JP2007169063A - Image forming system and its paper feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably solve the problem posed in a related technology such as an image forming device transmits a stopping command to a paper feeder by serial communication. <P>SOLUTION: A first signal conductor is arranged for transmitting an output signal to the respective paper feeders from a sensor arranged in the paper feeder positioned in the uppermost stage among a plurality of paper feeders and detecting recording paper. A stopping means stops carrying processing of the recording paper in the respective paper feeders in response to the output signal transmitted via the first signal conductor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming system and a paper feeding device thereof.

Conventionally, an image forming apparatus capable of connecting a plurality of option units in multiple stages has been proposed (Patent Document 1). This image forming apparatus controls each option unit through a general controller.
Japanese Patent Laid-Open No. 08-286567

  Incidentally, in order to increase the number of recording sheets that can be fed, it is desired that a plurality of optional paper feeding units (paper feeding devices) can be connected to the image forming apparatus in multiple stages. In such an image forming apparatus, serial communication is often employed to transmit a motor stop command, a drive start command, and the like to each sheet feeding device.

  However, when the command is transmitted to each sheet feeding device by serial communication, the time at which the command reaches each sheet feeding device is shifted according to the distance from the image forming apparatus (FIG. 8).

  For example, the command arrival time for each sheet feeding device connected to the image forming apparatus is different. Therefore, the gap between the preceding recording sheets and the succeeding recording sheets varies due to the difference in arrival time. In such a configuration, even if an attempt is made to improve the throughput by increasing the paper feed speed, there is a limit because it is necessary to consider the variation between the papers. Also, due to variations in command arrival time, a jam can occur if the paper gap is too short than the preferred value.

  For example, when paper is fed using a plurality of paper feeding devices, variation between papers occurs when the paper feeding port is switched from one paper feeding device to another. In other words, there is a possibility that the gap between the sheets spreads due to the difference in the command arrival time to each sheet feeding device and the throughput is reduced, or conversely, the gap between the sheets is jammed and a jam occurs. In addition, when recording paper is transported across a plurality of paper feeding apparatuses, a stoppage of recording paper occurs when a stop instruction is given. That is, since the stop command arrival time to each paper feeding device is different, the recording paper is stopped in a state where it is pushed in, or stopped in a state where it is pulled by each paper feeding device, so that a jam may occur.

  Also, image adjustment processing (for example, toner density adjustment processing or registration adjustment processing) executed between sheets cannot be performed sufficiently. This is not preferable because the image quality deteriorates.

  Therefore, an object of the present invention is to solve at least one of such problems and other problems. Other issues can be understood throughout the specification.

In order to solve the above problems, the present invention provides:
The present invention, for example, in a configuration in which a plurality of paper feeding devices are connected, reduces image-to-paper variations due to variations in communication time to each paper feeding device, and can realize high-speed image forming system and paper feeding device As realized. Another aspect of the present invention is realized as, for example, an image forming system and a sheet feeding device that can reduce a jam that occurs due to variations in communication time with each sheet feeding device.

  Specifically, the present invention is preferably applied to an image forming system including an image forming apparatus that forms an image and a paper feeding device that feeds recording paper. For example, a communication line for instructing an operation from the image forming apparatus to each of a plurality of sheet feeding apparatuses is provided. In addition, a drive signal line for transmitting an operation instruction signal for operating a plurality of paper feeding apparatuses is provided. When the operation instruction signal is output via the drive signal line in response to the paper feed start instruction transmitted from the image forming apparatus via the communication line, a plurality of paper feed apparatuses start driving and carry processing is performed. Execute.

  According to the present invention, by sharing the output signal from the sensor of the paper feeding device positioned at the uppermost stage with each paper feeding device, variation between papers due to variation in communication time to each paper feeding device, and jamming Occurrence can be reduced.

