JP2008122971A - Optical writing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical writing unit designed, such that image blur and inadequate resolution caused by vibrations of a mirror are suppressed and faults such as image distortions and magnification errors, resulting from degradation in the flatness of the mirror, are prevented, and to provide an image forming apparatus. <P>SOLUTION: The optical writing unit converts image data into an optical signal, reflects a light beam, corresponding to the level of the optical signal by means of a light-returning mirror 21, thereby performing optical writing on a photoreceptor so as to correspond to the image of a document. In the light-returning mirror 21, reinforcing members 34 are jointed to the mirror face and to the sides, except the back of the mirror face along the length of the mirror 21. It is preferable that this optical writing unit be adopted as an optical writing unit for use in the image forming apparatus, that forms an electrostatic latent image on the photoreceptor by means of the optical writing unit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and an optical writing unit applicable to the image forming apparatus.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, reflected light from a document is read and optically processed to convert it into an electrical signal or an image signal. The electrical signal having the image information is optically processed using a laser diode (LD) or the like to form an image. In this case, the reflected light from the manuscript and the beam from the laser diode (LD) are folded by one or more optical folding mirrors, and then collected by a lens, and charged by a CCD (Charge Coupled Device) or An image is formed on the photosensitive drum.

  The accuracy of the light folding mirror also affects the quality of the formed image. That is, when the optical folding mirror vibrates due to vibrations of the motor, the moving body, and other vibration sources, the quality of the formed image deteriorates. Therefore, in the laser beam optical system in which the laser beam is reflected by the mirror and applied to the photosensitive member, the vibration isolating structure of the laser beam optical system mirror having a rigid plate bonded to the back surface of the mirror via an elastic bonding portion. It is known (see, for example, Patent Document 1).

  In the anti-vibration structure of the laser beam optical system mirror described in Patent Document 1, a reinforcing member 23 such as a metal plate or a glass plate is provided on a surface opposite to the reflecting surface of the mirror 21 as shown in FIG. The purpose of this is to increase the rigidity of the mirror 21, increase the resonance frequency, shift the vibration resonance point, and eliminate the vibration of the mirror 21 by bonding with, for example.

  However, the conventional example has a problem in that the reinforcing member 23 is bonded on the side opposite to the side used as the reflecting surface of the mirror 21. Usually, the float glass plate used as the mirror material has a flatness on one side that is better than the other, and the surface with the better flatness is used as the reflecting surface. When the reinforcing member 23 is bonded to the side, even if the flatness is relatively good, the glass slightly bends along the curved surface on the back side due to this bonding, and as a result, the flatness on the reflection surface side of the mirror is reduced. As a result, the image formed becomes distorted and a change in magnification occurs. In addition, due to the uneven thickness of the adhesive member such as the double-sided tape 24 and the variation in the adhesive force depending on the location, a non-uniform force is applied between the reinforcing member 23 and the mirror 21 in the thickness direction, and the surface of the mirror reflecting surface is subtly. The degree may go crazy.

Japanese Utility Model Publication No. 1-142913

  The present invention has been made to solve the above-described problems, and is a light capable of suppressing image shake and resolution failure due to mirror vibration, and preventing problems such as image distortion and magnification error due to deterioration of mirror flatness. An object is to provide a writing unit and an image forming apparatus.

  In order to solve the above-mentioned problem, the invention according to claim 1 converts image data into an optical signal, reflects a light beam according to the optical signal level by an optical folding mirror, and outputs light corresponding to an original image on a photosensitive member. An optical writing unit for writing, wherein the optical folding mirror has a reinforcing member bonded to a side surface other than the mirror surface and the back surface of the mirror surface along the longitudinal direction thereof.

  According to a second aspect of the present invention, there is provided an image forming apparatus for forming an electrostatic latent image on a photosensitive member by an optical writing unit, wherein the optical writing unit is the optical writing unit according to the first aspect. .

  According to the present invention, in the image forming apparatus such as a copying machine and the optical writing unit used therefor, the reinforcing member is provided on one or both sides of the side surface along the longitudinal direction of the optical folding mirror for folding the reflected light from the document. Since the mirror is bonded, the rigidity of the mirror can be increased and the natural vibration frequency can be increased, the occurrence of vibration due to the natural vibration of the mirror can be prevented, and compared with the case where the reinforcing material is attached to the back surface of the mirror, The flatness of the reflecting surface of the mirror can be maintained fairly accurately, and it is possible to prevent problems such as image distortion and magnification error due to deterioration in flatness while suppressing image shake and resolution failure due to mirror vibration.

