JP2007169044A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of improving operation efficiency in the image forming device, while detecting double feeding. <P>SOLUTION: This image forming device has a recording medium loading part 8 capable of loading a plurality of recording media P, a recording medium carrying means 59 carrying the recording medium supplied from this recording medium loading part to an image forming part 14 and a double feeding detecting means 500 detecting whether or not the recording medium is doubly fed from the recording medium loading part, and can automatically supply the recording medium from the recording medium loading part, and is characterized by making control of the recording medium carrying means different in response to a double feeding quantity detected by a double feeding quantity detecting means, by arranging the double feeding quantity detecting means 1001 detecting the double feeding quantity of the doubly fed recording medium by converting the quantity into time when the double feeding detecting means detects the double feeding of the recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that includes a recording medium stacking unit that can stack a plurality of recording media and can automatically supply the recording medium.

  As an image forming apparatus in which a recording medium fed by a paper feeding unit is fed to an image forming unit and an image formed on an image carrier of the image forming unit is transferred to the recording medium, a laser printer, a copying machine Machines, facsimiles, etc. are known. This type of image forming apparatus is provided with a double feed detection means for preventing double feed of a recording medium fed by the paper feed means, for example, recording paper, and receives a double feed detection signal sent from the means. Thus, the recording paper conveyance is stopped and controlled to minimize paper waste due to double feeding. In such an image forming apparatus, since the conveyance is stopped every time the double feeding of the recording paper is detected, there is a problem that the total print speed is remarkably slow and a smooth image forming operation cannot be performed.

Therefore, in order to solve such a problem, it is desired that the recording medium is not wasted even when the recording medium is double-fed, and that a smooth image forming operation can be performed without reducing the total print speed. In order to solve such a problem, there is provided a double feed detecting means for detecting double feed of the recording medium fed by the paper feed means, and when the recording medium is detected as double feed by the double feed detecting means, The distance from the leading edge of the recording medium positioned opposite the image carrier to the leading edge of the recording medium located on the opposite side is detected, and the timing of feeding the recording medium to the image carrier is changed by the detected distance. An image forming apparatus to be operated is disclosed in Japanese Patent Application Laid-Open No. 2004-228561. According to such an image forming apparatus, the recording medium is double-fed by the double-feed detection unit, and the distance from the leading end of the recording medium located opposite to the image carrier to the leading end of the recording medium located on the opposite side is determined. Since the detection medium detects and the recording medium feeding timing to the image carrier is changed by the detected distance, the image formation can be continued at the normal position of the recording medium even if double feeding occurs. It is possible to eliminate the waste of the recording medium and prevent the total printing speed from being lowered.
Japanese Patent Laid-Open No. 7-121079

  In the above-described image forming apparatus, the image is detected by detecting that the recording medium is a double feed and the distance from the leading end of the recording medium positioned opposite the image carrier to the leading end of the recording medium positioned on the opposite side. Since the recording medium feeding timing to the carrier is changed by the detected distance, image formation can be continued at the normal position of the recording medium even if double feeding occurs. However, even when double feed is detected, depending on the level of double feed and the distance between papers, even if the paper is transported as it is, printing is performed as usual. It was desired to be implemented.

  Accordingly, the present invention has been made in view of the above-described problems of conventional image forming apparatuses, and an object of the present invention is to improve the operation efficiency of the image forming apparatus while detecting double feeding. It is another object of the present invention to provide a new and improved image forming apparatus.

  In order to solve the above problems, according to an embodiment of the present invention, a recording medium stacking unit capable of stacking a plurality of recording media and a recording medium supplied from the recording medium stacking unit are conveyed to an image forming unit. An image forming apparatus capable of automatically supplying a recording medium from a recording medium stacking unit, the recording medium transporting unit configured to detect whether the recording medium is double-fed from the recording medium stacking unit. In addition, when the double feed detection means detects double feed of the storage medium, double feed amount detection means is provided for detecting the double feed amount of the double fed storage medium in terms of time. An image forming apparatus is provided in which the control of the recording medium conveying unit is varied according to the detected double feed amount.

  With this configuration, when the double feeding of the recording medium is detected, the distance between the leading edge of the fed recording medium (first sheet) and the leading edge of the double feeding recording medium (second sheet) is set. If the calculated distance is equal to or less than the predetermined amount, the recording medium is discharged without detecting jamming, so that the control can be varied according to the double feed amount of the recording medium. For this reason, it is possible to continuously print without stopping the operation of the image forming apparatus in the jam determination, and the copy efficiency is improved.

  At this time, in the above-described embodiment, the double feed detection unit may detect the double feed amount of the storage medium by ultrasonic waves.

  By adopting such a configuration, the frequency is attenuated when ultrasonic waves pass through the substance, so that the recording medium to be transported is not in a three-stage state of 0 sheets, 1 sheet passing, and 2 sheets passing. It becomes possible to grasp by contact type.

  Further, in the above embodiment, the double feed detection means may perform jam detection. Specifically, when the double feed amount is a predetermined amount or less, the jam detection operation is stopped and When the feeding amount is a predetermined amount or more, jam detection may be activated.

  By adopting such a configuration, the operation of the double feed detection sensor for jam detection can be stopped to shorten the jam release time, so that the copy efficiency is improved.

  In the above-described embodiment, the predetermined amount may be a required inter-paper distance defined by a minimum recording medium interval required when the recording medium is continuously conveyed.

  By adopting such a configuration, it is possible to minimize the operation stop at the image forming unit due to the jam detection, so that it is possible to minimize a decrease in copy efficiency.

  Further, in the above-described embodiment, when the double feed is detected by the double feed detection unit, the image formation executed by the image forming unit may be stopped.

  By adopting such a configuration, it is possible to solve the problem that toner consumption can be suppressed without forming a defective image, and good printing cannot be obtained.

  In the above-described embodiment, the image forming unit includes an image fixing unit that melts and fixes the toner image transferred onto the recording medium. When the double feed detection unit detects double feed, The fixing temperature of the fixing unit may be changed.

  By adopting such a configuration, it becomes possible to perform good printing, and it is possible to reduce unnecessary paper and the number of copies.

  In the above embodiment, the control of the recording medium transport unit may be a change in the timing of transporting the recording medium to the image forming unit. Specifically, when the double feed amount is a predetermined amount or less. Is the normal paper feeding timing, which is the timing for transporting the recording medium to the image forming unit at normal times, and if the double feed amount is greater than or equal to the predetermined amount, the required inter-sheet distance from the double feed amount of the storage medium The recording medium may be conveyed at the extended paper feed timing obtained by adding the paper feed extended time calculated from the value obtained by subtracting the value to the normal paper feed timing.

  By adopting such a configuration, it is possible to perform continuous printing without extending the operation of the image forming apparatus by extending the paper feed time, so that the copy efficiency is improved.

  Further, in the above embodiment, when the double feed is detected by the double feed detecting means, the paper discharge tray that is the discharge destination of the recording medium conveyed subsequent to the recording medium being double fed is changed. It is good.

  With such a configuration, the discharge tray as the discharge destination is changed depending on the state of the recording medium being conveyed, so that sorting becomes easy and work efficiency increases.

