JPS6271916A - Air/magnetic bearing type optical deflector - Google Patents

Abstract

PURPOSE:To reduce sharply contact between the outer surfaces of the 1st and 2nd fixing shafts and the inner surface of a hollow rotary body by cancelling force generated by the resiliency of a thrust magnetic bearing part and orientated from the axis to the outside with force orientated to the axis out of attraction force. CONSTITUTION:Attraction force Fr generated between a rotary magnet 45 and a york iron plate 64 includes the components of force Fxr, -Fxr orientated to the axis and the components are generated in the reverse direction to force Fxb, -Fxb applied to the thrust bearing part and orientated from the axis to the outside. Therefore, two force can be cancelled with each other by setting up the size of the force Fxr, -Fxr orientated to the axis equally to that of the force Fxb, -Fxb orientated from the axis to the outside. Since the outer surfaces of the 1st and 2nd fixing shafts 51, 52 or the inner surface of the hollow rotary shaft 41 is pressed by the force Fxb, -Fxb orientated from the axis to the outside, both the surfaces are not contacted. Consequently, abrasion can be reduced even if the rotary body is repeated started or stopped, and an optical diflector characterized with long life can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coreless flat DC brushless motor suitable for use in laser printers, digital copying machines, facsimile machines, and other optical information processing devices equipped with various laser deflectors. This article relates to a super-heavy air/magnetic bearing type optical deflector that uses a 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. , the jitter characteristics are improved by increasing the inertia, and the hysteresis and
By applying the principle of a synchronous motor, we are improving an air/magnetic bearing type optical deflector that can perform accurate speed control with a simple control circuit. 6. Prior Art Regarding Air/Magnetic Bearing Type Optical Deflector, Which Reduces Abrasion During Starting and Stopping of Rotating Body, Stabilizes Operation, and Extends Lifespan by Decrease 6. Conventional Technology Conventionally, the laser of laser printer In various optical information processing devices such as deflectors, laser deflectors for digital copying machines, laser deflectors for facsimile machines, and barcode readers for PoS terminals, there is a need to deflect laser beams for reading and writing. , 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.

In image output devices such as laser printers that use such laser beam deflectors, image jitter caused by uneven rotation of the polygon mirror is particularly problematic.

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 polygon mirror optical deflector using a dynamic pressure air bearing, when the power is turned on, a rotating body including a one-rotation hook-shaped mirror body 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 polygon mirror and the outer diameter part of the fixed shaft, and the air flows into the head of the lower and upper journals. The pumping action of the bone grooves firmly supports the rotating body in the radial direction.

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.

Such an operation rotates the rotating body provided with the one-rotation hook surface mirror body.

However, the conventional optical deflector using a hydrodynamic air bearing requires complicated groove machining on the hydrodynamic air bearing portion (i.e., the outer diameter surface of the fixed shaft), and also requires the use of a long rotating polyhedron. The surface of the inner diameter part also requires ultra-precise surface processing, which makes processing difficult and increases costs.

Second, 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.

A third point related to this second point 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 large. This may cause premature wear.

Furthermore, as a fourth point related to the first point above, since the structure of the rotating body is complex and the number of parts is large, it is difficult to correct the balance, which is also a factor in increasing costs.

In addition, the fifth point is that the inner rotor type has the disadvantage that the inertia is essentially small and the image jitter characteristics are poor, and at the same time, the axis of rotation becomes long, so the optical deflector The problem is that it becomes larger.

Finally, the sixth point is that since a magnet field DC brushless motor is used, a rotor position detector and speed detection type are required, and the stator side configuration is also complicated and the number of parts increases. . As a result, reliability decreases and
This causes an increase in costs.

In this way, in the conventional optical deflector using a dynamic pressure air bearing,
There were various problems, and the original effect of air bearings could not 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.・By preventing the rotating body from contacting the bearing when stopped, it stabilizes the operation and extends its lifespan. It also simplifies the configuration of the rotating body and fixed shaft to reduce the weight of each rotating body, thereby improving optical deflection. An air/magnetic bearing type optical deflector that achieves miniaturization and low cost, and also prevents uneven rotation by applying the principle of a hysteresis synchronized motor and has good single-image jitter characteristics. (A patent application filed on September 24, 1985, with the title of the invention ``Air/Magnetic Bearing Type Optical Deflector'').

