JP2013023373A - Sheet conveying device, automatic document feeder and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a control part from performing erroneous processing when signals are erroneously output from a circuit part to the control part due to electromotive force during jam processing.SOLUTION: In an image forming apparatus, an interlock switch 7 shuts off a power line 11 and a power source 9 and connects the power line 11 and a wiring line 13 while a cover for covering a conveying path is opened. When a paper sheet clogged in the conveying path is pulled out while the cover is opened, a roller rotates, and when motors 137a and 137b are rotated following the rotation of the rotor and the electromotive force (electromotive force during jam processing) is generated, electromotive force detection signals are output from an electromotive force detection part 700. When the signals from the circuit part 15 are input to the control part 500 before a predetermined period elapses after the electromotive force detection signals are input to the control part 500, the control part 500 does not perform the processing to be executed by the input of the signals from the circuit part 15.

Description

  The present invention relates to a sheet conveying apparatus having an interlock function, and an automatic document feeder and an image forming apparatus including the sheet conveying apparatus.

  The image forming apparatus conveys a sheet along a conveyance path by a rotating roller, forms an image on the conveyed sheet, and outputs the image. When paper is jammed in the transport path (ie, when a jam occurs), the user must remove the paper jammed in the transport path. When the paper jammed in the transport path is pulled out and the paper is removed from the transport path, the roller rotates, and when the motor rotates following this, an electromotive force (hereinafter referred to as an electromotive force during jam processing) is generated. .

  The image forming apparatus includes a circuit unit that outputs a detection signal when a predetermined error is detected. When the detection signal is input to the control unit, the control unit performs processing corresponding to the detection signal (for example, processing for displaying an error notification image on the display unit). If a current generated by an electromotive force at the time of jam processing flows to the circuit unit, the circuit unit may be broken or a detection signal may be erroneously output.

  Therefore, a technique has been proposed in which when an electromotive force is generated during jam processing, a motor is rotated by the electromotive force to consume the electromotive force (see, for example, Patent Document 1).

  When the cover of the image forming apparatus is opened and closed and the operation of the interlock switch is interlocked, the motor is connected to the motor power supply (24 V power supply) by the interlock switch, and when the cover is opened, the motor Is connected to another power source (5V power source) by an interlock switch, and when an electromotive force is generated at the time of jam processing with the cover opened, a technique is proposed in which the current generated thereby flows to the other power source (for example, , See Patent Document 2).

JP 2008-199707 A JP 2010-28972 A

  In the above two technologies, if an electromotive force is generated at the time of jam processing, it is configured to consume this, thereby preventing the circuit unit from erroneously outputting a detection signal. However, the possibility that the circuit unit erroneously outputs the detection signal cannot be denied because the electromotive force at the time of jam processing cannot be consumed and the current generated by the electromotive force flows to the circuit unit.

  The present invention relates to a sheet conveying device capable of preventing a control unit from performing erroneous processing when a signal is erroneously output from a circuit unit to a control unit due to an electromotive force during jam processing, and An object of the present invention is to provide an automatic document feeder and an image forming apparatus including the same.

  A sheet conveying apparatus according to one aspect of the present invention that achieves the above object includes a power line, a motor connected to the power line, a conveying path, and the sheet by rotating the sheet with a driving force of the motor. A roller that conveys along the conveyance path, a cover that is opened when accessing the conveyance path to take out a sheet jammed in the conveyance path, a wiring line, and the power supply in a state where the cover is closed. A line and a power supply are connected, the power supply line and the wiring line are cut off, the power supply line and the power supply are cut off while the cover is open, and the power supply line and the wiring line are connected An interlock switch, a control unit, a circuit unit connected to the power supply line and outputting a signal to the control unit, and the cover being opened When an electromotive force is generated by the rotation of the motor following the rotation of the roller, a threshold is set in advance based on the magnitude of an electrical signal flowing through the wiring line, and the wiring line An electromotive force detection unit that outputs an electromotive force generation signal to the control unit when an electrical signal detected from the control unit exceeds the threshold, and in advance after the electromotive force generation signal is input to the control unit When a signal from the circuit unit is input to the control unit before a predetermined period elapses, the control unit does not perform a process to be executed when a signal from the circuit unit is input, When a signal from the circuit unit is input to the control unit after the period has elapsed, the control unit performs a process to be executed when the signal from the circuit unit is input.

