JP2013218280A - Image forming apparatus - Google Patents

Abstract

Toner waste is prevented when re-feeding.
When it is determined that there is no paper feeding at the registration roller position, paper re-feeding is executed. Before re-feeding the toner image, the re-feed is completed before the paper transfer position is reached, and the re-feed paper is stopped at the registration roller position. Then, based on the fact that the reference mark formed outside the toner image formation on the intermediate transfer belt has passed the detection position, the paper is fed from the registration roller position to the secondary transfer position after a predetermined time has elapsed by the timer count. The next transfer was performed.
[Selection] Figure 1

Description

  An embodiment of the present invention relates to an image forming apparatus in which a plurality of photoconductors are arranged side by side, and a color image is obtained by synthesizing images of respective colors created on the photoconductors.

  When transferring each image formed on a plurality of photoconductors onto the transfer body in an overlapping state, the arrival time until the image formed at the exposure position on the photoconductor reaches the transfer position is determined for each photoconductor. Misalignment correction is performed to adjust the rotation speed of each photoconductor so as to be constant.

  By the way, when the distance from the exposure position to the photoconductor to the image paper transfer position is longer than the distance from the paper feed position or paper registration roller position to the transfer position, the control to start the exposure operation prior to the paper feed operation. Need to do.

  However, when the paper cannot be fed for some reason and is fed again, all the toner images formed by the exposure and development are discarded, and the exposure and redevelopment are performed again. For this reason, there is a problem that the toner is wasted because it is necessary to discard the toner every time re-feeding occurs.

JP 2006-047990 A

  The problem to be solved by the present invention is to provide an image forming apparatus capable of preventing waste of toner when paper is fed again.

  An image forming apparatus according to an embodiment is an electrophotographic apparatus having an intermediate transfer belt in which a distance from an exposure position to a photoconductor to a paper transfer position is longer than a distance from a paper feed position or a paper registration roller position to the transfer position. A printing function unit that prints a reference mark in a range corresponding to a printing position of a sheet to which the toner image is transferred when the toner image is printed on the intermediate transfer belt; and a detection sensor that detects the reference mark; A paper feed sensor that detects whether the paper has been fed to a predetermined normal position, and when the paper feed sensor detects a paper feed failure, the paper is first formed on the intermediate transfer belt A toner image is held on the intermediate transfer belt, and the detection sensor detects the reference mark and then re-feeds the toner image at a predetermined timing. It was to be transferred.

  The image forming apparatus according to the embodiment is an electrophotographic apparatus having an intermediate transfer belt in which the distance from the exposure position to the photoconductor to the paper transfer position is longer than the distance from the paper feed position or the paper registration roller position to the transfer position. When the toner image is printed on the intermediate transfer belt, a reference mark in which a plurality of reference marks are formed in an outer range corresponding to the printing position of the paper onto which the toner image is transferred, and the reference mark is detected. A detection sensor and a paper feed sensor that detects that the paper has been fed to a predetermined normal position. When the paper feed sensor detects a paper feed failure, the first sensor is formed on the intermediate transfer belt. Holding the toner image on the intermediate transfer belt, detecting the reference mark from among the plurality of reference marks in the vicinity of the detection sensor, and detecting the intermediate transfer Relative to the reference marks belt is that same extraction and circulating, re-fed at a predetermined timing, and the image toner on the intermediate transfer belt so as to transfer to the paper.

1 is a schematic diagram illustrating a schematic configuration of a first embodiment according to an image forming apparatus. It is a schematic diagram which expands and shows the principal part of FIG. 2 is a block diagram illustrating a configuration of a main control unit and a motor control unit of the image forming apparatus. FIG. It is a figure for demonstrating the reference | standard mark Ms. FIG. 6 is a diagram for describing timing for secondary transfer of a toner image on an intermediate transfer belt to a sheet. FIG. It is a figure for demonstrating 2nd Embodiment concerning an image forming apparatus.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a schematic configuration of a first embodiment relating to an image forming apparatus. FIG. 2 is a schematic diagram showing an enlarged main part of FIG.

