JP2021109330A - Image formation device - Google Patents

Abstract

To enable a user to recognize a kind of an error (a defect) occurring by looking at a sheet ejected after detection of the error, while saving consumption of color materials as much as possible.SOLUTION: An image sensor of an image formation device reads out a sheet that is carried toward an image formation part. On the basis of data on a carried/read-out image obtained by the reading-out, an image control part detects occurrence of an error in the carried sheet. The image control part generates image data for a waste sheet by which consumptions of color materials can be made smaller than in performing printing on the basis of image data for normal printing, with respect to the sheet in which the error in the carried sheet is detected and the waste sheet which is a sheet fed following the sheet, and performs printing on the basis of the image data.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus that forms an image (printing, drawing).

In the image forming apparatus, an error may occur during printing. Due to the occurrence of an error, the print position may shift or the image may be chipped. Even if you continue printing even though you cannot print the image correctly, it is a waste of paper and color materials. Patent Document 1 describes a technique for reducing waste of paper and toner when an underrun error (delay of image data) occurs.

Specifically, in Patent Document 1, the second medium is fed prior to the other-side printing of the first medium that has been printed on one side, the second medium is printed on one side, and parallel to the single-sided printing of the second medium. Communicates with a device capable of double-sided printing (alternate feeding) in which the first medium is fed by performing a transport operation for double-sided printing of the medium, printing one side of the second medium, and then performing a transport operation for double-sided printing. Then, print data based on application data is generated, print data according to the print page order by alternate feeding is output to the printing device via the interface, status information of the printing device is acquired, and printing status information based on the print data is obtained. Is acquired, and the speed of video output of image data to the printing mechanism unit is faster than the speed of receiving image data from the information processing device for a medium that is newly fed based on the acquired status information. In addition, when the phenomenon that the image data reception buffer becomes empty during printing and the image is cut off in the middle and printing fails (underrun error) is detected, the print page order by alternate feeding is already changed. Outputs print data of unprinted pages on a medium that has been fed and printed on one side and is stagnant, and prints unprinted pages on a medium that is stagnant with one side failing to print due to an underrun error. As the data, an information processing device that outputs blank data to the printing device is described. With this configuration, even if an underrun error occurs when performing double-sided printing by alternating paper feed, the second side of the paper that has been successfully printed on the first side and remains is printed correctly on the second side, which is wasteful. An attempt is made to suppress the occurrence (Patent Document 1: Claim 1, paragraph [0016]).

Japanese Unexamined Patent Publication No. 2008-071479

When an error occurs during printing, a blank sheet may be output to prevent wasteful consumption of color materials. If you output blank paper, you can eject the paper out of the machine as it is plain. Paper can be reused. In the blank page output, for example, blank page image data may be used. The blank image data is image data in which all pixel values of the image data are pixel values (white) without using a coloring material. Using blank image data, the image forming mechanism does not place the coloring material on the paper. The paper is transported as blank paper. Printing on erroneous paper (defective paper, damaged paper) can be prevented.

The consumption of color materials can be reduced by outputting blank paper that is determined to have an error or paper that has been fed following this paper. However, the paper is ejected as blank paper. Therefore, there is a problem that it is difficult to recognize what kind of error (defectiveness) has occurred and the degree of the error that has occurred even when looking at the ejected paper.

In the information processing apparatus described in Patent Document 1, even if a blank output is viewed, it is only possible to know that an underrun error has occurred. I don't know how long the delay in image data generation and transmission is. Moreover, we do not know if there are any other errors. Since only the underrun error is supported, if an error other than the underrun error occurs, the color material and paper may be wasted. Therefore, the technique described in Patent Document 1 cannot solve the above problem.

In view of the above problems, the present invention makes it possible to recognize what kind of error (defect) has occurred by looking at the paper ejected after the error is detected, while suppressing the consumption of the coloring material as much as possible.

The image forming apparatus according to the present invention includes a paper transport unit, an engine control unit, an image forming unit, an ejection tray, an image sensor, and an image control unit. The paper transport unit includes a transport roller. The paper transport unit transports paper. The engine control unit controls the paper transport unit. The image forming unit forms an image on the conveyed paper. The printed paper is ejected from the ejection tray. The image sensor is provided on the upstream side in the paper transport direction with respect to the image forming portion. The image sensor reads the paper conveyed toward the image forming unit. The image control unit detects that a conveyed paper error has occurred in each of the conveyed sheets based on the conveyed read image data obtained by reading the image sensor. The image control unit normally generates image data for printing. The image control unit causes the image forming unit to print the paper that does not detect the paper for which the conveyed paper error is detected, based on the image data for normal printing. The image control unit prints the paper that has detected the conveyed paper error and the paper that has been fed after the paper that has detected the conveyed paper error, based on the normal printing image data. It also generates image data for paper that consumes less coloring material. The image control unit causes the image forming unit to print the waste paper based on the image data for the waste paper.

According to the present invention, it is possible to recognize what kind of conveyed paper error (defectiveness) has occurred and the degree thereof by looking at the printed waste paper. Moreover, the consumption of the coloring material can be suppressed as much as possible.

It is a figure which shows an example of the main body apparatus of the printer which concerns on embodiment. It is a figure which shows an example of the main body apparatus of the printer which concerns on embodiment. It is a figure which shows an example of the printed matter transfer apparatus which concerns on embodiment. It is a figure which shows an example of the reading unit which concerns on embodiment. It is a figure which shows an example of the flow of the image data in the printer which concerns on embodiment. It is a figure which shows an example of the transport reading image data which concerns on embodiment. It is a figure which shows an example of the process at the time of detecting the transport paper error in the printer which concerns on embodiment. It is a figure which shows an example of the processing when the transport paper error is detected at the time of double-sided printing.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 8. The printer 100 will be described as an example of the image forming apparatus. The printer 100 ejects ink to print. The printer 100 may be, for example, a multifunction device including a scanner. Further, the printer 100 may use toner as a coloring material.

In the following description, an example in which the printer 100 includes the main body device 101 and the printed matter transport device 102 will be described. The main body device 101 conveys paper. The main body device 101 prints the paper to be conveyed. The main body device 101 ejects the printed paper out of the machine or feeds it into the printed matter conveying device 102. The printed matter transport device 102 transports the fed paper and discharges it to the outside of the machine.

(Overview of Printer 100)
First, the outline of the printer 100 according to the embodiment will be described with reference to FIGS. 1 and 2. 1 and 2 are diagrams showing an example of the main device 101 of the printer 100 according to the embodiment.

