JP5331568B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a multifunction machine, a copier, and a facsimile machine.

  2. Description of the Related Art Conventionally, an image forming apparatus accommodates and mounts printing paper, feeds paper during printing, and prints on the paper. When feeding paper, a plurality of sheets (for example, two sheets) may be fed at the same time due to various factors such as moisture, friction between sheets, static electricity, and the like. The paper is overlapped and conveyed in the machine.

  When double feeding occurs, it is likely to be caught on the conveyance path and wound around various rotating bodies (for example, conveyance rollers) provided on the conveyance path, and clogging (jam) may occur. Further, when printing is performed in the double feed state, the content of one sheet may be printed on a plurality of sheets. In view of this, some image forming apparatuses include, for example, a sheet that is reversely fed to a sheet feeding unit and printing is performed after a double feed is canceled (retry is performed) when double feed is detected.

An example of such an image forming apparatus is described in Patent Document 1. In Patent Document 1, an ultrasonic transmitter and an ultrasonic receiver are arranged in the vicinity of the paper feeding unit with the conveyance surface of the conveyance path interposed therebetween, and the ultrasonic receiver receives the attenuated ultrasonic wave according to the attenuation amount. A double feed detection sensor that outputs a detected signal, a double feed determination unit that compares a threshold value and a signal output from the double feed detection sensor to determine double feed, and feeds transfer paper supported in a forward and reverse rotation manner. The sheet feeding unit includes a sheet feeding roller that conveys and a separation roller that is pressed against the sheet feeding roller to prevent double feeding of the transfer sheet. An image forming apparatus is described in which the transferred transfer paper is returned to the paper feed tray. With this configuration, the multi-fed transfer paper is returned to the paper feed tray to save waste of transfer paper and human labor, and to eliminate the need to interrupt the image forming operation (Patent Document 1: Claim 1, Paragraph [0018] etc.).
JP 2004-284805 A

  With double feeds where the sheets are neatly stacked, the transport of the paper is relatively stable, and even if a retry operation is performed, the possibility of jamming is low. If this is done, there is an advantage that the trouble of removing the sheet from the conveyance path can be saved. However, when the sheets do not overlap cleanly and there are misalignments, the sheets are conveyed in an unstable state, and the retry operation may cause damage such as folding or tearing of the sheets or jamming. The damaged paper cannot be used for printing and is wasted. In addition, if a retry operation is forcibly performed and a jam occurs, it may take time to remove the paper from the transport path, rather than stopping the transport and removing the paper before the jam occurs. Further, a jam during the retry operation can cause a plurality of sheets to be jammed almost simultaneously, and the sheet removal operation can be very troublesome. Therefore, if the retry operation is uniformly performed when double feeding is detected, there is a problem that it may cause damage to the paper or jam.

  Here, in the image forming apparatus described in Patent Document 1, the double feed detection unit uses the double feed detection sensor to determine the double feed, but does not recognize the misalignment of each sheet in the double feed state. If double feed is detected, the retry operation is performed uniformly regardless of the displacement of each sheet (see Patent Document 1: Claim 1, paragraph [0058], etc.). Therefore, in the image forming apparatus described in Patent Document 1, a retry operation is performed even if there is a large misalignment between the sheets in the double feed state, and the sheets may be damaged or jammed.

  The present invention has been made in view of the above-described problems of the prior art, grasps the deviation of each sheet in a double feed state, performs a retry operation only when it is recognized that the conveyance is stable, and performs a retry. It is an object to prevent damage to the paper and jamming caused by operation.

  An image forming apparatus according to a first aspect of the present invention sandwiches a sheet to be conveyed between a sheet feeding unit that supplies sheets at the time of printing, a transmission unit that is provided downstream of the sheet feeding unit in the sheet conveying direction, and that transmits sound waves. And processing the output voltage of the receiving unit, the ultrasonic sensor including a receiving unit whose output voltage changes due to the pressure received from the received sound wave disposed opposite to the transmitting unit, and the reception level of the receiving unit A signal processing unit that outputs a reception level signal, a rotating body that is freely rotatable forward and backward, and that conveys a sheet fed from the sheet feeding unit to an installation position of the ultrasonic sensor, and an operation of the rotating body. And a control unit that receives the reception level signal and grasps the reception level, and the control unit receives the reception level more than when the sheet does not pass between the transmission unit and the reception unit. Has been reduced, The arrival of the paper to the ultrasonic sensor is detected, and after the arrival of the paper, the amount of deviation of the paper in the double feed state is grasped based on the time until the reception level further decreases, and the deviation is determined in advance. If the value is smaller than the given value, the rotating body is rotated in the reverse direction, and a retry operation is performed to return the double-fed paper toward the paper feeding unit.

  According to this configuration, the retry operation is performed only when the misalignment of each sheet in the double feeding state is small and the sheets are neatly overlapped. Therefore, the retry operation is not performed forcibly until the misalignment of each sheet in the double feed state is large, and the damage or jam to the sheet due to the retry operation can be eliminated. Note that the predetermined value is a threshold value for the grasped deviation amount in order to determine whether or not to perform a retry operation so as not to perform a retry operation that causes a jam. The predetermined value can be determined as appropriate based on experimental data or the like performed in advance so that, for example, the probability of occurrence of damage or jamming on the paper when the retry operation is performed is less than a certain value. For example, the predetermined value can be determined in a range of 1 mm or more and 10 mm or less, for example.

Further, the prior SL controller, is greater than the shift amount is a predetermined value, it was decided to stop all of the rotating body.

  According to this configuration, the retry operation is not performed when the misalignment between the sheets in the double feed state is large. Therefore, the user needs to remove the paper from the paper conveyance path, but does not reach a severe jam that requires time for removal, such as a plurality of paper jams almost simultaneously in the retry operation. Therefore, the user can easily remove the sheet from the conveyance path.

According to a first aspect of the present invention, there is provided an image forming apparatus including detection bodies arranged side by side in a direction perpendicular to the paper transport direction on the paper transport path, and each of the detection bodies detects the arrival of the paper to the detection body. And the control unit recognizes the occurrence of skew of the sheet from the time difference of arrival detection based on the output of each detection body, and when the amount of deviation is equal to or less than a predetermined value, If the time difference is not less than or equal to a predetermined time, the retry operation is not performed and all the rotating bodies are stopped.

