JP2011191504A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that performs a cleaning process only when toner sticks to a transfer roller. <P>SOLUTION: On the basis of a detection signal from a resist sensor, which is a paper detection sensor, the length of conveyed paper is calculated (S101). On the basis of the calculated length of paper, a determination is made whether or not the size of conveyed paper and the output size of image data match (S102). If they do not match, the determination is made whether or not the output size of the image data falls in the size of the conveyed paper, and whether or not toner sticks to the transfer roller is checked (S103). If the determination is made that toner sticks to the transfer roller, the cleaning process for the transfer roller is performed (S104). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that performs an image forming process by transferring a toner image formed on a photoreceptor onto a sheet.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, or a facsimile machine, an electrostatic latent image is formed on the surface of a photoreceptor, developed with toner, transferred to a sheet, and the toner image on the sheet is heated and melted to form a sheet. An electrophotographic image forming apparatus to be fixed has been put into practical use. In such an image forming apparatus, in order to deal with a plurality of different sizes of paper, for example, a sensor for detecting the size of the paper set in a plurality of paper feed cassettes is provided, and the paper has a size suitable for the size of the image data. Are automatically fed to perform image forming processing.

  Some image forming apparatuses are not provided with a sensor for detecting the size of the paper set in the paper feed tray. In such an apparatus, the leading or trailing edge of the paper fed and conveyed is detected. The sensor detects the passage time of the paper being transported, calculates the length in the paper transport direction from the paper transport speed and time, and determines whether the specified paper size has been fed. Yes.

  If it is determined that a sheet different from the designated size has been fed, a size error is displayed and the user is notified to determine whether or not to continue the image forming process. When the image forming process is continued, the toner image formed in accordance with the designated size is transferred to a different size paper, and the portion of the toner image protruding from the paper is attached to the transfer roller. Become. Since the toner adhering to the transfer roller adheres to the back side of the paper and becomes dirty during transfer, it is necessary to clean the transfer roller and remove the adhering toner.

  However, such a cleaning process of the transfer roller takes time when the amount of toner attached is large, and therefore, if it is frequently performed, there is a disadvantage that the efficiency of the image forming process is deteriorated.

  As a preventive measure against toner adhesion to the transfer roller due to paper size mismatch, for example, in Patent Document 1, the length of the paper in the main scanning direction is detected using a line sensor, and an image is based on the detected length. By narrowing the frame and deleting the image data to be transferred outside the image frame, toner transfer to the transfer belt is prevented.

  In Patent Document 1, since the detection result of the line sensor is used, it is difficult to cope with a type of apparatus in which the line sensor is not provided. Further, when cleaning the toner that has actually adhered, it is necessary to perform the cleaning process assuming that the toner amount is most adhering, and since the required processing time is set long, the efficiency of the image forming process does not decrease. I won't. In addition, when paper of a size larger than the specified size is fed, the toner image will fit in the paper and no toner will adhere to the transfer roller. However, if the paper sizes do not match, the cleaning process is performed. If done, the cleaning process is performed even when the toner is not attached to the transfer roller, which is inefficient.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of performing a cleaning process only when toner adheres to a transfer roller.

  An image forming apparatus according to the present invention is conveyed in an image forming apparatus including an image forming unit that forms a toner image on an image carrier based on image data, and a transfer unit that transfers the formed toner image onto a sheet. Paper detection means for detecting the paper to be detected, size calculation means for calculating the paper size based on a detection signal from the paper detection means, and determination whether the calculated paper size matches the output size of the image data A size determining unit that determines whether or not toner is attached to the transfer unit when it is determined that the size of the paper does not match the output size of the image data. And a cleaning means for cleaning the toner adhering to the transfer means. Further, the image processing device is characterized by further comprising image processing means for partially masking the image data based on the calculated paper size. Further, the image processing means masks the image data based on a maximum width corresponding to the calculated paper size. The image forming apparatus further includes an adhesion calculating unit that calculates an adhesion amount of toner adhered to the transfer unit. Further, the cleaning unit changes a cleaning voltage applied to the transfer unit based on the calculated toner adhesion amount. Further, the cleaning means changes the cleaning time based on the calculated toner adhesion amount. Further, the cleaning means is characterized in that the toner adhering is cleaned when the calculated toner adhering amount exceeds a predetermined amount. Further, the image forming apparatus includes a set detection unit that detects the presence or absence of the paper set in the paper feed tray, and the cleaning unit cleans the toner adhered when the set detection unit detects the absence of the paper. In addition, a tray detection unit that detects that the paper feed tray has been replaced is provided, and the cleaning unit cleans toner adhering when it is detected that the tray detection unit has been replaced.

