Abstract:
An image forming apparatus includes an image forming apparatus body provided with an image formation unit and plural paper feeding apparatuses. Paper conveyance paths of the plural paper feeding apparatuses are daisy-chained with respect to the image forming apparatus body. An output unit outputs an instruction signal which instructs a specified paper feeding apparatus to start feeding a paper. A paper feed unit feeds the paper upon receipt of the instruction signal. A recognition unit recognizes a delay time until an analysis that the instruction signal is a paper feed instruction. A correction unit corrects an output timing of the instruction signal based on the delay time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2009-052110 filed Mar. 5, 2009. 
     BACKGROUND 
     1. Technical Field 
     The invention relates to an image forming apparatus, a computer readable medium, a paper feed control method, and an image forming system. 
     2. Related Art 
     A technique in which controllers of each of an image forming apparatus and a peripheral device (a large capacity paper tray) communicate with each other via a serial communication line and a hotline is provided. Communications are not easily influenced by noise, whereby an accuracy of conveying a paper from a paper tray to the image forming apparatus is improved. 
     SUMMARY 
     According to a first aspect of the invention, there is provided an image forming apparatus including: an image forming apparatus body provided with an image formation unit which forms an image on a paper based on image information; a plurality of paper feeding apparatuses, each of the plurality of paper feeding apparatuses accommodating the paper therein and feeding the paper to the image forming apparatus body, paper conveyance paths of the plurality of paper feeding apparatus being daisy-chained with respect to the image forming apparatus body; an output unit that, using a signal transmission path, outputs an instruction signal which instructs a specified one of the paper feeding apparatuses to start feeding the paper when the image is formed by the image formation unit; paper feed units disposed in the plurality of paper feeding apparatuses and that feed the paper upon receipt of the instruction signal from the output unit; a recognition unit disposed in the image forming apparatus body and that recognizes a delay time of each of the plurality of paper feeding apparatuses the delay time being from after the instruction signal is received until it is determined by analysis that the instruction signal is a paper feed instruction; and a correction unit that corrects an output timing of the instruction signal from the output unit based on the delay time of each of the paper feeding apparatuses recognized by the recognition unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a general view showing the configuration of an image forming system in the present exemplary embodiment; 
         FIG. 2  is a schematic view showing the configuration of the image forming system in the present exemplary embodiment; 
         FIG. 3  is a block diagram illustrating the configuration of hardware in the image forming system in the exemplary embodiment; 
         FIGS. 4A to 4C  each are charts schematically illustrating flows of noise detection filtering; 
         FIG. 5A  is a timing chart illustrating transmission and reception of a hot line signal, to which the present exemplary embodiment is not applied; 
         FIG. 5B  is a timing chart illustrating transmission and reception of a hot line signal in the exemplary embodiment; 
         FIGS. 6A and 6B  are diagrams schematically illustrating a flow of transmission of a delay time of a paper feeding apparatus; 
         FIG. 7  is a flowchart illustrating a delay time transmission routine in a paper feed controller in the exemplary embodiment; and 
         FIG. 8  is a flowchart illustrating a paper feed instruction routine by a main controller in the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description will be given below of exemplary embodiments according to the present invention with reference to the attached drawings. Explanation will be made on an image forming apparatus for forming an image by electrophotography, to which the invention is applied. 
     (Configuration of Image Forming System) 
       FIG. 1  is a general view showing the configuration of an image forming system  10  including an image forming apparatus  12  in the present exemplary embodiment. The image forming system  10  in the exemplary embodiment is constituted of the image forming apparatus  12  and external paper feeding apparatuses  14 A,  14 B, and  14 C (generically called “a paper feeding apparatus  14 ”) for feeding a recording paper P. The image forming apparatus  12  and the paper feeding apparatus  14  are connected to each other via a connector, not shown. In the exemplary embodiment, the image forming system  10  is provided with the paper feeding apparatuses  14 A,  14 B, and  14 C, however members to be provided are not limited to these. 