  In this embodiment, a digital multifunction peripheral (MFP) 100 in which a color electrophotographic apparatus is used as an image forming apparatus is taken as an example. FIG. 1 illustrates a configuration diagram of an image forming apparatus that is a four-tandem color printer as an example of a color electrophotographic apparatus of the MFP 100. The MFP 100 includes a printer unit 20, a paper feed unit 30, and a paper discharge unit 40. Note that the illustration of the automatic document feeder and the scanner is omitted.

  The printer unit 20 conveys the endless intermediate transfer belt 21 along a direction indicated by a colored arrow in the drawing. The intermediate transfer belt 21 is stretched around the driving roller 211 and the driven rollers 212 to 214 and conveyed in a circulating manner. The intermediate transfer belt 21 uses, for example, semiconductive polyimide from the viewpoint of heat resistance and wear resistance. The printer unit 20 includes a secondary transfer roller 23 for transferring an image on the intermediate transfer belt 21 onto the transfer medium 22, and four colors of black (K), cyan (C), magenta (M), and yellow (Y). The image forming units 24K, 24C, 24M, and 24Y for colors are arranged.

  The image forming units 24K, 24C, 24M, and 24Y include photoconductors 25K, 25C, 25M, and 25Y that are image carriers. Each image forming unit includes chargers 26K, 26C, 26M, and 26Y as charging means, a developing roller that is a developing member, and the like around each photoconductor. Each image forming unit includes developing units 27K, 27C, 27M, and 27Y in which developers including toner particles of yellow, magenta, cyan, and black and carrier particles are stored. Further, each image forming unit includes primary transfer rollers 28K, 28C, 28M, and 28Y as transfer means. The primary transfer rollers 28K, 28C, 28M, and 28Y are arranged along the rotation direction of the photosensitive members 25K, 25C, 25M, and 25Y.

  The primary transfer rollers 28K, 28C, 28M, and 28Y are disposed inside the intermediate transfer belt 21, and sandwich the intermediate transfer belt 21 with the corresponding photosensitive members 25K, 25C, 25M, and 25Y.

  In the laser exposure device 29, exposure points are formed on the outer peripheral surfaces of the photoreceptors 25K, 25C, 25M, and 25Y between the chargers 26K, 26C, 26M, and 26Y and the developing devices 27K, 27C, 27M, and 27Y, respectively. Arrange so that. A secondary transfer roller 23 is disposed outside the intermediate transfer belt 21 so as to be in contact therewith. The laser exposure device 29 includes a polygon mirror, an imaging lens system, and a mirror. The laser exposure device 29 scans the laser beam emitted from the semiconductor laser element and modulated by the image data in the axial direction of the photosensitive members 25K, 25C, 25M, and 25Y rotated by the polygon mirror.

  The paper feed unit 30 accommodates paper PA of various sizes. In FIG. 1, only one sheet feeding unit 30 is shown. The paper discharge unit 40 accommodates the paper PA on which an image is formed and discharged.

  Further, between the paper feed unit 30 and the paper discharge unit 40, a paper feed roller 12, a registration roller 13, and the like that take out the paper PA in the paper feed unit 30 are provided. Further, a fixing device 14 is provided downstream of the registration roller 13 in the sheet conveyance direction at a position after the secondary transfer position C of the intermediate transfer belt 21. A paper discharge roller 15 and a paper discharge unit 40 are provided downstream of the fixing device 14. The paper discharge unit 40 discharges the paper PA on which the toner image is fixed by the fixing device 14. In the case of having a double-sided printing function, a reverse conveyance path (not shown) is arranged downstream of the fixing device 14 to reverse the paper PA and lead it to the direction of the secondary transfer roller 23, which is used when performing double-sided printing.

  The paper PA taken out from the paper supply unit 30 by the paper supply roller 12 is conveyed to the intermediate transfer belt 21 and the secondary transfer roller 23 (secondary transfer position C) via the registration roller 13. When the paper PA passes through the secondary transfer position C, a secondary transfer voltage is applied to the paper PA by the secondary transfer roller 23, and the toner image on the intermediate transfer belt 21 is secondarily transferred to the paper PA. The paper PA onto which the toner image is transferred is discharged to the paper discharge unit 40 after the toner image is fixed by the fixing device 14.

