JP2016126268A - Optical scanner and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce falling of a rotation axis of a rotation polygon mirror in an optic axis direction with a simple structure.SOLUTION: The invention is configured so that, relative to inclination of an optic axis direction of a rotation axis determined based on inclination of a straight line rotation axis direction connecting seating faces 306, 307 disposed in the vicinity of a rotation axis of a scanner motor 42, when a deflector 41 is fixed to the seating faces 306, 307, 308, an angle formed of the straight line connecting the seating faces 306, 307 which crosses an optic axis direction of the optic beam deflected by a rotation polygonal mirror 45, and inclination of the rotation axis direction of the seating faces 306, 307, inclination of the optic axis direction of the rotation axis determined based on inclination of the straight line rotation axis direction connecting contact parts 101, 102 when the deflector 41 is fixed to the seating faces 306, 307, 308 and the contact parts 101, 102 contact the deflector 41, an angle formed of the straight line connecting the contact parts 101, 102 and crossing the optic axis direction, and inclination of the optic axis direction of the rotation axis when the deflector 41 is fixed to the seating faces 306, 307, 308, is small.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus, and more particularly to an optical scanning apparatus provided in an electrophotographic image forming apparatus such as a digital copying machine, a laser beam printer, and a facsimile apparatus.

  Conventionally, in an optical scanning device used in an electrophotographic image forming apparatus, a light beam emitted from a light source is deflected by a rotating polygon mirror and condensed by a scanning imaging optical system toward a surface to be scanned. A light spot is formed on the scanning surface. The optical scanning device is configured to scan the surface to be scanned with this light spot to form a latent image on the surface to be scanned. The formed latent image is developed with a developer (toner), and the toner image is transferred onto a recording sheet, fixed on the recording sheet, and then discharged. A rotating polygon mirror that deflects laser light and a scanner motor that rotationally drives the rotating polygon mirror are installed in a deflector, and together with a scanning imaging optical system such as a lens and a mirror, a predetermined housing (hereinafter referred to as an optical scanning device). It is generally mounted in an optical box).

  In the optical scanning device, the state in which the rotation axis of the rotary polygon mirror is tilted is referred to as the rotation axis tilting of the rotary polygon mirror (hereinafter simply referred to as “rotation axis tilt”). Due to the tilting of the rotation axis, the laser beam is irradiated to a position deviated from the assumed irradiation position of the lens. As a result, the imaging performance is deteriorated and the condensing power is changed. Distortion of the light spot shape occurs. This distortion of the spot shape affects the formation of a latent image on the photosensitive drum and causes a reduction in image quality. The rotary polygon mirror is attached to the brushless motor with high accuracy, and the brushless motor is composed of a rotor portion to which the rotary polygon mirror is attached, a drive board, and a bearing portion that couples a stator portion including the motor portion. In some optical scanning devices, the deflector is fixed to the optical box by screwing through a plurality of screw holes provided in the drive substrate of the deflector.

  Also, in recent years, with the progress of miniaturization and space saving of optical scanning devices, the distance between the rotary polygon mirror and the lens of the scanning imaging optical system has been shortened, and the substrate of the deflector has been miniaturized. Yes. Shortening the distance between the rotary polygon mirror and the lens of the scanning imaging optical system increases spot shape fluctuations due to tilting of the rotation axis, and downsizing of the deflector substrate greatly increases rotation axis tilting due to the height of the seating surface. To do. Therefore, the importance of reducing the rotation axis collapse is increasing. For example, in Patent Document 1, a seating surface for fixing a rotary polygon mirror and an optical box is installed in the direction of rotation axis tilting that is most sensitive to spot shape fluctuations, and the effect of the seating surface height and tilt on the rotation axis tilting is affected. Techniques have been proposed for reducing tilting of the rotating shaft by supporting each other on their seating surfaces.

JP 2005-201941 A

  In the optical scanning device having the above-described configuration, a screw is used to fix the deflector including the rotary polygon mirror to the optical box. If there is an error (height difference) in the height of multiple mounting seat surfaces of the optical box to which the deflector is screwed, the deflector will be tilted and fixed, and the rotating polygon mirror will tilt. There was a problem that it would occur. The two mounting seat surfaces of the optical box provided near the center of the rotation axis of the rotary polygon mirror and screwed together support each other when an inclination occurs in the normal direction of the straight line connecting the mounting seat surfaces. In addition, the inclination of the mounting seat surface directly affects the tilting of the rotating shaft. Further, as the tendency of the rotation axis to fall, the rotation axis fall in the traveling direction (optical axis direction) of the laser light when entering the lens of the scanning imaging optical system in the optical scanning device is a spot shape formed on the photosensitive drum. Affect the fluctuations of Therefore, in the configuration of the optical scanning device in which the mounting seat surface is installed in the normal direction of the laser beam traveling direction when the lens is incident, the rotation axis tilt in the laser beam traveling direction that changes the spot shape may be affected. become.

  Since the rotation axis tilt does not affect the spot shape, the accuracy of the height difference required for the height of the mounting seat surface of the optical box may require a value in the range of 1/1000 mm. However, in the molding process when mass-producing an actual optical box, the accuracy of the height difference is generally about 1/100 mm to 2/100 mm, and the accuracy of the height difference of the mounting seat surface is increased in the molding process. Therefore, it is difficult to reduce the rotation axis collapse.

