JP2007131414A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of suppressing non-paper feeding caused by various causes effectively and conveying a recording paper securely when conveying the loaded recording paper. <P>SOLUTION: An operation plate provided on a paper feeding cassette loads a recording paper. A sheet face height setting part 320 lifts the operation plate so that the uppermost face of recording paper has predetermined height, and a conveyance control part 315 conveys the recording paper on the uppermost face reaching the predetermined height. A resist sensor 200 detects the recording paper in a predetermined section on a conveyance path for conveying the recording paper, and a non-paper feeding determining part 331 determines that the recording paper does not reach the predetermined height based on non-detection of the recording paper by the resist sensor 200. A sheet face height correction part 330 lifts the operation plate again to correct a position of the operation plate in accordance with the determination by the non-paper feeding determining part 331. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile machine, and a multifunction machine having two or more of these functions.

  Conventionally, various image forming apparatuses such as printers, copiers, and facsimiles have been used. Among these image forming apparatuses, an image forming apparatus such as a so-called multifunction machine having two or more functions is also used.

  The image forming apparatus is provided with a paper tray for stacking paper. In the case where a large capacity of paper can be loaded, the paper tray can be driven up and down. The sheet moves as the tray is driven up until the uppermost surface is detected to have reached a predetermined height by a sensor such as a photo interrupter. A paper feed roller is provided at this position, and one uppermost sheet is conveyed from this position to the photosensitive drum.

  Here, even if the height of the raised paper is one sheet, if the paper height is lower than the predetermined height for some reason, the paper feed roller can press the paper only with a weak pressure. , Idling occurs and conveyance fails (so-called no-feed).

Patent Document 1 discloses a technique for suppressing such non-feeding. In the technique of Patent Document 1, attention is paid to the fact that the paper is distorted when it is brought into contact with the paper feed roller, and the paper is slightly dented to change the height of the paper.
JP 2002-2972 A

  However, there are various reasons for the absence of paper feed in addition to the change in the height of the paper. For example, if the paper is changed to another paper having a different quality, the friction is the same as that of the paper. The paper feed roller changes and no paper feed occurs. In addition, the pressure at which the paper feed roller presses the paper changes due to individual differences in the springs that bias the paper feed roller, which may cause no paper feed. In addition, the above-described sensors for detecting that the paper has reached a predetermined height also have individual differences, and the position where the paper reaches slightly differs from machine to machine. It was. For these reasons, the technique disclosed in Japanese Patent Laid-Open No. 2004-228620 can prevent no paper feeding only in a very limited case.

  The present invention has been made in view of the above-described problems, and effectively suppresses no paper feeding caused by various causes, and an image in which the recording paper is reliably conveyed when the stacked recording paper is conveyed. An object is to provide a forming apparatus.

  An image forming apparatus according to the present invention includes a stacking unit that stacks recording sheets, a lifting unit that lifts the stacking unit so that the uppermost surface of the recording sheet has a predetermined height, and the uppermost surface of the raised recording sheets. A conveying means for conveying the recording paper, a detecting means for detecting the recording paper conveyed by the conveying means at a predetermined location on the conveying path, and when the recording means is not detected by the detecting means, the stacking means And correcting means for correcting the height of the stacking means by raising again.

  According to this configuration, the recording sheet is stacked on the stacking unit, the stacking unit is raised so that the uppermost surface of the recording sheet has a predetermined height, and the uppermost recording sheet among the raised recording sheets is transferred to the conveying unit. The recording sheet that is conveyed and conveyed at a predetermined location on the conveyance path is detected by the detection means. If this detection is not made, the stacking means is raised again to correct the height of the stacking means.

  Therefore, when the recording paper does not reach the predetermined height conveyed to the conveying means and no paper feeding occurs, the position of the stacking means is corrected regardless of the cause. Can be effectively suppressed, and the recording paper can be reliably conveyed.

  In the above image forming apparatus, the detection unit detects a non-feed state of the recording sheet when the recording unit does not detect the recording sheet within a predetermined period after the conveying unit starts conveying, and the correcting unit Preferably, when the no-paper-feed state is detected by the detection means, the height of the stacking means is corrected.

  According to this configuration, when the recording sheet is not detected within a predetermined period after the conveying unit starts conveying, the non-feed state of the recording sheet is detected, and when the non-feed state is detected, the stacking unit The height of is corrected.

  Therefore, the determination can be easily made based on the period from the start of conveyance of the recording paper to the detection of the recording paper by the detecting means, and the image forming apparatus can be simplified.

  In the above image forming apparatus, after one end of the recording sheet reaches a predetermined position and is detected by the detection unit, the recording sheet passes through the predetermined position to the other end as it is conveyed, and the recording unit receives the recording sheet. A multi-feed determining unit that measures a time until no longer is detected, and determines a multi-feed state of the recording paper based on the measured time being longer than a predetermined time, and the correcting unit includes the multi-feed determination It is preferable to correct the height of the stacking means by lowering the stacking means in accordance with the determination result by the means.

