JP2012078378A - Optical scanner and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner and an image forming device capable of stabilizing optical performance by preventing position variation of a polygon mirror caused by heat deformation of a substrate where a polygon motor is mounted.SOLUTION: The optical scanner X includes the polygon motor 12 for rotationally driving the polygon mirror 11 which scans light irradiated from a light source and the approximately rectangular substrate 13 where the polygon motor 12 is mounted. The substrate 13 is fastened and fixed to a body 1 at least at the both ends of the longitudinal direction of the substrate 13. The body 1 has openings 2 and 3 formed on the outside of the longitudinal direction of the substrate 13 near the fastening spot of the substrate 13 and the body 1. The deformation generated due to heat expansion of the substrate 13 is absorbed through deformation of the openings 2 and 3, and the stress onto the substrate 13 is reduced, which prevents warpage.

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus in which a polygon mirror that scans light irradiated from a light source onto a photosensitive member and a polygon motor that rotationally drives the polygon mirror are housed in a casing.

An optical scanning device is mounted on an electrophotographic image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine having these functions. In the case of this optical scanning device, there are a polygon mirror (rotating polygonal mirror) that scans the laser beam emitted from the laser light source on the photosensitive member, a polygon motor (driving motor) that rotates the polygon mirror, and a polygon mirror. An optical device such as an fθ lens that forms an image of the scanned light on the photosensitive member, a light detection sensor (BD sensor) that detects the light scanned by the polygon mirror at a predetermined position in order to measure image writing timing, and the like are provided. It is done.
Conventionally, in the optical scanning device configured as described above, the housing is deformed due to heat generated by driving the polygon motor, and the positional relationship of the polygon mirror, the optical device, the BD sensor, etc. is shifted, and the laser beam irradiation is performed. The problem is that optical performance such as position accuracy deteriorates. On the other hand, for example, Patent Document 1 proposes to suppress heat transfer from the polygon motor to the optical device by providing an opening between the polygon motor and the optical device in the housing. Patent Document 2 proposes that a windshield member for blocking heat generated by the polygon motor is provided between the polygon motor and the optical device.

JP 2001-264666 A JP 2010-26233 A

By the way, in the optical scanning device, a polygon motor is mounted on a substrate, and the substrate may be fastened and fixed to the casing with screws or the like, whereby the polygon motor may be fixed to the casing. FIG. 5A is a schematic diagram showing a configuration example of such a conventional optical scanning device Y.
In the optical scanning device Y shown in FIG. 5A, the polygon motor 102 connected to the polygon mirror 101 is mounted on a rectangular substrate 103. The substrate 103 is fastened and fixed to the housing 100 by screws 201 to 204 at the four corners. The housing 100 has fθ lenses 301 to 304 for imaging light scanned by the polygon mirror 101 on the photosensitive member, and light reflected by the reflection mirrors 401a and 402a after scanning by the polygon mirror 101 at a predetermined position. Are also provided.
In the optical scanning device Y, the substrate 103 and the housing 100 may be thermally expanded due to heat generated when the polygon motor 102 is driven. If the deformation amount of the substrate 103 and the casing 100 due to the thermal expansion is different, stress (distortion) is generated in the substrate 103, and there is a possibility that the position and orientation of the polygon mirror 102 are displaced. Here, FIG. 5B shows the state remarkably for convenience. When the deformation amount due to the thermal expansion of the substrate 103 is larger than the deformation amount due to the thermal expansion of the housing 100, the fastening portion between the substrate 103 and the housing 100 moves outward as shown in FIG. As a result, the substrate 103 is warped and the polygon mirror 101 is tilted. In particular, the housing 100 of the optical scanning device is made of resin, whereas a metal substrate is often used for the substrate 103 on which the polygon motor 102 is mounted, and there is a difference in thermal expansion coefficient. Differences in deformation are likely to occur.
However, the inventions described in Patent Documents 1 and 2 are intended to suppress heat transfer from the polygon motor to the installation location of the optical device, and the polygon motor caused by the heat generated by the polygon motor. It does not consider the thermal deformation of the mounting board.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to stabilize the optical performance by preventing the position fluctuation of the polygon mirror caused by the thermal deformation of the substrate on which the polygon motor is mounted. It is an object of the present invention to provide an optical scanning device and an image forming apparatus that can perform the above.

