Photoreceptor unit of image forming apparatus

A photoreceptor unit of an image forming apparatus includes an attachment body, a photoreceptor body, a first gripping portion, and a second gripping portion. The attachment body is attached to the image forming apparatus and is detachable from the image forming apparatus. The photoreceptor body is rotatably provided in the attachment body. The first gripping portion is provided in the attachment body. The second gripping portion is provided in the attachment body and is contactable with the photoreceptor body when the photoreceptor unit is gripped. The second gripping portion does not contact the photoreceptor body when the photoreceptor unit is attached to the image forming apparatus. The photoreceptor body is provided between the first gripping portion and the second gripping portion and is allow to be gripped by using the first gripping portion and the second gripping portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority under 35 USC 119 from Japanese Patent Application No. 2010-050093, filed Mar. 8, 2010.

BACKGROUND

Technical Field

The present invention relates to a photoreceptor unit of an image forming apparatus.

SUMMARY OF THE INVENTION

According to an aspect of the invention, a photoreceptor unit of an image forming apparatus includes an attachment body, a photoreceptor body, a first gripping portion, and a second gripping portion. The attachment body is attached to the image forming apparatus and is detachable from the image forming apparatus. The photoreceptor body is rotatably provided in the attachment body. The first gripping portion is provided in the attachment body. The second gripping portion is provided in the attachment body and is contactable with the photoreceptor body when the photoreceptor unit is gripped. The second gripping portion does not contact the photoreceptor body when the photoreceptor unit is attached to the image forming apparatus. The photoreceptor body is provided between the first gripping portion and the second gripping portion and is allow to be gripped by using the first gripping portion and the second gripping portion.

DETAILED DESCRIPTION

An embodiment of the present invention will be hereinafter described with reference to the drawings.

(1) Basic Configuration and Operations of Printer

First, a basic configuration and operations of a printer (image forming apparatus) according to the embodiment will be described.

FIG. 1shows an appearance of the printer1according to the embodiment, andFIG. 2shows its internal configuration. InFIGS. 1 and 2, reference numeral10denotes an apparatus main body having a cabinet11. As shown inFIGS. 3 and 4, the apparatus main body10has an opening that occupies a top portion and a front portion (inFIGS. 1-4, the front side is indicated by arrow F) and the opening is closed by a front cover12and a top cover13. The front cover12serves to cover the front portion and a top-front portion of the apparatus main body10and has an inverted-L shape in cross section. As shown inFIG. 2, the bottom end of the front cover12is hinged to the apparatus main body10(reference numeral12A denotes a hinge shaft which extends in the right-left direction (i.e., perpendicularly to the paper surface of FIG.2)), whereby the front cover12is opened when it is rotated toward the front side and closed when it is rotated toward the rear side. The rear end of the top cover13is hinged to the apparatus main body10(reference numeral13A denotes a hinge shaft which is parallel with the hinge shaft12A), whereby the top cover13is opened when it is rotated upward and closed when it is rotated downward.

As shown inFIG. 2, a sheet housing unit14for housing a number of stacked sheets P occupies a bottom portion of the apparatus main body10. A sheet P to be subjected to printing is picked up from the sheet housing unit14, goes up along a sheet conveyance path20which is formed in a front portion of the apparatus main body10, and is ejected to an ejected sheet tray15which is a top portion of the top cover13.

As shown inFIG. 2, in the printer1which is a tandem full-color printer, the apparatus main body10incorporates a transfer belt31which is rotatable (rotates in the direction indicated by arrow A) and is stretched so as to be inclined with its front side down (as viewed inFIG. 2, with its left side down), four-color image forming units4Y,4M,4C, and4K which are juxtaposed under the transfer belt31, a secondary transfer unit23, a fusing unit24, etc. The image forming units4Y,4M,4C, and4K are arranged parallel with the inclination direction of the transfer belt31.

The four image forming units4Y,4M,4C, and4K serve to form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively, and the same basic configuration. Each of the image forming units4Y,4M,4C, and4K is equipped with a developing device5and a photoreceptor unit40having a photoreceptor drum41as a main component. The photoreceptor unit40is set in the apparatus main body10so as to be able to be detached from above, and the developing device5is fixed to the apparatus main body10.

