Abstract:
A method and apparatus for providing transfer quality optimization in printers is disclosed. A transfer belt subassembly includes a transfer belt and a storage device. The transfer belt also includes a home position indicator. The transfer belt subassembly is measured and characterized relative to the home position indicator before being installed in a printer. The measurement and calibration data for the transfer belt is then stored in the storage device that is part of the transfer belt subassembly. When the transfer belt subassembly is inserted into a printer, a controller within the printer is placed in communication with the storage device. A sensor is used to determine the home position of the transfer belt from the indicator, and a resulting signal indicating when the belt is at the home position is provided to the controller. The controller utilizes the measurement and calibration data from the storage device to provide correction with respect to each color station of the color printer, taking into account and compensating for variations in the transfer belt subassembly. In such a manner, the measurement and calibration data is predetermined before the transfer belt subassembly is inserted into the printer, thereby simplifying the printer composition. By use of the calibration and measurement data, precise alignment of the color planes with respect to one another is achieved, and the proper electrical transfer setting suited to that belt is obtained for improved transfer quality.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/398,617 filed Sep. 17, 1999, U.S. Pat. No. 6,198,897 
    
    
     BACKGROUND OF THE INVENTION 
     In color printers a plurality of color planes are sequentially aligned and deposited onto a transfer media such as a transfer belt. The transfer belt is then used to transfer the accumulated color planes to a piece of paper or other media. A problem associated with this process is misregistration or misalignment of one or more of the color planes. Alignment of the color planes and optimization of the transfer is crucial in achieving a high quality image. Due to the fact that each individual color plane is transferred onto the belt or paper at different locations along the travel path of the transfer belt, variations of the transfer quality and positioning of the belt within the travel path must be compensated for with a high degree of precision. 
     There are many instances where position variations and transfer quality variations can develop and cause a concomitant degradation in the resulting image. Factors such as variations in the width of the belt, the belt tension, and the belt resistivity are examples of factors that lead to transfer quality and belt position variations. It would be desirable to have a method and apparatus that compensates for variations within a printer which is inexpensive to implement and does not add complexity to the printer. 
     BRIEF SUMMARY OF THE INVENTION 
     A method and apparatus for providing transfer quality optimization in printers is disclosed. A transfer belt subassembly includes a transfer belt and a storage device. The transfer belt also includes a home position indicator. The transfer belt subassembly is measured and characterized relative to the home position indicator before being installed in a printer. The measurement and calibration data for the transfer belt is then stored in the storage device that is part of the transfer belt subassembly. When the transfer belt subassembly is inserted into a printer, a controller within the printer is placed in communication with the storage device. A sensor is used to determine the home position of the transfer belt from the indicator, and a resulting signal indicating when the belt is at the home position is provided to the controller. The controller utilizes the measurement and calibration data from the storage device to provide correction with respect to each color station of the color printer, taking into account and compensating for variations in the transfer belt subassembly. In such a manner, the measurement and calibration data is predetermined before the transfer belt subassembly is inserted into the printer, thereby simplifying the printer composition. By use of the calibration and measurement data, precise alignment of the color planes with respect to one another is achieved, and the proper electrical transfer setting suited to that belt is obtained for improving transfer quality. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a diagram illustrating the apparatus of the present invention wherein the image is accumulated on an intermediate transfer member (ITM). 
     FIG. 2 is a diagram illustrating the apparatus of the present invention wherein the image is accumulated on a print medium. 
     FIG. 3 shows a typical transfer operating characteristic curve that can be included in the ITM memory. 
     FIG. 4 is an example of a graphical representation of the transfer characteristics for 4 colors at the 1 st  transfer stations. 
     FIG. 5 is an example of a graphical representation of the transfer characteristics for 2 media at the 2 nd  transfer station. 
     FIG. 6 is a flow chart illustrating the method of the present invention. 
     FIG.  7 . is a diagram illustrating the apparatus of the present invention wherein the image is accumulated on a print medium using “plate-like” transfer members. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Color printers typically utilize a transfer belt assembly to accumulate an image from a plurality of color planes. The color planes are placed onto the belt in succession as the transfer belt passes by the photoconductive (PC) drum associated with each color station. Once the belt has traversed all of the PC drums a resulting image, which will later be transferred to a print medium, is provided on the transfer belt. Alternatively, the transfer belt is used to transport a piece of print medium, such as paper, card stock, or transparencies, and the color planes are deposited directly onto the print medium as the medium passes by the PC drums of each color station. 
