Attachment mechanism of optical scanner and image forming apparatus

An attachment mechanism of an optical scanner includes a supporting structure with an opening and a fixing member. The fixing member positions and fixes the optical scanner with a positioning boss held by the opening. The fixing member includes an annular part having an outer circumference face fitted in the opening and an internal circumference face fitted on the positioning boss. One of the internal circumference face and an outer circumference face of the positioning boss includes a projection and another includes a depression for insertion of the projection. A top face of the projection and/or a bottom face of the depression slope(s) slanted from the circumference. By inserting the positioning boss in the opening, fitting the annular part in the opening, and turning the fixing member to narrow a gap between the top face and bottom face, the optical scanner is fixed to the supporting structure.

INCORPORATION BY REFERENCE

This application is based on and claims the benefit of priority from Japanese Patent application No. 2012-118484 filed on May 24, 2012, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to an attachment mechanism of an optical scanner in an image forming apparatus, such as a copying machine, a printer or a multifunction machine, and the image forming apparatus.

An image forming apparatus typified by a copying machine, a printer or a multifunction machine is provided with a unit structure. In the unit structure, to a frame as a supporting structure arranged inside the image forming apparatus, a laser scanning unit (LSU) as an optical scanner is positioned and fixed.

As positioning and fixing parts of the LSU to the frame, for example, as shown inFIG. 9, it is well-known that an image forming apparatus is configured to fix LSUs40arranged for respective colors of four types of toners (developers) to a rectangular-liked frame42by fixing members41. In detail, as shown inFIG. 10, on one side face of each LSU40in a longitudinal direction, a pair of positioning bosses43with round-shaped sections are formed. In the frame42, openings44(refer toFIG. 11) capable of insertion of the positioning bosses43are formed. Moreover, the fixing member41is formed in a horizontally long rectangular plate-liked shape and, in an upper part of the fixing member41, a pair of annular parts45aand45bare formed side by side.

In a lower part of one annular part45a, as shown inFIG. 11, a back extending part46extending backward is formed and an outer circumference face of the back extending part46is configured to be capable of fitting to an internal circumference face of the opening44. In addition, on internal circumference faces of both annular parts45aand45b, a plurality of ribs47projected slightly inward are formed and the ribs47are configured to be capable of fitting to outer circumference faces of the positioning bosses43. On a back face of the fixing member41, a projection48is provided outside and adjacent to the other annular part45band configured to capable of fixing a penetrating hole49correspondingly bored adjacent to the opening44of the frame42.

Under such a configuration, in a situation of holding the positioning bosses43of the LSUs40by the openings44of the frame42, the projection48is inserted in the penetrating hole49and the annular parts45aand45bare inserted between the positioning bosses43and the openings44. Then, the outer circumference face of the back extending part46is fitted to the internal circumference face of the opening44and the ribs47are fitted to the outer circumference faces of the positioning bosses43. Thus, after the positioning bosses43and annular parts45are positioned, the LSUs40are fixed to the frame42by screws50and a header pin51(refer toFIG. 10).

However, in the above-mentioned positioning and fixing parts, as shown inFIG. 12, transverse sections of respective opposite faces of the rib47and positioning boss43are formed in a straight line-liked shape. Therefore, when accuracy of these dimensions becomes uneven, a groove between these is caused to increase backlash in the attachment. Thereby, it is fear that accuracy of positioning the LSU is decreased and that, under the influence of oscillation, an image error is caused.

In addition, as other positioning and fixing parts for the LSU, another image forming apparatus is configured, when the LSU is located on an active position, to put a pair of left and right positioning axes in contact with positioning grooves of left and right side plates and to put a supporting projection in contact with a rear sideplate. Subsequently, in a situation of putting the LSU in non-contact with a rotating axis, the LSU is supported to an apparatus main body. In a further image forming apparatus, the LSUs are located side by side between a front side plate and the rear side plate and partitioned by a stay fixed between the front side plate and rear side plate. Moreover, an attachment member is attached between the side plates and the stay is also fixed to the attachment member. Subsequently, the attachment member is rotated in a situation of being applied to a stopper, thereby bringing the positioning of the attachment member.

However, in these techniques, it is fear that accuracy of dimensions of components becomes uneven to decrease accuracy of positioning the LSU.

Moreover, in a furthermore image forming apparatus, after a position adjusting part adjusts a positioning gap of an LSU attached to a block, the block with the positioning adjusted LSU is installed to a frame.

However, this technique requires labor and equipment for the positioning in separate process from the attachment.

