JP2018174518A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus, capable of reading an image of a document and overwriting and printing an image on the document, having high positional accuracy of overwriting printing.SOLUTION: The image forming apparatus capable of reading an image of a document and overwriting and printing an image on the document, instructs execution of at least either one of change in a document posture and correction of a printing image to be overwritten and printed on the document by using first image information including information associated with an end portion of the document and second image information including information associated with a tip portion after inverting.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a laser beam printer that forms an image on a sheet, and more particularly to an image forming apparatus having an image reading unit that reads an image of a document.

  In an image forming apparatus that forms an image on a sheet, an image forming apparatus capable of reading an image of a document and overprinting a print image corresponding to the image of the document on the document has been proposed. In the image forming apparatus described in Patent Document 1, after the image information of the original is read by the image reading unit, the original is conveyed to the image forming unit while being reversed. As a result, the image can be overwritten after the entire image information of the original is read regardless of the length of the original in the conveyance direction. In such an image forming apparatus, it is desirable that the position of the image to be overwritten coincides with the position of the original image with high accuracy.

  On the other hand, like the image reading device described in Patent Document 2, it is possible to detect the posture of the document by detecting the edge of the document using the image reading unit, and to correct the posture of the read image information. An image reading apparatus has been proposed.

JP 2014-219471 A JP 2005-57813 A

  Under such circumstances, an image forming apparatus capable of reading an image of a document and overprinting the image on the document is required.

  Therefore, the present invention provides an image reading unit that reads an image of a document, a document transport unit that transports a document in a first direction toward the image reading unit, and a downstream side of the image reading unit in the first direction. The document passing through the image reading unit is transported in the first direction, or the document is reversed and transported toward the image reading unit in a second direction opposite to the first direction. An original reversing unit, an image forming unit that forms an image on a sheet, and an image forming conveyance that conveys the original that has been reversed and conveyed in the second direction by the original reversing unit via the image reading unit to the image forming unit And a control unit that controls an operation of reading an image of the document by the image reading unit and overwriting printing the image on the document by the image forming unit. When transported in the direction of 1, the image First image information including information relating to an edge portion of the document acquired via the capture unit, and the document acquired via the image reading unit when the document is conveyed in the second direction. Image formation for executing at least one of a change in posture of the document and correction of a print image to be overwritten on the document using at least second image information including information relating to the tip portion after inversion A device is provided.

  According to the present invention, it is possible to provide an image forming apparatus capable of reading an image of a document and overprinting the image on the document with high positional accuracy of the overwrite printing.

Main sectional view of image forming apparatus in Embodiment 1 Partial enlarged view of FIG. The figure which shows the structure of the conveyance sensor in Example 1. Explanatory drawing of the method of detecting the attitude | position of the original document in Example 1. FIG. 10 is a diagram illustrating a structure of a double-sided conveyance roller and a method for changing the posture of an original in Example 2. Main sectional view of image forming apparatus in Embodiment 3 Partial enlarged view of FIG. Main sectional view of image forming apparatus in Embodiment 4

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not intended to limit the scope of the invention only to them.

[Example 1]
The image forming apparatus according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a main cross-sectional view showing the overall configuration of the image forming apparatus 1001, and FIG. 2 is an enlarged cross-sectional view of the vicinity of the image reading unit 1100 of the image forming apparatus 1001. In this embodiment, a full color laser beam printer provided with a plurality of photosensitive drums is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, the present invention can also be applied to a monochrome copying machine or printer having one photosensitive drum.

  As shown in FIG. 1, a cassette 1002 for storing a recording material as a recording target sheet is accommodated in a lower portion of the image forming apparatus 1001 so as to be drawable. Near the end of the cassette 1002, a cassette feeding unit 1003 is disposed as a feeding unit for feeding the recording material. On one side surface of the image forming apparatus 1001, a manual feeding unit 1004 as a feeding unit that feeds a recording material as a recording target sheet is disposed. The cassette feeding unit 1003 and the manual feeding unit 1004 are configured to separate the recording materials one by one and feed them to the registration rollers 1005. A conveyance sensor 1200a that detects the passage of the recording material is disposed downstream of the registration rollers 1005 in the recording material conveyance direction. When the conveyance sensor 1200a is pushed up by the recording material and is positioned at a position indicated by a dotted line in the drawing, it is detected that the recording material is correctly conveyed.

