Abstract:
Apparatus and method are provided for controlling a second cassette feeder (SCF) in an image forming device. The control apparatus comprises a main body; a SCF mounted in the main body for supplying sheets of paper; a control unit in the main body for controlling the image forming device; and a SCF control unit for communicating a state of the SCF to the control unit and controlling the SCF. The control method comprises steps of initializing the main body and SCF; deciding whether the SCF is mounted; sending SCF-driving data to the SCF from the main body control unit if the SCF is mounted; and controlling the SCF by the SCF control unit using the driving data. SCFs are therefore compatible since the control unit in the main body downloads driving-related data into the SCF when the SCF is detected, while the SCF programmable ROM and firmware are shared.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the benefit of Korean Patent Application No. 2003-26271, filed on Apr. 25, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to an apparatus and a method for controlling a second cassette feeder provided for loading more sheets of paper to be fed in electrophotographic image forming devices such as photocopiers, laser printers, facsimile machines, and so on, for photocopying and printing in use of plain print sheets.  
           [0004]    2. Description of the Related Art  
           [0005]    [0005]FIG. 1 shows a printer as one of the electrophotographic image forming devices, which is used in general. If a user presses a print button, a photoconductive drum  50  is uniformly charged by the corona discharge of a charging unit  42 , and, in a laser beam printer (LBP), as the photoconductive drum  50  rotates, the charged portions are exposed through the exposure unit  41  with mirrors and lenses to light emitted from a light source such as a light emission diode or a laser diode and reflected from a document. In a photocopier, after processing based on a contraction/magnification factor and so on by four mirrors and lenses, the same electrostatic latent image that is an image on the document is formed on the photoconductive drum  50 . At this time, the formed electrostatic latent image is developed into a visible image with toner during passing through a developing unit  44 , and the visible image of the photoconductive drum  50  is transferred by the operations of a transfer unit  48  on a sheet of paper  46  fed by a feeding roller  45 . At this time, the sheet of paper  46  comes in close contact with the photoconductive drum  50  by an electrostatic force, and a separator  49  separates the closely contacted sheet of paper. Thereafter, as the separated sheet  46  passes through a heating roller  51  and a press roller  52 , the document image is fixed and printed as desired on the sheet  46  by heat and pressure.  
           [0006]    In the meantime, there exists the residual toner and latent image on the surface of the photoconductive drum  50  passing through the transfer unit  48 . The toner is removed by a cleaner (not shown) and the latent image is eliminated by a pre-erase lamp array  43 .  
           [0007]    The printer operating as above has the cassette feeder  55  capable of loading 150 to 250 sheets, and may optionally have a second cassette feeder (SCF)  55   a  driven by a separate driving mechanism for more sheets of paper to be fed as shown in FIG. 1. Such an SCF  55   a  is generally installed under a main cassette feeder  55  for the supply of sheets  46   a.  At this time, the sheets  46   a  are not transferred to a paper feeding roller  39  of the main body of the printer by a pickup motor  45   a  alone for sheet supply, so relay rollers  56  are mounted over the upper part of the SCF  55   a.  Further, a roller-opening unit (not shown) such as a spring or the like is generally formed to split the relay rollers  56  against paper jams between the relay rollers  56 .  
           [0008]    A schematic control block diagram for the printer as above is shown in FIG. 2. In FIG. 2, a control unit  60  controls the applications of predetermined voltages to the charging unit  42 , developing unit  44 , and transfer unit  48 , and also controls the overall printer system to print image data or images on sheets, while checking operation states through various sensors (not shown). The SCF  55   a  has a SCF control unit  70 , a motor drive  71  and a programmable ROM  72 . The programmable ROM  72  stores programs necessary for the system initialization, programs necessary for communication protocols, and data necessary for driving the SCF such as an acceleration table and the like necessary for driving motors. The SCF control unit  70  generally receives data as electrical signals through a communication cable  80  from the control unit  60 , interprets the data, and executes corresponding commands. That is, the SCF control unit  70  picks up sheets of paper, drives and stops the pickup motor  45   a , and drives and stops the relay rollers  56  as its main operations, as well as recognizes paper sizes and sends to the control unit  60  signals notifying of ‘paper empty’, ‘tray out’, and so on. In particular, the SCF control unit  70  controls a motor drive IC  71  to drive motors in accordance with the acceleration table stored in the programmable ROM  72 .  
