JP3456777B2 - Dynamic pressure air bearing type optical deflector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure air bearing type optical deflector used in information equipment, image equipment and measuring equipment.

[0002]

2. Description of the Related Art The structure and operation of an example of a conventional dynamic pressure air bearing type optical deflector will be described with reference to FIGS.

FIG. 11 is a sectional view of a conventional dynamic pressure air bearing type optical deflector. FIG. 12 is a top view of a conventional dynamic pressure air bearing mechanism, and FIG. 13 is a partially enlarged view of FIG. This dynamic pressure air bearing type optical deflector includes a rotating portion and a fixed portion. The case and a fixed shaft that is erected on the case form a fixed part, and the outer periphery of the fixed shaft is formed by a motor or the like that is rotatably provided to form the rotary part. The rotary part is housed in the case of the fixed part. ing. Reference numeral 21 denotes a fixed shaft, which is fixed to a case 11 forming a fixed portion, and the outer peripheral surface of the fixed shaft 21 has a herringbone for generating a dynamic pressure having suction angles opposite to each other as shown in FIG. A groove 23 is provided. A stator iron core 13 fixed to the inside of a case 11 forming a fixed portion,
By exciting the coil 14 with a motor that forms a rotating portion composed of the coil 14, the hall element 15, and the magnet 12 provided on the outer circumference of the hollow rotating shaft 22 that is rotatable outside the fixed shaft 21, the coil 14 is excited as shown in FIG. When driven in the direction of the arrow shown, the hollow rotary shaft 22 to which the magnet 12 is fixed rotates, and at the same time, the rotary polygon mirror 3 mounted and fixed on the mirror mounting portion 4 of the hollow rotary shaft 22 is supported by the thrust magnetic bearing 8 to rotate. To do. At this time, the fluid introduced from the air inlet S in the gap between the fixed shaft 21 and the hollow rotary shaft 22 generates a dynamic pressure in the gap, and the dynamic pressure causes rigidity, whereby a portion indicated by reference numeral 24. Is a dynamic pressure air bearing mechanism. Reference numeral 27 is an air circulation hole for discharging internal air during operation of the dynamic pressure air bearing mechanism.

Here, when the herringbone groove 23 is not formed on the outer periphery of the fixed shaft 21, a perfect circular dynamic pressure air bearing mechanism is formed, and when the rotating shaft is vertical, rigidity occurs, but the whirl phenomenon is always present. Occurs, the state becomes unstable at any rotation speed. There is a parameter called critical mass that expresses the performance of a dynamic pressure air bearing.This critical mass indicates the maximum mass of a rotating body that can be rotated in a stable state at a certain number of revolutions. In the case of compressed air bearings, this critical force is zero at all speeds. However, by providing the herringbone groove 23 on the outer periphery of the fixed shaft, it can be configured to have a desired critical mass up to a certain number of rotations. Therefore, in the conventional hydrodynamic air bearing type optical deflector, in order to prevent the occurrence of the whirl phenomenon and rotate in a stable state, the herringbone groove 23 is provided on the outer periphery of the fixed shaft and the air of the hydrodynamic bearing mechanism 24 is exposed to the outside. The circulation hole 27 for discharging to is adopted.

[0005]

In the conventional hydrodynamic air bearing type optical deflector, a herringbone groove must be formed on the outer peripheral surface of the fixed shaft, and when the outer shape is a perfect circle shaft, the outer peripheral shape is formed. However, if it is necessary to process the herringbone groove in this way, then perform lathe processing or polishing processing to produce the outer peripheral shape, and then perform herring processing. In order to process the bone groove, etching or blasting must be performed, which requires a lot of processing time and increases costs. Further, due to the shape of the herringbone groove, the rotation direction of the rotating portion is limited to one direction, so that there is a problem that it can be rotated only in either a clockwise direction or a counterclockwise direction. .

