Patent Publication Number: US-10775728-B2

Title: Image forming system that performs communication control and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to an image forming apparatus for forming an image, such as a copying machine and a printer, and to an image forming system that performs control of communication with optional apparatuses attached to the image forming apparatus. 
     Description of the Related Art 
     In a conventional image forming apparatus, a plurality of attachable/detachable optional apparatuses is connected to the image forming apparatus main body. The image forming apparatus performs communication between the image forming apparatus main body (master) and the optional apparatuses (slaves) to achieve, for example, sheet feeding conveyance and sheet discharge conveyance in a cooperative manner. 
     For example, Japanese Patent Application Laid-Open No. 2006-133996 discusses a technique for performing communication between an image forming apparatus main body and a plurality of optional apparatuses connected to the main body in cascade. Specifically in the communication method, the image forming apparatus main body first registers unique identifier (ID) information to one optional apparatus connected to the image forming apparatus main body. Then, the one optional apparatus permits the image forming apparatus main body to make communication connection with another optional apparatus connected in cascade. The image forming apparatus main body repetitively registers unique II) information to each newly connected optional apparatus, and thus registers individual ID information to all of the optional apparatuses. When communicating with one specific optional apparatus, the image forming apparatus main body transmits a command signal as communication data including an ID information. If an optional apparatus has a corresponding ID information, out of the optional apparatuses that have received the command signal, the optional apparatus returns a status signal in response to the command signal. 
     The above-described image forming apparatus main body and optional apparatuses perform communication in the following procedures. When power of an optional apparatus is turned off (e.g., a sleep state of the image forming apparatus main body), the ID information registered in the optional apparatuses is cleared. Subsequently, when power of the optional apparatus is turned back to ON (e.g., return from the sleep state), the image forming apparatus main body registers the ID information for all of the optional apparatuses. Then, the image forming apparatus main body transmits a status information request command to all of the optional apparatuses to confirm the state of each optional apparatus. After the confirmation, the image forming apparatus main body performs power return processing. However, there has been an issue that separately performing each piece of processing described above prolongs total processing time, and thus resulting in downtime. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present disclosure, an image forming system includes an image forming apparatus, an external apparatus connectable to the image forming apparatus, and a communication unit configured to perform communication between the image forming apparatus and the external apparatus. The image forming apparatus includes a first control unit configured to communicate with the external apparatus by using the communication unit to transmit a registration command for setting identification information in the external apparatus. The external apparatus includes a second control unit configured to communicate with the image forming apparatus by using the communication unit to set the identification information therein based on the registration command. The first control unit transmits, in a state where the identification information is not set in the external apparatus, a confirmation command for confirming a state of the external apparatus to the second control unit before the first control unit transmits the registration command to the external apparatus. 
     Further features of the present disclosure 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 schematic view illustrating a configuration of an image forming apparatus and optional apparatuses. 
         FIG. 2  is a control block diagram illustrating an image forming apparatus main body and optional sheet feeding apparatuses. 
         FIG. 3  is a timing chart illustrating communication operation between the image forming apparatus main body and the optional sheet feeding apparatuses. 
         FIGS. 4A and 4B  are timing charts illustrating communication operation between the image forming apparatus main body and the optional sheet feeding apparatuses. 
         FIGS. 5A and 5B  are timing charts illustrating a processing flow in which a main body control unit of the image forming apparatus main body controls a sleep return operation of the optional sheet feeding apparatuses. 
         FIG. 6  is a flowchart illustrating a sleep return operation. 
         FIGS. 7A and 7B  are timing charts illustrating another processing flow in which the main body control unit of the image forming apparatus main body controls the sleep return operation of the optional sheet feeding apparatuses. 
         FIG. 8  is another flowchart illustrating the sleep return operation. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings. The following exemplary embodiments do not limit the present disclosure according to the appended claims. Not all of the combinations of the features described in the exemplary embodiments are indispensable to the solutions for the present disclosure. 