  In the double feed state, the conveyance of the paper is unstable as compared with the case where one paper is being conveyed, and the skew of the paper can be severed by the retry operation. If the skew of the paper becomes severe, the paper is likely to be damaged or jammed due to catching in the transport path, etc. According to this configuration, if the paper is skewed, the retry operation is not performed. No paper damage or jam due to retry operation.

Further, the prior SL controller, when the shift amount is a value less than a predetermined time deviation of arrival detection is equal to or less than a predetermined time, it was decided to perform the retry operation.

  According to this configuration, the time difference between the detection of the arrival and passage of the paper by each detection body is within a predetermined time, and even if the degree of skew of the paper performs the retry operation, the paper is damaged or skewed. If there is not enough, retry operation is performed. Therefore, even when the skew is severe, the retry operation is not performed forcibly, and the damage or jam to the paper due to the retry operation can be eliminated. As the time difference between arrival and passage of paper at each skew detection sensor is larger, it can be determined that the conveyed paper is tilted and the degree of skew is greater. The predetermined time is, for example, experimental data obtained in advance. Based on the above, for example, the probability of damage to the paper and the occurrence of jam when the retry operation is performed is determined to be a certain level or less.

According to a second aspect of the present invention, in the first aspect of the present invention, between the ultrasonic sensor and the paper feeding unit, a first roller that rotates in a direction of feeding paper to the ultrasonic sensor, and the paper A separating unit having a second roller that rotates in a direction to send back to the sheet feeding unit is provided, and the control unit operates the separating unit during the retry operation.

  According to this configuration, it is possible to pick up the overlapped sheets during the retry operation, and the user does not need to perform removal work from the sheet conveyance path.

  As described above, the retry operation is performed only when the misalignment of each paper in the double feed state is grasped and the conveyance is recognized to be stable, so that it is possible to prevent the paper from being damaged or jammed by the retry operation. Thus, an image forming apparatus that is highly convenient for the user can be provided.

1 is an external perspective view illustrating an example of a multifunction peripheral according to an embodiment. 1 is a schematic cross-sectional view of an example of a multifunction machine according to an embodiment. 1 is a block diagram illustrating an example of a multifunction machine according to an embodiment. (A) shows an example of arrangement | positioning of the ultrasonic sensor which concerns on embodiment, (b) shows an example of a signal processing part. It is explanatory drawing which shows an example of the relationship between the paper conveyance which concerns on embodiment, and the output waveform from a sample hold circuit. It is a figure which shows an example of the structure which performs detection and the grasp | ascertainment of a grade which concern on embodiment, (a) is normal, (b) describes an example of a skew state. 2A and 2B are schematic cross-sectional views illustrating an example of a conveyance path from a sheet feeding unit to a registration roller pair in the multifunction peripheral according to the embodiment, in which FIG. An example is shown and (c) shows an example of a re-transport state. 6 is a flowchart illustrating an example of sheet conveyance control in the multifunction peripheral according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. However, each element such as configuration and arrangement described in each embodiment does not limit the scope of the invention and is merely an illustrative example.

(Schematic configuration of MFP 100)
First, an outline of an electrophotographic digital multifunction peripheral 100 (corresponding to an image forming apparatus) according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an external perspective view showing an example of a multifunction peripheral 100 according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating an example of the multifunction peripheral 100 according to the embodiment of the present invention.

  As shown in FIG. 1, the multifunction peripheral 100 according to the present embodiment includes an operation panel 10 on the upper front side as a portion for inputting instructions and settings to the multifunction peripheral 100. As shown in FIG. 1 (illustrated by broken lines in FIG. 2), the operation panel 10 displays a setting screen on which various keys for setting are displayed, the status of the multifunction device 100, an error message, and the like, and a touch panel type liquid crystal display. Part 10a, numeric keypad part 10b, and the like.

  As shown in FIG. 1, the front cover 10 </ b> F below the operation panel 10 can be opened and closed, for example, in the direction of a solid line arrow. Further, the side cover 10S on the right side surface of the multifunction device 100 can be opened and closed. Then, when the multifunction peripheral 100 stops when the paper P is jammed or double feed occurs, the user can open the front cover 10F and the side cover 10S to remove the paper P and perform processing operations.

  Next, a description will be given with reference to FIG. As shown in FIG. 2, the multifunction peripheral 100 according to the present embodiment includes the document conveying device 2 at the top, and the image reading unit 3, the paper feeding unit 4, and the conveyance path 5 are provided in the lower part of the multifunction peripheral 100 main body. In addition, an image forming unit 6 and a fixing unit 7 are provided.

  First, the document conveying device 2 automatically and continuously conveys a document on which an image is read toward the feed reading contact glass 31 (reading position) on the upper surface of the image reading unit 3. Optical system members such as an exposure lamp, a mirror, a lens, and an image sensor are provided inside the image reading unit 3 below the document conveying device 2 (not shown).

  In this embodiment, the contact glass on the upper surface of the image reading unit 3 can be roughly divided into two. In FIG. 2, the feed reading contact glass 31 is arranged on the left side, and the placement reading contact glass 32 is arranged on the right side. . Then, the exposure lamp irradiates the document passing through the feed reading contact glass 31 or the document placed on the placement reading contact glass 32, and the reflected light of the document is used as an image sensor by a mirror and a lens. Lead. The image sensor converts an optical signal into an electrical signal for each pixel, and obtains image data of the document. For example, in the MFP 100, printing is performed based on the image data obtained by the image reading unit 3 (copy function).

  The paper supply unit 4 supplies paper P at the time of printing and is provided at the lowermost part of the multifunction peripheral 100, and supplies paper such as copy paper, OHP paper, and label paper. The paper feed unit 4 includes a cassette 40, a paper feed roller 41, and the like. The cassette 40 can store various sizes and various types of paper P and can be attached to and detached from the multifunction peripheral 100. For example, the cassette 40 is removed at the time of paper supply, jam processing, and the like. The paper feed roller 41 is in contact with the uppermost paper P and is rotationally driven in a predetermined direction (clockwise in FIG. 2) by a motor (not shown) to send the paper P to the transport path 5 one by one.

