Abstract:
A variable developer forming method and apparatus that replenishes toner in an image forming apparatus, including a controller that determines a first supply amount and a second supply amount based on an analysis of a document to be printed, a toner storage device that variably releases toner into a developer supply device based on the first supply amount and a carrier storage device that variably releases carrier into the developer supply device based on second supply amount.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to image forming devices. 
     2. Description of Related Art 
     Toner particles are used with a transfer drum or development roll to create patterns on a recording medium. To enable electrostatic charging and transfer of toner particles, the toner is mixed with carrier beads of opposite polarity. Carrier material generally comprises low friction beads that interact with the toner particles to ensure proper charging and even toner flow. 
     Developer results when toner particles are mixed with carrier material in the appropriate ratio. Developers in cartridges or in housings are replaced when either the toner or the carrier degrades to an unacceptable level. Conventionally, toner and carrier are mixed at a ratio of 75% carrier to 25% toner, initially forming a mixture called replenisher. Replenisher can then be added to developers in cartridges or in housings to extend the life of the developer by replacing the carrier material at the same time toner is added. Spent developer is gathered into a waste container for disposal. 
     SUMMARY OF THE INVENTION 
     This invention relates to systems and methods for dynamically adjusting the ratios of toner and carrier added to a developer mixture. 
     For example, low area coverage images require little toner. However, the developer is churned the same amount regardless of the amount toner used, to ensure good quality printing. Thus, when forming a low area coverage image, the carrier is aged more than in a high area coverage image. The systems and methods of this invention adjust the ratios of toner and carrier added depending on the area coverage or density of a particular image. Thus, the time between replacement of the developer or developer cartridge can be increased, leading to better quality images at a lower cost. 
     These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments of the invention will be described in detail with reference to the following figures, wherein like numerals reference like elements, and wherein: 
     FIG. 1 illustrates the conventional system for replenishing developer in a developer cartridge or housing; 
     FIG. 2 is a block diagram illustrating a first exemplary embodiment of the structure of an image forming device that incorporates various exemplary embodiments having a variable ratio developer supplying system according to this invention; 
     FIG. 3 is a block diagram of one exemplary embodiment of a developer cartridge or housing having a variable ratio developer supplying system according to this invention; 
     FIG. 4 is a flowchart outlining one exemplary embodiment of a method for determining the mixture of toner and carrier according to this invention; 
     FIG. 5 is a table showing exemplary results of determining the amount of toner needed; 
     FIG. 6 is a block diagram illustrating a second exemplary embodiment of the structure of a color printing device according to the invention; and 
     FIG. 7 is a block diagram illustrating a second exemplary embodiment of a developer cartridge having a variable ratio developer supplying system according to this invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows a conventional system  100  for replenishing developer in a trickle developer unit  110 . The trickle developer unit  110  includes an agitator  145 , a supply path  151  to a carrier sink  150 , and a supply path  161  to a transfer drum  160 . The trickle developer unit  110  also includes toner particles  141  and carrier particles  143  located in a developer sump  140 . 
     When producing images, the agitator  145  agitates the toner particles  141  and the carrier particles  143  in the developer sump  140 . Toner is then transferred via the supply path  161  to the transfer drum  160  or developer roll so that an image can be produced. Waste carrier is transferred via the supply path  151  to the carrier sink  150 . As the developer, i.e., the combined toner particles  141  and the carrier particles  143 , is used to produce images, the developer in the developer sump  140  will age and the toner will be consumed. 
     To replenish the developer in the trickle developer unit  110 , a replenisher  190  adds developer to the developer sump  140  through a developer replenisher path  191 . The replenisher  190  stores premixed developer created by combining 25% toner particles  143  with 75% carrier particles  141  during manufacture of the replenisher  190 . 
     However, eventually the developer in the trickle developer unit  110  will age and image quality will be compromised. Continuing addition of replenisher to the developer will no longer rejuvenate the developer. At this point it is necessary to replace the trickle developer unit  110 . FIG. 2 is a block diagram of an image forming device  200 . The image forming device  200  includes a trickle developer unit  110  that transfers toner to a transfer drum  160  or transfers developer to a developer roll under the control of a controller  170 . The controller  170  receives image information from an image data source  10 . The trickle developer unit  110  includes a toner storage device  120  and a carrier storage device  130 , which feed toner particles  141  and carrier particles  143 , respectively, to a developer sump  140 . The used carrier particles are discarded from the developer sump  140  into a carrier sink  150 . 