           [0009]    A brief description will now be made about the operations of the SCF for a printer having the SCF structured as above. In generally, the printer waits for a command from the control unit  60 . The SCF  55   a  on which the sheets  46   a  are loaded is completely inserted in the frame (not shown). If a paper-feeding request signal is received through the cable  80 , the SCF control unit  70  controls the motor drive IC  71  to rotate the pickup motor  45   a  in accordance with the acceleration table stored in the programmable ROM  72  so that the sheets  46   a  are fed from the SCF  55   a  at a certain speed continuously to the paper feeding roller  39  of the main body according to the rotations of the relay roller  56 . The subsequent operations are to carry out usual print jobs based on the controls of the main control unit  60 .  
           [0010]    However, the printer having the SCF structured as above has a problem in that it uses a programmable ROM dedicated to each SCF. In other words, all SCF-related driving data is stored in the programmable ROM for the corresponding SCF. Thus, the programmable ROMs cannot be shared with one another since the programmable ROM specifications for individual SCFs are different from one another. For example, the motor speeds for SCFs are decided based on paper discharge speeds. Since the all the paper discharge speeds are different, the printer cannot use, for the SCF mounted, a programmable ROM  72  storing the motor-drive acceleration data that is for a different printer model. That is, a motor speed is determined based on a pulse frequency inputted to a motor. Accordingly, a predetermined frequency value should be inputted for a DC motor, and an acceleration table is used for a stepping motor. The acceleration data should be continuously changed for a stepping motor used as a general printer motor, and the data is stored in the programmable ROM  72  for the SCF in the form of a table (refer to Table 1 in the disclosure). Since the motor speeds are stored for use in respective programmable ROMs in the form of a table even through the operations of the SCF are basically the same, the programmable ROM for the SCF cannot be shared. Further, there exists a problem in that the SCF is newly classified for use all the time, even in case of the same mechanical specifications and hardware.  
         SUMMARY OF THE INVENTION  
         [0011]    In order to solve the above problems, it is an aspect of the present invention to provide a second cassette feeder control apparatus and method capable of controlling a second cassette feeder in the same manner as usual and sharing a programmable ROM and firmware for the second cassette feeder by downloading to the second cassette feeder data related to the driving of the second cassette feeder when a control unit of an image forming device detects the installation of the second cassette feeder.  
           [0012]    In order to achieve the above aspect, a second cassette feeder control apparatus for an image forming device according to the present invention comprises a main body of the image forming device; at least one second cassette feeder (SCF) mounted in the main body, and for auxiliarily supplying sheets of paper; a control unit installed in the main body, and for controlling a printer system of the image forming device; communication cables for connecting the control unit and the second cassette feeder for communications therebetween; a connection line for connecting the control unit and the second cassette feeder; and at least one SCF control unit provided in correspondence to the second cassette feeder, and for receiving SCF-driving data from the control unit and controlling operations of the second cassette feeder.  
           [0013]    Moreover, the apparatus further comprises a connection detecting unit for detecting a signal inputted through the connection line and deciding a connection state of the second cassette feeder, wherein the control unit sends the SCF-driving data to the SCF control unit through the communication cables if the connection detecting unit detects the connection of the second cassette feeder or electric power is supplied.  
           [0014]    The second cassette feeder further includes a programmable ROM for storing system initialization and communication-related programs; and a RAM for storing the SCF-driving data sent from the control unit.  
           [0015]    Preferably, the SCF-driving data is motor-driving data.  
           [0016]    Further, the SCF control unit controls a motor in use of the motor-driving data stored in the RAM if a motor-driving command is received from the control unit.  
           [0017]    Preferably, if plural second cassette feeders are detected, the control unit sequentially sends data to respective SCF control units or first sends the data to a specified SCF control unit out of the plural SCF control units before the remaining SCF control units receives the sent data from the specified SCF control unit.  
           [0018]    The control unit further includes at least one or more sensors for deciding a state of the second cassette feeder, and a multiplexer for inputted outputs of the sensors, wherein the SCF control unit converts the output of the multiplexer into data and sends the data to the control unit.  