  Further, in the above embodiment, when the image forming apparatus includes a post-processing device that executes processing after discharging the recording medium instead of the paper discharge tray, when double feed is detected by the double feed detection unit, Switching means for switching the function of the post-processing device between valid and invalid may be provided.

  By adopting such a configuration, for example, when the post-processing is staple, since all the sheets cannot be combined into one bundle, the staple processing function is invalidated. In the case of punching, double feeding is performed. Since punching is possible except for paper, the punching function can be kept valid. By taking such a measure, it is possible to use a processing function that can be used as it is without wasteful stapling needles, and can improve the efficiency by reducing unnecessary operations, thereby eliminating waste.

  As described above, according to the present invention, when double feeding of recording paper is detected, the distance between the leading edge of the fed recording paper and the leading edge of the double feeding recording paper is calculated, and the distance is determined. If it is less than the fixed amount, the control can be changed according to the double feed amount by discharging the recording paper without detecting jamming, so continuous printing without stopping the operation of the image forming apparatus by jam judgment Copy efficiency is improved.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
First, the configuration of the image forming apparatus according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing the overall configuration of the first embodiment of the image forming apparatus of the present invention, and FIG. 2 is a partial detailed view showing the configuration of the apparatus main body of the image forming apparatus.

  The image forming apparatus 1A according to the present embodiment uses image data read by a scanner or the like or image data transmitted from the outside to a predetermined sheet-like recording sheet (hereinafter referred to as a sheet) as a recording medium by electrophotography. The sheet feeding tray (recording medium stacking unit) 8 on which a plurality of sheets P can be stacked, and the sheet P supplied from the sheet feeding tray 8 as an image forming unit. 14 is provided with a sheet conveying section (recording medium conveying means) 59 for conveying the sheet P to the sheet feeding tray 8 automatically.

  As shown in FIG. 1, the image forming apparatus 1 </ b> A mainly includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a charger 4, a charge removal device 41, a cleaner unit 5, a fixing unit 6, a paper conveyance path 7, The apparatus main body 1A1 includes a paper feed tray 8, a paper discharge tray 9, a transfer mechanism 10, and the like, and an automatic document processing apparatus 1A2.

  A document placing table 21 made of transparent glass on which a document is placed is provided on the upper surface portion of the apparatus main body 1A1, and the automatic document processing device 1A2 is swingably opened upwards above the document placing table 21. On the other hand, a scanner unit 22 serving as a document reading unit that reads image information of a document is disposed below the document placing table 21.

  Below the scanner unit 22, an exposure unit 1, a developing device 2, a photosensitive drum 3, a charger 4, a charge eliminating device 41, a cleaner unit 5, a fixing unit 6, a paper transport path 7, a paper discharge tray 9, and a transfer mechanism. 10 is disposed, and a paper feed tray 8 in which the paper P is stored is disposed below.

  The exposure unit 1 performs exposure by irradiating the surface of the photosensitive drum 3 uniformly charged by the charger 4 with laser light according to image data (printing image information) output from an image processing unit (not shown). Thus, the electrostatic latent image corresponding to the image data is written and formed on the surface of the photosensitive drum 3. The exposure unit 1 is disposed immediately below the scanner unit 22 and above the photosensitive drum 3, and employs laser scanning units (LSU) 13 a and 13 b including a laser irradiation unit 11 and a reflection mirror 12. In the present embodiment, in order to perform high-speed printing processing, it is assumed that a technique of using a plurality of laser beams to reduce the irradiation timing and adopting a two-beam technique. In the present embodiment, the laser scanning units (LSU) 13a and 13b are used for the exposure unit 1, but light emitting elements are arranged in an array, for example, an EL or LED writing head is used. Also good.

  The photosensitive drum 3 has a substantially cylindrical shape, is disposed below the exposure unit 1, and is controlled to rotate in a predetermined direction (the direction of arrow A in the figure) by a driving unit and a control unit (not shown). . Along the outer peripheral surface of the photosensitive drum 3, the sheet peeling claw 31, the cleaner unit 5, the charger 4 as an electric field generating unit, and the development head toward the downstream side in the rotational direction of the photosensitive drum with reference to the position after completion of image transfer. The device 2 and the static eliminator 41 are arranged in this order.

  The sheet peeling claw 31 is disposed so as to be able to contact and separate from the outer peripheral surface of the photosensitive drum 3 by a solenoid 32. The sheet peeling claw 31 is stuck to the surface of the photosensitive drum 3 when the unfixed toner image on the photosensitive drum 3 is transferred to the sheet P in a state of being in contact with the outer peripheral surface of the photosensitive drum 3. The sheet P is peeled off. Note that a driving motor or the like may be adopted as the driving means for the sheet peeling claw 31 instead of the solenoid 32, and other driving means can be selected.

  The developing device 2 visualizes the electrostatic latent image formed on the photosensitive drum 3 with black toner, and is downstream of the charger 4 in the rotating direction of the photosensitive drum (the direction of arrow A in the figure). It is arranged substantially horizontally (right side in the figure) on the side of the photosensitive drum 3. A registration roller 15 is disposed below the developing unit 2 on the upstream side in the recording medium conveyance direction.

  The registration roller 15 aligns the leading end of the paper P supplied from the paper feed tray 8 and the toner image on the photoconductive drum 3 and conveys them between the photoconductive drum 3 and the transfer belt 103 (not shown). The operation is controlled by the driving means and the control means.

  The charger 4 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential, and is disposed above the photosensitive drum 3 and in the vicinity of the outer peripheral surface thereof. In this embodiment, the charger type charger 4 is used. However, a contact type roller type or a brush type may be used instead.

  The static eliminator 41 is a pre-transfer static eliminator for reducing the surface potential of the photosensitive drum 3 in order to facilitate the transfer of the toner image formed on the surface of the photosensitive drum 3 to the paper P. It is disposed downstream of the developing device 2 in the rotating direction of the photosensitive drum and close to the outer peripheral surface below the photosensitive drum 3. In the present embodiment, the static eliminator 41 is configured using a static elimination electrode. However, a static elimination lamp may be used instead of the static elimination electrode, or static elimination may be performed by other methods. good.

  The cleaner unit 5 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer. The cleaner unit 5 is located at a position substantially opposite to the developing device 2 with the photosensitive drum 3 interposed therebetween. The drum 3 is disposed substantially horizontally (left side in the drawing) on the side.

  As described above, the electrostatic image visualized on the photosensitive drum 3 is applied from the transfer mechanism 10 onto the paper P on which the electric field having the opposite polarity to the charge of the electrostatic image is conveyed. Transferred onto P. For example, when the electrostatic image has a charge of (−) polarity, the applied polarity of the transfer mechanism 10 is (+) polarity.

  The transfer mechanism 10 is constituted by a transfer belt type unit in which a transfer belt 103 having a predetermined resistance value is disposed while being bridged by a driving roller 101, a driven roller 102, and other rollers. Thus, the surface of the transfer belt 103 is disposed so as to contact a part of the outer peripheral surface of the photosensitive drum 3. The transfer belt 103 conveys the paper P while pressing it against the photosensitive drum 3. At the contact portion between the photosensitive drum 3 and the transfer belt 103, an elastic conductive roller 105 capable of applying a transfer electric field with a conductivity different from that of the driving roller 101 and the driven roller 102 is disposed.