     Referring to FIG. 1, a preferred embodiment of an apparatus  10  for compensating for transfer belt positioning variations, transfer quality variations, belt resistivity and transfer roll resistivities, which may vary from subassembly to subassembly, is shown. While the preferred embodiment refers to a printer, it should be appreciated that the present invention relates to any image forming apparatus. The apparatus  10  includes a transfer belt subassembly  15 , a controller  90  and color stations  42 - 45 . Each color station pertains to a different color plane. In this embodiment color station  42  is utilized for providing a yellow (Y) color plane, color station  43  for providing a cyan (C) color plane, color station  44  for providing a magenta (M) color plane and color station  45  for providing a black (K) color plane. Other embodiments may have different numbers (one or more) of color stations. 
     Each of the color stations includes a print head  30 , a developer assembly  32  and a PC drum  34 . (This detail is shown only for color station  42 .) The print head  30  forms a latent image on the PC drum  34 . Toner (not shown) is supplied to the PC drum via developer assembly  32  to produce a developed toned image, also known as a color plane, from the latent image on the PC drum. Each color station may be realized through any one of a plurality of prior art configurations of these elements. 
     The transfer belt subassembly  15  contains a transfer belt  20 , one or more home position sensors ( 70  and  71 ), a memory device  80  and a plurality of rollers. As shown in FIGS. 1 and 2, the transfer belt is disposed about, or adjacent to, said rollers. The plurality of rollers include an end roller  41  (also referred to as a tension roller), a drive roller  40 , a first transfer roller  50 , a second transfer roller  51 , a third transfer roller  52 , and a fourth transfer roller  53 . (Note: A transfer roller is one category of a transfer member, discussed further hereafter.) The accumulated image is then transferred to a print medium (not shown) by transfer roller  55 , which is adjacent to said transfer belt. Depending upon the embodiment, other rollers may be useful or necessary. It should be appreciated that other embodiments not including transfer rollers may also be utilized. Referring to FIG. 2, a second embodiment of an apparatus  11  for providing transfer belt correction is shown. The apparatus  11  is similar to the apparatus disclosed in FIG. 1, except that the color planes are directly deposited onto a print medium disposed upon and transported by the transfer belt. 
     In the simplified embodiment of FIG. 2, the transfer belt  20  surrounds and traverses an ellipsoidal path defined by rollers  40  and  41 . The transfer belt  20  also includes a home position indicator  75  that is useful for accurately identifying a specific position of the transfer belt  20  with respect to the transfer belt subassembly  15 . The home position indicator  75  of the transfer belt  20  provides a reference point for the measurement and calibration data. The indicator  75  may be realized as a hole punched in the transfer belt  20  or as indicia printed or painted on the belt. The indicator  75  may also be realized as a magnetic or an electrostatic device. While the home position sensor  70  is shown as part of the subassembly  15  in this embodiment, the home position sensor  70  could also be located external to the subassembly  15 . The home position sensor  70  must be able to detect the presence of the home position indicator  75 . Thus, when the home position indicator  75  comprises a hole punched in the transfer belt  20 , an optical sensor may be used to detect the presence of the hole. When painted or printed indicia are used to indicate the home position a reader must be used to sense the presence of the indicia. Similarly, when a magnetic or electrostatic device is used as the home position indicator a sensor sensitive to the magnetic or electrostatic device is used to determine the presence of the home position indicator  75 . 
     Roller  40  is used as a drive roller and is in mechanical communication with a drive motor  60 . Roller  40  thus provides for movement of the transfer belt  20  through the belt path. 
     Alignment of the color planes on the transfer belt is crucial for providing a high quality resulting image. There are a number of factors that affect the alignment of the color planes on the transfer belt. For example, there may be variations in the thickness or width of the belt as well as variations in the tension of the belt along the belt path. In the second embodiment, the print medium may move with respect to the transfer belt. In addition, both the mechanical and the electrical parameters of belts may vary around the belt circumference and on average between subassemblies. 
