Patent Publication Number: US-7590362-B2

Title: Image forming apparatus for communicating with sheet processing apparatus for executing post-process to sheet

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an image forming apparatus for detecting an abnormality of a sheet processing apparatus. 
   2. Description of the Related Art 
   Hitherto, an image forming system in which a plurality of post-processing apparatuses are connected to an image forming apparatus in tandem and predetermined post-processes are executed has been known. In such an image forming system, in order to avoid such a situation that the whole system cannot be used if an error occurred in one post-processing apparatus, a selecting portion to select use/non-use of the post-processing apparatus is provided. The non-use of the error-occurred post-processing apparatus is clearly selected in the selecting portion, thereby making control so that a part of the whole system can be used without disabling the whole system to be used (Japanese Patent Application Laid-open No. H09-301618. 
   However, the above conventional image forming system has the following problems. After the error occurred, by disconnecting the error-occurred apparatus from the image forming system, it is possible to avoid such a situation that the whole system cannot be used. However, when the error has occurred, since the whole image forming system is temporarily halted, for example, even in the case where an inputted job is not concerned with the error-occurred apparatus, such a job cannot be continued. 
   If an abnormality is detected in communication with a sheet processing apparatus for a period of time during which a power source of the image forming system is actually turned off after the operation to turn off the power source was executed, there is a case where in spite of the fact that a flow for turning off the power source has been predetermined, an error process is executed and an operability deteriorates. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an image forming apparatus which can solve the foregoing problem. 
   Another object of the invention is to provide an image forming apparatus in which when an error has occurred in a sheet processing apparatus which is not concerned with a job, the job can be continued without halting a whole image forming system, and usability of the user can be improved. 
   Other objects of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings. 
   According to the first aspect of the invention, there is provided a control method for an image forming system having an image forming apparatus which forms an image onto a sheet and a sheet processing apparatus which is connected to the image forming apparatus and executes a process to the sheet, comprising: a detecting step of detecting an abnormality in communication between the image forming apparatus and the sheet processing apparatus; an avoiding step of executing an avoiding process for the abnormality when the communication abnormality is detected in the detecting step; a preprocessing step of executing a preprocess for a power shutdown in accordance with an operation of a power switch to shut down a power source of the image forming system; and a control step of ignoring the communication abnormality even if the communication abnormality is detected in the detecting step during the preprocessing step and not executing the avoiding step. 
   Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
   Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a vertical sectional view showing an internal construction of an image forming system according to the first embodiment. 
       FIG. 2  is a diagram showing a communication network  120  for connecting an image forming apparatus  101 , a stacker  102 , a finisher  103 , a sheet feeding apparatus  104 A, and a sheet feeding apparatus  104 B. 
       FIG. 3  is a block diagram showing internal constructions of a controller  3000  and a printer controller  3100 . 
       FIG. 4  is a block diagram showing a construction of a controller  700  of each sheet-feeding/discharge apparatus connected to the image forming apparatus  101 . 
       FIG. 5  is a diagram showing an operating portion  307  of the image forming apparatus  101 . 
       FIG. 6  is a flowchart showing a procedure for an abnormality detecting process in inter-device communication which is made by the image forming apparatus  101 . 
       FIG. 7  is a flowchart showing a procedure for a responding process of the abnormality detecting operation in the inter-device communication which is made by the sheet-feeding/discharge apparatuses. 
       FIG. 8  is a flowchart showing a procedure for an error occurrence process. 
       FIG. 9  is a diagram showing an abnormality detecting state of the inter-device communication in the image forming system in the case where an image forming job is continued even if the occurrence of a communication error has been detected. 
       FIG. 10  is a diagram showing an abnormality detecting state of the inter-device communication in the image forming system in the case of halting the image forming system by the detection of the occurrence of the communication error. 
       FIG. 11  is a diagram showing a display panel  508  of the operating portion  307  at the time of the occurrence of the communication error in step S 34 . 
       FIG. 12  is a diagram showing the display panel  508  of the operating portion  307  at the time of the occurrence of the communication error in step S 40 . 
       FIG. 13  is a diagram showing the display panel  508  of the operating portion  307  at the time of the occurrence of the communication error in step S 37 . 
       FIG. 14  is a block diagram showing internal constructions of the controller  3000  and the printer controller  3100  in the second embodiment. 
       FIG. 15  is a block diagram showing a construction of the controller  700  of each sheet-feeding/discharge apparatus connected to the image forming apparatus  101 . 
       FIG. 16  is a flowchart showing a procedure for a power shutdown control process of the image forming apparatus  101 . 
       FIG. 17  is a flowchart showing a procedure for an operating process of the image forming system. 
       FIG. 18  is a diagram showing a display example of a relation among statuses of a plurality of sheet-feeding/discharge apparatuses and jobs. 
   

   DESCRIPTION OF THE EMBODIMENTS 
   Embodiments of an image forming system, an image forming apparatus, and an operation control method of the invention will be described hereinbelow with reference to the drawings. 
   First Embodiment 
     FIG. 1  is a vertical sectional view showing an internal construction of the image forming system according to the first embodiment. The image forming system is constructed by an image forming apparatus  101 , a stacker  102 , a finisher  103 , a sheet feeding apparatus  104 A, and a sheet feeding apparatus  104 B. Constructions and the operations of those apparatuses are shown here. 