  According to this configuration, after one end of the recording sheet reaches a predetermined position and is detected by the detection unit, the recording sheet is detected by the detection unit after passing through the predetermined position to the other end as it is conveyed. The time to disappear is measured. Then, based on the measured time being longer than the predetermined time, the double feed state of the recording paper is determined, and the stacking unit is lowered according to the determination result, and the height of the stacking unit is corrected.

  Accordingly, although the stacking means is raised to a relatively high position and the number of occurrences that the double feed is likely to occur increases, the double feed state is determined by the double feed determination means, and according to this determination Since the loading means is lowered and the height of the loading means is corrected, double feeding can be suppressed. As a result, it is possible to suppress a paper feed failure with a good balance including double feeding.

  Here, “multiple feeding” means that two or more recording sheets that have been stacked on the stacking unit are transported as they are stacked in two or more sheets. The “double feed state” is a state in which double feed is performed.

  The image forming apparatus may further include a recording unit that records the height information for specifying the height of the stacking unit that has been corrected by the correcting unit, and the ascending unit has a height on the recording unit. When information is recorded, it is preferable to raise and lower the stacking means according to the height information.

  According to this configuration, when the height information for specifying the height of the loading means corrected is recorded in the correction means, and the height information is recorded, the lifting means is loaded according to the height information. Raise and lower means.

  Therefore, when the raising means raises the loading means, it is not necessary to wait for the detection by the detection means and the correction of the height of the loading means by the correction means. Since the stacking means is raised and lowered according to the height information, it is possible to realize an image forming apparatus that operates efficiently with little wasteful operation.

  The “height information for specifying the height of the loading means” includes information on the relative distance from the specific position up to that height. For example, the height information may be information on a relative distance by which the loading unit is moved from the position before correction, or information on a relative distance from another predetermined height. Further, the height information may specify the height by control information for a stepping motor or other driving means for driving the stacking means. For example, it may be specified by information on the number of input pulses for a stepping motor as a driving means.

  According to the present invention, the position of the stacking unit is corrected regardless of the cause when the recording paper does not reach the predetermined height to be conveyed to the conveying unit and the non-feed occurs. Thus, the recording paper can be reliably conveyed by effectively suppressing the non-feeding caused by the recording paper.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing an internal configuration of a digital color copier according to an embodiment of the present invention. In this embodiment, a case where the present invention is applied to a copying machine as an example of an image forming apparatus will be described. However, the present invention can also be applied to, for example, a printer apparatus, a facsimile apparatus, a scanner apparatus, and a multifunction apparatus having these functions. It is.

  In FIG. 1, an image forming apparatus 1 constitutes a tandem type digital color copying machine, and an image reading unit 7 for reading a document image and a document image read by the image reading unit 7 are transferred to a recording sheet. A main body 2 for recording, and a recording paper discharge unit 6 for discharging the recording paper onto which the original image is transferred by the main body 2.

  The image reading unit 7 includes a scanner 71 composed of a CCD (Charge Coupled Device) or the like. The image reading unit 7 reads an image of a document placed on the first contact glass 72 by the scanner 71, and sequentially reads a plurality of documents stacked on the document placement unit 73 to the second contact glass 74. The image of the original passing through the second contact glass 74 is read out. Image data read by the scanner 71 is stored in a memory.

  The main body 2 includes a paper feeding unit 100 disposed in the lower part of the housing 3, an image forming unit 30 disposed in the upper part of the housing 3, and a lower part of the image forming unit 30 in the housing 3. The transfer conveyance unit 40 disposed in the housing 3, the fixing unit 50 disposed on the downstream side of the transfer conveyance unit 40 in the housing 3, and the recording paper fed from the paper supply unit 100 are transferred to the transfer conveyance unit 40 side. A first paper transport unit 20 for sending out and a second paper transport unit 21 for discharging the recording paper that has passed through the fixing unit 50 to the recording paper discharge unit 6 are provided. Note that an operation panel 9 for instructing the start of printing and setting copying conditions such as the recording paper size is provided at an appropriate position of the main body 2.

  The paper feeding unit 100 feeds a stack of recording papers 101 stacked on the paper feeding cassette 110 one by one from the uppermost recording paper 101 to the first paper transporting unit 20 side by rotating the paper feeding roller 111. It is configured to pay out. The first paper transport unit 20 transports the paper fed from the paper feed unit 100 to a registration roller 24 provided in front of the image forming unit 30 (image forming unit 30K) by various roller pairs 22. The registration roller 24 adjusts the timing between the image forming operation and the paper feeding operation by the image forming units 30Y, 30M, 30C, and 30K.

  A paper feed sensor 81 that detects the leading edge of the recording paper that has passed through the paper feed roller 111 is provided downstream of the paper feed roller 111 in the transport direction. A registration sensor 200 that detects the leading edge of the recording paper that has reached the registration roller 24 is provided upstream of the registration roller 24 in the transport direction. The paper feed sensor 81 and the registration sensor 200 are composed of, for example, a transmissive photosensor, and are disposed at positions where the light emitting element and the light receiving element face each other across the recording paper conveyance path. The paper feed sensor 81 and the registration sensor 200 detect the passage of the leading end of the recording paper when the light received by the light receiving element is blocked by the recording paper. In the case of the registration sensor 200, after the leading edge passes, the recording paper further moves downstream as it is conveyed, and finally, the trailing edge passes through the registration sensor 200, and the recording paper 101 moves to the registration sensor 200. It is also used to detect the timing when it is no longer detected.