In order to achieve the above object, the present invention comprises a drive motor for rotationally driving a rotary polygon mirror that scans light emitted from a light source, and a substantially rectangular substrate on which the drive motor is mounted. Is an optical scanning device that is fastened and fixed to the housing at least at both ends in the longitudinal direction of the substrate, wherein the housing is in the vicinity of a fastening portion between the substrate and the housing, and the longitudinal direction of the substrate. The optical scanning device is characterized by having an opening formed outside in the direction.
According to the present invention, when the substrate is deformed by the heat generated by the drive motor, the amount of deformation is absorbed by the deformation of the opening of the housing. Therefore, even when the deformation amount of the substrate and the case is different, the stress (distortion) generated in the substrate can be suppressed, and the positional deviation of the rotary polygon mirror can be prevented, and the optical performance can be stabilized. Can be made.
In particular, when the materials of the substrate and the housing are different, the thermal expansion coefficients of the substrate and the housing are different, and the difference in the amount of change in thermal expansion increases, resulting in stress (strain) generated on the substrate. Therefore, the present invention is suitable. For example, it is conceivable that the substrate is made of metal and the housing is made of resin. Of course, if the substrate and the casing are made of the same material, the coefficients of thermal expansion are the same. However, since the amount of deformation differs depending on the size and shape, it is obvious that the effects of the present invention are achieved.
Here, when the substrate is fastened and fixed to the casing at the four corners of the substrate, the opening extends over a region exceeding a corresponding range between fastening portions at both ends in the short direction of the substrate. It is desirable that it is formed. Thereby, the said fastening location of the said housing | casing is easy to deform | transform into the opening inner side of the said opening part, and is suitable for suppression of the stress (distortion) of the said board | substrate. The opening may be one or a plurality of through holes (round holes).
By the way, in the configuration further comprising the light detecting means for detecting the light irradiated to the predetermined position by the rotating polygon mirror, the light detecting means or the reflection for reflecting the light from the rotating polygon mirror to the light detecting means. It is desirable that a mirror is disposed at a position where the opening is interposed between the mirror and the drive motor. As a result, heat transfer from the drive motor to the light detection means and the installation location of the reflection mirror is suppressed by the opening, so that a shift in light detection timing by the light detection means can be prevented.
The present invention may be understood as an invention of an image forming apparatus including one or a plurality of the optical scanning devices.

  According to the present invention, when the substrate is deformed by the heat generated by the drive motor, the amount of deformation is absorbed by the deformation of the opening of the housing. Therefore, even when the deformation amount of the substrate and the case is different, the stress (distortion) generated in the substrate can be suppressed, and the positional deviation of the rotary polygon mirror can be prevented, and the optical performance can be stabilized. Can be made.