  An embodiment of the present invention is shown below. Of course, the individual embodiments described below will be helpful in understanding various concepts such as the superordinate concept, intermediate concept and subordinate concept of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

  FIG. 1 is a schematic cross-sectional view of an image forming system according to an embodiment. The image forming system includes an image forming apparatus 100 and optional paper feeding apparatuses 120, 130, and 140. As shown in the figure, optional sheet feeding devices 120, 130, and 140 are connected to the lower part of the image forming apparatus 100 in multiple stages. The first sheet feeding device 120 located at the uppermost stage is directly connected to the lower part of the image forming apparatus 100. A second paper feeding device 130 is connected to the lower part of the first paper feeding device 120. Further, a third paper feeding device 140 is connected to the lower part of the second paper feeding device 130. Note that a fourth paper feeding device may also be connected to the lower portion of the third paper feeding device 140. The image forming apparatus is sometimes called a printing apparatus, a printer, a copier, a multifunction machine, or a facsimile.

  The image forming apparatus 100 includes a paper feed cassette 110. The recording paper S loaded in the paper feed cassette 110 is fed to the transport roller 102 by the pickup roller 101. Further, the recording paper S is transported in the transport path 103 by the transport roller 102. Note that the leading edge and the trailing edge of the recording sheet S are detected by a sheet sensor 104 provided in the middle of the conveyance path 103. The registration roller 108 sends the recording paper S to the image forming unit 105 while adjusting the leading end position of the recording paper S according to the detection result of the sheet sensor 104. Note that the recording paper may be called a recording material, a recording medium, a paper, a sheet, a transfer material, or a transfer paper.

  The image forming unit 105 forms an image on the surface of the recording paper S. The fixing unit 106 fixes the image formed on the surface of the recording paper S. Thereafter, the recording paper S is discharged to the paper discharge tray 107 by the paper discharge roller 109.

  The first paper feeding device 120 is provided with a pickup roller 121, a conveyance roller 122, and a sheet sensor 123. The sheet sensor 123 is an example of a recording sheet detection sensor, and detects the leading end of the recording sheet S fed by the pickup roller 121. Note that the sheet sensor 123 also detects the leading edge of the recording paper S conveyed from any of the paper feeding devices connected below the paper feeding device 120. The conveyance roller 122 conveys these recording sheets S further upward (for example, the image forming apparatus 100).

  The second paper feeder 130 is provided with a pickup roller 131, a transport roller 132, and a sheet sensor 133. The sheet sensor 133 detects the leading edge of the recording paper S fed by the pickup roller 131. Note that the sheet sensor 133 also detects the leading edge of the recording paper S conveyed from any of the paper feeding devices connected below the paper feeding device 130. The conveyance roller 132 conveys these recording sheets S further upward (for example, the first paper feeding device 120).

  The third paper feeding device 140 is provided with a pickup roller 141, a conveyance roller 142, and a sheet sensor 143. The sheet sensor 143 detects the leading edge of the recording paper S fed by the pickup roller 141. When a paper feeding device is further connected below the paper feeding device 130, the sheet sensor 143 also detects the leading edge of the recording paper S conveyed from the paper feeding device. The conveying roller 142 conveys these recording sheets S further upward (for example, the second sheet feeding device 130).

  FIG. 2 is a diagram illustrating a connection example between control units according to the embodiment. The main body control unit 200 includes an image processing unit that develops image data and the like, and an engine control unit that controls an image forming engine such as the image forming unit 105. The option control unit 220 is a control unit for controlling the motor and the like of the first paper feeding device 120. The option control unit 230 is a control unit for controlling the motor and the like of the second paper feeding device 130. The option control unit 240 is a control unit for controlling the motor and the like of the third paper feeding device 140.

