JPS6292911A - Pneumatic and magnetic bearing type optical deflector - Google Patents

Abstract

PURPOSE:To stabilize the operation of an optical polarizer and extend the life by providing an abnormality detecting means, which detects the abnormality of temperature or humidity to stop a revolving shaft in a fixed shaft which supports the hollow revolving shaft having a mirror with a dynamic pressure pneumatic bearing and a magnetic bearing. CONSTITUTION:A hollow revolving shaft 11 having a mirror 12 is thrust- supported pivotally through an upper magnet 18 magnetically and is radially supported pivotally by heading bone grooves 21b, 21c, etc., to which air is flowed, pneumatically and is attracted and driven by a rotor magnet 16. A heat generation detector 41 and an abnormal oscillation detector 42 are provided in a fixed shaft 21 in a revolving shaft 11, and abnormal heat generation due to existence of minute dust or abnormal oscillation due to operation miss is detected to stop rotation of the revolving shaft. Thus, bad influences of abnormal heat generation and disturbing oscillation are avoided to protect the optical polarizer, and the stable operation and the long life are attained.

Description

[Detailed Description of the Invention] Skin Distribution - This invention can be used in laser printers, digital copying machines, facsimile machines, and other optical information processing devices and optical measuring instruments equipped with various laser deflectors. The present invention relates to a super-heavy air/magnetic bearing type optical deflector that employs a suitable coreless flat DC brushless motor system.

More specifically, by constructing an air/magnetic bearing type optical deflector using a hydrodynamic air bearing as a radial bearing and a magnetic bearing as a thrust bearing, the friction of the bearing part during startup and stop is reduced. In addition to prolonging the lifespan of the optical deflector, by making it a flat and simple structure, it is possible to reduce the number of parts and facilitate assembly, making the optical deflector smaller and easier to assemble. By increasing the inertia and improving jitter characteristics, and by applying the principle of a hysteresis synchronous motor, the air speed can be controlled accurately with a simple control circuit.
Regarding the improvement of magnetic bearing type optical deflectors, we are particularly concerned with detecting abnormal conditions such as abnormal heat generation and abnormal disturbance vibrations in air bearings, which have minute bearing gaps and are susceptible to heat, and have low bearing rigidity and are susceptible to external disturbances. .

By stopping the operation of the optical deflector, the air/magnetic bearing is protected. At the same time, by drying the inside of the deflector to remove moisture, condensation, rust, etc. are prevented, and the bearing area is protected. This invention relates to an air/magnetic bearing type optical deflector with improved reliability.

BACKGROUND ART Conventionally, various optical information processing devices such as laser deflectors of laser printers, laser deflectors of digital copying machines, laser deflectors of facsimile machines, and image scanners of PO8 terminals, as well as of paper currency, iron plates, etc. In measuring instruments for inspecting the presence of scratches, as well as various optical measuring instruments such as length measuring instruments, it is used to deflect the laser beam used for reading or writing calligraphy, or for inspecting the presence of scratches. , an optical deflector using a polygon mirror (polygon mirror) is used.

An optical deflector using this polygon mirror has a high deflection speed and is capable of continuous optical deflection, so it can record or read information at high speed and with high accuracy.

Image output devices that use such laser beam deflectors, such as laser printers, are particularly susceptible to image jitter caused by uneven rotation of the polygon mirror.

Incidentally, as this type of optical deflector, one using a magnet field DC brushless motor is conventionally known.

That is, the rotor of this DC brushless motor is a cylindrical magnet, and a hollow shaft (a so-called rotating polygon) to which a rotating polygon mirror is attached is fixed to the inner diameter of the rotor magnet. A fixed shaft is provided on the inner diameter of the rotating polyhedron, and the inner diameter surface of the rotating polyhedron and the outer diameter surface of the fixed shaft constitute a hydrodynamic air bearing.

In such a rotating polygonal mirror optical deflector using a dynamic pressure air bearing, when the power is turned on, a rotating body including a rotating polygonal mirror or the like starts rotating.