Embodiments of an optical writing unit and an image forming apparatus according to the present invention will be described below with reference to the drawings.
In the scanner device 1 of the analog copying machine shown in FIG. 4, a first traveling body 100 and a second traveling body 101 are disposed below the contact glass 11 on which the document 16 is placed. The 1st traveling body 100 has the illumination lamp 14 and the 1st mirror 12-1, and the illumination lamp 14 and the 1st mirror 12-1 can move integrally. The first mirror 12-1 reflects the reflected light from the document in the horizontal direction. The second traveling body 101 includes a second mirror 12-2 and a third mirror 12-3, and the second and third mirrors 12-2 and 12-3 are movable together. . The second and third mirrors 12-2 and 12-3 are obliquely arranged so that the reflecting surfaces are perpendicular to each other, and the reflected light from the first mirror 12-1 is folded back in the horizontal direction. Thereafter, the reflected light is focused by the lens 13 and reflected by the fourth mirror 12-4 to form a latent image on the photosensitive drum 15. The latent image is visualized by a developing unit (not shown) to form an image.

  The first traveling body 100 and the second traveling body 101 are both movable in the direction of the arrow shown in FIG. 4 using a traveling body motor (not shown) as a drive source. At this time, in order to maintain a constant optical distance from the document being exposed to the photosensitive drum 15, the first traveling body 100 moves at a speed V twice that of the second traveling body 101. ing. 4 indicate the positions of the mirrors 12-1, 12-2, and 12-3 after the document 16 is scanned. The illumination lamp 14, the first to fourth mirrors 12-1, 12-2, 12-3, 12-4, and the lens 13 operate as described above.

  In the scanner device 2 of the digital copying machine as shown in FIG. 5, the light emitted from the illumination lamp 14 is reflected by the document 16, and the reflected light is reflected by the first mirror 12-1 and the second mirror 12-2. The third mirror 12-3 and the fourth mirror 12-4 are reflected in this order, and pass through the lens 13 to form an image on the photoelectric conversion surface of the CCD 17 serving as a photoelectric conversion element. The image signal of the original is taken out from the CCD 17 as an electric signal.

  The image signal converted into an electrical signal in the scanner device 2 is converted into a latent image by the optical writing unit 3 shown in FIG. The optical writing unit 3 includes a laser diode as an optical element (not shown), a light emission drive control unit (not shown), a polygon scanner 31 and a rotation motor (not shown), f / θ lenses 32-1 and 32-2, and a folding mirror 33-1. Etc. In the optical writing unit 3, the image data (which may be color image data) from the scanner 2 is converted into an optical signal, optical writing corresponding to the original image is performed, and an electrostatic latent image is formed on the photosensitive drum 15. Form. Light emitted from a laser light source (not shown) is reflected by a polygon scanner 31 that rotates at high speed, guided to lens systems 32-1 and 32-2 having an fθ function, and reflected obliquely downward by a folding mirror 33-1. An image is formed as a light beam that passes through the lens 32-3 and is reflected by the light folding mirror 33-2 to reciprocate on the photosensitive drum 15. The laser beam is ON / OFF controlled by a computer or the like according to the image signal intensity level of the read original, and an image is formed on the photosensitive drum 15.

  The optical folding mirror used in the scanner devices 1 and 2 and the optical writing unit 3 is usually configured as shown in FIG. The mirror 21 is only fixed by fixtures 25, 25 provided at both ends of the mirror in the longitudinal direction, and vibrations and the like generated in the movable parts of the scanner devices 1, 2 and the optical writing unit 3 are easily transmitted. There was a problem that the mirror 21 caused transverse natural vibration, and as a result, the formed image had an adverse effect such as shaking and defocusing.