     The object of this invention is to provide an intermediate transfer member (ITM) subassembly for a color EP printer that functions as a modular subassembly in which characterization data critical to function is measured at time of manufacture and stored in a memory device affixed to the ITM subassembly. Characterization data includes belt resistivity range for transfer current/voltage adjustment; transfer roll resistivity; surface velocity profile for drive velocity correction (primarily due to belt thickness variation); and belt tracking profile for correction of image position perpendicular to the direction of belt travel. The characterization data is accessible to the machine into which the ITM subassembly is installed, enabling the machine microcontroller to provide proper operating points for transfer quality, feed-forward velocity control for process direction registration of color planes, and imaging start of scan delays for scan direction registration of color planes. Additional information stored at time of manufacture may include: a) date of manufacture of component parts, b) source of component parts, c) diameters of drive and idler rolls, d) belt length, e) belt tension, f) drive motor initialization values, g) allowable lifetime in cycles, and h) EC level. A unique serial number or bit pattern is recorded in the memory either as received from the memory component supplier or at time of manufacture for identification and possible lockout of unauthorized subassemblies. The information stored at time of manufacture is write protected against later, unauthorized modification. Data is stored in a form readily accessible to the machine controller—in a tabular format. 
     Remaining memory is allocated for use while the ITM subassembly is installed in the color EP machine. The machine writes number of cycles of use into the memory so that overall usage of the subassembly can be tracked. The machine displays an end of life warning and may force an end-of-life lockout based upon this recorded cycle count. Life is recorded in the preferred embodiment by burning bits in a sequence of memory locations—in which each bit represents nominally 1000 cycles and total life is 255K cycles, thus consuming 255 bits of memory plus a lockout bit. Page count and job count may be similarly recorded as other ways of accessing subassembly life. 
     As described above, this invention serves multiple functions, as exemplified by the function of the Memory device affixed to ITM subassembly: (See  80  in FIG. 1.) 
     a) Stores serial number and bit pattern enabling the machine to recognize an authorized unit and to lock out an unauthorized unit. 
     b) Stores information about the ITM subassembly used by the machine for control. 
     i) OEM ID 
     ii) ITM subassembly EC Level 
     iii) Belt length in zones for velocity control 
     iv) Belt length in zones for start of imaging control 
     v) Belt cycle end-of-life limit 
     vi) Belt pages end-of-life limit 
     vii) Belt job count end-of-life limit 
     viii) Belt DC time between sensors vs. temperature relationship 
     ix) Time between sensors for 108.21 mm/sec at 30° C. with AC feed-forward 
     x) Time between sensors for 108.21 mm/sec at 30° C. without AC feed-forward 
     xi) Function enable: 1) cycle lockout, 2) page lockout, 3) job lock-out, 4) DC velocity correction enable, 5) AC velocity feed-forward enable, 6) start of scan delay feed-forward enable, 7) transfer offset enable. 
     c) Stores details of components which comprise the ITM subassembly. This is of an information nature; and not used by the machine for control purposes. 
     i) Date of manufacture of ITM subassembly 
     ii) Date of manufacture of component parts 
     iii) Source of component parts 
     iv) Diameters of drive and idler rolls 
     v) Belt length 
     vi) Belt tension 
     d) The preferred memory, the DS 1985, has a write protection feature to protect data written at time of manufacture against unauthorized modification. 
     e) Has memory allocated for use while the ITM subassembly is operated in the associated color EP machine to track life cycles, pages and jobs. Here, cycles can be recorded by burning one bit for every 1000 cycles, consuming 255 bits of memory to tally 255K cycles, with one bit remaining as a lockout bit. Pages and jobs are tallied in the same way. 
     f) Has an end-of-life lockout feature to prevent further operation once cycles, pages, or jobs, or a combination thereof, has exceeded an allowable criterion. 
     g) Stores transfer operating point data either as a modification to the setpoint (preferred) or as a complete setpoint table to provide best print quality when the ITM assembly is operated in the associated color EP machine. 
     h) Stores process direction velocity characterization data in a format that allows the machine microcontroller to correct velocity errors that affect color plane registration in the process direction. 
     i) Stores lateral or “scan direction” (perpendicular to process direction) belt tracking characterization data in a format that allows the machine microcontroller to correct for tracking errors that affect registration of color planes in the scan direction relative to black. 
     In order to compensate for variations in the belt the transfer belt subassembly  15  is measured and characterized in a special test fixture at the time the subassembly  15  is manufactured. The data that reflects the measured and characterized transfer belt subassembly  15  is stored in a storage device (also called an integrated circuit)  80 , which is part of the belt subassembly  15 . The storage device  80  may be a semiconductor memory such as a DS1985 non-volatile and one-time programmable 16K bit memory available from Dallas Semiconductor Corp. of Dallas, Tex. The stored data is also referred to as calibration data. 
     Other non-volatile memories that can be used include the Dallas Semiconductor DS1982, 1K bit Add-Only memory that can be used only if a subset of the disclosed functions are implemented and memory is conservatively managed. Larger memory devices and conventional EPROMS, EEPROM and NVRAM memories with read/write capabilities can be used with loss of write protection at time of manufacture and possible (unauthorized) resetting of the subassembly life-tracking bits. 