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 drawing, 11 is a hollow rotating shaft, 11a is a flange part, llb is a step part, llc is a screw part, 12 is a mirror,
13 is a mirror fixing ring, 13A is a fixing screw, 14
16 is a magnet rotor assembly, 16 is a rotor magnet, 17 is a non-magnetic holder case, 17a is its ventilation hole, 17b is a threaded part, 18 is an upper magnet for the thrust magnetic bearing, 19 is a holder case 17 21 is a fixing shaft, 21a is a fixing convex part, 21b and 21c are heading bone grooves provided at the upper and lower parts of the outer circumference of the fixed shaft 21, respectively, 21cl is a stepped part, and 21e is a fixing ring.
2 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, and 31a is a protrusion 21 for fixing the fixed shaft 21.
31b is the air pressure adjustment groove, 32 is the upper case, 32a is the window, 33 is the coil board, 34
is a coil, 35 is a magnetic yoke, and g is a 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 is composed of a hollow rotating shaft 11, a mirror 12, rotor assemblies 14 to 6, 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 FIG. After being installed from above, with the top surface suppressed 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, a non-magnetic holder case 17 is fixed above the hollow rotating shaft 11 by a fixing ring 19. This holder case 17 functions to support a ring-shaped upper magnet 18 for a 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 figure 3,
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 21, the holder case 22 is fixed by fitting a convex part of a non-magnetic holder case 22 into a recessed part at the upper end thereof, and a ring-shaped thrust magnetic bearing is mounted on the fixed shaft 21. The lower magnet 23 is supported.

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. Furthermore, an opening for an air pressure adjustment communication hole 21a is provided on the lower surface of the fixed shaft 21, 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 7, the fixed shaft 21 is provided with an air pressure adjustment communication hole 21e.

The air pressure adjustment communication hole 21e is a communication path through which the opening penetrated in the radial direction and the annular gap formed by the air pressure adjustment groove 31b are ventilated.
An annular gap formed in the center of the fixed shaft 21 by the step 21d of the hollow rotating shaft 11 and the step 11b of the hollow rotating shaft 11,
That is, it acts to equalize the air pressure in 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 21a for fixing the fixed shaft 21.
A hole 31a into which is fitted is provided, 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 reduce wind damage and wind noise, and the upper part has a small diameter convex shape in consideration of ease of mounting and transportation. It is formed in the shape of

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 repulsion force of 1.

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.

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.
The repulsive force between the rotating body and the rotating body is generated by the repulsive force between the rotating body and the rotating body. On the other hand, the downward pulling blade is generated by the attraction force between the rotor magnet 16 and the yoke 35,
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 compared to the supply voltage of the motor.

In addition, when explaining using Bit's law, the force of F=Bli (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, since the rotor magnet 16 is a flat ring magnet, it is possible to shorten the length of one rotating body in the axial direction. In this way, the configuration of the motor drive section is simple and low cost.

However, in the air/magnetic bearing type optical deflector proposed earlier, the repulsive force generated in the thrust magnetic bearing part is not only a one-plane force but also a force directed outward from the axis, so it is difficult to rotate. There will be some contact between the body and the fixed shaft, which will reduce the service life due to wear. There is also the problem.

Therefore, in the air/magnetic bearing type optical deflector of the present invention, the previously proposed air/magnetic bearing type optical deflector is further improved.
By canceling the force directed outward from the shaft center generated by the thrust magnetic bearing, the contact pressure between the rotating body and the fixed shaft is further reduced, resulting in less wear on both and stable operation with less jitter. The purpose of the present invention is to realize an optical deflector that is capable of the following and has a long service life.

Structure For this purpose, the air/magnetic bearing type optical deflector of the present invention includes a hollow rotating body having a mirror, and a heading bone disposed inside the rotating body and forming a hydrodynamic air bearing on the outer peripheral surface of the hollow rotating body. An optical deflector comprising a fixed shaft having a groove, and a casing part that supports the fixed shaft, houses the fixed shaft and the rotating body, and has a window part forming an optical path to the mirror. The fixed shaft is divided into two parts, and the first fixed shaft has one end fixed to the center bottom of the lower half of the casing, and has a radial dynamic pressure bearing groove on its outer surface. and includes a permanent magnet for a thrust magnetic bearing fixed to the upper end thereof, and the second fixed shaft is fixed to the center of the upper half of the housing.

