JP2021107271A - Sheet transport device and image formation device - Google Patents

Abstract

To provide a sheet transport device which can distinguish incorrect setting of a sheet length from feeding of overlapping sheets to inhibit unnecessary repetitive operations.SOLUTION: A sheet transport device includes: a paper cassette 50 which stores sheets; a separated paper feeding part 51 which transports each sheet stored in the paper cassette 50; an operation part 306 which sets a length as seen in a transport direction (a sheet setting length) of the sheets stored in the paper cassette 50; a transport sensor 61 for detecting a length as seen in the transport direction of each transported sheet (a sheet measurement length); and an overlap feeding detection sensor 60 for detecting whether or not two or more of the sheets are transported overlapping each other. The sheet transport device determines whether or not to transport the sheet based on a detection result of the overlap feeding detection sensor 60 when the sheet measurement length is longer than the sheet setting length.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sheet transfer device having a function of detecting a state in which two or more sheets are transferred in an overlapping manner, and an image forming device including the sheet transfer device.

The image forming apparatus forms an image while conveying the sheets one by one by the sheet conveying device. If two or more sheets are stacked and transported, a blank product may be discharged or the sheets may be jammed. The state in which two or more sheets are stacked and transported is called "double feeding". Double feeding is detected by, for example, the technique of Patent Document 1. The image forming apparatus of Patent Document 1 compares the length of the sheet in the transport direction (measured length of the sheet) measured during transport with the length of the sheet in the transport direction set by the user (set length of the sheet). Double feed is detected when the sheet measurement length is longer than the standard value or more than the sheet set length.

When the image forming apparatus detects the double feed, the image forming apparatus notifies the user that the double feed has occurred. Further, the sheet determined to be double-fed is discharged through, for example, another transport path different from the transport path at the time of normal printing processing. By automatically ejecting a sheet when double feeding is detected and printing on another sheet, the printing process can be continued without bothering the user.

Japanese Unexamined Patent Publication No. 2014-56161

A setting error may occur in which the seat setting length is set shorter than the length in the transport direction (seat length) of the sheet to be actually transported. For example, A4 size may be set even though the sheet is actually A3 size. In this case, there is a possibility that the sheet is ejected and printing is performed again even though double feeding has not occurred. In reprinting due to such a setting error, the same operation is repeated many times, so that toner and sheets are wasted.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet conveying device capable of distinguishing between a mistake in setting a sheet length and double feeding of a sheet and suppressing unnecessary repetitive operations.

The sheet conveying device of the present invention has a sheet accommodating means for accommodating a sheet, a conveying means for conveying a sheet accommodated in the sheet accommodating means, and a length of the sheet accommodated in the sheet accommodating means in a conveying direction. A sheet setting means for setting a certain first length, a sheet measuring means for detecting a second length which is the length of the sheet being conveyed by the conveying means in the conveying direction, and two sheets by the conveying means. When the double feed detecting means for detecting whether or not the sheets are overlapped and conveyed and the second length measured by the sheet measuring means are longer than the first length, the double feed is performed. It is characterized by including a control means for determining whether or not to transport the next sheet based on the detection result by the detection means.

According to the present invention, it is possible to distinguish between a mistake in setting the sheet length and double feeding of the sheet, and to suppress unnecessary repetition of operations.

The block diagram of the image forming apparatus. Configuration diagram of the control system. Explanatory drawing of the double feed detection sensor. (A) and (b) are explanatory diagrams of reception levels. Illustration of the setting screen of the seat feature. A flowchart showing the double feed detection process. Another flowchart showing the double feed detection process Illustration of the setting screen of the continuation setting.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The technical scope of the present invention is determined by the scope of claims, and is not limited by the following individual embodiments.

(Configuration of image forming apparatus)
FIG. 1 is a configuration diagram of an image forming apparatus of the present embodiment. The image forming apparatus 101 includes a sheet feeding mechanism for feeding sheets, an image forming unit 20 for forming an image, a fixing device 12, and an operating unit 306. The image forming apparatus 101 prints an image on the sheet by transferring the image generated by the image forming unit 20 to the sheet fed by the sheet feeding mechanism.

