JP2019020540A - Scanning optical device and image forming apparatus including the same - Google Patents

Abstract

To solve the problem in which: when the temperature of a first housing alone is increased due to heat generated through the rotation of a motor for deflection, a dimensional difference in attachment pitch occurs between the first housing and a second housing due to linear expansion to bend an optical box, which causes color shift.SOLUTION: A first housing is screw-fixed to a second housing at two attachment fitting parts arranged near both ends of the contour of the first housing, and projected shape parts provided on both ends outside an optical lens on the first housing are elastically fixed to predetermined portions of the second housing.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a scanning optical device used in an image forming apparatus such as an electrophotographic copying machine or a printer, and an image forming apparatus including the scanning optical device.

  A scanning optical device provided in an electrophotographic image forming apparatus includes a light source for exposing a photosensitive drum in the direction of the rotation axis of the drum, and a rotary polygon mirror (hereinafter, polygon) that deflects and scans laser light emitted from the light source. Mirror). The laser light emitted from the light source is deflected and scanned by a rotating polygon mirror to scan the photosensitive drum (hereinafter, the scanning direction is a main scanning direction, and the direction orthogonal to the main scanning direction is a sub-scanning direction. Call it.)

  An electrostatic latent image is formed on the photosensitive drum by the scanned laser light. The electrostatic latent image is developed with toner, and the toner image on the photosensitive drum is transferred to the recording medium to form an image on the recording medium.

  During rotation of the polygon mirror, a bearing of a deflection motor that rotationally drives the polygon mirror, a drive coil, an IC, and the like generate heat. The inside of the housing is heated by direct conduction from the motor mounting portion and a warmed airflow generated when the polygon mirror rotates. If the temperature distribution is non-uniform, or if the casing is a molded product of glass reinforced resin, there is anisotropy of linear expansion, so that the casing will undergo minute deformation due to temperature rise. Since the optical element is attached with high accuracy inside the housing, there is a problem that the optical performance deteriorates even with a minute deformation.

  Further, when the deflection motor rotates, vibration is generated. However, if the vibration is transmitted to the optical element, the scanning light is also affected, which may cause image deterioration.

  Patent document 1 is disclosed as a configuration for preventing image degradation due to vibration in a scanning optical device including a plurality of casings. In Patent Document 1, as a method of attaching the casing 1 on which the deflection motor is mounted to another casing 2, substantially four ends of the first casing are designated.

2009-066987

  However, since the first casing is fixed to the second casing at the four corners of the first casing, only the first casing is heated by the heat generated by the rotation of the deflection motor. Then, a dimensional difference is generated between the mounting pitches of the first housing and the second housing due to linear expansion, and the second housing is curved like the curved shape shown in FIG. As a result, a beam shift occurs, resulting in a color shift defect.

In order to solve the above problems, a scanning optical device according to the present invention includes:
In a scanning optical device having a tandem configuration (optical paths for irradiating four photosensitive drums in one housing), a first housing that houses a deflection motor and a pair of optical lenses is a light source In the configuration combined with the second casing that accommodates other optical elements, the first casing has a straight line passing through the substantially central portion of the deflection motor of the second casing and parallel to the sub-scanning direction. The protrusion-shaped parts provided at both ends on the outer side of the optical lens on the first housing are screwed and fixed to the first housing with two attachment fitting portions arranged near the outer end portions of both ends. The second housing is elastically fixed to a predetermined location.

  According to the scanning optical device of the present invention, when the temperature of the first housing is increased, the curvature of the second housing due to the difference in linear expansion is limited to the main scanning direction, and a plurality of occurrences are caused by deformation in the sub scanning direction. Since the change in the irradiation position of the laser beam is suppressed, the color shift is reduced.

Sectional drawing explaining an image forming apparatus External view of Example 1 of the present invention Partial external view of an embodiment of the present invention Assembly explanatory diagram of Embodiment 1 of the present invention External view of Example 2 of the present invention Sectional drawing explaining the effect of the Example of this invention

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  The configuration of the image forming apparatus according to the first embodiment will be described below.

  FIG. 1 is a schematic configuration diagram showing the overall configuration of the tandem type color laser beam printer of this embodiment.

