JPH09179055A - Bearing part for optical deflector and dynamic pressure air bearing type optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the bearing rigidity while reducing the windage loss at the time of the rotation of a rotary polygon mirror or rotary single-surface mirror by lowering the pressure in the optical deflector constituted by putting a motor rotation part, which is freely rotatable around the outer periphery of a dynamic pressure shaft together with the rotary polygon mirror or rotary single-surface mirror, hermetically in a case and a cover member. SOLUTION: A center hole which communicates with the outside air is bored along the length of the center part of a dynamic pressure shaft 1 having a feed herringbone groove (q) (or (r)) bored on one side of a dynamic pressure bearing M and a hole (b) is provided in the center of the herringbone groove (d) of the dynamic pressure bearing M and the feed herringbone groove (q), or a hole (c) is formed in the center of the herringbone groove (e) of the dynamic pressure bearing M and the feed herringbone groove (r).

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art The structure and operation of an example of a conventional dynamic air bearing type optical deflector will be described with reference to FIGS.
FIG. 8 is a sectional view of a conventional dynamic air bearing type optical deflector. The dynamic pressure shaft 1a is firmly fixed to the motor case 3 by shrink fit or the like. The dynamic pressure shaft 1a and the cover member 4 are fixed to each other via an O-ring 20, and the cover member 4 and the motor case 3 are fixed to each other via an O-ring 21 without any gap.
A Hall element 18 is provided on a support plate 17 that is provided over an opening of the motor case 3. A cylindrical sleeve 2 is fitted on the outer periphery of the dynamic pressure shaft 1a, and a magnet 22 is further fitted and fixed on the outer periphery of the sleeve 2 and provided in a vertical side wall of the motor case 3 so as to face the sleeve 2. The coil 15 is wound around the yoke 16. A thrust dynamic pressure bearing 12 is provided on the inner wall of the motor case 3 over the outer periphery of the dynamic pressure shaft 1 a, and a washer 13 is provided on the thrust dynamic pressure bearing 12. Reference numeral 14 is provided at the lower end of the magnet 22,
The spacer is fixed to the washer 13. Cover member 4
Inside, a hub 6 fixed to the outer periphery of the sleeve 2 and a rotary polygon mirror 5 fixed to the hub 6 horizontally with screws 9 are housed together with the sleeve 2 such that the outer periphery of the dynamic pressure shaft 1a is rotatable.
A pair of thrust suppressing magnets 10 and 11 having different polarities are disposed on the upper end of the sleeve 2 and the inner surface of the cover member 4 facing the upper end. The space inside the motor rotating part and the outside communicate with a longitudinal center hole Hg having an inlet K provided in the dynamic pressure shaft 1a, which will be described later, through a gap between the dynamic pressure shaft 1a and the sleeve 2. Flow through the openings of the holes Hb and Hc. When the coil 15 is energized, the yoke 1
6. The motor drive unit comprising the Hall element 18 and the magnet 22 is operated, and the cylindrical sleeve 2 in which the magnet 22 is inserted and fixed is supported by the thrust dynamic pressure bearing 12 on the outer periphery thereof, with the dynamic pressure shaft 1a as the core. Rotate. At the same time, the rotary polygon mirror 5 is used together with the hub 6 provided on the outer periphery of the sleeve 2.
Rotates. At this time, a dynamic pressure is generated between the dynamic pressure shaft 1a and the sleeve 2, and the dynamic pressure generates bearing rigidity. An appropriate gap is held between the magnets 10 and 11 by the repulsive force of the magnets. The pressure distribution of the air in the gap between the dynamic pressure shaft 1a and the sleeve 2 will be described with reference to FIGS. FIG. 9 is a plan view of the dynamic pressure shaft 1a and shows a bearing portion. Dynamic pressure shaft 1a
Is provided with one dynamic bearing Ma composed of herringbone grooves Hd and He having suction angles β opposite to each other and a non-grooved portion Hf. FIG. 10 is a cross-sectional view of the upper half of the dynamic pressure shaft 1a. In the longitudinal direction of the central portion of the dynamic pressure shaft 1a, a central hole Hg having an inlet K communicating with the atmosphere and a central hole Hg communicating with the central hole Hg. Holes Hb, H that open in the direction of the sleeve 2
c is drilled. A filter 23 is provided near the entrance K (FIG. 8). The openings of the holes Hb and Hc are located at the centers of the herringbone grooves Hd and He, and the boundary condition of the dynamic pressure bearing Ma of the conventional dynamic pressure air bearing type optical deflector shown in FIG. This means that the air pressure at the opening of Hc is equal to the atmospheric pressure. When the rotation is stable,
As shown in FIG. 1, the mass flow rate in the axial direction is 0 at the air suction port, so the pressure distribution in this dynamic pressure bearing Ma is as shown in FIG. In FIG. 12, the vertical axis represents the dimensionless pressure P whose representative value is atmospheric pressure, and when P = 1, the air pressure is equal to atmospheric pressure. In this conventional example, FIG.
As shown in FIG. 2, the air pressure at the air suction ports at both ends of the dynamic pressure bearing portion Ma becomes lower than the atmospheric pressure, so that the air pressure in the dynamic pressure air bearing type optical deflector shown in FIG. 8 becomes lower than the atmospheric pressure. Although the windage loss is reduced, the maximum air pressure inside the dynamic pressure bearing Ma is atmospheric pressure as described above.