The sheet feeding mechanism is provided in each of a plurality of sheet accommodating portions (paper cassettes 50 and 55) each capable of accommodating a plurality of sheets, a transport path, a vertical paper feed path, and a horizontal pass 30. It is provided with a roller for transporting a sheet and a sensor. In the present embodiment, a configuration in which a plurality of paper cassettes 50 and 55 are provided will be described, but the number of paper cassettes may be one or more.

The sheets housed in the paper cassette 50 are fed one by one from the paper cassette 50 to the transport path by the separate paper feed units 51 and 52 such as pickup rollers. A transport sensor 61 is provided in the transport path. The transport sensor 61 is used to detect the sheet measurement length (second length), which is the length of the sheet being transported in the transport direction. The sheet conveyed from the paper cassette 50 to the transfer path is conveyed to the paper feed vertical path. A vertical pass roller 53 is provided in the paper feed vertical pass. The vertical pass roller 53 conveys the sheet to the horizontal pass 30.

The sheets housed in the paper cassette 55 are fed one by one from the paper cassette 55 to the transport path by the separate paper feed units 56 and 57 such as pickup rollers. A transport sensor 62 is provided in the transport path. The transport sensor 62 is used to detect the length of the sheet being transported in the transport direction (sheet measurement length). The sheet conveyed from the paper cassette 55 to the transfer path is conveyed to the paper feed vertical path. A vertical pass roller 58 is provided in the paper feed vertical pass. The vertical pass roller 58 conveys the sheet to the horizontal pass 30.

The horizontal pass 30 includes a transport roller 40, a transport roller 41, a transport roller 42, a resist roller 11, and a paper ejection roller 13. The sheet guided from the paper feed cassette 50 or the paper feed cassette 55 to the horizontal path 30 is conveyed to the resist roller 11 by the transfer rollers 40, 41, 42. The resist roller 11 corrects the skew of the sheet conveyed along the horizontal pass 30. The fuser 12 is provided on the horizontal path 30.

A reference sensor 64 is provided on the upstream side of the transport roller 40 in the sheet transport direction. A double feed detection sensor 60 for detecting double feed in which two or more sheets are overlapped and transported is provided between the transfer roller 40 and the transfer roller 41. The double feed detection sensor 60 is composed of an ultrasonic sensor. The double feed detection sensor 60, triggered by the detection of the passage of the sheet by the reference sensor 64, emits ultrasonic waves toward the sheet when the sheet passes through the double feed detection position, and emits the ultrasonic waves transmitted through the sheet. Receive. Whether or not two or more sheets are overlapped and conveyed is determined by the intensity of the received ultrasonic waves.

The image forming unit 20 includes photoconductors 22 to 25, an intermediate transfer body 26, and a secondary transfer unit 21. Toner images of different colors are formed on the photoconductors 22 to 25. Photoreceptors 22 to 25 are, for example, uniformly charged on the surface and then exposed to laser light to form an electrostatic latent image. When the electrostatic latent images of the photoconductors 22 to 25 are developed with toner of the corresponding color, a toner image of the corresponding color is formed. The toner images formed on the photoconductors 22 to 25 are sequentially superimposed and transferred on the intermediate transfer body 26. As a result, a full-color toner image is formed on the intermediate transfer body 26. The intermediate transfer body 26 conveys the toner image to the secondary transfer unit 21. The secondary transfer unit 21 is provided on the horizontal path 30.

The sheet feeding mechanism conveys the sheet to the secondary transfer unit 21 by the resist roller 11 according to the timing at which the toner image on the intermediate transfer body 26 is transferred to the secondary transfer unit 21. The secondary transfer unit 21 transfers the toner image on the intermediate transfer body 26 to the sheet. The secondary transfer unit 21 conveys the sheet on which the toner image is transferred to the fixing device 12. The fuser 12 heats and melts the toner and pressurizes the toner and the sheet to fix the toner image on the sheet. The sheet on which the toner image is fixed is discharged from the fixing device 12 to the outside of the image forming apparatus 101 via the paper ejection roller 13.

