JP2020116886A - Image forming apparatus - Google Patents

Abstract

To effectively reduce the deviation between a center position of a print sheet and a center position of an image formed on the print sheet at a relatively low cost.SOLUTION: A control unit (a) uses a print engine to print a scale image 131 having a plurality of segment images 131a whose positions in a main-scanning direction are different from each other at a plurality of positions in a sub-scanning direction and which are in parallel with each other in the sub-scanning direction for each graduation image 131b on a front surface and a rear surface of a print sheet for test chart, and (b) moves a center position of an image to be printed so as to reduce the deviation of the image to be printed that is caused by the deviation between a reference center position of the print engine and the reference center position of the line sensor that is identified on the basis of the graduation image 131b in which the segment image 131a of the scale image 131 on the front surface and the segment image 131a of the scale image 131 on the rear surface match each other.SELECTED DRAWING: Figure 7

Description

The present invention relates to an image forming apparatus.

An image forming apparatus (hereinafter, referred to as a first image forming apparatus) detects the center of the paper with a line sensor, identifies the deviation between the center of the paper and the center of the image to be printed, and the conveyance roller nips the paper. By moving the transport roller in the paper width direction in this state, the deviation is reduced (for example, see Patent Document 1).

An image forming apparatus (hereinafter referred to as a second image forming apparatus) includes a plurality of paper feed trays and stores a fixed center position deviation amount corresponding to each of the plurality of paper feed trays. The image formed in the electrophotographic process is moved by mechanically adjusting the optical system for the electrophotographic process by an amount corresponding to the center position shift corresponding to the sheet feeding tray (see Patent Document 2).

In addition, a certain image forming apparatus (hereinafter, referred to as a third image forming apparatus), in order to match the position of the front (front) image and the position of the back image of the paper, along the sub-scanning direction, The main scale image is printed on the front (front) side and the vernier scale image is printed on the back side, and the user is prompted to input the matching position of the scale between the main scale image and the vernier scale image. The deviation between the position of the front surface image and the position of the rear surface image is suppressed (for example, see Patent Document 3).

JP, 2014-139110, A Japanese Patent Laid-Open No. 5-313447 JP, 2003-262990, A

However, in the first image forming apparatus, it is possible to reduce the deviation of the center position corresponding to the center position of the sheet being conveyed, but a mechanism for mechanically moving the conveying roller is necessary, and The cost will be high.

Further, in the second image forming apparatus, the center position of the image formed by the electrophotographic process is mechanically corrected in accordance with the fixed center position deviation amount, and thus the cost of the apparatus is also high. In addition, it is difficult to effectively reduce the deviation of the center position without considering the variation of the center position that occurs for each sheet.

Since the third image forming apparatus aims to suppress the deviation between the position of the front (front) surface image and the position of the back surface image, the third image forming apparatus is formed on the print sheet at the center position. It is difficult to reduce the deviation between the center position of the image and the center position of the image.

The present invention has been made in view of the above problems, and effectively reduces the deviation between the center position of a print sheet and the center position of an image formed on the print sheet at a relatively low cost. An object is to obtain an image forming apparatus.

An image forming apparatus according to the present invention includes a print engine that physically prints an image to be printed on a print sheet, a sheet conveying unit that conveys the print sheet, and a direction perpendicular to the conveyance direction of the print sheet. A line sensor arranged to detect the positions of both edges of the print sheet; and (a) a center position of the print sheet as a sheet center actual position based on the positions of both edges of the print sheet detected by the line sensor. And (b) a control unit that adjusts the center position of the image to be printed based on the difference from the actual position of the sheet center. Then, (a) the plurality of positions in the main scanning direction which are different from each other in the main scanning direction are parallel to each other on the front surface and the back surface of the print sheet for the test chart. (B) the line segment image of the scale image on the front side and the line segment image of the scale image on the back side are printed by the print engine. Are specified based on the scale images that match each other, the print is performed so as to reduce the deviation of the image to be printed due to the deviation between the reference center position of the print engine and the reference center position of the line sensor. The center position of the image to be moved is moved.