  Here, the conveyance sensor 1200a will be described with reference to FIG. It is a figure which shows the structure of a conveyance sensor. As shown in FIG. 3, the transport sensor 1200 a includes a sensor arm 1201 that is disposed so as to protrude from the transport path 1203 and is supported rotatably about a shaft support 1202, and a detection unit that detects the movement of the sensor arm 1201. 1204. The sensor arm 1201 is maintained at the position indicated by the solid line in FIG. 3 by a biasing portion (not shown) such as a spring. When the recording material S moves in the direction of the solid arrow in FIG. 3 and reaches the conveyance sensor 1200a, the sensor arm 1201 is pushed up by the recording material S and moves to the position of the broken line in FIG. The detection unit 1204 detects the movement of the sensor arm 1201 and transmits a signal notifying that the recording material S has reached the conveyance sensor 1200a to the control unit (control unit 1300 in FIG. 1). Thereafter, when the recording material S further moves and the end 1206 on the upstream side in the conveyance direction of the recording material S moves away from the sensor arm 1201, the sensor arm 1201 moves to the position of the solid line in FIG. Here, an end facing the downstream side in the conveyance direction of the recording material S is a front end, and an end facing the upstream side is a rear end. The detection unit 1204 detects the movement of the sensor arm 1201 and transmits a signal notifying that the recording material S has passed the conveyance sensor 1200a to the control unit (the control unit 1300 in FIG. 1). Further, as the transport sensor 1200a, a method other than the above may be used. For example, a method of detecting reflected waves by irradiating light or ultrasonic waves to a passing recording material may be used.

  As illustrated in FIG. 1, the image forming apparatus 1001 includes an image forming unit 1006 that forms an image on a recording material as a recording target sheet. The image forming unit 1006 includes image forming stations 1006Y, 1006M, 1006C, and 1006K corresponding to the respective colors of yellow, magenta, cyan, and black. The image forming unit 1006 is provided with photosensitive drums 1007Y, 1007M, 1007C, and 1007K (hereinafter unified with the photosensitive drum 1007) as image carriers. The image forming unit 1006 is provided with charging devices 1008Y, 1008M, 1008C, and 1008K that uniformly charge the surface of the photosensitive drum 1007. The image forming unit 1006 is provided with a scanner unit 1009 that irradiates a laser beam based on print image information held in the control unit 1300 to form an electrostatic latent image on the photosensitive drum 1007. The image forming unit 1006 is provided with developing devices 1010Y, 1010M, 1010C, and 1010K that develop toner images by attaching toner to the electrostatic latent image. Further, the image forming unit 1006 is provided with primary transfer units 1012Y, 1012M, 1012C, and 1012K (hereinafter unified with the primary transfer unit 1012) that transfer the toner image on the photosensitive drum 1007 to the transfer belt 1011. The toner image on the transfer belt 1011 onto which the toner image has been transferred by the primary transfer unit 1012 is transferred to the recording material by the secondary transfer unit 1013. Here, the print image information held in the control unit 1300 is created based on information received from a computer on the network, an external recording device directly connected to the image forming apparatus 1001, or the like, or the control unit 1300 is held in advance.

  Thereafter, the recording material is conveyed to the fixing device 1014 and passes through a nip formed by a heating unit 1014a inside the fixing device 1014 and a pressure roller 1014b that is in pressure contact with the heating unit 1014a. The toner image transferred to the recording material is fixed by the fixing device 1014. As shown in FIG. 2, a conveyance sensor 1200b is disposed downstream of the fixing device 1014. The conveyance sensor 1200b detects that the recording material is correctly conveyed by being pushed up by the recording material and positioned at a position indicated by a dotted line in the drawing.

  Thereafter, the sheet that has passed through the fixing device 1014 is guided to the discharge roller 1016 or the switchback roller 1017 disposed above the discharge roller 1016 by the double-sided switching member 1015a. The discharge roller 1016 is a discharge unit that discharges the recording material on which the image is formed in the image forming unit 1006 toward the recording material stacking unit 1018. The switchback roller 1017 is a reversing unit that reverses the conveyance direction of the recording material on which an image is formed on one surface in the image forming unit 1006. The double-sided switching member 1015 a is a switchable switching unit that guides the sheet on which an image has been formed in the image forming unit 1006 to the discharge roller 1016 or the switchback roller 1017.

  Here, when the recording material is discharged to the outside of the apparatus, as shown in FIG. 2, the double-sided switching member 1015a is indicated by a solid line using a driving unit (not shown) until the leading end of the recording material passes through the fixing device 1014. Move to position. As the drive unit, a solenoid, a motor, a spring, or the like can be used. Thereafter, the recording material is conveyed from the fixing device 1014 to the discharge roller 1016 and is discharged to the recording material stacking portion 1018 by the discharge roller 1016. Here, a conveyance path for conveying the recording material discharged by the discharge roller 1016 to a processing device (not shown) disposed in the vicinity of the image forming apparatus 1001 is formed, and after sorting, binding, sorting, and the like of the recording material Processing may be performed.