1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus Z according to an embodiment of the present invention. The principal part schematic diagram which shows schematic structure of the optical scanning device X which concerns on embodiment of this invention. The principal part schematic diagram which shows the other structural example of the optical scanning device X. FIG. The principal part schematic diagram which shows the other structural example of the optical scanning device X. FIG. The principal part schematic diagram which shows the structural example of the conventional optical scanning device Y. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
First, a schematic configuration of an image forming apparatus Z according to an embodiment of the present invention will be described with reference to FIG. The image forming apparatus Z is an electrophotographic image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine having these functions, and includes one or a plurality of optical scanning devices X described later. is there.
As shown in FIG. 1, the image forming apparatus Z includes four image forming units 51, two optical scanning devices X1, X2, an intermediate transfer belt 52, a secondary transfer device 53, a paper feeding device 54, and a fixing device 55. , And a paper discharge unit 56 and the like.
Here, the four image forming units 51 execute an image forming process of transferring toner images of four colors of black, yellow, cyan, and magenta to the intermediate transfer belt 52, respectively. They are arranged in the order of black, yellow, cyan, and magenta from the downstream side of the transfer belt 52 in the moving direction).
Each of the image forming units 51 is an image forming unit mounted on a general image forming apparatus, and in addition to a photosensitive drum 59 that carries a toner image, a charging device that charges the surface of the photosensitive drum 59, , A developing device for developing the electrostatic latent image written on the surface of the charged photosensitive drum 59 by the irradiation (exposure) of the laser beam with toner, and a toner image developed and formed on the photosensitive drum 59 by intermediate transfer A primary transfer device for transferring to the belt 52 and a cleaning device for removing toner remaining on the photosensitive drum 59 are provided.
The two optical scanning devices X1 and X2 correspond to the two image forming units 51, respectively, and are arranged below the image forming units 51. Specifically, one of the optical scanning devices X1 corresponds to the two image forming units 51 from the right and outputs laser light for writing electrostatic latent images to the photosensitive drums 59 for black and yellow. It is. The other optical scanning device X2 corresponds to the two image forming units 51 from the left, and outputs laser light for electrostatic latent image writing to the photosensitive drums 59 for cyan and magenta. . Here, since the optical scanning devices X1 and X2 are configured in the same manner, the optical scanning device X will be collectively described below. Note that a configuration in which one optical scanning device is provided corresponding to each image forming unit 51, or a configuration in which one optical scanning device is provided corresponding to four image forming units 51 is also an image according to the present invention. Other embodiments of the forming apparatus are conceivable.
The intermediate transfer belt 52 is an endless belt made of a material such as rubber or urethane, and is stretched and supported by a driving roller 57 and a driven roller 58. When the intermediate transfer belt 52 is rotationally driven by the drive roller 57, the intermediate transfer belt 52 passes between the photosensitive drum 59 and the primary transfer device, thereby causing the photosensitive drum 59 to rotate. Each toner image is sequentially transferred onto the intermediate transfer belt 52 in a superimposed manner.
The secondary transfer device 53 transfers the full-color toner image formed on the intermediate transfer belt 52 onto a recording sheet fed one by one from the paper feeding device 54. The fixing device 55 melts and fixes the toner image on the recording paper that has been transferred by the secondary transfer device 53. Then, the recording paper on which the image is formed is discharged to the paper discharge unit 56.
The image forming apparatus Z configured as described above is characterized by the configuration of the optical scanning apparatus X. Hereinafter, the configuration of the optical scanning device X will be described.

  As shown in FIG. 2, the optical scanning device X is a polygon mirror 11 (of a rotating polygon mirror) that scans laser light emitted from a laser light source (not shown) that emits laser light corresponding to two image forming units 51. An example), a polygon motor 12 (an example of a drive motor) that rotationally drives the polygon mirror 11, a substrate 13 on which the polygon motor 12 is mounted, and laser light scanned by the polygon mirror 11 Fθ lenses 21 to 24 for forming an image on the surface of the photosensitive drum 59 (see FIG. 1), BD sensors 31 and 32 for detecting laser light scanned by the polygon mirror 11, and each of these components And a housing 1 made of resin. The light that has passed through the fθ lenses 23 and 24 in the optical scanning device X is reflected by a reflection mirror (not shown) and formed on the corresponding photosensitive drum 59.