  The image forming unit 30 is configured to multiplexly form a plurality of toner images on a recording sheet, and includes a first image forming unit 30Y that forms a yellow toner image and a second image forming that forms a magenta toner image. The unit 30M includes a third image forming unit 30C that forms a cyan toner image and a fourth image forming unit 30K that forms a black toner image. The image forming units 30Y, 30M, 30C, and 30K are arranged at predetermined intervals along the recording paper conveyance direction.

  Each of the image forming units 30Y, 30M, 30C, and 30K includes a photosensitive drum 31, a charging unit 32 disposed to face the peripheral surface of the photosensitive drum 31, and a downstream side of the charging unit 32 and the photosensitive unit. An exposure unit 33 disposed facing the peripheral surface of the drum 31, a developing unit 34 disposed downstream of the exposure unit 33 and opposed to the peripheral surface of the photosensitive drum 31, and the developing unit 34 And a cleaning unit 35 disposed opposite to the circumferential surface of the photosensitive drum 31. Further, a transfer roller 36 described later is disposed on the peripheral surface of the photosensitive drum 31 between the developing unit 34 and the cleaning unit 35, thereby forming the transfer unit 36. Note that the photosensitive drums 31 of the image forming units 30Y, 30M, 30C, and 30K are rotated in the clockwise direction shown in the drawing by a drive motor.

  The transfer conveyance unit 40 includes a driven roller 42 disposed in the vicinity of the first image forming unit 30Y, a driving roller 43 disposed in the vicinity of the fourth image forming unit 30K, and a driven roller 42. The transfer belt 41, which is an endless image carrier disposed across the drive roller 43, and the image forming units 30Y, 30M, 30C, 30K are transferred to positions downstream of the developing unit 34 of the photosensitive drum 31. And four transfer rollers 44 disposed so as to be capable of being pressed against each other via a belt 41.

  In the transfer transport unit 40, the recording paper transported from the first paper transport unit 20 is electrostatically attracted onto the transfer belt 41 rotated in the counterclockwise direction shown in the figure by a drive motor and transported downstream. The toner images are transferred to the recording paper at the positions of the transfer portions 36 of the image forming units 30Y, 30M, 30C, and 30K.

  The fixing unit 50 performs a fixing process by heating the recording paper on which the toner images formed on the surface of the photoreceptor drum 31 of each of the image forming units 30Y, 30M, 30C, and 30K are transferred in a multiple manner. And a pressure roller 52 disposed in pressure contact with the heating roller 51. The second paper transport unit 21 discharges the paper on which the image is formed in the image forming units 30Y, 30M, 30C, and 30K and the fixing unit 50 to the recording paper discharge unit 6 by the transport roller pair 23.

  Here, a basic operation of the image forming apparatus 1 configured as described above will be described. First, an original is placed on the first contact glass 72, or an original is placed on the original placement portion 73, the operation panel 9 is operated to set the number of copies, and the start button is operated. Then, the original image is captured by the scanner 71 of the image reading unit 7 and stored in the image memory. The image data stored in the image memory is transmitted to the image forming unit 30.

  In each photosensitive drum 31 of the image forming unit 30, the photosensitive drum 31 rotating in the clockwise direction in FIG. 1 is uniformly charged by the charging unit 32, and the exposure unit 33 (laser) based on the transmitted image data or the like. An electrostatic latent image is formed on the photosensitive drum 31 by a laser beam from an operation unit or the like, and a developer (toner) is attached to the electrostatic latent image by the developing unit 34 to form a toner image.

  On the other hand, the recording paper is fed out from the paper supply unit 100 and conveyed to the image forming unit 30 side by the first paper conveyance unit 20. Then, the timing of the image forming operation of the image forming unit 30 is set by the registration roller 24 and then conveyed to the transfer conveying unit 40, and the toner images are sequentially formed on the recording paper by the image forming units 30Y, 30M, 30C, and 30K. Transcribed.

  The recording sheet on which the toner image has been transferred is conveyed to the fixing unit 50, is nipped by the heating roller 51 and the pressure roller 52 while being heated by the heating roller 51, and is conveyed to the downstream side. 21 is discharged to the recording paper discharge unit 6. The toner remaining on the surface of each photosensitive drum 31 having the toner image transferred onto the recording paper is removed by the cleaning unit 35.

  The image forming apparatus 1 includes an image read by a scanner 71 such as a central processing unit (CPU), a random-access memory (RAM), a read only memory (ROM), and an electrically erasable programmable read-only memory (EEPROM). An information processing apparatus for performing the above processing is provided. This is not shown in FIG.

  Next, the configuration of the sheet feeding unit 100 will be described in detail.

  In the paper feeding unit 100, the paper feeding cassette 110 can be taken out of the image forming apparatus 1 when the recording paper 101 is used one after another for image formation, and when the remaining recording paper runs short or runs out. Although not shown, the image forming apparatus 1 has an opening, and the paper feed cassette 110 can be taken out from the opening. The paper feed cassette 110 is taken out and replenished with new recording paper 101, and then returned to the position shown in FIG. When the paper feed cassette 110 is returned to the position shown in FIG. 1, the cassette insertion detection sensor 118 detects this. The cassette insertion detection sensor 118 detects that the paper feed cassette 110 has been optically inserted.