   (Image Forming Apparatus) 
   The image forming apparatus  101  has: an image reader  20  for reading an image of an original; and a printer  30  as an image forming portion. An automatic document feeder (ADF)  5  is provided for the image reader  20 . The ADF  5  is constructed in such a manner that sheets of document (original sheets) set on a document tray in a face-up state are sequentially fed one by one to the left from the first page, and each of the fed original sheets is conveyed on a platen glass  6  through a curved path from the left side to the right side through a flow-reading position and, thereafter, discharged toward an external discharge tray  7 . 
   When the original sheet which is conveyed passes through the flow-reading position on the platen glass  6  from the left to the right, the image of the original sheet (also referred to as an original image hereinbelow) is read by a scanner unit  21  held at the flow-reading position. Such a reading method is a method which is generally called an original flow reading. 
   Specifically speaking, when the original passes through the flow-reading position, a reading surface of the original is illuminated by light of a lamp (not shown) of the scanner unit  21 . Reflection light from the original is guided to a lens  23  through mirrors  22   a ,  22   b , and  22   c . The light which has passed through the lens  23  is formed as an image onto an image pickup surface of an image sensor  24 . 
   The optically-read image is converted into image data by the image sensor  24  and outputted. The image data outputted from the image sensor  24  is subjected to a predetermined process in an image signal controller and, thereafter, inputted as a video signal to an exposure controller  31  of a printer  30 . 
   The exposure controller  31  of the printer  30  modulates a laser beam on the basis of the inputted video signal and outputs it. The modulated laser beam is irradiated onto a photosensitive drum  32  while being scanned by a polygon mirror. An electrostatic latent image according to the scanned laser beam is formed on the photosensitive drum  32 . In the case of fixedly reading the original, the exposure controller  31  outputs the laser beam so as to form an image which is not a mirror image. 
   A plurality of sheet feed cassettes  33  for enclosing sheets adapted to form images are provided in the printer  30  so that they can be pulled out in an apparatus front direction. The sheets can be supplied one by one to the printer  30  from each sheet feed cassette  33  by a separation feeding portion  33   a  provided in correspondence to each sheet feed cassette  33 . 
   In the case of performing a duplex (two-sided) copy to form an image onto a back side of the sheet in which an image has already been formed on one side, the following paths are provided: a reversing path  34  for reversing the sheet in which an image has already been formed on one side; and a duplex conveying path  35  for supplying the reversed sheet to the printer  30  again. 
   The electrostatic latent image on the photosensitive drum  32  is visualized as a developer image by a developer which is supplied from a developing unit (not shown). The sheet is fed from each sheet feed cassette  33  or the duplex conveying path  35  at the timing synchronized with the start of the irradiation of the laser beam. This sheet is transported between the photosensitive drum  32  and a transfer portion  36 . The developer image formed on the photosensitive drum  32  is transferred onto the sheet by the transfer portion  36 . 
   The sheet to which the developer image has been transferred is conveyed to a fixing portion  37 . The fixing portion  37  fixes the developer image onto the sheet by heating and pressing the sheet. The sheet which has passed through the fixing portion  37  passes through a conveying roller and a discharge roller  38  and is discharged toward the stacker  102  from the printer  30 . 
   In the case of discharging the sheet in the state where the image forming surface faces downward (face-down), the sheet which has passed through the fixing portion  37  is temporarily guided into the reversing path  34  by the switching operation of a flapper (not shown) provided in a branch portion of the reversing path  34 . After a rear edge of the sheet passed through the flapper, the sheet is switched back and discharged from the printer  30  by the discharge roller  38 . Such a sheet discharge form is called a “reverse discharge”. The reverse discharge is performed in the case of sequentially forming images from the first page as in the case where images read by using the ADF  5  are formed, the case where images outputted from the computer are formed, or the like. The order of sheets after the reverse discharge is the correct page order. 
   Further, if the duplex recording for forming images onto both sides of the sheet has been set, the sheet is guided to the reversing path  34  by the switching operation of the flapper (not shown) provided in the branch portion of the reversing path  34 , the sheet is conveyed to the duplex conveying path  35 . The sheet guided to the duplex conveying path  35  is fed again between the photosensitive drum  32  and the transfer portion  36  at predetermined timing. 
   (Stacker) 
   The stacker  102  executes a process for sequentially fetching the sheets from the image forming apparatus  101  and stacking onto a stack tray  211  or a process for sending the sheets to the finisher  103 . The stack tray  211  stacks a number of sheets which have been ejected from the image forming apparatus  101  and sequentially fetched into the apparatus. A sheet restricting member  212  is provided to improve the sheet stacking performance of the stack tray  211 . A sheet entrance portion  201  receives the sheets ejected from the image forming apparatus  101 . A conveying path  202  conveys the sheets in the stacker. A conveying path  203  for stacking the sheets is used in the case of stacking the sheets ejected from the image forming apparatus  101  onto the stack tray  211  in the stacker  102 . 
   A conveying path  204  for ejection to the downstream apparatus is used in the case of the sheets ejected from the image forming apparatus  101  to the finisher  103 . A conveying path change-over flapper  205  switches the conveying path of the sheets to either the sheet stacking conveying path  203  or the conveying path  204  for ejection to the downstream apparatus. In the case of guiding the sheets to the stack tray  211  in the stacker  102 , the flapper  205  switches the conveying path so as to select the sheet stacking conveying path  203 . On the other hand, in the case of ejecting the sheets to the finisher  103 , the flapper  205  switches the conveying path so as to select the conveying path  204  for ejection to the downstream apparatus. 
   A conveying roller R conveys the sheets along the conveying paths  202 ,  203 , and  204 . Sensors  206  and  208  are used to control an ascent and a descent of the stack tray  211 . 
