Patent Application
20140071508
The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2012-197760 filed in Japan on Sep. 7, 2012, Japanese Patent Application No. 2013-073110 filed in Japan on Mar. 29, 2013 and Japanese Patent Application No. 2013-143579 filed in Japan on Jul. 9, 2013.
1. Field of the Invention
The present invention relates to an optical device with a reflecting mirror as a long mirror, an optical scanning device, and an image forming apparatus.
2. Description of the Related Art
An optical scanning device used in an electrophotographic image forming apparatus employs an optical device that includes a reflecting mirror as a long mirror used to direct a light beam emitted from a light source to an image carrier. The optical scanning device, however, is installed in the body of the image forming apparatus, and therefore the reflecting mirror is shaken by vibration of a drive system of the image forming apparatus body. Consequently, the optical scanning device has a problem of uneven image density, so-called banding, due to displacement of an image location of the light beam on the image carrier. Therefore, a technology has been known in which a drive frequency of the image forming apparatus body and a resonance point of the reflecting mirror are displaced from each other and the vibration of the reflecting mirror is suppressed by attaching a vibration damping material to the reflecting mirror or by pressing the reflecting mirror with a plate spring. In addition, Japanese Laid-open Patent Publication No. 11-142767 discloses a countermeasure against vibration of a reflecting mirror by increasing the strength and the volume of the reflecting mirror by bonding a mirror reinforcing member to the reflecting mirror for the purpose of suppressing the vibration of the reflecting mirror and preventing the banding.
In the conventional countermeasures against the vibration by attaching the vibration damping material to the reflecting mirror or pressing the reflecting mirror with the plate spring, it is required to change a natural frequency of the reflecting mirror according to a device or a model because a drive frequency of the drive system of the image forming apparatus body changes depending on the device or the model. Therefore, the shape of the vibration damping material or the pressing force of the plate spring has to be changed, which makes it difficult to change the natural frequency of the mirror appropriately. In addition, troublesome attachment of the vibration damping material to the reflecting mirror and an increase in the number of components of the vibration damping material or of the plate spring cause a cost increase.
In Japanese Laid-open Patent Publication No. 142767, the vibration of the reflecting mirror can be suppressed, but the natural frequency of the mirror cannot be changed appropriately according to a drive frequency of the drive system of the image forming apparatus body. In addition, because the mirror reinforcing material is bonded to the reflecting mirror, the troublesome task and the increase in the number of components lead to the cost increase.
Therefore, there is a need to provide an optical device capable of easily changing a natural frequency and a vibration mode and having a low-cost new vibration damping structure without requiring troublesome task, an optical scanning device, and an image forming apparatus.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to an embodiment, an optical device that includes a long mirror; a mirror pressing member configured to fix the long mirror; a mirror-reflective-surface receiving member configured to be in contact with a reflective surface of the long mirror; and at least two mirror receiving members configured to be in contact with a face other than the reflective surface of the long mirror in a mirror longitudinal direction so that a distance between the mirror receiving members in the mirror longitudinal direction is variable.
According to another embodiment, an optical device that includes a long mirror; a mirror pressing member configured to fix the long mirror; a mirror-reflective-surface opposite-face receiving member configured to be in contact with an opposite face to a reflective surface of the long mirror; and at least two mirror receiving members configured to be in contact with a face other than the reflective surface of the long mirror in a mirror longitudinal direction so that a distance between the mirror receiving members in the mirror longitudinal direction is variable.
According to still another embodiment, an optical scanning device that includes the optical device according to any one of the above embodiments; a light source; an imaging optical element configured to condensing light emitted from the light source; a rotary deflector configured to rotationally change the light emitted from the light source; and a scanning optical element configured to scan the deflected light. The long mirror of the optical device is configured to guide the scanned light to an image carrier.
According to still another embodiment, an image forming apparatus that includes the optical scanning device according to the above embodiment.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Embodiments of the present invention has characteristics as follows when vibration of the reflecting mirror as the long mirror provided in the optical device is to be suppressed. In other words, the embodiments are characterized in that when the reflecting mirror is held, the mirror receiving member for receiving the reflective surface of the reflecting mirror or a face other than the opposite face to the reflective surface of the long mirror in the mirror longitudinal direction is provided in at least two locations in the mirror longitudinal direction, a distance between the mirror receiving members can be changed, and the distance between the mirror receiving members is changed to thereby change the mirror vibration frequency and the vibration mode of the reflecting mirror.
Exemplary embodiments of the present invention will be explained below with reference to the accompanying drawings.