  The present invention has been made under such circumstances, and an object of the present invention is to reduce the rotation axis tilt of the rotary polygon mirror in the optical axis direction with a simple configuration.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) A deflector having a polygon mirror that reflects and deflects a light beam from a light source, a drive unit that rotates the polygon mirror about a rotation axis, and an optical box in which the deflector is fixed by a screw. An optical scanning device that scans the light beam on a surface to be scanned, wherein the optical box is installed at a bottom of the optical box and faces a hole of the deflector into which the screw is inserted. A plurality of seating surfaces for supporting a portion pressed by the screw of the deflector and fixing the deflector to the optical box; and a bottom part of the optical box, wherein the deflector is Two abutting portions that abut a portion of the deflector that does not abut against the plurality of seating surfaces when being fixed to the seating surface, and the deflector is secured to the plurality of seating surfaces. Provided in the vicinity of the rotating shaft of the drive unit among the plurality of seating surfaces. The inclination of the straight line connecting the two seating surfaces in the direction of the rotation axis, the angle at which the straight line connecting the two seating surfaces intersects the optical axis direction of the light beam deflected by the polygon mirror, and the two seats The deflector is fixed to the plurality of seating surfaces, and the two abutments are applied to the deflector more than the inclination of the rotation axis in the optical axis direction obtained based on the inclination of the surface in the rotation axis direction. The inclination of the straight line connecting the two contact parts when the contact part is in contact with the rotation axis direction, and the angle when the straight line connecting the two contact parts intersects the optical axis direction; The inclination of the rotation axis in the optical axis direction obtained based on the inclination of the rotation axis when the deflector is fixed to the plurality of seating surfaces is smaller. Optical scanning device.

  (2) The photoconductor, the optical scanning device according to (1) that irradiates the photoconductor with a light beam to form an electrostatic latent image on the photoconductor, and the static formed by the optical scanning device. An image forming apparatus comprising: a developing unit that develops an electrostatic latent image to form a toner image; and a transfer unit that transfers a toner image formed by the developing unit to a recording medium.

  According to the present invention, the rotation axis of the rotary polygon mirror in the optical axis direction can be reduced with a simple configuration.

Schematic cross-sectional view showing the overall configuration of the image forming apparatus of Examples 1 and 2, and cross-sectional view of the optical scanning device The top view which shows the optical scanner of Example 1,2. FIG. 3 is a perspective view illustrating a configuration of an optical scanning device on which the deflector according to the first embodiment is mounted. The perspective view which shows the structure of the optical box of the optical scanning apparatus of the prior art example for a comparison with Example 1. FIG. The perspective view for demonstrating the structure of the optical box of Example 1. FIG. The figure which shows the rotating shaft fall reduction effect by the presence or absence of the butting part of Example 1. The top view for demonstrating the structure of the optical box of Example 1. FIG. The figure showing the rotating shaft fall reduction effect of Example 1 A top view for explaining the configuration of the optical box of the second embodiment

  Embodiments of the present invention will be described below in detail with reference to the drawings.

[Outline of image forming apparatus]
The configuration of the image forming apparatus according to the first embodiment will be described below. FIG. 1A 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 rotational axis direction of the rotary polygon mirror 45 described later is the Z-axis direction, the main scanning direction that is the scanning direction of the light beam, or the longitudinal direction of the folding mirror described later is the Y-axis direction, the Y-axis, and the Z-axis. The direction perpendicular to the axis is taken as the X-axis direction. Further, the X-axis direction is a traveling direction (optical axis direction) of the laser light when entering the lens of the scanning imaging optical system in the optical scanning device described above.

  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 FIGS. The optical scanning device 40 is shared by all image forming engines 10Y, 10M, 10C, and 10Bk, and includes four semiconductor lasers (not shown) that emit laser beams that are modulated in accordance with image information of each color. The optical scanning device 40 also includes a rotary polygon mirror 45 that is a deflecting unit that deflects the light beam so that the light beam corresponding to each photosensitive drum 50 scans in the axial direction (Y-axis direction) of the photosensitive drum 50, and the rotation. A scanner motor 42 which is a drive unit for rotating the polygon mirror 45 is provided. Each light beam deflected by the rotary polygon mirror 45 is guided by an optical member installed in the optical scanning device 40 and guided onto the photosensitive drum 50 (on the photosensitive member) 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 potential. Each image forming engine 10 includes a developing unit 13 that is a developing unit that develops an electrostatic latent image formed on the photosensitive drum 50 by being exposed by irradiation with a light beam to form a toner image. Yes. 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 transferred from the paper feed cassette 2 stored in the lower part of the printer housing 1 to the inside of the printer, specifically, the intermediate transfer belt 20 and the secondary transfer roller 65 as a transfer means. Supplied to the location. 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 optical scanning device 40 exposes the photosensitive drum 50 of each image forming engine 10 at a predetermined timing in accordance with 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 optical scanning 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.

[Configuration of optical scanning device]
FIG. 1B is a schematic view showing an entire image of the optical component attachment of the optical scanning device 40. A light source unit 201 (see FIG. 2 described later) on which a light source that emits a light beam (laser light) is mounted, a rotary polygon mirror 45 that deflects the light beam, and a scanner motor 42 are installed inside and around the optical scanning device 40. Is installed. Further, the optical scanning device 40 is provided with fθ lenses 46a to 46d and folding mirrors 47a to 47h for guiding each light beam onto the photosensitive drum 50 to form an image.

  A light beam 154 (also referred to as a Y scanning line 154) corresponding to the photosensitive drum 50Y emitted from the light source unit 201 (see FIG. 2) is deflected by the rotary polygon mirror 45 and enters the fθ lens 46a. The light beam 154 that has passed through the fθ lens 46a enters the fθ lens 46b, passes through the fθ lens 46b, and is reflected by the folding mirror 47a. The light beam 154 reflected by the folding mirror 47a passes through a transparent window (not shown) and scans the photosensitive drum 50Y.

  A light beam 155 (also referred to as an M scanning line 155) corresponding to the photosensitive drum 50M emitted from the light source unit 201 (see FIG. 2) is deflected by the rotary polygon mirror 45 and enters the fθ lens 46a. The light beam 155 that has passed through the fθ lens 46a enters the fθ lens 46b, passes through the fθ lens 46b, and is reflected by the folding mirror 47b, the folding mirror 47c, and the folding mirror 47d. The light beam 155 reflected by the folding mirror 47d passes through a transparent window (not shown) and scans the photosensitive drum 50M.

