JP7415564B2 - image forming device - Google Patents

Description

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

In image forming apparatuses, errors may occur during printing. Occurrence of errors may cause misalignment of the printing position or chipping of the image. Even if you continue printing even though the image cannot be printed 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 in image data) occurs.

Specifically, in Patent Document 1, a second medium is fed prior to printing on the other side of a first medium that has already been printed on one side, the second medium is printed on one side, and the second medium is fed in parallel with the printing on one side of the second medium. Communication with a device capable of double-sided printing (alternate paper feeding) that fed the first medium, which carried out a conveyance operation for double-sided printing of the medium, and after printing one side of the second medium, performed a conveyance operation for double-sided printing. generates print data based on the application data, outputs the print data according to the order of print pages by alternate paper feeding to the printing device via an interface, obtains status information of the printing device, and generates printing status information based on the print data. The speed of video output of image data to the print mechanism is faster than the speed of receiving image data from the information processing device for newly fed media based on the acquired status information. When a phenomenon (underrun error) is detected where the image data reception buffer becomes empty during printing and the image is cut off in the middle, causing printing to fail (underrun error). Outputs print data for unprinted pages on media that has been fed, printed on one side, and is stuck, to the printing device, and prints unprinted pages on media that is stuck with printing failed on one side due to an underrun error. An information processing device that outputs blank data to a printing device as data is described. With this configuration, even if an underrun error occurs when double-sided printing is performed using alternate paper feeding, if the first side has been successfully printed and the remaining paper remains, the second side will be printed correctly and waste will be avoided. (Patent Document 1: Claim 1, paragraph [0016]).

Japanese Patent Application Publication No. 2008-071479

When an error occurs during printing, a blank page may be output to prevent unnecessary consumption of color materials. If you output a blank page, the paper can be ejected from the machine without any color. Paper can be reused. For blank page output, for example, blank page image data may be used. Blank image data is image data in which all pixel values of the image data are pixel values (white) that do not use coloring material. When blank image data is used, the image forming mechanism does not place coloring material on the paper. The paper is conveyed as a blank sheet. Printing on paper with errors (defective paper, waste paper) can be prevented.

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

In the information processing apparatus described in Patent Document 1, even when looking at a blank output, only the fact that an underrun error has occurred can be seen. It is also unclear how much delay there will be in image data generation and transmission. Additionally, I don't know if there are other errors. Since it only deals with underrun errors, if an error other than an underrun error occurs, color materials 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 ejected paper after error detection, while suppressing the consumption of coloring material as much as possible.

An image forming apparatus according to the present invention includes a paper transport section, an engine control section, an image forming section, an ejection tray, an image sensor, and an image control section. The paper transport section includes a transport roller. The paper transport section transports paper. The engine control section controls the paper transport section. The image forming section forms an image on the sheet being conveyed. Printed paper is ejected to the ejection tray. The image sensor is provided upstream of the image forming section in the paper transport direction. The image sensor reads the paper being conveyed toward the image forming section. The image control unit detects that a conveyance paper error has occurred for each conveyed sheet based on conveyance read image data obtained by reading by the image sensor. The image control section generates image data for normal printing. The image control unit causes the image forming unit to perform printing on the paper for which the transport paper error has been detected and for the paper for which the transport paper error has not been detected, based on the normal printing image data. The image control unit prints the paper for which the conveyed paper error has been detected and the damaged paper that is the paper fed later than the paper for which the conveyed paper error has been detected, rather than printing based on the normal printing image data. It also generates image data for waste paper that consumes less coloring material. The image control unit causes the image forming unit to print the waste paper based on the waste paper image data.

According to the present invention, it is possible to recognize what kind of transport paper error (defect) has occurred and its extent by looking at the printed waste paper. Moreover, the consumption of coloring materials can be suppressed as much as possible.

FIG. 1 is a diagram illustrating an example of a main body device of a printer according to an embodiment. FIG. 1 is a diagram illustrating an example of a main body device of a printer according to an embodiment. FIG. 1 is a diagram illustrating an example of a printed matter conveying device according to an embodiment. FIG. 3 is a diagram showing an example of a reading unit according to an embodiment. FIG. 3 is a diagram illustrating an example of the flow of image data in the printer according to the embodiment. FIG. 3 is a diagram illustrating an example of transport read image data according to the embodiment. FIG. 3 is a diagram illustrating an example of processing when a conveyance paper error is detected in the printer according to the embodiment. FIG. 6 is a diagram illustrating an example of processing when a transport paper error is detected during double-sided printing.

Embodiments of the present invention will be described below using FIGS. 1 to 8. A printer 100 will be described as an example of an image forming apparatus. The printer 100 prints by ejecting ink. Note that 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 will be described in which the printer 100 includes a main body device 101 and a printed matter conveying device 102. The main body device 101 transports paper. The main device 101 prints on the paper being transported. The main body device 101 discharges the printed paper to the outside of the machine or sends it to the printed material conveying device 102 . The printed matter conveying device 102 conveys the fed paper and discharges it outside the machine.