  The transport path 5 is a path for transporting the paper P supplied from the paper feed unit 4 to the discharge tray 51. In order to carry the inside of the apparatus, the paper path P can be rotated in the forward and reverse directions in order from the upstream side, and the paper P fed from the paper feeding unit 4 can be placed in the conveyance path 5 in order from the upstream side. A sheet conveying roller such as a conveying roller pair 53 (corresponding to a rotating body), a registration roller pair 54, and a discharge roller pair 55 is provided. A number of guide members 56 for guiding the paper P are provided in the transport path 5.

  The webbing unit 52 includes a progressive roller 57 (corresponding to the first roller) on the upper side in FIG. 2 that rotates between the ultrasonic sensor 8 and the paper feeding unit 4 in the direction of feeding the paper P to the ultrasonic sensor 8. 2 has a reverse feed roller 58 (corresponding to a second roller) on the lower side in FIG. For example, the winding unit 52 receives the driving force of the winding motor 52M provided in the multifunction peripheral 100, and the progressive roller 57 rotates in the direction of transporting the paper P in the downstream direction. On the other hand, the reverse feed roller 58 rotates in a direction in which the paper P is transported in the upstream direction (the paper feed unit direction). In addition, the separation unit 52 operates during the retry operation, and spreads a plurality of sheets P conveyed toward the sheet feeding unit 4 (details will be described later).

  The transport roller pair 53 (corresponding to a rotating body) is a rotating body that transports the paper P toward the registration roller pair 54, receives a driving force from the transport motor 53M (see FIG. 3), and rotates to drive the paper. . The transport roller pair 53 can transport the paper P both in the upstream direction and in the downstream direction, for example, by switching between forward and reverse rotations of the transport motor 53M. The discharge roller pair 55 receives the driving force of the discharge motor 55M and rotates to discharge the paper P to the discharge tray 51. The registration roller pair 54 is provided on the upstream side of the image forming unit 6 in the paper conveyance direction. The registration roller pair 54 abuts on the conveyed paper P, bends the paper P, and then rotates.

  Then, the registration roller pair 54 sends out the paper P in time with the toner image formed by the image forming unit 6. In addition, the transmitting unit 81 that transmits sound waves and the transmitting unit 81 facing the transmitting unit 81 so as to sandwich the transported paper P between the registration roller pair 54 upstream of the sheet conveying direction and downstream of the sheet feeding unit 4 in the sheet conveying direction. Thus, an ultrasonic sensor 8 including a receiving unit 82 whose output voltage changes depending on the pressure received from the received sound wave is provided. The ultrasonic sensor 8 can also detect the inclination of the sheet P that is bent by being abutted against the registration roller pair 54.

  The image forming unit 6 forms a toner image based on the image data obtained by the image reading unit 3 and the image data transmitted from the user terminal 200, and transfers the toner image to the paper P to form the image on the paper P. To do. Specifically, the image forming unit 6 includes a photosensitive drum 61, a charging device 62, a developing device 63, an exposure device 64, a transfer roller 65, a cleaning device 66, and the like disposed around the photosensitive drum 61.

  The photosensitive drum 61 is provided at substantially the center of the image forming unit 6 and is supported so as to be rotatable in the arrow direction shown in FIG. The charging device 62 is provided above the photosensitive drum 61 and charges the surface of the photosensitive drum 61 to a predetermined potential. The exposure device 64 is composed of, for example, a laser scanning unit or the like, and irradiates light onto the surface of the photosensitive drum 61 based on image data, performs scanning exposure, and forms an electrostatic latent image. The developing device 63 is provided on the right side of the photosensitive drum 61, charges the toner, supplies the toner to the electrostatic latent image on the photosensitive drum 61, and develops it.

  The transfer roller 65 provided below the photoconductive drum 61 is pressed against the photoconductive drum 61 to form a nip. When printing or the like, the photoconductive drum 61 and the transfer roller 65 rotate to convey the paper P. To do. Further, when the paper P sent out from the registration roller pair 54 passes through the nip, a predetermined voltage is applied to the transfer roller 65, and the toner image on the photosensitive drum 61 is transferred to the paper P. The cleaning device 66 cleans the toner remaining on the surface of the photoreceptor drum 61 for the next toner image formation after the transfer is completed.

  The fixing unit 7 is provided downstream of the image forming unit 6 in the sheet conveyance direction, and fixes the toner image formed by the image forming unit 6 and transferred to the sheet P while conveying the sheet. The fixing unit 7 in the present embodiment is mainly composed of a heating roller 71 and a pressure roller 72 in which a heat source is built. The pressure roller 72 is pressed against the heating roller 71 to form a nip. The heating roller 71 and the pressure roller 72 rotate to convey the paper P that has entered the nip. When the paper P passes through the nip, it is heated and pressurized, the toner is melted and heated, and the toner image is fixed on the paper P. The fixed sheet P is discharged to the discharge tray 51, and one image forming process is completed.

(Hardware configuration of MFP 100)
Next, based on FIG. 3, the hardware configuration of the multifunction peripheral 100 according to the embodiment of the present invention will be described with an emphasis on paper conveyance. FIG. 3 is a block diagram illustrating an example of the multifunction peripheral 100 according to the embodiment of the present invention.

  First, as shown in FIG. 3, a control unit 1 including a CPU 11, electronic components (not shown), and the like is provided in the main body for controlling the operation of the entire multifunction peripheral 100. The CPU 11 functions as a central processing unit, performs various calculations based on programs and data stored in or input to the storage unit 12, and controls each unit of the multifunction peripheral 100.

  Further, the CPU 11 issues an operation instruction to the controller 14 that controls various motors that supply driving force for paper conveyance in the machine. That is, the operation of various rotating bodies in the multifunction peripheral 100 is controlled. The control unit 1 is connected to the signal processing unit 15 that processes the output voltage of the reception unit 82 and outputs a reception level signal LV indicating the reception level of the reception unit 82, and receives the reception level signal LV from the signal processing unit 15. The reception level of the reception unit 82 is grasped. The timer unit 16 provided in the controller 1 (may be outside the controller 1) is a timer, and counts various times for control.