     The image forming apparatus  12  is adapted to form an image on an intermediate transfer member based on image data, transfer the image formed on the intermediate transfer member onto a paper, and form (i.e., print) an image on the paper. The paper feeding apparatus  14  is an external type that feeds the paper to the image forming apparatus  12 . A post-processing device may be connected to the image forming apparatus  12 , thereby post-processing (e.g., stapling, punching, folding (into two or three leaves), sticking, trimming, or the like) the paper having the image formed thereon in the image forming apparatus  12 . 
     (Schematic Configuration of Image Forming System) 
     As shown in  FIG. 2 , the paper feeding apparatus  14 A is connected to the image forming apparatus  12  in the image forming system  10  in the exemplary embodiment. The other paper feeding apparatuses  14  will be omitted below. 
     The image forming apparatus  12  includes an image forming engine  16  that carries out image forming processing on the recording paper P based on the image data. The image forming engine  16  corresponds to an image formation unit. 
     The image forming engine  16  is provided with a photoreceptor drum  20 . The photoreceptor drum  20  is rotated at a predetermined speed in a direction indicated by an arrow A in  FIG. 2  by a driving force of a driving unit such as a motor, not shown. A charger  22  that electrically charges an peripheral surface of the photoreceptor drum  20  is disposed at the upper right portion of the photoreceptor drum  20  in  FIG. 2 . 
     An optical beam scanner  24  is arranged at the upper left side of the charger  22  in  FIG. 2 . The optical beam scanner  24  scans the peripheral surface of the photoreceptor drum  20  electrically charged by the charger  22  with a light beam in parallel to an axis of the photoreceptor drum  20  based on image data. In this manner, an electrostatic latent image is formed on the peripheral surface of the photoreceptor drum  20 . For the sake of simple explanation, only one set of the photoreceptor drum  20  and the like is shown in  FIG. 2 . 
     A developing device  26  is disposed at the left side of the photoreceptor drum  20  in  FIG. 2 . The developing device  26  includes a developing roller  26 A, and contains a toner therein. The developing roller  26 A allows the toner to adhere onto the electrostatic latent image formed on the periphery of the photoreceptor drum  20 , and then, develops the image. 
     Under the photoreceptor drum  20  in  FIG. 2 , an endless intermediate transfer belt  28  is arranged. The intermediate transfer belt  28  is wound around plural rollers  29 , and further, its periphery is brought into contact with the peripheral surface of the photoreceptor drum  20 . Each of the rollers  29  rotates the intermediate transfer belt  28  at the same rotational speed as that of the photoreceptor drum  20  in a direction indicated by an arrow B in  FIG. 2  by a driving force transmitted from a motor, not shown. 
     A transfer device  32  is disposed at a contact position between the photoreceptor drum  20  and the intermediate transfer belt  28  and at an opposite side of the photoreceptor drum  20  such that the transfer device  32  holds the intermediate transfer belt  28  with the photoreceptor drum  20 . The toner image developed on the photoreceptor drum  20  is transferred onto the intermediate transfer belt  28  by the transfer device  32  at a transfer position in which the transfer device  32  contacts with the intermediate transfer belt  28  according to the rotation of the photoreceptor drum  20 . 
     A charge removal and cleaner device  30 , which has functions of electrically discharging the periphery of the photoreceptor drum  20  and removing an unnecessary toner remaining on the periphery, is arranged at a downstream side of the transfer position on the periphery of the photoreceptor drum  20  in a rotational direction. After transferring the toner onto the intermediate transfer belt  28 , a region which has carried the transferred toner image, on the periphery of the photoreceptor drum  20  is cleaned by the charge removal and cleaner device  30 . 