(Overview of printer 100)
First, an overview of the printer 100 according to the embodiment will be described using FIGS. 1 and 2. 1 and 2 are diagrams illustrating an example of the main body device 101 of the printer 100 according to the embodiment.

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

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 processes based on the control program and control data stored in the storage unit 2. The storage unit 2 includes nonvolatile storage devices such as ROM and storage (HDD, flash ROM), and volatile storage devices such as RAM.

The operation panel 3 includes a display panel 31 and a touch panel 32. The display panel 31 displays setting screens and information. The control unit 1 causes the display panel 31 to display operation images such as keys, buttons, and tabs. 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 device 101 includes an engine control section 9, an image control section 8, a paper feed section 4, a paper transport section 5, and an image forming section 6 as parts related to printing. Based on a print instruction from the main control section 10, the engine control section 9 controls the operations of the paper feed section 4 and the paper conveyance section 5. Based on the image data, the image control section 8 causes the image forming section 6 to form an image.

The paper feed section 4 accommodates a stack of paper. The paper feed section 4 includes a paper feed roller 41 . The paper feed roller 41 comes into contact with the uppermost paper among the papers set in the paper feed section 4 . A paper feed motor (not shown) that rotates the paper feed roller 41 is provided. During 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 sent out from the paper feed section 4 to the paper conveyance section 5 (first conveyance section 5a). Note that a paper feeding device (not shown) can be separately attached to the side surface (right side in FIG. 2) of the main device 101. The connected paper feeding device can accommodate a large amount of paper, and feeds the paper to the first conveyance section 5a of the main device 101.

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

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

The first transport section 5a includes a transport unit 54. The conveying unit 54 includes a driving roller 55, a plurality of driven rollers 56, and a conveying belt 57. The conveyor belt 57 is wound around the drive roller 55 and each driven roller 56 . During a 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 (transport belt 57) takes over and transports the paper transported by the first transport roller pair 51. Note that the transport unit 54 includes a suction section. The suction unit suctions the paper onto the conveyor belt 57 by sucking air or by electrostatic force. The suction unit fixes the position of the paper and the distance between each nozzle and the paper. During printing, the engine control section 9 operates the suction section.

The first transport roller pair 51 on the upstream side of the transport belt 57 and closest to the transport belt 57 is a registration roller pair. A registration sensor 58 is provided upstream of the pair of registration rollers. The output of the registration sensor 58 is input to the control section 1 (engine control section 9). Based on the output of the registration sensor 58, the control unit 1 recognizes the arrival of the paper to the pair of registration rollers and the passage of the paper from the registration sensor 58. When the paper reaches the pair of registration rollers, the control unit 1 stops the pair of registration rollers. The leading edge of the paper hits a pair of registration rollers. The control unit 1 rotates a conveyance roller upstream of the pair of registration rollers to bend the paper. By creating the deflection, the skew of the paper is corrected. When a predetermined deflection creation time has elapsed from the paper arrival recognition, the control unit 1 rotates the pair of registration rollers. The paper is sent out toward the conveyor belt 57. When recognizing the passage of the paper based on the output of the registration sensor 58, the control unit 1 stops the pair of registration rollers.

The image forming section 6 forms an image by ejecting ink onto the conveyed paper. Image forming section 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 discharges black ink. The line head 60C discharges cyan ink. The line head 60M discharges magenta ink. The line head 60Y discharges yellow ink. The image control section 8 supplies image data to each line head 60. Each line head 60 discharges ink based on the supplied image data.

Each line head 60 is provided above the conveyor belt 57. The position of each line head 60 is fixed. Each line head 60 includes multiple nozzles. A nozzle is provided on the bottom surface of each line head 60. The nozzles are arranged in the main scanning direction (direction perpendicular to the transport direction). Each nozzle discharges ink onto the paper being conveyed. Each nozzle (ink ejection port) faces the conveyor belt 57. During printing, the paper transport section 5 transports the paper toward the line head 60 and also transports the paper facing the nozzle.

A space (gap) is provided between the lower surface (nozzle) of each line head 60 and the conveyor belt 57. Paper enters into this interval. The length of the interval is predetermined. The spacing is, for example, about 1 mm to several mm. The ink ejected from the nozzle lands on the conveyed paper. As a result, an image is formed (recorded). Note that each line head 60 is provided with an ink tank that supplies ink.

The control unit 1 (engine control unit 9) causes the paper that has passed through the line head 60 to be conveyed to the second conveyance unit 5b. The second conveyance section 5b conveys the paper toward the printed matter conveyance device 102, the switchback conveyance section 5s, or the first discharge tray 103. The second transport section 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) that rotates 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 conveyance path.

