JPH06308414A - Polygon mirror driving device - Google Patents

Abstract

PURPOSE:To provide a polygon mirror driving device which suppresses vibration and noise caused by whirling being a problem at the time of driving at very high speed which is inexpensive and whose durability is excellent in the polygon mirror driving device used for a laser beam printer or the like. CONSTITUTION:A bearing sleeve 203 provided with a herringbone groove and a thrust receiving plate 104 provided with a spiral groove 111 are assembled to a bracket 105 where the stator core 110 of an inner rotor type brushless motor is fitted. Besides, a bearing sleeve 202 provided with the heringbone groove is fitted also to a cover 115 fitted in order to shield wind whistle at the rotating time and to prevent a mirror from being stained. Since a rotor including the mirror 107 is positioned between the upper and the lower bearings, a rotating body which hardly causes the vibration and the noise is obtained. Besides, since a dynamic pressure fluid bearing by lubricating oil is used as the bearing, the device is inexpensive and suitable for mass production.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygon mirror driving device using a hydrodynamic bearing, and more particularly 2000
The present invention relates to a polygon mirror driving device having a dynamic pressure bearing structure which is operated at an ultra-high speed exceeding 0 rpm and has excellent durability.

[0002]

2. Description of the Related Art In recent years, a polarization scanning motor for rotatably driving a polygon mirror in a laser beam printer or the like is required to have a rotation speed of 20000 rpm or more from the viewpoint of high printing speed and high precision printing, and the size of the polygon mirror is also required. Since the inscribed circle is as large as 50 mm or more, there is a strong demand that the performance required of the drive device be low in vibration and noise and inexpensive. Ball bearings are generally used as motor bearings, but 20000r
The limit is up to pm, and the dynamic pressure air bearing is excellent in performance in order to obtain a higher rotation speed, but it is very expensive. Further, an example in which a hydrodynamic bearing using lubricating oil is adopted is disclosed in JP-A-2-308119 and JP-A-3-37411, but the rotation speed is 10,000 rp.
The rotation speed is about m.

A conventional polygon mirror driving device will be described below. FIG. 3 is a sectional view of a conventional polygon mirror driving device using a hydrodynamic bearing. In FIG. 3, a shaft 301 and a sleeve 302 are rotatably fitted to each other, and a thrust receiving plate 303 having a spiral groove is arranged at a lower end portion of the sleeve 302 together with a fixing plate 304 and fixed to an outer cylinder 305. Shaft 3
A flange 306 is fixed to 01, a polygon mirror 307 is fixed to the upper part of the flange 306, and a yoke 309 to which a driving magnet 308 is fixed is fixed to the lower part. A stator core 310 fixed to the outer cylinder 305 is installed at a position facing the driving magnet 308.

The operation of the polygon mirror driving device constructed as described above will be described below. First, in the thrust receiving plate 303, a spiral shallow groove 311 is formed on a surface facing the end of the shaft 301 to form a dynamic pressure thrust bearing. In addition, on the outer peripheral surface of the shaft 301, at a position facing the inner peripheral surface of the sleeve 302,
A single herringbone-shaped shallow groove 312 is engraved to form a dynamic pressure radial bearing. The helical groove 313 is a shallow groove for preventing oil outflow.

The rotating body configured as described above rotates without contact due to the dynamic pressure of the lubricating oil.

[0006]

However, in the above-mentioned conventional structure, since the polygon mirror is arranged outside the position supported by the radial bearing, the polygon mirror is unbalanced or vibrated by external vibration. When motion is caused, the shake of the polygon mirror portion becomes large, and the image characteristics of the laser beam printer and the like deteriorate. Normally, as the motor rotates at a higher speed, it is necessary to increase the diameter of the rotating shaft in order to withstand the eccentric load on the polygon mirror.However, the peripheral speed of the shaft diameter increases, and a large centrifugal force acts on the lubricating oil to retain it. Since it becomes difficult and the bearing load torque also increases, there is a problem that it is not suitable for high speed rotation.

The present invention solves the above-mentioned problems of the prior art by providing a hydrodynamic bearing structure having low vibration, low noise, low cost, and excellent durability even when operated at an ultrahigh speed of over 20000 rpm. An object is to provide a polygon mirror driving device.

[0008]

In order to achieve this object, a polygon mirror driving device of the present invention comprises (I) a bearing sleeve having herringbone grooves formed at both ends of a shaft of a rotor having a polygon mirror. In addition, the bearing structure further includes a thrust receiving plate having a thrust load spiral groove formed at one end of the shaft.