The image forming apparatus 101 provides an escape path 31 that branches from the horizontal path 30 and a flapper 43 for switching the sheet transfer direction from the horizontal path 30 to the escape path 31 between the transfer roller 41 and the transfer roller 42. Be prepared. The escape path 31 is provided with a transfer roller 70, a transfer roller 71, and a transfer sensor 63. When the sheet measurement length detected by the transfer sensor 61 or the transfer sensor 62 is longer than a predetermined reference value by a predetermined reference value or more, the image forming apparatus 101 conveys the sheet to the escape path 31 by the flapper 43. .. The preset sheet size is the sheet set length (first length), which is the length of the sheet in the transport direction. Further, the image forming apparatus 101 also conveys the sheet determined to be double feed to the escape path 31. The sheet conveyed to the escape path 31 is discharged to the escape tray 32 by the transfer rollers 70 and 71. The transport sensor 63 detects the discharge of the sheet from the escape path 31 to the escape tray 32. Since the escape path 31 does not pass through the secondary transfer unit 21, no image is formed on the sheet ejected through the escape path 31.

The operation unit 306 is a user interface including an input interface and an output interface. The input interface is various key buttons and a touch panel. The output interface is a display or a speaker.

(Control system configuration)
FIG. 2 is a configuration diagram of a control system that controls the operation of the image forming apparatus 101. The control system includes a control unit 200 and a printer control unit 201. The control unit 200 controls the overall operation of the image forming apparatus 101. The printer control unit 201 controls the operation of each unit in the image forming apparatus 101 in response to the instruction of the control unit 200.

The control unit 200 includes a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, and a ROM (Read Only Memory) 303. The CPU 301 controls the operation of the entire image forming apparatus 101 by executing the computer program stored in the ROM 303. The RAM 302 provides a work area when the CPU 301 performs various processes. The PDL (Page Description Language) control unit 304 and the internal interface (I / F) unit 305 are connected to the CPU 301. The PDL control unit 304 is a processing circuit for processing, accumulating, image processing, and the like of print data. The internal I / F unit 305 is a communication interface for communicating with the printer control unit 201.

The operation unit 306 is also connected to the CPU 301. The CPU 301 receives various instructions and settings via the input interface of the operation unit 306. The CPU 301 controls the output interface of the operation unit 306 to display and notify various screens.

The printer control unit 201 includes a CPU 311, a RAM 312, and a ROM 313. The CPU 311 controls each part of the image forming apparatus 101 by executing a computer program stored in the ROM 313. The RAM 312 provides a work area when the CPU 311 performs various processes. The device control unit 314 and the internal interface (I / F) unit 315 are connected to the CPU 311.

The device control unit 314 is an electric circuit including an input / output port for controlling each component provided inside the image forming apparatus 101. A double feed detection sensor 60, transport sensors 61, 62, 63, a reference sensor 64, and the like are connected to the device control unit 314. Although not shown, the device control unit 314 is connected to a drive mechanism for driving each roller that conveys the sheet, a drive mechanism for driving the flapper 43, a drive mechanism for driving the image forming unit 20, and the like. NS. The internal I / F unit 315 is a communication interface for communicating with the control unit 200. The internal I / F unit 315 and the internal I / F unit 305 transmit and receive an image signal and a timing signal. The CPU 311 and the CPU 301 communicate with each other via the internal I / F units 315 and 305, and perform various processes in cooperation with each other.

The CPU 311 receives an image signal from the control unit 200 and controls the device control unit 314 to execute the printing process. Further, the CPU 311 controls the operation of the double feed detection sensor 60 to determine the double feed according to the detection result of the double feed detection sensor 60. Further, the CPU 311 determines the double feed according to the detection results of the transport sensors 61 and 62.

(Double feed detection sensor)
FIG. 3 is an explanatory diagram of the double feed detection sensor 60. The double feed detection sensor 60 detects the overlap of the sheets conveyed between the two guide plates 402a and 402b constituting the horizontal path 30 by ultrasonic waves. As described above, the double feed detection sensor 60 of the present embodiment is composed of an ultrasonic sensor, and includes a transmission unit 401a and a reception unit 401b. The transmitting unit 401a and the receiving unit 401b are diagonally opposed to each other with the horizontal path 30 in between.

