JPH03187026A - Galvanomirror - Google Patents

Abstract

PURPOSE:To obviate the disconnection of feeders and to facilitate assembly by using a permanent magnet subjected to radial multiple magnetization as a rotor and providing braking adjustment mechanisms. CONSTITUTION:The permanent magnet 4 subjected to the multiple magnetization in the radial direction is the rotor supported by bearings 3, 9. A mirror 1 is fixed to the front end of a supporting shaft 2. Driving mechanisms 5, 6 and the braking adjustment mechanisms 7, 8 are disposed by having a specified distance from the magnet 4. The state in which the tooth 10 of a stator core 5 for driving faces the boundary position between the N pole and S pole of the magnet 4 is the oscillation center of the rotor. While the stator core 7 for braking is so fixed that the position of the tooth equals to the stator core for driving, this position may be shifted by half the pitch of the magnetization pitch of the magnet 4. The rotor generates a rotational displacement in both directions from the oscillation center by the current direction of the coil 6 for driving, by which the optical axis of the incident laser beam on the mirror 1 is oscillated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a movable magnet type galvanomirror (hereinafter referred to as GM) used for tracking control of a laser beam of an optical memory device.

[Prior Art] Conventionally, the GM used in the optical head of an optical memory device is
For example, as seen in Japanese Unexamined Patent Application Publication No. 63-12334, there were many configurations in which the movable part was a coil and the movable part was connected using an elastic member.

[Problems to be solved by the invention] However, in the conventional technology, disconnection of the power supply line to the moving coil,
There is a problem that poor adhesion due to overheating of the coil and accompanying thermal deformation of the coil are likely to occur. In addition, the process of connecting the power supply line is complicated and time-consuming, and depending on the power supply method, the power supply line itself may have an adverse effect on the high-speed operation of the moving parts, and high-order resonance due to the elastic member may occur, hindering high-speed operation. become. Therefore, the rotational speed of the optical disc cannot be increased, and the data transfer speed is limited. Furthermore, unless the processing accuracy of elastic members is strictly controlled, there will be extremely large variations in dynamic characteristics, and changes over time will also be large, making it difficult to obtain stable characteristics.

The present invention is intended to solve these problems, and its purpose is to provide an easy-to-assemble structure in which high-order resonance in the movable parts is less likely to occur and there is no need to supply power to the movable parts. , provides a GM with excellent high-speed operation. This makes it possible to realize an optical memory device with high reliability and high data transfer speed.

[Means for Solving the Problems] The GM of the present invention has a structure in which a permanent magnet is part of a movable part as a tracking control means for a laser beam of an optical memory device, in which a mirror is fixed and radial magnetization is multipolarized. A structure in which a rotor is made of a cylindrical permanent magnet applied to a rotor, and an iron cable is excited to the same polarity by an excitation coil, which has teeth equal to the number of magnetic poles of the permanent magnet through a constant gap with the outer peripheral surface of the permanent magnet. The stator core is further provided with a non-contact braking adjustment mechanism on the rotor.

[Function] According to the above configuration of the present invention, the movable part can be kept neutral and rotated minutely by the magnetic force acting between the radially multipolar magnetized permanent magnet and the teeth of the stator core. Furthermore, the non-contact damping adjustment mechanism allows the primary resonance point to be adjusted without worrying about higher-order resonance.

[Example] The present invention will be described in detail below based on examples.

FIG. 1 is a sectional view showing an embodiment of the GM of the present invention. A rotor 4 is a cylindrical permanent magnet magnetized with multiple poles in the radial direction and supported by bearings 3 and 9.

The tip of the support shaft 2 serves as a mirror holder to which the mirror 1 is fixed. Drive mechanism 5, 6 and brake adjustment mechanism 7.8
are placed at a certain distance from the permanent magnet. Second
As shown in the figure, the rotor's oscillation center is when the teeth 10 of the driving stator core 5 face the boundary between the north and south poles of the permanent magnet.The poles shown on the permanent magnet in the figure are: These are the poles that appear on the outer peripheral surface of the cylinder. The same applies to the following figures. The braking stator core 7 is fixed so that the tooth position is equal to that of the driving stator core, but it may be shifted by a half pitch of the magnetization pitch of the permanent magnet. The spring constant of oscillation can be adjusted by changing the area. Furthermore, the damping performance can be adjusted by changing the specifications of the braking coil 8 wound around the braking stator core. Here, the braking coil is not connected to the drive circuit, and the rotor generates rotational displacement in both directions from the center of swing depending on the current direction of the drive coil 6, making it possible to swing the optical axis of the laser beam incident on the mirror. Figure 3 (a), (
b) and (c) show the facing state of the tooth and the permanent magnet, (a
) is a neutral state in which no current flows through the drive coil. (b) shows the case where a coil current is applied, and the motor becomes stable at a position where the torque generated by the coil current and the force of attraction between the permanent magnet and the teeth of the stator core match. (C
) is the case when the coil current is increased.If the current is increased any further, the coil will move to the next neutral state, so if necessary, a stopper that regulates the rotation angle of the swinging part can be provided to prevent the movement of the neutral state. It can be prevented. The number of magnetized poles of the permanent magnet can be determined depending on the required swing angle and drive sensitivity, and is not limited to the example shown in FIG. 3.