     In a first embodiment, the system includes four imaging stations. The system may also include a transfer station for transferring the image from the belt to a print medium. The term transfer station is used here to define both (1) the location where the black or color belts transfer images to the transfer belt (sometimes referred to hereafter as first transfer stations) and (2) the location where the image is transferred from the transfer belt to the print medium (sometimes referred to hereafter as the second transfer station). Each imaging station includes an image bearing member, which may be a photoconductive (PC) drum, an optical source such as a laser assembly operative to produce latent images on the image bearing member, a toner source, and a developing member operative to produce developed toned images from the latent image on the image bearing member. An electrically biased first transfer member is associated with each imaging station. The transfer members, which are disposed adjacent to each image bearing member, are operative in conjunction with the image bearing member upon application of the appropriate voltages to transfer toner from the image bearing member to a substrate passing through the nip between the image bearing member and the transfer member. Servo operations are used to set the operating voltages on each of the transfer members at first transfer. Variations in first transfer members include, but are not limited to, (1) transfer rolls and (2) “plate-like” transfer members that have rubbing contact rather than rolling contact at the first transfer stations. Transfer rolls typically comprise a supporting steel shaft 6 to 8 mm in diameter with a 3 to 6 mm thick layer of resistive urethane or EPDM foam that is molded or bonded with an electrically conductive path to the supporting shaft. Foam resistivity is typically 10 6  to 10 10  ohm-cm and foam durometer is typically 25 to 80 Shore 00. Other shaft materials and foam materials and thicknesses are also possible. Plate-like transfer members ( 150 ,  151 ,  152 ,  153  of FIG. 7 ) that may be used in place of rollers at first transfer include resistive urethane blades and resistive fiber brushes which have a stiffness sufficient to press the transfer belt into contact with the photoconductor drum with a force in the range of 10 to 100 g/cm. Material resistivity is chosen to produce a voltage drop of 1 to 400 volts through the plate-like member when a current of 0.5 uA/cm is passed through the plate-like transfer member. 
     In operation, to transfer toner from the PC drum  34  to the transfer belt  20  at the first transfer assembly, the rotating PC drum surface is charged by a charging assembly. Portions of the drum surface are selectively discharged by the optical energy from a laser, LED array, or the like. Toner is transferred to the drum as determined by the pattern of charge on the drum and as developed by a developing assembly. The developed toner is then transferred to the transfer belt  20  at the nip between the PC drum  34  and the transfer roller  50 . To effect the movement of the toner to the ITM belt, a high voltage power supply  68  (not shown) is electrically connected to each transfer roller shaft to apply a voltage to the transfer roller opposite in polarity to the charge on the toner. Alternatively, the high voltage power supply can be in the form of (1) a plurality of power supplies, one being for each transfer roll or (2) a single high voltage power supply shared among the first transfer rolls. There may be an independent high voltage power supply for the second transfer roll, said power supply possibly having a larger voltage range to handle a wide variety of media. Another alternative could be the combining of the power supply for the second transfer roll with that of one or more of the first transfer rolls (e.g., the black color roll). Other combinations are also possible. Preferably, there is an independent power supply for the second transfer roll. To aid in the transfer of the toner, a velocity difference between the PC drum and the ITM belt is optionally utilized to agitate the toner and improve the transfer efficiency. The velocity difference is between −2.5% and +2.5%, but is nominally 0% in the preferred embodiment. Any suitable controller  90  controls all operations. 
     The transfer belt  20  is nominally neutral in charge as it enters the first color PC/transfer roller nip. However, it may have a tribo-electrically generated charge from the feed process or a slight residual charge remaining from a previous revolution. Charged areas on the PC drum are at nominally −1000 V and discharged (toner-covered) areas at nominally −340 V. The PC drum core is at −200 V. 
     When the leading edge of the PC image arrives at the nip between the PC drum  34  and the transfer roller  50 , the transfer “image” voltage is applied to the transfer roller shaft. Immediately prior to the end of the PC image exiting the nip, the transfer “inter-image” voltage is applied to the transfer roller shaft. This timing applies the transfer “image” voltage only to the image areas of the PC drum. Non-imaged areas see only the “inter-image” transfer voltage that is set to minimize toner transfer and to avoid excess current flow. 
     The transfer operating points are defined for each transfer of the image to and from the belt. The transfer operating points include the transfer voltage and current limits. The operating points may be changed to reflect differences in the belt resistivity in order to produce an optimal image. The printer includes a setting for low, normal, and high modes. The characterization data also includes a low, normal and high mode. The following table reflects the setting achieved by the mode selected in the printer in conjunction with the mode stored as part of the characterization data. 
     