  An instruction to start paper feeding (pickup) from the main body control unit 200 is transmitted to the paper feeding device 120, 130, or 140 through the serial communication line 201. In the present invention, apart from the serial communication line 201, two signal lines 202 and 203 are provided in the paper feeding devices 120, 130, and 140. The first signal line 202 transmits an output signal (detection signal) of the sheet sensor 123 provided in the sheet feeding device (for example, the first sheet feeding device 120) located at the uppermost stage to the sheet feeding devices 120 to 140. Hardware signal line for transmitting The second signal line 203 is a hardware signal line for transmitting a signal (for example, an operation instruction signal) for stopping or starting the conveyance processing in each sheet feeding apparatus to the sheet feeding apparatuses 120 to 140 at the same time. . Therefore, the first signal line 202 can also be called a sensor signal line. The second signal line 203 may also be called a motor drive signal line.

  FIG. 3 is a block diagram of an exemplary option control unit according to the embodiment. In the present embodiment, for convenience of explanation, it is assumed that the configurations of the option control units 220, 230, and 240 are common. However, the configurations of the option control units 220, 230, and 240 do not have to be completely the same as long as the functions described below can be achieved.

  The controller 301 is a control circuit that comprehensively controls each unit in the sheet feeding device. The controller 301 can be realized using at least one of a logic circuit, an ASIC, or a CPU. The switch 302 is a switch for switching whether or not to connect the output signal of the sheet sensor to the first signal line 202. The switch 302 of the sheet feeding device 120 located at the uppermost stage connects the output signal of the sheet sensor 123 to the first signal line 202. However, the respective switches 302 of the sheet feeding apparatuses 130 and 140 that are not positioned at the uppermost level disconnect the output signals of the sheet sensors 133 and 143 from the first signal line 202. As a result, only the output signal from the sheet sensor 123 provided in the sheet feeding device 120 located at the uppermost stage is transmitted to the sheet feeding devices 120, 130, and 140.

  Note that the first signal line 202 is electrically connected between a plurality of paper feeding devices 120 to 140 connected in multiple stages. The connector 309a is electrically connected to the connector 309b of the sheet feeding device connected upward. On the other hand, the connector 309b is electrically connected to the connector 309a of the sheet feeding device connected below. When the image forming apparatus 100 is connected above the sheet feeding device, the connector 309a is open. Further, when nothing is connected below the sheet feeding device, the connector 309b is opened.

  Each controller 301 of the sheet feeders 120, 130, and 140 monitors a signal transmitted through the first signal line 202. For example, the controller 301 determines whether or not the signal level of the first signal line 202 is a predetermined level that means TRUE. The signal level of the first signal line 202 becomes a predetermined level when the sheet sensor 123 detects the recording paper S.

  When this signal level reaches a predetermined level, the controller 301 changes the signal level on the second signal line 203 from a start level (TRUE) for starting the transport process to a stop level (FALSE) for stopping the transport process. And switch. For example, when the signal level of the first signal line 202 becomes TRUE, the controller 301 causes the timer 305 to measure a predetermined time. When the predetermined time is counted, the controller 301 switches the switch 306 so that the second signal line 203 is connected from Vcc to GND (ground). Vcc is a power supply line for supplying a voltage of a start level (TRUE) indicating simultaneous driving of the motor 303. GND is a ground line for setting a stop level (FALSE) indicating simultaneous stop of the motor 303.

  The driving unit 304 controls the motor 303 for driving the conveyance roller 122 and the like according to the signal level of the second signal line 203. For example, the drive unit 304 stops the operation of the motor 303 when the signal level of the second signal line 203 becomes FALSE. If the operation of the motor 303 is stopped, the transport roller 122 and the like are stopped, so the transport of the recording paper S is also stopped. The predetermined time is determined empirically so that the leading edge of the recording paper S stops at the pre-feed position P (FIG. 1).

  Note that the second signal line 203 is electrically connected between a plurality of paper feeding devices 120 to 140 connected in multiple stages. The connector 310a is electrically connected to the connector 310b of the sheet feeding device connected upward. On the other hand, the connector 310b is electrically connected to the connector 310a of the sheet feeding device connected below. When the image forming apparatus 100 is connected above the sheet feeding device, the connector 310a is open. Further, when nothing is connected below the sheet feeding device, the connector 310b is opened.

