Abstract:
A printer system calculates toner (or other marking agent) levels in a toner cartridge over an upper portion of the cartridge, while sensing toner levels in the remaining lower portion of the cartridge. The system provides the accuracy of a sensed toner environment when it is most needed, during the latter portion of a toner cartridge lifespan. A less accurate, but useful method of calculating the toner level is employed during the earlier stages of the toner cartridge lifespan. Thus, the system avoids the high cost associated with a completely sensed toner environment while providing the increased accuracy of a sensed toner environment when it is most beneficial to the system user.

Description:
TECHNICAL FIELD 
     The present invention relates to reporting the toner level in a print device toner cartridge and, more particularly, to reporting a calculated toner level from a first portion of the toner cartridge and reporting a sensed toner level from the remaining portion of the toner cartridge. 
     BACKGROUND 
     Consumable items in printing devices mostly include “marking agent” components that are consumed with each printed page as part of the printed product, and rotating components that deteriorate over time as a result of wear and tear. Marking agent consumables include ink, wax, powder toner, thermal agents, and the like. Marking agents are often housed in some type of cartridge, such as a toner cartridge, and dispensed onto rotating components that transfer the agents to a print medium during a printing process. As a marking agent is depleted, it is useful to have information about the amount of agent remaining in a cartridge in order to approximate the number of pages available for printing during the remaining life of the cartridge. Various methods exist that provide information regarding the remaining useful life of a cartridge. 
     A page counting method does not involve direct measurement information about the level of toner (i.e., marking agent) present in a cartridge. Instead, this method provides an expected life span for a toner cartridge measured by the number of pages that the cartridge is expected to print. The life span is reduced by one page for each page that is printed. A disadvantage of this simple method is that it can be inaccurate. 
     The inaccuracy of this method can result from at least two factors. First, the expected number of pages available from a toner cartridge is a rough estimate set by the cartridge designer based on numerous examples of like cartridges. The actual number of available pages can vary significantly from cartridge to cartridge. Second, the amount of toner put on each printed page may vary dramatically from page to page. These factors often mean that more or less toner is left in a cartridge than expected, which can result in significant differences in the number of pages expected to be printed and the number of pages that can actually be printed by a given cartridge. 
     A pixel counting method also does not involve direct measurement information about the level of toner present in a cartridge. Rather, this method starts with an assumed maximum number of pixels available to be expended over the life of the cartridge. In a color laser printer, the number of pixels expended can be estimated by tracking the number of laser pulses used to discharge a photoconductor drum (OPC). A finite number of laser pulses is used to discharge the OPC in preparation to attract a pixel (or dot) of toner. The number of laser pulses can be measured for each printed page, and the appropriate number of pixels can be subtracted from the maximum pixels available, thereby providing a measure of the percentage of pixels (i.e., toner) remaining in the cartridge. 
     Unfortunately, this method suffers disadvantages similar to the previous method. The maximum number of available pixels is assumed by the cartridge designer based on numerous examples of like cartridges. The actual number of available pixels can vary significantly from cartridge to cartridge. In addition, counting laser pulses can be an inaccurate method of determining the number of expended pixels on a printed page. Although the error per page may be slight, it can add up over the life of the cartridge (e.g., 10,000 printed pages) and create a significant difference in the expected percentage of toner available and the actual percentage of toner available. Moreover, the largest errors are seen toward the end of the cartridge life cycle, which is the time when it is most important to have accurate toner level information. 
     Another method of determining the toner level within a cartridge utilizes antenna sensor technology. This method provides direct information about the level of toner in a cartridge and is therefore more accurate than the previously discussed methods. The level of toner in a cartridge is determined by passing current from one end of the cartridge to the other through an antenna. The current induces voltage signals in coils within the cartridge that are proportional to the amount of toner present in the cartridge. Although this direct measurement of the toner level is beneficial, it too has disadvantages. 
     One disadvantage of using antenna sensor technology is its cost. Where page counting and pixel counting methods can be implemented by simple software executing on pre-existing computer hardware, the antenna technology requires the installation of hardware into each toner cartridge. In addition to the cost of the antenna hardware itself, there are design costs associated with fitting the hardware inside different cartridges of varying shapes and sizes. Moreover, the physical size constraints of some cartridges prohibit antenna sensor coverage throughout the entire cartridge, thus limiting toner level sensing to only part of the cartridge. 