   (Finisher) 
   The finisher  103  sequentially fetches the sheets from the stacker  102  and executes various kinds of post-processes to the fetched sheets. There are the following post-processes: a process for aligning the plurality of fetched sheets and binding them into one bundle; a stapling process for stapling a rear edge of the bundle of sheets by using a stapler; a. punching process for forming holes in positions near the rear edge of each of the fetched sheets; a sorting process; a non-sorting process; a booklet process; and the like. 
   The finisher  103  has an entrance roller pair  61  for guiding the sheets ejected from the stacker  102  to the inside. The downstream of the entrance roller pair  61  is branched to a processing tray path  62  and a booklet path  63  of the sheets. At this branch point, a change-over flapper (not shown) to guide the sheets to either the processing tray path  62  or the booklet path  63  is provided. The sheet guided to the processing tray path  62  is sent to a buffer roller  64  through a conveying roller pair (not shown). A punch unit  65  is provided on the way of the processing tray path  62 . If a punch mode has been set, the holes are formed in the positions near the rear edge of each of the conveyed sheets. 
   The buffer roller  64  is a roller which can overlay and wind a predetermined number of conveyed sheets around its outer periphery. The sheets wound around the buffer roller  64  are conveyed in the rotating direction of the buffer roller  64 . 
   Change-over flappers  66  and  67  are arranged near an outer peripheral conveying path of the buffer roller  64 . The change-over flapper  66  on the upstream side is a flapper for peeling off the sheets wound around the buffer roller  64  therefrom and guiding them to a non-sorting path  68  or a sorting path  69 . The change-over flapper  67  on the downstream side is a flapper for peeling off the sheets wound around the buffer roller  64  therefrom and guiding them to the sorting path  69  or a buffer path  60  in the state where the sheets wound around the buffer roller  64  have been wound. 
   The sheets guided to the non-sorting path  68  by the change-over flapper  66  are ejected onto a sample tray  71  through a discharge roller pair (not shown). A discharge sensor (not shown) is provided on the way of the non-sorting path  68 . The sheets guided to the sorting path  69  by the change-over flapper  66  are stacked onto a processing tray  72  through a conveying roller (not shown). The sheets stacked as a bundle on the processing tray  72  are subjected to the aligning process, stapling process, or the like as necessary and, thereafter, ejected onto a stacking tray  73  by a discharge roller (not shown). A stapler  74  is used for the stapling process to staple the sheets stacked as a bundle on the processing tray  72 . The stacking tray  73  is constructed so as to be movable in the vertical direction and is moved in accordance with a stacking amount of the bundle of sheets. 
   The sheets from the booklet path  63  are enclosed in an enclosing guide  76  by a conveying roller pair  75  and are, further, conveyed until front edges of the sheets are come into contact with a sheet positioning member  77 . The sheet positioning member  77  is movable in the vertical direction. A pair of right and left staplers  78  are provided at halfway positions of the enclosing guide  76  and constructed so as to staple the center portion of the bundle of sheets. 
   A folding roller pair  80  is provided in a downstream position of the staplers  78 . A protruding member  81  is provided at a position which faces the folding roller pair  80 . By projecting the protruding member  81  toward the bundle of sheets enclosed in the enclosing guide  76 , the bundle of sheets are pushed out between the pair of folding rollers  80 . After the bundle of sheets were folded by the folding roller pair  80 , they are ejected to a saddle discharge tray  83  through a folded sheet discharge roller  82 . 
   (Sheet Feeding Apparatus) 
   The sheet feeding apparatuses  104 A and  104 B are optional sheet feeding apparatuses which are connected to the upstream side of the image forming apparatus  101 . In a manner similar to the image forming apparatus  101 , a plurality of sheet feed cassettes  401  are provided for the sheet feeding apparatuses  104 A and  104 B so that they can be freely pulled out in the apparatus front direction. A separation feeding portion  401   a  provided in correspondence to each of the sheet feed cassettes  401  supplies the sheets one by one to the image forming apparatus  101  from each sheet feed cassette  401 . The sheets are conveyed to the downstream apparatus through conveying paths  402  and  403 . 
     FIG. 2  is a diagram showing a communication network  120  for connecting the image forming apparatus  101 , stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B. A controller  3000  to manage jobs and a printer controller  3100  to control the image forming operation are provided for the image forming apparatus  101 . A stacker controller  3200  for conveying the sheets is provided for the stacker  102 . A finisher controller  3300  for executing the sheet process is provided for the finisher  103 . Sheet feeding apparatus controllers  3400 A and  3400 B for feeding the sheets are provided for the sheet feeding apparatuses  104 A and  104 B, respectively. The image forming apparatus  101 , stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B transmit and receive sheet information and timing information which are necessary for the sheet process through the communication network  120 . 
     FIG. 2  is illustrated for convenience of explanation as if the sheet-feeding/discharge apparatuses (stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B) were connected to the image forming apparatus  101  by communication lines in a one-to-one correspondence relational manner. However, naturally, all of the sheet-feeding/discharge apparatuses (sheet processing apparatuses) can be also network-connected by one communication line. 
     FIG. 3  is a block diagram showing internal constructions of the controller  3000  and the printer controller  3100 . In the controller  3000 , a CPU  301  is connected to each of a ROM  303  and a RAM  302  through an address bus and a data bus. A control program which is executed by the CPU  301  has been written in the ROM  303 . Data which is processed by the CPU  301  is stored into the RAM  302 . A job management area  302   a  to store information of an image forming job (hereinafter, simply referred to as a job) has been allocated to the RAM  302 . 