     Plural paper trays  34  (four in the exemplary embodiment) are installed under the image forming engine  16  in the image forming apparatus  12 . Each of the paper trays  34  may change a size of a recording paper P which is to be accommodated therein by adjusting a position of an inside partition or the like. The plural recording papers P are accommodated inside of each of the paper trays  34 . Plural mechanical switches, not shown, for detecting the size of the accommodated recording paper P are disposed in each of the paper trays  34 . When each of the mechanical switches is brought into contact with the accommodated recording paper P, the combination of turning-on and off is changed according to the size of the recording paper P. The size of the accommodated recording paper P is detected based on a combination of turning-on and off of the mechanical switches. 
     A taking-out roller  36  is disposed at the diagonally upward to the left of each of the paper trays  34  in  FIG. 2 . Plural roller pairs  38  are arranged in sequence at a downstream side in the taking-out direction of the recording paper P of the taking-out roller  36  in each of the paper trays  34 . The uppermost recording paper P accommodated on each of the paper trays  34  is taken out from the paper tray  34  according to the rotation of the taking-out roller  36 , and then, the paper is conveyed to the intermediate transfer belt  28  in synchronism with the transferred toner image via a conveyance path  40  by the plural roller pairs  38 . 
     At the center left portion of the image forming apparatus  12  in  FIG. 2 , there is provided a manual tray  42 , on which the recoding paper P is manually placed. A taking-out roller  44  is disposed at the diagonally upward to the right of the manual tray  42  in  FIG. 2 . The recoding paper P placed on the manual tray  42  is guided onto the conveyance path  40  by the taking-out roller  44  and the roller pairs  38 , and then, is conveyed to the intermediate transfer belt  28  through the conveyance path  40 . 
     At the lower portion of the image forming apparatus  12  in  FIG. 2 , there is provided a paper inlet  46 , through which the recoding paper P is fed from the paper feeding apparatus  14 A. The recoding paper P fed through the paper inlet  46  is guided at a portion in which a recoding paper P conveyed from a paper tray  34  of the second stage conveys on the conveyance path  40  by the roller pairs  38 , and then, the paper P is conveyed to the intermediate transfer belt  28  through the conveyance path  40 . 
     A transfer device  48  is disposed at an opposite side of the lowermost roller  29  sandwitching the intermediate transfer belt  28 . The recoding paper P conveyed to the intermediate transfer belt  28  through the conveyance path  40  is fed between the intermediate transfer belt  28  and the transfer device  48 , and then, the toner image on the intermediate transfer belt  28  is transferred on the recording paper P by the transfer device  48 . An endless conveyor belt  52  wound around two rollers  50  is disposed at a downstream side of the transfer device  48  in the conveyance direction of the recoding paper P. The recoding paper P having the toner image transferred thereonto is conveyed to a fixing device  54  via the conveyor belt  52 , followed by melting and fixing by the fixing device  54 , and then, the recording paper P is ejected outside of the image forming apparatus  12  onto a ejecting tray, not shown. 
     The image forming apparatus  12  is provided with a double-sided recording reverse path  56 . The reverse path  56  includes plural roller pairs  58 . The recoding paper P having the image recorded on either side thereof is reversed on the reverse path  56 , and then, is conveyed to the intermediate transfer belt  28 . Images may be recorded on both sides of the recoding paper P. 
     A connecting unit  68  has a paper outlet  71  at a position facing to the paper inlet  46  provided in the image forming apparatus  12 . The paper feeding apparatus  14 A is installed in such a manner that the paper outlet  71  faces the paper inlet  46 . 
     A paper feed unit  62  includes plural paper trays  70  (two in the exemplary embodiment). Each of the paper trays  70  also may contain the recording papers P of various sizes therein by adjusting the position of an inside partition or the like. The plural recording papers P are accommodated inside of each of the paper trays  70 . Each of the paper trays  70  includes plural mechanical switches, not shown, for detecting the size of the accommodated recording paper P, like the above-described paper trays  34 . 