  A belt cleaner 16 is disposed near the driven roller 212 of the intermediate transfer belt 21 to clean residual toner that has not been transferred to the paper PA in the secondary transfer process. A mark sensor Sm for detecting a reference mark Ms (see FIG. 4), which will be described later, written outside the printing area 61 of the intermediate transfer belt 21 is installed at a position facing the driven roller 214. Further, a paper feed sensor Sf for detecting whether the paper PA has been fed is installed near the registration roller 13.

  FIG. 3 is a block diagram illustrating configurations of the main control unit 51 and the motor control unit 52 of the image forming apparatus.

  The image forming apparatus shown in FIG. 3 has a main control unit 51 that controls the entire image forming apparatus and motors Mk, Mc, Mm, and My that rotate the photoconductors 25K, 25C, 25M, and 25Y, respectively, and the rotational speeds. The motor control part 52 to control is provided.

  The main control unit 51 includes a main CPU (Central Processing Unit) 511 and an image processing unit 512. The image processing unit 512 outputs an image forming reference signal instructing the start and end of each color image area to the main CPU 511 and the laser exposure device 29 for writing in accordance with the image data.

  The motor control unit 52 includes a sub CPU 521 and motor drive units 522M, 522C, 522M, and 522Y for individually controlling the drive and rotation speed of the motors Mk, Mc, Mm, and My. The motor control unit 52 individually controls the driving and rotation speeds of the motors Mk, Mc, Mm, and My via the motor driving units 522M, 522C, 522M, and 522Y in accordance with instructions from the main control unit 51.

  The main control unit 51 processes image data and controls image formation, and controls the motors Mk, Mc, Mm, and My via the motor control unit 52. That is, the main control unit 51 instructs to start and stop the motors that rotate the photoconductors 25K, 25C, 25M, and 25Y, and controls the rotation speed of each motor.

  The motor control unit 52 drives the motors Mk, Mc, Mm, My according to the instructions received from the main control unit 51. The motor control unit 52 drives the registration motor Mr that rotates the registration roller 13 and the secondary transfer motor Mt that rotates the secondary transfer roller 23 according to the instruction received from the main control unit 51. In addition, the motor control unit 52 also drives a motor (not shown) that drives the paper feed roller 12, the paper discharge roller 15, and the like in accordance with the instruction received from the main control unit 51.

  The laser exposure device 29 scans by deflecting the laser beam according to the image data, and forms an electrostatic latent image on the photoconductors 25K, 25C, 25M, and 25Y.

  The main control unit 51 instructs writing of a reference mark Ms, which will be described later, outside the printing area of the intermediate transfer belt 21 in order to determine the timing for driving the registration roller 13. The main control unit 51 controls the registration roller 13 based on the result of the mark sensor Sm detecting the reference mark Ms. Further, the main control unit 51 instructs writing of a color misregistration detection pattern for detecting color misregistration onto the transfer belt, detects the detection pattern by a sensor, and measures the color misregistration amount of the color misregistration detection pattern. Also, color misregistration is detected.

  FIG. 4 is a diagram for explaining the reference mark Ms. FIG. 4 shows a state in which, for example, black toner is used on the intermediate transfer belt 21 outside the printing area 61 and the reference mark Ms is printed at the leading edge of the toner image at a predetermined timing. FIG. 5 is a diagram for explaining the timing at which the toner image transferred to the intermediate transfer belt 21 is secondarily transferred to a sheet.

  Here, as shown in FIG. 2, the exposure position of the photoconductor 25K is A1, the intermediate transfer position is B1, the exposure position A2 of the photoconductor 25C, the intermediate transfer position is B2, the exposure position A3 of the photoconductor 25M, and the intermediate The transfer position is B3, the exposure position of the photoconductor 25Y is A4, and the intermediate transfer position is B4.