     [Image Forming Apparatus] 
       FIG. 1  is a schematic view illustrating a configuration of an image forming apparatus and optional apparatuses according to a first exemplary embodiment.  FIG. 1  illustrates, as an example, an image forming apparatus main body  100 , and a plurality of optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  connectable with the image forming apparatus main body  100 . The present exemplary embodiment will be described below centering on a direct transfer type color laser beam printer using a conveyance belt  9  as an example, the present disclosure is not limited thereto. As long as optional apparatuses can be attached and detached, the image forming apparatus may be an intermediate transfer type color laser beam printer, a monochrome laser beam printer, or an inkjet printer. Optional apparatuses can be external apparatuses connectable to the image forming apparatus main body  100 . Further, the image forming apparatus and optional apparatuses are collectively referred to as an image forming system. 
     The image forming apparatus main body  100  forms a color image by overlapping images of four different colors (i.e., yellow (Y), magenta (M), cyan (C), and black (Bk)). Hereinafter, reference numerals of color-related components are supplied with additional characters a, b, c, and d corresponding to yellow, magenta, cyan, and black, respectively. If a color is not particularly specified, the additional characters may be omitted. 
     The image forming apparatus main body  100  includes photosensitive drums  1  as photosensitive members. A charging roller  2  as a charging unit, an exposure unit  3  including a light source as an exposure unit, and a development unit  4  including a developing roller as a development unit are disposed around each photosensitive drum  1 . A transfer roller  5  as a transfer unit and a cleaning blade  6  as a cleaning unit are also disposed. These components can be collectively referred to as an image forming unit. 
     When the surface of a photosensitive drum  1  is uniformly charged by the charging roller  2 , and the surface is exposed to light by the exposure unit  3 , an electrostatic latent image is formed. Further, the development unit  4  applies toner to the electrostatic latent image formed on the photosensitive drum  1  to develop a toner image. The transfer roller  5  transfers the developed toner image onto a recording material. Residual toner remaining on the photosensitive drum  1  is removed by the cleaning blade  6 . 
     Next, feeding operation of a recording material from a sheet feeding unit will be described. The sheet feeding unit in the image forming apparatus main body  100  will be described below as an example. Since the configuration of the sheet feeding unit in each optional apparatus has a similar configuration to the sheet feeding unit in the image forming apparatus main body  100 , descriptions of the optional apparatuses will be omitted. A recording material stacked on the sheet feeding unit is fed to a feed roller  21   a . The recording material is conveyed by conveyance rollers  22   a  and  23   a  and is detected by a registration sensor  24   a . Further, the recording material is conveyed to the image forming unit by the conveyance belt  9  stretched around rollers  9   a ,  9   b  and  9   c , and toner images of the respective colors are sequentially transferred onto the recording material. Accordingly, a multi-color image is formed on the recording material, and then, the recording material is heated and fixed by a fixing unit  10  including a pressure roller  10   a  as a pressure member and a heating film  10   b  as a heating member. Then, the recording material is discharged to a discharge tray  12  by a discharge roller  11 . 
     [Communication Interfaces] 
     Next, communication interfaces as communication units between the image forming apparatus main body  100  and the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  illustrated in  FIG. 1 , will be described. The optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  include optional control units  210 ,  220 ,  230 , and  240  and switches  215 ,  225 ,  235 , and  245 , respectively. The main body control unit  200  of the image forming apparatus main body  100  is connected in cascade (series) connection with the optional control units  210 ,  220 ,  230 , and  240  of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . 
     Three kinds of signals are used for interface signals: a clock signal, a command signal, and a status signal. The clock signal (hereinafter referred to as a “CLK signal”) is for taking synchronization in communication operation between the image forming apparatus and the optional sheet feeding apparatuses. The CLK signal is transmitted via a clock signal line. The command signal (hereinafter referred to as a “CLK signal”) is for transmitting data from the image forming apparatus main body  100  to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . The CMD signal is transmitted via a command signal line. The status signals (hereinafter referred to as “STS signals”) is for transmitting data from the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  to the image forming apparatus main body  100 . The STS signals are transmitted through a status signal line. The image forming apparatus main body  100  and the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  can communicate with each other by using the above-described signal lines. 
     In order to transmit and receive CLK signals, a CLK transmission signal  201  on the side of the main body control unit  200  is connected with CLK reception signals  211 ,  221 ,  231 , and  241  on the side of the optional control units  210 ,  220 ,  230 , and  240 , respectively. In order to transmit and receive CMD signals, a CMD transmission signal  202  on the side of the main body control unit  200  is connected with CMD reception signals  212 ,  222 ,  232 , and  242  on the side of the optional control units  210 ,  220 ,  230 , and  240 , respectively. In order to transmit and receive STS signals, an STS reception signal  203  on the side of the main body control unit  200  is connected with STS transmission signals  213 ,  223 ,  233 , and  243  on the side of the optional control units  210 ,  220 ,  230 ,  240 , respectively. 