     A taking-out roller  72  is disposed at a diagonally upward to the right of each of the paper trays  70  in the paper feed unit  62  in  FIG. 2 . Plural roller pairs  74  are arranged in sequence from a downstream side in the recording paper P taking-out direction of the taking-out roller  72  in the paper feed unit  62 . The recording paper P is taken out from the paper tray  70  according to the rotation of the taking-out roller  72 , and then, is conveyed to the paper outlet  71  via a conveyance path  80  provided in the connecting unit  68  by the plural roller pairs  74 . 
     The recording paper P conveyed to the paper outlet  71  is fed to the image forming apparatus  12  through the paper inlet  46 , and then, the recording paper P is conveyed to the intermediate transfer belt  28  via the conveyor path  40  by the roller pairs  38 . 
     In the paper feeding apparatus  14 A, a first paper detection sensor  84  is disposed on the conveyor path  80  and at an upstream side of the paper outlet  71  in the conveyance direction. The first paper detection sensor  84  detects whether or not the recording paper P exists at a position at which the sensor  84  faces the recording paper P, and outputs a signal indicating the existence of the recording paper P. 
     The paper feeding apparatuses  14 B and  14 C, not shown, also have a similar configuration. Recording papers P accommodated in the paper feeding apparatuses  14 B and  14 C are taken from paper trays  70  according to rotation of taking-out rollers  72 , and then, are conveyed to a joining unit  66  in the paper feeding apparatus  14 A. In the joining unit  66 , the recording paper P reaches at a confluence portion between a conveyor path  82  and the conveyor path  80  inside of the connecting unit  68  by plural roller pairs  76  and the plural roller pairs  74 , and then, the recording paper P is conveyed to the paper outlet  71  through the conveyor path  80 . A second paper detection sensor  86  is disposed at an upstream side of the confluence portion between the conveyor path  82  and the conveyor path  80  in the conveyance direction, and thus the sensor  86  detects whether or not the recording paper P exists at a position at which the sensor  86  faces the recording paper P. 
     (Control System of Image Forming System  10 ) 
     As illustrated in  FIG. 3 , the image forming apparatus  12  and the plural paper feeding apparatuses  14  are daisy-chained in the image forming system  10  in the exemplary embodiment. 
     The image forming apparatus  12  manages and controls all the processing, and includes a main controller  90  and a memory  92 . The paper feeding apparatus  14  includes a paper feed controller  94  ( 94 A to  94 C) for controlling the entire apparatus  14  and a memory  96  ( 96 A to  96 C). The main controller  90  corresponds to an output unit, a recognition unit, and a correction unit. 
     The image forming apparatus  12  (i.e., the main controller  90 ) and the paper feeding apparatuses  14  (i.e., the paper feed controllers  94 ) are connected to each other via an interactively receivable serial communication line  100  and a hot line  102 . The hot line  102  is adapted to carry a direct electric signal which is unidirectionally output from the main controller  90  to the paper feed controller  94 . The electric signal is off in a normal state, and the electric signal is turned on when the paper is started to be fed to the paper tray  70  in the paper feeding apparatus  14 . In other words, the signal triggers feeding in the paper feeding apparatus  14 . The paper feed controller  94  corresponds to a paper feed unit. 
     The paper feed controller  94  performs detection filtering (i.e., periodic software filtering) to avoid an influence by noise in detecting the signal on the hot line. Therefore, the filtering induces a delay in signal detection. 
     For example, as illustrated in  FIG. 4A , an ON instruction (i.e., an instruction to feed a paper) is determined to have been sent when an ON signal via the hot line  102  is successively detected twice at periods 10 ms apart. Specifically, filtering is performed at periods 10 ms apart (in 10 ms cycles), whereby if an ON signal is not detected successively, that is, if an ON signal is detected only once, the signal is determined to be noise. If an ON signal is successively detected twice, an ON instruction is determined to have been sent. Therefore, if an ON signal begins before the period at which the first detection is made, since the detection timing is constant, a delay of from 10 ms to 20 ms until the second detection is made arises. 
       FIG. 4B  illustrates that ON is determined when the ON signal on the hot line  102  is successively detected twice at periods 50 ms apart. In this case, a delay in signal detection of 50 ms to 100 ms occurs. 
