JPH0614185Y2 - Air magnetic bearing type optical deflector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an air magnetic bearing type optical deflector, and more particularly, to an air magnetic type applicable to optical writing of a laser printer or the like by a laser deflector using a polygon mirror. The present invention relates to a bearing type optical deflector.

(Prior Art) As an optical deflector using a polygon mirror, a conventional Japanese Patent Publication No.
The thing described in 3-6854 is known. In this optical deflector, a rotary mirror, that is, a polygon mirror is arranged above the rotary shaft, a magnet constituting a thrust magnetic bearing is arranged below, and a dynamic pressure bearing of a tailing pad type is adopted as a radial bearing. I'm running.

Since this type of optical deflector has an inner rotor type motor system, the motor section is large and the overall length is long, and the thrust magnetic bearing is only at the lower end, so the rigidity is weak when the upward displacement is large. In addition, since the magnetic bearing is simply repulsive, there is no restoring force even when the rotating shaft swings around at the time of starting and stopping, so that the pad and the rotating shaft may come into contact with each other to generate abrasion powder, which makes it impossible to rotate.

On the other hand, recently, a mirror is provided at the center of the hollow rotor, a face-opposed motor is provided at the bottom, and a thrust magnetic bearing is provided at the top, and a fixed shaft for a radial dynamic pressure bearing is provided at the inner diameter of the rotor. An optical deflector configured so as to be provided is also considered. However, even in such an optical deflector, the rigidity of the thrust magnetic bearing portion is weak, the gear cup is unstable during abnormal disturbance, and abrasion powder is generated when the rotating upper portion and the fixed upper portion come into contact with each other, which adversely affects the rotation. However, it has a disadvantage that the radial rigidity at the time of starting and stopping is weak.

(Purpose) The present invention has been made to eliminate the drawbacks and inconveniences of the above-mentioned conventional device. The purpose of the present invention is to construct a magnetic bearing part in the upper and lower parts of a hollow rotary shaft and a fixed shaft to form a pair. It is an object of the present invention to provide an air magnetic bearing type optical deflector in which a plurality of magnets having a radial and thrust bearing effect are provided.

(Structure) In order to achieve the above object, the present invention comprises a dynamic bearing at the upper and lower parts of a hollow rotary shaft and a fixed shaft, which are floated by the repulsive force of a plurality of magnets, and the hollow rotary shaft, a mirror, In an air magnetic bearing type optical deflector in which a drive source for a rotor consisting of a rotor magnet assembly and some of the magnets is a face-to-face motor provided with the rotor magnet assembly, the plurality of magnets are hollow. A pair of magnets is formed at the upper and lower ends of the rotating shaft, the magnets of the pair are concentrically ring-shaped and are magnetized in the radial direction, and each of the magnets of the pair is axially displaced, and the displacement directions are opposite at the upper and lower portions. In addition, the rotating hollow shaft is axially open at the upper and lower ends.

Hereinafter, a detailed description will be given based on an embodiment of the present invention.

1 is a cross-sectional view showing an embodiment of an air magnetic bearing type optical deflector according to the present invention, wherein 1 is a hollow rotary shaft arranged in the center of a casing 12, and 2 is a peripheral part of a hollow rotary body 1. Mirrors 3, a housing for housing the rotor magnet 4 and the rotor yoke 5, 6 are magnets arranged around the upper end of the hollow rotary shaft 1, 7 are magnets arranged around the lower end of the hollow rotary shaft 1, and 8 is a hollow Fixed shafts disposed inside the rotary shaft 1, 8a and 8b are two pairs of herringbone grooves provided on the fixed shaft 8 for the dynamic pressure bearing, and 9 and 10 are provided on the upper and lower ends of the fixed shaft 8, respectively. A magnetic bearing magnet, 11 a pedestal into which the fixed shaft 8 is press-fitted, 13 a coil,
14 is a stator yoke.

In the above embodiment, the hollow rotary shaft 1 is equipped with the mirror 2 and the face-to-face motor, the rotor magnet assembly including the housing 3, the rotor magnet 4, and the rotor yoke 5, and the upper and lower magnets 6 and 7 for magnetic bearings. It is composed of a rotating body. Two pairs of herringbone grooves 8a for hydrodynamic bearings,
Magnetic bearing magnets 9 and 10 are attached to the upper and lower ends of the fixed shaft 8 provided with 8b, and a pedestal 11 is press-fitted and fixed to the lower end of the fixed shaft 8.