SUMMARY

In accordance with an embodiment of the present disclosure, an attachment mechanism of an optical scanner includes a supporting structure and a fixing member. In the supporting structure, an opening is formed. The fixing member is configured to position and fix the optical scanner in which a positioning boss held by the opening is formed. The fixing member also includes an annular part having an outer circumference face capable of fitting in the opening and an internal circumference face capable of fitting on the positioning boss. One of the internal circumference face of the annular part and an outer circumference face of the positioning boss includes a projection and another includes a depression capable of insertion of the projection. At least one of a top face of the projection and a bottom face of the depression slopes to one side on the circumference of the annular part and positioning boss. In a situation of inserting the positioning boss in the opening, by fitting the annular part in the opening and by turning the fixing member in a direction of narrowing a gap between the top face of the projection and bottom face of the depression, the optical scanner is fixed to the supporting structure.

In accordance with an embodiment of the present disclosure, an image forming apparatus includes an attachment mechanism of an optical scanner. The attachment mechanism includes a supporting structure and a fixing member. In the supporting structure, an opening is formed. The fixing member is configured to position and fix the optical scanner in which a positioning boss held by the opening is formed. The fixing member also includes an annular part having an outer circumference face capable of fitting in the opening and an internal circumference face capable of fitting on the positioning boss. One of the internal circumference face of the annular part and an outer circumference face of the positioning boss includes a projection and another includes a depression capable of insertion of the projection. At least one of a top face of the projection and a bottom face of the depression slopes to one side on the circumference of the annular part and positioning boss. In a situation of inserting the positioning boss in the opening, by fitting the annular part in the opening and by turning the fixing member in a direction of narrowing a gap between the top face of the projection and bottom face of the depression, the optical scanner is fixed to the supporting structure.

DETAILED DESCRIPTION

First, with reference toFIG. 1, the entire structure of a color printer1as an image forming apparatus will be described, which is provided with a unit structure27as an attachment mechanism having a laser scanning unit (LSU)9as an optical scanner fixed to a frame26. Hereinafter, it conveniently will be described so that the front side of each component is positioned at the front-hand side ofFIG. 1.FIG. 1is a schematic diagram schematically showing the color printer according to an embodiment of the present disclosure. The reference characters “Y”, “C”, “M” and “K” appeared suitably in the specification and figure indicate colors of yellow, cyan, magenta and black.

The color printer1includes a box-formed case2. In a lower part of the case2, a sheet feeding cartridge3configured to store sheets for transferring (not shown) is installed and, in an upper part of the case2, an ejected sheet tray4is formed.

In the upper part of the case2, an intermediate transferring belt5as an image carrier is bridged over a plurality of rollers. Below the intermediate transferring belt5, an exposure device10is installed. The exposure device10consists of four laser scanning units (LSU)9(Y),9(C),9(M) and9(K) (hereinafter, collectively indicated by “LSU9”) arranged for respective colors of toners (developers). Along a lower part of the intermediate transferring belt5, four image forming units6(Y),6(C),6(M) and6(K) (hereinafter, collectively indicated by “image forming unit6”) are installed for respective colors of toners.

One of the four image forming units will be described. In each image forming unit6, a photosensitive drum7is rotatably attached. Around the photosensitive drum7, a charger8, a development device11, a first transferring unit12, a cleaning device13and a static eliminator14are located.

In a lower part of the development device11, a pair of stirring rollers15are installed, diagonally above of the stirring rollers15, a magnetic roller16is installed and, diagonally above of the magnetic roller16, a developing roller17is installed. Above the development device11, four containers18(Y),18(C),18(M) and18(K) (hereinafter, collectively indicated by “container18”) as toner cases corresponding to the image forming units6are installed for respective colors of the toners.

At one side (the right-hand side of the figure) in the case2, a sheet conveying path20of the sheet is arranged. At an upper stream end of the conveying path20, a sheet feeder21is positioned. At an intermediate stream part of the conveying path20, a second transferring unit22is positioned in contact with one end (a right end of the figure) of the intermediate transferring belt5. At a lower stream part of the conveying path20, a fixing unit23is positioned and, at a lower stream end of the conveying path20, an ejection opening24is positioned.

Next, the operation of forming an image by the color printer1having such a configuration will be described. When the power is supplied to the color printer1, various parameters are initialized and initial determination, such as temperature determination of the fixing unit23, is carried out. Subsequently, in the color printer1, when image data is inputted and a printing start is directed from a computer or the like connected with the color printer1, image forming operation is carried out as follows.

