Abstract:
An apparatus to identify a replacement of a developing machine comprises a fuse which is disposed at a desired position of the developing machine; a switching part which is disposed at a desired position of a printer body corresponding to the fuse and applies a level of current to the fuse according to a control signal so as to disconnect the fuse; a control unit which outputs a control signal to the switching part so as to check whether the fuse is disconnected when a warming-up operation of a printer is started, and which outputs a control signal to a power controller so as to disconnect the fuse if the fuse is not disconnected and then initializes a printing counter, wherein the developing machine is determined to have been replaced, if the fuse is not disconnected.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled APPARATUS AND METHOD TO IDENTIFY REPLACEMENT OF DEVELOPING MACHINE earlier tiled in the Korean Industrial Property Office on Sep. 15, 1998, and there duly assigned Ser. No. 38030/1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of electrophotographic devices, and more particularly to an apparatus and method to recognize when a developing machine is replaced in an electrophotographic apparatus. 
     2. Description of the Related Art 
     Generally, in an electrophotographic apparatus such as a copying machine or a laser printer, a photosensitive drum is charged to a high voltage by a high voltage charging roller. Then, an electrostatic latent image is formed on the photosensitive drum by a ray of light from an exposing apparatus such as a laser diode. 
     At this time, the electrostatic latent image is passed through a developing machine so as to be converted into a visible image formed by toner discharged from the developing machine. The visible image on the photosensitive drum is then transferred to a paper fed by a pickup roller. After the visible image transferred to the paper is thermally fused by heat and pressure of a fixing device, the paper is discharged. 
     In the laser printer described as above, the developing machine which contains the toner should be replaced after being used for printing a predetermined number of papers. There are two ways for sensing the replacement of the developing machine. One is to provide a separate sensor in the laser printer, to indicate when the developing machine needs to be replaced. However, such a sensor is expensive. 
     The other way is to continuously count the number of the printed papers after the replacement of the developing machine and to compare the counting number with a printing number corresponding to the life of the developing machine provided by a manufacturer, thereby determining the replacement time of the developing machine. However, in order to identify the replacement time of the developing machine as described above, a counter must be reset. To reset the counter, generally a separate sensor which is expensive should be provided. 
     In addition to the cost of the sensor itself, the mounting of the separate sensor makes the mechanical construction of the laser printer complicated, and the manufacturing cost is increased. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved electrophotographic apparatus. 
     It is a further object of the invention to provide an electrophotographic apparatus with an improved apparatus and method for recognizing when a developing machine has been replaced. 
     It is a yet further object of the invention to provide an electrophotographic apparatus which is simpler in design. 
     It is a still further object of the invention to provide an electrophotographic apparatus which does not require a sensor to indicate replacement of the developing machine. 
     It is another object of the present invention to provide an electrophotographic apparatus which is less complex and less expensive to manufacture. 
     The objects of the present invention are met in the present invention which provides an apparatus and method to identify a replacement of a developing machine which identifies the replacement of the developing machine by confirming whether a fuse provided on the developing machine is disconnected when an upper cover of the printer is opened and then closed or power source is off, and which initializes a counter when the developing machine is replaced with new one, whereby a user can identify the replacement status of the developing machine so as to decide the replacement time of the developing machine without using a separate sensor. 
     To achieve the above objects and other advantages, there is provided an apparatus to identify a replacement of a developing machine which includes: a fuse which is disposed at a desired position of the developing machine; a switching part which is disposed at a desired position of a printer body corresponding to the fuse and applies a level of current to the fuse according to a control signal so as to disconnect, that is, blow, the fuse; a control unit which outputs a control signal to the switching part so as to check whether the fuse is disconnected when a warming-up operation of a printer is started, and which outputs a control signal to a power controller so as to disconnect the fuse if the fuse is not disconnected and then initializes a printing counter, wherein the developing machine is determined to have been replaced, if the fuse is not disconnected. 
     Preferably, the control unit comprises a central processing unit which entirely controls the apparatus and a RAM which initializes the printing counter if the fuse is disconnected by the control signal. 