  The storage unit 12 includes, for example, a memory such as a RAM, an HDD, and a flash ROM, and is connected to the control unit 1. The storage unit stores a control program, control data, image data, and setting information of the MFP 100 by the user. And the control part 1 (CPU11) reads a program, data, etc. from the memory | storage part 12 for control, and performs control.

  The control unit 1 communicates with the document conveying device 2, the image reading unit 3, the paper feeding unit 4, the conveyance path 5, the image forming unit 6, the fixing unit 7, the I / F unit 13 and the like that constitute the multifunction peripheral 100. The operation of each unit is controlled on the basis of a program stored in the storage unit 12 and the like.

  The I / F unit 13 includes a connector and a socket for connecting to the user terminal 200 (for example, a personal computer) directly or via a network. A modem for FAX communication is also provided. As a result, the multifunction peripheral 100 can receive and print image data transmitted from the user terminal 200 (printer function). Further, the image data read by the image reading unit 3 can be transmitted to the user terminal 200 (scanner function). Further, image data can be transmitted / received to / from the counterpart FAX apparatus 300 (FAX function).

  In the multi-function device 100 of the present embodiment, an ultrasonic sensor 8 is provided in order to detect double feeding of the paper P, and further, a skew detection sensor for grasping the skew and skew of the paper P. 9A and a skew detection sensor 9B are also provided. The control unit 1 instructs to drive the ultrasonic sensor 8, and the output voltage of the ultrasonic sensor 8 is processed by the signal processing unit 15 and then input to the control unit 1 (CPU 11). The output voltages of the skew detection sensor 9A and the skew detection sensor 9B are input to the control unit 1 (CPU 11). Details of the skew detection will be described later.

  The control unit 1 is connected to a controller 14 that controls various motors that rotate various rotating bodies for paper conveyance and image formation. Then, the control unit 1 gives an instruction to the controller 14 such as a motor to be operated, and the controller 14 receives an instruction from the control unit 1 and controls each motor and the like. In addition, if the control part 1 bears the function of the controller 14, the controller 14 is unnecessary and you may comprise the control part 1 and the controller 14 integrally. In addition, in FIG. 3, the relationship of the driving force supplied to each member from a motor is shown with the dashed-two dotted line.

  For example, as a motor provided in the multifunction peripheral 100, a conveyance motor 53M for rotating the conveyance roller pair 53 and the registration roller pair 54, a separation motor 52M for rotating each roller of the separation unit 52, and the image forming unit 6 are provided. A main motor 6M that rotates a member that rotates during printing, such as the photosensitive drum 61, a fixing motor 7M that rotates the heating roller 71 and the pressure roller 72 of the fixing unit 7, and a discharge motor 55M that rotates the discharge roller pair 55. There is. The controller 14 controls the operation of each motor, such as turning on / off the rotation. For example, the number of motors installed may be reduced by supplying driving force from one motor to a plurality of rollers, such as rotating the discharge roller pair 55 by the fixing motor 7M.

  Here, the registration roller pair 54 of the present embodiment starts rotating in accordance with the toner image formed by the image forming unit 6 after the sheet P is abutted and bent to correct skew. Accordingly, the rotation timing is different from that of the transport roller pair 53. Therefore, an electromagnetic clutch 59 is provided to control ON / OFF of driving force transmission to the registration roller pair 54.

  The controller 1 is connected to a switch SW1 for detecting opening / closing of the front cover 10F and a switch SW2 for detecting opening / closing of the side cover 10S. The switches SW1 and SW2 are, for example, interlock switches that are switched ON / OFF by opening / closing each cover, and the control unit 1 detects opening / closing of the front cover 10F and the side cover 10S.

(Configuration of ultrasonic sensor 8 and signal processing unit 15)
Next, based on FIG. 4, the configuration of the ultrasonic sensor 8 according to the embodiment of the present invention and the signal processing unit 15 that processes the output voltage of the receiving unit 82 of the ultrasonic sensor 8 will be described. 4A shows an example of the arrangement of the ultrasonic sensors 8 according to the embodiment of the present invention, and FIG. 4B shows an example of the signal processing unit 15.

  First, a description will be given based on FIG. As described with reference to FIG. 2, in the multi-function device 100 of this embodiment, the ultrasonic sensor 8 is provided upstream of the registration roller pair 54 (between the conveyance roller pair 53 and the registration roller pair 54). Accordingly, the rotating body shown on the left side of FIG.

  The ultrasonic sensor 8 includes a transmission unit 81 that transmits ultrasonic waves and a reception unit 82 that receives sound waves from the transmission unit 81. For example, in the ultrasonic sensor 8, a piezoelectric body (for example, piezoelectric ceramic) is built in each of the transmitter 81 and the receiver 82. In the transmitter 81, a voltage is applied between the electrodes of the piezoelectric body at a frequency in the ultrasonic range, mechanical deformation corresponding to the voltage occurs in the piezoelectric body, and ultrasonic waves are radiated from the transmitter 81. When the ultrasonic wave radiated from the transmitter 81 is applied to the piezoelectric body of the receiver 82, a voltage corresponding to the wave is extracted between the electrodes of the piezoelectric body.

  As shown in FIG. 4A, the transmitter 81 and the receiver 82 are arranged to face each other so that the detection surfaces sandwich the paper P therebetween. In other words, the transmitter 81 and the receiver 82 are provided so as to sandwich the paper P in a direction perpendicular to the paper transport direction. The transmitter 81 emits sound waves toward the paper P, and the receiver 82 receives the sound waves transmitted over the paper P and outputs a voltage.

  Next, an example of the signal processing unit 15 that processes the output voltage (signal) of the receiving unit 82 and inputs it to the CPU 11 will be described with reference to FIG.