   The following portions are also connected to the CPU  301 : an external I/F portion  304  to communicate with the outside; a PDL controller  305  to execute modification, storage, and an image process of the received data; an internal I/F portion  306  to communicate with the printer controller  3100 ; and an operating portion  307 . The CPU  301  controls a display portion and a key input portion provided for the operating portion  307 . When the user instructs the CPU  301  to switch display contents through the key input portion, the CPU  301  allows the display portion of the operating portion  307  to display an operation status of the apparatus, an operating mode set by the key input, and the like. 
   In the printer controller  3100 , a CPU  311  is connected to each of a ROM  313  and a RAM  312  through an address bus and a data bus. The CPU  311  makes fundamental control of the image forming operation. A control program which is executed by the CPU  311  has been written in the ROM  313 . Data which is processed by the CPU  311  is stored into the RAM  312 . An error memory area  312   a  to store information showing an abnormality in the communication of each of the sheet-feeding/discharge apparatuses has been allocated to the RAM  312 . 
   A device controller  314 , an internal I/F portion  315 , and an inter-device I/F portion  316  are connected to the CPU  311 . The device controller  314  includes an input/output port to control each of the component parts of the printer portion, and the like. The internal I/F portion  315  communicates with the controller  3000  and transmits and receives image signals and timing signals. The inter-device I/F portion  316  transmits and receives sheet information and timing information to/from other apparatuses. 
   In accordance with the control program, the CPU  311  receives the image signals through the controller  3000  and the internal I/F portion  315 , controls the device controller  314 , and executes the image forming operation. The CPU  311  also transmits and receives the sheet information and the timing information to/from other apparatuses through the inter-device I/F portion  316  and executes the sheet conveying operation. 
   The CPU  311  in the printer controller  3100  and the CPU  301  in the controller  3000  can mutually transmit and receive information through the internal I/F portions  306  and  315  and can execute processes shown in a flowchart of  FIG. 8 , which will be explained hereinafter, and the like in cooperation with each other. 
     FIG. 4  is a block diagram showing a construction of a controller  700  of each of the sheet-feeding/discharge apparatuses connected to the image forming apparatus  101 . As a sheet-feeding/discharge apparatus, each of the stacker controller  3200 , the finisher controller  3300 , and the sheet feeding apparatus controllers  3400  ( 3400 A and  3400 B) has the controller  700  of the same construction. In the controller  700 , a CPU  711  is connected to each of a ROM  713  and a RAM  712  through an address bus and a data bus. The CPU  711  controls the sheet conveyance and the sheet process. A control program which is executed by the CPU  711  has been written in the ROM  713 . Control data is stored into the RAM  712 . 
   A device controller  714  and an inter-device I/F portion  716  are connected to the CPU  711 . The device controller  714  has an input/output port and the like to control each of the component parts of the sheet-feeding/discharge apparatus. The inter-device I/F portion  716  transmits and receives the sheet information and the timing information to/from other sheet-feeding/discharge apparatuses or image forming apparatus. The CPU  711  transmits and receives the sheet information and the timing information to/from other apparatuses through the inter-device I/F portion  716  in accordance with the control program and executes the sheet conveying operation and the sheet process. 
     FIG. 5  is a diagram showing the operating portion  307  of the image forming apparatus  101 . In the diagram, a power lamp  500  is a lamp to indicate that a power source has been turned on. The power lamp  500  is lit on/off in accordance with the switching of ON/OFF of the power source by a power switch  501 . 
   A ten-key  502  is used to input various kinds of numerical values when the number of image forming (copies), the operating mode, or the like is set or used to input a telephone number in a facsimile setting mode. A clear key  503  is used to clear the setting contents inputted through the ten-key  502 . A reset key  504  is used to return the set value of the number of image forming copies, the various set operating modes, the selected sheet feed cassette, and the like to default values. By pressing a start key  505 , the copying operation can be started. 
   A stop key  506  is used to stop the image forming operation. 
   A display panel  508  is constructed by a liquid crystal touch panel. In  FIG. 5 , a setting display screen of the copy operating mode is displayed on the display panel  508 . A plurality of touch keys  511  to  517  are displayed on the setting display screen. Among those touch keys, a sheet select key  511  is a touch key to select the recording paper of a desired size. A reduce key  512 , a same size key  513 , and an enlarge key  514  are touch keys to set a reduction copy mode, a same size copy mode (direct copy mode), and an enlargement copy mode, respectively. By using the sheet select key  511 , not only the sheets in the sheet feed cassette  33  in the image forming apparatus  101  but also the sheets in the sheet feed cassette  401  in the sheet feeding apparatus  104 A or the sheet feeding apparatus  104 B can be selected. 
   A special mode key  515  is a touch key to display a display screen for setting various copy modes. A two-sided key (duplex operation setting key)  516  is a touch key to set various kinds of modes regarding the duplex copying operation. 
   A discharge process key  517  is a touch key which is used when discharge to the stacker  102  is designated, various operating modes of the finisher  103  are set, a sorting mode of the output sheet using an image memory is set, or the like. Among the touch keys displayed on the display panel  508 , with respect to each of the touch keys which cannot be used at the present point of time, its display frame is displayed by a broken line or the whole display portion is displayed by a hatched region. The contents of the set copying operation and the current operation status are displayed in an upper region of the display panel  508 . Operation statuses of other function modes are displayed in an lower region of the display panel  508 . 
   A copy function key  523 , a fax (facsimile) function key  526 , and a printer function key  529  are function keys which are used to set the functions of the copying operation, facsimile operation, and printer operation, respectively. By operating those function keys, the display contents of the display panel  508  are also switched. Buttons of those function keys are constructed by semitransparent key buttons. A display lamp (not shown) such as an LED or the like is provided in each key. Only the display lamp of the operated function key is lit on. Each of LEDs  524 ,  527 , and  530  arranged on the left side of those function keys displays the operation situation of each function. 