       FIG. 4C  illustrates that ON is determined when the ON signal on the hot line  102  is successively detected quadruple at periods 10 ms apart. In this case, a delay in signal detection of 30 ms to 40 ms occurs. 
     As illustrated in  FIG. 5A , even if the main controller  90  outputs a paper feed start request hot line signal (i.e., an ON signal) as an instruction signal to the paper feed controller  94  at a predetermined paper feed start request timing (X ms), which is determined in design, from a paper feed control reference timing of an upstream paper feeding apparatus, a delay in signal detection (a signal detection filtering delay time=Y ms) occurs at the paper feed controller  94 . 
     When the plural paper feeding apparatuses  14  are daisy-chained to the image forming apparatus  12 , the delays in signal detection due to the filtering are accumulated in a paper feeding apparatus  14  which is disposed at more downstream side. 
     In the exemplary embodiment, the main controller  90  acquired in advance a delay time of each of the paper feed controllers  94  via the serial communication line  100 . In this manner, the main controller  90  outputs the paper feed start request hot line signal earlier by the delay time (i.e., X−Y ms), and thus, the paper feed controller  94  detects the signal at the predetermined paper feed start request timing (i.e., X ms) (see  FIG. 5B ). 
     More specifically, as illustrated in  FIG. 6A , upon receipt of a notification command of the delay time of the paper feeding apparatus  14 C from the main controller  90  (a use signal which indicates that the main controller  90  intends to use the paper feeding apparatus  14 C), the paper feed controller  94 C acquires its own delay time (X ms) from the memory  96 C. The paper feed controller  94 C writes the delay time in a communication command, and then transmits the command, as a signal in response to the use signal, to the paper feed controller  94 B which is adjacent to the controller  94 C at the upstream side thereof. 
     The paper feed controller  94 B acquires its own delay time (Y ms) from the memory  96 B upon receipt of the communication command. Thereafter, the paper feed controller  94 B adds its own delay time to the delay time written in the communication command (X+Y ms). The paper feed controller  94 B replaces the delay time in the communication command with the added delay time, and then, transmits the replaced delay time to the paper feed controller  94 A (i.e., the paper feeding apparatus  14 A) which is adjacent to the controller  94 B at the upstream side. 
     In a similar manner, the paper feed controller  94 A adds its own delay time (Z ms) acquired from the memory  96 A to the delay time of the received communication command (X+Y+Z ms). 
     The main controller  90  acquires the communication command, and thus, stores the delay time (X+Y+Z ms) of the paper feed controller  94 C (i.e., the paper feeding apparatus  14 C) in the memory  92 . Accordingly, the delay times of the paper feed controllers  94  are acquired. Alternatively, the delay times of the paper trays  70  in the paper feeding apparatuses  14  may be stored in the memory  92 . 
     In the exemplary embodiment, the delay times of the paper feed controllers  94  (or the paper trays  70 ) are acquired, it is not limited to this. For example, delay times of the paper feed controllers  94  may be acquired by receiving a single communication command which has delay times of the paper feed controllers  94  written therein. 
     More specifically, as illustrated in  FIG. 6B , the main controller  90  transmits a notification command of a delay time to the paper feed controller  94 C which is disposed at the most downstream side. The paper feed controller  94 C transmits a communication command which has its own delay time (X ms) written at the top thereof to the paper feed controller  94 B which is adjacent to the controller  94 C at the upstream side based on the command from the main controller  90 . 
     The paper feed controller  94 B shifts down the delay time of the paper feed controller  94 C written at the top of the communication command, and then, writes its own delay time (Y ms) in the paper feed controller  94 B at the top of the communication command. Thereafter, the paper feed controller  94 B transmits the communication command to the paper feed controller  94 A. 
     Likewise, the paper feed controller  94 A shifts down the delay time written in the communication command, and then, writes its own delay time (Z ms) at the top of the communication command, so as to transmit it to the main controller  90 . 
