JPH1184296A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality by forming the shape of a cap member so as to hold the spaces of nearly equal spacing in compliance with the upper part shape of the rotary polyhedral mirror and dynamic pressure bearing in an optical deflection unit. SOLUTION: The upper thrust plate 111 of the dynamic pressure bearing projects from the front surface of the rotary polyhedral mirror 22. A screw 119, etc., for fixing the upper thrust plate 111, a lower thrust plate 112 and a radial shaft inside cylinder 113 project further from the surface of the upper thrust plate 111. The cap member 102 consists of an aluminum alloy sheet, etc., and the part near the central part is drawn to a projecting shape. The drawn projecting part 102A is formed to a conical surface of such a height and inclination as to form the narrow spacing of nearly the equal spacing according to the shape at which the upper thrust plate 111, screw 119, etc., project from the front surface of the rotary polyhedral mirror 22. The narrow spaces of nearly the equal spacing are formed between the upper thrust plate 111 and the rotary polyhedral mirror 22 and the cap member 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical apparatus having a built-in rotary polygon mirror for scanning a light beam on a photosensitive member in an image forming apparatus such as a laser printer.

[0002]

2. Description of the Related Art In an image recording apparatus such as a laser beam printer, a laser beam enters a rotating polygon mirror (polygon mirror) which rotates at a high speed based on information read as writing means of the image, and reflected light is scanned. Then, the image is recorded on the surface of the photoreceptor by projection.

FIG. 11 is a cross-sectional view showing the configuration of a conventional scanning optical device that deflects and scans a light beam by rotating a rotating polygon mirror.

[0004] In the case of low-speed rotation, the rotating polygon mirror is used directly fixed to the rotating shaft of the drive motor. However, in the case of high-speed rotation, the rotating polygon mirror is fixed to the outer cylinder of the radial shaft and the inner cylinder of the radial shaft is fixed. Driving rotation is performed by using an air bearing that rotates in a floating manner without touching it. The present applicant has disclosed an optical polarizing device having a dynamic pressure bearing as disclosed in
The technical disclosures are given in JP-A-243434, JP-A-7-259849, JP-A-8-114219 and JP-A-8-121471.

FIG. 11 is a diagram showing a cross-sectional structure of an optical polarization device (optical deflection unit, polygon motor) 100 having a dynamic pressure bearing 110 including an upper thrust plate 111, a lower thrust plate 112, a radial shaft inner cylinder 113, and the like. is there. In the figure, a radial shaft inner cylinder 113, a lower thrust plate 112, and a coil 115 constituting a static magnetic field of a motor are mounted integrally with a central shaft 114 of a housing 101 to form a dynamic pressure bearing 110. ing. A ring-shaped magnet (permanent magnet) 121 for a rotating magnetic field, an outer ring portion 122 made of aluminum, a radial shaft outer cylinder 123 made of ceramic, a rotating polygon mirror 124, and a mirror retainer 125 are connected to the outer ring portion 12.
The rotary polygon mirror 124 is sandwiched between the mirror holder 125 and the mirror holder 125, and the rotor 120 is formed concentrically and integrally. After the rotor 120 is fitted into the radial shaft inner cylinder 113, the upper thrust plate 111 is fixed concentrically to the radial shaft inner cylinder 113. A gap S of about 3 to 10 μm is formed between the radial shaft inner cylinder 113, the lower thrust plate 112, the upper thrust plate 111, and the upper and lower surfaces and the fitted inner peripheral surface of the radial shaft outer cylinder 123,
When the rotor 120 rotates, the rotor 120 is
Without touching 10, it floats up in the air and smooth rotation is maintained.

In other words, the rotating polygon mirror 124 also rotates with the rotation of the rotor 120, and the laser beam emitted from the laser unit deflects and scans a photosensitive member (not shown).

The housing 1 of the light deflection unit 100 comprising the rotary polygon mirror 124, the dynamic pressure bearing 110 and the rotor 120.
Reference numeral 01 denotes a cover member which is integrally formed by aluminum die-casting and has an upper opening made of a thin sheet metal or a synthetic resin plate.
2 is covered.

[0008]

[Problems to be solved by the invention]

(First Problem) When the laser beam emitted from the laser transmitter is scanned on the photosensitive member by rotating the rotor 120 using the above-described scanning optical device, the rotating polygon mirror 124 is used.
In addition, the turbulence of the air flow due to the rotation of the rotor 120 occurs, which causes problems such as harsh wind noise and noise due to the vibration of the housing 101. Especially,
In offices and the like where quietness is required, noise prevention and noise reduction measures are required.