     Accordingly, the need exists for a cost effective way to determine the level of toner present throughout the life of a toner cartridge in a manner that permits a high level of predictability as to the remaining useful life of the toner cartridge. 
     SUMMARY 
     A printer system calculates toner (or other marking agent) levels in a toner cartridge over an upper portion of the cartridge, while sensing toner levels in the remaining lower portion of the cartridge. The system provides the accuracy of a sensed toner environment when it is most needed (i.e., during the latter portion of a toner cartridge lifespan). A less accurate, but useful method of calculating the toner level is employed during the earlier stages of the toner cartridge lifespan. Thus, the system avoids the high cost associated with a fully sensed toner environment while providing the increased accuracy of a sensed toner environment when it is most beneficial to the system user. 
     Early in the lifespan of a toner cartridge, the system reports toner levels using a counting method. The method calculates toner levels based on the estimated availability and usage of page capacity or pixel capacity for the cartridge. Therefore, the calculations provide an estimated toner level for the system to report. 
     In addition, the system monitors readings from a partial sensor configured to sense toner levels in the lower portion of the toner cartridge. While the actual toner level remains above the upper threshold of the lower/sensed portion of the cartridge, the sensor readings generally indicate that the toner level is at 100% of the lower portion of the cartridge. Thus, the sensor readings become meaningful only when the actual toner level drops below the upper threshold of the sensed portion of the cartridge. 
     Because the estimated toner level is less accurate than the sensed toner level, the system switches from reporting the estimated toner level to reporting the sensed toner level at the first indication that the sensor is in play. That is, at the first indication that the sensor readings are meaningful, the system begins reporting toner levels based on the sensor readings. 
     There are three indications that prompt the system to switch from reporting the estimated toner level to reporting the sensed toner level. The first is when the estimated toner level drops below the threshold level of the lower portion of the cartridge, and the sensed toner level remains at the threshold. The second is when the estimated toner level remains above the threshold, and the sensed toner level drops below the threshold. The last indication, which is unlikely based on the inherent inaccuracy of the counting method, is when both the estimated and sensed toner levels drop below the threshold at the same time. Under each of these circumstances, the system begins reporting the sensed toner level. 
     The system continues reporting the sensed toner level throughout the remaining lifespan of the cartridge, providing a user with the more accurate toner level information when it is most useful. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The same reference numbers are used throughout the drawings to reference like components and features. 
     FIG. 1 illustrates a workstation and printing device as a suitable system environment in which to report toner levels from a partially sensed environment. 
     FIG. 2 is a block diagram illustrating a system such as that in FIG.  1 . 
     FIG. 3 illustrates a printer device which uses a number of toner cartridges and various other consumable components. 
     FIG. 4 is a flow diagram illustrating an example method of determining a reported toner level throughout the life of a toner cartridge. 
     FIG. 5 is a plot of percent of toner versus time throughout the life of a toner cartridge illustrating when the reported toner level changes from a calculated level to a sensed level. 
     FIG. 6 is a plot of percent of toner versus time throughout the life of a toner cartridge illustrating when the reported toner level changes from a calculated level to a sensed level. 
    
    
     DETAILED DESCRIPTION 
     The system and methods described herein relate to reporting the supply level of a marking agent (e.g., toner) in a print device cartridge. A counting method is employed to calculate an estimated level of toner in a toner cartridge over a portion of the useful life of the cartridge. During this period, the system uses the estimated level as the reported toner supply level. A sensor device is used to determine the reported toner supply level during the latter portion of the useful life of the cartridge. Costs associated with a fully sensed toner environment are avoided while the accuracy of toner level reporting is maintained during the time when accuracy is most beneficial. 
     Exemplary System for Reporting Toner Levels in a Partially Sensed Environment 
     FIG. 1 illustrates an example of a printing system that is suitable for reporting toner levels in a partially sensed environment. The system  100  of FIG. 1 includes a printer device  102  connected to a host computer  104  through a direct or network connection  106 . Network connections  106  can include LANs (local area networks), WANs (wide area networks), or any other suitable communication link. The invention is applicable to various types of printing devices that make use of marking agent consumables such as ink, wax, powder toner, thermal agents, and the like. Therefore, printer device  102  can include devices such as copiers, fax machines and scanners, and may also include multifunction peripheral (MFP) devices which combine the functionality of two or more peripheral devices into a single device. 