FIG. 4 shows another example of the brake adjustment mechanism.

Two yokes 11 face the magnetic poles of the permanent magnet 4,
A braking magnet 12 couples the yoke. By changing the distance between this braking mechanism and the permanent magnet 4, the spring constant can be adjusted.

Next, the permanent magnet used in this example will be described.

Sm allows for highly productive production of anisotropic magnets with high magnetic performance.
-Go resin-bonded magnets are very advantageous. Furthermore, this permanent magnet has a light I and can easily achieve high dimensional accuracy. In this example, an Sm-Co resin bonded compression molded magnet was used, but the magnet material and molding method are not limited to this. No, initially the composition is S m (CO@, 872c
u s, ss Feshi22Zr 192・) @,
The raw material is melted in an induction furnace so that it becomes zs. The ingot was heated at 1120 to 1180°C for 5 minutes in an Ar gas atmosphere.
A time solution treatment was performed, followed by an aging treatment at 850°C for 4 hours.

The 2-17 rare earth intermetallic alloy thus obtained is
The powder was ground to an average particle size of 20 μm (according to Fischer subsieve cider). A magnetic composition prepared by adding 2% by weight of a thermosetting two-component engineered poxy resin as a binder to the 2% by weight was oriented in a magnetic field using a powder molding magnetic field press machine and formed into a cylindrical shape, followed by a curing treatment. I did it. This was subjected to multi-pole magnetization in the radial direction.

GM of the present invention using the permanent magnet thus obtained
was mounted on an optical head, and tracking was performed by slightly changing the angle of the laser beam incident on the objective lens. The dynamic characteristics showed very good high-speed response.The present invention is easy to assemble because it does not use springs to maintain the movable part neutral, and high-order resonance, which has been a problem in the past, can be avoided. Furthermore, since a braking adjustment mechanism is provided that does not make contact with the movable part, the frequency and peak amount of the primary resonance point can be adjusted without worrying about higher-order resonance, making it easy to adapt to devices with different rotational speeds of optical discs.

[Effects of the Invention] As described above, according to the present invention, the following advantages are produced by using a radially multipolar magnetized permanent magnet in the movable part and installing a brake adjustment mechanism.

(1) There is no disconnection in the power supply line.

(2) Assembly is easy because there is no connection process for power supply lines.

(3) There is no need to worry about thermal deformation of the coil or poor adhesion.

(4) There is no support spring.

(5) The -order resonance point can be easily changed.

Therefore, a GM with excellent high-speed response and high reliability can be obtained.

The GM of the present invention can be applied to optical memory devices such as computer memories, optical disk files, CDs, CD-ROM% LVDs, etc., and has great effects such as improving the performance and miniaturizing the devices. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the GM of the present invention. FIG. 2 is a diagram showing the relationship between the stator core and magnetic poles. FIG. 3 is an explanatory diagram of the swinging neutral state. FIG. 4 is a diagram showing another example of the brake adjustment mechanism. 1...Mirror 4...Permanent magnet 5...Stator core for drive 6...Coil for drive 7...Stator core for braking 8...For braking Coil O: Teeth (part of stator core) 1: Yoke 2: Braking magnet or higher

Claims (1)

[Claims] (1) In a galvano mirror that uses a permanent magnet as part of the movable part as a tracking control means for the laser beam of an optical memory device, the mirror is fixed and the rotor is made of a cylindrical permanent magnet that is radially magnetized into multiple poles. and a stator core having a structure in which teeth are arranged in pairs with the magnetic poles of the permanent magnet with a certain gap between them and the outer peripheral surface of the permanent magnet, and the teeth are excited to the same polarity by an excitation coil; A galvanometer mirror characterized by having an adjustment mechanism.