  The elastic conductive roller 105 is made of a soft material such as elastic rubber or foamable resin. Since the elastic conductive roller 105 has elasticity, the photosensitive drum 3 and the transfer belt 103 are not in line contact but in surface contact having a predetermined width, so that the transfer efficiency to the conveyed paper P is improved. Can be planned.

  Further, on the downstream side of the transfer area of the transfer belt 103 in the paper conveyance direction, a static elimination roller 106 is transferred to neutralize the electric field applied to the conveyed paper P in the transfer area and smoothly carry it to the next process. It is arranged on the back side of the belt 103.

  As shown in FIG. 2, the transfer mechanism 10 is provided with a cleaning unit 107 that removes dirt from residual toner on the transfer belt 103 and a plurality of charge removal mechanisms 108 that remove charge from the transfer belt 103. As a technique for performing static elimination used in the static elimination mechanism 108, there is a technique of grounding through an apparatus or a technique of positively applying a polarity opposite to the polarity of the transfer electric field.

  The electrostatic image (unfixed toner) transferred onto the paper P by the transfer mechanism 10 is conveyed to the fixing unit 6 and is pressurized and heated to melt the unfixed toner and be fixed on the paper P. . As shown in FIG. 2, the fixing unit 6 includes a heating roller 6a and a pressure roller 6b. The heating roller 6a is rotated while the sheet P is sandwiched between the heating roller 6a and the pressure roller 6b. By passing between the toner 6a and the pressure roller 6b, the toner image transferred onto the paper P is melted and fixed. A conveyance roller 16 that conveys the paper P is provided downstream of the fixing unit 6 in the paper conveyance direction.

  The heating roller 6a has a sheet peeling claw 611, a thermistor 612 which is a roller surface temperature detecting member, and a roller surface cleaning member 613 arranged on the outer peripheral portion, and the heating roller surface is heated to a predetermined temperature (fixing setting) on the inner peripheral portion. A heat source 614 having a temperature of approximately 160 to 200 ° C. is provided. The pressure roller 6b is provided with a pressure member 621 that allows the pressure roller 6b to come into pressure contact with the heating roller 6a at a predetermined pressure amount at both ends of the roller. Further, the pressure roller 6b is heated on the outer periphery of the pressure roller 6b. Similarly to the outer periphery of the roller 6a, a sheet peeling claw 622 and a roller surface cleaning member 623 are arranged.

  As shown in FIG. 2, the fixing unit 6 heats and melts the unfixed toner on the conveyed paper P by the heating roller 6a at the pressure contact portion 600 between the heating roller 6a and the pressure roller 6b. The unfixed toner is fixed on the paper P by a throwing action on the paper P by the pressure contact force between the roller 6a and the pressure roller 6b.

  The paper feed tray 8 is used for accumulating a plurality of sheets (paper sheets) on which image information is output (printed). The exposure unit 1, the developing device 2, the photosensitive drum 3, the charger 4, and the charge eliminating device. The image forming unit 14 is configured below the image forming unit 14 including the apparatus 41, the cleaner unit 5, the fixing unit 6, and the like. A paper pickup roller 8 a is disposed on the upper side of the paper discharge side of the paper feed tray 8.

  The sheet pickup roller 8a picks up the sheets P stacked and stored in the sheet feed tray 8 one by one from the uppermost layer, and moves toward the downstream side (for convenience, the sheet P flow side, in other words, the cassette side is upstream, The sheet discharge side is the downstream.) The sheet is conveyed to the registration roller (also referred to as “idle roller”) 15 side on the sheet conveyance path 7.

  In the image forming apparatus 1A according to the present embodiment, in order to perform high-speed printing processing, a plurality of standard-size sheets P can be stored in each tray below the image forming unit 14 in a plurality of sheets. On the other hand, a large-capacity paper feed cassette 81 capable of storing a large amount of a plurality of paper types is disposed on the side of the apparatus. A manual feed tray 82 corresponding to standard size printing or the like is provided.

  The paper discharge tray 9 is disposed on the side of the apparatus opposite to the manual feed tray 82. Further, instead of the paper discharge tray 9, a post-processing device that performs stapling and punching processing of paper discharge, a multi-stage paper discharge tray, and the like can be arranged as options.

  The paper transport path 7 is configured between the photosensitive drum 3 and the paper feed tray 8 described above, and transports the paper P supplied from the paper feed tray 8 one by one to the transfer mechanism 10. A sheet on which the toner image is transferred from the photosensitive drum 3 is conveyed to the fixing unit 6, and after the unfixed toner image is fixed on the sheet in the fixing unit 6, a sheet conveyance path formed according to the designated processing mode. In addition, the sheet is conveyed by a branching claw.

  Here, the sheet conveyance path 7 will be described in detail with reference to the drawings. FIG. 3 is an explanatory diagram showing the configuration of the sheet conveyance path of the image forming apparatus according to the present embodiment, and FIG. 4 shows the branched sheet conveyance path that constitutes the sheet conveyance path and the branch claw that communicates them. FIG.

  As shown in FIGS. 3 and 4, the paper transport path 7 mainly includes the first paper transport path 7 a 1 from the paper feed tray 8 to the registration rollers 15, and the fixing unit 6 from the registration rollers 15 via the transfer mechanism 10. A second paper transport path 7a2 that passes through and reaches the downstream transport roller 16, a third paper transport path 7a3 that reaches the paper discharge roller 17 for discharging paper from the transport roller 16 to the paper discharge tray 9, and a transport roller 16 The fourth paper transport path 7a4 for reversing the paper P from the second paper, the fifth paper transport path 7a5 communicating with the fourth paper transport path 7a4, and the reverse transport roller 18 for transporting the paper P to the registration roller 15 again, the paper discharge roller A sixth paper conveyance path 7a6 that reverses from 17 and conveys the paper P, a seventh paper conveyance path 7a7 that communicates with the sixth paper conveyance path and avoids the fifth paper conveyance path 7a5, and a seventh paper conveyance path 7a7 Communicating switchback roller 1 9 and the eighth sheet conveyance path 7a8.

  A plurality of sheets P are arranged in the sheet transport path 7 according to the processing mode. In the present embodiment, as shown in FIG. 3, eight sheets P of (1) to (8) (indicated by encircled numbers in the figure) are arranged in the sheet transport path 7. However, the allowable number of sheets P in the sheet transport path can be changed depending on the configuration of the sheet transport path. Further, in the paper transport path 7, a plurality of branching claws for selecting the paper transport path according to the selected processing mode and changing the transport path of the paper P are provided at the branch points of the paper transport path. .

  As shown in FIG. 4, a branch claw 20a communicating with the third paper transport path 7a3 or the fourth paper transport path 7a4 is provided in the vicinity of the downstream side of the transport roller 16 so as to be able to swing and displace. The branch claw 20a is operated by a solenoid (not shown).

  On the downstream side of the fourth paper transport path 7a4, a branch claw 20b that connects the fourth paper transport path 7a4 and the fifth paper transport path 7a5 or the fifth paper transport path 7a5 and the sixth paper transport path 7a6 swings. Displaceable. The branch claw 20b is operated by a spring member (not shown) and the elastic force of the paper P.