Then, several seconds later, the thrust air bearing set in advance fully performs its function and reaches a constant rotational speed that allows the rotating body to levitate while maintaining the axial load.

At this time, air flows in from the lower part of the gap formed between the inner diameter of the internal fitting part of the rotating polyhedron and the outer diameter of the fixed shaft.
The inflowing air firmly supports the rotating body in the radial direction by the pumping action of the heading bone grooves in the lower and upper journals.

The incoming air supports the rotating body in the radial direction, and due to the effect of the spiral groove, it flows in the upper direction, generating upward pressure on the thrust stopper, and passes through the through hole to the upper part of the hydrodynamic air bearing. It flows out.

By such an operation, the M rolling body including the rotating polygon mirror is rotated.

However, the first problem with conventional optical deflectors using hydrodynamic air bearings is that they require complicated groove machining on the hydrodynamic air bearing portion (i.e., the outer diameter surface of the fixed shaft), and that The inner diameter surface of the rotating polyhedron also requires ultra-precise surface processing, which makes processing difficult and increases costs.

A second problem is that in the case of a hydrodynamic air bearing, since the bearing parts are in contact, there is no air bearing effect at startup, and there is a limit to the long life that is the most important feature of air bearings. That is, the bearing portion is worn out due to contact friction of the bearing portion during startup and stop.

The third problem related to this second problem is that since the motor system is a magnetic field type, the rotor is attracted in the direction of the iron core stator when it is stopped, and the frictional force of the bearing is Being large also causes premature wear.

Furthermore, the fourth problem related to the first problem mentioned above is that the structure of the five-rotator is complicated and the number of parts is large, so it is difficult to correct the balance, which is also a factor in Varnish 1 to Amplifier.

In addition, the fifth problem is that because it is an inner rotor type, the inertia is essentially small and the image jitter characteristics are poor.
Since the rotation axis becomes longer, there is a drawback that the optical deflector becomes larger.

Finally, the sixth problem is that since a magnet field DC brushless motor is used, the rotor position detector,
A speed detector is required, and the structure on the stator side is also complicated, resulting in a large number of parts. As a result, reliability decreases and this becomes a cause of cost increase.

In this way, in the conventional optical deflector using a dynamic pressure air bearing,
There are various drawbacks, and the original effect of air bearings cannot be fully obtained.

As a way to solve these inconveniences, the inventor of this invention first used a dynamic pressure air bearing as the radial bearing and a permanent magnet repulsion type magnetic bearing as the thrust bearing.・The rotating body does not come into contact with the bearing when stopped, making it possible to stabilize the operation and extend its life. In addition, the rotating body and fixed shaft are configured in a U-axis configuration, which reduces the weight of the rotating body and reduces light pollution. Air/magnetic bearing type optical deflector that realizes a smaller deflector and lower cost, and also prevents uneven rotation by applying the principle of a hysteresis synchronous motor and has good image jitter characteristics. (Patent Application No. 210563 filed in 1985 with the title of the invention "Air/Magnetic Bearing Type Optical Deflector")a The air/magnetic bearing type optical deflector of this invention is based on the previously proposed air/magnetic Since it is an improvement on the bearing type optical deflector,
First, the air/magnetic bearing type optical deflector proposed earlier will be explained.

FIG. 3 is a longitudinal sectional view showing the configuration of essential parts of an example of the previously proposed air/magnetic bearing type optical deflector. In the drawings, 11 is a hollow rotating shaft, 1 a is a flange portion thereof, 11 b is a stepped portion, llc is a threaded portion, ] 2 is a mirror, 13 is a mirror fixing ring, ], 3 A is a fixing screw, 14 to 16 are magnet rotor assemblies, 16 is a rotor magnet, 17 is a non-magnetic holder case, and 17a
17b is the ventilation hole, 17b is the screw part, 18 is the upper magnet for the thrust magnetic bearing, 19 is the fixing ring of the holder case 17, 21 is the fixing shaft, 21a is the fixing convex part,
21b and 21c are heading bone grooves provided at the upper and lower parts of the outer periphery of the fixed shaft 21, respectively; 21d is a stepped portion;
21e is a communication hole for air pressure adjustment, 22 is a non-magnetic holder case, 23 is a lower magnet for the thrust magnetic bearing,
31 is a housing, 31a is a hole into which the convex portion 21a for fixing the fixed shaft 21 is fitted, and 31b is a groove portion 5 for adjusting the air pressure.
32 is an upper case, 32a is a window, 33 is a coil board, 34 is a coil, 35 is a magnetic yoke, and 1
g indicates the gap between the upper magnet 18 and the lower magnet 23.

