Abstract:
An image forming apparatus for carrying out an image forming process with a detachably mountable image forming unit mounted thereon, when the mounting of the image forming unit has been detected, whether the mounted image forming unit is a new one is discriminated. Then, unit control information held by an information holding portion for holding unit control information corresponding to the image forming unit is updated on the basis of the results of discrimination at the last time and this time. By such a construction, image formation becomes executable on the mounted image forming unit always in an optimized state.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to an image forming apparatus using an electrophotographic process such as, for example, a printer or a copying machine.  
         [0003]     2. Description of the Related Art  
         [0004]     Generally in an image forming apparatus utilizing an electrophotographic printing method, a photoconductive drum and a cleaner and a developing unit around the drum are made into a unit, which in turn is constructed so as to be interchangeable with respect to a printer main body, i.e., an image forming apparatus main body. This unit is expendables and need be interchanged when its life expires. In order to inform a user that the interchange of the unit is necessary, the printer has a rotary part, e.g. a counter for counting the cumulative number of revolutions of the photoconductive drum. When the count value of the counter reaches a predetermined value, the printer displays a life alarm indicating that the interchange of a corresponding unit is necessary. By this alarm, the user can interchange the unit at an appropriate time.  
         [0005]     When an old unit is interchanged with a new unit, it is necessary to reset a counter for measuring the life of the photoconductive drum, and change charging potential to be applied in accordance with a new drum, and a table for converting image data into density information.  
         [0006]     In a conventional image forming apparatus, there has been proposed a method of disposing a non-volatile memory in a unit, and causing the memory to store a history of use therein, thereby detecting whether the unit is new or old (Japanese Patent Application Laid-open No. H09-185236). In a color image forming apparatus having a plurality of such units (drum units), however, it is necessary to dispose a memory in each unit and at the same time, it is necessary to dispose a communicating portion with the memory at a location whereat each unit and an image forming apparatus main body are in contact with each other. Therefore, the costs of the apparatus and the unit have become high, and there has also been a problem in respect of the apparatus size and unit disposition.  
         [0007]     In contrast, there has been proposed a method of judging by a fuse provided on a unit (drum unit) whether the unit is new or old (Japanese Patent Application Laid-open No. H05-61393 and Japanese Patent Application Laid-open No. H06-118736). This method is to detect the conducting state of the fuse of the unit mounted on an apparatus main body to thereby judge whether the unit is new or old, and when it judges the unit to be new, carry out a predetermined initializing process and cut the fuse. That is, an inexpensive fuse instead of a memory can be provided on the drum unit, and a unit new/old discriminating portion for detecting whether an electric current passes through the fuse, and a fuse fusing portion for supplying an overcurrent to the fuse can be provided in the apparatus main body. The unit new/old discriminating portion and the fuse fusing portion are both constituted by a relatively simple circuit and can therefore discriminate between the newness and oldness of the unit (drum unit) by inexpensive and simple structure.  
         [0008]     However, the following problem arises when design is made such that as described above, the conducting state of the fuse provided on the unit is detected to thereby judge whether the unit is new or old, and when the unit is judged to be new, a predetermined initializing process is carried out and the fuse is cut.  
         [0009]     For example, when a problem has arisen in an image formed by the image forming apparatus, it is necessary to discriminate whether the cause of the problem resides in the image forming apparatus main body or in the drum unit. Therefore, a serviceman or the user himself sometimes tries to mount a new drum unit on trial on an image forming apparatus main body in which a problem has arisen and check up the operation thereof. In this case, when the new drum unit is put into the apparatus, the image forming apparatus detects the newness of the drum and automatically performs the operation of initializing the drum, and adjusts a parameter in the interior of the machine to a state optimum for the new drum unit and also burns out the fuse of the drum unit. Thereafter, it outputs an image and checks up the operation, and if as the result, it is discriminated that the cause resides in the drum unit so far mounted, the new drum unit can be intactly used.  
