JPS61164458A - Linear motor - Google Patents

Abstract

PURPOSE:To obtain small-sized products of high thrust, by fitting a pair of magnets on the inner peripheral face of one end of a cylindrical yoke so that different poles may confront with each other, and by engaging the diameter sections of two coils forming a mover, with a wide slot in the axial direction of a center pole. CONSTITUTION:A cylindrical holder 11 made of light alloy is fitted at one end of a cylindrical yoke 10 with the both opening ends, and a pair of magnets 14, 14 are fitted on the inner peripheral face of the other end so that the different poles may confront together. A wide slit 12 in the axial direction is provided for a center pole 13, and after a mover 15 is inserted into the slot, the opening end of the center pole 13 is closed by a front yoke 13b. Two semi-circular coils are lumped together at the diameter section 15a3 by the mover 15, and the mover 15 is formed with a composite coil 15a for reversing the current direction of the both coils, an intermediate pipe 15b, and a fitting head 15c, and the diameter section 15a3 is engaged with the wide slot 12. Current flowing through coils is controlled, and the mover 15 is moved, In this manner, the distribution of magnetic flux is uniformed, and small-sized products of high thrust are produced.

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. 6 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.

Due to the above magnetic flux flow, the magnetic flux concentrates at the base of the center pole, and magnetic saturation tends to occur in this part, causing VCM
In order to increase the stroke, it was necessary not only to increase the length of the magnet, yoke, and center pole, but also to expand them three-dimensionally. Therefore, a long stroke VCM has to be heavy. Therefore, when designing a large-sized, large-thrust VCM, it is important to reduce the weight of the magnetic circuit as much as possible in consideration of the stroke.

Furthermore, when current is applied to the coil, a magnetic field is generated due to AT (Ampere Turn), which enters the center pole and merges with the magnetic field of the magnet, strengthening it when the directions are the same and weakening it when the directions are opposite. However, there is a problem in that it causes fluctuations in thrust force, and advanced technology is required to design a VCM with a good balance between the two.

[Object of the Invention] The present invention has been made based on the above circumstances, and even when a long stroke VCM is used, the yoke and center pole can be made small and lightweight, and the A when the coil is energized can be reduced.
To provide a VCM that solves the problem of magnetic fields caused by T.

[Summary of the Invention] The VCM of the present invention includes a cylindrical yoke, a pair of magnets located at both diametrical ends of the yoke and having different poles facing each other, and a pair of magnets arranged concentrically within the yoke. A center pole is arranged in a cylindrical shape and has a long hole in the axial direction that is symmetrical in a plane including its diameter, and a pair of approximately semi-cylindrical coils are wound oppositely to each other. It is characterized by having a composite coil that is formed in contact with each other and has the straight portion engaged with the elongated hole.

[Embodiments of the Invention] Fig. 1 is a perspective view of a cut model of the present invention-embodiment, Fig. 2 is a perspective view showing the mover taken out, and Fig. 3 is a perspective view of the mover coil. FIG. 4 is a cross-sectional view of the embodiment, and FIG. 5 is a longitudinal cross-sectional view thereof.

In FIG. 1, a ring plate-shaped rear holder 11 made of light alloy is attached to one end of a cylindrical yoke 10 with both ends open.
A center pole 13 having a cylindrical shape and having an axially elongated hole 12 having a symmetrical shape with respect to a surface including one diameter is supported concentrically with the yoke 10 on this rear holder. This center pole 1
3 is actually constructed by making a deep slit in a columnar material 13a, and closing the open end of the slit with a disc-shaped front yoke 13b. Further, the magnets 14 forming a part of the cylindrical surface are located at both diametrical ends of the yoke 10 and are attached to the inner surface of the yoke with different polarities facing each other. On the other hand, the movable element 15 has a composite coil 15a, an intermediate vibrator 15b, and a mounting head 15c, as shown in FIG. As shown in FIG. 3, the composite coil 15a is a combination of two approximately semicircular coils 15a1 wound in opposite directions, such as the one on the left in the figure being left-handed and the one on the right being cloth-wrapped. A flat portion 15a2 formed by combining the straight portions of the two coils is engaged with the elongated hole 12 of the center pole 13. Its assembly is performed as follows. First, before attaching the front yoke of the center pole, the flat portion 15a2 of the composite coil 15 is engaged with the slit in the center pole material, the intermediate vibe 15b is coupled thereto, and then the front yoke 13b is attached. The attachment head 15G is connected and fixed to the intermediate vibrator 15b attached to the composite coil 15a engaged with the center pole 13 as described above.