(II) A rotor shaft having a polygon mirror has a first shaft diameter and a second shaft diameter thicker than the first shaft diameter, and herringbone grooves are formed at both ends of the shaft having the first shaft diameter portion. Bearing shaft with a thrust bearing plate formed with a spiral groove for thrust load at one end of the shaft, and at least one of the bearing sleeves has a small gap in the second shaft diameter portion. This is a configuration in which a shaft hole for fitting is provided.

[0010]

With this structure, the rotor can be operated at an ultra-high speed without causing a grinding movement, and the shaft diameter of the bearing portion can be reduced, so that the peripheral speed of the shaft diameter can be reduced and the bearing load torque can be reduced. it can.

Further, by constructing the shaft with the first shaft diameter and the second shaft diameter which is thicker than that, the adverse effect due to the deflection of the shaft is suppressed, and the shaft diameter of the bearing portion is further reduced to reduce the bearing load torque. it can. By providing a shaft hole that fits in the second shaft diameter portion with a slight gap on at least one of the bearing sleeves, the lubricating oil of the bearing portion is attracted by the wind flow generated by the rotation of the mirror and is exposed to the outside. It does not prevent outflow and contaminate the polygon mirror or shorten the life of the bearing.

[0012]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the shaft 101 is rotatably fitted in the inner diameter holes of the bearing sleeves 102 and 103, and a thrust receiving plate 104 having a spiral groove is arranged at the lower end portion of the bearing sleeve 103. Together with the bearing sleeve 103, the cup-shaped bracket 105
It is fixed to. Flange 106 on shaft 101
Is fixed, a polygon mirror 107 is fixed on the upper portion of the flange 106, and a driving magnet 108 is fixed on a shaft portion below the flange via a yoke 109.
Further, a stator core 110 fixed to the bracket 105 is installed at a position facing the driving magnet 108, and a Hall element 114 for detecting a position during rotation is also installed. The other bearing sleeve 102 is fixed to the cover 115.

The operation of the polygon mirror driving device configured as described above will be described below. First, a spiral shallow groove 111 is formed on the surface of the thrust receiving plate 104 facing the end of the shaft 101 to form a dynamic pressure thrust bearing. Further, a herringbone-shaped shallow groove 112 is formed on the outer peripheral surface of the shaft 101 at a position facing the inner peripheral surface of the bearing sleeve 102, and similarly, a herringbone shape is formed at a position facing the inner peripheral surface of the bearing sleeve 103. Shallow groove 113 is engraved to form a dynamic pressure radial bearing. The rotating body configured in this way rotates without contact due to the dynamic pressure of the lubricating oil.

Here, since the polygon mirror 107 is arranged inside the positions supported by the radial bearings at both ends of the shaft 101, the polygon mirror 107 does not cause a rasping motion. Further, since there is no unbalanced load on the polygon mirror and the shaft diameter can be made small, the peripheral speed of the shaft diameter can be slowed down, the centrifugal force can be strengthened, the lubricating oil can be easily retained, and the bearing load torque also decreases, exceeding 20,000 rpm. It becomes possible to operate at such an ultra-high speed rotation.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, a thrust receiving plate 104 having a spiral groove is arranged at the lower end of the bearing sleeve 203, and the bearing sleeve 203 is fixed to the cup-shaped bracket 105. A polygon mirror 107 is fixed to the upper portion of the flange 106, and a driving magnet 108 is fixed to a shaft portion below the flange via a yoke 109. In addition, a stator core 110 fixed to the bracket 105 is provided at a position facing the driving magnet 108.
Is installed, and further, a Hall element 114 for detecting the position at the time of rotation is installed.

The bearing sleeve 202 has a cover 115.
It is fixed to. A spiral shallow groove 111 is formed in the thrust receiving plate 104 to form a dynamic thrust bearing. Further, a herringbone-shaped shallow groove 112 is engraved on the bearing sleeve 202, and similarly the bearing sleeve 203 is formed.
A herringbone-shaped shallow groove 113 is engraved therein to form a dynamic pressure radial bearing. The rotating body configured in this way rotates without contact due to the dynamic pressure of the lubricating oil. The above is Fig. 1
It has the same configuration and operation as.

The difference from FIG. 1 is that the shaft 201 has a first shaft diameter portion 201a and a thicker second shaft diameter portion 201b.
The bearing sleeves 202 and 203 are arranged at both ends of the shaft 201 having the first shaft diameter portion 201a, and the thrust receiving plate 104 is further provided at one end of the shaft 201. The adverse effect of the deflection can be suppressed, the shaft diameter of the bearing portion can be further reduced, and further ultra-high speed rotation is possible.