     Further, in the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , the CMD reception signals  212 ,  222 ,  232 , and  242  are branched and input to interrupt ports as command interrupt signals (hereinafter referred to as “CMD interrupt signals”)  214 ,  224 ,  234 , and  244 . When each of the CMD interrupt signals is set to a Low level, an interrupt occurs. The switches  215 ,  225 ,  235 , and  245  can change the connection state (e.g., connection or disconnection) of the CMD signals of the optional control units  210 ,  220 ,  230 , and  240  in cascade connection. At a time of registering identification information (hereinafter referred to as ID information) to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , all of the switches  215 ,  225 ,  235 , and  245  are once disconnected. Then, the switches are sequentially connected from the one for the optional sheet feeding apparatus to which the ID information is to be registered, and each ID information is sequentially registered to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . 
     Although, in this example, four different optional sheet feeding apparatuses are connected, the number of the optional apparatuses is not limited thereto, and any number of optional apparatuses are connectable. Further, in this example, optional sheet feeding apparatuses are used for target apparatuses. However, target apparatuses are not limited to the sheet feeding apparatus, and any optional apparatuses connectable to the image forming apparatus main body  100 , for example, optional discharge apparatuses are also applicable. 
     [Descriptions of Control Block Diagram] 
       FIG. 2  is a control block diagram illustrating the image forming apparatus main body  100  and the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . The main body control unit  200  instructs the feed control unit  20   a  to feed a recording material, instructs the recording material conveyance control unit  32  to convey the recording material, and instructs the image forming control unit  31  to perform image forming to form an image on the conveyed recording material. The main body control unit  200  instructs the fixing control unit  33  to perform fixing control to fix a toner image formed onto the recording material and instructs the discharge control unit  34  to perform discharge control to discharge the recording material. The fixing control unit  33  performs separation control on the fixing nip portion, when the image forming apparatus main body  100  enters a sleep state, to prevent distortion of a fixing nip portion. The fixing control unit  33  then performs pressure control on the fixing nip portion when the image forming apparatus main body  100  returns from the sleep state. 
     The main body control unit  200  includes an ID non-registration broadcast communication unit  200   a  and an individual communication unit  200   b . The ID non-registration broadcast communication unit  200   a  communicates with the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  on a broadcast basis when the ID information is not registered. The individual communication unit  200   b  communicates with an individual optional sheet feeding apparatus corresponding to added ID information after the ID information registration. The main body control unit  200  issues commands to the optional control units  210 ,  220 ,  230 , and  240  via a serial interface (I/F). 
     The optional control units  210 ,  220 ,  230 , and  240  instruct the sheet feeding control units  20   b ,  20   c ,  20   d , and  20   e , respectively, to feed a recording material. In order to prevent marks of feed rollers  21   b ,  21   c ,  21   d , and  21   e  from remaining on the recording material, the sheet feeding control units  20   b ,  20   c ,  20   d , and  20   e  perform separation control on the feed rollers when the image forming apparatus main body  100  enters the sleep state. When the image forming apparatus main body  100  returns from the sleep state, the sheet feeding control units  20   b ,  20   c ,  20   d , and  20   e  performs contact control on the feed rollers. 
     [Communication Timing Chart: Individual Communication] 
       FIG. 3  is a timing chart illustrating communication operation between the image forming apparatus main body  100  and the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . The timing chart illustrates individual communication in which, after registering unique ID information to each of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , the image forming apparatus main body  100  performs communication by specifying the ID information. 
     According to the present exemplary embodiment, for command data and status data, one piece of data is formed by performing 8-bit data communication twice. The command data having 16-bit includes ID information, a command content, and a parity bit (P), as illustrated in  FIG. 3 . The status data having 16-bit includes an error bit (E) indicating the presence or absence of an error, a status content, and a parity bit (P), as illustrated in  FIG. 3 . 
     The optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  enable interrupts by the CMD interrupt signals  214 ,  224 ,  234 , and  244  before starting communication. According to the present exemplary embodiment, an interrupt can be accepted when each of the CMD interrupt signals  214 ,  224 ,  234 , and  244  is set to the Low level. The main body control unit  200  of the image forming apparatus main body  100  sets the CMD transmission signal  202  to the Low level to start communication operation. When an interrupt occurs with the CMD interrupt signals, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determine the start of communication operation and prepares for command reception. 