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

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

The third conveyance section 5c conveys the paper switched back by the switchback conveyance section 5s. The third conveyance section 5c includes a third conveyance roller pair 53. A third transport motor (not shown) is provided to rotate the third transport roller pair 53. The control unit 1 causes the switched-back paper to be conveyed to the third conveyance unit 5c. The third transport section 5c returns the switched back paper to the upstream side of the line head 60. The third transport section 5c merges the switched back paper into the first transport section 5a.

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

(Print material conveyance device 102)
Next, an example of the printed matter conveying device 102 according to the embodiment will be described using FIGS. 1 to 3. FIG. 3 is a diagram showing an example of the printed matter conveying device 102 according to the embodiment.

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

Note that a post-processing device can be further connected to the downstream side (left side in FIG. 3) of the printed matter conveying device 102. Print conveyance device 102 includes a switchback mechanism. The printed matter conveying device 102 can send the printed matter to the post-processing device after reversing the front and back sides. For paper transport, the print transport device 102 includes a plurality of print transport roller pairs 105 . In FIG. 3, two consecutive circles indicate a pair of print conveyance rollers 105. To avoid cluttering the drawings, only the most upstream pair of print conveyance rollers 105 in the paper conveyance direction is labeled. Print conveyance device 102 includes a plurality of motors (not shown) for rotating print conveyance roller pairs 105 . Note that when a post-processing device is connected, the operation panel 3 accepts selection of post-processing to be performed by the post-processing device. When the selection to perform post-processing is made, the control unit 1 causes the printed matter transport device 102 to transport the paper toward the post-processing device.

1. Paper Conveyance in Single-sided Printing An example of the flow of paper conveyance in single-sided printing will be described using FIGS. 1 to 3. First, the engine control section 9 causes the paper feeding section 4 to feed paper. The engine control section 9 causes the first conveyance section 5a to convey the paper. The engine control section 9 allows the line head 60 (below the image forming section 6) to pass through. When the paper passes, the image control unit 8 causes the line head 60 to eject ink (printing execution). The engine control section 9 causes the second conveyance section 5b to convey the paper that has passed under the image forming section 6 and entered the second conveyance section 5b.

2. Paper Conveyance in Double-Sided Printing Next, an example of the flow of paper conveyance in double-sided printing will be described using FIGS. 1 to 3. First, the engine control section 9 causes the paper feeding section 4 to feed paper. The engine control section 9 causes the first conveyance section 5a to convey the paper. The engine control section 9 causes the paper to pass through a line head 60 (below the image forming section 6). When the paper passes, the image control unit 8 causes the line head 60 to eject ink. As a result, one side of the paper is printed. The engine control section 9 causes the second conveyance section 5b to convey the paper that has passed under the image forming section 6 and entered the second conveyance section 5b.

The engine control section 9 rotates the first switching guide 61, the second switching guide, and the third switching guide 63 so that the printed matter moves toward the switchback conveyance section 5s. The engine control unit 9 rotates the switchback roller pair 59 in the forward direction. Due to the rotation in the forward direction, the paper advances toward the back of the switchback transport section 5s (in the direction of arrow B in FIG. 2). Before the paper completely passes through the pair of switchback rollers 59, the engine control section 9 causes the pair of switchback rollers 59 to rotate in the reverse direction. In accordance with the reverse rotation, the engine control unit 9 switches the first switching guide 61, the second switching guide, The third switching guide 63 is rotated. As a result, the paper is transported so as to join upstream of the registration roller pair of the first transport section 5a (in the direction of arrow C in FIG. 2).

The engine control section 9 causes the first conveyance section 5a to convey the merged sheets. The engine control section 9 causes the paper to pass through the line head 60 (below the image forming section 6) again. When the paper passes, the image control unit 8 causes the line head 60 to eject ink. As a result, the other side of the paper is also printed. The engine control section 9 causes the second conveyance section 5b to convey the paper that has passed under the image forming section 6 and re-entered the second conveyance section 5b.