   LEDs  525 ,  528 , and  531  arranged on the right side of the copy function key  523 , fax function key  526 , and printer function key  529  are lit off when an abnormality has occurred in each function. 
   The key operations of those function keys  523 ,  526 , and  529  are received in any of the operating situations and the setting display screen displayed on the display panel  508  can be changed. The keys existing in the outside of the display panel  508  such as start key  505 , stop key  506 , reset key  504 , and the like function in correspondence to the function selected from the function keys. 
   The image forming operation in the case where the abnormality has been detected in the inter-device communication in the image forming system having the foregoing construction will now be described. As mentioned above, the image forming apparatus  101 , stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B are connected through the inter-device communication network  120 . The sheet information and the timing information which are necessary for the sheet process are transmitted and received among the apparatuses through the inter-device communication network  120 . It is, therefore, necessary to discriminate whether or not the communication has normally been made among the apparatuses. 
   First, the operation to detect the abnormality in the inter-device communication which is made by the image forming apparatus  101  will be explained.  FIG. 6  is a flowchart showing a procedure for an abnormality detecting process in the inter-device communication which is made by the image forming apparatus  101 . This processing program has been stored in the ROM  313  in the printer controller  3100  of the image forming apparatus  101  and is likewise executed every predetermined period by the CPU  311  in the printer controller  3100 . 
   First, the CPU  311  discriminates whether or not a first predetermined time has elapsed after the last communication was made (step S 1 ). If the first predetermined time does not elapse, the CPU  311  repeats the process of step S 1 . If it is confirmed in step S 1  that the first predetermined time has elapsed, the CPU  311  sends an Echo command through the inter-device communication network  120  to each of the sheet-feeding/discharge apparatuses connected to the image forming apparatus  101  (step S 2 ). 
   After that, the CPU  311  discriminates whether or not an EchoAck command has been received from the sheet-feeding/discharge apparatus to which the Echo command was sent (step S 3 ). If the reception of the EchoAck command from the sheet-feeding/discharge apparatus could be confirmed, the CPU  311  finishes the present processing routine. This processing routine is executed again after the predetermined period. When the first predetermined time has elapsed in step S 1 , similar processes in step S 2  and subsequent steps are executed. 
   If the reception of the EchoAck command from the sheet-feeding/discharge apparatus which sent the Echo command cannot be confirmed in step S 3 , the CPU  311  discriminates whether or not a second predetermined time has elapsed after the transmission of the Echo command (step S 4 ). If the second predetermined time does not elapse, the processing routine is returned to the process of step S 3 . The process to confirm the reception of the EchoAck command from each sheet-feeding/discharge apparatus which sent the Echo command is continued. 
   If the reception of the EchoAck command cannot be confirmed within the second predetermined time, the CPU  311  determines that some abnormality has occurred in the communication with the sheet-feeding/discharge apparatuses connected through the inter-device communication network  120 , so that the CPU  311  stores the error occurrence (step S 5 ). After that, the CPU  311  finishes the present processing routine. 
     FIG. 7  is a flowchart showing a procedure for a responding process of the abnormality detecting operation in the inter-device communication which is made by the sheet-feeding/discharge apparatuses. This processing program has been stored in the ROM  713  in the controller  700  of each sheet-feeding/discharge apparatus and is executed every predetermined period by the CPU  711 . As mentioned above, the sheet-feeding/discharge apparatus is one of the stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B. The responding process of the abnormality detecting operation in the inter-device communication is executed to the image forming apparatus  101  to which one of the sheet-feeding/discharge apparatuses is connected through the inter-device communication network  120 . 
   First, the CPU  711  discriminates whether or not the Echo command from the image forming apparatus  101  has been received (step S 11 ). If the reception of the Echo command from the image forming apparatus  101  is confirmed, the CPU  711  immediately sends the EchoAck command to the image forming apparatus  101  as a notification showing that the Echo command has been confirmed (step S 12 ). After that, the CPU  711  finishes the present processing routine. If the Echo command is not received, the CPU  711  finishes the present processing routine as it is. 
   As mentioned above, the image forming apparatus  101  executes in parallel the abnormality detecting operation in the inter-device communication with each sheet-feeding/discharge apparatus. By confirming the reception of the EchoAck command within the second predetermined time, the image forming apparatus  101  discriminates whether or not the communication is normally being made with each sheet-feeding/discharge apparatus through the inter-device communication network  120 . That is, the processes shown in the flowcharts of  FIGS. 6 and 7  are executed the number of times as many as the number of sheet-feeding/discharge apparatuses connected to the image forming apparatus  101 . 
     FIG. 8  is a flowchart showing a procedure for an error occurrence process. The error occurrence process is executed when the CPU  301  in the controller  3000  in the image forming apparatus  101  executes the control program stored in the ROM  303 . 
   First, to the printer controller  3100 , the CPU  301  discriminates whether or not data representing the occurrence of the communication error has been stored (step S 31 ). This confirmation is made when the CPU  311  refers to data stored in the error memory area  312   a  in the RAM  312 . If data representing the occurrence of the communication error is not stored, it is determined that the communication among all of the apparatuses in the image forming system is normally being made. To the printer controller  3100 , the CPU  301  confirms whether or not there is an occurrence of the communication error due to the abnormality detecting operation (refer to  FIGS. 6 and 7 ) in the inter-device communication (step S 32 ). If there is no occurrence of the communication error in step S 32 , the present processing routine is finished. 