     Further, it is preferred that the switching part comprises a transistor of which a base is connected with an output terminal and a collector is connected with a power terminal and an emitter is connected with the fuse so that the switching part is turned on if a first level of current is supplied from the CPU and a second level of current is supplied from the power terminal so as to disconnect the fuse; and a diode of which a cathode is connected with an input terminal of the CPU and an anode is connected with the transistor and a node of the fuse so that the diode is turned on by the second level of current through the transistor if the fuse is disconnected. 
     Further, according to the present invention, there is provided a method to identify a replacement of a developing machine, includes steps of: checking whether a fuse is disconnected when a warning-up operation of a printer is started; disconnecting the fuse and initializing a printing counter if the fuse is not disconnected; increasing a number of the printing counter by one whenever one paper is printed and storing the number in a storing means. 
     Preferably, the method further comprises a step of outputting the number of the printing counter stored in the storing means if the user inputs an order of checking the number of the printing counter. 
     It is preferred that the step of checking whether a fuse is disconnected comprises steps of: initializing the number of the printing counter and applying a power to the fuse so as to disconnect the fuse; checking whether the fuse is disconnected; increasing the number of the printing counter if the fuse is not disconnected, and comparing a predetermined standard number with the counting number; outputting an error message if the counting number is same with the standard number, and disconnecting the fuse if the counting number is less than the standard number. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages, thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 is a block diagram of a printer according to the present invention; 
     FIGS. 2A and 2B are flow charts showing a way of identifying the replacement of a developing machine according to the present invention; and 
     FIG. 3 illustrates an exemplary set of voltage waveforms generated during the operation of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. FIG. 1 is a block diagram of a printer according to the present invention, FIG. 2A and 2B are flow charts showing a way of identifying the replacement of a developing machine according to the present invention. 
     Referring to FIG. 1, if a document is written out by an application program of a personal computer such as a word processor, the document is converted into a printer command or a printer language by a printer driver and transferred through an interface part  40  to a central processing unit (CPU)  10 . The transferred data are converted into image data by the CPU  10  to be finally printed and then temporarily stored in RAM  22  of a memory  20 . The image data stored in the RAM  22  are transferred to an engine part  30  and controlled by the CPU  10  to be printed on a paper. Particularly, if a warming-up operation of the printer is started, that is, if an upper cover of the printer is opened and then closed or if a power source which was Off is turned On, a desired level of a current is output to a transistor  71  of a switching part  70  so as to determine whether a fuse  60  is disconnected. Then, if the fuse  60  is not disconnected (i.e., a developing machine has been replaced with a new one), the CPU  10  disconnects the fuse  10  through the switching part  70  and initializes a number of a printing counter stored in the memory  20 . 
     In ROM  21  of the memory  20 , there are stored various data and programs necessary to a system. In the RAM  22  of the memory  20 , there are temporarily stored the image data. Particularly, if the existing developing machine is replaced with a new one, the existing data stored in the RAM  22  are deleted by the CPU  10 . 
     Further, a state of the printer is displayed through a display window provided in an operational panel  50 . An operation of the printer such as an initialization of the printer is controlled by various keys on the operational panel  50 . 
     Meanwhile, the fuse  60  is disposed at one side of the developing machine so as to be disconnected, that is, blown, when current from a power terminal Vcc is applied through the switching part  70 . And, a base of the transistor  71  of the switching part  71  is connected with an output end  78  of the CPU  10 , its collector is connected with the power terminal Vcc and its emitter is connected with the fuse  60 . The transistor  71  receives a first level of current from the CPU  10  and is turned on, thereby supplying a second level of current from the power terminal Vcc to the fuse  60 . The second level of current is a minimum, that is, small but sufficient, current for disconnecting the fuse  60 . 
     The cathode of a diode  72  of the switching part  70  is connected with an input terminal  80  of the CPU  10  and the anode of the diode is connected to a node A between the transistor  71  and the fuse  60 . Therefore, if the fuse  60  is disconnected, the diode  72  is turned on by the second level of current applied through the transistor  71 . 