  On the downstream side of the sixth paper transport path 7a6, a branch claw 20c that communicates with the fifth paper transport path 7a5 or the seventh paper transport path 7a7 is provided so as to be swingable and displaceable. The branch claw 20c is operated by a solenoid (not shown).

  On the downstream side of the seventh paper transport path 7a7, a branch claw 20d that connects the seventh paper transport path 7a7 and the eighth paper transport path 7a8 or the fifth paper transport path 7a5 and the eighth paper transport path 7a8 is rocked. It is provided so that it can be displaced dynamically. The branch claw 20d is operated by a solenoid (not shown).

  On the upstream side of the fifth paper transport path 7a5, a branch claw 20e is provided for smoothly connecting the fourth paper transport path 7a4 and the eighth paper transport path 7a8 and the fifth paper transport path 7a5.

  With the paper conveyance path 7 configured as described above, the branch claws 20a to 20d are operated according to the requested processing mode, and the conveyance path of the paper P corresponding to the processing mode can be selected.

  Next, the configuration of the paper transport unit 59 according to the present embodiment will be described with reference to the drawings. FIG. 5 is a schematic diagram showing the configuration of the paper transport unit 59 provided in the image forming apparatus according to the present embodiment, and FIG. 6 is a block diagram showing the configuration of the double feed detection sensor 500 provided in the paper transport unit 59. It is.

  The paper transport unit 59 is configured to transport the paper P (P1, P2, P3) from the paper feed tray 8 to the image forming unit 14 via the paper transport path 7 in accordance with the processing mode of the image forming apparatus 1A. ing. In the present embodiment, as shown in FIG. 5, whether or not the paper P is double fed from the paper feed tray 8 to the paper transport path 7 between the paper feed tray 8 and the registration roller 15 is sent to the paper transport unit 59. When the paper P conveyed from the paper feed tray 8 to the image forming unit 14 is double-fed, the double-feed amount of the double-fed paper P is determined. As a double feed amount detection means for detecting in terms of time, a deviation amount detection timer 1001 for detecting a deviation amount of the overlapped sheets P with time is provided.

  In this way, by configuring the paper transport unit 59 provided in the image forming apparatus according to the present embodiment, the paper P1 fed from the paper feed tray 8 is fed when being transported to the registration rollers 15. The ultrasonic double feed detection sensor 500 installed in the paper conveyance path 7 between the tray 8 and the registration roller 15 can detect that the paper P1 has reached the registration roller 15 in a non-contact manner. The paper P to be double fed is strongly overlapped by static electricity or the like, and there is almost no change in the amount of deviation before and after passing through the registration roller 15, so that the double feed detection sensor 500 is on the front side before the paper P reaches the registration roller 15. In the present embodiment, the double feed detection sensor 500 can be used as a sensor for detecting a paper feed failure during paper conveyance.

  In the present embodiment, as described above, an ultrasonic type double feed detection sensor that detects whether one or a plurality of sheets are conveyed by ultrasonic waves is used as the double feed detection sensor 500. Ultrasound is transmitted or reflected when it hits a substance, but when transmitted, it has a characteristic that the frequency is attenuated. According to the characteristics of the ultrasonic wave, there are three stages: no paper, one sheet passing, and two or more sheets passing. Grasp the state of As shown in FIG. 6, the double feed detection sensor 500 includes an ultrasonic transmitter 503 and an ultrasonic receiver 504. On the ultrasonic transmitter 503 side, there is a transmitter circuit 501 that generates an electric pulse having an amplitude in the ultrasonic region, and an amplifier circuit 502 that amplifies the electric pulse to electric power until the ultrasonic generator 503 generates an ultrasonic wave. An ultrasonic transmitter 503 provided and receiving such an amplified electrical pulse generates ultrasonic waves.

  On the other hand, an ultrasonic receiver 504 that receives ultrasonic waves generated from the ultrasonic transmitter 503 is provided on the surface facing the ultrasonic transmitter 503. The ultrasonic wave received by the ultrasonic receiver 504 is resonated by converting the frequency into a voltage by the resonance circuit 505, and then the A / D circuit provided with the ultrasonic voltage by the resonance amplification circuit 506. Amplify to an area that can be discriminated at 507. In this way, the amplified ultrasonic analog signal is converted into a digital signal by the A / D circuit 507, and the CPU 508 performs arithmetic processing based on the digital signal. It is controlled by determining whether it is in a state of passing two or more sheets, in other words, whether or not the fed paper P is one sheet (multiple feeding).

  Next, an operation of detecting the double-fed paper by the double-feed detection sensor 500 provided in the image forming apparatus according to the present embodiment will be described with reference to the drawings. FIG. 7 is a timing chart showing how the double-fed paper is detected by the double-fed detection sensor 500.

  First, the double feed detection sensor 500 detects a paper out condition, but when the paper P is conveyed, the A / D value calculated by the CPU 508 provided in the double feed detection sensor 500 changes, and one sheet of paper is detected. The state is detected (time t1). At this time, the paper P is temporarily stopped by the registration roller 15 and waits until a desired image is formed on the transfer belt 103 by the exposure unit 1 and the photosensitive member 3 and preparation for transfer onto the paper P is completed. Thereafter, when the transfer preparation is completed, rotation of the registration roller 15 is started (time t2), and the paper P is conveyed to the transfer belt 103. At this time, simultaneously with the rotation of the registration roller 15, the operation of the deviation amount detection timer 1001 is also started.

  Thereafter, when the paper P is transported, in the case of double feeding, in order to detect the state of two or more sheets by the double feed detection sensor 500 (time t3), the deviation amount detection timer 1001 is stopped, The registration / multifeed detection time Trg-ju, which is the time from the start of operation of the registration roller 15 after completion of transfer preparation (time t2) to the detection of double feed of the paper P (time t3), is detected. If double feeding is performed after this time is detected, the A / D value detected by the double feed detection sensor 500 is in a state of two or more sheets, and if the sheet is continuously conveyed in this state, double feeding is performed. The trailing edge of the first sheet P1 among the sheets P that are being passed, the second sheet P2 is detected, and the A / D value detected by the multi-feed detection sensor 500 is the one sheet state (Time t4). Further, when the paper P2 is conveyed, all the papers P1 and P2 pass through the double feed detection sensor 500, and the A / D value detected by the double feed detection sensor 500 becomes a paper out state (time t5). ).

  Here, in order to facilitate understanding of the operation of detecting the double feed of the conveyed paper P in the image forming apparatus according to the present embodiment, refer to the drawing showing the double feed detection operation converted into actual time. However, it will be described below. FIG. 8 is an explanatory diagram of a state in which the distance between sheets is clogged during sheet conveyance in the image forming apparatus according to the present embodiment. FIG. 9 is a distance between sheets during sheet conveyance in the image forming apparatus according to the present embodiment. It is state explanatory drawing when is open.

