Patent Publication Number: US-8532507-B2

Title: Image forming apparatus in which genuine cartridge with and without memory device are usable

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of prior U.S. application Ser. No. 11/935,778, filed Nov. 6, 2007, which claims the foreign priority benefit under Title 35, United States Code, §119 (a)-(d), of Japanese Patent Application No. 2006-310282, filed on Nov. 16, 2006 in the Japan Patent Office, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image-forming apparatus, such as a laser printer and a digital copier, having a toner cartridge. 
     2. Description of Related Art 
     Typically, in a laser printer or a digital copier, as an example of the image-forming apparatus, a toner cartridge or other consumable part is installed removably and configured replaceably. In order to verify whether or not a toner cartridge installed for replacement is a genuine toner cartridge (hereinafter referred to also as “genuine product”), various image-forming apparatuses have been proposed. 
     In an image-forming apparatus disclosed in JP 2006-215441 A (claim 1 and FIG. 2), a memory device having an identification code stored therein is installed in the toner cartridge, so that the identification code stored in the memory device is retrieved to verify whether or not the toner cartridge is a genuine product. 
     Hereupon, the toner cartridge packaged and supplied together with the image-forming apparatus at the time of purchase of the apparatus (hereinafter referred to as “supplied toner cartridge”) is, needless to say, a genuine product, and thus theoretically need not have any memory device, such as a radio frequency identification (RFID), installed therein. However, a hitherto known apparatus always used to have a memory device installed in its supplied toner cartridge as well by necessity, because the verification would produce an erroneous result that the supplied toner cartridge is not a genuine product if it had no memory device installed therein. This would disadvantageously entail unnecessary cost. 
     It would thus be desirable to provide an image-forming apparatus which properly distinguishes between the genuine toner cartridge and the other toner cartridge (hereinafter referred to also as “non-genuine product”) to exercise control tailored to these two types of toner cartridge, even if the installed toner cartridge is a supplied toner cartridge without any memory device included therein. Against this backdrop, the present invention has been made in an attempt to overcome the disadvantages described above. 
     Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, there is provided an image-forming apparatus having a function of verifying genuineness of a toner cartridge with or without a memory device to form an image using toner contained in the toner cartridge. The image-forming apparatus according to an exemplary embodiment of the present invention comprises a counter, a cartridge detector, a reader and a controller. The counter is configured to count a value concerning image formation each time when the image-forming apparatus performs the image formation. The cartridge detector is configured to determine the presence or absence of the toner cartridge. The reader is configured to retrieve data from a memory device in the toner cartridge. The controller is configured to exercise one of two types of control over units of the image-forming apparatus. The type of control the controller is configured to exercise is either a first type of control conformable to a toner cartridge other than a genuine toner cartridge or a second type of control conformable to the genuine toner cartridge. The first type of control is exercised if the following conditions are satisfied: the cartridge detector determines that the toner cartridge is present; the value counted by the counter is greater than a predetermined value; and the reader has failed retrieval of predetermined data. Otherwise (if any of the above conditions is not satisfied), the second type of control conformable to the genuine toner cartridge is exercised. 
     With this configuration, the controller is configured to exercise the second type of control conformable to the genuine toner cartridge when the value counted by the counter is not greater than a predetermined value even if the reader has failed retrieval of predetermined data for reasons, such as the absence of the toner cartridge or the absence of the memory device in the toner cartridge. That is, if the value counted by the counter is not greater than the predetermined value, the controller assumes that a genuine toner cartridge without a memory device (e.g., a toner cartridge supplied together with the apparatus) is installed in the image-forming apparatus, and proceeds to exercise the second type of control conformable to the genuine toner cartridge. Accordingly, the image-forming apparatus configured as described above may be conformable to a genuine toner cartridge without a memory device such as a toner cartridge supplied together with the apparatus, as well as a genuine toner cartridge with a memory device and other toner cartridges. 
     Hereupon, the value concerning image formation counted each time when the image-forming apparatus performs the image formation may be a value increasing substantially in proportion to the quantity of operation for image formation, for example, the quantity of laser beam radiation for forming an electrostatic latent image on a photoconductor (i.e., the number of dots that has been printed), or the quantity of recording paper that has been consumed. 
     The image-forming apparatus according to another exemplary embodiment of the present invention comprises a cartridge detector, a toner detector, a reader and a controller. The cartridge detector is configured to determine the presence or absence of the toner cartridge. The toner detector is configured to determine whether or not the toner cartridge is empty of toner. The reader is configured to retrieve data from a memory device in the toner cartridge. The controller is configured to exercise one of two types of control over units of the image-forming apparatus. The type of control the controller is configured to exercise is either a first type of control conformable to a toner cartridge other than a genuine toner cartridge or a second type of control conformable to the genuine toner cartridge. The first type of control is exercised if the following conditions are satisfied: the cartridge detector determines that the toner cartridge is present; the toner detector has ever determined that the toner cartridge is empty of toner; and the reader has failed retrieval of predetermined data. Otherwise (if any of the above conditions is not satisfied), the second type of control conformable to the genuine toner cartridge is exercised. 