     In general, the host computer  104  outputs host data to the printer device  102  in a driver format suitable for the device  102 , such as PCL or postscript. The printer device  102  converts the host data and outputs it onto an appropriate recording media, such as paper or transparencies. 
     FIG. 2 illustrates the printer system  100  in more detail. The printer device  102  has a controller  200  that processes the host data. The controller  200  typically includes a data processing unit or CPU  202 , a volatile memory  204  (i.e., RAM), and a non-volatile memory  206  (e.g., ROM, Flash). Printer device  102  includes a print engine  208  and one or more consumable printing components  210 . Consumable(s)  210  represent marking agents typically housed in cartridges whose supply levels decrease with each printed page output by print device  102 . Therefore, consumable(s)  210  generally include cartridges and other containers that hold ink, wax, powder toner, thermal agents, and the like. Other typical print device consumables such as paper, photoconductors, transfer drums or belts, and fusers are not illustrated in FIG. 2, but are discussed below with reference to FIG.  3 . 
     Consumable(s)  210  include monitoring devices  212  that are configured to sense toner (i.e., marking agent) supply levels within a limited portion of a consumable  210 . The monitoring devices  212  are typically located within the consumable  210  itself. Instead of sensing toner supply levels throughout the entire consumable  210 , the monitoring devices  212  are only capable of sensing toner levels in the bottom portion of the consumable  210 . Monitoring devices  212  are therefore toner level sensors that are implemented within a consumable  210  (e.g., a toner cartridge) to a lesser than full degree, such that they provide a partially sensed toner environment rather than a fully sensed toner environment. 
     Monitoring devices  212  are preferably antenna sensor devices that measure supply levels within a cartridge by passing current through a partial plate capacitor antenna within the cartridge. The current induces voltage signals in coils within the cartridge that are proportional to the amount of toner present in the cartridge. Monitoring devices  212  can include any toner level sensor  212  that provides a partially sensed toner environment by virtue of its partial implementation within a toner cartridge (i.e., consumable  210 ). 
     The printer controller  200  processes host data and manages the print process by controlling the print engine  208  and consumable(s)  210 . Printer controller  200  includes printer driver software  214  executing on CPU(s)  202 . The printer driver software  214  is stored in memory  206  and controls toner level reports provided by the system  100 . The printer driver software  214  includes a switching module that executes to control whether the system  100  reports an estimated toner level or a sensed toner level. 
     An estimated toner level is calculated by the printer driver software  214  based on a counting method that uses the estimated availability and usage of toner capacity within a toner cartridge. Counting methods include pixel and page counting methods, with the pixel counting method being preferred. A pixel counting method begins with an estimated pixel capacity for a toner cartridge and reduces that capacity with each expended pixel. The percent of pixel capacity remaining is equated to a percent of toner remaining in the cartridge to provide an estimated toner level. Likewise, a page counting method begins with an estimated page capacity for a toner cartridge and reduces that capacity with each printed page. The percent of page capacity remaining is equated to a percent of toner remaining in the cartridge to provide an estimated toner level. 
     In addition to calculating an estimated toner level, the printer driver software  214  continually monitors a sensed toner level from a toner level sensor  212  (monitor device  212 ) as described above. Based on a method described herein below, the switching module portion of software  214  determines when the system  100  reports the estimated toner level and when the system  100  switches over to report the sensed toner level. 
     Toner level reports can be output on print device  102 , the host computer  104 , or any suitable display device coupled to print device  102 . Although the printer driver software  214  and switching module generally execute on print device  102 , they may also be stored and execute on the host computer  104  as illustrated by printer driver  222 . 
     The host computer  104  includes a processor  216 , a volatile memory  218  (i.e., RAM), and a non-volatile memory  220  (e.g., ROM, hard disk, floppy disk, CD-ROM, etc.). The host computer  104  may be implemented, for example, as a general-purpose computer, such as a desktop personal computer, a laptop, a server, and the like. The host computer  104  may implement one or more software-based printer drivers  222  that are stored in non-volatile memory  220  and executed on the processor  216  to configure data into an appropriate format (e.g., PCL, postscript, etc.) and output the formatted data to the printer device  102 . 