  In the image forming apparatus of the present embodiment, the process speed, which is the paper conveyance speed, is 100 (mm / sec), and the required inter-paper distance, which is the minimum required paper interval, is 100 (mm) during continuous feeding. And In the present embodiment, since the distance between the registration roller 15 provided in the image forming apparatus and the double feed detection sensor 500 is 50 (mm), the registration roller after the paper P passes through the double feed detection sensor 500. When converted to the resist sensor time Trg-sn, which is the time to reach 15, it is 0.5 (sec). If the registration / multifeed detection time Trg-ju, which is the time from the start of operation of the registration roller 15 after completion of transfer preparation to the detection of double feed of the paper P, is 1.5 (sec) at this time, The deviation amount time Tzure obtained by converting the deviation amount between the fed paper P1 and the paper P2 into time can be expressed by the sum of the registration sensor time Trg-sn and the registration / multifeed detection time Trg-ju. 5 (sec) +1.5 (sec) = 2.0 (sec) ”.

  As described above, since the necessary distance between sheets of the image forming apparatus according to the present embodiment is 100 (mm), the necessary distance between papers Tkami obtained by converting the necessary distance between sheets into time is “100 (mm)”. / 100 (mm / sec) = 1 (sec) ”. When comparing the deviation amount time Tzure (= 2.0 sec) calculated above with the necessary paper interval time Tkami (= 1 sec) of the image forming apparatus of the present embodiment, the deviation amount time Tzure is larger. For this reason, when the image forming apparatus according to the present exemplary embodiment conveys a sheet in a normal state, the sheet interval time Tkankaku obtained by converting the interval distance of each sheet into a time is conveyed so as to be conveyed at a necessary sheet interval (= 100 mm). When the normal paper feed timing Ttsujo that is the time for paper is determined, as shown in FIG. 7, the paper P3 that is fed next overlaps the paper P2 that overlaps the paper P1, and so-called jammed state. It becomes. Note that the normal paper feed timing Ttsujo for transporting A4 size paper with a vertical size of 210 (mm) is “210 (mm) / 100 (mm / sec) + required paper interval time Tkami (1 sec) = 3 .1 (sec) ".

  On the other hand, if the image forming apparatus of the present embodiment has determined the normal paper feed timing Ttsujo so that the paper interval time Tkankaku is conveyed by three times the required inter-paper distance (= 300 mm), the deviation amount time Since Tzure is 2 (sec), when converted to distance, “2 (sec) * 100 (mm / sec) = 200 (mm)”. Since the normal paper feed timing Ttsujo when the paper interval time Tkankaku is 300 (mm), there is a margin of “300 (mm) −200 (mm) = 100 (mm)”, which is necessary for the image forming apparatus of this embodiment. Since the distance between sheets (= 100 mm) can be secured, it can be conveyed without jamming as shown in FIG. The normal paper feed timing Ttsujo for transporting A4 size paper is “210 (mm) / 100 (mm / sec) + required paper interval time Tkami (1 sec) * 3 = 5.1 (sec)”. Become.

  As described above, when the paper interval time Tkankaku secured at the normal paper feed timing Ttsujo is larger than the sum of the deviation amount time Tzure and the required paper interval time Tkami, the next paper P3 fed without any problem. Since it can be conveyed, the operation of the double feed detection sensor 500 for jam detection is stopped, and the jam release time can be shortened. Further, when the paper interval time Tkankaku is smaller than the sum of the deviation amount time Tzure and the required paper interval time Tkami, the paper P1 and the paper P2 overlap each other, and the double feed detection sensor 500 detects a jam. That is, the double feed detection of the present embodiment is executed by the jam detection method.

  Next, a control system of the image forming apparatus 1A according to the present embodiment will be described with reference to the drawings. FIG. 10 is a block diagram showing the configuration of the electric control unit of the image forming apparatus according to the present embodiment.

  As shown in FIG. 10, image forming apparatus 1 </ b> A according to the present embodiment stores image reading processing, image processing, image forming processing, paper P conveyance processing, and the like in ROM (Read Only Memory) 55 in advance. In accordance with the program, a central processing unit (CPU) 54 serving as a control unit for each component included in the image forming apparatus 1A executes processing using a temporary storage unit such as a RAM (Random access Memory) 56. In place of the ROM 55 and the RAM 56, storage means such as an HDD (Hard Disk Drive) can be used.

  In the image forming apparatus 1A, document image data serving as image information of a document read by the scanner unit 22 or document image information transmitted from each terminal device connected to a communication network (not shown) is transmitted via the communication processing unit 58. Are input to the image processing unit 57.

  The image processing unit 57 processes the document image information stored in the storage unit such as the RAM 56 into a print image suitable for printing (image formation on paper) by the above program.

  The image information for printing is input to the image forming unit 14. The image forming unit 14, the sheet conveying unit 59 that detects and controls various types of sheets in the sheet conveying path 7, the paper discharge processing unit 60 that performs various types of detection and control of sheets in the fixing unit 6 and the sheet discharge roller 17, Each drive control unit 62 is linked.

  The sheet conveyed by the sheet conveying unit 59 is a printing process for executing a printing process of image information in the image forming unit 14, and then a fixing process executed by the fixing unit 6 for the printed sheet. After that, the paper is discharged to a paper discharge tray 9 serving as a paper discharge portion.

  The image forming apparatus 1 </ b> A is provided with an operating condition setting unit 77. The operating condition setting unit 77 sets the operating conditions such as image forming or conveying conditions of the image forming apparatus 1A according to the image forming conditions such as the image forming request or the type of the recording medium set by the user with the operation switches. It is to set.

  Further, the image forming apparatus 1 </ b> A is a document reading drive that is a driving actuator for the scanner unit 22, the sheet transport unit 59, the image forming unit 14, the fixing unit 6, the paper discharge processing unit 60, and the like according to the set operation conditions. Operation of the unit 64, the paper conveyance driving unit 66, the print processing driving unit 68, the fixing driving unit 70, and the paper discharge driving unit 72, that is, the operation synchronized with the command of the CPU 54 based on the program stored in the ROM 55. 62 is performed under the control.

  The document reading drive unit 64 is a drive actuator for the scanner unit 22. The paper transport drive unit 66 is a motor for driving the paper transport unit 59, specifically, the paper pickup roller 8 a and the registration roller 15 on the paper transport path 7 described above. The print processing drive unit 68 is a drive motor for the photosensitive drum 3. The fixing driving unit 70 is a driving motor for the heating roller 6 a and the pressure roller 6 b of the fixing unit 6. The paper discharge drive unit 72 is a drive motor such as a paper discharge roller 17. The drive motors of these drive units can be appropriately configured through a power transmission mechanism using the same or different motors as drive sources.

  Further, in the image forming apparatus 1A, as an optional configuration 74, a post-processing device 81 for executing stapling, punching, and the like and an automatic document reading device (automatic document processing device 1A2, etc.) are arranged. In addition to the control unit of the apparatus 1A, each optional configuration 74 has a control unit 74a, and is configured to synchronize timing adjustment with the apparatus via the communication processing unit 58 described above.

  The recording medium detection unit 78 detects that the leading edge of the paper reaches the fixing unit 6 or the carry-out unit. Specifically, the recording medium detection unit 78 includes a conveyance time measuring unit 79a that measures the conveyance time of the sheet after the sheet is sent out from the registration roller 15 that introduces the sheet at the entrance of the sheet conveyance path 7, and the registration roller. 15 includes a conveyance timing detection unit 79b that detects the conveyance timing of the sheet in the sheet conveyance path 7 based on the distance from the fixing unit 6 to be controlled and the discharge roller 17 and the conveyance speed of the sheet.