In the conventional scanning optical device, the cover member 102 covering the upper opening of the housing 101 of the light deflecting unit 100 has a planar shape as shown in FIG.
A space with a wide gap is formed between the inner surface side of the optical deflector 02 and the upper surface side of the rotating polygon mirror 124 and the dynamic pressure bearing 110 in the optical deflection unit 100. If the air volume in this space is large,
When the rotating polygon mirror 124 rotates at a high speed, a windage loss occurs, and the heat generated by the rotating polygon mirror 124 causes a decrease in surface accuracy due to thermal deformation, a rotation variation of the rotor 120, and the like. Image quality. This is particularly noticeable when the rotating polygon mirror 124 is rotated at a high speed to increase the recording density.

A first object of the present invention is to provide a rotating polygon mirror 124.
It is an object of the present invention to provide a scanning optical apparatus in which heat generation of a coil caused by windage loss caused by the rotation of the motor and an increase in current due to air resistance is suppressed.

(Second Problem) In a conventional scanning optical device,
The side wall of the lid member 102 that covers the upper opening of the housing 101 of the light deflection unit 100 has substantially the same shape as the side wall of the housing 101. An opening 101A for inputting and outputting a light beam is formed in a part of the housing 101.
A is shielded by a transparent window glass (light transmitting member) 104. In such a light deflecting unit 100, at the time of work, a work tool such as a driver contacts the light transmitting member 104 to damage the light transmitting member 104,
4 may be touched by a fingertip and stains such as fingerprints may be attached.

A second object of the present invention is to provide a light deflecting unit 1
It is an object of the present invention to provide a light deflecting unit 100 that protects the light transmitting member 104 during assembly, repair, and adjustment of 00, prevents breakage and dirt, and enables safe and easy work.

[0013]

A first object of the present invention is to provide a scanning optical apparatus for deflecting and scanning a light beam by rotating a rotating polygon mirror, wherein the rotating polygon mirror, a dynamic pressure bearing and a drive motor are used. The shape of the cover member that covers the upper opening of the housing of the light deflection unit is formed so as to maintain substantially equally spaced gaps according to the upper shapes of the rotary polygon mirror and the dynamic pressure bearing in the light deflection unit. This is achieved by a scanning optical device (the invention of claim 1).

A second object of the present invention is to provide a scanning optical device for deflecting and scanning a light beam by rotating a rotating polygon mirror, wherein the rotating polygon mirror, a dynamic pressure bearing, a drive motor, and a light beam input / output device. A cover member for covering an upper opening of a housing of the light deflecting unit accommodating the window glass, the cover member having an eave portion having a shape protruding from a side wall surface near the light beam input / output window glass of the housing. Apparatus (Claim 2
Invention).

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a scanning optical apparatus and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the overall configuration of a digital image forming apparatus according to the present invention.

The image forming apparatus main body 1 includes an image reading section A, an image processing section B, an image storage section C, an image writing section D,
It comprises an image forming unit E, a paper feeding unit F, and the like.

In the image reading section A, a document d placed on a platen glass (platen glass) 11 is illuminated by a halogen lamp 12 provided on a carriage moving on a slide rail. The reflected light from the document d is transmitted to the first mirror 13, the second mirror 14, and the third mirror 15
The linear optical image is sequentially photoelectrically converted into an electric signal by the CCD image sensor 17 through the imaging lens 16.

The analog signal photoelectrically converted by the CCD image sensor 17 is subjected to analog processing in an image processing unit, and then A / D converted. Shading correction, luminance / density conversion, EE processing, character / halftone discrimination, Filter / magnification processing, copy gamma correction, writing density correction, 2
After being subjected to beam control, error diffusion processing, data compression processing, etc., it is output to the image writing section D via the image storage section C.

In the image writing section D, the image data after the image processing is output by the semiconductor laser. The output from the semiconductor laser is rotationally scanned by a rotating polygonal mirror (polygon mirror) 22 rotated by a drive motor 21, passes through an fθ lens 23, a first mirror 24, a second mirror 25, a cylindrical lens 26, and a third Mirror 27
, And is emitted from the cover glass 28 and irradiated on the photosensitive drum 31.

The image forming section E includes a charger 32, a developing device 33, a transfer device 34,
It comprises a separator 35, a cleaning device 36 and the like. Further, on the downstream side of the separator 35, the transport unit 37, the fixing unit 3
8, a paper discharge unit 39 is disposed.