  In the embodiment of the present invention shown in FIG. 1, the reinforcing member 34 is bonded to the side surface along the longitudinal direction of the mirror 21 by the double-sided tape 24. In the example of FIG. 1, an example in which the reinforcing member 34 is bonded to only one side surface of the mirror 21 is shown, but the reinforcing member 34 may be bonded to both side surfaces. Further, the reinforcing member 34 may be bonded to the mirror 21 with an adhesive instead of the double-sided tape 24. Thus, since the reinforcing member 34 is bonded to one side or both sides of the side surface of the optical folding mirror 21 along the longitudinal direction, the mirror rigidity can be increased, the natural vibration frequency of the mirror can be increased, and the vibration due to the natural vibration of the mirror. Can be prevented. In addition, the flatness of the reflective surface of the mirror can be maintained fairly precisely compared to the case where the reinforcing material is bonded to the back surface of the mirror as in the past, while suppressing image fluctuations and poor resolution due to mirror vibration. In addition, problems such as image distortion and magnification error due to deterioration of flatness can be prevented.

  Both the mirror 21 and the reinforcing member 34 may be made of glass, or the materials of the mirror 21 and the reinforcing member 34 may have different expansion rates, so that the materials themselves may be different. Thus, by making the expansion coefficient of the material of the mirror 21 and the reinforcing member 34 approximately the same, even if the temperature rises due to the use of the image forming apparatus, the mirror 21 is displaced due to the difference in the thermal expansion coefficient due to the difference in the thermal expansion coefficient. Deformation and adhesion peeling do not occur.

  In FIG. 1, the mirror 21 and the reinforcing member 34 are bonded with a double-sided tape 24 having elasticity. If the double-sided tape 24 that bonds the folding mirror 21 and the reinforcing member is not stretchable, the mirror 21 and the double-sided tape 24 or the reinforcing member 34 and the double-sided tape 24 may have different thermal expansion coefficients due to changes in ambient temperature. 21 and the reinforcing member 34 are displaced, and the mirror 21 is deformed or peeled off. However, by using the double-sided tape 24 having elasticity as in the present invention, the problem of the bonded portion between the mirror 21 and the reinforcing member 34 due to temperature change is eliminated.

  In the example shown in FIG. 2, the mirror 21 and one reinforcing member 34 are bonded at three locations in the mirror longitudinal direction. In this way, according to the structure in which the reinforcing members 34 are bonded at a plurality of locations in the longitudinal direction of the mirror 21, the double-sided tape 24 is attached to the entire surface of the reinforcing member 34 as shown in FIG. Compared with the case where the adhesive is bonded, the bonding area can be reduced, and further, the bonding between the mirror 21 and the double-sided tape 24 or the reinforcing member 34 and the double-sided tape 24 due to the difference in thermal expansion coefficient or adhesion peeling It is possible to make the defect of the part less likely to occur. The bonding location can be changed as appropriate depending on the size of the mirror.

  The optical folding mirror structure used in the present invention is applicable not only to a fixed mirror but also to a movable mirror. For example, in the example of FIGS. 1 and 2, the first to fourth mirrors 12-1, 12-2, 12-3, 12-4, and the folding mirrors 33-1 and 33-2 in FIG. it can.

It is a perspective view which shows the example of the optical folding mirror applied to the optical writing unit and image forming apparatus concerning this invention. It is a perspective view which shows another example of the optical folding mirror applied to the optical writing unit and image forming apparatus concerning this invention. It is a side view which shows the Example of the image forming apparatus concerning this invention to which the said optical folding mirror is applied. It is a side view which shows an example of the scanner apparatus to which the said optical folding mirror is applied. It is a side view which shows another example of the said scanner apparatus. It is a perspective view which shows an example of the conventional optical folding mirror. It is a side view which shows another example of the conventional optical folding mirror.

Explanation of symbols

21 Optical Folding Mirror 24 Double-sided Tape 34 Reinforcing Member

Claims (2)

An optical writing unit that converts image data into an optical signal, reflects a light beam according to the optical signal level by an optical folding mirror, and performs optical writing corresponding to the original image on the photosensitive member,
The optical writing unit according to claim 1, wherein a reinforcing member is bonded to a side surface other than the mirror surface and the back surface of the mirror surface along the longitudinal direction. 2. An image forming apparatus for forming an electrostatic latent image on a photosensitive member by an optical writing unit, wherein the optical writing unit is the optical writing unit according to claim 1.

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