An image exposing device6which is common to the image forming units4Y,4M,4C, and4K is disposed under the image forming units4Y,4M,4C, and4K. The image exposing device6is equipped with four semiconductor lasers (not shown) which emit laser beams that are modulated according to image data of Y, M, C, and K, respectively.

Color image information is input to the printer1from a personal computer or the like. When color image information is input to the printer1, four laser beams corresponding to the respective colors are emitted from the semiconductor lasers of the image exposing device6. The laser beams are deflected by a polygon mirror and then pass through or reflected by lenses and mirrors (not shown), and the surfaces of the rotating, charged photoreceptor drums41of the image forming units4Y,4M,4C, and4K are scanned with the respective laser beams. As a result, electrostatic latent images of the respective colors are formed on the photoreceptor drums41.

The electrostatic latent images formed on the photoreceptor drums41are developed with developers containing toners of the respective colors by means of the developing devices5, and resulting toner images (color images) are transferred primarily to the outer circumferential surface of the rotating transfer belt31by primary transfer rollers32. The primary transfer operations of transferring the toner images from the photoreceptor drums41to the transfer belt31are performed in order with prescribed timing in the respective image forming units4Y,4M,4C, and4K. A full-color toner image is formed on the outer circumferential surface of the transfer belt31when the region concerned of the transfer belt31has passed the most downstream, black image forming unit4K.

Attached to the top cover13(seeFIGS. 3 and 4), the transfer belt31is opposed to the image forming units4Y,4M,4C, and4K (seeFIG. 2) when the top cover13is closed. And the primary transfer rollers32are disposed at such positions as to form nip regions between themselves and the photoreceptor drums41with the transfer belt31interposed in between. The transfer belt31is wound on a drive roller33, a follower roller34, and a tension roller35and is rotated in the direction indicated by arrow A when the drive roller33is rotated.

Referring toFIG. 2, the full-color toner image formed on the transfer belt31is transferred in the secondary transfer unit23to a sheet P that is elevated along the sheet conveyance path20with proper timing after being drawn out of the sheet housing unit14by a sheet feed unit21. The sheet feed unit21is equipped with a sheet feed roller21aand a sheet separation roller21b. Sheets P are separated into individual sheets by the sheet feed unit21, and each sheet P is conveyed to a registration roller pair22and stopped there. The sheet P is then sent to the secondary transfer unit23by the registration roller pair22which is rotationally driven with prescribed timing. The secondary transfer unit23is equipped with the above-mentioned drive roller33(on which the transfer belt31is wound) and a secondary transfer roller23awhich forms a nip region together with the drive roller33. The full-color toner image is transferred from the transfer belt31to the sheet P when the sheet P passes between the rollers33and23a.

The sheet P to which the full-color toner image has been transferred passes through the fusing unit24, whereby the color toner image is fused on the sheet P. The fusing unit24is equipped with a heat roller24aand a pressure roller24bwhich forms a nip region together with the heat roller24a. The full-color toner image is fused on the sheet P through pressure contact and heating when the sheet P passes between the rollers24aand24b. The sheet P that has passed through the fusing unit24is ejected to the ejected sheet tray15by a sheet ejection roller pair25. The sheet conveyance path20is a path that extends from the sheet feed unit21to the sheet ejection roller pair25via the registration roller pair22, the secondary transfer unit23, and the fusing unit24.

A sheet flipping mechanism26for flipping a sheet P is disposed in front of the sheet conveyance path20. As shown inFIG. 4, the sheet flipping mechanism26is attached to the front cover12. As shown inFIG. 4, the secondary transfer roller23aof the secondary transfer unit23, the fusing unit24, and the sheet ejection roller pair25which form the sheet conveyance path20are supported by the front cover12and rotated together with the front cover12.

(2) Configuration of Photoreceptor Unit

Next, the photoreceptor unit40according to the embodiment will be described in detail.

FIGS. 5-7show the whole of the photoreceptor unit40, andFIG. 8is a sectional view showing how the photoreceptor unit40is set in the apparatus main body10(arrow F indicates the front side). The outward form of the photoreceptor unit40is generally formed by a case-shaped support body (attachment body)42and the photoreceptor drum41, and the support body42is shaped so that it can be set in the apparatus main body10. In the following description, the directions such as the front-rear direction and the top-bottom directions are ones in a state that the photoreceptor unit40is set in the apparatus main body10.