  With the above-described configuration, the present invention determines whether or not the output size of the image data does not match based on the detected paper size, and whether or not the toner adheres to the transfer unit when the mismatch is determined. Therefore, the transfer means is cleaned, so that it can be performed only when a cleaning process is necessary.

1 is a schematic configuration diagram of an image forming apparatus according to an exemplary embodiment. 1 is a block configuration diagram relating to an image forming apparatus. 6 is a list of sheet lengths in a conveyance direction and sheet widths in a direction orthogonal to the conveyance direction with respect to a standard size sheet. It is explanatory drawing which shows the positional relationship of the output image of image data, and a paper. It is explanatory drawing regarding the mask process of an output image. It is an example of setting the cleaning voltage with respect to the toner adhesion amount. It is an example of setting the cleaning time with respect to the toner adhesion amount. It is a setting example of the cleaning voltage and the cleaning time with respect to the toner adhesion amount. This is a flow for detecting the size of the conveyed paper and performing a cleaning process. It is a processing flow in the case of performing mask processing and execution timing check before performing cleaning processing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment, and schematically shows a main part thereof. As illustrated, the image forming apparatus 1 includes a paper feed tray 4 that can store a plurality of sheets of paper P, a transfer belt 5 disposed above the paper feed tray 4, and a plurality of cartridges ( Electrophotographic process part) 6K, 6M, 6C, 6Y, exposure device 11 arranged above them, fixing means 20 provided in the conveyance path 40 of paper P, and the like. Here, the color component colors are black (K), magenta (M), cyan (C), and yellow (Y), and there are four color cartridges 6K, 6M, 6C, and 6Y. A color toner image is generated.

  The paper P in the paper feed tray 4 is stored in a state in which a plurality of sheets overlap each other, and is located at the top by a paper feed roller 2 that is driven to rotate in a predetermined direction (counterclockwise in the figure) during image formation. The paper is sequentially sent out toward the transport path 40 and fed. Further, the fed paper P is transported along the transport path 40 by a transport means such as a plurality of rollers 3, 7, 16, 21, 22, and 18 and discharged outside the apparatus.

  The transfer belt 5 is an endless belt that is an intermediate transfer body for transferring the toner images transferred from the cartridges 6K, 6M, 6C, and 6Y to the paper P. The secondary transfer driving roller 7 that can rotate and the transfer belt tension. It is wound around a roller 8. Among these rollers 7 and 8, the secondary transfer drive roller 7 is rotationally driven by a drive source (not shown) such as a motor, and a transfer belt 5 that is stretched along with a transfer belt tension roller 8 that is driven to rotate. It is supported so as to extend in the horizontal direction so as to face in the vertical direction. Accordingly, each of these rollers 7 and 8 and a driving source constitute a driving means for rotating and moving the transfer belt 5, and the transfer belt 5 is circulated between the rollers 7 and 8 in a predetermined direction (counterclockwise indicated by an arrow in the drawing). To rotate.