  In the sheet conveying apparatus according to one aspect of the present invention, when the cover is opened, the power supply line and the power supply are interrupted and the power supply line and the wiring line are connected by the interlock switch. The electromotive force detection unit outputs an electromotive force generation signal when an electrical signal detected from the wiring line exceeds a threshold value with the cover being opened. The threshold value is the magnitude of the electrical signal (voltage, current) that flows through the wiring line when an electromotive force (electromotive force during jam processing) is generated by turning the motor with the cover open. It is determined based on. If the electric signal detected from the wiring line exceeds the threshold value, the electric signal is considered to be caused by the electromotive force at the time of jam processing. When a signal from the circuit unit is input to the control unit until a predetermined period elapses after the electromotive force generation signal is input to the control unit, this signal is caused by the electromotive force during jam processing. Assuming that a jam has occurred, the control unit does not perform a process (for example, a process of displaying an image showing a jam occurrence point when the circuit unit is a jam detection sensor) when a signal from the circuit unit is input. On the other hand, when a signal from the circuit unit is input to the control unit after the period has elapsed, the control unit performs a process to be executed when the signal from the circuit unit is input. As described above, according to the sheet conveying device according to one aspect of the present invention, when a signal is erroneously output from the circuit unit to the control unit due to the electromotive force during the jam processing, the control unit is removed from the circuit unit. The process to be executed can be prevented from being performed when the signal is input.

  The predetermined period refers to a period during which a signal may be erroneously output from the circuit unit to the control unit when an electromotive force is generated during jam processing.

  In the above configuration, the wiring line may include one end connected to the interlock switch and the other end grounded.

  According to this configuration, the current generated by the electromotive force during the jam processing can be passed to the ground through the power supply line and the wiring line. Therefore, it is possible to prevent the circuit portion from being destroyed by the electromotive force during the jam processing.

  In the above configuration, the threshold value is set in advance based on the magnitude of a voltage detected from the wiring line when the electromotive force is generated, and the electromotive force detection unit is configured to detect the one end. Connected to the wiring line between the first end and the other end, detects the voltage of the wiring line, and if the voltage of the wiring line exceeds the threshold value, the electromotive force generation signal is sent to the control unit A voltage detection circuit that is output to

  According to this configuration, since the layout for grounding the wiring line is included in the electromotive force detection unit, the configuration is reduced in size and the number of parts compared to the case where the electromotive force detection unit and the layout for grounding the wiring line are provided separately. Can be reduced.

  An automatic document feeder according to another aspect of the present invention that achieves the above object conveys a tray on which the document as the sheet is set, and the document set on the tray to a position where the document is read. And a sheet conveying device.

  The automatic document feeder according to another aspect of the present invention has the same operation as the above-described sheet conveying apparatus according to one aspect of the present invention.

  An image forming apparatus according to another aspect of the present invention that achieves the above object forms and outputs an image on the sheet conveying apparatus that conveys the sheet as the sheet and the sheet conveyed by the sheet conveying apparatus. An image forming unit.

  The image forming apparatus according to still another aspect of the present invention has the same operation as the above-described sheet conveying apparatus according to one aspect of the present invention.

  According to the present invention, when a signal is erroneously output from the circuit unit to the control unit due to the electromotive force at the time of jam processing, the control unit can be prevented from performing erroneous processing.

1 is a diagram illustrating an outline of an internal structure of an image forming apparatus provided with a sheet conveying device according to an embodiment. It is a figure which shows the outline of the external appearance of the image forming apparatus shown in FIG. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus illustrated in FIG. 1. In this embodiment, it is a figure which shows an example of the connection relationship of a motor, an electromotive force detection part, and an interlock switch. It is a circuit diagram which shows an example of an electromotive force detection part. It is a circuit diagram which shows the other example of an electromotive force detection part. 6 is a flowchart illustrating an operation of the image forming apparatus when an interlock switch is on in the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating an outline of an internal structure of an image forming apparatus 1 provided with a sheet conveying device according to the present embodiment. FIG. 2 is a diagram showing an outline of the appearance of the image forming apparatus 1. The image forming apparatus 1 can be applied to, for example, a digital multifunction machine having functions of a copy, a printer, a scanner, and a facsimile. The image forming apparatus 1 is disposed on an apparatus main body 100, a document reading unit 200 disposed on the apparatus main body 100, a document feeding unit 300 disposed on the document reading unit 200, and an upper front surface of the apparatus body 100. An operation unit 400 is provided.

