JP2012236423A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue print processing without increasing the time and labor of a user, even when the paper is diagonally transported to the carrying direction.SOLUTION: An imaging part 14 takes a picture of paper P when the carrying direction upstream edge of the paper P taken out of a paper cassette 11 passes a resist roller pair 13. An image analysis part detects the end in the direction that is perpendicular to the carrying direction of the paper P from the image data obtained by the imaging part 14, and a skew amount calculating part calculates the amount of the skew. Then, if the calculated skew amount is larger than the reference skew amount, a control part makes an inkjet head 21 discontinue image formation, and makes the following paper P taken out of a paper cassette 11, and prints the identical image.

Description

  The present invention relates to an image forming apparatus capable of detecting a position of a recording medium and calculating a skew amount with respect to a conveyance direction.

In an image forming apparatus such as a copying machine or a printer, when a sheet is conveyed obliquely from a sheet cassette that stores the sheet to an image forming unit, image formation is not performed at a correct position on the sheet. In this case, the user needs to take another measure such as printing again. Therefore, Japanese Patent Laid-Open No. 2004-260260 describes a technique for detecting the position of a sheet conveyed to an image forming unit with an image sensor or the like and correcting the image forming position on the sheet according to the detection result.
JP 2006-44101 A

  However, Patent Document 1 describes a solution for a case where the paper position is shifted in a direction orthogonal to the transport direction, but a countermeasure for a case where the paper position is shifted obliquely with respect to the transport direction. Is not described at all.

  The present invention has been made to solve the above-described problem, and provides an image forming apparatus in which a printing process can be continued without increasing a user's effort even when a sheet is conveyed obliquely with respect to the conveying direction. It is intended to do.

  The image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium conveyed by a conveying belt, and a conveying unit that takes out the recording medium from a storage unit that stores the recording medium and conveys the recording medium to the conveying belt. A position detecting unit that detects a position of the recording medium conveyed to the image forming unit and outputs position information; and a skew amount that calculates a skew amount with respect to the conveyance direction of the recording medium based on the position information. A calculating means; a control means for controlling the image forming means in accordance with the calculated skew amount; a discharging means for discharging the recording medium that has passed through the image forming means; and the discharged recording First and second placement means for placing a medium, wherein the position detection means detects the position of the end of the recording medium in a direction orthogonal to the transport direction and obtains the position information. If the skew amount is larger than the reference skew amount, the control means performs control to stop image formation in the image forming means, and the second placing means controls the first discharge tray and the second discharge tray. And the discharge means discharges the recording medium on which the image has been formed to the first loading means, and the image forming is stopped from the control means because the skew amount is larger than the reference skew amount. When image formation is started by the image forming means at the time when the control is performed, the discharge means discharges the recording medium to the first discharge tray, and image formation is started by the image forming means. If not, the discharge means discharges the recording medium to the second discharge tray.

  The image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium, a conveying unit that takes out the recording medium from a storage unit that stores the recording medium and conveys the recording medium to the image forming unit, and the image Based on the position information, the position detection means for detecting the position of the end of the recording medium in the direction orthogonal to the transport direction of the previous recording medium and outputting position information for the recording medium conveyed to the forming means A skew amount calculating means for calculating a skew amount with respect to the conveyance direction of the recording medium, a control means for performing control to stop image formation in the image forming means if the skew amount is larger than a reference skew amount; A discharge unit that discharges the recording medium that has passed through the image forming unit to the outside; a first mounting unit that mounts the discharged recording medium; and a second mounting unit. hand Has a first discharge tray and a second discharge tray, and the discharge means discharges the recording medium on which the image has been formed to the first placement means, and the skew amount is larger than the reference skew amount. Therefore, when image formation is started by the image forming means at the time when the control of the image formation is controlled by the control means, the discharge means discharges the recording medium to the first discharge tray, When the image formation is not started by the image forming means, the discharge means discharges the recording medium to the second discharge tray.