  FIG. 2 is a diagram schematically showing details of a part of the paper feeding unit 100. As shown in FIG. 2, the sheet feeding unit 100 is omitted from FIG. 1 for the sake of convenience of explanation, and includes an operation plate 102, a gear 105, a lifting motor 104, a spring 103, and an interlocking member 112. And a sheet surface detection sensor 107. Components other than those already shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 1 in FIG.

  The operation plate 102 is a plate that is attached to the paper feed cassette 110 and on which a bundle of recording paper 101 is placed. The operation plate 102 can be lifted at one end and lifted from the bottom of the paper feed cassette 110 while the loaded recording paper 101 is still loaded, as indicated by an arrow X. The operation plate 102 is in a horizontal state when the paper feed cassette 110 is inserted into the image forming apparatus 1, but when the insertion of the paper feed cassette 110 is detected by the cassette insertion detection sensor 118 (see FIG. 1). Immediately, one end is raised to a high position as shown in FIG.

  The recording paper 101 and the operation plate 102 are lifted by being driven by a lifting motor 104 via a gear 105. The elevating motor 104 and the gear 105 can adjust the height at which the operating plate 102 is raised with high accuracy so that the recording paper 101 contacts the paper feed roller 111 with an appropriate pressure. For this reason, the raising / lowering motor 104 is comprised by the stepping motor which can be rotated accurately. The elevating motor 104 composed of a stepping motor rotates by a predetermined angle by inputting a pulse, and raises the operating plate 102 with high accuracy. In addition, you may comprise this raising / lowering motor 104 by other types of motors, such as a servomotor. When the recording paper 101 is raised and abuts against the paper feed roller 111, it is biased by the force of the spring 103, so that the paper feed roller 111 presses the recording paper 101. In this state, the paper feed roller 111 transports the recording paper 101 one by one to the first paper transport unit 20 side (see FIG. 1). Note that the height of the recording paper 101 (the height of the uppermost surface of the recording paper 101) at which the paper feeding roller 111 can appropriately transport the recording paper 101 one by one in this way is simply referred to as “predetermined transport height” below. ".

  If the uppermost surface of the recording paper 101 deviates from such a predetermined transport height, a paper feed failure occurs. First, when the recording paper 101 is at a position lower than a predetermined conveyance height, the paper feeding roller 111 presses the recording paper 101 with a weak force, and the paper feeding roller 111 rotates idly, and the recording paper 101 Cannot be transported (so-called no paper feed). On the other hand, when the recording paper 101 is at a high position and the recording paper 101 is pressed with too strong pressure by the paper feed roller 111, two or more recording papers 101 are simultaneously conveyed, so-called double feeding is performed. I get up. When the paper feed cassette 110 is inserted into the image forming apparatus 1 and a new recording paper 101 is loaded on the image forming apparatus 1, the friction of the surface is different for the new paper. Such a paper feed failure often occurs. In the image forming apparatus 1 of the present embodiment, such a paper feed failure is suppressed.

  The sheet surface detection sensor 107 detects when the recording paper 101 reaches a predetermined conveyance height when the operation plate 102 is raised by the elevating motor 104. The sheet surface detection sensor 107 is configured by a reflective photo interrupter. When the recording paper 101 rises and comes into contact with the paper feed roller 111, the spring 103 is slightly contracted, the paper feed roller 111 rises, and after a while, the recording paper 101 reaches a predetermined transport height. The movement of the paper feed roller 111 is interlocked with the interlocking member 112. The sheet surface detection sensor 107 detects that the recording paper 101 has reached a predetermined conveyance height based on the movement of the interlocking member 112.

  FIG. 3 is a block diagram showing a schematic configuration of the image forming apparatus 1 according to the present invention.

  The CPU 300 is a central processing unit that controls each part of the image forming apparatus 1 using the EEPROM 400 and the ROM 500. The EEPROM 400 is a nonvolatile memory in which data can be written and read, and the stored contents are retained even when the power is turned off. The ROM 500 is a read-only memory. Other cassette insertion detection sensors 118 and the like have been described with reference to FIGS.

  The CPU 300 functions as an image formation control unit 310, a conveyance control unit 315, a sheet surface height setting unit 320, a sheet surface height correction unit 330, a non-paper feeding determination unit 331, and a double feed determination unit 332. Realize the block. Although not shown, the ROM 500 stores a computer program for causing the CPU 300 to realize each of these functional blocks. The EEPROM 400 includes a correction pulse number storage unit 410 inside. The ROM 500 includes a required arrival time storage unit 501 and a required passage time storage unit 502 inside.

