JPH02301024A - Galvanomirror - Google Patents

Abstract

PURPOSE:To obtain a galvanomirror with simple structure and miniaturized and of light weight by using a radial multipole-magnetized permanent magnet in a movable part, and supporting the movable part with a superconducting shaft. CONSTITUTION:The galvanomirror is provided with a cylindrical permanent magnet 1 on which a mirror 5 is fixed and radial magnetization are applied on multiple poles, a supporting shaft 2 consisting of a superconducting material via the inner peripheral plane of the magnet 1 and a constant gap, and the tooth 8 for a couple of magnetic pole of the permanent magnet 1 via the outer peripheral plane of the permanent magnet 1 and the constant gap. The tooth 8 is part of a stator core 3, and is formed in such structure that it is excited in the same pole with an excitation coil 4. A state where the tooth 8 of the stator core 3 is confronted with a boundary position between an N pole and an S pole becomes the rocking center of the permanent magnet 1, and rotational displacement is generated in two directions from the rocking center with the direction of a coil current in the permanent magnet 1, and the optical axis of a laser beam made incident on the mirror 5 fixed on the permanent magnet can be rocked. Thereby, it is possible to obtain the galvanomirror without generating the thermal deformation and a defect in sticking in the coil 4 and with simple structure and miniaturized and of light weight.

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,
Bonding failure due to overheating of the coil and associated thermal deformation of the coil are likely to occur.Furthermore, 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 a negative effect on the high-speed operation of the moving parts. It has the problem of causing problems. In addition, variations in the coil shape tend to cause unbalance in the mass of the movable part, which causes high-order resonance and impedes high-speed operation. Therefore, the rotational speed of the optical disc cannot be increased, and the data transfer speed is limited. Furthermore, since changes in coil specifications (number of turns, wire diameter, etc.) lead to changes in the mass of the movable part, it is necessary to repeatedly cut and try with changes in the design of the actuator in order to find the optimum specifications for the coil. In addition, high-speed response deteriorates due to high-order resonance caused by the elastic member, and unless the machining accuracy of the elastic member is strictly controlled, variations in dynamic characteristics become extremely large, making it difficult to obtain stable characteristics.The assembly process is also complicated and requires manual labor. It was time-consuming.

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 support shaft made of a superconducting material is connected to a cylindrical permanent magnet with a constant gap between the inner peripheral surface of the permanent magnet, and a magnetic pole of the permanent magnet is connected through a constant gap to the outer peripheral surface of the permanent magnet. has logarithmic teeth,
The stator core is characterized in that the teeth are excited to the same polarity by an excitation coil.

[Function] According to the above-mentioned aspects of the present invention, the movable part can be kept neutral and rotated minutely by the magnetic force acting between the radially multipolarized permanent magnet and the teeth of the stator core. Further, the movable part can be supported without contact due to the Meissner effect of the support shaft made of a permanent magnet and a superconducting material.

[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. 1 is a cylindrical permanent magnet magnetized with multiple poles in the radial direction, 2 is a support shaft made of superconducting material, 3 is a stator core,
In the 0-wire configuration where 4 is a coil, the state where the teeth of the stator core face the boundary between the N and S poles of the permanent magnet becomes the center of swing of the permanent magnet, and the permanent magnet swings depending on the direction of the coil current. Rotational displacement occurs in both directions from the center, and the optical axis of the laser beam incident on the mirror 5 fixed thereto can be swung. Teeth 8 in Fig. 2 (a), (b), and (C)
The poles shown on the permanent magnet in Figure 0, which shows the facing state of permanent magnet 1, are the poles that appear on the outer peripheral surface of the cylinder, and the poles that appear on the inner peripheral surface.
The opposite polarity is occurring. FIG. 2(a) shows a state in which the coil current is not flowing in a neutral state. (b) shows the case where a coil current is passed, 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 a case where the coil current is increased, and the coil will move to the next neutral state, so if necessary, it is possible to prevent this shift from the neutral state by providing a stopper that regulates the rotation angle of the swinging part. . However, whether or not to provide a stopper is simply a structural issue and does not affect the basic technical scope of the present invention.The number of magnetized poles of the permanent magnet should be determined according to the required swing angle. The support mechanism is a non-contact type shaft and bearing using superconducting materials and permanent magnets, so stable rotation can be achieved even during high-speed driving. is obtained. The support in the left-right direction in FIG. 1 is also carried out using a cylindrical permanent magnet 1, a support shaft 2, a disk-shaped permanent magnet 6 magnetized in the thickness direction, and a ring-shaped superconductor 7. There is.