First, let's talk about the rotating body. In FIG. 3, the members constituting the rotating body are numbered in the 10s from 11 to 19.

The rotating body includes a hollow rotating shaft 11, a mirror 12, and rotor assemblies 14-16. and an upper magnet 18 for a thrust magnetic bearing.

For this purpose, the hollow rotating shaft 11 has a flange portion 11a for attaching the mirror 12 and the rotor assemblies 14 to 16, and the mirror 12 is attached to the flange portion 11a of the hollow rotating shaft 11 as shown in the figure. After being installed from above, with the top surface pressed by the mirror fixing ring 13,
The fixing screw 13A is tightened and fixed in a predetermined position.

Furthermore, rotor assemblies 14 to 16 constituting a motor section are attached below the flange section 11a of the hollow rotating shaft 11.

Further, above the hollow rotating shaft 11, a non-magnetic holder case 17 is fixed by a fixing ring ]9. This holder case 17 functions to support an upper magnetic screw 1-18 for a ring-shaped thrust magnetic bearing, and its threaded portion 17b engages with a threaded portion 11c provided on the hollow rotating shaft 11.

Next, the configuration of the fixed shaft will be described. In this third figure,
The members constituting the fixed shaft are numbered 21 to 23 in the 20s.

Heading bone grooves 21b and 21c are provided in the upper and lower parts of the body surface of the fixed shaft 21, respectively, and constitute radial dynamic pressure air bearings.

Further, above the fixed shaft 2, the holder case 22 is fixed by, for example, fitting the convex part of the non-magnetic holder case 22 into the recessed part at the upper end thereof, and the ring-shaped thrust magnetic Supports the lower magnet 23 for bearing.

A fixing protrusion 21a is formed at the lower part of the fixed shaft 21, and is fixed in a predetermined position by fitting into a hole 31a provided in the housing 31.

Note that the step portion 21d of the fixed shaft 21 forms an annular gap portion together with the step portion 11b of the hollow rotating shaft 11. Further, the lower surface of the fixed shaft 21 is provided with an opening for the air pressure adjustment communication hole 21e, and by covering the air pressure adjustment groove 31b of the housing 31 with this lower surface, an annular gap is similarly formed.

In order to connect these annular gaps, the fixed shaft 21 is provided with an air pressure adjustment communication hole 21e.

The air pressure adjustment communication hole 2], e is a communication path through which the opening penetrated in the radial direction and the annular cavity formed by the air pressure adjustment groove 31b are ventilated, and Step portion 21d and step portion 1 of hollow rotating shaft 11 ]
, b act to equalize the air pressure in the annular gap formed in the center of the fixed shaft 21, that is, the air escape part of the air bearing part, and the internal air pressure in the casing part.

The casing section includes a housing 31 and an upper case 32. A coil board 33 is fixed to this housing, and a coil 34 and a yoke 35, which constitute a stator of the motor drive section, are supported.

The housing 31 has a protrusion 2 + for fixing the fixed shaft 21.
, a into which the holes 31a are fitted, and an air pressure adjustment groove 31b is formed in the upper part of the hole 31a.

The upper case 32 has a small gap with the mirror 12 in order to suppress wind damage and wind noise, and the second part has a small diameter in consideration of ease of mounting and convenience during transportation. It is formed in a convex shape.