  The controller 301 receives various commands from the main body control unit 200 through the serial communication line 201 and transmits various types of information to the main body control unit 200. The connector 308a is a terminal for electrically connecting the serial communication line 201 to the upper image forming apparatus 100 or another sheet feeding apparatus. The connector 308b is a terminal for connecting the serial communication line 201 to the connector 308a of the lower sheet feeding device.

  For example, when the controller 301 receives a command for resuming conveyance from the main body control unit 200 through the serial communication line 201, the controller 301 switches the switch 306. As a result, the signal level of the second signal line 203 is changed from the stop level (FALSE) to the start level (TRUE). When the signal level of the second signal line 203 changes from FALSE to TRUE, the drive unit 304 starts the operation of the motor 303.

  Note that the signal change of the second signal line 203 is immediately transmitted to each of the sheet feeding devices connected in multiple stages through the connectors 310a and 310b. Therefore, the motors 303 in the paper feeding devices 120, 130, and 140 rotate at the same time. When the operation of the motor 303 starts, the conveyance rollers 122, 132, and 142 resume rotation all at once, so that the conveyance of the recording paper S is also resumed.

  The controller 301 that can switch the signal level of the second signal line 203 is preferably a controller that is mounted on a paper feeding device instructed to feed paper from the main body control unit 200. That is, it is desirable that the switches 306 included in the option control units 220, 230, and 240 operate exclusively. This is because the second signal line 203 is a signal line that is electrically coupled between a plurality of paper feeding apparatuses.

  In the configuration of the switch 306 shown in FIG. 3, when any one of the option controllers 220, 230, and 240 is connected to Vcc, the signal level of the second signal line 203 becomes TRUE. On the contrary, if all these switches 306 are not connected to GND, the signal level of the second signal line 203 does not become FALSE. Therefore, it is desirable that only the switch 306 mounted on the sheet feeding device instructed to feed by the main body control unit 200 operates.

  Of course, the present invention only needs to be able to stop or start the rotation of the motors 303 mounted on the paper feeding devices 120 to 140 all at once. Therefore, the signal level switching mechanism for the second signal line 203 may have another configuration. Note that “all at once” is not intended to mean that the stop and start timings of the respective sheet feeding apparatuses coincide completely and strictly. In other words, this is because a timing shift that does not cause the occurrence of the above-described jam and an extremely low throughput should be allowed.

  As described above, only the output signal from the sheet sensor 123 provided in the sheet feeding device 120 located at the uppermost stage is transmitted to the sheet feeding devices 120, 130, and 140. In order to realize this, a mechanism for switching the switch 302 is required. That is, each sheet feeding device needs a function of detecting or determining whether or not the sheet feeding device is the uppermost sheet feeding device.

  4A and 4B are schematic cross-sectional views of an exemplary mechanism for detecting the uppermost sheet feeder according to the embodiment. Reference numeral 401 denotes a bottom member of the image forming apparatus 100. In this example, a member (example: protrusion) 402 is provided on the joint surface of the bottom member 401 facing the uppermost sheet feeder. Further, a hole 411 for receiving a protrusion is provided on the joint surface of the paper feeding device facing the image forming apparatus 100. Reference numeral 410 denotes a top member of the sheet feeding device. That is, the hole 411 is provided in a part of the top member 410.

  A switch 306 is disposed below the hole 411. As shown in FIG. 4B, in the switch 302, since the push portion 425 is normally urged upward by an elastic member such as a spring, the fixed contact 426 and the movable contact 427 are opened. This state is OFF. On the other hand, when the push portion 425 is pushed downward by the protruding member 402, the fixed contact 426 and the movable contact 427 are short-circuited. That is, this state is ON. In this manner, the switch 302 also functions as a part that detects the presence of the protruding member 402. Note that such a protrusion is not provided on the lower portion 420 of each sheet feeding device. Therefore, when another sheet feeding device is connected above, the switch 302 remains OFF (FIG. 4B). In this way, only the switch 302 of the uppermost sheet feeder is turned on.