         [0010]     However, if conversely, it has been found that the cause resides in the image forming apparatus main body, a normal drum unit originally mounted on the apparatus becomes useless. That is, even if an attempt is made to return the normal drum unit originally mounted on the apparatus into the apparatus and use it, the control parameter has already been initialized so as to be optimum for the new drum unit at a point of time whereat the new drum unit has been mounted as a test. Therefore, the image forming apparatus cannot be used in a state optimum for the normal drum unit originally mounted on the apparatus. Also, the new drum unit used on trial has had its fuse cut and therefore, is not recognized as a new one even if it is newly mounted on other apparatus. Therefore, the initializing operation is not performed and the apparatus cannot be used in an optimum state.  
       SUMMARY OF THE INVENTION  
       [0011]     It is an object of the present invention to provide an image forming apparatus, which can execute image formation always in a state optimized for a mounted image forming unit.  
         [0012]     In order to achieve the above object, an image forming apparatus according to an embodiment of the present invention is an image forming apparatus for carrying out an image forming process with a detachably mountable image forming unit mounted thereon, having a mount detecting portion for detecting that the image forming unit has been mounted, a discriminating portion for discriminating, when the mounting of the image forming unit has been detected by the mount detecting portion, whether the mounted image forming unit is a new one, an information holding portion for holding unit control information corresponding to the image forming unit, and an information updating portion for updating the unit control information held by the information holding portion, on the basis of the result of the discrimination at the last time and this time by the discriminating portion.  
         [0013]     By such a construction, image formation becomes executable always in a state optimized for the mounted image forming unit.  
         [0014]     The above and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is an illustrative cross-sectional view of an image forming apparatus according to an embodiment of the present invention.  
         [0016]      FIG. 2  is an illustrative control block diagram for controlling the image forming apparatus according to the embodiment of the present invention.  
         [0017]      FIG. 3  shows the construction of the image memory portion of the image forming apparatus according to the embodiment of the present invention.  
         [0018]      FIG. 4  shows the construction of the external I/F processing portion of the image forming apparatus according to the embodiment of the present invention.  
         [0019]      FIG. 5  shows the construction of the image forming apparatus according to the present embodiment.  
         [0020]      FIG. 6  is a flow chart of the operation of discriminating between the newness and oldness of an image forming unit in the present embodiment.  
         [0021]      FIG. 7  is a flow chart of the fuse burning-out operation of the image forming unit in the present embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     Some embodiments of the present invention will hereinafter be described with reference to the drawings.  
         [0023]      FIG. 1  is an illustrative cross-sectional view of a color image forming apparatus. This color image forming apparatus is provided with four image forming portions (image forming units), i.e., image forming portions  1 Y,  1 M,  1 C and  1 Bk for forming yellow, magenta, cyan and black images, respectively. The four image forming portions  1 Y,  1 M,  1 C and  1 Bk are disposed in a row at predetermined intervals. Drum-shaped electrophotographic photosensitive members (hereinafter referred to as the photoconductive drums)  2   a ,  2   b ,  2   c  and  2   d  as image carrying members are installed in the image forming portions  1 Y,  1 M,  1 C and  1 Bk, respectively. Around the respective photoconductive drums  2   a ,  2   b ,  2   c  and  2   d , there are disposed primary charges  3   a ,  3   b ,  3   c ,  3   d , developing units  4   a ,  4   b ,  4   c ,  4   d , transfer rollers  5   a ,  5   b ,  5   c ,  5   d  as transferring portions, and drum cleaner devices  6   a ,  6   b ,  6   c ,  6   d . A laser exposing apparatus  7  is installed below the primary charging devices  3   a ,  3   b ,  3   c ,  3   d  and the developing units  4   a ,  4   b ,  4   c ,  4   d . A yellow toner, a magenta toner, a cyan toner and a black toner are contained in the developing units  4   a ,  4   b ,  4   c  and  4   d , respectively.  
         [0024]     Description will now be made of the image forming operation of the above-described image forming apparatus.  
         [0025]     When an image formation start signal is generated, the photoconductive drums  2   a ,  2   b ,  2   c  and  2   d  of the respective image forming portions  1 Y,  1 M,  1 C and  1 Bk rotatively driven at a predetermined process speed are uniformly charged to the negative polarity by the primary charging devices  3   a ,  3   b ,  3   c  and  3   d , respectively. Then, the exposing apparatus  7  applies a color-separation image signal inputted from the outside from a laser beam emitting element, and forms electrostatic latent images for respective colors on the photoconductive drums  2   a ,  2   b ,  2   c  and  2   d  via a polygon lens, a reflecting mirror, etc.  
