Patent Publication Number: US-2009220251-A1

Title: Image Forming Apparatus and Method of Determining Update of Identification Information

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image forming apparatus such as a color printer or a facsimile which forms an image by using an electrophotographic technique and a method of determining update of identification information, and more particularly to an image forming apparatus in which a cartridge storage portion for storing identification information including information about a lifetime is provided in a developing cartridge detachable from the image forming apparatus. 
     In general, an image forming apparatus such as a color printer using an electrophotographic technique includes an image forming unit constituted by a photosensitive member, a charging unit for charging the outer peripheral surface of the photosensitive member, an exposing unit for selectively exposing the outer peripheral surface of the photosensitive member to form an electrostatic latent image, and a developing cartridge for developing the electrostatic latent image into a toner image. A developing rotary having an almost cylindrical shape and supported rotatably is provided in an adjacent position to the photosensitive member, and developing cartridges (hereinafter referred to as cartridges) for four colors (yellow Y, magenta M, cyan C and black K) are exchangeably attached to the developing rotary. 
     Moreover, cartridge storage portions (hereinafter referred to as cartridge memories) are provided in the cartridges respectively, and the cartridge memories store identification information with which cartridges for a toner color, the amount of a residual toner, a driving time, the number of sheets to be printed and a manufacturing date accommodated in cases can be individually identified, respectively. Each of the cartridges is communicated with a control unit for controlling the operation of an image forming apparatus (hereinafter referred to as a body) through a communicating unit, and the identification information written to each of the cartridge memories is read by the control unit and is stored in a body memory. For the memory provided in each of the cartridges, a nonvolatile memory is usually used. 
     Then, the control unit of the body updates information about the lifetime of the cartridge such as the amount of the residual toner in the cartridge, the driving time and the number of sheets to be printed every time a development is carried out, and communicates with the cartridge memory through the communicating unit to write the current identification information to the cartridge memory when a predetermined event is generated. 
     As a technique for carrying out the communication of the memory of each cartridge with the control unit on the body side, there has been known a method of performing the read/write of the memory of the cartridge through an antenna portion in non-contact (for example, see JP-A-2002-296984 and JP-A-2000-187415). 
     Since the cartridge can be exchanged, it is also possible to propose a using way in which the cartridge in use is once taken out and stored and a new cartridge is attached to carry out mass printing, and the same cartridge is taken out and an old stored cartridge is reattached when the mass printing is to be performed, for example. In such a using method, it is necessary to write the current data on identification information about a lifetime to a cartridge memory and to cause the identification information about the lifetime to be coincident with the current data before taking out the cartridge. The reason is that the information about the lifetime which is read from the cartridge memory is inaccurate when the reattachment is carried out. For this reason, it is impossible to carry out the accurate lifetime management of the cartridge. 
     Also, in JP-A-2002-296984, when a cartridge is to be taken out, the control unit of a body communicates with a cartridge memory and writes the current data on the cartridge to the cartridge memory. In JP-A-2000-187415, moreover, when a cartridge is newly attached, the control unit of the body communicates with the cartridge memory of the cartridge thus attached and reads identification information written to the cartridge memory. 
     In the image forming apparatus of this type, an exchange position (an attaching and removing position) is predetermined as a position in which a cartridge can be normally taken out of a developing rotary, and the control unit of the body rotates a developing rotary to place the cartridge specified to be taken out in the exchange position when a predetermined operation is carried out in the operating portion of the body. Consequently, a user carries out an operation for opening the cover of the body and taking out a desirable cartridge, and attaching a new cartridge to the developing rotary and closing the cover, and can thus exchange the cartridge. By the execution of a serial operation for giving an instruction for taking out the cartridge and opening and closing the cover in the operating portion, the control unit of the body can recognize that the cartridge has been normally exchanged. 
     Thus, the cartridge cannot be taken out of the developing rotary in a normal state. There is a possibility that the cover of the body might be opened or the power supply of the body might be turned OFF due to the malfunction of the user when the developing rotary is rotated as in printing or an initialization processing to be carried out at time of power-ON. In such a case, the rotation of the developing rotary is stopped. In some cases in which the cover of the body is opened or the power supply of the body is turned OFF, however, a cartridge for a certain color is stopped in an attaching and removing position by chance. 
     At this time, it can be supposed that the user takes out the cartridge placed in the exchange position and attaches another cartridge for the same color. Referring to the exchange of the cartridge which is not normal, usually, the control unit of the body cannot detect that the cartridge for the certain color has been exchanged. 
     In this case, the identification information about the cartridge for the same color which is managed by the control unit of the body at this time is related to the cartridge taken out, and is not coincident with identification information written to the cartridge memory of a cartridge which is newly attached. For this reason, there is a problem in that an accurate lifetime management cannot be carried out for the cartridge if printing is then performed in this state. 
     For example, description will be given to the amount of a residual toner to be one of the information about the lifetime in the identification information and there is the following problem. For example, it is assumed that the situation described above is generated and a cartridge for a Y color is taken out, and the amount of the residual toner in the cartridge for the Y color is 1%. At this time, the control unit of the body stores 1% of the amount of the residual toner in relation to the cartridge for the Y color. On the other hand, it is assumed that the amount of the residual toner in a cartridge for a Y color which is newly attached is 90%. 
     As described above, the control unit of the body updates the amount of the residual toner in the cartridge for the Y color every development. However, the amount of the residual toner stored in relation to the cartridge for the Y color by the control unit of the body is 1%. Therefore, the control unit of the body updates the amount of the residual toner from 1% every development. When an event in which the identification information of the cartridge memory is to be updated is generated, the current identification information including information about a lifetime is written to the cartridge memory of the cartridge for the Y color. When the amount of the residual toner is 0%, it is decided that the cartridge is empty so that a request for exchanging the cartridge for the Y color is given to the user. In this case, accordingly, it is decided that the cartridge for the Y color which is newly attached is empty irrespective of the sufficient amount of the residual toner. Thus, there is a problem in that the cartridge for the Y color cannot be used. 
     To the contrary, assuming that the amount of the residual toner in the cartridge for the Y color which is taken out is 90% and the amount of the residual toner in the cartridge for the Y color which is newly attached is 1%, the control unit of the body recognizes that the toner still remains in a sufficient amount in the cartridge for the Y color which is newly attached. Actually, the amount of the residual toner is small. For this reason, there is a problem in that a situation in which a printed image is blurred is generated in the case that the printing is continuously carried out. 
     By the way, in JP-A-2002-296984, in the case that an instruction for taking out a cartridge is given, identification information is always written to a cartridge memory. For this reason, a long waiting time is required for a user to actually take out the cartridge. More specifically, in an image forming apparatus of this type, a position in which the control unit of a body can communicate with the cartridge memory and a position in which the cartridge can be taken out are usually determined. In the case that an instruction for taking out a certain cartridge is given, there is performed an operation for first rotating a developing rotary to move the cartridge specified to be taken out to the position in which the communication with the control unit of the body can be carried out, and writing the current identification information from the control unit of the body to the cartridge memory of the same cartridge therein, and then rotating the developing rotary to move the same cartridge to the take-out position. A long time is required for actually taking out the same cartridge. 
     On the other hand, a user desires to quickly take out a certain cartridge when carrying out such an operation as to give an instruction for taking out the same cartridge. For this purpose, in the case that the instruction for taking out the cartridge is given, it is preferable to immediately rotate the developing rotary, thereby moving the cartridge to the take-out position. Consequently, it is possible to shorten the waiting time of the user from the execution of the operation for giving the instruction for taking out the cartridge to the actual take-out of the cartridge. In such a case, however, there is a possibility that the identification information written to the cartridge memory of the cartridge thus taken out might not be the current as described above. 
     SUMMARY OF THE INVENTION 
     Therefore, it is a first object of the invention to provide an image forming apparatus and a method of determining update of identification information capable of carrying out an accurate lifetime management for a cartridge also in the case that the cartridge is exchanged when the control unit of the body cannot recognize that the cartridge is exchanged, for example, when the cover of the body is opened during the rotation of a developing rotary or a power supply is turned OFF. 
     Further, a second object of the invention is to provide an image forming apparatus and a method of determining update of identification information capable of immediately deciding whether or not the current identification information is written to the cartridge memory of the cartridge when an instruction for take-out is given. 
     Moreover, a third object of the invention is to provide an image forming apparatus and a method of determining update of identification information capable of taking out the cartridge to shorten the waiting time of a user in the case that the current identification information is written to the cartridge memory, and taking out the same cartridge after writing the current identification information to the cartridge memory of the cartridge and writing the current identification information to the cartridge memory of the cartridge thus taken out in the case that the current identification information is not written based on the result of the decision. 