According to the present invention, it is possible to obtain an image forming apparatus that can effectively reduce the deviation between the center position of the print sheet and the center position of the image formed on the print sheet at a relatively low cost.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a side view illustrating a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the image forming apparatus shown in FIG. FIG. 3 is a block diagram showing an electrical configuration of the image forming apparatus 10 according to the exemplary embodiment of the present invention. FIG. 4 is a diagram illustrating the correction amount of the image center position in the image forming apparatus 10 according to the first embodiment. FIG. 5 is a diagram showing an example of a scale image printed on the front surface and the back surface of the test chart. FIG. 6 is an enlarged view of the scale image in FIG. FIG. 7 is an enlarged perspective view of a test chart in which scale images are printed on the front surface and the back surface. FIG. 8 is a diagram illustrating positions where the scale images shown in FIGS. 5 and 6 are printed on the print sheet. FIG. 9 is a diagram for explaining the deviation of the reference center position CPp of the print engine 10a from the reference center position CPt of the conveyance system of the print sheet 101.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Embodiment 1.

FIG. 1 is a side view illustrating a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the image forming apparatus shown in FIG.

The image forming apparatus 10 according to this embodiment is a device such as a printer, a copier, a facsimile machine, and a multi-function machine. In this embodiment, a line-type inkjet type color printing mechanism is provided.

The image forming apparatus 10 illustrated in FIG. 1 includes a print engine 10a and a sheet conveying unit 10b. The print engine 10a physically prints an image to be printed on a print sheet (print paper or the like). The sheet transport unit 10b transports the print sheet to the print engine 10a.

In this embodiment, the print engine 10a includes line type inkjet recording units 1a to 1d corresponding to four ink colors of cyan, magenta, yellow, and black.

As shown in FIG. 2, in this embodiment, each inkjet recording unit 1a, 1b, 1c, 1d has a plurality of (here, three) head units 11. The heads 11 are arranged along the main scanning direction and are attachable to and detachable from the apparatus body. The number of heads 11 of each of the inkjet recording units 1a, 1b, 1c, 1d may be one.

Further, in this embodiment, the sheet conveying unit 10b includes an annular conveying belt 2 arranged to face the print engine 10a and conveys a print sheet, a driving roller 3 and a driven roller 4 suspended from the conveying belt 2. In addition, a suction roller 5 that nips a print sheet together with the transport belt 2 and a discharge roller pair 6 are provided.

The drive roller 3 and the driven roller 4 rotate the conveyor belt 2. Then, the suction roller 5 nips the print sheet conveyed from the sheet feeding cassettes 20-1 and 20-2, which will be described later, and the nipped print sheet is moved to the print position of the inkjet recording units 1 a to 1 d by the conveyance belt 2. The images are conveyed in order, and images of respective colors are printed by the inkjet recording units 1a to 1d. Then, the print sheet after the color printing is completed is discharged by the discharge roller pair 6 to a discharge tray (not shown) or the like.

Further, the sheet conveying unit 10b includes a plurality of sheet feeding cassettes 20-1 and 20-2. The paper feed cassettes 20-1 and 20-2 contain print sheets 101 and 102, and lift plates 21 and 24 push the print sheets 101 and 102 upward to bring them into contact with pickup rollers 22 and 25. The print sheets 101 and 102 placed on the paper feed cassettes 20-1 and 20-2 are picked up by the pickup rollers 22 and 25 one by one from the upper side to the paper feed rollers 23 and 26. The paper feed rollers 23 and 26 are rollers that convey the print sheets 101 and 102 fed by the pickup rollers 22 and 25 from the paper feed cassettes 20-1 and 20-2 one by one onto the conveyance path.

