JP7240594B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

A certain image forming apparatus (hereinafter referred to as the 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 nips the paper with a transport roller. The misalignment is reduced by moving the transport roller in the sheet width direction in a state where the sheet is folded (see, for example, Japanese Laid-Open Patent Publication No. 2002-100002).

A certain image forming apparatus (hereinafter referred to as a second image forming apparatus) has a plurality of paper feed trays, stores a fixed amount of center misalignment corresponding to each of the plurality of paper feed trays, and The image formed in the electrophotographic process is moved by mechanically adjusting the optical system for the electrophotographic process by the amount of center positional deviation corresponding to the paper feed tray (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003).

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

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

However, in the first image forming apparatus, although it is possible to reduce the deviation of the center position of the paper being conveyed, a mechanism for mechanically moving the conveying roller is required. Cost will be higher.

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

Note that the third image forming apparatus is intended to suppress misalignment between the position of the image on the front side and the position of the image on the back side. It is difficult to reduce the deviation between the center position of the image that is displayed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is capable of effectively reducing 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 of the present invention 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 section that conveys the print sheet, and a print sheet along the direction perpendicular to the conveying direction of the print sheet. (a) a center position of the print sheet as an actual sheet center position based on the position of the both edges of the print sheet detected by the line sensor; (b) a control unit that adjusts the center position of the image to be printed based on the difference from the sheet center actual position. (a) a plurality of test chart print sheets having different positions in the sub-scanning direction and parallel to the sub-scanning direction; (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; 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, which are specified based on the scale images that match each other. Move the center position of the image that should be

According to the present invention, it is possible to obtain an image forming apparatus which is relatively inexpensive and which effectively reduces the deviation between the center position of the print sheet and the center position of the image formed on the print sheet.

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

FIG. 1 is a side view for explaining the mechanical internal configuration of an image forming apparatus according to an embodiment of the invention. 2 is a plan view of the image forming apparatus shown in FIG. 1. FIG. FIG. 3 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the invention. FIG. 4 is a diagram for explaining the correction amount of the center position of the image in the image forming apparatus 10 according to the first embodiment. FIG. 5 is a diagram showing an example of scale images printed on the front and back surfaces 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 with scale images printed on the front and back. FIG. 8 is a diagram for explaining the 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 conveying system of the print sheet 101. FIG.

Embodiments of the present invention will be described below based on the drawings.

Embodiment 1.

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

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

The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a sheet conveying section 10b. The print engine 10a physically prints an image to be printed onto a print sheet (such as print paper). The sheet conveying section 10b conveys 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 of the inkjet recording units 1a, 1b, 1c, and 1d has a plurality of (here, three) head units 11. As shown in FIG. These head units 11 are arranged along the main scanning direction and are detachable from the apparatus main body. Note that each of the inkjet recording units 1a, 1b, 1c, and 1d may have one head unit 11. FIG.

Further, in this embodiment, the sheet conveying section 10b includes an annular conveying belt 2 arranged to face the print engine 10a and conveying the print sheet, and a driving roller 3 and a driven roller 4 on which the conveying belt 2 is suspended. , a suction roller 5 for nipping the print sheet together with the conveying belt 2, and a discharge roller pair 6. - 特許庁

A driving roller 3 and a driven roller 4 cause the conveying belt 2 to go around. Then, the print sheets conveyed from paper feed cassettes 20-1 and 20-2, which will be described later, are nipped by the suction roller 5, and the nipped print sheets are transported to the print positions of the inkjet recording units 1a to 1d by the conveying belt 2. The sheets are conveyed in order, and images of respective colors are printed by the inkjet recording units 1a to 1d. After color printing is completed, the print sheet is discharged to a discharge tray (not shown) or the like by the discharge roller pair 6 .