     In order to achieve the above object, according to the present invention, there is provided an image forming apparatus, comprising: 
     a developing rotary unit configured to attach a plurality of developing cartridges, the developing cartridges respectively having cartridge storage portions for respectively storing identification information about the corresponding developing cartridges; 
     a communicating unit that communicates with the cartridge storage portions; 
     a storage unit configured to store the identification information; and 
     a control unit that reads the identification information from the cartridge storage portions of all the developing cartridges through the communicating unit and writes the read identification information into the storage unit so as to update the identification information stored in the storage unit when a power supply of the image forming apparatus is turned ON or a body cover for the developing rotary unit is closed. 
     According to the present invention, there is also provided an image forming apparatus, comprising: 
     a developing rotary unit configured to attach a plurality of developing cartridges, the developing cartridges respectively having cartridge storage portions for respectively storing identification information about the corresponding developing cartridges; 
     a communicating unit that communicates with the cartridge storage portions; 
     a storage unit configured to store the identification information; and 
     a control unit that reads the identification information from the cartridge storage portions of all the developing cartridges through the communicating unit, compares the read identification information with the identification information stored in the storage unit and determines whether the identification information stored in the storage unit is updated with the read identification information based on a result of the comparison when a power supply of the image forming apparatus is turned ON or a body cover for the developing rotary unit is closed. 
     Preferably, the identification information include information about amounts of residual toners of the respective developing cartridges. 
     According to the present invention, there is also provided an image forming apparatus, comprising: 
     a developing rotary unit configured to attach a plurality of developing cartridges, the developing cartridges respectively having cartridge storage portions for respectively storing identification information about the corresponding developing cartridges; 
     a communicating unit that communicates with the cartridge storage portions; 
     a storage unit configured to store the identification information; and 
     a control unit that determines whether any of the developing cartridges is located at an exchange position in the developing rotary unit and determines whether the identification information stored in the storage unit is updated based on a result of the determination when a power supply of the image forming apparatus is turned ON or a body cover for the developing rotary unit is closed. 
     Preferably, the control unit reads the identification information from the cartridge storage portion located at the exchange position through the communicating unit and compares the read identification information with the identification information stored in the storage unit. The control unit determines whether the identification information stored in the storage unit is updated based on a result of the comparison. 
     According to the present invention, there is also provided a method of determining update of identification information, comprising: 
     reading identification information from cartridge storage portions of all developing cartridges through a communication unit; and 
     writing the read identification information into a storage unit of an image forming apparatus so as to update the identification information stored in the storage unit, 
     wherein the reading process and the writing process are performed when a power supply of the image forming apparatus is turned ON or a body cover for a developing rotary unit of the image forming apparatus is closed; and 
     wherein the developing rotary unit includes the developing cartridges, the developing cartridges respectively having the cartridge storage portions for respectively storing the identification information about the corresponding developing cartridges. 
     According to the present invention, there is also provided a method of determining update of identification information, comprising: 
     reading identification information from cartridge storage portions of all developing cartridges through a communicating unit; 
     comparing the read identification information with identification information stored in a storage unit of an image forming apparatus; and 
     determining whether the identification information stored in the storage unit is updated with the read identification information based on a result of the comparing process, 
     wherein the reading process, the comparing process and the determining process are performed when a power supply of the image forming apparatus is turned ON or a body cover for a developing rotary unit of the image forming apparatus is closed; and 
     wherein the developing rotary unit includes the developing cartridges, the developing cartridges respectively having the cartridge storage portions for respectively storing the identification information about the corresponding developing cartridges. 
     Preferably, the identification information include information about amounts of residual toners of the respective developing cartridges. 
     According to the present invention, there is also provided a method of determining update of identification information, comprising: 
     determining whether any of developing cartridges is located at an exchange position in a developing rotary unit of an image forming apparatus; and 
     determining whether identification information stored in a storage unit of the image forming apparatus is updated based on a result of the determining process of the exchange position, 
     wherein the determining process of the exchange position and the determining process of the update are performed when a power supply of the image forming apparatus is turned ON or a body cover for the developing rotary unit of the image forming apparatus is closed; and 
     wherein the developing rotary unit includes the developing cartridges, the developing cartridges respectively having the cartridge storage portions for respectively storing the identification information about the corresponding developing cartridges. 
     Preferably, the method further comprising; 
     reading the identification information from the cartridge storage portion located at the exchange position through a communicating unit; and 
     comparing the read identification information with the identification information stored in the storage unit, 
     wherein the determining process is performed based on a result of the comparing process. 
     By the above configurations and methods, when the power supply is turned ON or the body cover is closed, therefore, the identification information about the developing cartridge for each color in the storage portions are forcibly updated. Also in the case that the developing cartridge is exchanged when the control unit cannot recognize that the developing cartridge is exchanged, for example, when the body cover is opened during the rotation of the developing rotary unit or the power supply is turned OFF, consequently, an accurate lifetime management can be carried out for the developing cartridge. 
     By the above configurations and methods, the identification information about the developing cartridge of the storage unit can be updated for only the developing cartridge which is decided to be exchanged actually. Consequently, it is possible to avoid the generation of an error between information about the amount of a residual toner which is managed by the storage unit and information about the actual amount of a residual toner in the developing cartridge. Also in the case that the developing cartridge is exchanged when the control unit cannot recognize that the developing cartridge is exchanged, thus, the accurate lifetime management can be carried out for the developing cartridge. 
     By the above configurations and methods, whether the exchange has been carried out can be decided with high precision. 
     By the above configurations and methods, in the case that there is the developing cartridge placed in the exchange position when the power supply is turned ON or the body cover is closed, it can be supposed that the developing cartridge has been exchanged. Thus, it is possible to update the identification information about the developing cartridge of the storage unit. Also in the case that the developing cartridge is exchanged when the control unit cannot recognize that the developing cartridge is exchanged, consequently, it is possible to carry out the accurate lifetime management for the developing cartridge. 
     According to the present invention, there is also provided an image forming apparatus, comprising: 
     a developing rotary unit configured to attach a plurality of developing cartridges, the developing cartridges respectively having cartridge storage portions; 
     a communicating unit that communicates with the cartridge storage portions; and 
     a storage unit configured to store identification information about amounts of residual toners in the respective developing cartridges, wherein the storage unit includes a first storage region for storing current toner remaining amount information and a second storage region for storing a preceding writing toner remaining amount information. 
     Preferably, the image forming apparatus further comprising: 
     a receiving unit that receives an instruction for taking out the developing cartridge; and 
     a control unit that determines whether the current toner remaining amount information, for the developing cartridge specified by the instruction, stored in the first storage region corresponds to the preceding writing toner remaining amount information about the developing cartridge specified by the instruction, stored in the second storage region, 
     wherein the developing cartridge specified by the instruction is moved to an exchange position in the developing rotary unit when the current toner remaining amount information is corresponded to the preceding writing toner remaining amount information; and 
     wherein the developing cartridge specified by the instruction is moved to the exchange position after updating the identification information stored in the cartridge storage portion of the developing cartridge specified by the instruction with the current toner remaining amount information through the communication unit when the current toner remaining amount information is not corresponded to the preceding writing toner remaining amount information. 
     According to the present invention, there is also provided a method of determining update of identification information, comprising: 
     receiving an instruction for taking out any of developing cartridges; 
     determining whether a current toner remaining amount information about the developing cartridge specified by the instruction, stored in a first storage region corresponds to a preceding writing toner remaining amount information about the developing cartridge specified by the instruction, stored in a second storage region; 
     moving the developing cartridge specified by the instruction to an exchange position in a developing rotary unit when the current toner remaining amount information is corresponded to the preceding writing toner remaining amount information; and 
     moving the developing cartridge specified by the instruction to the exchange position after updating the identification information stored in the cartridge storage portion of the developing cartridge specified by the instruction with the current toner remaining amount information through a communication process when the current toner remaining amount information is not corresponded to the preceding writing toner remaining amount information. 
     In the above configurations and methods, by deciding whether or not the information written to the first storage region and the second storage region are coincident with each other, therefore, it is possible to easily and immediately decide whether or not the current toner remaining amount information is written to the cartridge storage portion. 