The transport roller 27 is a transport roller on a transport path common to the print sheets 101 and 102 transported from the paper feed cassettes 20-1 and 20-2.

The resist roller 28 temporarily stops the conveyed print sheets 101 and 102, and conveys the print sheets 101 and 102 to the print engine 10a at the secondary sheet feeding timing. The secondary paper feed timing is designated by the control unit 51, which will be described later, so that an image is formed at the designated position on the print sheets 101 and 102.

In this embodiment, when the print sheets 101 and 102 reach the registration roller 28, the transport roller 27 immediately before the registration roller 28 adjusts the transport time of the print sheets 101 and 102 to remove the print sheets 101 and 102. By bending, the skew (skew) of the print sheets 101 and 102 is reduced.

Further, the image forming apparatus 10 includes a line sensor 31 and a sheet detection sensor 32.

The line sensor 31 is an optical sensor that is arranged along the direction perpendicular to the print sheet conveyance direction and detects the positions of both edges of the print sheet. For example, the line sensor 31 is a CIS (Contact Image Sensor). In this embodiment, the line sensor 31 is arranged between the registration roller 28 and the print engine 10a in the print sheet conveyance path.

The sheet detection sensor 32 is an optical sensor that detects that the leading ends of the print sheets 101 and 102 have passed a predetermined position on the conveyance path.

FIG. 3 is a block diagram showing an electrical configuration of the image forming apparatus 10 according to the exemplary embodiment of the present invention.

As shown in FIG. 3, the image forming apparatus 10 further includes an operation panel 42, a storage device 43, and an arithmetic processing device 44 in addition to the image output unit 41 having the mechanical configuration shown in FIGS. 1 and 2. Prepare The image output unit 41 includes the line sensor 31 and the sheet detection sensor 32 described above.

The operation panel 42 is arranged on the surface of the housing of the image forming apparatus 10, and includes a display device such as a liquid crystal display, and an input device such as a hard key and a touch panel. The display device displays various messages to the user. A user operation is detected by the input device.

The storage device 43 is a non-volatile storage device (flash memory, hard disk drive, etc.) that stores data, programs, and the like necessary for controlling the image forming apparatus 10. The storage device 43 stores reference deviation amount data 43a described later.

The arithmetic processing unit 44 includes a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that executes a predetermined operation, and the like, and operates as various processing units. The computer includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and a program stored in the ROM, the storage device 43, etc. is loaded into the RAM and executed by the CPU. Thus, it operates as various processing units (along with the ASIC if necessary).

Here, the arithmetic processing unit 44 operates as the control unit 51 and the image processing unit 52.

The control unit 51 controls the image output unit 41 and executes the print job requested by the user. In this embodiment, the control unit 51 causes the image processing unit 52 to perform predetermined image processing, controls the head unit 11 to eject ink, and forms a print image on a print sheet. The image processing unit 52 performs predetermined image processing such as RIP (Raster Image Processing), color conversion, and halftoning on image data of an image to be printed on a print sheet.

In particular, the control unit 51 specifies (a) the center position of the print sheet as the sheet center actual position based on the positions of the both edges of the print sheet detected by the line sensor 31, and (b) based on the sheet center actual position. It has an automatic centering function that adjusts the center position of the image to be printed.

That is, the control unit 51 causes the print engine 10a to print an image by moving the image to be printed by the difference between the reference center position of the print engine 10a and the actual sheet center position along the main scanning direction.

In this embodiment, the control unit 51 controls the print sheet 101, 102 based on the both edges of the print sheet detected by the line sensor 31 at the timing when the leading edge of the print sheet 101, 102 being conveyed is detected by the sheet detection sensor 32. The center position of 102 (actual position of the seat center) is specified. By doing so, the actual position of the sheet center is measured at a fixed position on the print sheets 101 and 102. Therefore, even if a plurality of continuous print sheets 101 and 102 are skewed, the actual sheet center position under the same condition is measured on each print sheet 101 and 102.