  A light beam 156 (also referred to as a C scanning line 156) corresponding to the photosensitive drum 50C emitted from the light source unit 201 (see FIG. 2) is deflected by the rotary polygon mirror 45 and enters the fθ lens 46c. The light beam 156 that has passed through the fθ lens 46c is incident on the fθ lens 46d, and the light beam 156 that has passed through the fθ lens 46d is reflected by the folding mirror 47e, the folding mirror 47f, and the folding mirror 47g. The light beam 156 reflected by the folding mirror 47g passes through a transparent window (not shown) and scans the photosensitive drum 50C.

  A light beam 157 (also referred to as a K scanning line 157) corresponding to the photosensitive drum 50Bk emitted from the light source unit 201 (see FIG. 2) is deflected by the rotary polygon mirror 45 and enters the fθ lens 46c. The light beam 157 that has passed through the fθ lens 46c enters the fθ lens 46d, passes through the fθ lens 46d, and is then reflected by the folding mirror 47h. The light beam 157 reflected by the folding mirror 47h passes through a transparent window (not shown) and scans the photosensitive drum 50Bk.

[Outline of optical scanning device]
FIG. 2 is a top view showing an overall image of the optical scanning device 40 disposed in the printer shown in FIG. 2 is illustrated with the upper lid 70 removed from the optical box 49 shown in FIG. 1B. In FIG. 2, a typical light beam path (optical path) of the laser optical path including the optical axis of the scanning lens is shown in order from the upper side in the figure, Y scanning line 154, M scanning line 155, C scanning line 156, K scanning line 157. It is shown as The Y scanning line 154 exposes the photosensitive drum 50Y of the image forming engine 10Y described above. Similarly, the M scanning line 155, the C scanning line 156, and the K scanning line 157 expose the photosensitive drum 50M of the imaging engine 10M, the photosensitive drum 50C of the imaging engine 10C, and the photosensitive drum 50Bk of the imaging engine 10Bk, respectively.

  A light source unit 201 on which a light source that emits laser light is mounted is provided on the outer peripheral portion of the optical box 49 of the optical scanning device 40. The optical box 49 includes a rotary polygon mirror 45 that reflects and deflects the laser light emitted from the light source unit 201, a deflector 41 that supports and rotates the rotary polygon mirror 45, and a plurality of laser beams that are transmitted and reflected. An fθ lens 46, a folding mirror 47, and the like are installed. The fθ lens 46 and the folding mirror 47, which are optical members, guide the light beam (also referred to as laser scanning light) deflected by the rotating polygon mirror 45 onto each photosensitive drum 50 (on the scanned surface) that is the scanned surface. , It is installed as a scanning imaging optical system necessary for imaging. In the light source unit 201, the upper side in the figure is the light source unit 201 for the image forming engines 10Y and 10M, and the lower side in the figure is the light source unit 201 for the image forming engines 10C and 10K.

  As shown in FIG. 2, the optical scanning device 40 includes a light source unit 201, a deflector 41, an fθ lens 46, and a folding mirror 47. The light source unit 201 is a unit in which a semiconductor laser and a collimator lens are integrated, and the parallel light beam emitted from the semiconductor laser is converted into convergent light in the sub-scanning direction by the cylinder lens and then deflected. It is deflected by the device 41. The deflector 41 includes a rotating polygon mirror 45 having a plurality of reflecting surfaces for deflecting laser light, a scanner motor 42 that is a driving motor for rotating the rotating polygon mirror 45, a driving substrate 205, and an IC chip 206. It has. The laser light deflected by the rotary polygon mirror 45 of the deflector 41 is passed through an fθ lens 46 for forming an image on the surface of the photosensitive drum 50 and a folding mirror 47 for guiding the laser light to the photosensitive drum 50. The surface of the photosensitive drum 50 is scanned.

  When the laser light based on the input image data is emitted from the light source unit 201, the emitted laser light is incident on the reflecting surface of the rotary polygon mirror 45 that is driven to rotate. The laser beam reflected and deflected by the reflecting surface of the rotary polygon mirror 45 becomes scanning light of the photosensitive drum 50 and is imaged on the photosensitive drum 50 by the fθ lens 46. As described above, when the rotary polygon mirror 45 rotates, the photosensitive drum 50 performs main scanning (scanning in the rotation axis direction of the photosensitive drum 50) by the laser beam, and the photosensitive drum 50 is driven to rotate. Sub-scanning (scanning in the rotation direction of the photosensitive drum 50) is performed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 50.

  When attaching various optical components such as the deflector 41 to the optical box of the optical scanning device 40, it is necessary to perform an installation operation in consideration of the position and orientation of the optical components. Further, the deflector 41 needs to be firmly fastened to the optical box 49 in order to prevent vibrations caused by the rotation of the rotary polygon mirror 45. In the image forming apparatus including the optical scanning device 40, in order to reproduce a high-definition image, the optical path of the laser beam from the light source unit 201 is photosensitive while minimizing the deviation of the optical path so that the optical path of the laser beam is an ideal design path. It is important to guide the laser beam onto the drum 50. In particular, when the rotation axis of the rotary polygon mirror 45 is tilted, the optical path of the laser beam after being reflected by the rotation polygon mirror 45 is shifted from the central portion where the optical performance of the optical lens 712 is high due to the rotation axis tilting. The imaging performance on 50 will be reduced.

[Fastening configuration of optical box and deflector]
The optical scanning device 40 of this embodiment has a simple configuration and reduces the rotation axis tilt of the rotary polygon mirror 45 when the optical box 49 and the deflector 41 are fastened, thereby preventing the imaging performance from deteriorating. Below, the structure is demonstrated in detail.