[0003]

In the conventional dynamic air bearing type optical deflector, the rotation of the motor includes a rotating polygon mirror or a rotating single-sided mirror (hereinafter simply referred to as "rotating mirror"). Since the atmospheric pressure in the gap between the dynamic pressure shaft and the sleeve is set to the atmospheric pressure in order to reduce the atmospheric pressure at the outer circumference of the portion and reduce the windage loss of the rotating mirror, there is a problem that the bearing rigidity becomes low.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and includes a dynamic pressure shaft for forming a dynamic pressure bearing and a sleeve rotatable with respect to the dynamic pressure shaft. In a dynamic pressure air bearing type optical deflector in which a rotating mirror and its motor rotating portion are housed in a closed motor case, the dynamic pressure shaft is provided on one side of the dynamic pressure bearing in the direction of the dynamic pressure bearing. A herringbone groove for feeding air is provided, and a hole is formed at the center between the herringbone groove for feeding and the dynamic pressure bearing, and this hole is drilled in the longitudinal direction of the center of the dynamic pressure shaft. The bearing portion for the optical deflector was constructed by communicating with the atmosphere through the central hole provided. Further, a dynamic pressure air bearing for forming a dynamic pressure bearing, and a rotary mirror and its motor rotating portion via a sleeve rotatable with respect to the dynamic pressure shaft are housed in a sealed motor case. Type optical deflector, the dynamic pressure shaft is provided with one dynamic pressure bearing, and herringbone grooves for sending air in the direction of the dynamic pressure bearing are formed on both sides of the dynamic pressure bearing, and these are provided for feeding. Form a hole that opens at the center position between the herringbone groove and the dynamic pressure bearing,
A dynamic pressure air bearing type optical deflector was constructed by communicating this hole with the atmosphere through a central hole formed in the longitudinal direction of the center of the dynamic pressure shaft.

[0005]