       
         
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                               Transfer Setting 
                 Memory device 
               
             
          
           
               
                   
                 Machine mode 
                 01 = low 
                 00 = normal 
                 10 = high 
               
               
                   
                   
               
               
                   
                 Low 
                 Low 
                 Low 
                 Normal 
               
               
                   
                 Normal 
                 Low 
                 Normal 
                 High 
               
               
                   
                 High 
                 Normal 
                 High 
                 High 
               
               
                   
                   
               
             
          
         
       
     
     Thus, if the machine is set to low mode, and the characterization data from memory device indicates a 01 for low, the operating points will be set to their low values. If the memory device indicated a 00 for a normal setting while the machine is in the low mode, the operating points would again be set low. However, if the machine was set to low mode and the memory device indicates a 10 for high, the operating points would be changed to their normal setting. Accordingly, the mode of the machine may be further adjusted by taking into account the appropriate characterization data pertaining to the transfer station. 
     As an alternative to storing a value that selects from among a plurality of transfer modes stored in the printer, the transfer operating characteristic for a particular transfer belt can optionally be stored in the memory device in a form that completely describes the transfer characteristic for that belt. 
     In another embodiment, which consumes substantially more memory in the ITM, a complete set of transfer tables are contained in the ITM memory and made available to the machine controller. In contrast to the first embodiment that stores a low, normal, or high selection value that is used to select operating modes or offsets from tables stored in machine memory, the second embodiment stores the actual transfer control tables in the ITM memory. This second embodiment provides for significant differences in ITM transfer performance that can arise from multiple causes, including 1) change in ITM belt materials or supplier, 2) change in first transfer roll material, or 3) replacement of the first transfer rollers with lower-cost plate-like transfer members. Transfer operating data can also be provided in the form of an algorithm. 
     The machine that associates with the ITM module and attached memory uses a transfer servo process to compensate for shifts in the electrical properties of transfer rolls at 1 st  and 2 nd  transfer, the ITM belt, and the photoconductor drum coatings. Changes in the electrical properties of these elements arise as a result of temperature and humidity changes, mechanical wear, and electrical fatigue. To maintain high transfer efficiencies and good print quality, the transfer roll operating voltage needs to be adjusted to compensate for these changes. The process of determining the operating voltages at 1 st  and 2 nd  transfer is termed a servo process. A servo voltage is determined for each transfer roll as that voltage on the transfer roll shaft which delivers a fixed current of nominally 8 μA to the ITM belt and supporting photoconductor (PC) drum at 1 st  transfer or to the ITM belt and supporting backup roll at 2 nd  transfer. Each PC drum is charged to a predetermined surface potential of nominally −500 volts during the transfer servo process with the PC core potential at −200 volts. The ITM backup roll surface is set to nominally −600 volts during the servo process. The operating voltage applied to the shaft of each transfer roll during the printing process is calculated via a corresponding pre-determined transfer characteristic from the servo voltage. The transfer characteristic is stored in table form in machine memory or in the ITM memory. When the tables are stored in ITM memory, they may be read into machine memory and stored for rapid access. 
     A slope and offset representation of the transfer characteristic at each of the four color 1st transfer stations and a slope and offset representation of the 2nd transfer characteristic by media type and print mode (e.g. simplex/duplex) are provided in this implementation. An additional set of table entries is required for each significantly different machine process speed. The table values for a single color could be used in place of table values for the four individual colors at 1st transfer if toner charge/mass and belt initial conditions were similar at each of the four stations. 
     In the preferred embodiment, one set of tables is provided for transfer at 108 mm/second process speed and a second set for transfer at 4 mm/second. A total of eight tables are thus provided at 1 st  transfer for the four color stations at two process speeds. A total of 20 tables are provided at 2 nd  transfer for ten media types and print modes at two process speeds. 
     An example of the parametric representation of a transfer characteristic is shown in FIG.  3 . Here, each transfer characteristic is represented using an offset and a slope value for each of 3 line segments. The horizontal axis represents the transfer servo voltage required to produce an 8 μA servo current as previously described. The vertical axis represents the voltage applied to the transfer roll shaft during printing. The transfer servo slope breakpoints on the horizontal axis corresponding to 02 and 03 in FIG. 3 are common to all four 1 st  transfer tables and to 2 nd  transfer. Each of the six numerical values representing the slope and offsets for the three line segments is stored in an 8-bit byte; the transfer roll operating offset voltage is represented in 25 volt increments and slope is represented in 64th&#39;s. Each transfer characteristic thus consumes 48 bits of ITM memory. 
     The table values corresponding to a 108 mm/second process speed at each of the four 1 st  transfer color stations and at 2 nd  transfer for standard 20 pound paper media and transparencies are given in Table 1. Offsets are given relative to the −200 volt photoconductor drum core at 1 st  transfer and relative to the −600 volt ITM back up roll surface potential at 2 nd  transfer. 
     