   If it is decided in step S 32  that the error of the communication with one of the sheet-feeding/discharge apparatuses has occurred, the CPU  301  discriminates whether or not an image forming job using the sheet-feeding/discharge apparatus in which the communication error has occurred (hereinbelow, such an apparatus is referred to as an “error occurred apparatus”) is being executed (being inputted) (step S 33 ). As mentioned above, the job information has been managed in the job management area  302   a  in the RAM  302  in the controller  3000 . 
   When the image forming job using the error occurred apparatus is being executed, the CPU  301  halts the image forming system and displays a message showing the error occurrence to the operating portion  307  (step S 40 ; refer to  FIG. 12 ). After that, the present processing routine is finished. If the image forming job using the error occurred apparatus is not executed in step S 33 , the CPU  301  displays the communication error occurrence to the operating portion  307  and stores the error occurred apparatus (step S 34 ; refer to  FIG. 11 ). In the process of step S 34 , only the display of the error occurrence and the storage of the error occurred apparatus are executed and the halt of the image forming system is not performed. A display format of the error occurrence is set to a format which does not to obstruct the display regarding the image forming job which does not use the error occurred apparatus. After that, the present processing routine is finished. 
   If the occurrence of the communication error has been stored in step S 31 , the CPU  301  discriminates whether or not the image forming job using the error occurred apparatus in which data representing the communication error occurrence had been stored has been inputted or started (step S 35 ). If it is determined that the image forming job using the error occurred apparatus is not inputted or started, the CPU  301  confirms the presence or absence of the abnormality in the inter-device communication in order to discriminate whether or not the image forming job can be continuously executed for the printer controller  3100  (step S 32 ). 
   If the image forming job using the error occurred apparatus has been inputted or started in step S 35 , the CPU  301  decides that the image forming job cannot be normally executed, and halts the execution of the image forming job (step S 36 ). After that, the CPU  301  displays the communication error occurrence to the operating portion  307  and displays a message for allowing the user to confirm the job cancellation (step S 37 ; refer to  FIG. 13 ). 
   The CPU  301  discriminates whether or not the user has instructed to cancel the job (step S 38 ). If the job cancelling instruction by the user is confirmed, the image forming job using the error occurred apparatus is cancelled (step S 39 ). After that, the processing routine is returned to the process of step S 31  and the CPU  301  also makes a similar discrimination with respect to the subsequent image forming jobs. If the job cancellation is not instructed in step S 38 , since the image forming job cannot be continued, the CPU  301  displays the error occurrence to the operating portion  307  and halts the image forming system. 
   As mentioned above, even if the error occurred in the communication between the image forming apparatus  101  and one of the sheet-feeding/discharge apparatuses (stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B) which are connected through the inter-device communication network  120 , the invention can cope with such a situation. That is, in the case of the communication error of the sheet-feeding/discharge apparatus which is not concerned with the job, the job can be continued without immediately halting the whole image forming system by the management information of the image forming jobs managed in the controller  3000 . This is known as an avoiding process or abnormality countermeasure process. Therefore, usability can be improved. 
   Since the printing operation is continued without making the image forming system inoperative until a job for the error occurred apparatus is inputted, printing efficiency can be raised. Since the error occurrence situation is displayed even if the image forming system is not halted, the user can discriminate the error occurrence situation. 
     FIG. 9  is a diagram showing an abnormality detecting state in the inter-device communication in the image forming system. As mentioned above,  FIG. 9  is illustrated for convenience of explanation as if the sheet-feeding/discharge apparatuses (stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B) were connected to the image forming apparatus  101  by communication lines in a one-to-one correspondence relational manner. However, naturally, all of the sheet-feeding/discharge apparatuses can be network-connected by one communication line. 
   In the diagram, reference numeral  800  denotes a state where the communication error has occurred in the inter-device communication network. The apparatuses shown by hatched regions among the sheet-feeding/discharge apparatuses indicate the apparatuses which are not used in the inputted image forming job. In  FIG. 9 , the inter-device communication error has occurred between the image forming apparatus  101  and the finisher  103 . The finisher  103  and the sheet feeding apparatus  104 B are not used in the inputted image forming job. In the inputted image forming job, the image forming apparatus  101 , stacker  102 , and sheet feeding apparatus  104 A are used and the finisher  103  in which the communication error has occurred is not used. 
   In this state, when the communication error has occurred, only the display of the error occurrence and the storage of the error occurred apparatus are executed without immediately halting the image forming system, and the image forming job can be continued. 
     FIG. 10  is a diagram showing an abnormality detecting state in the inter-device communication in the image forming system. In  FIG. 10 , the state where the inter-device communication error has occurred between the image forming apparatus  101  and the finisher  103  is shown. The sheet feeding apparatuses  104 A and  104 B are not used in the inputted image forming job. The image forming apparatus  101 , stacker  102 , and the finisher  103  are used in the inputted image forming job. 
   In the case where the information showing that the communication error had occurred between the image forming apparatus  101  and the finisher  103  has been stored in the error memory area  312   a  in the RAM  312 , if such an image forming job has been started (inputted) or if the communication error occurrence is detected when the image forming job is being executed, it is determined that the image forming job is not normally completed. Therefore, the operation of the image forming system is halted. 
     FIG. 11  is a diagram showing the display panel  508  of the operating portion  307  when the communication error has occurred in step S 34 . A message showing that the copy job is at present being executed, a message showing the occurrence of the error in the communication with the finisher  103 , and the like are displayed on the display panel  508 . The state shown in  FIG. 11  is the state where although the error in the communication with the finisher  103  has occurred, since the finisher  103  is not used in the inputted job, the job is continuously executed without halting the whole image forming system as shown in  FIG. 9 . 