  As shown in FIGS. 5A to 5D, the exposure starts from the front end of the image of four colors (K, C, M, Y). The time from the position A1 to A4 until the leading edge of each color image reaches the intermediate transfer positions B1 to B4 from the start of exposure is the same. This time is T1. Further, the positions of the photoconductors 25K, 25C, 25M, and 25Y for the respective colors are equally spaced, and the intervals of the intermediate transfer positions B1 to B4 for the respective colors are also the same. The time required for passing this interval is T2. The time from the intermediate transfer position B4 of the photoconductor 25Y to the paper transfer position C for transferring to the paper is T3.

  Then, the exposure starts from the photoconductor 25K, and after T2, the photoconductor 25C is exposed, the photoconductor 25M is exposed after T2, and the photoconductor 25Y is exposed after T2. The leading edge of the image reaches the paper transfer position C. That is, T1 + T2 × 3 + T3 is required from the exposure start A1 of the photoreceptor 1 to the paper transfer position C.

  On the other hand, the paper PA is conveyed from the paper feed roller 12 to the registration roller 13, and during this time T4 is required. At this time, the paper PA is temporarily stopped, and the stop time is T5. Thereafter, when the paper PA drives the registration roller 13 at a timing when the image will move to the paper transfer, and the paper transport time from the registration roller 13 to the paper transfer position C is T6, the paper transport time reaches the paper transfer position. It takes T4 + T5 + T6.

  If the time relationship of T1 + T2 × 3 + T3> T4 + T5 + T6 is established, the exposure is started in advance and the timing for feeding paper later. This timing can achieve good transfer by the secondary transfer roller 23 at a desired position on the paper PA.

  However, since the exposure is preceded when the paper feeding fails, the time required for the re-feeding is set to T7. When T1 + T2 × 3 + T3 <T4 + T5 + T6 + T7, the leading edge of the image passes a predetermined position before the leading edge of the paper reaches the paper transfer position C. The toner image formed on the intermediate transfer belt 21 is removed from the intermediate transfer belt 21 by the belt cleaner 16 without being transferred onto the paper PA, and a toner image is formed again. Thus, since the toner image once formed is discarded, the toner is wasted.

  Therefore, as shown in FIG. 4, a mark is exposed outside the printing area 61 immediately before the start of image exposure, and a reference mark Ms is provided. The position of the reference mark Ms is printed upstream by the length L1 from the expected position Pi of the paper PA indicated by the one-dot chain line frame on the intermediate transfer belt 21. This printing is performed simultaneously with the transfer of the toner image onto the intermediate transfer belt 21.

  The length L1 is longer than (registration roller position E to paper transfer position C) − (detection sensor position F to paper transfer position C).

  FIG. 6 is a flowchart for describing an example of sheet feeding control and secondary transfer control of MFP 100 based on the sheet feeding state.

  Use the control panel to start printing. The main control unit 51 drives a motor that conveys the secondary transfer belt 21 related to transfer, a motor that rotates each photoconductor, a laser exposure device 29, and the like, and starts exposure (Act 1). On the photoconductors 25K, 25C, 25M, and 25Y, electrostatic latent images corresponding to toner data of the respective colors that form image data for image formation are formed. A toner image in which an electrostatic latent image is made visible is formed by toner of each color supplied from the developing units 27Y, 27M, 27C, and 27K.

  In Act1, after the exposure is started, the main control unit 51 drives the motor for the supply roller 12 at the paper feeding timing shown in FIG. 5G to start feeding the paper PA (Act2).

  Transfer of the toner image to the intermediate transfer belt 21 is started at the timing shown in FIG. 5F formed on the photoconductors 25K, 25C, 25M, and 25Y (Act 3). At this time, the reference mark Ms shown in FIG. 4 is printed with, for example, K toner on the intermediate transfer belt 21 upstream of the toner image start length L1 shown in FIG.

  The main control unit 51 determines whether or not the transfer of the toner image to the intermediate transfer belt 21 is completed (Act 4). If completed (Yes), it is determined from the detection result of the paper feed sensor Sf whether the paper PA sent by driving the paper feed roller 12 has reached the registration roller 13 (Act 5).

  If it is determined in Act 5 that the paper feeding up to the registration roller position E has been successful (No), the process proceeds to Act 6. The main control unit 52 conveys the paper PA from the registration roller position E to the paper transfer position C at a predetermined timing set in advance (Act 6).