The reference shift amount data 43a described above includes the reference center position of the print engine 10a (that is, the center position of the print area in the main scanning direction, that is, the center position of the print image without correction) and the reference center position of the line sensor 31. The amount of deviation (hereinafter referred to as the reference amount of deviation) is shown.

FIG. 4 is a diagram illustrating the correction amount of the image center position in the image forming apparatus 10 according to the first embodiment.

As shown in FIG. 4, in the read data of the line sensor 31, the pixels in the section of the width Wsheet of the print sheets 101 and 102 (from the pixel position Xs to the pixel position Xe) are the pixels corresponding to the colors of the print sheets 101 and 102. Since the pixels having a value and the other pixels have a pixel value corresponding to the background color, at the pixel positions Xs and Xe corresponding to the (physical) both edges of the print sheets 101 and 102, the edge on the image is appear. The control unit 51 detects the edge on this image and derives the actual seat center position P1 by the following equation. The pixel position is represented by the number of pixels from the reference position to the pixel position, with one end of the line sensor 31 as the reference position.

P1=(Xe-Xs)/2

The correction amount dx of the center position of the image to be printed includes the actual sheet center position P1, the reference center position CPp of the print engine 10a (specifically, the inkjet recording units 1a, 1b, 1c, 1d), and the line sensor. It is expressed by the following equation based on the 31 reference center positions CPs.

dx=(P1-CPs)+dP

However, dP=(CPs-CPp)

Here, (P1-CPs) is a deviation amount of the actual sheet center position P1 from the reference center position CPs of the line sensor 31, and is detected for each print sheet.

Further, dP is a deviation amount between the reference center position CPs of the line sensor 31 and the reference center position CPp of the print engine 10a (that is, the above-mentioned reference deviation amount), and is indicated by the reference deviation amount data 43a. The deviation amount dP in the reference deviation amount data 43a is updated by the adjustment work using the test chart.

FIG. 5 is a diagram showing an example of a scale image printed on the front surface and the back surface of the test chart. FIG. 6 is an enlarged view of the scale image in FIG. FIG. 7 is an enlarged perspective view of a test chart in which scale images are printed on the front surface and the back surface.

Specifically, the control unit 51 (a) prints a plurality of sheets in the sub-scanning direction on the front and back surfaces of the print sheets 101 and 102 for the test chart 121, as shown in FIGS. 5 and 6, for example. At the position, the scale image 131 including a plurality of line segment images 131a parallel to each other in the sub-scanning direction and having different positions in the main scanning direction is printed by the print engine 10a, and (b) as shown in FIG. 7, for example. In addition, the reference center position of the print engine 10a specified based on the scale image 131b in which the line segment image 131a of the front side scale image 131 and the line segment image 131a of the back side scale image 131 match each other. The center position of the image to be printed is moved so as to reduce the deviation between CPp and the reference center position Cps of the line sensor 31. In the case shown in FIG. 7, in the scale image 131b having the numerical value “+2”, the line segment image 131a of the front side scale image 131 and the line segment image 131a of the back side scale image 131 match each other.

Here, the line segment image 131a of the scale image 131 is arranged at a position shifted by a predetermined number of pixels (for example, one pixel) in the main scanning direction for each scale image 131b, and the center of the line segment image 131a is sub-scanned. It is arranged so as to be located on a straight line oblique to the direction. For example, the line segment image 131a is a thin line image having a predetermined pixel width (for example, 1 pixel width).

Further, each scale image 131b is a line segment image that intersects the line segment image 131a at a right angle and is parallel to the main scanning direction, and each scale image 131b has a position in the sub scanning direction of the scale image 131b. Corresponding numerical values are given, and when the reference center position CPp of the print engine 10a and the reference center position CPs of the line sensor 31 match each other, the line segment image 131a that matches the front surface and the back surface To the line segment image 131a, a numerical value “0” is attached to the line segment image 131a, and a numerical value corresponding to the distance (distance in the sub-scanning direction) from the line segment image 131a having the numerical value “0” (for example, FIG. 6). “+1”, “+2”, “−1”, “−2”, etc.) are added.