         [0026]     Then, the yellow toner is caused to adhere to the electrostatic latent image formed on the photoconductive drum  2   a , by the developing unit  4   a  to which a developing bias of the same polarity as the charging polarity (the negative polarity) of the photoconductive drum  2   a  has been applied, thereby visualizing the electrostatic latent image as a toner image. This yellow toner image is primary-transferred onto an intermediate transfer belt  8  being driven, by the transfer roller  5   a  to which a primary transfer bias (of a polarity (the positive polarity) opposite to that of the toners) has been applied in a primary transfer portion  32   a  between the photoconductive drum  2   a  and the transfer roller  5   a.    
         [0027]     The intermediate transfer belt  8  to which the yellow toner image has been transferred is moved to the image forming portion  1 M side. Then, also in the image forming portion  1 M, a magenta toner image formed on the photoconductive drum  2   b  is superposed on the yellow toner image on the intermediate transfer belt  8  and transferred to the intermediate transfer belt  8  in a primary transfer portion  32   b , in the same manner described previously. At this time, any untransferred toners residual on the respective photoconductive drums  2  are scraped off and collected by cleaner blades or the like provided in the drum cleaner devices  6   a ,  6   b ,  6   c  and  6   d.    
         [0028]     Thereafter, in a similar manner, cyan and black toner images formed on the photoconductive drums  2   c  and  2   d  of the image forming portions  1 C and  1 Bk are successively superposed on the yellow and magenta toners superposed on and transferred to the intermediate transfer belt  8  in respective primary transfer portions  32   c - 32   d . In the manner described above, a full-color toner image is formed on the intermediate transfer belt  8 .  
         [0029]     Then, in timed relationship with the movement of the leading edge of the full-color toner image on the intermediate transfer belt  8  to a secondary transfer portion  34  between a secondary transfer opposed roller  10  and a secondary transfer roller  12 , a transfer material (paper) P is conveyed to the secondary transfer portion  34  by registration rollers  19 . The transfer material (paper) P is selectively fed from a sheet supplying cassette  17  or a manually feeding tray  20  through a conveying path  18 . The full-color toner image is collectively secondary-transferred to the transfer material P conveyed to the secondary transfer portion  34 , by the secondary transfer roller  12  to which a secondary transfer bias (of the polarity (positive polarity) opposite to that of the toners) has been applied.  
         [0030]     The transfer material P on which the full-color toner image has been formed is conveyed to a fixing device  16 , and is heated and pressurized by a fixing nip portion  31  between a fixing roller  16   a  and a pressure roller  16   b , whereby the full-color toner image is heat-fixed on the surface of the transfer material P. Thereafter, the transfer material P is discharged onto a sheet discharging tray  22  on the upper surface of a main body, thus completing a series of image forming operations.  
         [0031]      FIG. 2  is an illustrative control block diagram for controlling the color image forming apparatus according to the present embodiment. A CPU  171  which effects the basic control of the image forming apparatus  100  has connected thereto a ROM  174  having a control program written therein, a work RAM  175  for carrying out processing, and an input-output port I/O  173  by an address bus and a data bus. The input-output port I/O  173  has connected thereto various loads (not shown) such as a motor and a clutch constituting the image forming apparatus, and an input (not shown) such as a sensor for detecting the position of the paper.  
         [0032]     The CPU  171  sequentially effects the control of an input and an output through the input-output port I/O  173  in accordance with the contents of the ROM  174 , and executes the image forming operation. Also, the CPU  171  is connected to an operation portion  172 , and controls the display portion and key input portion of the operation portion  172 . An operator instructs the CPU  171  to change over an image forming operation mode and display, through the key input portion, and the CPU  171  effects the display of the state of the image forming apparatus  100  and the setting of the operation mode by a key input. The CPU  171  has connected thereto an external I/F processing portion  400 , an image memory portion  300  and an image engine portion  200 .  
         [0033]     The external I/F processing portion  400  transmits and receives image data and processing data from an external device such as a personal computer (PC), and the image memory portion  300  is used for the expanding process of an image and temporary accumulation thereof. The image engine portion  200  carries out the process of exposing line image data forwarded from the image memory portion  300  by the exposing apparatus  7 .  
