JPS63259510A - Aeromagnetic bearing type of optical deflector - Google Patents

Abstract

PURPOSE:To execute a stable superhigh speed rotation by constituting a dynamic pressure bearing by inserting and holding a magnet of the upper end part at a gap by the upper and lower magnets without providing a thrust stopper for coming into contact with a hollow rotating body. CONSTITUTION:With respect to a revolving shaft 21, a thrust magnet holder 22 and a thrust magnet 23 are placed in its upper part, and also, a mirror 25, a mirror holder 24, a rotor magnet 26 and a balance correcting ring 27 are installed, by which a rotating body is constituted. That is, a motor part is constituted of a rotor magnet 26 and a coil part 32, and by switching an excitation, the rotating body rotates. Accordingly, it becomes possible to make the diameter of the rotor magnet 26 small remarkably, and also, a vibration caused by switching an excitation of the motor part is executed in the radial direction, and does not become a disturbance for practical use. In such a way, the centrifugal force becomes small, it is not feared that the rotor magnet is broken down, and a stable rotation can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a permanent magnet repulsion type air magnetic bearing type optical deflector.

This lightning deflector is used in laser beam writing systems such as laser printers and digital copying machines.

(Prior Art) FIG. 2 shows the configuration of a conventional aeromagnetic bearing type optical deflector.

In the figure, a hollow rotating body 1 has a mirror 3 in the center, rotor magnet assemblies 4, 7.8 of a surface-facing motor serving as a driving source in the lower part, and magnets 9 constituting a magnetic bearing in the upper part. is installed and configured.

On the other hand, the fixed shaft 11 has a magnetic bearing magnet 10 attached to its upper part. Further, the surface of the fixed shaft 11 has two pairs of herringbone grooves 11a and 11b for dynamic pressure air bearings. The lower end of the fixed shaft 11 is connected to the housing 1.
2 by a method such as press-fitting or shrink-fitting.

The thrust magnetic bearing has its function at the upper end of the rotating shaft, the upper end of the fixed shaft 11, and the upper end of the case 13. Both of the magnetic bearings are made of permanent magnets, the faces of the ms facing each other have the same polarity, and the magnets 9 are repelled from above and below, causing the rotating body 1 to bounce up. Moreover, the magnet holder 14 has a threaded part 14a, and by rotating this threaded part, the magnet 15 housed in the holder 14 moves up and down, and by changing the distance from the magnet 9, the magnet 9 can be attached. The flying height of the rotating body 1 can be adjusted.

Magnets 9 and 10.15 are each holder 14.1
It is stored in 6.17.

In the above configuration, since the motor part is a surface facing type, the diameter of the rotor magnet 4 inevitably becomes large, and when rotating at high speed, there is a risk that the rotor magnet 4 will be destroyed due to the influence of centrifugal force. Most likely.

Furthermore, there is also the drawback that vibration in the thrust direction occurs due to excitation switching of the motor section, which causes disturbance to the thrust magnetic bearing.

On the other hand, the motor system is not the above-mentioned surface facing type (inner rotor type is also known).

However, the conventional inner rotor type has a structure in which a thrust stop made of resin and having an air flow path in the center is provided at the upper end of the hollow rotating body (for example, Japanese Patent Application Laid-open No. 59-49516). .

Therefore, in such conventional examples, the upper end (thrust stop part) is in contact, so it cannot be rotated at particularly high speeds (30,000 to 40,000 rpm).
In this case, there is a problem in that if the start/stop is deformed, abrasion powder is generated and rotation is likely to become impossible.

(Objective) An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional example and to provide an optical deflector that can stably rotate at an ultra-high speed.

(Structure) The present invention uses an inner rotor type motor system at the front, and instead of providing a thrust stop that contacts the hollow rotating body as in the conventional example, the magnet at the upper end of the hollow rotating body is connected to the upper and lower magnets with a gap between the upper and lower magnets. The two are sandwiched together to form a dynamic pressure bearing.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a thrust magnet holder 22 and a thrust magnet 23 are arranged on the rotating shaft 21, a mirror 25, a mirror holder 24, and a rotor magnet 2.
G and a balance correction ring 27 are attached to form a rotating body.

The fixed shaft 28 is located at the top and the thrust magnet holder 29
and a thrust magnet 30, which are firmly fixed to the pedestal 31 at the lower end by a method such as press-fitting or shrink-fitting.

28a and 28b are upper and lower ring grooves provided on the outer peripheral surface of the fixed shaft 28.

As mentioned above, the motor system in the present invention is an inner rotor type.

That is, the rotor magnet 26 and the coil section 32 constitute a motor section, and the rotating body (assembly of the members 21 to 27) rotates by switching the excitation.

Therefore, the diameter of the rotor magnet 26 can be made much smaller than the conventional one. Furthermore, the vibration caused by excitation switching in the motor section is in the radial direction, and does not cause any disturbance in practice (because the bearing rigidity of a vertical hydrodynamic bearing is much higher than that of a thrust shaft bearing).

In addition, 33 is a case, 34 is an upper magnet attached to the case, and 35 is a case top lid.

(Effects) The present invention is as described above, and according to the present invention, the driving system of the rotating body is an inner rotor type, and the thrust magnetic bearing using three permanent magnet repulsion type is used for air magnetic bearing light deflection. (1) Even during ultra-high speed rotation, the centrifugal force can be smaller than that of the surface-facing type, so there is no risk of damage to the rotor magnet, and stable rotation is possible.

(2) Since there is no vibration in the thrust direction, vertical movement of the rotating body is suppressed as much as possible, allowing stable light deflection.

(3) Since there is no contact in the thrust direction when starting and stopping, there is almost no generation of abrasion powder (and the risk of non-rotation is minimized).

It has the following effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an air magnetic bearing type optical deflector according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of the same according to a conventional example. 23.30.34...Magnet, 26.32...
Inner rotor type motor component. Agent: Patent Attorney Kenji Take (Figure 1, 8b)

Claims (1)

[Claims] An air magnetic bearing that has a magnet at the tip that is held between a magnet at the tip of the fixed shaft and a magnet on the inner surface of the top wall of the case so that they repel each other, and a rotating body that floats due to this repulsive force and is rotated by the drive source. An air magnetic bearing type optical deflector characterized in that the motor system of the rotating body is an inner rotor type.