  FIG. 3 is a perspective view showing a configuration example in which the deflector 41 is installed in the optical box 49 of the optical scanning device 40 of the present embodiment. The drive board 205 is an iron circuit board on which electronic components such as an IC chip 206 for driving the rotary polygon mirror 45 are mounted. The drive substrate 205 is not limited to the substrate in which the circuit pattern is directly wired on the iron plate as in the present embodiment, and may be a substrate in which a printed substrate such as a glass epoxy resin is bonded on the iron plate. Screws 304 a, 304 b, and 304 c for fixing the drive substrate 205 to mounting seat surfaces 306, 307, and 308 provided on the installation surface 301 that is the bottom of the optical box 49 are inserted into the drive substrate 205 of the deflector 41. Three screw holes are provided. The installation surface 301 of the optical box 49 includes three mounting seats so that a part of the installation surface 301 is formed at a position corresponding to a plurality of screw holes provided in the drive substrate 205 and protrudes from the installation surface 301. Surfaces 306, 307, and 308 are provided. The contact surfaces of the mounting seat surfaces 306, 307, and 308 with which the drive substrate 205 abuts are circular, and have a flat surface with a small height difference, that is, high planar accuracy. In this embodiment, the contact surfaces of the mounting seat surfaces 306, 307, and 308 are circular, but the shape is not limited to a circular shape as long as the drive substrate 205 can be stably fixed. Absent. The drive board 205 and the mounting seat surfaces 306, 307, 308 are pressed and fastened by screws 304a, 304b, 304c through screw holes provided in the drive board 205. The peripheral portion of the screw hole of the drive board 205 comes into surface contact with the screws 304 a, 304 b, 304 c and the mounting seat surfaces 306 to 308, so that the drive board 205 is attached to the mounting seat surfaces 306 to 308, particularly the mounting seat surfaces 306, The inclination follows the inclination of the contact surface 307.

  Further, the shaft that supports the rotary bearing of the rotary polygon mirror 45 is welded to the drive substrate 205 with high positional accuracy, and the shaft also serves to position the deflector 41. Therefore, when the drive substrate 205 is fixed to the mounting seat surfaces 306, 307, 308, the shaft is fitted into a positioning hole 312 (see FIG. 5) provided in the optical box 49, and the optical box 49 is thus fitted. Positioning of the deflector 41 and the rotary polygon mirror 45 is performed.

  FIG. 4 is a perspective view showing the configuration of the optical box 49 of the conventional optical scanning device 40 for comparison with the present embodiment, and shows a state in which the drive substrate 205 shown in FIG. 3 is removed. As shown in FIG. 4, the installation surface 301 is provided with positioning holes 312 in which the mounting seat surfaces 306, 307, 308 and a shaft that supports the rotary bearing of the rotary polygon mirror 45 are fitted. The mounting seat surfaces 306, 307, and 308 in FIG. 4 are desirably formed horizontally, but due to variations in the molding process, the flatness (the height difference on the mounting seat surface) has an inclination of tens of μm. Yes. When the inclination due to the flatness (height difference) of the mounting seat surface occurs in the normal direction with respect to the straight line connecting the two seating surface centers of the mounting seat surfaces 306 and 307, the drive board 205 is attached to the mounting seat surface. Since it is screwed to 306 and 307, its inclination is equivalent to the inclination of the mounting seat surfaces 306 and 307. That is, when the contact surfaces of the mounting seat surfaces 306 and 307 with the drive substrate 205 are inclined, by screwing, the straight line connecting the two seat surface centers of the mounting seat surfaces 306 and 307 is used as an axis. Twist occurs. Thereby, the inclination of the contact surface of the mounting seat surfaces 306 and 307 becomes the inclination of the drive substrate 205. The inclination of the drive substrate 205 eventually leads to the rotation axis of the rotary polygon mirror 45 being tilted. That is, when the inclination occurs in the normal direction on the straight line connecting the centers of the two mounting seat surfaces 306 and 307, the rotation polygon of the rotary polygon mirror 45 is tilted. The mounting seat surface 308 is provided at a position farther from the rotation axis of the rotary polygon mirror 45 than the mounting seat surfaces 306 and 307, and the rotation axis collapse is affected by the flatness of the mounting seat surfaces 306 and 307. Since it is dominant, explanation here is omitted.

  As described above, the direction in which the spot shape on the photosensitive drum 50 is likely to vary is the traveling direction (optical axis direction) of the laser light when the lens of the scanning imaging optical system in the optical scanning device is incident. Therefore, when the mounting seat surfaces 306 and 307 are installed in the normal direction in which the spot shape on the photosensitive drum 50 is likely to fluctuate, that is, in the vicinity of the rotation axis of the rotary polygon mirror 45, the planes of the mounting seat surfaces 306 and 307 are provided. There is a high possibility that the rotation axis collapse caused by the degree occurs in the optical axis direction. Therefore, the direction in which the sensitivity of spot shape fluctuation due to the rotation axis collapse is high and the rotation axis collapse direction that is likely to occur due to the flatness of the mounting seat surface are the same direction, that is, the optical axis direction (X-axis direction).

[Configuration of the abutting section]
Next, the abutting portion that is a feature of the present embodiment will be described. FIG. 5 is a perspective view showing a configuration around a portion where the deflector 41 of the optical box 49 of the optical scanning device 40 of the present embodiment is installed, and shows a state where the drive substrate 205 shown in FIG. 3 is removed. ing. As shown in FIG. 5, the installation surface 301 of the optical box 49 is provided with abutting portions 101 and 102 which are abutting portions in addition to the mounting seat surfaces 306, 307 and 308 and the positioning hole 312. The abutting portions 101 and 102 are provided at symmetrical positions with the positioning hole 312 as the center, and can contact the driving substrate 205. When the drive substrate 205 is screwed to the mounting seat surfaces 306, 307, 308, the drive substrate 205 is inclined due to the inclination of the contact surfaces of the mounting seat surfaces 306, 307 that contact the drive substrate 205, and the rotation axis It may cause a fall. In this case, by providing the abutting portions 101 and 102, the surface facing the installation surface 301 of the driving substrate 205 abuts against the abutting portions 101 and 102, and the inclination of the driving substrate 205 is suppressed.