  5A and 5B are schematic cross-sectional views of an exemplary mechanism for detecting the uppermost sheet feeder according to the embodiment. As FIG. 5A and FIG. 5B show, the relationship between protrusions and holes may be reversed. That is, a hole 501 is provided as a member on the joint surface of the image forming apparatus 100 facing the uppermost sheet feeding device. Further, the switch 302 is provided with a push portion 425 as a protrusion that can be pushed down. In this case, in the switch 302, when the push part 425 protrudes, the fixed contact 526 and the movable contact 527 are short-circuited (FIG. 5A). That is, the switch 302 is turned on.

  On the other hand, when the push part 425 is pushed down, the fixed contact 526 and the movable contact 527 are opened (FIG. 5B). Therefore, the switch 302 is turned off. Of course, the hole 501 is not provided in the lower part 420 of the paper feeder. Alternatively, a protruding member 402 as shown in FIG. 4A may be provided in the lower part 420 of the sheet feeding device. In this way, the push unit 425 provided on the switch 302 of the lower sheet feeder is pushed down by the lower part 420 of the upper sheet feeder.

  6A and 6B are schematic cross-sectional views of an exemplary mechanism for detecting the uppermost sheet feeder according to the embodiment. In this example, the member of the image forming apparatus 100 is a plate 601 having electrical conductivity. The detection member of the paper feeding device may be two terminals 621 and 622 that are short-circuited by the plate 601. An insulating member 602 that opens these terminals is provided in the lower part 420 of the sheet feeding device. If the lower portion 420 itself is made of an insulating material, the additional insulating member 602 may not be necessary.

  In addition, the controller 301 of each paper feeding device may determine whether it is the paper feeding device positioned at the uppermost stage based on the information received from the image forming apparatus 100. The main body control unit 200 communicates with the option control units 220, 230, and 240 of each sheet feeding device during the initialization process to identify which sheet feeding device is present in the uppermost stage. The main body control unit 200 transmits, to the option control units 220, 230, and 240, information indicating whether or not the sheet feeding device is positioned at the uppermost stage through the serial communication line 201. Based on this information, the controller 301 of each paper feeding device determines whether it is the paper feeding device located at the top.

  FIG. 7 is a flowchart illustrating an exemplary control method of the sheet feeding device according to the embodiment. In step S <b> 701, the controller 301 determines whether a paper feed command has been received via the serial communication line 201. The paper feed command is an example of a paper feed start instruction. When the paper feed command is received, the controller 301 has acquired the authority to change the second signal line 203. On the other hand, if the paper feed command has not been received, the user does not have authority to change the second signal line 203, and thus the process proceeds to step S710.

  In step S702, the controller 301 switches the second signal line 203 to TRUE. That is, the controller 301 switches the switch 302 to the Vcc side. Further, the controller 301 rotates the pickup roller 121 and sends the recording paper S to the transport roller 122. Further, since the second signal line 203 has been changed to TRUE (S710), each drive unit 304 of the sheet feeding devices 120, 130, and 140 starts the rotation of the motor 303 (S711). Thereby, the conveyance rollers 122, 132, and 142 are driven all at once.

  In step S703, the controller 301 determines whether or not the first signal line 202 has become TRUE. If it is TRUE, the process proceeds to step S704. In step S704, the controller 301 activates the timer 305 to measure a predetermined time. The predetermined time is the time required for the leading edge of the recording paper S to reach the pre-feed position P after being detected by the sheet sensor 123. When the predetermined time is measured by the timer 305, the process proceeds to step S705.