The interval between the line segment images 131a in the main scanning direction (that is, the above-described predetermined number of pixels) and the number of pairs of the line segment image 131a and the scale image 131b are determined by the detection accuracy and the detection range of the reference shift amount to be detected. It is decided accordingly.

Further, the print engine 10a performs manual double-sided printing to print the above-described scale image 131 on the front and back surfaces, respectively.

FIG. 8 is a diagram illustrating positions where the scale images shown in FIGS. 5 and 6 are printed on the print sheet.

When the center position of the image to be printed is made to coincide with the reference center CPs of the line sensor 31 without considering the reference deviation amount dP, as shown in FIG. An image is printed centered on a position displaced from the center position by the reference displacement amount dP. Therefore, when the scale image 131 is printed on the front side and the back side, similarly, the shifts of the reference shift amounts dP occur in mutually opposite directions, and the position and the back side of the scale image 131 printed on the front side are the same. The relative displacement from the position of the scale image 131 printed on the image is 2×dP. Accordingly, when the scale image 131 printed on the front surface and the scale image 131 printed on the back surface are optically overlapped and observed through the test chart 121, the scale printed on the front surface is observed. The position where the image 131 and the scale image 131 printed on the back surface intersect (that is, the position where the line segment image 131a described above coincides) is displaced in the sub-scanning direction by the displacement amount dm corresponding to the reference displacement amount dP.

Therefore, the numerical value (“+2” in the example shown in FIG. 7) of the scale image 131b indicating the deviation amount dm is visually recognized by the user and input through the operation panel 42, and the control unit 51 receives the input. The reference deviation amount dP is specified based on the numerical value of the scale image 131b. Since the relationship between this numerical value and the reference deviation amount dP is linear, the reference deviation amount dP is calculated from the numerical value of the scale image 131b according to a predetermined linear expression.

For example, the user uses a light box or the like to see through the scale image 131 on the back side through the scale image 131 on the front side as shown in FIG. 7, and the scale image on which the line segment image 131a matches. 131b is specified, and the numerical value attached to the scale image 131b is specified.

Further, in this embodiment, (a) as the automatic centering function, the control unit 51 moves the scale image 131 along the main scanning direction by the reference displacement amount dP indicated by the reference displacement amount data 43a, and the print sheet 101, The print engine 10a is caused to print on each of the front surface and the back surface of 102, and (b) the current deviation between the reference center position CPp of the print engine 10a and the reference center position CPs of the line sensor 31 (the current reference deviation amount). The reference deviation amount data 43a is updated by adding

That is, since the scale image 131 is printed in consideration of the reference deviation amount indicated by the reference deviation amount data 43a at the present time, the variation amount from the reference deviation amount indicated by the reference deviation amount data 43a is detected as the reference deviation amount. Therefore, by adding the detected reference deviation amounts, the reference deviation amount indicated by the reference deviation amount data 43a becomes the current reference deviation amount.

Next, the operation of the image forming apparatus according to the first embodiment will be described.

When the control panel 51 detects a predetermined user operation on the operation panel 42, the control section 51 executes center position adjustment as follows.

The control unit 51 turns on the automatic centering function described above, and causes the image output unit 41 to print the scale image 131 on the front surface of the test chart 121. That is, at this time, the control unit 51 specifies the correction amount dx described above based on the reference deviation amount data 43a at the present time (that is, before adjustment) and the center position deviation (P1-CPs) in the line sensor 31, and specifies the correction amount dx. The scale image 131 is moved by the corrected amount dx in the main scanning direction to be printed by the print engine 10a.