  According to these configurations, by controlling the image forming unit in accordance with the skew amount of the recording medium, it is possible to take appropriate measures when the recording medium is transported obliquely. For example, when image formation is performed while the recording medium is conveyed in a skewed state, the image is formed obliquely on the recording medium, so that in many cases, the image formation is performed again due to a printing failure. Then, a recording medium and a recording agent (for example, ink) are consumed wastefully. Therefore, the edge of the recording medium is detected to calculate the skew amount, and when the skew amount is larger than the reference skew amount, the image formation is stopped, so that the recording medium or the recording agent necessary for the image formation is stopped. Wasteful consumption can be suppressed. Furthermore, the discharge destination of the recording medium can be distinguished according to the progress of image formation. That is, a recording medium on which image formation has been normally performed, a recording medium on which image formation has been interrupted, and a blank recording medium on which image formation has not been performed are distinguished and ejected, so the user himself / herself needs to sort the recording medium. Therefore, convenience as an image forming apparatus can be improved.

  The image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium conveyed by a conveying belt, and a conveyance that takes out the recording medium from a storage unit that accommodates the recording medium and conveys the recording medium to the conveying belt. Means for detecting the position of the recording medium conveyed to the image forming means and outputting position information, and a skew for calculating a skew amount with respect to the conveyance direction of the recording medium based on the position information. A line amount calculation unit; a control unit that controls the image forming unit according to the calculated skew amount; and a cleaning unit that cleans the surface of the conveyance belt. The position detection unit includes the conveyance unit. The position of the end of the recording medium in a direction orthogonal to the direction is detected and the position information is output. If the skew amount is larger than a reference skew amount, the control means Performs control for stopping the image formation in forming means, the cleaning means immediately after control of the image forming canceled from the control means during the image formation has been performed with respect to the recording medium to clean the surface of the conveyor belt.

  According to this configuration, the edge of the recording medium is detected, the skew amount is calculated, and if the skew amount is larger than the reference skew amount, the image formation is stopped, which is necessary for the recording medium and the image formation. Wasteful consumption of recording agents can be suppressed. Furthermore, the recording agent (for example, ink, toner, carrier, etc.) of the image formed outside the recording medium (that is, on the conveying belt) because the recording medium is conveyed obliquely can be appropriately removed, Next, it is possible to prevent printing defects due to adhesion of the recording agent to the recording medium conveyed next.

  Further, in the above configuration, the cleaning unit is controlled to stop image formation from the control unit during image formation on the recording medium, and an image is formed on the conveying belt by a predetermined number of dots or more. It is preferable to clean the surface of the conveyor belt immediately after.

  According to this configuration, the cleaning of the conveyor belt can be reduced to the minimum necessary number, the time required for cleaning can be shortened, and image formation can be performed smoothly.

  In the above configuration, it is preferable that the reference skew amount can be arbitrarily set.

  According to this configuration, it is possible to vary the allowable range of skew according to the purpose of use of the recording medium on which the image is formed. For example, when the recording medium is an in-house document, the image may be skewed somewhat, but when the recording medium is an official document, it is not preferable that the image is skewed. Accordingly, the user can arbitrarily set the reference skew amount in accordance with the purpose of use of the recording medium, thereby changing the allowable skew feed range and improving the convenience of the image forming apparatus.

  Further, in the above configuration, the position detection unit includes an imaging unit, and the imaging unit is disposed at a position where the recording medium conveyed on the upstream side in the conveyance direction from the conveyance belt can be photographed. preferable.

  According to this configuration, the imaging unit images the recording medium, the position detecting unit detects the edge of the recording medium, the skew amount calculating unit calculates the skew amount, and the control unit calculates the skew amount and the reference skew. The ratio at which image formation is performed on the recording medium becomes lower before it is determined whether or not to stop printing by comparing the line amount. Therefore, useless consumption of the recording medium and the recording agent can be suppressed.

  In the above configuration, the position detection unit includes an imaging unit, and the imaging unit is arranged at a position where the recording medium conveyed on the conveyance belt on the upstream side in the conveyance direction from the image forming unit can be photographed. It is preferable to be provided.

  According to this configuration, even when a skew phenomenon occurs when the recording medium is placed on the conveyance belt, the skew of the recording medium can be detected.