The paper supply section F includes a paper supply cassette 41 for storing the transfer paper p, and paper supply means 42 for separating and feeding the transfer paper p in the paper supply cassette 41.

FIG. 2 is a perspective view showing an embodiment of a multiple beam scanning optical device, and FIG. 3 is a plan view of the multiple beam scanning optical device.

In these figures, 200A, 200B
Is a semiconductor laser, 201A and 201B are collimating lenses (beam shaping optical systems), 202A and 202B are compression prisms for height adjustment, 203A is a set of prisms for fine adjustment in the main scanning direction, and 203B is a sub-scanning direction. One set of prisms for fine pitch adjustment, 204 is a beam combining prism for combining two beams, 205 is a first cylindrical lens, 22 is a rotating polygon mirror, and 23A and 23B are fθ.
Lens, 26 is a second cylindrical lens, 27 is a third lens
A mirror, 28 indicates a cover glass, and 31 indicates a photosensitive drum. 29 is an index mirror for detecting timing, 29S is an index sensor for detecting synchronization, and 21 is a drive motor for the rotary polygon mirror 22.

The light beam emitted from the semiconductor laser 200A is turned into parallel light by the collimating lens 201A.
Next, the light enters the beam combining prism 204. Similarly, the beam light emitted from the semiconductor laser 200B orthogonally arranged with respect to the semiconductor laser 200A is converted into parallel light by the collimator lens 201B, and thereafter enters the beam combining prism 204. The semiconductor laser 2
The light beam emitted from 00B is arranged at a predetermined pitch in the sub-scanning direction from the light beam emitted from the semiconductor laser 200A. The two light beams are the first
The light enters the rotary polygon mirror 22 via the first cylindrical lens 205 of the imaging optical system. This reflected light is transmitted to the fθ lens 2
The light beam passes through the second imaging optical system including 3A, 23B and the second cylindrical lens 26, and is passed through the third mirror 27 and the cover glass 28 onto the peripheral surface of the photosensitive drum 31 with a predetermined spot diameter in the sub-scanning direction. With a predetermined pitch shift in the direction
Scan lines simultaneously. The main scanning direction has already been finely adjusted by an adjustment mechanism (not shown). For synchronization detection for each line, the light beam before scanning is
Through the index sensor 29S.

FIG. 4 is a sectional view of the scanning optical device according to the present invention, and FIG. 5 is an enlarged sectional view of the vicinity of the light deflection unit 100 of the scanning optical device. Note that, in the reference numerals used in these drawings, parts having the same functions as those in FIG. 12 are denoted by the same reference numerals.

A drive motor 21 for driving and rotating the rotary polygon mirror 22 is provided with a coil (stator) 115 on the housing 101 side.
And a magnet (rotor) 121 on the rotating polygon mirror 22 side. The plurality of coils 115 are fixedly arranged on the insulating substrate 114. The plurality of coils 1
15 is wired in series, the connector 116, the lead 117
Through a power supply (not shown). A stator yoke 118 made of a silicon steel plate is fixedly provided on the surface of the housing 101 below the insulating substrate 114.

The upper surface of the plurality of coils 115 is close to the lower surface of the ring-shaped magnet (magnet) 121 with a predetermined gap therebetween. The upper surface of the magnet 121 is connected to the rotating polygon mirror 22 via a magnet yoke 126 made of a thin steel plate.
Adhesively fixed. After a part of the inner peripheral surface of the rotary polygon mirror 22 is positioned in contact with the outer peripheral surface of the radial shaft outer cylinder 123, an adhesive is injected into the concave portion and fixed. Accordingly, the magnet 121, the magnet yoke 126, and the rotary polygon mirror 22 are integrated with the radial shaft outer cylinder 123,
It is rotatable with respect to the dynamic pressure bearing 110.

The rotary polygon mirror 22 has a recess formed therein, and a magnet 121 and a magnet yoke 126 are provided.
The rotating member including the rotating polygon mirror 22 is reduced in thickness by burying it. This is effective for improving the rotation accuracy of the rotary polygon mirror 22 and reducing the size of the light deflection unit.

The upper end surface of the housing 101 of the light deflecting unit 100 is pressed by a cover member (inner cover) 102 and an elastic seal member 103, and the upper open space of the housing 101 is sealed. The elastic seal member 103 is formed of a foamable resin member or a rubber plate and is adhered to the inner surface of the lid member 102, which is effective in preventing noise.