       
         
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
             
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 A) Offset Voltage and Multiplier Representation of 
               
               
                 1st and 2nd Transfer Characteristics 
               
             
          
           
               
                   
                 Servo Range 
               
             
          
           
               
                   
                 0 to 500 
                 500 to 1000 
                 1000 to Max 
               
               
                   
                 volts 
                 volts 
                 output 
               
             
          
           
               
                 Transfer Station  
                 O1 
                 S1 
                 O2 
                 S2 
                 O3 
                 S3 
               
               
                   
               
             
          
           
               
                 1st 
                 Yellow 
                 28 
                 0.8 
                 28 
                 0.8 
                 28 
                 0.8 
               
               
                 Transfer 
               
               
                 1st 
                 Cyan 
                 100 
                 0.8 
                 100 
                 0.8 
                 100 
                 0.8 
               
               
                 Transfer 
               
               
                 1st 
                 Magenta 
                 200 
                 0.8 
                 200 
                 0.8 
                 200 
                 0.8 
               
               
                 Transfer 
               
               
                 1st 
                 Black 
                 300 
                 0.8 
                 300 
                 0.8 
                 300 
                 0.8 
               
               
                 Transfer 
               
               
                 2nd 
                 20# 
                 −96 
                 2.8 
                 454 
                 1.71 
                 1148 
                 1.02 
               
               
                 Transfer 
                 Paper 
               
               
                   
                 Simplex 
               
               
                 2nd 
                 Trans- 
                 0 
                 2.24 
                 520 
                 1.2 
                 1092 
                 0.63 
               
               
                 Transfer 
                 parency 
               
               
                   
               
             
          
           
               
                 B) 1-Byte per Entry Representation of 
               
               
                 1st and 2nd Transfer Characteristics (decimal) 
               
               
                 25 volts per bit Offset, 
               
               
                 signed integer, −3200 to +3175 volts; 
               
               
                 1/64th&#39;s per bit Slope, 
               
               
                 unsigned integer, 0 to 3.98 multiplier 
               
             
          
           
               
                   
                 Servo Range 
               
             
          
           
               
                   
                 0 to 500 
                 500 to 1000 
                 1000 to Max 
               
               
                   
                 volts 
                 volts 
                 output 
               
             
          
           
               
                 Transfer Station  
                 O1 
                 S1 
                 O2 
                 S2 
                 O3 
                 S3 
               
               
                   
               
             
          
           
               
                 1st 
                 Yellow 
                 1 
                 51 
                 1 
                 51 
                 1 
                 51 
               
               
                 Transfer 
               
               
                 1st 
                 Cyan 
                 4 
                 51 
                 4 
                 51 
                 4 
                 51 
               
               
                 Transfer 
               
               
                 1st 
                 Magenta 
                 8 
                 51 
                 8 
                 51 
                 8 
                 51 
               
               
                 Transfer 
               
               
                 1st 
                 Black 
                 12 
                 51 
                 12 
                 51 
                 12 
                 51 
               
               
                 Transfer 
               
               
                 2nd 
                 20# 
                 −4 
                 179 
                 18 
                 109 
                 46 
                 65 
               
               
                 Transfer 
                 Paper 
               
               
                   
                 Simplex 
               
               
                 2nd 
                 Trans- 
                 0 
                 143 
                 21 
                 77 
                 44 
                 40 
               
               
                 Transfer 
                 parency 
               
               
                   
               
             
          
         
       
     
     The tabular representation of the 1 st  transfer characteristics from Table 1 A) is shown in graphical format in FIG.  4 . Because the slope values for all four color stations are constant across all servo ranges, no breakpoints are visible in FIG.  4 . The tabular representation of the 2nd transfer characteristics from Table 1 A) is shown in graphical format in FIG.  5 . 
     Table 1B) duplicates Table 1A) with values shown in the 1 byte per entry format in which they are stored in the semiconductor memory. 
     The machine transfer control algorithm may also be parametrically altered based upon the ITM cycle count tallied (by cycles or pages) during the life of the ITM. 
     A map of the memory contents for one embodiment is shown below: 
     
       
         
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Page 
                 Bits 
                 Description 
               
               
                   
               
             
             
               
                 0 
                 256 
                 Reserved for Uniqueware component ID 
               
               
                 1 
                 256 
                 OEM ID 
               
               
                   
                   
                 Belt cycle end-of-life limit 
               
               
                   
                   
                 Belt pages end-of-life limit 
               
               
                   
                   
                 Belt job count end-of-life limit 
               
               
                   
                   
                 Time between sensors for 108.12 mm/sec at 30° C. 
               
               
                   
                   
                 with AC feed-forward 
               
               
                   
                   
                 Time between sensors for 108.12 mm/sec at 30° C. 
               
               
                   
                   
                 without AC feed-forward 
               
               
                   
                   
                 Belt DC time between sensors vs. temperature 
               
               
                   
                   
                 relationship (2 byte slope and offset) 
               
               
                   
                   
                 Belt length in zones for velocity control 
               
               
                   
                   
                 DC Velocity Count to set 108.12 mm/sec belt surface 
               
               
                   
                   
                 velocity at 30° C. 
               