  The document feeder 300 functions as an automatic document feeder to which the sheet conveying device according to the present embodiment is applied, and a document tray 305, a pickup roller 307, and a sheet separation mechanism 309 arranged in order from the upstream side in the document feeding direction. A registration roller 311, a transport drum 313, a paper discharge roller 315, a paper discharge tray 317, and document transport paths 323 a and 323 b.

  A document to be read is placed on the document tray 305. The document transport paths 323a and 323b are examples of transport paths, and are referred to as a document transport path 323 when it is not necessary to distinguish between them. The document conveyance path 323a is a conveyance path that connects the document tray 305 and the paper discharge tray 317, and is used when one side of the document is automatically read. In the case of automatically reading both sides of a document, a document transport path 323b is further used.

  The document placed on the document tray 305 is transported along the document transport path 323 by the rotation of the various rollers and the transport drum 313, and is sent to the paper discharge tray 317. The various rollers and the conveyance drum 313 are an example of a roller that conveys a sheet along a conveyance path by rotating with a driving force of a motor.

  The pickup roller 307 is disposed above the document tray 305 so as to be movable up and down. A sheet separation mechanism 309 is provided in the vicinity of the pickup roller 307. The paper separation mechanism 309 includes a driving roller 309a, a driven roller 309b, an endless belt 309c, and a separation roller 309d. The driving roller 309a is located downstream of the driven roller 309b. An endless belt 309c is stretched around the driving roller 309a and the driven roller 309b, and these rollers function as a paper feeding roller. A separation roller 309d is disposed below the driving roller 309a and the driven roller 309b so as to press the endless belt 309c.

  The pickup roller 307 and the driving roller 309 a rotate in a direction to send out the document placed on the document tray 305 from the document tray 305. On the other hand, the separation roller 309d rotates in a direction to return the document placed on the document tray 305 to the document tray 305. Accordingly, a plurality of originals taken one by one by the pickup roller 307 are prevented from being stacked and conveyed.

  A registration roller 311 is disposed in the vicinity of the sheet separation mechanism 309. The registration roller 311 includes a driving roller 311a and a driven roller 311b arranged so as to sandwich the document. The document conveyed from the sheet separation mechanism 309 is corrected to a correct angle by the registration roller 311 and sent to the conveyance drum 313. The original is passed over the original reading slit 233 by the transport drum 313 and then discharged to the paper discharge tray 317 by the paper discharge roller 315. The document reading slit 233 is provided in the document reading unit 200 described later.

  The document feeder 300 further includes a document reversing mechanism including a switching guide 319, a reversing roller 321 and a document conveying path 323b. The document reversing mechanism is used when automatically reading both sides of a document. At the time of double-sided reading, the switching guide 319 is switched to the lower side, and the original whose surface is read by the original reading unit 200 is conveyed to the original conveyance path 323b by the paper discharge roller 315 and the reverse roller 321. Thereafter, the switching guide 319 is switched to the upper side and the reverse roller 321 rotates in the reverse direction, whereby the document is sent again to the transport drum 313. Then, the back side of the document is read by the document reading unit 200, and the document is discharged to the discharge tray 317 by the discharge roller 315.

  The document feeder 300 includes a plurality of jam detection sensors. In FIG. 1, three jam detection sensors 325a, 325b, and 325c are shown. When it is not necessary to distinguish between these sensors, it is described as a jam detection sensor 325. The jam detection sensor 325 is arranged at a different location on the conveyance path 323 and detects a jam of the document conveyed on the conveyance path 323.

  The document feeder 300 includes a cover 5 that covers the interior of the document feeder 300. When the cover 5 is opened, the document conveyance path 323 appears. When a document jam occurs in the document conveyance path 323, the cover 5 is opened, and the document jammed in the document conveyance path 323 is removed. The cover 5 is an example of a cover that is opened when accessing the conveyance path in order to take out a sheet jammed in the conveyance path.