     With this configuration, the controller is configured to exercise the second type of control conformable to the genuine toner cartridge when the toner detector has never before determined that the toner cartridge is empty of toner even if the reader has failed retrieval of predetermined data for reasons, such as the absence of the toner cartridge or the absence of the memory device in the toner cartridge. That is, if the toner detector has never before determined that the toner cartridge is empty of toner, the controller assumes that a genuine toner cartridge without a memory device (e.g., a toner cartridge supplied together with the apparatus) is installed in the image-forming apparatus, and proceeds to exercise the second type of control conformable to the genuine toner cartridge. Accordingly, the image-forming apparatus configured as described above may be conformable to a genuine toner cartridge without a memory device such as a toner cartridge supplied together with the apparatus, as well as a genuine toner cartridge with a memory device and other toner cartridges. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above aspects, other advantages and further features of the present invention will become more apparent by describing in detail illustrative, non-limiting embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a vertical section of a laser printer according to an exemplary embodiment of the present invention; 
         FIG. 2  is a block diagram of a control unit; 
         FIG. 3  is a time chart for explaining a process of control exercised by the control unit according to a first embodiment, as illustrated with the time axis represented by the horizontal axis; 
         FIG. 4  is a flowchart showing a process of control at a time when printing is started, according to the first embodiment; 
         FIG. 5  is a flowchart showing a process of control at a time when printing is started, according to a second embodiment; 
         FIG. 6  is a block diagram of a control unit according to a third embodiment; 
         FIG. 7  is a time chart for explaining a process of control exercised by the control unit according to the third embodiment, as illustrated with the time axis represented by the horizontal axis; 
         FIG. 8  is a flowchart showing a process of control at a time when printing is started, according to the third embodiment; and 
         FIG. 9  is a flowchart showing a process of control at a time when printing is started, according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     First Embodiment 
     General Setup of Laser Printer 
     At the outset, a detailed description will be given of the exemplary embodiments of the present invention with reference made to the drawings where appropriate. 
     In the drawings to which reference will be made, shown in  FIG. 1  is a general setup of a laser printer as an example of an image-forming apparatus according to an exemplary embodiment of the present invention, and shown in a block diagram of  FIG. 2  is a control unit of the laser printer. 
     As shown in  FIG. 1 , the laser printer  1  includes a feeder unit  4  for feeding a sheet  3  into a body casing  2 , an image-forming unit  5  for forming an image on a sheet  3  fed by the feeder unit  4 , a control unit  100  (see  FIG. 2 ) as a controller configured to exercise control over each unit of the laser printer, and a number of other components. 
     Feeder Unit Setup 
     The feeder unit  4  includes a sheet feed tray  6  and a sheet pressure plate  7 . The sheet feed tray  6  is removably installed in a bottom space provided in the body casing  2 . The sheet pressure plate  7  is provided in the sheet feed tray  6 . The feeder unit  4  also includes a sheet feed roller  8 , a sheet feed pad  9 , and a paper powder remover rollers  10 ,  11 . The sheet feed roller  8  and the sheet feed pad  9  are provided above an edge of one side of the sheet feed tray  6 . The paper powder remover rollers  10 ,  11  are provided along a route of conveyance of the sheet  3  downstream relative to the sheet feed roller  8  in a direction of the conveyance of the sheet  3 . The feeder unit  4  further includes a registration roller  12  located downstream relative to the paper powder remover rollers  10 ,  11 . 
     The feeder unit  4  constructed as described above is configured to bring one sides of sheets  3  in the sheet feed tray  6  close to the sheet feed roller  8  by means of the sheet pressure plate  7 , feed the sheets  3  one after another by means of the sheet feed roller  8  and the sheet feed pad  9  to pass each sheet  3  through rollers  10 ,  11  and  12  to the image-forming unit  5  on a one-by-one basis. 
     Image-forming Unit Setup 
     The image-forming unit  5  includes a scanner unit  16 , a process cartridge  17 , a fixing unit  18 , and other components. 
     Scanner Unit Setup Outlined 
     The scanner unit  16  is disposed in an upper space provided in the body casing  2 . The scanner unit  16  includes a light source device (not shown), a polygon mirror  19 , an fθ lens  20 , a correcting lens  21 , and reflecting mirrors  22 ,  23 ,  24 . The polygon mirror  19  is typically shaped like a regular hexagonal prism having mirrors formed at its six sides, and configured to reflect a laser beam emitted from the light source device while being driven to spin so that the laser beam is biased to scan in a main scanning direction. The fθ lens  20  is configured to convert the laser beam made by the polygon mirror  19  to scan with a constant angular speed into a laser beam which scans a surface of a photoconductor drum  27  at a constant speed and forms an image thereon. 
     Process Cartridge Setup 
     The process cartridge  17  is disposed below the scanner unit  16 , and detachably installed in the body casing  2  through an opening over which is provided a front cover  13  swingably hinged at a sidewall of the body casing  2 . A hollow housing  51  making up the outer frame of the process cartridge  17  accommodates a toner cartridge  28 , a photoconductor drum  27 , a scorotron charger  29 , a transfer roller  30 , and other components. 
     The toner cartridge  28  is detachably attached to the housing  51 , and includes a development roller  31 , a doctor blade  32 , a supply roller  33  and a toner hopper  34 . Toner in the toner hopper  34  is supplied to the development roller  31  by the action of the supply roller  33  rotating in a direction indicated by arrow (counterclockwise), and at the same time becomes positively charged by friction between the supply roller  33  and the development roller  31 . The toner supplied onto the development roller  31  goes between the doctor blade  32  and the development roller  31  as the development roller  31  rotates in a direction indicated by arrow (counterclockwise), to form a thin film in a predetermined thickness, so that the film of toner is retained on the development roller  31 . 