Next, conveyance for ejecting printed paper (printed material) will be explained.
(1) When the first ejection tray 103 is the ejection destination The engine control unit 9 rotates the first switching guide 61 and the second switching guide so that the printed matter is in the position to be delivered to the first ejection tray 103. The engine control section 9 causes the second conveyance section 5b to convey the printed matter 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 in the position where the printed matter is sent to the second discharge tray 104 (print conveyance device 102). . The engine control section 9 causes the second conveyance section 5b to convey the printed matter toward the printed matter conveyance device 102. The printed matter conveying 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 it is in a position where the printed matter is sent to the second discharge tray 104. The engine control unit 9 causes the printed matter conveying device 102 to convey the printed matter 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 in the position to be sent to the printed matter conveying device 102. The engine control section 9 causes the second conveyance section 5b to convey the printed matter toward the printed matter conveyance 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 at a position where it is sent to the post-processing device. The engine control unit 9 causes the printed material conveying device 102 to transport the printed material 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 using 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 paper being conveyed. For example, the reading unit 7 is provided between the most upstream line head 60 (60Y) and a pair of registration rollers (see FIG. 2). As shown in FIG. 4, the reading unit 7 includes a conveyance image sensor 71. The conveyance image sensor 71 is a line sensor. Conveyance image sensor 71 includes a plurality of light receiving elements. The plurality of light receiving elements are lined up in the main scanning direction (direction perpendicular to the paper conveyance direction, direction perpendicular to the plane of the paper in FIG. 4). The conveyance image sensor 71 reads the conveyed paper in the main scanning direction.

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

The light source 70 is provided at a position facing the upper surface (light-transmitting plate 72) of the reading unit 7. The light source 70 is provided at a position where the conveyed paper passes between the light source 70 and the conveyed image sensor 71 . The light source 70 emits light along the main scanning direction. The light source 70 irradiates light toward the paper conveyance path 511, the conveyed paper, and the conveyance image sensor 71 (light-transmitting plate 72) (downward in FIG. 4). The optical path crosses the paper transport path 511 in the vertical direction. The conveyed 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 conveyance image sensor 71. Light from the light source 70 passes through the lens 73 and enters the conveyance image sensor 71 . Thus, the reading unit 7 is of the CIS type.

Conveyance image sensor 71 includes a plurality of light receiving elements. Each light receiving element is lined up in the main scanning direction. The conveyance image sensor 71 outputs the charges accumulated in each light receiving element as an analog image signal. The conveyance image sensor 71 outputs an analog image signal every time one line is read. By performing A/D conversion of the analog image signal, transport read image data i1 is generated. During paper conveyance, the conveyance image sensor 71 repeats reading line by line.

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 conveyance image sensor 71 . Therefore, in the conveyance read image data i1, pixels read in areas where there is no paper have bright (light, white) pixel values. 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 area where the paper is) 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 (end side) of the conveyed paper in the main scanning direction. Further, the control unit 1 can also recognize the position of the edge (end side) of the conveyed paper in the paper conveyance direction (sub-scanning direction).

(Image data flow)
Next, an example of the flow of image data in the printer 100 according to the embodiment will be described using FIG. 5. FIG. 5 is a diagram illustrating an example of the flow of image data in the printer 100 according to the embodiment.

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

The image control section 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 section 8. The image output circuit 84 is a circuit that generates image data to be supplied to the line head 60.

When receiving print data from the computer 200, the image generation circuit 12 generates first image data. The first image data is raster data (bitmap data). The print data includes data written in a page description language. The image generation circuit 12 generates 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 (eg, RAM).

The image processing circuit 13 reads out the first image data from the storage section 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, if the print setting for enlargement is made, the image processing circuit 13 performs image processing for enlargement on the first image data. The image processing circuit 13 also performs color space conversion and halftone processing to generate second image data. The second image data is image data in which ink ejection or non-ejection of each pixel is determined for each color component of CMYK. In this case, for example, there are 4 bits per pixel.

The image transmission circuit 14 transmits the generated second image data to the image control section 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 normal printing image data 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 normal printing image data for each page. Further, the conversion circuit 85 converts the normal printing image data for a specific page (paper) to generate waste paper image data (details will be described later).

The normal printing image data is image data to be passed (input) to each line head 60. The conversion circuit 85 generates normal printing image data for each color. The number of bits per pixel of image data for normal printing is determined in advance. The value of each pixel indicates the size of the ink droplet. For example, if there are six 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 selection of paper to be used for printing. The storage unit 2 stores data for determining the droplet size for each paper. The conversion circuit 85 determines the size of the droplet of each pixel according to the characteristics of the paper used (color, thickness, presence or absence of coating, etc.).

In the line head 60, a piezoelectric element (piezo element) is provided for each nozzle. Line head 60 includes a driver circuit 6a. The driver circuit 6a receives normal printing image data or waste paper image data (details will be described later) transmitted from the conversion circuit 85. The driver circuit 6a applies voltage to the piezoelectric element of the nozzle that ejects ink based on the 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 determined in advance for each type of droplet size. For example, the pattern of the voltage signal is such that the larger the size of the droplet, the more the ink in the nozzle is shaken and the amount of ink ejected increases. Based on the image data for normal printing or the image data for waste paper, the driver circuit 6a applies a voltage signal corresponding to the specified droplet size to the piezoelectric element of the nozzle that ejects ink.