     The main body control unit  200  transmits the command data on the CMD transmission signal  202  in synchronization with the CLK transmission signal  201 . The optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  analyze the received command to determine whether the ID information included in the command data coincides with the  1 D information registered in the optional sheet feeding apparatuses.  FIG. 3  illustrates an example of a command supplied with the II) information=3 that indicates a command for the optional sheet feeding apparatus  103 . The optional sheet feeding apparatuses  101 ,  102 , and  104  as non-target apparatuses determine that the ID information in the command is different from the ID information registered therein and prepare return status data FFh (all bits set to High). The sheet feeding apparatus  103  as a target apparatus determines that the ID information. In the command coincides with the ID information registered therein, analyzes the received command, and prepares return status data. Then, the sheet feeding apparatus  103  transmits the status data on the STS transmission signal  233  in synchronization with the CLK transmission signal  201  for status transmission. 
     The STS reception signal  203  is a low-True wired-OR connection signal. When all of the STS transmission signals  213 ,  223 ,  233 , and  243  of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , respectively, are set to High, the STS reception signal  203  is also set to High. As a result, the status data of the STS reception signal  203  coincides with the STS transmission signal  233  transmitted from the optional sheet feeding apparatus  103 . The main body control unit  200  receives the STS reception signal  203 . 
     [Communication Timing Chart: ID Non-Registration Broadcast Communication] 
       FIGS. 4A and 4B  are timing charts illustrating communication operation between the image forming apparatus main body  100  and the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 .  FIGS. 4A and 4B  illustrate ID non-registration broadcast communication in which the image forming apparatus main body  100  communicates with all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  on a broadcast basis before registering unique ID information to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . The timing charts illustrated in  FIGS. 4A and 4B  indicate an example of a non-ready confirmation command. Specifically, the image forming apparatus main body  100  transmits a command supplied with the ID information=0, which indicates broadcasting, to all of the optional sheet feeding apparatuses, to determine whether any optional sheet feeding apparatus is not ready. 
     The main body control unit  200  transmits command data with the CMD transmission signal  202  in synchronization with the CLK transmission signal  201 . The optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  analyze the received command to determine whether the ID information included in the command data is the one registered therein or information indicating broadcasting. In this case, the ID information is data indicating broadcasting. The optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determine the data as a non-ready confirmation command for themselves. Then, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  transmit a signal to indicate whether they are ready to the main body control unit  200 . 
       FIG. 4A  illustrates a case where all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready. As an example, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determine whether they are ready, by detecting the open or closed state of the door by using a door sensor (not illustrated). If a door of one of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  is open, the one of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determines that it is not ready. If the door is not open, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determine that they are ready. In this case, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determine that they are ready and prepare return status data FFh (all bits set to High). Since the status data received by the STS reception signal  203  is FFh (all bits set to High), the main body control unit  200  determines that all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready. 
       FIG. 4B  illustrates a case where the optional sheet feeding apparatuses  101 ,  102 , and  104  are ready, and the optional sheet feeding apparatus  103  is not ready. The optional sheet feeding apparatuses  101 ,  102 , and  104  detect the open or closed state of the door by using the door sensor (not illustrated). Since the door is not open, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  determine that they are ready and prepare return status data FFh (all bits set to High). The optional sheet feeding apparatus  103  detects the open or closed state of the door by using a door sensor (not illustrated). Since the door is open, the optional sheet feeding apparatus  103  determines that the optional sheet feeding apparatus  103  itself is not ready and prepares return status data 00h (all bits set to Low). Since the status data received with the STS reception signal  203  is 00h (all bits set to Low), the main body control unit  200  determines any one optional apparatus is not ready. Specifically, although the main body control unit  200  cannot determine which optional sheet feeding apparatus is not ready, the main body control unit  200  can determine that at least one of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  is not ready. 