Here, to explain the permanent magnet repulsion type thrust magnetic bearing used in the air/magnetic bearing type optical deflector proposed earlier, the upper magnet 1 provided on the hollow rotating shaft 11
8 and the lower magnet 23 provided on the fixed shaft 21 are arranged so that the same polarity faces each other so as to obtain a repulsive force.

In this case, the gap g is appropriately adjusted by rotating the fixing ring 19 and moving the holder case 17.

Next, the motor drive section includes magnet rotor assemblies 14 to 16 fixed to the hollow rotating shaft 11, a plurality of coils 34 arranged on a coil substrate 33, and a yoke 35.

Since the rotor magnet 16 is a flat ring magnet and is thin, the axial length of the rotating body can be shortened.

The following FIG. 4 is a block diagram of the main parts of the previously proposed air/magnetic bearing type optical deflector shown in FIG. 3, for explaining the operating principle of the thrust bearing section thereof. Reference numerals in the drawings are the same as in FIG. 3.

As shown in FIG. 4, in the air/magnetic bearing type optical deflector proposed earlier, the thrust bearing part is connected to the ring-shaped upper magnet 18, the lower magnet 23, the rotor magnet 16 of the motor drive part, and the yoke. It consists of 35.

First, the buoyancy is between the upper magnet 18 and the lower magnet 2.
3 is generated by the repulsive force between the rotating body and the rotating body to float upward. On the other hand, the downward pulling blade is generated by the attraction force between the rotor magnet 16 and the yoke 35, and the rotating body is pulled downward.

In this case, the upper magnet 18 and the lower magnet 23
The buoyant force between the rotor magnet 16 and the yoke 3
By making the suction force larger than the suction force between the rotor and the rotor 5, the hollow rotating body can be levitated.

This buoyant force can be adjusted to a desired size balanced with the suction force by rotating the fixing ring 19 and moving the holder case 17 that supports the upper magnet 18 to adjust the gap g.

FIG. 5 is a plan view showing an example of a rotor magnet 16 suitable for use in the previously proposed air/magnetic bearing type optical deflector.

The following FIG. 6 is a diagram showing an example of the arrangement of the coil 34 suitable for use in the air/magnetic bearing type optical deflector also proposed earlier.

Next, the rotation control of the motor for the air/magnetic bearing type optical deflector proposed above will be explained.

In this example, as shown in FIGS. 5 and 6 above, a case will be described in which the configuration of the motor drive section of the optical deflector is 8 poles, 3 phases, and 6 coils.

In the motor drive unit shown in Fig. 3, if the excitation phase is switched by the output signal of the rotor position detector (not shown) and the six coils are sequentially excited, Fleming's left-hand rule
According to the so-called 814 rule, the rotor is rotated at a rotational speed proportional to the supply voltage of the motor.

In addition, when explaining using the 814 rule, the force of F=B1i (where F is the generated force, B is the magnetic flux density, and i is the exciting current) is
This is the force acting on the coil. However, the air/magnetic bearing type optical deflector proposed earlier applies the principle of a brushless motor in which the coil is fixed and the rotor magnet rotates. The direction is the opposite direction of this 814 rule.

In this manner, in the air/magnetic bearing type optical deflector proposed above, the rotor magnet 16 is a flat ring magnet, so that the rotating body can be shortened in the axial direction. In this way, the configuration of the motor drive section is simple and low cost.

The previously proposed air/magnetic bearing type optical deflector has such a configuration, and its features and effects are listed as follows.

First, a hydrodynamic air bearing is used as the radial bearing, and a permanent magnet repulsion type magnetic bearing is used as the thrust bearing, so the rotating body does not come into contact with the bearing during startup or stop, and the operation is smooth. Stabilization and longer life are possible.

In addition, in the permanent magnet repulsion type thrust magnetic bearing, by rotating the fixing ring 19 and moving the holder case 17, the gap between the upper magnet 18 and the lower magnet 23, which are arranged so that the same polarity faces each other, is fixed. Since g is appropriately adjusted, the desired repulsive force can be obtained.