  When printing is also performed on the back surface (the other surface) of the recording material having an image formed on the front surface (the one surface), the printing is performed as follows. As shown in FIG. 2, the recording material is conveyed from the fixing device 1014 to the switchback roller 1017 by moving the double-sided switching member 1015a to the position indicated by the broken line until the leading edge of the recording material passes through the fixing device 1014. Thereafter, the switchback roller 1017 is rotated (forward rotation) in a direction in which the recording material is fed out of the apparatus (downward direction in FIG. 2), thereby recording until the rear end of the recording material passes the conveyance guide front end portion 1028. Transport material. Thereafter, by moving the double-side switching member 1015a to the position indicated by the solid line, a fourth conveyance path H4 for guiding the recording material from the switchback roller 1017 to the double-side conveyance roller 1025 is formed. After that, the switchback roller 1017 is temporarily stopped and then rotated (reversely rotated) in the direction in which the recording material is fed into the apparatus (upward in FIG. 2), whereby the recording material is transferred from the switchback roller 1017 to the duplex conveying roller. Transport to 1025. Thereafter, the recording material is conveyed to the duplex feeding roller 1026 using the duplex conveyance roller 1025.

  A conveyance sensor 1200c is disposed downstream of the double-sided conveyance roller 1025 as shown in FIG. The conveyance sensor 1200c detects the time when the leading edge of the recording material passes by being pushed down by the recording material and positioned at a position indicated by a dotted line in the drawing. The control unit 1300 uses the image forming unit 1006 to form a toner image to be transferred onto the back surface of the recording material on the transfer belt 1011. Thereafter, the duplex conveying roller 1025 and the duplex feeding roller 1026 are temporarily stopped after a lapse of a certain time after the leading edge of the recording material passes the conveyance sensor 1200c, and the leading edge of the recording material is sandwiched between the duplex feeding roller 1026. Hold. Thereafter, the double-sided conveyance roller 1025 and the double-sided feeding roller 1026 are set to the recording material with the timing adjusted so that the position in the conveyance direction of the toner image on the transfer belt 1011 and the recording material matches on the secondary transfer unit 1013. The registration roller 1005 is rotated in the conveying direction. Thereafter, the recording material is conveyed to the registration roller 1005, the secondary transfer unit 1013, and the fixing device 1014, and the recording material having the toner image transferred and fixed on the back surface is conveyed to the discharge roller 1016 and discharged to the recording material stacking unit 1018. .

  The configuration and operation of document feeding and discharging and image reading will be described below. In the upper right part of the image forming apparatus 1001, an image reading unit 1100 that reads an image of a document as a sheet to be read is arranged. The image reading unit 1100 includes a switchable document switching member 1015b, image reading units 1101a and 1101b (hereinafter unified with the image reading unit 1101), a document feeding tray 1102 for loading and storing documents, and document feeding for feeding documents. Part 1103. The image reading unit 1100 includes a document registration roller 1104 serving as a document transport unit that transports a document in a first direction, a document discharge roller 1105 that discharges a document that has read an image, and a document discharge tray 1106 that loads a document that has been read. Have Here, the first direction in which the document registration roller 1104 transports the document is a direction toward the image reading unit 1101. Further, the document feeding tray 1102 is disposed above the manual feeding unit 1004 in FIG. 1, and the document discharge tray 1106 is disposed above the recording material stacking unit 1018. As a result, the access direction when the user stacks and stores the document and the recording material and the access direction when the user removes the discharged document and the recording material are unified in the same direction, and the arrangement is more user-friendly.

  When reading an image of a document, the document switching member 1015b is moved to a position indicated by a solid line in FIG. 2 to move the document from the document registration roller 1104 to the first document insertion port 1101c on the document feeding unit 1103 side of the image reading unit 1101. A first transport path H1 for transporting to is formed. Thereafter, the documents stacked on the document feeding tray 1102 are separated one by one from the bottom by the document feeding unit 1103 and fed to the document registration roller 1104.

  Thereafter, the document is conveyed toward the image reading unit 1101 using the document registration roller 1104. The document whose image has been read by the image reading unit 1101 is conveyed by the document discharge roller 1105 in the first direction and is discharged to the document discharge tray 1106. Here, a transport path connecting the second document insertion port 1101d on the document discharge roller 1105 side of the image reading unit 1101 and the document discharge roller 1105 is defined as a second transport path H2. The document discharge roller 1105 is provided on the downstream side in the first direction from the image reading unit 1101. The document discharge roller 1105 conveys the document that has passed through the image reading unit 1101 in the first direction, or the document toward the image reading unit 1101 in a second direction opposite to the first direction. This is a document reversing unit for reversing conveyance.