Further, the sheet conveying section 10b has a plurality of sheet feeding cassettes 20-1 and 20-2. Paper feed cassettes 20-1 and 20-2 accommodate print sheets 101 and 102. Lift plates 21 and 24 push print sheets 101 and 102 upward and bring them into contact with pickup rollers 22 and 25, respectively. Print sheets 101 and 102 placed in paper feed cassettes 20-1 and 20-2 are picked up by pickup rollers 22 and 25 onto paper feed rollers 23 and 26 one by one from the upper side. The paper feed rollers 23 and 26 are rollers for conveying the print sheets 101 and 102 fed from the paper feed cassettes 20-1 and 20-2 by the pickup rollers 22 and 25 onto the conveyance path one by one.

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

The registration 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 timing of the secondary paper feed. The secondary paper feed timing is specified by the control section 51 to be described later so that the image is formed at the specified position on the print sheets 101 and 102 .

In this embodiment, when the print sheets 101 and 102 reach the registration rollers 28, the transport roller 27 immediately before the registration rollers 28 adjusts the transport time of the print sheets 101 and 102 to transport the print sheets 101 and 102. The skew of the print sheets 101 and 102 is reduced by bending them.

Furthermore, 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 conveying direction of the print sheet and that 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 transport path.

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

FIG. 3 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the 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. Prepare. Note that 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 hard keys and a touch panel. Detect user actions on the input device.

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

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

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

Control unit 51 controls image output unit 41 to execute a print job requested by the user. In this embodiment, the control unit 51 causes the image processing unit 52 to execute 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 (a) identifies the center position of the print sheet as the actual sheet center position based on the positions of both edges of the print sheet detected by the line sensor 31, and (b) specifies the actual sheet center 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 the image by moving the image to be printed in the main scanning direction by the difference between the reference center position of the print engine 10a and the actual sheet center position.

In this embodiment, the control unit 51 detects the edges of the print sheets 101 and 102 that are detected by the line sensor 31 at the timing when the sheet detection sensor 32 detects the leading edges of the print sheets 101 and 102 being conveyed. The center position of 102 (seat center actual position) is specified. By doing so, the actual sheet center position 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 can be measured for each of the print sheets 101 and 102 under the same conditions.

Further, the reference deviation amount data 43a described above is 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 printed image without correction) and the reference center position of the line sensor 31. and the amount of deviation (hereinafter referred to as the reference deviation amount).

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

As shown in FIG. 4, in the data read by 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) correspond to the colors of the print sheets 101 and 102. and the other pixels have pixel values corresponding to the background color. Therefore, at pixel positions Xs and Xe corresponding to (physical) both edges of the print sheets 101 and 102, edges on the image are appear. The control unit 51 detects edges on this image and derives the seat center actual position P1 by the following equation. Note that 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

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

dx = (P1-CPs) + dP

However, dP = (CPs-CPp)

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

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

FIG. 5 is a diagram showing an example of scale images printed on the front and back surfaces 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 with scale images printed on the front and back.

Specifically, the control unit 51 (a) applies a plurality of sub-scanning directions to 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. , the print engine 10a prints a scale image 131 having a plurality of line segment images 131a parallel to the sub-scanning direction and having different positions in the main scanning direction for each scale image 131b. Then, the reference center position of the print engine 10a is specified based on the scale image 131b in which the line segment image 131a of the scale image 131 on the front side and the line segment image 131a of the scale image 131 on the back side 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, the line segment image 131a of the scale image 131 on the front side and the line segment image 131a of the scale image 131 on the back side match each other in the scale image 131b with the numerical value "+2".

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 located at the sub-scanning direction. They are arranged on a straight line oblique to the direction. For example, the line segment image 131a is a thin line image with a predetermined pixel width (for example, 1 pixel width).

Each scale image 131b is a line segment image parallel to the main scanning direction that intersects the line segment image 131a at right angles. 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 on the front surface and the back surface. , and the other line segment image 131a is given a numerical value (for example, FIG. 6 "+1", "+2", "-1", "-2", etc.) are given.

Note that 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 images 131a and the scale images 131b are determined by the detection accuracy and detection range of the reference deviation amount to be detected. determined accordingly.

