JPS61164459A - Linear motor - Google Patents

Abstract

PURPOSE:To obtain the miniature linear motor of high thrust, by fitting a plurality of magnets so that mutually opposite polarities may be arranged on the first half section and the second half section on the inner peripheral face of a cylindrical yoke, and by fitting a spacer fitted on a center pole, loosely between the magnets for the first half section and the second half section. CONSTITUTION:A plurality (four units) of magnets 12, 13 at a distance D between them are fitted on the first half section and the second half section on the inner peripheral face of a cylindrical yoke so that the opposite polarities may be arranged. A head 16 is fitted at one end of a center pole 14, and four pieces of reinforcing rib 17 are set on the head 16 at intervals of 90 deg.. Coils 18, 19 wound up in the mutual opposite directions are fitted on the rib 17 at intervals. Four spacers 15 are fitted on the central section of the center pole 14, and are arranged to freely slide on the yoke 11 between the magnets 12, 13. The degree and direction of current flowing through the coils 18, 19 are controlled, and the yoke 11 is moved forward or backward in the axial direction against the center pole 14. In this manner, high thrust is obtained with short diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in linear motors, particularly voice coil linear motors (hereinafter referred to as VCM).

[Technical background of the invention and its problems] FIG. 5 shows an example of a conventional VCM. As can be seen from this figure, the conventional VCM includes a cylindrical yoke 1, a rear yoke 2 with one end closed, a cylindrical center pole 3 erected in the center of the rear yoke, and a side The yoke includes a pair of magnets 4 located at both diametrical ends of the yoke with the same poles facing each other, and a coil 5 engaged with the center pole 3. All the magnetic flux emitted from the front surface of the magnet 4 is concentrated on the center pole 3 and returns to the yoke 1 via the rear yoke 2 and, therefore, to the back surface of the magnet 4.

The thrust F of the linear motor is It is given by F=kBIl.

Where, B is the strength of the magnetic field (Gauss), I is the amount of electricity passed (A), and l is the wire length of the coil in the magnetic field (IIl).
shall be. As can be seen from this equation, in order to obtain high thrust, either increase the strength of the magnetic field or increase the area of the magnetic field,
It depends on whether the winding length of the coil is increased.

However, due to the above-mentioned flow of magnetic flux, the magnetic flux concentrates at the base of the center pole, and magnetic saturation tends to occur in this part.In order to increase the thrust of the V-CM, it is necessary to increase the cross-sectional area of the center pole. There was a need. Therefore, it has been difficult to increase the thrust when there are restrictions on the height, diameter, etc. of the VCM.

[Object of the invention] The present invention has been made based on the above circumstances, and has a high thrust,
Moreover, it is an object of the present invention to provide a VCM that can be constructed in a small size.

[Summary of the Invention] The VCM of the present invention has a plurality of magnets mounted on one half of the yoke in the axial direction with a gap in the axial direction with one pole in contact with the inner peripheral surface of the yoke, and the The same number of magnets as the magnets are installed so that the gap matches the gap between the magnets and the other pole is in contact with the inner peripheral surface of the yoke, and the gap is located between the magnets arranged in the axial direction and matches the gap between the magnets. A magnetic circuit is constructed by supporting a center pole within the yoke concentrically with the yoke by a spacer having an axial gap between the magnets,
The movable coil is configured by fixing coil units arranged on both sides of the spacer and spaced apart by the distance between the axial center positions of the magnets arranged in the axial direction to reinforcing ribs that penetrate the gap between the spacers. do.

[Embodiment of the Invention] Fig. 1 is a perspective view of a mover coil according to an embodiment of the present invention;
The figure is a perspective view of a cut model of the magnetic circuit, FIG. 3 is a cross-sectional view showing the embodiment with a part removed, and FIG. 4 is a longitudinal sectional view of the embodiment.

In FIGS. 2 to 4, inside the cylindrical yoke 11, there are four magnets 1 that form part of the cylindrical surface in one half of the axial direction.
2 is arranged with the north pole facing the center of the yoke 11, and four magnets 513 are similarly arranged on the other half with the south pole facing. The center pole 14 has a magnetic pole provided at the center in the axial direction.
It is supported within the yoke 11 by four spacers 15 made of any non-magnetic metal. Note that the spacer 15
The gap is made to match the gap between the magnets 12 and the gap between the magnets 13 in the circumferential direction. On the other hand, as shown in FIG. 1, the mover coil 10 is composed of two coil units wound in opposite directions around four reinforcing ribs 17 in the axial direction attached to a cylindrical head 16 at 90 degree intervals. 18 and 19 are installed at intervals. Coil unit 18.19
The distance between the magnets 12 and 13 is equal to the distance between the axial center positions of the magnets 12 and 13 arranged in the axial direction.