  Further, the conveyance sensor 1200f does not prevent the conveyance of the document. Specifically, the conveyance sensor 1200f can be moved to a position indicated by a dotted line h opposite to the position indicated by the dotted line g with respect to the position indicated by the solid line in FIG. As the conveyance sensor 1200f, a method other than the above may be used. For example, a sensor that detects a reflected wave by irradiating a document with light or ultrasonic waves may be used.

  When the number of documents specified by the user is fed or when there are no more documents on the document feeding tray 1102, the document feeding unit 1103 and the document registration roller 1104 are stopped. Presence / absence of a document on the document feed tray 1102 is detected by a stack detection sensor 1200d.

  The image reading unit 1101 is configured so that the image reading unit 1101a and the image reading unit 1101b have images of each other on the trajectory of the document when the document passes through the first transport path H1 and the second transport path H2. The reading surfaces are arranged so as to face each other. As the image reading unit 1101, a CIS (contact image sensor) or the like can be used. By disposing the two image reading units so as to face each other, images printed on both sides of the document that have passed between the two image reading units can be read at a time. If it is not necessary to read images printed on both sides of the document at once, the image reading unit may be provided only on one side of the document. The image reading unit 1101 starts a reading operation after a predetermined time has elapsed since the leading edge of the document has passed the conveyance sensor 1200e, and a predetermined time has elapsed since the trailing edge of the document has passed the conveyance sensor 1200e. The reading operation is finished later. An image read by the image reading unit 1101 is stored in a computer on the network as electronic information, or is transmitted to the control unit 1300 in FIG. 1 and converted into print image information by the control unit 1300 to be used as a new recording material. Duplicated.

  Next, the configuration and operation for overprinting an original will be described below. The operation of reading an image of a document and overprinting the image on the document, which will be described below, is controlled by the control unit 1300.

  First, the document to be overwritten is stacked and stored on the document feeding tray 1102. At this time, the original is stacked and stored on the original feed tray 1102 so that the surface to be overwritten faces upward. Thereafter, the operation from the original feeding tray 1102 through the image reading unit 1101 to the conveyance to the original discharge roller 1105 is the same as the above-described original image reading operation. At this time, the document image read by the image reading unit 1101 is transmitted to the control unit 1300 as electronic information. The control unit 1300 retains the received electronic information as first image information, and creates electronic information of a print image to be overwritten on the document based on the first image information, that is, print image information. The reason for using the image of the original before reversal (first image information) to create the print image information is to prevent the productivity of overwrite printing from being reduced. The reason is as follows.

  Since the information necessary for creating the print image may be in the vicinity of the trailing edge of the document after the reversal, it is necessary to read the image up to the trailing edge position of the document. When creating print image information using an image of a document before reversal, creation of a print image and formation of a toner image of the print image by the image forming unit 1006 can be performed while the document is reversed. On the other hand, when the print image information is created using the image of the original after reversal, the creation of the print image information is started after all the images of the original are read. This is necessary until the toner image of the print image is formed. It takes a relatively long time and productivity is reduced.

  After the trailing edge of the document has passed through the first document insertion port 1101c of the image reading unit 1101, the document switching member 1015b is moved to the position indicated by the dotted line in FIG. 2, and the document is transferred from the document insertion port 1101c to the duplex conveying roller 1025. A third transport path H3 to be transported is formed. After the trailing edge of the document passes through the second document insertion port 1101d of the image reading unit 1101, the document discharge roller 1105 is temporarily stopped. Thereafter, the document discharge roller 1105 is rotated in the direction of transporting the document to the right in FIG. 2, and the document is transported from the document discharge roller 1105 through the image reading unit 1101 to the duplex transport roller 1025. The double-sided conveyance roller 1025 functions as an image forming and conveying unit that conveys a recording material having an image formed on one side to the image forming unit 1006. Further, the double-sided conveyance roller 1025 functions as an image forming and conveying unit that conveys the document reversely conveyed in the second direction via the image reading unit 1101 by the document discharge roller 1105 to the image forming unit 1006. The document reversely conveyed from the double-sided conveyance roller 1025 serving as the image forming conveyance unit is conveyed to the image forming unit without being further reversed and conveyed. As a result, the length in the document transport direction can be made shorter than the image forming apparatus described in Japanese Patent Application Laid-Open No. 2014-219471, and productivity can be improved. The image reading unit 1101 starts a reading operation after a predetermined time has elapsed after the leading edge of the document reversely conveyed in the second direction passes the conveyance sensor 1200f, and the document reads the image reading unit 1101 in the posture of the document. The reading operation is terminated after the passage of a length necessary for detecting. Here, the length required for the original to detect the posture of the original by the image reading unit 1101 is a portion of image information including at least the front end portion of the original after being inverted.

