Patent Publication Number: US-6711363-B1

Title: Method of determining a charging device pre-fault status, a printing machine arranged with the same method, a method of forming a charging device service message and a method of triggering a cleaning cycle

Description:
FIELD OF THE INVENTION 
     This application relates generally to xerographic charging devices and more particularly to determining a pre-fault status condition in such charging devices. 
     BACKGROUND OF THE INVENTION 
     Xerographic printing machines are known. It is known that some xerographic engines have a problem with frequent DC pin scorotron “pin arcs”. The root cause is believed to be as a result of pin and/or grid contamination. Contamination can be the result of fuser silicone oil volitles getting into the xerographic cavity, which form silica dendrites on the pins and/or grids of charging devices. There is also the and possibly of pin and/or grid contamination with paper dust, toner and or toner additives. Pin scorotrons are typically operated under closed loop feedback control with a constant current maintained between the pins and grid. The voltage required to maintain this constant current is called the “operating voltage”. Pin and/or grid contamination will cause a variation in this operating voltage. Furthermore the contamination can vary in its electrical conductivity as a function device operation history (powered/unpowered). This contamination conductivity variation is likely the root cause of the operating voltage variation. 
     When a pin to grid arc occurs, the print engine does an immediate hard-down, requiring clearing of the paper path, a time consuming job. The arc energy is high enough to disrupt communications, which can require a re-boot to restore the machine to operation. Regardless of the mature machine interval between arcs, it is advantageous to predict when a pin arc is likely to occur. 
     BRIEF SUMMARY OF THE INVENTION 
     In a first aspect of the invention, there is described a method of determining a charging device pre-fault status, the charging device forming a charging device operating voltage that varies with time, the charging device comprising an included printing machine, the method comprising sampling the charging device operating voltage, forming a slope value based on a charging device operating voltage rate of change per unit time, and determining when the slope value falls in a charging device pre-fault status range of values. 
     In a second aspect of the invention, there is described a printing machine comprising a charging device, the charging device forming a charging device operating voltage that varies with time, the printing machine arranged to determine a charging device pre-fault status in accordance with a method, the method comprising sampling the charging device operating voltage, forming a slope value based on an charging device operating voltage rate of change per unit time, and determining when the slope value falls in a charging device pre-fault status range of values. 
     In a third aspect of the invention, there is described a method of forming a charging device service message based on a charging device operating voltage that varies with time, the charging device comprising an included printing machine, the method comprising sampling the charging device operating voltage, forming a slope value based on a charging device operating voltage rate of change per unit time, and forming a charging device service message when the slope value falls in a charging device pre-fault status range of values. 
     In a fourth aspect of the invention, there is described a method of triggering a cleaning cycle based on a charging device operating voltage that varies with time, the charging device comprising an included printing machine, the method comprising sampling the charging device operating voltage, forming a slope value based on a charging device operating voltage rate of change per unit time, and triggering a cleaning cycle in an included automatic cleaning system when the slope value falls in a charging device pre-fault status range of values. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 depicts a printing machine  100 . An included charging device  10  forms a charging device operating voltage  11 . The printing machine  100  determines a charging device  10  pre-fault status condition based on an included method  200 . Messages  110 ,  120  and  130  are sent to a user or operator  1  by means of any of an included display unit  2   a , internet communication network  2   b , or wireless or radio frequency communication network  2   c . The printing machine  100  optionally includes an automatic cleaning system  30 . 
     FlGS.  2 A and  2 B depict the method  200 . 
     FIG. 3 depicts an optional embodiment of step  204  in FIG.  2 A. 
     FIG. 4 depicts an optional step  401  of triggering a cleaning cycle. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Briefly, a printing machine comprises a charging device that forms a variable charging device operating voltage. A charging device pre-fault status condition indicates that a charging device fault condition is likely to occur. The printing machine determines the charging device pre-fault status condition by a method comprising sampling the operating voltage; forming a slope value based on a charging device operating voltage rate of change per unit time; and determining when the slope value falls in a charging device pre-fault status range of values. When the charging device pre-fault status determination is made, one of several messages is formed based on a current print count value. This message is then sent to a user or operator by means of an included display unit, internal communication network, or wireless or radio frequency communication network. When the print count value falls in a charging device replacement range of values, a replacement message is sent to inform the user or operator that the charging device needs to be replaced. Otherwise, when the print count value does not fall in this range of values, a cleaning message is sent to inform the user or operator that the charging device needs to be cleaned. 
     As a result of the present invention, monitoring of the charging device pin to grid voltage time track enables the machine control system to anticipate an upcoming pin arc event. The operator can then be notified (before an arc occurs) to clean or replace the charging device. 
     In one typical printing machine, the pin scorotron charging device operates on a constant current of 2.085 mA. The power supply output voltage varies to maintain this constant pin current. A pin voltage monitor signal is available to the machine control system along with the grid voltage. The pin to grid voltage can be calculated. Data show the pattern of decreasing pin to grid voltage and more voltage swinging before an arc occurs. New or well-cleaned charging devices do not exhibit this decrease in pin to grid voltages. 