     The operation of the apparatus to identify the replacement of the developing machine will be described more fully referring to FIG.  2 . First of all, the CPU  10  determines whether the warming-up operation of the printer is started (S 110 ). If the warming-up is started, the first level of current is supplied to the base of the transistor  71  so as to turn on the transistor  71 , thereby checking whether the fuse  60  of the developing machine is disconnected (S 120 ). And if the fuse  60  is not disconnected, i.e., an old developing machine has been replaced with a new one (S 130 ) having an intact fuse, the CPU  10  initializes the counting number to “0” (S 210 ). And the second level of current is then supplied through the transistor  71  to the fuse  60  so as to attempt to blow the fuse  60  (S 220 ). 
     If the fuse is a shape-memory type, the time necessary to blow the fuse is very short, usually less than several seconds. If the fuse is a simple wire type, the time to blow the fuse may be longer than one second. 
     Several attempts may be necessary to blow the fuse. Therefore, the CPU  10  then determines whether the fuse  60  is disconnected, that is, blown. If the fuse  60  is disconnected (S 230 ), the CPU  10  initializes the existing number of the printing counter stored in the RAM  22  of the memory  20  (S 240 ). 
     After that, if a printing order is received and a printing operation is performed (S 310 ), the number of the printing counter is incremented, for example, increased by one, whenever one paper is printed and the value is stored in the RAM  22 . 
     In addition, if the user inputs an order to check the printing counter number of the developing machine through a key on the operational panel  50  (S 410 ), the CPU  10  controls the engine part  30  to output the number of the printing counter stored in the RAM  22 . This number indicates how much the developing machine has been used. 
     Meanwhile, in step  130 , if the fuse is disconnected, i.e., the developing machine has not just been replaced, the current applied through the transistor  71  is applied to the diode  72 . Therefore, the diode  72  is turned on. And if the current is input through the diode  72  to the CPU  10 , the CPU  10  identifies the disconnection of the fuse  60 , and thereby passes to step  310 . 
     However, if instep  230 , if the fuse  60  is not disconnected, that is, the fuse did not blow upon application of current in S 220 , one is added to the printing counter number and a predetermined standard number N of the printing counter is compared with the printing counting number in order to check whether the counting number is same with the standard number N (S 232 ). Standard number N limits the number of attempts to blow the fuse, and the value chosen for N is an appropriate number for the particular design. If the counting number is same with the standard number N, the engine part  30  is controlled to output an error message on the operational panel  50  (S 233 ). Such an error message might be, for example, “Call service technician” or “initializing printing counter failed”. If the counting number is less than the standard number N, the process is returned to the step  220 . 
     FIG. 3 illustrates an exemplary set of voltage waveforms which might occur upon carrying out steps S 220 , S 230 , S 231  and S 232 . In FIG. 3, V base  is the voltage applied to base of transistor  71  from terminal  78  of CPU  10 . V fuse  is the voltage drop across fuse  60 . At time t 1 , an application of the second level of current of step S 220  is seen. In this case, the fuse does not blow, and there is no voltage drop across the fuse. Then step S 230  is performed with the first level of current to determine if the fuse is blown. This process is performed four times in this example without blowing the fuse. At t 2 , a fifth attempt to blow the fuse is successful, and a voltage drop is seen across the fuse. Step  230  then leads to determination that the fuse is blown, and step  220  is not repeated. Time t 3  is the time at which S 220  and S 230  would have been repeated N times if the fuse had not blown, at which point step S 233  would be performed. 
     Therefore, according to the present invention, a user can identify the replacement of the developing machine so as to decide the replacement time of the developing machine without the separate sensor. 
     This invention has been described above with reference to the aforementioned embodiments. It is evident, however, that many alternative modifications and variations will be apparent to those having skill in the art in light of the foregoing description. Accordingly, the present invention embraces all such alternative modifications and variations as fall within the spirit and scope of the appended claims.