  The cartridges 6K, 6M, 6C, and 6Y are arranged on the upper surface side of the transfer belt 5 at predetermined intervals in order from the upstream along the rotation direction. As will be described later, the cartridges 6K, 6M, 6C, and 6Y are cartridges in which a photosensitive unit including a photosensitive drum, a toner filling unit filled with toner, a developing device, a cleaning system, and the like are integrally docked. The toners of different colors are accommodated according to the colors of the images to be formed. Also, here, in order from the upstream side of the transfer belt 5, a first cartridge 6K that forms a black (K) image, a second cartridge 6M that forms a magenta (M) image, and a cyan (C) image. The third cartridge 6 </ b> C that forms the image and the fourth cartridge 6 </ b> Y that forms the yellow (Y) image are arranged in a line along the transfer belt 5.

  The exposure unit 11 applies laser beams 14K, 14M, 14C, and 14Y (indicated by dotted lines in the figure), which are exposure lights corresponding to image colors formed by the cartridges 6K, 6M, 6C, and 6Y, to the cartridges 6K, 6M, It is an apparatus for irradiating predetermined positions 6C and 6Y. Therefore, the exposure device 11 includes a plurality of (here, four) light sources (not shown) that generate the laser beams 14K, 14M, 14C, and 14Y, and the like, and the laser beams 14K, 14M, 14C, and 14Y are The photosensitive members 9K, 9M, 9C, and 9Y of the cartridges 6K, 6M, 6C, and 6Y are irradiated and exposed downward from the lower surface side.

  Next, the cartridges 6K, 6M, 6C, and 6Y will be described. They have the same internal configuration except that the colors of the toner images to be formed are different, and are configured similarly. Therefore, here, the first cartridge 6K (black image forming unit) located on the most upstream side (right side in the drawing) of the transfer belt 5 is described as an example, and other colors for forming images of other colors are described. Description of the cartridges 6M, 6C, 6Y is omitted. In addition, regarding the respective components of the cartridges 6K, 6M, 6C, and 6Y, the same components are assigned the same numbers, and thereafter, the above-described components corresponding to the colors formed by the cartridges 6K, 6M, 6C, and 6Y. These are distinguished by attaching the symbols K, M, C, and Y.

  The first cartridge 6K includes a photoconductor 9K that is a photoconductor drum provided facing the upper surface of the transfer belt 5, and a charger 10K, a developing device 12K, a cleaner blade 13K, and the like disposed around the photoconductor 9K. Has been.

  At the time of image formation, the outer peripheral surface of the photoconductor 9K is uniformly charged by the charger 10K in the dark, and is then exposed by the laser light 14K corresponding to the black image from the above-described exposure device 11, and the outer peripheral surface ( An electrostatic latent image is formed on the photosensitive surface. At that time, the exposure unit 11 controls the light emission of the light source of the laser beam 14K in accordance with the line image signal in the main scanning direction, for example, so that the generated light is used as a scanning beam at a predetermined cycle. Project to. At the same time, the photosensitive member 9K is moved (rotated) in the sub-scanning direction crossing the main scanning direction (the control in the sub-scanning direction is performed by the control of a motor (not shown) that rotates the photosensitive member 9K). Scan exposure of a two-dimensional image is performed.

  The developing device 12K develops the electrostatic latent image on the photoconductor 9K to make it visible with black toner, and forms a black toner image on the photoconductor 9K. Thereafter, the toner image is transferred to the transfer belt 5 by the action of the primary transfer roller 15K disposed opposite the photoconductor 9K across the transfer belt 5 at the position where the photoconductor 9K and the transfer belt 5 are in contact (primary transfer position). 5 is transferred. As a result, a monochrome image is formed on the transfer belt 5 with black toner. On the other hand, after the toner image transfer is completed, unnecessary toner remaining on the outer peripheral surface is wiped off and cleaned by the cleaner blade 13K, and the photoconductor 9K waits for the next image formation.

  The transfer belt 5 onto which the black toner image has been transferred by the first cartridge 6K through the above process is rotationally driven by the rotation of the secondary transfer driving roller 7, and the portion (surface) on which the toner image is formed. It moves to the next second cartridge 6M located on the downstream side in the rotation direction, and conveys the toner image to the lower position. In the second cartridge 6M, a magenta toner image is formed on the photoconductor 9M by the same process as the image forming process in the first cartridge 6K, and the black toner image formed on the transfer belt 5 is formed on this toner image. The toner image is transferred onto the toner image.