Second, by using a hydrodynamic air/magnetic bearing, it is possible to reduce the size, and since it is a flat type, it is possible to obtain a small-sized optical deflector.

Thirdly, since it is a flat type, it is possible to increase inertia, which is extremely advantageous in terms of jitter characteristics.

Fourthly, the air pressure adjustment communication hole 21e of the fixed shaft 21 is a communication path through which the opening penetrated in the radial direction and the annular cavity formed by the air pressure adjustment groove 34b are ventilated. The air pressure in the annular gap formed in the center of the fixed shaft 21 by the stepped portion 21d of the fixed shaft 21 and the stepped portion 11b of the hollow rotating shaft 11, that is, the air escape portion of the air bearing portion, and the casing. It acts to equalize the internal air pressure of the body, achieving stable operation.

Fifth, the upper case 32 has a small gap with the mirror 12 in order to reduce wind damage and wind noise. It is formed into a convex shape with a small diameter.

Sixth, because the structure is simple, the number of parts is small, and it is excellent in workability and assembly.Also, the configuration of the rotating body and fixed shaft is simplified, and the single rotating body can be made lighter. The optical deflector can be made smaller and lower in cost.

Seventh, since the principle of a hysteresis synchronous motor is applied, uneven rotation is prevented and an optical deflector with good image jitter characteristics can be obtained.

However, in the case of the previously proposed air/magnetic bearing type optical deflector, the following problem remains because the bearing gap in the air bearing portion is minute.

The first problem is that the presence of fine dust or the like inside the optical deflector may cause abnormal heat generation. That is the point.

For this reason, assembly work is performed in a clean room, but it is practically impossible to completely remove fine dust, and some fine dust remains.

Further, there is also some gas generated from the insulating material used as the coil substrate.

Furthermore, there is also the problem that moisture contained in the air inside the optical deflector condenses due to changes in the external temperature of the optical deflector.

That is, these fine particles, gas, moisture, etc. enter the bearing gap of the air bearing section and cause abnormal heat generation.

A second problem is that when the optical deflector is attached to, for example, a laser printer, large vibrations are often applied to the printer due to an operator's operational error.

Such abnormal vibrations have an adverse effect on the air/magnetic bearing type optical deflector. As already mentioned, the bearing clearance of air/magnetic bearings is minute and the bearing rigidity is low, so when large vibrations are applied, the fixed shaft 21 and the hollow rotating shaft 11
Contact occurs, making the operation unstable, and the contact causes scratches, etc., which accelerates wear and shortens the lifespan.

In this way, in the air/magnetic bearing type optical deflector proposed earlier, since the bearing gap in the air bearing part is minute, fine dust etc. may exist inside the deflector and cause abnormal heat generation. If large vibrations are applied from the outside, not only will the fixed shaft and rotating shaft come into contact and the operation will become unstable, but it will also cause scratches, accelerate wear, and shorten the life of the optical deflector. There is an inconvenience.

Purpose Therefore, the air/magnetic bearing type optical deflector of this invention further improves the previously proposed air/magnetic bearing type optical deflector.
When an abnormal condition occurs in the deflector, such as abnormal heat generation due to fine dust inside the deflector or abnormal vibration caused by external force.

By immediately detecting the occurrence of an abnormality and stopping its operation, the main purpose is to avoid the negative effects of abnormal heat generation and large disturbance vibrations, protect the optical deflector, and extend its life.

Furthermore, by removing moisture contained in the air inside the deflector, the purpose is to reliably prevent dew condensation, rust, etc., and achieve stable operation and longer life of the optical deflector. shall be.