The VCM of the present invention having the above configuration is assembled as follows. First, a magnetic circuit is assembled, then four reinforcing ribs 17 are attached to the head 16 of the mover coil, and the coil unit 18 on the head side is attached to these. In this state, the reinforcing ribs 17 are inserted into the gaps between the magnets 12, the spacers 15, and the magnets 13, and the movable coil is inserted into the magnetic circuit. When the insertion is completed, the assembly is completed by attaching the other coil unit 19 to the reinforcing rib.

The flow of magnetic flux in the VCM of the present invention having the above configuration is indicated by arrows in FIG. That is, regardless of whether the spacer 15 is made of magnetic or non-magnetic metal, the magnetic flux emitted from the surface of the head-side magnet 12 with its N pole directed toward the center of the yoke 11 enters the center pole 14 and flows inside the center pole. Go ahead, S
It enters the magnet 13 from the front surface of the magnet 13 with its pole facing the center of the yoke 11, enters the yoke 11 from the back surface, travels inside the yoke, and returns to the back surface of the magnet 12.

When a current is applied to the coil units 18 and 19 wound oppositely to each other in the flow of magnetic flux as described above, thrust is generated in the movable coil according to the direction of the current.

Since the VCM of the present invention has a magnetic flux flow as shown in FIG. 4, the magnetic flux does not concentrate at the base of the center pole unlike in the conventional VCM, and the center pole is less likely to cause magnetic saturation. High thrust can be obtained without increasing the cross-sectional area of the center pole.

Also, the coil units 18 and 19 are counter-wound, and current flows through them in opposite directions, so that the ampere-turn magnetic field that occurs when current is applied to the coils is canceled out. Therefore, the peak power can also be made significantly higher than in conventional VCMs.

Note that the present invention is not limited to the above embodiments.

For example, the shape of the magnetic circuit may be a polygonal cross section or a rectangular shape. Alternatively, the reinforcing rib may be made of a material that is resistant to sliding wear, such as an imide material or a material containing Teflon, and may be of a self-supporting type in which the reinforcing rib is slid on the spacer or center pole. This configuration is suitable for vertical operation. Also, as shown by the broken line in FIG. 4, a front plate 20 is attached to the yoke. If you install the rear plate 21, you can use a conventional VC of the same size.
The output can be approximately four times that of M.

[Effects of the Invention] As described above, the VCM of the present invention can have high thrust without increasing the cross-sectional area of the center pole, so it can be used without limiting its height and diameter and requiring small size and high thrust. It is ideal as a VCM for applications such as

[Brief explanation of drawings]

FIG. 1 is a perspective view of a mover coil according to an embodiment of the present invention, and FIG.
The figure is a perspective view of a cut model of the magnetic circuit of the embodiment, FIG. 3 is a cross-sectional view of the main parts of the embodiment, FIG. 4 is a longitudinal sectional view of the embodiment, and FIG. 5 is a longitudinal section of a conventional VCM. It is a front view. 1o...Mover coil 11...Yoke 12.1
3... Magnet 14... Center pole 15... Spacer 16... Head 17... Reinforcement rib 18.19... Coil unit application agent

Claims (1)

[Claims] On one half of the yoke in the axial direction, a plurality of magnets are attached with gaps in the axial direction with one pole in contact with the inner peripheral surface of the yoke, and on the other half, the same number of magnets as the magnets are attached with the gaps between the magnets. The center pole is mounted concentrically with the yoke by a spacer that is positioned between the magnets aligned in the axial direction and has a gap that matches the gap between the magnets. is supported in a yoke to form a magnetic circuit, and reinforcement ribs that penetrate the axial gap between the magnets and the spacer gap are arranged on both sides of the spacer, and between the axial center positions of the axially aligned magnets. A linear motor characterized in that a movable coil is constructed by fixing coil units separated by a distance.