     The photoconductor drum  27  is supported by the housing  51  in such a manner that the photoconductor drum  27  is rotatable in a direction indicated by arrow (clockwise). The photoconductor drum  27  has its drum body grounded, while a positively charged photoconductive layer made of polycarbonate is formed at a cylindrical surface of the drum body. 
     The scorotron charger  29  is disposed over the photoconductor drum  27  and opposed to the photoconductive surface of the photoconductor drum  27  with a gap left between the photoconductor drum  27  and the scorotron charger  29  so as to keep the scorotron charger  29  from contact with the photoconductor drum  27 . The scorotron charger  29  may be a known charger of scorotron type having a charging wire made of tungsten or the like for generating corona discharge and configured to positively charge the surface of the photoconductor drum  27  uniformly. 
     The transfer roller  30  is disposed under the photoconductor drum  27  and opposed to the photoconductive surface of the photoconductor drum  27 , so as to have contact with the photoconductive surface of the photoconductor drum  27 . The transfer roller  30  is supported by the housing  51  in such a manner that the transfer roller  30  is rotatable in a direction indicated by arrow (counterclockwise). The transfer roller  30  has a metal roller shaft covered with a conductive rubber material. In the transfer process, a transfer bias generated under constant-current control is applied to the transfer roller  30 . 
     In operation, the photoconductive surface of the photoconductor drum  27  is positively charged uniformly by the scorotron charger  29 , and then exposed to a rapidly scanning laser beam from the scanner unit  16 . This exposure process lowers the potential of an exposed area(s) on the photoconductive surface, thus forming an electrostatic latent image based upon the image data. Hereupon, “electrostatic latent image” is an invisible image produced on the uniformly positively charged surface of the photoconductor drum  27  with the exposed areas made lower in potential by exposure to the laser beam. Next, as the development roller  31  rotates, toner particles carried on the development roller  31  come in contact with the opposed photoconductor drum  27 ; then the toner particles are supplied onto the surface of the photoconductor drum  27 , and transferred to the areas corresponding to the electrostatic latent image formed thereon. The toner particles are retained selectively, i.e., solely in the areas corresponding to the electrostatic latent image, and thus visualize the latent image, to form a toner image. The process described above is called reversal process. 
     Thereafter, as the photoconductor drum  27  and the transfer roller  30  rotate so that the sheet  3  is held and fed forward between the rollers  27  and  30 , the toner image formed on the surface of the photoconductor drum  27  is transferred to the sheet  3  while the sheet  3  is conveyed between the photoconductor drum  27  and the transfer roller  30 . 
     Fixing Unit Setup 
     The fixing unit  18 , which is disposed downstream relative to the process cartridge  17 , includes a heating roller  41 , a pressure roller  42  opposed to the heating roller  41  and configured to be pressed against the heating roller  41 , and a pair of conveyor rollers  43  disposed downstream relative to the heating roller  41  and the pressure roller  42 . In the fixing unit  18  constructed as described above, the toner image transferred onto the sheet  3  is fixed by heating and fusing the toner while the sheet  3  goes between the heating roller  41  and the pressure roller  42 . Thereafter, the sheet  3  is conveyed by the conveyor rollers  43  to a sheet output path  44 . The sheet  3  forwarded to the sheet output path  44  is then discharged by sheet output rollers  45  onto a sheet output tray  46 , or returned by reverse rotation of the sheet output rollers  45  and switching of a flapper  49  into the apparatus, so that the sheet  3  is supplied again to a point upstream relative to the image-forming unit  5  by a plurality of reverse conveyor rollers  50 , for double-sided printing. 
     Control Unit Setup 
     To the control unit  100  as shown in  FIG. 2  are electrically and communicatively coupled a counter  110 , a nonvolatile memory  120 , a toner empty sensor  135 , a display  150 , a RFID tag reader  160 , and other components. The counter  110  in this embodiment is configured to count the number of lighting dots which is indicative of the quantity of laser beam radiation. The toner empty sensor  135  is an example of a cartridge detector configured to determine the presence or absence of the toner cartridge  28 , i.e., whether or not the toner cartridge  28  is installed in the laser printer  1 , by detecting the presence or absence of toner. The display  150  is a display device comprised, for example, of liquid crystal material and other components. The RFID tag reader  160  is an example of a reader configured to retrieve data from an RFID tag (as an example of a memory device)  52  provided in the toner cartridge  28 . 
     The RFID tag  52  includes a memory unit  52   a  configured to store data for the toner cartridge  28 , and a communication unit  52   b  configured to communicate with the control unit  100 . In the memory unit  52   a  is stored information on the toner cartridge  28  which includes identification information (hereinafter referred to as “ID”), date (year/month/day) of manufacture, serial number, and the like. The communication unit  52   b  is configured to respond to communication instructions transmitted through the RFID tag reader  160  from the control unit  100 ; upon receipt of the communication instructions, the communication unit  52   b  retrieves data from the memory unit  52   a  and transmits the retrieved data through the RFID tag reader  160  to the control unit  100 . Thus, a toner cartridge  28  with an RFID tag  52  can be identified as a genuine product without fail by the fact that the data such as a corresponding ID can be retrieved from the RFID tag  52 . 