     FIG. 12  is a diagram showing the display panel  508  of the operating portion  307  in the case where the communication error has occurred in step S 40 . The message showing the occurrence of the error in the communication with the finisher  103  and a message showing that the image forming system has been halted are displayed on the display panel  508 . The state shown in  FIG. 12  is the state where the communication error in the job using the finisher  103  has occurred or the state where the job has been inputted to the finisher  103  just after the occurrence of the communication error. By displaying the error occurrence situation to the display panel  508  as mentioned above, the user can recognize the situation of the image forming system. 
     FIG. 13  is a diagram showing the display panel  508  of the operating portion  307  at the time of the occurrence of the communication error in step S 37 . If the image forming job using the sheet-feeding/discharge apparatus in which the communication error has occurred is inputted, a display screen for allowing the user to discriminate whether or not the inputted job is cancelled is displayed. In the diagram, a “YES” key  550  is used to instruct the user to cancel the job. A “NO” key  551  is used to instruct the user not to cancel the job.  FIG. 13  shows the state where the error has occurred in the communication with the finisher  103  and the image forming job using the finisher  103  has been inputted. In the case where the error has occurred in the communication with the finisher, the image forming job is temporarily halted. When the “YES” key  550  to instruct the job cancellation is pressed, the inputted job is cancelled and the system waits for the input of the subsequent job without halting the image forming system. On the other hand, if the “NO” key  551  is pressed, since the image forming job using the error occurred apparatus cannot be executed, an error message is displayed and the image forming system is halted (refer to  FIG. 12 ). 
   According to the image forming system of the first embodiment, as mentioned above, if the error has occurred in the sheet-feeding/discharge apparatus which is not concerned with the job, the job can be continued without halting the whole image forming system and the usability of the user can be improved. 
   Since the image forming system is not made inoperative until the job using the error occurred apparatus is inputted, even if the error occurred, the printing operation without using the error occurred apparatus can be continued. Since the error occurrence situation is displayed even if the image forming system is not halted, the user can discriminate the error occurrence situation. 
   Second Embodiment 
   In an image forming system according to the second embodiment, when a power OFF is instructed by the operation of the power switch  501  of the operating portion  307 , power shutdown preprocesses are executed. As power shutdown preprocesses, for example, parts counter information and various kinds of image forming conditions are stored into a non-volatile memory, and a process for halting various kinds of devices in the stable state is executed and, thereafter, the supply of a current/voltage from the power source is shut down, thereby assuring performance of the image forming apparatus. 
   Since constructions of the image forming apparatus and each sheet-feeding/discharge apparatus in the image forming system according to the second embodiment are similar to those in the foregoing first embodiment, their explanation is omitted. Since the abnormality detecting operation of the inter-device communication is also similar to that in the first embodiment, its explanation is omitted. That is, also in the second embodiment, the processes shown in the flowcharts in  FIGS. 6 and 7  mentioned above are executed. The communication abnormality of each sheet-feeding/discharge apparatus is stored in the error memory area  312   a  allocated to the RAM  312  in the printer controller  3100 . 
     FIG. 14  is a block diagram showing internal constructions of the controller  3000  and the printer controller  3100  in the second embodiment. The same component elements as those in the first embodiment are designated by the same reference numerals and their description is omitted. Besides the external I/F portion  304 , PDL controller  305 , internal I/F portion  306 , operating portion  307 , a power shutdown portion  309  is connected to the CPU  301  in the controller  3000 . In accordance with an instruction from the CPU  301 , the power shutdown portion  309  shuts down the voltage/current which is supplied from the power source to the image forming apparatus  101 . 
     FIG. 15  is a block diagram showing a construction of the controller  700  of each sheet-feeding/discharge apparatus connected to the image forming apparatus  101 . The same component elements as those in the first embodiment are designated by the same reference numerals and their description is omitted. Besides the device controller  714  and the inter-device I/F portion  716 , a power shutdown portion  719  is connected to the CPU  711  in the controller  700 . In accordance with an instruction from the CPU  711 , the power shutdown portion  719  shuts down the voltage/current which is supplied from the power source to the sheet-feeding/discharge apparatus. For example, when the instruction to shut down the power source is received from the image forming apparatus  101  through the inter-device communication network  120 , the CPU  711  notifies the power shutdown portion  719  of the power shutdown instruction. 
     FIG. 16  is a flowchart showing a procedure for a power shutdown control process of the image forming apparatus  101 . The power shutdown control process is executed when the CPU  301  in the controller  3000  in the image forming apparatus  101  executes the control program stored in the ROM  303 . 
   First, the CPU  301  discriminates whether or not the power switch  501  on the operating portion  307  has been pressed by the user (step S 51 ). If the depression of the power switch  501  is not confirmed, the present processing routine is finished as it is. If the depression of the power switch  501  is confirmed in step S 51 , the CPU  301  executes the power shutdown preprocesses such as backup of various. kinds of information, stable halt of various kinds of devices, and the like (step S 52 ). 
   The CPU  301  discriminates whether or not all of the power shutdown preprocesses have been completed (step S 53 ). If NO, the CPU  301  waits for completion of the power shutdown preprocesses. If the completion of all of the power shutdown preprocesses is confirmed, the CPU  301  controls the power shutdown portion  309  so as to halt the supply of the voltage/current from the power source (step S 54 ). The confirmation of the completion of the power shutdown preprocesses in step S 53  can be made, for example, by receiving completion responses from the various kinds of devices. It is also possible to confirm it by a method whereby a timer is provided and, when the timer has detected the elapse of a predetermined time from the start of the power shutdown preprocesses, it is decided that they were completed. The power shutdown of each sheet-feeding/discharge apparatus may be performed simultaneously with the power shutdown of the image forming apparatus  101 . 