     The main controller  90  determines that the delay time (Z ms) written at the top of the communication command is a delay time of the paper feeding apparatus  14 A which is directly connected to the image forming apparatus  12 . Similarly, the main controller  90  determines that the delay time (Y ms) written under the delay time (Z ms) is a delay time of the paper feeding apparatus  14 B which is connected to the paper feeding apparatus  14 A, and further, that the delay time (X ms) written under the delay time (Y ms) is a delay time of the paper feeding apparatus  14 C which is connected to the paper feeding apparatus  14 B. 
     In other words, the main controller  90  finds that a delay time which is written more upward on the communication command corresponds to a paper feeding apparatus  14  which is disposed at more upstream side. Additionally, the main controller  90  finds from the number of delay times written in the communication command that the three paper feeding apparatuses  14  are connected to the image forming apparatus  12 . 
     A delay time may be written without shifting down a preceding delay time, and may be written under a preceding delay time in the communication command. 
     Explanation will be made below on the function produced by the exemplary embodiment. 
       FIG. 7  is a flowchart illustrating a delay time transmission routine in a paper feed controller  94 . 
     In step  110 , it is determined whether or not the main controller  90  outputs the transmission request for its own delay time. If the result is affirmative, the routine jumps to step  116 . To the contrary, if the result is negative, the routine proceeds to step  112 . 
     In step  112 , it is determined whether or not another paper feed controller  94  which is adjacent to the paper feed controller  94  at the downstream side outputs the communication command which has the delay time written therein. If the result is negative, the routine ends. To the contrary, if the result is affirmative, the routine proceeds to step  114 . 
     In step  114 , its own delay time is added to the delay time written in the received communication command. For example, the delay time which is obtained by adding its own delay time to the previously written delay time is written as a new delay time. Alternatively, its own delay time is added to the delay time previously written in the communication command to obtain a new delay time. Thereafter, the routine proceeds to next step  116 . 
     In step  116 , the communication command which has its own delay time (or, the added delay time) written therein is transmitted to another paper feeding apparatus  14  which is adjacent to the paper feeding apparatus at the upstream side or the image forming apparatus  12 . In this manner, the routine ends. 
       FIG. 8  is a flowchart illustrating a paper feed instruction routine by the main controller  90 . 
     In step  120 , the main controller  90  determines whether or not a job is input, and waits for an affirmative result. 
     In step  122 , the main controller  90  decides a paper feeding apparatus  14  based on print information on the input job. Moreover, the main controller  90  acquires a delay time of a paper feed controller  94  of the paper feeding apparatus  14  from the memory  92 . In the exemplary embodiment, the recording papers P of different sizes are accommodated in the paper feeding trays  70 . 
     In step  124 , the main controller  90  sets the paper feed start request timing. Specifically, the time (X ms) from the paper feed control reference timing to the paper feed start request timing has been predetermined, and thus, the acquired delay time is subtracted from the time (X−Y ms) (see  FIGS. 5A and 5B ). 
     In step  128 , it is determined whether or not a time until the paper feed start request timing which has been set in step  124  elapses, and waits for an affirmative result. 
     In step  130 , the main controller  90  transmits the paper feed start request signal to the paper feed controller  94 . The main controller  90  transmits an ON signal over the hot line communication. 
     In step  132 , it is determined whether or not all of jobs are finished. If the result is negative, the routine returns to step  128 . To the contrary, if the result is affirmative, the routine ends. 
     In the exemplary embodiment, the delay time is acquired every time the job is input, it is not limited to this. The delay time may be acquired once when the configuration of the image forming system  10  is determined, and then, the acquired delay time of each of the paper feed controllers  94  may be stored in the memory  92 . In this case, a delay time of a target paper feed controller  94  is read from the memory  92  and control the target paper feed controller  94  every time the job is input. 
     The foregoing description of the embodiments of the present invention has been provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.