Configuration To this end, the air/magnetic bearing type optical deflector of the present invention has the following main features: a hollow rotor having a mirror; and a hydrodynamic air bearing disposed inside the rotor, around the outer periphery of the rotor. an optical deflector comprising: a fixed shaft having a heading bone groove; and a housing portion supporting the fixed shaft, accommodating the fixed shaft and the rotor, and having a window portion forming an optical path to the mirror; Moreover, the hollow rotor includes a magnet fixed to an upper end thereof, and a rotor magnet fixed below the rotor and magnetized to different polarities in one circumferential direction, The fixed shaft has a magnet fixed at its upper end so as to face the magnet fixed to the rotor with the same polarity, and the repulsion generated between the magnet of the rotor and the magnet of the fixed shaft A thrust magnetic bearing is configured by the force, and a plurality of coils are provided inside the housing portion facing the rotor magnet fixed below the rotor, and the rotor magnet and the coil In an optical deflector in which a surface-facing motor is configured,
The fixed shaft has a communication hole for adjusting air pressure and a step, and an abnormality detection means for detecting abnormal conditions such as temperature and vibration is provided in the communication hole or step, or inside the housing. .

Furthermore, a desiccant is inserted inside the casing of the optical deflector,
Trying to remove moisture.

Next, regarding the air/magnetic bearing type optical deflector of this invention,
One embodiment will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the configuration of essential parts of an embodiment of the air/magnetic bearing type optical deflector of the present invention. The symbols in the drawings are the same as those in Figure 3 above, and 2
1f is a communication hole for adjusting air pressure, 31c is a draw-out hole for lead wires, etc., 41 is a heat generation detector, 42 is an abnormal vibration detector, 4
3 indicates a desiccant.

The configuration of the air/magnetic bearing type optical deflector of the present invention shown in FIG. 1 is basically the same as the previously proposed air/magnetic bearing type optical deflector shown in FIG. 3.

Regarding the air/magnetic bearing type optical deflector shown in Figure 1.

To explain its structural features, the heat generation detector 41
Also, an abnormal vibration detector 42 and a desiccant 43 are added.

As already mentioned, in the air/magnetic bearing type optical deflector proposed earlier, the bearing clearance of the air bearing part is small (I), so the presence of fine dust etc. inside the deflector may cause abnormal heat generation. In addition, if large vibrations are applied from the outside, the fixed shaft and rotating shaft will come into contact with each other, making the operation unstable, as well as causing scratches, accelerating wear, and shortening the lifespan of the optical deflector. There are still some inconveniences, such as shrinking the .

Therefore, as a first measure, if fine dust, gas, moisture, etc. exist inside the optical deflector and enter the bearing gap and cause abnormal heat generation, the first heat generation detector 41 detects the abnormal heat generation.

The heat generation detector 41 is attached to the air adjustment hole 21f or step 21d of the fixed shaft 21, the housing 31 constituting the casing, or the inside of the upper case 32.

The following FIG. 2 is a functional block diagram showing the main part configuration of the abnormal heat generation detection circuit used in the air/magnetic bearing type optical deflector of the present invention. The symbols in the drawing are the same as those in FIG. 3 above, and 44 is a reference voltage comparison circuit, 45 is a flip-flop (F/F) circuit, 46 is an AND gate circuit, and R
1-R3 is a resistor, and Es is a reference power source.

For example, a thermistor is used as the heat generation detector 41, and changes in resistance due to temperature changes are detected by the reference voltage comparison circuit 4.
4 is compared with the reference power source E5.

When an abnormal temperature is reached, the comparison output from the reference voltage comparison circuit 44 changes, so that the output of the F/F circuit 45 becomes, for example, H.
level, and the AND gate circuit 46 generates an abnormal heat generation detection signal.

By stopping the rotation of the optical deflector in response to this abnormal heat generation detection signal, the optical deflector is prevented from being driven in an abnormal state, thereby preventing destruction.

Furthermore, if large vibrations are applied from the outside due to an operator's operational error, the abnormal vibration detector 42 detects the occurrence of abnormal vibrations.

In this case as well, although not particularly shown, the occurrence of abnormal vibration is detected by an abnormal vibration detection circuit having a configuration similar to that shown in FIG.
Stop the rotation of the optical deflector.