In the above configuration, when the image formation by the image forming unit is stopped, the control unit causes the conveyance unit to convey the recording medium from the storage unit, and causes the recording unit to record the recording medium. It is preferable to perform control to form the same image as the image on which the image formation is stopped on the medium.

  According to this configuration, when the image formation is stopped, the same image formation is automatically performed on the next recording medium, so that the user does not need to perform the image formation operation again. Convenience can be improved.

  In the above configuration, the image forming unit preferably includes an inkjet head.

  According to this configuration, the image forming apparatus having the inkjet head can enjoy the same effects as the above configuration.

  According to the present invention, it is possible to take an appropriate measure when the recording medium is conveyed obliquely. Specifically, the amount of skew feeding is calculated by detecting the edge of the recording medium, and if the skew feeding amount is larger than the reference skew feeding amount, the image formation is stopped, so that it is necessary for the recording medium or image formation. Wasteful consumption of the recording agent can be suppressed. In addition, a recording medium on which image formation has been normally performed, a recording medium on which image formation has been interrupted, and a blank recording medium on which image formation has not been performed are distinguished and discharged, so the user needs to sort the recording medium himself / herself. Therefore, convenience as an image forming apparatus can be improved.

  Further, since the recording medium is conveyed obliquely, the recording agent of the image formed outside the recording medium (that is, on the conveying belt) can be appropriately removed, and the recording on the recording medium to be conveyed next is performed. It is possible to prevent printing defects due to adhesion of the agent.

1 is a side sectional view of an image forming apparatus according to a first embodiment. 1 is a block diagram showing an electrical configuration of an image forming apparatus according to a first embodiment. 6 is a flowchart illustrating a flow of printing processing according to the first embodiment. The figure which showed the positional relationship of the imaging | photography area by a paper and an imaging part. 7 is a modification of the image forming apparatus according to the first embodiment. FIG. 6 is a side cross-sectional view of an image forming apparatus according to a second embodiment. 6 is a modification of the image forming apparatus according to the second embodiment. 10 is a flowchart illustrating a flow of printing processing according to the second embodiment.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. The image forming apparatus according to the present invention can be applied to an electronic apparatus that prints an image or a character on a recording medium such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions. In the following embodiments, an ink jet printer will be described as an example of an image forming apparatus. Further, a general printing paper (hereinafter simply referred to as “paper”) will be described as an example of the recording medium, but any other printable medium such as a transparent film may be used.
[First Embodiment]
FIG. 1 is a side sectional view showing a schematic configuration of an image forming apparatus 1 according to the first embodiment. Here, an ink jet printer that performs color printing will be described as an example, but an ink jet printer that performs monochromatic printing or an image forming apparatus that uses other printing methods may be used. The image forming apparatus 1 includes a paper cassette 11, a pickup roller 12, a registration roller pair 13, an imaging unit 14, a light projecting unit 15, a suction roller 16, a conveyance belt 17, an ink jet head 21, an ink tank 22, a cleaning unit 23, and a discharge roller. A pair 24, a switching guide 25, a first discharge tray 26, a second discharge tray 27, and a third discharge tray 28 are provided.

  In the paper cassette 11, paper P before printing is stacked and stored. The paper P is picked up one by one by driving the pickup roller 12 and sent out to the first paper feed conveyance path 31. The registration roller pair 13 conveys the paper P that has passed through the paper feed conveyance path 31 to the second paper feed conveyance path 32.

  The imaging unit 14 captures a sheet P conveyed through the second paper feed conveyance path 32. For example, a solid-state imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is used. For example, a width in a direction orthogonal to the conveyance direction of the second paper feed conveyance path 32 (at least a width in a direction orthogonal to the conveyance direction of the paper P) can be photographed. Arranged. When using the imaging unit 14 in which the solid-state imaging elements are arranged one-dimensionally, the imaging unit 14 may be arranged so that the solid-state imaging elements are continuously arranged in a direction orthogonal to the conveyance direction of the paper P. desirable. The imaging unit 14 converts the captured image into an electrical signal and outputs it as image data to a control unit described later. The light projecting unit 15 is for irradiating light to a shooting location of the imaging unit 14, and is configured by, for example, an illumination device in which LEDs (Light Emitting Diodes) are arranged in an array.