  The difference in height of the tip portions of the abutting portions 101, 102, the distance between the abutting portions 101, 102, the center of the rotating shaft of the rotary polygon mirror 45 and the positional relationship between the abutting portions 101, 102, etc. Affects reduction. For example, when the distance between the abutting part 101 and the abutting part 102 is increased (the abutting parts 101 and 102 are set apart from each other), rotation caused by the height accuracy (height difference) of the abutting parts 101 and 102 Axis collapse is reduced. In general, the rotation angle of the mounting seat surfaces 306 and 307 is closer to the right angle when the straight line connecting the centers of the two mounting seat surfaces 306 and 307 and the straight line connecting the abutting portions 101 and 102 intersect each other. The impact of the shaft collapse can be suppressed by the abutting portions 101 and 102.

  In the present embodiment, with respect to the installation conditions (position and height) of the mounting seat surfaces 306 and 307, the abutting portions 101 and 102 having an appropriate shape are installed at appropriate positions to reduce the rotation axis collapse. be able to. In the present embodiment, the height of the abutting portions 101 and 102, more precisely the height from the bottom surface of the optical box 49, is 100 μm higher than the mounting seat surfaces 306 to 308. Therefore, the abutting portions 101 and 102 are configured to be in contact with a surface facing the installation surface 301 of the drive substrate 205 without fail. The value of 100 μm is determined in consideration of variations due to the height of the mounting seat surfaces 306 and 307, the flatness of the drive substrate 205, and the like. In this embodiment, the variation considering the height variation of the mounting seat surfaces 306 and 307 and the height variation due to the flatness of the drive substrate 205 is about 95 μm. In view of this, in this embodiment, the configuration of the abutting portions 101 and 102 higher than the mounting seat surfaces 306 and 307 by about 100 μm is adopted for this variation.

  In addition, regarding the abutting portion, not only the height described above but also the shape of the tip portion of the abutting portions 101 and 102 that abut against the drive substrate 205 is important. Here, the shape of the abutting portions 101 and 102 will be described with reference to FIG. 7 described later. FIG. 7 is a top view of the periphery of the location where the deflector 41 shown in the perspective view of FIG. 5 is installed as seen from above. The abutting portions 101 and 102 of the present embodiment have the same shape, and have a shape in which a truncated cone is installed on the installation surface 301 and a tip-shaped spherical cone is placed thereon. Further, the inclination of the side surface of the lower truncated cone is gentler than the inclination of the side surface of the upper cone. The shape of the abutting portion shown in FIG. 7 is an example, and is not limited to this shape. As will be described later, the shape of the tip of the abutting portion is in point contact with the drive substrate 205. If it is. Unlike the mounting seat surfaces 306 to 308 that are screwed to the drive board 205, the abutting portions 101 and 102 do not need to be screwed to the drive board 205. The drive substrate 205 abuts against the mounting seat surfaces 306 to 308 by being screwed. Therefore, the drive substrate 205 is affected by the inclination due to the height difference between the seating surfaces with which the mounting seating surfaces 306 and 307 come into contact, and as a result, the rotation axis of the rotary polygon mirror 45 is tilted. On the other hand, the abutting portions 101 and 102 push the tilted drive substrate 205 back by contacting the tip portion with the surface of the drive substrate 205 facing the installation surface 301, so that the rotation axis of the rotary polygon mirror 45 is reduced. Is done.

  Further, the shape of the tip portions of the abutting portions 101 and 102 that do not require screwing can reduce the contact area with the drive substrate 205 compared to the mounting seat surfaces 306, 307, and 308. As described above, the mounting seat surfaces 306 to 308 are pressed by the drive board 205 with screws, and the flatness (height difference in the seating surface) within the area of the mounting seat surface sensitively affects the rotation axis collapse. On the other hand, the tip portions of the abutting portions 101 and 102 have a spherical shape and are in contact with the drive substrate 205 at substantially one point (substantially point contact). Therefore, even when the abutting portions 101 and 102 are in contact with the drive substrate 205, since they are point contacts, unlike the case of the mounting seat surface that is in surface contact, it is possible to reduce the influence on the rotation axis collapse.

[Effects against tilting of rotating shaft by setting abutment]
FIG. 6 is a graph showing how much the rotation axis tilt of the rotary polygon mirror 45 on the drive substrate 205 is reduced with and without the abutting portions 101 and 120 being provided. FIG. 5 shows an optical box 49 in which six samples of the drive substrate 205 are prepared and the abutting portions 101 and 102 shown in FIG. 4 are not provided, and the optical box 49 provided with the abutting portions 101 and 102 shown in FIG. 49 shows how the rotating shaft collapses when installed at 49. In FIG. 6, the black graph shows the rotation axis tilt when the drive substrate 205 is installed in the optical box 49 without the abutting portions 101 and 102, and the white graph shows the abutting portion 101, The rotation axis collapse when it is installed in the optical box 49 provided with 102 is shown. Further, the vertical axis of FIG. 6 indicates the rotation axis tilt (unit: minute) in the optical axis direction, and the horizontal axis indicates the sample numbers (NO. 1 to NO. 6) of the six drive substrates 205 used. From the graph of FIG. 6, although there is variation in the rotation axis tilt depending on the sample, the rotation axis collapse is about 1/5 (in the case of NO.2) to about 1/8 (NO) by providing the abutting portions 101 and 102. (In the case of .6), it can be seen that it is reduced.