The transmission unit 401a is connected to the device control unit 314 via, for example, a power amplifier circuit (not shown). The device control unit 314 outputs a pulse signal having a predetermined frequency under the control of the CPU 311. The pulse signal is amplified by the power amplifier circuit and input to the transmission unit 401a. The transmitting unit 401a is driven by a pulse signal acquired from the power amplifier circuit to transmit ultrasonic waves toward the receiving unit 401b.

The receiving unit 401b is connected to the device control unit 314 via, for example, an output amplifier circuit and a rectifying / smoothing circuit (not shown). The receiving unit 401b outputs a detection signal at a level corresponding to the intensity of the ultrasonic wave received from the transmitting unit 401a. The detection signal is amplified by the output amplifier circuit, rectified by the rectifying smoothing circuit, and input to the CPU 311 via the device control unit 314. The CPU 311 detects double feed based on the level of the detection signal. For example, when the intensity (reception level) of the received ultrasonic waves represented by the detection signal is equal to or less than the threshold value for determining the double feed, the CPU 311 determines that the sheet is double feed. The CPU 311 that determines that the sheet is double-fed notifies the user of the occurrence of double-feeding by the operation unit 306 via the control unit 200. Such double feed detection processing is repeated during the printing processing.

FIG. 4 is an explanatory diagram of the intensity (reception level) of the ultrasonic wave received by the receiving unit 401b of the double feed detection sensor 60. FIG. 4A exemplifies the reception level when there is only one sheet. FIG. 4B exemplifies the reception level when two sheets are transported in an overlapping manner.

In FIG. 4A, ranges A and C represent reception levels when the sheet 501 is not within the range of the double feed detection sensor 60. The range B represents the reception level when the sheet 501 is within the range of the double feed detection sensor 60.
In the ranges A and C, the ultrasonic waves transmitted from the transmitting unit 401a are received by the receiving unit 401b without being attenuated by the sheet 501. Ideally, the ultrasonic waves transmitted from the transmitting unit 401a are received by the receiving unit 401b with 100% intensity at the same intensity as when they were transmitted. However, in reality, attenuation occurs while propagating in the air. In the present embodiment, the ultrasonic waves transmitted from the transmitting unit 401a are attenuated by 5% by being propagated in the air. Therefore, the receiving unit 401b receives ultrasonic waves having an intensity of 95% in the ranges A and C.
In the range B, since there is only one sheet 501, the ultrasonic wave is attenuated by one sheet 501. In the present embodiment, the ultrasonic waves transmitted from the transmitting unit 401a are attenuated by 30% by passing through one sheet 501. Therefore, the receiving unit 401b receives ultrasonic waves having an intensity of 70% in the range B.

In FIG. 4B, ranges A and E represent reception levels when the sheets 501 and 502 are not within the range of the double feed detection sensor 60. The ranges B and D represent the reception level when one sheet 501 or the sheet 502 is within the range of the double feed detection sensor 60. The range C represents the reception level when the two sheets 501 and the sheet 502 overlap within the range of the double feed detection sensor 60.
In the ranges A and E, the ultrasonic waves transmitted from the transmitting unit 401a are received by the receiving unit 401b without being attenuated by the sheet 501. In the present embodiment, the receiving unit 401b receives ultrasonic waves having an intensity of 95% in the ranges A and E. In ranges B and D, ultrasonic waves are attenuated by one sheet 501 or sheet 502. In the present embodiment, the receiving unit 401b receives ultrasonic waves having an intensity of 70% in the ranges B and D.
In range C, the ultrasonic waves are attenuated by two overlapping sheets 501 and 502. The ultrasonic waves are significantly attenuated by the air layer between the sheets 501 and 502. In the present embodiment, the ultrasonic waves transmitted from the transmitting unit 401a pass through the two sheets 501 and 502 to 75%. It shall be attenuated. Therefore, the receiving unit 401b receives ultrasonic waves having an intensity of 25% in the range C.