Arranged inside the optical housing 1 are a light source 2 that emits a light beam 5, a condenser lens (cylindrical lens) 3 serving as an imaging optical element for condensing the light beam 5 emitted from the light source 2, and a polygon motor 4 serving as a rotating polygon mirror for rotationally deflecting the condensed light beam 5. The light beam 5 emitted from the light source 2 and condensed by the condenser lens 3 is deflected by the polygon motor 4 rotating around its axis.
Arranged inside the optical housing 1 are also a plurality of scanning optical lenses 6 and 7 for scanning the deflected light beam 5 and a plate-like reflecting mirror 8 as a long mirror for guiding the scanned light beam 5 to a photoreceptor 111 as an image carrier. An opening 1A is formed in the optical housing 1 in a traveling direction of the light beam 5 reflected by the reflecting mirror 8. A dustproof glass (not shown) is provided in the optical housing 1 so as to cover the opening 1A, and the dustproof glass is held by a dustproof-glass holding member (not shown) for holding the dustproof glass.
Therefore, the deflected light beam 5 is scanned by the scanning optical lenses 6 and 7, is reflected by the reflecting mirror 8, and is guided from the opening 1A formed in the optical housing 1 to the photoreceptor 111 being the image carrier.
In the present embodiment, the scanning optical system is formed with the lens system; however, it may be formed with reflective optics, or may be formed in combination of the lens system and the reflective optics.
As shown in
As shown in
As shown in
The mirror edge line 15 of the reflecting mirror 8 is pushed by the arm portions 9a of the mirror pressing member 9 in the direction of arrow Y, and the mirror bottom end face 16 is thereby pressed against at least two of the mirror receiving members 17a to 17f formed in the optical housing 1 and is held. The mirror bottom end face 16 is a face adjacent to the reflective surface 8a of the reflecting mirror 8. Because the reflecting mirror 8 is pushed herein from up to down, a face adjacent to the reflective surface 8a (a face other than the reflective surface) becomes the mirror bottom end face 16. However, when its layout is such that the pushing direction is, for example, from down to up, a face adjacent to the reflective surface 8a (a face other than the reflective surface) becomes the mirror top end face 8c.
As shown in
In these embodiments, the same components are used for the two mirror pressing members 9; however, for example, different components may be used at two locations. In the embodiments, the mirror pressing member 9 is used at the two locations; however, the number of locations is not necessarily two and therefore the number of the mirror pressing members 9 to be used may be changed as needed. In the embodiments, the reflecting mirror 8 and the mirror pressing member 9 are assembled at two locations. With this structure, the reflecting mirror 8 is positioned in the optical housing 1 and is held. In the embodiments, the mirror pressing members 9 are fastened to the protrusions 101 and 102 in the optical housing 1 by screws 12 as shown in
As shown in
How to receive the mirror bottom end face 16 of the reflecting mirror 8 will be explained below with reference to
To support the mirror bottom end face 16 by at least two locations out of six locations of the mirror receiving members 17a to 17f, the mirror receiving members 17b and 17e are protruded more than the other mirror receiving members 17a, 17c, 17d, and 17f in the direction of arrow J (toward the mirror bottom end face 16). In other words, the inclined end faces 17 of the mirror receiving members 17b and 17e are protruded more than the inclined end faces of the other mirror receiving members toward the mirror bottom end face 16 side. Therefore, only two points of the inclined end faces 17 and 17 of the mirror receiving members 17b and 17e come in contact with the mirror bottom end face 16. In this case, the mirror receiving members 17a, 17c, 17d, and 17f serve as auxiliary mirror receiving members.
The optical scanning device 100 is installed in the body 201, and therefore there may be a case in which the natural frequency of the reflecting mirror 8 is desired to be changed depending on the drive frequency of the drive system of the image forming apparatus 200. In this case, the receiving positions, where the reflecting mirror 8 is usually received by the inclined end faces 17 and 17 of the mirror receiving members 17b and 17e, are changed. However, at that time, by using a simple structure such that a spacer 18 thicker than a protruded amount T of the mirror receiving members 17b and 17e as shown in
In the present embodiment, the inclined end faces 17 of the mirror receiving members 17b and 17e are protruded more than the inclined end faces of the mirror receiving members 17a, 17c, 17d, and 17f; however, it is preferable to arbitrarily determine the position of any mirror receiving member to be protruded depending on the drive frequency of the drive system of the image forming apparatus 200 and a mirror drive frequency of the reflecting mirror 8.
The spacer 18 is held by the elastic force of the mirror pressing members 9 (held by the two mirror receiving members and the reflecting mirror 8); however, the spacer 18 may be held by using an adhesive material to bond the spacer 18 to the two mirror receiving members or to the mirror bottom end face 16.