         [0034]      FIG. 3  is an illustrative control block diagram of the image memory portion  300  according to the present embodiment. In the image memory portion  300 , a memory controller portion  302  effects the access of the inputting and outputting of the image. That is, it receives image data from the external I/F processing portion  400 , writes the image data into a page memory  301  constituted by a DRAM or the like, and also reads out the image data stored in the page memory  301  to the image engine portion  200 .  
         [0035]     Also, the memory controller portion  302  judges whether the image data from the external device received from the external I/F processing portion  400  is compressed data. If the image data is judged to be compressed data, expansion processing is carried out by the use of a compressed data expansion processing portion  303 , whereafter the writing process into the page memory  301  is executed. The memory controller portion  302  generates the DRAM refreshing signal of the page memory  301 , and effects the adjustment of the access to the page memory  301  for the writing from the external I/F processing portion  400  and the reading-out to the image engine portion  200 . Further, it effects the control of the writing-in address into the page memory  301 , the reading-out address from the page memory  301 , and the reading-out direction, in accordance with the instructions of the CPU  171 .  
         [0036]     The construction of the external I/F processing portion  400  will now be described with reference to  FIG. 4 . In the external I/F processing portion  400 , image data and print command data transmitted from an external device  500  are received through any one of a USB I/F portion  401 , a centronics I/F portion  402  and a network I/F portion  403 . Also, the external I/F processing portion  400  transmits the state information or the like of the image forming apparatus judged by the CPU  171  to the external device  500 . The external device  500  is a computer, a work station or the like.  
         [0037]     The CPU  171  processes the print command data received from the external device  500  through any one of the USB I/F portion  401 , the centronics I/F portion  402  and the network I/F portion  403 , and effects the control of the setting and timing of the printing operation by the image engine portion  200 . The image data received from the external device  500  through any one of the USB I/F portion  401 , the centronics I/F portion  402  and the network I/F portion  403  is transmitted to the image memory portion  300  at the timing based on the print command data. Then, in the image memory portion  300 , the image data is processed to be formed into an image by the image engine portion  200 .  
         [0038]      FIG. 5  shows the construction of an image forming system in the present embodiment. An image forming unit  501  is a unit comprising the photoconductive drum  2 , the primary charging device  3 , the developing unit  4  and the drum cleaner device  6 . Also, the image forming unit  501  is designed to be detachably mountable on the image forming apparatus main body with Y, M, C and K colors independent of each other.  
         [0039]     This image forming unit  501  is further provided with a fuse  502  as a unit new/old discriminating member. The fuse  502  is disposed at a location in the end portion of the image forming unit  501  and contacting with the image forming apparatus. A new/old discriminating member breaking portion  503  is an electric current output circuit for supplying an overcurrent to the fuse  502  to thereby burn out the fuse  502 .  
         [0040]     A unit new/old discriminating portion  504  is a sensor for detecting an electric current flowing from one end of the fuse  502  at the other end thereof. When it is detected by the unit new/old discriminating portion  504  that the fuse  502  is conducting, the fuse  502  is not burned out and therefore, it is judged (discriminated) that the unit is new. When it is not detected that the fuse  502  is conducting, the fuse  502  is burned out and therefore, it is judged (recognized) that the unit is old. Also, the result detected by the unit new/old discriminating portion  504  is informed to the CPU  171  through the input/output port  173 .  
         [0041]     A unit interchange detecting portion  505  detects whether the unit has been interchanged. In the present embodiment, design is made such that when the interchange of the unit is to be effected, the upper cover of the image forming apparatus is opened and closed. Also, the image forming apparatus has a physical mechanism for memorizing the opening operation of the upper cover. So, when the opening of the upper cover has been detected by the physical mechanism, it is judged that there is the possibility that the unit has been interchanged.  
         [0042]     A count portion  507  measures the frequency (frequency of operation) with which image formation has been effected after each image forming unit  501  has been mounted on the image forming apparatus, or the time (working time) for which image formation has been effected, and the result of the measurement is stored in a counter  508 . A new/old discriminating member breakage execution deciding portion  509  instructs the new/old discriminating member breaking portion  503  to fuse the fuse  502 , in accordance with the result of the discrimination by the unit new/old discriminating portion  504  and the value of the counter  508 .  