  The image formation control unit 310 controls the operation of each of these functional units and each unit of the image forming apparatus 1 such as the cassette insertion detection sensor 118 described above. The image formation control unit 310 uses the sheet surface height setting unit 320 to raise the working plate 102 that is horizontal on the inner bottom surface of the sheet feeding cassette 110 so that the recording paper 101 reaches a predetermined conveyance height. Let The image forming control unit 310 detects when the paper feed cassette 110 is detected by the cassette insertion detection sensor 118 (see FIG. 1) and when the image forming apparatus 1 is turned on and the CPU 300 starts from the initial state. Do this rise. After raising the operation plate 102, the image formation control unit 310 waits until the user gives an instruction to start printing through the operation panel 9. When this print start instruction is issued, the image formation control unit 310 moves the recording paper 101 in the paper feed cassette 110 from the first paper transport unit 20 to the downstream side using the transport control unit 315. Thereafter, the image forming control unit 310 uses the sheet surface height correcting unit 330 to correct the position of the operation plate 102 based on the result of the conveyance. Further, if the recording paper 101 is not fed as a result of the conveyance, the image formation control unit 310 forms an image on the conveyed recording paper 101 using the image forming unit 30 or the like. At this time, the image formation control unit 310 also forms an image on the recording paper 101 to be conveyed using the transfer conveyance unit 40 and the fixing unit 50, and provides them to the user. Omitted.

  Based on an instruction from the image formation control unit 310, the sheet surface height setting unit 320 drives the horizontal operation plate 102 (see FIG. 2) upward by the lift motor 104, thereby moving the recording paper 101 to a predetermined transport height. To reach. At this time, the sheet surface detection sensor 107 detects that the recording paper 101 has reached a predetermined conveyance height. When this detection is made, the seat surface height setting unit 320 stops the operation plate 102 from rising. However, the sheet surface detection sensor 107 does not necessarily detect that the recording paper 101 has reached the predetermined conveyance height with complete accuracy. Depending on the situation, it may naturally be detected with a certain amount of error (deviation). Therefore, in order to absorb the error, the sheet surface height setting unit 320 finally moves the operation plate 102 slightly from the position detected by the sheet surface detection sensor 107 by a predetermined number of correction pulses. Thus, the operation plate 102 is accurately moved to a predetermined conveyance height.

  The corrected pulse number storage unit 410 provided in the EEPROM 400 stores the aforementioned corrected pulse number. The number of correction pulses is a positive integer or a negative integer. When the number of correction pulses is a positive integer, the seat surface height setting unit 320 raises the operating plate 102, and conversely, when it is a negative integer, it lowers. The number of correction pulses is set to “0” or other predetermined value in the factory shipment state. Different values may be set according to individual differences of the image forming apparatus 1.

  The conveyance control unit 315 controls each unit from the paper feed roller 111 to the second sheet conveyance unit 21 on the path along which the recording sheet 101 is conveyed, and conveys the recording sheet. First, a sheet feeding motor 111m (not shown in FIGS. 1 and 2) that rotates the sheet feeding roller 111 is rotated so that one sheet of recording paper 101 on the uppermost surface of the recording sheet 101 is on the downstream side. The movement is started toward the first sheet conveyance unit 20 side. Thereafter, the conveyance of the recording paper 101 in each of the first paper conveyance unit 20, the transfer conveyance unit 40, the fixing unit 50, and the second paper conveyance unit 21 is controlled, and the recording paper 101 finally becomes the recording paper discharge unit. 6 to ensure proper discharge. In FIG. 3, only the paper feed motor 111 m is representatively illustrated among the units controlled by the transport control unit 315.

  The sheet surface height correction unit 330 operates based on an instruction from the image formation control unit 310 to further finely correct the height of the working plate 102 set by the sheet surface height setting unit 320. Therefore, the sheet surface height correcting unit 330 is activated by the image forming control unit 310 after the recording sheet 101 actually starts moving from the operation plate 102 after the position of the operation plate 102 is set by the sheet surface height setting unit 320. Is done. The sheet surface height correction unit 330 detects that a paper feed failure has occurred in the conveyance of the recording paper 101 by the non-paper feed determination unit 331 and the double feed determination unit 332 and corrects the position of the operation plate 102. Then, the seat surface height correction unit 330 stores in the correction pulse number storage unit 410 the number of pulses that have moved the operation plate 102 by this correction, that is, the number of pulses that have been input to the lifting motor 104 to move the operation plate 102. Next, the sheet surface height setting unit 320 raises the operating plate 102 to increase or decrease the operating plate 102 (when the operating plate 102 is raised) or decreased (when the operating plate 102 is lowered). When the height 102 is set, the current correction is also reflected at that time. Here, since the correction pulse number storage unit 410 is configured by the EEPROM 400, the correction contents of this time are reflected even when the setting is performed next time after the image forming apparatus 1 is turned off. Can do.

  Both the non-feed determination unit 331 and the double feed determination unit 332 determine a non-feed and double feed failure based on the detection result of the registration sensor 200 whose position is shown in FIG. The non-paper feeding determination unit 331 and the double feed determination unit 332 make these determinations with reference to the required arrival time and the required passage time stored in the ROM 500, respectively.

  FIG. 4 is a diagram for explaining the required travel time and the required travel time. FIG. 4 shows the time required to reach and the time required to pass through the timings O, t1, t2, t3 at which the recording paper 101 moves downstream, starting with the feeding roller 111 transporting the recording paper 101. The description is based on t4. Time elapses in the order of timings O, t1, t2, t3, and t4.