Further, when the herringbone groove is formed, a dimensional difference occurs in the herringbone groove width (L1, L1 ') at the time of processing the herringbone groove or assembling the fixed shaft, and due to this dimensional difference. Airflow occurs in the axial direction of the fixed shaft. Therefore, it is technically difficult to effectively eliminate the dimensional difference in the herringbone groove widths (L1, L1 ') during operation, and in addition, external force such as vibration or impact is applied during the rotation of the hollow rotary shaft. Due to the same dimensional difference, the air circulation hole 27 is always required when forming the herringbone groove (FIG. 11). For this reason, it is impossible to configure an air chamber in a sealed state for suppressing the movement of the rotating portion in the thrust direction, and therefore, when external force such as vibration or impact causes vibration in the rotating portion in the thrust direction, There is a problem that this cannot be suppressed.

Further, the rotating portion is always a thrust magnetic bearing 8
When a shock greater than the holding force of the thrust magnetic bearing is applied from the outside, the constituent members collide with each other at the abutting part between the case of the fixed part and the rotating part, and the rotating polygon mirror or hollow Since there is a risk of damage to components such as the rotating shaft, the rotating part is fixed and protected by screws or the like during transportation to prevent such damage. However, there has been a problem that no measures have been taken against the impact that occurs during use.

In addition, the radial gap between the outer circumference of the fixed shaft and the inner circumference of the hollow rotary shaft is usually about 2 μm to 5 μm,
The cylindricity of the inner circumference of the hollow rotary shaft is about ± 1 μm, and a surface condition close to a mirror surface is required. In order to satisfy these requirements, polishing and lapping are required to finish the inner circumference of the hollow rotating shaft, which requires a lot of processing time and is costly. . Further, in the conventional hydrodynamic air bearing type optical deflector, both the fixed shaft and the hollow rotary shaft are made of stainless steel, ceramics, aluminum, etc. If the coefficients differ greatly,
Generally, in a temperature environment in which a dynamic pressure air bearing type optical deflector is used, it becomes impossible to maintain the radial gap between the outer circumference of the fixed shaft and the inner circumference of the hollow rotary shaft within a predetermined range, resulting in smooth rotation. There is a problem in that it is impossible to perform the above, or in an extreme case, the rotation stops, which makes it impossible to select the constituent material based on the convenience in processing.

In view of the above conventional drawbacks, the present invention is
It is easy to process and low in cost. It can suppress vibration of the rotating part in the thrust direction due to external force, prevent damage to component parts due to sudden external impact, and can rotate in any direction, which further improves rotation performance. An object is to provide a compressed air bearing type optical deflector.

[0010]

In order to solve the above-mentioned problems, the present invention provides a slight gap between the inner circumference of a hollow rotary shaft and the outer circumference of a fixed shaft, and the hollow rotary shaft is rotated to cause a gap in the gap. In a dynamic pressure air bearing type optical deflector equipped with a radial bearing mechanism for generating dynamic pressure, the fixed shaft outer peripheral shape is made into an equal-diameter multi-arc shape or an equal-diameter strain circular shape, and the fixed shaft outer circumference and the hollow rotary shaft are A dynamic pressure air bearing type optical device in which the shape of the gap with the circumference is formed in a sinusoidal shape of N, preferably an odd number, and an air chamber is provided for changing the internal pressure when the rotating part is displaced in the thrust direction. We provide a deflector. Further, according to the present invention, a shock absorbing member made of an elastic member or the like is provided at a contact portion between the rotating portion and the fixed portion, and the hollow rotating shaft is formed of a sintered metal having an equal linear expansion coefficient, and has an inner diameter. Sizing is performed, the surface of the fixed shaft is anodized, and the inner peripheral surface of the hollow rotary shaft is nickel-plated or impregnated with a polymer substance after nickel-plating, and after the nickel-plating is co-plated with the polymer substance. Alternatively, a dynamic pressure air bearing type optical deflector coated with a polymer material is provided.