           [0019]    In order to achieve the above object, a second cassette feeder control method for an image forming device having a second cassette feeder (SCF) mounted in a main body of the device for more sheets of paper to be fed, a main body control unit, and an SCF control unit, comprises steps of initializing the main body and the second cassette feeder if electric power is supplied; deciding by the main body control unit whether the second cassette feeder is mounted; sending SCF-driving data to the second cassette feeder through communication cables by the main body control unit if it is decided that the second cassette feeder is mounted in the step of deciding the mounting of the second cassette feeder; and controlling the second cassette feeder by the SCF control unit in use of the sent SCF-driving data.  
           [0020]    Further, the step of deciding the mounting of the second cassette feeder is carried out through a connection detecting line connecting the main body and the second cassette feeder.  
           [0021]    The step of initializing the second cassette feeder initializes the second cassette feeder in use of data stored in a programmable ROM of the second cassette feeder (SCF).  
           [0022]    Preferably, the SCF control unit further stores the sent SCF-driving data in a RAM.  
           [0023]    Further, it is preferable that the SCF-driving data is motor-driving data.  
           [0024]    In order to achieve the above object, another second cassette feeder control method comprises steps of deciding by the main body control unit whether the second cassette feeder is mounted; sending SCF-driving data to the second cassette feeder by the main body control unit if it is decided that the second cassette feeder is mounted in the step of deciding the mounting of the second cassette feeder; and storing the sent driving data in a RAM by the SCF control unit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:  
         [0026]    [0026]FIG. 1 is a side view for showing a printer in which a conventional second cassette feeder is mounted;  
         [0027]    [0027]FIG. 2 is a control block diagram for a conventional printer;  
         [0028]    [0028]FIG. 3 is a control block diagram for a printer according to an embodiment of the present invention;  
         [0029]    [0029]FIG. 4 is a flow chart for showing a process for data transfer flows according to an embodiment of the present invention; and  
         [0030]    [0030]FIG. 5 is a flow chart for showing a process for controlling a motor speed according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Hereinafter, descriptions will be made in detail on a printer, although other types of image forming devices can be used, having a second cassette feeder according to an embodiment of the present invention with reference to the attached drawings.  
         [0032]    [0032]FIG. 3 is a control block diagram for a printer according to an embodiment of the present invention. Further, like reference numerals are employed to the like elements shown in the perspective view of FIG. 1 for the printer having the second cassette feeder mounted, and the descriptions of which will be omitted.  
         [0033]    A control unit  100  controls the applications of voltages to the charging unit  42 , developing unit  44 , and the transfer unit  48 , controls printing on a sheet image data or an image corresponding to image data to be printed, and controls operation states through various sensors (not shown). The control unit  100  receives and sends general data with the SCF  55   a  in use of a data communication cable  120 , and reads the states of the SCF  55   a , and transfers data for driving the SCF  55   a  if necessary. In particular, the control unit  100  can send data for motor controls. That is, the control unit  100  transfers initial and final values, a slope, and the number of steps from the stepping motor acceleration table of Table 1. A connection detecting unit  101  is constructed to detect (e.g., substantially continually or periodically) a mounted or a dismounted state of the SCF  55   a , that is, whether the SCF  55   a  is mounted or dismounted, through a connection detecting line  130 . If the control unit  100  sends a state request signal SCF_CMD_RQST_STATE; 0xff to a SCF control unit  110  and any data is not sent from the SCF  55   a  (data to be actually sent is 0x00), the control unit  100  decides the SCF  55   a  is disconnected, and, if the printer normally operates, the control unit  100  can send data notifying of the mounted or dismounted state of the SCF  55   a , paper size, and ‘paper empty’. Preferably, the control unit  100  inputs the outputs of the sensors via a three-input multiplexer, and uses one bit of data to be sent to indicate the mounted or dismounted state of the SCF  55   a , three bits of the same data to indicate a paper size, and one bit of the same data to indicate the ‘paper empty’, when sending a state signal.  