The double feed detection sensor 60 transmits a predetermined number of ultrasonic waves by the transmission unit 401a at the timing when the sheet reaches the double feed detection position. The receiving unit 401b receives a predetermined number of ultrasonic waves and outputs a detection signal which is an electric signal according to the intensity of the received ultrasonic waves. The detection signal is an analog signal whose value increases as the intensity of the ultrasonic wave increases. The CPU 311 can determine the double feed by confirming whether or not the value of the detection signal acquired from the receiving unit 401b corresponds to the intensity of the ultrasonic wave in the range C of FIG. 4 (b). For example, the CPU 311 sets the threshold value for double feed detection between the level of the detection signal in the range B and D of FIG. 4 (b) and the level of the detection signal in the range C of FIG. 4 (b). Is set to the value of, and the occurrence of double feed is determined by comparing the threshold value with the level of the detection signal.

(Sheet feature settings)
FIG. 5 is an exemplary view of the seat feature setting screen. The sheet features set in the present embodiment are the set length of the sheet, which is the length in the transport direction of the sheet, the basis weight, and the surface property, but other sheet features may be set. The sheet features are set for the sheets accommodated in each of the paper cassette 50 and the paper cassette 55 before the start of printing. The seat feature setting screens 700a, 700b, 700c are displayed on the display of the operation unit 306 by the CPU 301. The seat features are set by the user operating the input interface of the operation unit 306 according to these setting screens 700a, 700b, 700c.

The seat setting length is set by the setting screen 700a. The user can set the sheet size (sheet setting length) by selecting an appropriate button from the sheet setting length setting button 701 in the setting screen 700a. The CPU 311 stores the sheet size (sheet set length) corresponding to the selected button in the RAM 312.

The basis weight of the sheet is set by the setting screen 700b. The user can set the basis weight of the sheet by selecting an appropriate button from the basis weight setting button 702 in the setting screen 700b. The CPU 311 stores the basis weight of the sheet corresponding to the selected button in the RAM 312.

The surface property of the sheet is set by the setting screen 700c. The user can set the surface property of the sheet by selecting an appropriate button from the surface property setting button 703 in the setting screen 700c. The CPU 311 stores the surface properties of the sheet corresponding to the selected button in the RAM 312.

(Double feed detection processing)
FIG. 6 is a flowchart showing the double feed detection process by the image forming apparatus 101. This process is performed after the sheet is fed from the paper cassette 50 or the paper cassette 55.

After feeding the paper, the CPU 311 detects the sheet measurement length, which is the length of the sheet being conveyed in the conveying direction (S701). The sheet measurement length is detected based on the detection result of the transport sensor 61 or the transport sensor 62. The sheet measurement length is represented by, for example, the product of the time during which the transfer sensors 61 and 62 have detected the sheet and the sheet transfer speed. For example, when the time during which the transfer sensors 61 and 62 detect the sheet is 0.42 seconds and the sheet transfer speed is 1000 [mm / s], the sheet measurement length is 420 [mm]. The CPU 311 stores the detected sheet measurement length in the RAM 312.

The CPU 311 compares the detected sheet measurement length with the preset sheet setting length, and determines whether or not the sheet measurement length is longer than a predetermined reference value by a predetermined reference value or more (S702). First, the CPU 311 reads out the seat measurement length and the seat set length stored in the RAM 312. The CPU 311 makes this determination based on whether or not the value obtained by subtracting the seat measurement length from the seat set length is larger than the reference value.

When the sheet measurement length is longer than the reference value or more than the sheet set length (S702: Y), the CPU 311 determines that double feeding has occurred. For example, when the seat setting length is 210 [mm], the sheet measurement length is 420 [mm], and the reference value is 50 [mm], the CPU311 is heavy because the sheet measurement length is longer than the reference value. Judge that the transmission has occurred. In this case, the CPU 311 performs the double feed detection process using the double feed detection sensor 60 (S703). The CPU 311 transmits ultrasonic waves to the sheet being conveyed by the transmitting unit 401a of the double feed detection sensor 60 in response to the sheet detection of the reference sensor 64. The receiving unit 401b receives the ultrasonic waves transmitted from the transmitting unit 401a and outputs a detection signal at a level corresponding to the intensity of the received ultrasonic waves. The CPU 311 stores the detection signal output from the receiving unit 401b in the RAM 312.

The CPU 311 conveys the sheet determined to be in the double feed state by the process of S702 to the escape path 31 and starts discharging to the escape tray 32 (S704). The CPU 311 waits until the sheet is ejected to the escape tray 32 (S705: N). The CPU 311 determines that the sheet has been ejected to the escape tray 32 when the transport sensor 63 detects the sheet and then does not detect the sheet.

