Patent Application
20080240783
The present application is directed to devices and methods for forming a toner image within an image forming device and, more particularly, to devices and methods that selectively drive developer members to prevent unnecessary wear on the toner.
Color image forming devices contain two or more cartridges, each of which transfers a different color of toner to a media sheet as required to produce a full color copy of a toner image. One common image forming device includes four separate cartridges for each of yellow, magenta, cyan, and black colors. Image formation for each cartridge includes moving the toner from a reservoir to a developer roll, from the developer roll to a photoconductive member, and from the photoconductive member to either a media sheet or an intermediate member. The toner image from each cartridge are formed on the media sheet in an overlapping arrangement that ultimately forms the final composite toner image.
In many devices, each cartridge is driven during image formation, even when one or more colors are not being used for the specific print job. When the cartridge is driven, the developer roll forces toner through multiple compressive nips, even when the developer roll is not actually transferring toner. Repeatedly passing toner through the compressive nips inflicts some level of damage to the toner. Worn or damaged toner particles may fail to transfer or may transfer too readily to the photoconductive member. Thus, each time a given particle of toner passes through a nip, the likelihood of that particle responding to the image formation process decreases.
Devices and methods to reduce or eliminate undue wear on the toner would result in better overall efficiency of the image forming device. This in turn would increase the amount of toner available for transfer to the media sheets, and would decrease the amount of wasted toner.
The present application is directed to methods and devices for controlling toner transfer during the formation of a toner image within an image forming device. One exemplary method comprises rotating one or more photoconductive members of the image forming device when forming a toner image, and selectively stopping or slowing the rotation of a developer member contacting at least a portion of one photoconductive member based on a color content of the toner image. For example, the method may rotate photoconductive and developer members associated with a first color when forming a first portion of the toner image containing the first color. When forming a second portion of the toner image lacking the first color, the method stops or slows the rotation of the developer member.
One exemplary forming device includes a toner reservoir that stores toner of a first color, a developer member that receives toner from the toner reservoir, a photoconductive member proximate the developer member that receives toner from the developer member, and a driver. The driver independently rotates the developer member and the photoconductive member. When a toner image being formed lacks the first color, the driver selectively stops or slows the rotation of the developer member while maintaining the normal rotation of the photoconductive member.
The present application is directed to methods and devices for reducing and/or eliminating undue churning of toner within a cartridge. In one embodiment, this includes selectively driving the developer member such that it is in motion long enough to ramp up to a desired rotational speed, transfer a desired amount of toner to the photoconductive member, and decelerate back to rest or to a slower, idle rotational speed.
Media sheets move from the input and feed into a primary media path. One or more registration rollers 13 disposed along the media path aligns the print media and precisely controls its further movement along the media path. A media transport belt 20 forms a section of the media path for moving the media sheets past the plurality of cartridges 100. Color image forming devices 10 typically include four cartridges 100 for up to four different colors of toner to produce a final, full-color toner image on the media sheet.
Each final toner image is formed by one or more different toner colors. If a particular color is to be included within the final toner image, an imaging device 22 forms a latent image at a predetermined electrical charge on a photoconductive member within the specific cartridge 100. A driver 60 rotates the photoconductive member 51 and the developer member 45 of each included cartridge 100 responsive to instructions from a controller 70. A separate toner image is created on each of the included photoconductive members 51 that is then transferred to the media sheet as it passes along on the transport belt 20. Some final toner images are formed with a single toner color (e.g., text messages formed exclusively with black toner). In these embodiments, only black toner from the corresponding black cartridge is transferred to the media sheet and no toner is transferred from the remaining cartridges 100. Some final toner images are formed with each of the available toner colors. In these embodiments, a separate toner image is formed on each photoconductive member 51 and then transferred to form a composite, overlapping arrangement on the media sheet as it passes along on the belt 20. It is to be understood that various other final toner images may be formed by combinations of two or more different toner colors.
The media sheet with loose toner then moves through a fuser 24 that adheres the toner to the media sheet. Exit rollers 26 rotate in a forward or a reverse direction to move the media sheet to an output tray 28 or a duplex path 30. The duplex path 30 directs an inverted media sheet back through the media path to form a toner image on a second side of the media sheet.
As illustrated in
The photoconductor unit 50 comprises the photoconductive member 51 disposed proximate the developer member 45. In one embodiment, the photoconductive member 51 abuts against the developer member 45. Photoconductive member 51 may comprise an aluminum hollow-core drum coated with one or more layers of light-sensitive organic photoconductive materials. The photoconductor unit 50 may also include a charger 52 that applies an electrical charge to the photoconductive member 51 in preparation to receive the electrostatic latent image from the imaging device 22 (
When the developer member 45 rotates, the toner move through multiple compressive nips including between the toner adder member 44 and developer member 45, between the developer member 45 and the doctor blade 46, and even between the agitating members 42 and the housing 43. Movement through these compressive nips occurs even when the toner does not transfer to the photoconductive member 51. This movement causes wear on the toner. The methods and devices of the present application reduce undue toner wear by selectively rotating the developer member 45 based on the color content of ah image. For example, when the portion of the toner image being formed contains the toner color associated with the particular cartridge 100, the driver 60 rotates the corresponding developer member 45 within that cartridge 100. When the portion of the toner image being formed lacks the toner color, driver 60 does not rotate the developer member 45.