     In the above configurations and methods, when the current toner remaining amount information is written to the cartridge storage portion of the developing cartridge specified by the instruction, therefore, the same developing cartridge is taken out immediately. Consequently, it is possible to shorten the waiting time of a user. In the case that the current toner remaining amount information is not written, furthermore, the current toner remaining amount information is written to the cartridge storage portion of the developing cartridge and is then taken out. Consequently, it is possible to write the current toner remaining amount information to the cartridge storage portion of the developing cartridge thus taken out. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
         FIG. 1  is a view showing main components constituting a printer; 
         FIGS. 2A to 2C  are typical views showing the stop position of a developing rotary unit; 
         FIG. 3  is a diagram showing the electrical structure of the printer; 
         FIGS. 4A and 4B  are diagrams for explaining the structure of a cartridge memory; 
         FIG. 5  is a diagram for explaining that two storage regions having the current toner remaining amount information storage region and a preceding writing toner remaining amount information storage region are allocated to a region of a body memory for storing information about the amount of a residual toner in each cartridge; 
         FIG. 6  is a flowchart showing the processing of a unit controller in printing; 
         FIG. 7  is a flowchart for explaining a first embodiment of a processing to be carried out when a power supply is turned ON or a body cover is closed according to the invention; 
         FIG. 8  is a flowchart for explaining a second embodiment of the processing to be carried out when the power supply is turned ON or the body cover is closed according to the invention; 
         FIG. 9  is a flowchart for explaining a third embodiment of the processing to be carried out when the power supply is turned ON or the body cover is closed according to the invention; 
         FIG. 10  is a flowchart for explaining a fourth embodiment of the processing to be carried out when the power supply is turned ON or the body cover is closed according to the invention; and 
         FIG. 11  is a flowchart for explaining an operation when an instruction for taking out a cartridge for a certain color is received via a take-out operating portion. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An image forming apparatus (for example, a color printer) according to an embodiment of the invention will be described below with reference to the drawings.  FIG. 1  is a schematic view typically showing main components constituting a color printer  10 . In  FIG. 1 , a vertical direction is shown in an arrow. 
     The printer  10  includes a charging unit  30 , an exposing unit  40 , a developing rotary unit  50 , a primary transfer unit  60 , an intermediate transfer member  70  and a cleaning blade  76  in the rotation direction of a photosensitive unit  20  as a latent image carrier for carrying a latent image, and furthermore, a secondary transfer unit  80 , a fixing unit  90 , a display unit  95  constituted by a liquid crystal panel for reporting a notice to a user, and a control unit  100  for controlling each of these units and controlling the operation of the printer  10 . The control unit  100  will be described below. 
     The photosensitive unit  20  has a cylindrical conductive base material and a photosensitive layer formed on an outer peripheral surface thereof and can be rotated around a central axis, and is assumed to be rotated clockwise as shown in an arrow of  FIG. 1 . 
     The charging unit  30  is a device for charging the photosensitive member  20 , and the exposing unit  40  is a device for forming a latent image on the photosensitive member  20  charged by irradiating a laser. The exposing unit  40  has a semiconductor laser, a polygon mirror and an F-θ lens, and irradiates a modulated laser onto the charged photosensitive member  20  based on an image signal input from the control unit  100 . 
     The developing rotary unit  50  has a rotary  55  to be a rotor and four cartridges attached to the rotary  55 . The rotary  55  is rotatable around a rotating shaft  50   a , and four cartridges  51 ,  52 ,  53  and  54  can be attached and removed through a cartridge exchange port which will be described below, respectively. 
     Moreover, a cartridge memory for storing identification information including information about a lifetime such as the amount of a residual toner is provided in each of the predetermined portions of the cartridges  51 ,  52 ,  53  and  54 , which is not shown in  FIG. 1 . The control unit  100  can communicate with each of the cartridge memories by wireless through an antenna  124  provided in the predetermined portion of the printer  10 . It is desirable that the cartridge memory should be a nonvolatile memory capable of saving the data also in a state in which a power supply is OFF or the printer  10  is removed. An EEPROM or a ferroelectric memory (Ferroelectric RAM) such as a flash memory can be employed for the nonvolatile memory. 
     The primary transfer unit  60  is a device for transferring a monochromatic toner image formed on the photosensitive member  20  onto the intermediate transfer member  70 , and a full color toner image is formed on the intermediate transfer member  70  when toners having four colors are sequentially superposed and transferred. 
     The intermediate transfer member  70  is an endless belt and is rotated and driven at an almost equal peripheral speed to the speed of the photosensitive unit  20 . A reading sensor RS for synchronization is provided in the vicinity of the intermediate transfer member  70 . The reading sensor RS for synchronization serves to detect the reference position of the intermediate transfer member  70 , and obtains a synchronizing signal Vsync in a secondary scanning direction which is orthogonal to a primary scanning direction. The reading sensor RS for synchronization has a light emitting unit for emitting a light and a light receiving unit for receiving a light. When the light emitted from the light emitting unit passes through a hole formed in the predetermined position of the intermediate transfer member  70  and is received by the light receiving unit, the reading sensor RS for synchronization generates a pulse signal. One pulse signal is generated every time the intermediate transfer member  70  carries out a rotation. 
     The secondary transfer unit  80  is a device for transferring a monochromatic toner image or a full color toner image formed on the intermediate transfer member  70  onto a recording medium such as a paper, a film or a cloth. 
     The fixing unit  90  is a device for fusing the monochromatic toner image or the full color toner image transferred onto the recording medium to the recording medium such as a paper, thereby forming a permanent image. 
     The cleaning blade  76  is formed of rubber and abuts on the surface of the photosensitive member  20 . The cleaning blade  76  scrapes off and removes the toner remaining on the photosensitive member  20  after a toner image is transferred onto the intermediate transfer member  70  by the primary transfer unit  60 . 
     A photosensitive unit  75  is provided between the primary transfer unit  60  and the exposing unit  40 , and has the photosensitive member  20 , the charging unit  30 , the cleaning blade  76 , and a waste toner housing portion for accommodating the toner scraped off by the cleaning blade  76 . 
     Next, the operation of the printer  10  thus constituted will be schematically described. First of all, when an instruction for printing is given, the photosensitive member  20  and the intermediate transfer member  70  are rotated by the control of the control unit  100 . Then, the reference position of the intermediate transfer member  70  is detected by the reading sensor RS for synchronization so that a pulse signal is output. The pulse signal is transmitted to the control unit  100 . Thereafter, the control unit  100  controls the following operation on the basis of the pulse signal which is received. 
     The photosensitive member  20  is sequentially charged by the charging unit  30  in a charging position with a rotation. The region of the photosensitive member  20  which is charged reaches an exposing position with the rotation of the photosensitive member  20  so that a latent image corresponding to image information for a first color, for example, yellow Y is formed in the same region by the exposing unit  40 . The latent image formed on the photosensitive member  20  reaches a developing position with the rotation of the photosensitive member  20 . At this time, the rotary  55  is rotated by the control of the control unit so that a cartridge for yellow is moved to an opposed position to the photosensitive member  20  and a development is carried out in a yellow toner by the cartridge for yellow. Consequently, a yellow toner image is formed on the photosensitive member  20 . 
     The yellow toner image formed on the photosensitive member  20  reaches the primary transfer position with the rotation of the photosensitive member  20  and is transferred onto the intermediate transfer member  70  by the primary transfer unit  60 . In this case, a primary transfer voltage having a reverse polarity to the charging polarity of the toner is applied to the primary transfer unit  60 . In the meantime, the secondary transfer unit  80  is separated from the intermediate transfer member  70 . 
     The processing is repetitively executed for second, third and fourth colors so that a toner image for each color corresponding to each image signal is superposed on the intermediate transfer member  70  and is thus transferred. Consequently, a full color toner image is formed on the intermediate transfer member  70 . 
     The full color toner image formed on the intermediate transfer member  70  reaches a secondary transfer position with the rotation of the intermediate transfer member  70 , and is transferred onto the recording medium by the secondary transfer unit  80 . The recording medium is delivered from a paper feed tray  92  to the secondary transfer unit  80  through a paper feed roller  94  and a registration roller  96 . When a transfer operation is to be carried out, moreover, the secondary transfer unit  80  is pressed against the intermediate transfer member  70 , and furthermore, a second transfer voltage is applied. 
     The full color toner image transferred onto the recording medium is heated and pressurized by the fixing unit  90  and is fused to the recording medium. On the other hand, the photosensitive member  20  passes through the primary transfer position and a toner stuck to a surface is then scraped off by the cleaning blade  76  to prepare for charging in order to form a next latent image. The toner thus scraped off is collected into the waste toner housing portion. 
     Next, description will be given to the stop position of the developing rotary unit  50 .  FIGS. 2A to 2C  are typical views showing the stop position of the developing rotary unit  50 . In  FIGS. 2A to 2C ,  58  denotes a cartridge exchange port,  51   a ,  52   a ,  53   a  and  54   a  denote developing rollers for the cartridges  51 ,  52 ,  53  and  54  respectively, and  51   b ,  52   b ,  53   b  and  54   b  denote cartridge memories for the cartridges  51 ,  52 ,  53  and  54  respectively. In the following description, it will be assumed that the cartridges  51 ,  52 ,  53  and  54  accommodate toners for C, M, K and Y, respectively. 
     The developing rotary unit  50  is rotated and driven in an opposite direction to the photosensitive member  20 , in this case, counterclockwise by the control of the control unit  100 . Three kinds of positions, that is, a standby position, a developing position (a communicating position) and a removing position are determined. The standby position is a position determined in a standby state in which the printer does not carry out an image forming operation, and a position in which the developing rollers of all of the cartridges are maintained to be separated from the photosensitive member  20 , and furthermore, any of the cartridges cannot be taken out through the cartridge exchange port  58  as shown in  FIG. 2A . 