Therefore, contact between the fixed @ 21 and the hollow rotating shaft 11, which are opposed to each other with a small gap, is reliably prevented and wear does not occur, making it possible to extend the life of the optical deflector.

Furthermore, in order to solve the problem that moisture contained in the air inside the deflector condenses due to changes in the external temperature of the optical deflector, the desiccant 43 is added to the upper case 32 constituting the casing.
Alternatively, it may be mounted inside the housing 31 by suitable fixing means.

Note that, unlike in FIG. 3, only one communication hole 21f for adjusting air pressure is provided at the axial center of the fixed shaft 21. However, this air pressure adjustment communication hole 2
1f does not necessarily have to be one, and may be the same as that shown in FIG. 3, or may be arranged in another manner.

In addition, as explained in detail in ``After heat generation detection'', the air/magnetic bearing type optical deflector of the present invention has a hollow rotor having a mirror and a A fixed shaft disposed inside and having a heading bone groove constituting a hydrodynamic air bearing on its outer periphery, supporting the fixed shaft, accommodating the fixed shaft and the rotor, and forming an optical path to the mirror. The hollow rotor has a magnet fixed to the upper end thereof, and a magnet fixed to the lower part of the rotor, which are different in the circumferential direction. The fixed shaft has a magnet fixed to the upper end thereof so as to face the magnet fixed to the rotor with the same polarity as the magnet fixed to the rotor. A thrust magnetic bearing is constructed by the repulsive force generated between the magnet of the fixed shaft and the magnet of the fixed shaft, and a plurality of coils are mounted on the housing in opposition to the rotor magnet fixed below the rotor. In an optical deflector that is provided inside a body part and in which a surface facing type motor is configured by the rotor magnet and the coil, the fixed shaft has a communication hole and a stepped part for adjusting air pressure, and this communication The structure is such that an abnormality detection means for detecting an abnormal state such as temperature or vibration is provided inside the hole or step or inside the casing.

Furthermore, as a second feature, moisture contained in the air inside is removed by inserting a desiccant into the casing of the optical deflector.

Therefore, according to the air/magnetic bearing type optical deflector of the present invention, the previously proposed air/magnetic bearing type optical deflector is further improved to prevent abnormalities caused by minute dust etc. existing inside the deflector. When an abnormal condition occurs such as heat generation or abnormal vibration caused by external force.

This makes it possible to immediately detect the occurrence of abnormalities.
By stopping the rotation of the optical deflector, the adverse effects of abnormal heat generation and large disturbance vibrations are avoided, the optical deflector is protected, and its lifespan is extended.

Furthermore, by inserting a desiccant into the interior of the casing of the optical deflector, the essential components contained in the air inside can be removed, so that the air is always kept in a dry state.

As a result, dew condensation, rust, etc. are completely prevented, making it possible to stabilize the operation and extend the service life.

In addition, it has the same effect as the previously proposed air/magnetic bearing type optical deflector, that is, it uses a hydrodynamic air bearing as the radial bearing and a magnetic bearing as the thrust bearing, so it Since the rotor does not come into contact with the bearing section, stable operation and a longer lifespan are also achieved from this point of view.

Similarly, the configuration of the rotor and stator is simplified, reducing the number of parts, improving workability and ease of assembly, and making it possible to reduce the weight of the rotor, making the optical deflector smaller and cheaper. In addition, since it is a flat type, it is possible to increase the inertia, and from this point of view as well, the jitter characteristics are advantageous.

Furthermore, since the principle of a hysteresis synchronous motor is applied, many excellent effects can be achieved, such as preventing uneven rotation and obtaining an optical deflector with good image jitter characteristics.

