JPS6327296Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic drive device suitable for use in focus control of optical video disc players, video disc recorders, and the like.

A typical video disk recorder has a motor 2 for rotating a disk 1, as shown in FIG.
an optical recording head 7 including a light source 3, a light modulator 4, a condensing lens 5, and a drive coil 6; It consists of a device 8. Note that the condensing lens 5 is coupled to the drive coil 6,
The drive coil 6 and the condenser lens 5 are displaced in the optical axis direction in response to changes in the current supplied from the focus control circuit 9 to the drive coil 6, and the beam 10 is focused by the condenser lens 5 and projected onto the disk 1. Ru.

The conventional electromagnetic drive method, that is, the voice coil type focus control mechanism in the video disc recorder or video disc player as described above, has a second
It is configured as shown in the figure. That is, permanent magnet 1
A drive coil 6 is disposed in a gap 15 of a magnetic circuit consisting of a magnetic circuit 1, upper and lower yokes 12 and 13, and a lower part 14a of a support 14 serving as a yoke.
The shaft portion 18 of is coupled. In addition, the driven body 1
7 is a condensing lens assembly 1 including the lens 5 of FIG.
9 and is attached to the support body 14 with two gimbal springs 20 and 21. Therefore, when a current is passed through the drive coil 6 in the magnetic field applied by the magnet 11, the coil 6 is displaced in its axial direction, and the bobbin 16 and the driven body 14 are accordingly displaced in their axial direction. , the focus of the axially projected light beam is controlled. At this time, since the lens assembly 19 is supported by gimbal springs 20 and 21,
Its radial and rotational displacements are restricted and it is displaced only in its axial direction.

By the way, the system supported by the gimbal springs 20 and 21 has the disadvantage that the Q of the primary resonance is high and sub-resonance occurs, so the gain of the focus servo cannot be increased, and the gimbal springs 20 and 21 age. There are drawbacks such as the fact that the control characteristics change with changes.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electromagnetic drive device that supports a driven body without using a spring and prevents the harmful effects caused by the spring.

In order to achieve the above object, the present invention uses a magnet,
a drive coil disposed in a magnetic field formed by the magnet and displaceable in the axial direction relative to the magnet according to changes in current; and a magnetic body extending in the direction of movement of the drive coil; a driven body having a shaft portion including a permanent magnet and coupled to the drive coil so as to be displaced in the axial direction following displacement of the drive coil; and a driven body having a minute gap in the shaft portion. A plurality of first electromagnets are arranged to face each other, and a plurality of second electromagnets are arranged to face each other with a very small distance from each other on the shaft portion and are provided at positions apart from the first electromagnets in the axial direction. an electromagnet, a first interval detector for detecting the interval between the first electromagnet and the shaft, and a second interval detector for detecting the interval between the second electromagnet and the shaft. control the current of the first electromagnet so that the distance between the first electromagnet and the shaft portion is maintained at a predetermined position based on the output of the first distance detector;
and a control circuit that controls the current of the second electromagnet so that the distance between the second electromagnet and the shaft portion is maintained at a predetermined value based on the output of a distance detector. It is something. Note that the first electromagnet in the present invention corresponds to the upper electromagnets 22, 23, 24, 25, 26, and 27 in the embodiment, and the second electromagnet corresponds to the lower electromagnets 28, 27 in the embodiment.
29, 30, 31, 32, and 33, the first spacing detector corresponds to the spacing detector 40 disposed opposite to the upper shaft portion 34 of the embodiment, and the second spacing detector corresponds to the spacing detector 40 of the embodiment. This corresponds to an interval detector 40 disposed opposite to the lower shaft portion 35 of the .

According to the present invention, the first and second electromagnets are provided at a distance in the axial direction of the driven body, and these are controlled by the outputs of the first and second distance detectors, so that no inclination occurs. The attitude of the driven body can be controlled as follows. That is, the driven body can be reliably kept vertical.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 6. However, in FIGS. 3 to 6, parts common to those in FIG. 2 are designated by the same reference numerals and their explanations will be omitted.

In the embodiment shown in FIGS. 3 to 6, six upper electromagnets 22 to 27 and six lower electromagnets 28 to 33 move the driven body 14 in the radial direction (radius direction) without using a gimbal spring. direction) and position in the rotational direction. These electromagnets 22 to 33
is fixed to the support body 14 to constitute a support-side magnetic attraction or repulsion section. The magnetic attraction or repulsion portion of the driven body 17 that faces the support side magnetic attraction or repulsion portion is configured by providing magnetic shaft portions 34 and 35 on the shaft portion 18 of the driven body 17. The magnetic shaft portions 34 and 35 have a pair of opposing flat surfaces 36 and 37 and a pair of circumferential surfaces 38 and 39, respectively. 40 is an interval detector, and electromagnet 2
The electromagnets 22 to 33 are arranged in parallel to each other in order to detect the distance between the electromagnets 2 to 33 and the magnetic shafts 34 and 35. Note that this interval detector 40 includes the magnetic shaft portion 34,
It is constituted by an electromagnetic pickup whose output changes depending on the change in the distance between the pickup and the pickup. However, the present invention is not limited to this, and may be a combination of a Hall element and a magnet, or an optical sensor.

In this embodiment, a control circuit as shown in FIG. 6 is connected to each electromagnet in order to control the distance between the electromagnets 22 to 33 and the magnetic shafts 34 and 35. In FIG. 6 showing the control circuit of the electromagnet 22, the output of the interval detector 40 arranged in parallel to the electromagnet 22 is compared with a reference voltage REF by a voltage comparator 41, and this comparison output is amplified by an amplifier 42. A voltage corresponding to the comparison output is supplied to the electromagnet 22.
That is, control is performed to keep the distance between the electromagnet 22 and the shaft portion 34 constant.