  The paper P that has passed through the second paper feed transport path 32 is transported to a position facing the ink jet head 21 via the nip portion between the suction roller 16 and the transport belt 17. The surface of the suction roller 16 is in contact with the transport belt 17, and the paper P is pressed against the transport belt 17 and sucked. For example, a sheet made of dielectric resin is used as the conveyance belt 17, and an endless belt having both ends overlapped and joined or a seamless belt is used. The conveyor belt 17 is stretched around a driven roller 18 on the paper feed side (upstream side), a drive roller 20 on the paper discharge side (downstream side), and a tension roller 19. The drive roller 20 is counterclockwise on the paper surface. When it rotates around, the driven roller 18 rotates in conjunction with it, and the conveyor belt 17 rotates in the direction of the arrow Y1. The tension roller 19 is a roller that applies force so that the conveying belt 17 does not sag between the driving roller 20 and the driven roller 18. The conveyance belt 17 adsorbs and fixes the paper P by, for example, electrostatic adsorption, and conveys the paper P to a position facing the inkjet head 21.

  The inkjet head 21 is fixedly arranged in the casing of the image forming apparatus 1 and is a fixed head having a width wider than the length perpendicular to the paper conveyance direction of the maximum usable size corresponding to the number of necessary colors, a so-called line head, For example, ink droplets of four different colors (cyan, magenta, yellow, and black) are ejected toward the paper P to sequentially form images. Examples of the ink discharge method of the ink jet head 21 include a piezo method in which ink droplets are pushed out using a piezo element, a thermal ink jet method in which bubbles are generated by a heating element, and ink droplets are discharged with the pressure. The ink tank 22 is filled with ink corresponding to each color.

  The cleaning unit 23 is for removing ink adhering to the surface of the transport belt 17. When the paper P is attracted and transported to a normal position by the transport belt 17, the ink ejected from the inkjet head 21 adheres to the surface of the paper P, but when the paper P is transported obliquely, The ejected ink may come off the paper P and adhere to the transport belt 17. The ink adhering to the transport belt 17 not only adheres to the paper P to be transported later and causes printing defects, but also causes contamination of various components that come into contact with or adjacent to the transport belt 17, and is reliable as an image forming apparatus. It may cause a decline in sex. Therefore, the cleaning unit 23 cleans the surface of the conveyor belt 17.

  The sheet P on which the image has been formed passes through the discharge conveyance path 33 and is conveyed toward the switching guide 25 by the discharge roller pair 24. The switching guide 25 is for switching the discharge destination of the paper P to any one of the first discharge tray 26, the second discharge tray 27, and the third discharge tray 28, and responds to an instruction signal output from a control unit described later. Can be switched. The discharge destination of the paper P is sorted according to whether or not it has been normally printed. For example, the paper P that has been transported without being skewed and printed at a normal position on the paper surface is discharged to the third discharge tray 28. The On the other hand, the paper P, which has been canceled during printing due to being skewed, is discharged to the first discharge tray 26 and is also conveyed obliquely, but has been canceled before printing. (That is, the blank paper P) is discharged to the second discharge tray 27.

  FIG. 2 is a block diagram for explaining the electrical configuration of the image forming apparatus 1. In addition, about the component demonstrated above, the same code | symbol is attached | subjected and description is abbreviate | omitted. The control unit 41 is configured by a CPU or the like, executes processing based on a predetermined program in accordance with an input instruction signal or the like, outputs an instruction signal to each functional unit, transfers data, or the like, and performs image formation. Control 1 centrally.

  The control unit 41 includes an image analysis unit 411 and a skew amount calculation unit 412. The image analysis unit 411 detects the edge of the paper P from the image data output from the imaging unit 14. The skew amount calculation unit 412 calculates the skew amount of the paper P using the detection result by the image analysis unit 411.