The hollow rotating body has a radial dynamic pressure bearing groove on its outer circumferential surface, and secondly, the hollow rotating body has a radial dynamic pressure bearing groove on its inner diameter portion approximately at the center in the axial direction.
A permanent magnet for the thrust magnetic bearing is arranged and fixed so as to face the permanent magnet fixed to the fixed shaft with the same polarity, and a permanent magnet is also fixed to the outer diameter part of the rotating body at approximately the center in the axial direction.
The rotor magnet is magnetized with different polarities in the circumferential direction and has an umbrella-like shape that opens downward. The rotating body is equipped with a plurality of drive coils and a yoke iron plate arranged to face each other, and is rotatably supported in the radial direction by first and second fixed shafts.

The thrust direction is supported in a non-contact manner by the repulsive force of the permanent magnets fixed to the fixed shaft and the rotating body, and the attractive force between the rotor magnets and the yoke iron plate.

- Next, an embodiment of the air/magnetic bearing type optical deflector of the present invention 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. In the drawing, 41 is a hollow rotating shaft, 41a is a flange thereof, 42 is a mirror (polygon mirror), 43 to 45
is a magnet rotor assembly, 43 is a rotor housing, 44 is a magnet rotor assembly;
is a yoke iron plate, 45 is a rotor magnet, 46 is an upper magnet for the thrust magnetic bearing, 51 is a first fixed shaft, 51a is a convex part for fixing, and 51b is a heading bone groove provided on the outer peripheral surface of fixed t451. , 52 is a second fixed shaft, 52a is a thrust stop, 52b is a heading bone groove provided on the outer peripheral surface of the fixed shaft 52, 53 is a lower magnet for the thrust magnetic bearing, 61 is a main body housing, and 61a is a second fixed shaft. Convex portion 51a for fixing the fixed shaft 51 of 1
62 is an upper housing, 62a is a window, 63 is a drive coil, and 64 is a yoke iron plate.

First, the configuration of the fixed shaft, which is the first feature, will be described.

In this FIG. 1, the members constituting the fixed shaft include 51 to 53.
It is numbered in the 50s.

The fixed shaft is divided into two parts, a first fixed shaft 51 and a second fixed shaft.
and a fixed shaft 52.

A heading bone groove 51b forming a radial dynamic pressure air bearing is provided on the surface of the body of the first fixed shaft 51.

Furthermore, a lower magnet 53, which is a permanent magnet for a thrust magnetic bearing, is fixed to the upper end of the first fixed shaft 51.

At the lower part of the first fixed shaft 51, there is a protrusion 51a for fixing.
is formed, and is fixed at a predetermined position at the center bottom by fitting into a hole 61a provided in the main body housing 61.

The second fixed shaft 52 is fixed to the center of an upper housing 62 constituting the upper half of the casing, and is provided with a heading bone groove 52b forming a radial dynamic pressure air bearing on its outer peripheral surface. There is.

Note that a thrust stop 52a is provided at the lower end of the second fixed shaft 52.

Next, the second feature, the rotating body, will be described.

In this FIG. 1, 41 to 46 are included in the members constituting the rotating body.
It is numbered in the 40s.

The hollow rotating body is composed of a hollow rotating shaft 41, a mirror (polygon mirror) 42, magnet rotor assemblies 43 to 45, and an upper magnet 46 for a thrust magnetic bearing.

For this purpose, the hollow rotating shaft 41 has a flange portion 41 for attaching the mirror 42 and the magnet rotor assemblies 43 to 45.
It has a. The flange portion 41a is provided approximately at the center in the longitudinal direction (between the first fixed shaft 51 and the second fixed shaft 52), and the mirror 42 is mounted on the flange portion 41a.
After being attached from above, it is fixed in place by suitable fixing means (not shown).

Further, magnet rotor assemblies 43 to 45 constituting the motor section are attached below the flange portion 41a of the hollow rotating shaft 41, that is, at the outer diameter portion approximately at the center in the longitudinal direction thereof.