     Moreover, the developing position is determined when an electrostatic latent image on the photosensitive member  20  is to be formed with a selected toner color. As shown in  FIG. 2B , the developing roller of one of the cartridges (in the example of  FIG. 2B , the developing roller  51   a  provided in the cartridge  51 ) is opposed to the photosensitive member  20  and a predetermined developing bias is applied so that the electrostatic latent image is formed with a toner. Also in the developing position, any of the cartridges cannot be taken out through the cartridge exchange port  58 . 
     The developing position also serves as a communicating position for the other cartridges. The cartridge memories  51   b ,  52   b ,  53   b  and  54   b  are provided on the ends of the surfaces of the cartridges  51 ,  52 ,  53  and  54 , respectively. As described above, the cartridge memories  51   b ,  52   b ,  53   b  and  54   b  store identification information including information about the lifetime of the cartridge such as the amount of a residual toner. 
     When the developing rotary unit  50  is placed in the developing position as shown in  FIG. 2B , the cartridge memory of one of the cartridges other than the cartridge placed in the developing position (the cartridge memory  54   b  of the cartridge  54  in the example of  FIG. 2B ) is placed in an opposite position to the antenna  124  provided in the printer  10  body and the communication of the control unit  100  with the cartridge memory can be carried out through the antenna  124 . In  FIG. 2B , a first counterclockwise one of the cartridges placed in the developing position, that is, a cartridge for a color developed immediately before a color which is being developed is placed in the communicating position. This implies that the developing position is placed in the communicating position for the other cartridges. 
     In other words, a positional relationship among the cartridge memory of each of the cartridges, the photosensitive member  20  and the antenna  124  is determined in such a manner that the developing position is set to be the communicating position. 
     In the state shown in  FIG. 2B , accordingly, the development of the color of cyan C is carried out with respect to the photosensitive member  20  by the developing roller  51   a  of the cartridge  51 , while the control unit  100  can write the current identification information to the cartridge memory  54   b  of the cartridge  54 . With this structure, thus, the current identification information can be written to the cartridge memory of the cartridge for a color developed immediately before a color which is being developed. 
     Next, the exchange position will be described. The exchange position can be taken only when an operation for attaching and removing the cartridge is carried out. When the developing rotary unit  50  is placed in the exchange position, one of the cartridges appears in the cartridge exchange port  58  as shown in  FIG. 2C  and can be taken out through the cartridge exchange port  58 .  FIG. 2C  shows a state in which the cartridge  54  for yellow appears in the cartridge exchange port  58 . Moreover, a cartridge can be newly attached through the cartridge exchange port  58 . In the exchange position, the developing rollers provided in all of the cartridges are placed in positions set apart from the photosensitive member  20 . Thus, it is possible to take out only one cartridge appearing in the cartridge exchange port  58  when the developing rotary unit  50  is placed in the exchange position. Therefore, a user can be prevented from damaging the apparatus due to the careless attachment and removal of the cartridge. 
     Moreover, a home position sensor  106  (a home position will be hereinafter referred to as HP) for detecting the home position of the developing rotary unit  50  is provided in the printer  10 , which is not shown in  FIGS. 1 and 2 . 
     With reference to  FIG. 3 , the electrical structure of the printer  10  will be explained.  FIG. 3  shows a block structure according to the invention. Since a block for controlling the photosensitive unit  75  and a block for controlling the exposing unit  40  are not essential matters in the invention, they are not shown. 
     The control unit  100  includes two controllers, that is, a unit controller  101  and an image processing controller  102 . Both of these two controllers  101  and  102  have a CPU respectively. 
     The image processing controller  102  has the function of receiving various data such as image data created by the application software of an external computer system such as a personal computer (not shown) and converting RGB data on red, green and blue to be image data into YMCK data on yellow, magenta, cyan and black to create image data for print. Moreover, the image processing controller  102  has the function of counting a dot count value for each of the colors YMCK based on the image data for print on the YMCK which are thus created. Then, the image processing controller  102  transfers the image data for print on the colors YMCK and the dot count value for each color image of YMCK to the unit controller  101 . The dot count value indicates the number of dots to be formed on a recording paper when printing is carried out as is well known. 
     The unit controller  101  controls each of the charging unit  30 , the exposing unit  40 , the primary transfer unit  60 , the photosensitive unit  75 , the secondary transfer unit  80 , the fixing unit  90  and the display unit  95 , and controls the developing rotary unit  50  based on various signals such as image data for print which are input from the image processing controller  102 . In  FIG. 3 , a rotary driving portion  107  is shown as a component for driving the developing rotary unit  50 . The developing rotary unit  50  is driven by a stepping motor. 
     The unit controller  101  manages three memories, that is, an ROM  103 , an RAM  104  and a body memory  105 . The ROM  103  stores various programs for controlling the printer  10 , and the RAM  104  serves to temporarily store various information about the printer  10  and is used as a work memory. The body memory  105  will be described later. 
     Also, the unit controller  101  receives a signal from a take-out operating portion  206 . The take-out operating portion  206  serves to select a cartridge to be taken out of the developing rotary unit  50 . 
     Moreover, a detection signal is input from the HP sensor  106  to the unit controller  101 . Furthermore, the unit controller  101  monitors the state of a power switch (not shown in  FIGS. 1 and 2 )  108  and a body cover opening and closing detection switch (not shown in  FIGS. 1 and 2 )  109 , and detects the ON operation of a power supply if any and detects the opening and closing operation of the body cover (not shown in  FIGS. 1 and 2 ) if any. 
     Furthermore, the unit controller  101  can communicate with the cartridge memories  51   b ,  52   b ,  53   b  and  54   b  provided in the cartridges  51 ,  52 ,  53  and  54  attached to the developing rotary unit  50  through a transmitting/receiving portion  123  and the body side antenna  124  by wireless. The transmitting/receiving portion  123  has the function of modulating data transmitted from the unit controller  101  and demodulating data received from the cartridge memory. As described above, the cartridge memory which can communicate with the unit controller  101  is placed in the communicating position. 
     With reference to  FIGS. 4A and 4B , the structure of the cartridge memory will be described including the transmitting and receiving structure of the data.  FIG. 4A  is a perspective plan view showing the structure of the cartridge memory  54   b , and  FIG. 4B  is a block diagram for explaining the internal structures of the cartridge memory and the transmitting/receiving portion. Description will be given to the cartridge memory  54   b  provided in the cartridge  54  for yellow, and can also be applied to the other cartridge memories  51   b ,  52   b  and  53   b.    
     If a predetermined positional relationship between the cartridge memory  54   b  and the body side antenna  124 , for example, a mutual distance is less than 10 mm, information can be transmitted and received in a non-contact state with each other. The cartridge memory  54   b  wholly has a very small size and thickness, and can also be stuck as a seal to an object with either side having an adhesiveness. The cartridge memory  54   b  is referred to as a memory tag and various types have been put on the market. 
     The cartridge memory  54   b  has a planar coil to be a non-contact IC chip  54   c , a capacitor  54   d  for resonance which is formed by etching a metal coat and an antenna  54   e , and these are mounted on a plastic film and are covered with a transparent cover sheet. 
     The non-contact IC chip  54   c  has a rectifier  54   f , a signal analyzing portion RF (Radio Frequency)  54   g , a control portion  54   h  and a memory cell  54   i . The memory cell  54   i  is a nonvolatile memory capable of carrying out electrical read/write, for example, an NAND type flash ROM, and can store written information and can read stored information from an outside. 
     The antenna  54   e  of the cartridge memory  54   b  and the body side antenna  124  communicate with each other by wireless, and read information stored in the memory cell  54   i  and write information to the memory cell  54   i . Moreover, a high frequency signal generated in the transmitting/receiving portion  123  of the control unit  100  is induced as a high frequency magnetic field through the body side antenna  124 . The high frequency magnetic field is absorbed through the antenna  54   e  of the cartridge memory  54   b  and is rectified by the rectifier  54   f , and thus becomes a DC power supply for driving each circuit in the IC chip  54   c.    
     The identification information including information about the lifetime of the cartridge such as the amount of a residual toner is stored in the memory cell  54   i  of the cartridge memory  54   b , and is updated by the unit controller  101  every time a predetermined event is generated. 
     The body memory  105  serves to store identification information about the cartridges  51 ,  52 ,  53  and  54  attached to the developing rotary unit  50 . It is desirable that the body memory  105  should be a nonvolatile memory capable of saving data also when the power supply of the printer  10  is OFF. 