         [0043]     Unit information  510  is parameter information for effecting image formation in accordance with the characteristic of each image forming unit  501 . The unit information  510  is determined in accordance with the result of an initializing operation performed when the image forming unit  501  has been mounted on the image forming apparatus for the first time.  
         [0044]     In the present embodiment, toner density adjusting control is effected to keep the mixing ratio of a toner and a carrier in the developing unit  4  in a proper state. In this control, a toner pattern is formed on the intermediate transfer belt  8 , and the formed pattern is read by a sensor to thereby detect the density of the pattern. Then, the supply amount of the toner from a toner cartridge to the developing unit  4  is adjusted in accordance with the detected density of the pattern to thereby control the mixing ratio of the toner and the carrier in the developing unit  4 .  
         [0045]     When this control is effected, the density target value of the pattern formed on the intermediate transfer belt  8  is the density of a toner pattern formed on the intermediate transfer belt  8  in the initializing operation performed when the image forming unit  501  has been mounted on the image forming apparatus for the first time. This target value is stored in a non-volatile RAM area in the image forming apparatus as the unit information  510  conforming to the characteristic of each image forming unit  501 .  
         [0046]     A unit information holding portion  511  is for storing (saving) therein the unit information  510  of the image forming unit used (mounted) previously for a predetermined period when the image forming unit  501  has been interchanged, and like the unit information  510 , it is constructed in the non-volatile RAM area in the image forming apparatus.  
         [0047]      FIG. 6  shows a flow chart of the new/old discriminating operation of the image forming unit  501  in the present image forming apparatus.  
         [0048]     When at S 601 , the power supply of the image forming apparatus is switched on or the cover of the image forming apparatus is opened and closed, there is the possibility that the image forming unit  501  in the image forming apparatus has been interchanged and therefore, check-up is started. As described above, in the present embodiment, when the interchange of the unit is to be effected, it is necessary to open and close the upper cover, which is the cover of the image forming apparatus. Also, the image forming apparatus has the physical mechanism for memorizing the opening operation of the upper cover. Whether the upper cover has been opened and closed can be detected by this physical mechanism.  
         [0049]     At S 602 , whether the upper cover has been opened is detected. If it is detected that the upper cover has been opened, it is judged that the image forming unit  501  has been interchanged, and the new/old discrimination control of the image forming unit is started.  
         [0050]     At S 603 , the unit new/old discriminating portion  504  checks up whether the fuse  502  is conducting, and discriminates the newness or oldness of the image forming unit  501 . The result detected by the unit new/old discriminating portion  504  is informed to the CPU  171  through the input-output port  173 .  
         [0051]     If it is detected by the unit new/old discriminating portion  504  that the image forming unit  501  is new, at S 604 , reference is made to the state of the fuse  502  of the image forming unit  501  mounted the last time which is stored in the non-volatile RAM area in the interior of the image forming apparatus.  
         [0052]     When the state of the fuse  502  at the last time indicates a new one (that the fuse is not burned out), the image forming unit  501  is new and has not been interchanged, or has been interchanged to another new image forming unit  501  and therefore, the update of the unit information  510  is not effected.  
         [0053]     On the other hand, when the state of the fuse  502  at the last time indicates an old one (that the fuse is cut), it is judged that the image forming unit  501  has been interchanged from an old one to a new one.  
         [0054]     When it is judged that the image forming unit  501  has been interchanged from an old one to a new one, at S 605 , the unit information  510  of the image forming unit mounted the last time is copied and stored in the unit information holding portion  511 .  
         [0055]     Further, at S 606 , the value of the counter  508  which provides the reference for deciding whether the fuse  502  should be burned out is cleared.  
         [0056]     Thereafter, at S 607 , the initializing operation for determining the unit information  510  for effecting image formation in accordance with the characteristic of each newly mounted image forming unit  501  is performed, and at a point of time whereat the initializing operation has been terminated, the image forming apparatus assumes a standby state.  