     In accordance with the present invention, the pin to grid voltage signature is used as a fault trigger. The fault is used to instruct the operator to clean the device before an arc occurs. For example, the fault can be triggered if the pin to grid voltage variation is more than 100 volts in the last 60 seconds of operation. 
     Alternatively, the fault can look at the High Frequency Service Interval cleaning interval remaining on the faulted charging device and instruct the operator to clean or replace the charging device depending on the run time since the last cleaning. A charging device that trips the “Anticipated Arc Soon” fault shortly after a previous cleaning would be replaced. A fault that occurs close to the cleaning interval would instruct the operator to clean the device. 
     Referring now to FIG. 1, there is depicted a printing machine  100  coupled to any of a display unit  2   a , internet communication network  2   b , or wireless or radio frequency communication network  2   c . Items  2   a ,  2   b  and  2   c  are collectively designated reference number  2 . 
     In a first embodiment, the printing machine  100  comprises a copier. 
     In a second embodiment, the printing machine  100  comprises a network printer. 
     In a third embodiment, the printing machine  100  comprises a facsimile machine. 
     Printing machine  100  includes a charging device  10  that forms a charging device operating voltage  11  that varies with time. 
     In one embodiment, the operating voltage  11  is based on a charging device  10  pin to grid differential voltage that results from constant pin to grid current operation. 
     In one embodiment, the printing machine  100  includes a counter  20  that forms a print count value  21 . 
     In one embodiment, the print count value  21  is based on a total number of copies made using the charging device  10  since a first event of the charging device  10 &#39;s installation or a second event of the charging device  10 &#39;s most-recent cleaning, whichever event occurred last. 
     The printing machine  100  determines a charging device  10  pre-fault status condition in accordance with an included method  200 . The charging device  10  pre-fault status indicates that a changing device fault condition is likely to occur. 
     In one embodiment, the charging device  10  fault condition comprises a pin to grid arcing. 
     In accordance with the method  200 , various messages  110 ,  120  and  130  are formed and sent  211 ,  221  and  231  to a user or operator  1  by means of any of the items  2 . 
     FIGS. 2A and 2B depict the method  200 . 
     Referring now to FIG. 2A, the method begins with starting a print job, step  201 . The method then goes to step  202 . 
     In step  202  charging power is applied to the charging device  10 . The method then goes to step  203 . 
     In step  203  the charging device operating voltage  11  is sampled. The method then goes to step  204 . 
     In step  204  a slope value is formed based on a charging device operating voltage  11  rate of change per unit time. 
     In one embodiment, in step  204  the slope value is formed based on the optional steps  301 ,  302  and  303  that are described below in connection with FIG.  3 . 
     In another embodiment, in step  204  the slope value is formed based on any suitable process. 
     After forming the slope value in step  204 , the process goes to step  205 . 
     In step  205  it is determined when the slope value falls in a charging device pre-fault status range of values. 
     In one embodiment, the charging device pre-fault status range of values comprise slope values greater than a first threshold. 
     In another embodiment, the charging device pre-fault status range of values comprise slope values less than a second threshold. 
     In still another embodiment, the charging device pre-fault status range of values comprise slope values greater than a first threshold and slope values less than a second threshold. Optionally, in one embodiment, the first threshold equals the absolute value of the second threshold. 
     Still referring to step  205 , when the slope value falls in the charging device pre-fault status range of values, the step  205  determination is positive. 
     In one embodiment, after this step  205  positive determination the process goes in sequence to steps  210  and  211 , depicted in FIG. 2A, and then to step  217 , depicted in FIG.  2 B. However, in another embodiment, after this step  205  positive determination the process goes directly to step  217 , depicted in FIG.  2 B. 
     Still referring to step  205 , when the slope value does not fall in the charging device pre-fault status range of values, the step  205  determination is negative and the process goes to step  206 . 
     In step  206 , the process determines when to continue the current printing job. 
     When the current printing job continues, the determination  206  is positive and the process returns to step  203 . 
     Otherwise, when the current printing job does not continue, the determination  206  is negative and the process goes to step  290 . 
     In step  290  charging power is removed from the charging device  10 . The process then goes to step  299 . 
     In step  299  the current printing job stops. 
     Steps  210  and  211  are now described. 
     In step  210  a charging device pre-fault status message  110  is formed. The message  110  indicates that a charging device  10  fault condition is likely to occur. The process then goes to step  211 . 
     In step  211  the charging device pre-fault status message  110  is sent to the user or operator  1  by means of any of the display unit  2   a , the internet communication network  2   b  or the wireless or radio frequency communication network  2   c . The process then goes to step  217 , depicted in FIG.  2 B. 
     Referring now to FIG. 2B, in step  217  a current print count value  21  is formed. 
     In one embodiment, the current print count value  21  is formed by an included counter  20 . 
     In another embodiment, the print count value  21  is formed by any suitable means. 
     The process then goes to step  218 . 
     In step  218  it is determined when the print count value  21  falls in a charging device replacement range of values. 
     Still referring to step  218 , when the print count value  21  falls in the charging device replacement range of values, the step  218  determination is positive and the process goes in sequence to steps  220  and  221 . 
     In step  220  a charging device replacement message  120  is formed. The charging device replacement message  120  indicates that the charging device  10  needs to be replaced. The process then goes to step  221 . 
     In step  221  the charging device replacement message  120  is sent to the user or operator  1  by means of any of the display unit  2   a , the internet communication network  2   b  or the wireless or radio frequency communication network  2   c.    