  This laser beam printer (hereinafter simply referred to as a printer) includes four image forming engines 10Y, 10M that form toner images for each of yellow (Y), magenta (M), cyan (C), and black (Bk) colors. 10C, 10Bk (illustrated with a dashed line). The printer also includes an intermediate transfer belt 20 to which toner images are transferred from the image forming engines 10Y, 10M, 10C, and 10Bk, and the toner images that have been multiplex-transferred to the intermediate transfer belt 20 are recorded on a recording sheet P that is a recording medium. A color image is formed by transfer. Hereinafter, the symbols Y, M, C, and Bk representing each color are omitted unless necessary.

  In the following description, the rotation axis direction of the rotary polygon mirror 203 to be described later is the Z-axis direction, the main scanning direction, which is the scanning direction of the light beam, or the longitudinal direction of the reflection mirror is the Y-axis direction, perpendicular to the Y-axis and Z-axis This direction is the X-axis direction.

  The intermediate transfer belt 20 is formed in an endless shape and is wound around a pair of belt conveyance rollers 21 and 22, and the toner image formed by the image forming engine 10 of each color is transferred while rotating in the direction of arrow C. It is configured as follows. Further, a secondary transfer roller 65 is disposed at a position facing one belt conveying roller 21 with the intermediate transfer belt 20 interposed therebetween. The recording sheet P is inserted between the secondary transfer roller 65 and the intermediate transfer belt 20 that are in pressure contact with each other, and the toner image is transferred from the intermediate transfer belt 20.

  The four image forming engines 10Y, 10M, 10C, and 10Bk described above are arranged in parallel below the intermediate transfer belt 20, and toner images formed according to image information of each color are transferred to the intermediate transfer belt 20. (Hereinafter referred to as primary transfer). These four image forming engines 10 are arranged along the rotational direction of the intermediate transfer belt 20 (in the direction of arrow C), an image forming engine 10Y for yellow, an image forming engine 10M for magenta, and an image forming engine 10C for cyan. And an image forming engine 10Bk for black.

  Further, below the image forming engine 10, an optical scanning device 40 that exposes a photosensitive drum 50, which is a photosensitive member included in each image forming engine 10, according to image information is disposed. In FIG. 1A, detailed illustration and description of the optical scanning device 40 are omitted, and will be described later with reference to FIG. The optical scanning device 40 is shared by all the image forming engines 10Y, 10M, 10C, and 10Bk, and includes four semiconductor lasers (not shown) that emit laser beams that are modulated according to image information of each color. The optical scanning device 40 also includes a rotating polygon mirror 203 and a rotating polygon mirror that deflect each light beam so that the light beam corresponding to each photosensitive drum 50 scans along the axial direction (Y-axis direction) of the photosensitive drum 50. A polygon motor 203m, which is a drive source for rotating the 203, is provided. Each light beam deflected by the rotary polygon mirror 203 is guided by an optical member installed in the optical scanning device 40 and guided onto the photosensitive drum 50 to expose each photosensitive drum 50.

  Each image forming engine 10 includes a photosensitive drum 50 and a charging roller 12 that charges the photosensitive drum 50 to a uniform background portion potential. Each image forming engine 10 includes a developing device 13 that develops an electrostatic latent image formed on the photosensitive drum 50 by being exposed to a light beam to form a toner image. The developing device 13 forms a toner image corresponding to the image information of each color on the photosensitive drum 50.

  A primary transfer roller 15 is disposed at a position facing the photosensitive drum 50 of each image forming engine 10 so as to sandwich the intermediate transfer belt 20. The primary transfer roller 15 transfers a toner image on the photosensitive drum 50 to the intermediate transfer belt 20 by applying a predetermined transfer voltage.