  The document reading unit 200 optically reads a document image and generates image data. The document reading unit 200 includes a platen glass 231, a document reading slit 233, a light source 235, a first mirror 237, a second mirror 239, a third mirror 241, a first carriage 243, a second carriage 245, an imaging lens 247, and a CCD ( Charge Coupled Device) 249.

  The platen glass 231 and the document reading slit 233 are located on the upper surface of the document reading unit 200. The platen glass 231 is used in a flat bed reading mode, and an original is placed on the platen glass 231 and the original is read. The document reading slit 233 is located below the transport drum 313. The document reading slit 233 is used in the ADF reading mode, and the document conveyed by the conveyance drum 313 is read when passing between the document reading slit 233 and the conveyance drum 313.

  The light source 235 and the first mirror 237 are held by the first carriage 243. The second mirror 239 and the third mirror 241 are held by the second carriage 245. The light emitted from the light source 235 and reflected from the document is guided to the CCD 249 by the first mirror 237, the second mirror 239, the third mirror 241, and the imaging lens 247.

  In the flat bed reading mode, an original is placed on the platen glass 231 and the original is read by the CCD 249 while moving the carriage (the first carriage 243 and the second carriage 245) in the longitudinal direction of the platen glass 231 (sub-scanning direction Y). . On the other hand, in the ADF reading mode, the carriage (the first carriage 243 and the second carriage 245) is moved to a position facing the document reading slit 233, and the document sent from the document feeding unit 300 is read by the document. Read by the CCD 249 through the slit 233. As a result, the electrical signal output from the CCD 249 is subjected to predetermined processing by an image engine (not shown) provided in the document reading unit 200 and output as image data.

  The apparatus main body 100 includes a paper storage unit 101, an image forming unit 103, a fixing unit 105, and paper transport paths 111a and 111b. The paper transport paths 111a and 111b are examples of the transport path, and are referred to as the paper transport path 111 when it is not necessary to distinguish them. The paper conveyance path 111 a is a conveyance path that connects the paper storage unit 101, the stack tray 127, and the paper discharge tray 129, and is used when an image is formed on the paper in the paper storage unit 101.

  The sheet storage unit 101 is disposed at the lowermost part of the apparatus main body 100 and includes a plurality of sheet feeding cassettes 107 that can store a bundle of sheets. In the bundle of sheets stored in the sheet feeding cassette 107, the uppermost sheet is sent out toward the sheet conveying path 111a by driving the pickup roller 109. The sheet is conveyed to the image forming unit 103 through the sheet conveyance path 111a.

  The apparatus main body 100 further includes a manual feed tray 131. The transport path 111b joins the paper transport path 111a. When paper is fed using the manual feed tray 131, the paper is transported through the paper transport path 111b and sent to the paper transport path 111a.

  Various rollers 133 a, 133 b, 133 c, 133 d, 133 e, 133 f (referred to as roller 133 when there is no need to distinguish these) are disposed in the sheet conveyance path 111. The paper is conveyed along the paper conveyance path 111 by the rotation of the roller 133. The roller 133 is an example of a roller that conveys a sheet along a conveyance path by rotating with a driving force of a motor. The sheet conveying path 111 and the roller 133 constitute a sheet conveying apparatus according to the present embodiment.

  The apparatus main body 100 includes a plurality of jam detection sensors. In FIG. 1, three jam detection sensors 135a, 135b, and 135c are shown. When it is not necessary to distinguish between these sensors, it is described as a jam detection sensor 135. The jam detection sensor 135 is disposed at a different location on the paper transport path 111 and detects a jam of the paper transported on the paper transport path 111.

  The image forming unit 103 forms a toner image on the conveyed paper based on the image data. The image forming unit 103 includes a photosensitive drum 113, a charge eliminating unit 115, a charging unit 117, an exposure unit 119, developing units 121Bk, 121Y, 121M, and 121C, a transfer drum 123, and a transfer roller 125.

  The charge removal unit 115 is a device that removes residual charges from the peripheral surface of the photosensitive drum 113. The charging unit 117 is a device that charges the peripheral surface of the photosensitive drum 113 after charge removal. The exposure unit 119 generates light modulated in accordance with image data (image data output from the CCD 249 of the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.), and uniformly. This is an apparatus for forming an electrostatic latent image on the peripheral surface of the photosensitive drum 113 by irradiating the peripheral surface of the charged photosensitive drum 113.

