Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Patent
1997-01-14
1999-06-15
Gellner, Michael L.
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
335223, 335229, 359198, 359199, 359212, 359213, 359223, 359226, 310 36, G02B 718, G01R 1338
Patent
active
059126086
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a planar type electromagnetic actuator in which miniaturization has been realized through the use of semiconductor manufacturing technology, and in particular to a technique for reducing the cost of planar type electromagnetic actuators.
DESCRIPTION OF THE PRIOR ART
The present inventor has previously proposed a very small size planar type electromagnetic actuator which utilizes semiconductor technology. This device is suitable for example for a planar type mirror galvanometer (Japanese Patent Application Nos. 5-320524 and 6-9824).
A description of this planar type electromagnetic actuator is given below.
The electromagnetic actuator comprises a silicon substrate on which is integrally formed a planar movable portion, and an axial support portion of torsion bar construction for axially supporting the movable portion so as to be able to swing at a central location of the movable portion relative to the silicon substrate in a perpendicular direction thereof. A planar coil of thin copper film, for generating a magnetic field by means of a current, is provided on a peripheral upper surface of the movable portion. Moreover, permanent magnets serving as static magnetic field generating devices forming a pair with each other, are provided at the periphery of the movable portion so that the static magnetic field generated thereby acts on the planar coil portions located on the opposite sides of the movable portion which are parallel with the axial direction of the axial support portion. With the abovementioned patent applications, pairs of permanent magnets are respectively located above and below the opposite side portions of the movable portion, the construction being such that the static magnetic fields generated between the pairs of permanent magnets intersect the drive coil in predetermined directions.
Such an electromagnetic actuator is driven by passing a current through the planar coil. That is to say, a static magnetic field is formed by means of the permanent magnets on opposite sides of the movable portion, in a direction so as to intersect the planar coil lying along the planar face of the movable portion. When a current flows in the planar coil positioned in this static magnetic field, a magnetic force acts in a direction according to Fleming's left hand rule for current, magnetic flux density, and force, on the opposite sides of the movable portion in proportion to the current and magnetic flux density, as represented by the following equation (1), so that the movable portion is rotated. and B is the magnetic flux density of the static magnetic field generated by the permanent magnets.
On the other hand, the axial support portion is twisted with the rotation of the movable portion, producing a spring reaction force, so that the movable portion rotates to a position where the magnetic force and the spring reaction force are in equilibrium. The angle of rotation of the moveable portion is proportional to the current flowing in the planar coil, and hence the rotation angle of the movable portion can be controlled by controlling the current flowing in the planar coil.
Consequently, if for example a mirror is provided on a central surface of the movable portion, then the direction of reflection of a laser beam incident on the mirror in a plane perpendicular to the axis of the axial support portion, can be freely controlled. Hence the device can be used as a mirror galvanometer for carrying out laser beam scanning by cyclic operation to continuously change the mirror displacement angle.
One such electromagnetic actuator, has a two axis construction with two axial support portions at right angles to each other.
That is to say, the movable portion formed integral with the silicon substrate is made up of a frame like outer movable plate and a planar inner movable plate located within the frame of the outer movable plate. Moreover, the axial support portions comprise first torsion bars for axially supporting the outer movable plate, and a second torsi
REFERENCES:
patent: 4421381 (1983-12-01), Ueda et al.
patent: 4818966 (1989-04-01), Miyamoto et al.
patent: 5543956 (1996-08-01), Nakagawa et al.
Barrera Raymond
Gellner Michael L.
The Nippon Signal Co. Ltd.
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