When the sheet ejection to the escape tray 32 is completed (S705: Y), the sheet determined by the CPU 311 to be in the double feed state in the process of S702 is double fed even in the double feed detection process using the double feed detection sensor 60. It is determined whether or not it is detected (S706). The CPU 311 makes this determination by determining whether or not the reception level is the level at the time of double feeding based on the detection signal stored in the RAM 312 in the process of S703. For example, assuming that the intensity of the ultrasonic wave transmitted from the transmitting unit 401a is 100%, the CPU 311 has the intensity of the ultrasonic wave received by the receiving unit 401b of 40% or less when the threshold value of the double feed determination is 40%. If it is, it is judged that it is a double feed. If the intensity of the ultrasonic waves received by the receiving unit 401b is greater than 40%, the CPU 311 determines that double feeding has not occurred and that the seat setting length is set incorrectly.

When the double feed detection process using the double feed detection sensor 60 does not detect double feed (S706: N), the CPU 311 determines to interrupt printing because the sheet setting length is set incorrectly, and is shown in FIG. The process ends (S707). In this case, for example, the CPU 301 displays a screen prompting the resetting of the seat characteristics on the display of the operation unit 306. The user will reset the sheet features according to this screen.

When the double feed detection process using the double feed detection sensor 60 also detects the double feed (S706: Y), the CPU 311 determines that the sheet measurement length is set correctly. In this case, the CPU 311 increments the number of escapes of the sheet to the escape tray 32 by 1, and stores the number of escapes after the increment in the RAM 312 (S708). The number of escapes represents the number of times that double feed is continuously detected by the double feed detection process using the double feed detection sensor 60. The CPU 311 determines whether or not the number of escapes is a predetermined number of times or more (here, three times or more) (S709). When double feed is detected even after the printing process is repeated a predetermined number of times or more, the transport sensor 61 or the transport sensor 62 has failed to constantly detect the sheet, or the double feed detection sensor 60 has failed to perform double feed. It may be in an undetectable state. Therefore, when the number of escapes is equal to or greater than a predetermined number (S709: Y), the CPU 311 determines to interrupt printing and ends the process (S707). When the number of escapes is less than a predetermined number (less than 3 times) (S709: N), the CPU 311 determines to continue printing, starts feeding the next sheet, and returns to the process of S701 (S710).

When the sheet measurement length is not longer than the reference value or more than the sheet set length (S702: N), the CPU 311 performs the double feed detection process using the double feed detection sensor 60 (S711). This process is the same as the process of S703. Based on the result of the process of S711, the CPU 311 determines whether or not the double feed detection process using the double feed detection sensor 60 has detected the double feed (S712). This process is the same as the process of S706.

When double feed is detected by the double feed detection process using the double feed detection sensor 60 (S712: Y), the CPU 311 conveys the sheet determined to be in the double feed state to the escape path 31 and to the escape tray 32. Is started to be discharged (S713). The CPU 311 waits until the sheet is ejected to the escape tray 32 (S714: N). The CPU 311 determines that the sheet has been ejected to the escape tray 32 when the transport sensor 63 detects the sheet and then does not detect the sheet. When the ejection of the sheet to the escape tray is completed (S714: Y), the CPU 311 performs the processes after S708. That is, the CPU 311 increments the number of escapes by 1 (S708), and if the number of escapes after the increment is equal to or greater than a predetermined number, determines to interrupt printing and ends the process (S709: Y, S707). If the number of escapes after the increment is less than a predetermined number, the CPU 311 determines to continue printing and starts conveying the next sheet (S709: N, S710).

When the double feed detection process using the double feed detection sensor 60 does not detect the double feed (S712: N), the CPU 311 determines that the double feed does not occur and the sheet setting length is set correctly. In this case, the CPU 311 clears the number of escapes stored in the RAM 312 to 0 and ends the process (S715).

(Another example of double feed detection processing)
FIG. 7 is another flowchart showing the double feed detection process by the image forming apparatus 101. This process is performed after the sheet is fed from the paper cassette 50 or the paper cassette 55.

