includes a support having a base and a support projecting from the base, a first yoke fixed to one side of the support and extending in a longitudinal direction, and a second yoke fixed to the support so as to face the first yoke; And a permanent magnet attached to opposite surfaces of the first yoke and the second yoke and disposed to face opposite poles and to change polarity along the longitudinal direction. The first yoke and the second yoke are separated from each other and each is fixed to the support. The first yoke generally coincides with a width in a direction perpendicular to the longitudinal direction in a direction perpendicular to the longitudinal direction of the permanent magnet. The first yoke is trapezoidal, and the support is provided with a dovetail fitting groove into which the trapezoidal yoke is fitted. The support further includes a fixing piece fixed to an end of the support, and the first yoke is fixed by the coupling of the fixing piece.

Description

Yoke structure of brushless linear motors {YOKE STRUCTURE OF BRUSHLESS LINEAR MOTOR}

The present invention relates to a yoke structure of a brushless linear motor.

For linear driving, the rotational motion of the motor has been converted to linear motion. Recently, a linear motor that can be directly driven without a transducer is developed. Linear motors (linear motors) are expanding their range of applications by providing high speed, strong thrust and accurate position control.

Brushless linear motors in linear motors. Brushless linear motors usually have permanent magnets facing each other so that magnetic flux flows and coils are disposed between the permanent magnets so that current flows in a vertical direction.

1 and 2 show an example. 1 and 2, the linear motor 10 includes a support 12 and a U-shaped yoke 14. Yoke 14 is fixed to one side of the support (12). The permanent magnets 16 are fixed to the surfaces of the yoke 14 that face each other. The yoke 14 and the permanent magnet 16 constitute a fixed portion 17. The movable portion 22 has a coil 18 wound in an annular shape. The coil 18 is sandwiched between the permanent magnets 16. The coil 18 is fixed to the coil holder 20 provided in the movable part 22. A linear motion guide (pointing to a linear motion guide device such as a linear bearing) 24 is provided between the fixed portion 17 and the movable portion 22. The linear motor of FIG. 1 has a structure in which a U-shaped yoke is disposed on both sides of a center support. The case 26 is covered on the upper and side surfaces.

In the structure of the linear motor 10 'of FIG. 2, a yoke 14' is provided between both side walls 13 'and the center wall of the support 12'. The permanent magnet 16 'is fixed to the surfaces of the yoke 14' that face each other. The linear motor 10 'of FIG. 2 differs from the linear motor 10 of FIG. 1 in the relative position of the stator and the linear motion guide 24', but is identical in terms of driving principle.

Recent trends in technology ensure the same thrust or control performance but require smaller linear motors. In particular, if the height is higher than the width, the stability is poor and may cause problems in the position accuracy. As such, it is necessary to reduce the size while maintaining the other performance.

In view of this point, the present invention aims to provide a linear motor having a reduced size by improving the structure of the yoke.

It is also an object of the present invention to provide a brushless linear motor capable of obtaining a strong and uniform thrust while being reduced in size.

1 and 2 are longitudinal cross-sectional views of a linear motor having a yoke structure according to the related art.

3 is a longitudinal sectional view of a linear motor having a yoke structure according to an embodiment of the present invention;

4 is a perspective view showing the direction of magnetic flux of the linear motor of FIG.

5 and 6 are each a longitudinal cross-sectional view of a linear motor having a yoke fixed structure according to another embodiment of the present invention.

According to an aspect of the present invention, in the linear motor having a movable part having a coil and a fixing part extending in a long direction along the moving direction of the movable part, the fixing part is fixed to the support and the support facing each other Two side yokes separated from each other, a central yoke positioned between the two side yokes and spaced apart from the two side yokes, and on each side of the two side yokes and the central yoke facing each other. By having permanent magnets attached to each other and arranged to change polarity along the longitudinal direction,

A linear motor is provided that forms a circulating magnetic flux that exits one side yoke, passes through the central yoke, enters the other side yoke, and then passes through the central yoke to return to the one side yoke.

According to a preferred embodiment, the side yoke has a trapezoidal shape in which the longitudinal direction is vertically cut, and the support is provided with a dovetail fitting groove into which the side yoke is fitted. The support of the fixing part has a support facing each other, the support may further include a fixing piece fixed to the end of the support, the side yoke may be fixed to the support by the combination of the fixing piece. .

