Patent Application
20140126938
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1. Field of the Disclosure
The present disclosure relates generally to electrophotographic imaging devices such as a printer or multifunction device having printing capability, and in particular to an imaging device in which color toner images created by color imaging units are transferred to a sheet of media via the photoconductive member of a black imaging unit which forms black toner images.
2. Description of the Related Art
For many users of color printing devices, a vast majority of media sheets are printed in monochrome using only black toner. As a result, print performance characteristics that relate to monochrome printing are often considered when determining a printing device to purchase. A need thus exists for a color printing device having improved monochrome printing performance.
Embodiments of the present disclosure overcome shortcomings in prior toner transfer architectures and satisfy a significant need for a hybrid architecture in which black toner is efficiently transferred to a media sheet. According to an example embodiment, there is shown an imaging device including a plurality of color imaging units, each imaging unit selectively depositing a distinct toner color; an intermediate transfer member for cooperating with the color imaging units such that color toner is deposited onto the intermediate transfer member to form a color toner image; and a black imaging unit for depositing black toner, including a photoconductive member on which the black toner is deposited to form a black toner image. The intermediate transfer member and the black imaging unit are configured so that during a color print operation, the color toner image previously deposited on the intermediate transfer member is deposited onto the photoconductive member of the black imaging unit and the color toner image and the black toner image are subsequently deposited from the photoconductive member of the black imaging unit onto a media sheet. By transferring toner directly to the media sheet from the photoconductive drum of the black imaging unit, the time to first print (TTFP) and time to first copy (TTFC) for the imaging device having the above-described architecture are generally no more than such times for a monochrome printer employing only a black imaging unit.
The above-mentioned and other features and advantages of the disclosed embodiments, and the manner of attaining them, will become more apparent and will be better understood by reference to the following description of the disclosed embodiments in conjunction with the accompanying drawings, wherein:
It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
Terms such as “first”, “second”, and the like, are used to describe various elements, regions, sections, etc. and are not intended to be limiting. Further, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Furthermore, and as described in subsequent paragraphs, the specific configurations illustrated in the drawings are intended to exemplify embodiments of the disclosure and that other alternative configurations are possible.
Reference will now be made in detail to the example embodiments, as illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
Each imaging unit 150 includes a toner reservoir 154 to contain the toner. One or more agitating members may further be positioned within the reservoir to move the toner, and a toner adder roller 155 is positioned in the reservoir 154 to move the toner to a developer roller 156. Each imaging unit 150 also includes a photoconductive member 153 that receives toner from developer roller 156. A charging member 152 is positioned to charge the photoconductive (PC) member or drum 153. In one embodiment, each of the imaging units 150 is substantially the same except for the color of toner appearing therein. For purposes of clarity in
It is understood that each imaging unit 150 may be operably coupled to a distinct toner bottle (not shown) which delivers toner to reservoir 154 as toners levels therein fall below a predetermined threshold.
During color image formation, the surface of each PC drum 153 is charged to a specified voltage, such as −800 volts, for example. At least one laser beam from a printhead 160 is directed to the surface of each PC drum 153 and discharges those areas it contacts to form a latent image thereon. In one embodiment, areas on the PC drum 153 illuminated by the laser beam are discharged to approximately −100 volts. The developer roller 156 of each imaging unit 150 then transfers toner to PC drum 153 to form a toner image thereon. The toner is attracted to the areas of PC drum 153 surface discharged by the laser beam from the printhead 160.
ITM 120 is disposed adjacent to each of imaging unit 150. In this embodiment, ITM 120 is formed as an endless belt disposed about drive roller 130, tension roller 132 and back-up roller 134. During image forming operations, ITM 120 moves past the imaging units 150 in a clockwise direction as viewed in
ITM 120 rotates and collects the one or more toner images from the one or more imaging units 150 and then conveys the one or more toner images to a media sheet at a second transfer area 180. Second transfer area 180 includes a second transfer nip formed between back-up roller 134 and a second transfer roller 182.
Each imaging unit 220 includes a toner reservoir 222 to contain the toner which may be replenished as needed from a toner bottle 412 (see
During color image formation, the surface of each PC drum 228 is charged to a specified voltage, such as −800 volts, for example. At least one modulated laser beam from a printhead 230 is directed to the surface of each PC drum 228 and discharges those areas it contacts to form a latent image thereon. In one embodiment, areas on the PC drum 228 illuminated by the laser beam are discharged to approximately −100 volts, for example. Developer roller 226 of each imaging unit 220 then transfers toner to PC drum 228 to form a toner image thereon. The toner is attracted to the areas of the PC drum 228 surface discharged by the laser beam from the printhead 230.
ITM 240 is disposed adjacent to each imaging unit 220. In this embodiment, ITM 240 is formed as an endless belt disposed about drive roller 242, tension roller 244 and backup roll 246. During color image forming operations, ITM 240 moves past the imaging units 220 in a counterclockwise direction as viewed in
Imaging section 200 further includes black imaging unit or station 260K having toner reservoir 262 to contain toner. Reservoir 262 may be replenished as needed by a toner bottle 412B containing black toner (see
According to the example embodiment, a color toner image that is transferred to ITM 240 from imaging units 220 is then transferred to PC drum 268 of black imaging unit 260 at second transfer area 212. Second transfer area 212 may be formed between PC drum 268 of black imaging unit 260 and backup roll 246. This “back transfer” of toner from ITM 240 to PC drum 268 may be accomplished by the application of the appropriate electric field formed from voltages that are applied to backup roll 246 and charge member 269. By transferring the color toner image to PC drum 268 of black imaging unit 260, all toner is subsequently transferred to a media sheet at third transfer area 214.