In addition, the print engine 10a prints the scale image 131 on the front side and the back side by manual double-sided printing.

FIG. 8 is a diagram for explaining the 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 aligned with the reference center CPs of the line sensor 31 without considering the reference shift amount dP, as shown in FIG. The image is printed centering on a position shifted from the center position by the reference shift amount dP. Therefore, when the scale image 131 is printed on the front surface and the back surface, the deviation of the reference deviation amount dP is generated in the opposite directions, and the position of the scale image 131 printed on the front surface and the back surface are different from each other. The relative displacement from the position of the scale image 131 printed on 1 is 2×dP. As a result, when the test chart 121 is seen through and the scale image 131 printed on the front surface and the scale image 131 printed on the back surface are optically superimposed and observed, the scale image 131 printed on the front surface can be observed. The position at which the image 131 and the scale image 131 printed on the back side intersect (that is, the position where the above line segment image 131a matches) is shifted in the sub-scanning direction by a shift amount dm corresponding to the reference shift amount dP.

Therefore, when the numerical value ("+2" in the example shown in FIG. 7) of the scale image 131b indicating the amount of deviation dm is visually recognized by the user and input on the operation panel 42, the controller 51 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, as shown in FIG. 7, the user uses a light box or the like to see through the scale image 131 on the back side and visually recognizes the scale image 131 on the front side together with the scale image 131 on the front side. 131b is specified, and the numerical value attached to the scale image 131b is specified.

In this embodiment, the control unit 51 (a) performs an automatic centering function by moving the scale image 131 along the main scanning direction by the reference displacement amount dP indicated by the reference displacement amount data 43a. 102 are printed by the print engine 10a, 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 is calculated (current reference deviation amount ) to update the reference deviation amount data 43a.

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

Next, operation of the image forming apparatus according to Embodiment 1 will be described.

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

The control unit 51 turns on the automatic centering function and causes the image output unit 41 to print the scale image 131 of the front surface of the test chart 121 . In other words, at this time, the control unit 51 specifies the correction amount dx based on the current (that is, before adjustment) reference deviation amount data 43a and the center position deviation (P1-CPs) of the line sensor 31, and specifies The scale image 131 is moved in the main scanning direction by the corrected correction amount dx and 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 (the print sheets 101 and 102 whose front surfaces have been printed).

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

When the operation panel 42 detects the user's operation, 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 side of the test chart 121 . In other words, at this time, the control unit 51 specifies the correction amount dx based on the current (that is, before adjustment) reference deviation amount data 43a and the center position deviation (P1-CPs) of the line sensor 31, and specifies The scale image 131 is moved in the main scanning direction by the corrected correction amount dx and 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 of the scale read from the test chart 121 .

The user specifies the line segment image 131a that matches the front surface and the back surface 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 a number.

When the input numerical value is detected by 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 obtains the reference deviation amount. Update the quantity data 43a.

In this manner, the reference deviation amount is adjusted.

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

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 portion 10b conveys print sheets. The line sensor 31 is arranged along the direction perpendicular to the conveying direction of the print sheets 101 and 102 and detects the positions of the both end edges of the print sheets 101 and 102 . The control unit 51 (a) identifies the center positions of the print sheets 101 and 102 as actual sheet center positions based on the positions of the edges of the print sheets 101 and 102 detected by the line sensor 31, and (b) determines the actual sheet center positions. The center position of the image to be printed is adjusted based on the difference from the position. Further, the control unit 51 (a) prints each of the front and back surfaces of the print sheets 101 and 102 for the test chart 121 with different positions in the sub-scanning direction at a plurality of positions in the sub-scanning direction. The print engine 10a prints a scale image 131 having a plurality of line segment images 131a parallel to each other for each scale image 131b. To reduce deviation of an image to be printed due to deviation between a reference center position CPp of a print engine 10a and a reference center position CPs of a line sensor 31, which are specified based on a scale image 131b in which line segment images 131a match each other. The center position of the image to be printed is moved so that the

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 line sensor 31, the center positions of the print sheets 101 and 102 and the print sheet can be adjusted at a relatively low cost. The deviation from the center position of the image formed thereon is effectively reduced.