In the optical deflector bearing of the present invention, the rotation of the sleeve with respect to the dynamic pressure shaft causes the feeding herringbone groove to send out air to the atmosphere side through the central hole of the dynamic pressure shaft. Through the central hole of the shaft, the hydrodynamic bearing produces a bearing support force based on atmospheric pressure. Further, a hole for communicating with the atmosphere and a feeding herringbone groove are formed on both sides of one dynamic pressure bearing by the herringbone groove, and the rotary mirror and its motor rotating portion are housed in a hermetically sealed case via a sleeve. When the dynamic air bearing type optical deflector is configured, the internal pressure of the case is reduced without impairing the bearing supporting force, so that the bearing supporting rigidity can be increased while reducing the wind loss due to the rotating mirror.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a dynamic air bearing type optical deflector according to the present invention. In this embodiment, a dynamic pressure air bearing type optical deflector equipped with a rotating polygon mirror is described. However, a rotating single mirror may be fitted. Incidentally, among the reference numerals used in the description of the conventional dynamic pressure air bearing type optical deflector, those which are the same as those in the present embodiment indicate the same members. FIG. 1 is a sectional view of a dynamic pressure air bearing type optical deflector according to the present invention. The dynamic pressure shaft 1 is fixed to the motor case 3 by shrink fitting or the like without any gap. or,
The dynamic pressure shaft 1 and the cover member 4 are fixed to each other via an O-ring 20, and the cover member 4 and the motor case 3 are fixed to each other via an O-ring 21 without gaps. The space inside the motor rotating part and the outside are passed through a gap between the dynamic pressure shaft 1 and the sleeve 2, and a longitudinal center hole g provided on the dynamic pressure shaft 1, which will be described later, and holes b and c communicating therewith. It is distributed by the opening of. Yoke 16, coil 15,..., Hall element 18, magnet 2
When the motor unit composed of two magnets is driven, the magnet 2
The hollow cylindrical sleeve 2 to which the sleeve 2 is fixed rotates, and the rotary polygon mirror 5 fixed to the hub 6 fixed to the sleeve 2 by screws 9 further rotates. At this time, a dynamic pressure is generated between the dynamic pressure shaft 1 and the sleeve 2, and the dynamic pressure generates bearing rigidity.

The pressure distribution of air in the gap between the dynamic pressure shaft 1 and the sleeve 2 will be described with reference to FIGS. FIG. 2 is a sectional view of the dynamic pressure shaft 1, showing a bearing portion of the dynamic pressure air bearing type optical deflector. On the dynamic pressure shaft 1, two dynamic pressure bearings M, M having herringbone grooves d and e having opposite suction angles β and a groove non-machined portion f, and these two dynamic pressure bearings M are provided. , M, which are located at both ends of the feeding herringbone grooves d and e, and feeding herringbone grooves q and r having a suction angle β in the same U direction as the herringbone grooves d and e. Further, as shown in FIG. 4, the dynamic pressure bearing M may have only the herringbone grooves d and e which have been entirely processed without the groove non-processed portions. FIG. 3 is a cross-sectional view of the upper half of the dynamic pressure shaft 1, which has a central hole g having an inlet K communicating with the atmosphere in the longitudinal direction of the central portion of the dynamic pressure shaft 1 and a central hole g communicating with the central hole g. Holes b and c that open toward the sleeve 2 are provided. A filter 23 is provided near the entrance K. The openings of the holes b and c are located at the centers of the dynamic pressure bearings M and M and the feeding herringbone grooves q and r provided outside the dynamic pressure bearings M and M, respectively, according to the present invention shown in FIG. The boundary condition of the dynamic pressure shaft 1 of the dynamic pressure air bearing type optical deflector is that the pressure of the air at the openings of the holes b and c is equal to the atmospheric pressure.
In the stable rotation state, as shown in FIG. 6, the mass flow rate in the axial direction becomes 0 at the air suction port, so the pressure distribution in the dynamic pressure shaft 1 becomes the state shown in FIG. In FIG. 7, the vertical axis is the dimensionless pressure P whose representative value is atmospheric pressure,
When P = 1, it means that the air pressure is equal to the atmospheric pressure. According to the present invention, as described above, the air pressure at the opening portions of the holes b and c located at the centers of the dynamic pressure bearing M and the feeding herringbone grooves q and r becomes equal to the atmospheric pressure, so that it is shown in FIG. As described above, the air pressure in the air suction port becomes lower than the atmospheric pressure, and the air pressure in the dynamic pressure air bearing type optical deflector shown in FIG. 1 also becomes lower than the atmospheric pressure. The maximum air pressure in the gap becomes higher than the atmospheric pressure, and the bearing rigidity can be increased while reducing the wind loss.