         [0034]    The SCF control unit  110  has a motor drive IC  111 , a programmable ROM  112 , and a RAM  113 . The programmable ROM  112  stores programs necessary for system initializations and programs necessary for communication protocols, and the RAM  113  stores data for driving the SCF which is transferred through a communication cable  120  from the control unit  100 . In more detail, the programmable ROM  112  receives from the control unit  100  and stores in the RAM  112  data regarding paper pickups, paper size recognitions, and ‘paper empty’ and ‘tray out’ signals, among others, that are the main operations of the SCF. If necessary, the SCF control unit  110  reads out necessary data from the RAM  112 , and processes the data for related operations. In particular, the SCF control unit  110  can store data for driving a motor for the SCF. Accordingly, if the SCF control unit  110  inputs a command for driving the motor from the control unit  100 , the SCF control unit  110  controls the motor drive IC  111  to drive the motor (not shown) in use of the data stored in the RAM  112 . Further, if the SCF control unit  110  inputs a command as an electric signal through the cable  120  from the control unit  100 , the SCF control unit  110  interprets the command and executes related commands. That is, the SCF control unit  110  performs main operations such as paper pickups, paper size recognitions, ‘paper empty’ and ‘tray out’ signaling, and so on.  
         [0035]    Hereinafter, descriptions will be made on the operations of the second cassette feeder structured as above and the control method therefor with reference to FIG. 4 and FIG. 5. In particular, the descriptions of the present embodiment are restricted to data related to the driving of a motor out of the data for driving the SCF. FIG. 4 is a flow chart for showing a process for controlling a motor speed.  
         [0036]    If electric power is applied to a printer system, the control unit  100  and the SCF control unit  110  initialize the system, respectively (Step S 210 ). The connection detecting unit  101  of the control unit  100  decides whether the SCF  55   a  is mounted through the connection detecting line  130  (Step S 220 ). If it is decided that the SCF  55   a  is mounted in the step S 220 , the control unit  100  prepares data related to the driving of a motor, out of SCF-driving data, for a transmission to the control unit  110  (Step S 230 ). For example, information on initial and final values and the number of steps from the stepping motor acceleration table such as Table 1 below is transmitted among the data to be sent.  
         [0037]    If the data to be sent is completely prepared (S 240 ), the control unit  100  sends the related data to the SCF control unit  110  (S 250 ). If it is decided that the SCF  55   a  is not mounted in the step S 220 , the control unit  100  ends its controls, and, if the data to be sent is not completely prepared in the step S 240 , the control unit  100  repeats the step S 230 . The control unit  100  decides whether the data sent according to the predefined communication code is normally transmitted and received (S 260 ). If the data is normally transmitted and received in the step S 260 , the SCF control unit  110  stores the received motor-related data in the RAM  113  (S 270 ). If transmission errors occur in the step S 260 , the control unit  100  repeats the step S 250  till the transmissions are successfully completed.  
         [0038]    It is to be understood, for the second cassette feeder control method described herein, that electric power is initially applied, and that electric power is applied and the system is initialized in the same manner even when the SCF  55   a  in which the sheets  46   a  are loaded is inserted to be mounted in the frame (not shown).  
         [0039]    Hereinafter, a motor control method using a motor-driving acceleration table will be described with reference to FIG. 5.  
         [0040]    An exemplary stepping motor acceleration table provided by the control unit  100  is illustrated in Table 1.  
                                         TABLE 1                                   Steps   Control Values                                        1 st (initial value)   10000           2 nd     9910           3 rd     9820           .   .           .   .           100 th (final value)   1000                      
 
         [0041]    The control values are gradually changed in order to accelerate a stepping motor, and the above Table 1 shows that the number of steps for controlling the stepping motor is set to “100”, an initial value to “10000”, and a final value to “1000”. Accordingly, for the following description, it is to be understood that the control unit  100  sends the initial and final values and the number of steps to the SCF control unit  110 .  
         [0042]    The SCF control unit  110  decides whether it drives the pickup motor  45   a  (S 320 ) while running a general program according to a command received from the control unit  100  (S  310 ). The SCF control unit  110  reads out data such as initial and final values and the number of steps stored in the RAM  113  if it is necessary to drive a motor, and calculates slopes each of which is an increment or a decrement value by step. Accordingly, the SCF control unit  110  sets a value “startpps” to a final pulse width output value “OUTPUT” for controlling the motor. Further, the SCF control unit  110  inputs “0” to a value “COUNT” for counting the steps (S 330 ). In more detail, the value “startpps” is set to “10000”, a value “finalpps” to “1000”, and a slope value “slope” to “90”. That is, the slope is calculated when the interval between the initial value and the final value is divided by the number of entire steps.  