In this device, the lower limit of the driven body 17 is determined by the upper end of the center of the lower support 14a, and the upper limit is determined by the position where the lens assembly 19 hits the support 14. Further, although not shown in the drawings, elastic bodies are provided to improve the contact of the driven body 17 at the lower and upper limits.

When performing focus control using this device, a current is passed through the drive coil 6 and the electromagnet 22 is
A current is applied to ~23. When a current is applied to the drive coil 6, the drive coil 6 moves in its axial direction similarly to the voice coil of a speaker, and the driven body 17 also moves following this movement. Focus control is then performed using the constant displacement as a reference position. By the way, when a current is passed through the drive coil 6, a force mainly in an axial direction component is generated, but other forces in a radial direction component and a rotational direction component are also generated. Conventionally, this was limited by a gimbal spring, but in this device, it is limited by the magnetic action between the electromagnets 22 to 33 and the magnetic shafts 34 and 35. That is, electromagnet 2
2 to 33 to attract the magnetic shaft portions 34 and 35 in a balanced state in the radial direction, thereby limiting the displacement of the driven body 17 in the radial direction and also limiting the displacement in the rotational direction. are doing.
More specifically, if the magnetic body shaft portion 34 moves rightward in FIG. 5, the electromagnet 22 and the shaft portion 34
The distance between the electromagnet 25 and the shaft portion 34 becomes narrower.
The distance between the As a result, the current in the right electromagnet 22 is reduced and the current in the left electromagnet 25 is increased by the servo circuit as shown in FIG. As a result, the attraction force by the left electromagnet 25 increases, and the shaft portion 34 is pulled back to the left. Therefore,
It becomes possible to always hold the shaft portion 34 at the center position. Further, if the shaft portion 34 is rotated slightly clockwise, for example, the distance between the electromagnets 23, 26 and the shaft portion 34 becomes narrower, while the distance between the electromagnets 24, 27 and the shaft portion 34 becomes wider. Therefore, the interval detector 4
A difference occurs between the output of 0 and the reference voltage REF, and the attraction force of the electromagnets 23 and 26 becomes weaker, while the attraction force of the electromagnets 24 and 27 is controlled to become stronger, and the shaft portion 34 returns to its original angle. returned to position.

As is clear from the above, according to this example,
Since the displacement of the driven body in the radial and rotational directions can be limited without contact without using a gimbal spring, focus control is possible without the drawbacks caused by springs. Therefore, it is possible to increase the focus servo gain.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be further modified. For example, as shown in Figure 7,
The magnetic body shaft portion 34 is formed into a triangular shape, and the electromagnets 43,
44 and 45 may be arranged radially, facing each side of the triangle.

Further, as shown in FIG. 8, permanent magnets 46, 47, 48, and 49 are arranged on the shaft portion 18 of the driven body 17, and a fixed side, that is, a supporting side permanent magnet 5 is arranged opposite thereto.
0, 51, 52, and 53, and the displacement of the shaft portion 18 in the radial direction and rotational direction may be prevented by utilizing the repulsion of the opposing magnets.

Further, displacement in the radial direction and rotational direction may be prevented by a combination of a permanent magnet and an electromagnet. Further, in cases where displacement in the rotational direction is acceptable, or in the case where a mechanism for preventing displacement in the rotational direction is separately provided, the magnetic shaft portions 34 and 35 may be circular. Further, a dedicated stopper may be provided to determine the upper and lower limits of the driven body 17. It is also applicable to optical video disc players. It is also applicable to electromagnetic vibration devices. Further, the configuration in which the vertical relationship in FIG. 3 is reversed may also be used.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an optical video disc recorder according to an embodiment of the present invention, Fig. 2 is a sectional view showing a conventional focus control mechanism, and Fig. 3 is a focus control mechanism according to an embodiment of the present invention. 4 is a perspective view showing a part of the focus control mechanism shown in FIG. 3, FIG. 5 is a plan view showing the relationship between the shaft and the electromagnet, and FIG. 6 is a block diagram showing the electromagnet control circuit. , FIG. 7, and FIG. 8 are plan views showing modified examples. In addition, in the symbols used in the drawings, 6 is a drive coil, 11 is a permanent magnet, 14 is a support body, and 17
is a driven body, 18 is a shaft portion, 19 is a lens assembly,
22 to 33 are electromagnets, 34 and 35 are magnetic shaft parts,
40 is an interval detector.

Claims (1)

[Claims for Utility Model Registration] A magnet; a drive coil disposed in a magnetic field formed by the magnet and displaceable in the axial direction relative to the magnet in response to changes in electric current; a driven body having a shaft portion including a magnetic body or a permanent magnet extending in the moving direction of the drive coil, and coupled to the drive coil so as to be displaced in the axial direction following displacement of the drive coil; a plurality of first electromagnets arranged opposite to each other with a minute distance between them on the shaft; and a plurality of first electromagnets arranged opposite to each other with a minute distance on the shaft and separated from the first electromagnet in the axial direction. a plurality of second electromagnets provided at positions; a first distance detector for detecting the distance between the first electromagnet and the shaft; and a distance between the second electromagnet and the shaft. a second spacing detector for detecting the first spacing detector; controlling the current of the second electromagnet so that the distance between the second electromagnet and the shaft portion is maintained at a predetermined value based on the output of the second distance detector; An electromagnetic drive device consisting of a control circuit.