Further, the bearing sleeves 202 and 203
To form a labyrinth by providing shaft hole portions 202a and 203a that fit with the second shaft diameter portion 201b with a slight gap, and the lubricating oil of the bearing portion is attracted by the wind flow generated by the rotation of the mirror. It does not prevent leakage to the outside and contaminate the polygon mirror or shorten the life of the bearing.

In the first embodiment, the two bearing sleeves made of gun metal or the like may be attached to the bracket and the cover made of aluminum die casting with screws, or the material of the bearing sleeve may be bored by casting cutting. After that, the herringbone groove may be processed.

[0022]

As described above, the present invention has (I) a thrust bearing plate having a bearing sleeve having herringbone grooves formed at both ends of a shaft and further having a spiral groove for thrust load formed at one end of the shaft. Or (II) having a first shaft diameter portion and a thicker second shaft diameter portion, and forming herringbone grooves at both ends of the shaft having the first shaft diameter portion A shaft receiving hole having a bearing sleeve and a thrust receiving plate having a spiral groove for thrust load formed at one end of the shaft, and further having at least one of the bearing sleeves fitted in the second shaft diameter portion with a slight clearance. With the configuration including the portion, (1) the rotor can be operated at an ultra-high speed without causing a rasping motion.

(2) Since the shaft diameter of the bearing portion can be reduced, the peripheral speed of the shaft diameter can be reduced and the bearing load torque can be reduced.

(3) The adverse effect of bending can be eliminated by increasing the diameter of the second shaft. (4) The lubricating oil of the bearing portion is not attracted by the flow of wind generated by the rotation of the mirror and does not flow out to the outside to contaminate the polygon mirror or shorten the life of the bearing.
It is possible to realize an excellent polygon mirror driving device that can obtain the effects described above.

[Brief description of drawings]

1A is a cross-sectional view of a polygon mirror driving device according to a first embodiment of the present invention, FIG. 1B is a cross-sectional view of a bearing sleeve with a herringbone groove, and FIG. 1C is a top view of a thrust bearing plate with a spiral groove.

2A is a sectional view of a polygon mirror driving device according to a second embodiment of the present invention, FIG. 2B is a sectional view of a bearing sleeve with a herringbone groove, and FIG. 2C is a top view of a thrust bearing plate with a spiral groove.

FIG. 3 is a sectional view of a conventional polygon mirror driving device.

[Explanation of symbols]

 101, 201, 301 Shaft 102, 103, 202, 203 Bearing sleeve 104, 303 Thrust receiving plate 105 Bracket 106, 306 Flange 107, 307 Polygon mirror 108, 308 Driving magnet 109, 309 Yoke 110, 310 Stator core 111, 311 Spiral Shallow groove 112, 113, 312 Herringbone-shaped shallow groove 114 Hall element 115 Cover 201a, 201b Shaft diameter portion 202a, 203b Shaft hole portion 313 Helical groove

Claims (2)

[Claims] 1. A polygon mirror fixed to a flange of a tubular body having an L-shaped cross-section, which is attached to the outer periphery of a rotatably mounted shaft at a right angle thereto, and a cylinder coaxially fixed to the shaft below the flange. A cup-shaped bracket having a rotor provided with a mold driving magnet, a stator core surrounding the driving magnet via a cylindrical air gap, and a Hall element for sequentially controlling energization of the stator core, and the bracket for enclosing the rotor. The cover is attached to the open end of the bracket, and the thrust receiving plate having a spiral groove for thrust load formed in the center of the closed end side of the bracket and the bearing sleeve having a herringbone groove are fixed to the center of the cover. Also fix the bearing sleeve with the herringbone groove, and use the hydrodynamic bearings by the both ends of the shaft. A polygon mirror driving device characterized by being configured. 2. A shaft having a first shaft diameter portion and a second shaft diameter portion thicker than the first shaft diameter portion, and a flange of a tubular body having an L-shaped cross section attached to the outer periphery of the second shaft diameter portion at a right angle thereto. A fixed polygon mirror, a rotor provided with a cylindrical drive magnet fixed coaxially to a shaft below the flange, a stator core surrounding the rotor via a cylindrical air gap, and a Hall element for sequentially controlling energization of the stator core. And a cup-shaped bracket to which the rotor is attached, and a cover attached to the open end of the bracket so as to enclose the rotor, and a thrust receiving plate having a thrust load spiral groove formed in the center of the closed end of the bracket. The bearing sleeve with the herringbone groove is fixed, and the bearing sleeve with the herringbone groove is also fixed in the center of the cover. A hydrodynamic bearing is constituted by a sleeve hole formed with a shaft diameter portion and a herringbone groove, and at least one of the bearing sleeves is provided with a shaft hole portion that fits into the second shaft diameter portion with a slight gap. Characteristic polygon mirror drive device.