     The unit controller  101  carries out an operation for reading the identification information from the cartridge memory of each cartridge and writing the same identification information to the body memory  1051  then updating the information about the lifetime of the cartridge, for example, the amount of a residual toner in each cartridge, a driving time or the number of sheets to be printed every time a development is performed, and communicating with the cartridge memory to write the current identification information to the cartridge memory when a predetermined event is generated. 
     Further, the unit controller  101  carries out an operation for communicating with the cartridge memory of the cartridge when a new cartridge is attached to the developing rotary unit  50 , reading the identification information stored in the cartridge memory, and storing the same identification information in the body memory  1051  and then updating the information about the lifetime of the cartridge, for example, the amount of a residual toner in each cartridge, a driving time or the number of sheets to be printed every time a development is performed, and communicating with the cartridge memory to write the current identification information to the cartridge memory when a predetermined event is generated, for example. 
     The body memory  105  stores the identification information about the cartridges  51 ,  52 ,  53  and  54  attached to the developing rotary unit  50  and the information about the lifetime, for example, the amount of the residual toner is updated by the unit controller  101  every time the development is carried out as described above. In particular, two storage regions including the current toner remaining amount information storage region (hereinafter referred to as the current toner region) and a preceding writing toner remaining amount information storage region (hereinafter referred to as a preceding writing region) are allocated to a region for storing the information about the amount of the residual toner in each cartridge as shown in  FIG. 5 . These two storage regions are provided with regions for the four cartridges  51 ,  52 ,  53  and  54 , respectively. 
     A region for a cartridge for each color in the preceding writing region is a region for storing the information about the amount of the residual toner which is written to the respective cartridge memories when a close event to update the identification information is generated, more specifically, the memory cell of the cartridge memory. When printing is carried out, then, a toner having a color used in the printing is decreased. In that case, the unit controller  101  calculates the amount of the used toner for each color in the printing based on the dot count value transmitted from the image processing controller  102 , and furthermore, calculates the amount of the residual toner after the printing at this time. The current toner remaining amount is thus obtained and a region for storing the current toner remaining amount is the current toner region. 
     For the calculation to obtain the current toner remaining amount, for example, it is preferable to decrease the amount of the toner used at this time from the amount of the residual toner which is stored in the preceding writing region. Moreover, there have been known various methods of calculating the amount of the used toner based on the dot count value. It is preferable that any of the well-known methods should be used. 
     Referring to the region for storing the information about the amount of the residual toner in each cartridge of the body memory  105 , since the two storage regions, that is, the current toner region and the preceding writing region are provided, it is possible to immediately decide whether or not the current identification information, particularly, the current amount of a residual toner is written to the cartridge memory of a certain cartridge when an instruction for taking out the same cartridge is given by a user as is apparent from the following description. Further, it is possible to determines that whether the cartridge is actually exchanged or not. 
     Next, an operation for writing the identification information to the cartridge memory will be mainly described schematically with reference to  FIG. 6 .  FIG. 6  is a flowchart showing the processing of the unit controller  101  in the printing, in which it is assumed that an event in which the identification information of the cartridge memory is to be updated is a development. More specifically, it is assumed that the identification information of the cartridge memory is updated every time the development is carried out. 
     Upon receipt of image data for print and a print start signal from the image processing controller  102 , the unit controller  101  places a cartridge for a first color in the developing position by the rotary driving portion  107  and a development for the first color is thus carried out (Step S 10 ). When the development of the first color is ended, the unit controller  101  rotates the developing rotary unit  50  by the rotary driving portion  107  (Step S 11 ), and places a cartridge for a next color, in this case, a second color in the developing position. At this time, a cartridge for a last color, in this case, the first color is placed in the communicating position as shown in  FIG. 2B . In this state, accordingly, the unit controller  101  develops the second color, and furthermore, communicates with the cartridge memory of the cartridge for the last color to read the current identification information about the cartridge from the body memory  105  and to write the identification information to the cartridge memory (Step S 12 ). Consequently, the identification information of the cartridge memory is updated to be the current. This is a processing of updating the identification information about the development of the last color which is described in the Step S 12 . As a matter of course, the identification information also includes information about a lifetime such as the amount of a residual toner and a driving time. 
     When the development of a third color and the update of the identification information in the cartridge memory of the cartridge for the second color, and the development of a fourth color and the update of the identification information in the cartridge memory of the cartridge for the third color are ended in the same manner, a decision at Step S 13  is yes and the unit controller  101  rotates the developing rotary unit  50  by the rotary driving portion  107  (Step S 14 ) to carry out a processing of updating the identification information about the development of the last color (Step S 15 ). More specifically, in this case, the cartridge carrying out the development for the fourth color is placed in the communicating position to write the current identification information to the cartridge memory of the same cartridge. The unit controller  101  places the developing rotary unit  50  in the standby position (Step S 16 ) and the processing is thus ended. 
     While the number of sheets to be printed is one in the above description, it is preferable that a first color on a first page should be developed at the Step S 10  and the processings of the Steps S 11  to S 13  should be then repeated corresponding to the number of sheets to be printed in the case that a plurality of sheets are to be printed. 
     Referring to the amount of the residual toner in each cartridge, the body memory  105  includes the two storage regions having the current toner region and the preceding writing region as described above. Description will be given to the way of using information about the amount of the residual toner in these two storage regions in the update of the identification information about the cartridge memory of the cartridge for the last color at the Steps S 12  and S 15  in  FIG. 6 . Herein, only the amount of the residual toner will be described. 
     Assuming that a certain color (that is, a Y color) is developed, for example, the unit controller  101  calculates the amount of the residual toner in the cartridge for the Y color after the present development based on the dot count value of the Y color transmitted from the image processing controller  102 . This is the current toner remaining amount, and the unit controller  101  first writes information about the current toner remaining amount in a region for the Y-color cartridge in the current toner region of the body memory  105 . At this time, information about the region for the Y-color cartridge in the preceding writing region is not changed. 
     Subsequently, a next color is developed. At this time, the Y-color cartridge is placed in the communicating position. Therefore, the unit controller  101  communicates with the cartridge memory for the Y-color cartridge to read information about the amount of the residual toner from the region for the Y-color cartridge in the current toner region of the body memory  105  and to write the same information to the cartridge memory of the Y-color cartridge, and then, writes the same information to the region for the Y-color cartridge in the preceding writing region and to update the information about the amount of the residual toner in the region for the Y-color cartridge in the preceding writing region. 
     Referring to the update of the amount of the residual toner in the update of the identification information in the cartridge memory of the cartridge for the last color at the Steps S 12  and S 15  in  FIG. 6 , the above operation is repeated. 
     From the foregoing, referring to the cartridge for a certain color, in the case that the information about the amount of the residual toner which is written to the region for the cartridge of the same color in the current toner region and the information about the amount of the residual toner which is written to the region for the cartridge of the same color in the preceding writing region in the body memory  105  are coincident with each other, it is supposed that the current identification information is written to the cartridge memory. 
     Also in some cases in which the identification information of the cartridge memory is to be updated every time the development is carried out as described above, however, the information about the amount of the residual toner written to the region for the cartridge of a certain color in the current toner region and the information about the amount of the residual toner written to the region for the cartridge of the same color in the preceding writing region in the body memory  105  are not coincident with each other. Description will be given. 
     In order to write the current amount of the residual toner, that is, the amount of the residual toner after the last development to the cartridge memory of a cartridge for a last developed color at the Step S 12  or S 15  in  FIG. 6 , the calculation of the current amount of the residual toner based on the dot count value transmitted from the image processing controller  102  and the write of the current amount of the residual toner to the region for the cartridge of the same color in the current toner region of the body memory  105  are to be ended before a writing timing is reached. 
     However, a timing in which the dot count value is transmitted from the image processing controller  102  to the unit controller  101  is not constant. In some cases, the timing in which the dot count value is transmitted to the unit controller  101  is delayed for some cause, for example, the amount of the processing of the image processing controller  102  is large at that time, and the current amount of the residual toner cannot be written to the region for the cartridge of the same color in the current toner region of the body memory  105  before a timing for write to the cartridge memory is reached. 
     In these cases, the unit controller  101  writes, to the cartridge memory for the same color, the information about the amount of the residual toner which is written to the current toner region of the body memory  105  when the identification information of the same cartridge memory is to be updated. 
     After the identification information of the cartridge memory is updated, the unit controller  101  obtains information about the current amount of the residual toner based on the dot count value for the same color which is transmitted from the image processing controller  102  and writes the information about the current amount of the residual toner to the region for the cartridge of the same color in the current toner region of the body memory  105 . At this time, any processing is not carried out over the region for the cartridge of the same color in the preceding writing region. At this point, accordingly, the information about the current toner region and the information about the preceding writing region for the same color are not coincident with each other. 