[Abutting location]
Subsequently, the installation position of the abutting portion will be described. FIG. 7 is a top view of the periphery of the portion where the deflector 41 of the optical box 49 shown in the perspective view of FIG. 5 is installed as seen from above. FIG. 7 illustrates the mounting seat surfaces 306 and 307, the abutting portions 101 and 102, and the positioning hole 312 as viewed from above. The effect of reducing the rotation axis collapse when the abutting portions 101 and 102 are provided is determined by the installation positions of the mounting seat surfaces 306 and 307 and the abutting portions 101 and 102. That is, the distance between the mounting seat surfaces 306 and 307, the angle between the height difference and the optical axis direction, the distance between the abutting portions 101 and 102, the angle between the height difference and the optical axis direction, and the driving of the mounting seat surfaces 306 and 307 It is determined by the flatness (height difference) and diameter of the surface in contact with the substrate 205.

In FIG. 7, the distance from the rotation axis center of the rotary polygon mirror 45 (the center of the positioning hole 312 in the figure) to the center of one mounting seat surface 306 is a1, and the distance to the center of the other mounting seat surface 307 is the distance. Let a2. The height difference between the surfaces of the mounting seat surfaces 306 and 307 that are in contact with the drive board 205 is C2. In addition, an angle at which the Y axis, which is the main scanning direction of the light beam, orthogonal to the optical axis direction (X-axis direction) and a straight line connecting the centers of the mounting seat surfaces 306 and 307 intersect, is denoted by A (hereinafter referred to as mounting seat surface). It is referred to as angle A). Furthermore, D is the flatness of the mounting seat surfaces 306 and 307 (the height difference in the contact surface with the drive substrate 205), and R is the diameter of the surface that contacts (contacts) the drive substrate 205 of the mounting seat surfaces 306 and 307. To do. In this case, the rotation axis collapse in the X-axis direction, which is the optical axis direction in FIG. 7 when the abutting portions 101 and 102 are not installed, is expressed by the following formula (1).

  Equation (1) is composed of two terms. The first term (C2 / (a1 + a2)) indicates the inclination in the rotation axis direction (Z-axis direction) of the straight line connecting the centers of the mounting seat surfaces 306 and 307, and the inclination of this straight line is multiplied by sinA. Thus, the rotation axis collapse amount in the X-axis direction (optical axis direction) in FIG. 7 is calculated. The second term indicates the rotation axis tilt of the mounting seat surfaces 306 and 307 with respect to the drive board 205. As described above, when the surfaces of the mounting seat surfaces 306 and 307 that are in contact with the drive board 205 are inclined, the inclination is the inclination of the drive board 205 and the rotation axis is tilted. In this case, the rotation axis collapse occurs in a direction perpendicular to a straight line connecting the centers of the mounting seat surfaces 306 and 307. (D / R) in the second term indicates the inclination in the rotation axis direction (Z-axis direction) at the contact surfaces of the mounting seat surfaces 306 and 307 with the drive board 205, and the inclination at the contact surfaces is multiplied by cosA. As a result, the rotation axis collapse amount in the X-axis direction (optical axis direction) in FIG. 7 is calculated. Then, the rotation in the X-axis direction (optical axis direction) when the abutting portions 101 and 102 are not installed is obtained by adding the amount of rotation axis tilt in the X-axis direction calculated by the first term and the second term. The amount of axis collapse can be calculated. Formula (1) is a calculation formula for the amount of rotation axis collapse when the deformation of the drive substrate 205 due to screwing is not taken into consideration in the vicinity of the mounting seat surfaces 306 and 307. For this reason, for example, the larger the shape of the mounting seat surfaces 306 and 307 and the drive board 205, the more the calculated rotation axis tilt value deviates from the actual value. The value of the rotation axis tilt calculated by the equation (1) is appropriate.

Next, a calculation formula for the rotation axis collapse when the abutting portions 101 and 102 are installed will be described. In FIG. 7, the distances from the rotation axis center of the rotary polygon mirror 45 (center of the positioning hole 312 in the figure) to the centers of the butting portions 101 and 102 are b1 and b2, respectively, and the tips of the butting portions 101 and 102 Let the height difference of the part be C1. An angle at which the X axis, which is the optical axis direction, and a straight line connecting the centers of the abutting portions 101 and 102 intersect is defined as B (hereinafter referred to as an abutting angle B). In this case, the rotation axis collapse in the X-axis direction in FIG. 7 when the abutting portions 101 and 102 are installed is expressed by the following equation (2).

  Equation (2) is composed of two terms. The first term (C1 / (b1 + b2)) indicates the inclination in the rotation axis direction (Z-axis direction) of the straight line connecting the centers of the abutting portions 101 and 102, and the inclination of this straight line is multiplied by cosB. Thus, the tilt in the X-axis direction in FIG. 7, that is, the amount of rotation axis tilt in the X-axis direction is calculated. The second term is an expression obtained by multiplying Expression (1) by (B / 90). When the abutting parts 101 and 102 are installed, the abutting parts 101 and 102 calculated by Expression (1) are used. The amount of rotation axis tilting according to the abutting angle B when no is provided is added to the first term.

Therefore, the reduction amount of the rotation axis collapse due to the installation of the abutting portions 101 and 102 can be expressed by the following formula (3) obtained by subtracting the formula (2) from the formula (1).

The amount of rotation axis tilt reduction calculated by equation (3) depends on the positional relationship (distance, height difference, crossing angle with the X axis) and flatness of the abutting portions 101 and 102 and the mounting seat surfaces 306 and 307. Change. For example, as will be described later, when the angle at which the X axis intersects the straight line connecting the butting parts 101 and 102 is 0 °, the abutting parts 101 and 102 are compared with the case where there is no abutting part. By providing, rotation axis fall is reduced by about 70%. Further, as will be described later, depending on the mounting seat surface angle A and the abutting angle B, the rotation axis collapse may be further increased. Therefore, in order to reliably reduce the rotation axis collapse by installing the abutting portions 101 and 102 within the limits of the mounting seat surfaces 306 and 307, the reduction amount calculated by the equation (3) is a positive value, It is necessary to satisfy the conditions shown in the following formula (4).