  Timing O is timing when the paper feed roller 111 starts to rotate. As described above, when the user starts printing from the operation panel 9, rotation driving of the paper feed roller 111 is started by the conveyance control unit 315.

  When the paper feed roller 111 rotates, the uppermost sheet of the recording paper 101 is transported and enters the first paper transport unit 20 on the downstream side. The timing t1 is when the recording paper 101 reaches the registration sensor 200 located on the most downstream side of the first paper transport unit 20 (see FIG. 1). Here, the timing t2 shown following the timing t1 is the timing when the leading edge of the recording paper 101 arrives at the registration sensor 200 most recently. Such a delay in arrival occurs when the recording paper 101 is temporarily slipping with respect to the paper feed roller 111. In FIG. 4, the maximum delay time is shown as λ1. The required arrival time stored in the required arrival time storage unit 501 stores the time from timing O to timing t2.

  As long as no paper feeding occurs, the recording paper 101 is detected by the registration sensor 200 at timing t1 or the like before the required time for arrival has elapsed. For this reason, the non-paper feeding determination unit 331 determines that no paper feeding has occurred when the recording paper 101 is not detected by the registration sensor 200 during this period.

  On the other hand, the recording paper 101 whose leading edge has reached the registration sensor 200 at the timing t1 without slipping or the like finally reaches the registration sensor 200 as it is further conveyed downstream. pass. This is timing t3. On the other hand, the timing t4 shown after the timing t3 is the timing when the trailing edge of the recording paper 101 arrives at the registration sensor 200 most recently. Such a delay also occurs due to slipping of the recording paper 101 or the like. In FIG. 4, the maximum delay time is illustrated as λ2. The required passage time stored in the required passage time storage unit 502 stores the times from the timing t1 to the timing t4.

  Here, when double feeding occurs, the two recording sheets 101 overlap, and the sheet length becomes substantially longer by the amount that the two sheets deviate and overlap each other. An even greater delay occurs. Therefore, the double feed determination unit 332 measures the time (timing t1 to t3) from when the leading edge of the recording paper 101 is detected (timing t1) until the recording paper 101 is not detected by the registration sensor 200 thereafter. If the time is longer than the required passage time stored in the required passage time storage unit 502, it is determined that double feeding is occurring.

  In the above description, the determination of the non-feeding and double feeding is made based on the detection result of the registration sensor 200. However, other than the registration sensor 200, on the conveyance path on which the recording paper 101 is conveyed. The determination may be made based on the detection result of another paper detection sensor, for example, the paper feed sensor 81. Note that the determination of no paper feeding and double feeding may be performed based on detection results of different sensors.

  In addition, the recording paper 101 is aligned between the time when the recording paper 101 departs from the paper feeding cassette 110 and the time when the trailing edge passes through the registration sensor 200, and the recording paper 101 is conveyed. In the case of temporary stop, it is preferable to compare the required travel time and required travel time except for the temporary stop time. In this way, it is possible to make a determination with high accuracy.

  FIG. 5 is a flowchart for explaining the operation of the image forming apparatus 1. The operation of the image forming apparatus 1 will be described with reference to FIG.

  In step S <b> 2, the image formation control unit 310 detects whether the paper feed cassette 110 has been inserted or whether the CPU 300 has started up and execution of the image formation control unit 310 has started. In response to this detection, the operation of FIG. 5 is started.

  Next, in step S <b> 4, the image formation control unit 310 activates the sheet surface height setting unit 320. The sheet surface height setting unit 320 raises the horizontal working plate 102 to a predetermined conveyance height. First, the elevation motor 104 is driven until the recording sheet 101 is detected by the sheet surface detection sensor 107. Thereafter, the initial correction pulse number stored in the correction pulse number storage unit 410 is input to the lifting motor 104.

  Next, in step S <b> 6, the image formation control unit 310 waits until the user gives a print start instruction using the operation panel 9. The operation after the next step S8 starts when an instruction is given.

  In step S <b> 8, the image formation control unit 310 causes the conveyance control unit 315 to start conveying the recording paper 101.

  Next, in step S <b> 10, the image formation control unit 310 activates the sheet surface height correction unit 330. When activated, the sheet surface height correcting unit 330 performs processing of each step described below to detect no paper feed or to detect double feed, and corrects the position of the operation plate 102. .

  First, in step S <b> 10, the sheet surface height correction unit 330 detects whether or not no sheet feeding has occurred using the no sheet feeding determination unit 331. If no paper feeding has occurred (step S10: YES), the conveyance control unit 315 is instructed to interrupt conveyance through the image forming control unit 310 (step S10b), and the operation plate 102 is fed by the paper feeding roller 111. In addition, an input for raising the operating plate 102 is made to the elevating motor 104 by a predetermined number of pulses so as to be closer than now (step S10d). The predetermined number of pulses is, for example, 8 pulses. By such an input, the recording paper 101 is strongly pressed against the paper feed roller 111, so that no paper feed is difficult to occur. The sheet surface height correcting unit 330 stores the position of the working plate 102 in which no sheet feeding is difficult to occur in this manner in the EEPROM 400 so as to raise the working plate 102 earlier by the number of pulses input to the lifting motor 104. Then, the correction pulse number stored in the correction pulse number storage unit 410 is increased (incremented) (step S10f). Then, it returns to step S8 again (retry).