     A registration sensor  105  is provided along a route of conveyance of a sheet  3  in a position upstream relative to the registration roller  12 , and configured to be turned ON when a sheet  3  is brought into contact with an actuator thereof disposed on the route of conveyance of the sheet  3 , and turned OFF when no sheet  3  is brought into contact with the actuator. The registration sensor  105  outputs a detection signal that is either a high-level signal or a low-level signal corresponding to the ON or OFF of the actuator, which is received by the control unit  100 . The differentiated detection signal level (high or low) allows the control unit  100  to determine the presence or absence of the paper  3 . From another viewpoint, the registration sensor is thus able to determine the quantity of paper  3  consumed. 
     The counter  110  is configured to count the number of light-emitting dots, indicative of the quantity of laser light radiation, which varies according to the image data. The cumulatively totalized value of the number of dots correlates with the quantity of toner consumed. The counter  110  is configured to keep the count value from being reset. 
     The toner empty sensor  135  is comprised of an optical sensor having a light-emitting element and a light-receiving element. The light-emitting element and the light-receiving element are disposed at outsides of windows (not shown) provided respectively in opposed sidewalls of the toner cartridge  28 , so as to face each other through the windows. The toner empty sensor  135  uses the ratio of the quantity of light received by the light-receiving element to the quantity of light emitted from the light-emitting element, to determine the presence or absence of toner in the toner cartridge  28 , and outputs a detection signal to the control unit  100 . The toner empty sensor  135  is configured to detect the presence of toner in the toner cartridge  28 , and thus may serve as a cartridge detector to determine whether the toner cartridge  28  is installed. 
     The RFID tag reader  160  is provided at a sidewall of the body casing  2 , and arranged in such a position that it comes to a position opposed to the RFID tag  52  of the toner cartridge  28  when the toner cartridge  28  is installed. The RFID tag reader  160  electromagnetically reads data concerning the toner cartridge  28  in a noncontact manner from the memory unit  52   a  of the RFID tag  52 . 
     The cover sensor  170  is provided in the body casing  2  and arranged near the front cover  13  so that the front cover  13  comes in contact with an actuator (not shown) of the cover sensor  170  when the front cover  13  is closed properly and completely. The cover sensor  170  has its actuator located on a path along which the front cover  13  is closed, and thus turns ON in the wake of contact of the front cover  13  with the actuator followed by the closing operation of the front cover  13 . On the other hand, the cover sensor  170  remains OFF until the front cover  13  reaches an appropriate closed position and touches the actuator. The cover sensor  170  outputs a detection signal that is either high-level signal or a low-level signal corresponding to the ON or OFF of the actuator, which is received by the control unit  100 . Thus differentiated detection signal level (high or low) allows the control unit  100  to determine the state of the front cover  13 , i.e., whether the front cover  13  is open or closed. 
     The memory  120  is comprised, for example, of a nonvolatile random-access memory or NVRAM, and configured to hold a predetermined value for use as a reference in determining whether a toner cartridge currently in use is a supplied toner cartridge or not. The predetermined value, in this embodiment, is the number of dots printable derived from the quantity of toner in the supplied toner cartridge. That is, the count value counted by the counter  110  not greater than the predetermined value spells that there is toner remaining in the supplied toner cartridge and thus the supplied toner cartridge is installed. 
     The control unit  100  is comprised of a central processing unit or CPU, a random-access memory or RAM, a read-only memory or ROM, and other components, and configured to exercise control over units of the laser printer  1  to perform printing operation. The control unit  100  is also configured to cause the units to perform coordinated operations upon startup of printing according to the types of toner cartridge  28  installed. In order to exercise the control as mentioned above, the control unit  100  receives data on the toner cartridge  28  from the RFID tag  52  via the RFID tag reader  160 . The toner cartridge  28  may, for example, be of three types consisting of: (1) genuine toner cartridge with RFID tag  52 ; (2) genuine toner cartridge without RFID tag  52  which is supplied together with the laser printer  1  purchased; and (3) the other toner cartridge. 
     Method of Control Implemented by Control Unit 
     Next, a method of control implemented by the control unit according to the present embodiment will be described with reference to  FIG. 3 , in which a time chart for explaining a process of control exercised by the control unit according to the first embodiment is illustrated with a graph having the time axis represented by the horizontal axis. 
     At the outset, in the present embodiment, the quantity of toner in the supplied toner cartridge is converted into the number of dots printable with that quantity of toner, and the number of dots is set as a predetermined (reference) value in the counter  110 . It is assumed as shown in  FIG. 3  that the toner cartridge installed in the body casing  2  is a supplied toner cartridge if the count value (cumulatively increased from the time of purchase  1  of the laser printer  1 ) is not greater than the predetermined value. Accordingly, if the count value is not greater than the predetermined value, the control unit  100  exercises a particular type of control conformable to the genuine product. On the other hand, it is assumed that the toner cartridge to be installed (replaced) in the body casing  2  is either of the genuine product or the non-genuine product if the count value is greater than the predetermined value. Accordingly, if the count value is greater than the predetermined value, the control unit  100  selectively exercises one of two types of control; i.e., the particular type of control conformable to the genuine product is exercised when it is determined that a genuine toner cartridge is installed, while an alternative type of control conformable to the non-genuine product is exercised when it is determined that a non-genuine toner cartridge is installed. In order to exercise the control as mentioned above, the control unit  100  may be configured to perform a process, for example, as discussed below. 