Embodiment 2.

In the first embodiment, the case where the reference center position of the print engine 10a does not deviate from the reference center position of the transport system of the print sheets 101 and 102 will be described. If the reference center position of the print engine 10a deviates from the reference center position of the print engine 10a, the amount of deviation must also be considered. In the second embodiment, the amount of misalignment 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 misalignment.

In the second embodiment, the control unit 51 (a) causes the print engine 10a to print the scale image 131 on the print sheets 101 and 102 without performing the automatic centering function, and (b) causes the print engine 10a to print without performing the automatic centering function. The reference center position CPp of the print engine 10a is corrected by the difference between the reference center position CPp of the print engine 10a and the reference center position CPt of the conveying system of the print sheets 101 and 102 specified based on the scale image 131 obtained. The correction amount described above 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 conveying system of the print sheets 101 and 102. FIG. 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 the sides (edges) of the print sheets 101 and 102 parallel to the line segment image 131a, and measures the distance or The operator operates the operation panel 42 to input the difference between the calculated distance and a predetermined reference value (that is, the distance when there is no deviation). When the distance is input, the control section 51 calculates the above-described difference from the input distance. Then, the control unit 51 sets the input or calculated difference as the amount of deviation dT. If the difference is obtained in physical units, the difference may be converted to the number of pixels based on the print resolution.

Other configurations and operations of the image forming apparatus according to Embodiment 2 are the same as those in Embodiment 1, so description thereof will be omitted.

As described above, according to the second embodiment, the image to be formed on the print sheet is moved in consideration of the misalignment of the center position between the print engine 10a and the conveying system. The deviation between the center positions of the sheets 101 and 102 and the center positions of the images formed on the print sheets 101 and 102 is effectively reduced.

Various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of its subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the 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.

Also, in the above embodiment, there are two paper feed cassettes 20-1 and 20-2, but there may be three or more or one.

The present invention is applicable to, for example, image forming apparatuses such as printers and multi-function peripherals.

REFERENCE SIGNS LIST 10 image forming apparatus 10a print engine 10b sheet conveying section 31 line sensor 43 storage device 43a reference misalignment amount data 51 control section

Claims (3)

a print engine that physically prints an image to be printed onto a print sheet;
a sheet conveying unit that conveys the print sheet;
a line sensor arranged along the direction perpendicular to the conveying direction of the print sheet for detecting the positions of both edges of the print sheet;
(a) specifying the center position of the print sheet as an actual sheet center position based on the positions of both edges of the print sheet detected by the line sensor; and (b) determining the difference from the actual sheet center position. a control unit for adjusting the center position of the image to be printed,
(a) a plurality of lines parallel to the sub-scanning direction, the positions of which are different from each other in the sub-scanning direction at a plurality of positions in the sub-scanning direction; (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 printed by the print engine; The image to be printed so as to reduce misalignment of the image to be printed due to misalignment between a reference center position of the print engine and a reference center position of the line sensor, which are identified 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 , as a reference deviation amount, a deviation amount between the reference center position of the print engine and the reference center position of the line sensor;
(a) as an automatic centering function, the control unit moves the scale image along the main scanning direction based on the reference misalignment amount indicated by the reference misalignment amount data; and (b) detecting a current deviation amount between the reference center position of the print engine and the reference center position of the line sensor, and adding the detected deviation amount to the reference deviation amount data. updating the reference deviation amount data by adding to the reference deviation amount ;
The image forming apparatus according to claim 1, characterized by: The control unit (a) causes the print engine to print the scale image on the print sheet without performing the auto-centering function; and (b) based on the scale image printed without performing the auto-centering function. 2. The image forming apparatus according to claim 1, wherein the reference center position of the print engine is corrected by the deviation between the reference center position of the print engine and the reference center position of the print sheet conveying system specified by .

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