[Reduction rate of rotation axis collapse]
FIG. 8 is a graph showing the reduction rate of the rotation axis collapse depending on the presence or absence of the abutting portions 101 and 102. The reduction rate of the rotation axis collapse shown in FIG. 8 is the reduction amount of the rotation axis collapse (equation (3)) when the abutting portions 101 and 102 are provided, and the rotation axis collapse when the abutment portions 101 and 102 are not provided. It is calculated by dividing by the amount (formula (1)). In FIG. 8, (a) to (d) show the reduction rate of the rotation axis collapse according to the abutment angle B when the mounting seat surface angle A is 0, 60, 80, and 90 degrees, respectively. 8A to 8D, the vertical axis represents the rotation axis collapse reduction rate (unit:%), and the horizontal axis represents the abutting angle B (B = 0, 10, 20, 30, 40, 50). , 60, 70, 80, 90 degrees). Further, a positive value of the rotation axis collapse reduction rate indicates that the rotation axis collapse is reduced, and a negative value indicates that the rotation axis collapse increases. In calculating the reduction rate of the rotation axis collapse shown in FIG. 8, the values used in the above-described equations (1) and (3) are as follows. That is, the height difference C1 between the abutting portions 101 and 102 is 12 μm, the height difference C2 between the mounting seat surfaces 306 and 307 is 12 μm, the height difference D between the mounting seat surfaces 306 and 307 is 10 μm, and the mounting seat surface 306, The diameter R of 307 is 6 mm. Furthermore, the distance (b1 + b2) between the abutting portions 101 and 102 is 23 mm, and the distance (a1 + a2) between the mounting seat surfaces 306 and 307 is 33 mm.

  FIG. 8 (a) shows the reduction rate of the rotation axis collapse according to the abutment angle B when the mounting seat surface angle A is 0 degrees. As the abutment angle B increases, the rotation axis collapses. It can be seen that the reduction rate of is decreasing. Further, as described above, in the graph of the reduction rate of the rotation axis collapse shown in FIGS. 8A to 8D, the mounting seat surface angle A in FIG. It can be seen that the rotation axis collapse reduction rate at 0 degree is about 70%, which is the highest reduction rate. That is, when the straight line connecting the mounting seat surfaces 306 and 307 is parallel to the Y axis and the straight line connecting the abutting parts 101 and 102 is parallel to the X axis, the effect of reducing the rotation axis collapse by the abutting parts 101 and 102 is obtained. You can see that it is the largest.

  FIG. 8B shows the reduction rate of the rotation axis collapse according to the abutting angle B when the mounting seat surface angle A is 60 degrees. As in FIG. 8A, the abutting angle is shown. It can be seen that as B increases, the reduction rate of the rotation axis collapse decreases. In FIG. 8B, it can be seen that even when the abutting angle B is the same, the reduction rate of the rotation axis collapse is smaller than that in FIG. 8A. FIG. 8C shows a reduction rate of the rotation axis collapse according to the abutment angle B when the mounting seat surface angle A is 80 degrees. In FIG. 8C, when the abutting angle B is 0 degree, 10 degrees, and 20 degrees, the value of the rotation axis collapse reduction rate is a positive value, and the rotation axis collapse is reduced. It can be seen that when the angle B is larger than 30 degrees, the rotation axis collapse is not reduced and the direction is increased. It can be seen that the increase in rotation axis tilt is greatest when the abutment angle B is 50 degrees.

  FIG. 8D shows the reduction rate of the rotation axis tilting according to the abutment angle B when the mounting seat surface angle A is 90 degrees, that is, the straight line connecting the mounting seat surfaces 306 and 307 is parallel to the X axis. Has been. In FIG. 8D, since the reduction rate of the rotation axis collapse is negative in all cases of the abutment angle B, the rotation axis collapse increases, and the maximum is obtained when the abutment angle B is 30 degrees. I understand that From the graph shown in FIG. 8, depending on the mounting seat surface angle A and the abutment angle B, the reduction rate of the rotation axis collapse is negative, that is, when the abutment portions 101 and 102 are provided, the rotation axis collapse increases. (FIG. 8C, FIG. 8D). Therefore, it is possible to reduce the rotation axis collapse by determining appropriate positions and shapes of the abutting portions 101 and 102 that satisfy the condition shown in Expression (4) with respect to the mounting seat surface angle A and other parameters. it can.

  In this embodiment, the rotary polygon mirror 45 of the deflector 41 is a sleeve rotation type that is integrally fixed to the sleeve of the scanner motor 42 and rotates by the rotation of the sleeve. For example, even if the rotary polygon mirror 45 is fixed to the rotation shaft of the scanner motor 42 and is rotated by the rotation of the rotation shaft, the same effect is obtained.

  As described above, according to the present embodiment, it is possible to reduce the rotation axis of the rotary polygon mirror in the optical axis direction with a simple configuration. In this embodiment, in addition to the mounting seat surface for fixing the deflector and the optical box to the optical box, a simple configuration of providing a plurality of abutting portions with a height that surely abuts the deflector reduces the rotation axis collapse. be able to. Further, by setting an appropriate position and height accuracy of the abutting portion with respect to the position and planar accuracy of the mounting seat surface, it is possible to reduce the rotation axis collapse. Furthermore, by making the tip portion of the abutting portion spherical, the contact area with the drive substrate that comes into contact with the abutting portion can be reduced, and the rotation axis can be tilted down.

  In the first embodiment, the abutting portions 101 and 102 having a spherical shape at the tip portion in contact with the drive substrate 205 have been described so that the contact area with the drive substrate 205 is reduced. In the second embodiment, as in the first embodiment, the shape of the abutting portion that has the effect of reducing the rotation axis collapse and suppresses the deformation of the drive substrate 205 will be described.