The BD sensors 31 and 32 are light detection means for detecting that a laser beam scanned by the polygon mirror 11 has been irradiated to a predetermined position in order to write an image writing timing in the image forming unit 51. It is an example. Specifically, the BD sensors 31 and 32 are arranged at positions where the laser beams reflected by the reflection mirrors 31a and 32a provided at predetermined positions on the scanning path of the laser beams by the polygon mirror 11 are incident. Yes. The reflection mirrors 31a and 32a are disposed in the vicinity of the outside of one end of the fθ lenses 23 and 24.
In the optical scanning apparatus X configured as described above, the positional accuracy of the polygon mirror 11, the fθ lenses 21 to 24, and the BD sensors 31 and 32 is important for obtaining high optical performance. The optical scanning device X according to the present embodiment is characterized in that a high optical performance can be obtained by maintaining its high positional accuracy.

The substrate 13 is a metal substrate such as iron formed in a rectangular shape and is excellent in heat dissipation. That is, since the substrate 13 is made of metal and the casing 1 is made of resin, these materials are different. The substrate 13 is fastened and fixed to the housing 1 with screws 41 to 44 at two locations in the short direction at both ends in the longitudinal direction. That is, the substrate 13 is fastened and fixed to the housing 1 at the four corners. The method for fixing the substrate 13 is not limited to screwing. Further, the substrate 13 is not limited to a rectangle but may be a substantially rectangular one formed in a long shape.
The substrate 13 has the polygon motor 12 mounted thereon, and there is a possibility that thermal deformation may occur due to heat generated by driving the polygon motor 12. Therefore, in the optical scanning device X, the housing 1 is in the vicinity of a fastening portion (screwing portion of the screws 41 to 44) between the substrate 13 and the housing 1, and in the longitudinal direction of the substrate 13. Have openings 2 and 3 formed on the outside. Specifically, each of the openings 2 and 3 is a long opening having a short direction of the substrate 13 as a long direction, as shown in FIG. It is formed over the area | region exceeding the range corresponding between the fastening locations of the both ends of a direction.
As a result, even when the substrate 13 is elongated in the longitudinal direction due to thermal expansion due to the heat generated by the drive motor 12, the amount of deformation is absorbed by the deformation of the openings 2 and 3 of the housing 1. Is done. Specifically, as shown in FIG. 2B, the fastening locations of the screws 41 to 44 can move toward the inside of the openings 2 and 3 by the deformation of the openings 2 and 3. It is. In addition, FIG.2 (b) is AA arrow sectional drawing in Fig.2 (a). At this time, the openings 2 and 3 in the housing 1 are deformed so as to be curved inward, for example.
Thus, in the optical scanning device X, the stress (strain) generated in the substrate 13 by the openings 2 and 3 is reduced. In particular, since each of the openings 2 and 3 is formed longer than the interval between the fastening portions at both ends in the short direction of the substrate 13, it becomes easy to absorb the deformation in the longitudinal direction of the substrate 13. Therefore, it is suitable for suppressing the stress (strain) of the substrate 13.

As described above, in the image forming apparatus Z and the optical scanning device X according to the embodiment of the present invention, the opening portions 2 and 3 provided in the housing 1 cause the substrate 13 to be thermally expanded. It is possible to obtain a stable optical performance by reducing the stress acting on the substrate 13 to prevent warping and preventing the polygon mirror 11 connected to the polygon motor 12 from being shifted in the scanning direction of the laser beam. it can.
Of course, it is conceivable that an opening is further formed in the vicinity of the fastening portion between the substrate 13 and the housing 1 and on the outer side in the short direction of the substrate 13. Further, each of the openings 2 and 3 is not limited to one opening, and may be constituted by one or a plurality of openings or notches. In FIG. 2, the polygon mirror 11 and the polygon motor 12 are arranged on the right side of the longitudinal center of the substrate 13, but are not limited thereto. For example, the polygon mirror 11 and the polygon motor 12 may be provided in the center of the substrate 13.