     Still referring to step  218 , when the print count value  21  does not fall in the charging device replacement range of values, the step  218  determination is negative and the process goes in sequence to steps  230  and  231 . 
     In step  230  a charging device cleaning message  130  is formed. The charging device cleaning message  130  indicates that the charging device  10  needs to be cleaned. The process then goes to step  231 . 
     In step  231  the charging device cleaning message  130  is sent to the user or operator  1  by means of any of the display unit  2   a , the internet communication network  2   b  or the wireless or radio frequency communication network  2   c.    
     Referring to FIG. 3 there is depicted an optional embodiment of the step  204  of FIG.  2 A. Thus, the depicted steps  301 ,  302  and  303  comprise one possible method to form the slope value in step  204  of FIG.  2 A. 
     Referring to step  301 , in one embodiment, the process forms a first charging device operating voltage  11  value, V 1 , at a first time, T 1 . (Note that an alternate embodiment of step  301  is described below.) The process then goes to step  302 . 
     In step  302  the process forms a second charging device operating voltage  11  value, V 2 , at a second time, T 2 . The process then goes to step  303 . 
     In step  303  the process forms a slope value equal to a ratio of a difference of the second charging device operating voltage  11  value, V 2 , and the first charging device operating voltage  11  value, V 1  and a difference of the second time, T 2 , and the first time, T 1 . Thus, in step  303  the process forms a slope value equal to (V 2 −V 1 ) divided by (T 2 −T 1 ). 
     Referring still to FIG. 3, with momentary cross-reference back to FIG. 2A, it will be understood that the sequence of steps  301 - 303  is repeatedly performed while the current printing job continues to run. Hence, in an alternate embodiment, in step  301  the first charging device operating voltage  11  value, V 1 , is set to the value of the second charging device operating voltage  11  value, V 2 , that was formed in the prior step  302  in the prior iteration of the sequence of steps  301 - 303 , and the first operating time, T 1 , is set to the second time, T 2 , that was formed during the same prior step  302  in the same prior iteration of the sequence of steps  301 - 303 . 
     Referring again to steps  218 , in one embodiment, the charging device replacement range of values is based on a charging device  10  target cleaning interval. 
     For example, in one embodiment the target cleaning interval is 1,000 copies and the charging device replacement range of values is less than 500 copies. 
     In this example, first assume that when the charging device pre-fault status is determined to exist by step  205 , the corresponding print count value determined by step  217  is 490 copies. In this case, step  218  determines that the print count value (490 copies) falls in the replacement range of values (less than 500 copies). As a result, the step  218  determination is positive, and so a charging device replacement message  120  is formed by step  220  and sent by step  221  to the user or operator  1 . 
     In this same example, now second assume that when the charging device pre-fault status is determined to exist by step  205 , the corresponding print count value determined by step  217  is 910 copies. In this case, step  218  determines that the print count value (910 copies) does not fall in the replacement range of values (less than 500 copies). As a result, the step  218  determination is negative, and so a charging device cleaning message  130  is formed by step  230  and sent by step  231  to the user or operator  1 . 
     Referring again to FIG. 1, in one embodiment, the printing machine  100  comprises an automatic cleaning system  30 . In this embodiment, the pre-fault status determining step  205 , depicted in FIG. 2A, is used to trigger the cleaning cycle on the next cycle down, this triggering depicted as step  401  in FIG.  4 . 
     Thus, there has been described a method  200  of determining a charging device  10  pre-fault status, the charging device  10  forming a charging device operating voltage  11  that varies with time, the charging device  10  comprising an included printing machine  100 , the method  200  comprising sampling (step  203 ) the charging device operating voltage  11 , forming (step  204 ) a slope value based on a charging device operating voltage  11  rate of change per unit time, and determining (step  205 ) when the slope value falls in a charging device pre-fault status range of values. 
     Further, there has been described a printing machine  100  comprising a charging device  10 , the charging device  10  forming a charging device operating voltage  11  that varies with time, the printing machine  100  arranged to determine a charging device  10  pre-fault status in accordance with a method  200 , the method  200  comprising sampling (step  203 ) the charging device operating voltage  11 , forming (step  204 ) a slope value based on an charging device operating voltage  11  rate of change per unit time, and determining (step  205 ) when the slope value falls in a charging device pre-fault status range of values. 
     Further, there has been described a method  200  of forming a charging device  10  service message (the charging device replacement message  120  and the charging device cleaning message  130 ) based on a charging device  10  operating voltage  11  that varies with time, the charging device  10  comprising an included printing machine  100 , the method  200  comprising sampling (step  203 ) the charging device operating voltage  11 , forming (step  204 ) a slope value based on a charging device operating voltage  11  rate of change per unit time, and forming (step  220  and step  230 ) a charging device service message (the charging device replacement message  120  and the charging device cleaning message  130 ) when (step  205  determines that) the slope value falls in a charging device pre-fault status range of values. 
     Further, there has been described a method  200  of triggering  401  a cleaning cycle based on a charging device  10  operating voltage  11  that varies with time, the charging device  10  comprising an included printing machine  100 , the method  200  comprising sampling (step  203 ) the charging device operating voltage  11 , forming (step  204 ) a slope value based on a charging device operating voltage  11  rate of change per unit time, and triggering  401  a cleaning cycle in an included automatic cleaning system  30  when (step  205  determines that) the slope value falls in a charging device pre-fault status range of values. 
     The table below lists the drawing element reference numbers together with their corresponding written description: 
     
