JP2002258200A - Deflecting scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable deflecting scanner which facilitates working and mounting of component members of bearings and is capable of stably suppressing the vibration of a revolving shaft by decreasing the error factors to determine the volume of an air reservoir. SOLUTION: This defecting scanner has a motor housing 1 which has a through-hole, a stationary sleeve 2 which is fixed to these through-hole, the revolving shaft 3 which is freely rotatably fixed to the stationary sleeve 2, first and second permanent magnets 14 and 15 which axially float the revolving shaft by magnetic force and a thrust cover 17 which forms the air reservoir 16 by hermetically closing the lower side of the stationary sleeve 2, the deflecting scanner described above deflects and scans a light beam by a rotary polyhedral mirror 7 attached to the revolving shaft 3. The stationary sleeve 2 and the thrust cover 17 are both positioned and fixed in the axial direction by a projecting part 19 projectingly disposed within the through-hole of the motor housing 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection scanning device for deflecting and scanning an optical beam with a rotating mirror mounted on a rotating shaft, and more particularly to a device having a mechanism for supporting the rotating shaft with a dynamic pressure bearing.

[0002]

2. Description of the Related Art Heretofore, this type of deflection scanning apparatus has been widely used in electrophotographic image forming apparatuses such as laser beam printers, copiers and facsimile machines.

In recent years, this type of deflection scanning device has been required to rotate a rotary polygon mirror at high speed and with high accuracy. In particular, in a laser beam printer or the like, a non-contact rotating mirror is required to satisfy this requirement. A compressed air bearing is used.

FIG. 5 is a view showing a deflection scanning device having a dynamic pressure air bearing described in Japanese Patent Application Laid-Open No. 11-14929. In the figure, a rotating shaft 102 fixedly supporting a rotating polygon mirror 101 is rotatably fitted to a fixed sleeve 104 fixed to a housing 103. Rotating shaft 102
A gap of several μm is provided between the rotating shaft 102 and the fixed sleeve 104, and a dynamic pressure air bearing for supporting the rotating shaft 102 in the radial direction is formed.

[0005] A first permanent magnet 105 is fixed to the lower end surface of the rotating shaft 102, and a second permanent magnet 106 is fixed to the lower end surface of the fixed sleeve 104. The first and second permanent magnets 105 and 106 are arranged so as to generate a magnetic attraction force, and constitute a magnetic thrust bearing for floatingly supporting the rotating shaft 102 in the thrust direction.

However, if the rotary shaft 102 is only levitated and supported by magnetic attraction, the rotary shaft 1 is externally supported.
When vibrations or the like are applied to 02, the amplitude of the vibration of the rotating shaft 102 increases, or the decay time increases. An air reservoir 107 is provided below the first permanent magnet 105 in order to reduce the amplitude of the vibration of the rotating shaft 102 and shorten the decay time, and to seal the air reservoir 107. Is fixed to the lower end surface of the second permanent magnet 106.

The supporting member 1 is provided above the rotating shaft 102.
09 is fixed, and a driving magnet 110 is fixed to a side surface of the support member 109. The rotary polygon mirror 101 is mounted on the upper surface of the support member 109, and is fixed by a leaf spring 111, a holding plate 112, and a C ring 113. A board 114 is fixed on the upper surface of the housing 103, and a coil 115
A stator constituted by a motor and a core 116 is disposed so as to face the drive magnet 110, thereby forming a drive motor. A weight (not shown) is placed on the rotating polygon mirror 101 and the driving magnet 110 to balance the entire rotating body.

In such a deflection scanning device, the gap between the rotating shaft 102 and the fixed sleeve 104 is extremely narrowed to several μm, and the air reservoir 107 is sealed. Even if it moves, the pressure of the air reservoir 107 changes and the vibration of the rotary shaft 102 is attenuated, that is, it plays a role of an air damper.