  In step S705, the controller 301 switches the second signal line 203 to FALSE. Since the second signal line 203 has been changed to FALSE (S712), the drive units 304 of the paper feeding devices 120, 130, and 140 stop the rotation of the motor 303 (S713). As a result, the transport rollers 122, 132, and 142 are stopped simultaneously.

  In step S706, the controller 301 determines whether or not a command for starting driving again has been received. When this command is received, the process proceeds to step S707. In step S707, the controller 301 switches the second signal line 203 to TRUE. Since the second signal line 203 has been changed to TRUE (S710), each drive unit 304 of the sheet feeding devices 120, 130, and 140 starts the rotation of the motor 303 (S711). Thereby, the conveyance rollers 122, 132, and 142 are driven all at once.

  In step S708, the controller 301 determines whether or not the first signal line 202 has changed to FALSE. FALSE in this case means that the trailing edge of the recording paper has passed the sheet sensor 123. If FALSE, the process proceeds to step S708, and the controller 301 sets the second signal line 203 to FALSE.

  FIG. 8 is a diagram illustrating command arrival timing in the comparative example. In the system of this comparative example, five optional paper feeders are connected to the image forming apparatus 100 in multiple stages. Further, it is assumed that only the serial communication line 201 is used for communication between the image forming apparatus 100 and each sheet feeding device.

  FIG. 8A shows a state in which a command for instructing the operation is sent to the lowermost sheet feeder 5. First, a command is transmitted from the image forming apparatus 100 to the uppermost sheet feeder 1, and the uppermost sheet feeder 1 receives the command and transmits the command to the downstream sheet feeder 2. Each of the sheet feeding devices repeats this command reception and transmission, and a command for instructing the lowermost sheet feeding device 5 to start feeding is reached.

  That is, in the case of serial communication, there is a delay corresponding to the time for repeating transmission / reception of commands until the command transmitted from the image forming apparatus 100 reaches the lowermost sheet feeding device 5. In addition, the time for the command to arrive in each of the paper feeding devices 1 to 5 may also vary in transmission / reception timing depending on the state of each paper feeding device (for example, when a preparation operation is being performed). Therefore, in the configuration in which the paper feeding and transport speeds are faster, it is difficult to stop the recording paper at the prefeed position P with high accuracy.

  Further, not only the transmission of a command for instructing an operation, but also when the image forming apparatus 100 receives the status of each sheet feeding device as a status signal, the configuration of the comparative example takes time until the status signal is received. End up. FIG. 8 shows transmission and reception of commands and statuses until the image forming apparatus 100 transmits a command for requesting the state of the sheet feeding device 5 and receives a status signal, for example. Similarly to FIG. 8A, each sheet feeding device repeats command transmission / reception, and each sheet feeding device repeats status signal transmission / reception. In this configuration, it takes time to receive the status signal indicating the state of the lowermost sheet feeder 5.

  On the other hand, according to the present embodiment, by sharing the output signal from the sheet sensor 123 of the sheet feeding device 120 located at the uppermost stage with each sheet feeding device, the sheet feeding devices 120, 130, and 140 are transported all at once. Processing can be stopped. That is, the recording paper can be stopped at the pre-feed position P with high accuracy. Therefore, the present invention can preferably solve the problem that has occurred in the related art in which a stop command is transmitted to each sheet feeding device by serial communication. For example, wrinkles, jams, image quality degradation, throughput reduction, and the like that occur on recording paper can be preferably improved.

  In addition, it is desirable to provide a second signal line 203 for transmitting a signal for stopping or starting the conveyance processing in each sheet feeding apparatus to the sheet feeding apparatuses all at once. Further, when the level of the output signal transmitted through the first signal line 202 becomes the first level, the controller 301 carries the signal level on the second signal line from the start level for starting the carrying process. Switch to the stop level to stop processing. As a result, the recording paper can be stopped at the pre-feed position P with higher accuracy.