The main body device 101 of the printer 100 includes a control unit 1, a storage unit 2, an operation panel 3, a paper feeding unit 4, a paper transport unit 5, an image forming unit 6, and a communication unit 15. The control unit 1 controls each unit of the printer 100. The control unit 1 includes a main control unit 10, an image control unit 8, and an engine control unit 9. The main control unit 10, the image control unit 8, and the engine control unit 9 are, for example, substrates.

The main control unit 10 (main control board) includes a control circuit 11, an image generation circuit 12, an image processing circuit 13, and an image transmission circuit 14. The control circuit 11 is, for example, a CPU. The control circuit 11 performs calculations and processing based on the control program and control data stored in the storage unit 2. The storage unit 2 includes a non-volatile storage device such as a ROM and a storage (HDD, flash ROM), and a volatile storage device such as a RAM.

The operation panel 3 includes a display panel 31 and a touch panel 32. The display panel 31 displays a setting screen and information. The control unit 1 displays operation images such as keys, buttons, and tabs on the display panel 31. The touch panel 32 detects a touch operation on the display panel 31. Based on the output of the touch panel 32, the control unit 1 recognizes the operated operation image. The control unit 1 recognizes the setting operation performed by the user.

The main body device 101 includes an engine control unit 9, an image control unit 8, a paper feeding unit 4, a paper transport unit 5, and an image forming unit 6 as parts related to printing. Based on the print instruction of the main control unit 10, the engine control unit 9 controls the operations of the paper feed unit 4 and the paper transport unit 5. Based on the image data, the image control unit 8 causes the image forming unit 6 to form an image.

The paper feed unit 4 accommodates a bundle of paper. The paper feed unit 4 includes a paper feed roller 41. The paper feed roller 41 comes into contact with the highest-level paper among the paper loaded in the paper feed unit 4. A paper feed motor (not shown) for rotating the paper feed roller 41 is provided. At the time of a print job, the control unit 1 (engine control unit 9) rotates the paper feed motor to rotate the paper feed roller 41. As a result, the paper is fed from the paper feed unit 4 to the paper transport unit 5 (first transport unit 5a). A paper feeding device (not shown) can be separately attached to the side surface (right side in FIG. 2) of the main body device 101. The connected paper feed device can accommodate a large amount of paper and feeds the paper to the first transport unit 5a of the main body device 101.

The paper transport unit 5 transports paper. The main body device 101 includes a first transport unit 5a, a second transport unit 5b, a switchback transport unit 5s, and a third transport unit 5c as the paper transport unit 5. The first transport unit 5a conveys the paper supplied from the paper feed unit 4 toward the image forming unit 6. The second transport unit 5b transports the paper that has passed through the image forming unit 6 (line head 60) toward the printed matter transport device 102, the switchback transport unit 5s, or the first discharge tray 103. At the time of double-sided printing, the switchback transport unit 5s switches back the single-sided printed paper. The third transport unit 5c rejoins the paper switched back by the switchback transport unit 5s to the first transport unit 5a.

The control unit 1 (engine control unit 9) conveys the paper supplied from the paper feed unit 4 to the first transfer unit 5a toward the image forming unit 6. The thick line in FIG. 2 indicates the paper transport path. The first transport unit 5a includes a plurality of first transport roller pairs 51 along the transport path (paper transport path 511). A first transport motor (not shown) for rotating each first transport roller pair 51 is provided. At the time of the print job, the engine control unit 9 rotates the first transfer motor. As a result, the first transport roller pair 51 rotates.

The first transport unit 5a includes a transport unit 54. The transport unit 54 includes a drive roller 55, a plurality of driven rollers 56, and a transport belt 57. The transport belt 57 is hung around the drive roller 55 and each of the driven rollers 56. At the time of the print job, the control unit 1 rotates the belt motor. The belt motor rotates the drive roller 55. As a result, the transport unit 54 (convey belt 57) takes over and transports the paper transported by the first transport roller pair 51. The transport unit 54 includes a suction unit. The suction unit sucks the paper onto the transport belt 57 by sucking air or electrostatic force. The suction part fixes the position of the paper and the distance between each nozzle and the paper. At the time of printing, the engine control unit 9 operates the suction unit.

The first transfer roller pair 51 on the upstream side of the transfer belt 57, and the first transfer roller pair 51 closest to the transfer belt 57 is a resist roller pair. A resist sensor 58 is provided on the upstream side of the resist roller pair. The output of the resist sensor 58 is input to the control unit 1 (engine control unit 9). Based on the output of the resist sensor 58, the control unit 1 recognizes the arrival of the paper at the resist roller pair and the passage of the paper from the resist sensor 58. When the paper reaches the resist roller pair, the control unit 1 stops the resist roller pair. The tip of the paper abuts against the resist roller pair. The control unit 1 rotates a transfer roller upstream of the resist roller pair to bend the paper. The skew of the paper is corrected by creating the deflection. When a predetermined deflection creation time elapses from the paper arrival recognition, the control unit 1 rotates the resist roller pair. The paper is fed toward the transport belt 57. Upon recognizing the paper passage based on the output of the resist sensor 58, the control unit 1 stops the resist roller pair.

The image forming unit 6 ejects ink onto the transport paper to form an image. The image forming unit 6 includes a plurality of line heads 60. Specifically, the printer 100 includes four line heads 60 (60Bk, 60C, 60M, 60Y). The line head 60Bk ejects black ink. The line head 60C ejects cyan ink. The line head 60M ejects magenta ink. The line head 60Y ejects yellow ink. The image control unit 8 supplies image data to each line head 60. Each line head 60 ejects ink based on the supplied image data.

Each line head 60 is provided above the transport belt 57. The position of each line head 60 is fixed. Each line head 60 includes a plurality of nozzles. The nozzle is provided on the lower surface of each line head 60. The nozzles are arranged in the main scanning direction (direction perpendicular to the transport direction). Each nozzle ejects ink onto the conveyed paper. Each nozzle (ink ejection port) faces the transport belt 57. At the time of printing, the paper transport unit 5 transports the paper toward the line head 60 and also conveys the paper facing the nozzle.

A gap (gap) is provided between the lower surface (nozzle) of each line head 60 and the transport belt 57. Paper enters at this interval. The length of the interval is predetermined. The interval is, for example, about 1 mm to several mm. The ink ejected from the nozzle lands on the transport paper. As a result, an image is formed (recorded). An ink tank for supplying ink is provided for each line head 60.

The control unit 1 (engine control unit 9) conveys the paper that has passed through the line head 60 to the second transfer unit 5b. The second transport unit 5b transports the paper toward the printed matter transport device 102, the switchback transport unit 5s, or the first discharge tray 103. The second transport unit 5b includes a plurality of second transport roller pairs 52, a first switching guide 61, a second switching guide 62, and a third switching guide 63. A second transport motor (not shown) for rotating each second transport roller pair 52 is provided. The first switching guide 61, the second switching guide 62, and the third switching guide 63 are guide plates for switching the paper transport path.