[0009]

However, in the prior art as described above, the first and second permanent magnets 10 are used.
5 and 106, and the mounting accuracy of the first permanent magnet 105 and the cover 108, the volume of the air reservoir 107 may be large. Since the pressure change is small and the air damper effect for attenuating the vibration of the rotating shaft 102 does not work sufficiently, the rotating body including the rotating shaft 102 collides with the fixed member, thereby deteriorating accuracy or damaging the rotating member. May reduce the performance.

Further, the cover 108 is attached to the second permanent magnet 10.
6, the uncured adhesive may enter the air pocket 107 at the time of bonding. If the uncured adhesive reaches the hydrodynamic air bearing for supporting the radial direction, the operation of the bearing itself may be affected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to reduce an error factor for determining the volume of an air reservoir and to process and reduce the number of components of a bearing. As well as facilitating installation,
An object of the present invention is to provide a highly reliable deflection scanning device capable of stably suppressing vibration of a rotating shaft.

Further, a second object of the present invention is to prevent the adhesive for fixing the lid member from entering the air pocket or the bearing, thereby improving the reliability of the operation of the bearing.

[0013]

According to the present invention, there is provided a housing having a through-hole, a fixed sleeve fixed to the through-hole of the housing, and a rotatably mounted on the fixed sleeve. A rotating shaft fitted to the rotating shaft, a levitation means for floating the rotating shaft in the axial direction by magnetic force, and a lid member forming a sealed air reservoir below the rotating shaft; In the deflection scanning device for deflecting and scanning the light beam by the rotating mirror, the fixing sleeve and the lid member are both positioned and fixed in the axial direction by the housing.

According to this configuration, since the fixing sleeve and the lid member are positioned in the axial direction by the housing,
Error factors that determine the volume of the air pocket formed between the two members can be reduced.

The housing has a ridge on a peripheral surface of the through hole, and a lower end of the fixed sleeve is brought into contact with an upper surface of the ridge, and a lid member is provided on a lower surface of the ridge. The fixing sleeve and the lid member are preferably positioned in the axial direction by bringing the upper ends of the abutment into contact with each other.

Since the volume of the air pocket is determined by the axial thickness of the ridge of the housing (the dimension between the upper surface and the lower surface of the ridge), strict dimensional accuracy is required. Is sufficient only in the axial thickness of the ridge. In consideration of easiness of processing and mounting stability, it is preferable that the ridge portion is provided on the entire peripheral surface of the through hole of the housing.

[0017] The outer peripheral surface of the lid member and the peripheral surface of the through hole of the housing may be bonded to fix the lid member.

With this bonding, even if the uncured adhesive remains on the bonding surface between the lid member and the through hole,
Since the upper end of the lid member is in contact with the lower surface of the ridge of the housing, the adhesive is prevented from entering the bearing.

It is preferable that the lid member is adhered with an anaerobic ultraviolet curing type adhesive.

The levitation means includes: a first permanent magnet fixed to a lower end of the rotating shaft; a second permanent magnet fixed to a lower end of the fixed sleeve so as to face the first permanent magnet; It is good to have.

The thickness of the second permanent magnet in the axial direction is preferably equal to or less than the distance between the lower end of the fixed sleeve and the lid member.

[0022] It is preferable that the lid member has a protruding portion that protrudes into the air reservoir.

[0023]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) First, an overall configuration of a deflection scanning apparatus according to a first embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a plan view schematically showing the deflection scanning apparatus according to the present embodiment. In the figure, a deflection scanning device includes a light source 51 for generating a light beam (light flux) such as a laser beam.
And a cylindrical lens 51a for linearly condensing the light beam on the reflection surface of the rotary polygon mirror 7, and deflects and scans the light beam by rotation of the rotary polygon mirror 7, thereby forming an image forming optical system. An image is formed on the image forming surface of the photoconductor 54 on the rotating drum via the lens system 52 and the folding mirror 53. The imaging lens system 52 has a spherical lens 52a, a toric lens 52b, and the like, and has an fθ function for correcting a scanning speed of a point image formed on the photoconductor 54 and the like.