As shown inFIG. 8, the photoreceptor drum41occupies a top-rear space of the support body42and is supported rotatably via rotary shafts41A provided on both sides. A charging roller43for charging the surface of the photoreceptor drum41and a charge removing roller44for removing charge from the charged charging roller43are disposed under the photoreceptor drum41. The charging roller43and the charge removing roller44are supported rotatably by the support body42via rotary shafts (not shown) so as to be in contact with the bottom of the outer circumferential surface of the photoreceptor drum41and the bottom of the outer circumferential surface of the charging roller43, respectively. In a state that the photoreceptor unit40is set in the apparatus main body10, the axes43aand44aof the rotary shafts of the charging roller43and the charge removing roller and the axis41aof the photoreceptor drum41are approximately on the same vertical line.

As shown inFIG. 8, the support body42incorporates a frame45which is formed by sheet metal working. A cleaning blade46for removing toner that remains on (stuck to) the surface of the photoreceptor drum41by scraping it off is fixed to the top of the frame45. A waste toner room425for storing toner that is scraped off by the cleaning blade46and drops down is formed in front of the frame45in the support body42.

The support body42has a first gripping portion421and a second gripping portion422which are used for attaching or detaching the photoreceptor unit40to or from the apparatus main body10by gripping the entire photoreceptor unit40. The first gripping portion421is a recess which is formed in the support body42on the front side at the center in the longitudinal direction. That is, the first gripping portion421is formed in front of, obliquely below the photoreceptor drum41. As shown inFIG. 8, the first gripping portion421is formed with an approximately vertical gripping surface421aand a finger hooking surface421bwhich extends forward from the top of the gripping surface421a. The angle θ1formed by the gripping surface421aand the finger hooking surface421bis about 90° (e.g., 80° to 100°).

On the other hand, the second gripping portion422is formed in a plate423which is disposed behind, obliquely above the photoreceptor drum41. As shown inFIG. 5, the plate423bridges stays424which are formed at the two respective ends of the support body42and two end portions of the plate423are fixed to the respective stays424. The plate423has a top surface423band an inner surface423awhich is opposed to the outer circumferential surface of the photoreceptor drum41with a gap.

The second gripping portion422is a recess which is formed in the plate423on the rear side at the center in the longitudinal direction. That is, the second gripping portion422is formed somewhat above the axis41aof the rotary shafts41A. As shown inFIG. 8, the second gripping portion422is formed with a gripping surface422awhich is approximately parallel with the inner surface423aand a finger hooking surface422bwhich extends rearward (obliquely upward) from the top of the gripping surface422a. As in the case of the first gripping portion421, the angle θ2formed by the gripping surface422aand the finger hooking surface422bis about 90° (e.g., 80° to 100°).

The plate423is made of an elastic material such as a resin which can warp in the thickness direction (i.e., in the direction indicated by arrow T inFIG. 8). When the second gripping portion422is pushed toward photoreceptor drum41, the plate423is warped and its inner surface423acomes into contact with the outer circumferential surface of the photoreceptor drum41. At this time, a conductive protective sheet (protective member)47which is stuck to the inner surface423aof the plate423comes into contact with the photoreceptor drum41. The plate423is not warped in a state that the photoreceptor unit40is set in the apparatus main body10and a gap is secured between the inner surface423a(i.e., protective sheet47) and the photoreceptor drum41.

The photoreceptor drum41is interposed between the first gripping portion421which is located in front of, obliquely below the photoreceptor drum41and the second gripping portion422which is located behind, obliquely above the photoreceptor drum41. In other words, the first gripping portion421and the second gripping portion422are formed at such positions that the photoreceptor drum41is interposed between them. In this case, as shown inFIG. 8, the axis41aof the rotary shafts41A of the photoreceptor drum41exists between the straight lines L1and L2that connect the ends of the gripping surfaces421aand422aof the first gripping portion421and the second gripping portion422. A top portion of the photoreceptor drum41is exposed so as to project from the plane defined by a top surface42bof the support body42and the top surface423bof the plate423. The top surfaces42band423bexist in the same plane that is inclined in such a manner that the front side is lower. The second gripping portion422is lower than the first gripping portion421according to the inclination of the plate defined by the top surfaces42band423b.