The first switching guide 61 guides the paper to the printed matter transport device 102, the switchback transport unit 5s, or the first discharge tray 103. A first switching motor (not shown) is provided to rotate the first switching guide 61. The second switching guide 62 guides the paper to the switchback transport unit 5s (the discharge tray of the main body device 101) or the switchback transport unit 5s. A second switching motor (not shown) is provided to rotate the second switching guide 62. The third switching guide 63 guides the paper to the switchback transport unit 5s or the first transport unit 5a (upstream of the image forming unit 6). Further, in order to rotate the third switching guide 63, a third switching motor (not shown) is provided.

The switchback transport unit 5s includes a switchback roller pair 59. For double-sided printing, the control unit 1 reverses the front and back of the paper and the front and back of the paper to the switchback transport unit 5s.

The third transport unit 5c transports the paper switched back by the switchback transport unit 5s. The third transport unit 5c includes a third transport roller pair 53. A third transfer motor (not shown) is provided to rotate the third transfer roller pair 53. The control unit 1 transfers the switched back paper to the third transfer unit 5c. The third transport unit 5c returns the switched paper to the upstream side of the line head 60. The third transport unit 5c merges the switched back paper with the first transport unit 5a.

The control unit 1 is connected to the communication unit 15. The communication unit 15 includes a communication connector, a communication control circuit 11, and a communication memory. The communication memory stores communication software. The communication unit 15 communicates with the computer 200. The computer 200 is, for example, a PC or a server. The control unit 1 receives print data from the computer 200.

(Printed matter transport device 102)
Next, an example of the printed matter transport device 102 according to the embodiment will be described with reference to FIGS. 1 to 3. FIG. 3 is a diagram showing an example of the printed matter transport device 102 according to the embodiment.

The printed matter transport device 102 is connected to the main body device 101. The printed matter transport device 102 can be attached to the side surface of the main body device 101 (the left side surface in FIG. 2). The main body device 101 can be attached to the side surface (right side in FIG. 3) of the printed matter transport device 102. The printed matter transport device 102 includes a second discharge tray 104. The operation panel 3 accepts a selection of whether to discharge to the first discharge tray 103 of the main body device 101 or to the second discharge tray 104 of the printed matter transport device 102. The control unit 1 ejects the paper to the selected ejection tray.

A post-processing device can also be connected to the downstream side (left side in FIG. 3) of the printed matter transport device 102. The printed matter transport device 102 includes a switchback mechanism. The printed matter transport device 102 can feed the printed matter to the post-processing device after reversing the front and back sides. For paper transfer, the printed matter transfer device 102 includes a plurality of printed matter transfer roller pairs 105. In FIG. 3, two consecutive circles indicate the printed matter transport roller pair 105. Only the most upstream printed matter transport roller pair 105 in the paper transport direction is coded so that the drawings are not complicated. The printed matter transport device 102 includes a plurality of motors (not shown) for rotating the printed matter transport roller pair 105. When the post-processing device is connected, the operation panel 3 accepts the selection of post-processing to be performed by the post-processing device. When the selection to perform the post-processing is made, the control unit 1 conveys the paper to the printed matter conveying device 102 toward the post-processing device.

1. 1. Paper Transport in Single-sided Printing An example of the flow of paper transport in single-sided printing will be described with reference to FIGS. 1 to 3. First, the engine control unit 9 causes the paper feed unit 4 to feed paper. The engine control unit 9 transfers the paper to the first transfer unit 5a. The engine control unit 9 passes through the line head 60 (below the image forming unit 6). When the paper is passed, the image control unit 8 ejects ink to the line head 60 (printing is executed). The engine control unit 9 conveys the paper that has passed under the image forming unit 6 and has entered the second conveying unit 5b to the second conveying unit 5b.

2. Paper Transport in Double-sided Printing Next, an example of the flow of paper transport in double-sided printing will be described with reference to FIGS. 1 to 3. First, the engine control unit 9 causes the paper feed unit 4 to feed paper. The engine control unit 9 transfers the paper to the first transfer unit 5a. The engine control unit 9 passes the paper through the line head 60 (below the image forming unit 6). When passing through the paper, the image control unit 8 ejects ink to the line head 60. As a result, one side of the paper is printed. The engine control unit 9 conveys the paper that has passed under the image forming unit 6 and has entered the second conveying unit 5b to the second conveying unit 5b.

The engine control unit 9 rotates the first switching guide 61, the second switching guide, and the third switching guide 63 so that the printed matter faces the switchback transport unit 5s. The engine control unit 9 rotates the switchback roller pair 59 in the positive direction. Due to the rotation in the forward direction, the paper advances to the back side of the switchback transport unit 5s (in the direction of arrow B in FIG. 2). The engine control unit 9 reverse-rotates the switchback roller vs. 59 before the paper has passed the switchback roller vs. 59. In accordance with the reverse rotation, the engine control unit 9 sets the first switching guide 61, the second switching guide, and the printed matter toward the third transport unit 5c (the confluence of the first transport unit 5a and the third transport unit 5c). The third switching guide 63 is rotated. As a result, the paper is conveyed so as to merge upstream of the resist roller pair of the first conveying portion 5a (direction of arrow C in FIG. 2).

The engine control unit 9 conveys the merged paper to the first transfer unit 5a. The engine control unit 9 re-passes the paper at the line head 60 (below the image forming unit 6). When passing through the paper, the image control unit 8 ejects ink to the line head 60. This also prints the other side of the paper. The engine control unit 9 conveys the paper that has passed under the image forming unit 6 and re-entered the second transfer unit 5b to the second transfer unit 5b.

Next, the transport for discharging the printed paper (printed matter) will be described.
(1) When the first discharge tray 103 is the discharge destination The engine control unit 9 rotates the first switching guide 61 and the second switching guide so that the printed matter is delivered to the first discharge tray 103. The engine control unit 9 transports the printed matter to the second transport unit 5b toward the first discharge tray 103.
(2) When the second discharge tray 104 is the discharge destination The engine control unit 9 rotates the first switching guide 61 so that the printed matter is sent to the second discharge tray 104 (printed matter transport device 102). .. The engine control unit 9 transports the printed matter to the second transport unit 5b toward the printed matter transport device 102. The printed matter transport device 102 is provided with a fourth switching guide 64 for guiding the printed matter to the second discharge tray 104. The engine control unit 9 rotates the fourth switching guide 64 so that the printed matter is sent to the second discharge tray 104. The engine control unit 9 conveys the printed matter to the printed matter conveying device 102 toward the second discharge tray 104.
(3) When the post-processing device is the discharge destination The engine control unit 9 rotates the first switching guide 61 so that the printed matter is sent to the printed matter transport device 102. The engine control unit 9 transports the printed matter to the second transport unit 5b toward the printed matter transport device 102. The engine control unit 9 rotates the fourth switching guide 64 so that the printed matter passes through the second discharge tray 104 and is sent to the aftertreatment device. The engine control unit 9 conveys the printed matter to the printed matter conveying device 102 toward the post-processing device.