     For example, the cartridge for the Y color will be considered. It is assumed that both the information about the amount of the residual toner in the region for the cartridge of the Y color in the current toner region and the information about the amount of the residual toner in the region for the cartridge of the Y color in the preceding writing region in the body memory  105  are represented by A before the development of the Y color. Accordingly, it is supposed that the information about the current amount of the residual toner is written to the cartridge memory of the Y-color cartridge before the development. 
     Assuming that the transmission of the dot count value for the Y color from the image processing controller  102  is delayed after the development of the Y color and the current amount of the residual toner after the development of the Y color cannot be written to the region for the cartridge of the Y color in the current toner region of the body memory  105  before the timing for write to the cartridge memory of the Y-color cartridge is reached, however, information about the amount of the residual toner which is to be written to the cartridge memory of the Y-color cartridge at this time is represented by A written to the region for the cartridge of the Y color in the current toner region of the body memory  105 . 
     When the write to the cartridge memory is ended, then, the unit controller  101  writes A to the region for the cartridge of the Y color in the preceding writing region of the body memory  105 . After the identification information of the cartridge memory for the Y color is updated, subsequently, the unit controller  101  obtains the information about the current amount of the residual toner in the Y-color cartridge after a last development based on the dot count value of the Y color which is transmitted from the image processing controller  102 . In case of A′ (&lt;A), the unit controller  101  writes the current toner remaining amount information A′ to the region for the cartridge of the Y color in the current toner region of the body memory  105 . At this time, any processing is not carried out over the region for the cartridge of the Y color in the preceding writing region. For this reason, the information about the amount of the residual toner in the region for the cartridge of the Y color in the preceding writing region is maintained to be A. 
     In other words, at this point, the information about the amount of the residual toner which is written to the cartridge memory of the Y-color cartridge is A and the information about the amount of the residual toner which is written to the region for the cartridge of the Y color in the current toner region of the body memory  105  is A′, and the information about the amount of the residual toner which is written to the region for the cartridge of the Y color in the preceding writing region is A. 
     From the above description, it is found that the current identification information is not written to a cartridge for a certain color in the case that the information about the amount of the residual toner which is written to the region for the cartridge of the same color in the current toner region and the information about the amount of the residual toner which is written to the region for the cartridge of the same color in the preceding writing region of the body memory  105  are not coincident with each other. 
     The information about the lifetime in the identification information about the cartridge includes information about a driving time and the number of sheets to be printed in addition to the amount of the residual toner. The information about the lifetime other than the amount of the residual toner is always updated to the current information in the update of the identification information in the Steps S 12  and S 15  of  FIG. 6 . The reason is as follows. The information about the lifetime other than the amount of the residual toner, for example, the driving time and the number of sheets to be printed can be directly counted by the unit controller  101 . Therefore, the same information can be written to a predetermined region for the cartridge of the same color in the body memory  105  before the timing for the write to the cartridge memory is reached after the development. 
     Thus, the information about the amount of the residual toner in the information about the lifetime of the cartridge can be obtained based on the dot count value transmitted from the image processing controller  102 , while the other information about the lifetime can be directly counted by the unit controller  101 . In this respect, the information about the amount of the residual toner is different from the other information about the lifetime in some situation. 
     Based on the above structure, description will be given to four embodiments on a peculiar operation to the invention. All of the embodiments which will be described below are carried out when the unit controller  101  detects that a power supply is turned ON or detects that the body cover of the printer body  10  is closed. 
     More specifically, as described above, in the case that the carriage is exchanged when the control unit of the body cannot recognize that the cartridge is exchanged, for example, when the cover of the body is opened during the rotation of the developing rotary unit or the power supply is turned OFF, the invention can carry out the accurate lifetime management for the cartridge. Accordingly, it is preferable to cause the identification information of the body memory  105  to be coincident with the identification information of the cartridge memory when the body cover is closed or the power supply is turned ON. Therefore, the unit controller  101  executes a processing which will be described below when detecting that the power supply is turned ON or detecting that the body cover of the printer body  10  is closed. 
     First Embodiment 
       FIG. 7  is a flowchart showing a processing in a first embodiment according to the invention. When detecting that the power supply is turned ON by turning on the power switch  108  or detecting that the body cover is closed in accordance with the state of the body cover opening and closing detection switch  109  (in the case that a decision at Step S 20  is yes), the unit controller  101  controls the rotary driving portion  107  to rotate the developing rotary unit  50  (Step S 21 ). When a detection signal is received from the HP sensor  106 , then, HP is detected (Step S 22 ). When detecting the HP, the unit controller  101  controls the rotary driving portion  107  to move the first cartridge to the communicating position (Step S 23 ). Any of the four cartridges  51 ,  52 ,  53  and  54  which is to be a first cartridge is predetermined by the unit controller  101 . 
     Consequently, the communication of the unit controller  101  with the cartridge memory of the first cartridge can be carried out. Therefore, the unit controller  101  communicates with the cartridge memory to read all of identification information written to the cartridge memory (Step S 24 ). When reading the identification information from the cartridge memory, the unit controller  101  writes all of the identification information thus read to a region for writing the identification information about the first cartridge in the body memory  105  (Step S 25 ). Information about the amount of a residual toner which is read from the cartridge memory is written to both the current toner region for the color of the first cartridge and the preceding writing region. 
     Consequently, all of the identification information about the first cartridge in the body memory  105  are updated and are set to have the same contents as those regions of the cartridge memory in the first cartridge. 
     When the identification information about the first cartridge in the body memory  105  is updated, thus, the unit controller  101  subsequently controls the rotary driving portion  107  to rotate the developing rotary unit  50  (Step S 26 ), thereby moving a next cartridge, that is, a cartridge for a second color to the communicating position (Step S 27 ). 
     Consequently, the communication of the unit controller  101  with the cartridge memory of the cartridge for the second color can be carried out. Therefore, the unit controller  101  communicates with the cartridge memory to read the identification information written to the cartridge memory (Step S 28 ). 
     When reading the identification information from the cartridge memory, the unit controller  101  writes the identification information thus read to a region for writing the identification information about the cartridge for the second color (Step S 29 ). Similarly, the information about the amount of the residual toner which is read from the cartridge memory is written to both the current toner region for the color of the cartridge and the preceding writing region. 
     When the above processing is carried out over a cartridge for a third color and a cartridge for a fourth color, a decision at Step S 30  is yes. Therefore, the unit controller  101  ends the processing. 
     As described above, the first embodiment is based on a thought that the abnormal exchange of the cartridge is carried out irrespective of a decision whether the abnormal exchange of the cartridge is actually carried out. In the case that the power supply is turned ON or the body cover is closed, the identification information about the cartridge for each color in the body memory  105  is forcibly updated with the identification information read from the cartridge memory. Also in the case that the cartridge is exchanged when the unit controller  101  cannot recognize that the cartridge is exchanged, for example, when the body cover is opened during the rotation of the developing rotary unit  50  or the power supply is turned OFF, therefore, it is possible to carry out an accurate lifetime management for the cartridge. 
     Second Embodiment 
     According to the processing in the first embodiment, the identification information about the cartridge for each color in the body memory  105  is forcibly updated with the identification information read from the cartridge memory of the cartridge for each color and the contents of the information about the amount of the residual toner in both the current toner region and the preceding writing region in the region of the body memory  105  for storing the information about the amount of the residual toner in each cartridge are also updated to the information about the amount of the residual toner which is read from the cartridge memory. 
     As described above, however, the information about the amount of the residual toner which is written to the cartridge memory is not always corresponded to the current information about the amount of the residual toner which is written to the current toner region of the body memory  105 . According to the first embodiment, a situation in which the contents of the current toner region in the body memory  105  are updated to old information about the amount of the residual toner is occurred as follows in some cases. 
     For easy understanding, it is assumed that the abnormal exchange of the cartridge is not carried out but ending is performed in a normal state and a power supply is turned OFF. At this time, referring to a certain cartridge, there is a possibility that the transmission of a dot count value for the color from the image processing controller  102  might be delayed in the update of identification information after a last development before the power supply is turned OFF, and the current amount of the residual toner cannot be written to the region for the cartridge of the same color in the current toner region of the body memory  105  before a timing for write to the cartridge memory is reached. In this case, the information about the amount of the residual toner which is written to the cartridge memory is equivalent to information written to the preceding writing region. 
     According to the first embodiment, when the power supply is turned ON in such a state, both of the contents in the current toner region for the same color in the body memory  105  and the preceding writing region are rewritten to the information about the amount of the residual toner which is read from the cartridge memory and are thus updated. For this reason, the information about the amount of the residual toner which is written to the current toner region at this time is the old information about the amount of the residual toner, which is not correct. 
     In other words, in such a case, there is a possibility that a slight error might be made between the amount of the residual toner which is managed by the body memory  105  and the actual amount of the residual toner in the cartridge. When such a situation is repeated many times, the error between the amount of the residual toner which is managed by the body memory  105  and the actual amount of the residual toner is increased. 