In the optical scanning device X, each of the BD sensors 31 and 32 is disposed at a position where the openings 2 and 3 are interposed between the BD sensors 31 and 32. As a result, heat transfer from the polygon motor 12 to the BD sensors 31 and 32 can be reduced by the openings 2 and 3. Therefore, deformation of the casing 1 in the vicinity of the BD sensors 31 and 32 is suppressed, and changes in the detection timing of the laser beam by the BD sensors 31 and 32, that is, the image writing timing can be prevented. For example, image defects such as color misregistration, color change, and color unevenness in a color-compatible image forming apparatus in which a plurality of color toner images are formed by the plurality of optical scanning devices X can be prevented.
Since the heat transfer is suppressed by the openings 2 and 3, it is possible to make the size of the optical scanning device X compact by bringing the BD sensors 31 and 32 closer to the polygon motor 12.
Further, as shown in FIG. 2C, the laser light reflected from the polygon mirror 11 by the reflection mirrors 31a and 32a in the vicinity of the fθ lenses 23 and 24 is further reflected toward the BD sensors 31 and 32. A configuration in which the reflection mirrors 31b and 32b are arranged near the polygon motor 12 is also conceivable. In this case, as shown in FIG. 2C, the reflection mirrors 31b and 32b are arranged so that the openings 2 and 3 are interposed between the reflection mirrors 31b and 32b and the polygon motor 12. It is desirable to suppress the influence of heat on the reflecting mirrors 31b and 32b.

As shown in FIG. 3, the substrate 13 on which the polygon motor 12 is mounted is fastened and fixed to a metal plate 14 such as iron having a size larger than that of the substrate 13 with screws 41 to 44, and the metal plate 14 is further fixed. Is also conceivable to be fastened and fixed to the housing 1 with screws 45 to 48. That is, the substrate according to the present invention is constituted by the substrate 13 and the metal plate 14. Thereby, the heat dissipation characteristic of the polygon motor 12 can be further enhanced.
The present invention can also be applied to such a configuration. Specifically, the metal plate 14 to which the substrate 13 is fixed and the casing 1 are in the vicinity of the fastening portion, and the metal It is only necessary that the openings 2 and 3 are formed outside the longitudinal direction of the plate 14. Accordingly, when the metal plate 14 is deformed by heat from the polygon motor 12, the deformation of the housing 1 is absorbed by the openings 2 and 3, and the warpage of the metal plate 14 can be prevented.
In the embodiment and the present embodiment, the case where the openings 2 and 3 are a series of openings formed in a rectangular shape as shown in FIGS. 2 and 3 has been described. For example, FIG. As shown, each of the openings 2 and 3 may have a plurality of through holes (round holes). Of course, each of the openings 2 and 3 may be one through hole.

1: Housing 2, 3: Opening 11: Polygon mirror 12: Polygon motor 13: Substrate 14: Metal plates 21 to 24: fθ lens 31, 32: BD sensors 41 to 48: Screw X: Optical scanning device

Claims (7)

A driving motor for rotating and driving a rotary polygon mirror that scans light emitted from a light source; and a substantially rectangular substrate on which the driving motor is mounted. The substrate is at least at both ends in the longitudinal direction of the substrate. An optical scanning device fastened and fixed to a housing,
The optical scanning device characterized in that the housing has an opening formed in the vicinity of a fastening portion between the substrate and the housing and outside the longitudinal direction of the substrate.   The optical scanning device according to claim 1, wherein the substrate and the housing are made of different materials.   The optical scanning device according to claim 2, wherein the substrate is made of metal and the housing is made of resin. The board is fastened and fixed to the housing at the four corners of the board,
The optical scanning device according to claim 1, wherein the opening is formed over a region exceeding a corresponding range between fastening portions at both ends of the substrate in a short direction.   The optical scanning device according to claim 1, wherein the opening is one or a plurality of through holes. Further comprising light detecting means for detecting light irradiated at a predetermined position by the rotary polygon mirror,
6. The light detection means or a reflection mirror for reflecting light from the rotary polygon mirror to the light detection means is disposed at a position where the opening is interposed between the drive motor and the light detection means. An optical scanning device according to claim 1.   An image forming apparatus comprising one or a plurality of the optical scanning devices according to claim 1.

Images