The upper thrust plate 111 of the dynamic pressure bearing 110 protrudes from the upper surface of the rotary polygon mirror 22, and the upper thrust plate 11
1. Screws 119 for fixing the lower thrust plate 112, the radial shaft inner cylinder 113, and the like further protrude from the upper surface of the upper thrust plate 111. The lid member 102 is made of an aluminum alloy plate or the like, and has a central portion that is drawn in a convex shape. The drawn convex portion 102A has an upper thrust plate 111,
According to the shape of the screw 119 and the like protruding from the upper surface of the rotary polygon mirror 22, the screw 119 and the like are formed to have a height and an inclined conical surface so as to form a narrow space at substantially equal intervals. In this way, by forming a space between the upper thrust plate 111 and the rotary polygon mirror 22 and the lid member 102 so as to form a narrow space at substantially equal intervals,
The air volume in the housing 101 of the light deflecting unit 100 is optimized, and wind loss, heat generation, and wind noise caused by the rotating polygon mirror 22 rotating at high speed can be reduced.

In the optical device main body (image writing unit casing) 20 that houses the optical member of the scanning optical device, the upper end surface of the wall surface of the wall 20A that houses and fixes the light deflecting unit 100 defines the upper space of the wall 20A. Canopy member 20 to be sealed
6 and the elastic seal member 207, and the wall 2
The upper open space of OA is sealed. Canopy member 206
Is formed of a resin member having vibration damping characteristics such as ABS resin.

The elastic sealing member 207 is formed of a vibration absorbing material made of a foaming resin material such as urethane foam rubber or foamed ethylene propylene rubber (EPDM).
6, which is effective for preventing noise.

The vicinity of the center of the canopy member 206 is formed in a shape protruding in a convex shape, and the inner surface of the canopy member (outer cover) 206 and the outer surface of the cover member (inner cover) 102 have substantially equal intervals. Forms a narrow space.

The elastic sealing member 207 adhered to the inner surface of the canopy member 206 is pressed against the outer surface of the lid member 102 to make a sealed state. The elastic seal member 207 inserted and filled in the gap between the lid member 102 and the canopy member 206 is effective for preventing wind noise from the rotary polygon mirror 22 from leaking out and for damping vibration.

Reference numeral 208 denotes a cover member that covers the upper space of the optical device main body 20. The cover member 208 has an elastic seal member 208A on its inner surface, and is effective in dustproofing and soundproofing.

FIG. 6A is a plan view of the light deflecting unit 100 with the lid member 102 removed, FIG. 6B is a side view of the light deflecting unit 100 as indicated by the arrow A, and FIG. FIG. 3 is an enlarged plan view of the deflection unit 100 and an optical system.

A part of the side wall of the housing 101 is cut out to form an opening 101A. This opening 101A
Is an exit of the light beam L by the rotation of the rotary polygon mirror 22. On the outer surface of the opening 101A, a transparent light transmitting member (light entrance / exit window glass) 291 is provided with a double-sided adhesive tape 292.
Is glued through.

As the double-sided adhesive tape 292, adhesive strength,
Use a member with excellent sealing, durability and vibration absorption. For example, VHB bonding tape Y-4905J or Y-4920 (both manufactured by Sumitomo 3M Limited) was suitable.

FIG. 6C is an enlarged sectional view showing the layer structure of the double-sided adhesive tape 292. Joining tape Y-4905J
Or, each of Y-4920 is obtained by laminating an acrylic adhesive material b on both sides of an elastic acrylic foam base material, and protecting it by using a release film c on one surface of the acrylic adhesive material a before use. doing. This double-sided adhesive tape 2
By using No. 92, the conventional adhesive (silicone rubber-based or epoxy resin-based adhesive, etc.) requires a lot of time for curing, but achieves improved adhesiveness and improved adhesive workability. Was done.

FIG. 8A is a plan view of the light deflection unit 100 according to the present invention, and FIG.
0 is a sectional view.

A part of the lid member 102 for closing the upper opening of the housing 101 of the light deflecting unit 100 protrudes from the side wall surface near the opening 101A of the housing 101 to form an eave portion 102B. This eave portion 102B is provided with a light transmitting member 291.
Is a protective portion that widely covers the vicinity of the upper portion of the light deflecting unit 100. When the light deflecting unit 100 is operated, a work tool such as a driver contacts the light transmitting member 291 to damage the light transmitting member 291 or a fingertip touches the light transmitting member 291. To prevent the attachment of stains such as fingerprints.