  Subsequently, the transfer belt 5 moves in order to the third cartridge 6C and the fourth cartridge 6Y located further downstream, and the cyan belt formed on the photoreceptor 9C is processed by the same process and operation as before. The toner image and the yellow toner image formed on the photoreceptor 9 </ b> Y are sequentially transferred while being superimposed on the toner image on the transfer belt 5. In this way, a plurality of color toner images are transferred and superimposed on the transfer belt 5 to form a full-color superimposed image (color image), and then the color toner image carried on the transfer belt 5 is It moves to the position of the secondary transfer roller 16 with the rotation.

  Here, at the time of image formation, when forming an image of only black, the second to fourth cartridges 6M, 6C, 6Y are not operated, and the corresponding primary transfer rollers 15M, 15C, 15Y are respectively connected to the respective photoreceptors 9M, Retreat to a position separated from 9C and 9Y, and execute only the black image forming process by the first cartridge 6K.

  Further, in synchronization with the movement (rotation) of the transfer belt 5 described above, the transport operation along the transport path 40 of the paper P is also started. At that time, first, the paper P stored in the paper feed tray 4 is sequentially sent out from the uppermost position by the rotation of the paper feed roller 2, and once the leading edge of the paper P is detected by the registration sensor 30, the conveyance is temporarily stopped. Thus, the leading edge of the paper P is brought into contact with the registration roller 3. Then, it is pinched by the registration roller 3 and stands by on the front side (upstream side in the transport direction) of the secondary transfer roller 16. The rotation of the registration roller 3 starts when the position of the toner image conveyed by the transfer belt 5 and the sheet P is on the secondary transfer roller 16 (between the opposing secondary transfer drive roller 7). The registration roller 3 is rotated counterclockwise by a driving means (not shown), and the paper P is fed out.

  The sheet P sent out by the registration roller 3 is conveyed toward the downstream side of the conveyance path 40 as the toner image on the transfer belt 5 is transferred by the secondary transfer roller 16 and moved. Subsequently, the sheet P is heated and pressed through a nip formed between a fixing roller 21 and a pressure roller 22 which are a pair of rotating members of the fixing unit 20, and the toner image is heated. Heat-fixed by pressure. Thereafter, the paper P is discharged out of the image forming apparatus 1 (here, at the top) by a paper discharge roller 18 that is rotationally driven in a predetermined direction (here, clockwise) by a driving unit (not shown).

  On the other hand, when performing duplex printing on the paper P, the paper discharge roller 18 is rotated in the reverse direction (here, counterclockwise) before the paper P passes through the paper discharge roller 18, and the paper P is It is sent out to the duplex conveyance path 41. In the double-sided conveyance path 41, the paper P is conveyed again to the registration roller 3 via the rotating double-sided roller 19. The sheet P that has reached the registration roller 3 is fed again along the conveyance path 40 by the registration roller 3 and is transferred from the transfer belt 5 to the surface opposite to the surface on which the image has been previously formed by the secondary transfer roller 16. The toner image is transferred. Thereafter, a new toner image is heated and fixed by the fixing unit 20 in the same manner as described above, and the paper P is discharged to the outside of the image forming apparatus 1 by the paper discharge roller 18.

  In this example, the cartridge 6 that forms a toner image on the transfer belt 5 that is an image carrier, the primary transfer roller 15, and the drive means for the transfer belt 5 are image forming means, and the secondary transfer that transfers the toner image onto the paper P. The roller 16 is a transfer unit.

  When toner adheres to the secondary transfer roller 16, a cleaning voltage is applied between the secondary transfer driving roller 7 and the secondary transfer roller 16, and the toner attached to the secondary transfer roller 16 is applied to the transfer belt 5. Transfer. A belt cleaner 17 is disposed on the downstream side of the transfer belt 5 in the conveying direction, and collects toner transferred to the transfer belt 5.