The image control section 8 also processes image data generated by the reading unit 7. During printing (when transporting paper), the image control circuit 83 turns on the light source 70. When the light source 70 is turned on, the image control circuit 83 causes the conveyance image sensor 71 to perform reading. While the paper is passing above the conveyance image sensor 71, the image control circuit 83 turns on the light source 70 and causes the conveyance image sensor 71 to perform reading. The image control circuit 83 may start turning on the light source 70 and start reading in synchronization with the start of rotation of the pair of registration rollers.

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 (eg, amplifies) the analog image signal output by the conveyance image sensor 71. 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 conveyance 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 using FIGS. 5 and 6. FIG. 6 is a diagram illustrating an example of conveyance read image data i1 according to the embodiment.

As described above, the image control section 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 transported read image data i1. Based on the processing results, the image control unit 8 detects the occurrence of a paper conveyance error. The image control unit 8 detects centering errors, size mismatch errors, skew errors, and mask errors as paper conveyance errors.

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

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

The centering circuit 87 recognizes the center position of the sheet being conveyed 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 predetermined determination range data of the conveyance read image data i1. For example, the determination range data is conveyance read image data i1 obtained within a predetermined determination period after the registration roller pair starts rotating. The transport read image data i1 obtained within the determination period is 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 pair of registration rollers until the leading edge of the paper reaches the line head 60 which is the most upstream in the paper transport direction. For example, the determination period is shorter than the time obtained by dividing the transport distance from the pair of registration rollers to the line head 60 that is the most upstream 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 edge closest to one side in the main scanning direction for each line in the main scanning direction of the determination range data. The centering circuit 87 determines the average position of the edges closest to one side as the position of the edge on one side. The centering circuit 87 also recognizes the position of the edge on the other side in the main scanning direction for each line in the main scanning direction in the determination range data. The centering circuit 87 determines the average position of the edges on the other side as the position of the edge on the other side. The centering circuit 87 recognizes the center between the determined edge position on one side and the determined edge position on the other side as the center position of the sheet to be conveyed. The centering circuit 87 may recognize the center position of the paper using other methods.

Here, in the conveyance read image data i1, an ideal center position (coordinates) is determined in advance. The printer 100 is a central paper feed type printing device. The printer 100 is designed so that the center of the paper transport path 511 in the main scanning direction and the center of the paper in the main scanning direction coincide with each other and the paper is transported. Furthermore, the conveyance image sensor 71 is installed such that the center of the reading range of the conveyance image sensor 71 in the main scanning direction matches the center of the paper conveyance path 511 in the main scanning direction. Therefore, the ideal center position corresponds to the center of the paper transport path 511 in the main scanning direction and the center position of the transport read image data i1 in the main scanning direction. In FIG. 6, the ideal center position is indicated by a chain line. In FIG. 6, an example of the center position of the conveyed paper recognized by the centering circuit 87 is shown by a two-dot chain line.

The centering circuit 87 recognizes the amount and direction of deviation of the center position based on the difference between the center position of the sheet being conveyed and the ideal center position. The centering circuit 87 detects (determines) that a centering error has occurred when the absolute value of the amount of deviation is greater than or equal to a predetermined center deviation upper limit value V1. The storage unit 2 stores the center deviation upper limit value V1 in a non-volatile manner (see FIG. 1). The center deviation upper limit value V1 is determined in advance. 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 detecting a centering error, the image control section 8 notifies the main control section 10 and the engine control section 9.

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

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

Further, the size determination circuit 88 can determine the size of the conveyed paper in the sub-scanning direction. For example, for each line in the sub-scanning direction of the conveyance read image data i1, the size determination circuit 88 selects the sub-scanning direction from the edge pixel closest to one side (leading side, downstream side) in the sub-scanning direction detected by the edge detection circuit 86. Recognize the distance to the edge pixel on the other side (trailing side, upstream side) in the direction. The size determination circuit 88 determines the average value of the plurality of recognized distances as the size of the sheet to be conveyed in the sub-scanning direction. The size determination circuit 88 may determine the size in the sub-scanning direction using other methods.

For example, the operation panel 3 accepts selection of paper size to be used in a print job. Further, the main control unit 10 may recognize the paper size specified in 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 determined size of the 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 greater than or equal to a predetermined size difference upper limit value V2. The storage unit 2 stores the size difference upper limit value V2 in a non-volatile manner (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 or shorter than 0.5 mm. The operation panel 3 may accept the setting of the size difference upper limit value V2. When detecting a size mismatch error, the image control section 8 notifies the main control section 10 and the engine control section 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, for example, based on determination range data of the conveyed and read image data i1. For example, the skew determination circuit 89 recognizes the position of the edge closest to one side in the main scanning direction for each line in the main scanning direction of the determination range data. The skew determination circuit 89 determines 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 slope is equal to or greater than a predetermined slope upper limit value V3. The storage unit 2 stores the slope upper limit value V3 in a non-volatile manner (see FIG. 1). The skew determination circuit 89 may detect skew errors using other techniques.