The current flow and magnetic flux flow in the VCM of the present invention having the above configuration are as shown in FIGS. 4 and 5. First, current flows clockwise in the left coil that constitutes the composite coil 15a, and counterclockwise in the right coil.

Also, the magnetic flux emitted from one magnet first enters the leg of the center pole member 13a that is close to that magnet, but then it is diverted through the front yoke 13b and the rear side member and flows into the other leg. From there, it enters the magnet on the opposite side close to the leg, and then returns to the back side of the original magnet via the yoke 10. Thus, when a current is applied to the composite coil 15a consisting of the coils 15a1 wound in opposite directions (current is caused to flow in opposite directions) as described above, thrust is generated in the movable element 15.

In the VCM of the present invention having the above configuration, there is no concentration of magnetic flux seen in conventional VCMs, and there are no parts in the center pole or yoke that are particularly prone to magnetic saturation.
The same output can be obtained with a center pole and yoke that are 1/2 to 1/3 the weight.

Also, when increasing the stroke of the VCM, there is no need to increase the weight i of the center pole σ, etc.

Furthermore, since the flow of magnetic flux passes through the cylindrical yoke and enters the back surface of the other magnet, the rear holder can be made of a non-magnetic light metal, which also contributes to weight reduction.

Furthermore, in conventional VCMs, the AT (ampere-turn) magnetic field generated by energizing the coil enters the magnet and yoke, causing fluctuations in the magnetic field lines generated by the magnet, which can cause significant fluctuations in thrust force. In some cases, this may cause permanent demagnetization of the magnet. In the VCM of the present invention, the flow of magnetic flux generated by the two coils that make up the composite coil is limited to the center pole and does not easily affect the magnet, so there is no problem as described above, so the peak current value can be set high. It can be set, which is advantageous when starting and stopping VCM.

The coil may be with or without a bobbin, and the wire of the coil may be either a round wire or a rectangular wire. Furthermore, it goes without saying that the present invention can be applied not only to the illustrated short coil type but also to a long coil type.

C Effect of the Invention] As is clear from the above, the VCM of the present invention can be made much smaller than the conventional VCM if the output is the same, and conversely, if the size and weight are the same, it is significantly smaller. It can be a VCM with a large output. Further, even a VCM with a large stroke can be easily designed because there is no need to consider magnetic saturation of a center pole or the like as in the conventional case.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a cut model according to an embodiment of the present invention;
Figure 3 is a perspective view of the movable element, Figure 3 is a perspective view of the composite coil, Figure 4 is a cross-sectional view of the embodiment, Figure 5 is a vertical cross-section thereof, and Figure 6 is a vertical cross-section of a conventional VCM. It is a front view. 1o... Yoke 11... Rear holder 12.
...Long hole 13...Center pole 14...
Magnet 15...Mover 15a...Composite coil Fig. 1 Fig. 2 Oc Fig. 3 Fig. 4 Diagram No.a.

Claims (1)

[Claims] A cylindrical yoke, a pair of magnets arranged within the yoke at both ends of the diameter of the yoke with different poles facing each other, and a pair of magnets arranged concentrically within the yoke and having a cylindrical shape and whose diameter A center pole having a long hole in the axial direction symmetrical to the plane containing the center pole, and a pair of approximately semi-cylindrical coils wound oppositely to each other are formed by abutting the straight parts of the coils. A linear motor characterized by having a composite coil engaged with a long hole.