  In the present embodiment, the recording medium detection unit 78 detects the timing at which the sheet reaches the fixing unit 6 and the paper discharge roller 17 based on the conveyance timing of the recording medium detected by the conveyance timing detection unit 79b. I have to.

  Further, in the present embodiment, when the paper P conveyed from the paper feed tray 8 to the image forming unit 14 is double-fed, the deviation is detected as a deviation amount detection unit that detects the deviation amount of the overlapping paper P in time. A quantity detection timer 1001 is provided in the CPU 54.

  By configuring the control system of the image forming apparatus 1A according to the present embodiment as described above, for example, when the double feed detection sensor 500 detects double feed of the paper P, the double feed is performed to the image forming unit 14. By controlling to stop image formation on the conveyed paper P1, consumption of toner can be suppressed without forming a defective image. That is, when printing on the paper P, if the paper P is fixed in a double feed state, that is, in a state where two or more sheets are overlapped with a normal amount of heat, fixing failure occurs due to a shortage of heat, and good printing cannot be obtained. Can solve the problem.

  Further, when the image formation is not stopped even when the paper P is in the double feed state, the temperature of the fixing unit 6 is controlled to be changed for the paper P1 to be fed and transported, and good printing without fixing failure is performed. You can do it. For example, in the image forming apparatus of the present embodiment, in the case of one copy of plain paper, good fixability can be obtained when the temperature of the fixing unit 6 is around 190 ° C., but two sheets of plain copy paper are stacked. In this case, good fixing properties cannot be obtained unless the temperature is increased to + 20 ° C and 210 ° C. Therefore, the temperature of the fixing unit 6 is raised to 210 ° C. before carrying the double-fed paper to the fixing unit 6 so that good printing can be performed. With such a correspondence, it is possible to obtain an effect of reducing unnecessary sheets and the number of copies. Note that after the multi-feed paper P1 is printed, the temperature of the fixing unit 6 needs to be returned to the normal fixing temperature (around 190 ° C.) for the subsequent paper P that is being conveyed without any problem.

  Further, even when paper is discharged by the image forming apparatus, in the present embodiment, if the paper is discharged without the jam determination after the multi-feed determination, the multi-feed is performed from the CPU 54 to the paper discharge processing unit 60 at any time. The paper P3 discharged after the double feed determination is controlled so as to be discharged to another paper discharge tray 9 so that it can be clearly seen. For example, as shown in FIG. 5, when the paper P is normally discharged to the paper discharge tray 9-A, the paper discharge tray which is another paper discharge tray from the next paper P after the multi-feed determination is performed. Discharge to 9-B.

  In addition, depending on the transport timing of the paper P1 and the paper P2 being double-fed in the paper discharge processing unit 60, the paper is discharged to a paper discharge tray 9 that is different from the paper discharge tray 9 that has been discharged before the double-feed determination. By discharging the paper P3 after feeding to a paper discharge tray 9 different from the papers P1 and P2, the paper P3 may be divided into three types: pre-multifeed paper P1, P2 and multi-feed paper P3. For example, when the paper P is normally discharged to the paper discharge tray 9-A, the papers P1 and P2 that have been detected to be double-fed are discharged to the paper discharge tray 9-B, and the subsequent paper P is transferred from the paper P3. Then, the paper is discharged to the paper discharge tray 9-C. In this way, by changing the paper discharge tray 9 depending on the state of the paper, sorting becomes easier and work efficiency is improved.

  Further, in the present embodiment, since the post-processing device 81 which sets post-discharge processing functions such as staples and punches after discharging the paper P is provided, when the double feed is detected, the post-processing function set is used. Valid / invalid is determined. Specifically, in the case of stapling, since all sheets cannot be bundled unless one sheet is prepared, the stapling function is disabled. In the case of punching, it is possible to punch other than the double-fed sheets. Leave enabled. With such a measure, unnecessary staples are not generated, and unnecessary operations are reduced to increase efficiency. Further, since the processing functions that can be enabled can be used without any problem, the portions other than the double feed portion can be copied without any problem, so that it is not necessary to copy all the originals again, and waste can be omitted.

  Next, an operation flow of jam determination in the image forming apparatus according to the present embodiment will be described with reference to the drawings. FIGS. 11 to 13 are flowcharts for explaining the flow of the jam determination operation in the image forming apparatus according to the present embodiment.

  In the present embodiment, as shown in FIG. 11, when printing is started, the paper P1 is first fed (step S1). When the sheet P1 reaches the registration roller 15 (step S2), the exposure unit 1 and the photoreceptor 3 prepare for transfer, and wait for the completion of preparation (step S3). When the transfer preparation is completed, the registration roller 15 is rotated to convey the paper P1, and the deviation amount detection timer 1001 is started to measure the deviation amount time (step S4).

  While the paper is being transported, the double feed detection sensor 500 executes double feed detection (step S5). If no double feed is detected, the normal paper transport process (from step S6) is performed as shown in FIGS. ), And if double feeding is performed, as shown in FIG. 13, processing after double feeding determination (from step S18) is executed.

  If double feeding is not detected in step S5, it is confirmed whether or not the paper P is continuously printed (step S6). If the paper P is not continuously printed, as shown in FIG. The state of the paper P1 is checked (from step S13). When printing is performed continuously, it is checked whether the paper feed timing is the normal paper feed timing Ttsujo (step S7). P3 is fed (step S8), and if the feed timing is not reached, the next process (process after step S9) is executed.

In the transport state of the paper P3, it is confirmed whether or not the registration roller 15 has been reached (step S9). If the registration roller 15 has been reached, transfer preparation is performed by the exposure unit 1 and the photoreceptor 3 for the paper P3. If it does not reach the registration roller 15 (step S10), the following processing is performed.
The transfer preparation for the paper P3 is confirmed (step S11). If the transfer preparation is completed, the registration roller 15 is rotated and the paper P3 is conveyed, and the deviation detection timer 1001 for the paper P3 is started, and the deviation amount is started. Time is measured (step S12). If transfer preparation is not completed, the next process (process after step S13) is executed.

  Thereafter, it is confirmed whether or not the trailing edge of the paper P1 has passed the double feed detection sensor 500 (step S13). If it has passed, the deviation amount detection timer 1001 for the paper P1 is stopped and measurement is stopped ( Step S14). If the trailing edge of the sheet P1 does not pass the double feed detection sensor 500, the next process (process after step S15) is executed.

  After the step S13 or S14, the discharge timing of the paper P1 is confirmed (step S15), and if it is the discharge timing of the paper P1, the paper P1 is discharged to the discharge tray 9-A where the discharge tray 9 is set. (Step S16). If it is not the discharge timing of the paper P1, the process returns to the double feed detection step (from step S5), and the processing after step S5 described above is subsequently performed.

  After the paper P1 is discharged to the paper discharge tray 9, it is checked whether or not continuous paper feeding (paper P3 printing / paper feeding) is in progress (step S17). Returning to step S5), the processing from step 5 onward is continued. If not in continuous feeding, if necessary, processing steps after the post-processing step such as stapling and punching are performed (from step S32). At that time, first, it is confirmed whether or not post-processing is necessary (step S33). If post-processing is necessary, it is further confirmed whether or not printing is prohibited due to detection of double feed (step S34). If not prohibited, post-processing is executed (step S35). If post-processing is prohibited in step S34 and no post-processing is required in step S33, printing is terminated as it is.