  For example, the signal processing unit 15 includes an amplifier circuit 17 and a sample hold circuit 18. The receiving unit 82 outputs a voltage corresponding to the vibration of the sound wave. The output voltage of the receiving unit 82 is input to, for example, the amplifier circuit 17 and the amplitude is amplified. A sample hold circuit 18 is connected to the amplifier circuit 17. The sample hold circuit 18 includes a capacitor, for example. The sample hold circuit 18 charges the output signal of the amplifier circuit 17 in a built-in capacitor. In this way, the sample hold circuit 18 converts the output signal of the amplifier circuit 17 into DC and holds the level for a certain time. Then, the output terminal of the sample hold circuit 18 is connected to the A / D conversion port of the CPU 11 (an A / D converter may be provided), and the CPU 11 takes in the output of the sample hold circuit 18 at an arbitrary timing. In this way, the reception level signal LV indicating the reception level of the reception unit 82 is input to the CPU 11, and the CPU 11 grasps the reception level of the reception unit 82. In other words, the CPU 11 captures the output voltage of the sample hold circuit 18 as the reception level signal LV indicating the reception level of the reception unit 82. The sample and hold circuit 18 discharges the capacitor in the sample and hold circuit 18 in accordance with a signal from the CPU 11 issued at an arbitrary timing.

  Specifically, the amplitude of the output voltage of the reception unit 82 increases as the sound wave from the transmission unit 81 sufficiently reaches, so the voltage of the reception level signal LV that the CPU 11 captures from the sample hold circuit 18 (signal processing unit 15). The value gets bigger. As the number of sheets P between the transmitting unit 81 and the receiving unit 82 increases (one sheet for normal conveyance and two or more sheets for double feeding), sound waves are reflected and blocked by the sheet P and reach the receiving unit 82. The level of the sound wave becomes small and the amplitude of the output voltage of the receiving unit 82 becomes small. Therefore, if double feeding occurs, the voltage value of the reception level signal LV grasped by the CPU 11 becomes smaller than during normal paper conveyance.

(Detection of paper arrival and double feed detection)
Next, an example of detection of arrival of the paper P to the ultrasonic sensor 8 and double feed detection by the ultrasonic sensor 8 of the present embodiment will be described with reference to FIG. FIG. 5 is an explanatory diagram showing an example of the relationship between the sheet conveyance and the output waveform from the sample hold circuit 18 according to the embodiment of the present invention. The graph in FIG. 5 is grasped by the CPU 11 after the output voltage of the receiving unit 82 is amplified and inputted to the sample hold circuit 18 when the paper P is conveyed in the double feed state toward the ultrasonic sensor 8. It is an example of an output waveform (in other words, the reception level signal LV output from the signal processing unit 15), and the vertical axis indicates the amplitude.

  In FIG. 5, it can be seen that the reception level signal LV changes when the double-feed paper P passes through the transmitter 81 and the receiver 82. If the paper P has not yet reached the ultrasonic sensor 8, the sound wave is not blocked by the paper P, so that the amplitude of the output voltage of the sample hold circuit 18 is maximized (section of the “no paper” white arrow). . When the leading portion of the paper P in the multi-feed state reaches between the transmitting unit 81 and the receiving unit 82, if there is a deviation in the paper transport direction, the paper P existing between the transmitting unit 81 and the receiving unit 82 is This is one sheet (the section indicated by the white arrow of “1 sheet”). At this time, the amplitude of the output voltage of the sample-and-hold circuit 18 is clearly smaller than when there is no paper P, and the control unit 1 (CPU 11) can recognize that the reception level has decreased.

  Further, when there are two or more sheets of paper P between the transmitting unit 81 and the receiving unit 82 due to double feeding (section of white arrows of “double feeding”), the sound wave from the transmitting unit 81 is caused by the paper P. Reflected or shielded and hardly reaches the receiving unit 82, and the output voltage of the sample and hold circuit 18 becomes extremely small. Therefore, the control unit 1 (CPU 11) grasps that the reception level has further decreased.

  Therefore, an example of arrival of the paper P to the ultrasonic sensor 8 and double feed detection using the ultrasonic sensor 8 of the present embodiment will be described. The distance from the paper feed unit 4 to the ultrasonic sensor 8 is clear in advance. Further, the conveyance speed (circumferential speed) of the paper feed roller 41, the conveyance roller pair 53, etc. has an ideal speed in terms of specifications and is known in advance. For this reason, the control unit 1 can predict how many seconds after the sheet feeding start of the sheet feeding unit 4 the sheet P reaches the ultrasonic sensor 8. Therefore, as illustrated in FIG. 5, the control unit 1 causes the transmission unit 81 to perform transmission before the ultrasonic sensor 8 reaches the paper P.

  For example, the control unit 1 starts transmission from the transmission unit 81 before the expected arrival time to the ultrasonic sensor 8 from the start of paper feeding (for example, 0.5 to 1 second before) (in FIG. 5). "No paper" section). At this time, since the sheet P does not exist between the transmission unit 81 and the reception unit 82, the amplitude of the output waveform (reception level signal LV) of the sample hold circuit 18 is maximum, and the reception level of the reception unit 82 is maximum. It is grasped by the control unit 1.

  When only one sheet P is transported without double feeding, or when the leading portion of the sheet P in the double feeding state reaches the ultrasonic sensor 8, the reception level of the receiving unit 82 is "paper" It becomes smaller than "None". Accordingly, the control unit 1 can grasp that the paper P has reached the ultrasonic sensor 8 by grasping a change in which the voltage value of the reception level signal LV becomes smaller than that of “no paper”.

  After the arrival of the paper at the ultrasonic sensor 8 is detected, the reception level of the receiving unit 82 is further lowered due to the multi-feeding before returning to the reception level at the time of “no paper” due to paper passage. Therefore, the control unit 1 can detect double feeding. Furthermore, the time from when the paper arrival detection (decrease to the reception level when only one sheet P is detected) until the further decrease of the reception level of the receiving unit 82 due to double feeding is detected (for example, the time measuring unit 16 or By multiplying the CPU 11 by the paper transport speed at the transport roller pair 53, the shift amount D of each paper P in the double feed state in the paper transport direction can be grasped.