     In operation, the image data source  10  transfers image information to the image forming device  200  such that an image may be created. In particular, the controller  170  of the image forming device  200  receives the image information. The controller  170  then controls the transfer drum  160  and the trickle developer unit  110  to feed developer, i.e. toner and carrier, from the trickle developer unit  110  to the transfer drum  160 , which then transfers the toner to an image forming engine  180  of the image forming device  200 . Alternatively, the controller  170  may also be used to control the trickle developer unit  110  to feed developer, i.e. toner and carrier, from the trickle developer unit  110  to the developer roll, which then transfers the toner to an image forming engine  180  of the image forming device  200 . The image forming engine  180  uses the transferred toner to create a toner image and transfers the toner image to a recording medium. In other exemplary embodiments, any other known or later-developed device or apparatus can be used to transfer the developer from a developer mixer to a medium recording, as is well known in the art. 
     The trickle developer unit  110  can add appropriate amounts of the toner particles  143  from the toner storage unit  120  and the carrier particles  141  from the carrier storage unit  130  to the developer sump  140 . For example, in a low area coverage image, very little toner should be added from the toner storage unit  120 . In general, just enough of the toner should be transferred from the toner storage unit  120  to create the image on the recording medium. Additional amounts of the toner can be added to account for other losses, such as toner lost to the carrier sink  150 , as is known in the art. The actual amount of toner to be added can be determined by any known or later developed technique without departing from the spirit and scope of the invention. 
     The carrier storage unit  130  adds an appropriate amount of the carrier to the developer sump  140 . For example, if the image to be created is a high area coverage image, the toner storage unit  120  can add a large amount of the toner to the developer sump  140 . The carrier storage  130  can then add a small amount of the carrier to the developer sump  140 . The amount of carrier added from the carrier storage  130  can be determined by any known or later-devised method without departing from the spirit and scope of the invention. 
     In this exemplary embodiment, as additional toner and carrier particles are added to the developer sump  140 , waste carrier and residual toner are transferred to the carrier sink  150 . Thus, appropriate amounts of usable carrier and toner can be maintained in the developer sump  140 . However, other means of discarding or using toner and carrier are also possible. For example, in other exemplary embodiments, waste carrier can be retained within the developer sump  140 , or can be recycled into the carrier storage  130 . 
     FIG. 3 shows a first exemplary embodiment of the developer replenishing system according to this invention. As shown in FIG. 3, the trickle developer unit  10  includes the developer sump  140 , the toner supply path  121 , the developer supply path  161 , the carrier sink  150 , the supply path  151 , the toner storage unit  120 , the transfer drum  160 , the carrier storage unit  130 , and the carrier supply path  131 . 
     To create an image, the developer sump  140  transfers toner via supply path  161  to the transfer drum  160 . In addition, waste carrier is transferred via the supply path  151  to the carrier sink  150 . To replace the toner particles  143 , toner particles  143  are transferred to the developer sump  140  via the toner supply path  121  from the toner storage unit  120 . To replenish the carrier particles  141 , carrier particles are transferred to the developer sump  140  via the carrier supply path  131  from the carrier storage unit  130 . Toner particles  143  can be added from the toner storage unit  120  in an amount related to the amount of toner consumed by the imaging process. Carrier particles  141  are transferred from the carrier storage unit  130  in an amount related to the amount of carrier particles  141  that will be transferred to the carrier sink  150 . An even mixture is maintained by the agitator  145 , which agitates all of toner particles  143 , and carrier particles  141  in sump  140 . 
     Thus, the developer replenishing systems and methods of this invention directly add appropriate amounts of the toner particles and the carrier particles to the trickle developer unit  110 . The toner particles and carrier particles are separately stored in the image forming device  200 . The trickle developer unit  110  can thus be used for increased periods of time. In addition, the toner transferred to transfer drum  160  or the developer transferred to the developer roll can be of a predetermined quality. 