  An image read by the image reading unit 1101 is transmitted to the control unit 1300 as electronic information. The control unit 1300 retains the received electronic information as second image information, and uses it together with the first image information previously retained to detect a change in the orientation of the document, and a print image to be overwritten on the document The print image information is corrected so that the position of the image matches the position of the document. Here, regarding the posture change of the document, the control unit 1300 acquires the first posture information of the document from the first image information, and acquires the second posture information of the document from the second image information. Then, the control unit 1300 corrects the posture of the print image (print image information) to be overwritten on the document using the first posture information and the second posture information. The reason for correcting the print image information by using the orientation information of the original document before and after the original is inverted is that a part of the original is exposed to the outside of the apparatus when the original is inverted. This is because the posture of the document is likely to change due to an external force from an air current or an obstacle.

  An example of a method for detecting a change in posture of a document and a method for correcting print image information will be described below. A common reference coordinate system is defined to represent the orientation of the document when each of the first image information and the second image information is read, that is, the tilt and center position of the document. First, as shown in FIG. 4, the reference coordinate system is the center of the second conveyance path H2 with the direction (second direction) from the document discharge roller 1105 toward the image reading unit 1101 being positive on the second conveyance path H2. The axis along the line is the Y axis, and the axis orthogonal to the Y axis is the X axis. Next, as shown in FIG. 4A, the coordinates of the left end point and the right end point of the line segment of the rear end (upstream end in the transport direction) of the original G when the first image information is read are shown. Let (xa1, ya1) and (xb1, yb1) respectively. Here, the original G is conveyed in the direction of the arrow Q1 (first direction) in FIG.

  The inclination θ1 of the original G with respect to the reference coordinate system is expressed as shown in Expression (1).

  θ1 = Arctan {(yb1-ya1) / (xb1-xa1)} (1)

  Further, the coordinates (xc1, yc1) of the center point of the line segment at the rear end of the document G are expressed as in Expression (2) and Expression (3).

xc1 = (xb1-xa1) / 2 (2)
yc1 = (yb1-ya1) / 2 (3)

  Next, as shown in FIG. 4B, the coordinates of the left end point and the right end point of the line segment of the leading edge (downstream end in the transport direction) of the original G when the second image information is read are respectively shown. Let (xa2, ya2), (xb2, yb2). Here, the document G is conveyed in the direction of the arrow Q2 in FIG. 4B (second direction opposite to the first direction).

  The inclination θ2 of the original G with respect to the reference coordinate system is expressed as in Expression (4).

  θ2 = Arctan {(yb2-ya2) / (xb2-xa2)} (4)

  In addition, the coordinates (xc2, yc2) of the center point of the line segment at the leading edge of the document are expressed as Expression (5) and Expression (6).

xc2 = (xb2-xa2) / 2 (5)
yc2 = (yb2-ya2) / 2 (6)

  From Expressions (1) to (6), the change in the posture of the original G when the second image information is read with respect to the time when the first image information is read, that is, the difference Δθ in the inclination of the original G and the original G The difference (Δx, Δy) in the center position change is expressed as follows.

Δθ = θ2-θ1 (7)
Δx = xc2−xc1 (8)
Δy = yc2−yc1 (9)

  In order to correct the print image information so that the posture of the print image matches the posture of the original G when the second image information is read from the equations (7) to (9), for example, the following is performed. . The print image is printed so that it is rotated by Δθ with respect to the center position of the trailing edge of the original when the first image information is read, and is further translated by (Δx, Δy) with respect to the reference coordinate system. Information of each pixel in the image information is converted.

  Here, the trailing edge of the document (upstream end in the first direction) is used to obtain the orientation information of the document before the document is reversed, but an edge other than the trailing edge of the document is used. Is also possible. Further, by using the trailing edge of the document and the other edge together, more accurate document posture information can be obtained. Here, the orientation information of the document before reversing the document is acquired from the first image information including the edge of the document acquired through the image reading unit when the document is conveyed in the first direction. It is the first attitude information.

  Also, the leading edge of the document (the end on the downstream side in the second direction) is used to obtain the orientation information of the document after the document is reversed, but a part of the left and right edges of the document near the leading edge of the document It is also possible to use. Furthermore, it is possible to obtain more accurate document orientation information by using both the leading edge of the document and a part of the left and right edges of the document. Here, the orientation information of the document after the document is reversed is the second information including at least the front end portion of the document obtained through the image reading unit when the document is conveyed in the second direction. It is the second posture information acquired from the image information.