     FIG. 17  is a flowchart showing a procedure for an operating process of the image forming system. This process is executed when the CPU  301  in the controller  3000  in the image forming apparatus  101  executes the control program stored in the ROM  303 . This process is executed in parallel with the processing routine of  FIG. 16 . 
   As mentioned above, the abnormality detecting process of the inter-device communication between the image forming apparatus  101  and one of the stacker  102 , finisher  103 , sheet feeding apparatus  104 A, and sheet feeding apparatus  104 B which are connected through the inter-device communication network  120  is also executed in the second embodiment. 
   First, the CPU  301  discriminates whether or not the power shutdown preprocesses are being executed (step S 61 ). If NO, the CPU  301  discriminates whether or not the CPU  311  has detected the occurrence of the error in the inter-device communication (step S 62 ). If the communication error has been detected, the CPU  301  displays an error to the operating portion  307  and halts the image forming system (step S 63 ). After that, the present processing routine is finished. If there is no communication error in step S 62 , the present processing routine is finished as it is. If it is confirmed in step S 61  that the power shutdown preprocesses are being executed, the CPU  301  finishes the present processing routine without making the confirmation of the communication error in the abnormality detecting process of the inter-device communication by the CPU  311 . 
   As mentioned above, according to the image forming system of the second embodiment, there is no need to execute the abnormality detecting process of the inter-device communication during the power shutdown preprocesses and the unnecessary discrimination and display of the error occurrence can be omitted. Thus, the usability of the whole image forming system can be improved. After the power shutdown preprocesses, the power supply of the image forming apparatus  101  is certainly shut down and the image forming job is not newly inputted. 
   In the case where the presence or absence of the occurrence of the communication error is discriminated even during the power shutdown preprocesses in dependence on a construction of the program, it is preferable to ignore the error occurrence even if the occurrence of the communication error is detected. 
   The invention is not limited to the construction of the foregoing embodiments but can be applied to any construction so long as it can accomplish the functions shown in Claims of the invention and the functions provided by the constructions of the embodiments. 
   For example, although the communication abnormality which is detected by the inter-device communication has been used as an abnormality of the sheet-feeding/discharge apparatus in the foregoing embodiments, naturally, the invention is not limited to such an abnormality. For example, an abnormality such as defective punching operation, a defective stapling, or the like in the finisher  103  can be mentioned as another abnormality and the invention can be similarly applied to such an abnormality. 
   In the foregoing first embodiment, in the case where the job using the error occurred apparatus has been inputted, this job can be cancelled at a point of time of the job input (refer to the process of step S 38  in  FIG. 13 ). Further, the non-processed jobs stored in the job management area  302   a  can be also cancelled. That is, it is also possible to construct in such a manner that a list of non-processed jobs is displayed onto the display panel  508  of the operating portion  307  and the job using the error occurred apparatus can be cancelled from such a list. 
     FIG. 18  is a diagram showing a display example of a relation among statuses of the plurality of sheet-feeding/discharge apparatuses and the jobs. The necessary sheet-feeding/discharge apparatuses and their statuses are displayed on the display panel  508  every non-processed job. In the display example of  FIG. 18 , the state where the error in the communication with the stacker has occurred is shown. Jobs b and c using the stacker cannot be executed in this state. By selecting the jobs b and c and pressing a cancel key  610  on this display screen, the user cancels those jobs. Thus, a period of time during which the printing operation can be continued can be extended without halting the image forming system. 
   The specific examples of the sheet-feeding/discharge apparatuses are not limited to those in the foregoing embodiments but, naturally, arbitrary kinds of sheet processing apparatuses can be also used. 
   The object of the invention is also accomplished by a method whereby a storing medium in which program codes of software to realize the functions of the embodiments mentioned above is supplied to a system or an apparatus and a computer (or a CPU, an MPU, or the like) of the system or apparatus reads out and executes the which program codes stored in the storing medium. 
   In such a case, the program codes themselves read out of the storing medium realize the functions of the embodiments as mentioned above and the storing medium in which the program codes have been stored constructs the invention. 
   As a storing medium for supplying the program codes, for example, a Floppy (registered trademark) disk, a hard disk, a magnetooptic disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW, a DVD+RW, a magnetic tape, a non-volatile memory card, a ROM, or the like can be used. The program codes may be downloaded through a network. 
   The invention incorporates not only the case where the computer executes the read-out program codes, so that the functions of the embodiments are realized but also the case where an OS (Operating System) or the like which is operating in the computer executes a part or all of actual processes on the basis of instructions of the program codes and the functions of the embodiments as mentioned above are realized by those processes. 
   Further, the invention incorporates the case where the program codes read out of the storing medium are written into a memory provided for a function expanding board inserted in the computer or a function expanding unit connected to the computer, thereafter, a CPU or the like provided for the function expanding board or the function expanding unit executes a part or all of the actual processes on the basis of the instructions of the program codes and the functions of the embodiments are realized by those processes. 
   While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadcast interpretation so as to encompass all such modifications and equivalent structures and functions. 
   This application claims the benefit of Japanese Patent Application Nos. 2005-261120, filed Sep. 8, 2005 and 2006-227703 filed on Aug. 24, 2006 which are hereby incorporated by reference herein in their entirety.