  For example, two levels of threshold values are set for the reception level signal LV (voltage value of the reception level signal LV) input to the CPU 11 for detecting the arrival of one sheet and for detecting the double feed, and for detecting the arrival of one sheet. When the reception level signal LV falls below the threshold value, the control unit 1 may determine that the paper P has arrived. Further, when the reception level signal LV falls below the threshold for detecting double feed, the control unit 1 may determine that double feed has occurred. For example, the threshold value may be stored in the storage unit 12. As described above, the control unit 1 can detect the arrival of the sheet to the ultrasonic sensor 8 and the occurrence of the double feed by using the ultrasonic sensor 8, and the deviation amount of each paper P in the double feed state in the paper transport direction. D can be grasped.

(Detect skew and grasp the degree of skew)
Based on FIG. 6, the detection of the skew and the grasp of the degree in the sheet conveyance of the multifunction peripheral 100 according to the embodiment of the present invention will be described. FIG. 6 is a diagram illustrating an example of a configuration for detecting skew and grasping the degree according to the embodiment of the present invention. FIG. 6A illustrates an example of normal operation and FIG. 6B illustrates an example of a skew state.

  First, the skew detection sensor 9 is provided, for example, on the sheet transport path of the transport path 5 between the paper feed unit 4 and the image forming unit 6 in a direction perpendicular to the sheet transport direction. Detects the arrival and passage of the paper P to the detection area of the skew detection sensor 9. For example, as shown in FIG. 6, the skew detection sensor 9 is the same line in the direction perpendicular to the ultrasonic sensor 8 and the paper conveyance direction as compared with the ultrasonic sensor 8 provided substantially at the center in the width direction of the conveyance path 5. Above, they are provided side by side so as to face the end of the sheet P being conveyed (two in total).

  In FIG. 6, the upper one is labeled with the skew detection sensor 9 </ b> A, and the lower one is labeled with the skew detection sensor 9 </ b> B. However, in the following, A, The sign of B is omitted. Further, the two skew detection sensors 9A and 9B may be arranged closer to the center than the example shown in FIG. 6 so that the skew of a smaller size sheet can be detected. Further, two or more skew detection sensors 9 may be arranged on the same line in the direction perpendicular to the sheet conveyance direction.

  The skew detection sensor 9 can be an optical sensor including a light emitting unit (for example, including an LED) and a light receiving unit (for example, including a phototransistor or a photodiode). The output voltage of the light receiving portion of the skew detection sensor 9 is finally input to the CPU 11 (see FIG. 3). For example, in the skew detection sensor 9, if the paper P exists in the detection region of the skew detection sensor 9, the optical path from the light emitting unit to the light receiving unit is blocked by the paper P. Due to the decrease in the output voltage of the light receiving unit, the control unit 1 can detect that the paper has reached or is passing. If the output voltage of the light receiving unit recovers from the lowered state to the same level as when the paper P is not in the detection area, the control unit 1 can detect that the paper P has passed through the skew detection sensor 9.

  In the description of the present embodiment, a case where an optical sensor is used as the skew detection sensor 9 will be described. However, since the arrival of the paper P can be detected by an ultrasonic sensor, the ultrasonic sensor is used as the skew detection sensor 9. Also good. That is, when the ultrasonic sensor 8 is used, three ultrasonic sensors 8 are arranged in a direction perpendicular to the paper conveyance direction.

  First, FIG. 6A shows a normal sheet conveyance state in which the sheet P is not skewed or the skew amount is almost zero. In this case, each skew detection sensor 9 detects the arrival of the paper P at the same time or almost simultaneously, and the output is switched. Thereby, for example, the CPU 11 of the control unit 1 can detect that there is no skew that causes jamming such as catching on the conveyance path 5 and winding around each roller or the like during sheet conveyance.

  Next, FIG. 6B shows an example when the skew of the paper P occurs. In this case, since the paper arrival timing to each detection area of the skew detection sensor 9A and the skew detection sensor 9B is shifted, there is a time difference in the output change of each light receiving unit. Then, for example, the control unit 1 causes the time measuring unit 16 to measure the time from the decrease in the output voltage of one skew detection sensor 9 to the decrease in the output voltage of the other skew detection sensor 9. Further, since the control unit 1 grasps the sheet conveyance speed by controlling the rotation speed of the conveyance motor 53M that rotates each conveyance roller pair 53, the sheet in the sheet conveyance direction can be obtained by multiplying this time difference by the sheet conveyance speed. The difference in the position of the corner portion of the front end of P, that is, a standard for skewing (shown as Δ in FIG. 6B) can be obtained by calculation.

  Note that the greater the time difference between the output changes of the two skew detection sensors 9, the greater the paper P skews (Δ is greater). Therefore, this time lag can be used as a guide for skew. In this way, the control unit 1 can monitor the output of each skew detection sensor 9 and grasp the occurrence of skew and the degree of skew between the sheet feeding unit 4 and the registration roller pair 54.

  An example of jam occurrence detection in the multifunction machine 100 of this embodiment will be described. For example, the control unit 1 monitors the output of the ultrasonic sensor 8 and each skew detection sensor 9, and the ultrasonic sensor 8 and each skew detection sensor 9 are times when the paper arrival should be detected. If no arrival is detected, it is determined that a jam has occurred. In addition, the control unit 1 determines that a jam has occurred when the ultrasonic sensor 8 and each skew detection sensor 9 do not detect the passage of the paper P even though it is time to detect the passage of the paper.

  That is, the control unit 1 can also detect the occurrence of a jam with the ultrasonic sensor 8 and each skew detection sensor 9. In addition, the control part 1 should just make the time measuring part 16 time-measure. When the control unit 1 determines that a jam has occurred, the control unit 1 stops all the printing operations such as paper conveyance, paper feed, and image formation, displays the fact that a jam has occurred on the liquid crystal display unit 10a of the operation panel 10, and To inform.

  In the jam handling operation, the user removes the cassette 40, opens the front cover 10F, the side cover 10S, and the like in the same manner as in the paper removal operation of the conveyance path 5 at the time of double feed detection, which will be described later. Is removed, and all the paper P remaining in the transport path 5 is removed, including the paper P on which the jam has occurred. Then, the control unit 1 detects that each cover is closed with the switches SW1, SW2, and the like, and then detects that there is no paper P in the transport path 5 by the ultrasonic sensor 8 or each skew detection sensor 9. If it can be confirmed, the control unit 1 cancels the jammed state and starts reprinting.