     The second embodiment serves to avoid such a situation and will be described below with reference to a flowchart shown in  FIG. 8 . When detecting that the power switch  108  is turned ON so that the power supply is thus turned ON or detecting that the body cover is closed depending on the state of the body cover opening and closing detection switch  109  (in the case that a decision at Step S 40  is yes), the unit controller  101  controls the rotary driving portion  107  to rotate the developing rotary unit  50  (Step S 41 ). When a detection signal is received from the HP sensor  106 , HP is detected (Step S 42 ). 
     When detecting the HP, the unit controller  101  controls the rotary driving portion  107  to first move one cartridge to the communicating position (Step S 43 ). Any color for the cartridge to be moved to the communicating position at this time is predetermined by the unit controller  101 . 
     Consequently, the communication of the unit controller  101  with the cartridge memory of the first cartridge can be carried out. Therefore, the unit controller  101  communicates with the cartridge memory to read all of identification information written to the cartridge memory (Step S 44 ). The reason why all of the identification information are read is that the cartridge might be exchanged and all of the identification information about the cartridge in the body memory  105  are to be updated when the cartridge has been exchanged. 
     When reading the identification information from the cartridge memory, the unit controller  101  decides whether the cartridge has actually been exchanged or not (Step S 45 ). 
     Whether the cartridge has been exchanged is decided at the Step S 45  by comparing the identification information read from the cartridge memory at the Step S 44  with the identification information written corresponding to the cartridge for the same color in the body memory  105 . For information to be used for making the comparison, it is necessary to utilize information capable of making a clear distinction from another cartridge for the same color. For this purpose, it is preferable to use the information about a lifetime which is the characteristic information about each cartridge in the identification information. 
     While the information about a lifetime includes information about the amount of a residual toner, a driving time and the number of sheets to be printed, it is preferable to use the information about the amount of the residual toner in order to decide whether the cartridge has been exchanged or not at the Step S 45 . The reason is as follows. Although the amount of consumption of a toner in a development is very small, a difference in the amount of consumption of a toner in the development can also be expressed as the information about the amount of the residual toner. For this purpose, a greater bit count than a bit count for expressing the driving time or the number of sheets to be printed is allocated. By using the information about the amount of the residual toner, thus, it is possible to decide whether the cartridge has been exchanged or not at the Step S 45  with high precision. 
     The information about the amount of the residual toner which is written corresponding to the cartridge for the first color in the body memory  105  includes two sorts of information about the amount of the residual toner, that is, the amount of a residual toner which is written to the current toner region and the amount of a residual toner which is written to a preceding writing region. In the case that the information about the amount of the residual toner in the identification information read from the first cartridge memory at the Step S 44  is coincident with either the information about the amount of the residual toner which is written to the current toner region or the information about the amount of the residual toner which is written to the preceding writing region, it is decided that the first cartridge has not been exchanged. In the case that the information about the amount of the residual toner in the identification information is coincident with neither the information about the amount of the residual toner which is written to the current toner region nor the information about the amount of the residual toner which is written to the preceding writing region, it is decided that the first cartridge has been exchanged. 
     Apparently, it is possible to decide that the exchange has not been carried out in the case that the information about the amount of the residual toner in the identification information read from the first cartridge memory is coincident with the information about the amount of the residual toner which is written to the current toner region. 
     In the case that the information about the amount of the residual toner in the identification information read from the first cartridge memory is not coincident with the information about the amount of the residual toner which is written to the current toner region but the information about the amount of the residual toner which is written to the preceding writing region, moreover, it can be decided that the transmission of a dot count value for the same color from the image processing controller  102  is delayed in the update of the identification information after a last development before the power supply is turned ON or the body cover is closed for the first cartridge and the current amount of the residual toner cannot be written to a region for the cartridge of the same color in the current toner region of the body memory  105  before a timing for write to the cartridge memory is reached, and furthermore, the current information about the amount of the residual toner is written to the cartridge memory in the update of the identification information after the subsequent development as described above. For this reason, there is not a problem even if it is decided that the exchange has not been carried out. 
     When it is decided that the first cartridge has been exchanged at the Step S 45 , the unit controller  101  overwrites the identification information read from the first cartridge memory at the Step S 44  to a region for writing the identification information about the cartridge for the first color in the body memory  105  (Step S 46 ). At this time, the information about the amount of the residual toner which is read from the cartridge memory is written to both the current toner region for the color of the first cartridge and the preceding writing region. Consequently, the identification information about the cartridge for the same color in the body memory  105  is updated. 
     On the other hand, when it is decided that the first cartridge has not been exchanged at the Step S 45 , the processing proceeds to Step S 47  in which it is decided whether the processing has been ended for all of the four cartridges. 
     When the processing for the first cartridge is ended, accordingly, the unit controller  101  then repeats the processings from the Step S 43  to the Step S 47  for second, third and fourth cartridges. When the processings are carried out for all of the four cartridges, they are ended. 
     As described above, in the second embodiment, it is decided whether the cartridge has been exchanged or not. For only the cartridge which is decided to be exchanged, the identification information about the cartridge of the body memory  105  is updated. Therefore, it is possible to prevent an error from being made between the amount of the residual toner which is managed by the body memory  105  and the actual amount of the residual toner in the same cartridge. Moreover, the information about the amount of the residual toner is used as information for deciding whether the cartridge has been exchanged or not. Consequently, whether the exchange has been carried out can be decided with high precision. 
     As a result, also in the case that the cartridge is exchanged when the unit controller  101  cannot recognize that the cartridge is exchanged, for example, when the body cover is opened during the rotation of the developing rotary unit  50  or the power supply is turned OFF, it is possible to carry out an accurate lifetime management for the cartridge. 
     Third Embodiment 
     In a third embodiment, in the case that there is a cartridge which might have been exchanged, identification information about the cartridge in the body memory  105  is forcibly updated with identification information read from the cartridge memory of the cartridge, and description will be given with reference to a flowchart shown in  FIG. 9 . 
     When detecting that the power switch  108  is turned ON and the power supply is thus turned ON or detecting that the body cover is closed depending on the state of the body cover opening and closing detection switch  109  (in the case that a decision at Step S 50  is yes), the unit controller  101  controls the rotary driving portion  107  to rotate the developing rotary unit  50  (Step S 51 ). At this time, the rotary driving portion  107  supplies a driving pulse to a stepping motor and rotates the developing rotary unit  50 . In this case, the unit controller  101  fetches a driving pulse output from the rotary driving portion  107  and counts the number of driving pulses from the time that an instruction for starting the rotation is given to the rotary driving portion  107 . 
     Then, a detection signal is output from the HP sensor  106 . Based on the number of driving pulses counted from the time that the instruction for the rotation is given to the rotary driving portion  107  to the time that the detection signal is received from the HP sensor  106  (Step S 52 ), the unit controller  101  decides whether any cartridge is placed in the exchange position or not and decides the color of the cartridge if any (Step S 53 ). 
     More specifically, one HP is present for one rotation of the developing rotary unit  50 , and the position of the cartridge for each color in the developing rotary unit  50  is determined and is registered in the unit controller  101 . Moreover, the number of rotations of the developing rotary unit  50  in one driving pulse is also registered in the unit controller  101 . Accordingly, the unit controller  101  can find the number of rotations of the developing rotary unit  50  from the number of driving pulses counted from the time that the instruction for starting the rotation is given to the rotary driving portion  107  to the detection of the HP, and can decide whether any cartridge is placed in the exchange position or not and can decide the color of the cartridge if any. 
     When the unit controller  101  decides that the cartridge placed in the exchange position is not present at the Step S 53 , the processing is ended. If it is decided that a cartridge for a certain color is placed in the exchange position, the cartridge for the same color is moved to the communicating position (Step S 54 ) and all of the identification information are read from the cartridge memory of the cartridge (Step S 55 ), and the identification information thus read are written to the region for writing the identification information about the cartridge for the same color in the body memory  105  (Step S 56 ). Thus, this processing is ended. 
     The processings at the Steps S 55  and S 56  are the same as the processings at the Steps S 28  and S 29  in  FIG. 7 . In the processing at the Step S 56 , moreover, when the identification information read from the cartridge memory is to be written to the body memory  105 , the information about the amount of the residual toner which is read from the cartridge memory is written to both the current toner region for the color of the cartridge and the preceding writing region. 
     As described above, in the third embodiment, if there is a cartridge placed in the exchange position when the power supply is turned ON or the body cover is closed, the identification information about the cartridge in the body memory  105  is forcibly updated with the identification information read from the cartridge memory of the cartridge on the assumption that the cartridge has been exchanged. 
     As described above, according to the third embodiment, also in the case that the cartridge is exchanged when the unit controller  101  cannot recognize that the cartridge is exchanged, for example, when the body cover is opened during the rotation of the developing rotary unit  50  or the power supply is turned OFF, therefore, it is possible to carry out an accurate lifetime management for the cartridge. 