       
         
           
               
               
             
               
                   
               
               
                 Number: 
                 Description: 
               
               
                   
               
             
            
               
                  1 
                 operator or user 
               
               
                  2a 
                 display unit 
               
               
                  2b 
                 internet communication network 
               
               
                  2c 
                 wireless or radio frequency communication network 
               
               
                  2 
                 any of 2a, 2b and 2c 
               
               
                  10 
                 charging device 
               
               
                  11 
                 operating voltage 
               
               
                  12 
                 charging device pin to grid differential voltage 
               
               
                  20 
                 print counter 
               
               
                  21 
                 print count value 
               
               
                  30 
                 optional automatic cleaning system 
               
               
                 100 
                 printing machine (copier, network printer or facsimile) 
               
               
                 110 
                 charging device pre-fault status message 
               
               
                 120 
                 charging device replacement message 
               
               
                 130 
                 charging device cleaning message 
               
               
                 200 
                 method of determining a charging device pre-fault status 
               
               
                 201 
                 start print job 
               
               
                 202 
                 charging device power = on 
               
               
                 203 
                 sampling the charging device operating voltage 
               
               
                 204 
                 forming a slope value 
               
               
                 301 
                 forming a first charging device operating voltage value 
               
               
                   
                 at a first time 
               
               
                 302 
                 forming a second charging device operating voltage value 
               
               
                   
                 at a second time 
               
               
                 303 
                 forming a ratio of the difference of the second and first 
               
               
                   
                 charging device operating voltage values and a 
               
               
                   
                 difference of the second and first times 
               
               
                 205 
                 determining when the slope value falls in a charging device 
               
               
                   
                 pre-fault status range of values 
               
               
                 206 
                 continue job? 
               
               
                 207 
                 forming a print count value 
               
               
                 208 
                 determining when the print count value falls in a charging 
               
               
                   
                 device replacement range of values 
               
               
                 210 
                 forming a charging device pre-fault status message 
               
               
                 211 
                 sending the charging device pre-fault status message 
               
               
                 220 
                 forming a charging device replacement message 
               
               
                 221 
                 sending the charging device replacement message 
               
               
                 230 
                 forming a charging device cleaning message 
               
               
                 231 
                 sending the charging device cleaning message 
               
               
                 290 
                 charging device power = off 
               
               
                 299 
                 stop print job 
               
               
                 401 
                 trigger the cleaning cycle on the next cycle down 
               
               
                   
               
            
           
         
       
     
     While various embodiments of a method of determining a charging device pre-fault status, a printing machine arranged with the same method, a method of forming a charging device service message and a method of triggering a cleaning cycle, in accordance with the present invention, have been described hereinabove, the scope of the invention is defined by the following claims.