     FIG. 4 is a flowchart outlining one exemplary embodiment of a method for determining the mixture of toner and carrier. Beginning in step S 100 , control continues to step S 110 , where the print job is received. Then, in step S 120 , a first portion of a print job is selected. Next, in step S 130 , an amount of toner needed for the selected portion of the print job is determined. Control then continues to step S 140 . 
     In step S 140 , an amount of carrier needed is determined based on the amount of toner needed, the area coverage and density of the print job, the size of the print job, the speed at which the image system is run, and/or the period of time that the print job will take. Additional factors are possible and can be used without departing from the scope and intent of the invention. Next in step S 150 , the determined amounts of toner and carrier are fed to a sump. Then in step S 160 , the current portion of the print job is printed. Control then continues to step S 170 . 
     In step S 170 , a determination is made whether the print job is finished. If the print job is finished, control continues to step S 180 , where the method ends. Otherwise, if the print job is not finished, control jumps back to step S 120 . 
     FIG. 5 is one exemplary embodiment of a table  300  usable to determine, or showing the results of determining, the amount of toner needed. The table  300  includes a column  310  for print job, a column  320  for the percentage of black toner, a column  330  for the percentage of cyan toner, a column  340  for the percentage of magenta toner the and a column  350  for the percentage of yellow toner. 
     Thus, the table  300  is an exemplary embodiment of the results of the determination made in step S 130 . Alternatively, the table  300  is an exemplary embodiment of the results of the amount of the toner to be added to the developer sump  140  in FIG.  3 . 
     FIG. 6 shows an exemplary embodiment of a multicolor image forming device  400  according to the invention. The multicolor image forming device  400  includes a carrier storage unit  430 , a black toner storage unit  420 , a magenta toner storage unit  422 , a yellow toner storage unit  424  and a cyan toner storage unit  426 . The black toner storage unit  420  feeds black toner via a toner path  421  to a black developer sump  440 , which also receives carrier from the carrier storage unit  430  via a supply path  431 . The magenta toner storage unit  422  feeds magenta toner via a toner supply path  423  to a magenta developer sump  442 , which also receives carrier from the carrier storage unit  430  via a supply path  433 . The yellow toner storage unit  424  feeds yellow toner via a toner supply path  425  to a yellow developer-sump  444 , which also receives carrier from the carrier storage unit  430  via a supply path  435 . The cyan toner storage unit  426  feeds cyan toner via a toner supply path  427  to a cyan developer sump  446 , which also receives carrier from the carrier storage unit  430  via a supply path  437 . 
     FIG. 7 is a block diagram of second exemplary embodiment of a developer replenishing system according to this invention. As shown in FIG. 7, the image forming device  100  includes the trickle developer unit  110 , the transfer drum  160 , and the controller  170 . The trickle developer unit  110  includes the toner storage device  120 , the carrier storage device  130 , which feed the toner particles  143  and the carrier particles  141 , respectively to a replenisher  190 . The toner particles  143  and the carrier particles  141  are mixed in the replenisher  190 . The mixture is then supplied to the developer sump  140  through a supply line  191 . Used carrier is discarded into a carrier sink  150 . 
     The trickle developer unit  110  can add appropriate amounts of the toner from the toner storage unit  120  and the carrier from the carrier storage unit  130  to the replenisher  190 . For example, in a low area coverage image, very little toner should be added from the toner storage unit  120 . In general, just enough of the toner should be transferred from the toner storage unit  120  to create the image on the recording medium. Additional amounts of the toner can be added to account for other losses, such as toner lost to the carrier sink  150 , as is known in the art. The actual amount of toner added can be determined by any known or later developed technique without departing from the spirit and scope of the invention. 
     The carrier storage unit  130  can add an appropriate amount of the carrier to the replenisher  190 . For example, if the image to be created is a high area coverage image, the toner storage unit  120  can add a large amount of the toner to the replenisher  190 . The carrier storage  130  can then add a small amount of the carrier to the replenisher  190 . Alternately, the amount of carrier to be added can be increased or remain constant in relation to decreases in the amount of toner to be added. The amount of carrier added from the carrier storage  130  can be determined by any known or later-devised method without departing from the spirit and scope of the invention. 
     In this exemplary embodiment, as additional toner and carrier particles are added to the replenisher  190 , which then adds the mixture to the developer sump  140 , appropriate amounts of usable carrier and toner can be maintained in the developer sump  140 . 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.