As shown inFIG. 8, the photoreceptor drum41can be inserted into or removed from the apparatus main body10by gripping the photoreceptor unit40by inserting the thumb into the first gripping portion421and inserting the other fingers into the second gripping portion422. That is, the photoreceptor unit40can be gripped with the photoreceptor drum41put between the thumb and the other fingers using the first gripping portion421and the second gripping portion422. The fingers can be hooked reliably on the first gripping portion421and the second gripping portion422by bringing the finger tips into contact with the gripping surfaces421aand422aand bringing the cushions of the fingers into contact with the finger hooking surfaces421band422b, whereby the photoreceptor unit40can be gripped without coming off the hand. When the photoreceptor unit40is gripped, the plate423is warped toward the photoreceptor drum41and the protective sheet47comes into contact with it.

As described above, in a state that the photoreceptor unit40is gripped, the photoreceptor drum41is put between the thumb and the other fingers using the first gripping portion421and the second gripping portion422and the axis41a(one form of a center of rotation; in the embodiment, the center of gravity) of the shafts41A of the photoreceptor drum41exists between the straight lines connecting the ends of the gripping surfaces421aand422aof the gripping portions421and422(in a sectional view). Since the charging roller43and the charge removing roller44are located under the mid point between the gripping portions421and422, the center of gravity of the entire photoreceptor unit40is not deviated to either side and hence the photoreceptor unit40can be gripped in a well-balanced manner. In addition, since the finger hooking surfaces421band422bof the gripping portions421and422form angles of about 90° with the gripping surfaces421aand422a, respectively, the fingers are hooked on the finger hooking surfaces421band422breliably.

Therefore, the photoreceptor unit40can be moved while being gripped stably without being coming off the hand, as a result of which it can be inserted into or removed from the apparatus main body10smoothly. In a state that the photoreceptor unit40is set in the apparatus main body10, the plane that is defined by the top surfaces42band423bof the support body42and the plate423is inclined in such a manner that the front side is lower. This facilitates insertion of the fingers into the gripping portions421and422and hence contributes to the smooth insertion and removal of the photoreceptor unit40, too.

Although the plate423is warped toward the photoreceptor drum41when pushed via the second gripping portion422, it does not come into direct contact with the photoreceptor drum41. Instead, the protective sheet47which is stuck to the plate423comes into contact with the photoreceptor drum41and pushes it. The protective sheet47prevents formation of a scratch on the photoreceptor drum41. Being conductive, the protective sheet47prevents the photoreceptor drum41from being charged through friction between them. This prevents an electrostatic memory phenomenon that a positive charging history item remains on the surface of the photoreceptor drum41and streaks occur at the time of printing.

Where unlike in the embodiment a photoreceptor unit is gripped using gripping portions that are distant from a photoreceptor drum, the size of the photoreceptor unit is increased. Furthermore, since a portion that is distant from the center of gravity is gripped, the gripping portions receive a heavy load and hence tend to be deformed. To prevent such deformation, the gripping portions are required to be strong. This configuration is thus associated with a problem that the photoreceptor unit is increased in weight and cost. In contrast, in the embodiment, since the photoreceptor unit40is gripped with the photoreceptor drum41interposed between the first gripping portion421and the second gripping portion422, the gripping portions421and422need not be strong and hence the photoreceptor unit40is reduced in size and cost.

Although in the embodiment the axis41aof the rotary shafts41A of the photoreceptor drum41exists between the lines that connect the ends of the gripping surfaces421aand422aof the first gripping portion421and the second gripping portion422, the axis41amay be located under that range. Even in this case, the photoreceptor unit40can be gripped stably because the center of gravity of the photoreceptor drum41is located under the gripping surfaces421aand422a.

Although in the embodiment the photoreceptor unit40is set from above in a detachable manner in a state that the top portion of the apparatus main body10is opened, the invention is not limited to such a case. The invention can be applied in various manners as appropriate according to forms of image forming apparatus such as a form in which the user grips a photoreceptor unit and attaches or detaches it to or from the front side, right side, or left side in a state that a front portion, a right portion, or a left portion, for example, of an apparatus main body is opened and a form in which the user pulls out a photoreceptor unit from the front side, right side, or left side in the longitudinal direction of the photoreceptor unit and then grips the photoreceptor unit and detaches it in a state that a front portion, a right portion, or a left portion, for example, of an apparatus main body is opened.