  Further, the controller 301 may switch the level of the signal on the second signal line 203 from the stop level to the start level in response to an instruction from the image forming apparatus 100. That is, when an instruction indicating driving resumption is received, the conveyance process can be resumed all at once.

  Of the controllers 301 included in each sheet feeding device, it is desirable that only the controller 301 included in the sheet feeding device instructed to transport from the image forming apparatus 100 switches the signal level on the second signal line 203. The second signal line 203 is a simple hardware signal line that only transmits TRUE or FALSE. Therefore, only the single controller 301 or the switch 302 switches the signal level of the second signal line 203 so that the image forming system operates stably.

  Further, when each sheet feeding device is a sheet feeding device positioned at the uppermost stage, the sheet sensor provided in the sheet feeding device is connected to the first signal line 202 by the switch 302. On the other hand, each sheet feeding device separates its own sheet sensor from the first signal line by the switch 302 when the sheet feeding device is not the uppermost sheet feeding device. As a result, an output signal from the sheet sensor 123 of the sheet feeding device located at the uppermost stage always flows through the first signal line 202. The sheet sensor 123 of the sheet feeding device located at the uppermost stage can detect the recording sheet S fed from any of the sheet feeding devices 120, 130, and 140. Therefore, it is desirable that the sheet sensor 123 of the sheet feeding device located at the uppermost stage is connected to the first signal line 202.

  Even if the connection order of the sheet feeding devices 120, 130, and 140 changes, it is desirable that the sheet sensor of the sheet feeding device that is always located at the uppermost stage is connected to the first signal line 202. For example, by detecting a member (for example, a protrusion-like member 402, a hole 501, or a conductive plate 601) provided on the joint surface of the image forming apparatus 100 facing the uppermost sheet feeding device 120, It can be determined whether or not the upper sheet feeder. In each sheet feeding device, the controller 301 may determine whether the controller 301 is the sheet feeding device positioned at the uppermost stage based on information received from the image forming apparatus 100.

  The first signal line 202 and the second signal line 203 are physically different signal lines from a signal line (for example, serial communication line 201) for receiving an instruction from the image forming apparatus 100. desirable. The serial communication line 201 needs to be provided from the image forming apparatus 100 to each sheet feeding device, but the first signal line 202 and the second signal line 203 need only be provided between the sheet feeding devices. This can be realized if the first signal line 202, the second signal line 203, and the serial communication line 201 are physically different signal lines.

  Incidentally, there may be a case where the first signal line 202 and the second signal line 203 are added from the image forming apparatus 100 to each sheet feeding apparatus. In this case, it is necessary for the image forming apparatus 100 to directly monitor the sheet sensor or to control the stop / drive of the motor 303. However, in this case, there is a drawback that the control burden on the image forming apparatus 100 becomes heavy. Further, the image forming apparatus 100 also requires a signal line and a connector, and thus an increase in cost is inevitable. In general, a product model including only an image forming apparatus main body that does not include an optional sheet feeding device is necessary in terms of sales strategy. Such a product model does not require the signal lines and connectors described above, so it should be avoided if possible. Therefore, it is desirable that the first signal line 202 and the second signal line 203 are provided only between the sheet feeding apparatuses.

  Although the present invention has been described above, the following concept can be derived from the above description. The image forming system includes an image forming apparatus that forms an image and a plurality of paper feed units that are connected to the image forming apparatus in multiple stages and feed recording paper. Furthermore, a drive signal line and a control unit are included. For example, the drive signal line transmits an operation instruction signal for stopping or starting the conveyance processing of each of the plurality of sheet feeding units to each sheet feeding unit. For example, the control unit controls the conveyance processing of each paper feed unit in accordance with the operation instruction signal transmitted through the drive signal line.