The receiving positions of the mirror bottom end face 16 by the two mirror receiving members are changed by placing the spacer 18 between the mirror bottom end face 16 and the two mirror receiving members; however, each protruded amount of the positions of the mirror receiving members is adjusted through machine processing, and the receiving positions of the mirror bottom end face 16 by the two mirror receiving members may thereby be changed. Alternatively, by installing a mechanical mechanism capable of changing a protruded amount at each of the positions of the mirror receiving members, the protruded amount can be adjusted, and the receiving positions of the mirror bottom end face 16 by the two mirror receiving members may thereby be changed.
Distances of the mirror receiving members 17a to 17f in the mirror longitudinal direction will be explained below with reference to
Respective centers of the mirror receiving members 17a and 17f which are both ends and are arranged on the outermost sides in the mirror longitudinal direction are located at positions 15 mm inward from end faces 80a and 80b of the reflecting mirror 8 at both ends in the mirror longitudinal direction. Respective centers of the mirror receiving members 17b and 17e are located at positions 50 mm inward of the reflecting mirror 8 from the mirror receiving members 17a and 17f, respectively. Respective centers of the mirror receiving members 17c and 17d are located at positions 50 mm inward of the reflecting mirror 8 from the mirror receiving members 17b and 17e, respectively. A center distance between the mirror receiving members 17c and 17d (distance between the receiving members) is set to 65 mm. In the present embodiment, the mirror receiving members 17a to 17f are arranged at the positions of the optical housing 1 as represented in the above manner; however, the length of the reflecting mirror 8 in the longitudinal direction and the layout of the mirror receiving members 17a to 17f are preferably changed so that the reflecting mirror 8 will obtain a desired natural frequency. In other words, the distance between the receiving positions is preferably changed.
In the present embodiment, because the structure is such that the mirror bottom end face 16 is received by the two inclined end faces of the mirror receiving members 17b and 17e, the distance between the mirror receiving members 17b and 17e becomes 165 mm. As explained in the way to receive the end face of the reflecting mirror in
The experimental conditions of Experiment 1 are such that the mirror receiving member is two points of the mirror receiving members 17b and 17e and the distance between the end-face receiving members at that time is 165 mm. Under the conditions of Experiment 1, the mirror vibration frequency of the reflecting mirror 8 becomes 455 Hz, and the vibration mode of the reflecting mirror 8 shows that an antinode of the vibration occurs at near the center of the mirror longitudinal direction.
The experimental conditions of Experiment 2 are such that the mirror receiving member is two points of the mirror receiving members 17a and 17f and the distance between the end-face receiving members at that time is 265 mm. Under the conditions of Experiment 2, the mirror vibration frequency of the reflecting mirror 8 becomes 245 Hz, and it is found that it is largely changed from the mirror vibration frequency of 455 Hz in the case of Experiment 1. The mirror vibration mode remains the same as the result of Experiment 1 and shows that an antinode of the vibration occurs at near the center of the mirror longitudinal direction.
The experimental conditions of Experiment 3 are such that the mirror receiving member is two points of the mirror receiving members 17a and 17d and the distance between the end-face receiving members at that time is 165 mm. Under the conditions of Experiment 3, the mirror vibration frequency of the reflecting mirror 8 becomes 452 Hz, which is a similar value to the mirror vibration frequency of 455 Hz as a result of Experiment 1. In addition, the mirror vibration mode represents that the position where the end face is received becomes a node of the vibration and an antinode of the vibration occurs at two locations, and shows that the mirror vibration mode is changed from that as the results of Experiments 1 and 2.
As explained above, when the reflecting mirror 8 is to be held, by changing the receiving positions of the mirror bottom end face 16 by at least two mirror receiving members, i.e., by changing the distance of the mirror receiving members 17a to 17f and the receiving positions of the mirror bottom end face 16, the mirror vibration frequency and the mirror vibration mode of the reflecting mirror 8 can be easily changed. Therefore, only by changing the holding positions (support positions) of the reflecting mirror 8, the natural frequency and the vibration mode of the reflecting mirror 8 can be easily changed, and the vibration of the reflecting mirror 8 can also be prevented without the troublesome attachment of the vibration damping material to the reflecting mirror 8 and the occurrence of cost for another member such as a plate spring.