DETAILED DESCRIPTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3, a linear motor 30 is shown in accordance with one embodiment of the present invention. The linear motor 30 has a fixed portion 32 and a movable portion 34.

The fixing part 32 has a support body 36. The support 36 has a base 38 and supports 40, 42 extending up from the base 38 and extending side by side in the longitudinal direction (direction perpendicular to the paper plane in the drawing). Both supports 40 and 42 face each other. The support 36 is designed in a structure that maintains rigidity so as not to be deformed by a force generated when the motor is driven, and selects a material according thereto. In addition, a material having a property of approaching the weak magnetic body or the reverse magnetic body is selected so as not to affect the magnetic flux.

As the material of the support, it is preferable to use a glass fiber having properties close to the inverse magnetic body and excellent in mechanical strength and rigidity. Alternatively, a weak magnetic metal such as aluminum alloy may be used. The support of the aluminum material can be made by extrusion. Other support materials include stones such as granite. Stone is cut and used. The support can also be made by mixing stone (for example granite) powder with a resin such as epoxy and molding it.

The side yoke 44 is fixed by the bolts 46 at positions facing each other near the upper ends of the supports 40, 42. Yoke 44 extends in the longitudinal direction as well shown in FIG. In the space between the two supports 40 and 42, a central yoke 48 which is long in the longitudinal direction and extends to the base 38 in the vertical direction is located. The central yoke 48 is secured by bolts 50 protruding upward from the base 38. The central yoke 48 is provided with jaws 54 on which the permanent magnets 52 can be seated on both upper ends. Since the magnetic flux does not mainly pass through the lower circumference 48z (the portion where the bolt is coupled) of the central yoke 48, this may be omitted. Instead, the central yoke 48 may consist of only the parts sandwiched between the upper permanent magnets, and the lower part thereof (ie, the portion corresponding to the lower column 48z of FIGS. 3 and 4) may be formed by extending the support 36. have.

When fixing the side yoke 44 and the center yoke 48, the yoke 44, 48 is fixed by using several bolts 46 and 50 at regular intervals in the longitudinal direction. Instead of using bolts, an adhesive may be secured between the yoke and the support.

Unlike the structure of FIG. 1, the structure of FIG. 3 does not require such mechanical properties in the yoke because the support 36 is rigid enough to maintain the shape of the linear motor. However, it is necessary to have excellent magnetic properties. In particular, the saturation magnetic flux density is good. As materials of the side yoke and the center yoke, carbon steel, supermalloy, and permalloy can be used. Among them, the use of permalloy, which is 45% nickel alloy steel, is preferable in terms of miniaturization and improved performance.

3 and 4, the permanent magnets 521, 522, 523, 524 (when referring to the permanent magnets without distinguishing reference numeral 52) are used in which the N-S pole is magnetized in the thickness direction. The permanent magnet is joined to yokes 441, 442, 48 (note that reference numeral 44 is used to refer to the side yoke without distinction) so that the poles are alternately arranged with a magnet having a constant width in the longitudinal direction. Permanent magnets are alternately attached to unit magnets in which the N-S poles are magnetized alternately. Alternatively, permanent magnets may be attached to the long magnets alternately magnetized in alternating N-S poles. As the permanent magnets 521 to 524, it is preferable to use a rare earth permanent magnet.

Referring to Figure 4, most of the magnetic flux coming out of the permanent magnet is a magnetic flux line is formed along the arrow direction shown. That is, when considering the rightmost magnet of Fig. 4, first, the magnetic flux emerges from the magnet 521 attached to the right yoke 441, passes through the magnet 552 attached to the center yoke, and then passes through the center yoke 48. After passing through the magnets 523 and 524 in the longitudinal direction from the left yoke 442, passing it through the neighboring magnets, passing through the magnets and the central yoke 48 and again passing two magnets, the right yoke 441 ) Is returned to the neighboring magnet 521. Of the central yoke 48, only the portion in contact with the permanent magnets 522 and 523 substantially contributes to the flux.

This configuration is compared with the yoke of FIGS. 1 and 2. Also in the yokes 14 and 14 'of FIGS. 1 and 2, the portion of the magnetic flux flowing substantially contacts the permanent magnets 16 and 16'. Although it passes slightly through the other parts H2 and H2 ', the magnetic flux passing through this part does not contribute much to pushing the coils 18 and 18'. Therefore, in the present invention, thus eliminating the portion that does not contribute to the flow of the magnetic flux.