     As illustrated in  FIGS. 4A and 4B , the main body control unit  200  can determine whether all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready by performing broadcast communication. After the main body control unit  200  determines that all of the optional sheet feeding apparatuses are ready, the main body control unit  200  can perform the following processing such as the ID registration. Although the main body control unit  200  determines whether the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready based on the open state of the door, the main body control unit  200  may determine they are ready based on the open state of a sheet feed tray or other state. In other words, the determination criterion can be suitably set. At least, the main body control unit  200  can confirm whether all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready through broadcast communication, even in a state where the ID information is not registered. 
     [Sleep Return Operation] 
       FIG. 5  is a timing chart illustrating a processing flow in which the main body control unit  200  of the image forming apparatus main body  100  controls a sleep return operation of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . For example, when the image forming apparatus main body  100  enters the sleep state, the main body control  200  turns off power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  and sets the  1 D information to be not registered. When the image forming apparatus main body  100  enters the sleep state, the main body control unit  200  also sets the fixing nip portion to be changed from the contact state to the separated state. The description is given of sleep return processing of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , and the fixing nip portion changed from the separated state to the contact state, when the image forming apparatus main body  100  returns from the sleep state. 
       FIG. 5A  illustrates a method for confirming whether any one of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  is not ready via the ID non-registration broadcast communication unit  200   a  before registering the ID information according to the present exemplary embodiment. When the main body control unit  200  determines to perform a sleep return, the main body control unit  200  turns on power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  and waits for the activation of the optional sheet feeding apparatuses. Then, the main body control unit  200  confirms whether all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready through broadcast communication. When all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are determined to be ready, the main body control unit  200  performs processing for registering unique ID information to each of the optional sheet feeding apparatuses. In parallel with the ID registration, the main body control unit  200  also performs processing for changing the fixing nip portion from the separated state to the contact state. Upon completion of the processing, the main body control unit  200  determines that the sleep return operation is completed. If the main body control unit  200  has received a print command, the main body control unit  200  starts printing. 
     As a comparative example,  FIG. 5B  illustrates a method for confirming the ready state of each optional sheet feeding apparatus after registering unique ID information to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . Referring to  FIG. 5B , when the main body control unit  200  determines to perform a sleep return, the main body control unit  200  turns on power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  and waits for the activation of the optional sheet feeding apparatuses. Then, the main body control unit  200  registers unique ID information to all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  through serial communication. The main body control unit  200  also confirms whether all of the optional sheet feeding apparatuses are ready through serial communication. When all of the optional sheet feeding apparatuses are determined to be ready, the main body control unit  200  performs processing for changing the fixing nip portion from the separated state to the contact state. Upon completion of the processing of the fixing nip portion, the main body control unit  200  determines that the sleep return operation is completed. If the main body control unit  200  has received a print command, the main body control unit  200  starts printing. 
     According to the present exemplary embodiment, as described above, the main body control unit  200  can confirm at one time whether all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready through broadcast communication. In other words, the main body control unit  200  can confirm the ready state of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  through one-time communication. When all of the sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are determined to be ready, it becomes possible to perform in parallel processing for registering the ID information as a sleep return operation in the optional sheet feeding apparatuses and processing for changing the fixing nip portion to the contact state as a sleep return operation in the image forming apparatus main body  100 . Accordingly, the use of control according to the present exemplary embodiment makes it possible to reduce the sleep return time in comparison with the comparative example. 
       FIG. 6  is a flowchart illustrating the sleep return operation according to the present exemplary embodiment. In step S 601 , the main body control unit  200  turns on power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . In step S 602 , the main body control  200  waits for the activation of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . When the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are activated, the ID information is not registered and the switches  215 ,  225 ,  235 , and  245  are in connection state. 
     In step S 603 , the main body control unit  200  collectively transmits a non-ready command to all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  through broadcast communication via the ID non-registration broadcast communication unit  200   a . In step S 604 , the main body control unit  200  receives the STS transmission signals from the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  to check whether any optional sheet feeding apparatus is not ready. 
     When the main body control unit  200  determines that all of the optional sheet feeding apparatuses are ready (YES in step S 604 ), the processing proceeds to step S 605 . In step S 605 , the main body control unit  200  issues a fixing and pressurization command to change the fixing nip portion to the contact state as a sleep return operation in the image forming apparatus main body  100 . In step S 606 , the main body control unit  200  performs the sleep return operation in the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  in parallel with the sleep return operation in the image forming apparatus main body  100 . The main body control unit  200  transmits a switch disconnection command to each optional sheet feeding apparatus via the ID non-registration broadcast communication unit  200   a . Upon reception of the switch disconnection command, each optional sheet feeding apparatus disconnects a switch. 