FIG. 9A is a side view of the light deflecting unit 100 according to the present invention, and FIG.
FIG. 9C shows a housing 1 of the light deflection unit 100.
FIG. 10 is a sectional side view of the image forming apparatus main body 1.

A plurality of radiating fins 101B are provided in a lower portion of the housing 101 of the light deflection unit 100 in a parallel arrangement. The parallel arrangement direction of the radiation fins 101 </ b> B is arranged substantially in parallel with the blowing direction K by the blowing unit 30 for lowering the temperature inside the image forming apparatus main body 1. This makes it possible to make the flow of the exhausted hot air to the radiating fins 101B good, and to improve the cooling effect even with the same amount of the exhausted hot air.

[0045]

As described above, in the scanning optical device according to the first aspect of the present invention, the shape of the lid member that covers the upper opening of the housing of the optical deflection unit including the rotary polygon mirror, the dynamic pressure bearing, and the drive motor is provided. In accordance with the shape of the rotating polygon mirror and the dynamic pressure bearing in the light deflection unit, the gap is formed so as to maintain substantially equally spaced gaps, so that the wind generated as the rotating polygon mirror rotates. It is possible to reduce loss and heat generation, thereby reducing surface accuracy due to thermal deformation of the rotating polygon mirror, preventing rotation fluctuation of the drive motor, and eliminating scanning unevenness and image distortion on the screen. Excellent effect on image quality improvement. This is particularly effective when the rotating polygon mirror is rotated at a high speed to increase the recording density.

A scanning optical device according to a second aspect of the present invention is a cover member for covering an upper opening of a housing of an optical deflection unit for accommodating a rotary polygon mirror, a dynamic pressure bearing, a drive motor, and a light beam input / output window glass. Has an eaves portion having a shape protruding from a side wall surface near the light beam input / output window glass of the housing, so that when assembling, repairing, and adjusting the light deflection unit, the light transmitting member is protected and damaged. In addition, dirt is prevented, and safe and easy work is possible.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a digital image forming apparatus according to the present invention.

FIG. 2 is a perspective view showing an embodiment of a multiple beam scanning optical device.

FIG. 3 is a plan view of the multi-beam scanning optical device.

FIG. 4 is a sectional view of the scanning optical device.

FIG. 5 is an enlarged sectional view near a light deflection unit of the scanning optical device.

FIG. 6 is a plan view of the light deflecting unit with the lid member removed, a side view of the light deflecting unit as indicated by an arrow A, and an enlarged cross-sectional view illustrating a layer structure of the double-sided adhesive tape.

FIG. 7 is an enlarged plan view of the optical deflection unit and the optical system.

FIG. 8 is a plan view and a sectional view of the light deflection unit.

FIG. 9 is a side view, a rear view, and a cross-sectional view of the light deflection unit.

FIG. 10 is a side sectional configuration diagram of an image forming apparatus main body.

FIG. 11 is a cross-sectional configuration diagram of a light polarizing device having a conventional dynamic pressure bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 20 Optical apparatus main body (image writing part casing) 20A Wall (side wall) 21 Drive motor 22, 124 Rotating polygon mirror (polygon mirror) 28 Cover glass 30 Blowing means 100 Optical deflecting unit 101 Housing 101A Opening 104 , 291 Light transmission member (light entrance / exit window glass) 101B Radiation fin 102 Cover member (inner cover) 102B Eave portion 103, 207, 208A Elastic seal member 110 Dynamic pressure bearing 120 Rotor 206 Top cover member (outer cover) 208 Cover member 292 Double-sided adhesive tape

Claims (2)

[Claims] 1. A scanning optical device that deflects and scans a light beam by rotating a rotary polygon mirror. A lid that covers an upper opening of a housing of an optical deflection unit including the rotary polygon mirror, a dynamic pressure bearing, and a drive motor. A scanning optical device, wherein a shape of a member is formed so as to keep substantially equally spaced gaps in accordance with an upper shape of the rotary polygon mirror and the dynamic pressure bearing in the light deflection unit. 2. A scanning optical device for deflecting and scanning a light beam by rotating a rotary polygon mirror, wherein a light deflection housing the rotary polygon mirror, a dynamic pressure bearing, a drive motor, and a light beam input / output window glass. A scanning optical device, wherein a lid member that covers an upper opening of a housing of the unit has an eave portion having a shape protruding from a side wall surface near a light beam input / output window glass of the housing.