(Light source 70 and reading unit 7)
Next, an example of the reading unit 7 according to the embodiment will be described with reference to FIGS. 2 and 4. FIG. 4 is a diagram showing an example of the reading unit 7 according to the embodiment.

The reading unit 7 reads the conveyed paper. For example, the reading unit 7 is provided between the most upstream line head 60 (60Y) and a pair of resist rollers (see FIG. 2). As shown in FIG. 4, the reading unit 7 includes a transport image sensor 71. The transport image sensor 71 is a line sensor. The transport image sensor 71 includes a plurality of light receiving elements. The plurality of light receiving elements are arranged in the main scanning direction (direction perpendicular to the paper transport direction, vertical direction on the paper surface in FIG. 4). The transport image sensor 71 reads the transport paper in the main scanning direction.

In the main body device 101 (paper transport unit 5), a paper transport path 511 is formed by the transport guide 510. The paper transport path 511 is a part of the paper transport unit 5 (first transport unit 5a). For example, the reading unit 7 is provided below the paper transport path 511. The reading unit 7 includes a light transmitting plate 72. The upper surface of the reading unit 7 is a light transmitting plate 72. The translucent plate 72 is a glass plate or a translucent resin plate. The translucent plate 72 is, for example, contact glass. The transport image sensor 71 faces the translucent plate 72 for printing. The transport image sensor 71 reads the paper passing over the translucent plate 72. The translucent plate 72 also functions as a transport guide 510.

The light source 70 is provided at a position facing the upper surface (transmissive plate 72) of the reading unit 7. The light source 70 is provided at a position where the transfer paper passes between the transfer image sensor 71 and the transfer image sensor 71. The light source 70 irradiates light along the main scanning direction. The light source 70 irradiates light toward the paper transport path 511, the transport paper, and the transport image sensor 71 (transmissive plate 72) (downward in FIG. 4). The optical path crosses the paper transport path 511 in the vertical direction. The transport paper blocks this optical path.

The upper surface of the reading unit 7 transmits light. For example, a lens 73 (rod lens array) is provided inside the reading unit 7. The lens guides light to the transport image sensor 71. The light from the light source 70 passes through the lens 73 and is incident on the carrier image sensor 71. As described above, the reading unit 7 is of the CIS type.

The transport image sensor 71 includes a plurality of light receiving elements. The light receiving elements are arranged in the main scanning direction. The transport image sensor 71 outputs the electric charge stored in each light receiving element as an analog image signal. The transport image sensor 71 outputs an analog image signal every time one line is read. By performing A / D conversion of analog image signals, carrier-read image data i1 is generated. At the time of paper transport, the transport image sensor 71 repeats reading in line units.

When there is no paper between the light source 70 and the reading unit 7, the light from the light source 70 is incident on the transport image sensor 71. Therefore, in the conveyed-read image data i1, the pixels obtained by reading the portion without paper have a bright (thin, white) pixel value. If there is paper between the light source 70 and the reading unit 7, the optical path is blocked by the paper. Therefore, the pixels that read the paper (the pixels in the portion where the paper is located) have dark (dark, black) pixel values. Based on the position of the boundary between the high-density pixel and the low-density pixel, the control unit 1 can recognize the position of the edge (edge) in the main scanning direction of the conveyed paper. In addition, the control unit 1 can also recognize the position of the edge (edge) of the conveyed paper in the paper conveying direction (secondary scanning direction).

(Flow of image data)
Next, an example of the flow of image data in the printer 100 according to the embodiment will be described with reference to FIG. FIG. 5 is a diagram showing an example of the flow of image data in the printer 100 according to the embodiment.

As shown in FIG. 5, the main control unit 10 includes an image generation circuit 12, an image processing circuit 13, and an image transmission circuit 14. Further, the engine control unit 9 includes an engine control circuit 90 and an engine memory 91. The engine control circuit 90 is, for example, a CPU. The engine memory 91 stores programs and data related to paper feed control and paper transport control.

The image control unit 8 includes an image receiving circuit 81, a storage memory 82, an image control circuit 83, and an image output circuit 84. The image control circuit 83 is a circuit that controls the operation of each circuit included in the image control unit 8. The image output circuit 84 is a circuit that generates image data to be supplied to the line head 60.

When the print data is received from the computer 200, the image generation circuit 12 generates the first image data. The first image data is raster data (bitmap data). The print data includes data described in the page description language. The image generation circuit 12 generates the first image data based on the description in the page description language. For example, the image generation circuit 12 stores the generated first image data in the storage unit 2 (for example, RAM).

The image processing circuit 13 reads out the first image data of the storage unit 2. The image processing circuit 13 performs image processing on the first image data. The image processing circuit 13 performs image processing according to the print settings included in the print data. For example, when the enlargement print setting is made, the image processing circuit 13 performs the enlargement image processing on the first image data. Further, the image processing circuit 13 performs color space conversion and halftone processing to generate second image data. The second image data is image data in which ink ejection and non-ejection of each pixel are defined for each color component of CMYK. In this case, for example, it is 4 bits per pixel.

The image transmission circuit 14 transmits the generated second image data to the image control unit 8. The image receiving circuit 81 receives the transmitted second image data. The image receiving circuit 81 stores (stores) the received second image data in the storage memory 82. The image output circuit 84 generates image data for normal printing based on the second image data.

Specifically, the image output circuit 84 includes a conversion circuit 85, an edge detection circuit 86, a centering circuit 87, a size determination circuit 88, a skew determination circuit 89, and a mask processing circuit 810.

The conversion circuit 85 converts the second image data of each page and generates image data for normal printing for each page. Further, the conversion circuit 85 converts the image data for normal printing for a specific page (paper) to generate the image data for paper (details will be described later).

The image data for normal printing is image data to be passed (input) to each line head 60. The conversion circuit 85 generates image data for normal printing for each color. The number of bits per pixel of normal print image data is predetermined. The value of each pixel indicates the size of the ink droplet. For example, when there are six types of droplet sizes, none, S (minimum level), M, L, LL, and 3L (maximum level), the number of bits required for one pixel is three.