Next, the control unit 51 displays on the operation panel 42 an instruction screen prompting the user to set the test chart 121 (print sheets 101 and 102 whose front surface has been printed).

The user sets the test chart 121 in a predetermined paper feed tray or the like in a predetermined direction and performs a predetermined user operation.

When the control unit 51 detects the user operation on the operation panel 42, the control unit 51 turns on the automatic centering function, and causes the image output unit 41 to print the scale image 131 on the back surface of the test chart 121. That is, at this time, the control unit 51 specifies the correction amount dx described above based on the reference deviation amount data 43a at the present time (that is, before adjustment) and the center position deviation (P1-CPs) in the line sensor 31, and specifies the correction amount dx. The scale image 131 is moved by the corrected amount dx in the main scanning direction to be printed by the print engine 10a.

After that, the control unit 51 displays on the operation panel 42 an input screen prompting the user to input the numerical values on the scale read from the test chart 121.

The user specifies the line segment image 131a that matches the front side and the back side in the test chart 121, reads the numerical value of the scale image 131b of the line segment image 131a, operates the operation panel 42, and Enter the value.

When the control unit 51 detects the input numerical value with the operation panel 42, the control unit 51 detects the current deviation amount based on the numerical value, adds the detected deviation amount to the value of the reference deviation amount data 43a, and adds the reference deviation amount. The quantity data 43a is updated.

In this way, the reference deviation amount is adjusted.

After that, the control unit 51 uses the adjusted reference shift amount to specify the above-described correction amount for each print sheet, and moves the position of the image to be printed in the main scanning direction by the correction amount. The print engine 10a prints.

As described above, according to the first embodiment, the print engine 10a physically prints the image to be printed on the print sheet. The sheet conveying unit 10b conveys a print sheet. The line sensor 31 is arranged along a direction perpendicular to the conveyance direction of the print sheets 101 and 102, and detects the positions of both edges of the print sheets 101 and 102. The control unit 51 specifies (a) the center position of the print sheets 101 and 102 as the sheet center actual position based on the positions of the edges of the print sheets 101 and 102 detected by the line sensor 31, and (b) the sheet center actual position. The center position of the image to be printed is adjusted based on the difference from the position. Further, (a) the control sheet 51 has a plurality of positions in the sub-scanning direction on the front surface and the back surface of the print sheets 101 and 102 for the test chart 121, which are different from each other in the main-scanning direction. A scale image 131 having a plurality of line segment images 131a parallel to each other for each scale image 131b is printed by the print engine 10a, and (b) of the line segment image 131a of the front side scale image 131 and the scale image 131 of the back side. Reduction in deviation of an image to be printed due to deviation between the reference center position CPp of the print engine 10a and the reference center position CPs of the line sensor 31, which is specified based on the scale image 131b in which the line segment image 131a matches each other. As described above, the center position of the image to be printed is moved.

As a result, the image to be formed on the print sheet is moved in consideration of the deviation of the center position between the print engine 10a and the line sensor 31, so that the center position of the print sheets 101 and 102 and the print sheet are relatively low. The deviation of the image formed above from the center position is effectively reduced.

Embodiment 2.

The first embodiment describes the case where the reference center position of the print engine 10a is not displaced from the reference center position of the conveyance system of the print sheets 101 and 102, and the conveyance system of the print sheets 101 and 102 is described. When the reference center position of the print engine 10a is deviated from the reference center position of No. 3, it is necessary to consider the amount of the deviation as well. In the second embodiment, the amount of the shift is measured, and the correction amount of the position of the image to be printed in the first embodiment is adjusted by the amount of the shift.

In the second embodiment, the control unit 51 causes the print engine 10a to print the scale image 131 on the print sheets 101 and 102 without (a) performing the automatic centering function, and (b) printing without performing the automatic centering function. The reference center position CPp of the print engine 10a is corrected by the deviation between the reference center position CPp of the print engine 10a and the reference center position CPt of the transport system of the print sheets 101 and 102, which is specified based on the scale image 131. The above-mentioned correction amount is adjusted by correcting the reference center position CPp of the print engine 10a.