Next, the permanent magnet and superconductor used in this example will be described. Sm-Go resin bonded magnets are very advantageous because they can produce anisotropic magnets with high magnetic performance with good productivity. Furthermore, this permanent magnet is lightweight and can easily achieve high dimensional accuracy.

In this example, a Sm-Go resin bonded compression molded magnet was used, but the magnet material and molding method are not limited to this.
@sF e @, 22Zr s, 52s) *, The raw material is melted in an induction furnace so that it becomes s5. The ingot was subjected to solution treatment at 1120 to 1180°C for 5 hours in an Ar gas atmosphere, and then aged at 850°C for 4 hours. The 2-17 rare earth intermetallic alloy thus obtained was ground to an average particle size of 20 μm (by Fischer subsieve cider), and the powder was 98% by weight.
A magnet composition prepared by adding 2% by weight of a thermosetting two-component engineered poxy resin as a binder was oriented in a magnetic field using a powder molding magnetic field press machine, molded into a cylindrical shape, and then cured. . This was subjected to multi-pole magnetization in the radial direction.

Also, it is desirable that the critical temperature is higher than that of superconducting material 1.
Although an oxide superconductor was used in this example, it is not limited to this. First, the composition is Bi+, aPbs, sS r
The acetate salts of each component are added to pure water and stirred and dispersed so that the amount becomes 2 Ca2 cu 30 v. This liquid is dried by the Drais Buissie method and simultaneously combusted to obtain a fine powder. Next, this fine powder is calcined in an oxygen atmosphere at 800° C. for 2 hours. Furthermore, the fired fine powder was pressed into the shape of a support shaft, and then sintered in air at 845°C.

The GM of the present invention using the permanent magnet and superconducting shaft thus obtained is mounted on an optical head, cooled to liquid nitrogen temperature, and tracking is performed by slightly changing the angle of the laser beam incident on the objective lens. I did it. 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 the movable parts can be supported without contact, unnecessary parasitic vibrations and friction can be avoided and stable high-speed operation can be achieved.

[Effects of the Invention] - As shown above, according to the present invention, the following advantages are produced by using a radially multipolar magnetized permanent magnet in the movable part and supporting the movable part by a superconducting shaft. .

(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) Simple structure, small size, and light weight.

(6) Since the movable parts are supported without contact, there is no unnecessary parasitic vibration or friction.

Therefore, a GM with excellent high-speed response and high reliability can be obtained6.
The GM of the present invention can be applied to optical memory devices such as computer memory, optical disk 7 files, CDs, CD-ROMs, and LVDs, and has great effects such as improving the performance and miniaturizing the devices. be.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the GM of the present invention. FIG. 2 is an explanatory diagram of GM's neutral state. 1...Permanent magnet 2...Support shaft 3... Stator core 4... Coil 5...Mirror 8...Teeth (part of stator core) or more

Claims (1)

[Claims] (1) In a galvanometer mirror having 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, the mirror is fixed and a cylindrical permanent magnet is radially magnetized into multiple poles, and the permanent magnet is A support shaft made of a superconducting material that is connected to the inner peripheral surface of the magnet with a certain gap therebetween, and a pair of teeth of the magnetic poles of the permanent magnet that are connected to the outer peripheral surface of the permanent magnet and have a certain gap therebetween,
A galvanometer mirror comprising a stator core having a structure in which the teeth are excited to the same polarity by an excitation coil.