  On the other hand, the recording sheet P is supplied from the paper feed cassette 2 stored in the lower portion of the printer housing 1 to the inside of the printer, specifically, to the secondary transfer position where the intermediate transfer belt 20 and the secondary transfer roller 65 abut. The A pickup roller 24 and a paper feed roller 25 for pulling out the recording sheet P accommodated in the paper feed cassette 2 are arranged in parallel on the upper part of the paper feed cassette 2. A retard roller 26 that prevents double feeding of the recording sheet P is disposed at a position facing the paper feed roller 25. The conveyance path 27 of the recording sheet P inside the printer is provided substantially vertically along the right side surface of the printer housing 1. The recording sheet P drawn from the paper feed cassette 2 located at the bottom of the printer casing 1 moves up the transport path 27 and is sent to a registration roller 29 that controls the timing of the recording sheet P entering the secondary transfer position. It is done. Thereafter, after the toner image is transferred at the secondary transfer position, the recording sheet P is sent to a fixing device 3 (shown by a broken line) provided on the downstream side in the transport direction. Then, the recording sheet P on which the toner image is fixed by the fixing device 3 is discharged through a discharge roller 28 to a discharge tray 1a provided on the upper portion of the printer casing 1.

  In forming a color image by the color laser beam printer configured as described above, first, the scanning optical device 40 exposes the photosensitive drum 50 of each image forming engine 10 at a predetermined timing according to image information of each color. As a result, a latent image corresponding to the image information is formed on the photosensitive drum 50 of each image forming engine 10. Here, in order to obtain a high quality image, the latent image formed by the scanning optical device 40 is accurately reproduced at a predetermined position on the photosensitive drum 50, and a light beam for forming the latent image is formed. The amount of light must always be stable and produce a desired value.

  Next, the scanning optical device 40 in this embodiment will be described with reference to FIG.

  The scanning optical device 40 is provided with a plurality of light sources 101 corresponding to the respective colors. Laser light is emitted from the light source 101 according to the image data. Laser light emitted from the light source 101 is scanned in a predetermined direction by a polygon mirror 102 (rotating polygonal mirror) serving as a deflector. The polygon mirror 102 is rotationally driven by a deflection motor 103. The laser light deflected and scanned by the polygon mirror 102 is incident on optical lenses 104 (104a, 104b) and 105 (105a, 105b, 105c, 105d) as optical members, and the laser light is guided onto the photosensitive drum. The optical lenses 104 and 105 have optical characteristics for performing constant-speed scanning while imaging (condensing) laser light on a scanned object.

  It should be noted that an optical lens having the ability to diffuse light may be disposed at the installation position of these optical lenses instead of an optical lens having the ability to condense light. Installation depends on the configuration of the device. In this embodiment, the optical lens is composed of a plurality of lenses, the first optical lens 104 and the second optical lens 105, but the number of optical elements forming the optical system is not limited to this. Absent.

  The two lenses of the first optical lenses 104a and 104b are shared by beams corresponding to yellow and magenta, cyan and black, and the second optical lens 105 is arranged for each color. Further, folding mirrors 106 (106a to 106h) for guiding the laser beam subjected to the deflection scanning to each photosensitive drum are disposed on the optical path of each beam. The folding mirror 106g is disposed below the folding mirror 106b and guides the laser beam corresponding to magenta that has passed through the optical lens 104a to the folding mirror 106b. Similarly, the folding mirror 106h is disposed below the folding mirror 106e, and guides the laser beam corresponding to cyan that has passed through the optical lens 104b to the folding mirror 106e. Each folding mirror 106 is fixed (held) to each mounting portion of the scanning optical device 40.

  FIG. 3 is an explanatory diagram in which the vicinity of the deflection motor of the scanning optical device 40 is cut out, and FIG. 4 is an assembly explanatory diagram of the scanning optical device 40.

  The housing of the scanning optical device 40 includes a first housing 110 that houses a deflection motor 103 and a pair of optical lenses 104, and a second housing 100 that houses a light source and other optical elements. The reason for the division into the first housing and the second housing is that the first housing which is a common part and the second housing corresponding to the photosensitive drum mounting position of the main body, for example, The main reasons are to make the scanning optical device versatile and to isolate the deflection motor as a heat source from other optical elements. In this embodiment, only the deflection motor and the pair of optical lenses are mounted on the first casing, but even if a light source is further mounted, the above object can be met.

  The first casing 110 is provided with two mounting shapes 112 and 113 on the straight line in the sub-scanning direction passing through the substantially central portion of the deflection motor, and each of the first casing 110 is provided on the second casing 100. The positioning shapes 107a and 107b are fitted to be positioned at predetermined positions. The attachment shapes 112 and 113 are fastened and fixed to the second housing with screws in a state where the attachment shapes 112 and 113 are positioned at the predetermined positions.