Similar to the processes of S701 to S705 of FIG. 6, the CPU 311 compares the sheet measurement length with the sheet set length, performs the double feed detection process by the double feed detection sensor 60, and ejects the sheet to the escape tray 32 (S801). ~ S805). When the ejection of the sheet to the escape tray 32 is completed, the CPU 311 determines that the sheet is double-fed in the process of S802 in the same manner as the process of S706 in FIG. It is determined whether or not double feeding is detected even in the detection process (S806).

When the double feed detection process using the double feed detection sensor 60 does not detect the double feed (S806: N), the CPU 311 determines that the seat setting length is set incorrectly. In this case, the CPU 311 determines whether or not to change the paper feed cassette and continue printing (S807). Whether or not to change the paper cassette and continue printing is preset by the user (continuation setting).

FIG. 8 is an example diagram of a continuation setting setting screen for presetting whether or not to change the paper feed cassette and continue printing. The setting screen 800 is prepared as one of the basic settings of the image forming apparatus independently of the print job. Whether or not to change the paper cassette and continue printing is set by the user operating the input interface of the operation unit 306 according to the setting screen 800. On the setting screen 800, the buttons 802 and 803 that can be selected by the user are displayed together with the question text 801. The user changes the paper cassette by selecting button 802 when changing the paper cassette and setting to continue printing, or by selecting button 803 when setting to interrupt printing. Set whether to continue printing. The CPU 311 stores the setting information corresponding to the selected button in the RAM 312. Note that this setting screen may be displayed when an instruction to start execution of each print job is input. If it is determined that the sheet setting is incorrect during printing execution, the CPU 311 determines S807 based on the setting information stored in the RAM 312.

When the paper cassette is changed and printing is not continued (S807: N), the CPU 311 determines to interrupt printing and ends the process (S809), as in the process of S707 of FIG. When the paper cassette is changed and printing is continued (S807: Y), the CPU 311 determines whether or not there is a paper cassette containing a sheet having the same characteristics as the sheet determined to be double-fed in the process of S802 (S808). ). Sheet features include sheet set length, basis weight, and surface properties, as described above. The CPU 311 reads out these sheet features set before the start of printing from the RAM 312 and makes a determination in S808. If all the sheet features match, the CPU 311 determines that the sheets with the same features are also housed in another paper cassette.

When there is no paper cassette for accommodating a sheet having the same characteristics as the sheet determined to be in the double feed state (S808: N), the CPU 311 determines to interrupt printing as in the process of S707 of FIG. The process ends (S809). When there is a paper cassette containing a sheet having the same characteristics as the sheet determined to be in the double feed state (S808: Y), the CPU 311 stores the paper cassette information representing the paper cassette in the RAM 312. The CPU 311 feeds the next sheet from the changed paper cassette and determines to continue printing (S812). At this time, if the paper cassette information is stored in the RAM 312, the CPU 311 feeds the sheet from the paper cassette corresponding to the paper cassette information and erases the paper cassette information. If the paper cassette information is not stored in the RAM 312, the CPU 311 feeds the sheet from the same paper cassette as the sheet discharged to the escape tray 32.

When double feed is detected by the double feed detection process using the double feed detection sensor 60 in the process of S806 (S806: Y), the CPU 311 performs the same process as S708 to S710 in FIG. 6 (S810 to S812). .. When the sheet measurement length is not longer than the reference value or more than the sheet set length in the process of S802 (S802: N), the CPU 311 performs the same process as in S711 to S715 of FIG. 6 (S813 to S817).

The image forming apparatus 101 of the present embodiment as described above can distinguish the erroneous detection of the double feed due to the setting error of the sheet setting length from the actual double feed, and can correctly detect the double feed. Therefore, it is possible to prevent wasteful consumption of toner and sheets due to reprinting due to erroneous detection of double feeding.

In this embodiment, the double feed detection during sheet transport by the image forming apparatus 101 has been described, but the present invention is not limited to this, and any device including a sheet transport device that transports sheets can be subjected to the same processing as in this embodiment. , It is possible to reliably detect the occurrence of double feeding. In the case of the sheet transfer device, the continuation or interruption of the next sheet transfer is determined instead of the continuation or interruption of printing. For example, the present embodiment can be applied to an automatic document transfer device provided in a scanner.