When the rotary polygon mirror 7 is rotated in the direction of arrow A by a motor (not shown), its reflecting surface is
Rotates at a constant speed around the axis of. As described above, the light source 51
The angle between the optical path of the light beam generated by the optical lens and condensed by the cylindrical lens 51a and the normal to the reflection surface of the rotary polygon mirror 7, that is, the angle of incidence of the light beam on the reflection surface is determined by the rotation of the rotary polygon mirror 7. And the reflection angle also changes with time, so that the point image formed by condensing the light beam on the photoconductor 54 moves (scans) in the axial direction (main scanning direction) of the rotating drum.

The imaging lens system 52 focuses the light beam reflected by the rotary polygon mirror 7 on the photosensitive member 54 into a point image having a predetermined spot shape, and scans the point image in the main scanning direction. Is designed to keep the speed constant.

The point image formed on the photoreceptor 54 is formed by an electrostatic latent image due to the main scanning by the rotation of the rotary polygon mirror 7 and the sub-scanning by the rotation of the rotating drum having the photoreceptor 54 around its axis. Form an image.

Around the photosensitive member 54, a charging device for uniformly charging the surface of the photosensitive member 54, and a charging device for visualizing an electrostatic latent image formed on the surface of the photosensitive member 54 into a toner image. A developing device, a transfer device (not shown) for transferring a toner image to recording paper, and the like are provided, and recording information by a light beam generated from a light source 51 is printed on recording paper or the like.

The detection mirror 55 reflects the light beam upstream of the optical path of the light beam entering the recording information writing position on the surface of the photosensitive member 54 in the main scanning direction, and has a photodiode or the like via a lens 56a. The light is introduced to the light receiving surface of the light receiving element 56b. The light receiving element 56b outputs a scan start signal for detecting a scan start position (write start position) when the light receiving surface is irradiated with the light beam.

The light source 51 generates a light beam corresponding to a signal provided from a processing circuit 57 for processing information from a host computer. The signal given to the light source 51 is
The processing circuit 57 corresponds to information to be written to the photoconductor 54, and the processing circuit 57 uses the signal representing the information corresponding to one scanning line, which is a locus formed by a point image formed on the surface of the photoconductor 54, as one unit, Give to. This information signal is transmitted in synchronization with the scanning start signal given from the light receiving element 56b via the line 56c.

The rotary polygon mirror 7, the imaging lens system 52 and the like are housed in an optical box 50, and the light source 51 and the like are mounted on the side wall of the optical box 50. After the rotating polygon mirror 7, the imaging lens system 52, and the like are assembled in the optical box 50, a lid (not shown) is attached to the upper opening of the optical box 50.

Next, the configuration of the bearing of the rotary polygon mirror of the deflection scanning device according to the present embodiment will be described in detail with reference to FIGS.

FIG. 1 is a half sectional view showing a configuration of a bearing section of the deflection scanning apparatus according to the present embodiment, and FIG. 2 is a sectional view showing a main part of FIG.

As shown in FIG. 1, a fixed sleeve 2 made of, for example, a ceramic material is provided in a through hole of the motor housing 1.
Has been fixed. On the peripheral surface of the through hole of the motor housing 1, a ridge 19 having a substantially rectangular cross section in the axial direction is provided.
The fixed sleeve 2 is positioned in the axial direction by bringing a part of the lower end surface into contact with the upper surface of the ridge portion 19.

A rotary shaft 3 made of, for example, a ceramic material is rotatably fitted to the fixed sleeve 2. A gap of several μm is provided between the fixed sleeve 2 and the rotating shaft 3 to form a dynamic pressure air bearing for supporting the rotating shaft 3 in the radial direction. A magnetic thrust bearing (described later) for supporting the rotating shaft 3 in the thrust direction is formed below the rotating shaft 3.