               
                   
                   
                 AC Velocity Count, Initial Offset from DC count at 
               
               
                   
                   
                 Home Location (2 bytes, signed) 
               
               
                   
                   
                 AC Velocity Count, Number of steps (Ns) per table 
               
               
                   
                   
                 increment (4 lsb&#39;s of byte) 
               
               
                   
                   
                 Start of Scan, Initial Offset for K, M, C, &amp; Y 
               
               
                   
                   
                 (2 bytes each, unsigned) 
               
               
                   
                   
                 Start of Scan, Number of slices (N) per table 
               
               
                   
                   
                 increment for K, M, C, &amp; Y (1 or 2), 2 bits each 
               
               
                   
                   
                 Reserved for Future Use (Calibration Motor 
               
               
                   
                   
                 Halls/Rev, FG&#39;s/Rev, Ref Clock) 
               
               
                   
                   
                 Function enable (1 bit each): 1) cycle 
               
               
                   
                   
                 lockout, 2) page lockout, 3) job lock-out, 
               
               
                   
                   
                 4) DC velocity correction, 5) AC velocity feed- 
               
               
                   
                   
                 forward, 6) Start of Scan Delay feed-forward, 
               
               
                   
                   
                 7) transfer offset enable, 8) transfer table enable 
               
               
                   
                   
                 Page locked at time of manufacture (if Dallas 
               
               
                 2 
                 256 
                 Semiconductor i-Button) 
               
               
                   
                   
                 ITM subassembly EC Level 
               
               
                   
                   
                 Date of manufacture of ITM subassembly 
               
               
                   
                   
                 Date of manufacture of component parts 
               
               
                   
                   
                 Source of component parts 
               
               
                   
                   
                 Diameters of drive and idler rolls 
               
               
                   
                   
                 Belt tension, Belt length 
               
               
                   
                   
                 Page locked at time of manufacture 
               
               
                 3 
                 256 
                 ITM subassembly cycle tally @ 1000 cycles per bit = 
               
               
                   
                   
                 255K cycles max + lockout bit 
               
               
                 4 
                 256 
                 ITM subassembly page tally @ 1000 pages per bit = 
               
               
                   
                   
                 255K pages max + lockout bit 
               
               
                 5 
                 256 
                 ITM subassembly job tally @ 1000 jobs per bit = 255K 
               
               
                   
                   
                 jobs max + lockout bit 
               
               
                 6-8 
                 512 
                 Transfer operating point offsets  or  complete transter 
               
               
                   
                   
                 tables, 1st transfer PC&#39;s to belt 
               
               
                   
                   
                 Transfer Offset Table, 2 bits per Color, 00 or 
               
               
                   
                   
                 10 = Normal, 01 = High, 11 = Low 
               
               
                   
                   
                 Transfer table for each color at 1st transfer at 
               
               
                   
                   
                 1 byte per constant: 
               
               
                   
                   
                 [Slope breakpoints at full speed (2 bytes), 
               
               
                   
                   
                 Slope breakpoints at ½ speed (2 bytes)] 
               
               
                   
                   
                 [Offset 1, Slope 1, Offset 2, Slope 2, Offset 3, Slope 3] 
               
               
                   
                   
                 4 Tables for 1st transfer (4 colors) at full 
               
               
                   
                   
                 speed; 4 tables at ½ speed operation 
               
               
                   
                   
                 Pages locked at time of manufacture. 
               
               
                 8-11 
                 1024 
                 Transfer operating point offsets  or  complete 
               
               
                   
                   
                 transfer tables, 2nd transfer belt to media 
               
               
                   
                   
                 Transfer Offset Table, 2nd Transfer, 2 lsb&#39;s: 00 or 
               
               
                   
                   
                 10 = Normal, 01 = High, 11 = Low 
               
               
                   
                   
                 Transfer table for each media type at 1st transfer at 
               
               
                   
                   
                 2nd transfer 
               
               
                   
                   
                 [Slope breakpoints at full speed (2 bytes), 
               
               
                   
                   
                 Slope breakpoints at ½ speed (2 bytes)] 
               
               
                   
                   
                 [Offset 1, Slope 1, Offset 2, Slope 2, Offset 3, Slope 3] 
               
               
                   
                   
                 10 Tables for 10 media types at full speed; 10 tables for 
               
               
                   
                   
                 10 media types at ½ speed 
               
               
                   
                   
                 Pages locked at time of manufacture. 
               