Claims (12)

Seat accommodating means for accommodating seats
A transport means for transporting the sheet accommodated in the sheet accommodating means, and a transport means.
A sheet setting means for setting a first length which is a length in a transport direction of the sheet accommodated in the sheet accommodating means, and a sheet setting means.
A sheet measuring means for detecting a second length, which is the length of the sheet being conveyed by the conveying means in the conveying direction, and a sheet measuring means.
A double feed detecting means for detecting whether or not two or more of the sheets are overlapped and transported by the transport means, and a double feed detecting means.
When the second length measured by the sheet measuring means is longer than the first length, a control means for determining whether or not to transport the next sheet based on the detection result by the double feed detecting means, and It is characterized by having
Sheet transfer device. The control means determines that the transfer of the sheet is interrupted if the second length is longer than the first length and the double feed detecting means does not detect the double feed, and the double feed detecting means. Is characterized in that it is determined to continue the transportation of the sheet if the double feed is detected.
The sheet transport device according to claim 1. A plurality of the sheet accommodating means are provided.
If the second length is longer than the first length and the double feed detecting means does not detect the double feed, the control means feeds the sheet from another sheet accommodating means to feed the sheet. Characterized by continuing transportation,
The sheet transport device according to claim 1. When the second length is longer than the first length and the double feed detecting means does not detect the double feed, the control means accommodates a sheet having the same length as the first length. If there is another sheet accommodating means, the sheet is fed from the other sheet accommodating means to continue the transport of the sheet, and the other sheet accommodating means for accommodating the sheet having the same length as the first length. If there is no sheet, the sheet transportation is interrupted.
The sheet transport device according to claim 3. When the second length is longer than the first length and the double feed detecting means does not detect the double feed, the sheet is fed from another sheet accommodating means and the sheet is continuously conveyed. It also has a setting means to set in advance,
When the continuation setting is performed by the setting means, the control means feeds a sheet from another sheet accommodating means to continue transporting the sheet, and the continuation setting is performed by the setting means. It is characterized in that the transportation of the sheet is interrupted when there is no such thing.
The sheet transport device according to claim 3. The control means is characterized in that the transfer of the sheet is interrupted when the number of times the double feed detecting means continuously detects the double feed is equal to or more than a predetermined number of times.
The sheet transport device according to any one of claims 1 to 5. The control means is characterized in that the number of times is cleared to 0 when the second length is not longer than the first length and the double feed detecting means does not detect the double feed.
The sheet transport device according to claim 6. The path through which the sheet is conveyed by the conveying means includes a first pass and a second pass different from the first pass.
When the second length is longer than the first length, or when the double feed detecting means detects the double feed, the control means causes the transport means to transport the sheet to the second pass. Features,
The sheet transport device according to any one of claims 1 to 7. When the second length is longer than the first length by a predetermined reference value or more, the control means determines whether or not to continue transporting the sheet based on the detection result by the double feed detecting means. Features,
The sheet transport device according to any one of claims 1 to 8. The sheet measuring means has a sensor for detecting the sheet transported by the transporting means, and the first is based on the time during which the sensor detects the sheet being transported and the transport speed of the sheet. 2 The length is detected,
The sheet transport device according to any one of claims 1 to 9. The double feed detecting means includes a transmitting means for transmitting ultrasonic waves and a receiving means for receiving ultrasonic waves, and the ultrasonic waves transmitted from the transmitting means pass through the sheet and are received by the receiving means. The transmitting means and the receiving means are arranged so as to be used, and the overlap of the sheets is determined by the intensity of the ultrasonic waves received by the receiving means.
The sheet transport device according to any one of claims 1 to 10. The sheet transport device according to any one of claims 1 to 11,
An image forming means for printing an image on a sheet conveyed by the sheet conveying device is provided.
In the control means, the second length, which is the length in the transport direction of the sheet being transported by the transport means measured by the sheet measuring means, is the length in the transport direction of the sheet accommodated in the sheet accommodating means. When it is longer than a certain first length, it is characterized in that it is determined whether or not to continue printing by the image forming means based on the detection result by the double feed detecting means.
Image forming device.

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