The magnetic bearing portion is composed of the magnets 6 and 9 and the magnets 7 and 10, and is located at the upper end and the lower end of the hollow rotary shaft 1 and the fixed shaft 8, respectively. The magnet 6 on the rotating side is magnetized in the radial direction like the magnet 9 on the stationary side, and the outer circumference of the magnet 9 and the inner circumference of the magnet 6 have the same pole. The shapes of these magnets 6 and 9 are concentric and ring-shaped. On the other hand, the rotating side magnet 6 is axially displaced from the fixed side magnet 9. In this embodiment, the magnet 6 is displaced to the lower side of the magnet 9, but it may be displaced to the upper side.

The magnets 7 and 10 are similar to the magnets 6 and 9 described above, but the axial deviation is relatively opposite between the upper end and the lower end. Since the magnetic bearings are provided at the upper end and the lower end of the hollow rotary shaft 1 which are displaced in the axial direction as described above, the hollow rotary shaft 1 has high rigidity in both the thrust direction and the radial direction, and the aligning property is made more effective. Is possible. In addition, the upper end and the lower end of the hollow rotary shaft 1 are opened in the axial direction, so that there is no risk of the fixed shaft 8 and the hollow rotary shaft 1 coming into axial contact with each other during a sudden large vibration. Therefore, it is possible to suppress the risk of being unable to rotate due to abrasion powder as much as possible.

On the other hand, the flying height is
Thrust direction repulsive force of the magnetic bearing portion consisting of 10 and rotor magnet 4, rotor yoke 5 and coil 1
3 and the starter yoke 14 in the thrust direction of the motor, and the rotating body composed of the hollow rotary shaft 1, the mirror 2, the housing 3, the rotor magnet 4, the rotor yoke 5, the magnets 6 and 7 assembled together. It is uniquely determined by the weight.

According to the configuration of the above embodiment, it is possible to increase the rigidity in both the radial and thrust directions with a simple magnet structure.
A low-cost air magnetic bearing type optical deflector can be achieved.

(Effect) As described above, according to the present invention, the dynamic bearings are formed on the upper and lower parts of the hollow rotary shaft and the fixed shaft, and the hollow rotary shaft and the mirror are floated by the repulsive force of a plurality of magnets. In an air magnetic bearing type optical deflector in which a drive source of a rotor consisting of a rotor magnet assembly and some of the magnets is a face-to-face motor provided with the rotor magnet assembly, the plurality of magnets are Pairs are formed at the upper and lower ends of the hollow rotating shaft, the magnets of the pair are concentrically ring-shaped and are magnetized in the radial direction, and each of the pair of magnets is axially displaced, and the direction of this displacement is made up and down. Since the opposite was done, the shape of the magnet is simple like a ring, so the magnet itself is easy to process, and the accuracy is easy to obtain, and also the accuracy is easy to obtain at the time of assembly. The production cost is low. Also, since each pair of magnets is axially displaced and the displacement directions are opposite at the upper and lower parts, they can be supported by magnetic force in both the thrust and radial directions despite their simple shape. With respect to, the magnetic force acts so as to sandwich the rotating body by the pair of magnets provided on the upper and lower portions of the rotating body, and thus the stability is excellent.

In addition, since the rotary hollow shaft is opened in the axial direction at the upper and lower ends, there is no risk of the fixed shaft and the hollow rotary shaft contacting each other in the axial direction during sudden large vibrations. The possibility of being unable to rotate due to is suppressed as much as possible.

[Brief description of drawings]

The drawing is a sectional view showing an air magnetic bearing type optical deflector of the present invention. 1 ... Hollow rotating shaft, 2 ... Mirror, 4 ... Rotor magnet,
6, 7, 9, 10 ... Magnet for magnetic bearing, 8 ... Fixed shaft, 13 ... Coil.

Claims (2)

[Scope of utility model registration request] 1. Hollow rotary shafts and fixed shafts are provided with dynamic pressure bearings above and below, which are floated by the repulsive force of a plurality of magnets, and the hollow rotary shafts, mirrors, rotor magnet assemblies, and the magnets. In an air magnetic bearing type optical deflector in which the drive source of the rotating body consisting of several of the above is a surface-opposed motor equipped with the rotor magnet assembly, the plurality of magnets form a pair at the upper and lower ends of the hollow rotating shaft. Air, characterized in that the magnets of the pair are concentrically ring-shaped and are magnetized in the radial direction, each of the magnets of the pair is axially offset and the offset directions are opposite at the top and bottom. Magnetic bearing type optical deflector. 2. The air magnetic bearing type optical deflector according to claim 1, wherein the rotary hollow shaft is opened in the axial direction at the upper and lower ends.