  FIG. 2 is a block configuration diagram relating to the image forming apparatus 1. The image forming apparatus 1 includes a control unit 50 that controls the operation of the entire apparatus. The control unit 50 includes the registration sensor 30 and the set detection sensor 31 that detects the presence or absence of the paper P in the paper feed tray 4. , And a detection signal from each sensor such as a tray detection sensor 32 that detects replacement of the paper feed tray 4 is input. Further, the operation display unit 51 transmits an operation input signal to the control unit 50 based on operation keys operated by the user, and displays the display information transmitted from the control unit 50. The storage unit 52 stores setting data and the like necessary for operation control of the apparatus and accumulates image data for image forming processing, and the control unit 50 performs data reading processing and writing processing. The transmission / reception unit 53 transmits / receives data to / from an external device, and the control unit 50 receives image data and the like from the external device via the transmission / reception unit 53.

  In order to perform the image forming process described above, the control unit 50 includes an image forming unit 54 including the image forming unit, a transfer unit 55 including the transfer unit, a fixing unit 56 including the fixing unit 20, and the transport unit. The driving unit 57 and the sheet feeding unit 58 including sheet feeding rollers are driven and controlled.

  The control unit 50 includes a size calculation unit 501 that calculates the size of the conveyed paper P, a size determination unit 502 that determines whether the calculated size of the paper P matches the output size of the image data, and a toner image on the paper P. An adhesion calculation unit 503 that calculates the amount of toner adhered to the secondary transfer roller 16 when the toner that has protruded during transfer is transferred. When the size of the paper P and the output size of the image data do not match, the toner enters the secondary transfer roller 16. An adhesion determination unit 504 that determines whether to adhere, an image processing unit 505 that partially masks image data when the size of the paper P does not match the output size of the image data, and toner that adheres to the secondary transfer roller 16 Is transferred to the transfer belt 5 and is collected in the belt cleaner 17.

  The size calculation unit 501 calculates the sheet length from the leading edge to the trailing edge in the conveyance direction of the paper P from the paper detection time and the conveyance speed when the paper P to be conveyed is detected by the registration sensor 30. When the paper P is a standard size, the size of the paper P can be determined from the calculated paper length.

  FIG. 3 is a list of the sheet length in the transport direction and the sheet width in the direction orthogonal to the transport direction for the standard size sheet. In FIG. 3, when the paper is set so that the short side direction coincides with the transport direction, the horizontal size is set. When the paper is set so that the long side direction coincides with the transport direction, the vertical size is set. .

  The size determination unit 502 registers the paper size data shown in FIG. 3 in the storage unit 52, determines the paper size to be conveyed from the calculated paper length, and outputs the output size of the image data to be subjected to image formation processing. The paper size is compared to determine whether they match.

When the determination is made based on the paper length, the paper length may be set in consideration of a margin amount due to slippage or sensor chattering when the paper is conveyed. For example, an A5 size sheet has a sheet width of 148.0 mm and a sheet length of 210.0 mm, and a width size of 210.0 mm and a sheet length of 148.0 mm. When an A5 size paper is formed in an A5 size, if the A5 size paper is erroneously set and conveyed in the vertical size, the calculated paper length is 210.0 mm. In this case, a margin amount of 4.00 mm is set for the horizontal paper length of 148.0 mm, and it is determined that the sizes match if the calculated paper length L ₁ is within the following range.
148.0-4.00 <L ₁ <148.0 + 4.00
However, since L ₁ = 210.0 mm, it is determined that the sizes are out of range and the sizes do not match.

  FIG. 4 is an explanatory diagram showing the positional relationship between the output image M (A5 size horizontal size) of the image data and the paper P (A5 size vertical size). Since the output image M and the paper P are aligned so that the center lines thereof coincide with the paper conveyance direction Y and the leading edges thereof coincide, both side portions m1 and m2 of the output image M protrude from the paper P. Become. Therefore, when the toner image corresponding to the output image M is transferred to the paper P, the toner images corresponding to the both side portions m1 and m2 are not transferred to the paper P but attached to the secondary transfer roller 16.