Imaging section 200 may further include a retraction mechanism 280 operably coupled to backup roll 246 for selectively retracting backup roll 246 from engagement with PC drum 268 of black imaging unit 260. Retraction mechanism 280 may be activated to retract backup roll 246 from PC drum 268, for example, following transfer of toner thereto, and during a print operation in which only black toner is used.
A benefit of imaging section 200 being disposed along an axis that is angled as shown in
Imaging device 400 also includes controller 406 which generally controls the operation thereof, including imaging section 200 such as imaging units 220 and 260, ITM 240, transfer roller 250, drive roller 242, and backup roll 246. Controller 406 may include one or more processors, software, firmware and/or hardware logic necessary to control the functions of imaging device 400, and may be implemented as one or more application specific integrated circuits (ASICs). Controller 406 may also include or be associated with a memory 408 which may be any volatile and/or non-volatile memory such as, for example, random access memory (RAM), read only memory (ROM), flash memory and/or non-volatile RAM (NVRAM). A pick mechanism 410, controlled by controller 406, may pick the top media sheet from a stack thereof situated in media input tray 402 and move the picked sheet towards third transfer area 214 for receiving a toner image.
Imaging device 400 further includes toner bottles 412, each for supplying toner to its corresponding imaging unit as needed. Toner bottle 412K supplies black toner to black imaging unit 260K, toner bottle 412M supplies magenta toner to imaging unit 220M, toner bottle 412C supplies cyan toner to imaging unit 220C and toner bottle 412Y supplies toner to imaging unit 220Y. Toner delivery from each toner bottle 412 to its corresponding imaging unit may be controlled by controller 406. Toner bottles 412 may be accessed by a user for replacement via one or more doors disposed along imaging device 400.
As shown in
Controller 406 may coordinate the timing of an imaging operation with a media feed operation whereby a top sheet of a stack of media is picked from media input tray 402 by pick mechanism 410 and delivered to third transfer area 214. For a color print operation, prior to or during the time the top media sheet is picked by pick mechanism 410 and moved towards third transfer area 214, a color toner image is formed on ITM 240 by imaging units 220. In particular, imaging unit 220Y may form a yellow toner image on ITM 240, followed by imaging unit 220C selectively forming a cyan toner image on ITM 240 that is aligned with the yellow toner image, and imaging unit 220M selectively forming a magenta toner image on ITM 240 that is aligned with the yellow and cyan toner images so as to form a single color toner image. It is understood that any one or more of imaging units 220 may form a color toner image on ITM 240 during a color print operation.
A black toner image may be formed on photoconductive drum 268 of imaging unit 260K during the color print operation, the particular timing of which is chosen so that the black toner image is aligned with the color toner image appearing on ITM 240 when the color toner image is transferred at second transfer area 212 from ITM 240 to photoconductive drum 268. Such timing may depend upon the size of photoconductive drum 268 of black imaging unit 260K relative to the size of the photoconductive drum 228 of imaging units 220 and the spacing along ITM 240 between imaging unit 220Y and second transfer area 212. Once the color toner image is back transferred to photoconductive drum 268, forming a complete image with the black toner image, retraction mechanism 280 may retract backup roll 246 so that ITM 240 no longer contacts photoconductive drum 268 of black imaging unit 260K. In addition, around this time imaging units 220 may no longer be activated, thereby reducing churn.
Movement of the picked media sheet is timed so that it enters third transfer area 214 at the same time as the complete toner image on photoconductive drum 268 reaches same. Following transfer of the complete image onto the picked media sheet, the sheet passes through fuser assembly 404 where the toner is fused to the media sheet. Upon exiting fuser assembly 404, the sheet may either be fed into duplex path 420 for printing on a second surface thereof, or ejected from imaging device 400 at output area 418.
For a monochrome print operation only involving black toner, retraction mechanism 280 may retract backup roll 246 from photoconductive drum 268 of imaging unit 260K, and imaging units 220 and ITM 240 are not activated for participating in the print operation, thereby reducing churn. A black toner image is formed on photoconductive drum 268 which is transferred to a picked media sheet at third transfer area 214. By transferring the black toner image directly from photoconductive drum 268 onto the picked media sheet, imaging section 200 advantageously allows for substantially the same toner transfer efficiency in performing a monochrome print operation as the toner transfer efficiency in monochrome printing devices.
According to an example embodiment, imaging device 400 may be initially configured as a monochrome imaging device which only provides black toner images, without imaging units 220, ITM 240, toner bottles 412M, 412C and 412Y, and the components supporting same. Imaging units 220, ITM 240, toner bottles 412M, 412C and 412Y and their supporting components may be acquired separately from imaging device 400, either individually or collectively as a single, insertable unit, in order to upgrade the monochrome machine to include color imaging capability.
It is understood that imaging device 400 may be a multifunction product including scan, copy and/or facsimile functionality.
The foregoing description of several methods and example embodiments has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.