  After the original on which the first image information and the second image information are read is conveyed to the duplex conveying roller 1025, the original is conveyed again to the registration roller 1005. Here, the procedure of conveying the document to the double-sided conveyance roller 1025 and then conveying it again to the registration roller 1005 is a process of conveying the recording material using the double-sided conveyance roller 1025 in the printing on the back surface of the recording material described above. The procedure is the same as the subsequent steps. At this time, the image forming unit 1006 forms a toner image on the primary transfer unit 1012 based on the corrected print image information overwritten on the document held in the control unit 1300. Thereafter, the document is conveyed in the order of the secondary transfer unit 1013 and the fixing device 1014 to transfer and fix the toner image on the surface on which the document is overwritten, conveyed to the discharge roller 1016 and discharged to the recording material stacking unit 1018. As described above, the discharge roller 1016 serving as a discharge unit that discharges the recording material also serves as a document discharge unit that discharges an overprinted document.

  When overprinting is performed also on the back side of the document, the document is conveyed again to the registration roller 1005 in the same manner as the printing on the back side of the recording material described above.

  As described above, according to this embodiment, an image forming apparatus capable of reading an image of a document and overprinting the image corresponding to the image of the document on the document while maintaining the position accuracy of the overwriting printing is produced. It is possible to further improve the performance.

[Example 2]
The image forming apparatus according to the second embodiment will be described with reference to FIG. FIG. 5A is a diagram illustrating the structure of the double-sided conveyance roller, and FIG. 5B is a diagram illustrating a method for changing the posture of the document by the double-sided conveyance roller. The only structural difference between this embodiment and Embodiment 1 is that the double-sided conveyance roller 1025 has a function of changing the posture of the document. Therefore, here, the structure of the double-sided conveyance roller 1025 and a part of the overwriting printing process on the document will be described.

  An example of the structure of the double-sided conveyance roller 1025 in this embodiment will be described. As shown in FIG. 5A, the double-sided conveyance roller 1025 has double-sided conveyance rollers 1025L and 1025R that can be rotated at mutually independent conveyance speeds as the center line of the conveyance path (Y axis in FIG. 5A). On the other hand, the structure is arranged on the left and right. The double-sided conveyance rollers 1025L and 1025R include driving rollers 1025La and 1025Ra, shafts 1025Lb and 1025Rb, driven rollers 1025Lc and 1025Rc, and driving units 1025Ld and 1025Rd, respectively. The driving rollers 1025La and 1025Ra are fixed to the shafts 1025Lb and 1025Rb so that the distance between the centers is W. The shafts 1025Lb and 1025Rb are constrained so that the central axes of the shafts 1025Lb and 1025Rb have only the degree of freedom of rotation around the respective shaft centers. The driven rollers 1025Lc and 1025Rc are arranged so that the positions where the driven rollers 1025Lc and 1025Rc are pressed against the driving rollers 1025La and 1025Ra are on the same plane parallel to the conveyance path in order to sandwich and convey the original G. A shaft 1025Lb and a shaft 1025Rb are connected to each of the drive units 1025Ld and 1025Rd, and the drive rollers 1025La and 1025Ra can be rotated at independent speeds according to an instruction from the control unit 1300.

  A method for changing the posture of the document by the duplex conveying rollers 1025L and 1025R will be described below. As shown in FIG. 5B, consider a reference coordinate system in which the center of the transport path is the Y axis and the axis on the transport path surface orthogonal to the center is the X axis. The positive direction of the Y axis is the same direction as the transport direction (the direction of arrow Q in FIG. 5B). In order to change a document (angle shown in G1) inclined at an angle θ with respect to the reference coordinate system to a posture with zero inclination (position shown in G2) with respect to the reference coordinate system, the following may be performed.

  First, until the time T0 when the document is sandwiched between both the duplex conveyance rollers 1025L and 1025R, both the duplex conveyance rollers 1025L and 1025R are rotated so that the conveyance speed becomes V. At time T0, the document is at a position indicated by G1 in FIG. Thereafter, from time T0 to time (T0 + ΔT), each double-sided conveyance roller is rotated so that the conveyance speed of the double-sided conveyance roller 1025R is V and the conveyance speed of the double-sided conveyance roller 1025L is V + ΔV. At time (T0 + ΔT), the document is at a position indicated by G2 in FIG. From time T0 to time (T0 + ΔT), assuming that the distance that the duplex conveying roller 1025R conveys the document is L and the distance that the duplex conveying roller 1025L conveys the document is (L + ΔL), L and ΔL are expressed by the following equation (7): ) And (8).