  The adhesion calculating unit 503 thus determines the secondary transfer roller 16 based on the length of the toner image along the transport direction Y of the portion where the output image M protrudes from the paper P due to the mismatch between the size of the output image M and the size of the paper P. The amount of toner attached to the toner is calculated.

  The toner adhesion amount of the secondary transfer roller 16 can be represented by the length of the toner image adhered while the secondary transfer roller 16 rotates with respect to the toner image formed on the transfer belt 5. For example, in the case of the secondary transfer roller 16 having an outer peripheral length of 50 mm, if the toner adheres while rotating with respect to a 200 mm toner image, the amount of toner adhering is four revolutions. Since the toner image adheres so that the secondary transfer roller rotates and is laminated on the outer peripheral surface, the length of the adhered toner image becomes an index indicating the layer thickness of the toner adhering to the outer peripheral surface. If the cleaning process is performed based on the length of the toner image, the toner attached from the secondary transfer roller can be removed cleanly.

Next, let us consider a case where the output image M can be transferred without protruding even in the case of the paper P having a paper length of 210.0 mm. First, a margin amount of 4.00 mm is set for the paper length of 210.0 mm, and the size of the output image M in which the paper length L ₂ is within the following range is searched.
210.0−4.00 <L ₂ <210.0 + 4.00
In this case, the corresponding sizes from the list shown in FIG. 3 are the B6 size horizontal size, the A5 size vertical size, and the HLT vertical size. Since the minimum width among the paper widths of these sizes is 128.0 mm, which is a B6 size horizontal size, if the output image M has a paper width of 128.0 mm or less, even when the sizes do not match, the transfer is performed. In addition, toner does not adhere to the secondary transfer roller 16. In the list shown in FIG. 3, if the output image has an A6 size vertical size, the calculated paper length is 210.0 mm, and the toner does not adhere to the secondary transfer roller 16 even if the sizes do not match. Therefore, there is no need to perform cleaning.

  In this way, the adhesion determination unit 504 determines whether or not the size of the output image fits in the sheet based on the calculated sheet length and accurately checks whether the toner adheres to the secondary transfer roller. Can do.

The image processing unit 505 processes the image data in advance so as to mask and output an area where the output image protrudes from the paper corresponding to the calculated paper length. For example, as shown in FIG. 5A, when the output image M is a horizontal size, a mask area H is set at a portion protruding from both sides of the paper width d ₁ determined from the calculated paper length. Perform mask processing. As shown in FIG. 5B, when the output image M is a vertical size, the leading edge of the output image M is aligned with the leading edge of the output image M based on the calculated paper length d ₂ . Mask processing is performed by setting a mask region H for the rear protruding portion.

  Thus, the amount of toner adhering to the secondary transfer roller 16 can be reduced by masking the portion of the output image that protrudes from the paper and performing image formation processing.

  The cleaning processing unit 506 performs a cleaning process on the secondary transfer roller 16 when the adhesion determination unit 504 determines that the toner has adhered to the secondary transfer roller 16. In the cleaning process, the secondary transfer roller 16 and the transfer belt 5 are rotated synchronously, and a cleaning voltage is applied between the secondary transfer driving roller 7 and the secondary transfer roller 16 to the secondary transfer roller 16. The adhered toner is transferred to the transfer belt 5. The toner transferred to the transfer belt 5 is collected by a belt cleaner 17 disposed on the downstream side of the transfer belt 5 in the conveyance direction.

  In the cleaning process, the cleaning voltage and the cleaning time are adjusted according to the toner adhesion amount of the secondary transfer roller 16. If it is desired to complete the cleaning process within a predetermined time, the cleaning voltage may be changed in accordance with the toner adhesion amount.