  Four protrusion-shaped portions 111 are provided at both ends on the outside of the optical lens 104 on the first housing. The protrusion-shaped part 111 is elastically fixed by being pressed by the spring member 120 in the Z direction of the second casing 100.

  The folding mirror 106b and the folding mirror 106f are fixed to predetermined positions of the second casing 100 after the second casing 100 is attached.

  When the deflection motor rotates, the bearing of the deflection motor, the drive coil, the IC, etc. generate heat. The inside of the housing is heated by direct conduction from the motor mounting portion and a warmed airflow generated when the polygon mirror rotates. When the deflection motor 103 is housed in the first casing 110 as in the present invention and a substantially sealed space is formed by the first casing 110, the heated air is transferred to the second casing. 100 cannot be reached directly. Further, since both the casings are molded products of glass reinforced resin, the thermal conductivity is low, and the temperature increase of the first casing 110 does not directly increase the temperature of the second casing 100.

  This can suppress an increase in the temperature of the optical element mounting portion of the second casing 100 as compared with the case where the casing is not a divided structure. However, since a temperature difference occurs between the first housing 110 and the second housing 100, when the first housing 110 and the second housing 100 are fastened, linear expansion causes Distortion occurs.

  FIG. 5 shows an undesired deformation of the tandem scanning optical device. When the scanning optical device is deformed as shown in the curved line diagram in FIG. 5, the emitted light beam moves in the direction of the arrow in the drawing, and the photosensitive drum Changes the position where Y, M, C, and Bk are pitched. This is recognized as a color misregistration defect for each color on the output image.

  In the configuration of the present invention, two fixed attachment portions are provided on the straight line in the sub-scanning direction passing through the substantially central portion of the deflection motor, and both outer end portions are elastically held. Even if one housing 110 extends in a direction in which the protrusion-shaped portion 111a and the protrusion-shaped portion 111c move away due to linear expansion, the second housing 100 is not deformed.

  4 is a scanning optical device having substantially the same configuration as that of the first embodiment, and in FIG. 4, the outer edges of both ends of the first housing on a straight line in the sub-scanning direction passing through the substantially central portion of the deflection motor of the second housing The protrusion-shaped portions 114 provided at both ends of the outer side of the optical lens on the first housing are screwed and fixed to the first housing with two attachment fitting portions arranged in the vicinity of the second portion. Is fixed to a predetermined portion of the casing elastically by an adhesive having a soft hardness after bonding.

40 scanning optical device, 100 second casing, 103 deflection motor,
104 optical lens, 106 folding mirror, 110 first housing,
111 Protrusion shape portion, 112, 113 Mounting shape, 114 Protrusion shape portion

Claims (4)

In a scanning optical device configured to emit and scan a plurality of laser beams for irradiating a plurality of photosensitive drums,
A first housing that houses at least a deflector and an optical lens; and a second housing that houses an optical element and a light source;
The first casing is fixed to two predetermined positions of the second casing at two locations provided at both ends of the outer shape of the first casing on the axis perpendicular to the scanning direction of the laser beam with the deflector as the center. A scanning optical device, wherein the outer end of the optical lens of the first casing is elastically fixed to the first casing by a plurality of fixing sections. In a scanning optical device configured to emit and scan a plurality of laser beams for irradiating a plurality of photosensitive drums,
A first housing that houses at least a light source, a deflector, and an optical lens; and a second housing that houses an optical element;
The first casing is fixed to two predetermined positions of the second casing at two locations provided at both ends of the outer shape of the first casing on the axis perpendicular to the scanning direction of the laser beam with the deflector as the center. A scanning optical device, wherein the outer end of the optical lens of the first housing is elastically fixed to the second housing by a plurality of fixing portions. 3. The scanning optical device according to claim 1, wherein the outer edge of the outer optical lens of the first housing is elastically fixed to the second housing by a spring member. 4. The outer end of the outer optical lens of the first casing is fixed to the second casing with an adhesive that maintains viscoelasticity even after curing. Scanning optical device.