If the paper is tilted significantly, the tilt of the printed image will also be large. When it is recognized that the skew of the paper and the image is large, the image control unit 8 determines that a skew error has occurred. Note that the slope upper limit value V3 is determined in advance. When detecting a skew error, the image control section 8 notifies the main control section 10 and the engine control section 9 of the occurrence of the skew error.

The mask processing circuit 810 performs mask processing. Mask processing is performed on all pages. Mask processing is processing for preventing drawing (ink ejection) outside the paper. The mask processing circuit 810 overlaps the image data for normal printing or the image data for waste paper and the conveyance read image data i1. The mask processing circuit 810 overlaps the image data for normal printing or the image data for waste paper so that the corners of the paper match the corners of the image data for normal printing or the image data for waste paper. The mask processing circuit 810 detects pixels that eject ink in areas where there is no paper on the transport read image data i1, among the pixels that eject ink in the image data for normal printing or the image data for waste paper.

The mask processing circuit 810 converts the pixel value of a pixel for ejecting ink to a location where there is no paper into a pixel value indicating no ejection. As a result, even if, for example, paper with punch holes is mixed in or the edges of the paper are folded, it is possible to prevent the inside of the machine from becoming dirty due to drawing in 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 change is made to non-ejection of ink), 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 a process performed when a transport 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 illustrating an example of a process when a paper conveyance error is detected in the printer 100 according to the embodiment. FIG. 8 is a diagram illustrating an example of a process when a transport paper error is detected during double-sided printing.

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

Further, the main control unit 10 instructs the engine control unit 9 to prohibit feeding of new paper due to the occurrence of a conveyance paper error. Based on this instruction, the engine control section 9 determines that there is an error in conveying paper, and then prevents the paper feeding section 4 from feeding a new paper. Note that for the paper that is being fed when a transport paper error is detected, the engine control unit 9 causes the paper feeding unit 4 to continue feeding the paper to the end without interrupting the paper feeding. After determining that a transport paper 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 one of the discharge trays.

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

The image control unit 8 sets waste paper (defective paper, waste paper) (step #11). Specifically, the image control unit 8 controls the paper for which a conveyance paper error has been detected and the paper fed after the paper for which a conveyance paper error has been detected (paper that has not been printed on both sides at the time of detection of a conveyance paper error). It is determined that There are multiple causes of conveyance paper errors. In commercial printing, print quality is important. Depending on the cause, the same error may be carried over to the paper following the paper on which the conveyance paper error was detected. The image control unit 8 treats the paper for which a transport paper error has been detected and the paper following the paper as a torn paper.

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

In the case of double-sided printing, the engine control unit 9 transports the waste paper twice so as to face the lower surface (nozzle) of the line head 60 (same as when the paper is not a waste 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 conveyance unit 5s, and turns the waste paper upside down. Subsequently, the engine control section 9 causes the waste paper to rejoin the first conveyance section 5a. The engine control unit 9 causes the waste paper to enter the lower surface of the line head 60 again.

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

Specifically, the image control unit 8 (conversion circuit 85) generates image data for waste paper so that the amount of color material consumed is smaller than when printing based on image data for normal printing. The image control unit 8 converts the normal printing image data that was planned to be used for printing the waste paper, and generates the waste paper image data. The image control unit 8 converts the pixel value of each pixel of the normal printing image data to generate waste paper image data.

Specifically, the image control unit 8 (conversion circuit 85) generates image data for waste paper so that the amount of droplets per pixel is smaller than when printing based on normal printing image data. The image control unit 8 reduces the size of the droplet compared to the normal printing image data.

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

The image control unit 8 (conversion circuit 85) may also perform thinning processing to reduce the amount of coloring material used. The thinning process is a process of reducing the number of pixels on which ink is ejected from the image data for normal printing. For example, if the number of pixels that eject ink is reduced to 1/2, the amount of coloring material used will also be reduced to approximately 1/2. The image control unit 8 converts the value of a pixel for which ink is ejected from the image data for normal printing into a value indicating non-ejection of ink.

The image control unit 8 (conversion circuit 85) may perform both droplet size reduction processing and thinning processing, or may perform only one of them. Then, the image control unit 8 prints the waste paper using the waste paper image data (step #13). In the case of single-sided printing, the image control unit 8 prints on one side of the waste paper. In the case of double-sided printing, the image control unit 8 prints on both sides of the waste paper. After printing all the waste sheets, the main control section 10, image control section 8, and engine control section 9 end the print job (end).

The engine control unit 9 discharges the paper printed based on the normal printing image data and the paper printed based on the waste paper image data to different ejection trays (step #14). The engine control unit 9 discharges paper that is not a waste paper in the print job to the discharge tray selected as the discharge 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 separate paper that is damaged and paper that is not.