  Then, the main control unit 51 drives the secondary transfer roller 23 to transfer the toner image on the intermediate transfer belt 21 to the paper PA at the paper transfer position C (Act 7).

  The main control unit 51 continues to drive the secondary transfer roller 23, heats the paper PA onto which the toner image has been transferred in the process of passing through the fixing device 14, and fixes the toner image on the paper PA (Act 8).

  The main control unit 51 drives the paper discharge roller 15 to discharge the paper PA on which the toner image is fixed in Act 8 to the paper discharge unit 40 (Act 9).

  In Act 5, when it is determined that the sheet feeding up to the registration roller position E has failed (Yes), the main control unit 51 drives the toner image without removing it from the intermediate transfer belt 21 (Act 10). At this time, since the toner image is formed on the intermediate transfer belt 21 before being driven again, this toner image is used. Therefore, the exposure process is not executed by driving the laser exposure device 29 or the like. At the same time, the main control unit 51 controls the secondary transfer roller 23 and the belt cleaner 16 to be separated from the driving roller 211. This prevents the toner image on the intermediate transfer belt 21 from being removed.

  Subsequently, the main control unit 51 drives the paper feed roller 12 to start refeeding the paper PA (Act 11).

  The main control unit 51 determines whether the paper PA has reached the registration roller position E from the detection result of the paper feed sensor Sf (Act 12).

  In Act 12, when it is determined that the paper feeding up to the registration roller position E has failed (Yes), the main control unit 51 determines that the paper PA is jammed (Act 13) and ends the printing process.

  If it is determined in Act 12 that the paper feeding up to the registration roller position E has been successful (No), the process proceeds to Act 14. In Act 14, the main control unit 51 determines whether the mark sensor Sm has detected the reference mark Ms printed with toner on the intermediate transfer belt 21 being conveyed.

  If it is determined in Act 14 that the reference mark Ms has been detected, the paper PA is conveyed from the registration roller position E to the paper transfer position C at a predetermined timing in consideration of the distance L1 between the reference mark Ms and the leading edge of the toner image. (Act 6).

  Then, after the processing of Act6, the process proceeds to Act7 for secondary transfer, and the fixing (Act8) and paper discharge (Act9) processes are executed.

  As described above, when there is no paper feeding at the registration roller position E, the paper feeding is executed again. At this time, before the toner image reaches the paper transfer position, refeeding is completed, and the refeed paper is stopped at the registration roller position. Then, based on the fact that the reference mark has passed the detection position, the paper is fed from the registration roller position E to the secondary transfer position C when a predetermined time is reached by the timer count.

  In this embodiment, the paper refeeding is performed once. Of course, it is possible to do it twice or more, but even if the number is increased too much, considering the waste of waiting time of the user for re-feeding, it is effective when considering efficiency from 1 to 3 times at most and about 5 times at most It is.

  In this embodiment, re-feeding is possible without discarding the toner image, and unnecessary toner consumption can be eliminated in the case of re-feeding due to a paper feed error.

(Second Embodiment)
FIG. 7 is a diagram for explaining a second embodiment of the image forming apparatus.

  In this embodiment, unlike the first embodiment, the reference mark Ms is not printed with toner each time printing is performed. In this embodiment, a plurality of reference marks Ms1 to Msn are formed at regular intervals outside the printing range 61 of the intermediate transfer belt 21 in advance.

  The reference marks Ms1 to Msn are formed by printing or attaching a tape so that they cannot be removed. The positions of the reference marks Ms <b> 1 to Msn are detected by a mark sensor (not shown) arranged opposite to each other, and the detection result is stored in the main control unit 51. The stored point position is read out when the paper PA is transported to the registration roller position E when re-feeding, and is used as a timing signal for transporting the paper PA.

  The exposure is started after a predetermined time with any reference mark among the reference marks Ms1 to Msn as a reference. For example, consider a case where the reference mark Ms1 is in the vicinity of the mark sensor Sm at the time of refeeding. In this case, exposure is started with reference to the reference mark Ms1. That is, the exposure is started after the paper transport time T6 from the registration roller 13 to the paper transfer position C. At the time of re-feeding due to paper feeding failure, the same reference mark Ms1 that has circulated the intermediate transfer belt 21 is used as a reference.