For example, the operation panel 3 accepts the selection of paper to be used for printing. The storage unit 2 stores data for determining the size of the droplet for each paper. The conversion circuit 85 determines the size of the droplets of each pixel according to the characteristics of the paper to be used (color, thickness, presence / absence of coating, etc.).

In the line head 60, a piezoelectric element (piezo element) is provided for each nozzle. The line head 60 includes a driver circuit 6a. The driver circuit 6a receives the image data for normal printing or the image data for burnt paper (details will be described later) transmitted from the conversion circuit 85. The driver circuit 6a applies a voltage to the piezoelectric element of the nozzle that ejects ink based on these received image data. The driver circuit 6a deforms the ink flow path connected to the nozzle for each nozzle. The pattern of the voltage signal applied to the piezoelectric element is predetermined for each type of droplet size. For example, the larger the size of the droplet, the larger the ink in the nozzle is shaken, and the amount of ejected ink increases. Based on the image data for normal printing or the image data for burnt paper, the driver circuit 6a applies a voltage signal corresponding to the indicated droplet size to the piezoelectric element of the nozzle that ejects ink.

The image control unit 8 also processes the image data generated by the reading unit 7. At the time of printing (during paper transport), the image control circuit 83 turns on the light source 70. When the light source 70 is lit, the image control circuit 83 causes the transport image sensor 71 to read. While the paper is passing above the transport image sensor 71, the image control circuit 83 turns on the light source 70 and causes the transport image sensor 71 to read. The image control circuit 83 may start lighting the light source 70 and start reading in accordance with the start of rotation of the resist roller pair.

The reading unit 7 includes, for example, a data generation circuit 74. The data generation circuit 74 includes, for example, an AFE circuit (analog front-end circuit) and an A / D conversion circuit 85. The AFE circuit processes the analog image signal output by the carrier image sensor 71 (for example, amplification). The A / D conversion circuit 85 performs A / D conversion based on the processed analog image signal. The data generation circuit 74 stores (stores) the conveyed read image data i1 generated by A / D conversion in the storage memory 82.

(Processing of image control unit 8)
Next, an example of the processing of the image control unit 8 according to the embodiment will be described with reference to FIGS. 5 and 6. FIG. 6 is a diagram showing an example of the conveyed reading image data i1 according to the embodiment.

As described above, the image control unit 8 (image output circuit 84) includes an edge detection circuit 86, a centering circuit 87, a size determination circuit 88, a skew determination circuit 89, and a mask processing circuit 810. These are circuits that perform processing based on the conveyed and read image data i1.

The edge detection circuit 86, the centering circuit 87, the size determination circuit 88, the skew determination circuit 89, and the mask processing circuit 810 process the carrier-read image data i1. Based on the processing result, the image control unit 8 detects the occurrence of a paper transport error. The image control unit 8 detects a centering error, a size mismatch error, a skew error, and a mask error as paper transport errors.

The edge detection circuit 86 is a circuit that detects the edge of the paper and the non-paper portion of the conveyed read image data i1. For example, the edge detection circuit 86 determines that a pixel whose absolute value of the difference in pixel value from the adjacent pixel is equal to or greater than a predetermined threshold value is regarded as an edge pixel. For example, the edge detection circuit 86 can detect the positions of the edges at both ends of the paper in the main scanning direction. For example, the edge detection circuit 86 detects an edge for each line in the main scanning direction (direction perpendicular to the paper transport direction).

FIG. 6 is a diagram showing an example of transport-read image data i1 obtained by reading paper. The high density portion indicates a portion where the paper is present (pixels obtained by reading the paper). The low density portion indicates a portion where there is no paper (pixels where the paper is not read). In FIG. 6, an example of the position of the edge of the paper detected by the edge detection circuit 86 in the conveyed reading image data i1 is shown by a broken line.

The centering circuit 87 recognizes the center position of the conveyed paper in the main scanning direction. The centering circuit 87 recognizes the center point of the edges at both ends of the paper in the main scanning direction detected by the edge detection circuit 86 as the center position. For example, the centering circuit 87 may recognize the center position based on the predetermined determination range data in the conveyed reading image data i1. For example, the determination range data is the conveyed reading image data i1 obtained within a predetermined determination period after the start of rotation of the resist roller pair. The conveyed read image data i1 obtained within the determination period is the data of the leading portion of the paper.

For example, the determination period may be shorter than the time from the start of rotation of the resist roller pair until the tip of the paper reaches the most upstream line head 60 in the paper transport direction. For example, the determination period is shorter than the time obtained by dividing the transport distance from the resist roller pair to the most upstream line head 60 in the paper transport direction by the paper transport speed. In this case, the determination can be made before the paper enters the line head 60.

For example, the centering circuit 87 recognizes the position of the most unilateral edge in the main scanning direction for each line in the main scanning direction in the determination range data. The centering circuit 87 defines the average position of the edge on the one side as the position of the edge on the one side. Further, the centering circuit 87 recognizes the position of the edge on the farthest side in the main scanning direction for each line in the main scanning direction in the determination range data. The centering circuit 87 defines the average position of the edge on the other side as the position of the edge on the other side. The centering circuit 87 recognizes the center of the determined position of the edge on one side and the position of the edge on the other side as the center position of the paper to be conveyed. The centering circuit 87 may recognize the center position of the paper by another method.

Here, the ideal center position (coordinates) is predetermined in the conveyed and read image data i1. The printer 100 is a central paper-passing type printing device. The printer 100 is designed so that the center of the paper transport path 511 in the main scanning direction coincides with the center of the paper in the main scanning direction to transport the paper. Further, the transport image sensor 71 is installed so that the center of the main scanning direction in the reading range of the transport image sensor 71 coincides with the center of the paper transport path 511 in the main scanning direction. Therefore, the ideal center position corresponds to the center position of the paper transport path 511 in the main scanning direction and the center position of the transport reading image data i1 in the main scanning direction. In FIG. 6, the ideal center position is indicated by a chain double-dashed line. In FIG. 6, an example of the center position of the transport paper recognized by the centering circuit 87 is shown by a two-dot chain line.

The centering circuit 87 recognizes the deviation amount and the deviation direction of the center position based on the difference between the center position of the conveyed paper and the ideal center position. The centering circuit 87 detects (determines) that a centering error has occurred when the absolute value of the deviation amount is equal to or greater than a predetermined center deviation upper limit value V1. The storage unit 2 non-volatilely stores the center deviation upper limit value V1 (see FIG. 1). The center deviation upper limit value V1 is predetermined. The center deviation upper limit value V1 is, for example, 0.5 mm. The center deviation upper limit value V1 may be longer or shorter than 0.5 mm. The operation panel 3 may accept the setting of the center deviation upper limit value V1. When the centering error is detected, the image control unit 8 notifies the main control unit 10 and the engine control unit 9.