An example of the flow of printing after a conveyance paper error is detected in double-sided printing will be described with reference to FIG. 8. The first diagram in FIG. 8 shows an example of a finished image of a double-sided printed product. FIG. 8 shows an example of double-sided printing on six sheets of paper. In FIG. 8, for convenience, the printed content on the first side (back side) is an alphabet without a character surround. Further, as the print content on the second side (front side), alphabets surrounded by dashed lines are written (alphabets A, C, E, G, I, K).

The second diagram in FIG. 8 shows an example of the printing order (order of passage of the line head 60) of double-sided printed matter. A certain amount of time is required for the switchback (circulation of the paper and rejoining of the paper to the first transport section 5a). FIG. 8 shows an example of printing the first side (single side, back side) of the next sheet while switching back the sheet.

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

In the case of double-sided printing, even after it is determined that an error has occurred based on the transport read image data i1, there are pages that are printed based on the image data for normal printing. The image control unit 8 controls the image control unit 8 for normal printing for paper for which feeding was started before it was determined that an error had occurred, and for paper that had already been printed on one side and that had reentered the line head 60 after switching back after the error was detected. Print based on image data.

In this way, the image forming apparatus (printer 100) according to the embodiment includes the paper transport section 5, the engine control section 9, the image forming section 6, the ejection tray, the transport image sensor 71, and the image control section 8. The paper transport section 5 includes transport rollers. The paper transport section 5 transports paper. The engine control section 9 controls the paper conveyance section 5. The image forming section 6 forms an image on the sheet being transported. Printed paper is ejected from the ejection tray. The conveyance image sensor 71 is provided upstream of the image forming section 6 in the paper conveyance direction. The conveyance image sensor 71 reads the sheet conveyed toward the image forming section 6 . The image control unit 8 detects that a conveyance paper error has occurred for each conveyed sheet based on the conveyance read image data i1 obtained by reading by the conveyance image sensor 71. The image control unit 8 generates image data for normal printing. The image control unit 8 causes the image forming unit 6 to perform printing based on the normal printing image data for the paper for which a transport paper error has been detected and for the paper for which the paper has not been detected. The image control unit 8 uses color material rather than printing based on the normal printing image data for the paper for which a conveyance paper error has been detected and the paper that has been fed after the paper for which the conveyance paper error has been detected. Generate image data for waste paper that consumes less paper. The image control section 8 causes the image forming section 6 to print on the waste paper based on the image data for the waste paper.

Based on the results of printing on waste paper, it is possible to visually confirm (recognize) what kind of transport paper error (defect) has occurred and the degree of the error that has occurred. For example, it is possible to recognize the cause of misalignment of the printing position for each sheet of paper and the amount of misalignment. High-density printing is not necessary to understand the type and extent of transport paper errors. When printing on waste paper, the amount of color material consumed is reduced compared to when no transport paper error occurs. Therefore, consumption of coloring material can be suppressed. Furthermore, since the cause of the paper conveyance error can be quickly grasped, the problem can be promptly resolved. As a result, frequent occurrence of transport paper errors can be prevented. Since frequent occurrence of errors can be prevented, repeated wasteful consumption of color materials and paper can be eliminated.

When the absolute value of the amount of deviation between the center position in the main scanning direction of the paper to be conveyed and the ideal center position exceeds the center deviation upper limit V1, the image control unit 8 controls the paper selected to be used for printing. When the absolute value of the difference between the paper size and the paper size recognized based on the transport read image data i1 exceeds the size difference upper limit value V2, and when it is determined that the paper is skewed based on the transport read image data i1, the transport If one or more of the following conditions apply when the color material is placed on an area where there is no paper when the scanned image data i1 and the image data for normal printing are superimposed, the transport It is determined that a paper error has occurred. In commercial printing, delivered printed matter may be inspected. Misalignment of the printing position will cause the product to be rejected during inspection. It is possible to detect the occurrence of paper defects (transfer paper errors) that would result in a rejection.

There are a plurality of ejection trays (first ejection tray 103, second ejection tray 104). The engine control unit 9 causes the paper printed based on the image data for normal printing and the paper printed based on the image data for waste paper to be ejected to different ejection trays. It is possible to automatically sort paper with problems (damaged paper) from paper that was printed without any problems. It is possible to easily check only the broken paper.

The coloring material is ink. The image forming section 6 includes a line head 60 that prints on the transported paper using ink. The line head 60 includes a plurality of nozzles, and performs printing by ejecting ink droplets from the nozzles. The conversion circuit 85 generates waste paper image data such that the amount of droplets per pixel is smaller than when printing based on normal printing image data. The amount of ink consumed when printing on waste paper can be reduced compared to normal printing (printing when there is no paper transport error).