     Process of Control Upon Startup of Printing 
     Process of control upon startup of printing of the laser printer  1  will be described with reference to a flowchart of  FIG. 4 , in which is shown a process of control at a time when printing is started, according to the first embodiment. The illustrated process flow may be implemented by the CPU of the control unit  100  executing programs stored in the RAM or ROM. 
     When the laser printer  1  is powered on, and the closed state of the front cover  13  is confirmed by a detection signal received from the cover sensor  170  (step S 10 ), determination as to whether or not toner is available is made based upon a detection signal received from the toner empty sensor  135  (step S 11 ). 
     If it is determined that toner is not available (No in step S 11 ), then the control unit  100  transmits a display instruction to the display  150 , and the display  150  in turn displays a “toner empty error” message (step S 12 ). In this way, a user is prompted to install or replace a toner cartridge  28 , and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that toner is available (Yes in step S 11 ), then the control unit  100  determines that a toner cartridge  28  is installed, and proceeds to subsequent determination as to whether the value counted in the counter  110  is not greater than the predetermined value (step S 13 ). 
     If it is determined that the count value of the counter  110  is not greater than the predetermined value (Yes in step S 13 ), then it is assumed that toner in the toner cartridge initially installed in the laser printer  1  still remains therein and thus the currently installed toner cartridge  28  is the supplied toner cartridge. Therefore, the control unit  100  exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform normal printing operation (step S 14 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that the count value of the counter  110  is greater than the predetermined value (No in step S 13 ), then the control unit  100  attempts to retrieve data on the toner cartridge  28  from the RFID tag  52  through the RFID tag reader  160 , and determines whether or not a predetermined ID is retrievable (step S 15 ). 
     If the predetermined ID of the toner cartridge  28  is not retrievable (No in step S 15 ), then the installed toner cartridge  28  turns out to be a non-genuine product. The control unit  100  then exercises control of the type conformable to the other toner cartridge, thus proceeding to transmit a display instruction to the display  150 , and the display  150  in turn displays a “Please use a genuine product” message (step S 16 ). In this way, a user is invited to use a genuine product; thereafter, the control unit  100  proceeds to cause the units of the laser printer  1  to perform normal printing operation (step S 17 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if the predetermined ID of the toner cartridge  28  is retrieved (Yes in step S 15 ), then the installed toner cartridge  28  turns out to be a genuine product. The control unit  100  then exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 18 ), and the process of the control unit  100  comes to an end. After the process comes to an end, in the present embodiment, the above-described process steps are performed every time when power is switched on or when the front cover  13  is closed. 
     By using the laser printer  1  configured as described above according to the present embodiment, the following advantageous effects can be exerted. 
     The control unit  100  is configured to exercise control of the type conformable to the non-genuine product only when the toner cartridge  28  turns out to be installed, the count value of the counter  110  is greater than a predetermined value, and a predetermined ID is not retrievable by the RFID tag reader  160  from the toner cartridge  28 . That is, if the count value of the counter  110  is not greater than the predetermined value, control of the type conformable to the genuine product is exercised regardless of whether or not the predetermined ID is retrievable from the toner cartridge  28 . Therefore, the RFID tag  52  which used to be necessitated in every toner cartridge does not have to be incorporated in the supplied toner cartridge which is packaged with the main body of the apparatus. Consequently, the production cost can be reduced and the productivity can be improved. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. The general setup of a laser printer of the present embodiment may be implemented in a manner similar to that of the first embodiment as illustrated in  FIGS. 1 and 2 . The method of control in this embodiment may also be implemented by the control unit in a manner similar to that of the first embodiment as illustrated in  FIG. 3 . In the present embodiment, the process of control upon startup of printing as in the first embodiment is implemented with some steps thereof modified. Hereafter, the process of control upon startup of printing in the laser printer  1  according to the second embodiment of the present invention will be described with reference to a flowchart shown in  FIG. 5 . 
     Process of Control Upon Startup of Printing 
     When the laser printer  1  is powered on, and the closed state of the front cover  13  is confirmed by a detection signal received from the cover sensor  170  (step S 30 ), determination as to whether or not toner is available is made based upon a detection signal received from the toner empty sensor  135  (step S 31 ). 
     If it is determined that toner is not available (No in step S 31 ), then the control unit  100  transmits a display instruction to the display  150 , and the display  150  in turn displays a “toner empty error” message (step S 32 ). In this way, a user is prompted to install or replace a toner cartridge  28 , and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that toner is available (Yes in step S 31 ), then the control unit  100  determines that a toner cartridge  28  is installed. Then, the control unit  100  attempts to retrieve data on the toner cartridge  28  from the RFID tag  52  through the RFID tag reader  160 , and determines whether or not a predetermined ID is retrievable (step S 33 ). 
     If the predetermined ID of the toner cartridge  28  is retrieved (Yes in step S 33 ), then the installed toner cartridge  28  turns out to be a genuine product. The control unit  100  then exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 38 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if the predetermined ID of the toner cartridge  28  is not retrievable (No in step S 33 ), then the installed toner cartridge  28  turns out to be a non-genuine product. Then, determination is made as to whether the count value of the counter  110  is not greater than the predetermined value (step S 34 ). 