[Brief explanation of drawings]

The disaster mouse is a vertical cross-sectional view showing the main parts of an embodiment of the air/magnetic bearing type optical deflector of this invention, and m is the abnormal heat generation used in the air/magnetic bearing type optical deflector of this invention. Figure 4 is a functional block diagram showing the configuration of the main parts of the detection circuit. The main part configuration diagram for explaining the operating principle of the thrust bearing part of the air/magnetic bearing type optical deflector proposed above,
Figure 5 is a plan view showing an example of the rotor magnet 16 suitable for use in the air/magnetic bearing type optical deflector proposed earlier, and Figure 6 is the air/magnetic bearing type optical deflector also proposed earlier. FIG. 4 is a diagram illustrating an example of the arrangement of coils 34 suitable for use in FIG. In the drawing, 11 is a hollow rotating shaft, lla is its flange, llb is a step, llc is a threaded portion, 12 is a mirror, 13 is a mirror fixing ring, 13Δ is a fixing screw,
14 to 16 are magnet rotor assemblies, 16 is a rotor magnet, 17 is a holder case, 17a is its ventilation hole,
17b is a screw part, 18 is an upper magnet, 19 is a ring for fixing the holder case 17, 21 is a fixing shaft, 21a
21b and 21c are convex parts for fixing, 21b and 21c are heading bone grooves, 21d is a step part, 21e and 21f are communication holes for adjusting air pressure, 22 is a holder case, 23 is a lower magnet, 3
1 is a housing, 31a is a hole, 31b is a groove for adjusting air pressure, 31c is a hole for pulling out lead wires, etc., 32 is an upper case, 32a is a window, 33 is a coil board, 34 is a coil, 35 is a yoke, 41 is a heat generation detector, 42 is an abnormal vibration detector, 43 is a desiccant, 44 is a reference voltage comparison circuit, and 45 is a flip-flop circuit. Biit Procedural Amendment (Spontaneous) February 15, 1985 Patent Application No. 232951 2, Relationship to the Title of Invention Case Patent Applicant 1-3-6 Nakamagome, Ota-ku, Tokyo (674) Riko Co., Ltd.-4, agents and others up to the 10th line “Synchronous Motor”,
Corrected to "coreless flat DC brushless motor." 2) "Accurate speed control with a simple control circuit" on page 3, line 11 is corrected to "precise speed control." 3) "Magnet field" in the first line of page 5 is corrected to "inner rotor type magnet field." 4) In the second line of page 7, "Because it is a magnet field type" is corrected to "Because it is an inner rotor type magnet field type." 5) "Magnet field" at the end of line 15 on page 7 is corrected to "inner rotor type magnet field." 6) From "hysteresis synchronization" at the end of line 13 on page 8, Correct the lines up to "Eggplant motor" to read "Coreless flat DC brushless motor." 7) In the same page, page 15, line 8, ``more than the suction force'' is corrected to ``more than the suction force and the rotating weight.''8> Correct "hysteresis synchronous motor" in line 4 of page 19 to "coreless flat DC brushless motor". 9) "Hysteresis synchronous mode" on page 29, line 17 is corrected to "coreless flat DC brushless mode."that's all

Claims (1)

[Claims] 1. A hollow rotor having a mirror, a fixed shaft disposed inside the rotor and having a heading bone groove constituting a hydrodynamic air bearing on its outer periphery, and the fixed shaft The hollow rotor is fixed to the upper end of the optical deflector. and a rotor magnet fixed below the rotor and magnetized with different polarities in the circumferential direction, and the fixed shaft has an upper end thereof that is the same as the magnet fixed to the rotor. A thrust magnetic bearing is provided with magnets fixed such that their polarities face each other, and a thrust magnetic bearing is configured by a repulsive force generated between the magnet of the rotor and the magnet of the fixed shaft, and In an optical deflector, a plurality of coils are provided inside the housing portion to face a rotor magnet fixed below, and a surface facing type motor is configured by the rotor magnet and the coils, The fixed shaft has a communication hole for adjusting air pressure and a step, and an abnormality detection means for detecting an abnormal state such as temperature or vibration is provided inside the communication hole or step or the casing. Characteristic air/magnetic bearing type optical deflector. 2. An air/magnetic bearing type optical deflector according to claim 1, characterized in that a desiccant is inserted inside the casing.