[0011]

[Function] The dynamic pressure air bearing type optical deflector constructed as described above.
In the device, the hollow rotary shaft rotates by exciting the coil.
However, by rotating this hollow rotary shaft, the outer peripheral shape is
The outer circumference of the fixed shaft configured in an arc shape or a circle of equal diameter strain
Dynamic pressure is generated in the gap between the inner circumference of the hollow rotary shaft and the
It can be rotated in any direction without
The inside of the rotor due to the displacement of the rotating part in the thrust direction
The sealed air chamber that changes the pressure of
Vibration in the last direction can be suppressed and fixed shaft or hollow rotation
The surface treatment of the shaft keeps the friction coefficient low and further improves rotation performance.
It can be installed at the contact part between the rotating part and the fixed part.
With a shock absorbing member, it can be used not only during transportation but also during use.
Even if there is, it will absorb external shocks and prevent damage to the components.
You can stop. Furthermore, the fixed shaft and the linear expansion coefficient are almost
By making them the same and configuring the hollow rotary shaft with sintered metal,
This makes it easier to process the hollow rotary shaft and further reduces costs.
In a wide range of operating temperature environment
Also, stable rotation performance can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in the drawings.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a top view of the fixed shaft 1, and FIG. 2 is a plan view of the fixed shaft 1 and the hollow rotary shaft 2 when the outer peripheral shape of the fixed shaft 1 is a tri-arc shape with an equal diameter and the inner peripheral shape of the hollow rotary shaft 2 is a perfect circle. It is an axial top view when it combines with. Further, FIG. 3 shows the shape of the gap formed by the outer circumference of the fixed shaft 1 and the inner circumference of the hollow rotary shaft 2 in this case, which is developed in the circumferential direction. Figure 4
FIG. 3 is a sectional view of a dynamic pressure air bearing type optical deflector according to the present invention. The same reference numerals as those used in describing the conventional example are the same members, and thus detailed description thereof will be omitted.
1 to 4, one embodiment of the present invention will be described.
More specifically, the fixed shaft 1 is made of a material such as aluminum, and the outer peripheral shape of the shaft is formed in a multi-arc shape, for example, a tri-arc shape, and the shaft surface is anodized.
Is stuck to. The hollow rotary shaft 2 is formed by sizing a sintered metal having a linear expansion coefficient equivalent to that of the fixed shaft 1 into a perfect circular inner circumference, and the surface of the inner circumference is electroless nickel plated. It is supported by a thrust magnetic bearing 8 which is fixed to and is rotatably held on the outer periphery of the fixed shaft 1. Here, the surface treatment is performed by electroless nickel plating, but in addition to this, a polymer (for example, fluororesin, P
The surface treatment may be performed by impregnating a resin having a low friction coefficient such as TFE (polytetrafluoroethylene), co-plating a polymer with nickel or the like, or coating a polymer. FIG. 3 is a diagram in which the shape of the gap formed between the outer circumference of the fixed shaft 1 and the inner circumference of the hollow rotary shaft 2 is developed in the circumferential direction. In this figure, the horizontal line clearance Cr is, for example, N = 3. Are formed into individual sine waves,
The dynamic pressure air bearing mechanism 9 is configured using this gap.
Reference numeral 4 denotes a mirror mounting portion, which is fixed to the outer periphery of the hollow rotary shaft 2 and rotates as the hollow rotary shaft 2 rotates. Reference numeral 3 denotes a rotary polygon mirror, which is fixed to the mirror mounting portion 4 by a cap 5 or the like, and the mirror mounting portion 4 is rotated as the hollow rotary shaft 2 rotates.
Rotate with. Further, the cap 5 is provided above the fixed shaft 1.
The hollow rotary shaft 2 is hermetically sealed by the hollow rotary shaft 2, and the internal pressure is changed as the rotary part including the hollow rotary shaft 2, the mirror mounting portion 4, the mirror 3, and the magnet 12 is displaced in the thrust direction during operation. An air chamber 6 is formed. or,
In order to form the air chamber 6, a screw 10 for fixing the cap 5 and the hollow rotary shaft 2 can be used as shown in FIGS. 5, 6 and 7. Reference numeral 7a denotes a shock absorbing member such as rubber, which is fitted into the outer peripheral recess of the fixed shaft 1, and other elastic members such as a columnar elastic member 7b, a spring 7c and a leaf spring 7d are provided on the inner surface of the case 11. ing.