When it is determined that no centering error has occurred, the centering circuit 87 mainly uses image data for normal printing so that the ink ejection position (pixel drawing position) shifts in the recognized shift direction by the recognized shift amount. Shift in the scanning direction.

The size determination circuit 88 determines the size of the conveyed paper in the main scanning direction. For example, the size determination circuit 88 is based on the distance from the pixel at the edge of one end in the main scanning direction detected by the edge detection circuit 86 to the pixel at the edge at the other end, in the main scanning direction of the conveyed paper. Determine the size. For example, the size determination circuit 88 may determine the size in the main scanning direction based on the number of pixels from the position of the edge on one side to the position of the edge on the other side determined by the centering circuit 87. The size determination circuit 88 may determine the size in the main scanning direction by using another method.

Further, the size determination circuit 88 can determine the size of the conveyed paper in the sub-scanning direction. For example, the size determination circuit 88 performs sub-scanning from the edge pixel on the most one side (head side, downstream side) in the sub-scanning direction detected by the edge detection circuit 86 for each line in the sub-scanning direction of the conveyed read image data i1. Recognize the distance to the edge pixel on the farthest side (tail side, upstream side) in the direction. The size determination circuit 88 determines that the average value of the recognized plurality of distances is the size in the sub-scanning direction of the conveyed paper. The size determination circuit 88 may determine the size in the sub-scanning direction by using another method.

For example, the operation panel 3 accepts the selection of the paper size used in the print job. Further, the main control unit 10 may recognize the paper size specified by the print data received from the computer 200 as the paper size used in the print job.

The size determination circuit 88 recognizes the difference between the size of the determined paper in the main scanning direction and the size of the paper selected for printing in the main scanning direction. The size determination circuit 88 detects (determines) that a size mismatch error has occurred when the absolute value of the difference is equal to or greater than a predetermined size difference upper limit value V2. The storage unit 2 non-volatilely stores the size difference upper limit value V2 (see FIG. 1). The size difference upper limit value V2 is, for example, 0.5 mm. The size difference upper limit value V2 may be longer than 0.5 mm or shorter. The operation panel 3 may accept the setting of the size difference upper limit value V2. When the size mismatch error is detected, the image control unit 8 notifies the main control unit 10 and the engine control unit 9 of the occurrence of the size mismatch error.

The skew determination circuit 89 detects (determines) that a skew error has occurred in the conveyed paper. The skew determination circuit 89 detects a skew error based on, for example, the determination range data in the conveyed read image data i1. For example, the skew determination circuit 89 recognizes the position of the most unilateral edge in the main scanning direction for each line in the main scanning direction in the determination range data. The skew determination circuit 89 obtains the slope of a straight line connecting adjacent edges. The skew determination circuit 89 detects (determines) that a skew error has occurred when the obtained inclination is equal to or greater than a predetermined inclination upper limit value V3. The storage unit 2 non-volatilely stores the inclination upper limit value V3 (see FIG. 1). The skew determination circuit 89 may detect a skew error by using another method.

The greater the tilt of the paper, the greater the tilt of the printed image. When it is recognized that the inclination of the paper and the image is large, the image control unit 8 determines that a skew error has occurred. The inclination upper limit value V3 is predetermined. When the skew error is detected, the image control unit 8 notifies the main control unit 10 and the engine control unit 9 of the occurrence of the skew error.

The mask processing circuit 810 performs mask processing. The masking process is performed on all pages. The mask process is a process for preventing drawing (ink ejection) on the outside of the paper. The mask processing circuit 810 superimposes the image data for normal printing or the image data for burnt paper and the image data i1 for transport reading. The mask processing circuit 810 is overlapped so that the corners of the paper are aligned with the corners of the image data for normal printing or the image data for burnt paper. The mask processing circuit 810 detects the pixels that eject ink in the image data for normal printing or the image data for burnt paper, and the pixels that eject ink in the place where there is no paper on the conveyed reading image data i1.

The mask processing circuit 810 converts the pixel value of the pixel that ejects ink where there is no paper into a pixel value indicating that there is no ejection. As a result, for example, even if paper with punched holes is mixed in or the edges of the paper are broken, it is possible to prevent the inside of the machine from being soiled by drawing at a position where there is no paper. When the pixel value of the image data for normal printing is converted by mask processing (when the ink is not ejected), the mask processing circuit 810 determines that a mask error has occurred. The mask processing circuit 810 detects the occurrence of a mask error. The image control unit 8 notifies the main control unit 10 and the engine control unit 9 that a mask error has occurred.

(Processing when a transport paper error is detected)
Next, an example of processing when a conveyed paper error is detected in the printer 100 according to the embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram showing an example of processing when a conveyed paper error is detected in the printer 100 according to the embodiment. FIG. 8 is a diagram showing an example of processing when a conveyed paper error is detected during double-sided printing.

During the print job, the engine control unit 9 feeds paper and conveys the paper. When there is an abnormality in the conveyed paper, the image control unit 8 detects (determines) that a conveyed paper error has occurred based on the conveyed read image data i1. The image control unit 8 notifies the main control unit 10 that a transport paper error has occurred and the type of the detected transport paper error. Upon receiving this notification, the main control unit 10 causes the display panel 31 to display a message notifying that a transport paper error has occurred and the type of the notified transport paper error.

Further, the main control unit 10 instructs the engine control unit 9 to prohibit the feeding of new paper due to the occurrence of a conveyed paper error. Based on this instruction, the engine control unit 9 does not allow the paper feed unit 4 to feed new paper after determining that the paper is conveyed. Regarding the paper being fed when the conveyed paper error is detected, the engine control unit 9 causes the paper feeding unit 4 to feed the paper to the end without interrupting the paper feeding. After determining that a paper transport error has occurred, the engine control unit 9 transports the paper that has already started feeding and remains in the paper transport unit 5 to any of the discharge trays.

FIG. 7 is a diagram showing an example of processing when a conveyed paper error during execution of a print job is detected. The start of FIG. 7 is when the image control unit 8 detects the occurrence of a transport paper error (centering error, size mismatch error, skew error, mask error) based on the transport-read image data i1.

The image control unit 8 sets the waste paper (defective paper, waste paper) (step # 11). Specifically, the image control unit 8 separates the paper that has detected the conveyed paper error and the paper that has been fed after the paper that has detected the conveyed paper error (the paper that has not been printed on both sides when the conveyed paper error is detected). Is determined. There are multiple causes of transport paper errors. In commercial printing, print quality is important. Depending on the cause, the same error may be inherited to the paper following the paper on which the conveyed paper error is detected. The image control unit 8 treats the paper on which the conveyed paper error is detected and the paper following the paper as a waste paper.