  In the case of n reference marks Ms1 to Msn, the reference mark Ms1 after counting n is used as a reference, and the timing at which the exposure is virtually started after the predetermined time is reached, and the printing operation can be performed in a sequence as in normal printing. it can.

  The reference marks Ms1 to Msn may be formed on the surface opposite to the surface of the intermediate transfer belt 21 on which the toner image is formed in a state that does not disappear.

  In this embodiment, a plurality of reference marks that do not use toner are formed on the intermediate transfer belt outside the toner image formation. The plurality of reference marks can be aligned with the leading edge of the toner image at the time of refeeding and the sheet conveyed from the registration roller position to the secondary transfer position. The plurality of fiducial marks are not printed by toner each time they are printed and are not removed after use. Therefore, wasteful consumption of toner can be omitted.

  In each of the above embodiments, various sensors for detecting the state of the toner image on the intermediate transfer belt 21 are installed. For example, in order to maintain the image density on the intermediate transfer belt 21, a density sensor that detects the density is installed. Further, in order to correct the toner positions of the four colors on the intermediate transfer belt 21, a mark detection sensor for printing a correction mark and detecting the correction mark is installed. These density sensors or mark detection sensors can be used as detection sensors for detecting the reference mark Ms or the reference marks Ms1 to Msn. In this case, the reference mark Ms is printed at a position that passes through the density sensor and the mark detection sensor.

  In addition, the image forming apparatus has been described with respect to refeeding of color printing, but can also support monochrome refeeding.

  Furthermore, when refeeding occurs, special paper such as one having a small surface friction coefficient or one having a large basis weight such as thick paper is generally used. When such a special sheet is used, the sheet is set in advance, and it is determined whether or not the refeed control according to this embodiment is performed. When printing on general paper, the reference mark is not printed, and an excessive amount of toner is not used. Similarly, such special paper is generally manually fed, but such control is performed only when manually feeding, for example. In this way, it is possible to determine whether or not to perform refeed control at the paper feed source.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

12 Feed roller 13 Registration roller 14 Fixing device 15 Discharge roller 21 Intermediate transfer belt 23 Secondary transfer rollers 24K, 24C, 24M, 24Y Image forming units 25K, 25C, 25M, 25Y Photoconductors 26K, 26C, 26M, 26Y Charging Units 27K, 27C, 27M, 27Y Developing units 28K, 28C, 28M, 28Y Primary transfer roller 29 Laser exposure devices A1, A2, A3, A4 Exposure positions B1, B2, B3, B4 Intermediate transfer position C Paper transfer position E Registration roller Position Ms, Ms1 to Msn Reference mark

Claims (5)

An electrophotographic apparatus having an intermediate transfer belt in which a distance from an exposure position to a photoconductor to a paper transfer position is longer than a distance from a paper feed position or a paper registration roller position to the transfer position,
A printing function unit that prints a reference mark in an outer range corresponding to a printing position of a sheet onto which the toner image is transferred when the toner image is printed on the intermediate transfer belt;
A detection sensor for detecting the reference mark;
A paper feed sensor that detects whether the paper has been fed to a predetermined normal position,
When the paper feed sensor detects a paper feed failure, the first toner image formed on the intermediate transfer belt is held on the intermediate transfer belt, and the detection sensor detects the reference mark. An image forming apparatus that re-feeds paper at a predetermined timing to transfer the image toner on the intermediate transfer belt.   The image forming apparatus according to claim 1, wherein the re-feeding function unit performs re-feeding after failed feeding.   The image forming apparatus according to claim 1, wherein the reference mark is printed using a toner for printing on a sheet.   The image forming apparatus according to claim 1, wherein the reference mark sensor is also used as a sensor for detecting an image density or a temperature sensor for detecting a position of each toner color.   The image forming apparatus according to claim 1, wherein whether or not to perform processing using the re-feeding function unit in the case where feeding is failed is set by a selected feeding source.

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