When the coil 14 is excited, the magnet 12 facing it and the hollow rotary shaft 2 to which the magnet 12 is fixed rotate, and at the same time as the hollow rotary shaft 2 rotates, the mirror mounting portion provided on the hollow rotary shaft 2 is rotated. 4 and the rotary polygon mirror 3 fixed to the mirror mounting portion 4 rotate. At this time, dynamic pressure is generated in the gap formed between the outer circumference of the fixed shaft 1 and the inner circumference of the hollow rotary shaft 2 to generate rigidity, and at the same time, the fixed shaft 1
Since the outer peripheral shape of is not a perfect circle but is formed into a multi-circular shape of equal diameter or a circular shape of equal diameter strain, the whirl phenomenon does not occur and the dynamic pressure air bearing mechanism 9 having a desired critical mass is configured. can do.

An air chamber which is provided above the fixed shaft 1 and whose internal pressure changes as the rotating part is displaced in the thrust direction when external vibration or shock is applied during rotation of the hollow rotating shaft 2. Due to the damper effect of 6, vibration of the rotating portion in the thrust direction is suppressed, and stable rotation without vibration in the thrust direction can be obtained. Unlike the conventional herringbone type dynamic pressure air bearing mechanism, this air chamber 6 does not allow air to flow in the axial direction, so that an air flow hole with the outside is unnecessary and a sealed state can be created. . Therefore, it is possible to obtain a remarkable damper effect which is not present in the conventional dynamic pressure air bearing type optical deflector which requires the air circulation hole 27. Further, since there is no circulation of air with the outside, there is no problem that foreign matter such as dust is caught between the fixed shaft 1 and the hollow rotary shaft 2, so that more stable rotation performance can be obtained.

The operation of the air chamber 6 will be described with reference to FIGS. 8 to 9. FIG. 8 is a diagram showing the vibration damping state in the thrust direction with and without the air chamber,
(A) When there is no air chamber, when vibration or impact is applied from the outside, the generated vibration in the thrust direction continues for a considerable time, but (B) when there is an air chamber It can be seen that the vibration in the thrust direction is attenuated in a short time due to the damper effect of the air chamber. Also,
FIG. 9 is a diagram showing the vibration amplitude in the thrust direction with respect to the external vibration frequency with and without the air chamber. (A) When there is no air chamber, the thrust due to resonance occurs at a specific vibration frequency. Although the vibration width in the directional direction increases, it can be seen that (B) when there is an air chamber, the vibration width in the thrust direction due to such resonance does not increase due to the damper effect of the air chamber.

Since the hollow rotary shaft 2 is made of sintered metal having a linear expansion coefficient equal to that of the fixed shaft 1, the linear expansion coefficient of the fixed shaft 1 and the hollow rotary shaft 2 is wide under a wide range of operating temperature environment. Since there is no dimensional change between the two members due to the difference, the gap between the two members can be maintained at an appropriate size, and stable rotation can always be obtained. Also,
The hollow rotary shaft 22 of the conventional hydrodynamic air bearing type optical deflector requires polishing or lapping to finish the inner circumference, but in the present invention, the hollow rotary shaft 2 is made of sintered metal. Since it is formed, it is possible to obtain the structure shown in FIG.
As shown in FIG. 0, the hollow rotary shaft 2 is fixed by a fixing jig 16 so that the hollow rotary shaft 2 does not move, and a sizing pin 17 or a ball (not shown) having an outer diameter slightly larger than the inner diameter of the hollow rotary shaft 2 is attached. By passing it through the inner periphery of the, the inner diameter is expanded and it is easy to finish to a predetermined size, and the porous of the sintered metal is crushed to obtain a surface state close to a mirror surface. Further, since the finished dimensional accuracy of the inner diameter of the hollow rotary shaft 2 by this method is very high, about ± 1 μm, no further machining is required and the cost can be reduced. Further, as the constituent material of the sintered metal, when the fixed shaft 1 is stainless steel, stainless sintered metal or iron-based sintered metal is used, and when the fixed shaft 1 is an aluminum alloy, aluminum alloy sintered metal is used. Sintered metal having the same linear expansion coefficient can be appropriately used depending on the material of the fixed shaft 1, such as the use of metal or aluminum-based sintered metal.