A metal support member 4 is fixed to the upper portion of the rotating shaft 3 by shrink fitting or the like, and a metal rotor 5 is fixed to the lower portion of the support member 4 by caulking or the like. A drive magnet 6 is attached to the inner peripheral surface of the motor 5.

A rotary polygon mirror 7 is fitted into the support member 4, and a leaf spring 8, a holding plate 9 and C
The rotating polygon mirror 7 is fixed to the support member 4 by arranging the rings 10 in sequence and attaching the C ring 10 to the support member 4.

A substrate 11 is fixed on the upper surface of the motor housing 1, and the coil 1 is mounted on the upper surface of the substrate 11.
A stator composed of the core 2, the core 13, and the like is arranged so as to face the drive magnet 6, thereby forming a drive motor.

A first permanent magnet 14 is provided on the lower end surface of the rotating shaft 3.
Are fixed by bonding or the like. A second permanent magnet 15 is fixed to the lower end surface of the fixed sleeve 2 by bonding or the like. First and second permanent magnets 14 and 15 as levitation means
Are arranged so as to be balanced at a neutral point in the axial direction by mutual magnetic force, and constitute a magnetic thrust bearing that levitates and supports the thrust direction of the rotating shaft 3.

A thrust cover 17 as a cover member is attached to the lower end of the through hole of the motor housing 1, and an air reservoir 16 is provided below the rotating shaft 3 and the fixed sleeve 2 (first permanent magnet 4). Has formed. At this time, the upper surface of the thrust cover 17 is
Is positioned and fixed by being brought into contact with the lower surface of the ridge portion 19.

The thrust cover 17 is provided on the motor housing 1.
Is completely sealed, and the fixing sleeve 2
It can be said that the air reservoir 16 is sufficiently sealed since the gap between the shaft and the rotating shaft 3 is set to several μm.

At this time, if the rotating shaft 3 is pushed down and collides with the thrust cover 17, the rotating shaft 3 and the thrust cover 17 may be damaged and the sealing performance may not be maintained. Must be configured.

Here, since the fixed sleeve 2 and the thrust cover 17 are positioned and fixed in the motor housing 1 in the axial direction as described above, the distance between the fixed sleeve 2 and the thrust cover 17 is determined by the protrusion of the motor housing 1. Part 1
9 in the axial direction L.

By setting the thickness t of the second permanent magnet 15 fixed to the lower end surface of the fixed sleeve 2 in a relation of L ≧ t, that is, L is equal to or slightly smaller than t, the thrust cover 17 is formed. Can be fixed in close contact with the motor housing 1.

The thrust cover 17 is fixed by applying an anaerobic ultraviolet-curing adhesive 18 to the outer peripheral surface of the thrust cover 17 and bringing the adhesive 18 into close contact with the ridge 19 of the motor housing 1 and then irradiating ultraviolet rays. This is performed by curing the adhesive 18.

As described above, the upper surface of the thrust cover 17 is brought into close contact with the ridge portion 19 and the outer peripheral surface of the thrust cover 17 is used as an adhesive surface, thereby preventing the adhesive 18 from entering the bearing.

Further, as shown in FIG.
Of the second permanent magnet 15 and the thrust cover 1 are set slightly smaller than the thickness L of the ridge 19 in the axial direction.
If a gap is provided between the thrust cover 17 and the thrust cover 17, even if uncured adhesive enters inside, the adhesive can be retained in the gap and cured. Can be more reliably prevented from entering the bearing.

As described above, in the first embodiment, the distance between the fixed sleeve 2 and the thrust cover 17 can be determined only by the dimensional accuracy of the ridge 19 of the motor housing 1. Can be reduced, and an air damper effect of suppressing vibration of the rotating shaft 3 due to a pressure change of the air reservoir 16 when the rotating shaft 3 moves up and down can be more reliably obtained.