L = VΔT (7)
ΔL = ΔVΔT (8)

  As described above, the difference Δθ in the inclination of the document at each of the times T0 and (T0 + ΔT) is expressed as the following equation (9).

  Δθ = Arctan (ΔL / W) (9)

  Therefore, in order to set the original tilted at the angle θ with respect to the reference coordinate system at the time T0 to the inclination 0 with respect to the reference coordinate system at the time (T + ΔT), ΔV can be expressed by the following equation (10). Good.

  ΔV = WΔT {tan (−θ)} (10)

  After the time (T0 + ΔT), both the double-sided conveyance rollers 1025L and 1025R are rotated again so that the conveyance speed becomes V. Here, in order to simplify the explanation, the acceleration / deceleration time necessary for changing the conveyance speed of the double-sided conveyance rollers 1025L and 1025R is ignored. When taking into account the acceleration / deceleration time, the speed change of each double-sided conveyance roller may be obtained by time integration when obtaining ΔL in equation (8).

  When performing overwrite printing on a document, the document is reversed by the document discharge roller 1105, and then the tilt (posture) of the document is changed in a state where the document is held only by the duplex conveying roller 1025. The value for changing the inclination of the document is set to (θ1−θ2) so that the inclination θ2 of the original after inversion coincides with the inclination θ1 of the original before inversion. The change in the center position of the leading edge of the document is changed by translating the position of each pixel of the print image information using the same method as the correction of the print image described in the first embodiment.

  The structure of the double-sided conveyance roller 1025 raised here is one example, and the structure is not limited to this. Other structures may be used as long as the structure has a function of changing the posture of the document. For example, the double-sided conveyance roller 1025 may have a structure that rotates about the axis perpendicular to the conveyance path surface along the axis. In this embodiment, the orientation of the document is changed using the duplex conveying roller 1025. However, a new roller may be added as a document orientation correcting unit that changes the orientation of the document.

  According to the present embodiment, when the posture change of the original after reversal is large, it is possible to change the posture of the original with the double-sided conveyance roller 1025 so that the original does not touch the wall of the conveyance path and be damaged. It becomes.

Example 3
An image forming apparatus according to the third embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a main sectional view of the image forming apparatus 1001 according to the third embodiment. FIG. 7 is an enlarged cross-sectional view of the vicinity of the image reading unit 1100 of the image forming apparatus 1001. The structural difference between this embodiment and the first embodiment is that the double-side switching member 1015a, the switchback roller 1017, and the fourth transport path H4 in FIG. 2 are removed. As a result, it is possible to provide an image forming apparatus dedicated to single-sided printing and single-sided overwrite printing with a simplified structure and low manufacturing cost.

Example 4
The configuration of an example of the image forming apparatus and the overwriting printing operation on the original will be described below with reference to FIG.

  A document G having an image formed on one side is placed on the document feeding unit 90 so that the surface on which the image is formed faces upward in the figure, and fed using the first duplex conveying roller 41. G is conveyed to the image reading unit 100 on the common conveyance path 92. The image reading unit 100 reads an image of the original G and transmits it to the control unit 800 as image information. Based on the image information of the original G, the control unit 800 generates print image information to be overwritten on the original G and attitude information (first attitude information) of the original G when the image is read. Thereafter, the document G is transported to the document reversal transport path 92b using the second duplex transport roller 42. After that, after the trailing edge of the document G passes the leading edge of the flapper 83, the flapper 83 is switched to a position facing directly above in the figure, the second duplex conveying roller 42 is reversed, and the document G is conveyed to the document discharge conveying path 81. Transport to. Thereafter, the original G is transported to the document discharge roller 43 using the first double-sided transport roller 41. After that, after the trailing edge of the document G passes the leading edge of the flapper 88, the flapper 88 is switched to rotate in the clockwise direction in the figure, the document discharge roller 43 is reversed, and the document G is again placed on the common transport path 92. It is conveyed to the image reading unit 100. The image reading unit 100 reads an image in the vicinity of the leading edge of the document G and transmits it to the control unit 800 as image information. The control unit 800 creates posture information (second posture information) of the inverted document G based on image information near the leading edge of the document G. Further, the control unit 800 detects the change in the posture of the original G before and after the reverse using the first and second posture information of the original G, and corrects the print image information so as to correspond to the posture of the original G after the reverse. . Thereafter, the original G is conveyed to the U-turn unit 92a using the second double-sided conveyance roller 42, and at the same time, the toner image corresponding to the print image information transmitted from the control unit 800 is exposed using the optical unit 2 and the developing roller 11. Form on drum 10. Thereafter, the document G is transported in the order of the transfer unit 15 and the fixing unit 50 using the transport roller 40, and the toner image on the photosensitive drum 10 is transferred and fixed to the document G, and then the document G is transported using the paper discharge roller 60. The paper is discharged to the paper discharge unit 70.