The magnet rotor assemblies 43 to 45 are composed of a yoke iron plate 44, a rotor magnet 45, and a rotor housing 43 that supports them. It faces parallel to the iron plate 64.

The rotor magnet 45 is a rotor magnet that is magnetized with different polarities in the circumferential direction and has an umbrella-like shape that is inclined downwardly.

Furthermore, an upper magnet 46 for a thrust magnetic bearing is attached to the inner diameter portion of the hollow rotating shaft 41 at the substantially central portion in the long axis direction.
is fixed. This upper magnet 46 is a permanent magnet fixed to the first fixed shaft.

That is, it is arranged and fixed so as to face the lower magnet 53 with the same polarity.

In this way, the upper magnet 46 and the lower magnet 53 that constitute the magnetic thrust bearing section have the same polarity and are opposite to each other, and a repulsive force (Fyb) is generated therebetween.

The magnitude of this repulsive force (Fyb) is determined by the weight W of the rotating body and the vertical force (-Fyb) acting on the rotor magnet 45.
r), and supports the rotating body in a non-contact manner in the thrust direction.

That is, the radial support of the rotating body is provided by the first fixed shaft 51 and the second fixed shaft 51 disposed on the inner diameter of the hollow rotating shaft 41.
is supported by a fixed shaft 52 of.

Since the clearance between them is about 2.5 to 5 μm, the first fixed shaft 51. It is rotatable about the second fixed shaft 52.

Finally, the casing section will be explained. Parts related to this housing section are numbered 61 to 64 for convenience, but also include a drive coil and a yoke iron plate.

The housing portion includes a main housing 61 and an upper housing 62.
It consists of Note that the main body housing 61 is provided with a hole 61a into which the fixing convex portion 51a of the first fixed shaft 51 is fitted, and the upper housing 62 is provided with a hole 61a that forms a passage for laser light. A window portion 62a is provided.

A drive coil 63 and a yoke iron plate 64, which constitute a stator of the motor drive section, are supported by a fixing means not particularly shown in the casing.

For this purpose, an inclined surface is formed on the upper part of the main body housing 61, and a yoke iron plate 64 for configuring the magnetic circuit of the drive unit is fixed to this surface. drive coil 63 and a Hall element (not shown) for detecting the position of the rotating body.
The array is fixed. The motor drive section includes a rotor magnet 45. Yoke iron plate 44, 1 drive coil 63. It is composed of a yoke iron plate 64.

In this way, since the yoke iron plate 64 is disposed facing the rotor magnet 45 fixed to the rotating shaft 41, an attractive force (Fr) is applied therebetween.

However, since the rotor magnet 45 and the yoke iron plate 64 are inclined and face each other in a downwardly open state, the attraction force (Fr) is generated not in the vertical direction but in the direction of the axis.

FIG. 2 explains the state in which the air/magnetic bearing type optical deflector of the present invention shown in FIG. 1 cancels the force acting outward from the axis by the permanent magnetic repulsion type magnetic thrust bearing part. This is a diagram for In the drawing, Fy
b is the repulsive force generated between the upper magnet 46 and the lower magnet 53, and Fxb and -Fxb are also the repulsive forces,
The component of the force directed outward from the axis, Fr is rotor magnet 4
5 and the yoke iron plate 64, -Fyr
is its vertical (major axis) component, Fxr and −Fxr
indicates the component in the axial direction.

As shown in FIG. 2, the thrust magnetic bearing section uses the repulsion force (Fyb) generated between the upper magnet 46 and the lower magnet 53 to generate vertical buoyancy. is unnecessary.

It is not possible to prevent the force (Fxb, -Fxb) from acting outward from the axis.

Therefore, in the air/magnetic bearing type optical deflector of the present invention, the shape and arrangement of the rotor magnet 45 and the yoke iron plate 64 are devised, and the vertical force (Fr) generated between them is
-Fyr), that is, a vertical component, and a force (Fxr, -Fxr) directed toward the axis.

First, to describe the relationship between the buoyant force and the attractive force caused by the thrust magnetic bearing, the repulsive force (F yb) that causes the buoyant force is the vertical force of the attractive force (Fr) generated between the rotor magnet 45 and the yoke iron plate 64. (-Fyr) and the weight W of the rotating body
The rotating body is levitated and supported in a non-contact manner at a position in the axial direction where the relational expression Fyb = Fyr + W holds true.