[0008]

As described above in detail, according to the bearing portion for an optical deflector of the present invention, it is possible to secure both the air sending action and the bearing support rigidity. Further, in the case where the optical deflector is constituted by the above bearing portion, the air pressure inside the dynamic pressure bearing, that is, in the gap between the dynamic pressure shaft and the sleeve can be increased while reducing the ambient pressure of the rotating mirror, so that the bearing rigidity is reduced. Without increasing the wind loss, it is possible to save the labor of the motor.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a dynamic pressure air bearing type optical deflector according to the present invention.

FIG. 2 is a plan view of an embodiment of a bearing portion of a dynamic pressure air bearing type optical deflector according to the present invention.

3 is an upper half sectional view of the bearing portion of FIG.

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

5 is an upper half sectional view of the bearing portion of FIG.

6 is a cross-sectional view of a bearing portion including a sleeve having a herringbone groove illustrated in FIG.

FIG. 7 is a diagram showing a pressure distribution around a bearing portion of the dynamic pressure air bearing type optical deflector shown in FIG.

FIG. 8 is a sectional view of a conventional dynamic pressure air bearing type optical deflector.

FIG. 9 is a plan view of a bearing portion of a conventional dynamic pressure air bearing type optical deflector.

10 is an upper half sectional view of the bearing portion of FIG.

11 is a cross-sectional view of a bearing portion including a sleeve having a herringbone groove illustrated in FIG.

12 is a diagram showing a pressure distribution around a bearing portion of the dynamic pressure air bearing type optical deflector shown in FIG.

[Explanation of symbols]

 1 Dynamic Pressure Shaft 2 Sleeve 3 Motor Case 4 Cover Member 5 Rotating Mirror (Rotating Polygon Mirror) 10 Thrust Suppression Magnet 11 Thrust Suppression Magnet 12 Thrust Dynamic Pressure Bearing 13 Washer 15 Coil 16 Yoke 20 O-ring 21 O-ring 22 Magnet 23 Filter b Hole c Hole d Herringbone groove e Herringbone groove q Feeding herringbone groove r Feeding herringbone groove f Groove unprocessed part g Center hole K Inlet M Dynamic bearing

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Rie Wakashima 110-1 Shinkushita Nitta, Iruma City, Saitama Copal Electronics Co., Ltd.

Claims (2)

[Claims] 1. A dynamic housing in which a dynamic pressure shaft for forming a dynamic pressure bearing, a rotary mirror and its motor rotating portion are housed in a hermetically sealed motor case via a sleeve rotatable with respect to the dynamic pressure shaft. In the compressed air bearing type optical deflector, the dynamic pressure axis is
A herringbone groove for sending air is provided on one side of the hydrodynamic bearing to send air in the direction of the hydrodynamic bearing, and a hole is formed at the center position between the herringbone groove for sending and the hydrodynamic bearing. A bearing part for an optical deflector, characterized in that the hole communicates with the atmosphere through a central hole formed in the longitudinal direction of the central part of the dynamic pressure shaft. 2. A dynamic pressure shaft for forming a dynamic pressure bearing, a dynamic mirror in which a rotary mirror and its motor rotating portion are housed in a hermetically sealed motor case via a sleeve rotatable with respect to the dynamic pressure shaft. In the compressed air bearing type optical deflector, the dynamic pressure axis is 1
Two dynamic pressure bearings are provided, and feed herringbone grooves for sending air in the direction of the dynamic pressure bearings are formed on both sides of the dynamic pressure bearings, and between these feed herringbone grooves and the above dynamic pressure bearings. A dynamic pressure air bearing type optical deflector characterized in that a hole opening at a central position is formed, and the hole is communicated with the atmosphere through a central hole formed in a longitudinal direction of a central portion of the dynamic pressure shaft.