     Exemplary Print Process for Reporting Toner Levels in a Partially Sensed Environment 
     FIG. 3 represents a color laser printer  300  as an example print device  102  that may be used in the printing system  100  of FIGS. 1 and 2. A general printing process will now be described with respect to color laser printer  300  for the purpose of illustrating a context for reporting toner levels in a partially sensed toner (i.e., marking agent) environment. 
     A typical color laser printer  300  produces an image using various colored toners. During an imaging process, a four color image is built sequentially onto a transfer element, such as an intermediate transfer belt  308 , before it is finally transferred to the print medium (e.g., paper or transparency) in one pass. The ultimate application of the toners to the print medium is controlled by an electrostatic imaging process. 
     Color printer  300  houses four toner cartridges  302  in a rotating carousel  304  that is operational with a photoconductor (OPC) drum  306 . Toner cartridges  302  contain the four main toner colors cyan (C), magenta (M), yellow (Y), and black (K). Although the toner cartridges  302  are illustrated as separate devices inserted into rotating carousel  304 , they may additionally be implemented as a single all-in-one color cartridge that includes the four toner colors. For example, the rotating carousel  304  may represent a single all-in-one color cartridge, while toner cartridges  302  represent separate housings within the all-in-one cartridge for accommodating the four color toners. In addition, OPC drum  306  may be implemented as one or more OPC drums. For example, there may be four OPC drums  306 , one to accommodate the transfer of each color toner. 
     To begin the imaging process, a primary charge roller  310  within the OPC drum assembly  312  applies an electrostatic charge to the OPC drum  306 . As the OPC drum  306  rotates, a laser assembly  314  writes the latent image for the first color onto the drum  306  with laser  316 . The toner carousel  304  then puts the first color toner cartridge  302  into position for operation with the OPC drum  306 . Within toner cartridge  302 , an agitator (not shown) guides toner to a developer roller  318 . As the developer roller  318  and OPC drum  306  rotate, the toner is developed to the latent image electrostatically formed on the OPC drum  306 . 
     Each color image is thus developed one at a time on the OPC drum  306 . Also, each color image is transferred one at a time to the rotating intermediate transfer belt (ITB)  308  because of attraction from electric charge on primary transfer roller  320 . Once the four-color image has been built on the ITB  308 , the secondary transfer roller  322  is activated to attract the image away from the ITB  308  and onto the paper in one pass of the ITB  308  over the paper. The paper is guided by guide rollers  324  from a paper tray  326  or external source  328  past the ITB  308  and then through the fuser assembly  330 . The fuser assembly  330  includes two hot rubber fuser rollers  332  that melt the toner, bonding it to the paper. From the fuser assembly  330 , the paper exits the printer  300  into the output tray  334 . 
     With each page printed by the color laser printer  300 , supply levels within toner cartridges  302  decrease. Printer driver software  214  (FIG. 2) executing on printer controller  200 , calculates estimated toner levels and monitors sensed toner levels from monitoring devices  212 . The printer controller  200  uses the estimated and sensed toner level information to create toner level reports that indicate the percentage of toner or other marking agent remaining in the cartridges  302 . The printing system  100  (FIGS. 1 and 2) typically presents toner level reports through a display on printer  300  or a display on host computer  104  upon request from a system user. Toner level reports can also be presented automatically on preset intervals, such as time based intervals or event based intervals. An event based interval can include events such as the periodic printing of a certain number of pages, the periodic decrease in reported toner level by a certain percent, or reaching a certain minimum reported toner level. 
     Exemplary Method for Reporting Toner Levels in a Partially Sensed Environment 
     An example method for determining and reporting toner levels from a partially sensed environment will now be described with primary reference to FIGS. 4,  5 , and  6 . 
     FIG. 4 is a flow diagram illustrating an example of a general method for determining and reporting toner levels from the partially sensed toner environment of a consumable  210 . Operations included in the method of FIG. 4 are ideally performed in a system  100  such as that shown in FIGS. 1 and 2, and are typically implemented on either a print device  102  or a host computer  104 . However, the method operations of FIG. 4 are not limited to being performed on a single device, but can also be performed alternately between devices such as print device  102  and host computer  104 . 
     FIGS. 5 and 6 are plots showing toner level versus time throughout the useful life of a toner cartridge. The plots illustrate when the system  100  reports an estimated (calculated) toner level and when the system reports a sensed toner level. The plots also illustrate two different scenarios in which the system  100  switches from reporting an estimated (calculated) toner level to reporting a sensed toner level. The two plots facilitate the following description of the method of FIG.  4 . 