Further, even if the uncured adhesive is present, there is a high possibility that the adhesive will be cured between the thrust cover 17 and the motor housing 1 or the second permanent magnet 15. The possibility of reaching between the fixed sleeve 2 and the rotating shaft 3 forming the dynamic pressure air bearing for supporting the direction can be almost eliminated. Therefore, a highly reliable deflection scanning device capable of suppressing vibration of the rotating shaft can be provided.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention. In the first embodiment, the thrust cover serving as the lid member is formed of a flat disk-shaped member. However, in the present embodiment, the thrust cover is provided with a step to form a protruding portion that protrudes into the air reservoir. I have.

FIG. 4 is a half sectional view showing a configuration of a bearing section of the deflection scanning device according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 4, the thrust cover 27 is provided with a step 27a concentrically with the rotating shaft 3, and the outer peripheral side of the step 27a projects into the air reservoir 26.
b. The diameter D of the step portion 27a is
Is slightly larger than the outer diameter d of the first permanent magnet 14 fixed to the lower end (D> d).

The inner peripheral side of the step portion 27a is
b, the depth of which is slightly reduced even when the lower end surface of the first permanent magnet 14 fixed to the lower end surface of the rotating shaft 3 reaches the lowest fulcrum. Is set so that a gap is formed. In the present embodiment, since the distance S between the lower end surface of the support member 4 and the upper end surface of the fixed sleeve 2 is closest, the upper surfaces of the first permanent magnet 14 and the concave portion 27 c of the thrust cover 27 are arranged. Is set such that the relationship K> S is satisfied. That is, the concave portion 27c is provided between the rotating shaft 3 and the first permanent magnet 1.
4 to be retracted from the range of vertical movement.

As in the first embodiment, the thrust cover 27 is positioned with its upper surface in contact with the lower surface of the ridge 19 of the motor housing 1, and an anaerobic ultraviolet curing type is provided on the outer periphery of the thrust cover 27. It is fixed by applying an adhesive 28 and irradiating ultraviolet rays.

According to the present embodiment, the thrust cover 2
By projecting a part of the air reservoir 7 toward the air reservoir 26, the volume of the air reservoir 26 can be reduced by the amount of the protrusion, so that the pressure change of the air reservoir 26 becomes large and the flatness as in the first embodiment is increased. An excellent air damper effect can be obtained as compared with a case where a thrust cover having a simple shape is provided.

Further, since the rotating member does not collide with the thrust cover 27 even when the rotating shaft 3 is pushed down to the lowermost fulcrum, a highly reliable deflection scanning device which is free from deterioration in accuracy or breakage can be realized. . Further, it is possible to increase the degree of freedom in designing, for example, it is possible to select an optimal size of the first and second permanent magnets 14 and 15 without increasing the volume of the air pocket.

In the present embodiment, the projection 27b is provided on the outer peripheral side of the thrust cover 27 and the recess 27c is provided on the inner peripheral side. However, the lowermost fulcrum of the rotary shaft 3 is relatively high. Alternatively, a projection may be provided on the inner peripheral side of the thrust cover as long as it does not interfere with the thrust cover. Also in that case, the volume of the air reservoir can be reduced to enhance the air damper effect.

[0059]

As described above, according to the present invention,
By positioning the position of the fixing sleeve and the lid member in the axial direction by the housing, it is possible to reduce an error factor for determining the volume of the air pocket formed between the two members. This facilitates the attachment, stabilizes the air damper effect, and improves the reliability of the deflection scanning device.

Further, if the fixing sleeve and the lid member are positioned by a ridge provided on the peripheral surface of the through hole of the housing, the volume of the air reservoir is determined by the axial thickness of the ridge. Therefore, strict dimensional accuracy is required only for the axial thickness of the ridge portion, and processing and mounting can be further facilitated.