  The developing units 121Bk, 121Y, 121M, and 121C have black (Bk), yellow (Y), magenta (M), and cyan (C) colors on the peripheral surface of the photosensitive drum 113 on which the electrostatic latent image is formed. This is an apparatus for forming a toner image. If there is no need to distinguish between the developing portions of the respective colors, they are referred to as developing portions 121. The toner for each color of black, yellow, magenta, and cyan is supplied from a toner supply container or a toner cartridge (not shown).

  On the peripheral surface of the transfer drum 123, the toner images of the respective colors formed on the photosensitive drum 113 are transferred and superimposed. The transfer roller 125 is a roller that transfers the toner image on the peripheral surface of the transfer drum 123 onto the sheet conveyed from the sheet storage unit 101.

  The sheet on which the toner image is transferred is sent to the fixing unit 105. In the fixing unit 105, heat and pressure are applied to the toner image and the paper to fix the toner image on the paper. Thereby, the printing of the image on the paper is completed. The sheet is discharged to the stack tray 127 or the discharge tray 129.

  The image forming apparatus 1 includes a cover 3 that covers the inside of the apparatus main body 100. When the cover 3 is opened, a paper transport path 111 appears. When a paper jam occurs in the paper transport path 111, the cover 3 is opened, and the paper jammed in the paper transport path 111 is removed. The cover 3 is an example of a cover that is opened when accessing the conveyance path in order to take out a sheet jammed in the conveyance path.

  The operation unit 400 includes an operation key unit 401 and a display unit 403. The display unit 403 has a touch panel function, and displays a screen including soft keys. The user operates the soft keys while viewing the screen to make settings necessary for executing functions such as copying.

  The operation key unit 401 includes operation keys including hard keys. Specifically, the operation key unit 401 includes a start key 407, a numeric key 409, a function switching key 405, and the like. A start key 407 is a key for starting operations such as copying and facsimile transmission. A numeric keypad 409 is a key for inputting numbers such as the number of copies and a facsimile number.

  The function switching key 405 includes a copy key, a transmission key, a scanner key, and the like, and is a key for switching between a copy function, a transmission function, a scanner function, and the like. When the copy key is operated, an initial copy screen is displayed on the display unit 403. When the transmission key is operated, an initial screen for facsimile transmission and mail transmission is displayed on the display unit 403. When the scanner key is operated, the initial screen of the scanner is displayed on the display unit 403.

  FIG. 3 is a block diagram showing the configuration of the image forming apparatus 1 shown in FIG. The image forming apparatus 1 has a configuration in which an apparatus main body 100, a document reading unit 200, a document feeding unit 300, an operation unit 400, a control unit 500, a communication unit 600, and an electromotive force detection unit 700 are connected to each other via a bus. The description of the configuration already described with reference to FIG. 1 is omitted.

  The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an image memory, and the like. The CPU executes control necessary for operating the image forming apparatus 1 on the above-described components of the image forming apparatus 1 such as the apparatus main body 100. The ROM stores software necessary for controlling the operation of the image forming apparatus 1. The RAM is used for temporary storage of data generated during execution of software, storage of application software, and the like. The image memory temporarily stores image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.).

  The communication unit 600 includes a facsimile communication unit 601 and a network I / F unit 603. The facsimile communication unit 601 includes an NCU (Network Control Unit) for controlling connection of a telephone line with a destination facsimile and a modulation / demodulation circuit for modulating / demodulating a signal for facsimile communication. The facsimile communication unit 601 is connected to the telephone line 605.

  A network I / F unit 603 is connected to a LAN (Local Area Network) 607. A network I / F unit 603 is a communication interface circuit for executing communication with a terminal device such as a personal computer connected to the LAN 607.

  The apparatus main body 100 includes motors 137a and 137b and a motor circuit 139 that drives and controls them. When it is not necessary to distinguish between the motors 137a and 137b, they are referred to as motors 137. The motor 137a rotates, for example, rollers 133a, 133b, 133c, 133d, and 133e that are used to transport the paper on the paper transport path 111a. The motor 137b rotates, for example, a roller 133f used for transporting the paper on the paper transport path 111b.