  The operation unit 42 includes a display panel that allows a user to visually recognize an operation screen, an error message, and the like, operation buttons for inputting various operation commands, and the like, which are not illustrated in FIG. It is disposed on the upper surface of the main body of the image forming apparatus 1.

  The communication unit 43 includes an interface for performing data transmission / reception with an external device. For example, when image data is transferred together with a print instruction signal from an external computer to the communication unit 43, the communication unit 43 outputs the image data to the control unit 41, and the control unit 41 outputs a control signal to each functional unit. Processing for printing an image corresponding to the image data on the paper P is performed.

  Hereinafter, the printing process in the image forming apparatus 1 will be described in detail. FIG. 3 is a flowchart showing the flow of printing processing of the image forming apparatus 1. The flowchart on the left side of the drawing shows the processing until the paper P is taken out from the paper cassette 11 and discharged to the outside. The flowchart on the right side of the drawing shows the processing flow in the control unit 41. . When image data is transferred together with a print instruction input from the operation unit 42 or a print instruction signal from an external device to the communication unit 43, the control unit 41 drives the pickup roller 12 to take out the paper P from the paper cassette 11. Then, the sheet is conveyed to the registration roller pair 13 via the first sheet feeding conveyance path 31 (step S11). When the sheet P passes through the registration roller pair 13, the control unit 41 receives a signal from a registration sensor (not shown) (step S12; YES), and the control unit 41 turns on the light projecting unit 15 and takes an image on the imaging unit 14. (Step S13). The control unit 41 inputs the image data output from the imaging unit 14 (step S31), and the image analysis unit 411 detects the edge of the paper P (step S32).

  Here, a method for detecting the edge of the paper P by the image analysis unit 411 will be described in detail. FIG. 4 is a diagram showing the positional relationship between the paper P passing through the second paper feed conveyance path 32 and the shooting area A by the imaging unit 14. In the figure, it is assumed that the paper P indicated by the solid line is conveyed in the direction indicated by the arrow Y2, and arrives at the position of the paper P indicated by the two-dot chain line after a predetermined time. The imaging unit 14 performs imaging at least twice at predetermined time intervals. As the first shooting, image data of an image shot when the paper P is positioned at the solid line is output from the imaging unit 14 to the control unit 41, and the edge portion is detected by the image analysis unit 411. For example, in the case of FIG. 4, the image analysis unit 411 detects that the position corresponding to the arrow X <b> 1 is the end of the paper P. The position corresponding to the arrow X1 is processed using, for example, coordinate values set in the image. Further, as the second shooting, the image data of the image shot when the paper P is positioned at the two-dot chain line is output from the imaging unit 14 to the control unit 41, and the edge portion is detected by the image analysis unit 411. The In the case of FIG. 4, the image analysis unit 411 detects that the position corresponding to the arrow X <b> 2 is the end of the paper P. Then, the image analysis unit 411 outputs a coordinate value corresponding to the detected end position to the skew amount calculation unit 412.

  Here, when the imaging unit 14 has a solid-state imaging device arranged one-dimensionally, the image analysis unit 411 determines the position of the left end or right end of the paper P from the line-shaped image data output from the imaging unit 14. To detect. When the imaging unit 14 has a solid-state imaging device arranged two-dimensionally, the image analysis unit 411 has a preset coordinate line (conveyance of the paper P) in the two-dimensional image data output from the imaging unit 14. (Line in a direction perpendicular to the direction) is extracted, and the position of the left end or right end of the paper P is detected from the extracted image data. When the imaging unit 14 has a solid-state imaging device arranged two-dimensionally and can capture almost the entire surface of the paper P by one imaging, the imaging unit 14 may perform imaging at least once. . In this case, image data of two preset coordinate lines (lines perpendicular to the transport direction of the paper P) is extracted from the two-dimensional image data obtained by one shooting, and each is extracted. The position of the left end or right end of the paper P is detected from the image data. At this time, in order to calculate the skew amount of the paper P more accurately, it is desirable that the two coordinate lines set in advance are as far as possible in the transport direction within a range within the size of the paper P.