     If it is determined that the count value of the counter  110  is not greater than the predetermined value (Yes in step S 34 ), then it is assumed that toner in the toner cartridge initially installed in the laser printer  1  still remains therein and thus the currently installed toner cartridge  28  is the supplied toner cartridge. Therefore, the control unit  100  exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 35 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that the count value of the counter  110  is greater than the predetermined value (No in step S 34 ), then it is assumed that the currently installed toner cartridge  28  is a non-genuine product. The control unit  100  then exercises control of the type conformable to the other toner cartridge, thus proceeding to transmit a display instruction to the display  150 , and the display  150  in turn displays a “Please use a genuine product” message (step S 36 ). In this way, a user is invited to use a genuine product; thereafter, the control unit  100  proceeds to cause the units of the laser printer  1  to perform the normal printing operation (step S 37 ), and the process of the control unit  100  comes to an end. After the process comes to an end, in the present embodiment, the above-described process steps are performed every time when power is switched on or when the front cover  13  is closed. 
     By using the laser printer  1  configured as described above according to the present embodiment, the following advantageous effects can be exerted. 
     The control unit  100  is configured to exercise control of the type conformable to the non-genuine product only when the toner cartridge  28  turns out to be installed, a predetermined ID is not retrievable by the RFID tag reader  160  from the toner cartridge  28 , and the count value of the counter  110  is greater than a predetermined value. That is, even when the predetermined ID is not retrievable from the toner cartridge  28 , if the count value of the counter  110  is not greater than the predetermined value, control of the type conformable to the genuine product is exercised. Therefore, the RFID tag  52  which used to be necessitated in every toner cartridge does not have to be incorporated in the supplied toner cartridge which is packaged with the main body of the apparatus. Consequently, the production cost can be reduced and the productivity can be improved. 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described. In the present embodiment, the control unit setup, the method of control by the control unit, and process of control upon startup of printing in the first embodiment are modified. 
     Control Unit Setup 
     To the control unit  100  as shown in  FIG. 6 , are electrically and communicatively coupled a nonvolatile memory  120 , a toner sensor  130 , a cartridge sensor  140 , an RFID tag reader  160  and other components. The toner sensor  130  is an example of a toner detector configured to determine the presence or absence of toner in the toner cartridge  28 . The cartridge sensor  140  is an example of a cartridge detector configured to determine the presence or absence of the toner cartridge  28 , i.e. whether or not the toner cartridge  28  is installed in the laser printer  1 . The display  150  is a display device comprised, for example, of liquid crystal material and other components. The RFID tag reader  160  is an example of a reader configured to retrieve data from an RFID tag (as an example of a memory device)  52  provided in the toner cartridge  28 . 
     The memory  120  is configured to have a storage space for recording toner empty error history data when the toner sensor  130  detects toner empty as will be described later. 
     The toner sensor  130  has the same configuration as the toner empty sensor  135  of the first embodiment. 
     In the present embodiment, the cartridge sensor  140  is provided in addition to the toner sensor  130 . The cartridge sensor  140  is provided in the body casing  2  and arranged near a location where the toner cartridge  28  is installed so that the toner cartridge  28  comes in contact with an actuator (not shown) of the cartridge sensor  140  when the toner cartridge  28  is installed in the body casing  2  of the laser printer  1 . The cartridge sensor  140  has its actuator located on a path along which the toner cartridge  28  is installed, and thus turns ON in the wake of contact of the toner cartridge  28  with the actuator followed by the operation of installing the toner cartridge  28 . On the other hand, the cartridge sensor  140  remains OFF until the toner cartridge  28  is properly installed and touches the actuator. The cartridge sensor  140  outputs a detection signal that is either high-level signal or low-level signal corresponding to the ON or OFF of the actuator, which is received by the control unit  100 . Thus differentiated detection signal level (high or low) allows the control unit  100  to determine the state of the toner cartridge  28 , i.e., whether the toner cartridge  28  is installed or not. 
     Method of Control Implemented by Control Unit 
     A method of control implemented by the control unit according to the present embodiment will be described with reference to  FIG. 7 , in which a time chart for explaining a process of control exercised by the control unit according to the third embodiment is illustrated with a graph having the time axis represented by the horizontal axis. 
     In the present embodiment, ever since the toner sensor  130  detects a toner empty error for the first time, data on each and every occurrence of the toner empty error is recorded in the memory  120 . As shown in  FIG. 7 , it is assumed that before the toner empty error occurs for the first time (from the time of purchase of the laser printer  1 ), the toner cartridge installed in the body casing  2  is a supplied toner cartridge. Thus, the control unit  100  is configured to exercise a specific type of control conformable to the genuine product before the toner empty error occurs for the first time. On the other hand, it is assumed that after the first occurrence of the toner empty error, the toner cartridge to be installed (replaced) in the body casing  2  is either of the genuine product or the non-genuine product. Thus, the control unit  100  is then configured to exercise a conformable type of control, i.e.; the particular type of control conformable to the genuine product is exercised when it is determined that a genuine toner cartridge is installed, while an alternative type of control conformable to the non-genuine product is exercised when it is determined that a non-genuine product is installed. In order to exercise the control as mentioned above, the control unit  100  may be configured to perform a process, for example, as discussed below. 