The engine control unit 9 continues to convey the waste paper. In the case of single-sided printing, the engine control unit 9 conveys the paper to the line head 60. The engine control unit 9 faces the lower surface (nozzle) of the line head 60 and conveys the scrap paper.

In the case of double-sided printing, the engine control unit 9 faces the lower surface (nozzle) of the line head 60 twice and conveys the burnt paper (similar to the case where it is not the burnt paper). After passing through the line head 60 for the first time, the engine control unit 9 causes the waste paper to enter the switchback transport unit 5s and reverses the front and back of the waste paper. Subsequently, the engine control unit 9 rejoins the waste paper to the first transport unit 5a. The engine control unit 9 re-enters the scrap paper into the lower surface of the line head 60.

The image control unit 8 generates image data for a piece of paper (step # 12). The image data for the shaving paper is the image data for printing the shaving paper. The image control unit 8 (conversion circuit 85) generates image data for normal printing based on the image data for normal printing that was planned to be used for printing the paper.

Specifically, the image control unit 8 (conversion circuit 85) generates image data for burnt paper so that the consumption of coloring material is smaller than that for printing based on normal print image data. The image control unit 8 converts the image data for normal printing, which was planned to be used for printing the burnt paper, to generate the burnt paper image data. The image control unit 8 converts the pixel value of each pixel of the normal print image data to generate the bad paper image data.

Specifically, the image control unit 8 (conversion circuit 85) generates image data for shaving paper so that the amount of droplets of one pixel is reduced as compared with the case of printing based on the image data for normal printing. The image control unit 8 makes the size of the droplet smaller than that of the image data for normal printing.

The image control unit 8 (conversion circuit 85) may generate image data for shaving paper so that the amount of droplets of one color ejected to one pixel becomes a predetermined minimum value. When the minimum value is the minimum droplet size, the image control unit 8 converts, for example, the value of a pixel having a droplet size larger than S into a value indicating S.

Further, the image control unit 8 (conversion circuit 85) may perform a thinning process to reduce the amount of the coloring material used. The thinning process is a process of reducing the number of pixels that eject ink from the image data for normal printing. For example, if the number of pixels that eject ink is halved, the amount of coloring material used is also halved. The image control unit 8 converts the value of the pixel that ejects the ink in the image data for normal printing into a value indicating that the ink is not ejected.

The image control unit 8 (conversion circuit 85) may perform both the process of reducing the size of the droplets and the process of thinning out, or may perform only one of them. Then, the image control unit 8 prints the shaving paper using the image data for the shaving paper (step # 13). In the case of single-sided printing, the image control unit 8 prints one side of the scrap paper. In the case of double-sided printing, the image control unit 8 prints both sides of the shaving paper. When all the scrap paper is printed, the main control unit 10, the image control unit 8, and the engine control unit 9 end the print job (end).

The engine control unit 9 ejects the paper printed based on the image data for normal printing and the paper printed based on the image data for bad paper to different ejection trays (step # 14). The engine control unit 9 ejects the paper that is not the waste paper in the print job to the ejection tray selected as the ejection destination on the operation panel 3. The engine control unit 9 discharges the waste paper to a discharge tray that has not been selected as a discharge destination. It is possible to automatically sort the paper that is not good and the paper that is not.

An example of the printing flow after detecting a conveyed paper error in double-sided printing will be described with reference to FIG. In FIG. 8, the first row shows an example of a finished image of a double-sided printed matter. FIG. 8 shows an example of double-sided printing of six sheets of paper. In FIG. 8, for convenience, an alphabet without a character enclosure is shown as the printed content on the first surface (back surface). Further, as the printed content on the second surface (front surface), an alphabet with a broken line character enclosure is written (alphabets A, C, E, G, I, K).

The second row of FIG. 8 shows an example of the printing order (passing order of the line head 60) of the double-sided printed matter. It takes a certain amount of time for the switchback (paper circulation, rejoining to the first transport unit 5a). FIG. 8 shows an example of printing the first side (one side, back side) of the next paper while switching back the paper.

In FIG. 8, the third row (the bottom row) shows an example of double-sided printing when it is determined that the paper is burnt. A page whose print content is lighter than the page in the upper figure indicates a page to be printed based on the image data for shaving paper.

In the case of double-sided printing, there is a page to be printed based on the normal printing image data even after it is determined that an error has occurred based on the conveyed reading image data i1. The image control unit 8 is for normal printing on the single-sided printed paper that has been started to be fed before it is determined that an error has occurred and has re-entered the line head 60 after the error detection and switchback. Print based on image data.

In this way, the image forming apparatus (printer 100) according to the embodiment includes a paper conveying unit 5, an engine control unit 9, an image forming unit 6, an ejection tray, a conveying image sensor 71, and an image controlling unit 8. The paper transport unit 5 includes a transport roller. The paper transport unit 5 transports paper. The engine control unit 9 controls the paper transport unit 5. The image forming unit 6 forms an image on the conveyed paper. Printed paper is ejected from the eject tray. The transport image sensor 71 is provided on the upstream side in the paper transport direction with respect to the image forming unit 6. The transport image sensor 71 reads the paper transported toward the image forming unit 6. The image control unit 8 detects that a transport paper error has occurred in each of the transport papers based on the transport read image data i1 obtained by reading the transport image sensor 71. The image control unit 8 normally generates image data for printing. The image control unit 8 causes the image forming unit 6 to print the paper on which the conveyed paper error is detected and which does not detect the paper, based on the image data for normal printing. The image control unit 8 uses a coloring material rather than printing based on normal printing image data for the paper that has detected the transport paper error and the paper that has been fed after the paper that has detected the transport paper error. Generates image data for paper that consumes less paper. The image control unit 8 causes the image forming unit 6 to print the shaving paper based on the image data for the shaving paper.

Based on the printing result on the burnt paper, it is possible to visually confirm (recognize) what kind of conveyed paper error (deficiency) has occurred and the degree of the error that has occurred. For example, it is possible to recognize the cause of the misalignment of the printing position on each paper and how much the misalignment is. Printing at high density is not necessary to understand the type and degree of transport paper error. Printing on burnt paper consumes less color material than when there are no transport paper errors. Therefore, the consumption of the coloring material can be suppressed. Moreover, since the cause of the transport paper error can be quickly grasped, the problem can be solved promptly. As a result, it is possible to prevent frequent occurrence of conveyed paper errors. Since frequent errors can be prevented, it is possible to eliminate repeated wasteful consumption of coloring materials and paper.