  Then, the skew amount calculation unit 412 calculates a skew amount indicating how much the sheet P is skewed in the main scanning direction using the coordinate values output from the image analysis unit 411 (step S33). Here, as a method of calculating the skew feeding amount, the skew amount is determined based on how much the position (coordinate value) of the edge of the paper P is shifted in the main scanning direction per unit time at the first detection time and the second detection time. In addition, the difference between the coordinate values for two times may be simply used as the skew amount. If the calculated skew amount is larger than the reference skew amount (step S34; YES), the control unit 41 outputs a print stop instruction signal to the inkjet head 21 (step S35).

  While the control unit 41 is detecting the position of the end of the paper P and calculating the skew amount, the paper P passes through the second paper feed transport path 32 and is transported to a position facing the inkjet head 21. 17 is sucked and conveyed (step S14). If the instruction signal for canceling printing is not output from the control unit 41 (step S15; NO), the control unit 41 causes the inkjet head 21 to eject ink and prints an image corresponding to the image data transferred to the communication unit 43. Printing is performed (step S16). When the printing is finished without outputting the print stop instruction signal from the control unit 41 (step S17; YES), the control unit 41 switches the switching guide 25 to the third discharge tray 28 side, and the sheet P is transferred to the third discharge tray 28. (Step S21). If the next page is printed (step S22; YES), the control unit 41 proceeds to step S11. If the next page is not printed (step S22; NO), the printing ends.

  On the other hand, if the skew amount of the paper P is larger than the reference skew amount and a print stop instruction signal is output from the control unit 41 (step S15; YES), the control unit 41 has already started printing (already It is determined whether or not ink has been ejected. When printing has been started (step S18; YES), the control unit 41 switches the switching guide 25 to the first discharge tray 26 side and discharges the paper P to the first discharge tray 26 (step S19). When printing is performed while the paper P is being transported while being skewed, the ejected ink may adhere to the transport belt 17 instead of the paper P. Then, the cleaning process of the conveyor belt 17 is performed (step S23). Then, the control unit 41 shifts the processing to step S11, takes out the paper P from the paper cassette 11, and prints the image whose printing is stopped again.

  In addition, when a printing stop instruction signal is output from the control unit 41 but printing has not started (step S18; NO), the control unit 41 switches the switching guide 25 to the second discharge tray 27 side to make a sheet. P is discharged to the second discharge tray (step S27), the process proceeds to step S11, the paper P is taken out from the paper cassette 11, and the image whose printing has been stopped is printed again.

  As described above, the sheet P being conveyed is photographed, the skew amount is obtained, and if the skew amount is larger than the reference skew amount, the printing is stopped and printing is performed obliquely with respect to the sheet. Printing failure can be prevented, and wasteful ink consumption can be suppressed. Furthermore, when printing is canceled, the canceled image is automatically reprinted, so that the user does not need to perform a print instruction operation again, and the image forming apparatus 1 that is highly convenient for the user is provided. it can. Then, the user himself / herself sorts the paper P by discharging the paper P in a case where printing is normally performed, printing is stopped in the middle of printing, and printing is stopped before printing. There is no need, and it can save time. In addition, when printing is performed in a state where the paper P is transported obliquely, the transport belt 17 is automatically cleaned after the paper P is discharged, so that ink adheres to the paper P to be transported next time. Can prevent printing defects.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, the reference skew amount may be determined by a designer and stored in a storage unit (not shown) included in the control unit 41 at the time of factory shipment, or the communication unit may be operated by an operation of the operation unit 42 by a user, an external computer, or the like. The setting may be arbitrarily set by changing the setting via 43. For example, it is considered that printed materials used in the office are allowed to be slightly skewed, but skewed printing is not preferable for official documents used outside the company. Therefore, a selection screen of “in-house document” or “official document” is displayed on the display panel of the operation unit 42 or the screen of the printer driver displayed on the external computer. When the user selects “in-house document”, the reference skew amount is automatically set to a larger value, and when “official document” is selected, the reference skew amount is automatically set to a smaller value. As a specific numerical value, for example, assuming that the shift in the main operation direction of the edge of the paper P when the paper P is conveyed 5 cm is the skew amount, the reference skew when “in-house document” is selected The amount is 0.51 mm, and the reference skew amount when “official document” is selected is 0.17 mm. Of course, the numerical value of the reference skew amount may be actually input.