     Process of Control Upon Startup of Printing 
     Process of control upon startup of printing of the laser printer  1  will be described with reference to a flowchart of  FIG. 8 , in which is shown a process of control at a time when printing is started, according to the third embodiment. 
     When the laser printer  1  is powered on, and the closed state of the front cover  13  is confirmed by a detection signal received from the cover sensor  170  (step S 50 ), determination as to whether or not a toner cartridge  28  is installed properly is made based upon a detection signal received from the cartridge sensor  140  (step S 51 ). 
     If it is determined that no toner cartridge  28  is installed properly (No in step S 51 ), then the control unit  100  transmits a display instruction to the display  150 , and the display in turn displays a “toner cartridge installation error” message (step S 52 ). In this way, a user is prompted to properly install (or correct improper installation of) the toner cartridge  28 , and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that the toner cartridge  28  is installed properly (Yes in step S 51 ), then the control unit  100  attempts to retrieve data on the toner cartridge  28  from the RFID tag  52  through the RFID tag reader  160 , and determines whether or not a predetermined ID is retrievable (step S 53 ). 
     If the predetermined ID of the toner cartridge  28  is retrieved (Yes in step S 53 ), then the installed toner cartridge  28  turns out to be a genuine product. The control unit  100  then exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 60 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if the predetermined ID of the toner cartridge  28  is not retrievable (No in step S 53 ), then the installed toner cartridge  28  turns out to be either a supplied cartridge or a non-genuine product. Then, determination as to whether or not toner remains available in the toner cartridge  28  is made based upon a detection signal received from the toner sensor  130  (step S 54 ). 
     If it is determined that no toner remains available in the toner cartridge  28  (No in step S 54 ), then the control unit  100  transmits a display instruction to the display  150 , which in turn displays a “toner empty error” message, and transmits the data on the occurrence of the toner empty error to the memory  120  so that the data is recorded in the memory  120  (step S 55 ). In this way, a user is prompted to install or replace a toner cartridge  28 , and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that toner remains available in the toner cartridge  28  (Yes in step S 54 ), then the control unit  100  retrieves data from the memory  120  to determine whether or not a toner empty error has ever occurred (step S 56 ). 
     If the control unit  100  determines that no toner empty error has occurred ever since (No in step S 56 ), then it is assumed that the toner cartridge  28  first installed in the laser printer  1  has not been replaced ever before and thus the currently installed toner cartridge  28  is the supplied toner cartridge. Therefore, the control unit  100  exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 57 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if the control unit  100  determines that one or more toner empty errors have occurred before (Yes in step S 56 ), then it is determined that the toner cartridge  28  first installed in the laser printer  1  has been replaced with another toner cartridge and thus the currently installed toner cartridge  28  is not the supplied toner cartridge but instead a non-genuine product. Accordingly, the control unit  100  exercises control of the type conformable to the other toner cartridge, thus proceeding to transmit a display instruction to the display  150 , and the display  150  in turn displays a “Please use a genuine product” message (step S 58 ). In this way, a user is invited to use a genuine product; thereafter, the control unit  100  proceeds to cause the units of the laser printer  1  to perform normal printing operation (step S 59 ), and the process of the control unit  100  comes to an end. After the process comes to an end, in the present embodiment, the above-described process steps are performed every time when power is switched on or when the front cover  13  is closed. 
     By using the laser printer  1  configured as described above according to the present embodiment, the following advantageous effects can be exerted. 
     The control unit  100  is configured to exercise control of the type conformable to the non-genuine product only when the toner cartridge  28  turns out to be installed, a predetermined ID is not retrievable by the RFID tag reader  160  from the toner cartridge  28 , and one or more toner empty errors have occurred before. That is, even when the predetermined ID is not retrievable from the toner cartridge  28 , if no toner empty error has ever occurred before, control of the type conformable to the genuine product is exercised. Therefore, the RFID tag  52  which used to be necessitated in every toner cartridge does not have to be incorporated in the supplied toner cartridge which is packaged with the main body of the apparatus. Consequently, the production cost can be reduced and the productivity can be improved. 
     Fourth Embodiment 
     Next, a fourth embodiment of the present invention will be described. The general setup of a laser printer of the present embodiment may be implemented in a manner similar to that of the first embodiment as illustrated in  FIGS. 1 and 2 . The method of control in this embodiment may be implemented by the control unit in a manner similar to that of the third embodiment as illustrated in  FIG. 7 . In the present embodiment, the process of control upon startup of printing as in the third embodiment is implemented with some steps thereof modified. Hereafter, the process of control upon startup of printing in the laser printer  1  according to the fourth embodiment of the present invention will be described with reference to a flowchart shown in  FIG. 9 . 
     Process of Control Upon Startup of Printing 
     When the laser printer  1  is powered on, and the closed state of the front cover  13  is confirmed by a detection signal received from the cover sensor  170  (step S 70 ), determination as to whether or not a toner cartridge  28  is installed properly is made based upon a detection signal received from the cartridge sensor  140  (step S 71 ). 
     If it is determined that no toner cartridge  28  is installed properly (No in step S 71 ), then the control unit  100  transmits a display instruction to the display  150 , and the display in turn displays a “toner cartridge installation error” message (step S 72 ). In this way, a user is prompted to properly install (or correct improper installation of) the toner cartridge  28 , and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that the toner cartridge  28  is installed properly (Yes in step S 71 ), then determination as to whether or not toner remains available in the toner cartridge  28  is made based upon a detection signal received from the toner sensor  130  (step S 73 ). 