First, the surface of the photosensitive drum7is electrically charged by the charger8. Then, exposure corresponding to the image data on the photosensitive drum7is carried out by a laser (refer to arrow P) from the exposure device10, thereby forming an electrostatic latent image on the surface of the photosensitive drum7. The electrostatic latent image is developed to a toner image having a correspondent color with the toner in the development device11. The toner image is first-transferred onto the surface of the intermediate transferring belt5in the first transferring unit12. The above-mentioned operation is repeated in order by the image forming units6, thereby forming the toner image having full color onto the intermediate transferring belt5. Toner and electric charge remained on the photosensitive drum7are eliminated by the cleaning device13and static eliminator14.

On the other hand, the sheet fed from the sheet feeding cartridge3or a manual bypass tray (not shown) by the sheet feeder21is conveyed to the second transferring unit22in a suitable timing for the above-mentioned image forming operation. Then, in the second transferring unit22, the toner image having full color on the intermediate transferring belt5is second-transferred onto the sheet. The sheet with the second-transferred toner image is conveyed to a lower stream on the conveying path20to enter the fixing unit23, and then, the toner image is fixed on the sheet in the fixing unit23. The sheet with the fixed toner image is ejected from the ejection opening24onto the ejected sheet tray4.

Next, the unit structure27configured to position and fix the above-mentioned LSUs9to the frame26as a supporting structure by fixing members25will be described. As shown inFIGS. 1 and 2, the unit structure27includes the four LSUs9, frame26and fixing members25. In the LSUs9, positioning bosses28are formed. In the frame26, openings29holding the positioning bosses28are formed. The fixing members25respectively positions and fixes the LSUs9to the frame26.

One of the four LSUs will be described. The LSU9is formed in a longitudinal box-liked shape. As shown inFIG. 2, in a front side (one side) of the LSU9in the longitudinal direction, a pair of positioning bosses28are formed side by side. The positioning bosses28are formed in a cylinder-liked shape. On the other hand, in a rear side (another side) of the LSU9in the longitudinal direction, other positioning bosses not shown are formed.

On an outer circumference face of the positioning boss28, as shown inFIGS. 3-6, groove-liked depressions30are formed to extend from a top edge of the positioning boss28backward. In the embodiment, the depressions30are respectively arranged at three positions on the outer circumference face of each positioning boss28. The depressions30are also located at equal intervals in a circumferential direction of each positioning boss28. A bottom face30aof the depression30slopes upward in a clockwise direction in a front view. That is, the depth of the depression30gradually shallows in the clockwise direction in the front view.

The frame26is attached, as shown inFIG. 1, inside the case2. This frame26is configured, as shown inFIG. 2, in a rectangular frame-liked shape in a planer view by a front side plate31, a rear side plate, a right side plate and a left side plate (not shown). An upper end and a lower end of the front side plate31are bent forward (laterally). In the bending part of the upper end of the front side plate31, the openings29capable of insertion of the positioning bosses28are formed in shapes and a positions respectively corresponding to the positioning bosses28. The opening29is formed by a cut-out over the bending part of the front side plate31. An inside diameter of the opening29is determined greater than an outside diameter of the positioning boss28. On the other hand, in the rear side plate, other openings (not shown) capable of insertion of the other positioning bosses in the rear side of the LSU9in the longitudinal direction is formed.

The fixing member25is formed, as shown inFIGS. 3 and 7, in a shape liked a plate which has a lower end cut out inward at both sides. In a lower part of the fixing member25, a penetrating hole34capable of insertion of a screw33(refer toFIGS. 2 and 8B) is bored, while, in an upper part of the fixing member25, a cylinder-liked annular part35is formed. An upper part of the annular part35is configured to protrude from an upper end of the fixing member25, and, in a lower part of the annular part35, a half cylinder-liked back extending part35a(refer toFIG. 3) extending backward is formed. An outer circumference face of the back extending part35ais configured in the dimensions capable of fitting to an internal circumference face of the opening29. In addition, an internal circumference face of the annular part35is configured in the dimensions capable of fitting to an outer circumference face of the positioning boss28.

On the internal circumference face of the annular part35, projections36insertable in the depressions30of the positioning boss28are formed. In the embodiment, the projections36are arranged at three positions on the internal circumference face of the annular part35corresponding to the depressions30and the projections36are located at equal intervals in a circumferential direction. A top face36aof the projection36slopes downward in the same direction as the bottom face30aof the depression30(the clockwise direction) in the front view. That is, the height of the projection36gradually lowers in the clockwise direction in the front view of the annular part35.

Next, a procedure for constructing the unit structure in such a configuration will be described. In the above-mentioned configuration, first, in a situation of inclining a front part of the LSU9upward, the other positioning bosses at the rear side of the LSU9are inserted in the openings of the rear side plate inside the frame26. Subsequently, around the inserted parts as a fulcrum, the front part of the LSU9is turned downward so as to lay down the LSU9, thereby inserting the positioning bosses28at the front side of the LSU9from above into the openings29of the front side plate32of the frame26.