  In the above description, the paper P is separated and discharged into at least three of the first discharge tray 26, the second discharge tray 27, and the third discharge tray 28. What is necessary is just to discharge | emit so that the user himself / herself does not need to separate the paper P which was not printed. That is, for example, there are two discharge trays, and the paper P when printing is stopped due to the paper P being skewed and conveyed to one discharge tray (during printing or blank paper P) is discharged. The paper P that has been printed normally may be discharged to the other discharge tray.

  In addition, when printing is already started on the paper P when the instruction to stop printing is output by the control unit 41, after the paper P is discharged to the first discharge tray 26, the cleaning unit 23 performs the conveyance belt 17. However, based on the skew amount of the paper P and the image data, the number of dots of ink ejected to the outside of the paper P (that is, on the surface of the transport belt 17) is calculated. The cleaning unit 23 may clean the conveyor belt 17 only when the number of dots is equal to or greater than a predetermined number of dots. By reducing the cleaning process to the minimum necessary number in this way, the time required for the cleaning process can be shortened, and printing can be performed smoothly. Alternatively, the cleaning unit 23 may be normally separated from the conveyance belt 17 so that the cleaning unit 23 contacts the conveyance belt 17 only when a cleaning process is necessary. By doing in this way, the abrasion of the conveyance belt 17 by contact | abutting the cleaning part 23 and the conveyance belt 17 can be suppressed to the minimum, and lifetime improvement of the conveyance belt 17 can be achieved. Further, if the dot density per unit area of the ink ejected on the conveying belt 17 is a predetermined value or more (for example, an image area ratio of 25% or more) continuously is a predetermined value or more (for example, 1 cm square or more), You may make it clean reliably by cleaning the part in which the ink was discharged directly at least twice or more.

Further, the method of adsorbing the paper P to the conveyance belt 17 is not limited to electrostatic adsorption. For example, a large number of fine through holes (not shown) are formed in the conveyance belt 17 as in the image forming apparatus 2 shown in FIG. A method may be used in which the sheet P is sucked by suction from the back side of the conveyance surface of the sheet P of the belt 17 by a suction device 50 or a decompression device.
[Second Embodiment]
In the first embodiment, the image forming apparatus 1 that captures the skew amount of the paper P by photographing the paper P transported through the second paper feed transport path 32 between the registration roller pair 13 and the suction roller 16 will be described. did. In the second embodiment, the image forming apparatus obtains the skew amount by photographing the sheet P conveyed between the suction roller 16 on the conveyance belt 17 and the upstream end of the inkjet head 21 in the sheet conveyance direction. Will be described. Note that the block diagram of the image forming apparatus in the present embodiment is the same as the block diagram of the image forming apparatus 1 in the first embodiment, and therefore the description thereof is omitted. The configuration of the image forming apparatus in the present embodiment is the first. The same components as those of the image forming apparatus 1 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  6 is a side sectional view showing a schematic configuration of the image forming apparatus 3 according to the second embodiment. FIG. 7 is a modification of the image forming apparatus 3 according to the second embodiment. The image forming apparatus 4 includes a suction device 50 on the back side of the conveyance surface.

  In the present embodiment, the imaging unit 14 photographs the paper P that has passed through the suction roller 16 and is sucked and fixed to the transport belt 17. In the image forming apparatus 1 according to the first embodiment, the sheet P before the sheet P is attracted to the conveyance belt 17 is photographed and the skew amount is calculated. Even if it is done, if it is skewed when adsorbed to the conveyor belt 17, the skew is not detected and printing is performed as it is. However, as in the present embodiment, when the sheet P is attracted and fixed to the conveyance belt 17, the sheet P is photographed and the skew amount of the sheet P is calculated, whereby the sheet P is inclined to the conveyance belt 17. When adsorbed, printing can be stopped and wasteful ink consumption can be suppressed.