  The electromotive force detection unit 700 will be described later when an electromotive force (electromotive force at the time of jam processing) is generated by the rotation of the motor 137 following the rotation of the roller 133 while the cover 3 is opened. A threshold value is set in advance based on the magnitude of the electrical signal flowing in the wiring line to be output, and if the electrical signal detected from the wiring line exceeds the threshold value, an electromotive force generation signal is output to the controller 500. To do.

  The electromotive force detection unit 700 will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of a connection relationship among the motors 137a and 137b, the electromotive force detection unit 700, and the interlock switch 7 in the present embodiment. The interlock switch 7 includes three terminals 7a, 7b, and 7c. The terminal 7 a is connected to a 24 V power supply 9 (an example of a power supply), the terminal 7 b is connected to the power supply line 11, and the terminal 7 c is connected to the wiring line 13.

  The interlock switch 7 is switched in conjunction with opening and closing of the cover 3 shown in FIG. That is, the power supply line 11 and the power supply 9 are connected while the cover 3 is closed, and the power supply line 11 and the wiring line 13 are disconnected. With the cover 3 opened, the power supply line 11 and the power supply 9 are cut off, and the power supply line 11 and the wiring line 13 are connected. FIG. 4 shows a case where the cover 3 is opened.

  The power supply line 11 is connected to control circuits 141a and 141b for controlling the motors 137a and 137b to rotate forward and backward, respectively. The control circuits 141a and 141b are included in the motor circuit 139 of the motors 137a and 137b, and are full bridges configured by four field effect transistors. Electric power for driving the motors 137 a and 137 b is supplied from the power supply 9 through the power supply line 11.

  The circuit unit 15 is connected to the power supply line 11 and outputs a signal to the control unit 500. That is, when the cover 3 is closed, the circuit unit 15 is connected to the power supply line 11, operates with the power supplied from the power supply line 11, and outputs a signal to the control unit 500.

  As the circuit unit 15, for example, a jam detection sensor 135 that detects the occurrence of a jam in the paper conveyance path 111 and its drive circuit, a sensor (not shown) that detects the near end of toner in the toner container, and its drive circuit, facsimile The communication unit 600 that has received

  The processing executed by the control unit 500 when the signal from the circuit unit 15 is input is, for example, when the circuit unit 15 is the jam detection sensor 135 and its driving circuit, an image indicating the jam occurrence location is displayed on the display unit 403. This is the process that is displayed on the screen. In the case where the circuit unit 15 is a sensor for detecting the near end of the toner and its driving circuit, it means a process of causing the display unit 403 to display an image indicating the near end of the toner. In the case where the circuit unit 15 is the communication unit 600 that has received a facsimile, it means a process of waiting for the facsimile received image to be formed on a sheet until the cover 3 is closed.

  The wiring line 13 is connected to the electromotive force detection unit 700. FIG. 5 is a circuit diagram illustrating an example of the electromotive force detection unit 700. The electromotive force detection unit 700 includes a voltage dividing circuit 71 and an open collector 73. The resistor R1 of the voltage dividing circuit 71 is connected to the wiring line 13, and the resistor R2 of the voltage dividing circuit 71 is grounded. The output of the voltage dividing circuit 71 is connected to the base of the open collector 73. The collector of the open collector 73 is connected to a power supply of 3.3 V via a pull-up resistor R3. The emitter of the open collector 73 is grounded. A signal output from the collector of the open collector 73 is input to the CPU of the control unit 500.

  The electromotive force detection unit 700 outputs an electromotive force generation signal when the voltage detected from the wiring line 13 exceeds the threshold value with the cover 3 being opened. More specifically, when an electromotive force is generated during jam processing with the cover 3 opened, the current I1 flows through the power supply line 11 to the circuit unit 15, and the current I2 occurs through the power supply line 11 and the wiring line 13. It flows to the power detection unit 700.

  The electromotive force detection unit 700 outputs an H level signal during normal operation (a voltage smaller than a predetermined threshold value) because the open collector 73 is off, and this signal is input to the CPU of the control unit 500. When the voltage exceeding the threshold is input to the base of the open collector 73 due to the occurrence of an electromotive force at the time of jam processing, the electromotive force detection unit 700 turns on the open collector 73 and an L level signal (ie, Electromotive force generation signal) is output to the CPU of the controller 500.