In such an inserting situation, faces of the fixing members25at the sides of the back extending parts35aare faced against the frame26and the fixing members25are inclined in a counterclockwise direction around the annular parts35in the front view. In such postures of the fixing members25, the annular parts35are put on the positioning bosses28insertionally so as to match each depression30with each projection36. At that time, the outer circumference face of each positioning boss28guides the internal circumference face of each annular part35. Thereby, as shown inFIG. 8A, the back extending part35aof the annular part35is positioned between the outer circumference face of the positioning boss28and internal circumference face of the opening29.

Subsequently, the annular part35is pushed further, and simultaneously, the fixing member25is turned in the clockwise direction in the front view (this turning direction is indicated by a reference character A). Accordingly, the outer circumference face of the back extending part35ais fitted to the internal circumference face of the opening29and a gap between the top face36aof the projection36and bottom face30aof the depression30is closed. Thereby, the internal circumference face of the annular part35is fitted on the outer circumference face of the positioning boss28. Thereafter, as shown inFIG. 8B, the screw33is inserted in the penetrating hole34and the screw33is screwed to a tapped hole26a(refer toFIG. 8A) of the frame26. Thereby, the LSU9is positioned and fixed to the frame26by the fixing member25.

In the embodiment, both the top face36aof the projection36and bottom face30aof the depression30slope in the same direction on the respective circumferences in the front view. Accordingly, even if accuracy of the dimensions of the annular part35and positioning boss28become uneven, by turning the fixing member in a direction of narrowing a gap between the top face of the projection and bottom face of the depression, the top face of the projection is fastened to the bottom face of the depression. It is therefore possible to fit the annular part and positioning boss to each other without any gap. Thereby, it is possible to fix the optical scanner to the supporting structure with great accuracy of the positioning. As a result, without requiring any separate positioning part and positioning process, it is possible to restrain backlash in the construction, to increase the accuracy of the positioning of the LSU9to the frame26and to restrain an image error depending on the influence of oscillation. In addition, because a slidingly contact area of the top face36aof the projection36and bottom face30aof the depression30is increasing, it is possible to securely position and fix the LSU9to the frame26.

On the internal circumference face of the annular part35, the projections36are arranged at three positions at equal intervals in the circumferential direction and, on the outer circumference face of the positioning boss28, the depressions30are arranged, according to the projections36, at three positions at equal intervals in the circumferential direction. Therefore, because the positioning boss28can be positioned and fixed over the entire circumference, it is possible to more increase the accuracy of the positioning of the LSU9to the frame26.

In the LSU9, a pair of the positioning bosses28are arranged side by side and a pair of the fixing members25are respectively provided according to the positioning bosses28. Therefore, because the positioning bosses28can be separately positioned, it is possible to furthermore increase the accuracy of the positioning of the LSU9to the frame26.

The above-mentioned embodiment was described about a case where the projections36are formed on the internal circumference face of the annular part35and the depressions30are formed on the outer circumference face of the positioning boss28. On the other hand, in another embodiment, the depressions30may be formed on the internal circumference face of the annular part35and the projections36may be formed on the outer circumference face of the positioning boss28.

Moreover, the above-mentioned embodiment was described about a case where both the top face36aof the projection36and bottom face30aof the depression30slope in the same direction on the respective circumferences in the front view. On the other hand, in a further embodiment, any one of the top face36aof the projection36and bottom face30aof the depression30may slope to one side on the circumference in the front view.

Furthermore, the above-mentioned embodiment was described about a case where the top face36aof the projection36slopes downward in the clockwise direction in the front view and the bottom face30aof the depression30slopes upward in the clockwise direction in the front view. On the other hand, in a furthermore embodiment, the slope directions of the top face36aof the projection36and bottom face30aof the depression30may be the reverse of the above-mentioned case. At that time, the fixing member25may be turned in a counterclockwise direction in the front view. That is, the fixing member25may be turned in a direction of narrowing a gap between the top face36aof the projection36and bottom face30aof the depression30.

In addition, the above-mentioned embodiment was described about a case where the projections36are arranged at three positions on the internal circumference face of the annular part35and the depressions30are arranged at three positions on the outer circumference face of the positioning boss28. On the other hand, in still another embodiment, each of the projection36and depression30may be formed at one position. That is, it is preferable to provide one or more pairs of the projection36and depression30.

While the present disclosure has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present disclosure.