  However, as the imaging position of the paper P by the imaging unit 14 goes to the downstream side in the transport direction, it becomes closer to the inkjet head 21. That is, the closer the shooting position is to the inkjet head 21, the higher the rate at which printing is progressing when the control unit 41 determines to cancel printing, and wastes ink when the paper P is skewed. The rate of ending up is also high. Accordingly, when the oblique suction of the paper P to the transport belt 17 can be prevented, it is transported between the registration roller pair 13 and the suction roller 16 as in the image forming apparatus 1 shown in the first embodiment. It is preferable to calculate the skew amount by photographing the sheet P to be printed.

  FIG. 8 is a flowchart showing the flow of printing processing of the image forming apparatus 3. The flowchart on the left side of the drawing shows the processing until the paper P is taken out from the paper cassette 11 and discharged to the outside, and the flowchart on the right side of the drawing shows the flow of processing in the control unit 41. Only steps different from the flowchart shown in FIG. 3 in the first embodiment will be described.

  When image data is transferred together with a print instruction input from the operation unit 42 or a print instruction signal from an external device to the communication unit 43, the control unit 41 drives the pickup roller 12 to take out the paper P from the paper cassette 11. Then, it is transported to the transport belt 17 through the first paper feed transport path 31 (step S41). When the paper P passes through the suction roller 16 (step S42; YES), the control unit 41 turns on the light projecting unit 15 and causes the imaging unit 14 to perform photographing (step S43). The control unit 41 receives the image data output from the imaging unit 14 (step S31), the image analysis unit 411 detects the edge of the paper P (step S32), and the skew amount calculation unit 412 determines the skew amount. Calculate (step S33). Since the subsequent processing flow is the same as that described in the first embodiment, the description thereof is omitted.

  As described above, by printing the sheet P adsorbed on the conveyance belt 17 and calculating the skew amount, printing can be stopped immediately even when the sheet P is obliquely adsorbed on the conveyance belt 17. , Wasteful consumption of ink can be suppressed.

1 Image forming device
11 Paper cassette
12 Pickup roller
13 Registration roller pair
14 Imaging unit
15 Projector
16 Suction roller
17 Conveyor belt
18 Followed roller
19 Tension roller
20 Drive roller 21 Inkjet head 22 Ink tank 23 Cleaning unit 24 Discharge roller pair 25 Switching guide 26 First discharge tray 27 Second discharge tray 28 Third discharge tray 31 First paper feed path 32 Second paper feed path 33 Discharge Conveyance path 41 Control unit 411 Image analysis unit 412 Skew amount calculation unit 42 Operation unit 43 Communication unit 50 Suction device P Paper

Claims (4)

Image forming means for forming an image on a recording medium;
A conveying unit that takes out the recording medium from a storage unit that stores the recording medium and conveys the recording medium to the image forming unit;
Position detection means for detecting the position of the end of the recording medium in the direction orthogonal to the conveyance direction of the previous recording medium and outputting position information for the recording medium conveyed to the image forming means;
A skew amount calculating means for calculating a skew amount with respect to a conveyance direction of the recording medium based on the position information;
Control means for performing control to stop image formation in the image forming means if the skew amount is larger than a reference skew amount;
Discharging means for discharging the recording medium that has passed through the image forming means to the outside;
First and second mounting means for mounting the discharged recording medium;
With
The second mounting means has a first discharge tray and a second discharge tray,
The discharge means discharges the recording medium on which the image has been formed to the first placement means, and the control means controls the image formation stop because the skew amount is larger than the reference skew amount. When the image formation is started by the image forming unit, the discharge unit discharges the recording medium to the first discharge tray, and when the image formation is not started by the image forming unit, The image forming apparatus discharges the recording medium to the second discharge tray.   The image forming apparatus according to claim 1, wherein the reference skew amount can be arbitrarily set.   When image formation by the image forming unit is stopped, the control unit causes the conveyance unit to convey the recording medium from the storage unit, and causes the image forming unit to form the image on the recording medium. The image forming apparatus according to claim 1, wherein control is performed to form the same image as the canceled image.   The image forming apparatus according to claim 1, wherein the image forming unit includes an inkjet head.

Images