JPH0898496A - Voice coil linear motor - Google Patents

Abstract

PURPOSE: To reduce interlinking of a flux generated from a field coil and a flux generated from a coil in the vicinity of an end part, as compared with a conventional case, by beveling permanent magnets, provided for outer and central yokes, at the opposite end parts in the direction of inner ring thereby reducing the leakage flux at the end part. CONSTITUTION: Permanent magnets 14, 14 are beveled C1 on the inside at the opposite ends thereof while permanent magnets 15, 15 are beveled C1 on the outside at the opposite ends thereof. Since the magnetomotive force distribution decreases gradually toward the axial outside at the end parts of the permanent magnets 14, 15 and the air gap thereat is large, flux leakage from the permanent magnets 14, 15 to yokes 11, 12, 13 can be prevented. A good conductor, e.g. a circular or rectangular copper wire, having beveled axial outer end except a linear part of predetermined width is wound into a pair of coils 2, 2 which are arranged, at same pitch as the permanent magnets 14, 14, between the permanent magnets 14, 14 and 15, 15 so that the current flows in reverse direction between adjacent coils.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice coil type linear motor, and more particularly to a structure for reducing magnetic flux leakage from a magnetic circuit and a coil.

2. Description of the Related Art As a first prior art, in order to align the windings of a voice coil motor coil, a voice having a coil portion formed by winding wire rods in a laminated coil and a coating resin covering the outer surface of the coil portion. In a coil for a coil motor, there is a coil in which the wire rod at the tip of the coil portion is laminated in a stepwise manner (for example, Japanese Utility Model Laid-Open No. 1-150474). Further, as a second conventional technique, a plurality of adjacent magnetic poles are alternately arranged on the inner side in the axial direction of a pair of flat outer yokes facing each other across a space and the outer side of a central yoke provided between the outer yokes. There is one in which permanent magnets for field magnets are arranged to face each other (for example, Japanese Utility Model Laid-Open No. 4-98876).

However, when the coil of the first prior art is applied to the magnetic circuit of the second prior art, the chamfering of the coil end is provided on only one side.
An imbalance occurs in the leakage magnetic flux from the chamfered and non-chamfered ends of the coil end to the outer yoke and the central yoke, resulting in non-uniform longitudinal electromagnetic force (side force), which easily causes pitching. Therefore, an object of the present invention is to provide a field permanent magnet and a coil in which a leakage magnetic flux is less likely to occur at an end portion and a longitudinal magnetic flux distribution is uniform, and to provide a linear motor in which pitching hardly occurs.

In order to solve the above problems, the present invention provides a pair of flat plate-shaped outer yokes facing each other with a space in between in the axial direction and outside of a central yoke provided between the outer yokes. , A linear motor in which a plurality of permanent magnets are arranged to face each other so that adjacent magnetic poles are alternately different, and a pair of coils having chamfered end faces are arranged between the permanent magnets. A voice coil type linear motor is constructed by providing chamfers at the outer ends of the permanent magnets arranged at both axial ends of the permanent magnets provided, or by providing chamfers on the inner and outer surfaces of the axial outer ends of the pair of coils. .