     In step S 607 , the main body control unit  200  determines the ID information to be registered to each optional sheet feeding apparatus. Specifically, the main body control unit  200  uniquely determines the ID information by setting the ID information to 1, 2, and 3 in this order. In step S 608 , the main body control unit  200  transmits an ID registration command supplied with the ID information to be registered to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . In this case, the main body control unit  200  first transmits an ID registration command supplied with the ID information=1. Upon reception of the ID registration command, each optional sheet feeding apparatus registers the ID information, changes the switch to the connection state, and transmits an ID registration notification status (meaning the completion of the ID registration) to the main body control unit  200 . 
     In step S 609 , the main body control unit  200  determines Whether the received status is an ID registration notification status. When the received status is an ID registration notification status (YES in step S 609 ), another optional sheet feeding apparatus may still be connected, and thus the processing returns to step S 607 . In step S 607 , the main body control unit  200  determines the ID information=2. The main body control unit  200  transmits an ID registration command supplied with the ID information=2 again to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . The main body control unit  200  repeats this sequence so that the ID information=1, 2, 3, and 4 is registered to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , respectively. The ID registration notification status is not returned in response to the ID registration command with the ID information=5. Thus, the main body control unit  200  determines that the ID registration has been completed for all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , and that the ID registration has ended with the ID information=4. On the other hand, when the ID registration notification status is not returned (NO in step S 609 ), the main body control unit  200  determines that the ID registration is completed, and the processing proceeds to step S 610 . In step S 610 , the main body control unit  200  confirms whether fixing and pressurization operations are completed. When these operations are completed, the main body control unit  200  determines that the sleep return operation is completed. 
     On the other hand, when the main body control unit  200  determines that any one optional sheet feeding apparatus is not ready (NO in step S 604 ), the processing proceeds to step S 611 . In step S 611 , the main body control unit  200  does not issue a fixing and pressurization command as a sleep return operation by the image forming apparatus main body  100 , and suspends the command issuance. The main body control unit  200  then registers the ID information to each optional sheet feeding apparatus. Processing in steps S 611  to S 614  is similar to the processing in steps S 606  to S 609 , and thus redundant descriptions thereof will be omitted. 
     In step S 615 , the main body control unit  200  transmits a state confirmation command to each optional sheet feeding apparatus by using the registered ID information and then determines which optional sheet feeding apparatus is not ready. In step S 616 , the main body control unit  200  determines whether the ready state confirmation is completed for all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . When the ready state confirmation is completed for all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  (YES in step S 616 ), the processing ends. Although the main body control unit  200  ends the processing when the ready state confirmation is completed, as an example, the present disclosure is not limited thereto. When the main body control unit  200  confirms that all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  have become ready, the main body control unit  200  may issue the suspended fixing and pressurization command. 
     As described above, the main body control unit  200  confirms at one time whether all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready through broadcast communication. In other words, the main body control unit  200  confirms the ready state of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  through one-time communication. When all of the sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are determined to be ready, it becomes possible to perform in parallel processing for registering the ID information as a sleep return operation in the optional sheet feeding apparatuses and processing for changing the fixing nip portion to the contact state as a sleep return operation in the image forming apparatus main body  100 . Accordingly, the time of the sleep return operation can be reduced. 
     Although, in the present exemplary embodiment, power is turned off when the optional sheet feeding apparatuses enter the sleep state as an example, the present disclosure is not limited thereto. The present exemplary embodiment is applicable to a case where broadcast communication is performed before registering the ID information of the optional sheet feeding apparatuses, for example, when power of the image forming apparatus is turned off not when the sleep state is entered. For either case, processing time can be reduced, in a state where the ID information is not registered, by first performing the state confirmation on the optional sheet feeding apparatuses and then, after the state confirmation, performing in parallel the ID information registration and other return processing. 
     Although the present exemplary embodiment has been described above centering on an example case where four different optional sheet feeding apparatuses are connected, the present disclosure is not limited thereto. One or a plurality of optional sheet feeding apparatuses can be connected. Regardless of the number of optional sheet feeding apparatuses, processing time can be reduced, in a state where the ID information is not registered, by first performing the state confirmation on the optional sheet feeding apparatuses and then, after the state confirmation, performing in parallel the ID information registration and other return processing. In consideration of serial communication with a plurality of optional apparatuses as in conventional cases, processing time can be decreased with increasing number of optional apparatuses to be connected. In addition to sheet feeding apparatuses, similar control is also applicable to other optional apparatuses, such as a sheet discharge apparatus, as long as the optional apparatus is capable of communicating with the image forming apparatus main body  100 . 