[Configuration of the abutting section]
FIG. 9 is a diagram showing a configuration around the portion where the deflector 41 of the optical box 49 of the optical scanning device 40 of the present embodiment is installed, and an upper surface showing a state in which the drive substrate 205 shown in FIG. 3 is removed. FIG. As shown in FIG. 9, the installation surface 301 of the optical box 49 is provided with butting portions 103 and 104 in addition to the mounting seat surfaces 306, 307 and 308 and the positioning hole 312. The abutting portions 103 and 104 are provided at positions symmetrical to the surface in the Z-axis direction including the positioning hole 312 and extend linearly in the Y-axis direction, which is the longitudinal direction of the substantially rectangular shape of the drive substrate 205 to be installed. It has a shape. As a result, the abutting portions 101 and 102 shown in the first embodiment are in point contact with the driving substrate 205, but the abutting portions 103 and 104 of this embodiment are a plurality of the driving substrate 205 and a plurality of Y-axis directions. It will contact at the point of. As a result, also in the second embodiment, as in the first embodiment, the rotation axis collapse can be reduced. Furthermore, in this embodiment, the abutting portions 103 and 104 can disperse stress by contacting the drive substrate 205 at a plurality of locations. Therefore, the deformation of the drive substrate 205 can be changed in the case of the first embodiment. In comparison, it can be further suppressed. In addition, in FIG. 9, the front-end | tip part of abutting part 103,104 is planar shape. For example, the shape of the abutment portions 103 and 104 viewed from the Y-axis direction is triangular so that the tip portions of the abutment portions 103 and 104 are linear so that the portion that contacts the drive substrate 205 is a point contact. It may be in shape. In FIG. 9, the abutting portions 103 and 104 have a linearly extending shape, but, for example, are symmetrical to the Z-axis direction surface including the positioning hole 312 and extend in a curved shape in the Y-axis direction. The shape may be different.

  As described above, according to the present embodiment, it is possible to reduce the rotation axis of the rotary polygon mirror in the optical axis direction with a simple configuration.

41 Deflector 42 Scanner Motor 45 Rotating Polygonal Mirrors 101, 102 Abutting portions 306, 307, 308 Mounting seating surface

Claims (9)

A deflector having a polygon mirror that reflects and deflects a light beam from a light source, and a drive unit that rotates the polygon mirror about a rotation axis;
An optical box in which the deflector is fixed by screws;
An optical scanning device that scans the light beam on a surface to be scanned,
The optical box is
A hole is provided at a bottom portion of the optical box and is opposed to a hole of the deflector into which the screw is inserted, supports a portion pressed by the screw of the deflector, and the deflector is attached to the optical box. A plurality of seating surfaces to be fixed to
Two abutting portions that are installed at the bottom of the optical box and abut against portions of the deflector that do not abut against the plurality of seating surfaces when the deflector is fixed to the seating surface;
Have
When the deflector is fixed to the plurality of seating surfaces, a straight line connecting two seating surfaces provided in the vicinity of the rotation shaft of the driving unit among the plurality of seating surfaces in the direction of the rotation axis. Based on the inclination, the angle when the straight line connecting the two seating surfaces intersects the optical axis direction of the light beam deflected by the polygon mirror, and the tilting of the two seating surfaces in the rotational axis direction Than the required inclination of the rotation axis in the optical axis direction,
When the deflector is fixed to the plurality of seating surfaces and the two contact portions are in contact with the deflector, a straight line connecting the two contact portions in the direction of the rotation axis; An angle when a straight line connecting the two contact portions intersects the optical axis direction, and an inclination of the rotation axis when the deflector is fixed to the plurality of seating surfaces in the optical axis direction. An optical scanning device characterized in that an inclination of the rotation axis in the optical axis direction obtained based on the optical axis is smaller. The positional relationship between the two seating surfaces and the two contact portions is as follows:
The angle when the straight line connecting the two seating surfaces intersects the direction orthogonal to the optical axis direction is A,
The angle when the straight line connecting the two contact portions intersects the optical axis direction is B,
The distance from the rotating shaft to one of the two seating surfaces is a1, and the distance from the rotating shaft to the other of the two seating surfaces is a2,
The distance from the rotation shaft to one of the two contact portions is b1, and the distance from the rotation shaft to the other contact portion of the two contact portions is b2.
The height difference between the two contact portions and the tip portion facing the deflector is C1,
The height difference between the two seating surfaces facing the deflector is C2,
The diameter of the seating surface facing the deflector is R,
When the flatness of the seating surface facing the deflector is D,

The optical scanning device according to claim 1, wherein the following condition is satisfied. The surface of the seating surface facing the deflector has a circular shape,
The optical scanning device according to claim 2, wherein the flatness of the seating surface is a height difference in the surface.   The contact area when the abutting portion comes into contact with the deflector is smaller than the contact area between each of the seating surfaces and the deflector when the deflector is fixed to the seating surface. The optical scanning device according to any one of claims 1 to 3.   The optical scanning device according to claim 4, wherein the contact portion is substantially point contact when contacting the deflector.   The optical scanning device according to claim 5, wherein a tip portion of the contact portion that contacts the deflector has a spherical shape.   The optical scanning device according to claim 1, wherein the two contact portions are provided symmetrically with respect to the rotation axis.   8. The height of the contact portion from the bottom of the optical box is higher than a height of the seating surface from the bottom of the optical box. Optical scanning device. A photoreceptor,
The optical scanning device according to claim 1, wherein an electrostatic latent image is formed on the photosensitive member by irradiating the photosensitive member with a light beam;
Developing means for developing an electrostatic latent image formed by the optical scanning device to form a toner image;
Transfer means for transferring the toner image formed by the developing means to a recording medium;
An image forming apparatus comprising:

Images