  The threshold value is determined based on a voltage detected from the wiring line 13 when an electromotive force (electromotive force at the time of jam processing) is generated by turning the motor 137 with the cover 3 opened. (Eg 3V). If the voltage detected from the wiring line 13 exceeds the threshold value, the voltage is considered to be caused by the electromotive force during the jam processing.

  FIG. 6 is a circuit diagram illustrating another example of the electromotive force detection unit 700. The electromotive force detection unit 700 includes a voltage dividing circuit 71 and a comparator 75. The non-inverting input terminal of the comparator 75 is connected to the output of the voltage dividing circuit 71. The inverting input terminal of the comparator 75 is connected to a power supply of 3.3 V via a resistor R4, and is grounded via a resistor R5. The + Vcc terminal of the comparator 75 is connected to a 3.3V power supply, and the -Vcc terminal is grounded.

  When a voltage smaller than the threshold value (that is, normal time) is input to the non-inverting input terminal of the comparator 75, an L level signal is output from the comparator 75, and this signal is output from the control unit 500. Input to the CPU. On the other hand, when a voltage exceeding the threshold is input to the non-inverting input terminal of the comparator 75 due to the occurrence of an electromotive force during jam processing, the output is inverted and an H level signal (that is, an electromotive force) Generation signal) is output, and this signal is input to the CPU of the controller 500.

  Next, the operation of the image forming apparatus 1 when the interlock switch 7 is on will be described. FIG. 7 is a flowchart for explaining this operation. The controller 500 determines whether an electromotive force generation signal is output from the electromotive force detector 700 (step S1). That is, it is determined whether an interrupt signal is input from the electromotive force detection unit 700 to the CPU of the control unit 500.

  If control unit 500 determines that an electromotive force detection signal is not output from electromotive force detection unit 700 (No in step S1), the process of step S1 is repeated. If the control unit 500 determines that the electromotive force detection signal is output from the electromotive force detection unit 700 (Yes in step S1), the control unit 500 operates a timer included in the control unit 500 to determine a predetermined period. Is measured (step S3). The predetermined period is a period in which when an electromotive force is generated at the time of jam processing, a current I1 caused thereby flows to the circuit unit 15 and a signal may be erroneously output from the circuit unit 15 to the control unit 500. (For example, several hundred ms). The predetermined period is described as a malfunction period.

  The controller 500 determines whether a signal is output from the circuit unit 15 (step S5). If the control unit 500 determines that no signal is output from the circuit unit 15 (No in step S5), the control unit 500 determines whether a malfunction period has elapsed (step S7).

  If control unit 500 determines that the malfunction period has not elapsed (No in step S7), it returns to step S5. If the controller 500 determines that the malfunction period has elapsed (Yes in step S7), the process returns to step S1.

  If the control unit 500 determines that a signal is output from the circuit unit 15 (Yes in step S5), the control unit 500 determines whether a malfunction period has elapsed (step S9). If the control unit 500 determines that the malfunction period has not elapsed (No in step S9), the control unit 500 regards that the signal is erroneously output from the circuit unit 15 due to the electromotive force during jam processing. 500 does not perform the process executed when the signal from the circuit unit 15 is input (step S11), and returns to step S5.

  On the other hand, if the control unit 500 determines that the malfunction period has elapsed (Yes in step S9), the control unit 500 performs a process to be executed by receiving a signal from the circuit unit 15 (step S13). Return to step S1.

  The main effects of this embodiment will be described. According to this embodiment, when the cover 3 is opened, the power supply line 11 and the power supply 9 are shut off by the interlock switch 7 and the power supply line 11 and the wiring line 13 are connected. The electromotive force detection unit 700 outputs an electromotive force generation signal when a voltage (an example of an electrical signal) detected from the wiring line 13 exceeds a threshold value with the cover 3 being opened. When a signal from the circuit unit 15 is input to the control unit 500 before a predetermined period elapses after the electromotive force generation signal is input to the control unit 500, this signal is the electromotive force during jam processing. Therefore, the control unit 500 does not perform the process executed when the signal from the circuit unit 15 is input. On the other hand, when a signal from the circuit unit 15 is input to the control unit 500 after the period has elapsed, the control unit 500 performs a process to be executed when the signal from the circuit unit 15 is input. As described above, according to the present embodiment, when a signal is erroneously output from the circuit unit 15 to the control unit 500 due to the electromotive force at the time of jam processing, the control unit 500 receives the signal from the circuit unit 15 as an input. As a result, the process to be executed can be prevented from being performed.