The movable part 34 has a coil fixing stand 56. The coil 58 is fixed to the coil holder 56. Although the coil 58 is not shown in detail in the drawing, one coil is a loop (ring) shape and extends upward and downward in a vertical direction perpendicular to the magnetic flux to exert a force across the magnetic flux path, and does not pass through the magnetic flux. It does not have a connecting coil portion. Coils of this configuration are arranged side by side. It is preferable that the width of the drive coil portion of the coil is 1/3 of the width of the magnet, and the width of the entire winding coil is 4/3. Hall sensors are installed in the middle of the coil to control the current applied to the coil. The configuration of such a coil may be a coil used in a conventional brushless linear motor. As described above, the coil may be an air core coil, or a coil core type coil in which a coil of another phase passes through the middle portion of the ring.

A linear motion guide 60 is installed between the movable portion 34 and the fixed portion 32 to guide linear movement of the movable portion. The side case 62 is fixed to the support 36 to prevent foreign substances such as dust from entering inward. As shown in Fig. 3, a position sensor 66 is provided between the side wall of the support and the movable portion. The limit sensor 68 is also provided between the support and the movable part.

5 is a linear motor 30a according to another embodiment of the present invention, the configuration of the other parts other than the shape of the side yoke 44a and a portion for fixing the side yoke 44a is linear motor 30 shown in FIG. ) And the same structure. A dovetail fitting groove 41 is provided in the support 40a of the support 36a. The side yoke 44a may have a trapezoidal cross section and fit into the dovetail fitting groove 41. Then, the side yoke 44a can be fixed. The support of this shape can be manufactured by aluminum extrusion. And yoke is put in after extrusion process. In addition to this method, when the aluminum support is extruded while feeding the prepared yoke and moving in accordance with the extrusion speed of the aluminum support to pass through the extrusion mold, the yoke fitting operation may be performed simultaneously with the operation of preparing the support.

In the embodiment shown in Fig. 5, the yoke 44a must be pushed in the longitudinal direction. In order to improve the assemblability, the support body 36a is provided with a fixing piece 43b. The fixing piece 43b and the fixing table 40b are provided with triangular grooves. When the fixing piece 43b is fixed to the fixing table 40a, the dovetail fitting groove 41b as shown in FIG. 5 is provided. To fix the side yoke 44b, the side yoke 44b is first inserted into the holder 40b, and the fixing piece 43b is positioned thereon and fastened with a bolt. In this way, assemblability is improved. The bolt can also be fastened directly to the yoke at the positions and directions indicated by arrows 431 and 432.

Although the present invention has been described with reference to the above embodiments, the present invention is not limited thereto. Those skilled in the art will appreciate that modifications and variations can be made without departing from the spirit and scope of the present invention and that such modifications and variations also fall within the present invention.

According to the configuration of the present invention as described above, since unnecessary portions (parts of H1, H1 'and H2') of the yoke are removed, the size (particularly, the height) can be reduced. Therefore, the height of the motor can be lowered, and the stability of the movement is increased. Since the yoke does not have to support the force generated by the motor, the choice of yoke material is wider, and it is possible to use the one having excellent magnetic properties.

Claims (4)

In a linear motor having a movable part having a coil and a fixed part extending in a long direction along the moving direction of the movable part, The fixing part is a support and a two side yoke fixed to face each other and separated from each other, and a central yoke positioned between the two side yoke and spaced apart from each other and the two side yoke, By having permanent magnets attached to each of the two side yokes and the opposite side surfaces of the central yoke, each of which is disposed to change polarity along the longitudinal direction, A linear motor that exits one side yoke, passes through a central yoke, enters a side yoke on the other side, and then passes back through the center yoke to form a return flux to the one side yoke. delete The linear motor according to claim 1, wherein the side yoke has a trapezoidal cross section perpendicular to its longitudinal direction, and the support has a dovetail fitting groove into which the side yoke is fitted. The support of claim 1, wherein the support of the fixing part includes supporters facing each other, and the support further includes a fixing piece fixed to an end of the support, and the side yoke is coupled to the support by coupling the fixing piece. Set linear motor.