  Even during the retry, no paper feed is determined (step S10). If no paper feed occurs again (step S10: YES), the operations of steps S10b to S10f are repeated. The operations after step S14 are performed when the operation exits from such a loop without being determined as no paper feed in step S10 (step S10: NO).

  In step S <b> 14, the sheet surface height correction unit 330 activates the double feed determination unit 332. The double feed determination unit 332 determines whether or not the recording paper 101 previously detected by the registration sensor 200 in the determination of no paper feed (step S10) has not been double fed. As a result, if it is not double feed (step S14: NO), operations such as image formation in step S16 are started. In the following, the operation in the case of double feeding will be left, and the operation after step S16 will be described first.

  In step S <b> 16, the image formation control unit 310 forms an image on the recording paper 101 being conveyed without causing no paper feeding or double feeding, and provides it to the user from the recording paper discharge unit 6.

  Finally, in step S18, the conveyance control unit 315 stops the operation of the conveyance roller pair 23 and the like.

  Here, after the image formation is completed in this way, when the operation of FIG. 5 is started again from step S2, the number of correction pulses previously recorded in step S10f is read and used. . When the insertion of the paper feed cassette 110 is detected or the power of the image forming apparatus 1 is detected, the operation in FIG. 5 is started again from step S2. The number of correction pulses previously recorded in step S10f is read in step S4 and input to the lifting motor 104. As a result, the operating plate 102 rises higher in step S4 by the amount corresponding to the previously corrected height. As a result, the operation plate 102 immediately rises to the corrected position without waiting for the operation in step S10b and subsequent steps to be performed later, so that an image forming apparatus that operates efficiently with little useless operation is obtained. Can be realized.

  Next, the case where determination of double feeding is made in step S14 (step S14: YES) will be described. In this case, prior to image formation (step S16), the operations of steps S14b and S14d are performed.

  In step S14b, the seat surface height correction unit 330 corrects the position of the operation plate 102. In this case, since the recording paper 101 is too close to the paper feed roller 111 and double feeding is occurring, the sheet surface height correction unit 330 lowers the operation plate 102 and slightly moves from the paper feed roller 111. Release. The lowered width is, for example, 8 pulses of the lifting motor 104.

  Next, in step S14d, the seat surface height correction unit 330 decreases the number of correction pulses stored in the correction pulse number storage unit 410 by the amount corresponding to eight pulses that descend the operation plate 102 (decrement). Due to this decrement, when the operation of FIG. 5 is performed again next time, the reduced correction pulse number is input to the lifting motor 104 in step S4. As a result, in the next step S4, the operating plate 102 is raised only to a lower position by the amount corresponding to the current correction.

  It should be noted that in the position correction of the operation plate 102 in step S10d, the operation plate 102 is greatly raised by a single correction from a low position where no paper feed has occurred, and greatly exceeds a predetermined conveying height, and double feed is performed. It is preferable that the correction is made only by a small amount of rise so as not to cause the occurrence of the problem. In this way, double feeding can be avoided. Further, the number of correction pulses is reset when the paper feeding cassette 110 is extracted from the image forming apparatus 1, and until the next writing, the sheet surface height setting unit 320 performs the correction pulse in step S4 in FIG. The number may not be input to the paper feed motor 104. In this way, when there is a possibility that the paper in the paper feed cassette 110 has been changed, the height of the operation plate 102 can be corrected accordingly to avoid paper feed failure.

  In this way, the recording paper 101 is stacked on the operating plate 102, the operating plate 102 is raised so that the uppermost surface of the recording paper 101 has a predetermined conveyance height, and the uppermost recording paper among the raised recording paper 101 is recorded. 101 is transported to the paper feed roller 111 and paper feed motor 111m, the first paper transport unit 20, the transfer transport unit 40, the fixing unit 50, and the second paper transport unit 21, and is transported at a predetermined location on the transport path. When the recording sheet 101 to be detected is detected by the registration sensor 200 and this detection is not made, the operation plate 102 is raised again, and the height of the operation plate 102 is corrected.

  Therefore, when the recording paper 101 does not reach the predetermined conveyance height and no paper feeding occurs, the position of the operation plate 102 is corrected regardless of the cause, so that no paper feeding caused by various causes can be effectively prevented. In this way, the recording paper 101 can be reliably conveyed.

  Further, when the recording paper 101 is not detected by the registration sensor 200 within a predetermined period (required arrival time) after the conveyance of the recording paper 101 is started, the non-feed state of the recording paper 101 is detected, and the operation plate The height of 102 is corrected.

  Therefore, it is possible to easily make a determination based on a period from when the conveyance of the recording paper 101 is started until the recording paper 101 is detected by the non-paper feeding determination unit 331, and the image forming apparatus is simply configured. be able to.

  In addition, the time from when the leading edge of the recording paper 101 is detected by the registration sensor 200 to when the recording paper 101 is no longer detected by the registration sensor 200 after passing through the detection point of the registration sensor 200 to the trailing edge as it is conveyed. Is measured, and based on the measured time being longer than the predetermined time (required arrival time), the double feed state of the recording paper 101 is determined, and the operation plate 102 is lowered according to the determination result to operate. The height of the plate 102 is corrected.