     According to the first exemplary embodiment, controlling the contact states of the nip portion is used as a sleep return operation in the image forming apparatus main body  100 . According to a second exemplary embodiment, controlling contact states of the feed rollers is used as a sleep return operation. For configurations similar to the ones according to the first exemplary embodiment, such as the configuration of the image forming apparatus, detailed descriptions thereof will be omitted. 
     [Sleep Return Operation] 
       FIG. 7  is a timing chart illustrating a processing flow in which the main body control unit  200  of the image forming apparatus main body  100  controls the sleep return operation of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . For example, when entering the sleep state, the main body control unit  200  turns off power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  and sets the ID information to be not registered. When entering the sleep state, the main body control unit  200  sets the feed rollers  21   b ,  21   c ,  21   d , and  21   e  of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , respectively, to be changed to the separated state. The following describes a case where contact processing of the feed rollers  21   b ,  21   c ,  21   d , and  21   e  is performed in parallel with the ID information registration to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , when returning from the sleep state. 
       FIG. 7A  illustrates a method for confirming whether any one of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  is not ready via the ID non-registration broadcast communication unit  200   a  before registering the ID information according to the present exemplary embodiment. When the main body control unit  200  determines to perform a sleep return, the main body control unit  200  turns on power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  and waits for the activation of the optional sheet feeding apparatuses. Then, the main body control unit  200  confirms whether all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  are ready through broadcast communication. When all of the optional sheet feeding apparatuses are determined to be ready, the main body control unit  200  performs processing for registering unique ID information to each of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . Further, the main body control unit  200  performs processing for changing the teed rollers  21   b ,  21   c ,  21   d , and  21   e  from the separated state to the contact state. Upon completion of the processing, the main body control unit  200  determines that the sleep return operation is completed. If the main body control unit  200  has received a print command, the main body control unit  200  starts printing. 
     As a comparative example,  FIG. 7B  illustrates a method for confirming the ready state of each optional sheet feeding apparatus after registering unique ID information to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . Referring to  FIG. 7B , when the main body control unit  200  determines to perform a sleep return, the main body control unit  200  turns on power of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  and waits for the activation of the optional sheet feeding apparatuses. Then, the main body control unit  200  registers unique ID information to all of the optional sheet feeding apparatuses through serial communication. Then, the main body control unit  200  also confirms whether all of the optional sheet feeding apparatuses are ready through serial communication. When all of the optional sheet feeding apparatuses are determined to be ready, the main body control unit  200  performs processing for changing the feed rollers from the separated state to the contact state. Upon completion of the processing of the feed rollers, the main body control unit  200  determines that the sleep return operation is completed. If the main body control unit  200  has received a print command, the main body control unit  200  starts printing. 
     According to the present exemplary embodiment, as described above, the main body control unit  200  can confirm at one time whether all of the optional sheet feeding apparatuses are ready through broadcast communication. In other words, the main body control unit  200  can confirm the ready state of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  through one-time communication. When all of the sheet feeding apparatuses are determined to be ready, it becomes possible to perform in parallel processing for registering the ID information and processing for changing the feed rollers to the contact state as sleep return operations in the optional sheet feeding apparatuses. Accordingly, the use of control according to the present exemplary embodiment makes it possible to reduce the sleep return tithe in comparison with the comparative example. 
       FIG. 8  is a flowchart illustrating the sleep return operation according to the present exemplary embodiment. Processing in steps S 801  to S 804  is similar to the processing in steps S 601  to S 604  illustrated in  FIG. 6  according to the first previous exemplary embodiment, and detailed descriptions thereof will be omitted. 
     When the main body control unit  200  determines that all of the optional sheet feeding apparatuses are ready (YES in step S 804 ), the processing proceeds to step S 805 . In step S 805 , the main body control unit  200  issues a standby operation command to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  via the ID non-registration broadcast communication unit  200   a . Upon reception of the standby operation command, the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  perform control to change the feed rollers from the separated state to the contact state as a standby operation when returning from the sleep state. In step S 806 , in parallel with the processing for changing the feed rollers from the separated state to the contact state, the main body control unit  200  transmits a switch disconnection command to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  via the ID non-registration broadcast communication unit  200   a . Upon reception of the switch disconnection command, each optional sheet feeding apparatus disconnects the switch. 