A structure in which the mirror receiving members are formed as different components from the optical housing 1 and the positions of the inclined end faces 17 can be changed to those in the mirror longitudinal direction will be explained below with reference to
As shown in
In this way, by forming the base 171 in the mirror receiving member 170 and forming the rail portion 1B in the optical housing 1, the position of the mirror receiving member 170 (end face 17) can be easily moved, so that the distance between the mirror receiving members 170 and 170 and the positions thereof can be changed. This enables the natural frequency of the reflecting mirror 8 to be changed. Therefore, the mirror receiving member 170 does not have to be provided in a plurality of locations as shown in
When the mirror receiving members 17a to 17f are formed integrally with the optical housing 1 as shown in
A fixing structure of the mirror receiving member to the optical housing 1 will be explained below with reference to
As shown in
In this way, by forming the fixing screw holes 1C in the mirror longitudinal direction, the positions and the distance of the mirror receiving members 170 are changed so that the mirror natural frequency becomes a desired value, and the mirror receiving members 170 can thereby be fastened thereto.
The base 171 of the mirror receiving member 170 can be attached and fixed to the optical housing 1, as shown in
The way to fix the mirror receiving member 170 to the optical housing 1 is not limited to the screw. As shown in
The configuration of the image forming apparatus 200 will be explained below with reference to
The image forming apparatus 200 forms monochrome images, and various components are attached to the apparatus body 201. The photoconductive photoreceptor 111 as an image carrier that is a body of a surface to be scanned is formed into a drum shape, is made to rotate clockwise at a constant speed, is uniformly charged by a charging roller 112 being a charging unit, and is optically scanned by the optical scanning device 100, so that a negative electrostatic latent image is written onto the photoreceptor 111.
The written electrostatic latent image is reversely developed by a developing device 113 to form a toner image. Pieces of transfer paper P being sheet-type recording media are stacked and stored in a cassette 118, and each of them is fed by a paper feed roller 120 and a trailing edge thereof is held by a registration roller 119. The registration roller 119 synchronizes the movement of the toner image formed on the photoreceptor 111 with the transfer paper P to feed the transfer paper P to a transfer unit.
In the transfer unit, a transfer roller 114 being a transferring unit transfers the toner image on the photoreceptor 111 onto the transfer paper P. The transfer paper P with the transferred toner image is fed into a fixing device 116 where the toner image is fixed, and is ejected onto a tray 123 by an ejection roller 122. The photoreceptor 111 after the toner image is transferred is cleaned by a cleaner 115, and residual toner and paper dust are removed therefrom.
Any one of the optical scanning devices described in the above explained specific examples is used as the optical scanning device 100, so that uneven image density (banding) occurring due to displacement of an image location of the light beam on the photoreceptor 111 can be suppressed at a low cost with such a simple configuration that the holding positions of the reflecting mirror 8 are changed. Thus, satisfactory monochrome images with less uneven image density can be formed.
The scope of application of the optical scanning device 100 according to the embodiments is not limited to the monochrome image forming apparatus. Therefore, it goes without saying that the present invention may be applied to any image forming apparatus that forms color images using developers of yellow, magenta, cyan, and black. In this case, four optical scanning devices 100 are installed in the image forming apparatus body according to the colors, and therefore the same advantageous effects as these of the present invention can be obtained. However, if the four optical scanning devices 100 are simply installed therein, the apparatus is upsized, and therefore the configuration as follows is preferable because by symmetrically arranging optical devices 20 with respect to the polygon motor 4, the optical devices 20 are stored in one optical housing 1 and by arranging a plurality of light sources 2 corresponding to the number of colors (four in this case) of the developers, the number of optical scanning devices 100 to be installed can be reduced.
The image forming apparatus includes, but not limited to, a copier, a printer, a facsimile, and a multifunction product of these devices, so that it can correspond to an electrophotographic type or an ink jet type as an image formation type.
According to the embodiments, the mirror receiving member that receives a face other than the reflective surface of the long mirror in the longitudinal direction or the opposite face to the reflective surface thereof is provided at least two locations in the mirror longitudinal direction and the distance between the mirror receiving members can be changed. Therefore, when the long mirror is to be held, the distance and the receiving positions of at least two points of the mirror receiving members are changed to thereby enable to change the mirror vibration frequency and the mirror vibration mode of the long mirror. Because of this, only by changing the long-mirror holding positions, the natural frequency and the vibration mode of the mirror can be easily changed and the vibration of the long mirror can also be prevented without the troublesome attachment of the vibration damping material to the long mirror and the occurrence of cost for another member such as a plate spring.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-197760 | Sep 2012 | JP | national |
| 2013-073110 | Mar 2013 | JP | national |
| 2013-143579 | Jul 2013 | JP | national |