  When the double feed is detected in the above-described step S5, as shown in FIG. 13, the deviation amount detection timer 1001 is stopped and the deviation amount time Tzure is calculated (step S18). Based on the deviation amount time Tzure obtained in step S18, it is determined that “paper interval time Tkankaku ≧ displacement amount time Tzure + interval time Tkami” (step S19). If the paper interval time Tkankaku is shorter, jam processing is performed. All operations are stopped (step S23), and printing is terminated.

  If the paper interval time Tkankaku is longer in step S19, the image formation for the paper P1 is completed (step S20), the jam determination operation is stopped (step S21), and the next paper P3 is ejected from the paper discharge tray 9. The destination is changed to the paper discharge tray 9-B (step S22). After that, the processing steps after confirming whether or not continuous printing is performed are executed (from step S6).

  In the above description of the operation, the image formation is stopped when the double feed is detected, and the paper discharge tray 9 is switched. However, when the printing of the paper P1 is discharged with good quality, the process S20 to the process S22. Is changed as described below.

  For example, when changing the fixing temperature, the jam determination operation is stopped after step S19 (step S24), and the printing of the paper P1 is changed from 190 ° C. to 210 ° C. as described above ( In step S25, the discharge destination of the subsequent paper P3 on the paper discharge tray 9 is changed to the paper discharge tray 9-B (step S26). Thereafter, the discharge of the paper P1 and the paper P2 is waited (step S27), the temperature of the fixing unit 6 is returned from 210 ° C. to 190 ° C. (step S28), and printing is continuously performed in the above-described step S6. (Step S6), and the subsequent processing steps are executed.

  Further, when the paper discharge is divided into three, steps S20 to S22 are changed as described later. That is, after the image formation for the paper P1 is completed (step S29), the jam determination operation is stopped (step S30), and the discharge destination of the paper discharge tray 9 for the paper P1 and the paper P2 is changed to the paper discharge tray 9-B. (Step S31), the discharge destination of the discharge tray 9 for the next sheet P3 is further changed to another discharge tray 9-C (Step S32). Thereafter, it is confirmed whether or not printing is continuously performed in the above-described step S6 (step S6), and the subsequent processing steps are executed.

(Second Embodiment)
A second embodiment of the image forming apparatus of the present invention will be described with reference to the drawings. Since the configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted.

  Next, the operation of detecting the double feed of the conveyed paper P in the image forming apparatus according to the present embodiment will be described with reference to the drawings. First, the multifeed detection operation will be described below with reference to a drawing showing the actual time converted. FIG. 14 is an explanatory diagram of a state in which the subsequent sheet is not yet fed even if the deviation amount is detected during sheet conveyance in the image forming apparatus of the present embodiment. FIG. 15 is a diagram illustrating the state of the present embodiment. FIG. 6 is an explanatory diagram of a state after changing the inter-paper distance in the image forming apparatus.

  In the first embodiment, the jam determination is made when “paper interval time Tkankaku <shift time Tzure + necessary paper interval time Tkami”, but in this embodiment, the next paper still following the paper P1 is still present. When P3 is not fed, the paper feed extension time Tencho is calculated by subtracting the required paper gap time Tkami from the deviation amount time Tzure so as to ensure the required paper gap time Tkami, and the paper feed extension is performed. The extended paper feed timing Tenkyu is calculated by adding the normal paper feed timing Ttsujo to the time Tencho. By using the extended sheet feeding timing Tenkyu calculated in this way, the sheet feeding timing is switched from the normal sheet feeding timing Ttsujo to the extended sheet feeding timing Tenkyu, so that the operation of the image forming apparatus is stopped by jam determination as in the past. Since it is not necessary, continuous printing is possible, and copy efficiency is improved. In other words, in the present embodiment, continuous printing can be performed without stopping the operation of the image forming apparatus by extending the paper feed time.

  In FIG. 8, which is an operation explanatory diagram of the first embodiment, the next sheet P3 is fed when the deviation amount time Tzure is detected. However, depending on the distance between the sheet feeding tray 8 and the registration roller 15, As shown in FIG. 14, there is a state in which the normal paper feed timing Ttsujo has not elapsed and the paper P3 is not fed. In this embodiment, if the sheet P3 is not fed as described above, the sum of the deviation amount time Tzure (2.0 sec) and the necessary inter-sheet time Tkami (1.0 sec) and the normal sheet feeding timing. A paper feed extension time Tencho, which is a difference time of the paper interval time Tkankaku (= 1 sec) in Ttsujo (3.1 sec), is calculated. In other words, “2.0 (sec) +1.0 (sec) −1.0 (sec) = 2.0” from “deviation amount time Tzure + required paper interval time Tkami−paper interval time Tkankaku = feeding extension time Tencho”. (Sec) "and the paper feed extension time Tencho are calculated.

  Thereafter, an extended paper feed timing Tenkyu (5.1 sec) that is a time obtained by adding the paper feed extended time Tencho (2.0 sec) calculated as described above and the normal paper feed timing Ttsujo (3.1 sec) is calculated. Thus, by changing the paper feed timing from the normal paper feed timing Ttsujo to the extended paper feed timing Tenkyu, the paper is conveyed at the operation timing shown in FIG. 15 and can be continuously fed without causing a jam. For this reason, it is not necessary to stop the operation during copying, so that the copy efficiency is improved.

  At this time, when paper is discharged even if double feeding is detected, the discharge destination to the paper discharge tray 9 is changed or the post-discharge processing function is enabled / disabled as in the first embodiment. It is also possible to switch invalidity.

  Next, an operation flow for changing the paper feed timing in the image forming apparatus according to the present embodiment will be described with reference to the drawings. 16 to 18 are flowcharts for explaining the flow of operation for changing the paper feed timing in the image forming apparatus according to the present embodiment.

  In the present embodiment, as shown in FIG. 16, as in the first embodiment, when printing is started, the sheet P1 is first fed (step S1), and when the sheet P1 reaches the registration roller 15 (step S1). Step S2), transfer preparation is performed by the exposure unit 1 and the photoconductor 3, and the completion of preparation is waited (step S3). When the transfer preparation is completed, the registration roller 15 is rotated to convey the paper P1, and the deviation amount detection timer 1001 is started to measure the deviation amount time (step S4).

  While the paper is being transported, double feed detection is executed by the double feed detection sensor 500 (step S5) as in the first embodiment, and if double feed is not detected, as shown in FIG. 16 and FIG. On the other hand, if the normal paper conveyance process (from step S6) is executed and double feed is performed, the process after the double feed determination (from step S18) is executed as shown in FIG.

  If double feeding is not detected in step S5, it is confirmed whether or not the paper P is continuously printed (step S6). If the paper P is not continuously printed, as shown in FIG. In step S13 and subsequent steps for confirming the state of the paper P1, printing is terminated through the same processing steps (steps S14 to S17 and S33 to S35) as in the first embodiment. In this embodiment, if it is determined in step S6 that continuous printing is performed, it is confirmed whether the paper feed timing is the normal paper feed timing Ttsujo (step S7). After feeding the paper (step S8), the paper feed timing is returned to the normal paper feed timing Ttsujo (step S36), and then the process proceeds to the subsequent processing (processing after step S9). If the subsequent paper P3 is not at the paper feed timing in step S7, the next processing (processing after step S9) is executed. In the present embodiment, steps S9 and after are the same as the operation flow of the first embodiment described above, and thus the description thereof is omitted.