  Therefore, the operating plate 102 is raised to a relatively high position, and the double feed state is determined in spite of an increase in the tendency of the double feeding to occur, and the operating plate 102 is determined according to this determination. By being lowered and the position is corrected, double feeding can be suppressed. As a result, it is possible to suppress a paper feed defect with a good balance including double feeding.

  Further, when height information (number of correction pulses) for specifying the height of the corrected working plate 102 is recorded and the height information is recorded, the sheet surface height setting unit 320 sets the height. The operation plate 102 is moved up and down according to the information.

  Therefore, when the seat surface height setting unit 320 raises the operation plate 102, it is not necessary to wait for the detection by the registration sensor 200 or the correction of the height of the operation plate 102 by the sheet surface height correction unit 330. Since the operation plate 102 is moved up and down in accordance with height information (number of correction pulses) for specifying the height of the corrected operation plate 102, an image forming apparatus that operates efficiently with little wasteful operation is realized. can do.

  A modification of the present embodiment will be described below.

  In the above description, in step 14b of FIG. 5, the operation plate 102 is relatively lowered by 8 pulses from the current position, but may be lowered to a predetermined position regardless of the current position. In this way, the image forming apparatus 1 can correct the position of the operation plate 102 greatly downward, and even if the recording paper 101 is considerably deviated from a predetermined conveyance height, double feed is avoided. It becomes possible to do.

  FIG. 6 is a diagram illustrating a data configuration of the history storage unit 420. The illustrated history storage unit 420 is provided in the EEPROM 400 for the image forming apparatus 1 described so far. And using this, the descending width of the working plate 102 is dynamically changed as follows.

  The history storage unit 420 stores the number of past correction pulses set as correction pulses as a history. In FIG. 6, “24 pulses”, “8 pulses”, “16 pulses”,... Are recorded as past correction pulses retroactively. The history storage unit 420 stores, for each pulse number, how many recording sheets 101 have been printed in a state where the pulse number is stored.

  Then, when the double feed occurs (step S14 in FIG. 5: YES), the seat surface height correction unit 330 refers to this update history and determines how many pulses are input to the lifting motor 104. (Step S14b). For example, in the case of FIG. 6, the total number of printed sheets when the number of pulses is 8 is the largest (170 + 102 + 342 = 614). In this way, the sheet surface height correcting unit 330 selects the number of pulses having the largest total number of stored prints, and lowers the operating plate 102 to the position indicated by it. Then, the sheet surface height correction unit 330 records the position in the correction pulse number storage unit 410 (step S14d).

1 is a diagram schematically showing an internal configuration of a digital color copier according to an embodiment of the present invention. FIG. FIG. 2 is a diagram schematically showing details of a part of a paper feeding unit 100. 1 is a block diagram showing a schematic configuration of an image forming apparatus 1 according to the present invention. It is a figure explaining arrival required time and passage required time. 3 is a flowchart for explaining the operation of the image forming apparatus 1. It is a figure which shows the data structure of the log | history memory | storage part 420. FIG.

Explanation of symbols

1: Image forming apparatus 20: First paper transport unit 40: Transfer transport unit 50: Fixing unit 21: Second paper transport unit 200: Registration sensor 110: Paper feed cassette 102: Operating plate 101: Recording paper 118: Cassette Insertion detection sensor 111: Paper feed roller 104: Lifting motor 105: Gear 107: Sheet surface detection sensor 111m: Paper feed motor 310: Image formation control unit 315: Conveyance control unit 320: Sheet surface height setting unit 330: Sheet surface height Length correction unit 331: No paper feed determination unit 332: Double feed determination unit 410: Correction pulse number storage unit 501: Time required for storage time storage unit 502: Time required for passage time storage unit

Claims (4)

Loading means for loading recording paper;
Lifting means for raising the stacking means so that the uppermost surface of the recording paper has a predetermined height;
A conveying means for conveying the uppermost recording paper among the raised recording paper;
Detecting means for detecting a recording sheet conveyed by the conveying means at a predetermined location on the conveying path;
An image forming apparatus, comprising: a correction unit that raises the stacking unit again to correct the height of the stacking unit when no recording sheet is detected by the detection unit. The detection means detects a non-feed state of the recording paper when the recording means does not detect the recording paper within a predetermined period after the conveying means starts conveying,
The image forming apparatus according to claim 1, wherein the correcting unit corrects the height of the stacking unit when a non-paper feeding state is detected by the detecting unit. Measures the time from when one end of the recording paper reaches a predetermined position and is detected by the detection means until it passes through the predetermined position to the other end as it is transported, and no recording paper is detected by the detection means. And a double feed judging means for judging the double feed state of the recording paper based on the measured time being longer than the predetermined time,
The image forming apparatus according to claim 1, wherein the correcting unit corrects the height of the stacking unit by lowering the stacking unit in accordance with a determination result by the double feed determination unit. Recording means for recording height information for specifying the height of the stacking means, which has been corrected by the correction means;
The image forming apparatus according to claim 1, wherein, when height information is recorded in the recording unit, the ascending unit raises and lowers the stacking unit according to the height information.

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