FIG. 6 is an example of setting the cleaning voltage when the toner adhesion amount is indicated by the peripheral length of the secondary transfer roller. In this example, if the cleaning voltage applied when the toner adhesion amount is up to four rounds (200 mm) is V _cd , the secondary transfer roller increases the absolute value of the cleaning voltage as the toner adhesion amount increases. The amount of toner transferred from the toner increases. For the setting example shown in FIG. 6, the cleaning voltage V can be determined using the following equation.
V = V _cd −INT (Y1 ÷ Y2 ÷ 4) × 50
Here, Y1 is the length of the adhered toner image, and Y2 is the circumferential length of the transfer roller.

  Further, when the attached toner image is thin, the cleaning time can be shortened by changing the cleaning time. In this case, the cleaning time indicates how many times the secondary transfer roller 16 has rotated.

FIG. 7 is an example of setting the cleaning time when the toner adhesion amount is indicated by the peripheral length of the secondary transfer roller. In this example, when the toner adhesion amount is up to 4 rounds (200 mm), the cleaning time is set to two rotations of the transfer roller. As the toner adhesion amount increases, the cleaning time is increased and the transfer from the secondary transfer roller is performed. The amount of toner to be increased is increased. For the setting example shown in FIG. 7, the cleaning time T can be determined using the following equation.
T = (Y2 ÷ W) × 2-INT (Y1 ÷ Y2 ÷ 4) × 2
Here, W is the transfer belt conveyance speed, Y1 is the length of the adhered toner image, and Y2 is the peripheral length of the transfer roller.

  You may make it change both the cleaning voltage and the cleaning time according to the length of the toner image to adhere. In the setting example shown in FIG. 8, when the toner adhesion amount is small, the cleaning time is increased, and when the toner adhesion amount is large, the cleaning voltage is increased. In this way, it is possible to set so as to perform the optimum cleaning process from the viewpoint of power consumption and processing time by changing both the cleaning voltage and the cleaning time.

  Further, if the cleaning process is frequently performed, the efficiency of the image forming process is lowered, and therefore the timing for performing the cleaning process can be minimized. For example, the cleaning process may be performed when a predetermined adhesion amount is exceeded based on the toner adhesion amount calculated by the adhesion calculation unit 503 and may not be performed every time the toner adheres to the transfer roller.

  In addition, when a paper having a size different from the output size of the image data is set in the paper feed tray 4 by mistake, the toner adheres to the same area of the transfer roller until the paper runs out, and the back side of the paper becomes less dirty. Therefore, the cleaning process may be continued at the timing when the set detection sensor 31 detects that the sheet has run out by removing the sheet from the sheet feeding tray. Similarly, the cleaning process may be performed at the timing when the tray detection sensor 32 detects that the paper feed tray has been removed in order to replace the paper feed tray containing the paper set in error.

  FIG. 9 is a flow for detecting the size of the conveyed paper and performing a cleaning process. When the paper set in the paper feed tray is fed and transported (S100), the paper length of the transported paper is calculated based on the detection signal from the registration sensor 30 (S101). Then, based on the calculated paper length, it is determined whether the size of the conveyed paper and the output size of the image data match (S102). If they match, the process ends without performing the cleaning process. If they do not coincide with each other, it is determined whether the output size of the image data fits in the conveyed paper, and whether or not the toner adheres to the transfer roller is checked (S103). If it is determined that there is no toner attached, the process ends without performing the cleaning process. If it is determined that toner is attached, a transfer roller cleaning process is performed (S104), and the process ends.

  Through the above processing, the cleaning process is performed by determining not only the mismatch between the size of the conveyed paper and the output size of the image data but also the presence or absence of toner on the transfer roller. In this case, useless cleaning processing is eliminated, and it is possible to prevent the efficiency of image forming processing from being reduced.