     Fourth Embodiment 
     In the third embodiment described above, the cartridge placed in the exchange position when the power supply is turned ON or the body cover is closed is treated to be exchanged and the identification information about the cartridge of the body memory  105  is forcibly updated with the identification information read from the cartridge memory of the cartridge. In that case, however, there is a possibility that an error might be made between the amount of the residual toner managed by the body memory  105  and the actual amount of the residual toner in the cartridge in relation to the cartridge placed in the exchange position for the same reason as that described at the beginning of the second processing configuration. 
     A fourth embodiment serves to avoid such a situation and a flowchart for the processing is shown in  FIG. 10 . The processings of Steps S 60 , S 61 , S 62 , S 63 , S 64  and S 65  in  FIG. 10  are identical to those of the Steps S 50 , S 51 , S 52 , S 53 , S 54  and S 55  in  FIG. 9  respectively, and the processings of Steps S 66  and S 67  in  FIG. 10  are identical to those of the Steps S 45  and S 46  in  FIG. 8  respectively. 
     Accordingly, repetitive and brief description will be given to the processing in  FIG. 10 . When detecting that the power switch  108  is turned ON and the power supply is thus turned ON or detecting that the body cover is closed depending on the state of the body cover opening and closing detection switch  109  (in the case that a decision at Step S 60  is yes), the unit controller  101  rotates the developing rotary unit  50  (Step S 61 ). At this time, the unit controller  101  fetches a driving pulse output from the rotary driving portion  107  and counts the number of driving pulses from the time that an instruction for starting the rotation is given to the rotary driving portion  107 . 
     Then, a detection signal is received from the HP sensor  106  (Step S 62 ). Based on the number of driving pulses counted from the time that the instruction for the rotation is given to the rotary driving portion  107  to the time that the detection signal is received from the HP sensor  106 , the unit controller  101  decides whether any cartridge is placed in the exchange position or not and decides the color of the cartridge if any (Step S 63 ). 
     When the unit controller  101  decides that any cartridge is not placed in the exchange position at the Step S 53 , the processing is ended. If it is decided that a cartridge for a certain color is placed in the exchange position, the cartridge for the same color is moved to the communicating position (Step S 64 ) and all of the identification information are read from the cartridge memory of the cartridge (Step S 65 ). 
     When reading the identification information from the cartridge memory, the unit controller  101  decides whether the cartridge has actually been exchanged or not (Step S 66 ). 
     Whether the cartridge has actually been exchanged is decided at the Step S 66  by comparing the identification information read from the cartridge memory at the Step S 65  with the identification information written corresponding to the cartridge in the body memory  105 . As described above, the information about the amount of the residual toner is used for the information to be utilized for making the comparison. 
     Therefore, the unit controller  101  decides that the cartridge placed in the exchange position has not been exchanged if the information about the amount of the residual toner in the identification information read from the cartridge memory at the Step S 65  is coincident with either the information about the amount of the residual toner which is written to the current toner region or the information about the amount of the residual toner which is written to the preceding writing region, and decides that the cartridge has been exchanged if the information about the amount of the residual toner in the identification information read from the cartridge memory is coincident with neither the information about the amount of the residual toner which is written to the current toner region nor the information about the amount of the residual toner which is written to the preceding writing region. 
     When it is decided that the cartridge has actually been exchanged at the Step S 66 , then, the unit controller  101  overwrites the identification information read from the cartridge memory at the Step S 65  to a region for writing the identification information about the cartridge for the same color in the body memory  105  (Step S 67 ). At this time, the information about the amount of the residual toner which is read from the cartridge memory is written to both the current toner region for the color of the same cartridge and the preceding writing region. Consequently, the identification information about the cartridge for the same color in the body memory  105  is updated. 
     On the other hand, when it is decided that the same cartridge has not been exchanged at the Step S 66 , the unit controller  101  ends the processing. 
     In the fourth embodiment, thus, if any cartridge is placed in the exchange position when the power supply is turned ON or the body cover is closed, it is decided whether the cartridge has actually been exchanged or not. Only in the case that the cartridge has actually been exchanged, the identification information of the body memory  105  is updated. This is based on a thought that the cartridge is not always exchanged even if there is the cartridge placed in the exchange position when the power supply is turned ON or the body cover is closed. 
     As described above, in the fourth embodiment, if any cartridge is placed in the exchange position when the power supply is turned ON or the body cover is closed, the cartridge might have been exchanged, and furthermore, it is decided whether the cartridge has actually been exchanged or not. If it is decided that the cartridge has been exchanged, the identification information about the cartridge of the body memory  105  is updated. Therefore, it is possible to prevent an error from being made between the amount of the residual toner which is managed by the body memory  105  and the actual amount of the residual toner in the same cartridge. Moreover, the information about the amount of the residual toner is used as information for deciding whether the cartridge has been exchanged or not. Consequently, whether the exchange has been carried out can be decided with high precision. 
     As a result, also in the case that the cartridge is exchanged when the unit controller  101  cannot recognize that the cartridge is exchanged, for example, when the body cover is opened during the rotation of the developing rotary unit  50  or the power supply is turned OFF, it is possible to carry out an accurate lifetime management for the cartridge. 
     Next, a fifth embodiment of the invention will be described with reference to  FIG. 11 . This operation shown in  FIG. 11  is carried out when the take-out operating portion  206  is operated to give an instruction for taking out a cartridge for a certain color. 
     A user gives an instruction for taking out a cartridge for a Y color by the take-out operating portion  206 . At this time, the unit controller  101  receives, from the take-out operating portion  206 , a control signal indicating that an instruction for taking out the cartridge for the Y color is given. Upon receipt of the control signal, the unit controller  101  decides that the instruction for take-out is given at Step S 21 , and subsequently, compares information about a region for the cartridge for the Y color in the current toner region of the body memory  105  with information about a region for the cartridge for the Y-color in a preceding writing region and decides whether they are coincident with each other or not (Step S 22 ). 
     If they are coincident with each other (yes at the Step S 22 ), the cartridge for the Y color may be exactly taken out because the current identification information including the current amount of a residual toner is written to the cartridge memory of the cartridge for the Y color. In this case, the unit controller  101  controls the rotary driving portion  107  to move the cartridge for the Y color to the exchange position (Step S 23 ). Consequently, the user can take out the cartridge for the Y color and can attach a new cartridge for the Y color. 
     If they are not coincident with each other (no at the Step S 22 ), however, the current amount of a residual toner is not written to the cartridge memory of the cartridge for the Y color. If the cartridge is set to be exactly taken out, consequently, the accurate lifetime management of the same cartridge cannot be carried out. In this case, therefore, the unit controller  101  controls the rotary driving portion  107  to move the cartridge for the Y color to the communicating position (Step S 24 ) and to communicate with the cartridge memory of the cartridge for the Y color, thereby updating the identification information of the cartridge memory (Step S 25 ). 
     At this time, the unit controller  101  writes, as the amount of a residual toner, the information about the amount of the residual toner in the region for the Y-color cartridge in the current toner region of the body memory  105 . Therefore, the identification information of the cartridge memory is updated to the current information including the information about the residual toner. When updating the identification information of the cartridge memory, moreover, the unit controller  101  writes the information about the amount of the residual toner for the Y-color cartridge in the current toner region of the body memory  105  to a region for the Y-color cartridge in the preceding writing region. Referring to the Y color, consequently, the information in the region for the Y-color cartridge in the current toner region is coincident with the information in the region for the Y-color cartridge in the preceding writing region. 
     When the identification information of the cartridge memory is updated, the unit controller  101  controls the rotary driving portion  107  to move the cartridge for the Y color to the exchange position (Step S 26 ). Consequently, the user can take out the cartridge for the Y color and can attach a new cartridge for the Y color. 
     As described above, according to the operation, in the case that the current identification information is written to the cartridge memory of the cartridge specified to be taken out, the cartridge is set to be immediately taken out so that the waiting time of the user can be shortened. In the case that the current identification information is not written, moreover, the cartridge is set to be taken out after the current identification information is written to the cartridge memory of the cartridge so that the current identification information can be written to the cartridge memory of the cartridge thus taken out. 
     While the above description has been given to the case that the event for updating the identification information written to the cartridge memory is the development, it is only illustrative and is not restricted. 
     Although the invention has been illustrated and described for the particular preferred embodiments, it is apparent to a person skilled in the art that various changes and modifications can be made on the basis of the teachings of the invention. It is apparent that such changes and modifications are within the spirit, scope, and intention of the invention as defined by the appended claims. 
     The present application is based on Japan Patent Application No. 2004-235762 filed on Aug. 13, 2004 and Japan Patent Application No. 2004-261968 filed on Sep. 9, 2004, the contents of which are incorporated herein for reference.