               
                 12- 
                 2656 
                 Belt AC velocity correction, serial correction 
               
               
                 21.375 
                   
                 with respect to home hole 2 bits/zone, up to 1328 
               
               
                   
                   
                 zones; Ns speed change steps per encoded increment/ 
               
               
                   
                   
                 decrement 
               
               
                   
                   
                 Correction Table: 00 or 10 - no change; 01 = +Ns steps; 
               
               
                   
                   
                 11 = −Ns steps (˜0.01% per step) 
               
               
                   
                   
                 Plan of Record: 1264 zones of ˜0.703 mm each, 
               
               
                   
                   
                 pages locked at time of manufacture 
               
               
                 21.375- 
                 2656 
                 Belt Black-Ref Delay to image serial correction 
               
               
                 31.75 
                   
                 table 2 bits/zone, up to 1328 zones; 
               
               
                   
                   
                 N slices per encoded increment/decrement (1 or 2 slices 
               
               
                   
                   
                 where 1 slice = 1/7200 inches) 
               
               
                   
                   
                 Correction Table: 00 or 10 = no change; 01 = +N slices; 
               
               
                   
                   
                 11 = −N slices 
               
               
                   
                   
                 Plan of Record: 1264 zones of 16.9 scans each at 
               
               
                   
                   
                 600 dpi (889 mm); locked at mfg 
               
               
                 31.75- 
                 2656 
                 Belt Magenta-Ref delay to image serial correction 
               
               
                 42.125 
                   
                 table 2 bits/zone, up to 1328 zones; 
               
               
                   
                   
                 N slices per encoded increment/decrement 
               
               
                   
                   
                 (1 or 2 slices where 1 slice = 1/7200 inches) 
               
               
                   
                   
                 Correction Table: 00 or 10 = no change; 01 = +N slices; 
               
               
                   
                   
                 11 = −N slices 
               
               
                   
                   
                 Plan of Record: 1264 zones of 16.9 scans each at 
               
               
                   
                   
                 600 dpi (889 mm); locked at mfg 
               
               
                 42.125- 
                 2656 
                 Belt Cyan-Ref delay to image serial correction table 2 
               
               
                 52.5 
                   
                 1328 bits/zone, up to zones; 
               
               
                   
                   
                 N slices per encoded increment/decrement (1 or 2 slices 
               
               
                   
                   
                 where 1 slice = 1/7200 inches) 
               
               
                   
                   
                 Correction Table: 00 or 10 = no change; 
               
               
                   
                   
                 01 = +N slices; 11 = −N slices 
               
               
                   
                   
                 Plan of Record: 1264 zones of 16.9 scans each at 600 dpi 
               
               
                   
                   
                 (889 mm); locked at mfg 
               
               
                 52.5- 
                 2656 
                 Belt Yellow-Ref delay to image serial correction table 
               
               
                 62.875 
                   
                 2 bits/zone, up to 1328 zones; 
               
               
                   
                   
                 N slices per encoded increment/decrement (1 or 2 slices 
               
               
                   
                   
                 where 1 slice = 1/7200 inches) 
               
               
                   
                   
                 Correction Table: 00 or 10 = no change; 
               
               
                   
                   
                 01 = +N slices; 11 = −N slices 
               
               
                   
                   
                 Plan of Record: 1264 zones of 16.9 scans each at 600 dpi 
               
               
                   
                   
                 (889 mm); locked at mfg 
               
               
                   
               
             
          
         
       
     
     The subassembly is a field replaceable unit. Thus a worn out subassembly can be easily replaced with another subassembly which also has its own stored calibration data. The printer can use the new subassembly, which has its own set of calibration data unique to the subassembly, to provide a high quality printed image. 
     Referring now to FIG. 6, a flowchart showing a method  100  for providing transfer quality optimization of color planes deposited on a transfer belt is provided. 
     At a first step  110 , an image transfer subassembly is provided. The subassembly includes a transfer belt and a memory device. The memory device is used to store characterization data particular to the subassembly. 
     The next step  120  establishes a set of Transfer Operating Points for each transfer station as part of the characterization of the subassembly. The Transfer Operating Points take into account differences in the belt and transfer roll resistivity and enable the machine microcontroller to adjust the power supply settings in accordance with variations in the belt and transfer roll resistivity. 
     At step  130  the characterization data is stored in the memory. Accordingly, the data remains with the subassembly such that when the subassembly is installed into a printer, the associated characterization data (which may be different for each subassembly) is also maintained with the subassembly. 
     Finally, at step  140 , the characterization data is applied from the memory to the controller to provide the proper adjusting of the power supplies to take into account variations in the resistivity of the belt that may differ from subassembly to subassembly. 
     By way of the above described apparatus and method, errors associated with variations of the transfer belt subassembly are removed or significantly reduced. By including the memory device as part of the transfer belt subassembly, the transfer belt subassembly can be removed and a replacement subassembly installed while still maintaining a high precision of color plane registration and transfer quality on the transfer belt. 
     Having described preferred embodiments of the present invention it should be apparent to those of ordinary skill in the art that other embodiments and variations of the presently disclosed embodiment incorporating these concepts may be implemented without departing from the inventive concepts herein disclosed. Accordingly, the invention should not be viewed as limited to the described embodiments but rather should be limited solely by the scope and spirit of the appended claims.