The surface of the fixed shaft 1 is anodized,
Since the inner peripheral surface of the hollow rotary shaft 2 is subjected to electroless nickel plating, it is possible to reduce the frictional resistance at the time of starting the motor, which allows the motor to be started quickly and is stable even at high speed rotation. It is possible to obtain the desired rotation performance. Further, the damages on the surfaces of both members can be reduced, and the service life can be extended.

In the conventional hydrodynamic air bearing type optical deflector, in order to prevent damage to the constituent members due to external impact during transportation, the rotating portion is temporarily fixed with screws or the like during transportation to deal with this. In many cases, there was no countermeasure against external shocks applied during use. However, as will be described later, due to the provision of the shock absorbing member, when a shock that cannot be held by the thrust bearing 8 is applied from the outside even during use, the rotating part and the fixed part are in contact with each other. The impact absorbing member provided in the contacting portion absorbs an excessive impact of the rotating portion generated in the thrust direction, and damages to the components such as the rotary polygon mirror 3 and the hollow rotating shaft 2 can be prevented in advance. it can. The impact absorbing member described above is made of an O-ring-shaped elastic member, for example, rubber 7a, which is fitted in the recess formed on the outer periphery of the fixed shaft 1 as in the first embodiment shown in FIG. In addition, like the other embodiments shown in FIGS. 5 to 7, the columnar elastic member 7b,
The spring 7c, the leaf spring 7d, etc. can be appropriately provided on the inner side surface of the case 11 of the fixed portion. The impact absorbing member of the present invention is not limited to these examples. Furthermore, in the present embodiment, only the structure that absorbs the downward impact of the excessive impact of the rotating portion that occurs in the thrust direction is described, but the same principle
It goes without saying that a shock absorbing member for absorbing the shock in the upward direction may be provided.

[0020]

As is apparent from the above description, the following effects can be obtained in the present invention.

By forming the outer circumference of the fixed shaft into a multi-arc shape of equal diameter or a circular shape of equal diameter strain, and forming the gap between the outer circumference of the fixed shaft and the inner circumference of the hollow rotary shaft into N sinusoidal shapes, By having a desired critical mass, it is possible to prevent the occurrence of the whirl phenomenon and form a dynamic pressure air bearing type optical deflector with stable rotation performance. Further, since it is not necessary to perform etching or blasting for processing the herringbone groove, the processing becomes easy, and the processing time and cost can be reduced. Furthermore, since the flow of air from the outside in the axial direction is blocked, foreign matter is not caught in the dynamic pressure air bearing mechanism, and a stable rotating function can be maintained.

By providing the air chamber whose pressure changes with the displacement of the rotating portion in the thrust direction, vibration in the thrust direction due to external vibration or shock can be suppressed, and stable against external disturbance. It is possible to obtain a highly accurate rotation.

Since the hollow rotary shaft is made of a sintered metal having a linear expansion coefficient equivalent to that of the fixed shaft, the dimension between the fixed shaft and the hollow rotary shaft due to the difference in linear expansion coefficient between the two members. Therefore, the size of the gap between both members can be maintained within a predetermined range, and stable rotation performance can be obtained under a wide range of operating temperature environments. Also, since the sintered metal is porous, no polishing or lapping steps are required when finishing the inner diameter of the hollow rotating shaft, and the desired dimensional and surface accuracy can be obtained simply by performing sizing or ball processing. As a result, processing work is facilitated, and processing time and cost can be reduced.

By applying the surface treatment to the outer circumference of the fixed shaft and the inner circumference of the hollow rotary shaft, the coefficient of friction between both members can be lowered, so that the start-up is smooth and stable rotation is obtained. be able to. Further, since damage to the outer and inner peripheral surfaces of both members can be reduced, the life of the dynamic pressure air bearing type optical deflector can be extended.