         Slope=(initial value−final value)/the number of steps  Equation 1 
         [0043]    The slope of “90” is obtained from the Equation 1 when related values are applied with reference to Table 1. However, the SCF control unit  110  outputs to the motor drive IC  111  a driving signal, which is a “HIGH” signal in general, for initially driving the control of the motor to drive the motor and, at the same time, starts decrementing “10000” inputted as a value “OUTPUT” via an internal clock (not shown). If the decrementing is completed to a value of “0”, the SCF control unit  110  turns the driving signal into “LOW” for an output.  
         [0044]    If it is decided that the motor driving signal is turned into “LOW” in the above step, the SCF control unit  110  increases the value “COUNT” by 1(S 340 ), and decides whether the value “COUNT” is “100” which is the number of total steps. If decided as the final step in the step, the SCF control unit  110  assigns “1000” to the final value “finalpps” for the value “OUTPUT”, and discounts via the internal clock (not shown) to apply a constant motor driving pulse. That is, the SCF control unit  110  decides whether to stop the motor in the step S 400 , and controls a constant driving pulse output by stopping the motor if there is an occasion that the motor has to stop, and repeating the steps S 390  and S 400  to output a constant driving pulse if there is not an occasion that the motor has to stop. The stable driving of the motor after all is not controlled with a control value in the last step that is obtained from decreasing a slope value prior to the last step, but controlled with the value “finalpps” corresponding to the predetermined final value. Thus, the present invention consistently controls the motor at a substantially constant speed in order for the constant number of sheets to be discharged per minute.  
         [0045]    Further, in case that the number of sheets to be discharged per minute increases with the printer performance improved, it is required that only the values of the acceleration table are modified and transmitted, so that it is convenient since there is no need to replace the programmable ROM  112  as in the Prior Art.  
         [0046]    If the step S 350  is not the last step, the SCF control unit  110  subtracts the slope value from the value “OUTPUT” and drives the motor in the same way as above (S 360 ), and increases the value “COUNT” by 1 again (S 370 ). Thereafter, the SCF control unit  110  decides whether the step is the last step (S 380 ), and, if it is decided that the step is not the last step, the SCF control unit  110  repeats the step S 360 .  
         [0047]    If it is decided that the step S 380  is the last step, the SCF control unit  110  sets “1000” to the value “OUTPUT”, and decrements via the internal clock (not shown) to apply a constant motor driving pulse. That is, the SCF control unit  110  decides whether the motor stops in the step S 400 , and controls the motor to drive at a constant speed by stopping the motor if there is an occasion that the motor has to stop, and repeating the steps S 390  and S 400  to output a constant driving pulse if there is not an occasion that the motor has to stop  
         [0048]    The above description of the present invention employed a structure whereby the SCF control unit has a programmable ROM in which basic programs necessary for system initializations and communication protocols are stored and a RAM in which data such as an acceleration table transmitted from the control unit is stored. The present invention, however, can be implemented using one RAM such as a non-volatile memory (NVRAM). That is, the SCF control unit uses, upon system initializations, the basic programs necessary for the system initializations and communication protocols that are stored in the NVRAM, and can receive from the control unit and use the data related to the driving of the SCF.  
         [0049]    Further, the above descriptions of the present invention employed one SCF mounted therein, but the present invention can control an apparatus having plural SCFs in the manner that the control unit sequentially sends data to the respective SCF control units, or first sends related data to a specified SCF control unit out of the plural SCF control units and the remaining SCF control units receive the sent related data from the specified SCF control unit.  
         [0050]    As described above, the second cassette feeder control apparatus and method according to the present invention enables all SCFs to be compatibly used since the control unit of the main body can download driving-related data into the second cassette feeder and control the second cassette feeder in the same manner as in the prior art if the control unit detects that the second cassette feeder is mounted, and, at the same time, the programmable ROM and the firmware for the SCF can be shared.  
         [0051]    Although the preferred embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments, but various changes and modifications can be made within the spirit and scope of the present invention as defined by the appended claims.