     In step S 807 , the main body control unit  200  determines the ID information to be registered to each optional sheet feeding apparatus. Specifically, the main body control unit  200  uniquely determines the ID information by setting the ID information to 1, 2, and 3 in this order. In step S 808 , the main body control unit  200  transmits an ID registration command supplied with the ID information to be registered to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . In this case, the main body control unit  200  first transmits an ID registration command supplied with the ID information=1. Upon reception of the ID registration command, each optional sheet feeding apparatus registers the ID information, changes the switch to the connection state, and transmits an ID registration notification status (meaning the completion of the registration) to the main body control unit  200 . 
     In step S 809 , the main body control unit  200  determines whether the received status is an ID registration notification status. When the received status is an ID registration notification status (YES in step S 809 ), another optional sheet feeding apparatus may still be connected, and thus the processing returns to step S 807 . In step S 807 , the main body control unit  200  determines the ID information=2. The main body control unit  200  transmits an ID registration command supplied with the ID information=2 again to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . The main body control unit  200  repeats this sequence so that the ID information=1, 2, 3, and 4 is registered to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , respectively. The ID registration notification status is not returned in response to the ID registration command with the ID information=5. Thus, the main body control unit  200  determines that the ID registration has been completed for all of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , and that the ID registration has ended with the ID information=4. When the ID registration notification status is not returned (NO in step S 809 ), the main body control unit  200  determines that the ID registration is completed, and the processing proceeds to step S 810 . In step S 810 , the main body control unit  200  transmits a standby operation confirmation command to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . In step S 811 , in response to the standby operation confirmation command, the main body control unit  200  confirms whether contact control for the feed rollers is completed in each optional sheet feeding apparatus. When the contact control is completed, the main body control unit  200  determines that the sleep return operation is completed (YES in step S 811 ). 
     On the other hand, when the main body control unit  200  determines that any one optional sheet feeding apparatus is not ready (NO in step S 804 ), the processing proceeds to step S 812 . In step S 812 , the main body control unit  200  does not issue a standby operation command to the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 , and suspends the command issuance. Further, the main body control unit  200  registers the ID information to each optional sheet feeding apparatus. Processing in steps S 812  to S 815  is similar to that in steps S 806  to S 809 , and descriptions thereof will be omitted. 
     In step S 816 , the main body control unit  200  transmits a state confirmation command to each optional sheet feeding apparatus by using the registered ID information and then determines which optional sheet feeding apparatus is not ready. In step S 817 , the main body control unit  200  determines whether the ready state confirmation is completed for all of the optional sheet feeding apparatuses. When the ready state confirmation is completed for all of the optional sheet feeding apparatuses (YES in step S 817 ), the processing ends. Although the main body control unit  200  ends the processing when the ready state confirmation is completed, the present disclosure is not limited thereto. When the main body control unit  200  confirms that all of the optional sheet feeding apparatuses have become ready, the main body control unit  200  may perform the suspended feed roller contact control. 
     As described above, the main body control unit  200  can confirm at one time whether all of the optional sheet feeding apparatuses are ready through broadcast communication. In other words, the main body control unit  200  confirms the ready state of the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104  through one-time communication. When all of the sheet feeding apparatuses are determined to be ready, it is possible to perform in parallel processing for registering the ID information and processing for changing the feed rollers to the contact state as sleep return operations in the optional sheet feeding apparatuses  101 ,  102 ,  103 , and  104 . This enables reducing the time of the sleep return operation. Although, in the present exemplary embodiment, feed roller contact control is performed as an example of a standby operation of the optional sheet feeding apparatuses, the present disclosure is not limited thereto. For example, control for elevating the sheet feed tray is also applicable. It is also possible to perform in parallel the standby operation of the optional sheet feeding apparatuses and the standby operation of the image forming apparatus main body  100  according to the first exemplary embodiment. 
     The present disclosure makes it possible to reduce downtime. 
     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 broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2018-167372, filed Sep. 6, 2018, which is hereby incorporated by reference herein in its entirety.