Since the impact absorbing member is provided at the abutting portion between the rotating portion and the fixed portion, it is possible to absorb an external impact during transportation or use, so that damage to the constituent members can be prevented. You can

[Brief description of drawings]

FIG. 1 is a top view of a fixed shaft according to the present invention.

FIG. 2 is a top view of a state in which a fixed shaft and a hollow rotary shaft according to the present invention are combined.

FIG. 3 is a development view of a gap formed by an outer circumference of a fixed shaft and an inner circumference of a hollow rotary shaft according to the present invention.

FIG. 4 is a sectional view of the first embodiment of the dynamic pressure air bearing type optical deflector according to the present invention.

FIG. 5 is a sectional view of a second embodiment of a dynamic pressure air bearing type optical deflector according to the present invention.

FIG. 6 is a sectional view of a dynamic pressure air bearing type optical deflector according to a third embodiment of the present invention.

FIG. 7 is a sectional view of a dynamic pressure air bearing type optical deflector according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a damping state of thrust direction vibration.

FIG. 9 is a diagram showing a thrust direction vibration amplitude with respect to an external vibration frequency.

FIG. 10 is an explanatory view of sizing processing of the hollow rotary shaft according to the present invention.

FIG. 11 is a cross-sectional view of a conventional dynamic pressure air bearing type optical deflector.

FIG. 12 shows a conventional dynamic pressure air bearing type optical deflector.
The top view of the state which combined the fixed shaft which provided the herringbone groove on the outer periphery, and the hollow rotating shaft.

13 is a partially enlarged view of FIG.

[Explanation of symbols]

1 fixed axis 2 Hollow rotating shaft 3 rotating polygon mirror 4 Mirror mounting part 5 caps 6 air chamber 7a, 7b, 7c, 7d Shock absorbing member 8 Thrust magnetic bearing 9 Dynamic pressure air bearing mechanism 10 screws 11 cases 12 magnets 13 Stator core 14 coils 15 Hall element 16 Fixing jig 17 Sizing Pin

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-5-106632 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 26/10

Claims (9)

(57) [Claims] 1. A hydrodynamic air bearing comprising a radial bearing mechanism for providing a dynamic pressure in the clearance by providing a slight clearance between the inner circumference of the hollow rotary shaft and the outer circumference of the fixed shaft. Type optical deflector, the outer circumference of the fixed shaft is formed into a multi-arc shape of equal diameter or a circular shape of equal diameter distortion, and the shape of the gap between the outer circumference of the fixed shaft and the inner circumference of the hollow rotary shaft is formed into N sine waves. , A dynamic pressure air bearing type optical deflector, characterized in that an air chamber for changing the internal pressure when the rotating part is displaced in the thrust direction is provided. 2. The dynamic pressure air bearing type optical deflector according to claim 1, wherein the N is an odd number. 3. The dynamic pressure air bearing type optical deflector according to claim 1, wherein a shock absorbing member is provided at a contact portion between the rotating portion and the fixed portion. 4. The dynamic pressure air bearing type optical deflector according to claim 3, wherein the shock absorbing member is made of an elastic member. 5. The dynamic air bearing type optical deflector according to claim 1, wherein the hollow rotary shaft is formed of sintered metal, and the inner diameter is subjected to sizing processing. 6. The dynamic air bearing type optical deflector according to claim 1, wherein the hollow rotary shaft is formed of a sintered metal having a linear expansion coefficient equal to that of the fixed shaft. 7. The dynamic pressure air bearing type optical deflector according to claim 1, 2, 5 or 6, wherein the surface of said fixed shaft is alumite treated. 8. The dynamic pressure air bearing type light according to claim 1, wherein the inner peripheral surface of the hollow rotary shaft is nickel-plated or impregnated with a polymer substance after nickel plating. Deflector. 9. The inner peripheral surface of the hollow rotating shaft is nickel-plated and then co-plated with a polymer material or coated with a polymer material.
5. A dynamic pressure air bearing type optical deflector according to 5, 6, 7 or 8.