By making the outer peripheral surface of the lid member an adhesive surface, it is possible to prevent the uncured adhesive from entering the bearing, and it is possible to improve the reliability of the operation of the bearing. .

Further, by providing a projection on the lid member that projects into the air reservoir, the volume of the air reservoir can be reduced and the air damper effect can be enhanced.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a configuration of a bearing unit of a deflection scanning device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of FIG.

FIG. 3 is a plan view schematically showing the deflection scanning device according to the first embodiment of the present invention.

FIG. 4 is a half sectional view showing a configuration of a bearing unit of a deflection scanning device according to a second embodiment of the present invention.

FIG. 5 is a half sectional view showing a configuration of a bearing of a conventional deflection scanning device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor housing 2 Fixed sleeve 3 Rotating shaft 4 Support member 5 Rotor 6 Drive magnet 7 Rotating polygon mirror 8 Leaf spring 9 Holding plate 10 C ring 11 Substrate 12 Coil 13 Core 14 First permanent magnet 15 Second permanent magnet 16 Air Pool 17 Thrust cover 18 Adhesive 19 Ridge 26 Air pocket 27 Thrust cover 27a Step 27b Projection 27c Concave 28 Adhesive 50 Optical box 51 Light source 51a Cylindrical lens 52 Imaging lens system 52a Spherical lens 52b Toric lens 53 Folded mirror Mirror 54 photoreceptor 55 detection mirror 56a lens 56b light receiving element 56c line 57 processing circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Fukutomi 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Tadashi Arai 1248 Shimokagemori, Oaza, Chichibu-shi, Saitama In-house (72) Inventor Mori Gen 1248 Shimokage Mori, Chichibu City, Saitama Prefecture Inside Canon Electronics Co., Ltd. (72) Inventor Shinya Kumagai 1248 Shimokage Mori, Chichibu City, Saitama Prefecture Canon Electronics F-term 2C362 BA08 BA10 DA17 2H045 AA24 AA28 5H605 AA04 AA08 BB05 BB19 CC01 CC02 CC04 CC05 DD03 EB03 EB06 5H607 AA04 BB01 BB14 BB17 CC01 CC05 DD01 DD02 DD03 DD08 DD09 DD16 FF12 GG01 GG02 GG03 GG12 GG03

Claims (7)

[The claims] 1. A housing having a through hole, a fixed sleeve fixed to the through hole of the housing, a rotating shaft rotatably fitted to the fixed sleeve, and the rotating shaft being axially moved by magnetic force. A deflecting / scanning device for deflecting and scanning an optical beam with a rotating mirror attached to the rotating shaft, comprising: a levitation means for floating; and a lid member forming a closed air reservoir below the rotating shaft. And the lid member is axially positioned and fixed by the housing. 2. The housing has a ridge on a peripheral surface of the through hole, and a lower end of the fixed sleeve is brought into contact with an upper surface of the ridge,
2. The deflection scanning device according to claim 1, wherein an upper end of the lid member is brought into contact with a lower surface of the ridge portion to position the fixed sleeve and the lid member in the axial direction. 3. The deflection scanning device according to claim 2, wherein the outer peripheral surface of the lid member and the peripheral surface of the through hole of the housing are adhered to each other to fix the lid member. 4. The deflection scanning device according to claim 3, wherein the lid member is bonded with an anaerobic ultraviolet curing type adhesive. 5. The levitation means comprises: a first permanent magnet fixed to a lower end of the rotating shaft; and a second permanent magnet fixed to a lower end of the fixed sleeve so as to face the first permanent magnet. The deflection scanning device according to any one of claims 1 to 4, further comprising: 6. The deflection scanning device according to claim 5, wherein an axial thickness of the second permanent magnet is equal to or less than a distance between a lower end of the fixed sleeve and the lid member. 7. The deflection scanning device according to claim 1, wherein the lid member has a protruding portion that protrudes into the air reservoir.