  In such an image forming apparatus, it is necessary to perform the operation of inverting the document twice, and it is necessary to transport a distance that is slightly less than twice the length in the document transport direction. The productivity of overwrite printing is not higher than the above configuration.

  In other words, in the configuration described in the first embodiment, in an image forming apparatus that can read an image of a document and overwrite-print the image on the document, productivity can be further improved while maintaining the position accuracy of overwrite printing. it can.

[Other Examples]
In the above-described embodiment, four image forming stations are used in the image forming unit. However, the number of used stations is not limited and may be set as needed.

  In the above-described embodiment, the electrophotographic method is exemplified as the recording method of the image forming unit. However, the recording method is not limited to this, and other recording methods such as an ink jet method may be used.

[Others]
In the embodiments described so far, the operation of the control unit has been specifically described. In summary, the control unit executes the following operation. The control unit acquires first image information including information relating to an end portion of the document acquired via the image reading unit when the document is conveyed in the first direction. The control unit then includes a second image including information relating to at least the front end portion of the document obtained through the image reading unit when the document is conveyed in the second direction opposite to the first direction. Get information. The control unit uses the first and second image information to instruct execution of at least one of a change in the orientation of the document and a correction of a print image to be overwritten on the document.

DESCRIPTION OF SYMBOLS 1001 ... Image forming apparatus 1003 ... Cassette feeding part 1004 ... Manual feed part 1006 ... Image forming part 1014 ... Fixing apparatus 1015a, 1015b ... Switching member 1016 ... Discharge roller 1017 ... Switchback roller 1025 ... Double-sided conveyance roller 1100 ... Image reading Units 1101, 1101a, 1101b ... Image reading unit 1101c ... First document insertion port 1101d ... Second document insertion port 1103 ... Document feeding unit 1105 ... Document discharge rollers 1200a, 1200b, 1200c, 1200e, 1200f ... Transport sensor 1200d ... Stacking Detection sensor 1300 ... control unit

Claims (8)

An image reading unit for reading an image of a document;
A document conveying unit that conveys a document in a first direction toward the image reading unit;
Provided downstream of the image reading unit in the first direction, the document that has passed through the image reading unit is conveyed in the first direction, or the document is directed toward the image reading unit. A document reversing unit that reversely conveys in a second direction opposite to the direction;
An image forming unit for forming an image on a sheet;
An image forming / conveying unit configured to convey the document reversely conveyed in the second direction by the document reversing unit via the image reading unit to the image forming unit;
A control unit that controls an operation of reading an image of the document by the image reading unit and overwriting the image on the document by the image forming unit;
Have
The control unit includes: first image information including information on an end portion of the document acquired through the image reading unit when the document is conveyed in the first direction; and Using the second image information including information on at least the front end portion of the original document obtained through the image reading unit when being conveyed in the direction of 2, and changing the posture of the original document. An image forming apparatus which instructs execution of at least one of correction of a print image to be overwritten on the original.   The control unit acquires first posture information of the document from the first image information, acquires second posture information of the document from the second image information, and stores the first posture information and The image forming apparatus according to claim 1, wherein the orientation of the print image is corrected using the second orientation information. A document orientation correction unit that changes the orientation of the document;
The image forming apparatus according to claim 1, wherein the control unit changes the posture of the document by the document posture correcting unit. The image forming and conveying unit has a function of changing a posture of the document;
The image forming apparatus according to claim 3, wherein the control unit changes a posture of the document by the image forming conveyance unit.   The image forming apparatus according to claim 1, further comprising: a feeding unit that feeds a sheet to the image forming unit; and a discharge unit that discharges a sheet on which an image is formed by the image forming unit.   The image forming apparatus according to claim 5, wherein the discharge unit also serves as a document discharge unit that discharges a document that has been overwritten by the image forming unit.   A reversing unit that reverses the conveyance direction of a sheet on which an image is formed on one surface by the image forming unit, and a switchable guide that guides the sheet on which the image is formed by the image forming unit to the discharge unit or the reversing unit. The image forming apparatus according to claim 5, further comprising: a switching unit; and a conveyance path that guides the sheet reversed and conveyed by the reversing unit to the image forming conveyance unit.   The image forming apparatus according to claim 1, wherein the image forming conveyance unit conveys the reversely conveyed document to the image forming unit without further reversing conveyance.

Images