(Retry operation)
Next, an example of a retry operation in the multifunction machine 100 of the present embodiment will be described based on FIG. FIG. 7 is a schematic cross-sectional view illustrating an example of a conveyance path from the sheet feeding unit 4 to the registration roller pair 54 in the multifunction peripheral 100 according to the present embodiment. FIG. b) shows an example of the reverse feed state, and (c) shows an example of the re-transport state. Although not actually linear, in each drawing of FIG. 7, for the sake of convenience, the paper conveyance path from the paper supply unit 4 to the registration roller pair 54 is shown linearly. Further, in each drawing of FIG. 7, the upper sheet P in the double feed is indicated by a solid line, and the lower sheet P in the double feed is indicated by a broken line.

  First, FIG. 7A shows a state where each paper P in the double feed state is conveyed to the ultrasonic sensor 8. In the MFP 100 according to the present embodiment, as described above, the multifeed is detected using the ultrasonic sensor 8. At this time, if the deviation amount D2 of the upper sheet P and the lower sheet P in the sheet conveyance direction is less than a predetermined value, the control unit 1 moves the conveyance roller as shown in FIG. The pair 53 is rotated in the reverse direction, and a retry operation is performed in which each paper P in the double feed state is conveyed toward the paper feed unit 4.

  Due to the retry operation, the paper P is fed back in the direction of the paper feed unit 4 and reaches the whirling unit 52 from the transport roller pair 53. Then, the paper P in the double feed state is picked up by the progressive feed roller 57 and the reverse feed roller 58 of the separation unit 52. Then, as shown in FIG. 7C, for example, the upper paper P is again sent in the direction of the registration roller pair 54, and the lower paper P is sent back to the paper feeding unit 4. In the state of FIG. 7C, the paper feed roller 41 may be rotated in the opposite direction to that during paper supply.

  By the retry operation by reverse feeding of the paper and the paper feeding, even if there is a double feed, normal paper conveyance is automatically performed without performing a paper removal operation or the like. However, when the deviation in the sheet conveyance direction of each sheet P in the multi-feed state is large, the sheet conveyance is unstable, skewing or the like is likely to occur, and the sheet P is easily caught on the conveyance path 5 and is caused by a retry operation. Reverse feed may cause a jam (paper jam). Therefore, when the deviation amount D2 is large, it is easier for the user to work by stopping the paper conveyance and removing the paper P from the conveyance path 5 before reaching the jam. Therefore, hereinafter, sheet conveyance control in the multifunction peripheral 100 of the present embodiment will be described.

(Double feed detection and paper transport control)
Next, based on FIG. 8, an example of double feed detection and paper transport control in the multifunction peripheral 100 according to the embodiment of the present invention will be described. FIG. 8 is a flowchart illustrating an example of sheet conveyance control in the multifunction peripheral 100 according to the embodiment of the present invention.

  First, the start of FIG. 8 is the start of printing on the multifunction peripheral 100, such as when copying starts or when image data is transmitted from the user terminal 200 and printing starts as a printer. Then, the paper P is fed (step # 1), the separation unit 52 is driven, and the paper P is conveyed toward the registration roller pair 54 (step # 2).

  Next, the control unit 1 drives the ultrasonic sensor 8 (step # 3), and the paper reaches the ultrasonic sensor 8 due to a decrease in the reception level of the ultrasonic sensor 8 (voltage value of the reception level signal LV). Detection is performed (step # 4). Next, the control unit 1 performs double feed detection based on whether or not the reception level of the ultrasonic sensor 8 further decreases, and checks whether or not double feed has occurred (step # 5). If double feed is not detected (No in step # 5), the control unit 1 bends the paper P by the registration roller pair 54, and then drives the registration roller pair 54, thereby causing the image forming unit 6 and the fixing unit 7 to move. Then, various rollers such as the discharge roller pair 55, a drum, and the like are rotated to perform sheet conveyance, printing, and sheet discharge (step # 6), and the sheet conveyance accompanying the printing is ended (end).

  On the other hand, if double feed is detected (Yes in step # 5), the control unit 1 grasps the deviation amount of each paper P in the double feed state (step # 7). Specifically, in a time period from when the ultrasonic sensor 8 detects the arrival of the paper P until when the reception level of the ultrasonic sensor 8 further decreases (voltage value of the reception level signal LV), By multiplying the grasped sheet conveyance speed (circumferential speed of the conveyance roller pair 53), the deviation amount in the sheet conveyance direction of each sheet P in the double feed state is obtained.

  Then, the control unit 1 confirms whether or not the grasped deviation amount is equal to or less than a predetermined value (step # 8). This predetermined value is a threshold value for the grasped deviation amount in order to determine whether or not to perform a retry operation so as not to perform a retry operation that causes a jam. The predetermined value can be determined as appropriate based on experimental data or the like performed in advance so that, for example, the probability of damage to the paper P or the occurrence of a jam when performing a retry operation is below a certain level. For example, the predetermined value can be determined in a range of 1 mm or more and 10 mm or less, for example. If the deviation amount is larger than 10 mm, it can be confirmed by experiments or the like that a jam occurs during the retry operation or it is easy to cause a jam. The predetermined value is set to 10 mm.

  If the amount of deviation is less than or equal to a predetermined value (Yes in step # 8), the control unit 1 confirms the time deviation of the paper arrival detection of the two skew detection sensors 9 (step # 9). In other words, the degree of skew of each paper P in the double feed state is confirmed. Furthermore, the control unit 1 confirms whether the time difference is equal to or less than a predetermined time (step # 10).

  As the time difference between arrival and passage of the paper P at each skew detection sensor 9 increases, it can be determined that the conveyed paper P is tilted and the degree of skew is large. For example, the predetermined time is set in advance. Based on the experimental data, for example, the probability of damage to the paper P and the occurrence of jam when the retry operation is performed is determined to be a certain level or less. If the time is longer than the predetermined time, the control unit 1 can determine that the skew feeding is likely to cause a jam if the retry operation is performed on the double-feed paper P.