     The example method of FIG. 4 begins at operation  400  with calculating an estimated toner level. As previously discussed, estimated toner levels are determined by calculations performed in a counting method, such as a page counting method or a pixel counting method. The method continues with monitoring a sensed toner level at operation  402 . The sensed toner level is provided by a toner level sensor  212  (monitoring device), also discussed above. Although the flow diagram of FIG. 4 indicates that the monitoring operation  402  occurs after the calculating operation  400 , the operations can occur in any order, and typically occur concurrently. The frequency of the operations can be based on a preset time interval, but is preferably based on an event such as the printing of a page or a change in the sensed toner level, or both. Thus, in accordance with the remaining method operations described below, each time a page is printed or the sensed toner level changes, the reported toner level is updated. 
     The method continues at operation  404  with comparing the estimated toner level (ETL) to a prescribed level. If the ETL is not less than the prescribed level, then the method proceeds with operation  406 , where the sensed toner level (STL) is compared to the prescribed level. Operations  404  and  406 , in conjunction with operation  408 , illustrate that as long as both the ETL and STL (i.e., the estimated and sensed toner levels) are not less than the prescribed level, then the ETL (estimated toner level) is used as the reported toner level for the system  100 . 
     However, operations  404  and  406 , in conjunction with operation  410 , illustrate that if either the ETL or the STL (i.e., the estimated or sensed toner level) drops below the prescribed level, then the system  100  switches to the STL (sensed toner level) as the reported toner level. Once either the ETL or the STL drops below the prescribed level, the system  100  only relies on the sensed toner level for reporting, as illustrated by repeating operations  410  and  412 . 
     The prescribed level used for comparison is the maximum level that a toner level sensor  212  can monitor within a toner cartridge (consumable  210 ). That is, the prescribed level is the 100% level of the partially sensed toner environment within the toner cartridge. Note that this level can be any level for which a toner level sensor  212  is designed as a partial sensor in a cartridge. Therefore, if the toner level sensor  212  is designed to monitor the last 25% of the toner cartridge, then the prescribed level is 25%. 
     FIGS. 5 and 6 illustrate the ongoing method of FIG.  4 . Both FIGS. 5 and 6 assume a toner level sensor  212  designed to monitor 25% of the toner environment within a toner cartridge (consumable  210 ). The solid lines plotted in both FIGS. 5 and 6 illustrate the toner level that is reported by the system  100 . The solid lines show where the reported toner level changes from the ETL (estimated toner level) to the STL (sensed toner level). The dotted lines represent the actual toner level within the toner cartridge, and the dashed lines represent the sensed toner levels (STL). 
     The plots of FIGS. 5 and 6 show that the estimated toner level (ETL) is the level that is reported by the system  100  throughout most of the lifespan of the toner cartridge. However, when either the estimated toner level (ETL) or the sensed toner level (STL) drops below the prescribed level of 25%, the system  100  begins using the sensed toner level (STL) as its reported toner level. 
     FIG. 5 specifically illustrates a scenario in which the estimated toner level (ETL) indicates a level that is higher than the actual toner level in the cartridge. Under this scenario, the sensed toner level (STL) will indicate that the actual level has dropped below 25% (the prescribed level) before the ETL provides such an indication. Upon this indication from the STL, because it is known that the STL is more accurate than the ETL, the system  100  switches from reporting the ETL to reporting the more accurate STL. 
     FIG. 6 specifically illustrates a scenario in which the estimated toner level (ETL) indicates a level that is lower than the actual toner level in the cartridge. Under this scenario, the estimated toner level (ETL) will indicate that the actual level has dropped below 25% (the prescribed level) before the STL provides such an indication. Upon this indication from the ETL, because it is known that the STL is more accurate than the ETL, the system  100  switches from reporting the ETL to reporting the more accurate STL. 
     Under another unlikely scenario, the estimated toner level (ETL) could be uncharacteristically accurate to the extent that both the ETL and STL drop below the prescribed 25% level at the same time. Under such a scenario, the system  100  would switch from reporting the ETL to reporting the more accurate STL. 
     Although the description above uses language that is specific to structural features and/or methodological acts, it is to be understood that the invention defined in the appended claims is not limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the invention.