         [0057]     On the other hand, if at  603 , the unit new/old discriminating portion  504  discriminates that the fuse  502  is not conducting, at S 608 , reference is made to the state of the fuse  502  of the image forming unit  501  mounted the last time which is stored in the interior of the image forming apparatus. When the state of the fuse  502  at the last time indicates an old one, the image forming unit  501  is an old one and has not been interchanged, or has been interchanged to another old image forming unit  501  and therefore, the update of the unit information  510  is not effected.  
         [0058]     In contrast, if at S 608 , the state of the fuse  502  at the last time indicates a new one, it is judged that the fuse  502  has been returned to the previous image forming unit  501  before the fuse is cut, and at S 609 , the information stored in the unit information holding portion  511  is copied and stored in the unit information  510 . That is, the unit information  510  copied and stored (saved) in the unit information holding portion  511  at S 605  is returned from the unit information holding portion  511  to the unit information  510 .  
         [0059]     By doing so, image formation at the applied charging potential conforming to the current image forming unit, particularly drum, and a table for converting image data into density information becomes possible. Thereafter, at a point of time whereat the update of the unit information  510  has been terminated, the image forming apparatus assumes a standby state.  
         [0060]     Reference is now had to the flow chart of  FIG. 7  to describe the flow of the fuse burning-out operation of the image forming unit  501 .  
         [0061]     The image forming apparatus counts up the value of the counter  508  each time it effects image formation.  
         [0062]     When at S 701 , the image forming apparatus finishes its image forming process, advance is made to S 702  in order to judge whether the fuse  502  of the image forming unit  501  should be burned out when the apparatus is stopped.  
         [0063]     At S 702 , the unit new/old discriminating portion  504  checks up whether the fuse  502  is conducting, and discriminates between the newness and oldness of the image forming unit  501 .  
         [0064]     If it is discriminated that the image forming unit is new (the fuse  502  is not burned out), at S 703 , the new/old discriminating member breakage execution deciding portion  509  judges whether the value of the counter  508  has reached a predetermined condition. In the present embodiment, it is the condition for burning out the fuse  502  that a predetermined number of sheets (50 sheets) of image formation has been effected from a point of time at which the image forming unit  501  has been interchanged to a new one.  
         [0065]     If the new/old discriminating member breakage execution deciding portion  509  judges that the value of the counter  508  has reached a predetermined condition, that is, the counter value has reached a predetermined or greater number of sheets, instructions to fuse the fuse  502  is given to the new/old discriminating member breaking portion  503 , and the fuse  502  is burned out (S 704 ).  
         [0066]     That is, design is made such that fusing is selectively not executed until a predetermined number of sheets is reached, whereby even if a new drum unit used as a test is used in another apparatus, it can be recognized as a new one. Also, it becomes possible to improve the usability by a serviceman or the user, and improve the working property when effecting the maintenance of the apparatus.  
       Other Embodiments  
       [0067]     While in the present embodiment, a fuse is used as a new/old discriminating member capable of discriminating physical breakage, the construction of the present invention can also be realized by a construction which effects the detection of the newness or oldness of a unit by other physical breakage.  
         [0068]     For example, a light emitting element and a light receiving element are disposed in an image forming apparatus, and a reflecting plate is disposed on a unit side. Further, a member constructed physically breakably and intercepting light is provided between the light emitting and receiving elements of the image forming apparatus and the reflecting plate of the unit.  
         [0069]     Thereby, it is possible to judge that if light emitted by the light emitting element of the image forming apparatus returns to the light receiving element, it is judged that the intercepting member has been broken and the unit is old, and to judge that if the light emitted by the light emitting element does not return to the light receiving element, the intercepting member is attached and the unit is new.  
         [0070]     Also, while in the present embodiment, an image forming unit has been described as a unit detachably mountable on an image forming apparatus main body, the unit to which the present invention is applicable may be only a photoconductive drum, and it is also possible to apply the present invention to the detection of the newness or oldness of not only an image forming portion, but also a toner cartridge.  
         [0071]     Besides, the present invention can also be applied to any interchangeable unit such as, for example, a fixing unit.  
         [0072]     This application claims priority from Japanese Patent Application No. 2004-334802 filed Nov. 18, 2004, which is hereby incorporated by reference herein.