  If the time difference is equal to or less than a predetermined time (Yes in Step # 10), the control unit 1 reversely rotates the conveyance roller pair 53 and operates the separation unit 52 to convey the predetermined time. The roller pair 53 is reversely rotated to operate the whirling portion 52 to perform a retry operation (step # 11). Thereafter, for example, the process returns to step # 2.

  That is, the control unit 1 detects the arrival of the paper P to the ultrasonic sensor 8 when the reception level is lower than when the paper P does not pass between the transmission unit 81 and the reception unit 82, and the paper P Based on the time until the reception level further decreases after the arrival detection, the shift amount of the paper P in the double feed state is grasped, and if the shift amount is smaller than a predetermined value, the rotating body is reversely rotated. Then, a retry operation is performed to send back the paper P in the double feed state toward the paper feed unit 4. Further, the control unit 1 recognizes the occurrence of skew of the paper P from the arrival detection time lag based on the output of each detection body. However, if the time difference between arrival and passage detection is within a predetermined time, the control unit 1 causes a retry operation to be performed.

  It should be noted that the amount of deviation of the double-feed state paper P in the paper conveyance direction is larger than a predetermined value (No in Step # 8), and the time deviation of the paper arrival detection of the skew detection sensor 9 is If the time is longer than the predetermined time (No in Step # 10), the probability that a jam will occur even if the retry operation is performed is high, and the control unit 1 stops the paper conveyance (Step # 12), and the operation panel. An error display indicating that the paper P should be removed from the transport path 5 is displayed on the ten liquid crystal display units 10a and the like (step # 13). That is, if the deviation amount is larger than a predetermined value, the control unit 1 stops all the rotating bodies.

  Then, the user removes the sheet from the conveyance path 5 (step # 14), and the control unit 1 detects that the front cover 10F and the side cover 10S are closed, and the ultrasonic sensor 8 and the skew detection. By confirming that the sheet P is not detected by the sensor 9 or the like, it is confirmed whether or not the sheet removal operation is completed (step # 15). If not completed (No in Step # 15), the process returns to Step # 14. If completed (Yes in Step # 15), the process returns to, for example, Step # 1 to resume printing.

  In this way, according to the configuration shown in the present embodiment, the retry operation is performed only when the misalignment of the sheets P in the double feed state is small and neatly overlapped. Accordingly, it is possible to eliminate damage and jam to the paper P due to the retry operation without forcibly performing the retry operation until the deviation of each paper P in the double feed state is large. Further, when the shift amount of each paper P in the double feed state is large, the retry operation is not performed. Therefore, although the user needs to remove the paper P from the conveyance path 5 of the paper P, a severe jam that requires time for removal, such as a plurality of paper P jammed substantially simultaneously by the retry operation, is reached. There is nothing. Therefore, the user can easily remove the paper P from the transport path 5.

  Further, in the double feeding state, compared with the case where one sheet P is being transported, the sheet transport is unstable, and the skew of the sheet P can be severed by the retry operation. If the skew of the paper P becomes severe, the paper P is liable to be damaged or jammed due to catching in the conveyance path 5, etc. However, if the paper P is skewed, the retry operation is not performed. No damage or jam to the paper P due to operation. Further, the time difference between the detection of the arrival and passage of the paper P by each skew detection sensor 9 (detection body) is within a predetermined time, and even if the degree of skew of the paper P performs the retry operation, the paper P If there is no damage or skew, retry operation is performed. Therefore, even if the skew is severe, the retry operation is not performed forcibly, and damage or jam to the paper P due to the retry operation can be eliminated. Further, the sheeting portion 52 can be used to pick up the overlapped sheets P during the retry operation, and the user does not need to perform the operation of removing the sheets P from the conveyance path 5.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention is applicable to an image forming apparatus that conveys paper.

DESCRIPTION OF SYMBOLS 1 Control part 15 Signal processing part 4 Paper feed part 52 Separation part 53 Conveyance roller pair (rotary body) 57 Progressive roller (1st roller)
58 Reverse feed roller (second roller) 8 Ultrasonic sensor 81 Transmitter 82 Receiver 9A Skew detection sensor (detection body) 9B Skew detection sensor (detection body)
100 MFP (image forming device)

Claims (2)

A paper feed unit that supplies paper during printing;
An output voltage is provided by a pressure received from a transmitting unit that is provided downstream of the sheet feeding unit in the sheet conveyance direction and transmits sound waves, and a received sound wave that faces the transmitting unit so as to sandwich the sheet to be conveyed. An ultrasonic sensor including a changing receiver;
A signal processing unit that processes an output voltage of the reception unit and outputs a reception level signal indicating a reception level of the reception unit;
A rotating body that can freely rotate forward and backward, and conveys a sheet fed from the sheet feeding unit to an installation position of the ultrasonic sensor;
A control unit that controls the operation of the rotating body, receives the reception level signal, and grasps the reception level ;
A detector arranged side by side in a direction perpendicular to the paper transport direction on the paper transport path ,
Each of the detection bodies detects the arrival of the paper to the detection body,
The control unit recognizes the occurrence of skew of the sheet from the time difference of arrival detection based on the output of each detection body , and the control unit is more than when the sheet is not passing between the transmission unit and the reception unit. When the reception level is reduced, the arrival of the paper to the ultrasonic sensor is detected, and the amount of deviation of the paper in the multifeed state is grasped based on the time until the reception level further decreases after the arrival of the paper is detected. When the deviation amount is larger than a predetermined value, all of the rotating bodies are stopped, and when the deviation amount is equal to or less than a predetermined value , the arrival detection time deviation is equal to or less than a predetermined time. If this is the case, a retry operation is performed in which the rotating body is rotated in the reverse direction and the double-fed paper is sent back toward the paper feed unit. If the time difference in arrival detection is not less than a predetermined time , the retry operation is performed. The rotating body does not operate Image forming apparatus characterized by stopping all. Between the ultrasonic sensor and the paper feeding unit, there is provided a separating unit having a first roller that rotates in a direction to send the paper to the ultrasonic sensor and a second roller that rotates in a direction to send the paper back to the paper feeding unit. Prepared,
Wherein, during the retry operation, the image forming apparatus according to claim 1, wherein the operating the separation unit.

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