  When the double feed is detected in the above-described step S5, as shown in FIG. 18, the deviation amount detection timer 1001 is stopped and the deviation amount time Tzure is calculated as in the first embodiment (step S18). . Based on the deviation amount time Tzure obtained in step S18, a determination is made of “paper interval time Tkankaku ≧ displacement amount time Tzure + interval time Tkami” (step S19). If the paper interval time Tkankaku is longer, the first Similarly to the embodiment, the image formation for the paper P1 is finished (step S20), the jam determination operation is stopped (step S21), and the discharge destination of the discharge tray 9 of the next paper P3 is set to the discharge tray 9. -B is changed (step S22). After that, the processing steps after confirming whether or not continuous printing is performed are executed (from step S6).

  In the present embodiment, when the paper interval time Tkankaku is shorter in the above step S19, it is first checked whether or not the subsequent paper P3 has already been fed (step S37). If the paper P3 has already been fed, jamming is performed and all operations are stopped (step S23), and printing is terminated. On the contrary, if the paper P3 has not been fed, the extended paper feed timing Tenkyu is calculated, and the paper feed timing is replaced with the extended paper feed timing Tenkyu from the normal paper feed timing Ttsujo (step S38). After that, the process process after process S6 mentioned above is performed.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be applied to an image forming apparatus such as a laser printer, a copying machine, and a facsimile, and in particular, can be applied to an image forming apparatus having a function of preventing a multi-feed in which a plurality of sheets are simultaneously fed. .

1 is an explanatory diagram showing the overall configuration of a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a partial detail view showing a configuration of an apparatus main body of the image forming apparatus according to the embodiment. FIG. 4 is an explanatory diagram illustrating a configuration of a sheet conveyance path of the image forming apparatus according to the embodiment. FIG. 4 is a partial detail view showing a configuration of a branched paper conveyance path constituting the paper conveyance path of the same embodiment and a branching claw for communicating them. FIG. 2 is a schematic diagram illustrating a configuration of a sheet conveying unit provided in the image forming apparatus according to the embodiment. FIG. 3 is a block diagram illustrating a configuration of a double feed detection sensor provided in a paper transport unit provided in the image forming apparatus according to the embodiment. 5 is a timing chart illustrating a state in which a double-fed sheet is detected by a double-fed detection sensor in the image forming apparatus of the embodiment. FIG. FIG. 6 is a state explanatory diagram when the distance between sheets is jammed during sheet conveyance in the image forming apparatus of the embodiment. FIG. 10 is an explanatory diagram of a state when a distance between sheets is open during sheet conveyance in the image forming apparatus of the embodiment. 2 is a block diagram illustrating a configuration of an electric control unit of the image forming apparatus according to the embodiment. FIG. 4 is a flowchart for explaining a flow of an operation of jam determination in the image forming apparatus of the embodiment. 4 is a flowchart for explaining a flow of an operation of jam determination in the image forming apparatus of the embodiment. 4 is a flowchart for explaining a flow of an operation of jam determination in the image forming apparatus of the embodiment. FIG. 10 is a state explanatory diagram when a subsequent sheet is not yet fed even if a deviation amount is detected during sheet conveyance in the image forming apparatus according to the second embodiment of the present invention. FIG. 6 is an explanatory diagram of a state after the inter-paper distance is changed in the image forming apparatus of the embodiment. 4 is a flowchart for explaining a flow of operation for changing a paper feed timing in the image forming apparatus of the embodiment. 4 is a flowchart for explaining a flow of operation for changing a paper feed timing in the image forming apparatus of the embodiment. 4 is a flowchart for explaining a flow of operation for changing a paper feed timing in the image forming apparatus of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A Image forming apparatus 1 Exposure unit 3 Photoconductor 6 Fixing unit 7 Paper conveyance path 8 Paper feed tray 9 Paper discharge tray 10 Transfer mechanism 15 Registration roller 103 Transfer belt 500 Double feed detection sensor 501 Transmission circuit 502 Transmission amplification circuit 503 Ultrasonic transmission 504 Ultrasonic receiver 505 Resonance circuit 506 Resonance amplification circuit 507 A / D circuit 508 CPU
1001 Deviation detection timer P1 First sheet P2 Double feed sheet P3 Next sheet fed

Claims (11)

A recording medium stacking unit capable of stacking a plurality of recording media, a recording medium transporting unit for transporting the recording medium supplied from the recording medium stacking unit to an image forming unit, and the recording medium stacking from the recording medium stacking unit. An image forming apparatus capable of automatically supplying the recording medium from the recording medium stacking unit.
When the double feed detection means detects double feed of the storage medium, double feed amount detection means is provided for detecting the double feed amount of the storage medium that has been double fed into time, and the double feed amount is provided. An image forming apparatus, wherein the control of the recording medium conveying unit is made different according to the double feed amount detected by the detecting unit.   The image forming apparatus according to claim 1, wherein the double feed detection unit detects a double feed amount of the storage medium using ultrasonic waves.   The image forming apparatus according to claim 1, wherein jam detection is performed in the double feed detection unit.   4. The jam detection operation is stopped when the double feed amount is a predetermined amount or less, and the jam detection is operated when the double feed amount is the predetermined amount or more. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 4, wherein the predetermined amount is a required inter-paper distance that is a minimum interval between the recording media that is required when the recording media are continuously conveyed.   The image forming apparatus according to claim 1, wherein when the double feed is detected by the double feed detection unit, the image formation executed by the image forming unit is stopped. The image forming unit includes image fixing means for melting and fixing the toner image transferred onto the recording medium,
The image forming apparatus according to claim 1, wherein a fixing temperature of the image fixing unit is changed when the double feeding is detected by the multi-feed detecting unit.   The image forming apparatus according to claim 1, wherein the control of the recording medium conveying unit is a change in timing of conveying the recording medium to the image forming unit. When the double feed amount is equal to or less than a predetermined amount, the recording medium is conveyed at a normal paper feeding timing that is a timing at which the recording medium is conveyed to the image forming unit at a normal time.
When the double feed amount is equal to or greater than a predetermined amount, a paper feed extension time calculated from a value obtained by subtracting the required inter-paper distance from the double feed amount of the storage medium is added to the normal paper feed timing. The image forming apparatus according to claim 8, wherein the recording medium is conveyed at an extended sheet feeding timing obtained in the above.   The discharge tray serving as a discharge destination of a recording medium conveyed subsequent to the double-fed recording medium is changed when the double-feed detection unit detects double-feeding. The image forming apparatus according to any one of 1 to 9.   In the case where the image forming apparatus includes a post-processing device that executes processing after discharging the recording medium instead of the paper discharge tray, the post-processing device is detected when double-feed is detected by the double-feed detection unit. The image forming apparatus according to claim 1, further comprising: a switching unit that switches the function between enabled and disabled.

Images