  The image forming system may include a sensor signal line and a stop unit. The sensor signal line is connected directly to the image forming apparatus among a plurality of paper feeding units, and outputs an output signal from a sensor for detecting the recording paper provided in the paper feeding unit located at the uppermost stage. Transmit to the paper unit. The stop unit stops the recording paper transport process in each paper feed unit in accordance with the output signal transmitted through the sensor signal line. The stop unit stops the conveyance process from the start level for starting the conveyance process when the level of the output signal transmitted through the sensor signal line becomes the first level. A switching unit for switching to the stop level may be included.

1 is a schematic cross-sectional view of an image forming system according to an embodiment. It is a figure which shows the example of a connection between the control parts which concern on embodiment. It is a block diagram of an example option control part concerning an embodiment. , , , , , It is a schematic sectional drawing of the example mechanism which detects the uppermost sheet feeder concerning embodiment. 6 is a flowchart illustrating an exemplary control method of the sheet feeding device according to the embodiment. , It is a figure which shows the arrival timing of the command in a comparative example.

Claims (12)

An image forming system including an image forming apparatus that forms an image and a plurality of paper feeding devices that feed recording paper,
A communication line for instructing an operation from the image forming apparatus to each of the plurality of sheet feeding apparatuses;
A drive signal line for transmitting an operation instruction signal for operating the plurality of sheet feeding devices,
When the operation instruction signal is output via the drive signal line in response to a paper feed start instruction transmitted from the image forming apparatus via the communication line, the plurality of paper supply apparatuses start driving. An image forming system characterized in that the conveyance process is executed. A sensor signal line for transmitting a detection signal from a recording paper detection sensor provided in the paper feeding device to another paper feeding device;
The image forming system according to claim 1, wherein the conveyance processing is stopped by stopping driving of the plurality of sheet feeding devices in response to the detection signal transmitted via the sensor signal line. .   Of the plurality of paper feeding devices, a detection signal from a recording paper detection sensor provided in the paper feeding device directly connected to the image forming device is transmitted to another paper feeding device via the sensor signal line. The image forming system according to claim 2.   When the level of the detection signal transmitted via the sensor signal line becomes the first level, the level of the signal in the drive signal line stops the transfer process from the start level for starting the transfer process. The image forming system according to claim 2, wherein the image forming system is switched to a stop level.   2. The image forming system according to claim 1, wherein each sheet feeding device switches a signal level in the drive signal line when receiving a sheet feeding start instruction via the communication line. Each paper feeder
The image forming system according to claim 3, further comprising a switch for connecting the recording paper detection sensor to the sensor signal line or disconnecting the recording signal detection sensor from the sensor signal line. Each paper feeder
The image forming system according to claim 3, further comprising a detection unit configured to detect a member provided on a joint surface of the image forming apparatus. Each paper feeder
4. The image forming system according to claim 3, wherein the image forming system determines whether it is a paper feeding device directly connected to the image forming apparatus based on information received from the image forming apparatus.   The image forming system according to claim 1, wherein the communication line is a signal line for performing serial communication. A paper feeding device connected to the image forming apparatus,
A communication unit that communicates with the image forming apparatus;
Drive signal lines for transmitting signals to all paper feeding devices connected to the image forming apparatus;
When the communication unit receives an operation instruction signal from the image forming apparatus, an operation instruction for starting driving of all other sheet feeding apparatuses connected to the image forming apparatus with respect to the drive signal line And a control unit that outputs a signal. A recording paper detection sensor for detecting the recording paper conveyed to the image forming apparatus;
A sensor signal line for transmitting a detection signal from the recording paper detection sensor to all other paper feeding devices connected to the image forming apparatus;
When the detection signal is output from the recording paper detection sensor, the control unit outputs a signal to the sensor signal line and drives all other paper feeding devices connected to the image forming apparatus. The paper feeding device according to claim 10, wherein a stop of the recording paper is instructed to stop the recording paper conveyance process.   The sheet feeding device according to claim 10, wherein the communication unit is a communication unit for serial communication with another sheet feeding device connected to the image forming apparatus.

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