The image control unit 8 selects paper to be used for printing when the absolute value of the amount of deviation between the center position in the main scanning direction and the ideal center position of the conveyed paper exceeds the center deviation upper limit value V1. When the absolute value of the difference between the size and the paper size recognized based on the transport-read image data i1 exceeds the size difference upper limit value V2, or when it is determined that the paper is skewed based on the transport-read image data i1, the paper is conveyed. When the scanned image data i1 and the image data for normal printing are overlapped and the position where the coloring material is placed is a portion without paper, when any one or more of them are applicable, the data is conveyed. Judge that a paper error has occurred. In commercial printing, the printed matter to be delivered may be inspected. Misalignment of the printing position causes the inspection to be rejected. It is possible to detect the occurrence of a defective paper (conveyed paper error) that causes a rejection.

There are a plurality of discharge trays (first discharge tray 103, second discharge tray 104). The engine control unit 9 ejects the paper printed based on the image data for normal printing and the paper printed based on the image data for bad paper to different discharge trays. It is possible to automatically sort problematic paper (bad paper) and paper that can be printed without problems. Only the scrap paper can be easily confirmed.

The coloring material is ink. The image forming unit 6 includes a line head 60 that prints the conveyed paper using ink. The line head 60 includes a plurality of nozzles, and prints by ejecting ink droplets from the nozzles. The conversion circuit 85 generates image data for shaving paper so that the amount of droplets of one pixel is reduced as compared with the case of printing based on the image data for normal printing. It is possible to reduce the amount of ink consumed in printing on bad paper as compared with normal printing (printing when there is no paper transport error).

The conversion circuit 85 generates image data for shaving paper so that the amount of droplets of one color ejected to one pixel becomes a predetermined minimum value. Ink consumption for printing on shaving paper can be reduced to the lowest level.

The conversion circuit 85 performs thinning processing to reduce the number of pixels that eject ink from the image data for normal printing, and generates image data for bad paper. It is possible to reduce the number of pixels that eject ink when printing on shaving paper. It is possible to reduce the amount of ink consumed when printing shaving paper.

The image forming apparatus includes a switchback transport unit 5s for performing double-sided printing. The switchback transport unit 5s includes a switchback roller pair 59. The switchback transport unit 5s uses the switchback roller pair 59 to invert the front and back sides of the single-sided printed paper on which the first side is printed when the image forming unit 6 passes through. When printing a plurality of sheets on both sides in succession, the image control unit 8 prints the second side of the single-sided printed paper returned to the upstream side in the paper transport direction from the image forming unit 6 after reversing the front and back. Let the forming unit 6 perform the process. The image control unit 8 is a paper that is conveyed between the waste paper and the waste paper, and the single-sided printed paper on which one side is printed without being determined as a transport paper error is based on the image data for normal printing. The image forming unit 6 is made to print the second side of the single-sided printed paper. When a transport paper error is detected during double-sided printing, paper that has been printed on one side before the transport paper error is detected can be printed as usual (without reducing the color material). For paper that is not a carrier paper error, double-sided printing can be completed.

Although the embodiments of the present invention have been described, the scope of the present invention is not limited to this, and various modifications can be made without departing from the gist of the invention.

The present invention can be used in an image forming apparatus that reads paper conveyed before printing.

100 Printer (image forming device) 103 1st discharge tray 104 2nd discharge tray 5 Paper transport section 51 1st transport roller vs. 52 2nd transport roller vs. 53 3rd transport roller vs. 59 Switchback roller vs. 5s Switchback transport unit 6 Image forming unit 60 Line head 71 Transport image sensor 8 Image control unit 85 Conversion circuit 9 Engine control unit i1 Transport read image data

Claims (7)

A paper transport unit that transports paper, including a transport roller,
An engine control unit that controls the paper transport unit and
An image forming unit that forms an image on the conveyed paper,
An eject tray from which printed paper is ejected, and
An image sensor provided on the upstream side in the paper transport direction with respect to the image forming portion and reading the paper conveyed toward the image forming portion, and an image sensor.
Based on the conveyed scanned image data obtained by reading the image sensor, it is detected that a conveyed paper error has occurred in each of the conveyed papers, and the conveyed paper error is detected.
Generate image data for normal printing
For the paper that does not detect the conveyed paper error, the image forming unit is made to print based on the image data for normal printing.
The amount of coloring material consumed for the paper for which the transport paper error is detected and the paper that is fed after the paper for which the transport paper error is detected is higher than that for printing based on the image data for normal printing. Generates image data for paper,
An image forming apparatus including an image control unit that causes the image forming unit to print the shaving paper based on the image data for the shaving paper. The image control unit
When the absolute value of the amount of deviation between the center position in the main scanning direction of the conveyed paper and the ideal center position exceeds the center deviation upper limit value.
When the absolute value of the difference between the paper size selected for printing and the paper size recognized based on the conveyed scanned image data exceeds the upper limit of the size difference.
When it is determined that the paper is skewed based on the conveyed scanned image data,
When the position where the color material is placed is a portion without paper when the conveyed scanned image data and the image data for normal printing are superimposed.
The image forming apparatus according to claim 1, wherein when any one or more of them are applicable, it is determined that the transport paper error has occurred. There are multiple discharge trays,
The engine control unit 1 or 2 is characterized in that the paper printed based on the image data for normal printing and the paper printed based on the image data for shaving paper are discharged to different discharge trays. The image forming apparatus according to. The image control unit includes a conversion circuit.
The coloring material is ink
The image forming unit includes a line head for printing the conveyed paper using the ink.
The line head includes a plurality of nozzles, and prints by ejecting ink droplets from the nozzles.
Claims 1 to 3 are characterized in that the conversion circuit generates the image data for burnt paper so that the amount of droplets of one pixel is reduced as compared with the case of printing based on the image data for normal printing. The image forming apparatus according to any one of the above items. The image control unit includes a conversion circuit.
4. The image forming apparatus according to item 1. The image control unit includes a conversion circuit.
Any of claims 1 to 5, wherein the conversion circuit performs a thinning process to reduce the number of pixels that eject the ink in the image data for normal printing to generate the image data for burnt paper. The image forming apparatus according to item 1. Equipped with a switchback transfer unit for double-sided printing
The switchback transport unit is
Including switchback roller pair
Using the switchback roller pair, the front and back sides of the single-sided printed paper on which the first side is printed when passing through the image forming portion are inverted.
When printing on both sides of a plurality of sheets in succession,
The image control unit
After reversing the front and back, the image forming section is allowed to print the second side of the single-sided printed paper returned to the upstream side in the paper transport direction from the image forming section.
The single-sided printed paper on which the one side is printed without being determined as the transport paper error is based on the image data for normal printing. The image forming apparatus according to any one of claims 1 to 7, wherein the second side of the single-sided printed paper is printed on the image forming unit.

Images