  Further, according to the present embodiment, as shown in FIGS. 5 and 6, the wiring line 13 includes one end connected to the interlock switch 7 and the other end grounded. As a result, the current generated by the electromotive force during the jam processing can be supplied to the ground through the power supply line 11 and the wiring line 13. Therefore, it is possible to prevent the circuit unit 15 from being destroyed by the electromotive force during the jam processing.

  Further, according to the present embodiment, as shown in FIGS. 5 and 6, the threshold value is based on the magnitude of the voltage detected from the wiring line 13 when an electromotive force is generated during jam processing. The electromotive force detection unit 700 is set in advance and is connected to the wiring line 13 between one end and the other end, detects the voltage of the wiring line 13, and the voltage of the wiring line 13 is If the threshold value is exceeded, a voltage detection circuit in which an electromotive force generation signal is output to the control unit 500 is included. According to this configuration, since the electromotive force detection unit 700 includes a layout for grounding the wiring line 13, the configuration is compact compared to the case where the electromotive force detection unit 700 and the layout for grounding the wiring line 13 are provided separately. And the number of parts can be reduced.

  In the present embodiment, the sheet conveying apparatus has been described as an example of conveying a sheet along the conveying path 111 of the apparatus main body 100. However, the present invention is not limited to this, and the present invention can also be applied to a sheet transport apparatus that sets a document on the document tray 305 and transports the document along the transport path 323 in the document feeder 300. The same effect as the above-described embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3, 5 Cover 7 Interlock switch 9 Power supply 11 Power supply line 13 Wiring line 15 Circuit part 111, 111a, 111b Paper conveyance path (an example of conveyance path)
133, 133a to 133f Rollers 137, 137a, 137b Motor 300 Document feeder (an example of an automatic document feeder)
305 Document tray (example of tray)
323, 323a, 323b Document transport path (an example of transport path)
700 Electromotive force detection unit

Claims (5)

A power line,
A motor connected to the power line;
A transport path;
A roller that conveys the sheet along the conveyance path by rotating with the driving force of the motor;
A cover that is opened when accessing the transport path in order to take out the sheet jammed in the transport path;
Wiring lines,
The power line and the power line are connected and the power line and the wiring line are disconnected while the cover is closed, and the power line and the power source are disconnected when the cover is open. And an interlock switch for connecting the power line and the wiring line,
A control unit;
A circuit unit connected to the power supply line and outputting a signal to the control unit;
When an electromotive force is generated by the rotation of the motor following the rotation of the roller with the cover open, the threshold is set based on the magnitude of the electrical signal flowing through the wiring line. An electromotive force detection unit that is preset and outputs an electromotive force generation signal to the control unit if an electrical signal detected from the wiring line exceeds the threshold value;
When a signal from the circuit unit is input to the control unit until a predetermined period elapses after the electromotive force generation signal is input to the control unit, the control unit receives from the circuit unit. If the signal from the circuit unit is input to the control unit after the period has elapsed without performing the processing to be executed when the signal is input, the control unit receives the signal from the circuit unit. sheet conveying apparatus that performs processing executed by the input.   The sheet conveying apparatus according to claim 1, wherein the wiring line includes one end connected to the interlock switch and the other end grounded. The threshold value is preset based on the magnitude of the voltage detected from the wiring line when the electromotive force is generated,
The electromotive force detection unit is connected to the wiring line between the one end and the other end, detects the voltage of the wiring line, and the voltage of the wiring line exceeds the threshold value. The sheet conveying apparatus according to claim 2, further comprising a voltage detection circuit that outputs the electromotive force generation signal to the control unit. A tray on which a document as a sheet is set;
An automatic document feeder comprising: the sheet conveying device according to any one of claims 1 to 3, which conveys the document set on the tray to a position where the document is read. The sheet conveying apparatus according to any one of claims 1 to 3, which conveys a sheet that is the sheet,
An image forming apparatus comprising: an image forming unit configured to form and output an image on the sheet conveyed by the sheet conveying apparatus.

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