FIG. 9 is a diagram for explaining the deviation of the reference center position CPp of the print engine 10a from the reference center position CPt of the transport system of the print sheets 101 and 102. As shown in FIG. 9, the center position of the print sheets 101 and 102 is the reference center position CPt of the transport system for the print sheets 101 and 102.

For example, the user measures the distance between a specific line segment image 131a in the scale image 131 and a side (edge) of the print sheets 101 and 102 parallel to the line segment image 131a, and the distance or the measurement thereof. The difference between the selected distance and a predetermined reference value (that is, the distance when there is no deviation) is input by operating the operation panel 42. When the distance is input, the control unit 51 calculates the above difference from the input distance. Then, the control unit 51 sets the input or calculated difference as the deviation amount dT. If the difference is obtained in physical units, the difference may be converted into the number of pixels based on the print resolution.

The other configurations and operations of the image forming apparatus according to the second embodiment are similar to those of the first embodiment, and thus the description thereof will be omitted.

As described above, according to the second embodiment, since the image to be formed on the print sheet is moved in consideration of the deviation of the center position between the print engine 10a and the transport system, the printing can be performed at a relatively low cost. The deviation between the center position of the sheets 101 and 102 and the center position of the image formed on the print sheets 101 and 102 is effectively reduced.

Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be covered by the appended claims.

For example, in the above-described embodiment, the print engine 10a is an inkjet print engine, but may be another print engine such as an electrophotographic print engine.

Further, in the above embodiment, the number of the sheet feeding cassettes 20-1 and 20-2 is two, but the number may be three or more or one.

The present invention can be applied to an image forming apparatus such as a printer or a multifunction peripheral.

10 Image Forming Apparatus 10a Print Engine 10b Sheet Conveying Section 31 Line Sensor 43 Storage Device 43a Reference Deviation Data 51 Control Section

Claims (3)

A print engine that physically prints the image to be printed on the print sheet,
A sheet conveying section for conveying the print sheet,
A line sensor that is arranged along a direction perpendicular to the conveyance direction of the print sheet, and detects the positions of both end edges of the print sheet,
(A) The center position of the print sheet is specified as a sheet center actual position based on the positions of both end edges of the print sheet detected by the line sensor, and (b) the center position of the print sheet is determined based on the difference from the actual sheet center position. With a control unit that adjusts the center position of the image to be printed,
(A) a plurality of lines parallel to the sub-scanning direction on the front side and the back side of the test chart print sheet, the positions of which are different from each other in the main-scanning direction; A scale image including a segment image for each scale image is printed by the print engine, and (b) the line segment image of the scale image on the front surface and the line segment image of the scale image on the back surface are mutually The image to be printed so as to reduce the shift of the image to be printed due to the shift between the reference center position of the print engine and the reference center position of the line sensor, which is specified based on the matching scale image. Moving the center position of
An image forming apparatus characterized by. Further comprising a storage device for storing reference deviation amount data indicating a deviation between the reference center position of the print engine and the reference center position of the line sensor,
The control unit (a) moves the scale image along the main scanning direction based on the reference deviation amount indicated by the reference deviation amount data as an automatic centering function, and thereby, the front surface and the back surface of the print sheet. And (b) updating the reference deviation amount data by adding the current deviation between the reference center position of the print engine and the reference center position of the line sensor.
The image forming apparatus according to claim 1, wherein: The control unit (a) causes the print engine to print the scale image on the print sheet without performing the automatic centering function, and (b) is based on the scale image printed without performing the automatic centering function. 2. The image forming apparatus according to claim 1, wherein the reference center position of the print engine is corrected by a deviation between the reference center position of the print engine and the reference center position of the print sheet conveying system. ..

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