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

The conversion circuit 85 performs thinning processing to reduce the number of pixels from which ink is ejected from the image data for normal printing, and generates image data for waste paper. The number of pixels that eject ink can be reduced when printing on thin paper. Ink consumption when printing on paper can be reduced.

The image forming apparatus includes a switchback transport section 5s for performing double-sided printing. The switchback conveyance section 5s includes a switchback roller pair 59. The switchback transport unit 5s uses a pair of switchback rollers 59 to turn over the single-sided printed paper on which the first side is printed when it passes through the image forming unit 6. When double-sided printing is performed on a plurality of sheets of paper continuously, the image control unit 8 prints the printing on the second side of the single-sided printed paper that has been returned to the upstream side of the paper conveyance direction from the image forming unit 6 after being reversed. The forming section 6 is made to perform the process. For single-sided printed paper that is conveyed between lost paper and lost paper and is printed on one side without being determined to be a conveyance paper error, the image control unit 8 performs normal printing based on the image data for normal printing. The image forming unit 6 is caused to print on the second side of the single-sided printed paper. When a transport paper error is detected during double-sided printing, the paper that was printed on one side before the transport paper error was detected can be printed as usual (without reducing the coloring material). Double-sided printing can be completed for paper that does not have a transport paper error.

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

INDUSTRIAL APPLICATION This invention can be utilized for the image forming apparatus which reads the paper conveyed before printing.

100 Printer (image forming apparatus) 103 First discharge tray 104 Second discharge tray 5 Paper conveyance section 51 First conveyance roller pair 52 Second conveyance roller pair 53 Third conveyance roller pair 59 Switchback roller pair 5s Switchback conveyance section 6 Image forming section 60 Line head 71 Conveyance image sensor 8 Image control section 85 Conversion circuit 9 Engine control section i1 Conveyance read image data

Claims (7)

a paper transport section that includes a transport roller and transports the paper;
an engine control section that controls the paper transport section;
an image forming unit that forms an image on the paper being transported;
an ejection tray from which printed paper is ejected;
an image sensor that is provided upstream of the image forming unit in the paper conveyance direction and reads the paper that is conveyed toward the image forming unit;
detecting that a conveyance paper error has occurred for each conveyed paper based on conveyance read image data obtained by reading the image sensor;
Generate image data for normal printing,
For the paper for which the transport paper error is not detected, the image forming unit performs printing based on the normal printing image data,
Regarding the paper on which the conveyance paper error was detected and the paper fed after the paper on which the conveyance paper error was detected, the amount of color material consumed is lower than when printing based on the image data for normal printing. Generates image data for paper that reduces
An image forming apparatus comprising: an image control section that causes the image forming section to print on the waste paper based on the waste paper image data. The image control unit includes:
When the absolute value of the deviation between the center position of the paper being conveyed in the main scanning direction 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 conveyance scan image data exceeds the size difference upper limit value,
When it is determined that the paper is skewed based on the conveyance read image data,
When the conveyance read image data and the normal printing image data are superimposed and the position where the coloring material is placed is an area where there is no paper,
The image forming apparatus according to claim 1, wherein the image forming apparatus determines that the transport paper error has occurred when any one or more of the conditions apply. There are multiple output trays,
3. The engine control unit is configured to eject the paper printed based on the image data for normal printing and the paper printed based on the image data for waste paper into different ejection trays. The image forming apparatus described in . The image control unit includes a conversion circuit,
the coloring material is ink;
The image forming unit includes a line head that prints on the transported paper using the ink,
The line head includes a plurality of nozzles, and prints by ejecting ink droplets from the nozzles,
4. The conversion circuit generates the image data for waste paper so that the amount of droplets per pixel is smaller than when printing based on the image data for normal printing. The image forming apparatus according to any one of the above. The image control unit includes a conversion circuit,
5. The conversion circuit generates the waste paper image data so that the amount of droplets of one color ejected to one pixel is a predetermined minimum value. The image forming apparatus according to item 1. The image control unit includes a conversion circuit,
5. The image forming apparatus according to claim 4 , wherein the conversion circuit generates the waste paper image data by performing a thinning process to reduce the number of pixels for ejecting the ink in the normal printing image data. Device. Equipped with a switchback transport section for double-sided printing,
The switchback conveyance section is
includes a pair of switchback rollers;
using the switchback roller pair to turn over the front and back of the single-sided printed paper on which the first side is printed when passing through the image forming section;
When performing double-sided printing on multiple sheets of paper continuously,
The image control unit includes:
After reversing the front and back sides, causing the image forming unit to print on the second side of the single-sided printed paper returned to the upstream side of the image forming unit in the paper conveyance direction;
For the single-sided printed paper that was fed before the transport paper error was detected and on which the first side was printed without being determined to be a transport paper error, the normal printing image data The image forming apparatus according to any one of claims 1 to 6 , wherein the image forming unit prints the second side of the single-sided printed paper based on the above.

Images