The controller 70 may use any method to determine the color content of the image. In one exemplary embodiment, the controller 70 may divide the image into tiles having a predetermined size. Exemplary tiles may comprise swaths across the width of the image having a predetermined height, such as ¼″. The controller 70 determines and stores the color content of each tile. Using this information, the controller 70 determines which toner colors are required for each tile, and controls the driver 60 to selectively rotate each included developer member 45 accordingly. Using the four cartridge image forming device 100 of
Controller 70 may further control a ramp up and/or ramp down process associated with each motor 62. For example, controller 70 may instruct the motor 62 associated with a particular developer member 45 to gradually accelerate up to the desired rotational speed each time the motor 62 begins rotating the developer member 45. To halt the rotation of a developer member 45, the controller 70 may instruct the motor 62 to gradually decelerate until the developer member 45 comes to a halt. To slow the rotation of a developer member 45, the controller 70 may instruct the motor 62 to gradually decelerate until the developer member 45 comes to a slower, idle rotational speed.
While
The independent and selective developer member control described above has several advantages. First, selectively driving a developer member 45 eliminates much of the unnecessary toner wear associated with conventional toner cartridges. This may increase the efficiency of the toner transfer process, as well as reduce toner waste, which increases the capacity of toner waste containers and reduces printing costs. Further, because slowing or stopping the developer member 45 results in fewer developer member rotations on average, heat caused by friction will be less on average, which may help reduce the overall operating temperature of the image forming device 10.
The above-described selective developer member control may also be used to perform periodic device maintenance. For example, the controller 70 may periodically instruct driver 60 to rotate one or more developer members 45 at a maintenance rotational speed to help lubricate and/or clean the interface between the developer member 45 and the doctor blade 46. In addition, such periodical rotations of the developer members 45 may help prevent the creation of flat spots on the developer member 45 caused by the doctor blade 46 and/or the rotating photoconductive member 51. It will be appreciated that the maintenance speed may be any desired rotational speed. In one embodiment, the maintenance speed is generally equivalent to the normal operational speed of the developer member 45.
The selective control of the developer member 45 may also be used to implement additional device features. For example, when the developer and photoconductive members 45, 51 abut, mechanical “scrubbing” forces work concurrently with the electrical charge on the photoconductive member 51 to transfer the toner from the developer member 45 to the photoconductive member 51. The ratio of the rotational speed of the photoconductive member to the rotational speed of the developer member defines a scrub rate. The scrub rate is directly related to the amount of toner transferred. For example, lower scrub rates correspond to less toner transfer. Because conventional systems simultaneously drive the developer member 45 and the photoconductive member 51, conventional systems typically have a fixed scrub rate. However, because the methods and devices of the present application independently drive each developer member 45, the controller 70 may vary the scrub rate by, for example, varying the speed of the motor 62 driving the developer member 45. Thus, the methods and devices of the present application may selectively control the amount of toner used to form a toner image by controlling the scrub rate. This feature may be used to implement a toner-saver mode, for example.
The embodiment disclosed in
One embodiment of a cartridge 100 is illustrated in
The controller 70 described above may be implemented as a single microcontroller or microprocessor that includes logic circuitry to implement the functions described above. The functions implemented by the controller may be embodied in hardware (including an application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc.) and/or software (including firmware, software, micro-code, etc.). Further, it will be appreciated that the controller 70 may be a separate device as shown in
The controller 70 evaluates the color content of the image to determine rotation of the developer members 45. In one embodiment described above, the controller 70 divides the image into tiles in the process direction having a predetermined size, such as ¼″. Controller 70 may further divide the image into other tile sizes, such as ½″, 1″, etc. In another embodiment, controller 70 determines rotation based on the entirety of a printed page. If a specific color is included at any point on the page, controller 70 will drive the corresponding developer member 45 at a desired rotational speed. In another embodiment, controller 70 determines rotation on an object basis.
As discussed above, driver 60 stops or slows the rotation of each developer members 45 associated with toner colors not present in an image. As used herein, “stopping” the rotation of a developer member 45 includes halting the movement of a rotating developer member 45, as well as not rotating or otherwise preventing the rotation of the developer member 45. In one embodiment, the driver 60 prevents the rotation of the developer member 45, even when the developer member 45 is in contact with a rotating photoconductive member 51. As used herein, “slowing” the rotation of a developer member 45 includes reducing the movement of a rotating developer member 45 to a rotational speed less than a normal operating rotational speed.
Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or feature, but do not preclude additional elements or feature. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. In one embodiment, the developer member 45 is spaced away from the photoconductive member 51. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