     If it is determined that no toner remains available in the toner cartridge  28  (No in step S 73 ), then the control unit  100  transmits a display instruction to the display  150 , which in turn displays a “toner empty error” message, and transmits the data on the occurrence of the toner empty error to the memory  120  so that the data is recorded in the memory  120  (step S 74 ). In this way, a user is prompted to install or replace a toner cartridge  28 , and the process of the control unit  100  comes to an end. 
     On the other hand, if it is determined that toner remains available in the toner cartridge  28  (Yes in step  73 ), then the control unit  100  retrieves data from the memory  120  to determine whether or not a toner empty error has ever occurred (step S 75 ). 
     If the control unit  100  determines that no toner empty error has occurred ever since (No in step S 75 ), then it is assumed that the toner cartridge first installed in the laser printer  1  is still installed therein without being replaced and thus the currently installed toner cartridge  28  is the supplied toner cartridge. Therefore, the control unit  100  exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 76 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if the control unit  100  determines that one or more toner empty errors have occurred before (Yes in step S 75 ), then it is assumed that the toner cartridge  28  first installed in the laser printer  1  has been replaced with another toner cartridge and thus the currently installed toner cartridge  28  is either of the genuine product or the non-genuine product. Therefore, the control unit  100  retrieves data on the toner cartridge  28  from the RFID tag  52  through the RFID tag reader  160 , and determines whether or not a predetermined ID is retrievable therefrom (step S 77 ). 
     If the predetermined ID of the toner cartridge  28  is not retrievable (No in step S 77 ), then the installed toner cartridge  28  turns out to be a non-genuine product. Accordingly, the control unit  100  exercises control of the type conformable to the other toner cartridge, thus proceeding to transmit a display instruction to the display  150 , and the display  150  in turn displays a “Please use a genuine product” message (step S 78 ). In this way, a user is invited to use a genuine product; thereafter, the control unit  100  proceeds to cause the units of the laser printer  1  to perform normal printing operation (step S 79 ), and the process of the control unit  100  comes to an end. 
     On the other hand, if the predetermined ID of the toner cartridge  28  is retrieved (Yes in step S 77 ), then the installed toner cartridge  28  turns out to be a genuine product. The control unit  100  then exercises control of the type conformable to the genuine product, thus proceeding to cause the units of the laser printer  1  to perform the normal printing operation (step S 80 ), and the process of the control unit  100  comes to an end. After the process comes to an end, in the present embodiment, the above-described process steps are performed every time when power is switched on or when the front cover  13  is closed. 
     By using the laser printer  1  configured as described above according to the present embodiment, the following advantageous effects can be exerted. 
     The control unit  100  is configured to exercise control of the type conformable to the non-genuine product only when the toner cartridge  28  turns out to be installed, one or more toner empty errors have occurred before, and a predetermined ID is not retrievable by the RFID tag reader  160  from the toner cartridge  28 . That is, if no toner empty error has occurred before, control of the type conformable to the genuine product is exercised irrespective of whether or not the predetermined ID is retrievable from the toner cartridge  28 . Therefore, the RFID tag  52  which used to be necessitated in every toner cartridge does not have to be incorporated in the supplied toner cartridge which is packaged with the main body of the apparatus. Consequently, the production cost can be reduced and the productivity can be improved. 
     Exemplary Embodiments Modified 
     Some exemplary embodiments of the present invention have been described above. The present invention is not limited to these embodiments, and may be carried out into practice in various other ways. Thus, it is contemplated that various modifications and changes may be made to the exemplary embodiments of the invention without departing from the spirit and scope of the embodiments of the present invention as defined in the appended claims. 
     In the embodiments described above, the memory device provided in the toner cartridge  28  and the reader for retrieving data therefrom are exemplified by the RFID tag  52  and the RFID tag reader  160  with which data from the RFID tag  52  is retrievable in a noncontact manner. The present invention is however not limited to these illustrative embodiments, but any other combinations available of memory devices and readers may be applied. For example, a proximity communication IC chip and a reader configured to retrieved data therefrom may be adopted in combination. 
     Although the above embodiments have described a counter configured to count the number of dots which varies in accordance with the image data as an example of a counter configured to count a value concerning image formation, the present invention is not limited thereto. For example, a counter configured to count the number of rotations of the photoconductor drum  27 , a counter configured to count the number of rotations of the development roller  31 , a counter configured to count the number of sheets to be printed which is detected by the registration sensor  105 , or any other counter available may be applied. 
     In the embodiments described above, the control of the type conformable to the other toner cartridge is exemplified by the control under which a specific message is displayed, but the present invention is not limited to these embodiments. For example, the control of the type conformable to the other toner cartridge may include a control under which a printing speed is reduced so as to prevent printing quality from becoming degraded, or a control under which the frequency of cleaning of the photoconductor drum  27  is increased. In these cases, a special printing operation for non-genuine product is carried out instead of the normal printing operation. 
     In the exemplary embodiments described above, the present invention is applied to a laser printer  1 ; however, the present invention is not limited thereto, but may be applied, for example, to a copier, an all-in-one printer, and other image-forming apparatuses.