However, as already explained, a force (Fxb, -Fxb) directed outward from the axis is applied to this thrust magnetic bearing due to a non-perpendicular component of the repulsive force, and the force (Fxb, -Fxb) is applied to the thrust magnetic bearing section outward from the axis. , the outer diameter surface of the second fixed shaft 52 and the inner diameter surface of the hollow rotating shaft 41 are configured to absorb a force (F) directed outward from this axis.
xb, -Fxb), so both are in contact.

Therefore, when one rotating body is repeatedly started and stopped, the outer diameter surface of the first fixed shaft 51 and the second fixed shaft 52, or the inner diameter surface of the hollow rotating shaft 41 wears out.

However, in the air/magnetic bearing type optical deflector of this invention,
The attraction force (Fr) generated between the rotor magnet 45 and the yoke iron plate 64 includes a force (Fxr, -Fxr) toward the axis.
), and the force (Fxb, -Fxb) acting on the thrust magnetic bearing section is directed outward from the axis, and
It occurs in the opposite direction.

Therefore, by making the force (Fxr, -Fxr) toward the axis equal to the force (Fxb, -Fxb) outward from the axis, the two forces can be canceled.

That is, in the air/magnetic bearing type optical deflector proposed earlier, only the force (Fxb, -Fxb) acting outward from the axis was applied, but with the air/magnetic bearing type optical deflector of this invention, For example, the outer diameter surfaces of the first fixed shaft 51 and the second fixed shaft 52, or the inner diameter surface of the hollow rotating shaft 41, are affected by a force (Fxb) directed outward from the shaft center.

-Fxb), so there is no contact between the two.

Therefore, even if the rotating body is repeatedly started and stopped, wear is reduced, and an optical deflector with a long life can be obtained.

Above that, a mirror 4 fixed to a hollow rotating shaft 41
2. Rotor housing 43. Rotor magnet 45. The yoke iron plate 44 is concentrated approximately at the center in the longitudinal direction. Therefore, the center of weight of one rotating body is located approximately at the center in the longitudinal direction.

As a result, even if whirling occurs due to unbalance in the radial direction of the rotating body, the whirling of the mirror 42 is reduced and jitter in the width scanning direction is reduced.

As explained in detail above, the air/magnetic bearing type optical deflector of the present invention includes a hollow rotating body having a mirror,
a fixed shaft disposed inside the rotating body and having a heading bone groove constituting a hydrodynamic air bearing on its outer circumferential surface;
In an optical deflector that supports the fixed shaft and includes a casing that houses the fixed shaft and the rotating body and has a window that forms an optical path to the mirror, firstly, there are two fixed shafts. The first fixed shaft has one end fixed to the center bottom of the lower half of the housing, has a radial dynamic pressure bearing groove on its outer peripheral surface, and is fixed to the upper end thereof. The second fixed shaft is equipped with a permanent magnet for a thrust magnetic bearing, the second fixed shaft is fixed to the center of the upper half of the housing, and has a radial dynamic pressure bearing groove on its outer peripheral surface; The hollow rotary body rotates once with a permanent magnet for a thrust magnetic bearing, which is arranged and fixed on the inner diameter of the hollow rotating body in its axially central part so as to face the permanent magnet with the same polarity as the permanent magnet fixed to the fixed shaft. It is fixed at the outer diameter of the body, approximately in the center in the same axial direction.

The rotor magnet is magnetized with different polarities in the circumferential direction and has an umbrella-like shape that opens downward. It is equipped with a plurality of driving coils and a yoke iron plate that are arranged to face each other, and the radial direction of the rotating body is rotatably supported by the first and second fixed shafts, and the thrust direction is rotatably supported by the fixed shafts. The rotor magnet is supported in a non-contact state by the repulsive force of the permanent magnet fixed to the body and the attractive force between the rotor magnet and the yoke iron plate.

Therefore, according to the air/magnetic bearing type optical deflector of the present invention, a hydrodynamic air bearing is used as the radial bearing and a magnetic bearing is used as the thrust bearing, similar to the previously proposed optical deflector. This prevents the rotating body from coming into contact with the fixed shaft when starting or stopping.