By the above means, the leakage magnetic flux at the end portion is reduced and the interlinking magnetic flux of the magnetic flux of the field magnet and the magnetic flux formed by the coil near the end portion is smaller than in the conventional case, so that the generation of side force is reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an embodiment of the present invention. Reference numeral 1 is a sun-shaped yoke made of a ferromagnetic material, and the outer yokes 1 are arranged in parallel.
1 and 11, a side yoke 12, 12 that closes both ends of the outer yokes 11, 11 and a central yoke 13 that connects the central portions of the side yokes 12, 12 to form a closed magnetic path. On the inner surface of the outer yokes 11 and 11 and the outer surface of the central yoke 13, permanent magnets 14, 14 and 15, 15 for field magnets are provided.
The polarities of the adjoining ones and the opposite ones are alternately switched, and they are provided at a predetermined pitch in the axial direction. Permanent magnet 1
At both ends / inside of 4,14 and both ends / outside of 15,15,
A chamfer C1 is provided. With the above-described configuration, the magnetomotive force distribution at the ends of the permanent magnets 14 and 15 becomes smaller toward the outside in the axial direction, and the gap at the ends is large. 1
It is possible to prevent leakage magnetic flux to 1, 12, and 13. It should be noted that the permanent magnets 14 and 15 may be unified to the permanent magnets 14a and 15a arranged at both ends in the axial direction in order not to increase the types of permanent magnets. Width W between the permanent magnets 14, 14 and 15, 15
A pair of coils 2 around which a good conductor such as a circle or a rectangular copper wire having a chamfered C2 on the outer end in the axial direction is wound while leaving the straight line portion of 1.
2 are provided at the same pitch as that of the permanent magnets 14, 14 and are connected so that the currents flowing through the adjacent coils are reversed. The chamfered portions C2 may be provided at both ends of the coil 2 in order to make the coil shape bilaterally symmetrical and to facilitate manufacturing. By configuring as described above, the coil end portion of the coil 2, the outer yokes 11 and 11, and the central yoke 1
The gap between the coil 3 and the coil 3 becomes large, and the leakage of the magnetic flux generated by the coil 2 can be prevented. A bobbin 3 made of a non-magnetic material is fitted on the inner diameter sides of the coils 2 and 2. The bobbin 3 may be fitted on the outer diameter side of the coils 2, 2. FIG. 2 shows a second embodiment, in which the ends of the coils 2 and 2 are chamfered in an arc shape, the air gap changes smoothly, and there is less change in the leakage magnetic flux at the ends than in the embodiment. FIG. 3 shows a third embodiment of the bobbin 3 in order to more securely fix the coils 2, 2 in the axial direction.
A triangular pyramid-shaped protrusion 31a matching the shape of the coil 2,
31b is annularly provided in the axial direction so that the bottom between both cones has a width W1, and the coil 2 is directly wound around the bobbin 3 so as to have the shape of the embodiment between the two cones. FIG. 4 shows a fourth embodiment, in which the bobbin 3 is provided with spacers 32a and 32b having a ring-shaped and ladder-shaped cross section and having a width W1 according to the shape of the coil 2.
The coil 2 is directly wound around the bobbin 3 as in the third embodiment. FIG. 5 shows a fifth embodiment, which is a spacer 34 provided with a recessed groove 33a conforming to the end shape of the embodiment and the second embodiment.
An annular spacer 34b provided with a knock for fitting the outer shape of the coil 2 to a and the outer diameter side is fixed to the outer diameter side of the bobbin 3 so as to be sandwiched from both ends of the preformed coil 2. When an exciting current is passed through the coil 2, the magnetic field created by the coil and the field created by the permanent magnet are interlinked, and thrust is generated on either the left or the right. At this time, since the leakage magnetic flux (vertical direction) at the axial end is small, the longitudinal magnetic force is small and the side force is reduced. Further, even if a malfunction occurs during assembly or a misalignment occurs during use, the operation is the same.

As described above, according to the present invention, the side force can be reduced and pitching is less likely to occur.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a coil showing a second embodiment of the present invention.

FIG. 3 is a sectional view of a bobbin showing a third embodiment of the present invention.

FIG. 4 is a sectional view of a bobbin showing a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a bobbin showing a fifth embodiment of the present invention.

[Explanation of symbols]

 1 yoke 11 outer yoke 12 side yoke 13 center yoke 14 and 15 permanent magnet 2 coil 3 bobbins 31a and 31b protrusions 32a, 32b, 34a and 34b spacer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Iwabuchi 2-1, Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Yasukawa Electric Co., Ltd.

Claims (7)

[Claims] 1. A plurality of permanent magnets are made to face each other so that adjacent magnetic poles are alternately different between a pair of flat plate-shaped outer yokes facing each other with a space therebetween and a central yoke provided between the outer yokes. In a voice coil type linear motor in which a pair of coils having chamfers are disposed between the permanent magnets, chamfers are provided on both inner and outer surfaces of axially outer ends of the pair of coils. Voice coil type linear motor. 2. The voice coil type linear motor according to claim 1, wherein the outer ends of the permanent magnets, which are arranged at both ends in the axial direction, are chamfered. 3. The voice coil type linear motor according to claim 1, wherein the cross-sectional shape of the coil is a hexagon having parallel planes at both ends which are orthogonal to the axis. 4. The voice coil type linear motor according to claim 1, wherein chamfers are provided at both ends of the coil so that the cross-sectional shape of the coil is an octagon having parallel surfaces at both ends. 5. The voice coil type linear motor according to claim 1, wherein the cross-sectional shape of the coil is substantially elliptical with round arcs at both ends. 6. The voice coil type linear motor according to claim 1, wherein a bobbin made of an insulating material is fitted to an inner diameter or an outer diameter of the coil. 7. The voice coil linear motor according to claim 6, wherein the coil fitting portion of the bobbin is provided with a locking portion adapted to a coil shape.