  FIG. 10 is a process flow in the case where the mask process and the execution timing are checked before the cleaning process is performed. This is a flow for detecting the size of the conveyed paper and performing a cleaning process. When the paper set in the paper feed tray is fed and transported (S200), the paper length of the transported paper is calculated based on the detection signal from the registration sensor 30 (S201). Then, it is determined whether the size of the conveyed paper and the output size of the image data match based on the calculated paper length (S202). If they match, the process ends without performing the cleaning process. If they do not match, it is determined whether the output size of the image data fits within the transported paper, whether toner is attached to the transfer roller is checked, and whether toner is attached to the maskable area is determined. (S203). For example, as shown in FIG. 5A, if both side portions H of the output image are set in a maskable area, it may be determined whether toner adheres to that area. When toner adheres to the maskable area, mask processing is performed on the image data (S204), and when toner adheres to areas other than the maskable area, the process proceeds to step S206 and cleaning processing is performed.

  It is checked whether it is time to perform the cleaning process after the mask process (S205). As described above, as the execution timing, when the toner adhesion amount calculated by the adhesion calculation unit 503 is equal to or greater than a predetermined amount, when the set detection sensor 31 detects that the paper in the paper feed tray is exhausted, or the tray In some cases, the detection sensor 32 detects the replacement of the paper feed tray, and in such a state, a cleaning process is performed (S206). If it is not the execution timing, the process is terminated without performing the cleaning process.

  As a result of the above processing, the toner adhesion is suppressed when the mask processing is performed. Therefore, the cleaning processing is not performed except for the execution timing, and the execution of the cleaning processing can be minimized. .

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Paper feed roller, 3 ... Registration roller, 4 ... Paper feed tray, 5 ... Transfer belt, 6K, 6M, 6C, 6Y ... Cartridge 7 ... secondary transfer drive roller, 8 ... transfer belt tension roller, 9K, 9M, 9C, 9Y ... photoconductor, 10K, 10M, 10C, 10Y ... charger, 11 ... exposure 12K, 12M, 12C, 12Y ... Developer, 13K, 13M, 13C, 13Y ... Cleaner blade, 14K, 14M, 14C, 14Y ... Laser light, 15K, 15M, 15C, 15Y ... Primary transfer roller, 16 ... secondary transfer roller, 17 ... belt cleaner, 18 ... paper discharge roller, 19 ... double-sided roller, 20 ... fixing means, 21 ... fixing roller, 22 ... Pressure roller

JP 2007-131385 A

Claims (9)

  An image forming unit that forms a toner image on an image carrier based on image data; and a sheet detecting unit that detects a conveyed sheet in an image forming apparatus including a transfer unit that transfers the formed toner image to a sheet. A size calculating unit that calculates a paper size based on a detection signal from the paper detecting unit, a size determining unit that determines whether the calculated paper size matches the output size of the image data, and a paper size Is determined not to match the output size of the image data, an adhesion determination unit that determines whether or not toner adheres to the transfer unit, and a toner that adheres to the transfer unit when it is determined that toner adheres An image forming apparatus comprising: a cleaning unit that cleans the image.   The image forming apparatus according to claim 1, further comprising an image processing unit that partially masks the image data based on the calculated paper size.   The image forming apparatus according to claim 2, wherein the image processing unit masks the image data based on a maximum width corresponding to the calculated paper size.   The image forming apparatus according to claim 1, further comprising an adhesion calculating unit that calculates an adhesion amount of the toner adhered to the transfer unit.   The image forming apparatus according to claim 4, wherein the cleaning unit changes a cleaning voltage applied to the transfer unit based on the calculated toner adhesion amount.   The image forming apparatus according to claim 4, wherein the cleaning unit changes a cleaning time based on the calculated toner adhesion amount.   The image forming apparatus according to claim 4, wherein the cleaning unit cleans the toner adhering when the calculated toner adhering amount exceeds a predetermined amount.   2. The apparatus according to claim 1, further comprising set detecting means for detecting the presence or absence of paper set in a paper feed tray, wherein the cleaning means cleans toner adhering when the set detecting means detects no paper. 8. The image forming apparatus according to any one of items 1 to 7.   2. A tray detection unit that detects that a paper feed tray has been replaced, and the cleaning unit cleans toner adhering when it is detected that the tray detection unit has been replaced. The image forming apparatus according to any one of items 1 to 8.

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