In particular, since the force directed outward from the shaft center caused by the repulsive force of the thrust magnetic bearing section is canceled by the force directed toward the shaft center among the attractive forces, the outer diameter surfaces of the first and second fixed shafts, Contact with the inner surface of the hollow rotating body is drastically reduced, and even if it does come into contact, the contact pressure is significantly reduced, so even if the rotating body is repeatedly started and stopped, wear is reduced. As a result, a long-life optical deflector can be obtained.

Above it is a mirror fixed to a hollow rotating body.

The rotor housing, rotor magnet, and yoke iron plate are
Since the weight is concentrated at approximately the center in the longitudinal direction, the center of weight of one rotating body is located approximately at the center in the longitudinal direction. As a result, even if whirling occurs due to unbalance in the radial direction of the rotating body, the whirling of the mirror is reduced and jitter in the one-width scanning direction is reduced.

In addition, the configuration of the rotating body and fixed shaft is simplified compared to when using conventional hydrodynamic air bearings, reducing the number of parts, improving workability and ease of assembly, and making it possible to reduce the weight of the rotating body. Therefore, the optical deflector can be made smaller and lower in cost.

Furthermore, since the principle of a hysteresis synchronous motor is applied, rotation unevenness can be prevented, and an optical deflector with good image jitter characteristics can be obtained, among other excellent effects. can get.

[Brief explanation of drawings]

Sakujosato is a vertical sectional view showing the configuration of essential parts of an embodiment of the air/magnetic bearing type optical deflector of the present invention, and Saku1 is the air/magnetic bearing type optical deflector of this invention shown in FIG. This is a diagram to explain how the deflector uses its permanent magnetic repulsion type magnetic thrust bearing to cancel the force acting outward from the axis. A vertical cross-sectional view showing the main part configuration of an example of LJ! L is the thrust bearing of the previously proposed air/magnetic bearing type optical deflector shown in Fig. 3. Fig. 6 is a diagram showing the main part configuration for explaining the operating principle of the part; 2 is a diagram showing an example of the arrangement of coils 34 suitable for use in the air/magnetic bearing type optical deflector also proposed previously. In the drawing, 41 is a hollow rotating shaft, 41a is a flange thereof, 42 is a mirror, 43 to 45 are magnet rotor assemblies, 43 is a rotor housing, 44 is a yoke iron plate, 4
5 is a rotor magnet, 46 is an upper magnet, 51 is a first fixed shaft, 51a is a fixing convex part, 51b is a heading bone groove, 52 is a second fixed shaft, 52a is a thrust stop, and 52b is a Heading bone groove, 53 is the lower magnet, 61 is the main body housing, 61a is the hole, 6
2 is an upper housing, 62a is a window, 63 is a drive coil, and 64 is a yoke iron plate. Underwear 1 Illustration 2 Illustration procedure amendment export) February 15, 1986

Claims (1)

[Claims] a hollow rotating body having a mirror; a fixed shaft disposed inside the rotating body and having a heading bone groove constituting a hydrodynamic air bearing on its outer peripheral surface; and a fixed shaft supporting the fixed shaft; and a casing section that houses a rotating body and has a window section that forms an optical path to the mirror, firstly, the fixed shaft is divided into two parts, and a first The fixed shaft has one end fixed to the center bottom of the lower half of the housing, has a radial dynamic pressure bearing groove on its outer peripheral surface, and has a permanent magnet for a thrust magnetic bearing fixed to its upper end. The second fixed shaft is fixed to the center of the upper half of the housing and has a radial dynamic pressure bearing groove on its outer peripheral surface, and secondly, the hollow rotating body is , a permanent magnet for a thrust magnetic bearing is arranged and fixed on the inner diameter part of the substantially central part in the axial direction so as to face the permanent magnet fixed to the fixed shaft with the same polarity; a rotor magnet that is fixed to an outer diameter portion at a substantially central portion in a direction, is magnetized with different polarities in a circumferential direction, and has an umbrella-like inclined shape that opens downward; An air/magnetic bearing type optical deflector, comprising a plurality of drive coils and a yoke iron plate provided inside the rotor to face a rotor magnet fixed to the rotating body.